JP2001153840A - Gas sensor and detecting method for flammable gas constituent concentration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor detecting two kinds or a pair of flammable gas concentrations with high precision. SOLUTION: An oxygen pump cell 3 consists of electrodes 3a, 3b putting a solid electrolyte material 4 between them, and one electrode 3a faces a first internal hollow 5a for introducing gas to be measured, while the other electrode 3b faces an atmosphere-depending hollow 8 for introducing the atmosphere as a reference oxygen concentration gas. A sensor cell 2 for residual constituents consists of electrodes 2a, 2b putting the solid electrolyte material 4 between them, and one electrode 2a faces a second internal hollow 5b on the downstream side of the first internal hollow 5a, while the other electrode 2b faces the atmosphere-depending hollow 8b. A part of flammable gas constituents in the gas to be measured is selectively oxidized in the first internal hollow 5a, and in this process, its concentration is detected from a current carrying amount in the oxygen pump cell 3. The residual flammable gas constituents are oxidized in the second internal hollow 5b, and in this process, their concentrations are detected from the current value or the voltage value of the sensor cell 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas sensor for measuring the concentration of a combustible gas component and a method for detecting the concentration of a combustible gas component, for example, in an exhaust gas of an internal combustion engine or a reformed gas of a fuel cell. It is suitable for use in measuring the concentration of combustible gas components contained.

[0002]

2. Description of the Related Art A gas sensor for measuring the concentration of a combustible gas component and a method for detecting the concentration of a combustible gas component are disclosed in Japanese Unexamined Patent Publication No.
Japanese Unexamined Patent Publication Nos. 247799/1995 and 11-83795 / 1999 are known. These devices introduce a gas to be measured into the space inside the sensor, control the oxygen concentration in the gas to be measured by an electrochemical oxygen pump cell, and then generate a voltage or a second voltage generated in a second electrochemical cell. The concentration of the combustible gas component in the gas to be measured is detected by the current flowing through the electrochemical cell.

[0003]

However, in each of the above-mentioned prior art publications, flammable gas components other than the object to be measured are burned by a catalyst having selectivity in advance, and sensitivity to the flammable gas components other than the object to be measured is increased. However, if the combustion reaction with the catalyst is insufficient or if the oxygen concentration in the measurement gas is low and the combustible gas components other than the measurement target cannot be completely burned, However, there is a problem that it is affected by the flammable gas component concentration.

In the conventional gas sensor and detection method described above, only one or one set of flammable gas component concentrations is detected, and two or two sets of flammable gas concentrations are detected.
No single or single sets could be detected. In view of the foregoing, an object of the present invention is to provide a gas sensor and a detection method capable of detecting two or two types of combustible gas concentrations with high accuracy.

[0005]

SUMMARY OF THE INVENTION According to the present invention, various combustible gases contained in a gas to be measured are different from each other in the susceptibility of an oxidation reaction to each other. The present invention focuses on making the oxygen pump cell have a concentration measuring function by detecting the amount of electricity of the electrochemical oxygen pump cell used only for controlling the concentration.

That is, according to the first aspect of the present invention, the internal space (5) into which the gas to be measured is introduced, the reference oxygen concentration gas existing space (8, 31) into which the reference oxygen concentration gas is introduced, and
A pair of electrodes (3a, 3b, 30a, 30) provided in contact with the oxygen ion conductive solid electrolyte material (4, 22) such that one electrode (3a, 30a) faces the internal space.
an oxygen pump cell (3, 30) having b) for introducing oxygen into the internal space by energizing the pair of electrodes and selectively oxidizing a part of the combustible gas component in the gas to be measured. ,
First current detecting means (100, 110) for detecting the amount of electricity between a pair of electrodes of the oxygen pump cell, and one electrode (2a, 20a) facing the internal space and the other electrode (2,
b, 20b) has a pair of electrodes provided in contact with the oxygen ion conductive solid electrolyte material (4, 22) so as to face the reference oxygen concentration gas existing space, and the remaining electrode between the pair of electrodes is provided. And a current generated between the remaining component sensor cells by controlling the voltage of a pair of electrodes in the sensor cell for the remaining component to a predetermined value. Second to detect the value
And a current detecting means (200).

Accordingly, by selectively oxidizing a part of the combustible gas component in the gas to be measured in the oxygen pump cell, the amount of electricity between a pair of electrodes of the oxygen pump cell changes based on this oxidation reaction. . By detecting the changed amount of current by the first current detecting means, the concentration of a part of the oxidized combustible gas component can be selectively measured.

The concentration of the remaining flammable gas component not oxidized by the oxygen pump cell can be measured by detecting the current value generated in the remaining component sensor cell by the second current detecting means. Therefore, according to the present invention, two types or two sets of flammable gas concentrations can be detected one by one or one set at a time, and two or two types of flammable gas concentrations can be detected with high accuracy. A gas sensor can be provided.

Further, according to the invention described in claim 2, according to claim 1,
Similarly to the described gas sensor, the gas sensor includes an inner space (5), a reference oxygen concentration gas existing space (8, 31), and an oxygen pump cell (3, 30), and further includes a pair of electrodes (3a, 3b) of the oxygen pump cell. , 30 a, 30 b), and a current detecting means (100, 110) for detecting the amount of current flow between the electrodes (2 a, 20 a) facing the internal space and the other electrode (2, 20 a).
b, 20b) has a pair of electrodes provided in contact with the oxygen ion conductive solid electrolyte material (4, 22) so as to face the reference oxygen concentration gas existing space, and the remaining electrode between the pair of electrodes is provided. A sensor cell for a residual component (2, 20) for generating a voltage depending on the concentration of the flammable gas component, a voltage detecting means (200) for detecting a voltage value generated between a pair of electrodes of the sensor cell for the residual component, It is characterized by having.

As in the present invention, the remaining component sensor cell generates a voltage between the pair of electrodes depending on the concentration of the remaining combustible gas component, and the voltage generated between the pair of electrodes of the remaining component sensor cell. Even if you detect the value,
It is possible to provide a gas sensor capable of detecting two or two types of flammable gas concentrations one by one or one by one, and detecting two or two types of flammable gas concentrations with high accuracy.

