JP4460188B2 - Magnetic sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic field sensor using a magnetoimpedance effect element.
[0002]
[Prior art]
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.
[0003]
The inductance voltage component in the output voltage between both ends of the wire generated when a high-frequency current is applied to an amorphous magnetic wire having zero magnetostriction or negative magnetostriction is generated by the circumferential magnetic flux generated in the cross section of the wire. This occurs because the easily magnetizable outer shell is magnetized in the circumferential direction. Accordingly, the circumferential magnetic permeability μθ depends on the circumferential magnetization of the outer shell.
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. Is deviated from the circumferential direction and magnetization in the circumferential direction is less likely to occur, and the circumferential magnetic permeability μθ changes. In other words, if the deviation of the magnetic flux from the circumferential direction when an external magnetic field is applied is φ, the circumferential magnetic flux is reduced by cos φ, and the μθ is reduced by this rotational magnetization. Therefore, the inductance voltage is reduced by the decrease in μθ.
[0004]
Further, when the frequency of the energizing current is in the order of MHz, a high-frequency skin effect appears greatly, and the skin depth δ = (2ρ / wμθ) ^1/2 (μθ is the circumferential permeability, as described above, ρ is The electrical resistivity, w is an angular frequency) changes with μθ, and this μθ changes with the external magnetic field as described above. Therefore, the resistance voltage component in the output voltage between both ends of the wire also changes with the external magnetic field.
[0005]
Therefore, the external magnetic field is detected from both the inductance voltage and the resistance voltage due to the external magnetic field, that is, the fluctuation of the output voltage between both ends of the wire (the fluctuation of the output voltage due to the external magnetic field is referred to as the magneto-impedance effect). Has been proposed (Japanese Patent Laid-Open No. 7-181239).
The characteristics of the magneto-impedance effect element itself are symmetric and non-linear.
[0006]
As shown in FIG. 5, the magnetic field detection device using the magneto-impedance effect element basically oscillates for supplying a high-frequency current or a pulse current to the magneto-impedance effect element 1 ′ and the magneto-impedance effect element 1 ′. A circuit unit A, a detection unit B for detecting an external magnetic field by demodulating a modulation wave based on an impedance change between both ends of the magneto-impedance effect device 1 ′ due to the external magnetic field Hex applied to the magneto-impedance effect device 1 ′, and a measurement unit C The negative feedback magnetic field generating coil 21 'applies negative feedback to make the detection output Eo linear and proportional to the external magnetic field Hex, and the bias magnetic field generating coil 22' applies a DC bias magnetic field. In addition, an external magnetic field can be detected regardless of the polarity.
[0007]
[Problems to be solved by the invention]
By the way, in the conventional magnetic sensor, two separate coils, a negative feedback magnetic field generating coil and a bias magnetic field generating coil, are disposed in the vicinity of the magneto-impedance effect element, which occupies a large space and is miniaturized. Not suitable.
[0008]
An object of the present invention is to make it possible to satisfactorily use one of the double coils as a negative feedback magnetic field generating coil and the other coil as a bias magnetic field generating coil in a magnetic sensor using a magneto-impedance effect element. Thus, it is intended to reduce the size of the magneto-impedance effect element with the negative feedback magnetic field generating coil and the bias magnetic field generating coil. .
[0009]
[Means for Solving the Problems]
The magnetic sensor according to the present invention is provided with a double coil around a magneto-impedance effect element or a magneto-impedance effect element mounting substrate, the inner coil of the double coil is used as a negative feedback magnetic field generating coil, and the outer coil generates a bias magnetic field. It is the structure characterized by setting it as the coil for operation.
[0010]
The magnetic sensor different from the above according to the present invention has a magneto-impedance effect element attached to a substrate, the magneto-impedance effect element attachment substrate is inserted into a bobbin or a tube, and a coil is wound around the bobbin or the tube twice. The coil is a negative feedback magnetic field generating coil, and the outer coil is a bias magnetic field generating coil.
[0011]
A magnetic sensor different from the above according to the present invention includes a magneto-impedance effect element mounted on a substrate, the magneto-impedance effect element covered with a protective cover, and a coil wound twice around the protective cover and the substrate. The negative feedback magnetic field generating coil is used, and the outer coil is a bias magnetic field generating coil.
[0012]
A magnetic sensor different from the above according to the present invention has a magneto-impedance effect element mounted on one surface of a substrate, a double coil mounted on the other surface of the substrate, an inner coil serving as a negative feedback magnetic field generating coil, and an outer coil. Is a coil for generating a bias magnetic field, and the double coil can be a coil formed by winding a coil around a C-shaped core.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a magnetic sensor according to claim 1, and the basic configuration of the magnetic sensor according to the present invention will be described with reference to FIG. 1.
In FIG. 1, reference numeral 1 denotes a magneto-impedance effect element, and normally an amorphous wire or amorphous ribbon having zero magnetostriction or negative magnetostriction is used. Reference numeral 2 denotes a double coil disposed around the magneto-impedance effect element 1, wherein the inner coil 21 is a negative feedback magnetic field generating coil and the outer coil 22 is a bias magnetic field generating coil.
