Ball screw

A ball screw comprising:

• a screw shaft having a helical ball rolling groove on an outer peripheral surface thereof;
• a nut having a helical loaded ball rolling groove facing the ball rolling groove of the screw shaft, on an inner peripheral surface thereof, a cavity being provided on an axial end of the nut;
• a circulating component where at least part of a return path connecting one end and the other end of the loaded ball rolling groove of the nut is formed, the circulating component being inserted along an axial face of the nut in the cavity of the nut;
• and
• a scooping portion extending radially inwards from the return path of the circulating component, the scooping portion being configured to scoop a deviating ball that deviates from a circulation raceway and that does not contact a contact portion on the outer peripheral side of the return path, the deviating ball rolling between the ball rolling groove of the screw shaft and the loaded ball rolling groove of the nut into the return path,
• wherein the contact portion whose cross-sectional shape is a Gothic-arch groove is configured to contact at least one non-deviating ball, the contact portion being formed on an outer peripheral side of the return path of the circulating component opposite to the scooping portion, the contact portion being configured to contact the at least one non-deviating ball at two contact points, in a cross-sectional view perpendicular to the return path, and the scooping portion is configured to scoop the deviating ball into the return path,
• a line connecting to a bottom of the contact portion of the circulating component is twisted around a center line of the return path in accordance with a change in the direction of a centrifugal force to act on the non-deviating ball so that the bottom of the contact portion is in the direction of the centrifugal force,
• the bottom of an end portion of the contact portion of the circulating component is continuous to a bottom of the loaded ball rolling groove of the nut, and
• a curvature of an end portion of the center line of the return path of the circulating component is substantially the same as a curvature of the loaded ball rolling groove of the nut, and the center line of the return path of the circulating component is a curve having a curvature that is gradually reduced with increasing distance from the loaded ball rolling groove of the nut, as viewed from the axial direction of the nut.