JP2015169454A - Solid electrolytic co sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolytic CO sensor capable of detecting a CO concentration even in an environment in which an oxygen concentration is varied.SOLUTION: A solid electrolytic CO sensor 1 includes: an oxygen ion conductive solid electrolyte 11; a detection electrode pair 12 comprising a first electrode 12a provided in the oxygen ion conductive solid electrolyte 11 and being active for oxidation of CO and a second electrode 12b provided in the oxygen ion conductive solid electrolyte 11 and being inactive for oxidation of CO; and a cancellation electrode pair 13 comprising a third electrode 13a provided in the oxygen ion conductive solid electrolyte 11 and being inactive for oxidation of CO and a fourth electrode 13b provided in the oxygen ion conductive solid electrolyte 11 and being inactive for oxidation of CO.

Description

  The present invention relates to a solid electrolyte CO sensor.

  Conventionally, a solid electrolyte type CO provided with an oxygen ion conductive solid electrolyte, an electrode provided on one side of the solid electrolyte and active for CO oxidation, and an electrode provided on the other side and inert to CO oxidation Sensors have been proposed. According to this solid electrolyte CO sensor, when the oxygen concentration is constant, the output current changes with respect to the CO concentration in the measurement atmosphere, and the CO concentration can be detected (see Patent Document 1).

JP 2012-42222 A

  In the solid electrolyte CO sensor described in Patent Document 1, oxygen ions are pumped to promote oxidation at an electrode active for CO oxidation. At this time, a current (hereinafter referred to as a base current) is supplied between both electrodes.

  Here, the solid electrolyte CO sensor described in Patent Document 1 can detect the CO concentration by changing the output current with respect to the CO concentration in the measurement atmosphere when the oxygen concentration is constant as described above. It becomes. However, in the solid electrolyte CO sensor described in Patent Document 1, the base current greatly changes in, for example, combustion exhaust gas in which the oxygen concentration changes. In addition, since the change amount of the base current is larger than the change amount of the output current with respect to the CO concentration, the CO concentration cannot be detected.

  The present invention has been made to solve such a conventional problem, and its object is to provide a solid electrolyte CO that can detect the CO concentration even in an environment where the oxygen concentration changes. It is to provide a sensor.

  The solid electrolyte type CO sensor of the present invention is provided with an oxygen ion conductive solid electrolyte, a first electrode active in the oxidation of CO provided in the oxygen ion conductive solid electrolyte, and the oxygen ion conductive solid electrolyte. A detection electrode pair comprising a second electrode inert to CO oxidation, a third electrode inert to CO oxidation provided on the oxygen ion conductive solid electrolyte, and the oxygen ion conductive solid And a cancel electrode pair comprising a fourth electrode which is provided on the electrolyte and is inert to CO oxidation.

  According to this solid electrolyte CO sensor, a detection electrode pair comprising a first electrode active for CO oxidation and a second electrode inactive for CO oxidation, a third electrode inactive for CO oxidation, A canceling electrode pair comprising a fourth electrode that is inactive to the oxidation of CO. Therefore, even if the base current changes greatly in an environment where the oxygen concentration changes, the current of the detecting electrode pair By subtracting the current value of the cancel electrode pair from the value, a current value corresponding to the CO concentration can be extracted. Therefore, the CO concentration can be detected even in an environment where the oxygen concentration changes.

  In the solid electrolyte CO sensor of the present invention, the oxygen ion conductive solid electrolyte has a substantially square shape in plan view, and the first electrode has a first corner on one surface of the oxygen ion conductive solid electrolyte. The second electrode is provided at a second corner that is diagonally opposite to the first corner on one surface of the oxygen ion conductive solid electrolyte, and the third electrode is the oxygen ion conductive solid. The other surface of the electrolyte is provided at a third corner excluding the first and second corners, and the fourth electrode forms a diagonal with the third corner on the other surface of the oxygen ion conductive solid electrolyte. It is preferable to be provided at the fourth corner.

