Explain the heating mechanism of sliding bearings in detail

As we know, shaft and sliding bearing are a pair of friction pairs, belonging to sliding friction.

Friction will give rise to heat, and the heat value is directly proportional to the friction force and the speed of motion; when the friction force is large, the heat is high, the speed is fast and the heat is more.
The friction of sliding bearing is directly proportional to the positive pressure and friction coefficient. From the design point of view, the total load is determined. After the bearing diameter and length are determined, the pressure per unit area is also fixed. If these conditions are met in operation, the bearing will not heat up, but the operation is variable. When the total load increases, the actual contact arc length and the actual contact length change, the single bearing will not heat up The pressure on the bit area will increase.
This is a problem. In fact, the friction coefficient increases with the increase of pressure per unit area. Once the friction coefficient increases, the friction heat will increase. Once the friction heat is greater than the heat that can be emitted, the bearing will be heated when the balance is broken.
In fact, when the pressure per unit area of the sliding bearing increases, its friction coefficient increases rapidly. For details, please refer to the table below.
When the pressure of the sliding bearing increases, its friction coefficient increases, because the friction work is equal to the product of friction coefficient, positive pressure and moving speed. When the contact is poor, the contact area decreases and the pressure increases; when the total load increases when the equipment vibrates, the pressure will increase, so the friction coefficient will increase, the heat generation will increase, and the sliding bearing must be heated.
Therefore, in any case, the contact accuracy of sliding bearing decreases and the load increases in any case, which will lead to the increase of local pressure of sliding bearing, thus increasing the friction coefficient and heating the bearing.

In order to avoid the friction between the shaft and the end of the bush caused by the inflexibility of the spherical bush, some open the bush mouth to a certain extent. Although the problem is solved to a certain extent, it actually increases the bearing unit in a certain sense. The force on the area will first shorten the life of the bearing, and secondly reduce the bearing’s ability to resist risks. Once there is wind, the bearing will generate heat, which is not conducive to stable operation.

In some cases, in order to improve the flexibility of the sliding bearing spherical tile, the contact area between the spherical tile and the tile seat is reduced to a small amount, especially if there is a grooved spherical tile in the middle, only a small part of the two sides of the groove are in contact, and the friction will be reduced. Will greatly increase, which is not conducive to the activities of spherical tiles.

　　 Although the huge pressure did not cause crushing, there will always be local high points pressed in, which is like rooting on both sides of a bridge, which increases the stability of the spherical tile. Therefore, in equipment management and maintenance, it is better to meet the design requirements as much as possible. For some parts with low machining accuracy, we should find ways to compensate by manual methods to make them meet the design requirements.

　　The friction coefficient of sliding bearing is not only related to the pressure, but also related to the speed of movement. The following is the relationship between the speed and the friction coefficient.

When the sliding bearing equipment is started, the friction coefficient is very large. After running, the friction coefficient decreases, but the change is relatively small within a certain interval. The magnitude of the change is relatively different from the influence of the pressure on the friction coefficient, so the cement is in the kiln The method of lowering the kiln speed is often used for fever. Although it is effective, most of it cannot change the fate of fever. This is the reason.

The sliding bearing is running well before the shutdown, but the tile is hot when the startup is turned on, and even partially burned. In fact, it is caused by the large friction when starting. At this time, not only the friction is large, but the lubrication conditions are not up to the requirements, especially without static pressure. The booted device.

Conversely speaking, if braking is different, the friction coefficient is from small to large. It is difficult to stop the equipment running at high speed. The sliding bearing is also equipped with a brake. The principle of inertia used to explain the difficulty of high-speed trains. Brakes, in fact, also have the effect of friction coefficient, at least extend the time of stopping.

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