Cell stack for fuel cells

Abstract

To provide a cell stack for fuel cells that can prevent increase in the contact resistance of fuel battery cells.SOLUTION: A cell stack for fuel cells comprises a plurality of fuel battery cells stacked in a thickness direction. Separators 14 sandwich a membrane electrode gas diffusion layer joint body 13 from both sides in the thickness direction. The separator 14 has recesses 18 and projections 19 arranged alternately with each other and formed by bending the separator 14. In the adjacent separators 14 of the fuel battery cells stacked in the thickness direction, the leading ends of projections 19 of the separators are welded to each other. Of the leading ends of the projections 19 of the adjacent separators 14, a convex part 20 curved to swell is formed at one leading end, and a concave part 21 curved to be recessed is formed at the other leading end. The leading ends of the projections 19 of the adjacent separators 14 are in contact with each other such that the convex part 20 is fitted into the concave part 21.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] As shown in Patent Document 1, a fuel cell stack is formed by stacking fuel cells in the thickness direction. A fuel cell is formed by sandwiching a membrane electrode gas diffusion layer assembly between plate-shaped separators from both sides in the thickness direction. The separator is formed by bending the separator so that recesses and protrusions are alternately positioned. The recesses are recessed toward the membrane electrode gas diffusion layer assembly. The protrusions protrude in a direction away from the membrane electrode gas diffusion layer assembly. Then, the adjacent separators of the fuel cells stacked in the thickness direction have the tips of their respective protrusions welded to each other.

[0003] A fuel gas such as hydrogen is passed between the separator in the fuel cell and the anode side of the membrane electrode gas diffusion layer assembly. Also, an oxidizing gas such as air is passed between the separator in the fuel cell and the cathode side 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. To suppress the temperature rise of the stack due to such power generation, a refrigerant such as cooling water is passed between the separators of adjacent fuel cells. And the stack is cooled by this refrigerant.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, fine irregularities resulting from the manufacturing of the separator occur on the surface of the separator in the fuel cell. For this reason, these fine irregularities also occur at the tips of the convex portions where adjacent separators are welded to each other. The surface roughness at the tips of the convex portions due to such fine irregularities causes a decrease in the adhesion between the tips of the convex portions of adjacent separators. Then, due to the decrease in the adhesion between the tips of the convex portions, the electrical resistance, that is, the contact resistance in the fuel cell increases.

Means for Solving the Problem

[0006] Hereinafter, the 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. The fuel cell is configured such that a membrane electrode gas diffusion layer laminate is sandwiched from both sides in the thickness direction by plate-shaped separators. The separator is formed by bending the separator so that concave portions and convex portions are alternately positioned. The concave portion is recessed toward the membrane electrode gas diffusion layer laminate. The convex portion protrudes in a direction away from the membrane electrode gas diffusion layer laminate. The adjacent separators of the fuel cells stacked in the thickness direction have the tips of their respective convex portions welded to each other. Of the tips of the convex portions of adjacent separators, a convex curved portion that curves so as to bulge is formed at one tip, and a concave curved portion that curves so as to be recessed is formed at the other tip. The tips of the convex portions of adjacent separators are in contact with each other such that the convex curved portion fits into the concave curved portion.

[0007] According to the above configuration, since the tips of the convex portions of adjacent separators are in contact with each other such that the convex curved portion fits into the concave curved portion, the contact area between the tips of the convex portions of adjacent separators increases. Even if the adhesion between the tips of the convex portions decreases due to surface roughness or the like at the tips of the convex portions, the contact area between the tips of the convex portions can be increased as described above, so that an increase in the electrical resistance, that is, the contact resistance, in the fuel cell can be suppressed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0009] Hereinafter, an embodiment of a cell stack of a fuel cell will be described with reference to FIGS. 1 to 3. FIG. 1 shows a fuel cell 11 for forming a cell stack of a fuel cell. The fuel cell 11 includes a resin plate 12, a membrane electrode gas diffusion layer joined body 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 joined body 13 is joined to the resin plate 12. Then, the resin plate 12 and the membrane electrode gas diffusion layer joined body 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 cell stack of the fuel cell 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. 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 end and one from the other end in the long side direction of the fuel cell 11. Each pair of holes 16 is used for flowing fluids such as fuel gas like hydrogen, oxidizing gas like air, and refrigerant like 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 respectively.

[0011] The seal member 17 disposed on the front surface side of the resin plate 12 surrounds a pair of 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 junction 13. Thereby, it becomes possible to flow fuel gas through the pair of holes 16 to the anode side of the membrane electrode gas diffusion layer junction 13. Further, the seal member 17 disposed on the back surface side of the resin plate 12 surrounds a pair of 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 junction 13. Thereby, it becomes possible to flow oxidizing gas through the pair of holes 16 to the cathode side of the membrane electrode gas diffusion layer junction 13.

