Fuel battery stack

Abstract

To provide a fuel battery stack capable of suppressing a path cut of a reaction gas with a simple configuration.SOLUTION: A fuel battery stack includes: a power generation part having a pair of gas diffusion layers sandwiching a membrane electrode assembly; a frame 40 having an accommodation hole 41 for accommodating the power generation part; and a pair of separators 50. In the separators 50, a partition rib 70 is provided between two first extending parts Lg1 and Lg2 in which a flow direction of a reaction gas is opposite to each other. The partition rib 70 includes a protrusion part 74 that bites into the gas diffusion layer. The protrusion part 74 has an opposed end part 76 opposed to an inner surface of the accommodation hole 41. A pressure loss increasing part P is provided at a boundary part between the opposing end part 76 and an inner surface of the accommodation hole 41.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] A single cell of a fuel cell stack includes a membrane electrode gas diffusion layer assembly and a pair of separators that sandwich the membrane electrode gas diffusion layer assembly. The membrane electrode gas diffusion layer assembly includes a membrane electrode assembly and a pair of gas diffusion layers that sandwich the membrane electrode assembly. Gas flow channels through which reactant gases flow are provided on the surfaces of the separators facing the gas diffusion layers. The gas diffusion layers have a plurality of pores that allow the reactant gases to pass through in order to diffuse the reactant gases.

[0003] The separator of the fuel cell described in Patent Document 1 has a serpentine-shaped gas flow channel that extends in a meandering manner. The separator has ribs that separate the gas flow channels where the reactant gases flow in opposite directions. The ribs are fixed to the gas diffusion layer via a liquid sealant. The liquid sealant is impregnated into the gas diffusion layer, so that pores in the gas diffusion layer that come into contact with the ribs are filled with the liquid sealant. This prevents the reactant gas from passing over the ribs within the gas diffusion layer and flowing between the gas channels, a phenomenon known as path cutting. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-4478 Summary of the Invention [Problem to be solved by the invention]

[0005] In the fuel cell described in Patent Document 1, a liquid sealant needs to be provided between the separator rib and the gas diffusion layer, which may increase the number of steps in the fuel cell manufacturing process. Therefore, it is desired to suppress the path cut of the reactant gas with a simple configuration. [Means for solving the problem]

[0006] A fuel cell stack for solving the above problems is a fuel cell stack constructed by stacking a plurality of unit cells, each unit cell including a power generation section having a membrane electrode assembly and a pair of gas diffusion layers sandwiching the membrane electrode assembly, a frame having an accommodation hole for accommodating the power generation section, and a pair of separators sandwiching the power generation section and the frame, wherein a gas flow path through which a reactant gas flows is provided on a surface of the separator facing the power generation section, and the gas flow path has a plurality of first extension parts that are parallel to each other and through which the reactant gas flows in mutually opposite directions, and a second extension part that connects end portions of two of the first extension parts that are parallel to each other. a partition rib separating the two first extension portions is provided between the two first extension portions, and the partition rib has a base portion that contacts the gas diffusion layer and extends along the first extension portion, and a protrusion portion that protrudes from the base portion, bites into the gas diffusion layer, and extends along the first extension portion, and the protrusion portion has an opposing end portion that faces the inner surface of the accommodating hole, and a pressure loss increasing portion is provided at the boundary between the opposing end portion and the inner surface of the accommodating hole to increase the pressure loss of the reaction gas that flows between the two first extension portions beyond the opposing end portion to be greater than the pressure loss of the reaction gas that flows through each of the two first extension portions.

[0007] According to the above configuration, the protrusions of the partition ribs bite into the gas diffusion layer, locally compressing the gas diffusion layer, making it difficult for the reactant gas to flow through the compressed portion of the gas diffusion layer, and therefore making it difficult for the reactant gas to flow over the protrusions and between the two first extension portions.

