WO2021008956A1

WO2021008956A1 - Method for producing a distributor structure

Info

Publication number: WO2021008956A1
Application number: PCT/EP2020/069205
Authority: WO
Inventors: Franz Wetzl; Volker Henrichs; Friedrich Kneule; Arne Stephen FISCHER; Andreas Burghardt
Original assignee: Robert Bosch Gmbh
Priority date: 2019-07-18
Filing date: 2020-07-08
Publication date: 2021-01-21
Also published as: DE102019210633A1

Abstract

The invention relates to a method for producing a distributor structure (10), in particular a bipolar plate for a fuel cell, comprising the following method steps: a) arranging, positioning and fixing at least one anode structure (16) and at least one cathode structure (20) in a stacked arrangement (52), and b) establishing contact between the components according to step a) in one step.

Description

Method for manufacturing a manifold structure

Technical area

The invention relates to a method for producing a

Distribution structure, in particular a bipolar plate for a fuel cell, made up of several components arranged in a stack.

State of the art

Fuel cells are electrochemical energy converters in which hydrogen (H2) and oxygen (O2) are converted into water (H2O), electrical energy and heat. The unit of H2, air and coolant distributor with a separator plate in between is called a bipolar plate. A stack of several bipolar plates with proton-conducting membranes and other layers such as electrode and catalyst layers in between forms a stack. The reaction gases H2 and O2 in the air and the cooling liquid flow parallel to the membrane, while the electrical current flows perpendicular to the membrane from the anode to the cathode of the neighboring cell through the bipolar plate. The ohmic losses occurring within the

Bipolar plates are made by the electrical resistance of the material, which is carbon or metal, as well as by the contact resistances at the interfaces between the gas-carrying structures and the

Caused separator plate. To the electrical power in the external

To maximize the circuit, the ohmic resistance losses within the fuel cell are to be minimized. This can be done, for example, in that contact surfaces are coated in order to, in the case of the superimposed, in

Stacked components to reduce the contact resistance.

US Pat. No. 7,770,394 B2 relates to fuel cells bonded directly or provided with a continuous metallic bond.

US 7,323,040 B2 relates to a special embodiment of a

Fuel cell module as well as certain integral joining processes such as electron beam welding, laser welding and ultrasonic welding and the like. Presentation of the invention

According to the invention, a method is proposed for producing a distributor structure, in particular a bipolar plate for a fuel cell, the following method steps being carried out according to the method: a) arranging, positioning and fixing at least one anode structure and at least one cathode structure in a stacked arrangement and b) creating a first cohesive one Connection to electrical

Contacting between the components according to process step a) in one operation.

The solution proposed according to the invention provides a method which produces an electrical connection between the metallic cathode structure, separator and anode structure, with a very low electrical resistance being established. Furthermore, such electrical contact can be made in a very short cycle time, so that it can be used in series production.

In a further development of the method proposed according to the invention, the first material connection can be produced by means of roller seam welding or spot welding.

In a further development of the solution proposed according to the invention, a second material connection between the components according to FIG

Process step a) at at least one sealing location by way of

Laser welding can be generated as a seal between the anode structure and the separator.

In the first variant of the method proposed according to the invention, roller seam welding to form the first material connection, a first roller on an upper side and a counterholder, for example a second roller or a welding table or plate, on a lower side of the stacked arrangement, is used to produce a

close-fitting seam in line shape. The counterholder not only functions as an electrode, but also serves, for example, as a plate, for better Contact pressure distribution and for better distribution of the electrical flow. The roller seam welding can be carried out using a sacrificial wire.

In the method proposed according to the invention, several first cohesive connections in line form can be carried out simultaneously by way of the

Roller seam welding can be generated or there can be several first

Cohesive connections are produced as cohesive point connections at the same time by means of spot welding. Simultaneous formation of several first material connections, d. H. electrical contact accelerates the cycle time.

In roller seam welding, which can be used to create the first material connection as electrical contact, a first roller runs on the top of the stacked arrangement in embossed channels of the anode structure, with a channel width of the embossed channels

Roll width exceeds the first roll. This allows the

Forces acting on components are minimized. Furthermore, a trouble-free process flow can be achieved.

