Patent ID: 8544356
Filing Date: 2013-10-01
Classification: B62D,F16H,Y10T

Abstract:
1. A ball screw unit, comprising: a threaded shaft that has an outer periphery in which a thread groove is formed; a ball screw nut that has an inner periphery in which a thread groove is formed; a spiral rolling-element path that is formed by aligning the thread groove of the threaded shaft with the thread groove of the ball screw nut; and a plurality of balls that are arranged within the rolling-element path, wherein a return path that serves as a shortcut between two points set within the rolling-element path and that allows infinite circulation of each of the balls that roll within the rolling-element path is formed in the ball screw nut, wherein the return path is formed by fitting a circulation member in a pair of fitting holes that pass through the ball screw nut in a radial direction of the ball screw nut and that are formed so as to correspond to the two points set within the rolling-element path, wherein a fitting recess portion that connects the fitting holes to each other is formed in a peripheral face of the ball screw nut, wherein the circulation member includes a pair of fitted portions that are fitted in the respective fitting holes, and a connecting portion that connects the fitted portions, wherein the return path is formed of first paths that are formed by the respective fitted portions fitted in the fitting holes, and a second path that is formed by the connecting portion that is fitted in the fitting recess portion, and wherein the second path is formed when the connecting portion is fitted in the fitting recess portion so that an opening is formed along the entire length of a communication groove that is formed along an axis of the connecting portion such that the opening is blocked by a bottom portion of the fitting recess portion.