JP6212768B2 - Electrochemical gas sensor - Google Patents

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. Therefore, industrial gas concentration measuring instruments, and recently, carbon monoxide detection alarms, etc. Widely used in

  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.

  In the above-described electrochemical gas sensor, when the temperature of the atmosphere changes, or when the amount of electrolyte in the electrochemical gas sensor changes due to a change in the relative humidity of the atmosphere, the air present in the electrochemical gas sensor expands. Or it contracts and an internal pressure changes. Such a phenomenon in which the internal pressure changes is particularly noticeable in the electrolytic solution storage part that stores the electrolytic solution. When the change in the internal pressure is large, the electrolytic solution overflows from the electrolytic solution storage part, and the case of the casing of the electrochemical gas sensor is increased. There was a risk of leakage to the outside.

  Accordingly, an object of the present invention is to provide an electrochemical gas sensor that can prevent inconvenience due to a change in internal pressure.

  In order to achieve the above object, the first characteristic configuration of the electrochemical sensor according to the present invention includes an electrode housing portion including a working electrode, a reference electrode, and a counter electrode, and an electrolyte solution in a housing. An electrolyte container is formed, and in the electrode container, the working electrode, the reference electrode, and the counter electrode are laminated in a state where they are insulated by a water-absorbing insulating member, and are porous with water repellency And sealing the outer periphery of the electrode housing portion with a porous porous sheet member, immersing a water-absorbing electrolyte holder in the electrolyte, and contacting a part of the electrolyte holder with the insulating member And soaking a porous internal pressure adjusting member having water repellency in the electrolytic solution, and contacting a part of the internal pressure adjusting member with a porous annular porous sheet member having water repellency, The electrode housing side It lies in the formation of the small hole.

  In this configuration, the porous internal pressure adjusting member having water repellency is in contact with the porous, annular porous sheet member having water repellency. That is, since the laminated body of the internal pressure adjusting member and the porous sheet member is formed of a porous material, it is a layer through which gas can permeate.

  Since the porous internal pressure adjusting member having water repellency is immersed in the electrolytic solution, the air present in the electrolytic solution accommodating portion permeates through the laminate composed of at least the internal pressure adjusting member and the porous sheet member, and the electrode It can move to the side of the accommodating part. Therefore, the air that has reached the electrode housing portion can be discharged to the outside of the housing through a small hole formed in the housing.

  As described above, the electrochemical sensor according to the present invention is configured so that the air present in the housing is separated from the path through which the electrolytic solution permeates the electrode housing portion via the electrolytic solution holder and the insulating member. It has a route that can discharge to the outside. Therefore, even if the temperature of the atmosphere changes or the amount of the electrolyte inside the electrochemical gas sensor changes due to the change in the relative humidity of the atmosphere, air that is present in the electrolyte container is moved outside the housing. Since it can be discharged, the internal pressure hardly changes, and it is possible to prevent the electrolyte from overflowing from the electrolyte container and leaking outside the casing of the electrochemical gas sensor.

  The second characteristic configuration of the electrochemical sensor according to the present invention resides in that the internal pressure adjusting member is extended to the bottom surface of the electrolytic solution housing portion.

In this configuration, the internal pressure adjusting member can be immersed in the electrolyte until reaching the bottom surface of the electrolyte container. The internal pressure adjusting member comes into contact with the air present in the electrolytic solution container until the electrolytic solution container is filled with the electrolytic solution. Therefore, regardless of the orientation of the housing, even if the amount of the electrolytic solution changes, the air present in the electrolytic solution housing portion passes through the laminate composed of the internal pressure adjusting member and the porous sheet member, and the electrode It is possible to reliably move to the side of the housing portion.
The third characteristic configuration of the electrochemical sensor according to the present invention resides in that the electrolytic solution holder and the internal pressure adjusting member are stacked so as to cross each other.
In this configuration, regardless of the orientation of the housing, the electrolyte can be permeated into the electrode housing portion, and air present inside the housing can be discharged to the outside of the housing.

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). Schematic showing the path through which the air in the electrolyte container is discharged outside the housing

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.

  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 11a provided on the bottom side in the outer housing 11 and a cylindrical portion 12a through which the hole portion 11a is inserted 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. A conducting wire 60 such as a Pt wire 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.
A small hole 13a is formed in the lid 13, and the gas to be detected is taken in from the small hole 13a. 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 gas diffusion electrodes including a catalyst and a hydrophobic resin. As the catalyst, platinum (Pt), gold (Au), ruthenium (Ru), ruthenium oxide (RuO ₂ ). ), Palladium (Pd), carbon (C) and the like are suitably used, and polytetrafluoroethylene (PTFE) resin and the like are suitably used as the hydrophobic resin.

  The working electrode 21, the reference electrode 22 and the counter electrode 23 are laminated on a porous (PTFE) gas permeable film 51 to 53 having water repellency, and each is made of a water absorbing insulating member (for example, a glass wool film) 54. Insulated and water-repellent porous and annular porous sheet members (for example, made of PTFE) 55a and 55b are pressed and fixed by an O-ring 56 in a state where the outer periphery of the electrode housing portion 20 is sealed. The O-ring 56 is pressed by the lid portion 13 that seals the opening portion 11 b of the outer casing 11. 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 unit 30 surrounded by the inner casing 12 and the inner casing lid 12b. The electrolytic solution 31 is immersed in an electrolytic solution holding body 32 and a porous internal pressure adjusting member 58 having water repellency. The electrolytic solution 31 is held in the water absorbing electrolytic solution holding body 32. The electrolytic solution holding body 32 is made of, for example, glass wool, and the electrolytic solution holding body 32 includes an acidic aqueous solution such as sulfuric acid (H ₂ SO ₄ ) or phosphoric acid (H ₃ PO ₄ ), water as an electrolyte. Alkaline aqueous solution such as potassium oxide (KOH) and room temperature molten salt are sufficiently impregnated. The electrolyte solution holder 32 is inserted through the hole 12c formed in the inner housing lid 12b.

