315D 319 D (Curso)
Short Description
Caterpillar 315D...
Description
SERV1850 February 2008
GLOBAL SERVICE LEARNING TECHNICAL PRESENTATION
315D/319D HYDRAULIC EXCAVATORS INTRODUCTION
Service Training Meeting Guide (STMG)
315D/319D HYDRAULIC EXCAVATORS INTRODUCTION AUDIENCE Level II - Service personnel who understand the principles of machine systems operation, diagnostic equipment, and procedures for testing and adjusting.
CONTENT This presentation provides an introduction for the 315D/319D Hydraulic Excavators and will cover the engine, pilot system, pumps and controls, main control valve group, swing system, and travel system. This presentation may be used for self-paced and self-directed training.
OBJECTIVES After learning the information in this presentation, the technician will be able to: 1. identify the major compon ents in the engine, pil ot system, pumps and control s, main control valve group, swing system, and travel system; 2. explain the operation of the majo r components in the engine, pilot sys tem, pumps and controls, main control valve group, swing system, and travel system; and 3. trace the oil flow through the systems.
REFERENCES 315DHydraulicExcavatorSpecalog 300D Series Hydraulic Excavators, 345C Hydraulic Excavator, and 365C & 385C Large Hydraulic Excavators Monitoring System C4.2/C6.4 and C4.4/C6.6 ACERT™ Engines with Common Rail Fuel System--MachineApplications"
AEHQ5865 SERV7032 SERV1837
PREREQUISITES "Fundamentals "Fundamentals "Fundamentals "Fundamentals
of of of of
Mobile Hydraulics Self Study Course" Power Train Self Study Course" Electrical Systems Self Study Course" Engines Self Study Course"
Estimated Time: 36 Hours Illustrations: 187 Form: SERV1850 Date: February 2008 © 2008 Caterpillar Inc.
TEMV3002 TEMV3003 TEMV3004 TEMV3001
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TABLE OF CONTENTS INTRODUCTION ........................................................................................................................5 MACHINE WALKAROUND ....................................................................................................10 OPERATOR'S STATION............................................................................................................21 ELECTRONIC CONTROL SYSTEM .......................................................................................37 Engine Speed Control...........................................................................................................39 Automatic Engine Control (AEC) ........................................................................................40 One Touch Low Idle .............................................................................................................42 Engine Speed Protection.......................................................................................................44 Travel Speed Control............................................................................................................46 Swing Brake Operation.........................................................................................................48 Back-up System ....................................................................................................................50 C4.2 ACERT™ ENGINE ...........................................................................................................53 Fuel System...........................................................................................................................59 Air Inlet System....................................................................................................................79 PILOT SYSTEM ........................................................................................................................83 Pilot Manifold.......................................................................................................................86 Hydraulic Activation Lever ..................................................................................................90 Pilot Controls and Valves .....................................................................................................92 MAIN HYDRAULIC PUMPS AND CONTROLS .................................................................101 MAIN CONTROL VALVE GROUP AND RETURN SYSTEM ............................................117 Main Control Valve Group .................................................................................................118 Return Hydraulic System....................................................................................................139 BOOM, STICK, AND BUCKET CIRCUITS ..........................................................................145 Boom Circuit.......................................................................................................................148 Boom Lowering Control Valves .........................................................................................164 Stick Circuit ........................................................................................................................167 Slow STICK IN - No Regeneration ...................................................................................170 Bucket Circuit.....................................................................................................................179 Cylinders.............................................................................................................................180 SWING SYSTEM ...................................................................................................................183 Swing System Components ................................................................................................184 Swing System Operation ....................................................................................................188 Swing Motor Operation ......................................................................................................193
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TABLE OF CONTENTS (continued) TRAVEL SYSTEM...................................................................................................................207 Travel System Components ................................................................................................208 Travel System Operation ....................................................................................................213 Travel Parking Brake ..........................................................................................................219 Straight Travel.....................................................................................................................227 Swivel .................................................................................................................................230 CONCLUSION.........................................................................................................................232 VISUAL LIST ..........................................................................................................................233 COLOR CODE HYDRAULIC SCHEMATIC.........................................................................236
NOTES
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© 2008 Cate rpillar Inc.
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INTRODUCTION
The 315D/319D Hydraulic Excavators incorporate design innovations and performance improvements from the 315C/318C Hydraulic Excavator Series and are a direct replacement for them. The machines feature a new cab for greater operator comfort. The cab provides the operator with excellent visibility of processing equipment, trucks, and railcars. The cab, consoles, and joysticks have been improved to provide a better access and understanding of all functions. The 315D and 319D Hydraulic Excavators feature a hydrostatic drive system, Side-By-Side (SBS) pumps, Negative Flow Controlled (NFC) hydraulic system, and pilot operated control valves similar to the 315C/318C. The machines have a monitoring system similar to that of the 320D. The 315D/319D HEX is equipped with the C4.2 ACERT™ engine which meets U.S Environmental Protection Agency (EPA) Tier 3 and European Union Stage IIIa emissions control standards. Illustrations of the 315D and the 319D are both used in this presentation. Where there is a significant difference it will be noted. NOTE:
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This chart displays the similarities and differences between the 315C/318C and 315D/319D Hydraulic Excavators. New and improved features include: Operator's Station: The operator's station has been improved over the previous models and is
similar to the 320D. The layout of the interior has been redesigned to maximize operator comfort and reduce operator fatigue. Frequently used switches have been relocated for easier access. The consoles and armrests have been redesigned for better comfort and adjustability. More seat options are available to choose from: the standard mechanical suspension seat, or the optional air suspension seat with heater. Engine: The 315D/319D machines are equipped with a C4.2 Tier III ACERT™ engine. Monitor: The monitor is a full color Liquid Crystal Display that provides vital operating and performance information, alerts in text, which are all in a simple, easy to navigate format. The monitor is the same as the 320D series machines. Tool Control: The tool control system for the 315D/319D is similar in function to the tool control systems for the 320D series machines.
The SmartBoom™ attachment enhances operation of the boom function and significantly reduces cycle times of the machine. Service and maintenance intervals have been extended to reduce machine service time and increase machine availability.
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Options include: Machine Security System (MSS): The Machine Security System (MSS), uses a special Caterpillar key with an embedded electronic chip for controlling unauthorized machine operation. Product Link: Product Link provides all kinds of information and working parameters through a satellite connection between an onboard computer and the machine. Product Link provided easier fleet management and improved preventive maintenance. PL121 and PL321
are available to chose from. MSS and Product Link are the same systems used on other Caterpillar machines. NOTE:
AccuGrade: AccuGrade, which provides precise control of the worktool using software. Auxiliary Hydraulic Options: Auxiliary Hydraulic Options Allows you to configure the machine to meet work tool needs, while increasing its versatility and are the same as the 315C/318C.
- Single Function Circuit – suited for tools that require one-way flow with both pumps, such as hammers and vibratory plate compactors. - Double Function Circuit – suited for tools that require two-way flow, utilizing one pump, such as thumbs or non-rotation grapples or shears.
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The main implement hydraulic system operation for the 315D/319D machines is very similar to the 318C machines The "D" Series continues using many of the "C" excavator features, such as automatic priorities and tool control systems. The machines use a negative flow type hydraulic system. The main control valve and pumps are similar to the "C" Series. The 315D/319D machines can be equipped with a medium pressure circuit to operate an auxiliary motor.
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The optional tool control system maximizes work tool productivity by configuring hydraulic flow, pressure, and operator controls to match a specific work tool. System versatility enables a wide range of tools to be used. The system stores pressure and flow information for several different work tools. Selectable Cat tools have preset flows and pressures. The 315D/319D can be equipped with the following factory installed tool control systems: - System 20 - System 23 - System 24 - Medium pressure (F3 valve) - Medium pressure (F4 valve) - Medium pressure (Danfoss valve)
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5 MACHINE WALK-AROUND
The 315D/319D Series track excavators have been designed for fast, easy service with extended service intervals, advanced filtration, convenient filter access, and user-friendly electronic diagnostics for increased productivity and reduced maintenance costs. The hydraulic system and component locations have been designed to provide a high level of system efficiency. The main pumps, control valves and hydraulic tank are located close together to allow for shorter tubes and lines between components which reduces friction loss and pressure drops in the lines. Components shown include: - stick (1) - boom (2) - operator station (3) - engine access cover (4) - access door to air cleaner, battery, and radiator compartment (5) - counterweight (6) - final drive (7) - track (8) - bucket (9)
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This illustration shows access to the top of the machine from the right side. The engine access cover (1) allows access to the engine from the top of the machine. The machine hydraulic oil reservoir (2) is located between the pump compartment and the diesel fuel tank on the right side of the machine and is accessed from the top of the machine. The diesel fuel filler cap (3) is accessed from the top of the machine. The storage compartment (4) is located in the front of the machine. The step and hand rail (5) at the right front of the machine can be used for access to the top of the machine.
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The compartment behind the operator station on the left side of the machine includes the following components: - primary fuel filter and water separator (1) - windshield washer fluid tank (2) - Machine ECM (3) - engine air filter housing (4) - ATAAC (5) - air conditioning condenser (6) - batteries (7) - engine coolant overflow tank (8) - battery disconnect switch and circuit breakers (9)
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The illustration shows the pump compartment on the right side of the machine. The compartment is accessed from the right side of the machine when the rear access door is open. Some of the visible components are: - engine oil filter (1) - engine oil S•O•S tap (2) - drive (right) pump (3) - pilot filter (4) - hydraulic oil S•O•S tap (5) - pilot pump (6) - idler (left) pump (7) - medium pressure circuit pump location (if equipped, 8) - pump pressure taps (9)
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The pilot manifold is located next to the main control valve group. Pilot manifold components visible are: - pilot accumulator (1) - hydraulic activation solenoid (2) - hydraulic activation valve (3) - swing brake solenoid (4) - two-speed travel solenoid (5)
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The main control valve group is located in the center of the upper structure of the machine. The main control valve group receives pilot oil signals from the operator controls in the cab. Each pilot signal then causes the appropriate control valve to shift in the correct direction. When a control valve shifts, oil flows from the main hydraulic pumps to the appropriate hydraulic cylinder or hydraulic motor to perform work. The 315D/319D main control valve is similar to the 315C/318C valve.
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The 315D/319D has one swing motor (1) that receives oil from the swing control valve. The swing control valve receives pump oil from the idler pump. The swing drive oil level can be checked with the dipstick (2). The swing motor case vent (3) is located on top of the swing motor. Travel motors (not shown) drive outboard final drives (4). A wide range of undercarriage (5) options are available to meet the needs of the machine application.
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The 315D/319D is equipped with a C4.2 ACERT™ Engine. Engine components visible are: - engine crankcase breather (1) - engine oil fill (2) - turbocharger (3) - secondary fuel filter (4) - fuel priming pump (5) - engine oil dipstick (6) - tertiary (third) fuel filter (7)
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In front of the engine is the radiator (1) and hydraulic cooler (2). The engine cooling fan (3) on the 315D/319D is mechanically driven off the front of the engine.
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This illustration lists the procedures to be performed for the daily or 10 hour walkaround inspection for the 315D/319D Hydraulic Excavators.
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OPERATOR'S STATION
The 315D/319D Hydraulic Excavator operator station has an updated look with a new color scheme similar to the 320D. The cab post and rear of the cab have been changed to black while the counterweight design has been changed with an enlarged CAT® decal and distinctive styling. The operator station contains a newly designed cab with improved visibility and operator comfort. Switches have been relocated and a full-text full color monitor make it easier to navigate. For operator comfort, the new cab offers a fully adjustable seat with spring support, or air suspended seat with side-to-side shock absorption, which provides maximum operator comfort. The new "D" series monitor provides increased functionality for the operator. Conveniently placed switches, gauges, information display, and controls improve operator comfort, awareness, and efficiency. The fuse panel is relocated to the left side of the lunch box compartment behind the operator's seat for easy access.
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Controls in the cab include the: - Left joystick (1) - Travel levers (2) - Monitor panel (3) - Right joystick (4) - Key start switch (5) - Engine speed dial switch (6) - Service hour meter (7) - Travel pedals (8)
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The hydraulic activation lever (1) has been redesigned for the new models, however, the lever's purpose is still the same. With the lever in the down position (top illustration), the hydraulic activation solenoid is in the de-activated position. No hydraulic functions are available with the lever in the down position. In the up position (bottom illustration), the hydraulic activation solenoid is energized and the hydraulic system can be operated. The ground level emergency engine shutoff switch (2) is located on the bottom of the seat mount. The shutoff switch will shut off the engine without having to climb into the cab and should be used only for an emergency or during machine servicing. Once the shutoff switch is turned ON and then OFF, the key start switch must be cycled for the machine to operate again.
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The soft switch panel includes switches that either turn a function on/off or allow the operator to toggle through different modes of the selected function. The soft switches provide the operator with the following functions: Two-speed travel (1): When the button is pushed the travel speed is toggled between low and auto.
- The rabbit indicator indicates auto speed. - The tortoise indicator indicates low speed . Automatic Engine Control (AEC) Switch (2): The AEC function automatically reduces engine speed while there is no hydraulic demand, which reduces noise and fuel consumption.
- The AEC switch disables and enables the AEC function. - The first stage AEC reduces the engine speed by 100 rpm after there has been no hydraulic demand for approximately three seconds. - The second stage AEC reduces the engine rpm to approximately 1300 rpm after there has been no hydraulic demand for an additional three seconds. - The second stage AEC delay times and rpm can be changed using the monitor or Caterpillar Electronic Technician (Cat ET).
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Travel alarm cancel (3): The travel alarm cancel switch is a momentary two-position switch.
- The travel alarm sounds when travel is detected. - The travel alarm stops immediately if the travel alarm cancel switch is depressed. - The travel alarm switch is reset every time the travel pressure switch opens. Work tool switch (4): The work tool switch will display the selected work tool on the monitor display. Press the switch repeatedly to change the selected work tool. When the desired work tool is highlighted in the monitor display press the "OK" button on the monitor to select the
work tool shown. Work lights (5): The work lights switch toggles between the different work light combinations.
- Pattern 1 - Chassis work lights and cab work lights. - Pattern 2 - Chassis work lights, cab work lights, and boom work lights. Upper window wipers (6): The wiper switch toggles between the different modes of the wipers.
- six second delay. - three second delay. - continuous operation. - off.
Some machines have one wiper arm on which upper and lower blades are mounted. NOTE:
Upper window washer (7): The windshield washer fluid switch is an ON/OFF switch. Heavy lift (8): Not used.
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The toggle and rocker switch panel contains switches that control additional functions: Quick coupler lock cont rol (1): The quick coupler lock control switch is a spring centered toggle switch.
- The top position locks the quick couple r. - The bottom position unlocks the quick coupler. Lower window wiper (2): The rear window wiper switch is a two-position rocker switch.
- The top position activates the wiper. - The bottom position deactivates the wiper. NOTE:
Some machines are not equipped with a rear window wiper.
Lower window washer (3): The rear window washer fluid switch is a two-position rocker switch.
- The top position activates the windshield washer fluid. - The bottom position deactivates the windshield washer fluid. NOTE:
Switch (3) is the leveling switch on some machines.
Seat h eater (4): The seat heater switch is a two-position toggle switch.
- The top position activates the seat heater. - The bottom position deactivates the seat heater.
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Fine swing control (5): The fine swing control switch is a two-position rocker switch.
- The top position activates fine swing control. Fine swing control improves the swing control during swing deceleration. - The bottom position deactivates fine swing control.
Fine swing control is not available on some machines and switch (5) is the radio ON/OFF switch on some machines. NOTE:
Overload warning device load (6): condition In lifting exists applications, the overload warning device informs the operator when an unstable by activating a buzzer.
- The top position activates the overload warning device. - The bottom position deactivates the overload warning device. Leveling switch (7): The leveling switch is used for smoother operation during finish grading.
- The top position activates the leveling fun ction - The bottom position deactivates the leveling function NOTE:
Switch (7) is the seat heater switch on some machines.
NOTE: Refer to the appropriate Operation and Maintenance Manual to identify switch locations specific to your machine.
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The heating and air conditioning system is electronically controlled. The control panel for the heating and air conditioning system is located on the right console. The switches on the control panel are the: On/Off switch (1): Push the ON/OFF switch in order to power on the system. Push the switch again in order to power off the system. Automatic control switch (2): In order to enter the full "AUTO" Mode for automatic climate control, push this switch. However, if the switch is pushed again, the air conditioning can not be turned off. When the system is in full "AUTO" Mode, specific functions can be manually changed by pushing another switch.
If a specific function is manually changed, "AUTO" will not appear in the display, but the unchanged functions will remain in "AUTO" mode. Press the "AUTO" switch for full "AUTO" mode. Push the temperature switch (3) in order to set the desired temperature. The temperature is shown in metric values, but can be changed to SAE values. All other functions of climate control will be handled automatically.
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In order to take advantage of the full "AUTO" setting of the climate control system, always keep the sunlight sensor clean. Do not obstruct the sunlight sensor. If the climate control system is in the full "AUTO" setting at engine start-up and the temperature inside the cab is too warm or too cool, the damper for fresh air ventilation may automatically close for a few minutes. This will help to bring the air temperature to the preset temperature more quickly. Temperature Switch (3): The switch controls the temperature of the air coming from the air outlets in order to achieve the preset temperature. The preset temperature appears on display. If the heating and air conditioning system is in the automatic mode, pushing these switches
changes the preset temperature. LCD panel (4): The panel displays the settings of the HVAC system. Fan switch (5): The fan switch directly controls the fan speed. If the climate control system is operating in the automatic mode, pushing this switch overrides the automatically selected fan speed. Compressor switch (6): Push the switch in order to turn on the compressor or push the switch in order to turn off the compressor. In humid conditions, the compressor may be used to remove moisture from the air in the cab. In cool weather, operate the compressor weekly in order to prevent leakage of the refrigerant gas and to help maintain the compressor in optimum working order. Defrost Mode (7): Depressing this switch will defog the windows. The air will also be dehumidified while the compressor is running. Air inlet select switch (8): This switch selects the position of the air inlet for recirculation or for fresh air. Air outlet select switch (9): This switch selects the position of each air outlet. Each switch controls a different air outlet. The air outlets are the:
- upper body - upper body and floor - floor - floor and defroster NOTE: In order to convert the temperature reading from Degrees Celsius to Degrees Fahrenheit, depress both keys of the fan switch at the same time for five seconds. The
same action is used for converting the temperature reading from Degrees Fahrenheit to Degrees Celsius.
