Patent ID: 8272289

Claim:
A roller screw comprising: a screw shaft with a spiral roller rolling groove formed on an outer peripheral surface thereof; a nut with a spiral roller rolling groove formed on an inner peripheral surface thereof to be opposed to the spiral roller rolling groove of the screw shaft; and a plurality of rollers arranged in a load roller rolling path between the spiral roller rolling groove of the screw shaft and the spiral roller rolling groove of the nut, wherein a linear roller return path is provided inside the nut, the linear roller return path extending linearly in parallel with an axis line of the nut, direction change path forming members are respectively attached to opposite end faces of the nut in an axis line direction of the nut, each of the direction change path forming members includes an arc-shaped direction change path that connects the load roller rolling path and the linear roller return path, the linear roller return path is twisted to rotate an attitude of each of the rollers for a period during which each of the rollers moves in the linear roller return path, center lines of the direction change paths cross each other at a predetermined open angle as viewed from the axis line direction of the screw shaft, the linear roller return path rotates the attitude of each of the rollers the predetermined open angle, in each of the direction change path forming members is formed a portion bent in the shape of a curve conforming to the shape of an inner periphery of each of the direction change paths while protruding to the inside of the nut from respective opposite end faces of the nut to which the direction change path forming members are attached, and escape grooves conforming in shape to the portion bent in the shape of a curve are respectively formed in the opposite end faces of the nut to which the direction change path forming members are attached.