Current sensor and current measuring apparatus

Abstract

To provide a clamp type current sensor capable of opening and closing a magnetic flux detection section without reducing detection accuracy of current flowing through a measured conductor irrespective of a structure of the magnetic flux detection section obtained by dividing a magnetic saturation core, and a measuring apparatus including the current sensor.SOLUTION: A current sensor 3 comprises one side sensor section 22a and the other side sensor section 22b. Current flowing through a measured conductor X is detected. Both sensor sections 22a, 22b are provided with, in the vicinity of an end face of a first magnetic core 31a formed of a first material and in the vicinity of an end face of a second magnetic core 31b, an end face magnetic material 34 formed of second material with lower magnetic permeability than the first material, respectively. When the one side sensor section 22a and the other side sensor section 22b surround and close the measured conductor X, the first magnetic core 31a forms a closed magnetic circuit via the end face magnetic material 34 to provide a first magnetic saturation core 26a while the second magnetic core 31b forms the closed magnetic circuit via the end face magnetic material 34 to provide a second magnetic saturation core 26b.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a current sensor having a plurality of magnetically saturated cores and a measuring device including this current sensor. [Background technology]

[0002] Conventionally, current detection devices (through-type current sensors) have been disclosed (for example, Patent Document 1). This current detection device is configured by stacking two annular-shaped fluxgate magnetic field sensors (fluxgate magnetic sensors) with an insulating layer between them, housing the stacked FG magnetic field sensors within a circular main core, and evenly winding a feedback winding around the entire outer surface of the main core. In the current detection device described in Patent Document 1, a triangular wave excitation circuit supplies phase-inverted excitation signals to the two FG magnetic field sensors, and a differential amplifier circuit amplifies the differential voltage between the voltages generated by each FG magnetic field sensor. In addition, a synchronous detection circuit synchronously detects the signal output from the differential amplifier circuit with a reference signal having twice the frequency of the excitation signal to detect a signal proportional to the current flowing in the electric wire (conductor under test). An amplifier generates a drive current based on the detected signal and supplies it to one end of the feedback winding. Furthermore, a detection resistor arranged between the other end of the feedback winding and ground converts the drive current supplied to this feedback winding into a voltage, which is then amplified by an amplifier section and output as a signal indicating the current flowing through the wire being measured.

[0003] In the current detection device of the above configuration, the FG type magnetic field sensor housed in the main core as a magnetic detection means and the feedback winding wound evenly around the main core are arranged in a circumferentially symmetrical structure, so that it is possible to minimize the influence of the position of the electric wire to be measured (the conductor to be measured) inserted into the main core and the influence of external magnetic fields.

[0004] The wideband current detector (through-type current detector) disclosed in Patent Document 2 has a space through which the conductor to be measured, through which the measurement current flows, can be inserted, and is composed of two FG-type magnetic field sensors formed in a ring shape with first and second saturable ring cores arranged to surround this space, first and second high-frequency coils wound around the first and second saturable ring cores with the same number of turns in the same or opposite directions, and generating a magnetic field in the opposite direction when current is passed through them, first and second unsaturated ring cores arranged in a sandwich shape sandwiching the first and second high-frequency coils from both radial sides, and the first and second unsaturated ring cores are placed in the center and wound around the outside.

[0005] As described in Patent Document 2, a high-frequency current that saturates the first and second saturable ring cores is passed through the first and second high-frequency coils, the differential voltage across the first and second high-frequency coils is extracted, and a current corresponding to this differential voltage is passed through a cancel coil to excite the first and second unsaturable ring cores in the opposite direction to the excitation by the measurement current, thereby canceling out the differential voltage.The current flowing through the conductor under test in the low-frequency range, including DC, can be measured from the current passed through the cancel coil. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4621543 [Patent Document 2] Patent No. 4884394 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0007] However, since the ring core used in the above-mentioned FG-type magnetic sensor is made of a ferromagnetic material that is weak to stress, such as permalloy or amorphous, and has a thickness of about 0.1 mm, if the measurement target electric wire is configured to be introduced into an openable magnetic flux detection section, as in a general clamp-type current sensor using a divided magnetic core, it is extremely difficult to accurately face the end faces of the divided, narrow ring core made of a very thin, stress-sensitive ferromagnetic material to each other in a circular shape without applying stress.In addition, if the magnetic material at the contacting part becomes magnetically saturated due to contact error between the facing end faces, it may become difficult to obtain accurate measurement values.

