Bipolar plate with insertable shutter and fuel cell stack

Abstract

The invention relates to a bipolar plate (1) for a fuel cell, having an active area (3) and a peripheral area (4) surrounding the active area (3), the peripheral area being assigned a first medium guide (10) which is in flow-mechanical connection with a first through-opening (5) and a second medium guide (7) which is in flow-mechanical connection with a second through-opening (6), and having a medium channel (8) which extends through the active area (3) and which flow-mechanically connects the first through-opening (5) with the second through-opening (6). At least one of the medium guides (10, 7) comprises a first sub-chamber (2) and a second sub-chamber (11) having a through-opening (5, 6). Between the first sub-chamber (2) and the second sub-chamber (11), the flow cross-section of the medium guide (10, 7) is tapering and a shutter (9) is inserted or insertable into the second sub-chamber (11). The invention also relates to a fuel cell stack.

Description

Technical Field

[0001] This invention relates to a bipolar plate for a fuel cell, the bipolar plate having an active region and an edge region surrounding the active region, the edge region being provided with a first medium guide portion having a first through-hole and a second medium guide portion having a second through-hole. Furthermore, a medium channel extending through the active region mechanically connects the first through-hole and the second through-hole.

[0002] The present invention also relates to a fuel cell stack having at least one bipolar plate. Background Technology

[0003] Fuel cell devices are used to chemically convert fuel and oxygen into water to generate electricity. For this purpose, a fuel cell contains a so-called membrane electrode assembly (MEA) as its core component. The MEA is a composite consisting of a proton-conducting membrane and two electrodes (anode and cathode) arranged on either side of the membrane. Furthermore, gas diffusion layers (GDLs) can be arranged on either side of the MEA on the side of the electrodes facing away from the membrane. In the operation of a fuel cell device having multiple fuel cells assembled into a fuel cell stack, fuel, especially hydrogen (H2) or a hydrogen-containing gas mixture, is supplied to the anode, where H2 to H2 is converted into hydrogen upon electron donation. + Electrochemical oxidation. Proton H+ is achieved via an electrolyte or a membrane that hermetically isolates and electrically insulates the reaction space. + The transport from the anode space to the cathode space. Electrons supplied at the anode are transported to the cathode via wires. Oxygen or an oxygen-containing gas mixture is supplied to the cathode, thus causing O2 to be converted to O2 upon electron absorption. 2- The reduction occurs. Simultaneously, in the cathode space, these oxygen anions react with protons transported via the membrane to form water.

[0004] The 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 guided through the bipolar plates, thus guiding three different media through the bipolar plates in a minimal (or very small, i.e., kleinstem) space.

[0005] To meet high power requirements, multiple fuel cells are combined or stacked to form a fuel cell stack. Here, the medium guide can be configured as a medium port with a void in the edge region, which can create multiple three-dimensional spaces when the layers of the fuel cell stack are stacked. Alternatively, the medium guide can also be configured as a functional component assigned to and separately constructed from the edge region of the fuel cell and bipolar plate, forming a three-dimensional space within this functional component. In other words, the stacked fuel cells and bipolar plates can be equipped with external manifolds. Thus, multiple three-dimensional spaces are formed along the stacking direction for supplying reactants and cooling media to the active region of the fuel cell, and multiple three-dimensional spaces are formed along the stacking direction for discharging reactants, products, and cooling media. A channel structure consisting of medium channels is typically formed through the active region of the bipolar plate, which mechanically connects one medium guide (e.g., a medium port) in the medium guide to another medium guide in the medium guide. Here, at least one through-hole is implemented in the bipolar plate body of the bipolar plate, the through-hole mechanically connecting the medium guide, such as the medium port, to the one or more medium channels.

[0006] The efficiency of a fuel cell is significantly affected by the mass flow of the medium through the medium channels. This mass flow is largely determined by the choice of the diameter of the flow cross-section, i.e., the through-hole, during the manufacture of the bipolar plates. The choice of diameter here represents a trade-off between different requirements for power delivery and humidification of the fuel cell. This makes it difficult to quickly adapt the power profile (Leistungsprfils) of the fuel cell stack during operation.

