DE102009036039A1 - Multi-layer bipolar plate for use in e.g. fuel cell system, has contact points arranged such that contact points rest on both sides of line, which enters into plane between lift/recess of layer and lift/recess of another layer - Google Patents

Abstract

The plate (1) has layers (2, 3) connected with each other in a material-fit manner, where lifts/recesses (2a, 2b) of one of the layers and lifts/recesses of the other layer engage with each other and contact in planes in a form-fit manner. Contact points (30b, 31b) are arranged such that the contact points rest on both sides of a virtual straight line (5b), which runs in a main direction of one of the lifts/recesses of the latter layer and enters into one of the planes between one of the lifts/recesses of the former layer and the lift/recess of the latter layer.

Description

The The present invention relates to a bipolar plate and a method for their production.

• – Elektrische Kontaktierung der Elektroden der einzelnen elektrochemischen Zellen und Weiterleitung des Stroms zur benachbarten Zelle (Serienschaltung der Zellen),
• – Versorgung der Zellen mit Reaktanden wie z. B. Wasser oder Gase und z. B. Abtransport des erzeugten Reaktionsgases über eine entsprechende Verteilerstruktur,
• – Weiterleiten der bei der Erzeugung in der elektrochemischen Zelle entstehenden Abwärme, sowie
• – Abdichten der verschiedenen Medien- bzw. Kühlkanäle des sog. Flowfields gegeneinander und nach außen.

The bipolar plate according to the invention is applicable in an electrochemical system, for example a fuel cell system or an electrolyzer. There are several types of electrochemical systems are known in which an electrochemical cell stack with a layering of several electrochemical cells, which are each separated by bipolar plates, constructed. The bipolar plates have several tasks:

• - Electrical contacting of the electrodes of the individual electrochemical cells and forwarding of the current to the adjacent cell (series connection of the cells),
• - Supplying the cells with reactants such. As water or gases and z. B. removal of the generated reaction gas via a corresponding distributor structure,
• - Forwarding of the resulting in the generation in the electrochemical cell waste heat, as well
• - Sealing the various media or cooling channels of the so-called. Flowfield against each other and to the outside.

For the intended large industrial Application is of high importance, large numbers of bipolar plates with a high quality at low cost. Here is the compliance of tight dimensional tolerances of the utmost importance, otherwise there will be functional or even safety-related malfunctions can come. This is especially true for welded multilayer bipolar plates essential.

So far to ensure accurate positioning of the layers to each other positioning holes used. Will these positioning holes, the exact positioning the at least two Bipolarplattenlagen ensure each other, at the same time with the rest Through holes as well the trimming of the outer edges introduced the bipolar plate layers, has been shown in practice, that the accuracy and reproducibility of the positioning of the Layers insufficient to each other is. In particular, this leads to the offset of the channel geometries the layers. At extreme offset then becomes when connecting the layers the bipolar plate welded at locations where the bipolar plate layers do not lie on top of each other so that burns can occur.

It is therefore the object of the present invention, a method for producing a multilayer bipolar plate and a multilayer Bipolarplatte provide, with the large industrial multi-layer bipolar plates in high quality at low cost available can be made.

These Task is governed by the objects of independent claims solved.

A first embodiment a method of manufacturing a multilayer bipolar plate suggest that in at least two layers each at least a first and a second survey / depression are formed and the layers be positioned on each other. In the fully positioned state The layers pick up the first elevation / depression of the first layer and the first survey / deepening of the second layer into each other and touch form fit in a plane E1 (first contact point). At the same time, the second survey / depression will take effect the first layer and the second layer / recess the second layer im completely positioned state of the layers into each other and touch each other in a plane E2 only in sections in at least two sections (second contact point). These points of contact are arranged that they are on both sides of a virtual line that is in the main direction the elevation / depression of the second layer along the longest extent this elevation / depression in the second layer runs arranged are. Between the second survey / deepening of the first situation and the second survey / deepening of the second situation occurs in the Level E2 not positive fit. The at least two layers are using material-fit Procedures joined together, here the surveys / depressions of at least one position are in complementary surveys / depressions held a fixing device.

These Arrangement has the consequence that in the fully positioned state, d. H. the arrangement immediately before the joining of the layers, no compensation movement between the layers in the direction of a virtual straight line through the two contact points more is possible is. On the other hand, a compensation movement between the layers in Direction perpendicular to this virtual line within the scope of the proportions the two second surveys / wells to each other very well possible.

Preferably, in the same method step with the elevations / depressions, the channel structures are formed in the at least two layers. The orientation of the channel structure is usually such that its main direction is parallel to the direction in which the elevations / depressions allow a limited balance between the layers of the plate. The distance of the respective second elevation / depression for both layers to the respective channel structure is determined before forming. This makes it possible to reproduce a displacement of the channels between the mutually associated layers perpendicular to their main direction from the outset to avoid.

Of the Term elevation / depression is used in the context of this invention for a Section of a layer of a bipolar plate used from the Level of the particular situation stands out. Depending on the viewing direction it can be a survey or a depression. The supplementary Term deepening / elevation emphasizes the opposite to the survey / depression Direction.

A second embodiment a method for producing a multilayer bipolar plate sees in that in at least two layers at least one first, a second and a third survey / depression are formed, and the layers are positioned one on top of the other. In the fully positioned State grab each the first survey / depression of the first Situation and the first survey / deepening of the second situation (first contact point), the second survey / deepening of the first situation and the second survey / depression the second location (second contact point) and the third elevation / depression the first situation and the third survey / depression of the second situation (third contact point) into each other and touch each other in levels E2, E3 and E4 only in sections in at least two sections without it to a positive connection between the interlocking Elevations / depressions of the first and second position would come. The contact points are arranged so that they are in the plane E2, E3 and E4 on both Sides of a virtual line, the main direction of the respective second Elevation / depression in the second layer is, lie. This virtual Straight lines through the first and second contact points extend in relation to each other Essentially parallel. "In the essentially parallel "means in the context of this invention at an angle of -10 ° to 10 °. The virtual Straight through the third contact point is substantially perpendicular to the two aforementioned virtual lines. In the context of this Invention is "im essentially vertical "as an angle of 80 ° 100 ° defined.

