JP3094398B2 - Electrochemical gas sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochemical gas sensor for measuring the concentration of a gas dissolved in a gas phase or water, for example, a gas such as oxygen or hydrogen.

[0002]

2. Description of the Related Art In order to measure the concentration of an oxidizing gas, for example, oxygen dissolved in a gas phase or water, a galvanic cell type or an electrochemical oxygen gas sensor, such as an electrochemical oxygen gas sensor, is generally used.

[0003] Both sensors basically comprise a positive electrode, a negative electrode, a diaphragm provided outside the positive electrode for limiting the permeation of oxygen to the positive electrode, an electrolytic solution, and a resin container for accommodating them. Have been.

The measurement principle is the same. When the positive electrode and the negative electrode are electrically connected outside the container, a reduction reaction of oxygen occurs at the positive electrode and an oxidation reaction of the reducing active material of the negative electrode occurs at the same time. At this time, the oxygen gas concentration is known from the current value by utilizing that the current flowing between the two electrodes is proportional to the oxygen gas concentration.

In the former, a positive electrode and a negative electrode are connected via a resistor, and the output is always in proportion to the concentration of oxygen. On the other hand, in the latter, a constant voltage is applied between both electrodes from the outside. In that an output proportional to the oxygen concentration is obtained only at that time.

The same applies to other oxidizing gases such as ozone and chlorine.

On the other hand, in order to measure the concentration of a reducing gas, for example, hydrogen dissolved in a gas phase or water, generally,
Galvanic cell type which is an electrochemical hydrogen sensor or
A polaro hydrogen sensor is used.

Each of the sensors basically comprises a positive electrode, a negative electrode, a diaphragm provided outside the negative electrode for restricting permeation of hydrogen to the negative electrode, an electrolytic solution, and a resin container for accommodating these. Have been.

The measurement principle is the same as that of the oxidizing gas sensor. When the positive electrode and the negative electrode are electrically connected outside the container, an oxidation reaction of hydrogen occurs at the positive electrode, and at the same time, a reduction reaction of the oxidizing active material of the positive electrode. Occurs. At this time, the oxygen gas concentration is known from the current value by utilizing the fact that the current flowing between the two electrodes is proportional to the hydrogen gas concentration.

In the former, a positive electrode and a negative electrode are connected via a resistor and always output in proportion to the concentration of hydrogen. On the other hand, in the latter, a constant voltage is applied between both electrodes from the outside. In that an output proportional to the hydrogen concentration is obtained only at that time.

The same applies to other reducing gases such as carbon monoxide.

[0012]

As described above, in the electrochemical gas sensor, the gas concentration is known from the value of the current flowing between the positive electrode and the negative electrode. Therefore, it is necessary to take out a lead wire from the positive electrode and the negative electrode housed in the resin container together with the electrolytic solution to the outside of the container and electrically connect them.

Therefore, there is a problem that it is very difficult to seal the lead outlet and the electrolyte is liable to leak from the sealing part if the sealing is not performed firmly. The lead extraction and sealing are very complicated in manufacturing. It is a process.

Further, the life of the sensor is limited by the weight of the negative electrode in the case of an oxygen sensor and by the weight of the positive electrode in the case of a hydrogen sensor. Alternatively, the size of the positive electrode may be increased, but there is a problem that the number of leads must be increased because the current density is reduced with one lead.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrochemical gas sensor which can be miniaturized and does not require a conventional lead extraction from the electrolyte to the outside.

[0016]

An electrochemical gas sensor according to a first aspect of the present invention comprises a positive electrode case having conductivity, a positive electrode provided in the case for electrochemically reducing an oxidizing gas, and a negative electrode. A separator for limiting the amount of oxidizing gas supplied to the positive electrode; and an electrolyte. The negative electrode, the diaphragm, and the electrolyte are arranged in a positive electrode case so that the oxidizing gas can be introduced into the positive electrode through the diaphragm. At the same time, an oxidizing gas inlet is formed in the negative electrode, and a diaphragm for sealing the inlet is attached. The negative electrode is made of lead, a cladding agent of lead and a corrosion-resistant metal, or a lead-resistant metal. Is plated, disposed on the positive electrode case so that the lead surface is inward, and the positive electrode is in contact with the diaphragm located in the introduction hole,
The positive electrode case and the negative electrode are swaged and sealed.

