JPH0411985B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel cell end sealing device for sealing a reactant gas of a fuel cell at a peripheral edge of a matrix and an end face of an electrode base material.

[Conventional technology]

A conventional end sealing device for a fuel cell will be described below, but first, an example of a unit cell constituting a cell stack of a fuel cell will be described. FIG. 8 is a partially exploded perspective view of a ribbed electrode type unit cell, in which a porous fuel electrode 12 and an oxidizer electrode 13 are arranged on both sides of a matrix layer 11 impregnated with an electrolytic solution. Porous ribbed electrode base materials 14 and 15 are disposed in close contact with the electrodes, respectively, and the ribbed electrode base material 14 on the fuel electrode 12 side has a groove 14a for supplying fuel gas.
The ribbed electrode base material 15 on the side is provided with grooves 15a for supplying oxidizing gas in a direction perpendicular to the direction of the grooves 14a to constitute a unit cell, and a gas diffusing separate plate 16 is provided between the unit cells. These are interposed and stacked to form a cell stack.

During operation of the fuel cell, fuel gas is supplied to the supply groove 14.
The oxidant gas flows into the supply groove 15a and is supplied to the oxidizer electrode 13, causing an electrochemical reaction in the unit cell to generate electricity. At this time, the end faces of the fuel electrode 12, oxidizer electrode 13, and ribbed electrode base materials 14 and 15 are Fluororubber latex is applied to the peripheral edges to form airtight sealing surfaces 122 and 123, respectively. The separate plate 16 is covered with a sealing sheet 24 to prevent leakage to the outside from this sealing surface when the reactant gas manifold is attached.

The conventional fuel cell end sealing device has a fluorine rubber coated seal corresponding to the thickness of the matrix 11 between the sealing surfaces 122 and 123 whose end faces and peripheral edges have been airtightly treated as described above. The layer is formed by applying fluoro rubber latex and drying.
Each electrode substrate was adhered using an adhesive (phenolic resin) to form an end seal.

[Problem to be solved by the invention]

The conventional end seal device as described above has the following problems.

In order to construct the above-mentioned end seal, the following steps are generally required, so the processing and assembly steps take a long time.

Applying fluoro rubber latex to the sealing surface → heating and drying → thickness inspection → surface leveling → adhesive application → curing → inspection → lamination.

Phenol resin used as adhesive,
The heat resistance against the operating temperature of the battery is insufficient,
Furthermore, the chemical resistance against phosphoric acid used as an electrolytic solution, especially at high temperatures, is insufficient, so the life span is short.

It is susceptible to thermal stress that occurs when battery temperature fluctuates, and heat cycles can cause the fluororubber to deform and protrude outward, leading to gas leaks.

Since the batteries are stacked while being bonded, even if a unit battery in the stack fails, that unit battery cannot be easily replaced.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an end sealing device for a fuel cell that has high reliability and can simplify processing and assembly steps.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention provides a fuel cell in which a matrix is sandwiched between each electrode base material having a fuel electrode and an oxidizer electrode, and these are stacked and fixed by tightening. In the fuel cell end sealing device for sealing the end face of the matrix and the end face of each electrode base material, a flat gasket is placed at the periphery of the matrix between the end face parts of each electrode base material whose end face and periphery have been previously air-tightly treated. The flat gasket is made by laminating unfired fluororesin sheets having different compressive elastic moduli, and the layers at both ends have a lower compressive elastic modulus when viewed in the stacking direction, and the inner layer has a lower compressive elastic modulus. The layer is an unfired fluorocarbon resin sheet having a higher compressive modulus than the layers at both ends.

〔Example〕

FIG. 9 is a sectional view showing an embodiment of the present invention,
Corresponding to the XX cross section of FIG. 8, the same members as those in FIG. 8 are given the same reference numerals and their explanations will be omitted.

