How to attach a gasket to a bipolar plate

Abstract

The present invention relates to a method for attaching a gasket (4) to a bipolar plate (12). The method comprises the steps of applying and aligning a first gasket film (4a) to a second gasket film (4b) having a joining cut-out (8), bonding the first gasket film (4a) to the second gasket film (4b) to form a gasket (4), placing the gasket (4) on the bipolar plate (12) such that the second gasket film (4b) with the joining cut-out (8) abuts against the bipolar plate (12), and performing an embossing process, in which an embossing force is applied by an embossing tool (20) in the area of ​​the joining cut-outs (8) so that embossed adhesive points (24) are formed and the first gasket film (4a) is bonded to the bipolar plate (12) via adhesive means (16) arranged in the joining cut-outs (8) on the first gasket film (4a).

Description

[Technical field]

[0001] The present invention relates to a method for attaching a gasket to a bipolar plate and to a fuel cell manufactured according to such a method. [Background technology]

[0002] Fuel cells are electrochemical energy converters in which, for example, hydrogen and oxygen are converted into water, electrical energy and heat. Fuel cells or fuel cell stacks consist of cells of multiple parts, with membrane electrode units and bipolar plates arranged one above the other. The bipolar plates are used to supply reactants to the electrodes and to cool the fuel cell stack. For this purpose, the bipolar plates have distributor structures that guide reactant-containing fluids along the electrodes. Furthermore, the distributor structures serve to guide a cooling fluid along further distributor structures. These distributor structures are designed as channels through which different fluids can be guided.

[0003] DE 10 2005 058 370 A1 describes a fuel cell with two bipolar plates, between which a membrane electrode unit is arranged and between which a gas diffusion layer is arranged, the membrane electrode unit being arranged on a support frame, an ultrasonic welded joint being formed between the membrane electrode unit and the support frame, and via which the membrane electrode unit is joined to the support frame.

[0004] It is also known from the prior art that the support frame is directly joined to the bipolar plate via an ultrasonic welded joint. Likewise, instead of an ultrasonic welded joint, a welded joint produced by a laser can be used. These methods have the advantage that no additional material is required, but they still require a rough surface. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] DE 102005058370

[0006] SUMMARY OF THE PRESENT EMBODIMENT It is an object of the present invention to provide a method for attaching a gasket to a bipolar plate that allows the gasket to be attached to the bipolar plate simply and economically without the use of significant additional material.

[0007] In order to achieve the above object, a method for attaching a gasket to a bipolar plate and a fuel cell manufactured according to such a method are provided, having the features of claim 1. Advantageous further embodiments of the invention result from the respective dependent claims.

[0008] Disclosure of the Invention A method for attaching a gasket to a bipolar plate is proposed, which comprises the steps of applying and aligning a first gasket film to a second gasket film having a joining cutout, bonding the first gasket film to the second gasket film so as to form a gasket, and placing the gasket on the bipolar plate so that the second gasket film with the joining cutout abuts against the bipolar plate. In a further method step, an embossing step is performed, in which an embossing force is applied by an embossing tool in the region of the joining cutout, so as to form embossed adhesive points, and the first gasket film is bonded to the bipolar plate via adhesive means arranged in the joining cutouts on the first gasket film.

[0009] A joining cutout in the sense of the present invention is understood to be an opening through the second gasket film that allows joining. A gluing point is understood to be the area where the first gasket film is joined to the bipolar plate. By the stamping process, the gasket is joined to the bipolar plate only in the area of ​​the joining cutout. This joining is achieved by a simple stamping process. Furthermore, only the area of ​​the joining cutout needs to be provided with an adhesive means. As a result, almost no adhesive means are required to attach the gasket to the bipolar plate. Thus, only little additional material is required. As a result, furthermore, such a method can be carried out simply and economically.

[0010] In a preferred embodiment of the invention, before bonding the first gasket film to the second gasket film, an adhesive means is applied to at least the first gasket film. The first and second gasket films are thus bonded to one another via an adhesive bond. The adhesive means is further arranged in this region through the bonding cutout. The gasket is bonded to the bipolar plate via the adhesive means. An additional step for applying the adhesive means is thus not required. Since the adhesive means is applied to bond the first and second gasket films, no additional material is required to bond the gasket to the bipolar plate. Such a method can thus be implemented simply and economically.

[0011] In a further preferred embodiment of the invention, the adhesive means is a UV adhesive, which is therefore cured by a UV source. Preferably, at least the first gasket film is transparent to UV light, and therefore the adhesive means can be cured using a UV source. This method step allows the gasket to be bonded to the bipolar plate at a given time, so that it is still possible to correct the position. Furthermore, curing via UV light allows for a simple and controlled installation.

[0012] Preferably, the adhesive means is a hot melt adhesive, so that the gasket films are bonded together by a lamination process. A hot melt adhesive is an adhesive means that changes to an adhesive state when exposed to heat. Such a method step allows two gasket films to be bonded together simply by heating. In the lamination process, the two gasket films are bonded together, preferably at a temperature of 100-200°C and a pressure of 0.5-5 MPa.

