Gas sensor

Abstract

The present invention provides a gas sensor that can measure a target gas, such as hydrogen gas, with higher accuracy than the gas used for measurement. A gas sensor 100 comprises a sensor element 101 and a control unit therefor, wherein the sensor element 101 comprises: a base part 102; a reference gas chamber 42 formed between a proton-conducting solid electrolyte layer 5 and an oxygen-ion-conducting solid electrolyte layer 3 within the base part 102, wherein outside gas is introduced into the reference gas chamber 42 via an external gas diffusion rate limiting path 43; a hydrogen reference electrode 23 arranged on the proton-conducting solid electrolyte layer 5 in the reference gas chamber 42; a hydrogen generation pump cell 31 comprising a hydrogen generation electrode 32 arranged on the oxygen-ion-conducting solid electrolyte layer 3 in the reference gas chamber 42;and a detection electrode 22, which is arranged on the proton-conducting solid electrolyte layer 5, to be in contact with a gas of measurement; and the control unit comprises: a reference gas adjustment part for setting a hydrogen concentration in the reference gas chamber 42 by means of the hydrogen generation pump cell 31; and a detection part for detecting a target gas to be measured.

Description

TECHNICAL AREA

[0001] The present invention relates to a gas sensor comprising a sensor element that uses an ionically conductive solid electrolyte. This application claims priority from Japanese patent application No. 2023-077521, filed on May 9, 2023, the contents of which are hereby incorporated by reference. TECHNICAL BACKGROUND

[0002] Various measuring devices are used to measure the concentration of a target gas component in a mixed gas, and one example is a gas sensor known that uses a hydrogen ion-conducting (or proton-conducting) solid electrolyte (namely, a proton conductor). For example, Non-Patent Document 1 and Non-Patent Document 2 disclose a hydrogen sensor that uses a proton-conducting solid electrolyte. The hydrogen sensor detects hydrogen by means of an electromotive force (EMF) between an electrode located on a surface of the proton-conducting solid electrolyte in contact with a target gas and a reference electrode located on a surface of the proton-conducting solid electrolyte in contact with a reference gas.

[0003] JP 6667192 B2 discloses an ammonia sensor element that uses a proton-conducting solid electrolyte. In the ammonia sensor element, a reference electrode is formed opposite a reference gas chamber and in contact with a reference gas.

[0004] For example, JP 7122935 B2 discloses a carbon dioxide detection device equipped with a sensor element and a control unit. As an embodiment of the sensor element, JP 7122935 B2 discloses a sensor element comprising an ion conductor that conducts oxygen ions, a proton conductor that conducts hydrogen protons, and a gas chamber formed between the ion conductor and the proton conductor. The sensor element has a water detection electrode formed on a surface of the proton conductor and a reference electrode formed on a surface of the proton conductor opposite the surface on which the water detection electrode is formed. The reference electrode is in contact with a reference gas.

[0005] JP 2022-110596 A discloses a water vapor sensor having a junction surface where a proton-conducting solid electrolyte layer and an oxide ion-conducting solid electrolyte layer are joined, and which does not require a standard gas (namely a reference gas). CITATION LIST PATENT DOCUMENTS Patent document 1: JP 6667192 B2 Patent Document 2: JP 7122935 B2 Patent Document 3: JP 2022-110596 A NON-PATENT DOCUMENTS Non-patent document 1: MK Hossain et al., Nanomaterials 2022, 12, 3581 Non-patent document 2: Y. Okuyama et al., RSC Advances 2016, 6, 34019-34026 Brief description of the invention; problems to be solved by the invention

[0006] A gas sensor that uses a proton conductor is typically equipped with a reference electrode that serves as a reference for measuring the hydrogen concentration. The reference electrode is in contact with a reference gas, which acts as the reference for the hydrogen concentration. If a gas with a predetermined hydrogen concentration is used as the reference gas, a gas cylinder or similar device is required to supply the reference gas, and the gas sensor becomes large. On the other hand, non-patent documents JP 6667192 B2 and JP 7122935 B2 disclose that air is used as the reference gas. In this case, the gas sensor can be minimized. However, the hydrogen concentration in air is extremely low and unstable. In such a case, there is a risk that the measurement accuracy of hydrogen gas, or any gas containing a hydrogen atom, in the gas sensor could be compromised.Gases containing hydrogen atoms include ammonia (NH3), water vapor (H2O), hydrocarbons (HC), and the like. Examples of hydrocarbons (HC) are alkanes such as methane (CH4) and alkenes such as ethylene (C2H4).

[0007] Therefore, it is an object of the present invention to provide a gas sensor that can measure hydrogen gas or a gas (such as ammonia NH3, water vapor H2O and hydrocarbon HC) containing a hydrogen atom in a sample gas with higher accuracy. MEANS TO SOLVENT THE PROBLEMS

[0008] The inventor of the present invention has carried out intensive investigations and found that by generating hydrogen from water vapor in an external gas by means of a hydrogen generation pump cell, in order to provide a hydrogen-containing reference gas in a reference chamber, hydrogen gas or a gas (such as ammonia NH3, water vapor H2O and hydrocarbon HC) containing a hydrogen atom can be measured in a sample gas with higher accuracy.

[0009] The present invention includes the following aspects. (1) A gas sensor for detecting a target gas to be measured in a gas of a measuring object, wherein the gas sensor comprises a sensor element and a control unit for controlling the sensor element, wherein the sensor element includes: a base part in elongated plate form, which includes a proton-conducting solid electrolyte layer and an oxygen-ion-conducting solid electrolyte layer; a reference gas chamber formed between the proton-conducting solid electrolyte layer and the oxygen-ion-conducting solid electrolyte layer within the base part, wherein an external gas is introduced into the reference gas chamber via an external gas diffusion rate limiting path; a hydrogen reference electrode that is arranged on the proton-conducting solid electrolyte layer in the reference gas chamber; a hydrogen generation pump cell comprising: a hydrogen generation electrode arranged on the oxygen-ion-conducting solid electrolyte layer in the reference gas chamber; and an external electrode arranged at a position on the oxygen-ion-conducting solid electrolyte layer different from the reference gas chamber and corresponding to the hydrogen generation electrode; and a sensing electrode arranged on the proton-conducting solid electrolyte layer to be in contact with a gas used in the measurement; and The control unit includes: a reference gas adjustment component for setting a hydrogen concentration in the reference gas chamber by actuating the hydrogen generation pump cell; and A detection element for detecting a target gas to be measured in a measuring object gas. (2) The gas sensor according to the foregoing (1), wherein the reference gas adjusting part adjusts the hydrogen concentration in the reference gas chamber by applying a predetermined voltage between the hydrogen generation electrode and the outer electrode of the hydrogen generation pump cell to decompose water vapor in the outside gas introduced into the reference gas chamber at the hydrogen generation electrode so that hydrogen and oxygen are produced, and to pump out the produced oxygen and any oxygen contained in the outside gas from the reference gas chamber. (3) The gas sensor according to (1) or (2) above, wherein the sensing part detects the target gas to be measured in the gas of the object being measured on the basis of an electromotive force between the sensing electrode and the hydrogen reference electrode. (4) The gas sensor according to any of the preceding (1) to (3), wherein the sensor element further comprises a sample gas cavity formed within the base part, wherein the sample gas is introduced into the sample cavity via a sample gas diffusion rate limiting path, the detection electrode exits into the gas cavity of the object being measured and The detection element detects the target gas to be measured in the gas of the object being measured based on a current flowing between the detection electrode and the hydrogen reference electrode. The detection (or concentration measurement) of the target gas to be measured in the sample gas can be carried out, as in the case of (3) above, on the basis of the electromotive force between the detection electrode and the hydrogen reference electrode, or, as in the case of (4) above, on the basis of the current between the detection electrode and the hydrogen reference electrode. Alternatively, it is conceivable that the detection based on the electromotive force according to (3) above and the detection based on the current according to (4) above are carried out in parallel. (5) The gas sensor according to any of the preceding (1) to (4), the sensor element comprising: a pretreatment chamber formed between the proton-conducting solid electrolyte layer and the oxygen-ion-conducting solid electrolyte layer within the base part and adjacent to the reference gas chamber via the external gas diffusion rate limiting path, wherein the external gas is introduced into the pretreatment chamber via a pretreatment diffusion rate limiting path; and an oxygen pump cell comprising: an oxygen pump electrode arranged on the oxygen-ion-conducting solid electrolyte layer in the pretreatment chamber; and an external electrode arranged at a position on the oxygen-ion-conducting solid electrolyte layer and corresponding to the oxygen pump electrode, different from the reference gas chamber and the pretreatment chamber; and The reference gas adjusting unit adjusts the hydrogen concentration in the reference gas chamber by actuating the oxygen pump cell to pump out oxygen from the outside gas introduced into the pretreatment chamber; and actuating the hydrogen generating cell to decompose water vapor from the outside gas introduced into the reference gas chamber after the oxygen in the outside gas has been pumped out in the pretreatment chamber, so that hydrogen and oxygen are generated, and to pump out the generated oxygen and the oxygen contained in the outside gas from the reference gas chamber. (6) The gas sensor according to any one of the preceding (1) to (5), wherein the sensor element further comprises an oxygen reference electrode arranged on the oxygen ion-conducting solid electrolyte layer in the reference gas chamber and The reference gas adjustment part actuates the hydrogen generation pump cell based on an electromotive force between the hydrogen reference electrode and the oxygen reference electrode. (7) The gas sensor according to any of the preceding (1) to (6), wherein the outer electrode of the hydrogen generation pump cell is arranged so that it is in contact with the gas of the object being measured. (8) The gas sensor according to any of the preceding (1) to (7), wherein the target gas to be measured is hydrogen, ammonia, water vapor or methane. (9) A sensor element for detecting a target gas to be measured in a gas of the object being measured, the sensor element comprising: a base part in elongated plate form, which includes a proton-conducting solid electrolyte layer and an oxygen-ion-conducting solid electrolyte layer; a reference gas chamber formed between the proton-conducting solid electrolyte layer and the oxygen-ion-conducting solid electrolyte layer within the base part, wherein an external gas is introduced into the reference gas chamber via an external gas diffusion rate limiting path; a hydrogen reference electrode that is arranged on the proton-conducting solid electrolyte layer in the reference gas chamber; a hydrogen generation pump cell comprising: a hydrogen generation electrode arranged on the oxygen-ion-conducting solid electrolyte layer in the reference gas chamber; and an external electrode arranged at a position on the oxygen-ion-conducting solid electrolyte layer different from the reference gas chamber and corresponding to the hydrogen generation electrode; and a detection electrode that is arranged on the proton-conducting solid electrolyte layer to be in contact with a gas used in the measurement. (10) A gas control device comprising: a gas chamber which is at least partially surrounded by a proton-conducting solid electrolyte layer and an oxygen-ion-conducting solid electrolyte layer, wherein an external gas is introduced into the gas chamber via an external gas diffusion rate limiting path; a hydrogen generation pump cell comprising: a hydrogen generation electrode located on the oxygen-ion-conducting solid electrolyte layer in the gas chamber; and an external electrode located at a position on the oxygen-ion-conducting solid electrolyte layer and corresponding to the hydrogen generation electrode, different from the gas chamber; a hydrogen reference electrode arranged on the proton-conducting solid electrolyte layer in the gas chamber; and A gas control unit for adjusting the hydrogen concentration in the gas chamber by actuating the hydrogen generation pump cell. (11) A gas control device comprising: a gas chamber which is at least partially surrounded by a proton-conducting solid electrolyte layer and an oxygen-ion-conducting solid electrolyte layer, wherein an external gas is introduced into the gas chamber via an external gas diffusion rate limiting path; a hydrogen generation pump cell comprising: a hydrogen generation electrode located on the oxygen-ion-conducting solid electrolyte layer in the gas chamber; and an external electrode located at a position on the oxygen-ion-conducting solid electrolyte layer and corresponding to the hydrogen generation electrode, different from the gas chamber; a hydrogen reference electrode arranged on the proton-conducting solid electrolyte layer in the gas chamber; and a gas control element for adjusting a hydrogen concentration in the gas chamber by actuating the hydrogen generation pump cell, wherein The gas control unit adjusts the hydrogen concentration in the gas chamber by applying a predetermined voltage between the hydrogen generation electrode and the outer electrode of the hydrogen generation pump cell, in order to decompose water vapor in the external gas introduced into the gas chamber at the hydrogen generation electrode, so that hydrogen and oxygen are produced, and to pump the produced oxygen and any oxygen contained in the external gas out of the gas chamber; and supplies the gas, whose hydrogen concentration is adjusted, to the hydrogen reference electrode. EFFECTS OF THE INVENTION

