JP2013130540A - Gas detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-vehicle gas detector which is prevented from being damaged with a simple structure in on-vehicle environment and allows normal operations to be hardly disturbed.SOLUTION: An on-vehicle gas detector X comprises a gas detecting element 10 which detects a gas to be detected, a casing 20 having an accommodation space 21 for accommodating the gas detecting element 10, and a gas permeable waterproof membrane 30 which is arranged at an introduction part 22 for introducing the gas to be detected to the gas detecting element 10 and allows the gas to be detected to pass through. A bridge part 40 arranged in the radial direction of an opening 23 of the introduction part 22 covers a portion of the gas permeable membrane 30 from outside the gas permeable membrane 30.

Description

  The present invention relates to an in-vehicle gas detector that detects leakage of hydrogen gas in an in-vehicle fuel cell system, for example.

  In a fuel cell system (on-vehicle type, stationary type, etc.) using hydrogen gas as an energy source, the necessity of a hydrogen gas sensor that accurately detects the concentration of hydrogen gas is extremely high.

  In the fuel cell system, hydrogen is supplied to the anode as fuel, air is supplied to the cathode as oxidant, and hydrogen ions generated by the catalytic reaction at the anode move through the solid polymer electrolyte membrane to the cathode, and at the cathode. It generates electricity by causing an electrochemical reaction with oxygen.

  From the cathode, unreacted air (referred to as off-gas) is discharged out of the system. In this case, it is necessary to install a hydrogen gas detector in the discharge system on the cathode side of the fuel cell and confirm that no hydrogen gas is present in the off-gas by the hydrogen gas detector.

  In a hydrogen gas detector that detects leakage of hydrogen gas in an in-vehicle fuel cell system, a sensor that detects combustible gas such as a catalytic combustion gas sensor is used (Patent Document 1). The catalytic combustion type gas sensor is composed of a detection element to which a catalyst is attached and a temperature compensation element to which no catalyst is attached, and uses the heat that is burned when the gas to be detected (hydrogen gas) contacts the catalyst. Thus, the concentration of the gas to be detected is detected from the difference in electrical resistance between the detection element and the temperature compensation element.

  Usually, the off gas contains fine water droplets such as warm water and produced water, and the hydrogen gas detector may be exposed to the off gas containing these water droplets. If many water droplets adhere to the element of the catalytic combustion type gas sensor (gas detection element), local temperature distribution non-uniformity occurs on the surface of the gas detection element, and the sensitivity of the detection element decreases, There is a risk of damage.

  In order to prevent such adhesion of water droplets, it has been proposed to dispose a waterproof gas permeable membrane in an opening (detected gas inlet) formed in a casing that houses the gas detection element (patent) Literature 1, Patent Literature 2). Thereby, it is possible to prevent the gas detection element from being exposed to water droplets.

Japanese Patent No. 4803813 JP 2000-187014 A

  In order to detect leakage of hydrogen gas in an in-vehicle fuel cell system, the hydrogen gas detector is disposed on the vehicle body as an in-vehicle member. For this reason, hydrogen gas detection is required to operate normally even in harsh environments and to detect hydrogen gas accurately.

  When a hydrogen gas detector is mounted on the vehicle, the hydrogen gas detector may be placed in a state where it is directly exposed to the external environment. In this case, another object contacts the hydrogen gas detector while the vehicle is running. If this is done, the hydrogen gas detector may be damaged.

For example, since the hydrogen gas detector described in Patent Document 1 is provided with a cover that covers the opening through which the gas to be detected is introduced, the other object is unlikely to directly damage the gas permeable membrane.
This cover is provided with a disk-shaped flat top plate that faces the opening and covers the opening, and is provided with a concentric double annular protrusion (an outer protrusion and an inner protrusion) on the periphery, each having a cut. Forming. These protrusions are arranged so that the inner protrusions block the wrinkles of the outer protrusions when the center side is viewed from the side of the cover. The gas passage through which the gas to be detected is introduced from the outside into the gas detection element is formed by communicating the cut between the outer projections, the gap between the outer projection and the inner and outer projections, and the cut between the inner projections.

