JP5170376B2 - Fuel cell sealing structure - Google Patents

Description

  The present invention relates to a sealing structure for sealing between a membrane electrode assembly and separators arranged on both sides thereof in a fuel cell.

  A fuel cell is a stack in which a plurality of fuel cell cells are sandwiched between separators on both sides in the thickness direction of a membrane electrode assembly (MEA) in which a pair of catalyst electrode layers are provided on both sides of a polymer electrolyte membrane (ion exchange membrane) It has become. Then, an oxidizing gas (oxygen) is supplied to one catalyst electrode layer from an oxidizing gas passage formed on one surface of each separator, and a fuel gas (hydrogen) is formed on the other surface of each separator. Electric power is generated by an electrochemical reaction that is the reverse reaction of water electrolysis, that is, a reaction that generates water from hydrogen and oxygen, which is supplied from the flow path to the other catalyst electrode layer.

  In this type of fuel cell, it is necessary to seal fuel gas, oxidizing gas, water discharged from the cathode surface, excess oxidizing gas, refrigerant, and the like, and a gasket for this purpose is provided in each fuel cell. It is well known that the gasket is made of a rubber-like elastic material and is integrally provided on the surface of the separator and is in close contact with the surface of the membrane electrode assembly.

  FIG. 9 is a partial cross-sectional view showing a fuel cell sealing structure according to the prior art in a separated state. In FIG. 9, reference numeral 110 is a polymer electrolyte membrane (proton membrane) 111 and laminated on both sides thereof. A membrane electrode assembly (MEA) including a catalyst electrode layer 112 and a gas diffusion layer (GDL) 113, and separators 120 are stacked on both sides of the membrane electrode assembly 110 to constitute the fuel cell 100. .

  In the membrane electrode assembly 110, the periphery of the polymer electrolyte membrane 111 projects from the periphery of the catalyst electrode layer 112 and the gas diffusion layer 113, and the projecting portion 111a is provided integrally with the separators 120 on both sides thereof. The gasket 130 is in close contact. The gasket 130 is made of a rubber-like elastic material, and a seal protrusion 131 is formed to obtain a required surface pressure.

  However, since the polymer electrolyte membrane 111 in the membrane electrode assembly 110 is thin and flexible, in a state where a large number of fuel cells 100 are stacked and tightened and assembled as a stack, the polymer electrolyte membrane 111 (the overhang portion 111a) is assembled. If the gaskets 130, 130 on both sides of () have an offset (displacement) due to the assembling accuracy, the required seal surface pressure cannot be secured due to the displacement δ of the surface pressure maximum due to the seal protrusion 131, The polymer electrolyte membrane 111 may be damaged by receiving a large bending moment.

Therefore, as a method of preventing the bending deformation and breakage of the polymer electrolyte membrane 111 due to such an offset, as shown in FIG. It is known that the polymer electrolyte membrane 111 is sandwiched between the gasket 130 having the gasket 130 and the gasket 140 on which the flat seal surface 141 is formed (see Patent Document 1 below).
JP 2005-276820 A

  However, in this case, although the required surface pressure can be secured on the sealing surface by the seal protrusion 131, the surface pressure is lower on the gasket 140 side where the seal surface 141 is flat compared to the seal protrusion 131 side. There is a problem that the sealability of the above cannot be obtained. Accordingly, in order to compensate for such a decrease in sealing performance, a gasket 150 having a sealing protrusion 151 and a flat sealing surface 152 is shown in FIG. It is conceivable that the separators 120 on both sides are provided symmetrically so that the polymer electrolyte membrane 111 is sandwiched between the seal protrusion 151 and the flat seal surface 152 at two places in the width direction. There is a problem that the width becomes large.

  The present invention has been made in view of the above points, and the technical problem thereof is that, in a fuel cell sealing structure, the gaskets on both sides of the membrane electrode assembly are offset due to assembly accuracy. Even if it exists, it is in making it possible to ensure a required sealing surface pressure and to suppress the bending moment to a membrane electrode composite.

