Double-circular-arc tooth profile design and parametric analysis on the comprehensive performance of the harmonic drive

Abstract

A tooth profile is of significant importance to the performance of a harmonic drive. Available studies about designing a tooth profile only consider the influence of the tooth profile on the meshing characteristics from a macro perspective. However, the effects of the surface roughness and contact geometry of the tooth on the lubrication characteristics from the micro perspective are rarely reported. In the present study, a double-circular-arc tooth profile is used as the basic tooth profile of the flexspline. Based on the modified kinematic method, a conjugate profile is calculated and the tooth profile of the circular spline is obtained. On this basis, the mathematical model for the mixed lubrication of the harmonic drive with a double-circular-arc tooth profile is established by considering the factors of the normal load of meshing point, relative velocity, contact geometry, and surface roughness. The comprehensive performance under different double-circular-arc tooth profile parameters (tooth face radius, tooth flank radius, and common inclination) is analyzed. To verify the correctness of the research, four sets of harmonic drives are designed and machined for testing their basic performance. The results show that the parameters of the double-circular-arc tooth profile have multiple influences on the comprehensive performance. The meshing performance and lubrication performance are restricted. Parameter control can effectively improve comprehensive performance and different tooth profile parameters should be designed for different applications.