Patent ID: 7148680
Filing Date: 2006-12-12
Classification: G01D

Abstract:
1. A rotation angle detecting device for a rotary object comprising: a rotor connected to the rotary object and including a yoke and a pair of permanent magnets fixed to said yoke at portions thereof opposite to each other with respect to a rotation axis thereof, said pair of permanent magnets being magnetized in a direction to be different in polarity from each other; and a magnetic detector, disposed at the rotation axis of the rotation object, for detecting magnetic flux density of the magnetic flux; wherein at least one of said pair of permanent magnets has a circumferentially extending rut-shape concavity around said magnetic detector, said rut-shape concavity having a surface curved in a plane that includes said rotation axis to make magnetic flux density in the vicinity of said magnetic detector constant in an axial direction parallel with the center axis.