Continuously variable transmission report


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Continuously variable transmission report

  1. 1. PROJECT REPORT ONDESIGN AND FABRICATION OF MINIATURE OF CONTINUOUSLY VARIABLE TRANSMISSION By:- RAHUL CHOUDHARY (0712840030) AMIT KUMAR (0812831013) GAUTAM CHAUDHARY (0812810037) ROHIT KUMAR (0812810077) 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
  2. 2. CERTIFICATEThis is to certify that Project Report entitled “DESIGN AND FABRICATION OFMINIATURE OF CONTINUOUSLY VARIABLE TRANSMISSION” which is submittedby RAHUL CHAUDHRY, AMIT KUMAR, GAUTAM CHAUDHARY, ROHIT KUMAR,in partial fulfillment of the requirement for the award of degree B. Tech. in Department ofMECHANICAL ENGINEERING of G.B. Technical University, is a record of the candidateown work carried out by him under my/our supervision. The matter embodied in this thesis isoriginal and has not been submitted for the award of any other degree.Date: …….KULDEEP SINGH PAL VIKAS B. SINGH (H.O.D. Mechanical deptt.) (Project guide) 2
  3. 3. DECLARATIONI hereby declare that this submission is my own work and that, to the best of myknowledge and belief, it contains no material previously published or written by anotherperson nor material which to a substantial extent has been accepted for the award of anyother degree or diploma of the university or other institute of higher learning, exceptwhere due acknowledgment has been made in the text.Date ……….Rahul choudhary 0712840030Sign……..Amit kumar 0812831013Sign……Gautam chaudhary 0812810037Sign …….Rohit kumar 0812810077Sign…….. 3
  4. 4. ACKNOWLEDGEMENTIt 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 ofMechanical Engineering, Bharat institute of Technology, Meerut for his constant support and guidancethroughout the course of our work. His sincerity, thoroughness and perseverance have been a constantsource 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 andassistance during the development of the project.We also do not like to miss the opportunity to acknowledge the contribution of all faculty members of thedepartment for their kind assistance and cooperation during the development of our project. Last but notthe least, we acknowledge our friends for their contribution in the completion of the project.Date………Name : Rahul choudhary 0712840030Signature:Name : Amit kumar 0812831013Signature:Name : Gautam chaudhary 0812810037Signature:Name : Rohit kumar 0812810077Signature: ABSTRACT 4
  5. 5. One hardly needs to be an automotive engineer to understand that the less fuel an engineconsumes, the fewer pollutants produced, and the cleaner the air we breathe. Unfortunately,improving the variables in that equation is becoming increasingly difficult. To achieveadditional fuel economy improvements, we have begun to focus on increasing efficiency in areaswhere improvements are much more difficult and costly to achieve - largely on powertraincomponents such as the transmission This stems from the fact that transmissions operate over arange of power conditions, such as low speed-high torque to high speed-low torque, as well asthrough a variety of gear ratios. To achieve gains in this area, we have challenged theconventional thinking associated with powertrain functions and designs.Conventional powertrain configurations consist of an internal combustion engine operatingacross 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 itdifficult to reach maximum engine fuel efficiency because the opportunities for operating at thelowest fuel consumption or best "brake specific fuel consumption" are restricted and generallydo 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, whichmeans that the engine is operating at its highest average adiabatic efficiencies. For internalcombustion 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. Theunderlying theories and mechanisms are also discussed. TABLE OF CONTENTS Page 5
  6. 6. DECLARATION............................................................................. 2CERTIFICATE ............................................................................ 3ACKNOWLEDGEMENTS............................................................. 4ABSTRACT .................................................................................... 5CHAPTER 1 1.1 Introduction ......................................................................... 7 1.2 History.................................................................................. 8CHAPTER 2 2.1 How CVT works................................................................... 11 2.2 Uses of CVT.......................................................................... 12 2.3 Advantages and disadvantages of CVT................................ 13 CHAPTER 3 3.1 Types of CVTs....................................................................... 14 3.2 Warko’s working principle.................................................... 25 3.3 Radial roller CVT................................................................... 29 CHAPTER 4 4.1 Components used.................................................................... 30 4.2 Component details................................................................... 31 4.2.2 Design of main components................................................. 32 4.3 Construction details.................................................................. 44 4.4 Working.................................................................................... 46 4.5 Power transmission to wheel shaft........................................... 48Observations .......................................................................................... 52FUTURE PROSPECTS OF CVTs........................................................ 53CONCLUSION...................................................................................... 54REFERENCES....................................................................................... 55 CHAPTER 1 6
