Solid polymer electrolytic fuel cell

Elastic members that are integrally joined to a frame member are placed between an outer edge of an electrode unit and an inner edge of the frame member, and in the assembled state of the single cell module, the elastic members are elastically deformed in the thickness direction of a membrane-electrode-frame assembly so that the gap between the membrane-electrode-frame assembly and the separator is sealed in a tight contact state.

TECHNICAL FIELD

The present invention relates to a solid polymer electrolytic fuel cell, and more particularly to an improved sealing structure for a fuel cell between an electrolyte membrane-electrode assembly and a conductive separator.

BACKGROUND ART

The most typical solid polymer electrolytic fuel cell is configured by a polymer electrolyte membrane supported by a frame member having a gasket for sealing gas placed on its peripheral portion, an electrolyte membrane-electrode assembly (MEA) formed by an anode joined to one of the surfaces of the electrolyte membrane and a cathode joined to the other surface of the electrolyte membrane, and an anode-side conductive separator plate and a cathode-side conductive separator plate that sandwich the MEA, and a gas supply unit for supplying a fuel gas and an oxidizing agent gas to the anode and the cathode, respectively, is formed on a peripheral edge of the center portion in the separator plate, which is placed in contact with the MEA.

However, as shown inFIG. 12, since this conventional solid polymer electrolytic fuel cell has a gap303between the inner edge of a frame member300and an electrode302, which is required upon assembling the frame member300and the separator301, a phenomenon referred to as a cross-leak, in which a part of gas supplied into the fuel cell is discharged through this gap303, tends to occur.

In order to prevent this phenomenon, as shown inFIG. 13, a structure has been proposed in which a second gasket308is placed in this gap303(Patent Document 1), and a method (Patent Document 2) has been proposed in which one portion of an inner edge of a gasket and an outer edge of an electrode302are disposed so as to be partially placed in contact with each other.

Moreover, the polymer electrolyte membrane is assembled virtually in the center of the thickness of the frame member, and with respect to its joining method, methods such as thermal compression bonding, bonding agent, and mechanical cramping, have been adopted.

DISCLOSURE OF INVENTION

Subject to be Solved by the Invention

However, the above-mentioned joining methods for the polymer electrolyte membrane by the use of thermal compression bonding or a bonding agent tend to cause degradation in the performance of the polymer electrolyte membrane due to heat and volatile components of the bonding agent, and the application conditions are consequently limited. Moreover, the joining method by the use of mechanical cramping causes an issue in that cross-leak easily occurs through a fine gap between the polymer electrolyte membrane and the frame member.

The method of the above-mentioned Patent Document 1, which needs to install a second gasket308for eliminating the gap303between the inner edge of the frame member300and the electrode302, has an issue of high costs. Moreover, another issue is that, when this gasket308is partially fused to fill the gap, it becomes difficult to properly control the dimension.

The method of the above-mentioned Patent Document 2 in which one portion of the inner edge of a gasket and the outer edge of the electrode302are partially placed in contact with each other fails to provide a sufficient effect, or since the gas diffusion electrode is mainly made from carbon fibers that are bristle in general, another issue is that upon assembling, the electrode tends to be damaged.

Therefore, the object of the present invention is to overcome the above-mentioned issues, that is, to provide a solid polymer electrolytic fuel cell which makes it possible to effectively restrain a cross-leak phenomenon that occurs through the gap between the polymer electrolyte membrane and the frame member, and also to improve the rates of utilization of a reducing agent gas and an oxidizing agent gas respectively, as well as further enhancing the performance of a polymer electrolyte fuel cell.

Means for Solving the Subject

In order to achieve the above-mentioned objects, the present invention is provided with the following arrangements.

According to a first aspect of the present invention, there is provided a solid polymer electrolytic fuel cell, which is a polymer electrolytic fuel cell configured by laminating single cell modules, each comprising:

a membrane-electrode-frame assembly having an electrode unit configured by an anode electrode joined onto one of surfaces of a polymer electrolyte membrane and a cathode electrode joined onto the other surface of the electrolyte membrane and a manifold-forming frame member that is placed on a peripheral edge of the electrode unit and provided with a gas supply unit for supplying a fuel gas and an oxidizing agent gas respectively to the anode electrode and the cathode electrode; and

a pair of separators sandwiching the electrode unit and the membrane-electrode-frame assembly from an anode side as well as from a cathode side, wherein

an elastic member is placed between an outer edge of the electrode unit and an inner edge of the frame member, and the elastic member is integrally joined to the frame member and has a length equal to or longer than a gap dimension between the membrane-electrode-frame assembly and the separator in an assembled state of the single cell modules, with the elastic member being elastically deformed in a thickness direction of the membrane-electrode-frame assembly in the assembled state of the single cell modules, so that the gap between the membrane-electrode-frame assembly and the separator is sealed in a tight contact state.

According to a second aspect of the present invention, there is provided the solid polymer electrolytic fuel cell according to the first aspect, wherein the elastic member is provided with a plurality of short-cut preventing ribs that are placed in contact with the separator to be elastically deformed so that, in the assembled state of the single cell modules, the ribs are elastically deformed in a direction orthogonal to the thickness direction of the membrane-electrode-frame assembly.

According to a third aspect of the present invention, there is provided the solid polymer electrolytic fuel cell according to the second aspect, wherein a concave section into which elastically deformed portions of the ribs and an elastically deformed portion of the elastic member are released is placed between the ribs so that the elastically deformed portion of the elastic member and the elastically deformed portions of the ribs are extended into the concave section.

According to a fourth aspect of the present invention, there is provided the solid polymer electrolytic fuel cell according to the second aspect, wherein in a portion near the gas supply unit, the elastic member has a length less than the gap dimension between the membrane-electrode-frame assembly and the separator in the assembled state of the single cell modules so that a gas supplying space is formed between the elastic member and the separator.

According to a fifth aspect of the present invention, there is provided the solid polymer electrolytic fuel cell according to any one of the first to fourth aspects, wherein the elastic member is placed only on one of an anode side and a cathode side of the membrane-electrode-frame assembly, and an extended portion which is formed by extending the frame member toward a center in an inner edge direction so as to receive a compressing pressure of the elastic member upon laminating the separator, is prepared on the other side of the membrane-electrode-frame assembly.

According to a sixth aspect of the present invention, there is provided the solid polymer electrolytic fuel cell according to any one of the first to fourth aspects, wherein the elastic member is placed on each of an anode side and a cathode side of the membrane-electrode-frame assembly, with a position of the elastic member on the anode side and a position of the elastic member on the cathode side being shifted from each other.

According to a seventh aspect of the present invention, there is provided the solid polymer electrolytic fuel cell according to the fifth aspect, wherein the elastic member is placed on each of the anode side and the cathode side of the membrane-electrode-frame assembly, with a position of the elastic member on the anode side and a position of the elastic member on the cathode side being shifted from each other.

According to an eighth aspect of the present invention, there is provided the solid polymer electrolytic fuel cell according to the sixth aspect, wherein a position of an outer edge of the anode electrode joined to one of the surfaces of the polymer electrolyte membrane and a position of an outer edge of the cathode electrode joined to the other surface of the polymer electrolyte membrane are placed with a shift from each other so that the positions of the elastic member on the anode side and the elastic member on the cathode side are shifted from each other.

According to a ninth aspect of the present invention, there is provided the solid polymer electrolytic fuel cell according to the seventh aspect, wherein a position of an outer edge of the anode electrode joined to one of the surfaces of the polymer electrolyte membrane and a position of an outer edge of the cathode electrode joined to the other surface of the polymer electrolyte membrane are placed with a shift from each other so that the positions of the elastic member on the anode side and the elastic member on the cathode side are shifted from each other.

