JP6989448B2 - Constant potential electrolytic oxygen sensor - Google Patents

Description

The present invention relates to a compact and portable constant potential electrolytic oxygen sensor.

The constant-potential electrolytic oxygen sensor is, for example, a water-repellent porous body capable of permeating the test gas, which is provided so as to close the casing for accommodating the electrolytic solution and the test gas introduction port formed in the casing. It comprises a quality film, a working electrode formed on the inner surface of the water-repellent porous film, a counter electrode arranged apart from the working electrode, and a reference electrode arranged between the working electrode and the counter electrode. It is a thing. In this constant-potential electrolytic oxygen sensor, for example, the potential of the working electrode is controlled to a constant potential at which a reduction reaction of oxygen occurs by a potentiostat, and the oxygen concentration is measured from the value of the current flowing between the working electrode and the counter electrode. Will be done.

Further, as a small constant potential electrolytic oxygen sensor, the working electrode, the reference electrode and the counter electrode are laminated in Patent Document 1 via an electrolytic solution holding member made of a hydrophilic non-woven fabric impregnated with an electrolytic solution. The one provided with the electrode laminated structure is disclosed.

In such a constant potential electrolytic oxygen sensor, the electrode laminated structure has a working electrode, a reference electrode laminated on the working electrode via an electrolytic solution holding member, and an electrolytic solution holding member on the reference electrode. It consists of a laminated counter electrode and a pressure adjusting film integrally provided on the counter electrode. A cylindrical partition wall is provided around the electrode laminated structure, and an electrolytic solution chamber for accommodating the electrolytic solution is formed around the partition wall. Further, the electrolytic solution holding member between the reference electrode and the counter electrode is formed so that four tongue pieces protruding outward in the plane direction are arranged at equal intervals in the circumferential direction. Is provided so as to extend into the electrolyte chamber via the partition wall. As a result, the electrolytic solution contained in the electrolytic solution chamber is supplied to the electrolytic solution holding member.

Further, sulfuric acid is generally used as the electrolytic solution. Sulfuric acid absorbs water or evaporates water depending on the humidity of the environment in which the constant potential electrolytic oxygen sensor is used, and as a result, the volume of the electrolytic solution increases or decreases. Therefore, in the constant potential electrolytic oxygen sensor, the electrolytic solution is sufficiently impregnated over the entire electrolytic solution holding member even when used in a low humidity environment, and even when used in a high humidity environment, it absorbs moisture. It is required that the increased electrolyte can be accommodated in the electrolyte chamber.

U.S. Pat. No. 7,608,177

However, the constant potential electrolytic oxygen sensor having the above configuration has the following problems.
In the constant potential electrolytic oxygen sensor described in Patent Document 1, an electrolytic solution holding member is provided between the working electrode and the reference electrode, and between the reference electrode and the counter electrode, so that, for example, the reference electrode can be used. Twice the amount of electrolytic solution is required as compared with the one without the configuration. Therefore, twice the volume of the electrolytic solution chamber is required. Further, in order to supply the electrolytic solution to the electrolytic solution holding member, the tongue piece portion of the electrolytic solution holding member is formed so as to extend into the electrolytic solution chamber formed around the electrode laminated structure, so that the electrolytic solution holding member is held. The volume of the member increases. Along with this, the amount of the required electrolytic solution also increases, so that it is necessary to increase the volume of the electrolytic solution chamber. Therefore, it is difficult to further reduce the size of the constant potential electrolytic oxygen sensor.
On the other hand, when the volume of the electrolytic solution chamber is reduced in order to reduce the size of the constant potential electrolytic oxygen sensor, the electrolytic solution is sufficiently applied to the entire electrolytic solution holding member when used in a low humidity environment. There is a problem that it becomes difficult to impregnate, or it becomes difficult to store the electrolytic solution in the electrolytic solution chamber when used in a high humidity environment.

Therefore, an object of the present invention is to provide a constant potential electrolytic oxygen sensor that is compact and can be used in an environment with a wide humidity range.

