JP4337394B2 - Fuel cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell using a solid polymer electrolyte membrane as an electrolyte membrane, and more particularly to a seal configuration of a reaction gas and a cooling medium flowing in a flow channel of a separator constituting a single cell.
[0002]
[Prior art]
The solid polymer electrolyte fuel cell is configured in this way by sandwiching a membrane electrode assembly in which electrodes are arranged on both sides of an electrolyte membrane, with a separator having a reaction gas flow channel on the surface to form a single cell. It is usual that a plurality of single cells are stacked.
FIG. 3 is a front view illustrating the configuration of a separator that is assembled to face a fuel electrode in a conventional fuel cell of this type. As shown in the figure, the separator 2 facing the fuel electrode is formed with a flow groove 3 for fuel gas, which is supplied from one fuel gas manifold 6, for example, the fuel gas manifold 6 located at the lower right in the figure. The flowd fuel gas flows through the flow groove 3 and is then discharged to the outside from the other fuel gas manifold 6, for example, the fuel gas manifold 6 located at the upper left in the drawing. Manifolds indicated by 7 and 8 in the figure are an air manifold and a cooling medium manifold that supply and discharge air or a cooling medium to and from a flow groove formed in another separator, respectively. Further, a seal groove 4 is provided on the outside of the flow groove 3 and the fuel gas manifold 6 and on the outer periphery of the air manifold 7 and the cooling medium manifold 8. A gasket is disposed in the seal groove 4 and tightened. Thus, the reaction gas flowing through the flow groove and the cooling medium are sealed. A cover plate 9 is provided at a connection portion between the fuel gas manifold 6 and the flow groove 3 to receive the stress of the gasket facing each other with the electrolyte membrane interposed therebetween.
In this configuration, the gasket used for sealing the reaction gas and the cooling medium is classified into two types, a fitting gasket and an integrally formed gasket, depending on the method of fixing to the separator. The former is a method in which a pre-formed gasket such as an O-ring is fitted and fixed in the seal groove of the separator, and the latter is a method in which the gasket is formed and fixed on the surface of the separator by injection molding.
[0003]
In order to improve the sealing performance, which is the most important function required for gaskets, it is effective to increase the stress due to elastic deformation of the gasket, and high sealing performance can be obtained by increasing the amount of deformation or using a hard gasket material. It is done. However, in this type of gasket used in a fuel cell, compressing the gasket with a high pressure is not preferable because the gasket undergoes permanent deformation with long-term operation, and the compressive force applied to the cell varies greatly. As a means for avoiding this difficulty, as shown in FIG. 4, in Patent Document 1, etc., a gasket 1 provided with a protrusion is arranged in a seal groove of a separator 2, and a membrane electrode is interposed between the protrusions of two gaskets 1. A configuration is disclosed in which high sealing performance is secured with a small compressive force by sealing with a joined body interposed therebetween.
[0004]
Further, in this type of gasket used for a fuel cell, in order to facilitate the assembly of the fuel cell, even if the gaskets disposed on the two separators facing each other across the membrane electrode assembly are slightly displaced, a predetermined amount is obtained. The sealing performance needs to be maintained. In response to this requirement, Patent Document 2 shows a configuration in which the width of the facing gasket is changed. Further, Patent Document 1 shows a configuration in which the convex portion of the gasket 1 is disposed in the seal groove of the separator 2 and the wide surface is disposed on the membrane electrode assembly side as shown in FIG. Yes.
Further, since the fuel cell is assembled by alternately laminating a large number of membrane electrode assemblies and separators, this type of gasket used in the fuel cell is configured not to fall off from the separator when the fuel cell is assembled. It is necessary. For this reason, in the conventional fuel cell, a method of tightly fitting the gasket and the seal groove of the separator to prevent the dropping or a method of fixing the gasket to the seal groove of the separator with an adhesive are employed.
[0005]
The integral molded gasket does not drop off from the separator, but is likely to be misaligned. For example, in the protrusion structure as shown in FIG. 4, there is a high possibility that the sealing performance is impaired due to misalignment. As a configuration for solving this difficulty, as shown in FIG. 6, Patent Document 3 discloses a configuration in which a protrusion is provided on one gasket (lower side in the figure) and the other gasket (upper side in the figure) is formed in a planar shape. It is shown.
