Installation and adjustment of high-speed bearings:
1.The fit and clearance of high-speed bearings Because high-speed bearings should meet the requirements of both high-precision bearings and high-temperature bearings, the following two points should be taken into account when considering the fit and clearance of high-speed bearings:
(1) Pay attention to the size change and hardness change of bearings from room temperature to high temperature
(2) The change of force system and shape of bearing 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 bearings from the selection of fit and clearance.In order to ensure that the raceway deformation after bearing installation is small, the interference amount of interference fit can not be too large, and the centrifugal force at high speed and thermal expansion at high temperature, or offset the normal pressure on the fit surface.Therefore, bearing interference must be carefully calculated on the premise of taking the above two factors into account. The effective interference at room temperature and constant speed may be invalid for high-speed bearings.If the calculation results of this contradiction is too big (usually only at ultra-high speed), only to take the bearing ring lubrication method and hydrostatic lubrication method and double lubrication measures, and this scheme is likely to make the bearing DMN value breakthrough 3 million mark.
When considering the clearance of high-speed FAG bearings, not only the above factors should be taken into account, but also the influence of therm elongation of the shaft on the clearance. It is required that the bearings have the best clearance under the working condition, that is, at the working temperature, and this clearance is formed under the precise alignment of the center of the inner and outer ring ball groove.Because high-speed bearings strive to reduce relative sliding and internal friction, it is best not to adjust the clearance of ball bearings by using the method of relative dislocation of the inner and outer rings along the axial direction.
When considering the fit interference and clearance of bearings, we should 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 temperature changes from room temperature to high temperature for many times.
- Requirements for the relevant parts of the main engine
High-speed bearing requirements bearing in rotary system after dynamic balancing precision, shaft and hole bearing installation of the parts should be higher than the general requirements of dimensional accuracy, form and position accuracy, especially high-speed bearing alignment of hole or shaft neck and shoulder verticality, and considering these problems, also must pay attention to the high speed and high temperature factors in the operation of high-speed bearing.
High speed bearing shaft supporting system requires 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 stiffness of high speed bearing, and the hollow shaft of high speed bearing can be used to reduce the system mass.