Fuel cell stack

Abstract

A fuel cell stack is provided with a plurality of stacked unit cells. Each single cell includes a power generation unit, a frame having a housing hole, and a pair of separators. Each of the separators has a surface facing the power generation unit, and the surface is provided with a gas flow path. The gas flow path has a plurality of first extension portions and second extension portions. And a separation rib is arranged between the two first extension parts connected by the second extension part. The partition rib has: a base section that is in contact with a corresponding gas diffusion layer in the power generation section; and a protruding portion that protrudes from the base portion and sinks into the corresponding gas diffusion layer. The protruding portion has an opposing end portion that opposes the inner surface of the housing hole. A pressure loss increasing portion is provided at a boundary portion between the opposing end portion and the inner surface of the housing hole.

Description

Technical Field

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

[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. A gas flow path for allowing a reaction gas to flow is provided on a surface of the separator that faces the gas diffusion layer. The gas diffusion layer has a plurality of pores that allow the reaction gas to pass through in order to diffuse the reaction gas.

[0003] The separator of the fuel cell described in Japanese Patent Application Laid-Open No. 2008-4478 has a so-called serpentine gas flow path that extends in a meandering manner. The separator has ribs that partition portions in the gas flow path where the flow directions of the reaction gas are opposite to each other. The ribs are fixed to the gas diffusion layer by means of a liquid sealing material. Since the liquid sealing material is impregnated in the gas diffusion layer, the pores in the portion of the gas diffusion layer that contacts the ribs are filled with the liquid sealing material. Thereby, so-called pass cut, in which the reaction gas flows between the gas flow paths across the ribs in the gas diffusion layer, is suppressed. Summary of the Invention

[0004] Problems to be Solved by the Invention

[0005] In the fuel cell described in the above publication, since it is necessary to provide a liquid sealing material between the ribs of the separator and the gas diffusion layer, the man-hours of the manufacturing process of the fuel cell may increase. Therefore, it is desired to suppress the pass cut of the reaction gas with a simple structure.

[0006] Means for Solving the Problems

[0007] A fuel cell stack according to an aspect of the present disclosure includes a plurality of stacked single cells. Each single cell includes: a power generation unit having a membrane electrode assembly and a pair of gas diffusion layers sandwiching the membrane electrode assembly; a frame having a receiving hole for receiving the power generation unit; and a pair of separators sandwiching the power generation unit and the frame. Each separator of each single cell has a surface facing the power generation unit, and a gas flow path for the reaction gas is provided on this surface facing the power generation unit. The gas flow path has: a plurality of first extension portions that are juxtaposed with each other and in which the reaction gas flows in opposite directions; and a second extension portion that connects the ends of two juxtaposed first extension portions to each other. A partition rib that separates the two first extension portions is provided between the two first extension portions connected by the second extension portion. The partition rib has: a base portion that contacts a corresponding one of the pair of gas diffusion layers of the power generation unit and extends along the first extension portion; and a protrusion that protrudes from the base portion and sinks into the corresponding gas diffusion layer and extends along the first extension portion. The protrusion has an opposing end portion that opposes the inner surface of the receiving hole, and a pressure loss increasing portion is provided at the boundary between the opposing end portion and the inner surface of the receiving hole. The pressure loss increasing portion increases the pressure loss of the reaction gas flowing between the two first extension portions across the opposing end portion compared to the pressure loss of the reaction gas flowing in the two first extension portions respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a cross-sectional view showing a fuel cell stack according to an embodiment.

[0009] Figure 2 is showing Figure 1 exploded perspective view of a single cell.

[0010] Figure 3 is showing Figure 1 top view of the gas flow path of the separator.

[0011] Figure 4 is to Figure 3 magnified top view showing the partition rib of the separator enlarged.

[0012] Figure 5 is along Figure 4 sectional view taken along line 5-5.

[0013] Figure 6 is along Figure 4 sectional view taken along line 6-6.

[0014] Figure 7It is a top view of the partition rib showing the first modification example.

[0015] Figure 8 It is a top view of the partition rib showing the second modification example.

[0016] Figure 9 It is a cross-sectional view of the partition rib showing the third modification example. Detailed implementation mode

[0017] Hereinafter, with reference to Figures 1 to 6 a fuel cell stack 10 of an embodiment will be described.

