Method and Roller Arrangement for Manufacturing a Single Bipolar Plate
The roller arrangement with controlled web tension and auxiliary embossments addresses the challenge of achieving high flatness and uniformity in bipolar plate production, enabling efficient high-density flow field channel manufacturing without defects.
Patent Information
- Application Number
- JP2025546239
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-02-10
- Filing Date
- 2024-02-07
- Publication Date
- 2026-02-27
AI Technical Summary
Existing methods for manufacturing bipolar plates struggle to achieve high flatness and uniformity in web guidance, particularly when increasing the density of flow field channels, leading to issues like wrinkles and folds during the roll-forming process at high feed rates.
A roller arrangement with controlled web tension and auxiliary embossments on rollers ensures precise web guidance, using tangential web feeding and controlled braking to maintain tension, preventing wrinkles and folds, and enabling high-density flow field channel production.
The method achieves high flatness and uniformity in bipolar plates, allowing for efficient production of high-density flow field channels without defects, enhancing the mechanical strength of graphite-based webs.
Smart Images
Figure 2026506911000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to a method and a roller arrangement for manufacturing a single bipolar plate. A method according to the preamble of claim 1 is known from US 2017 / 0348811 A1.
[0002] The production of single bipolar plates, both metallic and graphite-based, requires flatness and uniformity of the web guide. To ensure this, a suitable web guiding is required. For this purpose, it is known from US 2017 / 0348811 A1 to guide the material web through a roller gap tangentially to the two rollers forming the embossing gap.
[0003] To increase the efficiency of fuel cells, the density of flow field channels in bipolar plates must be further increased, which, among other things, requires a further decrease in the distance between adjacent parallel flow field channels, thereby requiring the production of fold- and wrinkle-free flow field shapes in the roll-forming process at the highest possible feed rates.
[0004] To this end, a method according to claim 1 and a roller arrangement according to claim 13 are proposed. Advantageous embodiments of the invention are the subject matter of the respective dependent claims.
[0005] A single bipolar plate can be half of a bipolar plate, and two joined single bipolar plates can form a single bipolar plate. The material web can be and / or include, among other things, sheet metal, e.g., made from stainless steel, or a graphite web, e.g., made from expandable graphite. The expandable graphite web can be compressed during the described roll-forming process, thereby improving its mechanical strength in addition to embossing the flow field shape. This is described in US2017 / 0348811A1.
[0006] The unwinder can be braked to maintain tension in the web, for which purpose it can be braked by a brake device on the unwinder.
[0007] By braking, the rotationally driven roller pair pulls the material film into the embossing gap, and the braked rewinder generates an opposing holding force, so that the material web can be fed into the embossing gap with a desired web tension.
[0008] The unwinder may be slowed down depending on the rotational speed of the roller pair or depending on the detected tension in the material web, so that a desired tension value is achieved.
[0009] After the roller pair, the material web can be wound onto another roll or separated into a single bipolar plate by a separation step.
[0010] Furthermore, the material web can be fed to a cutting process after the roller gap in the conveying direction, and holes can be optionally introduced in the region of each single bipolar plate and / or the contour of each single bipolar plate can be formed, in particular cut. For this purpose, the material web can be led out of the roller gap after passing through the roller gap with substantially no tension or with a web tension that is much lower than the web tension when the material web is fed to the roller gap after unwinding.
[0011] According to a second aspect, the invention relates to a single bipolar plate manufactured using an embodiment of the manufacturing method described.
[0012] Further details of the invention are explained using the following figures. [Brief explanation of the drawings]
[0013] [Figure 1] 1 shows a first embodiment of a roller arrangement.
[0014] [Figure 2] Shows a second embodiment of the roller arrangement.
[0015] [Figure 3] Shows an exemplary embodiment of an embossing roller for use with the roller pair of FIG. 1 or FIG. 2.
[0016] [Figure 4] Shows an exemplary embodiment of an adhesive structure.
[0017] [Figure 5] Shows a further exemplary embodiment of an adhesive structure.
Mode for Carrying Out the Invention
[0018] The bipolar plate, which is made of metal and is also graphite-based, requires high flatness and uniformity. To ensure this, appropriate web guidance is necessary. FIG. 1 shows a roller arrangement comprising a rewinder a and a pair of rollers b provided with two embossing rollers that can be designed as male and female dies. The best results can be achieved using a tangential web guide. In this case, braking is performed by a force F1 in front of the embossing gap (for example, by the rewinder a), and the embossing unit pulls in against the braking force with a force F2.
[0019] The web speed of the metal web is optionally 0 m / min < v1 < 300 m / min. The embossing of the non-breaking bipolar plate is ensured by the web tension. In the exit gap, the web is preferably conveyed without web tension. However, it is also possible to convey the web with a light web tension F3. In order not to change the embossing (for example, the length of the embossing) and to ensure further processing of the web, it is a principle that F3 << F1. For example, if the web tension F3 is too high, punching of the web becomes impossible or very difficult. Deflection rollers or dancer units can also extrude the embossing from the web.
