JP5310991B2 - Manufacturing method of seal structure for fuel cell - Google Patents

Description

  The present invention relates to a fuel cell, and more particularly to a seal structure in a fuel cell.

  The fuel cell has a membrane electrode assembly (MEA) composed of a combination of an electrolyte membrane and an electrode, a gas diffusion layer (GDL), a separator, a gasket, and the like as its main components, and a fuel such as hydrogen from the anode side. It has a mechanism for generating power by supplying an oxidizing gas such as air from the gas and cathode side. As the material of the component parts, carbon and metal are used for the separator, and elastomers such as rubber and resin adhesive are used for the gasket.

  In addition, there are various types of seal structures incorporated in the fuel cell, and one of them is a gasket mounting groove provided on the separator with a rubber-made elastic gasket integrally formed on the MEA or a frame stacked on the MEA. There is one that suppresses leakage of the reaction gas inside the cell to the outside of the cell by being in close contact with the inner surface. In this type, the MEA used in the fuel cell is about several μm to several tens of μm and is very thin and easily deformed. Therefore, the gasket is integrally formed for the purpose of protecting this and improving the handleability. A technique of sticking a frame such as a resin film on the outside of the power generation area is conventionally used (see Patent Documents 1 and 2).

  However, according to the above prior art, the reaction gas such as fuel gas should flow from the manifold inlet of the cell to the manifold outlet while generating power through the power generation area. Short cuts may occur from the inlet to the manifold outlet via the gasket mounting groove. If this happens, the gas used for the shortcut will not contribute to the power generation operation at all, resulting in a loss of power generation efficiency. Yes. This gas shortcut is particularly likely to occur when the separator is made of metal. This is because metal separators form irregularities such as grooves by pressing, so that the gasket mounting groove is independent and accurate like a carbon separator. This is because it is difficult to make the gas, and thus the gas tends to go around the gasket mounting groove.

Japanese Patent No. 3820883 JP 2003-56704 A

  In view of the above, the present invention suppresses the shortcut of the reactive gas from the manifold inlet to the manifold outlet through the gasket mounting groove without going through the power generation area, thereby improving the power generation efficiency of the fuel cell. It is an object of the present invention to provide a fuel cell seal structure capable of performing

In order to achieve the above object, a manufacturing method of a seal structure according to claim 1 of the present invention provides an inner surface of a gasket mounting groove in which a gasket made of a rubber-like elastic body integrally formed on an MEA or a frame stacked on the MEA is provided on a separator. The fuel cell sealing structure prevents the reaction gas inside the cell from leaking to the outside of the cell by being in close contact with the fuel cell , so that the reaction gas does not flow into the mounting groove and short-circuit inside the cell. A fuel cell in which a gas inflow prevention portion is provided in a side edge portion of the mounting groove, and the gas inflow prevention portion sandwiches a thin film seal formed integrally with the gasket on the MEA or the frame between the MEA or the frame and the separator. Plate structure that is made into a frame by punching performed later A molding process in which a gasket and a thin film seal are integrally formed using a mold as a material, and a punching process in which the frame is formed by punching a plate-shaped material integrally molded with the gasket and the thin film seal are sequentially performed. In the molding step, the thin-film seal is molded as a burr-like shape, and in the punching step, the thin-film seal molded into the burr-shape is punched together with a plate-shaped material so that the thin-film seal has a predetermined planar shape. It is characterized by shaping .

  In the seal structure of the present invention having the above configuration, the gas inflow prevention portion is provided at the side edge portion of the gasket mounting groove so that the reaction gas does not flow into the gasket mounting groove inside the cell and thereby perform a shortcut. The gas inflow prevention portion prevents the reaction gas from flowing into the gasket mounting groove. Therefore, the gas flow flowing from the manifold inlet to the manifold outlet via the gasket mounting groove is blocked, thereby preventing a shortcut. The gas inflow prevention part is used as a seal part by sandwiching a MEA or a thin-film seal integrally formed with a gasket with a gasket between the MEA or the frame and a separator. The channel is closed. To close the shortcut flow path inside the gasket mounting groove, a rib is integrally formed on the side of the gasket and this rib is used as a weir to press fit into the mounting groove. There is a risk that overfilling occurs due to accuracy reasons, and this may cause distortion in the MEA and the separator. According to the method of the present invention, it is possible to prevent such inconvenience from occurring. It becomes possible.

