Method and apparatus for manufacturing a fuel cell stack

Abstract

The invention relates to a method for producing a fuel cell stack (1), comprising the following steps: providing a plurality of first layers (3; 7) of the fuel cell stack (1) provided with projections (6) and transferring the first layers separately to a first motor-driven conveyor belt pair (9) which is encircled around a first end (12), wherein the two individual encircling conveyor belts (11) of the first conveyor belt pair extend at a distance from each other so that the conveyor belts each receive one of the projections (6) of the first layer (3; 7); providing a plurality of second layers (7; 3) of the fuel cell stack (1) provided with projections (6) and transferring the second layers The method comprises transferring the first layer (3; 7) provided with the projection (6) to a region of the conveyor belt (11) of the second conveyor belt pair (10) which is located between two second layers (7; 3) conveyed by the second conveyor belt pair (10) and which is separately transferred to a motor-driven second conveyor belt pair (10) which is encircled around a second end (13), the two individual encircling conveyor belts (11) of the second conveyor belt pair extending at a distance from one another so that the conveyor belts each receive one of the projections (6) of the second layer (7; 3) and transfer the first layer (3; 7) provided with the projection (6) at the first end (12) of the first conveyor belt pair (9) to the region of the conveyor belt (11) of the second conveyor belt pair (10) which is located between the respective two second layers (7; 3) conveyed by the second conveyor belt pair (10). The invention also relates to a device (8) for carrying out the method.

Description

Technical Field

[0001] The invention relates to a method and a device for producing a fuel cell stack of a fuel cell device. Background Art

[0002] Fuel cell devices are used to chemically convert fuel and oxygen into water in order to generate electrical energy. To this end, the fuel cell contains a so-called membrane electrode assembly (MEA) as a core component, which is a composite consisting of a proton-conducting membrane and electrodes (anode and cathode) arranged on both sides of the membrane. In addition, a gas diffusion layer (GDL) can be arranged on both sides of the membrane electrode unit on the side of the electrode facing away from the membrane. During the operation of a fuel cell device having a plurality of fuel cells combined to form a fuel cell stack, fuel, in particular hydrogen H2 or a hydrogen-containing gas mixture, is supplied to the anode, where the conversion of H2 to H2 occurs with the release of electrons. + Electrochemical oxidation of protons H + The electrons supplied at the anode are fed to the cathode via an electrical circuit. Oxygen or a gas mixture containing oxygen is supplied to the cathode, and the conversion of O2 to O2 is carried out by absorbing electrons. 2- At the same time, in the cathode compartment, these oxygen anions react with protons transported via the membrane to form water.

[0003] Reactant gases are supplied to the electrodes of the fuel cell via bipolar plates. In addition to the reactant gases, a cooling medium is also passed through the bipolar plates due to the heat generated in the fuel cell reaction, so that three different media are passed through the bipolar plates in a very small space.

[0004] When reactants are supplied to a fuel cell, they are directed via main channels (ports) into the bipolar plates. These plates distribute the reactants across the active area, ensuring that the entire electrode surface is supplied as evenly as possible thanks to the flow field. Because multiple bipolar plates and membrane electrode units are stacked in a fuel cell stack, seals are used that seal the main channels longitudinally through the fuel cell stack. Furthermore, a good seal must be achieved against the coolant flowing in the cooling channels.

[0005] Stacking membrane electrode assemblies and bipolar plates to produce a fuel cell stack is slow, expensive, and inefficient. In particular, the two fuel cell stack components must be aligned with one another with high precision so that the supply openings provided in the components and also the active areas lie precisely one above the other. To stack the components, the membrane electrode assemblies and bipolar plates are typically pumped, lifted, and lowered using appropriate handling equipment, such as robots or gantries. This process requires relatively long cycle times and the investment in such stacking equipment is very high.

