Fuel cell stack

Abstract

[Problem] To provide a fuel cell stack that can facilitate the connection of piping without causing an increase in size. [Solution] A fuel cell stack 1 has a cooling medium inlet communication hole 32, a cooling medium outlet communication hole 35, a first reaction gas inlet communication hole 31, a second reaction gas inlet communication hole 34, a first reaction gas outlet communication hole 36, and a second reaction gas outlet communication hole 33 that pass through each of a first end plate 3 and a power generation cell 2 in a first direction. On one end side of the power generation cell in a second direction orthogonal to the first direction, the first reaction gas inlet communication hole, the cooling medium inlet communication hole, and the second reaction gas outlet communication hole are arranged in a staggered manner in the aforementioned order in a third direction orthogonal to the first direction and the second direction. On the other end side of the power generation cell in the second direction, the second reaction gas inlet communication hole, the cooling medium outlet communication hole, and the first reaction gas outlet communication hole are arranged in a staggered manner in the aforementioned order in the third direction.

Description

fuel cell stack

[0001] The present invention relates to a fuel cell stack.

[0002] In recent years, efforts to realize a low-carbon or carbon-free society have become more active, and CO ２ Research and development into electrification technologies is being conducted to reduce emissions and improve energy efficiency. In particular, fuel cells are ２ Because it does not emit CO2, it is attracting attention as a sustainable energy source with a low environmental impact.

[0003] Patent Document 1 discloses a fuel cell stack having a plurality of stacked power generating cells and a first end plate and a second end plate sandwiching the plurality of power generating cells. A plurality of communication holes for circulating cooling water or reactant gases are formed in each of the first end plate and the power generating cells. A plurality of pipes for circulating the cooling water or reactant gases are connected to the open ends of the communication holes in the first end plate.

[0004] Japanese Patent Application Laid-Open No. 2016-134335

[0005] When multiple communication holes are arranged in a straight line, the distance between each communication hole becomes small, making it difficult to secure space for connecting the piping, which leads to the problem of the fuel cell stack becoming larger in size in order to facilitate the piping connections.

[0006] In view of the above background, an object of the present invention is to provide a fuel cell stack that can easily connect pipes without increasing the size of the stack, and to improve energy efficiency by making it possible to reduce the size of the fuel cell stack.

[0007] In order to solve the above-mentioned problems, one aspect of the present invention is a fuel cell stack (1) having a plurality of power generation cells (2) stacked in a first direction, and a first end plate (3) and a second end plate (4) that sandwich the plurality of power generation cells along the first direction, each of the plurality of power generation cells having an electrolyte membrane electrode assembly (10) and separators (21, 22) provided on both sides of the electrolyte membrane electrode assembly, wherein a cooling medium inlet passage (32) and a cooling medium outlet passage (35) that penetrate the first end plate and the power generation cells, respectively, in the first direction and that allow a cooling medium to flow, and a cooling medium outlet passage (35) that connects the first end plate and the power generation cells, respectively, in the first direction. a first reactant gas inlet manifold (31), a second reactant gas inlet manifold (34), a first reactant gas outlet manifold (36), and a second reactant gas outlet manifold (33) that penetrate the cell in a direction perpendicular to the first direction and allow a reactant gas to flow therethrough, and at one end side of the power generation cell in a second direction perpendicular to the first direction, the first reactant gas inlet manifold, the coolant inlet manifold, and the second reactant gas outlet manifold are staggered in the order described in a third direction perpendicular to the first and second directions, and at the other end side of the power generation cell in the second direction, the second reactant gas inlet manifold, the coolant outlet manifold, and the first reactant gas outlet manifold are staggered in the order described in the third direction.

[0008] According to this aspect, the communication holes are staggered in the third direction, so that the communication holes can be spaced apart from one another, thereby providing a fuel cell stack that can easily connect pipes without increasing the size.

[0009] In the above aspect, the first reactant gas inlet manifold and the second reactant gas outlet manifold may be positioned closer to the center of the power generation cell in the second direction than the coolant inlet manifold, and the second reactant gas inlet manifold and the first reactant gas outlet manifold may be positioned closer to the center of the power generation cell in the second direction than the coolant outlet manifold.

[0010] According to this aspect, the distance in the second direction between the coolant supply passage and the coolant discharge passage can be increased, and the power generating cells can be cooled efficiently.

