gas sensor

Abstract

The objective is to provide a gas sensor that can suppress the deterioration of the internal electrode. [Solution] A gas sensor comprising a containment section for containing the gas to be measured, an inner electrode provided inside the containment section, and an outer electrode provided outside the containment section, wherein the concentration of a specific gas in the gas to be measured contained in the containment section is measured by measuring the voltage between the inner electrode and the outer electrode, and the inside of the containment section is provided with a filter section to remove a predetermined component in the gas to be measured that would degrade the inner electrode.

Description

Technical Field

[0001] The present invention relates to a gas sensor for measuring the concentration of a specific gas in a gas to be measured.

Background Art

[0002] In measuring the concentration of a specific gas (for example, oxygen) in a gas to be measured such as exhaust gas from an automobile engine or the ambient gas existing in a container used in various manufacturing processes, a gas sensor using a solid electrolyte such as zirconia is employed.

[0003] Such a gas sensor 900 includes a housing portion 910 that houses the gas to be measured, an inner electrode 920 provided inside the housing portion, and an outer electrode 930 provided outside the housing portion 910, as shown in FIG. 3. Then, by bringing a reference gas having a constant concentration of the specific gas to be measured into contact with the outer electrode 930, the voltage generated between the two electrodes of the inner electrode 920 and the outer electrode 930 is measured based on the concentration difference between the specific gas in the gas to be measured in contact with the inner electrode 920 and the specific gas in the reference gas in contact with the outer electrode 930, and the concentration of the specific gas in the gas to be measured is measured from the measurement result (for example, Patent Document 1 below).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the above gas sensor 900, the inner electrode 920 sometimes deteriorated. Specifically, the gas being measured may contain components that degrade the inner electrode 920, such as corrosive components (e.g., sulfur dioxide) or toxic components (e.g., silicon) (hereinafter referred to as degrading components). In the above gas sensor 900, in order to measure the concentration of a specific gas in the gas being measured, the gas to be measured is contained in the containment section 910 and brought into contact with the inner electrode 920. Therefore, if the gas being measured contains degrading components, the degrading components also come into contact with the inner electrode 920. As a result, the inner electrode 920 deteriorates, and there was a problem that the period during which the function of the gas sensor 900 could be guaranteed was shortened.

[0006] This invention has been made in view of the above-mentioned problems, and aims to provide a gas sensor that can suppress the deterioration of the inner electrode. [Means for solving the problem]

[0007] To solve the above problems, the gas sensor of the present invention comprises a containment section for containing a gas to be measured, an inner electrode provided inside the containment section, and an outer electrode provided outside the containment section, and measures the concentration of a specific gas in the gas to be measured contained in the containment section by measuring the voltage between the inner electrode and the outer electrode, wherein a filter section is provided inside the containment section to remove a predetermined component in the gas to be measured that degrades the inner electrode.

[0008] According to the gas sensor described above, since the filter is located inside the housing, the filter can remove certain components in the gas being measured that degrade the inner electrode (hereinafter referred to as "degradation components"). This prevents the degradation components from coming into contact with the inner electrode. Therefore, degradation of the inner electrode can be suppressed.

[0009] Furthermore, the filter portion may be configured to be made of a porous material.

[0010] With this configuration, since the filter section is made of a porous material, as the gas to be measured passes through the porous material, degraded components in the gas are collected and removed by the porous material.

[0011] Furthermore, the porous member may be formed of multiple particles and filled within the containment portion.

[0012] With this configuration, since the porous member is made up of multiple particles, the gaps between the porous member through which the gas being measured passes are larger compared to when the porous member is made of cotton, making clogging of the porous member less likely.

[0013] Furthermore, the porous member may be made of activated alumina.

[0014] With this configuration, the porous material is activated alumina that has adsorption properties for specific components such as degradation components, making it easier to capture and remove degradation components with the porous material. This further suppresses contact between degradation components and the inner electrode.

[0015] Furthermore, the porous member may be configured to be coated with an oxidation catalyst.

[0016] In this configuration, an oxidation catalyst capable of oxidizing specific components such as degradation components and purifying them into harmless components is coated onto the porous material. Therefore, the degradation components collected by the porous material can be purified into components that do not degrade the inner electrode. This further suppresses contact between degradation components and the inner electrode. [Effects of the Invention]

[0017] According to the gas sensor of the present invention, it is possible to suppress the deterioration of the inner electrode. [Brief explanation of the drawing]

[0018] [Figure 1]It is a cross-sectional view showing a gas sensor in one embodiment of the present invention. [Figure 2] It is an enlarged cross-sectional view of a part of the gas sensor in one embodiment of the present invention. [Figure 3] It is a view showing a conventional gas sensor.

Mode for Carrying Out the Invention

[0019] Embodiments of the gas sensor according to the present invention will be described with reference to the drawings.