[0020] As an alternative to the embodiment shown in Figure 1, in the embodiment shown in Figure 2, the pulling force is generated via a pulling device. The material web is guided from the unwinder a via a braked friction roller c. In this variant, the braking force F1 can be precisely controlled and is therefore particularly suitable for flow field shapes with flow field lines in the circumferential direction. However, flow field shapes in any other direction can also be embossed without breaks or creases.
[0021] The tensile stress is calculated as follows: tensile stress = force F1 / cross-sectional area of material web.
[0022] For stainless steel material webs, the tensile stress is preferably 100 N / mm 2 and in the case of a titanium material web, the tensile stress is preferably 50 N / mm 2 Exceeds.
[0023] When the material web is a graphite web, it may preferably comprise and / or consist of expandable graphite. Alternatively, the graphite web may comprise and / or consist of impregnated expandable graphite. The graphite web may comprise a highly graphite-filled polymer.
[0024] FIG. 3 shows a schematic view of the shell or barrel surface of an embossing roller with engraved flow field shapes, taken along an axial direction, specifically perpendicular to the axial direction of the embossing roller. Roller 1 has embossed structures for bipolar plates. The structured shell surface also has structural elements 2 for media openings. The material web has a width 3. Engraved auxiliary embossments are formed in region 4 on the structured shell surface. The engraved flow field shapes have embossed structures 5 for forming flow field channels.
[0025] To prevent the material web from slipping, especially under high tensile stresses, auxiliary embossments 4 are formed on the roller 1. The auxiliary embossments 4 can be located outside the embossing structure for the bipolar plate. Furthermore, the auxiliary embossments 4 can be formed in the region of the media opening 2 to prevent the embossments from folding in this region. The auxiliary embossments 4 can be at least as wide as the material web, wider, or narrower.
[0026] The embossing structure of the bipolar plate can cause the two embossing rollers to be pushed out of position. This can result in uneven embossed images or even cut-off embossing. The auxiliary embossing 4 can counteract this effect with an appropriate shape.
[0027] Any shape that returns the roller to its original position during embossing is suitable for the auxiliary embossing. For example, a pyramid can be designed as the shape (Fig. 4, I, II). However, other elements are also possible, such as a trapezoidal cone or a simple line (Fig. 4, III). The line may have, for example, a triangular cross section in a plane perpendicular to the longitudinal direction, which is optionally perpendicular to the axial direction and / or parallel to the circumference of the embossing roller or at a different angle to the longitudinal direction.
[0028] One of the two rollers may be provided with a cone with a raised tip. In case of slight misalignment, a concave counterpart can be formed on the other roller so that the embossing force guides the embossment back to its original position. The same applies to linear arrangements. The flank angle beta can be 0°<beta<=90°.
[0029] It is also possible to arrange the auxiliary embossings on separate rings, which can be attached to the outside of the roller, in particular the embossing roller.
[0030] The auxiliary embossing can also have flat pyramids and / or pyramids rotated by 45°. The length x of the base side (FIG. 5) can be between 1 mm and 10 mm. The height of the elements can be between 0.05 mm and 3 mm. Furthermore, calendering of the material web can be avoided.
[0031] Figure 4 shows possible forms of auxiliary embossing. I and II show top views of pyramidal guide elements, with raised areas marked in white and recessed areas marked in black. III shows an example of a linear arrangement of left and right guide elements. IV shows an exemplary line pattern (white: raised, black: recessed). The cross section of the linear embossing can be triangular.
[0032] The features of the invention disclosed in the above description, in the drawings and in the claims may, both individually and in any combination, be essential for the realization of various embodiments of the invention.
Claims
1. 1. A method for manufacturing a single bipolar plate, comprising: unwinding the material web from an unwinder and feeding the unwound material web in a conveying direction of the material web into a roller gap between two rollers, at least one of which is a three-dimensional structure roller; while maintaining the conveying direction, guiding the unwound material web through a roller gap between two rollers, at least one of which is a three-dimensional structure roller, and wherein a flow field shape is embossed into the material web; the method, wherein when the flow field shape is embossed into the material web, a channel arrangement of parallel flow field channels is created in the material web, the parallel flow field channels extending parallel to the conveying direction.
2. The method of claim 1 , wherein the material web is guided tangentially relative to the two rollers during feeding.
3. 3. The method according to claim 1, wherein the material web is removed from the roller gap after being guided tangentially relative to the two rolls.
4. 4. The method of claim 3, wherein after passing through the roller gap, the material web is led out of the roller gap with substantially no tension or with a web tension that is much lower than the web tension when the material web is fed into the roller gap after unwinding.
5. 10. A method according to any one of the preceding claims, wherein a metal foil or a graphite sheet, preferably an expandable graphite sheet or a polymer-filled graphite sheet, is unwound from the unwinder.
