Fuel cell stack

Abstract

This fuel cell stack (13) comprises a plurality of single cells (12) that are stacked. Each single cell (12) has two coolant supply holes (24, 28) that supply a coolant to a coolant flow field (38) and two coolant discharge holes (26, 30) that discharge the coolant from the coolant flow field (38). The coolant flow field (38) is provided with a guide part (40) that guides the coolant such that, when the coolant is supplied to the coolant flow field (38) from the two coolant supply holes (24, 28), two flows are formed, one being the flow of the coolant from one of the two coolant supply holes to one of the two coolant discharge holes, and the other being the flow of the coolant from the other of the two coolant supply holes to the other of the two coolant discharge holes.

Description

Fuel cell stack

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

[0002] Patent Document 1 discloses a fuel cell stack formed by stacking a plurality of rectangular plate-shaped power generation cells. A power generation cell includes a membrane electrode assembly with a resin frame, and a first metal separator and a second metal separator that sandwich the membrane electrode assembly with a resin frame from both sides in the thickness direction. An oxidant gas supply communication hole, a coolant supply communication hole, and a fuel gas discharge communication hole are provided at one end in the long side direction of the power generation cell.

[0003] A fuel gas supply communication hole, a coolant discharge communication hole, and an oxidant gas discharge communication hole are provided at the other end in the long side direction of the power generation cell. The power generation cell generates power when fuel gas is supplied to one surface of the membrane electrode assembly through the fuel gas supply communication hole, and oxidant gas is supplied to the other surface of the membrane electrode assembly through the oxidant gas supply communication hole. The fuel gas and oxidant gas supplied to the membrane electrode assembly are discharged to the fuel gas discharge communication hole and the oxidant gas discharge communication hole, respectively.

[0004] Each power generation cell generates heat along with power generation. Therefore, between the first metal separator of one power generation cell and the second metal separator of the other adjacent power generation cell in the stacking direction of the fuel cell stack, a coolant flow path through which a coolant flows is formed. The coolant is guided from the coolant supply communication hole to the coolant flow path, flows through the coolant flow path, and is then discharged to the coolant discharge communication hole. Thereby, each power generation cell is cooled.

[0005] Japanese Patent Application Laid-Open No. 2024-144111

[0006] Incidentally, in the above-described fuel cell stack, the coolant is guided to the coolant flow path through one coolant supply communication hole provided in each power generation cell and discharged to one coolant discharge communication hole. In the above-described fuel cell stack, there is room for improvement in efficiently cooling the power generation cells.

[0007] A fuel cell stack according to one aspect of the present disclosure comprises a plurality of stacked single cells, each single cell having a power generation section and a pair of separators flanking the power generation section, and having a plate shape with mutually orthogonal first and second sides, wherein the fuel cell stack has a cooling medium flow region between the separators that are in contact with each other in two adjacent single cells in the stacking direction of the plurality of single cells, and when the direction in which the first side extends is defined as the first direction and the direction in which the second side extends is defined as the second direction, the contact surface of the separator that is in contact with the power generation section is provided with a gas flow path that extends in the first direction and through which a reaction gas flows, and the single cell has two cooling medium supply holes for supplying the cooling medium to the cooling medium flow region and two cooling medium discharge holes for discharging the cooling medium from the cooling medium flow region, and two of the cooling medium The cooling medium supply holes and the two cooling medium discharge holes are arranged such that, in the first direction, there is one cooling medium supply hole and one cooling medium discharge hole on each side of the cooling medium flow region, or the two cooling medium supply holes and the two cooling medium discharge holes are arranged such that, in the first direction, there are opposite sides of the cooling medium flow region, and the cooling medium flow region is provided with guides for guiding the cooling medium such that when the cooling medium is supplied to the cooling medium flow region from the two cooling medium supply holes, two flows of the cooling medium are formed: a flow of the cooling medium from one of the two cooling medium supply holes toward one of the two cooling medium discharge holes, and a flow of the cooling medium from the other of the two cooling medium supply holes toward the other of the two cooling medium discharge holes.

[0008] Figure 1 is a schematic cross-sectional view of a fuel cell according to the first embodiment. Figure 2 is an exploded perspective view showing a single cell of the fuel cell according to the first embodiment. Figure 3 is a schematic cross-sectional view of the irregularities constituting the first flow path of the first separator and the second flow path of the second separator according to the first embodiment. Figure 4 is a schematic view of the fuel cell stack according to the first embodiment as seen from the stacking direction of the single cells. Figure 5 is an enlarged view showing a part of Figure 4. Figure 6 is an enlarged view showing the main part of Figure 4. Figure 7 is a schematic view of the fuel cell stack according to the second embodiment as seen from the stacking direction of the single cells. Figure 8 is an enlarged view showing a part of Figure 7. Figure 9 is an enlarged view showing the main part of Figure 7. Figure 10 is a schematic view of a modified fuel cell stack as seen from the stacking direction of the single cells. Figure 11 is a schematic view of another modified fuel cell stack as seen from the stacking direction of the single cells. Figure 12 is a schematic view of yet another modified fuel cell stack as seen from the stacking direction of the single cells.

