Mechanism Research Of Coupled Vibration Between Transmission System And Car Body Of FR Automobile

Multi-purpose vehicle (MPV) is favored by domestic consumers all of these days because of its large ride space, great driving experience and van function. However, with the improvement of ride comfort requirement of the consumers and the intense competition among automobile factories, the vibration and noise problem existed in many kinds of MPV is more and more prominent. The mechanism research and improvement of vibration and noise of automobile are widely noticed in auto industry.This paper studies the vibration problem of FR automobile with five-link dependent suspension on the background of the interior noise problem of a type of MPV.In the XY plane of vehicle, the single side of five-link dependent suspension is simplified to a four-link structure to analyze the relative motion relationship among suspension links. Based on the relationship, the 23 dimensionality nonlinear coupled equations of the system is deduced according to the statics analysis of rear axle and suspension system and solved in MATLAB, the solving result has a high precision. The analysis shows, the driving torque from transmission system can make car body produce displacement which is mainly along the Z axis. When the driving torque alternates, the car body will vibrate.The coupling method between transmission system and car body through main retarder is put forward according to the statics analysis of rear axle and suspension system. A coupling vibration mechanical model between transmission system and car body which considers the main retarder coupling path and tire coupling path is deduced and its free and forced vibration characteristic is analyzed. The study indicates, the transmission system vibration, car vertical vibration and longitudinal vibration are coupled when considers the main retarder coupling path; when not, the transmission system vibration can’t impact the vertical vibration of car body and the car vertical vibration also can’t impact the transmission system vibration and car longitudinal vibration.Under the guidance of the coupling theory, the geometric modeling of the hypoid gear in main retarder is researched and its simulation method is improved to accommodate the simulation of the entire car. After researching the simulation method of tire and road, non-linear damping of suspension and flexible car body in ADAMS/View, a fine coupling vibration simulation model of the entire vehicle including the whole transmission system is constructed.The free and forced vibration of the coupling simulation model is simulated to research the coupling vibration characteristic between the transmission system and car body, and compared with the results from experiment or theory to prove the accuracy of the model. The comparing shows, the emulational and theory calculative meshing force of hypoid gear is basically the same which means the modeling and simulating of hypoid gear is feasible; according to the free vibration of the transmission system including the hypoid gear of main retarder, the transmission system has a torsional vibration modal around 50Hz; comparing the emulational and experimental forced vibration response of the same measure points around the entire vehicle, the vibration characteristic and amplitude of those two methods are basically the same.In order to reduce the vehicle interior noise, the vehicle vibration characteristic at several speed conditions which has serious interior noise problem is analyzed based on the simulation model and the noise generation mechanism is researched in a view of vibration source, transfer path and the vibration of sheet metal parts of car body. Some noise control measures are proposed which can provide a basis for the solving of automobile NVH problem caused by transmission system.