JPH0658906A - Electrochemical gas detector - Google Patents

Abstract

PURPOSE:To flow an electrolyte to the electrode surface without using a string-shaped liquid-guiding member through the electrode. CONSTITUTION:In an electrochemical gas detector for detecting the concentration of a gas to be detected as an electrolytic current by allowing at least an action pole and an opposite pole to contact an electrolyte, a water-containing plate 5 is allowed to contact an electrode surface 2b of an electrode boy 2 which becomes the action pole and is housed in a container 1 by enclosing in sandwich with the water-containing plates 4 and 5 for contacting at both front and rear surfaces of the electrode body 3 which becomes the opposite pole and the periphery part. An electrolyte is sucked via the water-containing plate 4 and the electrolyte is routed to the water-containing plate 5 which exists between the electrode bodies 2 and 3 from the periphery part of the water-containing plate 4, thus causing the electrode surfaces 2b and 3b of both electrode bodies 2 and 3 to contact the electrolyte and generating art electrolytic current corresponding to the concentration of the gas. Then, when the electrolyte is included in the water-containing plates 4 and 5, gas can be detected and the electrolyte in the container can be reduced as much as possible, thus absorbing the increase and decrease in the electrolyte due to moisture at a space which is generated in the container.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochemical gas detection in which a gas to be detected is caused to act on an electrolytic solution sealed by a gas permeable porous film and the concentration of the gas to be detected is detected from an electrolytic current at this time. Vessel, and more specifically, to a technique for supplying an electrolytic solution to an electrode.

[0002]

2. Description of the Related Art An electrochemical gas detector is an opening of a container formed by an electrode plate formed by layering an electrode material such as platinum black on a membrane having water repellency and air permeability such as fluororesin. Is sealed, and an electrolytic solution such as dilute sulfuric acid and a counter electrode are housed in the cell. Since this detector uses a liquid having a hygroscopic property such as dilute sulfuric acid as the electrolytic solution, the volume of the electrolytic solution changes in accordance with the change of humidity in the environment, and the liquid level in the container changes. If this change suddenly occurs, pressure acts on the electrode film to cause distortion, which causes a problem of measurement error. In order to solve such a problem, an electrochemical gas detector is proposed in which a small amount of electrolytic solution is housed inside the cell and the electrode plate and the electrolytic solution are liquid-junctioned by a string-shaped water-conducting member having water absorbability. (JP-A-57-147048).

[0003]

When such a water guiding member is used, the amount of the electrolytic solution can be reduced as much as possible to cope with the increase or decrease of the electrolytic solution due to environmental humidity. However, in order to guide the water guiding member to the working electrode. Since the through hole for passing the water conducting member is required in the center of the electrode plate which is the counter electrode, not only the electrode area is reduced, but also the insertion work of the string-shaped water conducting member for making the liquid junction between the electrolyte and the electrode. However, there is a problem in that the manufacturing process becomes complicated due to the need for

[0004]

In order to solve such a problem, in the present invention, at least the working electrode and the counter electrode are housed in a container so as to come into contact with the electrolytic solution, and the concentration of the test gas is electrolyzed. In an electrochemical gas detector for detecting as an electric current, the working electrode and the counter electrode sandwich a first water-containing plate capable of absorbing the electrolytic solution, and the electrolytic solution side of the counter electrode has a peripheral portion of the counter electrode. A second water-containing plate, which extends further outside and is capable of absorbing the electrolytic solution, is brought into contact with at least a part of the second water-containing plate to be brought into contact with the electrolytic solution.

[0005]

The electrolytic solution is sucked up through the water-containing plate in contact with the back surface of the counter electrode, and the electrolytic solution flows from the peripheral portion of the water-containing plate to the water-containing plate existing between the working electrode and the counter electrode. As a result, the electrode surface of the working electrode and the electrode surface of the counter electrode come into contact with the electrolytic solution to generate an electrolytic current corresponding to the gas concentration. Therefore, if the water-containing plate contains the electrolytic solution, the gas detection operation can be performed, so that the electrolytic solution to be stored in the container is reduced as much as possible to secure a space, and thus the electrolytic solution can be increased or decreased depending on the humidity. Can be absorbed in this space.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. FIG. 1 shows an embodiment of the present invention, in which reference numeral 1 is a tubular body forming a cell,
Frame bodies 2 and 3 for attaching an electrode body described later to the opening 1a at one end
Can be fixed.

