CVT By- RAVI KUMAR

By- RAVI KUMAR MECHANICAL ENGG(7th SEM) REG. NO-0801219048 COLLEGE OF ENGINEERING BHUBANESWAR : 

By- RAVI KUMAR MECHANICAL ENGG(7th SEM) REG. NO-0801219048 COLLEGE OF ENGINEERING BHUBANESWAR SEMINAR ON CONTINUOUSLY VARIABLE TRANSMISSION ( CVT)

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Basics of 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 to make more effective use of the engine's torque as driving conditions change.

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PROBLEMS WITH MANUAL & AUTOMATIC TRANSMISSION The traffic condition has become annoying in our big cities. In such a case will automatics transmission make sense to the Indian customer. But conventional automatics always consume slightly more fuel than manual transmission and the lack of sophisticated automatics.

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Today automobiles use either a conventional manual or automatic transmission with multiple planetary gear sets that use clutches to achieve discrete gear ratios . The continuously variable transmission replaces discrete gear ratios with infinitely adjustable gearing through one of several basic CVT designs Introduction of CVT

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Overview of a CVT: Varies the transmission ratio continuously Shifts automatically with an infinite number of ratios. Seamless power delivery Constantly changes its gear ratio to optimize engine efficiency Allows the engine to rev almost immediately to deliver maximum torque

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Components of CVT 1.A variable –input driving pulley 2.An output(driven) pulley 3.A metal belt/rollers 4.Sensors and microprocessors

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Working principle 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) 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.

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HOW CVT WORKS?

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Types of CVT Metal Push Belt CVT. Toroidal Drive CVT. Variable Diameter Elastomer Belt CVT Nutating Traction Drive CVT

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Simulation of CVT Push Belt This belt transmits power between two conical pulleys, or sheaves, one fixed and one movable . A sensor reads the engine output and then electronically increases or decreases the distance between pulleys, and thus the tension of the drive belt

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Toroidal Traction Drive CVT : Uses rollers to transmit torque between the input disc and output disc. A viscous fluid transmits torque between rollers and discs. Rollers and discs never touch. The angle of the rollers changes relative to shaft position resulting in a change in gear ratio. The change in angle by a roller must be mirrored by the opposing roller.

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Toroidal CVT

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ADVANTAGES Decreases engine fatigue “infinite” number of gear ratios, maintaining the engine in its optimum power range More mechanically efficient than Automatic transmissions. Greater fuel efficiency than both manual and automatic transmissions.(Fuel savings of more than 17%). Smooth, responsive and quiet to drive

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CVT Vs. Manual Transmission Theoretical comparison under “ideal” conditions 1991 FIAT UNO M=1250 KG,TORQUE=101.2 NM 0-100 KMPH MT-11.9 SEC /CVT-8.8 SEC CVT proved 35% more efficient than the MT. With same car and engine, the CVT takes only 75% of the time to accelerate to 100km/h, compared to the MT.

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DRAWBACKS Limited torque capacity when compared to manual transmissions. Additional gear train required for reverse conditon . Larger and more costly than manual transmissions. Unwillingness to discard billions of dollars in development in MT & AT’s.

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The IC engine is nearing both perfection and obsolescence; advancements in fuel economy and emissions have effectively stalled. CVTs could potentially allow IC vehicles to meet the first wave of new fuel regulations C osts will be reduced further and performance will continue to increase. Ultimately it will give CVTs a solid foundation in the world’s automotive infrastructure. Future of CVT

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THANK you