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Explain the heating mechanism of sliding bearing in detail
Author:admin Date:2022-11-11
As we know, shaft and sliding bearing are a pair of friction pairs, belonging to sliding friction.
Friction will generate heat, and the amount of its heat is proportional to the friction and the speed of movement; The friction is large, the heat is large, the speed is fast and the heat is much.
The friction force of sliding bearing is in direct proportion 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 constant. If these conditions are met during operation, the bearing will not generate heat, but the operation is variable. When the total load increases, the actual contact arc length and the actual contact length change, the pressure per unit area will increase.
This is a problem. In fact, the friction coefficient also increases with the increase of the 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, and the balance is broken, the bearing will heat up.
In fact, when the pressure on the unit area of sliding bearing increases, its friction coefficient increases rapidly.
When the pressure of sliding bearing increases, its friction coefficient increases, because the friction work is equal to the product of friction coefficient, positive pressure and motion speed. When the contact is poor, the contact area decreases and the pressure increases; When the total load of the equipment is increased during vibration, its pressure will increase, so the friction coefficient will increase, the heat generation will increase, and the sliding bearing will certainly heat up.
Therefore, the contact accuracy of sliding bearing decreases in any case, and the load increases in any case, which will cause the local pressure of sliding bearing to increase, thus increasing the friction coefficient and heating the bearing.
In order to avoid the friction between the shaft and the end of the bearing caused by the inflexibility of the spherical pad, some people open the pad mouth very much. Although the problem has been solved to a certain extent, in a sense, it actually increases the force on the unit area of the bearing, which will shorten the bearing life, and reduce the bearing's ability to resist risks. As soon as the wind blows, the bearing will heat up, which is not conducive to stable operation.
In order to improve the flexibility of the spherical pad of sliding bearing, the contact area between the spherical pad and the pad seat is reduced to a small extent, especially the spherical pad with grooves in the middle. Only a few parts of the two sides of the grooves are in contact, so the friction will increase greatly, which is not conducive to the activities of the spherical pad.
Although the huge pressure does not cause collapse, there will always be local high points pressed in, which is like taking root on both sides of the bridge, and increases the stability of the spherical tile. Therefore, in the process of equipment management and maintenance, it is better to meet the design requirements as much as possible. For some parts with low processing accuracy, manual methods should be used to make up for them to meet the design requirements.
The friction coefficient of sliding bearing is not only related to the pressure, but also to the speed of movement. The following is the relationship between speed and 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 range, and the influence of the relative pressure on the friction coefficient varies greatly. Therefore, the method of reducing the kiln speed is often used for the heating of cement in the kiln. Although it is effective, most of them cannot change the fate of heating. That is the reason.
The sliding bearing runs well before shutdown, but the pad gets hot and even partially burnt when starting, which is actually caused by the large friction during startup. At this time, not only the friction is large, but also the lubrication conditions can not meet the requirements, especially for equipment without hydrostatic startup.
On the other hand, if braking is different, the friction coefficient will increase from small to large, which means that it is difficult for high-speed running equipment to stop instantaneously. The sliding bearing is also the holding brake. In the past, inertia principle was often used to explain that high-speed running trains are difficult to brake. In fact, the friction coefficient also has an impact, at least extending the parking time.
Friction will generate heat, and the amount of its heat is proportional to the friction and the speed of movement; The friction is large, the heat is large, the speed is fast and the heat is much.
The friction force of sliding bearing is in direct proportion 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 constant. If these conditions are met during operation, the bearing will not generate heat, but the operation is variable. When the total load increases, the actual contact arc length and the actual contact length change, the pressure per unit area will increase.
This is a problem. In fact, the friction coefficient also increases with the increase of the 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, and the balance is broken, the bearing will heat up.
In fact, when the pressure on the unit area of sliding bearing increases, its friction coefficient increases rapidly.
When the pressure of sliding bearing increases, its friction coefficient increases, because the friction work is equal to the product of friction coefficient, positive pressure and motion speed. When the contact is poor, the contact area decreases and the pressure increases; When the total load of the equipment is increased during vibration, its pressure will increase, so the friction coefficient will increase, the heat generation will increase, and the sliding bearing will certainly heat up.
Therefore, the contact accuracy of sliding bearing decreases in any case, and the load increases in any case, which will cause the local pressure of sliding bearing to increase, thus increasing the friction coefficient and heating the bearing.
In order to avoid the friction between the shaft and the end of the bearing caused by the inflexibility of the spherical pad, some people open the pad mouth very much. Although the problem has been solved to a certain extent, in a sense, it actually increases the force on the unit area of the bearing, which will shorten the bearing life, and reduce the bearing's ability to resist risks. As soon as the wind blows, the bearing will heat up, which is not conducive to stable operation.
In order to improve the flexibility of the spherical pad of sliding bearing, the contact area between the spherical pad and the pad seat is reduced to a small extent, especially the spherical pad with grooves in the middle. Only a few parts of the two sides of the grooves are in contact, so the friction will increase greatly, which is not conducive to the activities of the spherical pad.
Although the huge pressure does not cause collapse, there will always be local high points pressed in, which is like taking root on both sides of the bridge, and increases the stability of the spherical tile. Therefore, in the process of equipment management and maintenance, it is better to meet the design requirements as much as possible. For some parts with low processing accuracy, manual methods should be used to make up for them to meet the design requirements.
The friction coefficient of sliding bearing is not only related to the pressure, but also to the speed of movement. The following is the relationship between speed and 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 range, and the influence of the relative pressure on the friction coefficient varies greatly. Therefore, the method of reducing the kiln speed is often used for the heating of cement in the kiln. Although it is effective, most of them cannot change the fate of heating. That is the reason.
The sliding bearing runs well before shutdown, but the pad gets hot and even partially burnt when starting, which is actually caused by the large friction during startup. At this time, not only the friction is large, but also the lubrication conditions can not meet the requirements, especially for equipment without hydrostatic startup.
On the other hand, if braking is different, the friction coefficient will increase from small to large, which means that it is difficult for high-speed running equipment to stop instantaneously. The sliding bearing is also the holding brake. In the past, inertia principle was often used to explain that high-speed running trains are difficult to brake. In fact, the friction coefficient also has an impact, at least extending the parking time.
