The driven spiral bevel gear of automobile rear axle is an important part of automobile main reducer. At first, in the 1980s when the rolling technology was not fully developed, most domestic factories forged this part by the following three methods:
① Firstly, the blank is made by air hammer and then forged by friction press;
② Die forging hammer forging;
③ Hot die forging press forming.
However, these three methods have disadvantages such as high equipment investment cost and material consumption. First air hammer blank making and then ring rolling machine forming are developed. This production process has a good effect of reducing energy consumption and saving materials. Different from the original production process of driven spiral bevel gear blank, rolling is a forming technology in which local pressure accumulates deformation and finally realizes integral forming. Therefore, the deformation force of blank in the forming process is small, which greatly eliminates vibration and noise pollution and improves the working environment of the factory. According to the production verification of a gear factory, the original fetal film forging process for the production of rear axle driven bevel gear blank takes about 6 minutes / piece, while the new ring rolling process only takes about 30 seconds / piece, which greatly improves the production efficiency. The new technological process of rolling blank of driven bevel gear of automobile rear axle is as follows: bar blanking of band saw, heating of induction furnace, air hammer upsetting, punching and sizing, rolling forming of rolling machine – die forging of die forging machine.
At present, many scholars have conducted in-depth research on this technology. Wang Aizhen compares the advantages and disadvantages of the traditional forming process of spiral bevel gear blank with the ring rolling forming process. It is concluded that the traditional open and closed die forging process has the disadvantages of machine noise, high material cost and low material utilization rate, while the ring rolling forming process has the advantages of good working environment, high material utilization rate and small equipment tonnage. Song Jinsheng compared and studied the process of forging process and ring rolling process to produce driven spiral bevel gear blank. Through comparison, it was found that ring rolling process can save energy and materials, shorten product production time, improve productivity, improve production environment and improve die service life. At the same time, he also pointed out that there are two key problems worthy of attention in the ring rolling process: the dimensional accuracy of the preform, that is, the thickness of the preform and the coaxiality of the outer circle and inner hole of the preform. Taking the driven spiral bevel gear of an automobile rear axle as an example, Hualin et al. Studied several key problems in the ring rolling process. In terms of blank design and manufacturing, the inclination design of the inner hole bottom surface of ring rolling blank can avoid the occurrence of tensile crack and warpage during ring rolling; In terms of rolling pass design, the cross-section shape of rolling pass determines the shape of forgings. A reasonable blank can produce rings that meet the requirements of all aspects through one pass; In terms of process operation, blank heating and ring rolling feed speed have a great impact on the quality and accuracy of formed forgings. Zhu Chundong and others improved the forming process of spiral bevel gear blank and optimized the preform before ring rolling. It is proved that the preform before ring rolling is calibrated by the shape calibration die with an inclination of 45 °. The results show that the preform obtained by such mold inclination has very small flash and good quality. Cao Jianguo and others analyzed the causes of basin tooth blank flash in the ring rolling forming process, and pointed out two methods to improve the blank accuracy, that is, by expanding the inner hole of the reaming step and finishing the blank after ring rolling, which can reduce the working margin of the subsequent machining process. Zhu Chundong et al. Established a mathematical model and carried out digital control of forming size in the measurement and control system of rolling machine, which is a new method to control the rolling size of spiral bevel gear blank of automobile rear axle basin.