| 摘要 |
PURPOSE:To discriminate easily the number of kinds of sheet jacket by detecting whether an induced current which varies with the number (including 0) of yokes which are components of a detecting means exists or not, or the state of pulses. CONSTITUTION:When a spindle motor 52 is rotated, a magnetic disk 28 is rotated, and the tips of yokes 37 provided while exposed to the top end surface of the center core 31 of the magnetic disk 28 move on a track shown by a broken line in a figure while facing the end parts coils 12 and 12 on the side of a chassis 3 in keeping a slight interval. At this time, induced currents are generated intermittently at the coils 12 and 12. Those induced currents are detected by the current detecting circuit of a control circuit through winding end parts of the coils 12 and 12. The number of pulses of the detected induced currents is counted to detect the number of revolutions of the magnetic disk 28, and the kind of a loaded sheet jacket is discriminated by detecting whether the currents are present or not or the state of the pulses. |
