Fuel cell system

Abstract

The present application relates to a fuel cell system, the fuel cell system (10) including a branch flow path (28) branched from a position of a supply pipe (24) outward of an inner surface (F1) of a wall portion (22W) of a case (22), and communicating with an inside of the case (22), wherein the case (22) covers a fuel cell stack (18). In a set state of the fuel cell system (10), a position of an outlet end of the branch flow path (28) is set to a position lower than a gas exchange port (220).

Description

Technical Field

[0001] This invention relates to fuel cell systems. Background Technology

[0002] A fuel cell system includes a fuel cell stack that generates electricity using hydrogen and an oxidant gas. The fuel cell stack is sometimes housed within a casing. For example, Patent Document 1 discloses an apparatus for removing liquid water from the interior of a fuel cell casing used to house the fuel cell stack. In this apparatus, air is supplied to the interior of the fuel cell casing by a ventilation fan located outside the casing, and the liquid water inside the casing is discharged to the outside of the casing during ventilation.

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2009-289426 Summary of the Invention

[0004] The problem that the invention aims to solve However, Patent Document 1 requires a ventilation fan for ventilating the interior of the fuel cell housing, increasing the number of components. Furthermore, Patent Document 1 creates an airflow from top to bottom of the fuel cell housing. However, gases lighter than air, such as hydrogen, tend to move upwards towards the fuel cell housing, making it difficult to exhaust them to the outside, resulting in low efficiency.

[0005] The purpose of this invention is to solve the above-mentioned problems.

[0006] Solution for solving the problem One aspect of the present invention is a fuel cell system comprising: a fuel cell stack that generates electricity through an electrochemical reaction of hydrogen and an oxidant gas; a housing that encloses the fuel cell stack; a supply pipe that connects to an oxidant gas supplier disposed outside the housing and the fuel cell stack, and passes through a wall of the housing; a branch flow path that branches off from the supply pipe at a location outside the inner surface of the housing wall, and communicates with the interior of the housing; and a venting port disposed in the housing for exchanging the hydrogen gas within the housing. In the configuration of the fuel cell system, the outlet end of the branch flow path is positioned lower than the venting port.

[0007] The effects of the invention According to one aspect of the invention, the interior of the housing can be efficiently ventilated. Specifically, a branch flow path is provided that branches off from the supply pipe and communicates with the interior of the housing, thus allowing oxidant gas to be guided into the housing even without a ventilation fan. Furthermore, in the fuel cell system configuration, the output end of the branch flow path is positioned lower than the ventilation port, thereby creating an oxidant gas flow from the lower to the upper part of the housing. Therefore, hydrogen gas, which tends to stagnate at the top of the housing, can be efficiently discharged to the outside of the housing.

[0008] The following embodiments will be described with reference to the accompanying drawings. Based on the description of these embodiments, the above-described objectives, features, and advantages can be easily understood. Attached Figure Description

[0009] Figure 1 This is a schematic diagram illustrating the structure of a fuel cell system according to an embodiment.

[0010] Figure 2 This is a diagram showing the branch flow path and the exterior of the housing of the fuel cell system in its set-up state.

[0011] Figure 3 It is along Figure 2 A cross-sectional view in the direction of arrow III-III.

[0012] Figure 4 This is a block diagram showing a portion of the structure of a fuel cell system.

[0013] Figure 5 This is a diagram showing the flow of oxidant gas.

[0014] Figure 6 This is a diagram showing the flow of oxidant gas when the supply of oxidant gas is adjusted.

[0015] Figure 7 This is a diagram showing the flow of oxidant gas when oxidant gas is supplied to the casing.

[0016] Figure 8 This is a flowchart showing the sequence of ventilation processes performed by the control device. Detailed Implementation

[0017] Figure 1 This is a schematic diagram showing the structure of a fuel cell system 10 according to an embodiment. The fuel cell system 10 includes an oxidant gas supplier 12, an intercooler 14, a humidifier 16, a fuel cell stack 18, a hydrogen assembly 20, a housing 22, a supply piping 24, and an exhaust piping 26.

[0018] An oxidant gas supplier 12 is disposed outside the housing 22. The oxidant gas supplier 12 supplies oxidant gas to the fuel cell stack 18 via a supply pipe 24. The oxidant gas supplier 12 can be a pump or a blower, etc. The oxidant gas can be air, etc. The oxidant gas can be any gas containing oxygen, and is not limited to air.