[0008] Furthermore, according to the above configuration, a pressure loss increasing portion is provided at the boundary between the opposing ends of the protrusion and the inner surface of the accommodating hole. The pressure loss increasing portion increases the pressure loss of the reactant gas flowing between the two first extension portions beyond the pressure loss of the reactant gas flowing through each of the two first extension portions. As a result, the reactant gas flowing through the first extension portion is less likely to flow between the two first extension portions beyond the opposing ends, and is more likely to flow between the two first extension portions via the second extension portion.

[0009] For these reasons, the path cut of the reactant gas, which occurs when the reactant gas crosses the partition rib and flows between the two first extension portions within the gas diffusion layer, is suppressed. Therefore, the path cut of the reactant gas can be suppressed by a simple configuration in which the partition rib is provided with a protrusion. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view showing a fuel cell stack according to one embodiment. [Figure 2] FIG. 2 is an exploded perspective view showing the unit cell of FIG. [Figure 3] FIG. 3 is a plan view showing the gas flow paths of the separator of FIG. [Figure 4] FIG. 4 is an enlarged plan view showing a partition rib of the separator of FIG. [Figure 5] FIG. 5 is a cross-sectional view taken along line 5-5 in FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line 6-6 in FIG. [Figure 7] FIG. 7 is a plan view showing a partition rib of the first modified example. [Figure 8] FIG. 8 is a plan view showing a partition rib of the second modified example. [Figure 9] FIG. 9 is a cross-sectional view showing a partition rib of a third modified example. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of a fuel cell stack will now be described with reference to FIGS. (Fuel cell stack 10) 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.

[0012] (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 a pair of second sides 22 perpendicular to the first sides 21 and extending parallel to each other.

[0013] 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 X-axis direction, and the direction in which the second side 22 extends will be referred to as the Y-axis direction. The stacking direction, the X-axis direction, and the Y-axis direction are perpendicular to each other.

[0014] 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.

[0015] The manifolds M1 to M4 are, for example, oval-shaped and long in the Y-axis direction. The fuel gas supply manifold M1 and the oxidant gas discharge manifold M4 are located at one end of the unit cell 20 in the X-axis direction, and are lined up in this order from one side to the other in the Y-axis direction. The fuel gas discharge manifold M2 and the oxidant gas supply manifold M3 are located at the other end of the unit cell 20 opposite to the one side in the X-axis direction, and are lined up in this order from the other side to one side in the Y-axis direction. The fuel gas is, for example, hydrogen. The oxidant gas is, for example, air.

[0016] The unit cell 20 has two coolant supply manifolds M5 that supply a coolant to the inside of the fuel cell stack 10, and two coolant discharge manifolds M6 that discharge the coolant to the outside of the fuel cell stack 10. Each coolant supply manifold M5 and each coolant discharge manifold M6 has, for example, an elliptical shape that is long in the X-axis direction. The two coolant supply manifolds M5 are located at the other end of the unit cell 20 in the Y-axis direction, and are arranged side by side with a gap between them in the X-axis direction. The two coolant discharge manifolds M6 are located at one end of the unit cell 20 in the Y-axis direction, and are arranged side by side with a gap between them in the X-axis direction. The coolant is, for example, water.

[0017] The unit cell 20 includes a power generation section 30, a frame 40, and a pair of separators 50. The power generation section 30 is sheet-shaped. The frame 40 surrounds the outer periphery of the power generation section 30. The pair of separators 50 sandwich the power generation section 30 and the frame 40 from both sides in the stacking direction. The power generation section 30 and the separators 50 are, for example, square-shaped in plan view. The frame 40 is, for example, square-frame-shaped in plan view.

[0018] (Power Generation Unit 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 that sandwich the membrane electrode assembly 31. The anode-side gas diffusion layer 32 has a plurality of pores that allow the fuel gas to pass through. The cathode-side gas diffusion layer 33 has a plurality of pores that allow the oxidant gas to pass through.

[0019] Although not shown, the membrane electrode assembly 31 includes an electrolyte membrane, and an anode electrode catalyst layer and a cathode electrode catalyst layer that sandwich the electrolyte membrane. The anode-side gas diffusion layer 32 is laminated on the anode electrode catalyst layer. The cathode-side gas diffusion layer 33 is laminated on the cathode electrode catalyst layer.

