Patent ID: 6555808
Filing Date: 2003-04-29
Classification: G01D

Abstract:
A rotational angle detecting apparatus, wherein, a relative rotational angle of a rotary body is measured with respect to a reference angle, the apparatus comprising:a disk, which is coaxial with the rotary body, wherein the disk rotates integrally with the rotary body; a first group of openings, wherein the first group of openings includes a plurality of openings arranged about the entire circumference of the disk and spaced from one another by a predetermined pitch, wherein the openings of the first group are used for detecting the relative rotational angle; a first detecting element, which detects openings of the first group and generates a first binary code; a computing means for computing the relative rotational angle of the rotary body in accordance with the first binary code; a second group of openings, wherein the second group of openings includes a plurality of openings arranged concentrically with the first group, wherein the openings of the second group are used for detecting a plurality of reference angle positions that are located at predetermined positions; a second detecting element, which detects openings of the second group and generates a second binary code; a third group openings, wherein the third group includes a plurality of openings arranged concentrically with the first and second groups, wherein the openings of the third opening group are located relative to one another in accordance with a predetermined arrangement; a third detecting element, which detects openings of the third group and generates a third binary code; a memory, which stores a combination of the first binary code and the third binary code in correspondence with angle data, wherein the combination varies depending on the position of the rotary body; and a determining means for determining the reference angle in accordance with the associated combination of the first and third binary codes that are stored by the memory.