Continuously Variable transmission
-
Upload
sharique-ahssan -
Category
Engineering
-
view
178 -
download
4
description
Transcript of Continuously Variable transmission
Title:
Continuously Variable Transmission
Presented by:Mr. Sanket Rairker (53)
Guided by: Prof. N. H . Khandare
Contents1. Introduction
2. Types :o Pulley basedo Toroidalo Hydrostatic
3. Recent Developmentso Infinitely variable transmission by Subaru, Japano Honda CR-Z CVTo Nissan XTRONIC
4. Advantages and Disadvantages
5. Future scope
6. Conclusion
7. References
Introduction
• Fuel economy dilemma solution : CVT , a type of AT• How is it different from conventional transmission?• History:-
• Birth- Leonardo da Vinci’s sketches• GM revives it 500 years later• DAF creates first commercially successful model in
1958.• Subaru and Nissan further refine it.• Ford starts the trend for chain driven models.• Nissan uses toroidal CVT’s
TYPES1. Pulley Based CVT • Contains :Drive pulley, driven pulley and a belt
connecting them. • Diameter of pulleys is variable.• Effective speed ratio maintained.
2. Toroidal CVT• Contains two discs( i /p , o/p),and
two rollers.
• Rollers maintain contact between discs , transmit power.
• Corresponding areas of contacts of each disc determines the speed ratio.
• Rollers are pivoted such that a large no. of speed ratios can be obtained.
• Effective for high torque apps due to greater durability(no belts).
3. Hydrostatic CVT
• Contains a variable displacement(i/p) pump and a hydraulic motor(o/p).
• Pump drives the motor using the fluid. Flow of fluid varied by the pump.
• Consequently, motor speed varies, thus varying the torque.
• Fluid circulates between the two components continuously.
• Useful for high torque applications , but prone to contamination.
• Costlier than other types.
Recent Developments
1. Infinitely variable transmission (IVT) , by Subaru, Japan
• An IVT is a CVT featuring a “zero”
ratio ;zero o/p for finite i/p speed, thus ratio is ∞.
• Zero relates to idling• Enables reversal of rotation.• Output shaft connected to a
epicyclic gear set , which helps shift between three modes: forward , neutral , reverse.
2. Honda CR-Z CVT• Used in mid sized vehicles.
• Features a highly efficient oil pump containing sintered gears for improved performance.
• G-Design Shift, a new coordinated control system for gearing, throttle and hydraulic control, responds quickly to driver input, maintains strong and smooth acceleration and helps realize an exciting and sporty driving feel.
• Also features “Idle stop” technology which temporarily stops the engine if idling for longer.
• 5 percent higher fuel economy than a conventional CVT.
3. The Nissan Xtronic :
• Ratios about 30% faster, providing instantaneous response to the driver's intention, in addition to a natural feeling of poweGear ratio range from low to high gear is expanded to approximately 6.
• Pulley and steel belt improvements and the use of high performance ATF (Automatic Transmission Fluid).
• Improved the electronic control system and the hydraulic system components that control the elements of the CVT.
• Result: Improved acceleration , fuel economy and driving experience.
Advantages and Disadvantages
Advantages• Improved fuel efficiency.• No shift shock to the engine
as well as the driver.• Engine runs at its most
efficient speed, virtually independent of vehicle speed.
• Faster acceleration and increased driving comfort.
Disadvantages• High cost.• Not suitable for use in very
high torque engines.• Design of belt and the
pulleys is difficult.• Slippage in the drive belt or
rollers.
Future scope
• CVT can be improved with research on the belt design permitting use in high performance vehicles.
• Hybrid vehicles will also feature with this type of transmission : • Electric motors can avoid the low speed/ high torque
problems often associated with CVTs, through an innovative double-motor system.
• Kia recently tested a system where the CVT allows the engine to run at constant speed and the motor allows the engine to run at constant torque independent of driving conditions.
• In the future a major amount of cars will feature CVT .
Conclusion
• The applications and benefits of continuously variable transmissions can only increase based on today’s research and development.
• With an increase in the number of companies opting for CVTs there will be a consequent decrease in the cost of the vehicle as well as the transmission.
• CVTs can as well replace the existing automatic transmissions and thus become the most frequently used transmission system.
References
• N. Srivastava, I. Haque A review on belt and chain continuously variable transmissions (CVT): Dynamics and control, Mechanism and Machine Theory 44 (2009) 19–41.
• Manring,Al-Ghrairi,Vermillion,2013,”Designing a hydraulic continuously variable-transmission (CVT) for retrofitting a rear-wheel drive automobile”, Journal of mechanical design , ASME , Volume 1.35,December 2011.
• http://www.nissanglobal.com/EN/TECHNOLOGY/OVERVIEW/cvt.html.• "SEAT Exeo 2.0 TSI technical information". Retrieved 14 September
2009.• "Suzuki Electrically-controlled Continuously Variable Transmission
(SECVT)". Global Communications Magazine (Suzuki Motor Corp.) 1. 2002. Retrieved 18 October 2013.
• https://www.subaru.com/engineering/transmission.html