JP2008210531A - Gasket, and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gasket capable of improving hermeticity of a fuel cell. <P>SOLUTION: An intermediate part 103 of a gasket comprises a small crosssectional area part 103a which is so formed that the crosssectional area of a border part 103a to contact parts 101 and 102 is smaller than the contact area of a separator 40 to the contact parts 101 and 102. The contact part 101 is sufficiently thinner than the thickness of the intermediate part, and the small crosssectional area part 103a of the intermediate part is easy to break under the pressure in the direction of enlargement/reduction of clearance when compared with other parts. So the intermediate part 103 expands/contracts against the pressure in the direction of enlargement/reduction of clearance for the most part. Therefor, the contact part 101 of a gasket 100 is so formed that the contact area between a contact surface 101a and the separator 40 does not change, in other words, it is kept constant. The clearance between the separators 40 smoothly enlarges following expansion/contraction of a MEGA25. Thus, damages on the MEGA25 is suppressed for improved power generation efficiency of a fuel cell. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell component, and more particularly, to a gasket structure that improves airtightness.

  Examples of the fuel cell include a polymer electrolyte fuel cell. The polymer electrolyte fuel cell includes an electrolyte membrane, a pair of electrode layers (anode, cathode) disposed on both sides of the electrolyte membrane, a porous gas diffusion layer disposed on both sides of the electrode layer, and an electrolyte membrane. A plurality of cells each having a separator for sandwiching an electrode layer are stacked. A reactive gas used for power generation of a fuel cell, such as a fuel gas or an oxidizing gas, flows through a manifold formed inside the fuel cell by stacking separators, and is supplied to the membrane electrode assembly through the gas diffusion layer. In such a fuel cell, a gasket is disposed on the outer periphery of the membrane electrode assembly and the diffusion layer between the separators, and the reaction gas from the membrane electrode assembly and the gas diffusion layer leaks from the interface between the separator and the gasket. Is suppressed.

  The gasket is formed of, for example, a resin and adheres to the separator under pressure from the outside to seal between the gasket and the separator. The gasket expands and contracts following the expansion and contraction of the membrane electrode assembly and gas diffusion layer during operation of the fuel cell, sealing the interface between the separator and the gasket, and damaging the membrane electrode assembly and gas diffusion layer. Suppress.

JP 2005-302526 A

  However, the contact area between the gasket and the separator may change due to expansion and contraction of the membrane electrode assembly and the gas diffusion layer. Therefore, the adhesive force between the gasket and the separator is increased, and the followability to expansion and contraction of the membrane electrode assembly and the gas diffusion layer is reduced, which may cause damage to the membrane electrode assembly and the gas diffusion layer. is there.

  The present invention has been made in view of the above-described problems, and aims to suppress damage to fuel cell components.

  In order to solve at least a part of the problems described above, the first aspect of the present invention is arranged so as to surround the contents between the first plate and the second plate arranged with the contents sandwiched therebetween. And a gasket that expands and contracts according to the expansion and contraction of the contents and seals between the two plates. The gasket according to the first aspect includes a first contact portion that contacts the first plate member with a constant first contact area regardless of expansion and contraction of the contents, and a constant second contact regardless of expansion and contraction of the contents. A second contact portion that contacts the second plate member in area, and an intermediate portion formed integrally with the first contact portion and the second contact portion, wherein the first contact portion and the second contact portion And an intermediate portion having a predetermined thickness that is thicker than the thickness of the second contact portion and having a cross-sectional area smaller than the first contact area and the second contact area. .

  According to the gasket of the first aspect, the contact area between the first plate member and the first contact portion and between the second plate member and the second contact portion can be kept constant regardless of the expansion or contraction of the contents. . Further, since the intermediate part is thicker than the first connection part and the second connection part, the intermediate part mainly expands and contracts with respect to the pressure in the direction of enlargement / reduction of the clearance. Therefore, deformation of the first contact portion and the second contact portion can be suppressed. In addition, since the intermediate portion includes a small cross-sectional area portion at the boundary portion between the first contact portion and the second contact portion, the intermediate portion is more vulnerable to pressure in the direction of expansion / contraction of the clearance than other portions of the gasket. It is. Therefore, the stretchability of the gasket can be improved, and the followability to the expansion and contraction of the contents can be improved. Therefore, the contents can be smoothly expanded and contracted, and damage to the contents can be suppressed while maintaining airtightness.

  In the gasket of the first aspect, the first contact portion and the second contact portion may be formed in a flat plate shape having a predetermined thickness that is thinner than the thickness of the intermediate portion.

