Fuel cell stack, fuel cell device, and motor vehicle having a fuel cell device

Abstract

The invention relates to a fuel cell stack (1) having a plurality of fuel cells (2) arranged in a stacking direction, which are clamped by means of clamping elements (3), wherein at least one, preferably each, has a cell voltage tap (6) for electrical connection to a cell monitoring unit (7), wherein the at least one cell voltage tap (6) is mechanically fixed in terms of the connection to the fuel cell (2) by at least one of the clamping elements (3). The invention also relates to a fuel cell arrangement and to a motor vehicle having a fuel cell arrangement.

Description

Technical Field

[0001] This invention relates to a fuel cell stack having a plurality of fuel cells arranged in a stacking direction and clamped by means of clamping elements, wherein at least one, preferably each, has a battery voltage tap for electrical connection to a battery monitoring unit, wherein the at least one battery voltage tap is mechanically secured to the fuel cell by at least one of the clamping elements. The invention also relates to a fuel cell device and a motor vehicle having a fuel cell device. Background Technology

[0002] Fuel cell devices are used to chemically convert oxygen-containing fuel into water to generate electricity. For this purpose, a fuel cell includes a so-called membrane electrode assembly (MEA) as its core component, which is a composite consisting of a proton-conducting membrane and electrodes, namely the anode and cathode, arranged on opposite sides of the membrane. Furthermore, a gas diffusion layer can be arranged on either side of the MEA on the side of the electrodes facing away from the membrane. To improve performance, multiple fuel cells can be combined in series in a fuel cell stack.

[0003] During operation, fuel, especially hydrogen (H2) or a hydrogen-containing gas mixture, is supplied to the anode, where electrons are released. - In the case of H2 to H + Electrochemical oxidation. Proton H+ is generated via a membrane that separates the reaction chambers in an airtight manner and makes them electrically insulating. + Transport of water or anhydrous gases from the anode chamber to the cathode chamber. Electrons supplied at the anode are fed to the cathode via electrical circuitry. Oxygen or an oxygen-containing gas mixture is supplied to the cathode, thus allowing O2 to be transported to O2 in the presence of electrons. 2- The reduction occurs. Simultaneously, in the cathode chamber, the oxygen anions react with protons transported via the membrane in the formation of water. Careful temperature management is also necessary here, so that, apart from the reactants, the coolant used for proper temperature control of the fuel cell stack is separately directed to the respective active regions of the fuel cell, where supply and discharge occur via so-called media guides. Therefore, in addition to the membrane electrode assembly, the fuel cell typically has bipolar plates, with an inlet line, an outlet line, and at least one media channel constructed for each medium, which in the case of reactants typically extends into a flow field.

[0004] Multiple fuel cells combined in a fuel cell stack are typically compressed by clamping elements with forces in the range of tens of thousands of Newtons to achieve sufficient contact pressure at the catalyst coating membrane to reduce ohmic losses and to prevent unsealing by means of high compression.

[0005] In a fuel cell stack, the voltage of each individual fuel cell is monitored to diagnose fault-free functionality. For this purpose, each individual fuel cell is electrically connected and linked to a battery monitoring unit. This electrical connection must adhere to specific quality requirements, especially when the fuel cell stack is used in fuel cell devices for motor vehicles. When using plug-in connectors for each fuel cell, a locking plug-in connection is typically required to prevent damage to the electrical connection from vibration or mechanical shock. However, this results in limited structural space at the bipolar plates used, further increasing their complexity. This is also disadvantageous in terms of structural and assembly costs, as cable connections typically exist between the plug-in connectors and the battery monitoring unit.

[0006] DE 10 2017 215 560 A1 illustrates a fuel cell stack with a clamping device having a tension body at which cables for a battery monitoring unit are secured. EP 1037 296 A1 discloses a fuel cell stack in which individual fuel cells are clamped together by means of tie rods. The tie rods also serve as busbars. A conductive clamping element for energizing one of the busbars is known from EP 3 035430 A1. US2007 / 0087237A1 illustrates a fuel cell stack in which end plates are clamped by tie rods. Holes are formed in the tie rods for threading electrical connections for the battery monitoring unit. Summary of the Invention

[0007] The objective of this invention is to provide an improved fuel cell stack, an improved fuel cell device, and a motor vehicle having a fuel cell device, which mitigate or even eliminate the aforementioned disadvantages.

