Research On Coupling Vibration Of Powertrain And Rear Axle For One FR Vehicle

Front-engine Rear-drive(FR)is a most common layout of some best-selling multi-purpose vehicle(MPV)and sports utility vehicle(SUV),it uses segmented driving shafts and rear axle to transfer power from front axle to driving axle which is prone to cause rear axle vibration and excite noise in vehicle,thus it cannot meet consumers' increasing demand for comfort.Therefore,it is of theoretical and engineering value to study the vibration mechanism of the rear axle and how to match the transmission system,the rear axle and the rear suspension with better vibration performance.This paper focuses on the abnormal vibration and noise of the rear axle on a domestic MPV,and the key research locates in the coupling vibration of powertrain and rear axle-suspension system.Firstly,based on previous research and structure of the car,the act process of the internal and external excitation to the rear axle is analyzed,and the coupling mechanism of the powertrain torsional vibration and the rear axle vibration is explained.Vehicle test is done,and vibration of the rear axle is determined to be direct cause of the vehicle vibration by data analysis and vibration transfer path analysis.The vibration of rear axle is excited by powertrain through torsional and bend vibration of driving shaft,gear mesh vibration and shell vibration in rear axle,and coupling vibration of powertrain with rear axle-suspension system.Torsional vibration model of the powertrain system is established,both free and forced vibration analysis are done,and torsional vibration is proved not to be the main cause of rear axle vibration.Multi-body dynamic model including powertrain,driving system,rear axle,rear suspension and simplified vehicle body is built,forced vibration analysis is carried out and Comparison with vehicle test is done,the mechanism of coupling vibration is validated.The coupling vibration consists of two aspects,one is coupling of main drive shaft's vertical vibration and of rear axle's pitch vibration,and the other is the coupling vibration of driving torque in the powertrain and the driving force acted on the rear axle through tire.Based on the above research,two improvement means are raised aiming to weaken the vibration source or reduce the coupling vibration,and both are proved to work well by simulation.Theoretical reference and effective improvement measures for improving rear axle vibration are provided for further research.