cvr-outside-front-ssp275 6/30/03 1:59 PM Page 1
The Phaeton Air Suspension Design and Function Vibrating Mass
Spring Travel
Rebound Amplitude
Amplitude
Position of Rest Bump P
Self-Study Program Course Number 899303
Volkswagen of America, Inc. Service Training Printed in U.S.A. Printed 08/2003 Course Number 899303 ©2003 Volkswagen of America, Inc. All rights reserved. All information contained in this manual is based on the latest information available at the time of printing and is subject to the copyright and other intellectual property rights of Volkswagen of America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, nor may these materials be modified or reposted to other sites without the prior expressed written permission of the publisher. All requests for permission to copy and redistribute information should be referred to Volkswagen of America, Inc. Always check Technical Bulletins and the Volkswagen Worldwide Repair Information System for information that may supersede any information included in this booklet. Trademarks: All brand names and product names used in this manual are trade names, service marks, trademarks, or registered trademarks; and are the property of their respective owners.
Table of Contents
Introduction ................................................................................................... 1 Suspension and Damping Basics ................................................................ 2 Vehicle Suspension, Types of Vibration Acting on a Vehicle, Vibrations, Definitions, Suspension System, Spring Characteristics, Spring Travel Air Suspension Basics .................................................................................. 9 Air Suspension, Characteristics of Air Springs, Spring Characteristics, Air Spring Design Damping System Basics ............................................................................. 15 Shock Absorbers, Twin-Tube Gas Pressure Shock Absorber, Shock Absorber Tuning System Description ..................................................................................... 19 Air Suspension with Continuously Controlled Damping, Component Locations, Operation and Display, Self-Leveling Suspension, Damper Tuning, Control Strategy of the Self-Leveling Suspension, Manual Deactivation and Activation, Actions of Air Suspension After “Ignition Off,” Shock Absorber Control, Diagram of Air Suspension System with Continuously Controlled Damping, Schematic Diagram of the Overall System, System Overview Design and Function ................................................................................... 34 Level Control System Control Module J197, Air Spring Struts, Air Supply Module, Compressor Unit, Pressure Accumulator, Air Supply Strategy, Self-Leveling Suspension Pneumatic Diagram, Solenoid Valves, Level Control Pump Temperature Sensor G290, Level Control Pressure Sensor G291, Vehicle Level Control System Sensors, Body Acceleration Sensors, Wheel Acceleration Sensors, Interfaces, Functional Diagram – Air Suspension with Continuously Controlled Damping, Additional Interfaces, Emergency Running Mode
New!
Service .......................................................................................................... 66 Self-Diagnosis Knowledge Assessment ............................................................................. 69
Important/Note! The Self-Study Program provides you with information regarding designs and functions. The Self-Study Program is not a Repair Manual. For maintenance and repair work, always refer to the current technical literature.
i
Introduction
Vehicle contact with the road is controlled by the suspension system components.
One solution is a controlled suspension system including:
Conflicting requirements for maximum comfort, optimum driving safety, and minimum noise transmission from the road surface to the vehicle interior place heavy demands on suspension system designers.
• Full load-bearing self-leveling suspension system. • Continuously controlled damping.
Vehicles like the Phaeton, which are expected to meet high standards of comfort, represent a special challenge that necessitates a compromise between the various requirements on the suspension system.
Control is based on the “skyhook control strategy.” In a perfect world, damping would be controlled as if the vehicle body were suspended by a hook from the sky, floating above the road without interference from the surface of the road. The purpose or this Self-Study Program is to introduce and describe this new system.
SSP275/20a
1
Suspension and Damping Basics Vehicle Suspension When a vehicle is moving, the external forces that act upon it produce movements in the three possible directions of motion – the transverse, longitudinal, and vertical axes. The aim of good suspension and damping system design is to minimize the effect of these forces on driving comfort, driving safety, and operating safety by striking a balance between the suspension system and the vibration damping system. A basic distinction can be drawn between the suspension system and the vibration damping system. The task of both systems
is to absorb and reduce the forces produced and, if possible, to keep them away from the vehicle body and its occupants: Driving safety – They help maintain continuous tire contact with the road, which is important for steering and braking. Driving comfort – Harmful or unpleasant vibrations are kept away from the passengers and the cargo remains intact. Operational safety – The vehicle body and assemblies are protected against high impact and vibration loads.
SSP275/001
2
Suspension and Damping Basics Types of Vibration Acting on a Vehicle In addition to the upward and downward movement of a moving vehicle, vibrations occur about and in the direction of the longitudinal, transverse, and vertical axes. The following terms are generally used to describe the vibrations that can occur in a motor vehicle. Longitudinal axis vibration terminology: • Twitching – Vibration in the direction of the longitudinal axis (shudder, back-and-forth motion). • Rolling – Torsional vibration (rotation) around the longitudinal axis (snaking, rolling, and tilting motion).
Transverse axis vibration terminology: • Drifting – Vibration in the direction of the transverse axis (side slip, side-to-side motion). • Pitching – Torsional vibration (rotation) around the transverse axis (up-and-down motion of the front of the vehicle relative and opposite to the motion of the rear). Vertical axis vibration terminology: • Bouncing – Vibration in the direction of the vertical axis (road surface impacts, vertical vibration, up-and-down motion). • Yawing – Torsional vibration (rotation) around the vertical axis (side-to-side motion of the front of the vehicle relative and opposite to the motion of the rear).
Transverse Axis • Drifting • Pitching Longitudinal Axis • Twitching • Rolling Vertical Axis • Bouncing • Yawing
SSP275/009
3
Suspension and Damping Basics Vibrations
Definitions
The tires, suspension elements, body, and vehicle seat form a system which is capable of vibration, i.e. when an external force such as a bump on the road acts on this system, it oscillates back and forth about its position of rest. These vibrations repeat themselves until they die away.
Sprung mass – The weight of the car supported by its suspension including the engine, transmission and body. Vibration – Oscillating movement of a mass (e.g. bump and rebound of the vehicle body).
The vibrations are defined by their amplitude and frequency.
Amplitude – Maximum distance of an oscillating mass from its position of rest (vibration displacement, spring travel).
Intrinsic body frequency is a major factor in vehicle occupant comfort and safety.
Period – Duration of a single, complete vibration cycle.
• An intrinsic body frequency of less than 1 Hz can cause nausea, depending on one’s predisposition.
Frequency – Number of vibration cycles (periods) per unit of time. The customary designation for cycles per second is Hertz, abbreviated Hz.
• Frequencies above 1.5 Hz are detrimental to driving comfort. • Frequencies higher than 5 Hz are perceived as shocks. Intrinsic body frequency is essentially determined by the spring rate and the size of the sprung mass.
One complete vibration cycle per second = 1 Hz Intrinsic Frequency – Natural vibration frequency (free vibrations) of a given mass. Resonance – The physical characteristics of a mass that allow it to vibrate easily at its intrinsic frequency with very little excitation force, like a lightly plucked guitar string. Shock absorption – Describes the decay of vibrations.
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Suspension and Damping Basics
Vibrating Mass Position of Rest
Damped Vibration
Spring Travel
Rebound
Time
Bump Amplitude Period
Larger masses or softer springs produce a lower intrinsic body frequency with increasing spring travel (amplitudes).
Spring Travel
SSP275/003
Time
Smaller masses or firmer springs produce higher intrinsic body frequencies with decreasing spring travel.
SSP275/005
Spring Travel
Period
Time
Period
SSP275/004
The intrinsic frequency of unsprung masses like the wheels and tires with attached brake, hub, and axle components is approximately 10 to 16 Hz.
5
Suspension and Damping Basics Suspension System The tires, the springs, and the seats with their cushioning effect collectively form the vehicle suspension system.
On the vehicle, a distinction is made between unsprung masses and sprung masses.
As key components of this system, the spring and shock absorber elements are the link between the wheel suspension and the vehicle body.
Unsprung masses include items like wheels, brakes, final drive shafts, wheel bearings, and wheel bearing housings.
Suspension elements include: • Steel springs (leaf springs, helical springs, torsion bar springs) • Air springs (flexible air bladder springs and toroidal bellows springs) • Hydro-pneumatic springs (piston and diaphragm type hydraulic accumulators)
Sprung masses include the vehicle body with suspension and drivetrain parts. The general aim of vehicle tuning is to keep unsprung masses to a minimum. This minimizes interference with the vibration characteristics of the vehicle body and improves suspension response (and as a result, driving comfort).
• Rubber springs
The following components contribute to reducing unsprung masses:
• Anti-roll bars
• Light-alloy suspension parts
• Combinations of these elements
• Light-alloy brake calipers • Light-alloy hollow-spoke wheels • Weight optimized tires
Spring and Shock Absorber Element
Unsprung Mass
Sprung Mass
Seat Springs
Spring and Shock Absorber Element SSP275/002
6
Suspension and Damping Basics Spring Characteristics The characteristics of a spring are obtained by applying a force of increasing magnitude to a spring in a spring press and plotting the change in spring travel against the force applied.
