Magnetic field detection device and array of magnetic field detection devices

Abstract

In a magnetic field detection device capable of detecting a weak magnetic field without using a shield room, the number of components is reduced, and the circuit structure is simplified. A magnetic field detection device (1) includes: a cancellation coil (C2) wound around a winding core portion (13) of a bobbin (10); magnetic sensors (S1, S21-S24) fixed to mutually different positions of the bobbin (10); and a feedback circuit (31) that cancels an ambient magnetic field of a cancellation space by causing a cancellation current to flow through the cancellation coil (C2) in accordance with an output signal of the magnetic sensor (S1). The magnetic sensors (S21-S24) are disposed within the cancellation space. In this way, a common cancellation coil (C2) is used for the magnetic sensors (S1, S21-S24), so the number of components can be reduced, and the circuit structure can be simplified.

Description

TECHNICAL FIELD

[0001] The present application relates to a magnetic field detection device, and particularly to a magnetic field detection device capable of detecting a weak magnetic field without using a shield room. In addition, the present application relates to a magnetic field detection device array provided with a plurality of magnetic field detection devices. BACKGROUND

[0002] As a magnetic field detection device capable of detecting a weak magnetic field without using a shield room, a magnetic field detection device described in Patent Literature 1 is known. The magnetic field detection device of Patent Literature 1 detects an ambient magnetic field using a reference magnetic sensor, and causes an elimination current to flow through an elimination coil on the basis of the ambient magnetic field, thereby eliminating the ambient magnetic field applied to a measurement magnetic sensor. In addition, the magnetic field detection device of Patent Literature 1 detects a magnetic field using a plurality of magnetic sensors, and causes an elimination current to flow through an elimination coil provided for each of the plurality of magnetic sensors, thereby eliminating the ambient magnetic field applied to the plurality of magnetic sensors. Figure 1 The magnetic field detection device described in Patent Literature 1 detects an ambient magnetic field using a reference magnetic sensor, and causes an elimination current to flow through an elimination coil on the basis of the ambient magnetic field, thereby eliminating the ambient magnetic field applied to a measurement magnetic sensor. In addition, the magnetic field detection device of Patent Literature 1 detects a magnetic field using a plurality of magnetic sensors, and causes an elimination current to flow through an elimination coil provided for each of the plurality of magnetic sensors, thereby eliminating the ambient magnetic field applied to the plurality of magnetic sensors. Figure 7 The magnetic field detection device described in Patent Literature 1 detects an ambient magnetic field using a reference magnetic sensor, and causes an elimination current to flow through an elimination coil on the basis of the ambient magnetic field, thereby eliminating the ambient magnetic field applied to a measurement magnetic sensor. In addition, the magnetic field detection device of Patent Literature 1 detects a magnetic field using a plurality of magnetic sensors, and causes an elimination current to flow through an elimination coil provided for each of the plurality of magnetic sensors, thereby eliminating the ambient magnetic field applied to the plurality of magnetic sensors.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2017-133993 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] However, in the magnetic field detection device described in Patent Literature 1, different elimination coils are respectively assigned to the measurement magnetic sensor and the reference magnetic sensor, and the magnetic field detection device of Patent Literature 1 detects a magnetic field using a plurality of magnetic sensors, and causes an elimination current to flow through an elimination coil provided for each of the plurality of magnetic sensors, thereby eliminating the ambient magnetic field applied to the plurality of magnetic sensors. Figure 1 The magnetic field detection device described in Patent Literature 1 detects an ambient magnetic field using a reference magnetic sensor, and causes an elimination current to flow through an elimination coil on the basis of the ambient magnetic field, thereby eliminating the ambient magnetic field applied to a measurement magnetic sensor. In addition, the magnetic field detection device of Patent Literature 1 detects a magnetic field using a plurality of magnetic sensors, and causes an elimination current to flow through an elimination coil provided for each of the plurality of magnetic sensors, thereby eliminating the ambient magnetic field applied to the plurality of magnetic sensors. Figure 7 The magnetic field detection device described in Patent Literature 1 detects an ambient magnetic field using a reference magnetic sensor, and causes an elimination current to flow through an elimination coil on the basis of the ambient magnetic field, thereby eliminating the ambient magnetic field applied to a measurement magnetic sensor. In addition, the magnetic field detection device of Patent Literature 1 detects a magnetic field using a plurality of magnetic sensors, and causes an elimination current to flow through an elimination coil provided for each of the plurality of magnetic sensors, thereby eliminating the ambient magnetic field applied to the plurality of magnetic sensors. Figure 7 The magnetic field detection device described in Patent Literature 1 detects an ambient magnetic field using a reference magnetic sensor, and causes an elimination current to flow through an elimination coil on the basis of the ambient magnetic field, thereby eliminating the ambient magnetic field applied to a measurement magnetic sensor. In addition, the magnetic field detection device of Patent Literature 1 detects a magnetic field using a plurality of magnetic sensors, and causes an elimination current to flow through an elimination coil provided for each of the plurality of magnetic sensors, thereby eliminating the ambient magnetic field applied to the plurality of magnetic sensors.

