JPH0372939B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high pressure detection method and apparatus, and more particularly to a high pressure detection method and apparatus for magnetically detecting hydrostatic pressure up to at least 500 MPa=5 Kbar.

[Conventional technology and problems]

Generally, an electrical method is used to detect high voltage.

This electrical method utilizes the property that electrical resistance changes in response to changes in pressure. However, this electric resistance value changes discontinuously in a low temperature region, so there is a problem that accurate pressure measurement cannot be performed.

[Purpose of the invention]

The present invention has been made in view of these points, and it is an object of the present invention to provide a high pressure detection method and device that can accurately measure high pressure and satisfactorily even in a low temperature range by utilizing magnetic properties. With the goal.

[Summary of the invention]

The high pressure detection method of the present invention is based on magnetic anisotropy in response to changes in pressure of a pressure sensitive element formed of a single crystal or polycrystal of an iron-nickel alloy containing 30 to 50% by weight of nickel to iron. Determining the degree of change in the constant in advance, installing this pressure-sensitive element in a high-pressure region where pressure is to be detected, and extracting the change in the magnetic anisotropy constant of the pressure-sensitive element within the high-pressure region as a change in magnetic torque, The amount of change in the magnetic anisotropy constant is determined by Fourier analysis of this change in magnetic torque, and the amount of change in pressure with respect to the amount of change in the magnetic anisotropy constant determined in advance of the pressure sensitive element is calculated in the high pressure region. The pressure in the high pressure region is detected by setting the pressure to .

Further, the high pressure detection device of the present invention is formed of a single crystal or polycrystal of an iron-nickel alloy containing 30 to 50% by weight of nickel based on iron in the high pressure region, and is resistant to changes in pressure. A pressure-sensitive element whose degree of change in magnetic anisotropy constant is determined in advance is provided,
A magnetic torque detection means is provided for extracting a change in the magnetic anisotropy constant in the high pressure region of the pressure sensitive element as a change in magnetic torque, and the detected change in magnetic torque is subjected to Fourier processing to detect the magnetic anisotropy constant. The method is characterized in that a pressure measuring means is provided to determine the amount of change and to determine the amount of change in pressure with respect to the amount of change in the magnetic anisotropy constant determined in advance of the pressure sensitive element as the pressure in the high pressure region. .

[Embodiments of the invention]

Embodiments of the present invention will be described below along with the process leading to the invention based on the drawings.

In order to detect pressure, it is sufficient to utilize physical properties that change according to changes in pressure, and conversely detect pressure from the state of the physical properties.

In the present invention, magnetic anisotropy is utilized as the physical property.

That is, in the present invention, a pressure-sensitive element formed of a single crystal or polycrystal of an iron-nickel alloy containing nickel in an amount of 30 to 50% by weight based on iron has a magnetic anisotropy constant of It takes advantage of the fact that it changes in response to changes in.

In the present invention, the degree of change in the magnetic anisotropy constant with respect to the change in pressure of the pressure sensitive element is
The pressure is determined in advance by varying it from 0 to a desired high pressure. Next, this pressure-sensitive element is installed in a high-pressure region where pressure is to be detected, and a change in the magnetic anisotropy constant of the pressure-sensitive element within the high-pressure region is extracted as a change in magnetic torque. Next, the amount of change in the magnetic anisotropy constant is determined by Fourier analysis of this change in magnetic torque, and the amount of change in pressure with respect to the amount of change in the magnetic anisotropy constant determined in advance of the pressure sensitive element is calculated. The pressure in the high pressure area is detected as the pressure in the high pressure area.

Next, a method of obtaining the magnetic anisotropy constant of the pressure sensitive element in advance will be explained.

