JP2021018153A - Gas detector - Google Patents

Abstract

To provide a gas detector in which intrusion of ants is prevented.SOLUTION: A gas detector 1 of the prevent invention includes: a detection element 31 for detecting gas to be detected; and a housing case 5 which has a wall body 50 surrounding the detection element 31 and inside which the detection element 31 is included. The wall body 50 has one or a plurality of communication holes 2 communicating the inside of the housing case 5 with the outside thereof, and the opening diameter of the communication hole 2 or the diameter of an inscribed circle in the communication hole 2 is less than 0.2 mm.SELECTED DRAWING: Figure 2

Description

The present invention relates to a gas detector.

A gas detector for detecting a gas to be detected such as a flammable gas is known (see, for example, Patent Document 1). This type of gas detector includes a detection element for detecting the gas to be detected, a storage case for accommodating the detection element, and the like. A through-hole-shaped vent or the like is formed on the wall of the storage case. The gas detector may be installed in an automobile or the like and used outdoors.

JP-A-2018-194409

For example, when a car in which a gas detector is installed is stopped for a long time, ants may invade the inside of the storage case through an opening such as a vent provided in the storage case. When ants invaded, the parts inside the storage case were eaten up, and there was a risk that the gas detector would break down. Therefore, in the gas detector, measures to prevent the invasion of ants have been required.

An object of the present invention is to provide a gas detector in which the invasion of ants is suppressed.

The means for solving the above problems are as follows. That is,
<1> A gas detector including a detection element for detecting a gas to be detected, a wall body surrounding the detection element, and a storage case for accommodating the detection element inside. The wall body is the wall body. It has one or more communication holes that communicate the inside and the outside of the storage case, and the opening diameter of the communication holes or the diameter of the inscribed circle in the communication holes is less than 0.2 mm. Gas detector.

<2> A diffusion chamber formed of a concave portion including an opening opened on the inner side of the storage case, connected to the communication hole, and housed inside the storage case so as to cover the opening, and the diffusion chamber. The gas detector according to <1>, comprising a breathable water repellent filter facing the communication hole with the communication hole placed between the two.

<3> The wall body includes a thin wall body in which the communication holes are formed and a small thickness, and a thick wall body which is arranged around the thin wall body and has a thickness larger than that of the thin wall body. The gas detector according to <2>, wherein the diffusion chamber is composed of a portion surrounded by the thin wall body and the thick wall body.

According to the present invention, it is possible to provide a gas detector in which the invasion of ants is suppressed.

Sectional drawing of the gas detector according to Embodiment 1. Enlarged sectional view near the vent of the gas detector Top view of the vent Top view of the vent formed on the lid of the gas detector according to the second embodiment. Top view of the vent formed on the lid of the gas detector according to the third embodiment. Top view of the vent formed on the lid of the gas detector according to the fourth embodiment. Top view of the vent formed on the lid of the gas detector according to the fifth embodiment. Sectional view of the vicinity of the vent of the lid provided with the diffusion chamber used in Test 1 Cross-sectional view near the vent of the lid without the diffusion chamber used in Test 2 Graph showing the results of Test 1 and Test 2

<Embodiment 1>
Embodiment 1 of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a cross-sectional view of the gas detector 1 according to the first embodiment, FIG. 2 is an enlarged cross-sectional view of the vicinity of the vent 2 of the gas detector 1, and FIG. 3 is a plan view of the vent 2. is there.

The gas detector 1 is arranged in, for example, a system equipped with a fuel cell using hydrogen gas as an energy source (for example, a fuel cell vehicle or a household fuel cell system), and is a flammable gas, hydrogen gas (detected). Gas) is detected. With such a gas detector 1, a leak of hydrogen gas in the system can be detected.

The gas detector 1 includes a detection element assembly 3, a wiring board 4 on which the detection element assembly 3 is mounted, and a substantially box-shaped storage case (housing) 5 for accommodating the wiring board 4.

The detection element assembly 3 has a heat conduction type detection element 31, a pedestal 32 for the detection element 31, and a protective cap 33.

The storage case 5 is composed of a molded product having a composition containing a non-conductive synthetic resin (thermoplastic resin or the like). Electronic components (temperature measurement circuit, gas detection circuit, etc.) for driving and controlling the detection element 31 are mounted on the wiring board 4 by soldering.