[0009] (First Embodiment) The first embodiment will be described below with reference to the drawings. <Fuel Cell 11> As shown in Figure 1, the fuel cell 11 comprises a fuel cell stack 13 and a pair of end plates 14. The fuel cell stack 13 comprises a plurality of rectangular plate-shaped single cells 12 that generate electricity. The plurality of single cells 12 are stacked in their thickness direction Z. The pair of end plates 14 sandwich the fuel cell stack 13 from both sides in the thickness direction Z. In this example, the thickness direction Z of the single cell 12 coincides with the stacking direction of the plurality of single cells 12.

[0010] The pair of end plates 14 are fastened together at their outer edges by a plurality of bolts 15 and a plurality of nuts 16, thereby pressing the fuel cell stack 13 in the thickness direction Z to compress it. Between each of the pair of end plates 14 and the fuel cell stack 13 are interposed terminal plates (not shown) for collecting current and insulating plates (not shown) for insulation.

[0011] <Single Cell 12> As shown in Figure 2, the single cell 12 has a rectangular plate-shaped support frame 18 that supports the rectangular sheet-shaped power generation unit 17, a pair of rectangular sheet-shaped gas diffusion layers 19 that sandwich the power generation unit 17, and a pair of rectangular plate-shaped separators 20 that sandwich the support frame 18 in a state where the power generation unit 17 sandwiched between the pair of gas diffusion layers 19 is supported.

[0012] Of the pair of separators 20, one positioned on the cathode side is designated as the first separator 21, and the other positioned on the anode side is designated as the second separator 22. The power generation unit 17 is supported while housed in a rectangular opening 23 formed in the center of the support frame 18. The power generation unit 17 is composed of a membrane electrode assembly (MEA).

[0013] In the following explanation, the long side direction in a single cell 12 will be defined as the long side direction X, which is an example of the first direction in which the long side extends as an example of the first side. The short side direction in a single cell 12 will be defined as the short side direction Y, which is an example of the second direction in which the short side extends as an example of the second side. The thickness direction in a single cell 12 will be defined as the thickness direction Z. The long side direction X, the short side direction Y, and the thickness direction Z are mutually orthogonal directions.

[0014] <Flow path configuration in single cell 12> As shown in Figure 2, at one end of the long side direction X of the single cell 12, a first cooling medium supply hole 24 into which a cooling medium is supplied, an oxidant gas supply hole 25 into which an oxidant gas is supplied, a first cooling medium discharge hole 26 into which the cooling medium is discharged, and a fuel gas discharge hole 27 into which fuel gas is discharged are formed. The first cooling medium supply hole 24, the oxidant gas supply hole 25, the first cooling medium discharge hole 26, and the fuel gas discharge hole 27 are arranged in this order from one side to the other in the short side direction Y of the single cell 12.

[0015] At the other end of the long side direction X of the single cell 12, a second cooling medium supply hole 28 for supplying a cooling medium, a fuel gas supply hole 29 for supplying fuel gas, a second cooling medium discharge hole 30 for discharging the cooling medium, and an oxidant gas discharge hole 31 for discharging the oxidant gas are formed. The second cooling medium supply hole 28, the fuel gas supply hole 29, the second cooling medium discharge hole 30, and the oxidant gas discharge hole 31 are arranged in this order from one side to the other in the short side direction Y of the single cell 12.

[0016] Fuel gas is supplied to the fuel gas supply port 29, for example, a fuel gas containing hydrogen as an example of a reaction gas. Fuel gas is discharged from the fuel gas discharge port 27. Oxidizer gas is supplied to the oxidizer gas supply port 25, for example, an oxidizer gas containing oxygen as an example of a reaction gas. Oxidizer gas is discharged from the oxidizer gas discharge port 31. Cooling medium, such as cooling water, is supplied to the first cooling medium supply port 24 and the second cooling medium supply port 28. Cooling medium is discharged from the first cooling medium discharge port 26 and the second cooling medium discharge port 30.