In the conventional device shown in FIG. 8, airtight seal surfaces 122 and 123 were formed by coating the end face and peripheral edge of the electrode base material with fluorocarbon rubber latex, but in the embodiment shown in FIG. Seal sheets 22 and 23 made of rubber sheets are coated on the end faces and peripheral portions of the fuel electrode 12, oxidizer electrode 13, and ribbed electrode base materials 14 and 15, respectively. Instead of the sealing sheet, a sealing surface may be formed by coating and drying fluoro rubber latex. A flat gasket 51 is interposed at the periphery of the matrix between the end surfaces of each electrode substrate whose end surfaces and peripheries have been airtightly treated in advance in this way.

This flat gasket is made by laminating unfired fluorocarbon resin sheets with different compressive elastic moduli.The layers at both ends have a low compressive elastic modulus when viewed in the stacking direction, and the inner layer has a lower compressive elastic modulus than the layers at both ends. The sheet is made of the unfired fluororesin sheet having a higher compressive modulus. The configuration of the flat gasket will be explained in detail below.

Unfired fluorocarbon resin sheets with different compressive elastic moduli are made using the same manufacturing method as porous Teflon sheets used for sealing screws (for example, those sold under the trade name ``Tape Seal'' by Nihon Valqua Co., Ltd.). It is something that This manufacturing method involves kneading fine powder, which is a powder of PTFE (polytetrafluoroethylene) resin, with a forming aid, such as naphtha, forming it into a sheet by roll forming, and then completely scattering the aid at around 180°C. It will be done. At this time, pores in which the auxiliary agent has been scattered remain inside the sheet, and the compressive elastic modulus of the sheet differs depending on the pore content. That is, the porosity within the sheet can be adjusted by adjusting the amount of the auxiliary agent added, and a desired compressive elastic modulus can be obtained.

As a sealing material for such porous PTFE resin materials, there is a material in which pores are created in the sheet by mechanical processing after Teflon is fired at a temperature above its melting point. /cm ² ) has the disadvantage that sufficient sealing performance cannot be obtained. On the other hand, unfired fluororesin sheets are not fired at a temperature higher than the melting point of the fluororesin after forming the sheet.
The force caused by the entanglement of fibers within the sheet becomes weaker,
Therefore, sufficient sealing performance can be obtained even with a low tightening force.

The flat gasket used in the present invention is obtained by combining the above-mentioned unfired fluororesin sheets having different flexibility. For example, sheets with high porosity, ie, low compressive elastic modulus, are used for the layers on both sides of the sealing surface of the gasket to sufficiently adapt to the surface roughness and scratches of the sealing surface to ensure a good seal. It also has a sealing function with low tightening force, and in order to obtain a sufficient amount of deflection, sheets with different compressive elastic moduli are laminated. In this case, simply laminating sheets with a low compressive elastic modulus will not provide a sufficient amount of deflection, and gas will leak through the inside of the gasket. To prevent this, the gasket is made by laminating a plurality of unfired fluororesin sheets with low porosity, somewhat high compressive modulus, and gas sealability even with a small amount of deflection. A gasket laminated in this way has a low compressive elastic modulus in the layers at both ends, so it conforms well to the sealing surface, and by combining different compressive elastic moduli, the degree of freedom in compressive deflection characteristics can be increased, and the gasket's Since the material is a fluorine resin material, it is possible to obtain a gasket that is heat resistant (approximately 260°C) and acid resistant.

Next, characteristics and examples of the flat gasket used in the present invention will be explained based on the drawings. Figure 1 is a characteristic diagram showing the relationship between load and deflection of unfired fluorocarbon resins with different porosities, and sheets A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A.
For example, the porosity of A, B, and C is set to be A<40%, 40≦B<70%, and C≧70%, respectively. From this characteristic diagram, the higher the porosity, the greater the deflection under load, and the lower the compressive elastic modulus. This shows that when in contact with the sealing surface, the higher the porosity, the easier it is to conform to the sealing surface.

