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Proper use and common failures of rolling bearings

There are dozens of types of bearings on automobiles. Rolling bearings, large and small, include almost all common bearing types, and collisions and damage to rolling bearings are also common. Rolling bearings are generally installed inside the mechanism, so it is inconvenient to visually inspect them. You can only make a rough judgment based on the failure phenomenon, and then disassemble and inspect them. The correct use of rolling bearings is a reliable guarantee for reducing bearing failures and extending bearing life. Its content includes correct installation and reasonable lubrication. The following introduces the use requirements and common faults and damages of rolling bearings.

First, the correct use of rolling bearings

1. Disassembly and assembly of the bearing The bearing should be cleaned before installation. During installation, special tools should be used to press the auxiliary bearing straight and evenly. Do not hit it with a hammer. It is especially prohibited to hit directly on the bearing. When the bearing seat ring and seat hole are loosely matched, the seat hole should be repaired or the bearing replaced. Do not use pitting or copper padding on the bearing mating surface to force it. When disassembling the bearing, use a suitable puller to pull the bearing out. Do not hit the bearing with a chisel, hand hammer, etc.

2. Bearing lubrication Lubricants and greases are commonly used as lubricants for rolling bearings. When the peripheral speed of the shaft is less than 4-5m / s, or the parts of the car that cannot be lubricated with lubricating oil are lubricated with grease. The advantage of grease lubrication is that the sealing structure is simple, the grease is not easy to lose, and it is not affected by temperature. It can be used for a long time by adding grease once.

Second, the common failure of rolling bearings The failure phenomenon of rolling bearings is generally manifested in two kinds, one is that the temperature of the bearing installation part is too high, and the other is that there is noise during the operation of the bearing.

1. Bearing temperature is too high When the mechanism is running, the part where the bearing is installed is allowed to have a certain temperature. When touching the housing of the mechanism by hand, it should be normal to not feel hot, otherwise it means that the bearing temperature is too high. The reasons for the high bearing temperature are: the quality of the lubricating oil does not meet the requirements or deteriorates, the viscosity of the lubricating oil is too high; the mechanism assembly is too tight (lack of clearance); the bearing assembly is too tight; the bearing race rotates on the shaft or in the housing; Large; fragmented bearing cages or rolling elements.

2. Bearing noise Rolling bearings are allowed to have a slight running noise during operation. If the noise is too loud or there is abnormal noise or impact noise, it indicates that the bearing is faulty. The causes of noise produced by rolling bearings are more complicated. One is the wear of the matching surfaces of the bearing's inner and outer rings. Due to this wear, the cooperation relationship between the bearing and the housing, the bearing and the shaft is destroyed, resulting in the axis deviating from the correct position, and an abnormal noise is generated when the shaft is moving at high speed. When the bearing is fatigued, the surface metal peels off, which will also increase the radial clearance of the bearing and produce abnormal noise.

Third, the damage of rolling bearings When rolling bearings are disassembled and inspected, the failure of the bearing and the cause of damage can be judged according to the damage of the bearing.

1. Metal peeling on the raceway surface The rolling elements of the bearing and the raceway surfaces of the inner and outer rings are subject to periodic pulsating loads, resulting in cyclically changing contact stress. When the number of stress cycles reaches a certain value, fatigue spalling occurs on the working surfaces of the rolling elements or the inner and outer ring raceways. If the bearing is overloaded, this fatigue will be exacerbated. In addition, the bearing is not installed properly, the shaft is bent, and the raceway peeling phenomenon will also occur. Fatigue spalling of the bearing raceway will reduce the running accuracy of the shaft, causing the mechanism to vibrate and noise.

2. Bearing burns Burnt bearings have tempered colors on their raceways and rolling elements. The causes of burns are generally insufficient lubrication, the quality of the lubricant does not meet the requirements or deterioration, and the bearing assembly is too tight.

3. Plastic deformation Non-uniform pits on the contact surface between the raceway and the roller of the bearing indicate that the bearing has plastic deformation. The reason is that under the action of a large static or impact load on the bearing, the local stress on the working surface exceeds the yield limit of the material. This situation generally occurs on low-speed rotating bearings.

4. Cracks in bearing races Cracks in bearing races may be caused by over-tightening of the bearing fit, looseness of the bearing's foreign or inner ring, deformation of the bearing's containing parts, and poor surface processing of the mounted bearing.

5. The cage is broken. The cause is insufficient lubrication, broken rolling elements, skewed races, etc.

6. The metal of the cage is stuck to the rolling body. The possible cause is that the rolling body is stuck in the cage or the lubrication is insufficient.

7. Worn raceway raceway may be caused by foreign matter falling into the raceway, insufficient lubricant or inappropriate lubricant grade

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