JP2004170091A - Current sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable the measurement of a large current or the minute current by realizing the optimal magnetic field intensity at a desirable position. <P>SOLUTION: This current sensor outputs a voltage signal corresponding to the current flowing in an electric wire 1 in response to the intensity of a working magnetic field in the magnetic field inside a magnetic shield generated by the current flowing in the electric wire 1 to be detected as an object of measurement and arranged inside the magnetic shield 2 formed of a surrounding shield wall 20 for cutting external magnetic fields. A detecting coil 32 wound around an amorphous element 31, of which the internal magnetic field changes in response to the surrounding magnetic field, is arranged in the magnetic field to be generated by the current flowing in the electric wire to be detected, and the detecting coil 32 converts a change of the internal magnetic field to voltage with electromagnetic induction to form a magnet-inductive magnetism detecting unit 3. A signal converting circuit 33 for converting the voltage of the detecting coil to a voltage signal corresponding to the current flowing in the electric wire to be detected is provided, and magnetism distribution controlled by a void 21 formed in the surrounding shield wall is formed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is directed to a magnetic field generated by a current flowing through a detection target wire, which is a measurement target disposed in a magnetic shield including a surrounding shield wall that blocks an external magnetic field, from the magnitude of a magnetic field acting on the detection target wire. The present invention relates to a current sensor including a magneto-inductive magnetic detector that outputs a voltage signal corresponding to a current flowing through an electric wire.
[0002]
[Prior art]
In the conventional current sensor, as shown in FIG. 14, the strength of the magnetic field generated around the wire when the electric wire W to be detected placed in the magnetic shield DS having the upper and lower two-part structure for interrupting the disturbance magnetic field is energized. By providing a magnetic sensor comprising a magnetic impedance element M for generating a voltage in accordance with the voltage and a drive circuit DC for driving the magnetic impedance element M, measurement and detection based on the voltage of the magnetic impedance element M are performed. The value of the current flowing through the electric wire is determined (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP-A-2000-258644 (pages 5 to 6, FIG. 8)
[0004]
[Problems to be solved by the invention]
The principle of the above-described conventional current sensor is that, as shown in FIG. 3, a magnetic field is generated concentrically around the detected wire according to the right-handed screw rule by a current flowing through the detected wire W to be measured, The magnetic sensor S detects the magnetic field B whose strength attenuates with the distance L from the electric wire. Further, since the direction of the magnetic field is the tangential direction of the concentric circle, the magnetic sensor is disposed so that the axis at which the sensitivity is maximum is tangential, that is, orthogonal to the detection wire.
[0005]
On the other hand, the shield blocks a disturbance magnetic field other than the magnetic field B and other external magnetic fields to prevent the magnetic sensor from being affected as noise.
FIG. 15 shows a case where a detection wire W having a circular cross section indicated by a circle is arranged in a magnetic shield 2 made of, for example, a high magnetic permeability material, and the strength of a magnetic field generated by a current to be detected flowing through the wire. The result of having analyzed the distribution with the computer is shown.
[0006]
The analysis results show that the level of the strongest magnetic field in the immediate vicinity of the electric wire is 10, and the level where the magnetic field is practically regarded as 0 is 0, and the strength distribution of the magnetic field is expressed stepwise. The magnetic field strength is the same. According to this figure, the magnetic field is strongest in the immediate vicinity of the electric wire, and the numerical value indicating the magnetic field level is 10. The magnetic field gradually attenuates concentrically about the axis of the detection wire W as the distance from the shield wall increases. It is shown that the level is 6 in the immediate vicinity of 22, and that the level attenuates even further outside the shield with a numerical value of 5 outside the shield.
[0007]
When an amorphous element is used as a magnetic detector, the sensitivity is high, so that accurate measurement can be normally performed in the range of a magnetic field strength of about 0 to several (2 to 3) gauss. Has the property of becoming non-linear. Therefore, the magnetic-inductive magnetic detector is located at a position having an appropriate magnetic field strength so that the magnetic field due to the current to be measured is not too strong and the output of the magneto-inductive magnetic detector does not saturate or is too small to be buried in noise. Need to be placed.