[0010] According to the present invention, it is possible to provide a gas sensor that can measure hydrogen gas or a gas (such as ammonia NH3, water vapor H2O and hydrocarbon HC) containing a hydrogen atom in a gas of the object being measured with higher accuracy. BRIEF DESCRIPTION OF THE DRAWINGS [ Fig. 1] Fig. Figure 1 is a vertical sectional view in the longitudinal direction of a sensor element 101, showing an example of a schematic configuration of a gas sensor 100 of embodiment 1. [ Fig. 2] Fig. Figure 2 is a block diagram showing the electrical connections between a control unit 90 and the respective cells 20 and 31 of the sensor element 101 in the gas sensor 100 of embodiment 1. [ Fig. 3] Fig. Figure 3 is a vertical sectional view in the longitudinal direction of a sensor element 201, showing an example of a schematic configuration of a gas sensor 200 of embodiment 2. [ Fig. 4] Fig. Figure 4 is a block diagram showing the electrical connections between a control unit 290 and the respective cells 21 and 31 of the sensor element 201 in the gas sensor 200 of embodiment 2. [ Fig. 5] Fig. Figure 5 is a vertical sectional view in the longitudinal direction of a sensor element 301, showing an example of a schematic configuration of a gas sensor 300 of embodiment 3. [ Fig. 6] Fig. Figure 6 is a block diagram showing electrical connections between a control unit 390 and the respective cells 20, 31 and 51 of the sensor element 301 in the gas sensor 300 of embodiment 3. [ Fig. 7] Fig. Figure 7 is a vertical sectional view in the longitudinal direction of a sensor element 401, showing an example of a schematic configuration of a gas sensor 400 of embodiment 4. [ Fig. 8] Fig. Figure 8 is a block diagram showing electrical connections between a control unit 490 and the respective cells 20, 31 and 61 of the sensor element 401 in the gas sensor 400 of embodiment 4. [ Fig. 9] Fig. Figure 9 is a vertical sectional view in the longitudinal direction of a sensor element 501, showing an example of a schematic configuration of a gas sensor 500 of embodiment 5. FORMS OF EXECUTION OF THE INVENTION

[0011] A gas sensor of the present invention includes a sensor element and a control unit for controlling the sensor element.

[0012] The sensor element contained in the gas sensor of the present invention includes: a base part in elongated plate form, which includes a proton-conducting solid electrolyte layer and an oxygen-ion-conducting solid electrolyte layer; a reference gas chamber formed between the proton-conducting solid electrolyte layer and the oxygen-ion-conducting solid electrolyte layer within the base part, wherein an external gas is introduced into the reference gas chamber via an external gas diffusion rate limiting path; a hydrogen reference electrode that is arranged on the proton-conducting solid electrolyte layer in the reference gas chamber; a hydrogen generation pump cell comprising: a hydrogen generation electrode arranged on the oxygen-ion-conducting solid electrolyte layer in the reference gas chamber; and an external electrode arranged at a position on the oxygen-ion-conducting solid electrolyte layer different from the reference gas chamber and corresponding to the hydrogen generation electrode; and a detection electrode that is arranged on the proton-conducting solid electrolyte layer to be in contact with a gas used in the measurement.

[0013] A proton-conducting solid electrolyte layer (or proton conductor) is a solid material that has the property of attracting protons (hydrogen ions; H₂). + -ions). An oxygen-ion-conducting solid electrolyte layer (or oxygen ion conductor) is a solid material that has the property of conducting oxygen ions (O₂). 2- -ions).

[0014] The control unit contained in the gas sensor of the present invention includes: a reference gas adjustment component for setting a hydrogen concentration in the reference gas chamber by actuating the hydrogen generation pump cell; and A detection element for detecting a target gas to be measured in a gas used as a measuring object. [Version 1]

[0015] An embodiment of the gas sensor of the present invention will now be described with reference to the drawings. Fig. Figure 1 is a vertical sectional view in the longitudinal direction of a sensor element 101, showing an example of a schematic configuration of a gas sensor 100 of embodiment 1. The following are based on Fig. 1 the top and bottom in Fig. 1 each defined as top and bottom, and the left side and right side in Fig. 1 are defined as the front end and back end, respectively. In Fig. 1 The gas sensor 100 represents an example of a gas sensor which uses the sensor element 101 to detect hydrogen H2 in a measuring object gas and measures the concentration of H2.

[0016] Furthermore, the gas sensor 100 includes a control unit 90 for controlling the sensor element 101. Fig. Figure 2 is a block diagram showing the electrical connections between the control unit 90 and the sensor element 101. (Sensor element)

[0017] The sensor element 101 is an elongated plate-shaped element comprising a base part 102, also in an elongated plate shape, with a proton-conducting solid electrolyte layer and an oxygen-ion-conducting solid electrolyte layer. The elongated plate shape is also referred to as a long plate shape or ribbon shape.

[0018] The proton-conducting solid electrolyte layer consists of a proton-conducting solid electrolyte (i.e., a proton conductor) and extends longitudinally along the sensor element 101 (the base part 102). For example, a perovskite-type oxide or the like can be used as the proton-conducting solid electrolyte (proton conductor). A perovskite-type ceramic, represented by the following composition formula, can also be used as the proton-conducting solid electrolyte (proton conductor). AWAY x C 1-x )O 3-δ

[0019] Here, "A" is, for example, a divalent metal selected from the group consisting of Ba, Ca, and Sr. "B" is, for example, a tetravalent metal selected from the group consisting of Ce and Zr. "C" is, for example, a trivalent metal selected from the group consisting of In, Y, Yb, Mn, and Sc. "C" is a so-called dopant. "x" can be 0 or more and 0.7 or less.

[0020] The oxygen-ion-conducting solid electrolyte layer is formed from an oxygen-ion-conducting solid electrolyte (i.e., an oxygen-ion conductor) and extends longitudinally along the sensor element 101 (the base part 102). For example, stabilized zirconium dioxide or partially stabilized zirconium dioxide to which a rare-earth metal oxide or an alkaline-earth metal oxide has been added as a stabilizing agent can be used. Examples of stabilizing agents include yttrium oxide (Y₂O₃), calcium oxide (CaO), magnesium oxide (MgO), cerium oxide (CeO₂), and scandium oxide (Sc₂O₃). For example, yttrium oxide-stabilized zirconium dioxide can be used.

[0021] The base part 102 has a structure such that five layers are arranged one above the other, namely a first substrate layer 1, a second substrate layer 2, an oxygen ion conductor layer 3, a spacer layer 4, and a proton conductor layer 5, in that order when viewed from the bottom in the drawing. The first substrate layer 1 and the second substrate layer 2 are each a layer formed from an insulator such as aluminum oxide. The oxygen ion conductor layer 3 and the spacer layer 4 are each layers formed from an oxygen ion conductor and are dense and gas-tight. The proton conductor layer 5 is a layer formed from a proton conductor and is dense and gas-tight. These five layers can all have the same thickness, or the thickness can vary between the layers. The five layers are interconnected and integrated.The spacer layer 4 is a layer formed from the oxygen ion conductor in embodiment 1, but the present invention is not limited thereto. The spacer layer 4 must be dense and gas-tight, and the spacer layer 4 can be a layer formed from a proton conductor or a layer formed from an insulator such as aluminum oxide.

[0022] The sensor element 101, for example, is manufactured by stacking ceramic green plates corresponding to the individual layers after performing a predetermined processing, printing a circuit pattern and the like, and then firing the stacked ceramic green plates so that they are bonded together.

[0023] An oxygen outlet chamber 41 is formed between a lower surface of the proton conduction layer 5 and an upper surface of the oxygen ion conduction layer 3 in an end section in the longitudinal direction of the sensor element 101. Hereinafter, the end section in which the oxygen outlet chamber 41 is located is referred to as the front end section. The oxygen outlet chamber 41 is filled with a gas used in the measurement.

[0024] A reference gas chamber 42 is formed between the proton-conducting solid electrolyte layer (namely, the proton-conducting layer 5) and the oxygen-ion-conducting solid electrolyte layer (namely, the oxygen-ion-conducting layer 3) within the base part 102 at a position near one end part (namely, the front end part) in the longitudinal direction of the sensor element 101 (or the base part 102). That is, the reference gas chamber 42 is formed between the lower surface of the proton-conducting layer 5 and the upper surface of the oxygen-ion-conducting layer 3 at a position that is further from the front end than the oxygen outlet chamber 41. The oxygen outlet chamber 41 and the reference gas chamber 42 are separated from each other by the spacer layer 4 to prevent gas distribution between the oxygen outlet chamber 41 and the reference gas chamber 42.

[0025] Along the longitudinal axis of the sensor element 101 (or the base part 102) are formed an air diffusion rate limiting path 43 and an air inlet chamber 40, which are connected to the reference gas chamber 42 in that order. The air diffusion rate limiting path 43 corresponds to an external gas diffusion rate limiting path of the present invention. The air inlet chamber 40 has an opening in the other end part (hereinafter referred to as the rear end part) of the sensor element 101 (or the base part 102).

[0026] The oxygen outlet chamber 41, the reference gas chamber 42 and the air inlet chamber 40 form interiors of the sensor element 101. Each of the interiors is designed such that a section of the spacer layer 4 is hollowed out and the top of each interior is defined by the lower surface of the proton conductor layer 5, the bottom of each interior is defined by the upper surface of the oxygen ion conductor layer 3 and the side surface of each interior is defined by the side surface of the spacer layer 4.

[0027] The air diffusion rate limitation path 43 is formed as two laterally extended slots (with the longitudinal direction of the openings in the direction perpendicular to the figure in Fig. 1) provided. The air diffusion rate limiting path 43 can have such a shape that a desired diffusion resistance is generated, but the shape is not limited to the slots.

[0028] The reference gas chamber 42 is a chamber containing a reference gas that serves as a reference for measuring the hydrogen concentration. An external gas, such as air, is introduced into the reference gas chamber 42 from a space outside the sensor element 101 via the air inlet chamber 40 and the air diffusion rate limiting path 43. By converting the water vapor in the external gas (in this embodiment, air) introduced into the reference gas chamber 42 into hydrogen, the reference gas chamber 42 is filled with a reference gas containing hydrogen. The conversion of water vapor to hydrogen is carried out by a hydrogen generation pump cell 31.

[0029] The hydrogen generation pump cell 31 includes a hydrogen generation electrode 32, which is arranged on the oxygen-ion-conducting solid electrolyte layer (the oxygen-ion conductor layer 3) in the reference gas chamber 42; and an external electrode 33, which is arranged at a position on the oxygen-ion-conducting solid electrolyte layer (the oxygen-ion conductor layer 3) that is different from the reference gas chamber 42 and corresponding to the hydrogen generation electrode 32. The expression "corresponding to the hydrogen generation electrode 32" means that the hydrogen generation electrode 32 and the external electrode 33 are arranged adjacent to each other across the oxygen-ion-conducting solid electrolyte.