First, magnetic anisotropy is due to the fact that when a ferromagnetic material is magnetized by applying a magnetic field H from the outside, it is difficult to magnetize it depending on the direction of the material's crystal. is the internal energy difference described by the magnetocrystalline anisotropy constant K1 or K2 term. In addition, work-induced magnetic anisotropy occurs in iron, its alloys, etc. that have been subjected to rolling, compression, and tensile deformation. This machining-induced magnetic anisotropy constant is Ku. This shows that anisotropy also occurs in polycrystalline materials.

These magnetic anisotropy constants can be determined by measuring magnetic torque using a magnetic torque meter, which is a type of magnetic gauge.

In other words, the magnetic torque L in the (001) plane is expressed by the following formula: L=-K1/2sin4θ+Ku sin2θ'...(1) given by.

Here, θ is the angle formed by the external magnetic field from the <100> direction of the crystal, and θ' is the angle formed between the external magnetic field and the processing direction.

In the case of polycrystals, the first term in equation (1) can actually be ignored.

Then, the pressure change rates ΔK1 and ΔKu of each magnetic anisotropy constant in equation (1) are expressed as follows: ΔK1=1/K1・∂K1/∂P ΔKu=1/Ku・∂Ku/∂P (2) It is defined accordingly.

Here, ∂K1, ∂Ku, ∂P are K1, Ku, respectively
This is a change in P.

Transforming this equation (2) with respect to ∂P, we get ∂P=1/ΔK1・∂K1/K1 ∂P=1/ΔKu・∂Ku/Ku (3) becomes.

In the present invention, ΔK1, K1, on the right side of equation (3),
The relationship between ∂K1, ΔKu, Ku, ∂Ku and ∂P on the left side is
The pressure change rate of magnetic anisotropy constants such as ΔK1 and ΔKu in the high pressure region where the pressure is to be detected is detected by measurement in advance, and the pressure in the high pressure region is determined based on equation (3).

Further, in the present invention, as described above, a single crystal or polycrystal of an iron-nickel alloy containing 30 to 50% by weight of nickel based on iron is used as the pressure-sensitive element. This iron-nickel alloy was used because the inventor's extensive experiments and research revealed that the rate of pressure change in the magnetic anisotropy constant is stable.

FIG. 1 shows an apparatus for measuring changes in magnetic anisotropy constant with respect to changes in pressure of a pressure-sensitive element in this embodiment.

In the figure, reference numeral 1 denotes a cylinder, and this cylinder 1 is formed by screwing a cylindrical upper cylinder 2 into the upper end of a cylindrical lower cylinder 3 and connecting them airtightly and liquid-tightly via a sealing member 4. ing. A pressure chamber 6 in which a pressure sensitive element 5 is installed is formed within the lower cylinder 3. This pressure chamber 6 is connected to the lower cylinder 3,
It is formed by a piston 7 and a holder 8.
This piston 7 is formed by threading a lower piston 7b to the lower end of an upper piston 7a, and
A compression center 9 is fixed to the lower end of the lower piston 7b, and a plurality of pressure rings 10,
10 is installed. In addition, the upper piston 7a
The small diameter portion of the upper cylinder 2 is slidably inserted through the center shaft of the stopper 11 screwed into the upper end of the upper cylinder 2, and the lower large diameter portion abuts against the lower end of the stopper 11 to maintain a fixed position. is maintained. The pressure sensitive element 5 is fixed to the upper end of the holder 8 and is made of a single crystal or polycrystalline iron-nickel alloy containing 30 to 50% by weight of nickel to iron. In fact, the said iron-nickel alloy is 1300〓
The pressure-sensitive element 5 was annealed for 10 hours and then cold-worked into a disk shape with a diameter of 5 mm and a thickness of 1 mm. Further, a stopper bolt 12 is tightly secured to the center of the lower end of the lower cylinder 3 to seal it. and,
A plurality of large pressure rings 13,
13 is installed. At the lower end of the holder 8, an annular bulge 8a having a U-shaped cross section is formed to press down on the large pressure rings 13, 13. Further, each of these constituent parts is preferably made of a non-ferromagnetic material in order to prevent noise from entering into the detection of the magnetic anisotropy constant, etc. of the pressure sensitive element 5. In this embodiment, it is made of beryllium copper alloy.

