Analysis And Optimization Of Multi-Speed Automatic Transmission Case For Electric Bus

With the development of automotive industry.transmission,as an important part of drive system,is gradually developing towards miniaturization,lightweight and high efficiency.It is of great significance for improving vehicle performance to optimize the design of transmission case,improve the overall performance of transmission and power density of driving system,and improve the power and working efficiency of vehicles.Aiming at the problem of large quality and low efficiency of drive system of four-speed automatic transmission case of an electric bus and the requirement of high efficiency and high power density of drive system at present,this paper optimizes the structure of transmission case mainly from static load analysis and frequency analysis,combining with Jilin province science and technology development project "Integration and optimization of electric drive system of new energy bus".Reduce the quality of transmission case,achieve lightweight,and the natural frequency of the case is optimized to avoid the excitation frequency of the gear system,finally summarize the optimal design scheme of transmission case structure.Main research contents of this article are as follow:(1)The static analysis of the transmission case is carried out,the strength is checked and the topological optimization design of the case is completed.Finite element modeling of transmission case is completed,and the bearing-outer-ring-shell interaction model is established.The interaction stresses between the bearing rollers and the inner and outer rings under different gear shifting conditions are calculated,and the stresses are loaded on the bearing-outer-ring-shell interaction model for static analysis.Based on the static analysis of the transmission case,the static load topology optimization analysis of the transmission case is carried out under the constraints of the displacement at the thin wall and the ultimate stress of the shell material.The preliminary structural optimization of the case is carried out according to the density distribution nephogram,and the preliminarylightweight design model is obtained.(2)Frequency optimization of transmission case is completed according to the natural mode and frequency response.The free modal analysis and experimental verification of the transmission case are carried out to determine the weaknesses of the case.According to the actual constrained state of the transmission case,the constrained modal analysis and frequency response analysis are carried out.The results are compared with the output frequency of the gear system.Then the frequency optimization and frequency response optimization of the transmission case are carried out according to the output frequency of the gear system.Combining with the static load topology optimization results,the final structure of the optimal design of the transmission case is obtained.The service life of transmission case is checked,the working load spectrum of transmission case is established,and the life prediction analysis is carried out.(3)Compared with the shell before optimization,the quality of the transmission shell after optimization has been reduced,natural frequency avoids excitation frequency of gear system and the basic performance meets the application requirements.According to the process of structural optimization of transmission case,the technical route of structural optimization design of transmission/reducer case is summarized.(4)In order to compare with the structural optimization design scheme,the material optimization analysis is carried out at the end of this paper.Aluminum alloy ZL101 is used instead of cast iron HT250.Structural strengthening design is carried out for the aluminum alloy shell,and the material optimization design scheme for the transmission shell is obtained.