Fuel cell stack

Abstract

The present invention provides a fuel cell stack capable of suppressing peeling of welded separators from each other. The fuel cell stack is provided with a plurality of unit cells that overlap in the thickness direction. Each of the single cells is provided with a membrane electrode gas diffusion layer assembly and a plurality of plate-shaped separators that sandwich the membrane electrode gas diffusion layer assembly from both sides in the thickness direction. A hole is formed in the separator. Adjacent separators of the single cells that overlap in the thickness direction are formed with welded sections that are welded to each other so as to surround the hole by one circle. The hole of the separator is provided in a shape that is long in a predetermined direction. The welding part is provided with a long-distance part located at the long extension part and a plurality of short-distance parts located at positions closer to the hole than the long-distance part in the long extension part.

Description

Technical Field

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

[0002] As disclosed in Japanese Unexamined Patent Application Publication No. 2019-61754, a fuel cell stack is formed by overlapping single cells in the thickness direction. A single cell is formed by sandwiching a membrane electrode gas diffusion layer assembly from both sides in the thickness direction using plate-shaped separators. Holes for allowing fluids such as fuel gas like hydrogen and oxidizing gas like air to flow to the membrane electrode gas assembly are formed in the separators so as to penetrate the separators in the thickness direction.

[0003] In a fuel cell stack, welded portions are formed between adjacent separators of the single cells overlapped in the thickness direction, which are welded to each other in a manner surrounding the periphery of the above holes. This welding is used to seal the periphery of the holes. And, via the above holes between adjacent separators, fuel gas flows to the anode-side surface of the front and back surfaces of the membrane electrode gas diffusion layer assembly, and oxidizing gas flows to the cathode-side surface. As a result, power generation is performed based on the reaction between the fuel gas and the oxidizing gas in the membrane electrode gas diffusion layer assembly. Summary of the Invention

[0004] Problems to be Solved by the Invention

[0005] However, when fluids such as fuel gas and oxidizing gas flow into the holes of the separators in the single cell, a force in a direction separating the welded adjacent separators from each other is applied to the above welded portions based on the pressure of the fluids. In the case where the above holes are formed in a shape elongated in a specified direction, this force is likely to be larger at the portion of the welded portion corresponding to the length direction of the inner edge of the above hole, that is, the long extension portion, than at other portions of the welded portion. Therefore, the welded separators may peel off at the long extension portion of the above welded portion.

[0006] Solutions to the Problems

[0007] One aspect of the present disclosure relates to a fuel cell stack including a plurality of single cells stacked in a thickness direction. Each single cell includes a membrane electrode gas diffusion layer assembly and a plurality of plate-shaped separators that sandwich the membrane electrode gas diffusion layer assembly from both sides in the thickness direction. Holes for allowing a fluid to flow to the membrane electrode gas diffusion layer assembly are formed in the separators so as to penetrate the separators in the thickness direction. Welded portions are formed between adjacent separators of the single cells stacked in the thickness direction and are welded to each other so as to surround the periphery of the holes. The holes of the separators are formed in a shape that is long in a specified direction. The welded portion includes: a long-distance portion located at a long extension portion that corresponds to a portion of the inner edge of the hole that extends in the length direction of the hole; and a plurality of short-distance portions located at portions of the long extension portion that are closer to the hole than the long-distance portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 FIG. is an exploded perspective view showing a single cell.

[0009] Figure 2 FIG. is a front view showing a state of observing a separator in a single cell loaded from the direction of arrow A. Figure 1 into the single cell.

[0010] Figure 3 FIG. is Figure 2 an enlarged view of a hole and a welded portion in the separator of.

[0011] Figure 4 FIG. is Figure 3 an enlarged view of another example of the welded portion of.

[0012] Figure 5 FIG. is Figure 3 an enlarged view of another example of the welded portion of.

[0013] Figure 6 FIG. is Figure 3 an enlarged view of another example of the welded portion of.

[0014] Figure 7 FIG. is Figure 3 an enlarged view of another example of the welded portion of.

[0015] Figure 8 FIG. is Figure 3 an enlarged view of another example of the welded portion of.

[0016] Figure 9 FIG. is Figure 2 an enlarged view of another example of the hole of.

[0017] Figure 10 It is an enlarged view of other examples of the holes indicated by Figure 2 . Detailed implementation mode

[0018] Hereinafter, with reference to Figures 1 to 3 One implementation mode of a fuel cell stack will be described.

