Fuel cell stack

Abstract

Fuel cells each comprise: a resin or plastic frame body having an opening section; a membrane electrode assembly arranged on the opening section; and a first and a second separator facing each other through the frame body and the membrane electrode assembly. A first distributor opening is provided in a fuel cell stack. The frame body includes an inner frame edge that delimits the first distributor opening. The first separator comprises a first separator inner edge that delimits the first distributor opening, a flat section arranged along the first separator inner edge, a concave-convex section forming gas passages, and a boundary line between the flat section and the concave-convex section.If a specified line is defined as a line extending from the boundary line towards the first separator inner edge, the frame body inner edge is positioned on a side that is farther from the first distributor opening than the specified line.

Description

BACKGROUND OF THE INVENTION 1. Field of the invention

[0001] The technology disclosed in the present description relates to a fuel cell stack. 2. Description of the state of the art

[0002] Japanese patent application JP 2010-27381A discloses a fuel cell stack. The fuel cell stack has a structure in which a membrane electrode assembly is surrounded by a frame made of resin or plastic. Furthermore, the fuel cell stack has a structure in which the membrane electrode assembly, together with the frame, is arranged between a cathode separator and an anode separator. A distribution opening of the frame and distribution openings of both separators are layered or laminated, forming a distribution opening that extends in a lamination direction. Several gas passages are arranged on an inner circumferential surface of the distribution opening, extending in the direction of the membrane electrode assembly. SUMMARY OF THE INVENTION

[0003] In some cases, a water droplet remaining on the inner circumferential surface of the distributor opening spreads out in such a way that it covers all gas passages. If the wet, spread water droplet freezes and blocks all gas passages, the supply and removal of a reactant gas to the membrane electrode assembly cannot occur at the time of start-up, so that in some cases no power generation can take place.

[0004] A fuel cell stack disclosed in the present description is a fuel cell stack in which a plurality of fuel cells are layered or laminated. Each of the fuel cells comprises: a frame body made of resin or plastic and including an opening section; a membrane electrode assembly arranged on the opening section; and a first separator and a second separator, which are opposite each other through the frame body and the membrane electrode assembly. A first distributor opening is provided in the fuel cell stack, extending along a lamination direction. The frame body includes an inner frame edge that delimits the first distributor opening.The first separator comprises a first separator inner edge that delimits the first distributor opening, a flat section arranged along the first separator inner edge and on a surface facing the second separator, a concave-convex section provided with multiple gas passages, each extending from the flat section to the membrane electrode assembly, and a boundary line between the flat section and the concave-convex section, the boundary line being arranged along the first separator inner edge on the outside of the first separator inner edge.If a specified line is defined as a line that is a distance from the boundary line towards the inner edge of the first separator by the height of the gas passages, then the inner edge of the frame body is positioned on a side that is further away from the first distributor opening in a direction parallel to a surface of the frame body than the specified line.

[0005] In the event that the inner edge of the frame body projects beyond the boundary line between the flat section and the concave-convex section of the first separator in the direction of the first distributor opening, the flat section and the frame body face each other in the lamination direction. A groove is formed between the frame body and the flat section, extending along the inner edge of the frame body. The inventors have found that a water droplet easily spreads along the groove if the projection of the frame body's inner edge from the boundary line is equal to or greater than the height of the gas passage in the lamination direction. This is because the water droplet moves primarily by capillary pressure.If the projection of the inner edge of the frame body from the boundary line is equal to or greater than the height of the gas passage, the height of one side wall of the groove formed by the frame body reaches a sufficient height to exert capillary pressure. When capillary pressure is exerted in the groove, the wettability of the water droplets in the groove and in the gas passage becomes the same. Consequently, there is a risk that the spread of water droplets along the groove will cause all gas passages to be blocked by water droplets.