Opposite the first roller on the upper side, a counter holder is provided on the underside, with a width that supports the cathode structure along at least one channel width of the embossed channels in the anode structure. A deformation of the cathode structure can thereby be effectively avoided, so that the electrical resistance is not adversely affected.

In the method proposed according to the invention, the distributor structure is formed from the anode structure, separator and cathode structure, the

Cathode structure can have a porosity> 80% and during the production of the first material connection, the electrical energy is concentrated below the first role, since there is a local welding of

Anode structure, separator and cathode structure results, with the cathode structure in particular remaining in the undeformed state.

In the method proposed according to the invention, either the stacked arrangement of anode structure, separator and cathode structure can be moved relative to the rollers serving as electrodes, or it can alternatively, the rollers serving as electrodes are moved relative to a stationary stacked arrangement, so that both kinematic variants would be possible in the method proposed according to the invention.

There is the possibility of producing the first material connection for electrical contacting and the second material connection for sealing either at the same time or one after the other. Simultaneous generation of the first material connection and the second

A material connection would lead to a shorter cycle time and thus to a higher throughput in series production.

When making the second integral connection by means of laser welding, the first integral connections that have already been made - designed as longitudinal seams between the components of the stacked arrangement - can hold the anode structure, the separator and the cathode structure in position for electrical contacting. A separate clamping device can therefore be omitted when carrying out the method proposed according to the invention.

In the solution proposed according to the invention, the according to

Process step a) set anode structure on embossed channels. The channels in which the first material connection is produced are provided with either curved channel walls and / or widened attachment areas. The method proposed according to the invention can also be used in designs without foamed cathode structures; structures made only from sheet metal could also be joined to one another.

In addition, the invention relates to the use of the method according to one of the claims for making electrical contact and for sealing the anode structure, separator and cathode structure of a distributor structure, in particular a bipolar plate for fuel cell stacks.

Advantages of the invention

The method proposed according to the invention makes it possible to use the components of a distributor structure, in particular a bipolar plate, namely a cathode structure, a separator and an anode structure one operation of resistance welding, in particular over

To join seam welding or spot welding with one another. The number of welds produced respectively

Welding points are variable and can be adapted to the design of the distribution structure, a bipolar plate. Furthermore, with the method proposed according to the invention there is the possibility of producing a plurality of weld seams or weld points in parallel in order to achieve a short cycle time, in particular in series production. Also one

The cooling channels can optionally be sealed in

Realize roller seam welding processes.

In roller seam welding, the stacked arrangement is arranged, for example, between an upper and a lower roller, the upper roller running in embossed channels of the anode structure. It is possible to reduce the wear and tear on the first roller on top by using a sacrificial wire. The lower of the two rollers is at

Roller seam welding is designed to be wider than the upper one and, in particular, is wide enough that deformation of the cathode structure is excluded. Due to the cathode structure, in particular with a porosity of> 80%, the electrical energy is concentrated below the upper roller, whereby a local welding of all three components, namely the anode structure, the separator and the cathode structure, is carried out. The total electrical resistance of a structure, especially a bipolar plate, increases with the number of welds. A distance from weld seam to weld seam of approx. 10 mm is sufficient for the electrical

Efficiency.

If, during the electrical contact via the first material connection, material connections for sealing the cooling water channels are simultaneously produced, these roles are parallel to the

Establishing the electrical contact, further rollers are provided on the outer sides of the distributor structure in order to press the anode structure and the separator against one another along their length.

The sealing welds also help improve the electrical connection. The material-locking seams described for the electrical contact or for sealing can be produced at the same time or can be produced one after the other. For example, first the material connection for sealing and then the electrical contacting of the cathode structure with the anode structure and the separator.

As with the kinematic reversal, it is possible to use the cohesive

Connections with resting electrodes, d. H. To undertake rollers and a moving stacked arrangement or alternatively also the rollers serving as electrodes relative to the round workpiece, d. H. to move the stacked arrangement.

A particular advantage of the solution proposed according to the invention lies in the fact that the second material connections that the

Seals are advantageously produced in the laser welding process, the first material connections, which were previously executed, for example, as roller weld seams or as weld points

Components of the stacked arrangement; H. hold the cathode structure, separator and anode structure in place. Thermal distortion is thus prevented or at least reduced and a welding device is superfluous.

