PROJECT REPORT ON DESIGN AND FABRICATION OF MINIATURE OF CONTINUOUSLY VARIABLE TRANSMISSION By:RAHUL CHOUDHARY
Submitted to the Department of Mechanical Engineering In partial fulfillment of the requirements For the degree of Bachelor of Technology In Mechanical Engineering
BHARAT INSTITUTE OF TECHNOLOGY Gautam Buddha Technical University APRIL 2012 1
This is to certify that Project Report entitled “DESIGN AND FABRICATION OF MINIATURE OF CONTINUOUSLY VARIABLE TRANSMISSION” which is submitted by RAHUL CHAUDHRY, AMIT KUMAR, GAUTAM CHAUDHARY, ROHIT KUMAR, in partial fulfillment of the requirement for the award of degree B. Tech. in Department of MECHANICAL ENGINEERING of G.B. Technical University, is a record of the candidate own work carried out by him under my/our supervision. The matter embodied in this thesis is original and has not been submitted for the award of any other degree.
KULDEEP SINGH PAL
VIKAS B. SINGH
(H.O.D. Mechanical deptt.)
DECLARATION I hereby declare that this submission is my own work and that, to the best of my knowledge and belief, it contains no material previously published or written by another person nor material which to a substantial extent has been accepted for the award of any other degree or diploma of the university or other institute of higher learning, except where due acknowledgment has been made in the text.
Sign…….. Amit kumar
Sign…… Gautam chaudhary
Sign ……. Rohit kumar
It gives us a great sense of pleasure to present the report of the B. Tech Project undertaken during B. Tech. Final Year. We owe special debt of gratitude to Professor Vikas B. Singh, Department of Mechanical Engineering, Bharat institute of Technology, Meerut for his constant support and guidance throughout the course of our work. His sincerity, thoroughness and perseverance have been a constant source of inspiration for us. It is only his cognizant efforts that our endeavors have seen light of the day. We also take the opportunity to acknowledge the contribution of Mr.Kuldeep singh pal, Head, Department of Mechanical Engineering, Bharat institute of Technology, Meerut for his full support and assistance during the development of the project. We also do not like to miss the opportunity to acknowledge the contribution of all faculty members of the department for their kind assistance and cooperation during the development of our project. Last but not the least, we acknowledge our friends for their contribution in the completion of the project.
: Rahul choudhary
: Amit kumar
: Gautam chaudhary
: Rohit kumar
One hardly needs to be an automotive engineer to understand that the less fuel an engine consumes, the fewer pollutants produced, and the cleaner the air we breathe. Unfortunately, improving the variables in that equation is becoming increasingly difficult. To achieve additional fuel economy improvements, we have begun to focus on increasing efficiency in areas where improvements are much more difficult and costly to achieve - largely on powertrain components such as the transmission This stems from the fact that transmissions operate over a range of power conditions, such as low speed-high torque to high speed-low torque, as well as through a variety of gear ratios. To achieve gains in this area, we have challenged the conventional thinking associated with powertrain functions and designs. Conventional powertrain configurations consist of an internal combustion engine operating across a wide range of torque and speed conditions and a transmission that has, by comparison, only a few discrete gear ratios. The operational philosophy of conventional powertrains makes it difficult to reach maximum engine fuel efficiency because the opportunities for operating at the lowest fuel consumption or best "brake specific fuel consumption" are restricted and generally do not agree with the torque and speed conditions imposed on the engine by the vehicle. Using a CVT-configured powertrain, the engine operates at or near maximum load conditions. This allows the engine to operate at or near its best brake specific fuel consumption rate, which means that the engine is operating at its highest average adiabatic efficiencies. For internal combustion engines this would be 36 percent, while for diesel engines it is 45 percent. This project report evaluates the current state of CVTs and upcoming research and development, set in the context of past development and problems traditionally associated with CVTs. The underlying theories and mechanisms are also discussed.
TABLE OF CONTENTS
CHAPTER 1 1.1 Introduction .........................................................................
CHAPTER 2 2.1 How CVT works...................................................................
2.2 Uses of CVT..........................................................................
2.3 Advantages and disadvantages of CVT................................
CHAPTER 3 3.1 Types of CVTs.......................................................................
3.2 Warko’s working principle....................................................
3.3 Radial roller CVT...................................................................
CHAPTER 4 4.1 Components used....................................................................
4.2 Component details...................................................................
4.2.2 Design of main components.................................................
4.3 Construction details..................................................................
4.5 Power transmission to wheel shaft...........................................
FUTURE PROSPECTS OF CVTs........................................................
1.1 INTRODUCTION A Continuously variable transmission (CVT) is a transmission which can change steplessly through an infinite number of effective gear ratios between maximum and minimum values. This contrasts with other mechanical transmissions that only allow a few different distinct gear ratios to be selected. The flexibility of a CVT allows the driving shaft to maintain a constant angular velocity over a range of output velocities. This can provide better fuel economy than other transmissions by enabling the engine to run at its most efficient revolutions per minute (RPM) for a range of vehicle speeds. In order to enact new regulations for automotive fuel economy and emissions, the continuously variable transmission, or CVT, continues to emerge as a key technology for improving the fuel efficiency of automobiles with internal combustion (IC) engines. CVTs use infinitely adjustable drive ratios instead of discrete gears to attain optimal engine performance. Since the engine always runs at the most efficient number of revolutions per minute for a given vehicle speed, CVT-equipped vehicles attain better gas mileage and acceleration than cars with traditional transmissions. CVTs are not new to the automotive world, but their torque capabilities and reliability have been limited in the past. New developments in gear reduction and manufacturing have led to ever more-robust CVTs, which in turn allows them to be used in more diverse automotive applications. CVTs are also being developed in conjunction with hybrid electric vehicles. As CVT development continues, costs will be reduced further and performance will continue to increase, which in turn makes further development and application of CVT technology desirable.
