Patent ID: 7173413

Claim:
A rotation detection apparatus for detecting a rotation condition of a rotor that is formed of a magnetic material and has a circumferential periphery with a configuration of successively alternating protruding portions and recessed portions, the apparatus including a sensor chip having a plurality of magnetoresistive elements and a bias magnet for applying a bias magnetic field to said magnetoresistive elements, said detection being performed by sensing changes in resistance values of said magnetoresistive elements due to changes in a magnetic vector of said bias magnetic field as said circumferential periphery of said rotor rotates close to said sensor chip; wherein said magnetoresistive elements of said sensor chip are configured as an array of at least four magnetoresistive element bridges arranged in an orientation determined by a rotation direction of said rotor, and a first distance and a second distance are different from each other and respectively separately set with respect to an end face of said bias magnet, said end face being located directly opposite said circumferential periphery of said rotor, said first distance being a distance between said end face of said bias magnet and each of respective centers of at least two magnetoresistive element bridges which are located at outer positions within said array of magnetoresistive element bridges, and said second distance being a distance between said end face of said bias magnet and each of respective centers of at least two magnetoresistive element bridges which are located at inner positions within said array of magnetoresistive element bridges.