[0006] DE 10 2018 116 057 A1 discloses an assembly device in which membrane electrode assemblies and bipolar plates are automatically and alternately stacked to form a fuel cell stack. The membrane electrode assemblies and bipolar plates are alternately provided on a single conveyor belt, with a compressed air device used to bring the individual layers of the fuel cell to a height-adjustable stacking receptacle. DE 10 2015 220 399 A1 also discloses an assembly device in which bipolar plates and membrane electrode assemblies are alternately stacked one on top of the other, with a suction gripper used for this purpose to separately stack the fuel cell stacks. WO 2014 / 072704 A2 discloses a type of belt system in which bipolar plates and membrane electrode assemblies are placed or arranged in a common strip, which is then folded together to form the fuel cell stack. Summary of the Invention

[0007] It is therefore an object of the present invention to specify a device and a method for producing a fuel cell stack, in which the cycle time for producing the fuel cell stack is further reduced.

[0008] This object is achieved by a method having the features of claim 1 and a device having the features of claim 6. Advantageous embodiments with expedient developments of the invention are specified in the dependent claims.

[0009] The method according to the invention comprises in particular the following steps:

[0010] providing a plurality of first layers of fuel cell stacks provided with projections and transferring the first layers separately to a first motor-driven conveyor belt pair running around a first end, the two individual circulating conveyor belts of the first conveyor belt pair extending at a distance from one another such that the conveyor belts each receive one projection of the first layer,

[0011] - providing a plurality of second layers of fuel cell stacks provided with projections and transferring the second layers separately to a second motor-driven conveyor belt pair running around the second end, the two individual circulating conveyor belts of the second conveyor belt pair extending at a distance from one another such that the conveyor belts each receive one projection of the second layer, and

[0012] Transferring the first layer provided with the projections at the first end of the first conveyor belt pair to a region of the conveyor belt of the second conveyor belt pair which is located between respectively two of the second layers conveyed by the second conveyor belt pair.

[0013] In this way, two different conveyor assemblies are used to transport one of the layers, either the bipolar plate or the membrane electrode assembly, respectively. One of the two conveyor belt pairs ends before the other conveyor belt pair, and the layers of this conveyor belt pair are transferred to the other conveyor belt pair. In this way, two different conveyor belt pairs are used to alternately combine the individual layers and combine them into a fuel cell stack.

[0014] Advantageously, the conveyor belts of the second conveyor belt pair are guided through the opening of the press die and the first and second layers of the fuel cell stack are stacked alternately on the press die. Such a press die can thus generate dynamic pressure, whereby the individual layers of the fuel cell stack are pressed onto one another and are already partially compressed and stacked.

[0015] It has proven advantageous to configure the press die to receive the unipolar plates. This allows the unipolar plates to be placed on the press die first, and only then can the first and second layers of the fuel cell stack be stacked alternately on the unipolar plates held on the press die. Dynamic pressure is thus generated by the press die, which interacts with the unipolar plates, and is further facilitated by the forward movement of the two conveyor belt pairs. Once a sufficient number of individual layers of the fuel cell stack have been stacked, a second unipolar plate can be applied as a finishing touch. The two unipolar plates can then be tensioned against each other to form the completed fuel cell stack.

[0016] To ensure the desired spacing of the individual layers from one another, it has proven advantageous if the conveyor belt includes equally spaced structures that accommodate the layers provided with projections. These structures can, for example, be ridges, which can also be actively adjusted between an extended and retracted position, particularly if they are located near the press die or near the beginning of the stack. Furthermore, it is possible to push or plug these projections onto further guide means, thereby achieving a defined position for the individual media ports of the individual layers of the fuel cell stack.

[0017] Furthermore, there is the possibility of providing the first and / or second layer in a flat position on a conveyor belt, in which projections project laterally beyond the conveyor belt relative to the conveying direction, and a respective one of the conveyor belts is fed laterally relative to the conveying direction of the conveyor belt, wherein equidistantly arranged structures receive and (in particular suspendedly) transport the layers at the projections of the layers.

[0018] The advantages, advantageous embodiments and effects explained in conjunction with the method according to the invention also apply to the device according to the invention for producing such a fuel cell stack.