In this embodiment, ethyl alcohol is sealed in the pressure chamber 6 as a compressed fluid, and a desired pressure is applied to the pressure sensitive element 5 by changing the pushing length of the piston 7 into the cylinder 3. The magnetic anisotropy constant of the pressure element 5 was determined, and the pressure change rate of the magnetic anisotropy constant was detected. In this case, in order to keep the pushing length of the piston 7 constant, the stopper 11 is screwed into the stopper 11 until its lower end abuts the large diameter portion of the upper piston 7a. Furthermore, if ethyl alcohol is sealed in the pressure chamber 6 as in this embodiment, high pressure detection can be performed down to the low temperature at which the ethyl alcohol solidifies.

In order to obtain this magnetic anisotropy constant, it is sufficient to obtain the magnetic torque L in equation (1) using a magnetic gauge and perform Fourier analysis on the value.

FIG. 5 shows an example of this magnetic gauge.

This magnetic gauge places a pressure-sensitive element 5 housed in a cylinder 1 in a magnetic field (thin arrow part in the figure) formed between the north and south poles of a magnet, and It is formed by gripping a vertical shaft 15 of the torque meter 14 with a gripping portion 16 provided at the lower end thereof, and installing the vertical shaft 15 around the vertical axis via a bearing 17 . When measuring magnetic torque, the magnet is rotated in a horizontal plane around the cylinder 1 to rotate the magnetic field and measure the magnetic torque. That is, when the magnetic anisotropy of the pressure-sensitive element 5 changes in accordance with a change in pressure, the pressure-sensitive element 5 rotates by a certain angle together with the vertical axis 15 due to the interaction between the magnet and the magnetic field. The rotation angle of this vertical axis 15 is determined by the pointer 1.
8 and meter 9 to determine the magnetic torque acting on the pressure sensitive element 5.

The magnetic torque obtained in this way includes the torque LED caused by the eddy current generated when the cylinder 1 itself containing the pressure-sensitive element 5 is subjected to the rotation of the magnetic field.

That is, in such a magnetic gauge, the torque Led due to the eddy current that generally occurs when rotating the magnetic field is Led=kMv(1·1H) ² (4).

here, k: Torque coefficient of this magnetic gauge is 7.9μN・m M: mass of cylinder 1 v: Rotation speed of magnetic field H: Magnetic field strength It is.

From equation (4), it can be seen that the torque Led is proportional to the square of the magnetic field strength H.

The a curve in FIG. 2 shows the relationship between this LED and H. Curve b in the figure shows the value of the amplitude of magnetic torque on the (001) plane of pure nickel. According to this b curve, it is considered that pure nickel LEDs are already in the technical saturation region when the external magnetic field strength H is 0.25 Tesla (T).

In this example, H is 0.5T, v is 6 minutes/
Measured as rotation. In addition, measurements were taken at room temperature (approximately 290°C).

FIG. 3 shows the pressure sensitive element 5 determined in advance from the measured magnetic torque measured by the magnetic gauge in FIG.
The relationship between the magnetic anisotropy constant and pressure is shown.

That is, the measured magnetic torque measured by the magnetic gauge in FIG.
The magnetic torque due to the change in the magnetic anisotropy constant of Lani
However, in the present invention, by Fourier analysis of the measured magnetic torque value, only the amount of change in the magnetic anisotropy constant is calculated, and the pressure and the magnetic anisotropy constant are The relationship between pressure and pressure is determined in advance from pressure 0 to a desired high pressure. In FIG. 3, % indicates the nickel content of the iron-nickel alloy, and N1 indicates pure nickel. In addition, K1 indicates the magnetocrystalline anisotropy constant, and Ku
indicates the process-induced magnetic anisotropy constant, K1' indicates the K1 component obtained by rolling, and KU indicates the uniaxial magnetic anisotropy constant.