[0019] Figure 1 Fig. shows a single cell 11 for forming a fuel cell stack. The single cell 11 includes a resin plate 12, a membrane electrode gas diffusion layer laminate 13, and a plurality of separators 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. And, the resin plate 12 and the membrane electrode gas diffusion layer laminate 13 are clamped from both sides in their thickness directions by a plurality of separators 14. The separator 14 is formed in a rectangular plate shape from a metal such as stainless steel, titanium, and aluminum.

[0020] The fuel cell stack is formed by overlapping the above-described single cells 11 in the thickness direction. A plurality of holes 16 are formed in the resin plate 12 and the separator 14 of the single cell 11 so as to penetrate in the thickness direction. Three of the plurality of holes 16 are located at one end in the long side direction of the single cell 11, and the other three are located at the other end in the long side direction of the single cell 11. The plurality of holes 16 are formed in pairs by one hole on one side and one hole on the other side in the long side direction of the single cell 11. Each group of holes 16 is used for fluid such as fuel gas such as hydrogen, oxidizing gas such as air, and refrigerant such as cooling water to flow. A sealing member 17 is disposed between the separator 14 and the resin plate 12. The sealing member 17 can be disposed on the front and back surfaces in the thickness direction of the resin plate 12, respectively.

[0021] The sealing member 17 disposed on the surface side of the resin plate 12 surrounds two holes 16 in a pair located on one of the two diagonals in the resin plate 12 and the separator 14 and the anode-side surface of the membrane electrode gas diffusion layer laminate 13. Thereby, the fuel gas can flow to the anode-side surface of the membrane electrode gas diffusion layer laminate 13 via the two holes 16 in a pair. In addition, the sealing member 17 disposed on the back side of the resin plate 12 surrounds two holes 16 in a pair located on the other of the two diagonals in the resin plate 12 and the separator 14 and the cathode-side surface of the membrane electrode gas diffusion layer laminate 13. Thereby, the oxidizing gas can flow to the cathode-side surface of the membrane electrode gas diffusion layer laminate 13 via the two holes 16 in a pair.

[0022] Figure 2 Fig. shows from Figure 1The state of observing the separator 14 on the anode side of the membrane electrode gas diffusion layer assembly 13 in the separator 14 of the single cell 11 in the direction of arrow A. The separator 14 is adjacent to the separator 14 on the cathode side in another single cell 11 connected to the single cell 11. In this way, welding portions 18 are formed between the adjacent separators 14 and are welded to each other in a manner surrounding the periphery of the hole 16. Welding portions 18 are formed around two sets of holes 16 located on the diagonal of the separator 14, and no welding portion 18 is formed around the hole 16 located at the center in the short side direction of the separator 14. In addition, the outer edges of the adjacent separators 14 are welded to each other. Thus, the refrigerant can flow between the adjacent separators 14 through the hole 16 located at the center in the short side direction of the separator 14.

[0023] In a fuel cell stack formed by overlapping a plurality of single cells 11, the fuel gas flows to the anode-side surface of the membrane electrode gas diffusion layer assembly 13, and the oxidizing gas flows to the cathode-side surface of the membrane electrode gas diffusion layer assembly 13. In this way, when the fuel gas and the oxidizing gas flow to the anode-side surface and the cathode-side surface of the membrane electrode gas diffusion layer assembly 13, power generation is performed based on the reaction between these fuel gas and oxidizing gas in the membrane electrode gas diffusion layer assembly 13. In order to suppress the temperature rise of the fuel cell stack caused by such power generation, the refrigerant is made to flow between the separators 14 of the adjacent single cells 11. The fuel cell stack is cooled by using this refrigerant.

[0024] <Details of the welding portion 18>

[0025] As Figure 3 shown, the hole 16 of the separator 14 is formed in a shape elongated in a prescribed direction, and more specifically, in a rectangular shape. The welding portion 18 includes a long-distance portion 19 and a plurality of short-distance portions 20. The long-distance portion 19 is located at a long extension portion, which is a portion of the welding portion 18 corresponding to the portion of the inner edge of the hole 16 extending along the length direction of the hole 16, that is, the long side direction. The short-distance portion 20 is located at a portion of the long extension portion of the welding portion 18 closer to the hole 16 than the long-distance portion 19. The short-distance portion 20 is formed by bending a portion of the long extension portion of the welding portion 18, which is provided separately from the long-distance portion 19, in a manner protruding toward the hole 16.