[0030] That is, the hydrogen generation pump cell 31 is an electrochemical pump cell consisting of the hydrogen generation electrode 32, which is located on the upper surface of the oxygen ion conductor layer 3 in the reference gas chamber 42, the outer electrode 33, which is located on the upper surface of the oxygen ion conductor layer 3 in the oxygen outlet chamber 41, and the oxygen ion conductor layer 3, which is in contact with both the hydrogen generation electrode 32 and the outer electrode 33.

[0031] The hydrogen generation electrode 32 and the outer electrode 33 are porous cermet electrodes (electrodes in a state where a metal component and a ceramic component are mixed). The ceramic component to be used is not particularly restricted, but preferably an oxygen-ion-conducting solid electrolyte, as in the case of the oxygen-ion conductor layer 3. For example, ZrO2 (stabilized ZrO2) can be used as the ceramic component.

[0032] The hydrogen generation electrode 32 and the outer electrode 33 preferably contain a noble metal with catalytic activity (e.g., at least one of Pt, Rh, Ir, Ru, and Pd) as a metal component. For example, the hydrogen generation electrode 32 and the outer electrode 33 can be porous cermet electrodes made of Pt and ZrO2.

[0033] The hydrogen generation electrode 32 also acts as a catalyst, decomposing water vapor H2O in the outside gas (e.g., air) that is introduced into the reference gas chamber 42 through the air inlet chamber 40 and the air diffusion rate limiting path 43.

[0034] In the hydrogen generation pump cell 31, a predetermined pump voltage Vp2 is applied between the hydrogen generation electrode 32 and the external electrode 33 by means of a variable power supply 34. This causes a pump current Ip2 to flow between the hydrogen generation electrode 32 and the external electrode 33, thereby decomposing water vapor H2O in the reference gas chamber 42 at the hydrogen generation electrode 32 (2H2O → 2H2 + O2) to produce hydrogen H2 and oxygen O2. Furthermore, the oxygen produced by the decomposition of water vapor H2O and the oxygen originally contained in the external gas introduced into the reference gas chamber 42 can be pumped from the reference gas chamber 42 into the oxygen outlet chamber 41.

[0035] By operating the hydrogen generation pump cell 31, the hydrogen produced by the decomposition of H2O remains in the reference gas chamber 42, so that the reference gas chamber 42 is filled with the reference gas containing hydrogen gas.

[0036] In this embodiment, the external electrode 33 is arranged to be in contact with a gas used in the measurement. The external electrode 33 can be located at a different position than the reference gas chamber 42. The external electrode 33 can be arranged to be in contact with the gas used in the measurement, as in this embodiment. Alternatively, the external electrode 33 can be located in the gas 40 and in contact with the external gas (namely, air). The oxygen produced by the decomposition of H₂O in the external gas introduced into the reference gas chamber 42, and the oxygen originally contained in the external gas introduced into the reference gas chamber 42, are pumped to the external electrode 33. Preferably, the external electrode 33 can be arranged, as in this embodiment, to be in contact with the gas used in the measurement. In other words, oxygen can be pumped from the reference gas chamber 42 to the gas used in the measurement.In this case, the pumped-out oxygen has no effect on the outside gas introduced into the reference gas chamber 42, and therefore the hydrogen generation pump cell 31 can be operated more effectively.

[0037] A hydrogen reference electrode 23 is arranged on the proton conductor layer 5 (on the lower surface of the proton conductor layer 5) in the reference gas chamber 42. A detection electrode 22 is arranged on a region of the upper surface of the proton conductor layer 5 that corresponds to the hydrogen reference electrode 23. The detection electrode 22 is arranged to be in contact with a sample gas. In this embodiment, the detection electrode 22 is arranged on an outer surface of the sensor element 101. The gas sensor 100 is configured such that the sample gas is present around the front end portion of the sensor element 101 and the area surrounding the detection electrode 22 is within the sample gas atmosphere.

[0038] The sensing electrode 22, the hydrogen reference electrode 23, and the proton conductor layer 5, which is arranged between the sensing electrode 22 and the hydrogen reference electrode 23, form an electrochemical sensor cell, namely an electromotive force sensing sensor cell 20. The hydrogen partial pressure (hydrogen concentration) in the gas of the object being measured around the sensing electrode 22 can be determined from an electromotive force V1 measured in the electromotive force sensing sensor cell 20.

[0039] The detection electrode 22 and the hydrogen reference electrode 23 are porous cermet electrodes (electrodes in a state where a metal component and a ceramic component are mixed). The ceramic component to be used is not particularly restricted, but is preferably a hydrogen ion-conducting (proton) solid electrolyte, as in the case of the proton conductor layer 5. For example, yttrium (Y)-doped strontium zirconate can be used as the ceramic component.

[0040] The detection electrode 22 and the hydrogen reference electrode 23 preferably contain a noble metal with catalytic activity (e.g., at least one of Pt, Rh, Ir, Ru, and Pd) as a metal component. For example, the detection electrode 22 and the hydrogen reference electrode 23 can be porous cermet electrodes made of Pt and yttrium (Y)-doped strontium zirconate.

[0041] The sensor element 101 also includes a heater 72, which serves as a temperature regulator to heat and maintain the temperature of the sensor element 101 in order to enhance the hydrogen ion conductivity or the oxygen ion conductivity of the solid electrolytes.

[0042] The heater 72 is an electrical resistor sandwiched between the first substrate layer 1 and the second substrate layer 2, both of which consist of insulators. The heater 72 is connected to an external power source via a connecting lead (not shown). The heater 72 is externally powered to generate heat and heats and maintains the temperature of the solid electrolytes that form the sensor element 101.

[0043] The heater 72 is embedded over at least the entire surface of the reference gas chamber 42, so that the temperature of the entire sensor element 101 can be set to a temperature that activates the solid electrolytes (both of the proton conducting layer 5 and the oxygen ion conducting layer 3). The temperature can be set so that the hydrogen generation pump cell 31 and the electromotive force detection sensor cell 20 are operational. It is not necessary for the entire surface to be set to the same temperature; the sensor element 101 can have a temperature distribution. By maintaining the heater 72 at a desired temperature, the sensor element 101 can be kept at an operating temperature at which the solid electrolyte is activated, thus enabling accurate measurement of the hydrogen concentration.For example, the hydrogen generation pump cell 31 can have a temperature of about 700°C and the electromotive force detection sensor cell 20 can have a temperature of about 600°C.

[0044] In the sensor element 101 of the present embodiment, the heater 72 is embedded in the base part 102, but this form is not restrictive. The heater 72 can be arranged to heat the base part 102. That is, the heater 72 can heat the sensor element 101 to generate an oxygen ion conductivity sufficient to operate the hydrogen generation pump cell 31 and a hydrogen ion conductivity sufficient to operate the electromotive force sensing sensor cell 20. For example, the heater 72 can be embedded in the base part 102 in such a way that the heater 72 is positioned between the first substrate layer 1 and the second substrate layer 2, both of which consist of insulators, as in the present embodiment.

[0045] The first substrate layer 1 and the second substrate layer 2 need not be insulators and can be a proton-conducting solid electrolyte, as in the case of the proton-conducting layer 5, or an oxygen-ion-conducting solid electrolyte, as in the case of the oxygen-ion-conducting layer 3. In this case, an insulating layer of an insulator such as aluminum oxide can be formed on the upper and lower surfaces of the heater 72 to ensure electrical insulation between the heater 72 and the first substrate layer 1, as well as electrical insulation between the heater 72 and the second substrate layer 2. Alternatively, for example, a heater component can be configured as a heater substrate that is separate from the base component 102 and can be arranged in a position adjacent to the base component 102.

[0046] The sensor element 101 described above is installed in the gas sensor 100 in such a way that the front end section of the sensor element 101 comes into contact with the gas of the object being measured and the rear end section of the sensor element 101 comes into contact with the outside gas, such as air. (Control unit)

[0047] The gas sensor 100 of this embodiment includes the sensor element 101 described above and the control unit 90 for controlling the sensor element 101. In the gas sensor 100, each of the electrodes 22, 23, 32 and 33 of the sensor element 101 is electrically connected to the control unit 90 via a connecting line (not shown). Fig. Figure 2 is a block diagram showing the electrical connections between the control unit 90 and the hydrogen generation pump cell 31 and the electromechanical force sensing sensor cell 20 of the sensor element 101. The control unit 90 includes the variable power supply 34 described above and a control section 91. The control section 91 includes a reference gas adjustment section 92 and a sensing section 93.

[0048] The control unit 91 is implemented by a general-purpose or specialized computer, and the functions of the reference gas adjustment unit 92 and the detection unit 93 are implemented by a CPU, memory, or the like installed in the computer. It should be noted that if hydrogen in the exhaust gas from a motor vehicle engine is a target gas to be measured by the gas sensor 100, and the sensor element 101 is attached to an exhaust path, some or all of the functions of the control unit 90 (in particular, the control unit 91) can be implemented by an electronic control unit (ECU) installed in the motor vehicle.

[0049] The control unit 91 is configured to detect an electromotive force V1 in the electromotive force detection sensor cell 20 of the sensor element 101. The control unit 91 can further be configured to additionally detect a pump current Ip2 in the hydrogen generation pump cell 31. Furthermore, the control unit 91 is configured to output a control signal to the variable power supply 34.

[0050] The reference gas adjustment part 92 is configured to operate the hydrogen generation pump cell 31 in such a way that a hydrogen concentration in a reference gas is set in the reference gas chamber 42.

[0051] In this embodiment, the reference gas adjusting part 92 is configured to adjust the hydrogen concentration in the reference gas chamber 42 by applying a predetermined voltage (the pump voltage Vp2) between the hydrogen generation electrode 32 and the outer electrode 33 of the hydrogen generation pump cell 31 in order to decompose water vapor H2O in the outside gas introduced into the reference gas chamber 42 at the hydrogen generation electrode 32 (2H2O → 2H2 + O2) so that hydrogen H2 and oxygen O2 are produced, and to pump the produced oxygen O2 and any oxygen contained in the outside gas introduced into the reference gas chamber 42 (i.e., originally present) out of the reference gas chamber 42.

[0052] When a pump voltage Vp2 is applied between the hydrogen generation electrode 32 and the external electrode 33 in the hydrogen generation pump cell 31, causing oxygen to be pumped from the reference gas chamber 42 into the external space (i.e., the oxygen outlet space 41), the pump current Ip2 increases with increasing pump voltage Vp2 while the pump voltage Vp2 is low. At this point, the oxygen gas present in the reference gas chamber 42 is pumped out. Subsequently, when the pump voltage Vp2 is increased, the pump current Ip2 no longer increases and becomes saturated. A value of the saturated current at this point is called the first limiting current value. A region in which the pump current Ip2 exhibits the first limiting current value with respect to the pump voltage Vp2 is called the first limiting current region.In the first limiting current region, it is assumed that essentially all the oxygen in the external gas (in this embodiment, the air) introduced into the reference gas chamber 42 via the air diffusion rate limiting path 43 is pumped out by the hydrogen generation pump cell 31. Therefore, the first current limiting value is a value corresponding to the oxygen concentration in the reference gas chamber 42. In this case, the pump current Ip2 flows from the hydrogen generation electrode 32 to the external electrode 33 outside the sensor element 101.

[0053] If the pump voltage Vp2 continues to increase, the pump current Ip2 begins to rise again. This is because water vapor H2O begins to decompose at the hydrogen generation electrode 32. That is, at the hydrogen generation electrode 32, water vapor H2O is decomposed (2H2O → 2H2 + O2), producing hydrogen H2 and oxygen O2, and the generated oxygen O2 is pumped out of the reference gas chamber 42. If the pump voltage Vp2 subsequently increases further, the pump current Ip2 does not increase further and becomes saturated again. A value of the saturated current at this point is called the second limiting current value. A region in which the pump current Ip2 is at the second limiting current value with respect to the pump voltage Vp2 is called the second limiting current region.In the second limiting flow region, it is assumed that essentially all the water vapor in the outside gas (in this embodiment, the air), which is introduced into the reference gas chamber 42 via the air diffusion rate limiting path 43, is decomposed at the hydrogen generation electrode 32, and that essentially all the oxygen produced by the decomposition of the water vapor is pumped out by the hydrogen generation pump cell 31. The amount of oxygen produced by the decomposition of the water vapor corresponds to the water vapor concentration in the outside gas. Therefore, it is assumed that the second limiting flow value is the sum of the first limiting flow value described above, which corresponds to the oxygen concentration in the reference gas chamber 42, and a flow value corresponding to the water vapor concentration in the reference gas chamber 42.