[0020] FIG. 1 is a cross-sectional view showing a gas sensor 100 in one embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a part of the gas sensor 100 in one embodiment of the present invention, and the filter unit 4 is not shown. In the present embodiment, an example in which the gas sensor 100 is used for measuring the concentration of oxygen in the gas to be measured will be described, but it is not limited to the measurement of the oxygen concentration, and it can also be applied to the measurement of the concentration of a specific gas in the gas to be measured.

[0021] As shown in FIG. 1, the gas sensor 100 includes a housing portion 1 that houses the gas to be measured, an inner electrode 2 provided inside the housing portion 1, an outer electrode 3 provided outside the housing portion 1, and a measurement unit (not shown) that measures the voltage generated between the two electrodes of the inner electrode 2 and the outer electrode 3 and measures the oxygen concentration in the gas to be measured housed in the housing portion 1 from the measurement result. Then, a reference gas with a constant oxygen concentration to be measured is brought into contact with the outer electrode 3, and the voltage generated between the two electrodes of the inner electrode 2 and the outer electrode 3 is measured based on the concentration difference between the oxygen in the gas to be measured in contact with the inner electrode 2 and the oxygen in the reference gas in contact with the outer electrode 3 by the measurement unit, and the oxygen concentration in the gas to be measured is measured from the measurement result. Thereby, the oxygen concentration in the gas to be measured housed in the housing portion 1 is measured. <​The gas to be measured is a gas containing a specific gas to be the target of concentration measurement by the gas sensor 100, and in this embodiment, it contains oxygen. The reference gas is a gas serving as a reference when measuring the oxygen concentration in the gas to be measured by the gas sensor 100, and in this embodiment, a gas with a constant oxygen concentration (for example, air) is used.

[0023] The housing part 1 is for housing the gas to be measured. This housing part 1 is a cylindrical tube having a shape extending in one direction, and in this embodiment, it is formed of zirconia ceramics having the properties of a solid electrolyte in a high-temperature environment of 500°C or higher. As shown in FIG. 1, both longitudinal ends of the housing part 1 are open, the gas to be measured flows into the housing part 1 from one end and is housed, and then flows toward the other end and is discharged from the housing part 1. Further, the housing part 1 is arranged in a space filled with the reference gas and is heated to 500 to 700°C by a heater (not shown). Thereby, only the oxygen ions contained in the gas to be measured and the reference gas can be selectively permeated in and out of the housing part 1 due to the properties of the solid electrolyte of the housing part 1.

[0024] Also, an inner electrode 2 is provided inside the housing part 1, and an outer electrode 3 is provided outside the housing part 1. The inner electrode 2 and the outer electrode 3 are electrodes coated with platinum and are formed in a porous shape to allow oxygen ions to permeate. As shown in FIG. 2, the inner electrode 2 has a shape bent along the inner peripheral surface of the housing part 1 so as to be in close contact with the housing part 1. Further, the outer electrode 3 has a shape bent along the outer peripheral surface of the housing part 1 so as to be in close contact with the housing part 1, and is arranged so as to sandwich the housing part 1 with the inner electrode 2.

[0025] When the gas to be measured, contained in the containment section 1, comes into contact with the inner electrode 2, and the reference gas comes into contact with the outer electrode 3, ion conduction occurs between the inner electrode 2 and the outer electrode 3 via the wall of the containment section 1. Specifically, for example, if the oxygen concentration in the gas to be measured is higher than the oxygen concentration in the reference gas, oxygen molecules become oxygen ions at the inner electrode 2 in contact with the gas to be measured, and these oxygen ions move through the wall of the containment section 1 to the outer electrode 3, where they become oxygen molecules. This movement of oxygen ions between the inner electrode 2 and the outer electrode 3 generates a voltage between the two electrodes. By measuring this voltage with the measuring unit, the oxygen concentration in the gas to be measured is determined.

[0026] The measuring unit is for measuring the oxygen concentration in the gas being measured. This measuring unit includes a measuring instrument that measures the voltage generated between the inner electrode 2 and the outer electrode 3, and a calculation unit that calculates the oxygen concentration in the gas being measured from the measurement results of the measuring instrument.

[0027] The measuring instrument is a potentiometer that measures the voltage generated between the inner electrode 2 and the outer electrode 3, which changes in magnitude depending on the degree of ion conductivity proportional to the difference in oxygen concentration between the gas to be measured and the reference gas. This voltage is then measured as the potential difference between the inner electrode 2 and the outer electrode 3. The measurement results from this instrument are transmitted to the calculation unit. The calculation unit is a general-purpose computer that calculates the oxygen concentration in the gas to be measured using the Nernst theoretical formula based on the measurement results from the instrument. This allows the oxygen concentration in the gas to be measured contained in the containment unit 1 to be measured.

