JP3602235B2 - Magnetic sensor - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic sensor using an amorphous magnetic wire.
[0002]
[Prior art]
In an amorphous alloy, since the atomic structure does not have a long-range order but a short-range order, it has an electromagnetic property unique to amorphous and has zero magnetostriction or an outer shell that is easily magnetized in the circumferential direction. Negative magnetostrictive amorphous wires have been developed. For example, Co ₇₀ . ₅ B ₁₅ Si ₁₀ Fe ₄ has been developed.
When a high-frequency current is applied to the zero-magnetostriction or negative-magnetostriction amorphous wire, the circumferentially magnetizable outer shell is magnetized in the circumferential direction by the circumferential magnetic flux generated in the cross section of the wire. , The circumferential magnetic permeability μ ₁ becomes large, and an inductance voltage eL generated at both ends of the amorphous wire, that is, eL = wμ ₁ ι (Im−Ic) / 4π
Significantly increases. Here, l is the length of the wire, w is the frequency of the current, Im is the absolute value of the flowing current, Ic is 4πaHc, a is the radius of the wire, and Hc is the circumferential coercive force.
[0003]
When an external magnetic field in the wire axis direction is applied to this energized amorphous wire, the magnetic flux acting on the outer shell portion having the magnetizability in the circumferential direction is obtained by combining the circumferential magnetic flux and the external magnetic flux by the energization. shift direction from the circumferential direction of, the more hardly occur magnetization in the circumferential direction, the mu ₁ is decreased, the inductance voltage component eL is reduced.
[0004]
Thus, the inductance voltage eL is remarkably reduced, and the amorphous wire is incorporated into one side of the bridge in order to detect the external magnetic field using the inductance voltage eL. Of the (voltage drop due to the resistance and the voltage drop eL due to the inductance described above), only the inductance voltage eL is detected by canceling the resistance voltage, and the external voltage is determined from the fluctuation of the detected voltage with respect to the external magnetic field in the wire axis direction. It has been proposed to detect a magnetic field (JP-A-6-283344).
[0005]
[Problems to be solved by the invention]
A high S / N ratio is indispensable for improving the performance of the magnetic flux detection type reproducing magnetic head. Therefore, in order to use the external magnetic field detecting means as a magnetic head, it is required to further improve the detection sensitivity (S / N ratio) with respect to the external magnetic field. It has been proposed to anneal while a varying current is applied (Japanese Patent Laid-Open No. 176930/1994).
However, this proposal is a solution from the wire processing surface, and cannot avoid the restriction on the processing surface.
[0006]
An object of the present invention is to supply a current to an amorphous magnetic wire, detect only a voltage component due to an inductance in a voltage generated by the current, and detect an axial external magnetic field of the wire from a change in the detection voltage. It is an object of the present invention to provide a magnetic sensor which can sufficiently improve the detection sensitivity of an external magnetic field only by simple addition of a magnetic sensor.
[0007]
The magnetic sensor according to claim 1, wherein a current flows in the axial direction of the amorphous magnetic wire, and a circumferential magnetic field in the amorphous magnetic wire based on the current is changed by a detected magnetic field passing in the axial direction of the amorphous magnetic wire. In the magnetic sensor that changes the voltage between both ends of the wire based on the tilt and detects the magnetic field to be detected based on the voltage change, a high permeability material is welded to both ends of the amorphous magnetic wire. I do.
The magnetic sensor according to claim 2, wherein a current flows in the axial direction of the amorphous magnetic wire, and a circumferential magnetic field in the amorphous magnetic wire based on the current is changed by a detected magnetic field passing in the axial direction of the amorphous magnetic wire. The magnetic sensor changes the voltage between both ends of the wire based on the tilt, and detects the magnetic field to be detected based on the change in the voltage. One end of the magnetic wire is welded to one high magnetic permeability material, and the other end of the amorphous magnetic wire is welded to the other high magnetic permeability material.
The magnetic sensor according to claim 3, wherein a current flows in the axial direction of the amorphous magnetic wire, and a circumferential magnetic field in the amorphous magnetic wire based on the current is detected by a detected magnetic field passing in the axial direction of the amorphous magnetic wire. In the magnetic sensor that changes the voltage between both ends of the wire based on the tilt and detects the magnetic field to be detected based on the change in voltage, metal electrodes are provided on the substrate at predetermined intervals, and each metal electrode is A high permeability material is provided thereon, one end of the amorphous magnetic wire is welded to one high permeability material, and the other end of the amorphous magnetic wire is welded to the other high permeability material.
