The cause and countermeasure of gear transmission noise

Manufacturing reasons and countermeasures

1. Error impact

The main errors of transmission noise are the tooth shape error, tooth distance error and tooth direction error in manufacturing process. It is also a problem that the accuracy of gear transmission is difficult to ensure.
The noise of the gear with small tooth profile error and small tooth surface roughness is 10dB smaller than that of the ordinary gear under the same test conditions. The noise level of the gear with small pitch error is 6 ~ 12dB smaller than that of the ordinary gear under the same test conditions. However, if there is a pitch error, the influence of load on gear noise will be reduced.

The tooth direction error will lead to the transmission power is not the full tooth width transmission, the contact area turns to this or that end face of the tooth, due to the local force increases the tooth deflection, resulting in increased noise level. But at high load, the tooth deformation can partially compensate for the tooth orientation error.
The generation of gear noise is directly related to transmission accuracy.

2. Assembly concentricity and dynamic balance
Assembling different centers will lead to the unbalanced operation of shafting, and the noise will be aggravated because of the loose and tight tooth meshing. The unbalance of high precision gear transmission assembly will seriously affect the accuracy of the transmission system.

3. Tooth surface hardness
With the development of gear hard face technology, its characteristics of large bearing capacity, small volume, light weight and high transmission accuracy make its application field more and more extensive. However, the hardening of carburizing in order to obtain the hard tooth surface causes the gear deformation, which leads to the increase of gear transmission noise and the shortening of gear life. In order to reduce noise, the tooth surface needs to be finished. At present, in addition to the traditional grinding method, a hard tooth surface scraping method has been developed to reduce the impact of gear biting in and out by modifying the top and root of the tooth, or reducing the tooth shape of the main and passive wheels, thereby reducing the noise of gear transmission.

4. Verification of system indicators
Before assembly, the machining accuracy of the parts and the selection method of the parts (complete exchange, group selection, single selection, etc.) will affect the accuracy level of the system after assembly, and the noise level is also within the influence range. Therefore, the verification (or calibration) of the system indicators after assembly is crucial to control the system noise.

Source: Sound House