Fuel Cell Stack

Abstract

To provide a fuel cell stack that can suppress gas leakage even when an impact load acts in the stacking direction on a stack consisting of a plurality of unit cells.SOLUTION: When a tightening load in the stacking direction is applied to a stack of multiple unit cells of a fuel cell stack, the bead seals (outer bead seals 62, 82) of each separator (first separator 30, second separator 32) are compressed, and the height Hb2 of the bead seal in the stacking direction after compression is lower than the height Hb1 of the bead seal in the stacking direction before compression, and the height Hf of feed protrusions 52a, 52b, 72a, 72b in the stacking direction is lower than the height Hb2 of the bead seal in the stacking direction after compression.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a fuel cell stack in which unit cells are stacked. [Background technology]

[0002] A fuel cell stack is composed of a plurality of unit cells stacked together. Each unit cell includes a membrane electrode assembly (MEA) and a pair of separators (first separator, second separator) that sandwich the MEA. The MEA includes a solid polymer electrolyte membrane, an anode electrode, and a cathode electrode. The solid polymer electrolyte membrane is made of a polymer ion exchange membrane. The anode electrode is disposed on one side of the solid polymer electrolyte membrane. The cathode electrode is disposed on the other side of the solid polymer electrolyte membrane.

[0003] A plurality of protrusions are formed on both sides of each separator. As a result, a flow path for flowing a fuel gas (fuel gas flow path) and a bead seal for sealing the flow path are formed between the MEA and the first separator. In addition, a flow path for flowing an oxidant gas (oxidant gas flow path) and a bead seal for sealing the flow path are formed between the MEA and the second separator. In addition, in two unit cells adjacent to each other, a flow path for flowing a cooling medium (cooling medium flow path) is formed between the first separator of one unit cell and the second separator of the other unit cell.

[0004] Patent Document 1 discloses a separator for applying a uniform pressure load to a bead seal. The separator in Patent Document 1 has a protrusion between the bead seal surrounding the communication hole and the bead seal formed on the periphery of the separator. The height of the protrusion is lower than the height of the bead seal. With this structure, when the bead seal is compressed, the protrusion absorbs the displacement of the bead seal. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-136176 A Summary of the Invention [Problem to be solved by the invention]

[0006] For example, when an impact load acts in the stacking direction on a stack of unit cells due to a collision of a fuel cell vehicle, the bead seal is compressed and deformed. If the bead seal is significantly deformed, gas may leak from the flow path that the bead seal encloses.

[0007] The present invention aims to solve the above-mentioned problems. [Means for solving the problem]

[0008] An aspect of the present invention is a fuel cell stack in which unit cells each having a membrane electrode assembly and a pair of separators sandwiching the membrane electrode assembly are stacked, each of the pair of separators having a flow path convex portion protruding toward the membrane electrode assembly, a reactant gas flow path for flowing a reactant gas along an electrode surface of the membrane electrode assembly, a communication hole penetrating the separator in the thickness direction for flowing the reactant gas, a feed convex portion protruding toward the membrane electrode assembly, a plurality of feeds communicating the reactant gas flow path and the communication hole, and a bead seal protruding toward the membrane electrode assembly and sealing the reactant gas flow path and a space between the feed and the membrane electrode assembly, wherein a tightening load in the stacking direction is applied to a stack consisting of a plurality of the unit cells, so that the bead seal of each of the separators is compressed, and the height of the bead seal in the stacking direction after compression is lower than the height of the bead seal in the stacking direction before compression, and the height of the feed convex portion in the stacking direction is lower than the height of the bead seal in the stacking direction after compression. Effect of the Invention

[0009] According to the present invention, deformation of the bead seal can be suppressed. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of a fuel cell stack. [Diagram 2] FIG. 2 is an exploded perspective view of the fuel cell stack. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is an exploded perspective view illustrating a unit cell that constitutes the fuel cell stack. [Diagram 5] FIG. 5 is a plan view of the first separator as viewed from the MEA side. [Figure 6] FIG. 6 is a plan view of the second separator as viewed from the MEA side. [Figure 7] FIG. 7 is a plan view of the first separator as viewed from the opposing second separator side. [Figure 8] FIG. 8 is a plan view of the second separator as viewed from the opposing first separator side. [Figure 9] Fig. 9A is a schematic cross-sectional view of an outer bead seal perpendicular to a separator, and Fig. 9B is a schematic cross-sectional view of the outer bead seal, the feed protrusion, and the flow path protrusion perpendicular to the separator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [1 Configuration of fuel cell stack 10] 1 and 2, the fuel cell stack 10 includes a stack 14 in which a plurality of unit cells 12 are stacked in a first direction (the direction of arrow A). The fuel cell stack 10 is used, for example, as a fuel cell vehicle, a power generation facility, etc.

