JP2005249678A - Sensor for sensing conductor defective in electric wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a simple operation by which a defect is sensed from changes in a round circuit magnetic field distribution within a substantially narrow range, in the case a conductor element defective in one of twisted conductors in an electric wire is sensed from the changes in the round circuit magnetic field distribution on the basis of current flowing the twisted conductors, with respect to the round circuit magnetic field distribution of nondefective conductor elements. <P>SOLUTION: A change in the round circuit magnetic field distribution of a region isolated from a defective region, or a change in the round circuit magnetic field distribution in a range of approximate one pitch of twists in the twisted conductors is detected. In a sensor to be used, for example, two magnetic impedance effect elements are arranged around the electric wire at equal distances from the center of the electric wire so as to be spaced from each other through 180 degrees and connected in series so that their polarities become reverse to each other in their magnetically sensitive directions and so that their magnetically sensitive directions are perpendicular to a circumference being concentric with the electric wire. Sensor outputs are output from the magnetic impedance effect elements connected in series. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a sensor used to detect a defect in a stranded conductor of an electric wire, and a sensor useful for detecting defects such as disconnection, scratches, non-conductors, and deterioration due to stress corrosion cracking in an energized / hot line state. It is.

As one of the methods for detecting defects (defects) such as disconnection, scratches, non-conductivity, and deterioration such as stress corrosion cracking, the actual load current is disturbed in the defective part, and the magnetic field generated thereby Methods for detecting changes are known.
When a defect occurs in the stranded conductor of the electric wire, the contour of the conductor cross section at that point is made non-circular, and the current path center of the cross section is shifted. As a result, the distribution of the circumferential circuit magnetic field based on the conductor current changes.
In view of this, it has been proposed to detect a defect in the stranded conductor by detecting the change in the circumferential circuit magnetic field distribution and the center displacement of the current path cross section. (Patent Document 1, Non-Patent Document 1)

Japanese Patent Laid-Open No. 10-73631 Takashi Nonaka and two others, “Fundamental study on non-destructive magnetic flaw detection of distribution lines” T, IEEEjapan, Vol, 121-A, No. 3,2001, p282-287

In Patent Document 1, as shown in FIG. 11, search coils 1o and 1o ′ are arranged around the electric wire at a position equidistant from the center of the electric wire by a plurality of pairs separated by 180 °, and the search coil core direction and the electric wire are arranged. The tangential direction of the concentric circles is matched, and the difference between the outputs of both search coils of each pair is used as the sensor output.
In FIG. 11, when the displacement of the center of the current path cross section of the stranded wire conductor is zero, that is, there is no change in the circumferential circuit magnetic field distribution, the outputs of both coils are equal and the sensor output is 0, and it is evaluated that there is no defect. When the peripheral circuit magnetic field distribution change occurs, the outputs of both coils are not equal and a sensor output is generated, and it is determined that there is a defect.

任意座標点ｐ1(x1,y1)における磁束密度(Ｂｘ1，Ｂy1)及びｐ1(x2,y2)における磁束密度(Ｂｘ2，Ｂy2)をサーチコイルにより測定し、これらの測定値から電流路断面の中心座標Ｃ1(Cx1,Cy1)を計算し、この中心座標の変位から撚線導体の欠陥を評価しようとしている。 In Non-Patent Document 1, as shown in FIG. 12, the center C1 (Cx1, Cy1) of the current path cross section has arbitrary coordinate points p1 (x1, y1) and p2 (x2, y2) and these arbitrary coordinate points p1 (x1, y1). ) And p2 (x2, y2) and magnetic flux densities (Bx1, By1) and (Bx2, By2) are given by the following equation, that is, the center C1 (Cx1, Cy1) of the current path cross section as shown in FIG. Are arbitrary coordinate points p1 (x1, y1) and p2 (x1, y1) and magnetic flux densities (Bx1, By1) and (Bx2, By2) at these arbitrary coordinate points p1 (x1, y1) and p2 (x2, y2). From that given by

The magnetic flux density (Bx1, By1) at the arbitrary coordinate point p1 (x1, y1) and the magnetic flux density (Bx2, By2) at p1 (x2, y2) are measured by the search coil, and the center coordinates of the current path cross section are obtained from these measured values. C1 (Cx1, Cy1) is calculated, and the defect of the stranded conductor is to be evaluated from the displacement of the central coordinates.

When the conductor current is I, the magnetic flux density B at a distance r from the conductor center is
B = μ ₀ I / (2πr)
If the deviation distance of the conductor center is ΔL, the magnetic flux density change ΔB is ΔB∝BΔL / r.
A current of several tens of A to several hundreds of A is passed through the wired wire, and the magnetic flux density on the outer periphery of the wire is extremely high. For example, if the current value is 150 A and the wire radius is 15 mm, the magnetic flux density on the wire surface is as high as 1600 A / m. A magnetic field sensor such as a search coil has a measurement limit, and it is difficult to measure a magnetic field as high as 1600 A / m.

