JP5353558B2 - Fuel cell stack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology of restraining deterioration of a fuel cell stack after stop of operation. <P>SOLUTION: The fuel cell stack 100 is provided with a plurality of unit cells 110 laminated, a manifold 54 for oxygen discharge connected to a cathode electrode side of each unit cell 110, and piping 302 for oxygen discharge connected to each manifold for oxygen discharge. A valve 312 is provided at each piping 302 for oxygen discharge. Either the manifold 54 for oxygen discharge or the piping 302 for oxygen discharge is provided with an oxygen inflow control structure for restraining outside oxygen from flowing into the cathode side through the piping 302 for oxygen discharge, with the valve 312 in a closed state after stop of operation of the fuel cell stack 100. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a fuel cell.

  A fuel cell stack usually has a stack structure in which a plurality of single cells, which are power generation modules, are stacked, and generates power by receiving supply of fuel gas and oxidizing gas. By the way, in the fuel cell stack, if the fuel gas, the oxidizing gas, or moisture generated by an electrochemical reaction remains inside after the operation is stopped, components such as electrodes may be deteriorated (for example, Patent Document 1 below). However, until now, it has been the case that sufficient ingenuity has not been made for these problems.

JP 2007-179900 A JP 2001-202984 A JP-A 62-66580 JP 2009-035442 A

  An object of this invention is to provide the technique which suppresses deterioration of the fuel cell stack after an operation stop.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1]
A fuel cell stack, a power generation stack in which a plurality of power generation modules having a membrane electrode assembly in which an electrolyte membrane is sandwiched between an anode electrode and a cathode electrode, and a stacking direction of the power generation stack An exhaust gas manifold connected to the cathode electrode side of each of the plurality of power generation modules, an exhaust gas pipe connected to the exhaust gas manifold at an end of the power generation laminate, and an exhaust gas pipe The exhaust gas manifold or the exhaust gas pipe is connected to the cathode electrode side through the exhaust gas pipe when the valve is closed after the operation of the fuel cell stack is stopped. A fuel cell star having an oxygen inflow suppressing structure for suppressing oxygen from flowing in from the outside of the fuel cell stack Click.
According to this fuel cell stack, since the oxygen outside the fuel cell stack can be suppressed from flowing into the cathode electrode side through the exhaust gas pipe when the valve is closed, the fuel remaining in the fuel cell stack can be prevented. The increase in voltage in the fuel cell stack after shutdown is suppressed by the gas and oxygen flowing from outside. Therefore, the deterioration of the cathode electrode of the fuel cell stack after the operation is stopped is suppressed.

[Application Example 2]
The fuel cell stack according to Application Example 1, wherein the exhaust gas manifold is connected to the exhaust gas pipe and an upstream manifold portion that communicates with the plurality of power generation modules and extends from the upstream manifold portion. A fuel cell stack having a downstream manifold portion, wherein the downstream manifold portion functions as the oxygen inflow suppressing structure.
According to this fuel cell stack, the diffusion distance from the inflowing oxygen through the exhaust gas piping to the cathode electrode of each power generation module after the operation stop of the fuel cell stack is increased by the amount of the downstream manifold portion. Therefore, after the operation of the fuel cell stack is stopped, inflow of oxygen into each power generation module is suppressed, and deterioration of the cathode electrode in each power generation module is suppressed.

[Application Example 3]
The fuel cell stack according to Application Example 2, wherein a flow passage cross-sectional area of the upstream manifold portion is larger than a flow passage cross-sectional area of the downstream manifold portion.
According to this fuel cell stack, it is possible to prevent the exhaust gas from being discharged from each power generation module from being lowered due to the provision of the downstream manifold portion. Further, after the operation of the fuel cell stack is stopped, the inflow of oxygen to each power generation module is further suppressed by the amount that the flow path cross-sectional area of the downstream manifold portion is small.

[Application Example 4]
The fuel cell stack according to Application Example 2 or Application Example 3, wherein the upstream side manifold portion and the downstream side manifold portion are adjacent to each other via a partition wall, and the partition wall includes the upstream side manifold portion. A fuel cell stack in which a plurality of communication holes that communicate with each other and the downstream manifold portion are arranged along the stacking direction of the power generation stack.
According to this fuel cell stack, it is possible to suppress the exhaust gas from being discharged to the upstream manifold portion during operation of the fuel cell stack. Therefore, the reaction gas and waste water are prevented from remaining in the fuel cell stack, and the deterioration of the fuel cell stack after the operation is stopped is suppressed.

[Application Example 5]
The fuel cell stack according to any one of Application Examples 1 to 4, wherein the exhaust gas pipe or the exhaust gas manifold is closest to a connection position of the exhaust gas pipe from the valve. A catalyst part functioning as the oxygen inflow suppression structure is provided between the power generation module and the catalyst part, and the fuel gas remaining inside the fuel cell stack after the operation of the fuel cell stack is stopped. The fuel cell stack suppresses the inflow of the oxygen to the cathode electrode side by accelerating the reaction with oxygen flowing from the outside of the fuel cell stack and consuming the oxygen in the exhaust gas pipe .
According to this fuel cell stack, the reaction between oxygen flowing from the outside of the fuel cell stack through the exhaust gas pipe after the operation of the fuel cell stack is stopped and the fuel gas remaining inside the fuel cell stack is It is possible to suppress the oxygen from flowing into the cathode electrode of each power generation module. Therefore, the deterioration of the cathode electrode of the fuel cell stack after the operation is stopped is suppressed.

[Application Example 6]
The fuel cell stack according to Application Example 5, wherein the catalyst portion includes at least 3/3 of the exhaust gas manifold side of the entire range from the valve to the connection portion between the exhaust gas pipe and the exhaust gas manifold. A fuel cell stack provided within a range of 4.
According to this fuel cell stack, the oxygen flowing from the outside of the fuel cell stack via the exhaust gas pipe after the operation of the fuel cell stack is stopped, and the fuel gas remaining inside the fuel cell stack are more effective. Can be reacted.

[Application Example 7]
The fuel cell stack according to Application Example 5 or Application Example 6, wherein the catalyst unit includes at least the exhaust gas manifold in the entire range from the valve to a connection portion between the exhaust gas pipe and the exhaust gas manifold. A fuel cell stack provided within 5/8 of the side.
According to this fuel cell stack, the oxygen flowing from the outside of the fuel cell stack via the exhaust gas pipe after the operation of the fuel cell stack is stopped, and the fuel gas remaining inside the fuel cell stack are more effective. Can be reacted.

[Application Example 8]
The fuel cell stack according to any one of Application Example 5 to Application Example 7, wherein the catalyst portion is in a whole range from the valve to a connection portion between the exhaust gas pipe and the exhaust gas manifold. A fuel cell stack provided at least within a range of 1/2 of the exhaust gas manifold side.
According to this fuel cell stack, the oxygen flowing from the outside of the fuel cell stack via the exhaust gas pipe after the operation of the fuel cell stack is stopped, and the fuel gas remaining inside the fuel cell stack are more effective. Can be reacted.

[Application Example 9]
The fuel cell stack according to any one of Application Example 5 to Application Example 8, wherein the catalyst portion is in a whole range from the valve to a connection portion between the exhaust gas pipe and the exhaust gas manifold. A fuel cell stack provided from the center of the entire range to the connecting portion.
According to this fuel cell stack, the oxygen flowing from the outside of the fuel cell stack via the exhaust gas pipe after the operation of the fuel cell stack is stopped, and the fuel gas remaining inside the fuel cell stack are more effective. Can be reacted.

[Application Example 10]
The fuel cell stack according to any one of Application Example 5 to Application Example 9, wherein the catalyst unit is formed vertically along the flow direction of the exhaust gas in the exhaust gas pipe.
According to this fuel cell stack, the oxygen flowing from the outside of the fuel cell stack via the exhaust gas pipe after the operation of the fuel cell stack is stopped, and the fuel gas remaining inside the fuel cell stack are more effective. Can be reacted.