[0006] Therefore, in the structure described above, the inner edge of the frame body is positioned on the side furthest from the first distributor opening than the defined line. Consequently, the projection of the inner edge of the frame body from the boundary line is less than the height of the gas passage. This prevents sufficient capillary pressure from being exerted in the groove, even if a groove is formed between the frame body and the flat section. As a result, water droplets are more easily distributed in the gas passage than in the groove. This allows the water droplets to preferentially move into the gas passage, thus preventing them from spreading along the groove. It also prevents all gas passages from being blocked by water droplets. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The features and advantages as well as the technical and economic significance of exemplary embodiments of the invention are described below with reference to the accompanying drawings, in which the same reference numerals denote the same elements, showing: Fig. 1 an exploded view of a fuel cell 1; Fig. 2 an enlarged top view of a first distributor opening M1o; Fig. 3 a partial side view of an inner circumferential surface of the first distributor opening M10; Fig. 4 a partial sectional view along line IV-IV in Fig. 2; Fig. 5 a partial sectional view of a fuel cell 101 in a comparative example; Fig. 6 is a partial sectional view of the area around the first distributor opening M1o in embodiment 2; and Fig. Figure 7 is a partial sectional view of the area around the first distributor opening M1o in embodiment 3. DETAILED DESCRIPTION OF EXECUTION FORMS

[0008] An inner edge of the frame body can be positioned on a side that is further away from a first distributor opening in a direction parallel to a surface of a frame body than a boundary line.

[0009] In the configuration above, the inner edge of the frame body does not extend beyond the boundary line, and therefore no groove is formed between the frame body and a flat section. This prevents water droplets from spreading along the groove.

[0010] A second separator may have a second inner separator edge that delimits the first distributor opening. The second inner separator edge may be positioned on a side that is further away from the first distributor opening than the delimiting line, in a direction parallel to a surface of the second separator.

[0011] In the configuration above, the second separator is not facing a flat section of the first separator in the lamination direction. Consequently, no groove is formed between the second separator and the flat section. This prevents water droplets from spreading along the groove.

[0012] The first distributor opening can be an outlet opening through which a reactive gas introduced into a membrane electrode arrangement is expelled.

[0013] The number of water droplets is greater in the outlet port for the reactive gas than in an inlet port for the reactive gas. This is because the water droplets are contained within the gas after the reaction. In the configuration described above, it is possible to reduce the number of remaining water droplets in the outlet port, where a larger quantity of water droplets is generated. This would also more effectively prevent the gas passage from becoming blocked by the freezing of the water droplets.

[0014] The contact angle of water on the first separator and the second separator can be smaller than the contact angle of water on the frame body.

[0015] In the configuration above, the inner wall surfaces of the first and second separators can exhibit higher hydrophilicity than an inner wall surface of the frame body. Design 1 Schematic configuration of the fuel cell 1

[0016] Fig. Figure 1 is an illustrative diagram showing an exploded state of a fuel cell 1 in an embodiment of the present invention. The fuel cell 1 is a polymer electrolyte fuel cell that generates electricity by supplying hydrogen and oxygen. The fuel cell 1 mainly comprises a first separator 10, a second separator 20, a frame 30, and a membrane electrode assembly 40.

[0017] The frame body 30 is a frame-shaped resin or plastic element that encloses the entire circumference of the membrane electrode assembly 40. In this embodiment, polyethylene naphthalate (PEN) is used as the plastic element. However, various other plastic elements such as polypropylene, polyethylene, polyethylene terephthalate, and polyphenylene sulfide, as well as rubber materials, can also be used.

[0018] The frame body 30 includes in a central section an opening section 35 which encloses and contains the membrane electrode assembly 40. The membrane electrode assembly 40 is arranged in the opening section 35. Fig. Figure 1 shows the membrane electrode assembly 40 as a gray solid section. The structure of the membrane electrode assembly 40 will be described later. Furthermore, the frame body 30 includes distributor openings 61i, 610, 62i, 62o, 63 on the right and left sides (sides in the ±x direction) of the opening section 35.

[0019] The first separator 10 and the second separator 20 are oriented towards each other by the frame body 30 and the membrane electrode assembly 40. The first separator 10 and the second separator 20 are electrically conductive. For example, the first separator 10 and the second separator 20 can be formed by pressing a metal plate made of stainless steel, titanium, or an alloy thereof, or from a carbon-resin composite material or the like. In this embodiment, the first separator 10 and the second separator 20 are formed from the carbon-resin composite material.

[0020] In this embodiment, the first separator 10 is a separator on the cathode side and the second separator 20 is a separator on the anode side. The first separator 10 comprises distributor openings 11i, 11o, 12i, 12o, 13 at its outer edge. The second separator 20 comprises distributor openings 21i, 21o, 22i, 22o, 23 at its outer edge.

