JP2013064607A - Loop core for flux gate current sensor, and flux gate current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a loop core for a flux gate current sensor insusceptible to a geomagnetism influence.SOLUTION: The loop core for a flux gate current sensor includes: a pair of substantially E-shaped cores obtained by integrally aligning two plates bent into substantially U-shapes; and a soft magnetic interposing member having higher magnetic permeability than the pair of cores. The pair of cores are opposingly arranged such that respective first outer leg portions thereof abut on each other at least in part, respective second outer leg portions thereof abut on each other at least in part with the soft magnetic interposing member interposed therebetween, and a predetermined gap is maintained between each connected portion of two substantially U-shapes to form an annular loop contracted in the middle. The annular loop has a first ring portion for regulating a space to which an electric wire of a measurement target is inserted and passed on the side of the first outer leg portion, and has a second ring portion for regulating a space for arranging a magnetic probe that detects a magnetic field induced by electric current passing the electric wire, on the side of the second outer leg portion, when seen from the gap portion.

Description

  The present invention relates to a fluxgate current sensor for measuring a current flowing through a measurement object and a loop core for the fluxgate current sensor.

  As a sensor for measuring the current flowing through the measurement object, a fluxgate current sensor is known and is in practical use. A specific configuration of this type of fluxgate current sensor is described in Patent Document 1, for example.

  The fluxgate current sensor described in Patent Document 1 includes a magnetic field sensor (8) having a fluxgate core (18) around which a fluxgate coil (20) is wound. Moreover, it has the magnetic core (4) formed of two core parts (28a, 28b). The branch portions (32a, 32b) of the core portions (28a, 28b) are connected to the inner wall portions (40a, 40b) and the outer wall portions (42a, 42b) joined by the side wall portions (46a, 46b, 46a ′, 46b ′). have. The wall part (40a, 42a, 46a, 46a ′) of the branch part (32a) of the core part (28a) and the wall part (40b, 42b, 46b, 46b) of the branch part (32b) of the core part (28b). ') Is formed so as to partially surround the cavity (44) while leaving a predetermined air gap (54) between the free end edges (53a, 53b) of each other. A magnetic field sensor (8) is accommodated and supported in the cavity (44).

Special table 2011-510318 gazette

  In the fluxgate current sensor described in Patent Document 1, the magnetic field sensor (8) may not be able to accurately detect the current to be measured due to the influence of geomagnetism. In the fluxgate current sensor described in Patent Document 1, for example, when the direction of geomagnetism is the major axis direction of the branch portions (32a, 32b), a magnetic field sensor having a lower magnetic resistance than air at the air gap (54). The geomagnetism flows through (8). Further, for example, when the direction of geomagnetism is the long axis direction of the side branch portions (36, 34) of the core portions (28a, 28b), the geomagnetism is transferred from the side branch portions (36, 34) to the branch portion portions (32a, 32b) and flows in the air gap (54) through the magnetic field sensor (8) having a lower magnetic resistance than air.

  Thus, since the conventional fluxgate current sensor is easily affected by geomagnetism, it has a problem that the current to be measured cannot be accurately detected. The present invention has been made in view of the above circumstances, and the object thereof is a fluxgate current sensor that is not easily affected by geomagnetism, and a fluxgate current sensor suitable for such a fluxgate current sensor. It is to provide a loop core.

  A loop core for a fluxgate current sensor according to an embodiment of the present invention that solves the above-described problems includes a pair of substantially three-shaped cores that are formed by integrally connecting two plate shapes bent into a substantially U-shape. And a soft magnetic insertion member having a higher magnetic permeability than the pair of cores. The pair of cores are in contact with at least a part of each of the first outer legs, and at least a part of each of the second outer legs are in contact with each other via the soft magnetic insertion member. A predetermined gap is maintained between the connecting portions of the U-shape so as to form an annular loop with a halfway. The annular loop has a first ring portion that defines a space through which the electric wire to be measured is inserted and passed on the first outer leg side with the gap portion as a boundary, and the electric wire on the second outer leg side. A second ring portion that defines a space for arranging a magnetic probe for detecting a magnetic field induced by a flowing current is provided.

