Study On Efficiency And Carrying Capacity Of NGWN(?) Planetary Transmission With Low-loss And Asymmetric Gears

For meeting the design requirements of high speed ratios,Gear transmission systems of engineering equipments often use multistage cylindrical gears transmission or multistage NGW planetary transmissions,which will lead to that the gear transmission systems have big volume,heavy weight,high failure rate and poor reliability.To solve this problem,the high-speed-ratio NGWN(?)planetary transmission scheme,its ratio range is 50~500,is applied,which can shorten the transmission chain,reduce the number of components,enhance the reliability of the transmission systems,but NGWN(?)planetary transmission has the problem of low efficiency,which has limited its widespread application.This paper is the important component of the national major basic research program of China.Aiming at the above problems of NGWN(?)planetary transmission,the following research works have been carried out.(1)Focusing on the problem of low efficiency of NGWN(?),main reason of low efficiency of NGWN(?)is found,and the measures of improving the efficiency of NGWN(?)are given,including using low-loss gears,decreasing the circulating power of NGWN(?),and reducing the tooth surface friction coefficient.The influence of using low-loss gears on efficiency and carrying capacity of NGWN(?)is analysed specially,and the results show that the efficiency is improved,but the carrying capacity is weakened after using low-loss gears.(2)Focusing on the problem of weakening carrying capacity of NGWN(?)with low-loss gears,the method of using asymmetric gears is given to enhance carrying capacity.Tool models of single-arc rack cutter and gear cutter are established,Meshing characteristics of asymmetric gears are researched,and the analytic calculation method of stress of asymmetric gears is given.The calculation results show that increasing tooth pressure angle,bending stress,contact stress of external gear and contact stress of internal gear can be reduced,but bending stress of internal gear can be increased.Carrying capacity of NGWN(?)with common symmetric gear is researched,and the results indicate that the main limiting factor of carrying capacity of NGWN(?)is that contact strengths of two internal gear pairs are weak.The influence of parameters of asymmetric gear on carrying capacity of NGWN(?)is analysed,and the effectiveness of enhancing carrying capacity of NGWN(?)by using asymmetric gears is verified according to the results.(3)For simultaneously improving the efficiency and carrying capacity of NGWN(?)planetary transmission,the multi-objective optimization model is established,which is subject to the conditions such as teeth,interference and strength,and which is aimed at highest efficiency of NGWN(?),minimum volume of NGWN(?)and maximum weighted value of contact strength safety factors of two internal gear pairs.Pareto-optimal set is obtained by using NSGA-II algorithm,and a optimum solution selected from Paretooptimal set is analysed.The results show that the efficiency and carrying capacity of the NGWN(?)are improved by using low-loss and asymmetric gears simultaneously.