The at least two layers are interconnected by means of cohesive methods together, In doing so, the elevations / depressions of at least one position in complementary Elevations / depressions of a fixing device held and so ensures the exact positioning of the layers to each other.

This As a result, limited mobility through the two Contact points with a substantially parallel orientation of said virtual Straight line more evenly the entire plate surface is distributed. Especially with central arrangement of the contact point with this substantially vertical virtual line in the positioning of the layers to each other, the compensation of the shape tolerances both layers to each other on both sides of this contact point. at Production-related relative movements of the individual layers to each other thereby maintaining sufficient freedom, the position of the Layers to each other continue to be determined exactly. This solution shows its advantages especially with bipolar plates with almost square channel structure.

Also Here, the elevations / depressions are preferably in the same process step molded with the channel structures to defined distances between ensure the channel structures and the contact points in both layers.

at both embodiments It is with regard to an optimal positioning before joining the Layers preferably, if at least one elevation / depression has a passage opening through which can pass through a centering of the fixing device.

When Method of joining the layers together are preferably glued or welded, in particular laser welding used. The bipolar plates or their layers are preferably made of metal, in particular of steel, so that a shaping by means of hollow embossing, thermoforming, Hydroforming, adiabatic forming (forging, high energy forming) or roll embossing is preferred.

The Layers E1 and E2 or E2, E3 and E4 are preferably to the stacking direction a fuel cell stack substantially perpendicular Levels at height the touch between the two layers. These levels E1 and E2 or E2, E3 and E4 extend parallel to the plane E of the bipolar plate, apart from the for their function necessary imprints usually flat; the plane E extends in the middle between the two outer layers the bipolar plate. The levels E1 and E2 on the one hand and E2, E3 and E4, on the other hand, are thus parallel to one another - namely the touch slightly offset at the various contact points, but they can also be identical - namely if no such offset occurs.

A first embodiment of a bipolar plate according to the invention provides that it contains at least two layers, wherein at least two layers each contain at least a first and a second elevation / depression, wherein the first elevation / depression of the first layer and the first elevation / depression of the second layer in the fully positioned state of the layers interlock and touch each other in a positive manner in a plane E1 (first contact point). However, the second survey / deepening of the first situation and the second survey / deepening of the second situation are only touching Sectionally in the plane E2, namely along at least two short, in some cases only punctiform, sections (second contact point), which lie on both sides of a virtual straight line in the main extension direction of the second survey / recess of the second layer. However, the section-wise contact between the interlocking second elevations / depressions of the first and second layer does not cause a positive connection in the plane E2 in the region of the second contact point. In the direction of said virtual straight line, a spatially very limited translational tolerance compensation is possible parallel to the plane E2. A rotation, however, is not possible by the interaction of the two contact points.

hereby an exact positioning of both layers is achieved, wherein for tolerance compensation still a limited movement between the Layers possible is, namely in the direction substantially perpendicular to a virtual straight line both points of contact the second contact point.

at The bipolar plates should be noted that these are usually channel structures have on both the outer surfaces of the Bipolar plate for guiding of operating media (for example, molecular hydrogen on the one hand and air / oxygen on the other) as well as the targeted guiding of a refrigerant serve. The channel structures of two adjacent, mutually positioned bipolar plate layers give on its side facing a flowfield, usually for cooling media. Likewise, on the side facing away from this channel structure of the Location, ie on the other side of the respective bipolar plate layer a flowfield formed, usually for the Distribution of the reactants and removal of the reaction products. For metallic bipolar plates, the structures are on the two Pages of a layer usually complementary, d. H. a survey on the top has a depression on the Bottom to the episode. In addition to parallel and / or serpentine arranged continuous channel structures are also such distribution structures possible, the one crossing between virtual parallel flow lines, they are also referred to as channel structures hereinafter.

The Positioning of the layers by means of positioning embossments in the form of elevations / depressions is particularly suitable for metallic bipolar plates whose Layers deforming may have shape tolerances. Simultaneous molding the channel structures and the elevations / depressions ensures that the distance between these structures always remains constant. With The invention thus in particular the offset of the individual layers a bipolar plate minimized to one another and accurate positioning preferably embossed Structures of the individual layers, especially when joining in one Welding device (for example a laser welding device) allows. Advantages are that they are welded better and faster can, less waste during welding and other processes through the exact positioning arises. The tolerance of the blank can thus be enlarged. this leads to at a cost reduction, without thereby the quality negative is affected, especially when simpler cutting methods (eg punching) can be used.

Around a "puffing" of the multilayered To prevent bipolar plate is a welding, preferably laser welding at least the two outer layers the bipolar plate together meaningful. However, this is again to note that in the filigree canal structure the right Sections are welded together. This is special important, because of the tightness and the regulated flow of cooling media guaranteed are. It is thus again emphasized that the welding of the layers to the bipolar plate for the present invention is not exclusive to the outer periphery but also in the "internal area" between different channel structures takes place, and that right here highest precision necessary is.

