Single Plate Clutch: Diagram, Working & Application

Among various components in a vehicle, a clutch is an essential one. It helps to transmit the torque from a rotating driving motor into a transmission. A single plate clutch is the most common clutch type, with only one clutch plate.

It is important to understand the role of a clutch to choose the right one. Keep reading this article for all about a single plate clutch.

What is a Single Plate Clutch?

Single plate Clutch is the most common type of clutch used in motor vehicles. It consists of only one clutch plate, mounted on the splines of the clutch shaft.

The flywheel is mounted on the engine crankshaft and rotates with it. The pressure plate is bolted to the flywheel through clutch springs and is free to slide on the clutch shaft when the clutch pedal is operated.

When the clutch is engaged the clutch plate is gripped between the flywheel and the pressure plate. The friction linings are on both sides of the clutch plate.

Due to the friction between the flywheel, clutch plate and pressure plate, the clutch plate revolves with the flywheel. As the clutch plate revolves, the clutch shaft also revolves.

Single plate clutch diagram

Parts of Single Plate Clutch

A single-plate clutch assembly for the transmission of power consists of a flywheel, a clutch plate, pressure plates, clutch covers, release levers, and a primary or clutch shaft.

1. Flywheel
2. Pilot Bearing
3. Clutch plate or Disc plate
4. Pressure plate
5. Clutch cover
6. Release levers
7. Clutch shaft

1) Flywheel

The flywheel is an integral part of the engine, which is also used as a part of the clutch. It is a driving member and connects to the pressure plate of the clutch shaft and is housed with bearings in a flywheel. The flywheel rotates as the engine crankshaft rotates.

2) Pilot Bearing

The pilot bearing or bushing presses into the end of the crankshaft to support the end of the transmission input shaft. The pilot bearing prevents the transmission shaft and clutch disc from wobbling up and down when the clutch is released. It also assists the input shaft center of the disc on the flywheel.

3) Clutch plate or Disc plate

It is the driven member of the single-plate clutches and lines with friction material on both surfaces. It has a central hub with internal splines to limit the axial travel along the splined gearbox driving shaft.

This helps to provide damping actions against torsional vibrations or variations of the driving torque between the engine and transmission.

A clutch disc is a plate between the flywheel and the friction or pressure plate. It has a series of facings inverters on each side to enlarge the friction. These clutch facings are made of asbestos material. They are highly worn and heat resistant.

4) Pressure plate

The pressure plate is made of special cast iron. It is the heaviest part of the clutch assembly. The main function of the pressure plate is to establish even contact with the driven plate facing through which the pressure springs can exert a sufficient force to transmit the full torque of the engine.

The pressure plate presses the clutch plate onto the flywheel from its machined surface. Between the pressure plate and clutch cover assembly, pressure springs are fitted.

The pressure will be withdrawn from the flywheel whenever release levers are depressed by the toggle or release levers are pivoted accordingly.

5) Clutch cover

The clutch cover assembly bolts to the flywheel. It consists of a pressure plate, release lever mechanism, clutch cover, and pressure springs. Generally, the clutch plate revolves around the flywheel.

However, when the clutch has disengaged, the flywheel, as well as the pressure plates, are free to rotate independently from the driven plate and driving shaft.

6) Release levers

These pivots on pins to the clutch cover, their outer ends locate and position on pressure plate legs, and the inner ends are projecting towards the clutch shaft.

A careful and accurate adjustment of the release mechanism is one of the most important factors governing the performance of a clutch assembly.

7) Clutch shaft

It is a component of the gearbox. Since it is a splined shaft to the hub of the clutch plate, which is sliding on it. One end of the clutch shaft attaches to the crankshaft or flywheel and the other end connects to the gearbox or forms a part of the gearbox.