Here, when detecting the voltage value generated between the pair of electrodes of the remaining component sensor cell, compared to detecting the current value generated in the remaining component sensor cell,
The electrode (2a, 20a) facing the internal space (5) in the remaining component sensor cell (2, 20) is made of a Pt-Au alloy having low activity against oxidation of combustible gas (the invention of claim 8). Is preferred. This is because if the activity of the electrode facing the internal space in the remaining component sensor cell is high, the change in voltage depending on the concentration of the remaining combustible gas component becomes sharp, and the detection range is likely to be narrowed.

According to the third aspect of the present invention, the other electrode (3b) of the oxygen pump cell (3) faces the reference oxygen concentration gas existing space (8) so that the pair of electrodes (3a And 3b), while controlling the voltage value to a predetermined value and detecting the amount of current flowing between the electrodes. Since the amount of electricity between a pair of electrodes of the oxygen pump cell changes depending on the voltage value between the electrodes, controlling the voltage value between the electrodes to a predetermined value stabilizes the amount of electricity, that is, the gas component concentration. Can be detected.

In particular, when the voltage value between the pair of electrodes (3a, 3b) of the oxygen pump cell (3) is controlled to a predetermined value, the voltage value is adjusted to the detected oxygen value. It is preferable to perform feedback control based on the amount of electricity between a pair of electrodes of the pump cell. The voltage value dependence of the amount of electricity between the pair of electrodes of the oxygen pump cell varies somewhat depending on the amount of electricity, that is, the concentration of the gas component. Therefore, the above-described feedback control enables more accurate measurement.

The electrodes (3a, 30a) facing the internal space (5) in the oxygen pump cells (3, 30) are made of Pt-Au having a low activity for oxidizing a combustible gas.
It is preferable to use an alloy (the invention of claim 5). Thereby, it is preferable to selectively oxidize a part of the combustible gas component in the gas to be measured at the electrode facing the internal space in the oxygen pump cell.

According to the present invention, one electrode (40a) faces the internal space (5) and the other electrode (40a) faces the inner space (5).
b) has a pair of electrodes provided in contact with the oxygen ion conductive solid electrolyte material (4) so as to face the reference oxygen concentration gas existing space (8), and the internal space is provided between the pair of electrodes. An oxygen sensor cell (40) for generating a voltage dependent on the oxygen concentration at a location, and a pair of electrodes (30) of the oxygen pump cell (30) so that a voltage value generated between the pair of electrodes of the oxygen sensor cell becomes a predetermined value. It is characterized in that the amount of electricity between a pair of electrodes of the oxygen pump cell is detected while controlling the voltage between 30a and 30b).

According to the present invention, the current generated in the oxygen pump cell can be based not on the voltage of the oxygen pump cell itself but on the stable voltage generated in the oxygen sensor cell based on the reference oxygen concentration gas. Thereby, the concentration detection by the oxygen pump cell can be performed with higher accuracy without being affected by the change over time in the current-voltage characteristics of the oxygen pump cell.

Here, the electrode (40a) facing the internal space (5) in the oxygen sensor cell (40) is preferably made of a Pt-Au alloy. This is because, by using a Pt—Au alloy having low activity for oxidizing the flammable gas as the electrode, the oxidization of the flammable gas in the internal space by the oxygen sensor cell is suppressed, and the oxygen pump cell and the sensor cell for the remaining component are used. This is so as not to hinder the oxidation caused by the oxidation.

According to the ninth aspect of the present invention, the gas to be measured containing two or more kinds of combustible gas components, which are the gas components to be measured, is introduced into the internal space (5) partitioned from the surroundings. And introducing oxygen gas into the internal space by an electrochemical oxygen pump cell (3, 30) to selectively oxidize a part of the flammable gas component in the gas to be measured, and After measuring the oxidized combustible gas component concentration from the amount of electricity supplied to the pump cell, a pair of electrodes (2a,
The remaining combustible gas component concentration is measured based on the electromotive force or the current value generated in the pair of electrodes by the remaining component sensor cell having 2b, 20a, and 20b). ADVANTAGE OF THE INVENTION According to this invention, the detection method of the combustible gas component concentration which can detect two or two types of combustible gas concentrations with high precision can be provided.

Note that the reference numerals in parentheses of the above means are examples showing the correspondence with specific means described in the embodiments described later.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG.
1 is an overall sectional view of a gas concentration detection device used in exhaust gas of an internal combustion engine according to the present embodiment. Inside the cylindrical housing H having a threaded portion H0 for attachment on the outer periphery, the gas sensor 1 is housed with the outer periphery held by an insulating material. The gas sensor 1 has an elongated flat plate shape, and its tip (lower end in the figure) protrudes from the housing H and extends downward in the figure, and is housed in a container-shaped exhaust cover H1 fixed to the lower end of the housing H. ing.

The exhaust cover H1 has a double structure of an inner cover H11 and an outer cover H12 made of stainless steel. The side walls and the bottom wall of these covers H11 and H12 have:
Exhaust ports H13 and H14 for taking in the exhaust gas as the gas to be measured into the exhaust cover H1 are formed respectively.

At the upper end of the housing H, an air cover H2 composed of a cylindrical main cover H21 and a sub cover H22 covering the rear end is fixed. The main cover H21 and the sub-cover H22 have air ports H23 and H24 respectively at positions opposing the side walls thereof, and the air which is a reference oxygen concentration gas having a reference oxygen concentration higher than the air ports H23 and H24 is covered with the air cover H2. It is made to take in.

At the position where the air ports H23 and H24 are formed, the main cover H21 and the sub cover H2
2, a water-repellent filter H25 is provided for waterproofing. The air cover H2 has an open upper end, and a lead wire H connected to the rear end of the gas sensor 1.
Reference numeral 3 extends from the upper end opening to the outside, and is connected to an unillustrated external circuit (for example, an ECU of an automobile).

FIG. 1B is an overall sectional view of a gas concentration detecting device used in a reformed gas of a fuel cell (for example, a methanol reforming cell or the like). The basic configuration is shown in Fig. 1 (a)
However, an explosion-proof cover H4 is provided instead of the exhaust cover H1 for use in an atmosphere where a large amount of combustible gas is present. The explosion-proof cover H4 has a double structure of a stainless steel explosion-proof wire netting H41 for preventing flame propagation and an external cover H42 for protecting the surroundings.
An exhaust port H43 for taking in the inside is formed.