  In the hydrogen gas detector of Patent Document 1, it is possible to prevent the gas permeable membrane from being directly damaged by providing the cover, but the structure of the cover is complicated, and the gas to be detected is the complicated gas passage described above. Since it is necessary to reach the gas sensing element via the gas, it may take time to detect the gas to be detected.

  In addition, the hydrogen gas detector described in Patent Document 2 has a structure in which a cover (Patent Document 1) that covers the opening is not provided, so that other objects may be opened in the hydrogen gas detector while the vehicle is running. The gas permeable membrane disposed in the opening may be damaged. In this case, if the gas permeable membrane is torn, the contact combustion type gas sensor is directly exposed to, for example, off-gas containing water droplets, and the risk of sensitivity reduction and element damage increases.

  Accordingly, an object of the present invention is to provide a vehicle-mounted gas detector that can prevent damage in a vehicle-mounted environment with a simple configuration and that does not hinder normal operation.

  The first characteristic configuration of the on-vehicle gas detector according to the present invention for achieving the above object includes a gas detection element that detects a gas to be detected, and a casing that includes a storage space for storing the gas detection element, A gas permeable membrane disposed in an introduction part for introducing a gas to be detected into the gas detection element, allowing gas to be detected to be detected and having a waterproof property, and having a diameter of an opening in which the introduction part opens. The bridge portion arranged in the direction is provided outside the gas permeable film so as to cover a part of the gas permeable film.

  According to this configuration, even if another object flies into the opening of the hydrogen gas detector while the vehicle is running, the bridge part can prevent the other object from entering the introduction part. That is, other objects come into contact with the bridge portion and are bounced outward from the hydrogen gas detector, so that the other objects come into contact with the gas permeable membrane disposed in the introduction portion and the gas permeable membrane is damaged. Can be prevented in advance. For this reason, it is possible to prevent the gas permeable membrane from being damaged by other objects and causing the gas detection element to be directly exposed to, for example, off-gas containing fine water droplets to cause a decrease in sensitivity.

  Moreover, since the bridge portion is formed, for example, in a rod shape so as to cover a part of the gas permeable membrane, damage to the gas permeable membrane can be prevented with a simple configuration.

  As described above, the gas detector of this configuration operates normally even in a harsh environment such as when mounted on a vehicle, and can accurately detect hydrogen gas.

  The second characteristic configuration of the gas detector according to the present invention is that the bridge portion is separated from the gas permeable membrane.

  According to this configuration, since a gap can be formed between the bridge portion and the gas permeable film, the gas to be detected can pass through the gap. As a result, the gas to be detected easily flows into the introduction part, and the ventilation state is improved, so that, for example, fine water droplets contained in the off-gas hardly adhere to the introduction part. For this reason, for example, even in an environment where fine water droplets included in the off-gas are frozen due to a decrease in the outside air temperature, it is possible to easily prevent the water droplets from adhering and freezing at the introduction portion.

  A third characteristic configuration of the gas detector according to the present invention is that the shape of the bridge portion on the gas permeable membrane side is formed in an arc shape in a cross section intersecting with the axial direction of the bridge portion.

  According to this configuration, the flow of the detected gas that has flowed into the introduction portion can be made to follow the arc-shaped edge, so that the flow of the detection gas becomes smoother, and fine water droplets contained in the off gas are caused by the introduction portion. It becomes difficult to adhere. Even if the water droplets adhere, the attached water droplets easily flow away, so that the water droplets do not easily block the gap between the bridge portion and the gas permeable membrane.

It is a perspective view which shows the outline | summary of the hydrogen gas detector of this invention. It is a top view which shows the outline | summary of the hydrogen gas detector of this invention. It is the schematic which shows the III-III cross section of FIG. It is a block diagram which shows the outline of a structure of the hydrogen gas detector of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The vehicle-mounted gas detector of the present invention detects hydrogen gas leakage in a vehicle-mounted fuel cell system, for example.

  Some fuel cells that generate power using a fuel gas containing hydrogen have a stack structure in which a plurality of power generators are stacked with a separator interposed therebetween. In the case of a fuel cell stack, it is used especially for in-vehicle use, and a load or the like due to repeated operation / stopping is applied, for example, a crack is generated in a seal member arranged between the power generator and the separator, or fuel Due to the distortion of the battery stack, a gap may be formed between the power generator and the separator. At this time, fuel gas may leak from those cracks and gaps.

