Harshal Patil T-31Pooja Patil T-33Vijay Patil T-34Priyanka SalveT-43

Third Year, Mechanical Engineering Dept

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

Main types of CVT’s:

Metal Push Belt CVT

Toroidal Drive CVT

Cone CVT

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.

Austin 18 Used a CVT1934

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.

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.

Push Belt CVT Illustrations:

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.

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.

CVT Schematic :Belt Drive

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

Van Doorne Steel Belt (2):Assembled/Disassembled

CVT Vs. Manual TransmissionTheoretical 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=5700rpmCVT MT

8.8 sec. 11.9 sec.

0-100 km/h

CVT Simulation:

Audi A6 Multitronic

Audi A6 3.0 L0-100 kmph Mileage

A6 5-speed manual 8.2 sec9.9 litre/ 100km

A6 5-speed Tiptronic 9.4 sec10.6 litre/

100km

A6 Multitronic CVT 8.1 sec9.7 litre/ 100km

Our Model

(CATIA Model)

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)

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

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.