Fuel cell stack

Abstract

The invention provides a fuel cell stack. Each of the plurality of fuel cell cells is provided with: a resin frame having an opening; a membrane electrode assembly disposed in the opening; and first and second separators facing each other with the frame and the membrane electrode assembly interposed therebetween. The fuel cell stack includes a first manifold hole. The frame body has a frame body inner edge defining the first manifold hole. The first separator has a first separator inner edge defining the first manifold hole, a flat portion disposed along the first separator inner edge, a concavo-convex portion forming a plurality of gas passages, and a boundary line between the flat portion and the concavo-convex portion. When a determination line is defined by a line obtained by separating the boundary line toward the inner edge side of the first partition plate, the inner edge of the frame body is located on the side farther from the first manifold hole than the determination line.

Description

TECHNICAL FIELD

[0001] The technology disclosed in this specification relates to a fuel cell stack. BACKGROUND

[0002] A fuel cell stack is disclosed in Japanese Patent Application Publication No. 2010-27381. The fuel cell stack has a configuration in which a membrane electrode assembly is surrounded by a frame made of resin. In addition, the fuel cell stack has a configuration in which the membrane electrode assembly is sandwiched by two separators together with the frame using a cathode and an anode. A manifold hole extending in a stacking direction is formed by laminating a manifold hole of the frame and a manifold hole of the two separators. A plurality of gas passages extending toward the membrane electrode assembly are arranged on an inner peripheral surface of the manifold hole.

[0003] There is a case in which water droplets remaining on the inner peripheral surface of the manifold hole wetly spread in a manner of covering all of the plurality of gas passages. If the water droplets wetly spread freeze and all of the gas passages are clogged, it is not possible to supply a reaction gas to the membrane electrode assembly or exhaust a reaction gas at the time of startup, resulting in a case in which power generation is not possible. SUMMARY

[0004] The fuel cell stack disclosed in this specification is a fuel cell stack in which a plurality of fuel cell units are laminated. The plurality of fuel cell units each has a frame made of resin, an opening portion, a membrane electrode assembly arranged in the opening portion, and a first separator and a second separator opposed to each other with the frame and the membrane electrode assembly interposed therebetween. A first manifold hole extending in a stacking direction is formed in the fuel cell stack. The frame has a frame inner edge that defines the first manifold hole. The first separator has a first separator inner edge that defines the first manifold hole, a flat portion arranged along the first separator inner edge and arranged on an opposed surface opposed to the second separator, a concave-convex portion that forms a plurality of gas passages extending from the flat portion toward the membrane electrode assembly, and a boundary line that is a boundary line between the flat portion and the concave-convex portion and is arranged on an outer side of the first separator inner edge along the first separator inner edge. When a determination line is defined by a line obtained by moving the boundary line away from the first separator inner edge by an amount of a height dimension of the plurality of gas passages, the frame inner edge is located on a side farther from the determination line than the first manifold hole in a direction parallel to a surface of the frame.

[0005] In a case where the frame inner edge protrudes toward the first manifold hole beyond the boundary line of the flat portion and the concave-convex portion of the first partition, the flat portion and the frame are arranged to oppose each other in the stacking direction. A groove extending along the frame inner edge is formed between the frame and the flat portion. The inventors found that, in a case where the protruding amount of the frame inner edge from the boundary line is equal to or greater than the height dimension of the gas passage in the stacking direction, a water droplet easily wets and spreads along the groove. This is because the water droplet mainly moves according to capillary pressure. Also, when the protruding amount of the frame inner edge from the boundary line is equal to or greater than the height dimension of the gas passage, the height of the side wall of the groove formed by the frame reaches a height sufficient to exert capillary pressure. If capillary pressure is exerted in the groove, the wetting spreadability of the water droplet is equal in the groove and the gas passage. As a result, the water droplet wets and spreads along the groove, and thus the plurality of gas passages can be all clogged by the water droplet.

[0006] Therefore, in the above-described configuration, the frame inner edge is positioned at a position farther from the first manifold hole than the determination line. Therefore, the protruding amount of the frame inner edge from the boundary line is smaller than the height dimension of the gas passage. Thus, even in a case where the groove is formed between the frame and the flat portion, it is possible to be in a state where capillary pressure cannot be sufficiently exerted in the groove. Therefore, the water droplet is easily wetted and spread to the gas passage compared to the groove. Since it is possible to cause the water droplet to preferentially move to the gas passage, it is possible to suppress a case where the water droplet wets and spreads along the groove. It is possible to prevent a case where the plurality of gas passages are all clogged by the water droplet. BRIEF DESCRIPTION OF DRAWINGS

[0007] The features, advantages, and technical and industrial significance of exemplary embodiments of the application will be described in the following detailed description with reference to the accompanying drawings, in which:

[0008] Figure 1 is an exploded view of the fuel cell unit 1.