Examples of Spring Characteristics
Progressive Linear Firm
Spring rate = force : distance [pounds/inch (N/cm)]
Force
The spring rate is calculated from the ratio of change in force and change in travel.
Linear Soft
A “firm” spring has a steeper spring rate characteristic than a “soft” spring. If the spring rate is constant over the full distance traveled by the spring, then the spring has a linear characteristic.
Travel SSP275/006
If the spring rate increases over the distance traveled by the spring, then the spring has a “progressive” characteristic. The characteristics of a coil spring can be influenced as follows: • Spring diameter • Spring wire diameter
1
2
• Number of windings in the spring Features of springs with progressive characteristics include:
3
4
• Uneven winding pitch (1). • Conical winding shape (2). • Conical wire diameter (3). • Combinations of these elements (4).
SSP0275/007
7
Suspension and Damping Basics Spring Travel The necessary total spring travel (stot) of a vehicle without self-leveling suspension comprises the static bump (sstat) and the dynamic spring travel (sdyn) resulting from vehicle vibration when the vehicle is fully laden and when it is unladen. stot = (sstat (fully laden) – sstat (unladen)) + sdyn The static spring travel (sstat) is the distance which the spring is compressed when stationary depending on payload. This is the difference between the static compression of the fully laden vehicle (sstat (fully laden)) and the static compression of the unladen vehicle (sstat (unladen)). sstat = sstat (fully laden) – sstat (unladen)
Definitions The unladen position is the compression of the spring when the serviceable vehicle (including a full tank of fuel, tool kit, and spare wheel, but without a driver or passengers) is standing on its wheels. The design position is the position which the serviceable vehicle adopts when loaded with three persons, each weighing 150 pounds (68 kg). The controlled position is the position in which the vehicle is held by the self-leveling elements of the air suspension system, regardless of payload.
Payload
Where a spring characteristic performance curve is flat (soft spring), the difference, and so the static compression, between
the unladen and fully laden vehicle is large. Where the spring characteristic curve is steep (firm spring), the static compression is small.
Fully Laden Position
Firm Spring Performance Curve
Soft Spring Performance Curve
Unladen Position
Spring Travel (s) sstat Soft Spring sstat Firm Spring
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SSP275/008
Air Suspension Basics Air Suspension Air suspension is a variable-height vehicle suspension system and can be combined with continuously controlled damping.
The advantages of a self-leveling suspension are:
The self-leveling suspension keeps the vehicle body at constant pre-determined ground clearance level. The controlled position is equal to a constant distance between the center of the wheel and the lower edge of the fender wheel opening.
• The static level of the vehicle is constant, regardless of payload.
The vehicle level is controlled by adjusting the pressure acting on the air springs and the associated change of air volume in the air springs.
• Maximum rebound and bump travel are maintained in all load states.
Static compression is always set to sstat = 0, regardless of payload.
• The vehicle can be sprung comfortably.
• Reduced tire wear. • No payload-dependent change of drag coefficient (CD).
• Full ground clearance is maintained, even at maximum payload. • No changes of toe and camber due to changes in payload.
Controlled Position SSP275/010
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Air Suspension Basics In addition to the basic advantages of a self-leveling, full load-bearing air suspension system as described above, the system can also be used to set different vehicle heights.
Full load-bearing air suspension means that only air springs are used as load-bearing spring elements at all wheels.
Three level settings are possible on the Phaeton:
Combined suspension systems are described as partially load-bearing because they consist of a combination of hydraulically or pneumatically controlled steel and gas struts.
Constant
• The normal suspension level. • A raised suspension level for poor road surfaces or rough terrain. • A low suspension level that is set automatically while travelling at fast highway speeds.
Spring Characteristics Fully Laden Design Position Unladen
SSP275/063b
Load-Bearing Force
1124 lbs (5000 N)
899 lbs (4000 N)
674 lbs (3000 N)
450 lbs (2000 N)
225 lbs (1000 N)
Spring Travel -3.15 in (-80 mm)
-1.57 in (-40 mm)
0
Dynamic Rebound
+3.15 in (+80 mm)
Dynamic Bump sstat
10
+1.57 in (+40 mm)
SSP275/063a
Air Suspension Basics Characteristics of Air Springs Spring Force and Spring Rate The spring force or load-bearing force of an air spring is defined by its geometric dimensions (the effective circular area) and the excess pressure acting on the air spring. The effective circular area is defined by the effective circle diameter.
Load-Bearing Force
Excess Pressure
Circle Diameter
With the configuration of a piston in a cylinder, the piston diameter corresponds to the effective circle diameter.
SSP275/011
Load-Bearing Force
The effective diameter of the air spring is defined by the diameter at the lowest point of the air spring (rebounded and compressed). Minor changes in this effective diameter lead to relatively large changes in the area of the circle, and so the load-bearing force of the air spring.
Rebounded Diameter Compressed Diameter SSP275/012
11
Air Suspension Basics The load-bearing force of the spring can be adapted to the load situation simply by changing the effective internal pressure in the air spring.
Rebounded Bump Stop
The different pressures – depending on payload – result in different spring characteristics or spring rates. The spring rates do not change in direct proportion to total body weight. Air Spring Outer Guide
The intrinsic body frequency, a key factor in handling performance, remains almost constant. Spring compression changes the effective air spring diameter because it rolls back on the roll piston.
Roll Piston
Rebounded Diameter
The illustrations show the effect of roll piston contour on effective diameter. SSP275/014
Compressed
Compressed Diameter SSP275/014a
12
Air Suspension Basics In principle, the spring characteristic of an air spring with a cylindrical piston is progressive. The spring characteristic curve (steep or flat) is governed by the air spring volume. The existing air volume is compressed by dynamic compression. Assuming that bump travel is constant, the pressures in a low volume system rise more rapidly than in a system with a large air spring volume.
Load-Bearing Force of Spring
Spring Characteristics Steep Curve (Firm Spring) Small Air Spring Volume Flat Curve (Soft Spring) Large Air Spring Volume 131 psi (900 kPa)
• A flat spring characteristic curve (soft spring) is produced by a large air spring volume.
116 psi (800 kPa)
• A steep curve (firm spring), on the other hand, is produced by a small air spring volume.
102 psi (700 kPa)
The characteristic curve can be influenced by the roll piston contour. Modifying the contour of the roll piston changes the effective diameter, and so the load-bearing force (spring force), of the air spring. An air spring can be tuned for the required application by adjusting the following parameters:
87 psi (600 kPa)
-s
0
+s
• Size of effective circular area. • Amount of air spring volume (air volume).
Spring Travel s SSP275/015
• Outer contour of the roll piston.
13
Air Suspension Basics Air Spring Design There are two different types of air springs: • Partial load-bearing • Full load-bearing In the partial load-bearing type, a combination of steel and gas struts generates the load bearing force of the air spring.
In the full load-bearing type like those used on the Phaeton, the air springs function as the load-bearing spring elements. The full load-bearing air spring assembly includes: • Upper housing with outer guide • Air spring (flexible air bladder) • Roll piston (lower guide) • Auxiliary accumulator (where required)
Typical Externally Guided Full Load-Bearing Air Spring Air Volume
• Integrated shock absorber Upper Housing
Gas Cushion Outer Guide
Flexible Air Bladder The air spring is comprised of a special flexible air bladder made of a high-quality multi-layer elastomer material with reinforcing fabric inlays of nylon cord. The reinforcing fabric absorbs the forces arising in the air spring. The inner layer is specially designed to be airtight. The combination of individual layers in the flexible air bladder provides for good rolling characteristics of the air spring and precise response to the movement of the suspension.
Air Spring (Flexible Air Bladder) Roll Piston
Oil Reservoir
Twin-Tube Shock Absorber
The outer guide is a metallic sleeve used to absorb some of the internal pressure in the air spring and control the shape of the flexible air bladder as it moves over the roll piston. This is an externally guided air spring. Air springs configured without the outer guide are designated “unguided.”
SSP275/027
14
The materials are resistant to all external influences in a temperature range from -31°F to +194°F (-35°C to +90°C).
Damping System Basics Shock Absorbers The task of the shock absorbers is to reduce the vibration energy of structural and wheel vibrations as rapidly as possible by converting vibration energy to heat. Without shock absorbers, the vibrations introduced into the vehicle would build up to the extent that the wheels could lose contact with the road surface. As a result, the vehicle would no longer be steerable. There are several different types of shock absorbers. Single-Tube Gas Pressure Shock Absorber In a single-tube gas pressure shock absorber, the working and oil reservoirs are located in a single cylinder. Changes in oil volume, due to temperature effects and movement of the piston rod and piston when the springs are compressed, are equalized by the gas in the pressurized gas cushion – approximately 363 to 465 psi (2500 to 3000 kPa). The damping valves for the compression and tension stages are integrated into the piston.
