Rotation angle detector
View Patent ↗A rotation angle detector includes: a magnet attached to a rotating shaft and magnetized in a certain direction orthogonal to an axis of the rotating shaft; and a non-rotary magneto-electric transducer placed to be opposed to an end surface of the magnet, and configured to detect a rotation angle of the rotating shaft in cooperation with the magnet through magneto-electric transduction. A concave curved surface is formed in the end surface of the magnet in order to make a magnetic flux of a magnetic field facing the end surface of the magnet closer to the magnet and flattened. Accordingly, it is possible to provide a rotation angle detector which is compact in size and has a stable accuracy for detecting the rotation angle, by making the curvature of the magnetic flux near the end surface of the magnet small and placing the magneto-electric transducer in that location.
1. A rotation angle detector comprising:
a magnet attached to an end portion of a rotating shaft, and magnetized in a predetermined direction orthogonal to an axis of the rotating shaft; and
a non-rotary magneto-electric transducer placed so as to be opposed to an end surface of the magnet in a direction of the axis of the rotating shaft, that detects a rotation angle of the rotating shaft in cooperation with the magnet through magneto-electric transduction, wherein
the magnet has a similar diameter as the end portion of the rotating shaft and has a solid cylindrical shape, and
a concave curved surface is formed in the end surface of the magnet opposite the non-rotary magneto-electric transducer in order to direct a magnetic flux of a magnetic field of the magnet closer to the magnet in the direction of the axis of the rotating shaft.
2. The rotation angle detector according to claim 1 , wherein
the rotating shaft is formed with an anchor groove at its end portion and the magnet is provided to enter the anchor groove to increase a bonding strength between the rotating shaft and the magnet.
3. The rotation angle detector according to claim 1 , wherein
the concave curved surface is formed as a concave spherical surface having a center on the axis of the rotating shaft, and
a magnetism sensing center of the magneto-electric transducer is placed at or in a vicinity of the center.
4. The rotation angle detector according to claim 2 , wherein
the magnet is made from a magnetic synthetic resin, and
the magnet is molded on an end portion of the rotating shaft.