  According to the gasket of the first aspect, since the thickness of the contact portion is sufficiently thinner than the thickness of the intermediate portion, the deformation amount of the first contact portion and the second contact portion can be reduced, and the first contact portion and An increase in the contact area between the first plate member and the second contact portion and the second plate member can be suppressed. Accordingly, it is possible to improve the followability to the expansion and contraction of the contents.

  In the gasket according to the first aspect, the maximum value of the cross-sectional area of the intermediate portion at the time of deformation may be smaller than that of the first contact surface and the second contact surface.

  According to the gasket of the first aspect, even when the intermediate portion is deformed to the maximum extent, the contact between the first contact surface and the second contact surface and the intermediate portion can be suppressed with high accuracy.

  In the gasket according to the first aspect, the first contact surface and the first plate member, and the contact interface of at least one of the second contact surface and the second plate member may be bonded by an adhesive means.

  According to the gasket of the first aspect, the airtightness between the first contact surface and the first plate member, and the airtightness between the second contact surface and the second plate member can be improved, The load in the manufacturing process can be reduced.

  A second aspect of the present invention provides a fuel cell. The fuel cell according to the second aspect includes a membrane electrode assembly in which electrodes are formed on both sides of an electrolyte membrane, a membrane electrode assembly arranged so as to sandwich the membrane electrode assembly, and a reactive gas at a portion facing the membrane electrode assembly. A pair of separators formed with a flow path for supplying gas, and a gasket that is disposed between the pair of separators and on the outer periphery of the membrane electrode assembly and seals the reaction gas in contact with the pair of separators. Prepare. The gasket includes a first contact portion that contacts the first plate member with a constant first contact area regardless of the expansion and contraction of the contents, and a second contact area with a constant second contact area regardless of the expansion and contraction of the contents. The second contact portion that contacts the plate material, the first contact portion, and the second contact portion are integrated with the first contact portion and the second contact portion to a predetermined thickness that is thicker than the first contact portion and the second contact portion. An intermediate portion that is formed and has a small cross-sectional area portion whose cross-sectional area is smaller than the first contact area and the second contact area, and deforms following the change in the interval between the first plate member and the second plate member. The gist is to provide.

  The fuel cell according to the second aspect includes a gasket that can maintain a constant contact area between the separator and the first contact surface and between the separator and the second contact surface regardless of the expansion and contraction of the membrane electrode assembly. Therefore, according to the fuel cell of the second aspect, the followability of the gasket with respect to the expansion and contraction of the membrane electrode assembly can be improved. Therefore, since the membrane / electrode assembly can smoothly expand and contract, damage to the membrane / electrode assembly can be suppressed.

  In the present invention, the various aspects described above can be appropriately combined or partially omitted.

A. First Example A1. Schematic Configuration of Fuel Cell A schematic configuration of the fuel cell according to the first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view illustrating a schematic configuration of a fuel cell in the first embodiment. FIG. 2 is an explanatory view illustrating a cross-sectional view of the fuel cell in the first embodiment. The fuel cell 1000 according to the first embodiment is a solid polymer fuel cell that receives supply of hydrogen gas and air and generates power by an electrochemical reaction between hydrogen and oxygen.

  As shown in FIG. 1, the fuel cell 1000 includes an intermediate member 20 having an electrolyte membrane, and a separator 40 as a partition that collects electricity generated by an electrochemical reaction. The separator 40 and the intermediate member 20 are repeatedly laminated in order, and are sandwiched by end plates 85 and 86 from both ends thereof.

  The end plate 85 has a supply hole 85a for supplying anode gas, a supply hole 85b for supplying cathode gas, a discharge hole 85c for discharging anode off gas, a discharge hole 85d for discharging cathode off gas, and a supply hole 85e for supplying cooling water. A discharge hole 85f for discharging the cooling water is formed. The anode gas is supplied into the fuel cell 1000 from a hydrogen tank (not shown) through the supply hole 85a. The cathode gas is compressed by a compressor (not shown) and supplied into the fuel cell 1000 through the supply hole 85b. The cooling water is cooled by a radiator (not shown) and supplied to the fuel cell 1000 through the supply hole 85e.

  As shown in FIG. 2, the intermediate member 20 includes a membrane electrode assembly 24 (MEA: Membrane Electrode Assembly), gas diffusion layers 23 a and 23 b, a gasket 100, and a resin portion 30. The gas diffusion layers 23 a and 23 b are disposed on both surfaces of the MEA 24. In the first embodiment, a member composed of the MEA 24, the gas diffusion layer 23a, and the gas diffusion layer 23b is referred to as MEGA 25.