[0012] [1-1 Peripheral configuration of laminate 14] At a first end of the fuel cell stack 10 in the direction of arrow A1, a terminal plate 16a, an insulator 18a, and an end plate 20a are sequentially arranged outward (in the direction of arrow A1) (see FIG. 2). At a second end of the fuel cell stack 10 in the direction of arrow A2, a terminal plate 16b, an insulator 18b, and an end plate 20b are sequentially arranged outward (in the direction of arrow A2).

[0013] The terminal plates 16a and 16b are made of a conductive material. The insulators 18a and 18b are made of an insulating material. As shown in FIG. 2, a recess 22a that opens toward the laminate 14 is formed in the center of the insulator 18a. Similarly, a recess 22b that opens toward the laminate 14 is formed in the center of the insulator 18b. The terminal plate 16a is accommodated in the recess 22a. The terminal plate 16b is accommodated in the recess 22b. The laminate 14 is located between the insulators 18a and 18b.

[0014] As shown in FIG. 1, the end plates 20a, 20b are formed in a rectangular shape having long sides extending in a second direction (arrow B direction) and short sides extending in a third direction (arrow C direction). The first direction, the second direction, and the third direction are perpendicular to each other. A connecting bar 24 is disposed between each side of the end plates 20a, 20b. One end of each connecting bar 24 is fixed to the inner surface of the end plate 20a via a bolt 26. The other end of each connecting bar 24 is fixed to the inner surface of the end plate 20b via a bolt 26. As a result, a tightening load is applied to the stack 14 in the stacking direction (arrow A direction).

[0015] The insulator 18a and the end plate 20a are provided at first ends in the direction of arrow B1 with an oxidant gas inlet manifold 34a, a coolant inlet manifold 36a, and a fuel gas outlet manifold 38b. The insulator 18a and the end plate 20a are provided at second ends in the direction of arrow B2 with a fuel gas inlet manifold 38a, a coolant outlet manifold 36b, and an oxidant gas outlet manifold 34b.

[0016] [1-2 Configuration of the laminate 14 and unit cell 12] 3 and 4, each unit cell 12 constituting the laminate 14 has a membrane electrode assembly 28 (hereinafter also referred to as "MEA 28") and a pair of separators (a first separator 30 and a second separator 32). The first separator 30 and the second separator 32 sandwich the MEA 28. The first separator 30 and the second separator 32 are made of a thin metal plate such as a steel plate, a stainless steel plate, an aluminum plate, a plated steel plate, or the like. The surface of the thin metal plate may be subjected to a surface treatment for corrosion prevention.

[0017] In two adjacent unit cells 12, the first separator 30 of one unit cell 12 and the second separator 32 of the other unit cell 12 are bonded to each other. The bonded body consisting of the first separator 30 and the second separator 32 is called a bonded separator 33. In other words, the laminate 14 is also a structure in which the MEA 28 is sandwiched between two bonded separators 33.

[0018] As shown in FIG. 2, an oxidant gas inlet manifold 34a, a coolant inlet manifold 36a, and a fuel gas outlet manifold 38b are provided at a first end of the unit cell 12 in the direction of arrow B1. The oxidant gas inlet manifolds 34a of each unit cell 12 are arranged in the direction of arrow A and communicate with each other. The oxidant gas inlet manifold 34a of the stack 14 communicates with the oxidant gas inlet manifolds 34a of the insulator 18a and the end plate 20a. The coolant inlet manifolds 36a of each unit cell 12 are arranged in the direction of arrow A and communicate with each other. The coolant inlet manifold 36a of the stack 14 communicates with the coolant inlet manifold 36a of the insulator 18a and the end plate 20a. The fuel gas outlet manifolds 38b of each unit cell 12 are arranged in the direction of arrow A and communicate with each other. The fuel gas discharge passage 38b of the stack 14 communicates with the fuel gas discharge passage 38b of the insulator 18a and the end plate 20a.

