In recent years, the academic circles have made great progress in the research of helical gear modification methods. The modification effect is good, and the commonly used helical gear tooth direction modification methods include the following:

(1) Tooth end thinning

It refers to gradually thinning the tooth thickness towards the end, which can be carried out at one end of the helical gear tooth or at both ends at the same time. The shape and size are shown in Figure 1. The tooth end thinning method is simple to operate, but the trimming effect is poor. It is mostly used for single piece and small batch production.

(2) Spiral angle modification

Spiral angle modification refers to the method of adjusting its own parameters (spiral angle) to make it deviate from the theory to improve the stress. The spiral angle modification method is shown in Figure 2. Compared with tooth end thinning, the overall effect of spiral angle trimming is good. However, due to the small amount of angle trimming, it is not easy to operate and control, so it is impossible to ensure that a better effect can be obtained locally.

(3) Drum shape modification

Drum shape modification generally refers to the method of modifying the gear according to the equal radius arc to make the middle of the tooth width bulge and both ends symmetrical. The modification parameters are shown in Figure 3. The design method of the drum shaped gear modified by this method is relatively simple, easy to process, easy to control the modification quality, and easy to find problems, so it has a wide range of applications.

According to the introduction of the above three methods, the advantages and disadvantages of each method are comprehensively considered. In order to facilitate processing and practical application, the drum shape modification is the most important research.