| 摘要 |
In a ball screw according to the present invention, four circulation passages forming a circulation route are respectively arranged in the axial direction of the ball screw. The mounting positions of the second and third circulation passages A2 and A3 are set at positions which are reversed 180 degrees in the circumferential direction thereof with respect to the mounting positions of the first and fourth circulation passages A1 and A4. Accordingly, it is possible to provide a ball screw which can reduce variations in a load distribution along the axial direction of the ball screw caused by moments around a surface perpendicular to the axis of the ball screw that are generated by shifting circumferential-direction phases between circulation passages forming a circulation route from one another.
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