阅读说明：本技术 漏氢检测机构 (Hydrogen leakage detection mechanism ) 是由 森长正彦 于 2021-04-15 设计创作，主要内容包括：本发明的检测燃料电池系统的氢泄漏的漏氢检测机构具备收纳作为燃料电池系统的至少一部分的氢流通部的外壳部、氢传感器、以及以划定外壳部内的空间的至少一部分的方式配置并使氢在厚度方向上透过的多孔片,在外壳部内,在比多孔片靠下方的区域配置氢流通部,并且在比多孔片靠上方的区域配置氢传感器。(A hydrogen leakage detection mechanism for detecting hydrogen leakage in a fuel cell system includes a case section for housing a hydrogen circulation section as at least a part of the fuel cell system, a hydrogen sensor, and a porous sheet arranged to define at least a part of a space in the case section and allowing hydrogen to permeate therethrough in a thickness direction.)

1. A hydrogen leakage detection mechanism detects hydrogen leakage of a fuel cell system,

the hydrogen leakage detection mechanism is provided with:

a housing section that houses a hydrogen circulation section including at least one device selected from a fuel cell and a hydrogen tank that stores hydrogen supplied to the fuel cell, and a hydrogen pipe section having a hydrogen pipe connected to the device;

a hydrogen sensor disposed within the housing portion; and

a porous sheet that is disposed so as to define at least a part of the space in the housing portion and allows hydrogen to pass therethrough in the thickness direction,

the hydrogen circulation unit is disposed in a region below the porous sheet and the hydrogen sensor is disposed in a region above the porous sheet in the housing.

2. The hydrogen leak detection mechanism according to claim 1,

when the inside of the housing portion is viewed in the vertical direction, the connection portion of the hydrogen flow path included in the hydrogen circulation portion and the hydrogen sensor are disposed so as to overlap the porous sheet.

3. The hydrogen leak detection mechanism according to claim 2,

a plurality of the connecting portions are disposed so as to overlap with the porous sheet when the inside of the housing portion is viewed in the vertical direction.

4. The hydrogen leakage detection mechanism according to claim 2 or 3,

the hydrogen leakage detection means further includes another device different from the device, which is connected to the hydrogen piping unit and through which hydrogen flows,

the hydrogen piping section includes a plurality of the hydrogen pipes,

the connecting portion includes:

a connection part between adjacent hydrogen pipes among the plurality of hydrogen pipes,

A connection part between the hydrogen pipe and the device, and

a connection part between the hydrogen pipe and the other device

Any one of them.

5. The hydrogen leakage detection mechanism according to any one of claims 1 to 4,

the porous sheet has an opening ratio of 20 to 50%.

6. The hydrogen leakage detection mechanism according to any one of claims 1 to 5,

the hydrogen leakage detection mechanism is mounted on a fuel cell vehicle,

the housing portion is a front compartment of the fuel cell vehicle,

the hydrogen sensor is fixed to an inner wall surface of the front compartment and is located at a position different from a front cowl for opening and closing the front compartment.

Technical Field

The present disclosure relates to a hydrogen leakage detection mechanism that detects hydrogen leakage of a fuel cell system.

Background

When a part of a fuel cell system such as a fuel cell stack is disposed in a closed space such as a front compartment of a vehicle, it is desirable that hydrogen leakage occurs at a site where hydrogen flows such as the fuel cell stack, and hydrogen leakage is detected before the hydrogen concentration in the space becomes excessively high. As a structure for detecting such hydrogen leakage, a structure has been proposed in which a vehicle driving auxiliary device is coupled to the upper side of the fuel cell stack via a fixing member, and the fixing member has a cross-sectional shape that is open only upward when the vehicle is mounted (for example, japanese patent application laid-open No. 2005-124357). This suppresses the accumulation of leaked hydrogen below the fixed member, and facilitates the detection of hydrogen leakage by the hydrogen sensor provided in the front compartment.

However, even if hydrogen leaking from the fuel cell stack can move upward without being hindered by a fixing member or the like, detection of hydrogen leakage may be delayed. For example, if hydrogen leaks from the fuel cell stack, the leaked hydrogen moves upward and then stays near the upper inner wall in the front passenger compartment. In this case, when the hydrogen sensor is disposed at a position away from the portion where the leaked hydrogen moves upward and reaches the inner wall of the front passenger compartment as described above, it takes a long time until the hydrogen concentration around the hydrogen sensor becomes equal to or more than the detection limit amount, and the detection of the hydrogen leakage is delayed. As a method of suppressing the delay of the detection of the hydrogen leakage, a method of increasing the number of hydrogen sensors may be considered, but it is preferable to suppress the increase of the hydrogen sensors. Such a problem occurs not only in the case of a vehicle-mounted fuel cell system but also in a stationary fuel cell system.

Disclosure of Invention

The present disclosure can be implemented as follows.

(1) According to one embodiment of the present disclosure, a hydrogen leakage detection mechanism that detects hydrogen leakage from a fuel cell system is provided. The hydrogen leakage detection mechanism includes: a housing section that houses a hydrogen circulation section that includes at least one device selected from a fuel cell and a hydrogen tank that stores hydrogen to be supplied to the fuel cell, and a hydrogen pipe section having a hydrogen pipe connected to the device, as at least a part of the fuel cell system; a hydrogen sensor disposed in the housing portion; and a porous sheet that is disposed so as to define at least a part of a space in the housing portion and allows hydrogen to permeate therethrough in a thickness direction, wherein the hydrogen circulation portion is disposed in a region below the porous sheet in the housing portion, and the hydrogen sensor is disposed in a region above the porous sheet.