[0019] Intercooler 14 is disposed outside housing 22. Intercooler 14 cools the oxidant gas flowing in supply piping 24. For example, intercooler 14 is configured to exchange heat with refrigerant flowing in piping connected to radiator.

[0020] A humidifier 16 is disposed inside the housing 22. The humidifier 16 introduces water vapor into the supply pipe 24 to humidify the oxidant gas flowing through the supply pipe 24. Additionally, the humidifier 16 recovers moisture contained in the exhaust gas flowing through the discharge pipe 26 and vaporizes this moisture into water vapor. Alternatively, the humidifier 16 may introduce the vaporized water vapor into the supply pipe 24. The exhaust gas is a mixture containing oxidant gas and water vapor.

[0021] The fuel cell stack 18 generates electricity through an electrochemical reaction between hydrogen and oxidant gas. The fuel cell stack 18 has a first input section 18-1, a first output section 18-2, a second input section 18-3, a second output section 18-4, and multiple fuel cell cells (not shown).

[0022] In the fuel cell stack 18, oxidant gas flowing in from the first input section 18-1 and hydrogen gas flowing in from the second input section 18-3 are distributed to each fuel cell cell. Each fuel cell cell generates electricity through the electrochemical reaction between hydrogen and oxidant gas.

[0023] Oxidant gas that does not participate in the electrochemical reaction of each fuel cell cell, and water (water vapor) generated by the electrochemical reaction, are collected as exhaust gas and discharged from the first output section 18-2. Additionally, hydrogen gas that does not participate in the electrochemical reaction of each fuel cell cell is discharged from the second output section 18-4.

[0024] The hydrogen assembly 20 has: a hydrogen supply path 20-1, which is connected to the second input section 18-3 of the fuel cell stack 18; and a hydrogen recovery path 20-2, which is connected to the second output section 18-4 of the fuel cell stack 18.

[0025] The hydrogen assembly 20 supplies hydrogen from a hydrogen tank (not shown) located outside the housing 22 to the fuel cell stack 18 via hydrogen supply path 20-1. The hydrogen assembly 20 also supplies hydrogen from the fuel cell stack 18 via hydrogen recovery path 20-2 back to the fuel cell stack 18 via hydrogen supply path 20-1. In this case, the hydrogen assembly 20 may discharge a portion of the hydrogen to the outside of the housing 22 as needed.

[0026] The housing 22 encloses the humidifier 16, the fuel cell stack 18, and the hydrogen assembly 20. An air exchange port 220 is provided in the housing 22.

[0027] Supply piping 24 is used to guide oxidant gas supplied from oxidant gas supplier 12 to fuel cell stack 18. One end of supply piping 24 is connected to oxidant gas supplier 12, and the other end of supply piping 24 is connected to the first input section 18-1 of fuel cell stack 18. Supply piping 24 extends from oxidant gas supplier 12 sequentially through intercooler 14, wall 22W of housing 22, and humidifier 16 to fuel cell stack 18.

[0028] The exhaust pipe 26 is a pipe used to guide the exhaust gas discharged from the fuel cell stack 18 to the outside of the housing 22. One end of the exhaust pipe 26 is connected to the first output section 18-2 of the fuel cell stack 18. The other end of the exhaust pipe 26 is an open end, disposed outside the housing 22. The exhaust pipe 26 extends from the fuel cell stack 18, sequentially through the humidifier 16 and the wall 22W of the housing 22, to the outside of the housing 22.

[0029] The fuel cell system 10 also includes a branch flow path 28 and a bypass flow path 30. Branch flow path 28 is a flow path for guiding the oxidant gas supplied from the oxidant gas supplier 12 into the interior of the housing 22. Branch flow path 28 branches off from the supply pipe 24 and communicates with the interior of the housing 22. Bypass flow path 30 is a flow path for discharging the oxidant gas supplied from the oxidant gas supplier 12 to the outside, bypassing the fuel cell stack 18. Bypass flow path 30 is connected to the discharge pipe 26 and branch flow path 28.

