Installation coordination and adjustment of high-speed bearings:
1. Fit and clearance of high-speed bearings Since high-speed bearings must meet both high-precision bearing requirements and high-temperature bearing requirements, the following two points must be taken into consideration when considering their fit and clearance:
(1) Dimensional changes and hardness changes 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 high-speed and high-temperature conditions, it is difficult to maintain the accuracy and performance of bearings in terms of fit and clearance selection.
In order to ensure that the raceway deformation is small after the bearing is installed, the amount of interference fit cannot be too large, and the centrifugal force at high speed and thermal expansion at high temperature may offset the normal pressure of the mating surface. Or make the mating surface loose, so the interference must be calculated carefully taking into account the above two factors. The interference that is effective at normal temperature and speed may be invalid for high-speed bearings.
If the contradiction between the calculation results is too great (usually this is only the case at ultra-high speeds), the only way to adopt dual 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. The 3 million mark.
Thermal expansion at high temperatures may offset the normal pressure on mating surfaces. Or make the mating surface loose, so the interference must be calculated carefully taking into account the above two factors. The interference that is effective at normal temperature and speed may be invalid for high-speed bearings.
If the contradiction between the calculation results is too great (usually this is only the case at ultra-high speeds), the only way to adopt dual 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. The 3 million mark.
When considering the clearance of high-speed bearings, not only the above factors must be considered, but also the impact of the thermal elongation of the shaft on the clearance. The bearing is required to have optimal clearance under working conditions, that is, at operating temperature, and this This kind of clearance is formed when the centers of the inner and outer ring ball grooves are accurately aligned. Since high-speed bearings strive to reduce relative sliding and internal friction, it is best not to adjust the clearance of ball bearings by displacing the inner and outer rings relative to each other in the axial direction.
When considering the fit interference and clearance of the bearing, we should pay attention to the characteristics of the material becoming soft and easy to deform at high temperatures, and the possibility of certain permanent deformation caused by multiple temperature changes from normal temperature to high temperature.
2. Requirements for host-related parts
High-speed bearings require that the rotary system where the bearing is located must undergo precise dynamic balancing. The parts where the bearing is installed on the shaft and the seat hole should have dimensional accuracy and shape accuracy higher than the general requirements, especially the coaxiality and the alignment of the shoulder with the seat hole or journal. Verticality, and when considering these issues, we must also pay attention to the high-speed factors and high-temperature factors when the bearings are 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 taken to improve the support rigidity, and hollow shafts can be used to reduce system mass.
