What is the phenomenon and solution of bearing overheating?
The causes of overheating of rolling bearing are as follows:
1. Bearing selection
The bearing quality is divided by the manufacturing process of the bearing manufacturer. In addition to the detection level, it is also related to the material of bearing steel. The heat treatment process and calcination process are closely related. At present, the vacuum degassing bearing steel and vacuum remelting bearing steel used abroad have not been popularized in China, and are superior to the widely used bearing steel GCr15 and GCr15SiMn in China. Therefore, bearings should be imported, such as Swedish bearings SKF. NSK of Japan and KOYO. FAG of Germany. However, if you carefully check and screen before use, the three domestic bearing brands of Wafangdian, Harbin and Luoyang are also good choices. In short, try not to use inferior brands and "three no" products, otherwise the motor (especially the medium and large three-phase asynchronous motor) will have endless trouble.
2. Bearing extrusion
Because of the gap between them and the inner and outer sleeve of the bearing, the ball or roller can rotate freely in the raceway. If the inner or outer ring of the bearing sleeve is squeezed, the gap will become smaller. Because the value of bearing clearance is very small, it is very sensitive to the change of clearance. If the stroke clearance becomes smaller, the contact stress between the bearing rolling body and the ring will become larger, which will increase the friction heat of the bearing. Countermeasures to prevent extrusion: (1) The fit between the outer ring of the bearing and the bearing sleeve is mostly H7. In actual machining, because the interference fit between the bearing and the shaft is used, the tolerance of the bearing platform should be as high as possible. The tolerance of the bearing platform is k6 or m5. When the radial clearance of the bearing selected by k6.m5 is small, and the tolerance of the inner ring is also small, the radial fit is tight, and the radial clearance after assembly will be affected to a certain extent. During hot operation, the inner ring expands greatly, which may lead to negative clearance. Small negative clearance is beneficial to the normal operation of the bearing, but large negative clearance is very unfavorable to the operation of the bearing. The temperature is high, and the degree of negative clearance is reduced by the expansion of the outer ring. In addition, when the bearing is running, the bearing outer ring and bearing sleeve will inevitably have interference, which will cause the rolling body to be squeezed and cause the bearing to be damaged prematurely by heat. (2) In order to prevent the bearing sleeve from sliding around the bearing chamber, the accumulated tolerance of the end cap (or bearing sleeve) and the inner and outer cap of the bearing can be "+" and accumulated. At the plane joint surface of the outer cap, ensure the plane joint surface of the inner cap. The outer cap clamps the bearing sleeve (when designing the inner and outer cap of the bearing, the tolerance grade of the length of the end cap can be used H11 instead of h11). For flameproof motors, the clearance shall not be greater than 0.2mm. CNC or digital display machine tools can guarantee this tolerance. (3) When selecting the bearing clearance of three-phase asynchronous motor, according to production experience, 2P generally selects motor C3 group clearance, 4P can choose motor C3 group clearance or standard clearance, 6 group clearance or standard clearance, and P and above can use standard clearance. 2. High-voltage motors P and 4P generally select motor C3 group clearance, 6P and 8P motors select CM clearance, and 10P selects the above motor C0 clearance. Of course, the choice of this gap is only for the standard design of the motor. If the customer has special requirements, that is another matter.