According to a 10th aspect of the present invention, there is provided the solid polymer electrolytic fuel cell according to any one of the first to fourth aspects, wherein the frame member is provided with a gasket, formed on a frame member assembled surface corresponding to a surface on a side where the cathode electrode is positioned so as to protrude therefrom, which includes a manifold hole for an oxidizing agent gas and an oxidizing agent gas flow passage and surrounds an entire area of the cathode electrode through which the oxidizing agent gas is allowed to pass so that a manifold for an oxidizing gas is formed, and another gasket, formed on another frame member assembled surface corresponding to a surface of the frame member on a side where the anode electrode is positioned so as to protrude therefrom, which includes a manifold hole for a fuel gas and a fuel gas flow passage and surrounds an entire area of the anode electrode through which the fuel gas is allowed to pass so that a manifold for a fuel gas is formed, and in the assembled state of the single cell module, the gaskets are elastically deformed respectively in the thickness direction of the frame member so that the gap between the frame member and the separator is sealed in a tight contact state.

According to an 11th aspect of the present invention, there is provided the solid polymer electrolytic fuel cell according to the fifth aspect, wherein the frame member is provided with a gasket, formed on a frame member assembled surface corresponding to a surface on a side where the cathode electrode is positioned so as to protrude therefrom, which includes a manifold hole for an oxidizing agent gas and an oxidizing agent gas flow passage and surrounds an entire area of the cathode electrode through which the oxidizing agent gas is allowed to pass so that a manifold for an oxidizing gas is formed, and another gasket, formed on another frame member assembled surface corresponding to a surface of the frame member on a side where the anode electrode is positioned so as to protrude therefrom, which includes a manifold hole for a fuel gas and a fuel gas flow passage and surrounds an entire area of the anode electrode through which the fuel gas is allowed to pass so that a manifold for a fuel gas is formed, and in the assembled state of the single cell module, the gaskets are elastically deformed respectively in the thickness direction of the frame member so that the gap between the frame member and the separator is sealed in a tight contact state.

According to a 12th aspect of the present invention, there is provided the solid polymer electrolytic fuel cell according to the sixth aspect, wherein the frame member is provided with a gasket, formed on a frame member assembled surface corresponding to a surface on a side where the cathode electrode is positioned so as to protrude therefrom, which includes a manifold hole for an oxidizing agent gas and an oxidizing agent gas flow passage and surrounds an entire area of the cathode electrode through which the oxidizing agent gas is allowed to pass so that a manifold for an oxidizing gas is formed, and another gasket, formed on another frame member assembled surface corresponding to a surface of the frame member on a side where the anode electrode is positioned so as to protrude therefrom, which includes a manifold hole for a fuel gas and a fuel gas flow passage and surrounds an entire area of the anode electrode through which the fuel gas is allowed to pass so that a manifold for a fuel gas is formed, and in the assembled state of the single cell module, the gaskets are elastically deformed respectively in the thickness direction of the frame member so that the gap between the frame member and the separator is sealed in a tight contact state.

According to a 13th aspect of the present invention, there is provided the solid polymer electrolytic fuel cell according to the seventh aspect, wherein the frame member is provided with a gasket, formed on a frame member assembled surface corresponding to a surface on a side where the cathode electrode is positioned so as to protrude therefrom, which includes a manifold hole for an oxidizing agent gas and an oxidizing agent gas flow passage and surrounds an entire area of the cathode electrode through which the oxidizing agent gas is allowed to pass so that a manifold for an oxidizing gas is formed, and another gasket, formed on another frame member assembled surface corresponding to a surface of the frame member on a side where the anode electrode is positioned so as to protrude therefrom, which includes a manifold hole for a fuel gas and a fuel gas flow passage and surrounds an entire area of the anode electrode through which the fuel gas is allowed to pass so that a manifold for a fuel gas is formed, and in the assembled state of the single cell module, the gaskets are elastically deformed respectively in the thickness direction of the frame member so that the gap between the frame member and the separator is sealed in a tight contact state.

According to a 14th aspect of the present invention, there is provided the solid polymer electrolytic fuel cell according to the eighth aspect, wherein the frame member is provided with a gasket, formed on a frame member assembled surface corresponding to a surface on a side where the cathode electrode is positioned so as to protrude therefrom, which includes a manifold hole for an oxidizing agent gas and an oxidizing agent gas flow passage and surrounds an entire area of the cathode electrode through which the oxidizing agent gas is allowed to pass so that a manifold for an oxidizing gas is formed, and another gasket, formed on another frame member assembled surface corresponding to a surface of the frame member on a side where the anode electrode is positioned so as to protrude therefrom, which includes a manifold hole for a fuel gas and a fuel gas flow passage and surrounds an entire area of the anode electrode through which the fuel gas is allowed to pass so that a manifold for a fuel gas is formed, and in the assembled state of the single cell module, the gaskets are elastically deformed respectively in the thickness direction of the frame member so that the gap between the frame member and the separator is sealed in a tight contact state.

According to a 15th aspect of the present invention, there is provided the solid polymer electrolytic fuel cell according to the ninth aspect, wherein the frame member is provided with a gasket, formed on a frame member assembled surface corresponding to a surface on a side where the cathode electrode is positioned so as to protrude therefrom, which includes a manifold hole for an oxidizing agent gas and an oxidizing agent gas flow passage and surrounds an entire area of the cathode electrode through which the oxidizing agent gas is allowed to pass so that a manifold for an oxidizing gas is formed, and another gasket, formed on another frame member assembled surface corresponding to a surface of the frame member on a side where the anode electrode is positioned so as to protrude therefrom, which includes a manifold hole for a fuel gas and a fuel gas flow passage and surrounds an entire area of the anode electrode through which the fuel gas is allowed to pass so that a manifold for a fuel gas is formed, and in the assembled state of the single cell module, the gaskets are elastically deformed respectively in the thickness direction of the frame member so that the gap between the frame member and the separator is sealed in a tight contact state.

According to a 16th aspect of the present invention, there is provided a solid polymer electrolytic fuel cell comprising:

a polymer electrolyte membrane;

a first electrode and a second electrode that sandwich the polymer electrolyte membrane, and have at least a gas diffusion layer;

a first separator having a flow passage used for supplying and discharging a reaction gas to and from the first electrode;

a second separator having a flow passage used for supplying and discharging a reaction gas to and from the second electrode; and

a frame member that has rectangular opening sections placed on peripheral edge portions of the first electrode and the second electrode, wherein

a first elastic member is formed between an outer edge of the first electrode and an inner edge of the frame member on a first electrode side,

at least one portion of an outer edge of the gas diffusion layer of the first electrode is placed so as to be extended outside an outer edge of the gas diffusion layer of the opposing second electrode, and

at least one portion of the outer edge of the gas diffusion layer of the first electrode and at least one portion of an inner edge of the frame member on the second electrode side are placed to face with each other.

According to a 17th aspect of the present invention, there is provided the solid polymer electrolytic fuel cell according to the 16th aspect, wherein a second elastic member is further placed between the outer edge of the second electrode and the inner edge of the frame member on a first electrode side.

EFFECTS OF THE INVENTION

In accordance with the above-mentioned structure, for example, the anode-side elastic member having the frame shape on the plan view and the cathode-side elastic member having the frame shape on the plan view are placed on the edge portion inside the frame member supporting the polymer electrolyte membrane and the like, and each of the elastic members is allowed to have the length equal to or longer than the gap dimension between the membrane-electrode-frame assembly and the separator in the assembled state of the single cell modules, with the elastic member being elastically deformed in a thickness direction of the membrane-electrode-frame assembly in the assembled state of the single cell modules, so that the gap between the membrane-electrode-frame assembly and the separator is sealed in a tight contact state. With this arrangement, the anode-side elastic member is elastically deformed between the frame member and the anode-side separator at the time of assembling the single cells so that the elastically deformed anode-side elastic member is placed in tight contact in the gap between the frame member and the anode-side separator to seal the gap, thereby exerting a sealing effect. In the same manner, on the cathode side also, the cathode-side elastic member is elastically deformed between the frame member and the cathode-side separator at the time of assembling the single cells so that the elastically deformed cathode-side elastic member is placed in tight contact in the gap between the frame member and the cathode-side separator to seal the gap, thereby exerting a sealing effect.