[0026] More specifically, by bending the long extension portion of the welding portion 18 in a wave shape, the long-distance portion 19 and the short-distance portion 20 are formed. The long-distance portion 19 is formed at a portion of the wave-shaped long extension portion of the welding portion 18 protruding in a direction away from the hole 16. The short-distance portion 20 is formed at a portion of the wave-shaped long extension portion of the welding portion 18 protruding in a direction toward the hole 16.

[0027] In addition, a short distance portion 20 is formed on both sides of the long extension portion of the welding portion 18 at a position corresponding to the center of the long extension portion. In the welding portion 18, there is also a short extension portion extending in a direction different from the long extension portion and connected to the long extension portion. The short extension portion extends along the short side of the hole 16. The long extension portion of the welding portion 18 is connected to the short extension portion via the long distance portion 19. In detail, the long extension portion of the welding portion 18 is connected to the short extension portion by the long distance portion 19 intersecting the short extension portion.

[0028] The short extension portion of the welded portion 18 is also curved in a wave shape. The pitch of the wave shape in the long extension portion of the welded portion 18 is shorter than the pitch of the wave shape in the short extension portion.

[0029] Next, the effects of the fuel cell stack in this embodiment will be described.

[0030] (1) At the welding portion 18 where adjacent separators 14 are welded to each other in a circle around the hole 16, a force in a direction that separates the separators 14 from each other is applied based on the pressure of the fluid flowing in the hole 16. This force tends to become larger at the long extension portion of the welding portion 18 than at the other portion of the welding portion 18, i.e., the short extension portion. In other words, the force tends to become larger at the portion corresponding to the long side of the hole 16 than at the portion corresponding to the short side of the hole 16 in the welding portion 18. In order to cope with this situation, the welding portion 18 has a long distance portion 19 and a plurality of short distance portions 20 as follows. That is, the long distance portion 19 and the plurality of short distance portions 20 are formed at the portion of the welding portion 18 corresponding to the long side direction of the hole 16, i.e., the long extension portion. Furthermore, the plurality of short distance portions 20 are formed at a portion closer to the hole 16 than the long distance portion 19. In the long extension part of the welded portion 18, the force in the direction of separating the separators 14 from each other increases as the part is closer to the hole 16. Therefore, when a plurality of close distance parts 20 are formed in the long extension part of the welded portion 18, the force is dispersedly received by the plurality of close distance parts 20, thereby preventing the force from being locally increased in the long extension part of the welded portion 18. Therefore, it is possible to prevent the separators 14 welded in the long extension part of the welded portion 18 from being peeled off due to the action of the force.

[0031] (2) The short distance portion 20 is formed by bending a portion of the long extension portion of the weld portion 18 that is provided separately from the long distance portion 19 so as to protrude toward the hole 16. Thus, a plurality of short distance portions 20 that are connected to the long distance portion 19 can be formed in the long extension portion of the weld portion 18.

[0032] (3) By making the long extended portion of the welding part 18 be in a wavy bend, a remote portion 19 and a plurality of close portions 20 are formed at this portion. Therefore, it is easy to form a plurality of close portions 20 at the long extended portion of the welding part 18.

[0033] (4) The force that desires to separate the spacers 14 acting on the long extended portion of the welding part 18 is likely to become larger at a position corresponding to the center of the long extended portion. The plurality of close portions 20 in the long extended portion of the welding part 18 are respectively formed on both sides of the position corresponding to the center of the long extended portion. Therefore, when the above-mentioned force is dispersed and borne by the plurality of close portions 20, each close portion 20 can bear the above-mentioned force equally. As a result, it is possible to more effectively suppress the above-mentioned force from locally becoming larger at the long extended portion of the welding part 18.

[0034] (5) The long extended portion of the welding part 18 is connected to the short extended portion of the welding part 18 via the remote portion 19. Therefore, it is possible to suppress the shape of the portion where the long extended portion and the short extended portion of the welding part 18 intersect from becoming a shape where stress is likely to concentrate when the above-mentioned force that desires to separate the spacers 14 acts. Thus, it is possible to suppress the following situation: 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 welding part 18 intersect, the welding peels off in the direction of separating the spacers 14 along with the above-mentioned stress concentration.

[0035] In addition, the above-mentioned embodiment can be modified as follows, for example. The above-mentioned embodiment and the following modification examples can be implemented by combining them with each other within the scope where there is no technical contradiction.

[0036] · Instead of making the long extended portion of the welding part 18 intersect with the short extended portion, the two portions can be connected by a curved portion with a rounded corner shape protruding in a direction away from the hole 16.

