Fuel cell having a metal separator with a flat portion

A fuel cell includes a membrane electrode assembly and a metal separator. The membrane electrode assembly includes an electrolyte membrane, first and second electrodes, and a resin frame member. The resin frame member is provided on an outer peripheral portion of the membrane electrode assembly. The metal separator is stacked on the membrane electrode assembly in a stacking direction and includes a reactant gas channel, a reactant gas manifold, and a flat portion. The resin frame member of the membrane electrode assembly has an outer shape to be disposed further inward than the reactant gas manifold and includes a connection channel portion that is disposed outward from an electrode surface and that connects the reactant gas manifold and the reactant gas channel to each other. The flat portion is provided in contact with the connection channel portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2014-206045, filed Oct. 7, 2014, entitled “Fuel Cell.” The contents of this application are incorporated herein by reference in their entirety.

BACKGROUND

The present disclosure relates to a fuel cell.

2. Description of the Related Art

For example, a solid polymer electrolyte fuel cell includes a membrane electrode assembly (MEA), in which an anode electrode is disposed on one side of a solid-polymer electrolyte membrane and a cathode electrode is disposed on the other side of the solid-polymer electrolyte membrane. The solid-polymer electrolyte membrane is made from a polymer ion-exchange membrane. The MEA and a pair of separators, sandwiching the MEA therebetween, constitute a power generation cell (unit cell). Several tens to several hundreds of such power generation cells are stacked and used, for example, as a vehicle fuel cell stack.

Typically, a fuel cell has a so-called internal manifold structure for supplying a fuel gas and an oxidant gas, each of which is a reactant gas, respectively to anode electrodes and cathode electrodes of power generation cells that are stacked.

The internal manifold structure includes a reactant gas inlet manifold (fuel gas inlet manifold, oxidant gas inlet manifold) and a reactant gas outlet manifold (fuel gas outlet manifold, oxidant gas outlet manifold), each extending through the power generation cells in a stacking direction in which the power generation cells are stacked. The reactant gas inlet manifold is connected to an inlet of a reactant gas channel (fuel gas channel, oxidant gas channel), which supplies a reactant gas along an electrode surface; and the reactant gas outlet manifold is connected to an outlet of the reactant gas channel.

In this case, the reactant gas channel is connected to each of the reactant gas inlet manifold and reactant gas outlet manifold through a connection channel, which has parallel grooves or the like through which the reactant gas can flow smoothly and uniformly. Regarding such a structure, Japanese Patent No. 4634933, for example, describes a fuel cell that is devised to achieve a desirable sealing ability with an economical and simple structure.

In this fuel cell, a separator has a connection channel that connects a reactant gas manifold and a reactant gas channel to each other. At least one of gas diffusion layers of a membrane electrode assembly has a superposed portion that seals the connection channel by being superposed on the connection channel and pressed against the separator.

SUMMARY

According to one aspect of the present invention, a fuel cell includes a membrane electrode assembly and a metal separator. The membrane electrode assembly includes an electrolyte membrane and a pair of electrodes sandwiching the electrolyte membrane therebetween. The metal separator are stacked on the membrane electrode assembly. The metal separator includes a reactant gas channel through which a reactant gas is supplied along an electrode surface and a reactant gas manifold through which the reactant gas flows in a stacking direction in which the membrane electrode assembly and the metal separator are stacked. The membrane electrode assembly includes a resin frame member on an outer peripheral portion thereof. The resin frame member has an outer shape such that the resin frame member is disposed further inward than the reactant gas manifold. The resin frame member includes a connection channel portion that is disposed outward from the electrode surface and that connects the reactant gas manifold and the reactant gas channel to each other. The metal separator includes a flat portion that is in contact with the connection channel portion.

