Patent ID: 8258782

Claim:
An angle detecting apparatus comprising: a rotor fixed to a rotating shaft and for which when an XY orthogonal coordinate system is defined on a plane of rotation for the rotor with a center of rotation of the rotor defined as a coordinate origin, a sum of distances between the center of rotation and respective two points where two straight lines crossing at the center of rotation at a crossing angle of (π/n; (n) is any integer of at least two) cross an outer periphery of the rotor is constant and for which a planar shape of the rotor projected on the plane of rotation is symmetric with respect to Y=tan(π/2n)X; and a first magnetic sensor and a second magnetic sensor arranged close to the outer periphery of the rotor so as to have a difference in angle (π/n) with respect to the center of rotation, the first magnetic sensor detecting a change in magnetic field corresponding to a change in a first distance between the outer periphery of the rotor and the first magnetic sensor which distance varies periodically as the rotor rotates, to output a first detection signal, the second magnetic sensor detecting a change in magnetic field corresponding to a change in a second distance between the outer periphery of the rotor and the second magnetic sensor which distance varies complementarily in conjunction with variation in first distance, to output a second detection signal; differential operational means for performing differential operation on the first detection signal and the second detection signal to output a differential signal; and angle calculating means for calculating the angle of rotation of the rotating shaft based on the differential signal.