1.2 History Leonardo da Vinci, in 1490, conceptualized a stepless continuously variable transmission.The first patent for a friction-based belt CVT was filed in Europe by Daimler and Benz in 1886, and a US Patent for a toroidal CVT was granted in 1935. In 1910, Zenith Motorcycles built a V2 engined motorcycle with the Gradua-Gear, which was a CVT. This Zenith-Gradua was so successful in hillclimbing events, that it was evantually barred,so that other manufacturers had achance to win. In 1912, the British motorcycle manufacturer Rudge-Whitworth built the Rudge Multigear. The Multi was a much improved version of Zenith’s Gradua-Gear. In 1922, Browne offered a motorcycle with variable-stroke ratchet drive using a face ratchet. An early application of CVT was in the British Clyno car, introduced in 1923.A CVT, called Variomatic, was designed and built by Hub van Doorne, co-founder of Van Doorne's Automobiel Fabriek (DAF), in the late 1950s, specifically to produce an automatic transmission for a small, affordable car. The first DAF car using van Doorne's CVT, the DAF 600, was produced in 1958. Van Doorne's patents were later transferred to a company called VDT (Van Doorne Transmissie B.V.) when the passenger car division was sold to Volvo in 1975; its CVT was used in the Volvo 340. In 1995, VDT was acquired by Robert Bosch GmbH. Many snowmobiles use a rubber belt CVT. In 1974, Rokon offered a motorcycle with a rubber belt CVT. CVTs are used in some ATVs. The first ATV equipped with CVT was Polaris's Trail Boss in 1985. In early 1987, Subaru launched the Justy in Tokyo with an electronically controlled continuously variable transmission (ECVT) developed by Fuji Heavy Industries, which owns Subaru. In 1989 the Justy became the first production car in the U.S. to offer CVT technology. While the Justy saw only limited success, Subaru continues to use CVT in its kei cars to this day, while also supplying it to other manufacturers. Subaru offers CVT on the 2010 Legacy and 2010 Outback (Lineartronic). In the summer of 1987 the Ford Fiesta and Fiat Uno became the first mainstream European cars to be equipped with steel-belted CVT (as opposed to the less robust rubber-belted DAF design). This CVT, the Ford CTX was developed by Ford, Van Doorne, and Fiat, with work on the transmission starting in 1976. The 1992 Nissan March contained Nissan's N-CVT based on the Fuji Heavy Industries ECVT. In the late 1990s, Nissan designed its own CVT that allowed for higher torque and included a torque converter. This gearbox was used in a number of Japanese-market models. Nissan is also the only car maker to bring a roller-based CVT to the market in recent years. Their toroidal CVT, named the Extroid, was available in the Japanese market Y34 Nissan Gloria and V35 Skyline GT-8. However, the gearbox was not carried over when the Cedric/Gloria was replaced by the Nissan Fuga in 2004. The Nissan Murano, introduced in 2003, and the Nissan Rogue, introduced 8
in 2007, also use CVT in their automatic transmission models. In a Nissan Press Release, 12 July 2006, Nissan announced a huge shift to CVT transmissions when they selected their XTronic CVT technology for all automatic versions of the Versa, Cube, Sentra, Altima and Maxima vehicles in North America, making the CVT a mainstream transmission system. One major motivator for Nissan to make a switch to CVTs was as a part of their 'Green Program 2010' aimed at reducing CO2 emissions by 2010. The CVT found in Nissan’s Maxima, Murano and the V6 version of the Altima is considered to be the worlds first "3.5L class" belt CVT and can hold much higher torque loads than other belt CVTs. After studying pulley-based CVT for years, Honda also introduced their own version on the 1995 Honda Civic VTi. Dubbed Honda Multi Matic, this CVT gearbox accepted higher torque than traditional pulley CVTs, and also includes a torque converter for "creep" action. The CVT is also currently employed in the Honda City ZX that is manufactured in India and Honda City Vario manufactured in Pakistan. Toyota used a Power Split Transmission (PST) in the 1997 Prius, and all subsequent Toyota and Lexus hybrids sold internationally continue to use the system (marketed under the Hybrid Synergy Drive name). The HSD is also referred to as an Electronically controlled Continuously variable Transmission. The PST allows either the electric motor or the internal combustion engine (ICE) or both to propel the vehicle. In ICE-only mode, part of the engine's power is mechanically coupled to the drivetrain, with the other part going through a generator and a motor. The amount of power being channeled through the electrical path determine the effective gear ratio. Toyota also offers a non-hybrid CVT called Multidrive for models such as Avensis.Audi has, since 2000, offered a chain-type CVT (multitronic) as an option on some of its larger-engine models, for example the A4 3.0 L V6.Fiat in 2000 offered a Cone-type CVT as an option on its hit model Fiat Punto (16v 80 PS ELX,Sporting) and Lancia Y (1.2 16V). BMW used a belt-drive CVT (manufactured by ZF Friedrichshafen) as an option for the lowand middle-range MINI in 2001, forsaking it only on the supercharged version of the car where the increased torque levels demanded a conventional automatic gearbox. The CVT could also be manually "shifted" if desired with software-simulated shift points. MG-Rover used an identical ZF CVT transmission on its Rover 45 and MG ZS models. GM introduced its version of CVT known as VTi in 2002. It was used in the Saturn Vue and Saturn Ion models. Ford introduced a chain-driven CVT known as the CFT30 in their 2005 Ford Freestyle, Ford Five Hundred and Mercury Montego. The transmission was designed in cooperation with German automotive supplier ZF Friedrichshafen and was produced in Batavia, Ohio at Batavia Transmissions LLC (a subsidiary of Ford Motor Company) until 22 March 2007. The Batavia plant also produced the belt-driven CFT23 CVT which went in the Ford Focus C-MAX. Ford also sold Escort and Orion models in Europe with CVTs in the 1980s and 1990s.
Contract agreements were established in 2006 between MTD Products and Torotrak for the first full toroidal system to be manufactured for outdoor power equipment such as jet skis, skimobiles and ride-on mowers. The 2007 Dodge Caliber and the related Jeep Compass and Jeep Patriot employ a CVT using a variable pulley system as their optional automatic transmission. The 2008 Mitsubishi Lancer model is available with CVT transmission as the automatic transmission. DE and ES models receive a standard CVT with Drive and Low gears; the GTS model is equipped with a standard Drive and also a Sportronic mode that allows the driver to use 6 different preset gear ratios (either with the shifter or steering wheel-mounted paddle shifters). The 2009 SEAT Exeo is available with a CVT automatic transmission (multitronic) as an option for the 2.0 TSI 200 hp (149 kW) petrol engine, with selectable 'six-speeds'. In 2010, the US Patent Office issued patent number 7,647,768 B1 for a series of hydraulic Torque Converters that use hydraulic friction rather than mechanical friction as a CVT.
Subaru has again brought back CVT this time for its new 2010 Legacy and 2010 outback. It will be mated to a 2.5l 4 cylinder boxer engine.
CHAPTER 2 2.1 HOW CVT WORKS Traditional transmissions use a gear set that provides a given number of ratios (or speeds). The transmission (or the driver) shifts gears to provide the most appropriate ratio for a given situation: Lowest gears for starting out, middle gears for acceleration and passing, and higher gears for fuel-efficient cruising. Though there are several types of CVTs, most cars use a pair of variable-diameter pulleys, each shaped like a pair of opposing cones, with a metal belt or chain running between them. One pulley is connected to the engine (input shaft), the other to the drive wheels (output shaft).