[0008] Therefore, an object of the present application is to reduce the number of components and simplify the circuit structure in a magnetic field detection device capable of detecting a weak magnetic field without using a shield room and a magnetic field detection device array.

[0009] MEANS FOR SOLVING THE PROBLEMS

[0010] The magnetic field detection device of the present application is characterized by comprising: a bobbin; a cancellation coil wound around a winding core portion of the bobbin; first and second magnetic sensors fixed to mutually different positions of the bobbin and detecting magnetic field components in the same direction; and a feedback circuit that causes a cancellation current to flow through the cancellation coil based on an output signal of the first magnetic sensor, thereby canceling an ambient magnetic field in a cancellation space, the second magnetic sensor being disposed in the cancellation space.

[0011] According to the present application, since a common cancellation coil is used for the first and second magnetic sensors, the number of components can be reduced and the circuit structure can be simplified.

[0012] In the present application, the first and second magnetic sensors can each be disposed at a position overlapping with an inner diameter region of the cancellation coil when viewed in an axial direction of the cancellation coil. Thus, the overall size of the device can be reduced.

[0013] In the present application, the sensor heads of the first and second magnetic sensors can also be different in position in the axial direction of the cancellation coil. Thus, the signal magnetic field components can be prevented from being canceled by the cancellation coil. In this case, the winding core portion of the bobbin can also have a first chamber opened at the first flange portion and a second chamber opened at the second flange portion, the first magnetic sensor being housed in the first chamber and the second magnetic sensor being housed in the second chamber. Thus, the first and second magnetic sensors can be sufficiently separated in distance. Further, in this case, the sensor head of the first magnetic sensor can project from the first flange portion of the bobbin and the sensor head of the second magnetic sensor can project from the second flange portion of the bobbin. Thus, the distance between the measurement target and the second magnetic sensor can be made close.

[0014] The magnetic field detection device of the present application can further comprise a circuit substrate fixed to the first or second flange portion, and the feedback circuit can be provided on the circuit substrate. Thus, the first or second flange portion can be effectively utilized.

[0015] The magnetic field detection device of the present application can also comprise a plurality of second magnetic sensors. Thus, the spatial distribution of the signal magnetic field components can be measured.

[0016] The magnetic field detection device of the present application can also further comprise a resistor connected in parallel with the cancellation coil and having a resistance value greater than an equivalent series resistance of the cancellation coil. Thus, oscillation of a feedback loop constituted by the first magnetic sensor, the feedback circuit, and the cancellation coil can be prevented.

[0017] The magnetic field detection device array of one aspect of the present application is characterized by comprising a plurality of the above-described magnetic field detection devices, the above-described magnetic field detection devices comprising a plurality of second magnetic sensors, and the plurality of magnetic field detection devices being arranged in a matrix shape with the axial directions of the cancellation coils being mutually identical. According to the present application, the spatial distribution of the signal magnetic field components can be measured over a wide range.

[0018] Another aspect of the present invention is a magnetic field detection device array consisting of multiple magnetic field detection devices arranged in an array. The array is characterized in that at least one of the multiple magnetic field detection devices has the same structure as the aforementioned magnetic field detection device equipped with multiple second magnetic sensors, and the remaining portions of the multiple magnetic field detection devices have a structure that removes the first magnetic sensor from the aforementioned magnetic field detection device equipped with multiple second magnetic sensors. This configuration eliminates the ambient magnetic field of the elimination space by flowing an elimination current through the elimination coil. The multiple magnetic field detection devices are arranged in a matrix with the axes of the elimination coils aligned with each other. According to the present invention, the spatial distribution of the signal magnetic field components can be measured over a wide range, and the number of magnetic sensors used can be reduced.

