电驱刚体模态对某电动车路噪的影响分析

Analysis of the Influence of Electric Drive System Rigid Modes of a Battery Electric Vehicle on Road Noise

某纯电动汽车在粗糙路面上以60 km/h匀速行驶时,主观评价会有严重的压耳感。经过和目标值对比,以及对音频的滤波回放,确认30 Hz和40 Hz峰值是引起主观压耳感的主要原因。该电动车为后轴驱动,电驱动总成通过三点悬置安装在后副车架上,而后副车架与车身通过4个衬套连接,形成二级隔振系统。通过分层级传递路径分析,确认30 Hz峰值产生的根本原因为电驱总成刚体模态与尾门模态耦合,而40 Hz峰值主要为轮胎的扭转模态导致轮芯的激励力较大所致。通过优化悬置刚度,即第一级隔振系统刚度,将电驱总成对地的侧倾模态频率调整为40 Hz,将电驱总成设计成40 Hz的动力吸振器以降低整车40 Hz路噪峰值。再通过优化后副车架衬套刚度,即第二级隔振系统刚度,使得电驱总成在整车状态下的刚体模态与尾门模态避频,解决30 Hz路噪问题。经过试验验证,路噪30 Hz~40 Hz下降4 dB~5 dB,主观感受良好。运用电驱总成刚体模态解决低频路噪的思路,对类似的问题有一定的参考意义。

There is serious aural pressure feeling in subjective evaluation when a battery electric vehicle(BEV)running on rough road at speed of 60 km/h.According to the target and noise filtering and replaying,it is determined that the peaks of 30Hz and 40 Hz are the main causes of the aural pressure.This BEV is a rear wheel drive(RWD)vehicle,the electric drive system(EDS)is double-stage vibration isolation system which is mounted on the rear sub-frame through three supports,and the sub-frame is also connected to the vehicle’s body through four bushes.Through double-stage transfer path analysis,it is found that the essential cause of the 30 Hz peak is the coupling of EDS mode and tailgate pumping mode,while the 40 Hz peak is mainly due to the torsional mode of the tire,which leads to the larger excitation force at the spindle.By optimizing the EDS mounting stiffness,which is the first stage stiffness,the EDS pitch mode frequency to the ground is adjusted to be 40 Hz,and the EDS is designed to be a 40 Hz dynamic vibration absorber to reduce the 40 Hz peak.Furthermore,by optimizing the stiffness of the rear sub-frame bushing,the second stage stiffness,the EDS modal frequencies to the vehicle and the tailgate pumping modal frequencies are separated each other so as to solve the 30 Hz peak road noise problem.The result of prototype testing has validated the effectiveness of above-mentioned optimization scheme,the road noise in 30 Hz-40 Hz range is reduced by 4 dB-5 dB,and the subjective evaluation is good.Using EDS rigid mode to solve the low frequency road noise has some reference significance for the similar engineering problems.