Fuel battery stack

Abstract

To provide a fuel battery stack capable of suppressing variation in contact pressure acting on a single cell.SOLUTION: A fuel battery stack is constructed by laminating a power generation part and a plurality of single cells having a first separator 51 and a second separator 52 that have the same shape with each other. Each of the first separator 51 and the second separator 52 has a coolant groove 71 that is formed between two projections 81 and constitutes a cooling path 90. The cooling groove 71 is extended to a meandering shape so that straight line parts Lc1 to Lc3 are connected by a folding part. A portion constituing the straight line parts Lc1 to Lc3 from the projection 81 has a plurality of main ribs 82 and a wide rib 83. The cooling path 90 has a first cooling space 91 that is formed by contacting one wide rib 83 in one separator 50A and two main ribs 82 in the other separator 50B to a lamination direction.SELECTED DRAWING: Figure 6

Description

[Technical field]

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

[0002] The fuel cell stack described in Patent Document 1 is constructed by stacking a plurality of cells, each of which includes a membrane electrode assembly and a pair of separators that sandwich the membrane electrode assembly. A cooling water flow path through which cooling water flows is formed between the separators that contact each other in two cells adjacent in the stacking direction.

[0003] Each separator has a gas flow channel formed on its surface facing the membrane electrode assembly, through which reactant gases flow. Each separator has a surface opposite to the surface facing the membrane electrode assembly, on which a plurality of linearly extending ridges are provided in parallel with a gap between them, and grooves extending along the ridges between adjacent ridges. The ridges of the separators in two adjacent cells in the stacking direction come into contact with each other and the grooves face each other, thereby forming a coolant flow path. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-243499 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, when manufacturing a fuel cell stack, multiple cells are clamped in the stacking direction. At this time, if the positions of the protrusions on two separators that form a cooling water flow path are misaligned in the planar direction perpendicular to the stacking direction, the protrusions on one separator may get between the protrusions on the other separator. In this case, the surface pressure acting on the cells may vary, causing leakage of reactant gases or cooling water, or the membrane electrode assembly may be deformed due to locally high surface pressure occurring within the cells. For this reason, it is desirable to suppress the variation in the surface pressure acting on the cells. [Means for solving the problem]

[0006] A fuel cell stack for solving the above problems is configured by stacking a plurality of unit cells, each unit cell including a power generation section including a membrane electrode assembly, and a first separator and a second separator that sandwich the power generation section and have the same shape, and a cooling flow path through which a cooling medium flows is formed between the first separator and the second separator that are in contact with each other in two unit cells adjacent in the stacking direction, and each of the first separator and the second separator has a coolant groove that is formed between two ridges that extend in parallel to each other and that constitutes the cooling flow path. the refrigerant groove extends in a serpentine manner with a plurality of straight portions extending in a straight line parallel to each other connected by folded portions, and the portions of the protrusions constituting the straight portions include a plurality of main ribs extending in a straight line parallel to each other and a wide rib having a width larger than a width of the main ribs, and the cooling flow path includes a cooling space formed by contact in the stacking direction between one of the wide rib on either the first separator or the second separator and a plurality of the main ribs on the other of the first separator and the second separator which is different from the one of the first separator and the second separator.

[0007] According to this configuration, in the cooling space of the cooling flow path, one wide rib in either the first separator or the second separator and multiple main ribs in the other of the first separator or the second separator are in contact with each other in the stacking direction of the unit cells. Therefore, even if the position of the wide rib of one separator and the position of the main rib of the other separator are misaligned in a planar direction perpendicular to the stacking direction, the wide rib can be prevented from getting between the main ribs or from getting between the wide ribs. Therefore, the variation in the surface pressure acting on the unit cells can be suppressed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing a fuel cell stack according to one embodiment. [Diagram 2] FIG. 2 is an exploded perspective view showing the unit cell of FIG. [Diagram 3] FIG. 3 is a plan view showing the gas flow paths of the separator of FIG. [Figure 4] FIG. 4 is a plan view showing a cooling flow passage forming portion of the separator of FIG. [Diagram 5] FIG. 5 is a plan view showing a state in which the first separator and the second separator of FIG. 1 are in contact with each other. [Figure 6] FIG. 6 is a cross-sectional view taken along line 6-6 in FIG. [Figure 7] FIG. 7 is a cross-sectional view taken along line 7-7 in FIG. [Figure 8] FIG. 8 is a plan view showing the protrusions of the first modified example. [Figure 9] FIG. 9 is a plan view showing the protrusions of the second modified example. [Figure 10] FIG. 10 is a plan view showing the protrusions of the third modified example. [Figure 11] FIG. 11 is a plan view showing a protrusion of the fourth modified example. [Figure 12] FIG. 12 is a plan view showing a protrusion according to a fifth modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, one embodiment of a fuel cell stack will be described with reference to FIGS. As shown in FIG. 1, a fuel cell stack 10 is formed by stacking a plurality of unit cells 20 one on top of the other.