[0019] As shown in FIG. 2, a fuel gas inlet manifold 38a, a coolant outlet manifold 36b, and an oxidant gas outlet manifold 34b are provided at a second end of the unit cell 12 in the direction of arrow B2. The fuel gas inlet manifolds 38a of each unit cell 12 are arranged in the direction of arrow A and communicate with each other. The fuel gas inlet manifold 38a of the stack 14 communicates with the fuel gas inlet manifold 38a of the insulator 18a and the end plate 20a. The coolant outlet manifolds 36b of each unit cell 12 are arranged in the direction of arrow A and communicate with each other. The coolant outlet manifold 36b of the stack 14 communicates with the coolant outlet manifold 36b of the insulator 18a and the end plate 20a. The oxidant gas outlet manifolds 34b of each unit cell 12 are arranged in the direction of arrow A and communicate with each other. The oxidant gas discharge passage 34b of the stack 14 communicates with the oxidant gas discharge passage 34b of the insulator 18a and the end plate 20a.

[0020] [1-2-1 Configuration of Membrane Electrode Assembly 28 (MEA 28)] 3, each MEA 28 has an electrolyte membrane 40, an anode electrode 42, and a cathode electrode 44. A resin film (not shown) is provided on the outer periphery of the electrolyte membrane 40. The anode electrode 42 and the cathode electrode 44 sandwich the electrolyte membrane 40.

[0021] The electrolyte membrane 40 is, for example, a solid polymer electrolyte membrane (cation exchange membrane). The solid polymer electrolyte membrane is, for example, a thin film of perfluorosulfonic acid containing water. The electrolyte membrane 40 is, for example, a fluorine-based electrolyte. film In addition, a HC (hydrocarbon) electrolyte membrane can be used.

[0022] The anode electrode 42 and the cathode electrode 44 each have a gas diffusion layer (not shown) and an electrode catalyst layer (not shown). The gas diffusion layer is made of carbon paper or the like. The electrode catalyst layer is formed by uniformly applying porous carbon particles having a platinum alloy supported on the surface of the gas diffusion layer. The electrode catalyst layer is formed on both sides of the electrolyte membrane 40.

[0023] [1-2-2 Configuration of surface 30a of first separator 30] As shown in Fig. 4, the first separator 30 covers the cathode electrode 44 of the MEA 28. The first separator 30 has a front surface 30a facing the MEA 28 and a back surface 30b facing the second separator 32. A plurality of protrusions are formed on each of the front surface 30a and the back surface 30b by press molding. The protrusions on the front surface 30a that protrude toward the MEA 28 are referred to as inward protrusions 46a. The protrusions on the back surface 30b that protrude toward the second separator 32 are referred to as outward protrusions 46b.

[0024] 4 and 5, two oxidant gas feeds 48a, 48b and an oxidant gas flow field 50 are formed on the surface 30a of the first separator 30 by a plurality of inward protrusions 46a. The oxidant gas feed 48a flows the oxidant gas from the oxidant gas inlet manifold 34a to the oxidant gas flow field 50. The oxidant gas feed 48b flows the oxidant gas from the oxidant gas flow field 50 to the oxidant gas outlet manifold 34b. The oxidant gas flow field 50 is located between the oxidant gas feeds 48a and 48b and faces the cathode 44. The two oxidant gas feeds 48a, 48b and the oxidant gas flow field 50 communicate between the oxidant gas inlet manifold 34a and the oxidant gas outlet manifold 34b.

[0025] Of the multiple inward protrusions 46a, the inward protrusion 46a that forms the oxidant gas feed 48a is referred to as a feed protrusion 52a. Each feed protrusion 52a extends linearly from the oxidant gas inlet manifold 34a to a first end (the end in the direction of arrow B1) of the oxidant gas flow field 50. A feed groove 54a is located adjacent to the feed protrusion 52a.