[0017] The first cooling medium supply port 24 and the second cooling medium supply port 28 are arranged opposite each other in the long side direction X. The oxidizer gas supply port 25 and the fuel gas supply port 29 are arranged opposite each other in the long side direction X. The first cooling medium discharge port 26 and the second cooling medium discharge port 30 are arranged opposite each other in the long side direction X. The fuel gas discharge port 27 and the oxidizer gas discharge port 31 are arranged opposite each other in the long side direction X.

[0018] The first cooling medium supply port 24, the second cooling medium supply port 28, the first cooling medium discharge port 26, the second cooling medium discharge port 30, the fuel gas supply port 29, the fuel gas discharge port 27, the oxidizer gas supply port 25, and the oxidizer gas discharge port 31 in the single cell 12 each form a manifold extending in the thickness direction Z in the fuel cell stack 13.

[0019] <Separator 20> As shown in Figures 2 and 3, the first contact surface 32 of the first separator 21, which is an example of a contact surface that contacts the power generation section 17, has a first flow path 33 formed on it, which is an example of a plurality of gas flow paths through which the oxidizing gas flows. Each first flow path 33 is formed by the same uneven surface on both sides, which is formed by press-forming the metal plate that constitutes the first separator 21. The first contact surface 32 is located in the center of the first separator 21 and has a rectangular shape.

[0020] In this example, the irregularities forming each of the first flow channels 33 of the first separator 21 are trapezoidal in cross-sectional view. Each first flow channel 33 connects the oxidant gas supply hole 25 and the oxidant gas discharge hole 31. Oxidant gas flows through each first flow channel 33, and the oxidant gas is supplied to the power generation unit 17 between the oxidant gas supply hole 25 and the oxidant gas discharge hole 31.

[0021] The recessed portion 34 on the power generation section 17 side of the uneven surface of the first separator 21 forms the first flow path 33. The multiple recessed portions 34 that form the multiple first flow paths 33 extend at regular intervals. Protruding portions 35 are formed between the recessed portions 34 of the first separator 21. The uneven surface of the first separator 21 is such that the recessed portion 34 on one surface constitutes the protruding portion 35 on the other surface, and the protruding portion 35 on one surface constitutes the recessed portion 34 on the other surface.

[0022] The irregularities in the first separator 21 are configured such that the recessed portion 34 and the convex portion 35 are arranged alternately at equal intervals in the short-side direction Y, which is the direction in which the multiple first flow channels 33 are aligned. The multiple first flow channels 33 in the first separator 21 extend linearly in the long-side direction X.

[0023] As shown in Figures 2 and 3, the second contact surface 36, which is an example of a contact surface in the second separator 22 that contacts the power generation unit 17, has a second flow path 37 formed on it, which is an example of a plurality of gas flow paths through which fuel gas flows. Each second flow path 37 is formed by a single set of irregularities on both sides of the metal plate constituting the second separator 22, which is formed by press processing. The second contact surface 36 is located in the center of the second separator 22 and has a rectangular shape.

[0024] In this example, the irregularities forming each second flow path 37 of the second separator 22 are trapezoidal in cross-sectional view. Each second flow path 37 connects the fuel gas supply hole 29 and the fuel gas discharge hole 27. Fuel gas flows through each second flow path 37, and fuel gas is supplied to the power generation unit 17 between the fuel gas supply hole 29 and the fuel gas discharge hole 27.

[0025] The recessed portion 34 on the power generation section 17 side of the uneven surface of the second separator 22 forms the second flow path 37. The multiple recessed portions 34 that form the multiple second flow paths 37 extend at regular intervals. Protruding portions 35 are formed between the recessed portions 34 of the second separator 22. The uneven surface of the second separator 22 is such that the recessed portion 34 on one surface constitutes the protruding portion 35 on the other surface, and the protruding portion 35 on one surface constitutes the recessed portion 34 on the other surface.

[0026] The irregularities in the second separator 22 are configured such that the recessed portion 34 and the convex portion 35 are arranged alternately at equal intervals in the short-side direction Y, which is the direction in which the multiple second flow channels 37 are aligned. The multiple second flow channels 37 in the second separator 22 meander in the short-side direction Y and extend in the long-side direction X. That is, the multiple second flow channels 37 in the second separator 22 extend in a zigzag pattern in the long-side direction X.

[0027] When viewed from the thickness direction Z, the first separator 21 and the second separator 22 have overlapping first cooling medium supply holes 24, second cooling medium supply holes 28, first cooling medium discharge holes 26, second cooling medium discharge holes 30, fuel gas supply holes 29, fuel gas discharge holes 27, oxidizer gas supply holes 25, and oxidizer gas discharge holes 31, respectively.

