Fuel cell stack

Abstract

To provide a fuel cell stack capable of suppressing partial reduction in an amount of power generated in a power generation unit.SOLUTION: A fuel cell stack comprises a plurality of stacked single cells which each include a power generation unit and a pair of separators 50 sandwiching the power generation unit. A gas passage 60 and a rib 70 extending along the gas passage 60 are alternately arranged on a surface, of the separator 50, facing the power generation unit. The gas passage 60 includes a first extension part extending in a first direction while meandering in a wave form, and a second extension part connected to an end portion of the first extension part and extending in a second direction different from the first direction. There is provided an island-like branching rib 71 by which the gas passage 60 is branched into a plurality of branch passages 62, at a bent part Cg of the gas passage 60 that includes a connection part between the first extension part and the second extension part. The branch passages 62 each include an outer passage 63 extending outside the bent part Cg, and an inner passage 64 extending inside the bent part Cg with respect to the outer passage 63.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] Conventionally, a fuel cell is configured by stacking a plurality of single cells each including a power generation unit containing a membrane electrode assembly and a pair of separators sandwiching the power generation unit. On the surface of each separator facing the power generation unit, a gas flow path through which a reaction gas flows and ribs extending along the gas flow path are alternately provided side by side.

[0003] Patent Document 1 discloses a separator provided with a gas flow path having a plurality of wavy flow path grooves extending in a wavy shape. The gas flow path connects two wavy flow path grooves arranged in parallel with each other and has a folding portion that reverses the flow direction of the reaction gas. An embossed portion is provided in the folding portion. In the folding portion, the reaction gas flows in a direction different from the extending direction of the wavy flow path groove.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, when flowing the reaction gas in a direction different from the extending direction of the wavy flow path groove, it is conceivable to connect a groove-shaped extending portion extending in a direction different from the extending direction of the wavy flow path groove to the wavy flow path groove. Here, in order to increase the supply amount of the reaction gas to the power generation unit, it is preferable to arrange a plurality of gas flow paths in parallel in a state where they are close to each other. When a plurality of gas flow paths are arranged in parallel in a close state, the phase of the connection point with the extending portion in the wavy flow path groove, that is, the position of the connection point with the extending portion with respect to the wavy flow path groove, may be different for each gas flow path. In this case, the distance between two adjacent gas flow paths may partially increase at the connection portion between the wavy flow path groove and the extending portion, and there is a possibility that a wide portion is formed in the rib extending along the two gas flow paths. The portion of the power generation unit that contacts the wide portion is far from the gas flow paths adjacent to the wide portion, so it is difficult for the reaction gas to reach this portion. For this reason, there is a possibility that the power generation amount of the power generation unit may partially decrease.

Means for Solving the Problem

[0006] A fuel cell stack for solving the above problems is a fuel cell stack configured by stacking a plurality of single cells including a power generation unit including a membrane electrode assembly and a pair of separators sandwiching the power generation unit. On the surface of the separator facing the power generation unit, a gas flow path through which the reaction gas flows and ribs extending along the gas flow path are alternately arranged. The gas flow path has a first extending portion extending in a first direction while meandering in a wavy shape, and a second extending portion connected to an end of the first extending portion in the first direction and extending in a second direction different from the first direction. An island-shaped branch rib that protrudes toward the power generation unit and branches the gas flow path into a plurality of branch flow paths is provided at a bent portion of the gas flow path including a connection portion between the first extending portion and the second extending portion. The plurality of branch flow paths include an outer flow path extending outside the bent portion and an inner flow path extending inside the bent portion rather than the outer flow path.

[0007] According to the above configuration, the bent portion of the gas flow path is branched into a plurality of branched flow paths including an outer flow path and an inner flow path by the branch rib. Therefore, the inner flow path is located between the outer flow path and another gas flow path adjacent to the gas flow path including the outer flow path. As a result, even when the distance between the bent portions of the gas flow paths adjacent to each other becomes large, the width of the portion of the rib extending along the bent portion can be suppressed from increasing because the inner flow path is located inside the bent portion. Therefore, it is possible to suppress a partial decrease in the power generation amount of the power generation unit.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0009] Hereinafter, with reference to FIGS. 1 to 6, an embodiment of a fuel cell stack will be described. (Fuel Cell Stack 10) As shown in FIG. 1, the fuel cell stack 10 is configured by stacking a plurality of single cells 20.