[0008]
However, when the current to be measured is a large current of, for example, several tens of amperes or more, the magnetic field becomes too strong, so that the magnetic shield made of a material having high magnetic permeability is magnetically saturated, and the disturbance magnetic field, which is the original purpose, cannot be cut off. However, there is a problem that it is impossible to realize a current sensor having a high current.
[0009]
Further, the position at which the predetermined magnetic field strength at which the magneto-inductive magnetic detector can accurately detect the current is located very close to the shield wall as shown by point a in FIG. 15 and the magneto-inductive magnetic detector and the shield May mechanically interfere with each other, making it impossible to actually dispose them, or a position having a predetermined magnetic field strength may be outside the shield as at point b. As a result, the size of the magnetic shield must be increased due to the necessity of disposing the magneto-inductive magnetic detector at such a position having an appropriate magnetic field strength, and it becomes impossible to realize a small-sized current sensor. There was a problem.
[0010]
Conversely, when measuring a very small current, the magnetic field generated by the electric current of the electric wire is weak. Therefore, in order to detect the magnetic field with high accuracy, a magnetic-inductive magnetic field is applied to an area where the magnetic field attenuation is small and closest to the electric wire. A detector needs to be provided. That is, as shown in FIG. 15, it is necessary to dispose a magneto-inductive magnetic detector in a point very close to the detection wire, for example, in a very narrow area near point c. There was a problem that installation was difficult.
[0011]
In other words, in order to enable measurement from a very small current to a large current, the strength of the magnetic field is set to an appropriate value at a position where the magneto-inductive magnetic detector can be stably arranged without mechanical interference in the magnetic shield. There was a technical problem that had to be made possible.
[0012]
Therefore, the present inventor has proposed a magnetic field acting in a magnetic field in the magnetic shield generated by a current flowing through a detection target wire which is a measurement target disposed in a magnetic shield formed of a surrounding shield wall for blocking an external magnetic field. A current sensor that outputs a voltage signal corresponding to the current flowing through the detected wire from the size of the current sensor, the current sensor being disposed in a magnetic field generated by the current flowing through the detected wire, and an internal magnetic field corresponding to a surrounding magnetic field. A magneto-inductive magnetic detector is configured by converting the internal magnetic field change into a voltage by electromagnetic induction using a detection coil wound around an amorphous element in which the voltage of the detection coil changes. A signal conversion circuit that converts the voltage into a voltage signal corresponding to the above, and a magnetic distribution controlled by a gap formed in the surrounding shield wall is formed. Within the magnetic shield, the internal magnetic field change of the amorphous element corresponding to the magnetic field due to the current flowing through the detected electric wire is converted into a voltage by electromagnetic induction and detected as a voltage signal. Focused and further research and development, as a result of controlling the magnetic field distribution inside the magnetic shield by the air gap formed in the surrounding shield wall, the optimum magnetic field strength for the magneto-inductive magnetic detector was realized at the desired position The present invention solves this problem by making it possible, and attains the present invention that achieves the object of realizing a current sensor capable of measuring a large current or a small current.
[0013]
[Means for Solving the Problems]
The current sensor according to the present invention (first invention according to claim 1)
In the magnetic field in the magnetic shield generated by the current flowing through the electric wire to be measured disposed in the magnetic shield formed of the surrounding shield wall for blocking the external magnetic field, the magnetic field in the magnetic shield is determined by the magnitude of the acting magnetic field. A current sensor that outputs a voltage signal corresponding to a current flowing through a detection wire,
An amorphous element is disposed at a position where a linear relationship of output is maintained with respect to a magnetic field generated by a current flowing through the detected wire, and an internal magnetic field changes in accordance with a surrounding magnetic field;
A detection coil forming a magneto-inductive magnetic detector by converting a change in internal magnetic field of the amorphous element into a voltage by electromagnetic induction wound around the amorphous element;
A signal conversion circuit that converts the voltage of the detection coil into a voltage signal corresponding to a current flowing through the detected wire,
A gap for controlling magnetic distribution formed in the magnetic shield is formed in the surrounding shield wall of the magnetic shield.
Things.