According to another aspect of the present invention, a fuel cell includes a membrane electrode assembly and a metal separator. The membrane electrode assembly includes an electrolyte membrane, first and second electrodes, and a resin frame member. The first and second electrodes sandwich the electrolyte membrane between the first and second electrodes. The resin frame member is provided on an outer peripheral portion of the membrane electrode assembly. The metal separator is stacked on the membrane electrode assembly in a stacking direction and includes a reactant gas channel, a reactant gas manifold, and a flat portion. A reactant gas is supplied through the reactant gas channel along an electrode surface of the membrane electrode assembly. The reactant gas flows through the reactant gas manifold in the stacking direction. The resin frame member of the membrane electrode assembly has an outer shape to be disposed further inward than the reactant gas manifold and includes a connection channel portion that is disposed outward from the electrode surface and that connects the reactant gas manifold and the reactant gas channel to each other. The flat portion is provided in contact with the connection channel portion.

DESCRIPTION OF THE EMBODIMENTS

Referring toFIGS. 1 to 5, a fuel cell10according to an embodiment of the present disclosure includes a plurality of power generation units12. The power generation units12are stacked on top of each other in a horizontal direction (direction of arrow A) or in a vertical direction (direction of arrow C). The fuel cell10is used, for example, as a fuel cell stack mounted in a fuel cell electric vehicle.

Each of the power generation units12includes a first metal separator14, a first membrane electrode assembly16a(MEA), a second metal separator18, a second membrane electrode assembly16b(MEA), and a third metal separator20. The outer size of the first membrane electrode assembly16ais larger than that of the second membrane electrode assembly16b(seeFIGS. 3 and 4).

Each of the first metal separator14, the second metal separator18, and the third metal separator20is a rectangular metal plate that is, for example, a steel plate, a stainless steel plate, an aluminum plate, a galvanized steel plate, or any of these metal plates having an anticorrosive coating on the surface thereof. Each of the first metal separator14, the second metal separator18, and the third metal separator20, which has a rectangular shape in plan view, is made by press-forming a thin metal plate so as to have a corrugated cross section (seeFIGS. 1 and 2).

Referring toFIG. 1, an oxidant gas inlet manifold22aand a fuel gas outlet manifold24bare formed in the power generation unit12so as to extend in the direction of arrow A through one end portion of the power generation unit12in the longitudinal direction (the direction of arrow B). To be specific, the oxidant gas inlet manifold22aand the fuel gas outlet manifold24bare formed in one end portion of each of the first metal separator14, the second metal separator18, and the third metal separator20in the longitudinal direction. An oxidant gas, such as an oxygen-containing gas, is supplied through the oxidant gas inlet manifold22a.A fuel gas, such as a hydrogen-containing gas, is discharged through the fuel gas outlet manifold24b.

A fuel gas inlet manifold24aand an oxidant gas outlet manifold22bare formed in the power generation unit12so as to extend in the direction of arrow A through the other end portion of the power generation unit12in the longitudinal direction (the direction of arrow B). The fuel gas is supplied through the fuel gas inlet manifold24a.The oxidant gas is discharged through the oxidant gas outlet manifold22b.To be specific, the fuel gas inlet manifold24aand the oxidant gas outlet manifold22bare formed in the other end portion of each of the first metal separator14, the second metal separator18, and the third metal separator20in the longitudinal direction.

A pair of upper and lower coolant inlet manifolds25aare formed in the power generation unit12so as to extend in the direction of arrow A respectively through upper and lower end portions, near the oxidant gas inlet manifold22a, of the power generation unit12in the transversal direction (direction of arrow C). A coolant is supplied through the pair of coolant inlet manifolds25a.A pair of upper and lower coolant outlet manifolds25bare formed in the power generation unit12so as to extend respectively through upper and lower end portions, near the fuel gas inlet manifold24a, of the power generation unit12in the transversal direction. The coolant is discharged through the pair of coolant outlet manifolds25b.

Referring toFIG. 6, a first oxidant gas channel26, through which the oxidant gas inlet manifold22ais connected to the oxidant gas outlet manifold22b,is formed on a surface14aof the first metal separator14facing the first membrane electrode assembly16a.