[0013] In an advantageous further development, the embossing force is applied to the first gasket film. Alternatively, it is of course also possible to apply the embossing force to the bipolar plate. However, this allows a bond between the bipolar plate and the first gasket film to be formed more easily, since the first gasket film is more flexible than the bipolar plate. This also prevents damage to the distributor structure of the bipolar plate. Preferably, an embossing force in the range of 0.5-5 MPa is applied.

[0014] Advantageously, the embossing step heats the embossing tool, so that the hot melt adhesive arranged in the joining recess is bonded to the bipolar plate. In this way, the adhesive bond between the bipolar plate and the first gasket film can be achieved simultaneously with the embossing step, thereby reducing the number of method steps. Preferably, the embossing tool is heated to a temperature of 100-200°C. Particularly preferably, the temperature is 130-170°C.

[0015] Preferably, the hot melt adhesive is the adhesive applied to bond the first gasket film to the second gasket film, again eliminating the need for an additional method step to apply the hot melt adhesive or an additional hot melt adhesive.

[0016] Furthermore, a fuel cell for a fuel cell stack is proposed. The fuel cell has at least one bipolar plate and a gasket, the gasket comprising a first gasket film and a second gasket film, the second gasket film having a joining cutout and abutting the bipolar plate, the gasket being joined to the bipolar plate by means of adhesive means arranged in the joining cutout via embossed adhesive points formed in the region of the joining cutout. The fuel cell is preferably manufactured according to the method described above. Such a fuel cell exhibits substantially the advantages described with respect to the method. In particular, such a fuel cell exhibits a relatively high efficiency due to the positionally accurate arrangement of the gasket and the bipolar plate.

[0017] In a further advantageous embodiment, the bonding point has a geometric shape, one bonding point side of which extends parallel to and is aligned with the lateral central axis of the bipolar plate. In this context, a geometric shape is understood to be a two-dimensional geometric shape resulting from a top-down view of the bipolar plate through the bonding point. A bonding point side is a side of the geometric shape that extends as a line. A lateral central axis is an axis that crosses the bipolar plate and is arranged in the center of the bipolar plate. In addition to being arranged parallel, this bonding point side is located closer to the lateral central axis than the remaining sides of the bonding point.

[0018] Thus, the longitudinally directed peel force acts perpendicularly to the entire bond edge, which results in a better distribution of the peel force over this bond edge, which significantly improves the durability of such bonds.

[0019] According to a preferred embodiment, the bonding point further comprises a bonding point edge, which runs parallel to the longitudinal central axis and is aligned with said longitudinal central axis. The longitudinal central axis runs in the longitudinal direction of the bipolar plate corresponding to the lateral central axis and is arranged in the center of the bipolar plate. In principle, peel forces also occur in the lateral direction, but these are smaller than the longitudinal peel forces, so that the resistance of the bonding point against lateral peel forces is improved by an additional bonding point edge aligned parallel to the longitudinal central axis and aligned with the lateral center of the bipolar plate.

[0020] Furthermore, a fuel cell stack is proposed which comprises a number of fuel cells, such a fuel cell stack having the advantages mentioned above.

[0021] Exemplary embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. [Brief description of the drawings]

[0022] [Figure 1] 1 is a perspective view of a fuel cell structure according to the present invention; [Figure 2a-2c] 2a-2c show method steps for attaching a gasket to a bipolar plate. [Diagram 3] 1A-1D show fuel cells with different embodiments of adhesive sites;

[0023] FIG. 1 shows a perspective view of the structure of a fuel cell 1 according to the invention. The fuel cell 1 comprises at least one first gasket film 4a and at least one second gasket film 4b. The first gasket film 4a and the second gasket film 4b together form the gasket 4 of the fuel cell 1 and are directly stacked one on top of the other as shown in the drawing. In contrast to the first gasket film 4a, the second gasket film 4b has four joining cutouts 8, which are arranged symmetrically in the second gasket film 4b. In this embodiment, the joining cutouts 8 are designed as round holes. The fuel cell 1 further comprises a bipolar plate 12, on which the gasket 4 rests. As is known, the bipolar plate 12 has a distribution structure for guiding the reactants along the electrodes, not shown.

[0024] FIG. 2 shows a method step for attaching the gasket 4 to the bipolar plate 12. In this figure, a cross section through the region of the joining cutout 8 is shown. Partial view 2a shows that between the first gasket film 4a and the second gasket film 4b, adhesive means 16 are arranged, via which the two gasket films 4a, 4b are joined to one another. In this embodiment, the adhesive means 16 is a hot melt adhesive, via which the two gasket films 4a, 4b are joined to one another by a lamination process. Due to the presence of the joining cutout 8, no joining of the two gasket films 4a, 4b occurs in this region. Partial view 2a shows a step before the gasket 4 is placed on the bipolar plate 12.