[0028] Furthermore, the gas sensor 100 in this embodiment is further equipped with a filter section 4 that removes predetermined components in the gas to be measured that degrade the inner electrode 2 (hereinafter referred to as degrading components). The filter section 4 is for preventing the degrading components from coming into contact with the inner electrode 2 and is provided inside the housing section 1. This filter section 4 is made of a porous member 41, and as the gas to be measured passes through this porous member 41, the degrading components in the gas to be measured are collected and removed by the porous member 41.

[0029] The gas to be measured contained in the containment section 1 may contain corrosive degradation components such as sulfur dioxide, hydrogen sulfide, hydrogen chloride, chlorine, hydrogen fluoride, and fluorine, as well as toxic degradation components such as silicon, lead, phosphorus, zinc, tin, and arsenic. When the gas to be measured containing these degradation components comes into contact with the inner electrode 2, the inner electrode 2 deteriorates. In contrast, in the gas sensor 100 of this embodiment, since the filter section 4 is provided inside the containment section 1, the degradation components in the gas to be measured can be removed by the filter section 4. This prevents the degradation components from coming into contact with the inner electrode 2. Therefore, the deterioration of the inner electrode 2 can be suppressed.

[0030] Furthermore, the porous member 41 is made up of multiple particles and is filled into the containment section 1. When the porous member 41 is made up of multiple particles in this way, the gaps in the porous member 41 through which the gas to be measured passes become larger compared to when the porous member 41 is made of cotton, so clogging of the porous member 41 is less likely to occur.

[0031] Furthermore, the porous member 41 is activated alumina. Activated alumina is porous aluminum oxide and has adsorption properties for specific components such as degradation components. Therefore, it is easier to capture and remove degradation components with the porous member 41. This further suppresses contact between degradation components and the inner electrode 2.

[0032] Furthermore, the porous member 41 is coated with an oxidation catalyst (for example, platinum or palladium). The oxidation catalyst has the property of oxidizing specific components, such as degradation components, and purifying them into harmless components. Therefore, the degradation components collected by the porous member 41 can be purified into components that do not degrade the inner electrode 2. This further suppresses contact between the degradation components and the inner electrode. In addition, the cost can be reduced compared to forming the porous member 41 itself with an oxidation catalyst.

[0033] Furthermore, a lid 11 is provided on the inside of the containment section 1 to prevent the porous material 41 filled inside the containment section 1 from leaking out. This lid 11 is made of a mesh-like porous material 12 with larger gaps than the porous material 41, and is positioned near the end of the containment section 1 into which the gas to be measured flows. This prevents the porous material 41 filled inside the containment section 1 from leaking out, and also allows for the collection and removal of foreign matter such as dust floating in the gas to be measured before it reaches the porous material 41.

[0034] As described above, with the gas sensor 100, since the filter section 4 is provided inside the housing section 1, the filter section 4 can remove degraded components from the gas being measured. This prevents the degraded components from coming into contact with the inner electrode 2. Therefore, it is possible to prevent the inner electrode 2 from degrading.

[0035] Although embodiments of the present invention have been described in detail above with reference to the drawings, the configurations and combinations thereof in the above embodiments are merely examples, and additions, omissions, substitutions, and other modifications to the configurations are possible without departing from the spirit of the present invention. For example, in the above embodiments, an example was described in which the porous member 41 is formed of a plurality of particles, but it is not limited to this. For example, it may be formed of cotton.

[0036] Furthermore, Figure 1 shows an example in which a porous member 41 is filled between the lid 11 and the end of the containment 1 on the side from which the gas to be measured is discharged. However, the method is not limited to this example; it is sufficient that the porous member 41 is filled at least upstream of the inner electrode 2 in the flow direction of the gas to be measured. [Explanation of symbols]

[0037] 100 Gas Sensors 1. Storage area 11 Lid 12 Porous material 2 Inner electrode 3 outer electrode 4. Filter section 41 Porous material

Claims

1. A containment section for containing the gas to be measured, An inner electrode provided inside the housing portion, The facility comprises an external electrode provided on the outside of the housing portion, A gas sensor that measures the concentration of a specific gas in the gas to be measured contained in the housing by measuring the voltage between the inner electrode and the outer electrode, A gas sensor characterized in that a filter section is provided inside the housing section to remove a predetermined component in the gas being measured that would degrade the inner electrode.

2. The gas sensor according to claim 1, characterized in that the filter portion is formed of a porous material.

3. The gas sensor according to claim 2, characterized in that the porous member is formed of a plurality of particles and is filled in the housing portion.

4. The gas sensor according to claim 3, characterized in that the porous member is activated alumina.

5. The gas sensor according to any one of claims 2 to 4, characterized in that the porous member is coated with an oxidation catalyst.

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