[0008] The present invention has been made to improve upon such problems, and its main objective is to provide a clamp-type current sensor and a measuring device equipped with this current sensor that allows the magnetic flux detection section to be opened and closed without reducing the detection accuracy of the current flowing through the object to be measured, even when the magnetic flux detection section has a structure in which the ring core (magnetic saturation core) used in an FG type magnetic sensor is divided. [Means for solving the problem]

[0009] In order to solve the above problems, the current sensor of the present invention is a clamp-type current sensor comprising one-side sensor section and other-side sensor section pivotally supported on a measuring device body so as to be able to open and close, the one-side sensor section and other-side sensor section surrounding and closing a conductor to detect a current flowing through the conductor to be measured. This current sensor comprises a one-side sensor section having a semi-annular shape and one-side first magnetic core and one-side second magnetic core formed from a first material, one-side end-face magnetic elements formed from a second material having a magnetic permeability lower than that of the first material provided near the end faces of the one-side first magnetic core and one-side second magnetic core, and a other-side sensor section having a semi-annular shape and one-side second magnetic core formed from the first material, one-side end-face magnetic elements formed from the second material provided near the end faces of the other-side first magnetic core and one-side second magnetic core, The end face of the one-side sensor part that butts against the other-side sensor part and the end face of the other-side sensor part that butts against the one-side sensor part are each formed smoothly, and when the one-side sensor part and the other-side sensor part surround and close the conductor to be measured, the one-side first magnetic core and the other-side first magnetic core form a closed magnetic circuit via the one-side end face magnetic material and the other-side end face magnetic material, thereby becoming a first magnetically saturated core, and the one-side second magnetic core and the other-side second magnetic core form a closed magnetic circuit via the one-side end face magnetic material and the other-side end face magnetic material, thereby becoming a second magnetically saturated core.

[0010] In addition, the current sensor of the present invention is characterized in that the area of ​​the end face of the one-side end face magnetic material is formed larger than the area of ​​the end face of the one-side first magnetic core formed of the first material, and the area of ​​the end face of the other-side end face magnetic material is formed larger than the area of ​​the end face of the other-side first magnetic core.

[0011] Moreover, the current sensor according to the present invention is characterized in that the first material is permalloy PC, and the second material is any one of ferrite, silicon steel, and permalloy PC.

[0012] Moreover, the current sensor according to the present invention is characterized in that the first material is Permalloy PC, and the second material is Permalloy PC having a relatively lower magnetic permeability than the first material due to heat treatment or shape.

[0013] Furthermore, a current measuring device according to the present invention is characterized by comprising any one of the current sensors described above and a measuring unit that measures the current flowing through the conductor to be measured based on the detection result by the current sensor. [Effects of the Invention]

[0014] In the current sensor according to the present invention, a pair of first and second sensor sections are pivotally supported so as to be freely opened and closed. Each of the first and second magnetic cores is made of a first material. A smooth, end-face magnetic material is provided near the end faces of the first and second magnetic cores. When the first and second sensor sections surround and close the conductor under test, the first and second magnetic cores form a closed magnetic circuit via the first and second end-face magnetic material, forming a first magnetic saturation core. The second and second magnetic cores form a closed magnetic circuit via the first and second end-face magnetic material, forming a second magnetic saturation core. This current sensor configuration enables accurate measurement of the current flowing through the object to be measured. The smooth surface is preferably a mirror-polished, clean, and smooth surface.

[0015] In addition, the current sensor according to the present invention is configured so that the end surface area of ​​the end surface magnetic material made of the second material is larger than the end surface area of ​​the magnetic core. When the magnetic core, which is assembled separately into a pair of one-side sensor section and the other-side sensor section, is closed, the end surface magnetic material efficiently transfers the magnetic flux generated inside the first magnetic saturation core and the second magnetic saturation core to the opposing magnetic core. Therefore, the current sensor according to the present invention has a large joint surface area to reduce magnetic resistance, widening the tolerance range within which the performance of the first magnetic saturation core and the second magnetic saturation core can be maintained when the end surfaces are opposed. Furthermore, by using a material with low magnetic permeability for the end surfaces, it is possible to prevent magnetic saturation in the end surface material from interfering with the circulation of magnetic flux within the first magnetic saturation core and the second magnetic saturation core. Therefore, the current flowing through the conductor under test can be measured more accurately by forming a ring-shaped magnetic sensor with the end surfaces of the magnetic cores facing each other.