[0011] In the above aspect, the power generation cell may be formed into a rectangle extending from the first direction to the second direction, and when viewed from the first direction, the first reactant gas inlet communication hole and the first reactant gas outlet communication hole may be arranged at diagonal positions of the power generation cell, and the second reactant gas inlet communication hole and the second reactant gas outlet communication hole may be arranged at diagonal positions of the power generation cell.

[0012] According to this aspect, the reactant gas can flow diagonally across the power generation cell from the reactant gas inlet manifold toward the reactant gas outlet manifold, allowing the reactant gas to be efficiently supplied to each part of the power generation cell.

[0013] In the above aspect, one of oxidant gas and fuel gas may flow through the first reactant gas inlet manifold and the first reactant gas outlet manifold, and the other of oxidant gas and fuel gas may flow through the second reactant gas inlet manifold and the second reactant gas outlet manifold.

[0014] According to this aspect, the oxidant gas and the fuel gas can flow in the diagonal direction of the power generation cell, and the reactant gas can be efficiently supplied to each part of the power generation cell.

[0015] According to the above configuration, it is possible to provide a fuel cell stack that does not increase in size and allows easy connection of pipes.

[0016] A perspective view of a fuel cell stack. An exploded perspective view of a power generation cell. A cross section of the power generation cell in the stacking direction. A plan view of the first surface side of the first separator. A plan view of the first surface side of the second separator.

[0017] Hereinafter, an embodiment of the fuel cell stack 1 will be described with reference to the drawings. The fuel cell stack 1 may be mounted on a vehicle such as an electric vehicle, or may be used as a stationary type.

[0018] 1 , the fuel cell stack 1 includes a plurality of power generating cells 2 stacked in a first direction, and a first end plate 3 and a second end plate 4 that sandwich the power generating cells 2 along the first direction. A first terminal plate 6 and a first insulator 7 are interposed between the first end plate 3 and the power generating cells 2. A second terminal plate 8 and a second insulator 9 are interposed between the second end plate 4 and the power generating cells 2. The first and second insulators 7 and 9 are formed from an insulating material such as polycarbonate or phenolic resin.

[0019] The first end plate 3 and the second end plate 4 are connected to each other by a plurality of connecting rods 11 extending in a first direction. Each connecting rod 11 applies a clamping load in the first direction to the plurality of power generating cells 2.

[0020] The first direction extends horizontally. In a horizontal plane, a direction perpendicular to the first direction is referred to as a second direction. A direction perpendicular to the first and second directions is referred to as a third direction. The first direction may be referred to as a stacking direction, the second direction as a width direction, and the third direction as a height direction or a vertical direction.

[0021] 2 , each power-generating cell 2 has a membrane electrode assembly 20, and a first separator 21 and a second separator 22 provided on either side of the membrane electrode assembly 20. A resin frame member 23 is provided on the outer periphery of the membrane electrode assembly 20. The membrane electrode assembly 20 and the resin frame member 23 constitute a resin-framed MEA 24.

[0022] 3 , the membrane electrode assembly 20 includes an electrolyte membrane 26, an anode electrode 27 provided on one side of the electrolyte membrane 26, and a cathode electrode 28 provided on the other side of the electrolyte membrane 26. The electrolyte membrane 26 is, for example, a solid polymer electrolyte membrane (cation exchange membrane) such as a thin film of perfluorosulfonic acid containing water. The electrolyte membrane 26 is sandwiched between the anode electrode 27 and the cathode electrode 28. The electrolyte membrane 26 may be a fluorine-based electrolyte or a hydrocarbon-based electrolyte.

[0023] The anode electrode 27 has an anode electrode catalyst layer bonded to one surface of the electrolyte membrane 26 and an anode gas diffusion layer laminated on the anode electrode catalyst layer. The cathode electrode 28 has a cathode electrode catalyst layer bonded to the other surface of the electrolyte membrane 26 and a cathode gas diffusion layer laminated on the cathode electrode catalyst layer.

[0024] The anode electrode catalyst layer is formed, for example, by uniformly applying porous carbon particles having a platinum alloy supported on their surfaces together with an ion-conductive polymer binder to the surface of the anode gas diffusion layer. The cathode electrode catalyst layer is formed, for example, by uniformly applying porous carbon particles having a platinum alloy supported on their surfaces together with an ion-conductive polymer binder to the surface of the cathode gas diffusion layer. The cathode gas diffusion layer and the anode gas diffusion layer are formed from conductive porous sheets such as carbon paper or carbon cloth.