As a result, by the elastically deformed anode-side elastic member and the elastically deformed cathode-side elastic member, the gaps between the frame member and the anode-side separator as well as between the frame member and the cathode-side separator are respectively sealed in a tight contact state so that it becomes possible to effectively restrain a cross-leak phenomenon occurring through the gap between the polymer electrolyte membrane and the frame, and also to respectively restrain a short-circuiting flow of a reducing agent gas along the edge portion of the frame member and a short-circuiting flow of an oxidizing agent gas along the edge portion of the frame member, thereby making it possible to further improve the utilization rates of the reducing agent gas and the oxidizing agent gas, and consequently to further improve the performance of the polymer electrolytic fuel cell.

Moreover, by providing a number of anode-side ribs and cathode-side ribs that are placed in the edge portion inside the frame member supporting the polymer electrolyte membrane and the like at predetermined intervals, the anode-side elastic member and the anode-side ribs are respectively elastically deformed between the frame member and the anode-side separator at the time of assembling the single cells so that the elastically deformed portions are allowed to intrude into the space, for example, to the adjacent anode-side rib; thus, the elastically deformed anode-side elastic member and the elastically deformed anode-side ribs are placed in virtually continuous tight contact in the gap between the frame member and the anode-side separator to seal the gap, thereby exerting a sealing effect. Moreover, on the cathode side also, the cathode-side elastic member and the cathode-side ribs are respectively elastically deformed between the frame member and the cathode-side separator at the time of assembling the single cells so that the elastically deformed portions are allowed to intrude into the space, for example, to the adjacent cathode-side rib; thus, the elastically deformed cathode-side elastic member and the elastically deformed cathode-side ribs are placed in virtually continuous tight contact in the gap between the frame member and the anode-side separator to seal the gap, thereby exerting a sealing effect.

As a result, by the elastically deformed anode-side elastic member and the elastically deformed anode-side rib as well as by the elastically deformed cathode-side elastic member and the elastically deformed cathode-side rib, the gaps between the frame member and the anode-side separator as well as between the frame member and the cathode-side separator are respectively sealed in a tight contact state so that it becomes possible to effectively restrain a cross-leak phenomenon occurring through the gap between the polymer electrolyte membrane and the frame, and also to respectively restrain a short-circuiting flow of a reducing agent gas along the edge portion of the frame member and a short-circuiting flow of an oxidizing agent gas along the edge portion of the frame member, thereby making it possible to further improve the utilization rates of the reducing agent gas and the oxidizing agent gas, and consequently to further improve the performance of the polymer electrolytic fuel cell.

DETAILED DESCRIPTION OF THE INVENTION

Referring to drawings, the following description will discuss embodiments of the present invention in detail.

First Embodiment

FIG. 1is a schematic constitution view that schematically shows a structure of a fuel cell provided with a stack for a fuel cell in accordance with one embodiment of the present invention. Moreover,FIG. 2is a schematic exploded view that shows a stack for a fuel cell possessed by the fuel cell101shown inFIG. 1(hereinafter, referred to as stack).

The fuel cell101, which is, for example, a solid polymer electrolytic fuel cell (PEFC), is designed to generate electric power, heat, and water simultaneously, by allowing a fuel gas containing hydrogen and an oxidizing agent gas containing oxygen such as air to react with each other electrochemically. As shown inFIG. 1, the fuel cell101is provided with a stack30having a laminated structure in which a plurality of fuel cells (or a single cell), each having a pair of anode and cathode electrodes, are series-connected with one another, a fuel processing device31for taking out hydrogen from a fuel gas, an anode humidifier32for improving the power generating efficiency by humidifying a fuel gas containing hydrogen taken out by the fuel processing device31, a cathode humidifier33for humidifying the oxygen containing gas (oxidizing agent gas), and pumps34and35used for respectively supplying the fuel gas and the oxygen-containing gas. That is, the fuel processing device31, the anode humidifier32, and the pump34form a fuel supply device for supplying the fuel gas to the respective cells of the stack30, and the cathode humidifier33and the pump35form an oxidizing agent supply device for supplying the oxidizing agent gas to the respective cells of the stack30. Here, various other modes may be adopted as these fuel supply device and oxidizing agent supply device as long as they have functions for supplying the fuel and the oxidizing agent, and in the present embodiment, any supply devices may be used as long as they commonly supply the fuel and oxidizing agent to a plurality of cells possessed by the stack30so as to desirably obtain effects of the present embodiment, which will be described later.

Moreover, the fuel cell101is provided with a pump36used for circulating and supplying cooling water for effectively removing heat generated by the stack30upon generating power, a heat exchanger37used for heat-exchanging the heat removed by this cooling water (for example, liquid having no conductivity, such as pure water) into a fluid such as tap water and a hot-water reserving tank38used for storing the tap water that has been heat-exchanged. The fuel cell101is further provided with an operation control device40for controlling the operation for generating power by making these respective components associated with one another, and an electricity output unit41used for taking out electricity generated by the stack30.

Furthermore, as shown inFIG. 2, the stack30installed in the fuel cell101has a structure in which a plurality of single cells (single cell module)20, each serving as a basic unit component, are laminated, and these cells are fastened with one after another by applying a predetermined load from each of the two sides23through a collector plate21, an insulating plate22, and an end plate23. A current take-out terminal unit21ais attached to each of the collector plates21, and upon power generation, an electric current, that is, electricity, is taken out from this unit. Each of the insulating plates22insulates the collector plate21and the end plate23from each other, and introduction inlets and discharging outlets for gas and cooling water, not shown, are formed therein in some cases. The respective end plates23fasten the laminated single cells20, the collector plates21, and the insulating plates22with one another so as to be held therebetween by applying a predetermined load thereto from a pressing means, not shown.

As shown inFIG. 2, the single cell20is formed by sandwiching an MEA (membrane-electrode assembly)15between a pair of separators5band5c. The MEA15has a structure in which a catalyst layer (anode-side catalyst layer)112, mainly composed of carbon powder with a platinum-ruthenium alloy catalyst deposited thereon, is formed on an anode surface side of a polymer electrolyte membrane1athat selectively transfers hydrogen ions, while a catalyst layer (cathode-side catalyst layer)113, mainly composed of carbon powder with a platinum catalyst deposited thereon is formed on a cathode surface side thereof, with a gas diffusion layer114having both of a ventilating property for a fuel gas or an oxidizing agent gas and an electron conductive property being placed on the outer surface of each of the catalyst layers112and113. The polymer electrolyte membrane1ais generally prepared as a solid polymer material having a proton conductive property, for example, a perfluorosulfonic acid membrane (Nafion membrane made by Du Pont de Nemours and Company). Here, in the following description, the anode-side catalyst layer112and the gas diffusion layer114are combinedly referred to as an anode electrode1b, and the cathode-side catalyst layer113and the gas diffusion layer114are combinedly referred to as a cathode electrode1c.

Here, in the present specification and the claims, the electrode means one that includes at least a GDL (gas diffusion layer).