[0054] When the gas sensor 100 is operated as described above, the reference gas control unit 92 applies the predetermined voltage (the pump voltage Vp2) between the hydrogen generation electrode 32 and the outer electrode 33 of the hydrogen generation pump cell 31 to decompose water vapor H2O in the external gas (air in this embodiment) introduced into the reference gas chamber 42. The pump voltage Vp2 can be set as a voltage at which the decomposition of the water vapor occurs at the hydrogen generation electrode 32. Preferably, the pump voltage Vp2 can be set as a voltage at which the pump current Ip2 represents the second limiting current described above. Alternatively, the pump voltage Vp2 can be set as a voltage at which the pump current Ip2 assumes a predetermined current value, i.e., as a voltage at which a predetermined quantity of oxygen is pumped from the reference gas chamber 42.The pump voltage Vp2 can vary depending on the intended use of the gas sensor 100, the configuration of the sensor element 101, and the like, and the pump voltage Vp2 can be, for example, about 500 mV to 1500 mV.

[0055] When the pump voltage Vp2 is applied between the hydrogen generation electrode 32 and the outer electrode 33 of the hydrogen generation pump cell 31, essentially all of the oxygen gas in the air that was introduced into the reference gas chamber 42 is pumped into the oxygen outlet chamber 41. Additionally, water vapor in the air is decomposed into hydrogen and oxygen at the hydrogen generation electrode 32, and the oxygen produced is also pumped from the reference gas chamber 42 into the oxygen outlet chamber 41. Consequently, the reference gas in the reference gas chamber 42 contains a reference gas that includes hydrogen gas produced by the decomposition of the water vapor.

[0056] The detection element 93 is configured to detect a target gas to be measured (in this embodiment hydrogen) in a gas of the object being measured.

[0057] In this embodiment, the detection part 93 is configured to detect the target gas to be measured (hydrogen in this embodiment) in the object gas on the basis of an electromotive force V1 between the detection electrode 22 and the hydrogen reference electrode 23 in the electromotive force detection sensor cell 20.

[0058] As described above, the detection electrode 22 is arranged on the outer surface of the sensor element 101 and is in contact with the gas of the object being measured. As also described above, the reference gas, which contains the hydrogen gas produced by the decomposition of the water vapor, is present in the reference gas chamber 42. In other words, the hydrogen reference electrode 23 is in contact with the reference gas, which contains the hydrogen gas produced by the decomposition of the water vapor.

[0059] The sensing unit 93 can detect the electromotive force V1 between the sensing electrode 22 and the hydrogen reference electrode 23 in the electromotive force sensing sensor cell 20, calculate the H2 concentration in the gas sample based on a previously stored conversion parameter (electromotive force-H2 concentration conversion parameter) between the electromotive force V1 and the H2 concentration in the gas sample, and output the calculated H2 concentration as a measured value from the gas sensor 100. The electromotive force-H2 concentration conversion parameter is previously stored in the memory of the control unit 91, which functions as the sensing unit 93. The electromotive force-H2 concentration conversion parameter can be appropriately determined by those skilled in the art, for example, by first conducting an experiment with the gas sensor 100.The electromotive force-H2 concentration conversion parameter can be, for example, the coefficient of an approximate expression obtained through experiment or a theoretical formula (e.g., a logarithmic function), or a map showing the relationship between the electromotive force V1 and the H2 concentration in the gas being measured. The electromotive force-H2 concentration conversion parameter can be specific to each individual gas sensor or common to a large number of gas sensors.

[0060] It is assumed that air itself is used as the reference gas, as is the case with a conventional gas sensor. The amount of hydrogen gas contained in air is extremely small (approximately 5 × 10⁻⁶). -8 volume percent), and the concentration (partial pressure) of hydrogen varies. Fig. Paragraph 1 of non-patent document 2 discloses that the proton transport number of a proton-conducting solid electrolyte is significantly less than 1 at extremely low hydrogen partial pressures, such as in air. It is known that at a proton transport number of 1, the electromotive force generated between a pair of electrodes arranged on the proton-conducting solid electrolyte follows the so-called Nernst equation. That is, an electromotive force is generated according to the difference (or ratio) between the hydrogen partial pressure in a gas in contact with one electrode and the hydrogen partial pressure in a gas in contact with the other electrode. However, at extremely low hydrogen partial pressures, such as in air, the proton transport number is much smaller than 1.In such a case, it is assumed that the electrode potential of a reference electrode in contact with air deviates from a value derived from the Nernst equation. There is concern that such a deviation in the electrode potential of the reference electrode could lead to a reduction in the measurement accuracy of the hydrogen concentration.

[0061] To address this problem, it is being considered to use a gas with a predetermined hydrogen concentration as a reference gas, such that the proton transport number is 1 or essentially 1. For example, a gas cylinder filled with a gas having a predetermined hydrogen concentration could be used to supply the gas with the predetermined hydrogen concentration directly to the sensor element 101. However, in this case, the gas sensor could become large, making it unsuitable for use in vehicles or other applications with limited installation space.

[0062] On the other hand, in the present invention, the air introduced into the reference gas chamber 42 is adjusted to a reference gas containing hydrogen gas, and this adjusted reference gas is used as the reference gas. Therefore, it is considered possible to maintain a high measurement accuracy of the hydrogen concentration. Furthermore, since no gas cylinder is required and the gas sensor can be built compactly, it is assumed that the gas sensor is sufficiently suitable for use in vehicles or other applications.

[0063] The water vapor concentration in the air is not constant. Therefore, the amount of hydrogen produced by the decomposition of water vapor, i.e., the hydrogen concentration in the reference gas chamber 42, can vary. However, it is assumed that the range of hydrogen concentration in the reference gas chamber 42 is sufficiently higher than the initial hydrogen concentration in the air. Therefore, it is assumed that the proton transport number is maintained at 1 or essentially 1. This is considered suitable for keeping the electrode potential of the hydrogen reference electrode 23 stable and ensuring high measurement accuracy of the hydrogen concentration.

[0064] Furthermore, the sensing element 93 can be configured to detect the target gas to be measured (in this embodiment, hydrogen) in the sample gas based on the electromotive force V1 between the sensing electrode 22 and the hydrogen reference electrode 23 in the electromotive force sensing sensor cell 20 and the hydrogen concentration in the reference gas in the reference gas chamber 42. A hydrogen concentration in a sample gas can be detected with even higher accuracy, even if the hydrogen concentration in the reference gas chamber 42 varies.

[0065] For example, the sensing unit 93 can detect a water vapor concentration in the air and calculate the H2 concentration in the reference gas in the reference gas chamber 42 based on a previously stored relationship between the pump voltage Vp2 applied to the hydrogen generation pump cell 31 and the amount of hydrogen produced at each of the water vapor concentrations. The water vapor concentration in the air can be, for example, a value measured with a temperature and humidity meter or the like as the gas sensor. If, for example, the reference gas control unit 92 applies a pump voltage Vp2 such that the pump current Ip2 represents the second limiting current described above, the H2 concentration in the reference gas between the hydrogen generation electrode 32 and the outer electrode 33 of the hydrogen generation pump cell 31 is considered to be essentially proportional to the water vapor concentration in the air.

[0066] The sensing unit 93 can calculate the hydrogen concentration in the gas of the sample based on the electromotive force V1 between the sensing electrode 22 and the hydrogen reference electrode 23 in the electromotive force sensing sensor cell 20, taking into account the calculated H2 concentration in the reference gas. For example, the sensing unit 93 can store a map as the conversion parameter described above (the electromotive force-H2 concentration conversion parameter) between the electromotive force V1 and the H2 concentration in the gas of the sample, corresponding to the electromotive force V1, the H2 concentration in the reference gas, and the H2 concentration in the gas of the sample. [Version 2]

[0067] While embodiment 1 describes an example of an electromotive force-type gas sensor that measures a hydrogen concentration H2 in a sample gas, the gas sensor of the present invention is not limited thereto, and the gas sensor can be a limiting current type gas sensor. Gas sensor 200 of embodiment 2 is an example of a limiting current type gas sensor that measures a hydrogen concentration H2 in a sample gas. Fig. Figure 3 is a vertical sectional view in the longitudinal direction of a sensor element 201, showing an example of a schematic configuration of the gas sensor 200 of embodiment 2. Fig. 3 are identical components as in Fig. 1 with the same symbol. Fig. Figure 4 is a block diagram showing the electrical connections between a control unit 290 and the sensor element 201 in the gas sensor 200 of embodiment 2.

[0068] In the sensor element 201, the base part 202 has a structure such that seven layers are stacked on top of each other in this order, starting from the bottom, as shown in the drawing. These layers consist of a first substrate layer 1, a second substrate layer 2, an oxygen ion conductor layer 3, a spacer layer 4, a proton conductor layer 5, a second spacer layer 6, and a cover layer 7. The second spacer layer 6 and the cover layer 7 are each a layer formed from an insulator such as aluminum oxide, like the first substrate layer 1 and the second substrate layer 2. These seven layers can all have the same thickness, or the thickness can vary between the layers. The seven layers are interconnected and integrated.

[0069] In the sensor element 201 a measuring object gas cavity 12 is formed, into which a measuring object gas is introduced via a measuring object gas diffusion rate limiting path 11, which is formed within the base part 202.

[0070] In the sensor element 201, a gas inlet 10 is formed between a lower surface of the cover layer 7 and an upper surface of the proton conduction layer 5 in an end part (namely a front end part) in the longitudinal direction of the sensor element 201 (or the base part 202). The object gas diffusion rate limiting path 11 and the object gas cavity 12 are configured such that they are connected to each other in the longitudinal direction from the gas inlet 10 in this order.

[0071] The gas inlet 10 and the measuring object gas cavity 12 form interiors of the sensor element 201. Each of the interiors is designed such that a space of the second spacer layer 6 is hollowed out and the top of each of the interiors is defined by the lower surface of the cover layer 7, the bottom of each of the interiors by the upper surface of the proton conductor layer 5 and the side surface of each of the interiors by the side surface of the second spacer layer 6.

[0072] The object gas diffusion rate limitation path 11 is formed as two laterally extended slots (with the longitudinal direction of the openings perpendicular to the figure in Fig. 3) provided. The object gas diffusion rate limiting path 11 can have such a shape that a desired diffusion resistance is generated, but the shape is not limited to the slots.

[0073] In the sensor element 201, a detection electrode 22 is located in the gas cavity 12 of the object being measured. That is, the detection electrode 22 is arranged on the upper surface of the proton conductor layer 5 in the gas cavity 12 of the object being measured.

[0074] The gas inlet 10 is open to an external space in which a gas of the object being measured is present, and the gas of the object being measured is taken from the external space through the gas inlet 10 into the sensor element 201.

[0075] The object gas diffusion rate limitation path 11 generates a predetermined diffusion resistance for the object gas taken in through the gas inlet 10.

[0076] The measuring gas cavity 12 is designed as a chamber for measuring the hydrogen concentration in the measuring gas introduced through the measuring gas diffusion rate limiting path 11. The hydrogen concentration is measured by operating a current sensing pump cell 21.

[0077] The current sensing pump cell 21 includes the sensing electrode 22, which is arranged on the proton-conducting solid electrolyte layer (the proton-conducting layer 5) in the gas cavity 12 containing the object, and a hydrogen reference electrode 23, which is arranged at a position on the proton-conducting solid electrolyte layer (the proton-conducting layer 5) that is different from the gas cavity 12 containing the object and corresponding to the sensing electrode 22. The expression "corresponding to the sensing electrode 22" means that the sensing electrode 22 and the hydrogen reference electrode 23 are arranged adjacent to each other across the proton-conducting solid electrolyte.