According to the hydrogen leakage detection mechanism of this aspect, the hydrogen circulation portion is disposed in the housing portion in a region below the porous sheet, and the hydrogen sensor is disposed in a region above the porous sheet. Therefore, when a defect occurs in the hydrogen circulation unit and hydrogen in the hydrogen circulation unit is ejected from the defective portion, the range of the region where the ejected hydrogen becomes the hydrogen concentration detectable by the hydrogen sensor can be expanded by passing the ejected hydrogen through the porous sheet. As a result, the hydrogen sensor can detect the hydrogen leak early.

(2) The following may be configured: in the hydrogen leakage detection mechanism according to the above aspect, when the inside of the housing portion is viewed in the vertical direction, the connection portion of the hydrogen flow path included in the hydrogen circulation portion and the hydrogen sensor are disposed so as to overlap the porous sheet. According to the hydrogen leakage detection mechanism of this aspect, when a defect occurs in the connection portion of the hydrogen flow path included in the hydrogen circulation unit and hydrogen leakage occurs, the hydrogen leakage can be detected by the hydrogen sensor early.

(3) The following may be configured: in the hydrogen leakage detection mechanism according to the above aspect, the plurality of connection portions are disposed so as to overlap the porous sheet when the inside of the housing portion is viewed in the vertical direction. According to the hydrogen leakage detection mechanism of this aspect, when a defect occurs in any one of the plurality of connection portions and hydrogen leakage occurs, the number of hydrogen sensors can be suppressed, and hydrogen leakage can be detected by the hydrogen sensors early.

(4) The following may be configured: the hydrogen leakage detection mechanism according to the above aspect further includes another device different from the above-described device, which is connected to the hydrogen pipe section and through which hydrogen flows, wherein the hydrogen pipe section includes a plurality of the hydrogen pipes, and the connection section includes any one of a connection section between adjacent ones of the plurality of hydrogen pipes, a connection section between the hydrogen pipe and the above-described device, and a connection section between the hydrogen pipe and the other device. According to the hydrogen leakage detection mechanism of this aspect, when hydrogen leakage occurs at a connection portion where the possibility of hydrogen leakage is relatively high, hydrogen leakage can be detected quickly.

(5) The following may be configured: in the hydrogen leakage detection mechanism of the above aspect, the porous sheet has an aperture ratio of 20 to 50%. According to the hydrogen leakage detection mechanism of this aspect, the function of diffusing the hydrogen discharged from the pipe connection portion along the surface of the porous sheet can be improved while ensuring the efficiency of allowing the hydrogen to permeate through the thickness direction.

(6) The following may be configured: the hydrogen leakage detection mechanism of the above aspect is mounted on a fuel cell vehicle, the housing portion is a front compartment of the fuel cell vehicle, and the hydrogen sensor is fixed to an inner wall surface of the front compartment and is located at a different position from a front hood that opens and closes the front compartment. According to the hydrogen leakage detection mechanism of this aspect, by fixing the hydrogen sensor at a position different from the front cowl, the degree of freedom of arrangement of the hydrogen sensor can be increased without being restricted by pulling of the wiring or the like, and even if the hydrogen sensor is arranged in this manner, hydrogen moving upward can be detected, whereby the effect of early detection of hydrogen leakage by the hydrogen sensor can be increased.

The present disclosure can also be implemented in various ways other than the hydrogen leakage detection mechanism. For example, the present invention can be realized as a fuel cell system used together with the hydrogen leakage detection means, a fuel cell vehicle equipped with the hydrogen leakage detection means, a stationary power supply including the hydrogen leakage detection means and the fuel cell system, or a hydrogen leakage detection method.

Drawings

Fig. 1 is an explanatory diagram showing a schematic configuration of a fuel cell vehicle.

Fig. 2 is an explanatory diagram showing a schematic configuration of the fuel cell system.

Fig. 3 is a plan view showing the porous sheet.

Fig. 4 is an explanatory diagram schematically showing an example of the arrangement in the front compartment.

Fig. 5 is an explanatory diagram showing simulation results of the hydrogen leakage detection mechanism of the embodiment.

Fig. 6 is an explanatory diagram showing simulation results of the hydrogen leakage detection mechanism of the comparative example.

Fig. 7 is a graph showing a change in hydrogen concentration at a location where the hydrogen sensor is disposed.

Fig. 8 is an explanatory diagram showing simulation results of the hydrogen leakage detection mechanism of the embodiment.

Fig. 9 is an explanatory diagram showing simulation results of the hydrogen leakage detection mechanism of the comparative example.

Fig. 10 is a graph showing a change in hydrogen concentration at a location where the hydrogen sensor is disposed.

Fig. 11 is a plan view showing the porous sheet.

Fig. 12 is a plan view showing the porous sheet.

Detailed Description

A. Embodiment 1:

fig. 1 is an explanatory diagram showing a schematic configuration of a fuel cell vehicle 10 including a hydrogen leakage detection mechanism 12 as embodiment 1 of the present disclosure. Further, XYZ axes orthogonal to each other are shown in fig. 1 and fig. 4 described later. The + X direction is the "left side" of the fuel cell vehicle 10, and the-X direction is the "right side" of the fuel cell vehicle 10. The + Y direction is the "upper side" of the fuel cell vehicle 10, and the-Y direction is the "lower side". The Y direction is also the "vertical direction". The + Z direction indicates the front of the traveling direction of the fuel cell vehicle 10, and the-Z direction indicates the rear of the traveling direction of the fuel cell vehicle 10. The X-direction and Z-direction are also "horizontal directions".