  The MEA 24 includes a cathode electrode catalyst layer 22 a on one surface of the electrolyte membrane 21, and an anode electrode catalyst layer 22 b on the other surface of the electrolyte membrane 21. The electrolyte membrane 21 is made of Nafion, for example. The cathode electrode catalyst layer 22a and the anode electrode catalyst layer 22b formed on the surface of the electrolyte membrane 21 are formed by supporting a catalyst that promotes an electrochemical reaction, for example, platinum.

  The gas diffusion layers 23a and 23b are carbon porous bodies having a porosity of about 20%, and are formed of, for example, carbon cloth or carbon paper. The gas diffusion layers 23a and 23b are integrated with the MEA 24 by bonding to form the MEGA 25. The gas diffusion layers 23a and 23b diffuse the reaction gas in the thickness direction.

  The outer periphery of the MEGA 25 is surrounded by the gasket 100, and the MEGA 25 and the gasket 100 are integrally formed. A resin portion 30 is formed on the outer periphery of the gasket 100, and manifold communication holes 20a to 20f are formed in the resin portion 30 along the four sides of the intermediate member 20, as shown in FIG.

  The gasket 100 is made of an insulating resin material made of rubber, such as silicone rubber, butyl rubber, and fluorine rubber, and is integrally formed with the MEGA 25 by injection molding on the outer periphery of the MEGA 25. In this embodiment, silicone rubber is used as the material of the gasket 100. The gasket 100 includes contact portions 101 and 102 and an intermediate portion 103. Contact portion 101 contacts separator 40 at contact surface 101a, and contact portion 102 contacts separator 40 at contact surface 102a. The intermediate portion 103 is formed between the contact portions 101 and 102 so that the cross-sectional area of the boundary portion 103a between the contact portions 101 and 102 is smaller than the contact area between the contact portions 101 and 102 and the separator 40. Is formed. Such a boundary portion 103a is hereinafter referred to as a small cross-sectional area portion 103a in the first embodiment. The intermediate portion 103 of the gasket expands and contracts as the MEGA 25 expands and contracts. Accordingly, the interval between the separators 40 changes following the expansion and contraction of the MEGA 25. The followability of the gasket to the expansion and contraction of the MEGA 25 will be described later.

  Next, the separator 40 that collects electricity generated by an electrochemical reaction will be described. The separator 40 is a three-layer laminated separator 40 formed by laminating three thin metal plates. Specifically, a cathode plate 41 that is in contact with the gas diffusion layer 23a, an anode plate 43 that is in contact with the gas diffusion layer 23b, and an intermediate plate 42 that is sandwiched between the two plates and mainly serves as a cooling water flow path. It is composed of The three plates have a flat surface with no irregularities for the flow path in the thickness direction (that is, the contact surfaces with the gas diffusion layers 23a and 23b are flat), and are made of stainless steel, titanium, or titanium alloy. For example, it is made of a conductive metal material. Further, the three plates are provided with through holes that constitute the various manifolds described above. By laminating and joining the three plates having such a structure, flow paths for various fluids are formed inside the separator 40.

  The fuel cell 1000 is fastened with a predetermined fastening pressure. A gap formed between the separators 40 at the time of fastening with a predetermined fastening force is called clearance. In the first embodiment, the clearance at the time of fastening with a predetermined fastening force is L.

A2. Gasket details:
A detailed configuration of the gasket will be described with reference to FIGS. 3 and 4. FIG. 3 is a schematic diagram for explaining the contact area between the gasket and the separator 40 in the first embodiment. FIG. 4 is a schematic diagram for explaining the contact area between the gasket and the separator 40 in the prior art. In FIG. 3 and FIG. 4, in order to simplify the description, the gasket and the MEGA 25 are illustrated as not being integrally formed.

  As shown in FIGS. 3 and 4, in the fuel cell of the prior art and the fuel cell of the first embodiment, the gasket is in contact with the separator 40 at the contact area d1 at the time of fastening with a predetermined fastening pressure (normal time). Yes. The elastic force of the gasket at this time is the elastic force F1 in both the prior art and the first embodiment. Since the gasket is made of resin, it adheres to the separator 40 due to the fastening pressure applied when the fuel cell is fastened.

  When the MEGA 25 is expanded, the clearance increases from L. In the prior art, since the contact surface 201 of the gasket 200 with the separator 40 is substantially spherical, the gasket starts to peel from the separator 40 due to the increase in clearance, and the contact area between the gasket 200 and the separator 40 starts to decrease. For example, as shown in FIG. 4, the contact area between the gasket 200 and the separator 40 is d1 to d2 (d1> d2). At this time, the adhesive force F2 of the gasket 200 with respect to the separator 40 acts in the direction of preventing the clearance from being increased in order to maintain the adhesion with the separator 40, in other words, to suppress a decrease in the contact area with the separator 40. .