[0078] That is, the current sensing pump 21 is an electrochemical pump cell consisting of the sensing electrode 22, which is arranged on the upper surface of the proton conductor layer 5 in the measurement gas cavity 12, the hydrogen reference electrode 23, which is arranged on the lower surface of the proton conductor layer 5 in the reference gas chamber 42, and the proton conductor layer 5, which is arranged between the sensing electrode 22 and the hydrogen reference electrode 23.

[0079] In the current sensing pump 21, a predetermined pump voltage Vp1 is applied between the sensing electrode 22 and the hydrogen reference electrode 23 by means of a variable power supply 24 in order to allow a pump current Ip1 to flow between the sensing electrode 22 and the hydrogen reference electrode 23, and thus it is possible to pump hydrogen from the measuring object gas cavity 12 into the reference gas chamber 42.

[0080] Fig. Figure 4 is a block diagram showing the electrical connections between the control unit 290 and the respective pump cells 21 and 31 of the sensor element 201 in the gas sensor 200 of embodiment 2. Fig. 4. The same components will be used as in Fig. The two components are designated with the same symbol. The control unit 290 includes the variable power supplies 24 and 34, as well as a control section 291. The control section 291 includes a reference gas adjustment section 92 and a detection section 293.

[0081] Control unit 291 is configured to detect a pump current Ip1 in the current-sensing pump cell 21 of sensor element 201. Control unit 91 can be configured to additionally detect a pump current Ip2 in the hydrogen production pump cell 31. Furthermore, control unit 291 is configured to output control signals to variable power supplies 24 and 34.

[0082] In the gas sensor 200, the detection element 293 is configured to detect a target gas to be measured (in embodiment 2 hydrogen) in a measurement object gas on the basis of a current (pump current Ip1) that flows between the detection electrode 22 and the hydrogen reference electrode 23 in the current detection pump cell 21.

[0083] When a pump voltage Vp1 is applied between the sensing electrode 22 and the hydrogen reference electrode 23 of the current-sensing pump cell 21, causing hydrogen to be pumped from the sample gas cavity 12 into the reference gas chamber 42, the pump current Ip1 increases with increasing pump voltage Vp1 while the pump voltage Vp1 is low. At this point, the hydrogen gas present in the sample gas cavity 12 is pumped out. If the pump voltage Vp1 subsequently increases, the pump current Ip1 no longer increases with further increases and becomes saturated. The value of the saturated current at this point is called the limiting current value of the hydrogen gas. A region in which the pump current Ip1 reaches the limiting current value of the hydrogen gas with respect to the pump voltage Vp1 is called the limiting current region of the hydrogen gas.In the limiting flow region of the hydrogen gas, it is assumed that essentially all the hydrogen in the sample gas, which was introduced into the sample gas cavity 12 via the sample gas diffusion rate limiting path 11, is pumped through the current detection pump cell 21. In this case, the pump current Ip1 flows from the hydrogen reference electrode 23 to the detection electrode 22 outside the sensor element 201.

[0084] When operating the gas sensor 200, the detection unit 293 applies a predetermined voltage (the pump voltage Vp1) between the detection electrode 22 and the hydrogen reference electrode 23 of the current detection pump cell 21 in order to pump the gas of the object introduced into the gas cavity 12 out of the gas cavity 12 and detects the pump current Ip1 flowing in the process.

[0085] The pump voltage Vp1 can be set as a voltage at which the pump current Ip1 corresponds to the limiting current for hydrogen gas described above. In this way, essentially all the hydrogen is pumped out of the sample gas introduced into the sample gas cavity 12. In this case, the pump current Ip1 flowing through the current-sensing pump cell 21 is intended to be a current value corresponding to the hydrogen concentration in the sample gas. Therefore, the hydrogen concentration in the sample gas can be determined based on the pump current Ip1. The pump voltage Vp1 can vary depending on the intended use of the gas sensor 200, the configuration of the sensor element 201, and the like, and the pump voltage Vp1 can, for example, be approximately 400 mV to 1000 mV.

[0086] The sensing unit 293 can detect the pump current Ip1 flowing between the sensing electrode 22 and the hydrogen reference electrode 23 in the current-sensing pump cell 21, calculate the H2 concentration in a sample gas based on a previously stored conversion parameter (current-H2 concentration conversion parameter) between the pump current Ip1 and the H2 concentration in the sample gas, and output the H2 concentration as a measured value from the gas sensor 200. The current-H2 concentration conversion parameter is previously stored in the memory of the control unit 291, which functions as the sensing unit 293. The current-H2 concentration conversion parameter can be determined by those skilled in the art, for example, by previously conducting an experiment on the gas sensor 200 in a suitable manner.The current-H2 concentration conversion parameter can be, for example, the coefficient of an approximate expression (e.g., a linear function) obtained through experiment or a theoretical formula, or a map representing the relationship between the pump current Ip1 and the H2 concentration in a sample gas. The current-H2 concentration conversion parameter can be specific to each individual gas sensor or common to several gas sensors.

[0087] In the gas sensor 200, the hydrogen concentration in the reference gas chamber 42 is set by the reference gas adjustment element 92, and the electrode potential of the hydrogen reference electrode 23 is stable. Therefore, it is assumed that in the current-sensing pump cell 21, the relationship between the applied pump voltage Vp1 and the pump current Ip1 flowing through the current-sensing pump cell 21 better corresponds to the hydrogen concentration in the gas of the object being measured, and that the hydrogen concentration can therefore be measured more accurately. [Version 3]

[0088] In the present invention, as described above, a hydrogen-containing reference gas is present in the reference gas chamber 42. A further example of the configuration of the reference gas chamber 42 and its surroundings is shown. As gas sensor 300 of embodiment 3, a further example of an electromotive force-type gas sensor is shown, which measures a hydrogen concentration H2 in a gas sample. Fig. Figure 5 is a vertical sectional view in the longitudinal direction of a sensor element 301, showing an example of a schematic configuration of the gas sensor 300 of embodiment 3. Fig. 5 is the same component as in Fig. 1 is designated with the same characters. Fig. Figure 6 is a block diagram showing the electrical connections between a control unit 390 and the sensor element 301 in the gas sensor 300 of embodiment 3.

[0089] In the sensor element 301, a pretreatment chamber 44 is formed between the proton-conducting solid electrolyte layer (the proton conductor layer 5) and the oxygen ion-conducting solid electrolyte layer (the oxygen ion conductor layer 3) within a base part 302 and adjacent to the reference gas chamber 42 via the external gas diffusion rate limiting path (the air diffusion rate limiting path 43), wherein the external gas (in this embodiment the air) is introduced into the pretreatment chamber via a pretreatment diffusion rate limiting path 45.

[0090] The pretreatment chamber 44 forms an interior space of the sensor element 301. The interior space is designed as in the case of the reference gas chamber 42 such that a section of the spacer layer 4 is hollowed out and the top of the interior space is defined by the lower surface of the proton conductor layer 5, the bottom of the interior space is defined by the upper surface of the oxygen ion conductor layer 3 and the side surface of the interior space is defined by the side surface of the spacer layer 4.

[0091] The pretreatment diffusion rate limitation path 45 is, as in the case of the air diffusion rate limitation path 43, formed as two laterally extended slots (with the longitudinal direction of the openings in the direction perpendicular to the figure in Fig. 5) provided. The pretreatment diffusion rate limitation path 45 can have such a shape that a desired diffusion resistance is generated, but the shape is not limited to the slots.

[0092] The pretreatment chamber 44 is designed as a space for the prior removal of oxygen from an external gas (in this embodiment, air), which is introduced through the air inlet chamber 40 and the pretreatment diffusion rate limiting path 45. The oxygen in the air is pumped out by an oxygen pump cell 51.

[0093] The oxygen pump cell 51 comprises an oxygen pump electrode 52, which is arranged on the oxygen-ion-conducting solid electrolyte layer (the oxygen-ion conductor layer 3) in the pretreatment chamber 44; and an external electrode, which is arranged at a position on the oxygen-ion-conducting solid electrolyte layer (the oxygen-ion conductor layer 3) and corresponding to the oxygen pump electrode 52, different from the reference gas chamber 42 and the pretreatment chamber 44. The expression "corresponding to the oxygen pump electrode 52" means that the oxygen pump electrode 52 and the external electrode are adjacent to each other across the oxygen-ion-conducting solid electrolyte.

[0094] That is, the oxygen pump cell 51 is an electrochemical pump cell consisting of the oxygen pump electrode 52, which is arranged on the upper surface of the oxygen ion conductor layer 3 in the pretreatment chamber 44, the outer electrode 33, which is arranged on the upper surface of the oxygen ion conductor layer 3 in the oxygen outlet chamber 41 and the oxygen ion conductor layer 3, which is in electrically conductive contact with both the oxygen pump electrode 52 and the outer electrode 33.

[0095] In embodiment 3, the outer electrode 33 also functions as the outer electrode of the oxygen pump cell 51. The outer electrode of the oxygen pump cell 51 and the outer electrode of the hydrogen generation pump cell 31 can be designed as different electrodes or, as in this embodiment, as one electrode.

[0096] The oxygen pump electrode 52, like the hydrogen generation electrode 32 and the outer electrode 33, is a porous cermet electrode (an electrode in a state where a metal component and a ceramic component are mixed). The ceramic component to be used is not particularly restricted, but is preferably an oxygen-ion-conducting solid electrolyte, as in the case of the oxygen-ion conductor layer 3. For example, ZrO2 (stabilized ZrO2) can be used as the ceramic component.

[0097] The oxygen pump electrode 52 preferably contains, as in the case of the hydrogen generation electrode 32 and the outer electrode 33, a noble metal with catalytic activity (e.g., at least one of Pt, Rh, Ir, Ru, and Pd) as its metal component. For example, the oxygen pump electrode 52 can be a porous cermet electrode made of Pt and ZrO2.

[0098] In the oxygen pump cell 51, a predetermined pump voltage Vp3 is applied between the oxygen pump electrode 52 and the outer electrode 33 by means of a variable power supply 54. This causes a pump current Ip3 to flow between the oxygen pump electrode 52 and the outer electrode 33, thus allowing oxygen to be pumped from the pretreatment chamber 44 into the oxygen outlet chamber 41. After the oxygen has been pumped out by the operation of the oxygen pump cell 51, the outside gas (in this embodiment, air) is introduced into the reference gas chamber 42 via the air diffusion rate limiting path 43.

[0099] Fig. Figure 6 is a block diagram showing the electrical connections between the control unit 390 and the hydrogen generation pump cell 31, the oxygen pump cell 51, and the electromotive force detection sensor cell 20 of the sensor element 301 in the gas sensor 300 of embodiment 3. Fig. 6. The same components will be used as in Fig. The two components are designated with the same symbol. The control unit 390 includes the variable power supplies 34 and 54, as well as a control section 391. The control section 391 includes a reference gas adjustment section 392 and a detection section 93.

[0100] The control unit 391 is configured to detect an electromotive force V1 in the electromotive force detection sensor cell 20 of the sensor element 301. The control unit 391 can also be configured to additionally detect a pump current (Ip2, Ip3) in each of the respective pump cells 31 and 51. Furthermore, the control unit 391 is configured to output control signals to the variable power supplies 34 and 54.

[0101] In the gas sensor 300, the reference gas adjusting part 392 is configured to adjust the hydrogen concentration in the reference gas chamber 42 by actuating the oxygen pump cell 51 to pump oxygen out of an outside gas (in this embodiment, air) introduced into the pretreatment chamber 44; and actuating the hydrogen generation pump cell 31 to decompose water vapor in the outside gas introduced into the reference gas chamber 42 after the oxygen in the outside gas in the pretreatment chamber 44 has been pumped out, so that hydrogen and oxygen are generated, and to pump out the generated oxygen and the oxygen originally contained in the outside gas introduced into the reference gas chamber 42 from the reference gas chamber 42.