The storage case 5 includes a gas introduction port 51 for introducing the gas to be detected into the storage case 5. The gas introduction port 51 is provided with a metal body (metal mesh) 52 having a plurality of gas flow sections through which the gas to be detected passes. The metal body 52 has a function of preventing the flame from coming out of the gas detector 1 even when the heat-generating resistor of the detection element 31 becomes hot and the flammable gas to be detected ignites. Have.

The detection element assembly 3 is housed in a measuring chamber 7 formed in the housing case 5. Further, the detection element assembly 3 (detection element 31) is arranged so as to overlap the metal body 52 in the communication direction of the gas introduction port 51. Further, a water repellent filter 53 is arranged between the detection element assembly 3 and the metal body 52 so as to close the gas introduction port 51. The water repellent filter 53 is a member for preventing water from entering through the gas introduction port 51. Further, the water repellent filter 53 has a diffusion rate-determining function that realizes gas diffusion between the gas introduction port 51 and the measurement chamber 7 under a predetermined rate-determining condition.

The storage case 5 has a flat rectangular shape as a whole. The accommodating case 5 includes a main body portion 54 for accommodating the detection element assembly 3 and the like, and a connector portion 55 extending to an end portion of the main body portion 54. The connector portion 55 is used when the gas detector 1 is electrically connected to an external circuit. A plurality of connector pins 6 are provided inside the connector portion 55. Through holes 41 for connecting a plurality of connector pins 6 are formed on the wiring board 4. The individual connector pins 6 are fixed on the wiring board 4 by soldering while penetrating the through holes 41.

The storage case 5 includes a shallow-bottomed container-shaped lower case 56 that opens upward, and a lid portion 57 that closes the upper opening of the lower case 56. The lower case 56 and the lid 57 of the storage case 5 are formed by a wall body 50 having a predetermined thickness. The main body 54 of the storage case 5 described above is formed by a shallow container-like portion of the lower case 56 and a lid 57. Further, the connector portion 55 is formed at the end portion of the lower case 56.

In addition, on the side surface of the storage case 5, there is a flange portion (not shown) provided so as to project outward, and a bolt (not shown) is inserted into a bolt hole penetrating in the vertical direction in the center of the flange portion. The gas detector 1 is attached to an object to be attached (for example, a predetermined part of an automobile) by screwing while inserting the gas detector 1.

An annular first projecting portion 57a projecting upward is formed on the lid portion 57 of the storage case 5, and a tubular holder portion 58 is arranged inside the annular first projecting portion 57a. The holder portion 58 is a member that holds the metal body 52 described above, and a gas introduction port 51 is formed in the center of the holder portion 58 so as to penetrate in the vertical direction.

Further, the lid portion 57 of the storage case 5 is formed with an annular second projecting portion 57b projecting downward, and the second projecting portion 57b is interposed with the wiring board 4 via an annular sealing member 8. Is connected. A hole 57b1 larger than the gas introduction port 51 is formed inside the second protrusion 57b, and the above-mentioned water repellent filter 53 is arranged so as to cover the hole 57b1.

The measurement chamber 7 described above includes a space surrounded by a wiring board 4, a seal member 8, a second protruding portion 57b, a hole portion 57b1, and a water repellent filter 53.

Around the measurement chamber 7, there is a space S1 formed by being surrounded by the lid portion 57 of the storage case 5 and the lower case 56. A plurality of vents (communication holes) are formed so as to penetrate the plate-shaped (wall-shaped) lid portion 57 (wall body 50) in the thickness direction so as to communicate the space S1 in the storage case 5 with the outside. ) 2 is provided. The vent 2 is formed in a portion of the lid portion 57 that is arranged between the first protruding portion 57a and the connector portion 55.

As shown in FIG. 2, the lid portion 57 is arranged around a thin wall body 501 having a vent hole (communication hole) 2 and a small thickness and the thin wall body 501, and is arranged from the thin wall body 501. Also includes a thick wall body 502 with a large thickness. The portion surrounded by such a thin wall body 501 and the thick wall body 502 is a diffusion chamber 10 connected to a vent (communication hole) 2. The diffusion chamber 10 is composed of a concave portion 500 opened on the inner side of the storage case 5. When the vent 2 is connected to the diffusion chamber 10, the amount of ventilation of the vent 2 is secured to some extent, as will be described later.

The concave portion 500 is formed by a thin wall body 501 and a thick wall body 502. Further, a breathable water repellent filter 11 is provided so as to cover the opening 500a of the concave portion 500. The water-repellent filter 11 is housed inside the storage case 5 so as to cover the opening 500a, and faces the ventilation port (communication hole) 2 with the diffusion chamber 10 in between. The opening 500a has a circular shape in a plan view, and the opening diameter thereof is set to 2 mm. The water repellent filter 11 is made of, for example, a film-like porous body made of polytetrafluoroethylene fiber.

