| 摘要 |
PURPOSE:To make a drive shaft stand still when not being subject to control and to maintain the state at no power supply and no contact, by a method wherein brake torque is supplied to the drive shaft by brake torque generating means comprising a magnet and a magnetic disk. CONSTITUTION:An automatic apparatus Z-axis control mechanism has brake torque generating means for supplying a drive shaft 7 with brake torque in order that structure to be slid in the vertical direction through a screw is prevented from freely falling by means of force applied at still state including self weight due to rotation of the drive shaft 7. The brake torque generating means is composed of opposing magnet 1 and a magnetic disk 2. The magnet 1 comprises a plurality of permanent magnet pieces having alternately changed polarities and arranged in circular ring form, and the magnetic disk 2 is rotated integrally with the drive shaft 7 and receives brake torque from the fixed magnet 1.
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