Gas sensor and method for measuring concentration using a gas sensor

Abstract

To provide a gas sensor capable of measuring concentration of oxygen in addition to CO2 and H2O.SOLUTION: A sensor element of a gas sensor has a sub-adjustment hollow chamber, a first hollow chamber, a second hollow chamber, and a third hollow chamber successively connected from a gas introduction port via mutually different diffusion control parts, a sub-adjustment pump cell pumps out oxygen from measured gas introduced into the sub-adjustment hollow chamber within a range in which H2O and CO2 contained in the measured gas are not decomposed, a first pump cell pumps out oxygen from the first chamber such that all of H2O and CO2 contained in the measured gas introduced into the first hollow chamber from the sub-adjustment chamber are decomposed, concentration of H2O and CO2 is specified each from a pumped current when H2 and CO generated by decomposition are oxidized in the second chamber and the third chamber, and oxygen concentration of the measured gas is specified on the basis of the level of current flowing between an inner electrode and an outer electrode for sub-adjustment when pumping out oxygen from the sub-adjustment hollow chamber by the sub-adjustment pump cell.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a multi-gas sensor capable of detecting a plurality of types of detection target gas components and measuring the concentrations thereof. [Background Art]

[0002] Techniques for measuring the concentration of carbon dioxide (CO2) in measurement for managing emissions from automobile exhaust gas are already known (see, for example, Patent Document 1 and Patent Document 2). In the gas sensors disclosed in Patent Document 1 and Patent Document 2, it is possible to simultaneously measure not only carbon dioxide (CO2) components but also water vapor (H2O) components in parallel.

[0003] Further, for sensors for automobile exhaust gas, it is required that a single sensor can measure a plurality of gas types for cost reduction and space saving. A gas sensor that includes a sensor element having four internal cavities and can detect ammonia (NH3) and nitrogen monoxide (NO) in parallel is also known (see, for example, Patent Document 3). [Prior Art Literature] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent No. 5918177 [Patent Document 2] Japanese Patent No. 6469464 [Patent Document 3] Japanese Unexamined Patent Publication No. 2020-91283 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] Patent Document 1 shows that, in addition to CO2 and H2O, the concentration of oxygen (O2) can also be indirectly determined using multiple detection current values ​​(pump current values ​​in the pump cell). However, this method has the problem of large errors and poor accuracy because it combines multiple detection current values.

[0006] The present invention has been made in view of the above problems, and aims to provide a gas sensor that can measure the concentrations of CO2 and H2O, and can also suitably measure the concentration of oxygen. [Means for solving the problem]

[0007] To solve the above problems, a first aspect of the present invention is a gas sensor capable of measuring the concentrations of multiple target gas components contained in a gas to be measured, which includes at least water vapor and carbon dioxide, comprising: a sensor element having a structure made of an oxygen ion conductive solid electrolyte; and a controller for controlling the operation of the gas sensor, wherein the sensor element has a gas inlet into which the gas to be measured is introduced; a sub-adjustment chamber, a first chamber, a second chamber, and a third chamber which are main adjustment chambers, which are sequentially connected from the gas inlet via different diffusion rate-limiting sections; a sub-adjustment inner electrode formed facing the sub-adjustment chamber; and an outer electrode formed on the outer surface of the sensor element. A sub-adjustment pump cell comprising the sub-adjustment inner electrode and the solid electrolyte located between the outer electrode, a first pump cell comprising the first inner electrode formed facing the first cavity, the outer electrode, and the solid electrolyte located between the first inner electrode and the outer electrode, a second pump cell comprising the second inner electrode formed facing the second cavity, the outer electrode, and the solid electrolyte located between the second inner electrode and the outer electrode, a third pump cell comprising the third inner electrode formed facing the third cavity, the outer electrode, and the solid electrolyte located between the third inner electrode and the outer electrode, A sensor cell for a sub-adjustment void, comprising a reference electrode in contact with a reference gas, the sub-adjustment inner electrode, the reference electrode, and the solid electrolyte present between the sub-adjustment inner electrode and the reference electrode, wherein an electromotive force V0 corresponding to the oxygen concentration of the sub-adjustment void is generated between the sub-adjustment inner electrode and the reference electrode; and comprising a first inner electrode, the reference electrode, and the solid electrolyte present between the first inner electrode and the reference electrode, wherein an electromotive force V1 corresponding to the oxygen concentration of the first void is generated between the first inner electrode and the reference electrode. A first vacant sensor cell, a second inner electrode, a reference electrode, and a solid electrolyte located between the second inner electrode and the reference electrode, wherein an electromotive force V2 corresponding to the oxygen concentration of the second vacant cell is generated between the second inner electrode and the reference electrode; a third vacant sensor cell, a third inner electrode, a reference electrode, and a solid electrolyte located between the third inner electrode and the reference electrode, wherein an electromotive force V3 corresponding to the oxygen concentration of the third vacant cell is generated between the third inner electrode and the reference electrode;The controller comprises the following: The sub-regulating pump cell pumps oxygen from the gas to be measured introduced into the sub-regulating chamber from the gas inlet to the extent that the water vapor and carbon dioxide contained in the gas to be measured are not decomposed; the first pump cell pumps oxygen from the first chamber so that the water vapor and carbon dioxide contained in the gas to be measured introduced into the first chamber from the sub-regulating chamber are substantially all decomposed; the second pump cell pumps oxygen into the second chamber to selectively oxidize the hydrogen produced by the decomposition of water vapor contained in the gas to be measured introduced from the first chamber to the second chamber; the third pump cell pumps oxygen into the third chamber to oxidize the carbon monoxide produced by the decomposition of carbon dioxide contained in the gas to be measured introduced from the second chamber to the third chamber; and the controller Sub-adjustment pump cell control means controls the voltage applied between the sub-adjustment inner electrode and the outer electrode in the sub-adjustment pump cell so that the electromotive force V0 in the sub-adjustment vacant sensor cell is maintained at a predetermined target value within the range of 400mV to 700mV; First pump cell control means controls the voltage applied between the first inner electrode and the outer electrode in the first pump cell so that the electromotive force V1 in the first vacant sensor cell is maintained at a predetermined target value within the range of 1000mV to 1500mV The means includes: a second pump cell control means for controlling the voltage applied between the second inner electrode and the outer electrode in the second pump cell so that the electromotive force V2 in the second empty chamber sensor cell is maintained at a predetermined target value within the range of 250mV to 450mV; and a third pump cell control means for controlling the voltage applied between the third inner electrode and the outer electrode in the third pump cell so that the electromotive force V3 in the third empty chamber sensor cell is maintained at a predetermined target value within the range of 100mV to 300mV. The device is characterized by comprising: a water vapor concentration determination means for determining the concentration of water vapor contained in the gas to be measured based on the magnitude of the current flowing between the second inner electrode and the outer electrode when oxygen is pumped into the second chamber by the second pump cell; a carbon dioxide concentration determination means for determining the concentration of carbon dioxide contained in the gas to be measured based on the magnitude of the current flowing between the third inner electrode and the outer electrode when oxygen is pumped into the third chamber by the third pump cell; and an oxygen concentration determination means for determining the concentration of oxygen contained in the gas to be measured based on the magnitude of the current flowing between the sub-adjustment inner electrode and the outer electrode when oxygen is pumped out from the sub-adjustment chamber by the sub-adjustment pump cell.

[0009] This invention 2 The manner of is, 1 A gas sensor according to the above embodiment, characterized in that the sub-regulating pump cell control means controls the voltage applied between the sub-regulating inner electrode and the outer electrode in the sub-regulating pump cell so that the electromotive force V0 is maintained at 400 mV.

[0010] This invention 3The embodiment is a method for measuring the concentrations of multiple target gas components contained in a gas to be measured, which includes at least water vapor and carbon dioxide, using a gas sensor, wherein the gas sensor comprises a sensor element having a long plate-shaped structure made of an oxygen ion conductive solid electrolyte, the sensor element comprising a gas inlet into which the gas to be measured is introduced, and a sub-adjustment chamber, a first chamber, a second chamber, and a third chamber which are main adjustment chambers, which are sequentially connected from the gas inlet via different diffusion rate-limiting parts, an internal electrode for sub-adjustment formed facing the sub-adjustment chamber, an external electrode formed on the outer surface of the sensor element, and the internal electrode for sub-adjustment A sub-regulating pump cell comprising a side electrode and the solid electrolyte located between the outer electrode; a first pump cell comprising a first inner electrode formed facing the first cavity, the outer electrode, and the solid electrolyte located between the first inner electrode and the outer electrode; a second pump cell comprising a second inner electrode formed facing the second cavity, the outer electrode, and the solid electrolyte located between the second inner electrode and the outer electrode; a third pump cell comprising a third inner electrode formed facing the third cavity, the outer electrode, and the solid electrolyte located between the third inner electrode and the outer electrode; A sensor cell for a sub-adjustment void, comprising a reference electrode in contact with a reference gas, the sub-adjustment inner electrode, the reference electrode, and the solid electrolyte present between the sub-adjustment inner electrode and the reference electrode, wherein an electromotive force V0 corresponding to the oxygen concentration of the sub-adjustment void is generated between the sub-adjustment inner electrode and the reference electrode; and comprising a first inner electrode, the reference electrode, and the solid electrolyte present between the first inner electrode and the reference electrode, wherein an electromotive force V1 corresponding to the oxygen concentration of the first void is generated between the first inner electrode and the reference electrode. A first vacant sensor cell, a second inner electrode, a reference electrode, and a solid electrolyte located between the second inner electrode and the reference electrode, wherein an electromotive force V2 corresponding to the oxygen concentration of the second vacant cell is generated between the second inner electrode and the reference electrode; a third vacant sensor cell, a third inner electrode, a reference electrode, and a solid electrolyte located between the third inner electrode and the reference electrode, wherein an electromotive force V3 corresponding to the oxygen concentration of the third vacant cell is generated between the third inner electrode and the reference electrode; It is equipped with, a) By controlling the voltage applied between the inner electrode and the outer electrode in the auxiliary adjustment pump cell so that the electromotive force V0 generated between the auxiliary adjustment inner electrode and the reference electrode, depending on the oxygen concentration in the auxiliary adjustment chamber, is maintained at a predetermined target value within the range of 400mV to 700mV, The process of drawing oxygen from the gas to be measured, which has been introduced into the sub-regulating chamber from the gas inlet, using the sub-regulating pump cell, to the extent that the water vapor and carbon dioxide contained in the gas to be measured are not decomposed, and b) By controlling the voltage applied between the first inner electrode and the outer electrode in the first pump cell so that the electromotive force V1 generated between the first inner electrode and the reference electrode according to the oxygen concentration in the first void is maintained at a predetermined target value within the range of 1000mV to 1500mV, The first pump cell is designed to substantially decompose all of the water vapor and carbon dioxide contained in the gas to be measured that has been introduced from the sub-adjustment chamber into the first chamber. Before The process of drawing oxygen from the first empty chamber, and c) By controlling the voltage applied between the second inner electrode and the outer electrode in the second pump cell so that the electromotive force V2 generated between the second inner electrode and the reference electrode according to the oxygen concentration in the second void is maintained at a predetermined target value within the range of 250mV to 450mV, By the second pump cell Before Note: Oxygen was drawn into the second vacant room. Re, The hydrogen produced by the decomposition of water vapor contained in the gas to be measured, which is introduced from the first vacant chamber to the second vacant chamber, 、 The process of selectively oxidizing in the second vacant chamber, and d) By controlling the voltage applied between the third inner electrode and the outer electrode in the third pump cell so that the electromotive force V3 generated between the third inner electrode and the reference electrode according to the oxygen concentration in the third void is maintained at a predetermined target value within the range of 100mV to 300mV, By the third pump cell BeforeNote: Oxygen was drawn into the third vacant room. Re, The carbon monoxide produced by the decomposition of carbon dioxide contained in the gas to be measured, which is introduced from the second vacant room to the third vacant room, 、 The method is characterized by comprising: a step of oxidizing in the third void; e) a step of determining the concentration of water vapor contained in the gas to be measured based on the magnitude of the current flowing between the second inner electrode and the outer electrode when oxygen is pumped into the second void by the second pump cell; f) a step of determining the concentration of carbon dioxide contained in the gas to be measured based on the magnitude of the current flowing between the third inner electrode and the outer electrode when oxygen is pumped into the third void by the third pump cell; and g) a step of determining the concentration of oxygen contained in the gas to be measured based on the magnitude of the current flowing between the auxiliary adjustment inner electrode and the outer electrode when oxygen is pumped out from the auxiliary adjustment void by the auxiliary adjustment pump cell.

