JP2006012462A - Sealing structure for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve sealing properties at the periphery of an electrolyte film while suppressing dispersion of surface pressure distribution for an electrode surface. <P>SOLUTION: An anode-side electrode 9 and a cathode-side electrode 11 are arranged on both sides of the electrolyte film 7 and separators 15 and 17 are arranged at the outside of them. Plate-like sealing members 19 and 21, such as polycarbonate, having a large elastic coefficient are arranged on both surfaces of a projecting portion 7b of the electrolyte film 7 projecting from the electrodes 9 and 11 to the outside, and a gasket 23 made of rubber elastic material, such as silicone rubber, is inserted between the cathode-side separator and the plate-like member 21. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell sealing structure in which an anode side electrode is disposed on one side of an electrolyte membrane, and a cathode side electrode is disposed on the other side, and the outside is sandwiched between a pair of separators.

  A polymer electrolyte fuel cell includes a membrane-electrode assembly (MEA) in which an anode side electrode and a cathode side electrode are arranged on both sides of a polymer ion exchange membrane (cation exchange membrane) that is an electrolyte membrane. A unit battery is configured by sandwiching the two.

  Such a polymer electrolyte fuel cell is usually used as a fuel cell stack by stacking a predetermined number of unit cells.

  In the fuel cell stack described above, the fuel gas (hydrogen-containing gas) supplied to the anode side electrode is hydrogen ionized on the electrode and moves to the cathode side electrode side through the appropriately humidified electrolyte membrane. Electrons generated in the meantime are taken out to an external circuit and used as direct current electric energy. On the other hand, since an oxidant gas, for example, an oxygen-containing gas or air is supplied to the cathode side electrode, water reacts with the hydrogen ions, the electrons and the oxygen gas to generate water. The

  Further, at least one of the pair of separators is formed with a cooling medium flow path for flowing a cooling medium for suppressing heat generation during power generation on the surface opposite to the electrode.

  Since the fuel gas, the oxidant gas, and the cooling medium described above need to be passed through independent flow paths, a seal that partitions the flow paths is necessary. Examples of the sealing portion include a periphery of a communication hole penetrating in the unit cell stacking direction for distributing and supplying fuel gas, oxidant gas, and cooling medium to each unit cell of the fuel cell stack, an outer periphery of the MEA, and a separator In general, a soft and moderately repulsive material such as organic rubber is generally used as the sealing material.

By the way, with respect to the seal on the outer periphery of the MEA described above, as described in, for example, Patent Documents 1 and 2 below, at the protruding portion of the electrolyte membrane that protrudes outward from the pair of electrodes installed so as to sandwich the electrolyte membrane. Is going.
JP 2000-182039 A JP 2002-42837 A

  As described in Patent Document 1 described above, when a plate-like rubber seal is used as the two sealing materials, the reaction force from the rubber seal is large, so the separator is damaged due to an increase in stack tightening pressure, and the surface pressure against the electrode. In addition to the problem of variation in distribution, the sealing performance is impaired when the two sealing materials deviate from the symmetrical positions facing each other with the electrolyte membrane interposed therebetween.

  In addition, as described in Patent Document 2 above, when a plate-like rubber seal is used for one of the two sealing materials and a narrow rubber seal is used for the other, the seal position between the two sealing materials is shifted. However, the compressive stress is dispersed on the wide sealing material side to reduce the surface pressure, and the sealing performance on the wide sealing material side is deteriorated.

  Furthermore, as in the above Patent Documents 1 and 2, in a seal structure in which a compressible rubber seal is in direct contact with the electrolyte membrane, the electrolyte membrane is damaged by expansion and contraction of the electrolyte membrane during power generation, and the sealing performance is impaired. It becomes.

  Therefore, an object of the present invention is to improve the sealing performance on the outer peripheral side of the electrolyte membrane while suppressing variations in the surface pressure distribution with respect to the electrode surface.

  The present invention provides a fuel cell sealing structure in which an anode side electrode is disposed on one side of an electrolyte membrane, a cathode side electrode is disposed on the other side, and the outside is sandwiched between a pair of separators. And a protruding portion protruding outward from the anode side electrode and the cathode side electrode, a plate-shaped sealing material is provided on both surfaces of the protruding portion, and one of the plate-shaped sealing materials is bonded to the separator, and the plate-shaped seal An elastic sealing material having a narrower width than the plate-shaped sealing material is provided between the other material and the separator, and the plate-shaped sealing material has a larger elastic coefficient than the elastic sealing material.

