JP2024035229A - Pressure sensor and fluid monitoring sensor module using the pressure sensor - Google Patents

Abstract

[Problem] The present invention provides a pressure sensor having improved pressure resolution and excellent measurement accuracy compared to conventional pressure sensors, as well as stability for highly reactive fluids, and in which the input is linear with respect to the output, and a fluid monitoring sensor module using said pressure sensor. [Solution] The pressure sensor comprises a base 10 having an internal space sealed from the external space, and a first conductive member 21 attached to a surface of a thin-walled portion 12, one of the walls defining the internal space 11 of the base 10 and in which the wall is relatively thin, that faces the external space. The first conductive member 21 is made of a thin film having an isotropic gauge factor in a plane direction perpendicular to the normal to the thin-walled portion 12 to which the first conductive member 21 is attached. In addition, the full-scale error of the output value with respect to pressure is 3% or less. [Selected Figure] Figure 1

Description

The present invention relates to a pressure sensor that measures the pressure of a fluid with high precision, and more particularly to a pressure sensor suitable for highly sensitive pressure measurement in a highly reactive fluid, particularly in a hydrogen gas atmosphere. The present invention also relates to a fluid monitoring sensor module using the pressure sensor.

Recently, moves toward realizing a hydrogen energy society are accelerating, such as the spread of household fuel cells, the appearance of fuel cell vehicles, and the accompanying construction of hydrogen stations. The amount of hydrogen stored in a hydrogen storage alloy used to store and transport hydrogen increases monotonically with the applied hydrogen pressure as a variable. Therefore, by accurately measuring the applied hydrogen pressure, it is possible to accurately measure the amount of hydrogen stored in the hydrogen storage alloy.

However, highly reactive fluids such as hydrogen are highly chemically active and react with the sensing portion of the pressure sensor, reducing the accuracy and sensitivity of the sensor. For this reason, there is a need for the development of pressure sensors that are chemically stable with respect to highly reactive fluids. Furthermore, in order to realize a hydrogen energy society, there is a need for pressure sensors to be made smaller in order to increase convenience.

Patent Document 1 discloses a pressure sensor for hydrogen gas, and the sensor includes a first semiconductor substrate having a recess made of a Si semiconductor and a second semiconductor substrate formed by bonding with Si oxide. Further, the sensor measures pressure using a reference pressure chamber and a diaphragm formed by the first semiconductor substrate and the second semiconductor substrate.

Patent Document 2 discloses a fluid component for hydrogen gas equipped with a pressure sensor. According to the fluid component, since it has a vent hole for discharging permeating hydrogen gas to the outside of the system, pressure errors caused by hydrogen gas permeating the diaphragm and generating bubbles in the sensor element are suppressed. Such a structure prevents hydrogen embrittlement and thus deformation of the sensor element.

On the other hand, Patent Document 3 proposes a strain gauge containing a thin film mainly composed of Cr and N and a strain sensor using a ceramic substrate that can stably measure measurements in a hydrogen gas environment without being affected by hydrogen. has been done. Further, Patent Document 4 proposes a pressure sensor that does not use a strain body made of a thin film containing Cr and N as main components.

Patent No. 6425794 JP2010-266425A Japanese Patent Application Publication No. 2018-151204 Patent No. 6850642

However, the pressure sensor disclosed in Patent Document 1 requires a protective film against hydrogen gas such as Si ₃ N ₄ from the viewpoint of suppressing the piezoresistance and the Si oxide film from hydrogen embrittlement. The method becomes complicated and the degree of freedom of the sensor and thus of the fluidic components is reduced.

Further, the pressure sensor disclosed in Patent Document 2 has a certain degree of danger because hydrogen gas leaks to the outside from the vent hole for exhausting hydrogen gas. Furthermore, the presence of vent holes cannot completely suppress hydrogen penetration, and the strain gauge and diaphragm may become hydrogen embrittled.

The strain sensor disclosed in Patent Document 3 can reduce the effects of hydrogen embrittlement. A type of pressure sensor that does not use a strain body, such as Patent Document 4, which is made of a thin film mainly composed of Cr and N and is used in the strain sensor, can stably measure pressure at pressures of 1 MPa or more. On the other hand, since the sensitivity is low for low pressures of 1 MPa or less, there is a problem that fine pressure fluctuations cannot be measured.

According to FIG. 24, when hydrogen gas is applied between 0.1 and 1.0 MPa, the amount of hydrogen storage changes significantly, so when using a pressure sensor to measure the amount of hydrogen storage in a hydrogen storage alloy, It is necessary to detect the pressure in this section with high precision and high sensitivity. However, if conventional alloys or semiconductors for strain sensors are used in sensing parts for active substances such as hydrogen gas, the performance of the sensors will be significantly degraded due to hydrogen embrittlement. In addition, like general pressure sensors, when a metal diaphragm pressure sensor is installed at a location that separates hydrogen from the outside, such as on the wall of a hydrogen gas container, hydrogen may permeate through the thin diaphragm that forms the diaphragm, or the diaphragm may However, there is a problem in that there is a risk of hydrogen deterioration resulting in reduced durability or rupture.

Furthermore, when reducing the thickness of the flexure element in order to capture minute pressure fluctuations, the nonlinear influence becomes greater than the linear influence in the relationship between strain and pressure, and when used as a sensor, the sensor output ( There is a problem in that the sensor input (voltage, electrical resistance, etc.) becomes nonlinear with respect to the sensor input (pressure, strain, etc.), and the degree of freedom of the sensor is impaired.

In view of these problems, the present invention has superior pressure resolution and measurement accuracy that are improved over conventional pressure sensors, as well as stability with respect to various fluids including highly reactive fluids, and output. It is an object of the present invention to provide a pressure sensor that can be made compact and has a high degree of freedom, and which is linear with respect to input, and a fluid monitoring sensor module using the pressure sensor.

(1) The pressure sensor of the present invention includes:
a base having an internal space sealed to an external space;
a first electrically conductive member attached to a surface of a thin wall portion in which one of the wall portions defining the internal space of the base portion is relatively thin and is in contact with the external space;
The first conductive member is constituted by a thin film having an isotropic gauge factor in a plane direction perpendicular to a normal to a thin portion to which the first conductive member is attached,
It is characterized by a full scale error of output value with respect to pressure of 3% or less.

According to this configuration, the pressure in the internal space of the base is adjusted arbitrarily, so that the range of pressure difference between the external space of the base and the internal space is appropriate for the thin part of the base that functions as a strain body. It is controlled appropriately from the viewpoint of producing a large amount of strain. As a result, the output strength of the signal corresponding to the strain in the thin wall portion of the conductive member formed on the outer surface facing the external space of the base is improved, and the pressure in the external space of the base is thereby improved. This will improve measurement accuracy and resolution. Furthermore, since the conductive member has an isotropic gauge factor, even if the conductive member is formed anisotropically, it will resist the strain of various forms of strain-generating bodies (thin parts). This ensures sufficient output signal strength. Therefore, the degree of freedom in forming the conductive member attached to the surface of the thin portion of the base that is in contact with the external space can be improved. Further, since the diameter and thickness of the thin portion are adjusted, the output of the first conductive member has excellent linearity with respect to pressure.

Further, according to this configuration, the full scale error is 3% or less, so the output of the first conductive member has excellent linearity with respect to pressure. Therefore, as a pressure sensor, the output becomes linear with respect to the input, so the degree of freedom as a sensor is improved.