[0012] This invention 4 The manner of is, 3 A method for measuring concentration using a gas sensor according to the embodiment, characterized in that in step a), the voltage applied between the auxiliary adjustment inner electrode and the outer electrode in the auxiliary adjustment pump cell is controlled so that the electromotive force V0 is maintained at 400 mV.

[0013] This invention 5 The aspect is the first or The 2 state To Mr.The gas sensor according to claim [X], characterized in that the first pump cell performs, during the first pumping operation of pumping oxygen out of the first chamber such that substantially all of the water vapor and carbon dioxide contained in the measured gas introduced from the auxiliary adjustment chamber into the first chamber is decomposed, stopping the first pumping operation for a predetermined period of time, or performing a second pumping operation of pumping oxygen out of the first chamber within a range where the water vapor and carbon dioxide contained in the measured gas are not decomposed, whereby the reduction of water vapor and carbon dioxide in the first chamber is interrupted, and thus the water vapor generated in the second chamber and the carbon dioxide generated in the third chamber are discharged to the outside of the sensor element through the first chamber and the auxiliary adjustment chamber.

[0014] According to the first 6 aspect of the present invention, the gas sensor according to the 5 aspect, characterized in that the first pump cell alternately and periodically performs the first pumping operation and the stop of the first pumping operation or the second pumping operation, and the pumping of oxygen into the second chamber by the second pump cell and the pumping of oxygen into the third chamber by the third pump cell are performed periodically in accordance with the operation of the first pump cell.

[0015] According to the second 7 aspect of the present invention, the gas sensor according to the 6 aspect, characterized in that the pumping of oxygen into the second chamber by the second pump cell and the pumping of oxygen into the third chamber by the third pump cell are performed in synchronization with the stop of the first pumping operation by the first pump cell or the second pumping operation.

[0016] According to the third 8 aspect of the present invention, the gas sensor according to the 6A gas sensor according to an embodiment, wherein pumping oxygen into the second chamber by the second pump cell and pumping oxygen into the third chamber by the third pump cell are performed from a middle point of the first pumping-out operation by the first pump cell to a middle point of stopping the first pumping-out operation or to a middle point of the second pumping-out operation.

[0017] A first aspect of the present invention 9 relates to 3 or A 4 aspect To Mr. provides a concentration measurement method using a gas sensor according to the present invention, characterized in that: in the middle of said step b), said first pump cell stops a first oxygen pumping-out operation of pumping oxygen out of said first chamber for a predetermined time, wherein the first oxygen pumping-out operation is configured to pump oxygen out of said first chamber such that substantially all of water vapor and carbon dioxide contained in the gas to be measured introduced from said auxiliary adjustment chamber into said first chamber are decomposed; or, said first pump cell performs a second oxygen pumping-out operation of pumping oxygen out of said first chamber within a range that does not decompose water vapor and carbon dioxide contained in the gas to be measured; thereby interrupting reduction of water vapor and carbon dioxide in said first chamber, so that water vapor generated in said second chamber and carbon dioxide generated in said third chamber are discharged to the outside of said sensor element through said first chamber and said auxiliary adjustment chamber.

[0018] A second aspect of the present invention 10 relates to 9 a concentration measurement method using a gas sensor according to an embodiment, characterized in that: in said step b), said first pump cell alternately and periodically performs said first pumping-out operation, and stopping of said first pumping-out operation or said second pumping-out operation; pumping oxygen into the second chamber by said second pump cell in said step c) and pumping oxygen into the third chamber by said third pump cell in said step d) are periodically performed in accordance with the operation of said first pump cell in said step b).

[0019] A third aspect of the present invention 11 relates to 10A method for measuring concentration using a gas sensor according to the embodiment, characterized in that the pumping of oxygen into the second empty chamber by the second pump cell in step c) and the pumping of oxygen into the third empty chamber by the third pump cell in step d) are performed in synchronization with the stopping of the first pumping operation by the first pump cell or the second pumping operation in step b).

[0020] This invention 12 The manner of is, 10 A method for measuring concentration using a gas sensor according to the embodiment, characterized in that the pumping of oxygen into the second empty chamber by the second pump cell in step c) and the pumping of oxygen into the third empty chamber by the third pump cell in step d) are performed from the middle of the first pumping operation by the first pump cell in step b) until the middle of stopping the first pumping operation or the middle of the second pumping operation. [Effects of the Invention]

[0021] The first to the first of the present invention 12 According to this embodiment, a gas sensor capable of measuring the concentrations of water vapor and carbon dioxide can also determine the concentration of oxygen with better accuracy than conventional methods.

[0022] Furthermore, this invention 5 or the 12 According to this embodiment, the decrease in the measurement accuracy of the gas sensor caused by the re-reduction of water vapor and carbon dioxide produced by the oxidation of hydrogen and carbon monoxide is suitably suppressed. [Brief explanation of the drawing]

[0023] [Figure 1] This diagram schematically shows an example of the configuration of the gas sensor 100. [Figure 2] This is a block diagram showing the functional components implemented in the controller 110. [Figure 3]This is a schematic diagram showing the gas inflow and outflow in the four voids (internal cavities) of the sensor element 10. [Figure 4] This is a schematic diagram showing the gas inflow and outflow in the three voids (internal cavities) of the sensor element 10β. [Figure 5] This graph shows the relationship between the target value of the electromotive force V0 (control voltage) in the auxiliary vacant chamber sensor cell 84 and the oxygen pump current Ip0 flowing through the auxiliary regulating pump cell 80 when three different model gases are flowed through it. [Figure 6] This diagram illustrates a malfunction that may occur when the gas sensor 100 continuously performs measurements based on its basic operation. [Figure 7] This diagram illustrates a malfunction that may occur when the gas sensor 100 continuously performs measurements based on its basic operation. [Figure 8] This figure shows the time evolution of the target values ​​of electromotive forces V1, V2, and V3 during the generated gas discharge operation. [Figure 9] This is a schematic diagram showing the gas inflow and outflow in the four empty chambers during the generated gas discharge operation. [Figure 10] This figure shows yet another example of the generated gas discharge operation. [Modes for carrying out the invention]

[0024] <First Embodiment> <Gas sensor configuration> Figure 1 is a schematic diagram showing an example of the configuration of the gas sensor 100 according to this embodiment. The gas sensor 100 is a multi-gas sensor that detects multiple types of gas components using a sensor element 10 and measures their concentrations. In this embodiment, at least water vapor (H2O) and carbon dioxide (CO2) are assumed to be the main gas components to be detected by the gas sensor 100. The gas sensor 100 is used, for example, by being installed in the exhaust path of an internal combustion engine such as an automobile engine, and the exhaust gas flowing through the exhaust path is used as the gas to be measured. Figure 1 includes a vertical cross-sectional view along the longitudinal direction of the sensor element 10.

[0025] The sensor element 10 has a long, plate-shaped structure (base) 14 made of an oxygen ion conductive solid electrolyte, a gas inlet 16 formed at one end of the structure 14 (left end in the drawing) into which the gas to be measured is introduced, and a sub-adjustment chamber 18, a first chamber (main adjustment chamber) 19, a second chamber 20, and a third chamber 21 formed within the structure 14 and communicating sequentially from the gas inlet 16. The sub-adjustment chamber 18 communicates with the gas inlet 16 via a first diffusion rate-limiting section 30. The first (main adjustment) chamber 19 communicates with the sub-adjustment chamber 18 via a second diffusion rate-limiting section 32. The second chamber 20 communicates with the first (main adjustment) chamber 19 via a third diffusion rate-limiting section 34. The third chamber 21 communicates with the second chamber 20 via a fourth diffusion rate-limiting section 36.

[0026] The structure 14 is constructed by stacking multiple layers of substrates, for example, made of ceramics. Specifically, the structure 14 has a configuration in which six layers, consisting of a first substrate 22a, a second substrate 22b, a third substrate 22c, a first solid electrolyte layer 24, a spacer layer 26, and a second solid electrolyte layer 28, are stacked from bottom to top. Each layer is made of an oxygen ion conductive solid electrolyte, such as zirconia (ZrO2).

[0027] The gas inlet 16, the first diffusion rate-limiting section 30, the sub-adjustment chamber 18, the second diffusion rate-limiting section 32, the first (main adjustment) chamber 19, the third diffusion rate-limiting section 34, the second chamber 20, the fourth diffusion rate-limiting section 36, and the third chamber 21 are formed in this order on one end side of the structure 14, between the lower surface 28b of the second solid electrolyte layer 28 and the upper surface 24a of the first solid electrolyte layer 24. The section from the gas inlet 16 to the third chamber 21 is also referred to as the gas flow section.

