Embossing roller, method for the production thereof, plate for an electrochemical system, and method for producing a plate of this type

Abstract

The present invention relates to an embossing roller (210a, 210b) for embossing a plate (200) for an electrochemical system and to a method for the production thereof. It also relates to a plate (200) for an electrochemical system and to a method for the production thereof.

Description

[0001] Plate for an electrochemical such a plate

[0002] The present invention relates to an embossing roller for embossing a plate for an electrochemical system and a method for its production. Furthermore, it relates to a plate for an electrochemical system and a method for its production.

[0003] Plates for electrochemical systems, such as separator plates for a fuel cell, for an electrolyzer, or for a redox flow battery, have a layer which, in turn, has a set of flow channels for a medium embossed into the layer. Such a medium can be, for example, a reaction medium or a coolant. In electrolyzers, water is supplied as the reaction medium, and oxygen and hydrogen are removed. In fuel cells, for example, hydrogen and oxygen or air are supplied to the fuel cell as the reaction medium, and water is removed. Separator plates for electrochemical systems therefore have different areas with flow channels, in particular supply areas for reaction media, discharge areas for reaction media, and an active flow area for these media, in which the respective desired electrochemical reaction takes place.The channels in the respective areas should be designed as uniformly as possible, or with a defined depth and width, to create a defined flow of the respective medium. It is particularly advantageous if all channels in a flow area have a uniform depth and width.

[0004] Separator plates and frame plates for electrochemical systems, for example, are manufactured by roll stamping. For this purpose, a layer is passed between two embossing rollers, whereby the flow channels and, if necessary, other structures are embossed into the layer. For this purpose, the two embossing rollers, between which the layer is passed, are provided with suitable embossed structures that form the corresponding channels of the flow areas or flow region in the layer. Sealing elements, such as those known from DE 101 58 772 A1 and DE 10248 531 A1, can be molded in analogously. Due to the embossing load during the molding of the structures, the embossing rollers can bend and thus lead to a deviation of the axis of rotation from the original linear axis of rotation.In the case of both embossed flow channels and embossed sealing elements, the desired embossing result is not achieved without further measures due to the deflection of the embossing rollers when producing the plate by roll embossing.

[0005] Conventional embossing rollers therefore do not achieve a uniform embossing result across the entire surface or parts of the surface of the plate. This is because the embossing rollers bend between their two ends during the embossing process due to the embossing pressure, so that the embossing pressure of the rollers decreases toward the center of the plate. This leads to a situation where, despite uniform embossing structures in the embossing rollers, the channels and / or sealing elements formed in the separator plate or frame plate layer in the center of the rollers have a shallower embossing depth, thus also a shallower than planned channel depth or shallower than planned height or depth of the sealing element.

[0006] In particular, this leads to a non-uniform flow of the medium through the array of channels in an area where adjacent channels unintentionally differ in channel depth. In general, this means that the flow of the medium through the array of channels occurs with a smaller flow cross-section, and thus usually with a lower flow rate, than desired, at least in some of the channels. Furthermore, sealing elements with varying heights along their length can lead to inadequate sealing of the electrochemical system. Both of these factors impair the function of the separator or frame plate formed in this way.

[0007] The present invention therefore has for its object to provide an embossing roller, a method for producing such an embossing roller, a plate for an electrochemical system and a method for producing such a plate, in which the problems described above are largely or completely solved.

[0008] The present invention, which solves the above problems, provides an embossing roll, a method of manufacturing an embossing roll, a plate for an electrochemical system and a method of manufacturing such a plate for an electrochemical system according to any one of the claims.

[0009] In particular, the present invention solves the problem that the embossing result in roll embossing does not correspond to the desired one due to the bending of the embossing rollers.

[0010] For this purpose, an embossing roller is provided with which a plate for an electrochemical system, in particular a separator or frame plate for a fuel cell for an electrolyzer or for a redox flow battery, can be embossed. This embossing roller has a substantially cylindrical surface with an axis of rotation as the cylinder's longitudinal axis. According to the invention, the envelope of the surface of the embossing roller is now formed in at least one region such that it has a convex curvature in the direction of the axis of rotation. The region convexly curved in this way (hereinafter also referred to as a cambered region or spherical region) does not have to extend completely over the entire length of the embossing roller; it is sufficient if it extends only partially over the roller in the direction of the axis of rotation. It is also possible for several adjacent regions in the direction of the axis of rotation to be provided with a convex curvature in this way.In other words, the surface of the embossing roller is provided with a convex curvature of the envelope of these embossing structures over several embossing structures or over a longer area of ​​an embossing structure.

[0011] For example, the convex curvature can extend transversely to the direction of the axis of rotation over a length KU over at least part of the circumference of the embossing roller, for example in the circumferential direction completely over the area (217a, 217b) of the embossing roller (210) provided with embossing structures (217) for embossing the plate, or over the entire circumference of the embossing roller, for example over a length KU over at least part of the circumference of the embossing roller with the diameter PD of the embossing roller, where KU > PD / 50, advantageously KU > PD / 20, in particular KU > 4 mm, in particular KU > 5 mm.

[0012] Such a convex region does not necessarily extend over the entire circumference running perpendicular to the axis of rotation. It is sufficient if only one or more sections of this circumference exhibit a convex curvature or crowning in the direction of the axis of rotation.

