Research On Nonlinear Dynamic Characteristics Of Vehicle Transmission Gears Rattle

Vehicle transmission gears rattle noise is one of the important factors influencing the NVH performances of vehicle powertrain.With the improvement of consumer demands for NVH performance of the vehicle,researching on the dynamic characteristics of transmission gears rattle,then controlling the gear rattle noise of transmission is of great significance to improve the vehicle NVH performance.Based on the single pair of helical gears and transmission gears system consisting of the multi pairs of helical gears,the influence of structure and system parameters of transmission gears on the frequency and intensity of vehicle transmission gears rattle are studied in the paper.Then based on the theoretical research and the instance on improvement of vehicle transmission gears rattle noise,the methods of controlling the vehicle transmission gears rattle noise are studied.The main contents are as follows:Firstly,the nonlinear dynamic characteristics of the single pair of helical gear are studied in the paper.Then the dynamics equations on bending-torsion-axis directions of a single pair of helical gear are set up and the MATLAB/Simulink are used to solve the nonlinear equations.The influence law and degree are studied on the frequency and intensity of the single pair of gears rattle which caused by some factors such as gear meshing stiffness,gear meshing damping,gear clearance,gear error,torque fluctuations and the angular acceleration of driven gear.The results show that: A,the smaller gear meshing stiffness,larger gear meshing damping,appropriate gear clearance,smaller torque fluctuations and smaller angular acceleration of driven gear can reduce the gears rattle noise on a certain extent.B,various factors influence the gears rattle noise from strong to weak order for: the torque fluctuations,the gear meshing damping,the gear meshing stiffness,the gear clearance,the angular acceleration of driven gear and the gear error.Secondly,based on the research on dynamics characteristics of single pair of helical gears,the transmission systems consisting of three pairs of helical gear are set up and studied.Then the MATLAB/Simulink is used to solve the nonlinear equations.The influence law and degree on the frequency and intensity of the transmission gears rattle are studied in the paper,which caused by some factors such as the vehicle inertia,the inertia of engine flywheel,the torque fluctuation of transmission input shaft and the gear error.The results show that: A,larger vehicle inertia can reduce the frequency of transmission gears rattle,but not influence the intensity of transmission gears rattle.B,the inertia of engine flywheel influents the frequency and intensity of transmission gears rattle complicated,but influence degree is smaller.C,the larger torque fluctuation of transmission input shaft will intensify the frequency and intensity of transmission gears rattle.D,by adding the incentives on transmission torque fluctuation,the gear error intensify the frequency and intensity of transmission gears rattle too.Thirdly,based on the research on dynamics characteristics of the vehicle transmission and the instance on improvement of vehicle transmission gears rattle noise,the methods of controlling the vehicle transmission gears rattle noise are studied in the paper.Through the experiments,theoretical analysis and the conclusions in the paper are verified to be correct.The results show that: Dual mass flywheel(DMF)and the multi-stage torsional vibration damper can reduce the torque fluctuation of transmission input shaft efficiently,then controlling the transmission gears rattle noise within a reasonable range.