Installation Fit And Adjustment Of High-Speed Bearings

1. Fit and clearance of high-speed bearings Since high-speed bearings must meet the requirements of high-precision bearings and high-temperature bearings, when considering their fit and clearance, the following two points should be taken into account:

(1) Dimensional change and hardness change when rising from normal temperature to high temperature;
(2) Force system changes and shape changes caused by centrifugal force at high speed.

In short, under the condition of high speed and high temperature, it is difficult to maintain the precision and working performance of the bearing from the selection of fit and clearance.

In order to ensure that the deformation of the raceway after the bearing is installed is small, the interference of the interference fit cannot be too large, and the centrifugal force at high speed and thermal expansion at high temperature can offset the normal pressure of the mating surface. Or make the mating surface loose, so the interference must be carefully calculated 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 calculation result shows that the contradiction is too large (usually only at ultra-high speeds), the only way to adopt double lubrication measures is to use both the under-ring lubrication method and the static pressure lubrication method, and this solution may cause the dmn value of the bearing to break through 3000000.

When considering the clearance of high-speed bearings, not only the above factors must be considered, but also the influence of the thermal elongation of the shaft on the clearance should be considered. It is required that the bearing has the best clearance under the working condition, that is, at the working temperature, and this This kind of clearance is formed under the state of precise alignment of the centers of the ball grooves of the inner and outer rings. Since high-speed bearings strive to reduce relative sliding and internal friction, it is best not to use the method of relative displacement of the inner and outer rings in the axial direction to adjust the clearance of the ball bearing.

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

2. Requirements for host related parts

High-speed bearings require precise dynamic balance of the rotary system where the bearing is located. The position where the shaft and seat hole is installed with the bearing should have a higher dimensional accuracy and shape accuracy than the general requirements, especially the coaxiality and the distance between the shoulder and the seat hole or journal. Verticality, 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 possible. In order to overcome this contradiction, measures such as reducing surface roughness and improving surface strengthening can be taken to increase support stiffness, and hollow shafts can be used to reduce system mass.