[0030] Figure 2 This is an external view showing the branch flow path 28 and the housing 22 in the installed state of the fuel cell system 10. The installed state of the fuel cell system 10 refers to the state in which the housing 22 is disposed in a designated location of the fuel cell system 10. When the housing 22 is disposed in the designated location of the fuel cell system 10, the fuel cell stack 18 can generate electricity.

[0031] Branch flow path 28 has a first flow path section 32, a second flow path section 33 and a third flow path section 34 (see reference). Figure 1The first flow path 32 extends downward from the supply pipe 24. The second flow path 33 extends from the first flow path 32 toward the housing 22. The first flow path 32 and the second flow path 33 are disposed outside the housing 22 and are constituted by pipes.

[0032] The second flow path 33 has an inclined portion 36. In the installed state of the fuel cell system 10, the inner surface F1 of the wall portion 22W near the housing 22 ( Figure 1 The inclined portion 36 is formed by increasing its height. That is, when the fuel cell system 10 is installed, the inclined portion 36 is inclined upward toward the inner surface F1 of the wall 22W of the housing 22.

[0033] The third flow path 34 is disposed on the wall 22W of the housing 22 (see reference). Figure 1 ). Figure 3 It is along Figure 2 The cross-sectional view is shown in the direction of arrow III-III. The third flow path 34 is constituted by a pipe inserted into a through hole that penetrates the wall portion 22W of the housing 22. Alternatively, the third flow path 34 may be a through hole that penetrates the wall portion 22W of the housing 22.

[0034] A filter 38 is provided in the second flow path section 33. The filter 38 prevents foreign objects from flowing into the interior of the housing 22. A narrowed diameter section 40 is provided in the third flow path section 34. The narrowed diameter section 40 has an orifice (throttling orifice) in the third flow path section 34, the flow path cross-section of which is smaller than the flow path cross-section of the filter 38. This orifice includes the outlet end (outlet opening) of the branch flow path 28.

[0035] The outlet end (outlet opening) of the branch flow path 28 is disposed on the inner surface F1 of the wall 22W of the housing 22 and communicates with the interior of the housing 22. In the configuration of the fuel cell system 10, the outlet end (outlet opening) of the branch flow path 28 is positioned lower than the air exchange port 220 (see reference). Figure 1 , Figure 2 ).

[0036] Figure 4 This is a block diagram showing a portion of the structure of a fuel cell system 10. The fuel cell system 10 also includes a sealing valve 42, a second sealing valve 44, a bypass valve 46, a speed control valve 48, a hydrogen sensor 50, and a control device 52.

[0037] Sealing valve 42 is a valve capable of sealing the supply pipe 24. This valve can be an on / off valve capable of opening and closing the flow path, or an opening regulating valve capable of adjusting the opening degree of the flow path. Furthermore, when the opening degree of the opening regulating valve is at its minimum value (zero), the flow path is closed, and the fluid does not flow. On the other hand, the larger the opening degree of the opening regulating valve, the greater the flow rate.

[0038] Sealing valve 42 is located on supply pipe 24 (see reference) Figure 1 ). Figure 1 An example is shown where a sealing valve 42 is installed on a supply pipe 24 disposed on the wall portion 22W of the housing 22. The sealing valve 42 is located downstream of the branch point (input end of the first flow path portion 32) of the supply pipe 24 from the branch flow path 28. That is, the branch flow path 28 branches from the supply pipe 24 upstream of the sealing valve 42.

[0039] The second sealing valve 44 is a valve capable of sealing the discharge pipe 26. This valve can be an on / off valve or an opening adjustment valve. The second sealing valve 44 is located on the discharge pipe 26 (see reference). Figure 1 ). Figure 1 An example is shown where a second sealing valve 44 is installed on a discharge pipe 26 disposed inside the housing 22. The second sealing valve 44 is located upstream of the connection point of the bypass flow path 30 (the output end of the bypass flow path 30) on the discharge pipe 26.

[0040] Bypass valve 46 is an opening adjustment valve used to regulate the flow rate of oxidant gas flowing in bypass flow path 30. Bypass valve 46 is located in bypass flow path 30 (see reference). Figure 1 ).

[0041] Speed ​​control valve 48 is an opening adjustment valve used to adjust the flow rate of the oxidant gas flowing in branch flow path 28. Speed ​​control valve 48 is located in inclined section 36 (see reference). Figure 1 ).

