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How to control the radial clearance and positioning of motor bearings?

Clicks:303 Update time:2021-06-11

1.How to control the radial clearance of the bearing

Bearing internal clearance refers to the total distance that one bearing ring can move in the radial or axial direction relative to the other bearing ring. For the bearing clearance, it is necessary to distinguish the initial clearance before installation and the working clearance after installation and reach its operating temperature. The initial clearance of the bearing is generally larger than the working clearance, which is due to the tolerance fit of different interference amounts and the different degree of thermal expansion of the bearing ring and its adjacent parts, which causes the ring to expand or compress.


In order to make the motor bearings run well, the radial clearance is very important. It is necessary to select a suitable bearing to match it according to the actual characteristics and operating conditions of the motor. The general principle of bearing operation is that the working clearance of ball bearings should be zero or slightly preloaded; but for cylindrical roller bearings, a certain amount of residual clearance must be left during operation.

HC precision roller bearing.jpg

Under normal working conditions, you can get the proper working clearance by choosing ordinary group clearance bearings. However, when the working and installation conditions are different from the general situation, such as the inner ring and outer ring of the bearing are interference fit, or the temperature difference between the inner ring and the outer ring is greatly affected, the clearance should be selected compared with the ordinary group. Large or small bearings.

u type guide roller bearing.jpg

2.Bearing radial positioning and control points

In the actual bearing selection process, some motor manufacturers are accustomed to selecting bearings with larger load-bearing loads, but bearing noise problems often occur, especially in some motors, the bearing noise is louder during no-load operation, but running with load The sound at the time is particularly good. This problem may be related to the improper selection of the bearing. To make the bearing have a more ideal axial positioning is a necessary condition for the good operation of the bearing.


From the analysis of the operating characteristics of the bearing, to fully achieve the load carrying capacity of the bearing used, the entire circumference of the inner and outer rings of the bearing, or the shaft washer and seat ring of the thrust bearing, must be fully supported by solid and uniform support. The supporting surface can be a cylindrical or conical surface, and a flat surface should be used for the shaft washer and seat washer of the thrust bearing. Therefore, the machining of the mating surface with the bearing ring must reach a certain accuracy, and there should be no grooves, holes or other discontinuous shapes. In addition, the bearing ring must be securely fixed to prevent the bearing ring from rotating between its mating surfaces under load.

SG10 with bolt.jpg

Generally speaking, there must be a proper amount of interference so that the bearing ring can be fixed in the radial direction and be adequately supported. If the bearing ring is not properly or adequately fixed, it is easy to cause damage to the bearing and related components. But sometimes in order to facilitate installation and disassembly, or the bearing needs to have the function of axial movement because it is used on the floating end, interference fit cannot be used. In some cases where clearance fits are used, some special measures are needed to reduce the wear caused by creep, such as: the mating surfaces and shoulders of surface-hardened bearings, and special lubrication grooves to lubricate the mating surfaces and eliminate wear particles , Or use the positioning key groove on the side of the bearing to fix the bearing.

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