[0013] Such a crowning can also occur only over a part of the roll length or individual sections of the roll length and does not have to be continuous in the direction of rotation.

[0014] By designing an embossing roller in this way for embossing a plate, the natural deflection of the embossing roller is compensated for in those areas where this deflection would lead to an undesirable uneven design or unplanned configuration of flow channels and / or sealing elements. The convex curvature of the embossing roller is particularly important in the center of the roller in the direction of the rotation axis, as this is where the deflection of the embossing rollers is most pronounced. However, if the affected area with flow channels or sealing elements is not embossed in this center of the embossing roller, the cambered area can also be arranged in other sections in the direction of the rotation axis of the embossing roller.

[0015] The embossing roller according to the invention makes it possible to achieve a uniform embossing result in the desired area without unnecessarily increasing the embossing force required.

[0016] The shape of the crowning of an area can correspond to a circular arc section, an elliptical section or a parabolic section, whereby the surface of the embossing roller in the convexly curved areas can also have microstructures which, within the convex curvature of the envelope of the surface, the crowning is individually adjusted to the requirements of, for example, individual channel formations and / or individual sealing elements.

[0017] According to the invention, it has been found to be advantageous if the convex curvature has a height between 5 pm and 500 pm, advantageously 15 pm to 300 pm, either including or excluding the region boundaries. The height is defined as the height that results between the point of maximum height in the convex curvature and the point of minimum height of the convex curvature, usually at the ends of the convex curvature.

[0018] As already mentioned, the convex curvature can extend in the direction of the axis of rotation over the entire length of the embossing roller or only over a shorter section in the direction of the axis of rotation, for example less than or equal to 90%, for example less than or equal to 80%, for example less than or equal to 3 / 4, for example less than or equal to 2 / 3, for example less than or equal to %, for example less than or equal to 1 / 3 of the entire length of the embossing roller.

[0019] The convex curvature can also extend in the direction of rotation of the embossing roller only over the entire area of ​​the embossing roller provided with embossing structures for embossing a plate, or even just over part of it. In particular, it is also possible for this camber not to extend over areas with structures for auxiliary embossing. Auxiliary embossings are embossings that are located outside the areas that will form parts of the separator plate to be manufactured in the further production process. Examples of this are nubs in the embossing roller, which can serve, on the one hand, to introduce nubs into the metal sheet to be embossed in lateral areas of the embossing roller, which serve to guide the metal sheet, in particular coils, in further process steps at downstream production stations. On the other hand, such nubs in edge areas of the embossing rollers can also serve to directly guide the metal sheet during roll embossing.

[0020] Advantageously, the convex curvature has a minimum extension in the direction of the rotation axis, e.g. over a length KL with KL > 50 mm, advantageously KL > 100 mm, advantageously KL > 0.5 RL, KL > 2 / 3 RL, KL > 0.75 RL, KL > 0.9 RL or KL = RL, where RL is the total length of the embossing roller.

[0021] These convexly curved areas do not have to be arranged centrally on the embossing roller in the direction of rotation axis, but can also be positioned off-center at any point in the direction of rotation axis of the embossing roller, depending on the requirements or positioning of the area to be embossed as precisely as possible with flow channels, sealing elements, etc.

[0022] The point of maximum curvature of the convexly curved region can be located within the convexly curved region, either in the center of the convexly curved region as seen in the direction of the rotation axis, or off-center, in each case as seen in the direction of the rotation axis. Thus, asymmetric convexity is also possible.

[0023] The position of the convexly curved area will therefore essentially be determined by the deflection of the embossing roller as well as the positioning of the area that requires a particularly defined design of flow channels and / or sealing elements in the separator or frame plate.

[0024] What is essential to the present invention is that the embossing roller according to the invention has at least one convex curvature as described above. Further convex curvatures as described above are possible and frequently present. The number of convex curvatures formed according to the invention on an embossing roller according to the invention is therefore not fundamentally limited.

[0025] Conversely, it is advantageous if a convex curvature as described above extends in the direction of the axis of rotation over more than one embossed structure, in particular over at least ten or at least twenty embossed structures.

[0026] Such an embossing roller according to the invention can be produced with the region according to the invention with convex curvature in particular by means of three different methods.

[0027] On the one hand, a cylindrical embossing roller as starting material can first be provided with embossed structures for creating flow channels for a medium in a plate and / or sealing elements in a plate, for example grooves and webs. This is done, for example, by means of erosion, laser cutting or milling. The surface of the embossing roller can then be machined, for example ground, in such a way that the envelope of the surface of the embossing roller, at least in this area, at least in sections, has a convex curvature in the direction of the axis of rotation. If the embossed structures provided for embossing the channels and / or sealing elements, in particular depressions and elevations extending therebetween in the embossing roller, are introduced into the embossing roller in the first step with a uniform depth, i.e. with a constant distance between the bottom of the grooves of the embossed structure and the central axis orThe subsequent crowning of the surface causes these grooves to have a variable depth in the ready-to-use embossing roller, i.e., the depth of the grooves is greatest at the highest point of the crown and least at the lowest point. The use of such ground, crowned embossing rollers nevertheless makes it possible to create uniform or defined channel depths in this area, or uniform or defined sealing elements in a separator or frame plate along their entire length.