When detecting a flammable gas such as hydrogen contained in the reformed gas, the concentration of hydrogen in the gas to be measured becomes an explosion range and there is a risk of ignition, but the explosion-proof wire net H41 takes away the heat of the flame. Prevent it from spreading outside. In addition,
The explosion-proof wire mesh H41 usually has a double wire mesh structure with a space between the inner and outer wire meshes, and appropriately sets the size of the holes in the wire mesh to effectively suppress the diffusion of the flame.

The basic gas flow of such a gas concentration detecting device is as follows. The exhaust gas device for an internal combustion engine shown in FIG. 1A is attached to an exhaust gas passage (not shown) by a screw portion H0 of a housing H, and the fuel cell reforming device shown in FIG. The equipment for gas is
The housing H is attached to a flow path for the reformed gas (not shown) by a screw portion H0. In each of the detection devices, the exhaust cover H1 or H4 side is located in the flow passage and the atmosphere cover H2 side is located in the atmosphere with the housing H as a boundary.

In FIG. 1A, the gas to be measured such as the exhaust gas or the reformed gas flows, for example, as indicated by an arrow Y1 and is introduced into the gas sensor 1 from the exhaust ports H13 and H14 of the exhaust cover H1. In FIG. 1B, the gas flows, for example, as indicated by an arrow Y3 and is introduced into the gas sensor 1 from the exhaust port H43 of the exhaust cover H4. On the other hand, the atmosphere (reference oxygen concentration gas) is indicated by an arrow Y in FIGS. 1 (a) and 1 (b).
2, the air flows from the atmosphere ports H23 and H24 to the gas sensor 1 through the filter H25.

FIGS. 2 and 3 are a schematic sectional view and an exploded development view, respectively, of the tip of the gas sensor 1. As shown in FIGS. The gas sensor 1 includes a sensor cell 2 for a residual component and an oxygen pump cell 3
A sheet-shaped solid electrolyte material 4, a sheet-shaped partition wall 6 and a spacer 7 for forming an internal space 5, a sheet-shaped spacer 9 for forming an atmosphere presence space 8, And a heater 10 for heating the same.

In FIG. 2, the outer periphery of the gas sensor 1 has a measured gas existence space (or a reformed gas) as the gas to be measured introduced from the exhaust ports H13 and H14 (or H43). That is, the space inside the exhaust cover H1 or H4), and the atmosphere presence space 8 is a space in which the atmosphere introduced from the atmosphere ports H23 and H24 exists. The internal space 5 is separated from the measured gas existing space and the air existing space 8 by the solid electrolyte material 4, the partition wall 6, and the spacer 7.

The internal space 5 is a chamber (measurement gas introduction chamber) into which the gas to be measured is introduced from the space where the gas to be measured exists.
As shown in FIG. 3, the holes 7a and 7b of the spacer 7 located between the solid electrolyte material 4 and the partition 6 are formed. In the internal space 5, these two holes 7
A first internal space 5a is formed by a hole 7a and a second internal space 5a is formed by a hole 7b in order from the tip end side (left side in FIGS. 2 and 3) of the sensor 1 with a throttle 7c between the holes a and 7b. An internal space 5b is formed.

Further, the first internal space 5a communicates with the measured gas existing space via a pinhole 11 as a diffusion controlling means (diffusion resistance means) penetrating the partition wall 6. The size of the pinhole 11 is appropriately set so that the diffusion speed of the gas to be measured which is introduced into the first internal space 5a and the second internal space 5b through the pinhole 11 becomes a predetermined speed. .

Further, a porous protective layer 12 made of porous alumina or the like is formed on the partition wall 6 so as to cover the pinhole 11 from the space where the gas to be measured exists.
This prevents poisoning of the electrodes located inside and clogging of the pinhole 11. In addition, other than the pinhole, a diffusion-controllable means provided with a porous body capable of ventilation at the position where the pinhole 11 is formed may be used.

The atmosphere presence space 8 is a reference oxygen concentration gas presence space (reference gas chamber) into which the atmosphere as a reference oxygen concentration gas having a constant oxygen concentration is introduced.
Is formed by a hole 9a provided in the spacer 9 laminated below the substrate. The hole 9a is formed in the passage portion 9 as a groove extending toward the atmosphere ports H23 and H24 in the longitudinal direction of the gas sensor 1.
b, and the air is introduced through the passage 9b.
Here, the partition 6 and the spacers 7 and 9 are made of an insulating material such as alumina.

The solid electrolyte material 4 for forming the remaining component sensor cell 2 and the oxygen pump cell 3 is made of an electrolyte having oxygen ion conductivity (zirconia in this example) such as zirconia or ceria. The remaining component sensor cell 2 includes the solid electrolyte material 4 and a pair of electrodes 2a and 2b opposed to each other with the solid electrolyte material 4 interposed therebetween. One electrode 2a of the pair of electrodes 2a, 2b is a second internal space 5b located on the downstream side of the gas flow in the internal space 5.
The other electrode 2 b is provided in contact with the solid electrolyte material 4 facing the air space 8.

The oxygen pump cell (electrochemical oxygen pump cell) 3 is composed of a solid electrolyte material 4 and a pair of electrodes 3a and 3b arranged so as to sandwich the solid electrolyte material 4. One electrode 3a of the pair of electrodes 3a and 3b is
A first internal space 5a located on the upstream side of the gas flow in the internal space 5 is provided in contact with the solid electrolyte material 4, and the other electrode 3b is provided in the solid electrolyte material 4 facing the air presence space 8.
It is provided in contact with.

Here, the other electrode 2b of the remaining component sensor cell 2 and the other electrode 3b of the oxygen pump cell 3
For example, a Pt porous cermet electrode is preferably used. Further, one electrode (electrode facing the internal space) 2a of the sensor cell 2 for the remaining component is, for example, Pt, Pd, R
h or a porous cermet electrode made of an alloy thereof is preferably used.

In order to selectively oxidize a part of the flammable gas component in the gas to be measured, one electrode (electrode facing the internal space) 3a of the oxygen pump cell 3 is provided with a flammable gas. An electrode having low activity against oxidation and suppressing combustion of combustible gas is used. Specifically, Pt and A as main components
A porous electrode containing u is preferably used, and more preferably, a Pt-Au alloy electrode in which Pt and Au are alloyed, in particular, Pt-Au alloy powder and zirconia, paste such as alumina, It is preferable to use a fired porous cermet electrode. According to the study of the present inventors, the content of Au in the metal component is desirably about 1 to 10% by weight.

