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Gear tooth modification of transmission and its control

Mar 18, 2020

Gear tooth modification of transmission and its control


The modification of the gear teeth significantly improves the smoothness of the gear transmission, reduces the noise and vibration of the gear, and extends the service life of the gear.


This paper focuses on the modification of the shaving process and the control of the block diagram to reduce the noise.


Block diagram of gear wheel gear modification With the development of the automotive industry, various transmission manufacturers have been working hard to reduce transmission noise. As everyone knows, transmission noise is mainly generated during gear meshing operation. Due to unavoidable manufacturing and installation errors, elastic deformation of gear teeth, torsional deformation and thermal deformation, the gear will have shock and vibration during the meshing process. And eccentric load, if we only consider improving gear running quality by improving gear manufacturing and installation accuracy, it will inevitably increase gear manufacturing cost.


In order to improve product quality and reduce gear noise, our factory has carried out continuous exploration and testing, especially with overspeed transmissions. We have done a lot of work on the modification of gears, and have repaired the tops and roots of gear teeth. Edge, effectively improve the gear meshing performance, so that the transmission gear noise is effectively controlled.


The principle and characteristics of shaving teeth At present, the domestic automobile gear processing generally uses the following two processes: barrel grinding and rolling shaving. Although the grinding of teeth can improve the geometric accuracy of the gear teeth, the effect of reducing noise is not ideal, and the investment is large and the production efficiency is low. Shaving has the characteristics of low cost, high efficiency, and convenient dressing. Therefore, many manufacturers still use the shaving process. Our factory considers the actual situation of production, and most gears still use shaving. It is mainly based on the principle that relative slip will occur on the tooth surface when the staggered shaft helical gear pair works without backlash.


When the shaver is freely meshing with the gear being shaved, because the tooth surfaces of the shaver and the shaved gear are relatively sliding, the cutting edge on the shaver will shave off the remainder of the gear tooth surface to achieve cutting Purpose of processing. However, because there is no transmission chain between the shaver and the gear being shaved, it is not a forced transmission, so there will be a certain error copy, that is, the ability of the shaving tooth to correct the previous process is very limited. Generally speaking, the accuracy of shaving front teeth can only be lower than that required for shaving rear teeth. At the same time, because the precision of the teeth after shaving is affected by the deformation of the heat treatment in the future, and the conventional tooth-removing process that follows cannot improve the accuracy of the teeth after heat treatment, the modification of the shaving teeth must also take into account the modification of the heat treatment deformation shape. Only through repeated experiments and mastering a certain heat treatment deformation law can the shaving tooth shape tooth direction be corrected.


Shaving modification To shave the teeth can be modified, you must design the tooth shape and tooth direction according to the gear meshing state and heat treatment deformation. The design tooth shape is a tooth shape which is based on the involute curve and is modified by considering the influence of manufacturing errors and elastic deformation on noise, dynamic load and other factors. The design tooth direction requires a proper tolerance between the actual helix angle and the theoretical helix angle, or makes the tooth direction different from the helix angle to compensate for the helix angle distortion caused by multiple reasons of the gear teeth in the full tooth width range Therefore, the tooth width can be uniformly loaded, the gear tooth carrying capacity can be improved, and the meshing noise can be reduced.


'(The modification of the tooth profile is well known. When a pair of gears mesh, from the start of meshing to the disengagement, the load changes, especially the middle part of the gear teeth works alternately on the gear teeth, the work is not stable, so it is necessary to correct The gear teeth are modified by tooth profile. By trimming the edge and root of the tooth, the meshing of the gear teeth smoothly transitions from the repair edge area to the theoretical involute tooth shape area, thereby improving the meshing quality.


The general method of shape modification calculates the degree of coincidence of the end faces of the gear. Generally speaking, the degree of coincidence of the gear teeth after shaping should not be less than to ensure the smoothness of the gear meshing. If there is only one pair of gear teeth meshing, the coincidence degree ( , The trimming should not be performed, because in the single tooth meshing state, the deviation from the involute will only promote the occurrence of vibration. If the coincidence degree is close, the trimming edge can approach the pitch circle position, so it must be calculated The degree of coincidence of the end faces of the gears is determined according to the degree of coincidence.


According to the actual needs, the modification of the toothed gear can be the top of the pair of gear teeth, the root of the tooth, or the edge of the single gear tooth, and the root of the tooth. Each company can adjust the transmission according to the actual situation. Gear tooth modification and its control Ding Jinfu Xia Weiqiang manufacturing? Depending on the issue and needs of the material roll, the driving gear and driven gear should be treated separately. According to the principle of gear transmission, in the process of gear meshing, the driving gear is from the tooth root to the tooth top, and the driven gear must be from the tooth top to the tooth root, and the base of the driving gear should be omitted. It is larger than the base of the passive gear to prevent disengagement during meshing. The value is generally controlled within the range.


Modification amount and length Modification amount depends on the load size and accuracy, and spur gears and helical gears are also different. Relatively speaking, because helical gear transmission has more teeth pairs to participate in meshing, its repair The shape is relatively small. However, whether straight teeth or helical teeth, the amount of modification of the tooth tip and root is usually not large, and should generally be controlled between.


Block diagram design In order to facilitate the correction of the gear teeth and to better meet the needs of the design tooth profile evaluation, based on repeated tests, different tolerance zones for the top edge or root edge of the tooth are designed. The use of block diagrams can avoid disputes caused by differences in evaluation. It is easy to use, intuitive, easy to grasp, and unified in standards. It is used more abroad. In recent years, domestic companies have also begun to promote the application, thereby further promoting the improvement of manufacturing level. . Of course, when designing the block diagram, different methods must be adopted for the driving gear and driven gear according to the existing equipment conditions, processing methods and production batch sizes of the enterprise, combined with heat treatment deformation and other factors. Generally, the tooth top of the driving gear is skewed, and the pressure angle is slightly smaller, while the root of the driven gear is skewed, and the pressure angle is slightly larger. In short, the value can be determined according to different meshing states. Generally, the gear is not larger than that, which can be controlled under special circumstances. .


Calculate the effective mesh length. Calculate the base section. Assuming tooth top chamfers, the pair of gears can be modified for any reason. The second step is to calculate the amount of modification and length of the pair of gears. The extended length of the dot is the number of factors affecting the edge and the root of the tooth, and the mechanism is also very complicated. According to the relevant information and to facilitate the production of the block diagram, the tooth tip is usually repaired. According to the gear manual, the starting point of the tooth edge trimming is the starting point of the tooth root. Generally, the starting point of the trimming amount of the two gears can also be calculated. The third step follows the basic section of the active gear. The general principle is slightly larger than the base of the passive gear. The tooth top of the driving gear is slightly positive, and the tooth root of the driven gear is slightly positive. Select the appropriate tooth shape to determine the block diagram.


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