[0010] (20 single cells) 2, the unit cell 20 has, for example, a square plate shape. That is, the unit cell 20 has a pair of first sides 21 extending parallel to each other and second sides 22 perpendicular to the first sides 21 and facing each other.

[0011] Hereinafter, the stacking direction of the unit cells 20 will be simply referred to as the stacking direction. The direction in which the first side 21 extends will be referred to as the first direction X, and the direction in which the second side 22 extends will be referred to as the second direction Y. The stacking direction, the first direction X, and the second direction Y are perpendicular to each other.

[0012] The unit cell 20 has a fuel gas supply manifold M1 that supplies fuel gas to the inside of the unit cell 20, and a fuel gas discharge manifold M2 that discharges the fuel gas to the outside of the unit cell 20. The unit cell 20 also has an oxidizer gas supply manifold M3 that supplies oxidizer gas to the inside of the unit cell 20, and an oxidizer gas discharge manifold M4 that discharges the oxidizer gas to the outside of the unit cell 20.

[0013] The manifolds M1 to M4 are, for example, elliptical in shape in the second direction Y. The fuel gas supply manifold M1 and the oxidant gas discharge manifold M4 are located at one end of the unit cell 20 in the first direction X, and are lined up in this order from one side to the other side in the second direction Y. The fuel gas discharge manifold M2 and the oxidant gas supply manifold M3 are located at the other end of the unit cell 20 opposite to the one side in the first direction X, and are lined up in this order from the other side to one side in the second direction Y. The fuel gas is, for example, hydrogen. The oxidant gas is, for example, air.

[0014] The unit cell 20 has a coolant supply manifold M5 that supplies a cooling medium to the inside of the fuel cell stack 10, and a coolant discharge manifold M6 that discharges the cooling medium to the outside of the fuel cell stack 10. The coolant supply manifold M5 and the coolant discharge manifold M6 have, for example, an elliptical shape that is long in the first direction X. The coolant supply manifold M5 and the coolant discharge manifold M6 are located at one end and the other end of the unit cell 20 in the second direction Y, respectively. The cooling medium is, for example, water.

[0015] The unit cell 20 includes a power generation section 30, a frame 40, a first separator 51, and a second separator 52. The power generation section 30 is sheet-shaped. The frame 40 surrounds the outer periphery of the power generation section 30. The first separator 51 and the second separator 52 sandwich the power generation section 30 and the frame 40. Although not shown, a gasket is provided between two unit cells 20 adjacent to each other in the stacking direction to seal the space between the two unit cells 20.

[0016] The power generation section 30, the first separator 51, and the second separator 52 are, for example, square-shaped in plan view. The frame 40 is, for example, square-shaped in plan view.

[0017] (Power Generation Section 30) 1, the power generation section 30 includes a membrane electrode assembly 31, and an anode-side gas diffusion layer 32 and a cathode-side gas diffusion layer 33 which sandwich the membrane electrode assembly 31. Although not shown in the figure, the membrane electrode assembly 31 includes an electrolyte membrane, and an anode electrode catalyst layer and a cathode electrode catalyst layer which sandwich the electrolyte membrane.

[0018] A fuel gas is supplied to the anode side surface of the power generation unit 30 through a fuel gas supply manifold M1. An oxidant gas is supplied to the cathode side surface of the power generation unit 30 through an oxidant gas supply manifold M3. As a result, in the power generation unit 30, power is generated by an electrochemical reaction between the fuel gas and the oxidant gas. In the fuel cell stack 10, each unit cell 20 generates heat as the power generation unit 30 generates power. For this reason, a cooling medium is supplied to a cooling passage 90 formed inside the fuel cell stack 10 through a refrigerant supply manifold M5.

[0019] (Frame 40) As shown in FIG. 2, the frame 40 is made of an insulating resin material. The frame 40 has a receiving hole 41 in the center that receives the power generating unit 30. The receiving hole 41 is, for example, a stepped hole that penetrates the frame 40.

[0020] The frame 40 has through holes hf1 to hf6 on the outer periphery of the receiving hole 41, which constitute the manifolds M1 to M6. (First separator 51 and second separator 52) The first separator 51 is disposed on the anode side surface of the power generating section 30. The second separator 52 is disposed on the cathode side surface of the power generating section 30.

[0021] The first separator 51 and the second separator 52 have the same shape. The first separator 51 and the second separator 52 are disposed in an inverted position relative to the power generation section 30 about a virtual axis line extending in the second direction Y.

[0022] Hereinafter, when there is no need to distinguish between the first separator 51 and the second separator 52, the first separator 51 and the second separator 52 will be collectively referred to as the separator 50. The separator 50 is formed by press-molding a metal plate such as stainless steel or titanium alloy.

