Current sensor and measuring apparatus

Abstract

To improve current detection accuracy by a current sensor.SOLUTION: A current sensor 3 includes: a flux gate 32; an annular first core 31 that is made by a magnetic body and has a housing space 314 for housing the flux gate 32; and a signal generation circuit 50 for generating a signal based on magnetic flux detected by the flux gate 32. The current sensor detects a current flowing in an object 5 to be measured in a state where the object to be measured is inserted into the first core. In the current sensor 3, the flux gate 32 has: a second core 321 made by the magnetic body and extending in the housing space 314; and a coil 323 wound around the second core 321 along a direction in which the second core 321 extends. One end of the second core 321 in the extending direction is in contact with a portion of the first core 31, and the other end of the second core 321 in the extending direction is in contact with the other portion of the first core 31.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present invention relates to a current sensor and a measurement device, and more particularly to a current sensor including a fluxgate capable of detecting magnetic flux, and a measurement device including the current sensor. [Background technology]

[0002] Conventionally, a current sensor equipped with a fluxgate capable of detecting magnetic flux has been known as a detector for detecting a current flowing through a conductor. For example, Patent Document 1 discloses a current sensor having a core made of a magnetic material.

[0003] The current sensor disclosed in Patent Document 1 has a core configured in an annular shape with an air gap, and a fluxgate is provided near the air gap of the core. When the core is arranged in an annular shape to surround a conductor to be measured, the current sensor detects magnetic flux based on a magnetic field generated by a current flowing through the conductor using the fluxgate, and outputs a signal corresponding to the current flowing through the conductor. With this current sensor, since the fluxgate is arranged in the air gap of the core, more magnetic flux passes through the fluxgate, and the current detection accuracy can be improved. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-53810 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in recent years, in order to develop highly energy-efficient devices, there has been a demand for high-precision current measurement, and there is a demand for current sensors that can detect current with higher accuracy than conventional current sensors such as that disclosed in Patent Document 1.

[0006] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to improve the accuracy of current detection by a current sensor. [Means for solving the problem]

[0007] A current sensor according to a representative embodiment of the present invention includes a fluxgate for detecting magnetic flux, a ring-shaped first core made of a magnetic material and having an accommodation space for accommodating the fluxgate, and a signal generating circuit for generating a signal based on the magnetic flux detected by the fluxgate, and detects a current flowing through an object to be measured while the object to be measured is inserted through the first core. In the current sensor, the fluxgate includes a second core made of a magnetic material and extending into the accommodation space, and a coil wound around the second core along the extension direction of the second core, one end of the second core in the extension direction contacts a part of the first core, and the other end of the second core in the extension direction contacts another part of the first core. Effect of the Invention

[0008] According to the current sensor of the present invention, it is possible to improve the accuracy of current detection. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a configuration of a measurement device according to a first embodiment. [Figure 2A] 1 is a diagram for explaining the principle of current detection by a current sensor; [Figure 2B] 1 is a diagram for explaining the principle of current detection by a current sensor; [Diagram 3] 1 is a perspective view showing an external appearance of a current sensor according to a first embodiment. [Figure 4] FIG. 2 is a diagram showing the appearance of a sensor unit. [Diagram 5] FIG. 2 is a diagram showing the appearance of a magnetic detection unit. [Figure 6] 3 is a front view showing the appearance of a first core according to the first embodiment. FIG. [Figure 7] FIG. 2 is a perspective view of a first core according to the first embodiment. [Figure 8] 4 is an exploded perspective view (part) of a first core according to the first embodiment. FIG. [Figure 9] 3 is a cross-sectional view of a first core according to the first embodiment. FIG. [Figure 10] 1 is an exploded perspective view (all) of a first core according to embodiment 1. FIG. [Figure 11] 3 is a diagram illustrating a schematic positional relationship between a second core and a first core in the current sensor according to the first embodiment. FIG. [Figure 12] 11 is a front view showing the appearance of a first core according to embodiment 2. FIG. [Figure 13] 11 is an exploded perspective view (part) of a first core according to a second embodiment. FIG. [Figure 14] 11 is an exploded perspective view (all) of a first core according to a second embodiment. FIG. [Figure 15] 10 is a diagram illustrating a schematic diagram of a positional relationship between a second core and a first core in a current sensor according to a second embodiment. FIG. [Figure 16] FIG. 13 is a diagram showing another example of the arrangement of flux gates. [Figure 17] 1A and 1B are diagrams illustrating a current sensor in which a second core and a first core are integrally formed. [Figure 18] 10 is a diagram showing another example of the positional relationship between the second core and the first core in the current sensor. FIG. [Figure 19] 10 is a diagram showing another example of the positional relationship between the second core and the first core in the current sensor. FIG. [Figure 20] 10 is a diagram showing another example of the positional relationship between the second core and the first core in the current sensor. FIG. [Figure 21] 10 is a diagram showing another example of the positional relationship between the second core and the first core in the current sensor. FIG. [Figure 22] 10 is a diagram showing another example of the positional relationship between the second core and the first core in the current sensor. FIG. [Figure 23A] 1 is a perspective view showing the appearance of a through-type current sensor in which a first core is formed in an annular shape. [Figure 23B] 1 is a front view showing the appearance of a through-type current sensor in which a first core is formed in an annular shape. [Figure 24] 4A to 4C are diagrams illustrating an example of a first core formed of a plurality of magnetic members. [Diagram 25] FIG. 1 is a diagram showing an example of a circuit of a magnetic balance type current sensor using a fluxgate pair, which is a set of two fluxgates. [Figure 26] FIG. 1 is a diagram showing the configuration of a magnetic balance type current sensor using a fluxgate pair, which is a set of two fluxgates. [Figure 27] FIG. 2 is a diagram illustrating a schematic diagram of magnetic flux formed around a fluxgate pair, which is a set of two fluxgates. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] 1. Overview of the embodiment First, a typical embodiment of the invention disclosed in this application will be outlined. In the following description, as an example, reference numerals in the drawings corresponding to components of the invention are given in parentheses.

[0011] [1] A current sensor (3, 3A to 3H, 3J, 3K) according to a representative embodiment of the present invention includes a fluxgate (32, 32A, 32B, 32C, 32K_1, 32K_2) that detects magnetic flux, an annular first core (31, 31_1, 31_2) made of a magnetic material and having an accommodation space (314, 314K_1, 314K_2) that accommodates the fluxgate, and a signal generating circuit (50, 50A, 50K) that generates a signal based on the magnetic flux detected by the fluxgate, and detects a current flowing through a measurement target (5) when the measurement target is inserted into the first core. In the current sensor, the fluxgate has a second core (321, 321A, 321B, 321C, 321K) made of a magnetic material and extending into the accommodating space, and a coil (323, 323K_1, 323K_2) wound around the second core along the direction in which the second core extends, and one end of the second core in the extension direction is in contact with a part of the first core and the other end of the second core in the extension direction is in contact with another part of the first core.

[0012] [2] In the current sensor (3, 3A to 3H, 3J, 3K) described in [1] above, the second core may extend in a circumferential direction of the first core.

[0013] [3] In the current sensor (3, 3A to 3H, 3J, 3K) described in [1] or [2] above, the first core may be provided continuously in a circumferential direction of the first core on the outer circumferential side of the first core around the accommodating space.

[0014] [4] In the current sensor (3, 3A to 3H, 3J, 3K) described in [1] to [3] above, the first core may be provided continuously in a circumferential direction of the first core on the inner side of the first core around the accommodating space.

[0015] [5] In the current sensor (3, 3A, 3B, 3C, 3E to 3H, 3J, 3K) described in any one of [1] to [4] above, when one surface of the first core in the insertion direction of the object to be measured (P, Z axis directions) in the first core is an upper surface (310_1) and the other surface of the first core in the insertion direction of the object to be measured 5 is a lower surface (310_8), the first core may be continuously provided in the circumferential direction of the first core on at least one of the upper surface and the lower surface around the accommodating space.

[0016] [6] In the current sensor (3, 3A, 3B, 3C, 3E to 3H, 3J, 3K) described in any one of [3] to [5] above, the portion that is continuously provided in the circumferential direction of the first core may be formed as a single unit.