[0028] Alternatively, the embossing roller can be manufactured by machining the surface of a cylindrical embossing roller as the starting material (e.g., by grinding) such that the surface of the embossing roller has a convex curvature in the direction of the rotation axis in at least one region into which an embossed structure is to be introduced and which extends at least partially in the direction of the rotation axis and at least partially transverse to the rotation axis. Embossed structures are then introduced into the surface of the embossing roller to create at least one set of flow channels for a medium and / or at least one sealing element in a separator plate, for example, by erosion, laser cutting, or milling.

[0029] In both cases, the manufacturing process for the embossing roller can be designed in such a way that both uniform and different depths of the embossed structures, in particular embossed structures with at least partially uniform groove depths and / or embossed structures with at least partially different groove depths, are produced.

[0030] Alternatively, the embossing roller can be manufactured by determining the design of the surface of the embossing roller for an area that is to be convexly curved, including the design of the embossing structures and the convex curvature, before the embossing structures are created in an embossing roller. The corresponding embossing structures are then introduced directly into the surface of the embossing roller, for example by means of erosion, laser cutting, or milling. Even with an embossed embossing roller that is integrated in this way, it is possible to introduce uniform or defined channel geometries and / or sealing elements into a separator or frame plate in these areas. With this process, all of the grooves in the embossed structures can have a uniform depth, i.e. they can have a variable distance between their groove base and the central axis or axis of rotation of the embossing roller. The same applies to the height orDepth of the sealing elements.

[0031] According to the design of the embossing roller according to the invention, a plate according to the invention for an electrochemical system, in particular for separator plates of a fuel cell, for an electrolyzer, or for a redox flow battery, can be produced. This plate has a layer with at least one region with at least one set of flow channels embossed into the layer for a medium, for example coolant, reaction media, or reaction products. Alternatively or additionally, it has sealing elements, in particular sealing beads, embossed into the layer in at least one region. The plate according to the invention, in particular a separator or frame plate, has essentially uniform or defined flow channels and / or sealing elements within said at least one region due to the inventive design of one or both embossing rollers, between which the layer is passed in order to emboss structures into the layer.This means that within this range, the embossed flow channels and / or sealing elements have a substantially uniform or at least well-defined depth. Substantially uniform depth here means that the depth of the flow channels and / or sealing elements within this range varies by a maximum of 10%, advantageously a maximum of 5%, advantageously a maximum of 1%.

[0032] However, when considering the depth of the channels, one or more of the outermost channels and / or one or both ends of the channels can be disregarded from the group of river channels arranged in such an area. The statement that the river channels have an essentially uniform depth must in particular only apply to a maximum of 90% of the area of ​​the area, advantageously to a maximum of 80% of the area of ​​the area. The other parts of this area do not necessarily have to meet the condition of an essentially uniform depth. The statement that the river channels have an essentially uniform depth must in particular only apply to at least 50% of the area of ​​the area, advantageously to at least 20% of the area of ​​the area.

[0033] The same applies when considering the height of the at least one sealing element. Here, the statement that the at least one sealing element has a substantially uniform height or depth should apply to a maximum of 90% of its length, in particular to a maximum of 80% of its length. Conversely, the statement that the at least one sealing element has a substantially uniform height or depth only needs to apply to at least 50% of its length, in particular to at least 20% of its length.

[0034] In a separator plate, the flow channels of the region configured according to the invention have a depth KT, wherein the depth KT deviates by a maximum of 40 pm, advantageously a maximum of 10 pm, advantageously a maximum of 5 pm from the mean depth MKT averaged across the channels. Typically, the tolerances for separator plates of an electrolyzer are larger than for separator plates of a fuel cell. Analogous tolerances apply to the height or depth of the at least one sealing element.

[0035] For the individual flow channel, the following can apply: 0.92 MKT < KT < 1.08 MKT, preferably 0.95 MKT < KT < 1.05 MKT. The same applies to the height or depth of at least one sealing element.

[0036] The present invention can be used in particular for separator plates or frame plates. The plates according to the invention are manufactured by passing the layer of the plate, before cutting, between an embossing roller according to the present invention and a second embossing roller, which may also be designed according to the present invention, and thereby incorporating the embossed structures according to the invention into the layer.

[0037] The separator plate layer can be formed as a metallic plate, particularly made of stainless steel or titanium alloy. The plates can be coated or clad in sections or over their entire surface, for example, using a corrosion-inhibiting and / or conductivity-enhancing coating. Typical plate thicknesses for separator plates for fuel cells are in the range below 200 μm, particularly between 50 and 100 μm. In contrast, the plate thicknesses for separator plates for electrolyzers are usually between 200 and 500 μm.

[0038] Alternatively, the separator plate layer can be made of graphite-based material. There are two manufacturing options for this. One option involves compressing expanded graphite and then structuring the separator plate layer using an embossing process. To prevent the diffusion of the reaction media through the separator plate, the separator plate layer must also be impregnated. The second option is to manufacture the separator plate layer from a highly filled polymer. In this process, a polymer compound is enriched with up to 90% carbon. The carbon enables the necessary conductivity and heat transfer of the separator. To manufacture the separator plate, the highly filled polymer is formed into a sheet or web and then structured using an embossing process.

[0039] The embossing of the plates, in particular separator plates or frame plates, can be performed not only in a single-stage embossing process, but also in a two-stage process. The pre-embossing step of the first process stage does not have to be performed as described above, but can be performed conventionally, e.g., with a non-cambered roller or a pair of non-cambered rollers. It is then sufficient if the second, particularly the final embossing step is performed according to the invention.

