# US 2017/0254666 A1 · Rotation angle sensor and correction method for the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2017/0254666 A1 - Document ID: US20170254666A1 - Status: Published application - Kind: A1 - Application number: 15/266,457 - Filed: 2016-09-15 - Published: 2017-09-07 - Earliest claimed: 2016-03-03 - Assignees: Hitachi Metals, Ltd. - Applicants: Hitachi Metals, Ltd. - Inventors: Yukio IKEDA - Web page: https://patentgrep.com/patent/US20170254666A1 ## CPC - G01D 5/14: influencing the magnitude of a current or voltage - G01D 5/2449: {using hard-stored calibration data} - G01D 18/00: Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00 - G01D: MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR ## Abstract A rotation angle sensor includes a ring magnet that is provided around a rotating shaft, a magnetic field sensor that detects magnetic field strengths in radial and tangent directions of the rotating shaft, a rotation angle calculation section that calculates a rotation angle of the rotating shaft based on the magnetic field strengths detected by the magnetic field sensor, a correction value storage section that stores correction values preliminarily set for each magnetic pole or each pair of magnetic poles facing the magnetic field sensor, a facing magnetic pole detecting means that detects the magnetic pole or the pair of magnetic poles facing the magnetic field sensor, and a rotation angle correcting section that extracts correction values corresponding to the magnetic pole or the pair of magnetic poles detected, and corrects a rotation angle calculated in the rotation angle calculation section by using the extracted correction values. ## Claims ### Claim 1 A rotation angle sensor, comprising: a ring magnet that is provided around a rotating shaft subjected to rotation angle detection so as to be integrally rotated with the rotating shaft and is magnetized so as to have not less than one pair of magnetic poles with different polarities arranged in a circumferential direction; a magnetic field sensor that is provided so as to face the ring magnet in a radial direction of the rotating shaft and detects magnetic field strengths in radial and tangent directions of the rotating shaft; a rotation angle calculation section that calculates a rotation angle of the rotating shaft based on the magnetic field strengths detected by the magnetic field sensor; a correction value storage section that stores correction values preliminarily set for each magnetic pole, or each pair of magnetic poles, facing the magnetic field sensor; a facing magnetic pole detecting means that detects the magnetic pole or the pair of magnetic poles facing the magnetic field sensor; and a rotation angle correcting section that refers to the correction value storage section, extracts correction values corresponding to the magnetic pole or the pair of magnetic poles detected by the facing magnetic pole detecting means, and corrects a rotation angle calculated in the rotation angle calculation section by using the extracted correction values. ### Claim 2 (depends on 1) The rotation angle sensor according to claim 1, wherein the rotation angle calculation section comprises a relative rotation angle calculation portion for calculating a relative rotation angle within an angular range in which a given magnetic pole or a given pair of magnetic poles faces the magnetic field sensor, and wherein the rotation angle correcting section is configured to correct the relative rotation angle calculated by the relative rotation angle calculation portion by using the correction values. ### Claim 3 (depends on 2) The rotation angle sensor according to claim 2, wherein the correction value storage section previously stores an error relation between a rotation angle calculated by the rotation angle calculation section and an actual rotation angle for each of the angular range, approximates the relation by a straight line, and stores a correction coefficient and a correction intercept as the correction values, the correction coefficient being set such that the approximate line has a slope of 0 and the correction intercept being set such that an intercept of the approximate line is 0, and wherein the rotation angle correcting section is configured to correct the relative rotation angle by multiplying the relative rotation angle calculated by the relative rotation angle calculation portion by the correction coefficient and adding the correction intercept. ### Claim 4 (depends on 2) The rotation angle sensor according to claim 2, wherein the facing magnetic pole detecting means is configured to detect a rotation period that defines what number periodic change in the magnetic field strength detected by the magnetic field sensor from a reference position as a reference of the rotation angle of the rotating shaft, and wherein the rotation angle calculation section comprises an absolute rotation angle calculation portion that calculates a rotation angle from the reference position of the rotating shaft based on the rotation period detected by the facing magnetic pole detecting means and the relative rotation angle corrected by the rotation angle correcting section. ### Claim 5 (depends on 1) The rotation angle sensor according to claim 1, wherein the correction value storage section preliminarily stores correction values for each pair of magnetic poles facing the magnetic field sensor, wherein the facing magnetic pole detecting means is configured to detect the pair of magnetic poles facing the magnetic field sensor, and wherein the rotation angle correcting section is configured to extract correction values corresponding to the pair of magnetic poles detected by the facing magnetic pole detecting means and to correct the rotation angle calculated by the rotation angle calculation section by using the extracted correction values. ### Claim 6 A correction method for a rotation angle sensor, wherein the rotation angle sensor comprises: a ring magnet that is provided around a rotating shaft subjected to rotation angle detection so as to be integrally rotated with the rotating shaft and is magnetized so as to have not less than one pair of magnetic poles with different polarities arranged in a circumferential direction; a magnetic field sensor that is provided so as to face the ring magnet in a radial direction of the rotating shaft and detects magnetic field strengths in radial and tangent directions of the rotating shaft; and a rotation angle calculation section that calculates a rotation angle of the rotating shaft based on the magnetic field strengths detected by the magnetic field sensor, the method comprising: preliminarily setting correction values for each magnetic pole, or each pair of magnetic poles, facing the magnetic field sensor; and detecting the magnetic pole or the pair of magnetic poles facing the magnetic field sensor and correcting a rotation angle calculated by the rotation angle calculation section by using correction values corresponding to the detected magnetic pole or the detected pair of magnetic poles. ### Claim 7 (depends on 6) The method according to claim 6, wherein the rotation angle calculation section comprises a relative rotation angle calculation portion for calculating a relative rotation angle within an angular range in which a given magnetic pole or a given pair of magnetic poles faces the magnetic field sensor, and