  According to the present invention, the plate-shaped sealing material having a larger elastic coefficient than the elastic sealing material is provided on both surfaces of the protruding portion on the outer peripheral side of the electrolyte membrane, one of the plate-shaped sealing materials is joined to the separator, and the other plate-shaped sealing material An elastic sealing material that is narrower than the plate-shaped sealing material is provided between the material and the separator, so that the surface pressure distribution on the electrode surface is made uniform while suppressing the reaction force from the sealing material, and the sealing material on both surfaces of the electrolyte membrane Even if there is a mutual shift, the sealing performance can be secured, and the sealing performance can be secured by preventing the electrolyte membrane from being damaged due to expansion and contraction during power generation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the basic configuration and operation of a part that is common or similar to all the embodiments of the present invention will be described with reference to FIGS. The fuel cell according to the present invention is a solid polymer electrolyte fuel cell (hereinafter simply referred to as a fuel cell), and is mounted on, for example, a fuel cell vehicle. However, you may use other than a motor vehicle.

  FIG. 1 is a perspective view showing the entire fuel cell stack. In this fuel cell stack, a stack 3 is formed by stacking a plurality of unit cells 1 that generate an electromotive force of about 1V. Each of the plurality of unit cells 1 constituting the stacked body 3 functions as a fuel cell. As will be described later, this fuel cell stack is fastened using tension rods or the like that are arranged at the four corners and penetrate the interior. Here, the number of tension rods is not limited to four (four corners), and is not limited as long as the specification can secure a desired fastening force.

  FIG. 2 is an exploded perspective view showing the structure of the unit battery 1. The unit cell 1 includes an electrolyte membrane 7 made of a polymer ion exchange membrane, an anode side electrode (fuel electrode) 9 that is a gas diffusion electrode disposed on one surface of the electrolyte membrane 7, and the other surface of the electrolyte membrane 7. A membrane-electrode assembly (MEA) 13 is constituted by the cathode side electrode (air electrode) 11 which is the gas diffusion electrode arranged.

  Separators 15 and 17 forming fluid passages for supplying fuel gas (hydrogen) to the anode side electrode 9 and oxidant gas (oxygen, usually air) to the cathode side electrode 11 are respectively provided on both sides of the MEA 13. Deploy.

  Here, the electrolyte membrane 7 protrudes outside the anode side electrode 9 over the entire circumference, and a plate-shaped sealing material 19 is interposed between the protruding portion and the separator 15. The electrolyte membrane 7 protrudes outward from the cathode-side electrode 11 over the entire circumference, and is located between the protruding portion and the separator 17 on the separator 17 side of the plate-like sealing material 21 and the plate-like sealing material 21. A gasket 23 as an elastic sealing material is interposed.

  The electrolyte membrane 7 is a proton conductive ion exchange membrane formed of a solid polymer material such as a fluorine resin, and exhibits good electrical conductivity in a wet state. On the surface of the electrolyte membrane 7, platinum or an alloy made of platinum and another metal is supported as a catalyst.

  The gas diffusion electrode is formed of a member having sufficient gas diffusibility and conductivity, such as carbon cloth woven with yarn made of carbon fiber, carbon paper, or carbon felt.

  The separators 15 and 17 are formed of a material having sufficient conductivity, strength, and corrosion resistance. For example, the carbon material may be press-molded, or may be formed of other materials such as metal as long as sufficient corrosion resistance can be realized.

  A fuel gas flow path (not shown) is formed on the anode side electrode 9 side of the separator 15 and an oxidant gas flow path 25 is formed on the cathode side electrode 11 side of the separator 17, respectively. A cooling medium flow path 27 is formed. In FIG. 2, detailed flow channel shapes of the oxidant gas flow channel 25 and the cooling medium flow channel 27 are omitted.

  The gasket 23 is formed of a rubber-like elastic material such as silicon rubber, EPDM, or fluorine rubber. The gasket 23 may be integrated with the separator 17 or the plate-shaped sealing material 21. The plate-like sealing materials 19 and 21 are made of a material having a larger elastic coefficient than that of the gasket 23, such as polycarbonate or polyethylene terephthalate, and the electrolyte membrane 7 is made of, for example, thermosetting fluorine-based or thermosetting silicon. Adhering and bonding with a simple liquid seal.