The first oxidant gas channel26includes a plurality of wave-shaped channel grooves26a(or linear channel grooves) that extend in the direction of arrow B. Linear channel grooves26asand linear channel grooves26bsare respectively formed at an inlet end and at an outlet end of the first oxidant gas channel26. A planar first buffer contact portion28a,which is in contact with an inlet buffer portion70adescribed below, is disposed outward from the linear channel groove26as. A planar second buffer contact portion28b,which is in contact with an outlet buffer portion70bdescribed below, is disposed outward from the linear channel groove26bs.

Referring toFIG. 1, a part of a coolant channel30, through which the pair of coolant inlet manifolds25aare connected to the pair of coolant outlet manifolds25b,is formed on a surface14bof the first metal separator14. The coolant channel30is formed between the back side of the first oxidant gas channel26formed on the first metal separator14and the back side of a second fuel gas channel42formed on the third metal separator20.

A first fuel gas channel32, through which the fuel gas inlet manifold24ais connected to the fuel gas outlet manifold24b,is formed on a surface18aof the second metal separator18facing the first membrane electrode assembly16a. The first fuel gas channel32includes a plurality of wave-shaped channel grooves32a(or linear channel grooves) that extend in the direction of arrow B.

A planar first buffer contact portion34a,which is in contact with an inlet buffer portion81adescribed below, is disposed at an inlet end of the first fuel gas channel32. A planar second buffer contact portion34b,which is in contact with an outlet buffer portion81bdescribed below, is disposed at an outlet end of the first fuel gas channel32. In the first buffer contact portion34a,a plurality of supply holes36aare formed in the vicinity of the fuel gas inlet manifold24a.In the second buffer contact portion34b,a plurality of discharge holes36bare formed in the vicinity of the fuel gas outlet manifold24b.

Referring toFIGS. 1 and 7, a second oxidant gas channel38, through which the oxidant gas inlet manifold22ais connected to the oxidant gas outlet manifold22b,is formed on a surface18bof the second metal separator18facing the second membrane electrode assembly16b.The second oxidant gas channel38includes a plurality of wave-shaped channel grooves38a(or linear channel grooves) that extend in the direction of arrow B.

A planar first buffer contact portion40a,which is in contact with an inlet buffer portion84adescribed below, is disposed at an inlet end of the second oxidant gas channel38. A planar first buffer contact portion40b,which is in contact with an outlet buffer portion84bdescribed below, is disposed at an outlet end of the second oxidant gas channel38.

Referring toFIG. 1, the second fuel gas channel42, through which the fuel gas inlet manifold24ais connected to the fuel gas outlet manifold24b,is formed on a surface20aof the third metal separator20facing the second membrane electrode assembly16b.The second fuel gas channel42includes a plurality of wave-shaped channel grooves42a(or linear channel grooves) that extend in the direction of arrow B.

A planar first buffer contact portion44a,which is in contact with an inlet buffer portion96adescribed below, is disposed at an inlet end of the second fuel gas channel42. A planar second buffer contact portion44b,which is in contact with an outlet buffer portion96bdescribed below, is disposed at an outlet end of the second fuel gas channel42. In the first buffer contact portion44a,a plurality of supply holes46aare formed in the vicinity of the fuel gas inlet manifold24a.In the second buffer contact portion44b,a plurality of discharge holes46bare formed in the vicinity of the fuel gas outlet manifold24b.

A first sealing member48is integrally formed on the surfaces14aand14bof the first metal separator14so as to surround the outer peripheral end portion of the first metal separator14. A second sealing member50is integrally formed on the surfaces18aand18bof the second metal separator18so as to surround the outer peripheral end portion of the second metal separator18. A third sealing member52is integrally formed on the surfaces20aand20bof the third metal separator20so as to surround the outer peripheral end portion of the third metal separator20.

The first, second, and third sealing members48,50, and52are each made of an elastic material, such as a sealing material, a cushioning material, or a packing material. Examples of such materials include EPDM, NBR, fluorocarbon rubber, silicone rubber, fluorosilicone rubber, butyl rubber, natural rubber, styrene rubber, chloroprene-rubber, and acrylic rubber.