  When the relationship between the elastic force F <b> 1 and the adhesive force F <b> 2 is (Formula 1) below, airtightness by the gasket 200 is ensured, and the clearance between the separators 40 is smoothly expanded as the MEGA 25 expands. Therefore, the followability of the gasket 200 with respect to the expansion of the MEGA 25 is maintained.

  Elastic force F1-Adhesive force F2> 0 (Formula 1)

  However, when the elastic force F1 and the adhesive force F2 are in the relationship of (Equation 2), that is, when the adhesive force F2 is larger than the elastic force F1, the clearance between the separators 40 is approximately equal to the elastic force F1 and the adhesive force F2. Cannot expand from the state. Therefore, the followability of the gasket 200 with respect to the expansion of the MEGA 25 is not maintained. As a result, the MEA 25 expands and the MEA 24 and the gas diffusion layer are loaded and damaged, and the power generation efficiency of the fuel cell 1000 is reduced.

  Elastic force F1-Adhesive force F2 <0 (Formula 2)

  The adhesive force F2 increases as the contact time between the gasket 200 and the separator 40 increases and the contact pressure between the gasket 200 and the separator 40 increases. In such a case, the problem of low follow-up tends to occur. Further, since the elastic force F1 of the gasket 200 decreases in a low temperature environment, the influence of the adhesive force F2 is relatively increased. Therefore, the problem of low followability tends to occur even in a low temperature environment.

  On the other hand, in the gasket 100 of the first embodiment, the contact part 101 is formed in a flat plate shape having a predetermined thickness, and the intermediate part 103 has a small cross-sectional area of the boundary part 103a between the intermediate part 103 and the contact part 101. A small cross-sectional area 103a. Since the thickness of the contact portion 101 is sufficiently smaller than the thickness of the intermediate portion, and the small cross-sectional area portion 103a is more vulnerable to pressure in the direction of clearance enlargement / reduction than other portions, the clearance increases. The intermediate portion 103 mainly expands and contracts with respect to the pressure in the reduction direction. Therefore, the contact portion 101 of the gasket 100 is formed so that the contact area between the contact surface 101a and the separator 40 does not change due to expansion and contraction, that is, always constant. Further, the maximum value of the sectional area of the intermediate portion 103 of the gasket at the time of deformation is formed to be smaller than the contact area between the first contact surface and the separator and the contact area between the second contact surface 102a and the separator. Has been. If it carries out like this, it can suppress that an intermediate part contacts a separator at the time of a deformation | transformation.

  Therefore, when the MEGA 25 expands, even if the clearance changes, the contact area between the contact surface 101a of the gasket 100 and the separator 40 does not change, so the adhesive force F2 does not act in the direction opposite to the elastic force F1, Expansion of clearance is not hindered. Therefore, airtightness by the gasket 100 is ensured, and the clearance between the separators 40 is smoothly expanded as the MEGA 25 expands. Therefore, the followability of the gasket 100 with respect to the expansion of the MEGA 25 is maintained.

  According to the gasket 100 of the first embodiment, since the cross-sectional area of the boundary between the contact portion and the intermediate portion is formed to be smaller than the contact area between the contact portion and the separator 40, the clearance between the separators 40 is increased. Regardless, the contact area between the contact portion and the separator 40 can be kept constant. Therefore, it is possible to maintain the followability of the gasket with respect to the expansion of the MEGA 25 while maintaining the airtightness between the gasket and the separator 40. Therefore, damage to the MEA and the gas diffusion layer can be suppressed, and the power generation efficiency of the fuel cell can be improved.

  Further, according to the fuel cell of the first embodiment, at least one of the contact surfaces between the gasket and the separator 40 is bonded with an adhesive. Therefore, the airtightness can be improved and the manufacturing process load can be reduced.

B. Variation:
(1) FIG. 5 is a schematic view illustrating the configuration of a gasket in a modified example. As shown in FIG. 6, the intermediate portion of the gasket 400 may include a portion 401 having a smaller cross-sectional area than other portions of the intermediate portion. If it carries out like this, the expansion-contraction width | variety of a gasket can be increased with low reaction force, and follow-up property can be improved.

(2) FIG. 6 is a schematic view illustrating the configuration of the gasket 410 in the modification. As shown in FIG. 7, the intermediate portion 415 of the gasket 410 may be formed asymmetric with respect to the vertical direction (clearance increasing direction). Similarly, the gasket may not be formed symmetrically in the left-right direction (direction intersecting the clearance increasing direction).

