Since deep groove ball bearing should meet the requirements of both high-precision bearing and high-temperature bearing, the following two points should be taken into account when considering the fit and clearance: (1) the change of size and hardness from normal temperature to high temperature; (2) the change of force system and shape caused by centrifugal force at high speed. In a word, under the condition of high speed and high temperature, it is difficult to keep the accuracy and working performance of the bearing 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 cannot be too large, and centrifugal force at high speed and thermal expansion at high temperature can offset the normal pressure on the fitting surface. Therefore, the interference must be calculated carefully under the premise of considering the above two factors. The effective interference amount at normal temperature and constant speed may be invalid for deep groove ball bearings.
If the contradiction between the calculation results is too big, only the double lubrication measures of under ring lubrication method and static pressure lubrication method can be adopted, and the DMN value of bearing may exceed 3 million.
When considering the clearance of deep groove ball bearing, not only the above factors should be considered, but also the influence of shaft thermal elongation on the clearance should be considered. It is required that the bearing has the best clearance under the working condition, that is, under the working temperature, and this kind of clearance is formed when the center of inner and outer ring ball groove is accurately aligned. As the deep groove ball bearing strives to reduce the relative sliding and internal friction, it is better not to adjust the clearance of the ball bearing by means of relative dislocation of the inner and outer rings along the axial direction.
When considering the fit interference and clearance of bearing, it should be noted that the material becomes soft and easy to deform at high temperature, and the possibility of permanent deformation caused by many temperature changes from normal temperature to high temperature.