Analysis Of Dynamic Characteristics Of High-speed Gearbox On Electric Vehicles

With the increasing urgency of energy and environmental problems,automobile industry has been growing quickly along the way of energy saving and environmental protection.Under the support and guidance of national policies,new energy vehicles have become the mainstream,and electric vehicles,EVs,are favored by the market for their zero emission,low operating cost and outstanding advantages in intelligent networking.Electric drive system is the core of EVs.Due to the loss of masking effect of traditional fuel vehicle engine and the influence of high rotating speed of the motor,the vibration and noise of the transmission system become particularly prominent,which seriously affects the ride comfort of the vehicle,and makes the vehicle NVH face new challenges.Thus,it is of vital importance to analyze the vibration characteristics of the high-speed transmission system on EVs and the influencing factors of dynamic response on the highspeed gearbox,so as to reduce the system vibration and noise from the source and improve the vehicle NVH performance.In this paper,the dynamic characteristics of the high-speed gearbox transmission system on a pure electric vehicle are studied theoretically and experimentally.The main contents are as follows:(1)Based on the open source simulation platform Open Modelica,the entire vehicle model of a EV is built.Taking China Light-duty vehicle Test Cycle for Passenger car,CLTC-P,as the driving condition,the whole vehicle is simulated.The torque and speed of high-speed gearbox when running are obtained,and the characteristic conditions such as the maximum speed and torque of the whole vehicle are counted,which provides sufficient working conditions for the dynamic characteristics analysis of high-speed gearbox.(2)According to the lumped mass method,the dynamic model of two-stage helical gear transmission system on the EV is established.Combined with the actual layout of the transmission system,the relative position relationship of the tow action planes is determined.The excitation factors such as time-varying meshing stiffness,comprehensive meshing error and backlash are considered,and the maximum speed condition under CLTC-P is taken as the input condition.With the 4th-order Runge-Kutta method,the vibration response of the system is solved,and the dynamic characteristics of the system under the comprehensive influence of multiple excitation factors are analyzed.(3)Based on ABAQUS software,the finite element model of the housing is built,and the connection between each bearing center node of gear transmission system and bearing seat of the housing is established by point-surface coupling method,so as to complete the construction of comprehensive analysis model of gear-housing dynamics.Taking the dynamic reaction force at each bearing seat as the excitation,the vibration acceleration response of the housing surface under maximum torque condition at lowspeed and maximum power condition at high-speed is analyzed,and the sensitive effect of speed increase on the housing vibration is found.(4)The vibration bench test of high-speed gearbox is carried out,and the vibration acceleration data of the housing surface corresponding to the right end of high-speed shaft and intermediate shaft are collected.Moreover,the vibration acceleration response under various working conditions is analyzed from the time domain and frequency domain.The results show that the meshing frequency of the two-stage helical gear pairs is the main frequency component,which plays a leading role in the vibration of the system.(5)Considering the analysis results of the dynamic characteristics of the high-speed gearbox on EV and taking the maximum speed condition under CLTC-P as the target working condition,the modification design of each pinion is carried out.The transmission error and load distribution on tooth surface before and after modification are compared,and the vibration of the system is suppressed through the modification.