However, in the above-described conventional example, the search coil is arranged with its magnetic sensing direction directed to the direction of the circumferential circuit magnetic field of the electric wire. It is necessary to arrange them at positions that are considerably separated, and an increase in the size of the sensor is inevitable.
Furthermore, in the conventional example described in Patent Document 1, two search coils are arranged around the electric wire at positions spaced equidistant from the center of the electric wire in pairs separated by 180 °, and the current center of the conductor path cross section of the stranded wire conductor is arranged. The output difference between the two search coils at the time of deviation is used as the sensor output. As can be understood from the above ΔBΔBΔL / r, if the search coil is arranged at a position far away from the center of the wire and r is increased, only that The output difference between the two search coils is reduced, the sensor output is reduced, and it is difficult to guarantee sufficient detection sensitivity.

  Recently, magneto-impedance effect elements have been developed as magnetic field sensor elements with high magnetic field detection resolution and micro dimensions.

  An object of the present invention is to provide a sensor used in a method for detecting a defect in a conductor of a wire from a change in distribution of a peripheral circuit magnetic field based on the conductor current of the wire with respect to a reference peripheral circuit magnetic field when there is no conductor defect. The purpose is to improve the detection accuracy and miniaturization of the sensor using an impedance effect element.

  The sensor for detecting a defect in a conductor of an electric wire according to claim 1 is configured such that a defect in any conductor wire of a twisted conductor in an electric wire is detected when there is no wire defect in a peripheral circuit magnetic field based on an energization current of the twisted conductor. A sensor used in a method for detecting a change in distribution with respect to a circuit magnetic field, spaced at an angle of 180 ° around the wire and equidistant from the center of the wire, and the direction of magnetic sensing is perpendicular to the circumference concentric with the wire. Two pairs of magneto-impedance effect elements were arranged at a predetermined angle in the circumferential direction of the electric wire, and the paired magneto-impedance effect elements were connected in series so that the magnetosensitive direction was opposite in polarity. The sensor output is characterized by adding or superimposing outputs from the series-connected magneto-impedance effect elements.

  The sensor for detecting a conductor defect of an electric wire according to claim 2 is configured to detect a defect of any conductor wire of the twisted conductor in the electric wire when there is no wire defect of a peripheral circuit magnetic field based on an energization current of the twisted conductor. A sensor used in a method for detecting a change in distribution with respect to a circuit magnetic field, spaced at an angle of 180 ° around the wire and equidistant from the center of the wire, and the direction of magnetic sensing is perpendicular to the circumference concentric with the wire. Two pairs of magneto-impedance effect elements were arranged at a predetermined angle in the circumferential direction of the electric wire, and the paired magneto-impedance effect elements were connected in series so that the magnetosensitive direction was opposite in polarity. The output from the series-connected magneto-impedance effect element is subtracted or differentially amplified to obtain a sensor output.

  According to a third aspect of the present invention, there is provided a sensor for detecting a conductor defect of an electric wire, wherein a defect of any conductor wire of the twisted conductor in the electric wire is detected when there is no wire defect of a peripheral circuit magnetic field based on an energization current of the twisted conductor. A sensor used in a method for detecting a change in distribution with respect to a circuit magnetic field, spaced at an angle of 180 ° around the wire and equidistant from the center of the wire, and the direction of magnetic sensing is perpendicular to the circumference concentric with the wire. Two pairs of magneto-impedance effect elements are arranged at a predetermined angle in the circumferential direction of the wire, and one of the magneto-impedance effect elements of a different pair is connected in series so as to have the same polarity or opposite polarity, Similarly, the other magneto-impedance effect element is connected in series so as to have the same polarity or opposite polarity, and both the series-connected magneto-impedance effect elements are set to have opposite polarities. The output of scan effect element addition or superposition to is characterized in that as a sensor output.

  According to a fourth aspect of the present invention, there is provided a sensor for detecting a conductor defect of an electric wire, wherein a defect of a conductor wire of any of the twisted conductors in the electric wire is detected when there is no wire defect of a peripheral circuit magnetic field based on a current flowing through the twisted conductor. A sensor used in a method for detecting a change in distribution with respect to a circuit magnetic field, spaced at an angle of 180 ° around the wire and equidistant from the center of the wire, and the direction of magnetic sensing is perpendicular to the circumference concentric with the wire. Two pairs of magneto-impedance effect elements are arranged at a predetermined angle in the circumferential direction of the wire, and one of the magneto-impedance effect elements of a different pair is connected in series so as to have the same polarity or opposite polarity, Similarly, the other magneto-impedance effect element is connected in series so as to have the same polarity or opposite polarity, and both the series-connected magneto-impedance effect elements are set to have opposite polarities. The output of scan effect element by subtracting or differential amplifier, characterized in that as the sensor output.

  Changes in the circumferential circuit magnetic field distribution of the wire are detected from the magnetic field component perpendicular to the circumferential direction of the concentric circle with the wire, and this detected magnetic field component is sufficiently smaller than the circumferential magnetic field in the vicinity of the wire and within the measurement limits. The sensor element can be disposed close to the outer periphery of the electric wire, and the sensor can be miniaturized. The high detection capability of the magneto-impedance effect element and the removal of external noise by the pair arrangement of the magneto-impedance effect element separated by 180 ° or the removal of internal and external noise by using a differential amplifier circuit or a subtraction circuit are high. Sensitivity can be detected, and the change in the circumferential circuit magnetic field distribution at the separated location can be detected with high sensitivity.