Spot welding can also be used instead of roll seam welding. Analogous to the cohesive connections according to

When creating spot welded joints, roller seam welding decreases the electrical resistance as the distance between the weld spots decreases. Even with spot welding, the upper electrode can be kept small in order to be immersed in the channels of the anode structure, whereby the electrode lying below can be designed in such a way as to avoid deformation of the cathode structure.

With regard to procedural advantages in roll seam and

It should be pointed out to spot welding processes that the anode structure can be adapted in such a way that the positioning of the rollers serving as electrodes can be facilitated. For example, the channels can be made wider; in spot welding, the channels can be curved, for example, and attachment areas can be created that have a

Cause process facilitation. The processes require less complex equipment than laser welding, for example. By pressing the partners to be joined together, there are lower demands on the tolerances in terms of shape and position. In the case of spot welding, the upper spot electrodes can be designed to be adjustable, if necessary also automatically adjustable. This enables easy adaptation to customer variants.

The force to be applied in the resistance welding process enables tolerance compensation, which is a great advantage over the use of the laser process. Furthermore, roller seam welding can be integrated into a transport direction without an additional cycle

or process time arises.

Brief description of the drawings

Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

Show it:

Figure 1 is a schematic representation of the roller seam welding of

Distribution structure,

FIG. 2 top views of anode structures with exemplary locally modified channel structures to simplify the joining process,

FIG. 3 a schematic representation of the material connections of the distributor structure,

FIG. 4 shows a schematic representation of roller seam welding with sacrificial wire and

Figure 5 cooling media channels with curved channel walls and widened attachment areas.

Embodiments of the invention In the following description of the embodiments of the invention, the same or similar elements are denoted by the same reference numerals, a repeated description of these elements being dispensed with in individual cases. The figures represent the subject matter of the invention only schematically.

The illustration according to FIG. 1 is a schematic illustration of the

To see roller seam welding of a manifold structure 10.

The distributor structure 10 shown schematically in FIG. 1 is, for example, a bipolar plate which is assembled from the following components by means of material-locking joining processes:

In a stacked arrangement 52, an anode structure 16, possibly a separator 18 and a cathode structure 20 are arranged and positioned relative to one another. The anode structure 16 is, for example, an embossed sheet metal into which individual, open embossed channels 26 are let and coolant channels 22 running between these are implemented. The separator 18 can, for example, be an essentially flat sheet metal or a plastic component. The cathode structure 20 arranged at the bottom in the stacked arrangement 52 is, for example, a cathode foam layer, the porosity of which is> 80%. As an alternative to the foam layer, an expanded metal mesh or a

Wire mesh can be used.

In the illustration according to FIG. 1 it is shown that a first roller 30 dips into an embossed channel 26 running in the anode structure 16.

Opposite is located on the underside 14 of the stacked arrangement 52 according to the view in Figure 1, a counter holder 34, for example designed as a second roller. In this case, the roller 30 and the counterholder 34 serve as electrodes during roller seam welding. As can be seen from FIG. 1, a roll width 32 of the first roll 30 is smaller than the channel width 28 of the embossed channels 26.

In contrast to the first roller 30, the counter holder 34 is designed with a width 36 that corresponds to the channel width 28 of the embossed channels 26 in the

Anode structure 16 exceeds. The counter holder 34 is on the underside 14 of the stacked arrangement 52, the cathode structure 20 is supported over a larger area and in particular during the formation of the

cohesive first and second connection 62, 64 between the two elements serving as electrodes, the first roller 30 and the counter holder 34, supported over a relatively large width, so that the cathode structure 20 of the stacked arrangement 52 remains undeformed. Compared to the thickness of a separator 18 that may be used, the cathode structure 20 has a relatively large layer thickness 40.

The first roller 30 and a counter-holder 34 designed as a second roller, which serve as electrodes, rotate around those indicated schematically in FIG

Axes of rotation 38.

