Fluxgate type magnetic detector

Abstract

To provide a device and a method for detecting a flux-gate magnetism that can detect a minor magnetic field highly sensitively.SOLUTION: The present invention includes: a ring core 1 made of a magnetic body; a driving coil 2 wound around the ring core 1, for generating a driving magnetic field by receiving an applied voltage; and a detection coil 3 wound around the ring core 1 so that the direction in which a magnetic field is generated when a current is applied is the same around the ring core 1. The material of the detection coil 3 is made of a Litz wire formed by twisting a single wire made of plural conductors.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fluxgate type magnetic detector and a magnetic detection method capable of detecting a minute magnetic field, such as geomagnetism, or a minute current with high sensitivity. [Background technology]

[0002] This type of fluxgate magnetic detector is known from Patent Documents 1 and 2. The fluxgate magnetic sensor of Patent Document 1 has a structure in which two detection coils and an excitation coil, which are connected to each other in reverse windings, are wound around a core made of a magnetic material, the core being shaped like an elliptical or rectangular loop, and the two detection coils are wound around two opposing sides along the long axis of the loop.

[0003] The fluxgate magnetic sensor of Patent Document 2 has a loop-shaped core made of a thin magnetic film on a substrate, and an excitation coil and a detection coil that are provided above and below the core with insulating layers, thin conductive films, and contact parts, and that spirally wind around the core while passing inside and outside the loop. The excitation coil is wound uniformly around the loop core in the circumferential direction, and the detection coil is wound in four separate sections, each of which is ¼ of a turn around the loop core, with two opposing detection coils being wound in opposite directions and interconnected. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 09-318720 [Patent Document 2] Japanese Patent Application Publication No. 11-023683 Summary of the Invention [Problem to be solved by the invention]

[0005] The fluxgate type magnetic detectors shown in Patent Documents 1 and 2 have a configuration that merely changes the way the detection coil is wound around the core, and therefore have a problem in that they are not sufficient for detecting a weak magnetic field with high sensitivity.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and provides a flux-gate type magnetic detector and a magnetic detection method capable of detecting a minute magnetic field such as geomagnetism or a minute current with high sensitivity. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention proposes the following means. The fluxgate type magnetic detector shown in the first aspect of the present invention comprises a ring core made of a magnetic material, a drive coil wound around the ring core to generate a drive magnetic field when current is applied, and a detection coil wound around the ring core so that the direction of the magnetic field generated when current is applied is the same around the ring core, and is characterized in that the wire material of the detection coil is made of a Litz wire formed by twisting together single wires made of multiple conductors.

[0008] The fluxgate type magnetic detection method shown in the second aspect of the present invention is characterized in that in a fluxgate type magnetic detector having a ring core made of a magnetic material, a drive coil wound around the ring core to generate a drive magnetic field when current is applied, and a detection coil wound around the ring core so that the direction of the magnetic field generated when current is applied is the same around the ring core, the wire material of the detection coil is a litz wire formed by twisting together a single wire made of a plurality of conductors. Effect of the Invention

[0009] According to the present invention, by using a Litz wire made of multiple single conductor wires twisted together as the wire material for the detection coil of a fluxgate type magnetic detector, the detection coil can detect small magnetic fields such as the geomagnetic field or small currents with high sensitivity. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing a fluxgate type magnetic detector according to the present invention; [Diagram 2] 1 is a schematic diagram of a fluxgate magnetic detector according to a first embodiment. [Diagram 3] FIG. 2 is a diagram showing a voltage measurement circuit. [Figure 4] FIG. 11 is a schematic diagram of a fluxgate magnetic detector according to a second embodiment. [Diagram 5] FIG. 11 is a schematic diagram of a fluxgate magnetic detector according to a third embodiment. [Figure 6] FIG. 13 is a schematic diagram of a fluxgate magnetic detector according to a modified example. [Figure 7] FIG. 7 is a schematic diagram of a modification of FIG. 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The minimum configuration of a fluxgate magnetic detector 10 according to the present invention will be described with reference to FIG. The fluxgate magnetic detector 10 of the present invention mainly comprises a ring core 1, a drive coil 2, and a detection coil 3.

