Magnetic force sensor

{
  "publication_number": "US9574953B2",
  "country": "US",
  "kind": "B2",
  "title": "Magnetic force sensor",
  "abstract": "The present invention provides a magnetic force sensor that can precisely detect and correct variations in a magnetic field generated by a magnetic flux generating source. Therefore, a displacement magneto-electric transducer, which detects a change in the magnetic field caused by an external force, and a fixed magneto-electric transducer, where the change in the magnetic field caused by the external force does not occur, are provided to face end sides of magnetic poles of the magnetic flux generating source. The fixed magneto-electric transducer detects a variation of the magnetic field caused by, for example, changes with time and environmental variations such as a temperature rise in the interior of the sensor. On the basis of a detection amount thereof, an operational section performs a correction operation, so that a sensitivity coefficient or an offset of the displacement magneto-electric transducer is corrected.",
  "claims": [
    "1. A force sensor for obtaining a force applied to an action portion comprising: the action portion supported by a supporting member; a first magneto-electric transducer and a second magneto-electric transducer fixed to the action portion; a magnetic flux generating source disposed so as to face the first magneto-electric transducer and the second magneto-electric transducer; a third magneto-electric transducer disposed at a fixed position with respect to the magnetic flux generating source for obtaining a change in a magnetic field, wherein the force sensor obtains forces applied to the action portion in at least two different axes directions simultaneously, from changes in output values of the first magneto-electric transducer, the second magneto-electric transducer and the third magneto-electric transducer, and wherein a relative position of the first magneto-electric transducer and the second magneto-electric transducer with respect to the magnetic flux generating source and the third magneto-electric transducer is changed by the force applied to the action portion.",
    "2. The force sensor according to claim 1, further comprising an adjustor that feeds back an operational result of the operational processing section to the first magneto-electric transducer, wherein a feedback from the adjuster that cancels an offset of the first magneto-electric transducer is performed on the output of the first magneto-electric transducer, the offset of the first magneto-electric transducer being calculated on the basis of a difference between a previously set reference voltage value and a voltage value of the output of the third magneto-electric transducer for when an external force is not applied to the action portion.",
    "3. The force sensor according to claim 1, further comprising an adjuster that feeds back an operational result of the operational processing section to the first magneto-electric transducer, wherein, when a magnetic field that is generated by the magnetic flux generating source is B, and a variation of the magnetic field, generated by the magnetic flux generating source, calculated on the basis of the output of the third magneto-electric transducer is ΔB, a feedback from the adjuster for causing the output of the first magneto-electric transducer to be a (B−ΔB)/B-fold output is performed.",
    "4. The force sensor according to claim 1, wherein the third magneto-electric transducer is disposed near one of magnetic poles of the magnetic flux generating source, and the first magneto-electric transducer and the second magneto-electric transducer are provided near the other magnetic pole of the magnetic flux generating source.",
    "5. The force sensor according to claim 1, wherein the first magneto-electric transducer is fixed together with a first substrate for mounting the first magneto-electric transducer to the action portion at a position facing a face of one of magnetic poles of the magnetic flux generating source, the second magneto-electric transducer is fixed together with a second substrate for mounting the second magneto-electric transducer to the supporting member at a position facing a face of the other magnetic pole of the magnetic flux generating source, and the magnetic flux generating source is fixed to the supporting member via the second substrate."
  ],
  "description_excerpt": "The present invention relates to a magnetic force sensor that detects a force or a moment component and that detects a magnetic flux change in a magnetic flux generating source using a magneto-electric transducer. In particular, the present invention relates to a correction operation when a magnetic field generated at the magnetic flux generating source is changed.\n\nWhen, for example, parts are assembled using a robot arm, a force sensor is mounted to a wrist portion of the robot arm, detects a force or a moment component that is generated during an assembly work, and controls an orientation of a hand portion. A force sensor that makes use of a method of magnetically detecting a displacement of an action portion is discussed in Japanese Patent Laid-Open No. 2004-325328 (Patent Document 1).\n\nA related structure that is discussed in Japanese Patent Laid-Open No. 2004-325328 is shown in FIGS. 5A and 5B. In the related structure, a permanent magnet 14 embedded in a resilient member and four magneto- electric transducers 15 a to 15 d opposing magnetic poles of the permanent magnet are disposed. When an action force is applied to the resilient member, the permanent magnet 14 is displaced, and the magneto- electric transducers 15 a to 15 d, such as Hall elements, detect a change in a magnetic field that is generated thereby. On the basis of the detected change in the magnetic field, it is possible to detect force components in an X-axis direction, a Y-axis direction, and a Z-axis direction.",
  "cpc": [
    "G01L 1/14",
    "G01L 1/12",
    "G01L 1/2281",
    "G01L 5/009"
  ],
  "ipc": [
    "G01L 1/12",
    "G01L 1/14",
    "G01L 1/22",
    "G01L 1/25",
    "G01L 5/00"
  ],
  "assignees": [
    "Canon Inc"
  ],
  "inventors": [
    "Shuuichi Sato"
  ],
  "filing_date": "2014-11-19",
  "publication_date": "2017-02-21",
  "grant_date": "2017-02-21",
  "priority_date": "2009-11-26",
  "application_number": "US-201414548144-A",
  "family_id": "44067022",
  "cited_by_count": 4,
  "citations": [
    "US2888256A",
    "US4869108A"
  ]
}