Patent ID: 7278333

Claim:
A ball screw device, comprising: a screw shaft which has a shaft rolling groove in a spiral shape formed on an outer surface of the screw shaft; a nut which has a nut rolling groove formed on an inner surface of the nut and opposed to the shaft rolling groove, wherein the screw shaft is to be screwed in the nut so that the shaft rolling groove and the nut rolling groove are faced through a plurality of rolling balls; and a lubrication ring, which is made of a lubricant-including material, comes in slide contact with the screw shaft and is arranged in an end portion of the nut, wherein a non-contact portion, which does not come in slide contact with the screw shaft, is formed in the slide contact surface of the lubrication ring, wherein the non-contact portion is configured from a plurality of grooves, which are arranged so as to extend in the axial direction, and have a slit shape width in the circumferential direction, and wherein the non-contact portion forms a space that is closed in the axial direction; wherein the lubricating ring comprises a circumferential wall portion, and the non-contact portion is axially closed by the circumferential wall portion of the lubricating ring.