Production technology of spiral bevel gear for automobile rear axle in China

During the 12th Five Year Plan period, China’s automobile industry has made great progress, and the automobile production and sales volume have shown a double-digit high-speed growth trend [double-digit high-speed growth trend] for many years in a row. The continuous expansion of China’s automobile industry has also led to the development of upstream related parts industry. As the main transmission part of automobile rear axle main reducer, the demand of spiral bevel gear is increasing day by day, which also puts forward new requirements for product quality and production cost control.

The traditional manufacturing technology of spiral bevel gear mainly adopts forging and machining technology. The process scheme is backward and complicated, the loss of raw materials is large, more production equipment is needed, and the product performance is not stable. It is imperative to explore new technology to meet the market demand. This project attempts to get rid of the shackles of the traditional manufacturing process of spiral bevel gear, and is committed to exploring innovative ways to produce spiral bevel gear by casting forging composite forming process, so as to improve product quality, optimize process steps and reduce material loss.

The maximum outer diameter of the driven spiral bevel gear for the rear axle of an automobile is about 188mm, and the geometry of the tooth shape is complex. The material used for the gear is 20CrMoH, which belongs to low alloy steel with good processing performance. If the traditional sand casting process is used alone to produce the gear, although the metal utilization rate can be greatly improved, the production efficiency will be greatly reduced, the surface finish of the casting is low, and the casting defects that may occur locally will affect the product quality; if the cold forging process at room temperature is used to form the gear, the forming process of the gear shape part will pose a great challenge to the selection of equipment tonnage and die materials The forming temperature of warm forging process is between normal temperature and recrystallization temperature. The advantages of cold forging and hot forging process are used for reference: the forming force of workpiece is smaller than that of cold forging, and the forming quality is better than that of hot forging. But at present, the equipment cost of warm forging is high and the production practice is few.

All of the above traditional manufacturing processes are difficult to achieve high quality, high efficiency and low cost local production of automobile rear axle driven spiral bevel gear. This paper attempts to cross use a variety of material forming processes to produce products, and discusses the possibility of using casting forging composite forming process to produce driven spiral bevel gear: first use casting process instead of pre forging process to cast gear blank with tooth shape; clean the surface of casting and heat it; then realize the transformation of metal structure of gear blank from as cast to as forged by closed hot die forging After surface treatment and phosphorus saponification, cold precision forging process is used to improve the surface precision and size of gear blank forgings to meet the technical requirements of product parts. Finally, the final product is made by machining tapped holes.

If we use the method of field trial production to explore new technology, it will not only cost a lot of human and financial resources, greatly extend the R & D cycle of products, and the results of trial production are very random, so it is difficult to summarize the general rules. With the rapid development of computer technology and finite element theory, it has become a general trend to use computer simulation instead of on-site trial production. The computer simulation technology not only greatly reduces the test time, but also saves the expensive actual trial production cost. Finite element method combines the advantages of difference method and variational principle, and has been widely used in various engineering fields. It has become a normal practice to use the simulation software based on the finite element method to solve the engineering science problems with huge amount of calculation. Based on the above reasons, it is recommended to use the finite element numerical simulation software instead of the traditional test to carry out the research.