  According to this solid electrolyte type CO sensor, the first electrode is provided at a first corner on one surface of the oxygen ion conductive solid electrolyte, and the second electrode is a second corner that is diagonally opposite to the first corner on one surface. The third electrode is provided at the third corner on the other surface, and the fourth electrode is provided at the fourth corner that forms a diagonal with the third corner on the other surface. For this reason, the electrodes of the electrode pair provided on the same surface are provided at diagonal positions, and the distance between the electrodes can be increased. Therefore, the solid electrolyte CO sensor can be simplified.

  In the solid electrolyte CO sensor of the present invention, the oxygen ion conductive solid electrolyte has a substantially square shape in plan view, and the first electrode has a first corner on one surface of the oxygen ion conductive solid electrolyte. The second electrode is provided at a third corner excluding a second corner that is diagonal to the first corner on the other surface of the oxygen ion conductive solid electrolyte, and the third electrode is The fourth electrode is provided at the second corner on one surface of the oxygen ion conductive solid electrolyte, and the fourth electrode excludes the first, second and third corners on the other surface of the oxygen ion conductive solid electrolyte. It is preferable to be provided at the fourth corner.

  According to this solid electrolyte type CO sensor, the first electrode is provided at the first corner on one surface of the oxygen ion conductive solid electrolyte, and the second electrode is the second corner that forms a diagonal with the first corner on the other surface. Provided at the third corner excluding the corner, the third electrode provided at the second corner on one side, and the fourth electrode provided at the fourth corner on the other side excluding the first, second and third corners It has been. Therefore, the detection electrode pair is provided on one side of the oxygen ion conductive solid electrolyte, the cancel electrode pair is provided on the other side of the oxygen ion conductive solid electrolyte, and the first and second electrodes are The first and second electrodes are opposed to each other, and the third and fourth electrodes are opposed to each other. Therefore, ion conduction in oxygen ion pumping can be made smooth from such an opposing relationship.

  The solid oxide CO sensor of the present invention includes a first current detection unit that detects a current value flowing through the detection electrode pair, a second current detection unit that detects a current value flowing through the cancellation electrode pair, It is preferable that a concentration detection unit that detects a CO concentration based on a differential current value obtained by subtracting the current value detected by the second current detection unit from the current value detected by the first current detection unit.

  According to the solid electrolyte CO sensor, the CO concentration is detected based on the difference current value obtained by subtracting the current value flowing through the cancel electrode pair from the current value flowing through the detection electrode pair. In this case, the CO concentration can be detected.

  The solid electrolyte CO sensor of the present invention includes a first base current supply circuit that applies a constant voltage to the detection electrode pair to pump oxygen ions from the second electrode side to the first electrode side, and A second base current supply circuit that applies a constant voltage to the cancel electrode pair to pump oxygen ions from the fourth electrode side to the third electrode side, and the first base current supply circuit and the second base current supply circuit A constant voltage is applied at a different timing from the base current supply circuit, and the first current detection means detects a current value flowing through the detection electrode pair during application of the constant voltage by the first base current supply circuit. Preferably, the second current detection means detects a current value flowing through the cancel electrode pair during application of a constant voltage by the second base current supply circuit.

  According to this solid oxide CO sensor, the first base current supply circuit and the second base current supply circuit apply a constant voltage at different timings, and the first current detection means is a constant voltage generated by the first base current supply circuit. The current value flowing through the detection electrode pair during voltage application is detected, and the second current detection means detects the current value flowing through the cancellation electrode pair during application of the constant voltage by the second base current supply circuit. For this reason, it is possible to prevent the detected value from becoming unstable due to the pumping current in the second base current supply circuit being influenced during the detection of the current value by the first current detecting means, and to be controlled by the second current detecting means. It is possible to prevent the detected value from becoming unstable due to the influence of the pumping current in the first base current supply circuit during the detection of the current value. Therefore, the CO concentration detection accuracy can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the solid electrolyte type CO sensor which can determine a lifetime, and its lifetime determination method can be provided.