When the thin wall body 501 of the lid portion 57 is viewed from above in a plan view, the ventilation holes (communication holes) 2 are formed at a ratio of 10% or more with respect to the total area (100%) of the thin wall body 501. Is preferable. When the ratio of the vents 2 formed is such a value, sufficient air permeability can be ensured. In the case of the present embodiment, the thin wall body 501 has a circular shape when viewed in a plan view from above.

On the lower surface side of the lid portion 57, a concave accommodating portion 503 for accommodating the water repellent filter 11 is formed. The accommodating portion 503 includes a ceiling surface 503a and a peripheral wall surface 503b arranged around the ceiling surface 503a. The accommodating portion 503 is wider in the left-right direction than the diffusion chamber 10, and has a shape that extends outward from the diffusion chamber 10. In the case of this embodiment, the lower surface of the thick wall body 502 is the ceiling surface 503a. The water repellent filter 11 is heat-welded to the ceiling surface 503a of the accommodating portion 503.

The opening shape of the vent 2 of the present embodiment is circular in a plan view, and the opening diameter thereof is set to less than 0.2 mm (for example, 0.1 mm). The size (width) of the ant's head is usually 0.2 mm or more. Therefore, if the opening diameter of the vent 2 is set to such a size, the ants cannot pass through the vent 2 and cannot enter the storage case 5.

The opening shape of the vent 2 of the present embodiment is circular, but in other embodiments, the opening shape of the vent does not have to be limited to a circular shape, as will be described later. However, even in such a case, the opening shape of the vent is set so that the diameter of the inscribed circle inscribed in the vent is less than 0.2 mm when viewed in a plan view. The vent is set to a size that does not allow spheres smaller than 0.2 mm to pass through.

The vent 2 is formed by laser machining on the lid 57. The thickness of the lid 57 (thickness of the thin wall 501) on which the vent 2 is formed is preferably 1 mm or less. When the thickness is such a value, the vent 2 having a desired shape can be accurately formed by laser processing.

In the case of the present embodiment, the thickness of the thin wall body 501 is 0.5 mm, and the thickness of the thick wall body 502 is 2.0 mm. The height of the peripheral wall surface of the diffusion chamber 10 is 1.5 mm. The height of the accommodating portion 503 (height of the peripheral wall surface 503b) is 1.0 mm.

As described above, the gas detector 1 of the present embodiment is formed by forming a vent (communication hole) 2 having an opening diameter of less than 0.2 mm on the lid 57 of the housing case 5. The invasion of ants from 2 into the inside of the storage case 5 is suppressed. The vent (communication hole) 2 may be formed on the lid 57 by laser processing, which is advantageous in terms of cost.

If an ant invades the storage case 5 from the vent 2, for example, the water repellent filter 11 housed in the storage case 5 may be eaten by the ant. If the water-repellent filter 11 is broken, the humidity control function of the water-repellent filter 1 is impaired, which causes a failure of the gas detector 1. The vent (communication hole) 2 of the present embodiment is particularly excellent in suppressing the failure of the gas detector 1.

<Embodiment 2>
Next, the gas detector according to the second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a plan view of the vent 2A formed on the lid 57 of the gas detector according to the second embodiment. The gas detector of the present embodiment has a plurality of linear vents (communication holes) 2A instead of the plurality of circular vents 2 formed in the lid portion 57 (thin wall body 501) of the first embodiment. Is formed. The opening shape of the vent 2A is an elongated rectangular shape when viewed in a plan view, and the diameter of the inscribed circle X1 is set to be less than 0.2 mm. In FIG. 4, an example of the inscribed circle X1 is shown in the elongated rectangular vent 2A. The diameter of such an inscribed circle X1 is set to less than 0.2 mm. As in the present embodiment, the opening shape of the vent 2A may be an elongated rectangular shape (linear shape).

<Embodiment 3>
Next, the gas detector according to the third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a plan view of the vent 2B formed on the lid 57 of the gas detector according to the third embodiment. The gas detector of the present embodiment replaces the plurality of circular vents 2 formed in the lid portion 57 (thin-walled wall 501) of the first embodiment, and ventilates in a shape in which two lines intersect. The mouth (communication hole) 2B is formed. The diameter of the inscribed circle X2 at the vent 2B is set to be less than 0.2 mm. In FIG. 5, an example of the inscribed circle X2 is shown in the vent 2B at the intersection of the two lines. The diameter of such an inscribed circle X2 is set to less than 0.2 mm. As in the present embodiment, the opening shapes of the vents 2A may be such that they intersect each other.

