Writer: Eric Bearing Limited
The nature of NSK bearing noise
For the use of bearings, noise is very common. The same applies to the low-noise bearings in NSK bearings. So why is there noise? Today I will introduce the essence to you.
1. Bearing sound and control method
Raceway sound is a kind of smooth and continuous sound produced by the rolling body rolling on the raceway surface when the bearing is running. It is a unique basic sound that occurs in all rolling bearings. The general NSK bearing sound is the raceway sound plus other sounds.
The raceway sound of the ball bearing is irregular, the frequency is above 1000Hz, its main frequency does not change with the speed, but its total sound pressure level increases with the speed. For a bearing with a loud raceway sound, the sound pressure level of the raceway sound decreases with an increase in viscosity; while for a bearing with a low raceway sound, the sound pressure level changes from decreasing when the viscosity increases to about 20 mm2/s or more To increase.
The greater the rigidity of the bearing housing, the lower the total sound pressure level of the raceway sound. If the radial clearance is too small, the total sound pressure level and main frequency of the raceway sound will increase sharply as the radial clearance decreases. The methods to control the raceway sound are: select low-noise bearings, that is, bearings with very low waviness, and carefully select the conditions of use. The sound of the raceway often affects the noise of the whole machine. Reducing the sound of the raceway can reduce the noise of the whole machine.
2. Impact sound of rolling body and its control method
Larger ball bearings or cylindrical roller bearings run at low speed under pure radial load. Due to the small centrifugal force of the rolling elements, the rolling elements in the non-loaded area will impact the cage or raceway and emit noise. But as the speed increases, this noise will disappear.
The control methods for the impact sound of rolling elements include: appropriately reducing the radial clearance, using bearings with a cage with a reasonable structure and a compliant material.
3. NSK bearing rolling sound and its control method
Rolling noise is a harsh metal friction sound that can occur in cylindrical roller bearings in all occasions. Most of them occur in larger grease-lubricated bearings, and they are more likely to occur in greases with deteriorated base oil performance. Hardly happens. In addition, it is more likely to occur in winter. When it is subjected to pure radial load, it is easy to occur in the case of large radial clearance, and depending on the size of the model, it is easy to occur within a specific speed range, which will occur continuously. Will appear intermittently again.
The outer ring raceway adopts special processing methods to prevent the occurrence of rolling noise. If necessary, this type of bearing can be used, or the radial clearance of the bearing can be appropriately reduced, the grease with excellent performance and the rigidity of the matching parts of the bearing can be improved .
Analysis of raceway noise of NSK bearings
The raceway sound is due to the rolling body rolling in the raceway when the NSK bearing rotates, which stimulates a smooth and continuous noise. Only when the sound pressure level or tone is extremely large, people pay attention. In fact, the sound energy excited by the raceway sound is limited. For example, under normal circumstances, the high-quality 6203NSK bearing raceway sound is 25 to 27dB. This kind of noise is the most typical of single row deep groove ball NSK bearings that bear radial loads. It has the following characteristics:
1. Noise and vibration are random;
2. Vibration frequency is above 1kHz;
3. No matter how the rotation speed changes, the main frequency of the noise is almost unchanged and the sound pressure level increases with the increase of the rotation speed;
4. When the radial clearance increases, the sound pressure level increases sharply;
5. The rigidity of NSK bearing seat increases, the lower the total sound pressure level, even if the speed increases, the total sound pressure level 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 NSK bearing parts are processed with the most advanced manufacturing technology in the contemporary, 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 can excite the natural vibration of the vibration system.
Although the raceway noise of NSK bearings is inevitable, it is possible to adopt high-precision machining of the work surface of the parts, and the correct selection of NSK bearings and the precise use of NSK bearings can reduce noise and vibration. NSK 6300ZZ bearings online , pls click here :
Influencing factors of NSK bearing vibration
1. NSK bearing design parameters: including the number of NSK bearing rolling elements, ring wall thickness and clearance, etc.
2. The manufacturing error of NSK bearing parts: including the surface roughness, waviness and roundness difference of NSK bearing raceways and rolling elements. A large number of experimental studies have shown that the effect of waviness on bearing vibration is dominant, while the effects of surface roughness and roundness are relatively small.
3. Working conditions of NSK bearings: During the operation of NSK bearings, the three aspects of load, speed, and lubrication conditions have the greatest impact on bearing vibration.
4. NSK bearing installation parameters: the NSK bearing and shaft and bearing seat cooperation, installation deflection and other factors also affect the bearing vibration.
NSK bearing cleaning process
When overhauling the assembled NSK bearings, first record the appearance of the bearings, confirm the remaining amount of smoothing agent, and clean the bearings after sampling. The cleaning agent widely uses gasoline and kerosene. The removed bearing is divided into coarse washing and fine washing. Put the metal mesh in the container first so that the bearing does not directly contact the dirt in the container.
During rough washing, if the bearing rotates with dirt, it will damage the NSK bearing rolling surface, and it should be paid attention to. In the coarse washing oil, use a brush to come in smooth grease and stickies. After the foundation is clean, transfer to fine washing. Fine washing is to carefully wash the bearings while rotating in the cleaning oil. In addition, the cleaning oil should be changed frequently to maintain clean.