[0040] Examples of plates according to the invention, embossing rollers according to the invention, and methods according to the invention for producing such plates and rollers are given below. In all figures, identical or similar reference numerals designate identical or similar elements, so that the description of individual elements may not be repeated.

[0041] In the following examples, an embossing roller, a plate, a method for producing an embossing roller, and a method for producing a plate are presented in individual examples, wherein these examples demonstrate additional optional and / or advantageous developments of the invention. It is possible to use individual advantageous, optional developments not mentioned in the independent claims individually to further develop the present invention or to combine them with one another in any desired combination of individual such optional advantageous features in individual examples or even in different examples.

[0042] They show:

[0043] Fig. 1 shows a fuel cell stack;

[0044] Fig. 2 shows a unit cell of a fuel cell system; Fig. 3 shows an exploded view of a single cell of an electrolyzer;

[0045] Fig. 4 is a schematic representation of the roll embossing of a metallic layer;

[0046] Fig. 5 is a view of the roll embossing device in Fig. 4;

[0047] Fig. 6 is a view of another device for roll embossing;

[0048] Fig. 7 is a view of another device for roll embossing;

[0049] Fig. 8 is a view of an embossing roller;

[0050] Fig. 9 in two partial figures 9A and 9B an oblique view and a cross section of another embossing roller;

[0051] Fig. 10 is a view of another embossing roller;

[0052] Fig. 11 is a schematic representation of an integrated cambered surface of an embossing roller;

[0053] Fig. 12 is a schematic representation of a ground cambered surface of an embossing roller;

[0054] Fig. 13 is a view of another embossing roller; and

[0055] Fig 14 a view of another embossing roller.

[0056] Fig. 1 shows an electrochemical system 1 with a plurality of identical bipolar plates 2. The bipolar plates 2 are arranged as an array in a stack 6 and stacked along a z-direction 7 of a Cartesian coordinate system with z-axis 7, x-axis 8 and y-axis 9. The bipolar plates 2 of the stack 6 are clamped between two end plates 3, 4. The z-direction 7 is also called the stacking direction. In the present example, the system 1 is a fuel cell stack. Two adjacent bipolar plates 2 of the stack therefore define an electrochemical cell which, for example, serves to convert chemical energy into electrical energy. To form the electrochemical cells of the system 1, a membrane electrode assembly (MEA) is arranged between adjacent bipolar plates 2 of the stack (see MEA 10 in Fig. 2). The MEAs typically each contain a membrane, e.g. B. an electrolyte membrane.Furthermore, a gas diffusion layer (GDL) can be arranged on one or both surfaces of the MEA. The separator plates 2a, 2b of the bipolar plates 2 each define a plate plane E in their contact plane, which is aligned parallel to the xy plane and thus perpendicular to the stacking direction or the z axis 7 (see Figure 2). The end plate 4 has a plurality of media connections 5 through which media can be supplied to the system 1 and through which media can be removed from the system 1. These media that can be supplied to the system 1 and removed from the system 1 can include, for example, fuels such as molecular hydrogen or methanol, reaction gases such as air or oxygen, reaction products such as water vapor or depleted fuels, or possibly coolants such as water and / or glycol.

[0057] Fig. 2 shows a perspective view of two adjacent bipolar plates 2 of an electrochemical system of the type of system 1 in Fig. 1, as well as a membrane electrode assembly (MEA) 10 known from the prior art and arranged between these adjacent bipolar plates 2, wherein the MEA 10 in Fig. 2 is largely concealed by the bipolar plate 2 facing the viewer. Each of the bipolar plates 2 is formed from two materially joined separator plates 2a, 2b, of which only the first separator plate 2a facing the viewer is visible in Fig. 2, which conceals the second separator plate 2b. The MEA 10 has a reinforcing edge along its outer edge, at which edge the MEA is clamped in a fluid-tight manner between the two bipolar plates 2.

[0058] The separator plates 2a, 2b have through-openings aligned with one another, which form through-openings 11a-c of the bipolar plate 2. When stacking a plurality of bipolar plates of the type bipolar plate 2, the through-openings 11a-c, together with through-openings in the reinforcing edges of the MEAs aligned with the through-openings 11a-c, form lines that extend in the stacking direction 7 through the stack (reference numeral 6 in Fig. 1). Typically, each of the lines formed by the through-openings 11a-c is in fluid communication with one of the ports 5 in the end plate 4 of the system 1. For example, coolant can be introduced into or discharged from the stack via the lines formed by the through-openings 11a.The lines formed by the through-openings 11b, 11c, on the other hand, can be designed to supply the electrochemical cells of the fuel cell stack of system 1 with fuel and reaction gas, as well as to discharge the reaction products from the stack. The media-carrying through-openings 11a-11c are each formed substantially parallel to the plate plane. To seal the through-openings 11a-11c from the interior of the stack 6 and from the environment, the first separator plates 2a each have sealing arrangements in the form of sealing beads 12a-c, which are each arranged around the through-openings 11a-c and which completely enclose the through-openings 11a-c. The second separator plates 2b have corresponding sealing beads for sealing the through-openings 11a-c (not shown) on the rear side of the bipolar plates 2 facing away from the viewer of Fig. 2.