[0019] The device particularly comprises a first, motor-driven conveyor belt pair that loops around a first end, wherein the two individual, looping conveyor belts of the first conveyor belt pair extend at a distance from one another such that a plurality of first layers of the fuel cell stack provided with projections can be transported at discrete intervals between the conveyor belts. The device particularly comprises a second, motor-driven conveyor belt pair that loops around a second end, wherein the two individual, looping conveyor belts of the second conveyor belt pair extend at a distance from one another such that a plurality of second layers of the fuel cell stack provided with projections can be transported at discrete intervals between the conveyor belts. Preferably, the first end of the first conveyor belt pair is positioned relative to the second conveyor belt pair such that the first layers provided with projections are transferred to a region of the conveyor belt of the second conveyor belt pair that is located between respective two of the second layers being transported by the second conveyor belt pair.

[0020] In this way, a particularly efficient, alternating stacking of the individual layers (ie, bipolar plates and membrane electrode assemblies) is also achieved, with an accompanying reduction in the cycle time for producing the fuel cell stack.

[0021] In this process, it is advantageous if the second pair of conveyor belts is guided through openings in a stacking die, which is configured to stack the first and second layers of the fuel cell stack alternately. Due to these openings, the stacking die can apply dynamic pressure to the individual layers being transported. Furthermore, the stacking die can also be provided with corresponding guide structures to ensure targeted, orderly stacking of the individual layers.

[0022] Advantageously, the pressing die is also designed to hold monopolar plates onto which the first and second layers of the fuel cell stack can be stacked alternately. This eliminates the need for subsequent placement of the monopolar plate present at one end, as it is already provided from the outset. Therefore, only the second monopolar plate must be provided in order to be tensioned against the first monopolar plate held by the pressing die.

[0023] The conveyor belt preferably has equidistantly arranged structures, which are set up to carry and / or receive layers provided with protrusions, wherein there is the possibility that the equidistantly arranged structures can also be present adjustably at each conveyor belt so that the structures are transformed into a retracted configuration at the topmost layer of the existing stack and near the backfill die, so that the structures can be passed through the opening of the backfill die in a simple manner.

[0024] It is not absolutely necessary to provide active adjustability of the structure, so that an elastic design of the structure can also be achieved, i.e., the structure can be formed, for example, from an elastomer, in particular in one piece with a corresponding conveyor belt. In this way, the projections of the individual layers, i.e., the projections of the bipolar plates and the projections of the membrane electrode assembly, can slide on the elastic structure when they reach the stamping die.

[0025] Typically, the individual layers of a membrane electrode assembly are applied flat to a substrate or produced in a decaling process. Therefore, it is advantageous or practical for the membrane electrode assembly and the bipolar plates to be transported and prepared flat. In this process, it is advantageous for the first and / or second layer to be provided flat on a conveyor belt, wherein the projections project laterally beyond the conveyor belt relative to the conveying direction, and wherein a respective one of the conveyor belts is guided laterally relative to the conveying direction of the conveyor belt such that equidistantly arranged structures receive the projections of the layers and convey them (in particular, in a suspended manner).

[0026] This causes the individual layers to pivot, i.e., to rotate them 90 degrees or to stand upright. The two conveyor assemblies can thus be aligned with one another so that they push one of the two layers from above in the direction of gravity between the two other layers. To this end, one of the conveyor belt pairs extends at an angle relative to the other conveyor belt of the pair.

[0027] The features and feature combinations mentioned above in the description and the features and feature combinations mentioned below in the description of the figures and / or shown individually in the figures can be used not only in the respectively described combination but also in other combinations or individually without departing from the scope of the present invention. Therefore, embodiments that are not explicitly shown or explained in the figures but that can be derived and generated from the explained embodiments by individual feature combinations are also included in the present invention and are to be considered disclosed. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Further advantages, features and details of the invention are apparent from the claims, the following description of preferred embodiments and with reference to the accompanying drawings.