[0006]
[Patent Document 1]
JP 2001-283893 A [Patent Document 2]
JP-A-10-223241 [Patent Document 2]
Japanese Patent Laid-Open No. 2001-185174
[Problems to be solved by the invention]
As described above, this type of gasket incorporated in the separator of a fuel cell requires not only excellent sealing performance, but also a large tolerance for misalignment and that it does not fall off during assembly. The gasket which fills all is not obtained yet. That is, the sealing configuration using the fitting type gasket is excellent in sealing performance and has a large tolerance against the positional shift, but the conventional fitting type gasket has a drawback that the fixing to the separator is not sufficient. For this reason, when working with the gasket-attached surface facing downward in the assembly process of the fuel cell, part or all of the attached gasket comes off or falls off the seal groove, which requires a long time for assembly. Or there is a high risk of assembly failure. In particular, in the configuration as shown in FIG. 5 devised in order to increase the tolerance for the positional deviation, the separator is not sufficiently fixed and is likely to drop off. On the other hand, if the gasket and the seal groove are fitted more tightly, the separator can be prevented from falling off, but the gap for absorbing the deformation of the gasket is reduced, so that the compression force can be increased during tightening. This is necessary, and there is a drawback that a great deal of stress is applied to the membrane electrode assembly.
[0008]
On the other hand, the difficulty of a seal configuration using an integrally formed gasket is that it is difficult to achieve both an increase in tolerance for misalignment and securing of sealing performance. As already described, the configuration shown in FIG. 4 has a small tolerance for positional deviation, so the configuration shown in FIG. 6 has been proposed. However, in this configuration as well, the fuel gas manifold 6 and the flow groove 3 shown in FIG. In a place facing the cover plate 9 arranged at the connection point, there is a risk that the deformation amount of the gasket is insufficient and sufficient sealing performance cannot be obtained.
The present invention has been made in consideration of the current state of the art and problems, and the object of the present invention is to fix the gasket constituting the seal mechanism to the separator without causing displacement and without falling off. Another object of the present invention is to provide a fuel cell which is easy to assemble and in which reaction gas or cooling medium flowing in a flow groove provided in a separator is effectively sealed from each other.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention,
A membrane electrode assembly in which electrodes are formed on both surfaces of the electrolyte membrane, and a separator having a reaction gas or cooling medium flow groove on the surface are disposed so that the flow groove faces the membrane electrode assembly. In a fuel cell configured by stacking single cells,
(1) A separator provided with a seal groove and a fixed groove outside the flow groove, and a gasket for preventing leakage of a reaction gas or a cooling medium disposed between the membrane electrode assembly and the separator, The gasket has a first protrusion that forms a seal surface in contact with the bottom surface of the seal groove, a second protrusion that fits in the fixing groove and fixes the gasket, and a flat surface that contacts the membrane electrode assembly In addition, before the single cell is tightened, a gap is formed between the periphery of the first protrusion and the seal groove.
[0010]
(2) In the above (1), the gasket is further provided with a third protrusion that contacts the side surface of the seal groove and fixes the gasket.
(3) In the above (1) and (2), the thickness of the portion of the gasket provided with the second protrusion is made thinner than the thickness of the portion provided with the first protrusion.
When configured as described in (1) above, the first projection of the gasket is in contact with the bottom surface of the seal groove disposed outside the flow groove of the separator and sealed, so that it can be effectively sealed with a small tightening force. it can. In addition, since the gasket is provided with a second protrusion that fits into the fixed groove arranged outside the seal groove, the risk of causing displacement and dropping when the single cell is assembled is greatly suppressed. The
[0011]
In addition, when configured as described in (2) above, the gasket is not only fixed on the outside by the second protrusion, but also on the inside by the third protrusion. There is no risk of misalignment or dropout.
Further, when configured as described in the above (3), stress applied to the second protrusion at the time of tightening can be avoided, and sealing can be performed by applying a predetermined compressive force to the first protrusion.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an exploded cross-sectional view of a main part showing a configuration example of two separators and a gasket sandwiched between them in a fuel cell of the present invention. FIG. 2 is a front view showing a configuration of a separator that is assembled to face the fuel electrode of the fuel cell.
