JP2015172489A - Electrochemical type sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemical type gas sensor in which continuity of a work electrode and a conductor wire is not easily released.SOLUTION: The sensor stores a work electrode 21, a reference electrode 22, a counter electrode 23 and electrolytic solution contacting with the electrodes 21-23 in a housing, and has a plurality of conductor wires 60 individually connected to each of the work electrode 21, the reference electrode 22 and the counter electrode 23. At least part of a contact area of the work electrode 21 and a conductor wire 60 connected to the work electrode 21 is located to be pressed by a pressing member when seen from a top view, while a contact area of the reference electrode 22 and a conductor wire 60 connected to the reference electrode 22 is not located to be pressed by the pressing member when seen from the top view.

Description

  The present invention relates to an electrochemical sensor including a working electrode, a reference electrode, a counter electrode, and an electrolytic solution in contact with these electrodes inside a housing.

  The electrochemical gas sensor detects gas by taking out energy generated by a chemical reaction (oxidation-reduction reaction) as electric energy. Electrochemical gas sensors have features such as low power consumption, linear output characteristics, and relatively high gas selectivity, so they are used in industrial gas concentration measuring instruments, and in recent years carbon monoxide, hydrogen sulfide, and oxygen. Widely used in detection alarm devices.

  In the case of carbon monoxide, an oxidation reaction of carbon monoxide occurs at the working electrode, and hydrogen ions equivalent to the hydrogen ions generated thereby react with oxygen in the air at the counter electrode to generate water. Since the current generated by this series of reactions corresponds to the gas concentration on the working electrode side, the gas concentration can be detected by measuring this current.

  The electrochemical gas sensor includes a casing having an opening and a lid having a small hole, and an O-ring that presses and fixes a working electrode, a reference electrode, a counter electrode, and an electrode inside the casing. In addition, an electrolytic solution, a gas permeable membrane, and the like are accommodated.

  In the above-described electrochemical gas sensor, the casing may have a double structure including an outer casing and an inner casing, and the electrolytic solution may be contained in the inner casing included in the outer casing. In this case, a conductive wire connected to each of the working electrode, the reference electrode, and the counter electrode is inserted into the gap between the outer casing and the inner casing.

  The outer casing has a hole provided on the bottom side and an opening provided on the opposite side of the bottom side, and the inner casing can insert the electrolyte into the inner casing through the hole. It has a cylindrical part.

  The working electrode, the reference electrode, and the counter electrode were each laminated on a porous gas-permeable membrane having water repellency, and each of them was pressed and fixed by an O-ring while being insulated with a glass wool membrane or the like. The O-ring was pressed by a lid that seals the opening of the outer casing.

  In addition, since such an electrochemical gas sensor is a general technique, the prior art is not shown.

  The conducting wire connected to each of the working electrode, the reference electrode, and the counter electrode was electrically connected with its tip portion connected to each electrode. As described above, the gas to be detected reacts at the working electrode, and the gas concentration can be detected by measuring the current generated at the working electrode. However, since the connection between the conducting wire and the working electrode is only the tip portion of the conducting wire, if the connection of the leading end portion is unexpectedly disconnected from the working electrode, the conducting state of the working electrode and the conducting wire is released, and the detected object There was a problem that the gas concentration of the gas could not be detected.

  Accordingly, an object of the present invention is to provide an electrochemical sensor in which the conductive state of the working electrode and the conductor is difficult to be released.

In order to achieve the above object, a first characteristic configuration of an electrochemical sensor according to the present invention includes a working electrode, a reference electrode, a counter electrode, and an electrolyte solution in contact with these electrodes in a housing. ,
A plurality of conductive wires connected to each of the working electrode, the reference electrode, and the counter electrode, and at least a part of a contact region between the working electrode and the conductive wire connected to the working electrode is a top view. It exists in the position pressed by the pressing member, and the contact area | region of the said reference electrode and the said conducting wire connected to the said reference electrode exists in the point which does not exist in the position pressed by the said pressing member in top view.