[0029] Figure 1 a schematic diagram showing a fuel cell stack having a plurality of fuel cells with a bipolar plate showing a main channel,

[0030] Figure 2 A schematic top view of a membrane electrode assembly as one of the layers of a fuel cell is shown, with a detailed view of the projections present therein.

[0031] Figure 3A schematic top view of a bipolar plate as one of the layers of a fuel cell is shown, with a detailed view of the projections present there, and

[0032] Figure 4 A schematic diagram of an apparatus for manufacturing a fuel cell stack is shown. DETAILED DESCRIPTION

[0033] Figure 1 The fuel cell stack 1 shown in FIG. 1 is composed of a plurality of fuel cells 2 connected in series. Each fuel cell 2 includes an anode and a cathode, as well as a proton-conducting membrane separating the anode from the cathode. The two electrodes and the membrane together form a membrane electrode assembly 7 (abbreviated: MEA). The membrane is formed from an ionomer, preferably a polymer of sulfonated tetrafluoroethylene (PTFE) or perfluorosulfonic acid (PFSA). Alternatively, the membrane can be formed as a sulfonated hydrocarbon membrane.

[0034] The fuel (e.g. hydrogen) is supplied to the anode via the anode chamber within the fuel cell stack 1. In a polymer electrolyte membrane fuel cell (PEM fuel cell), at the anode, the fuel or fuel molecules are decomposed into protons and electrons. The membrane allows the protons (e.g. H + ) passes through, but the membrane is - ) is impermeable. Here, the following reaction occurs at the anode: 2H2 → 4H + +4e - (Oxidation / electron release). Protons pass through the membrane to the cathode, while electrons are directed to the cathode or to an accumulator via an external circuit. Cathode gas (e.g., oxygen or air containing oxygen) can be supplied to the cathode via the cathode chamber in the fuel cell stack 1, so that the following reaction occurs on the cathode side: O2 + 4H + +4e - →2H2O (reduction / acceptance of electrons).

[0035] Air compressed by a compressor is supplied to the fuel cell stack 1 via the cathode fresh gas line. Additionally, the fuel cell stack 1 is connected to the cathode exhaust gas line. On the anode side, hydrogen gas prepared from a hydrogen tank is supplied to the fuel cell stack 1 via the anode fresh gas line to provide the reactants required for the electrochemical reactions in the fuel cells 2. This gas is transferred to the bipolar plates 3, which have main channels 4 (ports) for distributing the gas to the membranes and for discharging it. Additionally, the bipolar plates 3 have main coolant channels 5 (ports) for guiding coolant in coolant channels 6, thereby channeling three different media in a minimal amount of space. Figure 1Also shown are the main channels 4, 5 of the plurality of fuel cells 2 forming the fuel cell stack 1, each connected in pairs, with bipolar plates 3. Ports are also present in the membrane electrode assembly 7, wherein seals are provided to prevent the operating medium and the cooling medium from undesirably escaping from the stack.

[0036] In the fuel cell stack 1, the membrane electrode assemblies 7 and bipolar plates 3 are arranged alternately so that they are aligned with each other as precisely as possible. In particular, the supply openings and seals should be arranged in precise alignment to form and seal the main supply channels that run through the stack in the stacking direction. However, the active areas (catalytic electrodes and flow fields) should also be aligned so as to overlap with each other in order to establish contact between the operating medium supplied via the bipolar plates 3 and the active centers of the catalytic electrodes and maximize the active area.

[0037] exist Figure 2 As can be seen in FIG, the membrane electrode assembly 7, which is the basis of the present invention, has been supplemented with projections 6, which are either produced integrally with the remaining material of the membrane electrode assembly 7 or are attached later. These projections 6, which are present on the left and right sides of this layer of the fuel cell, serve to control this layer. Accordingly, Figure 3 It is also indicated that the bipolar plate 3 is supplemented by projections 6 present on both sides.