[0010] (Single Cell 20) As shown in FIG. 2, the single cell 20 has, for example, a square plate shape. That is, the single cell 20 has a pair of first sides 21 extending parallel to each other and a pair of second sides 22 orthogonal to the first sides 21 and extending parallel to each other.

[0011] Hereinafter, the stacking direction of the single cell 20 will be simply referred to as the stacking direction for explanation. Also, the direction in which the first side 21 extends will be referred to as the X-axis direction, and the direction in which the second side 22 extends will be referred to as the Y-axis direction for explanation. The stacking direction, the X-axis direction, and the Y-axis direction are orthogonal to each other.

[0012] The single cell 20 has a fuel gas supply manifold M1 for supplying fuel gas inside the single cell 20 and a fuel gas discharge manifold M2 for discharging fuel gas outside the single cell 20. Also, the single cell 20 has an oxidant gas supply manifold M3 for supplying oxidant gas inside the single cell 20 and an oxidant gas discharge manifold M4 for discharging oxidant gas outside the single cell 20.

[0013] The manifolds M1 to M4 have, for example, an oval shape that is long in the Y-axis direction. The fuel gas supply manifold M1 and the oxidant gas discharge manifold M4 are located at one end of the single cell 20 in the X-axis direction and are arranged in this order from one side to the other side in the Y-axis direction. The fuel gas discharge manifold M2 and the oxidant gas supply manifold M3 are located at the other end of the single cell 20 on the side opposite to one side in the X-axis direction and are arranged in this order from the other side to the one side in the Y-axis direction. The fuel gas is, for example, hydrogen. The oxidant gas is, for example, air.

[0014] The single cell 20 has two refrigerant supply manifolds M5 that supply a cooling medium inside the fuel cell stack 10 and two refrigerant discharge manifolds M6 that discharge the cooling medium outside the fuel cell stack 10. Each refrigerant supply manifold M5 and each refrigerant discharge manifold M6 are, for example, oval in shape and long in the X-axis direction. The two refrigerant supply manifolds M5 are located at the other end of the single cell 20 in the Y-axis direction and are arranged side by side with a gap therebetween in the X-axis direction. The two refrigerant discharge manifolds M6 are located at one end of the single cell 20 in the Y-axis direction and are arranged side by side with a gap therebetween in the X-axis direction. The cooling medium is, for example, water.

[0015] The single cell 20 includes a power generation unit 30, a frame 40, and a pair of separators 50. The power generation unit 30 is in a sheet shape. The frame 40 surrounds the outer peripheral edge of the power generation unit 30. The pair of separators 50 sandwich the power generation unit 30 and the frame 40 from both sides in the stacking direction. The power generation unit 30 and the separators 50 are, for example, square in shape in plan view. The frame 40 is, for example, in a square frame shape in plan view.

[0016] (Power generation unit 30) As shown in FIG. 1, the power generation unit 30 includes a membrane electrode assembly 31, an anode side gas diffusion layer 32 that sandwiches the membrane electrode assembly 31, and a cathode side gas diffusion layer 33. Although not shown, the membrane electrode assembly 31 includes an electrolyte membrane, an anode electrode catalyst layer that sandwiches the electrolyte membrane, and a cathode electrode catalyst layer. The anode side gas diffusion layer 32 is laminated on the anode electrode catalyst layer. The cathode side gas diffusion layer 33 is laminated on the cathode electrode catalyst layer.

[0017] Fuel gas is supplied to the anode side surface of the power generation unit 30 through the fuel gas supply manifold M1. Oxidant gas is supplied to the cathode side surface of the power generation unit 30 through the oxidant gas supply manifold M3. Thereby, power generation is performed in the power generation unit 30 by an electrochemical reaction between the fuel gas and the oxidant gas.

[0018] In the fuel cell stack 10, each single cell 20 generates heat as power is generated in the power generation unit 30. Therefore, a cooling flow path 80, which will be described later, is formed inside the fuel cell stack 10. A cooling medium is supplied to the cooling flow path 80 through a refrigerant supply manifold M5.

[0019] (Frame 40) The frame 40 is formed of a resin material having insulation properties. The frame 40 has a housing hole 41 for housing the power generation unit 30 at the center.