[0059] In an area opposite the electrochemically active region of the MEA, the first separator plates 2a have, on their front side facing the viewer in Fig. 2, a flow field 17 with structures (channels and webs) for guiding a reaction medium along the front side of the separator plate 2a, i.e., a flow region with flow channels. These structures are provided in Fig. 2 by a plurality of webs and channels running between the webs and delimited by the webs. On the front side of the bipolar plates 2 facing the viewer in Fig. 2, the first separator plates 2a also each have at least one distribution region and one collection region, both of which are designated by the reference numeral 20.The distribution or collection area 20 comprises structures which are configured to distribute a medium introduced into the distribution or collection area 20 from a first of the two through-openings 11b via the flow field 17 and / or to collect or bundle a medium flowing from the flow field 17 to the second of the through-openings 11b.

[0060] The first separator plates 2a further each have a further sealing arrangement in the form of a perimeter bead 12d, which surrounds the flow field 17, the distribution areas and collection areas 20 and the through openings 11b and 11c and seals them against the through opening 11a, ie against the coolant circuit, and against the environment of the system 1.

[0061] In an electrolyzer, water is added to a stack similar to the one shown in Figure 1, and oxygen and hydrogen are removed. Figure 3 shows an exploded view of a single cell 100 of an electrolyzer. The single cell 100 comprises two separator plates 102a and 102b, each with a flow field 117a, 117b, two cell frames 130 and 130', sealing layers 120, 140, 120' and 140', and a membrane-electrode assembly 110 with media diffusion structures 150 and 150'. The media diffusion structure 150 comprises, for example, layers of carbon fleece, while the media diffusion structure 150' comprises metal, e.g., porous titanium. The separator plate 102b is arranged on the cathode side of the single cell 100. The separator plate 102a is arranged on the anode side of the single cell 100. The individual layers are pressed together to form a single cell.In the section shown, the individual layers each have water ports 11d arranged in alignment one above the other for introducing water, hydrogen ports 11e for discharging hydrogen, and positioning holes 11z. A flow area of ​​the separator plate 102a is defined by projecting the seal 12f, which surrounds all structures to be sealed in layer 120', onto the separator plate 102a. A flow area of ​​the separator plate 102b is defined by projecting the seal 12e, which also surrounds all structures to be sealed in layer 120, onto the separator plate 102b. The cell frame 130' has distribution channels 131' for distributing the introduced water. When an electrical potential is applied to the cell 100, hydrogen and oxygen can be generated from the supplied water.

[0062] The separator plates 2a, 2b, 102a, 102b, as well as the cell frames 130, 130' and the sealing layers 120, 140, 120', and 140', can each be made from a metal sheet, e.g., from a stainless steel sheet or a titanium alloy sheet. The sheets can be coated or plated in sections or over their entire surface, for example, using a corrosion-inhibiting and / or conductivity-enhancing coating. Alternatively, the separator plates can be made from a graphite-based material. There are at least two manufacturing options. One option is to compress expanded graphite and then structure the separator plate using an embossing process. To prevent the diffusion of the reaction media through the separator plate, impregnation of the separator plate is also necessary. The second option is to manufacture the separator plate from a highly filled polymer.In this process, a polymer compound is enriched with up to 90% carbon. The carbon enables the necessary conductivity and heat transfer of the separator. To produce the separator plate, the highly filled polymer is formed into a sheet or web and then structured using an embossing process.

[0063] The structures of the flow field 17, the webs and channels of the distribution or collection region 20 and the sealing beads 12a-d or the structures of the flow field 117a, 117b, the distribution channels 131, 131' and the sealing beads 12e, 12f are each formed integrally with the separator plates 2a, 2b, 102a, 102b or the cell frame 130, 130' or the sealing layers 120, 140, 120' and 140' and molded into them, e.g., in the present invention, in a roll-embossing process. The separator plates 2a and 2b or 102a and 102b can be joined to one another, e.g., B. be connected in a materially bonded manner, for example welded, soldered or glued, in particular by laser welding, for example, to form two-layer bipolar plates 2. In electrolyzers, in addition to bipolar plates constructed from two separator plates 102a, 102b, the single-layer separator plates 102a, 102b can also be used directly as bipolar plates.

[0064] Fig. 4 schematically shows a device for embossing a single-layer plate 200, for example a separator plate 2a, 2b, 102a, 102b, a frame plate 130, 130' or a sealing layer 120, 140, 120' and 140', by means of roll embossing. For this purpose, the metallic layer 200 of the plate in this example is passed in the feed direction 213 between two embossing rollers 210a and 210b. The rollers 210a and 210b each rotate in the directions of rotation 212a and 212b shown in the figure. On the surface 215a of the embossing roller 210a and on the surface 215b of the roller 210b, in Fig.

[0065] 4 embossed structures (hereinafter referred to as reference numeral 217) are not visible. These embossed structures form the male and female dies of an embossing device and emboss embossed structures 201 into the layer 200 as they pass through the embossing rollers 210a and 210b. These structures 201 can be, for example, channels for conducting a medium or sealing beads for sealing individual areas of the plate 200.

