| 摘要 |
<p>PURPOSE:To dispense with the need to consider false detection due to dust or the like by simple constructions of a mechanism and a circuit wherein a magnet ring comprising a multipolar magnetic field and a single-pole magnetic field is engaged with a cam fitted to a main body and variations of these magnetic fields are detected. CONSTITUTION:A cam 4 engages with a handle and rotates simultaneously with the handle. A magnetic ring 5 constructed of an upper magnetic member 5A formed of many magnetic poles and of a lower magnetic member 5B formed of a single magnetic pole and positioned under said member 5A is bonded and fixed to the cam 4. Magnetic fields of these members are detected by a sensor unit 8. As for the magnetic member 5A, two paired magnetoresistance elements detect the passage of the magnetic field and generate a fluctuation of voltage, and this fluctuation of voltage is changed into pulses, which are transmitted to a control device such as a microcomputer. The control device detects the amount of rotation from the number of pulses and the direction of rotation from a phase difference between two pulses. As for the magnetized member 5B, e.g. an N-pole, the initial position is detected from a change in a magnetic field in the same process as the above-mentioned by one magnetoresistance element disposed below the two elements.</p> |
