JP2020008340A - Gas sensor - Google Patents

Abstract

To provide a gas sensor with which it is possible to suppress an erroneous operation with a gas detection element.SOLUTION: A gas sensor 1 comprises: a housing 10 in which a gas introduction port 14 is formed; a gas detection element 2 provided inside the housing, for detecting a detection object gas flowing in from the gas introduction port; and an adsorption member 21 provided between the gas introduction port and the gas detection element inside the housing, for adsorbing a non-inspection object gas flowing in from the gas introduction port. The adsorption member includes a region that is narrowed at a position closer to the gas detection element than a position far from there in the progression direction of the adsorbed non-detection object gas. The adsorption member is provided with a cone shaped part 23 that is progressively narrowed as it goes closer to the gas detection element.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a gas sensor capable of removing a non-detection target gas.

The gas sensor is used for detecting gas leaks such as methane gas (CH ₄ ), propane gas (C ₃ H ₈ ), carbon monoxide (CO), and incomplete combustion. In order to selectively detect CO or the like in a predetermined temperature range by such a gas sensor, it is necessary to remove low-boiling alcohols and the like, which are non-detection target gases whose detection temperature is close to the detection target gas.

  Therefore, a sensitive part, a removing means made of a silica gel filter or activated carbon for removing the non-detection target gas, and an inflow limiting plate for limiting the inflow of the non-detection target gas released from the removing means due to a rise in the temperature of the atmosphere into the sensitive part. Is known (for example, refer to Patent Document 1). The detection element of Patent Document 1 includes a casing including a sensitive part and a removing unit, an opening is formed at an upper end side of the casing for a measurement atmosphere to contact the sensitive part, and the sensing element is removed so as to close the opening. Means are provided.

  In the removing means, when the casing is cylindrical, the casing is formed in a columnar or disk shape so as to fit along the inner peripheral surface of the cylinder. When a non-detection target gas enters through the opening, the non-detection target gas is adsorbed by the removing means, thereby preventing malfunction of the sensitive portion. In addition, when the non-detection target gas such as alcohol adsorbed by the removing means is released due to the temperature change of the atmosphere, the release is restricted by the inflow restriction plate.

  In the removing means of Patent Literature 1, the non-detection target gas is adsorbed on the opening side of the casing, and thereafter, the gas component adsorbed in the removing means advances in both directions of the opening side and the sensitive section side and is released. Further, in Patent Document 1, the removing means is formed in a columnar or disk shape.

JP-A-10-197470

  In the removing means of Patent Document 1, the non-detection target gas adsorbed is formed in a column shape or a disk shape, that is, the cross section orthogonal to the vertical direction has a uniform area. It is released in a large amount in a short time to the side. For this reason, there is a problem in that the concentration of the non-detection target gas adsorbed per unit time around the sensitive part becomes high, which causes malfunction of the sensitive part.

  Moreover, a large amount of the non-detection target gas adsorbed by the removing means is released to the sensitive portion side, so that the amount of the gas released at the opening side of the casing is reduced. Therefore, this also causes a problem that the non-detection target gas becomes high in concentration on the sensitive part side in the body and causes a malfunction of the sensitive part.

  The present invention has been made in view of such a point, and an object of the present invention is to provide a gas sensor that can suppress a malfunction in a gas detection element.

  The gas sensor according to the present invention includes a housing having a gas inlet formed therein, a gas detection element disposed in the housing to detect a gas to be detected flowing from the gas inlet, and the gas inlet in the housing. And an adsorbing member arranged between the gas detection element and adsorbing the non-detection target gas flowing from the gas inlet.The adsorbing member includes the gas in the traveling direction of the adsorbed non-detection target gas. It is characterized in that an area that is closer to the detection element is thinner than one that is farther away.

  According to this configuration, since the adsorbing member is provided with the narrowed region as described above, it is possible to avoid a large amount of the adsorbed non-detection target gas being discharged to the gas detection element in a short time. In other words, the adsorbed non-detection target gas is slowly released little by little to the gas detection element side, and the concentration of the non-detection target gas around the gas detection element per unit time is kept low, causing the gas detection element to malfunction. Actuation can be prevented.