[0023] The separator 50 has through holes hs1 to hs6 which form the manifolds M1 to M6. As described above, the first separator 51 and the second separator 52 are disposed in an inverted position relative to the power generation section 30. Therefore, the through hole hs1 of the first separator 51 and the through hole hs3 of the second separator 52 communicate with each other, and the through hole hs2 of the first separator 51 and the through hole hs4 of the second separator 52 communicate with each other. Furthermore, the through hole hs3 of the first separator 51 and the through hole hs1 of the second separator 52 communicate with each other, and the through hole hs4 of the first separator 51 and the through hole hs2 of the second separator 52 communicate with each other. Furthermore, the through hole hs5 of the first separator 51 and the through hole hs5 of the second separator 52 communicate with each other, and the through hole hs6 of the first separator 51 and the through hole hs6 of the second separator 52 communicate with each other.

[0024] (Gas flow path 60) The separator 50 has an uneven gas flow channel 60 through which a reactant gas, such as a fuel gas or an oxidant gas, flows. The gas flow channel 60 is formed on the surface of the separator 50 facing the power generation section 30. The gas flow channel 60 has a so-called serpentine shape that extends in a serpentine manner from the through hole hs1 to the through hole hs2. The reactant gas flows through the gas flow channel 60 and is supplied to the power generation section 30.

[0025] The gas flow passage 60 has straight portions Lg1 to Lg3 connected by turn-back portions Tg1 and Tg2 and extends in a serpentine shape. The straight portions Lg1 to Lg3 are parallel to one another in the second direction Y and extend linearly in the first direction X. The turn-back portions Tg1 and Tg2 extend linearly in the second direction Y. The straight portion Lg1 is connected to the through hole hs1. The straight portion Lg3 is connected to the through hole hs2. The straight portion Lg2 is located between the straight portion Lg1 and the straight portion Lg3. The turn-back portion Tg1 connects an end of the straight portion Lg1 opposite to the through hole hs1 and one end of the straight portion Lg2. The turn-back portion Tg2 connects the other end of the straight portion Lg2 and an end of the straight portion Lg3 opposite to the through hole hs2.

[0026] In the gas flow path 60, the reactant gas flows through the straight section Lg1, the turn-back section Tg1, the straight section Lg2, the turn-back section Tg2, and the straight section Lg3 in this order. The turn-back section Tg1 reverses the flow direction of the reactant gas flowing through the straight section Lg1, and the turn-back section Tg2 reverses the flow direction of the reactant gas flowing through the straight section Lg2.

[0027] The reactant gas supply system in the fuel cell stack 10 is, for example, a so-called counterflow system in which the fuel gas and the oxidant gas flow in opposite directions. In the following description, the upstream side of the gas flow passage 60 in the flow direction of the reaction gas will be simply referred to as the upstream side, and the downstream side of the flow direction will be simply referred to as the downstream side.

[0028] 3, the gas flow passage 60 has a plurality of gas grooves 61 extending in a serpentine shape in parallel to each other. The gas flow passage 60 has, for example, three gas grooves 61. The gas grooves 61 have a gas side main groove 62, a gas side wide groove 63 having a width larger than the width of the gas side main groove 62, and a gas side narrow groove 64 having a width smaller than the width of the gas side wide groove 63. The width of the gas side narrow groove 64 is smaller than the width of the gas side main groove 62. The gas side main groove 62, the gas side wide groove 63, and the gas side narrow groove 64 have the same depth.

[0029] The straight portions Lg1 to Lg3 are each formed, for example, of a gas side main groove 62, a gas side wide groove 63, and a gas side narrow groove 64. The turn-back portions Tg1 and Tg2 are each formed, for example, of the gas side main groove 62 only.

[0030] In the portion constituting the straight portion Lg1 of each gas groove 61, the gas side narrow grooves 64 and the gas side wide grooves 63 are alternately provided in order from the upstream side. The gas side narrow groove 64 is connected to the center portion in the width direction of the gas side wide groove 63. In the portion constituting the straight portion Lg1 of each gas groove 61, for example, there are two gas side narrow grooves 64 and two gas side wide grooves 63. Of the two gas side narrow grooves 64, the upstream gas side narrow groove 64 is connected to the through hole hs1. Of the two gas side wide grooves 63, the downstream gas side wide groove 63 is connected to the two gas side main grooves 62 at the downstream end. The two gas side main grooves 62 extend in parallel with a gap between each other over the downstream portion of the straight portion Lg1, the turn back portion Tg1, and the upstream portion of the straight portion Lg2.

[0031] Two gas side main grooves 62 extending in the upstream portion of the straight portion Lg2 of each gas groove 61 are connected to one gas side wide groove 63 at the downstream end. The gas side narrow groove 64 and the gas side wide groove 63 are connected to the downstream end of this one gas side wide groove 63 in order from the upstream side. The gas side wide groove 63 connected to the downstream side of the gas side narrow groove 64 is connected to two gas side main grooves 62 of the turn-back portion Tg2. These two gas side main grooves 62 extend over the turn-back portion Tg2 and the upstream portion of the straight portion Lg3. In addition, in the gas groove 61 closest to the through hole hs4 in the turn-back portion Tg2 among the multiple gas grooves 61, the gas side wide groove 63 connected to the downstream side of the gas side narrow groove 64 is connected to the two gas side main grooves 62 via the gas side narrow groove 64. The two gas-side main grooves 62 extend across the turn-back portion Tg2 and the upstream side of the straight portion Lg3.