[0019] In this invention, multiple second magnetic sensors disposed in multiple magnetic field detection devices may be arranged at the intersection points of multiple first imaginary lines extending in a first direction orthogonal to the axial direction of the elimination coil and multiple second imaginary lines extending in a second direction orthogonal to both the axial direction of the elimination coil and the first direction, with the spacing between the multiple first imaginary lines being equal to the spacing between the multiple second imaginary lines. This allows for the measurement of the spatial distribution of the signal magnetic field components in the xy plane, which serves as the detection surface, at equal intervals.

[0020] The effects of the invention

[0021] According to the present invention, a magnetic field detection device and magnetic field detection device array can be provided that can detect weak magnetic fields without using a shielded room, and has a small number of components and a simple circuit structure. Attached Figure Description

[0022] Figure 1 This is a schematic perspective view of the magnetic field detection device 1 of the first embodiment of the present invention, viewed from the measuring surface side.

[0023] Figure 2 This is a schematic three-dimensional view of the magnetic field detection device 1 viewed from the rear side.

[0024] Figure 3 This is a schematic perspective view showing the appearance of the winding tube 10.

[0025] Figure 4 This is a schematic diagram illustrating an example of the internal structure of magnetic sensors S1, S21 to S24.

[0026] Figure 5 This is a block diagram showing the circuit structure of the magnetic field detection device 1.

[0027] Figure 6 This is a schematic plan view of sensor chip 22.

[0028] Figure 7is a schematic cross-sectional view taken along the line A-A shown in Figure 6

[0029] Figure 8 is a circuit diagram of a feedback loop including the magnetic sensor S1, the feedback circuit 31, and the cancellation coil C2.

[0030] Figure 9 is a circuit diagram of the magnetic sensors S21 to S24 and the detection circuit 32.

[0031] Figure 10 is a schematic view for explaining the radial positions at which the magnetic sensors S1, S21 to S24 are provided.

[0032] Figure 11 is a schematic view for explaining the position of the cancellation space 40.

[0033] Figure 12 is a schematic view showing an example in which a plurality of magnetic field detection devices 1 are arranged in an array.

[0034] Figure 13 is a schematic cross-sectional view for explaining the structure of the magnetic field detection device 2 of the second embodiment of the present application.

[0035] Figure 14 is a schematic exploded perspective view showing the appearance of the magnetic field detection device 2.

[0036] Figure 15 is a circuit diagram of a feedback loop including the magnetic sensor S1, the feedback circuit 31, and the cancellation coils C2, C3.

[0037] Figure 16 is a schematic view showing one example of the internal structure of the magnetic sensors S1, S21 to S24 including the cancellation coil C3.

[0038] Figure 17 is a schematic perspective view showing the appearance of the magnetic field detection device 3 of the third embodiment of the present application.

[0039] Figure 18 is a schematic perspective view showing the appearance of the magnetic field detection device 4 of the fourth embodiment of the present application.

[0040] Figure 19 is a schematic perspective view showing the appearance of the magnetic field detection device 5 of the fifth embodiment of the present application.

[0041] Figure 20 is a schematic perspective view showing the appearance of the magnetic field detection device 6 of the sixth embodiment of the present application.

[0042] Figure 21 is a schematic perspective view showing the appearance of the magnetic field detection device 7 of the seventh embodiment of the present application.​ DETAILED DESCRIPTION

[0043] Hereinafter, a preferred embodiment of the present application will be described in detail with reference to the drawings.

[0044] Figure 1 and Figure 2 is a view showing the appearance of a magnetic field detection device 1 according to a first embodiment of the present application, Figure 1 is a schematic perspective view as viewed from the measurement surface side, Figure 2 is a schematic perspective view as viewed from the back surface side.

[0045] As shown in Figure 1 and Figure 2 , the magnetic field detection device 1 according to the first embodiment is provided with a bobbin 10 made of a resin material or the like, a cancellation coil C2 wound around the bobbin 10, and a plurality of magnetic sensors S1, S21 to S24 fixed to the bobbin 10. The structure of the bobbin 10 is shown in Figure 3 , which has a winding core portion 13 and flange portions 11, 12 provided at both ends in the z direction of the winding core portion 13. The outer peripheral surface of the winding core portion 13 is circular as viewed in the z direction. The cancellation coil C2 is wound around the winding core portion 13 of the bobbin 10, and thus the coil axis of the cancellation coil C2 is the z direction. The winding core portion 13 is cylindrical, and has a hollow portion 14 extending in the z direction.