[0016] In the current sensor according to the present invention, the first material is permalloy PC, and the second material is either ferrite silicon steel or permalloy PB. This configuration allows the end surface magnetic element to be manufactured using the second material, which is relatively inexpensive and easily available, and therefore does not lead to an increase in manufacturing costs.

[0017] In the current sensor according to the present invention, the first material is Permalloy PC, and the second material is Permalloy PC whose magnetic permeability is relatively lower than that of the first material due to heat treatment or shape. With this configuration, the same material as that of the magnetic core can be used as the second material, which does not lead to an increase in manufacturing costs. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic diagram illustrating a configuration of a current measuring device according to an embodiment of the present invention. [Figure 2] 1 is a perspective view of a current sensor according to an embodiment of the present invention; [Figure 3] 1 is an external view of a sensor body in a clamp portion of a current sensor according to an embodiment of the present invention. FIG. [Figure 4]FIG. 2 is a perspective view of a magnetic flux detection portion of the current sensor according to the embodiment of the present invention. [Figure 5] FIG. 2 is an exploded perspective view of a magnetic flux detection portion of the current sensor according to the embodiment of the present invention. [Figure 6] FIG. 2 is a perspective view of a magnetic saturation core of the current sensor according to the embodiment of the present invention. [Figure 7] FIG. 2 is an end view of a sensor body of a current sensor according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] The current sensor and current measuring device according to this embodiment will be described with reference to FIGS.

[0020] 1, the measurement device 1 according to this embodiment includes a measurement device main body 2 and a current sensor 3 connected to the measurement device 1 and provided outside the measurement device 1, and measures the current value of a current flowing through a measurement object (conductor to be measured) X clamped by the current sensor 3 in a non-contact state with respect to the measurement object X. Note that the current measurement device 1 is an example of a measurement device and is not limited to the above configuration.

[0021] The measurement device main body 2 mainly comprises a measurement unit 11, an operation unit 12, a display unit 13, a control unit 14, and a memory unit 15. The current sensor 3 is connected to the measurement unit 11, and measures the current value of the current flowing through the measurement object X via this current sensor 3.

[0022] Under the control of the control unit 14, the measurement unit 11 measures the current value of the current supplied to the measurement object X based on the detection signal output from the current sensor 3 when a current is supplied to the measurement object X clamped by the current sensor 3. Note that a detailed explanation of the measurement principle of the current value using the clamp-type current sensor 3 will be omitted.

[0023] The operation unit 12 includes various operation switches for setting measurement conditions, issuing a command to start measurement, etc., and outputs operation signals to the control unit 14 in response to switch operations.

[0024] Display unit 13 displays the results of measurement by measurement unit 11 (current value) and the like under the control of control unit 14.

[0025] The control unit 14 performs overall control of the current measuring device 1. Specifically, the control unit 14 controls the measurement unit 11 to execute a current value measurement process, and also controls the display unit 13 to display the current value, which is the measured value, based on the measurement result by the measurement unit 11.

[0026] The storage unit 15 temporarily stores the calculation results of the control unit 14, the measurement results of the measurement unit 11, and the like.

[0027] As shown in FIG. 2, the current sensor 3 includes a gripping portion 21, a clamping portion 22 provided on one end side of the gripping portion 21, and a connection cable 23 provided on the other end side of the gripping portion 21.

[0028] The gripping portion 21 is a portion that is gripped by a user when clamping the object to be measured X with the clamping portion 22, and the clamping portion 22 is disposed at one end (the left end in FIG. 2). A signal processing circuit board that generates a detection signal according to the detection result by the clamping portion 22 is housed inside the gripping portion 21. A connection cable 23 connected to this signal processing circuit board is drawn out from the other end (the right end in FIG. 2). The gripping portion 21 is provided with an opening / closing operation portion 21a for opening and closing the clamping portion 22. The detection signal is a voltage signal proportional to the current value of the current supplied to the object to be measured X.