  In addition, since the adsorbed non-detection target gas is slowly released little by little to the gas detection element side, the amount of the non-detection target gas released from the gas inlet side of the adsorption member to the outside of the housing can be increased. . Thus, the amount of the adsorbed non-detection target gas released to the gas detection element side can be reduced, and the concentration of the non-detection target gas around the gas detection element can be reduced to prevent malfunction of the gas detection element. .

  As described above, according to the above configuration, the action of slowly releasing the non-detection target gas adsorbed by the adsorbing member to the gas detection element side and the function of releasing the non-detection target gas adsorbed at the gas introduction port side of the adsorbing member are achieved. Two actions can be obtained simultaneously with the action of promoting the release. This makes it possible to better avoid malfunction of the gas detection element due to release of the adsorbed non-detection target gas.

  According to the present invention, the portion of the adsorbing member that adsorbs the non-detection target gas is formed thinner near the gas detection element, so that the concentration of the non-detection target gas around the gas detection element can be reduced, and an Operation can be suppressed.

FIG. 1 is a schematic vertical sectional view of a gas sensor according to a first embodiment. It is an outline longitudinal section of a gas sensor concerning a 2nd embodiment. It is an outline longitudinal section of a gas sensor concerning a 3rd embodiment.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the present invention is not limited to the following embodiments, and can be implemented with various modifications within the scope of the gist.

  FIG. 1 is a schematic longitudinal sectional view of the gas sensor according to the first embodiment. In the following description, “up” and “down” are used with reference to FIG. 1 unless otherwise specified.

  As shown in FIG. 1, the gas sensor 1 includes a gas detection element 2 disposed in a housing 10 and can be exemplified to be used for a gas detection device (not shown) such as a gas leak alarm. Although a detailed description of the configuration of the gas detection element 2 is omitted, a semiconductor fuel gas sensor formed by MEMS (Micro Electro Mechanical Systems) processing, a contact fuel gas sensor, or an electrochemical gas sensor can be exemplified. The gas detection element 2 detects, for example, a fuel gas (main component is methane, propane, butane), a carbon monoxide gas, a hydrogen gas, and the like generated when the fuel gas is incompletely burned, as the detection target gas.

  The housing 10 includes a disc-shaped sensor base 11 to which the gas detection element 2 is fixed on the upper surface. A lead terminal 12 protrudes from below the sensor base 11, and a power supply and a control means in a gas detection device (not shown) are connected to the lead terminal 12.

  The housing 10 includes a cylindrical case 13, and a lower end of the case 13 is fixed to a peripheral edge of the sensor base 11 and covers a periphery of the gas detection element 2. A gas inlet 14 is formed on the upper end surface of the case 13 as an opening through which gas flows. In the present embodiment, the gas inlet 14 is formed in a circular shape. The gas detection element 2 in the housing 10 detects a gas to be detected flowing from the gas inlet 14.

  The gas sensor 1 further includes a filter 20 disposed between the gas inlet 14 and the gas detection element 2 in the housing 10. The filter 20 is housed in a substantially upper half of the case 13, and the upper end is disposed near the gas inlet 14. The filter 20 includes a suction member 21 and a filter case 22 in which the suction member 21 is filled.

  The adsorbing member 21 is mainly composed of granular (powder, spherical, crushed) activated carbon. Such activated carbon performs physical adsorption by Van der Waals force in the gas phase. Activated carbon adsorbs non-detection target gases, such as so-called miscellaneous gases and acid gases, such as alcohol vapor, siloxane compounds, SOx, NOx, and VOCs, and does not adsorb the above-mentioned detection target gases. Further, as the adsorbing member 21, other materials such as silica gel and zeolite may be used as long as they adsorb with the same performance as activated carbon.

  Although not particularly limited, the filter case 22 is formed by processing or molding a metal such as stainless steel. The filter case 22 has an upper opening 22a and a lower opening 22b, and is formed in a funnel shape in which the lower opening 22b has a smaller opening area than the upper opening 22a. Therefore, the adsorbing member 21 filled in the filter case 22 has a substantially conical shape or a truncated conical shape, and is formed in a shape in which the cross-sectional area orthogonal to the vertical direction gradually decreases toward the gas detection element 2 side. ing. In other words, the adsorbing member 21 is provided in a shape including the cone-shaped portion 23 that becomes thinner as approaching the gas detection element 2.

