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What is a Clutch? Its Parts, Function, Working Principle, Requirements & More

In this article, we will discuss what is a clutch? its working principle, parts, the requirement of the clutch in the engine, and clutch plate or disc.

What is Clutch?

Clutch is a mechanical device used in the transmission system of a vehicle. It engages and disengages the transmission system from the engine. It is fixed between the engine and the transmission.

The power produced inside the engine cylinder is ultimately aimed to turn the wheels so that the vehicle can move on the road. The reciprocating motion of the piston rotates a crankshaft by rotating the flywheel through the connecting rod.

Clutch

The circular movement of the crankshaft is now to be transferred to the rear wheels. It is transmitted through the clutch, gearbox, universal points propeller shaft or driveshaft, differential, and axles extending to the wheels.

With the help of all these parts, the use of engine power for the driving wheel is called power transmission. The utilisation of engine power to the driving wheels through all these parts is called power transmission.

The power transmission system is normally the same on all passenger cars and trucks. But its design and arrangement may vary according to the method of drive and type of transmission units.

Read also: 9 Different Types of Clutches

Main Part of A Clutch

The main parts of a clutch are classified into three groups

  1. Driving members
  2. Driven members
  3. Operating members.

Driving member

The driving member has a flywheel mounted on the crankshaft of the engine. The flywheel is fixed to a cover which supports a pressure plate or driving disc, pressure springs and releasing levers.

The whole assembly of the flywheel and the cover rotate all the times. The clutch housing and the cover provided with an opening. From this opening, the heat is evaporated generated by the friction during the clutch operation.

Driven member

The driven member has a disc or plate, called the clutch plate. It is free to slide alongside on the splines of the clutch shaft. Driven member carries friction materials on both of its surface. When a driven member is held between the flywheel and the pressure plate, it helps to rotate the clutch shaft through the splines.

Operating member

The operating members have a foot pedal, linkage, release or throw-out bearing, release leavers and the springs essential to ensure the proper operation of the clutch.

Functions of Various Component’s of Transmission Power

Automobile Power Transmission System

The function of various components of the transmission system as follows:

Clutch

Its main function is to enable the driver to disconnect the engine from the driving wheels. Instantaneously and to engage drive from the engine to the driving wheels gradually while moving the vehicle from rest.

Gearbox (Transmission)

It helps to vary the speed ratios and hence torque between the engine and the driving wheels to suit the road condition.

Universal Joint

A universal joint is used where two shafts connected at an angle to transmit torque. The universal joint permits the torque transmission at an angle, and also while this angle is changing constantly while the vehicle is moving on the road.

Propeller Shaft

The propeller shaft connected between the gearbox and the differential with a universal joint at each end. It transmits the rotary motion of the gearbox output shaft to the differential.

Differential

While turning at the corners, the driving wheels must turn at different speeds. This is done with the help of differential.

How Clutch Works in a Vehicle

Clutch is a mechanical device used in the transmission system of a vehicle. It engages and disengages the transmission system from the engine. It is fixed between the engine and the transmission.

Working principle of clutch
  • When the clutch is engaged, the power is transmitted from the engine to the driving wheels through the transmission system and the vehicle starts moving.
  • When the clutch is disengaged, the power is not transmitted to the rear or driving wheels and the vehicle stops while the engine is still running.
  • The clutch is disengaged when starting the engine, when stopping the vehicle, when shifting the gears and when idling the engine.
  • The clutch is engaged when the vehicle is to move and is kept engaged when the vehicle is moving. Clutch also allows the continuous taking up of the load.

When properly operated, it prevents jerky motion of the vehicle and thus avoids putting undue strain on the remaining parts of the power transmission system.

Read also: Torque Converter: It’s Working Principle & It’s Parts

Working Principle of Clutch

The clutch works on the principles of friction, when two friction surfaces are bought in contact with each other and pressed they are united due to the friction between them. If one is revolved, the other will also revolve.

The friction between the two surfaces depends upon the area of the surfaces, the pressure applied upon them and coefficient of friction of the surface materials, The two surfaces can be separated and brought into contact when required.

One surface is considered as a driving member and the other as a driven number. The driving member is kept rotating when the driven member is brought in contact with the driving member, it also starts rotating. When the driven member is separated from the driving member it stops revolving. This is how a clutch operates.

The friction surfaces of the clutch are so designed that the driven member slips on the driving member when the pressure is first applied. As pressure increases the driven member is brought slowly to the speed of the driving member.

When the speeds of the members become equal, there’s no slip, the two members are in firm contact and the clutch is now fully engaged.

The driving member of a clutch is the flywheel. It is mounted on the crankshaft the driven member is the pressure plate. This is mounted on the transmission shaft. The clutch plates are between the two members.

When the clutch is engaged, the engine to the rear wheels through the transmission system. When the clutch is disengaged by pushing a clutch pedal, the engine is disconnected from the transmission. Thus, the power stops flowing to the rear wheels while the engine is still running.

The Requirement of a Clutch

Torque Transmission

The clutch should be able to transfer maximum torque to the engine.

Gradual Engagement

The clutch should engage gradually to avoid sudden jerks.

Heat Dissipation

The clutch should be able to dissipate a large amount of heat which is generated during the clutch operation due to friction.

Dynamic Balancing

The clutch should be dynamically balanced. This is especially required in the case of high-speed engine clutches.

Vibration Damping

The clutch should have a suitable mechanism to damp vibrations and to eliminate the noise produced during the power transmission.

Size

The clutch should be as small as possible in size so that t will occupy minimum space.

Free Pedal Play

To reduce effective clamping load on the carbon thrust bearing and wear on it. The clutch should have a free pedal play.

Easy in Operation

The clutch should be easy to operate requiring as little effort as possible on the part of the driver.

Lightness

The driven member of the clutch should be built as light as possible so that it will not continue to rotate for any time after the clutch has been disengaged.

Clutch Plate or Disc

The clutch plate is the driving member of the clutch and is gripped between the flywheel and the pressure plate. It is mounted on the clutch shaft through the splines. When it is gripped, rotates the clutch shaft and the power is transmitted from the engine to the transmission through the clutch.

Clutch plate

A pressure plate consists of two sets of facing or friction material mounted on steel cushion springs. The facing and cushion springs are riveted to a spring base disc and spring retainer plate which are slotted for the insertion of the torsion spring.

Clutch plate assembly

These springs contact the hub flanges that fit between the spring retainer plate and the disc and serve to transmit the twisting force applied to the facings to the splined hub. The spring action serves to reduce torsional vibrations and shocks between the engine and the transmission during clutch operation.

The facing and the plates rotate with respect to the hub to the limit of the compression of the springs or to the limit of the spring stops.

When the clutch is engaged, the pressure on the facing compresses the cushion springs sufficiently to cause the unit to decrease in thickness by 1 to 1.5 mm. This construction helps to make engagement smooth and chatterless.


That’s it

Thanks for reading. If you like our article on clutch share with your friends. If have any questions about “working principle of clutch” leave a comment.

Read more: Four Different Types of Gearbox That Are Used In Modern Vehicles

About Saif M

Saif M. is a Mechanical Engineer by profession. He completed his engineering studies in 2014 and is currently working in a large firm as Mechanical Engineer. He is also an author and editor at www.theengineerspost.com

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