Abstract: The present invention aims for providing a rotation angle detecting device which achieves both the reduction of a manufacturing cost and the elimination of the influence of a reverse magnetic field. A rotating magnet 12 is attached on a rotary shaft 11 and generates a rotating magnetic field by rotating together with the rotary shaft 11. A rotation angle detecting element unit 13 includes a magnetic detecting element and a quadrupole auxiliary magnet 160. The quadrupole auxiliary magnet 160 includes plural first pole pieces 161a to 161d arranged radially. Second pole pieces 162a and 162b are inserted between the first pole pieces 161a to 161d. The second pole pieces 162a and 162b erase a reverse magnetic field directed to a reverse direction of a composite magnetic field generated by the first pole pieces 161a to 161d.

Abstract: A rotational angle detection device enables rotational angle detection for rotational angles ranging from 0° to 360° with an extremely simple configuration. The rotational angle detection device includes: a rotating magnet 12, which is mounted on one end of a rotating shaft 11; a four-pole auxiliary magnet 14, which is mounted on a substrate 13 opposed to the rotating magnet 12 without contact; and a magnetic sensor 15, which is mounted on the opposite side of the substrate 13. The four-pole auxiliary magnet 14 converts one rotating magnetic field of 0° to 360° provided by the rotating magnet 12 in a region where the magnetic sensor 15 is positioned into another rotating magnetic field of 0° to 180°.

Abstract: A rotational angle detection device enables rotational angle detection for rotational angles ranging from 0° to 360° with an extremely simple configuration. The rotational angle detection device includes: a rotating magnet 12, which is mounted on one end of a rotating shaft 11; a four-pole auxiliary magnet 14, which is mounted on a substrate 13 opposed to the rotating magnet 12 without contact; and a magnetic sensor 15, which is mounted on the opposite side of the substrate 13. The four-pole auxiliary magnet 14 converts one rotating magnetic field of 0° to 360° provided by the rotating magnet 12 in a region where the magnetic sensor 15 is positioned into another rotating magnetic field of 0° to 180°.