| The traditional tooth profile of harmonic gear is prone to tooth surface wear and bending fatigue fracture under the conditions of high impact load and high load,which seriously affects the meshing performance of harmonic gear transmission,and ultimately reduces the service life of harmonic gear reducer.The "IH" tooth profile is a new tooth form invented on the basis of the "S" tooth profile,which enlarges the width of tooth groove opposite to the tooth thickness and the root radius,resulting in a reduction of tooth surface contact stress and root bending stress.Thus tooth surface wear is reduced,and tooth root fatigue fracture is effectively inhibited,and extends the service life of harmonic gear reducer.In the thesis,the model WX-CSG-17-80 harmonic gear reducer is taken as the research model,and the tooth shapes of circular spline and flexible spline are mainly studied,and its meshing performance and gear teeth force are analyzed.The main research contents are as follows:(1)The overall structure of harmonic gear drive and the structure of the circular spline,the flexible spline and the wave generator which are the main components of harmonic gear drive are designed.Then the main structural parameters and corresponding geometric dimensions are determined.Single-stage transmission as the overall structure is simple and universal,and its efficiency can reach 80%~90%.The flexible spline is a short cup type,which shortens the working space and increases the torsional rigidity.The circular spline is a single-ended boss type and is easy to fix and sealing.The contour of the wave generator is elliptical reducing the flexural surface deformation stress.(2)The tooth profiles of the circular spline and the flexible spline and the contour of the wave generator are designed and the corresponding equations are established.The 3D contour measurements are performed on the contour of the samples to obtain the point data,and the fitting is performed based on the least square principle by using MATLAB.The results show that the tooth profiles of the circular spline and the flexible spline are composed of two arcs at root of the tooth,the straight line and two arcs at the tip of the tooth,and the contour curve of the wave generator cam is the standard ellipse.(3)The process of meshing in and out the tooth slot of the circular spline with a single tooth of the flexible spline is simulated by a computer,and no interference between gear teeth is detected.At the same time,combined with the three indexes for evaluating the meshing performance,which are the number of simultaneous meshing teeth,the meshing backlash and the maximum meshing d epth,the overall meshing figure and backlash distribution curve are output by using MATLAB.The results show that the number of simultaneous meshing teeth is 50 pairs,which accounts for 31.25% of the total number of flexure teeth.The maximum depth of meshing is 0.3425.the change of backlash under no-load,rated load and overload conditions is relatively gentle,which reflects a good overall meshing performance.(4)The finite element analysis model of the harmonic gear drive is constructed.The contact model of the wave generator cam and the front wall of the flexible spline is proposed for the nonlinear problem in the flexible spline deformation process.Then the stress of the gear teeth of the flexible spline during the meshing transmission under the rated load is analyzed.The results show that the maximum stress of the root of the flexible gear is 330.11 MPa,which effectively relieves the stress concentration and improves the bearing capacity of the harmonic gear. |
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