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Automatic transmission has been widely used in the automotive industry, and novel automatic transmissions with simple structure and reliable operation are a research hotspot. This paper proposes an automatic transmission with multi-stage gears to simplify its working process. The automatic transmission comprises a case and a driving transmission shaft and driven shaft which are mounted on the case. The transmission gear pairs are superimposed on the driving and driven shafts similar to a tower. The gear pairs on the driving and driven shafts are always engaged. All the driving gears are connected to the driven shaft via a flat key, and the driven gear and the driven shaft are connected by a join key, which is used to connect or disconnect the gear and the driven shaft, and are controlled by a hydraulic shifting mechanism and have been designed in detail. Numerical simulation is adopted to verify the strength of the core components. In addition, the transmission performance of the gearbox is experimentally tested. The results indicate that the novel gearbox can achieve variable speed and work smoothly. The gearbox has a novel structure, the driving and driven shafts are simple and installed friendly, and the transmission gear meshes are reliable.

The axial self-infeed rolling process is an advanced and efficient process to form long threads such as lead screw and thread shaft. The experiments of axial self-infeed rolling process for the stainless steel were conducted with three blank diameters, forming speeds and two lubrication conditions. The effects of forming speed, blank diameter and lubrication condition on forming torque, microhardness and tooth height of forming threads were analyzed by the design of experiment and analysis of variance. And the characteristics of forming torque, microhardness distribution and tooth height were investigated. The results revealed the forming torque was more influenced by the blank diameter and the forming speed than the lubrication condition. The tooth height was sensitive to all these factors and the microhardness only was affected by the blank diameter.