The two elements 30, 34 produce a first material connection 62 (cf. illustration according to FIG. 3) running perpendicular to the plane of the drawing in the area of the embossed channel 26 during roller seam welding. This serves the electrical contacting of the stacked arrangement 52 of anode structure 16, separator 18 and cathode structure 20. To limit the wear of the first roller 30, it can be operated with a sacrificial wire 70, which during the formation of the first material connection 62 the material for this forms. Due to the cathode structure 20 on the underside 14 of the stacked arrangement 52 according to FIG. 1 with a porosity> 80%, the electrical energy is concentrated below the first roller 30, which leads to a local welding of all three components, namely the

Anode structure 16, the separator 18 and the cathode structure 20 comes. In an advantageous manner, the section between individual first cohesive connections 62 running next to one another (cf. illustration according to FIG. 3) is of the order of magnitude of 10 mm. This distance can vary, depending on the design of the distributor structure 10, which can in particular be a bipolar plate.

It should be noted that according to the schematic representation of the

Roller seam welding in Figure 1 an electrical contact between the cathode structure 20, the separator 18 and the anode structure 16 can be made with a very low electrical resistance in a very short cycle time, so that an application in series production is possible. It should be emphasized that the electrical contact in the context of the first material connection Connection 62, for example, as a longitudinal seam of the anode structure 16, des

Separator 18 and the cathode structure 20 takes place in a single work step. Due to the selected geometry of the elements 30, 34 serving as electrodes, it is ensured that the stainless steel foam, which is part of the cathode structure 20, is only slightly deformed by the integral joining process and essentially retains its original shape, so that a later impairment of a cell function of is excluded from the outset.

In the method proposed according to the invention, the number of first cohesive connections 62 or cohesive point connections 50 (cf. illustration according to FIG. 2) can be kept variable and adapted to the design of the distributor structure 10. There is the

Possibility of making a plurality of first cohesive connections at the same time in parallel as electrical contacting, or to design these as discrete cohesive point connections 50 within the scope of the spot welding process. If the first cohesive connection 62 - be it produced as a longitudinal seam by roller seam welding, be it discrete cohesive point connections 50 - is manufactured in parallel by means of spot welding, short, short cycle times suitable for series production can advantageously be achieved.

In a modification of the roll seam welding shown in FIG. 1 to produce the electrical contact between anode structure 16, separator 18 and cathode structure 20, seals can be implemented at sealing locations 24, even if not shown in the drawing. These can, for example, laterally seal the cooling medium channels 22 which are formed in the embossed anode structure 16. In addition to the electrical contacting, at the same time for partial or complete sealing of the cooling media channels 22 between the separator 18 and the anode structure 16 in a parallel arrangement to the illustrated elements, the first roller 30 and the counter holder 34, further roles can be provided in addition to the electrical contacting be arranged on the outer sides of the distributor structure 10 evenly at the sealing locations 24 in order to seal the anode structure 16 on the one hand and the separator 18 on the other hand against one another along the longitudinal side. Depending on the design of the distributor structure 10, which is preferably a bipolar plate, the second material connections 64, see illustration according to FIG Figure 3, which are used for sealing, also only between separator 18 and

Anode structure 16 can be manufactured without including the cathode structure 20.

The second material connections 64, see illustration according to FIG. 3, also contribute to improving the electrical connection.

The formation of the aforementioned first material connection 62, which is used for electrical contacting, and the second material connection 64, which is used for sealing, can either be carried out at the same time or also in chronological order, ie. H. can be done sequentially.

Furthermore, there is the possibility of making the first and second material connections 62, 64 when the electrodes are stationary, for example in the case of the first roller 30 and the counter holder 34 and moving workpiece, in this case the stacked arrangement 52, or alternatively, also the elements serving as electrodes, the first roller 30 and the counter holder 34, relative to the stationary workpiece, d. H. of the stacked assembly 52 to move. Both movement alternatives would be possible.

FIG. 2 shows views of the anode structure 16, viewed from the top 12 with examples of locally modified channel structures 42. As can be seen from the representations according to FIG. 2, the anode structure 16 can be designed with a number of embossed channels 26 in a first channel width 44. Individual embossed channels 26 run between these, a second

Have channel width 46 which exceeds the first channel width 44. The coined channels 26 formed in the second channel width 46 serve as

Running track for the stacked at the top 12 according to FIG

Arrangement 52 arranged first roller 30 serving as an electrode.

