Clutch release bearing is an important part of automobile. If it is not well maintained and fails, it will not only cause economic losses, but also troublesome disassembly and assembly, which will take a lot of man hours. Therefore, it is of great significance to find out the causes of clutch release bearing failure and maintain it reasonably in use, so as to prolong the service life of release bearing, improve labor productivity and obtain better economic benefits.
The clearance between the last part of the clutch bearing and the clutch fork is 4mm ~ away from the release sleeve of the left and right bearing, and the last part of the clutch fork is always held on the release sleeve of the clutch bearing through the release sleeve of the left and right bearing.
Since the clutch pressure plate and release lever operate synchronously with the engine crankshaft, and the release fork can only move along the axial direction of the clutch output shaft, it is obviously not possible to directly use the release fork to pull the release lever. Through the release bearing, the release lever can rotate and move along the axial direction of the clutch output shaft, so as to ensure smooth engagement and gentle separation of the clutch, reduce wear and prolong the service life of the clutch and the whole transmission system.
The clutch release bearing shall move flexibly without sharp sound or jamming. Its axial clearance shall not exceed 0.60mm and the wear of inner race shall not exceed 0.30mm.
If the clutch release bearing fails to meet the above requirements, it is regarded as a failure. After a fault occurs, first judge which phenomenon belongs to the damage of release bearing. After the engine is started, gently step on the clutch pedal. When the free stroke is just eliminated, if there is a "rustle" or "squeak" sound, continue to step on the clutch pedal. If the sound disappears, it is not the problem of the release bearing. If there is still a sound, it is the sound of the release bearing.
During inspection, remove the clutch bottom cover, and then press a little accelerator pedal to slightly increase the engine speed. If the noise increases, you can observe whether there is Mars. If there is spark, the clutch release bearing is damaged. If the sparks are in the form of channeling one by one, it means that the ball of the release bearing is broken. If there is no spark, but there is a sound of metal breaking, it indicates excessive wear.
In the process of use, it is affected by axial load, impact load and radial centrifugal force during high-speed rotation. In addition, since the thrust of the shift fork and the reaction force of the separation lever are not on the same line, a torsional moment is also formed. The clutch release bearing has poor working conditions, intermittent high-speed rotation and bears high-speed friction, high temperature, poor lubrication conditions and no cooling conditions.
Cause of damage
The damage of clutch release bearing is closely related to the driver's operation, maintenance and adjustment. The damage causes are roughly as follows:
1) Overheating occurs when the working temperature is too high
When turning or decelerating, many drivers often half step on the clutch, and some put their feet on the clutch pedal after shifting into gear; Some vehicles' free travel adjustment is too large, so that the clutch is not completely separated and is in the state of half engagement and half separation. This state causes dry friction and generates a large amount of heat to be transmitted to the release bearing. The heat of the bearing reaches a certain temperature, and the butter melts or dilutes, which further increases the temperature of the release bearing and burns out when the temperature reaches a certain degree.
2) Wear due to lack of lubricating oil
The clutch release bearing is lubricated with butter. There are two ways to add butter. For 360111 release bearing, open the rear cover of the bearing and fill it with grease when maintaining or removing the transmission, and then reinstall the rear cover; For 788611k release bearing, it can be removed and put down, soaked in molten grease, cooled and taken out to achieve the purpose of lubrication. In practical work, the driver is easy to ignore this point, resulting in the lack of oil in the clutch release bearing. In the case of no lubrication or less lubrication, the wear amount of release bearing is often several times to dozens of times that after lubrication. As the wear increases, the temperature will also increase greatly, which makes it easier to damage.
3) Free travel is too small or loaded too many times
According to the requirements, the clearance between the clutch release bearing and the release lever is generally 2.5mm, which is reflected in the free stroke on the clutch pedal of 30-40mm. If the free stroke is too small or there is no free stroke at all, the release lever and the release bearing will be in a constant engagement state. According to the fatigue failure principle, the longer the working time of the bearing, the more serious the damage is; The more loading times, the easier the release bearing is to produce fatigue failure. Moreover, the longer the working time, the higher the temperature of the bearing and the easier it is to burn, which reduces the service life of the release bearing.
4) In addition to the above three reasons, whether the release lever is adjusted smoothly and whether the return spring of the release bearing is good also has a great impact on the damage of the release bearing.
1) According to the operation regulations, avoid the semi engagement and semi disengagement of the clutch and reduce the use times of the clutch.
2) Pay attention to maintenance. Soak the butter with cooking method regularly or during annual inspection and maintenance to make it have sufficient lubricant.
3) Pay attention to leveling the clutch release lever to ensure that the elastic force of the return spring meets the regulations.
4) Adjust the free stroke to meet the requirements (30-40mm) to prevent the free stroke from being too large or too small.
5) Minimize the times of joint and separation and reduce the impact load.
6) Step gently and easily to make it connect and separate smoothly.