[0028] <Fuel Cell Stack 13> As shown in Figure 4, in the fuel cell stack 13, the first separator 21 of one of two single cells 12 adjacent in the stacking direction (thickness direction Z) and the second separator 22 of the other single cell 12 form a pair and are in contact with each other. Between the first separator 21 of one of the two single cells 12 adjacent in the stacking direction and the second separator 22 of the other single cell 12 in the fuel cell stack 13, a cooling medium flow region 38 is formed through which the cooling medium flows.

[0029] Each cell 12 has a first cooling medium supply hole 24 and a second cooling medium supply hole 28 for supplying cooling medium to the cooling medium flow region 38, and a first cooling medium discharge hole 26 and a second cooling medium discharge hole 30 for discharging cooling medium from the cooling medium flow region 38. The first cooling medium supply hole 24 and the second cooling medium supply hole 28 are located on opposite sides of the cooling medium flow region 38 in the long side direction X.

[0030] The first cooling medium discharge hole 26 and the second cooling medium discharge hole 30 are located on opposite sides of the cooling medium flow area 38 in the long side direction X. Therefore, the cooling medium supply holes 24, 28 and the cooling medium discharge holes 26, 30 are arranged such that there is one cooling medium supply hole and one cooling medium discharge hole on each side of the cooling medium flow area 38 in the long side direction X. The first cooling medium supply hole 24 and the first cooling medium discharge hole 26 are located side by side in the short side direction Y. The second cooling medium supply hole 28 and the second cooling medium discharge hole 30 are located side by side in the short side direction Y.

[0031] The cooling medium flow region 38 is provided with a dividing section 40, which is an example of a guide that divides the cooling medium flow region 38 into two divided regions 39 aligned in the long side direction X at the center of the long side direction X. The dividing section 40 extends in the short side direction Y. The dividing section 40 is the portion in the fuel cell stack 13 where there is no gap between the first separator 21 of one of two single cells 12 that are adjacent in the stacking direction and the second separator 22 of the other single cell 12.

[0032] In other words, the divided section 40 is designed so that the cooling medium does not flow through it. That is, the divided section 40 divides the cooling medium flow area 38 in the middle of the long side direction X, thereby dividing the cooling medium flow area 38 into two divided areas 39 aligned in the long side direction X.

[0033] As shown in Figure 5, in the cooling medium flow region 38, a non-flow portion 41 is formed between the irregularities of the first separator 21 and the irregularities of the second separator 22, where there is no gap for the cooling medium to enter and therefore the cooling medium does not flow, and a flow portion 42 is formed where there is a gap for the cooling medium to enter and therefore the cooling medium flows. The flow portion 42 is the portion between the irregularities of the first separator 21 and the irregularities of the second separator 22 other than the non-flow portion 41.

[0034] The non-flow portion 41 is composed of the portion in the cooling medium flow region 38 where the convex portion 35 of the uneven surface of the first separator 21 and the convex portion 35 of the uneven surface of the second separator 22 overlap and come into contact with each other. The flow portion 42 is composed of the portion in the cooling medium flow region 38 where the concave portions 34 of the first separator 21 and the second separator 22 are adjacent to each other, and the portion where the concave portion 34 of one of the separators (first separator 21 or second separator 22) is adjacent to the convex portion 35 of the other separator.

[0035] As shown in Figure 6, the divided portion 40 in the cooling medium flow region 38 is a non-flow portion 41 that extends continuously in the short-side direction Y. When forming the divided portion 40, it is necessary to make a part of the flow portion 42 a non-flow portion 41. In the portion where the recessed portions 34 of the first separator 21 and the second separator 22 that constitute the flow portion 42 are adjacent to each other, the non-flow portion 41 can be created by changing the recessed portions 34 of the first separator 21 and the second separator 22 to contiguous protruding portions 35 that are in contact with each other.

[0036] In the portion where the recessed portion 34 of the first separator 21 and the convex portion 35 of the second separator 22, which constitute the flow portion 42, are adjacent, the recessed portion 34 of the first separator 21 can be changed to a convex portion 35 that contacts the convex portion 35 of the second separator 22, thereby creating a non-flow portion 41.

[0037] In the portion where the convex portion 35 of the first separator 21 and the concave portion 34 of the second separator 22, which constitute the flow portion 42, are adjacent, the concave portion 34 of the second separator 22 can be changed to a convex portion 35 that contacts the convex portion 35 of the first separator 21, thereby creating a non-flow portion 41. In this example, the divided portion 40 extends in the short-side direction Y while meandering in the long-side direction X. In Figures 5 and 6, the non-flow portion 41 is indicated by shading.

