What is the reason for the running circle of the motor bearing?

certain company said that a batch of motors had bearing system failures. The bearing chamber of the end cover had obvious scratches, and the wave springs in the bearing chamber also had obvious scratches. Judging from the appearance of the fault, it is a typical problem of the outer ring of the bearing running. Today we will talk about the running circle of motor bearings.

Most motors use rolling bearings, the friction between the rolling body of the bearing and the inner and outer rings is rolling friction, and the friction between the two contact surfaces is very small. The fit between the bearing and the shaft, and between the bearing and the end cover is generally an interference fit , and in a few cases it is a transition fit . each otherThe extrusion force is relatively large, so static friction occurs, the bearing and the shaft, the bearing and the end cover remain relatively static , and the mechanical energy is transmitted by the rotation between the rolling element and the inner ring (or outer ring).

If the fit between the bearing, the shaft and the bearing chamber is a clearance fit , the torsion force will destroy the relative static state and cause slippage , and the so-called “running circle” occurs. Sliding in the bearing chamber is called running outer ring.

If the bearing runs around, the temperature of the bearing will be high and the vibration will be large. Disassembly inspection will find that there are slip marks on the surface of the shaft (bearing chamber) , and even grooves are worn out on the surface of the shaft or bearing chamber. From this situation, it can be concluded that the bearing is running.

The negative impact caused by the running of the outer ring of the bearing on the equipment is very large, which will intensify the wear of the matching parts, or even scrap them, and even affect the accuracy of the supporting equipment; in addition, because of the increased friction, a large amount of energy will be converted into heat and noise. The efficiency of the motor is greatly reduced.

(1) Fit tolerance: There are strict requirements on the fit tolerance between the bearing and the shaft (or bearing chamber). Different specifications, precision, stress conditions, and operating conditions have different requirements for fit tolerance.

(2) Machining and installation accuracy: refers to technical parameters such as machining tolerances, surface roughness, and assembly accuracy of shafts, bearings, and bearing chambers. Once the requirements are not met, it will affect the fit tolerance and cause the bearing to run around.

(3) The material of the shaft and bearing is very critical. Different types of bearings should be made of suitable bearing steel, with high strength and rigidity, good wear resistance, and a small friction coefficient of the bearing alloy, so as to ensure the normal use of the bearings and reduce the possibility of running circles.

At present, the common methods for repairing the running circle of bearings in China are inserting, pitting, surfacing, brush plating, thermal spraying, laser cladding, etc.

◆  Surface welding : Surfacing welding is a welding process that deposits a layer of wear-resistant, corrosion-resistant, heat-resistant metal layer on the surface or edge of the workpiece.

◆ Thermal spraying : Thermal spraying is a metal surface processing method that atomizes the molten spraying material on the surface of the part through high-speed airflow to form a sprayed layer.

◆ Brush plating : Brush plating is the process of obtaining a coating on the surface of the workpiece by electrolysis.

◆ Laser cladding : Laser cladding, also known as laser cladding or laser cladding, is a new surface modification technology.