[0007] Furthermore, a uniform distribution of reactants within the fuel cell stack is desirable to optimally supply moisture and fuel to all fuel cells. To this end, DE 10 2014 22 06 82 A1 describes a bipolar plate having multiple media ports forming collection channels into which insert elements can be inserted. The insert elements segmentally change the cross-section of the collection channels to supply the same volumetric flow of media to each fuel cell in the fuel cell stack. DE 102016 225 444 A1 also describes a baffle with multiple media ports forming collection channels into which insert elements can be inserted, each having multiple openings. This also allows for adaptation of the collection channel cross-section to different fuel cells. CN 207 690 923 U also describes a bipolar plate with a media inlet channel into which insert elements are arranged.

[0008] The disadvantage here is that the cross-sectional shape of the inserted element must either be adapted to the cross-sectional shape of the medium port, resulting in high material consumption, or a separate guide must be present for the inserted element. This increases the material consumption and the number of manufacturing steps for the bipolar plate, and therefore also increases the material consumption and the number of manufacturing steps for the fuel cell stack. Summary of the Invention

[0009] Therefore, the objective of this invention is to provide a bipolar plate and a fuel cell stack that reduce the aforementioned disadvantages in the case of said bipolar plate and fuel cell stack.

[0010] Tasks involving bipolar plates are solved using bipolar plates according to the invention. Tasks involving fuel cell stacks are solved using fuel cell stacks according to the invention.

[0011] The bipolar plate is characterized in that at least one of the dielectric guides comprises a first sub-chamber and a second sub-chamber having the through-portion, wherein the flow cross-section of the dielectric guide is tapered (or gradually narrowed) between the first and second sub-chambers, and a shield is inserted into or can be inserted into the second sub-chamber. The second sub-chamber of the dielectric guide is therefore used to receive and guide the shield. Therefore, additional guiding elements or additional guides for the shield can be omitted. This reduces material consumption and simplifies the manufacture of the bipolar plate.

[0012] Particularly advantageous is that the shielding member is adjustablely supported within the second sub-chamber by means of an actuator to adjust the flow cross-section of the through-passage. The shielding member is thus not only guided within the second sub-chamber but also adjustable therein, thereby achieving at least partial coverage of the through-passage and reducing the flow cross-section. The actuator-adjustable shielding member here achieves dynamic adjustment of the flow cross-section at the through-passage, which in turn adjusts the mass flow in the medium channel as needed. The shielding member is preferably adjustable between a first position and a second position, in which the through-passage is at least partially covered and the flow cross-section is thus reduced, and in the second position, the through-passage is uncovered. Here, the shielding member can also be adjusted by the actuator so that the through-passage is completely covered by the shielding member, thereby preventing the medium mass flow from passing through the through-passage into the medium channel. This rapid reduction in medium supply results in only the medium located in the active region being available for electrochemical reactions. This allows for a rapid reduction in the electrical power supplied by the fuel cell stack to respond to dynamic processes in the vehicle, such as interventions in the anti-lock braking system. Conversely, rapid power increases can also be achieved, or the dielectric guide can be adapted to power requirements to optimize dielectric consumption. Furthermore, by equipping the second through-section with a shielding element controllable by an actuator, the humidity balance of the fuel cell stack can be dynamically controlled.

[0013] The shielding element can preferably be arranged before or in the through section.

[0014] Here, the blocking member can have the same cross-sectional shape as the first and / or second through-parts; particularly advantageously, the blocking member is configured as an ellipse. This achieves simple manufacturing and good coverage of the through-parts. In an alternative embodiment, it is feasible for the cross-sectional shape of the blocking member to be polygonal, i.e., for example, rectangular, square, hexagonal, orthogonal, or triangular. Furthermore, the blocking member can also be formed by bending towards or against the direction of the through-parts.

[0015] Here, the blocking member can have the same cross-sectional shape as the first through portion and / or the second through portion; it is particularly advantageous that the blocking member is configured as an ellipse. This achieves simple manufacturing of the through portion and good coverage.

