For small-sized motors, sealed bearings are mostly used, which do not require special bearing covers. The end covers have shaft holes, and wave springs are placed at the bottom of the bearing chamber during assembly to meet and limit the axial displacement of the rotor during motor operation.

For motors without special requirements, the friction between the outer ring of the bearing and the bearing chamber of the end cover is sufficient to resist the axial force caused by thermal expansion and contraction during motor operation, and axial positioning through the inner cover of the bearing is not required.

However, for occasions with high requirements for axial dimensional accuracy, necessary positioning measures are also required. Without changing the structure and number of motor components, a retaining ring groove will be machined in the bearing chamber of the positioning end cover to limit the axial movement of the bearing.

The seal of bearings is firstly used in deep groove bearings with large quantity and wide application. In recent years, all kinds of rolling bearings have bearings with different seals. Therefore, sealing is one of the important directions of bearing technology development. Different structural bearings and different working conditions require different seals.

Sealed bearings are rolling bearings with corresponding sealing devices installed on both ends. The performance of the bearings with dust covers and sealing rings is different, one is dustproof and the other is sealing. The purpose of sealing is to prevent the grease (oil) inside the bearing from being lost during use, and to prevent the dirty grease from flowing in, so as to ensure that the bearing is in a lubricated state; dustproof is to protect the dust or harmful gas outside the bearing from entering the inner cavity of the bearing to prevent damage to the bearing.

Common seals include rubber or engineering plastic seals, and steel plate stamped seals (or dust covers). The seals have various sealing structures and different sealing effects. There is a gap between the seal and the rolling element of the bearing, which is called a non-contact seal. The smaller the gap, the better the sealing effect, but the lower the allowable shaft speed. There is no gap between the seal and the rolling element of the bearing, which is called a contact seal. The larger the contact area of the seal contact lip, the better the sealing effect, but the lower the allowable shaft speed.

There are many cases in this regard, and sometimes there are some ridiculous facts: for example, the motor with inner and outer bearing covers in the bearing system uses sealed bearings; the mixed use of contact and non-contact bearings, especially in the application of high-efficiency motors, has obvious differences, and different sealing structures have a greater impact on motor efficiency.

Whether the bearing uses a dust cover or a seal ring is related to the use requirements of the bearing. The dust cover does not contact the inner ring of the bearing, which is a non-contact installation. The seal ring contacts the inner ring of the bearing, which is a contact installation. Therefore, the maximum speed of the dust cover bearing is higher than that of the seal ring bearing, and the protection level of the seal ring bearing is higher than that of the dust cover. The seal ring bearing has good waterproof performance and can better prevent grease from flowing out.

For situations where the speed is high and the ambient temperature is also high, it is not suitable to use sealed bearings. Open bearings that are easy to oil and maintain should be used. For situations that are not easy to disassemble, the structure of oil injection and drainage without stopping the machine should be considered.