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Effect of FAG Rolling Bearing Structure on Vibration and Noise

Source: FAG bearings  Tags: News

1.Raceway sound

Raceway sound is due to the rolling body rolling in the raceway when the bearing rotates, which stimulates a smooth and continuous noise.Only when its sound pressure level or tone is extremely large,it attracts people's attention.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 to 27dB. This kind of noise is the most typical of single row deep groove ball bearings that bear radial loads. It has the following characteristics: 

(1)Noise and vibration are random; 

(2)The vibration frequency is above 1kHz;

(3)The main frequency of noise no matter how the speed changes Almost unchanged and the sound pressure level increases with increasing speed;

(4)When the radial clearance increases,the sound pressure level increases sharply; 

(5)The rigidity of the bearing seat increases, the lower the total sound pressure level, even if the speed increases, The total sound pressure level also does not increase much;

(6)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 the soap fiber can affect the noise value. 

The source of the raceway sound is caused by the natural vibration of the ferrule after being loaded.The elastic contact between the ring and the rolling element constitutes a nonlinear vibration system. When the lubrication or processing accuracy is not high, the natural vibration related to this elastic characteristic will be excited, and it will become noise when transmitted to the air. As we all know, even if the most advanced manufacturing technology is used to process FAG bearing parts, there will always be small geometric errors of varying degrees on the working surface, so that small fluctuations between the raceway and the rolling body will excite the natural vibration of the vibration system. Although it is inevitable, high-precision machining of the work surface of parts can be adopted, the correct selection of bearings and the precise use of bearings can reduce noise and vibration. 

2.Falling rolling sound

The noise is generally found in large bearings at low speeds and subjected to radial loads.When the bearing is running under radial load, the load area and non-load area of the bearing, if the FAG bearing has a certain radial clearance,the rolling elements in the non-load area do not contact the inner raceway, but due to the effect of centrifugal force The outer ring contacts. For this reason, at low speeds, when the centrifugal force is less than the weight of the rolling element, the rolling element will fall and collide with the inner raceway or cage and excite the natural vibration and noise of the bearing, and have the following characteristics:

(1)It is easy to produce when grease lubricating, but not easy to produce when oil lubricating.It is easier to produce when using inferior grease;

(2)Winter often occurs;

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

(4)The speed range of bearings of different sizes will also be generated within a certain range;

(5)It may be continuous or intermittent;

(6)The forced vibration often excites the second-order and third-order bending natural vibrations of the outer ring, thereby emitting the noise. The preload method can effectively reduce the noise, reduce the radial clearance of FAG bearings after installation, and use good lubricants can also be improved.  ERIC BEARING are professional FAG distributor , here share our FAG bearing stock photo :


3.Squeaking sound

It is a quite screaming sound caused by sliding friction between metals. Although the temperature rise of the bearing is not high at this time, it has little effect on the life of the FAG bearing and the life of the grease, nor does it affect the rotation, but it is not pleasant. Disturbing, especially the large short cylindrical roller bearings that bear radial loads often have this noise, and their characteristics are:

(1)It is easy to produce when the radial clearance of the bearing is large;

(2)Usually appears in grease lubrication, oil lubrication is rare;

(3)As the bearing size increases, it decreases and often appears within a certain speed range;

(4)It often appears in winter ;

(5)Its appearance is irregular and unpredictable, and is related to the amount and performance of grease filling, installation and operating conditions.This noise can be prevented by reducing the radial clearance of the bearing and using a shallow outer ring raceway structure. 

4.Cage sound

The free vibration of the cage during the rotation of the FAG bearing and its collision with the rolling element or the ring will emit 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)Both stamped cages and plastic cages can be produced; 

(2)Whether it is thin oil or grease lubrication will appear;    

(3)It is most likely to occur when the outer ring is subjected to bending moments;    

(4)It is easy to appear when the radial clearance is large.Since the cage pocket clearance and the cage and ferrule clearance inevitably exist in the finished bearing, it is very difficult to completely eliminate the cage sound, but it can be improved by reducing the assembly error, preferably by reasonable clearance and cage movement. 

Another kind of special sound of the cage is the noise caused by the self-excited vibration of the cage caused by the friction between the cage and the guide surfaces of other bearing parts.The deep-groove ball bearing has a thin stamping cage, low bending stiffness in the radial and axial planes, and poor overall stability. When the bearing rotates at high speed, it will generate self-excited vibration due to bending deformation, causing "buzzing sound." .   

When the rolling bearing is under the radial load and the grease performance is poor, the noise of "click, click" will be heard at the beginning of the operation, which is mainly due to the sudden acceleration of the rolling element after the rolling element leaves the load zone The noise generated by the collision is inevitable but will disappear after a period of operation. 

The measures to prevent the cage noise are as follows: 

(1)In order to stabilize the cage's orbital motion, the ring guide method should be used as much as possible and pay attention to give sufficient lubrication to the guide surface. The tapered roller bearing structure under high-speed conditions should be improved. The sub-guided L-shaped cage is changed to the ferrule-guided Z-shaped cage; 

(2)When the FAG bearing rotates at high speed, the vibration amplitude of the cage with a large pocket clearance is much greater than the vibration with a small pocket clearance Amplitude, so the value of the pocket clearance is particularly important; 

(3)Pay attention to minimize the radial clearance; 

(4)Try to increase the manufacturing accuracy of the holding price, improve the surface quality of the cage, and help reduce the occurrence of rolling elements and cage Noise caused by collision or friction; 

(5)Actively adopt advanced cleaning technology to effectively and thoroughly clean parts and products after assembly to improve the cleanliness of rolling bearings. 

5.Rolling elements through vibration

When FAG bearings operate under radial load, there are only a few rolling elements inside to bear the load. Due to the "spring" support formed by the elastic contact with the ring, the rolling elements pass the radial load line of action Periodic vibrations are generated, and the center of the shaft will move vertically or horizontally, causing noise. This kind of vibration is called rolling element passing vibration, especially when it is running at low speed. 

The amplitude is related to the type of rolling bearing, radial load, radial clearance and the number of rolling elements.Generally, the amplitude is small, and the hazard is only formed when the amplitude is large. Therefore, it is often reduced by reducing the radial clearance or applying an appropriate preload.