[0037] · As Figure 4 shown, the short extended portion of the welding part 18, that is, the portion corresponding to the short side of the hole 16, can be formed into a straight line shape.

[0038] · As Figure 5 shown, in the case where the short extended portion of the welding part 18 is formed into a straight line shape, this portion and the portion corresponding to the long side of the hole 16 can be connected by a curved portion 21 with a rounded corner shape protruding in a direction away from the hole 16.

[0039] · As Figure 6As shown, a linear long-distance portion 19 may also be formed at the long extended portion of the welding portion 18, that is, at the portion corresponding to the long side of the hole 16. Further, a short-distance portion 20 is formed by bending the portion of the long extended portion of the welding portion 18 that is provided separately from the long-distance portion 19 in a direction protruding toward the hole 16.

[0040] · As Figure 7 shown, a linear long-distance portion 19 may also be formed at the portion of the welding portion 18 corresponding to the long side of the hole 16. Further, as the welding portion 18, a plurality of short-distance portions 20 that spot-weld the partition members 14 to each other are formed at positions away from the long-distance portion 19 in a direction closer to the hole 16.

[0041] · As Figure 8 shown, a linear long-distance portion 19 may also be formed at the portion of the welding portion 18 corresponding to the long side of the hole 16. Further, as the welding portion 18, short-distance portions 20 that weld the partition members 14 to each other in a manner extending parallel to the long side of the hole 16 are formed at positions away from the long-distance portion 19 in a direction closer to the hole 16.

[0042] · The number of the short-distance portions 20 at the long extended portion of the welding portion 18 may also be increased. In this case, the pitch of the wavy bends in the long extended portion of the welding portion 18 may be constant, or may be different at the portion corresponding to the center and the portion corresponding to the end of the long extended portion.

[0043] If the pitch of the wavy bends in the welding portion 18 is different at the portion corresponding to the center and the portion corresponding to the end of the long extended portion, the following can be achieved. That is, when a force in a direction separating the partition members 14 from each other acts based on the pressure of the fluid flowing in the hole 16, the adjustment range when adjusting the pitch can be expanded so that the partition members 14 are not peeled off from each other due to this force.

[0044] · The pitch of the wavy bends in the long extended portion of the welding portion 18 does not necessarily need to be shorter than the pitch of the wavy bends in the short extended portion.

[0045] · As Figure 9 and Figure 10 shown, the hole 16 may also be a polygonal shape that extends relatively long in a specified direction. In the Figure 9 and Figure 10 examples, the left-right direction in the figure becomes the length direction of the hole 16.

Claims

1. A fuel cell stack, wherein: The fuel cell stack includes a plurality of cells stacked in a thickness direction. Each of the single cells includes a membrane electrode gas diffusion layer assembly and a plurality of plate-shaped separators that sandwich the membrane electrode gas diffusion layer assembly from both sides in the thickness direction. The separator has a hole formed therein so as to penetrate the separator in the thickness direction so as to allow a fluid to flow toward the membrane electrode gas diffusion layer assembly. The adjacent separators of the single cells stacked in the thickness direction are welded to each other so as to surround the hole. The hole of the separator is formed to be long in a predetermined direction. The welding portion comprises: a remote portion, the remote portion being located at a long extension portion, the long extension portion being a portion corresponding to a portion of the inner edge of the hole extending along the length direction of the hole; as well as A plurality of close distance portions are located at a portion of the long extension portion closer to the hole than the long distance portion.

2. The fuel cell stack according to claim 1, wherein: The close distance portion is formed by bending a portion of the long extension portion of the welding portion that is provided separately from the long distance portion so as to protrude in a direction approaching the hole.

3. The fuel cell stack according to claim 2, wherein: The long extension portion of the welding portion is curved in a wave shape, The long distance portion is formed at a portion of the corrugated long extension portion of the weld portion that protrudes in a direction away from the hole. The close distance portion is formed at a portion of the corrugated long extending portion of the weld portion that protrudes in a direction approaching the hole.

4. The fuel cell stack according to any one of claims 1 to 3, wherein: The plurality of close distance portions include close distance portions formed on both sides of a position corresponding to the center of the long extension portion in the long extension portion of the welding portion.

5. The fuel cell stack according to claim 3, wherein: The welding portion includes a short extension portion extending in a direction different from that of the long extension portion and connected to the long extension portion. The long extension portion of the welding portion is connected to the short extension portion via the long distance portion.

Images