JP2007017277A - Hydrogen pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify the structure, to increase the accuracy, and to provide a sufficient responsiveness, in a hydrogen pressure sensor for detecting the hydrogen pressure in mixture gas. <P>SOLUTION: The periphery of a pair of mutually facing substrates 12 and 13 is sealed with a spacer 14 using an MEMS technology or the like, thereby forming a sealed inner volume as a vacuum atmosphere. At least one of the pair of substrates 12 and 13 has flexibility, and at least one has hydrogen permeability. Variation of the inner volume due to hydrogen permeation is detected based on the variation of capacitance between the facing electrodes 15 and 16. Therefore, this sensor can be prepared in a simple process, and has higher accuracy and more sufficient responsiveness than a strain gauge or the like. Consumed electric current for detection can be reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydrogen pressure sensor that selectively measures only the hydrogen concentration in a coexisting gas.

  A typical conventional hydrogen concentration sensor is disclosed in, for example, Patent Document 1 and Patent Document 2, and requires a special material such as a hydrogen storage alloy or stabilized zirconia, which increases the cost.

  Therefore, in Patent Document 3 as another prior art, hydrogen is selectively taken out using a hydrogen permeable membrane and the concentration thereof is measured. FIG. 6 is a cross-sectional view showing the structure of the hydrogen pressure sensor. According to this prior art, a hydrogen permeable membrane 3 is provided on the other end of a stainless steel cylindrical body 2 whose one end is closed by a diaphragm 1 to form a reduced pressure sealed space, and expansion and contraction of the sealed space by hydrogen permeation is achieved. Detection is performed with a strain gauge 4 attached to the diaphragm 1.

In this prior art, the hydrogen permeable film 3 is a porous ceramic film in which a Pd film source or a Pd alloy film source is sucked. However, glass, resin, metal, etc., if the film thickness is thin, Permeation of hydrogen is sufficiently possible. Although helium, which has finer molecules than hydrogen, is easier to permeate, it does not affect the detection result of the hydrogen concentration because the ratio existing in nature is very small.
JP 2004-233097 A JP-A-10-123093 JP-A-9-145585

  The above-described prior art is made to solve the problem of a hydrogen pressure sensor using a semiconductor, and although using the hydrogen permeable membrane, it is large-scale and has a low accuracy by using a strain gauge, and There is a problem of low responsiveness.

  An object of the present invention is to provide a hydrogen pressure sensor that can be manufactured by a simple process and that can obtain high response and high responsiveness compared to a strain gauge or the like.

The hydrogen pressure sensor of the present invention is disposed so as to face each other, at least one of which is flexible and at least one of which is hydrogen permeable, and the surroundings are hermetically sealed, thereby providing a vacuum atmosphere. A pair of substrates forming a sealed inner volume, and a counter electrode formed to face at least a part of the pair of substrates, the pressure of the inner volume by hydrogen molecule permeation (= H ₂ partial pressure) ), The flexible substrate is bent, and the hydrogen partial pressure in the external atmosphere is detected from the change in capacitance between the counter electrodes due to the bending.

  According to the above configuration, by using a micro electro mechanical systems (MEMS) technique or the like, a hermetically sealed inner volume that forms a vacuum atmosphere is formed by hermetically sealing the periphery of a pair of substrates facing each other. By forming at least one of the pair of substrates to be flexible and at least one to be hydrogen permeable, hydrogen molecules permeate the hydrogen permeable substrate from the outside atmosphere and A hydrogen pressure sensor that increases an internal volume and detects a hydrogen partial pressure of an external atmosphere from the increased amount, and detects at least a part of a pair of substrates for detecting an increased amount of the internal volume. A counter electrode such as a metal thin film is formed oppositely, and a hydrogen partial pressure in the external atmosphere is detected from a change in capacitance between the counter electrodes.

  Therefore, it can be manufactured by a simple process, and it is possible to obtain a high responsiveness with high accuracy as compared with a strain gauge or the like. Further, current consumption for detection can be reduced.

  In the hydrogen pressure sensor according to the present invention, one of the pair of substrates is flexible and has hydrogen permeability, and the other substrate is a rigid substrate. .