(2) Also, according to the pressure sensor in (1),
The shape of the thin portion is approximately disc-shaped;
When the thickness of the thin part is t, the diameter of the thin part is a, the Young's modulus of the thin part is E, and the maximum value of the measurement range set for measuring pressure is P _MAX . , (a ² ·(P _MAX ))/(E · t ² ) is preferably less than 9.61×10 ⁻³ .

(3) Also, according to the pressure sensor of (1) or (2),
It is preferable that the thin portion is made of zirconia, that the thickness of the thin portion is 0.05 mm or more, and that the diameter of the thin portion is 2 mm or more and 4 mm or less.

(4) In addition, the pressure sensor of any one of (1) to (3) is
It is preferable to use it under a hydrogen gas atmosphere.

(5) The fluid monitoring sensor module of the present invention includes:
In the pressure sensor according to any one of (1) to (4), on the surface where the first conductive member is provided, the second conductive member is continuous or discontinuous in part or all of the circumference surrounding the thin part. It is characterized by being set up as follows.

According to this configuration, the second conductive member is provided on the same surface as the first conductive member. Therefore, the second conductive member can measure a pressure in a different range (for example, a higher range than the first conductive member) or a different physical quantity (for example, temperature) than the first conductive member. Therefore, the second conductive member can measure pressure in a range that cannot be measured by the first conductive member while maintaining excellent linearity. Furthermore, when the second conductive member measures temperature, it is possible to measure minute pressure fluctuations in the thin portion due to temperature changes, and pressure can be measured with high resolution. Additionally, since both pressure and temperature can be measured, the state of the fluid can be accurately determined.

(6) Also, according to the fluid monitoring sensor module of (5),
Preferably, the first conductive member is composed of a Cr-based thin film or a Cr--N thin film.

According to this configuration, since the first conductive member made of a Cr-based thin film or a Cr-N thin film is used, it is highly sensitive, and the fluid existing in the external space is hydrogen gas, and the pressure difference is 1 MPa. Even if the pressure is applied as external space pressure, the pressure is measured in a hydrogen gas atmosphere without being affected by hydrogen. Therefore, it is suitable as a pressure sensor for highly reactive fluids.

(7) Also, according to the fluid monitoring sensor module of (5) or (6),
Preferably, the second conductive member is made of a Ni thin film.

According to this configuration, the second conductive member is made of a Ni thin film. Therefore, compared to thermocouples and thermistors, Ni thin films provide an output with excellent linearity with respect to temperature, allowing the pressure in the internal space to be maintained and the pressure in the external space to be measured with high accuracy and sensitivity. can be measured.

(8) Furthermore, according to any one of (5) to (7), the fluid monitoring sensor module is preferably used in a hydrogen gas atmosphere.

FIG. 1 is a top view showing a schematic configuration of a fluid monitoring sensor module according to a first embodiment of the present invention. FIG. 2 is a diagram showing a cross section of the fluid monitoring sensor module according to the first embodiment of the present invention shown in FIG. 1, taken along line II-II. FIG. 3 is a diagram showing the relationship between applied pressure and strain in a thin wall portion obtained through structural analysis with the influence of large deformation. The relationship between the measurement error (Y - X) / FIG. FIG. 3 is a diagram showing the relationship among Young's modulus, diameter, thickness, and strain of a thin portion when an applied pressure is 0.9 MPa. FIG. 3 is a diagram showing the relationship among Young's modulus, diameter, thickness, and strain of a thin portion when an applied pressure is 0.1 MPa. FIG. 6 is a diagram showing time-series fluctuations in the pressure in the external space and the resistance value of the first conductive member when varying pressure is applied to the pressure sensor of the fluid monitoring sensor module of Example 1. FIG. 3 is a diagram showing time-series fluctuations in the pressure in the external space and the resistance value of the first conductive member when a constant pressure is applied to the pressure sensor of the fluid monitoring sensor module of Example 1. FIG. 3 is a diagram showing the relationship between the resistance value of the first conductive member and the pressure in the external space in the pressure sensor of the fluid monitoring sensor module of Example 1. 7 is a diagram showing the relationship between the resistance value of the second conductive member and the temperature of the external space in the temperature sensor of the fluid monitoring sensor module of Example 1. FIG. 7 is a diagram illustrating a comparison of temperature fluctuations measured by the second conductive member and temperature fluctuations measured by a thermocouple in pressure fluctuations for the temperature sensor of the fluid monitoring sensor module of Example 1. FIG. FIG. 3 is a diagram showing a comparison between the temperature fluctuation measured by the second conductive member and the temperature fluctuation measured by the thermocouple when a constant pressure is applied in the temperature sensor of the fluid monitoring sensor module of Example 1. . 7 is a diagram showing the relationship between the resistance value of the first conductive member and the pressure in the external space in the pressure sensor of Example 5. FIG. FIG. 3 is a diagram showing the relationship between strain and applied pressure in the thin portion of Comparative Example 1. FIG. 7 is a diagram showing the relationship between strain in a thin wall portion and applied pressure in Comparative Example 2. It shows the time-series variation in pressure when hydrogen gas is introduced into the external space (inside the pressure vessel) and the time-series variation in the resistance value of the first conductive member of the pressure sensor of the fluid monitoring sensor module configured in Example 3. It is a diagram. FIG. 7 is a diagram showing the relationship between the saturation value of the hydrogen applied pressure and the hydrogen storage amount when using the PCT device and Example 3. FIG. 18 is a diagram in which the relationship between the hydrogen applied pressure and the hydrogen storage amount is corrected when Example 3 of FIG. 17 is used. FIG. 6 is a diagram showing time-series fluctuations in the voltage value of the pressure sensor of the PCT device in hydrogen gas application experiment 2. 7 is a diagram showing time-series fluctuations in the resistance value of the first conductive member 21 of the fluid monitoring sensor module in the pressure vessel in hydrogen gas application experiment 2. FIG. Time-series fluctuations in the pressure measured by the pressure sensor of the PCT device based on the voltage value shown in FIG. 19 and the pressure measured by the fluid monitoring sensor module in the pressure vessel based on the resistance value shown in FIG. FIG. FIG. 7 is a diagram showing time-series fluctuations in temperature measured by the temperature sensor of the PCT device in hydrogen gas application experiment 2. , is a diagram showing time-series fluctuations in temperature measured based on the resistance value of the second conductive member of the fluid monitoring sensor module in the pressure vessel in hydrogen gas application experiment 2. FIG. 3 is a diagram showing the relationship between the saturation value of hydrogen applied pressure and the amount of hydrogen storage when a standard hydrogen storage alloy is used.

Embodiments of the invention are illustrated in the description and figures below. FIG. 1 is a diagram showing a top view of a fluid monitoring sensor module as a first embodiment of the present invention. Moreover, FIG. 2 is a diagram showing a cross-sectional view of the fluid monitoring sensor module according to the first embodiment of the present invention. The fluid monitoring sensor module of the present invention includes a base 10 having an internal space 11, and a first conductive member 21 and a second conductive member 22 attached to the surface of the thin portion 12 of the base 10 on the external space side. There is. To explain the positions and orientations of the components of the fluid monitoring sensor module, a three-dimensional cylindrical coordinate system (r, θ, Z) with the geometric center of gravity of the thin portion 12 as the pole point will be used.

