JP2003107045A - Oxygen pump element and oxygen pump device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that an oxygen pump device becomes complicated and high-cost because a temperature sensor must be provided separately. SOLUTION: By using the oxygen pump element in which a first working electrode 2, a first auxiliary electrode 3 and a second auxiliary electrode 4 are formed on one surface of an oxygen ion conductive substrate 1 and in which a second working electrode 5 is formed on the other surface, the temperature of the substrate 1 is detected on the basis of an oxygen ion current and on the basis of the potential difference between the electrode 3 and the electrode 4.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an oxygen pump.

[0002]

2. Description of the Related Art Conventionally, this type of oxygen pump element has been as follows.

JP-A-11-94792 discloses an oxygen pump in which working electrodes are formed on both surfaces of a solid electrolyte substrate having oxygen ion conductivity. However, the above publication does not describe any oxygen pump element having a temperature detecting function.

Japanese Patent Publication No. 10-500450 discloses a device in which a thermocouple is arranged near the oxygen pump element to maintain the oxygen pump element at an appropriate operating temperature.
However, this publication also does not describe any oxygen pump element having a temperature detecting function.

[0005]

Even in the above-mentioned known technique, the oxygen pump element does not have a temperature detecting function. Therefore, in order to keep the oxygen pump element at an appropriate operating temperature, it is necessary to use a signal from a temperature sensor such as a thermocouple arranged near the oxygen pump element.

Therefore, since the temperature sensor must be additionally provided, there is a problem that the oxygen pump device becomes complicated and the cost becomes high. Further, since the temperature of the temperature sensor is affected by the relative positional relationship between the oxygen pump element and the temperature sensor, there is a problem that the accuracy of correspondence with the temperature of the oxygen pump element is not sufficient.

[0007]

The oxygen pump element of the present invention has a first working electrode, a first auxiliary electrode and a second auxiliary electrode on one surface of an oxygen ion conductive substrate and a second working electrode on the other surface. In this structure, an electrode is formed and the first working electrode and the second working electrode face each other.

According to the above invention, the potential difference between the first auxiliary electrode and the second auxiliary electrode can be detected, and the oxygen ion current can also be detected. Since the value corresponding to the resistance value of the oxygen ion conductive substrate can be obtained from these amounts, the temperature of the substrate, that is, the temperature of the oxygen pump element can be detected from the resistance temperature characteristic of the substrate.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An oxygen pump element according to claim 1 of the present invention has a first surface on one surface of an oxygen ion conductive substrate.
The working electrode, the first auxiliary electrode, and the second auxiliary electrode are formed, and the second working electrode is formed on the other surface, and the first working electrode and the second working electrode face each other.

According to the above invention, the potential difference between the first auxiliary electrode and the second auxiliary electrode can be detected, and the oxygen ion current can also be detected. Since a value corresponding to the resistance value of the oxygen ion conductive substrate can be obtained from these amounts, the temperature of the substrate, that is, the oxygen pump element can be detected from the resistance-temperature characteristic of the substrate.

In the oxygen pump element according to claim 2 of the present invention, since the cathode electrode which is the second working electrode has a larger area than the anode electrode which is the first working electrode, the oxygen ion conductive substrate is provided with oxygen ions. Can be sufficiently supplied.

In the oxygen pump element according to claim 3 of the present invention, the first working electrode is provided on one surface of the oxygen ion conductive substrate, the first auxiliary electrode is provided around the first working electrode, and the first auxiliary electrode is provided. Since the second auxiliary electrode is formed around,
The area of both auxiliary electrodes can be increased, and therefore the internal resistance between both auxiliary electrodes can be reduced.

In the oxygen pump element according to the fourth aspect of the present invention, since the first working electrode, the first auxiliary electrode and the second auxiliary electrode are made of the same electrode material, the step of forming the first working electrode can be simplified. .

In the oxygen pump element according to claim 5 of the present invention, one surface excluding the first working electrode and the other surface excluding the second working electrode are covered with an insulating film. The potential difference between the first auxiliary electrode and the second auxiliary electrode can be stably measured.