  Further, in order to manufacture the seal structure of the present invention having the above-described configuration, a molding step of integrally molding a gasket and a thin film seal using a die on a plate-like material to be a frame by punching performed later, and the gasket and A stamping process for forming a frame by punching a plate-like material integrally formed with a thin film seal is sequentially performed. At this time, in the molding process, the thin film seal is formed as a burr, and then in the punching process. A predetermined planar shape is formed on the thin film seal by punching the thin film seal formed into a burr shape together with the plate material. According to such a method, not only can the planar shape of the frame and the thin film seal be made uniform, but also an air vent is actively provided in the mold, so molding such as air entering the molded product (gasket). It is possible to prevent the above inconvenience from occurring.

  The present invention has the following effects.

  That is, in the seal structure of the present invention, as described above, the gas inflow prevention portion is provided on the side edge portion of the gasket mounting groove so that the reaction gas does not flow into the gasket mounting groove inside the cell and is short-circuited. For this reason, the gas inflow prevention portion suppresses the reaction gas from flowing into the gasket mounting groove, prevents a shortcut, and the gas flows from the manifold inlet to the manifold outlet while generating power through the power generation area. Therefore, the power generation efficiency of the fuel cell can be improved.

  Further, in the manufacturing method of the present invention, as described above, not only can the planar shape of the frame and the thin film seal be made uniform, but also the mold is provided with an air vent, so that inconvenience in molding such as air entry. Can be prevented from occurring. Since the thin film seal is a thin film as the name suggests, punching does not become difficult.

  The present invention includes the following embodiments.

(1) The MEA integrated seal for fuel cells is a type in which a seal (gasket) is directly integrally formed at the end of the MEA, or a seal is integrally formed in advance on a frame (frame) such as a resin film, and this is applied to the MEA. There are types to paste. In any case, the mold is clamped at the time of seal molding, so a space for mold clamping is created between the power generation surface and the seal, and when combined with the separator plate groove, the fuel gas shortcut is used. Loss becomes a problem. As a method of preventing this shortcut, there is a method of providing a shortcut prevention rib on the side of the seal lip, but it is difficult to mold, and it is difficult to fill the gap well due to problems with the dimensional accuracy of the plate. There is a possibility of becoming.

(2) Therefore, in the present invention, as a means for preventing a shortcut, a thin film is formed on the MEA end surface or the frame surface by positively leaking burrs in an area conventionally used for mold pressing, and A structure is proposed in which the fuel gas does not easily enter the groove by making contact with the inner peripheral surface (inner peripheral portion) of the groove of the separator plate.

(3) The rubber material used in the present invention is not particularly defined, but is preferably a low-viscosity rubber material or a liquid rubber material. Examples of materials include silicone, fluororubber, EPDM rubber, butyl rubber, and the like that can withstand the usage environment of the fuel cell. In the case of being integrally formed on a frame such as a resin film, it is effective to use a rubber material having self-adhesiveness. In the case where the MEA is integrally formed, rubber materials that can be used are limited by the heat resistance of the MEA. Generally used ion exchange membranes have a heat resistance level of 150 degrees or less, and general rubber materials cannot be molded because the vulcanization temperature is too low. Become. By using liquid rubber, development with a view to impregnation of the MEA into the GDL part is possible. The burr state is controlled by adjusting the clamping force, injection pressure, speed, and temperature.

(4) By combining the inner peripheral surface (inner peripheral part) of the groove of the separator plate with a thin burr (thin film) on the MEA or on the frame, a fuel gas shortcut is prevented without providing a rib in the groove. can do. In addition, an air vent which is a problem during molding is positively attached, and robustness against molding defects such as air entry can be improved. Further, over-compression due to the ribs and deformation of the plate can be prevented.

  Next, examples of the present invention will be described. For convenience of explanation, first, comparative examples will be described.

Comparative example
FIG. 6 shows a cross section of the main part of a fuel cell according to a comparative example, and FIG. 7 shows the entire plane of the cell with the upper separator 5 in FIG. 6 removed. 6 is an enlarged cross-sectional view taken along line AA in FIG.

  In the cross-sectional view of FIG. 6, reference numeral 1 denotes an MEA (membrane electrode complex) in which electrodes (not shown) are superimposed on upper and lower surfaces of an electrolyte membrane (not shown). A GDL (gas diffusion layer) 2 is placed at the center of the plane (right side in the figure), and a frame (frame body) made of a planar resin film as shown in FIG. 3), and a gasket 4 made of a rubber elastic body having a planar shape shown in FIG. Reference numeral 5 denotes a pair of upper and lower separators that sandwich the above-described components.

