In motor failure cases, more than half of the failures are caused by the quality of the bearing system; the mildest ones are manifested as bearing noise, and the most serious ones are the disintegration of the bearing, which may cause the motor to sweep the hole or burn the winding; in the process of dissecting such faulty motors, at least one of the following symptoms can be found: dry grinding state of the bearing or lack of oil; the grease turns black and clumps; the bearing has obvious mechanical or electrical corrosion damage; the motor with such problems will show bearing noise in the early stage of the failure; because the object of the failure is clear, people are likely to blame the problem on the quality of the bearing, and naturally ignore the influence of grease and related factors.

 

　　Bearing rotation and movement cause grease to be thrown out:

The design of the bearing system is a key link in determining whether the motor can drive the equipment to operate reliably. For cylindrical roller bearings with separable inner and outer rings, especially when the positioning end is not well controlled, a certain range of axial movement will occur. Sometimes the frequency and intensity of the motor shaft movement just reach a level similar to that of a vibrating screen, so that the grease in the bearing continues to move in a certain direction, so under the centrifugal action of the bearing during the rotation of the bearing, the grease is constantly thrown out of the bearing cavity. The actual inspection process found that for the case of a large inner cavity of the bearing system, there is no good constraint on the grease being thrown out, which ultimately cannot play a lubricating effect and will hinder the heat dissipation of the bearing system.

For this problem, the following measures should be taken according to the specific situation: appropriately change the inner cavity size through the inner and outer covers of the bearing, add an oil baffle or oil throwing device, and check the positioning relationship of each bearing pivot.

 

　　Reasons for grease deterioration:

The main reason for grease deterioration is that the bearing heat is higher than the working temperature of the grease. If there is no problem with the processing and assembly accuracy of the bearing system, it may be related to the selection of grease, especially for motors running in high temperature environments. There are many other reasons for bearing heating problems, which will not be repeated here.

Bearing heating and grease degradation failure are directly related to two factors. Bearing heating to a certain extent will cause grease degradation, and grease degradation will aggravate bearing heating.

The grease running in the bearing is damaged by mechanical force, which makes the fibers of the thickener broken and shortened, reducing the ability to maintain the grease structure, that is, the viscosity changes. If the viscosity changes greatly, it will cause leakage from the working surface. At the same time, during operation, the grease will be affected by the temperature rise. Due to the colloid destruction of the grease, the base oil will evaporate or part of the base oil will be lost, which will reduce the oil content of the grease and may also cause oxidation and deterioration.

 

From the analysis of the actual operation effect of motor products, the matching relationship between bearing grease and bearing system and environmental conditions is very important. Moreover, for any motor, the cost of grease accounts for a very small proportion. The use of high-quality grease can greatly reduce bearing system failures.