  The present invention can be realized in various forms, for example, in the form of a fuel cell stack, a fuel cell system including the fuel cell stack, a vehicle equipped with the fuel cell system, and the like. Can do.

Schematic which shows the structure of the fuel cell stack in 1st Example. The schematic which shows the structure of the single cell in 1st Example, and the schematic which shows the structure of a seal | sticker integrated membrane electrode assembly. The schematic diagram which shows the flow of oxygen in the fuel cell stack of 1st Example. The schematic diagram which shows the structure of the manifold for oxygen discharge for every lamination | stacking member in the fuel cell stack of 1st Example. Explanatory drawing for demonstrating the change of the electric potential after the driving | operation stop of a fuel cell. The schematic diagram which shows the state change inside the fuel cell after a stop of operation in steps. The schematic diagram which shows the fuel cell stack of 1st Example after an operation stop. The schematic diagram which shows the other structural example of the fuel cell stack in 1st Example. The schematic diagram which shows the structure of the fuel cell stack in 2nd Example. The schematic diagram which shows the structure of the manifold for oxygen discharge for every lamination | stacking member in the fuel cell stack of 2nd Example. The schematic diagram which shows the structure of the fuel cell stack in 3rd Example. The schematic diagram which shows the structure of the fuel cell stack in 4th Example. The schematic diagram which shows the density | concentration distribution of oxygen and hydrogen in the fuel cell stack after an operation stop. The schematic diagram which shows the example of the range in which a catalyst part is formed in the fuel cell stack of 4th Example. Explanatory drawing in order to demonstrate the reduction effect of the leakage oxygen for every formation range of a catalyst part. Explanatory drawing for demonstrating the difference in the reaction efficiency of hydrogen and oxygen by the difference in the formation shape of a catalyst part. Explanatory drawing for demonstrating the difference in the reaction efficiency of hydrogen and oxygen by the difference in the formation shape of a catalyst part. The schematic diagram which shows the other structural example of the fuel cell stack of 4th Example. The schematic perspective view which shows the fuel cell stack of 5th Example, and the schematic diagram for demonstrating the structure of the manifold. The schematic when the fuel cell stack of 5th Example is seen from the front, and the schematic sectional drawing which shows the internal structure of the manifold for oxygen exhaustion. The schematic diagram for demonstrating the function of an expansion seal part. The schematic diagram which shows the other structural example of the oxygen inflow suppression structure in 5th Example. The schematic diagram which shows the other structural example of the oxygen inflow suppression structure in 5th Example. The schematic diagram which shows the other structural example of the oxygen inflow suppression structure in 5th Example. The schematic perspective view which shows the structure of the fuel cell stack and arbitrary single cells in 6th Example. The schematic diagram for demonstrating the oxygen inflow suppression structure provided in the fuel cell stack of 6th Example. The schematic diagram for demonstrating the other structural example of the oxygen inflow suppression structure provided in the fuel cell stack of 6th Example.

A. First embodiment:
FIG. 1 is a schematic view showing the configuration of a fuel cell stack as one embodiment of the present invention. The fuel cell stack 100 is a polymer electrolyte fuel cell that generates power by receiving supply of air (oxygen) as an oxidizing gas and supply of hydrogen as a fuel gas. The fuel cell stack 100 is not limited to a polymer electrolyte fuel cell, and can be configured as any of various types of fuel cells.

  The fuel cell stack 100 includes a plurality of single cells 110, two end plates 121a and 121b, two terminal plates 123a and 123b, and two insulator plates 124a and 124b. The single cells 110 are power generation modules and are electrically connected in series with each other by being stacked. The detailed configuration of the single cell 110 will be described later.

  The two terminal plates 123 a and 123 b are arranged at both ends of the stacked body of the single cells 110 (hereinafter also referred to as “cell stack”), and serve as connection terminals for external loads connected to the fuel cell stack 100. Function. The two insulator plates 124a and 124b are insulating members, and are disposed outside the two terminal plates 123a and 123b, respectively. The two end plates 121a and 121b are disposed outside the two insulator plates 124a and 124b, respectively. A fastening load along a stacking direction from a fastening member (not shown) is applied to each single cell 110 via the two end plates 121a and 121b.

  Here, the first end plate 121a includes hydrogen supply and discharge pipes 201 and 202, oxygen supply and discharge pipes 301 and 302, and refrigerant supply and discharge pipes 401. , 402 are connected. Each pipe 201, 202, 301, 302 for hydrogen and oxygen is provided with valves 211, 212, 312, 312 for controlling the flow of hydrogen or oxygen (reactive gas).

  As described above, in the fuel cell stack 100, the supply and discharge of the reaction gas and the refrigerant are performed on the first end plate 121a side. Hereinafter, in the fuel cell stack 100, the first end plate 121a side is referred to as “supply pipe connection side”, and the second end plate 121b side is referred to as “stack end side”.

  FIG. 2A is a schematic cross-sectional view illustrating a configuration of the single cell 110. The single cell 110 includes a seal-integrated membrane electrode assembly 10, an anode separator 20, and a cathode separator 30. The seal-integrated membrane / electrode assembly 10 includes a membrane / electrode assembly 5 which is a power generator in which an anode electrode 2 and a cathode electrode 3 are provided on both sides of an electrolyte membrane 1. The electrolyte membrane 1 is a solid polymer thin film that exhibits good proton conductivity in a wet state. The anode electrode 2 and the cathode electrode 3 can be formed of a member having gas diffusibility and conductivity carrying a catalyst (for example, platinum (Pt)) for promoting a power generation reaction. Specifically, the anode electrode 2 and the cathode electrode 3 can be formed by applying and drying a catalyst ink in which a medium-carrying carbon and an electrolyte solution are mixed on the outer surface of the electrolyte membrane 1.

  The seal-integrated membrane electrode assembly 10 includes a seal portion 12 that is integrally formed on the outer periphery of the membrane electrode assembly 5 in order to suppress fluid leakage. The seal portion 12 is formed by injection molding a thermosetting resin member so as to cover the outer peripheral ends of the electrolyte membrane 1, the anode electrode 2, and the cathode electrode 3. Manifolds 51 to 56 for reaction gas and refrigerant are formed in the seal portion 12 as through holes.

  FIG. 2B is a schematic view when the seal-integrated membrane electrode assembly 10 is viewed along the direction of the arrow B shown in FIG. 2A corresponds to a schematic cross-sectional view taken along the line AA shown in FIG. 2B. Here, in the seal-integrated membrane electrode assembly 10, a region surrounded by the seal portion 12 and generating power upon receiving the reaction gas is referred to as a “power generation region GA”. Each of the manifolds 51 to 56 is provided on both sides facing each other across the power generation area GA of the seal portion 12. Specifically, with respect to the power generation area GA, a hydrogen supply manifold 51, a refrigerant supply manifold 55, and an oxygen discharge manifold 54 are arranged in a line in order from the lower side on the left side of FIG. 2B. Has been. Further, with respect to the power generation area GA, an oxygen supply manifold 53, a refrigerant discharge manifold 56, and a hydrogen discharge manifold 52 are arranged in a row in this order from the lower side on the right side of FIG. 2B. .

  Here, the oxygen discharge manifold 54 of the single cell 110 shown in FIGS. 2A and 2B has first and second manifold portions 54 a and 54 b separated by a partition wall 57. The first manifold portion 54 a is provided on the power generation area GA side (inside), and the second manifold portion 54 b is provided on the outer peripheral end side of the seal portion 12. Further, the opening area of the first manifold portion 54a is larger than that of the second manifold portion 54b. In the fuel cell stack 100 of the present embodiment, there are portions where the configuration of the oxygen exhaust manifold 54 is different, and details thereof will be described later.

  The anode separator 20 and the cathode separator 30 (FIG. 2A) each have a conductive gas-impermeable plate shape that sandwiches the seal-integrated membrane electrode assembly 10 from the anode electrode 2 side and the cathode electrode 3 side, respectively. It is a member. The manifolds 51 to 56 are formed on the anode separator 20 and the cathode separator 30 in the same manner as the seal-integrated membrane electrode assembly 10. It should be noted that a channel groove for the reaction gas may be formed on the surface of the anode separator 20 and the cathode separator 30 facing the electrodes 2 and 3.

