1. Matching and clearance of high-speed
bearings Because high-speed bearings must be in accordance with high-precision bearing requirements and high-temperature bearing requirements, when considering the fit and clearance, the following two points should be considered:
(1) dimensional change and hardness change from normal temperature to high temperature;
(2) Force system changes and shape changes 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 the bearing from the selection of the fit and the clearance.
In order to ensure that the raceway deformation after the bearing is installed, 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 may offset the normal pressure of the mating surface. Or the mating surface is relaxed, so the interference must be carefully calculated under consideration of the above two factors, and the effective interference at normal temperature and normal speed may be ineffective for high-speed bearings.
If the calculation result is too contradictory (usually only under ultra-high speed), only the double lubrication measures used in the ring lubrication method and the static pressure lubrication method are adopted, and this scheme may make the dmn value of the bearing break through. The 3 million mark.
Thermal expansion at high temperatures, or offsetting the normal pressure of the mating surface. Or the mating surface is relaxed, so the interference must be carefully calculated under consideration of the above two factors, and the effective interference at normal temperature and normal speed may be ineffective for high-speed bearings.
If the calculation result is too contradictory (usually only under ultra-high speed), only the double lubrication measures used in the ring lubrication method and the static pressure lubrication method are adopted, and this scheme 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. It is required that the bearing has the best clearance under the working condition, that is, at the working temperature. The kind of play is formed in the state of precise alignment of the center of the inner and outer ring grooves. Since high-speed bearings strive to reduce relative sliding and internal friction, it is best not to adjust the clearance of the ball bearings by means of the relative misalignment of the inner and outer rings in the axial direction.
When considering the bearing interference and clearance of the bearing, it is necessary to notice that the material becomes soft and easily deformed at high temperatures, and the possibility of a certain permanent deformation caused by temperature changes from normal temperature to high temperature.
2. Requirements for host related parts
High-speed
bearings require precise dynamic balance of the rotating system where the bearing is located. The shaft and the seat hole should be mounted with the bearing with higher dimensional accuracy and shape accuracy than the general requirements, especially the coaxiality and the shoulder-to-seat or journal. Verticality, and when considering these issues, it is also necessary to pay attention to the high speed factor and high temperature factor when the bearing is running.
The shaft support system requires both high rigidity and light weight as much as possible. To overcome this contradiction, measures such as reducing surface roughness and improving surface strengthening can be adopted to improve the support rigidity, and the hollow shaft can be used to reduce the system quality.