Instead of the magneto-impedance effect element, a substrate on which the magneto-impedance effect element is attached may be used.
[0014]
The electrical coupling state of the negative feedback magnetic field generating coil 21 and bias magnetic field generating coil 22 and the magneto-impedance effect element 1 is as described with reference to FIG.
The impedance Z of the inner coil 21 as the negative feedback magnetic field generating coil is such that the inductance of the coil is L and the resistance is Rdc.
[Expression 1]
Z = (Rdc ² + Lw ² ) ^1/2 (1)
If the detection output is Eo, the negative feedback current If is given by
[Expression 2]
If = Eo / (Rdc ² + Lw ² ) ^1/2 (2)
If the cross-sectional area of the inner coil is S, the negative feedback magnetic field Hf is given by
[Equation 3]
Hf = IfL / S (3)
Given in.
The inductance L of the inner coil is as follows: n is the number of turns of the inner coil, λ is the Nagaoka coefficient, a is the inner radius of the inner coil, l is the length of the inner coil, and μo is the magnetic permeability of the space.
[Expression 4]
L = λμoSn ² / l = λμoπa ² n ² / l (4)
Given in.
Thus, from equations (3) and (4),
[Equation 5]
Hf = Ifλμon ² / l (5)
Is established.
[0015]
In the magnetic sensor according to the present invention, the inner coil 21 of the double coil 2 is used as a negative feedback magnetic field generating coil. The inner radius a of the inner coil 21 is smaller than the inner radius of the outer coil 22, and the equation (4) As can be seen from FIG. 5, since the inductance L is reduced accordingly, the negative feedback current If is increased as apparent from the equation (2). As a result, as shown in the equation (5), the negative feedback magnetic field Hf is increased accordingly. The Therefore, even if the frequency (angular frequency w) increases, a negative feedback magnetic field can be applied reliably, and a reliable and stable linearization of the detection output can be guaranteed.
On the other hand, in the bias magnetic field generating coil, the bias magnetic field is a DC magnetic field, and is set by the DC power source Vcc [see FIG. 5] or the adjusting resistor [Rx in FIG. 5], so that the outer coil 22 of the double coil 2 is biased. There is no problem in using it as a magnetic field generating coil.
Therefore, the negative feedback magnetic field generating coil and the bias magnetic field generating coil can be constituted by a common double coil while guaranteeing the linearity and nonpolarity of the output characteristics.
[0016]
2 (a) is a longitudinal sectional view showing an embodiment of the magnetic sensor of claims 2 and 3, and FIG. 2 (b) is a roll sectional view in FIG. 2 (1).
In FIG. 2, 31 is an insulating substrate, and for example, a ceramic substrate, a glass epoxy substrate, a paper phenol substrate or the like can be used. Reference numerals 32 and 32 are electrodes provided on one side of the insulating substrate, and are provided with an element connecting projection 321. This electrode can be provided by printing and baking a conductive paste, for example, a silver paste. A magneto-impedance effect element 1 is connected between the protrusions 321 and 321 of the electrodes 32 and 32 by soldering or welding. Usually, zero magnetostrictive or negative magnetostrictive amorphous wire, amorphous ribbon, sputtered film, or the like is used. . Reference numeral 33 denotes a conductor pin attached to each electrode 32 by soldering or welding.
4 is a hobbin into which the magneto-impedance effect element mounting substrate is inserted. A tube can be used instead of this hobbin. As the material of these bobbins and tubes, nonmagnetic materials are preferably used, and ceramics, plastics, metals, and the like can be used.
Reference numeral 2 denotes a double coil in which an insulating wire is wound around the hobbin 4. The inner coil 21 is a negative feedback magnetic field generating coil and the outer coil 22 is a bias magnetic field generating coil.
The inside of the bobbin 4 or the tube can be sealed with resin.
[0017]
3A is a plan view showing an embodiment of the magnetic sensor of claims 2 and 4, FIG. 3B is a front view, and FIG. 3C is a front view of FIG. -It is C sectional drawing.
In FIG. 3, reference numeral 11 denotes an insulating substrate. For example, a ceramic substrate, a glass epoxy substrate, a paper phenol substrate, or the like can be used. 32 and 32 are a pair of electrodes formed on one side of the substrate 31, and can be formed, for example, by printing and baking a conductive paste. Reference numeral 1 denotes a magneto-impedance effect element connected by soldering, welding or the like between the protrusions 321 and 321 of the electrodes 32 and 32, and an amorphous magnetic wire, ribbon, sputtered film or the like having zero or negative magnetostriction can be used. Reference numeral 30 denotes a protective plate, and it is preferable to use a nonmagnetic material. For example, a ceramic substrate, a glass epoxy substrate, a paper phenol substrate, or the like can be used. Reference numerals 33 and 33 denote pin conductors having a height capable of preventing contact between the magneto-impedance effect element 1 and the protection plate 30. Reference numeral 2 denotes a double coil provided by winding an insulating wire around the substrate 31 and the protective plate 30. The inner coil 21 is a negative feedback magnetic field generating coil and the outer coil 22 is a bias magnetic field generating coil.
