24-12-2012, 06:33 PM
Friction
friction clutches.pdf (Size: 304.56 KB / Downloads: 517)
disc clutch
A disc clutch consists of a clutch plate attached to a splined hub which is free
to slide axially on splines cut on the driven shaft. The clutch plate is made of
steel and has a ring of friction lining on each side. The engine shaft supports a
rigidly fixed flywheel.
A spring-loaded pressure plate presses the clutch plate firmly against the
flywheel when the clutch is engaged. When disengaged, the springs press
against a cover attached to the flywheel. Thus, both the flywheel and the
pressure plate rotate with the input shaft. The movement of the clutch pedal is
transferred to the pressure plate through a thrust bearing.
Figure 8.13 shows the pressure plate pulled back by the release levers and
the friction linings on the clutch plate are no longer in contact with the pressure
plate or the flywheel. The flywheel rotates without driving the clutch plate and
thus, the driven shaft.
multi-plate clutch,
In a multi-plate clutch, the number of frictional linings and the metal plates is
increased which increases the capacity of the clutch to transmit torque. Figure
8.14 shows a simplified diagram of a multi-plate clutch.
Centrifugal clutches
Centrifugal clutches are being increasingly used in automobiles and machines.
A centrifugal clutch has a driving member consisting of four sliding blocks
(Fig. 8.16). These blocks are kept in position by means of flat springs provided
for the purpose. As the speed of the shaft increases, the centrifugal force on the
shoes increases. When the centrifugal force exceeds the resisting force of the
springs, the shoes move forward and press against the inside of the rim and
thus, torque is transmitted to the rim. In this way, the clutch is engaged only
when the motor gains sufficient speed to take up the load in an effective
manner. The outer surfaces of the shoes are lined with some friction material.