<Embodiment 4>
Next, the gas detector according to the fourth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a plan view of the vent 2C formed in the lid portion 57 of the gas detector according to the fourth embodiment. The gas detector of the present embodiment has a plurality of semi-arc-shaped vents (communication holes) instead of the plurality of circular vents 2 formed in the lid portion 57 (thin-walled wall 501) of the first embodiment. It forms 2C. The vents 2C are formed on the lid portion 57 (thin-walled wall 501) so as to form concentric circles as a whole. The diameter of the inscribed circle X3 at those vents 2C is set to be less than 0.2 mm. In FIG. 6, an example of the inscribed circle X3 is shown in the vent 2C. The diameter of such an inscribed circle X2 is set to less than 0.2 mm. As in the present embodiment, the vent 2C having a curved opening shape may be formed.

<Embodiment 5>
Next, the gas detector according to the fifth embodiment of the present invention will be described with reference to FIG. 7. FIG. 7 is a plan view of the vent ports 2D1 and 2D2 formed on the lid portion 57 of the gas detector according to the fifth embodiment. The gas detector of the present embodiment replaces the plurality of circular vents 2 formed in the lid portion 57 (thin-walled wall 501) of the first embodiment, and ventilates in a shape in which two lines intersect. A port (communication hole) 2D1 and a plurality of circular vent holes (communication holes) 2D2 are formed. The vent 2D1 has the same shape as the vent 2B of the third embodiment. Further, the vent 2D2 has a circular opening shape as in the vent 2 of the first embodiment. As in this embodiment, vents 2D1 and 2D2 having different opening shapes may be used in combination.

<Verification of the effect of ventilation volume depending on the presence or absence of a diffusion chamber>
Here, the amount of gas ventilated (L / min) passing through the vent was measured by the method shown below in the case where the diffusion chamber connected to the vent (communication hole) was formed and in the case where it was not formed. ..

(Test 1: In the case of a lid with a diffusion chamber)
FIG. 8 is a cross-sectional view of the lid portion 57X provided with the diffusion chamber 10X used in Test 1 in the vicinity of the vent 2X. As shown in FIG. 8, as the storage case 5X, a lid portion 57X in which the ventilation port 2X and the diffusion chamber 10X were formed was prepared. Only one vent 2X is formed in the thin wall body 501X. The opening shape of the vent 2X is circular, and the opening diameter thereof is 0.2 mm. The thickness of the thin wall body 501X is 0.5 mm. The diffusion chamber 10X is composed of a concave portion 500X formed by a thin wall body 501X and a thick wall body 502X. The thickness of the thick wall body 502X is 2.0 mm, and the height of the peripheral wall surface of the diffusion chamber 10X is 1.5 mm.

On the lower surface side of the lid portion 57X, a concave accommodating portion 503X for accommodating the water repellent filter 11 is formed. The accommodating portion 503X includes a ceiling surface 503Xa and a peripheral wall surface 503Xb arranged around the ceiling surface 503Xa. The accommodating portion 503X has a width larger in the left-right direction than the diffusion chamber 10X, and has a shape that extends outward from the diffusion chamber 10X. In the case of the present embodiment, the lower surface of the thick wall body 502X is the ceiling surface 503Xa of the accommodating portion 503X. The water repellent filter 11 is heat-welded to the ceiling surface 503Xa while being housed in the housing portion 503X.

The opening 500Xa of the concave portion 500X has a circular shape in a plan view, and the opening diameter thereof is set to 2 mm. A breathable water repellent filter 11 is provided so as to cover the opening 500Xa. The water-repellent filter 11 is housed inside the storage case 5X (storage part 503X) so as to cover the opening 500Xa, and faces the ventilation port (communication hole) 2X with the diffusion chamber 10X in between. The height of the accommodating portion 503X (height of the peripheral wall surface 503Xb) is set to 1.0 mm.

A lid portion 57X of the storage case 5X having the above configuration is prepared, air having a pressure of 90 kPa is applied from one of the ventilation holes 2X using an air flow measuring device, and the air flow rate flowing from the ventilation port 2X ( The air volume (L / min)) was measured. The results are shown in FIG.