  7. 7. 1.1 INTRODUCTIONA Continuously variable transmission (CVT) is a transmission which can change steplesslythrough an infinite number of effective gear ratios between maximum and minimum values. Thiscontrasts with other mechanical transmissions that only allow a few different distinct gear ratiosto be selected. The flexibility of a CVT allows the driving shaft to maintain a constant angularvelocity over a range of output velocities. This can provide better fuel economy than othertransmissions 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 continuouslyvariable transmission, or CVT, continues to emerge as a key technology for improving the fuelefficiency of automobiles with internal combustion (IC) engines. CVTs use infinitely adjustabledrive ratios instead of discrete gears to attain optimal engine performance. Since the enginealways 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 traditionaltransmissions.CVTs are not new to the automotive world, but their torque capabilities and reliability have beenlimited in the past. New developments in gear reduction and manufacturing have led to evermore-robust CVTs, which in turn allows them to be used in more diverse automotiveapplications. CVTs are also being developed in conjunction with hybrid electric vehicles. AsCVT development continues, costs will be reduced further and performance will continue toincrease, which in turn makes further development and application of CVT technology desirable.1.2 HistoryLeonardo da Vinci, in 1490, conceptualized a stepless continuously variable transmission.Thefirst patent for a friction-based belt CVT was filed in Europe by Daimler and Benz in 1886, and aUS Patent for a toroidal CVT was granted in 1935. 7
  8. 8. In 1910, Zenith Motorcycles built a V2 engined motorcycle with the Gradua-Gear, which was aCVT. This Zenith-Gradua was so successful in hillclimbing events, that it was evantuallybarred,so that other manufacturers had achance to win.In 1912, the British motorcycle manufacturer Rudge-Whitworth built the Rudge Multigear. TheMulti was a much improved version of Zenith’s Gradua-Gear. In 1922, Browne offered amotorcycle 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, calledVariomatic, was designed and built by Hub van Doorne, co-founder of Van DoornesAutomobiel Fabriek (DAF), in the late 1950s, specifically to produce an automatic transmissionfor a small, affordable car. The first DAF car using van Doornes CVT, the DAF 600, wasproduced in 1958. Van Doornes patents were later transferred to a company called VDT (VanDoorne Transmissie B.V.) when the passenger car division was sold to Volvo in 1975; its CVTwas 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 rubberbelt CVT. CVTs are used in some ATVs. The first ATV equipped with CVT was Polariss TrailBoss in 1985.In early 1987, Subaru launched the Justy in Tokyo with an electronically controlled continuouslyvariable transmission (ECVT) developed by Fuji Heavy Industries, which owns Subaru. In 1989the Justy became the first production car in the U.S. to offer CVT technology. While the Justysaw only limited success, Subaru continues to use CVT in its kei cars to this day, while alsosupplying 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 carsto 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 thetransmission starting in 1976.The 1992 Nissan March contained Nissans 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 atorque converter. This gearbox was used in a number of Japanese-market models. Nissan is alsothe 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 SkylineGT-8. However, the gearbox was not carried over when the Cedric/Gloria was replaced by theNissan Fuga in 2004. The Nissan Murano, introduced in 2003, and the Nissan Rogue, introducedin 2007, also use CVT in their automatic transmission models. In a Nissan Press Release, 12 July2006, Nissan announced a huge shift to CVT transmissions when they selected their XTronicCVT technology for all automatic versions of the Versa, Cube, Sentra, Altima and Maximavehicles in North America, making the CVT a mainstream transmission system. One majormotivator for Nissan to make a switch to CVTs was as a part of their Green Program 2010aimed at reducing CO2 emissions by 2010. The CVT found in Nissan’s Maxima, Murano and 8
  9. 9. the V6 version of the Altima is considered to be the worlds first "3.5L class" belt CVT and canhold much higher torque loads than other belt CVTs.After studying pulley-based CVT for years, Honda also introduced their own version on the 1995Honda Civic VTi. Dubbed Honda Multi Matic, this CVT gearbox accepted higher torque thantraditional pulley CVTs, and also includes a torque converter for "creep" action. The CVT is alsocurrently employed in the Honda City ZX that is manufactured in India and Honda City Variomanufactured in Pakistan.Toyota used a Power Split Transmission (PST) in the 1997 Prius, and all subsequent Toyota andLexus hybrids sold internationally continue to use the system (marketed under the HybridSynergy Drive name). The HSD is also referred to as an Electronically controlled Continuouslyvariable Transmission. The PST allows either the electric motor or the internal combustionengine (ICE) or both to propel the vehicle. In ICE-only mode, part of the engines power ismechanically coupled to the drivetrain, with the other part going through a generator and amotor. The amount of power being channeled through the electrical path determine the effectivegear ratio. Toyota also offers a non-hybrid CVT called Multidrive for models such asAvensis.Audi has, since 2000, offered a chain-type CVT (multitronic) as an option on some of itslarger-engine models, for example the A4 3.0 L V6.Fiat in 2000 offered a Cone-type CVT as anoption 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 low-and middle-range MINI in 2001, forsaking it only on the