[0025] 2 and 3, the resin frame member 23 is formed in a frame shape. The inner peripheral edge of the resin frame member 23 is joined to the outer peripheral edge of the membrane electrode assembly 20.

[0026] 1 and 2 , when viewed along the first direction, the power generating cells 2, the first end plate 3, and the second end plate 4 are formed into a rectangle extending in the second direction. An oxidant gas inlet manifold 31, a coolant inlet manifold 32, and a fuel gas outlet manifold 33 are provided in this order from above at one end of the multiple power generating cells 2, the first end plate 3, and the first insulator 7 in the second direction. The oxidant gas inlet manifold 31, the coolant inlet manifold 32, and the fuel gas outlet manifold 33 penetrate the multiple power generating cells 2, the first end plate 3, and the first insulator 7 in the first direction.

[0027] 2 , a fuel gas inlet manifold 34, a coolant outlet manifold 35, and an oxygen-containing gas outlet manifold 36 are provided in this order from above at the other end in the second direction of the multiple power generating cells 2, the first end plate 3, and the first insulator 7. The fuel gas inlet manifold 34, the coolant outlet manifold 35, and the oxygen-containing gas outlet manifold 36 penetrate the multiple power generating cells 2, the first end plate 3, and the first insulator 7 in the first direction.

[0028] An oxygen-containing oxygen gas, such as air, is supplied to the oxygen-containing gas supply passage 31. The oxygen-containing gas is discharged from the oxygen-containing gas discharge passage 36. A coolant, such as pure water, ethylene glycol, or oil, is supplied to the coolant supply passage 32. The coolant is discharged from the coolant discharge passage 35. A fuel gas, such as hydrogen, is supplied to the fuel gas supply passage 34. The fuel gas is discharged from the fuel gas discharge passage 33.

[0029] The coolant inlet manifold 32, the coolant outlet manifold 35, the oxidant gas inlet manifold 31, the oxidant gas outlet manifold 36, the fuel gas inlet manifold 34, and the fuel gas outlet manifold 33 may be collectively referred to as "manifolds." The oxidant gas and the fuel gas may be collectively referred to as "reactant gas." The oxidant gas inlet manifold 31 and the fuel gas inlet manifold 34 may be collectively referred to as "reactant gas inlet manifolds," and the oxidant gas outlet manifold 36 and the fuel gas outlet manifold 33 may be collectively referred to as "reactant gas outlet manifolds."

[0030] 2, the first separator 21 and the second separator 22 are rectangular thin plates having a pair of long sides extending in the second direction and a pair of short sides extending in the third direction. The first separator 21 and the second separator 22 adjacent to each other in the first direction are joined to each other at their respective outer peripheries. This joining is achieved by welding, brazing, crimping, or the like.

[0031] The first separator 21 and the second separator 22 may be thin metal plates such as steel plates, stainless steel plates, aluminum plates, plated steel plates, and titanium plates. The first separator 21 and the second separator 22 are press-formed into a corrugated shape. The surfaces of the first separator 21 and the second separator 22 may be subjected to a surface treatment for corrosion prevention. An insulating resin material may be provided on the outer edges of the first separator 21 and the second separator 22. The first separator 21 and the second separator 22 each have a first surface 21A, 22A that faces the resin-framed MEA 24, and a second surface 21B, 22B that faces the resin-framed MEA 24.

[0032] As shown in FIG. 4 , the first surface 21A of the first separator 21 is provided with a plurality of annular beads 41A to 41G that protrude toward the resin-framed MEA 24. The beads 41A to 41G are formed integrally with the first separator 21 by press molding or the like. Grooves are formed in the second surface 21B sides of the beads 41A to 41G. The bead 41A surrounds the oxidant gas inlet manifold 31. The bead 41B surrounds the coolant inlet manifold 32. The bead 41C surrounds the fuel gas outlet manifold 33. The bead 41D surrounds the fuel gas inlet manifold 34. The bead 41E surrounds the coolant outlet manifold 35. The bead 41F surrounds the oxidant gas outlet manifold 36. The bead 41G integrally surrounds the beads 41A, 41C, 41D, and 41F. The beads 41B and 41D are disposed outside the bead 41G. The beads 41A to 41G do not intersect with one another. Furthermore, the areas surrounded by the beads 41A to 41F do not overlap one another. A portion of the bead 41G extends along the beads 41A to 41F. The beads 41A to 41G are in airtight contact with the resin-framed MEA 24, thereby preventing leakage of the oxidant gas, fuel gas, and coolant.