Working Of Single Plate Clutch

The working of Single Plate Clutch can be comprehended as follows:

• The pressure plate is affixed to the flywheel by means of clutch springs, utilising splines on the shaft for this connection. It has the freedom to move along the clutch shaft when the clutch pedal is operated.
• A single plate friction clutch comprises two flanges, with one flange securely attached to the driving shaft and the other free to move along the driven shaft due to a splined connection.
• Working on the principle of a single plate clutch, the action force is generated by a spring, which compels the driven flange to approach the driving flange. The surface of the drive flange is lined with friction materials like cork, leather, and asbestos.
• The pressure plate is supported by release levers, acting against compression springs, to keep the friction linings on the clutch plates separated from the flywheel and pressure plate.
• Upon releasing the pressure plate, the compression springs allow the pressure plate to move leftwards, bringing it into contact with the clutch.
• As the pressure plate shifts to the left, it slides along the splined cut on the hub along the driven shaft until the friction lining makes contact with the flywheel’s cone.
• The compression springs then cause the linings to be gripped between the pressure plate and the flywheel. The resulting friction between the linings, flywheel, and pressure plate initiates the rotation of the clutch plate around the driven shaft.
• Single plate clutches have relatively lower torque transmission capacity, reduced heat generation, and exhibit a high coefficient of friction.

Types of Single Plate Clutch

• Helical Spring Single Plate Clutches
• Diaphragm Spring Single Plate Clutches

1. Helical Spring Single Plate Clutch

For simplicity’s sake, the clutch pedal and other links causing movement of the pressure plate are not shown.

The clutch plate is mounted on the splined shaft and can move along the axis of the shaft. There is no relative movement between the plate and the shaft as far as rotational movement is concerned.

Both have the same rotational movement due to the splines provided on the shaft. The flywheel is mounted on the engine crankshaft and rotates with it. The pressure plate is bolted to the flywheel through clutch springs. It can slide freely along the axis of the clutch shaft.

The clutch is engaged due to the force exerted by the clutch springs. This force causes contact between the pressure plate, clutch plate, and flywheel. The clutch plate is located between the flywheel and the pressure plate. The clutch plate is provided with friction material on both sides.

The rotary movement from the flywheel is transferred to the clutch plate and the clutch shaft due to friction. The clutch shaft also acts as the output shaft.

When the clutch pedal is pressed the clutch is ‘disengaged.’ The pressure plate moves back against the force of the springs, and the clutch plate becomes free between the flywheel and the pressure plate.

Thus, the flywheel continues to rotate as long as the engine runs but the speed of the clutch plate declines and becomes zero. In this situation, motion is not transferred to the clutch shaft.

2. Diaphragm Spring Single Plate Clutch

In this type of clutch, the helical springs are replaced by a single diaphragm spring which is a saucer-shaped disc. The disc adopts a flat shape when the clutch is engaged. In the disengaged position, the disc adopts a buckled shape as shown.

The view shows the clutch in the ‘engaged’ position. The diaphragm spring exerts a force on the pressure plate, which causes contact between the pressure plate, clutch plate, and flywheel.

When force is applied through the clutch pedal, the diaphragm spring is buckled and contact between the pressure plate, clutch plate, and the flywheel is lost. The clutch is disengaged,’ and motion from the flywheel is not transferred to the clutch shaft.

Application of Single Plate Clutch

Single plate clutch applications are as follows :

• Single-plate clutches are used in Buses, Trucks, cars, etc.
• Single plate clutches are used where large radial space is available.
• This type of clutch does not require any lubricant for cooling.
• As sufficient surface area is available for heat dissipation in Single plate clutches, no cooling oil is required. Therefore, single plate clutches are dry type.
• Due to the high coefficient of friction, most of the vehicles use a single plate clutch. The amount of coefficient of friction is more than 0.3.

Advantages Of Single Plate Clutch

The main advantages of this clutch include:

• Single plate clutch is smooth in operation i.e engagement and disengagement of clutch is smooth.
• Very little slip occurs in its operation. Slip only occurs during the engagement of the clutch and after that, no slipping occurs and functioning becomes very smooth.
• Power loss is very less.
• Very little heat is generated as only one clutch plate is used.
• The operation in this type of clutch is very fast.

Disadvantages of Single Plate Clutch

The main disadvantages of this clutch include:

• Single plate clutches have high wear and tear rate.
• It has less torque transmitting capacity.
• The springs have to be stiffer hence greater force requires to disengage.
• It requires high maintenance.
• The space required to accommodate the clutch is more as compared to the multi-plate clutch.

FAQs.