Automatic Transmission System

1. Continuously Variable Transmission
(CVT)
Department of Mechanical Engineering
National Institute of Technology Durgapur
Durgapur, West Bengal 713209, India
Presented By:
Vinay Kumar Prajapati
Roll. No: 17ME4113
Email: vinayprajapati732@gmail.com
Presented To:
Dr. S. S. Roy

2. Contents
 Introduction
 Parts of CVT
 Working of CVT
 Advantage of CVT
 Applications

3. Introduction
• A continuously variable transmission (CVT), also known as a single-
speed transmission, stepless transmission and pulley transmission is
an automatic transmission that can change seamlessly through a
continuous range of effective gear ratios.
• This is different from other mechanical transmissions that offer a
fixed number of gear ratios.
• The flexibility of a CVT with suitable control may allow the input shaft
to maintain a constant angular velocity even as the output shaft
speed varies.
• Rather than selecting one of four or five gears, a CVT constantly
changes its gear ratio to optimize engine efficiency with a perfectly
smooth torque-speed curve.

5. Parts of CVT
 Belt
 Fixed Sheaves
 Adjustable sheaves
 Centrifugal weight
 Reverse clutch
 Forward clutch
 Input shaft
 Output shaft

6. Working of CVT
When we accelerates the engine, centrifugal forces on the weight
increases and radial distance between the masses increase.
Adjustable sheaves of input shaft moves toward the fixed sheaves and gap
between adjustable sheaves and fixed sheaves decrease and diameter on
input shaft for belt will increase.
At the same time on output shaft diameter decreases for the belt.
 So gear ratio ( output dia./input dia. ) decreases and speed of output shaft
will increase.

7.  When we de-accelerates the engine, centrifugal forces on the weight
decreases and radial distance between the masses also decrease.
 Adjustable sheaves on input shaft moves away from the fixed
sheaves and gap between fixed sheaves and adjustable sheave
increases and diameter on input shaft for belt will decrease.
 At that time on output shaft diameter increases for the belt.
 So gear ratio ( output dia./input dia. ) increases and speed of output
shaft will decrease.

8. Fixed sheavesAdjustable sheaves
Fixed sheaves
Output shaft
Adjustable sheaves
Input shaft
Belt

9. Position of centrifugal masses
When engine is at rest When engine is at full speed

10. Sheaves position when engine is at
rest
Sheaves moves outward when speed
increases
Input shaft sheaves

11. When engine accelerates When engine deaccelerates
Movement of sheaves
Output shaft
speed will
increase
Output shaft
speed will
decrease

12. At input shaft At output shaft
Belt position when engine is at rest

13. At input shaft At output shaft
Belt position when engine is at full speed

14. Advantage of CVT
 Infinite number of speed ratio achieved.
 Smooth in speed changes.
 Light weight and compact design.
 Cost effective.
 Easy maintenance.

15. Vehicles in which CVT is used
 Toyota Corolla Altis CVT
 Honda City SV CVT
 Honda Amaze VX CVT
 Nissan Micra XL CVT
 Maruti Suzuki Baleno
 Honda Activa