| Gear transmission system is a vital part of mechanical transmission system.With the scientific and technological development and the improvement of machinery industry,gear drive is more widely used in engineering application.In automobile industry,gear driving paly a key role in automobile transmission system.The smooth meshing of gear pair directly affects the performance of the automobile.Vehicle transmission gears rattling characteristics is one of the significant reasons which can influence the NVH properties of the vehicle powertrain.Reinforcing the behavior research of gear rattling dynamic of transmission gear system is an important approach to improve the performance of vehicle transmission system,then controlling the gear rattling noise of transmission is important to polish up the vehicle NVH performance.In this paper,based on the gear system dynamics theory,helical gear transmitssion system was studied and a more realistic bend-torsion-axes multi degree of freedom gear rattling system model was established.The finite element method and numerical method were used to analyze the inherent characteristics and dynamic response of the gear system,analyzing the influence of structure and system excitation parameter of transmission helical gears on the state and the frequency and the strength of rattling in order to improve automobile transmission gears rattling noise.The main contents of this paper are as follows:(1)Based on the gear system dynamics theory and principle of gear meshing,the gear rattling dynamic was analyzed,and the system dynamic excitations affecting the gear rattling were expounded.Fourier series method was used to numerically simulate the time-varying stiffness of meshing;Two types of gear errors were analyzed and were numerical simulated.(2)Each of different kinds of dynamic models methods and models were researched.On the basis of comparative study,lump parameter method was used to establish the bend-torsion-axes nonlinear rattling dynamic model.The rattling dynamic differential equations were established on the basis of the gear dynamic model.The differential equations were dimensionless in order to simplify the numericalcalculation.(3)The inherent characteristics of helical gear system were analyzed by Using the finite element method and the MATALB numerical method,and the natural frequency and vibration model of the dynamic system were obtained,indicating the theoretical vibration model is correct.(4)The MATLAB/Simulink was available to solve the nonlinear rattling differential equations.The Runge-Kutta numerical method was used to solve equations.This paper analyzes the influence rules on the state and the frequency and intension of the single pair of gears rattling that was caused via some factors,for example gear mesh damping,gear backlash,gear meshing error,gear time-varying meshing stiffness.On the basis of the study,rational proposals were proposed to choose a series of parameter values.The results of this paper show that:(1)larger gear meshing damping can improve the gear rattling noise on a certain extent.(2)The amplitude of the time-varying mesh stiffness is reduced which is positive to control helical gear rattling phenomenon.(3)When the torque flucation coefficient become from small to large,the dynamic rattling phenomenon in turn is: no rattling,single rattling and double ratttling.(4)The change of gear meshing error may influence the gear rattling a little.(5)The major direction of gear rattling is reverse rattling. |
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