  According to the present invention, the pair of second outer legs constituting the second ring portion surrounding the magnetic probe are in contact with each other via the soft magnetic insertion member having a higher permeability than the core. The magnetic resistance at the contact portion between the two outer legs is suppressed to a small value. Therefore, the geomagnetism that has reached this contact portion flows through the contact portion having a lower magnetic resistance without passing through the magnetic probe. That is, the loop core for a fluxgate current sensor according to the present invention is suitably configured to suppress the influence of geomagnetism on the magnetic probe.

  The soft magnetic insertion member is, for example, a soft material that deforms when inserted between the pair of second outer legs.

  Moreover, the soft magnetic insertion member has adhesiveness, and it is good also as a structure which adhere | attaches and fixes 2nd outer leg parts.

  At least a part of the second outer legs may be superposed with a soft magnetic insertion member interposed therebetween in the thickness direction of the second outer legs.

  A fluxgate current sensor according to an embodiment of the present invention that solves the above problems includes a flux core current sensor loop core, a magnetic probe disposed in a space surrounded by the second ring portion, and a flux gate current sensor. The coil has a coil wound around an insulator via a loop core.

  The insulator is, for example, a bobbin that surrounds at least a part of the side surfaces of the pair of second outer legs overlapped in the thickness direction of the second outer legs. In this case, the second outer leg portions may be configured such that the soft magnetic insertion member is pressed and held by pressing and holding with a bobbin and the second outer legs are fixed to each other.

  ADVANTAGE OF THE INVENTION According to this invention, the fluxgate current sensor which is hard to receive the influence of a geomagnetism, and the loop core for fluxgate current sensors suitable for such a fluxgate current sensor are provided.

The circuit diagram of the fluxgate current sensor which concerns on embodiment of this invention is shown. 1 shows a cross-sectional view of a fluxgate current sensor according to an embodiment of the present invention. The perspective view of the feedback core single-piece | unit with which the fluxgate current sensor which concerns on embodiment (this Example 1) of this invention is provided is shown. It is a figure explaining the assembly of the fluxgate current sensor of Example 1 of this invention. Sectional drawing of the feedback core single-piece | unit with which the fluxgate current sensor which concerns on Example 2 of this invention is provided is shown.

  Hereinafter, a fluxgate current sensor according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows a circuit diagram of a fluxgate current sensor 1 according to an embodiment of the present invention. The fluxgate current sensor 1 of this embodiment has a structure in which a probe 10 and a feedback coil 20 are attached to a feedback core 30. The feedback core 30 is made of, for example, PC permalloy that is one of soft magnetic alloys having high magnetic permeability. In the feedback core 30, a cable CL through which a current to be measured flows is disposed close to the feedback core 30. The fluxgate current sensor 1 measures the magnitude of the current flowing through the cable CL by detecting the magnitude of the magnetic field generated in the feedback core 30 by the current flowing through the cable CL.

  FIG. 2A shows a cross-sectional view of the main part of the fluxgate current sensor 1 including the probe 10, the feedback coil 20, and the feedback core 30. FIG. 2B shows the AA cross section of FIG. 2A, and FIG. 2C shows the BB cross section of FIG. FIG. 3 shows a perspective view of the feedback core 30 alone. As shown in FIG. 2 or FIG. 3, the feedback core 30 forms a loop by combining the first core portion 31, the second core portion 32, and the soft magnetic insertion member 35. Each of the first core portion 31 and the second core portion 32 has bent portions 31 a and 32 a that are largely bent toward the inner side of the loop of the feedback core 30, and two wide plate materials bent into a substantially U-shape. Is formed in a shape of approximately three. As shown in FIG. 2, the loop shape of the feedback core 30 includes a first ring portion 33 and a second ring portion 34 by bent portions 31 a and 32 a including a connecting portion that connects two substantially U-shaped shapes. In the middle, it is a ring (substantially 8 characters).

