Patent ID: 7530292
Filing Date: 2009-05-12
Classification: F16H,Y10T

Abstract:
1. A wave gear drive having a circular rigid internal gear, inside which is disposed a flexible external gear, inside which a wave generator is inserted, 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 tooth portion formed on an opening end side region of the cylindrical body being flexed into an elliptic shape by a deflection amount generated by the wave generator from a back end portion on the diaphragm side to a front end portion on the opening end side thereof that is approximately proportional to distance from the diaphragm, wherein: the rigid internal gear is a conical gear with a module m, the flexible external gear is a spur gear with a module m, a number of teeth of the flexible external gear is 2n (n being a positive integer) fewer than a number of teeth of the rigid internal gear, a deflection amount of the major axis of an elliptic rim neutral line of the flexible external gear in a cross-section of the flexible external gear perpendicular to an axis in a direction of the tooth trace thereof is set to be 2 κmn (κ>1), engagement of the teeth of the rigid internal gear and flexible external gear in a cross-section of the flexible external gear perpendicular to the axis in an intermediate portion in the direction of the tooth trace thereof (hereinafter referred to as the main cross-section) is approximated as rack engagement and a moving route of the teeth of the flexible external gear with respect to the teeth of the rigid internal gear that accompanies rotation of the wave generator is obtained, from the major axis to a tooth departure side on the moving route, employing a curved portion from a deepest engaged position of the two gears at which an inclination angle of a radial line to the moving route of the rigid internal gear is 90° to a position at which the inclination angle is α(0°<α<30°), employing as a tooth profile of the flexible external gear a first analogous curve obtained by enlarging the curved portion by λ times, and employing as a tooth profile of the rigid internal gear a second analogous curve obtained by enlarging the curved portion by (λ+1) times.