Rotation detector operable to measure magnetism direction change

#The present invention relates to a rotation detector, and more specifically, to a rotation detector including a rotor having magnets.

#FIG. 1 illustrates how an absolute position detection type detector detects rotational position. The rotation detector includes a rotor 30, which is fixed on a rotating shaft and integrally rotates with the shaft. An N pole zone 32 and an S pole zone 33 are alternately formed at sixty degree intervals on the rotor 30 in a circumferential direction. In positions facing the rotor 30, first to third magnetic resistance elements 31 are arranged around the axis O of the rotor 30 at forty-degree intervals. Each of the first to third resistance elements 31 detects the N pole zone 32 and the S pole zone 33, which alternately pass by the resistance elements 31 at sixty-degree intervals during the rotation of the rotor 30.

#When the N pole zone 32 is detected, the first to third resistance elements 31 respectively output signals SG1, SG2, SG3 having an H level. When the S pole zone 33 is detected, the resistance elements 31 respectively output the signals SG1, SG2, SG3 having an L level. When the zone detected by each resistance element 31 moves from the N pole zone 32 to the S pole zone 33, each of the signals SG1, SG2, SG3 changes from the H level to the L level. Contrarily, when the zone detected by each resistance element 31 moves from the S pole zone 33 to the N pole zone 32, each of the signals SG1, SG2, SG3 changes from the L level to the H level. As shown in FIG. 1, the signals SG1, SG2, SG3 of the resistance elements 31 change gradually between the L and H levels. The reason for this is because a direction of magnetic flux changes gradually when the detected zone moves from the N pole zone 32 to the S pole zone 33. Three comparators (not shown) respectively receive the signals SG1-SG3 and adjust the waveforms of the signals SG1-SG3, thus generating detection signals S1-S3, which change sharply between the L and H levels.

#The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

#FIG. 1 is a waveform diagram illustrating the operation of a prior art rotation detector;

#FIG. 2 is a partial exploded perspective view of a rotation detector according to a first embodiment of the present invention;

#In the drawings, like numerals are used for like elements throughout.

#First Embodiment

#FIG. 2 is a partial exploded perspective view of a rotation detector 1 according to a first embodiment of the present invention. The rotation detector 1 includes a rotor 2, which is preferably made of a metal plate, and a magnetism-detecting member 3. The rotor 2 rotates integrally with a steering shaft 4 about its axis O (FIG. 3).