Stresses in flex gear of a novel harmonic drive with and without pay load

Abstract

ABSTRACT Contrary to the harmonic drive with conventional oval-shaped cam, the novel harmonic drive consists of cam with circular arc at contact zones and involute toothed flex gear and circular gear. The novel harmonic drive has shown better gearing performance as it follows the conjugate action. However, the stresses developed in flex gear cup are more critical due to the shape of the cam, particularly where the cam takes a different curvature from the circular arc. FEM is adopted to establish the stress map of the whole flex gear cup. Critically stressed portions are identified and the strain results are compared with experiment. It is seen that both the results have good agreement. The stresses in the flex gear considering a geometrically optimum split-cam and with that of conventional cam are collated running the same gear pair, both under no-load and full-load conditions. It is observed that the optimised split-cam is better than the conventional cam in avoiding interference, maintaining constant gear ratio and producing less stresses in the flex gear cup and teeth at the gear meshing zones.