Any conductive material may be used as the separators5band5c, as long as it is a non-gas-permeable conductive material, and for example, a material formed by cutting a resin-impregnated carbon material into a predetermined shape and a material obtained by molding a mixture of carbon powder and a resin material are generally used. A concave-shaped groove portion is formed at a portion of each of the separators5band5c, which is placed in contact with the MEA15, and this groove portion is placed in contact with the gas diffusion layer114so that a gas flow passage, used for supplying a fuel gas or an oxidizing agent gas to an electrode surface, and for carrying excessive gas out therefrom, is formed. With respect to the base member for the gas diffusion layer114, a material made from carbon fibers is generally used, and for example, carbon fiber woven cloth may be used as such a base member.

FIGS. 3A and 3Bshow one example of the single cell20in an enlarged manner.

The single cell (single cell module)20is constituted by a membrane-electrode-frame assembly (MEA (membrane-electrode assembly))15that has an electrode unit1E configured by a rectangular polymer electrolyte membrane1ato one of the surfaces of which an anode electrode1bis joined, with a cathode electrode1cbeing joined to the other surface of the electrolyte membrane1a, and gas supply units2xand2y(seeFIGS. 8A to 8C) that are used for supplying a fuel gas and an oxidizing agent gas respectively to the anode electrode1band the cathode electrode1c, and placed on the peripheral edge portion of the electrode unit1E, and is also provided with a rectangular frame member2, made of a rigid member, and used for forming manifolds, and a pair of separators5band5cthat sandwich the electrode unit1E and the membrane-electrode-frame assembly15from the anode side and the cathode side, and these single cells20are laminated so that a polymer electrolytic fuel cell101is constructed.

In the above-mentioned structure, for example, the peripheral edge portion of the polymer electrolyte membrane1ais inserted to a slit2aof the frame member2for insertion of the polymer electrolyte membrane, and sandwiched therein so that the polymer electrolyte membrane1aand the frame member2are mechanically combined with each other. Moreover, the anode electrode1band the cathode electrode1care bonded to and secured on the two surfaces of the polymer electrolyte membrane1a.

In this manner, the MEA (membrane-electrode assembly)15is formed by bonding the anode electrode1band the cathode electrode1cto the two surfaces of the polymer electrolyte membrane1ato be secured thereon, and this MEA (membrane-electrode assembly)15is sandwiched by the pair of separators5band5cso that the above-mentioned single cell20is formed. In the single cell20, the separator5bon the anode electrode side faces the anode electrode1b, and the separator5con the cathode electrode side faces the cathode electrode1c.

As shown inFIGS. 3C and 3D, in the case of the single cell after the assembling process, with no elastic member attached thereto, which will be described below, a gap6in a range of from 0.1 mm to 10 mm is formed between each of the outer edge of the anode electrode1band the outer edge of the cathode electrode1cand each of the inner edges2band2cof the frame member2. When this gap6is present, a phenomenon, referred to as cross-leak, occurs in which one portion of the gas supplied into the fuel cell is discharged through this gap6. In order to eliminate this gap6, a method is proposed as shown inFIG. 3Ain which an anode-side elastic member4b, which has a rectangular frame-shape on the plan view and a rectangular shape on its cross section (in another example, a virtually parallelogram as shown inFIG. 4E), is placed so as to contact with both of the inner edge2bof the frame member2on the anode side and the outer edge of an anode electrode1b, and upon molding the frame member2and the anode electrode1b, the anode-side elastic member4bis integrally formed together with these. Moreover, a cathode-side elastic member4c, which has a rectangular frame-shape on the plan view and a rectangular shape on its cross section (in another example, a virtually parallelogram as shown inFIG. 4E), is placed so as to contact with both of the inner edge2cof the frame member2on the cathode side and the outer edge of a cathode electrode1c, and upon molding the frame member2and the cathode electrode1c, the cathode-side elastic member4cis integrally formed together with these. At this time, these elastic members4band4cmay be respectively placed in contact with the polymer electrolyte membrane1aand mechanically joined thereto, and need not be bonded thereto.

Upon laminating the separators5band5con the frame member2to be assembled thereon with the elastic members4band4cbeing installed therein, as shown inFIG. 3B, the frame member assembled surface9of the frame member2and the respective separator assembled surfaces10of the separators5band5care respectively placed close to each other, and at this time, the elastic members4band4care placed, with a gap8between the elastic members4b,4cand the opposing surfaces of the separators5b,5cbeing made smaller than a gap7between the frame member2and the separators5b,5c. With this arrangement, during the assembling process, the elastic members4b,4care positively placed in contact with the separators5band5cso that the elastic deformations thereof are started, before the frame member assembled surface9of the frame member2and the respective separator assembled surfaces10of the separators5b,5chave been placed at the closest positions (seeFIG. 3B). Moreover, upon completion of the assembling process, in other words, after the frame member assembled surface9of the frame member2and the respective separator assembled surfaces10of the separators5b,5chave been placed at the closest positions, as shown inFIG. 3B, the elastic members4band4care pressed by the separators5band5cinto elastically deformed states so that the elastic members4band4care subjected to compressing forces imposed from the separators5band5c. At this time, as indicated by reference numeral6G inFIG. 3A, before and after the assembling processes of the elastic members4band4c, the elastic members4band4care mutually widened along the separator assembled surfaces10by a dimension6G so that gaps between the elastic members4b,4cand step portions5b-1,5c-1of the separators5b,5con the separator assembled surface10(in other words, gaps through which one portion of gas supplied into the fuel cell is discharged) can be eliminated prior to the assembling process, thereby making it possible to effectively suppress the cross-leak phenomenon.

However, as shown inFIG. 3E, a slight gap6H might remain due to an error in assembling precision in some cases, and in such a case, as shown inFIG. 3FandFIGS. 4A to 4B, moderate inclined surfaces5fand5gare formed on the step portions5b-1and5c-1(seeFIG. 3A) of the separators5band5con the separator assembled surface10from the outside of the separators5band5cinFIG. 3Ftoward the inside thereof. Here, in association with these inclined surfaces5fand5g, an anode-side inclined surface4b-2and a cathode-side inclined surface4c-2having virtually the same inclined angle are formed on the elastic members4band4cwith cross-sectional shapes as shown inFIG. 3F, along the entire circumferences thereof in the shapes on the plan view. As a result, as shown inFIGS. 3F to 3Gas well as inFIGS. 4A to 4D, upon assembling the separators5band5con the frame member2so as to be laminated thereon, with the elastic members4band4cbeing attached thereto, before the frame member assembled surface9of the frame member2and the respective separator assembled surfaces10of the separators5band5c, whose opposing inclined surfaces are virtually kept in parallel with each other, have been placed at the closest positions (seeFIG. 3GandFIG. 4D), the elastic members4band4care positively placed in contact with the separators5band5cso that elastic deformations thereof are started. At this time, the inclined surfaces4b-2and4c-2of the elastic members4band4care placed in contact with the inclined surfaces5fand5gof the separators5band5c, and upon completion of the assembling process, in other words, after the frame member assembled surface9of the frame member2and the respective separator assembled surfaces10of the separators5b,5chave been respectively placed at the closest positions, as shown inFIGS. 3G and 4D, the elastic members4band4care pressed by the separators5band5cinto elastically deformed states respectively so that the elastic members4band4care subjected to compressing forces imposed from the separators5band5c, while the inclined surfaces4b-2and4c-2of the elastic members4band4care placed in tight contact with the inclined surfaces5fand5gof the separators5band5c, with the compressing forces being applied thereto. Therefore, such a slight gap6H that might be caused by an error in assembling precision can be eliminated so that it becomes possible to suppress a cross-leak phenomenon from occurring in the inner edge portion of the frame member, and consequently to further effectively restrain the cross-leak phenomenon as a whole.

