Listen to the sound, judge the motor bearing problem

Generally, there are many mechanical faults, most of which are serious bearing wear, lack of oil, etc. It can be judged that the bearing makes a sound when it is running. It can be distinguished by carefully listening to the bearing position of the front and rear end covers of the motor.

Raceway sound
Raceway noise is a kind of steady and continuous noise caused by the rolling of rolling element in raceway when the bearing rotates. People pay attention to it only when its sound pressure level or tone is extremely high. In fact, the sound energy excited by raceway sound is limited. For example, under normal conditions, the raceway sound of 6203 bearing with high quality is 25-27db. This kind of noise is most typical of single row deep groove ball bearing under radial load. It has the following characteristics: a. the noise and vibration are random; B. the vibration frequency is above 1kHz; C. No matter how the rotating speed changes, the main frequency of noise is almost unchanged, but the sound pressure level increases with the increasing of rotating speed; D. when the radial clearance increases, the sound pressure level increases sharply; e. the rigidity of bearing seat increases, and the total sound pressure level increases F. the higher the lubricant viscosity is, the lower the sound pressure level is. But for grease lubrication, the viscosity and the shape of soap fiber can affect the noise value.
The sound source of raceway is the natural vibration of the ring under load. The elastic contact between the ring and the rolling element constitutes a nonlinear vibration system. When the lubrication or machining accuracy is not high, the natural vibration related to this elastic feature will be excited, and it will become noise when it is transferred to the air. As we all know, even if the most advanced manufacturing technology is used to process the bearing parts, there will always be small geometric errors of different degrees on the working surface, which will cause small fluctuations between the raceway and the rolling element and stimulate the natural vibration of the vibration system. Although it is inevitable, we can adopt high-precision machining parts working surface, correct selection of bearings and accurate use of bearings to reduce noise and vibration.
Falling rolling sound
In general, the noise mostly appears in the large bearings with low speed and bearing radial load. When the bearing is running under radial load, if the bearing has a certain radial clearance between the load area and the non load area, the rolling element in the non load area will not contact with the inner raceway, but it may contact with the outer ring due to the centrifugal force. Therefore, at low speed, when the centrifugal force is less than the weight of the rolling element, the rolling element will fall down and collide with the inner raceway or cage, which will stimulate the fixation of the bearing There are vibration and noise, and have the following characteristics: A. grease lubrication is easy to produce, oil lubrication is not easy to produce. It is easier to produce when using inferior grease. b. It often happens in winter. c. When the radial load is applied only and the radial clearance is large, it is also easy to occur. d. In a certain range, there will be different bearing sizes with different speed range. e. It may be continuous or intermittent. f. The forced vibration often excites the second-order and third-order bending natural vibration of the outer ring. By using preloading method, the noise can be effectively reduced, the radial clearance of the bearing after installation can be reduced, and the selection of good lubricant can also be improved. Some foreign enterprises use light rolling elements, such as ceramic roller or hollow roller, to prevent the noise.
Chirp
Although the temperature rise of the bearing is not high at this time, it has little effect on the bearing life and grease life, and does not affect the rotation, but the unpleasant sound is disturbing, especially for the large short cylindrical roller bearing bearing bearing under radial load. Its characteristics are: A. It is easy to produce when the bearing radial clearance is large. b. It usually occurs in grease lubrication, but oil lubrication is rare. c. It decreases with the increase of bearing size, and often occurs in a certain speed range. d. It often appears in winter. e. Its appearance is irregular and unpredictable, and it is related to the amount and performance of filling grease, installation and operation conditions. This kind of noise can be prevented by reducing the radial clearance of bearing and adopting shallow outer ring raceway structure.

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