Fuel cell stack

Abstract

Provided is a fuel cell stack capable of suppressing an increase in contact resistance. This fuel cell stack is provided with a plurality of unit cells that overlap in the thickness direction. A single cell 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. The front ends of the convex parts of the adjacent separators of the single cells overlapping in the thickness direction are welded to each other. A convex curved portion is formed at the front end of one of the front ends of the convex portions of the adjacent separators, and a concave curved portion is formed at the front end of the other of the front ends of the convex portions of the adjacent separators. The front ends of the convex parts of the adjacent separators are in contact with each other in a manner that the convex curved parts enter the concave curved parts.

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. 2019-129124, a fuel cell stack is formed by overlapping single cells in the thickness direction. A 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. The separator is formed by bending in such a way that concave portions and convex portions are alternately located in the separator. The concave portion is recessed toward the membrane electrode gas diffusion layer assembly. The convex portion protrudes in a direction away from the membrane electrode gas diffusion layer assembly. Further, the front ends of the convex portions of adjacent separators of the single cells overlapped in the thickness direction are welded to each other.

[0003] A fuel gas such as hydrogen flows between the surface of the separator in the single cell and the anode side surface of the membrane electrode gas diffusion layer assembly. In addition, an oxidizing gas such as air flows between the surface of the separator in the single cell and the cathode side surface of the membrane electrode gas diffusion layer assembly. 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. In order to suppress the temperature rise of the fuel cell stack caused by such power generation, a refrigerant such as cooling water flows between the separators of adjacent single cells. And the fuel cell stack is cooled by the refrigerant. Summary of the Invention

[0004] Problems to be Solved by the Invention

[0005] Among them, minute irregularities are generated on the surface of the separator in the single cell during the manufacture of the separator. Therefore, the minute irregularities are also generated at the front ends of the convex portions where adjacent separators are welded to each other. The surface roughness at the front ends of the convex portions caused by such minute irregularities causes a decrease in the close contact between the front ends of the convex portions where adjacent separators are welded to each other. And due to the decrease in the close contact between the front ends of the convex portions, the resistance in the single cell, that is, the contact resistance, becomes large.

[0006] Means for Solving the Problems

[0007] One aspect of the present disclosure relates to a fuel cell stack including a plurality of single cells stacked in the 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. The separators are formed by bending in such a way that recesses and protrusions are alternately arranged on the separators. The recesses are recessed toward the membrane electrode gas diffusion layer assembly, and the protrusions protrude in a direction away from the membrane electrode gas diffusion layer assembly. The front ends of the protrusions of adjacent separators among the single cells stacked in the thickness direction are welded to each other. A convex curved portion that is curved in a bulging manner is formed at the front end of one of the front ends of the protrusions of adjacent separators, and a concave curved portion that is curved in a recessed manner is formed at the front end of the other. The front ends of the protrusions of adjacent separators are in contact with each other in such a way that the convex curved portion enters the concave curved 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 the separator inserted into the single cell from the direction of arrow A in FIG. Figure 1

[0010] Figure 3 FIG. is an enlarged cross-sectional view showing a state of observing a portion corresponding to the membrane electrode gas diffusion layer assembly of adjacent separators from the direction of arrow III-III in FIG. Figure 2

[0011] Figure 4 FIG. is a cross-sectional view showing another example of the concave curved portion and the convex curved portion in the separator of FIG. Figure 3

[0012] Figure 5 FIG. is a cross-sectional view showing another example of the concave curved portion and the convex curved portion in the separator of FIG. Figure 3 DETAILED DESCRIPTION

[0013] Hereinafter, an embodiment of a fuel cell stack will be described with reference to FIG. Figures 1 to 3

[0014] Figure 1 ​​​​​The single cell 11 for forming a fuel cell stack is shown. The single cell 11 includes a resin plate 12, a membrane electrode gas diffusion layer assembly 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 assembly 13 is joined to the resin plate 12. And the resin plate 12 and the membrane electrode gas diffusion layer assembly 13 are clamped from both sides in their thickness directions by the separators 14. The separators 14 are formed in a rectangular plate shape from metals such as stainless steel, titanium, and aluminum.

[0015] 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 separators 14 of the single cell 11. Among the plurality of holes 16, three 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 pair of holes 16 is used for fluids such as fuel gas like hydrogen, oxidizing gas like air, and refrigerant like 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 respectively disposed on the front and back surfaces in the thickness direction of the resin plate 12.

[0016] The sealing member 17 disposed on the surface side of the resin plate 12 surrounds the two - hole pairs located on one of the two diagonals in the resin plate 12 and the separators 14 and the anode - side surface of the membrane electrode gas diffusion layer assembly 13. Thereby, the fuel gas can flow through the two - hole pairs to the anode - side surface of the membrane electrode gas diffusion layer assembly 13. In addition, the sealing member 17 disposed on the back side of the resin plate 12 surrounds the two - hole pairs located on the other of the two diagonals in the resin plate 12 and the separators 14 and the cathode - side surface of the membrane electrode gas diffusion layer assembly 13. Thereby, the oxidizing gas can flow through the two - hole pairs to the cathode - side surface of the membrane electrode gas diffusion layer assembly 13.

