1. Rolling track sound

Raceway sound is a steady and continuous noise generated by the rolling body in the raceway when the bearing is rotating. Only when the sound pressure level or tone is very high, people will pay attention to it. In fact, the sound energy excited by raceway sound is limited. For example, under normal circumstances, the raceway sound of high quality 6203 bearings is 25 ~ 27dB. This kind of noise is most typical of single row deep groove ball bearing bearing radial load

It has the following characteristics:

1) Noise and vibration have randomness;

2) The vibration frequency is above 1kHz;

3) No matter how the speed changes, the main frequency of noise is almost unchanged while the SPL increases with the increase of the speed.

4) When the radial clearance increases, the SPL increases sharply;

5) As the rigidity of the bearing seat increases, the lower the SPL is, even if the speed increases, the SPL does not increase much;

6) The higher the lubricant viscosity, the lower the SPL, but for grease lubrication, its viscosity and the shape and size of soap fiber can affect the noise value. The source of raceway sound is the natural vibration of the ring after being loaded. The nonlinear vibration system is formed by the elastic contact between the ring and the rolling body. When the lubrication or machining accuracy is not high, it will excite the natural vibration related to the elastic characteristics, which will become noise when transmitted to the air.

As we all know, even if the most advanced manufacturing technology is used to process bearing parts, there will always be small geometric errors of varying degrees on the working surface, so as to generate small fluctuations between the raceway and the rolling body to stimulate the inherent vibration of the vibration system. Although it is inevitable, it can take high precision machining parts of the working surface, the correct selection of bearings and accurate use of bearings to reduce noise and vibration.

2, falling rolling sound

The noise generally occurs in large bearings bearing radial load at low speed. When the bearing runs under radial load, the load zone and the non-load zone in the bearing, if the bearing has a certain radial clearance, the rolling body in the non-load zone does not contact the inner raceway, but may contact the outer ring due to the centrifugal force. Therefore, at low speed, when the centrifugal force is less than the dead weight of the rolling body, The roller will fall down and collide with the inner raceway or cage and excite the inherent vibration and noise of the bearing

It has the following characteristics:

1) Easy to produce when grease lubrication, oil lubrication is not easy to produce. More likely to occur when using inferior grease.

2) It often happens in winter.

3) It is also easy to produce when only radial load is applied and radial clearance is large.

4) The speed range of bearings of different sizes is also different in a specific range.

5) The sound may be continuous or intermittent.

The forced vibration usually excites the second and third order bending natural vibration of the outer ring, thus producing the noise. By using the pre-load method can effectively reduce the noise, reduce the radial clearance of bearing after installation, the selection of good lubricant can also be improved, some foreign enterprises use light rolling body, such as ceramic roller or hollow roller and other technical measures to prevent the generation of this noise.

3. Screech

It is the sliding friction between metals produce quite intense screams, although the bearing temperature rise is not high at this time, bearing life and grease life does not have much impact, also does not affect rotation, but the unpleasant sound is disturbing, especially under the radial load of large short cylindrical roller bearings often have this noise

Its characteristics are:

1) It is easy to occur when the radial clearance of bearing is large.

2) Usually occurs in grease lubrication, oil lubrication is more rare.

3) Decreases with the increase of bearing size, and often occurs in a certain speed range.

4) Often occurs in winter.

5) Its appearance is irregular and unpredictable, and related to the amount of filling fat and performance, installation and operation conditions. This noise can be prevented by reducing radial clearance of bearings and using shallow outer raceway structure.

4, keep the rack sound

In the process of bearing rotation, the cage’s free vibration and its collision with the rolling body or the ring will produce this noise. It may appear in all kinds of bearings, but its sound pressure level is not too high and is low frequency.

Its characteristics are:

1) Stamping cage and plastic cage can be produced.

2) Both thin oil and fat lubrication will occur.

3) It is most likely to occur when the outer ring is subjected to bending moment.

4) It is easy to appear when the radial clearance is large.

It is very difficult to eliminate cage sound completely because cage hole clearance and cage and ring clearance are unavoidable in bearing finished products. However, it can be improved by reducing assembly error and optimizing reasonable clearance and cage flow momentum.

Another cage special sound is the noise caused by self-excited vibration of the cage caused by friction between the cage and the guide surface of other bearing parts. The stamping cage of deep groove ball bearings is thin, the bending stiffness in radial and axial planes is low, and the overall stability is poor. When the bearing is rotating at high speed, it will produce self-excited vibration due to bending deformation, causing “buzzer”.

When bearing under radial load and oil under the condition of poor performance, will hear a “kacha, kacha” in the early years of the operation noise, this is mainly due to the rolling element load area after you leave, rolling body acceleration and collided with cage and noise, the crash but as the inevitable operation after a period of time will disappear.

Measures to prevent cage noise are as follows:

1. In order to ensure the stability of cage revolution movement, the ring guide mode should be adopted as far as possible and the guide surface should be fully lubricated. The structure of tapered roller bearing under high-speed working conditions should be improved, and the L-type cage guided by roller should be changed to the Z-type cage guided by ring rim.

2. When the bearing rotates at high speed, the vibration amplitude of the cage of the bearing with large pocket clearance is much greater than that of the cage with small pocket clearance, so the value of pocket clearance is particularly important. Care should be taken to minimize radial clearance. It is beneficial to reduce the noise caused by the collision or friction between the rolling body and the cage by improving the manufacturing accuracy of the cage and improving the surface quality of the cage.

3. Actively use advanced cleaning technology to effectively and thoroughly clean the products after spare parts and sets, and improve the cleanliness of bearings.

4, when the bearing under the effect of radial load, its internal only several rolling element load bearing, due to the elastic contact with ring of “spring” of supporting roller in periodic vibration produced by radial load line, the rotation center so move the vertical or horizontal direction, at the same time cause noise.

This kind of vibration is called rolling body through vibration, especially at low speed. The amplitude is related to bearing type, radial load, radial clearance and number of rolling bodies. In general, the amplitude is small, and only when the amplitude is large will the hazard be formed. Therefore, radial clearance is often reduced by reducing the radial clearance or applying appropriate preload.