Referring toFIG. 2, the first sealing member48includes a planar seal portion48a,which extends along a separator surface and has a uniform thickness, and a protruding seal portion48b,which prevents leakage of the oxidant gas, the fuel gas, and the coolant.

Referring toFIG. 6, the first sealing member48includes a plurality of protruding portions48pa, which are disposed near the oxidant gas inlet manifold22a.A plurality of inlet paths54aare formed between the protruding portions48pa. An inlet flat portion55a,which is in contact with an inlet connection channel portion68adescribed below, is formed near the plurality of protruding portions48pa. The first sealing member48includes a plurality of protruding portions48pb, which are disposed near the oxidant gas outlet manifold22b.A plurality of inlet paths54bare formed between the protruding portions48pb. An outlet flat portion55b,which is in contact with an outlet connection channel portion68bdescribed below, is formed near the plurality of protruding portions48pb.

Referring toFIG. 2, the second sealing member50includes a planar seal portion50a,which extends along a separator surface and has a uniform thickness, and a protruding seal portion50b,which prevents leakage of the oxidant gas, the fuel gas, and the coolant.

Referring toFIG. 7, the second sealing member50includes a plurality of protruding portions50pa, which are disposed near the oxidant gas inlet manifold22a.A plurality of inlet paths56aare formed between the protruding portions50pa. An inlet flat portion57a,which is in contact with an inlet connection channel portion82adescribed below, is formed near the plurality of protruding portions50pa. The second sealing member50includes a plurality of protruding portions50pb, which are disposed near the oxidant gas outlet manifold22b.A plurality of outlet paths56bare formed between the protruding portions50pb. An outlet flat portion57b,which is in contact with an outlet connection channel portion82bdescribed below, is formed near the plurality of protruding portions50pb. Referring toFIGS. 6 and 7, the protruding portions50paand50pbare longer than the protruding portions48paand48pb.

Referring toFIG. 2, each of the first membrane electrode assembly16aand the second membrane electrode assembly16bincludes a solid polymer electrolyte membrane58(cation-exchange membrane). The solid polymer electrolyte membrane58is, for example, a thin film that is made of perfluorosulfonic acid copolymers and soaked with water. The solid polymer electrolyte membrane58is sandwiched between a cathode electrode60and an anode electrode62. Each of the first and second membrane electrode assemblies16aand16bis a so-called stepped MEA, in which the cathode electrode60has a size in plan view smaller than that of each of the anode electrode62and the solid polymer electrolyte membrane58.

Alternatively, the cathode electrode60, the anode electrode62, and the solid polymer electrolyte membrane58may have the same size in plan view. Further alternatively, the anode electrode62may have a size in plan view that is smaller than that of each of the cathode electrode60and the solid polymer electrolyte membrane58.

The cathode electrode60and the anode electrode62each include a gas diffusion layer (not shown) and an electrode catalyst layer (not shown). The gas diffusion layer is made of carbon paper or the like. The electrode catalyst layer is formed by uniformly coating a surface of the gas diffusion layer with porous carbon particles whose surfaces support a platinum alloy. The electrode catalyst layers are disposed on both sides of the solid polymer electrolyte membrane58.

Referring toFIGS. 1 to 4, in the first membrane electrode assembly16a,a first resin frame member64is disposed on an outer peripheral portion of the solid polymer electrolyte membrane58so as to be located outward from an edge of the cathode electrode60. The first resin frame member64is integrally formed, for example, by injection molding. Alternatively, a resin frame member that has been manufactured beforehand may be joined to the outer peripheral portion.

In the second membrane electrode assembly16b,a second resin frame member66is disposed on an outer peripheral portion of the solid polymer electrolyte membrane58so as to be located outward from an edge of the cathode electrode60. The second resin frame member66is integrally formed, for example, by injection molding. Alternatively, a resin frame member that has been manufactured beforehand may be joined to the outer peripheral portion.