[0009] Figure 2 is an enlarged plan view of the first manifold hole M1o.

[0010] Figure 3 is a partial side view of the inner peripheral surface of the first manifold hole M1o.

[0011] Figure 4 is a partial cross-sectional view of the IV-IV line of Figure 2

[0012] Figure 5 is a partial cross-sectional view of the fuel cell unit 101 of the comparative example.

[0013] Figure 6 is a partial cross-sectional view of the vicinity of the first manifold hole M1o in Example 2.

[0014] Figure 7 is a partial cross-sectional view of the vicinity of the first manifold hole M1o in Example 3.​ DETAILED DESCRIPTION

[0015] The frame inner edge can also be positioned further from the first manifold hole than the boundary line in a direction parallel to the surface of the frame.

[0016] According to the above structure, the frame inner edge does not protrude beyond the boundary line, and thus a groove is not formed between the frame and the flat portion. Therefore, it is possible to prevent the case where a water droplet wets and spreads along the groove.

[0017] The second partition plate can have a second partition plate inner edge that demarcates the first manifold hole. The second partition plate inner edge can also be positioned further from the first manifold hole than the boundary line in a direction parallel to the surface of the second partition plate.

[0018] According to the above structure, the second partition plate is not opposed to the flat portion of the first partition plate in the stacking direction. Therefore, a groove is not formed between the second partition plate and the flat portion. Thus, it is possible to prevent the case where a water droplet wets and spreads along the groove.

[0019] The first manifold hole can also be an exhaust hole that exhausts a reactive gas introduced to the membrane electrode assembly.

[0020] The amount of water droplets is larger in the exhaust hole of the reactive gas than in the introduction hole of the reactive gas. This is because the water droplets after the reaction are included. According to the above structure, it is possible to reduce the amount of residual water droplets in the exhaust hole where a larger amount of water droplets is generated. It is possible to more effectively suppress the case where the gas passage is blocked due to freezing of the water droplets.

[0021] The water contact angle of the first and second partition plates can also be smaller than the water contact angle of the frame.

[0022] According to the above structure, the inner wall surface of the first and second partition plates can be in a state where the hydrophilicity is higher than the inner wall surface of the frame.

[0023] Example 1

[0024] Outline structure of fuel cell unit 1

[0025] Figure 1 is an explanatory view that shows the fuel cell unit 1 in one embodiment of the present application, which is a solid polymer fuel cell unit that generates electricity by receiving supply of hydrogen and oxygen, and mainly includes a first partition plate 10, a second partition plate 20, a frame 30, and a membrane electrode assembly 40.

[0026] The frame 30 is a frame-shaped resin component that surrounds the entire area surrounding the membrane electrode assembly 40. In this embodiment, polyethylene naphthalate (PEN) is used as the resin component, for example. However, various other resin components or rubber materials such as polypropylene, polyethylene, polyethylene terephthalate, and polyphenylene sulfide can also be used as the resin component.

[0027] The frame 30 has an opening 35 in its central region that surrounds and houses the membrane electrode assembly 40. The membrane electrode assembly 40 is disposed in the opening 35. Furthermore, in... Figure 1 In the diagram, the membrane electrode assembly 40 is indicated by a gray filler. The structure of the membrane electrode assembly 40 will be described later. Additionally, the frame 30 has manifold holes 61i, 61o, 62i, 62o, and 63 on the left and right sides (±x direction sides) of the opening 35.

[0028] The first partition 10 and the second partition 20 are positioned opposite each other, separated by the frame 30 and the membrane electrode assembly 40. The first partition 10 and the second partition 20 are conductive. The first partition 10 and the second partition 20 can be formed, for example, by stamping a metal plate made of stainless steel, titanium, or their alloys, or by forming a carbon resin composite material. In this embodiment, the first partition 10 and the second partition 20 are formed of a carbon resin composite material.