The base 10 is configured to have an internal space 11 that is sealed from the external space. Although the outer shape of the base 10 is configured as a square prism, it is not limited to this. The outer shape of the base 10 may be a cylinder, a triangular prism, another polygonal prism, or any shape that is optimal for the measuring device. Moreover, in order to apply it to various circuits as a pressure measuring device, it may have an optimal shape that follows each circuit and measuring device. The shape of the internal space 11 is configured as a cylinder, but is not limited to this. The shape of the internal space 11 may be a cylinder, a truncated cone, a truncated pyramid, a cone, a pyramid, a square prism, other polygonal prisms, or any shape that is optimal for the measuring device. Furthermore, the outer shapes of the internal space 11 and the base 10 may be different or the same. In addition, the thickness, structure, and installation method of the base 10 may be selected so as to maintain the pressure in the internal space 11 without inducing deformation.

The base portion 10 is configured such that one of the wall portions defining the internal space 11 includes a thin portion 12 that is relatively thin. Although the thin portion 12 is configured integrally with the base 10, the present invention is not limited to this, and the thin portion 12 may be detachably attached to the base 10. In this case, the thin portion 12 is attached so as to seal the internal space 11 from the external space. As a method for attaching the thin wall portion 12 to the base 10, an attachment mechanism that can seal the internal space 11 from the external space may be used, such as adhesion using an adhesive, screwing using a screw, or suction using a suction device. It is attached.

The internal space 11 is configured to maintain the pressure in the internal space at a constant pressure. A fluid having a known pressure is introduced into the internal space 11 . The pressure in the internal space is selected to be an arbitrary pressure under the pressure regulated in the pressure-variable glove box before the thin wall portion 12 is attached. Furthermore, at this time, the fluid in the glove box is also arbitrarily selected, so that the fluid in the internal space is arbitrarily selected. Air, nitrogen, etc. are used as examples of fluids, but liquids such as oil can also be used, regardless of gases. Further, the internal space 11 maintains the pressure by being sealed from the external space, but the present invention is not limited thereto. In order to keep the pressure in the internal space 11 constant, a pressure adjustment mechanism disposed in the external space may be communicated with the internal space 11 of the base 10 . As the pressure adjustment mechanism, a vacuum suction device, a high pressure gas supply device, a high pressure fluid supply device, or the like is used.

When the thin part 12 is removable, the thin part 12 has a geometric center of gravity of the thin part 12 as the pole point O, the Z direction as the thickness direction, and a pair of main surfaces that are substantially parallel to the r-θ plane. It is formed to have a first surface 111 in contact with the external space and a second surface 112 in contact with the internal space 11 on the opposite side of the first surface 111. The shape of the thin portion 12 is selected from rectangular, circular, oval, triangular, other polygonal, and arbitrary shapes that are optimal for the measuring device, and has a structure that seals the internal space 11 from the external space. It is formed to have. At this time, the pole point 0 of the thin portion 12 and the geometric center of gravity of the z-axis projection of the internal space 11 may or may not coincide on the r-θ plane. The second surface 112 is provided with an attachment mechanism that continuously attaches the entire circumference of the thin portion 12 to the base 10 around the pole point 0.

Considering the use in a highly reactive fluid, the base 10 is not chemically affected and is chemically stable, does not deform even when a large pressure is applied, and can absorb the pressure in the internal space 11. Preferably, it is made of ceramic, especially zirconia, which can be kept constant. In the case of ceramics, the first conductive member 21 and the second conductive member 22 are not electrically affected, so an insulating film is not required. In this embodiment, zirconia is used as the base 10, but the base 10 is not limited to this. The base 10 may be made of metal with an insulating layer formed thereon, resin such as polyimide, ceramics other than zirconia, or other materials that are most suitable for the measuring device. Further, the material of the thin portion 12 may be the same as that of the base 10, or may be a different material. In particular, from the viewpoint of reducing scale errors, the thin portion 12 is preferably made of a material having a Young's modulus that satisfies the conditions described below.

A protective film may be provided on each of the first conductive member 21 and the second conductive member 22 in order to reduce the influence of physical contact or to further suppress the influence on highly reactive fluids. good. As the protective film, silicon dioxide (SiO ₂ ) is preferably used, but is not limited thereto, and aluminum oxide (Al ₂ O ₃ ), aluminum nitride (AlN), silicon nitride (Si ₃ N ₄ ), etc. can be used as described by those skilled in the art. For this purpose, commonly used materials may be used.

When the difference between the pressure in the internal space and the pressure in the external space is large, deformation (nonlinear deformation occurring between strain and stress) occurs in the thin wall portion 12 due to large deformation. Due to the large deformation, the output of the first conductive member 21 relative to the input becomes nonlinear, and the full-scale error (nonlinearity) also increases. Ideally, the full scale error of the pressure sensor is preferably 0 within a set pressure measurement range, but since an actual substance is used, it may be 0.01% or more. Therefore, as will be described in detail later, in the present invention, the full scale error of the pressure sensor is preferably 3% or less, more preferably 2.7% or less, and even more preferably 2.7% or less within the set pressure measurement range. It is better to keep it below %. Then, so that the full scale error of the pressure sensor is below a predetermined value in the set pressure measurement range, the strain occurring at the maximum pressure in the set pressure measurement range is below a predetermined value, that is, large deformation. It is preferable to set the material and shape of the thin portion 12 so that the influence is within a negligible range.

FIG. 3 shows the strain in the thin part 12 determined by structural analysis with the influence of large deformation when the material of the thin part 12 is zirconia (Young's modulus 210 GPa) and the shape of the thin part 12 is approximately disk-shaped. It is a figure showing the relationship between and applied pressure (0 MPa or more and 0.9 MPa or less). In FIG. 3, the diameter of the thin portion 12 is 2 mm. Referring to FIG. 5, it is clear that linearity is clearly poor when the thickness of the thin portion 12 is 0.04 mm or less.

FIG. 4 is a diagram showing the relationship between the measurement error between the strain and the applied pressure in FIG. 3 and the thickness of the thin portion 12. Here, in calculating the measurement error, the value obtained by multiplying the amount of strain at 0.1 MPa in Figure 3 by 9 is the theoretical value X, the amount of strain at 0.9 MPa in Figure 3 is set as the experimental value Y, and the measurement error is Calculated as (YX)/X. In calculating the measurement error, the theoretical value X can be calculated as (P ₂ /(P ₁ +ΔP))·ε(P ₁ +ΔP), and the experimental value Y can be calculated as ε(P ₂ ). Here, P ₁ is the minimum value of the pressure measurement range, P ₂ is the maximum value of the pressure measurement range, and ΔP is the resolution of the pressure sensor. Note that the strain ε is a function of the pressure P. Generally, when the measurement error exceeds 10%, the pressure value changes by 10%, making it less convenient to use as a measuring device. As shown in Table 1, which will be described later, when the thin portion 12 has a diameter of 2 mm and a thickness of 0.04 mm, the full scale error is 5.06%. From this, when the amount of strain increases from a state of good linearity, a full scale error of about 5% or more will increase the measurement error and significantly deteriorate the measurement accuracy. Therefore, the values surrounded by gray in Table 1, which will be described later, indicate poor conditions of approximately 5% or more (rounded to the first decimal place). On the other hand, the measurement error for values not surrounded by gray is comfortably less than 10%, so it is sufficient if the full-scale error is approximately 3% or less (rounded to the first decimal place). It can function as a sensor. Therefore, it is preferable that the full scale error is 3% or less.