[0014]
The current sensor according to the present invention (the second invention according to claim 2)
In the first invention,
The amorphous element around which the detection coil is wound and the signal conversion circuit are disposed in a package disposed in the magnetic shield.
Things.
[0015]
The current sensor according to the present invention (third invention according to claim 3)
In the second invention,
The detected wire is disposed in a spacer made of an insulating material disposed in the magnetic shield with a flat surface abutting on a flat surface of the package,
The magneto-inductive magnetic detector is disposed between the detected electric wire and a wall surface of the magnetic shield where the air gap is formed or a wall surface facing the wall surface where the air gap is formed.
Things.
[0016]
Function and Effect of the Invention
The current sensor according to the first invention having the above-described configuration corresponds to a magnetic field caused by a current flowing through the detected electric wire in the magnetic shield in which the magnetic distribution controlled by the gap formed in the surrounding shield wall is formed. Since the change in the internal magnetic field of the amorphous element is converted into a voltage by the detection coil by electromagnetic induction and detected as a voltage signal, the magnetic field distribution inside the magnetic shield is controlled by the gap formed in the surrounding shield wall. This makes it possible to achieve an optimum magnetic field strength at a desired position for the magneto-inductive magnetic detector, and to realize a current sensor that can measure a large current or a small current.
[0017]
A current sensor according to a second aspect of the present invention is the current sensor according to the first aspect, wherein the amorphous element around which the detection coil is wound and the signal conversion circuit are disposed in a package disposed in the magnetic shield. Since the distance between the amorphous element and the detected electric wire is accurately maintained, a stable and highly accurate large current can be measured, and the voltage signal detected in the magnetic shield is converted. This has the effect of enabling stable signal conversion.
[0018]
A current sensor according to a third aspect of the present invention is the spacer according to the second aspect, wherein the wire to be detected is made of an insulating material disposed in the magnetic shield with a flat surface abutting against a flat surface of the package. And the magneto-inductive magnetic detector is disposed between the detected electric wire and a wall surface of the magnetic shield in which the gap is formed or a wall surface facing the wall surface in which the gap is formed. Since the distance between the amorphous element and the detected electric wire is accurately maintained, an effect of enabling a stable and highly accurate measurement of a large current or a small current is achieved.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0020]
(1st Embodiment)
As shown in FIGS. 1 to 4, the current sensor according to the first embodiment flows through a detected electric wire 1 which is a measurement target and is disposed in a magnetic shield 2 including an enclosing shield wall 20 for blocking an external magnetic field. A current sensor that outputs a voltage signal corresponding to a current flowing through the detected wire 1 based on a magnitude of an acting magnetic field in a magnetic field in the magnetic shield 2 generated by a current. An amorphous element 31 disposed at a position where a linear relationship of output with respect to a magnetic field generated by a flowing current is maintained and an internal magnetic field changes in accordance with a surrounding magnetic field; and an amorphous element 31 wound around the amorphous element 31. The detection coil 32 and the detection coil which constitute the magneto-inductive magnetic detector 3 by converting a change in the internal magnetic field into a voltage by electromagnetic induction And a signal conversion circuit 33 for converting the voltage of the magnetic shield 2 into a voltage signal corresponding to the current flowing through the detected electric wire. The air gap 21 for controlling the magnetic distribution formed in the magnetic shield 2 is provided in the magnetic shield 2. 2 is formed on the surrounding shield wall 20 of the upper wall surface 201 in a slit shape, and the magneto-inductive magnetic detector 3 is a wall surface on which the gap 21 is formed between the detected electric wire 1 and the magnetic shield 2. Is disposed between the lower wall surface 202 and the lower wall surface 202 facing the lower surface.
[0021]
As shown in FIGS. 1 and 2, the magnetic shield 2 has a high magnetic permeability such as permalloy having four rectangular cross-sectional surfaces of an upper wall surface 201, a lower wall surface 202, and both side wall surfaces 203 and 204 for blocking an external magnetic field. An air gap 21 for controlling a magnetic distribution formed in the magnetic shield 2 is formed by an enclosing shield wall 20 made of a material, and the entire length of the upper wall surface 201 of the enclosing shield wall 20 of the magnetic shield 2 in the longitudinal direction is formed. Is formed in a slit shape.
