JP2006114227A - Sealing structure of fuel battery cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing structure of a fuel battery cell capable of down-sizing and weight reduction of the stack by thinning the fuel battery cell. <P>SOLUTION: This is the sealing structure for tightly sealing a passage 4 formed between a membrane electrode assembly 1 and separators 2, 2 on both sides in thickness direction. An elastic body 3 which is arranged between respective separators 2, 2 so as to surround a passage forming region A is installed at the membrane electrode assembly 1 and a projection 22a which is pressure contacted to the elastic body 3 extending so as to surround the passage forming region A is formed at each separator 2. Since an excellent sealing performance is obtained at the surface pressure maximum part by the pressure contact of the projection 22a to the elastic body 3, formation of a seal lip is not necessary for the elastic body 3 and thinning of the fuel battery cell is possible. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sealing structure for sealing a gas flow path between stacked fuel cells in a fuel cell.

  A fuel cell has many fuel cell cells sandwiched between separators on both sides in the thickness direction of a membrane electrode assembly (MEA) provided with a pair of catalyst electrode layers on both sides of a polymer electrolyte membrane. It has a stack structure in which several hundreds are stacked. 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.

The gasket for sealing the gas flow path of each cell in the stack is made of an elastic body, and is provided integrally on the surface of the separator so as to be in close contact with the surface of the membrane electrode assembly. Some are provided integrally on the surface of the electrode composite so as to be in close contact with the surface of the separator. In the latter case, it is common to form seal lips on both sides of the membrane electrode assembly to ensure the contact pressure with the separator (see, for example, Patent Document 1).
Tokurei 2002-089240

  In this type of fuel cell, in order to reduce the stack size and weight, it is indispensable to make each cell member thin. However, in the case where a sealing lip made of an elastic material is formed on the surface of the membrane electrode assembly, the height of the sealing lip cannot be made so small from the viewpoint of ensuring the long-term durability of the sealing function. It was difficult to convert.

  In addition, the gasket having a sealing function by the seal lip may cause the seal lip to collapse when the stack is assembled by stacking cells or when a fluid to be sealed (hydrogen gas, oxidizing gas, or the like) is pressurized.

  Furthermore, to make the stack smaller and lighter, it is effective to make the separator thinner. However, if the separator made of carbon or the like is made thinner, its mechanical strength decreases, so the compression reaction force of the seal lip This may cause the separator to be easily deformed or damaged.

  The present invention has been made in view of the above points, and its technical problem is to provide a fuel cell sealing structure capable of reducing the size and weight of the stack by reducing the thickness of the fuel cell. There is.

  As a means for effectively solving the technical problem described above, a fuel cell sealing structure according to the invention of claim 1 includes a flow formed between a membrane electrode assembly and separators on both sides in the thickness direction. A structure that seals a path, and an elastic body that is disposed between the separators so as to surround the flow path forming region is attached to the membrane electrode assembly, and the flow channel forming region is attached to each separator. A ridge that extends so as to surround and is pressed against the elastic body is formed. For this reason, it is not necessary to form a seal lip on the elastic body, and an excellent sealing performance is achieved at the surface pressure maximum portion due to the pressure contact of the protrusion to the elastic body.

  A fuel cell sealing structure according to a second aspect of the present invention is the structure according to the first aspect, wherein the elastic body is joined to the outer peripheral surface of the membrane electrode assembly. In this case, the thickness of the elastic body can be reduced by making the thickness of the elastic body equal to or less than the thickness of the membrane electrode assembly.

  According to a third aspect of the present invention, there is provided the fuel cell sealing structure according to the first aspect, wherein the protrusions formed on each separator are formed at different positions on both sides of the elastic body. In this case, the compressive stress due to the elastic body or the membrane electrode assembly being sandwiched between the protrusions can be alleviated.

  According to a fourth aspect of the present invention, there is provided the fuel cell sealing structure according to the first aspect, wherein the separator is made of a metal plate and the protrusion is made of a bent portion of the metal plate. Is intended to be thinner.

  According to the fuel cell sealing structure according to the first aspect of the present invention, it is not necessary to form a seal lip on the elastic body, so that the stack can be made smaller and lighter by reducing the thickness of the fuel cell. In addition, since a problem such as the fall of the seal lip cannot occur, a highly reliable sealing structure can be obtained.