[0028] The gas inlet 16, the sub-adjustment chamber 18, the first (main adjustment) chamber 19, the second chamber 20, and the third chamber 21 are formed so as to penetrate the spacer layer 26 in the thickness direction. In the upper part of the four chambers as seen in the drawing, the lower surface 28b of the second solid electrolyte layer 28 is exposed, and in the lower part as seen in the drawing, the upper surface 24a of the first solid electrolyte layer 24 is exposed. The sides of these four chambers are demarcated by the spacer layer 26 or one of the diffusion-limiting sections.

[0029] The first diffusion rate-limiting section 30, the second diffusion rate-limiting section 32, the third diffusion rate-limiting section 34, and the fourth diffusion rate-limiting section 36 are all equipped with two horizontally elongated slits. That is, they have openings that extend long in a direction perpendicular to the drawing, at the top and bottom of the drawing.

[0030] Furthermore, a reference gas introduction space 38 is provided at the other end (right end in the drawing) of the sensor element 10 opposite to the end where the gas inlet 16 is located. The reference gas introduction space 38 is formed between the upper surface 22c1 of the third substrate 22c and the lower surface 26b of the spacer layer 26. The side of the reference gas introduction space 38 is partitioned by the side surface of the first solid electrolyte layer 24. A reference gas, such as oxygen (O2) or air, is introduced into the reference gas introduction space 38.

[0031] The gas inlet 16 is a part that opens to the external space, and the gas to be measured is taken into the sensor element 10 from the external space through the gas inlet 16.

[0032] The first diffusion rate-limiting section 30 is a part that imparts a predetermined diffusion resistance to the gas to be measured, which is introduced from the gas inlet 16 into the sub-adjustment chamber 18.

[0033] The auxiliary adjustment chamber 18 is provided as a space for drawing oxygen from the gas to be measured, which is introduced into the auxiliary adjustment chamber 18 from the gas inlet 16. This oxygen drawing is achieved by the operation of the auxiliary adjustment pump cell 80.

[0034] Furthermore, the sub-adjustment chamber 18 also functions as a buffer space. That is, the sub-adjustment chamber 18 also has the function of canceling out concentration fluctuations of the gas being measured caused by pressure fluctuations of the gas being measured in the external space. Examples of such pressure fluctuations of the gas being measured include pulsations in the exhaust pressure of automobile exhaust gases.

[0035] The sub-regulation pump cell 80 is an electrochemical pump cell comprising an internal sub-regulation pump electrode 82 provided over substantially the entire area facing the sub-regulation cavity 18 on the lower surface 28b of the second solid electrolyte layer 28, an external pump electrode 44 provided on one main surface (upper surface in the drawing) of the second solid electrolyte layer 28 in a manner exposed to the external space, and the second solid electrolyte layer 28 sandwiched between the two electrodes.

[0036] In the sub-regulating pump cell 80, a voltage Vp0 is applied between the sub-regulating inner pump electrode 82 and the outer pump electrode 44 by a variable power supply 86 located outside the sensor element 10, generating an oxygen pump current (oxygen ion current) Ip0. This makes it possible to pump oxygen from the atmosphere inside the sub-regulating chamber 18 into the outside space.

[0037] The auxiliary adjustment inner pump electrode 82 and outer pump electrode 44 are provided as porous cermet electrodes with a rectangular shape in plan view, for example, containing platinum (Pt) or an alloy of platinum and gold (Au) (Pt-Au alloy) as the metallic component, such as Pt or Pt-Au alloy and zirconia (ZrO2).

[0038] Furthermore, the sensor element 10 has a sub-adjustment chamber sensor cell 84, which is an electrochemical sensor cell for determining the partial pressure of oxygen in the atmosphere within the sub-adjustment chamber 18. The sub-adjustment chamber sensor cell 84 is composed of a sub-adjustment internal pump electrode 82, a reference electrode 48, and a solid electrolyte present in the portion of the structure 14 sandwiched between the two electrodes.

[0039] The reference electrode 48 is an electrode formed between the first solid electrolyte layer 24 and the third substrate 22c, and is provided as a porous cermet electrode with a rectangular shape in plan view, containing platinum and zirconia, similar to the outer pump electrode 44.

[0040] A reference gas introduction layer 52, made of porous alumina and connected to a reference gas introduction space 38, is provided around the reference electrode 48. The reference gas from the reference gas introduction space 38 is introduced to the surface of the reference electrode 48 via the reference gas introduction layer 52. In other words, the reference electrode 48 is always in contact with the reference gas.

[0041] In the auxiliary adjustment vacant chamber sensor cell 84, an electromotive force V0 is generated between the auxiliary adjustment internal pump electrode 82 and the reference electrode 48, corresponding to the difference between the oxygen concentration (partial pressure of oxygen) in the auxiliary adjustment vacant chamber 18 and the oxygen concentration (partial pressure of oxygen) of the reference gas. Since the oxygen concentration (partial pressure of oxygen) of the reference gas is basically constant, the electromotive force V0 will be a value corresponding to the oxygen concentration (partial pressure of oxygen) in the auxiliary adjustment vacant chamber 18.

[0042] The second diffusion rate-limiting section 32 is a part that imparts a predetermined diffusion resistance to the gas to be measured, from which oxygen has been pumped out, as it is introduced from the sub-adjustment chamber 18 into the first (main adjustment) chamber 19.

[0043] The first (main adjustment) void 19 is provided as a space to reduce (decompose) H2O and CO2, which are contained as detection target gas components in the gas to be measured introduced through the second diffusion rate-limiting unit 32, to produce hydrogen (H2) and carbon monoxide (CO), so that the gas to be measured is substantially free of not only oxygen but also H2O and CO2. This reduction (decomposition) of H2O and CO2 is achieved by the operation of the first (main adjustment) pump cell 40.

[0044] The first (main regulating) pump cell 40 is an electrochemical pump cell composed of a first (main regulating) inner pump electrode 42, an outer pump electrode 44, and a solid electrolyte present in the portion of the structure 14 sandwiched between the two electrodes.

[0045] In the first (main adjustment) pump cell 40, a voltage Vp1 is applied between the first (main adjustment) inner pump electrode 42 and the outer pump electrode 44 by a variable power supply 46 located outside the sensor element 10, generating an oxygen pump current (oxygen ion current) Ip1. This makes it possible to pump the oxygen from the first (main adjustment) empty chamber 19 to the outside.

[0046] The first (main adjustment) inner pump electrode 42 is provided on substantially the entire surface of the upper surface 24a of the first solid electrolyte layer 24, the lower surface 28b of the second solid electrolyte layer 28, and the side surface of the spacer layer 26, which demarcate the first (main adjustment) void 19. The first (main adjustment) inner pump electrode 42 provided in these areas is electrically connected to one another. Furthermore, the first (main adjustment) inner pump electrode 42 provided on the lower surface 28b of the second solid electrolyte layer 28 is preferably positioned opposite the outer pump electrode 44 with the second solid electrolyte layer 28 in between.

[0047] The first (main adjustment) inner pump electrode 42 is provided as a porous cermet electrode with a rectangular shape in plan view, for example, containing platinum and zirconia as the metallic component.

[0048] Furthermore, the sensor element 10 has a first (main adjustment) vacant chamber sensor cell 50, which is an electrochemical sensor cell for determining the partial pressure of oxygen in the atmosphere inside the first (main adjustment) vacant chamber 19. This first (main adjustment) vacant chamber sensor cell 50 is composed of a first (main adjustment) inner pump electrode 42, a reference electrode 48, and a solid electrolyte present in the portion of the structure 14 sandwiched between the two electrodes.

[0049] In the first (main adjustment) vacant chamber sensor cell 50, an electromotive force V1 is generated between the first (main adjustment) inner pump electrode 42 and the reference electrode 48, corresponding to the difference between the oxygen concentration (partial pressure of oxygen) in the first (main adjustment) vacant chamber 19 and the oxygen concentration (partial pressure of oxygen) of the reference gas. The electromotive force V1 is a value corresponding to the oxygen concentration (partial pressure of oxygen) in the first (main adjustment) vacant chamber 19.

[0050] The third diffusion rate-limiting section 34 is a part that imparts a predetermined diffusion resistance to the gas to be measured, which is introduced from the first (main adjustment) vacant chamber 19 to the second vacant chamber 20 and contains H2 and CO, but substantially does not contain H2O, CO2, or oxygen.

[0051] The second void 20 is provided as a space for selectively oxidizing only H2 from the H2 and CO contained in the gas to be measured, which is introduced through the third diffusion rate-limiting section 34, in order to generate H2O again. This generation of H2O by oxidation of H2 is achieved by the operation of the second pump cell 54.

[0052] The second pump cell 54 is an electrochemical pump cell composed of a second inner pump electrode 56, an outer pump electrode 44, and a solid electrolyte present in the portion of the structure 14 sandwiched between the two electrodes.

[0053] In the second pump cell 54, a voltage Vp2 is applied between the second inner pump electrode 56 and the outer pump electrode 44 by a variable power supply 60 located outside the sensor element 10, generating an oxygen pump current (oxygen ion current) Ip2. This makes it possible to draw oxygen from the outside space into the second void chamber 20.

[0054] The second internal pump electrodes 56 are provided on substantially the entire upper surface 24a of the first solid electrolyte layer 24, the lower surface 28b of the second solid electrolyte layer 28, and the side surface of the spacer layer 26, which demarcate the second cavity 20. The second internal pump electrodes 56 provided in these areas are electrically connected to each other.

[0055] The second internal pump electrode 56 is provided as a porous cermet electrode with a rectangular shape in plan view, for example, containing a Pt-Au alloy as the metallic component and zirconia.

[0056] Furthermore, the sensor element 10 has a second vacant chamber sensor cell 58, which is an electrochemical sensor cell for determining the partial pressure of oxygen in the atmosphere inside the second vacant chamber 20. The second vacant chamber sensor cell 58 is composed of a second inner pump electrode 56, a reference electrode 48, and a solid electrolyte present in the portion of the structure 14 sandwiched between the two electrodes.

[0057] In the second vacant chamber sensor cell 58, an electromotive force V2 is generated between the second inner pump electrode 56 and the reference electrode 48, corresponding to the difference between the oxygen concentration (partial pressure of oxygen) in the second vacant chamber 20 and the oxygen concentration (partial pressure of oxygen) of the reference gas. The electromotive force V2 is a value corresponding to the oxygen concentration (partial pressure of oxygen) in the second vacant chamber 20.

[0058] The fourth diffusion rate-limiting section 36 is a part that imparts a predetermined diffusion resistance to the gas to be measured, which is introduced from the second void 20 to the third void 21 and contains H2O and CO but substantially no CO2 and oxygen.

