The so-called bearing clearance refers to the amount of movement when the inner ring or outer ring of the bearing is fixed when it is not installed on the shaft or bearing housing, and then the unfixed side moves radially or axially. . According to the moving direction, it can be divided into radial clearance and axial clearance. The size of the clearance during operation (called working clearance) has an impact on the rolling fatigue life, temperature rise, noise, vibration and other properties of the bearing. When measuring the bearing clearance, in order to obtain a stable measurement value, a specified measurement load is generally applied to the bearing. Therefore, the obtained measured value is larger than the real clearance (called theoretical clearance), which increases the amount of elastic deformation caused by the measurement load. But for roller bearings, since the amount of elastic deformation is small, it can be ignored. The internal clearance of the bearing before installation is generally expressed by the theoretical clearance.

Selection of Clearance

Subtract the expansion or shrinkage of the ring due to interference fit when the bearing is installed on the shaft or in the housing from the theoretical clearance It is called installation clearance. The effective clearance is the clearance r obtained by adding and subtracting the dimensional variation due to the temperature difference inside the bearing from the mounting clearance. The bearing is installed with the clearance when it is placed under a certain load on the machine, that is, the effective clearance plus the elastic deformation caused by the bearing load so as to be called the working clearance. When the working clearance is slightly negative, the fatigue life of the bearing is the longest, but the fatigue life decreases significantly with the increase of the negative clearance. Therefore, when selecting the bearing clearance, it is generally advisable to make the working clearance zero or slightly positive. The relationship between the working clearance and fatigue life In addition, when the rigidity of the bearing needs to be improved or the noise needs to be reduced, the working clearance should take a further negative value, and when the bearing temperature rises sharply, the working clearance should take a further positive value, etc. Specific analysis must also be made according to the conditions of use.