[0008] This task is accomplished by the fuel cell stack according to the invention, the fuel cell device according to the invention, and the motor vehicle according to the invention. Advantageous designs with suitable improvements to the invention are given in the remaining embodiments.

[0009] The aforementioned fuel cell stack is characterized in that the mechanical fixing of the battery voltage taps is achieved through pre-existing, indispensable components that are mechanically very robust and stable due to their intended use. Changes in the position of the battery voltage taps are suppressed by clamping elements.

[0010] Preferably, each battery voltage tap includes a connector for plug-in connection, and the connector is pre-assembled at the clamping element, because this reduces costs while the clamping element can also serve as an assembly aid and simplify the manufacturing of the fuel cell stack.

[0011] In this regard, it is advantageous that the clamping element has a pass-through portion for guiding the cable to the battery monitoring unit, so as to establish the necessary connection over a short distance and in the absence of external influences.

[0012] According to another embodiment, it is possible for each connector to be arranged at one location in the fuel cell, and for fasteners for the connectors to be housed in clamping elements for electrical connection with the battery monitoring unit. Here, the connectors are formed by sockets and the fasteners are formed by injection molding, through which the electrical connection portion of the fasteners is guided to a printed circuit board, which connects to the battery monitoring unit.

[0013] According to another preferred embodiment, the connector and fastener can be integrally combined into a single component.

[0014] Fuel cells are clamped between end plates by clamping elements, which form a rigid tension band, thus giving them high mechanical load capacity and making them suitable for fixing the position of connectors or sockets.

[0015] The aforementioned effects and advantages also apply, in a meaningful sense, to fuel cell devices having such fuel cell stacks and to motor vehicles having such fuel cell devices.

[0016] The features and combinations of features mentioned above in the specification, as well as the features and combinations of features mentioned below in the description of the drawings and / or shown separately in the drawings, can be used not only in the combinations described separately, but also in other combinations or individually, without departing from the scope of the invention. Therefore, the following embodiments, which are not explicitly shown or explained in the drawings, but are derived from and can be produced by individual combinations of features from the explained embodiments, should also be considered as included and disclosed by the invention. Attached Figure Description

[0017] Further advantages, features, and details of the invention will become apparent from the claims, the following description of preferred embodiments, and with the aid of the accompanying drawings. Hereinafter: Figure 1 A schematic diagram of a fuel cell stack is shown, which is constructed from multiple fuel cells. These fuel cells are compressed by clamping elements that also serve to secure the plug-in connections. Figure 2 It shows the corresponding Figure 1 The illustration shows a connector mounted on a fuel cell, the connector being connected to a battery voltage detection unit via a connecting element assigned to a clamping element. Figure 3 It shows the corresponding Figure 1 The diagram shows that the connectors and fasteners are integrated into the clamping element. Detailed Implementation

[0018] The fuel cell device has a fuel cell stack 1, which has a plurality of fuel cells 2 arranged in a stacking direction.

[0019] Each of the fuel cells 2 includes an anode and a cathode, and a proton-conducting membrane separating the anode and cathode. This membrane is formed of an ionomer, preferably a sulfonated tetrafluoroethylene polymer (PTFE) or a perfluorosulfonic acid polymer (PFSA). Alternatively, the membrane may also be formed as a sulfonated hydrocarbon membrane.

[0020] Fuel, especially hydrogen, can be supplied from the fuel tank to the anode via the anode chamber. In a polymer electrolyte membrane fuel cell (PEM fuel cell), the fuel, or fuel molecules, split into protons and electrons at the anode. The PEM allows protons to pass through, but electrons are impermeable. For example, the following reaction occurs at the anode: 2H₂ → 4H₂ + +4e - (Oxidation / Electron Release). During the process of protons reaching the cathode via the PEM, electrons are conducted to the cathode or energy storage via external circuitry.

[0021] A cathode gas (such as oxygen or oxygen-containing air) can be supplied to the cathode via the cathode chamber, thereby allowing the following reaction to occur on the cathode side: O₂ + 4H₂O + + 4e - →2H2O (reduction / electron absorption).