  Gas diffusion members 15 are disposed between the anode separator 20, the cathode separator 30, and the electrodes 2 and 3, respectively. The gas diffusion member 15 functions as a gas diffusion layer (gas flow path) for spreading the reaction gas over the entire anode electrode 2 and cathode electrode 3, and between the membrane electrode assembly 5 and the separators 20 and 30. It functions as a conductive path. The gas diffusion member 15 can be constituted by a porous member having conductivity such as carbon paper, carbon cloth, so-called expanded metal, punching metal or the like.

  The anode separator 20 and the cathode separator 30 are formed with gas flow paths for connecting the power generation region GA and the manifolds 51 to 54 for the reaction gas, but illustration and description thereof are omitted. Further, when the fuel cell stack 100 is configured, a refrigerant flow path connected to the refrigerant manifolds 55 and 56 is formed between the adjacent single cells 110 so as to cover the entire power generation region GA. The illustration and description thereof are omitted.

  FIG. 3 is a schematic diagram for explaining the flow of oxygen in the fuel cell stack 100. In FIG. 3, for convenience of explanation, the oxygen supply manifold 53 and the oxygen discharge manifold 54 are shown as if they are located on the same cut surface. FIG. 3 schematically shows pipes 301 and 302 connected to the oxygen manifolds 53 and 54 and valves 311 and 312 provided in the pipes 301 and 302 to show the flow of oxygen. An arrow is shown. In FIG. 3, the detailed internal configuration of each single cell 110 and manifolds and pipes for other fluids are not shown.

  The oxygen supply manifold 53 is a linear flow path formed from the first end plate 121a to a single cell 110 (hereinafter referred to as a “terminal single cell 110e”) located at the end of the stack. It is configured. On the other hand, the oxygen discharge manifold 54 is configured as a flow path that turns back and forth along the stacking direction of the fuel cell stack 100.

  The oxygen discharge manifold 54 has first and second manifold portions 54a and 54b and a connecting manifold portion 54c. The first manifold portion 54 a is provided on the upstream side of the exhaust gas and is connected to each single cell 110. The second manifold portion 54b is provided on the downstream side of the exhaust gas, and is connected to an external oxygen discharge pipe 302. The first and second manifold portions 54a and 54b are separated from each other by a partition wall 57, and are connected on the stack end side by a connecting manifold portion 54c. Here, in the fuel cell stack 100, the oxygen exhaust manifold 54 is formed for each laminated member such as the single cell 110 and the three plates 121a, 123a, and 124a by the configuration described below.

  FIGS. 4A to 4B are schematic views for explaining the configuration of the oxygen discharge manifold 54 for each stacked member in the fuel cell stack 100. 4A to 4B schematically show the manifolds 51 to 56 when viewed from the first end plate 121a side in FIG. 3 along the stacking direction. Each of the manifolds 51 to 53, 55, and 56 other than the oxygen exhaust manifold 54 is formed in the same manner as the single cell 110 in FIG.

  FIG. 4A shows the configuration of the oxygen exhaust manifold 54 in the first end plate 121a, the first insulator plate 124a, and the first terminal plate 123a. The oxygen discharge manifold 54 formed on these three plates 121a, 123a, and 124a has a first manifold portion 54a (shown by a broken line) closed, and only a second manifold portion 54b is formed. . Hereinafter, the configuration of the oxygen discharge manifold 54 is referred to as an “oxygen outlet manifold configuration”. The three plates 121a, 123a, and 124a are preferably formed with resin seal portions for preventing fluid leakage from the manifolds 51 to 56.

  FIG. 4B shows a configuration of the oxygen discharge manifold 54 in the single cells 110 other than the terminal single cell 110e. The configuration of the oxygen discharge manifold 54 shown in FIG. 4B is the same as the configuration described in FIG. Hereinafter, a configuration in which the oxygen discharge manifold 54 is separated into the first and second manifold portions 54a and 54b by the partition wall 57 is referred to as a “separation manifold configuration”.

  FIG. 4C shows the configuration of the oxygen discharge manifold 54 in the terminal single cell 110e. The oxygen discharge manifold 54 of the terminal unit cell 110e is formed as a single through hole in which the partition wall 57 is omitted and the first and second manifold portions 54a and 54b are connected. Hereinafter, the configuration of the oxygen exhaust manifold 54 for forming the connection manifold portion 54c is referred to as a “connection manifold configuration”.

  Here, in the fuel cell stack 100, oxygen flows as shown by arrows in FIG. That is, oxygen contained in the air supplied to the oxygen supply manifold 53 from the supply pipe connection side flows into all the single cells 110 and is used for the power generation reaction. Exhaust gas containing oxygen that has not been used in the power generation reaction is discharged to the first manifold portion 54a or the connecting manifold portion 54c, passes through the second manifold portion 54b, and passes through the oxygen discharge pipe 302 to the fuel cell stack 100. It is discharged outside. As described above, the flow path length of the oxygen discharge manifold 54 of the fuel cell stack 100 of the present embodiment is configured to be longer by the amount that the first and second manifold portions 54 a and 54 b are separated by the partition wall 57. . The reason for this will be described below.

FIG. 5 is a graph showing changes in potential after the operation of a general polymer electrolyte fuel cell is stopped. When the fuel cell is stopped (time T ₀ ), the electrical connection between the fuel cell and the external load is generally cut off, and the reactant gas supply side and discharge side valves are closed. Thereafter, the fuel cell transitions to a low voltage state where the voltage decreases and the voltage becomes approximately 0 V, and this state is maintained (time T _{1 to} T ₂ ). However, even if the valve is closed and the electrical connection with the external load is maintained, the voltage of the fuel cell rises again (time T _{2 to} T ₃ ). It is known that a part of the cathode electrode 3 deteriorates. It is assumed that the voltage increase after the shutdown is generated as follows.

  FIGS. 6A to 6D are schematic views showing stepwise changes in the state of the fuel cell after the operation is stopped. 6A to 6D schematically show a fuel cell 100a that is a solid polymer fuel cell. Specifically, the region between the electrolyte membrane 1 and the anode separator (not shown) is schematically shown as the anode An, and the region between the electrolyte membrane 1 and the cathode separator (not shown) is the cathode Ca. As schematically shown.

  Note that hydrogen supply and discharge pipes 201 and 202 are connected to the anode An, and oxygen supply and discharge pipes 301 and 302 are connected to the cathode Ca. Each pipe 201, 202, 301, 302 is provided with valves 211, 212, 311, 312 for controlling the gas flow, and all of them are closed. In addition, in the figure, it has shown that the flow of gas is interrupted | blocked by attaching | subjecting "x" to each piping 201,202,301,302.

FIG. 6A shows a state immediately after the operation of the fuel cell 100a is stopped (time T _{0 in} FIG. 5). At this time, in the anode An and the cathode Ca, hydrogen H ₂ and oxygen O _{2 as} reaction gases and nitrogen N _{2 as} an inert gas remain, respectively. The illustration and explanation of other gas molecules are omitted for convenience. Thereafter, a part of hydrogen H ₂ remaining in the anode An (hereinafter referred to as “residual hydrogen H ₂ ”) diffuses to the cathode Ca side through the electrolyte membrane 1 and burns by oxygen O ₂ on the cathode Ca side. (FIG. 6B). Further, part of the oxygen O ₂ on the cathode Ca side diffuses to the anode An side through the electrolyte membrane 1 and is consumed by the combustion reaction with the residual hydrogen H ₂ on the anode An side. According the amount of oxygen in the cathode Ca decreases, the voltage of the fuel cell 100a is decreased (time of FIG. 5 T ₀ ~T _1).

