JP2001141691A - Carbon monoxide detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon monoxide detector of a quick responsivity. SOLUTION: The carbon monoxide detector has a detecting element 1 comprising a first electrolytic film 8 with a hydrogen ion conductivity, a first catalytic electrode 9 disposed in contact with one face of the first electrolytic film 8, and a second catalytic electrode 10 set in contact with the other face of the first electrolytic film 8; a first gas pipe 14 as a first gas supply means for supplying a gas to be detected to the first catalytic electrode 9; a second gas pipe 15 as a second gas supply means for supplying one or, two or more kinds of an inert gas, a nitrogen gas and a carbon dioxide gas to the second catalytic electrode 10; a resistance 6 as a load connected between the first catalytic electrode 9 and the second catalytic electrode 10; and a voltmeter 7 as a potential difference-detecting means for detecting a potential difference between the first catalytic electrode 9 and the second catalytic electrode 10, which changes in the accordance with a concentration of a carbon monoxide gas in the gas to be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon monoxide detector for detecting the concentration of carbon monoxide gas contained in fuel gas used for a fuel cell, for example.

[0002]

2. Description of the Related Art In recent years, fuel cells have been actively developed, and a fuel cell using a hydrogen ion conductive membrane made of a solid polymer is most practically used. When the operating temperature is lower than 100 ° C., the device operates at a very low temperature as compared with other systems, and is easy to handle. Therefore, it is regarded as a favorite for home and automobile fuel cells.

As a fuel gas to be supplied to the fuel cell, pure hydrogen gas is desirable, but at present, almost no infrastructure has been provided for supplying pure hydrogen gas.
Therefore, a method of extracting hydrogen gas by reforming a liquid fuel such as methanol is becoming mainstream.
In this case, the fuel gas coming out of the reformer is mostly hydrogen gas and carbon dioxide gas, but may contain a very small amount of carbon monoxide gas of several tens ppm level. If this carbon monoxide gas is adsorbed on a platinum catalyst constituting an electrode of a fuel cell even at a level of several tens of ppm (this phenomenon is called poisoning), the electromotive force is reduced. Therefore, it is necessary to constantly monitor the concentration of the carbon monoxide gas in the fuel gas and control the reformer to reduce the carbon monoxide gas. Therefore, a carbon monoxide sensor is an essential component in a fuel cell using a reformer.

As a carbon monoxide sensor for detecting a carbon monoxide gas in a fuel gas (containing a large amount of hydrogen gas) supplied to function as a fuel cell as described above, JP-A-8-327590 discloses Are known.

FIG. 9 shows a cross section of a schematic structure of the carbon monoxide sensor. Reference numeral 110 denotes an electrolyte membrane made of a polymer having proton conductivity, on both surfaces of which an electrode 1 is prepared by kneading carbon powder carrying platinum for a catalyst on a carbon cloth.
12, 114 are joined by hot pressing. Mesh-shaped metal plates 116 and 118 are provided on the surfaces of the electrodes 112 and 114 that are not joined to the electrolyte membrane 110. The electrolyte membrane 110, the electrodes 112 and 114, and the metal plates 116 and 118 are formed by metal flanges 120 provided inside cylindrical holders 120 and 122.
a, 122a. On the electrolyte membrane 110 side of the end face of the holder 122, an O-ring 126 for gas sealing is provided.

Screw portions 120b and 122b are formed on the outer periphery of the holders 120 and 122, respectively, and these are formed inside an insulating member 124 made of polytetrafluoroethylene {for example, Teflon (trademark of DuPont)}. The holders 120 and 122 are fixed by being screwed into the screw portions 124a and 124b.

A gas inflow passage 12 is provided at one end of the holder 120.
8 is connected to one end, from which a gas to be detected (same as fuel gas) is introduced into the carbon monoxide sensor. on the other hand,
The gas inflow passage 128 is not connected to one end of the holder 122, and is open to the atmosphere.

The other end of the gas inflow passage 128 is connected to a branch port 14 provided in a part of a fuel gas passage 140 introduced into the fuel cell.
0a.

The holders 120 and 122 are provided with detection terminals 120T and 122T, respectively, to which an electric circuit 130 is connected. The electric circuit 130 has a configuration in which a voltmeter 132 and a resistor 134 for adjusting a load current are connected in parallel. The detection terminal 120T is a voltmeter 1
The detection terminal 122T is connected to the negative electrode 32, and the positive terminal, respectively.

Next, the operation of the carbon monoxide detector will be described. The gas to be detected (fuel gas) containing a large amount of hydrogen gas reaches the electrode 112 via the gas inflow passage 128. On the other hand, the electrode 114 is always in contact with oxygen gas in the atmosphere. Therefore, the following reactions (Chem. 1) and (Chem. 2) occur on the surface of the electrolyte membrane 110 in contact with the electrodes 112 and 114.