[0033] The first surface 21A of the first separator 21 is provided with a plurality of beads 43 that form an oxidant gas flow field 42 (reactant gas flow field). The beads 43 are protrusions formed at equal intervals on the resin-framed MEA 24 side when viewed in the third direction (up and down direction). Recesses formed between the beads 43 constitute the oxidant gas flow field 42. A portion 42A of the oxidant gas flow field 42 that faces the power generation unit, which is the membrane electrode assembly 20, is generally referred to as the power generation region. The plurality of beads 43 are formed integrally with the first separator 21 by press molding or the like. The plurality of beads 43 are arranged inside the beads 41G. Of the multiple beads 43 that form the oxidant gas flow path 42, the oxidant gas flow path inlet portion 42B extending from the bead 41A surrounding the oxidant gas inlet passage 31 to portion 42A (power generation region), and the oxidant gas flow path outlet portion 42C extending from portion 42A (power generation region) to the bead 41F surrounding the oxidant gas outlet passage 36 are referred to as the non-power generation region.

[0034] An oxidant gas inlet tunnel 45 penetrates the bead 41A and connects the oxidant gas inlet passage 31 and the oxidant gas flow path inlet 42B. An oxidant gas outlet tunnel 46 penetrates the bead 41F and connects the oxidant gas outlet passage 36 and the oxidant gas flow path outlet 42C. The oxidant gas flows from the oxidant gas inlet passage 31 to the oxidant gas outlet passage 36 by passing through the oxidant gas inlet tunnel 45, the oxidant gas flow path inlet 42B, the portion 42A, the oxidant gas flow path outlet 42C, and the oxidant gas outlet tunnel 46.

[0035] 5, the first surface 22A of the second separator 22 is provided with a plurality of annular beads 51A to 51G that protrude toward the resin-framed MEA 24. The beads 51A to 51G are formed integrally with the second separator 22 by press molding or the like. Grooves are formed in the second surface 22B of the beads 51A to 51G. The bead 51A surrounds the oxidant gas inlet manifold 31. The bead 51B surrounds the coolant inlet manifold 32. The bead 51C surrounds the fuel gas outlet manifold 33. The bead 51D surrounds the fuel gas inlet manifold 34. The bead 51E surrounds the coolant outlet manifold 35. The bead 51F surrounds the oxidant gas outlet manifold 36. The bead 51G integrally surrounds the beads 51A, 51C, 51D, and 51F. The beads 51B and 51D are disposed outside the bead 51G. The beads 51A to 51G do not intersect with one another. Furthermore, the areas surrounded by the beads 51A to 51F do not overlap one another. A portion of the bead 51G extends along the beads 51A to 51F. The beads 51A to 51F are in airtight contact with the resin-framed MEA 24, thereby preventing leakage of the oxidant gas, fuel gas, and coolant.

[0036] The first surface 22A of the second separator 22 is provided with multiple beads 53 that define a fuel gas flow field 52 (reactant gas flow field). The beads 53 are formed at equal intervals in the third direction (vertical direction) and are bulges that protrude toward the resin-framed MEA 24. Recesses formed between the beads 53 define the fuel gas flow field 52. A portion 52A of the fuel gas flow field 52 that faces the power generation unit, which is the membrane electrode assembly 20, is generally referred to as the power generation region. The multiple beads 53 are integrally formed with the second separator 22 by press molding or the like. The multiple beads 53 are arranged inside the beads 51G. The multiple beads 53 that define the fuel gas flow field 52 extend from the bead 51D surrounding the fuel gas inlet passage 34 to the bead 51C surrounding the fuel gas outlet passage 33. The fuel gas flow field 52 is formed between the beads 53.

[0037] As shown in FIGS. 2 and 5 , the fuel gas flow field 52 includes a portion 52A extending in the second direction and facing the membrane electrode assembly 20 to form a power generation section; a fuel gas flow field inlet 52B extending from one end of the portion 52A in the second direction to a bead 51D; and a fuel gas flow field outlet 52C extending from the other end of the portion 52A in the second direction to a bead 51C. In the portion 52A, each bead 53 extends linearly or wavy in the second direction. In the fuel gas flow field inlet 52B, each bead 53 extends linearly downward from the bead 51D toward the portion 52A. In the fuel gas flow field outlet 52C, each bead 53 extends linearly upward toward the portion 52A. Each bead 53 preferably abuts against the resin-framed MEA 24.