[0042] The hydrogen sensor 50 is a sensor that detects the concentration of hydrogen gas inside the housing 22. The hydrogen sensor 50 is disposed inside the housing 22 (see reference). Figure 1 ).

[0043] The control device 52 is a device for controlling the fuel cell system 10. The control device 52 can be located outside the housing 22 or inside the housing 22.

[0044] The control unit 52 controls the hydrogen assembly 20 to supply hydrogen to the fuel cell stack 18 and adjusts the amount of hydrogen supplied to the fuel cell stack 18.

[0045] Figure 5This diagram illustrates the flow of oxidant gas. Control device 52 controls the oxidant gas supplier 12, sealing valve 42, second sealing valve 44, bypass valve 46, and speed control valve 48 to supply oxidant gas to the fuel cell stack 18. In this case, control device 52 controls the oxidant gas supplier 12 to output oxidant gas to the supply pipe 24. Additionally, control device 52 opens sealing valve 42 and second sealing valve 44, and closes bypass valve 46 and speed control valve 48. Thus, the oxidant gas output to the supply pipe 24 is supplied to the fuel cell stack 18 from the first input section 18-1. The oxidant gas supplied to the fuel cell stack 18 is distributed to each fuel cell cell. Exhaust gas containing oxidant gas that did not participate in the electrochemical reaction of each fuel cell cell flows from the first output section 18-2 to the exhaust pipe 26 and is discharged to the outside via the exhaust pipe 26.

[0046] Figure 6 This diagram illustrates the flow of oxidant gas when the oxidant gas supply is adjusted. Control device 52 controls bypass valve 46 to adjust the supply of oxidant gas to fuel cell stack 18. In this case, control device 52 determines a target power generation based on at least one of the temperature, voltage, and generated power of fuel cell stack 18, and adjusts the opening of bypass valve 46 according to this target power generation. The smaller the target power generation, the larger the opening of bypass valve 46. Thus, a portion of the oxidant gas flowing in supply pipe 24 flows into discharge pipe 26 through branch flow path 28 and bypass flow path 30, thereby adjusting the supply of oxidant gas to fuel cell stack 18.

[0047] When the fuel cell stack 18 generates electricity, the control device 52 ventilates the interior of the housing 22 based on the hydrogen detected by the hydrogen sensor 50. Figure 7 This is a diagram showing the flow of oxidant gas when oxidant gas is supplied to the casing 22. Furthermore, Figure 7 An example is shown with bypass valve 46 closed.

[0048] If the hydrogen concentration detected by the hydrogen sensor 50 exceeds a predetermined threshold, the control device 52 opens the speed control valve 48. In this case, the control device 52 sets the opening degree of the speed control valve 48 according to the hydrogen concentration. As a result, a portion of the oxidant gas flowing through the supply pipe 24 passes through the branch flow path 28 and flows into the interior of the housing 22 from the output end (output opening) of the branch flow path 28. The oxidant gas flowing into the interior of the housing 22 is discharged to the outside of the housing 22 via the vent 220 provided in the housing 22.

[0049] In this embodiment, with the fuel cell system 10 in its configured state, the output end (output opening) of the branch flow path 28 is positioned lower than the air exchange port 220 (see reference). Figure 7 Therefore, an oxidant gas flow is formed that flows from the bottom to the top of the housing 22. Thus, hydrogen gas, which tends to stagnate above the housing 22, can be efficiently discharged to the outside of the housing 22.

[0050] With the speed control valve 48 open, the amount of oxidant gas required for power generation (the amount of oxidant gas corresponding to the target power generation) will only decrease by reducing the amount of oxidant gas supplied to the housing 22. Therefore, with the speed control valve 48 open, the control device 52 controls the oxidant gas supplier 12 so that the amount of oxidant gas output to the supply pipe 24 increases compared to before the speed control valve 48 is opened.

[0051] Furthermore, the amount of oxidant gas supplied to the housing 22 can be obtained based on the opening degree of the speed control valve 48. That is, the control device 52 obtains the amount of oxidant gas supplied to the housing 22 based on a form or formula representing the relationship between the amount of oxidant gas supplied to the housing 22 and the opening degree of the speed control valve 48.