A magnetic sensor according to a fourth aspect is characterized in that, in the magnetic sensor according to any one of the first to third aspects, bonding is performed instead of welding.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1A is a side view showing one magnetic sensor according to the present invention, and FIG. 1B is a plan view thereof.
In FIG. 1A and FIG. 1B, reference numeral 1 denotes a zero magnetostrictive or negative magnetostrictive amorphous wire having an easily magnetizable outer shell in a circumferential direction. Reference numerals 2 and 2 denote high magnetic permeability material heads connected to both ends of the amorphous wire. Soft magnetic materials having low remanence and high magnetic permeability, for example, permalloy (iron-nickel alloy), silicon steel, ferrite, etc. Can be used.
[0009]
FIG. 2 shows a bridge circuit for detecting an external magnetic field using the magnetic sensor according to the present invention.
In FIG. 2, reference numeral 3 denotes a high-frequency power supply. A current flows through the amorphous wire by the power supply 3, and a voltage including a resistance voltage component eR and an inductance voltage component eL is generated at both ends aa 'of the wire.
The bridge circuit is balanced so that only the inductance voltage eL is output to the output terminal bb ′. The inductance voltage component eL, as already described, the circumferential permeability of the amorphous wire 1 and mu _1,
│eL│∝μ ₁ It is given by (1). Thus, a zero magnetostrictive or negative magnetostrictive amorphous wire has an easily magnetizable outer shell in the circumferential direction, and the outer shell is easily formed by a circumferential magnetic flux generated by a wire axial current. since is magnetized in the circumferential direction, mu ₁ is large, ￨EL￨ also large.
[0010]
In FIG. 2, H is an external magnetic field to be detected, the magnetic field direction is the axial direction of the amorphous wire 1, and the magnetic flux entering the distal end face 21 of the high-permeability material head 2 passes through the amorphous wire 1. In this case, assuming that the area of the tip end face 21 of the high-permeability material head 2 is S, and the cross-sectional area of the amorphous wire 1 is s, the magnetic flux passing through the amorphous wire 1 is smaller than that without the high-permeability material head. / S (S / s = k≫1) times.
[0011]
The direction of the external magnetic field H is the axial direction of the amorphous wire 1, and the magnetic flux is a vector composite magnetic flux with the circumferential magnetic flux generated by the above-described wire energization. The direction of the magnetic flux acting in the wire 1 is inclined from the circumferential direction.
Thus, if the inclination angle of the magnetic flux when there is no high-permeability material head is φ, and the inclination angle of the magnetic flux when the high-permeability material head is present is Φ,
cosΦ / cosφ = k≫1 ▲ 2 ▼
Holds.
[0012]
Thus, in the present invention, a high-permeability material head is attached, and the inclination angle of the magnetic flux in the amorphous wire with respect to the circumferential direction becomes large, so that the circumferential magnetization of the outer shell portion of the amorphous wire becomes large. since the degree of circumferential permeability mu ₁ of said becomes small weakening increases, the │eL│ varies with high sensitivity. Therefore, an external magnetic field can be detected with high sensitivity.
[0013]
The shape of the high-permeability material head 2 may be a shape having a larger cross-sectional area toward the tip, for example, a conical shape as shown in FIG. The cross-sectional shape may be any of a rectangle such as a rectangle, a polygon other than a rectangle, a triangle, a circle, an ellipse, and the like.
The attachment of the high-permeability material head to the amorphous wire is usually performed by fixing the high-permeability material head to the end of the wire by welding or the like on the outer surface. As shown in FIG. It is also possible to provide a wire insertion hole 22 in 2 and press-fit the wire end into this hole and fix it with an adhesive 23.
[0014]
FIG. 4A shows another magnetic sensor according to the present invention, in which high magnetic permeability material heads 2, 2 are fixed on an insulating substrate, for example, a ceramic substrate 4, and an amorphous wire is provided between these heads 2, 2. 1 are connected by welding or the like.
FIG. 4B shows another example of another magnetic sensor according to the present invention, in which electrodes 5, 5 are coated on an insulating substrate 4, for example, a ceramic substrate by coating a metal (for example, silver-palladium alloy). A high magnetic permeability material head 2 is fixed on each electrode 5 and an amorphous wire 1 is connected between the heads 2 and 2 by welding or the like.
