High-speed precision spindle bearings and ball screw support bearings must be preloaded with a certain axial load under normal working conditions. The main purpose is to improve the rotation accuracy of the bearings, reduce the sliding of the rolling elements during high-speed operation, and improve the rigidity of the bearings. Reduce the axial and radial serial momentum of the support, increase the rotational speed of the bearing, reduce noise and increase the service life of the bearing.
- Preload and stiffness of angular contact ball bearings
The preload of angular contact ball bearings is usually divided into three levels: light (A), medium (B) and heavy (C).
There are two types of bearing preload: positioning preload and constant pressure preload, as shown in Figure 1 and Figure 2: The relative position of the supporting parts of the positioning preloaded bearing is fixed during use. When the angular contact ball bearing rotates at high speed, due to the action of centrifugal force, the rolling elements tend to be thrown outward, so that the inner and outer rings of the bearing have an axial relative The tendency to move, but because its position has been relatively fixed, the result must be that the pre-tightening force of the bearing increases, and the friction and heat increase. In addition, the change of working temperature will also affect the size of the bearing seat and the size of the two bearing components, which in turn will affect the preload state of the bearing. Therefore, when using the positioning preload method, attention should be paid to the influence of the change of the preload on the working performance of the bearing.
The constant pressure preload uses elastic elements such as coil springs and butterfly springs to make the bearings get a proper preload on the supporting parts. Since the preload rigidity of springs etc. is generally much smaller than that of bearings, the size of the constant pressure preload is determined by the preload device itself, and its value is constant. In addition, the preload of the bearing support is not affected by the work. The effect of temperature.
In short, positioning preload is beneficial to improve the rigidity of the bearing, while constant pressure preload is suitable for high-speed rotation.