[0029] In this embodiment, the first partition 10 is a cathode-side partition, and the second partition 20 is an anode-side partition. The first partition 10 has manifold holes 11i, 11o, 12i, 12o, and 13 in its outer edge region. The second partition 20 has manifold holes 21i, 21o, 22i, 22o, and 23 in its outer edge region.

[0030] A first manifold M1i for supplying the reactant gas (air) is formed by stacking manifold orifices 11i, 61i, and 21i on top of each other. A first manifold M1o for discharging the reactant gas (air) is formed by stacking manifold orifices 11o, 61o, and 21o on top of each other. A second manifold M2i for supplying the reactant gas (hydrogen) is formed by stacking manifold orifices 12o, 62o, and 22o on top of each other. A second manifold M2o for discharging the reactant gas (hydrogen) is formed by stacking manifold orifices 13, 63, and 23 on top of each other. A cooling water manifold Mw for forming a cooling water passage is formed. Furthermore, the specific structure of the cooling water passage is not directly related to the technical focus of this specification, therefore detailed descriptions are omitted. The first manifold orifices M1i and M1o, the second manifold orifices M2i and M2o, and the cooling water manifold Mw extend along the stacking direction (z-direction).

[0031] The first partition 10 has a flow path 15 from the first manifold M1i to M1o. This flow path 15 is formed by a protrusion 10p on the lower surface of the first partition 10 (i.e., the surface opposite the frame 30). The protrusion 10p will be described later. The reaction gas (air) flowing into the first manifold M1i passes through the membrane electrode assembly 40 via the flow path 15 and exits from the first manifold M1o (see reference). Figure 1 Arrow Y1).

[0032] Similarly, the second partition 20 has a flow path 25 from the second manifold M2i to M2o. This flow path 25 is formed by a protrusion 20p on the upper surface of the second partition 20 (i.e., the surface opposite to the frame 30). The reactant gas (hydrogen) flowing into the second manifold M2i passes through the membrane electrode assembly 40 via the flow path 25 and exits from the second manifold M2o (see reference). Figure 1 (arrow Y2).

[0033] Additionally, gaskets 511, 52, and 53 are disposed on the upper surface of the first partition 10. Gaskets 51, 52, and 53 are formed, for example, of silicone rubber. Gasket 51 is disposed to surround manifold orifices 11i and 11o, respectively. When multiple fuel cell cells 1 are stacked, gasket 51 ensures the sealing of the first manifold orifices M1i and M1o. Similarly, gasket 52 is disposed to surround manifold orifices 12i and 12o, respectively. When multiple fuel cell cells 1 are stacked, gasket 52 ensures the sealing of the second manifold orifices M2i and M2o. Furthermore, gasket 53 is disposed to surround the outer periphery of the first partition 10.

[0034] (Structure of the first manifold orifice M1o)

[0035] Figure 2 An enlarged top view of the first manifold orifice M1o in fuel cell cell 1 is shown. The first manifold orifice M1o is disposed in... Figure 1 The air exhaust manifold port is located on the lower left side of fuel cell unit 1. Additionally, Figure 3 The text shows from Figure 2 A partial side view of the inner circumferential surface of the first manifold orifice M1o when viewed in the direction of arrow Y11. Additionally, although... Figure 3 It is a side view, but a shading line is used for easier understanding of the opening 15a.

[0036] The flow path 15 has multiple first gas passages 15g. For example... Figure 3As shown, multiple first gas passages 15g are formed between the frame 30 and the first partition 10. Specifically, protrusions and recesses 10p are arranged along the y-direction on the lower surface 10b of the first partition 10. The lower surfaces of the protrusions and recesses 10p contact the upper surface of the frame 30, thereby forming first gas passages 15g between adjacent protrusions and recesses 10p. Therefore, in the first gas passage 15g, the sidewalls are formed by the protrusions and recesses 10p, the upper inner wall is formed by the lower surface 10b of the first partition 10, and the lower inner wall is formed by the upper surface 30u of the frame 30. The first gas passage 15g has a gas passage height Dc in the z-direction. The gas passage height Dc is the distance between the lower surface 10b of the first partition 10 and the upper surface 30u of the frame 30.

[0037] like Figure 2 As shown, multiple first gas passages 15g extend from the first manifold orifice M1o toward the membrane electrode assembly 40. Furthermore, the terminal openings of the multiple first gas passages 15g are disposed within a first region R1 on the inner circumferential surface of the first manifold orifice M1o. Therefore, as... Figure 3 As shown, within the first region R1, the opening 15a of the first gas passage 15g is exposed on the inner circumferential surface of the first manifold orifice M1o.