An electrochemical gas sensor according to a second invention comprises a negative electrode case having conductivity, a negative electrode provided in the case for electrochemically oxidizing a reducing gas, a positive electrode,
A separator for limiting the amount of reducing gas supplied to the negative electrode; and an electrolytic solution. The positive electrode, the diaphragm, and the electrolytic solution are arranged in a negative electrode case so that the reducing gas can be introduced into the negative electrode through the diaphragm. At the same time, a reducing gas inlet is formed in the positive electrode, and a diaphragm for sealing the inlet is attached. The positive electrode is formed of lead dioxide, a cladding agent of lead dioxide and a corrosion-resistant metal, or a corrosion-resistant metal. Is disposed on the negative electrode case with the lead oxide surface inside and the diaphragm located at the introduction hole and the negative electrode in contact with each other, and the negative electrode case and the positive electrode are caulked and sealed. It is characterized by having been done.

Further, the present invention is characterized in that, in the electrochemical gas sensor according to the first invention, the positive electrode is platinum, gold or an alloy of platinum, which is plated, vapor-deposited or sputtered on a corrosion-resistant metal.

Further, the present invention is characterized in that, in the electrochemical gas sensor according to the first invention, the negative electrode is platinum, gold or an alloy of platinum, which is plated, deposited or sputtered on a corrosion-resistant metal.

Further, the present invention is characterized in that in the electrochemical gas sensor according to the first to fourth inventions, the electrolyte is gelled.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an oxidizing gas sensor will be described below as an example of an electrochemical gas sensor according to the present invention. Here, the oxidizing gas is described as oxygen.

A sensor according to an embodiment of the present invention comprises a positive electrode case having conductivity, a positive electrode provided in the case made of platinum for electrochemically reducing an oxidizing gas, lead and high corrosion resistance. A negative electrode made of a clad material with a metal, the negative electrode having an oxygen introduction hole for introducing oxygen to the positive electrode, and a negative electrode provided on the highly corrosion-resistant metal surface side of the negative electrode so as not to leak from the oxygen introduction hole; A membrane for limiting the amount of oxygen supplied to the battery, and an electrolyte, wherein the negative electrode has a lead surface on the inside, and the positive electrode and the membrane are in contact with each other through an oxygen introduction hole of the negative electrode. The negative electrode is disposed in the positive electrode case with a gasket interposed between the peripheral edge and the positive electrode case portion where the peripheral edge is in contact, and the negative electrode and the positive electrode case are swaged and sealed.

Then, leads are attached to the corrosion-resistant metal surfaces of the positive electrode case and the negative electrode.

Needless to say, the space formed by the negative electrode, the diaphragm and the positive electrode case is filled with an electrolyte.

Therefore, unlike the conventional sensor in which the positive electrode and the negative electrode are housed in a resin container, the sensor of the present invention does not need to take out a lead wire from the inside of the sensor.

Further, since the positive electrode or the negative electrode is disposed in the conductive case or the upper edge of the opening of the case, only the negative electrode and / or the positive electrode and the electrolyte are accommodated in the case. It is simple and easy to miniaturize.

Here, the sealing cover of the positive electrode case is formed by the negative electrode and the diaphragm. However, the sealing cover may be provided only by the diaphragm, or a sealing lid may be separately provided. If another sealing lid is used, it must be shaped so that oxygen can be well taken into the diaphragm.

When a sealing lid is separately used, the material may be a resin, a corrosion-resistant metal, or the like.

Further, although platinum is used here as the positive electrode, other than this, platinum having a corrosion-resistant metal plated thereon, or platinum may be formed on the corrosion-resistant metal by sputtering, vapor deposition, or the like. Further, a metal obtained by plating, sputtering, or vapor-depositing a corrosion-resistant metal may be spot-welded to the positive electrode case, or platinum may be directly plated, sputtered, or vapor-deposited on the positive electrode case. in this case,
The structure must be such that the diaphragm and the positive electrode can come into contact with each other. For example, it is conceivable to adopt a case shape provided with a pedestal for forming the positive electrode or to change the shape of the diaphragm.

In addition to platinum, any platinum or gold alloy such as platinum and gold, platinum and iridium, platinum and ruthenium, or gold or any other material capable of reducing oxygen is sufficient. (In the case of a reducing gas, it is a portion corresponding to the negative electrode.)
The positive electrode case or the negative electrode case may be made of a corrosion-resistant metal such as stainless steel, titanium, or the like, or may be any material that is corrosion-resistant and shows electrical conductivity. The shape is not limited to a U-shape in cross section and a circular or square shape in top view as shown in the following embodiments, and is not particularly limited as long as it can function as a gas sensor and can be assembled. .

Here, a solution is used as the electrolytic solution, but a gelled version of the electrolytic solution may be used.

The sealing is not limited to caulking, but may be laser sealing, welding or the like, or may be heat sealed or ultrasonically welded depending on the sealing material.

The phrase "to allow the oxidizing or reducing gas to be introduced into the positive electrode through the diaphragm" means that one surface of the diaphragm can be in contact with the oxidizing or reducing gas, and at least one surface of the positive electrode has It refers to a state in which the electrolyte comes into contact with a part and an electrolyte exists at the contact interface.