[0012] The ring core 1 is a magnetic body formed in an annular shape. A drive coil 2 is wound around the ring core 1 and generates a drive magnetic field when a current is applied. The detection coil 3 is wound around the ring core 1 so that the direction of the magnetic field generated when a current is applied is the same around the ring core 1. The wire of the detection coil 3 is made of a Litz wire formed by twisting together a plurality of single conductor wires.

[0013] In the fluxgate type magnetic detector 10 described above, a Litz wire made of multiple conductors twisted together is used as the wire material of the detection coil 3, so that the detection coil 3 can detect minute magnetic fields such as geomagnetism or minute currents with high sensitivity.

[0014] (First embodiment) A fluxgate magnetic detector 100 according to this embodiment will be described with reference to FIGS. As shown in FIG. 2, the fluxgate magnetic detector 100 mainly comprises a ring core 101, a driving coil 102, a detection coil R103, and a detection coil L104.

[0015] The ring core 101 is a magnetic body formed in an annular shape. The drive coil 102 is made of enameled wire and is wound in a toroidal shape around the ring core 101 to generate a drive magnetic field when a current is applied. The detection coil R103 and the detection coil L104 constitute a detection coil 105, and are wound around the ring core 101 so that the direction of a magnetic field generated when a current is applied to the drive coil 102 is the same around the ring core 101. Moreover, the wires (indicated by symbols SA1 and SA2) of the detection coils R103 and L104 are made of Litz wires formed by twisting together a plurality of conducting wires.

[0016] The detection coil R103 and the detection coil L104 have a first detection portion M1 and a second detection portion M2 wound at opposing positions spaced 180° apart on the ring core 101, and wires SA1, SA2 are wound around the ring core 101 in opposite directions for the first detection portion M1 and the second detection portion M2.

[0017] More specifically, the wire SA1 of the detection coil R103 has a winding start position (indicated by reference symbol 103A) near the winding start position (indicated by reference symbol 102A) of the drive coil 102, and is wound in the same winding progression and rotation direction as the drive coil 102. In addition, the wire SA2 of the detection coil L104 is wound with its winding start position (indicated by reference symbol 104A) near the end of the winding of the drive coil 102 (indicated by reference symbol 102B), and at a position opposite to the detection coil R103, in the winding progression and rotation direction opposite to that of the drive coil 102.

[0018] Thereafter, the winding ends (indicated by reference characters 103B and 104B) of the wire SA1 of the detection coil R103 and the wire SA2 of the detection coil L104 are connected to each other at a connection portion 106. As a result, the detection coil R103 and the detection coil L104 are wired in series to form a detection coil 105 whose input side is the winding start side of the detection coil R103 (indicated by reference character 103A) and whose output side is the winding start side of the detection coil L104 (indicated by reference character 104A).

[0019] In FIG. 3, reference numeral 20 denotes a voltage measuring circuit, which has an output circuit 21 and a voltage detection circuit 22. The output circuit 21 includes an oscillator circuit 23 that applies an excitation current to the drive coil 102 at a constant cycle, a phase adjuster 24 , and an amplifier 25 . The voltage detection circuit 22 includes detectors 26 and 27, a high-pass filter (HPF), an amplifier 29, and an integrator 30, and receives signals from the detection coils R103 and L104 in accordance with the oscillation period of the oscillation circuit .

[0020] In such a voltage measurement circuit 20, an AC current serving as an excitation current can be applied to the drive coil 102 by applying a current from the output circuit 21. When an AC current is applied to the drive coil 102, an AC magnetic flux is generated along the ring core 101, and the AC magnetic flux penetrates the inside of each of the detection coils R103 and L104 in opposite directions. In this state, when an external magnetism acts on the detection coils R103 and L104, the magnetic flux caused by the magnetism acts on each of the detection coils R103 and L104 in the same direction.

