Continuously variable transmission
- 2. HISTORY: A Timeline of CVT Innovation 1490 - Da Vinci Sketches a stepless continuously variable transmission 1886 - First toroidal CVT patent filed 1935 - Adiel Dodge receives U.S. patent for toroidal CVT 1939 - Fully automatic transmission based on planetary gear system introduced 1958 - Daf (of The Netherlands) produces a CVT in a car 1989 - Subaru Justy GL is the first U.S.-sold production automobile to offer a CVT 2002 - Saturn Vue with a CVT debuts; first Saturn to offer CVT technology 2004 - Ford begins offering a CVT
- 3. TRANSMISSION ?? The job of the transmission is to change the speed ratio between the engine and the wheels of an automobile. The transmission uses a range of gears -- from low to high -- to make more effective use of the engine's torque as driving conditions change. The gears can be engaged manually or automatically
- 4. AT & MT AUTOMATIC TRANSMISSION: Changing gears without any interference of human effort accordingly to load and road conditions. MANUAL TRANSMISSION: Involves human effort in order to change gears.
- 5. DISAVANTAGES OF AT & MT: Engine torque > Drive shaft torque. Frictional losses.
- 6. Engine torque is inversely proportional to speed of the engine. More the speed less the torque.
- 7. CONTINUOUSLY VARIABLE TRANSMISSION (CVT) It’s a kind of transmission which can change steplessly through an infinite no of effective gear ratios between maximum and minimum.
- 8. WHAT DOES IT CONTAIN? This design does away with gears entirely. Instead it has two pulleys connected by a belt. The engine turns one pulley, and the other one is connected to the rest of transmission to the wheels. The magic of CVT is that the size of the pulleys can change from small to large, and infinite sizes in between. So to start off with, the engine’s pulley will be small and the other one large, just like first gear. But as the car gathers speed, the engine’s pulley smoothly increases in size, exactly as the other pulley decreases in size. In effect, you’re changing gear all the time. There’s a few different ways of achieving variation in pulley sizes, but the fundamental principle is always the same.
- 9. Continued….. What this means for the driver is that the engine can go directly to the best revolving range for a given situation. This revolving range is typically either the one that delivers the most efficiency, most power, or most torque. The result is a smoother, more efficient and quicker drive than an normal automatic.
- 11. Parts of pulley:
- 12. BELT: Its not a normal belt rather it’s a “push belt”. Contains: Elements Steel rings packs (9-12)
- 13. ELEMENTS AND RINGPACKS: Element parts: Neck radius Saddle Rocking edge
- 14. WORKING:
- 15. In both of these pulleys one side is fixed. while the other side can be hydraulically moved in and out, in effect altering the diameter of each pulley.
- 16. Reverse gear?? It has a carrier that is connected to pulley A sun gear connected to input shaft 3 sets of 2 planet gears A ring gear connected to planet and carrier. Has 2 clutches 1 & 2. One for foreword and other for reverse.
- 17. How does it work? First clutch: Connects sun and ring gear. This makes input power transfer through ring gear. Thereby achieving foreword gear. Second clutch: This makes ring gear stationary. This makes planet gears to work and they are 2 in number the output will be reverse of input. Thereby achieving reverse gear.
- 18. FLEXIBILITY OF CVT: Allows input shaft to maintain constant angular velocity. Belt driven pulley design offers 88% of efficiency.
- 19. ADVANTAGES OF CVT: Constant stepless acceleration. Engine speed is constant irrespective of vehicle speed. Less power loss. Response to change in throttle and speed is high. If same car, same engine, but transmission is cvt then consequences would be 75% of time to accelerate to 100 km/hr compared to manual transmission.
- 20. APPLICATIONS: Used in snow mobiles (new and old). Golf carts, power tools , mini machines.
- 21. DISADVANTAGES: High cost. High wear. Requires special lubricating oil. Small damage in belt tends to replace whole belt.
- 22. CONCLUSION Superior technology for transmission of power. Widely acceptable all over the world.