[0029] The clamping portion 22 includes a one-side sensor portion 22a formed in a semi-annular shape and an other-side sensor portion 22b formed in a semi-annular shape, and is configured to be able to clamp the measurement object X. The one-side sensor portion 22a and the other-side sensor portion 22b are arranged as a pair, thereby forming the clamping portion 22 in a ring shape. The one-side sensor portion 22a and the other-side sensor portion 22b have the same configuration, and are identical in shape and structure (including end face structure). The one-side sensor portion 22a and the other-side sensor portion 22b will collectively be referred to as sensor portions 22a and 22b.

[0030] As shown in Fig. 3, the sensor units 22a and 22b are each provided with a semi-annular sensor body 24a, 24b housed in a resin case (not shown), with a winding 27 wound around each magnetic flux detection unit 25 shown in Fig. 4. The sensor units 22a and 22b are configured to form an annular shape surrounding the electric wire or the like of the measurement object X.

[0031] As shown in Figures 5 and 6, the magnetic flux detection unit 25 includes a first magnetic core 31a, a second magnetic core 31b, core holders 32a, 32b, 32c, and 32d, FG winding portions 33a and 33b, end surface magnetic materials 34a, 34b, 34c, and 34d, insulating sheets 35a and 35b, shield plates 36a, 36b, 36c, and 36d, spacers 37a, 37b, 37c, and 37d, core end compression materials 38a, 38b, 38c, and 38d, and covers 39a and 39b. Hereinafter, the first magnetic core 31a and the second magnetic core 31b will be collectively referred to as magnetic core 31, the core holders 32a, 32b, 32c, and 32d will be collectively referred to as core holder 32, the end surface magnetic materials 34a, 34b, 34c, and 34d will be collectively referred to as end surface magnetic material 34, the end surface insulating sheets 35a and 35b will be collectively referred to as insulating sheet 35, the shield plates 36a, 36b, 36c, and 36d will be collectively referred to as shield plate 36, the spacers 37a, 37b, 37c, and 37d will be collectively referred to as spacer 37, the core end compression materials 38a, 38b, 38c, and 38d will be collectively referred to as core end compression material 38, and the covers 39a and 39b will be collectively referred to as cover 39.

[0032] The first magnetic core 31a and the second magnetic core 31b disposed below the first magnetic core 31a are made of a first material, Permalloy PC, and are formed in a semi-annular shape. The core holder 32 is formed using an insulating base material such as polyacetal resin, and includes a core holder 32b that supports the underside of the first magnetic core 31a, a core holder 32d that supports the underside of the second magnetic core 31b, a core holder 32a that covers the first magnetic core 31a and is in close contact with the core holder 32b, and a core holder 32c that covers the second magnetic core 31b and is in close contact with the core holder 32d (FIG. 5). The FG winding portion 33a is wound around the outside of the core holders 32a and 32b that cover the first magnetic core 31a, and is configured to form the semi-annular first magnetically saturated core 26a. Similarly, the FG winding portion 33b is wound around the outside of the core holders 32c and 32d that cover the second magnetic core 31b, and is configured to form the semi-annular second magnetically saturated core 26b.

[0033] The end surface magnetic materials 34a, 34b, 34c, and 34d are made of ferrite, which is the second material. Ferrite is a magnetic material with lower magnetic permeability than the permalloy PC that constitutes the first magnetic core 31a and the second magnetic core 31b. Therefore, ferrite is a magnetic material that is less susceptible to magnetic saturation. As shown in FIGS. 6 and 7, these end surface magnetic materials 34a, 34b, 34c, and 34d are closely attached to appropriate locations near the end faces of the semi-annular first magnetic core 31a and the second magnetic core 31b, and then mirror-polished to form clean, smooth surfaces. The end surface areas of the end surface magnetic materials 34a, 34b, 34c, and 34d are formed so that they are larger than the end faces of the first magnetic core 31a and the second magnetic core 31b. Silicon steel or permalloy PB can also be used as the second material.

[0034] The first magnetically saturated core 26a and the second magnetically saturated core 26b are incorporated into the one-side sensor unit 22a and the other-side sensor unit 22b, respectively. As shown in Fig. 3, when the sensor units 22a and 22b surround the measurement object X and the measurement object X is positioned inside the clamp unit 22, the end-face magnetic materials 34a, 34b, 34c, and 34d arranged on the sensor units 22a and 22b come into close contact with each other, forming a ring-shaped FG-type magnetic sensor. When a current is supplied to the measurement object X, it becomes possible to detect a magnetic field generated around the measurement object X.

