Fuel cell stack

Abstract

To provide a fuel cell stack that can suppress insufficient cooling. [Solution] On the side of the separator 50 opposite to the side facing the power generation section, a cooling channel 70 is provided that extends in the Y-axis direction while meandering in the X-axis direction, and through which a cooling medium flows. The cooling channel 70 has a plurality of third extending sections Lc that extend in a wave-like manner in the X-axis direction and are parallel in the Y-axis direction, and a fourth extending section Tc that connects one end of two adjacent third extending sections Lc in the Y-axis direction. The refrigerant supply manifold M5 and the refrigerant discharge manifold M6 are located on opposite sides of the cooling channel 70 in the X-axis direction. The fuel cell stack 10 is configured such that the pressure loss of the cooling medium passing through one third extending section Lc is greater than the pressure loss of the cooling medium passing through a third extending section Lc located upstream of that third extending section Lc in the direction of reaction gas flow.

Description

[Technical Field]

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

[0002] The fuel cell described in Patent Document 1 is configured by stacking a plurality of fuel cells each including an MEA containing a solid polymer electrolyte membrane and a pair of separators that sandwich the MEA. Each fuel cell is in the shape of a rectangular plate having long sides and short sides.

[0003] Three manifold portions for respectively supplying fuel gas, cooling water, and oxidant gas are provided at one end portion in the long side direction of the fuel cell. Three manifold portions for respectively discharging oxidant gas, cooling water, and fuel gas are provided at the other end portion in the long side direction of the fuel cell.

[0004] A gas flow channel through which a reaction gas, which is either fuel gas or oxidant gas, flows is provided on a surface of the separator facing the MEA. The gas flow channel has three linear flow channel portions arranged in parallel in the short side direction of the fuel cell, and two connecting portions that connect the downstream end and the upstream end of adjacent linear flow channel portions. The gas flow channel has a so-called serpentine shape that extends meandering over a plurality of times.

[0005] A cooling flow channel through which cooling water flows is provided on a surface of the separator opposite to the surface facing the MEA. The cooling flow channel has a serpentine shape similar to the shape of the gas flow channel. In two fuel cells adjacent in the stacking direction, between the two separators that contact each other, a space through which cooling water flows is formed by the cooling flow channels of the two mutually inverted separators. As cooling water flows through the space, the fuel cells that generate heat accompanying power generation are cooled. [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2009-170286 [Overview of the project] [Problems that the invention aims to solve]

[0007] In the separator described in Patent Document 1, the reaction gas flows in a meandering manner from the upstream side to the downstream side of the gas flow path. Since the reaction gas is consumed in conjunction with power generation in the MEA, the amount of heat generated in the fuel cell is greater on the upstream side of the gas flow path. In contrast, the cooling water that flows into the above space from the manifold section flows in a meandering manner from the upstream side to the downstream side of the cooling flow path, or it flows to the downstream side without passing through the upstream part of the cooling flow path. In this case, there is a risk that the cooling of the upstream part of the gas flow path, where the amount of heat generated in the fuel cell is greater, will be insufficient. [Means for solving the problem]

[0008] A fuel cell stack that solves the above problems is configured by stacking a plurality of single cells, each having a power generation unit including a membrane electrode assembly and a pair of separators sandwiching the power generation unit, wherein a cooling medium flows between the pair of separators that are in contact with each other in two single cells adjacent to each other in the stacking direction of the plurality of single cells, and when the direction perpendicular to the stacking direction is taken as the first direction, and the direction perpendicular to both the stacking direction and the first direction is taken as the second direction, a gas flow path is provided on the surface of the separator facing the power generation unit, which extends in the second direction while meandering in the first direction and through which the reaction gas flows, and the gas flow path of one separator and the gas flow path of the other separator are configured such that the reaction gas flows in opposite directions to each other, and on the surface of the separator opposite to the surface facing the power generation unit, A fuel cell stack is provided, which has a cooling channel that meanders in a first direction and extends in a second direction through which the cooling medium flows, the cooling channel having a plurality of corrugated sections that extend in a wave-like manner in the first direction and are parallel in the second direction, and a connecting section that connects one end of two adjacent corrugated sections in the second direction, the single cell having a refrigerant supply manifold that supplies the cooling medium to the cooling channel, and a refrigerant discharge manifold that discharges the cooling medium from the cooling channel, the refrigerant supply manifold and the refrigerant discharge manifold are located on opposite sides of the cooling channel in the first direction, and the pressure loss of the cooling medium passing through one corrugated section is greater than the pressure loss of the cooling medium passing through a corrugated section located upstream of that corrugated section in the flow direction of the reaction gas.

