METHOD AND DEVICE FOR PRODUCING A FUEL CELL STACK

Abstract

Amethod for producing a fuel cell stack includes: providing and individual handover of a plurality of first layers of the fuel cell stack, provided with overhangs, to a first conveyor belt pair which is motor driven and revolves around a first end, the two individual revolving conveyor belts of which run spaced apart so that they respectively receive one of the overhangs of the first layer, providing and individual handover of a plurality of second layers of the fuel cell stack, provided with overhangs, to a second conveyor belt pair which is motor driven and revolves around a second end, the two individual revolving conveyor belts of which run spaced apart so that they respectively receive one of the overhangs of the second layer, and handover of the first layers provided with overhangs at the first end of the first conveyor belt pair to a region of the conveyor belts of the second conveyor belt pair lying between two second layers transported by the second conveyor belt pair. A device for carrying out the method is also provided.

Claims

1. A method for producing a fuel cell stack, comprising: providing and individual handover of a plurality of first layers of the fuel cell stack provided with overhangs, to a first conveyor belt pair which is motor driven and revolves around a first end the two individual revolving conveyor belts of which run spaced apart so that they respectively receive one of the overhangs of the first layer providing and individual handover of a plurality of second layers of the fuel cell stack provided with overhangs to a second conveyor belt pair which is motor driven and revolves around a second end the two individual revolving conveyor belts of which run spaced apart so that they respectively receive one of the overhangs of the second layer; and handover of the first layers provided with overhangs at the first end of the first conveyor belt pair to a region of the conveyor belts of the second conveyor belt pair lying between two second layers transported by the second conveyor belt pair.

2. The method according to claim 1, wherein the conveyor belts of the second conveyor belt pair are led through openings of a ramp punch, and the first layers and the second layers of the fuel cell stack are stacked alternately on the ramp punch.

3. The method according to claim 2, wherein a unipolar plate is first placed on the ramp punch, and then the first layers and the second layers of the fuel cell stack are stacked alternately on the unipolar plate held on the ramp punch.

4. The method according to claim 1, wherein the conveyor belts comprise equidistantly arranged structures by which the layers provided with overhangs are received.

5. The method according to claim 1, wherein the first layers and/or the second layers are provided lying flat on a delivery belt, the overhangs sticking out to the side relative to the direction of movement of the delivery belt, and each one of the conveyor belts is moved laterally with respect to the direction of movement of the delivery belt so that the equidistantly arranged structures receive and transport the layers at their overhangs.

6. A device for producing a fuel cell stack, comprising: a first conveyor belt pair which is motor driven and revolves around a first end, the two individual revolving conveyor belts of which run spaced apart so that a plurality of first layers of the fuel cell stack provided with overhangs can be transported between the conveyor belts at discrete intervals; a second conveyor belt pair which is motor driven and revolves around a second end, the two individual revolving conveyor belts of which run spaced apart so that a plurality of second layers of the fuel cell stack provided with overhangs can be transported between the conveyor belts at discrete intervals; wherein the first end of the first conveyor belt pair is positioned such with respect to the second conveyor belt pair that the first layers provided with overhangs are handed over to a region of the conveyor belts of the second conveyor belt pair lying between two of the second layers transported by the second conveyor belt pair.

7. The device according to claim 6, wherein the second conveyor belt pair is led through openings of a ramp punch, which is adapted to alternately stack the first layers and the second layers of the fuel cell stack.

8. The device according to claim 7, wherein the ramp punch is adapted to hold a unipolar plate, on which the first layers and the second layers of the fuel cell stack are stacked alternately.

9. The device according to claim 6, wherein the conveyor belts comprise equidistantly arranged structures, which are adapted to carry along and/or receive the layers provided with overhangs.

10. The device according to claim 6, wherein the first layers and/or the second layers are provided lying flat on a delivery belt, the overhangs sticking out to the side relative to the direction of movement of the delivery belt, and each one of the conveyor belts is moved laterally with respect to the direction of movement of the delivery belt so that the equidistantly arranged structures receive and transport the layers at their overhangs.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0027] Further benefits, features and details will emerge from the claims, the following description of embodiments, and the drawings.

[0028] FIG. 1 shows a schematic representation of a fuel cell stack comprising a plurality of fuel cells with the bipolar plates showing the main ducts.

[0029] FIG. 2 shows a schematic representation of a membrane electrode assembly as one of the layers of the fuel cell, including a detail view of the overhang present there.

[0030] FIG. 3 shows a schematic representation of a bipolar plate as one of the layers of the fuel cell, including a detail view of the overhang present there.

[0031] FIG. 4 shows a schematic view of the device for the production of the fuel cell stack.

DETAILED DESCRIPTION

[0032] A fuel cell stack 1 shown in FIG. 1 consists of a plurality of fuel cells 2 switched in a row. Each of the fuel cells 2 comprises an anode and a cathode as well as a proton-conducting membrane separating the anode from the cathode. The two electrodes together with the membrane form a membrane electrode assembly 7 (MEA). The membrane is formed from an ionomer, such as a sulfonated tetrafluoroethylene polymer (PTFE) or a polymer of perfluorinated sulfonic acid (PFSA). Alternatively, the membrane can be formed as a sulfonated hydrocarbon membrane.