[0052] Furthermore, the amount of oxidant gas required for power generation (the amount of oxidant gas corresponding to the target power generation) can be obtained based on the target power generation. That is, the control device 52 uses a form or formula that represents the relationship between the target power generation and the amount of oxidant gas required for power generation to obtain the amount of oxidant gas required for power generation.

[0053] Even if the hydrogen concentration detected by the hydrogen sensor 50 does not exceed a predetermined threshold, there is still a margin for supplying oxidant gas to the casing 22 when the amount of oxidant gas required for power generation is relatively small. Therefore, when the hydrogen concentration detected by the hydrogen sensor 50 is below the predetermined threshold and the amount of oxidant gas required for power generation is below a predetermined amount, the control device 52 opens the speed control valve 48. This allows for active ventilation within the casing 22 without limiting the power generation of the fuel cell stack 18.

[0054] On the other hand, even when the hydrogen concentration detected by the hydrogen sensor 50 does not exceed a predetermined threshold and the amount of oxidant gas required for power generation is relatively large, there is sometimes insufficient oxidant gas to be supplied to the housing 22. Therefore, when the hydrogen concentration detected by the hydrogen sensor 50 is below the predetermined threshold and the amount of oxidant gas required for power generation exceeds a predetermined amount, the control device 52 controls the speed regulating valve 48 to reduce the flow rate of oxidant gas supplied to the housing 22 compared to the current flow rate. As a result, when the hydrogen concentration in the housing 22 is low and the fuel cell stack 18 needs to achieve high output, oxidant gas can be preferentially supplied to the fuel cell stack 18. Consequently, the power generation efficiency can be maintained while the hydrogen in the housing 22 is discharged to the outside.

[0055] Figure 8 This is a flowchart illustrating the sequence of ventilation processes performed by the control device 52. The ventilation process is repeated at predetermined intervals.

[0056] In step S1, the control device 52 acquires the hydrogen concentration detected by the hydrogen sensor 50. Once the hydrogen concentration is acquired, the gas exchange process proceeds to step S2.

[0057] In step S2, the control device 52 compares the hydrogen concentration with a predetermined threshold. If the hydrogen concentration is below the threshold (step S2: No), the gas exchange process proceeds to step S3. Conversely, if the hydrogen concentration exceeds the threshold (step S2: Yes), the gas exchange process proceeds to step S4.

[0058] In step S3, the control device 52 compares the amount of oxidant gas required for power generation (the amount of oxidant gas corresponding to the target power generation) with a predetermined amount. If the amount of oxidant gas required for power generation is less than the predetermined amount (step S3: No), the gas exchange process proceeds to step S4. Conversely, if the amount of oxidant gas required for power generation exceeds the predetermined amount (step S3: Yes), the gas exchange process proceeds to step S5.

[0059] In step S4, the control device 52 opens the speed control valve 48. In this case, the control device 52 sets the opening degree of the speed control valve 48 according to the hydrogen concentration. When the speed control valve 48 is opened, the gas exchange process ends.

[0060] In step S5, the control device 52 controls the speed regulating valve 48 to reduce the flow rate of the oxidant gas supplied to the housing 22 compared to the current flow rate. When the flow rate of the oxidant gas decreases, the venting process ends.

[0061] Alternatively, the above implementation method can be modified as follows.

[0062] (First variation) Alternatively, the output end (output opening) of the branch flow path 28 may be located inside the housing 22. In this case, the third flow path 34 is constituted by a pipe inserted into a through hole that passes through the wall portion 22W of the housing 22, and the pipe protrudes into the interior of the housing 22.

[0063] (Second variation) Alternatively, the branch flow path 28 may branch from the supply pipe 24 disposed in the wall portion 22W of the housing 22. In this case, the branch flow path 28 may be formed solely by a through hole that penetrates the wall portion 22W of the housing 22.

[0064] (Third variation) Alternatively, in the configuration of the fuel cell system 10, the output end (output opening) of the branch flow path 28 may not be entirely positioned lower than the ventilation port 220. That is, in the configuration of the fuel cell system 10, a portion of the output end (output opening) of the branch flow path 28 may be positioned higher than the lowest point of the ventilation port 220. Even in this case, the area in the ventilation port 220 higher than the output end (output opening) of the branch flow path 28 is larger than the area lower than that output end (output opening).