[0020] The frame 40 has through holes hf1 to hf6 that constitute the manifolds M1 to M6 on the outer peripheral side of the housing hole 41. The frame 40 has a plurality of slits 42 penetrating the frame 40 between the housing hole 41 and the through holes hf1 to hf4. The plurality of slits 42 are arranged in parallel at intervals in the Y-axis direction. Each slit 42 has an oval shape that is long in the X-axis direction. One end of each slit 42 communicates in the stacking direction with any one of the through holes hs1 to hs4 of a separator 50, which will be described later. The other end of each slit 42, which is opposite to one end, communicates in the stacking direction with the gas flow path 60 of the separator 50, which will be described later. Each of the manifolds M1 to M4 communicates with the gas flow path 60 through, for example, seven slits 42.

[0021] (Separator 50) The separator 50 is formed, for example, by press-molding a metal plate such as stainless steel, a titanium alloy, or pure titanium.

[0022] One of the pair of separators 50 is disposed on the anode-side surface of the power generation unit 30. The other of the pair of separators 50 is disposed on the cathode-side surface of the power generation unit 30.

[0023] Hereinafter, the separator 50 disposed on the anode side surface of the power generation unit 30 may be referred to as the anode separator 51, and the separator 50 disposed on the cathode side surface of the power generation unit 30 may be referred to as the cathode separator 52 for distinction.

[0024] The anode separator 51 and the cathode separator 52 have the same shape as each other. The anode separator 51 and the cathode separator 52 are arranged in poses that are inverted with respect to each other with respect to the power generation unit 30 with the virtual axis V as the axis of inversion. The virtual axis V is an axis that passes through the center in the X-axis direction of the separator 50 and extends in the Y-axis direction.

[0025] The separator 50 has through holes hs1 to hs6 that constitute the manifolds M1 to M6. As described above, the anode separator 51 and the cathode separator 52 are arranged in poses that are inverted with respect to each other with respect to the power generation unit 30. For this reason, the through hole hs1 of the anode separator 51 and the through hole hs3 of the cathode separator 52 communicate with each other, and the through hole hs2 of the anode separator 51 and the through hole hs4 of the cathode separator 52 communicate with each other. Also, the through hole hs3 of the anode separator 51 and the through hole hs1 of the cathode separator 52 communicate with each other, and the through hole hs4 of the anode separator 51 and the through hole hs2 of the cathode separator 52 communicate with each other. Also, the through hole hs5 of the anode separator 51 and the through hole hs5 of the cathode separator 52 communicate with each other, and the through hole hs6 of the anode separator 51 and the through hole hs6 of the cathode separator 52 communicate with each other.

[0026] As shown in FIG. 3, on the surface of the separator 50 facing the power generation unit 30, groove-shaped gas flow paths 60 through which the reaction gas flows and ribs 70 extending along the gas flow paths 60 are alternately arranged side by side. The separator 50 has, for example, eight gas flow paths 60 extending in parallel with each other. The shape of each gas flow path 60 is a so-called serpentine shape that extends in a meandering manner from the through hole hs1 to the through hole hs2.

[0027] Fuel gas flows as a reaction gas through the gas flow path 60 of the anode separator 51. Oxidant gas flows as a reaction gas through the gas flow path 60 of the cathode separator 52. The reaction gas is supplied to the power generation unit 30 by flowing through the gas flow path 60.

[0028] The supply method of the reaction gas in the fuel cell stack 10 is, for example, a so-called counterflow method in which the fuel gas and the oxidant gas flow in opposite directions to each other. Hereinafter, the upstream side in the flow direction of the reaction gas in the gas flow path 60 will be simply referred to as the upstream side, and the downstream side in the flow direction will be simply referred to as the downstream side for explanation.

[0029] Each gas flow path 60 is formed in a substantially S shape by connecting the first extending portions Lg1 to Lg3 with the second extending portions Tg1 and Tg2. The reaction gas flows in the order of the first extending portion Lg1, the second extending portion Tg1, the first extending portion Lg2, the second extending portion Tg2, and the first extending portion Lg3.

[0030] The first extending portions Lg1 to Lg3 are arranged in parallel with spaces therebetween in the Y-axis direction. The first extending portions Lg1 to Lg3 extend in the X-axis direction while meandering in a wave shape. The X-axis direction is an example of the "first direction".

[0031] The second extending portions Tg1 and Tg2 extend linearly while being inclined with respect to the virtual axis V so as to be located on one side in the X-axis direction toward the downstream side. The direction in which the second extending portions Tg1 and Tg2 extend is an example of the "second direction".