[0012] In the cell stack of the fuel cell 11, fuel gas is flowed to the anode side of the membrane electrode gas diffusion layer junction 13, and oxidizing gas is flowed to the cathode side of the membrane electrode gas diffusion layer junction 13. Thus, when fuel gas and oxidizing gas are flowed to the anode side and the cathode side of the membrane electrode gas diffusion layer junction 13, power generation is performed based on the reaction between the fuel gas and the oxidizing gas in the membrane electrode gas diffusion layer junction 13.

[0013] <Welding of adjacent separators 14 (1)> FIG. 2 shows a state in which the separator 14 located on the anode side of the membrane electrode gas diffusion layer junction 13 among the separators 14 of the fuel cell 11 is viewed from the direction of arrow A in FIG. 1. This separator 14 is adjacent to the separator 14 on the cathode side in another fuel cell 11 that contacts the fuel cell 11. The adjacent separators 14 are welded as shown by the two-dot chain line.

[0014] Specifically, the adjacent separators 14 are welded so as to go around the periphery of two sets of holes 16 located on the diagonal line of the separator 14, and the entire outer periphery of the separator 14 is welded. Thereby, it is possible to flow the refrigerant through the hole 16 located at the center in the short side direction of the separator 14 between the adjacent separators 14. When the refrigerant flows between the separators 14 of the adjacent fuel cells 11 in this way, the cell stack can be cooled when the temperature of the cell stack rises during power generation.

[0015] <Welding of adjacent separators 14 (2)> FIG. 3 shows an enlarged view of a portion corresponding to the membrane electrode gas diffusion layer junction 13 shown in FIG. 1 between adjacent separators 14 as viewed from the direction of arrow III-III in FIG. 2. As can be seen from FIG. 3, the separator 14 is formed by bending the separator 14 so that the recesses 18 and the protrusions 19 are alternately located. The recess 18 of the separator 14 is recessed toward the membrane electrode gas diffusion layer junction 13 sandwiched by the separator 14. The protrusion 19 of the separator 14 protrudes in a direction away from the membrane electrode gas diffusion layer junction 13 sandwiched by the separator 14. The recesses 18 and the protrusions 19 extend in the long side direction of the separator 14 as shown in FIG. 2.

[0016] The adjacent separators 14 have the tips of their respective convex portions 19 welded to each other by laser welding or the like. Of the tips of the convex portions 19 of the adjacent separators 14, a convex curved portion 20 that curves so as to bulge is formed at one tip, and a concave curved portion 21 that curves so as to be recessed is formed at the other tip. The tips of the convex portions 19 of the adjacent separators 14 are in contact with each other such that the convex curved portion 20 enters the concave curved portion 21.

[0017] The convex curved portion 20 and the concave curved portion 21 are formed at the tips of the convex portions 19 of the adjacent separators 14 as follows in detail. That is, the convex curved portion 20 and the concave curved portion 21 are respectively formed at the tips of the convex portions 19. At the center in the width direction of the convex portion 19 at one tip and the other tip of the tips of the convex portions 19, the concave curved portions 21 are respectively formed, and the convex curved portions 20 are respectively formed on both sides in the width direction of the concave curved portions 21.

[0018] The adjacent separators 14 are arranged such that, by shifting the relative positions in the width direction of the convex portions 19, the convex curved portion 20 at one tip of the tips of the convex portions 19 enters the concave curved portion 21 at the other tip, and the convex curved portion 20 at the other tip enters the concave curved portion at the one tip. As a result, the tips of the convex portions 19 are in contact with each other such that the convex curved portion 20 at one tip enters the concave curved portion 21 at the other tip, and the convex curved portion 20 at the other tip enters the concave curved portion 21 at the one tip.

[0019] Next, the operation and effect of the fuel cell stack in this embodiment will be described. (1) The tips of the convex portions 19 of adjacent separators 14 are in contact with each other such that the convex curved portion 20 enters the concave curved portion 21. For this reason, the contact area between the tips of the convex portions 19 of adjacent separators 14 becomes large. Therefore, even if the adhesion between the tips of the convex portions 19 decreases due to the roughness of the surface at the tips of the convex portions 19 or the like, since the contact area between the tips of the convex portions 19 can be increased as described above, an increase in the electrical resistance, that is, the contact resistance, in the fuel cell 11 can be suppressed.