  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 electrochemical sensor X of the present invention, the electrolytic solution holding body 32 is immersed in the electrolytic solution 31, a part of the electrolytic solution holding body 32 is brought into contact with the insulating member 54, and the water repellent property is further applied to the electrolytic solution 31. The porous internal pressure adjusting member 58 having the above is immersed, and a part of the internal pressure adjusting member 58 is brought into contact with the porous sheet member 55.

  In the present embodiment, as shown in FIG. 3, the electrolyte solution holding body 32 is formed in a U shape, both end portions 32 a are immersed in the electrolyte solution 31, and the intermediate portion 32 b is in contact with the insulating member 54. In addition, the internal pressure adjusting member 58 is also formed in a U shape so that both end portions 58a are immersed in the electrolytic solution 31, and the intermediate portion 58b is in contact with the porous sheet member 55b. The electrolyte solution holding body 32 and the internal pressure adjusting member 58 intersect with each other outside the electrolyte solution storage space 30 (upper part of the inner housing lid portion 12b).

  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 part 32 b is in contact with the water-absorbing insulating member 54, and the electrolyte 31 sucked up to the intermediate part 32 b is sucked up by the capillarity by the insulating member 54 and reaches the counter electrode 23 on the electrode housing part 20 side. . In this way, the electrolytic solution 31 sequentially reaches the reference electrode 22 and the working electrode 21 by capillary action.

On the other hand, the porous internal pressure adjusting member 58 having water repellency is in contact with the porous and annular porous sheet member 55b having water repellency at the intermediate portion 58b. That is, since the laminated body of the internal pressure adjusting member 58 and the porous sheet member 55b is formed of a porous material, it is a layer through which gas can permeate.
In the present embodiment, the porous sheet member 55 b is in contact with the gas permeable film 53, and the porous sheet member 55 a and the gas permeable film 51 are laminated in this order. Also in this case, the laminated body of the internal pressure adjusting member 58, the porous sheet member 55b, and the gas permeable film 53 is a layer through which gas can permeate.

  Therefore, the air present in the electrolyte solution storage unit 30 can pass through the laminate composed of at least the internal pressure adjusting member 58 and the porous sheet member 55b and move to the electrode storage unit 20 side. The air that has reached the electrode housing portion 20 can be discharged to the outside of the housing 10 through the small hole 13a formed in the lid portion 13 (FIG. 5).

  As described above, the electrochemical sensor X of the present invention is provided inside the housing 10 separately from the path through which the electrolytic solution 31 permeates the electrode housing portion 20 via the electrolytic solution holder 32 and the insulating member 54. There is a path through which the existing air can be discharged to the outside of the housing 10. Therefore, even if the amount of the electrolytic solution 31 inside the electrochemical gas sensor X is changed due to a change in the temperature of the atmosphere or a change in the relative humidity of the atmosphere, the air present in the electrolytic solution storage unit 30 is particularly removed from the casing 10. Therefore, it is possible to prevent the electrolyte 31 from overflowing from the electrolyte container 30 and leaking to the outside of the casing 10 of the electrochemical gas sensor X.

  The internal pressure adjusting member 58 is preferably extended to the bottom surface of the electrolytic solution storage unit 30. With this configuration, the internal pressure adjusting member 58 can be immersed in the electrolytic solution 31 until it reaches the bottom surface of the electrolytic solution storage unit 30. The internal pressure adjusting member 58 is in contact with the air present in the electrolyte container 30 until the electrolyte container 30 is filled with the electrolyte 31. Therefore, regardless of the orientation of the housing 10, even if the amount of the electrolytic solution 31 is changed, the laminate that includes the internal pressure adjusting member 58 and the porous sheet member 55 b is used to convert the air present in the electrolytic solution storage unit 30. And can be reliably transferred to the electrode housing portion 20 side.

  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 13a Small Hole 20 Electrode Housing 21 Working Electrode 22 Reference Electrode 23 Counter Electrode 30 Electrolytic Solution Storage Space 31 Electrolytic Solution 32 Electrolyte Holder 54 Insulating Member 55a, 55b Porous Sheet Member 58 Internal Pressure Adjusting Member

Claims (3)

Inside the housing, an electrode housing portion provided with a working electrode, a reference electrode, and a counter electrode, and an electrolyte solution housing portion for housing an electrolyte solution are formed,
In the electrode housing portion, the working electrode, the reference electrode, and the counter electrode are laminated in a state where they are insulated by a water-absorbing insulating member, and a porous and annular porous sheet member having water repellency The outer periphery of the electrode housing part is sealed with
While immersing a water-absorbing electrolyte holder in the electrolyte, a part of the electrolyte holder is brought into contact with the insulating member,
While immersing a porous internal pressure adjusting member having water repellency in the electrolytic solution, a part of the internal pressure adjusting member is brought into contact with a porous, annular porous sheet member having water repellency,
An electrochemical sensor in which a small hole is formed on the side of the electrode housing portion in the housing.   The electrochemical sensor according to claim 1, wherein the internal pressure adjusting member is extended to the bottom surface of the electrolyte container. 3. The electrochemical sensor according to claim 1, wherein the electrolytic solution holder and the internal pressure adjusting member are configured to intersect and be stacked.

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