  According to the above configuration, since a flexible substrate allows hydrogen molecules to pass therethrough, a rigid substrate that does not easily transmit hydrogen does not require thickness accuracy, and processing costs can be reduced. Can do.

  Furthermore, in the hydrogen pressure sensor of the present invention, in the one substrate having flexibility, the substantially central portion has rigidity, a counter electrode is formed in the portion, and the peripheral portion has flexibility. And having hydrogen permeability.

  According to the above configuration, in the one substrate having flexibility, the peripheral portion has flexibility (for example, a bellows shape) and has hydrogen permeability, so that the hydrogen molecules can be transmitted and It is possible to increase / decrease the internal volume. On the other hand, by making the substantially central portion rigid and forming the counter electrode in that portion, the counter electrode is not bent with respect to the increase in the internal volume, and the internal volume is the same pressure, Each time it swells in the same way, the parallelism and spacing of the counter electrodes can be reproduced in the same way.

  Therefore, the detection accuracy can be increased.

  In the hydrogen pressure sensor according to the present invention, in the one substrate having flexibility, the substantially central portion has rigidity, and a counter electrode is formed in that portion to form a detection electrode, and the peripheral portion thereof is flexible. And has hydrogen permeability, the outermost peripheral portion has rigidity, and becomes a mounting portion to the other substrate having the rigidity, and a counter electrode is formed in that portion, and a reference electrode And calculating means for calculating a difference between a capacitance component between the detection electrode and the opposite electrode on the other substrate and a capacitance component between the reference electrode and the opposite electrode on the other substrate. It is characterized by that.

  According to the above-described configuration, the pair of counter electrodes are provided not only at the central portion of one of the flexible substrates with rigidity, but also through the peripheral portion that realizes the flexibility. Further, it is provided on the outer peripheral side, and is also provided on the attachment portion to the other substrate having rigidity, which are used as a detection electrode and a reference electrode, respectively. Then, a calculation means is provided, and a difference in capacitance component formed between each electrode and the counter electrode of the other substrate is obtained. That is, a differential capacitance type electrostatic sensor is provided. For example, when the areas of the detection electrode and the reference electrode are equal to each other, the calculation means can remove the parasitic capacitance component by obtaining the difference, and when the area is different, Any one of these may be multiplied by a coefficient.

  Therefore, parasitic capacitance components can be removed and detection accuracy can be improved.

  Furthermore, the hydrogen pressure sensor of the present invention is characterized in that at least the hydrogen-permeable substrate is made of a resin or glass material and has a conductive film serving as the counter electrode on the surface.

  According to said structure, glass or a resin-type thing can also be utilized as said board | substrate which has hydrogen permeability, and since the permeability | transmittance of hydrogen is high, high sensor sensitivity can be ensured.

  The hydrogen pressure sensor of the present invention is characterized in that at least one of the substrates is made of a conductive material.

  According to said structure, electrode formation processing, such as film-forming in forming the said counter electrode, becomes unnecessary, and processing cost can be reduced.

  Furthermore, the hydrogen pressure sensor of the present invention is characterized in that the hydrogen permeable substrate is divided into a transmission region and a non-transmission region.

  According to the above configuration, the entire surface of the hydrogen permeable substrate is not used as a transmission region, but is limited to the transmission region, for example, by covering with a material that does not allow hydrogen to easily pass through or by forming a thickness that does not allow hydrogen to pass through. Is provided.

  Therefore, it is possible to increase the accuracy of sensitivity by predetermining the transmission area.

  As described above, the hydrogen pressure sensor of the present invention uses a MEMS technique or the like to hermetically seal the periphery of a pair of substrates facing each other, thereby forming a sealed internal volume that becomes a vacuum atmosphere, By forming at least one of the pair of substrates to be flexible and at least one to be hydrogen permeable, hydrogen molecules can permeate the hydrogen permeable substrate from the outside atmosphere and A hydrogen pressure sensor that increases a product and detects a hydrogen partial pressure of an external atmosphere from the increased amount, and is opposed to at least a part of a pair of substrates for detecting the increased amount of the internal volume. Then, a counter electrode such as a metal thin film is formed, and the hydrogen partial pressure in the external atmosphere is detected from the change in capacitance between the counter electrodes.