  The probe 10 is a magnetic probe in which a winding 12 is wound around a fluxgate core 11. The fluxgate core 11 is made of, for example, an amorphous material having a high magnetic permeability and is one of soft magnetic alloys. The fluxgate core 11 and the winding 12 are insulated by an insulator not shown. As shown in FIG. 2, the probe 10 is arranged in a space surrounded by the feedback core 30 in the second ring portion 34. When a current is passed through the winding 12, a magnetic field is generated in the fluxgate core 11.

  The feedback coil 20 has a first winding 21 and a second winding 22. The first winding 21 is disposed so as to surround a part of the first ring portion 33 (the first outer leg portion 31c of the first core portion 31 and the first outer leg portion 32c of the second core portion 32). It is wound around a first bobbin 41 having insulating properties. The second winding 22 is wound around a second bobbin 42 having insulation properties, which is disposed so as to surround the second ring portion 34 and the bent portions 31a and 32a. The first winding 21 and the second winding 22 are connected to each other so as to be electrically in series.

  The operation of the fluxgate current sensor 1 will be described below. Note that the cable CL through which the current to be measured flows is inserted into and passed through the space between the first winding 21 and the second winding 22 in the first ring portion 33.

  As shown in FIG. 1, a pulse power source 51 is connected to the winding 12 of the probe 10. A pulsed high-frequency rectangular wave current is supplied from the pulse power source 51 to the winding 12. When the high-frequency rectangular wave current is supplied to the winding 12, the magnetic flux density in the fluxgate core 11 is periodically saturated. Therefore, when a magnetic field is generated in the feedback core 30 by the current flowing through the cable CL, the waveform of the voltage applied to the winding 12 is distorted by an external magnetic field (a magnetic field generated in the feedback core 30). .

  The winding 12 is connected to the interface circuit 52. The interface circuit 52 converts the voltage between the windings 12 into a PWM signal. The PWM signal output from the interface circuit 52 is a signal having a duty ratio of 50% when an external magnetic field is not applied to the fluxgate core 11 (that is, when no current flows through the cable CL). The duty ratio of the PWM signal changes according to the external magnetic field applied to the fluxgate core 11.

  The PWM signal output from the interface circuit 52 is input to the low pass filter 53. The low-pass filter 53 converts the PWM signal into an analog signal (output voltage corresponding to the duty ratio), and outputs the converted output voltage to the driver 54.

The driver 54 includes an error amplifier and a feedback circuit. The feedback coil 20 is connected to the output stage of the driver 54. The error amplifier detects the difference between the output voltage from the low-pass filter 53 and a predetermined reference voltage _Vref . The feedback circuit causes a current having a magnitude based on the detected difference to flow through the feedback coil 20. When a feedback magnetic field is generated by the current flowing through the feedback coil 20, the magnetic field in the feedback core 30 induced by the current flowing through the cable CL is canceled out. That is, a negative feedback current flows through the feedback coil 20 so that the external magnetic field applied to the fluxgate core 11 becomes zero.

The fluxgate current sensor 1 measures the magnitude of the current flowing through the cable CL by measuring the current flowing through the feedback coil 20 (in other words, the output voltage V _OUT ) with the shunt resistor Rs. Note that the current flowing through the feedback coil 20 periodically changes at a high speed by the negative feedback. However, the differential amplifier 55 has a response speed several orders of magnitude lower than that of the driver 54. Therefore, the waveform of the output voltage V _OUT coincides with the current waveform to be measured, and is substantially a value correlated with the magnitude of the current flowing through the cable CL.