[0032] The upstream end of the first extending portion Lg1 is connected to the through hole hs1 via the slit 42 of the frame 40. The second extending portion Tg1 connects the downstream end of the first extending portion Lg1 and the upstream end of the first extending portion Lg2. The second extending portion Tg2 connects the downstream end of the first extending portion Lg2 and the upstream end of the first extending portion Lg3. The downstream end of the first extending portion Lg3 is connected to the through hole hs2 via the slit 42. When the reaction gas flows from the first extending portion Lg1 to the first extending portion Lg2 through the second extending portion Tg1 and when it flows from the first extending portion Lg2 to the first extending portion Lg3 through the second extending portion Tg2, the flow direction of the reaction gas is reversed. Therefore, the second extending portions Tg1 and Tg2 constitute the folded-back portion of the gas flow path 60.

[0033] The gas flow path 60 has a plurality of bending portions Cg1, Cg2, Cg3, and Cg4 that constitute the folded-back portion of the gas flow path 60. The bending portions Cg1, Cg2, Cg3, and Cg4 are located in this order from the upstream side. Hereinafter, the bending portions Cg1, Cg2, Cg3, and Cg4 may be collectively referred to as the bending portion Cg.

[0034] The bending portion Cg1 includes the connection portion between the first extending portion Lg1 and the second extending portion Tg1. The bending portion Cg2 includes the connection portion between the first extending portion Lg2 and the second extending portion Tg1. The bending portion Cg3 includes the connection portion between the first extending portion Lg2 and the second extending portion Tg2. The bending portion Cg4 includes the connection portion between the first extending portion Lg3 and the second extending portion Tg2.

[0035] As shown in FIGS. 3 and 4, at least one of the plurality of gas flow paths 60 is provided with a branch rib 71 that branches the gas flow path 60 into two branch flow paths 62 at any one of the bending portions Cg1 to Cg4. The branch rib 71 is in an island shape. The branch rib 71 has a gap with the rib 70 over the entire circumference. The shape of the branch rib 71 is substantially semi-circular in plan view. The branch rib 71 protrudes toward the power generation unit 30. The branch rib 71 is in contact with the anode side gas diffusion layer 32 or the cathode side gas diffusion layer 33.

[0036] As shown in FIG. 3, in the present embodiment, one branch rib 71 is provided in each of six out of the eight gas flow paths 60. Hereinafter, among the eight gas flow paths 60, in the order of the first extending portion Lg1 being closer to the through hole hs6, they are referred to as the first gas flow path 60, the second gas flow path 60, and so on.

[0037] The first and second gas flow paths 60 are provided with branch ribs 71 at the bent portion Cg2. The third and fourth gas flow paths 60 are provided with branch ribs 71 at the bent portion Cg4. The fifth and seventh gas flow paths 60 are not provided with branch ribs 71. The sixth gas flow path 60 is provided with a branch rib 71 at the bent portion Cg1. The eighth gas flow path 60 is provided with a branch rib 71 at the bent portion Cg3. The arrangement of the branch ribs 71 and the presence or absence of the branch ribs 71 in the gas flow path 60 are experimentally determined based on the pressure, flow rate, etc. of the reaction gas flowing through each gas flow path 60.

[0038] As shown in FIG. 4, the branch flow path 62 includes an outer flow path 63 and an inner flow path 64. The outer flow path 63 is a flow path that extends outside the bent portion Cg. The inner flow path 64 is a flow path that extends inside the bent portion Cg rather than the outer flow path 63. The outer flow path 63 extends in an arc shape. The inner flow path 64 extends linearly. The flow path length of the inner flow path 64 is shorter than the flow path length of the outer flow path 63.

[0039] As shown in FIG. 5, the flow path cross-sectional areas of the outer flow path 63 and the inner flow path 64 are the same. More specifically, the width and depth of the outer flow path 63 and the width and depth of the inner flow path 64 are the same. As shown in FIG. 4, the reaction gas flowing through the general portion 61, which is a portion of the gas flow path 60 different from the branch flow path 62, is distributed to two branch flow paths 62 by the branch rib 71 and then merges at the general portion 61 located on the downstream side of the two branch flow paths 62. That is, the general portion 61 has a merging portion 61a that includes the connection portion between the branch flow paths 62 on the upstream side and the downstream side of the branch rib 71. The flow path cross-sectional area of the portion of the general portion 61 excluding the merging portion 61a is the same as the flow path cross-sectional areas of the outer flow path 63 and the inner flow path 64 throughout.