In the oxygen pump element according to the sixth aspect of the present invention, the insulating film is the glass firing film, so that it can be manufactured by a simple process.

In the oxygen pump element according to claim 7 of the present invention, the widths of the first auxiliary electrode and the second auxiliary electrode are (0.5
.About.0.1 mm, the disturbance of equipotential lines in the oxygen ion conductive substrate can be reduced.

In the oxygen pump device according to claim 8 of the present invention, a DC power source, an oxygen pump element and an oxygen ion current detecting means are connected in series, and a potential difference is detected between the first auxiliary electrode and the second auxiliary electrode. The means is connected. Therefore, the potential difference with the ion electrode can be constantly monitored during the operation of the oxygen pump.

In the oxygen pump device according to the ninth aspect of the present invention, since the input resistance of the potential difference detecting means is 10 MΩ or more, the potential difference between the first auxiliary electrode and the second auxiliary electrode can be accurately detected.

In the oxygen pump device according to the tenth aspect of the present invention, since the resistance value calculating means is connected to the oxygen ion current detecting means and the potential difference detecting means, the oxygen ion conductivity is constantly maintained during the operation of the oxygen pump. The resistance value corresponding to the resistance value of the board can be monitored.

Since the oxygen pump device according to the eleventh aspect of the present invention has a construction in which the temperature conversion means is connected to the resistance value calculation means, the temperature of the oxygen ion conductive substrate can be constantly monitored during the operation of the oxygen pump. .

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view showing the structure of an oxygen pump element according to Embodiment 1 of the present invention.

In the oxygen pump element of the present invention, the first working electrode film 2, the first auxiliary electrode 3 and the second auxiliary electrode 4 are provided on one surface of the oxygen ion conductive substrate 1, and the second working electrode 5 is provided on the other surface. Is formed, and the first working electrode 2 and the second working electrode 5 face each other. As the oxygen ion conductive substrate 1, yttrium-doped zirconia (YSZ) or samarium-doped ceria (SDC) is used. Further, as the cathode electrode 2, the first auxiliary electrode 3, the anode electrode film 4 and the second auxiliary electrode 5, platinum (Pt), silver (Ag),
A sputtered film, a fired film, or a vapor-deposited film of complex metal oxide (SSCO) made of samarium strontium-cobalt is used.

When the first working electrode 2 is a cathode electrode, the second working electrode 5 acts as an anode electrode, or when the first working electrode 2 is an anode electrode, the second working electrode 5 acts as a cathode electrode. . In this embodiment, for convenience, a case where the first working electrode 2 is a cathode electrode and the second working electrode 5 is an anode electrode will be described.

The cathode electrode 2 has a negative potential, and the anode electrode 5
When a DC voltage is applied between the cathode electrode 2 and the anode electrode 5 with a positive potential, oxygen molecules in the cathode-side external space are taken into the oxygen ion conductive substrate 1 as oxygen ions by the cathode electrode 2 to generate oxygen ions. It reaches the anode electrode 5 as a current I _i . The oxygen ions that have reached the anode electrode 5 become oxygen molecules and diffuse into the external space on the anode side. At this time, the oxygen ion current I _i flows from the cathode electrode 2 to the anode electrode 5 along the line of electric force 6, and innumerable equipotential lines 7 are generated in the oxygen ion conductive substrate 1. The oxygen ion current I _i flows perpendicular to the equipotential line 7. Among these equipotential lines 7, the equipotential line 7a enters the first auxiliary electrode 3, and the equipotential line 7b different from the equipotential line 7a enters the second auxiliary electrode 4. Therefore, the equipotential line 7
A potential difference V _ab between a and the equipotential line 7b is observed between the first auxiliary electrode 3 and the second auxiliary electrode 4. An amount R _ab (= V _ab / I _i ) obtained by _{dividing the} potential difference V _ab by the oxygen ion current I _i becomes a resistance value corresponding to the resistance value of the oxygen ion conductive substrate 1 between the cathode electrode 2 and the anode electrode 5. . Therefore, by measuring the temperature dependence of the resistance value R _{ab in} advance, the temperature of the oxygen ion conductive substrate 1 can be obtained from the resistance value R _ab .