The constant-potential electrolytic oxygen sensor of the present invention is a constant-potential electrolytic oxygen sensor in which an electrode laminated structure having a working electrode, a counter electrode, and a reference electrode is arranged in a casing having a test gas inlet on the upper wall portion. And,
The electrode laminated structure includes the working electrode arranged facing the test gas inlet, an electrode composite having the counter electrode and the reference electrode arranged below the working electrode, and the action. It comprises a sheet-like electrolyte holding member impregnated with the electrolyte, which is arranged between the pole and the electrode composite.
The electrode complex is formed on the upper surface of a pressure adjusting membrane made of a hydrophobic porous material so that the counter electrode and the reference electrode are separated from each other.
The casing has a ventilation pipe portion that forms a ventilation hole and is provided so as to project inward from the lower wall portion and contact the lower surface of the pressure adjusting membrane.
An electrolytic solution chamber for accommodating the electrolytic solution, which leads to the space in which the electrode laminated structure is arranged, is formed around the ventilation pipe portion between the electrode laminated structure and the lower wall portion of the casing. Ori,
The electrode complex is supported by a support plate and is supported by a support plate.
The support plate is formed from the peripheral edge of the support plate around the electrode forming portion support portion that supports the electrode forming portion on which the counter electrode and the reference electrode are formed in the pressure adjusting film and the electrode forming portion support portion. It is characterized by having a tapered portion formed so as to approach the upper wall portion toward the electrode forming portion supporting portion.

In the constant potential electrolytic oxygen sensor of the present invention, the pressure adjusting film has at least three or more tongue pieces protruding from the peripheral edge of the electrode forming portion.
The support plate has a plurality of tongue piece support portions that support the tongue piece portion, which are formed corresponding to the tongue piece portion.
Each of the tongue piece support portions is formed with a through hole for the tongue piece portion into which the corresponding tongue piece portion enters.
It is preferable that each of the tongue pieces is formed so as to enter the through hole for the tongue piece and the tip of the tongue piece is located in the electrolytic solution chamber.

Further, in the constant potential electrolytic oxygen sensor of the present invention, the working electrode includes a gas permeable film having hydrophobicity and an electrode catalyst layer formed on the lower surface of the gas permeable film.
The gas permeable film is arranged on the upper wall portion of the casing so as to close the test gas introduction port, and is welded to the upper wall portion so as to surround the test gas introduction port.
It is preferable that the pressure adjusting membrane is welded to the tip surface of the ventilation pipe portion so as to surround the ventilation hole.

Further, in the constant potential electrolytic oxygen sensor of the present invention, the diameter of the electrolytic solution holding member is preferably 1 to 5 times the diameter of the working electrode.

In the present invention, "upper" and "lower" are defined when the constant potential electrolytic oxygen sensor of the present invention is arranged in a posture in which the surface of the casing on which the test gas introduction port is formed faces upward. It indicates the direction in the potential electrolysis type oxygen sensor. Therefore, for example, when the constant potential electrolytic oxygen sensor is arranged in a posture in which the surface of the casing on which the test gas inlet is formed faces downward, the "upper" and "lower" are actually in opposite directions, that is, When the constant potential electrolytic oxygen sensor is placed in the casing so that the surface on which the test gas inlet is formed faces to the left, the "up" and "down" indicate the "down" and "up" directions. , Actually indicate the "left" and "right" directions, respectively.

In the constant potential electrolytic oxygen sensor of the present invention, the electrolytic solution holding member need only be provided between the working electrode and the electrode composite, whereby the amount of the electrolytic solution can be reduced.
Further, the support plate that supports the electrode composite has a tapered portion formed so as to approach the upper wall portion of the casing from the peripheral edge of the support plate toward the electrode forming portion support portion, so that the electrolytic solution can be supported by the support plate. Since it is easy to collect from the peripheral edge of the electrode forming portion toward the support portion of the electrode forming portion, the electrolytic solution holding member having a small diameter can be impregnated with a sufficient amount of the electrolytic solution.
Further, since the electrolytic solution chamber is formed between the electrode laminated structure and the lower wall portion of the casing, it is possible to design an electrolytic solution chamber having a large volume even if the diameter of the casing is small.
Further, since the electrode composite is formed by forming a counter electrode and a reference electrode on the pressure adjusting film, it is not necessary to separately provide the pressure adjusting film, the number of parts is small, and the space inside the casing is reduced. It can be used efficiently.
Therefore, according to the constant potential electrolytic oxygen sensor of the present invention, it is possible to secure an electrolytic solution chamber having a large volume in spite of its small size, so that it can be used in an environment of a wide humidity range.

