Some Factors That Affect The Noise of Plastic Gear Transmission

Effect of the gear type on the noise

Different types of gears, due to their different geometric characteristics, will have different forms of engagement processes. For example, under the condition of the same load and speed, many application cases can be found that the noise of inclined gear is 3~10dB lower than that of straight gear;

Effect of pressure angle on gear noise

In order to transfer a certain power, F is a fixed value. If the pressure Angle a is increased, the normal force of the tooth surface increases Fn, which will increase the joint impact force and engagement force in the actual tooth surface with friction force, thus increasing the vibration and noise level. Although the distance error of gear center does not affect the accurate engagement of involute tooth shape, the change causes the periodic change of working pressure angle. For example, the eccentricity of the gear on the shaft changes the rotation frequency of the gear to the center distance, which will inevitably adjust the vibration and noise frequency of the gear drive, and the amplitude of the modulation will depend on the size of the eccentricity.

The influence of the coincidence degree on the gear noise

The wheel teeth vary to varying degrees when transferring the load. At the moment of entering and engagement, causing torsional vibration and noise.

If the average number of teeth in the moment is increased, that is, the coincidence degree is increased, the load can be distributed to more teeth to reduce the unit pressure of the tooth surface, thus reducing the deformation of the wheel teeth, improving the impact situation when entering and leaving the engagement, and thus the torsional vibration and noise of the gear drive are also reduced. As can be seen in the application case, when the coincidence degree increases from 1.19 to 2.07, the noise is reduced by 4dB at 1000rpm, while the noise is reduced by 6dB at 2000rpm.

For the inclined gear, the coincidence degree can be increased by changing the spiral angle β and the tooth width b, and can greatly exceed the straight gear, but the spiral Angle should not be too large, otherwise cause axial vibration. Increasing the number of teeth, the high coefficient of large teeth or reducing the pressure Angle can increase the coincidence degree, reduce vibration and reduce noise.

The influence of the gear accuracy on the noise

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

1. Dated distance:

Noise and the base section error is directly proportional to the increase and decrease, when the speed increases or the load increases, the gradient of noise increase and decrease also increases, and in the gear turn, even if there is a large gear error, the noise also increases significantly.

2. Dentate:

Only give the size of the tooth shape error, and can not judge the impact on the noise, the important thing is the error shape of the tooth shape, such as the "concave" near the node, will increase the noise a lot.

3. Radial beating of the tooth ring

Due to the modulation of sound, sometimes produced in the gear noise, eccentric and other causes the continuous changes of the weekly section, resulting in the long cycle 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 this field of high engagement frequency, where the sound pressure level is quite high and unpleasant sounds occur.

In the application of electric baby rocking chair and electric rocking machine reduction gear box first stage plastic gear, as well as all kinds of reduction gear box plastic gear, we can help you solve the following problems:

1. POM and PA66 gear noise is relatively large, fatigue resistance is not enough, POM gear easy to break tooth problem.

2.PA12 and TPEE gear, too soft torque is too small, wear resistance is not enough, above 60 degrees Celsius, the torque drops faster.

3. The corrosion resistance of POM and PA66 gear is not enough, and POM gear and injection functional parts are easy to wear powder.

4. The noise reduction of nylon 46 gear is not enough, and the size is greatly affected by the water. Z33 material as a strong wear-resistant engineering plastic, the most significant characteristics in the gear application are: wear resistance, silent, corrosion resistance, strong and not affected by water. The typical successful application of Z33 materials is: micro-small deceleration gearbox, electric pushrod, automotive steering system EPS gear, massager gear, gasoline machine cam, electric power bicycle middle motor gear, electric razor and other transmission gears.

The source of noise from the deceleration gearbox

1. Gear operation and vibration speed is too fast

The vibration speed of the gear operation is too fast, mainly because the frequency is too fast in the gear transmission, and the vibration frequency between the gears is too fast. The fast vibration speed in gear operation will affect the frequency of vibration and produce noise.

2. Fixed gear vibration caused by load impact

The gear drive is regarded as a vibration spring system here, and the gear naturally becomes a part of the system. When the gear is subjected to different degrees of load, the frequency of vibration and the direction of torsion will be different, most of which will form the vibration force in the circular direction. Add the gear itself with the noise, creating a smooth without screaming noise.

3. Resonant noise

Resonance can produce noise is everyone knows, gear transmission as the main way of working in the production room, naturally will also appear resonance in operation. The resonance brought by the gear transmission is based on the vibration generated by the rigidity difference of the gear itself and the vibration generated 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 brought by the resonance occurs.

4. Insufficient surface finish of some gears

As is well know, if the two objects are smooth, then the vibration generated during friction is small, vibration frequency and high frequency wave will be small, the noise degree is naturally small. However, a lot of gear surface is too rough, friction surface, vibration frequency is high, the noise is large and more.

5. Lack of correct lubrication method support

In gear maintenance and noise reduction, not only good lubricant can reduce the friction vibration between gears, good lubricant is also an important way to reduce and reduce noise. The traditional method of lubricant is to increase the dose of lubricant on the gear surface to reduce friction in operation, but this method has little effect on noise reduction. With the use of gear maintenance and noise reduction on lubrication in foreign countries, more attention is paid to the lubrication method, that is, the method of lubricant fully injected into the gear to reduce noise.

6. The material selection of the gear is not reasonable

If using more elastic wear-resistant materials instead of hard wear-resistant materials, to a certain extent, can also reduce the noise of gear transmission, such as in plastic gear applications, with wear-resistant silent gear special engineering plastic Wintone Z33 instead of conventional POM, Z33 materials in improving wear resistance fatigue resistance at the same time, can help greatly reduce the noise of gear transmission.

We in the past decade, solve the problem of noise tend to use nylon 12 or TPEE material, but in using PA12 to solve the problem of noise at the same time, another situation appeared, PA12 and TPEE gear can withstand torque is much smaller than POM gear, motor temperature is higher than 60 degrees Celsius, torque drop and too fast, and is the cost of PA12 is too high, also limited part of the application. Compared with nylon 12, Z33 improves the fatigue resistance at the same time, rigidity, toughness and vibration absorption compared with nylon 12. In many application cases of small miniature deceleration motor gearbox and planetary gearbox, Z33 material

In the application of the first stage plastic planetary gear and the second level plastic planetary gear, it can help you solve the traditional POM, nylon and soft rubber TPEE materials in large torque, low noise and good wear and fatigue resistance.