What is the preload of a bearing? What is the purpose of bearing preload?

Bearing preload refers to the force acting on a bearing by adjusting its axial direction relative to another bearing before applying a "use" load (external load), or the force generated by the "negative clearance" (internal preload) formed by the size of the inner raceway and rolling elements of the bearing.

The main purposes of bearing preload are as follows:

1. Improve the guiding accuracy of bearings. The shaft supported by preloaded bearings has higher guiding accuracy because the deflection ability of the shaft under load is limited by preloading. The preloaded differential bearing has high guiding accuracy and rigidity, which can maintain accurate and constant meshing, and the additional dynamic force is very small. Therefore, the operating noise is low and the meshing gear has a long service life.

2. Improve rigidity. The stiffness of a bearing is defined as the ratio of the force acting on the bearing to the elastic deformation of the bearing. Within a certain load range, the elastic deformation of bearings with preloading is smaller than that of bearings without preloading.

3. Low noise operation. The smaller the running clearance of the bearing, the better the guidance of the rolling elements in the no-load area, and the lower the noise during bearing operation.

4. Compensation for wear and pressure drop. During operation, the wear and pressure drop of the bearings increase the clearance, but it can be compensated for by preloading. Compensate for wear and pressure drop during operation, as well as extend working life.

5. Extend working life. In some cases, pairing bearings with preloading can improve operational reliability and extend working life. Because moderate preloading can improve the load distribution of bearings, it can increase their working life.