[0009] In the above configuration, the reaction gas flows in opposite directions in the gas flow path of one separator and the gas flow path of the other separator, meandering in opposite directions. As a result, the amount of electricity generated by a single cell increases in the upstream portion of the reaction gas flow direction, and therefore the amount of heat generated by a single cell increases in the upstream portion of the flow direction.

[0010] Here, the refrigerant supply manifold and the refrigerant discharge manifold are located on opposite sides of the cooling channel in the first direction, which is the direction in which the corrugated portion of the cooling channel extends. Therefore, the cooling medium supplied from the refrigerant supply manifold passes through multiple corrugated portions in the first direction before being discharged from the refrigerant discharge manifold.

[0011] According to the above configuration, the pressure loss of the cooling medium passing through one corrugated section is greater than the pressure loss of the cooling medium passing through a corrugated section located upstream of that section in the direction of reaction gas flow. Therefore, the cooling medium supplied from the refrigerant supply manifold tends to flow towards the corrugated section with the smaller pressure loss among the multiple corrugated sections. As a result, the cooling water tends to flow more easily to the upstream portion in the direction of reaction gas flow between one separator and the other separator, i.e., to the portion of the single cell where the heat generation is high. Therefore, insufficient cooling of the fuel cell stack can be suppressed. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is an exploded perspective view showing a single cell constituting a fuel cell stack of one embodiment. [Figure 2] Figure 2 is a cross-sectional view showing a single cell of Figure 1. [Figure 3] Figure 3 is a plan view showing the gas flow path of the separator in Figure 1. [Figure 4] Figure 4 is a plan view showing the cooling channel of the separator in Figure 1. [Figure 5] Figure 5 is a plan view showing a fuel cell stack in which the cooling channels for the anode separator and the cathode separator overlap. [Figure 6] Figure 6 is a cross-sectional perspective view of a fuel cell stack showing the portion of the cooling channel where the ribs of the anode separator and the ribs of the cathode separator are in contact. [Figure 7] Figure 7 is a cross-sectional perspective view of a fuel cell stack showing the portion of the cooling channel where the ribs of the anode separator and the ribs of the cathode separator are not in contact. [Figure 8] Figure 8 is a plan view of the fuel cell stack in the first modified example. [Figure 9] Figure 9 is a plan view of the fuel cell stack in the second modified example. [Modes for carrying out the invention]

[0013] An embodiment of a fuel cell stack will be described below with reference to Figures 1 to 7. (Fuel cell stack 10) As shown in Figures 1 and 2, the fuel cell stack 10 is composed of multiple single cells 20 stacked on top of each other. The fuel cell stack 10 is, for example, a polymer electrolyte fuel cell.

[0014] (20 single cells) As shown in Figure 1, the single cell 20 is, for example, in the shape of a square plate. That is, the single cell 20 has a pair of first sides that extend parallel to each other, and a pair of second sides that are perpendicular to the first sides and extend parallel to each other.

[0015] Hereafter, the stacking direction of multiple single cells 20 will be simply referred to as the stacking direction. Furthermore, the direction perpendicular to the stacking direction and in which the first edge of the single cell 20 extends will be referred to as the X-axis direction, and the direction perpendicular to both the stacking direction and the X-axis direction and in which the second edge of the single cell 20 extends will be referred to as the Y-axis direction. The X-axis direction is an example of the "first direction". The Y-axis direction is an example of the "second direction".