  The fluxgate current sensor 1 of the present embodiment is configured such that the magnetic resistance at the contact portion between the first core portion 31 and the second core portion 32 is reduced in order to effectively suppress current measurement errors based on geomagnetism. . Hereinafter, a plurality of specific examples of the fluxgate current sensor 1 will be described.

  2 also serves as a cross-sectional view of the fluxgate current sensor 1 according to the first embodiment, and FIG. 3 also serves as a perspective view of the feedback core 30 according to the first embodiment. FIGS. 4A to 4C are diagrams illustrating the assembly of the fluxgate current sensor 1 according to the first embodiment.

  As shown in FIGS. 2 (a), 2 (b), and 3, the feedback core 30 has a second outer leg portion 31b of the first core portion 31 and a soft magnetic medium, as viewed from the middle constricted position side. The insertion member 35 and the second outer leg portion 32b of the second core portion 32 are arranged in this order, and the upper surface 31bU of the second outer leg portion 31b and the lower surface 32bD of the second outer leg portion 32b are soft magnetic insertion members. 35 are superposed on each other. The soft magnetic insertion member 35 is a soft magnetic material having a higher magnetic permeability than the first core portion 31 and the second core portion 32, and is, for example, a permalloy tape in which a magnetic material mainly composed of a nickel alloy is formed in a foil shape. The soft magnetic insertion member 35 has flexibility and one surface is an adhesive surface having adhesiveness. Further, as shown in FIGS. 2A, 2C, and 3, the feedback core 30 has a first outer leg portion 31c of the first core portion 31 as viewed from the middle constricted position side. It arrange | positions in order of the 1st outer leg part 32c of the 2nd core part 32, and the lower surface 31cD of the 1st outer leg part 31c and the upper surface 32cU of the 1st outer leg part 32c mutually overlap.

  Referring to the assembly process of the fluxgate current sensor 1 shown in FIG. 4, the soft magnetic insertion member 35 is bonded and fixed to the upper surface 31 b U of the second outer leg portion 31 b of the first core portion 31. The second outer leg portion 31b is inserted and passed through the inside of the second bobbin 42, and the first outer leg portion 31c of the first core portion 31 is inserted and passed through the inside of the first bobbin 41 (FIG. 4A). )reference). When the probe 10 is assembled in the space surrounded by the feedback core 30 in the second ring portion 34 (see FIG. 4B), the second outer leg portion 32b of the second core portion 32 is the second bobbin. The first outer leg portion 32c of the second core portion 32 is inserted into and passed through the remaining space in the first bobbin 41 (see FIG. 4C). . At this time, the soft magnetic insertion member 35 is in surface contact with each surface of the upper surface 31bU of the second outer leg portion 31b of the first core portion 31 and the lower surface 32bD of the second outer leg portion 32b of the second core portion 32. Inserted in the state. In addition, the soft magnetic insertion member 35 may be a bonding surface on the surface in contact with the lower surface 32bD. In addition, the first bobbin 41 and the second bobbin 42 have the first winding 21 and the second winding 22 so that the insulation between the first winding 21 and the second winding 22 and the feedback core 30 is ensured. And the feedback core 30 are formed so as to surround at least a part thereof. In the first embodiment, as shown in FIGS. 2B and 2C, both the first bobbin 41 and the second bobbin 42 have a substantially square shape in cross section perpendicular to the major axis direction. ing.