[0046] In the present embodiment, eight chambers A1 to A8 are provided in the winding core portion 13 of the bobbin 10. The chambers A1 to A8 are through holes that pass through the winding core portion 13 in the z direction, and one end in the z direction of the chambers A1 to A8 is open at the flange portion 11, and the other end in the z direction of the chambers A1 to A8 is open at the flange portion 12. The radial positions of the chambers A1 to A8 are the same as each other. Also, in the present embodiment, the magnetic sensor S1 is housed in the chamber A6, and the magnetic sensors S21 to S24 are respectively housed in the chambers A1, A3, A5, A7. The sensor head of the magnetic sensor S1 protrudes in the z direction from the flange portion 11, and the sensor heads of the magnetic sensors S21 to S24 protrude in the z direction from the flange portion 12. The magnetic sensors S1, S21 to S24 are respectively connected to a circuit substrate 15 fixed to the flange portion 11 of the bobbin 10 via leads L0 to L4. In Figure 1 and Figure 2 , the chambers A2, A4, A8 are empty, but other magnetic sensors can be housed in the chambers A2, A4, A8. That is, up to eight magnetic sensors can be fixed to the bobbin 10.

[0047] According to this structure, the magnetic sensors S1, S21 to S24 are each disposed at a position overlapping with the inner diameter region of the canceling coil C2 when viewed in the z direction, and the positions of the sensor heads of the magnetic sensor S1 and the magnetic sensors S21 to S24 in the z direction are different from each other. The positions of the sensor heads of the magnetic sensors S21 to S24 in the z direction are the same as each other. In addition, the radial positions of the sensor heads of the magnetic sensor S1 and the magnetic sensors S21 to S24 with respect to the coil axis are the same as each other.

[0048] The magnetic sensor S1 is a sensor for detecting an environmental magnetic field component such as the earth's magnetic field, and the magnetic sensors S21 to S24 are sensors for detecting a signal magnetic field component emitted from a measurement target object. The sensitivity axes of the magnetic sensors S1, S21 to S24 are each the z direction, and most of them are located in the inner diameter region of the canceling coil C2. As described above, the sensor heads of the magnetic sensors S21 to S24 protrude from the flange portion 12. This is to make the sensor heads of the magnetic sensors S21 to S24 closer to the measurement target object. That is, if the sensor heads of the magnetic sensors S21 to S24 are buried in the bobbin 10, the distance between the measurement target object and the sensor heads of the magnetic sensors S21 to S24 becomes large. On the other hand, the sensor head of the magnetic sensor S1 does not need to protrude from the flange portion 11, but in order to improve the symmetry with the magnetic sensors S21 to S24, it is preferable to make the protruding amount of the magnetic sensor S1 from the flange portion 11 the same as the protruding amount of the magnetic sensors S21 to S24 from the flange portion 12.

[0049] Figure 4 is a schematic view showing one example of the internal structure of the magnetic sensors S1, S21 to S24.

[0050] In Figure 4 the example shown, the magnetic sensors S1, S21 to S24 have the same structure as each other, and each include a sensor housing 20, a substrate 21 housed in the sensor housing 20, a sensor chip 22 mounted on the substrate 21, and a magnet collector 23. The magnet collector 23 is a rod-shaped body extending in the z direction, and is made of a high-permeability material such as ferrite. One end of the magnet collector 23 in the z direction constitutes a sensor head H, and the other end of the magnet collector 23 in the z direction is disposed with the sensor chip 22. Thus, a signal magnetic field component in the z direction emitted from a measurement target object located in the vicinity of the sensor head H is collected by the magnet collector 23, and is applied to the sensor chip 22.

[0051] Figure 5 is a block diagram showing the circuit structure of the magnetic field detection device 1 of the present embodiment.

[0052] As Figure 5As shown, the magnetic field detection device 1 of this embodiment includes a feedback circuit 31 connected to the magnetic sensor S1 and a detection circuit 32 connected to the magnetic sensors S21 to S24. The feedback circuit 31 is a circuit that generates a feedback current F1 to cancel the ambient magnetic field component, and the feedback current F1 generated by the feedback circuit 31 is provided to the cancellation coil C2. Thus, the magnetic sensor S1, the feedback circuit 31, and the cancellation coil C2 constitute a feedback loop to cancel the ambient magnetic field component. On the other hand, the detection circuit 32 generates a detection signal Vout representing the signal magnetic field component emitted from the object being measured, based on the output signals from the magnetic sensors S21 to S24.

[0053] Figure 6 This is a schematic plan view of sensor chip 22. Figure 7 It is along Figure 6 The diagram shows a rough cross-section of line AA.

