Minimal Tooth Number of Flexspline in Harmonic Gear Drive with External Wave Generator

摘要

Wave generators are located inside of flexsplines in most harmonic gear drive devices. Because the teeth on the wheel rim of the flexspline are distributed radially, there is a bigger stress concentration on the tooth root of the flexspline meshing with a circular spline, where a fatigue fracture is more likely to occur under the alternating force exerted by the wave generator. Our solution to this problem is to place the wave generator outside of the flexspline, which is a scheme named harmonic gear drive (HGD) with external wave generator (EWG). A formula to calculate the minimal tooth number of a flexspline that satisfies the requirement in fatigue strength for the flexspline is derived in this paper.