| 摘要 |
PCT No. PCT/JP97/02155 Sec. 371 Date May 20, 1998 Sec. 102(e) Date May 20, 1998 PCT Filed Jun. 23, 1997 PCT Pub. No. WO97/48922 PCT Pub. Date Dec. 24, 1997A ball screw unit is provided including a screw shaft having a helical ball rolling groove on the outer peripheral surface thereof; a nut fitted about the screw shaft, having a helical load rolling groove on the inner peripheral surface thereof for forming a helical load ball path in opposing relationship with the ball rolling groove of the screw shaft, and having a ball return path along the axis thereof; a pair of end caps arranged at both ends of the nut, each end cap having change of direction paths for establishing communication between ends of the load ball path and ends of ball return path of the nut respectively; and a number of balls inserted into an endless circulation path which is formed by the load ball path, the ball return path and the change of direction paths, and disposed to circulate through the endless circulation path following the rotation of the screw shaft relative to the nut; wherein each of the change of direction paths formed on the pair of end caps includes a guide groove for guiding the balls which roll out from the load ball path in a direction different from a direction in which the ball rolling groove of the screw shaft extends, and for lifting the balls from the ball rolling groove along the inner peripheral surface of the ball rolling groove; and a ball guide hole to receive the balls lifted from the ball rolling groove by the guide groove, and guide the balls to an entrance of the ball return path of the nut.
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