It is explanatory cross-sectional view which shows the outline of the structure in the example of the constant potential electrolytic oxygen sensor of this invention. It is an exploded perspective view of the constant potential electrolytic oxygen sensor shown in FIG. It is explanatory cross-sectional view which expands and shows the working electrode in the constant potential electrolytic oxygen sensor shown in FIG. It is a perspective view of the support plate which supports the electrode complex in the constant potential electrolytic oxygen sensor shown in FIG. It is a top view of the support plate which supports the electrode complex in the constant potential electrolytic oxygen sensor shown in FIG. 1.

Hereinafter, embodiments of the constant potential electrolytic oxygen sensor of the present invention will be described.
FIG. 1 is an explanatory sectional view showing an outline of a configuration in an example of a constant potential electrolytic oxygen sensor of the present invention. FIG. 2 is an exploded perspective view of the constant potential electrolytic oxygen sensor shown in FIG.
This constant potential electrolytic oxygen sensor has a casing 10 that houses an electrode laminated structure 20 having a working electrode 21, a counter electrode 26, and a reference electrode 27.

The casing 10 is composed of a cylindrical casing main body 11 having a closed lower end and a disk-shaped lid member 12 that closes an opening at the upper end of the casing main body 11 to form an upper wall portion 14. The casing body 11 and the lid member 12 are each made of a thermoplastic resin such as polypropylene.

A circular first recess 18 is formed in the central region on the upper surface of the lid member 12 forming the upper wall portion 14, and a circular second recess 19 is formed in the central region on the bottom surface of the first recess 18. Is formed. At the central position on the bottom surface of the second recess 19, a test gas introduction port 13 for introducing the test gas into the inside of the casing 10 is formed so as to extend through the upper wall portion 14 in the thickness direction.

The internal space formed by the test gas introduction port 13 functions as a diffusion space for the test gas introduced through the pinhole 51 of the gas supply limiting means 50 described later.
The volume of the internal space formed by the test gas introduction port 13 is preferably ^{, for example, about 0.1 to 10 mm 3.} With such a configuration, the introduced test gas can be sufficiently diffused, and the amount of oxygen gas remaining inside the sensor after the power is turned off can be reduced.

At the center position of the bottom wall portion of the casing main body 11, that is, the lower wall portion 15 of the casing 10, a ventilation pipe portion 16 having a circular cross section is upward (inwardly) from the lower wall portion 15 along the axial direction of the casing main body 12. It is formed so as to protrude and come into contact with the lower surface of the pressure adjusting film 28 described later. The ventilation pipe portion 16 forms a ventilation hole V that leads from the outer surface of the lower wall portion 15 to the lower surface of the pressure adjusting membrane 28.

Around the ventilation pipe portion 16 in the lower wall portion 15 of the casing 10, the working electrode terminal 40, the counter electrode terminal 42, and the reference electrode terminal 43 are arranged so as to be spaced apart from each other in the circumferential direction. An electrolytic solution chamber S for accommodating the electrolytic solution is formed around the ventilation pipe portion 16 between the electrode laminated structure 20 and the lower wall portion 15 of the casing 10. The electrolytic solution chamber S leads to a space in which the electrode laminated structure 20 is arranged through a gap K between the peripheral wall portion 17 of the casing 10 and the support plate 30 described later.

Further, on the inner surface (upper surface) of the lower wall portion 15, a sealing resin material layer 45 formed by curing an adhesive such as an epoxy resin adhesive has a working electrode terminal 40, a counter electrode terminal 42, and a reference electrode terminal 43. It is formed to cover. By providing the sealing resin material layer 45, the electrolytic solution chamber S has a liquid-tight sealing structure in which the working electrode terminal 40, the counter electrode terminal 42, and the reference electrode terminal 43 are not corroded by the electrolytic solution.

In the second recess 19 of the lid member 12, a disk-shaped gas supply limiting means 50 that matches the shape of the second recess 19 is accommodated and arranged.
The gas supply limiting means 50 is formed so that a pinhole 51 extending in the thickness direction communicates with the test gas introduction port 13 of the lid member 12. By passing the test gas through the pinhole 51, the supply amount of the test gas introduced into the casing 10 from the test gas introduction port 13 is limited.

The pinhole 51 has an inner diameter of a uniform size in the axial direction. The size of the inner diameter of the pinhole 51 is preferably 1.0 to 200 μm, for example, 50 μm. The length of the pinhole 51 is, for example, 0.1 mm or more.