[0011]

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[0012]

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These reactions are similar to those of a fuel cell that generates electricity using hydrogen gas and oxygen gas as fuel, and an electromotive force is generated between the electrodes 112 and 114. Electrode 11
Since a resistor 134 is connected between the electrodes 2 and 114, a predetermined load current flows. At this time, a potential difference between the electrodes 112 and 114 is detected by a voltmeter 132.

In this state, if carbon monoxide gas is mixed in the gas to be detected, the carbon monoxide gas is adsorbed on the platinum catalyst in the electrode 112, and the electrode 112 is poisoned. As a result, the battery reaction by the hydrogen gas and the oxygen gas is inhibited, and the electrode 11
The potential difference between 2, 114 decreases. Since the concentration of carbon monoxide gas is reflected in the degree of poisoning, the electrodes 112, 114
The concentration of carbon monoxide gas in the gas to be detected can be known by measuring the potential difference between them.

The carbon monoxide detector shown in FIG.
FIG. 10 shows the result of measuring the relationship between the time when the carbon monoxide gas having a concentration of 0 ppm was supplied and the output potential difference.

In FIG. 10, the horizontal axis represents time, and the vertical axis represents the output potential difference. As a result, the output potential difference started to change about 5 minutes after the flow of carbon monoxide (50 ppm).

[0017]

In this carbon monoxide detector, as shown in the above (Chemical formula 2), a chemical reaction for producing water from hydrogen ion electrons and oxygen gas occurs to generate an electromotive force. The reaction for producing water is much slower than the reaction for producing hydrogen ions shown in the above (Chemical Formula 1). Therefore, even if carbon monoxide gas is mixed in the gas to be detected and the electrode 112 is poisoned and the generation of hydrogen ions is inhibited, the effect on the water generation reaction is not immediately exhibited. This poses a problem that the electromotive force does not change for a while and the carbon monoxide gas with a high response cannot be detected.

The present invention solves this problem.
An object of the present invention is to provide a carbon monoxide detector having a high response.

[0019]

In order to solve this problem, a carbon monoxide detector according to the present invention comprises a first electrolyte membrane having hydrogen ion conductivity and one surface of the first electrolyte membrane. A detection element comprising a first catalyst electrode having a catalyst disposed in contact with the second catalyst electrode having a catalyst disposed in contact with the other surface of the first electrolyte membrane; A first gas supply unit for supplying a gas to be detected to one catalyst electrode, and one or more of an inert gas, a nitrogen gas, and a carbon dioxide gas to the second catalyst electrode Second gas supply means, a load connected between the first catalyst electrode and the second catalyst electrode,
A potential difference detecting means for detecting a potential difference between the first catalyst electrode and the second catalyst electrode, which changes in accordance with the concentration of carbon monoxide gas in the gas to be detected. is there.

According to this configuration, a carbon monoxide detector having a fast response can be obtained.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention comprises a first electrolyte membrane having hydrogen ion conductivity and a catalyst arranged in contact with one surface of the first electrolyte membrane. A detection element including a first catalyst electrode having a first catalyst electrode and a second catalyst electrode having a catalyst disposed in contact with the other surface of the first electrolyte membrane; A first gas supply unit for supplying a gas, a second gas supply unit for supplying one or more of an inert gas, a nitrogen gas, and a carbon dioxide gas to the second catalyst electrode; A load connected between the first catalyst electrode and the second catalyst electrode, and the first catalyst electrode and the second catalyst electrode that change in accordance with the concentration of carbon monoxide gas in the gas to be detected. And a potential difference detecting means for detecting a potential difference between the two catalyst electrodes. It has the effect that the response of detecting carbon dioxide gas increases.

According to a second aspect of the present invention, in the first aspect of the present invention, a carbon powder having a catalyst supported on a carbon cloth is fixed to the outside of the first catalyst electrode and the second catalyst electrode. A metal plate-shaped first metal electrode processed so as to have at least one or more through-holes is arranged, and a first electrolyte membrane and a first catalyst electrode are formed by the two first metal electrodes. And the second catalyst electrode are fixed so as to sandwich the first catalyst electrode and the second catalyst electrode without disturbing gas diffusion to the first catalyst electrode and the second catalyst electrode. The two first metal electrodes can be brought into surface contact with each other, which has an effect that good output stability can be obtained.

According to a third aspect of the present invention, in the second aspect of the present invention, since the surfaces of the two first metal electrodes are processed smoothly and the gold plating layer is formed, the first catalyst is formed. The contact between the electrode and the second catalyst electrode and the two first metal electrodes is further improved, and an effect that a low-noise output is obtained.