FIG. 6C shows a state in which the oxygen O ₂ in the fuel cell 100a is consumed by the combustion reaction with the residual hydrogen H ₂ and almost no longer exists. This state corresponds to the low voltage state at times T _{1 to} T ₂ described in FIG. When this state continues for a while (for example, about several tens of minutes), external air (oxygen O ₂ ) gradually leaks into the fuel cell 100a through the oxygen discharge pipe 302 connected to the cathode Ca. (FIG. 6D). Oxygen O ₂ (hereinafter "leakage incoming oxygen O _2" hereinafter) for leaking into to the cathode Ca and, through an electrochemical reaction between the residual hydrogen H _2, the potential of the fuel cell 100a starts to rise again (Fig. 5 time T ₂ ~T ₃ of).

  Here, the fuel cell 100a is in a state in which the electrical connection with the external load is cut off and the exchange of electrons between the anode An and the cathode Ca is cut off. Therefore, in this electrochemical reaction, it is presumed that electrons used for the reaction are provided at each of the anode An and the cathode Ca. Specifically, in the cathode Ca, it is presumed that electrons generated by the oxidation reaction of the constituent members (platinum and carbon) in the local region of the electrode are used. Therefore, the cathode electrode is deteriorated by the voltage increase after the operation is stopped. In particular, when the fuel cell 100a has a stack structure in which a plurality of single cells are stacked, a single cell closer to the oxygen discharge pipe 302 has a larger amount of oxygen and hydrogen, and thus the cathode electrode 3 is significantly deteriorated. Become.

  FIG. 7 is a schematic diagram showing the fuel cell stack 100 after the operation is stopped. FIG. 7 is substantially the same as FIG. 3 except that the valves 311 and 312 are closed and the arrows indicating the flow of oxygen in the fuel cell stack 100 are different. Thus, according to the fuel cell stack 100 of the present embodiment, the diffusion distance of the leaked oxygen to the single cell 110 is increased by the amount folded back by the partition wall 57, and the leaked oxygen of each single cell 110 is reduced. Inflow is suppressed. In other words, the second manifold portion 54b of the oxygen discharge manifold 54 functions as an oxygen inflow suppression structure that suppresses external oxygen from flowing into the cathode electrode 3 in the stopped fuel cell stack 100. As a result, deterioration of the cathode electrode 3 due to oxygen intrusion after the operation of the fuel cell stack 100 is stopped is suppressed.

  Further, in the fuel cell stack 100 of this embodiment, the first manifold portion 54a connected to the single cell 110 is configured to have a larger flow path cross-sectional area than the second manifold portion 54b. As a result, in the fuel cell stack 100, a reduction in exhaust gas exhaustibility to the first manifold portion 54a during operation is suppressed, and leakage of oxygen into the second manifold portion 54b after operation stop is suppressed. Is done.

  FIG. 8 is a schematic diagram for explaining another configuration example of the fuel cell stack 100 in the present embodiment. FIG. 8 is substantially the same as FIG. 7 except that the length of the partition wall 57 is different and the arrow indicating the flow of leaked oxygen is different. As described above, the fuel cell stack 100 is configured to increase the number of unit cells 110 having a connection manifold configuration on the stack end side and to shorten the flow path lengths of the first and second manifold portions 54a and 54b. Also good. In this case, the partition wall 57 is preferably formed with a length of about 1/5 to 1/6 with respect to the distance between the two terminal plates 123a and 123b. Here, as described above, when the partition wall 57 is omitted in the oxygen discharge manifold 54, the deterioration of the cathode electrode 3 due to the leakage of oxygen becomes remarkable in the single cell 110 closer to the connection position of the oxygen discharge pipe 302. . Therefore, if the partition wall 57 is provided with a length of at least the above range, it is possible to suppress oxygen leakage into the single cell 110 at a position close to the connection position of the oxygen discharge pipe 302. It is possible to suppress the deterioration of the cathode electrode 3.

  As described above, in the fuel cell stack 100 of the present embodiment, the oxygen discharge manifold 54 has the second manifold portion 54b that functions as an oxygen inflow suppression structure. It is possible to suppress leakage into Therefore, it is possible to suppress the deterioration of the cathode electrode 3 of the fuel cell stack 100 after the operation is stopped.

B. Second embodiment:
FIG. 9 is a schematic diagram showing a configuration of a fuel cell stack 100A as a second embodiment of the present invention. FIG. 9 is substantially the same as FIG. 3 except that the configuration of the oxygen discharge manifold 54A is different and that the oxygen discharge pipe 302 is connected to the second end plate 121b side. The configuration of the fuel cell stack 100A is the same as that of the fuel cell stack 100 of the first embodiment except for the points described below. The oxygen exhaust manifold 54A of the second embodiment is formed as a through hole having the following shape for each stacked member of the fuel cell stack 100A.

  FIGS. 10A to 10C are schematic views similar to FIG. 4 for explaining the configuration of the oxygen discharge manifold 54A for each stacked member of the fuel cell stack 100A. FIG. 10A is a schematic diagram showing the configuration of an oxygen discharge manifold 54A in a single cell 110 (hereinafter referred to as “starting single cell 110t”) located at the end on the supply piping side. The oxygen discharge manifold 54A of the starting end single cell 110t has a connection manifold configuration.

  FIG. 10B is a schematic diagram showing the configuration of the oxygen discharge manifold 54A in all the unit cells 110 other than the starting end unit cell 110t. All the single cells 110 other than the starting single cell 110t have a separation manifold configuration. However, the oxygen discharge manifold 54A of the second embodiment has a partition wall 57 that connects the orthogonal inner wall surfaces, whereby the first manifold portion 54a has a substantially pentagonal shape and the second manifold. The part 54b has a substantially triangular shape.

  FIG. 10C is a schematic diagram showing the configuration of the oxygen discharge manifold 54A in the second end plate 121b, the second terminal plate 123b, and the second insulator plate 124b. These three plates 121b, 123b, and 124b have an oxygen outlet manifold configuration in which only the second manifold portion 54b is formed.

  In the fuel cell stack 100A of the second embodiment (FIG. 9), the exhaust gas from the cathode side flows to the supply pipe connection side in the first manifold portion 54a and is folded back in the connection manifold portion 54c. Then, the exhaust gas flows to the stack end side in the second manifold portion 54b, and is discharged to the outside of the fuel cell stack 100A through the oxygen discharge pipe 302. By using such a flow of exhaust gas, the exhaustability of exhaust gas can be improved as the single cell 110 on the supply pipe connection side.

  Even in such a configuration, when the operation of the fuel cell stack 100A is stopped, the diffusion distance of the leaked oxygen from the oxygen discharge pipe 302 is determined along the partition wall 57 from the second manifold portion 54b to the first manifold. It is increased by the amount folded back to the portion 54a. Therefore, deterioration of the cathode electrode 3 due to leaked oxygen in the fuel cell stack 100A during operation stop is suppressed.

  In the fuel cell stack 100A of the second embodiment, the first manifold portion 54a has a substantially pentagonal shape, and the second manifold portion 54b has a substantially triangular shape. As a result, the equivalent diameters of the first and second manifold portions 54a and 54b are increased as compared with the case where the first and second manifold portions 54a and 54b are substantially rectangular as in the first embodiment. Thus, pressure loss can be reduced. Therefore, the exhaust property of the exhaust gas on the cathode side can be improved.

C. Third embodiment:
FIG. 11 is a schematic diagram showing the configuration of a fuel cell stack 100B as a third embodiment of the present invention. FIG. 11 is almost the same as FIG. 3 except that the partition wall 57 has a portion where it is divided and the arrow indicating the flow of oxygen is different. In the fuel cell stack 100B, the single cells 110 having the connection manifold configuration (FIG. 10A) are interposed between the single cells 110 having the divided manifold configuration (FIG. 10B). As a result, a plurality of communication portions 58h that communicate with the first and second manifold portions 54a and 54b, which are arranged in the stacking direction, are formed in the partition wall 57 of the oxygen discharge manifold 54B.

  With such a configuration, the communication portion 58h functions as a shortcut for exhaust gas between the first, the manifold portion 54a, and the second manifold portion 54b. Therefore, in the oxygen discharge manifold 54B having the oxygen inflow suppression structure, the exhaust performance of the exhaust gas from each single cell 110 is improved.

