JP4463145B2 - Electrochemical gas sensor and manufacturing method thereof - Google Patents

Description

  The present invention relates to an electrochemical gas sensor such as a liquid electrolyte gas sensor or a proton conductor gas sensor, and a manufacturing method thereof.

  Patent Document 1 discloses a button battery type proton conductor gas sensor. In this sensor, an MEA in which a detection electrode and a counter electrode are connected to both surfaces of a proton conductor film is accommodated in a shallow metal can, and gas is supplied from the opening at the bottom of the metal can to the detection electrode. A counter electrode plate without an opening is attached to the upper part of the MEA, and the counter electrode plate is hermetically attached to the metal can with a gasket. For this reason, the metal can and the counter electrode plate serve as external terminals of the sensor, and the connection of each part of the sensor is maintained by pressure due to caulking.

  Patent Document 2 discloses a sensor body in which an MEA is sandwiched between a pair of metal plates, the metal plates are covered with upper and lower heat-shrinkable films, and the films are thermally contracted. The connection with the inside of the MEA and the metal plate is maintained by the pressure accompanying the heat shrinkage, and the portion where the metal plate protrudes from the film becomes the external terminal. A heat shrink film is attached to a water reservoir pack having an opening, and the opening of the film of the sensor body and the opening of the water reservoir pack are connected to introduce water vapor into the counter electrode.

  FIG. 11 of Patent Document 3 discloses a gas sensor similar to Patent Document 2. However, none of these gas sensors has been put into practical use. Since the gas sensor of Patent Document 1 has no water reservoir, it does not operate in a dry atmosphere. In the gas sensor of Patent Document 2, there is a question about the reliability of mounting the sensor main body to the water reservoir.

  For this reason, the inventors have put the gas sensor of FIG. This sensor has a constriction at the top of a deep metal can and supports the washer with the constriction. The space in the metal can at the bottom of the washer is used as a water reservoir, and water vapor is introduced into the counter electrode through an opening provided in the washer. A detection unit using a solid electrolyte or a liquid electrolyte is arranged on the top of the washer, and a cap containing a filter material is placed on the detection unit, and the metal can and the cap are caulked through a gasket. The inside of the detector, the connection between the washer and the cap, and the connection between the washer and the metal can are kept at the caulking pressure, and water leakage from around the washer is similarly prevented by the caulking pressure and the gasket.

However, since the gas sensor of FIG. 1 of Patent Document 3 is manufactured by disposing a detection unit, a cap, and a gasket on an upper part of a washer in a metal can, positioning of each member is difficult.
USP 5573648 WO 2002 / 097420A1 WO 2004 / 011923A1

  An object of the present invention is to provide an electrochemical gas sensor that is easy to manufacture and has little variation in characteristics, and a method for manufacturing the same.

The electrochemical gas sensor of the present invention is
A detection unit including at least a counter electrode, a liquid or solid electrolyte membrane, and a detection electrode is disposed in a shallow metal casing having a water vapor introduction hole, and is electrically connected to the detection unit and above the detection unit. A sensor body in which a metallic lid connected to each other is arranged and the periphery of the lid and the casing are caulked by a gasket;
A recess that supports the bottom surface of the casing and fits to the outer peripheral surface of the casing and further has the sensor body fixed conductively, and a water reservoir having at least a conductive path from the recess to a connection position with the outside. Become. The connection position with the outside is, for example, the bottom of the water reservoir or the outer surface of the recess.

Preferably, the water reservoir is a metal cylinder having a constriction in the middle and a bottom at the bottom, and the casing of the sensor body is fixed to the upper part of the constricted part, and water is held in the space below the constricted part. Yes.
Preferably, the water reservoir is a box-shaped member having a recess with a bottom plate at an upper portion, the sensor body is conductively fixed to the recess, and water is held in a space inside the box-shaped member. ing.

Preferably, the water reservoir and the casing of the sensor main body are caulked by the recess.
Particularly preferably, the space between the back surface of the recess and the surface of the casing is hermetically sealed with a sealant.
Preferably, the water reservoir and the casing of the sensor body are hermetically fixed by the conductive adhesive in the recess.

In the method of manufacturing an electrochemical gas sensor according to the present invention, a detection unit including at least a counter electrode, a liquid or solid electrolyte membrane, and a detection electrode is set in a shallow metal casing having a water vapor introduction hole. A step of manufacturing a sensor main body by arranging a metal lid so as to be conductively connected to the detection unit at the top of the detection unit, and caulking the periphery of the lid and the casing with a gasket;
Inspecting the sensor body after manufacture;
Inspected at the bottom of the recess of the water reservoir having a recess that fits the outer peripheral surface of the casing and supports the bottom surface of the casing, and at least a conductive path from the recess to the connection position with the outside. And a step of conductively fixing so as to support the casing of the sensor body.

  In this invention, since each member of the detection unit may be set not in the water reservoir but in the shallow casing, the positioning of these members is simple, and these members may move when the lid is caulked with a gasket. Few. For this reason, manufacturing is simple and each member can be easily set at a predetermined position, so that variations in sensor characteristics are small.

