Research On Cold Extrusion Technology Of Sun Gear For Truck Wheel-side Reducer

The sun gear is an important part of the planetary gear transmission mechanism.Because of its complex structure and high processing requirements,it is mainly produced by traditional cutting method.Even when the sun gear is processed by cold extrusion forming method,the external-gear is formed first,and then the inner-spline is processed by broaching process.It is inevitable that there are a series of problems such as low processing efficiency,high cutting waste,high cost and reduced mechanical properties of the material by adopting traditional mechanical processing methods such as gear broaching process.Cold extrusion technology is a kind of energy saving,high efficiency,green precision plastic forming method,more and more enterprises choose this little cutting,energy saving and environmental protection precision plastic forming technology to process the gears.But the sun gear with external and internal splines,complex shape,forming difficulties;metal flow is complicated during the forming process,forming quality of tooth shape is difficult to guarantee,which seriously hampered the popularization and application of cold extrusion technology in similar gears processing.In this article,the research object is a sun gear for truck wheel-side reducer,according to its structural characteristics and numerical simulation analysis results,step-by-step cold extrusion forming process for external-internal tooth of sun gear was determined.The laws of metal flow and influence of the process parameters on the forming quality and forming load were obtained by numerical simulation.The elastic-plastic finite element model was used to study the forming precision of the sun gear.The influence of the elastic expansion of the mold and the elastic recovery behavior of the extrusion pieces on the accuracy of the gear was obtained.A composite forming process of cold extrusion + finishing was proposed and the high precision of external gear and internal splines can be formed by this process.According to the numerical simulation results,the cold extrusion forming process test of the external-internal tooth of sun gear was carried out.Process tests show that the sun gear can be formed by the step-by-step cold extrusion process to produce qualified quality internal splines and external gear.Step-by-step forming process has increased an external gear cold finishing process,the forming quality of the external gear is improved while ensuring the quality of the internal spline.In order to meet the requirements of enterprises to further reduce production costs and improve production efficiency,a process scheme for the synchronous cold extrusion forming of external-internal tooth of sun gear with solid blanks was proposed.The influence of process parameters on the synchronous cold extrusion of sun gear was obtained by numerical simulation.The process parameters were optimized by orthogonal experiment design method,and the best combination of process parameters were obtained.