  Therefore, it can be manufactured by a simple process, and high response can be obtained with high accuracy as compared with a strain gauge or the like. Further, current consumption for detection can be reduced.

[Embodiment 1]
FIG. 1 is a view showing the structure of a hydrogen pressure sensor 11 according to a first embodiment of the present invention, FIG. 1 (a) is a plan view, and FIG. 1 (b) is a longitudinal sectional view. In the hydrogen pressure sensor 11, one substrate 12 made of rigid glass and the other substrate 13 made of flexible glass, resin, or the like are arranged so as to face each other, and the surroundings are hermetically sealed by spacers 14. It is configured by sealing.

  The substrate 12 has rigidity as described above, has a thickness sufficient to obtain a desired strength for the hydrogen pressure sensor 11 of, for example, about 1 mm, and hardly allows hydrogen to pass therethrough. On the other hand, the substrate 13 is provided with a thin bellows-like flexible portion 13b extending around the outer periphery of the thick detecting portion 13a having rigidity, and the outer periphery thereof. Is connected to the thick ring-shaped attachment portion 13c having rigidity, and is formed to have flexibility as described above. The flexible portion 13b is formed to a thickness that can be bent and deformed, for example, to about 0.1 to 0.3 mm, and preferably about 0.2 mm, and allows hydrogen to pass therethrough. On the rigid detection portion 13a and the portion of the substrate 12 facing it, counter electrodes 15 and 16 such as metal thin films are formed on the surfaces facing each other. Such a structure can be manufactured using MEMS technology or the like, and has a size of, for example, 3 mm square.

In the hydrogen pressure sensor 11 configured as described above, the periphery of the pair of substrates 12 and 13 facing each other is hermetically sealed with a spacer 14 to form a sealed internal volume that becomes a vacuum atmosphere. Yes. Then, by forming one substrate 13 so as to have flexibility and hydrogen permeability, the pressure of the inner volume (= H ₂ partial pressure) is obtained by hydrogen molecule permeation as indicated by reference numeral 17 in FIG. ) Rises, and as shown in FIGS. 1B to 2, the flexible substrate 13 is bent, and the hydrogen partial pressure in the external atmosphere is detected from the change in the capacitance of the counter electrodes 15 and 16. .

  Therefore, it can be manufactured by a simple process, and it is possible to obtain a high responsiveness with high accuracy as compared with a strain gauge or the like. Further, current consumption for detection can be reduced.

  In the hydrogen pressure sensor 11, one of the pair of substrates 12 and 13 has flexibility and hydrogen permeability, and the other substrate 12 is a rigid substrate. By adopting a structure in which the flexible substrate 13 allows hydrogen molecules to permeate, the rigid substrate 12 that is difficult to permeate hydrogen does not require thickness accuracy, and the processing cost can be reduced.

  Furthermore, the hydrogen pressure sensor 11 has an increase in the internal volume due to hydrogen permeation because the flexible portion 13b has flexibility and hydrogen permeability in the one substrate 13 having flexibility. On the other hand, if there is only flexibility, there will be a large difference in capacitance depending on how it swells. Therefore, the detection part 13a at the substantially central part is rigid, and the flexible part 13b at the periphery is If the internal volume is the same pressure by clearly separating the bending area and the non-flexing area so as to have flexibility, and forming the counter electrode 15 on the detection unit 13a, the same is applied each time. The parallelism and spacing of the counter electrodes 15 and 16 can be reproduced in the same way. Therefore, the detection accuracy can be increased.

  The counter electrodes 15 and 16 are not limited to the surfaces of the substrates 12 and 13 but may be formed by being embedded in the substrates 12 and 13.