[0026] Of the multiple inward protrusions 46a, the inward protrusion 46a that forms the oxidant gas feed 48b is referred to as a feed protrusion 52b. Each feed protrusion 52b extends linearly from the oxidant gas discharge passage 34b to a second end (the end in the direction of arrow B2) of the oxidant gas flow field 50. A feed groove 54b is located between two adjacent feed protrusions 52b.

[0027] Of the multiple inward protrusions 46a, the inward protrusions 46a that form the oxidant gas flow path 50 are referred to as flow path protrusions 56. In a plan view of the first separator 30, each flow path protrusion 56 is wavy and extends along the direction of arrow B. A flow path groove 58 is located between two adjacent flow path protrusions 56. Each flow path groove 58 is also wavy. Each flow path protrusion 56 contacts the cathode electrode 44 of the MEA 28 located in the direction of arrow A2. The multiple flow path grooves 58 become paths through which the oxidant gas flows.

[0028] Each of the communication holes (oxidant gas inlet manifold 34a, coolant inlet manifold 36a, fuel gas outlet manifold 38b, fuel gas inlet manifold 38a, coolant outlet manifold 36b, and oxidant gas outlet manifold 34b) is surrounded by an inward protrusion 46a. These inward protrusions 46a are referred to as communication hole bead seals 60. Each communication hole bead seal 60 contacts the MEA 28 located in the direction of arrow A2. As a result, the multiple communication hole bead seals 60 seal the multiple communication holes.

[0029] The communication hole bead seal 60 surrounding the oxidant gas inlet manifold 34a has a plurality of flow paths (not shown) that connect the oxidant gas inlet manifold 34a to the oxidant gas feed 48a. Similarly, the communication hole bead seal 60 surrounding the oxidant gas outlet manifold 34b has a plurality of flow paths (not shown) that connect the oxidant gas outlet manifold 34b to the oxidant gas feed 48b.

[0030] An area including the two oxidant gas feeds 48a, 48b, the oxidant gas flow field 50, the oxidant gas inlet manifold 34a, the fuel gas outlet manifold 38b, the fuel gas inlet manifold 38a, and the oxidant gas outlet manifold 34b is surrounded by an inward protrusion 46a. This inward protrusion 46a is referred to as an outer bead seal 62. The outer bead seal 62 comes into contact with the MEA 28 located in the direction of arrow A2. As a result, the outer bead seal 62 seals the area through which the oxidant gas flows between the surface 30a and the MEA 28 (the area including the two oxidant gas feeds 48a, 48b, the oxidant gas flow field 50, the oxidant gas inlet manifold 34a, and the oxidant gas outlet manifold 34b).

[0031] [1-2-3 Configuration of surface 32a of second separator 32] As shown in Fig. 4, the second separator 32 covers the anode electrode 42 of the MEA 28. The second separator 32 has a front surface 32a facing the MEA 28 and a back surface 32b facing the first separator 30. A plurality of protrusions are formed on each of the front surface 32a and the back surface 32b by press molding. The protrusions on the front surface 32a that protrude toward the MEA 28 are referred to as inward protrusions 66a. The protrusions on the back surface 32b that protrude toward the first separator 30 are referred to as outward protrusions 66b.

[0032] 4 and 6, two fuel gas feeds 68a, 68b and a fuel gas flow passage 70 are formed on the surface 32a of the second separator 32 by a plurality of inward protrusions 66a. The fuel gas feed 68a flows the fuel gas from the fuel gas inlet manifold 38a to the fuel gas flow passage 70. The fuel gas feed 68b flows the fuel gas from the fuel gas flow passage 70 to the fuel gas outlet manifold 38b. The fuel gas flow passage 70 is located between the fuel gas feeds 68a and 68b and faces the anode 42. The two fuel gas feeds 68a, 68b and the fuel gas flow passage 70 communicate between the fuel gas inlet manifold 38a and the fuel gas outlet manifold 38b.

[0033] Of the multiple inward protrusions 66a, the inward protrusions 66a that form the fuel gas feed 68a are referred to as feed protrusions 72a. Each feed protrusion 72a extends linearly from the fuel gas inlet passage 38a to a first end (the end in the direction of arrow B2) of the fuel gas flow field 70. between The feed groove 74a is located in the groove.