[0032] The portion of each gas groove 61 constituting the straight portion Lg3 has a shape obtained by rotating the portion of the gas groove 61 constituting the straight portion Lg1 by 180° around a virtual axis extending in the stacking direction. That is, the upstream end of the portion of each gas groove 61 constituting the straight portion Lg3 is constituted by two gas-side main grooves 62, and the downstream end is constituted by a gas-side narrow groove 64. This gas-side narrow groove 64 is connected to the through hole hs2.

[0033] The multiple gas-side wide grooves 63 located on the upstream side in the straight portion Lg1 and the multiple gas-side wide grooves 63 located on the downstream side in the straight portion Lg2 are arranged at intervals from each other in the second direction Y. The multiple gas-side wide grooves 63 located on the downstream side in the straight portion Lg1 and the multiple gas-side wide grooves 63 located on the upstream side in the straight portion Lg2 are arranged at intervals from each other in the second direction Y. The multiple gas-side narrow grooves 64 located on the downstream side in the straight portion Lg1 and the multiple gas-side narrow grooves 64 located between the gas-side wide grooves 63 in the straight portion Lg2 are arranged at intervals from each other in the second direction Y.

[0034] (cooling channel 90) 1, in a fuel cell stack 10, of two unit cells 20 adjacent in the stacking direction, a first separator 51 constituting one unit cell 20 and a second separator 52 constituting the other unit cell 20 are in contact with each other. A cooling flow path 90 through which a cooling medium flows is formed between the first separator 51 and the second separator 52 that are in contact with each other in the two unit cells 20 adjacent in the stacking direction.

[0035] 2, the separator 50 has an uneven cooling flow-path forming portion 70 that constitutes the cooling flow path 90. The cooling flow-path forming portion 70 is formed on the surface of the separator 50 opposite to the surface on which the gas flow path 60 is formed. The cooling flow-path forming portion 70 has a serpentine shape that extends in a serpentine manner from the through hole hs1 to the through hole hs2.

[0036] The cooling flow passage forming portion 70 has straight portions Lc1 to Lc3 connected by turn-back portions Tc1 and Tc2 and extends in a serpentine shape. The straight portions Lc1 to Lc3 are parallel to each other in the second direction Y and extend linearly in the first direction X. The turn-back portions Tc1 and Tc2 extend linearly in the second direction Y. The straight portion Lc1 is connected to the through hole hs1. The straight portion Lc3 is connected to the through hole hs2. The straight portion Lc2 is located between the straight portion Lc1 and the straight portion Lc3. The turn-back portion Tc1 connects an end of the straight portion Lc1 opposite to the through hole hs1 and one end of the straight portion Lc2. The turn-back portion Tc2 connects the other end of the straight portion Lc2 and an end of the straight portion Lc3 opposite to the through hole hs2.

[0037] 4, the cooling flow-path forming portion 70 has a plurality of coolant grooves 71 extending in a serpentine shape parallel to each other. The coolant grooves 71 are formed between two ridges 81 extending in a serpentine shape parallel to each other. The cooling flow-path forming portion 70 has, for example, three ridges 81. The coolant grooves 71 and the ridges 81 form straight portions Lc1 to Lc3 and folded portions Tc1, Tc2.

[0038] The protrusions 81 are formed by the back surface shape of the gas grooves 61. For this reason, it can also be said that the refrigerant groove 71 is located between two adjacent gas grooves 61. It can also be said that the side walls of the gas grooves 61 function as the side walls of the refrigerant groove 71.

[0039] The protrusion 81 has a main rib 82, a wide rib 83 having a width greater than that of the main rib 82, and a narrow rib 84 having a width smaller than that of the wide rib 83. The narrow rib 84 has a width smaller than that of the main rib 82. The main rib 82, the wide rib 83, and the narrow rib 84 each have the same protruding height.

[0040] The main rib 82 is formed by the back surface shape of the gas-side main groove 62. The wide rib 83 is formed by the back surface shape of the gas-side wide groove 63. The narrow rib 84 is formed by the back surface shape of the gas-side narrow groove 64.

[0041] The portions of each of the protrusions 81 constituting the straight portions Lc1 to Lc3 have, for example, a main rib 82, a wide rib 83, and a narrow rib 84. The portions of each of the protrusions 81 constituting the folded portions Tc1, Tc2 have, for example, only the main rib 82.