  As shown in FIG. 2A or 2B, the width from the upper surface 32bU of the second outer leg portion 32b of the second core portion 32 to the lower surface 31aD (or 32aD) of the bent portion 31a (or 32a). w1 is substantially equal to the distance d1 between the opposing inner wall surfaces of the second bobbin 42. Further, the width w2 from the upper surface 31bU to the lower surface 31aD (or 32aD) of the second outer leg portion 31b of the first core portion 31, the plate thickness t1 of the second outer leg portion 32b of the second core portion 32, and soft magnetism The sum of the insertion member 35 and the layer thickness t2 is also substantially equal to the distance d1. The width w1 (and the sum of the width w2, the plate thickness t1, and the layer thickness t2) and the distance d1 are defined by fit tolerance (intermediate fit or interference fit), for example. Therefore, when the second bobbin 42 is attached to the feedback core 30 (see FIG. 2A or FIG. 4C), the entire second ring portion 34, the bent portions 31a, and 32a are the inner wall surface of the second bobbin 42. It is sandwiched between and receives moderate tightening force. As a result, the upper surface 31bU of the second outer leg portion 31b and the lower surface 32bD of the second outer leg portion 32b are brought into close contact with each other with the soft magnetic insertion member 35 interposed therebetween, and become fixed.

  The distance d2 between the opposing inner wall surfaces of the first bobbin 41 is the sum of the plate thicknesses of the first outer leg part 31c of the first core part 31 and the first outer leg part 32c of the second core part 32. Almost equal. The total thickness and the distance d2 are defined by fit tolerance (intermediate fit or interference fit), for example. Therefore, when the first bobbin 41 is attached to the feedback core 30 (see FIG. 2A or 4C), the first outer leg portions 31c and 32c are sandwiched between the inner wall surfaces of the first bobbin 41, Receive moderate tightening force. As a result, the lower surface 31cD of the first outer leg portion 31c and the upper surface 32cU of the first outer leg portion 32c are in close contact with each other and are in a fixed state.

  In the first embodiment, the first core is formed so as to fill a gap between the upper surface 31bU of the second outer leg portion 31b of the first core portion 31 and the lower surface 32bD of the second outer leg portion 32b of the second core portion 32. A soft magnetic insertion member 35 having a higher magnetic permeability than the portion 31 and the second core portion 32 is bonded and inserted. Therefore, the magnetic resistance at the contact portion (via the soft magnetic insertion member 35) between the first core portion 31 and the second core portion 32 is suppressed to a small value. For example, consider the case where the direction of geomagnetism is the long axis direction of the probe 10. In this case, the geomagnetism that has reached the contact portion between the first core portion 31 and the second core portion 32 flows through the contact portion having a smaller magnetic resistance without passing through the flux gate core 11. Further, consider the case where the direction of geomagnetism is orthogonal to the long axis direction of the probe 10. For example, in the case of a direction orthogonal to the paper surface of FIG. 2A, the geomagnetism flows without being routed through the fluxgate core 11 and attracted into the feedback core 30 having a lower magnetic resistance. When parallel to the paper surface of FIG. 2 (a) (vertical direction in the drawing), the geomagnetism flows along the substantially 3 shape in the feedback core 30 having a smaller magnetic resistance without passing through the fluxgate core 11. Go. Thus, the fluxgate core 11 is not substantially affected by the geomagnetism or becomes very difficult to receive. Therefore, the fluxgate current sensor 1 can accurately detect the current flowing through the cable CL.

  Further, in the first embodiment, the second outer leg portion 31b and the soft magnetic material are formed by the second bobbin 42 in order to further improve the adhesion between the respective surfaces of the upper surface 31bU and the lower surface 32bD and the soft magnetic insertion member 35. The three members of the insertion member 35 and the second outer leg portion 32b are pressed and sandwiched. Thereby, the magnetic resistance in the contact part of the 1st core part 31 and the 2nd core part 32 is suppressed to the still smaller value.

  The configuration of the fluxgate current sensor 1 of the second embodiment is the same as that of the first embodiment except for the feedback core. Therefore, in the following, only the feedback core alone of the second embodiment will be described. In the second embodiment, the same components as those in the first embodiment are denoted by the same names and reference numerals, and the description thereof is simplified or omitted.

