Wave gear drive with continuous meshing, high ratcheting torque tooth profile

A wave gear drive, comprising:

• a circular rigid internal gear;
• a flexible external gear disposed within the rigid internal gear;
• a wave generator disposed within the flexible external gear;
• the flexible external gear having a flexible cylindrical body and an annular diaphragm that extends in a radial direction from a back end of the cylindrical body, a toothed portion formed on a front end opening portion of the cylindrical body that is flexed into an elliptical shape by a flexing amount generated by the wave generator from a back end portion on the diaphragm side to a front end portion on the opening side thereof that is approximately proportional to distance from the diaphragm;
• wherein a cross-section of the flexible external gear perpendicular to the axis at a prescribed location in a tooth trace direction of the flexible external gear is set to be a main cross-section;
• the rigid internal gear and flexible external gear are gears with a module m;
• the flexible external gear has a number of teeth that is set to be smaller by 2 n (n is a positive integer) than a number of teeth of the rigid internal gear;
• a radial flexing amount of a major axis of an elliptical rim neutral line of the flexible external gear is set at κmn (κ>1);
• a moving route M of a tooth of the flexible external gear with respect to a tooth of the rigid internal gear that accompanies rotation of the wave generator when meshing of the teeth in the main cross-section is approximated by rack meshing is obtained;
• on an entering side of the meshing of the teeth to the major axis of the moving route M, a first similar curve AC is obtained by similarity transformation of a pressure angle α defined as an angle of inclination in a direction orthogonal to the direction of the moving route M in a range that is from 90° at point A in an initial meshing phase to a minimum of 0° at point B, or a range that is midway from point A to point B, using a ratio of similitude λ(λ<1) with point A as center of similarity,
• the first similar curve AC is employed as a basic addendum tooth profile of the rigid internal gear,
• a second similar curve CB is obtained by rotating the first similar curve AC through an angle of 180° with the endpoint C thereof as center of similarity, and by similarity transformation in which the first similar curve AC is multiplied by a ratio of similitude (1−λ)λ, and
• the second similar curve CB is employed as a basic addendum tooth profile of the flexible external gear.