It is a block diagram of the solid electrolyte type CO sensor which concerns on 1st Embodiment of this invention. It is a top view which shows a partial structure of the solid electrolyte type CO sensor shown in FIG. It is a graph which shows the value of the electric current which flows into the detection electrode pair and cancellation electrode pair according to CO density | concentration. It is a graph which shows the variation | change_quantity of the base current in the electrode pair for a detection according to oxygen concentration, and the electrode pair for cancellation. It is a block diagram of the solid electrolyte type CO sensor which concerns on 2nd Embodiment. FIG. 6 is a plan view showing a partial configuration of the solid oxide CO sensor shown in FIG. 5. It is a graph which shows the value of the electric current which flows into the electrode pair for a detection according to CO concentration in 2nd Embodiment, and the electrode pair for cancellation. It is a graph which shows the variation | change_quantity of the base current in the electrode pair for a detection according to oxygen concentration in 2nd Embodiment, and the electrode pair for cancellation.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiments. FIG. 1 is a configuration diagram of a solid electrolyte type CO sensor according to a first embodiment of the present invention, and FIG. 2 is a plan view showing a partial configuration of the solid electrolyte type CO sensor shown in FIG.

  As shown in FIG. 1, the solid oxide CO sensor 1 includes a sensor unit 10, current supply circuits (first base current supply circuit, second base current supply circuit) 21, 22, and current sensors (first current detection). Means, second current detection means) 31, 32, a control unit (concentration detection means) 40, and switches 51, 52.

  The sensor unit 10 includes an oxygen ion conductive solid electrolyte 11 (hereinafter referred to as a solid electrolyte membrane 11), a detection electrode pair 12, and a cancel electrode pair 13.

The solid electrolyte membrane 11 is a so-called yttria-stabilized zirconia in which, for example, 92% mol of zirconia (ZrO ₂ ) powder is mixed with 8% mol of yttria (Y ₂ O ₃ ) powder, or lanthanum gallate type. It is comprised from the complex oxide of this. The solid electrolyte membrane 11 has a substantially quadrangular shape in plan view as shown in FIG.

  The detection electrode pair 12 includes a first electrode 12a and a second electrode 12b. The first electrode 12 a is an electrode that is active in oxidizing CO provided on the solid electrolyte membrane 11, and the second electrode 12 b is an electrode that is inactive in oxidizing CO provided on the solid electrolyte membrane 11. 1 and 2, the first electrode 12a is provided at the first corner 11a on one surface of the solid electrolyte membrane 11, and the second electrode 12b is provided on the other surface of the solid electrolyte membrane 11. It is provided at the third corner 11c excluding the second corner 11b that forms a diagonal with the first corner 11a.

  The cancel electrode pair 13 includes a third electrode 13a and a fourth electrode 13b. The third electrode 13a and the fourth electrode 13b are electrodes provided on the solid electrolyte membrane 11 and inactive to CO oxidation. As shown in FIGS. 1 and 2, the third electrode 13 a is provided at the second corner 11 b on one surface of the solid electrolyte membrane 11, and the fourth electrode 13 b is provided on the other surface of the solid electrolyte membrane 11. It is provided at the fourth corner 11d excluding the first, second and third corners 11a to 11c.

Note that the first electrode 12a is in RuO ₂ is composed of a material obtained by adding the Pt and / or Pd, preferably composed by those of Pt was added 10 wt% to RuO _2. The second to fourth electrodes 12b, 13a, 13b are made of a material made of a mixture of ITO (Indium Tin Oxide) + Au, and preferably made of ITO mixed with 10 wt% of Au. . Each electrode 12a, 12b, 13a, 13b is provided with a pad portion 16 as shown in FIG. 2, to which current supply circuits 21, 22 are connected.

  Further, the sensor unit 10 is provided with an integrated body of the above-described configurations 11 to 13 on the substrate 14, and a heater pattern 15 is formed on the opposite surface of the integrated body of the substrate 14. The substrate 14 is made of alumina, for example, and has a thickness of 0.35 mm, for example. The heater pattern 15 is composed of Pt, and is energized by the control unit 40 to adjust the temperature of the sensor unit 10.

  As shown in FIG. 1, only one surface of the first and third electrodes 12a and 13a is in contact with the solid electrolyte membrane 11, but the entire area of the second electrode 12b is covered with the solid electrolyte membrane 11 and the substrate 14. ing. The fourth electrode 13b is also covered with the solid electrolyte membrane 11 and the substrate 14 except for one side. However, since the solid electrolyte membrane 11 is porous, the second electrode 12b and the fourth electrode 13b are exposed to the detection target gas or the like.

