Roller screw

Abstract

Provided is a roller screw capable of preventing rollers moving from an unloaded return path to a loaded roller rolling path from coming into collision with a scooping portion. The roller screw has: a screw shafthaving a spiral roller rolling surfaceformed on an outer peripheral surface thereof; a nuthaving a loaded roller rolling surfaceformed in an inner peripheral surface thereof; a circulation memberhaving an unloaded return path connecting one end of the loaded roller rolling surfaceof the nutto an opposite end thereof; and a plurality of rollersarranged in a loaded roller rolling pathand the unloaded return path. In the circulation member, as a scooping portion that juts toward the screw shaftand provided for scooping the rollersmoving in the loaded roller rolling pathup into the unloaded return path, a pair of diagonal corresponding partsis provided which are in contact with diagonal partsof a rectangular side surface of each rollerand a width between which is gradually narrower as they are deeper in the unloaded return path in such a manner that a cross section of the unloaded return path is closer to a rectangle.