  As a means for effectively solving the technical problem described above, the fuel cell sealing structure according to the invention of claim 1 is configured such that the membrane electrode assembly is integrated with a separator disposed on one side in the thickness direction. In a sealing structure sandwiched between a first gasket made of a rubber-like elastic material provided and a second gasket made of a rubber-like elastic material provided integrally with a separator disposed on the other side in the thickness direction, the first gasket comprises: The first seal protrusion is in close contact with the membrane electrode assembly, and the second gasket is in close contact with the membrane electrode assembly in an extension shape corresponding to the extension shape of the first seal protrusion. A plurality of second seal protrusions are formed, and the second seal protrusions are formed in parallel with each other at a pitch smaller than the tight width of the first seal protrusion with respect to the membrane electrode assembly.

  According to the configuration of claim 1, the first seal protrusion always sandwiches the membrane electrode assembly with one or more second seal protrusions, that is, the first seal protrusion with respect to the membrane electrode composite. Since the close region of the stripe faces one or more second seal protrusions, a large bending moment is applied to the membrane electrode assembly even if the first gasket and the second gasket have an offset due to the assembly accuracy. Does not work. Moreover, a high surface pressure can be secured locally by the second seal protrusion on the second gasket.

  According to a second aspect of the present invention, there is provided a fuel cell sealing structure according to the first aspect, wherein the second seal protrusion has a central seal protrusion having an extended shape substantially the same shape and size as the first seal protrusion. It consists of a strip and one or more other seal projections formed on both sides thereof.

  According to the configuration of claim 2, when the first gasket and the second gasket are assembled in a properly positioned state, the first seal protrusion on the first gasket faces the center seal protrusion on the second gasket. If the first gasket and the second gasket have an offset due to the assembly accuracy, the first seal protrusion may be an inner periphery or an outer periphery of the seal protrusion depending on the offset direction. Oppose each other or stride across a plurality of seal protrusions.

  According to the fuel cell sealing structure of the first or second aspect of the invention, the sandwiching of the membrane electrode assembly is caused by the first seal protrusion in the first gasket and the plurality of second seal protrusions in the second gasket. Therefore, the surface pressure is not dispersed as in the case where the sealing surface of the second gasket is flattened, and sufficient sealing performance is ensured. For this reason, it is not necessary to increase the width of the gasket, and even if the first and second gaskets have an offset due to the assembly accuracy, the bending moment to the membrane electrode assembly is suppressed. Large bending deformation and breakage can be effectively prevented.

  Hereinafter, a fuel cell sealing structure according to the present invention will be described with reference to the drawings. FIG. 1 is a partial sectional view showing a fuel cell sealing structure according to a preferred embodiment of the present invention in a separated state.

  In FIG. 1, reference numeral 10 denotes a membrane electrode assembly (MEA) having a polymer electrolyte membrane (proton membrane) 11 and a catalyst electrode layer 12 and a gas diffusion layer (GDL) 13 provided on both sides in a laminated state. The separators 20A and 20B are overlapped on both sides of the membrane electrode assembly 10 to constitute the fuel cell 1.

  In the membrane electrode assembly 10, the periphery of the polymer electrolyte membrane 11 protrudes from the periphery of the catalyst electrode layer 12 and the gas diffusion layer 13, and the protruding portion 11 a is provided integrally with one separator 20 </ b> A. By being sandwiched between one gasket 30 and a second gasket 40 provided integrally with the other separator 20B, fuel gas (hydrogen), oxidizing gas, water generated and discharged by the electrochemical reaction, Excess oxidizing gas, refrigerant, and the like are sealed so as not to leak from the respective flow paths.

  The first gasket 30 and the second gasket 40 are made of a rubber-like elastic material selected from ethylene propylene rubber (EPDM), silicone rubber (VMQ), fluorine rubber (FKM), perfluoro rubber (FFKM), and the like. .

  Of these, the first gasket 30 has a chevron-shaped first seal protrusion 31 whose tip forms an R-surface, and uses the above-mentioned liquid rubber of a rubber-like elastic material, and is subjected to normal compression molding and LIM molding. Alternatively, it can be formed by SIM molding and then attached to the surface of the separator 20A, or can be integrally formed on the surface of the separator 20A.

  On the other hand, the second gasket 40 has an extended shape corresponding to the extended shape of the first seal protrusion 31 in the first gasket 30 and is in close contact with the protruding portion 11a of the electrolyte membrane 11 of the membrane electrode assembly 10 (illustration is shown). In this example, there are five) second seal protrusions 41 (41a to 41e). Like the first gasket 30, a liquid rubber of a rubber-like elastic material is used, and normal compression molding, LIM molding or It can be molded by SIM molding and then attached to the surface of the separator 20B, or can be integrally molded on the surface of the separator 20B.

