Gas sensor

Abstract

A gas sensor 1 detects the concentration of a gas to be measured contained in an environment to be measured. The gas sensor 1 includes: a substrate 11; a reference electrode 12; solid electrolyte bodies 13a, 13b; a first detection electrode 21 which detects the oxygen concentration; a first diffusion porous body 22; a second detection electrode 31a; a third detection electrode 31b which is disposed at a position facing the second detection electrode 31a with the solid electrolyte body 13b therebetween; a second diffusion porous body 32a; a third diffusion porous body 32b which has a reaction-accelerating catalyst function; and a gas concentration calculation unit 41.

Description

Gas Sensor

[0001] The present invention relates to a gas sensor that detects the concentration of a gas by utilizing the difference in diffusion coefficient between the gas and oxygen.

[0002] In recent years, hydrogen gas has been attracting attention as an alternative energy source to fossil fuels such as petroleum, and various systems utilizing hydrogen have been proposed. These hydrogen-based systems are equipped with gas sensors for detecting hydrogen.

[0003] Gas sensors for detecting hydrogen include various types of sensors, such as catalytic combustion type, thermal conduction type, and semiconductor type. For example, Patent Document 1 discloses a Si-MOSFET type hydrogen gas sensor that uses a platinum film as the gate electrode as an example of a semiconductor type gas sensor.

[0004] JP 2009-300297 A

[0005] When detecting hydrogen gas using various sensors such as catalytic combustion, thermal conduction, and semiconductor sensors, there are limitations on the range of gas temperatures and concentrations that can be used, and these sensors also have limitations on the environment in which they can be used, such as being unable to be used in condensation environments.

[0006] An object of the present invention is to provide a gas sensor that can be used in a wider range of environments.

[0007] [1] A gas sensor according to one aspect of the present invention detects the concentration of a measurement target gas contained in a measurement environment. a first sensing electrode disposed opposite the reference electrode with the solid electrolyte body sandwiched therebetween for detecting a potential difference between the first sensing electrode and the reference electrode; a first diffusing porous body disposed between the first sensing electrode and the environment to be measured; a second sensing electrode disposed on one surface of the solid electrolyte body; a third sensing electrode disposed opposite the second sensing electrode with the solid electrolyte body sandwiched therebetween; a second diffusing porous body disposed between the second sensing electrode and the environment to be measured; a third diffusing porous body disposed between the third sensing electrode and the environment to be measured and having a catalytic function for promoting a reaction; and a gas concentration calculation unit that calculates an oxygen concentration from the potential difference detected by the first sensing electrode, calculates an oxygen concentration ratio from the potential difference between the second sensing electrode and the third sensing electrode, and calculates the concentration of the target gas using the oxygen concentration and the oxygen concentration ratio.

[0008] Here, the third diffusion porous body having a catalytic function means either of the following: (1) The third diffusion porous body includes a diffusion porous body and a catalyst layer provided on the diffusion porous body to promote the reaction, or (2) The third diffusion porous body has a catalytic function to promote the reaction.

[0009] [2] A gas sensor according to another aspect of the present invention detects the concentration of a measurement target gas contained in a measurement environment. This gas sensor includes: a base; a reference electrode disposed on the base; a first solid electrolyte body disposed on the reference electrode; a first sensing electrode disposed opposite the reference electrode with the first solid electrolyte body interposed therebetween and detecting a potential difference between the reference electrode and the reference electrode; a first diffusion porous body disposed between the first sensing electrode and the environment to be measured; a hollow measurement chamber disposed on the first sensing electrode and into which the gas to be measured that has passed through the first diffusion porous body flows, the side of the measurement chamber being surrounded by an insulating layer made of an insulating portion and the first diffusion porous body; a second solid electrolyte body disposed on the measurement chamber; a second sensing electrode disposed on the measurement chamber side of the second solid electrolyte body; a third sensing electrode disposed opposite the second sensing electrode with the second solid electrolyte body interposed therebetween; and a second diffusion porous body disposed between the third sensing electrode and the environment to be measured and having a catalytic function for promoting a reaction. a gas concentration calculation unit that calculates an oxygen concentration from the potential difference detected by the first sensing electrode, calculates an oxygen concentration ratio from the potential difference between the second sensing electrode and the third sensing electrode, and calculates the concentration of the measurement target gas using the oxygen concentration and the oxygen concentration ratio.

[0010] Here, the second diffusion porous body having a catalytic function means either of the following: (1) The second diffusion porous body includes a diffusion porous body and a catalyst layer provided on the diffusion porous body to promote the reaction, or (2) The second diffusion porous body has a catalytic function to promote the reaction.

[0011] [3] A gas sensor according to another aspect of the present invention detects the concentration of a measurement target gas contained in a measurement environment. This gas sensor comprises: a base; a reference electrode disposed on the base; a first solid electrolyte body disposed on the reference electrode; a first sensing electrode disposed opposite the reference electrode with the first solid electrolyte body interposed therebetween and configured to detect a potential difference between the first sensing electrode and the reference electrode; a first diffusion porous body disposed between the first sensing electrode and the environment to be measured and having a catalytic function for promoting a reaction; a hollow measurement chamber disposed on the first sensing electrode and into which the gas to be measured that has passed through the first diffusion porous body flows, the side of the measurement chamber being surrounded by an insulating layer formed of an insulating portion and the first diffusion porous body; a second solid electrolyte body disposed on the measurement chamber; a second sensing electrode disposed on the second solid electrolyte body on the measurement chamber side; a third sensing electrode disposed opposite the second sensing electrode with the second solid electrolyte body interposed therebetween; and a second diffusion porous body disposed between the third sensing electrode and the environment to be measured. a gas concentration calculation unit that calculates an oxygen concentration from the potential difference detected by the first sensing electrode, calculates an oxygen concentration ratio from the potential difference between the second sensing electrode and the third sensing electrode, and calculates the concentration of the measurement target gas using the oxygen concentration and the oxygen concentration ratio. The first diffusion porous body is provided between the second sensing electrode and the measurement environment.

[0012] Here, the first diffusion porous body having a catalytic function means either of the following: (1) The first diffusion porous body includes a diffusion porous body and a catalyst layer provided on the diffusion porous body to promote the reaction, or (2) The first diffusion porous body has a catalytic function to promote the reaction.

[0013] [4] In the gas sensor according to any one of the above aspects of the present invention, the first diffusion porous body may have a catalytic function that promotes a reaction.

[0014] [5] In the gas sensor according to any of the above aspects of the present invention, the gas concentration calculation unit may calculate the concentration of the measurement target gas from the oxygen concentration, the oxygen concentration ratio, and a difference in diffusion coefficient from the measurement target gas.

[0015] [6] In the gas sensor according to any one of the above aspects of the present invention, the measurement target gas may be any one of hydrogen gas, ammonia gas, and propane gas.

