Patent ID: 7609057

Claim:
A rotation angle detecting device, which comprises: a magnetic generator arranged in a rotatable member and having a magnetic anisotropy in a circumferential direction around an axis of rotation; a plurality of linear magnetic sensor arrays arranged on a stationary member, confronting the magnetic generator in a direction along the rotational axis of the rotatable member; an AD converter circuit for converting respective outputs of the magnetic sensor arrays into digital signals; a zero-crossing-position detector for detecting a zero-crossing-position in a distribution of magnetic field in reference to an output of the AD converter circuit; an angle calculator for detecting an angle of rotation of the magnetic generator in reference to the zero-crossing-position detected by the zero-crossing-position detector; a detected-position storage for storing the zero-crossing-position, which is detected by the zero-crossing-position detector for each cycle of processing; a scanning range setting circuit for setting a subsequent scanning range for the magnetic sensor array at a predetermined standard on the basis of the zero-crossing-position that has been stored; and a scanning circuit for reading a detection signal of the magnetic sensor array within the scanning range set by the scanning range setting circuit; wherein the zero-crossing-position detector is operable to detect the zero-crossing-position with use of a partial detection signal of the scanning range that is a limited part of the magnetic sensor array and the angle calculator is operable to detect the angle of rotation in reference to the zero-crossing-position detected from the partial detection signal.