[0035] 6 and 7, insulating sheet 35a is sandwiched between end surface magnetic material 34a and end surface magnetic material 34c, and insulating sheet 35b is sandwiched between end surface magnetic material 34b and end surface magnetic material 34d. Insulating sheets 35a and 35b are members that separate the attachment positions of end surface magnetic material 34a and end surface magnetic material 34c, and end surface magnetic material 34b and end surface magnetic material 34d, thereby suppressing interference of magnetic flux generated in first magnetic core 31a and second magnetic core 31b.

[0036] 5 and 7, the spacer 37 is arranged along the side surfaces of the first magnetic core 31a, the second magnetic core 31b, and the end surface magnetic materials 34a, 34b. The spacer 37 determines the positions of the first magnetic core 31a, the second magnetic core 31b, the end surface magnetic materials 34a, 34b, and the core end compressed materials 38a, 38b, 38c, and 38d.

[0037] The core-end compressed materials 38a, 38b, 38c, and 38d are formed by forming a block of a microcellular polymer sheet with small residual compression strain. As shown in Figures 5 and 7, the core-end compressed materials 38a and 38b are sandwiched between the first magnetic core 31a and the shield plate 36a, and the core-end compressed materials 38c and 38d are sandwiched between the second magnetic core 31b and the shield plate 36b. These materials are compressed so that the magnetic core 31, the end-face magnetic material 34, and the insulating sheet 35 are in close contact with each other.

[0038] The shield plates 36a, 36b, 36c, and 36d are formed of semi-annular magnetic thin plates made of permalloy PC. As shown in Fig. 5, the shield plates 36a, 36b, 36c, and 36d are housed in covers 39a and 39b, respectively, in a state where they are arranged to cover the first magnetic saturation core 26a and the second magnetic saturation core 26b to which the magnetic core 31 is attached (the magnetic core 31 is housed), the end surface magnetic material 34, the insulating sheet 35, the spacer 37, and the core end compression material 38.

[0039] 4 and 5, the covers 39a and 39b accommodate the first and second magnetically saturated cores 26a and 26b, which are covered by the shield plates 36a, 36b, 36c, and 36d, the end surface magnetic material 34, the insulating sheet 35, the spacer 37, and the core end compression material 38. The cover 39 also functions as a bobbin for winding the common single winding 27 around the first and second magnetically saturated cores 26a and 26b.

[0040] Next, a method for manufacturing the current sensor 3 according to this embodiment will be described.

[0041] When manufacturing the current sensor 3, the magnetic flux detection unit 25 is first fabricated. Specifically, the first magnetic core 31a is sandwiched between core holders 32a and 32b, and the first magnetic core 31a is fitted into core holders 32a and 32b. Similarly, the second magnetic core 31b is sandwiched between core holders 32c and 32d, and the second magnetic core 31b is fitted into core holders 32c and 32d. Next, a polyurethane-coated copper wire, for example, is wound around the outside of core holder 32a to form FG winding portion 33a, thereby forming the first magnetically saturated core 26a. Similarly, a polyurethane-coated copper wire, for example, is wound around the outside of core holder 32d to form FG winding portion 33b, thereby forming the second magnetically saturated core 26b.

[0042] Next, with cover 39b facing the bottom, shield plate 36b is placed on the bottom, shield plate 36c is placed on the inside surface of the housing area, and shield plate 36d is placed on the outside surface of the housing area (FIG. 5). From this state, the positions of the components to be housed in cover 39b are determined by placing spacer 37a on the inside surface of the housing area on one end of shield plate 36d, spacer 37d on the inside surface of the housing area on the other end of shield plate 36d, spacer 37b on the inside surface of the housing area on one end of shield plate 36c, and spacer 37c on the inside surface of the housing area on the other end of shield plate 36c. From this state, on one end side, the core end compressed material 38c, the second magnetic core 31b of the second magnetic saturation core 26b, the end surface magnetic material 34c, the insulating sheet 35a, the end surface magnetic material 34a, the first magnetic core 31a of the first magnetic saturation core 26a, and the core end compressed material 38a are stacked and stored in this order so that they are sandwiched and stored between the spacers 37a and 37b, and on the other end side, matching the storage order on the one end side, the core end compressed material 38d, the second magnetic core 31b of the second magnetic saturation core 26b, the end surface magnetic material 34d, the insulating sheet 35b, the end surface magnetic material 34b, the first magnetic core 31a of the first magnetic saturation core 26a, and the core end compressed material 38b are stacked and stored in this order so that they are sandwiched and stored between the spacers 37c and 37d.