Reference numerals 2 and 3 respectively denote the above-mentioned electrode bodies, and one of the diaphragms 2a and 3a made of a fluororesin having air permeability and water repellency as shown in FIGS. 2 (a) and 2 (b). A substance with catalytic action such as platinum or platinum alloy on the surface,
The electrode surfaces 2b and 3b are formed by vapor deposition, or by mixing fine powder of platinum, so-called platinum black, with a binder and sintering them in layers. When these come into contact with the electrolytic solution, the electrode body 2 on the side in contact with the outside air acts as a working electrode, and the other electrode body 3 acts as a counter electrode.

Of the electrode bodies 2 and 3, the electrode body 2 serving as a working electrode in contact with the test gas is formed in the opening 1a of the cylindrical body 1 with the diaphragm 2a facing outward. Is mounted on the stepped portion 1b. In addition, the electrode body 3 serving as a counter electrode
Inserts a thin plate made of glass wool or cellulose, which absorbs the electrolytic solution and has chemical resistance, between two water-containing plates 4 and 5 which are formed to be larger than the size of the electrode 3 serving as a counter electrode. Sandwiched between the water-containing plates 4 and 5 in the second step 1d formed so as to have a height below the first step 1b and in contact with the upper surface water-containing plate 5 on the electrode surface 2b. It is received by being superposed on. After setting the electrode body 2, the water-containing plate 4, the electrode body 3, and the water-containing plate 4 in a layered manner in this manner, the O-ring 7 is positioned on the outer periphery of the electrode body 2 to form the frame 8 It is fixed to the cylindrical body 1 in a liquid-tight manner. Further, fine wires such as platinum are connected to the electrode surfaces 2b and 3b of the respective electrode bodies 2 and 3, and the thin wire is drawn out through a through hole formed in the cylindrical body 1 to measure the electrode surfaces 2b and 3b. Connected to the circuit.

In the other opening 1e of the tubular body 1, a reference electrode 10 is attached to a step portion 1f formed here, and an O-ring 11 is formed.
And is fixed to the cylindrical body 1 in a liquid-tight state by the frame body 12. In the figure, reference numeral 15 is a plug that seals the electrolyte injection port 16 formed in the cylindrical body 1, and 18 is a vent hole.

In this embodiment, when the electrode bodies 2 and 3 are installed so as to be vertical (FIG. 3), a part of the water-containing plate 4 on the electrolytic solution 20 side is immersed in the electrolytic solution 20, and the electrolytic solution is caused by surface tension. 20 spreads over the entire water-containing plate 4. When the electrolyte solution 20 permeates to the periphery of the water-containing plate 4 in this manner, the water-containing plate 5 in contact with the outer periphery of the electrode body 3 serving as the counter electrode absorbs the electrolyte solution 20 of the water-containing plate 4, and finally each The electrode surfaces 2b and 3b of the electrode bodies 2 and 3 form an electrolytic cell through the electrolytic solution 20 of the water-containing plate 5, and also form a conductive relationship with the reference electrode 10 through the electrolytic solution 20.

When the test gas comes into contact with the electrode body 2 in this state, the test gas that has passed through the diaphragm 2a comes into contact with the boundary between the electrode surface 2b and the electrolytic solution of the water-containing plate 5, and the electrode body 2, An electrolytic current corresponding to the gas concentration is generated between the three electrode surfaces 2b and 3b.

In this state, when the humidity of the external environment rises and the electrolytic solution 20 absorbs water, the volume of the electrolytic solution 20 increases, but the electrolytic solution 20 contained in the cylindrical body 1 is increased.
Is a small amount, so a sufficient space 21 is secured,
Therefore, the increased amount of the electrolytic solution 20 is sufficiently absorbed in the space 21. The increase in the pressure of the space gas due to the increase in the amount of the electrolytic solution 20 is released to the atmosphere through the ventilation holes 18 and the like. It should be noted that when the concentration of the electrolytic solution 20 is reduced to a certain extent by moisture absorption, the hygroscopic force and the evaporation amount are in equilibrium, so that the level is maintained at a constant value.