A commodity plastic, an engineering plastic, a super engineering plastic, or the like may be used as the material of the first resin frame member64and the second resin frame member66.

Referring toFIGS. 1 and 8, on a surface of the first resin frame member64on the cathode electrode60side, the inlet connection channel portion68aand the inlet buffer portion70aare disposed between the oxidant gas inlet manifold22aand an inlet of the first oxidant gas channel26. The inlet connection channel portion68ais disposed adjacent to the oxidant gas inlet manifold22aand includes a plurality of protrusions72athat have ends at one short side of the first resin frame member64. The protrusions72aextend from the oxidant gas inlet manifold22atoward the inlet buffer portion70a.Referring toFIG. 3, the protrusions72aare in contact with the inlet flat portion55aof the first metal separator14. Inlet connection channels74aare formed between the protrusions72a.

Referring toFIG. 8, the inlet buffer portion70ais disposed between the inlet connection channel portion68aand the first oxidant gas channel26. The inlet buffer portion70aincludes a plurality of embossed portions76anear the inlet connection channel portion68aand a plurality of bar-shaped protrusions78anear the first oxidant gas channel26. A plurality of linear paths80aare formed between the bar-shaped protrusions78a.The inlet buffer portion70amay include only the embossed portion76aor only the bar-shaped protrusions78a.Inlet buffer portions and outlet buffer portions described below have structures similar to those described above.

On a surface of the first resin frame member64on the cathode electrode60side, the outlet connection channel portion68band the outlet buffer portion70bare disposed between the oxidant gas outlet manifold22band the outlet of the first oxidant gas channel26. The outlet connection channel portion68bis disposed adjacent to the oxidant gas outlet manifold22band includes a plurality of protrusions72bthat have ends at the other short side of the first resin frame member64. The protrusions72bextend from the oxidant gas outlet manifold22btoward the outlet buffer portion70b. Referring toFIG. 4, the protrusions72bare in contact with the outlet flat portion55bof the first metal separator14. Outlet connection channels74bare formed between the protrusions72b.

Referring toFIG. 8, the outlet buffer portion70bis disposed between the outlet connection channel portion68band the first oxidant gas channel26. The outlet buffer portion70bincludes a plurality of embossed portions76bnear the outlet connection channel portion68band a plurality of bar-shaped protrusions78bnear the first oxidant gas channel26. A plurality of linear paths80bare formed between the bar-shaped protrusions78b.

Referring toFIG. 1, on a surface of the first resin frame member64on the anode electrode62side, the inlet buffer portion81ais disposed between the fuel gas inlet manifold24aand the first fuel gas channel32. The outlet buffer portion81bis disposed between the fuel gas outlet manifold24band the first fuel gas channel32. Detailed descriptions of the inlet buffer portion81aand the outlet buffer portion81b,which respectively have structures similar to those of the inlet buffer portion70aand the outlet buffer portion70b,are omitted.

Referring toFIGS. 1 and 9, on a surface of the second resin frame member66on the cathode electrode60side, the inlet connection channel portion82aand the inlet buffer portion84aare disposed between the oxidant gas inlet manifold22aand the second oxidant gas channel38. The inlet connection channel portion82ais disposed adjacent to the oxidant gas inlet manifold22aand includes a plurality of protrusions86athat have ends at one short side of the second resin frame member66. The protrusions86aextend from the oxidant gas inlet manifold22atoward the inlet buffer portion84a.Referring toFIG. 3, the protrusions86aare in contact with the inlet flat portion57aof the second metal separator18. Inlet connection channels88aare formed between the protrusions86a.

Referring toFIG. 5, the opening width l1of each inlet connection channel88aon an open end side that is adjacent to the second metal separator18is larger than the opening width l2of the inlet connection channel88aat a bottom side that is separated from the second metal separator18(l1>l2).

Referring toFIG. 9, the inlet buffer portion84ais disposed between the inlet connection channel portion82aand the second oxidant gas channel38. The inlet buffer portion84aincludes a plurality of embossed portions90anear the inlet connection channel portion82aand a plurality of bar-shaped protrusions92anear the second oxidant gas channel38. A plurality of linear paths94aare formed between the bar-shaped protrusions92a.