Although the oxygen sensor has been described as an embodiment, the same applies to other oxidizing gases, ozone, chlorine and the like. In the case of a reducing gas, the same configuration as described above is obtained by using the positive electrode in the case of an oxidizing gas as the negative electrode and the negative electrode as the positive electrode (lead dioxide). In addition, it goes without saying that the same configuration as described above can be used for other items of the present invention.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below using preferred embodiments.

Embodiment 1 FIG. 1 is a sectional structural view of an electrochemical oxygen sensor according to one embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a positive electrode in which a titanium column having a diameter of 2 mm and a height of 0.7 mm is provided with a 3 μm platinum (Pt) plating.

Reference numeral 2 denotes a positive electrode case made of titanium and having a U-shaped cross section and having a diameter of 10 mm and a thickness of 0.2 mm.
The depth is 1.2 mm. Reference numeral 6 denotes a negative electrode made of a clad material of lead 4 (thickness 0.3 mm) and titanium substrate 5 (thickness 0.1 mm).

Reference numeral 3 denotes an oxygen introduction hole (4 mm in diameter) for introducing oxygen to the positive electrode 1 formed on the negative electrode, and is formed at the center of the negative electrode here.

Reference numeral 7 denotes a diaphragm made of polyethylene having a thickness of 10 μm, which is welded to both surfaces of the titanium of the negative electrode 6, and covers the oxygen introduction hole 3.

Reference numeral 8 denotes an electrolytic solution composed of a mixed aqueous solution of acetic acid and potassium acetate, and 9 denotes a gasket made of synthetic resin. Reference numeral 10 denotes a positive electrode lead, and 11 denotes a negative electrode lead.

The positive electrode 1 is spot-welded to the center of the positive electrode case 2.

The negative electrode 6 is disposed in the positive electrode case 2 with the lead surface inside, and the negative electrode 6 and the positive electrode case 2 are swaged and sealed. At this time, the positive electrode 1 is in contact with the diaphragm 7 through the oxygen introduction hole 3 of the negative electrode 6.

The positive electrode lead wire 10 is connected to the positive electrode case 2
And the negative electrode lead wire 11 is connected to the titanium substrate 5 of the negative electrode 6,
Each is spot welded.

Needless to say, the space formed by the negative electrode 6, the diaphragm 7 and the positive electrode case 2 is filled with the electrolytic solution 8.

The reason why the positive electrode 1 is arranged at the center of the positive electrode case 2 is to prevent it from being easily collapsed when pressed from above.

[Comparative Example] FIG. 2 shows a sectional structural view of a conventional galvanic cell type oxygen sensor.

In FIG. 2, reference numerals 1, 7, 8, 10 and 11 indicate the same components as in FIG.
13 is an ABS resin container (diameter 28mm, height 42m)
m, a hollow cylindrical shape), 14 is an epoxy resin, and 15 is a lead wire outlet for extracting current from the inside of the container to the outside.

This sensor is composed of a positive electrode 1 in which a titanium disk having a diameter of 2 mm and a thickness of 1 mm is coated with a platinum (Pt) plating of 3 μm, a negative electrode 12 made of lead (1 × 10 × 3 mm),
A 10 μm-thick polyethylene diaphragm 7 located outside the positive electrode 1 and an electrolytic solution 8 composed of a mixed aqueous solution of acetic acid and potassium acetate are contained in a container 13 made of ABS resin.

The positive electrode lead wire 10 and the negative electrode lead wire 11 made of titanium provided in the positive electrode 1 and the negative electrode 12 housed in the container 13 pass through the lead wire outlet 15 provided in the resin container 13. It is led out of the resin container 13 and its outlet 15 is connected to the epoxy resin 1.
Sealed at 4.

Embodiment 2 FIG. 3 is a sectional structural view of an electrochemical hydrogen sensor according to one embodiment of the present invention.

In FIG. 3, reference numeral 21 denotes a negative electrode in which a titanium column having a diameter of 2 mm and a height of 0.7 mm is provided with a 3 μm platinum (Pt) plating.

Reference numeral 22 denotes a negative electrode case made of titanium and having a U-shaped cross section and having a diameter of 10 mm and a thickness of 0.2 m.
m, depth 1.2 mm. Reference numeral 26 denotes a positive electrode obtained by plating lead dioxide 24 on a titanium substrate 25 (thickness: 0.1 mm).

Reference numeral 23 denotes a hydrogen introduction hole (4 mm in diameter) for introducing hydrogen to the negative electrode 21 formed on the positive electrode, and is formed at the center of the positive electrode here.