[0038] Figure 4 It shows Figure 2 A partial sectional view at line IV-IV. Figure 4 This is a cross-sectional view through the central axis C1 of the first manifold orifice M1o and through the first gas passage 15g. Figure 4 The diagram shows a fuel cell stack with two stacked fuel cell cells 1. In actual fuel cell stacks, three or more fuel cell cells 1 are stacked. The membrane electrode assembly 40 includes an oxygen electrode 41, a hydrogen electrode 42, and an electrolyte membrane 43. The electrolyte membrane 43 is an ion exchange membrane with proton conductivity formed from a solid polymer material. The oxygen electrode 41 includes a first catalyst layer 44 and a first gas diffusion layer 45. The hydrogen electrode 42 includes a second catalyst layer 46 and a second gas diffusion layer 47. The first catalyst layer 44 and the second catalyst layer 46 are porous layers formed by resin-bonded carbon particles or metal oxides carrying the catalyst. The first gas diffusion layer 45 and the second gas diffusion layer 47 are conductive components with water permeability and gas permeability. Since known structures can be applied to the membrane electrode assembly 40, detailed descriptions are omitted.

[0039] A flange-shaped peripheral region PA is formed on the outer periphery of the membrane electrode assembly 40 via the oxygen electrode 41. An adhesive layer 49 is disposed on the lower surface 41b of the oxygen electrode 41 within the peripheral region PA. The adhesive layer 49 is a layer formed of an adhesive. Examples of adhesives include UV-curable adhesives and hot melt adhesives. The lower surface 41b of the oxygen electrode 41 is fixed to the upper surface 30u of the frame 30 using the adhesive layer 49.

[0040] The frame 30 has a three-layer structure comprising a first resin layer 31, a core layer 33, and a second resin layer 32 stacked in the thickness direction. The core layer 33 is a structural component with airtightness and insulation. The first resin layer 31 is bonded to the first partition 10. The second resin layer 32 is bonded to the second partition 20.

[0041] The first resin layer 31 and the second resin layer 32 may also have a lower melting point than the core layer 33. Specifically, the first resin layer 31 and the second resin layer 32 may also be thermoplastic resins such as acid-modified olefins and polyesters. In addition, the multilayer frame 30 can be formed by various methods. For example, it can also be formed by co-extrusion molding.

[0042] The frame 30 has an inner edge 30w. The inner edge 30w is a part that forms part of the inner wall of the first manifold hole M1o, defining the first manifold hole M1o.

[0043] The first partition 10 has an inner edge 10w, a protrusion 10p, a flat portion 10f, and a boundary line BL. The inner edge 10w of the first partition is a portion that forms part of the inner wall of the first manifold orifice M1o, defining the first manifold orifice M1o. The protrusion 10p is a portion that protrudes downward from the lower surface 10b of the first partition 10. Figure 4 In the sectional view, for ease of understanding, the uneven portions 10p existing in the depth direction on the paper surface are indicated by gray coloring. Additionally, as... Figure 2 As shown, a plurality of first gas passages 15g extending from the flat portion 10f toward the membrane electrode assembly 40 are formed by the uneven portion 10p.

[0044] The flat portion 10f is the area near the inner edge 10w of the first partition plate, and is the area where the protrusions 10p are not disposed. Furthermore, the flat portion 10f is disposed on the opposing surface (i.e., the lower surface 10b) opposite the second partition plate 20. Figure 2 As shown, the flat portion 10f is arranged along the inner edge 10w of the first partition. Furthermore, the flat portion 10f is also the part required for punching the manifold hole 11o. Since the cutting surface is formed by the flat portion 10f, the accuracy and machinability of the cutting surface can be improved.

[0045] A boundary line BL is formed between the flat portion 10f and the uneven portion 10p. For example... Figure 2As shown, the boundary line BL is disposed outside the inner edge 10w of the first partition plate. A first gas passage 15g is formed on the side further away from the boundary line BL from the first manifold hole M1o (+x direction side). On the other hand, a groove region CR is formed on the side closer to the boundary line BL from the first manifold hole M1o (-x direction side).

[0046] like Figure 4 As shown, the groove region CR is the region formed between the flat portion 10f and the surface opposite to the flat portion 10f (i.e., the upper surface 30u of the frame 30). The groove region CR has a groove region height Dm in the z-direction. The groove region height Dm is equal to the gas passage height Dc.