FIG. 1 shows an example of an electric wire to be subjected to conductor defect detection according to the present invention. A synthetic resin c such as polyethylene or polyvinyl chloride is placed on a twisted conductor b obtained by twisting a conductor wire a such as a hard copper wire. Extrusion coated.
It is assumed that a defect has occurred in any conductor wire of the twisted conductor of this electric wire. Assuming that the contact resistance between the strands is high enough to completely interrupt the current conduction between the strands, the deviation of the current center of the conductor cross section due to the defect occurs over the entire length of the wire, and therefore A change in the circumferential circuit magnetic field distribution based on the conductor current occurs over the entire length of the wire.
In FIG. 2, the strength H of the reference peripheral circuit magnetic field at the distance r from the wire center o when no deviation of the current center of the conductive path cross section occurs.

  H = I / (2πr)

Given in.
1a and 1a ′ are magneto-impedance effects in which the distance from the center of the wire is r and they are separated by 180 ° on a circle concentric with the center of the wire, and the axial direction (maximum magnetosensitive direction) is a direction perpendicular to the concentric circle. The element is shown and is not sensitive to the reference circuit magnetic field. If the angle between the axial direction of the magneto-impedance effect element and the direction of displacement is α and the displacement distance is ΔL,

x ² = r ² + (ΔL) ² −2r · ΔL cos α
sinγ / ΔL = sinα / x

And the magnetosensitive component of the magneto-impedance effect element 1a at the circumferential circuit magnetic field strength H ′ = I / (2πx) at the distance x under the conductive path cross-sectional center o ′, that is, the maximum magnetosensitive direction component ha. Is

  ha = H’sinγ

Given in.
When ha is obtained from the above equations,

[Formula 1] ha≈H (ΔL / r) sin α / [1-2 (ΔL / r) cos α]

Is established.
The magnetosensitive component ha ′ of the other magneto-impedance effect element 1a ′ takes into account that α is (π + α) in the ha and the direction of the circumferential circuit magnetic field is opposite.

[Formula 2] ha′≈H (ΔL / r) sin α / [1 + 2 (ΔL / r) cos α]

Given in.

For the magneto-impedance effect elements 1a and 1a ′ forming the above pair, as shown by 1b and 1b ′, a pair similar to the above is disposed at a position separated by an angle β in the circumferential direction,
The magnetosensitive component hb due to the change in the distribution of the peripheral circuit magnetic field of the added magneto-impedance effect element 1b is given by setting α as (α + β) in the ha.

[Formula 3] hb≈H (ΔL / r) sin (α + β) / [1-2 (ΔL / r) cos (α + β)]
Is established.
The magnetosensitive component hb ′ of the other magneto-impedance effect element 1b ′ is given by placing (α + β) as [π + (α + β)] in hb.

[Formula 4] hb′≈H (ΔL / r) sin (α + β) / [1 + 2 (ΔL / r) cos (α + β)]

Is established.

  The present invention detects a small magnetosensitive component in a direction perpendicular to the circumferential circuit magnetic field caused by a change in the circumferential circuit magnetic field distribution with high detectability of the magneto-impedance effect element, and reverses the polarity of the magneto-sensitive direction of the paired magneto-impedance effect element. Or by subtraction or in-phase cancellation in differential amplification to detect noise with a high sensitivity and detect a change in the circumferential circuit magnetic field distribution based on the conductor defect. It is possible to detect changes in the distribution of the magnetic field of the peripheral circuit even at locations far away from each other.

FIG. 3 shows a basic configuration of a magnetic sensor using a magneto-impedance effect element.
In FIG. 3, reference numeral 1 denotes a magneto-impedance effect element, which has a zero magnetostriction or a negative magnetostriction having an outer shell portion in which magnetic domains whose spontaneous magnetization directions are opposite to each other in the circumferential direction of the wire are alternately separated by domain walls. An amorphous alloy wire is used. The inductance voltage component in the output voltage between both ends of the wire generated when a high-frequency excitation current is passed through an amorphous magnetic wire having zero magnetostriction or negative magnetostriction is obtained by the circumferential magnetic flux generated in the cross section of the wire. This occurs due to the magnetization of the easily magnetizable outer shell in the circumferential direction. Therefore, the circumferential magnetic permeability mu _theta depends on the circumferential direction of magnetization of Dosotokara portion. Therefore, when a detected magnetic field is applied in the axial direction (maximum magnetosensitive direction) of the energized amorphous wire, the circumferential direction magnetic flux and the detected magnetic field magnetic flux generated by the energization are combined in the circumferential direction. The direction of the magnetic flux acting on the easily magnetized outer shell part is deviated from the circumferential direction, and the magnetization in the circumferential direction is less likely to occur, the circumferential permeability μ _θ changes, and the inductance voltage changes. Will do. This fluctuation phenomenon is called a magnetic inductance effect, which can be said to be a phenomenon in which the high-frequency excitation current (carrier wave) is modulated by a detected wave (signal wave). Further, when the frequency of the energization current is in the order of MHz, a high-frequency skin effect appears greatly, and the skin depth δ = (2ρ / wμ _θ ) ^1/2 (μ _θ is the circumferential permeability, ρ as described above. electrical resistivity, w is shows the angular frequency, respectively) is changed by mu _theta, as the mu _theta is the so changed by the detected magnetic field, the resistance voltage division also be detected magnetic field in the wire between both ends output voltage It will fluctuate with. This fluctuation phenomenon is called a magneto-impedance effect, which can be said to be a phenomenon in which the high-frequency excitation current (carrier wave) is modulated by a detected wave (signal wave).