By forming the first auxiliary electrode 3 and the second auxiliary electrode 4, the distribution of equipotential lines 7 is disturbed. In order to reduce this turbulence as much as possible, it is preferable that the width of both auxiliary electrodes is narrow, but in practice, the width may be (0.5 to 0.1) mm.

The cathode electrode 2, the first auxiliary electrode 3 and the second auxiliary electrode 4 are preferably made of the same electrode material. This is because these electrodes can be simultaneously formed in one electrode forming step.

The portion between the cathode electrode 2 and the first auxiliary electrode 3, the portion between the cathode electrode 2 and the second auxiliary electrode 4, the portion between the first auxiliary electrode 3 and the end of the oxygen ion conductive substrate 1, and the second If the insulation between the auxiliary electrode 4 and the end of the oxygen ion conductive substrate 1 is lowered, for example, if the insulation is lowered due to surface diffusion of the electrode material or adhesion of dirt, the distribution of equipotential lines 7 is It becomes easy to be disturbed. The same is true between the anode electrode 5 and the ends of the oxygen ion conductive substrate 1. In such a case, it is desirable to cover one surface of the oxygen ion conductive substrate 1 excluding the cathode electrode 2 and the other surface excluding the anode electrode 5 with an insulating film. This is because the surface diffusion of the electrode material and the attachment of dirt can be prevented. A glass firing film is preferable as the insulating film. This is because the glass firing film can be easily formed by printing the glass paste, drying it, and then firing it.

There is an overvoltage necessary for converting oxygen molecules into oxygen ions between the interface between the cathode electrode 2 and the oxygen ion conductive substrate 1, and the anode electrode 5 and the oxygen ion conductive substrate. Between the interfaces of the substrate 1, there is an overvoltage necessary to convert oxygen ions into oxygen molecules. Therefore, even if the applied voltage is reduced by the oxygen ion current I _i , the resistance value corresponding to the resistance value of the oxygen ion conductive substrate 1 cannot be obtained.

(Embodiment 2) In this embodiment, a case where the first working electrode 2 is an anode electrode and the second working electrode 5 is a cathode electrode will be described.

The cathode electrode 5 is a negative potential and the anode electrode 2 is
When the oxygen ion current flows by applying a DC voltage between the cathode electrode 5 and the anode electrode 2 with a positive potential, the lattice oxygen ions present in the oxygen ion conductive substrate 1 are extracted by the anode electrode 2, Oxygen molecules may be diffused to the external space at the anode electrode 2. As a result, the oxygen ion conductive substrate 1 is partially reduced,
This causes a decrease in oxygen ion conductivity. Therefore, it is necessary to reduce this reduction as much as possible.

In the oxygen pump element of the present embodiment, as shown in FIG. 2, the first working electrode 2 is the anode electrode, the second working electrode 5 is the cathode electrode, the second working electrode 5 is the first working electrode 2, It is configured to face the first auxiliary electrode 3 and the second auxiliary electrode 4. Therefore, the area of the cathode electrode 5 can be made larger than that of the anode electrode 2. As described in the section of Example 1, oxygen molecules in the cathode side outer space are taken into the oxygen ion conductive substrate 1 as oxygen ions by the cathode electrode 5. The number of oxygen ions taken into the oxygen ion conductive substrate 1 increases almost in proportion to the area of the cathode electrode 5. When the area of the cathode electrode 5 is larger than that of the anode electrode 2, the cathode electrode 5 has the ability to take in more oxygen ions. Therefore, it is possible to reduce the extraction of lattice oxygen ions by the anode electrode 2.

