How does a Single Plate Clutch work? Construction

SINGLE PLATE CLUTCH 

The single-plate clutch is the most common type of clutch used in motor vehicles. Basically, it consists of only one clutch plate, Mounted on the splines of the clutch shaft, as shown in Figure. The flywheel is mounted on the engine shaft and rotates with it. The pressure plate is bolted with the flywheel through clutch springs and is free to move on the clutch shaft during the clutch pedal is operated.

When the clutch is engaged, the clutch plate is gripped between the flywheel and the pressure plate. The friction materials are on both sides of the clutch plate. Due to the friction between the flywheel, pressure plate and clutch plate, the clutch plate revolves with the flywheel. As the clutch plate revolves, the clutch shaft also starts to revolve. The clutch shaft is connected to the transmission. Thus, the engine power is transmitted from the crankshaft to the clutch shaft.

Single Plate Clutch
Single Plate Clutch

OPERATION

When the clutch pedal is pressed, the pressure plate moves backward against the force of the springs and the clutch plate becomes free between the pressure plate and the flywheel. The flywheel remains rotating as long as the engine is rotating and the clutch shaft speed reduces slowly and finally, it stops rotating. As the clutch pedal is pressed, the clutch is said to be disengaged, otherwise, in normal conditions, it remains engaged due to the spring forces.

You can watch the animation video to know how a Single Plate Clutch Works?

Clutch Plate

The clutch plate plays a major role in the single plate clutch system of a motor vehicle. It carries a splined clutch shaft at it’s center and friction plates at its outer edge. the friction plates are mounted at both sides of it by rivets. And it also carries damp springs for the absorption of the jerks during power transmission. Any problems with it can stop the entire vehicle power transmission system.

clutch plate
clutch plate

Pressure Plate

The pressure plate, which is made of special cast iron, is the heaviest part of the cover assembly. The primary functions of the pressure plate are to establish even contact with the driven plate facing through which the pressure springs can exert sufficient force to transmit the full torque of the engine.   Since every time a clutch is engaged, there is bound to be a certain amount of slippage and since slippage always produces heat, the pressure plate must contain enough metal to absorb and radiate the heat thus generated without getting too hot.

pressure plate
pressure plate

In fact, the pressure plate should be able to absorb much more than the normal heat generated during clutch operation without getting warped or cracking its smooth annular surface.   It would be simple enough to design a pressure plate with enough metal to meet this requirement.

But, as explained earlier, since the pressure plate functions as part of the flywheel, every fraction of the metal added to the pressure plate will proportionately reduce the accelerating ability of the engine. Since the rapid acceleration of an engine is a very important sales feature, it is important that, while manufacturing, particular care should be taken to control the thickness and weight of the pressure plate.

Release Mechanism 

Careful and accurate adjustment of the release mechanism is one of the most important factors governing the performance of a clutch assembly. These adjustments can be correctly done only by clutch re-building units.

Single Plate Clutch
Single Plate Clutch

Clutch Balance

An unbalanced clutch cover assembly causes the engine to be rough at high speeds. With the help of a dynamic balancing machine, the clutch cover assembly operating at high speeds can be balanced accurately. Many factors can affect the balance of the clutch cover assembly  

  1. Incorrect location of the pressure plate in relation to the cover.
  2. Fitting an improperly turned or ground plate.
  3. In fact, changing any part of the clutch cover assembly can throw the assembly sufficiently out of balance as to affect the performance of an engine from very satisfied to very unsatisfactory.

Clutch Facings

The materials and methods used in the manufacture of clutch facings are of utmost importance for the correct operation and functioning of the modern clutch assembly. It is only after months of careful testing, in the laboratory and on proving grounds, that the vehicle manufacturers approve a clutch facing to be used as standard fitment. It is important to determine:

  1. The proper coefficient of friction of the clutch facings for each vehicle.
  2. How the coefficient of friction changes with heat,
  3. How the facings will be affected by moisture that will collect in the clutch housing through condensation.
  4. How much the facings will expand with heat.
  5. The burst strength.
  6. How well the facings can be held in position by rivets.
  7. Whether the facings will absorb oil vapor.
clutch facings
clutch facings

Riveting the Facings

When riveting the facings to the cushion segments, special locating fixtures should be used to project the segments from any possible damage. It is equally important to ensure that the facings are riveted correctly and accurately tight enough that they will not work loose and at the same time not too tight because it will cause the plate to buckle due to expansion through heat.

Runout/Friction Lag

All Repco clutch plates are individually tested on a special machine to ensure that the runout on facings is kept within specified limits; ensures shudder free clutch operation. On the testing machine, the facings are first compressed by a ram that exerts a force equal to the total force of the cover assembly pressure springs; and then released a specified distance, as determined by the vehicle manufacturer if the clutch plate is not out of alignment and the segments have the right amount of cushion, the plate will turn freely. IT the plate does not tum freely it is rejected.

Conclusion

Thus you came to know about all different parts of a Single Plate Clutch and their functions and drawbacks. Through intense experiments, we can completely eliminate the problems and issues that affect the performance of the Single Plate Clutch.

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G NAGESWAR REDDY

Creative Blogger And Automobile Engineer.

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