[0022]
The surrounding shield wall 20 is, for example, 0.5 mm thick, the width of the inner wall of the upper surface 201 and the lower surface 202 is 4 mm, the height of the inner wall of the left and right side surfaces 203 and 204 is 4 mm, and the length of the upper surface 201 is The gap 21 formed in a slit shape over the entire length in the direction, that is, the gap in the left-right direction in FIG. 2 is 0.5 mm.
[0023]
In order to explain the principle of the current sensor arranged in the magnetic shield 2 in which the gap 21 is formed, a magnetic field analysis by a computer performed to clarify a magnetic field distribution formed in the magnetic shield 2 Now that the magnetic field distribution shown in FIG. 2 has been clarified, it will be described with reference to FIG.
[0024]
As is clear from FIG. 2, a magnetic field distribution which is axisymmetric with respect to a straight line connecting the center of the gap 21 and the axis of the detected electric wire 1 is shown. An opening is formed on the upper wall surface 201 in which the gap 21 is formed, and is substantially U-shaped including the detected electric wire 1. The lower wall surface 202 of the detected electric wire 1 and the shield 2 facing the gap 21 of the shield 2. As the magnetic field in the interposed space moves away from the detected electric wire 1 having a magnetic field strength of 10 toward the lower wall surface 202 of the shield 2, the magnetic field strength increases as compared with the conventional case shown in FIG. Attenuates, and the magnetic field near the shield wall becomes practically close to 0 Gauss.
[0025]
In the first embodiment, the state in which the magnetic field is greatly attenuated is that the magnetic field strength from the detected electric wire 1 to the lower wall 202 of the shield 2 is distributed from 10 to 1 in FIG. Can be understood from
[0026]
As shown in FIG. 3, the current sensor according to the first embodiment operates in a magnetic field located at a distance L from the axis of the detected electric wire 1 generated by a current flowing through the detected electric wire 1 to be measured. This is a current sensor that outputs a voltage signal corresponding to the current flowing through the detected electric wire 1 based on the magnitude of the magnetic field B being applied.
[0027]
A gap 21 is formed in the shield 2 for suppressing magnetic saturation caused by current, and is housed inside the magnetic shield 2 having a substantially rectangular cross section and made of a cylindrical high magnetic permeability material. A position where the linear relationship of the output in the magnetic field generated by the flowing current is maintained and within a range of a predetermined magnetic field strength and is disposed in parallel with the direction of the magnetic field, and is arranged in accordance with the surrounding magnetic field due to the detected current. The magneto-inductive magnetic detector 3 is composed of an amorphous element 31 having a diameter of, for example, 30 μm and a length of 3 mm or less, which is wound around the amorphous element 31 and converts a change in the internal magnetic field of the amorphous element into a voltage by electromagnetic induction. And a signal conversion circuit for converting the voltage of the detection coil 32 and the voltage of the detection coil It is made of 33.
[0028]
As shown in FIG. 1, the current sensor according to the first embodiment has an axis perpendicular to the axial direction of the detection wire 1 so that the magnetic field below the detection target wire 1 can be detected with maximum sensitivity. And the signal conversion circuit 33 connected to the detection coil 32. The detection coil 32 detects changes in the internal magnetic field of the amorphous wire 31 by electromagnetic waves. It constitutes a magneto-inductive magnetic detector 3 which converts a voltage into a voltage by induction.
[0029]
As shown in FIG. 4, the signal conversion circuit 33 in the current sensor according to the first embodiment is configured such that the pulse generator 310 composed of a logic circuit is connected to the amorphous element 31 and the analog switch 321 of the detection circuit 320 by P1 and P2, respectively. Output a synchronized pulse. These two pulses are generated in the order of P1 and P2 and are repeated at a frequency of, for example, 1 MHz, so that the measurement of the magnetic field is performed at a frequency of 1 MHz.