[0021] Distributor openings 11i, 61i, and 21i are stacked or laminated on top of each other, forming a first distributor opening M1i, which serves to supply a reaction gas (air). Distributor openings 11o, 61o, and 21o are stacked or laminated on top of each other, forming a first distributor opening M1o, which serves to discharge the reaction gas (air). Distributor openings 12i, 62i, and 22i are stacked or laminated on top of each other, forming a second distributor opening M2i, which serves to supply a reaction gas (hydrogen). Distributor openings 12o, 62o, and 22o are stacked or laminated on top of each other, forming a second distributor opening M2o, which serves to discharge the reaction gas (hydrogen). The distributor openings 13, 63, 23 are stacked or laminated on top of each other, forming a coolant distributor opening Mw which forms a coolant channel.The specific configuration of the coolant channel is not directly related to the idea of ​​the present invention, therefore a detailed description is omitted. The first distributor openings M1i, M1o, the second distributor openings M2i, M2o and the coolant distributor opening Mw extend along a lamination direction (z-direction).

[0022] The first separator 10 comprises a flow channel 15 extending from the first distributor opening M1i to the first distributor opening M1o. The flow channel 15 is formed by concave-convex sections 10p on a bottom surface (i.e., a surface facing the frame body 30) of the first separator 10. The contents of the concave-convex section 10p are described later. The reaction gas (air) flowing into the first distributor opening M1i passes through the flow channel 15, through the membrane electrode assembly 40, and is discharged from the first distributor opening M1o (see arrow Y1 in Figure 1). Fig. 1).

[0023] Similarly, the second separator 20 includes a flow channel 25 extending from the second distributor opening M2i to the second distributor opening M2o. The flow channel 25 is formed by concave-convex sections 20p on a top surface (i.e., a surface facing the frame body 30) of the second separator 20. The reaction gas (hydrogen) flowing into the second distributor opening M2i passes through the flow channel 25, through the membrane electrode assembly 40, and is discharged from the second distributor opening M2o (see arrow Y2 in Figure 1). Fig. 1).

[0024] Furthermore, seals 51, 52, 53 are arranged on the upper surface of the first separator 10. Seals 51, 52, 53 are made of, for example, silicone rubber. The seals 51 are arranged to enclose the distributor openings 11i, 11o. When several fuel cells 1 are laminated or stacked, the seals 51 ensure the tightness of the first distributor openings M1i, M1o. Similarly, the seals 52 are arranged to enclose the distributor openings 12i, 12o. When several fuel cells 1 are laminated or stacked, the seals 52 ensure the tightness of the second distributor openings M2i, M2o. Additionally, seal 53 is arranged to enclose the outer circumference of the first separator 10. Construction of the first distributor opening M1o

[0025] Fig. Figure 2 shows an enlarged top view of the first distribution opening M1o in the fuel cell 1. The first distribution opening M1o is a distribution opening for air extraction, which is located in Fig. 1 is located on a lower left section in fuel cell 1. It further shows Fig. 3 a partial side view of an inner circumferential surface of the first distributor opening M1o, seen from the direction of an arrow Y11 in Fig. 2. Although Fig. 3 where a side view is shown, hatching is used to clearly show opening sections 15a.

[0026] The flow channel 15 comprises several initial gas passes of 15g. As in Fig. As shown in Figure 3, the first gas passages 15g are formed between the frame body 30 and the first separator 10. That is, the concave-convex sections 10p are arranged on a bottom surface 10b of the first separator 10 such that they are oriented in the y-direction. The bottom surfaces of the concave-convex sections 10p touch a top surface of the frame body 30, thus forming a first gas passage 15g between adjacent concave-convex sections 10p. Accordingly, in the first gas passage 15g, side walls are formed by the concave-convex sections 10p, an inner wall at the top is formed by the bottom surface 10b of the first separator 10, and an inner wall at the bottom is formed by a top surface 30u of the frame body 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 bottom 10b of the first separator 10 and the top 30u of the frame body 30.

[0027] As in Fig. As shown in Figure 2, the first gas passages 15g extend from the first distributor opening M1o to the membrane-electrode assembly 40. Furthermore, end opening sections of the first gas passages 15g are arranged in a first region R1 on the inner circumferential surface of the first distributor opening M1o. Accordingly, as shown in Fig. 3 shown, in the first area R1 opening sections 15a of the first gas passages 15g on the inner circumferential surface of the first distributor opening M1o.