[0016] According to the present invention, it is possible to provide a gas sensor that can be used in a wider range of environments.

[0017] FIG. 10 is a cross-sectional view schematically illustrating the internal configuration of a gas sensor according to an embodiment. FIG. 11 is a cross-sectional view schematically illustrating the configuration of a gas concentration detection element provided in a gas sensor according to a first embodiment. FIG. 12 is a cross-sectional view schematically illustrating the configuration of a gas concentration detection element provided in a gas sensor according to a second embodiment. FIG. 13 is a cross-sectional view schematically illustrating the configuration of a gas concentration detection element provided in a gas sensor according to a third embodiment. FIG. 14 is a cross-sectional view schematically illustrating the configuration of a gas concentration detection element provided in a gas sensor according to a modified example. FIG. 15 is a cross-sectional view schematically illustrating the configuration of a gas concentration detection element provided in a gas sensor according to a modified example. FIG. 16 is a cross-sectional view schematically illustrating the configuration of a gas concentration detection element provided in a gas sensor according to a fourth embodiment. FIG. 17 is a perspective view showing the schematic configuration of a limiting current type oxygen concentration detection element. FIG. 18 is a cross-sectional view schematically illustrating the configuration of an insulating layer portion of the oxygen concentration detection element shown in FIG. 8. FIG. 19 is a cross-sectional view schematically illustrating the configuration of a gas concentration detection element provided in a gas sensor according to a fifth embodiment. FIG. 19 is a cross-sectional view schematically illustrating the configuration of a gas concentration detection element provided in a gas sensor according to a sixth embodiment. １ and K. ２ FIG. 10 is an image diagram for explaining the above.

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. The names and functions of the components are also the same. Therefore, detailed description thereof will not be repeated.

[0019] In this embodiment, a gas sensor that detects a gas concentration by utilizing the difference in diffusion coefficient with respect to oxygen will be described. The gas sensor has a gas concentration detection element that detects a gas concentration by utilizing the difference in diffusion coefficient with respect to oxygen. The gas sensor can detect, for example, any of hydrogen gas, ammonia gas, and propane gas as a measurement target gas. The following description will be given by taking as an example a gas sensor 1 that detects the concentration of hydrogen gas, which is one of the measurement target gases.

[0020] First, the overall configuration of the gas sensor 1 will be described. Fig. 1 shows the internal configuration of the gas sensor 1 according to one embodiment. The gas sensor 1 mainly includes a sensor unit 2, a housing 3, a sensor cover 4, an atmosphere-side cover 5, wiring 8, and a sensor control unit 9.

[0021] The sensor unit 2 has, for example, an elongated flat plate shape and is inserted and held inside a cylindrical housing 3. The sensor unit 2 includes a gas concentration detection element 10 and a heater (not shown). The gas concentration detection element 10 detects the concentration of a measurement target gas contained in a measurement environment. In this embodiment, the gas concentration detection element 10 detects the concentration of hydrogen gas contained in a mixed gas G that has flowed into the sensor cover 4.

[0022] The housing 3 is made of, for example, metal and holds the sensor unit 2 therein. The tip end side in the longitudinal direction of the sensor unit 2 (i.e., the lower end side in FIG. 1 ) protrudes from the housing 3 and is housed in a sensor cover 4.

[0023] The sensor cover 4 is attached to the tip side of the housing 3. The sensor cover 4 is arranged to surround the periphery of the tip of the sensor unit 2. The sensor cover 4 is provided with a through-hole that serves as an inlet / outlet for mixed gas G containing the measurement target gas and the like.

[0024] The mixed gas G that passes through the through-hole and flows into the sensor cover 4 reaches the surface of the sensor unit 2 and is taken in. The base end side in the longitudinal direction of the sensor unit 2 (i.e., the upper end side in FIG. 1 ) protrudes from the housing 3 and is housed in the atmosphere-side cover 5. The cylindrical atmosphere-side cover 5 has through-holes that open to the outer circumferential side and serve as atmosphere holes, allowing the atmosphere A, which serves as a reference gas, to be taken in. In another embodiment, a configuration may be employed in which a predetermined level of reference oxygen is generated within the oxygen sensor using oxygen accumulated in the reference electrode portion, and this is used as the reference gas concentration (a so-called self-generating gas sensor).

[0025] The base end side of the sensor unit 2 is connected to a sensor control unit 9 via wiring 8. The sensor control unit 9 includes a gas concentration calculation unit 41. As will be described later, the gas concentration calculation unit 41 is a component of the gas concentration detection element 10 and is connected to each electrode in the gas concentration detection element 10 via wiring 8. The gas concentration calculation unit 41 can calculate the potential difference between the electrodes included in the gas concentration detection element 10. The gas concentration calculation unit 41 can also calculate the concentration of the target gas based on the oxygen concentration obtained based on the potential difference between the electrodes (e.g., the oxygen concentration obtained from the potential difference between the reference electrode 12 and the first sensing electrode 21), the oxygen concentration ratio obtained based on the potential difference between the electrodes (e.g., the oxygen concentration ratio obtained from the potential difference between the second sensing electrode 31 a and the third sensing electrode 31 b), the difference in diffusion coefficient between the target gas (e.g., hydrogen gas) and oxygen, and the reaction rate of the target gas on the catalyst.

[0026] The gas sensor 1 can be applied to any hydrogen utilization system, such as a fuel cell system. The gas sensor 1 is installed in a gas supply path or exhaust path through which a mixed gas G containing hydrogen gas flows, and can be used to detect the concentration of hydrogen gas in an atmosphere in which oxygen and multiple reducing gases coexist. The gas sensor 1 can also be used suitably in environments where conventional gas sensors cannot be used, such as condensation environments.

[0027] In the following, various embodiments will be described, each including a gas concentration detection element 10 having a different configuration. In the following description, the "gas concentration detection element" will also be simply referred to as the "detection element."

[0028] First Embodiment In the first embodiment, a gas sensor 1 will be described that includes a sensing element 10A, which is an example of a gas concentration sensing element 10. The sensing element 10A of this embodiment has a configuration that senses the oxygen concentration using the principle of a so-called zirconia oxygen sensor. Figure 2 shows the configuration of the sensing element 10A.

[0029] The detection element 10A has two elements separated from each other (i.e., a first element 110a shown on the left side of FIG. 2 and a second element 110b shown on the right side) and a gas concentration calculation unit 41 (see FIG. 1).

[0030] First, the configuration of the first element 110a will be described. The first element 110a includes a base 11, a reference electrode 12, a first solid electrolyte body 13a, a first sensing electrode 21, and a first diffusion porous body 22.

[0031] The base 11 is made of an insulating material. In one example, the base 11 contains alumina as a main component.

[0032] The reference electrode 12 is disposed on the substrate 11. The reference electrode 12 is formed of a platinum group element such as Pt, Pd, a Pt alloy, or a Pd alloy. The reference electrode 12 is configured to come into contact with a reference gas. The reference gas is, for example, the atmosphere. That is, the reference electrode 12 is configured to come into contact with the atmosphere A taken in through the atmosphere-side cover 5 of the gas sensor 1.

