| 摘要 |
PURPOSE:To improve the accuracy of a magnetic detecting element for detecting a magnetic force of a magnetic recording medium by providing a rotary magnet around the periphery of a ring-shaped wall portion located at the periphery of a rotor yoke so as to surround a rotating magnet from the periphery. CONSTITUTION:If a DC voltage is applied between electrodes T1 and T2, a current I flows to magnetism-sensitive portion 21 of magneto-resistance effect element(ME). If magnetic field perpendicular to the current I is applied to the magnetism-sensitive portion 21, the resistance changes. A magnetic recording medium(MM) 34 is magnetized alternately to N pole and S pole at the pitch p. If the ME33 approaches to the MM34 and is displaced in parallel in the direction of magnetic poles arranged, then the ME33 is subjected to a magnetic field change from magnetic poles N and S, and a synchronous resistance change equal to the magnetic pole pitch is obtained. The resistance change is taken out as a change in voltage at one side of a bridge and is converted into a pulse train signal by using a waveform forming circuit or the like. The pulse train signal corresponds to the magnetic pole pitch of magnetic poles N and S magnetized to the MM34. Thus, if the MM34 is fixed to a rotor yoke 21 and magnetic poles are alternately magnetized at the equal pitch on the same circumference, then a speed detection signal can be obtained. |