[0038] exist Figure 4 , a device 8 for producing a fuel cell stack 1 according to the present invention is shown. The device includes a first, motor-driven conveyor belt pair 9 that circulates around a first end 12. Two individual, circulating conveyor belts 11 of the first conveyor belt pair are spaced apart from one another so that the layers 3, 7 of the fuel cell stack 1 provided with projections 6 are transported at discrete intervals between the conveyor belts 11. The first conveyor belt pair 9 extends obliquely relative to a second, motor-driven conveyor belt pair 10, which also circulates around a second end 13. The two individual, circulating conveyor belts 11 of the second conveyor belt pair are also spaced apart from one another so that the second layers 7, 3 of the fuel cell stack 1 provided with projections 6 are transported at discrete intervals between the conveyor belts 11. The first end 12 of the first conveyor belt pair 9 is positioned relative to the second conveyor belt pair 10 so that the first layers 3, 7 provided with projections 6 are transferred to a region of the conveyor belt 11 of the second conveyor belt pair 10 that is located between two of the second layers 7, 3 being transported by the second conveyor belt pair 10.

[0039] Thus, in the illustrated embodiment, a membrane electrode assembly 7 is inserted from above at the first end 12 between every two bipolar plates 3 and suspended from the second conveyor belt pair 10. The two conveyor belt pairs 9, 10, in particular their conveyor belts 11, include equally spaced structures 14 designed to carry and / or receive the individual layers provided with projections 6. After the membrane electrode assembly 7 has been transferred between every two bipolar plates 3 to the second conveyor belt pair 10, each of the conveyor belts 11 of the second conveyor belt pair 10 passes through an opening 17 of a pressing die 16, thereby generating dynamic pressure that automatically causes the individual layers 3, 7 of the fuel cell to be stacked alternately.

[0040] To produce the fuel cell stack 1 even faster and thus reduce the cycle time, the press die 16 is designed to also provide and hold the monopolar plates 15 onto which the individual layers 3, 7 are alternately stacked. The structures 14 of the second conveyor belt pair 10 can be retracted, for example, or the structures of the second conveyor belt pair can be elastically formed so that they can be passed through the through-openings 17. Another option is to design the press die 16 with suitable (additional) guides so that the structures 14 push the projections 6 of the individual layers onto these (additional) guides, thereby enabling relative movement between the structures 14 and the individual layers 3, 7 of the fuel cell.

[0041] Since the bipolar plates 3 and also the membrane electrode assemblies 7 are laid flat during their manufacture and are therefore transported flat, it is advantageous if the bipolar plates and the membrane electrode assemblies are provided by means of a conveyor belt in such a way that the projections 6 project laterally beyond the conveyor belt relative to the conveying direction, and if a corresponding one of the conveyor belts 11 is guided laterally relative to the conveying direction of the conveyor belt in such a way that the equidistantly arranged structures 14 receive the layers at their projections 6 and transport them, in particular in a suspended manner, wherein the structures are also suspended and alternately pushed into each other and collected alternately at the stamping die 16.

[0042] The method according to the invention and the device according to the invention are therefore characterized by a significant reduction in cycle time when producing a plurality of fuel cell stacks 1 .

[0043] Reference Signs List

[0044] 1. Fuel cell stack

[0045] 2 Fuel Cells

[0046] 3 Bipolar plates

[0047] 4 Main channel for reactants

[0048] 5 Main cooling pipe for cooling medium

[0049] 6 protrusions / receiving points

[0050] 7. Membrane Electrode Assembly (MEA)

