Patent ID: 6559565
Filing Date: 2003-05-06
Classification: H02K,Y10S

Abstract:
A motor apparatus having a rotor placed rotatably on a stator base and provided with an FG signal for controlling the rotation of the rotor, the motor apparatus comprising:a driving magnet having an even number of magnetic poles evenly placed on the outer circumference of the rotor, wherein the even number is not less than 12 and not more than 32, and having a magnetic flux density pattern superposed with an â€œnâ€ th (n is either one of 3 and 5) harmonic component, wherein the driving magnet is made of Ndâ€”Feâ€”B system material, and wherein a peak value of the magnetic flux density pattern of the driving magnet is in the range of 0.2 to 0.6 T (Tesla) in order to suppress rotational fluctuation caused by controlling the rotation of rotor within 5%; and an FG coil provided on the circumference of the stator base in the position opposing to each of the magnetic poles of the driving magnet with keeping a predetermined gap between the FG coil and the driving magnet, wherein the FG coil has a folding pattern of being folded alternately in the radial direction by a fold pitch angle of 1/n of a pitch angle of the driving magnet.