supercharged version of the car wherethe increased torque levels demanded a conventional automatic gearbox. The CVT could also bemanually "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 andSaturn Ion models.Ford introduced a chain-driven CVT known as the CFT30 in their 2005 Ford Freestyle, FordFive Hundred and Mercury Montego. The transmission was designed in cooperation withGerman automotive supplier ZF Friedrichshafen and was produced in Batavia, Ohio at BataviaTransmissions LLC (a subsidiary of Ford Motor Company) until 22 March 2007. The Bataviaplant also produced the belt-driven CFT23 CVT which went in the Ford Focus C-MAX. Fordalso 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 firstfull toroidal system to be manufactured for outdoor power equipment such as jet skis, ski-mobiles and ride-on mowers.The 2007 Dodge Caliber and the related Jeep Compass and Jeep Patriot employ a CVT using avariable pulley system as their optional automatic transmission. 9
  10. 10. The 2008 Mitsubishi Lancer model is available with CVT transmission as the automatictransmission. DE and ES models receive a standard CVT with Drive and Low gears; the GTSmodel is equipped with a standard Drive and also a Sportronic mode that allows the driver to use6 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 optionfor 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 hydraulicTorque 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 22.1 HOW CVT WORKSTraditional transmissions use a gear set that provides a given number of ratios (or speeds). Thetransmission (or the driver) shifts gears to provide the most appropriate ratio for a givensituation: Lowest gears for starting out, middle gears for acceleration and passing, and highergears for fuel-efficient cruising.Though there are several types of CVTs, most cars use a pair of variable-diameter pulleys, eachshaped like a pair of opposing cones, with a metal belt or chain running between them. Onepulley is connected to the engine (input shaft), the other to the drive wheels (output shaft). 10
  11. 11. Fig 2.1 A Chain-driven CVTThe halves of each pulley are moveable; as the pulley halves come closer together the belt isforced to ride higher on the pulley, effectively making the pulleys diameter larger. Changing thediameter of the pulleys varies the transmissions ratio (the number of times the output shaftrevolves for each revolution of the engine), in the same way that a 10-speed bike routes the chainover larger or smaller gears to change the ratio. Making the input pulley smaller and the outputpulley larger gives a low ratio (a large number of engine revolutions producing a small numberof output revolutions) for better low-speed acceleration. As the car accelerates, the pulleys varytheir diameter to lower the engine speed as car speed rises. This is the same thing a conventionalautomatic or manual transmission does, but while a conventional transmission changes the ratioin stages by shifting gears, the CVT continuously varies the ratio -- hence its name.2.2 USES OF CVTsMany small tractors for home and garden use have simple rubber belt CVTs. For example, theJohn Deere Gator line of small utility vehicles uses a belt with a conical pulley system. They candeliver an abundance of power and can reach speeds of 10–15 mph (16–24 km/h), all withoutneed for a clutch or shift gears. Nearly all snowmobiles, old and new, and motor scooters useCVTs. 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 beadjusted independently of the engine speed. This allows the operator to slow down and speed upas needed to accommodate variations in thickness of the crop.CVTs have been used in aircraft electrical power generating systems since the 1950s and inSCCA Formula 500 race cars since the early 1970s. More recently, CVT systems have been 11
  12. 12. developed for go-karts and have proven to increase performance and engine life expectancy. TheTomcat 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 hasa pair of manually-adjustable conical pulley halves through which a wide drive belt from themotor loops. The pulley on the motor, however, is usually fixed in diameter, or may have a seriesof 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 reductiongearing system for the operator to precisely control the width of the gap between the pulleyhalves. This gap width thus adjusts the gearing ratio between the motors fixed pulley and theoutput shafts variable pulley, changing speed of the chuck; a tensioner pulley is implemented inthe belt transmission to take up or release the slack in the belt as the speed is altered. In mostcases, however, the drill press speed must be changed with the motor running.CVTs should be distinguished from Power Sharing Transmissions (PSTs), as used in newerhybrids, such as the Toyota Prius, Highlander and Camry, the Nissan Altima, and newer-modelFord Escape Hybrid SUVs. CVT technology uses only one input from a prime mover, anddelivers variable output speeds and torque; whereas PST technology uses two prime moverinputs, and varies the ratio of their contributions to output speed and power. These transmissionsare fundamentally different. However the Honda Insight hybrid, the Nissan Versa (only the SLmodel), Nissan Cube and the Nissan Altima use CVT.2.3 ADVANTAGES AND DISADVANTAGESAdvantages • 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 CVTs 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 12
