Patent ID: 6417587
Filing Date: 2002-07-09
Classification: H02K

Abstract:
A motor comprising:a rotor of the motor having a rotor magnet, said rotor magnet includes a driving motor portion and a frequency generator signal generating portion on said rotor magnet, said frequency generator signal generating portion having a plurality of N and S poles being alternatively magnetized at equal predetermined intervals, said frequency generator signal generating portion being magnetized with a narrower pitch of N and S poles than that of said driving portion, said frequency generator signal generating portion being magnetized by including between 240-360 poles; a magnetic resistance sensor having a magneto-sensitive surface, said sensor being positioned on a stator of the motor facing said frequency generator signal generating portion of said rotor with a predetermined gap, for sensing a frequency generator signal in a magnetic field generated by said frequency generator signal generating portion during a rotation of said rotor wherein;said magnetic resistance sensor comprises, a magneto-sensitive surface section for detecting said frequency generator signal and terminals electrically connected to said magneto-sensitive section; a pair of a magnetic resistance devices which are in parallel along a direction identical to the rotational direction of said rotor and are formed on said magneto-sensitive section in micro patterns made of magnetic resistance film such that they are displaced by Â½ pitch with respect to a magnetizing pitch of said frequency generator signal generating portion; a speed detection circuit for detecting the speed of said motor based on the detection results of said magnetic resistance sensor; wherein said frequency generator signal generating portion forming a magnetized area in which a magnetic flux intensity in a plane orthogonal to a principal magnetic flux of said frequency generator signal generating portion is greater than a rated sensitivity of said magnetic resistance sensor which results in said magnetic resistance sensor having an output signal which is in a saturated state in relation to all of said N and S poles of said frequency generator signal generating portion and which results in a through-rate for said output signal without errors at a zero cross point.