JP2000123857A - Solid polymer fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make lightweight and compact, and heighten electric insulation and gas tightness. SOLUTION: Tie rods 2 for fastening fastening plates 3A, 3B arranged opposite ends of a cell stack 1, on which an electric insulation treatment film 6 is formed, are housed in gas manifolds 4, 5 on the inside of the cell stack 1, a fastening component 7 is assembled through an electric insulating seal gasket 8 in the end of the tie rod 2 arranged in a counterbore part 10, and a gas sealing member 9 is assembled in an opening part of the counterbore part 10, and held in an airtight state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer electrolyte fuel cell using an ion exchange membrane as an electrolyte layer to obtain electric energy by an electrochemical reaction, and more particularly to a fastening structure and a sealing structure thereof.

[0002]

2. Description of the Related Art FIG. 3 is a front view showing the basic structure of a typical conventional polymer electrolyte fuel cell. In this figure, 2
1 is a battery stack, 22 is a tie rod, 23 is a fastening plate, 24 is a current collector, and 25 is an insulating plate. Battery stack 2
1 is to stack a plurality of unit cells each composed of a solid polymer membrane (membrane), an anode and a cathode via a separator,
A cooling plate for removing heat generated by power generation is inserted as needed. At both ends of the battery stack 21, current collecting plates 24 for extracting current to the outside are arranged.
The battery stack 21 is fastened and held by fastening the fastening plate 23 with a plurality of tie rods 22 arranged on the outer periphery. Tightening by the tie rods 22 is performed by fixing to the outer surface of the tightening plate 23 with a nut 26 disposed via a washer 29, a disc spring 28, and a washer 27.

The oxidizing gas inlet 31 shown in FIG.
The oxidant gas supply port is a supply port for an oxidant gas supplied to the cathode of each cell constituting the battery stack 21.
This is the outlet for the oxidizing gas that did not contribute to the reaction. Further, the fuel gas inlet 35 is a supply port of a fuel gas supplied to the anode of each of the cells constituting the cell stack 21, and the fuel gas outlet 36 is a discharge port of a fuel gas which has not contributed to the reaction. The cooling water inlet 33 and the cooling water outlet 34 are a supply port and a discharge port of the cooling water supplied to the cooling plate interposed in the battery stack 21.

[0004]

As described above, in a polymer electrolyte fuel cell having a configuration in which a plurality of cells are stacked and tightened, if the tightening pressure becomes non-uniform in the plane, the internal resistance of the cells and the cell resistance are reduced. There is a danger that the contact resistance between the batteries will increase to cause a decrease in the performance of the batteries, or, in some cases, the hermeticity will be insufficient and gas leakage or cooling water leakage will occur. Therefore, in the polymer electrolyte fuel cell of the present configuration, it is necessary to consider that the tightening pressure is uniform in the plane.

The conventional structure shown in FIG. 3 employs a method in which the battery stack 21 is fastened by a plurality of tie rods 22 arranged on the outer periphery. The plate 23 is warped, and the clamping pressure becomes non-uniform in the plane. Therefore, in the conventional polymer electrolyte fuel cell, a considerably thick plate is used as the clamping plate 23 so as not to cause warpage. For this reason, the polymer electrolyte fuel cell of this configuration becomes heavy, and for example, there is a problem that the weight becomes excessive for a fuel cell mounted on an automobile.

Further, in the above configuration, since the tie rods 22 are arranged on the outer periphery, it is necessary to use the tightening plate 23 which is slightly larger than the battery stack 21, so that a dead space is generated on the outer periphery of the battery. Also, a nut 26 for fastening the tie rod 22, a washer 27, a disc spring 2
8. Since fastening parts such as washers 29 protrude outside the fastening plate 23, dead spaces also occur at both ends in the stacking direction. Therefore, the polymer electrolyte fuel cell of this configuration has a problem that the required space is large.

On the other hand, recently, US Patent No.
As disclosed in US Pat. No. 5,484,666, by using a system in which a tie rod for tightening a battery stack is passed through a fuel gas or oxidizing gas manifold provided inside the battery stack, a polymer electrolyte fuel cell Attempts have been made to reduce the size. This method does not require a thick clamping plate as used in the configuration shown in FIG.
There is an advantage that the weight and size can be reduced, but on the other hand, there are problems in electrical insulation between the tie rod and the battery stack and a gas sealing method.

That is, for example, in the case of a polymer electrolyte fuel cell using Nafion 117 (trade name, manufactured by DuPont) as an electrolyte membrane, the above membrane has high ionic conductivity unless it is in a sufficiently wet state. When this type of ion exchange membrane is used as an electrolyte membrane, a fuel gas or an oxidizing gas, and depending on conditions, both gases are humidified beforehand and supplied to the battery stack. In general, a method for preventing the electrolyte membrane from drying is adopted. However, when the humidified gas is supplied to the manifold provided in the battery stack, water is condensed in a gap between the tie rod and the battery stack because a fastening tie rod penetrates the manifold. Risk of short circuit. In addition, the above U
Although not disclosed in S Patent No. 5,484,666, it is necessary to electrically insulate the clamping plate and the tie rod, and at the same time, it is necessary to provide a gas-tight structure.