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The back-up switches are located behind the right armrest. The right switch (1) controls the engine rpm. The left switch (2) toggles between back-up and auto. The left switch activates/deactivates the Back-up Mode. When Back-up Mode is active, a fixed power shift pressure is provided to the pumps. The fixed power shift pressure limits maximum pump output and allows the machine to continue operating in a Derate Mode. Machine productivity will be limited while the machine is in Back-up Mode. The right switch is used to control the engine speed while Back-up Mode is active. Holding the right switch in the DOWN position decreases the engine rpm. Holding the right switch in the UP position increases the engine rpm . The diagnostic connector (3) is located inside of the operator's station behind the right armrest, beside the back-up switches.
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The fuse panel (1) has been relocated to the left side of the lunch box panel behind the operator's seat. Some of the relays (2) are also part of the fuse panel. A decal (3) on the cover identifies the fuses.
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The 300D monitor has been updated. The new monitor is used on 311D-330D, 345C, 365C, and the 385C machines. The monitor is a full color Liquid Crystal Display (LCD) that displays the various parameters of the machine. - alert indicator (1) - clock (2) - fuel gauge (3) - hydraulic oil temperature gauge (4) - engine speed dial indicator (5) - engine coolant temperature gauge (6) - operating hours (7) - work tool indicator (8)
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The monitor contains eight buttons that control navigation on the monitor screen. The four directional buttons are: - left (1) - up (2) - down (3) - right (4) The directional buttons navigate the cursor through the various screens. The four navigational buttons are: - home (5) - menu (6) - back (7) - OK (8)
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Cat ET or the monitoring system can be used for testing and calibrating the machine. Extended fluid change intervals are available with the proper S•O•S procedures. Maintenance intervals for several components and systems on the machine are programmed into the monitor. The operator can access component maintenance intervals to see the hours remaining before maintenance is due. Some of the maintenance items are: - hydraulic oil and hydraul ic oil filter changes - swing drive oil change - travel drive oil change - engine oil and engine oil filter changes
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The illustration above shows the display setup for the 300D Series excavators. NOTE: Refer to the Self-study CD-ROM "300D Series Hydraulic Excavators, 345C Hydraulic Excavator, and 365C & 385C Large Hydraulic Excavators Monitoring System (form SERV7032) for more details on the monitor.
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ELECTRONIC CONTRO L SYSTEM
The electronic control system controls many of the functions of the 315D/319D Excavators and is very similar to the 320D-330D Excavators. The electronic control system uses two data links to communicate: - The Engine ECM, the Machine ECM, the monitor, Cat ET, the optional Product Link, and the optional Machine Security System communicate via the Cat Data Link. - The soft switch panel communicates with the ECMs and the monitor on the J1939 CAN Data Link. The soft switch panel is not connected to the Cat Data Link. The input and output components of the Machine ECM are shown in this illustration.
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The Machine ECM (1) is located on the left side of the machine in the compartment behind the cab. The inputs and outputs of the Machine ECM connect to the machine harness by two 54 pin connectors (2).
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Engine Speed Control
The Machine ECM converts the signal from the engine speed dial into a pulse width modulated (PWM) signal. The information is then sent to the Engine ECM over the Cat Data Link. The engine speed dial is divided into 10 positions. The dial position is displayed on the character display of the monitor panel.
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Automatic Engine Control (AEC)
The AEC will lower the engine speed if no load on the machine continues for approximately five seconds or a light load on the machine continues for ten seconds when the engine speed dial is set in a position of 5 to 10. This process is designed to reduce noise and fuel consumption. The engine speed dial, the AEC switch, the implement pressure switch, and the travel pressure switch send input signals to the Machine ECM. The Machine ECM processes the input signals and sends corresponding output signals to the Engine ECM to control the engine speed. The AEC has settings in two stages. The AEC is set by the AEC switch. The switch indicator will illuminate during the second setting of the AEC. The second setting of the AEC is available immediately after the engine start switch is turned to the ON position. The AEC can be set in the first stage and the second stage by alternately pressing the switch. The first setting of the AEC will lower the speed setting of the engine speed dial by approximately 100 rpm in the "no load" condition.
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The second setting of the AEC will reduce the engine speed to approximately 1300 rpm in the "no load" condition. When the main back-up switch is turned to the ON position (Manual), the AEC function is disabled. NOTE:
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One Touch Low Idle
When the one touch low idle switch is pressed and the machine is not under a load, the engine speed can be lowered by more than the speed setting of the AEC second stage. When normal operations have resumed, the engine speed for the dial setting will return to the corresponding rpm. The one touch low idle feature will activate during all "stopped" conditions of the implement, swing, travel, and tools. The one touch low idle switch, the implement pressure switch, and the travel pressure switch send input signals to the Machine ECM. The Machine ECM processes the input signals and sends corresponding output signals to the Engine ECM to control the engine speed. The following components are in the OFF position: the implement pressure switch, the travel pressure switch, and the attachment (ATT) pedal pressure switch. However, when the one touch low idle switch is pressed, the control will lower the engine speed to the speed of the "2" setting of the engine speed dial to approximately 1020 rpm. This control overrides the AEC.
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The one touch low idle will be released when any of the following conditions occur: - The one touch low id le switch is pressed again. - The implement pressure switch is set to the ON position. - The travel pressure switch is set to the ON position. - A pressure switch that is related to a tool is set to the ON pos ition.
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Engine Speed Protection
Engine speed protection is designed to prevent the engine from starting at a high speed during a condition of low oil pressure. After the engine oil filter is replaced, a long time may be required before the ending oil pressure will reach the specified level. Engine damage may occur if the engine runs at the speed dial position of 10. The following information describes this function. The engine oil pressure switch sends a signal to the Engine ECM. The Engine ECM controls the engine speed. The engine speed will be limited to the 5 position, if the engine oil pressure switch is open. The engine will start at speed dial position 5. Engine speed protection prevents damage to the engine that is caused by overspeed during an overheating condition. Work that requires high pressure will be restricted during an overheating condition. The engine and other components are protected during this condition. The engine speed will be decreased to the second setting of the AEC (1300 rpm).
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When it is cold and the temperature of the hydraulic oil is low, the machine may not operate smoothly. Pump output will decrease by a small amount. This allows the operations to be smoother until the temperature of the oil rises. When the hydraulic oil temperature sensor has detected an oil temperature below 15° C (59° F) the system limits hydraulic pump output pressure to 80% of maximum hydraulic horsepower. When the hydraulic oil temperature sensor detects an oil temperature that has risen above 20° C (68° F), normal control of the hydraulic oil will begin again.
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Travel Speed Control
There are two travel speed modes, low-speed (tortoise) and high-speed (rabbit). By selecting the "tortoise" mode, travel speed is limited to the low travel speed. By selecting the "rabbit" mode, travel speed will change automatically between low/high speeds. The change in travel speed is dependent on the delivery pressure of the pump. The travel speed switch, the implement pump pressure sensors, and the travel pressure switch send input signals to the Machine ECM. The Machine ECM processes the input signals and sends corresponding output signals to the travel speed change solenoid to control travel speed. The travel mode selector switch and travel mode indicators (tortoise and rabbit) are located on the switch panel. When the travel mode selector switch is pressed, the travel mode can be set to the rabbit mode or set to the tortoise mode. The indicator (tortoise or rabbit) will be illuminated to show the travel mode that is chosen.
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The travel speed will automatically be set to the LOW (tortoise) speed when the machine is first turned on. To select the HIGH (rabbit) speed mode, press the travel mode selector switch. While the circuit pressure at the pump output remains below a certain range, the machine will travel in the HIGH (rabbit) speed. The output pressure of the pump increases as the load on the machine increases. When the output pressure increases to a certain high level, the machine will automatically shift to travel in the LOW (tortoise) speed mode. The machine will automatically return to the HIGH (rabbit) speed mode when the pump output pressure decreases to the predetermined range. The automatic speed change function allows(rabbit) the machine adjust speeds without operator input. travel The machine will travel at HIGH speed to under a light load. The direct machine will travel at LOW (tortoise) speed under a heavy load. This ensures that the machine has high mobility and a high drawbar pull. When the travel is set to the tortoise mode, the travel is set at low speed and does not change.
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Swing Brake Operation
This machine is equipped with a swing lock system that is controlled by the Machine ECM. The swing lock system control circuit provides control for the swing motor, swing brake, fine swing function, and back-up system of the machine. The swing brake solenoid is controlled by the implement pressure switch through the Machine ECM. When the implement pressure switch closes, the Machine ECM energizes the swing brake solenoid. When the implement pressure switch opens, the swing brake solenoid is de-energizes by the Machine ECM 6.5 seconds later. The de-energized swing brake solenoid allows the machine upper structure to come to a complete stop before the swing brake is engaged. The hydraulic activation lever must be in the activated (UP) position before the spring brake solenoid will energize. If the main back-up switch is placed in the Manual position, then the swing brake is electrically released. The fine swing function (optional) provides smooth start and stop operation during swing movement.
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When the fine swing switch is activated, a signal is sent to the soft switch panel which sends a signal to the Machine ECM. The Machine ECM energizes the fine swing solenoid to activate the fine swing feature.
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Back-up System
The "Back-up System" allows an operator to manually control a limited amount of machine functions to move a machine in the event that other machine functions have failed. The main back-up switch is located to the right rear of the console. When the main back-up switch is turned to the MAN position, the power to the Machine ECM is removed, and the "Limited Mobility Mode" is activated. In Limited Mobility Mode, the engine speed dial does not function. The engine speed can be adjusted by the engine speed selector switch that is located to the right rear of the console. Also, the AEC switch and the low idle switch will not function. The Monitoring System will display the message "LIMITED MOBILITY MODE" on the Monitoring System and the Monitoring System will sound the action alarm. The back-up switch provides the minimum machine functions. The back-up switch allows a direct connection, through a resistor, between the key start switch and the Engine ECM, power shift solenoid, and swing brake solenoid.
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The Limited Mobility Mode allows the operator to maneuver the machine to the shop when the Machine ECM has failed. Excavating operations are not possible if the machine is in the Limited Mobility Mode.
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C4.2 ACERT™ ENGINE
The 315D/319D Excavators are equipped with a C4.2 ACERT™ Engine. The C4.2 engine is a 4.2 liter engine that uses a common rail fuel system. The common rail fuel system includes an electronically controlled high pressure fuel injection pump, a fuel manifold, and electronically controlled injectors. The A4:E2 Engine ECM controls the pump solenoid, which controls the injection pump fuel flow through high pressure lines to the fuel injectors. The Engine ECM also controls the on/off fuel injector solenoids. The C4.2 ACERT™ engines meet U.S. Environmental Protection Agency (EPA) Tier III Emissions Regulations for the North America market and Stage IIIa European Emissions Regulations. This presentation provides an overview of the common rail fuel system and covers 315D/319D Excavators engine component locations. For detailed information on the C4.2 ACERT™ Engine, refer to Service Training Meeting Guide "C4.2/C6.4 and C4.4/C6.6 ACERT™ Engines with Common Rail Fuel System--Machine Applications" (SERV1837). NOTE:
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Basic machine specifications for the C4.2 engine are: - Configuration: Four cylinders inline, 16-valve crossflow cylinder head - Fuel System: Direct injection, common rail - Aspiration: Turbo-ATAAC - ECM: A4:E2 - Rated power: 91 - 98 kW (122 - 131 hp) @ 1700 - 2200 rpm - Displacement: 4.2 liter (256 in3) - Bore: 102 mm (4.02 in.) - Stroke: 130 mm (5.12 in.) - Compression ratio: 16.5:1
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Some of the C4.2 ACERT™ engine features are: - The high pressure fuel pump is controlled by the Engine ECM and provides high pressure fuel to the injectors. - The electronically controlled injectors are controlled by the Engine ECM to inject high pressure fuel into the combustion chamber. - The cylinder head includes 4 valves per cylinder. - The engine block includes a scalloped crank case with extra ribbing, which provides a more ridged structure with a lower noise attenuation (sound absorption). - The aluminum pistons have im proved oil control. - The A4:E2 Engine ECM controls fuel pressure, speed governing, air/fuel ratio, engine start/stop strategy, and provides diagnostics. - The common rail fuel system allows tight control of injection events and optimizes engine performance across all load and speed ranges. The common rail system reduces combustion noise, and NOx and PM emissions.
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Contamination control is critical with the common rail fuel system. Very high pressures require close tolerances in the fuel injection pump and injectors. It is important that technicians pay close attention to cleanliness and contamination control during even the most routine maintenance. Keep components in their srcinal packaging until ready to install and inspect packaging to ensure components are still sealed and free of dirt or damage. High pressure fuel lines are single use items and must be replaced after unseating any fittings. The common rail fittings/ports and the injector fittings/ports must be capped immediately after unseating. Do not remove the caps from new components until just before the fittings are tightened. New pipes must be handled carefully and not bent in any way. If a sealing cap is not on each end of the pipe when a new pipe is removed from the packaging, it must not be used. Do not use compressed air or solvent to clean any fuel system components. All fittings must be torqued to the correct specification. If a leak occurs, replace the pipe with new pipe. The rubber boots that seal the valve cover opening are also single use parts. Similarly, any retaining clips that are removed should be replaced with new clips to ensure they fasten properly. During reassembly, be sure the clips are placed in the proper locations to prevent vibration and potential leaks from occurring. Fuel pressures between the injection pump and fuel injectors can reach 160 MPa (23,200 psi), so specific safety procedures must be carefully followed.
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WARNING
Never loosen or open a high pressure fuel line while cranking or running a Common Rail fuel system engine. Common Rail fuel systems operate at extremely high pressures often in excess of 160 MPa (23,200 psi). Extreme care should also be taken before disassembly of any high pressure fuel system components after an engine shutdown. Refer to the appropriate service information before performing any service on the high pressure fuel system components.
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This illustration shows an overhead view of the C6.4 engine cylinder head with the rocker cover removed. The C4.2 components are the same. The C4.2 is a four valve per cylinder engine with the valves arranged in an exhaust-intake manner from the front of the cylinder head to the rear. Exhaust valves are actuated by the short rocker arm (1) which presses down the exhaust valve bridge (2) and unseats the exhaust valve pair. Long intake rocker arms (3) are used to depress the intake valve bridge (4) and open the intake valves. The electronic fuel injector (5) is centrally located between the intake and exhaust valve pairs for each cylinder. The Engine ECM will control the duration and timing of the fuel injector in relation to sensor inputs to achieve maximum fuel efficiency emissions compliance. A large rubber boot (6) seals the opening in the valve cover base where the high pressure fuel injector supply line passes through the base and connects to the fuel injector. The cylinder head features a "crossflow" design where the intake air enters the right side of the cylinder head and the exhaust gasses exit the left side through the exhaust manifold (7).
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Fuel System
The common rail fuel system includes a low pressure fuel circuit and a high pressure fuel circuit. This schematic shows the fuel flow through the common rail fuel system. The low pressure fuel circuit supplies filtered fuel to the fuel injection pump at a constant rate. The low pressure fuel circuit consists of the following major components that are used to deliver low pressure fuel at approximately 296 - 400 kPa (43 - 58 psi) to the fuel injection pump: - Primary fuel filter. - Secondary fuel filter. - Tertiary (third) fuel filter. - Fuel tank. - Supply lines and return lines deliver the fuel to the different components.
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- Fuel transfer pump pulls fuel from the tank and supplies the fuel to the fuel injection pump. The transfer pump includes two orifices that control the pressure in the low pressure fuel circuit. - Fuel priming pump is used to evacuate the air from the fuel system. As the air is removed the system fills with fuel. The fuel transfer pump pulls fuel from the tank through the primary fuel filter and sends the fuel to the priming pump. From the priming pump fuel flows to the secondary and tertiary (third) filter to the high pressure fuel injection pump. The high pressure fuel circuit supplies high pressure fuel from the fuel injection pump through the fuel manifold to the fuel injectors. The fuel injection pump supplies fuel at a pressure up to 160,000 kPa (23,200 psi) to the fuel injectors. Fuel from the fuel injection pump is sent to the fuel manifold. The manifold distributes the fuel through high pressure fuel lines to the injectors. The manifold also contains a pressure relief valve and fuel pressure sensor. The pressure relief valve limits the maximum pressure in the high pressure fuel circuit. The fuel pressure sensor sends a signal to the Engine ECM indicating fuel pressure in the high pressure fuel circuit. The injectors inject the fuel into the combustion chamber based on an ON/OFF signal from the Engine ECM.
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This Engine Electronic Control Systemdiagram shows the input and output components of the C4.2 engine electronic control system. The Engine ECM has two 64-pin sockets connected to the engine harness and machine harness. The input components provide the Engine ECM with inputs that control the following outputs: the fuel, the injectors, and the fuel pump. The input components shown on the left provide the Engine ECM with inputs to control the engine functions. The engine electronic control system primarily performs the engine fuel control function. A solenoid on each injector receives an ON/OFF signal from the Engine ECM that triggers the timing and amount of fuel delivered to the combustion chamber. The engine electronic control system also monitors other functions that are critical for engine performance, such as lubrication, combustion air, and cooling.