  According to the fuel cell sealing structure of the second aspect of the invention, in addition to the effect of the first aspect, the elastic body is joined to the outer peripheral surface of the membrane electrode composite so that the membrane electrode composite is separated from the separator. Therefore, the thickness of the fuel cell can be further reduced, and the stack can be made smaller and lighter.

  According to the fuel cell sealing structure according to the invention of claim 3, in addition to the effect of claim 1, the protrusions formed on each separator are pressed against each other at different positions on both sides of the elastic body. Stress concentration can be prevented, and as a result, the fuel cell can be further thinned, and the stack can be made smaller and lighter.

  According to the fuel cell sealing structure of the invention of claim 4, in addition to the effect of claim 1, since the separator is made of a metal plate, the thickness of the fuel battery cell can be reduced by this, and the stack can be made compact.・ Weight reduction can be realized.

  Hereinafter, a preferred embodiment of a fuel cell sealing structure according to the present invention will be described with reference to the drawings. First, FIG. 1 is a partial cross-sectional view of a fuel cell showing a first embodiment of the present invention. In this fuel cell, reference numeral 1 is a membrane electrode assembly, and reference numeral 2 is a thickness of the membrane electrode assembly 1. Separators arranged on both sides in the direction, reference numeral 3 is an elastic body arranged so as to surround a power generation region by the membrane electrode assembly 1.

  The membrane electrode assembly 1 includes a polymer electrolyte membrane 11 sandwiched between a pair of catalyst electrodes 12 and 12 from both sides in the thickness direction, and a pair of gas diffusion layers 13 and 13 disposed on the outside in the thickness direction. It is. The gas diffusion layer 13 has air permeability for guiding hydrogen or oxygen to the catalyst electrode 12, and conductivity for guiding power generated by an electrochemical reaction between hydrogen and oxygen to the separator 2, for example, carbon. It consists of a porous material such as fiber.

  The separator 2 is made of a conductive metal thin plate, and each separator 2 is formed with a large number of grooves 21 by press molding. The grooves 21 form a gap between the gas diffusion layer 13 and the separator 21. A flow path 4 is formed through which fuel gas (hydrogen gas) or oxidizing gas (oxygen) is passed.

  The elastic body 3 is interposed between each separator 2 and the membrane electrode assembly 1 to prevent leakage of fuel gas or oxidizing gas from the flow path 4. The membrane electrode assembly 1 is integrally formed of a rubber-like elastic material so as to form a U-shaped cross section along the portion. That is, the elastic body 3 includes a pair of parallel elastic layers 31 and 31 bonded to a surface facing the separator 2 in the outer peripheral portion of the membrane electrode assembly 1 and a continuous extension between the outer edge portions and the membrane. It consists of an end wall portion 32 surrounding the outer peripheral surface of the electrode assembly 1.

  The rubber-like elastic material of the elastic body 3 is selected from VMQ (silicone rubber), FKM (fluorine rubber), EPDM (ethylene propylene rubber), etc., and this is used as a liquid rubber for the porous gas diffusion layers 13 and 13. Molded in an impregnated state. Reference numeral 33 in the drawing indicates a rubber-impregnated layer in the gas diffusion layer 13, and the rubber-impregnated layer 33 is continuous with the elastic body 3.

  Each separator 2 is formed with a flange portion 22 on the outer peripheral side of a flow path 4 formation area (hereinafter referred to as a flow path formation area) A so as to surround the elastic body 3 from both sides of the membrane electrode assembly 1. The flange portion 22 is formed with a chevron (V-shaped) protrusion 22a. That is, the protrusions 22a and 22a are bent by press molding of the separator 2, extend so as to surround the flow path forming region A, and are located at positions corresponding to each other on both sides of the elastic body 3. The electrode assembly 1 is press-contacted so as to bite into the elastic layers 31 and 31 bonded to the surface facing the separator 2 in the outer peripheral portion of the electrode assembly 1.

