| 摘要 |
PURPOSE:To obtain a large magnetomotive force with small power consumption by forming an electromagnetic coil so as to have a coil length along the major axis of the magnetic core longer than the thickness of the layer. CONSTITUTION:A plate or prismatic magnetic core 34 mounted with the electromagnetic coil 32 and the wedge shaped magnetic core prolonged part acting like to radiate a magnetic field to an optical disk 20 and prolonged from the magnetic core and whose thickness is decreased toward the tip are formed as a magnetic substance incorporatedly as a magnetic flux radiating part 37, and the electromagnetic coil 32 has a coil length along the major axis of the magnetic core part 34 larger than the thickness of the layer and one end of the magnetic flux radiating part 37 is mounted removably to the upper face of a yoke 38 being a seat subject to feedback with a magnetic flux radiated from the magnetic core prolonged part. Thus, the electromagnetic coil is formed thin and long and the length of wire required for one turn, then a large magnetomotive force is obtained with small power consumption.
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