Patent ID: 8336415

Claim:
A roller screw comprising: a screw shaft having a spiral roller rolling surface formed on an outer peripheral surface of the screw shaft; a nut having a loaded roller rolling surface formed in an inner peripheral surface of the nut, facing the roller rolling surface of the screw shaft; a circulation member provided on the nut and having an unloaded return path connecting one end of the loaded roller rolling surface of the nut to an opposite end thereof; a plurality of rollers arranged in a loaded roller rolling path between the roller rolling surface of the screw shaft and the loaded roller rolling surface of the nut and in the unloaded return path of the circulation member; and a scooping portion, provided in the circulation member, for scooping the rollers moving in the loaded roller rolling path up into the unloaded return path, the scooping portion having a pair of diagonal corresponding parts that are in contact with diagonal parts of a rectangular side surface of each of the rollers, a width between the pair of diagonal corresponding parts tapering as the diagonal corresponding parts are deeper in the unloaded return path in such a manner that the unloaded return path has a rectangular-shaped cross section, and the rollers that move from the loaded roller rolling path to the unloaded return path being scooped up into the unloaded return path while the diagonal parts of each of the rollers are held by the diagonal corresponding parts.