Table 1 shows the strain of the thin part 12 determined by structural analysis including the influence of large deformation when the material of the thin part 12 is zirconia (Young's modulus 210 GPa) and the shape of the thin part 12 is approximately disk-shaped. This is a table showing the full scale error (unit: %) between the applied pressure (0 MPa or more and 0.9 MPa or less), and Table 2 shows the full scale error (unit: %) between , is a table relating to the amount of strain in the thin portion 12 that occurs when a pressure of 0.9 MPa, which is the maximum pressure in the measurement range set to the thin portion 12, is applied. That is, in Table 1, the measurement range of the set pressure (applied pressure (difference between the pressure in the internal space and the pressure in the external space)) is 0 MPa or more and 0.9 MPa or less.

The thinner the thickness of the thin portion 12 and the longer the diameter of the thin portion 12, the more the strain is affected by large deformations, and the nonlinearity of strain as an output with respect to applied pressure increases. Therefore, the thickness and diameter of the thin portion 12 are set within a range that is not affected by large deformations and that allows sufficient strain to occur even under a pressure of about 1 MPa. Among the numerical values shown in Tables 1 and 2, the numerical values written in the gray columns are in the numerical range outside the numerical range of the present invention (within the range of 0 MPa or more and 0.9 MPa or less, the full scale error is (more than 3%). In order to satisfy such conditions, if a pressure sensor is used with a measurement range of 0 MPa or more and 0.9 MPa or less, and the thin part 12 is made of approximately disk-shaped zirconia, the thickness of the thin part 12 is preferably 0.05 mm. As mentioned above, the diameter is more preferably 0.07 mm or more and 1.0 mm or less, still more preferably 0.08 mm or more and 0.1 mm or less, and the diameter of the thin part 12 is preferably 4 mm or less, more preferably 2 mm or more and 4 mm or less, and Preferably it is 3 mm.

Furthermore, referring to Table 2, if the absolute amount of strain generated in the thin wall portion 12 at the maximum pressure in the set measurement range is 0.00173 or more, the full scale error of the pressure sensor will not exceed 3%. It became clear. That is, in order to suppress the influence of large deformation, the absolute amount of strain generated in the thin portion 12 is preferably less than 0.00173, more preferably 0.00151 or less, and still more preferably 0.00148 or less.

Generally, when the shape of the thin portion 12 is approximately disk-shaped, the strain generated in the thin portion 12 satisfies the following equation (1). Here, ε is the strain generated in the thin part 12, P is the applied pressure, t is the thickness of the thin part 12, a is the diameter of the thin part 12, and E is the thin part 12. Young's modulus of the portion 12, α is a constant.

ε=αP(a ² /(E・t ² )) ...(1)

FIG. 5 shows a diagram showing the relationship between the Young's modulus, the diameter, the thickness, and the absolute value of the amount of strain of the thin portion 12 of various materials, calculated based on Equation (1). Here, α is determined by structural analysis, and is 0.18 in the above embodiment. P is the maximum value of the measurement range set for measuring pressure, and as an example, 0.9 MPa was substituted. FIG. 5A is a diagram when the Young's modulus is 10 GPa, FIG. 5B is a diagram when the Young's modulus is 210 GPa, and FIG. 5C is a diagram when the Young's modulus is 500 GPa. FIG. 6 shows a diagram showing the relationship between the Young's modulus, the diameter, the thickness, and the absolute value of the amount of strain of the thin portion 12 of various materials, calculated based on equation (1). Here, α is determined by structural analysis, and is 0.18 in the above embodiment. P is the maximum value of the measurement range set for measuring pressure, and as an example, 0.1 MPa was substituted. FIG. 6A is a diagram with a Young's modulus of 10 GPa, FIG. 6B is a diagram with a Young's modulus of 210 GPa, and FIG. 6C is a diagram with a Young's modulus of 500 GPa. As mentioned above, from the viewpoint of suppressing the effects of large deformation and reducing full-scale errors, the absolute amount of strain generated in the thin wall portion 12 at the maximum pressure in the measurement range set for measuring pressure is important. is preferably less than 0.00173, more preferably 0.00151 or less, still more preferably 0.00148 or less. 5 and 6 each show an example in which the strain is at most 0.00148. That is, in each of FIGS. 5 and 6, the diameter and thickness depend on the Young's modulus and the maximum pressure in the measurement range, and are within the range of ε = 0.00148 or less, as shown in the diagram. is most preferred.

That is, when the shape of the thin part 12 is approximately a disk, in order to keep the full scale error within the measurement range to 3% or less, the thickness of the thin part 12 is t, the diameter of the thin part 12 is a, When the Young's modulus of the thin portion 12 is E and the maximum value of the measurement range set for measuring pressure is P _MAX , (a ² · (P _MAX ))/(E · t ² ) is, It is preferably less than 9.61 x ^10-3 , more preferably 8.39 x ^10-3 or less, even more preferably 8.22 x ^10-3 or less. In addition, when the shape of the thin part 12 is approximately a disk shape, from the viewpoint of generating enough strain to appropriately measure within the measurement range, (a ² · (P _MAX )) / (E · t ² ) is , preferably 1.0×10 ⁻¹⁰ or more, more preferably 5.56×10 ⁻⁹ or more, still more preferably 1.0×10 ⁻⁹ or more.

Further, the shape of the thin portion 12 is preferably approximately disk-shaped from the viewpoint of generating symmetrical strain with respect to applied pressure, and in the above embodiment, the approximately disk-shaped shape is described. However, the present invention is not limited to this, and even if the shape is not substantially disc-shaped, the Young's modulus of the thin-walled portion 12 and the moment of inertia of area with respect to one of the two axes constituting the first surface 111 of the thin-walled portion 12 are large. It may be adjusted from the viewpoint of suppressing deformation and full-scale error, and any material and shape may be adopted.

A first conductive member 21 is attached to the first surface 111 in a horizontal position so as to cover part or all of the thin portion 12 , and a second conductive member 22 is attached to the circumference surrounding the thin portion 12 . Part or all of it can be installed continuously or discontinuously in a horizontal position. At this time, the geometric center of gravity of the z-axis projection of each of the first conductive member 21 and the second conductive member 22 may coincide with the pole point 0 on the r-θ plane, but is not limited to this. Further, the shape of the first conductive member 21 is a rectangular thin film, but is not limited to this, and the shape of the second conductive member 22 is approximately U-shaped, but is not limited to this. . The shape of the first conductive member 21 may be a circle, an ellipse, a sector, a triangle, other polygons, a linear or strip shape along the outline of these shapes, or any shape that is optimal for the measuring device. The shape of the second conductive member 22 may be selected from among shapes, and the shape of the second conductive member 22 may be a circular ring, an elliptical ring, a polygonal ring, a shape with a part of these ring shapes missing, and a shape that is optimal for the measuring device. The shape may be selected from any arbitrary shape. Further, the first conductive member 21 may have an arrangement pattern as disclosed in Japanese Patent No. 6874045.

The first conductive member 21 has an isotropic gauge factor (gauge factor of 3 or more) in a plane direction perpendicular to the normal line of the thin portion 12, and is described in, for example, Patent Document 1. A Cr thin film consisting of Cr and unavoidable impurities, or a Cr--N thin film consisting of Cr, N and unavoidable impurities. The Cr--N thin film is, for example, represented by the general formula Cr _{1 0 0-x} N _x , and the composition ratio x is 0.0001≦x≦30 in atomic %.