With respect to the inner edges of the elastic members4band4c, upon laminating the separators5band5con the frame member2to be assembled thereon, even when the elastic members4band4ccome into contact with the separators5band5c, the possibility of the separators5band5cbeing damaged is low because of the elastic force of the elastic members4band4c; therefore, the gap6G between the separators5b,5cand the elastic members4b,4ccan be made narrower than that in the conventional structure without the elastic members. Depending on cases, even when the distance of the gap6G is zero, no issue arises because the elastic members4band4care prepared.

Moreover, another example is proposed in which, as shown inFIGS. 4E and 4F, an anode-side inclined surface4b-3and a cathode-side inclined surface4c-3are respectively prepared on the entire circumferences of the elastic members4band4c, and anode-side ribs4dand cathode-side ribs4ethat protrude for use in preventing a short-cut may be respectively formed on the anode-side inclined surface4b-3and the cathode-side inclined surface4c-3. The ribs4dand4eare formed respectively on the inclined surfaces4b-3and4c-3at predetermined intervals as protrusions integrally formed thereon. As shown inFIGS. 4G and 4H, upon assembling the single cells, these ribs4dand4eare compressed and elastically deformed by the anode-side inclined surface4b-3and the cathode-side inclined surface4c-3as well as by the inclined surfaces5fand5gof the separators5band5made virtually in parallel therewith so that they are placed in tight contact with the separators5band5cto prevent the gas leakage. When the respective ribs4dand4eare compressed and elastically deformed, the elastically deformed portions thereof are allowed to escape into an anode-side concave section (compressed volume releasing portion)4fbetween the adjacent anode-side ribs4dor a cathode-side concave section (compressed volume releasing portion)4gbetween the adjacent cathode-side ribs4e. As shown inFIG. 4I, these concave sections4fand4gare designed so that upon assembling the single cells, the anode-side elastic member4band the cathode-side elastic member4ccan be respectively compressed by the separators5band5cby, for example, 0.1 mm, with the anode-side rib4dand the cathode-side rib4ebeing respectively compressed by, for example, 0.05 mm. Here, the total volume of the anode-side concave section4fis set so as to be virtually equal to the total sum of the volume of the entire circumference of the rectangular-frame-shaped anode-side elastic member4bon the plan view and the total volume of the ribs4dplaced in the longitudinal direction of the anode-side elastic member4bat predetermined pitch intervals. In other words, this structure means that, when, upon assembling the single cell, compressed and elastically deformed between the separator5band the edge portion of the frame member2, both of the elastically deformed portion of the anode-side elastic member4band the elastically deformed portion of the rib4dare inserted into the anode-side concave section4fso that the anode-side concave section4fis filled with the elastically deformed portions without virtually any gap, and sealed. In the same manner, the total volume of the cathode-side concave section4gis set so as to be virtually equal to the total sum of the volume of the entire circumference of the rectangular-frame-shaped cathode-side elastic member4con the plan view and the total volume of the ribs4eplaced in the longitudinal direction of the cathode-side elastic member4cat predetermined pitch intervals. In other words, this structure means that, when, upon assembling the single cell, compressed and elastically deformed between the separator5cand the edge portion of the frame member2, both of the elastically deformed portion of the cathode-side elastic member4cand the elastically deformed portion of the rib4eare inserted into the cathode-side concave section4gso that the cathode-side concave section4gis filled with the elastically deformed portions without virtually any gap, and sealed. With this arrangement, after the separators have been assembled, no gaps are left in the concave sections4fand4g, thereby making it possible to effectively prevent the gas leakage.

Here, the bottom surface of the anode-side concave section4fand the bottom surface of the cathode-side concave section4gare respectively formed into the above-mentioned anode-side inclined surface4b-3and cathode-side inclined surface4c-3of the elastic members4band4c.

As shown inFIGS. 8A to 8C, at least one pair of manifold holes15bfor fuel gas, manifold holes15afor oxidizing agent gas and manifold holes15cfor cooling water are formed in the frame member2, and a plurality of through holes16used for inserting bolts (not shown) for mutually fastening the single cells20are also formed therein. An oxidizing agent gas is supplied to and discharged from the cathode electrode1cside through the pair of manifold holes15afor oxidizing agent gas of the frame member2. A fuel gas is supplied to and discharged from the anode electrode1bside through the pair of manifold holes15b. Moreover, cooling water is supplied to and discharged from the pair of manifold holes15cbetween the back surfaces of the separators5band5cof the adjacent single cells20facing with each other.

As shown inFIG. 8C, on a frame member assembled surface9corresponding to the surface with the cathode electrode1cformed thereon in the frame member2, a gasket3c, which includes the manifold holes15afor oxidizing agent gas and oxidizing agent gas flow passages (gas flow passages)2yand surrounds the entire area that allows the oxidizing agent gas to pass on the cathode electrode1cso as to form the manifold for oxidizing agent gas, is formed in a manner so as to form a semi-circular shaped convex portion in its cross section, with a rectangular frame shape on the plan view. Moreover, as shown inFIG. 8B, on a frame member assembled surface9corresponding to the surface with the anode electrode1bformed thereon in the frame member2, a gasket3b, which includes the manifold holes15bfor fuel gas and fuel gas flow passages (gas flow passages)2xand surrounds the entire area that allows the fuel gas to pass on the anode electrode1bso as to form the manifold for fuel gas, is formed in a manner so as to form a semi-circular shaped convex portion in its cross section, with a rectangular frame shape on the plan view. Moreover, the gaskets3band3care formed so as to be separated from the areas (manifolds) that allow the respective gases to pass, and allowed to surround only the manifold hole15cfor cooling water. Therefore, in the assembled state of the single cells, the gaskets3band3care respectively inserted into the concave sections5dand5eon the separator assembled surface10of the separators5band5c, and placed in contact therewith to be elastically deformed so that leakages of the fuel gas and the oxidizing agent gas as well as leakage of the cooling water are prevented independently on the cathode side and anode side respectively (seeFIGS. 4D,4H, etc.).

Moreover, on the surface of the cathode electrode1cof the MEA (membrane-electrode assembly)15, as shown inFIGS. 9A and 9B, a gas flow passage19from the manifold hole15afor oxidizing agent gas toward the cathode electrode1cside is designed in such a manner that a gas flow passage portion4c-1that is one portion of the frame shaped cathode-side elastic member4cand corresponds to the gas flow passage portion2yof the frame member2is made lower to the same level as the thickness of the frame member2, and with respect to a gas flow passage portion of the cathode-side separator5cthat faces the gas flow passage portion4c-1of the cathode-side elastic member4c, a gas flow passage concave section5c-1(a concave section corresponding to a parallelogram shaped portion with slanting lines indicated by reference numeral5c-1inFIG. 8A, and this portion with the slanting lines actually forms a space) is formed. Consequently, in the assembled state of the single cells, a space used for supplying gas is positively formed between the gas flow passage portion4c-1of the cathode-side elastic member4cand the cathode-side separator5c. Here, preferably, no cathode-side rib4eis placed near the gas flow passage portion4c-1of the cathode-side elastic member4cso as to ensure the gas flow passage.

Moreover, the same structure is formed also on the anode side, and on the surface of the anode electrode1bof the MEA (membrane-electrode assembly)15, a gas flow passage19from the manifold hole15bfor fuel gas toward the anode electrode1bside is designed in such a manner that a gas flow passage portion4b-1(seeFIG. 8B, the portion similar to the gas flow passage portion4c-1ofFIGS. 8A and 8C) that is one portion of the frame shaped anode-side elastic member4band corresponds to the gas flow passage portion2xof the frame member2is made lower to the same level as the thickness of the frame member2, and on a gas flow passage portion of the anode-side separator5bthat faces the gas flow passage portion4b-1of the anode-side elastic member4b, a gas flow passage concave section5b-1(not shown, the same as the gas flow passage concave section5c-1ofFIG. 8A) is formed. Consequently, in the assembled state of the single cells, a space used for supplying gas is positively formed between the gas flow passage portion4b-1of the anode-side elastic member4band the cathode-side separator5b. Here, preferably, no anode-side rib4dis placed near the gas flow passage portion4b-1of the cathode-side elastic member4bso as to ensure the gas flow passage.

