Installation Method of High-speed FAG Bearings

Writer: Eric Bearing Limited

Installation and adjustment of high-speed FAG bearings:

1. The coordination and clearance of high-speed FAG bearings Since high-speed FAG bearings are required to meet the requirements of high-precision FAG bearings and high-temperature FAG bearings, the following two points must be considered when considering their cooperation and clearance:

(1) Dimensional change and hardness change from normal temperature to high temperature;

(2) Changes in force system and shape caused by centrifugal force at high speed.

In short, under the conditions of high speed and high temperature, it is difficult to maintain the accuracy and working performance of FAG bearings from the choice of fit and clearance.

In order to ensure that the deformation of the raceway after FAG bearing installation is small, the interference of the interference fit cannot be made too large, and the centrifugal force at high speed and the thermal expansion at high temperature can offset the normal pressure of the mating surface. Or to loosen the mating surface, the interference must be carefully calculated in consideration of the above two factors. The effective interference at normal temperature and speed may not be effective for high-speed FAG bearings.

 

If the contradiction between the calculation results is too large (usually only at super high speeds), only dual lubrication measures using both the under-ring lubrication method and the static pressure lubrication method are used, and this scheme may make the dmn value of the FAG bearing Break through the 3 million mark.

Thermal expansion at high temperatures may offset the normal pressure on the mating surface. Or to loosen the mating surface, the interference must be carefully calculated in consideration of the above two factors. The effective interference at normal temperature and speed may not be effective for high-speed FAG bearings.

If the contradiction between the calculation results is too large (usually only at super high speeds), only dual lubrication measures using both the under-ring lubrication method and the static pressure lubrication method are used, and this scheme may make the dmn value of the FAG bearing Break through the 3 million mark.

When considering the clearance of high-speed FAG bearings, not only the above factors must be considered, but also the influence of the thermal elongation of the shaft on the clearance. It is required that FAG bearings have the best clearance under working conditions, that is, at working temperature. This kind of play is formed in the state that the center of the inner and outer ball grooves is precisely aligned. Because high-speed FAG bearings strive to reduce relative sliding and internal friction, it is best not to adjust the clearance of the ball FAG bearings by displacing the inner and outer rings in the axial direction.in

When considering the interference and clearance of FAG bearings, it should be noted that the material becomes soft and easily deformed at high temperatures, and the possibility of a certain permanent deformation caused by multiple temperature changes from normal temperature to high temperature.

2. Requirements for related parts of the host

High-speed FAG bearings require precise dynamic balancing of the rotating system where the FAG bearings are located. The parts where the FAG bearings are installed on the shaft and the seat holes should have higher dimensional accuracy and shape accuracy than the general requirements, especially the coaxiality and the shoulder to the seat holes or The verticality of the journal, and when considering these issues, we must also pay attention to the high-speed factors and high-temperature factors when the FAG bearing is running.

The shaft support system requires both high rigidity and light weight as much as possible. In order to overcome this contradiction, measures such as reducing the surface roughness and improving surface strengthening can be taken to increase the support rigidity, and the hollow shaft can be used to reduce the system mass.

3. Lubricant for high-speed FAG bearings

The lubricant of high-speed FAG bearings should be considered as the lubricant of high-temperature FAG bearings, that is, the synthetic oil with good performance at high temperature, or the grease based on this synthetic oil. Recently, diester-based MIL-L-7808 oil and MIL-L-23699 oil have been widely used in FAG bearings of jet engines.