[0017] In the fuel cell stack of the single cell 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. Thus, 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 of these fuel gas and oxidizing gas in the membrane electrode gas diffusion layer assembly 13.

[0018] <Welding (1) between adjacent separators 14>

[0019] Figure 2 Shown 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. This separator 14 is adjacent to the separator 14 on the cathode side in the other single cell 11 connected to the above single cell 11. The adjacent separators 14 are welded to each other as shown by the double-dashed line.

[0020] Specifically, the adjacent separators 14 are welded to each other in a manner that surrounds the two sets of holes 16 on the diagonal of the separator 14, and the outer edge of the separator 14 is welded throughout the circumference. Thereby, the refrigerant can flow between the adjacent separators 14 through the holes 16 located at the center in the short side direction of the separator 14. By allowing the refrigerant to flow between the separators 14 of the adjacent single cells 11 in this way, the battery stack can be cooled when the temperature rises during power generation of the battery stack.

[0021] <Welding of adjacent separators 14 to each other (2)>

[0022] Figure 3 From Figure 2 The state of observing the portion corresponding to the membrane electrode gas diffusion layer assembly 13 shown in Figure 1 in the adjacent separators 14 in the direction of arrow III-III is magnified and shown. According to Figure 3 it can be seen that the separator 14 is bent to form with the concave portion 18 and the convex portion 19 located on the separator 14. The concave portion 18 of the separator 14 is recessed toward the membrane electrode gas diffusion layer assembly 13 clamped by the separator 14. The convex portion 19 of the separator 14 protrudes in a direction away from the membrane electrode gas diffusion layer assembly 13 clamped by the separator 14. The concave portion 18 and the convex portion 19 extend along the long side direction of the separator 14 as shown in Figure 2

[0023] The front ends of the convex portions 19 of the adjacent separators 14 are welded to each other by laser welding or the like. A convex curved portion 20 that is bent in a bulging manner is formed at the front end of one of the front ends of the convex portions 19 of the adjacent separators 14, and a concave curved portion 21 that is bent in a recessed manner is formed at the front end of the other. The front ends of the convex portions 19 of the adjacent separators 14 are in contact with each other in such a way that the convex curved portion 20 enters the concave curved portion 21.

[0024] ​The convex curved portion 20 and the concave curved portion 21 are formed at the front ends of the convex portions 19 in adjacent partition members 14 as follows. That is, the convex curved portion 20 and the concave curved portion 21 are respectively formed at the front ends of the convex portions 19. The concave curved portion 21 is formed at a portion located at the center in the width direction of the convex portion 19 at the front end of one of the front ends of the convex portions 19, and the convex curved portions 20 are respectively formed on both sides in the width direction of the concave curved portion 21. The concave curved portion 21 is formed at a portion located at the center in the width direction of the convex portion 19 at the front end of the other front end of the convex portions 19, and the convex curved portions 20 are respectively formed on both sides in the width direction of the concave curved portion 21.

[0025] The adjacent partition members 14 stagger the relative positions in the width direction of the convex portion 19, so that one convex curved portion 20 at the front end of one of the front ends of the convex portions 19 enters the concave curved portion 21 at the front end of the other, and one convex curved portion 20 at the front end of the other enters the concave curved portion at the front end of the one. As a result, the front ends of the convex portions 19 are in contact with each other in such a way that one convex curved portion 20 at the front end of one of the front ends of the convex portions 19 enters the concave curved portion 21 at the front end of the other and one convex curved portion 20 at the front end of the other enters the concave curved portion at the front end of the one.

[0026] Next, the effects of the fuel cell stack in the present embodiment will be described.

[0027] (1) The front ends of the convex portions 19 of the adjacent partition members 14 are in contact with each other in such a way that the convex curved portion 20 enters the concave curved portion 21. Therefore, the contact area between the front ends of the convex portions 19 of the adjacent partition members 14 becomes larger. Thus, even if the close contact property between the front ends of the convex portions 19 is reduced due to the surface roughness or the like at the front ends of the convex portions 19, since the contact area between the front ends of the convex portions 19 can be increased as described above, an increase in the resistance in the single cell 11, that is, the contact resistance, can be suppressed.

[0028] (2) The convex curved portion 20 and the concave curved portion 21 are respectively formed at the front ends of the convex portions 19 in the adjacent partition members 14. And the front ends of the convex portions 19 in the adjacent partition members 14 are in contact with each other in such a way that the convex curved portion 20 at the front end of one of the front ends of the convex portions 19 enters the concave curved portion 21 at the front end of the other and the convex curved portion 20 at the front end of the other enters the concave curved portion at the front end of the one. Thereby, it is easy to increase the contact area between the front ends of the convex portions 19.