[Embodiment 2]
FIG. 3 is a longitudinal sectional view showing the structure of the hydrogen pressure sensor 21 according to the second embodiment of the present invention. FIG. 3 (a) shows a reduced state (hydrogen pressure is reduced), and FIG. The time of expansion (hydrogen pressure increase) is shown, and corresponds to FIG. 1 (b) and FIG. 2, respectively. It should be noted that in this hydrogen pressure sensor 21, the rigid substrate 22 and the flexible substrate 23 are both made of a metal material, and the thick substrate 22 and the detector 23 a and the mounting portion 23 c of the substrate 23 are rigid. The thin-walled flexible portion 23b is formed to have flexibility. These substrates 22 and 23 are made of, for example, iron and have hydrogen permeability. However, in order to obtain the rigidity and hydrogen permeability, the thick substrate 22 is formed up to 0.3 mm, preferably up to about 0.2 mm, and the flexible portion 23b has a good response speed. In order to realize, it is formed to a thickness of 0.05 mm or less, for example. The detection part 23a and the attachment part 23c of the substrate 23 may also be formed to a thickness having hydrogen permeability.

  Although iron is inferior to the resin and glass, hydrogen can be permeated even at about 0.3 mm like the substrate 22, but in terms of response speed, the iron is 0 like the flexible portion 23b. A thickness of 0.05 mm or less is preferable. On the other hand, Pd, Ni, Mo, stainless steel, and the like are unsuitable for the substrates 22 and 23 because they are difficult to pass hydrogen.

  When both the substrates 12 and 13 are formed of glass or resin like the hydrogen pressure sensor 11 described above, high sensor sensitivity can be ensured because of high hydrogen permeability. However, the conductive counter electrodes 15 and 16 are necessary, and the counter electrodes 15 and 16 can be made unnecessary by forming the substrates 22 and 23 together with a metal material like the hydrogen pressure sensor 21. Electrode forming processing such as film formation for forming the counter electrodes 15 and 16 becomes unnecessary, and processing costs can be reduced. In the present invention, it is sufficient that at least one substrate has hydrogen permeability and at least one substrate has flexibility.

[Embodiment 3]
4A and 4B are views showing the structure of the hydrogen pressure sensor 31 according to the third embodiment of the present invention. FIG. 4A is a longitudinal sectional view, and FIG. 4B is a plan view of the substrate 32. is there. In FIG. 4B, the cut surface of FIG. The hydrogen pressure sensor 31 is similar to the hydrogen pressure sensors 11 and 21 described above, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. It should be noted that in this hydrogen pressure sensor 31, a flexible substrate 33 made of a metal material becomes a detection portion 33a having a substantially central portion having rigidity, a peripheral portion thereof having flexibility, and hydrogen permeation. In correspondence with the fact that the outermost peripheral portion has rigidity and the mounting portion 33c to the other substrate having rigidity, the substrate 32 side is made of glass. In addition to the detection electrode 16 corresponding to the detection portion 33a being formed at a substantially central portion of the substrate 32, a reference electrode 36 having the same area as the detection electrode 16 is formed on the surface facing the attachment portion 33c. It is that. In the mounting portion 33 c, the outer peripheral portion excluding the facing portion of the annular reference electrode 36 is held on the substrate 32 by the spacer 34.

  The electrodes 16 and 36 are connected to external connection terminals 37 and 38, and the potentials of the external connection terminals 37 and 38 are input to an arithmetic circuit 39 which is arithmetic means. The arithmetic circuit 39 obtains the difference between the capacitance components formed by the electrodes 16 and 36 and the substrate 33 side. Here, when the capacitance between the detection electrode 16 of the substrate 32 and the detection portion 33a of the substrate 33 is C1, and the capacitance between the reference electrode 36 of the substrate 32 and the mounting portion 33c of the substrate 33 is C2, If the area of C1 and C2 is almost the same, the stray capacitance component generated from the surrounding area is equivalent to the stray capacitance component of C2, and the unstable stray component is removed by calculating as the differential capacitance C1-C2. It becomes possible to do.

  Thus, the hydrogen pressure sensor 31 becomes a differential capacitance type electrostatic sensor, and the arithmetic circuit 39 obtains a difference when the areas of the detection electrode 16 and the reference electrode 36 are equal to each other as described above. In the case where the parasitic capacitance component can be removed and there is a difference in the area, when the difference is obtained, an amplifier or the like may be used to multiply one of them by a coefficient.

  With this configuration, the parasitic capacitance component that hardly depends on bending can be removed, and detection accuracy can be improved.