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Input Components: Engine coolant temperature sensor - This sensor is an input to the Engine ECM supplying information on the temperature of the engine coolant. Intake manifold air pressure sensor - This sensor is an input to the Engine ECM supplying information about air pressure (boost) into the intake manifold. Engine oi l pressure sensor - This sensor is an input to the Engine ECM to supply information on engine oil pressure. The ECM uses this information for low oil pressure warnings, for
engine derates for low oil pressure, or for logged events. Intake manifold air temperature sens or - This sensor is an input to the Engine ECM to supply information about the air temperature entering the intake manifold from the turbocharger. Fuel rail pressure sensor - This input sensor sends the fuel manifold pressure feedback data to the Engine ECM. Turbocharger inlet pressure sensor - This sensor is an input to the Engine ECM to supply information about the air restriction before the turbocharger. The ECM uses this information for engine derates and logged events. Engine shutdown switch - This switch is an input to the Engine ECM. This input disables fuel injection when the engine is running or at engine start-up. Key start switch ON (+B) - The Key On input to the Engine ECM enables the ECM for operation and allows the Engine ECM to be recognized by any ECM on the machine. Primary Speed timing sensor - This sensor is an input to the Engine ECM to supply engine speed information. Secondary Speed timing sensor - This sensor is an input to the Engine ECM to supply fuel pump (camshaft) speed information. Engine speed dial - The engine speed dial is an input to the Machine ECM indicating desired engine speed. The Machine ECM sends an engine speed request signal to the Engine ECM via the Cat Data Link. Fuel pressure sensor - The fuel pressure sensor sends a signal to the Engine ECM indicating fuel pressure. Fuel differential pressure sensor - The fuel pressure sensor sends a signal to the Engine ECM
indicating fuel the secondary fuel filter differential pressure. Fuel temperature sensor - The fuel temperature sensor sends a signal to the Engine ECM indicating fuel temperature. Water-in-fuel sensor - The water-in-fuel sensor sends a signal to the Engine ECM indicating moisture in the fuel system.
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Output Components: Fuel injectors (quantity 4) - ON/OFF injector solenoids supply fuel to the engine. Pump solenoid - The pump solenoid controls the pump output pressure by allowing some of the high pressure fuel to return to the tank. Air inlet heater relay - This relay transfers power to the air inlet heater to heat the incoming air when the engine is cold.
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The C4.2 uses an A4:E2 Engine ECM (1). The ECM is mounted on a bracket in front of the A/C condenser (2) on the left side of the machine. The ECM controls: - Fuel pressure - Speed governing - Air/fuel ratio - Start/stop sequence - Engine protection devices/diagnostics The ECM features two 64-pin sockets for the machine harness connector (3) and the engine harness connector (4).
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The ECM case is completely sealed against dirt and moisture. When reinstalling the ECM, make sure the grounding strap (5) is secured to a clean connection and the fasteners are properly torqued. Anti-vibration mounts fit into the holes at each corner (6).
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Engine Components visible from the top of the C4.2 engine are: - Engine breather (1) - Oil fill cap (2) - Turbocharger (3) - Air inlet heater (4) - Secondary fuel filter (5) - Fuel priming pump (6) - Engine oil dipstick (7) - Tertiary (third) fuel filter (8)
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The primary fuel filter is located in the left rear compartment behind the cab. The primary fuel filter assembly consists of the fuel filter base (1), the primary fuel filter element (2), and the fuel/water separator (3). Water in a high pressure fuel system can cause premature failure of the fuel injectors due to corrosion and lack of lubrication. Water should be drained from the water separator daily using the drain valve (4) at the bottom of the filter. The water-in-fuel sensor (5) sends a signal to the Engine ECM indicating moisture in the fuel system.
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This illustration shows the left side of the engine with the counterweight removed. Engine components visible from the left side of the C4.2 engine are: - Alternator (1) - Turbocharger (2) - Muffler (3) - Starter (4) - Air inlet heater relay (5) - A/C Compressor (6)
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This illustration shows components visible from the right side of the C4.2 engine. The Safeguard fuel filter (1) is the tertiary (third) fuel filter in the C4.2 fuel system. Similar to the secondary fuel filter, the Safeguard filter is a high efficiency filter. All fuel entering the high pressure section of the injection pump must pass through the secondary fuel filter and the tertiary fuel filter. The secondary fuel filter (2) is a high efficiency filter located on the right side of the engine. Fuel flows from the transfer pump through the priming pump (3) and then to the inlet of the secondary filter. When replacing a fuel filter on the C4.2 engine, the fuel system must be primed prior to starting or cranking the engine. Do not prefill new fuel filters prior to installation on the engine. Prefilling the filters can introduce contaminants into the fuel system and cause damage. The maintenance schedule for the Safeguard filter is different than the maintenance schedule for the primary and secondary fuel filters. Refer to the appropriate operation and maintenance manual for the recommended service interval for all fuel system filters. NOTE:
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Priming is accomplished using the hand priming pump. Open the air bleed plug. Pump the plunger (4) more than 100 times to prime the system. After priming the fuel system there should be sufficient fuel in the fuel filters to allow the engine to start and run. Do not open any fuel lines during the priming procedure. Primary engine speed data is provided by the primary engine speed/timing sensor (5), or crank speed/timing sensor. The primary engine speed/timing sensor is located on the flywheel housing at the right rear of the engine block. Failure of the primary engine speed sensor while the engine is running will cause the Engine ECM will to look at the to secondary pump sensor for engine speed information. The engine continue run usingoronly thespeed secondary speed sensor signal for engine rpm. The primary and secondary speed/timing sensor are the same part number. The engine oil pressure sensor (6) is also located on the right side of the engine block. The sensor is installed in the right engine oil galley. Low engine oil pressure, sensor failure, or wiring failure will not result in an engine derate or shutdown but will cause a fault to be logged in the Engine ECM. The status of the primary engine speed sensor and the engine oil pressure sensor can be viewed with Cat ET. Also visible in this illustration is the engine oil dipstick (7) and the fuel injection pump (8).
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The fuel injection pump (1) is gear driven and mounts to the back of the front timing cover on the right side of the engine. The transfer pump (2) is mounted on the rear of the injection pump. The transfer pump includes a weep hole on the bottom of the pump to allow a fuel path if fuel seeps from the pump. To remove the fuel transfer pump, special tool 239-6824 is required. The injection pump and pump solenoid (3) are not serviceable. The injection pump is serviceable as a unit. The transfer pump and the secondary speed/timing sensor (4) are the only components serviced separately on the pump. The primary and secondary speed/timing sensor are the same part number. The pump must be removed from the engine to remove the secondary speed/timing sensor. NOTE:
The fuel injection pump must be timed to the engine and the pump must be removed to be timed. The injection pump gear is keyed to the pump shaft. To time the injection pump to the engine, the pump gear must be aligned to the engine gears by aligning the timing marks on each gear. Note the injections pump's srcinal position by observing the paint marks on the front gear train before removing the pump.
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The high pressure fuel injection pump is capable of developing pressures up to 160 MPa (23,200 psi). The high pressure pump is lubricated by engine oil supplied by a pressure line from the left side engine oil galley. Engine speed and engine position are determined by the secondary engine speed sensor. The Engine ECM monitors the secondary engine speed sensor and the primary engine speed sensor (located at the rear of the engine) to determine crankshaft position and engine rpm. If the Engine ECM does not receive a signal from the secondary speed/timing sensor due to a sensor or wiring fault,is the engine the willEngine not start. However, the down secondary sensor or wiring fails while the engine running, ECM will notifshut the engine. The Engine ECM will continue to fire the fuel injectors based on the primary speed position sensor signal the Engine ECM detected at last engine startup. The status of the engine speed sensors can be monitored using Cat ET. The coolant temperature sensor (5) is installed in the front left corner of the cylinder head. The coolant temp sensor is a "passive" two wire variable resistor type sensor that sends a signal to the Engine ECM indicating coolant temperature.
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The injection pump includes two pump plungers and two cam journals. Each cam journal includes two cam lobes, which causes each pump plunger to stroke two times for each revolution of the pump. The injection pump solenoid controls the injection pump output pressure to the common rail manifold. The Engine ECM sends a signal to the pressure control which will spill or "bleed off" excess pressure from the head of the high pressure pump. Excess fuel pressure not needed for injection is returned to the fuel tank. The fuel transfer pump sends fuel to the pump solenoid and to the chamber at the top of each plunger. When the engine is running and the drive shaft is rotating, the cam lobes move the plungers up which sends the fuel to the fuel manifold and through a shuttle valve to the pump solenoid. The fuel manifold distributes the fuel to the fuel injectors. The pump solenoid meters the fuel to the manifold.
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The fuel temperature sensor (1) and the fuel pressure sensor (2) are installed in the secondary filter base assembly. The fuel temperature sensor is part of the fuel filter monitoring system. By monitoring the temperature of the fuel entering the fuel filtration system, the fuel temperature sensor helps to prevent false fuel filter restriction events in either the primary or secondary filters due to cold, high viscosity fuel. The fuel pressure sensor monitors the fuel pressure in the low pressure fuel circuit. The fuel differential pressure sensor (3) monitors the secondary fuel filter for filter restriction. If the secondary fuel filter becomes clogged, the secondary fuel pressure switch will open and the Engine ECM will activate the action lamp in the cab and log a secondary fuel filter restriction event. The engine will also derate 20% if the secondary fuel filter is 80% restricted.
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This illustration shows the common rail fuel manifold (1). The common rail fuel manifold is mounted to the right side of the inlet air manifold on the right side of the engine. To access the manifold a cover (2) must be removed. High pressure fuel from the fuel injection pump enters the common rail manifold at the inlet fitting (not visible). The common rail manifold distributes the high pressure fuel evenly to the four fuel injector supply pipes (3). The steel fuel pipes pass through the valve cover base and connect to individual fuel injectors. A fuel rail pressure sensor (not visible) is used to monitor the pressure of the common rail high pressure fuel system. The Engine ECM will monitor the signal from the fuel rail pressure sensor and maintain optimum fuel system pressure for any given load or temperature condition. A fuel pressure relief valve (not visible) is used to protect the high pressure fuel system from fuel pressure spikes. The fuel pressure relief valve will open at a constant pressure of 130 MPa (18,855 psi) and withstand a pressure spike of up to 190 MPa (27,560 psi).
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The engine shutdown switch (arrow) is located on the left side of the operator's seat. When activated, the engine shutdown switch sends a signal to the Engine ECM to shutdown the engine.
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The left illustration shows the high pressure fuel injector. When replacing an injector, the following parts must also be replaced: - Injector pipe. - O-ring (1). - Copper injector washer. The copper washer is installed at the top of the injector tip (2). - Injector hold down bolt. - Rubber boot that seals the valve cover ope ning. - Valve cover gasket. When removing a pipe and reusing an injector, always cap the injector immediately until ready to install a new pipe. Finger tighten all pipes and clamps first, and then torque properly. Do not over tighten the solenoid connections on top of the injector. Use the proper torque specification in the service information.
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The injector serial number (3) and confirmation code (4) are used for trimming the injector. The bar code (5) is used during injector production. Document the injector serial number and confirmation code before installing a new injector. Cat ET is used to flash the ECM with the proper injector trim file. The injector trim file can be found on the CD that comes with the replacement injector or on the Service Information System (SIS) Web.
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Air Inlet Syst em
Intake air is drawn into the engine air precleaner by the vacuum created by the compressor wheel in the turbocharger. The precleaner removes any large particles from the intake air and ejects them through the exhaust stack. The intake air is then drawn through the air cleaner elements in the air cleaner housing where any fine contaminants are removed by the filter elements. Cleaned intake air is then drawn into the compressor side of the turbocharger. The turbocharger compresses the intake air and forces it out of the compressor outlet. The heated and compressed intake air next flows to the inlet of the ATAAC core. As the intake air passes through the ATAAC core, the air is cooled by the flow of air from the engine fan and becomes more dense. Compressed, cooled intake air is next directed to the inlet air manifold, through the inlet air tube, and into the cylinder head. During the intake stroke, air is forced into the cylinders around the intake valves in the cylinder head.
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The exhaust manifold directs exhaust gasses to the turbine side of the turbocharger. Hot, high pressure exhaust gasses contact the blades of the turbine wheel inside the turbine housing causing the turbine shaft to spin. The turbine shaft is mechanically connected to the compressor wheel on the inlet side of the turbocharger. The hot exhaust gas stream gives up most of its energy to the exhaust turbine wheel. This low energy exhaust stream exits the turbine housing through the turbine nozzle, flows through the exhaust pipe and into the muffler, and finally exits at the exhaust stack.
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For cold weather starting, the C4.2 engine uses an inlet air heater (1). The inlet air heater heats the incoming air to aid in engine starting during cold weather. The air inlet heater relay (2) is controlled by the Engine ECM. Based on the engine air and engine coolant temperature, the ECM will energize the air inlet relay, which provides power to the inlet heating element.
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This illustration shows the inlet air temperature sensor (1) and the inlet air pressure (boost) sensor (2) installed in the air inlet manifold on the right side of the C4.2 engine. The inlet air temperature sensor is a passive 2 wire sensor and is an input to the Engine ECM. The signals from the inlet air temperature sensor and the coolant temperature sensor are used to determine engine starting aid requirements and to trim (adjust) injector pulse width as engine operating temperatures change. The air inlet pressure sensor is an active 3 wire sensor. The Engine ECM will use the signal from this sensor to determine boost pressures supplied by the turbocharger. The air inlet pressure sensor is used with the Engine ECM to control the air/fuel ratio electronically. This feature allows very precise smoke control, which was not possible with mechanically governed engines. The air inlet pressure sensor also acts as an atmospheric pressure sensor by taking a snap shot of atmospheric pressure when the key start switch is first turned to the ON position. NOTE:
The status of the inlet air temperature sensor and the inlet air pressure sensor can be viewed with Cat ET.
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PILOT SYSTEM
The oil delivered from the pilot pump performs the following main functions. - Provides pilot oil pressure to the pilot control valves for implements, swing and travel to perform machine operations. - Creates pilot oil pressure to control the output flows of the main pumps. - Creates pilot oil pressure to automatically operate the control devices. The pilot circuit is classified into the following circuits and each circuit performs one of the above functions. - pilot control valve circuit
- power shift pressure system
- pressure switch circuits - swing parking brake
- straight travel valve circuit - boom priority
- swing priority
- automatic travel speed change
This section of the presentation will cover the pilot manifold, the implement joysticks, and the travel pilot valves.
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A gear-type pilot pump (1) provides oil flow to the pilot system. The pilot pump is mechanically connected to the drive pump. The oil delivery from the pilot pump flows through the pilot oil filter (2) and into the components in the pilot system. The pilot relief valve (3) is located on the mounting base for the pilot oil filter. The pilot relief valve limits the pressure in the pilot system. The pilot relief valve setting is adjustable. Pilot system pressure can be checked at the test port (4) on the right side of the filter base. Next to the pilot pressure test port is the pilot system S•O•S port (5).
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The filter element in the pilot oil filter removes contaminants from the pilot oil. If the pilot oil is extremely cold or if the flow of pilot oil through filter element becomes restricted by contaminants, the oil bypasses the filter element through the bypass relief valve. The bypass relief valve is built into the base for the pilot oil filter. The pilot oil flows from the pilot pump to the inlet port. When the pressure in the pilot oil system reaches the pressure setting of the pilot relief valve, part of the pilot oil flow is returned to the hydraulic tank through the port. The pressure of the pilot system oil in outlet lines is equal to the pressure setting of the pilot relief valve.
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Pilot Manifold
The pilot manifold is the same as the "C" pilot manifold. The pilot manifold is located next to the main control valve group. The hydraulic activation valve (1) and solenoid (2) are located in the pilot manifold along with the swing brake solenoid (3) and the two-speed travel solenoid (4). The accumulator (5) will provide pilot pressure oil to the pilot system when the pilot pump flow is inadequate. Insufficient pilot oil flow to the pilot system may be caused by the following two reasons: - Implements are lowered while the engine is stopped and oil supply to the main control valves is stopped. - Combined implement/swing/travel operations.
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Oil from the pilot pump enters the pilot manifold to be distributed to the various components of the machine. Some of the pilot oil flow is directed to the swing priority valve, and to the two speed travel solenoid valve. The rest of the pilot oil flows through the check valve. Two Speed Solenoid Valve: The two speed solenoid valve directs oil flow to the displacement change valve in the travel motor. In the illustration above, the solenoid is energized. Pilot oil is directed to the travel motors to shift the displacement change valves (not shown). When the displacement change valves shift, the motors will destroke for higher speed. Check Valve: The pilot manifold also contains a check valve. The check valve maintains pilot accumulator pressure in the pilot circuit when the engine is not running. Pilot Accumulator: The pilot accumulator is used to release the swing brake and for lowering the boom and stick in the event of a loss of pilot system pressure or a dead engine. The pilot accumulator also helps to dampen pressure spikes in the pilot system, which enhances the stability of the machine control systems.
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The accumulator stores pilot pressure oil for use at the main control valves. During some operations, the pilot system needs more oil because there is insufficient flow from the pilot pump. Implement Hydraulic Lockout Solenoid Valve and Hydraulic Activation Valve: These two valves work together to either prevent the implement control valves and the motors from being activated or to allow them to be activated. In the de-energized position, no pilot oil is available to operate the implements. Pilot oil is blocked at both valves.
When theswitch hydraulic lockout control lever by in the the control cab is inlever. or moved to theswitch LOCKED the limit plunger is not depressed The limit is in position, the OFF state. When the hydraulic activation control lever is in the LOCKED position, the hydraulic activation solenoid is not energized. The spool is held up by a spring. The spool blocks the pilot supply oil from going to the pilot valves. The spool also opens a passage to drain from the pilot valves to the tank. In the locked position, if the joysticks are moved the cylinders and the motors cannot be activated. Swing Brake Solenoid Valve: The swing brake solenoid valve energizes to release the spring-applied, hydraulically-released wet disc swing brake. The swing brake is automatically released when any implement joystick function is performed by the operator. With the swing brake solenoid valve de-energized the swing brake is engaged by springs.
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When the hydraulic lockout control lever in the cab is placed in the UNLOCKED position, the limit switch closes the circuit path and the lockout solenoid valve is energized. When the implement hydraulic lockout solenoid valve is energized, pilot oil is directed to move the hydraulic activation valve down. Pilot oil flows through the hydraulic activation valve to the swing brake solenoid valve, the left and right joysticks, and the travel pilot valves. When a implement is activated the swing brake solenoid is energized by the Machine ECM. Pilot oil is directed through the swing brake solenoid valve to release the swing park brake in the swing motor group.
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Hydraulic Activation Lever
The hydraulic lockout lever (arrow) is shown in the LOCKED position in the top illustration. The engine will not start unless the hydraulic activation lever is in the LOCKED position. Raise the lever activation lever to the UNLOCKED position (bottom illustration) to energize the implement hydraulic lockout solenoid valve and allow the operator to move the implements. If the machine is running, the operator can lockout the implement controls by returning the lever to the LOCKED position.