  In the fuel cell having the above-described configuration, one of the flow paths 4 and 4 formed on both sides of the membrane electrode assembly 1 is supplied with fuel gas (hydrogen) and the other is oxidized gas (oxygen). Supplied. Of the catalyst electrodes 12 and 12 of the membrane electrode assembly 1, on the side (anode) to which the fuel gas is supplied via the gas diffusion layer 13, a reaction for decomposing hydrogen molecules into hydrogen ions and electrons is performed. On the side (cathode) to which the oxidizing gas is supplied through the diffusion layer 13, a reaction for generating water by oxygen, hydrogen ions, and electrons is performed, thereby generating an electromotive force.

  The chevron ridges 22a formed on each separator 2 are stacked on the elastic layers 31 and 31 of the elastic body 3 integrally formed with the membrane electrode assembly 1 so as to surround the flow path forming region A. Since the surface pressure with the elastic layer 31 is maximized at the top of the ridge 22a, it has excellent sealing properties against the fuel gas or the oxidizing gas flowing through the flow path 4, and the membrane. It has a function of elastically holding the outer periphery of the electrode composite 1. Further, the elastic body 3 extends so that the end wall portion 32 surrounds the outer peripheral surface of the membrane electrode assembly 1 and the rubber-impregnated layer 33 is formed on the outer peripheral portion of the gas diffusion layer 13. Alternatively, the oxidizing gas does not leak through the porous gas diffusion layer 13 in the direction perpendicular to the thickness direction and leak to the outer peripheral side.

  And according to this form, as mentioned above, since the protrusion 22a of each separator 2 is press-contacted to the elastic body 3 (elastic layer 31), the surface pressure maximum portion effective for sealing is formed. It is not necessary to form a seal lip on the elastic body 3, and thus the thickness of the fuel cell can be reduced, and as a result, the stack, which is a stack of fuel cells, can be reduced in size and weight. Moreover, in the case of the sealing structure using the sealing lip, the sealing lip may fall when each cell is stacked or when the hydrogen gas or oxidizing gas to be sealed is pressurized. That's not the case.

  Moreover, since the separator 2 consists of a press-molded body of a metal plate, it can be made sufficiently thin as compared with a conventional separator using carbon or the like. For this reason, the thickness of the fuel battery cell composed of the membrane electrode assembly 1, the separators 2, 2 and the elastic body 3 can be reduced. As a result, the stack, which is a stack of fuel battery cells, can be reduced in size and weight. It becomes.

  Next, FIG. 2 is a partial cross-sectional view of a fuel battery cell showing a second embodiment of the present invention. In this fuel battery cell, the difference from the above-described embodiment of FIG. Since other parts are configured in the same manner as in the embodiment of FIG. 1, the same or corresponding parts as those in FIG.

  That is, in the form of FIG. 2, the protrusion 22a is formed so as to have a circular arc shape in cross section. Therefore, the surface pressure distribution of the pressure contact portion between the protrusion 22a and the elastic layer 31 changes gently as compared with the embodiment shown in FIG.

  Next, FIG. 3 is a partial cross-sectional view of a fuel cell showing a third embodiment of the present invention. In this fuel cell, the difference from the above-described form of FIG. 1 is the cross-sectional shape of the elastic body 3. Since other parts are configured in the same manner as in the embodiment of FIG. 1, the same or corresponding parts as those in FIG.

  That is, in the embodiment of FIG. 3, the elastic body 3 is formed in a rectangular cross-section having a thickness substantially equal to that of the membrane electrode assembly 1, and the polymer electrolyte membrane 11 is separated from the catalyst electrodes 12, 12 and is integrally formed on the outer peripheral surface of the laminated membrane electrode assembly 1 in which the gas diffusion layers 13 and 13 are arranged on the outer side in the thickness direction.

  The elastic body 3 is formed by using liquid rubber as in the embodiment of FIG. 1, and for this reason, at the joint portion with the elastic body 3 in the outer peripheral portion of the porous gas diffusion layers 13, 13, A rubber-impregnated layer 33 continuous from the elastic body 3 is formed.

  Each separator 2 made of a thin metal plate is formed with a flange portion 22 so as to surround the elastic body 3 from both sides in the thickness direction, and this flange portion 22 is formed with a chevron (V-shaped) protrusion 22a. Has been. The protrusions 22a and 22a are bent by press molding of the separator 2, extend so as to surround the flow path forming region A, are located at positions corresponding to each other on both sides of the elastic body 3, and the elastic body 3 is pressed to bite into both sides.