  The second seal protrusion 41 in the second gasket 40 has a tight width of the first seal protrusion 31 with respect to the protruding portion 11a of the electrolyte membrane 11 of the membrane electrode assembly 10 (for example, the width of the tip R surface of the first seal protrusion 31). ) A pitch p smaller than w is formed in parallel with the first seal protrusion 31. Each of the second seal protrusions 41 has an R surface at the tip, and the radius of curvature thereof is not more than ½ of the radius of curvature of the tip R surface of the first seal protrusion 31. Of the plurality of second seal protrusions 41a to 41e, the center seal protrusion 41c is formed in an extended shape that is substantially the same shape and size as the first seal protrusion 31, and therefore, the membrane electrode assembly 10, when the separators 20 </ b> A and 20 </ b> B (the first gasket 30 and the second gasket 40) are assembled in a properly positioned state, the first seal protrusions 31 of the first gasket 30 are connected to the second gasket 40. It faces the center seal protrusion 41c.

  FIG. 2 is a cross-sectional view showing an example of the shape of the second seal protrusion 41 of the second gasket 40. In the example shown in FIG. 2A, each of the second seal protrusions 41 has a bowl shape, and a valley bottom therebetween. The part 42 is formed flat, and in the example shown in (B), the second seal protrusion 41 and the valley bottom part 42 are formed in a wavy shape, and the example shown in (C) is the second The pitch p of the seal protrusion 41 is narrower than (A) and (B).

  The width of the second gasket 40 (the width from the outer second seal protrusions 41a to 41e) is appropriately determined in consideration of the assumed maximum offset amount.

  In the above configuration, in the state where a large number of fuel cells 1 are stacked and tightened with bolts and nuts (not shown) and assembled as a fuel cell stack, the overhanging portion 11a of the polymer electrolyte membrane 11 in the membrane electrode assembly 10 is It is sandwiched between the first seal protrusion 31 of the gasket 30 and the second seal protrusions 41 a to 41 e of the second gasket 40. At this time, regardless of whether or not the separators 20A and 20B (the first gasket 30 and the second gasket 40) are assembled in a properly positioned state, the intimate region of the first seal protrusion 31 with respect to the polymer electrolyte membrane 11 is One or more second seal ridges 41 are opposed to each other, that is, the compression force of the first seal ridge 31 always acts on one or more second seal ridges 41. Even if it exists, a big bending moment does not act on the polymer electrolyte membrane 11.

  Further, since the second gasket 40 receives the compressive force, each of the second seal protrusions 41a to 41e is crushed and the surface pressure is locally increased, so that the sealing is higher than when the seal surface is flat. Sex can be secured.

  FIG. 3 shows a state in which no offset is generated in the form of FIG. 1, that is, an uncompressed state (A) and a compressed state (B) when the first gasket 30 and the second gasket 40 are assembled in the proper positions. FIG. That is, when no offset occurs in the separators 20A and 20B (the first gasket 30 and the second gasket 40), as shown in FIG. In the compressed state shown in FIG. 3 (B), the compression force from the first seal protrusion 31 is a low-rigid thin polymer. It acts on the central second seal protrusion 41 c via the electrolyte membrane 11.

  FIG. 4 is a diagram showing the results of measuring the surface pressure on the first seal protrusion 31 side and the opposite side when compressed in the state shown in FIG. 3B, that is, in the state where no offset occurs. It is. As shown in FIG. 4, according to the configuration of FIG. 1, the surface pressure of the second seal protrusion 41 c is as high as that of the first seal protrusion 31. For this reason, the outstanding sealing performance is securable.

  FIG. 5 shows an uncompressed state (A) and a compressed state (B) when the offset is generated in the form of FIG. 1, that is, when the first gasket 30 and the second gasket 40 are assembled in a mutually shifted state. FIG. That is, as shown in FIG. 5A, when the separators 20 </ b> A and 20 </ b> B (the first gasket 30 and the second gasket 40) are offset, the first seal protrusion 31 is the second gasket 40. In the compressed state shown in FIG. 5 (B), the first seal ridge is opposed to the single or plural second seal ridges 41 at a position shifted to one side from the central second seal ridge 41c. The compressive force from 31 acts on the single or plural second seal protrusions 41 via the thin polymer electrolyte membrane 11 having low rigidity, but the deformation of the polymer electrolyte membrane 11 due to this is small. It can be suppressed.