Example 3 When observing the potential difference V _ab between the first auxiliary electrode 3 and the second auxiliary electrode 4, as shown in FIG. 3, the first action is made on one surface of the oxygen ion conductive substrate 1. It is preferable to form the electrode 2, the first auxiliary electrode 3 around the first working electrode 2, and the second auxiliary electrode 4 around the first auxiliary electrode.

The potential difference V _ab between the first auxiliary electrode 3 and the second auxiliary electrode 4 is measured by the voltage detecting means. At this time,
When the internal resistance between the first auxiliary electrode 3 and the second auxiliary electrode 4 is sufficiently smaller than the input resistance of the voltage detecting means, the potential difference V
_ab is measured accurately. Therefore, the first auxiliary electrode 3 and the second auxiliary electrode 3
It is desirable that the internal resistance between the auxiliary electrodes 4 is as small as possible and the input resistance of the voltage detecting means is as large as possible.

In order to reduce the internal resistance between the first auxiliary electrode 3 and the second auxiliary electrode 4, it is necessary to increase the area of the first auxiliary electrode 3 and the second auxiliary electrode 4. In the present embodiment, the first auxiliary electrode 3 is formed around the first working electrode 2 formed in the central portion, and the second auxiliary electrode 4 is formed around the first auxiliary electrode 3. The length of the electrode can be maximized within the range of the oxygen ion conductive substrate 1. Therefore, with this auxiliary electrode structure, the input resistance can be minimized within the range of the oxygen ion conductive substrate 1.

The input resistance of the voltage detecting means is usually 1 MΩ.
As described above, 10 MΩ or more is desirable for detecting the potential difference V _ab . As a result, the first auxiliary electrode 3 and the second auxiliary electrode 3
This is because if the internal resistance between the auxiliary electrodes 4 is 1 MΩ or less, the potential difference V _ab can be detected with an accuracy of about 10% or less, and there is no practical problem.

Although the disk-shaped oxygen ion conductive substrate 1 is used in the figure, it is obvious that the oxygen ion conductive substrate 1 may have a rectangular shape or a polygonal shape.

(Embodiment 4) In this embodiment, the case where the first working electrode 2 is the cathode electrode and the second working electrode 5 is the anode electrode will be described. However, the first working electrode 2 is the anode electrode and the second working electrode. Even when 5 is a cathode electrode, the contents described below hold similarly.

When operating the oxygen pump element, as shown in FIG. 4, a direct current power source 8, the positive electrode of this direct current power source is connected to the anode electrode 5, and the cathode electrode 2 is connected to one end of the oxygen ion current detecting means 9. Then, the other end of the oxygen ion current detecting means 9 is connected to the negative electrode of the DC power source 8, and further the voltage detecting means 10 is connected between the first auxiliary electrode 3 and the second auxiliary electrode 4 to form an oxygen pump device. Is desirable.

In this oxygen pump device, the oxygen ion current I _i and the potential difference V _ab can be continuously monitored simultaneously while the oxygen pump element is operating. Thus, since a potential difference V _ab oxygen ion current I _i Xu resistance value _{R ab (= V ab / I} i) can be easily calculated from the temperature dependence of the resistance value R _ab oxygen ion conductive substrate 1 temperature Can be asked.

However, a more preferable structure is such that the oxygen ion current detecting means 9 and the potential difference detecting means 10 are connected to the resistance value calculating means so that the resistance value R _ab (= V _ab / I _i ) can be directly read. That is. As a result, the resistance value R
The calculation of _ab (= V _ab / I _i ) can be automated. Furthermore, the most preferable structure is a structure in which the temperature conversion means is connected to the resistance value calculation means. Thereby, the resistance value R _ab can be automatically converted into the temperature of the oxygen ion conductive substrate 1 based on the temperature dependence of the resistance value R _ab .

[0042]

As described above, the oxygen-containing pump element according to the first aspect of the present invention has the first auxiliary in the oxygen ion conductive substrate when the oxygen ion current is flowing between the cathode electrode and the anode electrode. The potential difference between the equipotential line incident on the electrode and the equipotential line incident between the second auxiliary electrode can be detected.