  13. 13. as maximum fuel efficiency. This allows the CVT to provide quicker acceleration than a conventional automatic or manual transmission while delivering superior fuel economy.Disadvantages • 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 low- powered 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 CVTs 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 33.1 TYPES OF CVTs3.1.1 Variable-diameter pulley (VDP) or Reeves driveIn this most common CVT system, there are two V-belt pulleys that are split perpendicular totheir axes of rotation, with a V-belt running between them. The gear ratio is changed by movingthe two sections of one pulley closer together and the two sections of the other pulley fartherapart. Due to the V-shaped cross section of the belt, this causes the belt to ride higher on onepulley and lower on the other. Doing this change the effective diameters of the pulleys, whichchanges the overall gear ratio. The distance between the pulleys does not change, and neitherdoes the length of the belt, so changing the gear ratio means both pulleys must be adjusted (onebigger, the other smaller) simultaneously to maintain the proper amount of tension on the belt. 13
  14. 14. The V-belt needs to be very stiff in the pulleys axial direction in order to make only short radialmovements while sliding in and out of the pulleys. This can be achieved by a chain and not byhomogeneous rubber. To dive out of the pulleys one side of the belt must push. This again can bedone only with a chain. Each element of the chain has conical sides, which perfectly fit to thepulley if the belt is running on the outermost radius. As the belt moves into the pulleys thecontact area gets smaller. The contact area is proportional to the number of elements, thus thechain has lots of very small elements. The shape of the elements is governed by the static of acolumn. The pulley-radial thickness of the belt is a compromise between maximum gear ratioand torque. For the same reason the axis between the pulleys is as thin as possible. A film oflubricant is applied to the pulleys. It needs to be thick enough so that the pulley and the beltnever touch and it must be thin in order not to waste power when each element dives into thelubrication film. Additionally, the chain elements stabilize about 12 steel bands. Each band isthin enough so that it bends easily. If bending, it has a perfect conical surface on its side. In thestack of bands each band corresponds to a slightly different gear ratio, and thus they slide overeach 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 CVTsPeer into a planetary automatic transmission, and youll see a complex world of gears, brakes,clutches and governing devices. By comparison, a continuously variable transmission is a studyin simplicity. Most CVTs only have three basic components: • A high-power metal or rubber belt • A variable-input "driving" pulley • An output "driven" pulleyCVTs also have various microprocessors and sensors, but the three components described aboveare the key elements that enable the technology to work. 14
  15. 15. Fig 3.1.2(a) Variable pulleyThe variable-diameter pulleys are the heart of a CVT. Each pulley is made of two 20-degreecones facing each other. A belt rides in the groove between the two cones. V-belts are preferredif the belt is made of rubber. V-belts get their name from the fact that the belts bear a V-shapedcross 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 lowerin the groove, and the radius of the belt loop going around the pulley gets smaller. When thecones are close together (when the diameter decreases), the belt rides higher in the groove, andthe 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.Variable-diameter pulleys must always come in pairs. One of the pulleys, known as the drivepulley (or driving pulley), is connected to the crankshaft of the engine. The driving pulley isalso called the input pulley because its where the energy from the engine enters thetransmission. 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. 15
  16. 16. Fig 3.1.2(b) 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.When one pulley increases its radius, the other decreases its radius to keep the belt tight. As thetwo pulleys change their radii relative to one another, they create an infinite number of gearratios -- from low to high and everything in between. For example, when the pitch radius is smallon the driving pulley and large on the driven pulley, then the rotational speed of the driven pulleydecreases, resulting in a lower “gear.” When the pitch radius is large on the driving pulley andsmall on the driven pulley, then the rotational speed of the driven pulley increases, resulting in a 16
  17. 17. higher “gear”. Thus, in theory, a CVT has an infinite number of "gears" that it can run through atany time, at any engine or vehicle speed.The simplicity and stepless nature of CVTs make them an ideal transmission for a variety ofmachines and devices, not just cars. CVTs have been used for years in power tools and drillpresses. Theyve also been used in a variety of vehicles, including tractors, snowmobiles andmotor scooters. In all of these applications, the transmissions have relied on high-density rubberbelts, which can slip and stretch, thereby reducing their efficiency.The introduction of new materials makes CVTs even more reliable and efficient. One of the mostimportant 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 holdtogether high-strength, bow-tie-shaped pieces of metal. Fig.3.1.2(c) Metal belt designMetal belts dont 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 suchthat the two parts could fill the central hole of a torus. One disc is the input, and the other is theoutput (they do not quite touch). Power is transferred from one side to the other by rollers. When 17
  18. 18. the rollers axis is perpendicular to the axis of the near-conical parts, it contacts the near-conicalparts at same-diameter locations and thus gives a 1:1 gear ratio. The roller can be moved alongthe axis of the near-conical parts, changing angle as needed to maintain contact. This will causethe roller to contact the near-conical parts at varying and distinct diameters, giving a gear ratio ofsomething other than 1:1. Systems may be partial or full toroidal. Full toroidal systems are themost efficient design while partial toroidals may still require a torque converter, and hence loseefficiency.Toroidal CVTsAnother version of the CVT -- the toroidal CVT system -- replaces the belts and pulleys withdiscs and power rollers Fig.3.1.3(a)Extroid toroidal CVTAlthough such a system seems drastically different, all of the components are analogous to abelt-and-pulley system and lead to the same results -- a continuously variable transmission.Heres 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. 18