  When configured so that at least a part of the contact area between the working electrode and the conductive wire connected to the working electrode is in a position pressed by the pressing member in the top view as in this configuration, the pressing in the top view Since the pressing position by the member can be used as a conductive portion of the working electrode and the conductive wire, the electrochemical sensor is difficult to release the conductive state of the working electrode and the conductive wire.

  In this configuration, the contact region between the reference electrode and the conductive wire connected to the reference electrode does not exist at a position pressed by the pressing member in a top view. For this reason, there is no contact area between the reference electrode and the lead wire at the position pressed by the pressing member in the top view where the gas to be detected is likely to enter. Therefore, since the reference electrode can be prevented from coming into contact with the gas to be detected, the potential of the reference electrode can be prevented from changing.

  The second characteristic configuration of the electrochemical sensor according to the present invention is that a contact region between the counter electrode and the conductive wire connected to the counter electrode does not exist at a position pressed by the pressing member in a top view. is there.

  According to this configuration, the contact area between the counter electrode and the conductor does not exist at the position pressed by the pressing member in the top view where the gas to be detected is likely to enter. Therefore, since it is possible to prevent the counter electrode from coming into contact with the gas to be detected, a change in the potential of the counter electrode due to an undesired contact with the gas to be detected can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic of the external appearance of the electrochemical sensor of this invention ((a) top view (b) side view (c) bottom view). It is a cross-sectional schematic diagram of an electrochemical sensor. FIG. 3 is an exploded schematic view of the electrochemical sensor of FIG. 2. It is the schematic of each electrode ((a) working electrode (b) reference electrode (c) counter electrode). It is the schematic of another embodiment of a counter electrode.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIGS. 1 to 4, the electrochemical sensor X of the present invention has a working electrode 21, a reference electrode 22, a counter electrode 23, and an electrolyte solution in contact with these electrodes 21 to 23 inside the housing 10. 31.

In addition, the electrochemical sensor X includes a plurality of conductive wires 60 that are individually connected to the working electrode 21, the reference electrode 22, and the counter electrode 23, and the working electrode 21 is in contact with the conductive wire 60 connected to the working electrode 21. At least a part of the region is at a position pressed by the pressing member 56 in a top view.
Further, the electrochemical sensor X is configured such that the contact area between the reference electrode 22 and the conductive wire 60 connected to the reference electrode 22 does not exist at a position pressed by the pressing member 56 in a top view.

  The casing 10 includes an outer casing 11, an inner casing 12 that encloses the outer casing 11 and accommodates the electrolytic solution 31, and a lid portion 13 that seals the outer casing 11.

  The outer casing 11 has a hole 11a provided on the bottom side and an opening 11b provided on the opposite side of the bottom side, and the inner casing 12 has a cylindrical portion 12a inserted through the hole 11a.

  Furthermore, the electrochemical sensor X of the present invention has a welded portion 40 ′ in which the connection portions of the outer housing 11 and the inner housing 12 are thermally welded. In the present embodiment, a case will be described in which the connection portion is a hole portion 11 a provided on the bottom side in the outer housing 11 and a cylindrical portion 12 a that is inserted through the hole portion 11 a in the inner housing 12. In the present embodiment, the hole 11a and the cylindrical portion 12a are thermally welded at the welded portion 40 ′ in order to ensure airtightness and watertightness, but before the thermal welding, electrolysis is performed from the cylindrical portion 12a. The liquid 31 can be injected.

  The outer casing 11, the inner casing 12 and the lid portion 13 constituting the casing 10 are made of resin such as plastic. The housing 10 has a double structure composed of an outer housing 11 and an inner housing 12, and is separated from the working electrode 21, the reference electrode 22, and the counter electrode 23 in the gap between the outer housing 11 and the inner housing 12. The conducting wire 60 to be connected is inserted. In addition, the terminal installation hole 11 c in the outer housing 11 is provided with a plurality of electrode terminals 14 connected to the conducting wire 60.