Typical Single-Tube Gas Pressure Shock Absorber
Piston Rod
Oil Reservoir Piston with Valves
Pressure Valve
Tension Valve
Gas Cushion
Separating Piston
SSP275/081
15
Damping System Basics Twin-Tube Gas Pressure Shock Absorber The twin-tube gas pressure shock absorber has established itself as the automotive industry standard for vibration damping. As the name indicates, this type of shock absorber consists of two tubes, one inside the other.
Compression Stage
Typical Twin-Tube Gas Pressure Shock Absorber (Compression Stage)
The inner tube acts as the working cylinder. It is completely filled with hydraulic fluid. The piston together with the piston valves and the piston rod move up and down inside the working cylinder.
Piston Rod
Outer Tube
Gas Cushion
The outer tube surrounds the oil reservoir. It is only partially filled with oil. There is a gas cushion above the oil.
Inner Tube
Oil Reservoir Piston Non-Return Valve
Working Cylinder
Piston Bottom Non-Return Valve
Piston Damper Valve Bottom Damper Valve
16
The base of the working cylinder comprises the base plate and bottom valves.
SSP275/082
The oil reservoir equalizes changes in the volume of oil in the working cylinder. Vibrations are damped by the two damping valve units located on the piston and at the base of the working cylinder. They comprise a system of spring washers, coil springs, and valve bodies with restrictor bores. During the compression stage, damping is defined by the bottom damper valve and partly by the flow resistance of the piston. During the rebound stage, vibrations are damped by the piston damper valve alone. This valve produces a defined resistance to the oil as it flows through it to the bottom of the working cylinder.
Damping System Basics In vibration damping, there is a distinction to be made between the compression and rebound stages. The damping force during the compression stage is less than the damping force during the rebound stage. As a result, jolts caused by rough road surfaces are transmitted to a lesser degree to the vehicle body.
Spring Travel
Shock Absorber Tuning
Time
Low Degree of Damping
Shock absorber tuning affects both driving comfort and safety.
SSP275/017
The degree of damping indicates how quickly the vibrations must be reduced. It is dependent on the damping force of the shock absorber and the amount of the sprung mass. Given the same shock absorber tuning, increasing the sprung mass reduces the degree of damping and the vibrations are reduced more slowly. Conversely, a reduction in the sprung mass increases the degree of damping and the vibrations are reduced more quickly.
Spring Travel
Shock absorbers with adjustable damper tuning and continuous control are installed on luxury vehicles. The control module determines within a matter of milliseconds the degree of damping that is required for each wheel.
Time High Degree of Damping SSP275/018
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Damping System Basics
Damping Force The damping force of a shock absorber can be determined using a testing device that can generate different compression and rebound rates while maintaining a constant stroke.
Force-Velocity Diagrams Showing Shock Absorber Characteristic Curves
Compressive Force
Tractive Force
Progressive Action Damping Characteristic
1.17 (0.52)
0.85 (0.26)
The values determined in this way can be represented in force-velocity diagrams. These diagrams clearly show the characteristics of the shock absorbers. 0 -0.85 (-0.26)
-1.71 (-0.52)
Velocity ft/s (m/s) SSP275/019a
Compressive Force
Tractive Force
Digressive Action Damping Characteristic
1.17 (0.52)
0.85 (0.26)
0 -0.85 (-0.26)
-1.71 (-0.52)
Velocity ft/s (m/s) SSP275/019b
Compressive Force
Tractive Force
Linear Action Damping Characteristic
18
1.17 (0.52)
0.85 (0.26)
0 -0.85 (-0.26)
-1.71 (-0.52)
Velocity ft/s (m/s) SSP275/019c
A distinction is made between progressive, digressive, and linear action shock absorbers.
System Description Air Suspension with Continuously Controlled Damping The full load-bearing air suspension with continuously controlled damping used on the Phaeton keeps the vehicle at a constant level above the road, regardless of payload. A constant static ground clearance adapted to driver input or vehicle road speed is maintained between the road and the vehicle floor pan. The system includes: • Level Control System Control Module J197. • Air spring and a vehicle level control system sensor at each corner. • Adjustable shock absorber integrated into the air spring strut at each corner. • Compressor with air drier and temperature sensor. • Solenoid valve block with four strut valves, a drain valve, a pressure accumulator valve, and an integrated pressure sensor. • Pressure accumulator. • Air lines from the compressor to the individual air spring struts and to the pressure accumulator. • Wheel acceleration sensor on each air spring strut (measurement range ± 13 g). • Three body acceleration sensors (measurement range ± 1.3 g).
The Phaeton has three different suspension height settings, the first two of which are driver selectable: • “Normal” suspension level. • “High” suspension level, 1 inch (25 mm) above “Normal”; intended for driving on bad roads. • “Low” suspension level, 0.6 inch (15 mm) below “Normal”; intended for driving at high speed on a highway. Low ride height is selected and deselected automatically depending on vehicle road speed. The system also switches automatically to other levels depending on the driving situation by means of a special control strategy. Ride height adjustments are made in the background and are not normally noticed by the driver. When driving at high speeds, the ground clearance is automatically lowered from the “High” suspension level to the dynamically more stable “Normal” suspension level. At even higher speeds, the ground clearance is automatically reduced to the “Low” suspension level which is not selectable by the driver. The “Low” suspension level is automatically deselected when the vehicle speed drops below a pre-determined speed. The suspension damper tuning “Comfort” setting is automatically adjusted to firmer settings at higher speeds in order to ensure safe handling and track stability.
19
System Description Component Locations 3 2
4
70
5
60 50 40
6
80 100 120 140 160 180
30
Front Information Display Control Head J523 with Menu Selection Rotary Knob E460, Dampening Adjustment Button E387, and Level Control Button E388
CLIMATE
MAP
NAV
AUDIO
SETTINGS
ON/DARK
RESET
VEHICLE
NAV SET
TRIP DATA
MANUAL
HELP
1 50 80 110
20
FM
CD
AM
SCAN
7
60 30
90
1/4
1/2
3/4
20 10
120
Control Module with Indicator Unit in Instrument Panel Insert J285
Left Front Body Acceleration Sensor G341 Right Front Body Acceleration Sensor G342
Left Front Wheel Acceleration Sensor G337 Right Front Wheel Acceleration Sensor G338
Left Front Level Control System Sensor G78 Right Front Level Control Sensor G289
Residual Pressure Maintaining Valve Air Spring Strut, Front Axle (2)
20
12 10
14 16
BAL/FAD
--
200 220 240 260
System Description
Rear Body Acceleration Sensor G343 (Luggage Compartment)
Air Supply Module with Compressor, Air Drier, and Solenoid Valve Block with Integrated Level Control Pressure Sensor G291 Level Control Pump Temperature Sensor G290
Level Control System Control Module J197
Pressure Accumulator
Residual Pressure Maintaining Valve
Left Rear Level Control System Sensor G76 Right Rear Level Control System Sensor G77
Air Spring Strut, Rear Axle (2)
Left Rear Wheel Acceleration Sensor G339 Right Rear Wheel Acceleration Sensor G340
SSP275/020
21
System Description Operation and Display The system features a full load-bearing air spring with self-leveling suspension at each wheel on both the front and rear axles. Each air spring strut assembly combines an air spring integrated with a continuously adjustable damping shock absorber. The system is controlled by the Level Control System Control Module J197. The system is operated by Dampening Adjustment Button E387 and Level Control Button E388 as described in the operating manual. These buttons are located on the center console behind the gear selector lever.
Pressing the appropriate button opens a pop-up menu in the Infotainment display. Selections can then be made using Menu Selection Rotary Knob E460 and the display function keys. The driver can then select between two of the three suspension levels: • “Normal” suspension level (preset) • “High” suspension level Four suspension damper tuning settings are also driver selectable: • • • •
“Comfort” “Basic” (preset) “Sport 1” “Sport 2”
Display
Menu Selection Rotary Knob E460
CLIMATE
MAP
NAV
AUDIO
SETTINGS
ON/DARK
RESET
VEHICLE
NAV SET
TRIP DATA
MANUAL
HELP
Gear Selector Lever
Dampening Adjustment Button E387
FM
CD
AM
SCAN
BAL/FAD
--
Level Control Button E388
SSP275/038
22
System Description Self-Leveling Suspension The Level Control Button E388 must be pressed to set the level. By turning the Menu Selection Rotary Knob E460, the driver can select between “High” suspension level or “Normal” suspension level. The screen corresponding to the level selected is displayed.