Reference numeral 27 denotes a diaphragm made of polyethylene having a thickness of 10 μm, which is welded to both surfaces of the titanium of the positive electrode 26, and covers the hydrogen introduction hole 23.

Reference numeral 28 denotes an electrolyte comprising a mixed aqueous solution of acetic acid and potassium acetate, and 29 denotes a gasket made of synthetic resin. 3
0 is a negative electrode lead and 31 is a positive electrode lead.

The negative electrode 21 is spot-welded to the center of the negative electrode case 22.

The positive electrode 26 is disposed in the negative electrode case 22 so that the lead dioxide surface is on the inside, and the positive electrode 26 and the negative electrode case 22 are swaged and sealed. At this time, the negative electrode 21 is
And is in contact with the diaphragm 27 through the hydrogen introduction hole 23.

Then, the negative electrode lead wire 30 is connected to the negative electrode case 2
2 and the positive electrode lead wire 31 is the titanium substrate 2 of the positive electrode 26.
5 are spot-welded.

Needless to say, the space formed by the positive electrode 26, the diaphragm 27 and the negative electrode case 22 is filled with the electrolytic solution 28.

The reason why the negative electrode 21 is arranged at the center of the negative electrode case 22 is to prevent the negative electrode case 22 from being easily crushed when pressed from above.

[0062]

As described above, when the electrochemical gas sensor according to the present invention shown in FIGS. 1 and 3 is compared with the conventional sensor of the comparative example shown in FIG. 2, the electrochemical gas sensor according to the present invention is obtained. The gas sensor has a structure in which it is not necessary to take out the lead wire from the electrolyte in order to take out the current from the positive electrode and the negative electrode. The complicated work involved in the process of closing the take-out port is also eliminated. In addition, the structure of the sensor itself is extremely simple, so it is highly reliable,
In addition, a small electrochemical gas sensor can be provided.

In addition, it is possible to manufacture an inexpensive gas sensor, it is easy to manufacture, and it is very important to contribute to industry.

[Brief description of the drawings]

FIG. 1 is a sectional structural view of an electrochemical oxygen sensor according to one embodiment of the present invention.

FIG. 2 is a sectional structural view of a conventional battery-type oxygen sensor.

FIG. 3 is a sectional structural view of an electrochemical hydrogen sensor according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Positive electrode case 3 Oxygen introduction hole 4 Lead 5 Titanium 6 Negative electrode 7 Separator 8 Electrolyte 9 Gasket 10 Positive electrode lead wire 11 Negative lead wire 12 Negative electrode 13 ABS resin container 14 Epoxy resin 15 Lead wire outlet

Claims (5)

(57) [Claims] 1. A positive electrode case having conductivity, a positive electrode provided in the case for electrochemically reducing an oxidizing gas, a negative electrode, and a diaphragm for limiting a supply amount of the oxidizing gas to the positive electrode; An electrolyte is provided, and the anode, the diaphragm, and the electrolyte are arranged in the cathode case so that an oxidizing gas can be introduced into the cathode through the diaphragm, and an oxidizing gas inlet is formed in the anode. In addition, a diaphragm that seals the inlet is attached, and the negative electrode is lead, a cladding agent of lead and a corrosion-resistant metal, or a corrosion-resistant metal plated with lead, with the lead surface inside, and An electrochemical gas sensor, wherein a diaphragm located in the introduction hole and a positive electrode are arranged in a positive electrode case, and the positive electrode case and the negative electrode are caulked and sealed. 2. A negative electrode case having conductivity, a negative electrode provided in the case for electrochemically oxidizing a reducing gas, a positive electrode, and a diaphragm for restricting a supply amount of the reducing gas to the negative electrode, An electrolyte is provided, and the cathode, the diaphragm and the electrolyte are arranged in the anode case so that the reducing gas can be introduced into the anode through the diaphragm, and a reducing gas inlet is formed in the cathode. The cathode is made of lead dioxide, a cladding agent of lead dioxide and a corrosion-resistant metal, or a corrosion-resistant metal plated with lead dioxide. An electrochemical gas sensor, which is disposed inside a negative electrode case so that a negative electrode and a diaphragm located in the introduction hole are in contact with each other, and the negative electrode case and the positive electrode are caulked and sealed. 3. The electrochemical gas sensor according to claim 1, wherein the positive electrode is made of platinum, gold or an alloy of platinum, which is plated, deposited or sputtered on a corrosion-resistant metal. 4. The electrochemical gas sensor according to claim 2, wherein the negative electrode is made of platinum, gold or an alloy of platinum, which is plated, deposited or sputtered on a corrosion-resistant metal. 5. The electrochemical gas sensor according to claim 1, wherein the electrolyte is gelled.