| 摘要 |
PURPOSE:To obtain stable output by preventing a magnetoresistance effect element (MR sensor) composed of a ferromagnetic body from receiving magnetic interference, by providing a magnetic shield plate equipped with a flange to a cylindrical magnet for detecting magnetic pole position signals (U-, V- and W-phases). CONSTITUTION:This encoder is constituted of a rotary position detection signal output mechanism consisting of an MR sensor chip 1 and a magnetic recording medium 4 and a magnetic pole position detection signal output mechanism consisting of a cylindrical magnet 2 for detecting U-, V- and W-phases and Hall elements 9-11. A magnetic shield plate 13 equipped with a flange composed of a magnetic material absorbing the magnetic flux emitted from the magnet 12 is inserted between the magnet 12 and the medium 4. This shield plate 13 acts so as to enlarge the area absorbing the magnetic flux emitted from the magnet 12. By this constitution, the amount of the magnetic flux leaked from the magnet 12 reaching the chip 1 is reduced and the shield plate 13 acts so as to allow the magnetic flux to sufficiently cross the elements 9-11. |