Figure 2 shows sheets A, B, and C as sealing materials that are interposed and tightened on the flange surface of a container, filled with nitrogen gas at a constant pressure, and the amount leaking from the sheets is measured with a flowmeter. It is a characteristic diagram showing the results of determining the relationship between the amount of compressive elasticity and the tightening force, and it was found from this diagram that the higher the compressive elastic modulus, the smaller the amount of leakage.

FIG. 3 is a cross-sectional view of a gasket 1 made of laminated unfired fluororesin sheets having different compressive elastic moduli.
When viewed from the stacking direction of the gasket, sheets 2 and 4 having a low compressive elastic modulus are arranged in the layers at both ends, and a sheet 3 having a higher compressive elastic modulus than the sheets 2 and 4 is arranged inside them. In this case, since sheets with high porosity, that is, low compressive elastic modulus, are used for the layers at both ends of the gasket, they sufficiently adapt to the surface roughness and scratches of the sealing surface to ensure sealing performance. And a sheet 3 with low porosity and high compressive elastic modulus inside
is inserted. When the combinations of sheets 2, 3, and 4 constituting this gasket are respectively sheets C, A, and C and sheets C, B, and C explained in FIG. 1, the load and deflection of both gaskets are The characteristic curve of the relationship is shown in FIG. Figure 4 shows that gasket CBC with sheet B, which has a lower compressive modulus of elasticity, is more flexible than gasket CAC with sheet A, which has a higher compressive modulus than sheet B. This shows that gaskets with different compression properties can be obtained by using sheets with various compression moduli in the inner layer of the gasket.

Figure 5 is a characteristic curve obtained by using the same method as in Figure 2 to determine the relationship between the tightening surface pressure and the amount of gas leakage for the gaskets CAC and CBC. Since it is composed of sheet C with a low compressive elastic modulus, it adapts well to the roughness of the sealing surface, and the sealing performance on this surface is good. The overall sealing performance differs depending on the gasket, and gasket CAC, which has sheet A with small porosity and high compression elasticity, has a smaller amount of gas leakage than gasket CBC at the same tightening surface pressure. The laminated structure can be created by selecting sheets with appropriately different compressive elastic moduli to ensure a seal with low tightening force, depending on the amount of compressive deflection of the gasket and the gap between the seal parts, which are determined based on the seal structure of the structure. It turns out to be a good thing.

6 and 7 respectively show different embodiments of the flat gasket used in the present invention. In FIG. 6, the gasket 31 is a 4-layer gasket made by laminating sheets 32, 33, 34, and 35 having different compressive elastic moduli. It has a layered structure, and the sheets 33 and 34 located in the center are made of, for example, sheet A having a high compressive elastic modulus as explained in FIG. 1, and the sheets 32 and 33 located on the outside are Sheet C with a low ratio is used. In addition, FIG. 7 shows that the gasket 41 includes sheets 42 having different compressive elastic modulus,
43, 44, 45, and 46, and the sheet 44 located in the middle has a high compressive elastic modulus A as described in FIG. 1, and the sheets 42, 46 located outside Sheet C with low compressive elastic modulus is used for sheets 43 and 4.
Sheet B, which has a compressive modulus lower than Sheet A and higher than Sheet C, is used for No. 5.

The sheets 52, 53, and 54 constituting the flat gasket 51 shown in the embodiment of FIG. 9 are respectively composed of the aforementioned sheets C, A, and C, and sealing performance is ensured. This gasket 51 is
It is made of laminated unfired fluororesin sheets that have weak force due to tangled fibers, so it is suitable for phosphoric acid fuel cells where the clamping force of the cell is limited due to the possibility of damage to the matrix that holds the electrolyte. Maintains good sealing performance. Note that this flat gasket 5
1 uses gaskets with different amounts of compressive deflection depending on the seal gap and tightening force in which the gasket is inserted, such as a combination of sheets C, B, and C, or gaskets with other combinations to ensure sealing performance. .