Fig. 2 is an explanatory diagram showing a schematic configuration of the fuel cell system 15 mounted on the fuel cell vehicle 10. First, the fuel cell system 15 will be described with reference to fig. 2.

The fuel cell system 15 includes a fuel cell 110, a hydrogen supply system 20 for supplying hydrogen as a fuel gas to the fuel cell 110, an oxidizing gas supply system 30 for supplying air as an oxidizing gas to the fuel cell 110, and a cooling system 60 for circulating a refrigerant to the fuel cell 110.

The fuel cell 110 has a stack structure in which a plurality of unit cells 80 as power generation bodies are stacked. In the present embodiment, the fuel cell 110 is a polymer electrolyte fuel cell, but other types of fuel cells may be used.

The hydrogen supply system 20 includes a hydrogen tank 21, a hydrogen supply flow path 22 connecting the hydrogen tank 21 to the fuel cell 110, a hydrogen discharge flow path 24 connecting the fuel cell 110 and discharging the anode off-gas from the fuel cell 110, and a circulation flow path 25 connecting the hydrogen supply flow path 22 to the hydrogen discharge flow path 24 and circulating at least a part of the anode off-gas to the hydrogen supply flow path 22. The hydrogen supply flow path 22, the hydrogen discharge flow path 24, and the circulation flow path 25 are each provided with a plurality of hydrogen pipes, which are also referred to as "hydrogen pipe portions". In the hydrogen supply system 20, the hydrogen gas stored in the hydrogen tank 21 is supplied from the injector to the fuel cell 110 through the flow path opening/closing of the main stop valve 40 of the hydrogen supply flow path 22 and the pressure reduction in the pressure reducing valve 42. The pressure of the hydrogen circulating in the circulation flow path 25 is adjusted by the hydrogen pump 44. A part of the anode off gas is released to the atmosphere through a gas-liquid separator 45 and an opening/closing valve 46 provided in the hydrogen discharge passage 24. This makes it possible to discharge impurities (water vapor, nitrogen gas, and the like) other than hydrogen in the hydrogen gas circulating through the circulation channel 25 to the outside of the channel.

The oxidizing gas supply system 30 includes an air compressor 31, an oxidizing gas supply pipe 32, and an oxidizing gas discharge pipe 34. The air compressor 31 compresses air and supplies the air to the fuel cell 110 via the oxidizing gas supply pipe 32. The cathode off-gas discharged from the fuel cell 110 is discharged to the outside of the fuel cell system 15 via the oxidizing gas discharge pipe 34.

The cooling system 60 includes a refrigerant flow path 62, a radiator 61, and a refrigerant pump 63. Both ends of the refrigerant flow path 62 are connected to a refrigerant flow path provided in the fuel cell 110. The refrigerant pump 63 is provided in the refrigerant passage 62, and by driving the refrigerant pump 63, the refrigerant can be circulated between the refrigerant passage in the fuel cell 110 and the refrigerant passage 62. The radiator 61 is provided in the refrigerant flow path 62, and cools the refrigerant flowing through the refrigerant flow path 62.

Returning to fig. 1, in the fuel cell vehicle 10, a fuel cell 110 is disposed in a front compartment 70 covered with a front cowl 72. The front compartment 70 is a space provided in a front portion of the vehicle compartment in the fuel cell vehicle 10. The front compartment 70 is also referred to as a "shell portion". Fig. 1 shows a hydrogen tank 21 disposed in an underfloor space of a vehicle compartment of the fuel cell vehicle 10, and a hydrogen supply flow path 22 connecting the hydrogen tank 21 and the fuel cell 110. In a part of the fuel cell system 15 housed in the front compartment 70, a portion where hydrogen flows including the fuel cell 110 and a hydrogen piping portion connected to the fuel cell 110 is also referred to as a "hydrogen circulating portion".

Various devices are also disposed in the front compartment 70, but fig. 1 shows a case where the high-voltage unit 120 is disposed on the fuel cell 110 as an example, and the description of other devices in the front compartment 70 is omitted. The high-voltage unit 120 may include, for example, a DC-DC converter that boosts the output voltage of the fuel cell 110 to a voltage suitable for driving a vehicle drive motor and the air compressor 31, which are not shown, and an inverter that functions as an actuator for the hydrogen pump 44 and the refrigerant pump 63. In addition, various devices and apparatuses such as a vehicle drive motor and an air conditioner may be disposed in the front compartment 70 in addition to the fuel cell auxiliary machine.

A hydrogen sensor 50 is provided within the front compartment 70 and at a position away from the front hood 72. The porous sheet 52 is disposed in the front compartment 70. These hydrogen sensor 50 and porous sheet 52 constitute the hydrogen leakage detection mechanism 12 of the present embodiment together with a connection portion (joint) of a pipe or the like described later. The positional relationship of these components will be described in detail later.