  The first current supply circuit (first base current supply circuit) 21 applies a constant voltage to the detection electrode pair 12 to pump oxygen ions from the second electrode 12b side to the first electrode 12a side. . The second current supply circuit (second base current supply circuit) 22 applies a constant voltage to the cancel electrode pair 13 to pump oxygen ions from the fourth electrode 13b side to the third electrode 13a side. . The current supplied to the electrode pairs 12 and 13 by these current supply circuits 21 and 22 is referred to as a base current. The voltage values of these circuits 21 and 22 are the same.

  The first current sensor (first current detection means) 31 detects the value of the current flowing through the detection electrode pair 12, and the second current sensor (second current detection means) 32 flows through the cancellation electrode pair 13. The current value is detected.

  The control unit 40 detects the CO concentration based on the differential current value obtained by subtracting the current value detected by the second current sensor 32 from the current value detected by the first current sensor 31. Further, the control unit 40 has a function of performing on / off control of the switches 51 and 52.

Next, the operation of the solid oxide CO sensor 1 according to the first embodiment will be described. First, the sensor unit 10 is exposed to a measurement atmosphere such as in combustion exhaust gas. As a result, the following reaction occurs at the first electrode 12a of the detection electrode pair 12.
CO + O ²⁻ → CO ₂ + 2e ⁻

Further, the following reaction occurs at the second electrode 12 b of the detection electrode pair 12.
O ₂ + 4e ⁻ → 2O ²⁻

  Therefore, an electromotive force corresponding to the CO concentration is generated in the detection electrode pair 12, and a current value corresponding to the electromotive force is detected by the first current sensor 31.

  However, the solid oxide CO sensor 1 according to the first embodiment is exposed to an atmosphere in which the oxygen concentration changes, such as in combustion exhaust gas. For this reason, the supply current (base current) by the first current supply circuit 21 changes greatly. In addition, since the change amount of the base current is larger than the change amount of the output current with respect to the CO concentration, the CO concentration cannot be detected.

  However, the solid oxide CO sensor 1 according to the first embodiment includes a cancel electrode pair 13. Since the electrodes 13a and 13b of the cancel electrode pair 13 are both inactive to CO, the base current changes according to the oxygen concentration, but the current value does not change with respect to the CO concentration. Become.

  For this reason, the controller 40 subtracts the current value detected by the second current sensor 32 from the current value detected by the first current sensor 31. Thereby, the control part 40 can detect CO density | concentration based on the electric current value of a difference.

  FIG. 3 is a graph showing the value of the current flowing through the detection electrode pair 12 and the cancellation electrode pair 13 according to the CO concentration. In FIG. 3, the current value of the detection electrode pair 12 is indicated by a solid line (and a triangular symbol), and the current value of the cancellation electrode pair 13 is indicated by a broken line (and a cross symbol).

  As shown in FIG. 3, a current of about 0.5 μA flows through the detection electrode pair 12 when the CO concentration is about 100 ppm, and a current of about 1.5 μA flows at about 1000 ppm. A current of about 2 μA flows through the detection electrode pair 12 when the CO concentration is less than 3000 ppm. On the other hand, the cancellation electrode pair 13 indicates 0 μA in a region where the CO concentration is 1000 ppm or less, and a current of less than 0.5 μA flows even when the CO concentration is less than 3000 ppm.

  FIG. 4 is a graph showing the amount of change in the base current in the detection electrode pair 12 and the cancellation electrode pair 13 according to the oxygen concentration. In FIG. 4, the current value of the detection electrode pair 12 is indicated by a solid line (and a triangular symbol), and the current value of the cancellation electrode pair 13 is indicated by a broken line (and a cross symbol).

  As shown in FIG. 4, in the detection electrode pair 12, the base current is about −9 μA when the oxygen concentration is 5%, about −5.5 μA when 10%, about −4 μA when 15%, and 0 μA when 20%. It becomes. On the other hand, in the cancel electrode pair 13, the base current is about −8 μA when the oxygen concentration is 5%, about −5 μA when 10%, about −3 μA when 15%, and 0 μA when 20%.