The present invention has been made in consideration of the problems of the prior art as described above, and an object of the present invention is to provide a lighter, more compact, more electrically insulating, gas-tight, and more reliable device than before. An object of the present invention is to provide a polymer electrolyte fuel cell which can be operated stably at high speed.

[0010]

In order to achieve the above object, in the present invention, a plurality of unit cells each having an anode and a cathode disposed on both surfaces of an ion exchange membrane are stacked with a separator interposed therebetween. Then, the formed battery stack is fastened and supported by using the fastening plates arranged at both ends in the stacking direction of the stack batteries and tie rods for fixing the fastening plates, and penetrates inside the battery stack in the stacking direction. In a polymer electrolyte fuel cell that supplies a reaction gas to a gas manifold provided as described above and obtains electric energy by an electrochemical reaction, (1) the above-mentioned tie rods are disposed so as to penetrate inside the gas manifold, and An electrically insulating layer, for example, an electrically insulating layer formed by coating an electrically insulating resin on the surface of the inner penetrating portion of the gas manifold of the tie rod, or An electrically insulating layer formed of an electrically insulating heat-shrinkable tube is provided.

(2) The clamping plate further includes a counterbore on the outer surface of the through hole communicating with the gas manifold,
Inside the counterbore, fastening parts such as nuts and disc springs for fixing and supporting the tie rods to the fastening plate are sealed with an electrically insulating seal packing, for example, a seal packing made of polyethylene resin or polytetrafluoroethylene (PTFE) resin. To maintain electrical insulation between the plate and the clamping plate.

(3) Further, in the above (2), a gas seal member for keeping the inside of the counterbore portion airtight with the outside is arranged in the counterbore portion provided on the fastening plate.

As described in (1) above, if the tie rods are incorporated into the gas manifold disposed inside the battery stack and tightened, the battery stack can be in-plane even if the fastening plate is thin. Pressurization will be more uniform. In addition, since the outer dimensions of the fastening plate may be smaller than the outer dimensions of the battery stack, a compact configuration with less dead space can be provided. In addition, by disposing the electric insulation treatment layer on the surface of the tie rod, an electric short circuit between the tie rod and the battery stack is prevented.

Further, according to the above (2), since the fastening parts are housed inside the counterbore portion provided on the fastening plate, they do not protrude to the side as in the conventional case, and the dead space is small. Can be suppressed. Further, by providing the electrically insulating seal packing, electrical insulation between the tie rod and the fastening plate is ensured.

Further, if a gas seal member is provided in the counterbore portion as described in (3) above, leakage of the gas in the manifold to the outside can be prevented.

[0016]

FIG. 1 is a schematic sectional view showing a basic structure of an embodiment of a polymer electrolyte fuel cell according to the present invention, wherein 1 is a cell stack, 2 is a tie rod, and 3A and 3B are clamping plates. ,
Reference numerals 4 and 5 denote gas manifolds. In the configuration of this drawing, the fastening plates 3A and 3B also fulfill the function of a current collector, and the current collector 24 and the insulating plate 2 used in the conventional example of FIG.
5 is not incorporated.

In the configuration of this embodiment, the tie rods 2 are inserted into the gas manifold 4 for the fuel gas and the gas manifold 5 for the air, and the tie rods 2 are installed therein.
The battery stack is fastened at a predetermined pressure by attaching fastening parts 7 to both ends of the tie rod 2 arranged in the counterbore portion 10 of 3B. An electrically insulating seal packing 8 is arranged between the fastening component 7 and the bottom of the counterbore 10, and the seal packing 8 allows the tie rod 2
And the clamping plates 3A and 3B are electrically insulated. The gas seal member 9 is provided in the opening of the counterbore portion 10.
Is incorporated to maintain airtightness between the inside and the outside of the spot facing portion 10.

The fuel gas is supplied from a fuel gas inlet 11 provided in the clamping plate 3A, introduced into the gas manifold 4, and supplied to each unit cell. The reaction air is supplied from the air inlet 13, is introduced into the gas manifold 5, and is supplied to each cell. The fuel gas and the reaction air that have not contributed to the reaction are discharged from the fuel gas outlet 12 and the air outlet 14, respectively. As described above, in the polymer electrolyte fuel cell, a method is employed in which the fuel gas or the air, and depending on the conditions, both gases are humidified and supplied in advance in order to prevent the drying of the electrolyte membrane. Although there is a high possibility that water will condense in the inside, in the configuration of the present embodiment, since the electrically insulating treatment layer 6 is formed by mounting a fluororesin-based heat-shrinkable tube on the surface of the tie rod 2, the manifold Even if water condenses inside
There is no fear that the tie rod 2 and the battery stack 1 are electrically short-circuited.