[0018] (Fuel cell stack 10)

[0019] As Figure 1 shown, the fuel cell stack 10 is formed by stacking a plurality of single cells 20.

[0020] (Single cell 20)

[0021] As Figure 2 shown, the single cell 20 is formed in a square plate shape, for example. That is, the single cell 20 has a pair of first sides 21 extending parallel to each other and a pair of second sides 22 orthogonal to the first sides 21 and extending parallel to each other.

[0022] Hereinafter, the stacking direction of the single cells 20 will be simply referred to as the stacking direction for description. In addition, the direction in which the first side 21 extends will be referred to as the X-axis direction and the direction in which the second side 22 extends will be referred to as the Y-axis direction for description. The stacking direction, the X-axis direction, and the Y-axis direction are orthogonal to each other.

[0023] The single cell 20 has a fuel gas supply manifold M1 for supplying fuel gas to the inside of the single cell 20 and a fuel gas discharge manifold M2 for discharging fuel gas to the outside of the single cell 20. In addition, the single cell 20 has an oxidant gas supply manifold M3 for supplying oxidant gas to the inside of the single cell 20 and an oxidant gas discharge manifold M4 for discharging oxidant gas to the outside of the single cell 20.

[0024] The manifolds M1 to M4 are formed in an oval shape that is long in the Y-axis direction, for example. The fuel gas supply manifold M1 and the oxidant gas discharge manifold M4 are located at one end of the single cell 20 in the X-axis direction and are arranged in order from one side in the Y-axis direction to the other side. The fuel gas discharge manifold M2 and the oxidant gas supply manifold M3 are located at the other end of the single cell 20 on the opposite side to the one side in the X-axis direction and are arranged in order from the other side in the Y-axis direction to the one side. The fuel gas is hydrogen, for example. The oxidant gas is air, for example.

[0025] The single cell 20 has two refrigerant supply manifolds M5 that supply a cooling medium to the inside of the fuel cell stack 10 and two refrigerant discharge manifolds M6 that discharge the cooling medium to the outside of the fuel cell stack 10. Each refrigerant supply manifold M5 and each refrigerant discharge manifold M6 are formed, for example, in an oval shape that is long in the X-axis direction. The two refrigerant supply manifolds M5 are located at the other end of the single cell 20 in the Y-axis direction and are arranged at intervals in the X-axis direction. The two refrigerant discharge manifolds M6 are located at one end of the single cell 20 in the Y-axis direction and are arranged at intervals in the X-axis direction. The cooling medium is, for example, water.

[0026] The single cell 20 includes a power generation unit 30, a frame 40, and a pair of separators 50. The power generation unit 30 is formed in a sheet shape. The frame 40 surrounds the outer peripheral edge of the power generation unit 30. The pair of separators 50 sandwich the power generation unit 30 and the frame 40 from both sides in the stacking direction. The power generation unit 30 and the separators 50 are formed, for example, in a square shape when viewed from above. The frame 40 is formed, for example, in a square frame shape when viewed from above.

[0027] (Power generation unit 30)

[0028] As Figure 1 shown, the power generation unit 30 includes a membrane electrode assembly 31, an anode-side gas diffusion layer 32 that sandwiches the membrane electrode assembly 31, and a cathode-side gas diffusion layer 33. 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.

[0029] The membrane electrode assembly 31 includes an electrolyte membrane, an anode electrode catalyst layer that sandwiches the electrolyte membrane, and a cathode electrode catalyst layer, which are not shown here. 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.

[0030] The fuel gas is supplied to the anode-side surface of the power generation unit 30 through the fuel gas supply manifold M1. The oxidant gas is supplied to the cathode-side surface of the power generation unit 30 through the oxidant gas supply manifold M3. Thus, in the power generation unit 30, power generation is performed by the electrochemical reaction of the fuel gas and the oxidant gas.

[0031] In the fuel cell stack 10, each single cell 20 generates heat as the power generation unit 30 generates power. Therefore, a cooling flow path 80 described later is formed inside the fuel cell stack 10. The cooling medium is supplied to the cooling flow path 80 through the refrigerant supply manifold M5.

[0032] (Frame 40)

[0033] The frame 40 is formed of a resin material having insulating properties.

