Patent ID: 6600308
Filing Date: 2003-07-29
Classification: G01D,H03M

Abstract:
A magnetic encoder comprising:a magnetic drum which is provided on the outer peripheral surface thereof with a plurality of magnetized portions which are spaced at equal pitches; a magnetic sensor unit which is opposed to the outer peripheral surface of the magnetic drum, wherein one of said magnetic drum and said magnetic sensor constitute a rotational member, said rotational member being relatively rotatable with respect to the other of said magnetic drum and said magnetic sensor, wherein output detection signals from said magnetic sensor unit are cyclically varied in accordance with the relative rotation angle of the rotational member and said other of said magnetic drum and said magnetic sensor; a plurality of magnetic sensors which are provided in said magnetic sensor unit, wherein in order to correct harmonic distortion of an arbitrary order, said magnetic sensors are spaced at a distance smaller than one pitch of the magnetized portions, so that detection signals of each of said magnetic sensors are offset by a predetermined phase difference; and a calculation device for calculating two sets of vectorial signals, from detection-signal output levels of said plurality of magnetic sensors generated upon rotation of said rotational member, using the following equations (1) and (2): Aout=&Sgr;Wm=1VmÃ—sin &thgr;mâ€ƒâ€ƒ(1); and Bout=&Sgr;Wm=1VmÃ—cos &thgr;mâ€ƒâ€ƒ(2); wherein W designates the number of said plurality of magnetic sensors; Vm designates said detection-signal output levels of said plurality of magnetic sensors generated upon rotation of said rotational member; Aout designates a set of vectorial signals; and Bout designates another set of vectorial signals.