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A limit switch and plunger are located on a bracket with the hydraulic lockout lever. When the hydraulic activation control lever is moved forward, the lever pushes the plunger down to activate the limit switch. When the hydraulic lockout control lever is shifted to the rear to the LOCKED position, the implement lockout solenoid valve is not energized, so the hydraulic activation valve does not shift to direct pilot oil to the pilot control valves. The joysticks and/or travel pedals can not shift a control valve in the main control valve group when the hydraulic activation lever is in the locked position.
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Pilot Controls and Valves
Pilot controls in the cab include: - left (1) and right (2) travel pedals - left (3) and right (4) travel levers - hydraulic hammer pedal (5) (optional) - straight travel pedal (6) (optional) - left joystick (7) to control the swing and stick (SAE HEX pattern) - right joystick (8) to control the bucket and boom (SAE HEX pattern) - foot rest (9 and 10)
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When the pilot joystick lever is shifted, the joystick contacts the rod and pushes it down against its spring. The rod will contact the spool and move it down against its spring. Depending on how far the lever is shifted, determines how far the spool moves. As the spool moves down, the spool will close off the drain passage for the oil to the control valve and meter pilot oil to the control valve to cause the control spool (not shown) to shift. The greater the pilot oil flow to the control spool the greater the control spool travel. As pressure increases in the pilot line to the control valve, the pressure works on the spool to move the spool up to a balance position against the spool and plunger springs to maintain the pilot pressure in the pilot line. This action will maintain the position of the control spool in the control valve until the joystick is moved. In summary, once the pilot lever is shifted, the pilot valve becomes a pressure reducing valve which maintains a downstream pressure equal to the spring forces above the spool. When the joystick is released, the joystick will return to the NEUTRAL position due to the force of the spring moving the spool back up. When this occurs, the pilot oil is blocked by the spool from flowing to the control valves to shift the spool and pilot oil at the control spool is drained to the tank past the spool.
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The travel pilot control valve operates similar to the implement pilot valves. Depending on how far the the travel pedal or lever is moved, will determine the amount of pilot oil directed to the respective travel control valve. A dampening function is built into the travel pilot control valve which allows the operational speed of the travel lever/pedal to correspond to the movement of the operator's foot. The dampening function also prevents the vibration that occurs when the travel lever/pedal is released. When travel lever/pedal is moved suddenly from the NEUTRAL position, the rod is pushed downward. The rod moves the dampening piston downward. The hydraulic oil below the dampening piston is pressurized. An orifice check valve allows the trapped hydraulic oil below the dampening piston to gradually flow into into the metering spring chamber, which is open to the tank. The gradual flow of oil through the orifice check valve provides the the dampening function.
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The attachment circuits are controlled by proportional solenoid valves. The valves receive PWM signals from the Work Tool and Machine ECM to energize the solenoid. Depending on the amount of current sent will determine how far the solenoid shifts the spool. Pilot oil is directed to and from the attachment circuits to control the position of the control spool for the attachment.
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When the joysticks are operated, the pilot control valves send pilot pump oil through the pilot lines to pilot ports (arrows) at the main control valve group to shift the spools in the main control valve. Additional pilot lines are located below the main control valve to shift the control spools in the opposite direction.
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Pilot oil enters a control valve from either end to shift the main control spool. The control spool will shift in proportion to the amount of pilot oil sent to the control spool from the a pilot valve or solenoid. For some circuits proportional solenoid valves are used to direct pilot oil to shift the control spool.
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The pilot logic network is a series of open-center flow passages through the hydraulic control valves. These passages are internal to the main control valve group. Pilot oil flows through the logic circuit. The open-center flow passages are open to the tank when all valves are in NEUTRAL. When one or more of the implement control valves are activated, the open-center passage is blocked preventing oil flow to the tank.
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If one or both of the travel valves are moved, then oil is blocked from flowing through the pilot logic network to the tank. Pressure builds upstream of the shifted valve(s), closes the travel pressure switch, and sends a signal to the main relief valve. When the travel pressure switch is closed, a signal is sent to the Machine ECM to activate the travel alarm and resume the set dial speed if Automatic Engine Speed Control (AEC) or one-touch low idle was active. The signal to the main relief, raises the operating pressure of the hydraulic system. This allows for higher pressures to be delivered to the travel motors, increasing drawbar pull.
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If an implement valve is shifted, the implement pressure switch closes and a signal is sent to the Machine ECM. The Machine ECM activates the swing parking brake solenoid to release the swing parking brake. The ECM will also resume the engine speed requested by the speed dial position if the AEC or the one-touch low idle was active. For straight travel operation to occur both travel valves and an implement valve must be shifted. This causes all of the events that occur when either an implement or a travel valve is shifted. In addition, this sends a signal to the straight travel valve. The straight travel valve then shifts and allows one pump to be dedicated to the driving of the travel motors to allow the machine to track straight if an implement function is activated while traveling. Excess flow available from the implement functions is also now available for travel functions.
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MAIN HYDRAULIC PUMPS AND CONTROLS
This section of the presentation will cover the main hydraulic pumps and pump controls for the 315D/319D Hydraulic Excavators. The main hydraulic pumps are the same as the "C" series machines. The main pump group consists of a variable displacement piston drive pump and an idler pump. The drive pump and the idler pump are contained in an integral housing. The drive pump and the idler pump are identical in construction and operation. The pumps are sometimes referred to as S.B.S. (side by side) pumps The main difference between all of the pumps is the maximum pump flow for each model. Both the drive pump and the idler pump have individual pump control valves to control the pump flow.
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Power shift pressure is controlled by the Machine ECM, and assists in pump regulation. Power shift pressure is one of three pressures to control the pump. The pilot pump supplies the power shift PRV solenoid with pilot oil. The Machine ECM monitors the selected engine speed (from the engine speed dial), the actual engine speed (from the engine speed sensor and Engine ECM), and the pump output pressures (from the output pressure sensors). The power shift PRV solenoid regulates the pressure of the power shift oil depending upon the signal from the Machine ECM. When the engine speed dial is in position 10, the Machine ECM varies the power shift pressure in relation to the actual speed of the engine. The power shift pressure is set to specific fixed values dependent upon the position of the engine speed dial. The fixed power shift pressures assist cross sensing pressure with constant horsepower control. When the engine speed dial is on position 10 and a hydraulic load is placed on the engine, this condition causes the engine speed to decrease below the engine's target rpm.
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When this decrease occurs, the Machine ECM signals the power shift solenoid to send increased power shift pressure to the pump control valves. The increased power shift signal causes the pumps to destroke, and reduce the horsepower demand placed on the engine. With a decreased load from the hydraulic pumps the engine speed increases. This function is referred to as engine underspeed control. Engine underspeed control prevents the engine from going into a "stall" condition where engine horsepower cannot meet the demands of the hydraulic pumps. The power shift signal to the pump control valves enables the machine to maintain a desired or target engine speed for maximum productivity. Power shift pressure has the following effect on the main hydraulic pumps: - As power shift pressure decreases, pump output increases. - As power shift pressure increases, pump output decreases. Power shift pressure ensures that the pumps can use all of the available engine horsepower at all times without exceeding the output of the engine. The target rpm is the full load speed for a specific engine no load rpm. Engine target rpm is determined by the opening of one of the implement, swing, and/or travel pressure switches at the end of an operation. The Machine ECM then waits 2.5 seconds and records the engine speed. This specific rpm is the "new" no load rpm. NOTE:
The Machine ECM then controls the power shift pressure to regulate pump flow to maintain the full load (target) rpm for the recorded no load rpm. Target rpm can change each time the pressure switches open for more than 2.5 seconds.
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The solenoid operated proportional reducing valve for the power shift pressure is located on the right/drive pump control valve. The proportional reducing valve receives supply oil from the pilot pump. The solenoid receives a pulse width modulated signal (PWM signal) from the Machine ECM. The PWM signal sent from the Machine ECM causes the proportional reducing valve to regulate the pilot pressure to the pump control valves to a reduced pressure. This reduced pressure is called power shift pressure (PS). The output flow of the right/drive pump and the left/idler pump is controlled in accordance with the power shift pressure. The power shift pressure is used to control the maximum hydraulic pump output in relation to the engine rpm. A decrease in engine speed causes an increase in power shift pressure and a decrease in pump flow.
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When the speed dial is at dial position 10, if the Machine ECM senses a decrease in engine speed below target rpm, the Machine ECM increases the PWM signal sent to the solenoid. The magnetic force of the solenoid increases. As the magnetic force of the solenoid becomes greater than the force of the spring, the spool moves down against the force of the spring. The downward movement of the spool blocks the flow of oil to the tank. More power shift pressure oil is now directed to the pump control valve. The increased power shift pressure acts on the drive pump control valve and the idler pump control valve. If both pumps are upstroked, then both pumps will destroke as a result of the increase in power shift pressure. If only one pump is upstroked, only the upstroked pump will destroke.
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If engine speed is above the target rpm, the Machine ECM decreases the power shift pressure to increase the pump flow. When the Machine ECM senses an increase in engine speed above the target speed the Machine ECM decreases the PWM signal sent to the solenoid. As the magnetic force of the solenoid becomes less than the force of the spring, the spool moves up. The upward movement of the spool restricts the pilot oil flow to the power shift passage and opens the power shift passage to the drain. The power shift pressure is reduced. The reduced power shift pressure acts on the drive pump control valve and the idler pump control valve. Depending on which circuits are activated, the drive pump and/or the idler pump will upstroke as a result of an decrease in power shift pressure.
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This illustration shows the main hydraulic pumps group. The drive pump (right pump) (1) is driven by the engine and the idler pump (left pump) (2) is driven by the drive pump. The pilot pump (3) is mounted on the idler pump. The optional medium pressure pump (not shown) is mounted to the drive pump. The drive pump supplies oil to the right half of the main control valve group and the following valves: - stick 2 control valve - boom 1 control valve - bucket control valve
- attachment control valve - right travel control valve
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The idler pump supplies oil to the left half of the main control valve group and the following valves: - left travel control valve - swing control valve - stick 1 control valve - boom 2 control valve - auxiliary valve for tool control The output of the variable-displacement piston pumps is controlled by the pump control valves (4 and 5) mounted to the ends of the main hydraulic pumps.
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The power shift PRV solenoid (1) provides a common power shift pressure for both pumps. The power shift PRV solenoid is controlled by the Machine ECM. The pump output pressure sensors (2) signal the Machine ECM of each pump's output pressure. The Machine ECM uses the pump output pressure, actual engine speed, and desired engine speed to determine the power shift pressure. The pressure sensors also signal the Machine ECM to cancel the AEC settings if the pump pressure increases above approximately 7370 kPa (1100 psi) and the engine rpm is still at an AEC setting. The horsepower adjusting screws (3) adjust the hydraulic horsepower output of each pump. The maximum angle screw (4) limits the maximum flow of each pump. The drive pump pressure tap (5) can be used to check the drive pump supply pressure. The idler pump pressure tap (6) can be used to check the idler pump supply pressure. Cat ET can also be used to check these two pressures.
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This illustration shows the pumps in STANDBY condition. The pump control valves will upstroke, destroke, or maintain the displacement of the pump depending on the conditions the pump control valve senses. The pump control valve controls oil pressure to the right side of the actuator, which controls the angle of the pump swashplate. Each pump has a pump control valve which senses the three following control signals: - a pump specific Negative Flow Control (NFC) signal from the main control valve group - a common power shift signal pressure generated by the power shift PRV - a common cross sensing signal pressure from the output of the two main pumps NFC: NFC pressure is the most significant controlling signal in a negative flow controlled hydraulic system. Each pump control valve receives a specific NFC signal that is based upon the hydraulic demand for that specific pump.
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Flow from the drive pump supplies the right half of the main control valve group, and has a corresponding NFC signal for the drive pump. Flow from the idler pump supplies the left half of the main control valve group, and has a corresponding NFC signal for the idler pump. The open-center valves in the main control valve group allow pump output to flow through unrestricted. An orifice in the NFC valve creates a restriction to the pump output which increase the NFC pressure. The NFC pressure then signals the corresponding pump control valve. Each pump will remain at STANDBY as long as a full NFC signal pressure is present. When a hydraulic control valve is shifted from the NEUTRAL position, the NFC signal Any pressure to the corresponding pump is reduced, which causes the pump to UPSTROKE. change in the movement of a valve in the main control valve group will effect the NFC signal because the valves send a variable NFC signal to the pump depending on the needed pump output. Output of each pump is unaffected by a change in the NFC signal to the other pump. NFC pressure has the following effect on the main hydraulic pumps: - As NFC pressure decreases, pump output increases, - As NFC pressure increases, pump output decreases. NFC signal pressure overrides all other control of the main hydraulic pumps. Cross Sensing: Cross sensing pressure is essentially an average pressure from the output of the drive pump and the idler pump.
The output of each pump flows respectively to the left and right halves of the main control valve group. The output of each pump also flows to the cross sensing orifices. The pressure on the pump control valve side of the cross sensing orifices is an average of the output pressure of the two pumps, and is referred to as cross sensing pressure. The cross sensing pressure compensates for the horsepower demand of each pump individually and for the two pumps together. With cross sensing assistance, the pumps constantly regulate to effectively use all of the available engine horsepower at any given time. This is referred to as constant horsepower control. Cross sensing pressure has the following effect on the main hydraulic pumps: - As cross sensing pressure decreases, pump output increases, - As cross sensing pressure increases, pump output decreases. Given a fixed NFC signal and a fixed powershift pressure, cross sensing signal pressure regulates the output of the main hydraulic pumps. NOTE:
Hydraulic horsepower is a function of pump output flow and pressure. As pump flow or pressure increases, the horsepower demand increases. As pump flow or pressure decreases, the horsepower demand decreases.
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The above illustration shows a cross sectional view of one of the main hydraulic pump control valves in STANDBY. The main pumps will be in STANDBY condition when the engine is running and all control valves are in the NEUTRAL position. Under these conditions the NFC pressure signal to the pump control valves is high. The pump can not upstroke until NFC signal pressure is reduced. The high NFC signal pressure causes the NFC control piston to move left against the force of the NFC spring on the right. When the NFC control piston moves left it contacts the shoulder on the pilot piston, which causes the pilot piston to move the horsepower control spool against spring force. The passage between horsepower control spool and the sleeve is now open to tank, causing the right end of the actuator to be open to the tank. The actuator moves to the right, moving the swashplate to a minimum angle, which causes pump output flow to be minimum. With the S.B.S. pumps, system pressure destrokes the pumps, while the signal pressure varies to upstroke the pumps. NOTE:
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The pumps must have a reduction in NFC pressure to upstroke from STANDBY. The illustration shows the pump control valves upstroking the pump due to a decrease in NFC signal pressure. As shown, there is no NFC signal pressure, indicating that at least one control valve has been fully shifted. When the joysticks or travel levers are moved from the NEUTRAL position, NFC signal pressure decreases proportionally to the amount the joystick or travel levers are moved. When the NFC signal pressure decreases, the spring on the control piston forces the control piston to the right. The horsepower control springs on the left overcome the cross sensing signal pressure and the power shift signal pressure to move the horsepower control spool to the right. With the horsepower control spool shifted to the right, the passages between the sleeve and the horsepower control spool are closed off to tank and pump output pressure is allowed to flow to the right side of the actuator. Because the right side of the actuator is larger than the left side, the greater force generated by the pressure on the right side causes the actuator to move left and upstroke the pump. The pump can also be upstroked by a decrease in either power shift or cross sensing pressure, but only after a reduction in NFC pressure has occurred.
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As the pump upstrokes, the movement of the actuator causes the control linkage to move the sleeve around the horsepower control spool. The sleeve moves to the right as the actuator moves to the left. Because of the geometry of the control linkage, a large movement of the actuator moves the sleeve a small amount (see Section D-D). The small movement of the sleeve causes the passages between the sleeve and the horsepower control spool to open partially to tank and partially to the pump output. The pressure signal on the right side of the actuator is now metered, which causes the actuator to reach a balance point where the pump does not upstroke or destroke. With the actuator at a fixed position, the swashplate angle of the pump is fixed. Constant flow is now achieved. Due to varying loading and operating conditions, this fixed output is rarely maintained for very long. When operating conditions change, the pump will UPSTROKE or DESTROKE.
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The three things which can cause the pumps to DESTROKE are: - an increase in NFC pressure - an increase in cross sensing pressure - in increase in power shift pressure This illustration shows the system under a heavy hydraulic load. As the supply pressure increases due to the heavy load, the cross sensing signal pressure rises as an average of the left and right pump delivery pressures. The cross sensing signal acts on the difference of the two areas on the pilot piston. As the cross sensing signal increases, the pilot piston moves to the left, which pushes the horsepower control spool left against the force of the horsepower control springs on the left. As the spool moves left, the large end of the actuator is opened to tank by a passage between the horsepower control spool and the sleeve. The pressure decreases on the right end of the actuator and the actuator moves to the right, which causes the pump to DESTROKE.
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An increase in power shift signal pressure has a similar effect as an increase in cross sensing signal pressure. If the hydraulic pump lugs the engine below full load speed, the Machine ECM increases the current to the power shift solenoid. The increased signal causes a higher power shift signal to be sent to the pump control valves. The power shift pressure acts on the right end of the pilot piston. The force generated from the power shift pressure assists cross sensing pressure to destroke the pump. As the pump destrokes the engine speed will increase due to the reduction in load. An increase in NFC signal pressure will cause the pump to destroke. If all control valves were returned to NEUTRAL, the NFC signal causes the pump to fully destroke and return to STANDBY.
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MAIN CONTROL VALVE GROUP AND RETURN SYSTEM
The main hydraulic system is a Negative Flow Controlled system that supplies hydraulic power at high pressures and high flow rates to perform work. Two main hydraulic pumps supply oil to the main control valve group. The individual hydraulic circuits are controlled by valves in the the main control valve group. The main hydraulic system supplies the following circuits: - swing - stick - left and right travel - bucket - auxiliary - boom Oil returning from these circuits flows back through the return system to the hydraulic tank.