  As shown in FIG. 7, a manifold inlet 11, a power generation area (power generation unit) 12 and a manifold outlet 13 are provided on the plane of the cell, and a reaction gas such as a fuel gas is supplied to the manifold as indicated by an arrow B. The power flows from the inlet 11 to the manifold outlet 13 through the power generation area 12 while generating power. Therefore, the gasket 4 is provided around the manifold inlet 11, the power generation area 12, and the manifold outlet 13 so that the reaction gas flowing in this way does not leak to the outside of the cell. On the plane of the cell, a required number of through-hole portions 14 for allowing other gases, cooling water, and the like to pass in the cell thickness direction are provided, and therefore, gaskets 4 are also provided around them.

  Returning to FIG. 6, the separator 5 is provided with a gasket mounting groove 6 for accommodating the gasket 4, and is located inside (right side in the drawing) to guide the reaction gas in the power generation area 12. A flow channel groove 7 is provided. Since the gasket mounting groove 6 accommodates the entire gasket 4, it is laid out in the same planar shape as the planar shape of the gasket 4 shown in FIG. The gasket 4 is mounted in the gasket mounting groove 6 and is in close contact with the inner surface thereof, thereby preventing the reaction gas from leaking from the inside of the cell to the outside of the cell.

  When the separator 5 is formed of metal, a dimensional error is likely to occur due to the convenience of pressing as described above, and therefore a relatively large gap C may be formed between the separator 5 and the frame 3. The gap C is formed everywhere on the plane of the cell. Therefore, since the reactive gas flows from the flow channel groove 7 in the power generation area 12 into the gasket mounting groove 6, the following inconvenience occurs according to the comparative example.

  That is, as shown in FIG. 7, the reaction gas should flow from the manifold inlet 11 through the power generation area 12 to the manifold outlet 13 as indicated by the arrow B in the figure, where the arrow C or D As shown in FIG. 6, there is a case where the shortcut from the manifold inlet 11 to the manifold outlet 13 via the gasket mounting groove 6 without passing through the power generation area 12 may occur. Since the reactive gas flowing through the shortcut path does not contribute to the power generation action at all, a loss of power generation efficiency occurs. The reaction gas flowing in the shortcut path flows along the longitudinal direction of the gasket in the gasket mounting groove 6, and in FIG. 6, the reaction gas flows in the gasket mounting groove 6 in the direction perpendicular to the paper surface.

Example···
Therefore, in the seal structure according to the embodiment of the present invention, as shown in FIGS. 1 and 2, the gas inflow prevention portion 8 is provided at the side edge portion of the gasket mounting groove 6 so as to suppress the reactive gas shortcut. It was decided to suppress the reaction gas from flowing into the gasket mounting groove 6 inside the cell. The gas inflow prevention unit 8 closes the gap C by sandwiching a thin film seal 9 integrally formed with the gasket 4 on the plane of the frame 3 between the frame 3 and the separator 5.

  In this embodiment, the gasket 4 is formed by integrally forming a seal lip 4b at the center in the width direction of a pedestal-shaped gasket base portion 4a having a predetermined width dimension and height dimension. Close contact with the inner surface, that is, the groove bottom surface. The gasket 4 is disposed in the center of the gasket mounting groove 6 in the width direction, and the width dimension of the gasket base 4a, that is, the width dimension of the gasket 4 is set to be smaller than the width dimension of the gasket mounting groove 6. It does not reach the side surface of the groove 6. Therefore, the thin film seal 9 is integrally formed on the side edge portion of the gasket 4 and is sandwiched between the frame 3 and the separator 5. The thickness dimension of the thin-film seal 9 is set much smaller than the height dimension of the gasket 4, and is set much smaller than the height dimension of the gasket base 4a. The thin film seal 9 is provided over the entire length of the gasket 4.

  According to the seal structure having the above configuration, the gap C between the frame 3 and the separator 5 is closed by the thin film seal 9, so that the reaction gas does not flow into the gasket mounting groove 6 inside the cell. Accordingly, it is possible to suppress a shortcut through the gasket mounting groove 6.

  Next, the manufacturing method of the seal structure will be described. The frame 3, the gasket 4 and the thin film seal 9 are manufactured by the following procedure.

(1) Molding process First, as shown in FIG. 3 and FIG. 5 (A), a plate-like material 3A made of a resin plate that is used as a frame 3 by punching performed later is prepared, and one surface of this plate-like material 3A The gasket 4 is integrally molded. The integral molding is performed by molding the gasket 4 using a gasket molding die (not shown) and fixing the gasket 4 to the plate-like material 3A at the same time, inserting the plate-like material 3A into the die, The mold is clamped and a molding material is injected to mold and fix the gasket 4. When the molding material has self-adhesiveness, it is not necessary, but when it does not have self-adhesiveness, an adhesive treatment is performed in advance.