[0016] In this regard, it is preferable that the shielding member is movably, i.e., translatably supported in the second sub-cavity by means of an actuator, for adjusting the flow cross-section of the through section.

[0017] Alternatively, the through portion may be rotatably supported at or within the through portion.

[0018] Significantly, the cross-sectional area of ​​the second sub-chamber roughly corresponds to the cross-sectional area of ​​the shield. This achieves optimal guidance of the shield within the second sub-chamber. Furthermore, the shield or the second sub-chamber may also be fitted with a sealing lip to seal the second sub-chamber relative to the medium.

[0019] To simplify the manufacture of the bipolar plate, it is preferable that the tapered flow cross-section between the first and second sub-chambers is formed by at least one protruding protrusion. The protrusion thus forms part of the bipolar plate and can be produced in the same manufacturing steps as the bipolar plate. In other words, no additional manufacturing steps are required to construct the second and first sub-chambers. This reduces the complexity of the components and the material requirements, thereby achieving cost reduction.

[0020] Furthermore, it is advantageous that the narrowed flow cross-section between the first and second sub-chambers is formed by two opposing protruding bulges. This results in a symmetrical construction of the medium guide and reduces the complexity of the bipolar plate.

[0021] Particularly advantageous is that the protrusions form guide tracks for the shielding member. Furthermore, it is preferred that two protrusions form guide tracks for the shielding member.

[0022] To facilitate the adjustment of humidity levels within the fuel cell, it is advantageous that another medium guide in the medium guide also includes a first sub-chamber and a second sub-chamber with a through-hole. The flow cross-section of the medium guide is narrowed between the first and second sub-chambers, and a second shield is inserted into or can be inserted into the second sub-chamber.

[0023] Significantly in this regard, the second shield is adjustablely supported within the second sub-cavity by means of an actuator for adjusting the flow cross-section of the through-section. This enables the guiding of the medium and allows the mass flow of the medium to be adjusted via this other medium guide. The second shield can also be movably, i.e., translationally, supported within the second sub-cavity by means of an actuator. Furthermore, it is advantageous that the tapering portion of this other medium guide is formed by at least one protrusion projecting between the first and second sub-cavities, or by two opposing, protruding protrusions. The advantageous configuration described for the shield also applies to the second shield.

[0024] Alternatively, the cross-sectional area of ​​the second sub-chamber of the first medium guide may differ from the cross-sectional area of ​​the second sub-chamber of the second medium guide. Alternatively or additionally, the cross-sectional area of ​​the entire first medium guide may also differ from the cross-sectional area of ​​the second medium guide. This also allows for the adaptation of medium guidance by constructing a pressure drop.

[0025] A key feature of the fuel cell stack is the arrangement of multiple fuel cells stacked together along a stacking direction, each fuel cell having at least one bipolar plate and a membrane electrode assembly. The stacking of the fuel cells and bipolar plates forms a medium space extending along the stacking direction. Similarly, stacked second sub-chambers also form a three-dimensional space into which a shield is inserted or can be inserted to adapt to the flow cross-section of the through-passage. Particularly advantageous is that the shield is adjustablely supported along or against the stacking direction; this enables dynamic adaptation of the flow cross-section of the through-passage and thus dynamic adaptation of the medium mass flow. The advantages and design described for the bipolar plates are similarly applicable to fuel cell stacks having at least one bipolar plate.

[0026] 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 corresponding combinations given, but also in other combinations or individually, without departing from the scope of the invention. Therefore, the following embodiments are also included in the invention and are considered to be disclosed, embodiments not explicitly shown or explained in the drawings, but derived from and can be produced from the individual combinations of features in the explained embodiments. Attached Figure Description

[0027] Other advantages, features, and details of the invention will become apparent from the claims, the following description of preferred embodiments, and the accompanying drawings. Wherein: Figure 1 A schematic diagram of a bipolar plate is shown. Detailed Implementation

[0028] Figure 1 A bipolar plate 1 for a fuel cell is shown, having an active region 3 and an edge region 4 surrounding the active region 3. The edge region 4 has three first medium guides 10 configured as first medium ports: a medium port 10a for supplying a first reactant to the active region 3 of the bipolar plate 1, a medium port 10b for supplying a second reactant to the active region 3 of the bipolar plate 1, and a medium port 10c for supplying coolant to the active region 3 of the bipolar plate 1. Furthermore, there are three second medium guides 7 configured as second medium ports: a medium port 7a for discharging the first reactant, a medium port 7b for discharging the second reactant, and a medium port 7c for discharging coolant. Between the first medium guides 10 and the second medium guides 7, medium channels 8 extending over the active region 3 are provided, each medium channel forming a flow field for a corresponding working medium.