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Main Control Valve Group
The main control valve group is located in the center of the upper structure of the machine. The main control valve group receives pilot oil signals from the operator controls in the cab. Each pilot signal then causes the appropriate control valve to shift in the correct direction. When a control valve shifts, oil flows from the main hydraulic pumps to the appropriate hydraulic cylinder or hydraulic motor to perform work. The 315D/319D main control valve is similar to the "C" Series valve. The components shown above include: - auxiliary control valve (1) - stick 1 control valve (2) - swing control valve (3) - left travel control valve (4) - right travel control valve (5) - boom 1 control valve (6) - attachment line relief valve (7)
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- bucket line relief valve (8) - attachment control valve (9) - bucket control valve (10) - stick 2 control valve (11) - boom 2 control valve (12) - boom head end line relief valve (13) - boom lower solenoid valve (14) - main relief valve (15) - pilot pressure switches (16) - stick regen control valve (17) - swing priority valve (18) - stick rod end line relief valve (19) - attachment flow control valve (20) - attachment line relief valve (21)
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The above illustration shows a cross-sectional view of the main control valve group as viewed from the front of the machine. The main control valve group is constructed of two valve blocks that are connected together. The front valve block is shown on the left and the rear valve block is shown on the right. The drive pump provides oil flow for the right side of the main control valve group. The idler pump provides oil flow for the left side of the main control valve group. The pilot-operated, open-center control valves are of parallel feeder design. Because the main control valve group uses the open-center portion of the control valve to generate a NFC signal for the pumps, the oil must have another path to deliver oil to the work ports. This is accomplished through a parallel feeder path. A parallel feeder path runs parallel to the open-center path and supplies oil to the work port of each implement valve. When all of the joysticks and pedals are in the NEUTRAL position, drive pump oil flows through the drive pump inlet port to the right half of the main control valve group. In the right half of the main control valve group the oil flows two directions; to the center bypass passages, and to the parallel feeder passages.
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The oil in the center bypass passages flows in series through the center bypass passage of the right travel, the boom 1, the attachment, the bucket, and the stick 2 valves to the right NFC control orifice. The NFC control orifice allows the oil to return to tank with a restriction. This restriction is the NFC signal that is sent to the drive pump to maintain the drive pump at minimum angle. The NFC circuit and its components will be covered in greater detail later in this presentation. The oil in the parallel feeder passage flows in parallel to the boom 1, the attachment, the bucket, the stick 2 valves. When all are inthrough NEUTRAL, the oil in thetoparallel feeder isand blocked by the valve spools, andofallthe oilvalves must flow the center bypass the tank. The oil from the idler pump flows similarly through the left half of the control valve when all valves are in NEUTRAL.
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Control valve operation is similar for all of the valves in the main control valve group. The following explanation is for the basic operation of all of the valves in the main control valve group. The variations in each individual valve will be discussed later in more detail. The control valve above is shown in NEUTRAL. Spring force centers the valve spool to NEUTRAL when there is no pilot oil pressure directed to shift the spool. In the NEUTRAL position, the spool blocks the oil in Port A and Port B. Oil flows from the pump to the parallel feeder passage. The load check valve is seated because of the pressure differential and spring force present on the load check valve. In NEUTRAL, the valve spool allows oil to flow unrestricted through the center bypass passage, which directs a high NFC pressure signal to the pump control valve. The high NFC pressure causes the pump to destroke to a standby condition.
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When the operator begins to move the joystick to shift the control valve, metered pilot pressure causes the control valve to shift slightly. With the spool initially shifted, the center bypass passage is partially closed. This movement causes NFC pressure to decrease, which signals the pump to begin to upstroke. The movement of the spool partially opens a passage allowing the oil from Port B to work with the load check valve spring to keep the load check valve seated. The load check valve prevents unexpected implement movements when a joystick is initially activated at a low pump delivery pressure. The load check valve also prevents oil loss from a high pressure circuit to a lower pressure circuit. The combined force of the work port pressure from Port B and the force of the spring above the load check is greater than the pump supply pressure, causing the load check valve to remain closed.
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As the operator moves the joystick farther, the pilot pressure on the end of the spool increases. The increased pilot pressure causes the spool to fully shift. The center bypass passage is now closed, which blocks the oil flow to the NFC signal port to a pump control valve. When the NFC signal is reduced, the pump upstrokes and flow is increased. The increased flow can no longer return to tank through the center bypass passage. All oil now flows through the parallel feeder path. The increased oil flow to the parallel feeder passage causes pressure to rise in the parallel feeder passage. The increased oil pressure overcomes the force of the load check spring and the workport pressure in Port B, which causes the load check valve to unseat. Oil flows out to Port B. The oil returning from Port A flows past the spool and returns to tank. The load check valve is a loose fit in the load check seat to allow leakage past the check valve from the spring chamber. A separate spring chamber vent passage is not required with this load check design. NOTE:
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This illustration shows the operation of the main control valve when only the bucket spool has been shifted. All of the control valves in the left side are in the NEUTRAL position, and the center bypass passage is open. All of the flow from the idler pump flows through the center bypass passage to the NFC orifice. Because all of the oil flow from the idler pump is restricted by the NFC orifice, the NFC pressure is at maximum pressure. The NFC pressure flows through the control line to the idler pump control valve. The NFC pressure present at the pump control valve causes the pump control valve to move the swashplate to the minimum angle position. The output of the idler pump is decreased to STANDBY due to the increased NFC pressure. The bucket control spool is fully shifted by pilot oil when the joystick is fully moved to the down position. Flow from the drive pump flows into the right side of the main control valve and into the center bypass passage to the bucket control valve. Because the bucket control spool is fully shifted, all of the oil flow from the drive pump flows to the bucket cylinder. No oil flows to the NFC control orifice and no NFC signal pressure is generated. Because no NFC signal pressure flows to the pump control valve, the pump control valve moves the pump toward maximum angle. The drive pump output increases. The individual circuits of the main control valve group will be covered in more detail later.
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When the joystick is partially moved from the NEUTRAL position to perform a fine control operation, reduced pilot pressure shifts the control spool slightly to the left. The movement of the control spool partially opens a passage to Port B. The movement of the control spool also partially blocks the center bypass passage, which divides the flow from the one drive into two flow paths. A portion of the pump output flows through the center bypass passage to the NFC orifice at a reduced pressure. The remainder of the drive pump output flows through the parallel feeder passage and internal passages to Port B. Because the oil flow from the center passage to the NFC orifice decreases, the pressure to the drive pump control valve decreases. The reduced NFC pressure causes the drive pump to move toward maximum angle. The drive pump output increases proportional to the reduction in NFC pressure.
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The main relief valve (arrow) is located on the top of the main control valve group. The main relief valve limits the maximum hydraulic system pressure. The main relief valve is a two-stage relief valve. The travel setting is higher to increase drawbar pull. The main relief valve is adjusted while operating an implement. The travel pressure setting is not adjustable. NOTE:
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Oil from the drive pump flows to the straight travel valve and to the parallel feeder path for the right implement valves. The straight travel valve also directs drive pump oil to the main relief valve, the right travel valve, and to the center passage of the right implement valves. Oil from the idler pump flows to the straight travel valve, to the main relief valve, the left travel valve, and to the center passage of the left implement valves. The straight travel valve directs idler pump oil to the parallel feeder path for the left implement valves. The drive pump oil and idler pump oil pressures work against the two check valves. The check valves ensure that only the higher pressure from the idler or the drive pump flows to the main relief valve. The check valves also ensure that flow from the highest pressure circuit does not enter the other if the pressure is lower. For example, if the bucket was being closed at a high pressure and no other function was active, the left check valve would close (as shown in this illustration). The check valve would prevent the drive pump oil from flowing through the center bypass in the left circuit. This ensures that relief pressure occurs in a stalled condition.
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The main relief valve is a two-stage relief valve, with an implement setting and a travel setting. When an implement valve is activated, the main relief valve works against spring force and a low oil pressure. The main relief valve operates at the low (implement) setting. With the implement valve activated, pilot oil pressure increases and the implement pressure switch closes. The implement pressure switch sends a signal to the Machine ECM indicating that an implement has been activated.
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When a travel valve is activated, pilot oil pressure increases and the main relief valve works against spring force and a higher oil pressure. The main relief valve operates at the high (travel) setting. With the travel valve activated, pilot oil pressure increases and the travel pressure switch closes. The travel pressure switch sends a signal to the Machine ECM indicating that the travel function has been activated.
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This illustration shows the pilot operated main relief valve in the OPEN position when an implement valve is activated. The main relief valve operates at a lower pressure during an implement operation or a swing operation. During an implement operation or a swing operation, there is no oil flow from the pilot manifold to the end of the piston. The poppet is held in the closed position by spring force. At lower system pressures the poppet is held against the seat by spring force. System pressure in the passage flows through the orifice into the spring chamber to the left of the dump spool. When the force applied by system pressure is less than the value of the left spring, the poppet remains seated, causing the oil pressure in the right spring cavity to equal system pressure. The combined force of the right spring and system pressure holds the dump spool to the right. As the system pressure nears the main relief valve pressure setting, the force of the system pressure in the right spring chamber overcomes the force of the left spring. This causes the poppet to unseat, allowing system oil to flow around the poppet to the return passage. As the oil in the right spring chamber flows around the poppet, additional system pressure oil flows through the orifice into the right spring chamber at a reduced pressure.
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System pressure overcomes the force of the oil pressure in the right spring chamber and the spring, causing the dump spool to move left. As the dump spool moves left, system pressure oil is allowed to flow to the return passage. The amount of spring force acting on the poppet determines the main relief valve pressure setting. Adjustments to the main relief valve pressure setting are made by changing the spring force of the left spring.
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This illustration shows the pilot operated main relief valve in the OPEN position when a travel valve is activated. When the travel function is activated, the maximum system pressure increases. Pilot oil pressure acts on the left end of the piston. The pilot oil moves the piston to the right compressing the poppet spring to increase the maximum system pressure. The main relief valve is adjusted while operating an implement. The travel pressure setting is not adjustable. NOTE:
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The above illustration shows a line relief valve in the closed and in the open positions. The line relief valve is a combination single-stage relief valve, and a makeup valve. At lower system pressures, the poppet is held against a seat by the force of the left spring. The circuit pressure in the passage flows through a cross-drilled orifice in the piston to the spring chamber to the left of the inner spool. When the force applied by system pressure is less than the value of the left spring, the poppet remains seated, causing the oil pressure in the lower spring cavity to equal system pressure. The combined force of the lower spring and system pressure keep the inner spool seated. As the system pressure nears the line relief valve pressure setting the force of the system pressure in the right spring chamber overcomes the force of the left spring. This causes the poppet to unseat, allowing system oil to flow around the poppet to the return passage. As the oil in the right spring chamber flows around the poppet, additional system pressure oil flows through the orifice in the piston from the right spring chamber at a reduced pressure. System pressure overcomes the force of the oil pressure in the right spring chamber and the spring, causing the inner spool to move to the left. As the inner spool moves left, system pressure oil is allowed to flow to the return passage.
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The amount of spring force acting on the poppet determines the line relief valve pressure setting. Adjustments to the line relief valve pressure setting are made by changing the spring force of the upper spring. The position of the adjustment screw determines the spring force of the upper spring.
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The above illustration shows a line relief valve in the closed and in the makeup positions. The makeup function of the line relief valve prevents cavitation and voiding in the various circuits of the hydraulic system. Under normal operating conditions, the outer spool of the line relief valve is seated. The valve is held in the seated position by spring force and the hydraulic pressure in the spring chamber to the left of the inner spool. If hydraulic circuit pressure becomes lower than the tank pressure, the pressure in the spring chamber is reduced. Tank pressure surrounds the outer spool, and creates a force on the step of the outer spool. This force unseats the inner and outer spools and oil flows from the return system to the lower pressure hydraulic circuit.
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The NFC relief valves are located in the main control valve group next to the stick valve. One NFC valve controls the NFC signal to the drive pump and the other NFC valve controls the NFC signal to the idler pump. Both NFC valves work the same. Oil enters the NFC orifice from the center bypass passage. The returning oil flows through the NFC orifices to the return passage when the system is in STANDBY. The orifices restrict the flow back to tank, which causes an increase in pressure through the center bypass passages. This signal is sent to the pump control valve of the main hydraulic pump. When a hydraulic function is activated in the main control valve group, the center bypass passage is blocked. The NFC pressure at the pump control valve bleeds off through the NFC orifices to tank. The NFC relief valve is normally closed by spring force. The NFC relief valve is not adjustable. The left and righ t NFC relief valves can NOT be swapped for dia gnostic testing purposes. NOTE:
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The NFC relief valve only opens under sudden pressure spikes in the return system, which would occur if the pump was fully upstroked and the control valve returned suddenly to NEUTRAL. A sudden pressure spike in the return system would cause high flow through the center bypass passage. The high volume of oil could not flow quickly enough through the NFC orifice to the return system. The high pressure generated in the center bypass passage would open the NFC relief valve, which would relieve the sudden pressure spike. The valve would return with spring force to the closed position once the NFC orifice would allow an adequate amount of oil for the pressure in the return passage to decrease.
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Return Hydraulic System
The return hydraulic system transfers all of the hydraulic oil that has been used in the system to do work back to the hydraulic tank. The return hydraulic system has the following components: - slow return check valve - cooler bypass check valve group - hydraulic oil cooler - hydraulic oil filters - hydraulic oil tank
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The slow return check valve and the bypass check valve are in the cooler bypass valve group (arrow). The slow return check valve restricts return oil flowing from the main control valve, which maintains a constant back pressure in the return hydraulic system. The back pressure ensures that oil is available when needed for makeup in the various machine hydraulic circuits. The bypass check valve regulates return oil flow through the hydraulic oil cooler.
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Return oil from the main control valve flows from the return line to the slow return check valve. The back pressure created by the slow return check valve ensures that makeup oil is present at the various makeup valves in the hydraulic system. After flowing through the slow return check valve, oil flows to the cooler inlet line and the bypass check valve. At low temperatures, the high viscosity of the oil flowing through the hydraulic oil cooler causes the pressure to increase. The increasing pressure causes the bypass check valve to open. Most of the oil flows through the bypass check valve. Because only a small amount of oil flows through the cooler, the oil temperature increases. As the oil temperature increases, the bypass check valve begins to close and a greater portion of the oil flows through the hydraulic oil cooler. The bypass check valve maintains the oil at the optimum operating temperature.
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The hydraulic oil cooler (1) is part of the cooling package (2) on the left side of the machine at the rear. The hydraulic oil cooler reduces the temperature of the hydraulic oil in the system. Oil enters the hydraulic oil cooler from the slow return check valve. After passing through the cooler, oil is delivered to the hydraulic return filter.
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Return oil flow from the hydraulic oil cooler flows into the return filter (not shown), which is located in the hydraulic tank. The return filter contains a bypass valve that directs the return oil to the hydraulic tank if the filter becomes plugged. All returning oil from the hydraulic system is filtered by the return hydraulic filter. The tank has a vacuum breaker to limit the maximum tank pressure to 55 kPa (8 psi). The breaker opens at 13 kPa (2 psi) to prevent damage to the tank. Oil in the hydraulic tank flows through the suction screen located inside the tank before being delivered to the main hydraulic pump group.
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The hydraulic tank sight gauge (1) is located to the right of the pilot filter (2). The case drain filter (3) receives case drain oil from the swing motor, idler and drive main hydraulic pumps, and left and right travel motors. Oil from the case drain filter flows into the hydraulic tank. The purpose of the case drain filter is to reduce hydraulic contamination to the hydraulic system if a pump or motor fails.
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BOOM, STICK, AND BUCKET CIRCUITS
This presentation covers in more detail each implement circuit used for the 315D/319D Series Hydraulic Excavators. The circuits to be covered include: - boom - stick - bucket The idler pump provides oil to the boom 2 and stick 1 control valves. The drive pump provides flow to the bucket, boom 1, and stick 2 control valves. The boom, stick, and bucket control valves are shifted by pilot oil from the joystick pilot valves when they are activated. The main control valve group and return system are covered in another presentation. The attachment/auxiliary circuits will be covered in the tool control section. The ISO schematics were created primarily from "315D Hydraulic Schematic" (RENR9738). Hydraulic schematics for the 319D may have variations from illustrations shown. NOTE:
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The boom circuit uses two control valves to control the boom operation, boom 1 (1) and boom 2 (2). Both spools shift when fast boom movement is required. Both pumps provide flow to the boom for this condition. Boom 1 valve provides single pump flow, whenever the boom is shifted for slow movement. The stick circuit also uses to two control valves to control the stick operation, stick 1 (3) and stick 2 (4). Both spools shift when fast stick movement is required. The boom circuit and stick circuits also use regeneration valves and drift reduction valves. The regeneration valves (not shown) provide improved efficiency and require less engine horsepower for BOOM LOWER and STICK IN. The drift reduction valves reduce cylinder drift when the boom or stick are in NEUTRAL. Only one bucket control valve (5) is required to control the bucket. The bucket circuit is supplied with oil only from the drive pump.
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The two joysticks in the cab are used to control the movements of the boom, stick, swing and bucket circuits. - right joystick (1) to control the bucket and boom (SAE excavator pattern) - left joystick (2) to control the swing and stick (SAE excavator pattern)
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Boom Circuit
The boom circuit consists of the following major components: - boom 1 spool - boom 2 spool - boom cylinders - drift reduction valve - boom lowering control valves (if equipped) - boom regeneration valve - SmartBoom™ (if equipped) The 315D Hydraulic Schematic (RENR9738) was used to develop the ISO schematics. NOTE:
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Boom 1 Spool: The boom 1 spool controls oil flow from the drive pump. The boom 1 spool receives a BOOM RAISE pilot signal on the bottom of the valve, and a BOOM LOWER pilot signal on the top of the valve. Boom 2 Spool: The boom 2 spool controls oil flow from the idler pump. The boom 2 spool receives a BOOM RAISE pilot signal from the joystick on the top of the valve st em, when active. The boom 2 spool does not operate during BOOM LOWER. The boom 2 spool has no provisions for return oil from the boom cylinders.
Boom Cylinders: The boom work intoparallel control theboom raisecylinders, and lowerthe boom movement of the boom. Whencylinders oil is supplied the headtoend of the will raise. When oil is supplied to the rod end of the boom cylinders, the boom will lower. Boom Drift Reduction Valve: The boom drift reduction valve prevents oil from leaking from the head end of the boom cylinders. For BOOM LOWER, pilot oil from the joystick is used to unlock the lock check valve in the drift reduction valve. Boom Lowering Control Valves: The boom lowering control valves are infinitely variable, pilot operated control valves that control the movement of the boom during lowering. The boom lowering control valves are a safety device and prevent boom cylinder drift with valving mounted directly on each of the boom cylinders, that controls boom cylinder head end oil flow.