[0042] In the portion of each protrusion 81 constituting the straight portion Lc1, narrow ribs 84 and wide ribs 83 are alternately provided in order from the upstream side. The narrow rib 84 is connected to the center of the wide rib 83 in the width direction. In the portion of each protrusion 81 constituting the straight portion Lc1, for example, there are two narrow ribs 84 and two wide ribs 83. Of the two narrow ribs 84, the upstream narrow rib 84 is connected to the through hole hs1. Of the two wide ribs 83, the downstream wide rib 83 is connected to the two main ribs 82 at the downstream end. The two main ribs 82 extend in parallel with a gap between them over the downstream portion of the straight portion Lc1, the turn-back portion Tc1, and the upstream portion of the straight portion Lc2.

[0043] Two main ribs 82 extending in the upstream portion of the straight portion Lc2 of each protrusion 81 are connected to one wide rib 83 at the downstream end. The narrow rib 84 and the wide rib 83 are connected to the downstream end of the wide rib 83 in this order from the upstream side. The wide rib 83 connected to the downstream side of the narrow rib 84 is connected to two main ribs 82 of the turn-back portion Tc2. These two main ribs 82 extend over the upstream portion of the turn-back portion Tc2 and the straight portion Lc3. In addition, in the protrusion 81 closest to the through hole hs4 in the turn-back portion Tc2 among the multiple protrusions 81, the wide rib 83 connected to the downstream side of the narrow rib 84 is connected to the two main ribs 82 via the narrow rib 84. These two main ribs 82 extend over the upstream portion of the turn-back portion Tc2 and the straight portion Lc3.

[0044] The portion of each protrusion 81 that constitutes the straight portion Lc3 has a shape obtained by rotating the portion of the protrusion 81 that constitutes the straight portion Lc1 by 180 degrees around an imaginary axis extending in the stacking direction. That is, the upstream end of the portion of each protrusion 81 that constitutes the straight portion Lc3 is formed by two main ribs 82, and the downstream end is formed by a narrow rib 84. This narrow rib 84 is connected to the through hole hs2.

[0045] The multiple wide ribs 83 located on the upstream side in the straight portion Lc1 and the multiple wide ribs 83 located on the downstream side in the straight portion Lc2 are arranged at intervals from each other in the second direction Y. The multiple wide ribs 83 located on the downstream side in the straight portion Lc1 and the multiple wide ribs 83 located on the upstream side in the straight portion Lc2 are arranged at intervals from each other in the second direction Y. The multiple narrow ribs 84 located on the downstream side in the straight portion Lc1 and the multiple narrow ribs 84 located between the wide ribs 83 in the straight portion Lc2 are arranged at intervals from each other in the second direction Y.

[0046] The refrigerant groove 71 has a refrigerant side main groove 72, a refrigerant side wide groove 73 having a width larger than that of the refrigerant side main groove 72, and a closed groove 74 having the same width as the refrigerant side main groove 72. The refrigerant side main groove 72, the refrigerant side wide groove 73, and the closed groove 74 have the same depth.

[0047] The refrigerant side main groove 72 is formed between two wide ribs 83 adjacent to each other in the second direction Y in two parallel protrusions 81, and between two main ribs 82 adjacent to each other in the second direction Y in two parallel protrusions 81.

[0048] The refrigerant-side wide groove 73 is formed between two narrow ribs 84 adjacent in the second direction Y of two parallel protrusions 81 . The blocked groove 74 is formed between two main ribs 82 extending in parallel in each protrusion 81. Both longitudinal ends of the blocked groove 74 are blocked by wide ribs 83. The refrigerant groove 71 has a U-shaped blocked groove 74 extending over the straight portion Lc1, the turning portion Tc1, and the straight portion Lc2, and an L-shaped blocked groove 74 extending over the turning portion Tc2 and the straight portion Lc3.

[0049] The portions of each refrigerant groove 71 constituting the straight portions Lc1-Lc3 include, for example, a refrigerant side main groove 72, a refrigerant side wide groove 73, and a closed groove 74. The portions of each refrigerant groove 71 constituting the turn-back portions Tc1, Tc2 include, for example, the refrigerant side main groove 72 and the closed groove 74.

[0050] 5, the cooling flow passages 90 are formed by contacting the top faces of the protrusions 81 of the separators 50 that are in contact with each other in the stacking direction. The cooling medium supplied from the coolant supply manifold M5 flows through the cooling flow passages 90 and is discharged from the coolant discharge manifold M6.

[0051] The cooling flow path 90 includes a first cooling space 91 and a second cooling space 92. The first cooling space 91 and the second cooling space 92 are formed between the straight line portions Lc1, between the straight line portions Lc2, and between the straight line portions Lc3 of the separators 50 that are in contact with each other in the stacking direction.

[0052] Hereinafter, when one of the first separator 51 and the second separator 52 adjacent in the stacking direction is referred to as “one separator 50A,” the other different from the first separator 51 and the second separator 52 will be referred to as “the other separator 50B.”