[0017] [7] In the current sensor (3, 3A to 3H, 3J, 3K) described in any one of [1] to [6] above, one end (321Aa) of the second core (321A) in the extension direction and the other end (321Ab) of the second core (321A) in the extension direction may be covered by the first core.

[0018] [8] In the current sensor (3, 3A to 3H, 3J, 3K) described in any one of [1] to [7] above, the first core (31) is formed of a plurality of plate-shaped members (310_1 to 310_8) made of a magnetic material stacked in the insertion direction of the object to be measured 5 in the first core, and one end (321Aa) in the extension direction of the second core and the other end (321Ab) in the extension direction of the second core may be sandwiched between two of the plate-shaped members (310_4, 310_5) in the insertion direction.

[0019] [9] In the current sensor (3, 3A to 3H, 3J, 3K) according to any one of the above [1] to [8], a plurality of the flux gates may be provided.

[0020]

[10] The current sensor (3K) described in [9] above may have at least one fluxgate pair (32KP) consisting of two of the fluxgates, and the first fluxgate (32K_1) and the second fluxgate (32K_2) constituting the fluxgate pair may share the second core (321K), and the coil of the first fluxgate and the coil of the second fluxgate may each be wound around the second core shared by the first fluxgate and the second fluxgate.

[0021]

[11] In the current sensor (3K) described in

[10] above, the accommodating space may include a first accommodating space (314K_1) that accommodates the first fluxgate and a second accommodating space (314K_2) that accommodates the second fluxgate, the first accommodating space and the second accommodating space are formed side by side in the circumferential direction of the first core, and the first core may be continuously provided between the first accommodating space and the second accommodating space.

[0022]

[12] In the current sensor (3, 3A to 3H, 3J, 3K) according to any one of [1] to

[11] above, the first core (31, 31_1, 31_2, 31K) and the second core (321, 321A, 321B, 321C, 321K) may be integrally formed. In this case, the first core and the second core may be made of the same magnetic material.

[0023]

[13] In the current sensor (3, 3A to 3H, 3J, 3K) according to any one of [1] to

[12] above, the current may be detected by a zero flux method.

[0024]

[14] A representative measuring device (1) according to this embodiment is characterized in that it comprises a current sensor (3, 3A-3H, 3J, 3K) described in any one of [1] to

[13] above, and a measuring device main body (2) that measures the current flowing through the object to be measured based on the signal generated by the current sensor when the first core is in a ring-shaped state surrounding the object to be measured.

[0025]

[15] A representative measurement method according to this embodiment is a measurement method for measuring a current flowing through a measurement target using a current sensor (3, 3A to 3H, 3J, 3K). The current sensor includes a flux gate (32, 32A, 32B, 32C, 32K_1, 32K_2) for detecting a magnetic flux, a ring-shaped first core (31, 31_1, 31_2) made of a magnetic material and having an accommodation space (314, 314K_1, 314K_2) for accommodating the flux gate, and a signal generating circuit (50, 50A, 50K) for generating a signal based on the magnetic flux detected by the flux gate. The switch gate has a second core (321, 321A, 321B, 321C, 321K) made of a magnetic material and extending into the housing space, and a coil (323, 323K_1, 323K_2) wound around the second core along the direction in which the second core extends, with one end of the second core in the direction in which the second core extends contacting a part of the first core and the other end of the second core in the direction in which the second core extends contacting another part of the first core. The measurement method includes a first step of inserting the measurement object into the first core, and a second step of measuring a current flowing through the measurement object based on the signal generated by the signal generating circuit.

[0026] 2. Specific examples of embodiments Hereinafter, specific examples of the embodiments of the present invention will be described with reference to the drawings. In the following description, components common to each embodiment will be given the same reference numerals, and repeated description will be omitted. It should be noted that the drawings are schematic, and the dimensional relationships and ratios of each element may differ from the actual situation. The drawings may also include parts with different dimensional relationships and ratios.

[0027] First Embodiment 1, the measurement device 1 according to the first embodiment is, for example, a current measurement device capable of measuring a current flowing through a measurement object 5 (for example, a conductor). The measurement device 1 is configured to be able to measure the current flowing through the measurement object 5 without being in electrical contact with the measurement object 5.

[0028] Specifically, the measurement device 1 includes a current sensor 3 and a measurement device main body 2. For example, in a state where the measurement object 5 is surrounded by the current sensor 3 in a ring shape, the current sensor 3 detects a current flowing through the measurement object 5, and the measurement device main body 2 measures (calculates) a current value of the current flowing through the measurement object 5 based on the detection result by the current sensor 3.

[0029] The current sensor 3 is a device that detects a current flowing through the object to be measured 5 and outputs a signal according to the detection result. The current sensor 3 is a sensor that detects the current flowing through the object to be measured 5 in a non-contact manner while surrounding the object to be measured 5 in a ring shape, and examples of the current sensor 3 include a so-called through-type current sensor and a so-called clamp-type current sensor. In this embodiment, the case where the current sensor 3 is a clamp-type current sensor will be mainly described as an example.

[0030] As described below, the current sensor 3 has as its main components a first core 31 made of a magnetic material and a fluxgate 32 arranged inside the first core 31 and having a second core, and detects current by using the fluxgate 32 to detect magnetic flux passing through the second core of the fluxgate 32 via the first core 31.

[0031] In the following description, the first core 31 may be referred to as the "main core 31."

[0032] The measurement device main body 2 is a device that measures (calculates) the current value of the current flowing through the measurement object 5 based on the detection result (output signal Vout) by the current sensor 3. The measurement device main body 2 measures the current flowing through the measurement object 5 based on the output signal Vout generated by the current sensor 3 in a state in which the main core 31 surrounds the measurement object 5 to form a ring.

[0033] As shown in FIG. 1, the measurement device main body 2 includes, for example, a measurement section 11, an operation section 12, a display section 13, a control section 14, and a storage section 15.

[0034] The measurement unit 11 is a functional unit that calculates the current value of the current flowing through the measurement target 5 based on the output signal Vout as a detection result of the current output from the current sensor 3, in response to control from the control unit 14. The measurement unit 11 is realized by, for example, a program processing device such as a microcontroller.

[0035] Operation unit 12 is a user interface for inputting instructions and the like from the user to measurement device 1. Operation unit 12 is realized by, for example, an operation switch, a keyboard, a touch panel, and the like. Operation unit 12 outputs an operation signal corresponding to an operation on operation unit 12 by the user to control unit 14. By operating operation unit 12, the user can, for example, set information related to measurement conditions in measurement device 1 and instruct measurement device 1 to start and stop measurement.

[0036] In addition, settings and instructions of measurement conditions, etc. for the measuring device 1 are not limited to operations on the above-mentioned operation unit 12, and may be input, for example, from an information processing device such as a personal computer, a server, or a mobile terminal connected to the measuring device 1 via wired communication or wireless communication.

[0037] The display unit 13 is a device that displays various information. The display unit 13 is realized by a device that outputs information that can be viewed by a user, such as a liquid crystal display or an organic EL display. Under the control of the control unit 14, the display unit 13 displays, for example, menu information for inputting measurement conditions and information on the measurement results of the current value of the current flowing through the measurement target 5.

[0038] The storage unit 15 is a functional unit for storing, for example, a program for enabling the measuring device 1 to function as a current measuring device, various parameters, and measurement results of the measurement target 5. The storage unit 15 is realized by, for example, a non-volatile storage device such as an SSD or HDD.

[0039] The control unit 14 is a functional unit that comprehensively controls the measurement device 1. The control unit 14 is realized by a program processing device such as a microcontroller, similar to the measurement unit 11. For example, the control unit 14 controls the measurement unit 11, the display unit 13, and the storage unit 15 in response to an operation signal from the operation unit 12, thereby measuring the current flowing through the measurement target 5, storing and displaying the measurement results, and the like.

[0040] Here, a current detection method using current sensor 3 will be described with reference to FIGS. 2A and 2B.

[0041] FIG. 2A shows a magnetic proportional type (open loop type) current detection method, and FIG. 2B shows a magnetic balance type (closed loop type, zero flux type) current detection method.

[0042] 2A, in the magnetic proportional current detection method, a measurement object 5 (e.g., a conductor) is surrounded in a ring shape by a main core 31. In this state, a flux gate 32 disposed inside the main core 31 detects a magnetic flux 60 generated in the main core 31 by a current I1 flowing through the measurement object 5, and a signal generating circuit 50 generates an output signal Vout based on the magnetic flux 60 detected by the flux gate 32.

