JP2002151109A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce troublesome maintenance such as re-tightening the fastening bolts by which the whole fuel cell is fixed, and at the same time ensure sealing. SOLUTION: A joint body formed by arranging a pair of electrodes 3, 5 on both sides of a solid electrolyte membrane 1 is interposed between a pair of separators 7, 9 having gas passages 11, 13 through which humidified fuel gas and oxidizing gas are supplied, and sealing materials 19, 21 are arranged between other peripheral side ends of a pair of separators 7, 9. Swelling members 27, 29 swelling by absorbing moisture, and contact pressure transmission members 31, 33 increasing seal contact pressure by pressing the sealing materials 19, 21 by the swelling of the swelling members 27, 29 are installed in recesses 23, 25 formed in the surfaces facing the sealing materials 19, 21 of the separators 7, 9. The recesses 23, 25 in which the swelling members 27, 29 are house are communicated with the gas passages 11, 13 with internal communication passages 43, 45.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joined body having a pair of electrodes disposed on both sides of an electrolyte membrane, which is sandwiched and fixed between a pair of separators having gas flow paths to which fuel gas and oxidizing gas are respectively supplied. In addition, the present invention relates to a fuel cell in which a sealing material is disposed between outer peripheral edges of the pair of separators.

[0002]

2. Description of the Related Art A fuel cell is a device for obtaining an electromotive force by electrochemically reacting a fuel gas such as hydrogen and an oxidizing gas such as air, and has two electrodes, namely a cathode electrode and an anode, on both sides of an electrolyte membrane. The electrodes are arranged to form an electrode electrolyte membrane assembly called MEA. Generally, a number of cells constituting the MEA are stacked to form a fuel cell stack.

[0003] Outside the above-mentioned electrodes, a separator for mechanically joining a large number of laminated electrode electrolyte membrane assemblies and electrically connecting adjacent electrode electrolyte membrane assemblies is arranged. A gas passage for supplying a reaction gas to the electrode surface is formed in a portion between the separator and the electrode.

[0004] Among the fuel cells, a solid polymer membrane fuel cell having a particularly high output density has attracted attention as a power source for a mobile body such as an automobile, and uses a solid polymer electrolyte membrane having proton conductivity as an electrolyte. It has features. The solid polymer electrolyte membrane also plays a role as an isolation membrane that prevents the fuel gas on the anode side and the oxidizing gas on the cathode side from being mixed together with the electrochemical reaction caused by the proton conduction.

Conventionally, in order to prevent the above-mentioned mixture of the fuel gas and the oxidizing gas or the leakage of the fuel gas and the oxidizing gas to the outside of the battery at the outer peripheral portions of the respective electrodes, the outer peripheral portions of the separators are separated from each other. O-rings (see JP-A-6-119930) and gaskets (JP-A-7-226220, JP-A-2000-15623) as seal materials
No. 4 gazette).

[0006]

By the way, in a fuel cell, when used for a long period of time, the volume of the electrolyte membrane changes due to the absorption of water, and the distortion of the heat shrinkage between the components due to repeated humidification and cooling is remarkable. And deterioration of the sealing material also occurs. Further, when a fuel cell is used in an automobile, seal deterioration, distortion, and deflection occur due to vibration, uneven load, and heat history, and as a result, sealability is impaired, and both gases due to leakage of fuel gas and oxidizing gas are deteriorated. Therefore, there is a problem that the electromotive force of the fuel cell cannot be sufficiently obtained due to mixing of the fuel cells.

Further, when the sealing performance is deteriorated, leakage of by-product water and cooling water caused by an electrochemical reaction between the fuel gas and the oxidizing gas in the fuel cell also occurs, and the installation location of the fuel cell and peripheral equipment deteriorate. The problem of hastening is also secondary.

In order to cope with the above-mentioned problem, it is necessary to appropriately re-tighten fastening bolts for fixing the whole fuel cell stack, and the maintenance work of the fuel cell becomes complicated.

Accordingly, an object of the present invention is to secure sealing performance while reducing complicated maintenance work for a fuel cell.