[0015]
In the present invention, instead of the removal of the resistive voltage caused by the bridge, using a resonant circuit, the inductance voltage component eL in the wire across a-a 'voltage due to energization capacitor - canceled by adjusting the [mu ₁ iota = L _1, C 1 = adjust _{1 /} condenser so as to satisfy the (w√L ₁₎ to C _1], the deviation of the resonance when allowed to act the external magnetic field, also be detected inductance voltage change due to an external magnetic field It is possible.
[0016]
【Example】
[Example 1]
The amorphous wire has a composition of Co ₇₀ . In ₅ B ₁₅ Si ₁₀ Fe _4, it was from zero magnetostriction, outer diameter 50Myuemufai, length 2 mm.
As shown in FIG. 4B, electrodes 5 and 5 are formed of a silver-palladium alloy on a ceramic substrate 4, and 0.5 mm thick, 4.0 mm long and 1.6 mm wide iron are formed on the electrodes. A -50 nickel alloy plate 2 was fixed, and the amorphous wire 1 was welded between the plates 2 and 2.
[Example 2]
Example 1 was the same as Example 1 except that ferrite was used instead of the iron-50 nickel alloy.
(Comparative example)
Example 1 was the same as Example 1 except that an iron wire was not welded to the electrode without using an iron-50 nickel alloy plate.
[0017]
The magnetic sensors of these Examples and Comparative Examples were incorporated in a bridge circuit as shown in FIG. 2, and a weak current was applied to the wires so that the output voltage eL at an external magnetic field of 0 was 1.3 volts. The magnetic field when the output voltage eL was changed was measured by changing the external magnetic field in the wire axis direction while being inserted into the core of the coil, and was 4 G in the comparative example. 0.7 G, and it was confirmed that each of the examples had higher sensitivity than the comparative example.
[0018]
【The invention's effect】
In the magnetic sensor according to the present invention, when an external magnetic field is detected by utilizing the magnetic impedance effect of a zero-magnetostriction or negative-magnetostriction amorphous wire, the detection sensitivity can be obtained simply by attaching a high magnetic permeability material to the amorphous end. Can be sufficiently improved, and high sensitivity can be achieved at a low cost with a simple structure.
[Brief description of the drawings]
FIG. 1A is a side view showing a magnetic sensor according to the present invention, and FIG. 1B is a plan view thereof.
FIG. 2 is a circuit diagram showing a use state of the magnetic sensor according to the present invention.
FIG. 3 is a cross-sectional view illustrating a main part of another example of the magnetic sensor according to the present invention.
FIG. 4
[Explanation of symbols]
1 amorphous wire 2 high permeability material head 4 substrate

Claims (4)

A current is caused to flow in the axial direction of the amorphous magnetic wire, and a circumferential magnetic field in the amorphous magnetic wire based on the current is inclined with respect to the circumferential direction by a detected magnetic field passing in the axial direction of the amorphous magnetic wire. A magnetic sensor in which a high magnetic permeability material is welded to both ends of an amorphous magnetic wire, wherein the magnetic sensor changes a voltage between both ends of the wire and detects a magnetic field to be detected from the voltage change . A current is caused to flow in the axial direction of the amorphous magnetic wire, and a circumferential magnetic field in the amorphous magnetic wire based on the current is inclined with respect to the circumferential direction by a detected magnetic field passing in the axial direction of the amorphous magnetic wire. In a magnetic sensor that changes a voltage between both ends of a wire and detects a magnetic field to be detected based on the voltage change, a high permeability material is provided on a substrate at a predetermined interval, and one end of the amorphous magnetic wire is connected to one of the high permeability materials. A magnetic sensor, wherein the magnetic sensor is welded to a magnetic permeability material, and the other end of the amorphous magnetic wire is welded to the other high magnetic permeability material . A current is caused to flow in the axial direction of the amorphous magnetic wire, and a circumferential magnetic field in the amorphous magnetic wire based on the current is inclined with respect to the circumferential direction by a detected magnetic field passing in the axial direction of the amorphous magnetic wire. In the magnetic sensor that changes the voltage between both ends of the wire and detects a magnetic field to be detected from the changed voltage, metal electrodes are provided at predetermined intervals on a substrate, and a high magnetic permeability material is provided on each metal electrode. A magnetic sensor, wherein one end of an amorphous magnetic wire is welded to one high magnetic permeability material, and the other end of the amorphous magnetic wire is welded to the other high magnetic permeability material . The magnetic sensor according to claim 1, wherein the magnetic sensor is bonded instead of welding.

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