Further, the first conductive member 21 has a general formula Cr _{1 0 0-x} Mn _x (x is atomic % and satisfies 0.1≦x≦34) or a general formula Cr _{1 0 0-x} Al _x ( x is atomic %, and 4≦x≦25). The first conductive member 21 is expressed by the general formula Cr _{1 0 0-xy} Al _x N _y (x, y are atomic %, 4≦x≦25, 0.1≦y≦20). It may be composed of a Cr-based thin film. Since the Cr--N thin film has an extremely small temperature coefficient of resistance (TCR) (<±50 ppm/° C.) and is stable against temperature changes, the pressure sensitivity and pressure measurement accuracy are independent of temperature.

The method for forming the Cr-based thin film including the Cr thin film and the Cr--N thin film, which constitutes the first conductive member 21, is not particularly limited. sputtering method using a Cr target or an alloy target capable of forming a Cr-N thin film, a composite target or multiple targets, and a reactive method using a film-forming atmosphere containing nitrogen gas in the case of a Cr-N thin film. The film may be formed by a sputtering method, a vapor phase transport method using a raw material capable of forming the above-mentioned thin film, a liquid phase method including plating, or the like. Furthermore, when forming such a thin film, a mask method or the like may be used to form a thin film in a desired shape, or after forming a thin film, dry etching (plasma etching, sputter etching, etc.) or chemical etching may be used. It may be processed into an optimal shape for the measuring device by performing etching or trimming processing such as (corrosion method), lift-off method, or laser trimming method. Furthermore, Cr-based thin films including Cr thin films and Cr-N thin films may be used as they are, but at temperatures of 180°C or higher and 1000°C or lower in air, non-oxidizing gas, reducing gas, or vacuum. It is preferable to perform heat treatment at a temperature of .

In addition, the z-axis projection of the base 10, the shape of the thin portion 12, and the first conductive member 21 have rotational symmetry or It may have mirror symmetry with respect to a plane (for example, the rz plane) passing through the pole point O and perpendicular to the first plane 111.

When using the pressure sensor (first conductive member 21) of the fluid monitoring sensor module of the present invention as a pressure measuring device, the pressure sensor formed by the first conductive member 21 of the present invention is wire-connected by solder or wire bonding. , measured using a four-terminal method, but is not limited to this. It is configured as an optimal circuit for the configuration of the measuring device.

According to the fluid monitoring sensor module configured as described above, the electrical resistance value of the Cr-based thin film or Cr--N thin film constituting the first conductive member 21 is measured by the diaphragm method, so the sensitivity to pressure is high; Fluid pressure can be detected with high sensitivity. In addition, the width (area) of the diaphragm membrane can be reduced by circumferentially or locally arranging conductive members by utilizing the lateral sensitivity of Cr-based thin films including Cr thin films and Cr-N thin films, making the structure extremely simple. The fluid monitoring sensor module can be miniaturized and built into a small container to measure minute fluctuations in pressure within the container. Therefore, a fluid monitoring sensor module is realized that has a simpler structure than ever before, has high sensitivity, high precision, and can be miniaturized. Furthermore, since the components constituting the fluid monitoring sensor module can measure pressure without being affected by highly reactive fluids, it is suitable as a fluid monitoring sensor module for highly reactive fluids, especially in hydrogen gas atmospheres. . Further, since Cr-based thin films including Cr thin films and Cr--N thin films are stable against highly reactive fluids, there is no need to use a protective film. Therefore, the degree of freedom in production can be improved.

The second conductive member 22 can be made of the same material as the first conductive member 21 (a Cr-based thin film including a Cr thin film and a Cr—N thin film). In this case, it is preferable to manufacture by the same manufacturing method as above. Since the second conductive member 22 is arranged in a region different from the thin wall portion 12, it can be used as a pressure sensor in a high pressure range (1 MPa or more) as in Patent No. 6850642. By controlling which output of the first conductive member 21 and the second conductive member 22 is representative using a control device or the like, a wide range of pressure can be measured.

Furthermore, the second conductive member 22 may be a member that can serve as a sensor capable of measuring physical quantities of fluid other than pressure. For example, the second conductive member 22 is a member for measuring temperature. A material having a large resistance change (resistance temperature coefficient) with respect to temperature change is suitable for such a member, and for example, a Ni thin film, a Pt thin film, etc. may be used.

The manufacturing method of the thin film constituting the second conductive member 22 is not particularly limited, but when a Ni thin film is used as the second conductive member 22, a vapor deposition method using Ni as a raw material that can form a Ni thin film, a Ni target The film may be formed by a sputtering method using a method, a vapor phase transport method using a raw material capable of forming the above-mentioned thin film, a liquid phase method including plating, or the like. Furthermore, when forming such a thin film, a mask method or the like may be used to form a thin film in a desired shape, or after forming a thin film, dry etching (plasma etching, sputter etching, etc.) or chemical etching may be used. It may be processed into an optimal shape for the measuring device by performing etching or trimming processing such as (corrosion method), lift-off method, or laser trimming method. Further, the Ni thin film may be used as it is formed, but it is preferable to perform heat treatment at a temperature of 100°C or more and 500°C or less in the air, in a non-oxidizing gas, in a reducing gas, or in a vacuum. .

Note that the present invention is not limited to the above-described embodiments, and modifications and improvements can be made within the technical idea of the present invention by those having ordinary knowledge in the field. For example, in the above embodiment, the present invention is used to measure the pressure of an active gas atmosphere, particularly a hydrogen gas atmosphere. Good too. In addition, due to its excellent chemical stability with various fluids, it is resistant to corrosion, and is used for long-term atmospheric pressure measurement and underwater pressure measurement, as well as fluid monitoring sensor modules using this pressure sensor. It can also be used for

Examples of the present invention will be described below. Table 3 is a table showing examples of the present invention and comparative examples. Structure shape A is configured such that the first surface 111 of the base 10 is a square with a side of 4 mm, the height of the base is 3 mm, the thin part 12 has a thickness of 0.05 mm, and a diameter of 2 mm. It is a shape configured as a circle with. Structure shape B is configured such that the first surface 111 of the base 10 is a square with a side of 5 mm, the height of the base is 3 mm, the thin part 12 has a thickness of 0.07 mm, and a diameter of 3 mm. It is a shape configured as a circle with. Structure shape C is configured such that the first surface 111 of the base 10 is a square with a side of 10 mm, the height of the base is 5 mm, the thin part 12 has a thickness of 0.03 mm, and a diameter of 6 mm. It is a shape configured as a circle with. Structure shape D is configured such that the first surface 111 of the base 10 is a square with a side of 10 mm, the height of the base is 5 mm, the thin part 12 has a thickness of 0.1 mm, and a diameter of 6 mm. It is a shape configured as a circle with. Further, Examples 1 to 4 are fluid monitoring sensor modules of the first embodiment, in which a second conductive member 22 made of a Ni thin film is provided in a substantially U-shape surrounding the thin portion 12, and a second The electrically conductive member 22 was used as a temperature sensor, and electrical output was obtained using the four-pole terminal method.