[0034] Of the multiple inward protrusions 66a, the inward protrusion 66a that forms the fuel gas feed 68b is referred to as a feed protrusion 72b. Each feed protrusion 72b extends linearly from the fuel gas discharge passage 38b to a second end (the end in the direction of arrow B1) of the fuel gas flow field 70. A feed groove 74b is located between two adjacent feed protrusions 72b.

[0035] Of the multiple inward protrusions 66a, the inward protrusions 66a that form the fuel gas flow passage 70 are referred to as flow passage protrusions 76. In a plan view of the second separator 32, each flow passage protrusion 76 is wavy and extends along the direction of arrow B. A flow passage groove 78 is located between two adjacent flow passage protrusions 76. Each flow passage groove 78 is also wavy. Each flow passage protrusion 76 contacts the anode electrode 42 of the MEA 28 located in the direction of arrow A1. The multiple flow passage grooves 78 are fuel It becomes a passageway for gas to flow.

[0036] The waveforms of the flow passage convexities 76 and flow passage grooves 78 on the surface 32a of the second separator 32 and the waveforms of the flow passage convexities 56 and flow passage grooves 58 on the surface 30a of the first separator 30 differ in at least one of phase, period, and amplitude.

[0037] Each of the communication holes (fuel gas inlet manifold 38a, coolant outlet manifold 36b, oxidant gas outlet manifold 34b, oxidant gas inlet manifold 34a, coolant inlet manifold 36a, and fuel gas outlet manifold 38b) is surrounded by an inward protrusion 66a. These inward protrusions 66a are referred to as communication hole bead seals 80. Each communication hole bead seal 80 contacts the MEA 28 located in the direction of arrow A1. As a result, the multiple communication hole bead seals 80 seal the multiple communication holes.

[0038] The communication hole bead seal 80 surrounding the fuel gas inlet manifold 38a has multiple flow passages (not shown) that connect the fuel gas inlet manifold 38a to the fuel gas feed 68a. Similarly, the communication hole bead seal 80 surrounding the fuel gas outlet manifold 38b has multiple flow passages (not shown) that connect the fuel gas outlet manifold 38b to the fuel gas feed 68b.

[0039] An area including the two fuel gas feeds 68a, 68b, the fuel gas flow channel 70, the fuel gas inlet manifold 38a, the oxidant gas outlet manifold 34b, the oxidant gas inlet manifold 34a, and the fuel gas outlet manifold 38b is surrounded by an inward protrusion 66a. This inward protrusion 66a is referred to as an outer bead seal 82. The outer bead seal 82 comes into contact with the MEA 28 located in the direction of arrow A1. As a result, the outer bead seal 82 seals the area through which fuel gas flows between the surface 32a and the MEA 28 (the area including the two fuel gas feeds 68a, 68b, the fuel gas flow channel 70, the fuel gas inlet manifold 38a, and the fuel gas outlet manifold 38b).

[0040] [1-2-4 Configuration of rear surface 30b and rear surface 32b] 7, on the back surface 30b of the first separator 30, the outer convex portion 46b is located behind the grooves (feed grooves 54a, 54b, flow path groove 58, etc.) on the front surface 30a. An outer groove 84 is located next to the outer convex portion 46b. The outer groove 84 is located behind the inner convex portion 46a (feed convex portions 52a, 52b, flow path convex portion 56, etc.) on the front surface 30a.

[0041] 8, on the back surface 32b of the second separator 32, the outer convex portion 66b is located behind the grooves (feed grooves 74a, 74b, flow path groove 78, etc.) on the front surface 32a. The outer groove 86 is located next to the outer convex portion 66b. The outer groove 86 is located behind the inner convex portion 66a (feed convex portions 72a, 72b, flow path convex portion 76, etc.) on the front surface 32a.

[0042] The waveform of the outer convex portion 46b located on the back side of the flow groove 58 of the first separator 30 and the waveform of the outer convex portion 66b located on the back side of the flow groove 78 of the second separator 32 differ in at least one of phase, period, and amplitude.

