Patent ID: 8408087

Claim:
A screw device, comprising: a screw shaft comprising a spiral rolling-element rolling groove on an outer circumferential surface; a nut body comprising a spiral loaded rolling-element rolling groove on an inner circumferential surface to oppose the rolling-element rolling groove of the screw shaft, a rolling-element returning passage in the nut body, which returns rolling elements rolling in a loaded rolling-element rolling passage formed between the loaded rolling-element rolling groove and the rolling-element rolling groove of the screw shaft, and a concave portion formed at an end face of the nut body along less than all of an inner peripheral surface of the nut body, the concave portion being connected to the rolling-element returning passage; a circulation member attached to and inserted into the concave portion and comprising a direction changing passage entirely surrounded by the circulation member in cross-section, the direction changing passage connecting the loaded rolling-element rolling passage and the rolling-element returning passage; a disk-shaped sound insulating member attached and in direct contact with the end face of the nut body and comprising an inner circumferential surface coming into contact with the screw shaft, the sound insulating member covering the circulation member such that the circulation member is not exposed to the outside, thereby reducing sounds occurring from the circulation member, a cap member comprising (i) an intimate portion coming into intimate contact with the sound insulating member, and (ii) a seal holding portion, and a seal member inserted into the seal holding portion so as to remove foreign substances therefrom and to prevent a lubricant from leaking from inside the nut body, wherein the cap member is secured to the nut body by a fastening means so that the sound insulating member is held between the cap member and the nut body, and wherein the sound insulating member has a hole formed therein for inserting the screw.