The document discusses continuously variable transmissions (CVTs). It provides an overview of CVTs, noting they vary the transmission ratio continuously and allow the engine to operate in its optimal power range. The main types of CVTs are described as metal push belt, toroidal drive, and cone designs. A brief history of CVTs is given, along with illustrations of how metal push belt CVTs work. Advantages like fuel efficiency and disadvantages like limited torque capacity are outlined. An example compares the acceleration of a car with a CVT versus manual transmission. A CATIA model of a CVT is shown along with component details.

1. Harshal Patil T-31
Pooja Patil T-33
Vijay Patil T-34
Priyanka Salve T-43
Third Year, Mechanical Engineering Dept

2. 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

3. Main types of CVT’s:
Metal Push Belt CVT
Toroidal Drive CVT
Cone CVT

4. History of CVT’S:
 1490: Leonardo da Vinci drew sketches of his
ideas for a CVT.
 1886:The first CVT was built by Daimler and
Benz.
 1930’s: GM developed a toroidal CVT.
 1958: Daf (Netherlands) developed and
produced a belt driven CVT for a 0.6L
engine.

5. Austin 18 Used a CVT
1934

6. The good and the bad of CVT’s:
 ADVANTAGES
 Decreases engine fatigue
 Allows for an “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% have been
achieved)
 Cheaper and lighter than
Automatic trans.
 Smooth, responsive and quiet
to drive.
 DISADVANTAGES
 Limited torque capacity when
compared with manual
transmissions.
 Larger and more costly than
manual transmissions.
 Slipping in the drive belt or
pulleys.(NO LONGER AN ISSUE
DUE TO NEW ADVANCES).
 The automobile industry is
unwilling to discard billions of
dollars already invested in
development of MT & AT’s.

7. Metal Push Belt CVT:
 Uses a pair of axially adjustable sets
of pulley halves(Variators)
 Both pulleys have one fixed and one
adjustable pulley halve.
 The transmission ratio is varied by
adjusting the spacing between the
pulleys in line with the
circumference of the tapered pulley
halves.
 A “belt” is used to transfers the
engine's power from one shaft to
another.
 The variators are adjusted
hydraulically.

8. Push Belt CVT Illustrations:

9. Variator
The variator is a disc
containing weighted rollers
disposed radially in a cage
and fixed to the sliding front
pulley.
As it spins faster, the
weights climb ramps, forcing
the front pulley halves
together, and raising the
effective gearing.

10. Centrifugal Clutch
It operates in much the same
way as the variator, being of a
centrifugal design.
As you twist the throttle, the
engine increases its speed and
the belt drive spins the clutch.
As the rotational speed
increases, centrifugal force
causes the clutch inner to expand,
and begin driving the clutch outer,
which is connected to the rear
wheel.

11. CVT Schematic :Belt Drive

12. Van Doorne Steel Belt (1):
oAlmost all of today’s
belt driven CVT’s use
this design invented by
Dutch CVT specialist
Van Doorne.
o Maximum torque it
can withstand is
around 150 lb-ft
(190hp).
Used in:
• Honda Civic HX
• Nissan Primera
• Toyota Prius
• Honda Insight
• BMW Minicooper

13. Van Doorne Steel Belt (2):
Assembled/Disassembled

14. CVT Vs. Manual Transmission
Theoretical comparison under “ideal” conditions.
 The Continuously Variable
Transmission (CVT)
proved 35% more
efficient than the Manual
Transmission (MT).
 With same car and engine,
the CVT takes only 75% of
the time to accelerate to
100km/h, compared to
the MT.
1991 FIAT UNO: M=1250kg
Torque=101.2 N-m
n=5700rpm
CVT MT
8.8 sec. 11.9 sec.
0-100 km/h

15. CVT Simulation:
 Audi A6 Multitronic
Audi A6 3.0 L
0-100 kmph Mileage
A6 5-speed manual 8.2 sec
9.9 litre/
100km
A6 5-speed Tiptronic 9.4 sec
10.6 litre/
100km
A6 Multitronic CVT 8.1 sec
9.7 litre/
100km

16. Our Model
(CATIA Model)

17. Component used
 2- Conical pulleys
 12V Gear motor
 12V DC Battery
 Copper Wires and Switch
 Threading nut and bolt
 Wooden body frame
 Rubber belt(flat belt)

18. Calculations:
 Motor RPM, N=110 rpm, D2=10 cm, D1= 5 cm
 1st gear Ratio obtained, G1= D2/D1
= 2
 Final gear Ratio obtained, Gf= D1/D2
= 0.5
Therefore,
 Output speed at start, N1= N/G1
= 55 rpm
 Output speed at end, N2= N/Gf
= 220 rpm

19. Future of CVT’s:
 The internal combustion (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
 As CVT development continues, costs will be reduced further
and performance will continue to increase.
 This cycle of improvement will ultimately give CVTs a solid
foundation in the world’s automotive infrastructure.