[0054] like Figure 6 and Figure 7 As shown, four magnetoresistive elements M1 to M4 and an elimination coil C1 are integrated on the element forming surface of the sensor chip 22. The elimination coil C1 is covered by an insulating film 24, on which the magnetoresistive elements M1 to M4 are formed. The magnetoresistive elements M1 to M4 are covered by an insulating film 25. Furthermore, viewed from the z-direction, a magnetizer 23 is disposed between the magnetoresistive elements M1 and M2 and the magnetoresistive elements M3 and M4. As a result, the magnetic field in the z-direction collected by the magnetizer 23 is distributed in the +x and -x directions on the element forming surface of the sensor chip 22. Consequently, mutually opposite magnetic field components are applied to the magnetoresistive elements M1 and M2 and the magnetoresistive elements M3 and M4. Here, the fixed magnetization directions of the magnetoresistive elements M1 to M4 are all aligned in the +x or -x direction.

[0055] In addition, the elimination coil C1 is arranged to overlap with the magnetoresistive effect elements M1 to M4. When the elimination current flows through the elimination coil C1, mutually opposite elimination magnetic fields are applied to the magnetoresistive effect elements M1, M2 and M3, M4.

[0056] Figure 8 It is a circuit diagram of a feedback loop including a magnetic sensor S1, a feedback circuit 31, and an elimination coil C2.

[0057] like Figure 8As shown, the magnetoresistive elements M1 to M4 included in the magnetic sensor S1 are connected in a bridge configuration, and the resulting differential signal is provided to the differential amplifier 31a included in the feedback circuit 31. The differential amplifier 31a generates a feedback current F1 based on the differential signal. The feedback current F1 flows through the series-connected cancellation coils C1 and C2. As a result, the cancellation coils C1 and C2 generate a cancellation magnetic field in such a way that the differential signal component of the output signal of the magnetic sensor S1 becomes zero.

[0058] Furthermore, in this embodiment, a resistor R1 is connected in parallel with the elimination coil C2. The resistance value of resistor R1 is set to be greater than the equivalent series resistance (ESR) of the elimination coil C2, preferably more than 10 times the ESR, and more preferably more than 100 times the ESR. As a result, the low-frequency component of the feedback current F1, caused by the Earth's magnetic field, flows through the elimination coil C2, while the high-frequency component, which causes oscillations, bypasses resistor R1. Consequently, oscillations in the feedback loop can be prevented, and environmental magnetic field components such as the Earth's magnetic field can be accurately eliminated.

[0059] Figure 9 This is a circuit diagram of magnetic sensors S21 to S24 and detection circuit 32.

[0060] like Figure 9 As shown, the magnetoresistive elements M1 to M4 included in the magnetic sensors S21 to S24 are connected in a bridge configuration, and the resulting differential signal is supplied to the differential amplifier 32a included in the detection circuit 32. The differential amplifier 32a generates a feedback current F2 based on the differential signal. The feedback current F2 flows to the cancellation coil C1. As a result, the cancellation coil C1 generates a magnetic field cancellation in such a way that the differential signal component of the output signal of the magnetic sensors S21 to S24 becomes zero.

[0061] Furthermore, the detection circuit 32 includes a resistor R2 for converting the feedback current F2 to a voltage, and a voltage measuring circuit 33 for measuring the voltage across the resistor R2. Thus, when the feedback current F2 flows, a detection signal Vout proportional to the current quantity is generated.

[0062] Figure 10 This is a schematic diagram illustrating the radial positions of the magnetic sensors S1, S21 to S24.

[0063] like Figure 10As shown, the magnetic sensor S1 is disposed at a position offset from the center of the inner diameter region of the cancellation coil C2, as viewed in the axial direction (z direction) of the cancellation coil C2. As described above, the cancellation coil C2 generates a cancellation magnetic field in such a manner that the ambient magnetic field component applied to the magnetic sensor S1 becomes zero. However, the ambient magnetic field component becomes zero not only at the position where the magnetic sensor S1 is disposed, but also in the cancellation space 40 distributed in concentric circles with the cancellation coil C2. This is because, since the intensity distribution of the cancellation magnetic field is in concentric circles, if the ambient magnetic field component is the same, the ambient magnetic field component is completely cancelled in the region having the same radial position as the magnetic sensor S1.