[0043] Next, shield plate 36a is placed on the top surface, and cover 39b is placed over cover 39a, compressing and positioning each component, and each component is housed inside covers 39a and 39b. This completes the assembly of magnetic flux detection unit 25 (FIG. 4). Furthermore, the butting end faces of magnetic flux detection unit 25 are mirror-polished to create clean, smooth surfaces, and the end faces are tightly attached to form a circular ring shape.

[0044] Next, sensor bodies 24a and 24b are fabricated by winding wire 27 around covers 39a and 39b that constitute magnetic flux detection unit 25 (FIG. 3). Sensor bodies 24a and 24b are then housed in a resin case to fabricate sensor units 22a and 22b. Sensor units 22a and 22b are then attached to gripping unit 21, and the winding of FG winding unit 33, winding wire 27, and connection cable 23 are connected to the signal processing circuit board inside gripping unit 21, thereby completing current sensor 3 (FIG. 2).

[0045] Next, the effects of the current sensor 3 and the current measuring device 1 according to this embodiment will be described.

[0046] When measuring the current value of a current flowing through a measurement object X using the current sensor 3 according to this embodiment, the connection cable 23 of the current sensor 3 is connected to the measurement unit 11 of the measurement device main body 2, and the measurement object X is clamped by the clamp unit 22 as shown in Fig. 1. Next, the operation unit 12 of the measurement device main body 2 is operated to start the measurement process. In this case, the measurement unit 11 forms an FG type magnetic field sensor that applies phase-inverted excitation voltages to the FG winding portion 33a of the first magnetic saturation core 26a and the FG winding portion 33b of the second magnetic saturation core 26b while correctly opposing paired end faces of the first magnetic saturation core 26a and the second magnetic saturation core 26b in the one-side sensor unit 22a and the other-side sensor unit 22b, which are individually incorporated into the pair of one-side sensor unit 22a and the other-side sensor unit 22b, and simultaneously forms a zero-flux type current sensor that supplies a current that makes the output of the FG type magnetic field sensor zero from one end of the winding 27. At this time, a current corresponding to the object to be measured X flows through the winding 27, so a detection resistor is disposed between the other end of the winding 27 and ground, and the current flowing through the winding 27 is converted into a current-equivalent voltage and output to the control unit 14.

[0047] The control unit 14 measures the current value of the current flowing through the object to be measured X using the current-converted voltage from the measurement unit 11. In this case, in the current measuring device 1 (current sensor 3) according to this embodiment, as described above, the end faces of the FG-type magnetic sensor, which is pivotally supported and assembled separately into a pair of one-side sensor unit 22a and the other-side sensor unit 22b, are properly opposed to each other to form a ring shape, thereby preventing the magnetic material in the contact area from becoming magnetically saturated. Therefore, the current measuring device 1 can accurately measure the current value of the current flowing through the object to be measured X.

[0048] In the current sensor 3 according to this embodiment, the shield plate 36 disposed within the magnetic core 31 is made of permalloy PC, which has high magnetic permeability. Therefore, the detection of the magnetic field generated in the measurement object X, which is located on the inner periphery side of the magnetic flux detection unit 25, is not significantly hindered by the shield plate 36. Therefore, the current measuring device 1 (current sensor 3) can detect a magnetic field with a strength corresponding to the current value of the current flowing through the measurement object X.

