WO2016005176A1

WO2016005176A1 - Bipolar plate with a sealing element arranged in a bead, and method for producing a bipolar plate

Info

Publication number: WO2016005176A1
Application number: PCT/EP2015/063976
Authority: WO
Inventors: Friedhelm Walkling; Martin Buchenberger
Original assignee: Volkswagen Ag
Priority date: 2014-07-08
Filing date: 2015-06-22
Publication date: 2016-01-14
Also published as: DE102014213192A1

Abstract

The invention relates to a bipolar plate (20) for a fuel cell and to a method for producing a bipolar plate. The bipolar plate comprises a base (1) which has a temperature control side (2) and an operating medium side (3) opposite the temperature control side (2), and the bipolar plate also comprises a flow field (4) for distributing an operating medium for the fuel cell and a bead (6) which surrounds the flow field (4) and which opens away from the operating medium side (3) and forms a seal elevation (5) on the operating medium side (3). In order to allow an efficient cooling of the fuel cell, at least one sealing element (11) is arranged in a bead (6, 6') of the base (1).

Description

description

Bipolar plate with arranged in bead sealing element and

Method for producing a bipolar plate

The invention relates to a bipolar plate for a fuel cell, comprising a base plate, which has a tempering side and an operating medium side opposite the tempering side, and a flow field for distributing an operating medium for the fuel cell, and a bead at least partially encircling the flow field, which opens away from the operating medium side and forms a density elevation on the operating medium side. Furthermore, the invention relates to a method for producing a bipolar plate for a fuel cell, in which a base plate of the bipolar plate is formed with a flow field and a flow field at least partially circumferential bead.

The density raised bump allows easy and efficient sealing of a flow volume between the operating media side of the base plate and a membrane electrode assembly adjacent to the base plate so that operating media can be safely routed to the membrane electrode assembly along the operating media side. In this case, the density elevation may rest against the membrane-electrode arrangement and, in particular, be pressed against it, for example when the bipolar plate and the membrane-electrode arrangement are pressed together in a fuel cell stack.

However, along the bead opening to the tempering side, a tempering fluid flowing over the tempering side and thereby tempering the fuel cell can flow off undesirably, so that a large part of the tempering fluid, for example a mixture of water and alcohol, flows through the bead without a significant tempering effect. In order nevertheless to produce a sufficient cooling effect, the Temperierfluidstrom is to increase, however, which worsens the temperature control of the fuel cell.

The invention is based on the object to provide a bipolar plate for a fuel cell and a method for producing a bipolar plate, wherein a bipolar plate having the fuel cell is efficiently tempered and the bipolar plate can be easily manufactured. For the aforementioned bipolar plate, the object is achieved by at least one sealing element arranged in the bead. The object is achieved for the aforementioned method in that in the bead a sealing element is introduced.

By providing the sealing element in the bead, the amount of tempering fluid flowing through the bead is at least reduced, so that a larger proportion of the tempering fluid flowing over the tempering side is used to control the temperature of the fuel cell. Even if the tempering fluid flows into the bead, the running through the bead portion of the Temperiermittelstroms is blocked. If the temperature control agent does not flow through the bead, it can lie flat on the temperature control side and flow over it. Consequently, the fuel cell can be tempered more efficiently.

The solution according to the invention can be further improved by various configurations which are advantageous in each case and, if not stated otherwise, can be combined with one another as desired. These embodiments and the advantages associated with them are discussed below.

Thus, the base plate may have two tempering openings, which are arranged outside a circulation area circumscribed by the bead for a tempering fluid of the flow field, wherein the sealing element is arranged in a section of the flow area extending between the tempering openings and through the bead. By the

Tempering, which extend for example completely perpendicular through the base plate, tempering fluid can flow to the temperature control. If the bipolar plate is part of a fuel cell arrangement with several fuel cells, the two can

Tempering each part of a Temperierkanals be, for example, extends at least partially perpendicular to the base plate through the fuel cell assembly. Consequently, all the fuel cells of the fuel cell assembly can be easily replaced by the

Temperieröffnungen be supplied with the tempering fluid. In this case, the fluid can be conducted away from the temperature control side and in particular to the flow area through one of the temperature control openings and from there through the other of the temperature control openings. By arranging the sealing element in the bead extending between the tempering openings, a tempering fluid flow through the bead, which extends from one of the tempering openings to the other of the tempering openings, is reliably blocked, so that the tempering fluid can not flow off or only through the bead in a reduced amount. There may be provided two sealing elements, one of which blocks an entrance and the other an exit of the section passing through the bead. In a

Flow direction of the temperature control, the input is arranged, for example, behind the respective temperature control. The output is arranged in the flow direction in front of the respective other temperature control. Even if tempering fluid should flow into the bead between the input and the output, it can no longer flow through the output to the other tempering opening, which reliably prevents or at least severely limits the outflow of the tempering fluid.