[0022] The fuel cell stack 1 also has a clamping device formed by clamping elements 3 for compressing the fuel cell 2. Here, the end of the fuel cell 2 is equipped with an end plate 4, where the clamping device is connected for force introduction. Medium guides 5 for fuel, oxidant, and coolant are arranged at one or both end plates 4 (only at...). Figure 3 As shown in the figure, the embodiment shown in the figure is at the left end plate 4. The clamping element 3 is formed as a rigid tension band, which can be made of metal in particular, having corresponding mechanical properties in terms of strength and bending stiffness.

[0023] Furthermore, the fuel cell stack 1 preferably has a battery voltage tap 6 for each of the fuel cells 2 for electrical connection with the battery monitoring unit 7, thereby enabling fault-free diagnostics. The battery voltage tap 6 is mechanically secured to the fuel cell 2 by at least one of the clamping elements 3.

[0024] Here, Figure 1An embodiment is shown in which each battery voltage tap 6 includes a connector 8 for plug-in connection, thus emphasizing additional mechanical fixation in this embodiment. However, additionally, the connector 8 may also be pre-assembled at the clamping element 3, thereby enabling the use of the clamping element 3 as an assembly aid, wherein the clamping element 3 has a pass-through portion for guiding the cable to the battery monitoring unit 7.

[0025] Figure 2 An embodiment is shown in which each connector 8 is arranged at one of the fuel cells 2, wherein a fastener 9 for the connector 8 is housed in a clamping element 3 for electrical connection with the battery monitoring unit 7. More specifically, the connector 8 is formed by a socket 10 and the fastener 9 is formed by an injection molding part 11, through which the electrical connection is guided to a printed circuit board 12, which is electrically connected to and, in particular, mechanically connected to the battery monitoring unit 7.

[0026] Figure 3 An embodiment is shown in which the connector 8 and fastener 9 are integrally combined in a single component 13, which is integrated into the clamping element 3. The connection portion at component 13 is designed to have a protrusion 14, thereby enabling connection to the battery monitoring unit 7 via solder points on the printed circuit board 12.

[0027] Fuel cell devices with such fuel cell stacks 1 demonstrate their advantages, especially when used in motor vehicles, where there are specific mechanical loads and vibrations.

[0028] List of reference numerals 1. Fuel Cell Stack 2. Fuel Cell 3 Clamping elements 4 end plates 5. Medium guiding section 6. Battery voltage tap 7 Battery Monitoring Unit 8 Connectors 9 Fasteners 10 sockets 11 Injection Molded Parts 12 Printed Circuit Boards 13 components 14. Protrusion.

Claims

1. A fuel cell stack (1) having a plurality of fuel cells (2) arranged in a stacking direction and clamped by means of clamping elements (3), wherein at least one has a battery voltage tap (6) for electrical connection to a battery monitoring unit (7), wherein, The at least one battery voltage tap (6) is mechanically fixed to the fuel cell (2) by at least one of the clamping elements (3), characterized in that each battery voltage tap (6) includes a plug (8) for plug-in connection, and the plug (8) is pre-assembled at the clamping element (3), or each plug (8) is arranged at one of the fuel cells (2), and a fastener (9) for the plug (8) is accommodated in the clamping element (3) for electrical connection with the battery monitoring unit (7).

2. The fuel cell stack (1) according to claim 1, characterized in that, Each fuel cell (2) has a battery voltage tap (6).

3. The fuel cell stack (1) according to claim 1, characterized in that, The clamping element (3) has a guide portion for guiding the cable to the battery monitoring unit (7).

4. The fuel cell stack (1) according to claim 1, characterized in that, The connector (8) is composed of a socket (10), and the fastener (9) is composed of an injection molded part (11), through which the electrical connection part is guided to the printed circuit board (12), which is connected to the battery monitoring unit (7).

5. The fuel cell stack (1) according to claim 1, characterized in that, The connector (8) and the fastener (9) are integrally combined in a single component (13).

6. The fuel cell stack (1) according to any one of claims 1 to 5, characterized in that, The fuel cell (2) is clamped between end plates (4) by the clamping element (3), which is formed as a rigid tension band.

7. A fuel cell device having a fuel cell stack (1) according to any one of claims 1 to 6.

8. A motor vehicle having a fuel cell device according to claim 7.

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