According to a fourth aspect of the present invention, in the first aspect of the invention, one or more of an inert gas, a nitrogen gas and a carbon dioxide gas is mixed with the second catalyst electrode. Touching the inert gas, nitrogen gas,
A part of the gas chamber includes a gas chamber in which one kind or a mixed gas of two or more kinds of carbon dioxide gas is sealed, and a hydrogen gas removing unit for removing hydrogen gas released into the gas chamber. Therefore, it is not necessary to supply one or more of the inert gas, the nitrogen gas, and the carbon dioxide gas through the use of a flow path or the like, thereby providing a simple structure.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, since the hydrogen gas removing section is disposed above the detecting element, an inert gas, a nitrogen gas, and a carbon dioxide gas are removed. The hydrogen gas, which is lighter than one or two or more of the mixed gases, naturally moves upward and gathers around the hydrogen gas removing unit.

According to a sixth aspect of the present invention, in the fourth or fifth aspect of the present invention, the hydrogen gas removing section includes a second electrolyte membrane having hydrogen ion conductivity, an inert gas, a nitrogen gas, and a carbon dioxide. A third catalyst electrode having a catalyst disposed in contact with one surface of the second electrolyte membrane for dissociating hydrogen gas from one or a mixture of two or more of carbon gases; A hydrogen gas removing element comprising: a fourth catalyst electrode having a catalyst disposed in contact with the other surface of the second electrolyte membrane so as to touch the third electrolyte membrane;
And the fourth catalyst electrode, it is possible to remove the hydrogen gas in the gas chamber without supplying energy from the outside, and at the same time, to remove water at the fourth catalyst electrode. And has the effect of discharging water into the atmosphere.

According to a seventh aspect of the present invention, in accordance with the sixth aspect of the present invention, each of the third catalyst electrode and the fourth catalyst electrode in which carbon powder having a catalyst supported on a carbon cloth is fixed is provided outside the third catalyst electrode and the fourth catalyst electrode, respectively. A metal plate-shaped second metal electrode processed so as to have at least one or more through holes is arranged, and the two second metal electrodes are used to form a second electrolyte membrane and the third catalyst electrode. And the fourth catalyst electrode are sandwiched and fixed, so that gas diffusion to the third catalyst electrode and the fourth catalyst electrode is not hindered, and the third catalyst electrode and the fourth catalyst electrode are connected to each other. There is an effect that two second metal electrodes can be brought into surface contact and good hydrogen gas can be removed.

According to an eighth aspect of the present invention, in the invention of the seventh aspect, since the surfaces of the two second metal electrodes are smoothed and a gold plating layer is formed, the third second metal electrode is formed.
The contact between the catalyst electrode and the fourth catalyst electrode and the two second metal electrodes is further improved, and has an effect that excellent hydrogen gas can be removed.

According to a ninth aspect of the present invention, in the sixth or seventh aspect, the fourth catalyst electrode surface is arranged to be inclined with respect to the horizontal direction or to be arranged in parallel with the direction of gravity. Therefore, there is an effect that water generated on the fourth catalyst electrode can be discharged without collecting on the surface of the fourth catalyst electrode.

According to a tenth aspect of the present invention, in the invention of the sixth aspect, since the areas of the third and fourth catalyst electrodes are larger than the areas of the first and second catalyst electrodes. 2 has the effect that the hydrogen gas generated at the catalyst electrode can be removed from the gas chamber without leaving it.

According to an eleventh aspect of the present invention, in the first to tenth aspects, the concentration calculating means for obtaining the concentration of carbon monoxide gas in the gas to be detected from the voltage difference detected by the potential difference detecting means is provided. Since it is provided, it has an effect that the output voltage difference can be converted to the concentration of carbon monoxide gas with high accuracy.

According to a twelfth aspect of the present invention, in accordance with the eleventh aspect of the present invention, the concentration calculating means has a calculating part for converting the change rate of the output voltage difference into the concentration of carbon monoxide gas. This has the effect of increasing the response speed.

According to a thirteenth aspect of the present invention, in accordance with the first to twelfth aspects of the present invention, a heater is provided near the detecting element, and a heater control circuit for controlling the heater is connected. This has the function of recovering the poisoned first catalyst electrode.

According to a fourteenth aspect of the present invention, in the thirteenth aspect, the heating element constituting the heater is sandwiched between fluoropolymer sheets, and a hole or a slit is provided through the heating element and the sheet. Therefore, the poisoned first catalyst electrode can be recovered by heating without interrupting the diffusion of the gas to be detected to the first catalyst electrode with a simple configuration.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

(Embodiment 1) FIG. 1 is a cross-sectional view for explaining a schematic structure of a carbon monoxide detector according to Embodiment 1 of the present invention, and FIG. It is the exploded perspective view seen from the direction. FIG. 3 is a characteristic diagram showing the output potential difference of the carbon monoxide detector of the present invention.