Here, the base 10 of each structure shape has a diameter corresponding to the diameter of each thin part 12 and a depth of 0.5 mm for structure shapes A and B, and 1 mm for structure shapes C and D. A cylindrical recess is formed, and a thin part 12 having a thickness shown in each structure shape is adhered onto the base using an adhesive. At this time, the recessed portion is covered with the thin wall portion 12 from the outside space to form an internal space 11, and air of 0.1 MPa is introduced into the internal space 11 to maintain the pressure of the internal space 11 at 0.1 MPa. . In Examples 1 to 4 and Comparative Examples 1 and 2, the first conductive member 21 having a thickness of 0.1 μm and having a meandering shape was arranged at the center of the surface of the thin portion 12 that was in contact with the external space. , After forming a 0.5 μm thick Au/Ni/Cr laminated thin film on the electrode part, the conductive member is wired via solder to form a four-terminal circuit. The pressure in the space (applied pressure) was extracted as a signal. Note that in Examples 1 and 3, a protective film made of SiO ₂ was formed on the conductive member. Further, in Examples 5 and 6, a plurality of first conductive members 21 are provided in an arrangement pattern as shown in FIG. 12 in Japanese Patent No. 6874045, and the resistance value of each first conductive member 21 is A circuit (FIG. 13 in Japanese Patent No. 6874045) was formed using the bridge method, and the pressure in the external space (applied pressure) was extracted as a signal.

(Example 1)
The thin part 12 of the fluid monitoring sensor module formed with the configuration of the first embodiment is removed, and the atmosphere under the actual experimental environment is introduced into the recessed part, and the pressure in the internal space 11 is set to 0.1 MPa (the Atmospheric pressure), and the thinned part 12 was adhered to the base using an adhesive so as to seal the recess from the outside space. The fluid monitoring sensor module with the pressure in the internal space 11 adjusted as described above was inserted into the pressure vessel, and nitrogen gas containing unavoidable substances was introduced into the vessel. As shown in Fig. 7, the pressure inside the pressure vessel (pressure in the external space) is increased from 0.1 MPa to 1.0 MPa (applied pressure added to the pressure vessel of 0.1 MPa) in 0.1 MPa increments. The pressure in the external space is increased by increasing the pressure from 0MPa in 0.1MPa increments to 0.9MPa, and then decreasing the pressure in 0.1MPa increments to 0.1MPa (applied pressure is 0MPa). The output signal (resistance value of the first conductive member 21) of the fluid monitoring sensor module was taken out. In addition, in order to investigate the stability of the fluid monitoring sensor module when the pressure application state is maintained for a long time, the pressure was maintained in the pressure vessel at 1.0 MPa (applied pressure 0.9 MPa) for 64 hours as shown in Figure 8. While this was maintained, the output signal (resistance value of the first conductive member 21) of the fluid monitoring sensor module was taken out.

FIG. 9 is a diagram showing the relationship between pressure fluctuations (fluctuations in applied pressure) as shown in FIGS. 8 and 7 and the resistance value of the first conductive member 21. As shown in FIG. As shown in FIG. 9, it was confirmed that Example 1 has superior sensitivity in relation to pressure fluctuations in the external space compared to Patent Document 4. In Example 1, even when the pressure in the external space was applied up to 1.0 MPa (the applied pressure was 0.9 MPa), no disconnection of the element or a sudden change in the resistance value of the conductive member 20 was observed. Further, when the pressure in the external space is increased or decreased to 1.0 MPa (applied pressure is 0.9 MPa), the initial resistance value of the first conductive member 21 and the resistance value after the increased or decreased pressure do not change. . Furthermore, even if the pressure in the external space is maintained at 1.0 MPa (applied pressure: 0.9 MPa) for 64 hours, the resistance value against pressure does not change, so no hysteresis against pressure is observed. Furthermore, it was revealed that excellent linearity (full-scale error of 3% or less (see Table 3)) was exhibited because there was no effect of large deformation (nonlinear deformation caused by stress on strain). Further, during this change, S/N (Signal/Noise) is good. Furthermore, when a current of 0.1 mA was input to the measurement circuit, the pressure sensitivity was estimated to be 1 mV/MPa, and it was revealed that the sensor had excellent resolution as a pressure sensor.

FIG. 10 is a diagram showing a change in the relationship between the resistance value of the second conductive member 22 and the temperature of the fluid monitoring sensor module of the present invention. The pressure inside the pressure vessel (pressure in the external space) was measured with a general pressure gauge fixed to the vessel wall. As is clear from FIG. 10, the temperature characteristics of the second conductive member 22 showed a nearly linear change. Moreover, S/N (Signal/Noise) is good.

FIG. 11 is a diagram comparing the temperature estimated by the resistance value of the second conductive member 22, which changes based on pressure fluctuations and pressure increases and decreases, and the temperature measured by a thermocouple, and FIG. It is a figure which shows the time series fluctuation of the temperature measured by the 2nd electroconductive member 22 and the thermocouple in the state where the pressure of the external space was maintained at 1.0 MPa (applied pressure 0.9 MPa) for 64 hours. From FIGS. 11 and 12, it is clear that the second conductive member 22 of the fluid monitoring sensor module of the present invention can capture temperature fluctuations associated with pressure fluctuations and measure temperature in the same manner as a thermocouple. Furthermore, as shown in FIG. 12, the second conductive member 22 has less noise during temperature measurement and less influence of hysteresis on temperature and pressure than a thermocouple, so it is suitable as a temperature sensor for a fluid whose pressure fluctuates. Available. Furthermore, since pressure and temperature interact in determining the state of the fluid and the state of the base 10, by accurately measuring the temperature and pressure, the pressure and thus the state of the fluid can be accurately measured. .

Although Examples 2 to 4 are not shown, similar to Example 1, the strain and the resistance value of the first conductive member 21 have excellent linearity with respect to pressure (full scale error is 3% or less (see Table 3)). showed that.

(Example 5)
FIG. 13 is a diagram showing the relationship between the bridge output value and the applied pressure based on the first conductive member 21 of the fluid monitoring sensor module according to the fifth embodiment. From FIG. 13, it is clear that even if the first conductive member 21 is arranged in the circumferential direction, excellent linearity (full scale error of 3% or less) is exhibited. Further, during this change, S/N (Signal/Noise) is good. Although not shown, Example 6 also showed excellent linearity (full-scale error of 3% or less (see Table 3)) similar to Example 5.

(Comparative example 1)
FIG. 14 is a diagram showing the relationship between the strain generated in the thin wall portion 12 of the fluid monitoring sensor module according to Comparative Example 1 and the applied pressure. As mentioned above, in Comparative Example 1, since the thin wall portion 12 is configured as a circle with a thickness of 0.03 mm and a diameter of 6 mm, it is affected by large deformation, and the strain increases with respect to the applied pressure. , monotonically increasing. Since the nonlinear fluctuations due to large deformations are large compared to the linear fluctuations due to small deformations, the strain in Comparative Example 2 and the electrical output values (resistance values, etc.) are 0 to 0.9 MPa relative to the applied pressure. The full scale error within the range exceeds 3% (see Table 3), which impairs the flexibility of the pressure sensor and ultimately the fluid monitoring sensor module.

(Comparative example 2)
FIG. 15 is a diagram showing the relationship between the strain generated in the thin wall portion 12 of the fluid monitoring sensor module according to Comparative Example 2 and the applied pressure. As described above, in Comparative Example 2, the thin portion 12 is configured as a circle having a thickness of 0.1 mm and a diameter of 6 mm. Therefore, compared to Comparative Example 1, when the applied pressure is small (0.3 MPa or less), the strain in the thin wall portion 12 exhibits a linear behavior with respect to the applied pressure, but when it is 0.3 MPa or more, , the influence of large deformations becomes stronger and linearity is impaired. Therefore, the strain, and therefore the electrical output value (resistance value) of Comparative Example 2, has a full scale error of more than 3% in the range of 0 to 0.9 MPa (see Table 3) with respect to the applied pressure, and the pressure sensor and the fluid The degree of freedom as a monitoring sensor module is lost.

