Product knowledge

The similarities and differences between plain bearings and

Source:NETAuthor:UN Addtime:2022-05-09 Click:
Bearing, as an essential and important part of mechanical products, bearings play an important role in supporting rotating shafts. According to the different nature of friction in the bearing, the bearing is divided into rolling friction bearings (referred to as rolling bearings) and sliding friction bearings (referred to as sliding bearings). The two types of bearings have their own characteristics in the structure, performance advantages and disadvantages, the selection, combined with the actual comprehensive consideration.

1、Comparison of structure and movement
The most obvious difference between rolling bearing and sliding bearing is whether there is a rolling body or not.
 
Rolling bearing has rolling body (ball, cylindrical roller, tapered roller, needle roller), rely on its rotation to support the rotation axis, so the contact part is a point, the more rolling body, the more contact points.
 
Sliding bearing has no rolling body, relying on smooth surface to support the rotation axis, and thus the contact part is a surface.
 
The difference between the two structures determines the way of motion of rolling bearing is rolling, the way of motion of sliding bearing is sliding, so the friction situation is not the same at all.
 
2、Comparison of bearing capacity
 
Overall, due to the sliding bearing pressure bearing area, its bearing capacity is generally higher than rolling bearings, and rolling bearings to withstand the impact load capacity is not high, but completely liquid lubricated bearings due to the lubricant film to play a buffer, vibration absorption role, can withstand the larger impact load. When the speed is higher, the centrifugal force of the rolling body in the rolling bearing increases, to reduce its bearing capacity (easy to appear noise at high speed). For dynamic pressure sliding bearing, its bearing capacity increases with higher rotational speed. Picture
 
3、Friction coefficient and starting friction resistance comparison
Under general working conditions, the friction coefficient of rolling bearings is lower than that of sliding bearings, and the value is more stable. While the lubrication of sliding bearing is susceptible to the influence of speed, vibration and other external factors, the friction coefficient changes in a wide range. Start, because the sliding bearing has not formed a stable oil film, resistance to greater than rolling bearings, but the hydrostatic sliding bearing starting friction resistance and working friction coefficient are very small.
 
4、Applicable working speed comparison
Rolling bearing due to the centrifugal force of the rolling body and bearing temperature limit, the speed can not be too high, generally applicable to medium and low speed working condition. Incomplete liquid lubrication bearing due to bearing heat and wear, the working speed can not be too high. Complete liquid lubrication bearing high speed performance is very good, especially when the hydrostatic sliding bearing using air as lubricant, its speed up to 100000r/min.
 
5、Power loss comparison
Due to rolling bearing friction coefficient is small, its power loss is generally not large, less than incomplete liquid lubrication bearing, but when the lubrication and installation will be dramatically increased. Complete liquid lubrication bearing friction power loss is lower, but for the hydrostatic sliding bearing, due to the oil pump power loss, the total power loss may be higher than the dynamic pressure sliding bearing.
 
6、Comparison of service life
Rolling bearings due to material pitting and fatigue, the general design life of 5 to 10 years, or overhaul period for replacement. Incomplete liquid lubrication bearing shaft tile wear serious, need regular replacement. The life of completely liquid-lubricated bearings is theoretically unlimited, in fact, due to stress cycles, especially dynamic pressure sliding bearings, the shaft tile material may appear fatigue damage.
 
7、Rotational accuracy comparison
Rolling bearings due to small radial clearance, rotational accuracy is generally higher. Incomplete liquid lubrication bearing in the boundary lubrication or mixed lubrication state, operation is not stable, and more serious wear, lower precision. Complete liquid lubrication bearing has higher precision due to the existence of oil film and buffer vibration absorption. Hydrostatic plain bearing rotation accuracy is higher.
 
8、Other aspects of comparison
Rolling bearings use oil, grease or solid lubricant, the amount is very small, the amount is larger at high speed, the cleanliness of the oil quality requirements, so the requirement of sealing, but the bearing is easy to replace, generally do not need to repair the journal. For sliding bearings, in addition to incomplete liquid lubrication bearings, lubricants are generally liquid or gas, the amount is very large, the oil cleanliness requirements are also very high, bearing shingles need to be replaced often, and sometimes repair journals.


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