On a surface of the second resin frame member66on the cathode electrode60side, the outlet connection channel portion82band the outlet buffer portion84bare disposed between the oxidant gas outlet manifold22band an outlet of the second oxidant gas channel38. The outlet connection channel portion82bis disposed adjacent to the oxidant gas outlet manifold22band includes a plurality of protrusions86bthat have ends at the other short side of the second resin frame member66. The protrusions86bextend from the oxidant gas outlet manifold22btoward the outlet buffer portion84b. Referring toFIG. 4, the protrusions86bare in contact with the outlet flat portion57bof the second metal separator18. Outlet connection channels88bare formed between the protrusions86b.

Referring toFIG. 9, the outlet buffer portion84bis disposed between the outlet connection channel portion82band the second oxidant gas channel38. The outlet buffer portion84bincludes a plurality of embossed portions90bnear the outlet connection channel portion82band a plurality of bar-shaped protrusions92bnear the second oxidant gas channel38. A plurality of linear paths94bare formed between the bar-shaped protrusions92b.

Referring toFIG. 1, on a surface of the second resin frame member66on the anode electrode62side, the inlet buffer portion96ais disposed between the fuel gas inlet manifold24aand the second fuel gas channel42. The outlet buffer portion96bis disposed between the fuel gas outlet manifold24band the second fuel gas channel42. Detailed descriptions of the inlet buffer portion96aand the outlet buffer portion96b,which respectively have structures similar to those of the inlet buffer portion84aand the outlet buffer portion84b,are omitted.

When two power generation units12are stacked on top of each other, the coolant channel30is formed between the first metal separator14of one of the power generation units12and the third metal separator20of the other power generation unit12.

The operation of the fuel cell10, which has the structure described above, will be described below.

First, referring toFIG. 1, an oxidant gas, such as an oxygen-containing gas, is supplied to the oxidant gas inlet manifold22a.A fuel gas, such as a hydrogen-containing gas, is supplied to the fuel gas inlet manifold24a.A coolant, such as pure water, ethylene glycol, or oil, is supplied to the pair of upper and lower coolant inlet manifolds25a.

Therefore, referring toFIGS. 3 and 6, a part of the oxidant gas is introduced from the oxidant gas inlet manifold22aof the first metal separator14into the inlet connection channel portion68athrough the inlet paths54a.Referring toFIGS. 3, 6, and 8, in the inlet connection channel portion68a, the oxidant gas flows to the inlet buffer portion70athrough a space between the inlet connection channels74aand the inlet flat portion55a.Then, the oxidant gas is supplied to the first oxidant gas channel26of the first metal separator14through the inlet buffer portion70a.

Referring toFIGS. 3 and 7, the remaining part of the oxidant gas is introduced from the oxidant gas inlet manifold22aof the second metal separator18into the inlet connection channel portion82athrough the inlet paths56a. Referring toFIGS. 3, 7, and 9, in the inlet connection channel portion82a,the oxidant gas flows to the inlet buffer portion84athrough a space between the inlet connection channels88aand the inlet flat portion57a.Then, the oxidant gas is supplied to the second oxidant gas channel38of the second metal separator18through the inlet buffer portion84a.

Referring toFIG. 1, the part of the oxidant gas supplied to the first oxidant gas channel26flows along the first oxidant gas channel26in the direction of arrow B (horizontal direction), and is supplied to the cathode electrode60of the first membrane electrode assembly16a. The remaining part of the oxidant gas flows along the second oxidant gas channel38in the direction of arrow B and is supplied to the cathode electrode60of the second membrane electrode assembly16b.

A part of the fuel gas is supplied from the fuel gas inlet manifold24ato the inlet buffer portion81athrough the supply holes36aof the second metal separator18. The part of the fuel gas is supplied to the first fuel gas channel32of the second metal separator18through the inlet buffer portion81a.

