| The fatigue failure of the flexspline is one of the main failure modes of the harmonic reducer,the risk of this failure increases with the reduction of the transmission ratio.Therefore,the fatigue fracture of the flexspline is particularly significant in the harmonic reducer with a low speed ratio,which severely restricts the service life of the harmonic reducer with a low speed ratio.In response to the above problems and combined with the transmission characteristics of the low-speed ratio harmonic reducer,the paper proposes a support function-based optimization design method for the geometric parameters of the wave generator profile.Combining the principle of curve mapping and the principle of gear meshing,a harmonic gear tooth profile design model considering the load-bearing deformation of the flexspline is established.The established meshing motion simulation analysis model and finite element model are used to study the meshing characteristics of the harmonic gear after assembly and loading,and then the overall performance of the harmonic reducer is tested through experiments.For improving the service life of the low speed ratio harmonic reducer.It has important theoretical guidance and engineering significance.The main research contents of this thesis are as follows:(1)A mathematical model of the wave generator profile based on the support function is established.After the flexspline and the wave generator are assembled,the relationship between the circumferential bending stress of gear ring and the curvature difference before and after the neutral line deformation is deduced.Taking the geometrical structure properties of the wave generator as the constraint condition,an optimization method of the geometrical parameters of the wave generator profile is proposed,which take reducing the circumferential bending stress of the gear ring of the flexspline as the objective function.(2)The velocity equation of the meshing point of harmonic gear drive under no load is analyzed,and the relationship between the conjugate region and the pressure angle of tooth profile is obtained.Combining the theory of curve mapping and the theory of harmonic gear bidirectional conjugation,a two-dimensional tooth profile design model of harmonic gear considering the flexspline bearing deformation is established.Based on the analysis of the process characteristics of the flexspline hobbing processing and the torsional deformation of the cylinder,the machining displacement curve equation suitable for the flexspline three-dimensional tooth hobbing is put forward.(3)The meshing motion simulation model of the flexspline of harmonic gear at different sections is established,and the motion trajectory and meshing backlash of the flexspline tooth relative to the circular spline tooth are analyzed.By means of finite element method,the deformation law,stress distribution and meshing characteristics of harmonic gear under assembly and load are analyzed.The results show that the assembly stress is the main source of the tooth root stress of the low-speed ratio harmonic reducer,and the coincidence degree and the contact tooth width increase significantly with the increase of the load.Using the design method of the thesis can realize the separation of the action area of assembly stress and meshing stress(4)The processing and basic performance tests of the harmonic reducer is carried out.The wear position of the flexspline tooth surface and the wear condition of the outer ring surface of the flexible bearing is observed,and the coincidence degree between the theoretical prediction results and the actual test results is verified.The results show that when the wave generator rotates once,the no-load transmission error curve appears two cycles,the torsional stiffness of the harmonic reducer increases with the increase of the load,and the vibration frequency is mainly an even multiple of the input frequency. |
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