[0029] (3) A concave curved portion 21 is formed at a portion located at the center in the width direction of one of the front ends of the convex portions 19, and convex curved portions 20 are respectively formed on both sides in the width direction of the concave curved portion 21. A concave curved portion 21 is formed at a portion located at the center in the width direction of the other of the front ends of the convex portions 19, and convex curved portions 20 are respectively formed on both sides in the width direction of the concave curved portion 21. And the adjacent partition members 14 stagger the relative positions in the width direction of the convex portion 19 as follows. That is, the relative positions are staggered in such a manner that one convex curved portion 20 of one of the front ends of the convex portions 19 enters the concave curved portion 21 of the other front end and one convex curved portion 20 of the other front end enters the concave curved portion 21 of one front end. In this case, even if the shapes of the front ends of the convex portions 19 in contact with each other are set to be the same, by staggering the relative positions of the adjacent partition members 14 as described above, the contact area between the front ends of the convex portions 19 can be increased.

[0030] In addition, the above-described embodiment can be modified as follows, for example. The above-described embodiment and the following modification examples can be implemented in combination with each other within a range where there is no technical contradiction.

[0031] · As Figure 4 shown, one convex curved portion 20 can be formed at the front end of one of the front ends of the convex portions 19 of the adjacent partition members 14, and one concave curved portion 21 can be formed at the front end of the other. In this case, the front ends of the convex portions 19 in the adjacent partition members 14 are in contact with each other in such a manner that the convex curved portion 20 at the front end of one enters the concave curved portion 21 at the front end of the other.

[0032] · The convex curved portion 20 and the concave curved portion 21 can be formed as Figure 5 shown. That is, a convex curved portion 20 is formed at a portion located at the center in the width direction of one of the front ends of the convex portions 19 of the adjacent partition members 14, and concave curved portions 21 are respectively formed on both sides in the width direction of the convex curved portion 20. In addition, a concave curved portion 21 is formed at a portion located at the center in the width direction of the other front end, and convex curved portions 20 are respectively formed on both sides in the width direction of the concave curved portion 21. In this case, the front ends of the convex portions 19 in the adjacent partition members 14 are in contact with each other in such a manner that the convex curved portion 20 at the front end of one enters the concave curved portion 21 at the front end of the other and the convex curved portion 20 at the front end of the other enters the concave curved portion 21 at the front end of one.

Claims

1. A fuel cell stack, wherein: The fuel cell stack includes a plurality of cells stacked in a thickness direction. The 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. The separator is formed by bending in such a manner that concave portions and convex portions are alternately located on the separator, The recessed portion is recessed toward the membrane electrode gas diffusion layer assembly. The convex portion protrudes in a direction away from the membrane electrode gas diffusion layer assembly, The front ends of the convex portions of the adjacent separators of the single cells stacked in the thickness direction are welded to each other. A convex portion curved in a bulging manner is formed at one of the front ends of the convex portions of the adjacent separators, and a concave portion curved in a concave manner is formed at the other front end. The front ends of the convex portions of the adjacent separators are in contact with each other in such a manner that the convex curved portion enters the concave curved portion.

2. The fuel cell stack according to claim 1, wherein: The convex curved portion and the concave curved portion are respectively formed at the front ends of the convex portions of the adjacent separators. The front ends of the convex portions of adjacent separators are in contact with each other in such a manner that the convex portion of the front end of one of the convex portions enters the concave portion of the front end of the other and the convex portion of the front end of the other enters the concave portion of the front end of the one.

3. The fuel cell stack according to claim 2, wherein: The concave portion is formed at a position located at the center of the width direction of the convex portion at the front end of one of the front ends of the convex portions, and the convex portions are formed on both sides of the width direction of the concave portion, respectively. The concave portion is formed at a position located at the center of the width direction of the convex portion at the front end of the other of the front ends of the convex portions, and the convex portions are respectively formed on both sides of the width direction of the concave portion. The adjacent partitions are arranged such that the relative positions are offset in the width direction of the convex portion, so that one of the front ends of the convex portions enters the concave portion of the front end of the other side, and one of the front ends of the other side enters the concave portion of the front end of the one side.

4. The fuel cell stack according to claim 1, wherein: One of the front ends of the convex portions of the adjacent separators is formed with the convex portion, and the other front end is formed with the concave portion. The front ends of the convex portions of the adjacent separators are in contact with each other so that the convex curved portion at the front end of the one separator enters the concave curved portion at the front end of the other separator.

5. The fuel cell stack according to claim 1, wherein: The convex curved portion and the concave curved portion are respectively formed at the front ends of the convex portions of the adjacent separators. The convex portion is formed at a portion of the front end of one side located at the center of the convex portion in the width direction, and the concave portions are respectively formed on both sides of the convex portion in the width direction. The concave portion is formed at a portion of the front end of the other end that is located in the center of the convex portion in the width direction, and the convex portions are formed on both sides of the concave portion in the width direction. The front ends of the convex portions of the adjacent separators are in contact with each other so that the convex portion of the front end of one enters the concave portion of the front end of the other and the convex portion of the front end of the other enters the concave portion of the front end of one.

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