[0047] In addition, such as Figure 2 As shown, the groove region CR is arranged along the inner edge 10w of the first partition. That is, the groove region CR functions as a region that connects multiple first gas passages 15g along the inner edge 10w of the first partition.

[0048] Here, as Figure 4 As shown, the defining line SL is specified. The defining line SL is formed by shifting the boundary line BL parallel to the inner edge 10w of the first partition (the -x direction side) by the amount of gas passage height Dc. Furthermore, the inner edge 30w of the frame is located on the side (the +x direction side) further away from the defining line SL than the first manifold orifice M1o (refer to arrow Y21).

[0049] The second partition 20 has a second partition inner edge 20w. The second partition inner edge 20w is a portion that forms part of the inner wall of the first manifold M1o, defining the first manifold M1o. The second partition inner edge 20w is located on the side (+x direction side) further away from the boundary line BL from the first manifold M1o.

[0050] The water contact angles of the first separator 10 and the second separator 20 are smaller than the water contact angle of the frame 30. For example, the water contact angles of the first separator 10 and the second separator 20 may be less than 90°, while the water contact angle of the frame 30 may be greater than 90°. That is, the inner edges of the first separator 10w and the second separator 20w are more hydrophilic than the inner edge 30w of the frame. This is because the frame 30 is hydrophobic based on the inherent properties of the resin component described above. Furthermore, the first separator 10 and the second separator 20 are hydrophilic based on the inherent properties of the conductive material described above. It should be noted that the hydrophilicity mentioned here refers to the hydrophilicity in the power generation environment of the fuel cell (an environment with water droplets present under high temperature and high humidity conditions).

[0051] (Topic)

[0052] use Figure 5The topic will be illustrated using a comparative example fuel cell cell 101. The comparative example fuel cell cell 101 ( Figure 5 ) and the fuel cell unit 1 of this embodiment ( Figure 4 In contrast, the positional relationship of the inner edge 30w of the frame is different. Specifically, the inner edge 30w of the frame is located on the side (-x direction side) closer to the first manifold orifice M1o than the defining line SL (refer to arrow Y20). That is, in the comparative example, the protrusion PR0 of the inner edge 30w of the frame from the boundary line BL is above the gas passage height Dc. The other structures of the fuel cell cell 101 of the comparative example are the same as those of the fuel cell cell 1 of this embodiment, so the description is omitted.

[0053] In the comparative example fuel cell cell 101, a groove region CR is formed between the upper surface 30u of the frame 30 and the flat portion 10f of the first separator 10. The groove region CR is as follows... Figure 2 As shown, multiple first gas passages 15g are connected in a common manner along the inner edge 10w of the first partition. This results in water droplets remaining on the inner circumferential surface of the first manifold orifice M1o spreading and wetting along the groove region CR. If the water droplets spread to the entire area of ​​the first region R1, all the multiple first gas passages 15g will be completely covered by water droplets. When the water droplets freeze in this state, all the first gas passages 15g will be blocked. As a result, during startup, the intake and exhaust of reactive gases for the membrane electrode assembly cannot occur, thus preventing power generation.

[0054] (Solutions and Effects)

[0055] The inventors discovered that when the protrusion of the inner edge 30w from the boundary line BL is equal to or greater than the gas passage height Dc of the first gas passage 15g, water droplets easily spread and wet along the groove region CR. This is because the water droplets move primarily based on capillary pressure. Furthermore, when the protrusion of the inner edge 30w from the boundary line BL is equal to or greater than the gas passage height Dc, the height of the sidewall in the x-direction of the groove region CR formed by the upper surface 30u of the inner edge 30w reaches a sufficient height to utilize the capillary pressure. If the capillary pressure is fully utilized in the groove region CR, the ease of water droplet wetting and spreading is equal in the groove region CR and the first gas passage 15g. As a result, water droplets spread and wet along the groove region CR, potentially causing multiple first gas passages 15g to be completely blocked by water droplets.

[0056] Therefore, in this embodiment, the inner edge 30w of the frame is located on the +x direction side relative to the defining line SL (refer to...). Figure 4That is, in this embodiment, the protrusion PR1 of the inner edge 30w from the boundary line BL is less than the gas passage height Dc. Therefore, the height of the sidewall in the x-direction of the groove region CR is not high enough to exert capillary pressure. As a result, the first gas passage 15g is more likely to wet and spread with water droplets than the groove region CR. Since water droplets can preferentially move towards the first gas passage 15g, the wetting and spreading of water droplets along the groove region CR can be suppressed. This prevents all first gas passages 15g from being blocked by water droplets.