[0033] The first solid electrolyte body 13a is disposed on the reference electrode 12. The first solid electrolyte body 13a is made of, for example, zirconia (ZrO ２ ) with yttria (Y) as a stabilizer ２ O ３ It is composed of a partially stabilized zirconia sintered body to which zirconia (ZrO) or calcia (CaO) is added.

[0034] The first sensing electrode 21 is disposed in a position facing the reference electrode 12 with the first solid electrolyte body 13a sandwiched therebetween. The first sensing electrode 21 is formed of a platinum group element such as Pt, Pd, a Pt alloy, or a Pd alloy, similar to the reference electrode 12. The first sensing electrode 21 detects the first oxygen concentration using the potential difference between itself and the reference electrode 12.

[0035] The first diffusion porous body 22 is provided between the first sensing electrode 21 and the environment to be measured. Specifically, the first diffusion porous body 22 is provided so as to cover the first sensing electrode 21 (see FIG. 2). The first diffusion porous body 22 is exposed to the space inside the sensor cover 4 into which the mixed gas G flows. Therefore, the interior of the sensor cover 4 is the environment to be measured.

[0036] The first diffusion porous body 22 is made of alumina (Al ２ O ３ ) is a porous body made of the first diffusion porous body 22. By providing such a first diffusion porous body 22 between the first sensing electrode 21 and the environment to be measured, the speed at which the mixed gas G in the environment to be measured reaches the first sensing electrode 21 is adjusted. For this reason, the first diffusion porous body 22 is also called a rate-determining layer. The oxygen partial pressure ([O ２ ]' １ ) is reduced by the influence of hydrogen when the mixed gas G passes through the first diffusion porous body 22.

[0037] With the above-described configuration, in the first element 110a, the first solid electrolyte body 13a and a pair of electrodes (specifically, the reference electrode 12 and the first sensing electrode 21) disposed with the first solid electrolyte body 13a sandwiched therebetween constitute an oxygen concentration cell, and can output an electromotive force corresponding to the oxygen concentration in the mixed gas G. The oxygen concentration detected by the first element 110a is converted into a first oxygen concentration ([O ２ ]' １ )

[0038] Next, the configuration of the second element 110b will be described. The second element 110b includes a second solid electrolyte body 13b, a second sensing electrode 31a, a third sensing electrode 31b, a second porous diffusion body 32a, a third porous diffusion body 32b, and a catalyst layer 33.

[0039] The second solid electrolyte body 13b is made of, for example, zirconia (ZrO ２ ) with yttria (Y) as a stabilizer ２ O ３ It is composed of a partially stabilized zirconia sintered body to which zirconia (ZrO) or calcia (CaO) is added.

[0040] The second sensing electrode 31 a is disposed on one surface of the second solid electrolyte body 13 b. The third sensing electrode 31 b is disposed opposite the second sensing electrode 31 a with the second solid electrolyte body 13 b sandwiched therebetween. Like the first sensing electrode 21, the second sensing electrode 31 a and the third sensing electrode 31 b are formed of a platinum group element such as Pt, Pd, a Pt alloy, or a Pd alloy.

[0041] The second diffusion porous body 32a is provided between the second sensing electrode 31a and the environment to be measured. Specifically, the second diffusion porous body 32a is provided so as to cover the second sensing electrode 31a (see FIG. 2).

[0042] The second diffusion porous body 32a is made of alumina (Al ２ O ３ The second diffusion porous body 32a is provided between the second sensing electrode 31a and the measurement environment, thereby adjusting the speed at which the mixed gas G in the measurement environment reaches the second sensing electrode 31a. For this reason, the second diffusion porous body 32a is also called a rate-controlling layer.

[0043] The third diffusion porous body 32b is provided between the third sensing electrode 31b and the environment to be measured. Specifically, the third diffusion porous body 32b is provided so as to cover the third sensing electrode 31b (see FIG. 2).

[0044] The third diffusion porous body 32b is made of alumina (Al ２ O ３ The third diffusion porous body 32b is provided between the third sensing electrode 31b and the environment to be measured, thereby adjusting the speed at which the mixed gas G in the environment to be measured reaches the third sensing electrode 31b. For this reason, the third diffusion porous body 32b is also called a rate-controlling layer.

[0045] A catalyst layer 33 is provided on the third diffusion porous body 32b so as to cover the entire surface exposed to the measurement environment and promote the reaction. That is, the catalyst layer 33 decomposes hydrogen contained in the measurement environment to generate hydrogen ions and promotes the reaction of the generated hydrogen ions and electrons with oxygen in the air to produce water. The catalyst layer 33 is formed of, for example, a platinum (Pt) catalyst or a palladium (Pd) catalyst.

[0046] A second diffusion porous body 32a is provided between the second sensing electrode 31a and the measurement environment. This adjusts the speed at which the mixed gas G in the measurement environment reaches the second sensing electrode 31a. Here, hydrogen (H ２ ) is oxygen (O ２ ) and other combustible gases. As a result, the mixed gas G passes through the second diffusion porous body 32a and the oxygen partial pressure ([O ２ ]' １ ) decreases under the influence of hydrogen.

[0047] On the other hand, a third diffusion porous body 32b covered with a catalyst layer 33 is provided between the third sensing electrode 31b and the environment to be measured. As a result, when the mixed gas G in the environment to be measured reaches the third sensing electrode 31b, it first passes through the catalyst layer 33. In the catalyst layer 33, oxygen (O ２ ) and hydrogen (H ２ ) reacts with the element, and a part of the reaction rate (α) specific to the element is balanced. Therefore, at the third sensing electrode 31b, oxygen (O ２ ) and hydrogen (H ２ ) diffusion rate to reduce the effect of oxygen partial pressure ([O２ ]' ２ ) is detected.

[0048] With the above-described configuration, the second element 110b obtains an oxygen concentration ratio based on the potential difference between a pair of electrodes (specifically, the second sensing electrode 31a and the third sensing electrode 31b) that are arranged with the second solid electrolyte body 13b sandwiched therebetween. Specifically, the oxygen partial pressure ([O ２ ]' １ ), and the oxygen partial pressure ([O ２ ]' ２ ) and the ratio ([O ２ ]' ２ / [O ２ ]' １ ) is obtained.

[0049] The oxygen concentration ratio can be calculated based on the potential difference between the electrodes of the second element 110b by measuring the voltage between the electrodes, or by measuring the current that flows when the electrodes are connected by a load resistor.

[0050] The gas concentration calculation unit 41 calculates the concentration of the measurement target gas using the ratio of the first oxygen concentration detected by the first element 110a and the oxygen concentration detected by the second element 110b.