[0020] (2) Convex curved portions 20 and concave curved portions 21 are respectively formed at the tips of the convex portions 19 of adjacent separators 14. And the convex curved portion 20 at one tip of the tips of the convex portions 19 enters the concave curved portion 21 at the other tip, and the convex curved portion 20 at the other tip enters the concave curved portion 21 at one tip, so that the tips of the convex portions 19 of adjacent separators 14 are in contact with each other. Thereby, it becomes easy to increase the contact area between the tips of the convex portions 19.

[0021] (3) Concave curved portions 21 are respectively formed at the centers in the width direction of the convex portions 19 at one tip and the other tip among the tips of the convex portions 19, and convex curved portions 20 are respectively formed on both sides in the width direction of those concave curved portions 21. And the adjacent separators 14 are displaced in the relative position as follows in the width direction of the convex portion 19. That is, the relative position is displaced such that the convex curved portion 20 at one tip of the tips of the convex portions 19 enters the concave curved portion 21 at the other tip, and the convex curved portion 20 at the other tip enters the concave curved portion 21 at one tip. In this case, even if the shapes of the tips of the convex portions 19 that are in contact with each other are the same, by displacing the relative positions of the adjacent separators 14 as described above, the contact area between the tips of the convex portions 19 can be increased.

[0022] Note that the above embodiment can also be modified as follows, for example. The above embodiment and the following modification examples can be implemented in combination with each other within a range where there is no technical contradiction. · As shown in Fig. 4, among the tips of the convex portions 19 in adjacent separators 14, one convex curved portion 20 may be formed at one tip, and one concave curved portion 21 may be formed at the other tip. In this case, the tips of the convex portions 19 in adjacent separators 14 are brought into contact with each other such that the convex curved portion 20 at one tip enters the concave curved portion 21 at the other tip.

[0023] · As shown in Fig. 5, the convex curved portion 20 and the concave curved portion 21 may be formed. That is, a convex curved portion 20 is formed at the center in the width direction of the convex portion 19 at one tip among the tips of the convex portions 19 in adjacent separators 14, and concave curved portions 21 are formed on both sides in the width direction of the convex curved portion 20. Further, a concave curved portion 21 is formed at the center in the width direction of the convex portion 19 at the other tip, and convex curved portions 20 are formed on both sides in the width direction of the concave curved portion 21. In this case, the convex curved portion 20 at one tip enters the concave curved portion 21 at the other tip, and the convex curved portion 20 at the other tip enters the concave curved portion 21 at one tip, such that the tips of the convex portions 19 in adjacent separators 14 are brought into contact with each other.

Explanation of Signs

[0024] 11… Fuel cell 12… Resin plate 13… Membrane electrode gas diffusion layer assembly 14… Separator 16… Hole 17… Seal member 18… Concave portion 19… Convex portion 20… Convex curved portion 21… Concave curved portion

Claims

1. A fuel cell stack comprising 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 by bending the separators such that recesses and protrusions are alternately positioned, the recesses are recessed toward the membrane electrode gas diffusion layer assembly, the protrusions protrude in a direction away from the membrane electrode gas diffusion layer assembly, in a cell stack of a fuel cell in which adjacent separators of the fuel cells stacked in the thickness direction have the tips of their respective protrusions welded together, of the tips of the protrusions of adjacent separators, a convex curved portion that curves so as to bulge is formed at one tip, and a concave curved portion that curves so as to be recessed is formed at the other tip, a cell stack of a fuel cell in which the tips of the protrusions of adjacent separators are in contact with each other such that the convex curved portion fits into the concave curved portion.

2. A convex curved portion and a concave curved portion are respectively formed at the tips of the protrusions of adjacent separators, the cell stack of a fuel cell according to claim 1, wherein the convex curved portion at one tip of the tips of the protrusions fits into the concave curved portion at the other tip, and the convex curved portion at the other tip fits into the concave curved portion at the one tip, and the tips of the protrusions of adjacent separators are in contact with each other.

3. Of the tips of the protrusions, concave curved portions are respectively formed at the centers in the width direction of the protrusions at the one tip and the other tip, and convex curved portions are respectively formed on both sides in the width direction of those concave curved portions, the cell stack of a fuel cell according to claim 2, wherein adjacent separators are arranged such that, by shifting their relative positions in the width direction of the protrusions, the convex curved portion at the one tip of the tips of the protrusions fits into the concave curved portion at the other tip, and the convex curved portion at the other tip fits into the concave curved portion at the one tip.

4. Of the tips of the protrusions of adjacent separators, one convex curved portion is formed at one tip and one concave curved portion is formed at the other tip, The fuel cell stack according to claim 1, wherein the tips of the convex portions of adjacent separators are in contact with each other such that the convex curved portion at the tip of one side enters the concave curved portion at the tip of the other side.

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

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