[0057] In this embodiment, fuel cell unit 1 ( Figure 4 In the first partition, the inner edge 10w of the first partition protrudes towards the central axis C1 than the inner edge 30w of the frame. This allows a relatively hydrophilic component to be exposed on the inner circumferential surface of the first manifold orifice M1o in the first region R1 (the region where the opening 15a of the first gas passage 15g is located). This hydrophilicity facilitates the aggregation of water droplets adhering to the inner circumferential surface of the first manifold orifice M1o in the first region R1. Due to the increased volume of the water droplets, they are more easily expelled under the influence of gravity and the gas flow field. By significantly reducing the amount of water droplets remaining on the inner circumferential surface of the first manifold orifice M1o, blockage of the first gas passage 15g due to water droplet freezing can be suppressed. This improves the start-up performance of the fuel cell unit 1 at freezing points.

[0058] Compared to the first manifold orifice M1i, which serves as the inlet orifice for reactive gas, the first manifold orifice M1o, which serves as the outlet orifice for reactive gas, produces a greater amount of water droplets. This is because it contains water droplets generated after the reaction. In the fuel cell cell 1 of this embodiment, a hydrophilic component (the inner edge 10w of the first separator) protrudes towards the inner circumferential surface of the first manifold orifice M1o on the outlet side. As a result, the amount of residual water droplets can be reduced on the inner circumferential surface of the first manifold orifice M1o on the outlet side, where a greater amount of water droplets are generated, thus preventing the first gas passage 15g from becoming blocked.

[0059] (A variation of Example 1)

[0060] The structure of the first manifold port M1o on the discharge side described above can also be applied to the first manifold port M1i on the inlet side. That is, it can also have a structure in which the inner edge 30w of the frame is located on the side farther away from the first manifold port M1i than the defining line SL. Similarly, the structure of the first manifold ports M1o and M1i for air can also be applied to the second manifold ports M2o and M2i for hydrogen.

[0061] The structure of the inner edge 30w of the frame located on the side farther from the defining line SL from the first manifold hole M1o does not need to be formed on the entire circumference of the inner peripheral surface of the first manifold hole M1o, as long as it is formed at least in the first region R1. Figure 2That's it. The area outside the first region R1 is a region far away from the first gas passage 15g. Moreover, even if water droplets wet and spread in this distant region, the possibility of blocking the first gas passage 15g is relatively small.

[0062] The structure in which the inner edge 30w of the frame is located on the side farther away from the first manifold hole M1o than the defining line SL may not be formed in the first region R1. Figure 2 The entire area of ​​the first gas passage 15g can be formed, as long as it is formed in at least a portion of the area. This prevents the first gas passage 15g from becoming completely blocked due to freezing of the water droplets. By opening at least a portion of the first gas passage 15g, the fuel cell unit 1 can be started.

[0063] Example 2

[0064] Example 2 ( Figure 6 ) and Example 1 ( Figure 4 Compared to Embodiment 1, the positional relationship of the inner edge 30w of the frame is different. Specifically, the inner edge 30w of the frame is located on the side (+x direction side) further away from the boundary line BL from the first manifold hole M1o (refer to arrow Y31). In addition, the other structures of Embodiment 2 are the same as those of Embodiment 1. The common parts of Embodiments 1 and 2 are omitted.

[0065] The inner edge 20w of the second partition is located on the side (+x direction side) further away from the boundary line BL from the first manifold orifice M1o (refer to arrow Y32). That is, in the fuel cell cell 1 of Embodiment 2, the inner edge 30w of the frame and the inner edge 20w of the second partition are configured to extend inward (+x direction side) from the flat portion 10f of the first partition 10. Therefore, the surface opposite to the flat portion 10f is the first partition 10 of the adjacent fuel cell cell 1. As a result, the height Dm of the tank region CR is equal to the spacing between the cells of the fuel cell cells 1. That is, the height Dm of the tank region can be maximized.

