Patent ID: 8368392
Filing Date: 2013-02-05
Classification: G01D

Abstract:
1. A magnetic encoder comprising: a multi-pole magnet in which N-poles and S-poles are formed in alternating fashion at equiangular intervals along a circumferential direction; first and second magnetic detecting elements adjacently arranged so as to output a sinusoidal signal having a mutual phase difference of 90° in accompaniment with the rotation of the multi-pole magnet; third and fourth magnetic detecting elements adjacently arranged so as to output a sinusoidal signal having a mutual phase difference of 90° in accompaniment with the rotation of the multi-pole magnet; and a signal processing circuit whereby a signal that represents the rotational position of a rotational shaft to which the multi-pole magnet is coaxially secured is generated on the basis of a sum signal or a differential signal of the output signal of the first magnetic detecting element and the output signal of the third magnetic detecting element, and on the basis of a sum signal or a differential signal of the output signal of the second magnetic detecting element and the output signal of the fourth magnetic detecting element, wherein the number of magnetic poles P of the multi-pole magnet is an even number of 4 or higher; the third and fourth magnetic detecting elements are arranged at angular positions separated by a mechanical angle of about 180° along a circumferential direction of the multi-pole magnet with respect to the first and second magnetic detecting elements; the first and third magnetic detecting elements are arranged in the same angular positions or separated by an electrical angle of 180°; and the second and fourth magnetic detecting elements are arranged in the same angular positions or separated by an electrical angle of 180°.