Research On Abnormal Noise Of Hydraulic Shock Absorber In A Minibus Rear Suspension

As other noise sources in the vehicle are controlled,the abnormal noise of the shock absorber is gradually exposed.Because of the extremely complex mechanism,abnormal noise has become one of the most difficult problems for the shock absorber industry.The use of simulation analysis,vibration and noise testing to analyze the commonality of abnormal noise has become an important means for many manufacturers to resolve the abnormal noise of shock absorbers.The noise governance should be controlled from the source.This paper focuses on the abnormal noise of the shock absorber body,and conducts an in-depth study on the abnormal noise of the hydraulic shock absorber of a miniature passenger car rear suspension.The CAE method is used to investigate the mechanism of abnormal noise,and the inherent relationship between abnormal noise and damper valve structure and oil characteristics was analyzed.In combination with vibration and noise tests methods,a shock absorber fault sound library is established to meet the requirements for sound discrimination,which can form the ability to independently design and develop "antinoise" products and increase the competitiveness of enterprises.Firstiy,the PU probe is introduced into the MTS849 system for abnormal noise bench test to obtain external characteristic curves,sound pressure signals,sound speed signals,piston rod axial vibration acceleration signal and cylinder axial vibration acceleration signal of 50 shock absorbers and 10 new shock absorbers with different displacement excitations.After data processing,the subjective evaluation of the audio files collected by the PU probe is performed.Then compare the experimental data of abnormal and normal shock absorbers.Finally disassembling the shock absorber to find the factors that may cause abnormal sound.The analysis results show that the abnormal noise is caused by some impact when the piston is transformed by the extension and compression stroke.Then based on the experimental data,the CAE simulation analysis of the shock absorber is carries out by various means,and the mechanism and governance methods of the abnormal noise are explored.In order to improve the simulation efficiency,one-dimensional simulation of the shock absorber with AMESim was estsblished.Through adjusting the main design parameters and structural parameters,an improved method for the abnormal sound of the hydraulic shock absorber was explored.In order to determine whether there is resonance noise in the shock absorber,CAE modal analysis is performed on all parts and components of the shock absorber,and the natural frequency is compared with the vibration data obtained from the test.It can be considered that the resonance phenomenon of the shock absorber piston assembly and the bottom valve assembly will result in abnormal noise of the shock absorber.Based on the micro-process analysis of the shock absorber work cycle,the fluid-structure interaction simulation analysis is performed in ADINA for the idle stroke process and the abnormal valve opening process.A preliminary inquiry into the method of reducing abnormal sounds was also conducted.Finally,on the basis of analyzing the traditional abnormality discrimination method of shock absorbers,this paper proposes a new method of abnormal noise detection based on Empirical Mode Decomposition(EMD).According to a large number of sound speed test data collected by the PU probe,the sound characteristics and identification criteria of the abnormal noise are obtained.This method more accurately extracts the characteristic information of the shock absorber abnormal noise,which can provide reference for the evaluation of abnormal noise and the improvement of sound quality in the future.