[0049] Furthermore, in the current measurement device 1 (current sensor 3) according to this embodiment, the area of ​​the joint surfaces between the end-face magnetic elements 34a, 34b, 34c, and 34d formed from the second material is increased, widening the tolerance range that maintains the performance of the first magnetic saturation core 26a and the second magnetic saturation core 26b when the end faces are opposed to each other. Furthermore, by using a material with low magnetic permeability, when the sensor units 22a and 22b are closed, the respective end faces are properly opposed to each other and in close contact with each other, and magnetic flux circulation within the first magnetic saturation core 26a and the second magnetic saturation core 26b is prevented from being impeded. Therefore, for example, even if the clamp unit 22 that clamps the measurement object X is pivotally supported so as to be able to open and close, as shown in FIG. 1, the magnetic flux generated by both sensor units 22a and 22b can be efficiently transferred to the opposing sensor unit 22b. As a result, the current flowing through the measurement object X (e.g., an electric wire) can be accurately measured.

[0050] In the current sensor 3 according to this embodiment, the FG-type magnetic sensor is pivotally supported so as to be freely opened and closed, and is assembled separately into a pair of one-side sensor portion 22a and the other-side sensor portion 22b. End-face magnetic materials 34a, 34b, 34c, and 34d made of a second material having a lower magnetic permeability than the first material are attached to the end faces of the first and second magnetic cores 31a, 31b of the FG-type magnetic sensor. The end-face magnetic materials 34a, 34b, 34c, and 34d are adhered to the end faces of the first and second magnetic cores 31a, 31b, respectively, and are mirror-polished to form clean, smooth surfaces. In the current sensor 3, the end face area of ​​the end face magnetic material 34 made of the second material is larger than the end face area of ​​the magnetic core 31. The end-face magnetic material 34 made of the second material closes the first and second magnetic saturation cores 26 assembled separately into the one-side sensor portion 22a and the other-side sensor portion 22b, forming a ring shape. When the end-face magnetic materials 34 are annular, they efficiently transfer the magnetic flux generated in the first and second magnetic saturation cores 26a, 26b to the opposing first and second magnetic saturation cores 26a, 26b.

[0051] As described above, the current sensor 3 has a wider joint surface area to widen the tolerance when the end faces face each other, reducing magnetic resistance, and using a material with low magnetic permeability for the end faces, thereby preventing magnetic saturation. Therefore, by properly opposing the end faces of the first magnetically saturated core 26a and the second magnetically saturated core 26b of the FG-type magnetic sensor, the magnetic material in the contact area can be prevented from becoming magnetically saturated in the annular state, preventing the circulation of magnetic flux within the magnetically saturated core from being impeded, and allowing accurate measurement of the current flowing through the electric wire that is the measurement target X.

[0052] Furthermore, in the current sensor 3 according to this embodiment, by using permalloy PC as the first material and ferrite, silicon steel, or permalloy PB as the second material, it is possible to manufacture the end surface magnetic material 34 made of the second material, which is relatively inexpensive and easily available. Therefore, it is possible to manufacture the current sensor 3 and current measuring device 1 that can accurately measure the current flowing through the measurement object X without incurring a rise in manufacturing costs.

[0053] Furthermore, in the current sensor 3, by using permalloy PC as the first material and permalloy PC whose magnetic permeability is relatively lower than that of the first material due to heat treatment or shape as the second material, it is possible to use the same material as the first magnetic core 31a and the second magnetic core 31b as the second material. Therefore, it is possible to reduce manufacturing costs and manufacture the current sensor 3 and current measuring device 1 that can accurately measure the current flowing through the measurement object X.

[0054] Although the present embodiment has been described above, it is possible to select and / or change the configurations given in the above embodiment to other configurations as appropriate without departing from the spirit of the present invention.

[0055] In this embodiment, an example has been described in which permalloy PC is used as the first material and ferrite, silicon steel, permalloy PB, or permalloy PC whose magnetic permeability is relatively lower than that of the first material due to heat treatment or shape has been used as the second material, but the first and second materials are not limited to these, and various magnetic materials can be selected as long as the condition that the magnetic permeability of the second material is lower than that of the first material is satisfied. Specifically, each end surface magnetic element 34 can be formed using an amorphous magnetic material as the first material and permalloy PC as the second material.

[0056] In the above example, the shield plate 36a is made of a first material, Permalloy PC, and each end-face magnetic material 34 is made of a second material, such as ferrite, silicon steel, Permalloy PB, or Permalloy PC with its magnetic permeability reduced by heat treatment and shape. However, each end-face magnetic material 34 can also be made of a third material different from the first and second materials. When each end-face magnetic material 34 is made of a third material, a material with a lower magnetic permeability than the first material is used as the third material. As with the magnetic flux detection unit 25, current sensor 3, and current measurement device 1, this allows the end faces of the FG-type magnetic sensor, which is pivotally supported and assembled separately into a pair of sensor units 22a and 22b, to face each other correctly. When the magnetic material at the contact point becomes magnetically saturated in the annular shape, this prevents the circulation of magnetic flux within the FG-type magnetic sensor from being impeded.