[0102] More precisely, in the gas sensor 300, the reference gas adjustment part 392 applies a predetermined voltage (the pump voltage Vp3) between the oxygen pump electrode 52 and the outer electrode 33 of the oxygen pump cell 51 in order to pump out at least some of the oxygen in the air introduced into the pretreatment chamber 44.And for the air that is introduced into the reference gas chamber 42 after the oxygen has been pumped out of the pretreatment chamber 44, the reference gas adjusting part 392 is configured to adjust the hydrogen concentration in the reference gas chamber 42 by applying a predetermined voltage (the pump voltage Vp2) between the hydrogen generation electrode 32 and the outer electrode 33 of the hydrogen generation pump cell 31 in order to decompose water vapor H2O in the air at the hydrogen generation electrode 32 (2H2O 2H2+ O2) so that hydrogen H2 and oxygen O2 are produced, and to pump out the produced oxygen O2 and the oxygen O2 remaining in the air from the reference gas chamber 42.

[0103] When a pump voltage Vp3 is applied between the oxygen pump electrode 52 and the outer electrode 33 of the oxygen pump cell 51, causing oxygen to be pumped from the pretreatment chamber 44 into the outer chamber (namely the oxygen outlet chamber 41), the pump current Ip3 increases with increasing pump voltage Vp3 while the pump voltage Vp3 is low. At this point, the oxygen gas present in the pretreatment chamber 44 is pumped out. If the pump voltage Vp3 is subsequently increased, the pump current Ip3 does not increase further and becomes saturated. The value of the saturated current at this point is called the limiting current value of the oxygen gas. A region in which the pump current Ip3 is at the limiting current value of the oxygen gas at the pump voltage Vp3 is called the limiting current region of the oxygen gas.In the limiting flow region of the oxygen gas, it is assumed that essentially all the oxygen in the outside gas (in this embodiment, the air), which is introduced into the pretreatment chamber 44 via the pretreatment diffusion rate limiting path 45, is pumped out by the oxygen pump cell 51. In this case, the pump current Ip3 flows from the oxygen pump electrode 52 to the outside electrode 33 outside the sensor element 101.

[0104] When the gas sensor 300 is operated as described above, the reference gas control unit 392 applies the predetermined voltage (the pump voltage Vp3) between the oxygen pump electrode 52 and the outer electrode 33 of the oxygen pump cell 51 in order to pump out at least some of the oxygen in the outside gas (in this embodiment, the air). The pump voltage Vp3 can be set as a voltage at which at least some of the oxygen in the outside gas is pumped out through the oxygen pump cell 51. Preferably, the pump voltage Vp3 can be set as a voltage at which most of the oxygen in the outside gas is pumped out through the oxygen pump cell 51. More preferably, the pump voltage Vp3 can be set as a voltage at which the pump current Ip3 reaches the limit current value for oxygen gas described above.Furthermore, the pump voltage Vp3 can be set as a voltage at which water vapor in the air does not decompose. The pump voltage Vp3 can vary depending on the intended use of the gas sensor 300, the configuration of the sensor element 301, and the like, and the pump voltage Vp3 can, for example, be approximately 100 mV to 400 mV. The pump voltage Vp3 can, for example, be approximately 200 mV to 300 mV.

[0105] In the gas sensor 300, the reference gas control unit 392 first pumps out at least some of the oxygen from the outside gas (in this embodiment, air) introduced into the pretreatment chamber 44 by means of the oxygen pump cell 51. Subsequently, after at least some of the oxygen has been pumped out by the oxygen pump cell 51 (i.e., the air whose oxygen concentration has been adjusted to a low level), the air is introduced into the reference gas chamber 42. In the reference gas chamber 42, the reference gas control unit 392 decomposes water vapor in the air, whose oxygen concentration has been adjusted to the low level by the hydrogen generation pump cell 31, to produce hydrogen and oxygen.The reference gas adjustment unit 392 pumps the generated oxygen and the oxygen contained in the air (residual oxygen) through the hydrogen generation pump cell 31 to adjust the hydrogen concentration in the reference gas in the reference gas chamber 42. Thus, a reference gas containing hydrogen gas produced by the decomposition of water vapor is present in the reference gas chamber 42.

[0106] In the gas sensor 100 of embodiment 1 described above, the hydrogen generation pump cell 31 has two functions: one for pumping oxygen from the air and another for decomposing water vapor in the air and pumping out the generated oxygen. In contrast, in the gas sensor 300 of embodiment 3, the reference gas control element 392 is configured to first pump oxygen from the air through the oxygen pump cell 51. In other words, the oxygen pump cell 51 has a function for pumping oxygen from the air, and the hydrogen generation pump cell 31 primarily has a function for decomposing water vapor in the air and pumping out the generated oxygen. Consequently, in the gas sensor 300 of embodiment 3, the pump current Ip2 flowing through the hydrogen generation pump cell 31 is smaller compared to the gas sensor 100 of embodiment 1.Therefore, the pumping capacity of the hydrogen generation pump cell 31 has more leeway, and thus the ability to decompose water vapor can be maintained at a higher level. This allows the hydrogen concentration in the reference gas to be precisely adjusted. Even if the hydrogen generation electrode 32 gradually deteriorates due to prolonged use, the accuracy of the hydrogen concentration in the reference gas can be maintained. [Version 4]

[0107] Gas sensor 400 of embodiment 4 is shown as another example of an electromotive force-type gas sensor which measures a hydrogen concentration H2 in a gas of the object being measured. Fig. Figure 7 is a vertical sectional view in the longitudinal direction of a sensor element 401, showing an example of a schematic configuration of the gas sensor 400 of embodiment 4. Fig. 7 will use the same components as in Fig. 1 with the same symbol. Fig. Figure 8 is a block diagram showing the electrical connections between a control unit 490 and the sensor element 401 in the gas sensor 400 of embodiment 4.

[0108] An oxygen reference electrode 35 can further be arranged on the oxygen ion-conducting solid electrolyte layer (the oxygen ion conductor layer 3) in the reference gas chamber 42.

[0109] In the sensor element 401, the oxygen reference electrode 35 is arranged at a position that is further away from the outer gas diffusion rate limiting path (namely the air diffusion rate limiting path 43) than the hydrogen generation electrode 32 on the oxygen ion-conducting solid electrolyte layer (the oxygen ion conductor layer 3) in the reference gas chamber 42.

[0110] This means that the oxygen reference electrode 35 is located at a position closer to one end part (the front end part) in the longitudinal direction of the sensor element 401 (the base part 102) than the hydrogen generation electrode 32 on the upper surface of the oxygen ion conductor layer 3 in the reference gas chamber 42.

[0111] The oxygen reference electrode 35, like the hydrogen generation electrode 32 and the outer electrode 33, is a porous cermet electrode (an electrode in a state where a metal component and a ceramic component are mixed). The ceramic component to be used is not particularly restricted, but preferably an oxygen-ion-conducting solid electrolyte, as in the case of the oxygen-ion conductor layer 3. For example, ZrO2 (stabilized ZrO2) can be used as the ceramic component.

[0112] The oxygen reference electrode 35 preferably contains, as in the case of the hydrogen generation electrode 32 and the outer electrode 33, a noble metal with catalytic activity (e.g., at least one of Pt, Rh, Ir, Ru, and Pd) as its metal component. For example, the oxygen reference electrode 35 can be a porous cermet electrode made of Pt and ZrO2.

[0113] The hydrogen reference electrode 23, the oxygen reference electrode 35, the proton conducting layer 5, the spacer layer 4, and the oxygen ion conducting layer 3, located between the hydrogen reference electrode 23 and the oxygen reference electrode 35, form an electrochemical sensor cell, namely an electromotive force detection sensor cell 61 in the reference gas chamber. The water vapor partial pressure (water vapor concentration) in the reference gas chamber 42 can be determined from an electromotive force V4 measured in the electromotive force detection sensor cell 61 in the reference gas chamber.

[0114] In the electromotive force detection sensor cell 61 in the reference gas chamber, the proton-conducting solid electrolyte (the proton conductor layer 5) and the oxygen-ion-conducting solid electrolyte (the spacer layer 4 and the oxygen-ion conductor layer 3) are connected (or bonded) to each other. The hydrogen reference electrode 23 on the proton-conducting solid electrolyte (the proton conductor layer 5) and the oxygen reference electrode 35 on the oxygen-ion-conducting solid electrolyte (the spacer layer 4 and the oxygen-ion conductor layer 3) are both present in the reference gas chamber 42. That is, the hydrogen reference electrode 23 on the proton-conducting solid electrolyte (the proton conductor layer 5) and the oxygen reference electrode 35 on the oxygen-ion-conducting solid electrolyte (the spacer layer 4 and the oxygen-ion conductor layer 3) are both in contact with the same gas atmosphere.With reference to JP 2022-110596 A, it is assumed that in the electromotive force detection sensor cell 61 in the reference gas chamber with such a configuration, an electromotive force is generated corresponding to the water vapor partial pressure (water vapor concentration) in the reference gas chamber 42.

[0115] Fig. Figure 8 is a block diagram showing the electrical connections between the control unit 490 and the hydrogen generation pump cell 31, the electromotive force detection sensor cell 61 in the reference gas chamber, and the electromotive force detection sensor cell 20 of the sensor element 401 in the gas sensor 400 of embodiment 4. Fig. 8 will be the same component as in Fig. The two components are designated with the same symbol. The control unit 490 includes the variable power supply 34 and a control section 491. The control section 491 includes a reference gas adjustment section 492 and a detection section 93.

[0116] The control unit 491 is configured to detect an electromotive force (V1, V4) in each of the respective sensor cells 20 and 61 of the sensor element 401. The control unit 491 can also be configured to additionally detect a pump current Ip2 in the hydrogen generation pump cell 31. Furthermore, the control unit 491 is configured to output a control signal to the variable power supply 34.

[0117] In the gas sensor 400, the reference gas setting part 492 can be configured to actuate the hydrogen generation pump cell 31 on the basis of the electromotive force V4 between the hydrogen reference electrode 23 and the oxygen reference electrode 35 in the electromotive force detection sensor cell 61 in the reference gas chamber.

[0118] More precisely, in the gas sensor 400, the reference gas adjustment part 492 performs feedback control of the pump voltage Vp2 of the variable power supply 34 in the hydrogen generation pump cell 31, so that the electromotive force V4 between the hydrogen reference electrode 23 and the oxygen reference electrode 35 in the electromotive force detection sensor cell 61 in the reference gas chamber is set to a predetermined value (as setpoint V4). SETThe reference gas control unit 492 applies the pump voltage Vp2 to the hydrogen generation pump cell 31 to decompose water vapor H2O in the outside gas introduced into the reference gas chamber 42 at the hydrogen generation electrode 32 (2H2O 2H2 + O2), so that hydrogen H2 and oxygen O2 are produced, and to pump the produced oxygen O2 and any oxygen O2 originally contained in the outside gas introduced into the reference gas chamber 42 out of the reference gas chamber 42, thereby setting a hydrogen concentration in the reference gas chamber 42. The setpoint V4 SET can be set as a value at which essentially all the water vapor H2O in the external gas introduced into the reference gas chamber 42 is decomposed at the hydrogen generation electrode 32. By setting the setpoint V4 SETIn this way, water vapor (H2O) can be decomposed with greater accuracy, and therefore the hydrogen concentration in the reference gas chamber 42 can be set with greater accuracy. The setpoint V4 SET The target value V4 can vary depending on the intended use of the gas sensor 400, the configuration of the sensor element 401, and the like. SET For example, it can be approximately 500 mV to 1500 mV.

