The friction clutch is an important component of any automotive machine. It is a link between engine and transmission system which conducts power, in form of torque, from engine to the gear assembly. When vehicle is started from standstill clutch is engaged to transfer torque to the transmission; and when vehicle is in motion clutch is first disengaged of the drive to allow for gear selection and then again engaged smoothly to power the vehicle.
There is a rotating shaft from which power is to be transmitted, called as driver shaft; and there is a shaft to which power is transmitted, called driven shaft. To take power from driver to driven shaft clutch is engaged. Engaging the clutch means reducing the physical gap between the rotating parts and forcing the two surfaces to come in contact. Since one part is moving and the other part is stationary, there is a relative motion between them. This creates friction and as a result causes force or torque transfer.
Clutch actuation means engaging or disengaging the clutch such as to allow for power transmission or cut off the power or torque. Friction Clutches are mainly actuated through four means:
1. Mechanical: To actuate
clutch mechanically liver or pedal is operated by hand or foot. These livers or pedals are connected to the friction clutch through compound linkages.
2. Pneumatic: Air pressure is used to engage the clutch and disengagement is achieved through spring. Compressed air is used through pneumatic pipes and actuation Is controlled through valves and pistons
3. Hydraulic: Hydraulic oil is used to exert pressure on the pistons to actuate the clutch. Force is applied hydraulically through pipes and controlled by hydraulic valves and pistons.
4. Electrical: For electrical actuation the livers and pedals used in mechanical actuation are replaced by electromagnet or solenoid. Clutch is engaged and disengaged by these electromagnet and solenoid on being triggered by the operator through the electrical wires instead of compound linkages, as in case of mechanical actuation.
The clutches are designed in different forms according to the power transmission requirements and also based on design and space constraints. Next article takes up the different types of clutches used in automotives and industries.
>>Next Article: Types of Friction Clutches
Book: Advanced Vehicle Technology by Heinz Heisler
Website: http://machinedesign.com