Patent ID: 7002339

Claim:
A rotation angle detecting device comprising: a magnet provided in a rotary member, the magnet having a shape of one of a ring and a disc, a center of a peripheral circle of the magnet being substantially coaxially aligned with a rotational axis of the rotary member, the magnet having a magnetic flux generation section and a magnetic flux absorption section that are oriented in radial directions vertical to the rotational axis; a magnetic flux concentrator made of a magnetic material, the magnetic flux concentrator rotating integrally with the magnet, the magnetic flux concentrator having a shape of one of a ring and a disc, a center of a peripheral circle of the magnetic flux concentrator being substantially coaxially aligned with the rotational axis, the magnetic flux concentrator being disposed substantially parallel to the magnet; a first magnetic sensor provided on a fixed member, the first magnetic sensor being disposed between the peripheral circle of the magnet and the peripheral circle of the magnetic flux concentrator to detect variation in magnetism; and a second magnetic sensor provided on the fixed member, the second magnetic sensor being disposed between the peripheral circle of the magnet and the peripheral circle of the magnetic flux concentrator at a predetermined angle away from the first magnetic sensor in a rotational direction in order to detect variation in magnetism, wherein the rotation angle detecting device detects the rotation angle of the rotary member with respect to the fixed member by magnetic flux passing through the first and second magnetic sensors.