[0016] The single cell 20 comprises a fuel gas supply manifold M1 that supplies fuel gas to the interior of the single cell 20, and a fuel gas discharge manifold M2 that discharges fuel gas to the exterior of the single cell 20. The single cell 20 comprises an oxidant gas supply manifold M3 that supplies oxidant gas to the interior of the single cell 20, and an oxidant gas discharge manifold M4 that discharges oxidant gas to the exterior of the single cell 20. The single cell 20 comprises a coolant supply manifold M5 that supplies a cooling medium to the interior of the fuel cell stack 10, and a coolant discharge manifold M6 that discharges the cooling medium to the exterior of the fuel cell stack 10. The fuel gas is, for example, hydrogen gas. The oxidant gas is, for example, air. The cooling medium is, for example, water.

[0017] The fuel gas supply manifold M1, the coolant discharge manifold M6, and the oxidant gas discharge manifold M4 are located at one end of the single cell 20 in the X-axis direction, and are arranged in this order from one side toward the other side in the Y-axis direction. The oxidant gas supply manifold M3, the coolant supply manifold M5, and the fuel gas discharge manifold M2 are located at the other end of the single cell 20 in the X-axis direction, and are arranged in this order from one side toward the other side in the Y-axis direction.

[0018] The single cell 20 comprises 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 each have, for example, a square shape in a plan view. The frame 40 has, for example, a square frame shape in a plan view.

[0019] (Power Generation Unit 30) As shown in Figure 2, the power generation unit 30 comprises 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 through which fuel gas passes. The cathode-side gas diffusion layer 33 has a plurality of pores through which oxidant gas passes.

[0020] Although not shown in the diagram, the membrane electrode assembly 31 comprises an electrolyte membrane and an anode electrode catalyst layer and a cathode electrode catalyst layer sandwiching the electrolyte membrane. The anode-side gas diffusion layer 32 is superimposed on the anode electrode catalyst layer. The cathode-side gas diffusion layer 33 is superimposed on the cathode electrode catalyst layer.

[0021] (Frame 40) As shown in Figure 1, the frame 40 has a housing hole 41 in its center for housing the power generation unit 30. The frame 40 supports the outer periphery of the power generation unit 30 housed in the housing hole 41.

[0022] The frame 40 is formed from an insulating resin material. The frame 40 has through holes hf1 to hf6 that constitute the manifolds M1 to M6 in the outer peripheral portion of the housing hole 41.

[0023] The frame 40 has a plurality of grooves 42 in the portion between the housing hole 41 and each through hole hf1 to hf4. The grooves 42 are elongated oval shapes in the X-axis direction. The grooves 42 connect one of the manifolds M1 to M4 to the gas flow path 60, which will be described later. The plurality of grooves 42 located between the housing hole 41 and the through hole hf1, and the plurality of grooves 42 located between the housing hole 41 and the through hole hf2, open toward the anode separator 51, which will be described later. The plurality of grooves 42 located between the housing hole 41 and the through hole hf3, and the plurality of grooves 42 located between the housing hole 41 and the through hole hf4, open toward the cathode separator 52, which will be described later.

[0024] (Separator 50) The separator 50 is formed by press-forming a metal sheet, such as stainless steel, titanium alloy, or pure titanium.

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

[0026] Hereafter, the separator 50 located on the anode side of the power generation unit 30 may be referred to as the anode separator 51, and the separator 50 located on the cathode side of the power generation unit 30 may be referred to as the cathode separator 52 to distinguish them.