Fig. 3 is a plan view showing the porous sheet 52 of the present embodiment. The porous sheet 52 of the present embodiment is formed of a mesh and has a structure that allows hydrogen to pass through in the thickness direction. From the viewpoint of ensuring the efficiency of transmitting hydrogen in the thickness direction, the aperture ratio in a plan view of the porous sheet 52 is preferably 10% or more, more preferably 20% or more. As described later, the porous sheet 52 has a function of diffusing the hydrogen flow along the surface by allowing the hydrogen to permeate through the thickness direction and disturbing the hydrogen flow when the hydrogen leaking from the connection portion of the pipe or the like flows toward the surface of the porous sheet 52. Therefore, from the viewpoint of ensuring the function of diffusing the hydrogen flow on the surface of the porous sheet 52 as described above, the aperture ratio of the porous sheet 52 is preferably 60% or less, and more preferably 50% or less. However, the opening ratio of the porous sheet 52 may be less than 10% or more than 60%. The aperture ratio of the porous sheet 52 formed of the mesh, that is, the ratio of the area of the opening to the area of the entire mesh can be determined by the following expression (1) using the aperture diameter (distance between lines) and the pitch of the mesh (see fig. 3).

Opening ratio (%) (aperture/space)²×100…(1)

From the viewpoint of ensuring strength suitable for handling, the thickness of such a porous sheet 52 is preferably 0.2cm or more, more preferably 0.5cm or more. In addition, from the viewpoint of suppressing the space occupied by the porous sheet 52 or the weight of the porous sheet 52, the thickness of the porous sheet 52 is preferably 2.0cm or less, more preferably 1.0cm or less.

As the material constituting the porous sheet 52, various materials can be selected as long as they have strength to maintain the structure of the porous sheet 52 and heat resistance, cold resistance, and corrosion resistance to withstand the use environment of the porous sheet 52 even when hydrogen is ejected toward the surface of the porous sheet 52 at a pressure corresponding to the hydrogen pressure inside the pipe or the like due to a defect generated at the connection portion of the pipe or the like. For example, a metal material such as stainless steel, a nickel alloy, or an aluminum alloy, or a resin material such as polyester, nylon, polyphenylene sulfide (PPS), Polytetrafluoroethylene (PTFE), or polyether ether ketone (PEEK) can be used.

As shown in fig. 1, the porous sheet 52 is configured to define at least a portion of the space within the forward compartment 70. Further, when the interior of the front compartment 70 is viewed in the horizontal direction (when viewed in a direction parallel to the XZ plane), a structure including the fuel cell 110 and a hydrogen pipe portion (for example, a portion of the hydrogen supply passage 22 shown in fig. 1) connected to the fuel cell 110 is disposed as a hydrogen flow portion that is at least a part of the fuel cell system 15 in a region below the porous sheet 52 (in the (-Y direction). In fig. 1, a region below the porous sheet 52 is indicated as a region 70 a. When the interior of the front compartment 70 is viewed in the horizontal direction, the hydrogen sensor 50 is disposed in a region above (+ Y direction) the porous sheet 52. In fig. 1, a region above the porous sheet 52 is indicated as a region 70 b.

In the present embodiment, when the interior of the front compartment 70 is viewed in the vertical direction (Y direction), among the connection portions between the hydrogen pipes constituting the hydrogen pipe portion described above connected to the fuel cell 110, the connection portion between the hydrogen pipe constituting the hydrogen pipe portion and the fuel cell 110, and the connection portion between the hydrogen pipe and another device other than the fuel cell 110 connected to the hydrogen pipe portion and through which hydrogen flows, the hydrogen sensor 50 and the plurality of connection portions as the above-described arbitrary connection portions are disposed so as to overlap the porous sheet 52. Hereinafter, the 3 types of connection portions are also collectively referred to as "piping connection portions".

Fig. 4 is an explanatory diagram schematically showing an example of a state in which the interior of the front compartment 70 is viewed in the vertical direction (Y direction). In fig. 4, the position of the connection portion between adjacent ones of the plurality of hydrogen pipes constituting the hydrogen pipe portion (the hydrogen supply passage 22, the hydrogen discharge passage 24, and the circulation passage 25) connected to the fuel cell 110 is indicated by an arrow I. The position of the connection between the hydrogen pipe constituting the hydrogen pipe portion connected to the fuel cell 110 and the fuel cell 110 is indicated by an arrow II. The position of the connection between the hydrogen pipe and a device (in fig. 4, the hydrogen pump 44) different from the fuel cell 110, which is provided in the hydrogen pipe section connected to the fuel cell 110 and through which hydrogen flows, is indicated by an arrow III. In fig. 4, as an example, a case where 7 connection portions shown by an arrow I, two connection portions shown by an arrow II, and one connection portion shown by an arrow III are arranged together with the hydrogen sensor 50 so as to overlap with the porous sheet 52 when viewed in the Y direction is shown.

The number of the pipe connecting portions (joints) at the positions shown by arrows I, II, and III overlapping the porous sheet 52 when viewed in the Y direction can be any number, and in a typical example, the total number of the pipe connecting portions is 2 or more. The "device which is connected to the hydrogen pipe section and through which hydrogen flows and which is different from the fuel cell 110" may be a device other than the hydrogen pump 44 shown in fig. 4, and may be a valve provided in the hydrogen pipe section, such as the gas-liquid separator 45 and the on-off valve 46.

In fig. 4, a range in which the porous sheet 52 is disposed is surrounded and shown by a broken line. The porous sheet 52 can be fixed in the front compartment 70 by, for example, screw connection. Specifically, brackets may be attached to a plurality of locations (for example, 5 to 6 locations) such as the surface of the casing of the equipment disposed in the front compartment 70 and the inner wall surface of the front compartment 70, which constitute the high-voltage unit 120, and the porous sheet 52 may be screwed to the brackets. However, the porous sheet 52 may be fixed to the front compartment 70 by a method other than screw fastening. In the present embodiment, the porous sheet 52 is fixed to a portion of the front compartment 70 that is separated from the front cowl 72.