Fig 2.1 A Chain-driven CVT
The halves of each pulley are moveable; as the pulley halves come closer together the belt is forced to ride higher on the pulley, effectively making the pulley's diameter larger. Changing the diameter of the pulleys varies the transmission's ratio (the number of times the output shaft revolves for each revolution of the engine), in the same way that a 10-speed bike routes the chain over larger or smaller gears to change the ratio. Making the input pulley smaller and the output pulley larger gives a low ratio (a large number of engine revolutions producing a small number of output revolutions) for better low-speed acceleration. As the car accelerates, the pulleys vary their diameter to lower the engine speed as car speed rises. This is the same thing a conventional automatic or manual transmission does, but while a conventional transmission changes the ratio in stages by shifting gears, the CVT continuously varies the ratio -- hence its name. 11
2.2 USES OF CVTs Many small tractors for home and garden use have simple rubber belt CVTs. For example, the John Deere Gator line of small utility vehicles uses a belt with a conical pulley system. They can deliver an abundance of power and can reach speeds of 10–15 mph (16–24 km/h), all without need for a clutch or shift gears. Nearly all snowmobiles, old and new, and motor scooters use CVTs. Virtually all snowmobile and motor scooter CVTs are rubber belt/variable pulley CVTs. Some combine harvesters have CVTs. The CVT allows the forward speed of the combine to be adjusted independently of the engine speed. This allows the operator to slow down and speed up as needed to accommodate variations in thickness of the crop. CVTs have been used in aircraft electrical power generating systems since the 1950s and in SCCA Formula 500 race cars since the early 1970s. More recently, CVT systems have been developed for go-karts and have proven to increase performance and engine life expectancy. The Tomcat range of off-road vehicles also utilizes the CVT system. Some drill presses and milling machines contain a pulley-based CVT where the output shaft has a pair of manually-adjustable conical pulley halves through which a wide drive belt from the motor loops. The pulley on the motor, however, is usually fixed in diameter, or may have a series of given-diameter steps to allow a selection of speed ranges. A hand wheel on the drill press, marked with a scale corresponding to the desired machine speed, is mounted to a reduction gearing system for the operator to precisely control the width of the gap between the pulley halves. This gap width thus adjusts the gearing ratio between the motor's fixed pulley and the output shaft's variable pulley, changing speed of the chuck; a tensioner pulley is implemented in the belt transmission to take up or release the slack in the belt as the speed is altered. In most cases, however, the drill press' speed must be changed with the motor running. CVTs should be distinguished from Power Sharing Transmissions (PSTs), as used in newer hybrids, such as the Toyota Prius, Highlander and Camry, the Nissan Altima, and newer-model Ford Escape Hybrid SUVs. CVT technology uses only one input from a prime mover, and delivers variable output speeds and torque; whereas PST technology uses two prime mover inputs, and varies the ratio of their contributions to output speed and power. These transmissions are fundamentally different. However the Honda Insight hybrid, the Nissan Versa (only the SL model), Nissan Cube and the Nissan Altima use CVT.
2.3 ADVANTAGES AND DISADVANTAGES Advantages
The main advantage of CVTs is that they allow an engine to run at its ideal RPM regardless of the speed of the vehicle. For low speed special purpose vehicles the RPM is usually set to achieve peak efficiency. This maximizes fuel economy and reduces emissions. Alternatively the CVT can be setup to maximize performance and maintain the engine RPM at the level of peak power rather than efficiency. Automotive CVT's generally attempt to balance both of these functions by shooting for efficiency when the driver is only applying light to moderate amounts of accelerator i.e. Under cruise conditions, and power when the accelerator is being applied more generously. Engines do not develop constant power at all speeds; they have specific speeds where torque (pulling power), horsepower (speed power) or fuel efficiency is at their highest levels. Because there are no gears to tie a given road speed directly to a given engine speed, the CVT can vary the engine speed as needed to access maximum power as well as maximum fuel efficiency. This allows the CVT to provide quicker acceleration than a conventional automatic or manual transmission while delivering superior fuel economy.
CVT torque-handling capability is limited by the strength of their transmission medium (usually a belt or chain), and by their ability to withstand friction wear between torque source and transmission medium (in friction-driven CVTs). CVTs in production prior to 2005 are predominantly belt- or chain-driven and therefore typically limited to lowpowered cars and other light-duty applications. Units using advanced lubricants, however, have been proven to support a range of torques in production vehicles, including that used for buses, heavy trucks, and earth-moving equipment. Some CVTs in production vehicles have seen premature failures. Some CVTs transmit torque in only one direction, rendering them useless for regenerative or engine-assisted vehicle braking; all braking would need to be provided by disc brakes, or similar dissipative systems. The CVT's biggest problem has been user acceptance. Because the CVT allows the engine to rev at any speed, the noises coming from under the hood sound odd to ears accustomed to conventional manual and automatic transmissions. The gradual changes in engine note sound like a sliding transmission or a slipping clutch -- signs of trouble with a conventional transmission, but perfectly normal for CVT. Flooring an automatic car brings a lurch and a sudden burst of power, whereas CVTs provide a smooth, rapid increase to maximum power. To some drivers this makes the car feel slower, when in fact a CVT will generally out-accelerate an automatic.
CHAPTER 3 3.1 TYPES OF CVTs 3.1.1 Variable-diameter pulley (VDP) or Reeves drive In this most common CVT system, there are two V-belt pulleys that are split perpendicular to their axes of rotation, with a V-belt running between them. The gear ratio is changed by moving the two sections of one pulley closer together and the two sections of the other pulley farther apart. Due to the V-shaped cross section of the belt, this causes the belt to ride higher on one pulley and lower on the other. Doing this change the effective diameters of the pulleys, which changes the overall gear ratio. The distance between the pulleys does not change, and neither does the length of the belt, so changing the gear ratio means both pulleys must be adjusted (one bigger, the other smaller) simultaneously to maintain the proper amount of tension on the belt. The V-belt needs to be very stiff in the pulley's axial direction in order to make only short radial movements while sliding in and out of the pulleys. This can be achieved by a chain and not by homogeneous rubber. To dive out of the pulleys one side of the belt must push. This again can be done only with a chain. Each element of the chain has conical sides, which perfectly fit to the pulley if the belt is running on the outermost radius. As the belt moves into the pulleys the contact area gets smaller. The contact area is proportional to the number of elements, thus the chain has lots of very small elements. The shape of the elements is governed by the static of a column. The pulley-radial thickness of the belt is a compromise between maximum gear ratio and torque. For the same reason the axis between the pulleys is as thin as possible. A film of lubricant is applied to the pulleys. It needs to be thick enough so that the pulley and the belt never touch and it must be thin in order not to waste power when each element dives into the lubrication film. Additionally, the chain elements stabilize about 12 steel bands. Each band is thin enough so that it bends easily. If bending, it has a perfect conical surface on its side. In the stack of bands each band corresponds to a slightly different gear ratio, and thus they slide over each other and need oil between them. Also the outer bands slide through the stabilizing chain, while the center band can be used as the chain linkage.