[0034] The frame 40 has a receiving hole 41 for receiving the power generation unit 30 at the central portion. The receiving hole 41 is formed in a square shape along the outer peripheral edge of the power generation unit 30 in a plan view.

[0035] The frame 40 has through holes hf1 to hf6 forming manifolds M1 to M6 on the outer peripheral side of the receiving hole 41.

[0036] The frame 40 has a plurality of slits 42 penetrating the frame 40 between the receiving hole 41 and the respective through holes hf1 to hf4. The plurality of slits 42 are juxtaposed at intervals in the Y-axis direction. Each slit 42 is formed in an oval shape that is long in the X-axis direction. One end portion of each slit 42 communicates with any one of through holes hs1 to hs4 of a partition member 50 described later in the stacking direction. The other end portion of each slit 42, which is on the side opposite to the one end portion, communicates with a gas flow path 60 of the partition member 50 described later in the stacking direction. Each of the manifolds M1 to M4 communicates with the gas flow path 60 via, for example, seven slits 42.

[0037] (Partition member 50)

[0038] The partition member 50 is formed, for example, by stamping a metal plate such as stainless steel, a titanium alloy, or pure titanium.

[0039] One of the pair of partition members 50 is disposed on the anode-side surface of the power generation unit 30. The other of the pair of partition members 50 is disposed on the cathode-side surface of the power generation unit 30.

[0040] Hereinafter, the partition member 50 disposed on the anode-side surface of the power generation unit 30 may be referred to as an anode partition member 51, and the partition member 50 disposed on the cathode-side surface of the power generation unit 30 may be referred to as a cathode partition member 52 for distinction.

[0041] The anode partition member 51 and the cathode partition member 52 have the same shape as each other. The anode partition member 51 and the cathode partition member 52 are disposed in a posture where they are flipped with respect to the power generation unit 30 with an imaginary axis V as a rotation axis. The imaginary axis V is an axis that passes through the center in the X-axis direction of the partition member 50 and extends along the Y-axis direction.

[0042] The separator 50 has through-holes hs1 to hs6 that constitute manifolds M1 to M6. As described above, the anode separator 51 and the cathode separator 52 are arranged in a posture where they are flipped with respect to each other with respect to the power generation unit 30. Therefore, the through-hole hs1 of the anode separator 51 communicates with the through-hole hs3 of the cathode separator 52, and the through-hole hs2 of the anode separator 51 communicates with the through-hole hs4 of the cathode separator 52. In addition, the through-hole hs3 of the anode separator 51 communicates with the through-hole hs1 of the cathode separator 52, and the through-hole hs4 of the anode separator 51 communicates with the through-hole hs2 of the cathode separator 52. In addition, the through-hole hs5 of the anode separator 51 communicates with the through-hole hs5 of the cathode separator 52, and the through-hole hs6 of the anode separator 51 communicates with the through-hole hs6 of the cathode separator 52.

[0043] As Figure 3 shown, on the surface of the separator 50 facing the power generation unit 30, groove-shaped gas flow paths 60 for the reaction gas to flow and ribs 61 extending along the gas flow paths 60 are provided in an alternating arrangement. The separator 50 has, for example, eight gas flow paths 60 extending side by side. The shape of each gas flow path 60 is a so-called serpentine shape that extends in a meandering manner from the through-hole hs1 toward the through-hole hs2.

[0044] Fuel gas flows as the reaction gas in the gas flow path 60 of the anode separator 51. Oxidant gas flows as the reaction gas in the gas flow path 60 of the cathode separator 52. The reaction gas is supplied to the power generation unit 30 by flowing in the gas flow path 60.

[0045] The supply method of the reaction gas in the fuel cell stack 10 is, for example, a so-called countercurrent method in which the fuel gas and the oxidant gas flow in opposite directions.

[0046] Hereinafter, the upstream side in the flow direction of the reaction gas in the gas flow path 60 will be simply referred to as the upstream side, and the downstream side in this flow direction will be simply referred to as the downstream side for explanation.

[0047] Each gas flow path 60 is formed in a substantially S shape by connecting the first extension portions Lg1 to Lg3 with the second extension portions Tg1 and Tg2. The reaction gas sequentially flows in 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.

[0048] The first extension portions Lg1 to Lg3 are juxtaposed at intervals in the Y-axis direction. The first extension portions Lg1 to Lg3 extend along the X-axis direction while meandering in a wave shape.

