The Rationality Of Motor Bearing Clearance Selection Is The Basis For Ensuring The Reliability Of Its System Operation.

The Rationality of Motor Bearing Clearance Selection is the Basis for Ensuring the Reliability of Its System Operation.

Motor products with bearings, by the role of related parts, in the radial and axial direction are subject to positioning constraints, the end result will have an impact on the clearance of the bearing, which is manifested in the bearing initial clearance 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. 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. Due to the tolerance fit of different amounts of interference, as well as different degrees of thermal expansion of bearing rings and associated parts (such as motor shafts, end caps, etc.), resulting in ring expansion or compression, the working clearance of the bearing is generally smaller than the initial clearance.

In order to make the bearing good operation, radial clearance is very important. Control and mastery of the general principle: ball bearing working clearance should be zero, or have a slight preload. But 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 installation conditions are different from the general situation, such as the bearing of the two rings are interference fit, or the ring temperature difference is a great influence, 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 a 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.

The rigidity or rotational accuracy of a bearing configuration can be improved by preloading the bearing. 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 operate 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, whereas 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.