According to the fuel cell vehicle 10 equipped with the hydrogen leakage detection mechanism 12 of the present embodiment configured as described above, the hydrogen circulation unit is disposed in the front compartment 70 in a region below the porous sheet 52, and the hydrogen sensor 50 is disposed in a region above the porous sheet 52. When the interior of the front compartment 70 is viewed in the vertical direction, the plurality of pipe connection portions included in the hydrogen circulation unit and the hydrogen sensor 50 are disposed so as to overlap the porous sheet 52. Therefore, when a defect occurs in any one of the pipe connecting portions and the high-pressure hydrogen in the hydrogen circulating portion is discharged from the defective portion, the hydrogen sensor 50 can detect the hydrogen leakage early. As a result, measures such as stopping hydrogen leakage can be taken earlier, and safety can be improved.

Specifically, if a defect occurs in any one of the plurality of pipe connecting portions, hydrogen is ejected upward from the defect toward the porous sheet 52. As described above, various devices such as devices related to vehicle running and devices constituting a part of an air conditioner are disposed in the front compartment 70 in addition to the fuel cell 110 and the high voltage unit 120. Therefore, even if the direction of ejection of hydrogen at the defect is different from the upward direction, the flow of hydrogen is changed to the upward direction by the hydrogen flow coming into contact with the surrounding equipment. If the hydrogen flow flows upward and contacts the porous sheet 52, the hydrogen permeates through the inside of the porous sheet 52 in the thickness direction of the porous sheet 52 and further flows upward, and the hydrogen flow is disturbed, and the range of the hydrogen flow is expanded along the surface below the porous sheet 52. The fuel gas supplied to the fuel cell 110 is a hydrogen gas having a high purity, and the hydrogen ejected from the defect has a very high concentration as compared with the detection limit of the hydrogen sensor 50. Therefore, the hydrogen flows to contact the porous sheet 52 and permeate through the porous sheet 52, and the range of the region where the hydrogen concentration is relatively high, which can be detected by the hydrogen sensor 50, is expanded in the region above the porous sheet 52 as compared with the region below.

When the hydrogen sensor 50 is disposed vertically above the defect, even if the porous sheet 52 is not provided, the hydrogen ejected from the defect reaches the hydrogen sensor 50, and the hydrogen sensor 50 quickly detects the hydrogen leak. However, when the porous sheet 52 of the present embodiment is not provided and hydrogen leaks from a portion not overlapping with the hydrogen sensor 50 in the vertical direction, the leaked hydrogen rises upward and temporarily stays inside the front cowl 72, and then the hydrogen leakage is first detected by the hydrogen sensor 50 when the hydrogen concentration around the hydrogen sensor 50 becomes high and exceeds the detection limit of the hydrogen sensor 50. According to the present embodiment, even when the defective portion does not overlap the hydrogen sensor 50 in the vertical direction, the range in which hydrogen rises at a concentration equal to or higher than the detection limit of the hydrogen sensor 50 can be widened by providing the porous sheet 52, and the timing of detecting hydrogen leakage can be advanced by detecting hydrogen in the middle of the rise.

Further, by providing the porous sheet 52, the range in which the concentration of hydrogen increases by the amount equal to or more than the detection limit of the hydrogen sensor 50 can be widened, and thereby, even in the case where there are a plurality of sites (the above-described pipe connection parts) where defects that easily cause hydrogen leakage occur, hydrogen leakage at a plurality of pipe connection parts can be detected by a single hydrogen sensor 50. Therefore, the number of hydrogen sensors 50 to be provided for hydrogen leak detection can be suppressed.

In order to enhance the effect of early detection of hydrogen leakage when hydrogen leakage occurs at a portion not vertically overlapping the hydrogen sensor 50, the aperture ratio of the porous sheet 52, the distances between the above-described plurality of pipe connection portions and the porous sheet 52, the distances between the porous sheet 52 and the hydrogen sensor 50, and the like may be appropriately set in accordance with the expected flow rate of the hydrogen flow discharged from the defect, the detection limit amount of the hydrogen sensor 50, and the like.

In the present embodiment, since the porous sheet 52 is provided to expand the region in which the concentration of hydrogen is high during the rise in the horizontal direction, and the hydrogen sensor 50 only needs to detect hydrogen during the rise, the hydrogen sensor 50 can be provided below the front cowl 72 covering the upper end portion of the front cowl 70. In this way, since the hydrogen sensor 50 does not need to be provided in the front cowl 72 configured to be freely opened and closed, the degree of freedom in the arrangement of the hydrogen sensor 50 can be improved without being restricted by the wiring or the like.

Further, according to the present embodiment, by providing the porous sheet 52, it is possible to prevent a worker or the like who opens the front cowl 72 from coming into contact with high-voltage equipment such as the high-voltage cells 120 disposed below the porous sheet 52 when the front cowl 72 is opened, and it is possible to improve safety. Further, according to the present embodiment, even when the device disposed in the region below the porous sheet 52 is damaged for some reason, the porous sheet 52 can suppress scattering of the damaged member, and safety can be improved.

