JPH0222524A - Amorphous stress sensor - Google Patents

Abstract

PURPOSE:To pin the fluctuation of an output signal and to rapidly 4 respond to a stress change by impressing a magnetic field on a magnetic core vertically to the stress impressing direction. CONSTITUTION:A detection coil 2 is wound on the toroidally coiled magnetic core 1 made of a ferromagnetic amorphous alloy, both ends of the coil 2 are connected to an oscillation circuit consisting of the two capacitors C1 and C2 connected in series and an amplifier 10. Namely, a magnetic field generating means is provided to previously impress a magnetic field H on the magnetic core 1 vertically to the impressing direction of stress P. When stress is exerted on the magnetic core 1, the permeability of the magnetic core 1 changes in accordance with the stress, hence the stress can be detected as the change in the frequency and voltage from the output of the coil 2 wound on the magnetic core 1, and the stress exerted on the magnetic coil 1 can be detected. In addition, the permeability changes rapidly in conformity to the exerted stress, and is hardly affected by the external magnetic field.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of use on m-beams) The present invention relates to an amorphous stress sensor capable of detecting weight, tension, pressure, etc.

(Prior Art) A technique is already known in which an amorphous alloy is wound into a toroidal shape and applied to a stress sensor or a displacement transducer. FIGS. 12 and 13 show the basic form of a stress sensor using such an amorphous alloy. In FIGS. 12 and 13.

A detection coil 2 is wound around a magnetic core 1 made of a ferromagnetic amorphous alloy wound in a toroidal shape. Both ends of the detection coil 2 are connected in series with two capacitors C,
, C, and an oscillation circuit consisting of an amplifier 1o.

In the above basic form, the frequency f of the output of the oscillation circuit is and the above C is C1G.

C=-c1+cz (2). When stress P is applied to the toroidal magnetic core 1 made of an amorphous alloy and the magnetic core 1 is deformed, the magnetic permeability of the magnetic core 1 changes. With this change in magnetic permeability, the inductance L of the coil 2 changes, and the oscillation frequency of the oscillation circuit changes. Therefore, the stress applied to the magnetic core 1 can be detected by detecting the change in the count value while counting the oscillation frequency.

(Problem to be solved by the invention) Since amorphous alloys have high magnetic permeability and are non-crystalline, it takes about 100 to 200 seconds for the magnetic permeability to reach equilibrium under a certain stress and the output to become stable. There was a problem in that it required In addition, it is extremely sensitive to external magnetic fields, and there is a problem that the output fluctuates even if there is a slight change in the external magnetic field, and there is a "fluctuation" in the frequency that is unrelated to the external magnetic field. The range of change in frequency output with respect to stress P, that is, the sensitivity, is determined by the composition of the amorphous, toroidal number, toroidal diameter, number of turns of the detection coil, and other components, so it is possible to create a sensor with higher sensitivity in the same shape. That was difficult.

The present invention has been made to solve the problems of the prior art, and shortens the time required for the magnetic permeability to reach an equilibrium state with respect to the stress P, thus speeding up the response. To provide an amorphous stress sensor capable of suppressing changes in output over time, fluctuations and "fluctuations" in output by stabilizing magnetic permeability, and increasing sensitivity by increasing frequency change range. With the goal.

(Means for Solving the Problems) The present invention is a stress sensor that winds a coil around a toroidal magnetic core made of an amorphous alloy and detects magnetic changes due to stress such as external force or displacement applied from the coil to the magnetic core. The present invention is characterized in that a magnetic field generating means is provided for applying a magnetic field in a direction perpendicular to the stress application direction of the toroidal magnetic core.

(Function) When stress is applied to a magnetic core made of an amorphous alloy, the magnetic permeability of the magnetic core changes depending on the stress. This change in magnetic permeability can be detected as a change in frequency, a change in voltage, etc. from the output of a coil wound around the magnetic core, and thereby the stress applied to the magnetic core can be detected. Since a magnetic field is applied to the magnetic core in advance in a direction perpendicular to the direction of stress application,
It is magnetically balanced and stable, and its magnetic permeability changes rapidly in response to applied stress. Furthermore, since a magnetic field is applied in advance, the range of frequency change with respect to the applied stress increases.

Less susceptible to external magnetic fields.

(Example) Examples of the amorphous stress sensor according to the present invention will be described below. In Figures 1 and 2, a magnetic core 1 made of a ferromagnetic material of an amorphous alloy wound in a toroidal shape has a detection coil 2.
is wound around the detection coil 2, and both ends of the detection coil 2 are connected to an oscillation circuit consisting of two series-connected capacitors C1 and C2 and an amplifier 10. The components consisting of the magnetic core 1, detection coil 2, and oscillation circuit are the same as the basic form of the amorphous stress sensor shown in FIGS. 12 and 13. However, in the above embodiment, the toroidal magnetic core 1 is provided with a magnetic field generating means for previously applying a magnetic field H in a direction perpendicular to the direction in which the stress P is applied, as shown in FIGS. 12 and 13. This is different from the basic form. The magnetic field generation means is a magnet (
It may be a permanent magnet) or a Helmholtz coil.

