CLUTCH OPERATION IN AUTOMOBILE AND FRICTIONAL CLUTCHES

                        CLUTCH (AUTOMOBILE)

A clutch is a mechanism designed to connect or disconnect the transmission of power from engine to the driving wheel.

1. It is coupling device which makes power transmission possible between engine and driving wheel.

• The clutch drives the engine to run without driving the car i.e. without delivering power to power train.

• Without clutch changing of gear would be very difficult, even with vehicle moving already.

Deselecting the gear while the transmission is under load requires large force and selecting a gear rerquires the revolution speed of engine to be held at very precise value which depends on the vehicle speed and desired gear.


ENGAGEMENT OF CLUTCH

• In the car it is usually operated by application of pedal .

• When the clutch pedal is fully pressed the transmission is disengaged and no torque is delivered from engine to driving wheel.

• In this condition it is possible to select the gear or even stop the vehicle without stopping the engine.

DISENGAGEMENT OF CLUTCH

• When the clutch pedal is fully released the clutch gets fully engaged. Generally all the engine torque is delivered to the transmission line. In coupled state all the clutches do not slip, but rather acts as rigid coupling and power is transmitted to wheel with minimum loss of heat.

• In between complete engagement and disengagement clutch slips various degrees. In these case also the torque is transmitted by means of friction .

CLUTCH REQUIREMENT

1. TORQUE TRANSMISSION- It is designed to transmit maximum power of engine to the driving wheel. Under all condition. The clutch face should must have sufficient coefficient of friction on the faces so that coupling can take place and transmission of power is made without slip. 

   2. HEAT DISSIPATION - Due to rubbing of surface in frictional contact,large amount of heat is generated. This heat should must be dissipated. The clutch with its good surface area does the job.
    
     3.VIBRATION DAMPING - It is designed to eliminate noise and damp vibration of engine and the noise produced.
     4.EASE OF OPERATION - The driver should feel strain free while shifting gears, this is done by clutch.
    5. SIZE - Its size should be as compact as possible.
                                             
                                           FIG:- CLUTCH
      

TYPES OF CLUTCHES

•  FRICTIONAL CLUTCHES

• FLUID FLY WHEEL CLUTCHES

FRICTIONAL CLUTCH

• WET TYPE

• DRY TYPE

DRY TYPE FRICTIONAL CLUTCHES

1. Dog clutch
2. Cone clutch
3. Multi plate clutch
4. Centrifugal clutch

FRICTIONAL CLUTCH--OPERATION

ENGAGEMENT BY FRICTIONAL SURFACE

FIG: A

FIG:-B

• The operation is based on frictional contact between the driving and driven member.
• The frictional contact helps to transmit power from engine to driving wheel.

When the clutch pedal is applied the clutch gets completely engaged, this rotates the driven member and power is transmitted.

Initially slippage occurs while both members (driving and driven ) comes in contact and it continues until the speed of both member are same.

The heat produced must be liberated through the clutch components and should be dissipated  in air. When the clutches are completely engaged no slip occurs and hence no power loss is there.

EXPLANATION

To understand, consider FIG (A), suppose left side is transmission coming from engine and "F" force is applied on right side to which engine power is to be delivered. By application of clutch pedal. As the force is applied, the engagement takes place. As the driven member comes in contact, it starts rotating. Initially the speed of driven member is less and slip occurs, but as the rpm of both the members becomes equal, slip diminishes. This is how friction clutch works.

               

TORQUE TRANSMITTED (T) = Coefficient of friction*Axial force*Effective mean radius of friction surface.