[0030]
When a pulse P1 is generated and a pulse current P1 is applied to the amorphous element 31, a peripheral magnetic field generated by the pulse current P1 and the current flowing through the detected electric wire 1 on which the amorphous element 31 is placed is applied to the amorphous element 31. , An internal magnetic field change occurs. At this time, a voltage corresponding to the change in the internal magnetic field is generated in the detection coil 32 by the electromagnetic induction.
[0031]
When the analog switch 321 of the detection circuit 320 constituting the signal conversion circuit 33 is momentarily closed, the capacitor C321 constituting the sample and hold circuit holds this voltage. An amplifier 330 composed of an operational amplifier amplifies the voltage of the detection circuit 320 and outputs a voltage signal corresponding to a current to be measured to an output terminal.
[0032]
The current sensor according to the first embodiment having the above-described operation is provided in the magnetic shield 2 in which the magnetic distribution controlled by the air gap 21 formed in the surrounding shield wall 20 of the shield 2 is formed. Since the change in the internal magnetic field of the amorphous element 31 corresponding to the magnetic field caused by the current flowing through the detection wire 1 is converted into a voltage by the detection coil 32 by electromagnetic induction and detected as a voltage signal, the change is formed on the surrounding shield wall 20. By controlling the magnetic field distribution inside the magnetic shield 2 by the gap 21 thus made, it is possible to realize an optimum magnetic field strength at a desired position for the magneto-inductive magnetic detector 3 and to realize a large current or minute current. This has the effect of realizing a current sensor that enables current measurement.
[0033]
Further, in the current sensor of the first embodiment, since the gap 21 is formed in the shield 2, the magnetic shield 2 is prevented from being magnetically saturated even when a large current flows through the detected wire 1 by the gap 21. Therefore, there is an effect (first effect) that the disturbance magnetism, which is an original purpose of the shield, can be blocked to prevent noise from being mixed.
[0034]
Further, in the current sensor of the first embodiment, the magnetic field in the space between the lower wall surface (side) 202 facing the upper wall surface 201 of the shield 2 provided with the gap 21 and the electric wire 1 to be detected is: As the distance from the electric wire 1 toward the shield lower wall surface 202 increases, the strength of the magnetic field is greatly attenuated as compared with the conventional case, and the magnetic field near the shield wall surface can be made practically close to 0 Gauss. As can be seen from the fact that the magnetic field strength between the electric wire 1 and the shield wall surface 202 is distributed from 10 to 1 in FIG. 2, as shown in FIG. The numerical value indicating the weakest magnetic field level near the shield wall surface is 6, whereas FIG. 2 showing the magnetic field distribution in the first embodiment further lowers the magnetic field level. The effect (second effect) that can be made.
[0035]
According to the above-described second effect, a predetermined magnetic field strength can be obtained in a shield of a predetermined size without increasing the size of the magnetic shield 2, thereby realizing a small-sized high-current sensor. Is what makes it possible.
[0036]
In addition, the current sensor of the first embodiment can widely create a region of the strongest magnetic field around point d in FIG. 2, that is, in the space between the electric wire 1 and the gap 21 of the magnetic shield. In the case of the conventional shield having no air gap, the region where the magnetic field is strongest is limited to the vicinity of the wire W to be detected, whereas in FIG. As can be understood from the fact that the level of the magnetic field strength is 10 which is the highest in a wide area of 1/4 or more of the entire area up to the air gap, the magneto-inductive magnetic detector 3 is mechanically moved without approaching the electric wire 1. There is an effect (third effect) that a region of a strong magnetic field can be distributed at a position where there is no interference, and a small current sensor can be realized.
[0037]
In the current sensor according to the first embodiment, as described above, the magnetic shield 2 is not magnetically saturated even if the detected wire 1 flows a current due to the first effect of the gap 21 of the magnetic shield 2 as described above. A magnetic-inductive magnetic detector 3 can be installed inside the magnetic shield 2 without increasing the size of the magnetic shield 2 by the second effect described above. In order to realize a magnetic field of a predetermined strength that does not occur, an effect of realizing a small and highly accurate current sensor is achieved.