As shown in FIG. 1, the two separators 2 sandwiching the membrane electrode assembly in which the electrodes 12 are formed on both surfaces of the electrolyte membrane 11 are fixed to the seal groove 4 at the portion facing the electrolyte membrane 11 at the end. A groove 5 is provided. The gasket 1 includes a first protrusion 1 a that contacts the bottom surface of the seal groove 4, a second protrusion 1 b that fits in the fixing groove 5, and a third contact that contacts the inner side surface of the seal groove 4. The projection 1c is provided. The seal groove 4 of the separator 2 is formed on the outer side surrounding the flow groove 3 and the fuel gas manifold 6, as shown in the separator 2 assembled to face the fuel electrode illustrated in FIG. 2, the air manifold 7, and the cooling medium. It is provided on the outer side that surrounds the manifold 8, and a fixed groove 5 is provided on the outer side of these flow grooves 3. In this configuration, the first to third protrusions are inserted into the seal groove 4 and the fixing groove 5 of the separator 2 and the gasket 1 is mounted and tightened, but in this configuration, the second protrusion 1b is used. Not only is the outside fixed by being fitted into the fixing groove 5, but the third protrusion 1 c is supported from the inside of the seal groove 4, so that the mounted gasket 1 is attached more firmly by the separator 2. Therefore, there is no possibility that the position of the gasket 1 will be displaced at the time of mounting, and there is no possibility that the gasket will be detached at the time of assembly of the fuel cell. If the gasket of this configuration is tightened, the first protrusion 1a that is in contact with the bottom surface of the seal groove 4 is sealed, so that it can be sealed with a small tightening force. In addition, in the gasket 1 used for this structure, compared with the part provided with the 1st protrusion 1a, the thickness of the part provided with the 2nd protrusion 1b is formed thinly, and it tightens and compresses. At this time, the second protrusion 1b is not excessively compressed.
[0013]
Note that the gasket cutting portion receiving groove 10 formed in the vicinity of the fuel gas manifold 6 on the lower right side in FIG. 2 is longer when the gasket 1 in the portion overlapping the cover plate 9 is cut and used. It is a groove for storing the cut gasket 1. If the gasket cutting portion receiving groove 10 is provided in this way and the gasket 1 is cut longer, the risk of damaging the portion of the first projection necessary for sealing is avoided.
[0014]
【The invention's effect】
As described above, according to the present invention,
A membrane electrode assembly in which electrodes are formed on both surfaces of the electrolyte membrane, and a separator having a reaction gas or cooling medium flow groove on the surface are disposed so that the flow groove faces the membrane electrode assembly. Since the fuel cell configured by stacking the single cells is configured as described in claim 1, and further, as claimed in claim 2, the gasket constituting the seal mechanism is not displaced. And a fuel cell that is fixed to the separator without falling off, can be easily assembled, and the reaction gas or cooling medium flowing in the flow groove provided in the separator is effectively sealed to each other. became.
[Brief description of the drawings]
FIG. 1 is an exploded cross-sectional view of a main part showing a configuration example of two separators and a gasket sandwiched between them in the fuel cell of the present invention. FIG. 2 is a separator assembled to face the fuel electrode of the fuel cell of FIG. FIG. 3 is a front view illustrating the configuration of a separator that is assembled to face a fuel electrode of a conventional fuel cell. FIG. 4 is a cross-sectional view of a principal part illustrating a conventional example of a fuel cell gasket. 5] Cross-sectional view of the main part showing another conventional example of a gasket for a fuel cell. [Fig. 6] Cross-sectional view of the main part showing another conventional example of a gasket for a fuel cell.
DESCRIPTION OF SYMBOLS 1 Gasket 1a 1st protrusion 1b 2nd protrusion 1c 3rd protrusion 2 Separator 3 Flow groove 4 Seal groove 5 Fixing groove 6 Fuel gas manifold 7 Air manifold 8 Cooling medium manifold 9 Cover plate 10 Gasket cutting part accommodation groove 11 Electrolyte Membrane 12 electrode

Claims (3)

A membrane electrode assembly in which electrodes are formed on both surfaces of the electrolyte membrane, and a separator having a flow groove for a reaction gas or a cooling medium on the surface are disposed so that the flow groove faces the membrane electrode assembly. In a fuel cell configured by stacking formed single cells,
A separator having a seal groove and a fixed groove outside the flow groove;
A gasket for preventing leakage of a reaction gas or a cooling medium disposed between the membrane electrode assembly and the separator;
The gasket has a first protrusion that forms a seal surface in contact with the bottom surface of the seal groove, a second protrusion that fits in the fixing groove and fixes the gasket, and a flat surface that contacts the membrane electrode assembly And a gap between the periphery of the first protrusion and the seal groove before the single cell is tightened. The fuel cell according to claim 1, wherein the gasket includes a third protrusion that contacts the side surface of the seal groove and fixes the gasket. 3. The fuel cell according to claim 1, wherein the portion of the gasket having the second protrusion is formed thinner than the portion of the gasket having the first protrusion. 4.

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