Friends who have a certain understanding of the use of bearings should know that preloading bearings can improve their rotational accuracy, increase their rigidity, reduce friction, and thereby enhance the overall performance and service life of the bearings. So, how should bearings be preloaded? What are the differences in preloading for different types of bearings? Let's take a look at the preloading of bearings together!

Radial preloading method

This preloading method is mostly used in tapered bore bearings that bear radial loads. A prominent example is the double-row precision short cylindrical roller bearing. The axial position of the bearing is adjusted by using the nut, so that the inner ring can have an appropriate expansion amount, thereby obtaining the radial negative clearance. This preloading method is mostly used in machine tool spindles and jet engines.

Axial preloading method

Axial preloading methods can be classified into three types: positioning preloading, constant pressure preloading and variable preloading.

1. Positioning pre-tightening

The adoption of positioning preloading has a positive effect on increasing the rigidity of bearings. Meanwhile, due to the increased rigidity of the bearings, the impact on the bearing load is also much smaller. The main operation steps of positioning pre-tightening are to select the appropriate inner and outer ring gaskets or spacers in advance, so that the inner and outer rings of the bearing are in a fixed position, thereby enabling the bearing to obtain an appropriate pre-tightening amount. The appropriate preload can be adjusted by measuring or controlling the starting friction torque, or the preload can be achieved directly by using the paired double bearings with a pre-adjusted preload amount.

2. Constant pressure pre-tightening

Unlike positioning preloading, the preloading amount of constant pressure preloading does not change much during the use of the bearing and is not affected by temperature. This method mainly uses devices such as disc springs and helical springs for pre-tightening during operation. Since the rigidity of the spring is less than that of the bearing, the relative position of the constant pressure preload bearing will change during use due to the influence of rotational speed and external load, but the preload remains approximately unchanged.

3. Variable preload

Considering that the preload of precision bearings will increase with the high-speed operation of the bearings, excessive preload may cause the bearing temperature to be too high, and in severe cases, it may even shorten the service life of the bearings. Therefore, in order to balance the processing stiffness at low speed and the load weight during high-speed preloading, we can use a device that changes the load, switch the preload according to the demand, or adopt positioning preloading at low speed to ensure stiffness and choose constant pressure preloading at high speed.