[0038] As shown in Figure 4, the cooling medium flow region 38 of the fuel cell stack 13 is divided into two divided regions 39 aligned in the long side direction X by a dividing portion 40 that extends in the short side direction Y at the center of the long side direction X. Therefore, when cooling medium is supplied from the first cooling medium supply hole 24 to one of the two divided regions 39, the cooling medium flows in that divided region 39 from the first cooling medium supply hole 24 toward the dividing portion 40, flows along the dividing portion 40, and then flows toward the first cooling medium discharge hole 26.

[0039] When cooling medium is supplied from the second cooling medium supply hole 28 to the other of the two divided regions 39, the cooling medium flows in the other divided region 39 from the second cooling medium supply hole 28 toward the divided portion 40, flows along the divided portion 40, and then flows toward the second cooling medium discharge hole 30.

[0040] In other words, when cooling medium is supplied to the cooling medium distribution area 38 from the first cooling medium supply hole 24 and the second cooling medium supply hole 28, as shown by the arrows in Figure 4, two flows are formed: one from the first cooling medium supply hole 24 through the dividing section 40 toward the first cooling medium discharge hole 26, and another from the second cooling medium supply hole 28 through the dividing section 40 toward the second cooling medium discharge hole 30. In short, the cooling medium is guided by the dividing section 40 to form a predetermined flow.

[0041] <Operation of First Embodiment> As shown in FIGS. 1, 2 and 4, when an oxidant gas, a fuel gas, and a cooling medium are supplied to the fuel cell 11, power generation is performed in each unit cell 12 constituting the fuel cell stack 13. When power generation is performed by the unit cells 12, the oxidant gas is supplied from an oxidant gas supply hole 25, and the fuel gas is supplied from a fuel gas supply hole 29.

[0042] When the oxidant gas is supplied from each oxidant gas supply hole 25 in the unit cell 12, the oxidant gas is diffused by the cathode-side gas diffusion layer 19 while flowing through each first flow path 33 toward the oxidant gas discharge hole 31, and is supplied to the cathode-side surface of the power generation unit 17. The oxidant gas that has flowed to each oxidant gas discharge hole 31 is discharged to the outside of the fuel cell stack 13.

[0043] On the other hand, when the fuel gas is supplied from each fuel gas supply hole 29 in the unit cell 12, the fuel gas is diffused by the anode-side gas diffusion layer 19 while flowing through each second flow path 37 toward the fuel gas discharge hole 27, and is supplied to the anode-side surface of the power generation unit 17. The fuel gas that has flowed to each fuel gas discharge hole 27 is discharged to the outside of the fuel cell stack 13.

[0044] At this time, in each unit cell 12, power is generated based on an electrochemical reaction in the power generation unit 17 between the oxidant gas supplied to the cathode-side surface of the power generation unit 17 and the fuel gas supplied to the anode-side surface of the power generation unit 17.

[0045] Each unit cell 12 generates heat through power generation based on this electrochemical reaction. However, a cooling medium is supplied from a first cooling medium supply hole 24 and a second cooling medium supply hole 28 respectively to a cooling medium flow area 38 formed between the first separator 21 of one unit cell 12 and the second separator 22 of the other unit cell 12 among two adjacent unit cells 12 in the stacking direction of the fuel cell stack 13.

[0046] Then, as shown by the arrows in FIG. 4, two flows of cooling medium are formed in the cooling medium flow region 38: a flow of cooling medium from the first cooling medium supply hole 24 via the dividing portion 40 toward the first cooling medium discharge hole 26, and a flow of cooling medium from the second cooling medium supply hole 28 via the dividing portion 40 toward the second cooling medium discharge hole 30. That is, a separate flow of cooling medium is formed for each of the two divided regions 39 constituting the cooling medium flow region 38.

[0047] For this reason, compared to the case where cooling medium is supplied from one cooling medium supply hole to the cooling medium flow region 38 where the dividing portion 40 is not provided, and the cooling medium is discharged from the cooling medium flow region 38 through one cooling medium discharge hole, the cooling performance of the cooling medium for each unit cell 12 is improved, so each unit cell 12 is efficiently cooled by the cooling medium.

[0048] <Effects of the First Embodiment> According to the first embodiment described in detail above, the following effects are exhibited. (1-1) In the fuel cell stack 13, the unit cell 12 has a first cooling medium supply hole 24 and a second cooling medium supply hole 28 that supply cooling medium to the cooling medium flow region 38, and a first cooling medium discharge hole 26 and a second cooling medium discharge hole 30 that discharge cooling medium from the cooling medium flow region 38. The first cooling medium supply hole 24 and the second cooling medium supply hole 28 are arranged on opposite sides of the cooling medium flow region 38 in the long side direction X. The first cooling medium discharge hole 26 and the second cooling medium discharge hole 30 are arranged on opposite sides of the cooling medium flow region 38 in the long side direction X. The first cooling medium supply hole 24 and the first cooling medium discharge hole 26 are arranged side by side in the short side direction Y. The second cooling medium supply hole 28 and the second cooling medium discharge hole 30 are arranged side by side in the short side direction Y. The cooling medium flow region 38 is provided with a dividing portion 40 that divides the cooling medium flow region 38 into two divided regions 39 aligned in the long side direction X at the central portion in the long side direction X, and through which no cooling medium flows.