[0043] The signal generating circuit 50 includes, for example, a driving circuit 51, a signal processing circuit 52, and an amplifier circuit (AMP) 54. The fluxgate 32 is operable by power supply from the driving circuit 51. The fluxgate 32 generates a voltage according to the detected magnetic flux 60. The signal processing circuit 52 generates a voltage by synchronously detecting or pulse-width modulating the voltage generated by the fluxgate 32. The amplifier circuit 54 amplifies the voltage generated by the signal processing circuit 52 and outputs it as an output signal Vout.

[0044] As shown in FIG. 2B, in the magnetic balance current detection method, similar to the magnetic proportional current detection method, with the main core 31 surrounding the object to be measured 5 in a ring shape, the flux gate 32 detects the magnetic flux 60 generated in the main core 31 by the current I1 flowing through the object to be measured 5, and the signal generating circuit 50A generates an output signal Vout based on the magnetic flux 60 detected by the flux gate 32.

[0045] The signal generating circuit 50A includes a driving circuit 51, a signal processing circuit 53, an amplifier circuit (AMP) 57, a coil 55 wound around the main core 31, and a voltage generating circuit (e.g., a shunt resistor) 56. The fluxgate 32 is operable by power supply from the driving circuit 51. The fluxgate 32 detects a magnetic flux 60 generated by a current I1 flowing through the measurement target 5, and generates a voltage according to the detected magnetic flux 60. The signal processing circuit 53 generates a voltage by synchronously detecting or pulse-width modulating the voltage generated by the fluxgate 32, converts the voltage into a current, and outputs it.

[0046] The amplifier circuit 57 supplies a current I2 to the coil 55 based on the current output from the signal processing circuit 53 so as to generate a magnetic flux 61 that cancels out the magnetic flux 60 (magnetic flux due to the current I1) detected by the flux gate 32 (zero flux operation). The voltage generation circuit (e.g., a shunt resistor) 56 converts the current I2 flowing through the coil 55 into a voltage and outputs it as an output signal Vout.

[0047] Next, the configuration of the current sensor 3 will be described. In the present embodiment, as an example, the current sensor 3 will be described as having a configuration capable of detecting current by a magnetic balance system.

[0048] As shown in FIG. 3, the current sensor 3 includes, for example, a grip portion 21, a sensor portion 22, and a connection cable 23.

[0049] The sensor unit 22 includes the main core 31 and the fluxgate 32 as the main components of the current sensor 3 described above, and is configured to be capable of clamping the object to be measured 5. Here, clamping refers to surrounding the object to be measured 5 (e.g., a conductor) in a ring shape.

[0050] The sensor unit 22 is configured to be able to open and close (deform) in a ring shape. For example, as shown in Fig. 3, the sensor unit 22 is realized by combining a first sensor unit 22_1 and a second sensor unit 22_2 configured in a semi-ring shape when viewed from the front.

[0051] One circumferential end of the first sensor portion 22_1 and one circumferential end of the second sensor portion 22_2 are configured to be able to come into contact with each other. As shown in Fig. 3, one circumferential end of the first sensor portion 22_1 and one circumferential end of the second sensor portion 22_2 come into contact with each other, so that the sensor portion 22 (main core 31) becomes a ring shape.

[0052] The detailed configurations of the first sensor portion 22_1 and the second sensor portion 22_2 will be described later.

[0053] The gripping portion 21 is a portion that is gripped by a user when the sensor portion 22 clamps the measurement target 5. As shown in FIG. 3, the sensor portion 22 is disposed on one end side (the left end side in FIG. 3) of the gripping portion 21. A circuit board (not shown) on which the above-mentioned signal generating circuit 50A (50) is configured is housed inside the gripping portion 21. In addition, a connection cable 23 connected to the signal generating circuit 50A (50) is drawn out from the other end side (the right end side in FIG. 4) of the gripping portion 21. The connection cable 23 inputs the detection result of the current sensor 3 to the measuring device 1. Specifically, the connection cable 23 is configured to include a conductor for inputting the output signal Vout output from the signal generating circuit 50A (50) to the measuring device 1.

[0054] The gripping portion 21 is provided with an opening / closing operation portion 210 for opening and closing the sensor portion 22. For example, when the opening / closing operation portion 210 is not operated by a user, the first sensor portion 22_1 and the second sensor portion 22_2 are in a state in which one end in the circumferential direction of the first sensor portion 22_1 and one end in the circumferential direction of the second sensor portion 22_2 are in contact with each other by a biasing means such as a spring. On the other hand, when the user presses down the opening / closing operation portion 210, at least one of the one end of the first sensor portion 22_1 and the one end of the second sensor portion 22_2 moves in a direction away from the other, and the one end of the first sensor portion 22_1 and the one end of the second sensor portion 22_2 are in a non-contact state.

[0055] As shown in FIG. 3, for example, the first sensor portion 22_1 and the second sensor portion 22_2 are covered with resin cases 20_1 and 20_2, respectively.

[0056] FIG. 4 shows the sensor unit 22 with the cases 20_1 and 20_2 removed. 4, the first sensor unit 22_1 has a magnetic detection unit 25_1 that detects magnetic flux and a coil 26 wound around the magnetic detection unit 25_1. Similarly, the second sensor unit 22_2 has a magnetic detection unit 25_2 that detects magnetic flux and a coil 26 wound around the magnetic detection unit 25_2. The coil 26 constitutes the coil 55 in the signal generating circuit 50A described above.

[0057] FIG. 5 shows the external appearance of the magnetic detection portion 25_1 and the magnetic detection portion 25_2. Since the magnetic detection unit 25_1 and the magnetic detection unit 25_2 shown in Fig. 4 have substantially the same configuration, only the magnetic detection unit 25_1 is representatively shown in Fig. 5, and the magnetic detection unit 25_2 is not shown. Also, in Fig. 5, the coil 26 is not shown.

[0058] 4 and 5, the magnetic detection units 25_1 and 25_2 each have, for example, a cover 38_1 or 38_2 around which the coil 26 is wound, and a main core 31_1 or 31_2 housed in the cover 38_1 or 38_2. The magnetic detection units 25_1 and 25_2 each have a fluxgate 32 disposed inside the main core 31_1 or 31_2. In the first embodiment, the main core 31 is composed of the main cores 31_1 and 31_2.

[0059] The covers 38_1, 38_2 are configured to be able to house the main cores 31_1, 31_2 and the fluxgate 32, and are provided with a plurality of flanges for preventing the coil 26 from becoming uncoiled so as to function as bobbins for winding the coil 26 around the main cores 31_1, 31_2.

[0060] Although FIG. 4 illustrates an example in which the coil 26 is wound around the main cores 31_1, 31_2 via the covers 38_1, 38_2, for example, the coil 26 may be wound directly around the main cores 31_1, 31_2 without providing the covers 38_1, 38_2.

[0061] Fig. 6 shows a front view of the main cores 31_1 and 31_2 in a state where the sensor unit 22 is annular. Fig. 6 shows a case where the main cores 31_1 and 31_2 are arranged in a three-dimensional space formed by three reference axes of the X-axis, the Y-axis, and the Z-axis such that the circumferential direction of the main core 31_1 is parallel to the XY plane.

[0062] The main cores 31_1 and 31_2 are formed of a magnetic body (magnetic member). Examples of the magnetic body forming the main cores 31_1 and 31_2 include a nickel-iron alloy containing 35 to 80% of ferromagnetic nickel Ni (so-called permalloy, PC permalloy), an amorphous magnetic body, and the like.

[0063] The main cores 31_1 and 31_2 are configured in a semi-annular shape in a front view so as to match the shape of the sensor section 22. For example, when the measurement target 5 is clamped by the sensor section 22, that is, when one circumferential end of the first sensor section 22_1 and one circumferential end of the second sensor section 22_2 come into contact with each other and the first sensor section 22_1 and the second sensor section 22_2 become annular, one end of the main core 31_1 in the circumferential direction Q comes into contact with one end of the main core 31_2 in the circumferential direction Q, and the other end of the main core 31_1 in the circumferential direction Q comes into contact with the other end of the main core 31_2 in the circumferential direction Q. This forms one annular main core 31 as shown in FIG. 6.