[0020] Fuel gas is supplied to the anode side surface of the power generation unit 30 through a fuel gas supply manifold M1. 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, power is generated in the power generation unit 30 by an electrochemical reaction between the fuel gas and the oxidant gas.

[0021] In the fuel cell stack 10, each unit cell 20 generates heat as the power generation section 30 generates power. For this reason, a cooling flow path 80, which will be described later, is formed inside the fuel cell stack 10. A cooling medium is supplied to the cooling flow path 80 through a refrigerant supply manifold M5.

[0022] (Frame 40) The frame 40 is made of an insulating resin material. The frame 40 has a housing hole 41 in the center that houses the power generation section 30. The housing hole 41 has a square shape that follows the outer periphery of the power generation section 30 in a plan view.

[0023] The frame 40 has through holes hf1 to hf6 that form manifolds M1 to M6 on the outer circumferential side of the receiving hole 41. The frame 40 has a plurality of slits 42 penetrating the frame 40 between the accommodation hole 41 and each of the through holes hf1 to hf4. The plurality of slits 42 are arranged in parallel at intervals in the Y-axis direction. Each slit 42 has an elliptical shape that is long in the X-axis direction. One end of each slit 42 communicates in the stacking direction with one of the through holes hs1 to hs4 of the separator 50, which will be described later. The other end of each slit 42, opposite to the one end, communicates in the stacking direction with the gas flow path 60 of the separator 50, which will be described later. Each of the manifolds M1 to M4 communicates with the gas flow path 60 via, for example, seven slits 42.

[0024] (Separator 50) The separator 50 is formed by press-molding a metal plate made of, for example, stainless steel, titanium alloy, pure titanium, or the like.

[0025] One of the pair of separators 50 is disposed on the anode side surface of the power generation section 30. The other of the pair of separators 50 is disposed on the cathode side surface of the power generation section 30.

[0026] Hereinafter, the separator 50 disposed on the anode side of the power generation section 30 may be referred to as an anode separator 51, and the separator 50 disposed on the cathode side of the power generation section 30 may be referred to as a cathode separator 52.

[0027] The anode separator 51 and the cathode separator 52 have the same shape. The anode separator 51 and the cathode separator 52 are disposed in positions that are inverted relative to each other with respect to the power generation section 30, with an imaginary axis V as the axis of inversion. The imaginary axis V passes through the center of the separator 50 in the X-axis direction and extends in the Y-axis direction.

[0028] The separator 50 has through holes hs1 to hs6 that form the manifolds M1 to M6. As described above, the anode separator 51 and the cathode separator 52 are disposed in an inverted position relative to the power generation section 30. Therefore, the through hole hs1 of the anode separator 51 and the through hole hs3 of the cathode separator 52 are in communication with each other, and the through hole hs2 of the anode separator 51 and the through hole hs4 of the cathode separator 52 are in communication with each other. Furthermore, the through hole hs3 of the anode separator 51 and the through hole hs1 of the cathode separator 52 are in communication with each other, and the through hole hs4 of the anode separator 51 and the through hole hs2 of the cathode separator 52 are in communication with each other. Furthermore, the through-hole hs5 of the anode separator 51 and the through-hole hs5 of the cathode separator 52 communicate with each other, and the through-hole hs6 of the anode separator 51 and the through-hole hs6 of the cathode separator 52 communicate with each other.

[0029] 3, groove-like gas flow paths 60 through which reactant gas flows and ribs 61 extending along the gas flow paths 60 are arranged alternately on the surface of the separator 50 facing the power generation section 30. The separator 50 has, for example, eight gas flow paths 60 extending in parallel with one another. Each gas flow path 60 has a serpentine shape that extends in a serpentine manner from the through hole hs1 to the through hole hs2.

[0030] Fuel gas flows as a reactant gas through the gas flow channel 60 of the anode separator 51. Oxidant gas flows as a reactant gas through the gas flow channel 60 of the cathode separator 52. The reactant gas flows through the gas flow channel 60 and is supplied to the power generation unit 30.