A circular buffer film 55 is housed and arranged in the first recess 18.
The buffer film 55 of this example is composed of a laminate having a gas diffusion layer 56 into which the test gas flows from the outer peripheral surface and a protective layer 57 having gas impermeableness and water repellency, and the whole is circular. It is formed in a plate shape.

The gas diffusion layer 56 is adhered and fixed to the bottom surface of the first recess 18 of the lid member 12 and the upper surface of the gas supply limiting means 50 by a double-sided adhesive tape 58 having a through hole 58a formed in the pinhole 51. ing.
The gas diffusion layer 56 can be made of a fluororesin film such as a PTFE film.
The gas diffusion layer 56 preferably has an air permeability of 0.05 to 0.5 L / day, and the thickness, outer diameter dimension, void ratio, and other specific configurations are such that the air permeability is within the above numerical range. Can be set to be.

The size of the inner diameter of the through hole 58a of the double-sided adhesive tape 58 is preferably 0.05 to 5 mm, for example. The thickness of the double-sided adhesive tape 58 is preferably 0.5 to 5 mm, for example.
With such a configuration, it is possible to obtain sufficient durability against the external environment without significantly deteriorating the gas responsiveness, and it is possible to surely obtain a stable indicated value.

The protective layer 57 is adhered and fixed to the upper surface of the gas diffusion layer 56 by a double-sided adhesive tape 59.
The protective layer 57 can be made of a composite film in which an aluminum foil is laminated on a resin film such as PET.

The electrode laminated structure 20 includes a circular sheet-shaped working electrode 21 arranged so as to face the test gas introduction port 13 and separated from each other, and an electrode composite 25 arranged below the working electrode 21. It is composed of a circular sheet-shaped electrolytic solution holding member 23 impregnated with the electrolytic solution, which is arranged between the working electrode 21 and the electrode composite 25.

As shown in FIG. 3, the working electrode 21 is configured by forming an electrode catalyst layer 21b on a gas permeable film 21a having hydrophobicity, respectively, and the electrode catalyst layer 21b is in contact with the electrolytic solution holding member 23. It is arranged like this. Further, the gas permeable film 21a at the working electrode 21 is arranged so as to close the test gas introduction port 13. Further, the upper surface of the gas permeable film 21a is heat-welded to the lower surface (inner surface) of the upper wall portion 14 so as to surround the test gas introduction port 13. Since the gas permeable film 21a is heat-welded to the upper wall portion 14, it is possible to prevent the electrolytic solution from leaking from between the gas permeable film 21a and the upper wall portion 14.

The working pole 21 is electrically connected to one end of the working pole lead member 46, and the working pole terminal 40 is electrically connected to the other end of the working pole lead member 46.
As the material constituting the lead member 46 for the working electrode, metals such as gold (Au), tungsten (W), niobium (Nb) and tantalum (Ta) can be used. Further, as the lead member 46 for the working electrode, a resin-coated platinum (Pt) wire can also be used.

As the gas permeable film 21a, a porous membrane made of a fluororesin such as polytetrafluoroethylene (PTFE) can be used.
The porous membrane preferably has a Garley number of 3 to 3000 seconds. The thickness and void ratio of the porous membrane can be set so that the number of garleys is within the above numerical range. For example, the void ratio is 10 to 70% and the thickness is 0.01 to 1 mm. Is preferable.

The electrode catalyst layer 21b is formed of catalyst fine particles such as fine particles of a catalyst metal insoluble in an electrolytic solution, fine particles of an oxide of the catalyst metal, fine particles of an alloy of the catalyst metal, or a mixture of these fine particles. .. As the catalyst metal insoluble in the electrolytic solution, for example, platinum (Pt), gold (Au), ruthenium (Ru), palladium (Pd), iridium (Ir) and the like can be used. Such an electrode catalyst layer 21b can be formed by preparing a paste containing catalyst fine particles and a binder, applying the paste to the surface of the gas permeable film 21a by screen printing or the like, and firing the paste. ..

