Types and features of motor end caps

The motor end cover is a structural part connecting the rotor and the frame. On the one hand, it protects the inside of the motor, and on the other hand, it ensures the relative position of the stator and rotor by means of rolling bearings placed in the end covers. There are many types of motor end caps, which can be divided into many different types from different angles.

According to the structure of the bearing chamber, the motor end cover can be divided into the through-hole bearing chamber end cover and the stepped hole bearing chamber end cover. When using end caps for through-hole bearing housings, an outer bearing cap must be used to prevent grease from escaping. This kind of end cap is widely used because of its simple structure, easy processing and convenient maintenance. The outside of the stepped hole bearing chamber end cover can be used as an outer bearing cover, which can reduce the number of parts and simplify the motor structure. This end cap is used for small motors with a centre height below 160mm.

According to the difference of the motor end cover blank, it can be divided into welded end cover and cast end cover. Welded end caps are welded from steel plates; cast end caps can be cast in cast iron, cast steel or aluminum alloy. Cast iron is cheap, has good casting performance and sufficient strength. Therefore, cast iron end caps are widely used in small and medium-sized motors. Only in special occasions, such as traction motors and explosion-proof motors with high mechanical strength requirements, use cast steel end caps or high-strength cast iron end caps. In mass production of low-power motors, aluminum die-cast end caps are often used to reduce machining time. The structural feature of the motor end cover is that the wall is thin and easy to deform, and it is not easy to be clamped during processing. The end cap is the connection between the stator and the rotor. The accuracy of the air gap of the motor is guaranteed by the matching accuracy of the joint and the bearing chamber, and the load and unloading wear and tear are required to have little effect on the accuracy. Therefore, joints and bearing chambers should have low surface roughness.

The machining process of the motor end cover is relatively simple, basically turning and drilling. However, the end cap is a thin-walled part and is easily deformed. Excessive clamping force or cutting volume may cause the end cap to be out of tolerance and deformed. A reduction in clamping force results in a reduction in cutting parameters, which reduces productivity. Therefore, turning is often divided into two processes: rough turning and fine turning. Different clamping forces are used to process on lathes of different precision levels.

When machining small motor end caps, self-centering chucks are often used to clamp the outer circumference of the end cap. The outer circle of the process joint should be machined in advance to control the clamping force and wall thickness uniformity. When machining the end cover of a medium-sized motor, the end cover should be radially clamped on the outer cylindrical surface of the flange, and the flange plane should be evenly supported to avoid vibration during turning and affect the machining quality.