[0066] In addition to Fig. 4, Fig. 5 shows a side view, arranged in a plane perpendicular to the feed direction 213, of the arrangement of the two embossing rollers 210a and 210b, which enclose the layer 200 of the separator plate between them. Both embossing rollers 210a and 210b have a cylindrical outer surface apart from the embossed structures incorporated into this surface. These embossed structures, not shown, emboss the layer 200. With such a conventional arrangement of embossing rollers as shown in Fig. 5, the two rollers 210a and 210b bend outward with their respective centers during the embossing process, so that the embossing pressure on the center of the layer 200, viewed in the feed direction 213, drops relative to the edges arranged to the left and right in Fig. 5. This leads to uneven embossing of the embossed structures of the layer 200.

[0067] Fig. 6 shows an arrangement of embossing rollers 210a and 210b corresponding to Fig. 5, which enclose a layer 200. In Fig. 6, the illustrated envelopes 218a and 218b of the embossed structures (not visible in Fig. 6) in the rollers 210a and 210b have a convex curvature over the entire length of the embossing rollers 210a and 210b. In Fig. 6, these convex curvatures are shown schematically and completely exaggerated. The actual elevation KH due to the convex curvature of the regions 216a and 216b of the envelopes 218a and 218b, respectively, is 50 pm in the example of Fig. 6.

[0068] Otherwise, the embossing rollers 210a and 210b are configured as in the prior art, which is shown in Fig. 5. The convex curvature of the regions 216a and 216b compensates for the reduced embossing pressure occurring in the center of the embossing rollers 210a and 210b during the embossing process due to the deflection of the embossing rollers 210a and 210b, so that the embossed structures 201 can be introduced in a defined manner, particularly in channels with a substantially uniform depth. Sealing structures with a substantially uniform depth or height can also be produced by compensating for the reduced embossing pressure in the center of the rollers 210a and 210b using the cambered regions 216a and 216b.

[0069] In Fig. 6, as well as in the other Figs. 7 to 10, no embossed structures 217 are shown in the surfaces 215a and 215b of the embossing rollers 210a and 210b, since these have too small a depth to be recognizable in the drawing sheet.

[0070] Fig. 7 shows a further example similar to that in Fig. 6 for an arrangement of two embossing rollers 210a and 210b. In contrast to Fig. 6, the embossing roller 210a is now without a convex curvature or camber, while the embossing roller 210b is designed the same as the embossing roller 210b in Fig. 6. Such a one-sided curvature of an embossing roller and use of a second conventional embossing roller, as shown in Fig. 5, can also be used according to the invention to achieve defined heights or depths of the embossed structures, in particular uniform depths or heights over a specific area of ​​a layer 200.

[0071] Fig. 8 shows a further embossing roller 210 according to the invention, which is designed similarly to the embossing roller 210a in Fig. 6. Overall, the roller 210 still has a convex curvature. However, not all surface sections in the axial direction have the convex curvature. Rather, it is only formed in individual sections 216a, 216b, 216c, 216d of the roller 210. For example, the end sections 216a, 216d of the roller have curvatures, as do two sections 216b, 216c spaced from them and immediately adjacent to the central region, whereby overall a convex curvature nevertheless results. The total length KL of the curved sections is KL = KLi + KL2 + KL3 + KL4 and in this example corresponds to approximately 70% of the total length RL of the embossing roller. Between the sections spanning the curvature there are sections that are cylindrical in shape.The roller 210 is suitable for producing a defined or uniform embossing in a corresponding area of ​​a layer. In Fig. 8, no embossed structures 217 are shown, but only the envelope 218 of the surface 215 of the embossing roller 210.

[0072] Fig. 9 shows in the partial figures 9A and 9B a further example of an embossing roller 210 according to the invention, wherein in Fig. 9A a plan view of the embossing roller

[0073] 210 in an oblique view and in Fig. 9B a cross section through the roller 210 along the line 219 in Fig. 9A.

[0074] The roller 210 in Fig. 9A is designed similarly to that in Fig. 8, wherein, however, the convexly raised region 216 arranged in the longitudinal direction along the rotational axis 211 of the roller 210 along the line 219 is not uniformly designed along the circumference of the embossing roller 210. Only certain regions on this circumference are themselves cambered. In particular, the region 216', which is also shown in cross-section along the line 219 in Fig. 9B, is not convexly raised as such, but it lies in the direction of the rotational axis.

[0075] 211 between convexly raised areas. The dashed circle in Fig. 9B represents the original cylindrical circumference of the roller 210 in the section plane, from which individual surface areas were removed to topographically adapt the surface, for example, to compensate for springback during embossing. This results in an even more uniform embossed image on the layer to be embossed, one that more closely corresponds to the desired embossing pattern.

[0076] Fig. 10 shows another embossing roller 210 according to the present invention, which is configured similarly to the one in Fig. 8. In this embossing roller 210, the cambered region 216 is also convexly raised. However, in contrast to the embossing roller in Fig. 8, the region 216 is not located centrally in the longitudinal direction along the rotational axis 211 of the embossing roller 210, but rather offset toward its left-hand end in the drawing. This example therefore illustrates that the cambered region 216 does not have to extend over the entire length of the embossing roller 210 and does not have to be arranged centrally in the embossing roller 210.