[0064] More specifically, the main core 31, which is composed of the main core 31_1 and the main core 31_2, is configured to form a ring shape surrounding the object to be measured 5 when measuring the current flowing through the object to be measured 5 (when the object to be measured 5 is clamped).

[0065] For example, when the opening / closing operation part 210 of the grip part 21 is not operated, the one end of the main core 31_1 and the one end of the main core 31_2 are in contact with each other. On the other hand, while the opening / closing operation part 210 is pressed down, at least one of the first sensor part 22_1 and the second sensor part 22_2 moves in a direction away from the other, so that the one end of the main core 31_1 and the one end of the main core 31_2 are in a non-contact state. Thus, in the clamp-type current sensor, the main core 31 is configured to be deformable (openable and closable) into an annular shape.

[0066] Here, the annular shape may be, for example, a circular shape (for example, a perfect circle or an ellipse) when viewed from the front, or a rectangular shape or a polygonal shape when viewed from the front. In the first embodiment, as an example, as shown in Fig. 6, the main core 31_1 and the main core 31_2 are in contact with each other in the circumferential direction to form one main core 31 having an elliptical shape when viewed from the front. Note that the main core 31_1 and the main core 31_2 may be integrally formed to be annular.

[0067] The main core 31 has an accommodation space 314 that accommodates the fluxgate 32. For example, as shown in Fig. 6, in the sensor unit 22, the main core 31 accommodates a plurality of fluxgates 32, and the fluxgates 32 are arranged apart from each other. Note that the main core 31 may have only one fluxgate 32.

[0068] In the first embodiment, as an example, one fluxgate 32 is accommodated in the accommodation space 314 of the main core 31_1, and one fluxgate 32 is accommodated in the accommodation space 314 of the main core 31_2. In addition, as shown in Fig. 6, the two fluxgates 32 are arranged at positions that are point-symmetrical with respect to the center or center of gravity P of the main core 31 when the annular main core 31 is viewed from the insertion direction of the measurement target 5 in the main core 31.

[0069] Next, the structure of the main cores 31_1 and 31_2 will be described in detail. In the first embodiment, it is assumed that the main cores 31_1 and 31_2 have the same structure, and the structure of the main core 31_1 will be representatively described in detail.

[0070] The configuration of the main core 31_1 is shown in Fig. 7 to Fig. 10. Fig. 7 to Fig. 10 show a case where the main core 31_1 is arranged in a three-dimensional space formed by three reference axes, the X-axis, the Y-axis, and the Z-axis, such that the circumferential direction of the main core 31_1 is parallel to the XY plane. Fig. 9 shows the cross-sectional shape of the main core 31_1 in the AA cross section in Fig. 7.

[0071] 8 to 10, the fluxgate 32 is disposed in the housing space 314 inside the main core 31_1. Note that the entire fluxgate 32 does not necessarily need to be housed in the housing space 314, and a part of the fluxgate 32 may protrude from the housing space 314. In this case, it is preferable that the part of the fluxgate 32 protruding from the housing space 314 is covered by the main core 31.

[0072] The fluxgate 32 is an example of a fluxgate that detects magnetic flux. The fluxgate 32 includes, for example, a core 321 (an example of a second core) made of a magnetic material, and a coil (winding) 323 wound around the core 321. The fluxgate 32 outputs a current from the coil 323 according to the magnetic flux passing through the core 321.

[0073] More specifically, as shown in Fig. 8 to Fig. 10, the fluxgate 32 further includes a bobbin 322 that houses the core 321. The bobbin 322 is configured in a hollow cylindrical shape. The core 321 is inserted into the hollow cylinder of the bobbin 322. A coil 323 is wound around the outer circumferential surface of the bobbin 322. The bobbin 322 is used to separate and insulate the core 321 and the coil 323, and to make it easier to wind the coil 323. By using other means (such as insulating tape) instead of the bobbin 322, the fluxgate 32 can be configured without the bobbin 322.

[0074] The core 321 is made of a magnetic material (magnetic member). For example, the magnetic material constituting the core 321 is an amorphous magnetic material or permalloy (for example, PC permalloy). It is desirable that the magnetic material constituting the core 321 has high magnetic permeability.

[0075] The core 321 is, for example, in the shape of a rod or a strip. In the first embodiment, as an example, the core 321 is formed in the shape of a thin plate extending in one direction.

[0076] The fluxgate 32 is covered by the main core 31, which is a magnetic material, when viewed from the positive X-direction side, the negative X-direction side, the positive Z-direction side, or the negative Z-direction side. For example, as shown in Figures 8 and 9, the fluxgate 32 is disposed in an accommodation space 314 formed inside the main core 31, and is surrounded by an inner wall 315 of the main core 31 that defines the accommodation space 314.

[0077] 8, on the outer circumferential side of the main core 31 in the accommodation space 314 (the positive side in the X-axis direction of the accommodation space 314), the main core 31 is integrally formed in the circumferential direction Q. Specifically, on the outer circumferential side of the accommodation space 314 of the main core 31, a connecting portion 310a that connects the main core 31 in the circumferential direction Q is formed. In other words, on the outer circumferential side of the accommodation space 314, no air gap is formed in the main core 31. According to this, the main core 31 formed integrally around the periphery of the accommodation space 314 serves as a shield for the fluxgate 32, making it less susceptible to the effects of an external magnetic field from the outer periphery.

[0078] 8, the main core 31 is integrally formed in the circumferential direction Q on the inner circumferential side of the main core 31 in the accommodation space 314 (the negative side in the X-axis direction of the accommodation space 314). Specifically, a connecting portion 310b that connects the main core 31 in the circumferential direction Q is formed on the inner circumferential side of the accommodation space 314 of the main core 31. In other words, no air gap is formed in the main core 31 on the inner circumferential side of the accommodation space 314. According to this, the main core 31 formed integrally around the periphery of the accommodation space 314 serves as a shield for the fluxgate 32, making it less susceptible to the effects of an external magnetic field from the inner periphery.

[0079] Furthermore, when the annular main core 31 is viewed from the insertion direction (Z-axis direction) of the measurement target 5 in the main core 31, the core 321 (accommodating space 314) of the fluxgate 32 is covered by the main core 31. In other words, when one surface of the main core 31 in the insertion direction (Z-axis direction) of the measurement target 5 in the main core 31 is an upper surface (a plate-like member 310_1 described later) and the other surface of the main core 31 in the insertion direction of the measurement target 5 is a lower surface (a plate-like member 310_8 described later), the main core 31 is integrally formed in the circumferential direction Q on at least one of the upper surface and the lower surface.

[0080] For example, as shown in Figures 6 and 8, the core 321 of the fluxgate 32 is less susceptible to the effects of external magnetic fields from the insertion direction (Z-axis direction) of the object to be measured 5 in the main core 31, since the main core 31 which is integrally formed around the accommodating space 314 acts as a shield for the fluxgate 32.

[0081] 7 to 10, the main cores 31_1 and 31_2 are formed with holes 312_1 and 312_8 penetrating from the inner wall 315 of the main cores 31_1 and 31_2 to the surface of the main cores 31_1 and 31_2, for example. The holes 312_1 and 312_8 are holes for drawing out wiring that connects the coil 323 of the fluxgate 32 arranged inside the main core 31 to a signal generating circuit 50A provided outside the main core 31. For example, both ends of the conductor constituting the coil 323 are drawn out from the holes 312_1 and 312_8, respectively, and connected to the signal processing circuit 53 (52) of the signal generating circuit 50A (50).

[0082] Here, the state in which "the fluxgate 32 is covered by the main core 31" includes not only a state in which the entire fluxgate 32 is completely covered by the main core 31, but also a state in which the above-mentioned holes 312_1, 312_8 and gaps (hereinafter referred to as holes, etc.) are formed in the main core 31 and a part of the fluxgate 32 is exposed from the holes, etc. of the main core 31.

[0083] As shown in Fig. 10, the main core 31_1 (31_2) may be configured by stacking a plurality of plate-like members 310_1 to 310_n (n is an integer of 2 or more) made of a magnetic material and having a semi-annular shape when viewed from the front. Fig. 10 shows, as an example, a case in which the main core 31_1 is configured by stacking eight (n=8) plate-like members 310_1 to 310_8 in the Z-axis direction.