[0027] The anode separator 51 and the cathode separator 52 have the same shape. The anode separator 51 and the cathode separator 52 are arranged in a reversed orientation relative to the power generation unit 30, with the virtual axis V as the reversal axis. The virtual axis V is an axis that 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 constitute the manifolds M1 to M6. As described above, the anode separator 51 and the cathode separator 52 are arranged in opposite orientations relative to the power generation unit 30. For this reason, the through holes hs1, hs2, hs3, hs4, hs5, and hs6 of the anode separator 51 are in communication with the through holes hs3, hs4, hs1, hs2, hs6, and hs5 of the cathode separator 52, respectively.

[0029] As shown in Figure 3, the surface of the separator 50 facing the power generation section 30 is provided with alternating groove-shaped gas channels 60 through which the reaction gas flows, and ribs 61 extending along the gas channels 60. The separator 50 has, for example, four gas channels 60 that extend in parallel to each other. The shape of the gas channels 60 is a so-called serpentine shape, which extends in a meandering manner. The gas channels 60 meander in the X-axis direction and extend in the Y-axis direction.

[0030] Fuel gas flows as a reaction gas through the gas channel 60 of the anode separator 51. Oxidizing gas flows as a reaction gas through the gas channel 60 of the cathode separator 52. The reaction gases are supplied to the power generation unit 30 by flowing through the gas channels 60.

[0031] The fuel cell stack 10 uses a so-called counterflow system in which the fuel gas and oxidizer gas flow in opposite directions. Specifically, the gas flow path 60 of the anode separator 51 and the gas flow path 60 of the cathode separator 52 are configured so that the reaction gases flow in opposite directions.

[0032] Hereafter, the flow direction of the reaction gas in the gas flow path 60 may be simply referred to as the flow direction, the upstream side of the flow direction may be simply referred to as the upstream side, and the downstream side of the flow direction may be simply referred to as the downstream side. The gas flow path 60 has three first extensions Lg arranged in parallel in the Y-axis direction, and two second extensions Tg connecting one end of two adjacent first extensions Lg in the Y-axis direction. The gas flow path 60 is formed in a substantially S-shape. Each first extension Lg extends in the X-axis direction while meandering in a wave-like manner. Each second extension Tg extends linearly in the Y-axis direction.

[0033] Hereafter, the three first extensions Lg will be referred to as first extension Lg1, first extension Lg2, and first extension Lg3, in order from the upstream side. The two second extensions Tg will be referred to as second extension Tg1 and second extension Tg2, in order from the upstream side.

[0034] The upstream end of the first extension Lg1 is aligned with the through hole hs1 in the X-axis direction and is connected to the through hole hs1 via a groove 42 (see Figure 1). The second extension Tg1 connects the downstream end of the first extension Lg1 to the upstream end of the first extension Lg2. The second extension Tg2 connects the downstream end of the first extension Lg2 to the upstream end of the first extension Lg3. The downstream end of the first extension Lg3 is aligned with the through hole hs2 in the X-axis direction and is connected to the through hole hs2 via a groove 42 (see Figure 1). The portion of the gas flow path 60 excluding the upstream end of the first extension Lg1 and the downstream end of the first extension Lg3 faces the power generation section 30.

[0035] The amplitudes of the three first extending sections Lg, which meander in a wave-like manner, are different from each other. More specifically, the amplitudes of the three first extending sections Lg are larger the further downstream they are in the flow direction. That is, the amplitude of the first extending section Lg2 is larger than the amplitude of the first extending section Lg1. Also, the amplitude of the first extending section Lg3 is larger than the amplitude of the first extending section Lg2. Note that the wavelengths and flow path widths of the first extending sections Lg1, Lg2, and Lg3 are constant.

[0036] (Cooling channel 70) As shown in Figure 2, in the fuel cell stack 10, the anode separator 51 of one single cell 20 and the cathode separator 52 of the other single cell 20 are in contact with each other. A cooling medium flows between the anode separator 51 and cathode separator 52 that are in contact with each other in the two single cells 20 that are adjacent in the stacking direction. Although not shown in the figure, a gasket is provided between the anode separator 51 and cathode separator 52 that are in contact with each other to seal the space between the two single cells 20.