  The fuel cell of FIG. 3 having the above configuration also has the same function as that of FIG. 1, and the chevron ridges 22 a formed on each separator 2 are membranes so as to surround the flow path forming region A. Since the elastic body 3 integrally formed with the electrode assembly 1 is pressed against the elastic body 3 so as to bite in the stacked state of the fuel cells, the surface pressure with the elastic body 3 is maximized at the top of the protrusion 22a. 4 has an excellent sealing property against fuel gas or oxidant gas flowing through the inside, and has a function of elastically supporting the outer peripheral portion of the membrane electrode assembly 1 via the elastic body 3. In addition, since the elastic body 3 extends so as to surround the outer peripheral surface of the membrane electrode assembly 1, and the rubber-impregnated layer 33 is formed on the outer peripheral portion of the gas diffusion layer 13, the fuel gas or the oxidizing gas is porous. The gas diffusion layer 13 having a quality structure is transmitted in a direction orthogonal to the thickness direction and does not leak to the outer peripheral side.

  In addition to the same effect as that of the embodiment of FIG. 1, the elastic body 3 has a thickness substantially the same as that of the membrane electrode assembly 1, and is formed on both sides in the thickness direction of the outer periphery of the membrane electrode assembly 1. Since such an elastic layer 31 is not formed, the thickness of the fuel cell can be further reduced, and the stack can be reduced in size and weight.

  Next, FIG. 3 is a partial cross-sectional view of a fuel cell showing a fourth embodiment of the present invention. This fuel cell differs from the above-described embodiment of FIG. 3 only in the cross-sectional shape of the protrusion 22a. Since other parts are configured in the same manner as in the embodiment of FIG. 1, the same or corresponding parts as those in FIG.

  That is, in the form of FIG. 4, the ridge 22a is formed so as to have an arcuate cross section as in FIG. Therefore, the surface pressure distribution of the pressure contact portion between the protrusion 22a and the elastic body 3 changes gently as compared with the configuration shown in FIG.

  Next, FIG. 5 is a partial cross-sectional view of a fuel cell showing a fifth embodiment of the present invention. In this fuel cell, in the form of FIG. 1 described above, the protrusions 22 a and 22 a having a mountain-shaped cross section of the separators 2 and 2 are formed at different positions on both sides of the elastic body 3. Since other parts are configured in the same manner as in the embodiment of FIG. 1, the same or corresponding parts as those in FIG. That is, the protrusions 22a of the upper separator 2 in FIG. 5 are formed relatively closer to the outer periphery than the protrusions 22a of the lower separator 2, and therefore the elastic layer of the elastic body 3 is formed. The press contact positions of the protrusions 22a and 22a with respect to 31 and 31 are shifted from each other.

  Next, FIG. 6 is a partial cross-sectional view of a fuel cell showing a sixth embodiment of the present invention. This fuel battery cell is also the same as that in FIG. 5 described above, and the ridges 22a and 22a having a circular arc shape in the form of FIG. 2 described above are formed at different positions on both sides of the elastic body 3. is there. Since the other parts are configured in the same manner as in the embodiment of FIG. 2, the same or corresponding parts as those in FIG. That is, the ridge 22a of the upper separator 2 in FIG. 6 is formed relatively closer to the outer periphery than the ridge 22a of the lower separator 2, and therefore, the elastic layer of the elastic body 3 is formed. The press contact positions of the protrusions 22a and 22a with respect to 31 and 31 are shifted from each other.

  1 or 2, the elastic layers 31 and 31 of the elastic body 3 and the gas diffusion layers 13 and 13 of the membrane electrode assembly 1 are compressed between the protrusions 22a and 22a facing each other. On the other hand, according to the form of FIG. 5 or FIG. 6, the protrusions 22 a and 22 a are pressed against the elastic layers 31 and 31 of the elastic body 3 at different positions, so that the elastic layers 31 and 31 and the gas diffusion layers 13 and 13 are in contact with each other. The compressive stress is less likely to concentrate, and therefore, the fuel cell can be made thinner than the embodiment of FIG. 1 or FIG.