In FIG. 1, reference numeral 1 denotes a first electrolyte membrane 8 for detecting the concentration of carbon monoxide gas in the gas to be detected, and first and second electrolyte membranes provided on both sides of the first electrolyte membrane 8. Of the catalyst electrodes 9 and 10. Detection element 1
Are provided with two ring-shaped first sealing rubbers 11, two first metal electrodes 2 having output terminal portions 13, two ring-shaped first insulating sealing rubbers 3, and a threaded portion at one end. The first pressing plate 4 made of stainless steel and formed with a hole at the center was sandwiched between the two first pressing plates 4, and was fixed between the two first pressing plates 4 with bolts 5. Further, a first gas pipe 14 as a means for supplying a gas to be detected is attached to the first catalyst electrode 9 side at each of the holes provided at the center of the two first pressurizing plates 4, and an inert gas, A second gas pipe 15 as a means for supplying one or more of a mixture gas of nitrogen gas and carbon dioxide gas (hereinafter, referred to as a counter electrode gas) is screwed to the second catalyst electrode 10 side. I have. Here the second
Gas pipe 15 is disposed above the first gas pipe 14,
Supply and dissociation of hydrogen gas in the gas to be detected to the detection element 1;
And the production function works smoothly. Further, an output terminal portion 13 provided on a part of each of the two first metal electrodes 2 is connected to a resistor 6 as an external load and a voltmeter 7 as a potential difference detecting means. The arrows shown in FIG. 1 indicate the directions of the flows of the detected gas and the counter electrode gas.

Referring to FIG. 2, the detection element 1 will be described in detail. Reference numeral 8 denotes a first electrolyte membrane having a hydrogen ion conductivity and having a diameter of 14 mm and made of a fluorine-based polymer material, and a carbon powder carrying a platinum catalyst is partially fixed on both surfaces thereof with the fluorine-based polymer material. A first catalyst electrode 9 and a second catalyst electrode 10 made of carbon cloth having a diameter of 6 mm are arranged. Further, two ring-shaped first portions are formed on the remaining portions (near the outer peripheral portion) on both surfaces of the first electrolyte membrane 8.
Is disposed. The first electrolyte membrane 8 was sandwiched between the first catalyst electrode 9, the second catalyst electrode 10, and the two first sealing rubbers 11, and the temperature was set to 130 ° C. and fixed by hot pressing.

The two first flat plates of stainless steel 14 mm in diameter and 1 mm in thickness processed so as to have four fan-shaped through holes 12 on both sides of the detection element 1 thus constructed. Metal electrode 2 is disposed. further,
The surface of the first metal electrode 2 is smoothed so that the average surface roughness is 1.6 μm or less, and N 1
i-plating is performed, and a gold plating layer having a thickness of about 1 μm is further formed thereon. In the present embodiment, the shape of the through-hole 12 is fan-shaped, but the shape and dimensions are not limited to this as long as the gas to be detected and the counter electrode gas can pass therethrough.

FIG. 1 also shows a detection circuit section composed of a resistor 6 and a voltmeter 7. More specifically, a resistor 6 and a voltmeter 7 are connected to output terminals 13 provided on the two first metal electrodes 2 via a cable. The voltmeter 7 is connected to a microcomputer (not shown) as a concentration calculating means for calculating the concentration of carbon monoxide gas in the gas to be detected from the detected potential difference. The microcomputer calculates the output potential difference for each fixed time (that is, the change speed of the output potential difference), and obtains a table (stored in ROM) in which the correlation between the change speed of the output potential difference and the concentration of carbon monoxide gas is obtained in advance. The value is converted into the concentration of carbon monoxide gas with reference to the output.

Next, the operation of the carbon monoxide detector according to the present embodiment will be described.

A part of the gas to be detected containing a large amount of hydrogen gas such as fuel gas supplied to the fuel cell is supplied to the first gas pipe 1.
4 and reaches the detection element 1 through the through hole 12 of the first metal electrode 2.

Since most of the first catalyst electrode 9 of the detection element 1 is made of carbon cloth, the gas to be detected diffuses in the carbon cloth and reaches carbon powder carrying a platinum catalyst.

On the other hand, the second catalyst electrode 10 is always in contact with a counter electrode gas such as an inert gas, a nitrogen gas or a carbon dioxide gas. Therefore, the following reactions (Chem. 3) and (Chem. 4) occur on the surfaces of the first electrolyte membrane 8 on the first catalyst electrode 9 side and the second catalyst electrode 10 side, respectively.