A Another alternative of the invention provides that these at least contains two layers, wherein at least two layers each have at least one first, one second and third survey / immersion included and the first Survey / deepening of the first situation and the first survey / depression the second layer (first contact point), the second point / depression the first layer and the second layer / recess the second layer (second contact point) and the third survey / recess of the first situation and the third survey / deepening of the second situation (third contact point) in full Positioned state of the layers interlock and get into the Layers E2, E3 and E4 only in sections in at least two Touch sections. Both contact points a contact point lie in the plane E2, E3 and E4 on both Pages of a virtual line that are in the main direction of each Elevation / depression in the second layer runs. This virtual line through the first and second contact point to each other in the essentially parallel while the virtual line through the third contact point essentially perpendicular to the two aforementioned virtual lines.

in the Following are developments of the bipolar plate according to the invention exemplified.

A further education provides that the Erhe tions / depressions of the first layer to the elevations / depressions of the second layer are designed self-centering. As a result, an alignment, especially in the height direction (stacking direction of a fuel cell stack) is unnecessary, since the layers themselves center each other.

A Another advantageous embodiment provides that the first and / or second survey / depression of the first and / or second layer punched is. Different sizes Lochgebung or Lochgebung in only one layer also allows a Visual control of correct layer assembly. Advantageously the elevations / depression are centrically perforated. Especially advantageous is that here both depressions or elevations are perforated. Generally allow the holes the engagement of a pin of a fixing device.

A Another advantageous embodiment provides that the one another gripping first surveys / recesses of the first and second Each location is circular are. At the same time it is envisaged that the second survey / recess the first layer is circular and the second elevation / depression the second layer is a slot-shaped or rounded polygonal but not circular elevation / depression is.

All in all here are all, especially in the stamping process easy to produce, geometries possible, are rounded for manufacturing reasons Geometries preferred. The geometry of the survey / depression and the fixing device are matched. In the context of this Invention means the term slot-shaped corresponding oval, rounded polygonal or oblong and includes the circular shape. Shaped slot refers exclusively the form, it does not have to be an opening, but it are usually surveys or depressions.

A Another advantageous embodiment provides that at least one the layers has a channel structure and the longitudinal direction of the second elevation / depression of the second layer parallel to the channel structure is arranged. This ensures that at a z. B. thermal expansion or production-related relative movement of both layers always guaranteed is that there is a "parallel shift" along the one to be joined Channel areas comes. It can thus be ensured that the "deepest Point of "the Channel thus always lies on each other in both situations and even when shifting the layers along the tolerance cross section always the desired ones Positions of both layers are in contact with each other. This is special advantageous in welding or laser welding, since there is no burn through during welding in this arrangement.

A Another advantageous embodiment provides that the elevations / depressions the first location a larger or have smaller cone angle than the cone angle of the complementary elevations / depressions the second location. As a result, a linear, circumferential contact between reached the surveys / depressions, so that in these areas one possible high surface pressure occurs. This is further supported when the surveys / pits one position less deep than the elevations / depressions of the different location.

In the following, in a somewhat different words, a particularly advantageous embodiment of the invention is described, which, however, is by no means to be understood as limiting:
To make an accurate positioning of the bipolar plates to each other, conical embossments - depending on the viewing angle elevations or depressions - introduced into the layers. It is advantageous if z. B. the anode-side bipolar plate layer has two circular imprints and the cathode-side bipolar plate layer has exactly a circular and a slot-like embossing. These positioning embossments should be designed so that z. B. the anode-side layer can be inserted into the cathode-side layer and on the cone of the embossing a positive centering of the layers is made to each other. The advantage of slot-shaped positioning embossing is that the plate system is not overdetermined and tolerance compensation is provided by the anode-side to the cathode-side bipolar plate layer. Therefore, it is advantageous if the slot-shaped positioning embossing runs parallel to this main direction of the channels of the flowfield. This avoids an offset in the y direction and thus perpendicular to the channel structures.

Another feature of Positionierprägung is that they also for a positive positioning within a device, for. B. a welding device can be used. For the same reason as described above, a receptacle of the device should have a complementary but somewhat larger shape than the corresponding elevation or depression of the bipolar plate layer. Thus, if a slot-shaped positioning stamping is used, the receptacle likewise has a slot shape, but is larger than the slot-shaped positioning stamping in the relevant position (see section CC in FIG 3e ). For a round positioning stamping a round receptacle is used, which in turn has a larger diameter than the positioning stamping. For a coarse pre-centering of the individual layers in the device, it is advantageous in each case a hole and a slot in the middle of Provide positioning stamping and a matching recording pin in the device. The pre-centering via the receiving pin ensures that the layers slide in into the receptacle of the device.

at the design of the associated positioning imprints in Different layers offer different variants. On the one hand Is it possible, that in both layers surveys relative to the other layer level be formed and the elevation of the arranged below location in the depression, which is on the bottom of the elevation in the on it arranged situation results intervenes. With regard to the other Structural elements of the relevant bipolar plate or its layers, but it is often not possible the elevations with the necessary height in a single direction ausformieren, since the surveys then, for example, the seal the layers stamped against each other Overhang beads and thus would prevent a seal. In this situation is then on the other hand advised, in both layers with a depression a larger diameter and bring in the area then, in turn, formulate an increase in this depression. The extent of the depression is altogether less than that of the increase. This allows a distribution the height the elevations / depressions on both sides of the plane of the respective bipolar plate layer. there is a substantially symmetrical height distribution as possible as an asymmetrical one.

The execution the positioning stamping can be chosen like that be that one layer has a steeper cone than the other Location. Furthermore it is advantageous to emboss at a location a little less deep, so that the two Layers in the region of the contact point only in their respective flank touch the cone sectionwise or circumferentially.

Farther it makes sense the round or slot-shaped recording of the device to be provided on its open side with a radius on which the slope of the outer cone an imposed situation comes to lie. It is also for positioning sufficient force / pressure to be applied to the positioning impression in the device from above, a form-fitting To achieve centering.

