Deepen your understanding of the clutch: functions, components and common fault analysis

The name of the clutch implies its unique working principle - precisely controlling the transmission of power through "disengagement" and "engagement". It consists of multiple parts such as friction plates, spring plates, pressure plates and power output shafts, and is cleverly arranged between the engine and the gearbox. The main function of the clutch is to effectively transmit the torque stored on the engine flywheel to the gearbox, thereby ensuring that the vehicle can obtain the right amount of driving force and torque under different driving conditions. This is an indispensable part of the powertrain system. The clutch provides the driver with smooth starting, stopping and shifting operations by combining and separating the engine's power and transmission.

In order to give full play to the role of the clutch, it needs to meet a series of strict requirements: first, the clutch must be able to transmit the maximum torque generated by the engine and have a certain torque reserve; second, it must be thorough when disengaged and gentle when engaged, and have good heat dissipation capabilities; in addition, the rotational inertia of the driven part should be as small as possible, so that the speed can be easily changed when shifting gears to reduce the impact between gears. At the same time, the clutch must also have the ability to mitigate the impact of the rotation direction, attenuate vibration and reduce noise. In addition, the pressure of the pressure plate and the friction coefficient of the friction plate should remain stable to ensure the reliability of the working process. Finally, the clutch should be labor-saving to operate and easy to repair and maintain.

→ Detailed composition of the clutch ←
Active part: This mainly includes core components such as the flywheel, pressure plate and clutch cover.

Driven part: This part is mainly composed of the driven plate and the driven shaft (i.e. the first shaft of the transmission), which is responsible for receiving and transmitting power.

Compression part: The compression spring plays a key role here, which ensures the tight engagement of the clutch.

Operating mechanism: This part covers the release lever, release lever support column, swing pin, release sleeve, release bearing and clutch pedal, which together constitute the clutch control system.

→ Working principle and classification of clutch ←
The clutch transmits torque through the friction between its active part and the driven part, or uses liquid as the transmission medium, or adopts magnetic transmission. This design allows the clutch to allow the two parts to rotate relative to each other during the transmission process, while realizing the functions of temporary separation and gradual engagement. Next, we will explore the different classifications of clutches.
Coil spring clutch

The coil spring clutch is characterized by the uniform distribution of coil springs along the circumference, which is further divided into two types: circumferential spring clutch and central spring clutch.

The central spring clutch is characterized by the use of one or two inner and outer coil springs for compression, the axes of these springs completely coincide with the axis of the clutch, and the springs are carefully arranged in the center of the clutch.

Diaphragm spring clutch, a common type of clutch, has two structural designs: push-type and pull-type. In the push-type structure, the separation of the clutch depends on the forward thrust of the release bearing; while in the pull-type structure, the separation of the clutch is achieved under the backward pulling force of the release bearing.

→The role of the clutch→
Ensures a smooth start of the car.

Makes the gear shifting process smooth and unobstructed.

Prevents the transmission system from being overloaded.

Next, let's explore the common faults that the clutch may encounter.
Clutch slippage and incomplete clutch separation are the two common clutch faults.
Clutch vibration and abnormal clutch noise

During the use of the clutch, in addition to slipping and incomplete separation, you may also encounter problems such as clutch vibration and abnormal noise. These faults not only affect driving comfort, but may also have an adverse effect on the service life of the clutch. Therefore, it is crucial to detect and deal with these problems in a timely manner.
1. Clutch slippage

Fault phenomenon: During the driving process, the truck will show obvious lack of power, especially when starting in low gear, it is difficult, and even cannot start under heavy load. However, the engine can run stably, which is usually accompanied by a burnt smell, and even in severe cases.

Causes of the fault and troubleshooting methods:

1) The surface of the friction plate is covered with oil, causing slippage. At this time, the clutch needs to be disassembled and the friction plate and driven plate need to be thoroughly cleaned with gasoline.

2) Insufficient pressure of the clutch pressure plate spring, or even spring breakage, will lead to a decrease in positive pressure and friction. For this problem, the spring should be replaced immediately.

3) Excessive wear of the friction plate or exposed rivets will also reduce friction. For this, it is necessary to replace a new friction plate or re-rivet it.
4) The driven disc and friction plate are burned or deformed, and corresponding corrections should be made or a new clutch plate should be replaced.
5) The adjustment clearance of the clutch is too small or inconsistent, resulting in a lack of free travel of the pedal. At this time, the clearance should be adjusted to the specified range, and the three release levers should be ensured to be in the same plane.
2. Incomplete clutch separation

Failure phenomenon: When the clutch pedal is stepped to the limit, the power transmission between the clutch active disc and the driven disc cannot be completely cut off, which will lead to problems such as difficulty in shifting gears, gear teeth, inability to stop smoothly, and clutch overheating.

Failure causes and solutions:

1) The clearance between the three clutch release claws and the release bearing is too large.
It should be adjusted to between 0.3-0.5 mm.

2) The free travel of the clutch pedal is too large.
It should be adjusted to between 20-40 mm.

3) The clutch driven disc is warped or severely rusted.
It needs to be corrected, replaced or cleaned of rust.

4) The clutch shaft chain is worn, causing the driven disc to be unable to move.
It should be repaired or replaced with a new part.
5) The three release levers are not on the same rotation plane, and the spring force is inconsistent.
Need to be readjusted according to regulations.
6) The friction plate is broken or the clutch bearing is damaged, causing the clutch to move axially.
New plates and new bearings should be replaced.

3. Clutch vibration
Fault phenomenon: The vehicle vibrates when starting, especially when idling, lowering the gear and gradually releasing the clutch pedal to start, the vehicle has continuous impact.
Fault cause and troubleshooting method:
3. Clutch vibration
Fault phenomenon: The vehicle vibrates when starting, especially when idling, lowering the gear and gradually releasing the clutch pedal to start, the vehicle has continuous impact.
Fault cause and troubleshooting method:
1) The end faces of the three release lever heads are not in the same plane.
This requires re-adjusting the clutch to ensure that the end faces of the three release lever heads are in the same plane.
2) The elastic force of each spring of the pressure plate is uneven or broken.
The spring should be carefully checked. If necessary, the broken spring should be replaced in time, and the elastic force of each spring should be uniform.
3) The friction plate is arched and deformed.
The friction plate needs to be corrected, repaired or directly replaced to ensure its smoothness.

4. Abnormal clutch noise
Fault phenomenon: When the clutch pedal is pressed, the inner end face of the release bearing and the release lever will make a continuous "click, click, click" sound as soon as they come into contact; or when the clutch is engaged at the start and the clutch is separated during driving, there will be a sound and the vehicle will tremble.
Causes of the fault and troubleshooting methods:

1) The release bearing lacks lubrication or is damaged.
In this case, add an appropriate amount of lubricating oil to the release bearing. If the problem is not solved after adding, the release bearing needs to be replaced.

2) The driven plate or pressure plate is broken.
At this time, the clutch needs to be disassembled and the damaged parts replaced to ensure the normal operation of the clutch.