Research on the Lubrication Characteristics of Harmonic Gear Transmission Meshing Areas

Abstract

To analyse the lubrication characteristics of harmonic gears and lay the foundation for the study of its gear tooth failure performance and dynamic characteristics, based on the tooth contact geometry of harmonic gear, the integrated curvature radius, tooth load, and entrainment velocity at the meshing point of the gear teeth in the harmonic gear transmission are analysed. A finite-length line contact elastohydrodynamic lubrication (EHL) model for harmonic gears is established. The numerical calculation method is used to solve the oil film thickness and pressure distribution in the lubricating area, and the effects of rotational speed and temperature on the contacting load ratio and film thickness ratio of the meshing area are studied, as well as the change of oil film stiffness under different working conditions. The results show that along the meshing direction, the pressure is small at the end and reaches a peak at the centre, and the film thickness is the largest in the entrance area and is evenly distributed in the centre contact area. As the speed increases, the gear tooth contact load ratio decreases, the oil film thickness ratio increases, the stiffness of the oil film decreases significantly, and the lubrication effect is improved; but the temperature has the opposite effect. Proper increase of rotation speed and decrease of oil temperature can effectively improve the lubrication characteristics of the system.

Operating Performance of External Non-Involute Spur˝and Helical Gears: A Review

“…In general, the thickness of the oil film is calculated by solving the Reynolds differential equation. This procedure was used by Xu et al [29] in the case of harmonic gear transmission. Typically, the Dawson-Hamrock equation [30] is used for the calculation of the minimum oil-film thickness.…”

Numerical investigations on the lubrication characteristics of involute harmonic gears

“…Different from spur gears and bearings, the relative motion of flexspline–circular spline gear tooth surface in the harmonic drive process is of theoretical complexity. Considering the special meshing process, Xu et al (2020) analyzed the lubrication characteristics and film stiffness in the meshing area. Tang et al (2022) developed a mixed lubrication model for harmonic reducer and discussed the influence of double-circular-arc tooth profile on the comprehensive performance.…”