(3) The gasket of the first embodiment is formed so that the contact areas of the upper contact surface and the lower contact surface of the gasket with the separator 40 are substantially the same, but the upper contact surface and the lower contact surface The contact area with the separator 40 may be different. FIG. 7 is a schematic view illustrating the configuration of the gasket 420 in the modification. As shown in FIG. 8, for example, the contact area (X) of the upper contact surface of the gasket 420 may be larger than the contact area (Y) of the lower contact surface. Conversely, the contact area of the lower contact surface may be larger than the contact area of the upper contact surface.

(4) In the gasket of the first embodiment, the lower contact surface and the separator 40 are bonded to each other with an adhesive. However, an adhesive force is generated between the contact surface and the separator 40 due to the fastening pressure applied at the time of fastening. Adhesion with an agent is not necessary. However, by bonding, there is an advantage that the load of the manufacturing process can be reduced and the airtightness can be improved.

  Although various embodiments of the present invention have been described above, it is needless to say that the present invention is not limited to these embodiments and can take various configurations without departing from the spirit of the present invention.

The perspective view which illustrates schematic structure of the fuel cell in 1st Example. Explanatory drawing which illustrates sectional drawing of the fuel cell in 1st Example. The schematic diagram explaining the contact area of the gasket and separator in 1st Example. The schematic diagram explaining the contact area of the gasket and separator in a prior art. The schematic diagram which illustrates the structure of the gasket in a modification. The schematic diagram which illustrates the structure of the gasket in a modification. The schematic diagram which illustrates the structure of the gasket in a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 ... Intermediate member 21 ... Electrolyte membrane 22a ... Cathode electrode catalyst layer 22b ... Anode electrode catalyst layer 23a ... Gas diffusion layer 23b ... Gas diffusion layer 24 ... Membrane electrode assembly 25 ... MEGA
DESCRIPTION OF SYMBOLS 30 ... Resin part 40 ... Separator 41 ... Cathode plate 42 ... Intermediate plate 43 ... Anode plate 85 ... End plate 85a, 85b, 85e ... Supply hole 85c, 85d, 85f ... Discharge hole 100 ... Gasket 101 ... Contact part 101a ... Contact surface DESCRIPTION OF SYMBOLS 102 ... Contact part 102a ... Contact surface 103 ... Intermediate | middle part 103a ... Small cross-sectional area part 200, 400, 410, 420 ... Gasket 201 ... Contact surface 415 ... Intermediate | middle part 1000 ... Fuel cell

Claims (5)

Between the first plate member and the second plate member arranged with the contents sandwiched therebetween, it is arranged so as to surround the contents, expands and contracts according to the expansion and contraction of the contents, and between the two plate members A gasket for sealing,
A first contact portion that contacts the first plate member at a constant first contact area regardless of expansion and contraction of the contents;
A second contact portion in contact with the second plate member at a constant second contact area regardless of expansion and contraction of the contents;
An intermediate portion formed integrally with the first contact portion and the second contact portion, and having a predetermined thickness that is thicker than the thicknesses of the first contact portion and the second contact portion. And a middle portion having a small cross-sectional area portion having a cross-sectional area smaller than the first contact area and the second contact area. The gasket according to claim 1,
The gasket in which the first contact portion and the second contact portion are formed in a flat plate shape having a predetermined thickness that is thinner than the thickness of the intermediate portion. The gasket according to claim 1,
The gasket having a maximum cross-sectional area of the intermediate portion at the time of deformation smaller than the first contact area and the second contact area. The gasket according to claim 1,
A gasket in which at least one contact interface between the first contact surface and the first plate member and between the second contact surface and the second plate member is bonded by an adhesive means. A fuel cell,
A membrane electrode assembly in which electrodes are formed on both sides of the electrolyte membrane;
A pair of separators arranged so as to sandwich the membrane electrode assembly and having a flow path for supplying a reaction gas to a portion facing the membrane electrode assembly;
A gasket that is disposed between the pair of separators and on the outer periphery of the membrane electrode assembly and seals the reaction gas in contact with the pair of separators,
The gasket is
A first contact portion that contacts the first plate member at a constant first contact area regardless of expansion and contraction of the contents;
A second contact portion in contact with the second plate member at a constant second contact area regardless of expansion and contraction of the contents;
An intermediate portion formed integrally with the first contact portion and the second contact portion, and having a predetermined thickness that is thicker than the thicknesses of the first contact portion and the second contact portion. And an intermediate portion having a small cross-sectional area portion having a cross-sectional area smaller than the first contact area and the second contact area.

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