Fig. 5 is an explanatory view showing the results of a simulation performed to confirm the effects of the hydrogen leakage detection mechanism 12 of the present embodiment, and fig. 6 is an explanatory view similar to fig. 5 showing the results of a simulation in a comparative example not having the porous sheet 52. Fig. 5 and 6 show a state of distribution of hydrogen concentration when hydrogen leaks from a joint of a pipe routed below the fuel cell 110, as viewed in the horizontal direction in the front compartment 70. Fig. 5 and 6 show the results of the simulation under the same conditions except for the presence or absence of the porous sheet 52. Specifically, fig. 5 and 6 show the results of simulations in which conditions were set such that the hydrogen pressure in the pipe was 200kPa, the hydrogen flow rate in the pipe was 25NL/min, the discharge direction of hydrogen at the joint was vertically upward, the concentration of hydrogen leaking from the joint was 100%, and the size of the leak portion in the pipe was 10mm in diameter. In fig. 5, the opening ratio of the mesh as the porous sheet 52 is set to 30%. In fig. 5 and 6, the leak portion in the pipe is set to a position where the hydrogen discharged vertically upward hits the bottom surface of the fuel cell 110, and the hydrogen concentration is assumed to be 3.5% as the detection limit of the hydrogen sensor 50.

In comparison between fig. 5 and 6, in fig. 5, the hydrogen concentration distribution in the region 70a, which is a region below the position where the porous sheet 52 is disposed, is the same in fig. 5 and 6. Fig. 5 and 6 show an example of a range in which the hydrogen concentration is 4% or more at a position in the region 70a at the same distance from the leak portion in the vertical direction, by an arrow α. In fig. 5 and 6, the range of the hydrogen concentration of 4% or more at the position horizontally overlapping the hydrogen sensor 50 in the region 70b, which is the region above the position where the porous sheet 52 is disposed, is shown by the arrow β 1 and the arrow β 2, respectively. In comparison between fig. 5 and 6, the length of the arrow α (the width of the region in which the hydrogen concentration is 4% or more) is the same in fig. 5 and 6, but the length of the arrow β 1 in fig. 5 is longer than the length of the arrow β 2 in fig. 6. In fig. 5, the hydrogen sensor 50 is included in the range in which the hydrogen concentration is 4% or more, but in fig. 6, the hydrogen sensor 50 is located outside the range in which the hydrogen concentration is 4%. As can be seen from a comparison of fig. 5 and 6, the hydrogen leakage can be detected early by using the porous sheet 52.

Fig. 7 is a graph showing changes in hydrogen concentration at the site where the hydrogen sensor 50 is disposed, for the simulation results shown in fig. 5 and 6. A coordinate diagram corresponding to the simulation result of fig. 5 according to the present embodiment is shown as a coordinate diagram (a), and a coordinate diagram corresponding to the simulation result of fig. 6 according to the comparative example is shown as a coordinate diagram (b). In fig. 7, the change with time of the hydrogen concentration at the site where the hydrogen sensor 50 is disposed is shown with the timing when hydrogen leakage occurs at the pipe joint being taken as time 0. As can be seen from fig. 7, when the porous sheet 52 is provided, the range of high hydrogen concentration is widened by providing the porous sheet 52, and as a result, the hydrogen concentration around the hydrogen sensor 50 rapidly rises, and hydrogen leakage is detected early. In contrast, in the comparative example in which the porous sheet 52 was not provided, it was found that the increase in the hydrogen concentration around the hydrogen sensor 50 was greatly delayed. In the graph (b) corresponding to the comparative example, immediately after the occurrence of the hydrogen leakage, the hydrogen concentration at the portion where the hydrogen sensor 50 is disposed becomes relatively high. This is presumably because the leaked hydrogen contacts a surrounding structure such as the fuel cell 110, disturbs the hydrogen flow, thereby generating a cluster in a range where the hydrogen concentration is relatively high, and such a cluster rises and passes through the position where the hydrogen sensor 50 is disposed.

Fig. 8 and 9 are explanatory views showing simulation results based on conditions different from those of fig. 5 to 7, similarly to fig. 5 and 6. Fig. 8 shows the results of the present embodiment having the porous sheet 52, and fig. 9 shows the results of the comparative example not having the porous sheet 52. The conditions of the simulation results shown in fig. 8 and 9 are the same as those in fig. 5 and 6 except for the arrangement of the hydrogen leakage site. In fig. 8 and 9, the leaking portion in the pipe is set to a position where the hydrogen discharged vertically upward flows upward without contacting surrounding equipment such as the fuel cell 110.

In fig. 8 and 9, as in fig. 5 and 6, in the region 70a which is a region below the position where the porous sheet 52 is disposed, the hydrogen concentration distribution is the same regardless of the presence or absence of the porous sheet 52 (see arrow α in fig. 8 and 9). In the region 70b which is a region above the position where the porous sheet 52 is disposed, the width of the region having a hydrogen concentration of 4% or more is larger in fig. 8 than in fig. 9 (see arrow β 1 in fig. 8 and arrow β 2 in fig. 9), and the hydrogen sensor 50 is included in the range having a hydrogen concentration of 4% or more in fig. 8, unlike in fig. 9. From this, it is understood that even in the arrangement of the leak portions shown in fig. 8 and 9, the hydrogen leak can be detected early by using the porous sheet 52.

