Study on Tooth Profiles of the Harmonic Drive

The present paper deals with an analysis of the kinematics and geometry of the tooth engagement of the harmonic drive, and presents a new method for determining tooth profiles of the harmonic drive. First, two assumptions are set up: (1) Though there is relative motion among the respective teeth of the flexspline during flexing, the individual teeth themselves can be considered to be rigid. (2) The pitch between the respective teeth of the flexspline is constant on the neutral line. Experiments confirm the existence of a neutral line along the flexspline rim which maintain the same length as that prior to bending. Then, tooth profiles of the circular spline and the flexspline are determined according to the theory of gear mechanism that the common tooth normal at the meshing point passes through the pitch point. The analysis is carried out in a plane mechanism.