| As one of the power train excitation sources, the noise and vibration performance of the drive axle directly affects the NVH performance of the vehicle, and it is necessary to have a deep level research about it. The object of this paper is a driving-axle-housing from a mini car. Around the noise and vibration performance of the housing, this paper has completed6aspects of work by using testing and CAE analysis methods:(1) Have completed the vehicle road testing for the noise and vibration performance of the driving axle. Under WOT&Coast Down of3rd,4th and5th gear conditions, test and compare samples of driving axles with different final drives, and pick up excitations from the final drive. The other hand, the direct cause of the driving axle noise is the vibration of the housing. Therefore, in order to improve the noise and vibration performance of the driving axle, not only to control the quality of the final drive, but also to research the noise and vibration performance of the housing.(2) Have completed the constraint modal analysis of the housing. It is resulted that most modals under2000Hz of the housing are entirety modals, and the1st modal frequency of the housing is119.1Hz, but the excitation frequency of road would not be higher than50Hz and much lower than the1st modal frequency, so the excitation from the final drive should be considered principally while analyzing the noise and vibration performance of the housing.(3) Have completed the frequency response analysis of the housing by using excitation signals picked up from the vehicle road testing. The result shows that the distribution of vibration response is related to excitation frequencies and the vibration amplitude is related to excitation amplitudes. It performs as a whole vibration when gets excitations. Areas which have the biggest vibration amplitude are the back cover, the bow and the connection part of bow and axle tube.(4) Have completed the radiated noise analysis of the housing basing on the frequency response analysis. It is resulted that the main radiating areas on the housing are the back cover, the bow and the connection part of bow and axle tube.(5) Have completed the sound insulation performance of the housing. It is tested that the housing has a good sound insulation performance and its sound transmission loss are bigger than50dB (A) under2000Hz. But the sound transmission loss drops rapidly at some frequencies, such as1070Hz and1105Hz where the sound transmission loss is13.87dB (A) and16.54dB (A) only. There are two modals at these two frequencies and this explains that the modal would affect the sound insulation performance of the housing.(6) Basing on the CAE analysis and the structure of the housing, two improvement programs are raised:changing thickness of the back cover and adding stiffeners on the bow. It is proved to be effective by the CAE analysis.This topic has the follow innovation points:(1) Every extreme excitation boundary condition of different gear has been considered, and has pointed out that the reason of the housing noise is the whole vibration of the housing, not the local vibration of the housing.(2) Different from other people, this paper has analyzed the sound insulation performance of the housing, and both of the sound insulation performance and the acoustic radiation performance have been considered while improving the structure of the housing. |