  In the fuel cell stack described above, current collecting plates 29 and 31, insulating plates 33 and 35, and end plates 37 and 39 are disposed at both ends in the stacking direction of the stacked body 3 composed of a plurality of unit cells 1, respectively, as shown in FIG. To do. Then, the tension rod described above is passed through, for example, the four corners of the fuel cell stack, and the nut 41 is screwed and fastened to the screw portion formed at the end of the tension rod, thereby fastening the stack components.

  The tension rod is formed of a material having rigidity, for example, a metal material such as steel, and an insulating process is performed on the surface in order to prevent an electrical short circuit between the unit cells 1.

  The current collecting plates 29 and 31 are formed of a gas impermeable conductive member such as dense carbon or a copper plate, and the insulating plates 33 and 35 are formed of an insulating member such as rubber or resin.

  The end plates 37 and 39 are formed of a material having rigidity, for example, a metal material such as steel. The two current collecting plates 29 and 31 are provided with output terminals 43 and 45, respectively, and the electromotive force generated in the fuel cell stack is output through the output terminals 43 and 45.

  In the above-described method of tightening the fuel cell stack with the tension rods, it is not necessary to pass all the tension rods into the stacked body 3, and tension rods for tightening the end plates 37, 39 may be provided outside the stack.

  Also, as shown in FIG. 3, an inner end plate 47 is disposed between an end plate 39 on one end side in the stacking direction of the fuel cell stack and an insulating plate 35 provided on the inner side in the stacking direction of the end plate 39, A structure in which a pressurizing mechanism 49 made of a spring or the like is installed between the plate 39 and the inner end plate 47 and the end plates 37 and 39 are tightened with a tension rod may be employed. As a fastening mechanism, a screw hole may be provided in one end plate without using the nut 41, and a screw portion at the tip of the tension rod may be fastened to this screw hole.

  As shown in FIG. 1, the end plate 37 at one end of the fuel cell stack has a fuel gas inlet 51 and outlet 53, an oxidant gas inlet 55 and outlet 57, a cooling medium inlet 59 and outlet, as shown in FIG. 61 are provided. The distribution passages for the fuel gas, the oxidant gas, and the cooling medium that communicate with the respective inlets, and the collective flow paths for the fuel gas, the oxidant gas, and the cooling medium that communicate with the respective outlets are connected to a current collector plate 29 and an insulating plate 33 and the laminated body 3 are formed.

  Each of the distribution channels and the collecting channels described above includes the fuel gas channel formed on the anode side electrode 9 side of the separator 15, the oxidant gas channel 25 formed on the cathode side electrode 11 side of the separator 17, and the cooling medium. Each of the flow paths 27 communicates with the corresponding flow path.

  In order to form a distribution channel in the above-described laminated body 3, as shown in FIG. 2, the separator 15, the plate-shaped sealing material 19, the electrolyte membrane 7, the plate-shaped sealing material 21, the gasket 23, and the separator 17 include fuel. Fuel gas inlet communication holes 15a, 19a, 7a, 21a, 23a, 17a are formed at positions corresponding to the gas inlet 51, respectively.

  Similarly, corresponding communication holes are provided in the fuel gas outlet 53, the oxidant gas inlet 55 and the outlet 57, the cooling medium inlet 59 and the outlet 61, respectively.

(First embodiment)
FIG. 4 is a cross-sectional view of the outer peripheral portion of the unit cell 1 showing an example of the seal structure of the fuel cell according to the first embodiment of the present invention. A fuel gas channel 63 as an anode gas channel not shown in FIG. 2 is formed on the surface of the separator 15 facing the anode side electrode 9.

  The plate-shaped sealing materials 19 and 21 described above are bonded to both surfaces of the protruding portion 7b of the electrolyte membrane 7 protruding outward with respect to the anode side electrode 9 and the cathode side electrode 11, respectively. Among them, one plate-like sealing material 19 located at the bottom in FIG. 4 is bonded to the anode-side separator 15. In FIG. 4, a gasket 23 having a circular or elliptical cross section narrower than the plate-shaped sealing materials 19, 21 is interposed between the other plate-shaped sealing material 21 positioned at the upper portion and the cathode-side separator 17. .