[0037] As shown in Figure 4, on the side of the separator 50 opposite to the side facing the power generation section 30, groove-shaped cooling channels 70 through which the cooling medium flows and ribs 71 extending along the cooling channels 70 are arranged alternately. The cooling channels 70 are formed by the shape of the back surface of the ribs 61. The ribs 71 are formed by the shape of the back surface of the gas channels 60.

[0038] The separator 50 has, for example, three cooling channels 70 that extend in parallel to each other. The shape of the cooling channels 70 is a serpentine shape that extends in a meandering manner. The cooling channels 70 meander in the X-axis direction and extend in the Y-axis direction.

[0039] The cooling channel 70 has three third extensions Lc arranged in parallel in the Y-axis direction, and two fourth extensions Tc connecting one end of two adjacent third extensions Lc in the Y-axis direction. The cooling channel 70 is formed in a roughly S-shape. Each third extension Lc extends in the X-axis direction while meandering in a wave-like manner. Each fourth extension Tc extends linearly in the Y-axis direction. The third extension Lc is an example of a "wave-like section". The fourth extension Tc is an example of a "connecting section".

[0040] Hereafter, the three third extensions Lc will be referred to as third extension Lc1, third extension Lc2, and third extension Lc3, in order from the upstream side. The two fourth extensions Tc will be referred to as fourth extension Tc1 and fourth extension Tc2, in order from the upstream side.

[0041] The upstream end of the third extension Lc1 is aligned with the through hole hs1 in the X-axis direction. The fourth extension Tc1 connects the downstream end of the third extension Lc1 to the upstream end of the third extension Lc2. The fourth extension Tc2 connects the downstream end of the third extension Lc2 to the upstream end of the third extension Lc3. The downstream end of the third extension Lc3 is aligned with the through hole hs2 in the X-axis direction.

[0042] The amplitudes of the three meandering third extensions Lc are different from each other. More specifically, the amplitudes of the three third extensions Lc are larger the further downstream they are in the flow direction. That is, the amplitude of the third extension Lc2 is larger than the amplitude of the third extension Lc1. Also, the amplitude of the third extension Lc3 is larger than the amplitude of the third extension Lc2. As a result, the fuel cell stack 10 is configured such that the pressure loss of the cooling medium passing through the three third extensions Lc is larger the further downstream they are in the flow direction. Note that the wavelengths and flow widths of the third extensions Lc1, Lc2, and Lc3 are constant.

[0043] As shown in Figure 5, the phases of the third extensions Lc1, Lc2, and Lc3 of the anode separator 51 and the phases of the third extensions Lc1, Lc2, and Lc3 of the cathode separator 52 that contacts the anode separator 51 are different from each other. Therefore, the ribs 71 of the anode separator 51 and the ribs 71 of the cathode separator 52 are in partial contact.

[0044] The refrigerant supply manifold M5 and the refrigerant discharge manifold M6 are located on opposite sides of the cooling passage 70 in the X-axis direction, or more specifically, on opposite sides of the third extension Lc2 in the X-axis direction. The cooling medium supplied from the refrigerant supply manifold M5 flows between the cooling passage 70 of the anode separator 51 and the cooling passage 70 of the cathode separator 52, and is discharged from the refrigerant discharge manifold M6.

[0045] As shown in Figure 6, at the point where the ribs 71 of the anode separator 51 and the ribs 71 of the cathode separator 52 are in contact with each other, multiple closed spaces are formed by the cooling channels 70 of the anode separator 51 and the cathode separator 52. Therefore, the cooling medium flows through these multiple closed spaces.

[0046] As shown in Figure 7, in the portion where the ribs 71 of the anode separator 51 and the ribs 71 of the cathode separator 52 are not in contact with each other, the cooling medium flows between the anode separator 51 and the cathode separator 52. More specifically, the cooling medium flows through the cooling channels 70 of the anode separator 51 and the cathode separator 52, overcoming the ribs 71 of both the anode separator 51 and the cathode separator 52. Therefore, the cooling channels 70 flow in the planar direction of the single cell 20.