  In FIG. 3, 2 is a high-frequency power source for applying a high-frequency excitation current to the magneto-impedance effect element, and 3 is a modulation of the high-frequency excitation current (carrier wave) by a detected magnetic field (signal wave) acting in the axial direction of the magneto-impedance effect element. Demodulation circuit for demodulating the modulated wave thus generated, 4 an amplification circuit for amplifying the demodulated wave, 5 an output terminal, 6 a negative feedback coil, and 7 a bias magnetic field coil. For the magneto-impedance effect element 1, an amorphous ribbon, an amorphous sputtered film, or the like can be used in addition to zero magnetostrictive or negative magnetostrictive amorphous wires.

In the magneto-impedance effect element, as described above, the direction of the magnetic flux acting on the outer shell portion that is easily magnetized in the circumferential direction is obtained by combining the circumferential magnetic flux based on the excitation current and the axial magnetic flux due to the detected magnetic field. Due to the deviation from the circumferential direction, the circumferential magnetic permeability μ _θ changes, the inductance is changed, and the impedance is changed by the change of the skin depth of the high frequency skin effect of the circumferential magnetic permeability μ _θ . Accordingly, although even the circumferential direction positional shift phi by the synthesized magnetic field by ± of the detected magnetic field becomes ± phi, the circumferential direction of the magnetic field reduction ratio cos (± phi) is unchanged, the degree of reduction in thus mu _theta is of the detected magnetic field It does not change depending on the direction. Accordingly, the detected magnetic field-output characteristics are substantially bilaterally symmetric with respect to the y axis when the detected magnetic field is on the x axis and the output is on the y axis as shown in FIG. This detected magnetic field-output characteristic is non-linear. With non-linear characteristics, it is difficult to measure with high sensitivity. Therefore, negative feedback is applied by a negative feedback coil to linearize the characteristics as shown in FIG. In FIG. 4B, Δw is a linear range in which the gain A without negative feedback is very large and the gain is determined only by the feedback rate β. However, with this output characteristic, since the polarity of the magnetic field to be detected cannot be determined, a bias magnetic field is applied by the bias coil 7 so that the polarity can be determined as shown in FIG. That is, the characteristic of (b) in FIG. 4 is moved in the negative direction of the x-axis by the bias magnetic field, and the maximum range of the detected magnetic field −Hmax to + Hmax is within the range of the single oblique line region. Further, as shown in FIG. 4D, a linear characteristic passing through the origin is obtained by adjusting the zero point. Therefore, in FIG. 4D, if the detected magnetic field is + He, the output is + Eo, and if the detected magnetic field is -He, the output is -Eo, and the detected magnetic field can be accurately measured based on polarity discrimination. .

As shown in FIG. 5, an operational amplifier (negative feedback path insertion impedance Z ₂ , input side insertion impedance Z ₁ ) in which negative feedback is applied to the inverting input terminal from the output is used to obtain the linear output characteristics capable of discriminating the polarity. You can also In this case, if the resistance inserted in the negative feedback coil is R, the number of turns of the coil is n, the length is L, the gain of the demodulation amplifier B is A, the detected magnetic field is Hex, and the output is Eout,

A >> Z ₁ RL / (Z ₂ n)

Under

Eout = RLZ ₁ Hex / (nZ ₂ ) + VccZ ₁ R / [Z ₂ (Z ₂ + R)]

Is established, and the output characteristics can be shifted in the ± direction of the x-axis by adjusting various constants (Z ₁ , Z ₂ , resistance R, coil turns n, etc.), and the diagonal straight line portion whose polarity can be discriminated by the adjustment Can be positioned within the range of the maximum detected magnetic field ± Hmax, and the linearity output characteristics capable of discriminating the polarity as shown in FIG. 4 (d) can be obtained by adjusting the zero point in the y-axis direction. it can.

  As the high frequency excitation current, a normal high frequency such as a continuous sine wave, a pulse wave, or a triangular wave can be used. As the high frequency excitation current source, for example, a Hartley oscillation circuit, a Colpitts oscillation circuit, a collector tuning oscillation circuit, a base tuning oscillation circuit can be used. In addition to the normal oscillation circuit, a rectangular wave generator that integrates the square wave output of the crystal oscillator through a DC cut capacitor with an integration circuit and amplifies the triangular wave of the integration output with an amplification circuit, and the COMS-IC as an oscillation unit The used triangular wave generator etc. can be used.

  The demodulating circuit includes, for example, a configuration in which a modulated wave is half-wave rectified by an operational amplifier circuit, and this half-wave rectified wave is processed by a parallel RC circuit or an RC low-pass filter to obtain an envelope output of the half-wave rectified wave. A configuration in which the modulated wave is half-wave rectified by a diode and the half-wave rectified wave is processed by a parallel RC circuit or an RC low-pass filter to obtain an envelope output of the half-wave rectified wave can be used.

In the above embodiment, the detected amount is extracted by demodulating the modulated wave. However, the present invention is not limited to this, and the detected amount corresponding to the detected magnetic field is detected from the magnetic field detection signal by the detected magnetic field acting on the magneto-impedance effect element. Any circuit configuration can be used as long as the amount can be extracted.
The negative feedback coil and the bias magnetic field coil can be wound around a magneto-impedance effect element. Further, as shown in FIG. 6, a negative feedback coil and a bias magnetic field coil can be wound around an iron core constituting a magneto-impedance effect element and a loop magnetic circuit.