The Bipolar plate according to the invention contains like already set out at least two layers, but it may still be be more layers. This can be particularly advantageous when in Inside the bipolar plate, for example, coolant is guided. Especially with an unstructured liner as the third Location, it is advisable to integrate this in the bipolar plate that they left out in the area of the elevations / depressions of the outer layers so that the elevations / depressions of an outer layer through the recesses into the depressions / elevations of the each other external situation can intervene.

Besides is it just as possible the layers of the plate in pairs as before for two individual Layers described to each other to position. In the positioning impressions, which lead to positive locking in the x-y plane, more precisely the plane E1, is it is easily possible, but not necessarily, in the same place in all situations the corresponding one Provide survey / depression, while the positioning impressions, in the corresponding touch level E2, E3 or E4 do not lead to form fit, from adjacent layer pair to adjacent layer pair must be arranged offset. These Arrangement is for structured, d. H. z. B. embossed Liners preferred because the positioning impressions then with the other structure but it is also unstructured Liners can be used.

in the The invention will be explained with reference to several figures. Same Reference numerals refer to the same elements. Show it:

1a to 1d the exemplary construction of an electrochemical cell stack containing at least one bipolar plate,

2 a layer of a bipolar plate according to the invention,

3a to 3g Views, sections and further details of a first embodiment of a bipolar plate according to the invention,

4a to 4c a view and a section of a second embodiment of a bipolar plate according to the invention,

5a to 5h different top views on contact points,

6 a sectional view of another embodiment of a bipolar plate according to the invention,

7 a sectional view of the contact points of another embodiment of a three-layer bipolar plate according to the invention and

8th Details for the laser welding of the layers of a bipolar plate according to the invention.

1a and 1d show the structure of a fuel cell unit 7 , A variety of these fuel cell units 7 stratified forms the zwi end plates 70 and 71 arranged region of a fuel cell assembly 8th (please refer 1c ). 1b shows several superimposed fuel cell units 7 without the end plates. In 1a and 1d is a fuel cell unit in oblique view and top view from above 7 to see with their regular components which, for example, a polymer membrane 9 which has in the middle area 9a provided with a catalyst layer on both sides. In the fuel cell unit 7 are two bipolar plates 1 provided between which the coated polymer membrane is arranged. In the area between each bipolar plate 1 and the coated polymer membrane 9 is also a gas diffusion layer 10 arranged. The bipolar plates 1 on the one hand have a bead 4a on top of that the flowfield, ie the channel structure 4 , sealing surrounds. In addition, another bead is 4a indicated that a media line of repeat unit 7 ' to repeat unit 7 ' seals. In the following figures, the illustration of the sealing elements is omitted for reasons of clarity of the figures.

In the context of this application, the following terms are distinguished: Under the actual fuel cell, the ensemble of the first gas diffusion layer 10 , coated polymer membrane 9 and second gas diffusion layer 10 Understood. The fuel cell unit 7 includes an anode-side layer of a bipolar plate 1 , the just-defined fuel cell and the cathode-side layer of a second bipolar plate 1 , as well as possibly other layers of a bipolar plate 1 , This means that a bipolar plate 1 always between two fuel cell units 7 is shared. This is different from the repeat unit 7 ' containing a complete bipolar plate 1 and a fuel cell as defined above. In 1d is also indicated that the layers at least in the area of the beads 4a circumferentially welded together (welding lines 11 ). Here is the larger embossing depth of the dense beads 4a opposite the channel structures 4 clear. 1d also shows the different compartments of the channel structures 4 : Reactant channels 41 . 42 on the sides of the layers facing away from each other 2 . 3 and coolant channels 43 between the sections contacting layers 2 . 3 ,

The following is the structure of the bipolar plate 1 and their production methods are explained in greater detail by way of example.

2 shows a location 3 a bipolar plate according to the invention. In the example shown, this is a metal layer 3 with a continuous, straight channel structure 4 of a plurality of parallel channels, wherein the channel structure has an approximately five times greater extent in the x direction than in the y direction. Besides that is in the metal layer 3 a circular depression 3a and a slot-shaped depression 3b available. The round well 3a has a circular bore centrally. The slot-shaped depression 3b has a central opening in the form of a slot. The longitudinal direction 5 (ie a virtual straight line in the direction of the longest extent of the slot-shaped depression) is arranged parallel to the course (ie the fluid-guiding direction) of the channel structure 4 , This means that the channel structures of the fluid (either a cooling fluid inside the later bipolar plate or a medium on the outside of the later bipolar plate) lead in just this direction.

In the 2 shown location 3 is connected to at least one further layer so that a bipolar plate results. These two layers are connected by laser beam welding, wherein also in the "internal region" of the bipolar plate, that takes place between the channels, a welding, so as to prevent "swelling" of the plate with increased pressure of the cooling liquid inside the bipolar plate. In order to ensure a safe and accurate welding, it is advantageous that the longitudinal direction 5 is parallel to the channel structure.

3a shows a plan view of a joined bipolar plate 1 according to the invention. The bipolar plate consists of at least two layers 2 and 3 by means of a laser welding 11 respectively. 11 ' and 11 '' are joined. The laser welding 11 is guided along the continuous line. This means that the area around the channel structure (possibly interrupted by inlets and outlets) is welded accordingly. In addition, the areas of the elevations or depressions (depending on the viewing direction, see reference numerals 2a and 2 B ), interconnected, see dashed lines 11 ' , Next are the two layers of the bipolar plate 1 also in the area of the flowfield with section-wise line-shaped welds, whose position is the arrow 11 '' by way of example.

Shown here is an upper first layer 2 , including one location 3 only partially visible, in the area of holes. The bore diameter in the area of the elevations / depressions is at the lower position 3 smaller, so that an annular section is still visible (see 3a , top right). This makes it possible to check whether the correct layers have been put together, even by inspection or automated.