  The conducting wire 60 may be formed of platinum, gold, nickel, or the like. Further, the shape of the conducting wire 60 is not particularly limited as long as it is electrically connected to each of the electrodes 21, 22, 23. However, the contact area with each of the electrodes 21, 22, 23 is made wider so that more reliable conduction can be achieved. From the standpoint of realization, for example, a wide shape such as a ribbon shape or a belt shape is preferable.

  A small hole 13a is formed in the lid 13, and the gas to be detected is taken in from the small hole 13a. The number of small holes 13a is not particularly limited as long as an appropriate amount of gas to be detected can be taken in, and the number depends on the hole diameter, but it is possible to provide a large diameter hole or a large number of holes. It is not preferable in terms of configuration. Therefore, the small hole 13a may be configured so that an appropriate amount of the gas to be detected can be taken in, for example, about 1 to 5 holes, and from the viewpoint of evenly taking the gas to be detected into the electrochemical sensor X, the small hole 13a. The number of is particularly preferably 5. A known waterproof / dustproof filter 13b is attached to the outer surface of the lid portion 13.

The electrodes 21 to 23 are accommodated in an electrode accommodation portion 20 formed inside the housing 10.
The working electrode 21, the reference electrode 22 and the counter electrode 23 are made of a gas diffusion electrode containing a catalyst and a hydrophobic resin. As the catalyst, platinum (Pt), gold (Au), ruthenium (Ru), ruthenium oxide (RuO ₂ ). ), Palladium (Pd), carbon (C), platinum-carrying carbon (Pt / C), gold-carrying carbon (Au / C), etc. are preferably used, and polytetrafluoroethylene (PTFE) is used as the hydrophobic resin. Resins are preferably used.

  The working electrode 21, the reference electrode 22 and the counter electrode 23 are laminated on porous (PTFE) gas permeable membranes 51 to 53 each having water repellency, and each is insulated by a water absorbing insulating member (for example, a glass wool membrane) 54. In addition, the outer peripheral surface of the electrode housing portion 20 is sealed with an O-ring 56 that is a pressing member in a state where the outer periphery of the electrode housing portion 20 is sealed with a porous and annular porous sheet member (for example, made of PTFE) 55a and 55b having water repellency ( FIG. 3). The porous sheet member 55 a is interposed between the working electrode 21 and the reference electrode 22, and the porous sheet member 55 b is disposed below the counter electrode 23. The O-ring 56 is a pressing member that presses and fixes the working electrode 21, the reference electrode 22, the counter electrode 23, the gas permeable films 51 to 53, the insulating member 54, and the porous sheet members 55a and 55b in a laminated state. When the portion 13 seals the opening 11 b of the outer casing 11, a pressing force is generated by the lid portion 13.

  The O-ring 56 directly presses the peripheral edge of the gas permeable film 51 located at the uppermost portion, and when a pressing force is generated by the lid portion 13, the working electrode 21, the reference electrode 22, and the counter electrode positioned below the gas permeable film 51. The electrode 23, the gas permeable membranes 52 and 53, the insulating member 54, and the porous sheet members 55a and 55b are in close contact with the adjacent members by the pressing force.

  Since the O-ring 56 directly presses the periphery of the gas permeable membrane 51 located at the top, the periphery of the porous sheet members 55a and 55b and the periphery of the gas permeable membrane 53 are pressed by the O-ring 56 in a top view. Position. As shown in FIGS. 3 and 4, the conductive wire 60 connected to each of the working electrode 21, the reference electrode 22, and the counter electrode 23 is connected to each of the electrodes 21 to 23 to be conductive. Yes. At this time, the present invention is configured such that at least a part of the contact area between the working electrode 21 and the conductive wire 60 connected to the working electrode 21 is in a position pressed by the O-ring 56 in a top view. is there. Further, the contact region between the reference electrode 22 and the conductive wire 60 connected to the reference electrode 22 is configured not to exist at a position pressed by the O-ring 56 in a top view.