  19. 19. • 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 CVTThe wheels can rotate along two axes. They spin around the horizontal axis and tilt in or outaround the vertical axis, which allows the wheels to touch the discs in different areas. When thewheels are in contact with the driving disc near the center, they must contact the driven disc nearthe rim, resulting in a reduction in speed and an increase in torque (i.e., low gear). When thewheels 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 ofthe wheels, then, incrementally changes the gear ratio, providing for smooth, nearlyinstantaneous 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 ratiosof output shaft speed to input shaft speed includes a zero ratio that can be continuouslyapproached from a defined "higher" ratio. A zero output speed (low gear) with a finite input 19
  20. 20. speed implies an infinite input-to-output speed ratio, which can be continuously approached froma given finite input value with an IVT. Low gears are a reference to low ratios of output speed toinput speed. This low ratio is taken to the extreme with IVTs, resulting in a "neutral", or non-driving "low" gear limit, in which the output speed is zero. Unlike neutral in a normalautomotive 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 oscillatingmotion and back to rotary motion using roller clutches. The stroke of the intermediateoscillations is adjustable, varying the output speed of the shaft. This original design is stillmanufactured today, and an example and animation of this IVT can be found here. Paul B. Pirescreated a more compact (radially symmetric) variation that employs a ratchet mechanism insteadof roller clutches, so it doesnt have to rely on friction to drive the output. An article and sketchof this variation can be found hereMost IVTs result from the combination of a CVT with a planetary gear system (which is alsoknown as an epicyclic gear system) which enforces an IVT output shaft rotation speed which isequal to the difference between two other speeds within the IVT. This IVT configuration uses itsCVT as a continuously variable regulator (CVR) of the rotation speed of any one of the threerotators of the planetary gear system (PGS). If two of the PGS rotator speeds are the input andoutput of the CVR, there is a setting of the CVR that results in the IVT output speed of zero. Themaximum output/input ratio can be chosen from infinite practical possibilities through selectionof additional input or output gear, pulley or sprocket sizes without affecting the zero output orthe continuity of the whole system. The IVT is always engaged, even during its zero outputadjustment.IVTs can in some implementations offer better efficiency when compared to other CVTs as inthe preferred range of operation because most of the power flows through the planetary gearsystem and not the controlling CVR. Torque transmission capability can also be increased.Theres also possibility to stage power splits for further increase in efficiency, torquetransmission 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 CVRratcheting 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 enginecan displace from zero to 27 cubic inches per revolution forward and zero to -10 cubic inches perrevolution reverse. The rear unit is capable of zero to 75 cubic inches per revolution.3.1.5 OVERVIEW OF THE IVT SYSTEMA generic simplified layout of the IVT is shown below, this represents a layshaft layout, and acoaxial layout is also possible. Beneath the diagram a brief description of each component isgiven. 20
  21. 21. Fig 3.1.5 IVTThe 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 theplanet gear in the epicyclic gear train.The epicyclic gearset - is the means by which the running engine can be connected to thestationary 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 ofthe epicyclic gearset and the input of the high regime clutch. An idling gear can be used insteadof 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 CVTThe ratcheting CVT is a transmission that relies on static friction and is based on a set ofelements that successively become engaged and then disengaged between the driving system andthe driven system, often using oscillating or indexing motion in conjunction with one-way 21
  22. 22. clutches or ratchets that rectify and sum only "forward" motion. The transmission ratio isadjusted by changing linkage geometry within the oscillating elements, so that the summedmaximum 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, andtherefore when it is locked into a static friction mode where the driving & driven rotatingsurfaces momentarily rotate together without slippage.These CVTs can transfer substantial torque, because their static friction actually increasesrelative to torque throughput, so slippage is impossible in properly designed systems. Efficiencyis generally high, because most of the dynamic friction is caused by very slight transitionalclutch speed changes. The drawback to ratcheting CVTs is vibration caused by the successivetransition in speed required to accelerate the element, which must supplant the previouslyoperating and decelerating, power transmitting element.Ratcheting CVTs are distinguished from VDPs and roller-based CVTs by being static friction-based devices, as opposed to being dynamic friction-based devices that waste significant energythrough slippage of twisting surfaces. An example of a ratcheting CVT is one