Numerical Simulation Of Cold Forging On Automobile Conjunction Gear And Process Research

Gear as an important transmission part, is widely used in cars, ships, planes,machine tools, precision instruments and meters and other kinds of products, especiallyin automobiles. There are nearly dozens of gears in a car. With the continuousdevelopment of automobile industry, people’s requirements on gear’s performanceconstantly improve. After decades of development, automobile gear gradually formedprecision die forging for the target of production mode. Nearly half of automobile gearshave been achieved in precision die forging, such as starter gears, synchronizer blockingrings, a portion of spur gear and etc. Precision die forging possesses high materialutilization, good mechanical performance, high production efficiency, saves energy,reduces cost and environmental pollution compared with gear produced by traditionalmachining method. In this way, it improves products competitiveness and createsremarkable benefit in social and economic. Conjunction gear is an important part inautomobile transmission, but reports are few, about the studies on it, which havecomplicated structure and great difficulty of being formed. Though German and JapanCompanies have developed precision forging forming processes on conjunction gear,which have been applied to production, but due to technical security, there is no publicpapers. In this paper, its target is to realize the precision die forging of this gear.Classical plastic forming theory and finite element simulation are used to study theforming mechanism and application of divided flow forging technology.Because conjunction gear can’t demould smoothly, so we divided forging processinto two steps, namely form spur tooth first, after crush cone. Rigid-plastic Finiteelement method (FEA) is employed to analyze the conjunction gear closed forgingprocess, research the influence of different blank on the forming process, get thedistribution of metal flow. With Ladder-like hollow billet forming, most of metal of theblank flows along the radial and appears backflow phenomenon. The last filling regionis the lock angel of conjunction gear and fold can be found at the inner side of tooth.The load’s change is stationary first and then drastic. With ring blank forming, the metalflows along the axial and the load’s change is smooth during the whole forging. Overallboth loads of them are too large.Divided flow forging technology can be applied to optimize die structure, whichmake all metal flow along the axial and can lowers the load. Analyzed rule of load influenced by forging size. With inner bore diameter increasing, the load descends firstand then ascends, because contact area and the space of metal free flow change, as wellas their influence on the forging load. The load descends with fillet increasing, whileascends with tooth length and friction factor’s increase. Distribution of temperature,stress, strain and damage are analyzed. The temperature during forging processsurpasses200℃and the maximum temperature is at tooth root fillet. The equivalentstress surpasses800Mpa and the main region is at the middle and tooth deformationzone. The equivalent strain is fluctuant on the choosy path. Path A on root circle isunimodal and path C on outside circle is doublet. Every point’s equivalent strainincreased during the forging process. The damage became higher from the outside to theinner side of the gear tooth. Because of the confluence of material, a small peak appearsin the middle of the damage distribution curve along the teeth tipIn this paper, finite element simulation is used to develop new process, whichchanges the situation that designing die structure totally depend on the designer’sexperience, Improves reliability of the mold design, shorts the cycle of productdevelopment, saves development costs, avoids the possible mistakes and is conducive toimprove the enterprise markets competitiveness. The conclusions and rules obtained inthis paper can be applied to optimize design in other similar long axis products, and canprovides effective technical support for the development of new products andoptimization design.