JPH0476422B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a mechanical quantity-inductance conversion type sensor detection method using an amorphous alloy plate.

Prior Art A conventional detection method will be explained using a pressure sensor. FIG. 4 is a sectional view of a pressure sensor using an amorphous magnetic alloy plate. 1 is an amorphous alloy plate with magnetostriction, 2 is a core made of soft magnetic ferrite, and 3 is a coil installed in the core 2. When a current is applied to the coil 3, the amorphous alloy plate 1 and core 2 A magnetic circuit H is configured. The whole thing is housed in Case 4. Pressure is applied to a part of the other surface of the amorphous alloy plate 1 by a pressure transmitting means 7 consisting of an introduction part 5 and a through hole 6.
When strain occurs in the amorphous alloy plate 1 due to the application of pressure, the magnetism of the amorphous alloy plate 1 changes due to the magnetostrictive effect, and the change is detected by the detection unit 10 consisting of the oscillation power supply 8 and the inductance measurement circuit 9. , pressure is sensed by inductance.

Conventionally, detection was performed using a single frequency alternating current signal as shown in Figure 5, but the change in pressure-inductance was small and the reproducibility was poor, hysteresis occurred with respect to pressure, and amorphous magnetic alloy Stability is also poor due to the day accommodation (hereinafter abbreviated as DA) on board 1.

FIG. 6 is a diagram showing the pressure-inductance relationship of the pressure sensor of FIG. 3 using a single frequency alternating current signal as shown in FIG. Arrows indicate the order of measurements. Moreover, FIG. 7 shows how the inductance changes over time when the pressure is constant.

This change indicates that insufficient DA and demagnetization of the amorphous alloy plate 1 deteriorate the reproducibility of the inductance. Therefore, if demagnetization is repeated as a sensor detection method, the characteristics can be improved. Figure 8 shows a normal low-frequency demagnetization waveform, which continuously decreases from a sufficiently large amplitude to zero amplitude, and for measurement it is necessary to switch to a high-frequency, constant-amplitude measurement signal. . However, although it is essential for this switching to be free of chattering, there is a drawback in that the detection section becomes expensive in order to achieve this.

Problems to be Solved by the Invention When the inductance of a sensor using an amorphous alloy plate is detected using an AC signal of a single frequency,
The value has poor stability due to DA and poor reproducibility. Furthermore, an alternating current signal of a single frequency does not show a large change in the magnetic permeability or stress of the amorphous alloy plate, and the change in the inductance of the coil is small.

On the other hand, even in repeated demagnetization, it is difficult to switch between the demagnetizing current and the measurement current without affecting the characteristics.

Means for Solving the Problems In order to solve the above problems, the present invention continuously changes the signal from the oscillation power supply temporally from low frequency to high frequency when detecting the inductance of the coil, and after applying the low frequency, the high frequency Pressure is detected by inductance when applied.

Furthermore, in order to improve sensitivity, an AC signal on which a DC signal is superimposed is used.

Action For AC signals that have a constant voltage and vary from low frequency to high frequency, if the inductance is constant, the impedance increases in proportion to the frequency, so the magnitude of the current changes from large amplitude at low frequency to small amplitude at high frequency. It works to change the amplitude. In other words, this AC signal has a demagnetizing effect. Therefore, by repeatedly using this AC signal, it is possible to detect stable inductance immediately after demagnetization.

The reason is that when demagnetization is performed, the magnetic domain structure of the amorphous alloy plate is reset. In other words, the magnetic domain structure is in its initial state. Therefore, the coil inductance has better repeatability and less hysteresis. Furthermore, since demagnetization moves the domain wall significantly and then resets it, the environment of the domain wall becomes new after demagnetization, and this is the first part where DA begins, so if the measurement is carried out in a short period of time, it is possible to escape from the influence of DA itself. . Therefore, if demagnetization is repeated as a sensor detection method, the characteristics can be improved.

Although the demagnetization effect alone is effective for stabilizing the inductance, when a DC signal is further superimposed, that is, when a DC magnetic field is superimposed, the sensitivity of a sensor using an amorphous magnetic alloy plate to stress and strain increases. The reason why such an effect is obtained is considered to be due to the following reasons.

When strain occurs within an amorphous magnetic alloy plate, magnetic permeability decreases in the portion where the strain occurs. As a result, since the magnetic flux is continuous within the magnetic circuit, the DC and AC magnetic fields are larger in the distorted part than in other parts. As the DC magnetic field increases, the magnetic permeability of the amorphous magnetic alloy plate decreases like a normal soft magnetic material, so the decrease in magnetic permeability becomes greater than the decrease in magnetic permeability due to initial strain alone. This change has a large effect in the portion corresponding to the shoulder of the B-H loop, where the dependence of magnetic permeability on the AC magnetic field on the DC magnetic field is large. If the DC magnetic field is set to correspond to the shoulder of this B-H loop, the magnetic resistance will increase several times. This portion is considered to correspond to the DC magnetic field region where the sensor output increases. Since the magnetic permeability reducing effect and magnetic resistance increasing effect due to this DC magnetic field are large, there is almost no effect even if the AC magnetic field component amplitude becomes slightly large.