[0021] As a result, the AC magnetic flux passing through each of the detection coils R103 and L104 is biased in the opposite directions by the external magnetism. As a result, an AC voltage signal that is proportional to the external magnetic field and has a frequency twice that of the excitation current can be extracted at both ends of the detection coil R103 and the detection coil L104. In other words, when an external magnetic field Hs is applied, the relationship between the external magnetic flux Hs in the detection coil R103 and the driving magnetic field Hdr generated by the AC magnetic flux in the detection coil L104 is "Hdr-Hs" and "Hdr+Hs", respectively, and an output signal proportional to the output difference "2Hs" is induced in the detection coil 105.

[0022] This output signal can be amplified by, for example, an AC amplifier 29, rectified, and then detected to obtain a voltage signal proportional to the external magnetic field, thereby forming a magnetic sensor with good sensitivity and stability against temperature. On the other hand, when the external magnetic field Hs is not present, the windings of detection coil R103 and detection coil L104 rotate in different directions, so that voltages of opposite polarities are induced and no output is generated in detection coil 105.

[0023] In the fluxgate type magnetic detector 100 described above, a Litz wire made of multiple twisted conductors is used as the wire material for the detection coil R103 and the detection coil L104. Therefore, the detection coils R103 and L104 can be arranged at high density, making it possible to detect minute magnetic fields such as the earth's magnetic field or minute currents with high sensitivity.

[0024] Second embodiment A fluxgate magnetic detector 200 according to the second embodiment will be described with reference to FIG. A fluxgate magnetic detector 200 according to the second embodiment has a configuration different from that of the fluxgate magnetic detector 100 according to the first embodiment in the way in which the wires SA1 and SA2 forming the detection coils R103 and L104 are wound.

[0025] That is, the wire SA1 of the detection coil R103 wound in a spiral shape at the first detection portion M1 is routed to the second detection portion M2, and then wound in a spiral shape at the second detection portion M2. The wire SA2 of the detection coil L104 wound in a spiral shape at the second detection portion M2 is routed to the first detection portion M1 and wound in a spiral shape at the first detection portion M1. At this time, the wires SA1, SA2 are wound around the ring core 101 in the first detection portion M1 and the second detection portion M2 in opposite directions. The wire SA1 of the first detection portion M1 is made of a twisted wire of single wires a and b, and the wire SA2 of the second detection portion M2 is made of a twisted wire of single wires c and d. Moreover, these two wires SA1 and SA2 are connected to each other at connection portions 107 to 109, so that a solid wire is laid out in the order of "a→c→b→d."

[0026] That is, in this example, a single wire a of wire SA1 that is routed from detection coil R103 to detection coil L104 becomes a single wire c of wire SA2 in detection coil L104, and is arranged alternately and densely with other single wires d of wire SA2. Furthermore, an example is shown in which the single wire c of the wire SA2 that is routed from the detection coil L104 to the detection coil R103 becomes a single wire b of the wire SA1 in the detection coil R103, and is arranged alternately and densely with the other single wires a of the wire SA1.

[0027] In this fluxgate type magnetic detector 200, a Litz wire made of multiple twisted conductors is used as the wires SA1, SA2 of the detection coil R103 and the detection coil L104, so that the detection coil R103 and the detection coil L104 can detect minute magnetic fields such as the earth's magnetic field or minute currents with high sensitivity. Furthermore, in the detection coil R103 and the detection coil L104, the single wires of the wire rods SA1 and SA2 passing through the opposing detection coils L104 and R103, respectively, are arranged alternately and in a staggered manner. As a result, in the detection coil R103 and the detection coil L104, the number of turns of the wires SA1, SA2 can be increased and the wires SA1, SA2 can be arranged more densely, which also makes it possible to detect minute magnetic fields such as the earth's magnetic field with high sensitivity.