prototyped as abicycle transmission protected under U.S. Patent 5,516,132 in which strong pedalling torquecauses this mechanism to react against the spring, moving the ring gear/chainwheel assemblytoward a concentric, lower gear position. When the pedaling torque relaxes to lower levels, thetransmission self-adjusts toward higher gears, accompanied by an increase in transmissionvibration.3.1.7 HYDROSTATIC CVTSHydrostatic transmissions use a variable displacement pump and a hydraulic motor. All power istransmitted by hydraulic fluid. These types can generally transmit more torque, but can besensitive to contamination. Some designs are also very expensive. However, they have theadvantage that the hydraulic motor can be mounted directly to the wheel hub, allowing a moreflexible suspension system and eliminating efficiency losses from friction in the drive shaft anddifferential components. This type of transmission is relatively easy to use because all forwardand reverse speeds can be accessed using a single lever.An integrated hydrostatic transaxle (IHT) uses a single housing for both hydraulic elements andgear-reducing elements. This type of transmission, most commonly manufactured by Hydro-Gear, has been effectively applied to a variety of inexpensive and expensive versions of riddenlawn mowers and garden tractors. Many versions of riding lawn mowers and garden tractorspropelled by a hydrostatic transmission are capable of pulling a reverse tine tiller and even asingle bladed plow.One class of riding lawn mower that has recently gained in popularity with consumers is zeroturning radius mowers. These mowers have traditionally been powered with wheel hub mountedhydraulic motors driven by continuously variable pumps, but this design is relatively expensive.Hydro-Gear, created the first cost-effective integrated hydrostatic transaxle suitable forpropelling consumer zero turning radius mowers. 22
  23. 23. Some heavy equipment may also be propelled by a hydrostatic transmission; e.g. agriculturalmachinery including foragers, combines, and some tractors. A variety of heavy earth-movingequipment manufactured by Caterpillar Inc., e.g. compact and small wheel loaders, track typeloaders 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 theheat that is generated by the flowing oil. Fig 3.1.7 Honda DN-01 motorcycleThe Honda DN-01 motorcycle is the first road-going consumer vehicle with hydrostatic drivethat employs a variable displacement axial piston pump with a variable-angle swashplate.3.1.8 VARIABLE TOOTHED WHEEL TRANSMISSIONA variable toothed wheel transmission is not a true CVT that can alter its ratio in infiniteincrements, but rather approaches CVT capability by having a large number of ratios, typically49. This transmission relies on a toothed wheel positively engaged with a chain where thetoothed wheel has the ability to add or subtract a tooth at a time in order to alter its ratio relativeto the chain it is driving. The "toothed wheel" can take on many configurations including ladderchains, drive bars and sprocket teeth. The huge advantage of this type of CVT is that it is apositive mechanical drive and thus does not have the frictional losses and limitations of theroller-based or VDP CVT’s. The challenge in this type of CVT is to add or subtract a tooth fromthe toothed wheel in a very precise and controlled way in order to maintain synchronizedengagement with the chain. This type of transmission has the potential to change ratios underload because of the large number of ratios, resulting in the order of 3% ratio change differencesbetween ratios, thus a clutch or torque converter is necessary only for pull-away. No CVTs ofthis type are in commercial use, probably because of above mentioned development challenge. 23
  24. 24. 3.1.9 CONE CVTSThis category comprises all CVTs made up of one or more conical bodies that function togetheralong 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 thecone, 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 ofcones (according to the torque to be transmitted) to a central, barrel-shaped hub. The side surfaceof the hub is convex with a specified radius of curvature, smaller than the concavity radius of thecones. In this way, there will be only one (theoretical) contact point between each cone and thehub.A new CVT using this technology, the Warko, was presented in Berlin during the 6thInternational 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 alwaysconnected to the wheels, and the rear drive is obtained by means of an epicyclic system inoutput. This system, named “power split”, allows the condition of geared neutral or "zeroDynamic": when the engine turns (connected to the sun gear of the epicyclic system), thevariator (which rotates the ring of the epicyclic system in the opposite sense to the sun gear), in aparticular position of its range, will compensate for the engine rotation, having zero turns inoutput (planetary = the output of the system). As a consequence, the satellite gears roll within aninternal ring gear.3.2 WARKOS WORKING PRINCIPLE 24
  25. 25. Fig 3.2.1Starting from the complete configuration of all the components required for the motiontransmission (picture to the left) we can examine every single step of the Warko CVTs assemblyto understand its working principle. Fig 3.2.2Following the motion transmission process, we will see that the motion deriving from the engineshaft is transmitted to the main gear, named sun gear. 25
  26. 26. Fig 3.2.3From the sun gear, the motion is transmitted to a certain number of gears, called satellites orplanet gears, laid out in a crown shape on it. Fig 3.2.4Each satellite is connected by means of a little shaft and two joints to a frustum cone-shapedbody, hereinafter called "satellite cone". The side surface of the satellite cones is concaveaccording to a given radius of curvature. 26