The electrode complex 25 is composed of a pressure adjusting film 28 made of a hydrophobic porous material, and a counter electrode 26 and a reference electrode 27 made of semicircular catalyst layers formed on the upper surface of the pressure adjusting film 28 so as to be separated from each other. Has been done. The pressure adjusting film 28 in the electrode complex 25 is arranged so as to close the ventilation hole V on the upper end surface of the ventilation pipe portion 16 in the casing 10. As a result, the internal space of the casing 10 is opened to the outside atmosphere through the pressure adjusting membrane 28 and the ventilation holes V. Further, the lower surface of the pressure adjusting membrane 28 is heat-welded to the upper end surface of the ventilation pipe portion 16 so as to surround the ventilation hole V. Since the pressure adjusting membrane 28 is heat-welded to the upper end surface of the ventilation pipe portion 16, it is possible to prevent the electrolytic solution from leaking from between the pressure adjusting membrane 28 and the upper end surface of the ventilation pipe portion 16. ..

The counter electrode 26 and the reference pole 27 are electrically connected to one end of the counter electrode lead member 48 and the reference pole lead member 49, and the counter electrode terminal 42 is connected to the other ends of the counter electrode lead member 48 and the reference pole lead member 49. And the reference electrode terminal 43 is electrically connected.
As a material constituting the counter electrode lead member 48 and the reference electrode lead member 49, metals such as gold (Au), platinum (Pt), tungsten (W), niobium (Nb) and tantalum (Ta) may be used. can.

As the pressure adjusting film 28, for example, a porous film made of a fluororesin such as polytetrafluoroethylene (PTFE) can be used.
The porous membrane preferably has a Garley number of 3 to 3000 seconds. The thickness and void ratio of the porous membrane can be set so that the number of garleys is within the above numerical range. For example, the void ratio is 10 to 70% and the thickness is 0.01 to 1 mm. Is preferable.

The catalyst layer constituting the counter electrode 26 and the reference electrode 27 may be fine particles of a catalyst metal insoluble in an electrolytic solution, fine particles of an oxide of the catalyst metal, fine particles of an alloy of the catalyst metal, or a mixture of these fine particles. It is formed by catalyst fine particles. As the catalyst metal insoluble in the electrolytic solution, for example, platinum (Pt), gold (Au), ruthenium (Ru), palladium (Pd), iridium (Ir) and the like can be used. The catalyst layer constituting the counter electrode 26 and the reference electrode 27 is formed by preparing a paste containing catalyst fine particles and a binder, applying the paste to the surface of the pressure adjusting film 28 by screen printing or the like, and firing the paste. be able to.

The pressure adjusting film 28 has a circular electrode forming portion 28a on which the counter electrode 26 and the reference electrode 27 are formed, and three or more extending radially outward from the outer peripheral edge of the electrode forming portion 28a, respectively (4 in the illustrated example). It is composed of a rectangular tongue piece portion 28b. Each of the tongue piece portions 28b is formed so as to be arranged at equal intervals in the circumferential direction of the electrode forming portion 28a.

The diameter of the electrolytic solution holding member 23 is preferably 1 to 5 times, more preferably 1.2 to 2 times the diameter of the working electrode 21. When the diameter of the electrolytic solution holding member 23 is too small, when the water content in the electrolytic solution evaporates and the volume of the electrolytic solution decreases, the air inside the casing 10 comes into contact with the working electrode 21 and reacts. As a result, the measurement instruction value may increase, so that there is a problem that the measurement accuracy is lowered. On the other hand, when the diameter of the electrolytic solution holding member 23 is excessive, a sufficient amount of the electrolytic solution is not absorbed by the electrolytic solution holding member 23 unless the amount of the electrolytic solution used is increased, and the inside of the casing 10 is not absorbed. There is a problem that the air of the above comes into contact with the working electrode 21 and a reaction occurs. Further, when the amount of the electrolytic solution is increased, the volume of the electrolytic solution chamber S must also be increased, which causes a problem that it becomes difficult to reduce the size of the constant potential electrolytic oxygen sensor.

The thickness of the electrolytic solution holding member 23 is such that the volume of the electrolytic solution holding member 23 can be as small as possible while being able to impregnate a sufficient amount of the electrolytic solution. It is about 0.5 mm. With such a configuration, highly reliable gas detection can be performed even in a high humidity environment.
As the electrolytic solution holding member 23, for example, a glass fiber filter paper or a non-woven fabric made of glass fiber, PP fiber, PP / PE composite fiber or ceramic fiber can be used.