  Next, FIG. 7 is a partial cross-sectional view of a fuel cell showing a seventh embodiment of the present invention. In this fuel cell, in the form of FIG. 3 described above, the ridges 22a and 22a having a mountain-shaped cross section of the separators 2 and 2 are formed at different positions on both sides of the elastic body 3. Since the other parts are configured in the same manner as in the embodiment of FIG. 3, the same or corresponding parts as those in FIG. That is, the ridge 22a of the upper separator 2 in FIG. 7 is formed so as to be relatively closer to the outer periphery than the ridge 22a of the lower separator 2, and therefore, the ridge to the elastic body 3. The pressure contact positions of 22a and 22a are shifted from each other.

  Next, FIG. 8 is a partial cross-sectional view of a fuel battery cell showing an eighth embodiment of the present invention. In this fuel cell, in the form of FIG. 4 described above, the protrusions 22a and 22a having a circular arc cross section of the separators 2 and 2 are formed at different positions on both sides of the elastic body 3. Since the other parts are configured in the same manner as in the embodiment of FIG. 4, the same or corresponding parts as those in FIG. That is, the ridge 22a of the upper separator 2 in FIG. 8 is formed so as to be relatively closer to the outer periphery than the ridge 22a of the lower separator 2, and therefore, the ridge to the elastic body 3. The pressure contact positions of 22a and 22a are shifted from each other.

  3 or 4, the elastic body 3 is compressed between the ridges 22a and 22a facing each other, whereas the ridges 22a and 22a are compressed according to the embodiment of FIG. Since the elastic body 3 is pressed against both surfaces of the elastic body 3 at different positions, the elastic body 3 is less likely to generate compressive stress between the protrusions 22a and 22a. Therefore, the elastic body 3 is compared with the embodiment shown in FIG. 3 or FIG. Therefore, it is possible to further reduce the thickness of the fuel cell.

It is a fragmentary sectional view of the fuel cell which shows the 1st form of the sealing structure of the fuel cell concerning the present invention. It is a fragmentary sectional view of the fuel battery cell which shows the 2nd form of the sealing structure of the fuel battery cell which concerns on this invention. It is a fragmentary sectional view of the fuel cell which shows the 3rd form of the sealing structure of the fuel cell concerning this invention. It is a fragmentary sectional view of the fuel cell which shows the 4th form of the sealing structure of the fuel cell concerning this invention. It is a fragmentary sectional view of the fuel cell which shows the 5th form of the sealing structure of the fuel cell concerning this invention. It is a fragmentary sectional view of the fuel cell which shows the 6th form of the sealing structure of the fuel cell which concerns on this invention. It is a fragmentary sectional view of the fuel cell which shows the 7th form of the sealing structure of the fuel cell concerning this invention. It is a fragmentary sectional view of the fuel cell which shows the 8th form of the sealing structure of the fuel cell which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Membrane electrode complex 11 Polymer electrolyte membrane 12 Catalytic electrode 13 Gas diffusion layer 2 Separator 21 Groove 22 Flange 22a Projection 3 Elastic body 31 Elastic layer 32 End wall 33 Rubber impregnated layer 4 Channel A Channel formation region

Claims (4)

  A structure in which a flow path (4) formed between a membrane electrode assembly (1) and separators (2) on both sides in the thickness direction is sealed, and the flow path ( The elastic body (3) arranged so as to surround the formation region (A) of 4) is attached to the membrane electrode assembly (1), and the formation region of the flow path (4) is attached to each separator (2). (A) A fuel cell sealing structure, characterized in that a protrusion (22a) extending so as to surround (A) and pressed against the elastic body (3) is formed.   The fuel cell sealing structure according to claim 1, wherein the elastic body (3) is joined to the outer peripheral surface of the membrane electrode assembly (1).   The fuel cell sealing structure according to claim 1, wherein the protrusions (21) formed on each separator (2) are formed at different positions on both sides of the elastic body (3).   The fuel cell sealing structure according to claim 1, wherein the separator (2) is made of a metal plate, and the protrusion (22a) is made of a bent portion of the metal plate.

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