Vibration Analysis And Shaping Optimization Of Electric Vehicle Gearbox

The gearbox is an important part of the automobile transmission system,and the gear is the core part of the automobile gearbox,its running stability has a great impact on the reliability,NVH performance and transmission efficiency of the whole gearbox.Therefore,while meeting the gear strength requirements,designing low-vibration and low-noise gear drives has become the goal of gear dynamics research.Based on this technical background,this thesis specifically conducts the following research:First,the structural composition of the three-gear gearbox system of electric vehicles and the working principle of the gearbox in different gears are introduced,and the performance advantages of the electric bus using the gearbox compared to the electric bus without the gearbox are analyzed.Then,the three most common dynamic models of gearbox are established,and the dynamic equations of each model are listed,which provide the theoretical basis for the modal analysis and dynamic response of gearbox.The modal analysis of the gearbox helical gear system is carried out on the workbench platform,and the first 10 natural frequencies of the gear system are obtained,and the modal vibration modes corresponding to each natural frequency of the helical gear system are obtained.The meshing excitation frequencies of the gear pair under four load conditions of the three speed gearbox of the pure electric vehicle are calculated and it is compared with the first 10 natural frequencies of the helical gear system to avoid resonance of the whole gear system.Then based on the workbench software,using the mode superposition method to analyze and calculate the transient dynamic characteristics of the gear pair 1 in the gear system,the equivalent stress nephogram and the contact pressure nephogram of the gear mesh surface in the process of gear mesh transmission are obtained.According to the structure and working principle of the third gear box of the electric vehicle,the simulation model of the gear transmission system is established,and the static and dynamic analysis and calculation of the third gear box are carried out.Then,taking the 50% load condition of the common gearbox as an example,themodal analysis of the electric vehicle gearbox is carried out to solve the inherent modal frequency and vibration mode,so as to avoid the resonance problem of the gearbox.Finally,the transmission error of four pairs of transmission gears under 50%load condition and the dynamic meshing force of gears under the excitation of transmission error are calculated,which paves the way for further optimization design of the macro and micro parameters of the third gear box of electric vehicle.Taking the maximum coincidence degree of gears as the optimization objective,the basic parameters of four pairs of gears in three speed gearbox are optimized under multiple constraints.On this basis,the four pairs of gears of the gearbox were modified with a combination of toothed drum shape and tooth profile drum shape.Finally,through simulation calculation,the optimized transmission error and contact stress diagram of the four pairs of gear pairs are obtained.The simulation results show that the load-carrying capacity of the optimized gear is improved,the transmission error fluctuation range is reduced,the maximum contact stress is reduced and the contact stress distribution is more uniform,which improves the NVH performance of the gearbox,and provides theoretical basis and relevant data for further research of the gearbox.