[0045]

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[0046]

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By these reactions, the first catalyst electrode 9
An electromotive force is generated between the first catalyst electrode 10 and the second catalyst electrode 10. Further, since a resistor 6 of about 5Ω is connected between the first catalyst electrode 9 and the second catalyst electrode 10, a predetermined load current flows. At this time, the first catalyst electrode 9 and the second catalyst electrode 1
The potential difference between 0 and 0 is detected by the voltmeter 7.

When carbon monoxide gas (CO) is mixed in the gas to be detected under such a condition, the carbon monoxide gas is adsorbed on the surface of the platinum catalyst in the first catalyst electrode 9, and the first gas is removed. The catalyst electrode 9 is poisoned. As a result, the potential difference between the first catalyst electrode 9 and the second catalyst electrode 10 decreases. Since the concentration of carbon monoxide gas is reflected in the degree of poisoning, the potential difference between the first catalyst electrode 9 and the second catalyst electrode 10 is measured to detect a large amount of hydrogen gas. The concentration of carbon monoxide gas in the gas can be known.

FIG. 3 shows an output potential difference characteristic when the gas to be detected flows through the carbon monoxide detector according to the present embodiment. 3, the horizontal axis represents time, and the vertical axis represents the output potential difference. As shown in FIG. 3, when the concentration of the carbon monoxide gas was 0 ppm, the output potential difference was constant and was about 55 mV. However, at the same time as the carbon monoxide gas was mixed into the gas to be detected, the output potential difference began to decrease with time. In this tendency, the time during which the output potential difference decreases (that is, the change speed of the output potential difference) differs depending on the concentration of the carbon monoxide gas. This is because the higher the concentration, the faster the platinum catalyst is poisoned. The concentration of the carbon monoxide gas could be known by obtaining the rate of change of the output potential difference from the amount of change in the output potential difference at regular intervals in a microcomputer.

In the carbon monoxide detector according to the present embodiment, hydrogen gas generated at the second catalyst electrode 10 is removed by the counter electrode gas supplied by the second gas pipe 15. .

Further, in the present embodiment, the first metal electrode 2 is a flat plate, the surface of which is smoothed and gold-plated, so that the first catalyst electrode 9 and the second catalyst electrode 10 are formed. And the contact potential was good, and an extremely stable output potential difference was obtained.

(Embodiment 2) FIG. 4 is a cross-sectional view for explaining a schematic structure of a carbon monoxide detector according to Embodiment 2 of the present invention, and FIG. FIG. 6 is an exploded perspective view seen from the direction of arrow B. FIG. 6 is a side view of the hydrogen gas removing unit in the detector shown in FIG.

In the present embodiment, since a part has the same structure as that of the first embodiment, the same components are denoted by the same reference numerals, detailed description thereof will be omitted, and only different portions will be described in detail.

In the carbon monoxide detector described in the first embodiment, the hydrogen gas generated at the second catalyst electrode 10 is released into the counter electrode gas flowing through the second gas pipe 15. The hydrogen gas can be removed by the flow of the counter electrode gas. In the present embodiment, instead of the second gas pipe 15 used in the first embodiment, a gas chamber 16 in which a counter electrode gas is sealed as shown in FIG. A hydrogen gas removal unit 17 for removal is provided to make the system more compact.

In FIG. 4, the gas chamber 16 is arranged at a position corresponding to the position of the second gas pipe 15 shown in FIG. 1, and is fixed to the first pressure plate 4 by screws. Further, the hydrogen gas removing section 17 is disposed above the gas chamber 16, and both are fixed by screws. The arrows in the figure indicate the direction of the flow of the gas to be detected.

Next, the details of the hydrogen gas removing section 17 will be described. The hydrogen gas removing element 18 has two second metal electrodes 19 having connection terminal portions 23, two ring-shaped second insulating sealing rubbers 20, and a screw portion formed at one end, and a hole at the center. The second pressing plate 21a made of stainless steel provided, and a second pressing plate 21b made of stainless steel provided with only a hole at the center without having a screw portion at one end, is sandwiched by two second pressing plates 21b. Between the pressurizing plates 21a and 21b are fastened and fixed by bolts 22. Further, a part of the lower side of one second pressurizing plate 21a is screwed and fixed to the gas chamber 16, and the other second pressurizing plate 21b is open to the atmosphere. Thus, the hydrogen gas removing unit 17
Is disposed above the gas chamber 16, and the hydrogen gas released into the gas chamber 16 is supplied to the hydrogen gas removing element 18, and the dissociation and generation operations function smoothly. A connection terminal portion 23 is formed on a part of each of the two second metal electrodes 19, and is connected to an external resistor 24.