[0029] The first dielectric guide 10 has a plurality of first through-sections 5. The second dielectric guide 7 has a plurality of second through-sections 6. Furthermore, a plurality of dielectric channels 8 are constructed, extending through the active region 3 of the bipolar plate 1. The dielectric channels 8 mechanically connect the first through-sections 5 of the first dielectric guide 10 to the corresponding second through-sections 6 of the second dielectric guide 7. The dielectric channels 8 in… Figure 1 The diagram is simplified. Therefore, the dielectric channel 8 is preferably configured as a dielectric channel network that preferably extends meanderingly through the active region 3 of the bipolar plate 1. In particular, the dielectric channel 8 extends open on one side to supply dielectric to the active region of the layer adjacent to the bipolar plate 1. A first through-hole 5 and a second through-hole 6 are constructed within the bipolar plate body 15, thereby tunneling beneath the bipolar plate 1.

[0030] The first medium guide portion 10 has a first sub-chamber 2 and a second sub-chamber 11 having a through portion 5. Between the first sub-chamber 2 and the second sub-chamber 11, the flow cross-section of the first medium guide portion 10 is narrowed. In other words, a medium guide channel 12 with a reduced flow cross-section is arranged between the first sub-chamber 2 and the second sub-chamber 11. A baffle 9 is inserted into or can be inserted into the second sub-chamber 11. Currently, the baffle 9 is movably supported within the second sub-chamber 11 by means of an actuator, so that the flow cross-section of one or more through portions 5 can be adapted by moving the baffle 9. The cross-sectional area of ​​the second sub-chamber 11 here approximately corresponds to the cross-sectional area of ​​the baffle 9, thereby achieving an increased contact area between the baffle 9 and the through portion 5 to achieve a corresponding medium seal.

[0031] To facilitate the manufacture of the bipolar plate 1, the medium guiding channel 12, or the narrowed flow cross-section between the first sub-chamber 2 and the second sub-chamber 11, is formed by two opposing protruding protrusions 13, which, for clarity, are indicated only in one of the second medium guiding sections 7. The protrusions 13 are thus constructed within the bipolar plate body 15 itself. The medium guiding channels 12 of the two sub-chambers 2, 11 and the corresponding medium guiding sections 10, 7 can thus be manufactured in a single manufacturing step. The protrusions 13 here form a guide track for the shield 9, allowing the shield to move along the second sub-chamber 11 without additional guiding or fixing elements.

[0032] Figure 1 The embodiments also show that at least one of the second media guides 7 also includes a first sub-chamber 2 and a second sub-chamber 11 having a through-portion 6. Between the first sub-chamber 2 and the second sub-chamber 11, the flow cross-section of the second media guide 7 is tapered. A second blocking member 14 is also inserted into or can be inserted into the second sub-chamber. The second blocking member 14 can also be adjusted within the second sub-chamber 11 by means of an actuator, particularly being movably supported, so that the flow cross-section of the through-portion 6 can be adjusted. The blocking member 9 is preferably inserted into all the second sub-chambers 11 of the first media guide 10, and this blocking member can be adjusted by an actuator. It is possible that the actuator-adjustable blocking member 14 is additionally inserted into all the second sub-chambers 11 of the second media guide 10.

[0033] According to Figure 1 In one embodiment, the cross-sectional area of ​​the second sub-chamber 11 of the first medium guide portion 10 corresponds to the cross-sectional area of ​​the second sub-chamber 11 of the second medium guide portion 7. However, in an alternative embodiment, the cross-sectional area of ​​the second sub-chamber 11 may also be different, which leads to additional adjustment possibilities for medium supply and medium discharge.

