Listen to the sound to judge the motor bearing problem
Listen to the sound to judge the motor bearing problem
1. Raceway sound
Raceway noise is a smooth and continuous noise generated by the rolling elements rolling in the raceway when the bearing rotates. It only attracts people's attention when the sound pressure level or tone is extremely high. In fact, the sound energy excited by the raceway sound is limited. For example, under normal circumstances, the high-quality 6203 bearing raceway sound is 25-27dB. This type of noise is most typical for single-row deep groove ball bearings bearing radial loads. It has the following characteristics: a. Noise and vibration are random; b. The vibration frequency is above 1kHz; c. No matter how the speed changes, the main frequency of the noise Almost unchanged and the sound pressure level increases with the increase of the speed; d. When the radial clearance increases, the sound pressure level increases sharply; e. The rigidity of the bearing seat increases, the lower the total sound pressure level, even if the speed increases , the total sound pressure level does not increase much; f. The higher the viscosity of the lubricant, the lower the sound pressure level, but for grease lubrication, its viscosity and the shape and size of soap fibers can affect the noise value.
The source of raceway noise is the natural vibration of the ring after being loaded. Due to the elastic contact between the ring and the rolling element, a nonlinear vibration system is formed. When the lubrication or machining accuracy is not high, the inherent vibration related to this elastic feature will be excited, and it will become noise when it is transmitted to the air. As we all know, even if the bearing parts are processed with the most advanced manufacturing technology, there will always be small geometric errors of varying degrees on the working surface, which will cause small fluctuations between the raceway and the rolling elements to excite the natural vibration of the vibration system. Although it is unavoidable, high-precision machining of the working surface of the part, correct selection of bearings and precise use of bearings can reduce noise and vibration.
2. Falling body rolling sound
Under normal circumstances, this noise mostly occurs in large bearings that are subjected to radial loads at low speeds. When the bearing is running under radial load, if the bearing has a certain radial clearance between the inner load area and the non-load area, the rolling elements in the non-load area do not contact the inner raceway, but due to the centrifugal force, they may contact the outer raceway. For this reason, at low speed, when the centrifugal force is less than the weight of the rolling body, the rolling body falls and collides with the inner raceway or cage and excites the inherent vibration and noise of the bearing, and has the following characteristics: a. Grease lubrication It is easy to produce, and it is not easy to produce when oil is lubricated. It is more likely to occur when inferior grease is used. b. Occurs frequently in winter. c. It is also easy to occur when only radial load is applied and the radial clearance is large. d. It will also be produced in a certain range and the speed range of bearings of different sizes is also different. e. It may be a continuous sound or an intermittent sound. f. The forced vibration often excites the second-order and third-order bending natural vibrations of the outer ring, thereby emitting the noise. The noise can be effectively reduced by adopting the preload method, and the radial clearance of the bearing after installation can be reduced. The selection of a good lubricant can also improve it. Some foreign companies use light rolling elements, such as ceramic rollers or hollow rollers, and other technical measures to prevent this noise.
3. Squeal
It is a fairly violent squeaking sound produced by sliding friction between metals. Although the temperature rise of the bearing is not high at this time, it has little effect on bearing life and grease life, and does not affect rotation, but the unpleasant sound is disturbing, especially Large short cylindrical roller bearings that bear radial loads often have this noise, and its characteristics are: a. It is easy to generate when the radial clearance of the bearing is large. b. Usually occurs in grease lubrication, but rare in oil lubrication. c. Decreases as the bearing size increases, and often occurs within a certain speed range. d. It often appears in winter. e. Its appearance is irregular and unpredictable, and it is related to the amount of grease filling, performance, and installation and operating conditions. This noise can be prevented by reducing the radial clearance of the bearing and adopting a shallow outer ring raceway structure.