[0038]
(2nd Embodiment)
In the current sensor according to the second embodiment, as shown in FIGS. 5 to 8, the magneto-inductive magnetic detector 3 is housed in a package 40, and a flat surface on the upper surface of the package 40 is sandwiched between spacers made of an insulating material. In the structure, the detected electric wire 14 is abutted, and the detected electric wire 14 and the magnetic detector 24 are set at a predetermined distance stably and accurately, and the periphery of the magnetic detector 3 and the detected electric wire 14 is A magnetic shield 2 having a gap formed by coating with a high magnetic permeability material, wherein the magnetic detector 3 is disposed between the detected electric wire 1 and the inner wall surface of the magnetic shield 2 having no gap. There is a feature.
[0039]
The magnitude of the magnetic field due to the measured current detected by the amorphous element is attenuated as the distance from the detected wire increases, as is apparent from the description using FIG.
That is, if the distance between the detected electric wire and the amorphous element fluctuates, the sensitivity as a current sensor will vary.
[0040]
In the second embodiment, as shown in FIGS. 5 and 6, a small rectangular package 40 accommodating the magneto-inductive magnetic detector 3 including an amorphous element 34 wound with a detection coil and a signal conversion circuit 35. The electric wire 14 to be detected and the magneto-inductive magnetic detector 3 are arranged by a holder 142 which is formed integrally with the electric spacer 14 for arranging the electric wire 14 with the insulating spacer 141 in contact with the flat surface S40 of the upper surface of the electric wire. Can be easily and stably arranged at a predetermined distance with high precision, and by covering the periphery with a magnetic shield having a gap made of a high magnetic permeability material as described above, there is no noise contamination and high accuracy and mechanically It is intended to make a stable current sensor an inexpensive product.
[0041]
That is, the magnetic detector according to the second embodiment is a small package provided with a plurality of IC electrodes 55 by forming an amorphous wire 34 wound with a detection coil and a signal conversion circuit 35 into an IC as shown in FIG. It is constituted by an IC-type magneto-inductive magnetic detector 3 housed in 40.
[0042]
In FIG. 6, the contact surface S141 of the spacer 141 to be contacted is illustrated separately from the surface S40 of the package 40 for easy description.
In the sectional view of FIG. 6, the upper part 201 of the magnetic shield 2, which is divided into two parts, an upper part 201 and a lower part 202, is not shown directly above the detected wire 14 in parallel with the detected wire. Are formed with voids 21. FIG. 7 is a cross-sectional view of the detecting wire 14 in FIG. 8 viewed from the axial direction to show the position of the gap.
[0043]
FIG. 8 is an electric circuit of a specific signal converter of the IC type magneto-inductive magnetic detector 3, which is basically the same as the circuit in the first embodiment, but is used for an automobile. Is different from that of the first embodiment in that a reference potential generation circuit including resistors R331 and R332 provided so as to operate with a single-pole power supply is added.
[0044]
In the current sensor according to the second embodiment having the above configuration, the spacer 141 sandwiched between the detected electric wire 14 and the IC-type magneto-inductive magnetic detector 3 is integrated with the holder 142 that holds the detected electric wire 14. By making the contact surface S141 of the spacer 141 into contact with one surface S40 of the IC magnetic detector 24, the electric wire 14 to be detected and the amorphous wire 34 built in the IC magnetic detector 24 are formed. There is an effect that the distance can be easily and stably and accurately set.
[0045]
In the current sensor according to the second embodiment, both the IC type magnetic detector 3 and the holder 142 are covered and fixed with a plate 143 made of a high magnetic permeability material, and are magnetically shielded by the action of the high magnetic permeability material. At the same time, high accuracy is achieved by eliminating a magnetic field such as geomagnetism which becomes noise, so that an effect of realizing a high-precision current sensor free from noise mixing is achieved.
[0046]
Furthermore, since the current sensor of the second embodiment uses the IC-type magneto-inductive magnetic detector 3 as described above, it is possible to manufacture a high-precision and stable large-current sensor without noise contamination at low cost. It works.
[0047]
(Third embodiment)
As shown in FIGS. 9 and 10, the current sensor according to the third embodiment provides the magnet 21 with the gap 21 provided in the upper portion 201 of the magnetic shield 2 in the lower portion 202 in the second embodiment. The inductive magnetic detector 3 is disposed between the detected electric wire 14 and the magnetic shield wall surface having a gap, and the means 335 for applying magnetic feedback to the amorphous element 31 of the magneto-inductive magnetic detector 3 The provision is different from the above embodiment.