[0034] Figure 1 The bipolar plate 1 described herein can be integrated into a fuel cell stack having multiple fuel cells stacked together along a stacking direction. For this purpose, a membrane electrode assembly is placed between every two such bipolar plates 1 to supply reactants to the membrane electrode assembly via the flow field of the bipolar plates 1. This stacking creates a media space extending substantially parallel to the stacking direction. The media space forms a three-dimensional second sub-chamber 11 extending along the stacking direction, into which common shielding elements 9, 14 are inserted and adjustably supported. This enables dynamic guidance and regulation of the media within the fuel cell stack.

[0035] List of reference numerals 1 bipolar plate 2 First subchamber 3 active regions 4 Edge regions 5 First Penetrating Section 6 Second Penetrating Section 7 Second Medium Guiding Section 7a is used for the second medium port of the first reactant. 7b is used for the second medium port of the second reactant. 7c is the second medium port for coolant. 9 shielding parts 10 First Medium Guiding Section 10a is used for the first medium port of the first reactant. 10b is used for the first medium port of the second reactant. 10c is used for the first medium port of the coolant. 11 Second sub-chamber 12 media guidance channels 13 protrusions 14 Second shielding component 15. Bipolar plate main body.

Claims

1. A bipolar plate (1) for a fuel cell, the bipolar plate having an active region (3) and an edge region (4) surrounding the active region (3), the edge region being provided with a first medium guide (10) fluidly mechanically connected to a first through-hole (5) and a second medium guide (7) fluidly mechanically connected to a second through-hole (6), and the bipolar plate having a medium channel (8) extending through the active region (3) fluidly mechanically connecting the first through-hole (5) and the second through-hole (6), characterized in that, At least one of the media guides (10,7) includes a first sub-chamber (2) and a second sub-chamber (11) having the through portion (5,6), wherein the flow cross section of the media guide (10,7) is tapered between the first sub-chamber (2) and the second sub-chamber (11), and a shield (9) is inserted into or can be inserted into the second sub-chamber (11).

2. The bipolar plate (1) according to claim 1, characterized in that, The shield (9) is adjustablely supported in the second sub-chamber (11) by means of an actuator to adjust the flow cross-section of the through-hole (5,6).

3. The bipolar plate (1) according to claim 1, characterized in that, The shield (9) is movably supported in the second sub-chamber (11) by means of an actuator for adjusting the flow cross-section of the through-hole (5,6).

4. The bipolar plate (1) according to any one of claims 1 to 3, characterized in that, The tapering flow cross section between the first sub-chamber (2) and the second sub-chamber (11) is formed by at least one protruding protrusion (13).

5. The bipolar plate (1) according to any one of claims 1 to 3, characterized in that, The narrowed flow cross section between the first sub-chamber (2) and the second sub-chamber (11) is formed by two opposing protruding protrusions (13).

6. The bipolar plate (1) according to claim 4, characterized in that, The protrusion (13) forms a guide track for the shield (9).

7. The bipolar plate (1) according to any one of claims 1 to 3, characterized in that, Another medium guide (7, 10) in the medium guide also includes a first sub-chamber (2) and a second sub-chamber (11) having the through-hole (5, 6). Between the first sub-chamber (2) and the second sub-chamber (11), the flow cross section of the medium guide (7, 10) is constructed to be narrower, and a second shield (14) is inserted into or can be inserted into the second sub-chamber (11).

8. The bipolar plate (1) according to claim 7, characterized in that, The second shield (14) is adjustablely supported in the second sub-chamber (11) by means of an actuator to adjust the flow cross-section of the through-hole (5,6).

9. The bipolar plate (1) according to claim 7, characterized in that, The cross-sectional area of ​​the second sub-chamber (11) of the first medium guide (10) is different from the cross-sectional area of ​​the second sub-chamber (11) of the second medium guide (7).

10. A fuel cell stack, the fuel cell stack being formed by a plurality of fuel cells stacked together in a stacking direction, the fuel cells comprising at least one bipolar plate and membrane electrode assembly according to any one of claims 1 to 9.

Images