[0010]

In order to achieve the above object, according to the first aspect of the present invention, a fuel cell and an oxidizing gas are supplied to a joined body having a pair of electrodes disposed on both sides of an electrolyte membrane. A fuel cell having a pair of separators provided with a gas flow path, which is sandwiched and fixed, and a sealing material is arranged between the outer peripheral edges of the pair of separators, in the sealing material and the separator, absorbing moisture. A swelling member that swells and a surface pressure transmitting member that presses the sealing material by swelling of the swelling member are provided.

According to a second aspect of the present invention, in the configuration of the first aspect, a swelling member is housed in a space formed between the separator and the surface pressure transmitting member.

According to a third aspect of the present invention, in the configuration of the second aspect of the present invention, an internal communication path for communicating the space with the gas flow path is provided.

According to a fourth aspect of the present invention, in the configuration of the second or third aspect, an external communication path is provided for communicating the space with the outside of the fuel cell.

According to a fifth aspect of the present invention, in the configuration according to any one of the second to fourth aspects, the space is formed by a concave portion formed on a surface of the separator facing the sealing material.

According to a sixth aspect of the present invention, in the configuration of any of the second or second aspects of the present invention, the sealing surface communicating between the surface pressure transmitting member and the separator and the sealing interface between the sealing material and the separator is provided. The communication passage is provided.

[0016]

According to the first aspect of the present invention, the swelling member provided between the sealing material and the separator absorbs moisture and swells, so that the surface pressure transmitting member is pressed by the sealing material. The sealing surface pressure between the pair of separators and the sealing material, which sandwiches and fixes a joined body having a pair of electrodes disposed on both sides of the electrolyte membrane, is increased, and the sealing is performed without performing a complicated maintenance work on the sealing surface pressure. It is possible to cope with the deterioration of sex.

According to the second aspect of the present invention, since the swelling member is accommodated in the space, the pressing operation on the sealing material by the surface pressure transmitting member accompanying the swelling of the swelling member is reliably performed.

According to the third aspect of the invention, the water contained in the gas flowing through the gas flow path can be easily introduced into the swelling member through the internal communication passage.

According to the fourth aspect of the present invention, the gas flowing through the gas flow path and the by-product water generated by the reaction at the electrode are:
If leakage from the seal portion to the outside of the fuel cell or cooling water for cooling the fuel cell leaks to the outside of the fuel cell, this leakage is introduced into the swelling member in the space through the external communication path. Due to the pressing operation of the surface pressure transmitting member against the sealing material due to the swelling of the swelling member, the sealing surface pressure between the pair of separators and the sealing material is increased, and without performing a complicated maintenance work on the sealing surface pressure, the sealing is performed. It is possible to cope with the deterioration of the performance and to prevent the leaked water from being taken into the fuel cell, so that the aging of the fuel cell installation location and peripheral devices can be suppressed.

According to the fifth aspect of the present invention, the swelling member accommodated in the recess formed in the separator absorbs moisture and swells, so that the surface pressure transmitting member is pressed by the sealing material. The surface pressure between the pair of separators and the sealing material, which sandwiches and fixes a joined body in which a pair of electrodes are arranged on both sides of the electrolyte membrane, increases, and the sealing performance is degraded without performing complicated maintenance work on the sealing surface pressure. Can be dealt with.

According to the invention of claim 6, the moisture in the gas leaked from the sealing interface between the sealing material and the separator is:
Since the swelling member is introduced into the swelling member through the sealing surface communication passage, the sealing surface pressure between the pair of separators and the sealing member increases due to the pressing operation of the surface pressure transmitting member against the sealing member due to the swelling of the swelling member. In addition, it is possible to deal with the deterioration of the sealing property without performing a complicated maintenance work for the sealing surface pressure. Further, in this case, the sealing surface pressure can be selectively increased with respect to the leaking seal portion, and it is possible to reliably cope with the deterioration of the sealability.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a part of a polymer electrolyte membrane fuel cell according to a first embodiment of the present invention.
The fuel cell includes an electrolyte membrane 1 made of a solid polymer membrane,
Two electrodes 3, 5 arranged on both sides of the electrolyte membrane 1
(A fuel electrode and an oxygen electrode), and two separators 7 and 9 provided on both sides of the two electrodes 3 and 5, respectively. Although not shown, the two separators 7, 9 are connected to the electrolyte membrane 1 and the electrodes 3, 5 by fasteners such as bolts.
Are fixedly fastened so as to pinch and fix them. In an actual fuel cell, a large number of electrode electrolyte membrane assemblies composed of an electrolyte membrane 1 and electrodes 3 and 5 are stacked with separators 7 and 9 interposed therebetween to form a fuel cell stack. A description will be given using a single cell as an example.