[0025] Partial view 2b shows the step in which the embossing process is carried out by means of an embossing tool 20. In this step, the second gasket film 4b rests directly against the bipolar plate 12. The embossing tool 20 is arranged in the region of the joining cutout 8 and applies an embossing force to the first gasket film 4a. As a result, the adhesive means 16 arranged on the first gasket film 4a is brought into contact with the bipolar plate 12. In this embodiment, the embossing tool 20 is heated, whereby the first gasket film 4a is bonded to the bipolar plate 12 via the adhesive means 16, which is configured as a hot melt adhesive.

[0026] The embossing process results in the formation of embossed bonding points 24, which are essentially defined by the shape of the mating cut-out 8 and by the shape of the embossing tool 20. Partial view 2c shows the corresponding part of the fuel cell 1 after the embossing tool 20 has been removed. It can now be seen that the embossing tool 20 has created a recess 28 in the first gasket film 4a, which extends into the mating cut-out 8 of the second gasket film 4b. This further improves the mechanical bond between the two gasket films 4a, 4b.

[0027] Figure 3 shows a top view of the fuel cell 1 produced in this way, where, apart from the round joint cut-outs 8 shown in Figure 1, four further embodiments of the joint cut-outs 8 are shown in dashed lines. By the joint cut-outs 8 produced in this way, a corresponding geometric shape of the bonding points 24 is generated.

[0028] The bond site 24, shown as a triangle in the upper right corner, has a bond site side q formed parallel to the lateral central axis 32 of the fuel cell 1. Furthermore, this bond site side q faces the lateral central axis 32, which results in a peel force being applied to bond site side q that is directed longitudinally toward the edge 36 of the fuel cell 1, thereby improving the durability of the bond site 24. The bottom right bond site 24 and the bottom left bond site 24 show further possible geometric configurations that also have these advantages.

[0029] In the upper left corner, a bond point 24 is shown which is configured as a rectangle, which in addition to the previously mentioned bond point side q has a further bond point side l which is arranged parallel to and faces the longitudinal central axis 40. This further improves the resistance of the bond point 24 to transverse peel forces. [Explanation of symbols]

[0030] 1 fuel cell 4 Gasket 4a First gasket film 4b Second gasket film 8 Joint notch 12 Bipolar Plates 16 Adhesion means 20 Embossing tools 24 Glue points 28 Recess 32 lateral center axis 36 Edge 40 Longitudinal central axis q Glue edge l Gluing edge

Claims

1. A method for attaching a gasket (4) to a bipolar plate (12), comprising the steps of: - applying and aligning a first gasket film (4a) to a second gasket film (4b) having a joining cutout (8); - bonding the first gasket film (4a) to the second gasket film (4b) to form the gasket (4); - placing the gasket (4) on the bipolar plate (12) so that the second gasket film (4b) with the joining notch (8) abuts the bipolar plate (12); - performing an embossing process, in which an embossing force is applied by an embossing tool (20) in the area of ​​the joining cut-outs (8), thereby forming embossed adhesion points (24) and bonding the first gasket film (4a) to the bipolar plate (12) via adhesive means (16) arranged in the joining cut-outs (8) on the first gasket film (4a); A method comprising:

2. 2. The method according to claim 1, characterized in that, prior to joining the first gasket film (4a) to the second gasket film (4b), an adhesive means (16) is applied to at least the first gasket film (4a).

3. Method according to claim 1 or 2, characterized in that the adhesive means (16) is a UV adhesive, thus the UV adhesive is cured by a UV source.

4. 3. A method according to claim 2, characterized in that the adhesive means (16) are hot melt adhesives, so that the gasket films (4a, 4b) are joined together by a lamination process.

5. 5. The method according to claim 1, wherein the embossing force is applied to the first gasket film (4a).

6. 5. The method according to claim 4, characterized in that the stamping step heats the stamping tool (20), thereby bonding the hot melt adhesive disposed in the bonding notches (8) to the bipolar plate (12).

7. A fuel cell (1) for a fuel cell stack, comprising: The fuel cell (1) comprises at least one bipolar plate (12) and a gasket (4); The gasket (4) comprises a first gasket film (4a) and a second gasket film (4b); The second gasket film (4b) has a joining notch (8) and abuts against the bipolar plate (12); The first gasket film (4a) and the second gasket film (4b) are joined by an adhesive means (16); the gasket (4) is bonded to the bipolar plate (12) by adhesive means (16) arranged in the joint cutouts (8) via embossed adhesive points (24) formed in the area of ​​the joint cutouts (8), Fuel cell (1).

8. said bonding points (24) having a predetermined geometric shape; One bonding point side (q) of said geometric shape extends parallel to and is aligned with the lateral central axis (32) of said bipolar plate (1).

8. The fuel cell (1) according to claim 7, characterized in that

9. The bonding portion (24) further has one bonding portion side (l), The bonding edge (l) extends parallel to the longitudinal central axis (40) and is aligned with the longitudinal central axis (40).

9. The fuel cell (1) according to claim 8, characterized in that

10. A fuel cell stack comprising a plurality of fuel cells (1) according to any one of claims 7 to 9.

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