[0028] Fig. Figure 4 shows a partial sectional view along line IV-IV in Fig. 2. Fig. Figure 4 is a sectional view passing through a central axis C1 of the first distributor opening M10 and through first gas passages 15g. Fig. Figure 4 shows a fuel cell stack in which two fuel cells 1 are laminated or stacked. In an actual fuel cell stack, three or more fuel cells 1 are stacked. The membrane electrode assembly 40 comprises an oxygen electrode 41, a hydrogen electrode 42, and an electrolyte membrane 43. The electrolyte membrane 43 is an ion exchange membrane made of a solid polymer material and exhibiting proton conductivity. The oxygen electrode 41 comprises a first catalyst layer 44 and a first gas diffusion layer 45. The hydrogen electrode 42 comprises a second catalyst layer 46 and a second gas diffusion layer 47. The first catalyst layer 44 and the second catalyst layer 46 are each porous layers in which carbon particles or metal oxides carrying a catalyst are bound by resin.The first gas diffusion layer 45 and the second gas diffusion layer 47 are each electrically conductive elements that are permeable to water and gas, respectively. A known structure can be used for the membrane-electrode arrangement 40, therefore a detailed description is omitted.

[0029] The oxygen electrode 41 forms an outer circumferential region PA with a flange shape on the outer circumference of the membrane electrode assembly 40. An adhesive layer 49 is arranged on a lower surface 41b of the oxygen electrode 41 within this outer circumferential region PA. The adhesive layer 49 is a layer formed by an adhesive agent. Examples of adhesive agents include a UV-curable adhesive agent and a hot-melt adhesive agent. The adhesive layer 49 secures the lower surface 41b of the oxygen electrode 41 to the upper surface 30u of the frame body 30.

[0030] The frame body 30 has a three-layer structure in which a first resin layer 31, a core layer 33, and a second resin layer 32 are laminated in the thickness direction. The core layer 33 is a gas-tight and insulating component. The first resin layer 31 is a layer that adheres to the first separator 10. The second resin layer 32 is a layer that adheres to the second separator 20.

[0031] The first resin layer 31 and the second resin layer 32 can each have a lower melting point than the core layer 33. In particular, the first resin layer 31 and the second resin layer 32 can each consist of a thermoplastic resin such as an acid-modified olefin resin and a polyester resin, respectively. The multilayer frame body 30 can be manufactured by various processes. For example, the frame body 30 can be manufactured by co-extrusion.

[0032] The frame body 30 includes an inner frame body edge 30w. The inner frame body edge 30w is a location that forms part of the inner wall of the first distribution opening M1o and limits the first distribution opening M1o.

[0033] The first separator 10 comprises a first separator inner edge 10w, the concave-convex sections 10p, a flat section 10f, and a boundary line BL. The first separator inner edge 10w is a location that forms part of the inner wall of the first distributor opening M1o and delimits the first distributor opening M1o. The concave-convex section 10p is a location that projects downwards from the bottom surface 10b of the first separator 10. In the sectional view in Fig. Figure 4 illustrates a concave-convex section 10p, present in the depth direction with respect to the plane of the sheet, shown as a gray solid section. As in Fig. As shown in Figure 2, the first gas passages 15g, extending from the flat section 10f towards the membrane electrode arrangement 40, are formed by the concave-convex sections 10p.

[0034] The flat section 10f is a region near the first separator inner edge 10w and is a region where the concave-convex section 10p is not located. Furthermore, the flat section 10f is located on a surface facing the second separator 20 (i.e., the bottom 10b). As shown in Fig. As shown in Figure 2, the flat section 10f is arranged along the first inner edge 10w of the separator. The flat section 10f also serves as the location required for the punching operation of the distributor opening 11o. The flat section 10f forms a cutting surface, which improves the precision and machinability of the cut surface.

[0035] The boundary line BL is formed between the flat section 10f and the concave-convex section 10p. As shown in Fig. As shown in Figure 2, the boundary line BL is located along the outside of the first separator inner edge 10w. The first gas passage 15g is formed on a side (side in the +x direction) that is further away from the first distributor opening M1o than the boundary line BL. Conversely, a groove area CR is formed on a side (side in the -x direction) that is closer to the first distributor opening M1o than the boundary line BL.