The electrolyte membrane 1 is formed as a proton-conductive ion exchange membrane from a polymer material such as a fluororesin. The two electrodes 3 and 5 are made of carbon cloth containing platinum or a catalyst made of platinum and another metal, and are formed so that the surface where the catalyst exists is in contact with the electrolyte membrane 1.

The separators 7 and 9 are made of a gas-impermeable, dense carbon material.
A large number of ribs 15 and ribs 17 for securing the fuel gas passage 11 and the oxidizing gas passage 13 are formed on the surfaces respectively corresponding to the gas passages 11 and 13.
Although not shown on the surface opposite to the surface on which
A cooling water passage is formed.

The fuel gas supplied to the fuel gas flow channel 11 is mainly composed of hydrogen, and may include nitrogen gas, carbon dioxide gas and carbon monoxide gas as other gas components. Furthermore, a methanol solution diluted with water instead of hydrogen may flow. The gas supplied to the oxidizing gas flow path 13 is mainly composed of oxygen, and may further contain nitrogen gas. These fuel gas and oxidizing gas are sufficiently humidified before being supplied to the fuel cell.

The electrolyte membrane 1 has an outer peripheral end extending to substantially the same position as the outer peripheral ends of the separators 7 and 9.
A sealing material 1 made of a fluororesin gasket is provided between the electrolyte membrane 1 and the separators 7 and 9 at the outer peripheral end.
9 and 21 are provided. Concave portions 23 and 25 are formed on the surfaces of the separators 7 and 9 facing the seal members 19 and 21. In the concave portions 23 and 25, swelling members 27 and 29 swelling by absorbing moisture are provided. Due to the swelling of the swelling members 27, 29, the surface pressure transmitting members 31, which move against the separators 7, 9 and press the sealing members 19, 21,
33 are accommodated respectively. Therefore, the inside of the concave portions 23 and 25 forms a space in which the swelling members 27 and 29 are accommodated.

The swelling members 27 and 29 are made of a water-absorbing gel or a water-absorbing resin material, and swell by absorbing and absorbing moisture in the humidified fuel gas and oxidizing gas. The swelling members 27 and 29 can take various forms such as powder, film, and fiber, but do not flow out into the fuel gas passage 11 and the oxidizing gas passage 13 in the separators 7 and 9. The shape is selected. In the case of powder, it may be fixed with a water-permeable membrane or film (for example, Lanseal: manufactured by Nippon Exlan Co., Ltd., Drytech: manufactured by Dow Chemical Company).

The surface pressure transmitting members 31 and 33 are made of a sealing material 1.
Pressing portions 35 and 37 that come into contact with 9, 21;
37 comprises side wall portions 39a and 39b, 41a and 41b extending toward the bottom surfaces of the concave portions 23 and 25 from both ends. When the fuel cell is assembled, the surfaces of the pressing portions 35 and 37 on the side of the seal members 19 and 21 form the same surfaces as the surfaces of the separators 7 and 9 on the side of the seal members 19 and 21.

Through holes 39c and 41c are formed in the side wall portions 39b and 41b on the left side of the surface pressure transmitting members 31 and 33 in the drawing, and the through holes 39c and 41c are in contact with the separators 7 and 9 contacting the side wall portions 39b and 41b. Through holes 7a and 9a are formed to match the holes 39c and 41c. The above-mentioned through hole 3
9c, 41c and the through holes 7a, 9a, the gas flow path 11,
Internal communication passages 43 and 45 for communicating the space 13 and the spaces in the recesses 23 and 25 are formed.

