| 摘要 |
PROBLEM TO BE SOLVED: To provide a ball screw capable of inhibiting the fall of a ball in assembling and conveying it without increasing the cost.SOLUTION: A ball screw includes: a nut, on the inner circumferential surface of which a female screw groove is formed; a screw shaft, on the outer circumferential surface of which a male screw groove is formed; balls disposed between a track formed by the female screw groove of the nut and the male screw groove of the screw shaft; and a ball circulating passage, which returns the balls from the end point to the start point of the track. A fall inhibiting part, which inhibits the fall of the balls, is formed integrally on the screw shaft. A minimum value M of a distance between the outer circumferential surface of the fall inhibiting part and the center of the screw shaft is expressed by the following expression (1): M>Dni/2-Da, where Dni denotes the inner diameter of the land part of the female screw groove, and Da the diameter of the balls respectively. |