[0036] As in Fig. As shown in Figure 4, the groove area CR is a region formed between the flat section 10f and a surface (i.e., the top surface 30u of the frame body 30) facing the flat section 10f. The groove area CR has a groove height Dm in the z-direction. The groove height Dm is equal to the gas passage height Dc.

[0037] Furthermore, as in Fig. Figure 2 shows the groove area CR arranged along the first separator inner edge 10w. That is, the groove area CR functions as an area that connects the first gas passages 15g along the first separator inner edge 10w.

[0038] As in Fig. As shown in Figure 4, a specific line SL is defined. This specific line SL is a line that is parallel to the boundary line BL and extends along the gas passage height Dc to the side of the first separator inner edge 10w (side in the -x direction). Furthermore, the frame body inner edge 30w is positioned on a side (side in the +x direction) that is farther from the first distributor opening M1o than the specific line SL (see arrow Y21).

[0039] The second separator 20 includes a second separator inner edge 20w. The second separator inner edge 20w is a location that forms part of the inner wall of the first distributor opening M1o and delimits the first distributor opening M1o. The second separator inner edge 20w is positioned on a side (side in the +x direction) that is further away from the first distributor opening M1o than the boundary line BL.

[0040] The contact angle of water on the first separator 10 and the second separator 20 is smaller than the contact angle of water on the frame body 30. For example, the contact angle of water on the first separator 10 and the second separator 20 can be less than 90°, and the contact angle of water on the frame body 30 can be greater than 90°. This means that the inner edge of the first separator 10w and the inner edge of the second separator 20w exhibit higher hydrophilicity than the inner edge of the frame body 30w. This is because the frame body 30 is water-repellent due to a property of the resin element described above. Furthermore, the first separator 10 and the second separator 20 are hydrophilic due to a property of the electrically conductive material described above.Hydrophilicity refers to the hydrophilicity under the conditions of power generation by the fuel cell (under conditions where water droplets are present at high temperatures and high humidity). problem

[0041] A problem is illustrated using a fuel cell 101 in a comparative example in Fig. 5 described. The fuel cell 101 ( Fig. 5) in the comparative example differs from fuel cell 1 ( Fig. 4) In the embodiment, the positional relationship of the inner frame body edge 30w is described. In particular, the inner frame body edge 30w is positioned on a side (side in the -x direction) that is closer to the first distributor opening M10 than the defined line SL (see arrow Y20). That is, the projection PR0 of the inner frame body edge 30w from the boundary line BL is equal to or greater than the gas passage height Dc. The other structures of the fuel cell 101 in the comparative example are the same as those of the fuel cell 1 in the embodiment and are therefore not described.

[0042] In the fuel cell 101 in the comparative example, the slot area CR is formed between the top surface 30u of the frame body 30 and the flat section 10f of the first separator 10. As in Fig. As shown in Figure 2, the groove area CR connects the first gas passages 15g along the first separator inner edge 10w. Thus, the water droplets remaining on the inner circumferential surface of the first distributor opening M1o spread, in some cases, along the groove area CR. If the water droplets spread over the entire area of ​​the first region R1, all first gas passages 15g become covered with water droplets. In this state, all first gas passages 15g are blocked when the water droplets freeze. Consequently, in some cases, the supply and removal of reaction gases to the membrane electrode assembly cannot be carried out at startup, and no power generation can occur. Solution and effect

[0043] The inventors have found that the water droplet spreads easily along the groove area CR when the projection of the frame body's 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. This is because the water droplet moves primarily by capillary pressure. When the projection of the frame body's inner edge 30w from the boundary line BL is equal to or greater than the gas passage height Dc, the height of the side wall in the x-direction of the groove area CR formed by the top 30u of the frame body's inner edge 30w reaches a sufficient height to exert capillary pressure. When the capillary pressure in the groove area CR is sufficiently exerted, the ease of wet propagation of the water droplet between the groove area CR and the first gas passage 15g is equal to the pressure exerted by capillary pressure.As a result, there is a risk that the wet spread of the water droplet along the groove area CR will cause all first gas passes of 15g to be blocked by the water droplet.