[0053] As shown in FIG. 6, the first cooling space 91 is a space formed by contact between one wide rib 83 of one separator 50A and multiple main ribs 82 of the other separator 50B in the stacking direction. Specifically, the first cooling space 91 is a space formed by contact between one wide rib 83 of the first separator 51 and two main ribs 82 of the second separator 52. The first cooling space 91 is also a space formed by contact between one wide rib 83 of the second separator 52 and two main ribs 82 of the first separator 51. The first cooling space 91 can also be said to be a space in which a portion of the closed groove 74 of one separator 50A extending in the first direction X is covered by the wide rib 83 of the other separator 50B.

[0054] 5, a plurality of first cooling spaces 91 are formed at intervals in the second direction Y, and a plurality of first cooling spaces 91 are formed at intervals in the first direction X. In each of the three straight line portions Lc1 to Lc3, three rows of four first cooling spaces 91 are formed, each arranged at intervals in the first direction X. However, in the straight line portion Lc2, two first cooling spaces 91 are formed at a portion where the protrusions 81 closest to the refrigerant supply manifold M5 contact each other. Therefore, a total of 34 first cooling spaces 91 are formed between two unit cells 20 adjacent in the stacking direction.

[0055] The cooling medium flowing through the first cooling space 91 flows in the first direction X along the closed grooves 74 . As shown in FIG. 7, the second cooling space 92 is a space formed by the narrow rib 84 of one separator 50A and the space between the two main ribs 82 of the other separator 50B facing each other. Specifically, the second cooling space 92 is a space formed by the narrow rib 84 of the first separator 51 and the space between the two main ribs 82 of the second separator 52 facing each other. The second cooling space 92 is also a space formed by the narrow rib 84 of the second separator 52 and the space between the two main ribs 82 of the first separator 51 facing each other. The second cooling space 92 can also be said to be a space in which a portion of the closed groove 74 of one separator 50A extending in the first direction X is covered by a portion in which the narrow rib 84 of the other separator 50B is formed.

[0056] 5, a plurality of second cooling spaces 92 are formed at intervals in the second direction Y, and a plurality of second cooling spaces 92 are formed at intervals in the first direction X. In each of the three straight line portions Lc1 to Lc3, three rows of two second cooling spaces 92 arranged at intervals in the first direction X are formed. Therefore, a total of eighteen second cooling spaces 92 are formed between two unit cells 20 adjacent to each other in the stacking direction. Each second cooling space 92 communicates with two first cooling spaces 91 adjacent to each other in the first direction X.

[0057] The cooling medium flowing through the second cooling space 92 flows in a first direction X, which is the direction in which the straight line portions Lc1-Lc3 extend, along the blocked grooves 74. As shown by arrows in Fig. 7, the cooling medium flowing through the second cooling space 92 flows in a second direction Y while meandering in the stacking direction along the narrow ribs 84 and the main ribs 82. Note that in regions of the cooling flow passage 90 where the protrusions 81 do not contact each other, the cooling medium can flow in the second direction Y in portions excluding the first cooling spaces 91.

[0058] The operation of this embodiment will be described. In the first cooling space 91 of the cooling flow path 90, one wide rib 83 of one separator 50A and two main ribs 82 of the other separator 50B are in contact with each other in the stacking direction. Therefore, even if the positions of one separator 50A and the other separator 50B are misaligned in a planar direction perpendicular to the stacking direction, it is possible to prevent the wide rib 83 from getting between the main ribs 82 or the main rib 82 from getting between the wide ribs 83.

[0059] The effects of this embodiment will be described. (1) The cooling flow path 90 has a first cooling space 91 formed by contact between one wide rib 83 of the separator 50A on one side and two main ribs 82 of the separator 50B on the other side in the stacking direction.

[0060] According to this configuration, the above-mentioned effects are achieved, and therefore the variation in the surface pressure acting on the unit cell 20 can be suppressed. (2) The cooling passage 90 has a second cooling space 92 formed by the narrow rib 84 of one separator 50A facing the space between two adjacent main ribs 82 of the other separator 50B.

[0061] According to this configuration, the cooling medium flows in the first direction X in the first cooling space 91, while flowing in both the first direction X and the second direction Y in the second cooling space 92. This makes it easier for the cooling medium to spread throughout the entire cooling flow passage 90. Therefore, the cooling efficiency of the fuel cell stack 10 can be improved.

[0062] (3) The cooling passage 90 has a plurality of first cooling spaces 91 formed separately from one another, and a second cooling space 92 communicating with two adjacent first cooling spaces 91 . According to this configuration, since the multiple first cooling spaces 91 are formed away from each other, it is possible to prevent the wide rib 83 from getting between the main ribs 82 and the main rib 82 from getting between the wide ribs 83 over a wide range of the cooling flow path 90. Furthermore, since the second cooling space 92 communicating with two adjacent first cooling spaces 91 is formed in the cooling flow path 90, the movement of the cooling medium in the second direction Y within the cooling flow path 90 is promoted. Therefore, it is possible to both suppress the variation in the surface pressure acting on the unit cells 20 and improve the cooling efficiency of the fuel cell stack 10.

