JP4986654B2 - Magnetic detection method - Google Patents

Description

  The present invention relates to a method for detecting only a magnetic substance from an object in which a magnetic substance and a conductive substance coexist with a magnetic impedance effect sensor, and for example, detecting a magnetic foreign substance such as a machine piece entering an aluminum foil laminate pack beverage. It is used for

As an amorphous alloy wire, an amorphous alloy wire having zero magnetostriction or negative magnetostriction has been developed, which has 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 separated by a domain wall. Yes.
The inductance voltage component in the output voltage between both ends of the wire generated when a high frequency current is applied to the zero magnetostrictive or negative magnetostrictive amorphous magnetic wire is easily increased in the circumferential direction by the circumferential magnetic flux generated in the cross section of the wire. It occurs due to the magnetized outer shell being magnetized in the circumferential direction. Therefore, the circumferential magnetic permeability mu _theta depends on the circumferential direction of magnetization of Dosotokara portion.
Therefore, when an external magnetic field is applied to the energized amorphous wire, the magnetic flux acting on the outer shell portion having the easily magnetizable property in the circumferential direction is obtained by synthesizing the circumferential magnetic flux and the external magnetic flux by the energization. direction deviates from the circumferential direction, correspondingly hardly occur magnetization in the circumferential direction, the circumferential permeability mu _theta changes, the inductance voltage content will vary.
Thus, this fluctuation phenomenon is called a magnetic inductance effect, and an amorphous wire or the like that exhibits this effect is called a magnetic inductance effect element.

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, as described above, ρ is electrical resistivity, w is shows the angular frequency, respectively) is changed by mu _theta, as the mu _theta is the so changed by an external magnetic field, the resistance voltage of the in wire ends between the output voltage under the external magnetic field It will fluctuate.
Thus, this fluctuation phenomenon is called a magnetoimpedance effect, and an amorphous wire or the like that exhibits this effect is called a magnetoimpedance effect element.

  Therefore, an external magnetic field detection method using the magneto-impedance effect element (see, for example, Patent Document 1) and an external magnetic field detection method using the magnetic inductance effect (see, for example, Patent Document 2) have been proposed.

  In the above, the positive and negative of the external magnetic field causes the circumferential shift φ of the magnetic field to be positive or negative, but the reduction factor cos (± φ) of the circumferential magnetic field does not change. Does not change. Accordingly, the external magnetic field-output characteristics are substantially symmetrical with respect to the y-axis as shown in FIG. 2A when the magnetic field is taken on the x-axis and the output is taken on the y-axis. In addition, as shown in FIG.

As shown in FIG. 6, the magnetic field detection circuit using this magneto-impedance effect element basically has (1) a high-frequency current source 2 ′ for applying a high-frequency excitation current to the magneto-impedance effect element 1 ′, and (2 ) A magneto-impedance effect element 1 ′, (3) a detection circuit 3 ′ that demodulates the modulated wave obtained by modulating the high-frequency excitation current (carrier wave) with the external magnetic field Hex applied to the magneto-impedance effect element, and (4) the demodulated wave It comprises an amplifier 4 'for amplifying and (5) a detection output terminal 5'.
3A shows the detected magnetic field (external magnetic field) Hex applied to the magneto-impedance effect element, FIG. 3B shows the high-frequency excitation current wave (carrier wave) Ic passed through the magneto-impedance effect element, and FIG. A modulated wave as an output of the impedance effect element is shown, and (d) shows a demodulated wave.

The relationship between the amplitude Hex of the detected magnetic field and the amplitude of the output Eout can be expressed as shown in FIG.
Therefore, in the circuit of FIG. 6, the characteristic is linearized as shown in FIG. 2B by applying negative feedback with a negative feedback coil 6 '.
Further, as shown in FIG. 2C, the characteristics shown in FIG. 2B can be moved in the direction of the arrow by a bias magnetic field as shown in FIG. It has been broken.
In FIG. 5, reference numeral 7 'denotes a bias magnetic field coil.