[0028] Third embodiment A fluxgate magnetic detector 300 according to the third embodiment will be described with reference to FIG. The fluxgate magnetic detector 200 according to the third embodiment has a configuration different from that of the fluxgate magnetic detector 200 according to the second embodiment in the way in which the wires SA1 and SA2 forming the detection coils R103 and L104 are wound.

[0029] That is, the wire SA1 of the detection coil R103 shown in the third embodiment is wound spirally around the ring core 101 from left to right in the figure, and then at the opposing position, it becomes the detection coil L104 and is similarly wound spirally around the ring core 101 from left to right in the figure. On the other hand, the wire SA2 of the detection coil L104 is wound spirally around the ring core 101 from the right side to the left side in the figure, and then at the opposing position, it becomes the detection coil R103 and is similarly wound spirally around the ring core 101 from the right side to the left side in the figure.

[0030] At this time, in the first detection portion M1 and the second detection portion M2, the wires SA1, SA2 are wound around the ring core 101 in opposite directions. The wire SA1 of the first detection portion M1 is made of a twisted wire of single wires a and b, and the wire SA2 of the second detection portion M2 is made of a twisted wire of single wires c and d. Moreover, these two wires SA1 and SA2 are connected to each other at connection parts 107 to 109, so that a solid wire is laid out in the order of "a→c→b→d."

[0031] That is, in this example, a single wire a of wire SA1 that is routed from detection coil R103 to detection coil L104 becomes a single wire c of wire SA2 in detection coil L104, and is arranged alternately and densely with other single wires d of wire SA2. Furthermore, an example is shown in which the single wire c of the wire SA2 that is routed from the detection coil L104 to the detection coil R103 becomes a single wire b of the wire SA1 in the detection coil R103, and is arranged alternately and densely with the other single wires a of the wire SA1.

[0032] As a result, in the detection coil R103 and detection coil L104 of the third embodiment, similar to the second embodiment, the single wires of the wires SA1 and SA2 that pass through the opposing detection coil L104 and detection coil R103, respectively, are arranged alternately and alternately, so that the wires SA1 and SA2 can be arranged at a higher density, and in this respect too, it is possible to detect minute magnetic fields such as the geomagnetic field with high sensitivity.

[0033] (Modification) Flux-gate type magnetic detectors 400 and 400' according to modified examples will be described with reference to FIGS. The fluxgate magnetic detectors 400, 400' differ in configuration from the fluxgate magnetic detectors 100, 200, 300 shown in the first to third embodiments in the arrangement of the litz wires L1, L2 used as the wires of the detection coil and drive coil.

[0034] 6 and 7 show a winding structure using two litz wires L1 and L2 each made of two solid wires twisted together. The litz wire L1 is made of a twisted wire of a solid wire S1 (shown by a thick line) and a solid wire S2 (shown by a solid line). The litz wire L2 is made of a twisted wire of a solid wire S3 (shown by a dashed line) and a solid wire S4 (shown by a dotted line). Among these single wires S1 to S4, the single wire S2 (shown by a solid line) and the single wire S4 (shown by a dashed line) are used as a drive coil 102. The single wire S1 (shown by a thick line) and the single wire S3 (shown by a dashed line) are used as detection coils R103 and L104. In addition, in Figs. 6 and 7, reference numerals 410 and 411 denote connection parts for connecting solid wires.

[0035] In addition, in Figs. 6 and 7, the single line S1 (shown by a thick line) and the single line S3 (shown by a dashed line) have their intermediate portions omitted to avoid complicating the drawings. In addition, in Figs. 6 and 7, the configurations and uses of the litz wires L1 and L2 used are the same except for the winding direction. Specifically, in Fig. 6, the litz wires L1 and L2 are both wound clockwise from position A to position B. In Fig. 7, the litz wire L1 is wound clockwise from position A to position B, and the litz wire L2 is wound counterclockwise.

