Cell stack of fuel battery

Abstract

To prevent a situation where, when fluid flows in holes of adjacent separators, welded parts for welding the separators to each other and surrounding the periphery of the holes are peeled off by force that acts in a direction to separate the separators from each other.SOLUTION: A fuel battery cell is obtained by sandwiching a membrane electrode gas diffusion layer joined body with plate-like separators 14 from both sides in a thickness direction. The separator 14 has holes 16 for causing fluid to flow to the membrane electrode gas diffusion layer joined body, which is formed to penetrate the separator 14 in the thickness direction. The adjacent separators 14 of the fuel battery cell stacked in the thickness direction are provided with welded parts 18 for welding the separators to each other and surrounding the periphery of the holes 16. The holes 16 of the separator 14 are formed in a rectangular shape. The welded part 18 includes long distance parts 19 located at portions corresponding to the long sides of the hole 16, and a plurality of short distance parts 20 located at portions corresponding to the long sides of the hole, the portions closer to the hole 16 than the long distance parts 19.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] As shown in Patent Document 1, a cell stack of a fuel cell is formed by stacking fuel cells in the thickness direction. A fuel cell is formed by sandwiching a membrane electrode gas diffusion layer laminate from both sides in the thickness direction with plate-shaped separators. The separator is formed with holes for flowing fluids such as fuel gas such as hydrogen and oxidation gas such as air through the membrane electrode gas laminate so as to penetrate the separator in the thickness direction.

[0003] In the cell stack, between adjacent separators of the fuel cells stacked in the thickness direction, a welded portion is formed which is welded to each other so as to go around the periphery of the holes. This welding is for sealing around the holes. And through the holes between adjacent separators, fuel gas is flowed to the anode-side surface of the front and back surfaces of the membrane electrode gas diffusion layer laminate, and oxidation gas is flowed to the cathode-side surface. As a result, power generation is performed based on the reaction between the fuel gas and the oxidation gas in the membrane electrode gas diffusion layer laminate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, when a fluid such as fuel gas or oxidizing gas flows through the holes of the separator in the fuel cell, a force acts on the welded portion in a direction to separate the adjacent separators welded thereto based on the pressure of the fluid. When the hole is shaped to be long in a defined direction, this force is likely to be greater at the elongated portion, which is the portion corresponding to the longitudinal direction of the hole among the inner edges of the hole in the welded portion, than at other portions of the welded portion. Therefore, there is a risk that the welded separators will peel off at the elongated portion of the welded portion.

Means for Solving the Problem

[0006] Hereinafter, means for solving the above problems and their effects will be described. The cell stack of the fuel cell that solves the above problems includes a plurality of fuel cells stacked in the thickness direction. Each fuel cell has a membrane electrode gas diffusion layer assembly sandwiched between plate-shaped separators from both sides in the thickness direction. The separator is formed with holes for allowing a fluid to flow through the membrane electrode gas diffusion layer assembly so as to penetrate the separator in the thickness direction. A welded portion is formed between adjacent separators of the fuel cells stacked in the thickness direction, which surrounds the periphery of the hole and is welded to each other. The hole of the separator is shaped to be long in a defined direction. The welded portion includes a remote portion at an elongated portion corresponding to the portion extending along the longitudinal direction of the hole among the inner edges of the hole, and a plurality of near portions closer to the hole than the remote portion at the elongated portion.

[0007] According to the above configuration, based on the pressure of the fluid flowing through the holes of the separator in the fuel cell, a force acting in the direction of separating the separators from each other acts on the welded portion where adjacent separators are welded to surround the periphery of the hole. This force tends to be larger at the extended portion of the welded portion than at other portions of the welded portion. To address this, the welded portion includes the following long-distance portion and a plurality of short-distance portions. That is, the long-distance portion and the plurality of short-distance portions are formed at the extended portion of the welded portion. And the plurality of short-distance portions are formed at positions closer to the hole than the long-distance portion. At the extended portion of the welded portion, the closer the position is to the hole, the greater the force in the direction of separating the separators from each other. Therefore, when a plurality of short-distance portions are formed at the extended portion of the welded portion, the plurality of short-distance portions disperse and receive the force, thereby suppressing the local increase in the force at the extended portion of the welded portion. Accordingly, it is possible to suppress the separation of the welded separators from each other due to the action of the force at the extended portion of the welded portion.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

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Figure 8

Figure 9

Figure 10

Best Mode for Carrying Out the Invention

[0009] Hereinafter, an embodiment of a fuel cell stack will be described with reference to FIGS. 1 to 3. FIG. 1 shows a fuel cell 11 for forming a fuel cell stack. The fuel cell 11 includes a resin plate 12, a membrane electrode gas diffusion layer laminate 13, and a separator 14. The resin plate 12 is formed in a rectangular frame shape. The outer edge of the membrane electrode gas diffusion layer laminate 13 is joined to the resin plate 12. The resin plate 12 and the membrane electrode gas diffusion layer laminate 13 are sandwiched by the separator 14 from both sides in their thickness directions. The separator 14 is formed in a rectangular plate shape from a metal such as stainless steel, titanium, and aluminum.