[0059] The third void 21 is provided as a space for oxidizing all the CO contained in the gas to be measured, which is introduced through the fourth diffusion rate-limiting section 36, and generating CO2 again. This generation of CO2 through the oxidation of CO is achieved by the operation of the third pump cell 61.

[0060] The third pump cell 61 is an electrochemical pump cell composed of a third inner pump electrode 62, an outer pump electrode 44, and a solid electrolyte present in the portion of the structure 14 sandwiched between the two electrodes.

[0061] In the third pump cell 61, a voltage Vp3 is applied between the third inner pump electrode 62 and the outer pump electrode 44 by a variable power supply 68 located outside the sensor element 10, generating an oxygen pump current (oxygen ion current) Ip3. This makes it possible to draw oxygen from the outside space into the third void chamber 21.

[0062] The third internal pump electrode 62 is provided on substantially the entire upper surface 24a of the first solid electrolyte layer 24 that partitions the third void 21.

[0063] The third internal pump electrode 62 is provided as a porous cermet electrode with a rectangular shape in plan view, for example, containing platinum and zirconia as the metallic component.

[0064] Furthermore, the sensor element 10 has a third vacant chamber sensor cell 66, which is an electrochemical sensor cell for determining the partial pressure of oxygen in the atmosphere inside the third vacant chamber 21. The third vacant chamber sensor cell 66 is composed of a third inner pump electrode 62, a reference electrode 48, and a solid electrolyte present in the portion of the structure 14 sandwiched between the two electrodes.

[0065] In the third vacant chamber sensor cell 66, an electromotive force V3 is generated between the third inner pump electrode 62 and the reference electrode 48, corresponding to the difference between the oxygen concentration (partial pressure of oxygen) in the third vacant chamber 21 and the oxygen concentration (partial pressure of oxygen) of the reference gas. The electromotive force V3 is a value corresponding to the oxygen concentration (partial pressure of oxygen) in the third vacant chamber 21.

[0066] Furthermore, the sensor element 10 has an electrochemical sensor cell 70 composed of an outer pump electrode 44, a reference electrode 48, and a solid electrolyte present in the portion of the structure 14 sandwiched between the two electrodes. In this sensor cell 70, the electromotive force Vref between the outer pump electrode 44 and the reference electrode 48 is a value corresponding to the partial pressure of oxygen in the gas to be measured, which is present outside the sensor element 10.

[0067] In addition to the above, the sensor element 10 is equipped with a heater 72 sandwiched between the second substrate 22b and the third substrate 22c from above and below. The heater 72 generates heat by being supplied with power from the outside via a heater electrode (not shown) provided on the lower surface 22a2 of the first substrate 22a. The heater 72 is embedded throughout the entire range from the sub-adjustment chamber 18 to the third chamber 21, and is capable of heating the sensor element 10 to a predetermined temperature and even maintaining that temperature. The heat generated by the heater 72 increases the oxygen ion conductivity of the solid electrolyte constituting the sensor element 10.

[0068] Above and below the heater 72, a heater insulating layer 74 made of alumina or the like is formed to provide electrical insulation from the second substrate 22b and the third substrate 22c. Hereinafter, the heater 72, heater electrode, and heater insulating layer 74 will be collectively referred to as the heater section.

[0069] The gas sensor 100 also includes a controller 110 that controls the operation of the sensor element 10 and is responsible for determining the concentration of the target gas component based on the current flowing through the sensor element 10.

[0070] Figure 2 is a block diagram showing the functional components realized in the controller 110. The controller 110 is composed of, for example, one or more CPUs (Central Processing Units) and one or more electronic circuits having a memory device, etc. The electronic circuit is also a software function unit in which predetermined functional components are realized by the CPU executing a predetermined program stored in the memory device, for example. Of course, it may also be composed of an integrated circuit such as an FPGA (Field-Programmable Gate Array) in which multiple electronic circuits are connected according to their functions.

[0071] Furthermore, if the gas sensor 100 is installed in the exhaust path of an automobile engine and the exhaust gas flowing through the exhaust path is used as the gas to be measured, some or all of the functions of the controller 110 may be implemented in the automobile's ECU (Electronic Control Unit).

[0072] The controller 110 is a functional component realized by the execution of a predetermined program in the CPU, and includes an element operation control unit 111 that controls the operation of each part of the sensor element 10 described above, and a concentration identification unit 112 that is responsible for the process of identifying the concentration of the target gas component contained in the gas to be measured.

[0073] The element operation control unit 111 mainly comprises a sub-adjustment pump cell control unit 111A that controls the operation of the sub-adjustment pump cell 80, a first (main adjustment) pump cell control unit 111B that controls the operation of the first (main adjustment) pump cell 40, a second pump cell control unit 111C that controls the operation of the second pump cell 54, a third pump cell control unit 111D that controls the operation of the third pump cell 61, and a heater control unit 111E that controls the operation of the heater 72.

[0074] On the other hand, the concentration identification unit 112 mainly comprises a water vapor concentration identification unit 112C and a carbon dioxide concentration identification unit 112D, which identify the concentrations of H2O and CO2, respectively, which are the main gas components to be detected in the gas sensor 100, and further comprises an oxygen concentration identification unit 112A, which identifies the concentration of oxygen contained in the gas being measured. In other words, in the gas sensor 100 according to this embodiment, in addition to H2O and CO2, which are the main gas components to be detected, oxygen is also detected as an incidental gas component to be detected, and its concentration is identified. The details will be described below.

[0075] <Multi-gas detection and concentration determination> Next, we will explain how to detect multiple types of gases (multi-gas detection) and how to determine the concentration of the detected gases, which are realized in the gas sensor 100 having the configuration described above.Hereafter, we will assume that the gas to be measured is exhaust gas containing oxygen, H2O, and CO2.

[0076] Figure 3 is a schematic diagram showing the gas inflow and outflow in the four voids (internal cavities) of the sensor element 10 of the gas sensor 100. Figure 4 is a schematic diagram showing the gas inflow and outflow in the three voids (internal cavities) of a sensor element 10β that does not have a sub-adjustment void 18 and a second diffusion rate-limiting unit 32, for comparison. In the sensor element 10β, the gas inlet 16 and the first void 19 are in communication via the first diffusion rate-limiting unit 30. Furthermore, the sensor element 10β does not have a sub-adjustment pump cell 80 and a sensor cell 84 for the sub-adjustment void corresponding to the sub-adjustment void 18, and naturally, a gas sensor equipped with the sensor element 10β does not require a sub-adjustment pump cell control unit 111A and a variable power supply 86. The sensor element 10β is generally equivalent to the sensor element of a conventional gas sensor having three internal cavities, as disclosed in Patent Document 1.

[0077] First, in the sensor element 10 of the gas sensor 100 according to this embodiment, as described above, the gas to be measured is introduced from the gas inlet 16 to the sub-adjustment chamber 18. In the sub-adjustment chamber 18, oxygen is drawn out from the introduced gas to be measured by the operation of the sub-adjustment pump cell 80.

[0078] The oxygen pumping is performed by the sub-regulating pump cell control unit 111A of the controller 110 setting the target value (control voltage) of the electromotive force V0 in the sub-regulating empty chamber sensor cell 84 to a value within the range of 400mV to 700mV (preferably 400mV), and then feedback-controlling the voltage Vp0 that the variable power supply 86 applies to the sub-regulating pump cell 80 according to the difference between the actual value of the electromotive force V0 and the target value, so that the electromotive force V0 is maintained at the target value. For example, when the gas to be measured, which contains a large amount of oxygen, reaches the sub-regulating empty chamber 18, the value of the electromotive force V0 deviates significantly from the target value, so the sub-regulating pump cell control unit 111A controls the pump voltage Vp0 that the variable power supply 86 applies to the sub-regulating pump cell 80 so that the deviation decreases.

[0079] In this manner, oxygen is pumped out of the sub-regulating chamber 18 by the sub-regulating pump cell 80, so that the partial pressure of oxygen in the sub-regulating chamber 18 is kept at a sufficiently low value so as not to cause reduction of H2O and CO2 contained in the gas being measured. For example, if V0 = 400mV, then 10 -8 It will be about the same as an ATM.

[0080] Figure 5 is a diagram illustrating why oxygen is pumped within a range where the reduction of H2O and CO2 does not occur, by setting the target value of the electromotive force V0 to a value within the range of 400mV to 700mV. Specifically, Figure 5 is a graph showing the relationship between the target value of the electromotive force V0 (control voltage) in the sub-control room sensor cell 84 and the oxygen pump current Ip0 flowing through the sub-control pump cell 80 when three different model gases are flowed through it. Specifically, the three model gases are a first gas containing 10% oxygen, a second gas containing 10% each of oxygen and CO2, and a third gas containing 10% each of oxygen and H2O. In all gases, the remainder was nitrogen (N2). The temperature of the sensor element 10 was set to 800°C, and the temperature of the model gases was set to 150°C.

[0081] Figure 5 shows that, for the first gas, the oxygen pump current Ip0 remains approximately constant in the range where the control voltage is 0.4V or higher. In contrast, for the second and third gases, the profile is approximately the same as that of the first gas in the range where the control voltage is 0.7V or lower, but when the control voltage exceeds 0.7V, the oxygen pump current Ip0 increases again. This increase is caused by the superposition of reduction currents for H2O or CO2, which flow when H2O or CO2 contained in the measured gas is reduced (decomposed) to generate oxygen.

[0082] Based on this, in this embodiment, the target value of the electromotive force V0 is set to a value within the range of 400mV to 700mV. However, from the viewpoint of ensuring the durability of the electrodes, it is preferable to keep the electromotive force V0 as low as possible, so it is judged that the target value of the electromotive force V0 is preferably 400mV.

[0083] The gas to be measured, from which oxygen has been drawn in the secondary adjustment chamber 18, is introduced into the first (main adjustment) chamber 19. In the first (main adjustment) chamber 19, the first (main adjustment) pump cell 40 operates, drawing out even more oxygen from the gas to be measured that was introduced after oxygen had been drawn out in the secondary adjustment chamber 18. As a result, the reduction (decomposition) reaction of H2O and CO2 contained in the gas to be measured (2H2O → 2H2 + O2, 2CO2 → 2CO + O2) proceeds, and virtually all of the H2O and CO2 are decomposed into hydrogen (H2), carbon monoxide (CO), and oxygen, and the resulting oxygen is also drawn out.

