Clutch: Description and Operation
Clutch System Description
Delay Orifice Mechanism
Function
The delay orifice mechanism improves clutch operation by delaying the slave cylinder release speed when the clutch pedal is suddenly released. The delay orifice mechanism is built into the slave cylinder.
Fluid flow operation
When the clutch pedal is pressed, the fluid pressure from the master cylinder moves the one-way valve in the direction shown in the illustration. The fluid flows through two passages: the orifice-part and the filter-part. It then flows out to the piston cylinder to release the pressure plate and clutch disc joint.
When the clutch pedal is released, the fluid pressure from the piston cylinder moves the one-way valve in the direction shown in the illustration. The one-way valve blocks the filter-part passage and delays the clutch release speed by returning the fluid to the master cylinder through only the orifice-part passage.
Self-Adjusting Clutch (SAC)
Function
On conventional clutches, the clutch pedal load increases as the clutch disc wears. The self-adjusting clutch is designed so the clutch pedal load will not increase even when the clutch disc wears. This is done by automatically adjusting the fulcrum of the diaphragm spring as the clutch disc wears. The clutch pedal load stays consistent even when the clutch disc is worn.
Construction
The self-adjusting clutch consists of a pressure plate, a sensor spring, a diaphragm spring, an adjusting ring, three coil springs, a pressure plate cover, and a compensation spring. They are riveted together and must not be disassembled. If there is problem with any part of the pressure plate or the clutch disc, they must be replaced together as a set.
Operation
Minor clutch disc wear:
As the clutch begins to wear, the release load increases slightly. However, this does not affect the operation of the clutch because the release load does not exceed that of the sensor.
Major clutch disc wear:
The sensor spring starts to deflect as the clutch disc is worn further and the release load exceeds that of the sensor.
The fulcrum then moves following the amount of sensor spring deflection. As this takes place, the fulcrum of the diaphragm spring is adjusted, keeping the release load consistent.
Dual Mass Flywheel
Function
The dual mass flywheel is designed to reduce the noise and vibration produced by the engine, the clutch, and the transmission during acceleration and cruising.
Construction
The flywheel assembly is actually two flywheels in one, which raises the inertial mass on both the engine and transmission when the clutch is engaged. The inner and outer flywheels are connected by high and low torsion springs. This combination effectively dampers changes in engine speed before they are transmitted to the transmission.
Since there are high and low torsion springs between the flywheels, none are used in the clutch disc, which reduces the inertial mass on the mainshaft when the clutch is disengaged. This reduction of the rotating inertial mass reduces the load on the synchro rings, allowing the transmission to shift smoothly.