  For example, the working electrode 21 is provided on the gas permeable film 51 in a state of a smaller diameter than the circular gas permeable film 51 having substantially the same diameter as the O-ring 56, and a part (extension portion 21 a) thereof is an O-ring. The shape is such that it extends to the peripheral region of the gas permeable membrane 51 pressed by 56. In other words, the working electrode 21 is brought into contact with the conducting wire 60 at least in the extending portion 21a extending to the peripheral region of the gas permeable membrane 51 by the pressing force of the O-ring 56, so that the working electrode 21 and the conducting wire 60 are reliably connected. Can be made.

  As will be described later, the electrolytic solution 31 sequentially reaches the counter electrode 23, the reference electrode 22, and the working electrode 21 by capillary action. At this time, the electrolytic solution 31 is unlikely to reach the position pressed by the O-ring 56 when viewed from above by the pressing force of the O-ring 56. For this reason, the gas to be detected easily enters the position pressed by the O-ring 56 when viewed from above. Since the extending portion 21a of the working electrode 21 is present at a position pressed by the O-ring 56 in a top view, when the gas to be detected comes into contact, the reaction of the gas to be detected occurs, and the working electrode 21 (extension) The gas concentration can be detected by measuring the current generated at the outlet 21a).

  The reference electrode 22 is provided on the gas permeable film 52 in the same diameter as the circular gas permeable film 52 having a smaller diameter than the O-ring 56. In the present embodiment, the reference electrode 22 is formed so as to cut out the central portion of the counter electrode 23. If the gas to be detected contacts the reference electrode 22, the gas to be detected reacts at the reference electrode 22 and the potential of the reference electrode 22 changes. The reference electrode 22 is required not to change in potential. In the present invention, the contact region between the reference electrode 22 and the conductive wire 60 connected to the reference electrode 22 does not exist at a position pressed by the O-ring 56 in a top view. Therefore, the contact area between the reference electrode 22 and the conductive wire 60 does not exist at the position pressed by the O-ring 56 in the top view where the gas to be detected is likely to enter. Therefore, since the reference electrode 22 can be prevented from coming into contact with the gas to be detected, the potential of the reference electrode 22 can be prevented from changing.

Further, the counter electrode 23 can be provided on the gas permeable film 53 in a state of a smaller diameter than the annular gas permeable film 53 having substantially the same diameter as the O-ring 56. That is, the contact region between the counter electrode 23 and the conductive wire 60 connected to the counter electrode 23 is configured not to exist at a position pressed by the O-ring 56 in a top view.
Also in this case, the contact area between the counter electrode 23 and the conductive wire 60 does not exist at the position pressed by the O-ring 56 in the top view where the gas to be detected is likely to enter. Therefore, since it is possible to prevent the counter electrode 23 from coming into contact with the gas to be detected, a change in the potential of the counter electrode 23 due to an undesired contact with the gas to be detected can be suppressed.

  A buffer filter 57 is disposed on the side of the lid 13 of the working electrode 21.

  The gas permeable membranes 51 to 53 may be any material that does not permeate the electrolyte solution 31 and permeates the gas to be detected. For example, a conventionally known material such as a tetrafluoroethylene hexafluoropropylene copolymer resin (FEP membrane) is used. Is applicable.

The electrolytic solution 31 is accommodated in an electrolytic solution accommodating space 30 surrounded by the inner casing 12 and the inner casing lid portion 12b. Further, the electrolytic solution holding body 32 and the internal pressure adjusting member 58 are immersed in the electrolytic solution 31, and the electrolytic solution 31 is held by the water-absorbing electrolytic solution holding body 32. The electrolyte solution holding body 32 is made of, for example, filter paper-like glass fiber, cellulose fiber, foamed plastic (for example, foamed polyethylene), glass wool, or the like. The electrolyte solution holding body 32 contains sulfuric acid (H ₂₎ as an electrolyte. It is sufficiently impregnated with an acidic aqueous solution such as SO ₄ ) or phosphoric acid (H ₃ PO ₄ ), an alkaline aqueous solution such as potassium hydroxide (KOH) or sodium hydroxide (NaOH), or a room temperature molten salt. The electrolyte solution holder 32 is inserted through the hole 12c formed in the inner housing lid 12b. The internal pressure adjusting member 58 is made of, for example, a porous membrane (including PTFE and PE).