[0043] 4, the back surface 30b of the first separator 30 and the back surface 32b of the second separator 32 face each other, and some of the outer protrusions 46b and some of the outer protrusions 66b are welded to each other. Furthermore, the peripheral edge of the first separator 30 and the peripheral edge of the second separator 32 are welded to each other. Furthermore, the first separator 30 and the second separator 32 located around each communication hole are welded to each other. As a result, a coolant flow field 88 is formed between the back surface 30b of the first separator 30 and the back surface 32b of the second separator 32.

[0044] A portion of the outer protrusion 46b of the first separator 30 contacts a portion of the outer protrusion 66b of the second separator 32. A portion of the outer groove 84 of the first separator 30 overlaps a portion of the outer groove 86 of the second separator 32.

[0045] The communication hole bead seal 60 surrounding the coolant inlet manifold 36a of the first separator 30 has a plurality of flow passages (not shown) that connect the coolant inlet manifold 36a to the outer groove 84. Similarly, the communication hole bead seal 80 surrounding the coolant inlet manifold 36a of the second separator 32 has a plurality of flow passages (not shown) that connect the coolant inlet manifold 36a to the outer groove 86.

[0046] The communication hole bead seal 60 surrounding the coolant outlet communication hole 36b of the first separator 30 has a plurality of flow passages (not shown) that connect the coolant outlet communication hole 36b to the outer groove 84. Similarly, the communication hole bead seal 80 surrounding the coolant outlet communication hole 36b of the second separator 32 has a plurality of flow passages (not shown) that connect the coolant outlet communication hole 36b to the outer groove 86.

[0047] [2 Operation of fuel cell stack 10] 1, an oxidant gas (e.g., oxygen-containing gas) is supplied to an oxidant gas inlet passage 34a in the end plate 20a. A fuel gas (e.g., hydrogen-containing gas) is supplied to a fuel gas inlet passage 38a in the end plate 20a. A coolant (e.g., pure water) is supplied to a coolant inlet passage 36a in the end plate 20a. In each unit cell 12, each fluid flows as follows.

[0048] As shown in FIG. 4, the oxidant gas supplied to the oxidant gas inlet passage 34a flows into the oxidant gas feed 48a. The oxidant gas that flows into the oxidant gas feed 48a is evenly distributed to the multiple flow grooves 58 of the oxidant gas flow field 50 and flows therein. In the oxidant gas flow field 50, the oxidant gas is supplied to the cathode electrode 44 of the MEA 28. Meanwhile, the fuel gas supplied to the fuel gas inlet passage 38a flows into the fuel gas feed 68a. The fuel gas that flows into the fuel gas feed 68a is evenly distributed to the multiple flow grooves 78 of the fuel gas flow field 70 and flows therein. In the fuel gas flow field 70, the fuel gas is supplied to the anode electrode 42 of the MEA 28. In the MEA 28, a chemical reaction occurs between the oxidant gas supplied to the cathode electrode 44 and the fuel gas supplied to the anode electrode 42, generating electricity. Water is generated as a result of the chemical reaction.

[0049] Next, the unreacted oxidant gas and water flow from the oxidant gas flow field 50 into the oxidant gas feed 48b. The oxidant gas that flowed into the oxidant gas feed 48b then flows out to the oxidant gas outlet passage 34b. Meanwhile, the unreacted fuel gas flows from the fuel gas flow field 70 into the fuel gas feed 68b. The fuel gas that flowed into the fuel gas feed 68b then flows out to the fuel gas outlet passage 38b.

[0050] The cooling medium supplied to the cooling medium inlet manifold 36a flows into the cooling medium flow path 88. In the cooling medium flow path 88, the cooling medium cools the MEA 28 located in the direction of arrow A. The cooling medium in the cooling medium flow path 88 flows out to the cooling medium outlet manifold 36b.

[0051] [3 Height of inner protrusions 46a, 66a] 9A and 9B, the height of each of the inward protrusions 46a, 66a of the first separator 30 and the second separator 32 in the stacking direction (arrow A direction) will be described. Among the inward protrusions 46a, 66a, each bead seal (communicating hole bead seals 60, 80 and outer bead seals 62, 82) has the same height. Here, the height of the outer bead seal 62 of the first separator 30 will be described, and descriptions of the height of the communicating hole bead seal 60 of the first separator 30, the height of the communicating hole bead seal 80 of the second separator 32, and the height of the outer bead seal 82 of the second separator 32 will be omitted.

