Study On Dynamic Characteristics Of High-Speed-Ratio Planetary Gear Trains With Asymmetric Low-Loss Gears

NGWN(I)-type planetary gearing,a type of high-speed-ratio planetary gear transmission,which has the advantages of compact structure and large transmission ratio,has been widely used in large engineering machinery.However,this system has the problem of low transmission efficiency in engineering practice.Low-loss gear is used to improve the efficiency in this paper,which may affect the dynamic performance of the transmission system as a result of the introduction of a smaller contact ratio.In addition,under the actual operating conditions,the dynamic characteristics of NGWN(I)transmission are not clear,and there is little research on that.Therefore,it is very necessary to study and analyze the dynamic characteristics of the high-speed-ratio planetary gear transmission.This topic comes from the National 973 Plan(NO.2014CB046304).Focusing on these problems of NGWN(I)-type planetary gear transmissions,the main research work of this paper is as follows.(1)For the dynamics of NGWN(I)-type planetary gearing,the corresponding dynamic model is firstly developed by the method of lumped-parameter mass.Then on this basis,taking each component as the research object,the elastic dynamic differential equation of transmission system is derived by Newton’s second law.(2)The dynamic characteristics of NGWN(I)-type planetary gear transmission are studied.Firstly,the natural frequency and vibration mode of the transmission system are researched,the corresponding vibration modes are analyzed,and the resonance speed of the system is studied based on the theory of resonance.In order to understand the dynamic characteristics of the planetary gear transmission,then the dynamic response of the system is solved,and the influence of the relevant parameters on the dynamic characteristics is studied.(3)Low-loss gear is used to improve the efficiency of NGWN(I)planetary gear transmission.This method can reduce the power loss by optimizing the gear parameters for the reduction of contact ratio,which can greatly improve the efficiency of transmission system.However,the low contact ratio may affect the vibration stability of the transmission system.Therefore,based on the established dynamic model,with the contact ratio of low-loss gear pairs as design variables,the dynamic load coefficient and the vibration intensity as the evaluation index of vibration,the vibration of the transmission system is analyzed.Results show that the transmission system has high efficiency and low vibration intensity with the contact ratio of low-loss gear pair in a certain range.In addition,the low-loss gear makes the dynamic load characteristics of the system relatively worse.(4)On the basis above,the basic parameters of NGWN(I)-type planetary gearing with asymmetric low-loss gears is designed.Based on the research idea of the main target method in multi objective design,the objective function and design variables are determined,the design variables are discretized with the consideration of rationality of model solving process,and the objective function value is calculated by the method of global search.The final design results are compared with each other from the aspects of transmission efficiency and dynamic performance.The results show that the optimal design method of asymmetric low-loss gears for NGWN(I)-type planetary gearing is effective and feasible,which can improve the efficiency and ensure the transmission system has good dynamic performance.