Bearing small lecture hall | the difference between rolling bearing and sliding bearing

As an indispensable part of mechanical products, bearings are divided into rolling friction bearings (referred to as rolling bearings) and sliding friction bearings (referred to as sliding bearings) according to the friction properties in bearings. Bearings have their own characteristics in structure, and each has its own advantages and disadvantages. When selecting, it must be combined with actual considerations.

Performance comparison between rolling bearing and plain bearing

Comparison of structure and movement

The most obvious difference between a rolling bearing and a plain bearing is whether there is a rolling element.

Rolling bearings have rolling elements (balls, cylindrical rollers, tapered rollers, needle rollers) that are rotated to support the rotating shaft, so that the contact portion is a point, and the more rolling elements, the more the contact points.

The sliding bearing has no rolling elements and supports the rotating shaft by a smooth surface, so that the contact portion is a face.

The difference between the two structures determines that the rolling bearing moves in a rolling manner, and the sliding bearing moves in a sliding manner, so the frictional situation is completely different.

Comparison of carrying capacity

Generally speaking, due to the large bearing area of the sliding bearing, its bearing capacity is generally higher than that of the rolling bearing, and the rolling bearing is not capable of withstanding the impact load, but the fully lubricated bearing can withstand the effect of buffering and absorbing the lubricating oil film. Large impact load. When the rotational speed is high, the centrifugal force of the rolling elements in the rolling bearing increases, and the load carrying capacity is lowered (noise is likely to occur at high speed). For dynamic pressure sliding bearings, the load carrying capacity increases as the rotational speed increases.

Comparison of friction coefficient and starting friction resistance

Under normal working conditions, the friction coefficient of the rolling bearing is lower than that of the sliding bearing, and the value is relatively stable. The lubrication of the sliding bearing is susceptible to external factors such as rotational speed and vibration, and the friction coefficient varies widely.

At the time of starting, since the sliding bearing has not formed a stable oil film, the resistance is greater than that of the rolling bearing, but the static sliding bearing has a small starting frictional resistance and a working friction coefficient.

Applicable working speed comparison

Rolling bearings are limited by the centrifugal force of the rolling elements and the temperature rise of the bearings. The speed cannot be too high, and it is generally suitable for medium and low speed working conditions. Incompletely liquid-lubricated bearings cannot be operated at too high a speed due to the heat and wear of the bearings. The high-speed performance of fully liquid-lubricated bearings is very good, especially when the hydrostatic plain bearings use air as a lubricant, the speed can reach 100000r/min.

Other aspects comparison

Rolling bearings use oil, grease or solid lubricants, the amount is small, the amount is high at high speed, the oil quality is required to be clean, so sealing is required, but the bearing replacement is convenient, generally no need to repair the journal. For sliding bearings, in addition to incompletely liquid-lubricated bearings, the lubricant is generally liquid or gas, the amount is large, the oil quality is also very clean, the bearing bush needs to be replaced frequently, and sometimes the journal is repaired.