[0051] The first oxygen concentration detected by the first element 110a is an oxygen concentration calculated using the potential difference between the first sensing electrode 21 and the reference electrode 12. In this embodiment, the first oxygen concentration is calculated based on the oxygen partial pressure ([O ２ ]' １ ) means

[0052] The oxygen concentration ratio detected by the second element 110b is calculated using the potential difference between the second sensing electrode 31a and the third sensing electrode 31b ([O ２ ]' ２ / [O ２ ]' １ )

[0053] More specifically, the gas concentration calculation unit 41 calculates the concentration of the target gas from the first oxygen concentration, the oxygen concentration ratio, the difference between the diffusion coefficient of oxygen gas and the diffusion coefficient of the target gas, and the reaction rate of the target gas on the catalyst.

[0054] Here, when the gas to be measured is hydrogen gas, the hydrogen gas concentration ([H ２ ]) is calculated using the following formula 1.

[0055]

[0056] In the above formula 1, each symbol has the following meaning: ２ ]' １ : First oxygen concentration (oxygen concentration when not affected by the catalyst layer) [O ２ ]' ２ : Second oxygen concentration (oxygen concentration when influenced by the catalyst layer) D Ｈ２ : Diffusion coefficient of hydrogen gas D Ｏ２ : Diffusion coefficient of oxygen gas α: H ２ O ２ Response rate to

[0057] The hydrogen gas concentration ([H ２ ]) may be calculated from the following formula 2 obtained based on the above formula 1.

[0058] In the above formula 2, K １ =D Ｈ２ / D Ｏ２ and K ２ = {α + (1-α) K １}. K １ and K. ２ can be determined experimentally.

[0059] In FIG. １ and K. ２ The image of the measurement is shown in FIG. ２ +1 / 2O ２ = H ２ From O, H of concentration X ２ When burned, O with a concentration of X / 2 ２ In addition, in Table 1, K １ and K.２ The actual measurement results and an example of the calculated value of α are shown below. １ and K. ２ It can be calculated from the measured values ​​by the following formula: α = (K ２ -K １ ) / (1-K １ )

[0060]

[0061] Oxygen concentration in the oxygen-containing space [O ２ ] sensor output [O ２ ] Ｓ１ and the sensor output when hydrogen of concentration X is mixed into the space [O ２ ] Ｓ２ Also, measure [O ２ ] Ｓ１ - [O ２ ] Ｓ２ =ΔO ２ Let's say.

[0062] Here, K １ is the sensor output for the sensor without a catalyst, and ΔO ２ The ratio of (i.e., K １ =ΔO ２ / (X / 2)). Also, K ２ is the sensor output when the catalyst is present, and ΔO is the ratio of X / 2 to ２ The ratio of (i.e., K ２ =ΔO ２ / (X / 2)).

[0063] In addition, in the above formula 1, the difference between the first oxygen concentration and the second oxygen concentration ([O ２ ]' １ - [O ２ ]' ２ ) is the first oxygen concentration ([O ２ ]' １ ) and oxygen concentration ratio ([O ２ ]' ２ / [O ２ ]' １ ) can be calculated using the following method.

[0064] The first element 110a (the element on the left side shown in FIG. 2) measures a first oxygen concentration [O ２ ]' １ Furthermore, the oxygen concentration ratio ([O ２ ]' ２ / [O ２ ]' １ ) = B is obtained. Here, A × B = [O ２ ]' １ × ([O ２ ]' ２ / [O ２ ]' １ ) = [O ２ ]' ２ The second oxygen concentration [O ２ ]' ２ is obtained.

[0065] From the above, the difference between the first oxygen concentration and the second oxygen concentration ([O ２ ]' １ - [O ２ ]' ２ ) is obtained.

[0066] The diffusion coefficients of hydrogen gas and oxygen gas in the atmosphere (m ２ / s) are as follows: Hydrogen gas: D Ｈ２ = 6.65 x 10 －５ Oxygen gas: D Ｏ２ = 1.80 x 10 －５

[0067] Diffusion coefficients of other target gases in the atmosphere (m ２ / s) are as follows: Ammonia gas: D ＮＨ３ = 0.844 × 10 －５ Propane gas: D Ｃ３Ｈ８ = 0.987 × 10 －５

[0068] As described above, the sensing element 10A according to this embodiment detects the concentration of a target gas, such as hydrogen gas, contained in a mixed gas G in a measurement environment. The sensing element 10A includes a first element 110a and a second element 110b. The first element 110a includes a substrate 11, a reference electrode 12, a first solid electrolyte body 13a, a first sensing electrode 21 for detecting an oxygen concentration (e.g., a first oxygen concentration), and a first diffusion porous body 22. The second element 110b includes a second sensing electrode 31a, a second solid electrolyte body 13b, a third sensing electrode 31b disposed opposite the second sensing electrode 31a with the second solid electrolyte body 13b interposed therebetween, a second diffusion porous body 32a, a third diffusion porous body 32b, and a catalyst layer 33 provided to cover the third diffusion porous body 32b.

[0069] The sensing element 10A also has a gas concentration calculation unit 41. The gas concentration calculation unit 41 measures the oxygen concentration ratio from the potential difference between the second sensing electrode 31a and the third sensing electrode 31b, and calculates the concentration of the measurement target gas using the oxygen concentration and the oxygen concentration ratio.

[0070] Specifically, the gas concentration calculation unit 41 calculates the first oxygen concentration ([O ２ ]' １ ), oxygen concentration ratio ([O ２ ]' ２ / [O ２ ]' １ ), the diffusion coefficient of oxygen gas (D Ｏ２ ) and the diffusion coefficient of the measurement target gas (for example, D Ｈ２ ) and the reaction rate (e.g., α) of the gas to be measured on the catalyst, the concentration of the gas to be measured is calculated.

[0071] With the above configuration, the concentration of hydrogen gas contained in the mixed gas G can be detected based on the first oxygen concentration obtained by the first sensing electrode 21 and the oxygen concentration ratio obtained by the second sensing electrode 31a and the third sensing electrode 31b. The sensing element 10A having the above configuration can detect a wider range of gas concentrations than methods of detecting hydrogen gas using various sensors such as catalytic combustion, thermal conduction, and semiconductor sensors. Furthermore, the sensing element 10A can be used in a wider range of temperature environments or in condensation environments.

[0072] Therefore, the gas sensor 1 including the sensing element 10A can measure the concentration of a target gas such as hydrogen gas under a wider range of environmental conditions. For example, when measuring the concentration of hydrogen gas using the gas sensor 1, the concentration of hydrogen gas can be detected regardless of the gas composition as long as the environment contains any of oxygen, water, and carbon dioxide.

[0073] This makes it possible to provide a more versatile gas sensor 1. The gas sensor 1 can be used to detect hydrogen in, for example, a hydrogen production process, a methanation process, a hydrogen engine, a hydrogen burner, and the like.