  Here, when the non-detection target gas is adsorbed by the adsorption member 21, the non-detection target gas advances toward the upper opening 22a and the lower opening 22b and is released. That is, the traveling direction of the non-detection target gas adsorbed by the adsorption member 21 is the vertical direction. Since the adsorbing member 21 has a shape provided with the above-described cone-shaped portion 23, the direction closer to the gas detection element 2 (downward) is farther (upper) in the traveling direction (vertical direction) of the non-detection target gas. It has an area that is narrower than that.

  The upper opening 22a is formed in a planar shape larger than the gas inlet 14, and the entire area of the gas inlet 14 is accommodated inside the upper opening 22a.

  The gas sensor 1 further includes a first metal mesh 31 and a second metal mesh 32 arranged in the housing 10. The first metal mesh 31 is attached inside the case 13 and covers the gas inlet 14. A nonwoven fabric 33 is interposed between the first metal mesh 31 and the upper surface of the filter 20, and the adsorption member 21 is fixed between the first metal mesh 31 and the nonwoven fabric 33 so as not to leak to the gas inlet 14 side. The second metal mesh 32 is mounted inside the case 13 and below the filter 20. A nonwoven fabric 34 is interposed between the second metal mesh 32 and the lower surface of the filter 20, and the adsorption member 21 is fixed between the second metal mesh 32 and the nonwoven fabric 34 so as not to drop to the gas detection element 2 side.

  The gas sensor 1 further includes an alcohol oxidation catalyst 36 disposed between the gas inlet 14 and the gas detection element 2 in the housing 10. The alcohol oxidation catalyst 36 is in contact with the lower end surface of the filter 20, that is, in contact with the adsorbing member 21 through the lower opening 22b of the filter case 22. The alcohol oxidation catalyst 36 may be any one that adsorbs alcohol vapor and decomposes at room temperature. In addition to using 2-azaadamantane-N-oxyl, an oxidation catalyst made of granular or sheet activated carbon-Pt (platinum) Can be adopted. As the alcohol oxidation catalyst 36, Pt may be supported on a sheet of activated carbon, Pt may be supported on an adsorbent such as zeolite or silica gel, or activated carbon-Pd, activated carbon-RuO2, carbon black-Pt may be used. Oxidation catalysts such as Fe2O3-Au, LaCoO3-Pt, LaCrO3-Pt, MnO2-CuO-Pt, and MnO2-Pt may be used.

  In the illustrated configuration example, the planar size of the alcohol oxidation catalyst 36 is set along the inner peripheral surface of the case 13, but may be reduced as long as the lower opening 22b can be accommodated therein.

  In the gas detection by the gas sensor 1 of the present embodiment, a non-detection target gas flows into the case 13 through the gas inlet 14 in addition to the detection target gas. Most of the non-detection target gas is adsorbed by the adsorption member 21 of the filter 20, and reaches the gas detection element 2 in a very small amount. Although a very small amount of the gas to be detected is adsorbed by the adsorption member 21, most of the gas reaches the gas detection element 2 through the adsorption member 21. Therefore, in the gas sensor 1, the non-detection target gas is removed by the adsorption member 21, so that the detection target gas is detected with high accuracy by the gas detection element 2.

  In such gas detection, when a non-detection target gas is adsorbed by the adsorption member 21, the non-detection target gas is sequentially placed on both sides (upper and lower sides) of the filter 20 on the gas inlet 14 side and the gas detection element 2 side. Evolved and released. That is, a part of the adsorbed non-detection target gas is released from the gas inlet 14 and another part is released to the gas detection element 2 side in the housing 10.

  Here, in order to explain the function and function of the filter 20 in the gas sensor 1 of the present embodiment, a conventional structure will be described as a comparison object. In such a conventional structure, the adsorbing member for adsorbing the non-detection target gas has a columnar or disk shape, and a cross section orthogonal to the vertical direction has a uniform area. For this reason, after the adsorbed non-detection target gas progresses to the gas detection element with time, a large amount of the non-detection target gas is released toward the gas detection element in a short time. As a result, in the conventional structure, the concentration of the non-detection target gas per unit time increases around the gas detection element in the housing, and the gas detection element that detects methane, carbon monoxide, and the like easily malfunctions.