The following is to the surveys / depressions of the contact points 23a and 23b be particularly received, especially with reference to the sectional views BB (see 3b ) as well as CC and DD (see 3e and 3f ). The corresponding section-wise schematized top Views in the areas D1 and D2 result 3c u. 3g , Complementary will also on 3d received, the angular relationships of the surveys / wells according to 3b shows. Even under the upper layer lying elements, such as the oblong-shaped elevation / depression are here - although not actually visible from above - indicated by continuous lines. The same applies below for 4a ,

3a clarifies that at the contact point 23a in both positions 2 and 3 , circular elevations / depressions 2a and 3a are provided. The contact point 23a shows, however, a round survey / depression 2 B in a position 2 and a long hole-shaped elevation / depression 3b in a position 3 on. These interlocking elevations / depressions 2 B and 3b have two points of contact 30b and 31b on. Relative to the circular elevation 2 B the situation 2 extend the contact points 30b and 31b only over a very short part of the circumference, are only punctiform. The two points of contact 30b and 31b lie opposite each other on different sides of the circle. A virtual line through the centers of the respective points of contact, 32b and 33b shows the direction in which no movement is possible. This direction is perpendicular to the main direction of the channel structure 4 or the direction of the welds 11 '' , In the direction perpendicular to this virtual line, along the line 5b However, the two layers can move against each other and to a small extent, so that small tolerances or heat expansion or process-related relative movements along the channel structures of both layers can be compensated.

3b shows a bipolar plate according to 3a which in the recording 6c a fixing device 6 is inserted. The fixing device further comprises a centering pin 6a on as well as radii 6b , Shown is a detail view according to section BB, in which under a first layer 2 (on the anode side) a second layer 3 (on the cathode side) is inserted. Both layers are made of a thin metal sheet, in particular steel sheet. A first survey 2a the first layer is in a first recess 3a the second location 3 plugged in. The mentioned surveys / depressions 2a respectively. 3a are in the plane E1 parallel to the plane E (plate level or leaf level xy according to 2 ) arranged positively to each other, so that here in any surface direction, a translation is not possible.

As in 3b to see is both the first survey 2a as well as the first deepening 3a each with a circular opening 2ax respectively. 3ax Mistake. The circle diameter or the circular area of the opening 3ax the first well 3a is smaller than the diameter or the area of the opening 2ax the first survey 2a ,

These ratios are also due to the two orthogonal double arrows in the simplified representation of the area D1 without holes in 3c again clarified. There it is visible that in plane E or E1 no surface movement is possible. The first survey 2a as well as the first depression 3a are thus arranged self-centering to each other.

The fixing device itself has around the fixing bolt around the actual, here circular cylindrical, recording 6c on, which upwards by means of a radius 6b rounded transition to level E shows.

As in 3d in a detailed view corresponding to the area F1 of 3b to see more clearly, the cone angle α2 between the vertical (ie the direction of the main axis of the fixing bolt 6a ) and the outer surface of the survey 2a slightly smaller than the angle α3 between this vertical and the inner surface of the recess 3a , As a result, only a linear circumferential contact of the outer surface of the first survey 2a with the inner circumferential surface of the first recess 3a allows that leads to the positive connection in the plane E1.

It can also be seen that the height h2 of the first survey 2a is less than the height / depth h3 of the depression 3a , This means that no "touchdown" of the first layer 2 in the area around the centering bolt 6a around on the second layer 3 done and the two layers 2 and 3 in the connection area are in contact only at its circumferential contact line.

3e shows a section according to CC in the area around a second fixing bolt 6d the fixing device 6 , In addition is in 3f the section perpendicular to this DD shown. You can see a second survey 2 B the situation 2 , this is circular and has a circular centric opening 2bx on, concentric with the outer jacket of the second fixing bolt 6d in the recording 6f is arranged. This second survey 2 B is in a second recess 3b the underlying location 3 fitted. As in 3b Here is the cross section of the opening 3bx the second well 3b (At least in this cross-sectional view) slightly smaller than that of the corresponding opening of the second survey 2 B , However, the second recess is 3b elongated, so that the second survey 2 B in 3e is arranged from left to right partially displaceable, so there has no positive connection. In contrast to this, on average, DD 3f a touch of the two surveys / depressions 2 B . 3b to the touch point th 30b . 31b in the plane E2 instead. This is based on the in 3g shown simplified sketch of the area D2, in which was dispensed with the representation of the openings, again schematically illustrated. The vertical double-headed arrow indicates that a movement of the second survey 2 B within the second well 3b in y-direction is not possible. In contrast, the horizontal double arrow shows the possibility of movement for tolerance compensation in the x direction.

In order to clarify the scale of the invention, the extent of the elevation / depression in the x or y direction is 2 to 25 mm, preferably 4 to 15 mm. Next is the depth of the shot 6f around the fixing bolt 6d around 0.5 to 1 mm, the diameter of the recording 6f in the fixing device 6 is preferably between 1 and 10 mm. The clearance of the openings, so for example the openings 2bx or 3bx relative to the fixing bolt is usually 0.1 to 3 mm, preferably 0.1 to 1 mm.

3a to 3g thus show a bipolar plate 1 containing at least two layers 2 . 3 , where at least two layers 2 . 3 each contain at least a first and a second survey / depression, wherein the first survey / depression 2a the first location 2 and the first survey / depression 3a the second location 3 in the fully positioned state of the layers 2 . 3 interlock and touch each other in a positive fit in a plane E1, wherein the second survey / depression 2 B the first location 2 and the second survey / depression 3b the second location 3 in the fully positioned state of the layers 2 . 3 interlock and in a plane E2 only partially in at least two sections 30b . 31b touch, with the touch points 30b . 31b are arranged so that they are on both sides of a virtual line 5b , in the main direction of the survey / depression 3b the second location 3 runs, lie and in the plane E2 no positive connection between the surveys / wells 2 B and 3b entry.