[0084] The decomposition of H2O and CO2 and the pumping out of the resulting oxygen are carried out by the first (main adjustment) pump cell control unit 111B of the controller 110 setting the target value (control voltage) of the electromotive force V1 in the first (main adjustment) empty room sensor cell 50 to a value within the range of 1000mV to 1500mV (preferably 1000mV), and then feedback-controlling the voltage Vp1 that the variable power supply 46 applies to the first (main adjustment) pump cell 40 according to the difference between the actual value of the electromotive force V1 and the target value, so that the electromotive force V1 is maintained at the target value. It should be noted that it is preferable to set the target value of the electromotive force V1 to a value within the range of 1000mV to 1500mV, as can be seen from the graph shown in Figure 5.

[0085] In this manner, the operation of the first (main regulating) pump cell 40 keeps the oxygen partial pressure in the first (main regulating) vacant chamber 19 at an even lower value than the oxygen partial pressure in the secondary regulating vacant chamber 18. For example, if V1 = 1000 mV, then 10 -20 The pressure will be around atm. As a result, the measured gas will effectively contain no H2O, CO2, or oxygen.

[0086] The gas to be measured, which contains H2 and CO but substantially no H2O, CO2, and oxygen, is introduced into the second vacant room 20.

[0087] On the other hand, in the case of the sensor element 10β shown in Figure 4, the gas to be measured, which is taken into the element from the gas inlet 16, is introduced into the first void chamber 19. In this first void chamber 19, the first pump cell 40 operates to simultaneously decompose the H2O and CO2 contained in the introduced gas to be measured into hydrogen (H2), carbon monoxide (CO), and oxygen, and to pump out the oxygen.

[0088] This is achieved by the first pump cell control unit 111B setting a target value (control voltage) for the electromotive force V1 in the first vacant chamber sensor cell 50 to a value within the range of 1000mV to 1500mV, and then feedback-controlling the voltage Vp1 applied by the variable power supply 46 to the first pump cell 40 according to the difference between the actual electromotive force V1 and the target value, so that the target value is achieved. Therefore, the resulting gas is similar to that of the sensor element 10, containing H2 and CO, while substantially free of H2O, CO2, and oxygen. This gas is then introduced into the second vacant chamber 20.

[0089] The subsequent processing is common to both sensor element 10 and sensor element 10β. First, in the second void chamber 20, oxygen is drawn in by the operation of the second pump cell 54, and only the H2 contained in the gas to be measured is oxidized.

[0090] The oxygen supply is performed by the second pump cell control unit 111C of the controller 110 setting the target value (control voltage) of the electromotive force V2 in the second empty chamber sensor cell 58 to a value within the range of 250mV to 450mV (preferably 350mV), and by feedback-controlling the voltage Vp2 applied by the variable power supply 60 to the second pump cell 54 according to the difference between the actual value of the electromotive force V2 and the target value, so that the electromotive force V2 is maintained at the target value.

[0091] In this manner, the operation of the second pump cell 54 promotes the oxidation (combustion) reaction 2H2 + O2 → 2H2O within the second empty chamber 20, thereby generating an amount of H2O that correlates with the amount of H2O introduced from the gas inlet 16. In this embodiment, the correlation between the amounts of H2O or CO2 means that the amount of H2O or CO2 introduced from the gas inlet 16 and the amount of H2O or CO2 generated again by the oxidation of the H2 and CO produced by their decomposition are equal in amount or within a certain error range that is acceptable in terms of measurement accuracy.

[0092] By setting the target value of the electromotive force V2 to a value within the range of 250mV to 450mV, the oxygen partial pressure in the second vacant chamber 20 is maintained at a value in which almost all H2 is oxidized but CO is not oxidized. For example, if V2 = 350mV, then 10 -7 It will be about the same as an ATM.

[0093] At this time, the oxygen pump current Ip2 (hereinafter also referred to as the water vapor detection current Ip2) flowing through the second pump cell 54 is approximately proportional to the concentration of H2O produced by the combustion of H2 in the second void 20 (there is a linear relationship between the water vapor detection current Ip2 and the concentration of H2O produced). The amount of H2O produced by this combustion correlates with the amount of H2O in the gas being measured that is introduced from the gas inlet 16 and then decomposed in the first (main adjustment) void 19. Therefore, when the water vapor detection current Ip2 is detected in the second pump cell control unit 111C, it means that H2O in the gas being measured has been detected.

[0094] Furthermore, a linear relationship exists between the water vapor detection current Ip2 and the water vapor concentration in the gas being measured. Data showing this linear relationship (water vapor characteristic data) is predetermined using a model gas with a known water vapor concentration and is stored in the water vapor concentration identification unit 112C. In the gas sensor 100 according to this embodiment, the water vapor concentration identification unit 112C acquires the value of the water vapor detection current Ip2 detected by the second pump cell control unit 111C. The water vapor concentration identification unit 112C refers to the water vapor characteristic data and identifies the value of the water vapor concentration corresponding to the acquired water vapor detection current Ip2. This determines the water vapor concentration in the gas being measured.

[0095] Furthermore, if H2O is not present in the gas being measured introduced from the gas inlet 16, then naturally, no decomposition of H2O will occur in the first (main adjustment) vacant chamber 19, and therefore H2 will not be introduced into the second vacant chamber 20, resulting in a water vapor detection current Ip2 being almost zero.

[0096] As H2 is oxidized to H2O, the gas to be measured contains H2O and CO, but substantially no CO2 or oxygen. This gas to be measured is introduced into the third vacant chamber 21. In the third vacant chamber 21, the third pump cell 61 operates to draw in oxygen, and the CO contained in the introduced gas to be measured is oxidized.

[0097] The oxygen supply is performed by the third pump cell control unit 111D of the controller 110 setting the target value (control voltage) of the electromotive force V3 in the third empty chamber sensor cell 66 to a value within the range of 100mV to 300mV (preferably 200mV), and by feedback-controlling the voltage Vp3 applied by the variable power supply 68 to the third pump cell 61 according to the difference between the actual value of the electromotive force V3 and the target value, so that the electromotive force V3 is maintained at the target value.

[0098] In this manner, the operation of the third pump cell 61 promotes the oxidation (combustion) reaction 2CO + O2 → 2CO2 within the third vacant chamber 21, thereby generating a quantity of CO2 that correlates with the amount of CO2 introduced from the gas inlet 16.

[0099] By setting the target value of the electromotive force V3 to a value within the range of 100mV to 300mV, the partial pressure of oxygen in the third vacant chamber 21 is maintained at a value within the range where almost all of the CO is oxidized. For example, if V3 = 200mV, then 10 -4 It will be about the same as an ATM.

[0100] At this time, the oxygen pump current Ip3 (hereinafter also referred to as the carbon dioxide detection current Ip3) flowing through the third pump cell 61 is approximately proportional to the concentration of CO2 produced by the combustion of CO in the third void 21 (there is a linear relationship between the carbon dioxide detection current Ip3 and the concentration of CO2 produced). The amount of CO2 produced by this combustion correlates with the amount of CO2 in the gas being measured that has been introduced from the gas inlet 16 and then decomposed in the first (main adjustment) void 19. Therefore, when the carbon dioxide detection current Ip3 is detected in the third pump cell control unit 111D, it means that CO2 in the gas being measured has been detected.

[0101] Furthermore, a linear relationship exists between the carbon dioxide detection current Ip3 and the carbon dioxide concentration in the gas being measured. Data showing this linear relationship (carbon dioxide characteristic data) is predetermined using a model gas with a known carbon dioxide concentration and is stored in the carbon dioxide concentration identification unit 112D. In the gas sensor 100 according to this embodiment, the carbon dioxide concentration identification unit 112D acquires the value of the carbon dioxide detection current Ip3 detected by the third pump cell control unit 111D. The carbon dioxide concentration identification unit 112D refers to the carbon dioxide characteristic data and identifies the carbon dioxide concentration value corresponding to the acquired carbon dioxide detection current Ip3. This determines the carbon dioxide concentration in the gas being measured.

[0102] Furthermore, if CO2 is not present in the gas being measured introduced from the gas inlet 16, then naturally, no decomposition of CO2 will occur in the first (main adjustment) vacant chamber 19, and therefore CO will not be introduced into the third vacant chamber 21, resulting in a carbon dioxide detection current Ip3 of approximately zero.

[0103] As described above, regardless of whether the gas sensor is equipped with sensor element 10 or sensor element 10β, it is possible to suitably determine the water vapor concentration and carbon dioxide concentration.

[0104] In addition, in the case of the gas sensor 100 according to this embodiment, the sensor element 10 further includes a sub-adjustment chamber 18, and the sensor element 10β performs the oxygen extraction and decomposition of H2O and CO2, which are carried out in conjunction with the gas to be measured introduced into the first (main adjustment) chamber 19, in two separate steps at the sub-adjustment chamber 18 and the first (main adjustment) chamber 19, thereby enabling the determination of the oxygen concentration contained in the gas to be measured.

[0105] Specifically, in the gas sensor 100 according to this embodiment, as described above, oxygen is pumped out from the gas to be measured introduced from the gas inlet 16 in the sub-adjustment chamber 18. This oxygen pumping is performed in a range where no reduction of H2O and CO2 occurs, by the operation of the sub-adjustment pump cell 80. At that time, the oxygen pump current Ip0 (hereinafter also referred to as oxygen detection current Ip0) flowing through the sub-adjustment pump cell 80 is approximately proportional to the concentration of oxygen contained in the gas to be measured introduced from the gas inlet 16. In other words, a linear relationship is established between the oxygen detection current Ip0 and the oxygen concentration in the gas to be measured. Data showing this linear relationship (oxygen characteristic data) is determined in advance using a model gas with a known oxygen concentration and is stored in the oxygen concentration determination unit 112A. In the gas sensor 100 according to this embodiment, the oxygen concentration determination unit 112A acquires the value of the oxygen detection current Ip0 detected by the sub-adjustment pump cell control unit 111A. The oxygen concentration identification unit 112A refers to the oxygen characteristic data and identifies the oxygen concentration value corresponding to the acquired oxygen detection current Ip0. This determines the oxygen concentration in the gas being measured.

[0106] To confirm, in the case of the sensor element 10β shown in Figure 4, the target value (control voltage) of the electromotive force V1 in the first vacant chamber sensor cell 50 is set to a value within the range of 1000mV to 1500mV, thereby enabling the first pump cell 40 to pump oxygen from the first vacant chamber 19 and reduce H2O and CO2. However, the range of the target value of the electromotive force V1 falls within the range where reduction of H2O and CO2 occurs in the graph shown in Figure 5. Therefore, it is not possible to determine the concentration of oxygen contained in the gas to be measured introduced from the gas inlet 16 based on the value of the pump current Ip1 flowing through the first pump cell 40 at this time.

