2.  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.

3. An automatic transmission
is an automobile gearbox
that can change gear
ratios automatically as the
vehicle moves, freeing the
driver from having to shift
gears manually.

4. Planetary GearboxDirect Shift Gear Box
CVT

5. • This unique transmission does not have several set of gears like most
transmissions, but rather have an infinite number of gear ratios.
• CVT does not strictly require the presence of a clutch, allowing the
dismissal thereof.
• Seamless acceleration with a “direct” drive feel for enhanced driving
pleasure.
• With fewer moving parts, CVT is simpler than Automatic Transmission
in principle.
• CVT is emerging as a keystone technology that enables other

6. o 1490 - Da Vinci sketches a stepless continuously variable
transmission
o 1886 - First Toroidal CVT patent filed
o 1935 - Adiel Dodge receives U.S. patent for Toroidal CVT
o 1939 - Fully Automatic Transmission based on Planetary gear
system introduced
o 1958 - Daf (of The Netherlands) produces a CVT in a car
o 1989 - Subaru Justy GL is the first U.S.-sold production
automobile to offer a CVT
o 2002 - Saturn Vue with a CVT debuts; first Saturn to offer CVT
technology
o 2004 - Ford begins offering a CVT

7. o Provide engine torque in optimum condition (road
loads / drive shaft torque)
o No shift clonk
o Transmission ratio can be adjusted continuously
o Improved fuel efficiency
o Better acceleration
o Eliminates gear hunting especially when going up
a hill

9.  Audi A4, a5, A6, A7
 Fiat Punto, Ford Fiesta
 Honda City, Jazz
 Mercedes Benz A & B Class
 Nissan Micra
 Suzuki SX4
 Toyota Prius

10. Toroidal CVTs Hydrostatic CVTs
Pulley Based CVTs

11.  The variable-diameter pulleys
are the heart of a CVT. Each
pulley is made of two 20-degree
cones facing each other. A belt
rides in the groove between the
two cones.
 V-belts are preferred if the belt is
made of rubber. V-belts get their
name from the fact that the belts
bear a V-shaped cross section,
which increases the frictional
grip of the belt.

12. Driver Gear
Primary Pulley
Driver and Driven
Shaft
Secondary Pulley
V - belt

13. o Driving gear, as in the name it is
situated at the driving side of the
pulley based continuous variable
transmission system. The driving
gear is the most complex parts of
pulley based continuous variable
transmission system. It comprises
of many types gears system and
clutch.
o It comprises of planetary gears,
annular gear, sun gear, and two
different sets of clutch system –
Forward gear clutches and
Reverse gear clutches.

14. Side View Front View

15. The primary pulley is situated at
the driving side of the pulley based
continuous variable transmission
system. It supports the driving
gear and belt from maintaining its
position at different situations.

16. Side View

17.  The driving and driven shaft are the base of pulley based
continuous variable transmission system.
 The driving and driven shaft are at the driving and driven side of
the pulley based continuous variable transmission system.

18. Side View Front view

19. There are two secondary pulley
in the pulley based continuous
variable transmission system.
Both the secondary pulleys are
situated at the driven end of the
pulley based continuous
variable transmission system. It
is at both situated on the driven
shaft facing opposite to each
other.

20. Side View of Secondary Pulley 1 and 2

21. Front View of Secondary Pulley 1 and 2

22. The common characteristic of
the V-belt drives is the use of
a drive and driven sheave,
each with variable diameters.
The effective diameter of the
sheave is adjusted by varying
the distance between the two
halves of the sheave .

23. Side View of 3 different V-Belts

24.  In low gear ratio the radius of the
belt in minimum at driving end
and maximum at driven end.
 Low speed due to minimum
radius at of belt at driving end

25. Side ViewTop View

26.  If we compare continuous
variable transmission system
with a 6-speed manual
gearbox then we can say the
semi-intermediate gear ratio is
somewhat similar to 2nd gear
of the 6-speed manual
gearbox.
 At this stage the radius of the
belt is somewhat 40-60
position, 40 at driving end and
60 at driven end.

27. Side ViewTop View

28.  At this stage the radius of the belt
is somewhat 50-50 position, 50 at
driving end and 50 at driven end.
 At this stage the distance
between the driving gear and the
primary pulley at the driving end
and the distance between the two
secondary pulleys at the driven
becomes equal.
 The belt radius is equal at both
end.

29. Side ViewTop View

30.  If we compare continuous
variable transmission system with
a 6-speed manual gearbox then
we can say the semi-high gear
ratio is somewhat similar to 4th
gear of the 6-speed manual
gearbox.
 This stage just opposite to the
semi-intermediate stage.

31. Side ViewTop View

32.  This stage just opposite to the
first stage i.e., at low gear.
 If we compare continuous
variable transmission system with
a 6-speed manual gearbox then
we can say the high gear ratio is
somewhat similar to 5th gear of
the 6-speed manual gearbox.

33. Side ViewTop View

34.  The main advantage of CVTs is
that they allow an engine to run
at its ideal RPM regardless of
the speed of the vehicle. This
improves fuel economy and by
effect, exhaust emissions.
 CVT equipped vehicles
consumes 10% less fuel when
compared with the automatic
transmissions.
(from Nissan motor’s journal)

35.  Wider gear ratio range.
 In CVT, the gear ratio range from low to high gear is expanded,
attaining a top-of-class final gear reduction ratio of about 6.
 The extended low end of the range to improve acceleration,
and the high end to improve fuel economy.
 Flexibly tunable to match engine characteristics, thereby
enabling optimization of the balance between combustion
efficiency and acceleration.

36.  There are 25% fewer moving parts to a CVT transmission.
 Less power loss in a CVT than a typical automatic
transmission.
 Responds better to changing conditions, such as changes in
throttle and speed.

37.  Many small tractors for home and garden use simple rubber
belt CVTs.
 All snowmobiles, old and new, and motor scooters use CVTs.
 Some combine harvesters have CVTs.
 CVTs have been used in aircraft electrical power generating
systems and in Formula race cars.
 Some drill presses and milling machines contain a pulley-based
CVT.

38. Much Of The Existing Literature Is Quick To Admit That The
Automotive Industry Lacks A Broad Knowledge Base Regarding
Cvts. Whereas Conventional Transmissions Have Been
Continuously Refined And Improved Since The Very Start Of The
20th Century, CVT Development Is Only Just Beginning. 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 To Develop Cvts Now, While The Field Is Still In Its Infancy,
Risk Being Left Behind As CVT Development And Implementation
Continues Its Exponential Growth. Moreover, Cvts Are Do Not Fall
Exclusively In The Realm Of IC Engines.

39.  CVT is the most superior technology for power transmission.
 And it would be the widely acceptable technology throughout
the world.

40. Prepared By –
ANDALIB SHADAN
DEBJIT PAL
SIDDHARTHA SAHA
SUBHASISH BHADRA
SUMIT KUMAR
CHOUDHARY
WARIS AHMED