[0010] The fuel cell stack is formed by stacking the above-described fuel cells 11 in the thickness direction. A plurality of holes 16 are formed in the resin plate 12 and the separator 14 of the fuel cell 11 so as to penetrate in the thickness direction. Among the plurality of holes 16, three are located at one end in the long side direction of the fuel cell 11, and the other three are located at the other end in the long side direction of the fuel cell 11. The plurality of holes 16 are grouped in pairs, one from one of the long side directions of the fuel cell 11 and one from the other. Each pair of holes 16 is used for flowing a fluid such as a fuel gas such as hydrogen, an oxidizing gas such as air, and a refrigerant such as cooling water. A seal member 17 is disposed between the separator 14 and the resin plate 12. The seal member 17 can be disposed on both the front and back surfaces in the thickness direction of the resin plate 12.

[0011] The seal member 17 disposed on the front surface side of the resin plate 12 surrounds a pair of two holes 16 located on one of the two diagonals of the resin plate 12 and the separator 14 and the anode side of the membrane electrode gas diffusion layer assembly 13. Thereby, it is possible to flow fuel gas through the pair of two holes 16 to the anode side of the membrane electrode gas diffusion layer assembly 13. Further, the seal member 17 disposed on the back surface side of the resin plate 12 surrounds a pair of two holes 16 located on the other diagonal of the resin plate 12 and the separator 14 and the cathode side of the membrane electrode gas diffusion layer assembly 13. Thereby, it is possible to flow oxidizing gas through the pair of two holes 16 to the cathode side of the membrane electrode gas diffusion layer assembly 13.

[0012] Figure 2 shows a state in which the separator 14 located on the anode side of the membrane electrode gas diffusion layer assembly 13 among the separators 14 of the fuel cell 11 is viewed from the direction of arrow A in Figure 1. This separator 14 is adjacent to the separator 14 on the cathode side in another fuel cell 11 in contact with the fuel cell 11. Welding portions 18 are formed by welding the adjacent separators 14 to each other so as to go around the periphery of the holes 16. The welding portions 18 are formed around two sets of holes 16 located on the diagonal of the separator 14, and are not formed around the hole 16 located at the center in the short side direction of the separator 14. Further, the outer edges of the adjacent separators 14 are welded to each other. Thereby, it is possible to flow a refrigerant through the hole 16 located at the center in the short side direction of the separator 14 between the adjacent separators 14.

[0013] In the cell stack of the fuel cell 11, fuel gas is flowed on the anode side of the membrane electrode gas diffusion layer assembly 13, and oxidizing gas is flowed on the cathode side of the membrane electrode gas diffusion layer assembly 13. Thus, when fuel gas and oxidizing gas are flowed on the anode side and the cathode side of the membrane electrode gas diffusion layer assembly 13, power generation is performed based on the reaction of these fuel gas and oxidizing gas in the membrane electrode gas diffusion layer assembly 13. In order to suppress the temperature rise of the cell stack due to such power generation, a refrigerant is flowed between the separators 14 of adjacent fuel cells 11. The cell stack is cooled by this refrigerant.

[0014] <Details of the welded portion 18> As shown in FIG. 3, the hole 16 of the separator 14 is formed in a shape that becomes long in a defined direction, more specifically, in a rectangular shape. The welded portion 18 includes a long-distance portion 19 and a plurality of short-distance portions 20. The long-distance portion 19 is at a long extension portion corresponding to a portion extending along the longitudinal direction, that is, the long side direction, of the inner edge of the hole 16 in the welded portion 18. The short-distance portion 20 is at a location closer to the hole 16 than the long-distance portion 19 in the long extension portion of the welded portion 18. The short-distance portion 20 is formed by curving a portion different from the long-distance portion 19 in the long extension portion of the welded portion 18 in a direction approaching the hole 16.