[0040] (Cooling flow path 80) As shown in FIG. 1, in the fuel cell stack 10, among two adjacent single cells 20 in the stacking direction, the anode separator 51 constituting one single cell 20 and the cathode separator 52 constituting the other single cell 20 are in contact with each other. A cooling flow path 80 through which a cooling medium flows is formed between the anode separator 51 and the cathode separator 52 that are in contact with each other in two adjacent single cells 20 in the stacking direction. Although not shown, a gasket for sealing between the two single cells 20 is provided between the anode separator 51 and the cathode separator 52 that are in contact with each other.

[0041] As shown in FIG. 2, the separator 50 has a plurality of cooling grooves 81 that constitute the cooling flow path 80. The cooling grooves 81 are formed on the surface of the separator 50 opposite to the surface on which the gas flow path 60 is formed. The cooling grooves 81 are formed by the back surface shape of the rib 70. The shape of the cooling grooves 81 is a serpentine shape that extends in a meandering manner from the through hole hs1 to the through hole hs2. The cooling flow path 80 is constituted by the gap between the cooling grooves 81 of the anode separator 51 and the cooling grooves 81 of the cathode separator 52. The cooling medium supplied from the refrigerant supply manifold M5 flows through the cooling flow path 80 and is discharged from the refrigerant discharge manifold M6.

[0042] <Operation of the present embodiment> As shown in FIG. 4, the bent portion Cg of the gas flow path 60 is branched into two branch flow paths 62 including an outer flow path 63 and an inner flow path 64 by the branch rib 71. For this reason, the inner flow path 64 is located between the outer flow path 63 and another gas flow path 60 adjacent to the gas flow path 60 including the outer flow path 63. Thereby, even when the distance between the bent portions Cg of the adjacent gas flow paths 60 increases, the width of the portion of the rib 70 extending along the bent portion Cg can be suppressed from increasing because the inner flow path 64 is located inside the bent portion Cg.

[0043] When the separator 150 of the comparative example shown in FIG. 6 does not have the bent portion Cg with the branch flow path 62, the width of the portion of the rib 70 extending along the bent portion Cg may increase. In this case, as indicated by the arrow in FIG. 6, in the portion of the power generation unit 30 that contacts the rib 70 having a large width, the reaction gas hardly reaches, so the power generation amount of the power generation unit 30 may partially decrease.

[0044] On the other hand, according to the separator 50 of the present embodiment, since the bent portion Cg has the branch flow path 62, as indicated by the arrow in FIG. 5, the reaction gas easily reaches the portion of the power generation unit 30 that contacts the rib 70.

[0045] <Effects of the Present Embodiment> (1) An island-shaped branch rib 71 that branches the gas flow path 60 into two branch flow paths 62 is provided at the bent portion Cg of the gas flow path 60. The two branch flow paths 62 include an outer flow path 63 that extends outside the bent portion Cg and an inner flow path 64 that extends inside the bent portion Cg rather than the outer flow path 63.

[0046] According to the above configuration, since the above-described operation is exhibited, it is possible to suppress a partial decrease in the power generation amount of the power generation unit 30. (2) The flow path cross-sectional areas of the two branch flow paths 62 are the same as each other.

[0047] According to the above configuration, a difference hardly occurs in the flow rate of the reaction gas in the two branch flow paths 62. Therefore, it is possible to suppress a partial decrease in the power generation amount in the portion of the power generation unit 30 facing the bent portion Cg.

[0048] (3) The outer flow path 63 extends in an arc shape. The inner flow path 64 extends linearly. For example, when both the outer flow path 63 and the inner flow path 64 extend in a curved manner, the area of the merging portion 61a where the outer flow path 63 and the inner flow path 64 merge may increase. In this case, when the power generation unit 30 sinks into the merging portion 61a, the flow path cross-sectional area of the merging portion 61a may become small.

[0049] In this regard, according to the above configuration, it is possible to suppress an increase in the area of the confluence portion 61a where the branch channels 62 merge as compared with the case where both the outer channel 63 and the inner channel 64 are curved and extend. Therefore, it is possible to suppress the sinking of the power generation unit 30 in the confluence portion 61a.