6 (a) is a side view showing an example of a magnetic impedance effect unit with an iron core, FIG. 6 (b) is a bottom view, and FIG. 6 (c) is a cross-sectional view of FIG. FIG.
In FIG. 6, reference numeral 100 denotes a substrate chip, and for example, a ceramic plate can be used. Reference numeral 101 denotes an electrode provided on one surface of the substrate piece, and includes an element connecting projection 102. This electrode can be provided by printing and baking a conductive paste, for example, a silver paste. 1x is a magneto-impedance effect element connected between the protrusions 102 and 102 of the electrodes 101 and 101 by soldering or welding. As described above, an amorphous wire, amorphous ribbon, sputtered film or the like having zero or negative magnetostriction can be used. 103 is a C-type iron core, 6x is a negative feedback coil wound around the C-type iron core, 7x is also a bias magnetic field coil, and the magneto-impedance effect element 1x and the C-type iron core 103 constitute a loop magnetic circuit. Thus, both ends of the C-shaped iron core 103 are fixed to the other surface of the substrate piece 100 with an adhesive or the like. The iron core material may be a magnetic material having a small residual magnetic flux density. Examples thereof include permalloy, ferrite, iron, amorphous magnetic alloy, magnetic powder mixed plastic, and the like.

7 (a) is a drawing showing an embodiment of a sensor for detecting a conductor defect of an electric wire according to claim 1, and FIG. 7 (b) is a circuit diagram of the sensor.
In FIG. 7, 8 is an electric wire, and 9 is a sensor substrate. The magnetic sensing direction is a direction perpendicular to the circumference concentric with the electric wire at an angle of 180 ° around the electric wire and equidistant from the electric wire center. A pair of magneto-impedance effect elements are arranged in two pairs of a and b with a predetermined angle β in the circumferential direction of the electric wire, and the paired magneto-impedance effect elements 1a, 1a ′ and 1b, 1b ′ are in the magnetosensitive direction. Are connected in series so as to have reverse polarity, and the outputs from the series-connected magneto-impedance effect elements are added or superimposed to form a sensor output. Reference numerals 3a and 3b denote demodulation circuits, and Ad denotes an addition or superposition circuit.
The magneto-impedance effect element 1a is magnetized when the magneto-sensitive component due to the change in the circumferential circuit magnetic field distribution of one magneto-impedance effect element 1a of the pair a is ha and the magneto-sensitive component with respect to external noise such as geomagnetism is Na. The magnetic field strength Ha is Ha = ha + Na.
The magnetic field strength Ha ′ sensed by the other magneto-impedance effect element 1a ′ of the pair a is Ha ′ = − (ha ′ + Na) because the magnetosensitive direction of both elements 1a and 1a ′ is reversed. .
Therefore, the magnetic field strength (Ha + Ha ′) that the magneto-impedance effect element 1a, 1a ′ of the pair a connected in series has a magnetic sensitivity is (Ha + Ha ′) = (ha−ha ′), and noise can be eliminated. The magnetic field strength (Ha + Ha ′) is obtained from the above equations (1) and (2).

(Ha−ha ′) ≈4H (ΔL / r) ² sinαcosα = 2H (ΔL / r) ² sin2α

Given in.
When the magnetosensitive component due to the change in the circumferential circuit magnetic field distribution of one magneto-impedance effect element 1b of the other pair b is hb and the magneto-sensitive component for external noise such as geomagnetism is Nb, the magneto-impedance effect element is magnetosensitive. The magnetic field strength Hb to be applied is Hb = hb + Nb.

The magnetic field strength Hb ′ that the other magneto-impedance effect element 1b ′ of the pair b senses is Hb ′ = − (hb ′ + Nb) because the magnetosensitive direction of both elements is opposite in polarity.
Therefore, the magnetic field strength (Hb + Hb ′) that the magneto-impedance effect elements 1b and 1b ′ of the pair b connected in series are magnetically sensitive is (Hb + Hb ′) = (hb−hb ′), and external noise can be eliminated. The magnetic field strength (Hb + Hb ′) is obtained from the above equations (1) and (2).

(Hb−hb ′) ≈4H (ΔL / r) ² sin (α + β) cos (α + β) = 2H (ΔL / r) ² sin2 (α + β).

  In the embodiment shown in FIG. 7, the polarities of the pair b magneto-impedance effect elements 1a and 1a 'connected in series and the pair b magneto-impedance effect elements 1b and 1b' connected in series are the same. The direction of these magneto-impedance effect elements is set. Therefore, the sensor output Eout is expressed by assuming that the proportionality coefficient of the output characteristic shown in FIG.

Eout = k (ha−ha ′) + k (hb−hb ′) ≈2 kH (ΔL / r) ² [sin2α + sin2 (α + β)]

Given in.
The orientation of the magneto-impedance effect elements 1a and 1a ′ of the pair b connected in series and the polarity of the magneto-impedance effect elements 1b and 1b ′ of the pair b connected in series are reversed. If you want to

Eout = k (ha−ha ′) − k (hb−hb ′) ≈2 kH (ΔL / r) ² [sin2α−sin2 (α + β)]
Is established.
The magnetosensitive amounts (ha−ha ′) and (hb−hb ′) are small because ΔL << r, and the sensor can be downsized. Even if each detected amount (ha−ha ′) and (hb−hb ′) is small, the output of each series-connected element can be increased for the high detection resolution of the element because of the high detection resolution of the magneto-impedance effect element. Highly accurate detection is possible.
Therefore, even if the deviation ΔL of the current center of the conductor path cross section of the conductor becomes small from the conductor defective portion of the electric wire, it can be detected because of its high sensitivity, and the magnetic field at a location several tens of meters away from the conductor defective portion. Detection can also detect defects.