[0038] A fuel gas inlet tunnel 55 penetrates the bead 51D and connects the fuel gas inlet manifold 34 and the fuel gas flow path inlet 52B. A fuel gas outlet tunnel 56 penetrates the bead 51C and connects the fuel gas outlet manifold 33 and the fuel gas flow path outlet 52C. The fuel gas flows from the fuel gas inlet manifold 34 to the fuel gas outlet manifold 33 by passing through the fuel gas inlet tunnel 55, the fuel gas flow path inlet 52B, the portion 52A, the fuel gas flow path outlet 52C, and the fuel gas outlet tunnel 56.

[0039] 2 and 3 , a coolant flow field 58 is formed between the second surface 21B (the back surface of 21A) of the first separator 21 and the second surface 22B of the second separator 22, which face each other. The coolant flow field 58 is formed by the shape of the second surface 21B of the first separator 21 and the shape of the second surface 22B of the second separator 22. The coolant flow field 58 may be formed between the grooves on the second surface 21B side of the bead 43 and the second surface 22B of the second separator 22, between the grooves on the second surface 22B side of the bead 53 and the second surface 21B of the first separator 21, and between the grooves on the second surface 21B side of the bead 43 and the grooves on the second surface 22B of the bead 53. When viewed from the first direction, the grooves of the beads 43 on the second surface 21B side and the grooves of the beads 53 on the second surface 22B side overlap at multiple locations to form a continuous passage. The coolant flow field 58 extends in the second and third directions along the surfaces of the first and second separators 21, 22.

[0040] 4 , the first separator 21 or the second separator 22 is provided with a coolant inlet tunnel 61 that connects the coolant inlet passage 32 and the coolant flow field 58. The coolant inlet tunnel 61 communicates with the internal spaces of the beads 41B and 41G and opens into the wall surfaces of the beads 41B and 41G. That is, the coolant inlet tunnel 61 extends through the beads 41B and 41G.

[0041] The first separator 21 or the second separator 22 is provided with a coolant outlet tunnel 62 that connects the coolant outlet passage 35 and the coolant flow field 58. The coolant outlet tunnel 62 communicates with the internal spaces of the beads 41E and 41G and opens into the wall surfaces of the beads 41E and 41G. The coolant outlet tunnel 62 extends through the beads 41E and 41G. The coolant passes through the coolant inlet tunnel 61, the coolant flow field 58, and the coolant outlet tunnel 62 to flow from the coolant inlet passage 32 to the coolant outlet passage 35.

[0042] The grooves on the second surface 21B side of the bead 41G and the grooves on the second surface 22B side of the bead 51G face each other to form an annular bypass flow path 63 along the beads 41G and 51G. The bypass flow path 63 is connected to the coolant inlet tunnel 61 and the coolant outlet tunnel 62.

[0043] The first separator 21 or the second separator 22 is provided with a first air vent tunnel 65 (first air vent passage) that connects the upper end of the coolant inlet manifold 32 and the bypass flow path 63 (full bead 41G). The first air vent tunnel 65 communicates with the internal spaces of the beads 41B and 41G, and may also communicate with the internal spaces of the beads 51B and 51G. The connection between the first air vent tunnel 65 and the bypass flow path 63 is preferably located higher than the connection between the first air vent tunnel 65 and the coolant inlet manifold 32. The connection between the first air vent tunnel 65 and the bypass flow path 63 is preferably located higher than the connection between the uppermost coolant inlet tunnel 61 and the bypass flow path 63.

[0044] The first separator 21 or the second separator 22 is provided with a second air vent tunnel 66 (second air vent passage) that connects the upper end of the coolant outlet manifold 35 and the upper end of the bypass flow path 63. The second air vent tunnel 66 may penetrate through the beads 41E and 41G, or through the beads 51E and 51G. The connection between the second air vent tunnel 66 and the bypass flow path 63 is preferably located above the upper end of the membrane electrode assembly 20. The connection between the second air vent tunnel 66 and the coolant outlet manifold 35 is preferably located above the upper end of the membrane electrode assembly 20.

[0045] Air that has accumulated in the upper part of the coolant supply passage 32 passes through the first air vent tunnel 65, the bypass passage 63, and the second air vent tunnel 66 and is discharged to the coolant outlet passage 35. This makes it difficult for air to enter the coolant flow field 58.

[0046] 3, a seal member 68 is provided between the beads 41A to 41G of the first separator 21 and the resin frame member 23. A seal member 69 is provided between the beads 51A to 51G of the second separator 22 and the resin frame member 23. The seal members 68 and 69 are pressed against the resin frame member 23 to prevent leakage of the oxidant gas, fuel gas, or coolant.

