Three Dimensional Profile Design And Analysis Of Harmonic Drive With Double-Circular-Arc Common-tangent Tooth Profile

Harmonic drive(HD) is one of the important core and key components for the aerospace, medical equipment, military equipment and robot, the tooth profile has significant effect on engagement performance of HD. However, at present, the HD with high performance still mainly rely on imports, therefore, in order to promote the technology of HD and to break the technology of core parts of high equipment blockade and monopoly by other countries, the HD with double-circular-arc common-tangent tooth profile(DCTP) is designed and analyzed. The conjugate theory is studied, moreover, the influence of meshing parameters and structure parameters on the conjugate exist domain(CED) and conjugate tooth profile(CTP) are researched and analyzed, which is obviously reveal the tooth profile relative motion characteristics of flexspline(FS) and circular spline(CS). What’s more, a reasonable tooth profile design method is to proposed which, is capable of maintaining the 3D teeth meshing engagement over a wide range by correctly shifted the tooth profile portions of FS, while considering the influence of axial inclination angle, and the relative meshing engagement of the HD with three dimensional DCTP has been analyzed by computer simulation.First of all, the composition, classification, transmission ratio and basic working principles of HD are analyzed in detail, and the rotation angles of FS, the deformation of FS and the curve of wave generator are calculated by the relative motion of HD. According to the exact calculations or the approximate calculation of the rotation angles of FS, an exact or approximation conjugate principle based on envelope theory or modified kinematic method was presented, respectively.Secondly, the effect of the structure of FS, the tooth profile and elastic deformation of HD and conjugate theory were considered here, in order to research the problems such as conjugate tooth profile problem, parameters optimization design problem and the influence of different conjugate principle problem.Finally, the two dimensional DCTP of HD was designed based on the exact modified kinematic method, the least-squares fitting approach is adopted to fit it, and the tooth profile interference was tested. More importantly, proposed a reasonable tooth profile design method which, without any additional-processing like grinding, relieving and the like on teeth, is capable of maintaining the teeth meshing engagement over a wide range in main cross-section and to keep a partial meshing engagement in other sections along the tooth trace direction without any interference or no contact of the teeth, while considering the influence of axial inclination angle, and the relative meshing engagement of the HD with three dimensional DCTP has been analyzed by MATLAB simulation, such as assembly features, movement locus, meshing backlash and contact ratio. For the purpose of analyzing the effect of different tooth profile, the engagement performance of HD with DCTP and HD with traditional involute tooth profile were analyzed and compared, which was obviously verified the better engagement performance of HD with DCTP and the validity and rationality of the research and analysis that presented in this paper.