Further, as shown in FIG.
Leads 2c, 2d, 3c, and 3d for extracting electric signals from these electrodes are formed integrally with a, 2b, 3a, and 3b. Here, the electrode 2a on the solid electrolyte 4
In the portions other than the solid electrolyte 4 and the lead 2c and the like, in particular, in order to prevent a parasitic cell from being formed by the solid electrolyte 4 and the lead 2c and the like, an alumina or the like is interposed between the solid electrolyte 4 and the lead 2c and the like. It is preferable to form an insulating layer (not shown).

The heater 10 is formed by patterning a heater electrode 14 for energizing and generating heat on an upper surface of a heater sheet 13 made of alumina, and forming an alumina layer for insulation on the upper surface (surface on the spacer 9 side) of the heater electrode 14. 15 are formed. As the heater electrode 14, a cermet of Pt and a ceramic such as alumina is usually used. This heater 1
Numeral 0 indicates that the heater electrode 14 is heated by external power supply to heat the cells 2 and 3 to the activation temperature.

As shown in FIG. 3, the heater electrode 14 and the electrodes 2a of the cells 2 and 3 are connected to the leads 2c and the through-holes formed on the sheets 6, 7, 9, 13, and 15, respectively. The terminal is connected to a terminal (pad electrode) P of the sensor base through the hole SH. And this terminal P
Is connected to the lead wire H3 via a connector by crimping, brazing, or the like.
3 and the heater 10 can be exchanged.

The solid electrolyte material 4, the partition walls 6, the spacers 7 and 9, the alumina layer 15, and the heater sheet 13 can be formed into a sheet shape by a doctor blade method, an extrusion molding method, or the like. In addition, each of the above electrodes 2a
The leads 2c and the like and the terminals P can be formed by screen printing or the like. And each sheet is integrated by baking and baking.

Next, the first gas sensor 1
The current detection means and the second current detection means of FIG.
This will be described with reference to the explanatory diagram shown in FIG. The first and second current detecting means 100 and 200 are provided in an external circuit (not shown) connected to the lead wire H3.

The first current detecting means 100 is electrically connected to the pair of electrodes 3a, 3b of the oxygen pump cell 3 and detects the amount of current between these electrodes 3a, 3b.
Specifically, the oxygen pump current measuring unit 101 that measures the amount of electricity (oxygen pump current Ip) between the electrodes 3a and 3b.
And the oxygen pump current measuring unit 101 having a variable resistance and the like.
And an inter-electrode voltage control unit 102 for controlling the voltage between the electrodes 3a and 3b (inter-electrode voltage Vp) to a predetermined value based on the measurement value from

The second current detecting means 200 is electrically connected to the pair of electrodes 2a, 2b of the sensor cell 2 for the remaining component, and changes the voltage between these electrodes 2a, 2b (inter-electrode voltage Vs) to a predetermined value. And a current value (sensor cell current I) generated between the electrodes 2a and 2b at the predetermined value voltage.
s). In addition, the second current detecting means 200 includes a pair of electrodes 2 a of the remaining component sensor cell 2,
It also functions as voltage detecting means for detecting a voltage value generated between 2b.

Next, the operation principle of the gas sensor 1 having the above configuration will be described. As an example, the detection principle of H2 and CH3OH, which are combustible gases in the reformed gas of a fuel cell, will be described. In FIG. 2, the gas to be measured passes through the porous protective layer 12 and the pinhole 11, and is introduced into the first internal space 5a on the upstream side of the gas flow. H2, CH3OH, H
The amount of gas to be introduced, including a gas such as 2O, is determined by the diffusion resistance of the porous protective layer 12 and the pinhole 11.

A pair of electrodes 3a, 3b of the oxygen pump cell 3
A voltage of about 1 V is generated between the two electrodes due to the difference in oxygen concentration between the electrodes and the electrode 3b on the side of the air presence space 8 as a positive electrode. By controlling this voltage to a predetermined value to be described later, oxygen is reduced on the other electrode 3b to become oxygen ions, and moves to the one electrode 3a side by the pumping action. Reacts with the combustible gas in the cavity 5a.

Here, one electrode 3 of the oxygen pump cell 3
a is a material that suppresses combustion of combustible gas, for example, Pt
-Since it is a porous cermet electrode made of an Au alloy, of the combustible gas (H2, CH3 OH), highly reactive H2 is selectively oxidized to H2 O, but low reactive CH3 O
H is hardly oxidized.

FIG. 5 is a diagram showing the voltage-current characteristics of the oxygen pump cell 3. The horizontal axis represents the voltage V between the electrodes of the oxygen pump cell 3.
p, the vertical axis is the oxygen pump current Ip. As shown in FIG. 5, the voltage-current characteristics of the oxygen pump cell 3 show a constant current region (portion parallel to the Vp axis) corresponding to the H2 concentration. The speed and the introduction speed of H2 introduced into the first internal space 5a are balanced.

That is, based on the relationship between the interelectrode voltage Vp and the oxygen pump current Ip shown in FIG.
Is a control point (for example, a broken line in FIG. 5) in a predetermined constant current region.
By controlling the oxygen pump cell 3 by 00, H2 in the first internal space 5a can be oxidized without excess or deficiency. At the same time, the H2 concentration can be detected by measuring the oxygen pump current Ip.

Here, if the interelectrode voltage Vp is different even in the constant current region, the oxygen pump current Ip (H2
Concentration) may fluctuate. Therefore, in the present embodiment, in the oxygen pump cell 3,
The oxygen pump current measuring unit 101 detects the oxygen pump current Ip while controlling the voltage value between the electrodes 3a and 3b to a predetermined value by the interelectrode voltage control unit 102 based on the electrode 3b facing I have. Thereby, H2 can be oxidized accurately without excess or shortage, and an accurate H2 concentration can be detected stably.

In the present embodiment, in particular, in the first current detecting means 100, the value of the oxygen pump current Ip measured by the oxygen pump current
2, the inter-electrode voltage control unit 1
In step S02, the inter-electrode voltage Vp is controlled to a predetermined value according to the H2 concentration, as shown by the broken line in FIG. When feedback control is performed in this manner, H2 can be oxidized more accurately without excess or deficiency. Therefore, the detection characteristic of the H2 concentration based on the oxygen pump current Ip is as shown in FIG.
Higher precision measurement becomes possible. Here, the measurement gas conditions in FIG. 6A are such that H2 is 0 to 40% and CH3OH is 100%.
0 ppm, balance gas is N2.