[0119] Furthermore, in the gas sensor 400, the sensing element 93 can also be configured to detect the target gas to be measured (in this embodiment, hydrogen) in the sample gas based on the electromotive force V1 between the sensing electrode 22 and the hydrogen reference electrode 23 in the electromotive force sensing sensor cell 20 and the hydrogen concentration in the reference gas in the reference gas chamber 42. A hydrogen concentration in a sample gas can be detected with even higher accuracy, even if the hydrogen concentration in the reference gas chamber 42 varies.

[0120] For example, the sensing unit 93 can detect a water vapor concentration in the air, calculate a concentration of residual water vapor (a quantity of residual water vapor) in the reference gas chamber 42 from the electromotive force V4 in the electromotive force sensing sensor cell 61 in the reference gas chamber, and calculate a quantity (a quantity of decomposed water vapor) of the water vapor decomposed in the reference gas chamber 42 from the difference between the detected water vapor concentration in the air and the calculated concentration of residual water vapor in the reference gas chamber 42. Since the quantity of decomposed water vapor corresponds to a quantity of hydrogen produced, the sensing unit 93 can calculate the H2 concentration in the reference gas in the reference gas chamber 42 based on the quantity of decomposed water vapor.For example, the water vapor concentration in the air can be measured using a temperature and humidity meter or similar device as a gas sensor.

[0121] The sensing unit 93 can calculate the hydrogen concentration in the gas of the sample based on the electromotive force V1 between the sensing electrode 22 and the hydrogen reference electrode 23 in the electromotive force sensing sensor cell 20, taking into account the calculated H2 concentration in the reference gas. As the conversion parameter described above (the electromotive force-H2 concentration conversion parameter) between the electromotive force V1 and the H2 concentration in the gas of the sample, the sensing unit 93 can first store a map that maps the electromotive force V1, the H2 concentration in the reference gas, and the H2 concentration in the gas of the sample to each other.

[0122] In the sensor element 401 described above, the oxygen reference electrode 35 is positioned further away from the air diffusion rate limiting path 43 than the hydrogen generation electrode 32 on the oxygen ion conductor layer 3 in the reference gas chamber 42. That is, on the oxygen ion conductor layer 3 in the reference gas chamber 42, the oxygen reference electrode 35 and the hydrogen generation electrode 32 are arranged in series, in that order, from one side near the front end part along the longitudinal direction of the sensor element 401. However, the position of the oxygen reference electrode 35 is not limited to this.

[0123] The oxygen reference electrode 35 can be arranged on the oxygen ion conductor layer 3 in the reference gas chamber 42. The oxygen reference electrode 35 can be positioned closer to the air diffusion rate limiting path 43 than the hydrogen generation electrode 32. That is, on the oxygen ion conductor layer 3 in the reference gas chamber 42, the hydrogen generation electrode 32 and the oxygen reference electrode 35 can be arranged in series, starting from the side near the front end and running longitudinally along the sensor element 401. Alternatively, the oxygen reference electrode 35 and the hydrogen generation electrode 32 can be arranged parallel to each other longitudinally along the sensor element 401.

[0124] In the sensor element 401 described above, the oxygen reference electrode 35 and the hydrogen generation electrode 32 are arranged as separate electrodes, but the oxygen reference electrode 35 and the hydrogen generation electrode 32 can be arranged as an integrated electrode. That is, the integrated electrode can serve as both the oxygen reference electrode 35 and the hydrogen generation electrode 32. In this case, the integrated electrode, the outer electrode 33, and the oxygen ion conductor layer 3 can form the hydrogen generation pump cell 31, and the integrated electrode, the hydrogen reference electrode 23, the oxygen ion conductor layer 3, the spacer layer 4, and the proton conductor layer 5 can form the electromotive force detection sensor cell 61 in the reference gas chamber.

[0125] With reference to the aforementioned JP 2022-110596 A, it is necessary that the proton-conducting solid electrolyte and the oxygen-ion-conducting solid electrolyte be connected (or bonded) to each other in order to detect the electromotive force V4 corresponding to a water vapor concentration in the reference gas chamber 42 in the electromotive force sensing sensor cell 61 in the reference gas chamber. The spacer layer 4 present between the proton-conducting layer 5 and the oxygen-ion-conducting layer 3 can be an oxygen-ion-conducting solid electrolyte layer, as in the case of the sensor element 401. In this case, the proton-conducting solid electrolyte and the oxygen-ion-conducting solid electrolyte are connected (or bonded) between the lower surface of the proton-conducting layer 5 and the upper surface of the spacer layer 4. Alternatively, the spacer layer 4 can be a proton-conducting solid electrolyte layer.In this case, the proton-conducting solid electrolyte and the oxygen-ion-conducting solid electrolyte are connected (or bonded) between the lower surface of spacer layer 4 and the upper surface of oxygen-ion-conducting layer 3. A bonded surface between the proton-conducting solid electrolyte and the oxygen-ion-conducting solid electrolyte may be present within spacer layer 4. The entire spacer layer 4 need not consist of the proton-conducting solid electrolyte and / or the oxygen-ion-conducting solid electrolyte. It is sufficient if the proton-conducting solid electrolyte and the oxygen-ion-conducting solid electrolyte are connected (or bonded) through at least a portion of spacer layer 4.

[0126] Embodiments 1 to 4 have been described above as examples of embodiments according to the present invention, but the present invention is not limited thereto. The present invention may include a gas sensor with any structure comprising a sensor element and a control unit, as long as the object of the present invention can be achieved, i.e., a gas sensor capable of measuring hydrogen gas or a gas containing a hydrogen atom (such as ammonia NH3, water vapor H2O, and hydrocarbon HC) in a sample gas with higher accuracy.

[0127] The preceding embodiments 1 to 4 show examples of gas sensors that measure a hydrogen concentration in a sample gas, but the target gas to be measured is not limited to hydrogen. Examples of target gases other than hydrogen (H₂) include ammonia (NH₃), water vapor (H₂O), and hydrocarbons (HC). Examples of hydrocarbons (HC) include alkanes such as methane (e.g., methane (CH₄), ethane (C₂H₆), propane (C₃H₈), and butane (C₄H₆). 10 ) and alkenes such as ethylene (e.g., ethylene C2H4, propylene C3H6, and butylene C4H8). That is, a gas sensor of the present invention can measure hydrogen gas or a gas containing a hydrogen atom (such as ammonia NH3, water vapor H2O, and hydrocarbon HC) in a gas sample.

[0128] In the case of measuring a gas containing a hydrogen atom (such as ammonia NH3, water vapor H2O and hydrocarbon HC), for example, the following can be determined: Fig. The sensor element 201 shown in Figure 3 is used. When measuring ammonia NH3 as a gas containing a hydrogen atom, the detection electrode 22 also acts, for example, as a catalyst that decomposes ammonia NH3 in the sample gas, which is introduced into the sample gas cavity 12 through the sample gas diffusion rate limiting path 11.

[0129] The sensing unit 293 can apply a predetermined voltage (pump voltage Vp1) between the sensing electrode 22 and the hydrogen reference electrode 23 of the current-sensing pump cell 21 to decompose ammonia NH3 in the sample gas, which has been introduced into the sample gas cavity 12 at the sensing electrode 22, and to pump the hydrogen produced by the decomposition out of the sample gas cavity 12 through the current-sensing pump cell 21. Ammonia NH3 can be measured by detecting the pump current Ip1 flowing at this time.

[0130] The pump voltage Vp1 can be set to a value at which essentially all the ammonia NH3 in the sample gas introduced into the sample gas cavity 12 is decomposed. In this case, the pump current Ip1 flowing through the current-sensing pump cell 21 is a current value corresponding to the concentration of ammonia NH3 in the sample gas. Therefore, the concentration of ammonia NH3 in the sample gas can be determined based on the pump current Ip1. The concentration of a gas containing a hydrogen atom other than ammonia NH3 (e.g., water vapor H2O, alkanes such as methane CH4, and alkenes such as ethylene C2H4) can be determined in the same way.When measuring a gas containing a hydrogen atom, the pump voltage Vp1 can vary depending on the target gas type, the intended use of the gas sensor 200, the configuration of the sensor element 201, and the like, and the pump voltage Vp1 can be, for example, about 800 mV to 1200 mV.

[0131] In the preceding embodiments 1 to 4, the sensing electrode 22 is arranged on the region of the upper surface of the proton conductor layer 5 that corresponds to the hydrogen reference electrode 23. However, the present invention is not limited thereto. The sensing electrode 22 can be arranged on the proton conductor layer 5 such that it is in contact with a gas used in the measurement. For example, the sensing electrode 22 can be arranged at a position that differs from the hydrogen reference electrode 23 in the longitudinal direction of the sensor element on the proton conductor layer 5. The sensing electrode 22 can, for example, be arranged on the lower surface of the proton conductor layer 5 in the oxygen outlet chamber 41. Alternatively, the sensing electrode 22 can be arranged on a side surface or a front end surface of the proton conductor layer 5.

[0132] Both the gas sensor 300 of embodiment 3 with the oxygen pump cell 51 and the gas sensor 400 of embodiment 4 with the electromotive force-sensing sensor cell 61 in the reference gas chamber are examples of electromotive force-type gas sensors. In the electromotive force-type gas sensor, either the oxygen pump cell 51 or the electromotive force-sensing sensor cell 61 can be used in the reference gas chamber. In the current-limiting type gas sensor, the oxygen pump cell 51 and / or the electromotive force-sensing sensor cell 61 can be used in the reference gas chamber.

[0133] In the preceding embodiments 1 to 4, both the proton conduction layer 5 and the oxygen ion conduction layer 3 are layers that extend over the entire length in the longitudinal direction of the sensor element, but the layer configuration is not limited thereto. For example, the proton conduction layer and / or the oxygen ion conduction layer can be present on a portion of the total length of the sensor element where electrodes are to be arranged. Fig. Figure 9 is a vertical sectional view in the longitudinal direction of a sensor element 501, showing an example of a schematic configuration of the gas sensor 500 of embodiment 5. The gas sensor 500 of embodiment 5 is a variant of the gas sensor 400 of embodiment 4, in which the layer configuration of the sensor element is different. Fig. 9 will be the same component as in Fig. 7 are designated with the same symbol.

[0134] In the sensor element 501, the base part 502 has a structure such that six layers, namely a first substrate layer 1, a second substrate layer 2, an oxygen ion conductor layer 3, a spacer layer 4, a proton conductor layer 505, and a second oxygen ion conductor layer 506, are arranged one above the other in this order, viewed from the underside, as shown in the drawing. The first substrate layer 1, the second substrate layer 2, the oxygen ion conductor layer 3, the spacer layer 4, and the second oxygen ion conductor layer 506 are each layers that extend along the entire length in the longitudinal direction of the base part 502.The proton conduction layer 505, on the other hand, is located at a position extending from the front end part longitudinally along the sensor element 501 to essentially the entire surface in the reference gas chamber 42, between the lower surface of the second oxygen ion conduction layer 506 and the upper surface of the spacer layer 4. The second oxygen ion conduction layer 506 is a layer that, like the oxygen ion conduction layer 3, is formed from an oxygen ion conductor. The proton conduction layer 505 and the second oxygen ion conduction layer 506 are each dense and gas-tight.

[0135] In the sensor element 501, a hydrogen reference electrode 523 is arranged on the proton conductor layer 505 (on the lower surface of the proton conductor layer 505) in the reference gas chamber 42. A detection electrode 522 is arranged on the proton conductor layer 505 (on the lower surface of the proton conductor layer 505) in the oxygen outlet chamber 41. The oxygen outlet chamber 41 is filled with a gas containing the object being measured, as described above. The detection electrode 522, the hydrogen reference electrode 523, and the proton conductor layer 5, which is in contact with both the detection electrode 522 and the hydrogen reference electrode 523, form an electrochemical sensor cell, namely an electromotive force detection sensor cell 520.The hydrogen partial pressure (hydrogen concentration) in the gas of the object being measured around the detection electrode 522 can be determined from an electromotive force V1 measured in the electromotive force detection sensor cell 520.