“Normal” Suspension Level Display AUTO
AUTO
When the “High” suspension level is set, Level Control Button E388 is lit. The driver can exit the menu by pressing the Menu Selection Rotary Knob E460.
CLIMATE
MAP
NAV
AUDIO
SETTINGS ON SSP275/034
“High” Suspension Level Display AUTO
CLIMATE
MAP
AUTO
NAV
AUDIO
SETTINGS ON SSP275/035
23
System Description Damper Tuning “Comfort” Damper Tuning Display AUTO
AUTO
The driver can select damper tuning by pressing Dampening Adjustment Button E387. By turning the Menu Selection Rotary Knob E460, the driver can select one of the following four damper tuning settings: • “Comfort” • “Basic” (preset) • “Sport 1” • “Sport 2” The corresponding screen is displayed.
CLIMATE
MAP
NAV
AUDIO
SETTINGS ON SSP275/036
“Sport 2” Damper Tuning Display AUTO
CLIMATE
MAP
AUTO
NAV
AUDIO
SETTINGS ON SSP275/037
24
The driver can exit the menu by pressing Menu Selection Rotary Knob E460. In the “Comfort,” “Sport 1,” and “Sport 2” settings, the Dampening Adjustment Button E387 is lit. The damper tuning always resets from the “Sport 2” position to the “Basic” position when the ignition is turned off.
System Description Control Strategy of the Self-Leveling Suspension The relative positions of the vehicle body and the wheels are measured by four level control system sensors located between the axle carriers and the lower wishbones: • Left Front Wheel Acceleration Sensor G337 • Right Front Wheel Acceleration Sensor G338 • Left Rear Level Control System Sensor G76 • Right Rear Level Control System Sensor G77 The reading from each sensor is compared with a default that is stored in the Level Control System Control Module J197 for the corresponding wheel. The Level Control System Control Module J197 must learn these defaults. The air required for self-leveling is normally provided by the compressor up to a maximum pressure of 232 psi (1600 kPa). At road speeds above 22 mph (35 km/h), adjustments are controlled by the compressor. The pressure accumulator is also replenished as required. At road speeds below 22 mph (35 km/h), adjustments are controlled by the pressure accumulator, which has a capacity of 1.32 gallons (5 liters). A sufficient pressure difference of approximately 44 psi (300 kPa) between the pressure accumulator and the air spring is required for this purpose.
Effect of Changes in Vehicle Payload If the height of the vehicle in relation to the road surface changes due to changes in vehicle payload, the Level Control System Control Module J197 readjusts the suspension to the preset default level. Level adjustments are made through several valves integrated into the solenoid valve block. To increase the height, air is channeled to the four air springs through the four suspension strut solenoid valves: • Left Front Suspension Strut Valve N148 • Right Front Suspension Strut Valve N149 • Left Rear Suspension Strut Valve N150 • Right Rear Suspension Strut Valve N151 To decrease the height, air is discharged to the atmosphere through the Solenoid for Level Control System N111, which is essentially a drain valve. Activation of the compressor to replenish air pressure in the pressure accumulator is independent of the leveling adjustments.
25
System Description Automatic Level Adjustments
Automatic increase in suspension level occurs from:
Changes in vehicle speed will trigger automatic adjustments in the self-leveling suspension system.
• “Low” to “Normal”: — After 60 seconds at speeds of 62 mph (100 km/h) or less.
Automatic decrease in suspension level occurs from: • “High” to “Normal” at speeds of 75 mph (120 km/h) or greater.
— Immediately at 50 mph (80 km/h) or less.
• “Normal” to “Low”: — After 30 seconds at 87 mph (140 km/h) or greater. — Immediately at 112 mph (180 km/h) or greater.
Level “High” Level +1 inch (+25 mm)
“Normal” Level
30 seconds
0 inch (0 mm) “Low” Level
60 seconds
- 0.6 inch (-15 mm)
0 (0)
50 (80)
62 (100)
75 (120)
87 (140)
99 (160)
112 (180)
124 mph (200) (km/h)
Manual Adjustment Automatic Adjustment SSP275/021
26
System Description Manual Deactivation and Activation In special situations, it may be necessary to deactivate the self-leveling suspension system. To change a wheel or to carry out work on the vehicle while it is raised on a hoist for example.
The self-leveling suspension is automatically raised to the “Normal” level again after the engine, and therefore the compressor, has been running for a short period of time.
When the vehicle is raised on a hoist or other lifting equipment at the lift points, air is allowed to escape from all four air springs until the Level Control System Control Module J197 determines that the vehicle has been lifted.
Deactivating the System
The self-leveling suspension initially detects when the vehicle body is too high in relation to the wheels and adjusts the vehicle height accordingly by allowing air to escape from the springs.
A message indicating that the self-leveling suspension has been deactivated will appear on the instrument panel display.
As a result, the vehicle may have a very low ground clearance when the lifting equipment is lowered.
The suspension system can be reactivated manually by pressing both Dampening Adjustment Button E387 and Level Control Button E388 simultaneously for about five seconds.
To avoid this discharge of air, the self-leveling suspension must be deactivated before lifting the vehicle.
The self-leveling suspension can be deactivated by pressing both Dampening Adjustment Button E387 and Level Control Button E388 simultaneously for about five seconds.
Activating the System
The system will automatically reactivate when the Level Control System Control Module J197 determines that the vehicle is travelling at a speed of 6.2 mph (10 km/h) or greater.
27
System Description Actions of Air Suspension After “Ignition Off” System Response to Immediate Level Changes After “ignition off,” the Level Control System Control Module J197 remains active for approximately one minute. During this time it can execute suspension adjustments to compensate for changes in payload, provided that sufficient pressure is available in the pressure accumulator. The Level Control System Control Module J197 always remains active for one minute until no further door hood, or luggage compartment lid operations are detected.
28
System Response to Gradual Level Changes Gradual level changes can occur when the air in the air springs heats up during vehicle operation and cools down again at the end of the trip. To compensate for gradual level changes, three adjustments are made to achieve optimum ground clearance after “ignition off.” These adjustments are made after approximately two, five, and ten hours, provided that sufficient pressure is available in the pressure accumulator.
System Description Shock Absorber Control The damping control system registers the condition of the road surface and the movements of the vehicle using four wheel acceleration sensors and three body acceleration sensors. The characteristics of the individual shock absorbers are adjusted according to the calculated damping requirements. In this case, the shock absorbers function as active components during compression and rebound cycles. Continuous damping control is based on shock absorbers whose characteristics are electrically adjustable. These shock absorbers are integrated in the air spring struts. Damping force can be set depending on the characteristic map via the proportional dampening adjustment valves built into the shock absorbers. As a result, they can adapt the damping force to the
driving situation and road conditions within milliseconds. Shock absorber damping is adjusted depending on the vertical acceleration rates of the wheels and the vehicle body. The Level Control System Control Module J197 always attempts to set the damping force according to the “skyhook control strategy.” Ideally, this strategy would control damping as if the vehicle body were suspended by a hook in the sky and hovering above the road without interference from the surface of the road. Maximum driving comfort is achieved by attempting to reach this ideal. Firm damping is achieved by low control rates. Soft damping is achieved by high control rates.
Characteristic Map of Damper Force in Phaeton Front Axle lbs
(dN)
13.49 (600)
50 mA
Rebound Stage
Damper Force in Pounds (dN)
Compression Stage
600 mA
11.24 (500) 1200 mA 8.99 (400) 1800 mA 6.74 (300)
4.50 (200)
50 mA 600 mA 1200 mA 1800 mA
2.25 (100)
0
(0) 78.74 (2000)
59.06 (1500)
39.37 (1000)
19.69 (500)
0 (0)
19.69 (500)
39.37 (1000)
Damper Speed in Inches per Second (mm/s)
59.06 (1500)
78.74 (2000)
in/s (mm/s) SSP275/022
29
System Description Diagram of Air Suspension System with Continuously Controlled Damping This system diagram highlights the relationships with other vehicle systems as well as display and operating elements.
