Determination of load capacity for flexible spline of harmonic drive

Abstract

Harmonic gear drives are mechanical drives with engaging flexible and circular splines having substantial features that determine the area of their application. These features include large gear ratio in one stage, light weight of a drive relative to the transmitted load, possibility of motion transmission through a sealed wall, a flexible spline and wave generator. Due to the nature of transmission, a flexible spline is permanently deformed by a rotating wave generator. There are alternating stresses arising in it. Alternating stresses in a flexible spline often lead to its fatigue failure. The paper presents the analysis of stresses in the flexible spline, and dependences to determine these stresses are considered. Correction factors are introduced to the considered dependencies. These factors account for the influence of the gear rim on the flexible spline rigidity as well as the influence of certain gear dimensions ratio. These factors were obtained on the basis of experiments. As a result, the analysis of flexible gears load capacity dependence on their dimensions and key differentiator, being the thickness of a flexible spline under the gear rim, was conducted.