Strength Analysis And Topology Optimization Design Of Gearbox Housing In Electric Bus

To alleviate the environmental pollution which brings by automobile and the pressure in the field of energy, simultaneously in response to national policy of energy conservation and emissions reduction, more and more cities have chosen pure electric bus as public transport in the city. In the chain of transmission of electric vehicles, the gearbox case as a support part of gear transmission system is subjected to a variety of complex loads from drive system, and it often bears larger bending, twisting and impact forces together. At the same time, because the advantage of adjustable range wide of motor speed and torque, the clutch between the motor and gearbox has been canceled, and then the torque of the motor directly acts on gearbox. Therefore, one puts forward higher requirements for the bearing capacity of gearbox case. In this context, more advanced digital technology is used to develop gearbox case which has high strength, high stiffness, light weight, low vibration, low noise and low cost, which has the important research significance for improving the international market competitiveness. In this paper, a certain electric three-gear gearbox housing is taken as the research object, the combination of the multi-body system dynamics simulation technology, the finite element analysis technology and topology optimization technology is used to optimize the performance of gearbox case. The main research work is as follows.(1) The domestic and foreign research present situation and development trend related to this topic are set forth, then, the key problems in research process to which should pay attention are pointed out, and finally, the study content and goal of the present paper are proposed.(2) The overall structure of gearbox is introduced in detail, the force analysis of gearbox drive system is performed and the professional3-D modeling software Creo2.0is used to establish a3-D model of gearbox. It makes a preparation for further research.(3) Based on the multi-body system dynamics theory, a method that combines ADAMS and ABAQUS softwares is adopted to establish a rigid-flexible coupling simulation model of gearbox of first gear of gearbox. The revoving speed of the drive shaft and contact force of gear pair are obtained by simulation and compared with the theoretical calculation value to validate their correctness. Then, the dynamic loads of bearings are calculated, thus providing the accurately incentive loads for the mechanical analysis of gearbox structure. (4) On the basis of relevant theory of finite element analysis, a finite element model of gearbox is established by using ABAQUS. In order to simplify the loading method of bearing load, the multipoint coupling constraints of MPC in the center of bearing hole is built. Then the simplified bearing load is applied on the primary nodes, and a finite element transient dynamics analysis of housing structure is carried out. Through the analysis, we have first understanding of stress and displacement distribution of housing structure and judge whether the case needs to further optimize according to the analytical results.(5) Based on the topology optimization theory, the optimization designs of static stiffness and dynamics characteristic for housing structure under various running conditions have been performed to seek the load-carrying path of structure. Thus, the weak links and remianing regions of structure can be found out timely, and then the optimization scheme can be proposed. The finite element transient dynamics analysis of the case after optimization is once agian performed to verify whether the case still meets the design requirements of stiffness and strength.(6) Based on the relevant theory of finite element modal, the dynamic performance analysis of the optimized gearbox housing is carried out. Through modal analysis of the housing, the data allows us to understand the natural frequency and modal shape of housing structure and to compare external excitation frequency with gear meshing frequency. Thus we can prevent the resonance of structure. Finally, the fast Fourier transform for the rotation speed of drive shaft and contact force of gear is carried out to study the vibration rule of transmission drive system, thus providing the reference basis for the fault diagnosis of gearbox’s interior.The results show that the gearbox housing after optimization not only meets the design requirements of stiffness and strength, but also avoids the resonance of structure when the weight of case reduces about10%, thus improving the overall performance of gearbox housing. The research techniques and the results of the present paper can provide the a theoretical reference for the research and development of gearbox housing of other types.