[0050] (4) The second extending portion Tg1 connects the downstream end of the first extending portion Lg1 and the upstream end of the first extending portion Lg2. The second extending portion Tg2 connects the downstream end of the first extending portion Lg2 and the upstream end of the first extending portion Lg3.

[0051] According to the above configuration, the gas flow path 60 is folded back by the first extending portion Lg1, the second extending portion Tg1, and the first extending portion Lg2. Also, the gas flow path 60 is folded back by the first extending portion Lg2, the second extending portion Tg2, and the first extending portion Lg3. In the bent portion Cg formed in the folded-back portion of the gas flow path 60, the degree of bending tends to be large. In this case, in a plurality of bent portions Cg arranged in parallel with each other, a difference in the degree of bending is likely to occur, so a difference is also likely to occur in the width of the rib 70 located between the bent portions Cg.

[0052] In this regard, according to the above configuration, since the branch rib 71 is provided in the bent portion Cg, it is possible to suppress an increase in the width of the rib 70 located between the bent portions Cg. <Modification Example> This embodiment can be implemented with the following modifications. This embodiment and the following modification examples can be implemented in combination with each other within a range that is not technically contradictory.

[0053] · The shape of the branch rib 71 is not limited to a semicircular shape in plan view. For example, as shown in FIG. 7(a), the branch rib 71 may have a rectangular shape having a long side extending in the flow direction. As shown in FIG. 7(b), the branch rib 71 may have an elliptical shape. As shown in FIG. 7(c), the branch rib 71 may have a triangular shape. As shown in FIG. 7(d), the branch rib 71 may have a crescent shape. In these modification examples, the flow path cross-sectional areas of the outer flow path 63 and the inner flow path 64 are different from each other.

[0054] · A plurality of branch ribs 71 may be provided on the bent portion Cg. In this case, the shapes of the plurality of branch ribs 71 may be different from each other. For example, as shown in FIG. 8(a), a plurality (two in this modification example) of branch ribs 71 may be provided side by side in the width direction of the bent portion Cg. As shown in FIG. 8(b), two branch ribs 71 may be provided side by side in the flow direction on the bent portion Cg. As shown in FIG. 8(c), three branch ribs 71 may be provided side by side in the flow direction on the bent portion Cg. According to these modification examples, the bent portion Cg is branched into three or more branch channels 62 including the outer channel 63 and the inner channel 64 by the plurality of branch ribs 71. Therefore, the reaction gas can be supplied to a wider range of the portion of the power generation unit 30 facing the bent portion Cg. Therefore, it is possible to suppress a partial decrease in the power generation amount of the power generation unit 30.

[0055] · The cross-sectional area of the flow path of the portion of the general portion 61 excluding the confluence portion 61a may be different from the cross-sectional areas of the outer flow path 63 and the inner flow path 64. · The second extending portions Tg1, Tg2 may extend in a direction orthogonal to the direction in which the first extending portions Lg1, Lg2, Lg3 extend, that is, in the direction in which the virtual axis V extends.

[0056] · The second extending portions Tg1, Tg2 may extend while meandering in a wave shape. · The shape of the gas flow path 60 does not have to be a serpentine shape as long as it has the first extending portion Lg1 and the second extending portion Tg1. The gas flow path 60 may have, for example, a first extending portion Lg1 facing the power generation unit 30 and two second extending portions Tg1 connected to the upstream end and the downstream end of the first extending portion Lg1, respectively. In this case, each second extending portion Tg1 may be connected to any one of the manifolds M1 to M4.

[0057] · The supply method of the reaction gas in the fuel cell stack 10 may be a so-called co-flow method in which the fuel gas and the oxidant gas flow in the same direction in the first extending portions Lg1, Lg2, Lg3.

[0058] ·Each slit 42 does not have to penetrate the frame 40 and may be in a groove shape that opens to one side in the thickness direction of the frame 40. In this case, the frame 40 may have a slit 42 between the accommodation hole 41 and each through hole hf1, hf2 on the surface facing the anode separator 51. Further, the frame 40 may have a slit 42 between the accommodation hole 41 and each through hole hf3, hf4 on the surface facing the cathode separator 52.

[0059] ·The material of the separator 50 may be a carbon material or a composite material containing a carbon material and a resin material. ·The separator 50 may be formed by cutting or injection molding.