[0031] 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 in the flow direction will be simply referred to as the downstream side.

[0032] Each gas flow path 60 is formed in a substantially S-shape by connecting first extension portions Lg1 to Lg3 by second extension portions Tg1 and Tg2. The reactant gas flows through the first extension portion Lg1, the second extension portion Tg1, the first extension portion Lg2, the second extension portion Tg2, and the first extension portion Lg3 in this order.

[0033] The first extending portions Lg1 to Lg3 are arranged in parallel with one another at intervals in the Y-axis direction. The first extending portions Lg1 to Lg3 extend in the X-axis direction in a wavy, meandering manner. The second extending portions Tg1 and Tg2 extend linearly and inclined with respect to the imaginary axis V so as to be positioned on one side in the X-axis direction as they move downstream.

[0034] The upstream end of the first extension portion Lg1 is connected to the through-hole hs1 via a slit 42 in the frame 40. The second extension portion Tg1 connects the downstream end of the first extension portion Lg1 to the upstream end of the first extension portion Lg2. The second extension portion Tg2 connects the downstream end of the first extension portion Lg2 to the upstream end of the first extension portion Lg3. The downstream end of the first extension portion Lg3 is connected to the through-hole hs2 via a slit 42. When the reactant gas flows from the first extension portion Lg1 to the first extension portion Lg2 via the second extension portion Tg1, and when the reactant gas flows from the first extension portion Lg2 to the first extension portion Lg3 via the second extension portion Tg2, the flow direction of the reactant gas is reversed. Therefore, the second extension portions Tg1 and Tg2 form a turning portion of the gas flow path 60.

[0035] (Partition rib 70) Among the plurality of gas flow paths 60, a partition rib 70 is provided between the two first extension portions Lg1, Lg2 in the gas flow path 60 where the distance between the two first extension portions Lg1, Lg2 is shortest. The partition rib 70 separates the two first extension portions Lg1, Lg2. The partition rib 70 extends along the two first extension portions Lg1, Lg2. Among the plurality of gas flow paths 60, a partition rib 70 is provided between the two first extension portions Lg2, Lg3 in the gas flow path 60 where the distance between the two first extension portions Lg2, Lg3 is shortest. The partition rib 70 extends along the two first extension portions Lg2, Lg3. The two partition ribs 70 have the same configuration and function.

[0036] Hereinafter, the configuration of the partition rib 70 that separates the two first extension portions Lg1, Lg2 will be described, and the configuration of the partition rib 70 that separates the two first extension portions Lg2, Lg3 will not be described. Also, the configuration of the partition rib 70 of the anode separator 51 will be described, and the configuration of the partition rib 70 of the cathode separator 52 will not be described.

[0037] 4 and 5, the partition rib 70 has a base 71 that separates the two first extending portions Lg1, Lg2, and a protrusion 74 that protrudes from the base 71 toward the anode-side gas diffusion layer 32. The base 71 and the protrusion 74 extend along the two first extending portions Lg1, Lg2.

[0038] 5, the base 71 has a flat contact surface 71a that contacts the anode gas diffusion layer 32. The amount of protrusion of the base 71 is the same as the amount of protrusion of the rib 61. The protrusion 74 protrudes from the contact surface 71a to one side in the stacking direction. The protrusion 74 protrudes to a position facing the inner surface of the accommodation hole 41 of the frame 40. The protrusion 74 is embedded in the anode-side gas diffusion layer 32. The protrusion 74 has a flat top surface and a pair of side surfaces that become increasingly distant from each other as they extend from the top surface toward the contact surface 71a. The width of the protrusion 74 and the amount of protrusion from the contact surface 71a are constant throughout the entire length of the protrusion 74.

[0039] If the protrusion 74 protrudes excessively, cracks may occur in the anode-side gas diffusion layer 32. For this reason, the protrusion amount of the protrusion 74 is preferably about several percent of the protrusion amount of the base 71. In this embodiment, the protrusion amount of the protrusion 74 is set to about 7% of the protrusion amount of the base 71. In each drawing, the protrusion amount of the protrusion 74 is exaggerated.