On the other hand, in parts of the magnetic circuit where no distortion occurs, the magnetic field decreases, magnetic permeability increases, and magnetic resistance decreases.
However, since the magnetic resistance of this portion is connected in series with the magnetic resistance of the strained portion, the overall magnetic resistance change is mainly due to the large magnetic resistance change of the strained portion. Therefore, it is thought that the sensitivity of the sensor increases with the application of a DC magnetic field.

Furthermore, when measurement is performed using an alternating current magnetic field superimposed with a direct current magnetic field, the measurement uses a rotational magnetization process. In the domain wall displacement magnetization process, the domain wall crosses an energy barrier that easily changes depending on the temperature inside the magnetic body, so it is easily affected by temperature, but in the rotational magnetization process, magnetic permeability is not affected by temperature much. This is because the magnetic permeability is determined only by the temperature characteristics of the magnetic moment due to the magnetization process due to rotation of magnetization. For these reasons, a sensor with good temperature characteristics can be constructed by performing measurements with an alternating current magnetic field superimposed on a direct current magnetic field.

Embodiment FIG. 1 shows signals from an oscillation power supply in this embodiment.

a indicates a voltage waveform, and b indicates a magnetic field waveform generated in the coil. That is, the signal is temporally changed continuously from a low frequency to a high frequency, and when a high frequency is applied after the low frequency is applied, the inductance is measured and the pressure is detected.

If the inductance of the coil is L, its impedance Z can be found using the frequency as follows: Z=2π・L (1). Therefore, the magnetic field H generated in the coil, which is proportional to the current, is expressed as H∝i∝V/2π·L (where V is the voltage amplitude). Therefore, by using a signal such as a that changes continuously from a low frequency to a high frequency with a constant voltage, a demagnetizing waveform as shown in figure b can be realized.

That is, by applying the signal shown in FIG. 1, a sensor with good reproducibility and less influence of DA can be obtained.

Figure 2 shows how the inductance when a DC magnetic field is superimposed on the pressure sensor shown in Figure 4 changes depending on the magnitude of the DC magnetic field Hdc at 0 atmospheres and 30
It is shown in atmospheric pressure. The measurement temperature is 50
℃, the frequency is 20KHz. It can be seen from this that the output increases when a DC magnetic field is superimposed, rather than when measuring only with an AC magnetic field.

FIG. 3a shows a signal of another embodiment in which a DC voltage is superimposed on the signal of FIG. 1a. FIG. 4b shows the relationship between the pressure and inductance of the pressure sensor of FIG. 4 when the signal of a is used. It can be seen that by applying a DC magnetic field and repeating demagnetization, the reproducibility, sensitivity, and stability were significantly improved over the conventional example.

Effects of the Invention As described above, if the detection method according to the present invention is used, the mechanical quantity using magnetostriction of an amorphous magnetic alloy plate -
In the inductance conversion type sensor, a sensor with good output reproducibility and stability, little change over time, and a large output can be obtained, and its effects are extremely large.

[Brief explanation of the drawing]

Figure 1a is a diagram showing the signal waveform of the detection method according to an embodiment of the present invention, Figure 1b is a diagram showing the magnetic field waveform, and Figure 2 is the inductance of the pressure sensor when 0 atm and 30 atm are applied. FIG. 3a is a diagram showing the signal waveform of another embodiment,
Fig. 3b is a diagram showing the relationship between pressure and inductance using the same, Fig. 4 is a cross-sectional view of a pressure sensor using an amorphous alloy plate, Fig. 5 is a diagram showing a conventional signal waveform, and Fig. 6 is a diagram showing the relationship between pressure and inductance. FIG. 7 is a diagram showing the relationship between pressure and inductance according to the conventional detection method, FIG. 7 is a diagram showing the change in inductance over time according to the conventional detection method, and FIG. 8 is a diagram showing the conventional demagnetization waveform. 1...Amorphous magnetic alloy plate, 2...Core, 3...
Coil, 7...pressure transmission means, 8...oscillation power supply,
9...Inductance measurement circuit, 10...Detection section.

Claims (1)

[Claims] 1. A core made of a soft magnetic material is provided on one surface of an amorphous magnetic alloy plate having magnetostriction, a coil is provided in the core, and a magnetic circuit is configured by the amorphous magnetic alloy plate and the core. A pressure transmitting means is provided on a part of the other surface of the amorphous magnetic alloy plate, a detection section consisting of an oscillation power source and an inductance measuring circuit is provided on the coil, and the amorphous magnetic alloy plate is detected by the pressure voltage means. In a sensor that detects the strain that occurs in a part using the inductance of a coil, the signal from the oscillating power source is changed continuously from low frequency to high frequency over time, and when a high frequency is applied after a low frequency is applied, the inductance causes pressure to be applied. A sensor detection method characterized by detecting. 2. The sensor detection method according to claim 1, wherein a DC signal is superimposed on an AC signal.