[0064] As shown in FIG. 1, the magnetic field detection device 1 according to the present embodiment includes a cancellation coil C2, a magnetic sensor S1, and a magnetic sensor S21. The cancellation coil C2 is disposed in the center of the flange portion 11 of the housing 10. The magnetic sensor S1 is disposed in the center of the flange portion 12 of the housing 10. The magnetic sensor S21 is disposed in the center of the flange portion 12 of the housing 10. Figure 11 As shown, the cancellation space 40 is not only symmetrically formed on the flange portion 11 side where the sensor head of the magnetic sensor S1 is located, but also symmetrically formed on the flange portion 12 side where the sensor heads of the magnetic sensors S21 to S24 are located. Also, in the present embodiment, the magnetic sensors S21 to S24 are disposed within the cancellation space 40 formed on the flange portion 12 side. Thereby, the ambient magnetic field component applied to the magnetic sensors S21 to S24 also becomes zero, and thus only the signal magnetic field component emitted from the measurement target is applied to the magnetic sensors S21 to S24. Therefore, it is possible to detect a weak magnetic field without using a shield room. Moreover, since the cancellation coil C2 commonly used for the five magnetic sensors S1, S21 to S24 is allocated, it is possible to reduce the number of components and to simplify the circuit structure.

[0065] In the present embodiment, the radial positions of the chambers A1 to A8 are the same as each other, and thus, even if the magnetic sensors S21 to S24 are housed in any of the chambers, the ambient magnetic field component applied to the magnetic sensors S21 to S24 is zero. Also, in the present embodiment, the sensor head of the magnetic sensor S1 for detecting the ambient magnetic field component is provided on the flange portion 11 side, and the sensor heads of the magnetic sensors S21 to S24 for detecting the signal magnetic field component are provided on the flange portion 12 side, and thus, the signal magnetic field component emitted from the measurement target is hardly applied to the magnetic sensor S1, and thus, a part or all of the signal magnetic field component is not cancelled. Moreover, if the measurement is performed in a state where the measurement target generating a weak magnetic field is brought close to the sensor heads of the magnetic sensors S21 to S24, it is possible to detect the signal magnetic field component emitted from the measurement target in real time. In addition, since the cancellation coil C2 and the magnetic sensors S1, S21 to S24 are fixed to the same bobbin 10, positional displacement between the cancellation coil C2 and the magnetic sensors S1, S21 to S24 is hardly generated.

[0066] In this way, if the magnetic field detection device 1 of the present embodiment is used, it is possible to detect a weak magnetic field with high sensitivity by a simple structure. In addition, as shown in FIG. 2, the magnetic field detection device 1 can be used as a magnetic field sensor 1A for detecting a weak magnetic field. Figure 12If the magnetic field detection device 1 of the present embodiment is arranged in an arrayed manner in such a manner that the axial mutual consistency of the cancellation coils is eliminated, the magnetic sensors S21 to S24 for detecting the signal magnetic field components can be arranged in a matrix on the xy plane. Figure 12 In the example shown, the magnetic sensors S21, S22, S23, or S24 are arranged at each intersection of the imaginary lines x1 to x6 extending in the x direction and the imaginary lines y1 to y6 extending in the y direction. Here, if designed in such a manner that the pitch P of the imaginary lines x1 to x6 is equal to the pitch P of the imaginary lines y1 to y6, the spatial distribution of the signal magnetic field components can be measured over a wide range.

[0067] In the case where a plurality of magnetic field detection devices 1 are arranged in an arrayed manner, the magnetic sensor S1 for detecting the ambient magnetic field components need not be provided in all of the magnetic field detection devices 1, and the magnetic sensor S1 can be provided in any one of the magnetic field detection devices 1, and the feedback current F1 is supplied to the cancellation coil C2 of each magnetic field detection device 1. Thereby, the number of magnetic sensors used can be reduced.

[0068] Figure 13 is a schematic cross-sectional view for explaining the structure of a magnetic field detection device 2 of a second embodiment of the present application. In addition, Figure 14 is a schematic exploded perspective view showing the appearance of the magnetic field detection device 2.

[0069] As Figure 13 shown, the magnetic field detection device 2 of the second embodiment is provided with another bobbin 50 inserted into the hollow portion 14 of the bobbin 10 and a cancellation coil C3 wound around the winding core portion 53 of the bobbin 50. The other basic structure is the same as that of the magnetic field detection device 1 of the first embodiment, and therefore the same elements are denoted by the same symbols, and the repeated explanation is omitted.