[0048]
FIG. 9 is a cross-sectional view of the detected electric wire 14 as viewed from the axial direction. FIG. 9 shows a state in which the detecting electric wire 14 is generated between the gap 21 formed in the lower surface 202 of the magnetic shield 2 and the detecting electric wire 14. In a region where the magnetic field to be distributed is most strongly distributed, one flat surface S40 of a small rectangular parallelepiped package 40 in which the integrated magneto-inductive magnetic detector 3 is accommodated is detected with an insulating spacer 141 interposed therebetween. The electric wire 14 to be detected and the magneto-inductive magnetic detector 3 are held at a predetermined distance by a holder 142 formed integrally with the spacer for contacting the electric wire 14.
[0049]
FIG. 10 shows an electric circuit of the signal conversion circuit 35 of the IC-type magneto-inductive magnetic detector 3, which is basically the same as the circuit shown in FIG. 8, but in order to further improve the accuracy of the magnetic field measurement. The difference is that a feedback circuit 335 including a negative feedback coil 32a newly wound around the amorphous wire 31 is added.
[0050]
In the current sensor according to the third embodiment, the electric wire to be detected is formed by a holder 142 that is integrated with the electric wire 14 to be in contact with the electric wire 14 to be in contact with the insulating spacer 141 that is in contact with the flat surface S40 of the package 40. 14 and the magneto-inductive magnetic detector 24 are maintained at a predetermined distance, so that they can be easily and stably and accurately set, and as described above, high sensitivity can be obtained by capturing a small current as a strong magnetic field by the third effect. The present invention has the effect that a current sensor that is highly accurate and mechanically stable without noise contamination can be manufactured as an inexpensive product.
[0051]
Further, in the current sensor according to the third embodiment, as shown in FIG. 10, the feedback circuit 335 including the resistor R335 connected to the output terminal of the amplifier 330 and the negative feedback coil 32a does not need to apply any magnetic field. Since a negative feedback current is applied so that the internal magnetic field of the amorphous wire 31 is always zero, the operating point of the amorphous element 31 is not changed by the negative feedback. It has the effect of making it possible.
[0052]
The above-described embodiment has been described by way of example, and the present invention is not limited to the embodiment. It will be recognized by those skilled in the art from the claims, the detailed description of the invention, and the drawings. Modifications and additions are possible without violating the technical idea of the present invention.
[0053]
For example, in the above embodiment, the position of the electric wire is arranged substantially at the center of the shield, and the cross-sectional shape of the magnetic shield is shown as a square. The shape can be changed to an elliptical shape, an oval shape, a petal shape having a wavy or other irregular shape, a polygonal shape, or any other cross-sectional shape according to the shape required for the current sensor, and the arrangement of the detected electric wire in the shield. The position is not limited to the center and the center, but may be arranged at a position eccentric from the center or a position near the periphery as necessary.
[0054]
The first modification of the second embodiment described above is provided with current range switching in order to expand the range of current that can be measured. As shown in FIG. 11 showing a cross section and FIG. The detected electric wires 14a, 14b, and 14c to be energized according to the magnitudes of the three levels of current to be measured are selected and used.
[0055]
In order for each current flowing through the wires 14a, 14b, 14c to have a predetermined value of the strength of the magnetic field applied to the magneto-inductive magnetic detector, the detected wires of the wires 14a, 14b, 14c are connected to the holder 142 and The spacer 141 enables the magnet-inductive magnetic detector to be stably disposed at a predetermined distance from the magneto-inductive magnetic detector, and the magnet-inductive magnetic detector and the electric wire stored in the package 40 as the current increases. Distance is great.
[0056]
The second modification of the above-described second embodiment is an example embodied as a device that can easily measure a current without cutting an existing electric wire that is energized, that is, an electric wire to be detected, as shown in FIG. is there.