[0057] Furthermore, by adopting a configuration in which the FG winding portion 33 and the winding 27 are each used as a magnetic detection element, a zero-flux current sensor can be configured. Furthermore, while the current measuring device 1 has been described as being configured with the measuring device main body 2 and the current sensor 3 as separate entities, the configuration of the current measuring device is not limited to this, and the housing that houses the measuring portion (the measuring device main body 2 and the grip portion 21 in the current measuring device 1) and the current sensor can also be configured as an integrated unit. Even in an integrated configuration, as with the current measuring device 1 described above, the FG magnetic sensor is assembled separately into a pair of openable and closable sensor portions 22a and 22b. By properly opposing the end faces of the FG magnetic sensor, the end face magnetic material 34 of the contact portion can be prevented from becoming magnetically saturated in the annular state, preventing the circulation of magnetic flux within the FG magnetic sensor from being impeded. [Explanation of symbols]

[0058] 1 Current measuring device 2. Measuring device body 3 Current Sensor 11 Measuring part 22 Clamp section 22a One side sensor part 22b Other side sensor part 25 Magnetic flux detector 26a First magnetic saturation core 26b Second magnetic saturation core 27 windings 31a First magnetic core 31b Second magnetic core 32a, 32b, 32c, 32d Core holder 33a, 33b FG winding section 34a,34b,34c,34d Edge magnetic material 35a, 35b Insulation sheet 36a, 36b, 36c, 36d Shield plates 37a, 37b, 37c, 37d spacers 38a, 38b, 38c, 38d Core end compression material X Measurement object (conductor to be measured)

Claims

1. A clamp-type current sensor includes a first sensor unit and a second sensor unit that are pivotally supported on a measuring device body so as to be able to open and close freely, the first sensor unit and the second sensor unit surrounding and closing a conductor to be measured, and detecting a current flowing through the conductor to be measured, the one-side sensor portion has a one-side first magnetic core and a one-side second magnetic core, each having a semi-annular shape and made of a first material, and one-side end surface magnetic materials made of a second material having a lower magnetic permeability than the first material are provided near the end faces of the one-side first magnetic core and the one-side second magnetic core, respectively; the other-side sensor portion includes a semi-annular first magnetic core and a second magnetic core formed from the first material, and a second end surface magnetic material formed from the second material is provided near an end surface of the first magnetic core and near an end surface of the second magnetic core, respectively; an end surface of the one-side sensor portion that is to be abutted against the other-side sensor portion and an end surface of the other-side sensor portion that is to be abutted against the one-side sensor portion are each formed smooth; When the one-side sensor part and the other-side sensor part surround and close the conductor to be measured, the one-side first magnetic core and the other-side first magnetic core form a closed magnetic circuit via the one-side end surface magnetic material and the other-side end surface magnetic material, thereby becoming a first magnetically saturated core, and the one-side second magnetic core and the other-side second magnetic core form a closed magnetic circuit via the one-side end surface magnetic material and the other-side end surface magnetic material, thereby becoming a second magnetically saturated core. A current sensor characterized by:

2. The area of ​​the end face of the one-side end face magnetic material is formed to be larger than the area of ​​the end face of the one-side first magnetic core formed of the first material, the area of ​​the end face of the other-side end surface magnetic material is formed to be larger than the area of ​​the end face of the other-side first magnetic core; 2. The current sensor according to claim 1.

3. the first material is Permalloy PC; The second material is any one of ferrite, silicon steel, and permalloy PC.

3. The current sensor according to claim 1 or 2.

4. the first material is Permalloy PC; The second material is Permalloy PC, which has a relatively lower magnetic permeability than the first material due to heat treatment or shape.

3. The current sensor according to claim 1 or 2.

5. A current sensor according to any one of claims 1 to 4; a measurement unit that measures the current flowing through the conductor to be measured based on the detection result of the current sensor; A current measuring device characterized by:

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