What factors will affect the noise of gear transmission

Influence of gear type on noise
Different types of gears will have different meshing processes due to their different geometric characteristics. For example, under the condition of the same load and speed, through many application cases, it can be found that the noise of helical gear can be 3~10dB lower than that of spur gear;

Influence of pressure angle on gear noise
In order to transmit a certain power, it is necessary to keep F as a fixed value. If the pressure angle a is increased, the normal force Fn on the tooth surface must be increased, which will increase the pitch line impulse and meshing impulse on the actual tooth surface with friction, thus leading to the increase of vibration and noise level. Although the gear center distance error does not affect the accurate meshing of the involute tooth profile, its change causes the periodic change of the working pressure angle. For example, the eccentricity of the gear on the shaft will be changed from the rotation frequency of the gear to the variable center distance, which will inevitably modulate the frequency of the vibration and noise of the gear transmission. The amplitude of the modulation will depend on the magnitude of the eccentricity.

Influence of coincidence on gear noise
The gear teeth change in different degrees when transferring load. In this way, the meshing impulse along the direction of the meshing line will be generated at the moment of entering and disengaging, resulting in torsional vibration and noise.

If the instantaneous average number of teeth is increased, that is, the coincidence degree is increased, the load can be distributed on more teeth, so that the unit pressure on the tooth surface is reduced, thus reducing the deformation of the gear teeth, improving the impact when entering and disengaging, and thus reducing the torsional vibration and noise of the gear transmission. It can be seen from some application cases that when the coincidence ratio increases from 1.19 to 2.07, the noise will be reduced by 4dB at 1000rpm and 6dB at 2000rpm.

For helical gears, the helical angle can be changed β And tooth width b, which can greatly exceed the spur gear, but the helix angle should not be too large, otherwise it will cause axial vibration. Increasing the number of teeth, increasing the coefficient of addendum height or reducing the pressure angle can increase the coincidence, reduce vibration and reduce noise.

Influence of gear accuracy on noise
Gear noise is greatly affected by gear accuracy. An important step to reduce gear noise is to improve gear accuracy. For gears with extremely low accuracy, any other noise reduction measures will often encounter a futile situation. Among the single errors, the most influential factors are the tooth pitch (base pitch or circumferential pitch) and tooth shape:

1. Tooth pitch:
The noise increases or decreases in direct proportion to the base pitch error. When the speed increases or the load increases, the gradient of noise increase or decrease will also increase. Moreover, even if there is a large pitch error in the gear rotation, the noise will also increase significantly.

2. Tooth shape:
Just giving the size of the tooth shape error can not judge its impact on noise. The important thing is that the error shape of the tooth shape, such as the "concave" near the node, will increase the noise a lot.

3. Ring gear radial runout
Due to the modulation of sound, there are sometimes many kinds of squeals in the gear noise. Eccentricity and other factors cause continuous changes in the pitch, resulting in long-period noise related to the gear rotation frequency. The human ear is very sensitive to this, especially at high speed.

4. Tooth surface roughness
Gear error has a great impact on noise, especially in the field of high meshing frequency, the sound pressure level is quite high, which makes an unpleasant sound.

In the application of eccentric wheels and swing frames of various kinds of micro diaphragm pumps, micro water pumps, air pumps and vacuum pumps, the engineering plastics specially used for wear-resistant and silent gears of Wintone Z33 in Suzhou, compared with traditional POM materials, has better wear-resistant, fatigue resistance and soundness, which can help solve the problem that the pressure and water pressure of POM eccentric wheels and swing frames change greatly due to wear after a period of time, As well as the problem that the POM eccentric wheel is easy to wear and be punctured after a period of time, the eccentric wheel and swing frame of Z33 material can help reduce the transmission noise at the same time. In addition, the excellent chemical resistance of Z33 material, such as acid and alkali resistance, hot water and steam resistance, salt water resistance, has also greatly broadened the application scenarios of micro diaphragm pumps and various types of micro pumps.