With respect to the material for the elastic members4b,4cand the ribs4d,4e, for example, a thermoplastic resin elastomer is preferably used. The reason for this is explained as follows: if a thermoplastic resin was used as the elastic members4band4c, the electrodes1band1cwould be impregnated with the thermoplastic resin to the inside thereof, because of its high flowability (see arrow66), and this might make the effective area of each of the portions of the electrodes1band1csmaller (seeFIG. 8D). In contrast, in the case when a thermoplastic resin is used for the elastic members4band4cas in the present embodiment, when, upon molding, the flowing fused resin is placed in contact with the electrodes1band1c, it is quickly cooled and solidified so that the insides of the electrodes1band1care not impregnated with the resin; thus, no adverse effects are given to the effective area of the portion of each of the electrodes1band1c, and it becomes possible to form a precise seal (in other words, a seal having a desired shape providing a superior transferring property) that matches the shape of the joining portions between the frame member2and the electrodes1band1cby utilizing the molding pressure.

Examples of specific materials for the elastic members, ribs and gaskets include M3800, which is a high hardness product of MILASTOMER (registered trademark) made by Mitsui Chemicals, Inc., and one kind of olefin-based thermoplastic resin elastomer. Here, with respect to the elastic members and ribs, conditions for allowing them to have respective elastic deformations are given by the elasticity of A50 to A90 or D37 to D60, defined by JIS K 6253 (ISO 7619).

Specific examples of the material for the frame member2include R-250G or R-350G made by Prime Polymer Co., Ltd., and with respect to the separators5band5c, a metal material obtained by surface-treating metal such as stainless steel (SUS) with gold plating or a metal material obtained by surface-treating titanium with gold plating may be used, and specific examples of the materials for the separators5band5cinclude a resin impregnated graphite plate (glassy carbon made by Tokai Carbon Co., Ltd.) having an outside dimension of 120 mm×120 mm and a thickness of 3.0 mm. Here, in particular, with respect to the material for use in automobiles, a metal separator or the like, formed by subjecting stainless steel (SUS) to a surface treatment, may be preferably used.

With respect to the effects obtained by the presence of the frame member2, in addition to the effect by which the manifolds are formed, the handling of the parts is made easier, and the separators5band5ccan be contact-stopped by the frame member2; thus, the contact pressure between the separators5b,5cand the electrodes1b,1ccan be optimally maintained. For example, in the case when, as shown inFIG. 8E, the gaskets3band3care directly placed on the polymer electrolyte membrane1awithout using the frame member2, since the electrodes1band1care soft, the gaskets3band3chave become squashed after a long-term use as shown inFIG. 8F(initial state) andFIG. 8G(after a long-term use) so that the gap dimension between the separators5band5cis gradually narrowed to make the separators5band5ccome into contact with the electrodes1band1cwith a higher contacting force (see arrow67in the drawing). At this time, as shown inFIGS. 8H and 8I, the separators5band5care placed in contact with the frame member2to be stopped therein so that the gap dimension68between the separators5band5ccan be maintained stably with respect to the long-term compressing load.

When, upon assembling the single cells20, the separators5band5care stacked on a membrane-electrode-frame assembly15, the elastic members4band4cand the ribs4dand4eare respectively compressed by the separators5band5c, as shown inFIGS. 3B,4G and4H. As a result, since the polymer electrolyte membrane1ais pressed along the thickness direction of the polymer electrolyte membrane1aby compressing forces of the elastic members4band4c, the gap12(seeFIG. 3A) between the elastic members4b,4cand the polymer electrolyte membrane1ais positively sealed by this pressing force and the elastic forces of the elastic members4band4c, even when the polymer electrolyte membrane1aand the elastic members4band4care not bonded to each other. Moreover, by utilizing the elastic deformations of the elastic members4b,4cand the ribs4d,4ebetween the separators5b,5cand the frame member2, a gap6(seeFIG. 3D) between each of the outer edges of the anode electrode1band the cathode electrode1cand each of the inner edges2b,2cof the frame member2can be made greatly smaller in comparison with those of the conventional example so that the space of the gap6can be made greatly smaller or the gap6can be eliminated.

Here, in accordance with the first embodiment, the anode-side elastic member4bhaving a frame shape on the plan view and the cathode-side elastic member4chaving a frame shape on the plan view, as well as a number of anode-side ribs4dand cathode-side ribs4eplaced at predetermined intervals, are respectively placed on the edge portion inside the frame2that holds the polymer electrolyte membrane1aor the like; therefore, upon assembling the single cells20, the anode-side elastic member4band each of the anode-side ribs4bare elastically deformed respectively in a direction orthogonal to the thickness direction of the membrane-electrode-frame assembly15, with the elastically deformed portions being respectively inserted into the anode-side concave section (compressed volume releasing section)4fthat is a space formed between the adjacent anode-side ribs4d, so that the elastically deformed anode-side elastic member4band the elastically deformed anode-side ribs4dare virtually continuously placed in tight contact in the gap between the frame member2and the anode-side separator5bto seal the gap, thereby making it possible to exert a sealing effect. Moreover, on the cathode side also, upon assembling the single cells20, the cathode-side elastic member4cand each of the cathode-side ribs4care elastically deformed respectively between the frame member2and the cathode-side separator5c, with the elastically deformed portions being respectively inserted into the cathode-side concave section (compressed volume releasing section)4gthat is a space formed between the adjacent cathode-side ribs4d, so that the elastically deformed cathode-side elastic member4cand the elastically deformed cathode side ribs4eare virtually continuously placed in tight contact in the gap between the frame member2and the cathode-side separator5cto seal the gap, thereby making it possible to exert a sealing effect.

As a result, the frame member2and the anode-side separator5bas well as the cathode-side separator4care respectively placed in tight contact and sealed with each other by the elastically deformed anode-side elastic member4band the elastically deformed anode-side ribs4das well as by the elastically deformed cathode-side elastic member4cand the elastically deformed cathode-side ribs4eso that it becomes possible to effectively restrain a cross-leak phenomenon that occurs through the gap12(seeFIG. 3A) between the polymer electrolyte membrane1aand the frame member2(a phenomenon in which a cross-leak as indicated by an arrow18inFIG. 8Aoccurs in the conventional example), and also to prevent a short-circuiting flow of a reducing agent gas11aalong the edge portion of the frame member2and a short-circuiting flow of an oxidizing agent gas11balong the edge portion of the frame member2(seeFIG. 3A) respectively; thus, it becomes possible to further improve the rates of utilization of the reducing agent gas11aand the oxidizing agent gas11b, respectively, and consequently to further enhance the performance of a polymer electrolyte fuel cell.

Second Embodiment

FIG. 5Ais a schematic cross-sectional view that schematically shows a structure of single cells of a fuel cell provided with a stack for a fuel cell in accordance with a second embodiment of the present invention.