[0136] The hydrogen reference electrode 523, the oxygen reference electrode 35, the proton conducting layer 505, the spacer layer 4, and the oxygen ion conducting layer 3, which are arranged between the hydrogen reference electrode 523 and the oxygen reference electrode 35, form an electrochemical sensor cell, namely an electromotive force detection sensor cell 561 in the reference gas chamber. The water vapor partial pressure (water vapor concentration) in the reference gas chamber 42 can be detected from an electromotive force V4 measured in the electromotive force detection sensor cell 561 in the reference gas chamber.

[0137] The gas sensor 500 of embodiment 5 can measure hydrogen in the gas of the object being measured in the same way as the gas sensor 400 of embodiment 4. In the gas sensor 500 of embodiment 5, the proton conduction layer 505 is shorter and thinner in the longitudinal direction of the sensor element 501 than in other layers. For example, a ceramic green sheet produced by strip casting can be used as the plate for the first substrate layer 1, the second substrate layer 2, the oxygen ion conduction layer 3, the spacer layer 4, and the second oxygen ion conduction layer 506 in the manufacture of the sensor element 501. A ceramic green sheet produced by strip casting can be used for the proton conduction layer 505, as for the other layers. Alternatively, the proton conduction layer 505 can be formed on a layer designated as the second oxygen ion conduction layer 506 by another method, such as screen printing.If the proton conductor layer 505 is formed by a different process, the number of layers to be produced by strip casting can be reduced. This can have a positive effect on productivity, for example by reducing the consumption of the proton conductor.

[0138] In the sensor element 501, the oxygen ion conductor is used as a base, and the proton conductor is arranged in a region where the detection electrode 522 and the hydrogen reference electrode 523 are to be located. However, the present invention is not limited to this. In contrast, the proton conductor can be used as a base, and the oxygen ion conductor can be arranged in a region where the hydrogen generation electrode 32, the outer electrode 33, and the oxygen reference electrode 35 are to be located. Alternatively, an insulator such as aluminum oxide can be used as a base, and the proton conductor and the oxygen ion conductor can be arranged in a region where the respective electrodes are to be located.While the gas sensor 500 of embodiment 5 has a configuration corresponding to the gas sensor 400 of embodiment 4, the proton conductor layer and / or the oxygen ion conductor layer can also be present on a part of the total length of the sensor element, as in embodiments 1 to 3, where the individual electrodes are to be arranged.

[0139] Furthermore, the present invention includes a gas adjustment device described below.

[0140] A gas adjustment device comprising: a gas chamber which is at least partially surrounded by a proton-conducting solid electrolyte layer and an oxygen-ion-conducting solid electrolyte layer, wherein an external gas is introduced into the gas chamber via an external gas diffusion rate limiting path; a hydrogen generation pump cell comprising: a hydrogen generation electrode located on the oxygen-ion-conducting solid electrolyte layer in the gas chamber; and an external electrode located at a position on the oxygen-ion-conducting solid electrolyte layer and corresponding to the hydrogen generation electrode, different from the gas chamber; a hydrogen reference electrode arranged on the proton-conducting solid electrolyte layer in the gas chamber; and A gas control unit for adjusting the hydrogen concentration in the gas chamber by actuating the hydrogen generation pump cell. Here, the gas control unit can adjust the hydrogen concentration in the gas chamber by applying a predetermined voltage between the hydrogen generation electrode and the outer electrode of the hydrogen generation pump cell. This causes water vapor in the external gas introduced into the gas chamber to decompose at the hydrogen generation electrode, producing hydrogen and oxygen. The unit then pumps the produced oxygen and any oxygen contained in the external gas out of the gas chamber and delivers the gas, with the adjusted hydrogen concentration, to the hydrogen reference electrode.

[0141] The configuration of the gas adjustment device described above is in Fig. 1 and Fig. 2 shown. The reference gas chamber 42 in Fig. 1 corresponds to the gas chamber in the gas adjustment device, and the reference gas adjustment part 92 in Fig. 2 corresponds to the gas adjustment part in the gas adjustment device. The components and their functions in the gas adjustment device are as described in the preceding embodiment 1. Reference symbol list

[0142] EXPLANATION OF THE REFERENCE MARKS IN THE DRAWINGS

[0157] 1 first substrate layer; 2 second substrate layer; 3 Oxygen ion conductor layer; 4 spacer layer; 5,505 proton conductor layer; 506 second oxygen ion conductor layer; 6 second spacer layer; 7 Top layer; 10 Gas inlet; 11. Measured object gas diffusion rate limitation path; 12 Measuring object gas cavity; 20,520 electromotive force detection sensor cell; 21 Electricity collection pump cell; 22 Detection electrode; 23 Hydrogen reference electrode; 24 variable power supply (of the power acquisition pump cell); 31 Hydrogen generation cell; 32 Hydrogen generation electrode; 33 External electrode; 34 variable power supply (of the hydrogen production cell); 35 Oxygen reference electrode; 40 Air intake chamber; 41 Oxygen outlet room; 42 Reference gas chamber; 43 Air diffusion rate limitation pathway; 44 Pretreatment chamber; 45 Pretreatment diffusion rate limitation pathway; 51 Oxygen pump cell; 52 Oxygen pump electrode; 54 variable power supply (of the oxygen pump cell); 61, 561 electromotive force detection sensor cell in the reference gas chamber; 72 stokers; 90, 290, 390, 490 control unit; 91, 291, 391, 491 Control unit; 92, 392, 492 Reference gas adjustment part; 93, 293 Recording section; 100, 200, 300, 400, 500 gas sensor; 101, 201, 301, 401, 501 Sensor element; and 102, 202, 302, 502 Basic part. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2023-077521

[0001] JP 6667192 B2 [0003, 0005, 0006] JP 7122935 B2 [0004, 0005, 0006] JP 2022-110596 A [0005, 0114, 0125] Cited non-patent literature

[0000] MK Hossain et al., Nanomaterials 2022, 12, 3581

[0005] Y. Okuyama et al., RSC Advances 2016, 6, 34019-34026

[0005]

Claims

[1] Gas sensor for detecting a target gas to be measured in a gas of a measuring object, wherein the gas sensor comprises a sensor element and a control unit for controlling the sensor element, wherein the sensor element comprises: a base part in elongated plate form, which includes a proton-conducting solid electrolyte layer and an oxygen-ion-conducting solid electrolyte layer; a reference gas chamber formed between the proton-conducting solid electrolyte layer and the oxygen-ion-conducting solid electrolyte layer within the base part, wherein an external gas is introduced into the reference gas chamber via an external gas diffusion rate limiting path; a hydrogen reference electrode that is arranged on the proton-conducting solid electrolyte layer in the reference gas chamber; a hydrogen generation pump cell comprising: a hydrogen generation electrode arranged on the oxygen-ion-conducting solid electrolyte layer in the reference gas chamber; and an external electrode arranged at a position on the oxygen-ion-conducting solid electrolyte layer different from the reference gas chamber and corresponding to the hydrogen generation electrode; and a sensing electrode arranged on the proton-conducting solid electrolyte layer to be in contact with a gas used in the measurement; and The control unit includes: a reference gas adjustment component for setting a hydrogen concentration in the reference gas chamber by actuating the hydrogen generation pump cell; and A detection element for detecting a target gas to be measured in a measuring object gas. [2] Gas sensor according to claim 1, wherein the reference gas adjusting part adjusts the hydrogen concentration in a reference gas in the reference gas chamber by applying a predetermined voltage between the hydrogen generation electrode and the outer electrode of the hydrogen generation pump cell to decompose water vapor in the outside gas introduced into the reference gas chamber at the hydrogen generation electrode, so that hydrogen and oxygen are produced, and to pump the produced oxygen and any oxygen contained in the outside gas out of the reference gas chamber. [3] Gas sensor according to claim 1, wherein the sensing part detects the target gas to be measured in the gas of the object being measured on the basis of an electromotive force between the sensing electrode and the hydrogen reference electrode. [4] Gas sensor according to claim 1, wherein the sensor element further comprises a measuring object gas cavity formed within the base part, wherein the measuring object gas is introduced into the measuring object gas cavity via a measuring object gas diffusion rate limiting path, the detection electrode exits into the gas cavity of the object being measured and The detection element detects the target gas to be measured in the gas of the object being measured based on a current flowing between the detection electrode and the hydrogen reference electrode. [5] Gas sensor according to claim 1, wherein the sensor element comprises: a pretreatment chamber formed between the proton-conducting solid electrolyte layer and the oxygen-ion-conducting solid electrolyte layer within the base part and adjacent to the reference gas chamber via the external gas diffusion rate limiting path, wherein the external gas is introduced into the pretreatment chamber via a pretreatment diffusion rate limiting path; and an oxygen pump cell comprising: an oxygen pump electrode arranged on the oxygen-ion-conducting solid electrolyte layer in the pretreatment chamber; and an external electrode arranged at a position on the oxygen-ion-conducting solid electrolyte layer and corresponding to the oxygen pump electrode, different from the reference gas chamber and the pretreatment chamber; and The reference gas adjustment unit adjusts the hydrogen concentration in the reference gas chamber by actuating the oxygen pump cell to pump out oxygen from the outside gas introduced into the pretreatment chamber; and actuating the hydrogen generation pump cell to decompose water vapor in the outside gas introduced into the reference gas chamber after pumping out the oxygen from the pretreatment chamber, so that hydrogen and oxygen are produced, and to pump out the produced oxygen and the oxygen contained in the outside gas from the reference gas chamber. [6] Gas sensor according to claim 1, wherein the sensor element further comprises an oxygen reference electrode arranged on the oxygen ion-conducting solid electrolyte layer in the reference gas chamber, and the reference gas control element actuates the hydrogen generation pump cell on the basis of an electromotive force between the hydrogen reference electrode and the oxygen reference electrode. [7] Gas sensor according to claim 1, wherein the outer electrode of the hydrogen generation pump cell is arranged such that it is in contact with the gas of the object being measured. [8] Gas sensor according to claim 1, wherein the target gas to be measured is hydrogen, ammonia, water vapor or methane. [9] Sensor element for detecting a target gas to be measured in a gas of the object being measured, wherein the sensor element comprises: a base part in elongated plate form, which includes a proton-conducting solid electrolyte layer and an oxygen-ion-conducting solid electrolyte layer; a reference gas chamber formed between the proton-conducting solid electrolyte layer and the oxygen-ion-conducting solid electrolyte layer within the base part, wherein an external gas is introduced into the reference gas chamber via an external gas diffusion rate limiting path; a hydrogen reference electrode that is arranged on the proton-conducting solid electrolyte layer in the reference gas chamber; a hydrogen generation pump cell comprising: a hydrogen generation electrode arranged on the oxygen-ion-conducting solid electrolyte layer in the reference gas chamber; and an external electrode arranged at a position on the oxygen-ion-conducting solid electrolyte layer different from the reference gas chamber and corresponding to the hydrogen generation electrode; and a detection electrode that is arranged on the proton-conducting solid electrolyte layer to be in contact with a gas used in the measurement. [10] Gas control device comprising: a gas chamber which is at least partially surrounded by a proton-conducting solid electrolyte layer and an oxygen-ion-conducting solid electrolyte layer, wherein an external gas is introduced into the gas chamber via an external gas diffusion rate limiting path; a hydrogen generation pump cell comprising: a hydrogen generation electrode located on the oxygen-ion-conducting solid electrolyte layer in the gas chamber; and an external electrode located at a position on the oxygen-ion-conducting solid electrolyte layer and corresponding to the hydrogen generation electrode, different from the gas chamber; a hydrogen reference electrode arranged on the proton-conducting solid electrolyte layer in the gas chamber; and a gas control unit for adjusting the hydrogen concentration in the gas chamber by actuating the hydrogen generation pump cell.

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