[0015] More specifically, the long-distance portion 19 and the short-distance portion 20 are formed by curving the long extension portion of the welded portion 18 in a wave shape. The long-distance portion 19 is formed at a portion protruding in a direction away from the hole 16 among the wave-shaped long extension portions in the welded portion 18. The short-distance portion 20 is formed at a portion protruding in a direction approaching the hole 16 among the wave-shaped long extension portions in the welded portion 18.

[0016] Moreover, the short-distance portions 20 are formed on both sides of the elongated portion of the welded portion 18, sandwiching the position corresponding to the center of the elongated portion. The welded portion 18 also has a short extension portion that extends in a direction different from the elongated portion and is connected to the elongated portion. This short extension portion extends along the short side of the hole 16. The elongated portion of the welded portion 18 is connected to the short extension portion via the long-distance portion 19. Specifically, the long-distance portion 19 intersects the short extension portion, thereby connecting the elongated portion and the short extension portion in the welded portion 18.

[0017] The short extension portion of the welded portion 18 is also curved in a wave shape. The pitch of the wave-shaped curvature in the elongated portion of the welded portion 18 is shorter than the pitch of the wave-shaped curvature in the short extension portion.

[0018] Next, the operation and effect of the cell stack of the fuel cell in the present embodiment will be described. (1) In the welded portion 18 where adjacent separators 14 are welded to surround the periphery of the hole 16, a force in the direction of separating the separators 14 acts based on the pressure of the fluid flowing through the hole 16. This force is more likely to be larger in the elongated portion of the welded portion 18 than in the short extension portion which is other parts of the welded portion 18. In other words, this force is more likely to be larger at the location corresponding to the long side of the hole 16 than at the location corresponding to the short side of the hole 16 in the welded portion 18. To address this, the welded portion 18 includes the following long-distance portion 19 and a plurality of short-distance portions 20. That is, the long-distance portion 19 and the plurality of short-distance portions 20 are formed in the elongated portion which is the location corresponding to the long side direction of the hole 16 in the welded portion 18. And the plurality of short-distance portions 20 are formed at locations closer to the hole 16 than the long-distance portion 19. In the elongated portion of the welded portion 18, the closer to the hole 16, the larger the force in the direction of separating the separators 14. Therefore, when a plurality of short-distance portions 20 are formed in the elongated portion of the welded portion 18, the plurality of short-distance portions 20 disperse and receive the force, thereby suppressing the local increase in the force in the elongated portion of the welded portion 18. Accordingly, it is possible to suppress the separation of the welded separators 14 from each other due to the action of the force in the elongated portion of the welded portion 18.

[0019] (2) The short-distance portion 20 is formed by curving a portion of the elongated portion of the welded portion 18, which is different from the long-distance portion 19, in a direction approaching the hole 16. As a result, a plurality of short-distance portions 20 that are connected to the long-distance portion 19 can be formed at the elongated portion of the welded portion 18.

[0020] (3) By curving the elongated portion of the welded portion 18 in a wave shape, the long-distance portion 19 and a plurality of short-distance portions 20 are formed at that portion. Therefore, it becomes easy to form a plurality of short-distance portions 20 at the elongated portion of the welded portion 18.

[0021] (4) The force that attempts to separate the separators 14 acting on the elongated portion of the welded portion 18 tends to be large at a position corresponding to the center of the elongated portion. The plurality of short-distance portions 20 at the elongated portion of the welded portion 18 are respectively formed on both sides sandwiching the position corresponding to the center of the elongated portion. Therefore, when receiving the force by dispersing it with the plurality of short-distance portions 20, each short-distance portion 20 can receive the force evenly. As a result, it is possible to more effectively suppress the local increase in the force at the elongated portion of the welded portion 18.

[0022] (5) The elongated portion of the welded portion 18 is connected to the short elongated portion of the welded portion 18 via the long-distance portion 19. Therefore, it is possible to suppress the portion where the elongated portion and the short elongated portion of the welded portion 18 intersect from becoming a shape that is prone to stress concentration when the force that attempts to separate the separators 14 acts. Accordingly, it is possible to suppress the welding from peeling off in the direction in which the separators 14 separate due to the stress concentration at the portion where the portion corresponding to the long side of the hole 16 and the portion corresponding to the short side of the hole 16 in the welded portion 18 intersect.

[0023] Note that the above embodiment can be modified as follows, for example. The above embodiment and the following modification examples can be implemented in combination with each other within a technically non-conflicting range. · Instead of crossing the above-mentioned long extension part and the above-mentioned short extension part of the welding part 18, the two parts may be connected by an R-shaped curved part protruding in a direction away from the hole 16.