In Figure 3, the fact that K1 is positive means that K1 is positive.
1 means that the axis of easy magnetization appears parallel to the <100> direction. Regarding Ku, the case where the axis of easy magnetization appears in the same direction as the direction of the rolled crystal is defined as positive, and −Ku in the figure is defined as positive.
It shows.

As can be seen from the values of the constants in FIG. 3, the magnetic anisotropy constants K1, K1', Ku, and KU decrease almost linearly as the pressure increases, and the rate of pressure change is negative.

Then, each of the magnetic anisotropy constants K1, K1',
Ku and KU are determined in advance by changing the measurement temperature.

FIG. 4 shows the relationship between the pressure change rate of the magnetic anisotropy constant determined in this manner and the nickel concentration of the iron-nickel alloy.

The subscript c in FIG. 4 indicates the case of compression.
In addition, in the same figure, ΔK1 of an iron-nickel alloy with a nickel content of 40% by weight is -10.3 (Pa ^-1 ),
ΔKu is −3.8 (Pa ⁻¹ ).

From FIG. 4, it can be seen that the iron-nickel alloy that can be used for high pressure detection has a nickel content in the range of 30 to 50% by weight. In particular, the content of nickel
The 36.8 to 40.8 wt% iron-nickel alloy has a large K1 pressure change rate of -1 x 10 ^-4 (bar ^-1 ), and 0 to 40.8% by weight.
It changes by 5% up to 500MPa, so the pressure sensitive element 5
When used as a pressure sensor, pressure can be detected accurately.

Next, with reference to FIG. 6, a case will be described in which the pressure in the high pressure region 31 in the casing 30, where the pressure is unknown, is detected together with the configuration of the high pressure detection device.

First, the pressure sensing element 5, whose relationship between the pressure change rate of the magnetic anisotropy constant and the pressure has been determined in advance as described above, is fixedly installed in the cylinder 32 connected to the casing 30, and then It is provided so that the pressure of the high pressure region 31 acts directly on the pressure sensing element 5. This pressure sensitive element 5
The predetermined relationship between the magnetic anisotropy constant and pressure is stored as data in a pressure measuring means 38, which will be described later.

Next, the magnetic torque measuring means 33 measures a magnetic torque corresponding to a change in the magnetic anisotropy constant of the pressure sensitive element 5, which changes depending on the pressure in the high pressure region 31. That is, when the magnetic anisotropy constant of the pressure-sensitive element 5 changes, the permanent magnets N and S attached to the vertical shaft 34, which is rotatably supported by a bearing 35, with the pressure-sensitive element 5 symmetrically sandwiched between them. rotates by a predetermined angle, and the rotation angle is read by the pointer 36 and meter 37 to measure the magnetic torque.

Next, a calculation section (not shown) of the pressure measurement means 38
The amount of change in the magnetic anisotropy constant of the pressure sensitive element 5 is calculated by Fourier analysis of the measured magnetic torque. Next, a characteristic corresponding to the temperature of the high-pressure region 31 is selected from the characteristics of the magnetic anisotropy constant and pressure determined in advance and stored as data, and the calculated amount of change in the magnetic anisotropy constant is calculated. The amount of change in pressure corresponding to is displayed as the pressure in the high pressure region 31 by an appropriate method.