7 (a) and 7 (b) show a known magneto-impedance effect element with a coil in the magneto-impedance effect sensor. In the case shown in FIG. 6 'and a bias magnetic field coil 7' are wound. In the case shown in FIG. 7A, the magneto-impedance effect element 1 'is disposed on one surface of the substrate 100', and the iron core is disposed on the other surface of the substrate. 103 'is arranged to form a magnetic loop circuit with the magnetic impedance effect 1', and a negative feedback coil 6 'and a bias magnetic field coil 7' are wound around the iron core 103 '(Patent Document) 3).
JP 7-181239 A JP-A-6-283344 JP 2002-289940 A

  According to the magnetic impedance effect sensor, magnetic foreign matters such as iron pieces can be detected by a scanning method. Iron is usually magnetized due to stress received during processing and use, exposure to magnetic fields such as geomagnetism, etc. Even if the magnetic field generated by the magnetic dipole is weak, if a magnetic impedance effect sensor is used, Detectable due to high sensitivity.

By the way, in the magneto-impedance effect sensor using the coiled magneto-impedance effect element shown in (b) of FIG. .
When the reason is verified, the magnetic field generated around the magneto-impedance effect element by energization of the exciting current is applied to the conductive material, the eddy current flows through the conductive material, and the magnetic field generated by the eddy current, that is, the reaction magnetic field As a result, the applied magnetic field is reduced, and the change in output occurs due to the change in the magnetic field when the magneto-impedance effect element passes over the conductive material.
Therefore, when inspecting whether or not a beverage pack packaged with an aluminum foil / paper laminate pack contains iron-based strips such as mechanical debris, even normal products that do not contain iron-based strips will output. Occurrence and confusion between the normal product output and the iron product containing product output cannot be avoided, and an accurate inspection cannot be performed.

  An object of the present invention is to reliably detect a magnetic material by a magnetic impedance effect sensor even in the presence of a conductive material.

According to a first aspect of the present invention, there is provided a magnetic substance detection method comprising: a magneto-impedance effect element; a high-frequency current source for supplying a high-frequency excitation current to the element; and a detected magnetic field acting in an axial direction of the magneto-impedance effect element. A detector circuit that demodulates the modulated wave modulated with the high-frequency excitation current, an amplifier circuit that amplifies the demodulated wave, a negative feedback circuit that negatively feeds the output of the amplifier circuit to the element via a negative feedback coil, A bias magnetic field coil for applying a bias magnetic field to the element; a clip circuit between the amplifier circuit and the detection output terminal; and an excitation current circumferential magnetic field generated inside and outside the element by the high-frequency excitation current A method for detecting a magnetic substance from an object in which a magnetic substance may coexist with a conductive substance using a magneto-impedance effect sensor. While moving a non-coexisting conductive object relative to the magneto-impedance effect sensor, an exciting current is passed through the element of the magneto-impedance effect sensor to cause an exciting current circumferential magnetic field to act on the conductive object, and the conductivity The exciting current is changed by the reaction magnetic field generated from the object, the changed magneto-impedance effect element output terminal voltage is output to the amplifier circuit output terminal through the detection circuit, and the reference value of the clip circuit is set so as to cut this output. Under this setting, in the movement of the object including the magnetic material in the conductive material with respect to the magneto-impedance effect sensor, the magnetic field generated by the magnetic material is modulated by the magneto-impedance effect and the reaction magnetic field of the magnetic material The output voltage of the magneto-impedance effect element that has been changed in step 1 is demodulated by the detection circuit, and the demodulated wave is amplified And wherein the to be output to the detection output terminal via the clipping circuit of the reference value setting.
The magnetic substance detection method according to claim 2 is the magnetic substance detection method according to claim 1, wherein a negative feedback coil for negatively feeding back the output to the magneto-impedance effect element and a bias for applying a bias magnetic field to the element are provided. The magnetic field coil uses a magneto-impedance effect sensor wound around an iron core constituting a loop magnetic circuit with a magneto-impedance effect element.
The magnetic substance detection method according to claim 3 is the magnetic substance detection method according to claim 1 or 2, wherein the conductive substance is an aluminum foil of an aluminum foil laminated packaging container, and the magnetic substance is contained in the contents of the container. It is a foreign material.

