How to install high-speed bearings1

Installation coordination and adjustment of high-speed bearings:

1. Fit and clearance of high-speed bearings Since high-speed bearings must meet the requirements of both high-precision bearings and high-temperature bearings, the coordination should be considered. and clearance, the following two points should be considered:

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

(2) caused by centrifugal force at high speed Force system changes and shape changes.

In a word, it is difficult to maintain the accuracy and performance of the bearing from the selection of fit and clearance under the conditions of high speed and high temperature.

In order to ensure the small deformation of the raceway after the bearing is installed, the interference of the interference fit cannot be too large, and the centrifugal force at high speed and thermal expansion at high temperature may offset the normal direction of the mating surface. pressure. Or make the mating surface slack, so the interference must be calculated carefully under the premise of considering the above two factors. The effective interference at normal temperature and speed may be invalid for high-speed bearings.

If the contradiction in the calculation results is too large (usually only at ultra-high speed), only the dual lubrication measures of the under-ring lubrication method and the hydrostatic lubrication method are adopted, and this scheme has It may make the dmn value of the bearing break through the 3 million mark.

Thermal expansion at high temperature, or normal pressure to counteract mating surfaces. Or make the mating surface slack, so the interference must be calculated carefully under the premise of considering the above two factors. The effective interference at normal temperature and speed may be invalid for high-speed bearings.

If the contradiction in the calculation results is too large (usually only at ultra-high speed), only the dual lubrication measures of the under-ring lubrication method and the hydrostatic lubrication method are adopted, and this scheme has It may make the dmn value of the bearing break through the 3 million mark.

When considering the high-speed bearing clearance, not only the above factors should be considered, but also the influence of the thermal elongation of the shaft on the clearance should be considered. The best clearance is formed when the center of the inner and outer ring ball grooves are precisely aligned. Since high-speed bearings strive to reduce relative sliding and internal friction, it is best not to adjust the clearance of the ball bearing by displacing the inner and outer rings in the axial direction.

When considering the fit interference and clearance of the bearing, it is necessary to pay attention to the characteristics of the material becoming soft and easy to deform at high temperature, and the permanent deformation caused by repeated temperature changes from normal temperature to high temperature. possibility.

2. Requirements for the relevant parts of the main engine

The high-speed bearing requires that the rotary system where the bearing is located must undergo precise dynamic balance, and the shaft and the seat hole where the bearing is installed should have higher than general requirements. Dimensional accuracy and shape and position accuracy, especially the coaxiality and the verticality of the shoulder to the seat hole or journal, and when considering these issues, it is also necessary to pay attention to the high-speed factors and high-temperature factors when the 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 surface roughness and improving surface strengthening can be taken to improve the support rigidity. Reduce system mass, etc.