[0084] 10, when the positive direction of the Z axis is defined as up and the negative direction of the Z axis is defined as down, holes (through holes) 313_2-313_7 that define an accommodation space 314 for accommodating the fluxgate 32 are formed in the intermediate plate members 310_2-310_7 provided between the top plate member 310_1 and the bottom plate member 310_8, respectively. The holes 313_2-313_7 have an opening area large enough to accommodate the fluxgate 32. The top plate member 310_1 and the bottom plate member 310_8 are formed with holes 312_1 and 312_8, respectively, for drawing out the above-mentioned wiring.

[0085] 10, by stacking the plate-like members 310_1 to 310_8 in the Z-axis direction, the accommodation space 314 formed by the holes (through holes) 313_2 to 313_7 of the plate-like members 310_2 to 310_7 in the intermediate layer is blocked from the Z direction by the plate-like member 310_1 in the uppermost layer and the plate-like member 310_8 in the lowermost layer. As a result, the periphery of the core 321 of the fluxgate 32 is covered by the plate-like members 310_1 to 310_8, making it possible to easily realize a structure that is less susceptible to the effects of an external magnetic field.

[0086] The number of layers of the plate-like members 310 in the intermediate layer and the areas of the holes 313_2 to 313_7 are not limited to the examples shown in FIGS. 8 to 10, and may be changed according to the size of the fluxgate 32 to be accommodated.

[0087] Fig. 11 is a diagram illustrating a schematic positional relationship between the fluxgate 32 and the main core 31 in the current sensor 3 according to the embodiment 1. Fig. 11 illustrates a cross-sectional structure of the fluxgate 32 accommodated in the main core 31 along the XY plane.

[0088] 11, the core 321 of the fluxgate 32 extends into the accommodation space 314. Specifically, the core 321 is arranged to extend along the circumferential direction Q of the annular main core 31. When the core 321 is arranged to extend along the circumferential direction Q of the annular main core 31, the length of the core 321 in the extension direction is no longer limited by the radial width of the main core 31, and therefore the fluxgate 32 can be made larger, thereby improving the current detection accuracy. The coil 323 is wound around the core 321 along the direction in which the core 321 extends.

[0089] One end 321a of the core 321 in the extending direction contacts a part of the main core 31 in the circumferential direction Q, and the other end 321b of the core 321 in the extending direction contacts another part of the main core 31 in the circumferential direction Q. For example, the end 321a of the core 321 contacts one surface of the inner wall 315 of the main core 31 that defines the accommodation space 314 in the circumferential direction Q, and the end 321b of the core 321 contacts the other surface of the inner wall 315 in the circumferential direction. Fig. 11 shows, as an example, a case where both end portions 321a, 321b of the core 321 contact the inner wall 315 of the plate-like member 310_5.

[0090] According to the current sensor 3 having the above-described structure, it is possible to suppress fluctuations in the detection accuracy of the magnetic flux due to the position of the measurement object 5 (conductor) relative to the main core 31, and it is possible to suppress deterioration in the detection accuracy of the current.

[0091] That is, in the conventional current sensor, magnetic flux leaks from the air gap of the main core, so that a flow of magnetic flux occurs outside the main core 31 and the core 321 of the fluxgate 32, and the detection accuracy fluctuates due to the influence of the flow. In contrast, in the current sensor 3 having the above-mentioned configuration, one end 321a of the core 321 of the fluxgate 32 contacts a part of the main core 31, and the other end 321b of the core 321 of the fluxgate 32 contacts another part of the main core 31. In other words, the core 321 of the fluxgate 32 connects the air gap of the main core. Since no air gap is formed, the fluctuation in the detection accuracy of the magnetic flux due to the position of the measurement target 5 (conductor) relative to the main core 31 is suppressed, and it is possible to suppress a decrease in the detection accuracy of the current.

[0092] Moreover, by winding the coil 323 around the core 321 (bobbin 322) to assemble the fluxgate 32, and then disposing the fluxgate 32 in the accommodation space 314 of the main core 31, one end of the core 321 in the extension direction can be brought into contact with the main core 31 facing that one end, and the other end of the core 321 in the extension direction can be brought into contact with the main core 31 facing the other end. In this way, the current sensor 3 can be easily assembled.

[0093] Furthermore, as described above, by using a structure in which the fluxgate 32 arranged in the accommodation space 314 is covered by the main core 31, there is no need to provide a separate component to function as a magnetic shield, making it possible to realize a small-sized current sensor 3 that is less susceptible to the effects of external magnetic fields while keeping costs down.

[0094] Second Embodiment 12 to 15 show the configuration of a current sensor 3A according to the second embodiment. 12 to 15 show a case where the main core 31_1 is arranged so that the circumferential direction of the main core 31_1 is parallel to the XY plane in a three-dimensional space formed by three reference axes of the X-axis, the Y-axis, and the Z-axis. Specifically, FIG. 12 shows a front view of the annular main cores 31_1 and 31_2. FIG. 13 shows an exploded perspective view (part) of the main core 31_1 (31_2) according to the second embodiment. FIG. 14 shows an exploded perspective view (whole) of the main core 31_1 (31_2) according to the second embodiment. FIG. 15 shows a cross-sectional structure of the fluxgate 32A along the XY plane.

[0095] The current sensor 3A of embodiment 2 differs from the current sensor 3 of embodiment 1 in that both ends 321Aa, 321Ab of the core (second core) 321A constituting the fluxgate 32A are covered by the main cores 31_1, 31_2 (first cores), but is otherwise similar to the current sensor 3 of embodiment 1.

[0096] The fluxgate 32A has a core (an example of a second core) 321A made of a magnetic material, similar to the fluxgate 32 according to the first embodiment. The core 321A is configured in a thin plate shape, similar to the core 321 according to the first embodiment. The core 321A is housed in a hollow cylinder of the bobbin 322. For example, as shown in FIGS. 12 to 15, one end 321Aa and the other end 321Ab in the extension direction of the core 321A protrude from both ends of the bobbin 322.

[0097] As shown in Figs. 12 to 15, the core 321A of the fluxgate 32A extends along the circumferential direction Q of the main core 31 (31_1, 31_2). Specifically, a part of the core 321A extends into the accommodation space 314, and one end 321Aa and the other end 321Ab in the extending direction of the core 321A protrude from the accommodation space 314 and are covered by the main core 31 (31_1, 31_2). For example, when the length in the circumferential direction Q of the holes 313_2 to 313_7 formed in the plate-like members 310_2 to 310_7 (310_5) constituting the main core 31 (the length in the circumferential direction Q of the accommodation space 314) is La, and the length in the extending direction (circumferential direction Q) of the core 321A of the fluxgate 32A is Lpg, La <Lpgである。

[0098] As shown in Fig. 12 to Fig. 15, one end 321Aa of the core 321A of the fluxgate 32A in the extending direction and the other end 321Ab of the core 321A in the extending direction are sandwiched between two plate-like members 310 in the insertion direction of the measurement target 5 in the main core 31. For example, both ends 321Aa, 321Ab of the core 321A protruding from the bobbin 322 of the fluxgate 32A are sandwiched between two plate-like members 310 (e.g., 310_4 and plate-like member 310_5) of the intermediate layer constituting the main core 31_1. As a result, both ends 321Aa, 321Ab of the core 321A are covered and fixed by the main core 31. In particular, since the core 321A is formed in a thin plate shape, it becomes easier to sandwich the core 321A between the two plate-like members 310 of the intermediate layer constituting the main core 31_1, and it becomes easier to fix the core 321A. Furthermore, the core of the fluxgate must in principle be brought into a magnetically saturated state, but by forming core 321A into a thin plate shape, it is easy to bring it into a magnetically saturated state.

[0099] As described above, according to the current sensor 3A of the second embodiment, the ends 321Aa, 321Ab of the core 321A are covered by the main core 31, so that the core 321 of the fluxgate 32A can be brought into contact with the main core 31 more reliably. This increases the contact area between the main core 31 and the core 321, so that leakage of magnetic flux can be more reliably prevented. In addition, by sandwiching the ends 321Aa, 321Ab of the core 321A between the two plate-like members 310 constituting the main core 31, the fluxgate 32 can be easily fixed in the main core 31 while being in contact with the main core 31. This makes it easy to assemble the main core 31 and the fluxgate 32.