Since the magneto-impedance effect element is not surrounded by the negative feedback coil or the bias magnetic field coil, the magnetic field generated from the magneto-impedance effect element when the excitation current is applied acts on the conductive material, and eddy current flows through the conductive material. The exciting current is changed by the reaction magnetic field generated by the eddy current, and an output is generated due to the change of the exciting current. However, since the output is subtracted to obtain the detection output, the conductive material is not detected.
For a magnetic material, the excitation current is modulated by the magnetism of the magnetic material (magnetic impedance effect), and the magnetism is detected by demodulating the modulated wave.
Therefore, only the magnetic substance can be detected from the target in which the conductive substance and the magnetic substance coexist.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1-1 shows an example of a circuit diagram of a magneto-impedance effect sensor used in the present invention.
In FIG. 1-1, 10 is a magneto-impedance effect element with a coil. Reference numeral 1 denotes a magneto-impedance effect element of the coiled magneto-impedance effect element 10, which has the characteristics shown in FIG. In FIG. 2A, Hex is a detected magnetic field acting in the axial direction of the magnetoimpedance effect element, and Eout is an output. Reference numeral 6 denotes the negative feedback coil, and the above characteristic is a linear characteristic as shown in FIG. Reference numeral 7 denotes the bias magnetic field coil, and the characteristics shown in FIG. 2B are shifted by the bias magnetic field Hb so that the polarity can be discriminated.

1-2 (a) is a side view showing an example of the coiled magneto-impedance effect element, FIG. 1-2 (b) is a bottom view, and FIG. 1-2 (c) is FIG. 1-2. It is a ha sectional drawing in (b).
In FIG. 1-2, 100 is a board | substrate chip and can use a ceramic board, for example. Reference numeral 101 denotes an electrode provided on one side of the substrate piece, and includes a magneto-impedance effect element connecting projection 102. This electrode can be provided by printing and baking a conductive paste, for example, a silver paste. Reference numeral 1 denotes a magneto-impedance effect element connected between the protrusions 102 and 102 of the electrodes 101 and 101 by welding, and 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 made of iron or ferrite, 6 is a negative feedback coil wound around the C-type iron core, 7 is a bias magnetic field coil, and the magneto-impedance effect element 1 and the C-type iron core 103 The both ends of the C-type iron core 103 are fixed to the other surface of the substrate piece 100 with an adhesive or the like so as to constitute a loop magnetic circuit. 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.

The magneto-impedance effect element 1 includes a zero magnetostrictive or negative magnetostrictive amorphous alloy wire 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 a domain wall. 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. Thus, when a signal magnetic field is applied in the axial direction of the amorphous wire being energized, the outer shell portion having the easily magnetizable property in the circumferential direction is obtained by synthesizing the circumferential magnetic flux and the signal magnetic field magnetic flux by the energization. direction of magnetic flux acting deviates from the circumferential direction, correspondingly hardly occur magnetization in the circumferential direction, the circumferential permeability mu _theta changes, the inductance voltage content will vary to. 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 magnetic field (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, so changed by the mu _{as theta} is the signal magnetic field, the resistance voltage of the in wire ends between the output voltage variation at the signal magnetic field To come. This fluctuation phenomenon is called a magneto-impedance effect. As shown in FIG. 3, the high-frequency excitation current (carrier wave) shown in (b) of FIG. 3 is detected magnetic field (signal wave) shown in (a) of FIG. Thus, it can be said that the phenomenon is modulated as shown in FIG.

  1-1, 2 is a high-frequency current source circuit for applying a high-frequency excitation current to the magneto-impedance effect element, and 3 is a detected magnetic field H (signal wave) acting in the axial direction of the magneto-impedance effect element. Detection circuit for demodulating a modulated wave modulated by (carrier wave), 4 an amplifier circuit for amplifying the demodulated wave, 60 a negative feedback circuit, 70 for a bias magnetic field + Vcc power supply, and 50 for an amplifier circuit output with a predetermined clip value The clip circuit 5 for subtracting at 5 is a detection output terminal.