The following is an alternative embodiment according to 4a to 4c a bipolar plate according to the invention shown. All the above statements also apply to this embodiment, as far as differences are not referred to below.

Shown here is in 4a in plan view, a bipolar plate 1' with a top position this time 3 ' , The leadership of the section EE is based on 4c in a plan view of a plate in which only the positioning stampings are shown, explained, the corresponding section EE is in 4b shown. Shown here is how the elevation 2a ' into the depression 3a ' intervenes, the survey 2 B' into the depression 3b ' as well as the survey 2c ' into the depression 3c ' , These are three contact points 23a ' . 23b ' and 23c ' each with survey / depression pairings according to 3e to 3g , This means that the elevations / depressions of a contact point, for example the contact point 23b ' in a plane E3, each in two sections touching, these touch points 30b ' and 31b ' on both sides of the virtual line 5b are opposite. The same applies to the contact point 23a ' in the plane E2 with the touch points 30a ' and 31a ' as well as the virtual line 5a or the contact point 23c ' in the plane E4 with the touch points 30c ' and 31c ' as well as the virtual line 5c , The virtual line 5a at the contact point 23a ' and the virtual line 5b at the contact point 23b ' In the example shown, they run essentially parallel and therefore allow this direction, namely parallel to the main direction of the channel structure 4 and thus also the welds 11 '' a slight compensation movement too. For this purpose runs vertically approximately in the middle between the two contact points 23a ' and 23b ' the virtual line 5c , This indicates the compensation direction at the contact point 23c ' at.

Shown is thus a bipolar plate 1' containing at least two layers 2 ' . 3 ' , where at least two layers 2 ' . 3 ' each contain at least a first, a second and a third survey / depression, wherein the first survey / depression 2a ' the first location 2 ' and the first survey / depression 3a ' the second location 3 ' , the second survey / depression 2 B' the first location 2 ' and the second survey / depression 3b ' the second location 3 ' as well as the third survey / depression 2c ' the first location 2 ' and the third survey / depression 3c ' the second location 3 ' in the fully positioned state of the layers 2 ' . 3 ' interlock and in the planes E2, E3 and E4 each only in sections in at least two sections 30a ' . 31a ' . 30b ' . 31b ' . 30c ' . 31c ' touch, with the touch points 30a ' . 31a ' . 30b ' . 31b ' . 30c ' . 31c ' are arranged so that they respectively on both sides of a virtual line 5a . 5b respectively. 5c , each in the main direction of the survey / depression 3a ' . 3b ' respectively. 3c ' extend, lie, wherein in the planes E2, E3 and E4 no positive connection between the elevations / wells 2a and 3a . 2 B and 3b such as 2c and 3b enters, with the virtual line 5a and the virtual line 5b at an angle of -10 ° to 10 ° to each other and the virtual line 5c at an angle of 80 ° to 100 ° to the virtual line 5a and 5b runs.

5 shows the design of interlocking surveys ( 2a . 3a . 2 B . 3b ) of the first and second layers ( 2 . 3 ). The examples of 5a to 5d show examples that lead to a positive fit between the elevations / depressions in their touch level, while the examples of the 5e to 5h cause no positive connection between the respective interlocking elevations / depressions. A representation of possible openings for fixing bolts or for the position control was omitted in favor of the illustrative clarity. 5a shows how two circular elevations / depressions ( 2a . 3a ) mesh. The circular elevations / depressions ( 2a . 3b ) are touching, as already in 3b and 3c shown, encircling.

5b represents a triangular elevation / depression 2a which is in a circular elevation / depression 3a engages and touches them with the three corners of the triangle. These three contact points are sufficient for it to be between the elevations / depressions 2a and 3a comes to a positive conclusion. A larger number of vertices of a polygon also leads to the form fit, as the example of 5c illustrated in which a square elevation / depression engages in a circular elevation / depression and contacted the latter in the plane of contact with its four corners. However, to avoid unnecessary tool wear, polygons with rounded corners are preferable.

5d indicates that the intervention of a long hole-shaped elevation / depression 2a in a circular elevation / depression 3a can lead to a positive fit with suitable dimensions. Conversely, the procedure leads to a circular elevation / depression 2 B in a long hole-shaped elevation / depression 3b Although to touch the interlocking elevations / depressions, but not to form fit, as from 5e follows and previously based 3e to 3g was demonstrated.

The engagement of a survey / depression in the form of an equilateral polygon, for example a square 2 B , in a slot-shaped elevation / depression 3b , leads - depending on the orientation of the polygon - to points of contact at the corners (shown) and / or the side edges (not shown) of the polygon with the oblong hole shape, but does not have a positive fit with the appropriate dimensions, such as 5f shows. Also two longhole-shaped elevations / depressions 2 B . 3b can interlock and touch each other at the appropriate width along the side edges. Here it depends on the choice of the length, whether it comes to a form fit or not. As long as in the 5g example shown, the outer dimension of the engaging survey / depression is less than the inner dimension of the survey / depression, is intervened, resulting in no positive connection.

5h shows in addition that the contact of the interlocking surveys / depressions 2 B . 3b does not have to be limited to two positions, one each on the two sides of the virtual line 5b but that a larger number of touch points, especially a different number on both sides of the virtual line 5b is possible to realize the non-positive engagement.