wherein the relative rotation angle calculated by the relative rotation angle calculation portion is corrected by using the correction values. ### Claim 8 (depends on 7) The method according to claim 7, further comprising: previously storing an error relation between a relative rotation angle calculated by the relative rotation angle calculation portion and an actual rotation angle for each angular range, approximating the relation by a straight line, and storing a correction coefficient and a correction intercept as the correction values, the correction coefficient being set such that the approximate line has a slope of 0 and the correction intercept being set such that an intercept of the approximate line is 0; and correcting the relative rotation angle by multiplying the relative rotation angle calculated by the relative rotation angle calculation portion by the correction coefficient and adding the correction intercept. ### Claim 9 (depends on 7) The method according to claim 7, further comprising: detecting a rotation period that defines what number periodic change in the magnetic field strength detected by the magnetic field sensor from a reference position as a reference of the rotation angle of the rotating shaft; and calculating a rotation angle from the reference position of the rotating shaft based on the detected rotation period and the corrected relative rotation angle. ### Claim 10 (depends on 6) The method according to claim 6, further comprising: preliminarily storing correction values for each pair of magnetic poles facing the magnetic field sensor; detecting the pair of magnetic poles facing the magnetic field sensor; and correcting the rotation angle calculated by the rotation angle calculation section by using the correction values corresponding to the detected pair of magnetic poles. ### Claim 11 (depends on 3) The rotation angle sensor according to claim 3, wherein the facing magnetic pole detecting means is configured to detect a rotation period that defines what number periodic change in the magnetic field strength detected by the magnetic field sensor from a reference position as a reference of the rotation angle of the rotating shaft, and wherein the rotation angle calculation section comprises an absolute rotation angle calculation portion that calculates a rotation angle from the reference position of the rotating shaft based on the rotation period detected by the facing magnetic pole detecting means and the relative rotation angle corrected by the rotation angle correcting section. ### Claim 12 (depends on 2) The rotation angle sensor according to claim 2, wherein the correction value storage section preliminarily stores correction values for each pair of magnetic poles facing the magnetic field sensor, wherein the facing magnetic pole detecting means is configured to detect the pair of magnetic poles facing the magnetic field sensor, and wherein the rotation angle correcting section is configured to extract correction values corresponding to the pair of magnetic poles detected by the facing magnetic pole detecting means and to correct the rotation angle calculated by the rotation angle calculation section by using the extracted correction values. ### Claim 13 (depends on 3) The rotation angle sensor according to claim 3, wherein the correction value storage section preliminarily stores correction values for each pair of magnetic poles facing the magnetic field sensor, wherein the facing magnetic pole detecting means is configured to detect the pair of magnetic poles facing the magnetic field sensor, and wherein the rotation angle correcting section is configured to extract correction values corresponding to the pair of magnetic poles detected by the facing magnetic pole detecting means and to correct the rotation angle calculated by the rotation angle calculation section by using the extracted correction values. ### Claim 14 (depends on 4) The rotation angle sensor according to claim 4, wherein the correction value storage section preliminarily stores correction values for each pair of magnetic poles facing the magnetic field sensor, wherein the facing magnetic pole detecting means is configured to detect the pair of magnetic poles facing the magnetic field sensor, and wherein the rotation angle correcting section is configured to extract correction values corresponding to the pair of magnetic poles detected by the facing magnetic pole detecting means and to correct the rotation angle calculated by the rotation angle calculation section by using the extracted correction values. ### Claim 15 (depends on 11) The rotation angle sensor according to claim 11, wherein the correction value storage section preliminarily stores correction values for each pair of magnetic poles facing the magnetic field sensor, wherein the facing magnetic pole detecting means is configured to detect the pair of magnetic poles facing the magnetic field sensor, and wherein the rotation angle correcting section is configured to extract correction values corresponding to the pair of magnetic poles detected by the facing magnetic pole detecting means and to correct the rotation angle calculated by the rotation angle calculation section by using the extracted correction values. ### Claim 16 (depends on 8) The method according to claim 8, further comprising: detecting a rotation period that defines what number periodic change in the magnetic field strength detected by the magnetic field sensor from a reference position as a reference of the rotation angle of the rotating shaft; and calculating a rotation angle from the reference position of the rotating shaft based on the detected rotation period and the corrected relative rotation angle. ### Claim 17 (depends on 7) The method according to claim 7, further comprising: preliminarily storing correction values for each pair of magnetic poles facing the magnetic field sensor; detecting the pair of magnetic poles facing the magnetic field sensor; and correcting the rotation angle calculated by the rotation angle calculation section by using the correction values corresponding to the detected pair of magnetic poles. ### Claim 18 (depends on 8) The method according to claim 8, further comprising: preliminarily storing correction values for each pair of magnetic poles facing the magnetic field sensor; detecting the pair of magnetic poles facing the magnetic field sensor; and correcting the rotation angle calculated by the rotation angle calculation section by using the correction values corresponding to the detected pair of magnetic poles. ### Claim 19 (depends on 9) The method according to claim 9, further comprising: preliminarily storing correction values for each pair of magnetic poles facing the magnetic field sensor; detecting the pair of magnetic poles facing the magnetic field sensor; and correcting the rotation angle calculated by the rotation angle calculation section by using the correction values corresponding to the detected pair of magnetic poles. ### Claim 20 (depends on 16) The method according to claim 16, further comprising: preliminarily storing correction values for each pair of magnetic poles facing the magnetic field sensor; detecting the pair of magnetic poles facing the magnetic field sensor; and correcting the rotation angle calculated by the rotation angle calculation section by using the correction values corresponding to the detected pair of magnetic poles.