[0051] 8 Devices

[0052] 9 First conveyor belt pair

[0053] 10 Second conveyor belt pair

[0054] 11 Conveyor belt

[0055] 12 First end

[0056] 13 Second end

[0057] 14 structure / lock position

[0058] 15. Monopolar plate

[0059] 16 Backlog of punching dies

[0060] 17 Opening

Claims

1. A method for manufacturing a fuel cell stack (1), the method comprising the following steps: - providing a plurality of first layers (3; 7) of the fuel cell stack (1) provided with projections (6) and transferring the first layers separately to a first motor-driven conveyor belt pair (9) running around a first end (12), wherein the two individual circulating conveyor belts (11) of the first conveyor belt pair extend at a distance from each other so that the conveyor belts each receive one of the projections (6) of the first layer (3; 7), - providing a plurality of second layers (7; 3) of the fuel cell stack (1) provided with projections (6) and transferring the second layers separately to a second motor-driven conveyor belt pair (10) which is encircled around a second end (13), the two individual encircling conveyor belts (11) of the second conveyor belt pair extending at a distance from each other so that the conveyor belts each receive one of the projections (6) of the second layer (7; 3), and - Transferring the first layer (3; 7) provided with the projection (6) at the first end (12) of the first conveyor belt pair (9) to the following area of the conveyor belt (11) of the second conveyor belt pair (10), which is located between respective two of the second layers (7; 3) conveyed by the second conveyor belt pair (10).

2. The method according to claim 1, characterized in that The conveyor belt (11) of the second conveyor belt pair (10) is guided through an opening (17) of a pressing die (16) and alternately stacks the first layer (3; 7) and the second layer (7; 3) of the fuel cell stack (1) on the pressing die (16).

3. The method according to claim 2, characterized in that First, a monopolar plate (15) is placed on the overmolding die (16), and then a first layer (3; 7) and a second layer (7; 3) of the fuel cell stack (1) are alternately stacked on the monopolar plate (15) held at the overmolding die (16).

4. The method according to any one of claims 1 to 3, characterized in that The conveyor belt (11) comprises equidistantly arranged structures (14) which receive the layers (3, 7) provided with the projections (6).

5. The method according to claim 4, characterized in that The first layer (3; 7) and / or the second layer (7; 3) are provided in a flat position on a conveyor belt, in which the projections (6) project laterally beyond the conveyor belt relative to the conveying direction, and a respective one of the conveyor belts (11) is guided laterally relative to the conveying direction of the conveyor belt in such a way that equidistantly arranged structures (14) receive and transport the layers (3, 7) at the projections (6) of the layers.

6. A device (8) for manufacturing a fuel cell stack (1), comprising: a first motor-driven conveyor belt pair (9) which circulates around a first end (12), wherein two individual circulating conveyor belts (11) of the first conveyor belt pair extend at a distance from one another such that a plurality of first layers (3; 7) of the fuel cell stack (1) provided with projections (6) can be conveyed at discrete intervals between the conveyor belts (11); a second conveyor belt pair (10) driven by a motor and extending around the second end (13), wherein the two individual circulating conveyor belts (11) of the second conveyor belt pair extend at a distance from one another such that a plurality of second layers (7; 3) of the fuel cell stack (1) provided with projections (6) can be conveyed at discrete intervals between the conveyor belts (11); The first end portion (12) of the first conveyor belt pair (9) is positioned relative to the second conveyor belt pair (10) in such a way that the first layer (3; 7) provided with the projection (6) is transferred to the following area of the conveyor belt (11) of the second conveyor belt pair (10), which is located between corresponding two second layers (7; 3) transported by the second conveyor belt pair (10).

7. The device (8) according to claim 6, characterized in that The second pair of conveyor belts (10) is guided through an opening (17) of an overlay die (16) which is set up to alternately stack first layers (3; 7) and second layers (7; 3) of the fuel cell stack (1).

8. The device (8) according to claim 7, characterized in that The overmolding die (16) is set up to hold a monopolar plate (15) onto which the first layer (3; 7) and the second layer (7; 3) of the fuel cell stack (1) are alternately stacked.

9. The device (8) according to any one of claims 6 to 8, characterized in that The conveyor belt (11) comprises equidistantly arranged structures (14) which are designed to carry and / or receive layers (3, 7) provided with projections (6).

10. The device (8) according to claim 9, characterized in that The first layer (3; 7) and / or the second layer (7; 3) is provided lying on a conveyor belt, in which the projections (6) project laterally beyond the conveyor belt relative to the conveying direction, and a corresponding one of the conveyor belts (11) is guided laterally relative to the conveying direction of the conveyor belt in such a way that the equidistantly arranged structures (14) receive and transport the layers at their projections (6).

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