[0049] The second extension parts Tg1 and Tg2 extend linearly and obliquely with respect to the imaginary axis V in such a manner that they are located on one side in the X-axis direction more downstream.

[0050] The upstream end of the first extension part Lg1 is connected to the through-hole hs1 via the slit 42 of the frame 40. The second extension part Tg1 connects the downstream end of the first extension part Lg1 to the upstream end of the first extension part Lg2. The second extension part Tg2 connects the downstream end of the first extension part Lg2 to the upstream end of the first extension part Lg3. The downstream end of the first extension part Lg3 is connected to the through-hole hs2 via the slit 42. When the reaction gas flows from the first extension part Lg1 to the first extension part Lg2 via the second extension part Tg1 and when it flows from the first extension part Lg2 to the first extension part Lg3 via the second extension part Tg2, the flow direction of the reaction gas is reversed. Therefore, the second extension parts Tg1 and Tg2 constitute the folded-back portions of the gas flow path 60.

[0051] (Partition rib 70)

[0052] A partition rib 70 that separates the two first extension parts Lg1 and Lg2 is provided between the two first extension parts Lg1 and Lg2 of the gas flow path 60 where the distance between the two first extension parts Lg1 and Lg2 in the plurality of gas flow paths 60 is the closest. This partition rib 70 extends along the two first extension parts Lg1 and Lg2. A partition rib 70 that separates the two first extension parts Lg2 and Lg3 is provided between the two first extension parts Lg2 and Lg3 of the gas flow path 60 where the distance between the two first extension parts Lg2 and Lg3 in the plurality of gas flow paths 60 is the closest. This partition rib 70 extends along the two first extension parts Lg2 and Lg3. The two partition ribs 70 have the same structure and function.

[0053] Hereinafter, by explaining the structure of the partition rib 70 that separates the two first extension parts Lg1 and Lg2, the explanation of the structure of the partition rib 70 that separates the two first extension parts Lg2 and Lg3 is omitted. In addition, by explaining the structure of the partition rib 70 of the anode separator 51, the explanation of the structure of the partition rib 70 of the cathode separator 52 is omitted.

[0054] As Figure 4 and Figure 5 shown, the partition rib 70 has a base 71 that separates the two first extension parts Lg1 and 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 extension parts Lg1 and Lg2.

[0055] As Figure 5As shown, the base 71 has a planar contact surface 71a that contacts the anode-side gas diffusion layer 32. The protruding amount of the base 71 is the same as the protruding amount of the rib 61.

[0056] The protrusion 74 protrudes from the contact surface 71a toward one side in the stacking direction. The protrusion 74 protrudes to a position facing the inner surface of the receiving hole 41 of the frame 40. The protrusion 74 sinks into the anode-side gas diffusion layer 32. The protrusion 74 has a planar top surface and a pair of side surfaces that are farther apart from each other as they face the contact surface 71a. The width of the protrusion 74 and the protruding amount from the contact surface 71a are constant throughout the entire length direction of the protrusion 74.

[0057] In addition, when the protruding amount of the protrusion 74 is too large, cracks may occur in the anode-side gas diffusion layer 32. Therefore, the protruding amount of the protrusion 74 is preferably about several percent of the protruding amount of the base 71. The protruding amount of the protrusion 74 in the present embodiment is set to about 7% of the protruding amount of the base 71. In each figure, the protruding amount of the protrusion 74 is exaggeratedly shown.

[0058] As Figure 4 shown, the base 71 has a first corrugated portion 72 and a wide portion 73. The first corrugated portion 72 is located between two first extension portions Lg1, Lg2 and extends in a corrugated shape along the first extension portions Lg1, Lg2. The wide portion 73 is located between the first extension portion Lg1 and the bent portion 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 corrugated portion 72 is larger 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 as it moves away from the first corrugated portion 72.