[0074] Second Embodiment In the second embodiment, a gas sensor 1 including a sensing element 10B, which is an example of a gas concentration sensing element 10, will be described. In the first embodiment, a configuration was described in which a catalyst layer that promotes a reaction is provided on the third diffusion porous body so as to cover the entire surface exposed to the measurement environment. However, in another embodiment, the rate-limiting layer itself may have a catalytic function that promotes a reaction. Therefore, in this embodiment, a sensing element 10B having such a configuration will be described.

[0075] Fig. 3 shows the configuration of the sensing element 10B. The sensing element 10B has two separate elements (i.e., a first element 110a shown on the left side of Fig. 3 and a second element 110b shown on the right side) and a gas concentration calculation unit 41 (see Fig. 1). The first element 110a and the gas concentration calculation unit 41 have the same configuration as those in the first embodiment.

[0076] The second element 110b has a second solid electrolyte body 13b, a second sensing electrode 31a, a third sensing electrode 31b, a second porous diffusion body 32a, and a third porous diffusion body 132b.

[0077] The third diffusion porous body 132b is provided between the third sensing electrode 31b and the environment to be measured, and has a catalytic function for promoting the reaction. The third diffusion porous body 132b is made of alumina (Al ２ O ３ The third diffusion porous body 132b is obtained by adding a catalyst such as a platinum (Pt) catalyst or a palladium (Pd) catalyst to a porous body made of a metal (ZnO) or a palladium (Pd) catalyst. By having such a third diffusion porous body 132b, when the mixed gas G in the measurement environment passes through the third diffusion porous body 132b and reaches the third sensing electrode 31b, the oxygen (O ２ ) and hydrogen (H ２ ) reacts with the oxygen (O ２ ) and hydrogen (H ２ ) diffusion rate to reduce the effect of oxygen partial pressure ([O ２ ]' ２ ) can be measured. Therefore, the sensing element 10B does not have a catalyst layer.

[0078] In the second element 110b, the configuration other than the third diffusion porous body 132b can be the same as that of the first embodiment. As in the first embodiment, in the second element 110b, the oxygen concentration ratio ([O ２ ]' ２ / [O ２ ]' １ ) is detected.

[0079] According to the above configuration, the concentration of hydrogen gas contained in the mixed gas G can be detected based on the first oxygen concentration obtained by the first sensing electrode 21 and the oxygen concentration ratio obtained by the second sensing electrode 31 a and the third sensing electrode 31 b. For example, when the gas to be measured is hydrogen gas, the hydrogen gas concentration ([H ２ ]) is calculated using Equation 1 above.

[0080] Third Embodiment In a third embodiment, a gas sensor 1 including a detection element 10C that is an example of the gas concentration detection element 10 will be described. In this embodiment, a configuration in which the first element 110a further includes a catalyst layer will be described as an example.

[0081] Fig. 4 shows the configuration of the sensing element 10C. The sensing element 10C has two separate elements (i.e., a first element 110a shown on the left side of Fig. 4 and a second element 110b shown on the right side) and a gas concentration calculation unit 41 (see Fig. 1). The second element 110b and the gas concentration calculation unit 41 have the same configuration as those in the first embodiment.

[0082] The first element 110a has a base 11, a reference electrode 12, a first solid electrolyte body 13a, a first sensing electrode 21, a first diffusion porous body 22, and a catalyst layer 123. The catalyst layer 123 is provided on the first diffusion porous body 22 so as to cover the entire surface exposed to the environment to be measured. The catalyst layer 123 is formed from the same material as the catalyst layer 33, and decomposes hydrogen contained in the environment to generate hydrogen ions and the like, and promotes a reaction in which the generated hydrogen ions and electrons react with oxygen in the air to produce water.

[0083] In this embodiment, a first diffusion porous body 22 covered with a catalyst layer 123 is provided between the first sensing electrode 21 and the environment to be measured. As a result, when the mixed gas G in the environment to be measured reaches the first sensing electrode 21, it first passes through the catalyst layer 123. In the catalyst layer 123, oxygen (O ２ ) and hydrogen (H ２ ) reacts with the element, and a part of the reaction rate α specific to the element is equilibrated. Therefore, in the first sensing electrode 21, oxygen (O ２ ) and hydrogen (H ２ ) diffusion rate to reduce the effect of oxygen partial pressure ([O ２ ]' ２ ) is detected.

[0084] In the second element 110b, similarly to the first embodiment, the oxygen concentration ratio ([O ２ ]' ２ / [O２ ]' １ ) is detected.

[0085] In this embodiment, the oxygen concentration detected by the first element 110a is calculated by multiplying the second oxygen concentration ([O ２ ]' ２ ) (i.e., the oxygen concentration affected by the catalyst layer). In this embodiment, the difference between the first oxygen concentration and the second oxygen concentration in the above formula 1 ([O ２ ]' １ - [O ２ ]' ２ ) is the second oxygen concentration ([O ２ ]' ２ ) and oxygen concentration ratio ([O ２ ]' ２ / [O ２ ]' １ ) can be calculated using the following method.

[0086] The first element 110a (the element on the left side shown in FIG. 4) measures the second oxygen concentration [O ２ ]' ２ Furthermore, the oxygen concentration ratio ([O ２ ]' ２ / [O ２ ]' １ ) = B is obtained. Here, A÷B = [O ２ ]' ２ ÷ ([O ２ ]' ２ / [O ２ ]' １ ) = [O ２ ]' １ The first oxygen concentration [O ２ ]' １ is obtained.

[0087] From the above, the difference between the first oxygen concentration and the second oxygen concentration ([O ２ ]' １ - [O ２ ]' ２ ) is obtained.

[0088] According to the above configuration, the concentration of hydrogen gas contained in the mixed gas G can be detected based on the second oxygen concentration obtained by the first sensing electrode 21 and the oxygen concentration ratio obtained by the second sensing electrode 31 a and the third sensing electrode 31 b. For example, when the gas to be measured is hydrogen gas, the hydrogen gas concentration ([H ２ ]) is calculated using Equation 1 above.

[0089] (Modifications) Modifications of the first to third embodiments will be described below. Figures 5 and 6 show the configuration of a sensing element according to the modifications.

[0090] The detector element 10D shown in Fig. 5 includes an element having one solid electrolyte body 13 and a gas concentration calculation unit 41 (see Fig. 1). As shown in Fig. 5, for example, a first detection electrode 21 and a reference electrode 12 are disposed on the left side of the solid electrolyte body 13, with the solid electrolyte body 13 sandwiched therebetween, and a second detection electrode 31a and a third detection electrode 31b are disposed on the right side of the solid electrolyte body 13, with the solid electrolyte body 13 sandwiched therebetween. That is, the detector element 10D has a configuration in which the first solid electrolyte body 13a and the second solid electrolyte body 13b of the detector element 10A of the first embodiment are integrated. Other configurations can be applied that are similar to those of the first embodiment.