[0044] Therefore, in the technology of the embodiment, the inner edge of the frame body 30w is positioned on the side in the +x direction of the specified line SL (see Fig. 4) That is, in this embodiment, the projection PR1 of the inner edge of the frame body 30w from the boundary line BL is smaller than the gas passage height Dc. Accordingly, the height of the side wall in the x-direction of the groove area CR does not reach a sufficient height to exert capillary pressure. As a result, the water droplets may spread more easily in the first gas passage 15g than in the groove area CR. It is possible to preferentially move the water droplets into the first gas passage 15g, thus preventing them from spreading along the groove area CR. It is possible to prevent all first gas passages 15g from being blocked by the water droplets.

[0045] Fuel cell 1 ( Fig. 4) In this embodiment, the first separator inner edge 10w projects towards the central axis C1 relative to the frame body inner edge 30w. This allows a relatively hydrophilic element to be exposed on the inner circumferential surface of the first distributor opening M1o in the first region R1 (the region where the opening section 15a of the first gas passage 15g is located). The hydrophilicity facilitates the aggregation of water droplets on the inner circumferential surface of the first distributor opening M1o in the first region R1. The volume of the water droplets increases, allowing them to be easily carried away by gravity and the gas flow. It is possible to reduce the number of water droplets remaining on the inner circumferential surface of the first distributor opening M1o, thus preventing the first gas passages 15g from being blocked by the freezing of the water droplets.The starting capability of fuel cell 1 below freezing can be improved.

[0046] The quantity of water droplets is greater in the first distributor opening M1o, which is the outlet opening for the reactive gas, than in the first distributor opening M1i, which is the inlet opening for the reactive gas. This is because the water droplets are contained therein after the reaction. In the fuel cell 1 of the embodiment, the hydrophilic element (first separator inner edge 10w) protrudes from the inner circumferential surface of the first distributor opening M1o on the outlet side. This reduces the quantity of remaining water droplets on the inner circumferential surface of the first distributor opening M1o on the outlet side, where a larger quantity of water droplets is formed. Therefore, it is possible to prevent clogging of the first gas passages 15g. Modification of embodiment 1

[0047] The structure of the first distributor opening M1o on the outlet side, as described above, can also be applied to the first distributor opening M1i on the inlet side. That is, a structure is permissible in which the inner edge of the frame body 30w is positioned on a side that is further away from the first distributor opening M1i than the specified line SL. Likewise, the structures of the first distributor openings M1o and M1i for air can also be applied to the second distributor openings M2o and M2i for hydrogen.

[0048] The structure in which the inner edge of the frame body 30w is positioned on the side that is further away from the first distributor opening M1o than the specified line SL does not have to be formed over the entire inner circumferential surface of the first distributor opening M1o, but only at least in the first area R1 ( Fig. 2) Areas other than the first area R1 are areas located 15g away from the first gas passages. Even if the water droplets spread wet to these distant areas, there is little risk of them blocking the first gas passages 15g.

[0049] The structure in which the inner edge of the frame body 30w is positioned on the side that is further away from the first distributor opening M1o than the specified line SL, does not have to cover the entire area of ​​the first area R1 ( Fig. 2) must be fully formed, but only in at least a partial area. This prevents all initial gas passages of 15g from being blocked by the freezing of the water droplets. Since at least some of the initial gas passages of 15g are open, fuel cell 1 can be started. Design 2

[0050] One embodiment 2 ( Fig. 6) differs from embodiment 1 ( Fig. 4) in the positional relationship of the inner edge 30w of the frame body. In particular, the inner edge 30w of the frame body is positioned on a side (side in the +x direction) that is further away from the first distributor opening M1o than the boundary line BL (see arrow Y31). The other structures in embodiment 2 are the same as in embodiment 1. Descriptions of common parts between embodiment 1 and embodiment 2 are omitted.

[0051] The second separator inner edge 20w is positioned on a side (side in the +x direction) that is further away from the first distributor opening M1o than the boundary line BL (see arrow Y32). That is, in fuel cell 1 in embodiment 2, the frame body inner edge 30w and the second separator inner edge 20w are located on the rear side (side in the +x direction) of the flat section 10f of the first separator 10. Accordingly, the surface facing the flat section 10f is the first separator 10 of the adjacent fuel cell 1. Therefore, the slot area height Dm of the slot area CR is equal to the cell spacing between the fuel cells 1. That is, it is possible to maximize the slot area height Dm. Effect

[0052] In the technology of embodiment 2, maximizing the groove area height Dm makes it possible to minimize the capillary pressure generated in the groove area CR. This is because, in general, the capillary pressure is lower the greater the width (i.e., the groove area height Dm) of the groove serving as the flow passage.