[0059] The protrusion 74 has a second corrugated portion 75 protruding from the first corrugated portion 72 and an opposing end portion 76 protruding from the wide portion 73. The second corrugated portion 75 extends in a corrugated shape along the first extension portions Lg1, Lg2. The second corrugated portion 75 extends throughout substantially the entire length direction of the first corrugated portion 72 in such a manner as to pass through the center in the width direction of the first corrugated portion 72. The opposing end portion 76 is the end portion on the side farther from the second extension portion Tg1 among the two end portions in the length direction of the protrusion 74. The opposing end portion 76 faces the inner surface of the receiving hole 41 in the X-axis direction. The opposing end portion 76 is bent from the second corrugated portion 75 and extends along the Y-axis direction. More specifically, the opposing end portion 76 extends from the second corrugated portion 75 toward the bent portion Cg. The opposing end portion 76 is bent in a manner that protrudes toward the inner surface of the receiving hole 41 when viewed in the stacking direction. The middle portion between the base end portion and the tip end portion of the opposing end portion 76 is closer to the inner surface of the receiving hole 41 in the X-axis direction than the base end portion and the tip end portion.

[0060] A pressure loss increasing portion P is provided at the boundary between the opposed end portion 76 and the inner surface of the receiving hole 41. The pressure loss increasing portion P has a function of increasing the pressure loss of the reaction gas flowing between the two first extending portions Lg1 and Lg2 across the opposed end portion 76 compared to the pressure loss of the reaction gas flowing in the two first extending portions Lg1 and Lg2 respectively. The pressure loss increasing portion P is constituted by a gap G between the opposed end portion 76 and the inner surface of the receiving hole 41. The gap G gradually becomes larger as it goes from the base end portion of the opposed end portion 76 toward the intermediate portion, and on the other hand, gradually becomes smaller as it goes from the intermediate portion toward the end portion.

[0061] Here, the opposed end portion 76 may also be in contact with the inner surface of the receiving hole 41. However, when the opposed end portion 76 and the frame 40 overlap in the stacking direction, there may be an accidental gap between the frame 40 and the separator 50, resulting in leakage of the reaction gas to the outside of the single cell 20. Therefore, in the present embodiment, in order to avoid the opposed end portion 76 and the frame 40 overlapping in the stacking direction, a gap G is provided between the opposed end portion 76 and the inner surface of the receiving hole 41 in consideration of the manufacturing tolerance of the fuel cell stack 10. The cross-sectional area of the gap G is smaller than the cross-sectional area of the flow paths of the first extending portions Lg1 and Lg2 respectively. In addition, the cross-sectional area of the gap G varies according to the position in the X-axis direction. In the present embodiment, the maximum value of the cross-sectional area of the gap G is smaller than the cross-sectional area of the flow paths of the first extending portions Lg1 and Lg2 respectively.

[0062] (Cooling flow path 80)

[0063] As Figure 1 shown, in the fuel cell stack 10, the anode separator 51 of one of the two single cells 20 adjacent to each other in the stacking direction and the cathode separator 52 of the other single cell 20 are in contact with each other. A cooling flow path 80 for the cooling medium to flow is formed between the anode separator 51 and the cathode separator 52 that are in contact with each other among the two single cells 20 adjacent to each other in the stacking direction. A gasket for sealing between the two single cells 20 is provided between the mutually contacting anode separator 51 and cathode separator 52, and illustration thereof is omitted.

[0064] As Figure 2 shown, the separator 50 has a plurality of cooling grooves 81 that constitute the cooling flow path 80. The cooling grooves 81 are formed on the surface of the separator 50 on the side opposite to the surface where the gas flow path 60 is formed. The cooling grooves 81 are formed by the back surface shape of the ribs 61. The shape of the cooling grooves 81 is a serpentine shape that extends in a meandering manner from the through hole hs1 toward the through hole hs2.

[0065] 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 refrigerant supply manifold M5 flows through the cooling flow path 80 and is discharged from the refrigerant discharge manifold M6.

[0066] <Function of the Present Embodiment>

[0067] As Figure 5 shown, the protrusion 74 of the partition rib 70 sinks into the anode-side gas diffusion layer 32, so that the anode-side gas diffusion layer 32 is locally compressed. At the compressed portion of the anode-side gas diffusion layer 32, the reaction gas hardly flows, so that the reaction gas hardly flows between the two first extension portions Lg1 and Lg2 across the protrusion 74.