[0091] 6 includes two separate elements (i.e., a first element 110a shown on the left side of FIG. 6 and a second element 110b shown on the right side) and a gas concentration calculation unit 41 (see FIG. 1). The second element 110b and the gas concentration calculation unit 41 have the same configuration as those in the second embodiment.

[0092] The first element 110a includes a substrate 11, a reference electrode 12, a first solid electrolyte body 13a, a first sensing electrode 21, and a first diffusion porous body 122. The first diffusion porous body 122 is provided between the first sensing electrode 21 and the environment to be measured, and has a catalytic function that promotes a reaction. The first diffusion porous body 122 has a configuration similar to that of the third diffusion porous body 132b.

[0093] As a result, when the mixed gas G in the measurement environment reaches the first sensing electrode 21, it passes through the first diffusion porous body 122 having a catalytic function. In the first diffusion porous body 122, oxygen (O ２ ) and hydrogen (H ２ ) reacts with the element, and a part of the reaction rate α specific to the element is equilibrated. Therefore, in the first sensing electrode 21, oxygen (O ２ ) and hydrogen (H ２ ) diffusion rate to reduce the effect of oxygen partial pressure ([O ２ ]' ２ ) is detected. Therefore, the concentration of hydrogen gas contained in the mixed gas G can be detected in the same manner as in the third embodiment.

[0094] In the modification shown in Fig. 6, the first diffusion porous body 122 may be replaced by a first diffusion porous body 22 and a catalyst layer 123. In addition, in the modification shown in Fig. 6, the third diffusion porous body 132b may be replaced by a third diffusion porous body 32b and a catalyst layer 33. In addition, in the modification shown in Fig. 6, the first solid electrolyte body 13a and the second solid electrolyte body 13b may be integrated into one body, similar to the configuration shown in Fig. 5.

[0095] In the above-described embodiments, a sensing element having a configuration for detecting oxygen concentration using the principle of a zirconia oxygen sensor has been described. Hereinafter, a sensing element including a configuration for detecting oxygen concentration using the principle of a limiting current oxygen sensor in addition to the principle of a zirconia oxygen sensor will be described.

[0096] Fig. 7 shows the configuration of a gas concentration sensing element 200A according to this embodiment. The sensing element 200A has two separate elements (i.e., a first element 210a shown on the left side of Fig. 7 and a second element 110b shown on the right side) and a gas concentration calculation unit 41 (see Fig. 1). The first element 210a is a limiting current type oxygen concentration sensing element. The second element 110b has a configuration similar to that of the second element 110b of the sensing element 10A shown in Fig. 2.

[0097] Fig. 8 shows a schematic configuration of a sensing element 210, which is an example of a limiting current type oxygen concentration sensing element. Fig. 9 shows a schematic configuration of a horizontal cross section of an insulating layer 220 of the sensing element 210. The sensing element 210 is formed of a plate-shaped base 211. A measurement chamber 215 and the like are provided at one end of the base 211. A connection terminal 252 is provided at the other end of the base 211. A plurality of connection terminals 252 are provided corresponding to the respective electrodes. The connection terminals 252 are connected to a gas concentration calculation unit 41 in the sensor control unit 9 via wiring 8.

[0098] One end of the base 211 (i.e., the end where the measurement chamber 215 is provided) may be covered with a breathable porous protective film 251. The measurement chamber 215 is formed by forming an opening in a portion of the insulating layer 220. The side of the measurement chamber 215 is surrounded by an insulating portion (e.g., insulating portion 223) and a diffusion porous body (e.g., first diffusion porous body 222). The cross-sectional view of the first element 210a shown in FIG. 7 corresponds to the cross-sectional configuration taken along line A-A in FIG. 9.

[0099] The first element 210a has a first base 211a, a reference electrode 212a, a first solid electrolyte body 213a, a first sensing electrode 221, an insulating layer 220, a fourth solid electrolyte body 214a, a first ventilation layer 216a, and a first pair of electrodes 217a.

[0100] The insulating layer 220 includes an insulating portion 223 and a first diffusion porous body 222. A hollow first measurement chamber 215a is present above the first sensing electrode 221, into which the mixed gas G (containing the measurement target gas and oxygen gas) that has passed through the first diffusion porous body 222 flows. The side of the first measurement chamber 215a is surrounded by an insulating layer 220 made of the insulating portion 223 and the first diffusion porous body 222.

[0101] The fourth solid electrolyte body 214a is disposed above the first measurement chamber 215a and functions as an oxygen pump cell. The first pair of electrodes 217a are disposed on the upper and lower surfaces of the fourth solid electrolyte body 214a.

[0102] In the first element 210a, the direction and magnitude of the current flowing between the first pair of electrodes 217a arranged with the fourth solid electrolyte body 214a therebetween are adjusted so that the voltage (electromotive force) generated between the electrodes arranged with the first solid electrolyte body 213a therebetween (i.e., between the reference electrode 212a and the first sensing electrode 221) becomes a predetermined value (e.g., 450 mV). This makes it possible to linearly detect the oxygen concentration in the mixed gas G in accordance with the current flowing through the fourth solid electrolyte body 214a.

[0103] With the above configuration, the first element 210a has a first oxygen concentration ([O ２ ]' １ ) is detected.

[0104] In the second element 110b, similarly to the first embodiment, the oxygen concentration ratio is obtained based on the potential difference between a pair of electrodes (specifically, the second sensing electrode 31a and the third sensing electrode 31b) arranged with the second solid electrolyte body 13b sandwiched therebetween. Specifically, the oxygen partial pressure ([O ２ ]' １ ), and the oxygen partial pressure ([O ２ ]' ２ ) and the ratio ([O ２ ]' ２ / [O ２ ]' １ ) is obtained.

[0105] With the above configuration, in the second element 110b, the oxygen concentration ratio ([O ２ ]' ２ / [O ２ ]' １ ) is detected.

[0106] The gas concentration calculation unit 41 calculates the first oxygen concentration ([O ２ ]' １ ), the oxygen concentration ratio ([O ２ ]' ２ / [O ２ ]' １ ), the diffusion coefficient of oxygen gas (D Ｏ２) and the diffusion coefficient of the measurement target gas (for example, D Ｈ２ ) and the reaction rate (e.g., α) of the gas to be measured on the catalyst, the concentration of the gas to be measured is calculated.

[0107] The calculation method here can be the method described in the first embodiment. For example, when the measurement target gas is hydrogen gas, the hydrogen gas concentration ([H ２ ]) is calculated using Equation 1 above.

[0108] In the first element 210a according to this embodiment, a catalyst layer may be provided on the first diffusion porous body 222 so as to cover the entire surface exposed to the measurement environment. Furthermore, instead of the first diffusion porous body 222 and the catalyst layer, a first diffusion porous body 122 (see FIG. 6) having a catalytic function may be provided.

