| 摘要 |
A ball screw apparatus having a revolving position detector for detecting revolutions of a ball screw nut and a ball spline nut and a number-of-revolutions altering means for issuing a command to decrement or increment the number of revolutions of the ball screw nut so that a difference between sets of revolution numbers becomes zero. In the ball screw apparatus, a driving motor is disposed in parallel with a driving shaft. An output of the driving motor is transmitted via a belt to each nut. When driving the motor in a clutch-off/brake-on state, only the ball screw nut is driven to revolve, and the driving shaft is slid in the axial direction. When driving the motor in a clutch-on/brake-off state, the two nuts revolve together, and the driving shaft is rotationally driven. A reduction ratio on the side of the ball screw nut is set equal to that on the side of the ball spline nut, whereby the two nuts synchronously revolve.
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