(Test 2: In the case of a lid without a diffusion chamber)
FIG. 9 is a cross-sectional view of the lid portion 57Y not provided with the diffusion chamber used in Test 2 in the vicinity of the vent port 2Y. As shown in FIG. 9, as the storage case 5Y, a lid portion 57Y having a vent 2Y not connected to the diffusion chamber was prepared. Only one vent 2Y is formed in the lid portion 57Y so as to penetrate the thick wall body 502Y. The opening shape of the vent 2Y is circular, and the opening diameter is set to 0.2 mm. The thickness of the thick wall body 502Y is 2.0 mm.

On the lower surface side of the lid portion 57Y, a concave accommodating portion 503Y for accommodating the water repellent filter 11 is formed. The accommodating portion 503Y includes a ceiling surface 503Ya and a peripheral wall surface 503Yb arranged around the ceiling surface 503Ya. The water-repellent filter 11 is housed in the housing portion 503Y so as to cover the open end of the vent 2X, and is heat-welded to the ceiling surface 503Ya. The height of the accommodating portion 503Y (height of the peripheral wall surface 503Yb) is set to 1.0 mm.

A lid portion 57Y of the storage case 5Y having the above configuration is prepared, air at a pressure of 90 kPa is applied from one of the vent ports 2Y using an air flow measuring device, and the air flow rate flowing through the vent 2Y ( The air volume (L / min)) was measured. The results are shown in FIG.

FIG. 10 is a graph showing the results of Test 1 and Test 2. The vertical axis is the air volume (L / min). As shown in FIG. 10, the air volume in Test 1 (with a diffusion chamber) was 0.52 L / min. On the other hand, the air volume in Test 2 (without diffusion chamber) was 0.17 L / min. As described above, it was confirmed that by providing the diffusion chamber 10X under the vent (communication hole) 2X, a large distribution amount can be secured even if the opening diameter of the vent 2X is small.

<Other embodiments>
The present invention is not limited to the embodiments described in the above description and drawings, and for example, the following embodiments are also included in the technical scope of the present invention.

(1) In the first embodiment and the like, the vent (communication hole) is formed in the lid portion forming the upper portion of the storage case, but the present invention is not limited to this, for example, the bottom side of the lower case. It may be provided so as to penetrate the wall body or the wall body on the side wall side.

(2) In the first embodiment and the like, the vent is a communication hole of the present invention, but the present invention is not limited to this, and a through hole formed in the wall body of the storage case for a purpose other than ventilation is provided. It may be the communication hole of the present invention.

(3) In the first embodiment or the like, the storage case in which the vent (communication hole) is formed is composed of a molded product of a composition containing a synthetic resin (thermoplastic resin, etc.), but the object of the present invention It may be formed of another material (for example, glass, ceramics, etc.) as long as it does not impair.

1 ... Gas detector, 2 ... Vent (communication hole), 3 ... Detection element assembly, 31 ... Detection element, 32 ... Pedestal, 33 ... Protective cap, 4 ... Wiring board, 41 ... Through hole, 5 ... Storage case, 50 ... wall body, 51 ... gas inlet, 52 ... metal body, 53 ... water repellent filter, 54 ... main body part, 55 ... connector part, 56 ... lower case, 57 ... lid part, 57a ... first protruding part, 57b ... 2nd protruding part, 58 ... holder part, 500 ... concave part, 500a ... opening, 501 ... thin wall body, 502 ... thick wall body, 503 ... accommodating part, 6 ... connector pin, 7 ... measuring chamber, 8 ... Seal member, 10 ... Diffusion chamber, 11 ... Water repellent filter, S1 ... Space, X1 ... Inscribed circle

Claims (3)

A detection element that detects the gas to be detected and
A gas detector having a wall body surrounding the detection element and internally including a storage case for accommodating the detection element.
The wall body has one or more communication holes that communicate the inside and the outside of the storage case.
A gas detector characterized in that the opening diameter of the communication hole or the diameter of the inscribed circle in the communication hole is less than 0.2 mm. A diffusion chamber composed of a concave portion including an opening opened on the inner side of the storage case and connected to the communication hole, and a diffusion chamber.
The gas detector according to claim 1, further comprising a breathable water-repellent filter that is housed inside the storage case so as to cover the opening and that faces the communication hole with the diffusion chamber in between. .. The wall body has a thin wall body having the communication holes formed and a small thickness, and a thick wall body arranged around the thin wall body and having a thickness larger than that of the thin wall body.
The gas detector according to claim 2, wherein the diffusion chamber includes a portion surrounded by the thin wall body and the thick wall body.

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