Two extending through the bead portions of the flow area, the

Temperieröffnungen connect with each other, both sections are blocked on the input side and output side. Although the bead can absorb tempering fluid between the sealing elements blocking the bead. However, this can not be done by one of

Temperature control openings to the other of the temperature control through the two sections of the bead flow, since this flow path is blocked by the at least one sealing element.

The at least one sealing element preferably completely fills a cross section of the bead, so that the amount of tempering fluid which can flow past the sealing element through the bead is negligible.

The at least one sealing element may be dimensioned similarly along the bead, as transverse to the bead. Such a sealing element may be sufficient to sufficiently block the tempering fluid flow through the bead. Alternatively, the at least one sealing element may extend along the bead and thus be dimensioned larger along the bead than transversely to the bead. In particular, the at least one sealing element can substantially fill the bead along its course extending between the tempering openings, that is to say a section of the throughflow area extending through the bead. If the sealing element completely fills out at least one section of the bead extending between the tempering fluid openings, it can not only block the tempering fluid from flowing from one of the tempering openings to the other of the tempering openings through the bead. Rather, such a sealing element can also prevent the tempering laterally from the

Base plate drains and thus is no longer available for heat exchange with the tempering.

In order to bring the sealing element into the bead can, even if the bipolar plate is connected on the temperature side with another bipolar plate, the base plate a fluidly connected to the bead and, for example, up to an edge of the

Having base plate extending groove can be injected through the material for the sealing element in the bead.

In particular, the bipolar plate may have two base plates according to the invention whose tempering sides point towards one another and their operating media sides away from one another, and whose beads form at least one line blocked by the at least one sealing element. The beads can open to each other and perpendicular to the base plate limit the line so that the line extends parallel to the base plate. The conduit may be at least partially open towards a center of the base plate to a

To be able to influence the flow behavior of the operating media on the operating media side of the base plate.

In order to bring the at least one sealing element in the bead, this can be arranged in the bead before the base plate with another base plate for

Bipolar plate is joined together. For example, before the welding of the two base plates together a sealing compound, such as silicone, are inserted at a predetermined location in the bead. As an alternative to silicone, which can be injected as a liquid silicone in the bead, the sealing element may be solid in nature and, for example, an elastomeric stopper.

Alternatively, the sealing element can be introduced after the joining of the two base plates in the bead. To access the bead from outside the bipolar plate, it may have the groove. The groove is accessible from outside the bipolar plate. For example, in the mounted state of the bipolar plate, the groove can form a injection channel opening laterally of the bipolar plate, through which a liquid material, for example liquid silicone, can be injected into the bead to form the sealing element.

Both in the unassembled and in the assembled state of the bipolar plate can

Sealing element be formed so that it does not extend much further along the bead than transverse to the bead. Alternatively, the sealing element along the bead have a greater extent than transversely thereto and fill the bead in particular completely.

The invention is explained below in embodiments with reference to the accompanying drawings. Show it: Figure 1 is a schematic plan view of a first embodiment of a

Base plate of the bipolar plate according to the invention,

Figure 2 is a schematic sectional view of another embodiment of the bipolar plate according to the invention, and

Figures 3 and 4 are schematic representations of embodiments of the

inventive method for producing a bipolar plate.

The invention is explained below by way of example with reference to embodiments with reference to the drawings. The different features of the embodiments can be combined independently of each other, as in the individual advantageous

Embodiments has already been explained.

First, the structure and function of a base plate of a bipolar plate according to the invention with reference to the embodiment of Figure 1 are described.

1 shows a base plate 1 of the bipolar plate according to the invention in a schematic plan view of a tempering 2 of the base plate. 1 Opposite the temperature control side 2, the base plate 1 has an operating medium side 3 with a flow field 4 for uniform distribution of operating media, for example hydrogen and air, within one

Fuel cell and in particular to a membrane electrode assembly of the fuel cell.