[0065] (Fourth variation) Alternatively, the inclined portion 36 may be disposed in the third flow path portion 34 instead of in the second flow path portion 33. Alternatively, the inclined portion 36 may be disposed in both the second and third flow path portions 33 and 34. In this case, the inclined portion 36 disposed in the third flow path portion 34 may be formed continuously with the inclined portion 36 disposed in the second flow path portion 33, or it may be formed discontinuously with the inclined portion 36 disposed in the second flow path portion 33.

[0066] (Fifth variation) Alternatively, the bypass flow path 30 can be connected to the supply piping 24 and the discharge piping 26. In this case, both the branch flow path 28 and the bypass flow path 30 branch from the supply piping 24. The bypass flow path 30 can branch upstream of the branch flow path 28 of the supply piping 24, or it can branch downstream of the branch flow path 28 of the supply piping 24.

[0067] (Sixth variation) Alternatively, the hydrogen sensor 50 can detect the amount (absolute amount) of hydrogen. In this case, if the amount of hydrogen detected by the hydrogen sensor 50 exceeds a predetermined threshold, the control device 52 will open the speed control valve 48.

[0068] (Seventh variation) Alternatively, the higher the hydrogen concentration (or amount) detected by the hydrogen sensor 50, the greater the opening of the speed control valve 48 caused by the control device 52. That is, the higher the hydrogen concentration (or amount), the greater the flow rate of hydrogen supplied to the housing 22 by the control device 52. In this case, it is not necessary to compare the hydrogen concentration (or amount) detected by the hydrogen sensor 50 with a predetermined threshold.

[0069] (Eighth variation) The above-described embodiments and variations can be combined in any way without departing from the purpose of the present invention.

[0070] Below, we record the inventions and their effects that can be understood based on the above records.

[0071] 1. The fuel cell system 10 of the present invention comprises: a fuel cell stack 18 that generates electricity through an electrochemical reaction of hydrogen and an oxidant gas; a housing 22 that covers the fuel cell stack; a supply pipe 24 connected to an oxidant gas supplier 12 disposed outside the housing and the fuel cell stack, and passing through a wall 22W of the housing; a branch flow path 28 that branches off from the supply pipe at a location outside the inner surface F1 of the housing wall and communicates with the interior of the housing; and a vent 220 disposed in the housing for exchanging the hydrogen gas inside the housing. In the configuration state of the fuel cell system, the outlet end of the branch flow path is positioned lower than the vent.

[0072] This allows for efficient ventilation of the casing's interior. Specifically, because it has branch flow paths that branch off from the supply piping and connect to the interior of the casing, oxidant gas can be directed into the casing even without a ventilation fan. Furthermore, in the fuel cell system configuration, the output end of the branch flow path is positioned lower than the ventilation port, thus creating an oxidant gas flow from the bottom up of the casing. Therefore, hydrogen gas, which tends to stagnate at the top of the casing, can be efficiently discharged to the outside of the casing.

[0073] 2. The fuel cell system of the present invention may also include a sealing valve 42, which is disposed in the supply pipe, and the branch flow path branches from the supply pipe upstream of the sealing valve. Thus, even if the sealing valve cannot operate due to freezing of moisture remaining in the supply pipe between the sealing valve and the fuel cell stack when power generation of the fuel cell stack stops, ventilation of the interior of the casing can still be achieved.

[0074] 3. In the fuel cell system of the present invention, the branch flow path may also have an inclined portion 36, which, in the installed state of the fuel cell system, is inclined upward toward the inner surface of the wall of the housing. This suppresses the inflow of moisture, such as condensation, generated upstream of the inclined portion into the interior of the housing.

[0075] 4. The fuel cell system of the present invention may also further include: an exhaust pipe 26 for discharging exhaust gas from the fuel cell stack; and a bypass flow path 30 for connecting the branch flow path to the exhaust pipe. Thus, a portion of the branch flow path can be shared as both a flow path to the casing and a flow path to the exhaust pipe.

[0076] 5. The fuel cell system of the present invention may also further include: a hydrogen sensor 50 for detecting hydrogen within the housing; a speed control valve 48 disposed in the branch flow path for adjusting the flow rate of the oxidant gas flowing to the housing; and a control device 52 for controlling the speed control valve based on the amount or concentration of hydrogen detected by the hydrogen sensor, thereby adjusting the flow rate of the oxidant gas. This allows for adjustment of the ventilation rate inside the housing.