[0070] The bobbin 50 has the winding core portion 53 and the flange portions 51, 52 provided at both ends in the z direction of the winding core portion 53. The cancellation coil C3 is wound around the winding core portion 53 of the bobbin 50, and therefore the coil axis direction of the cancellation coil C3 is the z direction. As Figure 15 shown, the cancellation coil C3 is connected in series with the cancellation coil C2. Thereby, compared with the magnetic field detection device 1 of the first embodiment, a stronger cancellation magnetic field can be generated.

[0071] As Figure 16 shown, the cancellation coil C3 can also be wound around the magnetic concentrator 23 inside the magnetic sensor S1. Thereby, even in the case where the ambient magnetic field components are relatively strong, the magnetic saturation of the magnetic concentrator 23 can be prevented. Figure 16 The structure shown can also be applied to the magnetic sensors S21 to S24.

[0072] Figures 17-19are schematic perspective views each showing an external appearance of a magnetic field detection device 3 to 5 according to a third to fifth embodiment of the present application.

[0073] As shown in Figure 17 , the magnetic field detection device 3 of the third embodiment differs from the magnetic field detection device 1 of the first embodiment in that the shape of the bobbin 10 viewed from the z direction is a quadrangle. As shown in Figure 18 , the magnetic field detection device 4 of the fourth embodiment differs from the magnetic field detection device 1 of the first embodiment in that the shape of the bobbin 10 viewed from the z direction is an octagon. As shown in Figure 19 , the magnetic field detection device 5 of the fifth embodiment differs from the magnetic field detection device 1 of the first embodiment in that the shape of the bobbin 10 viewed from the z direction is an ellipse.

[0074] As exemplified by the magnetic field detection devices 3 to 5 of the third to fifth embodiments, in the present application, the shape of the bobbin is not limited to a circle.

[0075] Figure 20 is a schematic perspective view showing an external appearance of a magnetic field detection device 6 according to a sixth embodiment of the present application.

[0076] As shown in Figure 20 , the magnetic field detection device 6 of the sixth embodiment differs from the magnetic field detection device 1 of the first embodiment in that the positions of the magnetic sensor S1 and the magnetic sensors S21 to S24 in the z direction are the same, and the radial positions of the magnetic sensor S1 and the magnetic sensors S21 to S24 with the coil axis as the center are different from each other. In the example shown in Figure 20 , the magnetic sensor S1 is located at the center of the coil axis.

[0077] As exemplified by the magnetic field detection device 6 of the sixth embodiment, in the present application, the positions of the magnetic sensor S1 and the magnetic sensors S21 to S24 in the z direction can also be the same. In the present embodiment, the radial positions of the magnetic sensor S1 and the magnetic sensors S21 to S24 with the coil axis as the center are different from each other, and therefore, if the environmental magnetic field component is completely eliminated at the position where the magnetic sensor S1 is provided (the center of the coil axis), the environmental magnetic field component remains at the positions where the magnetic sensors S21 to S24 are provided (positions offset from the center of the coil axis). Therefore, in the present embodiment, it is not necessary to completely eliminate the environmental magnetic field component at the position where the magnetic sensor S1 is provided, but it is necessary to adjust the gain of the feedback loop so that the environmental magnetic field component is completely eliminated at the positions where the magnetic sensors S21 to S24 are provided.

[0078] Figure 21 is a schematic perspective view showing an external appearance of a magnetic field detection device 7 according to a seventh embodiment of the present application.

[0079] AsFigure 21 The magnetic field detection device 7 of the seventh embodiment differs from the magnetic field detection device 1 of the first embodiment in that the area in the radial direction of the flange portions 11, 12 is enlarged, and other chambers B1 to B8 are provided on the outer side in the radial direction than the winding core portion 13. In the example shown, four magnetic sensors S21 to S24 are housed in the chambers A1 to A8 on the inner side in the radial direction, and four magnetic sensors S1 are housed in the chambers B1 to B8 on the outer side in the radial direction. Figure 21

[0080] As exemplified by the magnetic field detection device 7 of the seventh embodiment, it is not necessary that the radial positions of the chambers for housing the magnetic sensors are all the same, and a plurality of chambers having different radial positions can be provided on the bobbin. In addition, the number of magnetic sensors S1 for detecting the ambient magnetic field component is not limited to one, and a plurality of magnetic sensors S1 can be used.

[0081] The preferred embodiments of the present application have been described above, but the present application is not limited to the above-described embodiments, and various modifications can be made within the scope of the present application without departing from the spirit of the present application, and of course these are included in the scope of the present application.