On the other hand, when the humidity of the environment decreases and the amount of water vaporized in the electrolytic solution 20 is large, the electrolytic solution 20 reduces its volume, but as described above, the hygroscopic force increases as the concentration increases. When the liquid level rises and drops to a certain level, the reduction stops. Even in this state, a part of the water-containing plate 4 on the side facing the electrolyte solution 20 is still in contact with the electrolyte solution, and the whole water-containing plate 4 contains the electrolyte solution. An electrolytic battery is formed between the electrode surfaces 2b and 3b through an electrolytic solution. Needless to say, the gas detection sensitivity does not depend on the concentration of the electrolytic solution, and since distortion of the electrode bodies 2 and 3 due to changes in humidity does not occur, it is possible to maintain sufficient accuracy for practical use regardless of the magnitude of humidity. it can.

In this embodiment, the example of the three-pole type using the reference electrode 10 has been described, but the same action can be obtained even when applied to the two-pole type consisting of the working electrode and the counter electrode. Is clear. Also, in this embodiment, the reference electrode 1
Although 0 is arranged in an isolated state, as shown in FIG. 4, it is possible to further reduce the size by arranging 0 in close contact with each other via a water-containing plate.

That is, in the embodiment shown in FIG. 4, a counter electrode and a reference electrode are provided between the electrode body 30 forming the working electrode, the electrode body 31 forming the counter electrode, and the electrode body 32 forming the reference electrode. Hydrous plate 3 having a size larger than the electrode bodies 31 and 32
After inserting 3, 34 or abutting the water-containing plate 35 on the other surface of the reference electrode 32, a spacer member 36 for further securing a space for accommodating the electrolytic solution, and further ensuring air permeability And a diaphragm 37 for preventing liquid leakage are overlapped, and O-rings 38 and 39 are applied to the peripheral portions of the top and bottom surfaces of the diaphragm 37 to press-fit them into a case or the like, and the space is secured by the spacer member 36. Is to be injected.

According to this embodiment, the water-containing plates 33, 34, 3
Since the respective peripheral edge portions 33a, 34a, 35a of 5 are pressed into contact with each other, the electrolytic solution contained in the space of the spacer 36 is absorbed by the peripheral edge portions 33a, 34a, 35a of the respective water-containing plates 33, 34, 35.
And reaches the electrode surfaces of the electrode bodies 30, 31, 32, and an electrolytic cell is constructed in the same manner as described above.

Further, in the above-mentioned embodiment, a plurality of water-containing plates sandwiching the electrode body are contacted at their entire peripheral edges. However, as shown in FIG. 5A, the peripheral edge of the water-containing plate 40 is dyed with the electrolytic solution. Projections 40a, 40a, 40a ...
Is formed and is brought into contact with the other water-containing plate 41 that sandwiches the electrode body through the convex portions 40a, 40a, 40a, ..., It is possible to prevent the pressure contact force of the peripheral portion from reaching the central portion. It is possible to prevent wrinkles from occurring.

Further, although the water-containing plate is formed in a plate shape in the above-mentioned embodiment, as shown in FIG. 5B, the water-containing plate 41 on the side facing the electrolytic solution has through holes 41a, 41a. ,
41a, ... Provided with these through holes 41a, 41a, 41a.
It is possible to reduce the volume of the container by containing the electrolytic solution in the space formed by.

Further, in the above-mentioned embodiment, the electrode plate is wrapped in a sandwich shape by two independent water-containing plates, but the cellulose dissolved in the paste form is applied so as to protrude to the peripheral edge of the electrode plate, It is apparent that the same action can be achieved by drying this to form a hydrous plate integrated with the electrode body.

Further, in the above-mentioned embodiment, the respective electrode bodies 2 and 3 are supported by separate step portions, but the same effect can be obtained even if they are received by a common step portion. Is clear.

Further, in the above-mentioned embodiment, the electrode body serving as the counter electrode is formed on the surface of the diaphragm. However, the same applies when the electrode constituent substance is vapor-deposited on the substrate or a thin plate formed of the substance itself is used. It is clear that it works.

FIGS. 6 (a) and 6 (b) show other embodiments of the present invention, respectively, in which reference numeral 50 denotes a material having durability against an electrolytic solution, for example, glass wool. It is a water supply member formed by rolling the constructed filter paper so as to have a ring-shaped cross section. The density, in this embodiment, is housed so as to cover the inner peripheral surface of the cylindrical body portion 1 with one layer.