In order to prevent the operating media can escape laterally from a fuel cell stack in which the base plate 1 is arranged, without the operating medium for

Membrane electrode assembly has been passed, and / or to ensure that the operating media does not mix in the tempering fluid, the base plate 1 a

Density elevation 5, which circulates the flow field 4 and projecting from the flow field 4 on the operating medium side 3. If the base plate 1 is formed as an embossed sheet, the formation of the sealing elevation 5 produces a bead 6 which opens on the tempering side 2 and which circulates the flow field 4 on the tempering side 2. If, for example, the base plate 1 contacts another base plate on the temperature side, the bead 6 can be sealed at least in sections transversely to its course by the contact of the two base plates 1.

To guide one of the operating media to the operating media side 3, the base plate 1 operating medium openings 7, 7 ', 8, 8', which extend vertically through the base plate 1. Each of the operating medium openings 7, 7 ', 8, 8' can on the tempering 2 of a Be sealed sealing edge 9, 9 ', wherein the sealing edge 9, 9' as well as the density elevation 5 in which the Grundpplatte 1 possibly forming sheet be embossed, but can project from the tempering 2. The sealing edge 9, 9 'prevents fluid flowing via the temperature-control side 2 from mixing with the respective operating medium. On the operating medium side 3, one of the operating medium openings 7, 7 'or 8, 8' can likewise be circulated by a sealing edge 9, 9 ', so that either the operating medium flowing through the operating medium openings 7, 7' or through the operating medium openings 8, 8 ' is directed to the operating medium side 3 when the base plate 1 is arranged in the fuel cell stack.

In addition to the operating medium openings 7, 7 ', 8, 8', the base plate 1 preferably has two tempering openings 10, 10 ', which likewise extend perpendicularly through the base plate 1. In the embodiment of Figure 1, only the operating media openings 7, 7 ', 8, 8', but not the tempering 10, 10 'of the bead 6 rotate. The

Temperature control openings 10, 10 'are located diagonally opposite each other. Also the

Operating medium openings 7, 8 are diagonally opposite to the

Operating medium openings 7 ', 8' arranged. In this case, the base plate 1 is shown in the embodiment of Figure 1 by way of example rectangular. If the base plate 1 is not rectangular, then it must be ensured in the positioning of the openings 7, 7 ', 8, 8', 10, 10 'that the operating media and the tempering fluid over as large an area as possible of the base plate 1 of one of Operating media openings 7, 7 'or 8, 8' to the other of the

Operating medium openings 7, 7 'or 8, 8' or from one of the temperature control openings 10, 10 'to the other of the temperature control openings 10, 10' can flow.

At least in the area of the tempering openings 10, 10 ', the tempering fluid can flow transversely to the course of the bead 6 through it, from one of the tempering openings 10, 10' to a throughflow area D arranged between the tempering openings 10, 10 'and from there to the other of the tempering openings 10, 10 'to be able to flow, even if the base plate 1 contacted, for example, on the temperature side another base plate.

The flow field 4 is arranged between the operating medium openings 7, 8 and 7 ', 8' and distributes one of the operating media on the operating medium side 3 during operation of the fuel cell. The flow field 4 can be structured for this purpose and have, for example, ducts, the structure of the flow field 4 in FIG the figure 1 is not shown for clarity. If the tempering fluid now flows through one of the tempering openings 10, 10 'and, for example, through the tempering opening 10, onto the tempering side 2, there is the risk that a not insignificant amount of the tempering fluid passes through the bead 6 to the respective other of the tempering openings 10, 10' and For example, to the temperature control 10 'flows. Between the tempering 10, 10 'extends the flow area D for the tempering, wherein the flow area D temperierseitig the flow field 4 and the adjacent to the flow field 4 bead 6 may include. A portion T of the flow area D extending through the bead 6 can form a flow path P, through which a not insignificant proportion of the tempering fluid can flow during operation of the fuel cell.

The proportion of the tempering fluid flowing through the bead 6, for example, can make up 30% of the total tempering fluid conducted via the tempering side 2, is no longer available for the efficient exchange of heat with the tempering side 2, so that a larger amount of tempering fluid flows via the tempering side 2 must be promoted. As a result, the temperature control of the fuel cell is reduced. In order to prevent now that large amounts of tempering fluid flow through the bead 6, at least one sealing element 1 1 is provided, which is arranged in the bead 6. The sealing element 1 1 thus blocks the

Flow path P, so that the tempering fluid only to a reduced extent or not at all by the running through the bead 6 flow path P of one of

Temperature control openings 10, 10 'to the other of the temperature control openings 10, 10' can flow.