[0068] In addition, as Figure 4 shown, a pressure loss increasing portion P is provided at the junction between the opposed end portion 76 of the protrusion 74 and the inner surface of the receiving hole 41. The pressure loss increasing portion P increases the pressure loss of the reaction gas flowing between the two first extension portions Lg1 and Lg2 across the opposed end portion 76 compared to the pressure loss of the reaction gas flowing in the two first extension portions Lg1 and Lg2 respectively. As a result, the reaction gas flowing in the first extension portions Lg1 and Lg2 hardly flows between the two first extension portions Lg1 and Lg2 across the opposed end portion 76, so that it easily flows between the two first extension portions Lg1 and Lg2 via the second extension portion Tg1.

[0069] <Effect of the Present Embodiment>

[0070] (1) The separator 50 is provided with a partition rib 70. The partition rib 70 is provided between two first extension portions Lg1 and Lg2 in which the flow directions of the reaction gas are opposite to each other. The partition rib 70 has a protrusion 74 that sinks into the anode-side gas diffusion layer 32. The protrusion 74 has an opposed end portion 76 that faces the inner surface of the receiving hole 41. A pressure loss increasing portion P is provided at the junction between the opposed end portion 76 and the inner surface of the receiving hole 41 of the frame 40.

[0071] According to the above structure, due to the above-mentioned function, the cutting off of the flow path in which the reaction gas flows across the partition rib 70 in the anode-side gas diffusion layer 32 and between the two first extension portions Lg1 and Lg2 is suppressed. Therefore, the cutting off of the reaction gas flow path can be suppressed by a simple structure of providing the protrusion 74 on the partition rib 70.

[0072] (2) The pressure loss increasing portion P is formed by the gap G between the opposed 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 extension portions Lg1 and Lg2.

[0073] According to the above structure, the pressure loss increasing portion P can be embodied by a simple structure such as providing a gap G between the opposed end portion 76 and the inner surface of the receiving hole 41.

[0074] (3) The opposed end portion 76 extends along the arrangement direction of the two first extending portions Lg1, Lg2.

[0075] According to the above structure, the formation range of the gap G between the opposed end portion 76 and the inner surface of the receiving hole 41 can be increased. Thereby, the range in which the pressure loss of the reaction gas increases can be increased. Thus, the suppression effect of cutting off the flow path of the reaction gas can be improved.

[0076] (4) The width of the protrusion 74 is constant throughout the entire length direction of the protrusion 74.

[0077] At the compressed portion of the anode-side gas diffusion layer 32 formed based on the protrusion 74, the reaction gas hardly flows. Therefore, when there are portions with different widths in the protrusion 74, at the portion with a larger width, the reaction gas reaching the power generation portion 30 may be relatively insufficient. As a result, the power generation amount of the power generation portion 30 may be locally reduced.

[0078] In view of this, according to the above structure, the width of the protrusion 74 is constant throughout the entire length direction of the protrusion 74. Therefore, it is possible to suppress a local reduction in the power generation amount of the power generation portion 30.

[0079] (5) The base portion 71 and the protrusion 74 extend while meandering in a wave shape along the first extending portions Lg1, Lg2.

[0080] For example, when the first extending portions Lg1, Lg2 extend while meandering in a wave shape and the protrusion 74 extends linearly, the width of the base portion 71 that meanders in a wave shape and extends simultaneously may become larger. In this case, the area where the partition rib 70 contacts the anode-side gas diffusion layer 32 increases. As a result, the reaction gas hardly reaches the portion of the power generation portion 30 that contacts the partition rib 70, and thus the power generation amount of the power generation portion 30 may be locally reduced.

[0081] In view of this, according to the above structure, the base portion 71 and the protrusion 74 extend while meandering in a wave shape along the first extending portions Lg1, Lg2. Therefore, compared with the case where the protrusion 74 extends linearly, it is possible to suppress an increase in the width of the partition rib 70. Thus, it is possible to suppress a local reduction in the power generation amount of the power generation portion 30.

[0082] <Change Example>

[0083] This embodiment can be implemented with the following changes. This embodiment and the following change examples can be implemented in combination with each other within a range where there is no technical contradiction.

[0084] · Alternatively, the first extension portions Lg1 to Lg3 may extend while being wavy and meandering, and the second wavy portion 75 of the protruding portion 74 may extend linearly along the X-axis direction.

[0085] · Alternatively, the first extension portions Lg1 to Lg3 may extend linearly along the X-axis direction, and the second wavy portion 75 of the protruding portion 74 may extend while being wavy and meandering along the X-axis direction.

