Motor products with bearings, by the role of the associated components, both in the radial and axial direction are subject to positioning constraints, the end result of which will have an impact on the clearance of the bearing, which is manifested in the initial clearance of the bearing and the difference between the working clearance.
The clearance in a bearing is the total distance that one of the bearing rings can move in radial or axial direction relative to the other bearing ring. With regard to the clearance of a bearing, a distinction must be made between the clearance before mounting and the clearance after mounting and reaching its operating temperature. The working clearance of a bearing is generally smaller than the initial clearance due to tolerance fits with different amounts of interference and different degrees of thermal expansion of the bearing rings and associated parts (e.g. motor shafts, end caps, etc.), resulting in ring expansion or compression.
General principles of control and mastery: The operating clearance of ball bearings should be zero or have a slight preload. However, for cylindrical roller, spherical roller and other bearings, there must be a certain residual clearance in operation, even if it is very small.
Generally under normal operating conditions, a suitable operating clearance can be obtained by selecting bearings with a common group clearance. However, when the working and mounting conditions are different from the general situation, such as bearings of both rings are interference fit, or ring temperature difference is very influential, then the clearance should be selected than the ordinary group of large or small bearings.
Depending on the application, the bearings should be configured with positive or negative working clearance. In most cases, the working clearance should be positive, i.e. the bearing should operate with a certain amount of residual clearance. On the other hand, there are many applications where negative working clearance – i.e. preload – is required.
Preloading of bearings can be used to increase the rigidity or rotational accuracy of bearing configurations. Examples include spindle bearings in machine tools, pinion bearings in automotive driveshafts, bearings in small motors, or bearing configurations for reciprocating motion. In some applications where the bearings are not, or are only, subjected to very small loads and are operated at high speeds, preload should be applied to the bearing configuration. In this case, the purpose of preload is to provide a minimum load to the bearing to prevent the rolling elements from slipping and causing damage to the bearing.
Preload can be radial or axial depending on the type of bearing. Cylindrical roller bearings, for example, can only have preload applied in the radial direction due to their design, while thrust ball bearings and cylindrical roller thrust bearings can only have preload applied in the axial direction. Single row angular contact ball bearings and tapered roller bearings are generally subjected to axial preload and are usually used in back-to-back or face-to-face pairs with another bearing of the same type. Deep groove ball bearings are usually also applied with the same axial preload, in order to achieve the purpose of preload, should be used with a greater than ordinary group of radial internal clearance, so that it can be such as angular contact ball bearings do have a contact angle greater than zero.
Post time: Jun-05-2024
