Patent ID: 8330456

Claim:
A rotational angle sensing device comprising: a yoke made of a magnetic material and configured into a tubular form; a first magnet installed to a first section of an inner peripheral wall of the yoke; a second magnet installed to a second section of the inner peripheral wall of the yoke to oppose the first magnet in a first direction across a central axis of the yoke, said first direction being perpendicular to said central axis, wherein a polarity of a magnetic pole at a radially inner side of the second magnet is opposite from a polarity of a magnetic pole at a radially inner side of the first magnet; and a magnetic sensor configured to sense a magnetic field that is generated between the first magnet and the second magnet, wherein: the magnetic sensor is placed in the magnetic field and outputs an electrical signal that corresponds to a direction of the magnetic field, said magnetic field changing when a relative rotation occurs between the magnetic sensor and the first and second magnets; the yoke is constructed from at least one plate material that is processed to have the tubular form; at least one contact portion, at each of which a corresponding circumferential end part of the at least one plate material and another corresponding circumferential end part of the at least one plate material contact with each other, is placed radially outward of at least one of the first magnet and the second magnet; the yoke has a first inner diameter that is measured in the first direction; the yoke has a second inner diameter that is measured in a second direction that is perpendicular to both of the first direction and the central axis of the yoke; the second inner diameter of the yoke is larger than the first inner diameter of the yoke; a radius of curvature of a radially outer side wall of the first magnet is larger than a radius of curvature of the first section of the inner peripheral wall of the yoke; and a radius of curvature of a radially outer side wall of the second magnet is larger than a radius of curvature of the second section of the inner peripheral wall of the yoke.