3.1.2 Pulley-based CVTs Peer into a planetary automatic transmission, and you'll see a complex world of gears, brakes, clutches and governing devices. By comparison, a continuously variable transmission is a study in simplicity. Most CVTs only have three basic components: A high-power metal or rubber belt A variable-input "driving" pulley An output "driven" pulley CVTs also have various microprocessors and sensors, but the three components described above are the key elements that enable the technology to work.
Fig 3.1.2(a) Variable pulley
The variable-diameter pulleys are the heart of a CVT. Each pulley is made of two 20-degree cones facing each other. A belt rides in the groove between the two cones. V-belts are preferred if the belt is made of rubber. V-belts get their name from the fact that the belts bear a V-shaped cross section, which increases the frictional grip of the belt. When the two cones of the pulley are far apart (when the diameter increases), the belt rides lower in the groove, and the radius of the belt loop going around the pulley gets smaller. When the cones are close together (when the diameter decreases), the belt rides higher in the groove, and the radius of the belt loop going around the pulley gets larger. CVTs may use hydraulic pressure, centrifugal force or spring tension to create the force necessary to adjust the pulley halves. 15
Variable-diameter pulleys must always come in pairs. One of the pulleys, known as the drive pulley (or driving pulley), is connected to the crankshaft of the engine. The driving pulley is also called the input pulley because it's where the energy from the engine enters the transmission. The second pulley is called the driven pulley because the first pulley is turning it. As an output pulley, the driven pulley transfers energy to the driveshaft.
The distance between the centers of the pulleys to where the belt makes contact in the groove is known as the pitch radius. When the pulleys are far apart, the belt rides lower and the pitch radius decreases. When the pulleys are close together, the belt rides higher and the pitch radius increases. The ratio of the pitch radius on the driving pulley to the pitch radius on the driven pulley determines the gear. 16
When one pulley increases its radius, the other decreases its radius to keep the belt tight. As the two pulleys change their radii relative to one another, they create an infinite number of gear ratios -- from low to high and everything in between. For example, when the pitch radius is small on the driving pulley and large on the driven pulley, then the rotational speed of the driven pulley decreases, resulting in a lower ―gear.‖ When the pitch radius is large on the driving pulley and small on the driven pulley, then the rotational speed of the driven pulley increases, resulting in a higher ―gear‖. Thus, in theory, a CVT has an infinite number of "gears" that it can run through at any time, at any engine or vehicle speed. The simplicity and stepless nature of CVTs make them an ideal transmission for a variety of machines and devices, not just cars. CVTs have been used for years in power tools and drill presses. They've also been used in a variety of vehicles, including tractors, snowmobiles and motor scooters. In all of these applications, the transmissions have relied on high-density rubber belts, which can slip and stretch, thereby reducing their efficiency. The introduction of new materials makes CVTs even more reliable and efficient. One of the most important advances has been the design and development of metal belts to connect the pulleys. These flexible belts are composed of several (typically nine or 12) thin bands of steel that hold together high-strength, bow-tie-shaped pieces of metal.
Fig.3.1.2(c) Metal belt design
Metal belts don't slip and are highly durable, enabling CVTs to handle more engine torque. They are also quieter than rubber-belt-driven CVTs.
3.1.3 Toroidal or roller-based CVT Toroidal CVTs are made up of discs and rollers that transmit power between the discs. The discs can be pictured as two almost conical parts, point to point, with the sides dished such that the two parts could fill the central hole of a torus. One disc is the input, and the other is the output (they do not quite touch). Power is transferred from one side to the other by rollers. When the roller's axis is perpendicular to the axis of the near-conical parts, it contacts the near-conical parts at same-diameter locations and thus gives a 1:1 gear ratio. The roller can be moved along the axis of the near-conical parts, changing angle as needed to maintain contact. This will cause the roller to contact the near-conical parts at varying and distinct diameters, giving a gear ratio of something other than 1:1. Systems may be partial or full toroidal. Full toroidal systems are the most efficient design while partial toroidals may still require a torque converter, and hence lose efficiency.
Toroidal CVTs Another version of the CVT -- the toroidal CVT system -- replaces the belts and pulleys with discs and power rollers
Fig.3.1.3(a)Extroid toroidal CVT
Although such a system seems drastically different, all of the components are analogous to a belt-and-pulley system and lead to the same results -- a continuously variable transmission. Here's how it works:
One disc connects to the engine. This is equivalent to the driving pulley. Another disc connects to the drive shaft. This is equivalent to the driven pulley. Rollers, or wheels, located between the discs act like the belt, transmitting power from one disc to the other.
Fig 3.1.3(b)Toroidal CVT
The wheels can rotate along two axes. They spin around the horizontal axis and tilt in or out around the vertical axis, which allows the wheels to touch the discs in different areas. When the wheels are in contact with the driving disc near the center, they must contact the driven disc near the rim, resulting in a reduction in speed and an increase in torque (i.e., low gear). When the wheels touch the driving disc near the rim, they must contact the driven disc near the center, resulting in an increase in speed and a decrease in torque (i.e., overdrive gear). A simple tilt of the wheels, then, incrementally changes the gear ratio, providing for smooth, nearly instantaneous ratio changes.