Because the valves are mounted directly to each of the boom cylinders, the boom lowering control valves will prevent the boom from falling, even if a hose becomes defective from the main control valve to the cylinders. The boom lowering control valves also work in conjunction with the SmartBoom™ system to control the boom with the function active. Regeneration Valve: The regeneration valve allows return oil from the head end of the boom cylinders to be directed into the rod end of the cylinders when the boom is lowered fast. The 315D/319D is also equipped with a Boom Electronic Regeneration feature, that includes a solenoid and a pressure switch. SmartBoom™: The SmartBoom™ attachment enhances operation of the boom function and significantly reduces cycle times of the machine. The SmartBoom™ is essentially a boom float attachment, which allows the operator to lower the boom under its own weight or for the boom to raise up due to stick force. The SmartBoom™ attachment is typically used in EAME.
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When the boom joystick is moved less than half of the travel distance for BOOM RAISE, low pilot oil pressure is supplied to the boom 1 control valve and the boom 2 control valve. The force of the centering spring in the boom 1 control valve is less than the force of the centering spring in the boom 2 control valve. When the boom is raised at a low speed, the boom 1 control valve opens and the boom 2 control valve remains closed due to the low pilot pressure. The drive pump supply oil supply oil flows past the boom 1 control valve and unseats the check valve in the drift reduction valve and flows to the head end of the boom cylinders. Return oil from the rod end of the boom cylinders returns back to the tank through the boom 1 control valve. With the boom valve partially shifted less oil is directed to the NFC relief valve. Less oil to the NFC relief valve results in a reduced NFC signal to the drive pump. The drive pump control valve causes the pump to upstroke to provide flow to operate the boom. A BOOM RAISE operation at low speed is accomplished when only the drive pump is supplied to the head end of the boom cylinders.
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When the operator begins to move the joystick, metered pilot pressure causes the boom 1 spool to shift slightly. The boom 2 spool does not shift as previously described. With the boom 1 spool initially shifted, the center bypass passage is partially closed. This movement causes NFC pressure to decrease, which signals the drive pump to begin to upstroke. The load check valve prevents unexpected implement movements when a joystick is initially activated at a low pump delivery pressure. The load check valve also prevents oil loss from a high pressure circuit to a lower pressure circuit. As the pump supply pressure increases, the load check valve opens to allow pump supply oil in the parallel feeder passage to flow to the control spool. The control spool meters pump supply oil to the head ends of the boom cylinders.
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A BOOM RAISE operation at high speed is accomplished when supply oil from both the idler pump and the drive pump is supplied to the head end of the boom cylinders. Boom 1 control valve and boom 2 control valve are both shifted during high speed operation.
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As the operator moves the joystick farther, the pilot pressure on the end of the spool increases. The increased pilot pressure causes the boom 1 spool to shift further to the right. The center bypass passage is now closed, which blocks the oil flow to the NFC signal port on the right pump control valve. When the NFC signal is reduced, the pump upstrokes and flow is increased. The increased flow can no longer return to tank through the center bypass passage. All oil now flows through the parallel feeder path. The increased oil flow to the parallel feeder passage causes pressure to rise in the parallel feeder passage. The increased oil pressure overcomes the force of the load check spring and the boom head end pressure, which causes the load check valve to unseat. Oil flows out to boom cylinders. The oil returning from the rod end of the cylinders flows past the spool and returns to tank. The pilot oil flow shifts the boom 2 control valve. The idler pump supply oil in the parallel feeder passage flows past the check valve and flows out to the head end of the boom cylinders. The idler pump supply oil combines with the drive pump supply oil at the boom drift reduction valve (not shown) and flows to the head end of boom cylinders.
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Return oil from the rod end of boom cylinders flows to the boom 1 control valve and then to the tank. The boom 2 control valve does not handle any of the return flow for the boom circuit.
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During combined operations of BOOM RAISE and STICK IN, the boom raise pilot oil pressure shifts the boom priority valve to reduce the stick in pilot pressure for the stick 2 control valve. With the reduction in stick in pilot pressure to the stick 2 control valve, more pump flow is directed to the boom cylinders during this combined hydraulic operation. For STICK IN, the stick circuit regeneration valve will shift to direct return oil from the rod end of the stick cylinder to the head end of the cylinders. NOTE:
When the joystick for the stick is moved to the STICK IN position, a portion of the pilot oil from the pilot control valve for the stick flows through the pressure reducing valve for the boom priority to the stick 2 control valve. As the joystick for the boom is moved farther for a BOOM RAISE, pilot oil pressure from the pilot control valve for the boom increases. This gradual increase in pilot oil pressure causes the spool in the boom priority valve to gradually shift. A portion of the pilot oil to the stick 2 control valve from the stick pilot control valve is restricted by the boom priority valve. The pilot oil pressure acting on the stick 2 control valve decreases.
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The stick 2 control valve shifts toward the NEUTRAL position. The amount of oil flow from the main pumps to the stick hydraulic circuit decreases. This change causes a greater portion of the oil flow from the main pumps to flow to the head end of the boom cylinders. Since the pilot oil pressure from the boom pilot control valve directly corresponds to the amount of movement or position of the boom joystick a gradual change to boom priority occurs. Thus, boom priority is controlled by the position of the joystick for the boom and boom priority automatically activates when the joystick reaches a certain position during a BOOM RAISE operation. The above information describes the condition of BOOM RAISE and STICK IN. During any combined function of BOOM RAISE and STICK IN, the boom priority valve reduces pilot pressure to the stick 2 control valve. If the joysticks are fully shifted for BOOM RAISE and STICK IN, stick in pilot pressure on the bottom of the boom 2 cancels the boom raise pilot pressure on top of the boom 2 spool. At the same time the boom priority valve prevents stick in pilot pressure from going to the stick 2 control valve. NOTE:
These two actions result in the drive pump supplying oil to the boom cylinders and the idler pump providing oil to the stick cylinder.
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For BOOM LOWER only the boom 1 control valve is used. The drive pump partially strokes to provide flow to the rod end of the boom cylinders. The boom 2 control valve is a regeneration valve that directs oil from the head end of the boom cylinders to the rod end of the boom cylinders. When the joystick is shifted pilot oil moves the boom 1 control spool up, and unlocks the drift reduction valve. Pilot oil also flows to the boom regeneration solenoid valve. When the boom 1 control spool is fully shifted, the center bypass valve is never fully closed off. By not closing off the center passage, there is an NFC signal to the drive pump. The drive pump never fully upstrokes. Due to the force of gravity, with the lock valve unlocked, the weight of the boom and the load on the boom force the return oil out of the cylinder head ends back to the boom 1 control valve and to the boom 2 control valve. The boom 1 control valve restricts the return oil flow. The boom 2 valve functions as a regeneration valve. When the boom regeneration solenoid is energized by the Machine ECM, pilot oil moves the boom 2 valve up and oil from the head end of the boom cylinders flows to the rod end of the boom cylinders.
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The return oil from the head end enters the supply passage to the rod end to help fill the cylinders and prevent cylinder cavitation. The boom 2 valve allows the excavator to operate more efficiently. The main pump supply oil not required to lower the boom is available to operate another circuit.
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The 315D/319D boom electronic regeneration circuit provides engine speed control and regeneration valve control. If the boom is lowered when the engine speed dial is in position 10, the engine speed will decrease which conserves fuel. The boom lower pilot pressure switch and the engine speed dial send a signal to the Machine ECM. The Machine ECM processes the signals and sends a signal over the Data Link to the Engine ECM, which decreases engine speed. The boom 2 (regeneration) valve size has been increased resulting in a faster boom down speed. The boom regeneration solenoid is used to lower the boom slowly when the engine speed dial is in positions 1-8. When the boom regeneration solenoid is de-energized by the Machine ECM, the boom 2 spool is closed and oil from the head end of the cylinder returns to tank through the boom 1 spool but is blocked at the boom 2 spool. Since the boom 1 control valve restricts the return oil flow from the head end of the boom cylinders, the boom lowers at a slower speed.
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The boom pilot oil flow shifts the boom control spool to the left against the force of the centering spring. Supply oil from the drive pump in the parallel feeder passage flows past the load check valve to the rod end of the boom cylinders. Some of the oil in the center bypass passage flows past the center land to provide a reduced NFC signal. The reduced NFC signal causes the drive pump to only partially upstroke. Part of the return oil from the head end of boom cylinders flows to the boom drift reduction valve.
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Boom Drift Reduction Valve: The boom drift reduction valve prevents oil from leaking from the head end of the boom cylinders. The boom drift reduction valve is located on the main control valve group. The boom drift reduction valve has the following components:
- the shuttle valve - the check valve - the line relief valve In NEUTRAL, the shuttle valve and check valve are closed by spring force. Oil is blocked between the boom control valve and the boom cylinders. For BOOM RAISE, the shuttle valve is closed by spring force. When closed, the shuttle valve allows oil from the boom control valves to act on one end of the check valve. Oil pressure from the boom control valves acts on the other end of the check valve. The check valve opens (due to pressure differential on check valve) to allow oil flow to the rod end of the boom cylinders.
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For BOOM LOWER, the shuttle valve is opened by pilot oil from the joystick. The shuttle valve allows oil from the spring end of the check valve to return to tank. Oil pressure from the boom cylinder head end opens the check valve. The check valve allows oil flow from the head end of the boom cylinders to return to the boom control valve.
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The boom lowering control valves (1 and 2) are mounted on the head end of the boom cylinders. The boom lowering control valves serve several purposes: - prevent the boom from falling rapidly in case of hose failure - provide BOOM LOWER control with SmartBoom™ (if equipped) activated - prevent boom drift The lowering control valves are equipped with head end line relief valves (3) to protect the cylinders from sudden shocks. A pilot line (4) directs pilot oil to unlock the lowering control valve so the boom can be lowered. The tube (5) provides supply oil from the boom control valve. A hose (6) connects both lowering control valves. The line provides for equalization of pressures in the head end of the cylinders when the boom is raised or lowered to provide smooth movement.
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Boom Lowering Control Valves
The boom circuit is equipped with boom lowering control valves (or load control valves), which are attached directly to each of the boom cylinders. The boom lowering control valves contain the following major components: - boom head end line relief - boom lowering control valve spool - orifice - manual lower - piston When the joystick is in the HOLD position, the boom cylinders are held in the raised position. Spring force moves spool 1 up and oil is trapped between the head end of the boom cylinders and spool 1. The boom lowering control valve keeps the boom cylinder from drifting down.
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When the joystick is moved to the BOOM RAISE position, pump oil flows from main control valve to the boom lowering control valve. The boom lowering spool moves down and pump oil flows to the head end of the boom cylinders, which raises the boom.
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When the joystick is moved to the BOOM LOWER position, pilot oil moves the piston down. When the piston moves down, oil from the bottom of the boom lowering spool is directed to tank and the spool moves up. Oil from the head end of the boom cylinders flows to the tank and the boom lowers.
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Stick Circuit
The stick circuit consists of the following major components: - stick 1 spool - stick 2 spool - stick cylinder - stick regeneration valve - stick unloading valve (part of stick regeneration valve) - stick lowering control valves (not shown) - stick drift reduction valve The stick priority systems and the stick drift reduction valve will be discussed in more detail later in this presentation. NOTE:
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Stick 1 Spool: The stick 1 spool controls oil flow from the idler pump. The stick 1 spool receives a STICK IN pilot signal on the bottom of the valve, and a STICK OUT pilot signal on the top of the valve. Stick 2 Spool: The stick 2 spool controls oil flow from the drive pump. The stick 2 spool receives a STICK IN pilot signal from the joystick on the bottom of the valve stem. The stick 2 spool receives a STICK OUT pilot signal from the joystick on the top of the valve stem. Stick Cylinder: When oil is supplied to the rod end of the stick cylinder, the stick will retract
for a STICK OUT. When extend for a STICK IN. oil is supplied to the head end of the stick cylinder, the stick will Stick Regeneration Valve: The stick regeneration valve opens during STICK IN to allow returning oil from the rod end of the stick cylinder to be directed to the head end of the stick cylinders during STICK IN. Regeneration is used to reduce "stick wag" and increase the STICK IN speed. Stick Unloading Valve:The unloading valve allows the oil to return to the tank when regeneration is not necessary. Stick Drift Reduction Valve: The stick drift reduction valve is placed in the stick circuit between the main control valve and the stick cylinder. The stick drift reduction valve prevents oil from leaking from the rod end of the stick cylinder.
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When the stick hydraulic circuit is operated independently of other hydraulic circuits, stick 1 control valve and stick 2 control valve are operational for both the STICK IN and STICK OUT operation. When the stick 1 control valve and the stick 2 control valve are operated, the supply oil from the idler pump and the drive pump is combined. The supply oil from both pumps flows to the stick cylinder. The supply oil from the drive pump flows through the parallel feeder passage in the main control valve group to the stick 2 control valve. The supply oil from the idler pump flows through the center bypass passage in the main control valve group to the stick 1 control valve. When the joystick for the stick is moved to STICK OUT, the pilot oil flows from the pilot control valve to the stick 1 control valve and the stick 2 control valve. The pilot oil shifts the stick 1 and stick 2 control valve spool. Supply oil is directed from both spools to the stick drift reduction valve. The lock check valve in the drift reduction valve shifts and combined pump oil flows to the rod end of stick to retract the cylinder. Return oil from the head end of the stick cylinder flows back to the stick 1 and stick 2 control valves and to the tank.
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Slow STICK IN - No Regeneration
Depending on the position of the stick, for a slow STICK IN, regeneration may not be required due to the supply oil from the pump being able to fill and pressurize the head end of the stick cylinder to force the stick in. For a slow STICK IN the pilot signal is reduced and will only partially shift the stick 1 spool. The stick 2 control valve may or may not shift. Pilot oil shifts the regeneration valve down, which allows return oil to be sensed at the check valve. The regeneration valve also allows pump supply oil pressure to be sensed at the unloading valve. The unloading valve does not shift due to the supply oil pressure being below the setting of the unloading valve spring. A reduced NFC signal is sensed at the idler pump, and the pump upstrokes to provide flow.
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Most of the supply oil from the idler pump is directed to the stick cylinder head end through the stick 1 control spool. Return oil from the rod end flows to the drift reduction valve. The lock check valve in the drift reduction valve is unseated and return oil flows back to the tank through the stick 1 control valve. Even though the return oil is restricted through the stick 1 control spool, the back pressure created is insufficient to cause the return oil pressure to be above the supply pressure. The check valve remains seated.
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Fast STICK IN - Regener ation: For a fast STICK IN, or whenever the return oil pressure from the rod end is higher than the supply pressure to the head end, the check valve will unseat.
When the check valve unseats, the return oil is added to the supply oil going to the head of the stick cylinder. The regeneration valve allows the excavator to operate more efficiently. The main pump supply oil not required to move the stick in is available to operate another circuit. NOTE:
Stick regeneration only occurs when the position of the stick is between full stick out and stick vertical.
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Stick unloading occurs when the stick reaches vertical to the ground. A pressure spike occurs which helps to open the unloading valve to rapidly reduce rod end pressure. When the unloading valve opens, the oil flow to the stick cylinder is from the pumps. When the regeneration valve is shifted and the supply oil to the head end of the stick cylinder is higher than the return oil from the rod end, the check valve will close. No return oil enters the passage to the head end. As the pressure in the head end of the cylinder increases, the pressure moves the unloading valve lower. When the unloading valve moves down, most of the return oil from the rod end of the cylinder returns to the tank past the unloading valve instead of through the stick 1 control valve. Stick regeneration and stick unloading will not be active at the same time.
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Stick unloading occurs when the stick reaches vertical to the ground. A pressure spike occurs which helps to open the unloading valve to rapidly reduce rod end pressure. When the unloading valve opens, the oil flow to the stick cylinder is from the pumps. When the regeneration valve is shifted and the supply oil to the head end of the stick cylinder is higher than the return oil from the rod end, the check valve will close. No return oil enters the passage to the head end. As the oil pressure in the head end of the cylinder increases, the oil pressure moves the piston to the left which moves the unloading valve to the left. When the unloading valve moves to the left, most of the return oil from the rod end of the stick cylinder returns to the tank past the unloading valve instead of through the stick 1 control valve. Stick regeneration and stick unloading will not be active at the same time.
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Summary of stick regeneration functions: The lack of a passage to drain in the stick 2 valve and the restricted oil flow through the stick 1 valve maintains back pressure in the rod end as STICK IN is performed.
This back pressure maintains pressure on the stick cylinder, which prevents "stick wag" from occurring. Stick regeneration allows the returning oil from the rod end of the cylinders to combine with main pump flow to move the stick cylinders out. The unloading valve allows a means to relieve the back pressure from the returning rod end oil, when the oil is no longer needed for regeneration.
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The stick drift reduction valve is located in the stick circuit on the main control valve group as part of the stick 1 spool. The stick drift reduction valve prevents oil from leaking from the rod end of the stick cylinder. The stick drift reduction valve has the following components: - shuttle valve - lock check valve - line relief valve In the NEUTRAL position, the shuttle valve and lock check valve are closed by spring force. Oil is blocked between the stick control valve and the stick cylinder.
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For STICK OUT, the shuttle valve does not shift. The shuttle valve allows oil from the stick control valves to act on one end of the lock check valve. Oil pressure from the stick control valves acts on the other end of the check valve. The check valve opens (due to the pressure differential on the check valve) to allow oil flow to the rod end of the stick cylinder.
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For STICK IN, the shuttle valve is moved down by pilot oil from the joystick. The shuttle valve allows oil in the lock valve spring chamber to flow to the tank. Return oil from the stick cylinder rod end moves the lock check valve to the left against the lock check valve spring. The open lock check valve allows oil flow from the rod end of the stick to return to the stick 1 control valve and the regeneration valve.
