Clutch And Its Function
A clutch is a device used in the power transmission system of a motor vehicle to engage and disengage the engine to the transmission. That’s is why the clutch is located between the engine and the transmission. When it is in the engaged position, the power flows from the engine to the rear wheels through the power transmission system and the vehicle moves. When it is in the disengaged position, the power is not able to transmit to the rear wheels and the vehicle stops while the engine is still running.
The clutch is disengaged during starting the engine, shifting the gears, when stopping the vehicle and during idling the engine. It is engaged when the vehicle is to move and is kept engaged when the vehicle is moving continuously. It also allows the gradual taking up of the load. When properly operated, it avoids the jerky motion of the vehicle and thus prevents putting unwanted strain on the remaining parts of the power transmission system.
The clutch works on the principles of friction. When two rough surfaces are brought in contact with each other and pressed by force, they are united due to the friction between them. If no 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 the coefficient of friction of the surface materials. The two surfaces can be separated and also can bring into contact when required.
One surface is considered as a driving member and the other as a driven member. The driving member is kept rotating. When the driven member is made in contact with the driving member, it can able to starts rotating. When the driven member has moved away or separated from the driving member, it does not revolve. This is the principle of the clutch in which it operates.
The friction surfaces of the clutch are designed in such a way that the driven member slips on the driving member when the pressure is starting to applied. As pressure increases the driven member is brought gradually to the speed of the driving member. When the speeds of both members become equal, there is no slip, the two members are in tight contact and the clutch is now fully engaged.
The driving member of the clutch is the flywheel that mounted on the crankshaft, the driven member is the pressure plate. Friction surfaces are between the two members. When the clutch is engaged, the engine is connected to the transmission and the power flows from the engine to the rear wheels through the transmission system. When it is disengaged by pressing the pedal, the engine is disconnected to the gearbox. Thus, the power not able to flow to the wheels while the engine is still running.
REQUIREMENTS OF A CLUTCH
- Torque transmission. It must be able to transmit the maximum amount of torque to the engine.
- Gradual engagement. It must engage gradually to avoid sudden jerks.
- Heat dissipation. It should be able to dissipate a large amount of heat which is generated during the clutch operation due to friction.
- Dynamic balancing. It should be dynamically balanced. This is largely required in the case of high-speed engine clutches.
- Vibration Damping. It should have a suitable mechanism to damp vibrations and to eliminate the noise produced during the power transmission
- Size. It should be as small as possible in size so that it will occupy minimum space.
- Free pedal play. It must have a free pedal play in order to reduce clamping load on the carbon thrust bearing and wear of it.
- Easy in operation. It must be easy to operate requiring as little effort as possible by the part of the driver.
- Lightness. The driven member must be made as light as possible so that it will not continue to rotate for any period of time after the clutch has been disengaged.
To understand how does a clutch works watch the animation video below:
MAIN PARTS OF CLUTCH
The main parts of a clutch are mainly divided into three types:
- Driving members.
- Driven members.
- Operating members.
The driving members having a flywheel mounted on the engine crankshaft. The flywheel is bolted to a cover which carries a pressure plate or driving disc, pressure springs, and release levers. Thus, the whole assembly of the flywheel and the cover always rotate. The clutch housing and the covers are provided with openings to dissipate the heat generated by the friction during the clutch engagement.
The driven member consists of a disc called the clutch plate. It is free to slide longitudinally on the splines of the clutch shaft. The clutch plate carries friction materials on both of its surfaces. When it is gripped between the flywheel and the pressure plate, it rotates the clutch shaft through the splines.
The operating accessories consist of a foot pedal, release, linkage or throw-out bearing, springs and the release levérs necessary to confirm the proper operation of the clutch.