3.1.4 INFINITELY VARIABLE TRANSMISSION (IVT) A specific type of CVT is the infinitely variable transmission (IVT), in which the range of ratios of output shaft speed to input shaft speed includes a zero ratio that can be continuously approached from a defined "higher" ratio. A zero output speed (low gear) with a finite input speed implies an infinite input-to-output speed ratio, which can be continuously approached from a given finite input value with an IVT. Low gears are a reference to low ratios of output speed to input speed. This low ratio is taken to the extreme with IVTs, resulting in a "neutral", or nondriving "low" gear limit, in which the output speed is zero. Unlike neutral in a normal automotive transmission, IVT output rotation may be prevented because the back driving (reverse IVT operation) ratio may be infinite, resulting in impossibly high back driving torque; ratcheting IVT output may freely rotate forward, though. The IVT dates back to before the 1930s; the original design converts rotary motion to oscillating motion and back to rotary motion using roller clutches. The stroke of the intermediate oscillations is adjustable, varying the output speed of the shaft. This original design is still manufactured today, and an example and animation of this IVT can be found here. Paul B. Pires created a more compact (radially symmetric) variation that employs a ratchet mechanism instead of roller clutches, so it doesn't have to rely on friction to drive the output. An article and sketch of this variation can be found here Most IVTs result from the combination of a CVT with a planetary gear system (which is also known as an epicyclic gear system) which enforces an IVT output shaft rotation speed which is equal to the difference between two other speeds within the IVT. This IVT configuration uses its CVT as a continuously variable regulator (CVR) of the rotation speed of any one of the three rotators of the planetary gear system (PGS). If two of the PGS rotator speeds are the input and output of the CVR, there is a setting of the CVR that results in the IVT output speed of zero. The maximum output/input ratio can be chosen from infinite practical possibilities through selection of additional input or output gear, pulley or sprocket sizes without affecting the zero output or the continuity of the whole system. The IVT is always engaged, even during its zero output adjustment. IVTs can in some implementations offer better efficiency when compared to other CVTs as in the preferred range of operation because most of the power flows through the planetary gear system and not the controlling CVR. Torque transmission capability can also be increased. There's also possibility to stage power splits for further increase in efficiency, torque transmission capability and better maintenance of efficiency over a wide gear ratio range. An example of a true IVT is the SIMKINETICS SIVAT that uses a ratcheting CVR. Its CVR ratcheting mechanism contributes minimal IVT output ripple across its range of ratios.
Another example of a true IVT is the Hydristor because the front unit connected to the engine can displace from zero to 27 cubic inches per revolution forward and zero to -10 cubic inches per revolution reverse. The rear unit is capable of zero to 75 cubic inches per revolution.
3.1.5 OVERVIEW OF THE IVT SYSTEM A generic simplified layout of the IVT is shown below, this represents a layshaft layout, and a coaxial layout is also possible. Beneath the diagram a brief description of each component is given.
Fig 3.1.5 IVT
The variator - is how the Torotrak IVT creates its continuous variation of ratio. The input gearset - transmits the power from the engine via the low regime clutch to the planet gear in the epicyclic gear train.
The epicyclic gearset - is the means by which the running engine can be connected to the stationary road wheels without a slipping clutch or torque converter, learn more.
Fixed ratio chain - takes the drive from the output discs and transmits it to the sun gear of the epicyclic gearset and the input of the high regime clutch. An idling gear can be used instead of a chain.
High regime clutch - engaged for all forward speeds above the equivalent of a second gear. The IVT facilitates the optimum management of the engine by use of computer control.
3.1.6 RATCHETING CVT The ratcheting CVT is a transmission that relies on static friction and is based on a set of elements that successively become engaged and then disengaged between the driving system and the driven system, often using oscillating or indexing motion in conjunction with one-way clutches or ratchets that rectify and sum only "forward" motion. The transmission ratio is adjusted by changing linkage geometry within the oscillating elements, so that the summed maximum linkage speed is adjusted, even when the average linkage speed remains constant. Power is transferred from input to output only when the clutch or ratchet is engaged, and therefore when it is locked into a static friction mode where the driving & driven rotating surfaces momentarily rotate together without slippage. These CVTs can transfer substantial torque, because their static friction actually increases relative to torque throughput, so slippage is impossible in properly designed systems. Efficiency is generally high, because most of the dynamic friction is caused by very slight transitional clutch speed changes. The drawback to ratcheting CVTs is vibration caused by the successive transition in speed required to accelerate the element, which must supplant the previously operating and decelerating, power transmitting element. Ratcheting CVTs are distinguished from VDPs and roller-based CVTs by being static frictionbased devices, as opposed to being dynamic friction-based devices that waste significant energy through slippage of twisting surfaces. An example of a ratcheting CVT is one prototyped as a bicycle transmission protected under U.S. Patent 5,516,132 in which strong pedalling torque causes this mechanism to react against the spring, moving the ring gear/chainwheel assembly toward a concentric, lower gear position. When the pedaling torque relaxes to lower levels, the transmission self-adjusts toward higher gears, accompanied by an increase in transmission vibration.
3.1.7 HYDROSTATIC CVTS Hydrostatic transmissions use a variable displacement pump and a hydraulic motor. All power is transmitted by hydraulic fluid. These types can generally transmit more torque, but can be sensitive to contamination. Some designs are also very expensive. However, they have the advantage that the hydraulic motor can be mounted directly to the wheel hub, allowing a more flexible suspension system and eliminating efficiency losses from friction in the drive shaft and 22
differential components. This type of transmission is relatively easy to use because all forward and reverse speeds can be accessed using a single lever. An integrated hydrostatic transaxle (IHT) uses a single housing for both hydraulic elements and gear-reducing elements. This type of transmission, most commonly manufactured by HydroGear, has been effectively applied to a variety of inexpensive and expensive versions of ridden lawn mowers and garden tractors. Many versions of riding lawn mowers and garden tractors propelled by a hydrostatic transmission are capable of pulling a reverse tine tiller and even a single bladed plow. One class of riding lawn mower that has recently gained in popularity with consumers is zero turning radius mowers. These mowers have traditionally been powered with wheel hub mounted hydraulic motors driven by continuously variable pumps, but this design is relatively expensive. Hydro-Gear, created the first cost-effective integrated hydrostatic transaxle suitable for propelling consumer zero turning radius mowers. Some heavy equipment may also be propelled by a hydrostatic transmission; e.g. agricultural machinery including foragers, combines, and some tractors. A variety of heavy earth-moving equipment manufactured by Caterpillar Inc., e.g. compact and small wheel loaders, track type loaders and tractors, skid-steered loaders and asphalt compactors use hydrostatic transmission. Hydrostatic CVTs are usually not used for extended duration high torque applications due to the heat that is generated by the flowing oil.
Fig 3.1.7 Honda DN-01 motorcycle
The Honda DN-01 motorcycle is the first road-going consumer vehicle with hydrostatic drive that employs a variable displacement axial piston pump with a variable-angle swashplate.