6 shows an embodiment of the bipolar plate according to the invention 1 , in which the positioning embossing is formed in both layers on both sides of the plate plane E. For example, in the upper layer 3 an increase 3a * formed with a height h3x, which - shown is the circular positioning stamping - has a diameter d3. Within this circular elevation 3a * is a likewise circular depression 3a + arranged having a height h3i, wherein h3i is greater than h3x, so that the recess 3a + is lowered towards the plate plane E down. The positioning of the position 2 is comparable configured, where there is the diameter of the increase 2a * , d2, is less than that of the increase 3a * , d3, so that the outer elevations 2a * . 3a * only provide for the optimization of the height conditions within the layers, for the actual positioning or the positive locking, but not contribute. 6 illustrates, moreover, that the total height of the positioning embossing in both layers, he, substantially the total height of the channel structure 4 , hf, corresponds, so that from the positioning embossing no impairment of the seal in the region of the outer edge of the relevant bipolar plate, not shown here.

Im in 7 illustrated embodiment, the bipolar plate 1 a total of three layers 2 . 100 and 3 on. The middle position 100 points in the area of contact points 23a and 23b each recesses whose extent is so large that the wells 3a respectively. 3b through them into the depressions 2a respectively. 2 B can intervene. The positioning of the two outer layers 2 . 3 Thus, as in the two-layered embodiments described above, the intermediate layer is interposed.

8th shows an example of a welding of a first layer 2 with a second location 3 by means of a laser beam 12 in the area of a channel structure 4 , The location 2 as well as the location 3 have channel structures, wherein in the area to be welded (ie the bottleneck in the middle in 8th ) flat portions are adjacent to each other in areas. As an example, this is the width of the flat portion of the first layer 2 with 200 microns and the width of the bearing surface of the situation 3 towards the 170 μm area. The width of a laser beam 12 is about 50 microns in this area. With the invention it is possible that the Auflageberei have an overlap region of at least 100 microns, so that even with slight inaccuracy of the leadership of the laser beam still a full-surface bond between the first layer 2 and second location 3 done in this area.

For this purpose, according to 3a to 3g the two layers 2 and 3 placed on each other by means of appropriate fixing bolts 6a respectively. 6d the fixing device 6 and laser welding performed in this position.

The above are merely exemplary. It is important that Combinations of all Embodiments shown here within the scope of the invention and also the objects of Under claims, if not excluded, can be combined as desired.

Claims (20)