[0063] (4) The width of the narrow rib 84 is smaller than the width of the main rib 82 . According to this configuration, the flow passage cross-sectional area of ​​the second cooling space 92 can be increased compared to when the width of the narrow rib 84 is equal to or greater than the width of the main rib 82. This makes it possible to suppress an increase in the flow passage resistance of the cooling flow passage 90. Therefore, the cooling efficiency of the fuel cell stack 10 can be further improved.

[0064] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

[0065] As shown in FIG. 8 to FIG. 12, the wide rib 83 may have at least one of gradually changing portions 83a, 83b whose width gradually decreases as it approaches the narrow rib 84. The gradually changing portion 83a has a pair of inclined surfaces inclined with respect to the first direction X so that the distance between them decreases as it approaches the narrow rib 84. The gradually changing portion 83b has an inclined surface inclined with respect to the first direction X so that it is located on one side of the second direction Y as it approaches the narrow rib 84. In these cases, a portion whose flow path cross-sectional area is gradually changed is formed between the refrigerant side wide groove 73 and the refrigerant side main groove 72. According to this configuration, the cooling medium flows in the refrigerant groove 71 along the gradually changing portions 83a, 83b, so that the increase in the flow path resistance of the refrigerant groove 71 can be suppressed. Therefore, the cooling efficiency of the fuel cell stack 10 can be further improved.

[0066] 9, the narrow rib 84 may be connected to the inclined surface of the gradually changing portion 83a. In this case, the narrow rib 84 extends at an angle with respect to the first direction X. 10 , two narrow ribs 84 arranged side by side in the second direction Y may extend from each of a pair of inclined surfaces of the gradually changing portion 83a. In this case, the space between the two narrow ribs 84 arranged side by side in each protrusion 81 becomes part of the refrigerant groove 71.

[0067] As shown in Fig. 11, the narrow rib 84 may extend from one end of the gradually changing portion 83b in the second direction Y. In the modification shown in Fig. 11, a wide rib 83 having a gradually changing portion 83b and a wide rib 83 having a gradual changing portion 83a are formed at an interval from each other in this order from the upstream side.

[0068] As shown in Fig. 12, the protrusion 81 may be formed by forming two wide ribs 83 having gradually changing portions 83b at a distance from each other. In the modification shown in Fig. 12, the planar directions of the inclined surfaces of the gradually changing portions 83b of the two wide ribs 83 intersect.

[0069] The width of the narrow rib 84 may be the same as or larger than the width of the main rib 82. If the width of the narrow rib 84 is larger than the width of the main rib 82, the width of the narrow rib 84 is preferably large enough so that the second cooling space 92 is not blocked.

[0070] The portion of the protrusion 81 that constitutes the straight line portions Lc1 to Lc3 may include one wide rib 83 and one narrow rib 84, or may include three or more wide ribs and one narrow rib 84. The narrow rib 84 may be omitted from the protrusion 81. In this case, it is preferable that the wide rib 83 is connected to the through holes hs1 and hs2.

[0071] In the straight portion Lc1, the main rib 82 may be connected to the through hole hs1, and the wide rib 83 and the narrow rib 84 may be connected in this order to the downstream end of the main rib 82. In the straight portion Lc3, the main rib 82 may be connected to the through hole hs2, and the wide rib 83 and the narrow rib 84 may be connected in this order to the upstream end of the main rib 82.

[0072] The portion of the protrusion 81 that constitutes the folded-back portions Tc1, Tc2 may include at least one of the wide rib 83 and the narrow rib 84. The number of straight portions and folded portions in the gas flow passage 60 and the cooling flow passage forming portion 70 may be changed as appropriate.

[0073] The reactant gas supply system in the fuel cell stack 10 may be a so-called co-flow system in which the fuel gas and the oxidant gas flow in the same direction. The above embodiment includes the configurations described in the following supplementary notes.

[0074] [Note 1] A fuel cell stack is configured by stacking a plurality of unit cells, each unit cell including a power generation section including a membrane electrode assembly, and a first separator and a second separator having the same shape as each other and sandwiching the power generation section, and a cooling flow path through which a cooling medium flows is formed between the first separator and the second separator that are in contact with each other in two unit cells adjacent in the stacking direction, wherein each of the first separator and the second separator has a coolant groove that is formed between two ridges that extend in parallel to each other and that constitutes the cooling flow path, and the coolant grooves are a fuel cell stack, wherein a plurality of parallel straight portions extending in a straight line are connected by folded portions and extend in a serpentine manner, and portions of the protrusions constituting the straight portions include a plurality of main ribs extending in a straight line in parallel to each other and a wide rib having a width greater than a width of the main ribs, and the cooling flow path includes a cooling space formed by contact in the stacking direction between one of the wide rib on one of the first separator and the second separator and a plurality of the main ribs on the other of the first separator and the second separator which is different from the one of the first separator and the second separator.