[0052] As shown in FIG. 1, a plurality of connecting bars 24 are fixed to two end plates 20a, 20b with bolts 26, and thereby a clamping load is applied to the stack 14 in the stacking direction (the direction of arrow A). As shown in FIG. 9A, the outer bead seal 62 of the first separator 30 has a height Hb1 before the clamping load in the stacking direction is applied to the stack 14. When the clamping load in the stacking direction is applied to the stack 14, the outer bead seal 62 of the first separator 30 is compressed in the stacking direction by the MEA 28 and the second separator 32. As shown in FIG. 9B, the compressed outer bead seal 62 has a height Hb2. The height Hb2 after compression is lower than the height Hb1 before compression.

[0053] On the other hand, the flow passage protrusion 56 of the first separator 30 has a height Hp. The height Hp of the flow passage protrusion 56 does not change before and after a tightening load in the stacking direction is applied to the stack 14. The height Hp of the flow passage protrusion 56 is the same as the height Hb2 of the compressed outer bead seal 62.

[0054] The feed protrusions 52a, 52b of the first separator 30 have a height Hf. The height Hf of the feed protrusions 52a, 52b does not change before and after a fastening load in the stacking direction is applied to the stack 14. The height Hf of the feed protrusions 52a, 52b is lower than the height Hb2 of the compressed outer bead seal 62. In other words, the height Hb2 of the compressed outer bead seal 62 is higher than the height Hf of the feed protrusions 52a, 52b. For this reason, a gap 92 is formed between the tops 90 of the feed protrusions 52a, 52b and the MEA 28. In other words, the tops 90 of the feed protrusions 52a, 52b do not contact the MEA 28 when a fastening load is applied to the stack 14.

[0055] For example, when an impact load in the direction of arrow A acts on the fuel cell stack 10, such as a collision of a fuel cell vehicle, the stack 14 is pressed in the stacking direction (the direction of arrow A). Furthermore, when the impact load exceeds the load capacity of the outer bead seal 62, the stack 14 is compressed in the stacking direction. Then, the outer bead seal 62 is further compressed from the height Hb2. When the height of the outer bead seal 62 reaches the height Hf of the feed protrusions 52a, 52b, a resistance force against the compression of the outer bead seal 62 acts by the feed protrusions 52a, 52b. In other words, when a load larger than the tightening load is applied in the stacking direction of the stack 14 due to an impact load or the like, the feed protrusions 52a, 52b come into contact with the MEA 28. If the impact load acting on the fuel cell stack 10 is not extremely large, the compression of the outer bead seal 62 can be stopped at this stage. In this way, according to this embodiment, the deformation of the outer bead seal 62 can be suppressed. Therefore, according to this embodiment, the outer bead seal 62 can maintain the sealing function of the oxidant gas flow field 50. As a result, according to this embodiment, leakage of the oxidant gas from the oxidant gas flow field 50 can be prevented.

[0056] Furthermore, in this embodiment, the existing feed protrusions 52a, 52b are utilized as a structure for suppressing deformation of the outer bead seal 62. Therefore, according to this embodiment, it is not necessary to provide new protrusions. Therefore, the processing and structure of the first separator 30 can be simplified.

[0057] The above description also applies to each of the communication hole bead seals 60 of the first separator 30, each of the communication hole bead seals 80 of the second separator 32, and the outer bead seal 82 of the second separator 32.

[0058] [4 Inventions Obtained from the Embodiments] The invention that can be understood from the above embodiment will be described below.

[0059] An aspect of the present invention is a fuel cell stack (10) in which unit cells (12) each having a membrane electrode assembly (28) and a pair of separators (30, 32) sandwiching the membrane electrode assembly are stacked, and each of the pair of separators has a flow path protrusion (56, 76) protruding toward the membrane electrode assembly, and has reactant gas flow paths (50, 70) for flowing a reactant gas along an electrode surface of the membrane electrode assembly, communication holes (34a, 34b, 38a, 38b) penetrating the separators in the thickness direction and for flowing the reactant gas, and feed protrusions (52a, 52b, 72a, 72b) protruding toward the membrane electrode assembly, and the reactant gas flow paths and the communication holes and a bead seal (60, 62, 80, 82) protruding toward the membrane electrode assembly and sealing the reactant gas flow path and the space between the feed and the membrane electrode assembly, wherein a tightening load in a stacking direction is applied to a stack (14) consisting of a plurality of the unit cells, whereby the bead seal of each of the separators is compressed, and the height of the bead seal in the stacking direction after compression is lower than the height of the bead seal in the stacking direction before compression, and the height of the feed convex portion in the stacking direction is lower than the height of the bead seal in the stacking direction after compression.