[0086] · Alternatively, the first extension portions Lg1 to Lg3 may extend linearly along the X-axis direction, and the second wavy portion 75 of the protruding portion 74 may extend linearly along the X-axis direction.

[0087] · The width of the protruding portion 74 may not be constant throughout the entire protruding portion 74. For example, the width of the opposing end portion 76 may be larger than the width of the second wavy portion 75.

[0088] · As Figure 7 shown, the opposing end portion 76 may also extend linearly in the Y-axis direction along the inner surface of the receiving hole 41.

[0089] · As Figure 8 shown, the opposing end portion 76 may also extend from the second wavy portion 75 toward the side away from the bending portion Cg in the Y-axis direction.

[0090] · The opposing end portion 76 may not extend along the arrangement direction of the first extension portions Lg1 to Lg3. The opposing end portion 76 may extend along the X-axis direction.

[0091] · As Figure 9 shown, the opposing end portion 76 may also contact the inner surface of the receiving hole 41. In addition, the side surface of the protruding portion 74 may stand perpendicular to the contact surface 71a. In this case, the side surface of the protruding portion 74 makes surface contact with the inner surface of the receiving hole 41. At this time, no gap G is formed at the boundary portion between the opposing end portion 76 and the inner surface of the receiving hole 41. Even with the above structure, since the boundary portion between the opposing end portion 76 and the inner surface of the receiving hole 41 functions as a pressure loss increasing portion P, the above effect (1) can be achieved.

[0092] · The supply method of the reaction gas in the fuel cell stack 10 may also be a so-called coflow method in which the fuel gas and the oxidant gas flow in the same direction in the first extension portions Lg1, Lg2, and Lg3 of each separator 50.

[0093] · Each slit 42 may not penetrate the frame 40 and may be formed in a groove shape that opens on one side in the thickness direction of the frame 40. In this case, the frame 40 may also have a slit 42 at a portion between the accommodation hole 41 and each through hole hf1, hf2 in the surface facing the anode separator 51. In addition, the frame 40 may also have a slit 42 at a portion between the accommodation hole 41 and each through hole hf3, hf4 in the surface facing the cathode separator 52.

[0094] · The material of the separator 50 may also be a carbon material or a composite material including a carbon material and a resin material.

[0095] · The separator 50 may also be formed by machining or injection molding.

Claims

1. A fuel cell stack comprising a plurality of single cells stacked thereon, wherein, each single cell includes: a power generation part having a membrane electrode assembly and a pair of gas diffusion layers sandwiching the membrane electrode assembly; a frame having a receiving hole for receiving the power generation part; and a pair of separators for sandwiching the power generation part and the frame, each separator of each single cell has a surface facing the power generation part, and a gas flow path for allowing a reaction gas to flow is provided on the surface facing the power generation part, the gas flow path has: a plurality of first extension parts which are arranged side by side with the flow direction of the reaction gas being opposite to each other; and a second extension part which connects the ends of two of the first extension parts arranged side by side, a partition rib for separating the two first extension parts is provided between the two first extension parts connected by the second extension part, the partition rib has: a base portion which contacts a corresponding one of the pair of gas diffusion layers of the power generation part and extends along the first extension part; and a protrusion which protrudes from the base portion and sinks into the corresponding gas diffusion layer and extends along the first extension part, the protrusion has an opposing end portion opposing the inner surface of the receiving hole, a pressure loss increasing portion is provided at the junction of the opposing end portion and the inner surface of the receiving hole, and the pressure loss increasing portion increases the pressure loss of the reaction gas flowing between the two first extension parts across the opposing end portion compared to the pressure loss of the reaction gas flowing in the two first extension parts respectively.

2. The fuel cell stack according to claim 1, wherein, the pressure loss increasing portion is constituted by a gap between the opposing end portion and the inner surface of the receiving hole, the cross-sectional area of the gap is smaller than the flow path cross-sectional area of each of the two first extension parts.

3. The fuel cell stack according to claim 1, wherein, the opposing end portion extends along the arrangement direction of the two first extension parts.

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

5. The fuel cell stack according to any one of claims 1 to 3, wherein, the first extension part extends while being wavy and meandering, the base portion and the protrusion extend while being wavy and meandering along the first extension part.

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