Patent ID: 7207234

Claim:
A ball screw comprising: a screw shaft having a first helical ball rolling groove in an outer periphery thereof; a nut having a second helical ball rolling groove in an inner periphery thereof; a ball rolling path formed between first and second helical ball rolling grooves; a return path connecting one end of said ball rolling path and the other end of said ball rolling path, said return path formed in said nut; an endless circulation path formed by both said ball rolling path and said return path; and load balls disposed within said endless circulation path, wherein a position of said return path in said endless circulation path for said ball screw includes two or more positions, and wherein retaining pieces are interposed between said load balls; and wherein said return path is a tubular tube made of metal; wherein said ball screw is configured so that said nut rotates; wherein said return path has a plurality of return paths and wherein said plurality of return paths are disposed in a peripheral direction of said outer periphery of said nut in such a manner that they are shifted in phase from each other.