Alternatively, there is the possibility of designing the anode structure 16 in such a way that it is initially provided with embossed channels 26, the channel width 28 corresponding to the first channel width 44. Locally modified channel structures 42 can be formed in individual embossed channels 26 in such a way that they have small diamond-shaped flat areas 48 in which later - as an alternative to roller seam welding - individual discrete cohesive point connections 50 can be made by means of spot welding. With regard to the first material connection, see illustration according to FIG. 3, Both roll seam welding and spot welding are thus available as manufacturing options.

FIG. 3 shows a schematic representation of material connections 62, 64 on the distributor structure 10.

From the top view according to FIG. 3 of an anode structure 16 selected here by way of example, it can be seen that the anode structure 16 on the one hand comprises an active region 60 through which embossed channels 26 pass. A first inlet / outlet area 66 or a second inlet / outlet area 68 adjoins the active area 60. The individual geometries of the inlet and outlet areas 66, 68 are no longer shown in FIG.

The illustration according to FIG. 3 shows that first material connections 62 run as longitudinal seams in individual ones of the embossed channels 26 of the anode structure 16. They extend essentially in the vertical direction of the anode structure 16, while the second material connections 64, which essentially serve for sealing, run transversely thereto in the horizontal direction. The first material connections 62 designed as longitudinal weld seams are produced by roller seam welding and are used for electrical contact within the active area 60 on the one hand and for sealing the cooling media channels 22 on the outside of the anode structure 16, as indicated in Figure 1 by the sealing location 24. In contrast, the second material connections 64, which are designed as transverse weld seams, and in an alternative, serve

Welding processes for example the laser welding process are produced, the seal. Alternatively, the seal can also through

Seam welding are generated.

If the second material connections 64 are preferred as

Cross welds carried out, so can previously by way of

First material connections 62 produced by roller seam welding hold the components anode structure 16, separator 18 and cathode structure 20 in position and prevent thermal distortion. As a result, a welding device to be kept separately is not required. As already mentioned, this can also be used as an alternative to seam welding

Spot welding can be used. Analogous to the number of the first

Material connections 62, which are produced by means of roller seam welding, during spot welding the electrical resistance decreases as the distance between the individual discrete material connection 50 from one another decreases. Even with spot welding, the electrode present on the upper side 12 should be small enough to dip into the embossed channels 26 of the anode structure 16, whereas the electrode located below should have a size such that a deformation of the cathode structure 20 on the lower side 14 of the stacked arrangement 52 according to the figure 1 is avoided.

Advantageously, both in roller seam welding and in spot welding, the seam structure, d. H. the embossed channels 26 in the

Anode structure 16 can be adapted to such an extent that attachment of the electrodes, for example the first roller 30 and the counter holder 34, can be simplified. For example, each of the embossed channels 26, which is to be welded by roll seam, can be made with a somewhat larger width - for example the second channel width 46 - in order to enlarge a contact surface for the first roller 30 serving as an electrode. The broadening of

Attachment areas 74 for the electrode, d. H. the first roller 30, allows the use of larger electrodes, whereby the wear of the electrodes can be reduced.

The illustration according to FIG. 4 shows that a sacrificial wire 70 is located below the first roller 30. This lies in one of the embossed channels 26 of the anode structure 16. If the cohesive joining of the

Anode structure 16 with the cathode structure 20 with the interposition of the separator 18, the sacrificial wire 70 is melted in the area of the sacrificial wire 70 as soon as the first roller 30 and the counter holder 34 are placed against one another and the first material connection 62 is produced as a longitudinal seam. Analogously to the illustration according to FIG. 1, the cathode structure 20 is supported by the counter holder 34. The counterholder 34 has the width 36 which exceeds the roll width 32 of the first roll 30, so that the cathode structure 20 is supported as a longitudinal seam in the area where the material connection 62 is produced. The illustration according to FIG. 5 shows that there in the

Anode structure 16, the embossed channels 26 are each arranged, preferably embossed, in a widened attachment region 74 with respect to one another. In contrast to the design variants according to FIGS. 1 and 4, the embossed channels 26 in the design variant according to FIG. 5 are not limited by straight channel walls, but these are kept much more curved, see item 72. The curved channel walls 72 shown in FIG have a convex or concave curvature to allow insertion

or to facilitate the entry of the first roller 30, which is required for roller seam welding, into the respective embossed channel 26, in that the material connection 62 is to be produced as a longitudinal seam.

