Motor bearings, also known as electric motor bearings or motor bearings, are specialized bearings used in electric motors. A motor bearing is a component that supports the shaft, guiding its rotation and supporting rotating parts on the shaft. There are four common types of motor bearings: rolling bearings, plain bearings, spherical plain bearings, and oil-impregnated bearings. The most common type of motor bearing is the rolling bearing, which has rolling elements.
Working principle
Motor bearings utilize smooth metal balls or rollers and lubricated inner and outer ring metal surfaces to reduce friction. These balls or rollers "bear" the load, support the motor shaft, and allow the motor (rotor) to rotate smoothly.
Bearing usage type
Most small and medium-sized motors use rolling bearings. Large and medium-sized motors also use rolling bearings. Small motors use ball bearings (such as deep groove ball bearings) at both ends. Medium-sized motors use roller bearings (such as cylindrical roller bearings and tapered roller bearings) at the load end, and ball bearings at the non-load end (but there are also cases where the opposite is true, such as in a 1050kW motor). Rolling bearings are lubricated with grease, but some are also lubricated with oil.
Bearing installation
The quality of motor bearing installation directly affects its precision, lifespan, and performance. Therefore, please thoroughly study bearing installation procedures and follow the operating standards that include the following items.
● Clean the motor bearings and related parts. (Bearings that are already grease-lubricated and have oil seals or dust covers on both sides, as well as bearings with sealing rings, do not need to be cleaned before installation.)
●Inspect the dimensions and finish of the relevant parts.
Installation method
The installation of motor bearings should be determined based on the bearing structure, size, and fit of the bearing components. Pressure should be applied directly to the end face of the tightly fitted raceway and should not be transmitted through the rolling elements. The following methods are generally used for motor bearing installation:
1. Press-fit
When the inner ring of the motor bearing is tightly fitted to the shaft, and the outer ring is loosely fitted to the bearing housing bore, a press can be used to press the motor bearing onto the shaft first, and then the shaft and bearing are installed together into the bearing housing bore. During press fitting, a soft metal fitting tube (copper or soft steel) is placed on the end face of the inner ring of the motor bearing.
When the outer ring of the motor bearing is tightly fitted to the bearing housing bore, and the inner ring is loosely fitted to the shaft, the motor bearing can be pressed into the bearing housing bore first. In this case, the outer diameter of the fitting tube should be slightly smaller than the diameter of the housing bore.
If the motor bearing race is tight-fitted with the shaft and housing bore, the inner and outer races must be pressed into the shaft and housing bore simultaneously during installation. The structure of the mounting sleeve should be able to simultaneously press the end faces of the inner and outer races of the bearing.
2. Heating combination
This installation method, which uses thermal expansion to convert a tight fit into a loose fit by heating the motor bearing or bearing housing, is a common and labor-saving method. It is suitable for motor bearings with large interference fits. Before heat installation, the motor bearing or the ring of a separable bearing is placed in an oil bath and heated evenly to 80-100℃. Then, it is removed from the oil and quickly installed onto the shaft. To prevent the inner ring end face from not fitting tightly against the shaft shoulder after cooling, the motor bearing can be axially tightened after cooling. When the outer ring of the motor bearing is tightly fitted to a bearing housing made of light metal, using the heat installation method by heating the bearing housing can prevent scratches on the mating surfaces.
When heating motor bearings in an oil tank, a mesh screen should be placed at a certain distance from the bottom of the tank, or the motor bearings should be suspended by hooks. The motor bearings should not be placed on the bottom of the tank to prevent impurities from entering the motor bearings or uneven heating. A thermometer must be placed in the oil tank, and the oil temperature must be strictly controlled not to exceed 100℃ to prevent tempering and reduce the hardness of the bearing rings.