[0082] For example, in the magnetic field detection device 1 of the first embodiment, four magnetic sensors that detect the signal magnetic field component and one magnetic sensor that detects the ambient magnetic field component are provided, but the number of magnetic sensors that detect the signal magnetic field component and the number of magnetic sensors that detect the ambient magnetic field component are not particularly limited.

[0083] Explanation of symbols

[0084] 1 to 7 … Magnetic field detection device

[0085] 10, 50 … Bobbin

[0086] 11, 12, 51, 52 … Flange portion

[0087] 13, 53 … Winding core portion

[0088] 14 … Hollow portion

[0089] 15 … Circuit substrate

[0090] 20 … Sensor housing body

[0091] 21 … Substrate

[0092] 22 … Sensor chip

[0093] 23 … Magnet collector

[0094] 24, 25 … Insulating film

[0095] 31 … Feedback circuit ​

[0096] 31a … differential amplifier

[0097] 32 … detection circuit

[0098] 32a … differential amplifier

[0099] 33 … voltage measurement circuit

[0100] 40 … cancellation space

[0101] A1 to A8, B1 to B8 … chambers

[0102] C1 to C3 … cancellation coils

[0103] F1, F2 … feedback currents

[0104] H … sensor head

[0105] L0 to L4 … leads

[0106] M1 to M4 … magnetoresistive elements

[0107] R1, R2 … resistors

[0108] S1, S21 to S24 … magnetic sensors

Claims

1. A magnetic field detection device, characterized in that, have: winding tube; Eliminate the coil, which is wound around the core portion of the winding tube; The first magnetic sensor and the second magnetic sensor are fixed at different positions on the winding tube and detect magnetic field components in the same direction. as well as The feedback circuit cancels the ambient magnetic field of a first cancellation space located on one side of the axial direction of the cancellation coil and a second cancellation space located on the other side of the axial direction of the cancellation coil by causing a cancellation current to flow through the cancellation coil according to the output signal of the first magnetic sensor. The sensor head of the first magnetic sensor is disposed within the first elimination space. The sensor head of the second magnetic sensor is disposed within the second elimination space.

2. The magnetic field detection device according to claim 1, characterized in that, Both the first and second magnetic sensors are positioned at locations that overlap with the inner diameter region of the elimination coil when viewed from the axial direction.

3. The magnetic field detection device according to claim 1, characterized in that, The winding core portion of the winding tube has a first chamber opening at a first flange and a second chamber opening at a second flange. The first magnetic sensor is housed in the first chamber. The second magnetic sensor is housed in the second chamber.

4. The magnetic field detection device according to claim 3, characterized in that, The sensor head of the first magnetic sensor protrudes from the first flange portion of the winding tube. The sensor head of the second magnetic sensor protrudes from the second flange of the winding tube.

5. The magnetic field detection device according to claim 3, characterized in that, It also includes a circuit board fixed to the first or second flange portion. The feedback circuit is disposed on the circuit board.

6. The magnetic field detection device according to any one of claims 1 to 5, characterized in that, It has multiple second magnetic sensors.

7. The magnetic field detection device according to any one of claims 1 to 5, characterized in that, It also has a resistor connected in parallel with the canceling coil, and the resistance value is greater than the equivalent series resistance of the canceling coil.

8. A magnetic field detection device array, characterized in that, Possessing multiple magnetic field detection devices as described in claim 6, The plurality of magnetic field detection devices are arranged in a matrix with the axes of the elimination coils aligned with each other.

9. A magnetic field detection device array, characterized in that, The magnetic field detection device array is composed of multiple magnetic field detection devices arranged in an array. At least one of the plurality of magnetic field detection devices has the same structure as the magnetic field detection device of claim 6. The remaining portions of the plurality of magnetic field detection devices have a structure that removes the first magnetic sensor from the magnetic field detection device of claim 6, configured to cancel the ambient magnetic field of the elimination space by allowing the elimination current to flow through the elimination coil. The plurality of magnetic field detection devices are arranged in a matrix with the axes of the elimination coils aligned with each other.

10. The magnetic field detection device array according to claim 8 or 9, characterized in that, The plurality of second magnetic sensors disposed in the plurality of magnetic field detection devices are arranged at the intersection points of a plurality of first imaginary lines extending along a first direction orthogonal to the axial direction of the elimination coil, and a plurality of second imaginary lines extending along a second direction orthogonal to both the axial direction of the elimination coil and the first direction. The spacing between the plurality of first imaginary lines is equal to the spacing between the plurality of second imaginary lines.

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