3.1.8 VARIABLE TOOTHED WHEEL TRANSMISSION A variable toothed wheel transmission is not a true CVT that can alter its ratio in infinite increments, but rather approaches CVT capability by having a large number of ratios, typically 49. This transmission relies on a toothed wheel positively engaged with a chain where the toothed wheel has the ability to add or subtract a tooth at a time in order to alter its ratio relative to the chain it is driving. The "toothed wheel" can take on many configurations including ladder chains, drive bars and sprocket teeth. The huge advantage of this type of CVT is that it is a positive mechanical drive and thus does not have the frictional losses and limitations of the roller-based or VDP CVT’s. The challenge in this type of CVT is to add or subtract a tooth from the toothed wheel in a very precise and controlled way in order to maintain synchronized engagement with the chain. This type of transmission has the potential to change ratios under load because of the large number of ratios, resulting in the order of 3% ratio change differences between ratios, thus a clutch or torque converter is necessary only for pull-away. No CVTs of this type are in commercial use, probably because of above mentioned development challenge.
3.1.9 CONE CVTS This category comprises all CVTs made up of one or more conical bodies that function together along their respective generatrices in order to achieve the variation. In the single-cone type, there is a revolving body (a wheel) that moves on the generatrix of the cone, thereby creating the variation between the inferior and the superior diameter of the cone. In a CVT with oscillating cones, the torque is transmitted via friction from a variable number of cones (according to the torque to be transmitted) to a central, barrel-shaped hub. The side surface of the hub is convex with a specified radius of curvature, smaller than the concavity radius of the cones. In this way, there will be only one (theoretical) contact point between each cone and the hub. A new CVT using this technology, the Warko, was presented in Berlin during the 6th International CTI Symposium of Innovative Automotive Transmissions, on 3-7 December 2007. A particular characteristic of the Warko is the absence of a clutch: the engine is always connected to the wheels, and the rear drive is obtained by means of an epicyclic system in output. This system, named ―power split‖, allows the condition of geared neutral or "zero Dynamic": when the engine turns (connected to the sun gear of the epicyclic system), the variator (which rotates the ring of the epicyclic system in the opposite sense to the sun gear), in a particular position of its range, will compensate for the engine rotation, having zero turns in output (planetary = the output of the system). As a consequence, the satellite gears roll within an internal ring gear.
3.2 WARKO'S WORKING PRINCIPLE
Starting from the complete configuration of all the components required for the motion transmission (picture to the left) we can examine every single step of the Warko CVT's assembly to understand its working principle.
Following the motion transmission process, we will see that the motion deriving from the engine shaft is transmitted to the main gear, named sun gear.
From the sun gear, the motion is transmitted to a certain number of gears, called satellites or planet gears, laid out in a crown shape on it.
Each satellite is connected by means of a little shaft and two joints to a frustum cone-shaped body, hereinafter called "satellite cone". The side surface of the satellite cones is concave according to a given radius of curvature.
All the satellite cones transmit via friction the motion to a central "barrel"-shaped hub.
Finally, the motion is transmitted to the output shaft by means of an internal gearing.
The lateral surface of the hub is convex according to a given radius of curvature, which is inferior than the radius of concavity of the cones. In this way, there will be only a (theoretical) contact point between a cone and the hub. Since the cone can oscillate on the hub, it realizes all the possible couplings with the diameters of the same hub.The contact between the satellite cones and the hub is kept and forced by a pneumatic (or hydraulic) system (not shown) which pushes all the satellite cones against the hub and the outside ring named Reaction Ring.
The concavity radius of the satellite cones and the convexity radius of the hub are calculated in such a way so as to keep the external diameter constant = the internal diameter of the Reaction Ring.
3.3 RADIAL ROLLER CVT The working principle of this CVT is similar to that of conventional oil compression engines, but, instead of compressing oil, common steel rollers are compressed. The motion transmission between rollers and rotors is assisted by an adapted traction fluid, which ensures the proper friction between the surfaces and slows down wearing thereof. Unlike other systems, the radial rollers do not show a tangential speed variation (delta) along the contact lines on the rotors. From this, a greater mechanical efficiency and working life are obtained. The main advantages of this CVT are the manufacturing inexpensiveness and the high power efficiency.
3.4 TRACTION-DRIVE CVT A completely new type of CVT is the traction-drive CVT. Traction-drive CVT's are stated as being the most efficient type of CVT's at the moment. One model is commercially produced as the Fallbrook Technologies NuVinci, which employs elements of both CVT and planetary transmissions.
CHAPTER 4 4.1 Component used 1. 4- Special design pulley (design on CNC machine). 2. Geared motor. 3. Bearing (608, 6801 and 6807). 4. Bearing stand. 5. Sprocket and chain drive. 6. Mild steel design shafts. 7. Bike timing gear and chain drive. 8. Threading nut and bolt. 9. Wheels. 10. Wooden body frame. 11. Rubber belt.
4.2 Component Details 4.2.1 - Pulley Size of pulley or discs-
Fig 4.2.1 Tapered disc
Disks are made up of mild steel. The density of the mild steel is 7860kg/m3. Disks have tapered surface of 8 degree on one side to work as pulley when came in contact. Diameter of the disk is 125mm and has the thickness of 10mm.
4.2.2 – DESIGN OF CHAIN
Fig 4.2.2 Bike timing chain
It is assumed that, Theeth on smaller sprocket z1 =7 Teeth on larger sprocket
z2 = 44
Velocity ratio = 44/7 = 6.285 For this velocity ratio(6 to 7) minimum centre distance Cmin= 1.5(d1+d2)/2+(30 to 50) `
Cmin=1.5(185+32)/2+40 Cmin=202.75 mm So it is adopted that C = 205 mm
Pitch of chain P = C/(30 to 60) P = (205)/(30 to 60) = 3.41 to 6.83 32
So it is adopted that P = 6.83 mm No. of Links m = (2C/P)+(z1+z2)/2+P(z2-z1)2/(4π2C) m = 60.025+25.5+1.01 m = 86.03 The nearest number is adopted m = 86
length of chain l = mP l = 86*6.83 = 588 mm(approx.) By this simple method We can design the another chain. No. of teeth on both the sprockets = 17 Centre distance C = 205 P = (205)/(30 to 60) P = 6.21 (approx.) m = (2C/P)+(z1+z2)/2+P(z2-z1)2/(4π2C) m = 83.02 m = 84 (approx.) Length of chain l = m*P l = 84*6.21 l = 524 mm(approx.)