  As shown in FIGS. 3 and 4, a current corresponding to the CO concentration flows through the detection electrode pair 12, but a current according to the CO concentration does not flow through the cancellation electrode pair 13. Further, in the detection electrode pair 12 and the cancellation electrode pair 13, the base current shows the same amount of change according to the oxygen concentration. Therefore, the control unit 40 can extract only the current value corresponding to the CO concentration by subtracting the current value detected by the second current sensor 32 from the current value detected by the first current sensor 31. CO concentration can be detected.

  Furthermore, in the first embodiment, the control unit 40 varies the on / off timing of the switches 51 and 52. That is, the first current supply circuit 21 and the second current supply circuit 22 apply a constant voltage at different timings, and the first current sensor 31 detects the detection electrode while the first current supply circuit 21 is applying the constant voltage. The current value flowing through the pair 12 is detected, and the second current sensor 32 detects the current value flowing through the cancel electrode pair 13 during application of a constant voltage by the second current supply circuit 22.

  For this reason, while the current value is detected by the first current sensor 31, the pumping current (base current) in the second current supply circuit 22 has an influence to prevent the detected value from becoming unstable, and the second It is possible to prevent the detected value from becoming unstable due to the influence of the pumping current (base current) in the first current supply circuit 21 during the detection of the current value by the current sensor 32.

  Thus, according to the solid oxide CO sensor 1 according to the first embodiment, the detection electrode pair including the first electrode 12a active for CO oxidation and the second electrode 12b inactive for CO oxidation. 12 and a cancel electrode pair 13 composed of a third electrode 13a inactive to CO oxidation and a fourth electrode 13b inactive to CO oxidation. Even if the current changes greatly, the current value corresponding to the CO concentration can be extracted by subtracting the current value of the cancel electrode pair 13 from the current value of the detection electrode pair 12. Therefore, the CO concentration can be detected even in an environment where the oxygen concentration changes.

  In addition, the first electrode 12a is provided at the first corner 11a on one surface of the solid electrolyte membrane 11, and the second electrode 12b is a third surface excluding the second corner 11b that forms a diagonal with the first corner 11a on the other surface. The third electrode 13a is provided at the second corner 11b on one side, and the fourth electrode 13b is the fourth corner excluding the first, second, and third corners 11a to 11c on the other side. 11d. Therefore, the detection electrode pair 12 is provided on one side of the solid electrolyte membrane 11, and the cancel electrode pair 13 is provided on the other side of the solid electrolyte membrane 11, so that the first and second electrodes 12a and 12b are provided. Are opposed to each other, and the third and fourth electrodes 13a and 13b are opposed to each other. Therefore, ion conduction in oxygen ion pumping can be made smooth from such an opposing relationship.

  Further, since the CO concentration is detected based on the difference current value obtained by subtracting the current value flowing through the cancel electrode pair 13 from the current value flowing through the detection electrode pair 12, the CO concentration can be reduced even in an environment where the oxygen concentration changes. Can be detected.

  The first current supply circuit 21 and the second current supply circuit 22 apply a constant voltage at different timings, and the first current sensor 31 detects the detection electrode during application of the constant voltage by the first current supply circuit 21. The current value flowing through the pair 12 is detected, and the second current sensor 32 detects the current value flowing through the cancel electrode pair 13 during application of a constant voltage by the second current supply circuit 22. For this reason, while the current value is detected by the first current sensor 31, the pumping current in the second current supply circuit 22 is prevented from affecting the detected value, and the second current sensor 32 It is possible to prevent the detected value from becoming unstable due to the influence of the pumping current in the first current supply circuit 21 during the detection of the current value. Therefore, the CO concentration detection accuracy can be improved.

  Next, a second embodiment of the present invention will be described. The solid oxide CO sensor according to the second embodiment is the same as that of the first embodiment, but the configuration is partially different. Only differences from the first embodiment will be described below.