A support plate 30 for supporting the composite electrode body 25 is provided at the upper end portion of the ventilation pipe portion 16. A perspective view of the support plate 30 is shown in FIG. 4, and a top view of the support plate 30 is shown in FIG.
The support plate 30 has an electrode forming portion supporting portion 31 that supports the electrode forming portion 28a in the pressure adjusting film 28, and the electrode forming portion supporting portion from the peripheral edge of the supporting plate 30 around the electrode forming portion supporting portion 31. A tapered portion 33 formed so as to approach the upper wall portion 14 toward 31 and a tongue piece portion supporting the tongue piece portion 28b formed corresponding to each of the tongue piece portions 28b in the pressure adjusting film 28. It has a support portion 35.

In the illustrated example, a step portion is formed on the upper surface of the support plate 30 between the electrode forming portion supporting portion 31 and the tapered portion 33. As a result, a substantially circular recess R in the pressure adjusting film 28 that receives and supports the electrode forming portion 28a is formed on the electrode forming portion supporting portion 31.

Further, at the central position of the electrode forming portion support portion 31, a through hole 32 for the ventilation pipe portion having an inner diameter suitable for the outer diameter of the ventilation pipe portion 16 in the casing 10 is formed. The tip portion of the ventilation pipe portion 16 is fitted into the through hole 32 for the ventilation pipe portion.

The angle formed by the plane perpendicular to the thickness direction of the support plate 30 and the surface of the tapered portion 33 is preferably 5 to 30 °. When this angle is too small, the difference between the distance from the upper wall portion 14 on the inner peripheral edge of the tapered portion 33 and the distance from the upper wall portion 14 on the outer peripheral edge of the tapered portion 33 is too small, so that the electrolytic solution is used. Is difficult to collect in the center of the support plate 30, and there is a risk that the electrolytic solution will not be supplied to the electrolytic solution holding member 23. On the other hand, when this angle is excessive, it becomes difficult for the electrolytic solution to move in a region where the distance between the support plate 30 and the upper wall portion 14 is large, and it is difficult to effectively utilize the electrolytic solution. It becomes.

Each of the tongue piece support portions 35 is formed by a groove G extending in the radial direction from the recess R toward the outer peripheral surface of the support plate 30.
The tongue piece support portion 35 is formed with a through hole 36 for the tongue piece portion at each bottom surface position of the groove G. Each of the tongue piece portions 28b in the pressure adjusting membrane 28 enters the tongue piece portion through hole 36, and the tip portion of the tongue piece portion 28b is formed so as to be located in the electrolytic solution chamber S. According to such a configuration, regardless of the posture of the constant potential electrolytic oxygen sensor, the internal pressure of the casing 10 can be kept constant by the ventilation of the outside air to the inside of the casing 10.

In this constant potential electrolytic oxygen sensor, the working electrode 21 and the reference electrode 27 are maintained at a constant potential by, for example, a potentiostat circuit (not shown). Then, the test gas introduced from the test gas introduction port 13 of the casing 10 permeates the gas permeable film 21a at the working electrode 21, and oxygen (O ₂ ) contained in the test gas permeates the electrode catalyst layer 21b. _{In contact with, a reduction reaction of oxygen (O 2} ) occurs in the electrode catalyst layer 21b, and a decomposition reaction _{of water (H 2} O) occurs in the counter electrode 26.

At this time, since the value of the current generated between the working electrode 21 and the counter electrode 26 is proportional to the concentration of oxygen in the test gas, the current flowing between the working electrode 21 and the counter electrode 26 is measured by measuring the current. The concentration of oxygen in the test gas can be measured.
Further, in the counter electrode 26, oxygen (O ₂ ) is generated by the electrolysis of water, and the pressure inside the casing 10 is adjusted by the pressure adjusting membrane 28.

In the constant potential electrolytic oxygen sensor of the present invention, the electrolytic solution holding member 23 need only be provided between the working electrode 21 and the electrode composite 25, thereby reducing the amount of the electrolytic solution. Can be done.
Further, the support plate 30 that supports the electrode composite 25 has a tapered portion 33 formed so as to approach the upper wall portion 14 of the casing 10 from the peripheral edge of the support plate 30 toward the electrode forming portion support portion 31. As a result, the electrolytic solution tends to collect from the peripheral edge of the support plate 30 toward the electrode forming portion support portion 31, so that even if the electrolytic solution holding member 23 having a small diameter is used, a sufficient amount of electrolytic solution is used for the electrolytic solution holding member 23. Can be impregnated.
Further, since the electrolytic solution chamber S is formed between the electrode laminated structure 20 and the lower wall portion 15 of the casing 10, it is possible to design the electrolytic solution chamber S having a large volume even if the diameter of the casing 10 is small. It is possible.
Further, since the electrode complex 25 is formed by forming the counter electrode 26 and the reference electrode 27 on the pressure adjusting film 28, it is not necessary to separately provide the pressure adjusting film 28, the number of parts is small, and the casing is used. The space inside the 10 can be used efficiently.
Therefore, according to the constant potential electrolytic oxygen sensor of the present invention, it is possible to secure an electrolytic solution chamber S having a large volume in spite of its small size, so that it can be used in an environment with a wide humidity range.