[0100] <<Extension of the embodiment>> The invention made by the inventor of the present application has been specifically described above based on an embodiment, but it goes without saying that the present invention is not limited thereto and can be modified in various ways without departing from the spirit of the invention.

[0101] For example, in the above-mentioned first and second embodiments, the main core 31 is illustrated as having two fluxgates 32 (32A) as fluxgates, but the number of fluxgates 32 is not limited to this. Specifically, the main core 31 may have an even number of fluxgates 32 (32A).

[0102] 16, when six fluxgates 32 are provided in the main core 31, three accommodation spaces 314 are provided in each of the main cores 31_1 and 31_2, and a fluxgate 32 is disposed in each accommodation space 314. In this case, as shown in FIG. 16, one fluxgate 32 (32A) and another fluxgate 32 (32A) may be disposed at positions that are point-symmetrical with respect to the center or center of gravity P of the main core 31 when the annular main core 31 is viewed from the insertion direction of the measurement target 5 in the main core 31.

[0103] In this way, by arranging a plurality of fluxgates 32 (32A), calculating the average value of the detection results of each fluxgate 32 (32A), and using the calculated value as the current detection result, it is possible to realize a current sensor with higher accuracy. That is, by providing a plurality of fluxgates on the main core 31, it is possible to reduce the bias in detection due to the position of the measurement target 5 (conductor) relative to the main core 31, so it is possible to realize a current sensor with higher accuracy.

[0104] In addition, for example, in the first and second embodiments, the main core 31 and the cores 321, 321A of the fluxgate 32 are formed separately, but the present invention is not limited to this. For example, as in the current sensor 3B shown in Fig. 17, the main core 31 and the core 321B of the fluxgate 32B may be integrally formed. This makes it easier to manufacture the current sensor 3B incorporating the fluxgate 32B, as described below.

[0105] An example of a method for manufacturing the fluxgate 32B shown in FIG. 17 will be described. First, two holes 314a, 314b are formed in at least one plate-like member 310 (for example, plate-like member 310_5) constituting the main core 31 along the Q direction, spaced apart from each other in the radial direction of the plate-like member 310, and a portion of the plate-like member 310 between the two holes 314a, 314b is used as the core 321B (second core) of the fluxgate 32B. Next, two halves of the bobbin 322 cut in half along the center line or center of gravity of the hollow cylinder are arranged and fixed so as to sandwich the core 321, which is a portion of the plate-like member 310 between the two holes 314a, 314b. Next, the coil 323 is wound around the bobbin 322. Finally, the plate-like members 310_1 to 310_8 are stacked in the Z-axis direction. In this manner, by integrally forming the main core 31 and the core 321B of the fluxgate 32B, the current sensor 3B incorporating the fluxgate 32B can be easily manufactured. Alternatively, two holes 314a, 314b may be formed in a plurality of plate-like members 310 adjacent to each other to realize a thicker core 321B (second core).

[0106] In the above first and second embodiments, the cores 321, 321A of the fluxgates 32, 32A extend in the circumferential direction Q of the main core 31, but this is not limiting. That is, the cores 321, 321A of the fluxgates 32, 32A may extend in a direction different from the circumferential direction Q of the main core 31 (a direction intersecting the circumferential direction Q) and may be in contact with the main core 31.

[0107] 18, a core 321C of a fluxgate 32C is disposed to extend along the radial direction R of the annular main core 31. One end 321Ca of the core 321C in the extension direction is in contact with one end 315c of the inner wall 315 that defines the accommodation space 314 in the radial direction R. The other end 321Cb of the core 321C in the extension direction is in contact with the other end 315d of the inner wall 315 in the radial direction R. As with the current sensor 3A, the two end portions 321Ca, 321Cb of the core 321 may be sandwiched between two plate-shaped members 310 (e.g., 310_4 and plate-shaped member 310_5) of the intermediate layer constituting the main core 31, thereby realizing a structure in which the two end portions 321Ca, 321Cb of the core 321 are inserted into the main core 31.

[0108] According to this, as with the current sensors 3, 3A according to the above-mentioned embodiments 1 and 2, no air gap is formed between the main core 31 and the core 321C of the fluxgate 32C, so that leakage of magnetic flux can be prevented and deterioration of the current detection accuracy can be suppressed.

[0109] In the above embodiment, the core 321 (321A, 321B, 321C) of the fluxgate 32 (32A, 32B, 32C) is entirely covered by the main core 31, but the present invention is not limited to this. Specifically, the main core 31 does not have to be continuously provided in the circumferential direction Q around the housing space 314, or at least a part of the main core 31 may be continuously provided in the circumferential direction Q.

[0110] 19, the core 321A (321) of the fluxgate 32A (32) may not be covered by the main core 31 in the radial direction R (X-axis direction) of the main core 31. In other words, the main core 31 may not be provided continuously in the circumferential direction Q on the outer circumferential side and inner circumferential side of the main core 31 in the accommodation space 314. In this case, the fluxgate 32 may or may not be covered by the main core 31 in a direction perpendicular to the radial direction R and circumferential direction Q of the main core 31 (the insertion direction of the measurement target 5 in the main core 31 (Z-axis direction)).

[0111] Also, for example, the fluxgate 32 may be covered by the main core 31 only on the outer periphery side of the main core 31. Specifically, as in a current sensor 3E shown in Fig. 20, the main core 31 may be provided continuously in the circumferential direction Q on the outer periphery side of the accommodation space 314. In this case, the fluxgate 32 may or may not be covered by the main core 31 in the insertion direction of the measurement target 5 in the main core 31 (Z-axis direction).

[0112] Also, for example, the fluxgate 32 may be covered by the main core 31 only on the inner circumferential side of the main core 31. Specifically, as in a current sensor 3F shown in Fig. 21 , the main core 31 may be provided continuously in the circumferential direction Q on the inner circumferential side of the accommodation space 314. In this case, the fluxgate 32 may or may not be covered by the main core 31 in the insertion direction of the measurement target 5 in the main core 31 (Z-axis direction).

[0113] 22, the fluxgate 32 may be covered by the main core 31 on the outer and inner peripheral sides of the main core 31, but may not be covered by the main core 31 in a direction perpendicular to the radial direction R and circumferential direction Q of the main core 31 (the stacking direction (Z-axis direction) of the main core 31). In other words, an opening may be formed in a region overlapping with the accommodation space 314 when viewed from the Z-axis direction on at least one of the upper surface (plate-shaped member 310_1) and the lower surface (plate-shaped member 310_8) of the main core 31.

[0114] Also, for example, the magnetic permeability of the magnetic material constituting the core 321 (321A, 321C) of the fluxgate 32 (32A, 32C) may be greater than the magnetic permeability of the magnetic material constituting the main core 31_1 (31_2). This allows magnetic flux to easily pass through the core 321 (321A, 321C) of the fluxgate 32 (32A, 32C), thereby realizing a current sensor with higher sensitivity.

[0115] Also, for example, all of the plurality of plate-like members 310_1 to 310_n constituting the main core 31_1 (31_2) may be integrally formed, which reduces the number of parts and thus the number of manufacturing steps.

[0116] In the above embodiment, the signal generating circuit 50A (50) is provided in the current sensor 3, but the signal generating circuit 50, 50A may be built into the measurement device main body 2. In this case, the current sensor 3 (3A to 3G) may include at least the main core 31 and the flux gates 32 (32, 32A, 32B, 32C).

[0117] In addition, in the above embodiment, the current sensor 3 etc. has been described as a clamp-type current sensor in which the main core 31 can be deformed into a ring shape, but this is not limited to this, and the current sensor 3 etc. may also be a so-called through-type current sensor in which the main core 31 is formed into a ring shape, as shown in Figures 23A and 23B.

[0118] 23A and 23B differs from the clamp-type current sensor 3 etc. described above in that the sensor portion (main core) is not deformable, but in other respects is similar to the other current sensors 3 etc. For example, the current sensor 3H is used by inserting the measurement target 5 (conductor) along the insertion direction into the insertion hole 200 of the annular sensor portion 22 and then fixing the current sensor 3H to the installation location.