Front Information Display Control Head J523 with Menu Selection Rotary Knob E460
Level Control System Control Module J197 Inputs via CAN Data Bus: • ABS Control Module with EDL/ASR/ESP J104 • Engine Control Module • Control Module with Indicator Unit in Instrument Panel Insert J285 • Vehicle Electrical System Control Module J519 • Infotainment System
Level Control Button E388 Compressor
Dampening Adjustment Button E387
Pressure Accumulator
Control Module with Indicator Unit in Instrument Panel Insert J285
Air Spring Strut with Electrically Adjustable Shock Absorber
Connection via CAN Data Bus
Wheel Acceleration Sensors: Left Front Wheel Acceleration Sensor G337 Right Front Wheel Acceleration Sensor G338 Left Rear Wheel Acceleration Sensor G339 Right Rear Wheel Acceleration Sensor G340
Connection via On-Board Power Supply
Body Acceleration Sensors: Left Front Body Acceleration Sensor G341 Right Front Body Acceleration Sensor G342 Rear Body Acceleration Sensor G343
30
SSP275/025
Diagnosis via K Wire
Schematic Diagram of the Overall System
Diagnosis via CAN Data Bus
System Description
Battery Management
Control Module with Indicator Unit in Instrument Panel Insert Convenience CAN Data Bus J285 with Data Bus On-Board Infotainment Diagnostic Interface J533
Steering Angle Sensor G85
Drivetrain CAN Data Bus
Electronic Stabilization Program
Door, Hood, and Luggage Compartment Lid Signals
Engine Control Module
Terminal 30 and Terminal 15 Status Signals
Relay for Compressor Level Control System J403
Dampening Adjustment Button E387 and Level Control Button E388
Level Control System Control Module J197
Headlight Range Control
Level Control Pump Temperature Sensor G290
Level Control Pressure Sensor G291
Solenoid for Level Control System N111 (Drain Valve)
Left Front Dampening Adjustment Valve N336
Left Front Suspension Strut Valve N148 Right Front Suspension Strut Valve N149 Left Rear Suspension Strut Valve N150 Right Rear Suspension Strut Valve N151 Level Control Accumulator Valve N311
Left Rear Level Control System Sensor G76
Left Front Wheel Acceleration Sensor G337
Right Front Dampening Adjustment Valve N337
Right Rear Level Control System Sensor G77
Right Front Wheel Acceleration Sensor G338
Left Rear Dampening Adjustment Valve N338
Left Front Level Control System Sensor G78
Left Rear Wheel Acceleration Sensor G339
Right Rear Dampening Adjustment Valve N339
Right Front Level Control Sensor G289
Right Rear Wheel Acceleration Sensor G340 Left Front Body Acceleration Sensor G341 Right Front Body Acceleration Sensor G342 Rear Body Acceleration Sensor G343 SSP275/023
31
System Description System Overview Sensors
Dampening Adjustment Button E387 Level Control Button E388
Left Rear Level Control System Sensor G76 Right Rear Level Control System Sensor G77 Left Front Level Control System Sensor G78 Right Front Level Control Sensor G289
Level Control Pump Temperature Sensor G290
Level Control Pressure Sensor G291 (Integrated in Solenoid Valve Block)
Left Front Wheel Acceleration Sensor G337 Right Front Wheel Acceleration Sensor G338 Left Rear Wheel Acceleration Sensor G339 Right Rear Wheel Acceleration Sensor G340
Left Front Body Acceleration Sensor G341 Right Front Body Acceleration Sensor G342 Rear Body Acceleration Sensor G343
Additional Signals: Door, Hood, and Luggage Compartment Lid Contact Signals
32
CLIMATE
MAP
NAV
RESET
VEHICLE
NAV SET
FM
CD
AM
SCAN
AUDIO
SETTINGS ON/DARK
MANUAL
BAL/FAD
--
HELP
System Description Actuators
Level Control System Control Module J197
Solenoid for Level Control System N111 (Drain Valve Integrated in Solenoid Valve Block)
Left Front Suspension Strut Valve N148 Right Front Suspension Strut Valve N149 Left Rear Suspension Strut Valve N150 Right Rear Suspension Strut Valve N151 (Integrated in Solenoid Valve Block)
Level Control Accumulator Valve N311 (Integrated in Solenoid Valve Block)
Left Front Dampening Adjustment Valve N336 Right Front Dampening Adjustment Valve N337 Left Rear Dampening Adjustment Valve N338 Right Rear Dampening Adjustment Valve N339 (Integrated in Air Spring Struts) 3 2
4
70
5
60 50 40
6
30
1 50 80 110
20
7
60 30
90 120
1/4
1/2
3/4
20 10
80 100 120 140 160 180 200 220 240 260
12 10
14 16
Control Module with Indicator Unit in Instrument Panel Insert J285 with Data Bus On-Board Diagnostic Interface J533 16-Pin Connector T16 (Diagnostic Connection)
Relay for Compressor Level Control System J403
Left Headlight Range Control Module J567 Right Headlight Range Control Module J568 (Integrated in the Headlights)
SSP275/026
33
Design and Function Level Control System Control Module J197 The Level Control System Control Module J197 is located in the luggage compartment on the left-hand side behind the side trim. It is bolted behind the backup fuse and electronics boxes. The Level Control System Control Module J197 has the following tasks:
The Level Control System Control Module J197 has a redundant processor design (dual processors); the air spring algorithm runs primarily on the first processor and damping control runs primarily on the second processor.
• Control air suspension and the shock absorbers. • Monitor the overall system. • Diagnose the overall system. • Communicate via the drivetrain CAN data bus.
SSP275/083
34
Design and Function Air Spring Struts Air spring struts with externally guided, two-layer air springs are used on the front and rear axles of the Phaeton. The air spring is a flexible air bladder arranged concentrically around the twin-tube gas-filled shock absorber. The thin wall of the air spring provides excellent suspension response. The desired spring rate is achieved by combining the effects of the roll piston contour, the outer guide, and an auxiliary accumulator directly attached to the strut. Front Axle Air Spring Strut
Different auxiliary accumulators are used at the front and rear axles. • The cylindrical accumulators on the front axle struts have a capacity of 24.4 cubic inches (0.4 liter). • The ball accumulators on the rear axle struts have a capacity of 73.2 cubic inches (1.2 liters). Dampening Adjustment Valve Connecting Wires
Strut Support Bearing Compression/Rebound Bearing
Air Spring Cover Auxiliary Spring (Bump Stop)
Air Spring Shock Absorber Piston Rod Roll Piston
Outer Guide
Protective Bellows
Auxiliary Accumulator
Shock Absorber
SSP275/027a
35
Design and Function The air spring struts are designed to minimize the effect of transverse forces on the shock absorbers. The special design of the strut support bearing on the front axle air spring struts and the controlled flexing at the fluid-cushioned top ends of the rear struts help reduce the effects of transverse forces on the shock absorbers.
Rear Axle Air Spring Strut
A residual pressure maintaining valve is mounted directly on the air connection of each air spring strut. It maintains a residual pressure of about 51 psi (350 kPa) in the air spring strut. This permits easy assembly and mounting of the components. The outer guide protects the air spring against dirt and damage besides its function of guiding the flexible air bladder and the protective bellows. Air Spring Cover
Dampening Adjustment Valve Connecting Wires Auxiliary Accumulator
Compression/Rebound Bearing
Auxiliary Spring (Bump Stop) Shock Absorber Piston Rod Outer Guide
Air Spring
Roll Piston
Protective Bellows
Shock Absorber SSP275/028
36
Design and Function Dampening Adjustment Valves The continuous damping control twin-tube gas-filled shock absorbers are adjustable over a wide range of damping forces via electrically controlled valves integrated in their pistons: • Left Front Dampening Adjustment Valve N336 • Right Front Dampening Adjustment Valve N337
Example of a Dampening Adjustment Valve
Dampening Adjustment Valve Connecting Wires
Hollow Piston Rod
Housing
• Left Rear Dampening Adjustment Valve N338 • Right Rear Dampening Adjustment Valve N339 The oil flow through these valves, and hence the damping force, can be adapted to momentary demands within a few milliseconds by varying the electric current flowing through the adjustment valve solenoids. The wheel acceleration sensors mounted on each shock absorber generate signals which, together with the signals supplied by the three body acceleration sensors, are used to calculate the required damper setting. Since the system can rapidly detect and control rebound and compression stages, it permits adjustment of the damping force required for the momentary driving situation. The driving situation dependent control maps for system reaction to various driving situations are stored in the Level Control System Control Module J197.
Solenoid Armature Container Tube
Valve Spring
Cylinder Tube Main Damping Valve Auxiliary Valve
Oil Flow SSP275/093
In certain driving dynamic states – e.g. longitudinal or transverse dynamics – the “skyhook control” is deactivated and the shock absorbers are controlled by other dynamic models.
37
Design and Function Air Spring Strut, Front Axle Shock Absorber Components (Green Highlighted Area)
Air Spring Components (Blue Highlighted Area)
Connection for Dampening Adjustment Valve
Piston Rod Air Spring
Flexible Air Bladder
Shock Absorber
Left Front Dampening Adjustment Valve N336 or Right Front Dampening Adjustment Valve N337
Auxiliary Accumulator
SSP275/086
38
SSP275/084
Design and Function Air Spring Strut, Rear Axle Shock Absorber Components (Green Highlighted Area)
Air Spring Components (Blue Highlighted Area)
Connection for Dampening Adjustment Valve
Air Spring
Piston Rod
Auxiliary Accumulator Shock Absorber Flexible Air Bladder
Left Rear Dampening Adjustment Valve N338 or Right Rear Dampening Adjustment Valve N339
SSP275/087
SSP275/085
39
Design and Function Air Supply Module The air supply module is a compact unit. It is mounted to the underbody on an anti-vibration mount in the spare-wheel well adjacent to the activated charcoal filter (EVAP canister). A plastic cover with vents provides protection from dirt. The compressor is supplied with air from the luggage compartment. Air is drawn into the compressor through the silencer with air filter, cleaned, and pumped into the system.