  As described above, the plate-like sealing materials 19 and 21 having a larger elastic coefficient than the gasket 23 are bonded to both surfaces of the electrolyte membrane 7, and the gasket 23 which is a compressible elastic sealing material is provided only on one side thereof. Compared to the case where rubber seals are used on both sides, the reaction force from the rubber seals is reduced, and the damage to the separators 15 and 17 can be prevented by suppressing the stack tightening pressure. The surface pressure distribution is uniform, and the sealing performance can be ensured even when the gasket 23 is slightly deviated from the center position in the width direction as shown in FIG.

  Further, since the wide plate-like sealing material 21 and the plate-like sealing material 19 that are in contact with the narrow gasket 23 have a larger elastic coefficient than that of the gasket 23, the wide plate-like sealing material 21. , 19 can be suppressed, and a reduction in sealing performance on the wide plate-shaped sealing material 21 side can be prevented.

  Furthermore, since the plate-like sealing materials 19 and 21 having a larger elastic coefficient than the gasket 23 are in direct contact with the electrolyte membrane 7 and the gasket 23 which is a compressible rubber seal is not in direct contact with the electrolyte membrane 7, the electrolyte membrane 7 generates power. Even if it expands and contracts sometimes, damage can be prevented and sealing performance can be secured.

  Further, bonding the plate-like sealing materials 19 and 21 to both surfaces of the electrolyte membrane 7 also has an effect of improving the handleability of the MEA 13.

  Furthermore, by adhering the plate-shaped sealing material 19 to the anode-side separator 15, the sealing performance against hydrogen, which is the fuel gas flowing through the fuel gas channel 63, can be more reliably maintained, and the reliability is improved.

  Note that the cross-sectional shape of the gasket 23 in the first embodiment described above is not limited to a circle or an ellipse, and may be another shape. This also applies to other embodiments described below.

(Second Embodiment)
FIG. 5 is a cross-sectional view of the outer peripheral portion of the unit cell 1 showing an example of the seal structure of the fuel cell according to the second embodiment of the present invention. The overall structure is the same as that of the first embodiment shown in FIG. It is. 4 shows the state after stack fastening, while FIG. 5 shows the state before stack fastening, that is, before assembly.

  In this embodiment, as shown in FIG. 5, the total thickness d1 of the protruding portion 7b of the electrolyte membrane 7 and the two plate-like sealing materials 19 and 21 provided on both surfaces thereof is set to the thickness of the MEA 13, that is, the electrolyte. The total thickness d2 of the membrane 7 and the anode side electrode 9 and the cathode side electrode 11 provided on both sides thereof is set to be thinner than a predetermined value.

  By setting in this way, the displacement of the gas diffusion electrode at the time of stack tightening can be sufficiently secured, and the surface pressure to be applied to the gas diffusion electrode can be maintained.

(Third embodiment)
FIG. 6 is a cross-sectional view of the outer peripheral portion of the unit cell 1 showing an example of a fuel cell seal structure according to the third embodiment of the present invention. Note that FIG. 6 also shows the state before stack fastening, as in FIG.

  Here, the thickness d2 of the MEA 13 becomes non-uniform as a whole due to variations in the thickness of the gas diffusion electrode, for example, as shown in FIG. Therefore, in the third embodiment, the total thickness d1 of the electrolyte membrane 7 and the two plate-shaped sealing materials 19 and 21 provided on both surfaces thereof is thinner than the minimum value of the thickness d2 of the MEA 13 by a predetermined value or more. It is set to become.

  Thereby, even if the thickness d2 of the MEA 13 is not uniform as a whole, the displacement of the gas diffusion electrode at the time of stack tightening can be ensured over the entire region, and the surface pressure to be applied to the gas diffusion electrode can be maintained over the entire region. Can be generated.

(Fourth embodiment)
FIG. 7 is a cross-sectional view of the outer peripheral portion of the unit cell 1 showing an example of a fuel cell seal structure according to the fourth embodiment of the present invention. In this embodiment, the gasket 23 is set in the vicinity of the cathode-side electrode 11 with respect to the first embodiment shown in FIG. Other configurations are the same as those of the first embodiment.

