How to install high-speed bearings

Installation coordination and adjustment of high-speed bearings:

1. The fit and clearance of high-speed bearings. Because high-speed bearings must meet the requirements of high-precision bearings and high-temperature bearings, they are considering their fit The following two points should be taken into consideration when adjusting the clearance and clearance:

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

(2) Centrifugal force at high speed Force system changes and shape changes.

In short, under high-speed and high-temperature conditions, it is difficult to maintain the accuracy and 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 the thermal expansion at high temperature may offset the normal direction of the mating surface pressure. Or to loosen the mating surface, 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 calculation result is too contradictory (usually only at super high speeds), only the dual lubrication measures of the under-ring lubrication method and the static pressure lubrication method should be adopted, and this scheme has The dmn value of the bearing may exceed the 3 million mark.

Thermal expansion at high temperature, or offset the normal pressure of the mating surface. Or to loosen the mating surface, 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 calculation result is too contradictory (usually only at super high speeds), only the dual lubrication measures of the under-ring lubrication method and the static pressure lubrication method should be adopted, and this scheme has The dmn value of the bearing may exceed the 3 million mark.

When considering the clearance of a high-speed bearing, not only the above factors must be considered, but also the influence of the thermal elongation of the shaft on the clearance. The bearing is required to be in working condition, that is, the maximum Good clearance, and this clearance is formed under the state of precise alignment of the inner and outer ring ball groove centers. As 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 relative to each other in the axial direction.

When considering the 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 temperature changes from normal temperature to high temperature repeatedly cause a certain permanent deformation Possibility.

2. Requirements for related parts of the main engine

High-speed bearings require that the rotating system where the bearing is located have undergone precise dynamic balance, and the shaft and seat hole where the bearing is installed should be higher than the 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, we must also 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 adopted to increase the rigidity of the support. Reduce system quality, etc.