FIG. 7 shows a cylinder 20 that is small and can store high pressure. This cylinder 20 is similar to the cylinder 1 shown in FIG. It is formed. and,
In order to improve the pressure resistance of the cylinder 20 itself, especially the pressure resistance of the axial end opposite to the pushing direction of the piston 22, the portion of the cylinder 20 that forms the pressure chamber 6 is divided into an inner cylinder 20a and an outer cylinder 20b. It has a heavy structure, and a reinforcing member 23 is installed between the axial ends of each cylinder.
is interposed. And further inner cylinder 20
A reinforcing member 23 is shrink-fitted to the protruding portion 24 of a to be integrated, and the inner cylinder 20a and the reinforcing member 23 are shrink-fitted together into the outer cylinder 20b. As a result, the strength of the cylinder 20 is increased, and even if the wall thickness of the cylinder 20 is made thin, a high pressure, for example, 1 GPa, can be accumulated. Further, the piston 22 has two pistons 22a and 22b as in the previous embodiment.
It is held in a fixed position by a stopper 11 screwed into the end of the cylindrical portion 20c of the cylinder 20. Further, a sealing member 25 is provided to prevent leakage of ethyl alcohol from the pressure chamber 6 between the piston 22 and the cylinder 20.

Note that the present invention is not limited to the above-mentioned embodiments, and can be modified as necessary.

〔Effect of the invention〕

Since the high pressure detection method and device of the present invention are configured and operate in this way, high pressure can be measured accurately and well even in a low temperature range by determining the pressure change rate of the magnetic anisotropy constant. It has the following effects:

[Brief explanation of drawings]

The drawings show embodiments of the present invention; Fig. 1 is a half-sectional view of a cylinder for pressure detection, Fig. 2 is a characteristic diagram of the relationship between torque due to eddy current and magnetic field strength, and Fig. 3 is a diagram showing magnetic anisotropy. Figure 4 is a characteristic diagram of the relationship between the constant and pressure; Figure 4 is a diagram of the relationship between the pressure change rate of the magnetic anisotropy constant and the nickel content of an iron-nickel alloy; Figure 5 is a schematic perspective view showing an example of a magnetic gauge; FIG. 6 is a schematic diagram showing one embodiment of the high pressure detection device, and FIG. 7 is a half sectional view showing another embodiment of the cylinder. 1...Cylinder, 5...Pressure sensitive element, 6...Pressure chamber, 14
...Magnetic gauge, 20...Cylinder, 31...High pressure area,
33...Magnetic torque measuring means, 38...Pressure measuring means.

Claims (1)

[Claims] 1. Magnetic anisotropy constant with respect to changes in pressure of a pressure-sensitive element formed from a single crystal or polycrystalline iron-nickel alloy containing 30 to 50% by weight of nickel based on iron. The degree of change in the pressure-sensitive element is determined in advance, the pressure-sensitive element is installed in a high-pressure region where pressure is to be detected, and the change in the magnetic anisotropy constant of the pressure-sensitive element within the high-pressure region is extracted as a change in magnetic torque. The amount of change in the magnetic anisotropy constant is determined by Fourier analysis of the change in magnetic torque, and the amount of change in pressure in the high pressure region is calculated based on the amount of change in the magnetic anisotropy constant determined in advance of the pressure sensitive element. A high pressure detection method for detecting the pressure in the high pressure region by measuring the pressure. 2. The high pressure detection method according to claim 1, wherein the pressure sensitive element is made of an iron-nickel alloy containing 36.8 to 40.8% by weight of nickel. 3 It is formed from a single crystal or polycrystal of an iron-nickel alloy containing 30 to 50% by weight of nickel based on iron in a high-pressure region, and the degree of change in magnetic anisotropy constant with respect to changes in pressure is A predetermined pressure sensitive element is provided, a magnetic torque detection means is provided for extracting a change in the magnetic anisotropy constant in the high pressure region of the pressure sensitive element as a change in magnetic torque, and the detected change in magnetic torque is detected using a Fourier method. Pressure measurement in which the amount of change in the magnetic anisotropy constant is determined by analysis, and the amount of change in pressure with respect to the amount of change in the magnetic anisotropy constant determined in advance of the pressure sensitive element is determined as the pressure in the high pressure region. A high pressure detection device characterized in that it is formed by providing means. 4. The high pressure detection device according to claim 3, wherein the pressure sensitive element is made of an iron-nickel alloy containing 36.8 to 40.8% by weight of nickel.