FIG. 2 is an enlarged view of a portion A shown in FIG. 1 of this embodiment. As shown in the figure, in the counterbore portion 10 of the fastening plate 3A, the fastening components 7 incorporated at both ends of the tie rod 2 include nuts 7a and washers 7b,
The disc spring 7c includes a disc spring 7c and a washer 7d. The nut 7a is screwed into the tip of the tie rod 2 to compress the disc spring 7c. By adding expansion power,
The battery stack 1 is held by applying a compressive force. As described above, the seal packing 8 made of PTFE is incorporated between the washer 7d and the bottom of the counterbore portion 10, and the seal packing 8 maintains electrical insulation between the tie rod 2 and the clamping plate 3A. I'm dripping.

Further, the gas seal member 9 shown in FIG.
A gasket screw 9a and a packing 9b made of PTFE are provided. The packing 9b is arranged on a shelf in the middle of the counterbore portion 10. By screwing the gas seal screw 9a into the opening of the counterbore portion 10, the counterbore is formed. The inside of the part 10 is kept airtight to the outside. Therefore, even if the fuel gas introduced into the gas manifold 4 leaks through the gap between the tie rod 2 and the seal packing 8 to the inside of the counterbore 10, it does not leak out of the counterbore 10.
The gas manifold 4 is kept airtight.

[0021]

As described above, according to the present invention, a tie rod having an electric insulation treatment layer on its surface is disposed so as to penetrate into a gas manifold inside a battery stack, and is electrically connected to a clamping plate. A structure in which insulating packing is inserted and tightened with tightening parts using screws and disc springs. Further, a counterbore portion is provided on the tightening plate to house the tightening parts, and the opening thereof is sealed with a gas seal member. As a result, a polymer electrolyte fuel cell which is lighter and more compact than before, and has excellent electric insulation and gas tightness, and can be operated stably with high reliability can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a basic configuration of an embodiment of a polymer electrolyte fuel cell according to the present invention.

FIG. 2 is an enlarged view of a portion A of the embodiment shown in FIG.

FIG. 3 is a front view showing the basic configuration of a typical conventional polymer electrolyte fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery laminated body 2 Tie rod 3A, 3B Clamping plate 4 Gas manifold 5 Gas manifold 6 Electric insulation treatment layer 7 Fastening parts 7a Nut 7b Washer 7c Disc spring 7d Washer 8 Seal packing 9 Gas seal member 9a Gas seal screw 9b Packing 10 Counterbore 11 Fuel gas inlet 12 Fuel gas outlet 13 Air inlet 14 Air outlet

Claims (6)

[Claims] 1. A battery stack formed by stacking a plurality of unit cells each having an anode and a cathode on both sides of an ion exchange membrane with a separator interposed therebetween, at both ends in the stacking direction of the battery stack. The clamped plate and the tie rod for fixing the clamped plate are used to fasten and support the clamped plate, and to supply a reaction gas to a gas manifold provided to penetrate in the stacking direction inside the battery stack, and perform an electrochemical reaction. In a polymer electrolyte fuel cell for obtaining electric energy, the tie rod is disposed so as to penetrate inside a gas manifold, and an electric insulation treatment layer is provided on a surface of a part of the tie rod which penetrates inside the gas manifold. A polymer electrolyte fuel cell characterized by the above-mentioned. 2. The polymer electrolyte fuel cell according to claim 1, wherein the electrically insulating layer provided on the surface of the tie rod is formed by coating an electrically insulating resin. Solid polymer fuel cell. 3. The polymer electrolyte fuel cell according to claim 1, wherein the electrically insulating layer provided on the surface of the tie rod is formed of an electrically insulating heat-shrinkable tube. Solid polymer fuel cell. 4. The polymer electrolyte fuel cell according to claim 1, wherein the fastening plate has a counterbore on an outer surface of a through hole communicating with the gas manifold, and inside the counterbore, A polymer electrolyte fuel cell, wherein a tightening part for fixedly supporting the tie rod on the tightening plate is arranged while maintaining electrical insulation between the tightening plate and the sealing plate by an electrically insulating seal packing. 5. The polymer electrolyte fuel cell according to claim 4, wherein the electrically insulating seal packing for maintaining electrical insulation between the fastening plate and a fastening component for fixing and supporting the tie rod to the fastening plate comprises: A polymer electrolyte fuel cell comprising a polyethylene resin or a polytetrafluoroethylene resin. 6. The polymer electrolyte fuel cell according to claim 4, wherein a gas seal member is provided at the counterbore portion provided on the fastening plate to keep the inside of the counterbore portion airtight from the outside. A polymer electrolyte fuel cell.