The Design And Research Of The System Of Rigid Gear And Flexible Gear Of A Harmonic Drive

The rigid gear and flexible gear system is the core component of a harmonic drive of which the main form of failure is the fatigue damage of flexible gear. According to the survey, the extant researches on the fatigue problem of flexible gear were used to ignore the interaction between assembly process and meshing process, and use pure static method to tackle the problem of flexible gear without taking the change of boundary conditions of flexible gear into account. As a result, it may cause the results of the analysis are not that accurate compared with the reality. Therefore, it’s of great importance to do research on the problem of rigid gear and flexible gear system according to its actual working conditions which works for improving the credibility of the results of the analysis.The thesis takes the rigid gear and flexible gear system as the research object. Aiming at its fatigue damage problem on complex working conditions, the main research works are as follows:1. The design of the rigid and flexible gear system. Based on the basic theory of harmonic drive, the research first choose double-circular-arc tooth profile as the basic tooth profile and design the whole structure of the flexible gear, then, fatigue strength is checked. Next, the relevant characteristic curve of the wave generator and structure of the rigid gear is worked out according to deformation characteristics and kinematics characteristics of flexible gear. Finally, three-dimensional models of the whole flexible gear system are built in UG software.2. The analysis of the process of assembly and meshing of the rigid gear and flexible gear system. Aiming at the characteristics of large deformation and meshing, the finite element simulation models of the assembly process and meshing process under rated load on the basis of the actual working condition of this system are established. Then, the deformation, displacement and stress of the flexible gear in the two process are analyzed to judge the reliability and the feasibility as well as necessity of the method used in the thesis is explained. Last, determining the maximum stress size as well as position and checking the strength of the flexible gear is carried out.3. The research on the influential structure factors of the fatigue life of the flexible gear. Based on the theory of fatigue life, to predict the fatigue life of the flexible gear under rated load condition, simulation is executed after the S-N curve of the material and the load time history of rate d load condition have been determined. In order to know the effect of structural parameters on the fatigue life of the flexible gear, the length of the cylinder, the thickness of the cylinder,the length of tooth,and the size of chamfering radius of tooth end are taken as variables to analyze.The thesis solves practical engineering problems b y the way of simulation and analysis according to the theoretical knowledge. The analysis on the problem of rigid gear and flexible gear system which is close to the real condition and combined with production practice is of important reference value to t he research of a harmonic drive.