CONTINUOUS

S Y S T E M

V A R I A B L E TRANSMISSION

Basics of Transmission 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.

Automatic Transmission

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.

Classification

Planetary GearboxDirect Shift Gear Box

CVT

CVT – An Introduction

• 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 innovations.

A Timeline of CVT Innovation

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

Benefits of CVT

o Provide engine torque in optimum condition (road loads / drive shaft torque)

o No shift clonko Transmission ratio can be adjusted

continuouslyo Improved fuel efficiencyo Better accelerationo Eliminates gear hunting especially when

going up a hill

Behavior of CVT

Cars with CVT

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

Classification

Toroidal CVTs Hydrostatic CVTsPulley Based CVTs

Pulley based CVT 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.

Parts

Driver GearPrimary PulleyDriver and Driven

ShaftSecondary PulleyV - belt

Driver Gear

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.

Measurement

Side View Front View

Primary Pulley

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.

Measurement

Side View Front View

Driver and Driven Shaft

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.

Measurement

Side View Front view

Secondary pulley

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.

Measurement

Side View of Secondary Pulley 1 and 2

Front View of Secondary Pulley 1 and 2

V - belt

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 .

Measurement

Side View of 3 different V-Belts

Low Gear

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

Side ViewTop View

Semi-intermediate gear

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.

Side ViewTop View

Intermediate

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.

Side ViewTop View

Semi-high gear

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.

Side ViewTop View

High Gear

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.

Side ViewTop View

Advantages

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)

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.

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.

Applications

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.

Future ProspectiveMuch 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.

Conclusion

CVT is the most superior technology for power transmission.

And it would be the widely acceptable technology throughout the world.

Thank You

Prepared By –

ANDALIB SHADAN

DEBJIT PAL

SIDDHARTHA SAHA

SUBHASISH BHADRA

SUMIT KUMAR

CHOUDHARY

WARIS AHMED