[0047] 2, 4, and 5, the oxidant gas inlet manifolds 31, the coolant inlet manifolds 32, and the fuel gas outlet manifolds 33 are arranged in a staggered pattern facing downward at one end of the power-generating cell 2 in the second direction. At the other end of the power-generating cell 2 in the second direction, the fuel gas inlet manifolds 34, the coolant outlet manifolds 35, and the oxidant gas outlet manifolds 36 are arranged in a staggered pattern facing downward at the same order.

[0048] When viewed from the first direction, the oxidant gas inlet manifold 31 and the oxidant gas outlet manifold 36 are disposed at diagonal positions of the power generation cell 2. When viewed from the first direction, the fuel gas inlet manifold 34 and the fuel gas outlet manifold 33 are disposed at diagonal positions of the power generation cell 2. As a result, the oxidant gas flows diagonally from the oxidant gas inlet manifold 31 toward the oxidant gas outlet manifold 36 of the power generation cell 2. Also, the fuel gas flows diagonally from the fuel gas inlet manifold 34 toward the fuel gas outlet manifold 33 of the power generation cell 2. As a result, the oxidant gas and the fuel gas can be efficiently supplied to each part of the power generation cell 2.

[0049] The fuel gas inlet manifold 34 and the oxygen-containing gas outlet manifold 36 are disposed closer to the center of the power generation cell 2 in the second direction than the coolant outlet manifold 35. The oxygen-containing gas inlet manifold 31 and the fuel gas outlet manifold 33 are disposed closer to the center of the power generation cell 2 in the second direction than the coolant inlet manifold 32.

[0050] The central end portions of the oxidant gas inlet manifold 31 and the fuel gas outlet manifold 33 in the second direction are disposed closer to the center in the second direction than the central end portions of the coolant inlet manifold 32. The central end portion of the coolant inlet manifold 32 in the second direction is disposed closer to the center in the second direction than the one end portions of the oxidant gas inlet manifold 31 and the fuel gas outlet manifold 33 in the second direction.

[0051] The central ends of the fuel gas inlet communication hole 34 and the oxidant gas outlet communication hole 36 in the second direction are positioned closer to the center in the second direction than the central end of the coolant outlet communication hole 35 in the second direction.

[0052] The distance between the oxidant gas inlet manifold 31 and the coolant inlet manifold 32 is greater than the distance between the coolant inlet manifold 32 and the fuel gas outlet manifold 33. A gap is disposed between the oxidant gas inlet manifold 31 and the coolant inlet manifold 32 in the third direction. The lower end of the coolant inlet manifold 32 is disposed below the upper end of the fuel gas outlet manifold 33.

[0053] The distance between the oxygen-containing gas discharge passage 36 and the coolant discharge passage 35 is greater than the distance between the coolant discharge passage 35 and the fuel gas inlet passage 34. The oxygen-containing gas discharge passage 36 and the coolant discharge passage 35 are arranged with a gap in between in the third direction.

[0054] The fuel gas inlet manifold 34 is disposed adjacent to the coolant outlet manifold 35. The distance between the oxidant gas inlet manifold 31 and the coolant inlet manifold 32 is greater than the distance between the coolant outlet manifold 35 and the fuel gas inlet manifold 34. This makes it possible to suppress condensation of the oxidant gas in the oxidant gas inlet manifold. The fuel gas is hydrogen, which is not prone to condensation. Therefore, even if the fuel gas inlet manifold 34 and the coolant outlet manifold 35 are disposed adjacent to each other, condensation is unlikely to occur in the fuel gas inlet manifold 34.

[0055] The upper end of the coolant outlet manifold 35 is located at the same height as or above the upper end of the fuel gas inlet manifold 34. The coolant outlet manifold 35 extends upward, passing laterally in the second direction of the fuel gas inlet manifold 34.

[0056] The coolant inlet manifold 32 and the coolant outlet manifold 35 extend in a third direction. In the third direction, the width of the coolant inlet manifold 32 is greater than the width of the oxygen-containing gas inlet manifold 31 and the width of the fuel gas outlet manifold 33. In the third direction, the width of the coolant outlet manifold 35 is greater than the width of the oxygen-containing gas outlet manifold 36 and the width of the fuel gas inlet manifold 34.