The air supply module also includes a solenoid valve block with: • Control valves for each air spring strut: — Left Front Suspension Strut Valve N148 — Right Front Suspension Strut Valve N149 — Left Rear Suspension Strut Valve N150 — Right Rear Suspension Strut Valve N151
The Level Control Pump Temperature Sensor G290 protects the compressor against overheating and ensures availability of the air supply for the air suspension in all climatic and driving conditions.
• Control valve for the for the pressure accumulator:
The air supply module includes a compressor unit with:
• Monitor for the pressure accumulator:
• Electric motor • Dry-running compressor • Air drier • Residual pressure maintaining unit • Maximum pressure limiter • Solenoid for Level Control System N111 (drain valve) • Silencer with air filter • Level Control Pump Temperature Sensor G290 (temperature sensor for overheating protection) • Pneumatic drain valve with pressure relief valve
40
— Level Control Accumulator Valve N311 — Integrated Level Control Pressure Sensor G291
Design and Function
Vibration Isolator
Intake/Drain Line
Solenoid Valve Block
Silencer/Filter
Electric Motor
T-Connection for Intake Circuit and Drain Circuit
Compressor
Level Control Pump Temperature Sensor G290 Drain Line Pneumatic Drain Valve
Air Drier
SSP275/031
41
Design and Function Compressor Unit Compressed air is produced by a single-stage piston compressor with integrated air drier.
The Solenoid for Level Control System N111 (drain valve), a pneumatic drain valve with pressure limiting valve, and three non-return valves are integrated in the air drier housing.
To prevent internal contamination of the air springs and the air drier cartridge, compressor design is of the dry-running type. Lifetime-lubricated bearings and a piston ring made of polytetrafluorethylene ensure a long service life.
To protect the compressor against overheating, it is turned off if excess temperature occurs.
Air Drier Non-Return Valve 3
Non-Return Valve 1
Pneumatic Drain Valve with Pressure Limiting Valve
Cylinder Diaphragm Valve “Closed”
Solenoid for Level Control System N111 (Drain Valve)
Piston Ring
Pressure Connection
Lifting Piston
Drain Connection
Intake Fitting
Non-Return Valve 2 Electric Motor SSP275/032
42
Design and Function Intake/Compression Cycles During the upward movement of the piston, air is drawn into the compressor crankcase through the intake fitting via the silencer/filter. Air in the cylinder is compressed above the piston and flows into the air drier via non-return valve 1.
The compressed and dried air flows via non-return valve 2 and the pressure connection to the valves and the pressure accumulator.
Air Drier Non-Return Valve 1
Piston Moves Upward Intake Fitting
Pressure Connection
Compressor Crankcase
Non-Return Valve 2
SSP275/039
43
Design and Function Bypass Air Flow
Fill/Lift Cycles
During the downward movement of the piston, air drawn into the crankcase bypasses the diaphragm valve and flows into the cylinder.
To fill the air springs and thus raise the vehicle, the Level Control System Control Module J197 activates the compressor relay (Relay for Compressor Level Control System J403) and the four air spring suspension strut valves at the same time.
Diaphragm Valve “Open” Cylinder Bypass Air Flow
Piston Moves Downward
SSP275/040
44
Design and Function Drain/Lowering Cycles (Front Axle Components Shown) Left Front Suspension Strut Valve N148, Right Front Suspension Strut Valve N149, and Solenoid for Level Control System N111 (drain valve) are activated (open)
during the drain cycle. The air spring pressure flows toward the pneumatic drain valve and from there via the air drier, the pressure limiting valve, and the silencer/filter into the spare-wheel well in the luggage compartment. Pneumatic Drain Valve “Open”
Pressure Limiting Valve and Solenoid for Level Control System N111 (Drain Valve) “Open”
Air Drier
To Silencer/Filter SSP275/041
Drain Cycle Pneumatic Diagram (Front Axle Components Shown) Signal from Relay for Compressor Level Control System J403
Signal from Level Control System Control Module J197
Pneumatic Drain Valve Drain Restrictor M
Silencer/Filter
Non-Return Valve 1
Non-Return Air Drier Valve 3
Non-Return Valve 2
Solenoid for Level Control System N111 (Drain Valve)
Left Front Suspension Strut Valve N148 Right Front Suspension Strut Valve N149
Signals from Level Control System Control Module J197
SSP275/042
45
Design and Function Pneumatic Drain Valve The pneumatic drain valve performs two functions: • Residual pressure maintenance • Pressure limitation To prevent damage to the air springs (flexible air bladders), a specific minimum pressure of at least 51 psi (350 kPa) must be maintained. This is referred to as the air spring residual pressure. The maintenance residual pressure ensures that pressure in the air spring system does not drop below 51 psi (350 kPa) during pressure relief during normal operation. Residual pressure cannot be maintained if there is a leak in the system upstream of the pneumatic drain valve.
When an air spring pressure of more than 51 psi (350 kPa) is applied, the valve body lifts against the spring force of the two valve springs and opens valve seats 1 and 2. The air spring pressure is then admitted into the air drier via the flow restrictor and non-return valve 3. After passing through the air drier, the air passes the open valve seat of the pressure limiting valve and through the silencer/filter in the spare-wheel well in the luggage compartment. A sharp decrease in pressure downstream of the flow restrictor leads to a reduction in relative atmospheric humidity, thereby increasing the amount of moisture that will be absorbed by the air that is discharged into the luggage compartment. Valve Body
Pneumatic Drain Valve
Flow Restrictor Non-Return Valve 3
Pressure Limiting Valve “Open” Air Drier
Valve Seat 1 Solenoid for Level Control System N111 (Drain Valve) “Open”
Valve Seat 2
Line to Solenoid Valve Block To Silencer/Filter
46
SSP275/043
Design and Function Pressure Limiting Valve
In such a case, the pressure limiting valve will open against the spring force when the pressure exceeds approximately 290 psi (2000 kPa), and air conveyed by the compressor will escape through the silencer/filter.
The pressure limiting valve protects the system against excessively high pressures, as for example if the compressor fails to cut out due to a defective contact in the Relay for Compressor Level Control System J403 or a defective Level Control System Control Module J197. Pressure Limiting Valve “Open”
Lifting Piston Intake Fitting
To Silencer/Filter SSP275/044
Pressure Limiting Valve Actuation Pneumatic Diagram No “Cut Out” Signal from Relay for Compressor Level Control System J403
No “Drain Valve Open” Signal from Level Control System Control Module J197
Pneumatic Drain Valve with Pressure Limiting Valve
M Compressor
Silencer/Filter
SSP275/044a
47
Design and Function Air Drier The air in the self-leveling air suspension system must be dehumidified to avoid problems caused by the condensation of water in the system:
As a result of this regenerative process, the air drier requires no maintenance. It is not subject to a replacement interval.
• Corrosion • Freezing An air drier is used to dehumidify the air. The air drier uses a regenerative process to remove moisture from the air. The air compressed in the self-leveling air suspension system is routed through a silicate granulate and dried in the process.
Since the air drier is only regenerated by discharged air, the compressor must not be used to fill other vessels with compressed air. Moisture in the system signifies that the air drier has failed or the system is otherwise malfunctioning.
This granulate is able to absorb atmospheric humidity amounting to over 20% of its natural weight, depending on temperature. When the air in the system is released to lower the air springs, it flows back through the silicate granulate and is discharged to the atmosphere. During this phase, the dry air extracts the moisture from the granulate that was absorbed during the intake cycle. SSP275/033
Air Drier with Silicate Granulate Filling
SSP275/045
48
Design and Function Pressure Accumulator
Air Supply Strategy
Extraction of compressed air from the pressure accumulator allows the vehicle level to be raised quickly with a minimum of noise. The pressure accumulator is only filled while the vehicle is moving. As a result, compressor operation is barely audible.
At road speeds below 22 mph (35 km/h), air is primarily supplied by the pressure accumulator, provided that sufficient pressure is available.
Provided that sufficient pressure is available in the pressure accumulator, the vehicle level can be raised even if the compressor is not running. Pressure is sufficient when the pressure difference between the pressure accumulator and the air springs is at least 44 psi (300 kPa) before increasing the level.
At road speeds above 22 mph (35 km/h), air is primarily supplied by the compressor.