[0119] In the current sensor 3H, the sensor unit 22H has a main core 31H formed in an annular shape and a case 20H that covers the main core 31H. A fluxgate 32 is provided in the accommodation space 314 of the main core 31H, and both ends of a core (second core) 321 are in contact with the main core 31H. The main core 31 may be formed of one annular magnetic member, or may be formed by connecting a plurality of magnetic members (main cores 31_1, 31_2) as shown in FIG. 6. In addition, the same configuration as any one of the above-mentioned current sensors 3, 3A, 3B, 3C, 3D, 3E, 3F, and 3G can be adopted as the configuration of the fluxgate 32 in the current sensor 3H and the configuration of the main core 31 around the fluxgate 32.

[0120] According to the current sensor 3H, like the current sensors 3 according to the other embodiments, improvement in current detection accuracy can be expected.

[0121] In the above embodiment, the main core 31 is realized by connecting two magnetic members (main cores 31_1 and 31_2) as shown in Fig. 6, but the present invention is not limited to this. For example, the main core 31 may be realized by one magnetic member, or may be realized by connecting three or more magnetic members.

[0122] At least one of the main cores 31_1 and 31_2 may be made of a plurality of magnetic members. For example, as in the current sensor 3J shown in FIG. 24, the main core 31J_1 may be made of a first magnetic member 31Ja (plate-shaped member 310Ja) and a second magnetic member 31Jb (plate-shaped member 310Jb). In this case, it is sufficient that the first magnetic member 31Ja and the second magnetic member 31Jb are in contact with each other in the circumferential direction of the main core 31J_1. When the main core 31 is realized by a plurality of magnetic members, the magnetic members may be made of different types of magnetic materials.

[0123] In the above embodiment, a current sensor using one fluxgate is exemplified, but this is not limiting. For example, the technical features of the present disclosure can also be applied to a current sensor using a fluxgate pair, which is a set of two fluxgates. Hereinafter, a detailed description will be given with reference to the drawings.

[0124] FIG. 25 is a diagram showing an example of a circuit of a magnetic balance type current sensor 3K using a fluxgate pair, which is a set of two fluxgates.

[0125] As shown in FIG. 25, a current sensor 3K has a main core 31K, a fluxgate pair 32KP consisting of two fluxgates 32K_1 and 32K_2, and a signal generating circuit 50K.

[0126] The current sensor 3K is provided with at least one fluxgate pair 32KP. The fluxgate 32K_1 and the fluxgate 32K_2 configure a differential type fluxgate pair 32KP. That is, the fluxgates 32K_1 and 32K_2 are arranged on the main core 31K so that the magnetic fluxes excited from the fluxgates 32K_1 and 32K_2 are generated in directions opposite to each other.

[0127] The signal generating circuit 50K includes, for example, driving circuits 51_1 and 51_2, a signal processing circuit 53K, an amplifier circuit (AMP) 57, a coil 55 (feedback winding) wound around the main core 31, and a voltage generating circuit (for example, a shunt resistor) 56. The fluxgate 32K_1 is operable by power supply from the driving circuit 51_1. The fluxgate 32K_2 is operable by power supply from the driving circuit 51_2. The fluxgates 32K_1 and 32K_2 detect a magnetic flux 60 generated by a current I1 flowing through the measurement target 5, and generate a voltage according to the detected magnetic flux 60. The fluxgates 32K_1 and 32K_2 generate voltages of opposite phases to each other. The signal processing circuit 53K generates voltages by synchronously detecting or pulse-width modulating the voltages generated by the fluxgates 32K_1 and 32K_2, converting the voltages into currents, and outputting the currents.

[0128] The amplifier circuit 57 supplies a current I2 to the coil 55 based on the current output from the signal processing circuit 53 so as to generate a magnetic flux 61 that cancels the magnetic flux 60 (magnetic flux due to the current I1) detected by the flux gates 32K_1 and 32K_2 (zero flux operation). The voltage generation circuit (for example, a shunt resistor) 56 converts the current I2 flowing through the coil 55 into a voltage and outputs it as an output signal Vout.

[0129] FIG. 26 is a diagram showing the configuration of a magnetic balance type current sensor 3K using a fluxgate pair, each of which is made up of two fluxgates.

[0130] FIG. 26 shows a cross-sectional structure of fluxgates 32K_1 and 32K_2 in current sensor 3K along the XY plane.

[0131] The current sensor 3K differs from the current sensor 3 according to embodiment 1 in that the current sensor 3K has at least one flux gate pair 32KP consisting of two flux gates 32K_1 and 32K_2, but is otherwise similar to the current sensor 3A according to embodiment 2. In Fig. 26, as an example, a portion of the current sensor 3K on the main core 31K_1 side is representatively illustrated.

[0132] The fluxgate 32K_1 and the fluxgate 32K_2 that constitute the fluxgate pair 32KP share the core 321K. In other words, the fluxgate 32K_1 and the fluxgate 32K_2 have one common core 321K.

[0133] The core 321K is made of, for example, a rod-shaped or band-shaped (thin plate-shaped) magnetic body, similar to the core 321 according to embodiment 1. For example, as shown in Fig. 26, the core 321K extends along the circumferential direction Q of the main core 31K.

[0134] The coil 323K_1 of the fluxgate 32K_1 and the coil 323K_2 of the fluxgate 32K_2 are each wound around a core 321K shared by the fluxgates 32K_1 and 32K_2. Specifically, the coil 323K_1 and the coil 323K_2 are each wound around the core 321K via a bobbin.

[0135] More specifically, the fluxgates 32K_1 and 32K_2 have bobbins 322K_1 and 322K_2, respectively. As shown in FIG. 26, the bobbins 322K_1 and 322K_2 are arranged side by side so that the circumferential direction Q of the main core 31K and the center line or center of gravity of the hollow cylinders of the cylindrical bobbins 322K_1 and 322K_2 are parallel to each other. The core 321K is inserted into the bobbins 322K_1 and 322K_2 along the center line or center of gravity of the hollow cylinders of the bobbins 322K_1 and 322K_2. A coil 323K_1 is wound around the outer circumferential surface of the bobbin 322K_1, and a coil 323K_2 is wound around the outer circumferential surface of the bobbin 322K_2.

[0136] The fluxgate 32K_1 and the fluxgate 32K_2 are disposed in different accommodation spaces. As shown in Fig. 26, the main core 31K_1 (31K_2) is formed with an accommodation space 314K_1 for accommodating the fluxgate 32K_1 and an accommodation space 314K_2 for accommodating the fluxgate 32K_2.

[0137] Here, it is preferable that the accommodation space 314K_1 and the accommodation space 314K_2 are formed to be spaced apart from each other in the circumferential direction Q of the core 321K. In other words, the core 321K (magnetic body) is continuously formed between the accommodation space 314K_1 and the accommodation space 314K_2. Here, when the distance between the accommodation space 314K_1 and the accommodation space 314K_2 is Ls, it is preferable that 1.0 mm≦Ls≦10.0 mm. More preferably, 1.0 mm≦Ls≦5.0 mm.

[0138] In this case, it is preferable that the main core 31K is formed continuously in the circumferential direction Q of the main core 31K on at least one of the outer circumferential side and the inner circumferential side of the accommodation spaces 314K_1, 314K_2 (see Figs. 20 and 21). Fig. 26 shows, as an example, a case in which the main core 31K is formed continuously in the circumferential direction Q on both the outer circumferential side and the inner circumferential side of the accommodation spaces 314K_1, 314K_2. Note that in the insertion direction of the measurement target 5 in the main core 31 (Z-axis direction), the fluxgates 32K_1, 32K_2 (accommodation spaces 314K_1, 314K_2) may or may not be covered by the main core 31K.

[0139] As shown in Fig. 26, the bobbin 322K_1 around which the coil 323K_1 is wound and the core 321K is inserted is accommodated in the accommodation space 314K_1, and the bobbin 322K_2 around which the coil 323K_2 is wound and the core 321K is inserted is accommodated in the accommodation space 314K_2. As a result, the fluxgates 32K_1 and 32K_2 are arranged side by side in the circumferential direction Q of the main core 31K, sandwiching the magnetic body as the main core 31K_1 (31K_2). In this case, it is preferable to determine the winding directions of the coils 323K_1 and 323K_2 so that the magnetic fluxes excited by the fluxgates 32K_1 and 32K_2 are generated in directions facing each other.