[0057] When viewed from the first direction, the oxidant gas inlet manifold 31 and the oxidant gas outlet manifold 36 are disposed at diagonal positions of the power generation cell 2. When viewed from the first direction, the fuel gas inlet manifold 34 and the fuel gas outlet manifold 33 are disposed at diagonal positions of the power generation cell 2.

[0058] The upper end of the coolant outlet manifold 35 extends higher than the upper end of the coolant flow field 58. The upper end of the coolant flow field 58 extends horizontally. The upper end of the coolant flow field 58 is formed by the abutting portion between the first separator 21 and the second separator 22. The abutting portion between the first separator 21 and the second separator 22 may be joined by welding. The upper end of the coolant flow field 58 extends linearly in the second direction above the membrane electrode assembly 20. The upper end of the coolant outlet manifold 35 extends higher than the portion of the upper end of the coolant flow field 58 that is located above the membrane electrode assembly 20.

[0059] When viewed from the first direction, the upper end of the membrane electrode assembly 20 extends linearly in parallel to the second direction. The upper end of the coolant outlet manifold 35 is located above the upper end of the membrane electrode assembly 20.

[0060] As shown in FIG. 1 , the first end plate 3 is fitted with an oxidant gas supply pipe 71 connected to the oxidant gas inlet manifold 31, an oxidant gas discharge pipe 72 connected to the oxidant gas outlet manifold 36, a fuel gas supply pipe 73 connected to the fuel gas inlet manifold 34, a fuel gas discharge pipe 74 connected to the fuel gas outlet manifold 33, a cooling medium supply pipe 75 connected to the cooling medium inlet manifold 32, and a cooling medium discharge pipe 76 connected to the cooling medium outlet manifold 35.

[0061] The oxidant gas supply pipe 71, the oxidant gas discharge pipe 72, the fuel gas supply pipe 73, the fuel gas discharge pipe 74, the coolant supply pipe 75, and the coolant discharge pipe 76 have flanges 71A to 76A that are fastened to the first end plate 3. The oxidant gas supply pipe 71, the oxidant gas discharge pipe 72, the fuel gas supply pipe 73, the fuel gas discharge pipe 74, the coolant supply pipe 75, and the coolant discharge pipe 76 are preferably made of a resin material. Adjacent flanges 71A to 76A may be formed integrally with one another.

[0062] A first power output terminal 78 connected to the first terminal plate 6 protrudes outward from the center of the first end plate 3. A second power output terminal 79 connected to the second terminal plate 8 protrudes outward from the center of the second end plate 4.

[0063] The following describes the operation of the fuel cell stack 1. The oxidant gas passes through the oxidant gas supply pipe 71 and the oxidant gas inlet manifold 31 and is supplied to the oxidant gas flow field 42 of each power generation cell 2. The fuel gas passes through the fuel gas supply pipe 73 and the fuel gas inlet manifold 34 and is supplied to the fuel gas flow field 52 of each power generation cell 2. The coolant passes through the coolant supply pipe 75 and the coolant inlet manifold 32 and is supplied to the coolant flow field 58 of each power generation cell 2.

[0064] In each membrane electrode assembly 20, the oxidant gas supplied to the cathode electrode 28 and the fuel gas supplied to the anode electrode 27 are consumed by electrochemical reaction in the electrode catalyst layer, thereby generating electricity.

[0065] The oxidant gas partially consumed at the cathode 28 of the membrane electrode assembly 20 and the water vapor generated at the cathode 28 pass through the oxidant gas outlet manifold 36 and the oxidant gas discharge pipe 72 and are discharged to the outside of the fuel cell stack 1. The fuel gas partially consumed at the anode 27 of the membrane electrode assembly 20 passes through the fuel gas outlet manifold 33 and the fuel gas discharge pipe 74 and is discharged to the outside of the fuel cell stack 1.

[0066] The coolant is supplied to the plurality of coolant flow paths 58 via the coolant supply pipe 75 and the coolant inlet manifold 32, and cools each of the power-generating cells 2. The coolant passes from the plurality of coolant flow paths 58 through the coolant outlet manifold 35 and the coolant discharge pipe, and is discharged to the outside of the fuel cell stack 1.

[0067] With the above configuration, the upper end of the coolant outlet manifold 35 extends higher than the upper end of the coolant flow field 58, which makes it easier for air that has entered the coolant flow field 58 to flow through the coolant outlet manifold 35. This allows the air in the coolant flow field 58 to be efficiently discharged to the outside via the coolant outlet manifold 35. Since no dedicated air vent flow field is required in addition to the coolant outlet manifold 35, the fuel cell stack 1 can be made more compact. As described above, it is possible to provide a fuel cell stack 1 that can discharge air from the coolant flow field without increasing the size of the stack.