10 Casing 11 Case sink body 12 Lid member 13 Test gas inlet 14 Upper wall part 15 Lower wall part 16 Ventilation pipe part 17 Peripheral wall part 18 First recess 19 Second recess 20 Electrode laminated structure 21 Working electrode 21a Gas permeation Sex film 21b Electrode catalyst layer 23 Electrolyte holding member 25 Electrode composite 26 Counter electrode 27 Reference electrode 28 Pressure adjustment film 28a Electrode forming part 28b Tongue piece part 30 Support plate 31 Electrode forming part Support part 32 Through hole for vent pipe 33 Tapered Part 35 Tongue piece support part 36 Tongue piece through hole 40 Working electrode terminal 42 Counter electrode terminal 43 Reference electrode terminal 45 Sealing resin material layer 46 Working electrode lead member 48 Counter electrode lead member 49 Reference electrode lead member 50 Gas supply limiting means 51 Pinhole 55 Buffer film 56 Gas diffusion layer 57 Protective layer 58a Through hole 58 Double-sided adhesive tape 59 Double-sided adhesive tape G Groove K Gap R Recess S Electrolyte chamber V Vent hole

Claims (4)

A constant-potential electrolytic oxygen sensor in which an electrode laminated structure having a working electrode, a counter electrode, and a reference electrode is arranged in a casing having a test gas introduction port on an upper wall portion.
The electrode laminated structure includes the working electrode arranged facing the test gas inlet, an electrode composite having the counter electrode and the reference electrode arranged below the working electrode, and the action. It comprises a sheet-like electrolyte holding member impregnated with the electrolyte, which is arranged between the pole and the electrode composite.
The electrode complex is formed on the upper surface of a pressure adjusting membrane made of a hydrophobic porous material so that the counter electrode and the reference electrode are separated from each other.
The casing has a ventilation pipe portion that forms a ventilation hole and is provided so as to project inward from the lower wall portion and contact the lower surface of the pressure adjusting membrane.
An electrolytic solution chamber for accommodating the electrolytic solution, which leads to the space in which the electrode laminated structure is arranged, is formed around the ventilation pipe portion between the electrode laminated structure and the lower wall portion of the casing. Ori,
The electrode complex is supported by a support plate and is supported by a support plate.
The support plate is formed from the peripheral edge of the support plate around the electrode forming portion support portion that supports the electrode forming portion on which the counter electrode and the reference electrode are formed in the pressure adjusting film and the electrode forming portion support portion. A constant potential electrolytic oxygen sensor having a tapered portion formed so as to approach the upper wall portion toward the electrode forming portion supporting portion. The pressure adjusting film has at least three or more tongue pieces protruding from the peripheral edge of the electrode forming portion.
The support plate has a plurality of tongue piece support portions that support the tongue piece portion, which are formed corresponding to the tongue piece portion.
Each of the tongue piece support portions is formed with a through hole for the tongue piece portion into which the corresponding tongue piece portion enters.
The first aspect of claim 1, wherein each of the tongue pieces enters the through hole for the tongue piece and the tip of the tongue piece is formed so as to be located in the electrolytic solution chamber. Constant potential electrolytic oxygen sensor. The working electrode has a gas permeable film having hydrophobicity and an electrode catalyst layer formed on the lower surface of the gas permeable film.
The gas permeable film is arranged on the upper wall portion of the casing so as to close the test gas introduction port, and is welded to the upper wall portion so as to surround the test gas introduction port.
The constant potential electrolytic oxygen sensor according to claim 1 or 2, wherein the pressure adjusting membrane is welded to the tip surface of the ventilation pipe portion so as to surround the ventilation hole. The constant potential electrolytic oxygen sensor according to any one of claims 1 to 3, wherein the diameter of the electrolytic solution holding member is 1 to 5 times the diameter of the working electrode.

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