[0107] Furthermore, even in the case of a gas sensor equipped with sensor element 10β, it is possible to indirectly determine the concentration of oxygen contained in the gas being measured. Roughly speaking, this is the difference between the concentration of oxygen drawn out from the first void chamber 19 (let's call this C1) and the concentrations of oxygen drawn into the second void chamber 20 and the third void chamber 21 (let's call them C2 and C3, respectively). C = C1 - C2 - C3 ... (1) However, this corresponds to the oxygen concentration in the gas being measured, which is introduced from the gas inlet 16. Since C1, C2, and C3 are values ​​that are approximately proportional to the oxygen pump currents Ip1, Ip2, and Ip3, respectively, if the relationship (proportionality constant) between C1 and Ip1, C2 and Ip2, and C3 and Ip3 is determined in advance, it is possible to determine the oxygen concentration in the gas being measured from the detected values ​​of the oxygen pump currents Ip1, Ip2, and Ip3. Hereafter, this method will be referred to as the finite difference method.

[0108] However, since each detected oxygen pump current Ip1, Ip2, and Ip3 has an independent measurement error, the maximum error in equation (1) becomes larger according to the law of error propagation.

[0109] In contrast, in the case of the gas sensor 100 according to this embodiment, since the oxygen detection current Ip0 and the oxygen concentration are approximately proportional, if the proportionality constant is experimentally determined in advance, the oxygen concentration can be directly determined from the value of the oxygen detection current Ip0. Hereinafter, the method for deriving the oxygen concentration that can be performed with the gas sensor 100 according to this embodiment will be referred to as the direct method. According to this direct method, a value with better accuracy can be obtained than when the concentration value is determined by the difference method described above.

[0110] As described above, according to this embodiment, in a gas sensor capable of measuring the concentrations of H2O and CO2, the concentration of oxygen can be determined with even greater accuracy than in conventional devices.

[0111] <Example of the first embodiment> We evaluated the measurement errors of oxygen concentration using both the difference method and the direct method.

[0112] (difference method) First, regarding the oxygen concentrations C1, C2, and C3 and the oxygen pump currents Ip1, Ip2, and Ip3, the following proportional relationships are assumed to hold between C1 and Ip1, between C2 and Ip2, and between C3 and Ip3, respectively. Note that the units for oxygen concentrations C1, C2, and C3 are %, the units for oxygen pump currents Ip1, Ip2, and Ip3 are mA, and the direction in which oxygen is pumped out is considered positive for oxygen pump currents Ip1, Ip2, and Ip3.

[0113] C1 = 19.69Ip1; C2 = -21.65Ip2; C3 = -29.53Ip3.

[0114] Thus, equation (1) can be expressed as follows:

[0115] C=19.69Ip1+21.65Ip2+29.53Ip3 ····(2) A model gas containing 10% each of oxygen, CO2, and H2O, with the remainder being nitrogen, was used as the gas to be measured. The oxygen pump currents Ip1, Ip2, and Ip3 were measured using a gas sensor equipped with a sensor element 10β. The temperature of the sensor element was set to 800°C, and the temperature of the model gas was set to 150°C.

[0116] As a result, the following values ​​were obtained.

[0117] Ip1 = 2.27mA; Ip2 = -1.37mA; Ip3 = -0.17mA.

[0118] Note that the values ​​of Ip2 and Ip3 are negative because the oxygen pump current is considered positive when it is being pumped out.

[0119] Here, assuming a measurement error of ±1% for each oxygen pump current Ip1, Ip2, and Ip3, the ranges of oxygen pump currents Ip1, Ip2, and Ip3 considering this measurement error are as follows.

[0120] Ip1 = 2.27 ± 0.0227 mA; Ip2 = -1.37 ± 0.0137 mA; Ip3 = -0.17 ± 0.0017 mA.

[0121] Considering these ranges, the range of the concentration value C, including the error, obtained from equation (2) is: C = 10 ± 0.8 (%) This means that the concentration value C obtained by the difference method may have an error of up to ±8 / 100 relative to the median.

[0122] (direct method) First, assume that the following proportional relationship holds between the oxygen concentration C and the oxygen pump current (oxygen detection current) Ip0. Note that the unit of oxygen concentration C is %, and the unit of oxygen pump current Ip0 is mA.

[0123] C=37.04Ip0 ····(3) As the gas to be measured, a model gas containing 10% each of oxygen, CO2, and H2O, with the remainder being nitrogen, was used, as in the case of the finite difference method, and sensor element 1 0 The oxygen pump currents Ip0, Ip1, Ip2, and Ip3 were measured using the provided gas sensor. The sensor element temperature was set to 800°C, and the model gas temperature was set to 150°C. The following values ​​were obtained as a result.

[0124] Ip0 = 0.27mA; Ip1 = 1.85mA; Ip2 = -1.24mA; Ip3 = -0.15mA.

[0125] Here, assuming a measurement error of ±1% for each oxygen pump current Ip0, the range of oxygen pump current Ip0 considering this measurement error is as follows.

[0126] Ip0 = 0.27 ± 0.0027 mA.

[0127] Considering the relevant range, the range of the concentration value C, including error, obtained from equation (3) is: C = 10 ± 0.1 (%) This means that the concentration value C obtained by the direct method may have an error of up to ±1 / 100 of the median value.

[0128] Comparing these results with those obtained using the finite difference method, it can be seen that the measurement error in the direct method is suppressed to 1 / 8 of that of the finite difference method. These results indicate that the direct method is a superior method for determining oxygen concentration compared to the finite difference method.

[0129] <Second Embodiment> <Concentration determination considering continuous use> Hereafter, the operating mode of the gas sensor 100 equipped with the sensor element 10, as explained with reference to Figure 3, will also be referred to as the basic operation. Figures 6 and 7 are diagrams illustrating potential problems that may occur when measurements based on the basic operation of the gas sensor 100 are performed continuously.

[0130] When the gas sensor 100 measures the concentrations of H2O, CO2, and oxygen in the gas being measured according to the basic operation described above, the H2O generated in the second empty chamber 20 is basically introduced into the third empty chamber 21 or remains in the second empty chamber 20. Similarly, the CO2 generated in the third empty chamber 21 is basically retained in the third empty chamber 21. Therefore, as the measurement continues, the amount of H2O and CO2 generated in the second empty chamber 20 and the third empty chamber 21 will increase.

[0131] Then, when the concentration of the gas to be measured newly introduced from the first diffusion rate-limiting section 30 (gas inlet 16) is relatively small, as shown in Figure 6, a concentration gradient can be formed in the gas flow section from the gas inlet 16 to the third void 21 such that the concentrations of H2O and CO2 increase as you move from the gas inlet 16 towards the third void 21, which is the innermost internal void.

[0132] As a result of this concentration gradient, diffusion of H2O and CO2 present in the third or second vacant chamber 21 or vacant chamber 20 from the third and second vacant chambers 21 and 20 to the first vacant chamber 19 may occur. In other words, a backflow of H2O and CO2 into the first vacant chamber 19 may occur.

[0133] As described above, in the first vacant chamber 19, the first pump cell 40 operates, continuously reducing H2O and CO2. Therefore, as shown in Figure 7, if H2O and CO2 flow back from the third vacant chamber 21 and the second vacant chamber 20, they will be (re)reduced back to H2 and CO without being distinguished from the H2O and CO2 that are the original targets of measurement at that time and are contained in the gas being measured introduced from the gas inlet 16.

[0134] When such re-reduction occurs, the H2 oxidized by the second pump cell 54 when oxygen is drawn into the second empty chamber 20 will include the H2 produced by the re-reduction, and the CO oxidized by the third pump cell 61 when oxygen is drawn into the third empty chamber 21 will include the CO produced by the re-reduction. As a result, the water vapor detection current Ip2 flowing through the second pump cell 54 and the carbon dioxide detection current Ip3 flowing through the third pump cell 61 will be superimposed with currents originating from the re-reduction H2O and CO2. In other words, the values ​​of the water vapor detection current Ip2 and the carbon dioxide detection current Ip3 will no longer correspond to the concentrations of H2O and CO2 originally contained in the gas being measured, resulting in a decrease in measurement accuracy.

[0135] In the gas sensor 100 according to this embodiment, the operation of each pump cell is controlled so as not to cause a decrease in measurement accuracy due to the backflow of H2O and CO2. In general terms, rather than suppressing the backflow of H2O and CO2 generated in the second and third void chambers 20 and 31, the operation is performed to discharge the H2O and CO2 that have backflowed into the first void chamber 19 or further into the sub-adjustment void chamber 18 to the outside of the sensor element 10, thereby ensuring measurement accuracy. This mode of operation is also referred to as the generated gas discharge operation.

[0136] Figure 8 shows the time evolution of the target values ​​of electromotive forces V1, V2, and V3 during the generated gas discharge operation. Figure 9 is a schematic diagram showing the gas inflow and outflow in the four voids (internal cavities) during the generated gas discharge operation.

[0137] As described above, in basic operation, the target value of the electromotive force V1 in the first vacant room sensor cell 50 is set to a value within the range of 1000mV to 1500mV, and the electromotive force V1 The voltage Vp1 applied to the first pump cell 40 is feedback-controlled to maintain the relevant target value.

[0138] In contrast, during the generated gas discharge operation, the operation of the first pump cell 40 is temporarily stopped, and as shown in Figure 8(a), the feedback control that maintains the target value of the electromotive force V1 in the first vacant room sensor cell 50 at a predetermined value V1a is temporarily stopped.

[0139] Here, the value V1a is within the range of 1000mV to 1500mV, similar to the target value of the electromotive force V1 in the basic operation. The value V1a may be set to the same value as the target value of the electromotive force V1 during the basic operation.

[0140] While the target value of the electromotive force V1 is set to the applicable value V1a, the first pump cell 40 pumps oxygen from the first empty chamber 19 to the outside, just as in the basic operation, so that substantially all of the H2O and CO2 contained in the gas being measured are reduced.

[0141] In contrast, when the operation of the first pump cell 40 is stopped, the reduction of H2O and CO2 in the first vacant chamber 19 is temporarily interrupted.

[0142] In other words, during the generated gas discharge operation, the first pump cell 40 temporarily stops its operation in the middle of pumping oxygen from the first empty chamber 19 so that substantially all of the water vapor and carbon dioxide contained in the gas being measured are reduced.

[0143] On the other hand, the target values ​​for electromotive force V2 and electromotive force V3 are set in the same way as in the basic operation. Specifically, the target value for electromotive force V2 is set to a value within the range of 250mV to 450mV (preferably 350mV), and the target value for electromotive force V3 is set to a value within the range of 100mV to 300mV (preferably 200mV).