[0077] Figures 11 and 12 schematically show two manufacturing processes for a cambered region 216 of an embossing roller 210 according to the present invention. Fig. 11 shows the production of an integrated cambered embossing roller 210, wherein only the region 216 with the convex elevation is shown in the detail and in cross-section. For this purpose, in a first step, the embossed structure 217 to be introduced into the surface 215 of the embossing roller and the required camber are determined. The embossed structure 217 is then directly introduced into an initial embossing roller with an initial surface 214 into which no embossed structure has yet been introduced and which is a cylindrical embossing roller surface, taking into account both the embossed structure 217 and the required camber, for example by milling and / or by laser and / or by erosion and / or by etching.As a result, the finished surface 215 of the embossing roller 210 then contains embossed structures 217 that have an envelope 218 that is convexly curved in a region 216. The embossed structures 217 can all be designed with a uniform channel depth KT, starting from the surface 215, so that although they have a different distance from the rotational axis 211 of the embossing roller 210, they nevertheless result in a uniform embossing of the layer of a separator plate or another plate.

[0078] Fig. 12 shows the production of an embossing roller 210 as a ground, cambered embossing roller 210, wherein likewise only the region 216 with a convex curvature is shown in the detail and in cross-section. In this process, the embossed structure 217 is first introduced into a starting surface 214 of a purely cylindrical embossing roller 210, for example, by milling, lasering, eroding and / or etching. For example, the embossed structures 217, as in the present example, can all or partially have the same depth after this step. The embossed structure thus produced is then ground in order to create a convexly cambered envelope 218 of the embossed structures 217 in the region 215. In this process, the grooves of the embossed structures then have different depths, so the channel depth KT varies from groove to groove.The groove bottoms of the embossed structures 217 are all furthermore equidistant from the rotational axis 211 of the embossed roller 210. Even with such a ground cambered embossed roller 210, defined embossed structures can be produced in plates, for example separator plates or frame plates, in particular in an area corresponding to the area 216 on the plate's position, with structures of a defined, in particular uniform, depth or height.

[0079] In both Fig. 11 and Fig. 12, the convexly arched envelope 218 extends over several embossed structures 217, the number shown being only symbolic.

[0080] Fig. 13 shows a further embossing roller 210 according to the present invention, which is designed similarly to the one in Fig. 10. In this embossing roller 210, too, the cambered region 216, which is arranged centrally here, is convexly raised and extends in the longitudinal direction of the embossing roller 210 or the direction of the axis of rotation over the entire region 217a of the embossing roller 210, which is provided with embossed structures 217 for introducing embossed structures into a separator plate, for example the separator plate 2a in Fig. 2. Only a section of the embossed structures in the circumferential direction is shown. At each of the longitudinal ends of the embossing roller 210, regions are provided in which no embossing of the separator plate takes place and into which the convex curvature 216 therefore does not extend. In these lateral areas, ie outside of an outermost circumferential embossed element 22, which for example corresponds to the formation of a sealing bead 12d from Fig. 2 or a sealing bead 12e, 12f from Fig.3, nubs 300 are distributed around the circumference of the embossing roller 210. These nubs serve to guide a metal sheet to be embossed. The separator plate to be produced is then punched out of this sheet in such a way that the embossing created by these nubs 300 does not become part of the separator plate. Such embossings are therefore also referred to as auxiliary embossings.

[0081] Fig. 14 shows another embossing roller 210 according to the present invention, which is configured similarly to the one in Fig. 10. In contrast to Fig. 10, the convex region 216 is now significantly raised and offset from the regions adjacent to the longitudinal ends of the embossing roller 210. Thus, here too, the convex region of the curvature extends as a uniform curvature over the entire embossing region 217 of the embossing roller 210.

Claims

Claims 1. Embossing roller (210) for embossing a plate (2a, 2b, 102a, 102b, 120, 120', 130, 130', 140, 140', 200), in particular a separator plate or frame plate for an electrochemical system (1), in particular for a fuel cell, for an electrolyzer or for a redox flow battery, with a substantially cylindrical surface and the cylinder's longitudinal axis as the axis of rotation (211), characterized in that the envelope (218) of the surface (215) of the embossing roller (210) has a curvature that is convex in the direction of the axis of rotation, at least in one region (216) that extends at least partially in the direction of the axis of rotation and at least partially in this region transversely to the axis of rotation (211).

2. Embossing roller (210) according to the preceding claim, characterized in that the convex curvature in the direction of the axis of rotation extends over at least part of the area (217a, 217b) of the embossing roller (210) provided with embossed structures (217) for embossing the plate or completely over the area (217a, 217b) of the embossing roller (210) provided with embossed structures (217) for embossing the plate.

3. Embossing roller (210) according to one of the preceding claims, characterized in that the convex curvature in the direction of the axis of rotation extends over the entire length RL of the embossing roller (210) or only over a length KL with KL < RL, advantageously KL < 2 / 3 RL, advantageously KL < 1 / 3 RL.

4. Embossing roller (210) according to one of the preceding claims, characterized in that the convex curvature in the direction of the axis of rotation extends over a length KL, where KL > 50 mm, in particular KL > 100 mm, in particular KL > 0.5 RL, KL > 2 / 3 RL, KL > 0.75 RL, KL > 0.9 RL or KL = RL, where RL is the entire length of the embossing roller (210).

5. Embossing roller (210) according to the preceding claim, characterized in that the convex curvature extends in the direction of the axis of rotation over a length KL, wherein the convex curvature extends centrally or off-center with respect to the cylinder longitudinal axis on the embossing roller.

6. Embossing roller (210) according to one of the preceding claims, characterized in that the convex curvature has a superelevation KH with 5 pm < KH < 500 pm, advantageously 15 pm < KH < 300 pm.

