| 摘要 |
PROBLEM TO BE SOLVED: To provide an annular magnetic encoder capable of detecting accurately an absolute position by specifying the shape of a magnetized pattern. SOLUTION: This annular magnetic encoder A wherein each magnetic pole 2a of the N-pole and the S-pole is formed in the magnetized state alternately at equal pitches along the circumferential direction of a toroidal magnetic body 2 has an unequal pitch domain 20 equivalent to a portion of a plurality of magnetic poles 2a at least on one spot in the circumferential direction of the toroidal magnetic body. The unequal pitch domain 20 comprises one center specific pole part 2b and a different pole part 2c positioned on the periphery thereof and having a different pole from the specific pole part, and has characteristics wherein the magnetized pattern by the specific pole part 2b and the different pole part 2c is formed axisymmetrically with respect to a center crossing line of the unequal pitch domain 20, and the area of the specific pole part 2b is 40-60% of the area of the unequal pitch domain 20. COPYRIGHT: (C)2008,JPO&INPIT
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