[0144] In this case, the operation of the gas sensor 100 is the same as in the basic operation while the target value of the electromotive force V1 is set to value V1a. However, when the operation of the first pump cell 40 is stopped, the H2O and CO2 contained in the gas to be measured introduced into the first void 19 are no longer reduced. As a result, the H2O and CO2 generated in the second void 20 and the third void 21 accumulate, creating a concentration gradient as shown in Figure 6. Even if H2O and CO2 flow back into the first void 19, as shown in Figure 9, the backflowing H2O and CO2 are not re-reduced in the first void 19 but are discharged to the outside of the element via the sub-adjustment void 18. This weakens the concentration gradient, and as a result, the re-reduction of the backflowing H2O and CO2 becomes less likely after the target value of the electromotive force V1 is set back to value V1a. In other words, in the gas sensor 100 according to this embodiment, the pumping operation from the first void chamber 19 by the first pump cell 40 is temporarily stopped, so that H2O and CO2 generated by the selective oxidation of H2 and CO in accordance with the concentration gradient occurring in the gas flow section inside the sensor element 10 are suitably discharged to the outside of the element via the first void chamber 19 and further through the sub-adjustment void chamber 18.

[0145] The operation of the first pump cell 40 may be stopped at any time, or at a predetermined time. Alternatively, it may be stopped when certain conditions are met. For example, the longer the measured values ​​of H2O and CO2 in the gas sensor 100 remain high, the greater the amount of H2O and CO2 generated in the second and third void chambers 20 and 21. Therefore, the operation of the first pump cell 40 may be stopped based on the integrated value of these measured values.

[0146] The time during which the operation of the first pump cell 40 is stopped is preferably within the range of 1 ms to 1 s. If the setting time is shorter than 1 ms, the diffusion of H2O and CO2 from the second or third void 20 or void 21 may not proceed sufficiently, which may result in the concentration gradient not weakening sufficiently and the measurement accuracy remaining low, so this is undesirable. Also, if the setting time is longer than 1 s, the time during which the H2O and CO2 contained in the newly introduced gas to be measured cannot be reduced becomes longer, meaning that the time during which concentration measurement cannot be performed becomes longer, which is undesirable because the responsiveness decreases.

[0147] Alternatively, the first pump cell 40 may alternately and periodically perform pumping operations and their stopping to periodically temporarily halt the reduction of H2O and CO2. At the same time, the target values ​​(set values) of the electromotive force V2 in the second empty chamber sensor cell 58 and the electromotive force V3 in the third empty chamber sensor cell 66 may also be periodically changed in a manner synchronized with the periodic changes in the operation of the first pump cell 40, as shown in Figure 8(b). In other words, the pumping of oxygen by the second pump cell 54 and the third pump cell 61 may be synchronized with the stopping of the operation of the first pump cell 40.

[0148] The target values ​​for electromotive force V2 and electromotive force V3 are set to 0 while the target value of electromotive force V1 is set to value V1a and the first pump cell 40 is operating. Only when the first pump cell 40 is stopped are they set to a value within the same range as during basic operation. Note that in Figure 8(b), for the sake of illustration, both are shown in a single graph, but in reality, electromotive force V2 and electromotive force V3 are set to different values.

[0149] In this case, the reduction of H2O and CO2 in the first void 19 and the selective oxidation of H2 and CO in the second void 20 and third void 21, respectively, occur at different timings. That is, while H2 and CO are being reoxidized in the second void 20 and third void 21, the H2O and CO2 contained in the gas being measured that was introduced into the first void 19 are not reduced. Even in this case, even if the H2O and CO2 generated in the second void 20 and third void 21 accumulate and a concentration gradient as shown in Figure 6 occurs, the H2O and CO2 that flow back into the first void 19 will not be re-reduced in the first void 19 and will be discharged directly to the outside of the device.

[0150] In this case, it is preferable that the time during which the target value of the electromotive force V1 is set to the value V1a is within the range of 1 ms to 1 s.

[0151] Figure 10 shows yet another example of the generated gas discharge operation. In this case, as shown in Figure 10(a), the periodic change in the operation of the first pump cell 40 is the same as in Figure 8(a), but as shown in Figure 10(b), the phase (timing) of the periodic change in the target values ​​of electromotive force V2 and electromotive force V3 is shifted from the case shown in Figure 8(b). More specifically, the start of oxygen pumping into the second vacant chamber 20 and the third vacant chamber 21 is determined by the pumping of the first pump cell 40. broth The start time is advanced to the middle of the operation, and the pumping is completed while the first pump cell 40 is still in operation. However, the extent to which the start time is advanced is such that the first pump cell 40 is pumping. broth Time during operation (electromotive force) V1The target value is set to be less than 50% of the time Δt (the time during which the value V1a is set).

[0152] As described above, according to this embodiment, in a gas sensor having four empty chambers sequentially connected from a gas inlet, similar to the gas sensor according to the first embodiment, the reduction of H2O and CO2 in the first empty chamber is temporarily or periodically stopped, thereby allowing the H2O and CO2 generated by the oxidation of H2 and CO to be discharged from the first empty chamber to the outside of the sensor element using the concentration gradient. This effectively suppresses the decrease in measurement accuracy caused by the re-reduction of H2O and CO2 generated by the oxidation of H2 and CO.

[0153] <Modified form of the second embodiment> Instead of stopping the operation of the first pump cell 40 during the generated gas discharge operation, feedback control may be performed in which the target value of the electromotive force V1 in the first vacant chamber sensor cell 50 is set to a value less than or equal to the value set as the target value of the electromotive force V0 in the sub-adjustment vacant chamber sensor cell 84. In this case, the first pump cell 40, like the sub-adjustment pump cell 80, performs the operation of pumping out the oxygen present in the first vacant chamber 19 to the outside, within a range that does not cause reduction of H2O and CO2 contained in the gas being measured. In this case as well, the H2O and CO2 that remain in the second vacant chamber 20 and the third vacant chamber 21 and flow back into the first vacant chamber 19 are discharged to the outside of the element via the sub-adjustment vacant chamber 18 without being re-reduced in the first vacant chamber 19. [Explanation of Symbols]

[0154] 10, 10β sensor element 14 Structure 16 Gas inlet 18 Sub-adjustment vacant rooms 19. Vacant Room No. 1 (Main Adjustment) 20. Second vacancy. 21. Third vacant room 30 First diffusion-limiting section 32 Second diffusion-limiting section 34 Third diffusion-limiting region 36. Fourth diffusion-limiting region 38. Reference gas introduction space 40. First (main adjustment) pump cell 42. First (main adjustment) inner pump electrode 44 External pump electrode 46, 60, 68, 86 Variable power supply 48 Reference electrode 50. First (main adjustment) vacant room sensor cell 54 Second pump cell 56 Second Inner Pump Electrode 58 Sensor cell for the second vacant room 61 Third pump cell 62 Third Inner Pump Electrode 66 Sensor cell for the third vacant room 72 Heater 80 Sub-adjustment pump cell 82. Sub-adjustment internal pump electrode 84 Sub-adjustment vacant room sensor cell

Claims

1. A gas sensor capable of measuring the concentrations of multiple target gas components contained in a gas to be measured, which includes at least water vapor and carbon dioxide, A sensor element having a structure composed of an oxygen ion conductive solid electrolyte, A controller that controls the operation of the gas sensor, Equipped with, The aforementioned sensor element A gas inlet into which the gas to be measured is introduced, The system comprises a sub-regulating chamber, a first chamber, a second chamber, and a third chamber, which are connected sequentially from the gas inlet via different diffusion rate-limiting sections, A sub-adjustment pump cell comprising an inner electrode for sub-adjustment formed facing the sub-adjustment cavity, an outer electrode formed on the outer surface of the sensor element, and the solid electrolyte located between the inner electrode and the outer electrode, A first pump cell comprising a first inner electrode formed facing the first void, the outer electrode, and the solid electrolyte located between the first inner electrode and the outer electrode, A second pump cell comprising a second inner electrode formed facing the second cavity, the outer electrode, and the solid electrolyte located between the second inner electrode and the outer electrode, A third pump cell comprising a third inner electrode formed facing the third cavity, the outer electrode, and the solid electrolyte located between the third inner electrode and the outer electrode, A reference electrode in contact with a reference gas, A sensor cell for a sub-adjustment void, comprising the sub-adjustment inner electrode, the reference electrode, and the solid electrolyte located between the sub-adjustment inner electrode and the reference electrode, wherein an electromotive force V0 corresponding to the oxygen concentration of the sub-adjustment void is generated between the sub-adjustment inner electrode and the reference electrode, A first vacant chamber sensor cell comprising the first inner electrode, the reference electrode, and the solid electrolyte present between the first inner electrode and the reference electrode, wherein an electromotive force V1 corresponding to the oxygen concentration of the first vacant chamber is generated between the first inner electrode and the reference electrode, A second vacant chamber sensor cell comprising the second inner electrode, the reference electrode, and the solid electrolyte present between the second inner electrode and the reference electrode, wherein an electromotive force V2 corresponding to the oxygen concentration of the second vacant chamber is generated between the second inner electrode and the reference electrode, A third vacant chamber sensor cell comprising the third inner electrode, the reference electrode, and the solid electrolyte present between the third inner electrode and the reference electrode, wherein an electromotive force V3 corresponding to the oxygen concentration of the third vacant chamber is generated between the third inner electrode and the reference electrode, Equipped with, The auxiliary adjustment pump cell draws oxygen from the gas to be measured, which is introduced into the auxiliary adjustment chamber from the gas inlet, to the extent that the water vapor and carbon dioxide contained in the gas to be measured are not decomposed. The first pump cell pumps oxygen from the first chamber so that substantially all of the water vapor and carbon dioxide contained in the gas to be measured, which has been introduced into the first chamber from the sub-adjustment chamber, is decomposed. The second pump cell, by pumping oxygen into the second void, selectively oxidizes the hydrogen produced by the decomposition of water vapor contained in the gas to be measured, which is introduced from the first void to the second void, in the second void. The third pump cell, by drawing oxygen into the third void, oxidizes the carbon monoxide produced by the decomposition of carbon dioxide contained in the gas to be measured, which is introduced from the second void to the third void, in the third void. The aforementioned controller, A sub-regulating pump cell control means controls the voltage applied between the sub-regulating inner electrode and the outer electrode in the sub-regulating pump cell so that the electromotive force V0 in the sub-regulating vacant chamber sensor cell is maintained at a predetermined target value within the range of 400 mV to 700 mV. A first pump cell control means controls the voltage applied between the first inner electrode and the outer electrode in the first pump cell so that the electromotive force V1 in the first vacant room sensor cell is maintained at a predetermined target value within the range of 1000 mV to 1500 mV, A second pump cell control means controls the voltage applied between the second inner electrode and the outer electrode in the second pump cell so that the electromotive force V2 in the second vacant sensor cell is maintained at a predetermined target value within the range of 250 mV to 450 mV, A third pump cell control means controls the voltage applied between the third inner electrode and the outer electrode in the third pump cell so that the electromotive force V3 in the third vacant sensor cell is maintained at a predetermined target value within the range of 100 mV to 300 mV, A water vapor concentration determination means for determining the water vapor concentration contained in the gas to be measured, based on the magnitude of the current flowing between the second inner electrode and the outer electrode when oxygen is pumped into the second empty chamber by the second pump cell, A carbon dioxide concentration determination means for determining the concentration of carbon dioxide contained in the gas to be measured, based on the magnitude of the current flowing between the third inner electrode and the outer electrode when oxygen is pumped into the third empty chamber by the third pump cell, An oxygen concentration determination means for determining the concentration of oxygen contained in the gas to be measured, based on the magnitude of the current flowing between the auxiliary adjustment inner electrode and the outer electrode when oxygen is pumped out from the auxiliary adjustment chamber by the auxiliary adjustment pump cell, A gas sensor characterized by comprising the following features.