[0109] In such a configuration, the oxygen concentration detected by the first element 210a is calculated by multiplying the second oxygen concentration ([O ２ ]' ２ ) (i.e., the oxygen concentration affected by the catalyst layer). As in the third embodiment, the concentration of hydrogen gas contained in the mixed gas G can be detected based on the second oxygen concentration obtained by the first sensing electrode 21 and the oxygen concentration ratio obtained by the second sensing electrode 31 a and the third sensing electrode 31 b.

[0110] Fifth Embodiment In a fifth embodiment, a gas sensor 1 including a sensing element 310 that is an example of the gas concentration sensing element 10 will be described.

[0111] 10 shows the configuration of the sensor element 310. The sensor element 310 has a base 311, a reference electrode 312, a plurality of solid electrolyte bodies (a first solid electrolyte body 313a and a second solid electrolyte body 313b), a plurality of sensing electrodes (a first sensing electrode 321, a second sensing electrode 331, and a third sensing electrode 341), two diffusion porous bodies (a first diffusion porous body 322 and a second diffusion porous body 332), a catalyst layer 333, and a gas concentration calculation unit 41 (see FIG. 1).

[0112] The reference electrode 312 is disposed on the base 311. The first solid electrolyte body 313a is disposed on the reference electrode 312. A first sensing electrode 321 is disposed on the first solid electrolyte body 313a. The first sensing electrode 321 is disposed in a position facing the reference electrode 312 with the first solid electrolyte body 313a sandwiched therebetween. The first sensing electrode 321 detects the oxygen concentration contained in the mixed gas G (containing the measurement target gas and oxygen gas) using the potential difference between itself and the reference electrode 312. The first diffusion porous body 322 is disposed between the first sensing electrode 321 and the measurement environment.

[0113] A hollow measurement chamber 315 is present above the first sensing electrode 321, into which the mixed gas G flows after passing through the first diffusion porous body 322. The side of the measurement chamber 315 is surrounded by an insulating layer 320 made of an insulating part (not shown) and the first diffusion porous body 322.

[0114] The second solid electrolyte body 313b is disposed above the measurement chamber 315. A second sensing electrode 331 having the same potential as the first sensing electrode 321 is provided on the surface of the measurement chamber 315 facing the second solid electrolyte body 313b. A first diffusion porous body 322 is provided between the second sensing electrode 331 and the environment to be measured.

[0115] The third sensing electrode 341 is provided on the surface of the second solid electrolyte body 313b opposite to the measurement chamber 315. The third sensing electrode 341 is disposed at a position facing the second sensing electrode 331 with the second solid electrolyte body 313b interposed therebetween.

[0116] The second diffusion porous body 332 is provided between the third sensing electrode 341 and the environment to be measured. The second diffusion porous body 332 is provided with a catalyst layer 333 provided to cover the entire surface exposed to the environment to be measured. The catalyst layer 333 decomposes hydrogen contained in the environment to generate hydrogen ions and promotes a reaction in which the generated hydrogen ions and electrons react with oxygen in the air to produce water. Like the catalyst layer 33, the catalyst layer 333 is formed of, for example, a platinum (Pt) catalyst or a palladium (Pd) catalyst.

[0117] With the above configuration, the first sensing electrode 321 detects the first oxygen concentration ([O ２ ]' １ ) is detected.

[0118] Furthermore, between a pair of electrodes (i.e., the second sensing electrode 331 and the third sensing electrode 341) disposed with the second solid electrolyte body 313b sandwiched therebetween, an oxygen concentration ratio is obtained based on the potential difference between these electrodes. Specifically, the oxygen partial pressure ([O ２ ]' １ ) and the oxygen partial pressure ([O ２ ]' ２ ) and the ratio ([O ２ ]' ２ / [O ２ ]' １ ) is obtained.

[0119] The gas concentration calculation unit 41 calculates the concentration of the target gas from the first oxygen concentration, the oxygen concentration ratio, the difference between the diffusion coefficient of oxygen gas and the diffusion coefficient of the target gas, and the reaction rate of the target gas on the catalyst.

[0120] The calculation method here can be the method described in the first embodiment. For example, when the measurement target gas is hydrogen gas, the hydrogen gas concentration ([H ２ ]) is calculated using Equation 1 above.

[0121] In addition, in the detection element 310 of this embodiment, instead of the second diffusion porous body 332 and the catalyst layer 333, a second diffusion porous body having catalytic function (a diffusion porous body having the configuration of the third diffusion porous body 132b of the second embodiment) can also be provided.

[0122] Sixth Embodiment In a sixth embodiment, a gas sensor 1 including a sensing element 410 that is an example of the gas concentration sensing element 10 will be described.

[0123] 11 shows the configuration of the sensor element 410. The sensor element 410 has a base 411, a reference electrode 412, a plurality of solid electrolyte bodies (a first solid electrolyte body 413a and a second solid electrolyte body 413b), a plurality of sensing electrodes (a first sensing electrode 421, a second sensing electrode 431, and a third sensing electrode 441), two diffusion porous bodies (a first diffusion porous body 422 and a second diffusion porous body 432), a catalyst layer 433, and a gas concentration calculation unit 41 (see FIG. 1).

[0124] The reference electrode 412 is disposed on the base 411. The first solid electrolyte body 413a is disposed on the reference electrode 412. A first sensing electrode 421 is disposed on the first solid electrolyte body 413a. The first sensing electrode 421 is disposed in a position facing the reference electrode 412 with the first solid electrolyte body 413a sandwiched therebetween. The first sensing electrode 421 detects the oxygen concentration contained in the mixed gas G (containing the measurement target gas and oxygen gas) using the potential difference between itself and the reference electrode 412. The first diffusion porous body 422 is disposed between the first sensing electrode 421 and the measurement environment.

[0125] A hollow measurement chamber 415 is present above the first sensing electrode 421, into which the mixed gas G flows after passing through the first diffusion porous body 422. The side of the measurement chamber 415 is surrounded by an insulating layer 420 made of an insulating part (not shown) and the first diffusion porous body 422.

[0126] The first diffusion porous body 422 is provided with a catalyst layer 433 that covers the entire surface exposed to the measurement environment. The catalyst layer 433 is formed of, for example, a platinum (Pt) catalyst or a palladium (Pd) catalyst, similar to the catalyst layer 33, and promotes the reaction. This allows the mixed gas G (containing the measurement target gas and oxygen gas) in the measurement environment to pass through the catalyst layer 433, then pass through the first diffusion porous body 422, and flow into the measurement chamber 415.

[0127] The second solid electrolyte body 413b is disposed above the measurement chamber 415. A second sensing electrode 431 having the same potential as the first sensing electrode 421 is provided on the surface of the measurement chamber 415 facing the second solid electrolyte body 413b. A catalyst layer 433 and a first diffusion porous body 422 are provided between the second sensing electrode 431 and the environment to be measured.

