As we know, the shaft and the sliding bearing are a pair of friction pairs, which belong to sliding friction.
Friction heats up, and the amount of its heat is proportional to the friction force, and proportional to the speed of motion;High friction, high heat, high speed, high heat.
And sliding bearing friction is proportional to the positive pressure, friction coefficient, from the design point of view, the total load is determined, in determining the bearing diameter, length, pressure is constant per unit area, satisfy these conditions, in the operation of the bearing is not hot, but is running change, when the total load increases, the actual length of contact arc length, the actual change, will increase the pressure on unit area.
And this is a problem, because the friction coefficient actually increases with the pressure per unit area, and once the friction coefficient increases, then the heat of friction increases, and once the heat of friction exceeds the heat that can be given off, the equilibrium is broken, and the bearing heats up.
In fact, when the pressure on the unit area of sliding bearing increases, its friction coefficient increases very quickly. For details, please refer to the following table.
When the pressure of the sliding bearing increases, its friction coefficient increases. Because the friction work is equal to the product of the friction coefficient, positive pressure and moving speed, when the contact is poor, the contact area decreases and the pressure increases.When the total load of equipment vibration increases, its pressure will increase, then the friction coefficient will increase, heat increase, sliding bearing must heat.
Therefore, in any case, the contact precision of sliding moving bearing decreases, and the increase of load in any case will lead to the increase of partial pressure of sliding bearing, which will increase the friction coefficient and heat the bearing.
Sliding bearing
Some in order to avoid the spherical tile not flexible shaft and friction of the end, is the tile edging on loud, although to a certain extent, solve the problem, but in a sense, actually increases the bearing force per unit area, shorten bearing life for a while, two will lower bearing resistance risk ability, the bearing will have trouble with fever, is not conducive to stable operation.
Some in order to improve the flexibility of sliding bearing spherical tile, the spherical tile and tile seat contact area shrink very small, especially in the middle of the groove spherical tile, only the two sides of the groove rarely contact, friction will increase, not conducive to the activity of the spherical tile.
Great pressure did not cause collapse, but the pressure of local high points will always have, this is like the root of both sides of the bridge, but also increased the stability of the spherical tile.Therefore, in the management and maintenance of equipment, it is better to meet the design requirements as far as possible. For some parts with low machining accuracy, manual methods should be tried to make up for them to meet the design requirements.
The friction coefficient of a sliding bearing is not only related to the pressure, but also to the speed of motion.
Sliding bearing device at startup, the friction coefficient is very large, after running, lower friction coefficient, but in a certain range change is relatively small, the size of the change relative to the pressure effect on the friction coefficient is large, so in cement kiln fever often in the way of kiln speed reduction, although have effect, but most can not change the fate of the fever, it is for this reason.
Sliding bearing in the shutdown before running well, but when the boot tile hot, even local burning, in fact, is the start of friction caused by large, this time not only friction, lubrication conditions can not meet the requirements, especially no static pressure start equipment.
So the other way round, such as brake is different, the coefficient of friction from small to large, said high speed running equipment instantaneous stop difficulties, sliding bearing is the brake is also, used the principle of inertia walk to explain the high speed train brake very hard, in fact is also the influence of friction coefficient, at the very least, extended the parking time.
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