In the previous article, we talked about the coaxiality control requirements of the motor bearing system. To ensure the coaxiality control requirements of the bearing system, the radial clearance and radial positioning control of the bearing are particularly critical and important.
The internal clearance of a bearing is the total distance that one bearing ring can move radially or axially relative to the other bearing ring. For the clearance of a bearing, it is necessary to distinguish between the initial clearance before installation and the operating clearance after installation and reaching its operating temperature. The initial clearance of a bearing is generally larger than the operating clearance due to the different interference tolerances and the different degrees of thermal expansion of the bearing rings and their adjacent parts, which causes the rings to expand or compress.
In order for the motor bearing to operate well, radial clearance is very important, which requires selecting appropriate bearings to match the motor according to its actual characteristics and operating conditions. 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 residual clearance must be left during operation.
Under normal working conditions, the appropriate working clearance can be obtained by selecting the normal clearance bearing. However, when the working and installation conditions are different from the general situation, such as the inner and outer rings of the bearing are interference fit, or the temperature difference between the inner and outer rings has a great influence, a bearing with a larger or smaller clearance than the normal group should be selected.
In the actual bearing selection process, some motor manufacturers are accustomed to choosing bearings with larger loads, but bearing noise problems often occur. In particular, some motors have loud bearing noise when running at no load, but the sound is particularly good when running under load. This problem may be related to improper bearing selection. Ideal axial positioning of the bearing is a necessary condition for the good operation of the bearing.
From the analysis of the operating characteristics of the bearing, in order to fully achieve the load-bearing capacity of the bearing used, the entire circumference of the inner and outer rings of the bearing, or the shaft ring and seat ring of the thrust bearing, must be fully and evenly supported. The support surface can be a cylindrical or conical surface. For the shaft ring and seat ring of the thrust bearing, a flat surface should be used. Therefore, the processing of the surface matching the bearing ring must reach a certain accuracy and should not have any grooves, holes or other discontinuous shapes. In addition, the bearing ring must be securely fixed to prevent the bearing ring from rotating between its matching surfaces under load.
Generally speaking, there must be a suitable interference fit so that the bearing rings can be fixed in the radial direction and receive adequate support. If the bearing rings are not properly or adequately fixed, it is easy to cause damage to the bearing and related components. However, sometimes, in order to facilitate installation and disassembly, or because the bearing is used at the floating end and needs to have the function of axial movement, an interference fit cannot be used. In some cases where a clearance fit is used, some special measures are needed to reduce the wear caused , such as: surface hardening of the mating surface and shoulder of the bearing, lubrication of the mating surface and removal of wear particles through special lubrication grooves, or fixing the bearing using a locating keyway on the side of the bearing.
From the elements of good bearing operation, it is easier to understand the requirements for ensuring the machining quality and process of the associated shaft and end cover bearing chamber.
Post time: Jan-27-2025