[0040] As shown in FIG. 4, the base 71 has a first wavy portion 72 and a wide portion 73. The first wavy portion 72 is located between the two first extension portions Lg1, Lg2 and extends wavy along the first extension portions Lg1, Lg2. The wide portion 73 is located between the first extension portion Lg1 and a bend Cg of the gas flow path 60 that connects the first extension portion Lg2 and the second extension portion Tg2. The width of the first wavy portion 72 is greater than the width of each of the two ribs 61 that form the first extension portions Lg1, Lg2 together with the partition rib 70. The width of the wide portion 73 gradually increases with increasing distance from the first wavy portion 72.

[0041] The protrusion 74 has a second wavy portion 75 protruding from the first wavy portion 72 and an opposing end portion 76 protruding from the wide portion 73. The second wavy portion 75 extends in a wavy pattern along the first extending portions Lg1 and Lg2. The second wavy portion 75 extends substantially the entire length of the first wavy portion 72, passing through the center of the width of the first wavy portion 72. The opposing end portion 76 is the end of the protrusion 74 in the length direction that is farther from the second extending portion Tg1. The opposing end portion 76 faces the inner surface of the accommodating hole 41 in the X-axis direction. The opposing end portion 76 bends from the second wavy portion 75 and extends in the Y-axis direction. More specifically, the opposing end portion 76 extends from the second wavy portion 75 toward the bent portion Cg. The opposing end portion 76 is curved so as to be convex toward the inner surface of the accommodating hole 41 when viewed from the stacking direction. An intermediate portion between the base end and the tip end of the opposing end 76 is closer to the inner surface of the receiving hole 41 in the X-axis direction than the base end and the tip end.

[0042] A pressure loss increasing portion P is provided at the boundary between the opposing end portion 76 and the inner surface of the accommodating hole 41. The pressure loss increasing portion P has the function of increasing the pressure loss of the reactant gas that flows between the two first extension portions Lg1, Lg2 beyond the pressure loss of the reactant gas that flows through each of the two first extension portions Lg1, Lg2. The pressure loss increasing portion P is formed by a gap G between the opposing end portion 76 and the inner surface of the accommodating hole 41. The gap G gradually increases from the base end toward the middle portion of the opposing end portion 76, and gradually decreases from the middle portion toward the tip portion.

[0043] Here, the opposing end 76 may be in contact with the inner surface of the accommodating hole 41. However, if the opposing end 76 and the frame 40 overlap in the stacking direction, an unintended gap may be formed between the frame 40 and the separator 50, which may result in leakage of reactant gas to the outside of the unit cell 20. Therefore, in this embodiment, in order to prevent the opposing end 76 and the frame 40 from overlapping in the stacking direction, a gap G is provided between the opposing end 76 and the inner surface of the accommodating hole 41, taking into consideration the manufacturing tolerance of the fuel cell stack 10. The cross-sectional area of the gap G is smaller than the flow path cross-sectional area of each of the first extension portions Lg1 and Lg2. Note that the cross-sectional area of the gap G varies depending on the position in the X-axis direction. In this embodiment, the maximum value of the cross-sectional area of the gap G is smaller than the flow path cross-sectional area of each of the first extension portions Lg1 and Lg2.

[0044] (Cooling channel 80) 1, in a fuel cell stack 10, of two unit cells 20 adjacent in the stacking direction, an anode separator 51 constituting one unit cell 20 and a cathode separator 52 constituting the other unit cell 20 are in contact with each other. A cooling flow path 80 through which a cooling medium flows is formed between the anode separator 51 and the cathode separator 52 that are in contact with each other in the two unit cells 20 adjacent in the stacking direction. Although not shown, a gasket that seals the space between the two unit cells 20 is provided between the anode separator 51 and the cathode separator 52 that are in contact with each other.