[0036] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design modifications and the like are also included within the scope of the present invention that does not deviate from the gist of the present invention. [Industrial Applicability]

[0037] The present invention relates to a fluxgate type magnetic detector and a magnetic detection method capable of detecting a minute magnetic field, such as geomagnetism, or a minute current with high sensitivity. [Explanation of symbols]

[0038] 1 Ring Core 2 Drive coil 3 Detection coil (Litz wire) 10 Fluxgate type magnetic detector 20 Voltage measurement circuit 21 Output circuit 22 Voltage detection circuit 100 Fluxgate type magnetic detector 101 Ring Core 102 Drive coil 102A Winding start 102B End of Volume 103 Detection coil R 103A Winding start 103B End of Volume 104 Detection coil L 104A Winding start 104B End of Volume 105 Detector coil 106 Connection 107 Connection 108 Connection 109 Connection 200 Fluxgate type magnetic detector 300 Fluxgate type magnetic detector 400 Fluxgate type magnetic detector 400´ Fluxgate type magnetic detector SA1 wire (litz wire) SA2 wire (litz wire) SB wire rod L1 Litz wire L2 Litz wire M1 First detection section M2 Second detector m1 1st part m2 second part

Claims

1. The magnetic sensor comprises a ring core made of a magnetic material, a drive coil wound around the ring core to generate a drive magnetic field when a current is applied, and a detection coil wound around the ring core so that the direction of the magnetic field generated when a current is applied is the same around the ring core, The wire of the detection coil is formed by twisting together a plurality of conductive wires, the detection coil has a first detection portion and a second detection portion wound at opposing positions on the ring core with the drive coil in between, The conductors of the first detection unit are a single wire a and a single wire b, and the conductors of the second detection unit are a single wire c and a single wire d, a wire having the solid wires a and b and a wire having the solid wires c and d are wound in a spiral shape such that the first detection unit and the second detection unit are wound around the ring core in opposite directions; the wire having the single wire a and the single wire b wound in a spiral shape at the first detection unit is connected to a wire having the single wire c and the single wire d wound in a spiral shape at the second detection unit, the single wire a at an end far from the drive coil of the first detection section and the single wire c at an end far from the drive coil of the second detection section are connected, and the single wire b at an end far from the drive coil of the first detection section and the single wire d at an end far from the drive coil of the second detection section are connected, A single wire b at an end of the first detection section close to the drive coil and a single wire c at an end of the second detection section close to the drive coil are connected to each other. Fluxgate type magnetic detector.

2. The magnetic sensor comprises a ring core made of a magnetic material, a drive coil wound around the ring core to generate a drive magnetic field when a current is applied, and a detection coil wound around the ring core so that the direction of the magnetic field generated when a current is applied is the same around the ring core, The wire of the detection coil is formed by twisting together a plurality of conductive wires, the detection coil has a first detection portion and a second detection portion wound at opposing positions on the ring core with the drive coil in between, The conductors of the first detection unit are a single wire a and a single wire b, and the conductors of the second detection unit are a single wire c and a single wire d, a wire having the solid wires a and b and a wire having the solid wires c and d are wound in a spiral shape such that the first detection unit and the second detection unit are wound around the ring core in opposite directions; the wire having the single wire a and the single wire b wound in a spiral shape at the first detection unit is connected to a wire having the single wire c and the single wire d wound in a spiral shape at the second detection unit, the single wire a at an end far from the drive coil of the first detection unit is connected to the single wire c at an end close to the drive coil of the second detection unit, and the single wire b at an end far from the drive coil of the first detection unit is connected to the single wire d at an end close to the drive coil of the second detection unit, The single wire b at an end close to the drive coil of the first detection unit and the single wire c at an end far from the drive coil of the second detection unit are connected to each other. Fluxgate type magnetic detector.

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