[0140] As described above, the current sensor 3K has the fluxgate pair 32KP in which the coils 323K_1 and 323K_2 are wound around one shared core 321K. This makes it possible to suppress the voltages generated from the coils 323K_1 and 323K_2 of the fluxgates 32K_1 and 32K_2 from being superimposed as noise on the main core 31 and the coil 55 (feedback winding) wound around the main core 31 via parasitic capacitance. For example, by arranging the fluxgate pair 32KP so that the fluxgates 32K_1 and 32K_2 generate voltages of opposite phases to each other, the noise generated from the fluxgate 32K_1 can be offset by the noise generated from the fluxgate 32K_1. This makes it possible to reduce the noise superimposed on the main core 31 and the coil 55 (feedback winding), and improve the accuracy of current detection by the current sensor 3K.

[0141] In the current sensor 3K, an accommodating space 314K_1 that accommodates the fluxgate 32K_1 and an accommodating space 314K_2 that accommodates the fluxgate 32K_2 are formed side by side in the circumferential direction Q of the main core 32K, and the main core 31K is continuously formed between the accommodating space 314K_1 and the accommodating space 314K_2. According to this, even if the fluxgate pair 32KP is arranged so that the fluxgates 32K_1 and 32K_2 generate voltages of opposite phases, it is possible to prevent the magnetic fluxes excited by the coil 323K_1 of the fluxgate 32K_1 and the coil 323K_2 of the fluxgate 32K_2 from canceling each other out. That is, as shown in FIG. 27, the magnetic body (main core 31K) exists between the accommodation space 314K_1 and the accommodation space 314K_2, so that the magnetic fluxes Φ1 and Φ2 generated from the coils 323K_1 and 323K_2 pass through the main core 32K existing around the fluxgates 32K_1 and 32K_2. As a result, the magnetic fluxes Φ1 and Φ2 are looped, and it is possible to prevent the magnetic fluxes Φ1 and Φ2 from canceling each other out, so that it is possible to easily realize a current sensor having a differentially configured fluxgate pair.

[0142] Moreover, by setting the distance Ls between the accommodation space 314K_1 and the accommodation space 314K_2 to 1.0 mm≦Ls≦10.0 mm, the two coils 323K_1, 323K_2 of the fluxgate pair 32KP can be brought closer to each other, thereby further reducing noise superimposed on the main core 31 and the coil 55. Furthermore, by setting the distance Ls to 1.0 mm≦Ls≦5.0 mm, the two coils 323K_1, 323K_2 of the fluxgate pair 32KP can be brought even closer to each other, thereby further reducing noise superimposed on the main core 31 and the coil 55.

[0143] 26 shows a case where a part of the core 321K extends into the housing spaces 314K_1 and 314K_2, and one end and the other end of the core 321A in the extending direction protrude from the housing spaces 314K_1 and 314K_2, as in the core 321A according to the second embodiment, but the present invention is not limited to this. For example, as in the core 321 according to the first embodiment, one end of the core 321K in the extending direction may contact one surface in the circumferential direction Q of the inner wall 315K_1 of the main core 31K that defines the housing space 314K_1, and the other end of the core 321K in the extending direction may contact the other surface in the circumferential direction of the inner wall 315K_2 of the main core 31K that defines the housing space 314K_2. Also, as in the current sensor 3B, the main core 31K and the cores 321K of the fluxgates 32K_1 and 32K_2 may be integrally formed. [Explanation of symbols]

[0144] 1...measuring device, 2...measuring device main body, 3, 3A to 3H, 3J, 3K...current sensor, 5...measurement object, 11...measuring section, 12...operation section, 13...display section, 14...control section, 15...memory section, 21...holding section, 22...sensor section, 22_1...first sensor section, 22_2...second sensor section, 23...connection cable, 25_1, 25_2...magnetic detection section, 26...coil, 31, 31_1, 31_2, 31J, 31K...main core (first core), 31Ja...first magnetic member, 31Jb...second magnetic member, 32, 32A, 32B, 32C, 32K_1, 32K_2...fluxgate, 32KP...fluxgate pair, 50, 5 0A, 50K...signal generating circuit, 51, 51_1, 51_2...drive circuit, 52, 53, 53K...signal processing circuit, 54, 57...amplification circuit, 55...coil, 56...voltage generating circuit, 310, 310_1 to 310_8, 310Ja, 310Jb...plate-shaped member, 312_1, 312_8...hole, 313_2 to 313_7...hole, 314, 314K_1, 314K_2...accommodating space, 315, 315K_1, 315K_2...inner wall, 321, 321A, 321B, 321C, 321K...core (second core), 322, 322K_1, 322K_2...bobbin, 323, 323K_1, 323K_2...coil (winding).

Claims

1. A current sensor comprising: a flux gate that detects magnetic flux; an annular first core made of a magnetic material and having an accommodation space for accommodating the flux gate; and a signal generating circuit that generates a signal based on the magnetic flux detected by the flux gate, the current sensor detecting a current flowing through an object to be measured while the object is inserted through the first core, The fluxgate has a second core made of a magnetic material and extending into the accommodation space, and a coil wound around the second core along a direction in which the second core extends, one end of the second core in the extending direction is in contact with a part of the first core, and the other end of the second core in the extending direction is in contact with another part of the first core; Current sensor.

2. 2. The current sensor according to claim 1, The second core extends in a circumferential direction of the first core. Current sensor.

3. 2. The current sensor according to claim 1, The first core is provided continuously in a circumferential direction of the first core on an outer circumferential side of the first core around the periphery of the accommodation space. Current sensor.

4. 2. The current sensor according to claim 1, The first core is provided continuously in a circumferential direction of the first core on an inner peripheral side of the first core around the accommodating space. Current sensor.

5. 2. The current sensor according to claim 1, When one surface of the first core in the insertion direction of the measurement target in the first core is defined as an upper surface and the other surface of the first core in the insertion direction of the measurement target in the first core is defined as a lower surface, the first core is provided continuously in a circumferential direction of the first core on at least one of the upper surface and the lower surface around the periphery of the accommodation space. Current sensor.

6. 4. The current sensor according to claim 3, The portion of the first core that is continuously provided in the circumferential direction is integrally formed. Current sensor.

7. 2. The current sensor according to claim 1, One end of the second core in the extending direction and the other end of the second core in the extending direction are covered by the first core. Current sensor.

8. 2. The current sensor according to claim 1, the first core is formed of a plurality of plate-like members made of a magnetic material that are stacked in a direction in which the object to be measured is inserted into the first core, One end of the second core in the extending direction and the other end of the second core in the extending direction are sandwiched between the two plate-like members in the insertion direction. Current sensor.

9. 2. The current sensor according to claim 1, The flux gate has a plurality of Current sensor.

10. 10. The current sensor according to claim 9, At least one fluxgate pair is provided, the pair including two of the fluxgates; a first fluxgate and a second fluxgate constituting the fluxgate pair share the second core; The coil of the first fluxgate and the coil of the second fluxgate are wound around the second core shared by the first fluxgate and the second fluxgate. Current sensor.

11. 11. The current sensor according to claim 10, the accommodation space includes a first accommodation space that accommodates the first fluxgate and a second accommodation space that accommodates the second fluxgate, The first accommodating space and the second accommodating space are arranged side by side in a circumferential direction of the first core, The first core is provided continuously between the first accommodation space and the second accommodation space. Current sensor.

12. 2. The current sensor according to claim 1, The first core and the second core are integrally formed. Current sensor.

13. 2. The current sensor according to claim 1, The current is detected by the zero flux method. Current sensor.

14. A current sensor according to any one of claims 1 to 13; a measurement device main body that measures a current flowing through the measurement object based on the signal generated by the current sensor. Measuring equipment.

15. A measurement method for measuring a current flowing through a measurement object using a current sensor, comprising: The current sensor includes a fluxgate that detects magnetic flux, an annular first core made of a magnetic material and having an accommodation space to accommodate the fluxgate, and a signal generating circuit that generates a signal based on the magnetic flux detected by the fluxgate. The fluxgate includes a second core made of a magnetic material and extending into the accommodation space, and a coil wound around the second core along the extension direction of the second core, one end of the second core in the extension direction contacts a part of the first core and the other end of the second core in the extension direction contacts another part of the first core. A first step of inserting the measurement object into the first core; A second step of measuring a current flowing through the measurement target based on the signal generated by the signal generating circuit. Measurement method.

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