Dimensions:Length: 588mm Groove: 86
Fig 4.2.3 Design of chain and sprockets
4.2.3 DESIGN OF SHAFT Weight of disc = 8.8 N Weight of pulley = 8.8*2 = 17.6 N 34
This weight of pulley acts as a point load on shaft (neglecting the weight of other components). Bending moment due to this point load M = wl/4 = (17.6*0.470)/4 M = 2.07 N m
Power of the motor used = 0.25 HP = 186.5 watt Speed of the motor = 1400 rpm (approx.) Torque produced by motor T = (P*60)/(2πN) = (186.5*60)/(2π*1400) T = 1.27 Nm Equivelent bending moment Me = [M+(M2+T2 )1/2]/2 Me = 2.24 Nm For mild steel, Allowable bending stess = 56 Mpa Allowable shear stress = 42 Mpa Factor of safety = 6
Now, Me = (π/32)*(σb/6 ) *d3 2.24 = (π/32)*(56*106/6 ) *d3 d = 14.44 mm Equivelent torque Te = (M2+T2)1/2 Te = (2.072+1.272)1/2 Te = 2.43 Nm Now, Te = (π/16)*(τ/6)*d3 2.43 = (π/16)*(42*106/6)*d3 d = 12.09 mm For the safe design of shafts we take the larger diameter i. e. d = 14.44 mm
4.2.3 Bike timing sprockets
Fig 4.2.3 Bike timing sprocket
Dimension:Teeth: 28 Length: 60mm
4.2.4 Dc motor One of the first electromagnetic rotary motors was invented by Michael Faraday in 1821 and consisted of a free-hanging wire dipping into a pool of mercury. A permanent magnet was placed in the middle of the pool of mercury. When a current was passed through the wire, the wire rotated around the magnet, showing that the current gave rise to a circular magnetic field around the wire. This motor is often demonstrated in school physics classes, but brine(salt water) is sometimes used in place of the toxic mercury. This is the simplest form of a class of electric motors called homopolar motors. A later refinement is the Barlow's Wheel. 37
Another early electric motor design used a reciprocating plunger inside a switched solenoid; conceptually it could be viewed as an electromagnetic version of a two stroke internal combustion engine. The modern DC motor was invented by accident in 1873, when Zénobe Gramme connected a spinning dynamo to a second similar unit, driving it as a motor. The classic DC motor has a rotating armature in the form of an electromagnet. A rotary switch called a commutator reverses the direction of the electric current twice every cycle, to flow through the armature so that the poles of the electromagnet push and pull against the permanent magnets on the outside of the motor. As the poles of the armature electromagnet pass the poles of the permanent magnets, the commutator reverses the polarity of the armature electromagnet. During that instant of switching polarity, inertia keeps the classical motor going in the proper direction. (See the diagrams below.)
Fig 4.2.4 DC motor
A simple DC electric motor. When the coil is powered, a magnetic field is generated around the armature. The left side of the armature is pushed away from the left magnet and drawn toward the right, causing rotation.
The armature continues to rotate.
When the armature becomes horizontally aligned, the commutator reverses the direction of current through the coil, reversing the magnetic field. The process then repeats. 39
4.2.5 Bearing Have you ever wondered how things like inline skate wheels and electric motors spin so smoothly and quietly? The answer can be found in a neat little machine called a bearing.
A tapered roller bearing from a manual transmission The bearing makes many of the machines we use every day possible. Without bearings, we would be constantly replacing parts that wore out from friction. In this article, we'll learn how bearings work, look at some different kinds of bearings and explain their common uses, and explore some other interesting uses of bearings. The Basics The concept behind a bearing is very simple: Things roll better than they slide. The wheels on your car are like big bearings. If you had something like skis instead of wheels, your car would be a lot more difficult to push down the road. That is because when things slide, the friction between them causes a force that tends to slow them down. But if the two surfaces can roll over each other, the friction is greatly reduced.
Bearings reduce friction by providing smooth metal balls or rollers, and a smooth inner and outer metal surface for the balls to roll against. These balls or rollers "bear" the load, allowing the device to spin smoothly.
Bearing Loads Bearings typically have to deal with two kinds of loading, radial and thrust. Depending on where the bearing is being used, it may see all radial loading, all thrust loading or a combination of both.
The bearings that support the shafts of motors and pulleys are subject to a radial load. The bearings in the electric motor and the pulley pictured above face only a radial load. In this case, most of the load comes from the tension in the belt connecting the two pulleys.
The bearings in this stool are subject to a thrust load. The bearing above is like the one in a barstool. It is loaded purely in thrust, and the entire load comes from the weight of the person sitting on the stool.
The bearings in a car wheel are subject to both thrust and radial loads. The bearing above is like the one in the hub of your car wheel. This bearing has to support both a radial load and a thrust load. The radial load comes from the weight of the car, the thrust load comes from the cornering forces when you go around a turn. Types of Bearings There are many types of bearings, each used for different purposes. These include ball bearings, roller bearings, ball thrust bearings, roller thrust bearings and tapered roller thrust bearings. BallBearings Ball bearings, as shown below, are probably the most common type of bearing. They are found in everything from inline skates to hard drives. These bearings can handle both radial and thrust loads, and is usually found in applications where the load is relatively small. 42
Cutaway view of a ball bearing In a ball bearing, the load is transmitted from the outer race to the ball, and from the ball to the inner race. Since the ball is a sphere, it only contacts the inner and outer race at a very small point, which helps it spin very smoothly. But it also means that there is not very much contact area holding that load, so if the bearing is overloaded, the balls can deform or squish, ruining the bearing.
4.3 CONSTRUCTION DETAILS As per our model we divide our project in two sections: 1. Section-A DRIVE PULLEY (ENGINE) 2.
Section-B WHEEL SHAFT PULLEY
Our design and working of model is discribe below steps:
Fig 4.3.1 Model of CVT
Fig 4.3.2 Construction details
4.4 WORKING As per the below diagram of section-1 our liver drive the power variable power transmission which is fixed on main power transmitting shaft. We insert on pink pulley with bearing no. 6201 in power transmission shaft rode and we lock that pulley with simple lock washer for smooth driving. Now, we insert second pulley in to power transmission rode. This pulley is attached with model body frame with help of bearing for smooth drive. We transmit rotation power from the motor (as engine) to the pulley with the help of gear and chain drive as shown below. Next to motor drive section pulley we thread and nut system. In which we reduce and increase pulley space by turning of liver shaft.
Fig 4.4.1 working
Fig 4.4.2 shifting of engine shaft
We attach one blue color gear which is attached with main power shaft. These gears transmit opposite rotation turn to next section-b with help of chain drive.
Fig 4.4.3 changing of clearance
4.5 Power transmission to wheel shaft As the above diagram opposite rotation turn transmit to the section-B rotate red pulley with the help of thread and nut system as shown below. In this section our pink pulley is fixed with wheel shaft.
We can see opposite turning in section-B and how increase space and decrease in between two pulleys
We insert one rubber pulley in between two sections to show complete working.
