Effective methods to reduce gear transmission noise
Gear drive has a wide range of applications in various machinery. It has many advantages compared with belt drive, chain drive, worm gear drive and so on. For example, the transmission speed range is wide, the transmission power is large, the transmission is reliable, the structure is compact, the life is long, and the constant instantaneous transmission ratio can be guaranteed, but one of its disadvantages is the noise. So, how to effectively reduce the noise of gear transmission.  
1. Select materials
Gear materials are generally carbon steel, forged steel, cast steel, cast iron and non-metallic materials (such as nylon, cloth plastic). In order to reduce the noise of gear transmission, in some occasions where the strength requirements are not high, non-metallic materials can be boldly used as the preferred gear material. Especially with the gradual deepening of the research and development of non-metallic materials by scientific and technological workers in China, the strength and accuracy of parts manufactured with non-metallic materials will gradually improve, and it will be more and more favored by mechanical design workers. At the same time, it can also be in a pair of meshing gears, one gear is made of non-metallic material, and the other gear is still made of metal material. Generally, non-metallic materials are used for small gears, and metal materials are used for large gears, which can reduce the noise of gear transmission.
Second, select the parameters of the gear When selecting the parameters of the gear, it should be conducive to reducing the noise of the gear transmission. When selecting the number of teeth of the gear, the number of teeth should be better. That is, after the center distance is determined, the modulus is reduced as far as possible under the premise of meeting the bending fatigue strength. Because d=mz, when the index circle diameter d of the gear is fixed, the smaller the modulus m, the more the number of teeth z, the more the overlap coefficient is increased, thus reducing the noise of the gear transmission. At the same time, due to the reduction of the modulus, the processing cost of the gear will also be reduced. On the other hand, when the gear module cannot be reduced, the helical gear should be considered first, which can also increase the overlap coefficient and reduce the noise of gear transmission. In the helical gear transmission, the choice of helix Angle is very high, because the helix Angle is small, does not reflect the advantages of helical gear transmission, and the larger the helix Angle, the corresponding increase in axial force, so the helix Angle is generally required between 8° and 20°. In practical applications, under the condition of small transmission power, the spiral Angle can be slightly greater than 16°, so that the effect of reducing noise is more obvious, and can not cause a large temperature rise (because the spiral Angle is large, the axial force increases, which will increase the idle work and produce high temperature). Thirdly, China's standard pressure Angle α=20° for gear transmission for general use, but for high-speed gear transmission with a coincidence coefficient close to 2, it is recommended to use a gear with a crest height coefficient of 1 ~ 1.2 and a pressure Angle of 16° ~ 18°, which can increase the flexibility of the gear teeth and reduce the noise of gear transmission.
3. Structural aspects
Gear as far as possible to avoid the use of solid structure, but should be designed into a web structure. That is, as long as the strength meets the requirements, the gear should reduce the weight as much as possible. This can reduce the natural frequency of the gear, thus reducing the noise of the mesh.
Iv. Assembly
Assembly quality has great influence on gear transmission noise. The assembly of the left and right rotating gears produced by the same machine tool will help to reduce the meshing noise of the gears. Before assembly, special attention should be paid to cleaning the burrs on the end face of the gear first, because the end face burrs directly produce noise in the process of meshing, and if conditions are available, the tooth profile can be interspaced to reduce noise.