  Therefore, the filter 20 of the present embodiment employs a configuration in which the adsorbing member 21 has the conical shape 23 as described above and gradually becomes thinner toward the gas detection element 2 side. According to this configuration, when the non-detection target gas adsorbed by the adsorbing member 21 is released to the gas detection element 2 side, the lower opening 22b of the filter 20 is slowly and gradually reduced by a small amount as compared with the comparative structure. Will be released. Thereby, it is possible to suppress a large amount of the adsorbed non-detection target gas being released to the gas detection element 2 in a short time. As a result, in the housing 10, the concentration of the non-detection target gas around the gas detection element 2 per unit time can be suppressed low, and malfunction of the gas detection element 2 can be prevented.

  Further, in the present embodiment, the non-detection target gas adsorbed by the adsorbing member 21 is slowly released little by little to the gas detecting element 2 side. The amount of the non-detection target gas discharged to the outside of the device can be increased. Therefore, the amount of the non-detection target gas released to the gas detection element 2 side can be relatively reduced, and the malfunction of the gas detection element 2 can be prevented by reducing the concentration of the non-detection target gas around the gas detection element 2. Can be.

  In the filter 20 of the present embodiment, in order to reduce the concentration of the non-detection target gas around the gas detection element 2 per unit time, the above two functions are simultaneously performed. That is, one is to slowly release the non-detection target gas adsorbed by the adsorbing member 21 to the gas detecting element 2 side slowly and gradually, and the other is to increase the amount of discharge at the gas inlet 14 side of the adsorbing member 21. ing. As described above, since the two functions can be obtained at the same time, in the present embodiment, it is possible to better avoid a malfunction of the gas detection element 2 due to the release of the adsorbed non-detection target gas. Thereby, even if the alcohol vapor adsorbed by the adsorbing member has a high concentration or a large amount of adsorption, the gas detection element 2 can detect the detection target gas satisfactorily.

  Further, in the present embodiment, since the alcohol oxidation catalyst 36 is provided, even if the non-detection target gas adsorbed by the adsorption member 21 contains alcohols, the alcohols are decomposed to the gas detection element 2 side. Release can be suppressed. Moreover, since the alcohol oxidation catalyst 36 and the lower end surface of the adsorbing member 21 are in contact with each other, the alcohols in the adsorbed state near the lower end surface of the adsorbing member 21 can be decomposed by the alcohol oxidation catalyst 36. Thereby, even before the release from the adsorption member 21, the decomposition of the alcohol can be advanced, and the release to the gas detection element 2 side can be further suppressed. As another form, the alcohol oxidation catalyst 36 may be provided in contact with the upper end surface of the filter 20, or may be provided in contact with both the upper end surface and the lower end surface of the filter 20.

  Next, other embodiments of the present invention will be described. Note that, in the following description, the same reference numerals may be used for components that are the same as or equivalent to the embodiment described before the embodiment to be described, and the description may be omitted or simplified.

[Second embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a schematic vertical sectional view of the gas sensor according to the second embodiment. As shown in FIG. 2, the second embodiment is different from the first embodiment in that the suction member 21 has an extension 25.

  In the suction member 21 of the second embodiment, the vertical dimension of the cone-shaped portion 23 is set to about half that of the first embodiment, and the extension 25 is connected to the lower end of the cone-shaped portion 23. It is formed to extend downward (on the gas detection element 2 side). The extension portion 25 has a substantially conical shape or a truncated cone shape that is inverted upside down from the cone-shaped portion 23, and is formed in such a shape that a cross-sectional area orthogonal to the vertical direction gradually increases toward the gas detection element 2 side. Have been. In other words, the extension part 25 becomes thicker as it approaches the gas detection element 2.

  In the upper part of the extension portion 25, there is a region where the cross-sectional area orthogonal to the vertical direction has the same cross-sectional area, but the formation of such a region may be omitted. Further, the filter case 22 is formed in a shape corresponding to the shape of the outer peripheral surface of the suction member 21.