[0068] Since the cooling medium flow path 58 and the upper end of the cooling medium flow path 58 extend horizontally, the cooling medium flows horizontally through the cooling medium flow path 58 from the cooling medium inlet manifold 32 toward the cooling medium outlet manifold 35, making it difficult for air to stagnate in the cooling medium flow path 58.

[0069] A second air vent tunnel 66 is formed between a pair of separators 21, 22, passing above the fuel gas inlet manifold 34 and connecting the upper end of the coolant flow field 58 to the coolant outlet manifold 35. This allows the air in the coolant flow field 58 to flow through the second air vent tunnel 66 to the coolant outlet manifold 35 without being obstructed by the fuel gas inlet manifold 34.

[0070] At one end of the power generating cell 2 in the second direction, the oxidant gas inlet manifold 31, the coolant inlet manifold 32, and the fuel gas outlet manifold 33 are staggered in the order described in the third direction, and at the other end of the power generating cell 2 in the second direction, the fuel gas inlet manifold 34, the coolant outlet manifold 35, and the oxidant gas outlet manifold 36 are staggered in the order described in the third direction, so that the manifolds 31 to 36 can be spaced apart from one another. This facilitates connection of the pipes 71 to 76 without increasing the size of the device.

[0071] Although the description of the specific embodiment has been completed above, the present invention is not limited to the above embodiment and can be widely modified and implemented.

[0072] REFERENCE SIGNS LIST 1: fuel cell stack 2: power generation cell 20: membrane electrode assembly 21: first separator 22: second separator 24: resin-framed MEA 31: oxidant gas inlet passage 32: coolant inlet passage 33: fuel gas outlet passage 34: fuel gas inlet passage 35: coolant outlet passage 36: oxidant gas outlet passage 41A-41G: beads 51A-51G: beads 52: fuel gas flow path 58: coolant flow path 63: bypass flow path 65: first air vent tunnel 66: second air vent tunnel 71: oxidant gas supply pipe 72: oxidant gas discharge pipe 73: fuel gas supply pipe 74: fuel gas discharge pipe 75: coolant supply pipe 76: coolant discharge pipe

Claims

1. A fuel cell stack comprising a plurality of power generation cells stacked in a first direction, and first and second end plates sandwiching the plurality of power generation cells along the first direction, each of the plurality of power generation cells having a membrane electrode assembly and a separator provided on either side of the membrane electrode assembly, wherein the fuel cell stack comprises a coolant inlet manifold and a coolant outlet manifold that penetrate the first end plate and each of the power generation cells in the first direction and allow a coolant to flow, and a first reactant gas inlet manifold, a second reactant gas inlet manifold, a first reactant gas outlet manifold, and a second reactant gas outlet manifold that penetrate the first end plate and each of the power generation cells in the first direction and allow a reactant gas to flow, wherein the first reactant gas inlet manifold, the coolant inlet manifold, and the second reactant gas outlet manifold are staggered in the order specified in a third direction that is perpendicular to the first and second directions at one end side of the power generation cells in a second direction perpendicular to the first direction, a fuel cell stack in which, at the other end side of the power generation cell in the second direction, the second reactant gas inlet manifold, the cooling medium outlet manifold, and the first reactant gas outlet manifold are staggered in the order described above in the third direction.

2. A fuel cell stack as described in claim 1, wherein the first reactant gas inlet manifold and the second reactant gas outlet manifold are positioned closer to the center of the power generation cell in the second direction than the coolant inlet manifold, and the second reactant gas inlet manifold and the first reactant gas outlet manifold are positioned closer to the center of the power generation cell in the second direction than the coolant outlet manifold.

3. A fuel cell stack as described in claim 2, wherein the power generation cell is formed in a rectangular shape extending from the first direction to the second direction, and when viewed from the first direction, the first reactant gas inlet manifold and the first reactant gas outlet manifold are arranged at diagonal positions of the power generation cell, and the second reactant gas inlet manifold and the second reactant gas outlet manifold are arranged at diagonal positions of the power generation cell.

4. A fuel cell stack as described in claim 1, wherein one of oxidant gas and fuel gas flows through the first reactant gas inlet manifold and the first reactant gas outlet manifold, and the other of oxidant gas and fuel gas flows through the second reactant gas inlet manifold and the second reactant gas outlet manifold.

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