[0047] <Operation of this embodiment> Fuel gas supplied from the fuel gas supply manifold M1 passes through the gas flow path 60 of the anode separator 51 of each single cell 20 and is discharged from the fuel gas discharge manifold M2. As the fuel gas flows through the gas flow path 60, it is diffused by the anode-side gas diffusion layer 32 and supplied to the power generation unit 30. Oxidizer gas supplied from the oxidizer gas supply manifold M3 passes through the gas flow path 60 of the cathode separator 52 of each single cell 20 and is discharged from the oxidizer gas discharge manifold M4. As the oxidizer gas flows through the gas flow path 60, it is diffused by the cathode-side gas diffusion layer 33 and supplied to the power generation unit 30. As a result, power is generated in the power generation unit 30 by an electrochemical reaction between the fuel gas and the oxidizer gas.

[0048] In the fuel cell stack 10, the reaction gases flow in opposite directions in the gas flow path 60 of the anode separator 51 and the gas flow path 60 of the cathode separator 52, meandering in opposite directions. As a result, the amount of electricity generated by a single cell 20 increases in the upstream portion of the flow direction, and therefore the amount of heat generated by a single cell 20 increases in the upstream portion of the flow direction.

[0049] Here, the refrigerant supply manifold M5 and the refrigerant discharge manifold M6 are located on opposite sides of the cooling passage 70 in the X-axis direction. Therefore, the cooling medium supplied from the refrigerant supply manifold M5 passes through the third extensions Lc1, Lc2, and Lc3 in the X-axis direction before being discharged from the refrigerant discharge manifold M6.

[0050] The fuel cell stack 10 is configured such that the pressure loss of the cooling medium passing through the three third extensions Lc is greater for third extensions Lc located further downstream in the flow direction. As a result, as shown by the white arrows in Figure 5, the cooling medium supplied from the refrigerant supply manifold M5 tends to flow towards the third extension Lc with the smallest pressure loss among the three third extensions Lc. In other words, the cooling medium flows more easily in the order of third extensions Lc1, Lc2, and Lc3. This makes it easier for the cooling water to flow to the upstream portion in the flow direction between the anode separator 51 and the cathode separator 52, i.e., to the portion of the single cell 20 that generates a large amount of heat.

[0051] <Effects of this embodiment> (1) The cooling channel 70 has three third extending sections Lc that extend in a wave-like manner in the X-axis direction and are parallel in the Y-axis direction, and two fourth extending sections Tc that connect one end of two adjacent third extending sections Lc in the Y-axis direction. The refrigerant supply manifold M5 and the refrigerant discharge manifold M6 are located on opposite sides of the cooling channel 70 in the X-axis direction. The fuel cell stack 10 is configured such that the pressure loss of the cooling medium passing through the three third extending sections Lc is greater for third extending sections Lc located on the downstream side in the flow direction.

[0052] According to the above configuration, the above-mentioned effects are achieved, thereby suppressing insufficient cooling of the fuel cell stack 10. (2) The amplitudes of the three third extensions Lc are configured to be larger for the third extensions Lc located on the downstream side in the flow direction.

[0053] With the above configuration, the pressure loss of the cooling medium passing through each third extending portion Lc can be easily adjusted for each third extending portion Lc by changing the amplitude of each third extending portion Lc.

[0054] (3) The cooling channel 70 is formed by the shape of the back surface of the rib 61. When the power generation unit 30 is equipped with an anode-side gas diffusion layer 32 and a cathode-side gas diffusion layer 33, power is generated in the power generation unit 30 as the reaction gas flowing through the gas channel 60 penetrates the anode-side gas diffusion layer 32 and the cathode-side gas diffusion layer 33. The flow velocity of the reaction gas flowing through the gas channel 60 decreases as it moves downstream. Therefore, the amount of reaction gas penetrating the anode-side gas diffusion layer 32 and the cathode-side gas diffusion layer 33 decreases as it moves downstream in the gas channel 60 of the power generation unit 30, resulting in less power generation. As a result, the power generation efficiency of the single cell 20 may decrease.