8A is a drawing showing an embodiment of the sensor for detecting a conductor defect of an electric wire according to claim 2, and FIG. 8B is a circuit diagram of the sensor.
In FIG. 8, 8 is an electric wire, and 9 is a sensor substrate. The magnetic sensing direction is a direction perpendicular to the circumference concentric with the electric wire at an angle of 180 ° around the electric wire and equidistant from the electric wire center. A pair of magneto-impedance effect elements are arranged in two pairs of a and b with a predetermined angle β in the circumferential direction of the electric wire, and the paired magneto-impedance effect elements 1a, 1a ′ and 1b, 1b ′ are in the magnetosensitive direction. Are connected in series so as to have a reverse polarity, and the output from each series-connected magneto-impedance effect element is subtracted or differentially amplified to obtain a sensor output. Reference numerals 3a and 3b denote demodulation circuits, and Dm denotes a differential amplifier.
The magneto-impedance effect element 1a is magnetized when the magneto-sensitive component due to the change in the circumferential circuit magnetic field distribution of one magneto-impedance effect element 1a of the pair a is ha and the magneto-sensitive component with respect to external noise such as geomagnetism is Na. The magnetic field strength Ha is Ha = ha + Na.
The magnetic field strength Ha ′ sensed by the other magneto-impedance effect element 1a ′ of the pair a is Ha ′ = − (ha ′ + Na) because the magnetosensitive direction of both elements 1a and 1a ′ is reversed. .
Therefore, the magnetic field strength (Ha + Ha ′) that the magneto-impedance effect element 1a, 1a ′ of the pair a connected in series has a magnetic sensitivity is (Ha + Ha ′) = (ha−ha ′), and noise can be eliminated. The magnetic field strength (Ha + Ha ′) is obtained from the above equations (1) and (2).

(Ha−ha ′) ≈4H (ΔL / r) ² sinαcosα = 2H (ΔL / r) ² sin2α

Given in.
When the magnetosensitive component due to the change in the circumferential circuit magnetic field distribution of one magneto-impedance effect element 1b of the other pair b is hb and the magneto-sensitive component for external noise such as geomagnetism is Nb, the magneto-impedance effect element is magnetosensitive. The magnetic field strength Hb to be applied is Hb = hb + Nb.

The magnetic field strength Hb ′ that the other magneto-impedance effect element 1b ′ of the pair b senses is Hb ′ = − (hb ′ + Nb) because the magnetosensitive direction of both elements is opposite in polarity.
Therefore, the magnetic field strength (Hb + Hb ′) that the magneto-impedance effect elements 1b and 1b ′ of the pair b connected in series are magnetically sensitive is (Hb + Hb ′) = (hb−hb ′), and external noise can be eliminated. The magnetic field strength (Hb + Hb ′) is obtained from the above equations (1) and (2).

(Hb−hb ′) ≈4H (ΔL / r) ² sin (α + β) cos (α + β) = 2H (ΔL / r) ² sin2 (α + β).

  In the embodiment shown in FIG. 8, the polarities of the pair b magneto-impedance effect elements 1a and 1a 'connected in series and the pair b magneto-impedance effect elements 1b and 1b' connected in series are reversed. The direction of these magneto-impedance effect elements is set. Therefore, the sensor output Eout is

Eout = k (ha−ha ′) − [− k (hb−hb ′)] ≈2 kH (ΔL / r) ² [sin2α + sin2 (α + β)]

Given in.
The orientations of the magneto-impedance effect elements 1a and 1a ′ of the pair b connected in series and the magneto-impedance effect elements 1b and 1b ′ of the pair b connected in series are set to the same polarity. If you want to

Eout = k (ha−ha ′) − k (hb−hb ′) ≈2 kH (ΔL / r) ² [sin2α−sin2 (α + β)]
Is established.
The magnetosensitive amounts (ha−ha ′) and (hb−hb ′) are small because ΔL << r, and the sensor can be downsized. Even if each detected amount (ha−ha ′) and (hb−hb ′) is small, the output of each series-connected element can be increased for the high detection resolution of the element because of the high detection resolution of the magneto-impedance effect element. Highly accurate detection is possible.
Therefore, even if the deviation ΔL of the current center of the conductor path cross section of the conductor becomes far away from the defective part of the electric wire, it can be detected because of its high sensitivity, and the magnetic field is detected at a place several tens of meters away from the defective part of the conductor. However, it is possible to detect defects.

