Patent ID: 8018224
Filing Date: 2011-09-13
Classification: G01D,G01P

Abstract:
1. A rotation detection sensor for detecting a rotational direction of a rotating body having a gear with a tooth moving with rotation of the rotating body, the rotation detection sensor comprising: a magnet configured to produce a magnetic field directed to the tooth of the gear, the magnetic field varying with movement of the tooth; a plurality of magnetic sensors located between the gear and the magnet and aligned along an imaginary straight line perpendicular to a magnetic center axis of the magnet, the plurality of magnetic sensors outputting a plurality of sensor signals shifted in phase from each other, each sensor signal having a voltage or current value that changes depending on the magnetic field; a rotational position detection circuit configured to receive the sensor signals from the plurality of magnetic sensors, the rotational position detection circuit performing a differential operation on the received sensor signals to output a position signal indicating a rotational position of the rotating body, one of the plurality of magnetic sensors being defined as a shared magnetic sensor; and a rotational direction detection circuit configured to receive the sensor signal from the shared magnetic sensor and receive the position signal from the rotational position detection circuit, the rotational direction detection circuit outputting a direction signal, indicating a rotational direction of the rotating body, based on the position signal and the received sensor signal, wherein a distance between an imaginary center line and the shared magnetic sensor is equal to or less than a distance between the imaginary center line and each of the plurality of magnetic sensors other than the shared magnetic sensor, and wherein the imaginary center line connects a rotational center of the rotating body and the imaginary straight line in the shortest distance.