[0055] In this regard, according to the above configuration, the cooling channel 70 is formed by the back surface shape of the rib 61 that extends along the gas channel 60. The cooling channel 70 is configured such that the pressure loss of the cooling medium downstream in the flow direction is greater than the pressure loss upstream. Therefore, the pressure loss of the reaction gas downstream of the gas channel 60 is greater than the pressure loss of the reaction gas upstream. As a result, the flow velocity of the reaction gas flowing through the gas channel 60 does not decrease as it moves downstream, that is, the flow rate of the reaction gas does not decrease as it moves downstream. Therefore, a decrease in the power generation efficiency of the single cell 20 can be suppressed.

[0056] <Example of changes> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0057] The cooling channel 70 does not have to be formed by the back surface shape of the rib 61, as long as it extends in a meandering manner generally along the gas channel 60. In this case, for example, the first extending portion Lg of the gas channel 60 does not have to extend in a wave-like meandering manner, but may extend in a straight line in the X-axis direction. Such a separator 50 can be formed, for example, by cutting or laser processing.

[0058] If the pressure loss of the cooling medium passing through one third extending portion Lc is greater than the pressure loss of the cooling medium passing through a third extending portion Lc located upstream of that third extending portion Lc in the flow direction, the amplitudes of the three third extending portions Lc do not have to be different from each other. For example, the amplitudes of third extending portions Lc1 and Lc2 may be the same and smaller than the amplitude of third extending portion Lc3.

[0059] As shown in Figure 8, the wavelengths of the three third extending sections Lc may differ from each other such that the pressure loss of the cooling medium passing through the three third extending sections Lc is greater for the third extending section Lc located downstream in the flow direction. In this first modified example, the wavelengths of the three third extending sections Lc are shorter for the third extending section Lc located downstream in the flow direction. The amplitude and flow path width of the third extending sections Lc1, Lc2, and Lc3 are constant.

[0060] In the first example of modification described above, if the pressure loss of the cooling medium passing through one third extending portion Lc is greater than the pressure loss of the cooling medium passing through a third extending portion Lc located upstream of that third extending portion Lc in the flow direction, the wavelengths of the three third extending portions Lc do not have to be different from each other. For example, the wavelengths of third extending portions Lc1 and Lc2 may be the same and longer than the wavelength of third extending portion Lc3.

[0061] As shown in Figure 9, the flow path widths of the three third extending sections Lc may differ from one another, such that the pressure loss of the cooling medium passing through the three third extending sections Lc is greater for the third extending section Lc located further downstream in the flow direction. In this second modified example, the flow path widths of the three third extending sections Lc are smaller for the third extending section Lc located further downstream in the flow direction. The amplitude and wavelength of the third extending sections Lc1, Lc2, and Lc3 are constant. The flow path width of the fourth extending section Tc1 gradually decreases from the third extending section Lc1 towards the third extending section Lc2. The flow path width of the fourth extending section Tc2 gradually decreases from the third extending section Lc2 towards the third extending section Lc3.

[0062] In the second example of modification described above, if the pressure loss of the cooling medium passing through one third extending section Lc is greater than the pressure loss of the cooling medium passing through a third extending section Lc located upstream of that third extending section Lc in the flow direction, the flow path widths of the three third extending sections Lc do not have to be different from each other. For example, the flow path widths of third extending sections Lc1 and Lc2 may be the same and greater than the flow path width of third extending section Lc3.

[0063] The above embodiments, the first modification, and the second modification may be combined. That is, at least one of the amplitude, wavelength, and flow path width may differ for each of the three third extending sections Lc such that the pressure loss of the cooling medium passing through the three third extending sections Lc is greater for the third extending section Lc located downstream in the flow direction.