D. Fourth embodiment:
FIG. 12 is a schematic diagram showing the configuration of a fuel cell stack 100D as a fourth embodiment of the present invention. In FIG. 12, the oxygen discharge manifold 54 </ b> D does not have the partition wall 57 and is formed as a straight flow path similar to the oxygen supply manifold 53, and the catalyst portion 350 is provided. Is substantially the same as FIG. In FIG. 12, the direction of gravity during operation of the fuel cell stack 100D is indicated by an arrow G.

  In this fuel cell stack 100D, the exhaust gas discharged from each single cell 110 to the oxygen discharge manifold 54D during operation flows to the supply pipe connection side as it is, and the fuel cell stack 100D of the fuel cell stack 100D is passed through the oxygen discharge pipe 302. It is discharged outside. In the operation, the fuel cell stack 100D is disposed so that the stacking direction is substantially horizontal, and the oxygen discharge manifold 54D side is lower than the oxygen supply manifold 53 side in the gravity direction. By being arranged in this way, the generated water generated in each single cell 110 can be guided to the oxygen discharge manifold 54D according to gravity, so that the drainage can be improved.

  The fuel cell stack 100D has a catalyst (for example, platinum or the like) for promoting the reaction between hydrogen and oxygen on the oxygen discharge pipe 302 between the valve 312 and the starting end single cell 110t and the inner wall surface of the oxygen discharge manifold 54D. The catalyst part 350 which apply | coated) is provided. More specifically, the catalyst unit 350 is a cathode of the start end single cell 110t in the oxygen discharge manifold 54D from a position where the valve 312 is closed (a contact position between the valve body and the valve seat in the valve 312). It is provided between the exhaust gas outlet from the side. Below, the function of the catalyst part 350 is demonstrated.

  FIGS. 13A and 13B are schematic views showing oxygen and hydrogen concentration distributions after the operation of the fuel cell stack 100D is stopped. 13A and 13B, the membrane electrode assemblies 5 of the fuel cell stack 100D, the hydrogen manifolds 51 and 52 connected to the membrane electrode assemblies 5, and the oxygen manifolds 53 and 54D, respectively. Is schematically illustrated. 13A and 13B, the oxygen discharge manifold 54D and the oxygen discharge pipe 302 are shown integrally, and the closed valve 312 is connected to the oxygen discharge pipe 302. It is shown as a constricted part. In the fuel cell stack 100D of FIGS. 13A and 13B, the hatching concentration is increased in the region where the hydrogen or oxygen concentration is higher.

  Here, as explained in FIG. 6, in general, in the fuel cell after the operation is stopped, when the valve of the flow path for the reaction gas is closed and sealed, most of the oxygen remaining in the fuel cell is It is consumed by reacting with hydrogen. Also in the fuel cell stack 100D, the membrane electrode assemblies 5 and the oxygen manifolds 53 and 54D are almost free of oxygen (FIG. 13A). However, a small amount of leaked oxygen exists upstream of the valve 312 in the oxygen exhaust pipe 302. The leaked oxygen gradually increases as time passes, and diffuses into the oxygen discharge pipe 302 and the oxygen discharge manifold 54D.

  On the other hand, when the oxygen concentration distribution is in the state of FIG. 13A, the hydrogen concentration distribution in the fuel cell stack 100D is higher on the supply pipe connection side, and on the stack end side and on the downstream side of the oxygen discharge pipe 302. Becomes low. Thereafter, hydrogen gradually diffuses toward the valve 312 side of the oxygen exhaust pipe 302.

  The catalyst unit 350 (FIG. 12) promotes the reaction between hydrogen diffusing into the oxygen discharge pipe 302 and the leaked oxygen, and consumes the leaked oxygen. The flow to the cathode electrode 3 is suppressed. That is, the catalyst unit 350 functions as an oxygen inflow suppression structure that suppresses external oxygen from flowing into the cathode electrode 3 while the operation is stopped.

  By the way, the catalyst part 350 is preferably provided on the inner wall surface on the upper side in the gravity direction. This is because the inner wall surfaces on the lower side in the gravity direction of the oxygen discharge manifold 54D and the oxygen discharge pipe 302 may be submerged by waste water generated during the operation of the fuel cell stack 100D. In addition, the catalyst part 350 is good also as what is provided in the following ranges.

  14A to 14F are schematic views showing examples of ranges in which the catalyst portion 350 is formed. Each of FIGS. 14A to 14F shows a part of the fuel cell stack 100D of FIG. 12, and the catalyst portion 350 is provided at a different position and range in each. In Example 1 shown in FIG. 14A, the catalyst portion 350 is provided in the vicinity of the valve 312. More specifically, the catalyst unit 350 is provided close to a position where the oxygen discharge pipe 302 is sealed when the valve 312 is closed.

  In Example 2 shown in FIG. 14B, the catalyst portion 350 is formed at the following position. Here, a hypothetical number line NL is assumed in which the position of the valve 312 is 0 and the position of the connection portion (hereinafter referred to as “pipe connection portion”) between the oxygen discharge pipe 302 and the oxygen discharge manifold 54D is 1. To do. At this time, the catalyst part 350 is formed so that the central part of the catalyst part 350 is located at a position in the oxygen discharge pipe 302 corresponding to a quarter position on the virtual number line NL. Here, the “position of the valve 312” means, more specifically, a position that is sealed when the valve 312 is closed in the oxygen exhaust pipe 302.

  In Example 3 shown in FIG. 14C, the center of the catalyst unit 350 is located at a position in the oxygen exhaust pipe 302 corresponding to the position 3/8 on the virtual number line NL. It is formed as follows. In Example 4 shown in FIG. 14 (D), the catalyst part 350 is located at the center of the catalyst part 350 at a position in the oxygen discharge pipe 302 corresponding to a half position on the virtual number line NL. It is formed as follows.

  In Example 5 shown in FIG. 14 (E), the catalyst portion 350 is provided only on the inner wall surface of the oxygen exhaust manifold 54D of the first end plate 121a. In Example 6 shown in FIG. 14F, the catalyst part 350 is formed from the position in the oxygen exhaust pipe 302 corresponding to ½ on the virtual number line NL to the pipe connection part.

FIG. 15 is a graph for explaining the leakage oxygen reduction effect when the catalyst unit 350 is provided at each position of Examples 1 to 6 described in FIGS. Graphs If _{1 to} If ₆ respectively show the results of simulating changes over time in the amount of oxygen present in the fuel cell stack 100D after the operation of the fuel cell stack 100D is stopped in the configurations of Examples 1 to 6. Further, the graph If _c shows a result of simulating a temporal change in the oxygen amount when the catalyst unit 350 is omitted as a comparative example. In the graphs If _{1 to} If ₅ , the case where the catalyst part 350 is formed with the same area and the same shape by changing only the formation position is simulated. Further, in the graph If ₆ , the area of the catalyst portion 350 is simulated to be the same as in the graphs If ₁ to If ₅ . Further, the simulation was performed assuming that the weight per unit area of the catalyst portion 350 is the same in any of the graphs If _{1 to} If ₆ .

As described above, the catalyst unit 350 provided on the upstream side can delay the time when oxygen starts to flow into the fuel cell stack 100D, and reduce the amount of oxygen flowing in itself. (Graphs If _{1 to} If ₆ ). More specifically, the catalyst unit 350 is preferably provided in at least a 3/4 range on the oxygen exhaust manifold 54D side in the entire range from the valve 312 to the pipe connection unit. Further, it is more preferable that the catalyst unit 350 is provided at least within a range of 5/8 on the oxygen exhaust manifold 54D side in the entire range, and a range of ½ on the oxygen exhaust manifold 54D side. More preferably, it is provided inside. In particular, the catalyst portion 350 is most preferably provided from the center position of the entire range to the pipe connection portion (graph If ₆ ).

In addition, it is preferable that the catalyst part 350 is formed vertically long along the flow direction (pipe direction) of the exhaust gas in the oxygen discharge pipe 302. Specifically, for example, when the catalyst unit 350 is provided with an area of 4 cm ² , the length along the gas flow direction is longer than the length along the gas flow direction of 10 mm and the width of 40 mm. Is preferably 40 mm and the width is 10 mm.