The gas to be measured whose H2 has been oxidized into H2O by the oxygen pump cell 3 is introduced into the second internal space 5b on the downstream side. A voltage is generated between the pair of electrodes 2a and 2b of the remaining component sensor cell 2 with the electrode 2b being a positive electrode due to the difference in oxygen concentration between the two electrodes. By controlling this voltage to a predetermined value by the second current detecting means 200, the electrode 2 on the side of the atmosphere existence space 8 is controlled.
The oxygen is reduced on b and becomes oxygen ions, moves to the electrode 2a side by the pumping action, and reacts with CH3OH (remaining combustible gas component) in the second internal space 5b on the electrode 2a.

The electrode 2a in the second internal space 5b of the sensor cell 2 is made of a material having high catalytic activity, such as Pt porous cermet, to promote the reaction between the pumped oxygen and CH3OH in the gas to be measured. Is formed from. The characteristics of the sensor cell 2 are the same as those of the oxygen pump cell 9 shown in FIG. That is, the voltage-current characteristic of the sensor cell 2 indicates a constant current region corresponding to the CH3 OH concentration. In this region, the oxygen supply speed supplied by the sensor cell 2 and the CH3 OH introduction speed introduced into the second internal space 5b are different. Balanced.

That is, based on the relationship between the inter-electrode voltage Vs of the sensor cell 2 and the current (sensor cell current) Is, the voltage Vs and the current Is are set to control points in a preset constant current region. The inter-electrode voltage Vs is controlled to a predetermined value by the second current detecting means 200. Thereby, the CH3OH in the second internal space 5b can be oxidized without excess or shortage, and the CH3OH is measured by measuring the sensor cell current Is.
The concentration can be detected.

FIG. 6B shows the detection characteristic of the CH3 OH concentration based on the sensor cell current Is when the inter-electrode voltage Vs of the sensor cell 2 is 0.45 V. Here, FIG.
The measurement gas condition of (b) is as follows: H2 is 20%, CH3OH is 0%.
~ 1000 ppm, balance gas is N2.

The CH 3 OH concentration is determined by the second current detecting means 200 as a voltage detecting means by the sensor cell 2.
It is also possible by detecting the inter-electrode voltage Vs. FIG. 6C shows the detection characteristic of the CH3 OH concentration based on the inter-electrode voltage Vs of the sensor cell 2. Here, FIG.
The measurement gas condition of (c) is as follows: H2 is 20%, CH3OH is 0%.
~ 1000 ppm, balance gas is N2.

In this case, if the catalytic activity of the electrode (electrode facing the inner space) 2a of the sensor cell 2 is high, the voltage change between the electrodes 2a and 2b with respect to the CH3OH concentration becomes steep, and it becomes difficult to detect the steep portion. Therefore, the detection range becomes narrow (broken line curve in the figure). Therefore, in order to widen the detection range, it is better to use an electrode that suppresses combustion of combustible gas.

Specifically, a porous electrode containing Pt and Au as main components is preferably used, and more preferably,
Pt-Au alloy electrode obtained by alloying Pt and Au, especially P
The t-Au alloy powder and ceramics such as zirconia and alumina are preferably pasted and fired to form a porous cermet electrode. According to the study of the present inventors, the content of Au in the metal component is desirably about 1 to 5% by weight.

As described above, the gas sensor 1 of the present embodiment
According to the above, by selectively oxidizing a part of the combustible gas component in the gas to be measured in the oxygen pump cell 3, the amount of electricity between the pair of electrodes 3a and 3b of the oxygen pump cell 3 is based on this oxidation reaction. Changes. By detecting the changed energization amount by the first current detection means 100, the concentration of a part of the oxidized combustible gas component can be selectively measured.

The remaining combustible gas component concentration not oxidized by the oxygen pump cell 3 is measured by detecting the current value or voltage value generated in the remaining component sensor cell 2 by the second current detecting means 200. can do. Therefore, according to the present embodiment, two types or two sets of flammable gas concentrations can be detected one by one or one set at a time, and two types or two sets of flammable gas concentrations can be detected with high accuracy. A gas sensor that can be provided.

Further, according to this embodiment, while controlling the voltage value between the pair of electrodes 3a and 3b of the oxygen pump cell 3 to a predetermined value, preferably, the amount of electricity between the electrodes 3a and 3b (combustible The amount of electricity between the electrodes 3a and 3b is detected while performing feedback control based on the concentration of the reactive gas component). Therefore, the amount of electricity, that is, the gas component concentration, can be detected stably and with high accuracy.

(Second Embodiment) In the present embodiment,
The differences from the first embodiment will be mainly described. FIGS. 7 and 8 are a schematic cross-sectional view and an exploded development view, respectively, of the distal end portion of the gas sensor 1 according to the second embodiment of the present invention.
The same parts as those in the first embodiment are denoted by the same reference numerals in the drawings. The gas sensor 1 of the present embodiment is different from those shown in FIGS. 2 and 3 in that the arrangement position of the oxygen pump cell 30 is changed and that the oxygen sensor cell 40 is added. It is.

In the gas sensor 1 of this embodiment, the partition 6 made of an insulating material such as alumina in the gas sensor 1 of the first embodiment is replaced with a sheet-like solid electrolyte material 22. This solid electrolyte material 22 is made of a material (zirconia or the like) having the same oxygen ion conductivity as the solid electrolyte material of the first embodiment, and is provided with a pinhole (diffusion controlling means) 11. Therefore, the inner space 5 (5
a, 5b) are defined by the solid electrolyte material 22, the spacer 7, and the solid electrolyte material 4.

The oxygen pump cell (electrochemical oxygen pump cell) 30 of the present embodiment includes a solid electrolyte material 22 different from the solid electrolyte material 4 constituting the sensor cell 2 for the remaining component.
It comprises a pair of electrodes 30a and 30b opposed to each other with the solid electrolyte material 22 interposed therebetween. One electrode 30a of the pair of electrodes is provided in contact with the solid electrolyte material 22 facing the first internal space 5a, and the other electrode 30b is provided in the solid electrolyte material 22 facing the gas existence space. It is provided in contact.

Note that, as shown in FIG.
Penetrates the pair of electrodes 30a and 30b, and the surface of the other electrode 30b is covered with the same porous protective layer 12 as in the first embodiment to prevent poisoning. Also,
As in the first embodiment, one electrode (the electrode facing the internal space) 30a of the oxygen pump cell 30 is an electrode that suppresses the combustion of combustible gas, specifically, Pt and A as main components.
A porous electrode containing u is preferably used, and a Pt porous cermet electrode is suitably used as the other electrode 30b.