As the magneto-impedance effect element, an amorphous wire having zero magnetostriction or negative magnetostriction, an amorphous ribbon, an amorphous sputtered film, or the like can be used.
The composition of the magneto-impedance effect element 1 is an alloy of transition metal and non-metal having a non-metal composition of 10 to 30 atomic%, particularly an alloy of transition metal and non-metal having a non-metal content of 10 to 30 atomic%. The transition metal is Fe and Co and the nonmetal is B and Si, or the transition metal is Fe and the nonmetal is B and Si. For example, the composition Co _70.5 B ₁₅ Si ₁₀ Fe _4.5 , length 2000 μm to 6000 μm, outer diameter 30 μm to 50 μmφ can be used.

  For 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 tuned oscillation circuit, a base tuned oscillation In addition to a normal oscillation circuit such as a circuit, a square wave generator that integrates the square wave output of a crystal oscillator via a DC cut capacitor with an integration circuit and amplifies the triangular wave of this integration output with an amplification circuit, and a CMOS-IC oscillation unit The triangular wave generator used as can be used.

As the detection circuit, 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.
Further, it is possible to use tuning detection in which a signal wave is sampled by multiplying the modulated wave by a square wave having a frequency fs tuned to the modulated wave (frequency fs).
In the above embodiment, the detected magnetic field (signal wave) is extracted by demodulating the modulated wave. However, the present invention is not limited to this, and the high frequency excitation modulated by the signal magnetic field (signal wave) acting on the magneto-impedance effect element. As long as the signal magnetic field can be detected from the current wave (carrier wave), an appropriate detection means can be used.

FIG. 4 shows an inspection line for an aluminum foil laminate pack beverage that detects magnetic materials such as mechanical fragments generated in the production process and dropped in the pack in the production process of the pack beverage according to the present invention. Conveyor P is an aluminum foil laminate pack beverage. S indicates a magneto-impedance effect sensor, and mechanical debris (magnetic debris) that has fallen into the pack usually sinks to the fixed surface in the pack. In order to shorten the distance between the debris and the magneto-impedance effect element as much as possible. The magneto-impedance effect element is disposed below the pack so as to face the bottom of the pack.
To carry out the present invention, an aluminum foil laminate pack beverage is run by a conveyor, and an exciting current is passed through the magneto-impedance effect element of the magneto-impedance effect sensor to generate a magnetic field.
Since the magneto-impedance effect element is not surrounded by a negative feedback coil, a bias magnetic field coil, etc., and there is no magnetic shielding, the magnetic field is widely distributed in the surrounding space of the magneto-impedance effect element and added to the packed beverage being transferred. . Therefore, an eddy current is generated in the aluminum foil of the pack due to its conductivity, and the excitation current is changed by the reaction magnetic field.
The fluctuation becomes maximum when the center point of the pack passes directly below the magneto-impedance effect element, and the output voltage of the magneto-impedance effect element of the fluctuating excitation current passes through the detection circuit to the output terminal of the amplifier circuit of FIG. (A) is output (the output value is indicated by ΔE). In FIG. 5A, time T is the time from the time when the center point of the previous pack passes directly under the magneto-impedance effect sensor to the time when the center point of the next pack passes directly under the magneto-impedance effect sensor. It matches.

When the pack containing the magnetic fragments passes immediately above the magneto-impedance effect element, the fragments are magnetized due to stress at the time of processing or fracture, so that the magnetic field generated by the magnetic dipole is magnetic impedance. Acting on the effect element, the exciting current is modulated by the magneto-impedance effect, and the modulation output at the end of the magneto-impedance effect element is demodulated by the detection circuit, and an output is obtained. As shown in FIG. 5 (b), this output is based on the output resulting from the excitation current being modulated by the magnetism of the magnetic fragment, that is, the output value E based on the magnetoimpedance effect and the reaction magnetic field of the aluminum foil of the pack. The output value ΔE is superimposed.
In the present invention, the output of the amplifier circuit is passed through a clip circuit and clipped at a value ΔE ′ slightly higher than the output ΔE to obtain a detection output. As shown in FIG. It is possible to reliably detect magnetic foreign matter intruding into the pack.