FIG. 5 essentially corresponds to the illustration according to FIG. 1, with the differences that in the embodiment variant according to FIG. 5 the anode structure 16 is widened between the individual cooling medium channels 22

Attachment areas 74 are indicated and the anode structure 16 is designed in such a way that the boundary walls of the embossed channels 26 are curved

Channel walls 72 are executed. In the embodiment variant according to FIG. 5, too, the cathode structure 20 is supported via the counter holder 34, the width 36 of which exceeds the roll width 32 of the first roll 30.

The invention is not restricted to the exemplary embodiments described here and the aspects emphasized therein. Rather, within the range specified by the claims, a large number of modifications are possible that are within the scope of expert knowledge.

Claims

Expectations

1. A method for producing a distributor structure (10), in particular a bipolar plate for a fuel cell with the following

Process steps: a) Arranging, positioning and fixing at least one

Anode structure (16) and at least one cathode structure (20) in a stacked arrangement (52), b) production of a first material connection (62) for electrical contacting between the components according to method step a) in one operation.

2. The method according to claim 1, characterized in that the first material connection (62) is produced by roll seam welding or by spot welding.

3. The method according to claim 1, characterized in that at least one separator (18) is provided in the stacked arrangement (52) according to method step a).

4. The method according to claim 1, characterized in that a

second material connection (64) between the components according to method step a) at a sealing location (24) by means of laser welding as a seal between the anode structure (16) and the separator (18).

5. The method according to claim 2, characterized in that the

Roller seam welding between a first roller (30) on an upper side (12) and a counter holder (34) - designed as a roller, as a plate or as a table - is carried out on an underside (14) of a stacked arrangement (52).

6. The method according to claim 2, characterized in that the

Roller seam welding is performed using a sacrificial wire (70).

7. The method according to claim 2, characterized in that a plurality of first cohesive connections (62) are produced in line form simultaneously by means of roller seam welding, or a plurality of first cohesive connections (62) as cohesive ones

Point connections (50) are produced simultaneously by way of spot welding.

8. The method according to claim 5, characterized in that the first roller (30) runs in embossed channels (26), the channel width (28) of which exceeds a roller width (32) of the first roller (30).

9. The method according to claim 5, characterized in that the

Counterholder (34) has a width (36) which supports the cathode structure (20) over at least one channel width (28) of the embossed channels (26) in the anode structure (16).

10. The method according to claim 2, characterized in that the first cathode structure (20) has a porosity> 80% and during the production of the first material connection (62) electrical energy is concentrated below the first roller (30) and a local weld of Anode structure (16), separator (18) and

Cathode structure (20) produced in the undeformed state.

11. The method according to claim 1, characterized in that the

stacked arrangement (52) of anode structure (16), separator (18) and cathode structure (20) is moved relative to the elements (30, 34) serving as electrodes, or these are moved relative to a stationary stacked arrangement (52).

12. The method according to claim 1 or claim 7, characterized

characterized in that the first material connection (62) for electrical contacting and the second material connection (64) for sealing are produced simultaneously or one after the other.

13. The method according to claim 4, characterized in that during the production of the second material connection (64) by means of laser welding, the first material connection already produced

Connections (62) for making electrical contact hold the anode structure (16), the separator (18) and the cathode structure (20) in position.

14. The method according to claim 1, characterized in that the

anode structure (16) used according to method step a) has embossed channels (26) and the embossed channels (26), in which the first material connection (62) is produced, a second channel width (46) and / or curved channel walls (72) and / or widened

Have attachment areas (74).

15. Use of the method according to one of the preceding claims for electrical contacting and sealing of the anode structure (16), separator (18) and cathode structure (20) of a distributor structure (10), in particular a bipolar plate, of a fuel cell stack.