The space between the substrate 31 and the protective plate 30 can be sealed with resin.
[0018]
4 (a) is a side view showing an embodiment of the magnetic sensor of claims 5 and 6, FIG. 4 (b) is a bottom view, and FIG. 4 (c) is a diagram in FIG. -It is C sectional drawing.
In FIG. 4, 31 is an insulating substrate. 32 and 32 are electrodes provided on one side of the insulating substrate. This electrode is a conductive paste, for example, a silver paste. A magneto-impedance effect element 1 is connected between the protrusions 321 and 321 of the electrodes 32 and 32 by soldering or welding. Usually, zero magnetostrictive or negative magnetostrictive amorphous wire, amorphous ribbon, sputtered film, or the like is used. . Reference numeral 33 denotes a pin conductor attached to each electrode 32 by soldering or welding. Reference numeral 2 denotes a coil in which an insulation wire is wound around the C-shaped core 20. Both ends of the C-shaped core 20 are fixed to the other surface of the substrate 31 with an adhesive or the like, and the inner coil 21 is used as a negative feedback magnetic field generating coil. The outer coil 22 is used as a bias magnetic field generating coil.
The C-shaped core 30 is divided into a leg part and a horizontal part, the leg part is fixed to the other surface of the substrate 31, and a horizontal part of a double coil in which the coil is wound around the C-shaped core horizontal part. Both ends can be bonded to the leg.
[0019]
In the present invention, the double coil means a single-layer or multi-layer outer coil having both terminals on a single-layer or multi-layer inner coil having both terminals. It goes without saying that it is not limited to only the outer layer.
[0020]
【The invention's effect】
In the present invention, in a magnetic sensor in which a negative feedback magnetic field generating coil and a bias magnetic field generating coil are attached to a magneto-impedance effect element, an inner coil having a low inductance is negatively fed back from an inner coil and an outer coil of a double coil. Since the magnetic field generating coil is used, the negative feedback current can be sufficiently increased even in a high frequency band to increase the negative feedback magnetic field. As a result, the negative feedback can be sufficiently applied to guarantee a reliable and stable linearization of the detection characteristics. Further, although the outer coil of the double coil is used as a bias magnetic field generating coil, a desired bias magnetic field can be applied by adjusting the DC power supply voltage or resistance.
Therefore, the negative feedback magnetic field generating coil and the bias magnetic field generating coil can be configured with a common double coil while guaranteeing the linearity and non-polarity of the output characteristics, and the entire magnetic sensor can be downsized by reducing the size of the coil. Can do.
[0021]
In particular, in the magnetic sensor of claims 2 to 6, the magneto-impedance effect element can be reinforced with the substrate, and the smooth production of the magnetic sensor can be ensured even though the magneto-impedance effect element is mechanically fragile.
[0022]
In particular, in the magnetic sensor according to the fifth and sixth aspects, since the outline of the magnetic sensor can be limited to the outline of the substrate, the planar dimension can be made extremely small, and further miniaturization can be achieved. Furthermore, the magneto-impedance effect element surface can be brought close to the detection object, which is advantageous in terms of detection sensitivity.
[Brief description of the drawings]
FIG. 1 is a view showing a magnetic field sensor according to claim 1;
FIG. 2 is a drawing showing an embodiment of a magnetic field sensor according to claim 2;
FIG. 3 is a view showing an embodiment of a magnetic field sensor according to claim 3;
FIG. 4 is a view showing an embodiment of a magnetic field sensor according to claim 4;
FIG. 5 is a circuit diagram showing a magnetic field detection device using a magneto-impedance effect element.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Magneto-impedance effect element 2 Double coil 20 C-shaped core 21 Inner coil 22 Outer coil 31 Substrate 30 Protective cover

Claims (6)

A magnetic sensor comprising a double coil around a magneto-impedance effect element, an inner coil of the double coil serving as a negative feedback magnetic field generating coil, and an outer coil serving as a bias magnetic field generating coil. A magneto-impedance effect element is attached to a substrate, a double coil is provided around the magneto-impedance effect element attachment substrate, an inner coil of the double coil is a negative feedback magnetic field generating coil, and an outer coil is a bias magnetic field generating coil Magnetic sensor characterized by that. A magneto-impedance effect element is attached to a substrate, the magneto-impedance effect element attachment substrate is inserted into a bobbin or tube, a coil is wound twice around the bobbin or tube, an inner coil is used as a negative feedback magnetic field generating coil, and an outer coil is A magnetic sensor characterized by being a bias magnetic field generating coil. A magneto-impedance effect element is attached to the substrate, the magneto-impedance effect element is covered with a protective cover, a coil is wound around the protective cover and the substrate, the inner coil is used as a negative feedback magnetic field generating coil, and the outer coil is a bias magnetic field. A magnetic sensor characterized by being a generating coil. The magneto-impedance effect element is attached to one side of the substrate, the double coil is attached to the other side of the substrate, the inner coil is a negative feedback magnetic field generating coil, and the outer coil is a bias magnetic field generating coil. Magnetic sensor. 6. The magnetic sensor according to claim 5, wherein the double coil is a coil in which a coil is wound around a C-shaped core.

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