  According to the second embodiment as well, the same operation as that of the first embodiment can be obtained in the cone-shaped portion 23, and the concentration of the non-detection target gas around the gas detection element 2 can be reduced. Malfunction of the gas detection element 2 can be prevented. Further, since the adsorbing member 21 is formed thicker toward the gas detection element 2 by the extension portion 25, the volume of the adsorbing member 21 itself can be increased, and the amount of adsorption of the non-detection target gas can be increased. it can.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 3 is a schematic vertical sectional view of the gas sensor according to the third embodiment. As shown in FIG. 3, in the third embodiment, a plurality of grooves 28 are formed in a columnar suction member 27. Each groove 28 extends in a direction orthogonal (intersecting) to the up-down direction, and one end reaches the outer peripheral surface of the suction member 27 and the other end is located inside the suction member 21 in a cross-sectional view of FIG. It is formed as follows. The grooves 28 are formed so as to be alternated in the vertical direction, and meander the traveling direction of the adsorbed non-detection target gas. In the initial stage of the adsorption of the non-detection target gas in the meandering direction of the non-detection target gas, the non-detection target gas is adsorbed on the entire upper surface of the adsorption member 27. When the adsorbed non-detection target gas travels inside the adsorption member 27 toward the gas detection element 2, it travels in a meandering manner in a region narrower than the upper surface of the adsorption member 27, being partitioned by the groove 28. Therefore, even in the adsorption member 27 according to the third embodiment, there is provided a region where the direction closer to the gas detection element 2 is narrower in the traveling direction of the adsorbed non-detection target gas than in the direction farther away.

  The filter case 22 is formed in a cylindrical shape corresponding to the outer peripheral surface shape of the suction member 27.

  According to the third embodiment as well, the same operation as in the first embodiment can be obtained by the suction member 27 in which the groove 28 is formed, and the non-detection target gas around the gas detection element 2 can be obtained. The malfunction of the gas detection element 2 can be prevented through the reduction in concentration.

  The present invention is not limited to the above embodiment, but can be implemented with various changes. In the above-described embodiment, the size, shape, direction, and the like illustrated in the accompanying drawings are not limited thereto, and can be appropriately changed without departing from the effects of the present invention. In addition, the present invention can be implemented with appropriate modifications without departing from the scope of the object of the present invention.

  For example, in the first and second embodiments, the shape of the cone-shaped portion 23 of the adsorbing member 21 may be approximately a pyramid or a truncated pyramid if the shape becomes narrower as the gas detection element 2 approaches. Various changes are possible.

  Further, in each of the above embodiments, it does not prevent adoption of a configuration in which the alcohol oxidation catalyst 36 is omitted.

  In each of the above embodiments, a gas selective permeable membrane may be provided between the gas inlet 14 and the gas detection element 2 in the housing 10, for example, at a position in contact with the lower end surface of the filter 20. The gas selective permeable membrane is made of porous ceramic or porous glass, and its pore size is set so as to allow the passage of the gas to be detected and regulate the passage of the gas not to be detected. By providing such a gas selective permeable membrane, malfunction of the gas detection element 2 can be prevented through lowering the concentration of the non-detection target gas around the gas detection element 2.

DESCRIPTION OF SYMBOLS 1 Gas sensor 2 Gas detection element 10 Housing 14 Gas inlet 21 Adsorption member 23 Conical shape part 25 Extension part 27 Adsorption member 28 Groove 36 Alcohol oxidation catalyst

Claims (8)

A housing in which a gas inlet is formed,
A gas detection element that is arranged in the housing and detects a detection target gas flowing from the gas introduction port,
An adsorbing member arranged between the gas inlet and the gas detection element in the housing and adsorbing a non-detection target gas flowing from the gas inlet is provided.
The gas sensor according to claim 1, wherein the adsorbing member has an area that is narrower in a direction in which the adsorbed non-detection target gas advances than in a direction far from the gas detection element.   The gas sensor according to claim 1, wherein the suction member includes a cone-shaped portion that becomes thinner as approaching the gas detection element.   3. The gas sensor according to claim 2, wherein the suction member includes an extension extending from the cone-shaped portion toward the gas detection element. 4.   4. The gas sensor according to claim 3, wherein the extension portion is formed in a cone shape that becomes thicker as approaching the gas detection element. 5.   The gas sensor according to any one of claims 1 to 4, wherein a groove is formed in the adsorption member, and a traveling direction of the non-detection target gas adsorbed by the groove is meandering.   The gas sensor according to any one of claims 1 to 5, wherein an alcohol oxidation catalyst is provided between the gas inlet and the gas detection element in the housing.   The gas sensor according to claim 6, wherein the alcohol oxidation catalyst is made of activated carbon carrying 2-azaadamantane-N-oxyl or platinum.   The gas sensor according to any one of claims 1 to 7, wherein a gas selective permeable membrane is provided between the gas inlet and the gas detection element in the housing.

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