16 and 17 are explanatory diagrams for explaining the difference in the reaction efficiency of hydrogen and oxygen due to the difference in the formation shape of the catalyst portion 350. FIG. The graphs of FIGS. 16A and 16B are the results of calculating the hydrogen and oxygen concentration distributions in the piping direction of the oxygen discharge pipe 302 at times t _{0 to} t ₆ after the fuel cell stack 100D is stopped. It is. 16A and 16B, the horizontal axis is along the piping direction where the position of the valve 312 of the oxygen discharge pipe 302 is 0.0 and the position of the pipe connection portion is 1.0. (Hereinafter referred to as “in-pipe position”). FIGS. 16A and 16B are the results of simulating the case where the catalyst portion 350 is provided in the range of 0.9 to 1.0 of the position in the pipe.

The graphs of FIGS. 17A and 17B respectively show the results of simulating the case where the catalyst unit 350 is provided in the range of 0.5 to 1.0 of the position in the pipe. ). FIGS. 17A and 17B show hydrogen and oxygen concentration distributions at times t _{1 to} t ₇ after the operation of the fuel cell stack 100D is stopped. Here, the catalyst part 350 is formed with the same area in both cases of FIG. 16 and FIG. That is, in the case of FIG. 17, the catalyst part 350 is formed longer and narrower along the piping direction than in the case of FIG.

  From the graphs of FIGS. 16 and 17, it can be seen that when the catalyst part 350 is formed vertically along the piping direction, the amount of hydrogen and oxygen used in the reaction is increased and the reaction efficiency is improved. As a result, hydrogen is prevented from diffusing to the valve 312 side, the amount of oxygen consumed in the oxygen exhaust pipe 302 is increased, and the inflow of oxygen into each single cell 110 is suppressed. .

FIG. 18 is a schematic diagram showing another configuration example of the fuel cell stack 100D of the fourth embodiment. In FIG. 18, except that the catalyst support member 352 is disposed in the oxygen discharge pipe 302 in place of the catalyst unit 350 and the oxygen discharge pipe 302 is inclined downward in the gravity direction. It is almost the same as FIG. The catalyst support member 352 is a member coated with a catalyst similar to that of the catalyst portion 350 and, like the catalyst portion 350, is for accelerating the reaction between leaked oxygen and hydrogen. The catalyst support member 352 may be a wire-like linear member having a diameter of about 1 mm to 2 mm, or a plate-like member having a thickness of about 1 mm to 2 mm. The oxygen discharge pipe 302 by the lower stream side thereof is attached to be inclined so that gravity direction lower side, the drainage is improved.

  As described above, in the fuel cell stack 100D of the fourth embodiment, the catalyst unit 350 and the catalyst support member 352 function as an oxygen inflow suppression structure provided in the oxygen exhaust pipe 302 and the oxygen exhaust manifold 54D. As a result, in the fuel cell stack 100D of the fourth embodiment, it is possible to suppress external oxygen from flowing into each single cell 110 after the operation is stopped, and it is possible to suppress deterioration of the cathode electrode 3.

E. Example 5:
FIG. 19A is a schematic perspective view showing a fuel cell stack 100E as a fifth embodiment of the present invention. The fuel cell stack 100E includes first and second cell stacks 111 and 112. The first and second cell stacks 111 and 112 are power generation stacks in which a plurality of single cells 110 similar to those described in the fourth embodiment are stacked, and the fuel cell stacks of the fourth embodiment are respectively provided. Manifolds 51 to 54D similar to 100D are formed.

  FIG. 19B is a schematic diagram for explaining the arrangement configuration of the manifolds 51 to 54D provided in the first and second cell stacks 111 and 112, respectively. FIG. 19B schematically shows the first and second cell stacks 111 and 112 when the fuel cell stack 100E is viewed along the stacking direction. In the fuel cell stack 100E, the hydrogen discharge manifold 52 and the oxygen supply manifold 53 of each of the first and second cell stacks 111 and 112 are formed at inner positions adjacent to each other. The hydrogen supply manifold 51 and the oxygen discharge manifold 54D of each of the first and second cell stacks 111 and 112 are formed at positions outside the fuel cell stack 100E.

  The first and second cell stacks 111 and 112 are clamped while being sandwiched from the stacking direction by the common first and second end plates 121a and 121b, respectively (FIG. 19A). Branch pipes 203, 204, 303, and 304 for supplying and discharging reaction gas are connected to the first end plate 121a. The supply branch pipes 203 and 303 are connected to the hydrogen supply manifold 51 or the oxygen supply manifold 53 of the first and second cell stacks 111 and 112, respectively. The discharge branch pipes 204 and 304 are connected to the hydrogen discharge manifold 52 or the oxygen discharge manifold 54 of the first and second cell stacks 111 and 112, respectively.

  The branch pipes 203, 204, 303, and 304 are provided with valves 211, 212, 311 and 312 that are closed when the operation of the fuel cell stack 100E is stopped. The fuel cell stack 100E is connected to piping for supplying and discharging refrigerant, but illustration and description thereof are omitted.

  FIG. 20A is a schematic view when the fuel cell stack 100E is viewed from the front. In FIG. 20A, illustrations of valves 212 and 312 provided in the branch pipes 204 and 304 are added. 20A shows a state after the operation of the fuel cell stack 100E is stopped, and shows a state where the valves 212 and 312 are closed. FIG. 20B is a schematic cross-sectional view for explaining the internal configuration of the oxygen discharge manifold 54D of the fuel cell stack 100E, and the bottom (end) of the oxygen discharge manifold 54D on the second end plate 121b side. 54De is shown.

  The end 54De of the oxygen discharge manifold 54D of the fuel cell stack 100E is provided with a through hole 141 that penetrates the second end plate 121b. Further, an expansion seal portion 142 is disposed at the end portion 54De of the oxygen discharge manifold 54D so as to cover the through hole 141. The expansion seal portion 142 is made of a resin member that can be expanded and contracted according to an external force, and an outer peripheral end portion thereof is hermetically bonded.

  FIG. 21 is a schematic diagram for explaining the function of the expansion seal portion 142. Here, in the fuel cell stack 100E after the operation is stopped, the oxygen remaining on the cathode side reacts with hydrogen and changes to a state in which it hardly exists (FIG. 6C). At this time, a negative pressure is generated on the cathode side of the fuel cell stack 100E, and this negative pressure promotes the leakage of external oxygen through the branch pipe 303 on the oxygen discharge side (FIG. 6D). However, in this fuel cell stack 100E, when a negative pressure is generated in the oxygen discharge manifold 54D, the expansion seal portion 142 expands in a direction to reduce the volume in the oxygen discharge manifold 54D to reduce the negative pressure ( FIG. 21). Therefore, in this fuel cell stack 100E, the leakage of oxygen after the operation is stopped is suppressed, and the deterioration of the cathode electrode 3 is suppressed. That is, in this fuel cell stack 100E, the expansion seal portion 142 provided in the oxygen discharge manifold 54D functions as an oxygen inflow suppression structure that suppresses external oxygen from flowing into the oxygen discharge manifold 54D after the operation is stopped. To do.

  FIGS. 22A and 22B are schematic views showing another configuration example of the oxygen inflow suppressing structure in the fifth embodiment. 22 (A) and 22 (B) are the same as FIGS. 20 (B) and 20B except that an accommodation container 143 for accommodating the expansion seal portion 142 is provided on the outer surface side of the second end plate 121b. 21 is almost the same. The other configuration of the fuel cell stack 100E in this configuration example is the same as the configuration described in FIG.