[0033] Through anode spaces inside the fuel cell stack 1 fuel is supplied to the anodes (for example, hydrogen). In a polymer electrolyte membrane fuel cell (PEM fuel cell), fuel or fuel molecules are split into protons and electrons at the anode. The membrane lets through the protons (for example, H.sup.+), but it is not permeable to the electrons (e.sup.-). At the anode the following reaction occurs: 2H.sub.2 .fwdarw. 4H.sup.+ + 4e.sup.- (oxidation/electron surrender). While the protons pass through the membrane to the cathode, the electrons are taken by an external circuit to the cathode or to an energy accumulator. Through cathode spaces inside the fuel cell stack 1 the cathodes can be supplied with cathode gas (such as oxygen or air containing oxygen), so that the following reaction occurs at the cathode side: O.sub.2 + 4H.sup.+ + 4e.sup.- .fwdarw. 2H.sub.2O (reduction/electron uptake).

[0034] Air compressed by a compressor is supplied to the fuel cell stack 1 by a cathode fresh gas line. In addition, the fuel cell stack 1 is connected to a cathode exhaust gas line. At the anode side, hydrogen kept in a hydrogen tank is supplied to the fuel cell stack 1 by an anode fresh gas line in order to provide the reactants needed for the electrochemical reaction in a fuel cell 2. These gases are handed over to bipolar plates 3, which comprise main ducts 4 (ports) for the distribution of the gases to the membrane and the exit line. In addition, the bipolar plates 3 comprise main coolant ducts 5 (ports) for the channeling of a cooling medium in a coolant duct 6, so that three different media are carried in the smallest of spaces. FIG. 1 furthermore shows the main ducts 4, 5 respectively combined into pairs of a plurality of fuel cells 2 with bipolar plates 3 forming the fuel cell stack 1. The ports are also present in the membrane electrode assemblies 7, and seals are present to guard the operating media and the cooling medium from an unwanted leakage from the stack.

[0035] In the fuel cell stack 1 the membrane electrode assemblies 7 and the bipolar plates 3 are arranged alternating such that they are oriented as exactly as possible to each other. In particular, the supply openings and also the seals should be arranged exactly aligned with each other, in order to form and seal off the main supply ducts interpenetrating the stack in the stacking direction. But also the active regions (catalytic electrodes and flow fields) should be oriented congruent to each other, in order to produce the contact between the operating media supplied through the bipolar plate 3 and the active centers of the catalytic electrode and maximize the active region.

[0036] In FIG. 2 one can see that the membrane electrode assemblies 7 described herein have been increased with an overhang 6, which has been produced either as a single piece with the rest of the material of the membrane electrode assembly 7 or has been added afterwards. These overhangs 6 present on the left and right side of this layer of the fuel cell are used to manipulate the layer. Accordingly, FIG. 3 also shows the increasing of the bipolar plate 3 with the overhangs 6 present on both sides.

[0037] FIG. 4 shows a device 8 for the production of a fuel cell stack 1, comprising a first conveyor belt pair 9 which is motor driven and revolves around a first end 12, the two individual revolving conveyor belts 11 of which run spaced apart so that a plurality of first layers 3, 7 of the fuel cell stack 1 provided with overhangs 6 can be transported between the conveyor belts 11 at discrete intervals. This first conveyor belt pair 9 runs at a slant relative to a second conveyor belt pair 10, which is motor driven and also revolves around a second end 13. These two individual revolving conveyor belts 11 run spaced apart so that a second layer 7, 3 of the fuel cell stack 1 provided with overhangs 6 is transported between the conveyor belts 11 at discrete intervals. The first end 12 of the first conveyor belt pair 9 is positioned such with respect to the second conveyor belt pair 10 that the first layers 3, 7 provided with overhangs 6 are handed over to a region of the conveyor belts 11 of the second conveyor belt pair 10 lying between two of the second layers 7, 3 transported by the second conveyor belt pair 10.

[0038] Thus, in the embodiment shown, each time a membrane electrode assembly 7 is inserted from above between every two bipolar plates 3 at the first end 12 and suspended in the second conveyor belt pair 10. The two conveyor belt pairs 9, 10, and especially their conveyor belts 11, comprise equidistantly arranged structures 14 which are adapted to carry along and/or take up the individual layers provided with overhangs 6. After the membrane electrode assembly 7 has been handed off to the second conveyor belt pair 10 between every two bipolar plates 3, each of the conveyor belts 11 of the second conveyor belt pair 10 runs through openings 17 of a ramp punch 16, thereby producing a back pressure which alternately stacks the individual layers 3, 7 of the fuel cell in automated manner.

[0039] In order to make the manufacturing of the fuel cell stack 1 even faster and thereby reduce the cycle times, the ramp punch 16 is adapted furthermore to provide and hold a unipolar plate 15, on which the individual layers 3, 7 are stacked alternately. The structures 14 of the second conveyor belt pair 10 can be retracted, for example, or they can be formed elastic, so that they can pass through the through holes 17. Another option is to configure the ramp punch 16 with a suitable (extra) guide, so that the structures 14 push the overhangs 6 of the individual layers onto this (extra) guide and thus make possible a relative movement between the structures 14 and the individual layers 3, 7 of the fuel cell.

[0040] Since the bipolar plates 3 and also the membrane electrode assemblies 7 are transported in a recumbent, and thus flat position during their manufacture, it may be advantageous for them to be provided by means of a delivery belt such that the overhangs 6 are sticking out to the side relative to the direction of movement beyond the delivery belt, and for each one of the conveyor belts 11 to be moved laterally with respect to the direction of movement of the delivery belt so that the equidistantly arranged structures 14 receive and transport the layers at their overhangs, especially hanging down, being also alternately interleaved handing down and alternately collected on the ramp punch 16.

[0041] Thus, the method and the device described herein are distinguished by a distinct reduction in cycle time for the production of multiple fuel cell stacks 1.

[0042] Aspects of the various embodiments described above can be combined to provide further embodiments. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled.