| 摘要 |
Provided is a ball screw device capable of downsizing a nut member (2), simplifying a circulation structure for balls (3), in which endless circulation of the balls (3) between the nut member (2) and a screw shaft (1) can be smoothly performed, and fluctuation of a rotation torque which occurs when the screw shaft (1) rotates relative to the nut member (2) can be suppressed as small as possible. A ball circulation groove (21) corresponding to all the periphery of the screw shaft (1) is formed on the inner peripheral surface of the nut member (2). The ball circulation groove (21) includes a load rolling groove (22) opposed to the ball rolling groove (10) in the screw shaft (1) and a ball returning groove (23) connecting one end and another end of the load rolling groove (22) to each other. The ball returning groove (23) is directly formed on the inner peripheral surface of the nut member (2) continuously with the load rolling groove (22) with no boundary, and a sectional shape of the ball returning groove (23), which is perpendicular to a ball advancing direction is formed in a Gothic arch shape so that each of the balls (3) is brought into contact with the ball returning groove (23) at two points. |