The oxygen sensor cell 40 is composed of the same solid electrolyte material 4 as the remaining component sensor cell 2, and a pair of electrodes 40 a and 40 b disposed so as to sandwich the solid electrolyte material 4. One electrode 40a of the pair of electrodes is
The other electrode 40b is provided in contact with the solid electrolyte material 4 so as to face the first internal space 5a and in contact with the solid electrolyte material 4 so as to face the air presence space 8.

As the one electrode (electrode facing the inner space) 40a of the oxygen sensor cell 40, the same Pt-Au porous cermet electrode as the one electrode 30a of the oxygen pump cell 30 is preferably used, and the other electrode is used. For Pb, a Pt porous cermet electrode is preferably used. The oxygen sensor cell 40 generates a voltage between the pair of electrodes 40a and 40b depending on the oxygen concentration in the first internal space 5a.

As shown in FIG. 8, the electrodes 30a, 30a of the oxygen pump cell 30 and the oxygen sensor cell 40 are used.
b, 40a and 40b have leads 30c, 30d, 40c and 40d for extracting electric signals from these electrodes.
Are integrally formed. Here, as in the first embodiment, a portion other than the electrodes 30a and the like on the solid electrolytes 4 and 22 and particularly a formation portion of the lead 30c and the like are provided between the solid electrolyte and the lead to prevent formation of parasitic cells. It is preferable to form an insulating layer (not shown) of alumina or the like.

Also in the present embodiment, an external circuit (not shown) and each of the cells 2 and 30 are connected via the through hole SH and the terminal (pad electrode) P formed as shown in FIG. , 40 and the heater 10 can be exchanged. Here, FIG. 9 shows a specific configuration of the first current detecting means 110 and the second current detecting means 200 provided in the external circuit in the present embodiment. The second current detecting means 200 is the same as that of the first embodiment.

The first current detecting means 110 is basically electrically connected to the pair of electrodes 30a and 30b of the oxygen pump cell 30, and detects the amount of electricity between these electrodes 30a and 30b. Specifically, an oxygen pump current measuring unit 101 similar to the first embodiment, an oxygen sensor cell voltage detecting unit 111 for detecting a voltage generated between a pair of electrodes 40a and 40b of the oxygen sensor cell 40, a variable resistor and the like So that the measured value (voltage value) of the oxygen sensor cell voltage detector 111 becomes a predetermined value.
Voltage control unit 1 for controlling inter-electrode voltage Vp in
12 is provided.

Next, the operation principle of the gas sensor 1 of the present embodiment will be described. As in the first embodiment, as an example, H2 and CH3OH as combustible gases in the reformed gas of the fuel cell are used.
Will be described. In the present embodiment, the voltage generated between the electrodes 40a and 40b of the oxygen sensor cell 40
Voltage between electrodes of oxygen pump cell 30 and oxygen pump current I
Feedback control is performed on p (the amount of current).

In FIG. 7, the gas to be measured passes through the porous protective layer 12 and the pinhole 11, and is introduced into the first internal space 5a. A pair of electrodes 40a, 4 of the oxygen sensor cell 40
Between 0b, a voltage of about 1 V is generated with the electrode 40b on the air presence space 8 side as a positive electrode due to the difference in oxygen concentration between these two electrodes.

The electrodes 30a and 30b of the oxygen pump cell 30
Voltage is applied between the first and second pumps, and the first
When oxygen is introduced into the internal space 5a, the oxygen pump cell 3
On the zero electrode 30a and the electrode 40a of the oxygen sensor cell 40, the combustible gas in the first internal space 5a reacts with oxygen. However, since the electrode 30a and the electrode 40a are porous cermet electrodes made of a material that suppresses the combustion of a combustible gas, for example, a Pt—Au alloy, the combustible gas (H
2, CH3OH), highly reactive H2 is selectively oxidized to H2O, but less reactive CH3OH is hardly oxidized.

FIG. 10 is a graph showing the characteristics of the current value (oxygen pump current Ip) of the oxygen pump cell 30 and the voltage value (oxygen sensor cell voltage Vos) of the oxygen sensor cell 40. The horizontal axis is the oxygen pump current Ip, and the vertical axis is the vertical axis. Is the oxygen sensor cell voltage V
os. As shown in FIG. 10, the voltage Vos generated between the electrodes 40a and 40b of the oxygen sensor cell 40 depends on the oxygen supply rate by the oxygen pump cell 30 and the first internal space 5a.
Changes suddenly when the H2 introduction speed introduced into the chamber is balanced.

Therefore, the electrode 4 of the oxygen sensor cell 40
By controlling the energization amount of the oxygen pump cell 30 so that the voltage value Vos generated between 0a and 40b becomes the voltage at this sudden change point, it is possible to oxidize H2 in the first internal space 5a without excess or shortage. it can. Further, similarly to the first embodiment, the H2 concentration can be detected by measuring the oxygen pump current Ip. Note that CH3 by the remaining component sensor cell 2
The principle of detecting OH is the same as in the first embodiment.

More specifically, the oxygen sensor cell voltage Vos generated in the oxygen sensor cell 40 depending on the oxygen concentration in the first internal space 5a is detected by the oxygen sensor cell voltage detector 111. The oxygen sensor cell voltage Vos detected at this time is a predetermined value (the voltage at the sudden change point, for example, 0.45
V), the interelectrode voltage control unit 112 performs feedback control of the interelectrode voltage Vp of the oxygen pump cell 30.

Thus, the amount of electricity (oxygen pump current Ip) of the oxygen pump cell 30 is also controlled, and the first internal space 5a
H2 inside can be oxidized without excess or shortage. And
The oxygen pump cell 30 is measured by the oxygen pump current measuring unit 101.
Is detected (oxygen pump current Ip). Thus, the H2 concentration can be detected accurately.

According to the present embodiment, it is possible to provide a gas sensor having the same functions and effects as those of the first embodiment. Further, according to the present embodiment, the current generated in the oxygen pump cell 30 can be based on the stable voltage generated in the oxygen sensor cell 40 based on the atmosphere (reference oxygen concentration gas). Thereby, the concentration detection by the oxygen pump cell 30 can be performed with higher accuracy without being affected by the temporal change of the current-voltage characteristics of the oxygen pump cell 30.