  27. 27. Fig 3.2.5All the satellite cones transmit via friction the motion to a central "barrel"-shaped hub. Fig 3.2.5Finally, the motion is transmitted to the output shaft by means of an internal gearing. 27
  28. 28. Fig 3.2.6The lateral surface of the hub is convex according to a given radius of curvature, which isinferior 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 ofthe same hub.The contact between the satellite cones and the hub is kept and forced by apneumatic (or hydraulic) system (not shown) which pushes all the satellite cones against the huband the outside ring named Reaction Ring.The concavity radius of the satellite cones and the convexity radius of the hub are calculated insuch a way so as to keep the external diameter constant = the internal diameter of the ReactionRing. 28
  29. 29. 3.3 RADIAL ROLLER CVTThe 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. Unlikeother systems, the radial rollers do not show a tangential speed variation (delta) along the contactlines on the rotors. From this, a greater mechanical efficiency and working life are obtained. Themain advantages of this CVT are the manufacturing inexpensiveness and the high powerefficiency.3.4 TRACTION-DRIVE CVTA completely new type of CVT is the traction-drive CVT. Traction-drive CVTs are stated asbeing the most efficient type of CVTs at the moment. One model is commercially produced asthe Fallbrook Technologies NuVinci, which employs elements of both CVT and planetarytransmissions. CHAPTER 44.1 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. 29
  30. 30. 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 Details4.2.1 - PulleySize of pulley or discs- 30
  31. 31. Fig 4.2.1 Tapered discDisks are made up of mild steel. The density of the mild steel is 7860kg/m3. Disks have taperedsurface of 8 degree on one side to work as pulley when came in contact. Diameter of the disk is125mm and has the thickness of 10mm.4.2.2 – DESIGN OF CHAIN 31
  32. 32. Fig 4.2.2 Bike timing chainIt is assumed that, Theeth on smaller sprocket z1 =7 Teeth on larger sprocket z2 = 44 Velocity ratio = 44/7 = 6.285For 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 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 32
  33. 33. 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: 588mmGroove: 86 33
  34. 34. Fig 4.2.3 Design of chain and sprockets4.2.3 DESIGN OF SHAFTWeight of disc = 8.8 NWeight of pulley = 8.8*2 = 17.6 NThis 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 34
  35. 35. Power of the motor used = 0.25 HP = 186.5 wattSpeed of the motor = 1400 rpm (approx.)Torque produced by motor T = (P*60)/(2πN) = (186.5*60)/(2π*1400) T = 1.27 NmEquivelent bending moment Me = [M+(M2+T2 )1/2]/2 Me = 2.24 NmFor 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 35
  36. 36. Equivelent torque Te = (M2+T2)1/2 Te = (2.072+1.272)1/2 Te = 2.43 NmNow, Te = (π/16)*(τ/6)*d3 2.43 = (π/16)*(42*106/6)*d3 d = 12.09 mmFor the safe design of shafts we take the larger diameter i. e. d = 14.44 mm 36
  37. 37. 4.2.3 Bike timing sprockets Fig 4.2.3 Bike timing sprocketDimension:-Teeth: 28Length: 60mm4.2.4 Dc motorOne of the first electromagnetic rotary motors was invented by Michael Faraday in 1821 andconsisted of a free-hanging wire dipping into a pool of mercury. A permanent magnet wasplaced in the middle of the pool of mercury. When a current was passed through the wire, thewire rotated around the magnet, showing that the current gave rise to a circular magnetic fieldaround the wire. This motor is often demonstrated in school physics classes, but brine(saltwater) is sometimes used in place of the toxic mercury. This is the simplest form of a class ofelectric motors called homopolar motors. A later refinement is the Barlows Wheel.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 internalcombustion engine.The modern DC motor was invented by accident in 1873, when Zénobe Gramme connected aspinning dynamo to a second similar unit, driving it as a motor. 37
  38. 38. The classic DC motor has a rotating armature in the form of an electromagnet. A rotary switchcalled a commutator reverses the direction of the electric current twice every cycle, to flowthrough the armature so that the poles of the electromagnet push and pull against the permanentmagnets on the outside of the motor. As the poles of the armature electromagnet pass the poles ofthe 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 properdirection. (See the diagrams below.) Fig 4.2.4 DC motorA simple DC electric motor. When the coil is powered, a magnetic field is generated around thearmature. The left side of the armature is pushed away from the left magnet and drawn towardthe right, causing rotation. 38
  39. 39. The armature continues to rotate.When the armature becomes horizontally aligned, the commutator reverses the direction ofcurrent through the coil, reversing the magnetic field. The process then repeats. 39
  40. 40. 4.2.5 BearingHave you ever wondered how things like inline skate wheels and electric motors spin sosmoothly and quietly? The answer can be found in a neat little machine called a bearing.A tapered roller bearing from a manual transmissionThe bearing makes many of the machines we use every day possible. Without bearings, wewould be constantly replacing parts that wore out from friction. In this article, well learn howbearings work, look at some different kinds of bearings and explain their common uses, andexplore some other interesting uses of bearings.The BasicsThe concept behind a bearing is very simple: Things roll better than they slide. The wheels onyour car are like big bearings. If you had something like skis instead of wheels, your car wouldbe 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 slowthem down. But if the two surfaces can roll over each other, the friction is greatly reduced. 40