  The storage container 143 includes first and second hollow portions 143a and 143b which are airtightly separated by the expansion seal portion 142. The container 143 is airtightly attached to the outside of the second end plate 121b so that the first hollow portion 143a communicates with the oxygen exhaust manifold 54D through the through hole 141. Further, the accommodation container 143 is provided with a through hole 143h so that outside air can enter the second hollow portion 143b. With this configuration, when a negative pressure is generated in the oxygen discharge manifold 54D, the expansion seal portion 142 expands toward the oxygen discharge manifold 54D. That is, the expansion of the expansion seal portion 142 reduces the volume of the first hollow portion 143a, and the negative pressure in the oxygen exhaust manifold 54D is reduced (FIG. 22B). As described above, according to the configuration example of FIG. 22 as well, oxygen leakage after the operation of the fuel cell stack 100E is stopped is suppressed, and deterioration of the cathode electrode 3 is suppressed.

  FIGS. 23A and 23B are schematic views showing another configuration example of the oxygen inflow suppressing structure in the fifth embodiment. FIGS. 23A and 23B are substantially the same as FIGS. 22A and 22B except that a piston 142a is provided in the housing container 143 in place of the expansion seal portion 142. FIGS. The piston 142a hermetically separates the first and second hollow portions 143a and 143b of the storage container 143, and can move in the storage container 143 according to the pressure difference between the outside air and the oxygen discharge manifold 54D. is there.

  The piston 142a is normally located on the relatively side of the housing container 143 (FIG. 23A). However, when a negative pressure is generated in the oxygen discharge manifold 54D, the piston 142a moves in a direction to reduce the volume of the first hollow portion 143a (FIG. 22B). Also in the configuration example of FIG. 23, as in the configuration example of FIG. 22, the leakage of oxygen after the operation of the fuel cell stack 100E is stopped is suppressed, and the deterioration of the cathode electrode 3 is suppressed.

  FIG. 24 is a schematic diagram showing another configuration example of the oxygen inflow suppressing structure in the fifth embodiment. FIG. 24 is substantially the same as FIG. 20A except that the containing container 143 having the expansion seal portion 142 described in FIG. 22 is connected to the branch pipe 304 for discharging oxygen. The housing container 143 is attached so that the first hollow portion 143 a communicates with the branch pipe 304. Thereby, when a negative pressure is generated in the branch pipe 403, the negative pressure is reduced by a change in the volume of the first hollow portion 143a by the expansion seal portion 142. Accordingly, oxygen leakage after the operation of the fuel cell stack 100E is stopped is suppressed, and deterioration of the cathode electrode 3 is suppressed.

  As described above, according to the fuel cell stack 100E of the fifth embodiment, the fuel cell stack 100E after the operation is stopped by changing the volume in the space communicating with the oxygen discharge manifold 54D and the oxygen discharge manifold 54D. Generation of negative pressure inside can be suppressed. Therefore, after the operation of the fuel cell stack 100E is stopped, oxygen leakage into the oxygen exhaust branch pipe 304 and the oxygen exhaust manifold 54D is suppressed, and deterioration of the cathode electrode 3 is suppressed. The oxygen inflow suppressing structure described in the fifth embodiment may be provided in a flow path on the oxygen supply side such as the oxygen supply manifold 53.

F. Example 6:
FIG. 25 (A) is a schematic perspective view showing the configuration of a fuel cell stack as a sixth embodiment of the present invention. The fuel cell stack 100F has the same configuration as the fuel cell stack 100D (FIG. 12) described in the fourth embodiment, and has a stack structure in which a plurality of single cells 110 are stacked. The first end plate 121a is connected to reaction gas supply pipes 201 and 202 and exhaust gas discharge pipes 301 and 302 for exhaust gas. Each pipe is provided with valves 211, 212, 311 and 312 which are closed when the operation of the fuel cell stack 100F is stopped, but illustration and description thereof are omitted.

  FIG. 25 (B) is a schematic perspective view showing an arbitrary single cell 110 of the fuel cell stack 100F. The single cell 110 has a seal-integrated membrane electrode assembly 10 sandwiched between an anode separator 20 and a cathode separator 30. In addition, although each manifold 51-54D provided in the single cell 110 is illustrated as a substantially cylindrical flow path, each manifold 51-54D may be configured as a flow path having another shape. good. Further, illustration and description of the refrigerant manifolds 55 and 56 are omitted.

  26 (A1), (A2), (B1), and (B2) are schematic diagrams for explaining the oxygen inflow suppression structure provided in the fuel cell stack 100F. 26 (A1), (A1), (B1), and (B2) schematically show oxygen discharge manifolds 54D provided in each single cell 110, respectively. 26 (A1) and (B1) show the oxygen discharge manifold 54D when viewed from the same direction as FIGS. 25 (A) and (B). FIGS. 26 (A2) and (B2) An oxygen exhaust manifold 54D is shown when viewed along the stacking direction of the single cells 110. 26 (A1), (A2), (B1), and (B2) show three-dimensional arrows x, y, and z corresponding to the three-dimensional arrows x, y, and z shown in FIG. 25, respectively. Has been.

  FIGS. 26A1 and 26A2 respectively show the state of the oxygen discharge manifold 54D during operation of the fuel cell stack 100F. The oxygen discharge manifold 54 </ b> D is connected to a communication channel 60 that communicates with the cathode electrode 3 side of the membrane electrode assembly 5, and the exhaust gas from the cathode electrode 3 passes through the communication channel 60 to the oxygen discharge manifold 54 </ b> D. Is discharged.

  Here, the oxygen discharge manifold 54D is provided with a sealing member 63 for sealing the communication channel 60. The sealing member 63 is a film-like member that can be in close contact with the inner wall surface of the oxygen exhaust manifold 54D, and an end portion 64 of the sealing member 63 is oxygen at the inlet of the communication channel 60 so that the communication channel 60 can be opened and closed. It is attached to the inner wall surface of the discharge manifold 54D. During the operation of the fuel cell stack 100F, the sealing member 63 is opened due to the wind pressure of the exhaust gas from the communication flow path 60.

  FIGS. 26B1 and 26B2 respectively show that oxygen in the fuel cell stack 100F is consumed by the reaction with the residual hydrogen after the operation of the fuel cell stack 100F is stopped (FIG. 6C). ) Shows the state of the oxygen discharge manifold 54D. At this time, on the cathode electrode 3 side of each unit cell 110, a negative pressure is generated as oxygen is consumed. By this negative pressure, the sealing member 63 is sucked toward the communication channel 60 and seals the communication channel 60. That is, in this fuel cell stack 100F, the valves 211, 212, 311 and 312 are closed after the operation is stopped, and the cathode outlet side of each unit cell 110 is sealed in the oxygen exhaust manifold 54D.

  As a result, the generation of negative pressure in the oxygen discharge manifold 54D is suppressed, and the leakage of oxygen into the oxygen discharge manifold 54D is suppressed. Even if oxygen leaks into the oxygen discharge manifold 54D, the communication channel 60 is closed by the sealing member 63, so that the leaked oxygen flows to the cathode electrode 3 side of each single cell 110. Inflow is suppressed. When the fuel cell stack 100F resumes operation, the sealing member 63 returns to the open state again by the wind pressure of the exhaust gas from the cathode electrode 3 side of each unit cell 110 (FIGS. 26A1 and 26A2). )).

  FIGS. 27A and 27B are schematic views for explaining another configuration example of the oxygen inflow suppressing structure provided in the fuel cell stack 100F. 27A and 27B are schematic sectional views of the oxygen discharge manifold 54D when the fuel cell stack 100F is cut along the stacking direction. FIG. 27A shows a state during operation of the fuel cell stack 100F, and FIG. 27B shows a state where negative pressure is generated inside the fuel cell stack 100F after the operation of the fuel cell stack 100F is stopped. ing.