  Therefore, in configuring a hydrogen energy system such as a fuel cell system, it is highly necessary to confirm that hydrogen gas is not present in the above-described fuel gas leakage or off-gas discharged outside the system. .

As shown in FIGS. 1 to 3, the gas detector X of the present invention includes a gas detection element 10 that detects a gas to be detected, a casing 20 that includes an accommodation space 21 in which the gas detection element 10 is accommodated, and a gas detection. A gas permeable film 30 is provided in the introduction portion 22 for introducing the gas to be detected into the element 10 and allows the gas to be detected to pass therethrough and has a waterproof property.
A bridge portion 40 is disposed across the radial direction of the opening 23 where the introduction portion 22 opens. The bridge portion 40 is provided outside the gas permeable membrane 30 so as to cover a part of the gas permeable membrane 30. is there.

(Gas detection element)
The gas detection element 10 may be in any form as long as it detects the gas to be detected. For example, a known semiconductor sensor element or contact combustion sensor element can be used. In the present embodiment, a case where a catalytic combustion type gas detection element 10 that detects hydrogen gas as a gas to be detected is provided will be described.

  The catalytic combustion type gas detection element 10 is constituted by a pair of a detection element 11 to which a catalyst is attached and a temperature compensation element 12 to which no catalyst is attached, and uses heat that is burned when hydrogen gas contacts the catalyst. Then, the concentration of hydrogen gas is detected from the difference in electrical resistance between the detection element 11 and the temperature compensation element 12.

  The gas detector X includes a detection unit 50 that receives and calculates a detection output that is output when the gas detection element 10 detects hydrogen gas that is a gas to be detected. The detection unit 50 includes a concentration calculation unit 51 that calculates a hydrogen gas concentration based on a detection output when the gas detection element 10 detects hydrogen gas. The calculated result is displayed by the display unit 52 capable of analog display or digital display. Further, the gas detector X includes a power supply unit (not shown) and a notification unit 60 that generates a warning in response to a signal from the detection unit 50.

(casing)
The casing 20 includes an accommodation space 21 that accommodates the gas detection element 10. The casing 20 is formed with an introduction portion 22 for introducing the gas to be detected into the gas detection element 10 and an opening portion 23 where the introduction portion 22 opens.

  In the present embodiment, a mode in which the gas detection element 10 is accommodated in the holder 24 and the holder 24 is disposed in the accommodation space 21 is shown. The gas detection element 10 is installed on a base 25 disposed opposite to the casing 20, and a packing 26 is provided between the holder 24 and the base 25 for dustproof and drip-proof.

  In the present embodiment, two fixing portions 27 for fixing the hydrogen gas detector X to the vehicle body are provided on the outer edge of the casing 20. The fixing portion 27 is formed with a screw hole 27a into which a fixing screw (not shown) is inserted. Further, the casing 20 is provided with a connecting portion 28 for connecting a power cable and the like.

(Gas permeable membrane)
The gas permeable film 30 is provided in the introduction part 22 so as to block the introduction part 22 which is a gas introduction path for introducing the gas to be detected into the gas detection element 10. The gas permeable film 30 may be a known thin film, such as polytetrafluoroethylene (PTFE), as long as it has a gas permeability that allows permeation of the gas to be detected and is waterproof. The gas permeable membrane 30 of the present embodiment is held by the introduction portion 22 with the periphery sandwiched between the casing 20 and the holder 24.

  By providing the gas permeable membrane 30 in this way, even if the hydrogen gas detector X is exposed to off-gas containing fine water droplets, the water permeable membrane 30 prevents the water droplets from reaching the gas detection element 10 in advance. Can be prevented.

(Bridge part)
The bridge portion 40 is a rod-like (long shape) member formed over the radial direction of the opening 23 where the introduction portion 22 opens. Although the case where the single bridge | bridging part 40 is provided is shown in this embodiment, it is not restricted to such an aspect, You may make it make the some bridge | bridging part 40 juxtapose or make it cross | intersect.