In the application of various types of plastic gears for reduction motors, the Wintone Z33 wear-resistant and silent gear special engineering plastics of Suzhou Weiben Engineering Plastics can help you solve the following problems:

1. The noise of POM and PA66 gears is relatively large, and the wear resistance and fatigue resistance are not enough.

2. The PA12 and TPEE gears are too soft, too small torque, and not enough wear resistance. When the temperature is above 60 ℃, the torque drops quickly.

3. The corrosion resistance of POM and PA66 gears is not enough, as well as the problem of broken teeth. POM gears and injection molded parts are prone to wear and pulverization.

4. The noise reduction of nylon 46 gear is not enough, and its size is greatly affected by moisture.

As a strong and wear-resistant engineering plastic, Z33 material has the most obvious characteristics in gear application: wear resistance, silence, corrosion resistance, strong and tough, and is not affected by moisture. Typical successful applications of Z33 materials are: miniature reduction gear box, electric push rod, EPS gear of automobile steering system, massager gear, gasoline engine cam, middle motor gear of electric bicycle, electric shaver and other transmission gears.

Sources of noise from reduction gearbox
1. The vibration speed of gear is too fast
The gear running vibration speed is too fast, which is mainly caused by too fast vibration frequency between gears caused by too fast frequency in gear transmission. The high speed of vibration in gear operation will affect the vibration frequency and generate noise.

2. Variable gear vibration caused by load impact
Here, the gear transmission is regarded as a vibrating spring system, and the gear naturally becomes a part of this system. When the gear is subjected to different degrees of load, the frequency of vibration and the direction of torsion will also be different, and most of them will form a circumferential vibration force. Coupled with the problem of the gear itself in dealing with noise, it will form a smooth and not screaming noise.

3. Noise generated by resonance
Everyone knows that resonance can produce noise. As the main way of working in the production room, gear transmission will naturally produce resonance in operation. The resonance caused by gear transmission is based on the vibration caused by the rigidity difference of the gear itself and the vibration caused by the friction between the gears at the same vibration frequency. At this time, the interaction between the two is easy to produce resonance and the noise caused by resonance.

4. The surface finish of some gears is insufficient
As we all know, if two kinds of objects are smooth, the vibration generated by friction will be small, the vibration frequency and high-frequency wave will also be small, and the noise level will also be small. However, the surface of many gears is too rough, the friction surface is large and the vibration frequency is high when they are rubbing with each other, and the noise is large and much.

5. Lack of support for correct lubrication method
In gear maintenance and noise reduction, it is not only good lubricant that can reduce the friction vibration between gears, but also good lubricant application method is an important method to reduce and reduce noise. The traditional method of using lubricant is to increase the lubricant dosage on the gear surface to reduce friction during operation, but this method has little effect on noise reduction. From the use of gear maintenance and noise reduction for lubrication in foreign countries, more attention is paid to the lubrication method, that is, the method of fully injecting lubricant into the gear to reduce noise.

6. The material selection of gear is unreasonable
If the harder wear-resistant materials are replaced by more elastic wear-resistant materials, the noise of gear transmission can also be reduced to a certain extent. For example, in the application of plastic gears, the special engineering plastic Wintone Z33 for wear-resistant silent gears is used to replace the conventional POM. The Z33 material can help significantly reduce the noise of gear transmission while improving the wear resistance and fatigue resistance.

In the past ten years, nylon 12 or TPEE materials are often used to solve the noise problem, but when PA12 is used to solve the noise problem, another situation arises: the torque that PA12 and TPEE gears can bear is much smaller than that of POM gears. When the motor temperature is higher than 60 ℃, the torque drops too fast, and the cost of PA12 is too high, which also limits some applications. Compared with nylon 12, the special engineering plastic Z33 for wear-resistant silent gear has improved its wear resistance and fatigue resistance, as well as its rigidity, toughness and vibration absorption. In many application cases of small and micro reduction motor gear boxes and planetary gear boxes, the gear molded from Z33 material has better mute effect than nylon 12 gear. Another point is very important. In terms of cost control, Z33 material has advantages over PA12 and TPEE of many specifications.

Source: Wikipedia