Fig. 10 is a graph showing changes in hydrogen concentration at a site where the hydrogen sensor 50 is disposed, for the simulation results shown in fig. 8 and 9, similarly to fig. 7. A coordinate diagram corresponding to the simulation result of fig. 8 according to the present embodiment is shown as a coordinate diagram (a), and a coordinate diagram corresponding to the simulation result of fig. 9 according to the comparative example is shown as a coordinate diagram (b). As can be seen from fig. 10, when the porous sheet 52 is provided, the range of high hydrogen concentration is widened by providing the porous sheet 52, and as a result, the hydrogen concentration around the hydrogen sensor 50 rapidly increases, and the timing of detecting hydrogen leakage is advanced as compared with the comparative example.

B. Embodiment 2:

fig. 11 is a plan view showing the porous sheet 152 according to embodiment 2 of the present disclosure. The porous sheet 152 of embodiment 2 is used as the porous sheet 52 of embodiment 1. As shown in fig. 11, the porous sheet 152 is formed of a porous body. The porous body constituting the porous sheet 152 may be, for example, a porous body having a three-dimensional mesh structure as a skeleton, or a foam. The porous sheet 152 may be formed of the same metal material or resin material as the porous sheet 52 of embodiment 1.

The porous sheet 152 has a function of allowing hydrogen leaking from a connection portion of a pipe or the like to permeate in the thickness direction when the hydrogen flows toward the surface of the porous sheet 152, and diffusing the hydrogen flow along the surface by disturbing the hydrogen flow, similarly to the porous sheet 52. Therefore, for the same reason as that of the porous sheet 52, the aperture ratio of the porous sheet 152 is preferably 10% or more, more preferably 20% or more. For the same reason as that of the porous sheet 52, the content is preferably 60% or less, and more preferably 50% or less. However, the aperture ratio of the porous sheet 152 may be 10% or less, or 60% or more. The aperture ratio in a plan view of the porous sheet 152 may be obtained by, for example, taking an image of the surface of the porous sheet 152 with a camera, enlarging the obtained image by 5 times, and performing image processing to calculate and obtain the ratio of the total area of the portions penetrating in the thickness direction to the entire area of the porous sheet 152 within a specific range in the image. For the same reason as the porous sheet 52, the thickness of the porous sheet 152 is preferably 0.2cm or more, more preferably 0.5cm or more. Further, it is preferably 2.0cm or less, more preferably 1.0cm or less.

With such a configuration, in the hydrogen leakage detection means 12, the porous sheet 152 is also arranged in the same manner as the porous sheet 52 of embodiment 1, whereby hydrogen leakage can be detected by the hydrogen sensors 50 early, the number of hydrogen sensors 50 can be suppressed, and the same effects as those of embodiment 1 can be obtained. In embodiment 2, the porous body constituting the porous sheet 152 has a three-dimensional complex structure as compared with the mesh constituting the porous sheet 52 of embodiment 1. Therefore, when hydrogen flows from the defect of the pipe connecting portion toward the surface of the porous sheet 152, the function of diffusing the hydrogen flow along the surface can be enhanced. As a result, the range of the hydrogen concentration that is equal to or greater than the detection limit of the hydrogen sensor 50 is widened in the region above the porous sheet 152, and the effect of early detection of hydrogen leakage by the hydrogen sensor 50 can be improved.

C. Embodiment 3:

fig. 12 is a plan view showing a porous sheet 252 according to embodiment 3 of the present disclosure. The porous sheet 252 of embodiment 3 is used similarly to the porous sheet 52 of embodiment 1. As shown in fig. 12, the porous sheet 252 is formed of a punched metal plate. The porous sheet 252 can be formed of the same metal material as the porous sheet 52 of embodiment 1.

The porous sheet 252 has a function of allowing hydrogen leaking from a connection portion of a pipe or the like to permeate in the thickness direction when the hydrogen flows toward the surface of the porous sheet 252, and diffusing the hydrogen flow along the surface by disturbing the hydrogen flow, similarly to the porous sheet 52. Therefore, for the same reason as the porous sheet 52, the aperture ratio of the porous sheet 252 is preferably 10% or more, more preferably 20% or more. For the same reason as that of the porous sheet 52, the content is preferably 60% or less, and more preferably 50% or less. However, the aperture ratio of the porous sheet 252 may be 10% or less, or 60% or more. The aperture ratio in a plan view of the porous sheet 252 may be obtained by, for example, photographing the surface of the porous sheet 252 with a camera, enlarging the obtained image by 5 times, and performing image processing to calculate and obtain the ratio of the total area of the holes of the punched metal plate to the entire area of the porous sheet 252 within a specific range in the image. For the same reason as the porous sheet 52, the thickness of the porous sheet 252 is preferably 0.2cm or more, more preferably 0.5cm or more. Further, it is preferably 2.0cm or less, more preferably 1.0cm or less.

With such a configuration, in the hydrogen leakage detection means 12, the porous sheet 252 is also arranged in the same manner as the porous sheet 52 of embodiment 1, whereby hydrogen leakage can be detected by the hydrogen sensors 50 early, the number of hydrogen sensors 50 can be suppressed, and the same effects as those of embodiment 1 can be obtained. In general, the perforated metal sheet constituting the porous sheet 252 greatly disturbs the flow of gas passing through the sheet (through the holes of the perforated metal sheet) as compared with a mesh or the like. Therefore, when hydrogen flows from the pipe connecting portion toward the surface of the porous sheet 252, the function of diffusing the flow of hydrogen along the surface can be enhanced, and the effect of expanding the range in which the hydrogen concentration is equal to or more than the detection limit of the hydrogen sensor 50 in the region above the porous sheet 252 can be enhanced. In addition, when the punched metal plate is used, the aperture ratio of the porous sheet 252 can be easily adjusted to a desired value by changing the diameter of the holes provided in the punched metal plate and the pitch which is the interval at which the holes are provided. Further, in the case of using the punched metal plate, it is easy to suppress the thickness of the porous sheet and secure the strength of the porous sheet, and even if the hydrogen ejected from the pipe connecting portion comes into contact with the porous sheet 252, the deformation of the porous sheet 252 is suppressed.