The remaining part of the fuel gas is supplied from the fuel gas inlet manifold24ato the inlet buffer portion96athrough the supply holes46aof the third metal separator20. The remaining part of the fuel gas is supplied to the second fuel gas channel42of the third metal separator20through the inlet buffer portion96a.

The part of the fuel gas supplied to the first fuel gas channel32flows along the first fuel gas channel32in the direction of arrow B and is supplied to the anode electrode62of the first membrane electrode assembly16a. The remaining part of the fuel gas flows along the second fuel gas channel42in the direction of arrow B and is supplied to the anode electrode62of the second membrane electrode assembly16b.

Accordingly, in each of the first membrane electrode assembly16aand the second membrane electrode assembly16b, the oxidant gas supplied to the cathode electrode60and the fuel gas supplied to the anode electrode62are consumed in electrochemical reactions in the electrode catalyst layers, and therefore electric power is generated.

Referring toFIG. 1, the oxidant gas supplied to the cathode electrode60of the first membrane electrode assembly16aand consumed, is introduced into the outlet buffer portion70bof the first metal separator14. Referring toFIGS. 4, 6, and8, the oxidant gas flows from the outlet buffer portion70bto the outlet connection channel portion68b.In the outlet connection channel portion68b,the oxidant gas is discharged to the oxidant gas outlet manifold22bthrough a space between the outlet connection channels74band the outlet flat portion55b.

Referring toFIG. 1, the oxidant gas supplied to the cathode electrode60of the second membrane electrode assembly16band consumed, is introduced into the outlet buffer portion84bof the second metal separator18. Referring toFIGS. 4, 7, and9, the oxidant gas flows from the outlet buffer portion84bto the outlet connection channel portion82b.In the outlet connection channel portion82b,the oxidant gas is discharged to the oxidant gas outlet manifold22bthrough a space between the outlet connection channels88band the outlet flat portion57b.

Referring toFIG. 1, the fuel gas, which has been supplied to the anode electrodes62of the first membrane electrode assembly16aand the second membrane electrode assembly16band consumed, is introduced into the outlet buffer portions81band96b.The fuel gas flows through the discharge holes36band46band is discharged to the fuel gas outlet manifold24b.

The coolant, which has been supplied to the pair of upper and lower coolant inlet manifolds25a,is introduced into the coolant channel30. The coolant temporarily flows inward in the direction of arrow C, then flows in the direction of arrow B, and cools the first membrane electrode assembly16aand the second membrane electrode assembly16b. Then, the coolant flows outward in the direction of arrow C and is discharged to the pair of upper and lower coolant outlet manifolds25b.

In the present embodiment, for example, referring toFIG. 8, on the surface of the first resin frame member64on the cathode electrode60side, the inlet connection channel portion68ais disposed between the oxidant gas inlet manifold22aand the inlet of the first oxidant gas channel26. The inlet connection channel portion68aincludes the plurality of protrusions72a,which form the inlet connection channels74a.

Likewise, on the first resin frame member64, the outlet connection channel portion68bis disposed between the oxidant gas outlet manifold22band the outlet of the first oxidant gas channel26. The outlet connection channel portion68bincludes the plurality of protrusions72b,which form the outlet connection channels74b.

Referring toFIGS. 3, 4, and 6, the first metal separator14includes the inlet flat portion55a,with which the protrusions72aare in contact, and the outlet flat portion55b,with which the protrusions72bare in contact. Therefore, it is not necessary to press-form the first metal separator14so as to form inlet connection channels and outlet connection channels. Accordingly, the shape of the first metal separator14is simplified and the first metal separator14can be easily press-formed, so that the first metal separator14can be made easily and economically.

Moreover, the amount of deformation of the first resin frame member64can be considerably reduced as compared with the first metal separator14, which is press-formed. To be specific, referring toFIG. 10, a power generation unit12ref, having an existing structure, includes a metal separator18ref, in which connection channels88ref are press-formed. A resin frame member66ref, which is disposed on an outer periphery of a membrane electrode assembly, may be formed by extending the outer periphery of a gas diffusion layer of an electrode. The resin frame member66ref has a flat surface facing the connection channels88ref.