  FIG. 5 is a configuration diagram of the solid electrolyte type CO sensor according to the second embodiment, and FIG. 6 is a plan view showing a partial configuration of the solid electrolyte type CO sensor shown in FIG. As shown in FIGS. 5 and 6, in the fixed electrolyte CO sensor 2 according to the second embodiment, the first electrode 12 a is provided at the first corner 11 a on one surface of the solid electrolyte membrane 11, and the second electrode 12 b is The second surface 11b of the solid electrolyte membrane 11 is opposite to the first corner 11b.

  The third electrode 13 a is provided at the third corner 11 c except for the first and second corners 11 a and 11 b on the other surface of the solid electrolyte membrane 11, and the fourth electrode 13 b is disposed on the other surface of the solid electrolyte membrane 11. Are provided at a fourth corner 11d that forms a diagonal with the third corner 11c.

  Thus, in the second embodiment, the detection electrode pair 12 is formed on the same surface of the solid electrolyte membrane 11, and the cancel electrode pair 13 is also formed on the same surface of the solid electrolyte membrane 11. This is also because the same effect as in the first embodiment can be obtained.

  The operation of the fixed electrolyte type CO sensor 2 according to the second embodiment is the same as that of the first embodiment.

  FIG. 7 is a graph showing values of currents flowing through the detection electrode pair 12 and the cancellation electrode pair 13 according to the CO concentration in the second embodiment. In FIG. 7, the current value of the detection electrode pair 12 is indicated by a solid line (and an inclined square symbol), and the current value of the cancellation electrode pair 13 is indicated by a broken line (and a square symbol).

  As shown in FIG. 7, a current of about 0.3 μA flows through the detection electrode pair 12 at a CO concentration of about 300 ppm, and a current of about 1.0 μA flows at about 1000 ppm. A current of about 1.5 μA flows through the detection electrode pair 12 with a CO concentration of less than 3000 ppm. On the other hand, the cancellation electrode pair 13 indicates 0 μA in a region where the CO concentration is 1000 ppm or less, and a current of less than 0.5 μA flows even when the CO concentration is less than 3000 ppm.

  FIG. 8 is a graph showing the amount of change in the base current in the detection electrode pair 12 and the cancellation electrode pair 13 according to the oxygen concentration in the second embodiment. In FIG. 8, the current value of the detection electrode pair 12 is indicated by a solid line (and a tilted square symbol), and the current value of the cancellation electrode pair 13 is indicated by a broken line (and a square symbol).

  As shown in FIG. 8, in the detection electrode pair 12, the base current is about −8 μA when the oxygen concentration is 5%, about −5.5 μA when 10%, about −3.5 μA when 15%, and about −3.5 μA and 20%. At 0 μA. On the other hand, the base current in the cancel electrode pair 13 is about −6.5 μA when the oxygen concentration is 5%, is about −4.5 μA when 10%, is about −2.5 μA when 15%, and is about 20%. At 0 μA.

  As shown in FIGS. 7 and 8, a current corresponding to the CO concentration flows through the detection electrode pair 12, but a current according to the CO concentration does not flow through the cancellation electrode pair 13. Further, in the detection electrode pair 12 and the cancellation electrode pair 13, the base current shows the same amount of change according to the oxygen concentration. Therefore, the control unit 40 can extract only the current value corresponding to the CO concentration by subtracting the current value detected by the second current sensor 32 from the current value detected by the first current sensor 31. CO concentration can be detected.

  Thus, according to the solid oxide CO sensor 2 according to the second embodiment, the CO concentration can be detected and the CO concentration can be detected even in an environment where the oxygen concentration changes, as in the first embodiment. The density detection accuracy can be improved.

  Furthermore, according to the second embodiment, the first electrode 12a is provided at the first corner 11a on one surface of the solid electrolyte membrane 11, and the second electrode 12b is a second surface that forms a diagonal with the first corner 11a on one surface. The third electrode 13a is provided at the third corner 11c on the other surface, and the fourth electrode 13b is provided at the fourth corner 11d that forms a diagonal with the third corner 11c on the other surface. ing. For this reason, the electrodes 12a, 12b, 13a, 13b of the electrode pairs 12, 13 provided on the same surface are provided at diagonal positions, and the distance between the electrodes can be increased. Therefore, the solid electrolyte CO sensor can be simplified.