FIG. 9A is a circuit diagram illustrating an embodiment of a sensor for detecting a conductor defect of an electric wire according to claim 3.
A pair of magneto-impedance effect elements having an angle of 180 ° around the electric wire and an equal distance from the center of the electric wire and having a magnetosensitive direction perpendicular to the circumference concentric with the electric wire, as in the sensor of claim 1. Are arranged in two pairs with a predetermined angle β in the circumferential direction of the electric wire.
In the sensor according to the third aspect, as shown in FIG. 9A, one of the magneto-impedance effect elements 1a and 1b ′ of different pairs a and b is connected in series so as to have the same polarity or opposite polarity, and the other magnet Impedance effect elements 1a 'and 1b are connected in series so as to have the same or opposite polarity, and a series-connected magnetoimpedance effect element of 1a and 1b' and a series-connected magnetoimpedance effect element of 1a 'and 1b The polarity is reversed, and the output from both series-connected magnetoimpedance effect elements is added or superimposed to obtain the sensor output. Ad represents an addition or superposition circuit.
In FIG. 9A, the magnetosensitive component of the magnetoimpedance effect element 1a of the pair a is ha, and the magnetosensitive component of the magnetoimpedance effect element 1a ′ of the pair a is ha ′ due to the distribution change of the peripheral circuit magnetic field as described above. The magnetosensitive component for external noise such as geomagnetism is Na, the magnetosensitive component of the magnetoimpedance effect element 1b of the pair b is hb, the magnetosensitive component of the magnetoimpedance effect element 1b ′ of the pair Wb is hb ′, and external noise such as geomagnetism. If the magnetic sensitive component for Nb is Nb,
The magnetosensitive magnetic field for each magneto-impedance effect element is ha + Na, ha ′ + Na, hb + Nb, and hb ′ + Nb. H ₁

[Formula 5] H ₁ = (ha + Na) ± (hb ′ + Nb)

The detection output based on this magnetosensitive magnetic field H ₁ is E ₁

E ₁ = kH ₁ = k [(ha + Na) ± (hb ′ + Nb)]
Since the other magneto-impedance effect element of the different pair is a series connection having a polarity opposite to that of the series-connected magneto-impedance effect element, the magneto-sensitive magnetic field H ₂ of the series-connected magneto-impedance effect element is

[Formula 6] H ₂ = − [(hb + Nb) ± (ha ′ + Na)]

Next, the detection output _{E 2} based on these sensitive magnetizing field _{H 2} is E ₂ = _kH 2 = -k [(hb + Nb) ± (ha '+ Na) ]

Given in.
Sensor output Eout is an addition or superposition of the two detection outputs E ₁ and E ₂ are

  Eout = k [(ha−ha ′) − (hb−hb ′)]

  Or

  Eout = k [(ha + ha ′) − (hb + hb ′)]

Thus, no magnetosensitive component for external noise Na, Nb such as geomagnetism is output.
The sensor output Eout is

[Formula 7] Eout≈kH (ΔL / r) [sin α−sin (α + β)]
Or

[Formula 8] Eout≈2 kHz (ΔL / r) ² [sin2α−sin2 (α + β)]

Given in.
9-2 is a drawing showing an embodiment of a sensor for detecting a conductor defect in an electric wire according to a fourth aspect.
Also in FIG. 9-2, as in FIG. 9-1, a pair of wires having an angle of 180 ° around the wire and equidistant from the center of the wire, with the magnetic sensing direction being perpendicular to the circumference concentric with the wire. Are arranged in two pairs a and b with a predetermined angle β in the circumferential direction of the wire, and one magnetoimpedance effect element 1a of the pair a and one magnetoimpedance effect element 1b of the pair b. Are connected in series so that they have the same or opposite polarity. Sensitive magnetizing field H ₁ of the same polarity or opposite polarity series magneto-impedance effect element pair one of the magneto-impedance effect element 1a and paired one of the magneto-impedance effect element 1b of b in a 'includes a sensor of Figure 9-1 Similarly, from Equation 5

H ₁ = (ha + Na) ± (hb ′ + Nb)

It is.
However, in the sensor of FIG. 9A, the other magneto-impedance effect elements 1a ′ and 1b are connected in series so as to have the opposite polarity to the series-connected magneto-impedance effect element (1a + 1b ′). In FIG. 9-2, the other magneto-impedance effect elements 1a ′ and 1b are connected in series so as to have the same polarity as the series-connected magneto-impedance effect element (1a + 1b ′). The series connection element (1a ′ + 1b) of the other magnetoimpedance effect element 1a ′ and 1b of the pair a and b has the same polarity as the series connection element (1a + 1b ′) of the series connection magnetoimpedance effect element 1a and 1b ′. Therefore, the magneto-sensitive magnetic field H ₂ of the series-connected magneto-impedance effect element (1a ′ + 1b) has an opposite sign to that of Equation 6 above.

H ₂ = + [(hb + Nb) ± (ha ′ + Na)]
Given in.
The modulated waves having the magneto-sensitive magnetic fields H ₁ and H ₂ as signal waves are demodulated by the demodulation circuits 3a′b and 3ab ′, and these demodulated waves are differentially amplified by the differential amplifier Dm to obtain the sensor output Eout. Because

Eout = kH ₁ −kH ₂ = k [(ha + ha ′) − (hb + hb ′)]

The sensor output Eout is given by

    Eout≈kH (ΔL / r) [sin α−sin (α + β)]

Or similar to Equation 8 above

Eout≈2 kHz (ΔL / r) ² [sin2α−sin2 (α + β)]

Given in.
In the sensor for detecting a conductor defect of an electric wire according to the present invention, the magnetosensitive strength changes with a waveform of sin 2α (or sin α), and α is 0, 90 ° and 180 ° (or 0, 180 ° and 360 °). 0.
Thus, the twisted conductor is twisted, α changes from 0 to 180 ° during a half pitch, α is 0, 90 ° and 180 ° (or α is 0, 180 ° and 360). Since the above detection cannot be satisfactorily performed at a position indicated by (°), it is effective to scan the sensor by several pitches of twisted conductors of the electric wire, preferably 3-5 pitches.