[0024] · As shown in FIG. 4, the above-mentioned short extension part of the welding part 18, that is, the part corresponding to the short side of the hole 16, may be formed linearly. · As shown in FIG. 5, even when the above-mentioned short extension part of the welding part 18 is formed linearly, the part and the part corresponding to the long side of the hole 16 may be connected by an R-shaped curved part 21 protruding in a direction away from the hole 16.

[0025] · As shown in FIG. 6, a linear long-distance part 19 is formed at the above-mentioned long extension part of the welding part 18, that is, the part corresponding to the long side of the hole 16. Further, among the above-mentioned long extension parts of the welding part 18, a part different from the long-distance part 19 may be curved so as to protrude in a direction approaching the hole 16 to form a short-distance part 20.

[0026] · As shown in FIG. 7, a linear long-distance part 19 is formed at the part corresponding to the long side of the hole 16 in the welding part 18. Further, as the welding part 18, a plurality of short-distance parts 20 in which the separators 14 are spot-welded to each other at a position away from the long-distance part 19 in a direction approaching the hole 16 may be formed.

[0027] · As shown in FIG. 8, a linear long-distance part 19 is formed at the part corresponding to the long side of the hole 16 in the welding part 18. Further, as the welding part 18, short-distance parts 20 in which the separators 14 are welded to each other at a position away from the long-distance part 19 in a direction approaching the hole 16 so as to extend parallel to the long side of the hole 16 may be formed.

[0028] · The number of the short-distance parts 20 at the above-mentioned long extension part of the welding part 18 may be increased. In this case, the pitch of the wavy curve at the above-mentioned long extension part of the welding part 18 may be constant, or may be different between the part corresponding to the center of the long extension part and the part corresponding to the end.

[0029] If the pitch of the wavy curvature in the welded portion 18 is made different between the portion corresponding to the center of the elongated portion and the portion corresponding to the end, the following can be achieved. That is, when a force acts in a direction to separate the separators 14 based on the pressure of the fluid flowing through the holes 16, the adjustment range when adjusting the pitch so that the separators 14 are not peeled off from each other by that force can be widened.

[0030] · The pitch of the wavy curvature in the elongated portion of the welded portion 18 does not necessarily have to be shorter than the pitch of the wavy curvature in the short elongated portion. · As shown in FIGS. 9 and 10, the holes 16 may be polygonal and extend long in a predetermined direction. In the examples of FIGS. 9 and 10, the left - right direction in the figure is the longitudinal direction of the holes 16.

Explanation of Reference Numerals

[0031] 11…Fuel cell 12…Resin plate 13…Membrane - electrode gas diffusion layer assembly 14…Separator 16…Hole 17…Sealing member 18…Welded portion 19…Remote portion 20…Proximal portion 21…Curved portion

Claims

1. A fuel cell stack including a plurality of fuel cells stacked in the thickness direction, wherein each fuel cell has a membrane electrode gas diffusion layer assembly sandwiched between plate-shaped separators on both sides in the thickness direction, the separators are formed with holes for allowing a fluid to flow through the membrane electrode gas diffusion layer assembly and penetrating the separators in the thickness direction, in a fuel cell stack, welding portions are formed by welding adjacent separators of the fuel cells stacked in the thickness direction so as to surround the periphery of the holes, the holes in the separators are shaped to be elongated in a defined direction, the welding portions include a long-distance portion at a long-extending portion corresponding to a portion extending along the longitudinal direction of the holes among the inner edges of the holes, and a plurality of short-distance portions at positions closer to the holes than the long-distance portion at the long-extending portion.

2. The fuel cell stack according to claim 1, wherein the short-distance portions are formed by curving a portion of the long-extending portion of the welding portion, which is a location different from the long-distance portion, so as to protrude in a direction approaching the holes.

3. The long-extending portion of the welding portion is curved in a wave shape, the long-distance portion is formed at a location of the wave-shaped long-extending portion of the welding portion that protrudes in a direction away from the holes, the short-distance portions are formed at locations of the wave-shaped long-extending portion of the welding portion that protrude in a direction approaching the holes.

4. The fuel cell stack according to any one of claims 1 to 3, wherein the short-distance portions are formed on both sides of the long-extending portion of the welding portion, sandwiching a position corresponding to the center of the long-extending portion.

5. The welding portion has a short-extending portion extending in a direction different from the long-extending portion and connected to the long-extending portion, the long-extending portion of the welding portion is connected to the short-extending portion via the long-distance portion.

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