[0064] The fourth extensions Tc1 and Tc2 may extend in the Y-axis direction while meandering in a wave-like manner. Manifolds M1 to M4 may be provided at both ends of the single cell 20 in the Y-axis direction. In this case, the upstream end of the third extension Lc1 may be provided alongside the through hole hs1 in the Y-axis direction, and the downstream end of the third extension Lc3 may be provided alongside the through hole hs2 in the Y-axis direction.

[0065] Each gas flow path 60 may have two or more first extended sections Lg. Each cooling channel 70 may have two or more third extensions Lc. [Explanation of Symbols]

[0066] hf1, hf2, hf3, hf4, hf5, hf6...Through hole hs1,hs2,hs3,hs4,hs5,hs6...Through hole Lg,Lg1,Lg2,Lg3...first extension part Tg, Tg1, Tg2…Second extension part Lc, Lc1, Lc2, Lc3...Third extension part (wavy part) Tc, Tc1, Tc2...4th extension part (connection part) M1…Fuel gas supply manifold M2…Fuel gas exhaust manifold M3... Oxidizer gas supply manifold M4... Oxidizer gas exhaust manifold M5... Refrigerant supply manifold M6… Refrigerant discharge manifold V...Virtual axis 10…Fuel cell stack 20... Single cell 30...Power Generation Department 31...Membrane electrode assembly 32... Anode-side gas diffusion layer 33... Cathode-side gas diffusion layer 40...frames 41…Containment port 42...Groove 50... Separator 51... Anode separator 52... Cathode separator 60…Gas flow path 61, 71… Ribs 70…Cooling channel

Claims

1. A fuel cell stack is constructed by stacking a plurality of single cells, each comprising a power generation unit including a membrane electrode assembly and a pair of separators that sandwich the power generation unit, wherein a cooling medium flows between the pair of separators that are in contact with each other in two of the single cells adjacent to each other in the stacking direction of the plurality of single cells, When the direction perpendicular to the stacking direction is defined as the first direction, and the direction perpendicular to both the stacking direction and the first direction is defined as the second direction, On the surface of the separator facing the power generation section, a gas flow path is provided that extends in the second direction while meandering in the first direction, through which the reaction gas flows. The gas flow path of one separator and the gas flow path of the other separator are configured such that the reaction gas flows in opposite directions. On the surface of the separator opposite to the surface facing the power generation section, a cooling channel is provided that extends in the second direction while meandering in the first direction, and through which the cooling medium flows. The cooling channel has a plurality of wavy sections extending in a wave-like manner in the first direction and parallel in the second direction, and a connecting section that connects one end of two adjacent wavy sections in the second direction. The single cell comprises a refrigerant supply manifold that supplies the cooling medium to the cooling channel, and a refrigerant discharge manifold that discharges the cooling medium from the cooling channel. The refrigerant supply manifold and the refrigerant discharge manifold are located on opposite sides of the cooling passage in the first direction. The cooling medium is configured such that the pressure loss of the cooling medium passing through one of the corrugated sections is greater than the pressure loss of the cooling medium passing through a corrugated section located upstream of the corrugated section in the flow direction of the reaction gas. Fuel cell stack.

2. The amplitude of one of the aforementioned wave-like portions is greater than the amplitude of the wave-like portion located upstream of that wave-like portion in the flow direction. The fuel cell stack according to claim 1.

3. The wavelength of one of the aforementioned wave-like portions is shorter than the wavelength of the wave-like portion located upstream of that wave-like portion in the flow direction. The fuel cell stack according to claim 1.

4. The flow path width of one of the aforementioned wavy sections is smaller than the flow path width of the wavy section located upstream of that wavy section in the flow direction. The fuel cell stack according to claim 1.

5. On the surface of the separator facing the power generation section, the gas flow path and ribs extending along the gas flow path are arranged alternately. The cooling channel is formed by the shape of the back surface of the rib. A fuel cell stack according to any one of claims 1 to 4.

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