  Aging and storage of the sensor can be performed only by the sensor main body and can be inspected only by the sensor main body. Further, the water in the water reservoir is not consumed until the sensor body is fixed to the water reservoir, and the life of the sensor is determined by the loss of the water in the water reservoir, so that the life of the sensor can be extended.

  Since the sensor main body is fixed so as to fit into the recess of the water reservoir, the sensor main body does not fall out of the water reservoir and the position of the sensor main body with respect to the water reservoir does not go wrong. The water reservoir is made of metal, for example, but may be made of conductive plastic. Alternatively, at least from the inner peripheral surface or bottom surface of the recess to the connection position with the outside may be connected with a metal strip or a metal film. In the present invention, the water reservoir can be conductively connected to the metal casing of the sensor body, so that it can be an external terminal of one electrode, and the metal lid is the other terminal. The sensor body is a separate member from the water reservoir, and there is little risk of liquid water entering the sensor body from the water reservoir.

  Here, water vapor may be lost from the gap between the casing and the recess. Therefore, preferably, when the casing is caulked in the recess, the space between the casing is hermetically sealed with a sealing agent. Preferably, the casing is fixed to the recess with a conductive adhesive, and the gap between the recess formed by the conductive adhesive and the casing is sealed.

  In the following, an optimum embodiment for carrying out the present invention will be shown.

1 to 5 show an embodiment and its modifications. In FIG. 1, 2 is a gas sensor, 4 is a sensor body, and 6 is a water reservoir. The structure of the sensor body 4 is common throughout the embodiments and the respective modifications. The sensor body 4 includes a shallow metal can 8 and a water vapor introduction hole 10 on the bottom surface. Reference numerals 12 and 16 denote hydrophobic conductive films, which are breathable carbon sheets that have been hydrophobized with, for example, PTFE (polytetrafluoroethylene). The detection unit 14 is composed of, for example, a solid proton conductor film or an electrolyte film such as a hydroxide ion conductor film on which the detection electrode and the counter electrode are arranged, and the counter electrode is directed to the metal can 8 side for detection. Point the pole to the other side. A liquid electrolyte membrane may be used for the detection unit 14. In this case, sulfuric acid, a KOH aqueous solution, an aqueous solution of MgSo ₄ , various organic sulfonic acid compounds, or the like is held in a porous separator. Preferably, a solid electrolyte membrane such as a proton conductor membrane is disposed on both sides of the separator, and a detection electrode and a counter electrode are disposed on the outside thereof. The type of electrolyte itself is arbitrary.

  Reference numeral 18 denotes a sealing agent, 20 denotes a metal cap, and a filter material 22 such as activated carbon or zeolite is accommodated therein, and 24 and 25 are openings for introducing a detection gas. A metal diffusion control plate 26 is disposed between the opening 25 and the hydrophobic conductive film 16, and a detection gas is supplied from the diffusion control hole 28. The diffusion control plate 26 may be any member that can limit the diffusion of gas to a detection electrode (not shown).

  30 is a gasket and 32 is a sealant, which seals the space between the gasket 30 and the inner surface of the metal can 8. The sealing agent 36 hermetically seals between the outer surface of the metal can 8 and the inner surface of the metal water reservoir 6. Further, the water reservoir 6 is a cylindrical member having a bottom, and a constricted portion 34 is provided slightly above the central portion, and the sensor body 4 is supported by this portion. Since the side surface of the sensor body 4, that is, the side surface of the metal can 8 is insulated by the sealing agent 36, the edge of the bottom of the metal can 8 is brought into contact with the constricted portion 34 to ensure conductivity. Further, the water reservoir 6 is caulked on the upper portion of the metal can 8 by the caulking portion 37, and the sealing agent 36 is also present between them. Water 38 is held at the bottom of the water reservoir 6, which may be liquid water or gelled water.

  FIG. 3 shows a modified gas sensor. The sensor main body 4 is as shown in FIG. 2, and a bottom plate 44 is welded and fixed to a lid 42 of a cylindrical or rectangular parallelepiped water reservoir 40 by a welding portion 46. 45 is a water vapor introduction hole. The lid 42 is deformed into a projection 48 at this portion by press working or the like. The sensor body 4 is caulked by a caulking portion 37 in a recess formed by the inside of the projection 48 and the bottom plate 44, and the space between them is sealed with a sealing material 36. Stop. The metal can 8 is pressed against the bottom plate 44 by the pressure from the caulking portion 37, and electrical connection to the lid 42 is maintained through the welded portion 46. The lid 42 is caulked to the other part of the water reservoir 40 by a caulking portion 50.

  In manufacturing the gas sensor of FIG. 3, after welding the bottom plate 44 to the lid 42, the sensor main body 4 is caulked, and then the caulking portion 50 is caulked.

  FIG. 4 shows another modified gas sensor. Also in this case, the water reservoir 52 has a cylindrical shape or a rectangular parallelepiped shape, and the lid 54 is press-deformed downward to form the recess 58. The sensor body 4 is set in the recess 58, and the metal can 8 and the back surface of the recess 58 are fixed by the conductive adhesive 56. As the conductive adhesive, for example, an acrylic resin or the like mixed with metal powder such as Cu powder may be used. In this case, when the water surface of the water 38 comes above the bottom surface of the metal can 8, for example, a waterproof membrane 60 having air permeability such as a PTFE membrane may be disposed between the bottom plate 44 and the metal can 8 to be waterproofed.