  For example, when the fuel cell stack is installed on the lower surface of the vehicle, the hydrogen gas detector X may be installed in a state of being directly exposed to the external environment. In this case, there is a possibility that another object may come into contact with the hydrogen gas detector X while the vehicle is running. However, in this configuration, since the bridge portion 40 is formed so as to cover a part of the gas permeable membrane 30 over the radial direction of the opening portion 23, it is assumed that another object is an opening of the hydrogen gas detector X. Even if it jumps to the part 23, the bridge part 40 can prevent the other object from entering the introduction part 22. That is, the other object comes into contact with the bridge portion 40 and is flipped outward from the hydrogen gas detector X, so that the other object comes into contact with the gas permeable membrane 30 disposed in the introduction portion 22 and the gas permeable membrane. It is possible to prevent the 30 from being damaged. Therefore, it is possible to prevent the gas permeable membrane 30 from being damaged by other objects and causing the gas detection element 10 to be directly exposed to, for example, off-gas containing fine water droplets and causing a decrease in sensitivity.

  Further, in this configuration, the rod-shaped bridge portion 40 is formed so as to cover a part of the gas permeable film 30 over the radial direction of the opening 23, so that the gas permeable film 30 is damaged with a simple configuration. Can be prevented. Furthermore, since the bridge portion 40 is not formed so as to cover the entire surface of the opening 23, the gas passage for introducing the gas to be detected from the outside to the gas detection element becomes simple, and the time for detecting the gas to be detected can be quickly detected. can do.

  In the present embodiment, the bridge portion 40 is disposed away from the gas permeable membrane 30. In this configuration, a gap can be formed between the bridge portion 40 and the gas permeable film 30, so that the gas to be detected can pass through the gap. As a result, the gas to be detected easily flows into the introduction portion 22. When the detection element 11 and the temperature compensation element 12 are used as the gas detection element 10 as in the present embodiment, it is preferable that the detection gas reaches the both elements as evenly as possible. If a gap is formed between the bridge portion 40 and the gas permeable film 30 as in this configuration, the gas to be detected can easily contact the detection element 11 and the temperature compensation element 12 equally.

  Furthermore, since the ventilation state becomes good and the gas to be detected easily flows into the introduction part 22, for example, fine water droplets contained in the off-gas hardly adhere to the introduction part 22. For this reason, for example, even in an environment where fine water droplets included in the off-gas are frozen due to a decrease in the outside air temperature, it is possible to easily prevent the water droplets from adhering and freezing in the introduction portion 22.

  In addition, the shape of the edge portion 41 of the bridge portion 40 on the gas permeable membrane 30 side may be formed in an arc shape in a cross section that intersects the axial direction of the bridge portion 40. The arc shape means that the cross section is formed in a curved shape such that the side of the gas permeable membrane 30 is curved, such as an R shape or a D shape.

  Since the edge 41 of the bridge portion 40 is formed in an arc shape as in this configuration, the flow of the gas to be detected that has flowed into the introduction portion 22 can be made to follow the arc-shaped edge 41. The flow of the detection gas becomes smoother and fine water droplets contained in the off gas are less likely to adhere to the introduction portion 22. Even if the water droplets are attached, the attached water droplets easily flow away, so that the water droplets do not easily block the gap between the bridge portion 40 and the gas permeable film 30.

  The gas detector of the present invention can be used, for example, to detect leakage of hydrogen gas in an in-vehicle fuel cell system.

X Gas detector 10 Gas detection element 20 Casing 21 Housing space 22 Introduction part 23 Opening part 30 Gas permeable membrane 40 Bridge part

Claims (3)

A gas detection element for detecting the gas to be detected;
A casing having an accommodation space for accommodating the gas detection element;
A gas permeable membrane disposed in an introduction part for introducing a gas to be detected into the gas detection element, allowing gas to be detected to pass and having a waterproof property,
A vehicle-mounted gas detector provided with a bridge portion disposed over the radial direction of the opening portion where the introduction portion opens so as to cover a part of the gas permeable membrane outside the gas permeable membrane. .   The gas detector according to claim 1, wherein the bridge portion is separated from the gas permeable membrane.   3. The gas detector according to claim 1, wherein a shape of the bridge portion on the gas permeable membrane side is formed in an arc shape in a cross section intersecting the axial direction of the bridge portion.

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