D. Other embodiments:

(D1) in each of the above embodiments, the porous sheet is disposed apart from the hydrogen sensor 50 and the plurality of pipe connection portions, but may have a different configuration. For example, a part of the hydrogen sensor 50, for example, a tip end part of the hydrogen sensor 50 may be connected to the porous sheet. Alternatively, a part of the plurality of pipe connecting portions may be connected to the porous sheet. However, in order to increase the effect of hydrogen ejected from a defect generated in the pipe connecting portion colliding with the porous sheet and diffusing in the horizontal direction, it is preferable that all of the plurality of pipe connecting portions are separated from the porous sheet.

(D2) In each of the above embodiments, the hydrogen leakage detection means 12 includes a single porous sheet, but may have a different structure. For example, a plurality of porous sheets arranged in a staggered manner in the horizontal direction may be provided in the front compartment 70. In this case, the same effects as those of the respective embodiments can be obtained by arranging at least one porous sheet so as to define at least a part of the space in the front compartment 70 and setting the positional relationship among the at least one porous sheet, the plurality of pipe connection portions, and the hydrogen sensor 50 to the positional relationship described in the respective embodiments.

(D3) In each of the above embodiments, the front chamber 70 is a housing portion of the hydrogen circulation unit including the hydrogen piping unit for housing the fuel cell 110 and the hydrogen pipe unit connected to the fuel cell 110, but a different configuration is also possible. For example, the outer shell may be a rear luggage compartment located behind the vehicle compartment in the underfloor space of the vehicle compartment.

(D4) In each of the above embodiments, the hydrogen circulation unit housed in the case portion and disposed in the region below the porous sheet includes the fuel cell 110 and the hydrogen pipe portion connected to the fuel cell 110, but may have a different configuration. Instead of the fuel cell 110, or in addition to the fuel cell 110, the hydrogen tank 21 may be included in the hydrogen circulation unit and housed in the housing. The same effects as those of the embodiments can be obtained by arranging the hydrogen circulation section including at least one of the fuel cell 110 and the hydrogen tank 21 and the hydrogen piping section connected to the hydrogen circulation section in the housing section, and setting the positional relationship among the porous sheet, the plurality of piping connection sections, and the hydrogen sensor 50 in the housing section to the positional relationship described in the embodiments.

(D5) In each of the above embodiments, when the inside of the housing portion is viewed in the vertical direction, the connection portion that is disposed together with the hydrogen sensor 50 so as to overlap the porous sheet is any one of the 3 types of pipe connection portions described above, but a different configuration is also possible. The plurality of connecting portions arranged to overlap the porous sheet may include a connecting portion different from the above-described piping connecting portion, as long as the connecting portion is a connecting portion of a hydrogen flow path included in the hydrogen circulation portion.

(D6) In each of the above embodiments, a plurality of connection portions are provided which are disposed so as to overlap the porous sheet together with the hydrogen sensor 50 when the inside of the housing portion is viewed in the vertical direction, but one connection portion may be provided. Even with such a configuration, the region where the hydrogen concentration is relatively high is expanded by the porous sheet, whereby the degree of freedom in the location of the hydrogen sensor is ensured, and the hydrogen leakage is detected early by the hydrogen sensor.

(D7) In each of the above embodiments, the connection portion and the hydrogen sensor included in the hydrogen circulation portion are disposed so as to overlap the porous sheet when the inside of the housing portion is viewed in the vertical direction. In the case, the hydrogen circulation unit may be disposed in a region below the porous sheet, and the hydrogen sensor may be disposed in a region above the porous sheet. When the inside of the housing portion is viewed in the vertical direction, the connection portion and the hydrogen sensor may not overlap the porous sheet, and the hydrogen leakage may be detected early by the hydrogen sensor by enlarging a region where the hydrogen concentration is relatively high by the porous sheet when hydrogen discharged from a defect generated in the hydrogen flow path portion is directed to the porous sheet, when the vehicle on which the hydrogen leakage detection mechanism 12 is mounted is inclined, for example, when traveling wind flows into the housing portion and leaked hydrogen flows toward the porous sheet.

(D8) In the above embodiment, the hydrogen leakage detection mechanism 12 is mounted on the fuel cell vehicle 10, but a different configuration is also possible. The hydrogen leakage detection mechanism 12 may be mounted on a mobile body other than a vehicle on which the fuel cell is mounted, or may be applied to a stationary power generation device including the fuel cell.

The present disclosure is not limited to the above-described embodiments, and can be implemented in various configurations without departing from the scope of the present disclosure. For example, in order to solve a part or all of the above-described problems or to achieve a part or all of the above-described effects, the technical features of the embodiments corresponding to the technical features of the respective embodiments described in the summary section of the invention may be appropriately replaced or combined. In addition, unless otherwise specified, technical features thereof are essential in the present specification and can be appropriately deleted. For example, the present disclosure can be realized by the following embodiments.