When the fuel cell having the above configuration is operated,
Each of the fuel gas and the oxidizing gas is supplied to the fuel gas passage 1.
1 and the oxidizing gas flow path 13. Each gas is sufficiently humidified before flowing into the fuel cell, and the moisture in the humidified gas and the moisture generated by the electrochemical reaction are passed through the internal communication passages 43 and 45 to form the recesses 23 and 45. 25, and is absorbed and absorbed by the swelling members 27 and 29.

The swelling members 27 and 29 swell by absorbing and absorbing moisture, and the surface pressure transmitting members 31 and 33 press the seal members 19 and 21 by the swollen swelling members 27 and 29.

At this time, the separators 7 and 9 are mutually sealed by fastening members such as bolts (not shown).
And the swollen swelling members 27 and 29 press the surface pressure transmitting members 31 and 33 toward the sealing members 19 and 21, thereby increasing the fastening pressure by the bolts and sealing. The nature will increase. For this reason, it is possible to suppress deterioration of the sealing property due to long-term use of the fuel cell, and it is possible to reduce complicated maintenance work such as retightening the fastening bolt.

The passages of the through holes 7a, 39c, 9a, 41c constituting the internal communication passages 43, 45 may be not only circular but also slit-shaped, and the swelling members 27, 29 are provided in the gas passages 11, 13. Any shape is acceptable as long as it does not move.

Further, the left side wall portions 39b and 41b of the surface pressure transmitting members 31 and 33 in the drawing may be in direct contact with the gas flow paths 11 and 13. In this case, the surface pressure transmitting member 3
It is necessary to provide a mechanism for restricting the movement of the first and third gas toward the gas flow paths 11 and 13.

FIG. 2 is a sectional view showing a part of a polymer electrolyte fuel cell according to a second embodiment of the present invention.
This fuel cell differs from the fuel cell of FIG. 1 only in the sealing structure formed at the outer peripheral end of the separators 7 and 9, and the other parts are the same.

The separators 7 and 9 facing the sealing members 19 and 21 are formed with notched recesses 47 and 49 that are also open on the outer side over the entire circumference.
49, swelling members 51 and 53 which swell by absorbing moisture, and surface pressure transmitting members 55 and 5 which press the seal members 19 and 21 by swelling of the swelling members 51 and 53.
7 are accommodated respectively. Therefore, the inside of the cutout recesses 47 and 49 forms a space in which the swelling members 51 and 53 are accommodated.

The surface pressure transmitting members 55 and 57 are made of a sealing material 1.
Pressing portions 59 and 61 that contact the first and second pressing portions 9 and 21,
The side wall portions 63a and 63b, 65a and 65b extend in the direction away from the sealing members 19 and 21 from both ends of the base member 61. Then, in a state where the fuel cell is assembled, the sealing material 1 of the pressing portions 59 and 61 is formed.
The surfaces on the sides 9 and 21 are sealing materials 19 for the separators 7 and 9.
The same surface as the surface on the 21 side is formed.

A gap 6 as an external communication passage is provided between the outer peripheral side of the surface pressure transmitting members 55 and 57, that is, between the ends of the side walls 63a and 65a on the right side in the figure and the separators 7 and 9.
7, 69 are formed, so that the insides of the cutout recesses 47, 49 communicate with the outside of the fuel cell. On the other hand, between the inner peripheral side of the surface pressure transmitting members 55 and 57, that is, between the side wall portions 63b and 65b on the left side in the figure and the swelling members 51 and 53, the separators 7 and 9 are directed toward the seal members 19 and 21. Protruding projections 7b, 9b are formed, and these projections 7b, 9b
Swelling member 51 between the swelling member 51 and the right side wall portions 63a, 65a.
53 are accommodated.

The above-mentioned left side wall portions 63b, 65b are
The length in the up-down direction in the figure is formed shorter than the side walls 63a and 65a on the right side, and the side wall 63 including the tip thereof is formed.
b, 65b, between the periphery of the separators 7, 9 and
Gaps are formed between the tips of the projections 7b, 9b and the surface pressure transmitting members 55, 57, and these gaps allow the sealing interfaces 71, 9 between the sealing materials 19, 21 and the separators 7, 9 to be formed. Bent seal surface communication passages 75, 7 communicating with 73
7.