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Bucket Circuit
The bucket circuit control valve operates as previously discussed. Two line relief valve and makeup valves are used to protect the lines from high pressures. The bucket is only supplied by the drive pump. Pilot oil from the joystick is directed to the bucket control valve to shift the control spool. When the control spool shifts, the NFC signal to the drive pump is reduced and the pump upstrokes to provide flow. For BUCKET CLOSE, the return oil from the rod end of the cylinder is restricted by the control spool to control the bucket speed.
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Cylinders
The boom, stick, and bucket use dual acting cylinders. The boom has a snubber for the rod end, while the stick uses snubbers on the rod and head end. Snubbers slow the speed of the cylinder as the cylinder reaches the end of the cylinder stroke.
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As the boom or stick cylinder moves to the end of the extension stroke, oil in the passage will be restricted by the snubber, which will slow the cylinder speed down. As the stick cylinder moves to the end of the retraction stroke, oil in the passage will be restricted by the snubber, which will slow the cylinder speed down.
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SWING SYSTEM
This presentation covers the 315D/319D swing system. The swing system includes the following components - swing control valve (part of the main control valve group) - swing motor - cushion crossover anti- reaction valves - swing brake - swing priority valve - slow return check valve The idler or left pump section in the main control valve supplies oil flow for the swing system. The swing control valve is shifted by pilot oil from the joystick pilot valves.
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Swing System Components
The swing circuit controls the rotation of the swing motor. The idler pump provides the pump flow to the swing motor. When either one of the joysticks is moved from the NEUTRAL position, the swing parking brake is released. The swing motor is mounted on top of the swing drive. The swing drive is installed on the upper structure and rotates the upper structure. When the hydraulic activation control lever is in the UNLOCKED position, pilot pump oil flows to the swing parking brake solenoid valve in the pilot manifold and to the swing pilot control valve. With the swing control valve in NEUTRAL, pump supply oil from the idler pump flows though the center bypass valve swing control valve to the NFC valve. The return oil creates a signal used to destroke the idler pump. The swing brake is currently on so the motor will not rotate.
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Since the implement hydraulic lockout solenoid has been energized, the hydraulic activation valve has shifted. Pilot oil is directed to the pilot joystick and the swing brake solenoid. Swing Pr iority Valve: This valve provides flow priority over the stick control valve when the stick and swing are operated together. Anti-reaction or Cushion Relief Valves: These valves dampen pressure spikes in the swing system whenever the swing is stopped. The valves also inhibit counterrotation of the swing motor when the swing is stopped, which reduces swing "wag." Slow Return Check Valve: The back pressure created by the slow return check valve ensures that makeup oil is present at the swing motor and the various makeup valves in the hydraulic system. Swing Parking Brake Solenoid Valve: When energized the solenoid valve directs pilot oil to release the swing parking brake. The solenoid will energize when either one of the joysticks is moved from the NEU TRAL position.
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The swing system uses one control valve (1) in the main control valve group (2) to control the swing operation. The slow return check valve is part of the slow return check valve and cooler bypass manifold group (3). The left joystick (4) in the cab is used to control the direction and speed of the swing. The swing control valve directs oil to and from the swing motor (5). Additional swing motor components shown are the: - swing drive oil level dipstick (6) - crossover relief valves (7) - anti-reaction valve group (8) - makeup valve (9) - swing motor case vent (10)
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The swing brake solenoid valve (1) is part of the pilot manifold (2). The manifold is located next to the main control valve. The hydraulic activation solenoid (3) must energize to shift the hydraulic activation valve (4). If the hydraulic activation valve is not shifted there is no pilot oil to the swing brake solenoid valve and the swing brake cannot be released. There is also no pilot oil available to the joystick pilot valves if the hydraulic activation valve is not shifted.
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Swing System Operation
When the swing joystick is fully shifted, pilot oil from the swing joystick flows to the swing control valve to shift the control spool. The control valve shifts and blocks the oil in the center passage from flowing to the idler pump. The idler pump fully upstrokes. Also, when the swing control valve shifts, pilot oil from the pilot manifold is blocked from flowing through the pilot logic network to the tank. The increased pilot pressure closes the implement pressure switch. The Machine ECM senses the switch is closed and energizes the swing brake solenoid. The swing brake solenoid directs pilot oil to release the swing brake. The load check valve unseats and supply oil from the pump is directed to the swing motor. The swing relief cushions the start of the swing motor. Return oil from the motor flows past the swing control valve to the tank.
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Also, when the swing joystick is fully shifted, the swing pilot oil shifts the swing priority valve up. Oil flowing from the straight travel valve to the stick 1 valve is blocked at the swing priority valve. In the illustration above, swing is the only circuit in operation.
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The swing priority valve provides a swing priority function over the STICK IN and STICK OUT functions when the swing function is activated at the same time as the stick function. The swing pilot oil pressure from the swing pilot control valve directly corresponds to the amount of movement or position of the swing joystick. The swing pilot oil pressure from the pilot control valve acts on the swing priority valve. The reduced pilot pressure during a partial swing movement will not move the swing priority valve up. If the stick 1 circuit is being operated at the same time as a partial swing, idler pump oil flows through the swing priority valve and is directed to the stick 1 control valve. The stick control valve directs oil to the stick cylinder. The stick cylinder speed is determined by how far the stick spool shifts. The stick 2 control valve also shifts for a full stick out. The stick 2 control valve is not affected by the variable swing priority valve.
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As the swing joystick is moved farther from the NEUTRAL position, the pilot oil pressure increases. This gradual increase in pilot oil pressure causes the swing priority valve to shift up. Oil from the idler pump parallel passage is blocked at the swing priority valve. The stick 1 valve receives pump supply through only an orifice restriction which causes a lower flow to be sent to the stick functions. Swing priority is controlled by the position of the swing joystick. Swing priority over the stick is hydraulically activated when the swing joystick reaches a certain position. For STICK IN, only the stick 1 control valve shifts. Due to the regeneration valve (not shown), the STICK IN speed is not affected unless the stick has reached the vertical position and the stick unloading valve is open. Without swing priority, during a full STICK IN, the stick circuit would receive most if not all of the idler pump flow. Since swing priority increases the swing acceleration whenever the stick is also used, swing priority is useful for loading operations. Swing priority is also useful for leveling operations and trenching operations when higher swing force is required.
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When the swing joystick is partially shifted, the pilot pressure oil from the swing pilot valve cannot overcome the swing priority valve spring to move the the valve spool left. The swing priority valve spool does not restrict oil to the stick 1 control valve as shown in this illustration. Unrestricted flow from the idler pump is available to the stick 1 control valve to operate the stick. When the swing pilot valve is fully shifted, pilot oil pressure moves the swing priority valve spool to the right against spring force. With the swing priority valve spool moves to the left, supply oil to the stick 1 control valve is restricted and the stick cylinder speed is reduced.
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Swing Motor Operation
The swing motor may be divided into the following three groups : - The rotary group: piston and barrel assembly, shoes, retainer plate, and drive shaft. - The parking brake: brake spring, brake piston, separator plates, and friction plates. - The relief valves and makeup valves. When a swing operation is started, pilot oil from the swing brake solenoid valve is directed to the swing brake piston. As the pilot pressure builds, the brake piston moves against the spring to release the swing brake. The brake separator plates and friction plates are no longer in contact and the motor barrel assembly can rotate freely. During a SWING RIGHT operation, the oil delivery enters the motor head from the swing control valve and flows through a plate in the motor into the piston and barrel assembly to cause the motor to rotate. Return oil flows back from the motor to the motor head and back to the swing control valve to return to the tank.
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As pressure increases in the fill chamber, the piston moves to the left. As the piston moves to the left, oil in the dampening chamber is forced out of the orifice in the piston. This feature modulates the movement of the piston to the left to gradually compress the the relief valve spring to increase the relief valve setting. In a swing stall condition, the piston is moved fully to the left to compress the spring even more. The swing relief valve is at the maximum setting.
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The swing parking brake is located in the swing motor. The swing parking brake consists of the following components: brake spring, brake piston, separator plates, and friction plates. The friction plates are splined to cylinder barrel. The separator plates are splined to the motor case. When the joysticks are moved from the NEUTRAL position, the implement pressure switch senses the increase in pilot oil pressure. The pressure switch closes and sends an input signal to the Machine ECM. The Machine ECM energizes the swing brake solenoid valve. When the swing brake solenoid valve is energized, the spool moves down against the spring. Pilot oil flows to the center of the spool and out to the swing motor. The pilot oil now enters the piston chamber. The pilot pressure causes the brake piston to move upward against the force of the brake spring. The separator plates and friction plates are no longer held together and the motor is able to rotate freely.
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When the joysticks are returned to the NEUTRAL position, idler pump supply oil to the swing motor is stopped. The implement pressure switch senses the decrease in pilot oil pressure. The implement pressure switch opens. The Machine ECM senses the change in state of the implement pressure switch and de-energizes the swing brake solenoid valve. The spool is moved upward by the force of the spring in the solenoid valve. The spool blocks pilot oil flow from flowing to the brake piston. Oil in the brake piston is open to the tank through the swing brake spool. The brake spring moves the brake piston down to press the separator plates and friction plates together to apply the swing parking brake. Since the Machine ECM does not de-energize the swing brake solenoid valve until approximately 6.5 seconds after the swing joystick is returned to the NEUTRAL position, the rotation of the swing motors stops hydraulically before the swing brake is engaged. If the solenoid is de-energized before the rotation of the swing motors stops, damage and wear to the swing parking brake would result.
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Two dual stage, swing relief valves are located in the head of the swing motor. These relief valves limit the maximum pressure in the left and right swing circuits. The pressure setting of the swing relief valves is less than the pressure setting of the main hydraulic relief valve. The dual stage, swing relief valves open initially at a lower pressure to reduce jerkiness in the swing circuits at swing start and swing stop or to handle short duration pressure spikes. The relief valves also allow for higher swing circuit pressures to provide increased swing force. The higher relief valve setting is modulated up to the relief valve maximum. In NEUTRAL, spring force moves the stem to the left to the closed position and moves the piston to the right against the stop. At the start of the swing operation or if a pressure spike occurs, system pressure moves the stem to the right, which opens the work port to drain. Oil also flows through the orifice in the left end of the stem to the chamber at the right end of the stem to the fill chamber on the right end of the piston.
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When the swing joystick is moved to stop the swing while swinging right, the swing control valve shifts to the NEUTRAL position. Since the swing control valve is in the NEUTRAL position, the supply oil and return oil passages to motor rotary group are blocked at the swing control valve. Due to inertia, the upper structure will attempt to continue to rotate. A vacuum is created on the supply side of the motor, while the return side is pressurized. The line relief opens and allows oil in the high pressure side to enter the drain line to the slow return check valve. The slow return check valve creates a back pressure and helps to force open the makeup valve in the low pressure line to the rotating group.
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Return oil from the main control valve group and from the swing motor group flows into the housing for the slow return check valve as shown in the above illustration. The back pressure created by the slow return check valve ensures that makeup oil is present at the swing motor and the various makeup valves in the hydraulic system. After flowing through the slow return check valve oil flows to the cooler inlet line and the bypass check valve. At low temperatures, the high viscosity of the oil flowing through the hydraulic oil cooler causes the pressure to rise. The rising pressure causes the bypass check valve to open. Most of the oil flows through the bypass check valve. Because only a small amount of oil flows through the cooler, the oil temperature increases. As the oil temperature increases, the bypass check valve begins to close and a greater portion of the oil flows through the hydraulic oil cooler. The bypass check valve maintains the oil at the optimum operating temperature.
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The anti-reaction valves are used to eliminate the reverse swing effect when the swing operation is stopped. When the swing hydraulic control valve is returned to NEUTRAL, the upper structure continues to rotate due to inertia. Without the anti-reaction valve, the swing motor acts like a pump and a hydraulic lock is formed in the swing lines between the motor and the swing control valve. This pressure causes the swing motor to turn the upper structure in reverse slightly after the upper structure is stopped. When the swing control valve is returned to NEUTRAL, pressure increases and is directed to the anti-reaction valve. The anti-reaction valve shifts to connect the outlet passage to the inlet passage through the valve allowing pressure oil to move to the low pressure side. As the upper structure slows to a smooth stop, pressure in the high pressure side decreases, allowing spring force to return the anti-reaction valve to the NEUTRAL position.
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This sectional view shows the anti-reaction valve in the ACTIVATED position. When the swing control valve is returned to NEUTRAL, the upper structure continues to swing. Pressure increases in the right side of the valve because of the pumping action of the swing motor. The pressure goes through the orifice to the center of the anti-reaction valve and to the spring chamber on the right end of the valve. As pressure increases, the valve moves slowly to the left until it contacts the retainer. Before the valve contacts the retainer, high pressure oil passes through the internal passages (shown by the arrow) to the "suction" side of the motor. The internal passage allows the pressure on each side of the motor to become equal. As the pressure on each side of the motor becomes balanced, the upper structure slows to a complete stop with no backlash in the swing gears.
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The swing drive consists of a series of planetary gears. The planetary gears reduce the rotational speed of the swing motor. The swing motor is bolted to the top of the swing drive. The swing drive is bolted to the upper structure. The teeth of the swing drive output pinion shaft engage with the bearing gear of the swing bearing. The pinion shaft rotates around the bearing gear. This rotation causes the machine to swing. The bearing gear is attached to the lower structure. The swing drive is divided into the following two groups : - The first group provided a double reduction of motor speed. The components of the first stage reduction are the first stage sun gear, the first stage planetary gears, the ring gear, and the first stage planetary carrier. The components of the second stage reduction are the second stage sun gear, the second stage planetary gear, the ring gear, and the second stage planetary carrier. - The second group reduces output speed of the motor. The components of the second group are the roller bearings and the pinion shaft. The roller bearings are installed in the housing and support the pinion shaft. The swing speed is reduced by a ratio of teeth on the sun gear to ring gear teeth by planetary reduction. Since the sun gear is inside of the ring gear, the swing drive is more compact than the reduction units with external teeth.
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The swing motor output shaft is splined to the first stage sun gear. The first stage planetary gears of the first stage planetary carrier mesh with the first stage sun gear. When the first stage sun gear rotates counterclockwise, the first stage planetary gears rotate in a clockwise direction on shafts. The first stage planetary gears move counterclockwise around the ring gear. The ring gear is bolted to the housing. The first stage planetary carrier rotates counterclockwise.
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Splines on inner circumference of the first stage planetary carrier engage with the splines on the second stage sun gear. This engagement causes the second stage sun gear to rotate counterclockwise when the first stage planetary carrier rotates. The second stage planetary gears turn clockwise on the shafts. The second stage planetary gears move in a counterclockwise direction around the ring gear. The second stage planetary carrier turns counterclockwise around the ring gear. The splines on the inner circumference of second stage planetary carrier engage with the splines of pinion shaft. When the second stage planetary carrier turns clockwise, the pinion shaft rotates counterclockwise.
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The pinion shaft engages with the bearing gear on the inner circumference of the swing bearing. The bearing gear is bolted to the lower structure. As the pinion shaft rotates counterclockwise, the pinion shaft moves in a clockwise direction around the bearing gear. The upper structure also rotates in a clockwise direction around bearing gear. This rotation causes the upper structure to swing to the right (clockwise rotation).
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TRAVEL SYSTEM
This presentation covers the 315/319D travel system. The travel system includes the following components - travel pedals/levers - travel pilot valves - left and right travel control valves - straight travel valve - two travel motors - travel park brake - two speed travel solenoid valve Both the drive pump and idler pump are used to provide flow to the travel system.
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Travel System Components
The idler pump and drive pump supply oil flow to the travel control valve group, which controls pump flow to the two travel motors. With the travel control valves in NEUTRAL, pump supply oil from the pumps flows though the center bypass valve through all other control valves to the NFC valves. The return oil from the pumps creates NFC signals to destroke the pumps. Pilot oil is available at the two speed travel solenoid valve. Since the implement hydraulic lockout solenoid has been energized, the hydraulic activation valve has shifted. Pilot oil is directed to the travel pilot valves.
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Two speed travel solenoid valve: This solenoid valve is used to select slow or high travel speed. Straight travel control valve: When both travel control valves are shifted and an implement/swing circuit is activated, the straight travel valve provides flow priority to the travel motors. Crossover Relief Valves: These valves dampen pressure spikes in the travel system whenever the travel is stopped. The valves also prevent or reduce travel motor cavitation. Slow Return Check Valve: The back pressure created by the slow return check valve ensures that makeup oil is present at the travel motor and the various makeup valves in the hydraulic system.
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The left travel valve (1) and right travel valve (2) are used to control the travel motors. The straight travel valve (3) provides flow priority for the travel system during a travel condition. The slow return check valve is part of the slow return check valve and cooler bypass manifold (4). The travel system uses foot pedals (5) or travel levers (6) to control the direction of machine travel. Each track is driven by a travel motor (7). A counterbalance valve (8) prevents overspeed while the machine is traveling downhill, prevents shocks to the system when travel is stopped, and helps to prevent motor cavitation. Crossover relief valves (9) are used to protect the travel motor from pressure spikes. The upper supply line (10) directs supply oil to the motor for reverse travel, while the lower supply line (11) directs supply oil to the motor for forward travel. The travel motor turns the final drive. The final drive is composed of a three stage planetary gear reduction to reduce the motor speed to drive the track.
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The two speed travel solenoid valve (1) is part of the pilot manifold. The manifold is located near the main control valve. The hydraulic activation solenoid (2) must energize to shift the hydraulic activation valve (3). If the hydraulic activation valve is not shifted there is no pilot oil to the travel pilot valves. When the two-speed travel soft switch (4) is pushed, the travel speed is toggled between low and auto. - The rabbit indicator indicates auto speed. - The tortoise indicator indicates low speed.
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The travel pilot control valve operates similar to the implement pilot valves. Depending on how far the the travel pedal or lever is moved will determine the amount of pilot oil directed to the respective travel control valve. A dampening function is built into the travel pilot control valve which allows the operational speed of the travel lever/pedal to correspond to the movement of the operator's foot. The dampening function also prevents the vibration that occurs when the travel lever/pedal is released. When the travel lever/pedal is moved from the NEUTRAL position, the rod is pushed downward. The rod moves the dampening piston downward. The hydraulic oil below the dampening piston is pressurized. An orifice check valve allows the trapped hydraulic oil below the dampening piston to gradually flow into the metering spring chamber, which is open to the tank. The gradual flow of oil through the orifice check valve provides the dampening function.