  In the embodiment and the modification, the sensor body 4 is set in a recess of a water reservoir and fixed by caulking or a conductive adhesive. The periphery of the sensor body 4 fits inside the recess, and the gap between them is sealed with a conductive adhesive or sealed with a sealing material 36. Thus, it is possible to prevent water vapor from evaporating from the gap and losing water in the water reservoir. Furthermore, since the sensor body 4 is fixed in the recess, it does not fall out of the water reservoir or move to an inappropriate position with respect to the water reservoir.

  In assembling the sensor body 4, various members may be set and caulked on the bottom of the shallow metal can 8. For example, if the member is disposed on a washer disposed on the constricted portion 34 in FIG. Since there is no, arrangement | positioning of a member is easy. As a result, the positional accuracy of the members can be kept high, and variations in sensor characteristics can be reduced. Since the metal can 8 can be made thin, the water vapor introduction hole 10 can be made small. When the water vapor introduction hole 10 is made small, the consumption of the water 38 in the water reservoir is reduced, and the life of the gas sensor 2 can be extended.

  FIG. 5 shows a manufacturing process of the gas sensor 2 of FIG. 1, and the same applies to the modified examples of FIGS. 3 and 4. An MEA, a separator, a solid electrolyte membrane, an electrode film, a hydrophobic conductive film, and the like are set in a metal can, and a diffusion control plate, a sealing agent 18 and the like are further set. Next, the cap body 20 and the gasket are set and caulked to complete the sensor body 4.

Since the sensor main body is completed at this stage, only the sensor main body is stocked and appropriately aged. And before assembling to a water reservoir, a sensor main body is test | inspected independently, for example, a gas sensitivity is measured. Select only non-defective sensor body, set the sensor body in the water reservoir recess, and fix it by caulking or conductive adhesive. Thus, the gas sensor 2 is completed.

Sectional view of the gas sensor of the embodiment Cross section of sensor body Cross-sectional view of a modified gas sensor Cross-sectional view of another modified gas sensor Manufacturing process diagram of gas sensor of embodiment

Explanation of symbols

2 Gas sensor 4 Sensor body 6 Water reservoir 8 Metal can 10 Water vapor introduction hole 12, 16 Hydrophobic conductive film 14 Detector 18 Sealing agent 20 Cap 22 Filter material 24, 25 Opening 26 Diffusion control plate 28 Diffusion control hole 30 Gasket 32, 36 Seal Agent 34 Constriction portion 37 Caulking portion 38 Water 40, 52 Water reservoir 42, 54 Lid 44 Bottom plate 45 Water vapor introduction hole 46 Welding portion 48 Projection 50 Caulking portion 56 Conductive adhesive 58 Recess 60 Waterproof film

Claims (7)

A detection unit including at least a counter electrode, a liquid or solid electrolyte membrane, and a detection electrode is disposed in a shallow metal casing having a water vapor introduction hole, and is electrically connected to the detection unit and above the detection unit. A sensor body in which a metallic lid connected to each other is arranged and the periphery of the lid and the casing are caulked by a gasket;
A recess that supports the bottom surface of the casing and fits to the outer peripheral surface of the casing and further has the sensor body fixed conductively, and a water reservoir having at least a conductive path from the recess to a connection position with the outside. An electrochemical gas sensor. The water reservoir is a metal tube having a constriction in the middle and a bottom at the bottom, the casing of the sensor body is fixed to the upper part of the constricted part, and water is held in the space below the constricted part. Item 1. The electrochemical gas sensor according to Item 1. The water reservoir is a box-shaped member having a recess with a bottom plate at the top, the sensor body is conductively fixed to the recess, and water is held in a space inside the box-shaped member. Item 1. The electrochemical gas sensor according to Item 1. The electrochemical gas sensor according to claim 1, wherein a water reservoir and a casing of the sensor body are caulked in the recess. The electrochemical gas sensor according to claim 4, wherein a gap between the back surface of the recess and the surface of the casing is hermetically sealed with a sealant. The electrochemical gas sensor according to claim 1, wherein the water reservoir and the casing of the sensor main body are hermetically fixed by the conductive adhesive in the recess. A detection unit having at least a counter electrode, a liquid or solid electrolyte membrane, and a detection electrode is set in a shallow metal casing having a water vapor introduction hole, and is electrically connected to the detection unit and above the detection unit. Placing a metal lid so as to be connected, and caulking the periphery of the lid and the casing with a gasket to produce a sensor body;
Inspecting the sensor body after manufacture;
Inspected at the bottom of the recess of the water reservoir having a recess that fits the outer peripheral surface of the casing and supports the bottom surface of the casing, and at least a conductive path from the recess to the connection position with the outside. A method for producing an electrochemical gas sensor, comprising the step of conductively fixing so as to support a casing of the sensor body.

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