  In the fuel cell stack 100F, a flow path opening / closing mechanism 65 is provided at a connection portion between the oxygen discharge pipe 302 and the first end plate 121a. The flow path opening / closing mechanism 65 includes a lid 66 having a shape similar to the flow path cross-sectional shape of the oxygen discharge pipe 302 and a seal ring 67 hermetically attached to the inner peripheral wall surface of the oxygen discharge pipe 302. With. The lid 66 is attached to the oxygen exhaust pipe 302 so that it can be opened and closed. The seal ring 67 hermetically contacts the outer peripheral end of the lid 66 when the lid 66 is closed. During the operation of the fuel cell stack 100F, the lid 66 is opened to the oxygen exhaust pipe 302 side by the wind pressure of the exhaust gas (FIG. 27A). When a negative pressure is generated inside the fuel cell stack 100F after the operation of the fuel cell stack 100F is stopped, the lid 66 is sucked toward the oxygen discharge manifold 54D and comes into contact with the seal ring 67 to discharge oxygen. The manifold 54D is closed. Thereby, leaked oxygen is suppressed from flowing into each single cell 110 via the oxygen discharge pipe 302.

  As described above, the oxygen discharge manifold 54D of the fuel cell stack 100F functions as an oxygen inflow suppressing structure in which the sealing member 63 and the flow path opening / closing mechanism 65 suppress the inflow of oxygen to the cathode electrode 3 after the operation is stopped. To do. Therefore, it is possible to prevent the cathode electrode 3 from being deteriorated by leaked oxygen after the operation of the fuel cell stack 100F is stopped. Note that the sealing member 63 in FIG. 26 is preferable because the communication channel 60 can be sealed for each single cell 110 and the inflow of oxygen can be more reliably suppressed.

G. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof, and is implemented by combining the configurations of the above-described examples. It is also possible. For example, the catalyst unit 350 of the fourth embodiment may be provided in the oxygen discharge pipe 302 of the fuel cell stack 100 of the first embodiment. Also, the following modifications are possible.

G1. Modification 1:
In the first to third embodiments, the flow passage cross-sectional area of the first manifold portion 54a is configured to be larger than the flow passage cross-sectional area of the second manifold portion 54b. However, the flow passage cross-sectional area of the first manifold portion 54a may not be configured to be larger than the flow passage cross-sectional area of the second manifold portion 54b. However, it is preferable to make the flow passage cross-sectional area of the first manifold portion 54a relatively large, since exhaustability of exhaust gas and waste water from the cathode electrode 3 side of each unit cell 110 during operation is improved.

G2. Modification 2:
In the first to third embodiments, the first and second manifold portions 54a and 54b of the oxygen discharge manifold 54 are formed by changing the configuration of the oxygen discharge manifold 54 formed for each single cell 110. It had been. However, the first and second manifold portions 54a and 54b may be formed by other methods. For example, the first and second manifold portions 54a and 54b may be formed by inserting and arranging a partition wall 57 formed of a plate-like member into a manifold having a connection manifold configuration.

G3. Modification 3:
In the fourth embodiment, the catalyst portion 350 and the catalyst support member 352 are provided on the upper side in the gravity direction in the oxygen exhaust pipe 302, but may be provided on the lower side in the gravity direction. Further, the catalyst portion 350 and the catalyst support member 352 may be provided over the inner periphery of the inner wall surface of the oxygen exhaust pipe 302. In the fourth embodiment, the fuel cell stack 100D is arranged substantially horizontally such that the oxygen discharge manifold 54D side is lower than the oxygen supply manifold 53 side in the direction of gravity. However, the fuel cell stack 100D may be disposed at an arbitrary angle or direction with respect to the direction of gravity.

G4. Modification 4:
In the fifth embodiment, the fuel cell stack 100E includes the two cell stacks 111 and 112. However, the fuel cell stack 100E may include only a single cell stack.

G5. Modification 5:
In the sixth embodiment, the sealing member 63 and the flow path opening / closing mechanism 65 are opened and closed by the gas pressure in the oxygen exhaust manifold 54D. However, the sealing member 63 and the flow path opening / closing mechanism 65 may be forcibly opened / closed by an electromagnetic external force, for example.

DESCRIPTION OF SYMBOLS 2 ... Anode electrode 3 ... Cathode electrode 5 ... Membrane electrode assembly 10 ... Seal integrated membrane electrode assembly 12 ... Seal part 15 ... Gas diffusion member 20 ... Anode separator 30 ... Cathode separator 51 ... Hydrogen supply manifold 52 ... Hydrogen discharge Manifold 53 ... Oxygen supply manifold 54, 54A, 54B, 54D ... Oxygen discharge manifold 54De ... End 54a ... First manifold portion 54b ... Second manifold portion 54c ... Connection manifold portion 55 ... Refrigerant supply manifold 56 ... Refrigerant discharge manifold 57 ... Partition wall 58h ... Communication part 60 ... Communication flow path 63 ... Sealing member 64 ... End part 65 ... Flow path opening / closing mechanism 66 ... Cover body 67 ... Seal ring 100 ... Fuel cell stack 100A ... Fuel cell stack 100B ... Fuel cell stack 100D ... Fuel cell Tack 100E ... Fuel cell stack 100F ... Fuel cell stack 100a ... Fuel cell 110 ... Single cell 110e ... Termination single cell 110t ... Start end single cell 111, 112 ... First and second cell stacks 121a ... First end plate 121b ... 2nd end plate 123a ... 1st terminal plate 123b ... 2nd terminal plate 124a ... 1st insulator plate 124b ... 2nd insulator plate 141 ... Through-hole 142 ... Expansion seal part 142a ... Piston 143 ... Housing container 143a ... 1st hollow part 143b ... 2nd hollow part 143h ... Through-hole 201,202,301,302 ... Pipe 203,204,303,304 ... Branch pipe 211,212,311,312 ... Valve 350 ... Catalyst part 352 ... Catalyst carrying part 401, 402 ... pipe 403 ... branch piping An ... anode Ca ... cathode GA ... power generation region

Claims (6)

A fuel cell stack,
A power generation laminate in which a plurality of power generation modules having a membrane electrode assembly in which an electrolyte membrane is sandwiched between an anode electrode and a cathode electrode are laminated;
An exhaust gas manifold that extends along the stacking direction of the power generation stack and is connected to the cathode electrode side of each of the plurality of power generation modules;
At the end of the power generation laminate, exhaust gas piping connected to the exhaust gas manifold,
A valve provided in the exhaust gas pipe;
With
In the exhaust gas manifold or the exhaust gas pipe, after the operation of the fuel cell stack is stopped, oxygen is supplied from the outside of the fuel cell stack to the cathode electrode side through the exhaust gas pipe when the valve is closed. It has an oxygen inflow suppression structure to suppress inflow ,
In the exhaust gas pipe, a catalyst part that functions as the oxygen inflow suppression structure is provided between the valve and the power generation module closest to the connection position of the exhaust gas pipe.
The catalyst unit promotes the reaction between the fuel gas remaining inside the fuel cell stack and the oxygen flowing from the outside of the fuel cell stack after the operation of the fuel cell stack is stopped. In the above, by consuming the oxygen, to suppress the inflow of the oxygen to the cathode electrode side,
The exhaust gas pipe is attached to the power generation laminate so that the downstream side is the lower side in the direction of gravity,
The fuel cell stack , wherein the catalyst part in the exhaust gas pipe is provided on an inner wall surface on the upper side in the gravity direction of the exhaust gas pipe . The fuel cell stack according to claim 1 , wherein
The catalyst section is provided in at least 3/4 of the exhaust gas manifold side of the entire range from the valve to the connection between the exhaust gas pipe and the exhaust gas manifold. stack. The fuel cell stack according to claim 1 or 2 , wherein
The catalyst unit is provided in at least 5/8 of the exhaust gas manifold side of the entire range from the valve to the exhaust gas pipe and the exhaust gas manifold. stack. A fuel cell stack according to any one of claims 1 to 3,
The catalyst section is provided in at least a half of the exhaust gas manifold side of the entire range from the valve to the connection portion of the exhaust gas pipe and the exhaust gas manifold. stack. A fuel cell stack according to any one of claims 1 to 4,
The fuel cell stack, wherein the catalyst section is provided from the center of the entire range to the connection section in the entire range from the valve to the connection section between the exhaust gas pipe and the exhaust gas manifold. A fuel cell stack according to any one of claims 1 to 5,
The catalyst unit is a fuel cell stack formed in a vertically long shape along a flow direction of exhaust gas in the exhaust gas pipe.

Images