Variable reluctance position sensor
First Claim
1. An apparatus for detecting movement of a target, the apparatus comprising:
- a flux concentrator comprising a material of high magnetic permeability, the flux concentrator shaped to provide a magnetic gap comprising a region of high magnetic reluctance;
a permanent magnet coupled to the flux concentrator and configured to establish a magnetic field across the magnetic gap;
a magnetic sensor positioned to measure the magnetic flux across the magnetic gap; and
a target configured to travel through the magnetic gap and modulate the reluctance across the magnetic gap in response to a change in travel distance.
1 Assignment
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Accused Products
Abstract
A position sensor is disclosed having a transducer formed by a Hall-effect device and permanent magnet secured within a housing on either side of a low permeability gap. A target secured to an active member, such as an EGR valve plunger moves within the gap. The target has a flux modulating property that varies with position along a direction of travel. In one embodiment, the reluctance of the target varies with position. Variable reluctance is achieved in some embodiments by varying the cross section of the target with position. In some embodiments, a second target having substantially constant reluctance secures to the active member and moves within a gap defined by a second transducer. The output of the second transducer is used to normalize the output of the first transducer and compensate for anomalies such as drift and movement other than in the direction of travel of the active member.
27 Citations
25 Claims
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1. An apparatus for detecting movement of a target, the apparatus comprising:
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a flux concentrator comprising a material of high magnetic permeability, the flux concentrator shaped to provide a magnetic gap comprising a region of high magnetic reluctance; a permanent magnet coupled to the flux concentrator and configured to establish a magnetic field across the magnetic gap; a magnetic sensor positioned to measure the magnetic flux across the magnetic gap; and a target configured to travel through the magnetic gap and modulate the reluctance across the magnetic gap in response to a change in travel distance. - View Dependent Claims (2, 3, 4)
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5. An apparatus for detecting movement, the apparatus comprising:
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an active member; a guide secured to the active member to permit motion thereof in a direction of travel; a target extending along the active member substantially parallel to the direction of travel and having a cross section varying along a direction perpendicular to the direction of travel; a magnetic field sensing device secured to the support having an output line; and at least one magnetic flux source secured to the support positioned relative to the magnetic field sensing device to impose a magnetic flux thereon, the target positioned relative to the magnetic field sensing device and the at least one magnetic flux source to interfere with the imposition of flux on the magnetic field sensing device. - View Dependent Claims (6, 7, 8, 9, 10)
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11. A method for measuring displacement, the method comprising:
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providing an active member; providing a target coupled to the active member to move in correspondence therewith, the target having a flux modulating property, the flux modulating property varying along at least one dimension of the target; providing a magnetic field sensing device; providing a magnetic flux source positioned relative to the magnetic field sensing device to impose a magnetic flux thereon, the target positioned relative to the magnetic field sensing device and magnetic flux source to interfere with the imposition of flux on the magnetic field sensing device; moving the active member an indeterminate amount; and measuring variation in the stimulation of the magnetic field sensing device to determine movement of the target. - View Dependent Claims (12, 13, 14)
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15. An EGR position sensor, the sensor comprising:
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an EGR valve comprising a cylinder secured to the vehicle, and a plunger positioned within the cylinder and slidable in a longitudinal direction in relation thereto; a target coupled to the plunger and constrained to move in correspondence thereto, the target having a cross section varying with change in position along at least one direction; a magnetic field sensing device secured to the vehicle; and a magnetic flux source secured to the vehicle proximate the magnetic field sensing device to impose a magnetic flux thereon, the target positioned relative to the magnetic field sensing device and magnetic flux source to interfere with the imposition of flux on the magnetic field sensing device. - View Dependent Claims (16, 17, 18, 19)
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20. An apparatus for detecting movement, the apparatus comprising:
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an active member; at least one magnetic flux source; a first and a second magnetic field sensing device, each positioned relative to one of the at least one magnetic flux sources to sense magnetic flux produced thereby; a first and a second target having a flux modulating property, the flux modulating property varying along at least one dimension of the target, the target coupled to the active member and constrained to move in substantial correspondence therewith, the first target positioned relative to the first magnetic field sensing device to modulate the imposition of flux thereon, the second target positioned relative to the second magnetic field sensing device to modulate the imposition of flux thereon; a control unit electrically coupled to the first and second magnetic field sensing devices, the control unit configured to compare signals from the first and second magnetic field sensing devices to perform error correction. - View Dependent Claims (21, 22, 23, 24, 25)
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Specification