1. Field of the Invention
The present invention relates to a sealing structure pinching a membrane-electrode assembly by gaskets which are integrally provided in separators which are arranged in both sides in a thickness direction of the same, in a fuel cell.
2. Description of the Conventional Art
The fuel cell has a structure obtained by alternately arranging a membrane-electrode assembly (MEA) provided with a pair of catalyst electrode layers on both surfaces of a high polymer electrolyte membrane and porous gas diffusion layers (GDL) laminated in both sides in a thickness direction thereof, and a separator made of a carbon or a metal so as to laminate, circulates a fuel gas and an oxidation gas to both surfaces of the membrane-electrode assembly, and generates an electric power on the basis of an electrochemical reaction corresponding to a reverse reaction to an electrolytic process of a water, that is, a reaction creating a water from a hydrogen and an oxygen.
In this kind of fuel cell, there is provided with a sealing structure for sealing the fuel gas and the oxidation gas, the water created by the reaction and the surplus oxidation gas, a cooling medium and the like. FIG. 8 is a partial cross sectional view which shows a sealing structure of a fuel cell in accordance with a prior art in a separated state. In this FIG. 8, reference numeral 110 denotes a membrane-electrode assembly which is constructed by a high polymer electrolyte membrane, and catalyst electrode layers provided in both sides thereof and the like, and separators 120 are laminated in both sides in a thickness direction of the membrane-electrode assembly 110.
A gasket 130 integrally provided in the separators 120 in both sides in the thickness direction thereof is brought into close contact with a peripheral edge of the membrane-electrode assembly 110. The gasket 130 is made of a rubber-like elastic material (a rubber or a synthetic resin material having a rubber-like elasticity), and a seal protrusion 131 is formed for obtaining a desired surface pressure.
In this case, since the membrane-electrode assembly 110 is thin and soft, there is such a problem that a sealing performance becomes unstable due to a displacement of a surface pressure maximum portion by the seal protrusion 131, if any slight offset (displacement) δ is generated by an assembling precision. Further, even if the desired sealing performance can be secured, a reaction force of the gasket 130 greatly fluctuates on the basis of the offset δ, there is a risk that a power generating performance becomes unstable due to an influence of a power generation region (not shown) to a lamination pressure.
Then, as a sealing structure of a fuel cell in accordance with the other prior art is shown in FIG. 9 in a separated state, as a method of preventing the problem due to the offset as mentioned above, there has been known a matter that a peripheral edge of the membrane-electrode assembly 110 is pinched by the gasket 130 having the seal protrusion 131, and a gasket 140 in which a flat seal portion 141 is formed as shown in Japanese Unexamined Patent Publication No. 2008-97899.
In this case, a desired surface pressure can be secured in a seal surface by the seal protrusion 131 of the gasket 130, however, since the surface pressure is dispersed in a seal surface by the flat seal portion 141 of the gasket 140, and the surface pressure is lowered in comparison with the seal protrusion 131 side, there is such a problem that a desired seal property can not be obtained. Accordingly, in order to compensate for the reduction of the seal property mentioned above, as a sealing structure of a fuel cell in accordance with further the other prior art is shown in FIG. 10 in a separated state, there can be thought such a structure that a gasket 150 having a seal protrusion 151 and a flat seal portion 152 is provided in the separators 120 in both sides so as to form a swirl shape with each other, and the pinching of the membrane-electrode assembly 110 by the seal protrusion 151 and the flat seal portion 152 is carried out by two positions in a width direction, however, there is such a problem that a width of the gasket 150 becomes large in this case.