Patent ID: 8616086

Claim:
A harmonic speed reducer for a robot having a housing, comprising; a frame formed in the housing; an annular circular spline fixed to the frame and having an inner periphery provided with inner teeth; a cylindrical flexspline inserted into the circular spline and having an outer periphery provided with outer teeth that are in engagement with the inner teeth, the flexspline being connected with an output shaft; an elliptical wave generator fitted into the flexspline and connected with an input shaft; and a circular spline mounting screw, wherein the frame has a through hole with its one open end having a peripheral edge portion provided with a circular spline mounting seat of which surface is planar in a direction perpendicular to a center axis line that is an extension of a center line of the output shaft of the harmonic speed reducer; the frame has an internal thread tapped parallel to the center axis line, the internal thread extending from the circular spline mounting seat to the inside of the frame, the internal thread in the circular spline mounting seat having a peripheral edge portion at an opening for the internal thread, the peripheral edge portion being formed with a recess having a diameter larger than a diameter of the internal thread; the circular spline having: (1) a substantially uniform thickness between the frame and a head of the circular spline mounting screw, and (2) a screw insertion hole at a position corresponding to the internal thread, the screw insertion hole being formed from one end face to the other end face of the circular spline so as to be parallel to the center axis line; the circular spline mounting screw is passed through the screw insertion hole of the circular spline and the recess, and threaded into the internal thread, for fixation of the circular spline onto the frame; and the recess has a depth larger than a height of a tapping uplift produced when the internal thread is tapped.