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ChangSha lkerui gear machinery CO.,LTD.

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The main causes and Countermeasures of gear transmission noise

The main causes and Countermeasures of gear transmission noise

Release time:
2018/10/10
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Traditionally, the two main factors to evaluate the performance of gear transmission are load capacity and fatigue life, which often neglect the transmission noise and transmission accuracy. With the promulgation of ISO14000 and ISO18000 standards, the importance of controlling gear transmission noise is becoming more and more obvious. The requirements of industrial development and demand for transmission errors of high-precision equipment are becoming more and more strict (gear transmission backlash). The known factors of gear noise can be analyzed from design, manufacture, installation, use and maintenance.
Design reasons and Countermeasures
1. gear accuracy rating
In the design of gear transmission system, the designer often takes economic factors into consideration and determines the gear accuracy level as economically as possible. Little is known that the accuracy level is the mark of gear noise level and backlash. Through extensive gear research, the American Gear Manufacturing Association has determined that high-precision grade gears produce much less noise than low-precision grade gears. Therefore, when conditions permit, it is necessary to improve the gear accuracy level as far as possible to reduce gear noise and transmission error.
2. gear width
When the gear transmission system is allowed, increasing the tooth width can reduce the unit load under constant torque. Reduce gear deflection, reduce noise excitation, thereby reducing transmission noise. According to the study of H Paz, Germany, the small tooth width is higher than the big tooth width noise curve when the torque is constant. At the same time, increasing the tooth width can increase the bearing capacity of the gear.
3. pitch and pressure angle
Small pitch can ensure that more teeth contact at the same time, gear overlap increases, reduce single gear flexure, reduce transmission noise, improve transmission accuracy. Because the contact angle and the lateral overlap ratio of gears are relatively large, the smaller pressure angle has the advantages of low noise and high accuracy.
4. speed of operation
According to the test results of H in Germany, the noise level increased as gear speed increased.
5. gear box structure
The test results show that the cylindrical gearbox is advantageous to shock absorption. Under the same other conditions, the noise level of the common structure gearbox is 6 dB higher than that of the cylindrical gearbox on average. By testing the resonance of the gearbox, finding out the resonance position and adding proper ribs (plates), the vibration and noise can be reduced obviously. In multi-stage gear transmission, the change of instantaneous transmission ratio is required to be as small as possible, which ensures stable transmission, low impact and vibration, and low noise.
Analysis of sound radiation characteristics of 6. gears
When choosing gears with different structural forms, the acoustic radiation model of the specific structure is established, and the dynamic analysis is carried out to evaluate the noise of the gear transmission system in advance. In order to meet the different requirements of users (use site, whether no one operates, whether in the urban area, whether there are specific requirements of ground and underground buildings, whether there is noise protection, or no other specific requirements) to meet.
Manufacturing causes and Countermeasures
1. error effect
Tooth error, pitch error and tooth orientation error are the main errors in the manufacturing process. It is also a difficult point to ensure the accuracy of gear transmission.
Under the same test condition, the noise of gear with small profile error and small surface roughness is 10 dB lower than that of common gear. Under the same test conditions, the noise level of gear with small pitch error is 6 to 12dB smaller than that of ordinary gear. However, if the pitch error exists, the influence of load on gear noise will be reduced.
Tooth alignment error will lead to transmission power is not full tooth width transmission, contact area steering gear face or that end face, due to local force increases the tooth flexure, resulting in higher noise level. However, when the load is high, the tooth deformation can partly compensate for the tooth error.
The generation of gear noise is directly related to the transmission accuracy.
2. concentricity and dynamic balancing of assemblies
The misalignment of the assembly will lead to the unbalanced operation of the shafting, and the noise will be aggravated because of the loose and tight half of the teeth engagement. The imbalance of high precision gear transmission assembly will seriously affect the accuracy of transmission system.
3. tooth hardness
With the development of gear hard tooth surface technology, its large bearing capacity, small volume, light weight, high transmission accuracy and other characteristics make it increasingly widely used in the field. But the carburizing and hardening used to obtain the hard tooth surface causes the deformation of the gear, which results in the increase of the noise of the gear transmission and the shortening of the service life. In order to reduce noise, we need to finish machining the tooth surface. At present, in addition to the traditional grinding method, a hard tooth surface scraping method has been developed. By modifying the tooth top and root, or adjusting the tooth profile of the active and passive wheels, the impact of the gear in and out of the gear can be reduced, thus reducing the noise of gear transmission.
4. system index verification
The machining precision of parts before assembly and the selection method of parts (complete interchange, grouping selection, single part selection, etc.) will affect the accuracy level of the system after assembly, and the noise level is also within the influence range. Therefore, after assembly, the system indicators are checked (or calibrated), and the noise of the control system is also affected. Sound is very important.