  Thereby, the space area | region between the gasket 23 and the cathode side electrode 11 becomes narrow, the reaction which does not participate in a power generation reaction, and oxidizing agent gas flow rate can be reduced, and the power generation efficiency of a fuel cell stack can be improved.

  According to the present invention, the total thickness of the protruding portion of the electrolyte membrane in the state before assembly and the two plate-like sealing materials provided on both surfaces thereof is set to the electrolyte membrane in the state before assembly. And the total thickness of the anode side electrode and the cathode side electrode provided on both sides thereof is set to be thinner than a predetermined value, so that sufficient displacement of the anode side electrode and the cathode side electrode when assembling the fuel cell can be secured. The surface pressure to be applied to the electrode can be maintained.

  Since the total thickness of the electrolyte membrane and the anode side electrode and the cathode side electrode provided on both surfaces thereof is the minimum value of the total thickness, the thickness of the anode side electrode and the cathode side electrode varies. In addition, the displacement of each electrode at the time of assembling the fuel cell can be ensured over the entire region, and the surface pressure to be applied to each electrode can be generated over the entire region.

  Since the separator for joining the plate-shaped sealing material has the anode gas flow path, the sealing performance of the fuel gas flowing through the anode side flow path can be more reliably maintained, and the reliability is improved.

  Since the elastic sealing material is disposed in the vicinity of the electrode located on the inside thereof, the reaction not involving the power generation reaction and the oxidant gas flow rate can be reduced, and the power generation efficiency of the fuel cell can be improved.

It is a perspective view which shows the basic structure of the fuel cell stack of this invention. FIG. 2 is an exploded perspective view of a unit cell in the fuel cell stack of FIG. 1. FIG. 2 is a front sectional view in which a part of the fuel cell stack of FIG. It is sectional drawing of the outer peripheral part of the unit cell which shows an example of the seal structure of the fuel cell concerning the 1st Embodiment of this invention. It is sectional drawing of the outer peripheral part of the unit cell which shows an example of the seal structure of the fuel cell concerning the 2nd Embodiment of this invention. It is sectional drawing of the outer peripheral part of the unit cell which shows an example of the seal structure of the fuel cell concerning the 3rd Embodiment of this invention. It is sectional drawing of the outer peripheral part of the unit cell which shows an example of the seal structure of the fuel cell concerning the 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 7 Electrolyte membrane 7b Extrusion part of electrolyte membrane 9 Anode side electrode 11 Cathode side electrode 15, 17 Separator 19, 21 Plate-shaped sealing material 23 Elastic sealing material 63 Fuel gas flow path (anode gas flow path)
d1 Total thickness of electrolyte membrane and two plate-shaped sealing materials d2 Total thickness of electrolyte membrane, anode side electrode and cathode side electrode

Claims (5)

  In the fuel cell seal structure in which the anode side electrode is disposed on one side of the electrolyte membrane and the cathode side electrode is disposed on the other side, and the outside is sandwiched between a pair of separators, the electrolyte membrane is formed on the anode side. A protruding portion protruding outward from the electrode and the cathode side electrode, a plate-shaped sealing material is provided on both sides of the protruding portion, one of the plate-shaped sealing materials is joined to the separator, and the other of the plate-shaped sealing material and An elastic sealing material having a narrower width than the plate-shaped sealing material is provided between the separator, and the plate-shaped sealing material has a larger elastic coefficient than the elastic sealing material.   2. The fuel cell seal structure according to claim 1, wherein a total thickness of the protruding portion of the electrolyte membrane in a state before assembly and the two plate-shaped sealing materials provided on both surfaces thereof is set before assembly. The fuel cell seal structure is characterized in that it is set to be thinner by a predetermined value or more than the total thickness of the electrolyte membrane and the anode-side electrode and cathode-side electrode provided on both surfaces thereof in the above state.   3. The fuel cell seal structure according to claim 2, wherein a total thickness of the electrolyte membrane and the anode side electrode and the cathode side electrode provided on both surfaces thereof is a minimum value of the total thickness. Fuel cell seal structure.   4. The fuel cell seal structure according to claim 1, wherein the separator to which the plate-shaped sealing material is joined includes an anode gas flow path. 5.   5. The fuel cell seal structure according to claim 1, wherein the elastic seal material is disposed in the vicinity of the electrode located inside thereof. 6.

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