PPT ON CONTINUOUSLY VARIABLE TRANSMISSION CVT by Pukhraj Palariya
A SEMINAR PRESENTATION
¥CONTINUOUSLY VARIABLE TRANSMISSION¥
ME Engg. final year
Head of mechanical
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
A continuously variable transmission (CVT) is
a transmission that can change seamlessly through an infinite
number of effective gear ratios between maximum and minimum
The flexibility of a CVT allows the input shaft to maintain a
constant angular velocity.
Varies the transmission ratio continuously
Shifts automatically with an infinite number of
Seamless power delivery
Constantly changes its gear ratio to optimize
Allows the engine to rev almost immediately to
deliver maximum torque
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.
There are 3 type of
PROBLEMS WITH MANUAL & AUTOMATIC TRANSMISSION
The traffic condition has become
annoying in our big cities so fuel
consumption is very high
In such a case will automatic
transmission make sense to the Indian
But conventional automatics always
consume slightly more fuel than manual
transmission and the lack of sophisticated
1. A variable –input driving
2. An output(driven) pulley
3. A metal belt/rollers
4. Sensors and microprocessors
A pair of variable-diameter pulleys, each shaped like a pair
of opposing cones, with a metal belt or chain running between
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
Changing the diameter of the pulleys varies the
Metal Push Belt CVT.
Toroidal Drive CVT.
Variable Diameter pulley Belt CVT
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
Uses rollers to transmit torque between the input disc and output
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
Decreases engine fatigue
“infinite” number of gear ratios, maintaining
the engine in its optimum power range
More mechanically efficient than Automatic
Greater fuel efficiency than both manual and
automatic transmissions.(Fuel savings of more than
Smooth, responsive and quiet to drive
CVTVs. Manual transmission
Theoretical comparison under “ideal”
1991 FIAT UNO
M=1250 KG,TORQUE=101.2 NM
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.
Limited torque capacity when compared to
Additional gear train required for reverse
Larger and more costly than manual
Unwillingness to discard billions of dollars
in development in MT & AT’s.
Many small tractors for home and garden use have simple
rubber belt CVTs. For example, the John Deere Gator line of
small utility vehicles use a belt with a conical pulley system.
They can deliver an abundance of power and can reach
speeds of 30–32 mph (48–51 km/h), all without need for a
clutch or shifting gears. Nearly all snowmobiles, old and
new, and motor scooters use CVTs, typically the rubber
belt/variable pulley variety.
In various ATV CVT is most widely used due to better fuel
The IC engine is nearing both perfection and obsolescence;
advancements in fuel economy and emissions have effectively
CVTs could potentially allow IC vehicles to meet the first
wave of new fuel regulations
Costs 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