In the above embodiment, the magneto-impedance effect sensor is fixed and the object to be detected is moved. However, the object to be detected can be arranged at a predetermined interval, and the magneto-impedance effect sensor can be moved directly above them.
In the above embodiment, it is inspected whether or not a magnetic material such as an iron fragment that should not be attached to a conductive material such as an aluminum foil is attached. The present invention can also be applied when inspecting whether or not the magnetic material has fallen off from the property.
In the above embodiment, the conductive material and the magnetic material are substantially integrated (a broken piece of aluminum foil laminate pack beverage with intrusion of iron fragments) and a conductive material (a normal aluminum foil laminated pack beverage without intrusion of iron fragments). ) To detect an object in which a conductive material and a magnetic material are substantially integrated, but may be used to detect a magnetic product from a magnetic product and a conductive product. it can.

It is a circuit diagram of an example of the magneto-impedance effect sensor used in the present invention. It is drawing which shows the magneto-impedance effect element with a coil of the magneto-impedance effect sensor of FIGS. 1-1. It is drawing which shows the output characteristic of a magneto-impedance effect element. It is drawing which shows the input / output waveform in various places in a magneto-impedance effect sensor. It is drawing which shows the goods conveyance line with which this invention is applied. It is drawing which shows the output of the magneto-impedance effect sensor in the line of FIG. It is a circuit diagram which shows the conventional magnetic impedance effect sensor. 6 is a view showing a magneto-impedance effect element with a coil of a conventional magneto-impedance effect sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magneto-impedance effect element 10 Magneto-impedance effect sensor 2 Excitation current source 3 Detection circuit 4 Amplification circuit 5 Detection output terminal 50 Clip circuit 6 Negative feedback magnetic field coil 7 Bias magnetic field coil

Claims (3)

A modulation in which the high frequency excitation current is modulated by the magnetic impedance effect with a magnetic impedance effect element, a high frequency current source for supplying a high frequency excitation current to the magnetoimpedance effect element, and a detected magnetic field acting in the axial direction of the magnetoimpedance effect element A detection circuit that demodulates the wave, an amplification circuit that amplifies the demodulation wave, a negative feedback circuit that negatively feeds back the output of the amplification circuit to the element via a negative feedback coil, and a bias magnetic field applied to the magneto-impedance effect element A magneto-impedance effect sensor that includes a coil for a bias magnetic field, includes a clip circuit between an amplifier circuit and a detection output terminal, and generates a circumferential magnetic field in the element inside and outside by the high-frequency excitation current. Use this method to detect magnetic materials from objects in which magnetic materials can coexist with conductive materials. Therefore, while moving the object of the conductive material that does not coexist with the magnetic material to the magneto-impedance effect sensor, an exciting current is passed through the element of the magneto-impedance effect sensor, and an exciting current circumferential magnetic field acts on the object of the conductive material. The clip is configured so that the exciting current is changed by the reaction magnetic field generated from the conductive material, the changed magneto-impedance effect element output terminal voltage is output to the amplifier circuit output terminal through the detection circuit, and the output is cut off. The reference value of the circuit is set, and under this setting, in the movement of the object including the magnetic material in the conductive material with respect to the magnetic impedance effect sensor, the magnetic force generated from the magnetic material is modulated by the magnetic impedance effect and magnetic The output voltage of the magneto-impedance effect element changed by the reaction magnetic field of the object is demodulated by the detection circuit, Detection method of a magnetic material, characterized in that to output the detected output through the clipping circuit of the amplifier circuit and the reference value setting waves. A negative feedback coil for negative feedback of the output to the magneto-impedance effect element and a bias magnetic field coil for applying a bias magnetic field to the element are wound around the iron core constituting the loop magnetic circuit with the magneto-impedance effect element. detection method according to claim 1 Symbol placement of magnetic material, characterized by using a magneto-impedance effect sensors being. 3. The method for detecting a magnetic material according to claim 1, wherein the conductive material is an aluminum foil of an aluminum foil laminated packaging container, and the magnetic material is a foreign substance in the contents of the container.

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