FIG. 5 shows the detailed structure of the hydrogen gas removing section 17. In FIG. 5, reference numeral 25 denotes a second electrolyte membrane having a hydrogen ion conductivity and having a diameter of 14 mm and made of a fluorine-based polymer material. Diameter 10 fixed with molecular material
A third catalyst electrode 26 and a fourth catalyst electrode 27 made of carbon cloth having a thickness of 2 mm are arranged. Further, two ring-shaped second sealing rubbers 28 are arranged on the remaining portions (near the outer peripheral portion) on both surfaces of the second electrolyte membrane 25. The second electrolyte membrane 25 was sandwiched between the third catalyst electrode 26, the fourth catalyst electrode 27, and the two second sealing rubbers 28, and the temperature was set to 130 ° C. and fixed by hot pressing. Note that the area of the third catalyst electrode 26 and the area of the fourth catalyst electrode 27 are larger than the area of the first catalyst electrode 9 and the second catalyst electrode 10 of the detection element 1. This is to enable the hydrogen gas removal element 18 to completely remove hydrogen gas generated on the second catalyst electrode 10.

The hydrogen gas removing element 18 thus constructed is made of stainless steel and has a diameter of 14 mm and a thickness of 1 m which has four fan-shaped through holes 29 on both sides.
Two second metal electrodes 19 having a flat plate shape of m are arranged. Further, the surface of the second metal electrode 19 is smoothened so that the average surface roughness is 1.6 μm or less, Ni plating is applied thereon as a base, and gold plating having a thickness of about 1 μm is further applied thereon. A layer is formed. In the present embodiment, the shape of the through-hole 29 is sector-shaped, but the shape and dimensions are not limited to this embodiment as long as they can transmit the counter electrode gas and the atmosphere.

In the hydrogen gas removing section 17 shown in FIG.
A resistor 24 is connected to a connection terminal portion 23 provided on each of the second metal electrodes 19 via a cable.

Next, the hydrogen gas removing unit 17 of the present embodiment
Will be described.

When the hydrogen gas generated on the second catalytic electrode 10 of the detecting element 1 and released into the gas chamber 16 reaches the hydrogen gas removing section 17, the through-hole 29 of the second metal electrode 19 is formed. Then, it reaches the hydrogen gas removing element 18.

The third catalyst electrode 2 of the hydrogen gas removing element 18
Since 6 is mostly made of carbon cloth, the hydrogen gas diffuses in the carbon cloth to reach the carbon powder carrying the platinum catalyst.

On the other hand, the fourth catalyst electrode 27 side is always in contact with the atmosphere. Accordingly, the reactions shown in (Chem. 5) and (Chem. 6) occur on the surfaces of the second electrolyte membrane 25 on the third catalyst electrode 26 side and the fourth catalyst electrode 27 side, respectively.

[0064]

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[0065]

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By these reactions, the third catalyst electrode 2
An electromotive force is generated between the sixth and fourth catalyst electrodes 27. Since the resistor 24 is connected between the third catalyst electrode 26 and the fourth catalyst electrode 27, a predetermined load current flows. As the reaction shown in the above (Chemical Formula 5) and (Chemical Formula 6) proceeds, the hydrogen gas in the gas chamber 16 becomes water and is removed.

In the present embodiment, since the second metal electrode 19 is a flat plate, the surface of which is smoothed and plated with gold, the third catalyst electrode 26 and the fourth catalyst electrode 27 are formed. The contact with hydrogen was improved, and a stable hydrogen gas removing effect was obtained.

In FIG. 6, the hydrogen gas removing element 18 of the hydrogen gas removing section 17 is attached at an angle of 45 ° with respect to the direction of gravity. This is provided with a drain portion 30 for smoothly draining water generated on the fourth catalyst electrode 27 side as shown in the above (Chem. 6). Thereby, the reaction shown in the above (Chem. 5) and (Chem. 6) proceeds extremely smoothly.

(Embodiment 3) FIG. 7 is an exploded perspective view for explaining a schematic structure of a carbon monoxide detector according to Embodiment 3 of the present invention. FIG. 8 is a block diagram for explaining a detection circuit section and a heater control circuit section of the detector.

In the present embodiment, most of the configuration is the same as that of the first embodiment. Therefore, the same components are denoted by the same reference numerals, detailed description thereof will be omitted, and only different portions will be described in detail.