(Hydrogen gas application experiment 1)
The thin part 12 of the fluid monitoring sensor module formed with the configuration of Example 3 is removed, the atmosphere is introduced into the recessed part, the pressure in the internal space 11 is maintained at 0.1 MPa (atmospheric pressure in the laboratory), and the thin part 12 is removed. 12 was glued to the base using adhesive to seal the recess against external space. The fluid monitoring sensor module that adjusted the pressure in the internal space 11 as described above was inserted into a pressure vessel, and hydrogen gas was introduced into the vessel. Additionally, a hydrogen storage alloy (LaNi ₅ alloy) is contained within the pressure vessel.

FIG. 16 shows time series fluctuations in the pressure applied to the pressure vessel and the resistance value of the first conductive member 21 of the fluid monitoring sensor module. In addition, in the experiment, the pressure vessel was immersed in a 40°C water bath, and the temperature inside the pressure vessel was maintained at 40°C. In this experiment, as shown in FIG. 16, the pressure inside the pressure vessel (pressure in the external space) was increased stepwise from 0 MPa to 1 MPa, and then reduced in steps. There was an interval of about 10 minutes before each pressurization or depressurization operation. At this time, the pressure and the hydrogen storage amount of the hydrogen storage alloy are measured, but in the measurement, the pressure and the hydrogen storage amount of the hydrogen storage alloy are measured using the general PCT (P: pressure, C: storage amount, T: temperature). Measurements are made using a characteristic evaluation device.

(Experimental result)
Referring to FIG. 16, it has been found that when a certain amount of hydrogen gas is introduced, the resistance value of the first conductive member 21 of the fluid monitoring sensor module changes as the pressure increases. In addition, by leaving the hydrogen storage alloy for about 10 minutes after each pressurization, the hydrogen storage alloy absorbs hydrogen, lowering the applied pressure inside the container and reaching each saturation pressure and becoming stable, but the fluctuation due to the pressure drop also causes the resistance value to decrease. It was found that there were changes in the. On the contrary, when the applied pressure of hydrogen gas was gradually decreased from 1 MPa, a change in resistance value was also observed as the pressure decreased. In addition, by leaving it for about 10 minutes after each depressurization, the hydrogen storage alloy releases hydrogen and increases the applied pressure inside the container, reaching each saturation pressure and becoming stable, but the fluctuation of the pressure increase also changes the resistance value. It became clear that changes were taking place. Further, during the experiment, the fluctuation in resistance value was linked to the fluctuation in pressure, and since the linkage did not deviate significantly, the fluid monitoring sensor module of the present invention can be suitably used in a hydrogen gas atmosphere.

Therefore, it has become clear that the first conductive member 21 of the fluid monitoring sensor module of the present invention can acquire changes in the pressure of hydrogen gas in a fine range. In addition, since it is possible to obtain information about the fluctuations in the pressure of hydrogen gas in the pressure vessel containing the hydrogen storage alloy, it has become clear that by using the equation of state, etc., it is possible to measure the amount of storage in the hydrogen storage alloy.

FIG. 17 shows the hydrogen storage amount (weight ratio) (horizontal axis) of the hydrogen storage alloy measured based on the pressure fluctuation measured by the first conductive member 21 of the fluid monitoring sensor module of the present invention and the hydrogen gas saturation. The relationship with pressure (MPa) (vertical axis) is shown. Note that the pressure in the first conductive member 21 of the fluid monitoring sensor module is calculated based on the aforementioned results regarding the relationship between pressure and resistance value. In FIG. 17, the results obtained using the pressure sensor of the present invention and the results obtained using the PCT device are shown simultaneously. Referring to FIG. 17, it has been revealed that the fluid monitoring sensor module of the present invention can measure the amount of hydrogen stored in the hydrogen storage alloy and the amount released thereof, similar to the existing PCT device. It should be noted that the results obtained with the fluid monitoring sensor module of the present invention show similar behavior to those obtained with the PCT device, and as is clear from the fact that the results obtained with the fluid monitoring sensor module of the present invention are accurate even in a hydrogen gas atmosphere. It is possible to detect increases and decreases in hydrogen gas. Although there is a slight difference between the pressure measured by the fluid monitoring sensor module of the present invention and the pressure measured by the PCT device, this is due to the difference between the pressure measured by the PCT device and the pressure measured by the fluid monitoring sensor module of the present invention. This is due to variations in the resistance value in the pressure measurement position and the measurement system of the fluid monitoring sensor module of the present invention. As is clear from the fact that the PCT device measures the pressure outside the pressure vessel, some errors occur in the fluid monitoring sensor module of the present invention, which measures the pressure inside the pressure vessel. In addition, when calibrating the resistance value and pressure of the first conductive member 21 of the fluid monitoring sensor module of the present invention, measurements are performed using four-terminal measurement, but in hydrogen gas application experiment 1, due to the measurement, two-terminal measurement was used. It is measured with. At this time, some errors occur due to changes in the resistance value of the measurement system.

FIG. 18 shows the results of the time-series pressure fluctuations of the fluid monitoring sensor module shown in FIG. 17 in which the resistance value fluctuations caused by changes in the measurement system are added. Referring to FIG. 18, it has become clear that the results of the fluid monitoring sensor module of the present invention show substantially the same results as the results of the PCT device. Therefore, the fluid monitoring sensor module of the present invention can directly and easily measure the pressure of hydrogen gas without requiring a large device like a PCT device. It can be applied in a wide range of fields, including the measurement of hydrogen storage capacity in hydrogen storage alloys.

(Hydrogen gas application experiment 2)
The thin wall portion 12 of the fluid monitoring sensor module formed with the configuration of Example 3 was removed, and air from within the laboratory was introduced into the recessed portion to maintain the pressure in the internal space 11 at 0.1 MPa (atmospheric pressure within the laboratory). , the thinned portion 12 was adhered to the base using an adhesive so as to seal the recess from external space. The fluid monitoring sensor module that adjusted the pressure in the internal space 11 as described above was inserted into a pressure vessel, and hydrogen gas was introduced into the vessel. Additionally, a hydrogen storage alloy (LaNi ₅ alloy) is contained within the pressure vessel.

In addition, in the experiment in which hydrogen gas was introduced, the pressure vessel was immersed in a 40°C water bath, and the temperature inside the pressure vessel was maintained at 40°C. Further, at this time, the pressure and temperature were measured using a PCT characteristic evaluation device as in the hydrogen gas application experiment 1.

In this experiment, hydrogen gas was introduced using a PCT characteristic evaluation device, and the pressure inside the pressure vessel (pressure in the external space) was increased stepwise from 0 MPa to 1 MPa, and then the pressure was reduced stepwise. Thereafter, the same process was repeated. Furthermore, an interval of approximately 10 minutes was provided before each pressurization or depressurization operation was started.