[0045] 2, the separator 50 has a plurality of cooling grooves 81 that form the cooling flow path 80. The cooling grooves 81 are formed on the surface of the separator 50 opposite to the surface on which the gas flow path 60 is formed. The cooling grooves 81 are formed by the rear surface shape of the rib 61. The cooling grooves 81 have a serpentine shape that extends in a serpentine pattern from the through hole hs1 to the through hole hs2.

[0046] The cooling flow path 80 is formed by the gap between the cooling groove 81 of the anode separator 51 and the cooling groove 81 of the cathode separator 52. The cooling medium supplied from the coolant supply manifold M5 flows through the cooling flow path 80 and is discharged from the coolant discharge manifold M6.

[0047] <Operation of this embodiment> 5, the protrusions 74 of the partition rib 70 bite into the anode-side gas diffusion layer 32, locally compressing the anode-side gas diffusion layer 32. Because the reactant gas is less likely to flow through the compressed portion of the anode-side gas diffusion layer 32, the reactant gas is less likely to flow over the protrusions 74 and between the two first extension portions Lg1, Lg2.

[0048] 4, a pressure loss increasing portion P is provided at the boundary between the opposing end 76 of the protrusion 74 and the inner surface of the accommodating hole 41. The pressure loss increasing portion P increases the pressure loss of the reactant gas that flows between the two first extension portions Lg1, Lg2 beyond the pressure loss of the reactant gas that flows through each of the two first extension portions Lg1, Lg2. As a result, the reactant gas that flows through the first extension portions Lg1, Lg2 is less likely to flow between the two first extension portions Lg1, Lg2 beyond the opposing end 76, and is more likely to flow between the two first extension portions Lg1, Lg2 via the second extension portion Tg1.

[0049] <Effects of this embodiment> (1) The separator 50 has a partition rib 70 between two first extending portions Lg1, Lg2, whose reactant gas flows in opposite directions. The partition rib 70 has a protrusion 74 that bites into the anode-side gas diffusion layer 32. The protrusion 74 has an opposing end 76 that faces the inner surface of the accommodation hole 41. A pressure loss increase portion P is provided at the boundary between the opposing end 76 and the inner surface of the accommodation hole 41 of the frame 40.

[0050] The above-described configuration achieves the above-described effect, thereby suppressing path cutting, which occurs when the reactant gas flows between the two first extension portions Lg1, Lg2 across the partition rib 70 within the anode-side gas diffusion layer 32. Therefore, the simple configuration of providing the protrusions 74 on the partition rib 70 can suppress path cutting of the reactant gas.

[0051] (2) The pressure loss increase portion P is formed by a gap G between the opposing end portion 76 and the inner surface of the receiving hole 41. The cross-sectional area of the gap G is smaller than the flow path cross-sectional area of each of the first extending portions Lg1 and Lg2.

[0052] According to the above configuration, the pressure loss increasing portion P can be realized by a simple configuration in which the gap G is provided between the opposing end portion 76 and the inner surface of the receiving hole 41. (3) The opposing end 76 extends in the direction in which the two first extending portions Lg1, Lg2 are arranged.

[0053] According to the above configuration, it is possible to increase the range of the gap G between the opposing end 76 and the inner surface of the accommodating hole 41. This increases the range in which the pressure loss of the reactant gas increases. Therefore, it is possible to enhance the effect of suppressing the path cut of the reactant gas.

[0054] (4) The width of the protrusion 74 is constant throughout the entire length of the protrusion 74 . The reactant gas is less likely to flow through the compressed portion of the anode-side gas diffusion layer 32 due to the protrusion 74. Therefore, if the protrusion 74 has portions with different widths, the amount of reactant gas reaching the power generation unit 30 may be relatively insufficient in the wider portions. As a result, the amount of power generated by the power generation unit 30 may be locally reduced.

[0055] In this regard, with the above configuration, the width of the protrusion 74 is constant over the entire length of the protrusion 74. This makes it possible to prevent the amount of power generated by the power generation section 30 from decreasing locally. (5) The base portion 71 and the protrusions 74 extend in a wavy, meandering manner along the first extending portions Lg1 and Lg2.