[0049] With the above configuration, the effects described in <Operation of the First Embodiment> above can be obtained, and each single cell 12 can be efficiently cooled by the cooling medium. (Second Embodiment) As shown in Figure 7, the fuel cell stack 50 of this second embodiment is the fuel cell stack 13 of the first embodiment in which the positions of the first cooling medium discharge hole 26 and the second cooling medium supply hole 28 of the single cell 12 are swapped, and a dividing section 52 is provided in the cooling medium flow region 38 that divides the cooling medium flow region 38 into two dividing regions 51 aligned in the short side direction Y at the center of the short side direction Y.

[0050] Other than the above, the fuel cell stack 50 of the second embodiment is the same as the fuel cell stack 13 of the first embodiment. Therefore, in this second embodiment, only the differences from the first embodiment will be described, and explanations that overlap with the first embodiment will be omitted. Also, in this second embodiment, the same reference numerals will be used for the same components as in the first embodiment.

[0051] <Fuel Cell Stack 50> As shown in Figure 7, in the fuel cell stack 50, the first cooling medium supply hole 24 and the second cooling medium supply hole 28, and the first cooling medium discharge hole 26 and the second cooling medium discharge hole 30 are arranged on opposite sides of the cooling medium flow region 38 in the long side direction X. The first cooling medium supply hole 24 and the second cooling medium supply hole 28 are arranged side by side in the short side direction Y. The first cooling medium discharge hole 26 and the second cooling medium discharge hole 30 are arranged side by side in the short side direction Y.

[0052] The first cooling medium supply hole 24 and the first cooling medium discharge hole 26 face each other in the long side direction X, with the cooling medium flow region 38 in between. The second cooling medium supply hole 28 and the second cooling medium discharge hole 30 face each other in the long side direction X, with the cooling medium flow region 38 in between.

[0053] The cooling medium flow region 38 is provided with a dividing section 52, which is an example of a guide that divides the cooling medium flow region 38 into two divided regions 51 aligned in the short-side direction Y at the center of the short-side direction Y. The dividing section 52 extends in the long-side direction X. The dividing section 52 is the portion in the fuel cell stack 50 where there is no gap between the first separator 21 of one of two single cells 12 that are adjacent in the stacking direction and the second separator 22 of the other single cell 12.

[0054] In other words, the divided section 52 is designed so that the cooling medium does not flow through it. That is, the divided section 52 divides the cooling medium flow area 38 in the center in the short-side direction Y, thereby dividing the cooling medium flow area 38 into two divided areas 51 aligned in the short-side direction Y. The first cooling medium supply hole 24, the first cooling medium discharge hole 26, the oxidizer gas supply hole 25, and the fuel gas supply hole 29 are located on one side of the divided section 52 in the short-side direction Y. The second cooling medium supply hole 28, the second cooling medium discharge hole 30, the fuel gas discharge hole 27, and the oxidizer gas discharge hole 31 are located on the other side of the divided section 52 in the short-side direction Y.

[0055] As shown in Figure 8, in the cooling medium flow region 38, a non-flow portion 41 is formed between the irregularities of the first separator 21 and the irregularities of the second separator 22, where there is no gap for the cooling medium to enter and therefore the cooling medium does not flow, and a flow portion 42 is formed where there is a gap for the cooling medium to enter and therefore the cooling medium flows. The flow portion 42 is the portion between the irregularities of the first separator 21 and the irregularities of the second separator 22 other than the non-flow portion 41.

[0056] The non-flow portion 41 is composed of the portion in the cooling medium flow region 38 where the convex portion 35 of the uneven surface of the first separator 21 and the convex portion 35 of the uneven surface of the second separator 22 overlap and come into contact with each other. The flow portion 42 is composed of the portion in the cooling medium flow region 38 where the concave portions 34 of the first separator 21 and the second separator 22 are adjacent to each other, and the portion where the concave portion 34 of one of the separators (first separator 21 or second separator 22) is adjacent to the convex portion 35 of the other separator.

