| 摘要 |
PURPOSE:To aim at enhancing an attracting force of a magnetic chuck and as well at preventing, for a long time, the attracting surface of the magnetic chuck from shifting, by disposing an irreversible permanent magnet and a reversible permanent magnet in a through hole in the surface plate of the magnetic chuck through the intermediary of a nonmagnetic material, and as well by surrounding the reversible permanent magnet with an energizing coil. CONSTITUTION:When an external magnetic field is applied to a reversible permanent magnet 28 in the direction reverse to the magnetizing direction thereof by feeding a pulse-like current to an energizing coil 32, the magnetizing direction of the reversible permanent magnet 28 is turned into the direction indicated by the arrow 40. With this arrangement, the area of the surface plate section 12c of an attracting surface 22 and the area of a magnetic pole member 18 are magnetized in different polarities with respect to each other. In this condition when a magnetic member 36 is set on the attracting surface 22, the magnetic member 36 is locked by closed magnetic fluxes offered by irreversible and reversible permanent magnets 24, 28. When the polarity of the energizing coil 32 is reversed, the attracting surface 22 is magnetically deenergized. With this arrangement, it is possible to prevent, for a long time, the attracting surface from shifting.
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