[0057]
That is, the shield 2 is divided into two members 222 and 223 that can relatively swing, and one of the shields 222 having the air gap 221 and the holder 142 made of a viscoelastic material are combined with the pinch mechanism 150 made of a nonmagnetic material. A package 40 including a magneto-inductive magnetic detector and a spacer 141, which is attached to one arm 151a and electrically wired to a printed circuit board 145 disposed on the other shield 223, is provided on the other side of the pinch mechanism. Of the arm 151b. The spacer 141 is an insulator having a groove having a concave cross section, and the groove 141a is for always bringing the detected electric wire 14 into contact at a stable position.
[0058]
The resilient force of the spring 153 inserted between the handles 152a, 152b of the pinch mechanism 150 causes the swinging arms 151a, 151b of the pinch mechanism to approach each other, and receives the force from the viscoelastic holder 142. Abuts on the groove 141a of the spacer. As a result, the electric wire and the magneto-inductive magnetic detector are always stably maintained at a predetermined distance.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a current sensor according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram for explaining a magnetic field distribution in a magnetic shield of the current sensor according to the first embodiment.
FIG. 3 is an explanatory diagram for explaining the principle of magnetic field measurement in the current sensor according to the first embodiment.
FIG. 4 is a circuit diagram showing an electric circuit in the current sensor according to the first embodiment.
FIG. 5 is a plan view showing a package containing an IC-type magneto-inductive magnetic detector 3 in the current sensor according to the second embodiment of the present invention.
FIG. 6 is a longitudinal sectional view showing a current sensor according to the second embodiment.
FIG. 7 is a cross-sectional view illustrating a current sensor according to the second embodiment.
FIG. 8 is a circuit diagram showing an electric circuit in the current sensor according to the second embodiment.
FIG. 9 is a cross-sectional view illustrating a current sensor according to a third embodiment of the present invention.
FIG. 10 is a circuit diagram showing an electric circuit in the current sensor according to the third embodiment.
FIG. 11 is a cross-sectional view showing a current sensor according to a first modification of the second embodiment.
FIG. 12 is a longitudinal sectional view showing a current sensor according to a first modification of the second embodiment.
FIG. 13 is a cross-sectional view illustrating a main part of a current sensor according to a second modification of the second embodiment.
FIG. 14 is a sectional view showing a conventional current sensor.
FIG. 15 is an explanatory diagram for explaining a magnetic field distribution in a magnetic shield of a conventional current sensor.
[Explanation of symbols]
1 Electric wire to be detected
2 Magnetic shield
20 Siege shield wall
21 void
201 Upper wall
202 Lower wall
3 magneto-inductive magnetic detector
31 Amorphous element
32 detection coil
33 signal conversion circuit

Claims (3)

In the magnetic field in the magnetic shield generated by the current flowing through the electric wire to be measured disposed in the magnetic shield formed of the surrounding shield wall for blocking the external magnetic field, the magnetic field in the magnetic shield is determined by the magnitude of the acting magnetic field. A current sensor that outputs a voltage signal corresponding to a current flowing through a detection wire,
An amorphous element is disposed at a position where a linear relationship of output is maintained with respect to a magnetic field generated by a current flowing through the detected wire, and an internal magnetic field changes in accordance with a surrounding magnetic field;
A detection coil which forms a magneto-inductive magnetic detector by converting a change in the internal magnetic field of the amorphous element into a voltage by electromagnetic induction by winding the amorphous element, and the voltage of the detection coil corresponds to the current flowing through the electric wire to be detected. And a signal conversion circuit that converts the voltage signal into
A current sensor, wherein a gap for controlling a magnetic distribution formed in the magnetic shield is formed in the surrounding shield wall of the magnetic shield. In claim 1,
A current sensor, wherein the amorphous element around which the detection coil is wound and the signal conversion circuit are disposed in a package disposed in the magnetic shield. In claim 2,
The detected wire is disposed in a spacer made of an insulating material disposed in the magnetic shield with a flat surface abutting on a flat surface of the package,
Wherein the magneto-inductive magnetic detector is disposed between the detected electric wire and a wall surface of the magnetic shield in which the gap is formed or a wall surface facing the wall in which the gap is formed. Current sensor.

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