A Temperierfluidstrom S is shown schematically in the embodiment of Figure 1 by arrows, which point in possible flow directions of the tempering. Along the flow directions, two inputs E, E 'of the flow path P extending between the temperature control openings 10, 10' are shown behind the tempering opening 10.

In the region of the inputs E, E 'is in each case a sealing element 1 1, 1 1' arranged so that no larger amounts of tempering fluid through the respective input E, E 'in the bead 6 can flow. Between the input E, E 'and in the flow direction of the Temperierfluids before the temperature control opening 10' located outputs A, A 'of the flow path P 6 adjacent portions of the base plate 1 may be formed on the bead so that they abut with a on the Temperierseite 2 another base plate enter into a substantially tempering fluid-tight connection. At least the base plates 1 can be designed so that no larger amounts of tempering fluid can flow through the bead 6. Although the bead 6 can run full of tempering fluid, a flow of the tempering fluid through the bead 6 is, however, through the sealing elements 1 1, 1 1 'and by optional in the outputs A, A' to be provided sealing elements 1 1 ", 1 1"'blocked.

The sealing elements 1 1, 1 1 ', 1 1 ", 1 1"' of the embodiment of Figure 1 seal the bead 6 only selectively. In order to prevent tempering fluid enters the bead 6 or even better to prevent the tempering fluid can flow through the bead 6, the at least one sealing element 1 1 can continue along the bead 6, as it is transverse to the bead. 6 expands. In particular, the at least one sealing element 1 1 can extend from the inlet E, E 'to the outlet A, A' of the flow path P extending through the bead 6. Preferably, the sealing element 1 1 fills the bead 6 between the inputs E, E 'and the outputs A, A' completely.

If the bipolar plate has symmetrically constructed base plates 1 along the tempering side 2, the tempering sides 2 of which are fastened to one another facing one another, the beads 6 of both base plates 1 can form a line. A cross section of the conduit may be completely filled by the sealing element 11 to block the flow path P. In particular, the sealing element 1 1 completely fill the line, so that not only a flow of the tempering through the bead 6, but also a flow of the tempering laterally away from the base plate 1, is prevented. In order to fill the cross section of the line of the bipolar plate, the at least one sealing element 1 1 from the bead 6 of

Stand out base plate 1 when the base plate 1 is not yet mounted to the bipolar plate.

Figure 2 shows a further embodiment of the bipolar plate according to the invention in a lateral sectional view. For elements which correspond in function and / or construction elements of the embodiment of Figure 1, the same reference numerals are used. For the sake of brevity, only the differences from the exemplary embodiment of FIG. 1 will be discussed below.

FIG. 2 schematically shows a bipolar plate 20 with two base plates 1, 1 'which are fastened to one another on the temperature side. Both base plates 1, 1 'each have a bead 6, 6', which together form the conduit 21, and form the operating medium side of the density elevations 5, 5 '.

Towards an edge region 22 of the bipolar plate 20, the line 21 is accessible from outside the bipolar plate 20. In order to make the line 21 accessible from outside the bipolar plate 20 by the edge region 22, at least one of the base plates 1, 1 'is provided with a groove 23 formed, which opens on the temperature side. If both base plates 1, 1 'each have a groove 23, 23', they can form a shot channel 24, through which a sealant, for example liquid silicone, can be injected into the line 21. For the purpose of forming the sealing element 11, the tempering mass can completely fill at least the cross-section of the line 21 and in particular the line 21. Even if tempering fluid can be exchanged with the conduit 21, the sealing element prevents flow through the conduit 21.

Figures 3 and 4 show two embodiments of inventive method for

Producing a bipolar plate 20 schematically as flowcharts. For elements of

Exemplary embodiments of FIGS. 1 and 2, which are used to explain the methods below, are given the same reference numerals below.

Both shown schematically in the figures 3 and 4 as flow charts method 30, 30 'start with a first method step 31, in which, for example, the base plate 1 is formed. If the base plate 1 is formed from a sheet, this can for example be punched and in particular embossed, wherein in the embossing in particular the bead 6 and, for example, the flow field 4 and the sealing edges 9, 9 'can be formed. When punching the openings 7, 7 ', 8, 8', 10, 10 'are formed. If the base plate 1 is not formed from a metal sheet but, for example, from a plastic, then the base plate 1 can also be injection-molded. Other shaping methods, such as milling, are also possible.