[0056] For example, if the first extension portions Lg1, Lg2 extend in a wavy, meandering manner and the protrusions 74 extend linearly, the width of the base portion 71 extending in a wavy, meandering manner may increase. In this case, the area where the partition rib 70 contacts the anode-side gas diffusion layer 32 increases. As a result, the reactant gases are less likely to reach the portions of the power generation section 30 that contact the partition rib 70, which may result in a local decrease in the amount of power generated by the power generation section 30.

[0057] In this regard, with the above-described configuration, the base 71 and the protrusions 74 extend in a wavy, meandering manner along the first extensions Lg1 and Lg2, which prevents the width of the partition rib 70 from increasing compared to when the protrusions 74 extend linearly. Therefore, it is possible to prevent a local decrease in the amount of power generated by the power generation unit 30.

[0058] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0059] The first extending portions Lg1 to Lg3 may extend in a wavy, meandering manner, and the second wavy portion 75 of the protruding portion 74 may extend linearly in the X-axis direction. The first extending portions Lg1 to Lg3 may extend linearly in the X-axis direction, and the second wavy portion 75 of the protruding portion 74 may extend in the X-axis direction in a wavy, meandering manner.

[0060] The first extending portions Lg1 to Lg3 may extend linearly in the X-axis direction, and the second wavy portion 75 of the protruding portion 74 may also extend linearly in the X-axis direction. The width of the protrusion 74 does not have to be constant over the entire protrusion 74. For example, the width of the opposing end 76 may be greater than the width of the second wavy portion 75.

[0061] As shown in FIG. 7, the opposing end 76 may extend linearly in the Y-axis direction along the inner surface of the receiving hole 41. As shown in FIG. 8, the opposing end 76 may extend from the second wavy portion 75 toward a side away from the bent portion Cg in the Y-axis direction.

[0062] The opposing end 76 does not have to extend in the arrangement direction of the first extending portions Lg1 to Lg3. The opposing end 76 may extend in the X-axis direction. 9, the opposing end 76 may be in contact with the inner surface of the accommodating hole 41. Alternatively, the side surface of the protrusion 74 may be erected perpendicular to the contact surface 71a. In this case, the side surface of the protrusion 74 is in surface contact with the inner surface of the accommodating hole 41. At this time, no gap G is formed at the boundary between the opposing end 76 and the inner surface of the accommodating hole 41. Even with these configurations, the boundary between the opposing end 76 and the inner surface of the accommodating hole 41 functions as the pressure loss increase portion P, and therefore the above-described effect (1) can be achieved.

[0063] 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 in the first extending portions Lg1, Lg2, and Lg3 of each separator 50.

[0064] Each slit 42 does not have to penetrate the frame 40, and may be a groove opening to one side in the thickness direction of the frame 40. In this case, the frame 40 may have slits 42 between the accommodation hole 41 and each of the through holes hf1, hf2 on the surface facing the anode separator 51. The frame 40 may also have slits 42 between the accommodation hole 41 and each of the through holes hf3, hf4 on the surface facing the cathode separator 52.

[0065] The material of the separator 50 may be a carbon material or a composite material containing a carbon material and a resin material. The separator 50 may be formed by cutting or injection molding.

[0066] <Additional Notes> The above embodiment includes the configurations described in the following supplementary notes. [Appendix 1] A fuel cell stack constructed by stacking a plurality of unit cells, each unit cell comprising: a power generation section having a membrane electrode assembly and a pair of gas diffusion layers sandwiching the membrane electrode assembly; a frame having an accommodation hole for accommodating the power generation section; and a pair of separators sandwiching the power generation section and the frame, wherein a gas flow path through which a reactant gas flows is provided on a surface of the separator facing the power generation section, and the gas flow path has a plurality of first extension parts that are parallel to each other and through which the reactant gas flows in mutually opposite directions, and a second extension part that connects end portions of two of the first extension parts that are parallel to each other, and a partition rib is provided between the two first extension portions to separate the two first extension portions, the partition rib having a base that contacts the gas diffusion layer and extends along the first extension portion, and a protrusion that protrudes from the base, bites into the gas diffusion layer, and extends along the first extension portion, the protrusion having an opposing end that faces an inner surface of the accommodating hole, and a pressure loss increasing portion that increases the pressure loss of the reactant gas that flows between the two first extension portions beyond the opposing end, to be greater than the pressure loss of the reactant gas that flows through each of the two first extension portions.

