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A Presentation on
Nalanda Institute of Technology, BBSR
1) Basics of Transmission.
2) Introduction of CVT.
4) Types of CVT
a) Variable Diameter Pulley (VDP) CVT.
b) Toroidal CVT.
c) Hydrostatic CVT.
5) Behavior of CVT.
6) Possible Markets & competitions of CVT.
7) Automobiles equipped with CVT.
8) Advantages of CVT.
9) Drawbacks of CVT.
It changes the speed ratio
between the engine and the
wheels of an automobile.
The transmission unit is
basically of three types-
Manual, Semi-Automatic &
In manual transmission gears
are shifted manually by the
driver while automatically in
CVT where no gears are used.
Basics of Transmission:
A Chain Driven CVT
A continuously variable
transmission (CVT) is a
transmission which can change the
speed steplessly through an infinite
number of gear ratios.
This allows the engine to putout
the proper amount of power
improving on efficiency of
A Timeline of CVT Innovation:
o 1490 - Da Vinci sketches a stepless continuously variable transmission.
o 1886 - First Toroidal CVT patent filed.
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
o 2004 - Ford begins offering a CVT.
Types of CVT:
Variable-diameter pulley CVT
Toroidal or roller-based CVT
1. Variable-Diameter pulley (VDP)
o This system has
two pulleys with
a V-belt running
o The gear ratio is changed
by moving the two
sheaves of one pulley
closer together and the
two sheaves of the other
pulley farther apart.
o The V-shaped cross
section of the belt,
this causes the belt
to ride higher on one
pulley and lower on
VDP Metal Belts & Chains:
Metal belts were introduced by Van
Doorne’s Transmission in 1987
Metal chains used in VDP
2. Toroidal or roller-based CVT
o Toroidal CVTs are made up of discs
and rollers that transmit power
between the discs.
o One disc is the input, and the other
is the output.
o Between the discs are rollers which
vary the ratio and which transfer
power from one side to the other.
o When the roller's axis is
perpendicular to the axis of the
near-conical parts, it contacts the
near-conical parts at same-
diameter locations and thus gives a
1:1 gear ratio.
o Hydrostatic transmissions use a
variable displacement pump and
a hydraulic motor.
o All power is transmitted by
o These are sensitive to
o Their designs are also very
o Frequently used in lawn mowers
and garden tractors.
o Working of a hydrostatic cvt is
shown in the video:
Behavior of CVT:
Comparison of vehicle speed with Manual Transmission & CVT on the
basis of Engine RPM
Possible Markets of CVT:
Can be used in cars, scooters & especially in off-road
Claims of a 20% gain in fuel economy compared to past
o Heavy Industry
Fully adaptable drive system for industrial Land
Adjustments and maintenance made easier through
smaller parts and computer monitoring technology.
o Wind Energy
Allows for a Possible 3.5 speed increase, allowing
for a increase in efficiency.
Prevents over speeding of fan blades.
Using CVT technology can reduce the cost of a
Fully automatic transmission systems
Traditional Gear box transmissions.
o Audi A4
o Audi A6
o Fiat Punto 1.2
o Ford Escape Hybrid
o Ford Focus C-MAX
o Honda Civic Hybrid
o Honda HR
o Honda Insight
o Honda City
Automobiles Equipped With CVT
CVTs can compensate for changing vehicle speeds, allowing the engine
speed to remain at its level of peak power and efficiency.
CVT improves fuel economy and reduce exhaust emissions.
Provide engine torque in optimum condition (road loads / drive shaft
No clutch & gear shift.
Becomes Jerky in automobile applications at slow speeds.
Intricate parts with high material cost.
Transmitting motion by friction causes greater wear.
CVT can be the future of transmission system.
This technology is still experimental, although some
companies have proven that CVT are practically beneficial.
With proper funding for research it is possible to create a
CVT to satisfy each of the three categories listed.
o https//www.audi.com/multitronic, 2001