In method 30, method step 31 is followed by method step 32, in which the at least one sealing element 11 is arranged in bead 6. After the sealing element 1 1 has been arranged in the bead 6, in the method 30, the method step 33 may follow, in which the base plates 1, 1 'to the bipolar plate 20 are joined together. For this purpose, the base plates 1, 1 'tempered together and, for example, welded together.

In the method 30 ', the method step 31 can be followed by the method step 33, in which the base plates 1, 1' are joined together. In method step 30, method step 32 may be followed by method step 32, in which the at least one sealing element 11 is arranged in bead 6. In particular, in the method 30 ', the groove 23 can additionally be formed during the method step 31, so that in the method step 32 of the method 30', a liquid and curable sealant can be introduced into the line 21 through the containment channel 24. LIST OF REFERENCE NUMBERS

I, 1 'base plate

2 tempering side

3 operating media page

4 river field

5, 5 'density survey

6, 6 'bead

7, 7 ', 8, 8' operating medium opening

9, 9 'sealing edge

10, 10 'tempering

I I, 1 1 'sealing element

1 1 ", 1 1" 'sealing element

20 bipolar plate

21 line

22 edge area of the bipolar plate

23, 23 'groove

24 shot-in channel

30, 30 'method

31 Form base plate

32 Arrange sealing element in bead

33 Assemble base plates

A, A 'outlet of the flow path

D flow area

E, E 'Entrance of the flow path

P flow path

5 tempering fluid stream

T section of the flow area extending through the bead

Claims

claims

1 . A bipolar plate (20) for a fuel cell, comprising a base plate (1), a temperature control side (2) and an operating medium side (3) opposite the temperature control side (2), and a flow field (4) for distributing an operating medium for the fuel cell, and the flow field (4) at least partially circumferential bead (6) extending from the

Operating media side (3) opens away and on the operating media side (3) forms a sealing elevation (5), characterized by at least one in the bead (6) arranged sealing element (1 1).

2. Bipolar plate (20) according to claim 1, characterized in that the base plate (1) has two tempering openings (10, 10 ') which outside of the bead (6) circulated Durchstömungsbereichs (D) for a tempering of the flow field (4 ) are arranged, wherein the sealing element (1 1) in a between the

Temperature control openings (10, 10 ') and through the bead (6) extending portion (T) of the flow area (D) is arranged.

3. bipolar plate (20) according to claim 2, characterized in that two sealing elements (1 1, 1 1 "') are provided, of which one input (E) and the other an output (A) by the bead ( 6) extending portion (T) blocked.

4. bipolar plate (20) according to one of claims 1 to 3, characterized in that two by the bead (6) extending portions (T) of the flow area (D), the temperature control openings (10, 10 ') interconnect, and that both sections (T) are blocked on the input side and output side.

5. bipolar plate (20) according to one of claims 1 to 4, characterized in that the at least one sealing element (1 1) completely fills a cross-section of the bead (6).

6. bipolar plate (20) according to one of claims 1 to 5, characterized in that extending the at least one sealing element (1 1) along the bead (6).

7. bipolar plate (20) according to one of claims 1 to 6, characterized in that the at least one sealing element (1 1) the bead (6) along its between the

Temperieröffnungen (10, 10) 'extending course substantially fills.

8. Bipolar plate (20) according to one of claims 1 to 7, characterized in that the base plate (1) has a fluid-conducting with the bead (6) connected groove (23, 23 ').

9. bipolar plate (20) according to one of claims 1 to 8, characterized in that the bipolar plate (20) has two base plates (1, 1 ') according to one of claims 1 to 8, the tempering (2) each other and their operating media sides (3) facing away from each other, and the beads (6, 6 ') at least one of the at least one

Seal element (1 1) form blocked line (21).

10. A method (30, 30 ') for producing a bipolar plate (20) for a fuel cell, in which a base plate (1) of the bipolar plate (20) with a flux field (4) and a flow field (4) at least partially encircling bead ( 6, 6 ') is formed, characterized

characterized in that in the bead (6, 6 ') at least one sealing element (1 1) is introduced.