[0060] <Supplementary Note> The above embodiment includes the configurations described in the following supplementary note. [Supplementary Note 1] A fuel cell stack configured by stacking a plurality of single cells including a power generation unit including a membrane electrode assembly and a pair of separators sandwiching the power generation unit, wherein on the surface of the separator facing the power generation unit, a gas flow path through which a reaction gas flows and ribs extending along the gas flow path are alternately arranged, the gas flow path has a first extending portion extending in a first direction while meandering in a wave shape, and a second extending portion connected to an end of the first extending portion in the first direction and extending in a second direction different from the first direction, and at a bent portion of the gas flow path including a connection portion between the first extending portion and the second extending portion, an island-shaped branch rib that protrudes toward the power generation unit and branches the gas flow path into a plurality of branch flow paths is provided, and the plurality of branch flow paths include an outer flow path extending outside the bent portion and an inner flow path extending inside the bent portion rather than the outer flow path.

[0061] [Supplementary Note 2] The fuel cell stack according to [Supplementary Note 1], wherein the flow path cross-sectional areas of the plurality of branch flow paths are the same as each other. [Appendix 3] The outer flow path extends in an arcuate curve, and the inner flow path extends linearly. The fuel cell stack according to [Appendix 1] or [Appendix 2].

[0062] [Appendix 4] The gas flow path has a plurality of the first extending portions that are parallel to each other and in which the flow directions of the reaction gas are opposite to each other. The second extending portion connects a downstream end portion in the flow direction of one of the first extending portions of the two first extending portions that are parallel to each other and an upstream end portion in the flow direction of the other first extending portion. The fuel cell stack according to any one of [Appendix 1] to [Appendix 3].

[0063] [Appendix 5] A plurality of the branch ribs are provided at the bent portion. The fuel cell stack according to any one of [Appendix 1] to [Appendix 4].

Explanation of Signs

[0064] Cg, Cg1, Cg2, Cg3, Cg4,... Bent portion hf1, hf2, hf3, hf4, hf5, hf6... Through hole hs1, hs2, hs3, hs4, hs5, hs6... Through hole Lg1, Lg2, Lg3... First extending portion Tg1, Tg2... Second extending portion M1... Fuel gas supply manifold M2... Fuel gas discharge manifold M3... Oxidant gas supply manifold M4... Oxidant gas discharge manifold M5... Refrigerant supply manifold M6... Refrigerant discharge manifold 10... Fuel cell stack 20... Single cell 21... First side 22... Second side 30... Power generation unit 31... Membrane electrode assembly 32... Anode side gas diffusion layer 33... Cathode side gas diffusion layer 40... Frame 41…Receiving hole 42…Slit 50, 150…Separator 51…Anode separator 52…Cathode separator 60…Gas flow path 61…General part 61a…Confluence part 62…Branching flow path 63…Outer flow path 64…Inner flow path 70…Rib 71…Branching rib 80…Cooling flow path 81…Cooling groove

Claims

1. A fuel cell stack configured by stacking a plurality of single cells each including a power generation unit containing a membrane electrode assembly and a pair of separators sandwiching the power generation unit, wherein on a surface of the separator facing the power generation unit, a gas flow path through which a reaction gas flows and ribs extending along the gas flow path are alternately provided side by side, the gas flow path has a first extending portion extending in a first direction while meandering in a wave shape, and a second extending portion connected to an end of the first extending portion in the first direction and extending in a second direction different from the first direction, an island-shaped branch rib that protrudes toward the power generation unit and branches the gas flow path into a plurality of branch flow paths is provided at a bent portion of the gas flow path including a connection portion between the first extending portion and the second extending portion, the plurality of branch flow paths include an outer flow path extending outside the bent portion and an inner flow path extending inside the bent portion rather than the outer flow path, a fuel cell stack.

2. The flow path cross-sectional areas of the plurality of branch flow paths are the same as each other. The fuel cell stack according to Claim 1.

3. The outer flow path extends in an arcuate curve, and the inner flow path extends linearly. The fuel cell stack according to Claim 1.

4. The gas flow path has a plurality of the first extending portions that are parallel to each other and in which the flow directions of the reaction gas are opposite to each other, and the second extending portion connects a downstream end of one of the first extending portions in the flow direction to an upstream end of the other first extending portion in the flow direction among the two first extending portions that are parallel to each other. The fuel cell stack according to Claim 1.

5. A plurality of the branch ribs are provided at the bent portion. The fuel cell stack according to any one of Claims 1 to 4.

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