The magnetic field H is a direct current magnetic field, and its direction does not matter.

FIGS. 3 to 5 show more specific examples of the above embodiment. In Figures 3 to 5.

A detection coil 2 is wound around a toroidal magnetic core 1 made of an amorphous alloy.
A plate 3 is placed between the upper and lower supports, and a compression coil is placed between the plates 3 on both sides of the magnetic core 1 in parallel with the magnetic core 1 to receive the stress P applied to the magnetic core 1. A spring 4 is arranged. The plate 3 of the receiver is made of non-magnetic metal or resin. The lower support plate 3 is fixed to the inner bottom of a U-shaped yoke 5. A magnet 6 serving as a magnetic field generating means is fixed to the inner surface of the rising portions 5a facing each other on both sides of the yoke 5 so as to sandwich the magnetic core 1 from the left and right sides. Each magnet 6 has a thickness direction,
That is, in FIG. 4, it is magnetized in the left-right direction, and a constant magnetic field H is applied to the magnetic core 1. The direction in which this magnetic field H is applied is.

This is a direction perpendicular to the direction of stress P applied to the magnetic core 1.

Next, the operation of the above embodiment will be explained.

First, we will explain changes in output over time and improvements in output fluctuations and "fluctuations" due to the influence of external magnetic fields. Figure 6 shows
This shows the relationship between the stress P before applying the magnetic field H and the oscillation frequency f, which is the detection output. Even if a constant stress P is applied, it takes time for the magnetic permeability to reach equilibrium. It is difficult to return to the origin and hysteresis occurs. On the other hand, FIG. 7 shows the relationship between the stress P and the output oscillation frequency when a magnetic field is applied to the magnetic core in a direction perpendicular to the stress application direction as in the present invention. That is, the change in oscillation frequency f with respect to stress P is reversed, and
It can be seen that the return to origin and hysteresis have been significantly improved, and the output changes over time have almost disappeared.

Further, although the cause of the "fluctuation" in the oscillation frequency is not necessarily clear, the following causes may be considered.

1) Stress strain on the cut surface of amorphous When amorphous is cut, strain remains on the cut surface, and the magnetic permeability becomes partially irregular.

2) Caused by toroidal shape The magnetic core is formed by winding an amorphous alloy into several tens of layers in a toroidal shape, but there is no insulation between each layer, and it is impossible to wind the magnetic core under strictly constant stress. , μm between the eyebrows
There is a gap of the order of magnitude, and the position and size of this gap change subtly under stress, which causes "fluctuation."

On the other hand, if an insulating layer is interposed between the amorphous layers, the amorphous layers will be separated from each other.

Magnetic permeability decreases and sensitivity decreases.

However, when a magnetic field is applied in a direction perpendicular to the stress applying force direction of the magnetic core as in the present invention, there is no change in one oscillation frequency over time, and there is no "fluctuation" in the oscillation frequency.

Furthermore, since amorphous alloys have high magnetic permeability, just the presence of a magnetic material such as iron in the vicinity changes the permeability and the output frequency. Various types of magnetic flux, including the earth's magnetic field, come in from the outside. If a magnetic field is not applied to the magnetic core in advance, the output will change due to the influence of these magnetic fluxes. However, in the present invention, on the contrary, a magnetic field generating means is provided based on the idea that it is sufficient to always apply a constant magnetic field to stabilize the magnetic characteristics to some extent. As a result, even if an external magnetic field is applied, the magnetic characteristics are stable and the output will not fluctuate.

Next, the improvement in sensitivity according to the present invention will be explained. The sensitivity of an amorphous stress sensor varies somewhat depending on the amorphous material, but before applying a magnetic field it is 0 as shown in Figure 8.
．． It was 5 to 1.5 Hz/gf.

However, when a magnetic field is applied as in the present invention, the sensitivity improves to about 4.2 Hz/gf, as shown in FIG.

Although the mechanism by which this sensitivity is improved is not necessarily clear, it is thought to be of the first order. Since amorphous alloys are amorphous, the atomic arrangement is disordered, and the magnetocrystalline anisotropy is extremely small and theoretically zero, and the magnetic moment specific to each atom is thought to be oriented in various directions. It will be done. When amorphous material is wound into a toroidal shape and stress σ is applied thereto, internal stress is generated in the amorphous material.

There is a relationship between the internal stress and the magnetocrystalline anisotropy constant as expressed by the following equation (3).

K= (3/2)λσ (3) However, K
; magnetocrystalline anisotropy constant λ; magnetostriction σ; internal stress In CO-based amorphous, magnetostriction is almost zero, but the magnetocrystalline anisotropy constant increases as stress increases. That is, the magnetic anisotropy increases. Specifically, looking at the relationship between the domain wall energy γ and the magnetic anisotropy constant in the 0th order, where magnetic anisotropy is thought to be induced by tension on the outside of the magnetic core and by compression force on the inside, γ= 4i (4). However, A is an exchange force constant. When the stress is zero, the domain wall energy γ is low according to equation (4),
Domain wall movement is smooth. As stress is applied, the magnetic anisotropy constant K increases and the domain wall energy increases. Domain walls can only exist in areas where the domain wall energy is high, so in a state of stress, domain walls can only exist in a limited range.In a state where domain walls can move freely, the magnetic permeability μ is large and the stress is low. Therefore, in a state where the domain wall cannot move freely, the magnetic permeability μ becomes low. As is well known, the magnetic permeability μ is proportional to the coil inductance L. Therefore, when no magnetic field is applied to the magnetic core, the slope of the curve showing the relationship between the oscillation frequency and the stress is positive, as shown in Figure 8. becomes.

