Patent ID: 8191439

Claim:
A wave-gear-type linear-actuation mechanism characterized in comprising: a first circular spline and a second circular spline coaxially disposed in parallel; a radially flexible cylindrical flexspline disposed inside the first and second circular splines; a wave generator fitted inside the flexspline, the wave generator bending the flexspline into a noncircular shape, and causing the flexspline to mesh with the first and second circular splines at a plurality of locations along a circumferential direction; a lead screw formed on an outer peripheral surface of the first circular spline; and a circular nut having a screw groove threaded onto the lead screw; wherein the first circular spline has the same number of teeth as the flexspline; the second circular spline has at least n more teeth than the flexspline (n is a positive integer); the second circular spline is restrained so as not to rotate; the wave generator has a hollow shaft, a first wave plug and a second wave plug, each of which plugs has a noncircular outline and is integrally formed on an outer peripheral surface of the hollow shaft with a fixed gap provided along an axial direction thereof between the first plug and the second plug, and first and second wave bearings are installed on the first and second wave plug, respectively, and, as the wave generator rotates, the flexspline rotates relative to the second circular spline at a rotational speed corresponding to a difference in a number of teeth on the second circular spline and a number of teeth on the flexspline, the first circular spline integrally rotates with the flexspline, and the circular nut threaded on the lead screw of the first circular spline moves in a direction of a central axis of the first circular spline as the first circular spline rotates.