7. Embossing roller (210) according to one of the preceding claims, characterized in that the convex curvature extends transversely to the direction of the axis of rotation over a length KU over at least part of the circumference of the embossing roller (210) or over the entire circumference of the embossing roller (210).

8. Embossing roller (210) according to one of the preceding claims, characterized in that the convex curvature extends transversely to the direction of the axis of rotation over a length KU over at least part of the circumference of the embossing roller (210) with the maximum diameter PD of the embossing roller (210), wherein KU > PD / 50, advantageously KU > PD / 20, in particular KU > 4 mm, in particular KU > 5 mm.

9. Embossing roller (210) according to one of the preceding claims, characterized in that the embossing roller (210) is ground cambered and / or integrated cambered to produce the convex curvature.

10. Embossing roller according to one of the preceding claims, characterized in that the embossing roller (210) is partially circular and / or parabolically cambered.

11. A method for producing an embossing roller (210) according to one of the preceding claims, characterized in that a) embossing structures (217) for producing at least one set of flow channels for a medium and / or at least one sealing element are introduced into a separator plate and the surface of the embossing roller is then machined in such a way that the envelope (218) of the surface (215) of the embossing roller (210) has a curvature which is convex in the direction of the axis of rotation at least in one region (216) with embossed structures which extends at least in regions in the direction of the axis of rotation and at least in sections in this region transversely to the axis of rotation (211);or b) the surface of a cylindrical embossing roller is machined in such a way that the surface (215) of the embossing roller (210) has a convex curvature in the direction of the axis of rotation in at least one region (216) into which an embossed structure is to be introduced, which extends at least partially in the direction of the axis of rotation and at least partially transversely to the axis of rotation (211), and embossed structures (217) are then introduced into the surface of the embossing roller (210) to produce at least one set of flow channels for a medium and / or at least one sealing element in a separator plate;or c) embossed structures (217) for producing at least one set of flow channels for a medium and / or at least one sealing element in a separator plate are introduced into the surface (214) of a cylindrical embossing roller (210) in such a way that in at least one region (216) which extends at least partially in the direction of the axis of rotation and in this region at least partially transverse to the axis of rotation (211), the envelope (218) of the embossed structures (217) has a curvature which is convex in the direction of the axis of rotation.

12. Plate (2a, 2b, 102a, 102b, 120, 120', 130, 130', 140, 140', 200) for an electrochemical system (1), in particular for a fuel cell, for an electrolyzer or for a redox flow battery, with a layer, in particular a metallic layer, a graphitic layer or a layer made of a graphite composite, wherein the layer has at least one region with at least one set of flow channels for a medium embossed into the layer, wherein the river channels have a channel bottom and channel walls arranged on both sides of the channel bottom and webs are arranged between adjacent channel walls of adjacent river channels, characterized in that for one, several or all regions the river channels have a substantially uniform depth within < 90% of the area of ​​the region.

13. Plate according to the preceding claim, characterized in that for one, several or all regions, the flow channels have a substantially uniform depth with the exception of one or more channel ends and / or one or more of the outermost channels.

14. Plate according to one of claims 8 and 9, characterized in that one, several or all regions is / are part of an active region, a supply region for media or a discharge region for media.

15. Plate according to one of claims 8 to 10, characterized in that each of the flow channels has a depth KT and all flow channels together have an average depth MKT, wherein for each of the flow channels the depth KT deviates from MKT by a maximum of 40 pm, advantageously a maximum of 10 pm, advantageously a maximum of 5 pm.

16. Plate according to one of claims 8 to 11, characterized in that each of the flow channels has a depth KT and all flow channels together have an average depth MKT with 0.92 MKT < KT < 1.08 MKT, preferably 0.95 MKT < KT < 1.05 MKT.

17. Plate according to one of claims 8 to 12, characterized in that the flow channels were embossed into the layer by means of roll embossing, in particular by means of an embossing roller according to one of claims 1-6.

18. Plate (2a, 2b, 102a, 102b, 120, 120', 130, 130', 140, 140', 200) for an electrochemical system (1), in particular for a fuel cell, for an electrolyzer or for a redox flow battery, with a layer, wherein the layer has at least one region with at least one sealing element embossed into the layer and the at least one sealing element has a straight or curved roof and flanks arranged on both sides of the roof, characterized in that for one, several or all regions the sealing element has a substantially uniform height of its roof within < 90% of the area of ​​the region.

19. A plate according to any one of claims 8 to 14, wherein the plate is a separator plate or a frame plate.

20. Method for producing a plate (2a, 2b, 102a, 102b, 120, 120', 130, 130', 140, 140', 200) according to one of claims 8 to 15, characterized in that the positioning of the plate (2a, 2b, 102a, 102b, 120, 120', 130, 130', 140, 140', 200) is carried out between a first embossing roller (210a) and a second embossing roller (210b) before cutting.

21. Method according to the preceding claim, characterized in that the first and / or the second embossing roller is an embossing roller according to one of claims 1 to 6.

22. Method according to one of claims 16 and 17, characterized in that the first embossing roller and / or the second embossing roller has a convex curvature over a length in the direction of rotational axis of the embossing roller which corresponds to the width of at least one of the regions of the plate transverse to the feed direction of the roll embossing or is greater or smaller than this width.

Images