〔Effect of the invention〕

As is clear from the above description, according to the present invention, in a fuel cell in which a matrix is sandwiched between each electrode base material having a fuel electrode and an oxidizer electrode, and these are stacked and fixed by tightening, In an end sealing device for a fuel cell that seals the peripheral edge of a matrix and the end face of each electrode base material, a flat plate-like seal is applied to the peripheral edge of the matrix between the end face parts of each electrode base material, the end face and the peripheral end of which have been previously airtightly treated. The flat gasket is made by laminating unfired fluorocarbon resin sheets with different compressive elastic moduli, and the layers at both ends when viewed in the stacking direction have a low compressive elastic modulus, while the inner layer has a low compressive elastic modulus. The layer located at each end is an unfired fluororesin sheet having a higher compressive elastic modulus than the layers at both ends, thereby achieving the following effects.

Since each layer constituting the flat gasket used in the present invention is made of an unfired fluororesin sheet, the force due to entanglement of fibers within the sheet is weak, so a sufficient seal can be obtained with a low tightening force.
In addition, since the layers on both ends of the gasket are made of sheets with low compressive elastic modulus, the surface roughness of the sealing surface
Adheres well to scratches and seals well.
The amount of compression deflection can be selected for the layer inside the gasket by combining various sheets with a higher compressive elastic modulus than the layers at both ends, so it is possible to use an appropriate gasket with a sealing function depending on the tightening force. , the end seal structure of the fuel cell can be easily assembled, and complicated processing steps required in conventional devices are not required.

Fluorine resin is heat resistant (approximately 260°C) and acid resistant, which improves the reliability of end seals in fuel cells used in high-temperature, acidic atmospheres, and extends the life of the seals.

Since the end seal is constructed without stacking the batteries while adhering them as in conventional devices, even if a cell in the stack fails, the cell can be easily replaced.

[Brief explanation of drawings]

Fig. 1 is a load and deflection characteristic diagram of the unsintered fluororesin constituting the flat gasket in the fuel cell end sealing device of the present invention, and Fig. 2 shows the characteristics of the unsintered fluororesin constituting the flat gasket. Figure 3 is a cross-sectional view of the flat gasket, Figure 4 is a load and deflection characteristic diagram of the flat gasket shown in Figure 3, Figure 5 is the flat plate shown in Figure 3. Fig. 6 is a cross-sectional view of a flat gasket according to a different embodiment, Fig. 7 is a cross-sectional view of a flat gasket according to another different embodiment, and Fig. 8 is a diagram of the gas leakage characteristics of a flat gasket according to another different embodiment. FIG. 9 is an exploded perspective view showing the structure of a unit cell of a battery, and FIG. 9 is a sectional view showing an embodiment of the end sealing device for a fuel cell according to the present invention. 1, 31, 41, 51: flat gasket,
2, 3, 4, 32, 33, 34, 35, 42, 4
3, 44, 45, 46, 52, 53, 54: unfired fluororesin sheet, 11: matrix layer, 1
4,15: Electrode base material.

Claims (1)

[Claims] 1. A fuel cell that seals the peripheral edge of the matrix and the end face of each electrode base material in a fuel cell in which a matrix is sandwiched between each electrode base material having a fuel electrode and an oxidizer electrode, and these are stacked and fixed by tightening. In a battery end sealing device, a flat gasket is interposed at the peripheral edge of the matrix between the end faces of each electrode substrate whose end faces and peripheral edges have been airtightly treated, and the flat gasket is compressed. It is made by laminating unfired fluorocarbon resin sheets with different moduli of elasticity, in which the layers at both ends have a lower compressive elastic modulus when viewed in the stacking direction, and the layers inside have a higher compressive elastic modulus than the layers at both ends. What is claimed is: 1. An end sealing device for a fuel cell, comprising an unfired fluororesin sheet.