Method for producing a bipolar plate ( 1 ) in at least two layers ( 2 . 3 ) at least a first and a second survey / depression ( 2a . 2 B . 3a . 3b ), and the layers ( 2 . 3 ) are positioned on each other, characterized in that the first survey / depression ( 2a ) of the first layer ( 2 ) and the first survey / depression ( 3a ) of the second layer ( 3 ) in the fully positioned state of the layers ( 2 . 3 ) engage each other and touch each other in a form-fitting E1 plane and that the second survey / depression ( 2 B ) of the first layer ( 2 ) and the second survey / depression ( 3b ) of the second layer ( 3 ) in the fully positioned state of the layers ( 2 . 3 ) intermesh and in a plane E2 only on average in at least two sections ( 30b . 31b ), the points of contact ( 30b . 31b ) are arranged so that they are on both sides of a virtual line 5b , in the main direction of the survey / depression 3b the second layer ( 3 ), lie and in the plane E2 no positive connection between the elevations / depressions 2 B and 3b occurs and where these layers ( 2 . 3 ) are joined together by means of cohesive methods and wherein the elevations / depressions of at least one layer in complementary elevations / depressions ( 6c . 6f ) a fixing device ( 6 ) are held. Method for producing a bipolar plate ( 1 ) in at least two layers ( 2 ' . 3 ' ) at least a first, a second and a third survey / depression ( 2a ' . 2 B' . 2c ' . 3a ' . 3b ' . 3c ' ), and the layers ( 2 ' . 3 ' ) are positioned on each other, characterized in that the first survey / depression ( 2a ' ) of the first layer ( 2 ' ) and the first survey / depression ( 3a ' ) of the second layer ( 3 ' ), the second survey / depression ( 2 B' ) of the first layer ( 2 ' ) and the second survey / depression ( 3b ' ) the second layer ( 3 ' ) and the third survey / immersion ( 2c ' ) of the first layer ( 2 ' ) and the third survey / depression ( 3c ' ) of the second layer ( 3 ' ) in the fully positioned state of the layers ( 2 ' . 3 ' ) and only in sections in at least two sections in a plane E2, E3 or E4 ( 30b . 31b ), the points of contact ( 30b . 31b ) are arranged so that they respectively on both sides of a virtual line 5a . 5b respectively. 5c , each in the main direction of the survey / depression 3a ' . 3b ' respectively. 3c ' the second layer ( 3 ) lie, wherein in the planes E2, E3 and E4 no positive connection between the elevations / wells 2a and 3a . 2 B and 3b such as 2c and 3b enters, with the straight line 5a and the straight line 5b at an angle of -10 ° to 10 ° to each other and the straight line 5c at an angle of 80 ° to 100 ° to the straight line 5a and 5b runs, whereby these layers ( 2 . 3 ) are joined together by means of cohesive methods and wherein the elevations / depressions of at least one layer in complementary elevations / depressions ( 6f ) a fixing device ( 6 ) are held. Method according to claim 1 or 2, characterized in that in at least two layers ( 2 . 3 . 2 ' . 3 ' ) in the same process step with the surveys / depressions ( 2a . 2a ' . 2 B . 2 B' . 2c ' . 3a . 3a ' . 3b . 3b ' . 3c ' ) a channel structure ( 4 ) is formed. Method according to one of claims 1 to 3, characterized in that at least one survey / depression ( 2a . 2a ' . 2 B . 2 B' . 2c ' . 3a . 3a ' . 3b . 3b ' . 3c ' ) a passage opening ( 2ax . 2ax ' . 2bx . 2bx ' . 2cx ' . 3ax . 3ax ' . 3bx . 3bx ' . 3cx ' ), by which a centering bolt ( 6a . 6d ) of the fixing device ( 6 ). Method according to one of claims 1 to 4, characterized in that the layers ( 2 . 3 ) are metallic and preferably made of steel. Method according to one of claims 1 to 5, characterized that the cohesive process Gluing or welding, preferably laser beam welding, is. Method according to one of claims 1 to 6, characterized in that the elevations / depressions ( 2a . 2a ' . 2 B . 2 B' . 2c ' . 3a . 3a ' . 3b . 3b ' . 3c ' ) and / or the channel structures ( 4 ) by means of hollow embossing, deep drawing, hydroforming, adiabatic forming or roll embossing. Bipolar plate ( 1 ) containing at least two layers ( 2 . 3 ), whereby at least two layers ( 2 . 3 ) contain at least a first and a second survey / well, the first survey / well ( 2a ) of the first layer ( 2 ) and the first survey / depression ( 3a ) of the second layer ( 3 ) in the completely positioned condition of the layers ( 2 . 3 ) engage each other and touch each other in a form-fitting manner in a plane E1, wherein the second survey / depression ( 2 B ) of the first layer ( 2 ) and the second survey / depression ( 3b ) the second layer ( 3 ) in the fully positioned state of the layers ( 2 . 3 ) and in a plane E2 only in sections in at least two sections ( 30b . 31b ), the points of contact ( 30b . 31b ) are arranged so that they are on both sides of a virtual line 5b , in the main direction of the survey / depression 3b the second layer ( 3 ), lie and in the plane E2 no positive connection between the elevations / depressions 2 B and 3b entry. Bipolar plate ( 1 ) containing at least two layers ( 2 ' . 3 ' ), whereby at least two layers ( 2 ' . 3 ' ) contain at least a first, a second and a third survey / well, the first survey / well ( 2a ' ) of the first layer ( 2 ' ) and the first survey / depression ( 3a ' ) of the second layer ( 3 ' ), the second survey / depression ( 2 B' ) of the first layer ( 2 ' ) and the second survey / depression ( 3b ' ) the second layer ( 3 ' ) and the third survey / immersion ( 2c ' ) of the first layer ( 2 ' ) and the third survey / depression ( 3c ' ) of the second layer ( 3 ' ) in the fully positioned state of the layers ( 2 ' . 3 ' ) and in the planes E2, E3 and E4 only in sections in at least two sections ( 30a ' . 31a ' . 30b ' . 31b ' . 30c ' . 31c ' ), the points of contact ( 30a ' . 31a ' . 30b ' . 31b ' . 30c ' . 31c ' ) are arranged so that they respectively on both sides of a virtual line 5a . 5b respectively. 5c , each in the main direction of the survey / depression 3a ' . 3b ' respectively. 3c ' the second layer ( 3 ) lie, wherein in the planes E2, E3 and E4 no positive connection between the elevations / wells 2a and 3a . 2 B and 3b such as 2c and 3b enters, with the straight line 5a and the straight line 5b at an angle of -10 ° to 10 ° to each other and the straight line 5c at an angle of 80 ° to 100 ° to the straight line 5a and 5b runs. Bipolar plate according to claim 8 or 9, characterized in that the elevations / depressions ( 2a . 2 B ) of the first plate ( 2 ) to the surveys / recesses ( 3a . 3b ) of the second plate ( 3 ) are executed self-centering. Bipolar plate according to claim 8, 9 or 10, characterized in that the first and / or second elevation / depression of the first ( 2 ) and / or second layer ( 3 ) is punched. Bipolar plate according to claim 11, characterized in that the elevation / depression ( 2a . 2 B . 3a . 3b ) is centrally punched. Bipolar plate according to one of claims 8 to 12, characterized in that the first elevations / depressions ( 2a . 3a ) the first ( 2 ) and second layer ( 3 ) are each circular or executed as a rounded polygon. Bipolar plate according to one of claims 8 and 10 to 13, characterized in that the second projection / depression ( 2 B ) of the first layer ( 2 ) is circular or rounded-polygonal and the second survey / depression ( 3b ) of the second layer ( 3 ) is a slot-shaped elevation / depression. Bipolar plate according to one of claims 8 to 14, characterized in that at least one of the layers ( 2 . 3 ) a channel structure ( 4 ) and the longitudinal direction ( 5 ) of the second survey / recess ( 3b ) of the second layer ( 3 ) parallel to the main direction of the channel structure ( 4 ) is arranged. Bipolar plate according to one of claims 8 to 15, characterized in that the channel structure ( 4 ) of the layers ( 2 . 3 ) at least one cavity between the layers ( 2 . 3 ) forms, in particular for guiding a cooling liquid. Bipolar plate according to one of claims 8 to 16, characterized in that the elevations / depressions ( 2a . 3a ) are conical. Bipolar plate according to claim 17, characterized in that the elevations / depressions of the first layer ( 2 ) have a larger or smaller cone angle (α2) than the cone angle (α3) of the complementary elevations / depressions of the second layer ( 3 ). Bipolar plate according to one of claims 8 to 18, characterized in that the elevations / depressions ( 2a or 3a ) one position ( 2 or 3 ) are less deep than the surveys / depressions ( 3a or 2a ) the other situation ( 3 or 2 ). Bipolar plate according to one of claims 8 to 19, characterized in that the elevations / depressions ( 2a . 2 B . 2a ' . 2 B' . 2c ' . 3a . 3b . 3a ' . 3b ' . 3c ' ) is formed in each case from a first elevation / depression in one direction and a second depression / elevation arranged within this deformed region in the opposite direction perpendicular to the plate plane E, wherein the second depression / elevation has a greater depth than the first elevation / Deepening.

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