[Embodiment 4]
FIG. 5 is a view showing the structure of a hydrogen pressure sensor 41 according to a fourth embodiment of the present invention, FIG. 5 (a) is a longitudinal sectional view, and FIG. 5 (b) is a bottom view of the substrate 42. is there. It should be noted that in this hydrogen pressure sensor 41, the rigid substrate 42 and the flexible substrate 43 are both made of a metal material, and the substrate 43 is made of a material that is difficult to pass hydrogen, such as Pd, Ni, Mo, and stainless steel. The substrate 42 is made of a material and thickness that facilitates the passage of hydrogen, such as iron, but a part of the bottom surface of the substrate 42 is made of a material that is difficult for hydrogen to penetrate, such as Pd, Ni, Mo, and stainless steel. It is covered with.

  Accordingly, in FIG. 5, as indicated by reference numeral 45, hydrogen can only pass through the opening 46, and thus the substrate 42 having hydrogen permeability is divided into a transmission region and a non-transmission region. . Instead of covering with the coating layer 44 that is difficult for hydrogen to permeate, the substrate 42 is formed so that the opening 46 serving as a transmission region is thin and the remaining portion serving as a non-transmission region is formed thick. Also good.

  Thus, it becomes possible to raise the precision of a sensitivity by predetermining the area which permeate | transmits.

It is a figure which shows the structure of the hydrogen pressure sensor which concerns on the 1st Embodiment of this invention. It is a longitudinal cross-sectional view which shows the state which the hydrogen pressure sensor shown in FIG. 1 expanded. It is a longitudinal cross-sectional view which shows the structure of the hydrogen pressure sensor which concerns on the 2nd Embodiment of this invention. It is a figure which shows the structure of the hydrogen pressure sensor which concerns on the 3rd Embodiment of this invention. It is a figure which shows the structure of the hydrogen pressure sensor 41 which concerns on the 4th Embodiment of this invention. It is sectional drawing which shows the structure of a typical prior art hydrogen pressure sensor.

Explanation of symbols

11, 21, 31, 41, Hydrogen pressure sensor 12, 22, 32, 42 Substrate 13, 23, 43 Substrate 14, 34 Spacer 13a, 23a, 33a Detection unit 13b, 23b, 33b Flexible portion 13c, 23c, 33c Attachment 15 and 16 Counter electrode 36 Reference electrode 37 and 38 External connection terminal 39 Arithmetic circuit 44 Cover layer

Claims (7)

Arranged to face each other, at least one has flexibility and at least one has hydrogen permeability, and hermetically seals the surroundings to form a sealed internal volume that creates a vacuum atmosphere A pair of substrates,
A counter electrode formed on at least a part of the pair of substrates so as to face each other,
The hydrogen pressure is characterized by detecting the hydrogen partial pressure in the external atmosphere from the change in the capacitance between the counter electrodes due to the deflection of the flexible substrate due to the increase in the internal volume pressure due to the permeation of hydrogen molecules. Sensor.   2. The hydrogen pressure sensor according to claim 1, wherein one of the pair of substrates is flexible and has hydrogen permeability, and the other substrate is a rigid substrate.   The one substrate having flexibility is characterized in that a substantially central portion has rigidity, a counter electrode is formed in that portion, a peripheral portion has flexibility, and hydrogen permeability. The hydrogen pressure sensor according to claim 2. In the one substrate having flexibility, the substantially central portion has rigidity, and a counter electrode is formed in that portion to become a detection electrode, and its peripheral portion has flexibility and hydrogen permeability. And the outermost peripheral portion has rigidity, and becomes a mounting portion to the other substrate having the rigidity, and a counter electrode is formed in that portion as a reference electrode,
And an arithmetic means for calculating a difference between a capacitance component between the detection electrode and the opposite electrode on the other substrate and a capacitance component between the reference electrode and the opposite electrode on the other substrate. The hydrogen pressure sensor according to claim 2, wherein:   5. The hydrogen pressure according to claim 1, wherein at least the substrate having hydrogen permeability is made of a resin or a glass material, and has a conductive film serving as the counter electrode on a surface thereof. Sensor.   The hydrogen pressure sensor according to claim 1, wherein at least one of the substrates is made of a conductive material.   The hydrogen pressure sensor according to claim 1, wherein the hydrogen permeable substrate is divided into a permeable region and a non-permeable region.

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