ROTATIONAL SPEED DETECTOR AND VALVE TIMING DETECTOR USING THIS ROTATIONAL SPEED DETECTOR

摘要

PROBLEM TO BE SOLVED: To provide a rotational speed detector, which can surely detect a rotational speed by having noise resistance and high reliability, and a valve timing detector using this rotational speed detector. SOLUTION: A permanent magnet 6 is provided, which makes a yoke 7, 8 capable of integrally rotating by attracting the yoke 8 to a side of the yoke 7 with an inflow of magnetic flux to a side of the yoke 8 in a location where the yokes 7, 8 are opposed adjacent, on the other hand, a DC exciting coil 12 is fixedly arranged, which makes the coil 7, 8 capable of relatively rotating by adjusting attraction force by the permanent magnet with an inflow of magnetic flux to a side of the yoke 8 in an arrangement side thereof. Further, in a magnetic flux route of the permanent magnet in the yoke 8 and the exciting coil, a rotary surface, such as periodically changing an air gap between a side of the yoke 8 and a side of the exciting coil according to rotation of the yoke 8, is provided, by counting a frequency of sinusoidal wave induction voltage generated in the exciting coil, a rotational speed of the yoke 7 is detected.