[0057] As shown in Figure 9, the divided portion 52 in the cooling medium flow region 38 is a non-flow portion 41 that extends continuously in the long side direction X. When forming the divided portion 52, it is necessary to make a part of the flow portion 42 a non-flow portion 41. In the portion where the convex portion 35 of the first separator 21 and the concave portion 34 of the second separator 22 that constitute the flow portion 42 are adjacent, the concave portion 34 of the second separator 22 can be changed to a convex portion 35 that contacts the convex portion 35 of the first separator 21, thereby creating a non-flow portion 41. In this example, the divided portion 52 extends linearly in the long side direction X. Note that in Figures 8 and 9, the non-flow portion 41 is indicated by shading.

[0058] As shown in Figure 7, the cooling medium flow area 38 of the fuel cell stack 50 is divided into two divided areas 51 aligned in the short-side direction Y by a dividing section 52 that extends linearly in the long-side direction X at the center of the short-side direction Y. Therefore, when cooling medium is supplied from the first cooling medium supply hole 24 to one of the two divided areas 51, the cooling medium flows in that divided area 51 from the first cooling medium supply hole 24 toward the first cooling medium discharge hole 26.

[0059] When cooling medium is supplied from the second cooling medium supply hole 28 to the other of the two divided regions 51, the cooling medium flows in the other divided region 51 from the second cooling medium supply hole 28 toward the second cooling medium discharge hole 30.

[0060] In other words, when the cooling medium is supplied to the cooling medium flow region 38 from the first cooling medium supply hole 24 and the second cooling medium supply hole 28, two flows are formed, as shown by the arrows in Figure 7: a flow of cooling medium from the first cooling medium supply hole 24 toward the first cooling medium discharge hole 26, and a flow of cooling medium from the second cooling medium supply hole 28 toward the second cooling medium discharge hole 30. That is, the cooling medium is guided by the dividing section 52 to form a predetermined flow.

[0061] <Operation of the Second Embodiment> Each single cell 12 generates heat through the power generation based on the electrochemical reaction described above. However, a cooling medium is supplied to the cooling medium flow region 38 formed between the first separator 21 of one of the two single cells 12 adjacent in the stacking direction in the fuel cell stack 50 and the second separator 22 of the other single cell 12, from the first cooling medium supply hole 24 and the second cooling medium supply hole 28, respectively.

[0062] As shown by the arrows in Figure 7, two flows of cooling medium are formed in the cooling medium flow region 38: one flow from the first cooling medium supply hole 24 toward the first cooling medium discharge hole 26, and the other flow from the second cooling medium supply hole 28 toward the second cooling medium discharge hole 30. In other words, separate flows of cooling medium are formed in each of the two divided regions 51 that constitute the cooling medium flow region 38.

[0063] Therefore, compared to the case where a cooling medium is supplied to the cooling medium distribution area 38 without a divided section 52 from one cooling medium supply hole and the cooling medium is discharged from the cooling medium distribution area 38 to one cooling medium discharge hole, the cooling performance of the cooling medium on each individual cell 12 is improved, so that each individual cell 12 is efficiently cooled by the cooling medium.

[0064] <Effects of the Second Embodiment> According to the second embodiment described in detail above, the following effects are achieved. (2-1) In the fuel cell stack 50, the single cell 12 has a first cooling medium supply hole 24 and a second cooling medium supply hole 28 that supply a cooling medium to the cooling medium flow region 38, and a first cooling medium discharge hole 26 and a second cooling medium discharge hole 30 that discharge the cooling medium from the cooling medium flow region 38. The first cooling medium supply hole 24 and the second cooling medium supply hole 28 and the first cooling medium discharge hole 26 and the second cooling medium discharge hole 30 are arranged on opposite sides of the cooling medium flow region 38 in the long side direction X. The first cooling medium supply hole 24 and the second cooling medium supply hole 28 are arranged side by side in the short side direction Y. The first cooling medium discharge hole 26 and the second cooling medium discharge hole 30 are arranged side by side in the short side direction Y. The cooling medium flow area 38 is divided into two divided areas 51 aligned in the short-side direction Y at the center of the short-side direction Y, and a divided section 52 is provided where the cooling medium does not flow.

[0065] According to the above configuration, the effects described in <Operation of the Second Embodiment> above can be obtained, and each single cell 12 can be efficiently cooled by the cooling medium. <Examples of Modifications> Each of the above embodiments can be implemented with the following modifications. Furthermore, each of the above embodiments and the following examples of modifications can be combined with each other to the extent that they do not contradict each other technically.

[0066] As shown in Figure 10, in the first embodiment, the divided portion 40 may be formed to extend in a direction that is inclined with respect to both the long side direction X and the short side direction Y. The same effects as in (1-1) above can be obtained even in this case.