[0066] (Effect)

[0067] In the technique of Embodiment 2, by maximizing the height Dm of the groove region, the capillary pressure generated in the groove region CR can be minimized. This is because capillary pressure generally exhibits the property that the larger the width of the groove (i.e., the height Dm of the groove region) that forms the flow path, the smaller the capillary pressure. Therefore, compared to the groove region CR, the first gas passage 15g allows for easier wetting and spreading of water droplets. Since water droplets can preferentially move towards the first gas passage 15g, the wetting and spreading of water droplets along the groove region CR can be suppressed.

[0068] Example 3

[0069] Example 3 Fuel Cell Unit 301 ( Figure 7 ) and Example 1 ( Figure 4Compared to fuel cell unit 1, the cell division method is different. Specifically, a second separator 20 is exposed on the upper surface of fuel cell unit 301 in the +z direction, and a membrane electrode assembly 40 is exposed on the lower surface in the -z direction. Furthermore, regarding Example 1 (… Figure 4 ) and Example 3 ( Figure 7 The common parts are marked with the same symbol and the explanation is omitted.

[0070] A first gas passage 15g is formed between opposing first and second partitions 10 and 20 in fuel cell cell 301. The first gas passage 15g has a gas passage height Dc in the z-direction. The first gas passage 15g is connected to the membrane electrode assembly 40 via a connecting hole 10h. Gas discharged from oxygen electrode 41 is discharged into the first gas passage 15g through the connecting hole 10h (refer to the dashed arrow YG).

[0071] The inner edge 30w of the frame is located on the side (+x direction side) further away from the boundary line BL from the first manifold orifice M1o (refer to arrow Y41). Similarly, the inner edge 20w of the second partition is located on the side (+x direction side) further away from the boundary line BL from the first manifold orifice M1o (refer to arrow Y42). Therefore, the surface opposite the flat portion 10f is the first partition 10 of the adjacent fuel cell cell 301. Consequently, the height Dm of the tank region CR is equal to the spacing between the individual cells of the fuel cell cells 301. By maximizing the height Dm of the tank region, the capillary pressure generated in the tank region CR can be minimized. This suppresses the wetting and spreading of water droplets along the tank region CR.

[0072] The embodiments have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes technologies obtained by various modifications and alterations to the specific examples described above. The technical elements illustrated in this specification or drawings exert their technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of application. Furthermore, the technology illustrated in this specification or drawings achieves multiple objectives simultaneously, and achieving one of these objectives is itself technically useful.

[0073] (Modified Example)

[0074] The technology described in this specification can be applied to either air-cooled or water-cooled fuel cells.

[0075] In this embodiment, the shapes of the first manifold holes M1i and M1o, the second manifold holes M2i and M2o, and the cooling water manifold hole Mw are set to rectangular shapes in the accompanying drawings. However, they can also be set to triangular, polygonal, or irregularly shaped manifold holes.

Claims

1. A fuel cell stack comprising multiple fuel cell cells, wherein, Each of the plurality of fuel cell cells has: The frame is made of resin and has an opening. A membrane electrode assembly disposed at the opening; and The first and second partitions are positioned opposite each other, separated by the frame and the membrane electrode assembly. The fuel cell stack has a first manifold orifice extending along the stacking direction. The frame has an inner edge that defines the first manifold opening. The first partition has: The inner edge of the first partition plate defines the first manifold hole; A flat portion is disposed along the inner edge of the first partition and on the opposing surface opposite to the second partition; The uneven portion forms a plurality of gas passages extending from the flat portion toward the membrane electrode assembly; as well as A boundary line, which serves as the boundary line between the flat portion and the uneven portion, is disposed along the inner edge of the first partition plate on the outer side of the inner edge of the first partition plate. When defining the determining line by measuring the height of the boundary line away from the plurality of gas passages towards the inner edge of the first partition, the inner edge of the frame is located on the side further away from the first manifold orifice than the determining line in a direction parallel to the surface of the frame.

2. The fuel cell stack according to claim 1, wherein, In a direction parallel to the surface of the frame, the inner edge of the frame is located on a side further away from the first manifold hole than the boundary line.

3. The fuel cell stack according to claim 1, wherein, The second partition has an inner edge that defines the first manifold orifice. In a direction parallel to the surface of the second partition, the inner edge of the second partition is located on the side further away from the first manifold orifice than the boundary line.

4. The fuel cell stack according to claim 1, wherein, The first manifold orifice is an outlet orifice for discharging reactive gases introduced into the membrane electrode assembly.

5. The fuel cell stack according to any one of claims 1 to 4, wherein, The water contact angles of the first and second partitions are smaller than the water contact angle of the frame.

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