[0128] The third sensing electrode 441 is provided on the surface of the second solid electrolyte body 413b opposite to the measurement chamber 415. The third sensing electrode 441 is disposed at a position facing the second sensing electrode 431 with the second solid electrolyte body 413b interposed therebetween.

[0129] The second diffusion porous body 432 is provided between the third sensing electrode 441 and the environment to be measured.

[0130] With the above configuration, the first sensing electrode 421 detects the second oxygen concentration ([O ２ ]' ２ ) is detected.

[0131] Furthermore, between a pair of electrodes (i.e., the second sensing electrode 431 and the third sensing electrode 441) disposed with the second solid electrolyte body 413b interposed therebetween, an oxygen concentration ratio is obtained based on the potential difference between these electrodes. Specifically, the oxygen partial pressure ([O ２ ]' ２ ) and the oxygen partial pressure ([O ２ ]' １ ) and the ratio ([O ２ ]' ２ / [O ２ ]' １ ) is obtained.

[0132] The gas concentration calculation unit 41 calculates the concentration of the target gas from the second oxygen concentration, the oxygen concentration ratio, the difference between the diffusion coefficient of oxygen gas and the diffusion coefficient of the target gas, and the reaction rate of the target gas on the catalyst.

[0133] The calculation method here can be the method described in the third embodiment. For example, when the measurement target gas is hydrogen gas, the hydrogen gas concentration ([H２ ]) is calculated using Equation 1 above.

[0134] In addition, in the detection element 410 of this embodiment, instead of the first diffusion porous body 422 and the catalyst layer 433, a first diffusion porous body having catalytic function (a diffusion porous body having the configuration of the third diffusion porous body 132b of the second embodiment) can also be provided.

[0135] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. Furthermore, configurations obtained by combining the configurations of the different embodiments described herein are also included in the scope of the present invention. In the present embodiment, a plate-shaped gas concentration sensing element has been described as an example of a gas concentration sensing element, but the gas concentration sensing element according to the present invention may also be a bottomed, cylindrical gas concentration sensing element.

[0136] 1: Gas sensor 10, 200A, 310, 410: Gas concentration detection element 11, 211a, 311, 411: Base body 12, 212a, 312, 412: Reference electrode 13, 213a, 214a, 313a, 313b, 413a, 413b: Solid electrolyte body 21, 221, 321, 421: First detection electrode 31a, 331, 431: Second detection electrode 31b, 341, 441: Third detection electrode 22, 122, 222, 322, 422: First diffusion porous body 32a, 332, 432: Second diffusion porous body 32b, 132b: Third diffusion porous body 33, 123, 333, 433: Catalyst layer 215a, 315, 415: Measurement chamber 220, 320, 420: Insulating layer 41: Gas concentration calculation unit

Claims

1. A gas sensor for detecting the concentration of a gas to be measured contained in a measurement environment, comprising: a substrate; a reference electrode disposed on the substrate; at least one solid electrolyte body disposed on the reference electrode; a first detection electrode disposed opposite the reference electrode with the solid electrolyte body interposed therebetween and detecting a potential difference between the first detection electrode and the reference electrode; a first diffusion porous body disposed between the first detection electrode and the measurement environment; a second detection electrode disposed on one surface of the solid electrolyte body; a third detection electrode disposed opposite the second detection electrode with the solid electrolyte body interposed therebetween; a second diffusion porous body disposed between the second detection electrode and the measurement environment; and a third diffusion porous body disposed between the third detection electrode and the measurement environment and having a catalytic function for promoting a reaction. a gas concentration calculation unit that calculates an oxygen concentration from a potential difference detected by the first sensing electrode, calculates an oxygen concentration ratio from a potential difference between the second sensing electrode and the third sensing electrode, and calculates the concentration of the measurement target gas using the oxygen concentration and the oxygen concentration ratio.

2. A gas sensor for detecting the concentration of a gas to be measured contained in a measurement environment, comprising: a base; a reference electrode disposed on the base; a first solid electrolyte body disposed on the reference electrode; a first detection electrode disposed opposite the reference electrode with the first solid electrolyte body sandwiched therebetween and detecting a potential difference between the reference electrode and the reference electrode; a first diffusion porous body provided between the first detection electrode and the measurement environment; a hollow measurement chamber disposed on the first detection electrode and into which the gas to be measured that has passed through the first diffusion porous body flows, the side of the measurement chamber being surrounded by an insulating layer consisting of an insulating portion and the first diffusion porous body; a second solid electrolyte body disposed on the measurement chamber; a second detection electrode disposed on the measurement chamber side of the second solid electrolyte body; and a third detection electrode disposed opposite the second detection electrode with the second solid electrolyte body sandwiched therebetween. a second diffusion porous body provided between the third sensing electrode and the measurement environment and having a catalytic function for promoting a reaction; and a gas concentration calculation unit that calculates an oxygen concentration from a potential difference detected by the first sensing electrode, calculates an oxygen concentration ratio from a potential difference between the second sensing electrode and the third sensing electrode, and calculates the concentration of the measurement target gas using the oxygen concentration and the oxygen concentration ratio.

3. A gas sensor for detecting the concentration of a measurement target gas contained in a measurement environment, comprising: a base; a reference electrode disposed on the base; a first solid electrolyte body disposed on the reference electrode; a first detection electrode disposed opposite the reference electrode with the first solid electrolyte body sandwiched therebetween and detecting a potential difference between the reference electrode and the reference electrode; a first diffusion porous body provided between the first detection electrode and the measurement environment and having a catalytic function for promoting a reaction; a hollow measurement chamber disposed on the first detection electrode and into which the measurement target gas flows after passing through the first diffusion porous body, the sides of the measurement chamber being surrounded by an insulating layer consisting of an insulating portion and the first diffusion porous body; a second solid electrolyte body disposed on the measurement chamber; a second detection electrode disposed on the measurement chamber side of the second solid electrolyte body; and a third detection electrode disposed opposite the second detection electrode with the second solid electrolyte body sandwiched therebetween. a second diffusion porous body provided between the third sensing electrode and the environment to be measured; and a gas concentration calculation unit that calculates an oxygen concentration from a potential difference detected by the first sensing electrode, calculates an oxygen concentration ratio from a potential difference between the second sensing electrode and the third sensing electrode, and calculates the concentration of the gas to be measured using the oxygen concentration and the oxygen concentration ratio, wherein the first diffusion porous body is provided between the second sensing electrode and the environment to be measured.

4. The gas sensor according to claim 1, wherein the first diffusion porous body has a catalytic function for promoting a reaction.

5. The gas sensor according to any one of claims 1 to 4, wherein the gas concentration calculation unit calculates the concentration of the measurement target gas from the oxygen concentration, the oxygen concentration ratio, and the difference in diffusion coefficient with the measurement target gas.

6. The gas sensor according to any one of claims 1 to 4, wherein the measurement target gas is any one of hydrogen gas, ammonia gas, and propane gas.