[0067] As shown in Figure 11, in the second embodiment, the dividing portion 52 may be changed to a partitioned portion 53, which is an example of a guide portion formed by omitting the central portion in the long side direction X of the dividing portion 52. That is, the two divided regions 51 may be connected at the central portion of the cooling medium flow region 38. The same effects as in (2-1) above can be obtained even in this way.

[0068] As shown in Figure 12, the positions of the first cooling medium discharge hole 26 and the second cooling medium supply hole 28 of the single cell 12 in the fuel cell stack 50 of Figure 11 may be swapped, and the fuel cell stack 50 may be positioned so that the fuel gas discharge hole 27 and the oxidizer gas discharge hole 31 are on the lower side. In this way, due to the action of gravity, two flows of the cooling medium (flows indicated by arrows in Figure 12) similar to those in the first embodiment can be formed in the cooling medium flow region 38. Therefore, the same effects as in (1-1) above can be obtained.

[0069] In the first embodiment, by changing the position of the dividing portion 40, the areas of the two divided regions 39 when viewed from the stacking direction of the single cell 12 may be made the same or different.

[0070] In the second embodiment, by changing the position of the dividing portion 52, the areas of the two divided regions 51, when viewed from the stacking direction of the single cell 12, may be made the same or different.

[0071] In the first and second embodiments, the positions of the first cooling medium supply hole 24 and the first cooling medium discharge hole 26 may be swapped, or the positions of the second cooling medium supply hole 28 and the second cooling medium discharge hole 30 may be swapped.

[0072] The second flow path 37 may extend linearly in the long-side direction X, similar to the first flow path 33. In this case, the first separator 21 and the second separator 22 may have the same configuration.

Claims

1. A fuel cell stack comprising a plurality of stacked single cells, each single cell having a power generation unit and a pair of separators flanking the power generation unit, and having a plate shape with mutually orthogonal first and second sides, wherein two adjacent single cells in the stacking direction of the plurality of single cells have a cooling medium flow region between the separators that are in contact with each other, and when the direction in which the first side extends is defined as the first direction and the direction in which the second side extends is defined as the second direction, the contact surface of the separator that is in contact with the power generation unit is provided with a gas flow path that extends in the first direction and through which the reaction gas flows, and each single cell has two cooling medium supply holes for supplying the cooling medium to the cooling medium flow region and two cooling medium discharge holes for discharging the cooling medium from the cooling medium flow region. A fuel cell stack wherein the two cooling medium supply holes and the two cooling medium discharge holes are arranged such that, in the first direction, one cooling medium supply hole and one cooling medium discharge hole are located on each side of the cooling medium flow region, or the two cooling medium supply holes and the two cooling medium discharge holes are arranged such that, in the first direction, the two cooling medium supply holes and the two cooling medium discharge holes are located on opposite sides of the cooling medium flow region, and the cooling medium flow region is provided with guides for guiding the cooling medium such that when the cooling medium is supplied to the cooling medium flow region from the two cooling medium supply holes, two flows of the cooling medium are formed: a flow of the cooling medium from one of the two cooling medium supply holes to one of the two cooling medium discharge holes, and a flow of the cooling medium from the other of the two cooling medium supply holes to the other of the two cooling medium discharge holes.

2. The fuel cell stack according to claim 1, wherein the two cooling medium supply holes and the two cooling medium discharge holes are arranged such that one cooling medium supply hole and one cooling medium discharge hole are located on each side of the cooling medium flow region in the first direction, and the cooling medium supply holes and the cooling medium discharge holes are located side by side in the second direction on each side, and the guide portion divides the cooling medium flow region into two divided regions aligned in the first direction at the center of the first direction, and is composed of a divided portion through which the cooling medium does not flow.

3. The two cooling medium supply holes and the two cooling medium discharge holes are arranged such that the two cooling medium supply holes and the two cooling medium discharge holes are located on opposite sides of the cooling medium flow region in the first direction, and the two cooling medium supply holes are aligned in the second direction, and one of the two cooling medium supply holes and one of the two cooling medium discharge holes face each other in the first direction across the cooling medium flow region, and the other of the two cooling medium supply holes and the other of the two cooling medium discharge holes face each other in the first direction across the cooling medium flow region, and the guide portion divides the cooling medium flow region into two divided regions aligned in the second direction at the center of the second direction, and is composed of a divided portion through which the cooling medium does not flow, and the cooling medium flows from one of the two cooling medium supply holes to one of the two cooling medium discharge holes in one of the two divided regions. The fuel cell stack according to claim 1, wherein the cooling medium flows from one of the two cooling medium supply holes to the other of the two cooling medium discharge holes in the other of the two divided regions.

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