In heavy duty mechanically operated clutches with high clutch spring pressure, the force required by the driver to release the clutch becomes excessive.
This can be remedied by the use of hydraulic operation.
This type of operation is also suitable for vehicles in which the clutch pedal and the clutch have to be located too far away from each other.
Hydraulically operated clutch may be either single plate clutch or more modern multi plate type.
This can be remedied by the use of hydraulic operation.
This type of operation is also suitable for vehicles in which the clutch pedal and the clutch have to be located too far away from each other.
Hydraulically operated clutch may be either single plate clutch or more modern multi plate type.
Hydraulic single plate clutch :-
Figure shows a hydraulically operated clutch.
When the clutch pedal is pressed the fluid under pressure from the master cylinder reaches the slave cylinder which is mounted on the clutch itself.
The fluid under pressure actuates slave cylinder pushrod which further operates the clutch release fork to disengage the clutch.
In India, this type of clutch has been used in Standard 20, Swaraj Mazda and Eicher Mitsubishi's 'canter' vehicles.
The detailed construction of the clutch master cylinder has been shown in figure.
In engaged condition when the clutch pedal is in the released position, the push rod rest against it stop due to the pedal return spring.
Also the pressure of Master cylinder spring keeps the plunger in its back position.
The flange at the end of the valve shank contacts the spring retainers.
As the plunger has moved to its rear position, valve shank has the valve seal lifted from its seat and seal spring compressed.
Hydraulic fluid can then flow past 3 distance pieces and valves seal in either Direction.
This means the pressure in the slave cylinder then is atmospheric and the clutch remains in its engaged position.
In engaged condition when the clutch pedal is in the released position, the push rod rest against it stop due to the pedal return spring.
Also the pressure of Master cylinder spring keeps the plunger in its back position.
The flange at the end of the valve shank contacts the spring retainers.
As the plunger has moved to its rear position, valve shank has the valve seal lifted from its seat and seal spring compressed.
Hydraulic fluid can then flow past 3 distance pieces and valves seal in either Direction.
This means the pressure in the slave cylinder then is atmospheric and the clutch remains in its engaged position.
However, when the clutch pedal is pressed to disengage the clutch, initial moment of the push rod and plunger permits the seal spring to press the valve shank and seal against its its seat.
This disconnects the cylinder from the reservoir.
Further the movement of the plunger displaces fluid through the pipelines to the slave cylinder and disengages the clutch.
The construction of the slave cylinder is made clear by means of figure.
The return Spring in the slave cylinder maintains some pressure on the release fork so that the thrust bearing is always in contact with the release Levers.
Moreover, in case of wear of clutch facing, the return Spring and the Piston move out automatically to take up the tilt of the release fork lever.
This disconnects the cylinder from the reservoir.
Further the movement of the plunger displaces fluid through the pipelines to the slave cylinder and disengages the clutch.
The construction of the slave cylinder is made clear by means of figure.
The return Spring in the slave cylinder maintains some pressure on the release fork so that the thrust bearing is always in contact with the release Levers.
Moreover, in case of wear of clutch facing, the return Spring and the Piston move out automatically to take up the tilt of the release fork lever.
Unlike cables, hydraulic operation does not involve frictional wear, especially when subjected to large forces.
Due to this reason hydraulic operation is particularly suitable for heavy duty application that is on large vehicles.
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