Preloading methods and differences of NSK bearings

NSK bearing pre-tightening methods are divided into two categories: radial pre-tightening method and axial pre-tightening method, which are described as follows.

1. NSK bearing radial pre-tightening method:

 Radial top tightening is often used in tapered bore bearings that accept radial loads. Typical examples are double row fine short cylindrical roller bearings. The nut is used to adjust the axial orientation of the bearing relative to the tapered journal. The circle has a suitable amount of expansion and a radial negative clearance. This method is mostly used in machine tool spindles and jet engines.

 2. NSK bearing axial preloading method:

 The NSK bearing axial pre-tightening method can be roughly divided into two types: positioning pre-tightening and constant-pressure pre-tightening. In the positioning pre-tightening, the appropriate pre-tightening amount can be obtained by adjusting the scale of the bushing or the gasket; the appropriate pre-tightening can also be adjusted by measuring or controlling the starting friction torque; The paired double bearings are used to achieve the pre-tightening intention. At this time, the user does not need to adjust again. In general, the bearings that are axially pre-tensioned will not change their relative orientation when used.

 The constant pressure pre-tightening is to use a spiral spring, a disc spring, etc. to make the bearing suitable for pre-tightening. The rigidity of the pretensioning spring is generally much smaller than the rigidity of the bearing, so the relative orientation of the bearing of the constant pressure preload will change during operation, but the preload amount is substantially unchanged.

 The comparison between NSK bearing positioning preloading and constant pressure preloading is as follows:

 (1) When the pre-tightening amount is equal, the positioning pre-tightening has a greater effect on the rigidity increase of the bearing, and the influence of the rigidity change on the bearing preload is much smaller on the bearing load.

 (2) Positioning preloading In operation, the axial length difference caused by the temperature difference between the shaft and the bearing housing, the large amount of radial expansion caused by the temperature difference between the inner and outer rings, and the displacement caused by the load, etc., will preload The amount changes; while the constant pressure preload is in use, the change in preload is negligible.