Clutches

Definition A clutch is a mechanism for connecting and disconnecting an engine and the transmission system in a vehicle, or the working parts of any machine. It allows a temporary separation of drive between drive source and driven mechanisms. When engaged this will allow for a smooth take up of drive as the clutch is gradually engaged.

Clutch Action Clutch action can be demonstrated by two discs Drive Disc Input Shaft to Transmission Drive disc attached to engine Driven disc attached to transmission input shaft Engine Driven Disc Driven disc disconnected, no drive Driven disc in contact with drive disc, drive applied next

Clutch System Parts Clutch system consists of: Flywheel Clutch Plate Clutch Housing Clutch Plate Flywheel Pressure Plate Assembly Release Bearing Release Bearing Clutch Fork Clutch Plate Clutch housing protects clutch components from outside elements Pressure Plate Assembly Clutch Fork Clutch Housing next

Clutch System Parts - Clutch Plate - 1 Friction Material Rivets Located between flywheel and pressure plate Splined Hub Splines mesh with input shaft Friction Ring Frictional material riveted to cushion springs on either side of friction ring Cushion Springs next

Clutch System Parts - Clutch Plate - 2 Cushioning springs cushion force as pressure plate pushes clutch plate onto flywheel Torsional Spring Cushion Springs Torsional springs soften load applied to clutch plate as it begins to turn Cushion Springs next

Clutch Operating Mechanisms - Hydraulic Master Cylinder Pipe connected between foot pedal and clutch fork Two cylinders: master cylinder and slave cylinder Slave Cylinder Pipe As foot pedal depressed, master cylinder builds pressure in system, slave cylinder activated As foot pedal released, springs return system to rest position end

Clutch Types & Applications Single Plate clutch is used in almost all motor vehicles where manual transmission takes place Cone clutch was used in some automobiles in the past, but now is restricted to racing / rally car & power boats Centrifugal clutch is used on a petrol powered lawn mower-as the lawn mower is revved at a higher speed, the centrifugal force spreads the clutch shoes apart so the clutch mechanism engages Multi Plate clutches are used in extreme car racing and in automatic gearboxes.

Flat Plate Clutch

Cone clutch α = semi-apex angle of the cone w T = μWrm cosecα Only one pair of driving surfaces is possible, n =1 α w Driving shaft Driven shaft Friction lining The maximum torque transmitted = T = μWrm cosecα

Centrifugal clutch F=mrω2 ω Driven shaft Driving shaft Friction lining Total friction torque , T = nµR(F-P) F=mrω2 ω P R

Multi plate clutches In a multi plate clutch, the torque is transmitted by friction between several pairs of co-axial annular driving faces maintained in contact by an axial thrust. Both sides of each plate are lined with friction material, so that a single-plate clutch has two pairs of driving faces in contact. The advantages of using these types of clutch are due to the frictional surface area used, a lesser diameter clutch plate can be used thus less space is used.

Multi plate clutch driver driven Pressure plates 1 2 3 4 6 5 Friction plates 2 1 4 3 6 5