Research On Radiation Noise Prediction And Optimization Of Transmission Cases Of Pure Electric Vehicles

In recent years,with the increasing prominence of the energy shortage problem and the increasing awareness of environmental protection,the new energy vehicle industry has entered a stage of rapid development.The popularity of electric vehicles is increasing and consumers have put forward more indicators for the performance of electric vehicles.Among them,the NVH(Noise,Vibration,Harshness)performance of electric vehicles has attracted more and more attention and has become an important indicator that affects the quality of electric vehicles.A large part of the vibration and noise of the vehicle transmission system comes from the contribution of the transmission.This article is based on a pure electric A0-class compact car.The two-speed fully electronically controlled automatic transmission equipped with it is used as the research object to optimize the radiated noise of the transmission housing under the first-speed common operating conditions.The transmission vibration test and the housing free modal test were carried out to verify the accuracy of the transmission bearing excitation solution and the reliability of the finite element model of the housing.Simulate the actual working state of the transmission and calculate the vibration response of the casing.Using the boundary element method,a rectangular sound field with a distance of 1 m from the center of the transmission is established and the radiated noise of the transmission housing is solved acoustically.Based on the calculation of acoustic contribution,the structure of the transmission housing was modified to improve the noise characteristic of the transmission housing.The specific analysis process of this article is as follows:The three-dimensional solid model is imported into the finite element software for preprocessing and meshing.The same method is used to mesh the motor housing and the differential housing.According to the detailed parameters of the internal structure of the transmission,a two-speed automatic transmission rigid-flexible virtual prototype model is established and the dynamic excitation at the bearing seat is solved.The modal and frequency response of the transmission case are studied.The natural frequencies and mode shapes of the various modes of the transmission housing were obtained through simulation and modal tests.The accuracy of the finite element model of the housing was verified by comparing the modal test results with the simulation results.The transmission bench vibration test was carried out and the accuracy of the virtual prototype model and bearing excitation was verified by comparing the frequency response test results of the transmission housing with the simulation results.The surface vibration response of the housing under dynamic load is solved and the radiated noise of the transmission is solved based on this.Based on the acoustic transfer vector and the modal acoustic contribution,the surface is divided.Through the calculation of the acoustic contribution of the surface,the area with a larger acoustic contribution is determined.the housing structure is improved and the noise characteristic of the transmission casing is improved.