  FIG. 6 is a diagram showing the results of measuring the surface pressure on the first seal protrusion 31 side and the opposite side when compressed in the state shown in FIG. . As shown in FIG. 6, according to the form of FIG. 1, in the state where the offset occurs, the surface pressure decreases as compared to the case where the offset does not occur as shown in FIG. 3 described above. It can be seen that the decrease is suppressed to about 10%, and that the second seal protrusion 41c has a surface pressure substantially equal to that of the first seal protrusion 31.

  7 shows, as a comparative example, an uncompressed state (A) and a compressed state (A) when the first gasket 30 having the first seal protrusion 31 and the gasket 50 on which the flat seal surface 51 is formed are assembled. B) is a cross-sectional view, and FIG. 8 is a diagram showing the results of measuring the surface pressure of the first seal protrusion 31 side and the seal surface 51 on the opposite side in the compressed state shown in FIG. 7B. . That is, as shown in FIG. 7A, since the first seal protrusion 31 in the first gasket 30 faces the flat seal surface 51 in the gasket 50, in the compressed state shown in FIG. The surface pressure on the flat seal surface 51 side is significantly lower than the surface pressure on the first seal protrusion 31 side.

  Therefore, the superiority by the form of FIG. 1 was confirmed from the above measurement result.

It is a fragmentary sectional view which shows the sealing structure of the fuel cell which concerns on preferable embodiment of this invention in the isolation | separation state. In the form of FIG. 1, it is sectional drawing which shows the example of a shape of the 2nd seal protrusion of a 2nd gasket. In the form of FIG. 1, it is sectional drawing which shows the uncompressed state (A) and compression state (B) at the time of assembling | attaching in the state in which the offset has not generate | occur | produced. In the form of FIG. 1, it is a diagram which shows the result of having measured the surface pressure of the 1st seal | sticker protrusion side in the state which has not generate | occur | produced, and the opposite side. In the form of FIG. 1, it is sectional drawing which shows the uncompressed state (A) and compression state (B) at the time of assembling | attaching in the state which offset generate | occur | produced. In the form of FIG. 1, it is a diagram which shows the result of having measured the surface pressure of the 1st seal | sticker protrusion side in the state which offset generate | occur | produced, and the opposite side. It is sectional drawing which shows the uncompressed state (A) and compression state (B) at the time of attaching the 1st gasket which has a 1st seal protrusion, and the gasket in which the flat seal surface was formed as a comparative example. It is a diagram which shows the result of having measured the surface pressure of the 1st seal protrusion side and the opposite side in the comparative example of FIG. It is a fragmentary sectional view which shows the sealing structure of the fuel cell by a prior art in a separated state. It is a fragmentary sectional view which shows the sealing structure of the fuel cell by another prior art in a separated state. It is a fragmentary sectional view which shows the sealing structure of the fuel cell by another prior art in a separated state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell 10 Membrane electrode assembly 11 Polymer electrolyte membrane 12 Catalytic electrode layer 13 Gas diffusion layer 20A, 20B Separator 30 First gasket 31 First seal protrusion 40 Second gasket 41 (41a-41e) Second seal protrusion Article

Claims (2)

  The membrane electrode assembly is provided integrally with a first gasket made of a rubber-like elastic material provided integrally with a separator arranged on one side in the thickness direction and a separator arranged on the other side in the thickness direction. In a sealing structure sandwiched by a second gasket made of a rubber-like elastic material, the first gasket has a first seal protrusion that is in close contact with the membrane electrode assembly, and the second gasket has the first seal protrusion. A plurality of second seal protrusions that are in close contact with the membrane electrode assembly in an extension shape corresponding to the extension shape of the stripes, and the second seal protrusions are the first seal protrusions with respect to the membrane electrode assembly. A fuel cell sealing structure, wherein the fuel cell sealing structure is formed in parallel with each other at a pitch smaller than the close width of the strip.   The second seal ridge is composed of a central seal ridge having an extended shape substantially the same shape and size as the first seal ridge, and other seal ridges formed at least one on each side thereof. The fuel cell sealing structure according to claim 1, wherein:

Images