  41. 41. Bearings reduce friction by providing smooth metal balls or rollers, and a smooth inner and outermetal surface for the balls to roll against. These balls or rollers "bear" the load, allowing thedevice to spin smoothly.Bearing LoadsBearings typically have to deal with two kinds of loading, radial and thrust. Depending onwhere the bearing is being used, it may see all radial loading, all thrust loading or a combinationof 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 thiscase, 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 loadcomes from the weight of the person sitting on the stool. 41
  42. 42. 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 aradial load and a thrust load. The radial load comes from the weight of the car, the thrust loadcomes from the cornering forces when you go around a turn.Types of BearingsThere 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.BallBearingsBall bearings, as shown below, are probably the most common type of bearing. They are foundin everything from inline skates to hard drives. These bearings can handle both radial and thrustloads, and is usually found in applications where the load is relatively small. 42
  43. 43. Cutaway view of a ball bearingIn a ball bearing, the load is transmitted from the outer race to the ball, and from the ball to theinner race. Since the ball is a sphere, it only contacts the inner and outer race at a very smallpoint, which helps it spin very smoothly. But it also means that there is not very much contactarea holding that load, so if the bearing is overloaded, the balls can deform or squish, ruining thebearing.4.3 CONSTRUCTION DETAILSAs per our model we divide our project in two sections: 1. Section-A DRIVE PULLEY (ENGINE) 2. Section-B WHEEL SHAFT PULLEYOur design and working of model is discribe below steps: 43
  44. 44. Fig 4.3.1 Model of CVT 44
  45. 45. Fig 4.3.2 Construction details4.4 WORKING 45
  46. 46. As per the below diagram of section-1 our liver drive the power variable power transmissionwhich is fixed on main power transmitting shaft. We insert on pink pulley with bearing no. 6201in power transmission shaft rode and we lock that pulley with simple lock washer for smoothdriving.Now, we insert second pulley in to power transmission rode. This pulley is attached with modelbody 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 increasepulley space by turning of liver shaft. Fig 4.4.1 working 46
  47. 47. Fig 4.4.2 shifting of engine shaftWe attach one blue color gear which is attached with main power shaft. These gears transmitopposite rotation turn to next section-b with help of chain drive. Fig 4.4.3 changing of clearance 47
  48. 48. 4.5 Power transmission to wheel shaftAs the above diagram opposite rotation turn transmit to the section-B rotate red pulley with thehelp of thread and nut system as shown below. In this section our pink pulley is fixed with wheelshaft. Fig 4.5.1 We can see opposite turning in section-B and how increase space and decrease in between two pulleys 48
  49. 49. Fig 4.5.2We insert one rubber pulley in between two sections to show complete working. 49
  50. 50. Fig 4.5.3 Low gear situation 50
  51. 51. Fig 4.5.4 High gear situationObservations:- 51
  52. 52. Rpm of Drive pulley Rpm of Driven pulleyAt low gear 1360 578 1360 755 1360 972At high gear 1360 1571 1360 1780 - From the above observation we have analyze that the rpm of the driven pulley can be varied continuously.Future Prospects for CVTsMuch of the existing literature is quick to admit that the automotive industry lacks a broadknowledge base regarding CVTs. Whereas conventional transmissions have been continuously 52
  53. 53. refined and improved since the very start of the 20th century, CVT development is only justbeginning. As infrastructure is built up along with said knowledge base, CVTs will become ever-more prominent in the automotive landscape. Even today’s CVTs, which represent first-generation designs at best, outperform conventional transmissions. Automakers who fail todevelop CVTs now, while the field is still in its infancy, risk being left behind as CVTdevelopment and implementation continues its exponential growth. Moreover, CVTs are do notfall exclusively in the realm of IC engines.ConclusionThe project has been tested efficiently. By this project we explored vast vistas of knowledge inthe field of Automobile and its components. It is also provided valuable experience on power 53
  54. 54. transmission etc. we became aware of challenges, work criterion, teamwork and other activitiesperformed during the project analysis and its implementation.The exercise has helped us to gain lot of technical and practical knowledge. We are sure that itwill 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 ofcontinuously variable transmissions can only increase based on today’s research anddevelopment. As automakers continue to develop CVTs, more and more vehicle lines will beginto use them. As development continues, fuel efficiency and performance benefits will inevitablyincrease; this will lead to increased sales of CVT-equipped vehicles. Increased sales will promptfurther 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 lowermanufacturing costs. Any technology with inherent benefits will eventually reach fruition; theCVT has only just begun to blossom.REFERENCES 1. "CVT concerns with a Nissan Primera - AA New Zealand". 2008-09-24. http:// Primera.aspx. 54
  55. 55. 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". "FEVj Infinitely Variable Transmission". 1994-08-02. http:// Nuvinci as Traction-drive CVT7. NuVinci overview8. Birch, Stuart. "Audi takes CVT from 15th century to 21st century". SAE International. Harris, William. "How CVTs Work". HowStuffWorks, Inc.. 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, 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 Dry22. 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.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. 55
  56. 56. 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. 56