How single and Multi-plate clutch works?

Clutch: A clutch is a mechanical device that engages and disengages the power transmission, especially from the driving shaft to the driven shaft.

In the most straightforward application, clutches connect and disconnect two rotating shafts. One post is typically attached to an engine or other power unit (driving member) in these devices, while the other shaft (the driven member) provides output for work.

Clutch And Its Necessity

A Clutch is a mechanism that enables the transmission of rotary motion from the driving shaft to the driven shaft without slipping. In the manual transmission system of an automobile, the power from the engine crankshaft to the drive wheels flows through a clutch located between the engine and gearbox. The clutch couples and uncouples the transmission and engine. When starting the engine, the clutch disconnects the engine crankshaft and the gearbox.

Engagement of clutch allows for power transfer from the engine to the transmission and eventually to the drive wheels. Disengagement of the grip provides the necessary half of power transfer that enables the engine to continue running while no power is supplied to wheels. The clutch is kept engaged when the vehicle is moving and needs to be disengaged when:

Starting the engine; any load will stall the engine
Shifting the gear; it is not possible to change two gears while any power is being transmitted through them
Modeling the engine and stopping the vehicle; there is no power transmission to the rear wheels, and the car stops while the engine is still running.

The clutch's engagement and disengagement are controlled by pedal (operated by the driver's foot) and clutch linkage.

Function And Requirements Of Clutch

The clutch is an essential part of manual transmission systems, and it has the following functions to perform:

To transmit the engine power to the road wheels and make the vehicle move,
To permit the driver to shift the transmission and select the proper gear ratio when the vehicle is in motion,
To permit coupling or uncoupling of gear for a stationary vehicle but with the engine running

Any automobile clutch is expected to meet the following requirements:

The grip requires a minimum of physical effort by the drive to engage or disengage.
The clutch should be free from slipping when engaged and must not drag on the idle member when disengaged for shifting the gear.
The clutch should permit the gradual load taking without jolting and causing any adverse change through shock to the transmission system.
The clutch should be easily accessible and have simple means of adjustment.
The clutch should be dynamically balanced, particularly when required to operate at high speeds.

Principle Of Clutch:

The gradual engagement clutch is friction clutch:

It operates on the principle of friction.
When two surfaces are brought in contact and are held against each other due to friction, they can be used to transmit power.
If one is rotated, then the other also rotates. One surface is connected to the engine, and the other to the transmission system of an automobile.
Thus, a clutch is nothing but a combination of two friction surfaces.

Clutch Components

A friction clutch used on most automobiles with manual transmission consists essentially of three principal parts, namely.

Driving members
Driven members
Operating members

Driving members: The unit comprises a flywheel, pressure plate, pressure springs, and releases levers—the flywheel servers as a foundation on which the whole clutch assembly is mounted. The clutch side is machined smooth to provide a fraction surface. Holes are drilled and tapped into the flywheel to attach the clutch cover plates to it.

The pressure plate is made of cast iron, is round and about the same diameter as the clutch (friction) disc. It is accurately machined on the side that presses the clutch disc against the flywheel.

Driven member: The unit has the clutch (friction) disc or plate gripped between the flywheel and pressure plate under the action of springs. it is round in shape and is generally constructed in two parts:
The outer disc is of thin high-quality steel
inner disc is reinforced and splined hub
Operating members: For proper operation of the clutch, the clutch assembly uses the following operating members:
afoot pedal and the linkage
release or throw-out bearing
release levers and springs

Single Plate And Multi-plate clutch

A single plate clutch consists of three parts, the driving plate or flywheel, clutch plate or driven plate, and the pressure plate. The clutch plate can be regarded as the "cheese between the sandwich, " the flywheel, and the pressure plate representing the two pieces of bread. Essentially it consists of a steel plate whose both sides are lined with friction material. The clutch permits a certain amount of slip on engagement. Friction caused by slipping generates heat which would tend to burn any of the materials used for clutch lining. The basis of most clutch lining is asbestos suitably banded with gum or resin. A wire is sometimes included in the bonding process to increase the resistance to wear. The clutch plate is mounted on a hub that is splined from inside and is thus free to slide over the shaft of the gearbox. There are springs arranged circumferentially, which provide axial force to keep the clutch in the engaged position. A pedal is offered to pull the pressure plate against the spring force whenever it is required to be disengaged.

Multi-Plate Clutch

When more torque is transmitted, such as in heavy transport vehicles and racings cars, use is made of multiple clutches in which more contact area is provided in a compact package by increasing the number of friction surfaces. The unit essentially consists of

Friction Plate, which has a friction lining on both sides. However, the plate adjacent to the flywheel has a friction lining only on the side away from the flywheel. These friction plates are attached at the top and to the flywheel and are free to move axially. These plates rotate with the flywheel and hence with driving shafts. The friction plates are in two sets. One sets slides in grooves on the flywheel while the other set moves on the splines made on the hub of the pressure plate. Further, the arrangement is such that the containers with outer and inner splines are set alternately.
Discs or plates which are supported on splines of the driven shafts. These plates are located in between the friction plates and can slide axially.