The selection of bearings is very important for the motor designers. One of the main tasks of the motor structure design is to analyze the design life and fatigue life of the bearing and determine the bearing size. Bearing selection should consider not only the life of grease, wear and noise, but also the accuracy, coordination, clearance, cage, grease, sealing structure, and other special requirements according to the different use of the motor.
When choosing a bearing, increasing the fatigue life coefficient means choosing a large bearing, but the strength, rigidity, installation size of the shaft must be taken in account. Fatique life is not necessarily the only limiting condition. The bearings used in all kinds of machinery, according to the conditions of use, have the reference life of design, and are represented by the empirical fatigue life coefficient.
When the bearing is installed, it is very important to match the inner diameter of the bearing with the shaft, and the match of outer diameter with shell is also important. When the match is too loose, the matching surface will be relatively slid, so that it is quickly worn and the shaft or shell will be damaged. At the same time, the powder caused by wear will invade the inner of the bearing, further aggravate the wear and cause the heat, vibration and damage.
With too tight or interference too large, on the one hand, the outer diameter of the outer ring will be smaller or the inner diameter of the inner ring will increase, and the internal clearance of the bearing will be reduced. On the other hand, due to the uneven deformation of the outer ring or inner ring, the bearing noise will increase. In addition, the geometric accuracy of the shaft and shell can also affect the original precision of the bearing ring, thus affecting the performance of the bearing.
In addition to the above factors, thera are many factors will affect the selection of motor bearings, such as the material, strength and thermal conductivity of shaft and bearing seat, external factors and so on.