[0067] [Appendix 2] A fuel cell stack as described in [Appendix 1], wherein the pressure loss increase portion is formed by a gap between the opposing end and the inner surface of the accommodating hole, and the cross-sectional area of the gap is smaller than the flow path cross-sectional area of the first extension portion.

[0068] [Appendix 3] The fuel cell stack according to [Appendix 1] or [Appendix 2], wherein the opposing end portion extends in the direction in which the two first extension portions are arranged. [Appendix 4] The fuel cell stack according to any one of [Appendix 1] to [Appendix 3], wherein the width of the protrusion is constant over the entire length of the protrusion.

[0069] [Appendix 5] A fuel cell stack described in any one of [Appendix 1] to [Appendix 4], wherein the first extension portion extends in a wavy, meandering manner, and the base portion and the protrusion portion extend in a wavy, meandering manner along the first extension portion. [Explanation of symbols]

[0070] Cg...bending part hf1, hf2, hf3, hf4, hf5, hf6...Through hole hs1,hs2,hs3,hs4,hs5,hs6...Through hole Lg1,Lg2,Lg3...first extension part Tg1,Tg2…Second extension part M1...Fuel gas supply manifold M2: Fuel gas discharge manifold M3...Oxidant gas supply manifold M4...Oxidant gas discharge manifold M5... Refrigerant supply manifold M6...Refrigerant discharge manifold G...gap P: Pressure loss increase area V: Virtual axis 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 42...Slit 50...Separator 51...Anode separator 52...Cathode separator 60...Gas flow path 61...Rib 70...Divider rib 71...Base 71a…Contact surface 72...First wavy section 73...Wide section 74...Protrusion 75...Second wavy section 76...opposite end 80...Cooling channel 81…Cooling groove

Claims

1. A fuel cell stack formed by stacking a plurality of unit cells, each unit cell including a power generation section having a membrane electrode assembly and a pair of gas diffusion layers sandwiching the membrane electrode assembly, a frame having an accommodation hole for accommodating the power generation section, and a pair of separators sandwiching the power generation section and the frame, a gas flow channel through which a reaction gas flows is provided on a surface of the separator facing the power generation section, the gas flow path includes a plurality of first extension portions that are parallel to each other and through which the reaction gas flows in opposite directions, and a second extension portion that connects end portions of two of the parallel first extension portions, a partition rib that separates the two first extension portions is provided between the two first extension portions, the partition rib has a base portion in contact with the gas diffusion layer and extending along the first extension portion, and a protrusion portion protruding from the base portion, biting into the gas diffusion layer, and extending along the first extension portion, the protrusion has an opposing end portion that faces the inner surface of the receiving hole, a pressure loss increasing portion that increases the pressure loss of the reactant gas that flows between the two first extension portions beyond the opposing end portions to be greater than the pressure loss of the reactant gas that flows through each of the two first extension portions; Fuel cell stack.

2. the pressure loss increasing portion is formed by a gap between the opposing end portion and an inner surface of the accommodating hole, The cross-sectional area of the gap is smaller than the flow path cross-sectional area of the first extension portion. The fuel cell stack of claim 1 .

3. The opposing end portions extend in the arrangement direction of the two first extension portions. The fuel cell stack according to claim 2 .

4. The width of the protrusion is constant throughout the length of the protrusion. The fuel cell stack according to any one of claims 1 to 3.

5. The first extension portion extends in a wavy, meandering manner, The base portion and the protrusion portion extend in a wavy, meandering manner along the first extension portion. The fuel cell stack according to any one of claims 1 to 3.

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