  FIG. 5 is a cross-sectional view of the feedback core 130 alone according to the second embodiment. As shown in FIG. 5, the feedback core 130 according to the second embodiment includes a first core portion 131, a second core portion 132, and a soft magnetic insertion member 135. The soft magnetic insertion member 135 is a soft magnetic material having a higher magnetic permeability than the first core portion 31 and the second core portion 32, and is, for example, an amorphous ribbon having flexibility. As shown in FIG. 5, in the soft magnetic insertion member 135, the vicinity of one end is between the tip of the second outer leg 131 b of the first core 131 and the side leg 132 s of the second core 132. The remaining portion is sandwiched between the upper surface 131bU of the second outer leg portion 131b and the lower surface 132bD of the second outer leg portion 132b through pressure contact by the second bobbin 42. . The soft magnetic insertion member 135 is inserted between the first core portion 131 and the second core portion 132 in a state of being bent in a substantially L shape as a whole.

  In the second embodiment, in addition to the gap between the upper surface 131bU of the second outer leg portion 131b of the first core portion 131 and the lower surface 132bD of the second outer leg portion 132b of the second core portion 132, the second outer leg The soft magnetic insertion member 35 having a higher permeability than the first core portion 31 and the second core portion 32 is inserted so as to fill a gap between the tip of the portion 131b and the side leg portion 132s of the second core portion 132. Has been. Therefore, the magnetic resistance at the contact portion between the first core portion 131 and the second core portion 132 is further suppressed, and the fluxgate core 11 is not substantially affected by the geomagnetism or very difficult to receive. Therefore, the fluxgate current sensor 1 of the second embodiment can accurately detect the current flowing through the cable CL.

  The above is the description of the exemplary embodiments of the present invention. Embodiments of the present invention are not limited to those described above, and can be arbitrarily changed within the scope of the technical idea expressed by the description of the scope of claims. For example, the insertion positions and materials of the soft magnetic insertion members 35 and 135 are not limited to those exemplified in the first and second embodiments.

DESCRIPTION OF SYMBOLS 1 Flux gate current sensor 10 Probe 20 Feedback coil 30, 130 Feedback core 35, 135 Soft magnetic insertion member

Claims (6)

A pair of substantially three-shaped cores that integrally connect two plate shapes bent into a substantially U-shape;
A soft magnetic insertion member having a higher magnetic permeability than the pair of cores;
Have
The pair of cores is
While at least a part of the mutual first outer leg parts are in contact with each other and at least a part of the mutual second outer leg parts are in contact with each other via the soft magnetic insertion member, the two substantially U-shapes. A predetermined gap is maintained between the connecting portions of the shapes, and is arranged to face each other so that a circular loop with a halfway is formed.
The annular loop has, on the first outer leg side with the gap portion as a boundary, a first ring part that defines a space through which a measurement target electric wire is inserted and passed, and the second outer leg side A loop core for a fluxgate current sensor, further comprising a second ring portion that defines a space for arranging a magnetic probe for detecting a magnetic field induced by a current flowing through the electric wire.   The loop core for a fluxgate current sensor according to claim 1, wherein the soft magnetic insertion member is a soft material that is deformed when inserted between the pair of second outer legs.   3. The loop core for a fluxgate current sensor according to claim 1, wherein the soft magnetic insertion member has adhesiveness, and the second outer legs are bonded and fixed to each other.   At least a part of the second outer legs are overlapped in the thickness direction of the second outer legs with the soft magnetic insertion member interposed therebetween, The loop core for flux gate current sensors according to any one of claims 1 to 3. A loop core for a fluxgate current sensor according to any one of claims 1 to 4,
A magnetic probe disposed in a space surrounded by the second ring portion;
A coil wound around an insulator on the loop core for the fluxgate current sensor;
A fluxgate current sensor comprising: The insulator is a bobbin that surrounds at least a part of the side surfaces of the pair of second outer legs that are overlapped in the thickness direction of the second outer legs.
The second outer legs are clamped by the bobbin so as to clamp the soft magnetic insertion member, and are fixed to each other. 5. The fluxgate current sensor according to 5.

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