In the second embodiment, the aforementioned single cell of the first embodiment is designed in such a manner that the inclined surface5fof the anode-side separator5band the inclined surface5gof the cathode-side separator5care not formed into an entirely circumferential frame shape on the plan view, but formed as a partial portion. Moreover, in the first embodiment, the anode-side inclined surface and the cathode-side inclined surface of the elastic members4band4care prepared as the bottom surface of the anode-side concave section4fand the bottom surface of the cathode-side concave section4g; however, not limited by this structure, these may be prepared as the surface of the anode-side rib4dand the surface of the cathode-side rib4e. Furthermore, not limited to the structure in which the bottom surface of the anode-side concave section4fand the bottom surface of the cathode side concave section concave section4g, or the surface of the anode-side rib4dand the surface of the cathode side rib4eare virtually placed in parallel with the inclined surface s5fand5gof the separators5band5c, the inclined angles may be slightly different from each other, as long as, in short, the above-mentioned tight contact sealing effect, obtained by the elastic deformations of the anode-side rib4dand the cathode-side rib4e, is exerted upon assembling the single cells.

With this arrangement, upon stacking the separators5band5con the membrane-electrode-frame assembly15, a tightly contacting and sealing process is carried out stably not only on the upper surfaces of the elastic members4band4c, but also on the inclined surface sides of the elastic members4band4cby using the anode-side rib4dand the cathode-side rib4e, so that it becomes possible to further improve the blocking properties for the reducing agent gas11aand the oxidizing agent gas11b, and also to allow these inclined surfaces to exert a guiding function for making easier the relative positioning process between the membrane-electrode-frame assembly15and the separators5b,5c, upon laminating and assembling the single cells; thus, it becomes possible to improve the assembling property.

Modified Examples

The present invention is not intended to be limited by the above-mentioned embodiments, and various modified modes may be carried out.

For example, in the polymer electrolyte membrane1aof each of the embodiments, in addition to the integrally-molded structure by using the elastic members4band4c, one more reinforcing membrane13(seeFIGS. 5A and 5B) may be placed to protect the anode electrode1band the cathode electrode1c, and the same effects can be obtained.

Moreover, another modified example may be used in which in each of the embodiments, at portions where the anode-side elastic member4band the cathode-side elastic member4care placed, since the same sealing effect for gases as that of the gaskets3band3cis obtained by the elastically deforming effect thereof, the reducing agent gas11aand the oxidizing agent gas11bare respectively sealed so that no gaskets3band3care required on the outer circumferential portion.

Still another modified example may be used in which in each of the embodiments, as shown inFIG. 6, an elastic member4hthat is the same as the elastic member4bor4cis placed only on one of the sides of the anode-side frame assembled surface9and the cathode-side frame assembled surface9of the frame member2partially or along the entire circumference, and on the other of the anode-side frame assembled surface9and the cathode-side frame assembled surface9, an extended portion2h, formed by extending the frame member2toward the center in the inner edge direction, may be placed so as to receive a compressing pressure from the elastic member4hupon stacking the separators5band5c. In this manner, even by the use of only one of the elastic members4h, the corresponding effect can be obtained, and since it is only necessary to place the elastic member4honly on one of the sides of the anode-side frame assembled surface9and the cathode-side frame assembled surface9of the membrane-electrode-frame assembly, the manufacturing processes become easier. In this case, as shown inFIG. 6, in order to form the extended portion2h, the position of the outer edge of the cathode electrode1cis set on the inner side from the position of the outer edge of the anode electrode1b.

Additionally, in this still another modified example, another modified example or the embodiments (except for those ofFIGS. 5A and 5B), no reinforcing membrane13is required.

Moreover, still another modified example may be used in which in each of the embodiments, as shown inFIG. 7A, by mutually shifting the positions of the elastic members4band4con the above-mentioned one side with respect to the frame member assembled surface9on the anode side and the frame member assembled surface9on the cathode side of the frame member2in the membrane-electrode-frame assembly, the molding pressure at the time of the integrally molding process can be easily received so that the deformation resistant strength of each of the elastic members4band4cagainst a molding pressure at the time of the molding process can be made smaller; thus, it becomes possible to enhance the degree of freedom in designing the single cell20. In this case also, the elastic members4band4cmay be placed partially or along the entire circumference. In this case also, as shown inFIG. 7A, in order to form the extended portion2h, the position of the outer edge of the cathode electrode1cis set on the inner side from the position of the outer edge of the anode electrode1b.

A specific example is proposed in which, as shown inFIG. 7A, in order to shift the positions of the elastic members4band4cby placing the position of the outer edge of the cathode electrode1con the inner side from the position of the outer edge of the anode electrode1b, the sizes of the anode electrode1band the cathode electrodes1cmay be made different from each other, as shown inFIGS. 7B to 7D. For example, a square shaped cathode electrode1cmay be made greater than a square shaped anode electrode1b.

Each of the structures ofFIGS. 7B to 7Dprovides a typical basic example of another modified example shown inFIG. 7A, and has a shape in which the elastic members4band4care simply placed on the entire circumference of the frame member2respectively, which provides a simplified structure.

Moreover, another specific example is proposed in which, as shown inFIG. 7A, in order to place the position of the outer edge of the cathode electrode1con the inner side from the outer edge of the anode electrode1bso that the positions of the elastic members4band4care shifted from each other, although the sizes of the anode electrode1band the cathode electrode1care the same as shown inFIGS. 7E to 7G, the layout positions thereof may be made different from each other. For example, a square shaped cathode electrode1cand a square shaped anode electrode1bhaving the same size may be shifted in their positions in a diagonal direction inFIG. 7F.

In accordance with the structures ofFIGS. 7E to 7G, the following effects are obtained. That is, in contrast to the structures ofFIGS. 7B to 7Din which the sizes of the anode electrode1band the cathode electrode1care made different, the structures ofFIGS. 7E to 7Gonly require, for example, one kind of a pressing mold so that the manufacturing process of electrodes can be made easier, with the circumferential lengths of the elastic members4band4cbeing made equal to each other, thereby making it possible to improve the moldability.

Moreover, another specific example is proposed in which in order to shift the position of the elastic member4coutside the cathode electrode1cand the position of the elastic member4boutside the anode electrode1bas shown inFIG. 7A, the sizes of the anode electrode1band the cathode electrode1cmay be made different from each other, as shown inFIGS. 7H to 7J, with the respective shapes being formed not into quadrangular shapes, but into shapes, each having flange portions that partially extend alternately at outer edges of the anode electrode1band the cathode electrode1c, while the layout positions of the elastic members4band4clocated on the outsides of the respective anode electrode1band the cathode electrode1cmay be formed not into a square shape, but into a zigzag shape along the outer edge of each of the electrodes1band1c. For example, the cathode electrode1cmay be made greater than the anode electrode1b, while the elastic member4cplaced along the outer edge of the cathode electrode1cin a zigzag shape and the elastic member4bplaced along the outer edge of the anode electrode1bin a zigzag shape are allowed to intersect with each other at predetermined intervals to be placed on the inner side and the outer side alternately. Here,FIG. 7Iis a schematic cross-sectional view showing a single cell of the stack for a fuel cell prior to an assembling process as well as prior to a molding process of an elastic member, and in this drawing, a gap6iused for forming the elastic member4band a gap6jused for forming the elastic member are continuously formed into a frame shape.FIG. 7Jis a schematic cross-sectional view showing a state in which the elastic members4band4care respectively molded and formed into the respective frame-shaped gaps6iand6j.

In accordance with the structures shown inFIGS. 7H to 7J, the centers of the anode electrode1band cathode electrode1ccan be made coincident with each other in comparison with the examples ofFIGS. 7E to 7Gso that the product can be well-balanced as a whole.

Furthermore, still another specific example is proposed in which in order to shift the position of the elastic member4coutside the cathode electrode1cand the position of the elastic member4boutside the anode electrode1bas shown inFIG. 7A, the sizes of the anode electrode1band the cathode electrode1cmay be made different from each other, as shown inFIGS. 7K to 7M, with the cathode electrode1cbeing allowed to clearly protrude from the longer side (or the shorter side) of the anode electrode1b.