The carbon monoxide detector described in the first embodiment does not include means for desorbing carbon monoxide gas from the poisoned platinum catalyst. For this reason, it has sufficient functions as an alarm or switch to notify that the concentration of carbon monoxide gas has exceeded a certain value, but once poisoned, the reaction is irreversible, so it is reversible. It is not sufficient as a carbon monoxide detector having a typical function. Therefore, in the present embodiment, as shown in FIG. 7, the heater 31 for recovering the function of the platinum catalyst by heating the platinum catalyst to which the carbon monoxide gas is adsorbed (poisoned) is connected to the first first catalyst.
On the metal electrode 2 side. The heater 31 is a heating element 32 made of a nichrome plate processed into a shape as shown in FIG.
Is also punched into a shape as shown in FIG. 7 and sandwiched with a fluorine-based polymer sheet 33 made of insulating polytetrafluoroethylene {for example, Teflon (trademark of DuPont)} and hot-pressed. It is formed by that. Since the through hole 34 is formed in the heater 31, the gas to be detected can be transmitted through the through hole 34. In the present embodiment, the through-hole 34 is provided. However, the through-hole 34 may be a slit as long as it can transmit the gas to be detected. Further, the shapes and dimensions of the through holes and the slits are not limited to the present embodiment.

The heater 31 is inserted and fixed between the first metal electrode 2 and the first insulating rubber 3 as shown in FIG.

The detection circuit shown in FIG. 8 is obtained by adding a heater control circuit 35 to the detection circuit shown in FIG. 1 described in the first embodiment.

Next, the basic operation principle of the carbon monoxide detector according to the present embodiment will be described. The basic operation of the carbon monoxide detector of the present embodiment is the same as that of the first embodiment, but there is a difference in the operation of the present embodiment due to the arrangement of the heater 31. That is, the carbon monoxide gas adsorbed on the platinum catalyst is desorbed by heating with the heater 31, so that it can be operated again as a carbon monoxide detector.

When the microcomputer (not shown) determines that the concentration of carbon monoxide gas is equal to or higher than a predetermined concentration, a signal is transmitted to the heater control circuit 35. Accordingly, the heater control circuit 35 sets the temperature of the heater 31 to about 130 ° C.
Apply current so that As a result, the first catalyst electrode 9
Is heated, and the carbon monoxide gas adsorbed on the platinum catalyst is desorbed. The above operation suggests that even if the platinum catalyst is poisoned, it can be repeatedly used as a carbon monoxide detector.

When such a carbon monoxide detector was manufactured and evaluated, basic output potential difference characteristics similar to those shown in FIG. 3 were obtained. After the poisoning, the heater 31
Is operated and heated to 130 ° C., then the power supply to the heater 31 is stopped, and the heater 31 is allowed to cool. When the potential difference between the two was measured, it almost recovered to the original output potential difference. From this, it was proved that a reversible carbon monoxide detector capable of recovering the detection function even if poisoned could be constituted.

Further, the specific material names described in the present embodiment are merely examples for constituting the carbon monoxide detector of the present invention, and are not limited to these materials.

As described above, a carbon monoxide detector having a simple structure and excellent response performance can be realized. Further, a carbon monoxide detector capable of recovering the detection function even if poisoned can be realized.

[0079]

As described above, the present invention relates to a first catalyst electrode having a first electrolyte membrane having hydrogen ion conductivity and a catalyst disposed in contact with one surface of the first electrolyte membrane. A detection element comprising: a second catalyst electrode having a catalyst disposed in contact with the other surface of the first electrolyte membrane; and a first element for supplying a gas to be detected to the first catalyst electrode. Gas supply means, second gas supply means for supplying one or more of an inert gas, nitrogen gas, and carbon dioxide gas to the second catalyst electrode, and the first catalyst A load connected between the electrode and the second catalyst electrode, and a load between the first catalyst electrode and the second catalyst electrode that changes according to the concentration of carbon monoxide gas in the gas to be detected. With the provision of the potential difference detecting means for detecting the potential difference, Carbon monoxide detector is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a first embodiment of a carbon monoxide detector of the present invention.

FIG. 2 is an exploded perspective view of the detector viewed from a white arrow A.

FIG. 3 is an output potential difference characteristic diagram of the detector.

FIG. 4 is a schematic cross-sectional view of Embodiment 2 of the carbon monoxide detector of the present invention.

FIG. 5 is an exploded perspective view of the hydrogen gas removing section of the detector as viewed from the direction of a white arrow B;

FIG. 6 is a side view of the hydrogen gas removing unit in the detector as viewed from the direction of a white arrow B;

FIG. 7 is an exploded perspective view illustrating a schematic structure of a carbon monoxide detector according to a third embodiment of the present invention.

FIG. 8 is a block diagram for explaining a detection circuit unit and a heater control circuit unit of the detector.

FIG. 9 is a schematic sectional view of a conventional carbon monoxide detector.