The oxygen pump according to the second aspect of the present invention can sufficiently supply oxygen ions into the oxygen ion conductive substrate.

The oxygen pump according to claim 3 of the present invention can reduce the internal resistance between the first auxiliary electrode and the second auxiliary electrode.

In the oxygen pump according to the fourth aspect of the present invention, the step of forming the first working electrode can be simplified.

In the oxygen pump according to the fifth aspect of the present invention, the potential difference between the first auxiliary electrode and the second auxiliary electrode can be stably measured.

In the oxygen pump according to the sixth aspect of the present invention, the insulating film can be manufactured by a simple process.

In the oxygen pump according to the seventh aspect of the present invention, the disturbance of the equipotential lines can be reduced.

In the oxygen pump device according to the eighth aspect of the present invention, the oxygen ion current and the potential difference can be directly detected.

In the oxygen pump device according to the ninth aspect of the present invention, the potential difference between the first auxiliary electrode and the second auxiliary electrode can be accurately detected.

In the oxygen pump device according to the tenth aspect of the present invention, the resistance value corresponding to the resistance value of the oxygen ion conductive substrate can be directly detected.

Further, in the oxygen pump device according to the eleventh aspect of the present invention, the temperature of the oxygen ion conductive substrate can be directly detected.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of an oxygen pump according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of an oxygen pump according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of an oxygen pump according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of an oxygen pump device according to a fourth embodiment of the present invention.

[Explanation of symbols]

1 Oxygen ion conductive substrate 2 First working electrode 3 First auxiliary electrode 4 Second auxiliary electrode 5 Second working electrode 6 lines of electric force 7 equipotential lines 7a Equipotential line incident on the first auxiliary electrode 7b Equipotential line incident on the second auxiliary electrode 8 DC power supply 9 Oxygen ion current detection means 10 Potential difference detection means

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Naoko Ikukawa             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 4D006 GA41 JA01A JA42A KE17P                       KE18P KE30R MC03 PA02                       PB62

Claims (11)

[Claims] 1. A first working electrode, a first auxiliary electrode, and a second auxiliary electrode are formed on one surface of an oxygen ion conductive substrate, and a second working electrode is formed on the other surface, and the first working electrode and the second working electrode are formed. Oxygen pump element with working electrode facing. 2. The first working electrode is an anode electrode, the second working electrode is a cathode electrode, and the second working electrode faces the first working electrode, the first auxiliary electrode and the second auxiliary electrode. Oxygen pump element. 3. A first working electrode is formed on one surface of an oxygen ion conductive substrate, a first auxiliary electrode is formed around the first working electrode, and a second auxiliary electrode is formed around the first auxiliary electrode. The oxygen pump element according to claim 1. 4. A first working electrode, a first auxiliary electrode and a second
The oxygen pump element according to claim 1, wherein the auxiliary electrodes are made of the same electrode material. 5. The oxygen pump element according to claim 1, wherein one surface excluding the first working electrode and the other surface excluding the second working electrode are covered with an insulating film. 6. The oxygen pump element according to claim 6, wherein the insulating film is a glass firing film. 7. The oxygen pump element according to claim 1, wherein the first auxiliary electrode and the second auxiliary electrode have a width of (0.5 to 0.1) mm. 8. A direct current power source, a positive electrode of the direct current power source is connected to an anode electrode, a cathode electrode is connected to one end of an oxygen ion current detecting means, and the other end of the current detecting means is connected to a negative electrode of the direct current power source. An oxygen pump device further comprising a potential difference detection means connected between the first auxiliary electrode and the second auxiliary electrode. 9. The oxygen pump device according to claim 8, wherein the input resistance of the potential difference detecting means is 10 MΩ or more. 10. The oxygen pump device according to claim 8, wherein resistance value calculation means is connected to the oxygen ion current detection means and the potential difference detection means. 11. The oxygen pump device according to claim 10, wherein temperature conversion means is connected to the resistance value calculation means.