Most motors use rolling bearings, and the friction between the rolling element of the bearing and the inner and outer rings is called rolling friction. The friction between the two contact surfaces is very small. The fit between bearings and shafts, as well as between bearings and end caps, is generally an interference fit, with a few cases being a transitional fit. The mutual squeezing force between each other is relatively large, resulting in static friction. The bearings and shafts, bearings and end caps remain relatively stationary, and mechanical energy is transmitted through the rotation between the rolling element and the inner (or outer) ring.

Bearing race

If the fit between the bearing and the shaft or bearing chamber is a clearance fit, torque will break the relative static state and cause sliding, resulting in the so-called "running ring". The sliding between the bearing inner ring and the shaft is called running inner ring, and the sliding between the bearing outer ring and the bearing chamber is called running outer ring.

The Appearance and Harm of Bearing Race

If there is a bearing race situation, the temperature of the bearing area will be too high and the vibration will be large. During disassembly inspection, it can be found that there are sliding 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 of bearing outer race on the equipment is very significant, which can exacerbate the wear of matching parts, even scrap them, and even affect the accuracy of matching equipment; In addition, due to increased friction, a large amount of energy is converted into thermal energy and noise, greatly reducing the efficiency of the motor.

Causes of bearing race

(1) Fit tolerance: There are strict requirements for the fit tolerance between bearings and shafts (or bearing chambers), and different specifications, accuracy, stress conditions, and operating conditions have different requirements for fit tolerance.

Once there is a problem with tolerance fit, the problem of motor bearing race will be a mass quality issue.

(2) Processing and installation accuracy: refers to the processing tolerance, surface roughness, assembly accuracy and other technical parameters of the shaft, bearing, and bearing housing. Once the requirements are not met, it will affect the fit tolerance and cause the bearing to run out of rings.

(3) The material of shafts and bearings is crucial. Different types of bearings should be made of suitable bearing steel, with high strength and stiffness, good wear resistance, and low friction coefficient of bearing alloy. This can ensure the normal use of bearings and reduce the possibility of running rings.

At present, the common methods for repairing bearing running rings in China are bushing, pitting, surfacing, brush plating, Thermal spraying, laser cladding, etc.

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

◆ Thermal spraying: Thermal spraying is a metal surface processing method that atomizes and sprays molten spraying materials on the surface of parts through Jet stream to form a spraying layer.

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

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