As described above in various ways, by shifting the position of the elastic member4bon the anode electrode1bside and the position of the elastic member4con the cathode electrode1cside, the molding pressure at the time of the integrally molding process can be easily received so that the deformation resistant strength of each of the elastic members4band4cagainst the molding pressure at the time of the molding process can be made smaller and the deformation of the polymer electrolyte membrane1acan be prevented, and the following description will discuss these effects in detail.

As shown inFIG. 11A, in the case when no shift is prepared between the positions of the elastic member4bon the anode electrode side and the elastic member4con the cathode electrode side, an anode electrode1bis placed in a mold61bon the anode electrode side, with a cathode electrode1cbeing placed in a mold61con the cathode electrode side, and the mold61bon the anode electrode side and the mold61con the cathode electrode side are clamped as shown inFIG. 11B, with a frame member2and a polymer electrolyte membrane1abeing sandwiched between the mold61bon the anode electrode side and the mold61con the cathode electrode side. Next, as shown inFIG. 11C, when fused resin is injected into the mold61bon the anode electrode side and the mold61con the cathode electrode side thus clamped, the pressure of the fused resin is received only by the polymer electrolyte membrane1ain a cavity61gwhere the elastic members4band4cface with each other. In this case, since the polymer electrolyte membrane1ais insufficient in strength, the polymer electrolyte membrane1amight be deformed by the pressure of the fused resin as indicated by reference numeral62inFIG. 11C.

In contrast, as shown inFIG. 11D, in the case when a shift is made between the positions of the elastic member4bon the anode electrode side and the elastic member4con the cathode electrode side, an anode electrode1bis placed in a mold61don the anode electrode side, with a cathode electrode1cbeing placed in a mold61eon the cathode electrode side, and the mold61don the anode electrode side and the mold61eon the cathode electrode side are clamped as shown inFIG. 11E, with a frame member2and a polymer electrolyte membrane1abeing sandwiched between the mold61don the anode electrode side and the mold61eon the cathode electrode side. Next, as shown inFIG. 11F, when fused resin is injected into the mold61don the anode electrode side and the mold61eon the cathode electrode side thus clamped, the fused resin is received by the mold61eplaced behind the polymer electrolyte membrane1ain a cavity61hof the elastic member4b, and in a cavity61iof the elastic member4c, the fused resin is received by the extended portion2hof the frame member2placed behind the polymer electrolyte membrane1aand the mold61don the anode electrode side. Therefore, the surfaces to receive the resin pressure at the time of the molding process are provided by the mold or the frame member2supported by the mold so that the polymer electrolyte membrane1ais not deformed.

Here, still another specific example may be proposed in which, in each of the above-mentioned embodiments, as shown inFIGS. 10A and 10B, the elastic members4band4care placed not on the frame member2, but on the separators5band5c.

Moreover, still another specific example is proposed in which, in each of the above-mentioned embodiments, the elastic members4band4care placed in the frame member2as shown inFIGS. 10C and 10D, and elastic members45band45c, which are allowed to come into contact with the elastic members4band4cto be placed in press-contact therewith, may also be placed on the separators5band5c. The elastic members45band45c, placed on the separators5band5c, are provided with inclined surfaces45b-1and45c-1that are the same as the inclined surfaces5fand5gof the separators5band5cso that the same functions are exerted.

The following description will discuss examples in which a polymer electrolytic fuel cell in accordance with the first embodiment is used.

InFIG. 5AandFIG. 8A, a polymer electrolyte membrane1awas formed by punching out a resin material, such as “Nafion (registered trademark) N-117 made by Du Pont de Nemours and Company, having a thickness of 50 μm by using a Thompson mold. To each of the surfaces of this polymer electrolyte membrane1awere joined an anode electrode1band a cathode electrode1c, and by using this polymer electrolyte membrane1a/electrode assembly15as an inserted part, a frame member2was resin-molded by using glass-fiber-added polypropylene (for example, R250G, made by Idemitsu Kosan Co., Ltd.).

In the frame member2thus formed, as shown inFIG. 8A, at least, respective pairs of manifold holes15bfor fuel gas, manifold holes15afor oxidizing agent gas and manifold holes15cfor cooling water were formed, and a plurality of through holes16used for inserting fastening bolts for cells thereto were also formed.

The frame member2was further provided with a gasket3c, formed on a frame member assembled surface9corresponding to the surface with the cathode electrode1cformed thereon, which includes manifold holes15afor oxidizing agent gas and oxidizing agent gas flow passages2y, surrounds the entire area that allows the oxidizing agent gas to pass on the cathode electrode1c, and also surrounds the manifold holes15cfor cooling water. Moreover, the frame member2was also provided with a gasket3b, formed on a frame member assembled surface9corresponding to the surface with the anode electrode1bformed thereon, which includes manifold holes15bfor fuel gas and fuel gas flow passages2x, surrounds the entire area that allows the fuel gas to pass on the anode electrode1b, and also surrounds the manifold holes15cfor cooling water. With respect to a gas flow passage19that is directed from each of the manifold hole15bfor fuel gas and the manifold hole15afor oxidizing agent gas toward each of the electrodes on each of the two surfaces of the anode electrode1band the cathode electrode1c, as shown inFIG. 9, gas flow passage portions4b-1and4c-1that form portions of the frame-shaped elastic members4band4c, and correspond to the gas flow passage portions2xand2yof the frame member2, are made lower to the same level as the thickness of the frame member2, and on gas flow passage portions of the separators5band5cthat face the gas flow passage portions4b-1and4c-1of the elastic members4band4c, gas flow passage concave sections5b-1and5c-1are formed, with reinforcing ribs4dand4ebeing formed in the gas flow passage direction.

In this example, each of the electrodes1band1chad an outer edge of 120 mm in square and a thickness of 0.5 mm, and the frame member2had a thickness of 2 mm and an inner edge of 125 mm in square. Moreover, by molding a thermoplastic resin elastomer between the outer edge of the electrode and the inner edge of the frame member, the electrodes1band1cand the frame member2were integrally formed. With respect to the elastic members4band4c, a thermoplastic resin elastomer was used, and with an initial thickness of 2.2 mm, the joined surfaces of the elastic members4band4cto the separators5band5cwere set to the same surface as that of the frame member2by the separators5band5c; thus, the compressed amount of the elastic member at the time of the laminating process was set to 0.10 mm respectively on the anode electrode side as well as on the cathode electrode side.

The inclined surface toward the electrode surface on the inner edge side of each of the elastic members4band4cis formed so as to be inclined by 30 degrees with respect to a direction orthogonal to the polymer electrolyte membrane1a.

The membrane-electrode-frame assembly15, thus manufactured, was sandwiched by the anode-side separator5band the cathode side separator5cfrom the two sides so that a single cell20was formed.

Fifty cells of these single cells20were laminated, and on each of the ends of the laminated fifty cells, a collector plate21made from metal, an insulating plate22made from an electric insulating material and an end plate23were secured by using a fastening rod; thus, hydrogen and air were supplied thereto, with cooling water being circulated, so that a fuel cell test was carried out. As a result, the gas utilization rate was improved by 6% in comparison with that of the structure without using the elastic members.

By properly combining the arbitrary embodiments of the aforementioned various embodiments, the effects possessed by the embodiments can be produced.

INDUSTRIAL APPLICABILITY

A solid polymer electrolytic fuel cell in accordance with the present invention makes it possible to effectively restrain a cross-leak phenomenon that occurs in the gap between the polymer electrolyte membrane and the frame member, and consequently to further improve the utilization rates of a reducing agent gas and an oxidizing agent gas; thus, the resulting fuel cell is effectively used as a polymer electrolytic fuel cell having further improved performance.