[0075] [Appendix 2] A fuel cell stack as described in [Appendix 1], wherein the portion of the protrusion that constitutes the straight portion includes a narrow rib that is connected to the wide rib and has a width smaller than that of the wide rib, and when the cooling space is a first cooling space, the cooling flow path is a space formed by opposing the narrow rib in one of the first separator or the second separator and a space between two adjacent main ribs in the other of the first separator or the second separator that is different from the one of the first separator and the second separator, and includes a second cooling space through which the cooling medium flows in a meandering manner in the stacking direction.

[0076] [Appendix 3] A fuel cell stack as described in [Appendix 2], wherein the portion of the protrusion that constitutes the straight portion includes a plurality of the wide ribs positioned apart from each other in the direction in which the straight portion extends, and the narrow rib connecting two of the wide ribs that are adjacent to each other in the direction in which the straight portion extends, and the cooling flow path includes a plurality of the first cooling spaces formed apart from each other, and the second cooling space communicating with two of the first cooling spaces that are adjacent to each other.

[0077] [Appendix 4] A fuel cell stack according to [Appendix 2] or [Appendix 3], wherein the width of the narrow rib is smaller than the width of the main rib. [Appendix 5] A fuel cell stack according to any one of [Appendix 2] to [Appendix 4], wherein the wide rib has a gradual change portion whose width gradually decreases toward the narrow rib. [Explanation of symbols]

[0078] hf1, hf2, hf3, hf4, hf5, hf6...Through hole hs1,hs2,hs3,hs4,hs5,hs6...Through hole Lc1,Lc2,Lc3…Straight section Lg1,Lg2,Lg3…Straight section M1…Fuel gas supply manifold M2…Fuel gas exhaust manifold M3…Oxidant gas supply manifold M4…Oxidant gas exhaust manifold M5…Refrigerant supply manifold M6…Refrigerant discharge manifold Tc1, Tc2... Turning part Tg1, Tg2...Folded section 10...Fuel cell stack 20...Single cell 21...First side 22...Second side 30…Power generation section 31...Membrane electrode assembly 32...Anode side gas diffusion layer 33...Cathode side gas diffusion layer 40…Frame 41...Housing hole 50…Separator 50A…One separator 50B: The other separator 51…First separator 52…Second separator 60...Gas flow path 61...Gas groove 62…Gas side main groove 63…Gas side wide groove 64…Gas side narrow groove 70...Cooling flow passage forming section 71...Refrigerant groove 72...Refrigerant side main groove 73…Refrigerant side wide groove 74...Occluded groove 81...projection 82…Main rib 83…Wide rib 83a, 83b... Gradual change part 84…Narrow rib 90…Cooling channel 91...1st cooling space 92…Second cooling space

Claims

1. A fuel cell stack is configured by stacking a plurality of unit cells, each unit cell including a power generation section including a membrane electrode assembly, and a first separator and a second separator that sandwich the power generation section and have the same shape, and a cooling flow path through which a cooling medium flows is formed between the first separator and the second separator that are in contact with each other in two unit cells adjacent to each other in a stacking direction, Each of the first separator and the second separator has a coolant groove that is formed between two protrusions that extend in parallel to each other and that constitutes the cooling flow path, The coolant groove has a plurality of straight portions extending in parallel to each other and connected by turn-back portions to extend in a serpentine shape, The portion of the protrusion constituting the linear portion includes a plurality of main ribs extending linearly in parallel with each other, and a wide rib having a width larger than a width of the main ribs, the cooling flow path includes a cooling space formed by contact between one of the wide rib of the first separator and the second separator and a plurality of the main ribs of the other of the first separator and the second separator, the other being different from the one of the first separator and the second separator, in the stacking direction. Fuel cell stack.

2. a portion of the protrusion constituting the linear portion includes a narrow rib that is connected to the wide rib and has a width smaller than a width of the wide rib, When the cooling space is a first cooling space, the cooling flow path is a space formed by opposing the narrow rib in one of the first separator and the second separator and a space between two adjacent main ribs in the other of the first separator and the second separator that is different from the one of the first separator and the second separator, and includes a second cooling space through which the cooling medium flows while meandering in the stacking direction. The fuel cell stack of claim 1 .

3. a portion of the protrusion constituting the straight portion includes a plurality of the wide ribs positioned apart from each other in the extending direction of the straight portion, and the narrow rib connecting two of the wide ribs adjacent to each other in the extending direction of the straight portion, The cooling flow path includes a plurality of the first cooling spaces formed apart from each other, and the second cooling space communicating with two adjacent first cooling spaces. The fuel cell stack of claim 2 .

4. The width of the narrow rib is smaller than the width of the main rib. The fuel cell stack according to claim 2 or 3.

5. The wide rib has a gradually changing portion whose width gradually decreases toward the narrow rib. The fuel cell stack according to claim 2 or 3.

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