In this embodiment, with each member assembled to the cylinder 1, an appropriate amount of electrolytic solution is supplied from the electrolytic solution inlet 16.
That is, at least the water-containing plates 4 and 5 and the water supply member 50 are filled with an amount of the electrolytic solution that is in a wet state, and the plug 15 is sealed. Since the water-containing plate 4 is in contact with the end surface of the water supply member 50, the contact surface with the water supply member 50 absorbs the electrolytic solution contained in the water supply member 50 by the capillary force. The water-containing plate 5 in contact with the water-supplying member 50 is driven by the capillary force.
Absorbs electrolyte from. The electrolytic solution of the water supply plate 4 is further absorbed by the water absorption plate 5 and causes the working electrode 2 and the counter electrode 3 to have a liquid junction in the same manner as described above. As a result, the working electrode 2 and the counter electrode 3 have the water-containing plate 5
The electrochemical gas sensor is configured through the electrolytic solution of, and an electrolytic current proportional to the concentration of the gas in contact with the working electrode 2 is generated.

By the way, in this embodiment, since the water supply member 50 is arranged inside the cylindrical body 1 so as to surround the inner peripheral surface thereof, the detector is installed at an inclination as shown in FIG. Even when the electrolytic solution 20 is present at one side of the bottom corner, the water supply member 50 has a part thereof constantly in contact with the electrolytic solution and sucks up the electrolytic solution 20 by a capillary force so as to absorb water. 5, the electrolytic solution is always supplied to the water-containing plate 5 regardless of the posture of the tubular body 1, that is, even if the water-containing plate 4 is not in direct contact with the electrolytic solution 20. . As a result, the working electrode 2 and the counter electrode 3 can always maintain the liquid junction state regardless of the attitude of the detector body.

When the humidity of the external environment rises and the electrolytic solution 20 absorbs water, the volume of the electrolytic solution 20 increases, but since the amount of the electrolytic solution 20 contained in the cylindrical body 1 is small, Since a sufficient space 21 is secured, the increased amount of the electrolytic solution 20 is sufficiently absorbed in the space 21, and the increased amount is released from the ventilation hole 18 and the like to the atmosphere.

On the other hand, when the humidity of the environment decreases and the amount of water vapor of the electrolytic solution 20 is large, the electrolytic solution 20 reduces its volume, but as described above, the hygroscopic force increases as the concentration increases. When the liquid level rises and drops to a certain level, the reduction stops. Even in this state, since the water-containing plates 4 and 5 and the water supply member 50 still contain the electrolytic solution, the electrode surfaces 2b and 3b of the electrode bodies 2 and 3 constitute the electrolytic cell via the electrolytic solution. It will be.

In this embodiment, a single winding is used, but if the winding is made a plurality of times so that a space can be secured in the cylindrical body, the electrolytic solution can be more reliably supplied to the electrode bodies 2, 3. .

Further, in this embodiment, the sheet-shaped water-supplying paper is shaped and accommodated in the cylindrical body, but as shown in FIG. In addition, a porous polymer material having hydrophilicity (for example, "Sunfine AQ" (registered trademark)) is injection-molded, cut, or the ceramic powder is sintered into a desired shape or cut. Or, after further forming the target shape with cellulose, or by reinforcing it with a polymer material to form a tubular shape into a size that can be accommodated in a container and using this as a water supply member, the same effect can be obtained. it is obvious.

FIG. 9 positively utilizes the rigidity of the tubular water supply member described above, and at least the side of the tubular portion 52a that contacts the water-containing plate 4 is made of the same material as the flat portion 52.
It is closed by b, and is formed into a cup shape so that the entire length thereof is substantially equal to the height of the space 21 of the container 1. Such a water supply member is formed by injection-molding a porous polymer material (for example, "Sunfine AQ" (registered trademark)) having relatively high rigidity and hydrophilicity such as a polyolefin-based polymer, It can be formed by cutting, sintering the ceramic powder into a desired shape, cutting, or by constructing the desired shape with cellulose and then reinforcing it with a polymer material.