(Third Embodiment) In the present embodiment,
The differences from the first embodiment will be mainly described. FIGS. 11 and 12 are a schematic cross-sectional view and an exploded development view, respectively, of the distal end portion of the gas sensor 1 according to the third embodiment of the present invention. In the same parts as those in the first and second embodiments, The same reference numerals are given. The gas sensor 1 of the present embodiment is different from the first embodiment in that the remaining component sensor cell 2
The main difference in the configuration is that the arrangement position of 0 is changed.

In the gas sensor 1 according to the present embodiment, the partition 6 made of an insulating material such as alumina in the gas sensor 1 according to the first embodiment is replaced with a sheet-like solid electrolyte material 22 as in the second embodiment. I have. The solid electrolyte material 22 is provided with a pinhole (diffusion controlling means) 11 and a porous protective layer 12. As shown in FIG. 12, a hole 7d is formed in the spacer 7 for forming the internal space 5 to form an atmosphere presence space 31 into which the atmosphere is introduced from the atmosphere ports H23 and H24. ing.

In this embodiment, the solid electrolyte material 4
Air existence spaces 8 and 31 are respectively formed on both sides of the solid electrolyte material 2, which is different from the solid electrolyte material 4 constituting the oxygen pump cell 3.
2 and a pair of electrodes 20a and 20b opposed to each other with the solid electrolyte material 22 interposed therebetween. One electrode 20a of the pair of electrodes is provided in contact with the solid electrolyte material 22 facing the second internal space 5b, and the other electrode 20a is provided.
b is provided in contact with the solid electrolyte material 22 so as to face the air space 31.

Here, one electrode (the electrode facing the internal space) 20a and the other electrode 20b in the sensor cell 20 for the remaining component are respectively connected to one electrode in the sensor cell 2 for the remaining component shown in the first embodiment. It has the same material and function as the electrode 2a and the other electrode 2b. These electrodes 20
As shown in FIG. 12, leads 20c and 20d for extracting an electric signal are formed integrally with a and 20b, respectively. Although not shown, the second current detecting means 200 is connected to these electrodes 20a and 20b, and operates in the same manner as in the first embodiment.

The operation principle of the gas sensor 1 of the present embodiment is the same as that of the first embodiment, and the same operation and effects are obtained. In the present embodiment, the oxygen pump cell 3 and the remaining component sensor cell 20 Are composed of the solid electrolyte materials 4 and 22 which are different from each other, so that the electric interference (electric noise) between the two cells 3 and 20 is small and the flammable gas with higher accuracy as compared with the first embodiment. Can be detected.

Incidentally, in each of the above embodiments, in addition to providing a gas sensor capable of detecting two or two types of combustible gas concentrations with high accuracy, two or two types of combustible gas concentrations can be provided. A method for detecting the concentration of a combustible gas component that can detect the concentration with high accuracy can be provided.

That is, a gas to be measured containing two or more kinds of combustible gas components, which are gas components to be measured, is introduced into the internal space 5 partitioned from the surroundings, and the electrochemical oxygen pump cell 3 is introduced into the internal space 5. , 30 to selectively oxidize a part of the combustible gas component in the gas to be measured by measuring the concentration of the oxidized combustible gas component from the amount of electricity supplied to the electrochemical oxygen pump cell. After that, the sensor cells 2 and 20 having a pair of electrodes measure the remaining combustible gas component concentration based on the electromotive force or current value generated in the pair of electrodes. A detection method can be provided.

Then, in this detection method, if the amount of electricity of the electrochemical oxygen pump cells 3 and 30 is detected while controlling the voltage value generated in the electrochemical oxygen pump cells 3 and 30 to a predetermined value, The amount of electricity, that is, the gas component concentration, can be detected more stably and with high accuracy.

(Other Embodiments) In the above-described embodiment, the detection principle has been described by taking H2 and CH3OH in the reformed gas of the fuel cell as an example.
It can also be applied to the detection of flammable gas in exhaust gas from gasoline and diesel engines. More specifically, for example, operating conditions of excess flammable gas (so-called rich region)
And the concentration of CH4 and other flammable gases (H2, CO,
It is possible to detect the concentration of each pair of HCs other than CH4.

In this case, the catalytic activities of the electrodes 3a, 30a of the oxygen pump cells 3, 30 and the electrode 40a of the oxygen sensor cell 40 are reduced so that CH4 is not oxidized. Then, the flammable gas other than CH4 is oxidized by the oxygen pump cells 3 and 30, the concentration thereof is detected from the oxygen pump current Ip of the oxygen pump cells 3 and 30, and the concentration is detected by the current Is or the voltage Vs of the remaining component sensor cells 2 and 20. CH4 is detected. As described above, in the gas sensor according to the present invention, two or two sets of flammable gas concentrations can be detected with high accuracy.

In the above embodiment, zirconia is preferable as the solid electrolyte, but other oxygen ion conductive solid electrolytes such as ceria may be used, and the present invention is not limited to this.

In the above embodiment, the throttle section 7 is provided between the first internal space 5a on the oxygen pump cell side (upstream side) and the second internal space 5b on the remaining component sensor cell side (downstream side).
By providing c, the gas atmosphere between the two cavities 5a and 5b is less likely to be affected by each other. In particular, the first internal space and the second internal space can be separated without providing the throttle. They may be separated to such an extent that the gas atmospheres do not easily affect each other. However, if the aperture is provided, both cavities can be arranged close to each other, which leads to a reduction in the size of the sensor.

[Brief description of the drawings]

FIG. 1 is an overall sectional view of a gas concentration detection device according to an embodiment of the present invention, where (a) is for exhaust gas of an internal combustion engine,
(B) is for a reformed gas of a fuel cell.

FIG. 2 is a schematic sectional view of the gas sensor according to the first embodiment of the present invention.

FIG. 3 is an exploded development view of the gas sensor shown in FIG.

FIG. 4 is an explanatory diagram showing each current detecting means according to the first embodiment.

FIG. 5 is a diagram showing voltage-current characteristics of the oxygen pump cell according to the first embodiment.

6A is a diagram showing a detection characteristic of the H2 concentration based on the oxygen pump current Ip, FIG. 6B is a diagram showing a detection characteristic of the CH3OH concentration based on the sensor cell current Is, and FIG. 6C is a diagram showing the detection voltage of the sensor cell based on the inter-electrode voltage Vs. FIG. 6 is a diagram showing detection characteristics of CH3OH concentration.