The opening width l3of the connection channel88ref on the resin frame member66ref side is larger than the opening width l4of the connection channel88ref on the bottom side that is separated from the resin frame member66ref (l3>l4). Therefore, there is a problem in that the resin frame member66ref is likely to become deformed so as to fall into the connection channels88ref and therefore the connection channels88ref might become blocked.

In contrast, according to the present disclosure, referring toFIG. 5, each inlet connection channel88ais formed in the second resin frame member66, and the opening width l1of the inlet connection channel88aon the open end side that is adjacent to the second metal separator18is larger than the opening width l2of the inlet connection channel88aon the bottom side that is separated from the second metal separator18(l1>l2). Accordingly, the second resin frame member66is not deformed easily, and blocking of the inlet connection channel88acan be suppressed.

Thus, with the present disclosure, the gas sealing ability and the gas distributing ability of the inlet connection channel portion68aand the outlet connection channel portion68bcan be significantly improved.

Moreover, with the second resin frame member66and the second metal separator18, advantages the same as those of the first resin frame member64and the first metal separator14can be obtained. In the above description, the present embodiment is used only on the anode side. However this is not a limitation, and the present embodiment can be easily applied also to the cathode side.

In the present disclosure, referring toFIG. 5, the cross-sectional shape of each inlet connection channel88ais trapezoidal. However, this is not a limitation. For example, as in a fuel cell10ashown inFIG. 11, inlet connection channels88aa, each having a semicircular cross-sectional shape, may be used. Likewise, other connection channels may have semicircular cross-sectional shapes or various other shapes.

In the present embodiment, each power generation unit12of the fuel cell10is a so-called thinned-out cooling fuel cell, which includes three separators and two MEAs. However, this is not a limitation. For example, the fuel cell may be an independent cooling fuel cell, in which one MEA is sandwiched between two separators.

A fuel cell according to the present disclosure includes a membrane electrode assembly including an electrolyte membrane and a pair of electrodes sandwiching the electrolyte membrane therebetween, and a metal separator stacked on the membrane electrode assembly. The metal separator includes a reactant gas channel through which a reactant gas is supplied along an electrode surface and a reactant gas manifold through which the reactant gas flows in a stacking direction in which the membrane electrode assembly and the metal separator are stacked. The membrane electrode assembly includes a resin frame member on an outer peripheral portion thereof.

The resin frame member has an outer shape such that the resin frame member is disposed further inward than the reactant gas manifold. The resin frame member includes a connection channel portion that is disposed outward from the electrode surface and that connects the reactant gas manifold and the reactant gas channel to each other. The metal separator includes a flat portion that is in contact with the connection channel portion.

Preferably, in the fuel cell, the connection channel portion of the resin frame member includes a plurality of protrusions that are disposed adjacent to the reactant gas manifold, and a connection channel is formed between the protrusions.

Preferably, in the fuel cell, a buffer portion is disposed between the connection channel portion and the reactant gas channel, the buffer portion including at least one of an embossed portion and a plurality of bar-shaped protrusions.

Preferably, in the fuel cell, an opening width of the connection channel portion on an open end side that is adjacent to the metal separator is larger than an opening width of the connection channel on a bottom side that is separated from the metal separator.

According to the present disclosure, the resin frame member includes the connection channel portion that connects the reactant gas manifold and the reactant gas channel to each other, and the metal separator includes a flat portion that is in contact with the connection channel portion. Therefore, the shape of the metal separator is simplified and the metal separator can be easily press-formed, so that the operation of manufacturing the metal separator can be simplified.

Moreover, the amount of deformation of the resin frame member is considerably smaller than that of the metal separator, which is made by press-forming. Accordingly, the cross-sectional area of the connection channel does not change, and the gas sealing ability and the gas distributing ability can be significantly improved.