Research On The Acceleration Booming Noise Of Vehicle Based On The Transfer Path Analysis Method

Powertrain system is one of the sources of NVH problems.Aiming at the problem of accelerating roar of a certain type of car,based on the analysis idea of TPA method,when checking the single contribution path,especially the problems caused by the powertrain mount system and the integration of the car body.Through the analysis results of TPA model,it is shown that the 2-order roaring noise at 2600 rpm is related to the running mode of rear antitorsion rod suspension and the stiffness of front frame.The 2-order roar at 4000 rpm is related to the vibration isolation amount of the right suspension rubber vibration and the stiffness of the right longitudinal beam of the body.Finally,the stiffness of the right suspension rubber,the structure of the rear torsion bar and the structure of the subframe were ameliorated to solve the roaring of the 2600 rpm and 4000 rpm in the car.Firstly,through the subjective evaluation of this problem,combined with the objective noise characteristics test and the modal frequency distribution of cavity in cavity simulation,it is determined that the noise is mainly caused by the second-order noise contribution at a specific speed,and then it is determined that the excitation source of the noise is from the powertrain system,and the frequency of second-order roaring noise is mainly at 87 H z and 133 Hz,corresponding to 2600 rpm and 4000 rpm.Secondly,after the diagnosis of the air(air intake noise,tail pipe noise,noise of engine body)and single structure(front-end exhaust pipe,the drive shaft)to roar unrelated,the transfer function,obtained by the results of two states before and after power assembly removal,was used to establish the suspension system’s transfer path analysis model.After the analysis of the accuracy of the two transfer path analysis models before and after powertrain disassembly,the size of the second order excitation load on the path,and the characteristics of the transfer function.It is determined that the contribution paths with large roaring in the vehicle at 2600 rpm and 4000 rpm were caused by the Z direction of the right suspension passive side and the Z direction of the passive side of the rear anti-torsion lever.Finally,the effect of the improvement program is predicted and the actual vehicle mass production program is verified.In the TPA model,the load and transfer function editing function of the software was applied to simulate the improvement effect of load and transfer function under the rotation speed and frequency of the problem points,and the vehicle roar was significantly improved at 2600 rpm and 4000 rpm.In the actual mass production scheme,by reducing the stiffness of the right suspended rubber to the lower deviation value,the vibration isolation amount of the suspended 2-order vibration was increased,and the 2-order roaring noise at 4000 rpm was optimized.By modifying the mode frequency of the rigid body under the running state of the anti-torsion rod suspension to 103 Hz,the 2-order roaring noise at 2600 rpm was optimized to avoid the 82 Hz sound cavity mode frequency in the car.By improving the stiffness of the front subframe and the noise transfer function from the passive side of the rear anti-twisting lever at 80hz-90 hz to the inside of the car,the 2nd order roaring noise at 2600 rpm was reduced.Meanwhile,the rigidity of the whole vehicle was also enhanced due to the strengthening of the subframe,and the 2nd order noise at 4000 rpm was also optimized to some extent.According to the application process of the transfer path analysis method,a set of diagnosis and analysis flow for the problem of rumbling caused by mount system is summarized.