The pressure accumulator is made of aluminum and has a capacity of 1.32 gallons (5 liters). The maximum operating pressure is about 232 psi (1600 kPa).
The pressure accumulator is only filled when the vehicle is travelling at speeds above 22 mph (35 km/h).
This supply strategy ensures that the system operates silently and conserves vehicle battery capacity. The compressor starts running when compressed air is extracted from the pressure accumulator even if the driver has not adjusted the vehicle’s level.
Pressure Accumulator
SSP275/064
49
Design and Function Self-Leveling Suspension Pneumatic Diagram Signal from Relay for Compressor Level Control System J403
Signal from Level Control System Control Module J197
Pneumatic Drain Valve
M
Silencer/Filter
Solenoid for Level Control System N111 (Drain Valve)
Motor for Compressor – Level Control System V66 Non-Return Valve 1
Drain Restrictor
Air Drier
Non-Return Non-Return Valve 3 Valve 2
p
Level Control Pressure Sensor G291
Level Control Accumulator Valve N311
Left Rear Suspension Strut Valve N150
Right Rear Suspension Strut Valve N151
Left Front Suspension Strut Valve N148
Right Front Suspension Strut Valve N149
Left Rear Air Spring Strut
Right Rear Air Spring Strut
Left Front Air Spring Strut
Right Front Air Spring Strut
Pressure Accumulator
SSP275/065
50
Design and Function Solenoid Valves The air spring self-leveling suspension system has six solenoid valves. The Solenoid for Level Control System N111 (drain valve) together with the pneumatic drain valve form a functional unit that is integrated in the air drier housing.
Compressor Connection Red – Left Front Suspension Strut Valve N148 Lilac – Level Control Accumulator Valve N311
The Solenoid for Level Control System N111 is a 3/2-way drain valve and is normally closed when de-energized. The pneumatic drain valve has two tasks: to limit total system pressure and to maintain residual pressure. Blue – Right Rear Suspension Strut Valve N151
The following valves are combined in the solenoid valve block: • Level Control Accumulator Valve N311 • The four air spring suspension strut valves: — Left Front Suspension Strut Valve N148 — Right Front Suspension Strut Valve N149
Black – Left Rear Suspension Strut Valve N150 Green – Right Front Suspension Strut Valve N149
Electrical Connection
— Left Rear Suspension Strut Valve N150 — Right Rear Suspension Strut Valve N151 The valves in the solenoid valve block are designed as 2/2-way valves and are normally closed when de-energized. The system pressure on the air spring and accumulator side acts in the closing direction. To avoid confusion when connecting them, the pressure lines and their matching connections on the solenoid valve block are color coded.
Solenoid Valve Block
SSP275/066
51
Design and Function Level Control Pump Temperature Sensor G290 To protect the compressor from overheating and thus ensure system availability, Level Control Pump Temperature Sensor G290 is attached to the compressor cylinder head.
The Level Control System Control Module J197 shuts the compressor down and inhibits starting when a maximum permissible compressor temperature is exceeded.
Level Control Pump Temperature Sensor G290
SSP275/067
52
Design and Function Level Control Pressure Sensor G291 The Level Control Pressure Sensor G291 is integrated in the solenoid valve block and monitors the pressure in the pressure accumulator and the air springs. Level Control Pressure Sensor G291 generates a voltage signal proportional to the pressure.
Level Control Pressure Sensor G291 Left Rear Suspension Strut Valve N150
p
Information on accumulator pressure is required to make plausibility checks on the up-control functions and perform self-diagnosis. The individual pressures of the air springs and the pressure accumulator can be determined by activating the solenoid valves accordingly. The individual pressures are measured while the air springs or the pressure accumulator are evacuating or filling. The pressures determined in this way are stored and updated by the Level Control System Control Module J197.
Level Control Accumulator Valve N311 Pressure Accumulator
During vehicle operation the accumulator pressure is determined and updated by the Level Control System Control Module J197 every six minutes.
Solenoid Valve Block SSP275/068
53
Design and Function Vehicle Level Control System Sensors Front Axle Vehicle Level Control System Sensor
The four vehicle level control system sensors are wheel angle sensors: • Left Rear Level Control System Sensor G76 • Right Rear Level Control System Sensor G77 • Left Front Level Control System Sensor G78 • Right Front Level Control Sensor G289 Changes in the level of the vehicle body are registered and converted to angular changes using coupling rod kinematics. The wheel angle sensors used operate according to the induction principle. SSP275/076
The signal output provides an angle-proportional pulse-width-modulated signal for the self-leveling suspension.
Rear Axle Vehicle Level Control System Sensor
The four sensors are identical; only the mounts and the coupling rod kinematics are specific for each side and axle. Deflection of the sender crank, and hence the output signal, is opposed on the left and right. As a result, during suspension compression for example, the output signal rises on one side and drops on the other side. SSP275/075
Coupling Rods
54
Design and Function
Level Control System Sensor Design A level control system sensor basically consists of a stator and a rotor. The stator comprises a multi-layer board that houses the exciter coil and three receiver coils, as well as the control and electronic evaluation module. The three receiver coils are star-shaped and arranged in an offset pattern. The stator exciter coil is located on the back of the board.
The rotor is connected to the actuating lever and moves with it. A closed conductor loop is located on the rotor. The conductor loop has the same geometric shape as the three receiver coils.
Actuating Lever on Rotor Contacts to Printed Circuit Board
Rotor with Conductor Loop Electrical Connection
Stator Exciter Coil Control and Electronic Evaluation Module
Contacts
Front of Multi-Layer Board with Receiver Coils
Back of Multi-Layer Board
SSP275/069
55
Design and Function Level Control System Sensor Function
Stator Board Alternating Current
Three Receiver Coils
V1
The electric current induced in the conductor loop of the rotor in turn produces an alternating electromagnetic field (second magnetic field) around the rotor conductor loop. The alternating fields of the exciter coil and the rotor act upon the three receiver coils and induce position-dependent AC voltages in the receiver coils.
V2
V3
Exciter Coil First Magnetic Field Around Exciter Coil Conductor Loop With Induced Current
Rotary Motion
Second Magnetic Field Around Conductor Loop
Alternating Current
Rotor Connected to Actuating Lever SSP275/070
56
An alternating current flows through the stator exciter coil and produces an alternating electromagnetic field (first magnetic field) around the exciter coil. This alternating field permeates the conductor loop of the rotor.
Whereas induction in the rotor is independent of the rotor’s angular position, induction in the receiver coils is dependent on their distance from the rotor, and hence their angular position in relation to the rotor.
Design and Function Since rotor overlap in relation to the individual receiver coils varies depending on angular position, the induced voltage amplitudes in the receiver coils vary according to their angular position.
The control and electronic evaluation module rectifies and amplifies the AC voltages of the receiver coils and proportions the output voltages of the three receiver coils (ratiometric measurement). After the voltage is evaluated, the result is converted to output signals from the level sensor and made available to the control modules for further processing.
Example of Voltage Amplitudes in the Receiver Coils Depending on Rotor Position V1
0 Time
Receiver Coil 1
V2
0 Time Receiver Coil 2
V3 0 Time Receiver Coil 3
SSP275/071
57
Design and Function Body Acceleration Sensors Left Front Body Acceleration Sensor G341 in Left Front Wheel Housing
The three body acceleration sensors measure the vertical acceleration of the vehicle body. • Left Front Body Acceleration Sensor G341 is located in the left front wheel housing. • Right Front Body Acceleration Sensor G342 is located in the right front wheel housing. • Rear Body Acceleration Sensor G343 is located in the right front area of the luggage compartment, behind the luggage compartment lining.
SSP275/079
Rear Body Acceleration Sensor G343 in Luggage Compartment
SSP275/080
58
Design and Function Wheel Acceleration Sensors There are four wheel acceleration sensors used in the Phaeton air suspension system with continuously controlled damping: • Left Front Wheel Acceleration Sensor G337 • Right Front Wheel Acceleration Sensor G338 • Left Rear Wheel Acceleration Sensor G339 • Right Rear Wheel Acceleration Sensor G340 They are all mounted directly on their respective air spring struts at the front and rear axles. They measure wheel acceleration. The Level Control System Control Module J197 uses these signals along with body acceleration signals to calculate the direction in which the struts are moving in relation to the vehicle body.
Left Front Wheel Acceleration Sensor G337 or Right Front Wheel Acceleration Sensor G338
SSP275/088
Left Rear Wheel Acceleration Sensor G339 or Right Rear Wheel Acceleration Sensor G340
SSP275/080 SSP275/089
59
Design and Function Function and Design of the Acceleration Sensors All of the body and wheel acceleration sensors used in the system are essentially the same and operate identically. They do have different mechanical attachments and measurement ranges (sensitivity). The acceleration sensors operate according to the capacitive measurement principle. A flexibly mounted mass (m) acting as a center electrode oscillates between capacitor plates and varies the capacitance of capacitors C1 and C2 in the opposite direction at the same rate as their oscillation.