2. A gas sensor according to claim 1, The sub-regulating pump cell control means controls the voltage applied between the sub-regulating inner electrode and the outer electrode in the sub-regulating pump cell so that the electromotive force V0 is maintained at 400 mV. A gas sensor characterized by the following features.

3. A method for measuring the concentrations of multiple target gas components contained in a gas to be measured, which includes at least water vapor and carbon dioxide, using a gas sensor, The gas sensor comprises a sensor element having a long, plate-shaped structure made of an oxygen ion conductive solid electrolyte, The aforementioned sensor element A gas inlet into which the gas to be measured is introduced, The system comprises a sub-regulating chamber, a first chamber, a second chamber, and a third chamber, which are connected sequentially from the gas inlet via different diffusion rate-limiting sections, A sub-adjustment pump cell comprising an inner electrode for sub-adjustment formed facing the sub-adjustment cavity, an outer electrode formed on the outer surface of the sensor element, and the solid electrolyte located between the inner electrode and the outer electrode, A first pump cell comprising a first inner electrode formed facing the first void, the outer electrode, and the solid electrolyte located between the first inner electrode and the outer electrode, A second pump cell comprising a second inner electrode formed facing the second cavity, the outer electrode, and the solid electrolyte located between the second inner electrode and the outer electrode, A third pump cell comprising a third inner electrode formed facing the third cavity, the outer electrode, and the solid electrolyte located between the third inner electrode and the outer electrode, A reference electrode in contact with a reference gas, A sensor cell for a sub-adjustment void, comprising the sub-adjustment inner electrode, the reference electrode, and the solid electrolyte located between the sub-adjustment inner electrode and the reference electrode, wherein an electromotive force V0 corresponding to the oxygen concentration of the sub-adjustment void is generated between the sub-adjustment inner electrode and the reference electrode, A first vacant chamber sensor cell comprising the first inner electrode, the reference electrode, and the solid electrolyte present between the first inner electrode and the reference electrode, wherein an electromotive force V1 corresponding to the oxygen concentration of the first vacant chamber is generated between the first inner electrode and the reference electrode, A second vacant chamber sensor cell comprising the second inner electrode, the reference electrode, and the solid electrolyte present between the second inner electrode and the reference electrode, wherein an electromotive force V2 corresponding to the oxygen concentration of the second vacant chamber is generated between the second inner electrode and the reference electrode, A third vacant chamber sensor cell comprising the third inner electrode, the reference electrode, and the solid electrolyte present between the third inner electrode and the reference electrode, wherein an electromotive force V3 corresponding to the oxygen concentration of the third vacant chamber is generated between the third inner electrode and the reference electrode, It is equipped with, a) A step of pumping oxygen from the gas to be measured, introduced into the sub-adjustment chamber from the gas inlet, within a range in which the water vapor and carbon dioxide contained in the gas to be measured are not decomposed, by controlling the voltage applied between the sub-adjustment inner electrode and the outer electrode in the sub-adjustment pump cell, so that the electromotive force V0 generated between the sub-adjustment inner electrode and the reference electrode according to the oxygen concentration in the sub-adjustment chamber is maintained at a predetermined target value within the range of 400 mV to 700 mV, b) A step of pumping oxygen from the first void by the first pump cell such that the electromotive force V1 generated between the first inner electrode and the reference electrode according to the oxygen concentration in the first void is maintained at a predetermined target value within the range of 1000 mV to 1500 mV, thereby causing the first pump cell to substantially decompose all of the water vapor and carbon dioxide contained in the gas to be measured that was introduced into the first void from the sub-adjustment void, c) A step of selectively oxidizing hydrogen produced by the decomposition of water vapor contained in the gas to be measured, which is introduced from the first to the second chamber, in the second chamber, by the second pump cell, by controlling the voltage applied between the second inner electrode and the outer electrode so that the electromotive force V2 generated between the second inner electrode and the reference electrode according to the oxygen concentration in the second chamber is maintained at a predetermined target value within the range of 250 mV to 450 mV, thereby drawing oxygen into the second chamber by the second pump cell, and selectively oxidizing hydrogen in the second chamber, which is contained in the gas to be measured, which is introduced from the first chamber to the second chamber, d) A step of pumping oxygen into the third chamber by the third pump cell, and oxidizing carbon monoxide produced by the decomposition of carbon dioxide contained in the gas to be measured, which is introduced from the second chamber to the third chamber, in the third chamber, by controlling the voltage applied between the third inner electrode and the outer electrode in the third pump cell so that the electromotive force V3 generated between the third inner electrode and the reference electrode according to the oxygen concentration in the third chamber is maintained at a predetermined target value within the range of 100 mV to 300 mV, e) A step of determining the concentration of water vapor contained in the gas to be measured based on the magnitude of the current flowing between the second inner electrode and the outer electrode when oxygen is pumped into the second void by the second pump cell, f) A step of determining the concentration of carbon dioxide contained in the gas to be measured based on the magnitude of the current flowing between the third inner electrode and the outer electrode when oxygen is pumped into the third empty chamber by the third pump cell, g) A step of determining the concentration of oxygen contained in the gas to be measured based on the magnitude of the current flowing between the auxiliary adjustment inner electrode and the outer electrode when oxygen is pumped out from the auxiliary adjustment chamber by the auxiliary adjustment pump cell, A method for measuring concentration using a gas sensor, characterized by comprising the following features.

4. A method for measuring concentration using a gas sensor as described in claim 3, In step a), the voltage applied between the auxiliary adjustment inner electrode and the outer electrode in the auxiliary adjustment pump cell is controlled so that the electromotive force V0 is maintained at 400 mV. A method for measuring concentration using a gas sensor, characterized by the following features.

5. A gas sensor according to claim 1 or claim 2, The first pump cell either stops the first pumping operation for a predetermined time during the first pumping operation, which pumps oxygen from the first chamber so that substantially all of the water vapor and carbon dioxide contained in the gas to be measured, introduced from the sub-adjustment chamber to the first chamber, are decomposed, or performs a second pumping operation, which pumps oxygen from the first chamber to the extent that the water vapor and carbon dioxide contained in the gas to be measured are not decomposed, thereby interrupting the reduction of water vapor and carbon dioxide in the first chamber. As a result, the water vapor generated in the second chamber and the carbon dioxide generated in the third chamber are discharged to the outside of the sensor element via the first chamber and the sub-adjustment chamber. A gas sensor characterized by the following features.

6. A gas sensor according to claim 5, The first pump cell alternately and periodically performs the first pumping operation and the stopping of the first pumping operation or the second pumping operation. The pumping of oxygen into the second vacant chamber by the second pump cell and the pumping of oxygen into the third vacant chamber by the third pump cell are performed periodically in accordance with the operation of the first pump cell. A gas sensor characterized by the following features.

7. A gas sensor according to claim 6, The pumping of oxygen into the second empty chamber by the second pump cell and the pumping of oxygen into the third empty chamber by the third pump cell are performed in synchronization with the stopping of the first pumping operation by the first pump cell or the second pumping operation. A gas sensor characterized by the following features.

8. A gas sensor according to claim 6, The pumping of oxygen into the second empty chamber by the second pump cell and the pumping of oxygen into the third empty chamber by the third pump cell are performed from the middle of the first pumping operation by the first pump cell until the middle of the stopping of the first pumping operation or until the middle of the second pumping operation. A gas sensor characterized by the following features.

9. A method for measuring concentration using a gas sensor according to claim 3 or claim 4, During step b), the first pump cell either stops the first pumping operation, which pumps oxygen from the first chamber so that substantially all of the water vapor and carbon dioxide contained in the gas to be measured introduced from the sub-adjustment chamber into the first chamber is decomposed, for a predetermined time, or performs a second pumping operation, which pumps oxygen from the first chamber to the extent that the water vapor and carbon dioxide contained in the gas to be measured are not decomposed, thereby interrupting the reduction of water vapor and carbon dioxide in the first chamber, and thereby discharging the water vapor generated in the second chamber and the carbon dioxide generated in the third chamber to the outside of the sensor element via the first chamber and the sub-adjustment chamber. A method for measuring concentration using a gas sensor, characterized by the following features.

10. A method for measuring concentration using a gas sensor as described in claim 9, In step b), the first pump cell alternately and periodically performs the first pumping operation and the stopping of the first pumping operation or the second pumping operation. The pumping of oxygen into the second empty chamber by the second pump cell in step c) and the pumping of oxygen into the third empty chamber by the third pump cell in step d) are performed periodically in accordance with the operation of the first pump cell in step b). A method for measuring concentration using a gas sensor, characterized by the following features.

11. A method for measuring concentration using a gas sensor according to claim 10, The pumping of oxygen into the second empty chamber by the second pump cell in step c) and the pumping of oxygen into the third empty chamber by the third pump cell in step d) are performed in synchronization with the stopping of the first pumping operation by the first pump cell or the second pumping operation in step b). A method for measuring concentration using a gas sensor, characterized by the following features.

12. A method for measuring concentration using a gas sensor according to claim 10, The pumping of oxygen into the second empty chamber by the second pump cell in step c) and the pumping of oxygen into the third empty chamber by the third pump cell in step d) are performed from the middle of the first pumping operation by the first pump cell in step b) until the middle of the stopping of the first pumping operation or until the middle of the second pumping operation. A method for measuring concentration using a gas sensor, characterized by the following features.

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