  As the room temperature molten salt, a molten salt mainly composed of a nitrogen-containing aromatic cation or aliphatic onium cation and a fluorine-containing anion that is in a liquid state at room temperature is used. As the nitrogen-containing aromatic cation, for example, an alkyl imidazolium ion or an alkyl pyridinium ion is used. As the fluorine-containing anion, for example, borofluoride ion, phosphorous fluoride ion or trifluoromethanesulfonate ion is used.

In the present embodiment, as shown in FIG. 3, the electrolyte solution holding body 32 and the internal pressure adjusting member 58 are each formed in a U shape, and the electrolyte solution holding body 32 and the internal pressure adjusting member 58 are arranged outside the electrolyte solution containing space 30. It intersects at (the upper part of the inner casing lid 12b). Both end portions 32 a of the electrolytic solution holding body 32 are immersed in the electrolytic solution 31, and the intermediate portion 32 b is in contact with the insulating member 54.
In this configuration, the water-absorbing electrolytic solution holding body 32 sucks up the electrolytic solution 31 by capillary action, and the electrolytic solution 31 reaches the intermediate portion 32b. The intermediate portion 32 b is in contact with the water-absorbing insulating member 54, and the electrolytic solution 31 sucked up to the intermediate portion 32 b is sucked up by the insulating member 54 by capillary action and reaches the counter electrode 23. In this way, the electrolytic solution 31 sequentially reaches the reference electrode 22 and the working electrode 21 by capillary action.

[Another embodiment]
In the above-described embodiment, the counter electrode 23 is formed so as to have a smaller diameter than the annular gas permeable membrane 53 having substantially the same diameter as the O-ring 56. However, the present invention is not limited to such an embodiment, and the counter electrode 23 may have a shape having an extending portion 23 a that extends to the peripheral region of the gas permeable film 53 that is partially pressed by the O-ring 56 ( FIG. 5). In this case, due to the pressing force of the O-ring 56, the counter electrode 23 comes into contact with the conducting wire 60 at least in the extended portion 23 a extending to the peripheral region of the gas permeable film 53, so that the opposing electrode 23 and the conducting wire 60 are securely It can be made conductive.

  Further, the counter electrode 23 may be formed to have substantially the same diameter as the gas permeable film 53. Further, the counter electrode 23 is formed so that only the region in contact with the conductive wire 60 is not provided at the position pressed by the O-ring 56, that is, the counter electrode 23 is only on the center side of the counter electrode 23 around the contact region. A part of the circle of the counter electrode 23 may be cut out so as to be retracted.

  The present invention can be used for an electrochemical sensor including a working electrode, a reference electrode, a counter electrode, and an electrolytic solution in contact with these electrodes inside a housing.

X Electrochemical sensor 10 Housing 21 Working electrode 22 Reference electrode 23 Counter electrode 31 Electrolytic solution 56 Pressing member 60 Conductor

Claims (2)

A working electrode, a reference electrode, a counter electrode, and an electrolytic solution in contact with these electrodes are accommodated inside the housing,
A plurality of conducting wires respectively connected to each of the working electrode, the reference electrode and the counter electrode;
At least a part of the contact area between the working electrode and the conductive wire connected to the working electrode is at a position pressed by the pressing member in a top view,
An electrochemical sensor in which a contact region between the reference electrode and the conductive wire connected to the reference electrode does not exist at a position pressed by the pressing member in a top view.   The electrochemical sensor according to claim 1, wherein a contact region between the counter electrode and the conductive wire connected to the counter electrode does not exist at a position pressed by the pressing member in a top view.

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