The water supply member 52 thus constructed is shown in FIG.
The space 21 of the cylindrical body 1 forming the detector as shown in FIG.
When the electrolyte solution is injected into the container and the electrolyte solution is injected, the electrolyte solution that has moved to the flat surface portion 52b along the tubular portion 52a that is in direct contact with the electrolyte solution 20 is absorbed by the water-containing plate 4 that is in contact with the flat surface portion 52b. It moves from the peripheral portion to the water-containing plate 5, and thereafter spreads over the electrode bodies 2 and 3 in the same manner as described above. By the way, the water supply member 52
Is the water-containing plate 4 whose upper part in the figure is closed by the flat part 52b.
Since it is in contact with the entire surface of the electrode bodies 2, 3, the electrode bodies 2, 3 are always supported, and the bending of the electrode bodies 2, 3 due to the rapid change in pressure is received, and the electrode materials 2, 3 are depressed toward the space side. Will be prevented. Needless to say, also in this embodiment, since the water supply member 52 is formed in a tubular shape and has the space 52c inside, an extra amount enough to absorb the increased amount of the electrolytic solution due to moisture absorption even if it is inserted into the space 21. It is clear that a large space can be secured.

In the above embodiment, the tubular portion 5
Although 2a and the flat surface portion 52b are integrally formed, the same effect can be obtained even if the cylindrical body and the disc that can seal the opening of the cylindrical body are divided and are used by stacking them. it is obvious.

[0032]

As described above, in the present invention,
A first water-containing plate capable of absorbing the electrolyte is sandwiched between the working electrode and the counter electrode, and a second electrode capable of absorbing the electrolyte that extends outside the peripheral portion of the counter electrode is disposed on the electrolyte side of the counter electrode. Since the water-containing plate was brought into contact and at least a part of the second water-containing plate was brought into contact with the electrolytic solution, the work of making a through hole in the electrode and conducting the string-like member becomes unnecessary, and the electrode is executed. Not only can the area be increased, but the manufacturing process can be simplified.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2A and FIG. 2B are enlarged views of electrode portions.

FIG. 3 is a diagram showing a usage state of the same apparatus.

FIG. 4 is a sectional structural view showing another embodiment of the present invention.

5 (a) and 5 (b) are views showing another embodiment of the water-containing plate, respectively.

6 (a) and 6 (b) are sectional views of an apparatus showing another embodiment of the present invention.

FIG. 7 is a view showing a usage state of the same apparatus.

FIG. 8 is a perspective view showing another embodiment of the water supply member.

9A and 9B are a perspective view and a cross-sectional view showing another embodiment of the water supply member, respectively.

FIG. 10 is a sectional view showing an embodiment of a detector using the same water supply member as above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical body 2,3 Electrode body 2a, 3a Diaphragm 2b, 3b Electrode surface 4,5 Water containing plate 8,12 Frame body 20 Electrolyte 50 Water supply member

Claims (3)

[Claims] 1. An electrochemical gas detector for accommodating at least a working electrode and a counter electrode in a container so as to be in contact with an electrolytic solution, and detecting the concentration of a test gas as an electrolytic current, the working electrode and the counter electrode. And sandwiching a first water-containing plate capable of absorbing the electrolytic solution, and the second side capable of absorbing the electrolytic solution extending outside the peripheral portion of the counter electrode on the electrolytic solution side of the counter electrode. An electrochemical gas detector in which a water-containing plate is brought into contact and at least a part of the second water-containing plate is brought into contact with an electrolytic solution. 2. An electrochemical gas detector for accommodating at least a working electrode and a counter electrode in a container so as to come into contact with an electrolytic solution and detecting the concentration of a test gas as an electrolytic current, wherein the working electrode and the counter electrode are provided. And sandwiching a first water-containing plate capable of absorbing the electrolytic solution, and the second side capable of absorbing the electrolytic solution extending outside the peripheral portion of the counter electrode on the electrolytic solution side of the counter electrode. An electrochemical gas in which a water-containing plate is brought into contact with the water-absorbing plate and at least a part of which is in contact with the electrolyte solution is brought into contact with the second water-absorbing plate and accommodated in the container. Detector. 3. The water supply member is configured as a tubular body, is formed in a cup shape in which at least one opening is closed by a flat surface, and the flat surface is always in contact with the second water-containing plate. 2. Electrochemical gas detector.