[0053] This allows the water droplets to spread more easily in the first gas pass (15g) than in the groove area CR. The water droplets are preferentially drawn towards the first gas pass (15g), thus preventing them from spreading moistly along the groove area CR. embodiment 3

[0054] A fuel cell 301 ( Fig. 7) of embodiment 3 differs from the fuel cell 1 of embodiment 1 ( Fig. 4) in the arrangement in the individual cell. In particular, the second separator 20 is exposed on a top side on the +z-side of the fuel cell 301, and the membrane electrode arrangement 40 is exposed on a bottom side on the -z-side. Common points between embodiment 1 ( Fig. 4) and embodiment 3 ( Fig. 7) are marked with identical reference symbols, and their descriptions are omitted.

[0055] The first gas passage 15g of the fuel cell 301 is located between the first separator 10 and the second separator 20, which face each other. 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. The gas expelled from the oxygen electrode 41 flows through the connecting hole 10h and is expelled into the first gas passage 15g (see dashed arrow YG).

[0056] The inner edge of the frame body 30w is positioned on a side (side in the +x direction) that is further away from the first distributor opening M1o than the boundary line BL (see arrow Y41). Furthermore, the inner edge of the second separator 20w is positioned on a side (side in the +x direction) that is further away from the first distributor opening M1o than the boundary line BL (see arrow Y42). Accordingly, the surface facing the flat section 10f is the first separator 10 of the adjacent fuel cell 301. Therefore, the groove height Dm of the groove area CR is equal to the cell spacing between the fuel cells 301. By maximizing the groove height Dm, it is possible to minimize the capillary pressure generated in the groove area CR. This prevents water droplets from spreading along the groove area CR.

[0057] The embodiments have been described above. These embodiments are merely examples and do not limit the scope of the claims. The technology described in the claims comprises various modifications and alterations of the specific examples described above. The technical elements described in this description or the drawings exert technical utility independently of one another or through various combinations and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies exemplified in this description or the drawings simultaneously achieve several purposes and already have technical utility by achieving just one of them. modification

[0058] The technology described here can be applied to both air-cooled and water-cooled fuel cells.

[0059] In the embodiments shown in the figures, each of the first distributor openings M1i, M1o, the second distributor openings M2i, M2o, and the coolant distributor opening Mw is rectangular. However, distributor openings with a triangular shape, a polygonal shape, or different opening shapes can also be used. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2010 - 27 381 A

[0002]

Claims

[1] Fuel cell stack in which a large number of fuel cells are layered, wherein: Each of the fuel cells includes: a frame body made of resin and including an opening section, a membrane electrode arrangement located at the opening section, and a first separator and a second separator, which are opposite each other through the frame body and the membrane electrode arrangement; wherein The fuel cell stack has a first distribution opening that extends along a lamination direction; the frame body has an inner frame body edge that limits the first distributor opening; the first separator includes a first separator inner edge that limits the first distributor opening, a flat section arranged along the first inner edge of the separator and on a surface facing the second separator, a concave-convex section provided with a plurality of gas passages, each extending from the flat section to the membrane electrode arrangement, and a boundary line between the flat section and the concave-convex section, wherein the boundary line is arranged along the first inner separator edge on an outside of the first inner separator edge; and If a specified line is defined as a line that is a distance from the boundary line towards the inner edge of the first separator by a height of the gas passages, the inner edge of the frame body is positioned on a side that is further away from the first distributor opening in a direction parallel to a surface of the frame body than the specified line. [2] Fuel cell stack according to claim 1, wherein the inner edge of the frame body is positioned on a side which is further away from the first distributor opening in a direction parallel to the surface of the frame body than the boundary line. [3] Fuel cell stack according to claim 1, wherein: the second separator has a second separator inner edge that limits the first distributor opening; and the second separator inner edge is positioned on a side that is further away from the first distributor opening than the boundary line in a direction parallel to a surface of the second separator. [4] Fuel cell stack according to claim 1, wherein the first distributor opening is an outlet opening through which a reactive gas introduced into the membrane electrode arrangement is expelled. [5] Fuel cell stack according to any one of claims 1 to 4, wherein a contact angle of water on the first separator and the second separator is smaller than a contact angle of water on the frame body.

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