(Experimental result)
FIG. 19 is a diagram showing time-series fluctuations in the voltage value of the pressure sensor of the PCT device in this experiment, and FIG. 20 is a diagram showing the resistance of the first conductive member 21 of the fluid monitoring sensor module in the pressure vessel in this experiment. FIG. 3 is a diagram showing time-series fluctuations in values. Moreover, FIG. 21 shows a time series of the pressure measured by the pressure sensor of the PCT device and the pressure measured by the fluid monitoring sensor module in the pressure vessel, which are measured based on the voltage value in FIG. 19 and the resistance value in FIG. 20. It is a figure showing a fluctuation. Referring to FIGS. 19 to 21, when a certain amount of hydrogen gas is introduced, the resistance value of the first conductive member 21 of the fluid monitoring sensor module changes as the pressure increases and decreases, similar to the hydrogen gas application experiment 1. Do you get it. In addition, by leaving the hydrogen storage alloy for about 10 minutes after each pressurization, the hydrogen storage alloy absorbs hydrogen, lowering the applied pressure inside the container and reaching each saturation pressure and becoming stable, but the fluctuation due to the pressure drop also causes the resistance value to decrease. It was found that there were changes in the. On the contrary, when the applied pressure of hydrogen gas was gradually decreased from 1 MPa, a change in resistance value was also observed as the pressure decreased. In addition, by leaving it for about 10 minutes after each depressurization, the hydrogen storage alloy releases hydrogen and increases the applied pressure inside the container, reaching each saturation pressure and becoming stable, but the fluctuation of the pressure increase also changes the resistance value. It became clear that changes were taking place. These results indicate that, as in hydrogen gas application experiment 1, the fluctuation in resistance value is linked to the fluctuation in pressure and voltage measured by the PCT device, and the linkage does not deviate significantly. It was further confirmed that this can be suitably used in a hydrogen gas atmosphere.

Therefore, in the hydrogen gas application experiment 2 as well as the hydrogen gas application experiment 1, it is clear that the first conductive member 21 of the fluid monitoring sensor module of the present invention acquires the fluctuations in hydrogen gas pressure in a fine range, and the hydrogen storage Since it is also possible to obtain information about changes in the pressure of hydrogen gas in the pressure vessel containing the alloy, it has become clear that by using the equation of state, etc., it is possible to measure the amount of hydrogen stored in the hydrogen storage alloy.

FIG. 22 is a diagram showing time-series fluctuations in temperature measured by the temperature sensor of the PCT device in this experiment, and FIG. 23 is a diagram showing the second conductive member 22 of the fluid monitoring sensor module in the pressure vessel in this experiment. FIG. 3 is a diagram showing time-series fluctuations in temperature measured based on the resistance value of . Referring to FIG. 23, it was found that when a certain amount of hydrogen gas was introduced, the temperature measured by the second conductive member 22 of the fluid monitoring sensor module suddenly increased due to instantaneous adiabatic compression. Furthermore, after each pressurization, by leaving the container for about 10 minutes, heat was removed from the container by the water bath, and fluctuations in the applied temperature inside the container were also measured. On the contrary, temperature fluctuation was also observed due to adiabatic expansion in which the applied pressure of hydrogen gas was gradually decreased from 1 MPa. In addition, after each pressure reduction, heat was applied inside the container by a water bath by leaving it for about 10 minutes, and fluctuations in the temperature inside the container were also measured. These results (temperature fluctuations due to adiabatic expansion and adiabatic compression) coincide with the time for applying hydrogen gas into the pressure vessel, and the interlocking does not deviate significantly. Therefore, the fluid monitoring sensor of the present invention It was found that the module can be suitably used in a hydrogen gas atmosphere for temperature measurement as well.

On the other hand, as shown in FIG. 22, the temperature measured by the PCT device was significantly different from the temperature measured inside the pressure vessel. This is due to the fact that the rate of temperature transfer (ie, heat conduction in hydrogen gas) is much lower than the rate of pressure transfer (ie, the speed of sound). In the current PCT device, the pressure sensor and temperature sensor are not inserted directly into the pressure vessel but into the hydrogen gas introduction path. Therefore, the PCT device cannot directly measure the temperature inside the pressure vessel, and while the water bath temperature is 40° C., the temperature measured by the PCT device varies between 27° C. and 29° C. In addition, since the temperature transmission rate is lower than the pressure transmission rate, it is difficult to directly measure the temperature. Hold constant. On the other hand, according to the fluid monitoring sensor module of the present invention, a temperature that substantially coincides with the temperature of the water bath was measured. The temperature being slightly higher than 40° C. is considered to be due to measurement errors due to problems with water bath control accuracy or systematic errors due to control outside the container and measurement inside the container. In the latter case, the temperature was measured by the fluid monitoring sensor module after the initial temperature was estimated at 40°C, so there was a sudden temperature change, but this was also due to a systematic error, and the temperature was overestimated by a certain degree. Therefore, it is considered that the value on the graph rose sharply from the initial value. It is clear that if the influence of systematic errors is corrected, that is, if a correction of about -1.7°C is added to the entire graph, the temperature will roughly match the water bath temperature, and temperature fluctuations due to adiabatic expansion or compression can be captured. I made it.

Therefore, the fluid monitoring sensor module of the present invention can reliably measure the pressure and temperature of hydrogen at a target location while being in direct contact with hydrogen gas. In addition, since the temperature of the target location is measured in detail, the measured temperature can be used to calibrate the pressure sensor, so it measures the pressure of hydrogen gas more accurately than conventional methods. It is possible to monitor the state of hydrogen gas. Furthermore, since the state of hydrogen gas can be measured without the need for a device such as a PCT device, the degree of freedom in measurement is greatly increased.

From the above, the pressure sensor and fluid monitoring sensor module of the present invention can obtain an output with excellent linearity with respect to pressure, so that the sensor output (voltage, electrical resistance value, etc.) is It becomes linear with respect to pressure), improving the degree of freedom of the sensor. Furthermore, the present invention provides a pressure sensor and a fluid monitoring sensor module that have better pressure resolution and measurement accuracy than conventional pressure sensors, and also have stability against various fluids including highly reactive fluids.

10; Base, 11; Internal space, 12; Thin part, 111; First surface, 112; Second surface, 21; First conductive member (Cr-based thin film or Cr-N thin film), 22; Second Conductive member (Ni thin film), O; pole

Claims (8)

a base having an internal space sealed to an external space;
A first electrically conductive member attached to a surface of a thin wall portion in which one of the wall portions defining the internal space of the base portion is relatively thin, and is in contact with the external space;
The first conductive member is constituted by a thin film having an isotropic gauge factor in a plane direction perpendicular to a normal to a thin portion to which the first conductive member is attached,
A pressure sensor characterized in that a full scale error in output value with respect to pressure is 3% or less. The pressure sensor according to claim 1,
The shape of the thin portion is approximately disk-shaped,
When the thickness of the thin part is t, the diameter of the thin part is a, the Young's modulus of the thin part is E, and the maximum value of the measurement range set for measuring pressure is P _MAX . , (a ² ·(P _MAX ))/(E · t ² ) is less than 9.61×10 ⁻³ . The pressure sensor according to claim 2,
A pressure sensor characterized in that the thin portion is made of zirconia, the thickness of the thin portion is 0.05 mm or more, and the diameter of the thin portion is 2 mm or more and 4 mm or less. The pressure sensor according to claim 1,
A pressure sensor characterized by being used in a hydrogen gas atmosphere. In the pressure sensor according to any one of claims 1 to 4, on the surface where the first conductive member is provided, the second conductive member is continuously or discontinuously disposed on a part or all of the circumference surrounding the thin part. A fluid monitoring sensor module comprising: The fluid monitoring sensor module according to claim 5,
A fluid monitoring sensor module characterized in that the first conductive member is composed of a Cr-based thin film or a Cr--N thin film. The fluid monitoring sensor module according to claim 5,
A fluid monitoring sensor module characterized in that the second conductive member is made of a Ni thin film. The fluid monitoring sensor module according to claim 5,
A fluid monitoring sensor module characterized by being used in a hydrogen gas atmosphere.

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