Research On Coupling Vibration Mechanism Between Powertrain And Main Reducer Gear System Of Automobile

FR is a common vehicle on the market,the powertrain of which consists of engine,clutch,transmission,drive shaft,rear axle and tire.During the running of the vehicle,the fluctuation of the engine output torque will stimulate the torsional modes of the powertrain and produce torsional vibration,which will produce the coupling effect on the body through the transmission paths of intermediate supports,rear axles,suspensions,tires,etc.,thus causing the vibration and noise in the vehicle and other NVH problems.In this paper,the coupling vibration mechanism between powertrain and main reducer gear system is researched theoretically in the light of the vibration and noise of the company's MPV FR vehicles.The equivalent model of powertrain torsional vibration considering the intermediate support and the dynamic meshing model of hypoid gears with time-varying meshing stiffness,gear backlash and other nonlinear factors are established.The torsional vibration model of the powertrain is coupled with the rear axle gear-rotor-bearing model,and the dynamic response of the powertrain and gear system is calculated by the numerical solution using MATLAB.On this basis,the influence of the parameters such as the gear backlash,meshing stiffness and the span between bearings on the driving gear on the dynamic characteristics of the coupling system is studied,and then the sweep characteristics is analyzed.The theoretical torsional vibration response peak value of 1600 rpm is calculated corresponding to the second-order torsional frequency of 53.3Hz.To verify the correctness of the theoretical model,a rigid-flexible coupled virtual prototyping model based on ADAMS was built to simulate the torsional vibration response of the powertrain under the second-order excitation of the engine.The amplitude of the torsional angular acceleration response at key parts of the powertrain is obtained and the sweep analysis is performed.Analysis show that there is a significant peak near 1700rpm(corresponding to the second-order torsional frequency 56.7Hz),which is basically consistent with the theoretical calculations.To further verify the correctness of the theoretical coupling model and simulation analysis,and to investigate the coupling characteristics of the actual powertrain torsional vibration and gear vibration,a real-vehicle powertrain motor gantry is set up to simulate the second-order torque fluctuation stimulation of the engine.The different amplitude of the fluctuating torque is subjected to a sweep test.The test results show that the powertrain has a torsional vibration mode of 55.7Hz,and its torsional vibration characteristic curve is basically consistent with the theoretical calculation and simulation results.The vibration response magnitude at the test point of the rear axle is basically consistent with the theoretical calculation result of the gear vibration response.The comparison of theoretical,simulation and experimental results verifies the correctness of the coupled vibration mechanism and the simulation model,which will provide theoretical basis and simulation reference for further optimizing the system parameters and improving the NVH performance of the vehicle.