  At this time, the thin film-like seal 9 is integrally formed as a burr-like one around the gasket 4 by a mold. The thin-film seal 9 is formed integrally with the gasket 4 and is fixed (attached) to the plate-shaped material 3A. The parting part of the mold may be provided with a special structure such as setting a gap between the mold and the plate-like material 3A so that the thin-film seal 9 is reliably molded. Burr-like products can be molded by using low-viscosity rubber materials or liquid rubber materials with high fluidity, or by adjusting the clamping force, injection pressure, injection speed, temperature, etc. The mold facility can be used as it is.

(2) Punching process Next, the plate-shaped material 3A integrally molded with the gasket 4 and the thin film seal 9 is punched using a punching die or the like, thereby forming the frame 3 shown in FIGS. 4 and 5B. To do. The punched frame 3 is formed with through holes and other through holes 14 to be the manifold inlet 11, the power generation area 12, and the manifold outlet 13. At this time, the thin film-shaped seal 9 formed in the burr shape is punched out together with the plate-shaped material 3A, thereby forming the same planar shape as the frame 3 on the thin-film seal 9.

  Since the boundary 15 between the manifold inlet 11 and the power generation area 12 and the boundary 16 between the power generation area 12 and the manifold outlet 13 are respectively normal flow paths for the reaction gas, it is not necessary to provide the thin film seal 9 here.

  According to the manufacturing method of the above procedure, not only the planar shape of the frame 3 and the thin film seal 9 can be made uniform, but also the thin film seal 9 forming part in the mold is formed by integrally forming the gasket 4 and the thin film seal 9. An air vent is provided at the end portion of the. Therefore, it is possible to prevent air from entering the gasket 4 in advance.

  In the above embodiment, the gasket 4 and the thin-film seal 9 are integrally formed on the frame 3, but they may be integrally formed on the MEA 1 depending on the cell structure. In each cross-sectional view, the thin-film seal 9 is provided not only on the inside of the gasket 4 (right side in the figure, inside the cell) but also on the outside (left side in the figure, outside the cell). 4, the thin film seal 9 only needs to be provided at least inside the gasket 4. The gasket mounting groove 6 may have a stepped shape in which the outer side surface is omitted.

Sectional drawing of the principal part which shows the state before the assembly of the fuel cell which has the seal structure which concerns on the Example of this invention. Cross-sectional view of the relevant part showing the assembled state of the cell It is explanatory drawing of the manufacturing process of the seal structure, and is a top view showing a state before frame punching It is explanatory drawing of the manufacturing process of the seal structure, and is a top view showing a state after frame punching (A) is an enlarged sectional view taken along line BB in FIG. 3, and (B) is an enlarged sectional view taken along line CC in FIG. Cross-sectional view of the main part of a fuel cell according to a comparative example Illustration of the internal structure of the cell

Explanation of symbols

1 MEA
2 GDL
3 Frame 3A Plate Material 4 Gasket 4a Gasket Base 4b Seal Lip 5 Separator 6 Gasket Mounting Groove 7 Channel Groove 11 Manifold Inlet 12 Power Generator 13 Manifold Outlet 14 Through Hole 15, 16 Boundary

Claims (1)

Fuel that suppresses leakage of reaction gas inside the cell to the outside of the cell by bringing a gasket made of rubber-like elastic material integrally formed on the MEA or a frame stacked on the MEA into close contact with the inner surface of the gasket mounting groove provided in the separator A sealing structure for a battery , wherein a gas inflow prevention portion is provided at a side edge portion of the mounting groove so that the reaction gas does not flow into the mounting groove inside the cell to cause a shortcut, and the gas inflow prevention portion Is a method of manufacturing a fuel cell seal structure in which a thin-film seal integrally molded with the gasket on the MEA or frame is sandwiched between the MEA or frame and the separator ,
A molding step of integrally forming a gasket and a thin film seal using a die on a plate-shaped material to be a frame by punching performed later, and a punching process of the plate-shaped material integrally molded with the gasket and the thin film seal The punching process for forming the frame is carried out sequentially,
In the forming step, the thin film seal is formed as a burr-like shape, and in the punching step, the thin film seal formed in the burr shape is punched together with a plate-shaped material to give the thin film seal a predetermined planar shape. method for producing a seal structure for a fuel cell, characterized by the form.

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