6. 10. A method according to any one of the preceding claims, wherein the material web is unwound from the unwinder during unwinding while maintaining a web tension in the transport direction.
7. The method of claim 6 wherein the unwinder is braked to maintain the web tension.
8. 7. The method of claim 6, wherein the unwinder is substantially free-running, and the material web unwound from the unwinder is fed to the roller gap in the conveying direction via a tensioning device that provides and maintains the web tension in the conveying direction.
9. 9. The method according to claim 8, wherein the material web is deflected in the tensioning device on a braked friction roller, the material web wrapping around at least 30%, particularly preferably at least 40%, very particularly preferably at least 50% of the circumference of the braked friction roller.
10. 10. The method according to claim 9, wherein the material web is deflected on a support roller in the transport direction of the material web from the unwinder to the braked friction roller on a support roller, the support roller preferably having an adjustable distance to the braked friction roller so that the degree of wrapping of the material web around the friction roller can be adjusted.
11. 10. The method according to any one of the preceding claims, wherein at least one of the two rollers between which the roller gap is formed is driven in its direction of rotation.
12. 10. A method according to any one of the preceding claims, wherein the material web is transported in the transport direction at a web speed of 0 to 300 m / min.
13. A roller arrangement for manufacturing a single bipolar plate, the roller arrangement including a rewinder, from which a material web is fed in a conveying direction into a roller gap between two rollers and guided through the roller gap while maintaining the conveying direction, at least one of the two rollers being a three-dimensionally structured roller, the two rollers being configured to emboss a flow field shape having a channel arrangement of parallel flow field channels into the material web.
14. 14. The roller arrangement of claim 13, wherein the embossing structure comprises a plurality of parallel, elongated structural elements for embossing the flow field channels, the structural elements extending in a circumferential direction of the at least one structured roller.
15. 15. A roller arrangement according to claim 13 or 14, wherein the material web is fed tangentially to the two rollers and the material web is led out of the roller gap in the conveying direction behind the roller gap, preferably while maintaining the conveying direction tangential to the two rollers.
16. 16. The roller arrangement according to claim 13, wherein the material web is led out of the roller gap in the conveying direction behind the roller gap with substantially no tension in the conveying direction or with a web tension in the conveying direction that is much lower than the web tension when the material web is fed from the unwinder to the roller gap.
17. 17. A roller arrangement according to any one of claims 13 to 16, wherein the material web is or comprises a metal foil or a graphite web, the graphite web being preferably an expandable graphite web or a web made from polymer-filled graphite.
18. A roller arrangement according to any one of claims 13 to 17, wherein the material web has a web tension directed in the conveying direction upstream of the roller gap.
19. The unwinder comprises: a. Slowed down, or 20. The roller arrangement of claim 18, wherein the substantially free-running material web unwound from the unwinder is fed to the roller gap in the conveying direction via a tensioning device, the tensioning device adapted to provide and maintain web tension in the conveying direction.
20. 20. The roller arrangement according to claim 19, wherein the material web is deflected in the tensioning device on a braked friction roller, the material web wrapping around at least 30%, particularly preferably at least 40%, very particularly preferably at least 50% of the circumference of the braked friction roller.
21. 21. The roller arrangement according to claim 20, wherein the material web is deflected on a support roller in the transport direction of the material web from the unwinder to the braked friction roller on a support roller, the support roller preferably having an adjustable distance to the braked friction roller so that the degree of wrapping of the material web around the friction roller can be adjusted.
22. 22. The roller arrangement according to any one of claims 13 to 21, wherein at least one of the two rollers between which the roller gap is formed is driven in its direction of rotation.
23. 23. The roller arrangement of claim 13, wherein at least one of the two rollers forming the roller gap has an adhesive structure on its roller shell, the adhesive structure being designed to increase the coefficient of friction between the roller having the adhesive structure and the material web compared to a smooth roller shell.
24. 24. The roller arrangement of claim 23, wherein the roller shell has a higher coefficient of friction in at least some areas outside of the structured area of the roller shell for embossing a flow field shape compared to the structured area.
25. 25. The roller arrangement of claim 24, wherein the region with the high coefficient of friction surrounds, preferably completely surrounds, at least two opposite sides of the structured region.
26. 26. The roller arrangement according to any one of claims 23 to 25, wherein the adhesive structure has an embossing structure with a plurality of regularly or irregularly arranged embossing projections, preferably the embossing projections are linear, pyramidal or conical, preferably with a triangular cross section, or trapezoidal pyramidal or trapezoidal conical.
27. 27. The roller arrangement according to any one of claims 13 to 26, wherein the rollers forming the roller gap therebetween are designed as a male and female die combination, at least with respect to a structured area of their roller shells for embossing a flow field shape.
28. 28. A roller arrangement according to any one of claims 23 to 27, wherein the roller is designed as a combination of a male and a female die in the area of the adhesive structure, in particular when the adhesive structure is designed as a plurality of regularly or irregularly arranged embossed structures.