Fig 4.5.3 Low gear situation
Fig 4.5.4 High gear situation
Observations:At low gear
At high gear
Rpm of Drive pulley 1360 1360 1360 1360 1360
Rpm of Driven pulley 578 755 972 1571 1780
- From the above observation we have analyze that the rpm of the driven pulley can be varied continuously.
Future Prospects for CVTs Much of the existing literature is quick to admit that the automotive industry lacks a broad knowledge base regarding CVTs. Whereas conventional transmissions have been continuously refined and improved since the very start of the 20th century, CVT development is only just beginning. As infrastructure is built up along with said knowledge base, CVTs will become evermore prominent in the automotive landscape. Even today’s CVTs, which represent firstgeneration designs at best, outperform conventional transmissions. Automakers who fail to develop CVTs now, while the field is still in its infancy, risk being left behind as CVT development and implementation continues its exponential growth. Moreover, CVTs are do not fall exclusively in the realm of IC engines.
Conclusion The project has been tested efficiently. By this project we explored vast vistas of knowledge in the field of Automobile and its components. It is also provided valuable experience on power transmission etc. we became aware of challenges, work criterion, teamwork and other activities performed during the project analysis and its implementation. The exercise has helped us to gain lot of technical and practical knowledge. We are sure that it will serve as an important experience in our professional career. Today, only a handful of cars worldwide make use of CVTs, but the applications and benefits of continuously variable transmissions can only increase based on today’s research and development. As automakers continue to develop CVTs, more and more vehicle lines will begin to use them. As development continues, fuel efficiency and performance benefits will inevitably increase; this will lead to increased sales of CVT-equipped vehicles. Increased sales will prompt further development and implementation, and the cycle will repeat ad infinitum. Moreover, increasing development will foster competition among manufacturers—automakers from Japan, Europe, and the U.S. are already either using or developing CVTs—which will in turn lower manufacturing costs. Any technology with inherent benefits will eventually reach fruition; the CVT has only just begun to blossom.
REFERENCES 1. "CVT concerns with a Nissan Primera - AA New Zealand". Aa.co.nz. 2008-09-24. http://www.aa.co.nz/motoring/tips/ask-jack/faults/Pages/CVT-concerns-with-a-NissanPrimera.aspx. 2. Fischetti, Mark (January 2006). "No More Gears". Scientific American 294: 92. 3. Jones, Franklin D., et al. (1930). Ingenious Mechanisms for Designers and Inventors. Industrial Press. 4. "drives". Zero-max.com. http://www.zero-max.com/products/drives/drivesmain.asp. 5. "FEVj Infinitely Variable Transmission". Fuel-efficient-vehicles.org. 1994-08-02. http://www.fuel-efficient-vehicles.org/FEV-IVTransmission.php. 6. Nuvinci as Traction-drive CVT 7. NuVinci overview 8. Birch, Stuart. "Audi takes CVT from 15th century to 21st century". SAE International. http://www.sae.org/automag/techbriefs_01-00/03.htm. 9. Harris, William. "How CVTs Work". HowStuffWorks, Inc.. http://auto.howstuffworks.com/cvt.htm. Retrieved 2007-12-03. 10. S. Birch: ―Audi takes CVT from 15th century to 21st century‖. Automotive Engineering International. 11. J. Yamaguchi: ―Nissan’s Extroid CVT‖. Automotive Engineering International. 12. M.A. Kluger and D.R. Fussner: ―An Overview of Current CVT Mechanisms, Forces and Efficiencies‖ SAE Paper No. 970688, in SAE SP-1241, Transmission and Driveline Systems. 13. Symposium, pp. 81-88 SAE, 1997. 14. U.S. Environmental Protection Agency, http://www.fueleconomy.gov/feg/findacar.htm. Accessed 4/15/00. 15. M. Boos and H. Mozer: ―ECOTRONIC – The Continuously Variable ZF Transmission (CVT)‖ SAE. 16. Paper No. 970685, in SAE SP-1241, Transmission and Driveline Systems Symposium, pp. 61-67 SAE, 1997. 17. J.L. Broge: ―GM Powertrain’s evolving transmissions‖. Automotive Engineering International. 18. J. Yamaguchi: ―Two new CVTs for mini cars‖. Automotive Engineering International. 19. D. Kobayashi, Y. Mabuchi and Y. Katoh: ―A Study on the Torque Capacity of a Metal Pushing V-Belt for CVTs‖ SAE Paper No. 980822, in SAE SP –1324, Transmission and Driveline Systems Symposium, pp. 31-39 SAE, 1998. 20. K. Abo, M. Kobayashi and M. Kurosawa: ―Development of a Metal Belt Drive CVT Incorporating a Torque Converter for Use with 2-liter Class Engines‖ SAE Paper No. 980823, in SAE SP-1324, Transmission and Driveline Systems Symposium, pp. 41-48 SAE, 1998. 21. T. Miyazawa, T. Fujii, K. Nonaka and M. Takahashi: ―Power Transmitting Mechanism of a Dry 22. Hybrid V-Belt for a CVT – Advanced Numerical Model Considering Block Tilting and Pulley Deformation‖ SAE Paper No. 1999-01-0751, in SAE SP-1440, Transmission and Driveline System Symposium, pp. 143-153 SAE. 55
23. K. Ohya and H. Suzuki: ―Development of CVT Pulley Piston Featuring Variable Thickness and Work-Hardening Technologies‖ SAE Paper No. 980826, in SAE SP-1324, Transmission and Driveline Systems Symposium, pp. 71-79 SAE. 24. S. Sakaguchi, E. Kimura and K. Yamamoto: ―Development of an Engine-CVT Integrated Control System‖ SAE Paper No. 1999-01-0754, in SAE SP-1440, Transmission and Driveline Systems Symposium, pp. 171-179 SAE. 25. M. Yasuoka, M. Uchida, S. Katakura and T. Yoshino: ―An Integrated Control Algorithm for an SI Engine and a CVT‖ SAE Paper No. 1999-01-0752, in SAE SP-1440, Transmission and Driveline Systems Symposium, pp. 155-160 SAE. 26. N. Hattori, S. Aoyama, S. Kitada and I. Matsuo: ―Functional Design of a Motor Integrated CVT for a Parallel HEV‖ SAE Paper No. 1999-01-0753, in SAE SP-144. 27. Transmission and Driveline Systems Symposium, pp. 161-167 SAE.C. Kim, E. NamGoong, S. Lee, T. Kim and H. Kim: ―Fuel Economy Optimization for Parallel Hybrid Vehicles with CVT‖ SAE Paper No. 1999-01-1148, in SAE SP-1440, Transmission and Driveline Systems Symposium.