Acceleration sensor measurement ranges: Acceleration due to the force of gravity varies depending upon where on the earth it is measured. The force of gravity is greater measured at the poles and less at the equator. The abbreviation “g” is the accepted unit of measurement for acceleration due to the force of gravity.
The plate distance d1 of one capacitor increases by the same amount as the distance d2 decreases in the other capacitor.
Acceleration due to gravity is normally designated as 1g, but the standard value of the factor for gravitational force varies slightly between different regions of the world.
The capacitance in the individual capacitors changes as a result.
• The U.S. customary standard used is 32.16 ft/sec2.
An electronic evaluation module supplies an analog signal voltage to the Level Control System Control Module J197.
• The European metric standard used is 9.81 m/sec2, which converts to 32.185 ft/sec2.
Capacitive Measurement Principle of the Acceleration Sensors
For an understanding of the acceleration sensors and how they operate, these minor differences are unimportant. The body acceleration sensors have a measurement range of ± 1.3 g.
C1
The wheel acceleration sensors have a measurement range of ± 13 g. d1 m d2
C2
SSP275/091
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Design and Function Interfaces CAN Data Bus Information Exchange Information on air suspension and damping control is exchanged between the Level Control System Control Module J197 and the networked control modules via the drivetrain CAN data bus, with the exception of a few interfaces.
This system overview shows examples of the type of information provided via the drivetrain CAN data bus and received and used by the networked control modules.
Engine Control Module:
Level Control System Control Module J197 System status (OK or Not OK)
Drivetrain CAN Data Bus High
Engine speed
ABS Control Module with EDL/ASR/ESP J104: ESP status
Self-diagnosis Fault memory entry Level status Front Information Display Control Head J523
Increase in level Information interchange with Infotainment system Operation of Infotainment system Information interchange with Control Module with Indicator Unit in Instrument Panel Insert J285
Information Sent from Level Control System Control Module J197 Information Received and Evaluated by Level Control System Control Module J197
Drivetrain CAN Data Bus Low
Decrease in level
Vehicle Electrical System Control Module J519
Driver Identification Control Module J589
SSP275/074
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Design and Function Functional Diagram – Air Suspension with Continuously Controlled Damping Components E256 E387 E388
ASR/ESP Button Dampening Adjustment Button Level Control Button
F213
Door Contact Switch, Driver’s Door
G76 G77 G78 G289 G290 G291 G337 G338 G339 G340 G341 G342 G343
Left Rear Level Control System Sensor Right Rear Level Control System Sensor Left Front Level Control System Sensor Right Front Level Control Sensor Level Control Pump Temperature Sensor Level Control Pressure Sensor Left Front Wheel Acceleration Sensor Right Front Wheel Acceleration Sensor Left Rear Wheel Acceleration Sensor Right Rear Wheel Acceleration Sensor Left Front Body Acceleration Sensor Right Front Body Acceleration Sensor Rear Body Acceleration Sensor
J104 J197 J403 J567 J568
ABS Control Module with EDL/ASR/ESP Level Control System Control Module Relay for Compressor Level Control System Left Headlight Range Control Module Right Headlight Range Control Module
N111 N148 N149 N150 N151 N311 N336 N337 N338 N339
Solenoid for Level Control System (Drain Valve) Left Front Suspension Strut Valve Right Front Suspension Strut Valve Left Rear Suspension Strut Valve Right Rear Suspension Strut Valve Level Control Accumulator Valve Left Front Dampening Adjustment Valve Right Front Dampening Adjustment Valve Left Rear Dampening Adjustment Valve Right Rear Dampening Adjustment Valve
S
Fuse
V66
Motor for Compressor – Level Control System
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Color Coding Input Signal Output Signal Positive Ground CAN Data Bus
Design and Function
30 15
S19 5A
F213
Can Data Bus – Low
S44 10A
Can Data Bus – High
30 15
S6 40A
J567/J568 G337
G338
G339
G340
G341
G342
G343
G76
G77
G78
G289
J197
E387
E388 t° M G291
E256
N148 N149 N150 N151
N311
N336
N337
N338
N339
G290 V66 N111
J403
J104 31
31 SSP275/073
63
Design and Function Additional Interfaces Door Contact Signal
Headlight Range Control Signal
This signal is a ground signal from the Vehicle Electrical System Control Module J519. It indicates that a vehicle door or the luggage compartment lid has been opened.
Level height adjustments are made for each axle. This would temporarily reduce the range of vision while driving at night. The Phaeton is equipped with a headlight range control. The automatic dynamic headlight range control keeps the light cone at a constant angle.
It serves as a “wake up signal” for the transition from sleep mode to standby mode. Terminal 50 Signal (Via CAN Data Bus) This signal indicates that the starter has been activated. It shuts down the level control system compressor during the start-up routine. This safeguards the start-up routine and conserves the battery. K Wire Self-diagnosis information is exchanged between the Level Control System Control Module J197 and the VAS 5051 via the CAN data bus connection to the Control Module with Indicator Unit in Instrument Panel Insert J285 (gateway), and from there to the VAS 5051 via the K wire.
To avoid constant, unnecessary adjustments in level height due to surface unevenness, such as bumps or potholes, the self-leveling suspension has long reaction times when the vehicle is travelling at relatively constant road speed and if there is little or no wheel acceleration. If level height is adjusted in highway mode for example, the Level Control System Control Module J197 sends a voltage signal to the Headlight Range Control Module J431. The headlight range control reacts immediately and adjusts the angle of the light cone depending on the change of body position. Level change sequence: • Raising – the level is raised at the rear axle first, followed by the level at the front axle. • Lowering – the level at front axle is lowered first, followed by the lowering of the level at the rear axle.
64
Design and Function Emergency Running Mode Both the air spring control system and the damping control system adopt stored emergency running strategies in the event of faults in the sensors, the actuators, or internal faults in the Level Control System Control Module J197. Control actions are limited under certain circumstances and an entry is made in the fault memory.
In these cases, a “Level Fault” or “Damper Fault” warning is issued and a warning symbol appears in the instrument cluster. The vehicle must be taken to the workshop for repair.
65
Service Self-Diagnosis Vehicle Diagnosis, Test and Information System VAS 5051 and Vehicle Diagnosis and Service Information System VAS 5052 are both suitable for communication with the Level Control System Control Module J197. Self-diagnosis can be accessed with this equipment using Address Word 34 – Self-leveling suspension. Resetting the Adjustment Position If the Level Control System Control Module J197, a vehicle level sensor, or the entire air supply module are replaced, then the adjustment position must be reset. The adjustment position is reset using the “Basic setting” function located in “Guided fault-finding.”
SS275/050a
SSP275/050b
66
Please note that repairs group 01 is integrated in “Guided fault-finding.”
Service The color coded sensors, actuators, and auxiliary signals are tested as part of the self-diagnosis and guided fault-finding for the Phaeton air suspension with continuously controlled damping.
CLIMATE
MAP
NAV
RESET
VEHICLE
NAV SET
FM
CD
AM
SCAN
AUDIO
TRIP DATA
AM
SETTINGS
ON/DARK
MANUAL
HELP
BAL/FAD
E387, E388
N111
J197
--
N148, N149, N150, N151
G76, G77, G78, G289
N311 G290
N336, N337, N338, N339 G291
3
4
70
5
2
6
1
7
60 50 40
80 100 120 140 160 180
30 50 80 110 20
G337, G338, G339, G340
60 30
90
1/4
1/2
3/4
20 10
120
200 220 240 260
12 10
14 16
J403
J285/J533 J567, J568
G341, G342, G343 Door/Hood/Luggage Compartment Lid Contact
T16
Terminal 15 Terminal 30
SSP275/096
67
Notes
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Knowledge Assessment
An on-line Knowledge Assessment (exam) is available for this Self-Study Program. The Knowledge Assessment may or may not be required for Certification. You can find this Knowledge Assessment at:
www.vwwebsource.com From the vwwebsource.com Homepage, do the following: – Click on the Certification tab – Type the course number in the Search box – Click “Go!” and wait until the screen refreshes – Click “Start” to begin the Assessment
For Assistance, please call:
Certification Program Headquarters 1 – 877 – CU4 – CERT (1 – 877 – 284 – 2378) (8:00 a.m. to 8:00 p.m. EST) Or, E-Mail:
[email protected]
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cvr-outside-back-ssp275 6/30/03 1:59 PM Page 1
Volkswagen of America, Inc. 3800 Hamlin Road Auburn Hills, MI 48326 Printed in U.S.A. August 2003