  As described above, the present invention has been described based on the embodiment, but the present invention is not limited to the above embodiment, and may be modified without departing from the gist of the present invention. For example, in the present embodiment, the configuration of the solid electrolyte CO sensor 1 has been described with reference to materials, but the materials are not particularly limited to those described above, and can be changed as appropriate. Further, the shape can be changed as appropriate.

DESCRIPTION OF SYMBOLS 1, 2 ... Solid electrolyte type CO sensor 10 ... Sensor part 11 ... Oxygen ion conductive solid electrolyte 11a-11d ... Corner | angular 12 ... Detection electrode pair 13 ... Cancel electrode pair 12a, 12b, 13a, 13b ... Electrode 14 ... Substrate DESCRIPTION OF SYMBOLS 15 ... Heater pattern 16 ... Pad part 21 ... 1st current supply circuit (1st base current supply circuit)
22 ... Second current supply circuit (second base current supply circuit)
31 ... 1st current sensor (1st current detection means)
32 ... 2nd current sensor (2nd current detection means)
40: Control unit (concentration detection means)
51, 52 ... switch

Claims (5)

An oxygen ion conductive solid electrolyte;
A detection electrode comprising: a first electrode active in oxidizing CO provided in the oxygen ion conductive solid electrolyte; and a second electrode inactive in oxidizing CO provided in the oxygen ion conductive solid electrolyte. Vs.
A canceling electrode comprising: a third electrode that is inert to CO oxidation provided on the oxygen ion conductive solid electrolyte; and a fourth electrode that is inert to CO oxidation provided on the oxygen ion conductive solid electrolyte. An electrode pair;
A solid electrolyte type CO sensor comprising: The oxygen ion conductive solid electrolyte has a substantially rectangular shape in plan view,
The first electrode is provided at a first corner on one surface of the oxygen ion conductive solid electrolyte,
The second electrode is provided at a second corner that is diagonal to the first corner on one surface of the oxygen ion conductive solid electrolyte,
The third electrode is provided at a third corner excluding the first and second corners on the other surface of the oxygen ion conductive solid electrolyte,
2. The solid electrolyte type according to claim 1, wherein the fourth electrode is provided at a fourth corner that forms a diagonal with the third corner on the other surface of the oxygen ion conductive solid electrolyte. 3. CO sensor. The oxygen ion conductive solid electrolyte has a substantially rectangular shape in plan view,
The first electrode is provided at a first corner on one surface of the oxygen ion conductive solid electrolyte,
The second electrode is provided at a third corner excluding a second corner that forms a diagonal with the first corner on the other surface of the oxygen ion conductive solid electrolyte,
The third electrode is provided at the second corner on one surface of the oxygen ion conductive solid electrolyte,
2. The fourth electrode according to claim 1, wherein the fourth electrode is provided at a fourth corner excluding the first, second, and third corners on the other surface of the oxygen ion conductive solid electrolyte. Solid electrolyte CO sensor. First current detection means for detecting a current value flowing through the detection electrode pair;
Second current detection means for detecting a current value flowing through the cancel electrode pair;
Concentration detecting means for detecting a CO concentration based on a differential current value obtained by subtracting the current value detected by the second current detecting means from the current value detected by the first current detecting means;
The solid electrolyte CO sensor according to any one of claims 1 to 3, further comprising: A first base current supply circuit that applies a constant voltage to the detection electrode pair to pump oxygen ions from the second electrode side to the first electrode side;
A second base current supply circuit that applies a constant voltage to the cancel electrode pair to pump oxygen ions from the fourth electrode side to the third electrode side,
The first base current supply circuit and the second base current supply circuit apply a constant voltage at different timings,
The first current detection means detects a current value flowing through the detection electrode pair during application of a constant voltage by the first base current supply circuit,
5. The solid oxide CO sensor according to claim 4, wherein the second current detection unit detects a current value flowing through the cancel electrode pair during application of a constant voltage by the second base current supply circuit. .

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