[0077] 6. In the fuel cell system of the present invention, the greater the amount or concentration of hydrogen, the greater the flow rate of the oxidant gas controlled by the control device. This allows for the exchange of gas inside the casing with an amount of oxidant gas corresponding to the amount or concentration of hydrogen.

[0078] 7. In the fuel cell system of the present invention, the control device may open the speed regulating valve when the amount or concentration of hydrogen exceeds a threshold. This allows for ventilation of the interior of the casing only when necessary.

[0079] 8. In the fuel cell system of the present invention, the speed control valve may also be disposed on the inclined portion. By disposing of the speed control valve on the inclined portion where water is unlikely to stagnate, the inability to adjust the speed control valve due to freezing of condensation water can be prevented.

[0080] 9. The fuel cell system of the present invention may also be configured such that, when the amount or concentration of hydrogen is below the threshold and the amount of oxidant gas required for power generation exceeds a predetermined amount, the control device reduces the flow rate of the oxidant gas compared to the current flow rate. This allows for preferential supply of oxidant gas to the fuel cell stack when the hydrogen concentration inside the casing is low and the fuel cell stack needs to achieve high output. As a result, it is possible to discharge hydrogen from the casing to the outside without reducing power generation efficiency.

[0081] Furthermore, the present invention is not limited to the above disclosure, and various structures can be adopted without departing from the spirit of the present invention.

Claims

1. A fuel cell system (10), characterized in that, have: The fuel cell stack (18) generates electricity through the electrochemical reaction of hydrogen and oxidant gas; Shell (22): which covers the fuel cell stack; A supply piping (24) is connected to an oxidant gas supplier (12) disposed outside the housing, the fuel cell stack, and through the wall (22W) of the housing; A branch flow path (28) branches out from the supply piping at a location on the outer side of the inner surface (F1) of the wall of the housing, and communicates with the interior of the housing; as well as A vent (220) is provided in the housing for exchanging the hydrogen gas inside the housing. In the configuration of the fuel cell system, the outlet of the branch flow path is positioned lower than the air exchange port. The branch flow path has an inclined portion (36), which, in the installed state of the fuel cell system, is inclined upward toward the inner surface of the wall of the housing. The fuel cell system also features: Exhaust piping (26) for discharging exhaust gas from the fuel cell stack; and A bypass flow path (30) connects the branch flow path to the discharge piping.

2. The fuel cell system according to claim 1, characterized in that, It also includes a sealing valve (42), which is disposed on the supply piping. The branch flow path originates from the supply piping upstream of the sealing valve.

3. The fuel cell system according to claim 1, characterized in that, It also has: A hydrogen sensor (50) detects the hydrogen gas inside the housing; A speed control valve (48) is provided in the branch flow path and is capable of adjusting the flow rate of the oxidant gas flowing to the housing; as well as The control device (52) controls the speed regulating valve based on the amount or concentration of hydrogen detected by the hydrogen sensor, thereby adjusting the flow rate of the oxidant gas.

4. The fuel cell system according to claim 2, characterized in that, It also has: A hydrogen sensor (50) detects the hydrogen gas inside the housing; A speed control valve (48) is provided in the branch flow path and is capable of adjusting the flow rate of the oxidant gas flowing to the housing; as well as The control device (52) controls the speed regulating valve based on the amount or concentration of hydrogen detected by the hydrogen sensor, thereby adjusting the flow rate of the oxidant gas.

5. The fuel cell system according to claim 3, characterized in that, The greater the amount or concentration of hydrogen, the more the control device increases the flow rate of the oxidant gas.

6. The fuel cell system according to claim 3, characterized in that, If the amount or concentration of hydrogen exceeds a threshold, the control device will open the speed regulating valve.

7. The fuel cell system according to claim 3, characterized in that, The speed control valve is located on the inclined section.

8. The fuel cell system according to claim 3, characterized in that, When the amount or concentration of hydrogen is below a threshold and the amount of oxidant gas required for power generation exceeds a predetermined amount, the control device reduces the flow rate of the oxidant gas compared to the current flow rate.

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