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EP-4357736-B1 - ANGLE DETECTING DEVICE

EP4357736B1EP 4357736 B1EP4357736 B1EP 4357736B1EP-4357736-B1

Inventors

  • KOIKE, TAKASHI
  • FUKUSHIMA, YASUYUKI

Dates

Publication Date
20260506
Application Date
20220608

Claims (4)

  1. An angle detecting (4, 4A, 4B) device comprising: an encoder unit (6, 6A, 6B) having a magnetic track on which N poles and S poles are alternately arrayed; and a magnetic sensor (7) facing the magnetic track with a gap (δ) interposed therebetween, wherein the magnetic track has, when being expressed with a reference magnetic pole width P and a reference magnetic pole pair number n, a main track (2) having a magnetic pole width of P and a sub track (3) having a magnetic pole width of Pn/(n-1), the main track (2) and the sub track (3) being provided adjacent and parallel to each other along a longitudinal direction of a sheet-shaped encoder magnetic material (1), the encoder unit (6, 6A, 6B) is formed of the sheet-shaped encoder magnetic material (1) which has a length not larger than a reference length L=2Pn and which is wound around and fixed to an outer circumference portion or an inner circumference portion of a rotary body (5, 5A, 5B), and the magnetic sensor (7) includes two magnetic detecting elements (8) each facing a corresponding one of the main track (2) and the sub track (3) and each configured to output a magnetic signal, and a calculator (9) configured to calculate an absolute angle of the rotary body (5, 5A, 5B) on the basis of the magnetic signals from the magnetic detecting elements (8), the angle detecting device (4, 4A, 4B) further comprising a correction calculator (10) configured to multiply the calculated absolute angle by a correction coefficient based on a diameter of the encoder unit (6, 6A, 6B), to correct the absolute angle of the rotary body (5, 5A, 5B).
  2. The angle detecting device (4, 4A, 4B) as claimed in claim 1, wherein when the encoder magnetic material having the reference length L is cut so as to have an arbitrarily-determined length and is wound around the outer circumference portion or the inner circumference portion of the rotary body (5, 5A, 5B) so as to be formed as the encoder unit having (6, 6A, 6B) a diameter S, the correction calculator (10) uses, as the correction coefficient, a value L/(πS) resulting from dividing the reference length L by a value resulting from multiplying the diameter S by a circle ratio π.
  3. The angle detecting device (4, 4A, 4B) as claimed in claim 1 or 2, wherein the encoder unit is formed of the encoder magnetic material (1) on which each of the main track (2) and the sub track (3) has a length L1 not larger than the reference length L, the encoder magnetic material (1) being wound around and fixed to the outer circumference portion or the inner circumference portion of the rotary body (5, 5A, 5B) having a circumferential length larger than the length L1, the angle detecting device (4, 4A, 4B) further comprising: a limit angle storage (12) configured to store therein limit angles corresponding to outputs, from the magnetic sensor (7), at both ends of the magnetic track; and a detection range determinator (13) configured to determine whether or not the absolute angle outputted from the magnetic sensor (7) is within a range between the limit angles, the detection range determinator (13) being further configured to output an identification signal indicating whether or not deviation from between the limit angles has occurred.
  4. The angle detecting device (4, 4A, 4B) as claimed in any one of claims 1 to 3, wherein the rotary body (5, 5A, 5B) is a rotary part for a robot joint.

Description

CROSS REFERENCE TO THE RELATED APPLICATION This application is based on and claims Convention priority to Japanese patent application No. 2021-099722, filed June 15, 2021, the entire disclosure of which is herein incorporated by reference as a part of this application. BACKGROUND OF THE INVENTION (Field of the Invention) The present invention relates to an angle detecting device that detects a rotation angle of a rotation shaft or the like, and in particular, relates to an angle detecting device that detects an angle within a range of not larger than 360° at a high resolution in order to position a robot joint or the like at a target position. (Description of Related Art) Various magnetic encoder devices that detect a rotation angle have been proposed. For a magnetic encoder device disclosed in Patent Document 1, a cylindrical base portion is formed of a sintered metal and subjected to sizing in which the outer circumferential surface, the inner circumferential surface, and both end surfaces of the base portion are pressed. Furthermore, the resultant base portion is inserted into a mold, and a resin material having a thermoplastic resin and magnetic powder as main components is subjected to injection molding into a cavity. Then, the resultant molded portion is subjected to multipole magnetization so as to form thereon two rows of magnetic encoder tracks which each have a plurality of magnetic poles arrayed in the circumferential direction thereof, and between which the number of pairs of the magnetic poles differs. The magnetic encoder having been thus produced is fixed to a rotary body, and a magnetic sensor is provided so as to be close to, and face, the magnetic encoder tracks. The magnetic sensor includes: two detecting elements facing the two respective rows of magnetic encoder tracks; and a calculator. The magnetic sensor calculates an absolute angle of the rotary body at a high resolution on the basis of the phase difference between magnetic signals detected by the two detecting elements, and outputs the absolute angle as a sensor output. A magnetic encoder disclosed in Patent Document 2 is composed of: a magnetic recording rotary body having an outer circumferential surface on which a tape-like magnetic scale member magnetized so as to alternately have N poles and S poles at regular pitches has been pasted; and a magnetic information detecting means disposed so as to be close to the magnetic recording rotary body. The magnetic information detecting means includes two magnetic information detecting elements arranged at an interval along the rotation direction of the magnetic recording rotary body. Magnetic information formed on the magnetic scale member is detected by the two magnetic information detecting elements, and signals for an A phase, a B phase, and a Z phase are generated from outputs obtained through the detection. Consequently, a magnetic encoder that has high accuracy and high reliability and that is highly versatile can be comparatively inexpensively realized. [Related Document] [Patent Document] [Patent Document 1] JP Laid-open Patent Publication No. 2015-75466[Patent Document 2] JP Laid-open Patent Publication No. 2012-141259 SUMMARY OF THE INVENTION The technique disclosed in Patent Document 1 involves: molding a plastic magnet such that the magnet is integrated with a sintered core metal having been subjected to press work; and then performing magnetization so as to obtain a predetermined number of magnetization poles for each rotation. A mass-produced product obtained by incorporating necessary functions into one package needs to be used as the magnetic sensor in order to realize a high-resolution angle detecting device in which a plurality of rows of magnetic encoders are used while satisfying constraint conditions regarding an available space, cost, and the like. Thus, main specifications such as a magnetic pole width and the number of pairs of magnetic poles are predetermined, and adaptation to individual specifications is impossible. For example, when specifications such as a magnetic pole width and the number of pairs of magnetic poles are determined, the diameter of an encoder unit is determined according to these specifications. Thus, the encoder unit cannot be produced with an arbitrarily-determined diameter, whereby the degree of freedom in designing is restricted. In addition, since molding-finished products are individually magnetized one by one, it is difficult to improve productivity. Furthermore, it is difficult to integrate the molded product with the rotary body, and a product having finished being magnetized needs to be attached as a separate part. Thus, a problem arises also in that the rotary body is upsized, and the mass of the rotary body increases. Moreover, a mold for the core metal and a mold for injection molding of the plastic magnet need to be manufactured in order to produce the magnetic encoder device. Thus, a problem arises in that production cost incr