In the design of the reducer, gear transmission, as the main power transfer and deceleration device, is widely used in the field of mechanical industry. However, with the increasing demand for gearbox noise control, gear drive noise control has become an important part of production quality control in the design and manufacture of modern reducers. By analyzing the mechanism of noise generation in gear drive, this paper studies the causes of noise formation in gear reducers in mechanical transmission, and then puts forward corresponding noise reduction measures and treatment methods according to the causes of noise generation, so that noise reduction has a scientific theoretical basis.
In the design of industrial machinery, gear transmission is the main part of gear reducer and the main form of system power transmission, so gear, as the main role of mechanical transmission, plays an important role in the whole mechanical system, but in the past, the evaluation of gear transmission performance only focused on transmission efficiency, smoothness, reliability and so on, ignoring the problem of gear transmission noise. With the improvement of the performance quality requirements of machinery and equipment, there are also high demands on the working environment, which makes the gear drive noise problem of the reducer stand out and become an urgent problem to be solved in the mechanical transmission.
The noise generation in gear drive.
1.1 System drive error.
In gear transmission, the composition of a whole mechanical system is often more complex, the complete gearbox as a complex transmission system, in the process of force transformation, will produce up to dozens of kinds of natural frequencies, so vibration forms are various. In physics we know that sound is generated by vibration, which is generated by any system drive. In system transmission, vibration is caused by system error, which is the main cause of vibration.
1.2 Gear drive error.
The main cause of noise in gear transmission is the error of gradually opening the line or the error of adjacent pitch between gears. The vibration amplitude and vibration frequency in gear transmission are the main measures of gear noise size, which is of great significance in noise research. However, the mechanical response of the gear system is very complex in practice, so the natural frequency of the system can be changed by adjusting the excitation. In summary, gear drive errors are the perturbation factors that act on the gears and the entire system and cause them to respond, resulting in noise spreading outwards through the air.
Analysis of the causes of noise in the mechanical drive of the gear reducer.
2.1 Parameter factors.
(1) Gear accuracy. Gear accuracy is an important measure of its design and processing quality, and high-precision gears run smoothly during mechanical transmission, producing less noise. However, in the actual tooth design and processing, for economic reasons, in order to reduce costs, designers often meet the basic strength requirements of the lower limit of the selection of low-precision gear grade, so ignored the accuracy level, low-precision gear noise and side gap as the main factor, resulting in increased noise. (2) Gear width. In the design range allowed by the gear drive, increase the width of the edging gear teeth as much as possible, which can increase the contact area, not only can improve the gear load capacity, but also improve the smoothness of the gear tooth drive, reduce vibration, to achieve the goal of reducing noise. (3) Pitch and pressure angle. Reducing the pitch within the appropriate range increases the number of teeth engaged and increases the re-engagement of the teeth, thereby reducing the deflection of the meshing gear, improving transmission efficiency and reducing noise generation. In addition, the smaller pressure angle can make the gear contact angle and lateral re-integration degree increase, so that the transmission is stable, reduce noise, improve transmission accuracy.
2.2 Accuracy factor.
(1) Meshing smoothness accuracy. The working smoothness accuracy accuracy of the gear refers to the change requirement of the gear instantaneous speed ratio in the gear drive. Corner errors occur multiple times during a week’s gear rotation, and changes in the momentary transmission ratio during gear meshing cause the gear to produce multiple impacts to form vibrations, which causes the gear to produce noise during transmission.
(2) Gear contact accuracy. Gear contact speckle size is the main index to evaluate the accuracy of gear contact, contact spot too small will inevitably cause gear transmission noise increase. The low gear contact accuracy is due to the tooth directional error affecting the lateral contact area of the teeth, while the gear tooth base joint deviation and profile error will affect the lateral contact area of the teeth.
(3) Gear motion accuracy. The motion accuracy of the gear mainly shows the accuracy of the motion transmission, that is, the large limit of the angle error of the gear after engaging in a cycle. The cumulative inter-tooth error of the gear ring radial beating during the rotation of the gear for one week produces low frequency noise, especially when the inter-tooth accumulative error increases gradually, which causes an impact when the gear engages, resulting in a change in ad angle speed, resulting in a significant increase in noise.
2.3 Assembly factor.
(1) The gear axial assembly gap is too small. If the gear does not remove its burrs in time before assembly, it will cause damage to the joint face between the gear end face and the front and rear cover during meshing, resulting in reduced gear motion accuracy and noise.
(2) Miscellaneous effects. Gearbox due to the entry of debris, resulting in increased wear between the teeth, gear in the rotation process of the smoothness of the reduction, not only reduce the efficiency of gear transmission, but also make noise increase.
Noise reduction measures for gear reducers in mechanical transmission.
3.1 The parameters of the gears are reasonably optimized.
(1) Increase the spiral angle of the active gear appropriately. Because when the helix angle increases, the gear re-fit increases, which greatly reduces the noise. Then, when the helix angle is too large, it will lead to poor gear processing and installation operability, the installation accuracy requirements are very high, if the accuracy is not achieved, it will make the actual re-engagement degree smaller, its noise reduction effect is worse than when the helix angle is smaller, so choose the appropriate spiral angle.
(2) Increase the width of the edging gear flank. An appropriate increase in tooth width will increase the rodentness of the teeth, thus enhancing the smoothness of the teeth drive. Therefore, the larger the tooth width of the gear, the better its smoothness, the better the noise reduction effect.
(3) Improve gear accuracy. The improvement of gear accuracy will greatly improve the roughness of the surface of the teeth, thus improving the motion accuracy of the gear and effectively reducing noise.
3.2 Reasonable selection of flank hardness, gear side gap Through experiments can be concluded: usually the module gear side gap is less than 0.04mm, the noise is low. Therefore, the proper reduction of gear side gaps within the design allows can reduce noise. In addition, with the same material and precision, the soft flank is 1.5-6dB less than the hard flank noise, and C is taken when the active gear hardness is 2-3HBC higher than the edging gear hardness, which can effectively reduce the noise.
3.3 Special treatment of the flanks If the gear strength design permits, gear machining may be made of high damping cast iron or some non-metallic materials, or it may be treated by coating the flanks with non-metallic materials. Because the selection of materials with good plasticity and toughness can reduce gear engagement force and thing line impact, by reducing vibration and impact methods, can effectively reduce noise.
3.4 Improved gear lubrication conditions The lubrication of the gears is based on the circular speed of the gears to select the appropriate lubrication method and lubricant, so that the noise can be effectively reduced. Therefore, depending on the decelerator and the difference in working conditions to choose the appropriate lubrication method and lubricant. In addition, for decelerators operating at high temperatures, only through the oil tank lubrication will not meet the moisturizing and requirements, so combined with circulating oil lubrication and other means of lubrication.
3.5 Reasonable design of the gearbox box structure In the process of gearbox design of the gearbox, a reasonable box structure can increase the sealing of the gear transmission box, so that it has a good noise reduction effect. Therefore, the gear is designed with a closed structure as far as possible, while the box is combined to install a shock-reducing device, while the decelerator is mounted on a fixed seat or support, using these methods can effectively reduce noise. In addition, in the case of high noise requirements for the reducer, a damping material layer, such as foam, can be set up on the surface of the box to reduce the noise of the reducer.
In this paper, by studying the motion of gear drive noise generation, the causes of noise in the process of gear transmission of reducers are analyzed, and the corresponding noise reduction method is proposed. However, with the improvement of people’s living standards and the increasing demand for noise control, the research on reducer noise reduction needs to be further deepened in order to find more effective methods for reducing noise.