[0060] When the outer bead seal is compressed and its height reaches the height of the feed protrusion, the feed protrusion applies a resistance to the compression of the outer bead seal. If the impact load acting on the fuel cell stack is not extremely large, the compression of the outer bead seal can be stopped at this stage. In this manner, the above configuration can suppress deformation of the outer bead seal. Therefore, the above configuration can allow the bead seal to maintain its sealing function for the reactant gas flow path. As a result, this embodiment can prevent gas leakage from the reactant gas flow path. According to this embodiment, there is no need to provide a new protrusion. Therefore, the processing and structure of the separator can be simplified.

[0061] In the above aspect, the height of the feed protrusion in the stacking direction does not change before and after the tightening load in the stacking direction is applied to the stack.

[0062] In the above aspect, the feed protrusion does not come into contact with the membrane electrode assembly after the clamping load in the stacking direction is applied to the stack.

[0063] In the above aspect, The laminate When a load larger than the fastening load is applied in the stacking direction, the feed protrusion may come into contact with the membrane electrode assembly.

[0064] The present invention is not limited to the above disclosure, and various configurations can be adopted without departing from the gist of the present invention. [Explanation of symbols]

[0065] 10...Fuel cell stack 12...Unit cell 14...Laminate 28...Membrane electrode assembly 30…First separator (separator) 32...Second separator (separator) 34a...oxidizer gas inlet passage (passage) 34b...Oxidant gas outlet communication hole (communication hole) 38a...Fuel gas inlet passage (passage) 38b...Fuel gas outlet communication hole (communication hole) 48a, 48b...oxidant gas feed (feed) 50...Oxidant gas flow path (reactant gas flow path) 52a, 52b, 72a, 72b...feed protrusions 56, 76...Flow passage convex part 60, 80...Communicating hole bead seal (bead seal) 62, 82...Outer bead seal (bead seal) 68a, 68b...Fuel gas feed (feed) 70...Fuel gas flow path (reactant gas flow path)

Claims

1. A fuel cell stack in which unit cells each having a membrane electrode assembly and a pair of separators sandwiching the membrane electrode assembly are stacked, Each of the pair of separators is a first flow path having a first protrusion protruding toward the membrane electrode assembly, facing an electrode surface of the membrane electrode assembly, and allowing a reactant gas to flow along the electrode surface of the membrane electrode assembly; a communication hole penetrating the separator in a thickness direction and allowing the reaction gas to flow; a plurality of second flow paths each having a second protrusion protruding toward the membrane electrode assembly, the second flow paths being formed between the first flow paths and the communication holes and communicating between the first flow paths and the communication holes; a bead seal protruding toward the membrane electrode assembly and sealing a space between the first flow path and the membrane electrode assembly, and between the second flow path and the membrane electrode assembly; having a clamping load is applied in a stacking direction to a stack of a plurality of unit cells, whereby the bead seal of each of the separators is compressed; A height of the bead seal in the stacking direction after compression is lower than a height of the bead seal in the stacking direction before compression, a height of the second protrusion in the stacking direction is smaller than a height of the bead seal after compression in the stacking direction.

2. 2. The fuel cell stack of claim 1, A fuel cell stack, wherein a height of the second protrusion in the stacking direction remains unchanged before and after the tightening load in the stacking direction is applied to the stack body.

3. 2. The fuel cell stack of claim 1, the second protrusion does not contact the membrane electrode assembly after the clamping load in the stacking direction is applied to the stack.

4. 4. The fuel cell stack of claim 3, a second protrusion contacting the membrane electrode assembly when a load greater than the clamping load is applied to the stack in the stacking direction.

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