FIG. 7 is a schematic sectional view of a gas sensor according to a second embodiment of the present invention.

8 is an exploded development view of the gas sensor shown in FIG.

FIG. 9 is an explanatory diagram showing each current detection unit according to the second embodiment.

FIG. 10 shows the oxygen pump current I in the second embodiment.
FIG. 6 is a diagram showing characteristics of p and oxygen sensor cell voltage Vos.

FIG. 11 is a schematic sectional view of a gas sensor according to a third embodiment of the present invention.

FIG. 12 is an exploded development view of the gas sensor shown in FIG.

[Explanation of symbols]

2, 20: sensor cell for remaining component, 2a, 20a: one electrode of sensor cell for remaining component (electrode facing internal space), 2b, 20b: other electrode of sensor cell for remaining component, 3, 30: oxygen pump cell One electrode of the oxygen pump cell (electrode facing the inner space);
b, 30b... the other electrode of the oxygen pump cell, 4, 22,.
Solid electrolyte material, 5: internal space, 8, 31: air space, 40: oxygen sensor cell, 40a: one electrode of the oxygen sensor cell (electrode facing the internal space), 40b: the other electrode of the oxygen sensor cell, 100, 110: first current detecting means, 200: second current detecting means (voltage detecting means)

Claims (10)

[Claims] An internal space (5) into which a gas to be measured is introduced.
A reference oxygen concentration gas existing space (8, 31) into which the reference oxygen concentration gas is introduced, and an oxygen ion conductive solid electrolyte material such that one electrode (3a, 30a) faces the internal space. A pair of electrodes (3a, 3b, 30a, 3a) provided in contact with (4, 22).
Ob), wherein oxygen is introduced into the internal space by energizing the pair of electrodes to selectively oxidize a part of the combustible gas component in the gas to be measured.
A first current detecting means (100, 110) for detecting an amount of electricity between the pair of electrodes of the oxygen pump cell; and one electrode (2a, 20a) facing the internal space and the other electrode (100, 110). 2b, 20b) has a pair of electrodes provided in contact with the oxygen ion conductive solid electrolyte material (4, 22) so as to face the reference oxygen concentration gas existing space, and the remaining electrode between the pair of electrodes is provided. Component sensor cell for generating a current depending on the flammable gas component concentration of the remaining component (2, 20)
And a second current detecting means (200) for detecting a current value generated between the electrodes by controlling the voltage of the pair of electrodes in the sensor cell for the remaining component to a predetermined value. Gas sensor. 2. An internal space (5) into which a gas to be measured is introduced.
A reference oxygen concentration gas existing space (8, 31) into which the reference oxygen concentration gas is introduced, and an oxygen ion conductive solid electrolyte material such that one electrode (3a, 30a) faces the internal space. A pair of electrodes (3a, 3b, 30a, 3a) provided in contact with (4, 22).
Ob), wherein oxygen is introduced into the internal space by energizing the pair of electrodes to selectively oxidize a part of the combustible gas component in the gas to be measured.
Current detection means (100, 110) for detecting the amount of electricity between the pair of electrodes of the oxygen pump cell; one electrode (2a, 20a) facing the internal space and the other electrode (2b, 20b). ) Has a pair of electrodes provided in contact with the oxygen ion conductive solid electrolyte material (4, 22) so as to face the reference oxygen concentration gas existing space, and the remaining flammable material is provided between the pair of electrodes. Sensor cell for remaining component that generates voltage dependent on gas component concentration (2, 20)
And a voltage detection means (200) for detecting a voltage value generated between the pair of electrodes of the remaining component sensor cell. 3. The other electrode (3b) of the oxygen pump cell (3) faces the reference oxygen concentration gas existing space (8), and between the pair of electrodes (3a, 3b) of the oxygen pump cell. 3. The gas sensor according to claim 1, wherein the amount of electricity between the pair of electrodes of the oxygen pump cell is detected while controlling the voltage value to a predetermined value. 4. 4. A feedback control of a voltage value between the pair of electrodes (3a, 3b) of the oxygen pump cell (3) based on the detected amount of electricity between the pair of electrodes of the oxygen pump cell. The gas sensor according to claim 3, wherein: 5. Electrodes (3a, 30a) facing said internal space (5) in said oxygen pump cell (3, 30).
The gas sensor according to any one of claims 1 to 4, wherein the gas sensor is made of a Pt-Au alloy. 6. An oxygen ion conductive solid such that one electrode (40a) faces the internal space (5) and the other electrode (40b) faces the reference oxygen concentration gas existing space (8). An oxygen sensor cell (40) having a pair of electrodes provided in contact with the electrolyte material (4) and generating a voltage depending on the oxygen concentration in the internal space between the pair of electrodes; The oxygen pump cell (30) such that a voltage value generated between the pair of electrodes of the sensor cell becomes a predetermined value.
The gas sensor according to any one of claims 1 to 5, wherein the amount of electricity between the pair of electrodes of the oxygen pump cell is detected while controlling the voltage between the pair of electrodes (30a, 30b). . 7. The electrode (40a) facing the internal space (5) in the oxygen sensor cell (40) is a Pt-A
The gas sensor according to claim 6, wherein the gas sensor is made of a u alloy. 8. The sensor cell for remaining components (2, 20).
(2a, 20) facing the internal space (5)
The gas sensor according to claim 2, wherein a) is made of a Pt-Au alloy. 9. A gas to be measured containing two or more types of combustible gas components, which is a gas component to be measured, is introduced into an internal space (5) partitioned from the surroundings, and electrochemical oxygen is introduced into the internal space. A part of the flammable gas component in the gas to be measured is selectively oxidized by introducing oxygen gas through the pump cells (3, 30), and the flammable gas oxidized from the amount of electricity supplied to the electrochemical oxygen pump cell. After measuring the component concentration, the remaining combustible gas component concentration is generated at the pair of electrodes by the remaining component sensor cell (2, 20) having the pair of electrodes (2a, 2b, 20a, 20b). Alternatively, a method for detecting the concentration of a combustible gas component, wherein the measurement is performed based on a current value. 10. The electrochemical oxygen pump cell (3,
The method for detecting the concentration of a combustible gas component according to claim 9, wherein the amount of electricity supplied to the electrochemical oxygen pump cell is detected while controlling the voltage value generated in (30) to a predetermined value.