However, when a magnetic field is applied in a direction perpendicular to the stress application direction of the magnetic core as in the present invention, the magnetic moments are aligned in the direction of the amorphous layer, leading to strong uniaxial anisotropy. Therefore, the -axis anisotropy constant becomes large, the domain wall energy increases according to equation (4), and the domain wall is strongly pinned. the result.

The magnetic permeability of the magnetic core decreases, and the oscillation frequency increases by 1.5 to 2.0 times as much as when no magnetic field is applied in a stress-free state. Therefore, the amount of change in the oscillation frequency with respect to the change in applied stress increases, resulting in improved sensitivity. When stress is applied with a magnetic field applied to the magnetic core, (
3) Magnetic anisotropy is derived according to the formula. Since this direction is along the plane of the amorphous ribbon, it is different from the direction in which the magnetic field is applied, resulting in multiaxial anisotropy as a whole. Multi-axis anisotropy has lower anisotropy energy and lower domain wall energy than -axis anisotropy. This frees up the domain walls, which were extremely difficult to move, to some extent, increasing magnetic permeability. As a result, the oscillation frequency decreases, and the slope of the curve showing the change in the oscillation frequency with respect to the stress change is opposite to that in the case where no magnetic field is applied, as shown in FIG.

Next, modified embodiments of the present invention will be described.

In the example shown in FIG. 10, a magnet 7 as a magnetic field generating means is arranged between a magnetic core 1 made of a toroidal amorphous alloy and compression coil springs 4 on both sides.Other configurations are similar to those shown in FIGS. There is no difference from the embodiment shown in FIG.

In the embodiment shown in FIG. 11, a magnet 8 is placed behind the magnetic core 1, and the magnetic core 1 is sandwiched between a yoke 9 extending forward integrally from both ends of the magnet 8. magnetic core 1
A magnetic field H is applied to via the yoke 9. This magnetic field H
The direction of is perpendicular to the direction of the stress P applied to the magnetic core l.6 The embodiments shown in FIGS. .

Note that the output signal is not limited to a change in one frequency, and may be extracted as a change in voltage.

(Effects of the Invention) According to the present invention, since a magnetic field is applied to the toroidal magnetic core made of an amorphous alloy in a direction perpendicular to the stress application direction, the "fluctuations" of the output signal are pinned, and the stress changes. It is possible to speed up the response to external magnetic fields, and it is also possible to eliminate the influence of external magnetic fields. In addition, when taking the oscillation frequency as an output, applying a magnetic field to the magnetic core significantly reduces the magnetic permeability of the magnetic core and increases the oscillation frequency, which not only improves detection sensitivity but also has advantages in terms of noise. becomes.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the basic form of the amorphous stress sensor according to the present invention, FIG. 2 is a circuit diagram of the same as above, FIG. 3 is a perspective view showing a specific example of the amorphous stress sensor according to the present invention, and FIG. Figure 5 is a front view of the same as above, Figure 5 is a side cross-sectional view of the same as above, Figure 6 is a diagram showing the relationship between stress and oscillation frequency when no magnetic field is applied to the magnetic core, and Figure 7 is a diagram showing the relationship between stress and oscillation frequency when a magnetic field is applied to the magnetic core. A diagram showing the relationship between oscillation frequencies, Figure 8 is a diagram showing the sensitivity when no magnetic field is applied to the magnetic core, Figure 9 is a diagram showing the sensitivity when a magnetic field is applied to the magnetic core, and Figure 10 is a diagram showing the sensitivity when no magnetic field is applied to the magnetic core. FIG. 11 is a front view showing another embodiment of the amorphous stress sensor according to the invention, FIG. 11 is a plan view showing still another embodiment of the amorphous stress sensor according to the invention, and FIG. 12 is a perspective view showing the basic shape of the amorphous stress sensor. FIG. 13 is a circuit diagram of the same as above. 1... Magnetic core 2... Coil 6, 7, 8, 9.
・・・Magnetic field generating means 瑯 6 Tsuenka P (do af) Horse 40 zuun・force P (￥3.f) Muscle diagram horse drawing 1 乃P (time drawing angle P (do 3f)

Claims (1)

[Claims] A stress sensor that winds a coil around a toroidal magnetic core made of an amorphous alloy, and detects magnetic changes due to stress such as external force or displacement applied to the magnetic core from the coil, and the sensor An amorphous stress sensor characterized by being provided with a magnetic field generating means for applying a magnetic field in a direction perpendicular to the opposite direction.