When amplification is performed by differential amplification as in the sensor of claim 2 or 4, the direction of the bias magnetic field Hb applied to one magnetoimpedance effect element and the bias magnetic field Hb applied to the other magnetoimpedance effect element as shown in FIG. Since the opposite directions of the demodulated outputs (magnetic field detection signals) are represented by E + and E− and the difference approaches a straight line as indicated by E ±, the negative feedback is omitted. Is also possible.
The present invention can also be implemented using four or more magneto-impedance effect elements.

It is sectional drawing which shows an electric wire. 2 is a view showing a magnetosensitive component of a magneto-impedance effect element separated by 180 ° in the present invention. It is drawing which shows the basic circuit of the magnetic field detection using a magnetic field impedance effect element. It is drawing which shows the output characteristic of the magnetic field detection using a magnetic field impedance effect element. It is drawing which shows another example of the basic circuit of the magnetic field detection using a magnetic field impedance effect element. It is drawing which shows a magnetic impedance effect element with a C type iron core. It is drawing which shows the sensor which concerns on Claim 1. It is drawing which shows the sensor which concerns on Claim 2. It is drawing which shows the sensor which concerns on Claim 3. It is drawing which shows the sensor which concerns on Claim 4. It is drawing for showing the linear characteristic of the sensor of Claim 2 or 4. 2 is a diagram showing the contents of Patent Document 1. 1 is a diagram showing the contents of Non-Patent Document 1.

Explanation of symbols

1, 1 ′ 180 ° -separated magnetoimpedance effect element 1a, 1a ′ 180 ° -separated magneto-impedance effect element 1b, 1b ′ 180 ° -separated magneto-impedance effect element Dm differential amplifier Ad addition or superposition circuit 8

Claims (4)

A sensor used in a method for detecting a defect in a conductor wire of any of the twisted conductors in an electric wire from a change in the distribution of the peripheral circuit magnetic field based on the energizing current of the twisted conductor when there is no wire defect. There is a pair of magneto-impedance effect elements in the circumferential direction of the electric wire, with an angle of 180 ° around the electric wire and at an equal distance from the electric wire center, and the magnetic sensing direction is perpendicular to the circumference concentric with the electric wire. Two pairs are arranged at a predetermined angle, and the paired magneto-impedance effect elements are connected in series so that the magnetosensitive direction is opposite in polarity, and the outputs from the series-connected magneto-impedance effect elements are added or superimposed. A sensor for detecting a conductor defect in an electric wire, characterized in that the sensor output is used. A sensor used in a method for detecting a defect in a conductor wire of any of the twisted conductors in an electric wire from a change in the distribution of the peripheral circuit magnetic field based on the energizing current of the twisted conductor when there is no wire defect. There is a pair of magneto-impedance effect elements in the circumferential direction of the electric wire, with an angle of 180 ° around the electric wire and at an equal distance from the electric wire center, and the magnetic sensing direction is perpendicular to the circumference concentric with the electric wire. Two pairs are arranged at a predetermined angle, and the paired magneto-impedance effect elements are connected in series so that the direction of magnetic sensing is reversed, and the output from each series-connected magneto-impedance effect element is subtracted or differentially amplified. A sensor for detecting a conductor defect in an electric wire, characterized in that a sensor output is obtained. A sensor used in a method for detecting a defect in a conductor wire of any of the twisted conductors in an electric wire from a change in the distribution of the peripheral circuit magnetic field based on the energizing current of the twisted conductor when there is no wire defect. There is a pair of magneto-impedance effect elements in the circumferential direction of the electric wire, with an angle of 180 ° around the electric wire and at an equal distance from the electric wire center, and the magnetic sensing direction is perpendicular to the circumference concentric with the electric wire. Two pairs are arranged at a predetermined angle, one of the magneto-impedance effect elements of different pairs is connected in series so as to have the same polarity or opposite polarity, and the other magneto-impedance effect element is also set to the same polarity or opposite polarity. So that both series-connected magneto-impedance effect elements have opposite polarities, and the outputs from both series-connected magneto-impedance effect elements are added or superimposed. Conductor defect detection sensor wire, characterized in that as the sensor output. A sensor used in a method for detecting a defect in a conductor wire of any of the twisted conductors in an electric wire from a change in the distribution of the peripheral circuit magnetic field based on the energizing current of the twisted conductor when there is no wire defect. There is a pair of magneto-impedance effect elements in the circumferential direction of the electric wire, with an angle of 180 ° around the electric wire and at an equal distance from the electric wire center, and the magnetic sensing direction is perpendicular to the circumference concentric with the electric wire. Two pairs are arranged at a predetermined angle, one of the magneto-impedance effect elements of different pairs is connected in series so as to have the same polarity or opposite polarity, and the other magneto-impedance effect element is also set to the same polarity or opposite polarity. Connected in series so that both series-connected magneto-impedance effect elements have the same polarity, and the output from both series-connected magneto-impedance effect elements is subtracted or differentially amplified Conductor defect detection sensor wire, characterized in that as the sensor output Te.

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