FIG. 10 is an output potential difference characteristic diagram of the detector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Detection element 2 1st metal electrode 3 1st rubber | gum for insulating seals 4 1st press plate 5 Volt 6 Resistance 7 Voltmeter 8 1st electrolyte membrane 9 1st catalyst electrode 10 2nd catalyst electrode 11th 1 sealing rubber 12 through hole 13 output terminal section 14 first gas pipe 15 second gas pipe 16 gas chamber 17 hydrogen gas removing section 18 hydrogen gas removing element 19 second metal electrode 20 second insulating seal Rubber 21a, 21b Second pressure plate 22 Bolt 23 Connection terminal 24 Resistance 25 Second electrolyte membrane 26 Third catalyst electrode 27 Fourth catalyst electrode 28 Second sealing rubber 29 Through hole 30 Drainage unit 31 Heater 32 Heating Element 33 Fluoropolymer Sheet 34 Through Hole 35 Heater Control Circuit

Claims (14)

[Claims] 1. A first electrolyte membrane having hydrogen ion conductivity, a first catalyst electrode having a catalyst arranged in contact with one surface of the first electrolyte membrane, and the first electrolyte membrane A detection element comprising a second catalyst electrode having a catalyst disposed in contact with the other surface of the first element; first gas supply means for supplying a gas to be detected to the first catalyst electrode; And supplying one or more of an inert gas, a nitrogen gas and a carbon dioxide gas to the second catalyst electrode.
Gas supply means, a load connected between the first catalyst electrode and the second catalyst electrode, and the first gas supply means, which varies depending on the concentration of carbon monoxide gas in the gas to be detected. A carbon monoxide detector comprising: a potential difference detecting means for detecting a potential difference between a catalyst electrode and the second catalyst electrode. 2. A metal processed to have at least one through hole outside each of a first catalyst electrode and a second catalyst electrode having carbon powder on which a catalyst is supported on a carbon cloth. A first metal electrode having a flat plate shape is arranged and fixed so as to sandwich a first electrolyte membrane, the first catalyst electrode and the second catalyst electrode by the two first metal electrodes. 2. The carbon monoxide detector according to 1. 3. The carbon monoxide detector according to claim 2, wherein the surfaces of the two first metal electrodes are smoothed and a gold plating layer is formed. 4. An inert gas, a nitrogen gas, or a gas mixture of at least one of an inert gas, a nitrogen gas, and a carbon dioxide gas in contact with the second catalyst electrode.
A part of the gas chamber includes a gas chamber in which one kind or a mixed gas of two or more kinds of carbon dioxide gas is sealed, and a hydrogen gas removing unit for removing hydrogen gas released into the gas chamber. The carbon monoxide detector according to claim 1. 5. The carbon monoxide detector according to claim 4, wherein the hydrogen gas removing section is disposed above the detection element. 6. A hydrogen gas removing section comprising: a second electrolyte membrane having hydrogen ion conductivity; and a hydrogen gas from one or more of an inert gas, a nitrogen gas, and a carbon dioxide gas mixed gas. A third catalyst electrode having a catalyst disposed in contact with one surface of the second electrolyte membrane for dissociating the catalyst, and a third catalyst electrode disposed in contact with the other surface of the second electrolyte membrane so as to be in contact with the atmosphere 5. A hydrogen gas removing element comprising a fourth catalyst electrode having a selected catalyst, and a load connected between the third catalyst electrode and the fourth catalyst electrode. 6. The carbon monoxide detector according to 5. 7. A metal processed to have at least one or more through-holes outside each of a third catalyst electrode and a fourth catalyst electrode each having a carbon powder on which a catalyst is supported on a carbon cloth. A second metal electrode having a flat plate shape is arranged and fixed so as to sandwich a second electrolyte membrane, the third catalyst electrode, and the fourth catalyst electrode by the two second metal electrodes. 7. The carbon monoxide detector according to 6. 8. The carbon monoxide detector according to claim 7, wherein the surfaces of the two second metal electrodes are smoothed and a gold plating layer is formed. 9. The carbon monoxide detector according to claim 6, wherein the fourth catalyst electrode surface is arranged to be inclined with respect to the horizontal direction or arranged in parallel with the direction of gravity. 10. The first and fourth catalyst electrodes have an area of
7. The carbon monoxide detector according to claim 6, wherein the area is larger than the area of the second catalyst electrode. 11. The carbon monoxide detector according to claim 1, further comprising a concentration calculating means for obtaining a concentration of the carbon monoxide gas in the gas to be detected from a voltage difference detected by the potential difference detecting means. 12. The carbon monoxide detector according to claim 11, wherein the concentration calculation means has a calculation unit for converting a change rate of the output voltage difference into a concentration of carbon monoxide gas. 13. The carbon monoxide detector according to claim 1, wherein a heater is provided near the detection element, and a heater control circuit for controlling the heater is connected. 14. The carbon monoxide detector according to claim 13, wherein the heating element constituting the heater is sandwiched between fluoropolymer sheets, and a hole or a slit penetrating the heating element and the sheet is provided.