According to the fuel cell having the above-described structure, the fuel gas and the oxidizing gas flowing through the fuel gas flow path 11 and the oxidizing gas flow path 13 flow into the fuel cell as in the fuel cell of FIG. Before the humidification, the moisture in the humidified gas and the moisture generated by the electrochemical reaction pass through the sealing interfaces 71 and 73 and the bent sealing surface communication passages 75 and 77 to form the notch recess 47. , 49 and is adsorbed and absorbed by the swelling members 51, 53.

The swelling members 51 and 53 swell by absorbing and absorbing moisture, and the surface pressure transmitting members 55 and 57 press the sealing members 19 and 21 by the swollen swelling members 51 and 53. At this time, the separators 7 and 9 are fastened and fixed to each other by fasteners such as bolts (not shown) so as to sandwich the seal members 19 and 21. Therefore, the swollen swelling members 51 and 53 are separated from the surface pressure transmitting members 55 and 57. Is pressed toward the sealing materials 19 and 21, the fastening pressure by the bolt is increased, and the sealing performance is improved.

For this reason, in the fuel cell shown in FIG. 2 as well, deterioration of the sealing property due to long-term use of the fuel cell can be suppressed, and complicated maintenance work such as retightening of fastening bolts can be reduced. .

In the case of this embodiment, the fuel gas and the oxidizing gas flowing out of the fuel cell from the seal portion and the water generated by the reaction flow into the notched recesses 47 and 49 through the gaps 67 and 69. As a result, the swelling members 51 and 53 absorb and absorb moisture to swell, and the surface pressure transmitting members 55 and 57 are moved in the same manner as described above.
As a result of pressing 21, the sealing performance is improved. In this case, the portion where the sealing property is impaired and the gas flows out of the fuel cell selectively increases the sealing surface pressure, so that it is possible to reliably cope with the deterioration of the sealing property.

Further, in this embodiment, even when cooling water for cooling the fuel cell leaks from the fuel cell,
The leaked cooling water enters the cutout recesses 47 and 49 through the gaps 67 and 69, and the swelling members 51 and 53 absorb and absorb moisture, thereby improving the sealing performance.

The fuel gas, oxidizing gas, and cooling water leaked to the outside of the fuel cell are taken into the fuel cell through the gaps 67 and 69 and are absorbed by the swelling members 51 and 53. It is also possible to suppress aging due to moisture in the water.

In each of the above embodiments, the sealing material 1
Fluororesin gaskets were used for 9 and 21,
A liquid gasket composed of an O-ring, a thermoplastic elastomer or the like may be used.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a part of a polymer electrolyte fuel cell according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a part of a polymer electrolyte fuel cell according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrolyte membrane 3,5 Electrode 7,9 Separator 11 Fuel gas flow path 13 Oxidizing gas flow path 19,21 Sealing material 23,25 Concave part (space) 27,29,51,53 Swelling member 31,33,55,57 Surface pressure transmitting member 43, 45 Internal communication path 47, 49 Notch recess (space) 67, 69 Gap (external communication path) 71, 73 Seal interface 75, 77 Seal surface communication path

Claims (6)

[Claims] 1. A joined body having a pair of electrodes disposed on both sides of an electrolyte membrane is sandwiched and fixed between a pair of separators provided with gas flow paths to which a fuel gas and an oxidizing gas are supplied, respectively. In a fuel cell in which a sealing material is arranged between outer peripheral edges of a fuel cell, a swelling member that absorbs moisture and swells between the sealing material and the separator, and a surface that presses the sealing material by swelling of the swelling member A fuel cell comprising a pressure transmitting member. 2. The fuel cell according to claim 1, wherein a swelling member is accommodated in a space formed between the separator and the surface pressure transmitting member. 3. The fuel cell according to claim 2, further comprising an internal communication passage communicating the space with the gas flow path. 4. The fuel cell according to claim 2, wherein an external communication path is provided for communicating the space with the outside of the fuel cell. 5. The fuel cell according to claim 2, wherein the space is formed by a concave portion formed on a surface of the separator facing the sealing material. 6. A seal surface communication passage which is provided between the surface pressure transmitting member and the separator so as to communicate with a seal interface between the seal member and the separator.
The fuel cell according to any one of the above.