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Travel System Operation
When the operator selects the low speed mode, the Machine ECM will not energize the two speed travel solenoid valve. The displacement change valve does not shift. Some of the supply oil to the motors is sent by the displacement change valve to the actuator piston on the left and drains the passage to the actuator on the right. The motor swashplate is moved to the maximum angle.
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Two swashplate actuator pistons control the angle of the motor swashplate. The pistons are controlled by the displacement change valve. The angle of the swashplate will limit the maximum speed. Since the displacement change valve has not shifted, the swashplate is in the low speed range. For the motor to turn, the parking brake must be released. To release the brake some of the supply oil is used to shift the parking brake piston against the parking brake spring. The travel valves direct oil to and from the motors.
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If the displacement change valve does not shift, supply oil to the motor is directed to the actuator piston on the right to hold the motor swashplate at maximum angle. At maximum angle, the motors will displace more flow and turn at a slower speed and provide more torque.
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When the operator selects high speed in the cab the Machine ECM will energize the two speed transmission solenoid valve in the pilot manifold. The two speed transmission solenoid valve directs the pilot pressure to shift the displacement change valve to the left. The displacement change valve directs some of the supply oil to the minimum angle actuator piston on the right and drains the oil to the actuator on the left. The motor swashplate angle is reduced.
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When the displacement change valve shifts due to the two speed travel solenoid being energized, the displacement change valve sends some of the supply oil to the lower actuator piston to decrease the swashplate angle. With a decreased swashplate angle, the motor pistons displace less flow as the piston and barrel assembly rotate. The motor now turns faster, with less torque than at low speed.
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When the two speed travel solenoid valve is energized, pilot oil is directed to the displacement change valve. The displacement change valve shifts and directs some of the supply oil to the actuator piston on the left to decrease the swashplate angle.
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Travel Parking Brake
The travel parking brake is located in the travel motor. The travel parking brake consists of the following components: the brake spring, the brake piston, the separator plates, and the friction plates. The friction plates are splined to the cylinder barrel. The separator plates are splined to the motor housing. When the travel pedals or levers are moved from the NEUTRAL position, supply oil from the pump flows to the inlet port of the travel motor from the travel control valve in the main control valve group. A portion of the supply oil enters the motor and unseats the brake pilot check valve. The oil then flows to the brake piston. As pressure builds in the brake piston, the piston moves to the left against the brake spring. The separator plates and friction plates are no longer held together and the motor is able to rotate.
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When the travel pedals or levers are returned to the NEUTRAL position, the supply oil to the motor is blocked by the travel control valves. The counterbalance valves shift back to NEUTRAL. The brake pilot check valve moves to the right The orifice in the brake pilot check valve allows the oil behind the brake piston to slowly flow to the motor case drain. The brake spring moves the brake piston to the left to press the separator plates and friction plates together to apply the travel parking brake. The travel park brake engages approximately four seconds after the travel control valves return to NEUTRAL.
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The travel brake valve consists of the counterbalance valve, two check valves, and two crossover relief valves. The orifice check valves are internal to the counterbalance spool. During normal travel, supply oil from the travel control valve enters the travel brake valve and flows to the counterbalance valve. Some of the supply oil flows through the orifice check valve to the right end to shift the counterbalance valve to the left. As the counterbalance initially shifts to the left, some of the supply oil is used to release the parking brake. As the counterbalance continues to move to the left, a return passage from the motor is opened. The supply pressure unseats one of the check valves and flows past the check valve to the motor. Return oil from the motor flows around the counterbalance valve, to the travel control valve, and back to the tank.
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When traveling downhill the weight of the machine will cause the machine to try to turn the travel motor faster than the supply oil from the pumps. When this occurs, the pressure drops in the supply passage to the motor. When the supply pressure drops, the counterbalance valve will shift to restrict the return oil from going back to the tank. This movement by the counterbalance valve slows the speed of the motor and reduces motor cavitation. One of the crossover reliefs valve may open to send the high pressure return oil into the supply side to prevent motor cavitation.
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When the travel pedals/levers are returned to NEUTRAL, the supply oil is blocked by the travel control valve. The pressure drops in the spring chamber on one end of the counterbalance valve. The counterbalance shifts to restrict the return oil. The crossover relief valve opens to dampen the shock when the motor stops and sends some of the high pressure oil in the return passage to the supply passage to prevent motor cavitation.
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The travel crossover relief valves provide a cushioning effect when they open, similar to the swing relief valves. The valves initially open at a lower pressure to handle pressure spikes of short duration and to reduce jerkiness at the start of travel. When travel is stalled, the circuit pressure is at maximum. NEUTRAL: In NEUTRAL the pistons are moved against the stops by the large springs. The large springs also seat the unloading valves. At this time the relief valves are at their minimum spring setting. Start of Travel: When travel is started, the high pressure oil in the supply side is sensed at the relief valve on the left. The unloading valve moves left against the large spring to allow some of the oil in the supply side to flow into the return passage to dampen the pressure spike. The relief valve opens at the lower pressure setting.
Since the pressure spike is short in duration, the oil sensed through the stem on the left end of the left relief valve does not increase sufficiently to move the piston to the right. Since the piston does not move, the spring is not compressed and the relief valve pressure setting is not increased.
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Travel Stall: The crossover relief valves are also able to handle high pressure increases.
When travel is stalled, the high pressure in the supply side is sensed at the left relief valve. Not only does the unloading valve move to the left, but oil sensed through the stem, allows for pressure to increase on the left end. As the pressure increases on the left end, the piston gradually moves to the right to compress the large spring, which causes a modulated increase in the maximum relief valve setting. Travel Stop: When travel is suddenly stopped the return oil is blocked by the counterbalance valve. Pressure in the return side is very high, while pressure in the supply side is very low.
The high pressure is sensed at the right relief valve. The oil sensed through the stem on the right end of the relief valve may move the piston to the left to partially compress the spring due to higher pressure in the system as compared to a travel start. At the same time the right unloading moves to the right and opens to allow the high pressure oil in the return loop to flow to the low pressure side.
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When the travel valve is returned to NEUTRAL, the counterbalance valve also returns to NEUTRAL. When the counterbalance valve returns to NEUTRAL, the supply pressure to the motor drops as the motor continues to try to turn. Return oil to the travel control can be used as makeup oil to the low pressure side. Due to the back pressure created by the slow return check valve, the check valve in the counterbalance valve can unseat and allow return oil to enter the low pressure side of the motor. The crossover relief valve will also open to send oil in the high pressure side to the low pressure side of the travel motor to reduce motor cavitation.
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Straight Travel
When both travel levers or pedals are shifted and at least one of the implements or the swing is selected, pilot oil pressure from the pilot manifold increases and shifts the straight travel valve down. The implement and travel pressure switches also close. The pressure switches send a signal to the Machine ECM indicating that machine travel and an implement have been activated. When the straight travel valve shifts down all of the idler pump flow is directed equally to the travel control valves. The drive pump flow is directed into the parallel feeder passages and to the activated implement circuit. In the illustration above forward travel and been selected and the bucket has been shifted to close. At the travel motors, the counterbalance valves shift and direct idler pump supply oil to the motors. At the same time some of the supply oil is used to release the parking brake. During straight travel mode, the machine can only run at low travel speed mode.
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This illustration shows the straight travel valve position when only the travel function is activated. Pilot pressure from the pilot manifold is low. Spring force keeps the spool shifted to the right. Oil flows from the drive pump through the right center bypass passage to the right travel control valve and through the right parallel feeder passage to the boom 1 control valve, the work tool control valve, the bucket control valve, and the stick 2 control valve. Oil flows from the idler pump through the left center bypass passage to the left travel control valve and through the left parallel feeder passage to the swing control valve, the stick 1 control valve, and boom 2 control valve.
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This illustration shows the straight travel valve position when both travel levers are activated and one of the implements are activated. Pilot pressure from the pilot manifold increases. Pilot oil pressure moves the spool to the left. Oil flows from the drive pump: - through the right parallel feeder passage to the boom 1 control valve, the work tool control valve, the bucket control valve, and the stick 2 control valve. - through the left parallel feeder passage to the swing control valve, the stick 1 control valve, and the boom 2 control valve. - into a passage in the center of the spool, through a check valve and orifice and combines with the idler pump oil flowing to the travel control valves. Oil flows from the idler pump through the left center bypass passage to the left travel control valve and through the right center bypass passage to the right travel control valve.
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Travel System
3
184
2
1
1
185
Swivel
The swivel (1) is mounted just to the front of the swing motor (2) and below the boom (3). Since the lower structure does not swing and the upper structure does, a swivel is required to direct oil to and from the travel motors.
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Various ports in the housing route oil to and from the travel valves in the main control valve group to the travel motors. The housing is bolted to the lower structure. The upper flange is fastened to the upper structure. The rotor rotates within the upper structure as the upper structure swings.
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This presentation has provided component location and systems operation information for the 315D/319D Hydraulic Excavators. When used in conjunction with the service manual information, the information in this package should permit the service technician to analyze problems on these machines.
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VISUAL LIST 1. 2. 3. 4. 5. 6. 7. 8.
Model view Similarities and differences Hydraulic system Optional tool control system Components Right side of machine Left side behind operator station Pump compartment, right side of
45. 46. 47. 48. 49. 50. 51. 52.
Harness connectors Engine components (top view) Left rear compartment behind cab Left side of engine Right side of engine components Fuel injection pump High pressure fuel pump Fuel temperature sensor
23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37.
machine Pilot manifold components Main control valve group Swing motor Final drives Engine componentsl Radiator Maintenance schedule Model view Cab controls Emergency engine shutoff switch Hydraulic activation lever Soft switch panel Toggle and rocker switch panel Heating and air con ditioning control panel Back-up switches Fuse panel Monitor display Directional and navigational buttons Monitoring system display Outline of display setup Machine ECM inputs and outputs Machine ECM Engine speed control Automatic engine control One touch low idle Engine speed protection Travel speed control Swing brake operation Back-up system
53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76.
Common rail fuel manifold Engine shutdown switch High pressure fuel injector Air intake and exhaust system Inlet air heater Air inlet heater relay Inlet air temperature sensor Pilot hydraulic system Pilot pump Pilot system filter Pilot manifold Pilot manifold - LOCKED Pilot manifold - UNLOCKED Hydraulic lockout lever - LOCKED Hydraulic lockout lever - UNLOCKED Hydraulic activation lever Pilot controls Pilot control valve Travel pilot control valve PWM solenoid valve Pilot ports Implement control valve - FULL SHIFT Pilot logic network - NEUTRAL Pilot logic network - TRAVEL V SHIFTED Pilot logic network - TRV/IMP V SHIFTED Hydraulic system pumps and controls Power shift pressure system Proportional red. V - PWM increase Proportional red. V - PWM decrease
38. 39. 40. 41. 42. 43. 44.
Engine Engine features Component parts Engine cylinder head Fuel delivery system Engine electronic control system Engine ECM
82. 83. 84. 85. 86. 87.
9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22.
77. 78. 79. 80. 81.
Main hydraulic pumps group Power shift PRV solenoid Pump schematic - STANDBY Main pump control valve - STANDBY Main pump control valve - UPSTROKE Main pump control v. - CONSTANT FLOW
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VISUAL LIST 88. 89. 90. 91. 92. 93.
Main pump control valve - DESTROKE Hydraulic system main control valve Main control valve group Main control valve - NEUTRAL Implement control valve - NEUTRAL Implement control valve - INITIAL MOVE 94. Implement control valve - FULL SHIFT
124. 125. 126. 127.
95. NEGATIVE 96. Hydraulic Implementsystem control-valve - FINE FLOW CONTROL 97. Main relief valve 98. Straight travel cont v. - IMPL ACTIVATED 99. Straight travel cont v. - TRV ACTIVATED 100. Main relief valve - IMPL ACTIVATED 101. Main relief valve - TRV ACTIVATED 102. Line relief valve 103. Line relief valve - MAKEUP 104. Negative flow control valve 105. Return hydraulic system 106. Cooler bypass valve group 107. Slow return check valve and bypass valve 108. Hydraulic oil cooler 109. Pilot filter 110. Case drain filter 111. Hydraulic system - IMPL CIRCUITS 112. Boom circuit 113. Joysticks 114. Hydraulic system - BOOM CIRC COMPS 115. Hydraulic system - BOOM RAISE SLOW 116. Boom control valves - BOOM RAISE PART 117. Hydraulic system - BOOM RAISE FAST 118. Boom control valve - BOOM RAISE
130. Stick hydraulic circuit - STICK OUT 131. Stick regen hyd circ - STICK IN SLOW w/o REG 132. Stick regen hyd circ - STI CK IN FAST w/ REG 133. Stick regen hyd circ - UNLOAD V ACTIVE 134. Stick regen valve - UNLOADING ACTIVE 135. Stick drift reduction valve - NEUTRAL 136. Stick drift reduction valve - STICK OUT 137. Stick drift reduction valve - STICK IN 138. Hydraulic system - BUCKET CLOSE 139. Cylinders 140. Snubber oper ation 141. Hydraulic system - SWING 142. Swing system - NEUTRAL 143. Swing system components 144. Swing brake solenoid 145. Swing system - FULL SWING LEFT 146. Swing system - PARTIAL SWING LEFT 147. Swing system - PRIORITY OVERSTICK 148. Swing priority valve - NO PRIORITY 149. Swing motor 150. Swing parking brake - OFF 151. Swing parking brake - ON 152. Swing relief valve 153. Swing makeup circuit - MOVED TO STOP 154. Slow return check valve and bypass
119. 120. 121. 122. 123.
FULL Hydraulic system - BOOM PRIORITY Hydraulic system - BOOM LOWER Boom elec regen - BOOM LOWER Boom control valves - BOOM LOWER Boom drift red valve - BOOM RAISE
Boom drift red valve - BOOM LOWER Boom lowering control valves Boom lowering control valve - HOLD Boom lowering control valve - BOOM RAISE 128. Boom lowering control valve - BOOM LOWER 129. Hydraulic system - STICK CIRC
155. 156. 157. 158. 159.
valve Anti-reaction valve - NEUTRAL Anti-reaction valve - ACTIVATED Swing drive Planetary assembly Swing drive - POWER FLOW
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VISUAL LIST 160. 161. 162. 163. 164. 165. 166. 167.
Pinion shaft rotation Hydraulic system - TRAVEL Travel system - NEUTRAL Travel system components Travel valves Travel soft switch Travel pilot control valve Left travel motor - SLOW SPEED
168. motor -change SLOWvSPEED 169. Travel Displacement - LG DISPLACEMENT 170. Left travel motor - HIGH SPEED 171. Travel motor - HIGH SPEED 172. Displacement change v - SM DISPLACEMENT 173. Travel parking brake - RELEASED 174. Travel parking brake - ENGAGED 175. Travel brake valve - TRAVEL 176. Travel brake valve COUNTERBALANCE 177. Travel brake valve - STOPPING 178. Travel crossover relief valves NEUTRAL 179. Travel crossover relief valve - STALL 180. Travel circuit - MAKEUP OPERATION 181. Travel hyd sys - FORWARD/HIGH SPEED 182. Straight travel control v - TRAVEL NEUTRAL 183. Straight travel control v - TRAVEL ACTIVATED 184. Swing motor 185. Swivel 186. Swivel cutaway 187. Conclusion
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HYDRAULIC SCHEMATIC COLOR CODE Black - Mechanical Connectio n. Seal
Red - High Pressure Oil
Dark Gray - Cutaway Section
Red / White Stripes - 1st Pressure Re duct ion
Light Gray - Surface Color
Red Crosshatch - 2nd Re duction in Pressure
White - Atmosphere or Air (No Pressure)
Pink - 3rd Reduction in
Purple - Pneumatic Pressure
Red / Pink Stripes - Secondary Source Oil Pressure
Yellow - M oving o r Activated Components
Orange - Pilot, Charge or Torque Converter Oil
Cat Yellow - (Restricted Usage) Identification of Components within a Moving Group
Orange / White Stripes - Reduced Pilot, Charge, or TC Oil Pressure
Pressure
Brown - Lubricating Oil
Orange / C rosshatch - 2nd Reduction Charge, or TC Oil Pressure
Green - Tank, Sump, or Retur n Oil
Blue - Trapped Oil
in Pilot,
Green / White Stripes Scavenge / Suction Oil or Hydraulic Void
HYDRAULIC SCHEMATIC COLOR CODE
This illustration identifies the meanings of the colors used in the hydraulic schematics and cross-sectional views shown throughout this presentation.
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E D O C R O L O C C I T A M E H C S C I L U A R D Y H
il O e r u s s e r P h ig H d e R
l a e S . n io t c e n n o C l a c i n a h c e M k c a l B
n o it c u d e R e r u s s re P t s 1 s e p i tr S e it h W / d e R
n o ti c e S y a w a t u C y a r G k r a D
re u s s re P n i n io t c u d e R d n 2 h c t a h s s ro C d e R
r lo o C e c a rf u S y a r G t h ig L
e r u s e r P in n o ti c u d e R rd 3 k n i P
) e r u s s e r P o (N ir A r o re e h p s o tm A e ti h W
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re u s s re P il O e rc u o S ry a d n o c e S s e p i tr S k n i P / d e R
re u s s e r P c ti a m u e n P e l rp u P
li O r tre e v n o C e u q r o T r o e g r a h C t, o il P e g n a r O
s t n e n o p m o C d te a v ti c A r o g n i v o M w o ll e Y
r o , e rg a h C ,t o il P d e c u d e R s e p i tr S e r e it u s h s We / r e P g il n O a r C OT
) e g a s U d e t c ir t s e R ( w o ll e Y t a C
s t n e n o p m o C f o n o ti a c i ift n e d I
t, o il P n i n o it c u d e R d n 2 h c t a h s s o r C / e g n a r O
p u o r G g n i v o M a in th i w
e r u s s e r P li O C T r o , e g r a h C
li O d e p p ra T e lu B
il O g in t a irc b u L n w o r
il O rn tu e R r o , p m u S , k n a T n e re
B
G
id o V c il u a r d y H r o - li s O e n p ir io t t S c u te i S h / We / g n n e e v a e r c G S
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