Study On Meshing Characteristics And Load Capacity Of Non-circular Gear Transmission

Non-circular gear is a gear mechanism that can achieve variable speed ratio.It has advantages of both variable ratio transmission of cams and accurate transmission of gears.Non-circular gears not only can substitute traditional variable ratio mechanisms and have incomparable advantages over them. At present, there are still some problems in analysis of meshing characteristics and calculation of load capacity for non-circular gear transmission. With the development trend to the power transmission of non-circular gears in recent years, it is becoming more and more important to solve these problems. The researches on meshing characteristics and load capacity of non-circular gears have been fulfilled in this dissertation, a theory basis for its design and manufacturing is provided. The main research works are as follows:1,Manufacturing methods of non-circular gears are studied, tooth profiles' equations generated by hobbing and shaping are derived. Based on AutoCAD platform, a program that can generate tooth profiles of non-circular gears automatically is compiled.2,The relationships between the pitch curve and pressure angle, contact ratio, transmission ratio, angular velocity and angular acceleration of driven gear are discussed, the effects of the rangeability of the pitch curve on the transmission quality of non-circular gears are analyzed, these researches have provided a theory basis for evaluating non-circular gear transmission.3,A method of determining the value and direction of the load on tooth profiles of non-circular gears is investigated, the effects of revolution speed, gravitation moment and rotation inertia on the load of tooth are analyzed, the variation trend of the load in the interval where only a pair tooth meshing have been revealed. These researches have provided a basis for studying on the calculation method of the load capacity of non-circular gears.4,Based on the finite element method, the worst load location on tooth profiles of non-circular gears is determined, the feasibility of calculating the tooth root bending stress of non-circular gears by the equivalent gears is studied in aspects of loading position, mechanical model and load. The effects of the difference of load factors, form factors, stress correction factors of non-circular gears and equivalent gears on the calculation results are deduced. 5,By comparisons between contact positions, length of contact line, comprehensive curvature radiuses of tooth profiles of non-circular gears and equivalent gears, the rationality of calculating the tooth surface contact stress of non-circular gears by the equivalent gears is verified, and the effects of correlate factors on the calculating accuracy are analyzed.6,The calculation results by methods of finite element and equivalent gears are compared, the correctness of calculating the load capacity of non-circular gears by equivalent gears is verified, and the rationality of derivative processes is also confirmed. According to elliptic and oval gears, the variation trends of the tooth root bending stress and tooth surface contact stress of non-circular gears are found out, and the design methods of enhancing the load capacity of non-circular gears have also been given.