Leakproofing device for fuel cell, unit and fuel cell comprising such a device

Abstract

Leakproofing device for a fuel cell intended to be interposed between an Electrodes Membrane Assembly and a polar or bipolar plate of a fuel cell unit, the device consisting of a rigid frame and of a leakproofing seal integral with the frame, the frame furnished with the leakproofing seal defining a plurality of apertures through the device, the apertures being delimited by the leakproofing seal.

Claims

1. An elementary cell of a fuel-cell stack, comprising two polar or bipolar stack plates sandwiching a membrane electrode assembly and two sealing devices each one of which is placed on an opposing side of the membrane electrode assembly and facing a corresponding plate in order to ensure reactive-fluid circuits are sealably separated in the cell and to ensure a set spacing within the cell, wherein: each sealing device comprises a rigid frame and a sealing bead securely fastened to the frame; the frame is equipped with the sealing bead defining a plurality of apertures through the device; the apertures are bounded by the sealing bead; the frame of each sealing device comprises centering holes and centering pins, the centering pins of one of the sealing devices interacting with centering holes formed in the other sealing device through orifices formed through the membrane electrode assembly in order to ensure the membrane electrode assembly is centered with respect to the plates; and at least one portion of an edge bounding at least one aperture consists only of a sealing bead.

2. The cell of claim 1, wherein the two sealing devices are of identical structure.

3. The cell of claim 1, wherein the two sealing devices are securely fastened via a pliable flexible joint.

4. The cell of claim 1, wherein the two sealing devices are securely fastened via a demountable joint.

5. The cell of claim 1, wherein peripheries of the facing plates each contain a notch level with a border of the MEA.

6. The cell of claim 5, wherein the notch is a bevel.

7. The cell of claim 1, wherein at least one of the pins is received into a corresponding housing in the plates of the cell.

8. The cell of claim 1, wherein each sealing device comprises two pins and two centering holes.

9. The cell of claim 1, wherein, in a plane of the frame and relative to a center of the frame, each pin is placed symmetrically to a centering hole.

10. A proton exchange membrane fuel-cell stack comprising a stack of a plurality of the elementary cells of claim 9.

11. The cell of claim 1, wherein the frame further comprises clamping holes provided for the passage of a clamping system.

12. The cell of claim 11, wherein the clamping system comprises tie rods.

13. The cell of claim 1, wherein: the sealing device comprises sealing bead portions on either side of a plane defined by the frame; and in cross section through a plane perpendicular to the plane of the frame, the frame is located between ends of the sealing bead that are located on either side of the plane of the frame.

14. The elementary cell of a fuel-cell stack of claim 1, wherein said cell comprises two polar stack plates, using at least one sealing device positioned between the two faces of the plates dedicated to cooling.

15. An elementary cell of a fuel-cell stack, comprising two polar or bipolar stack plates sandwiching a membrane electrode assembly and two sealing devices each one of which is placed on an opposing side of the membrane electrode assembly and facing a corresponding plate in order to ensure reactive-fluid circuits are sealably separated in the cell and to ensure a set spacing within the cell, wherein: each sealing device comprises a rigid frame and a sealing bead securely fastened to the frame; the frame is equipped with the sealing bead defining a plurality of apertures through the device; the apertures are bounded by the sealing bead; the frame of each sealing device comprises centering holes and centering pins, the centering pins of one of the sealing devices interacting with centering holes formed in the other sealing device through orifices formed through the membrane electrode assembly in order to ensure the membrane electrode assembly is centered with respect to the plates; and the sealing device comprises a plurality of peripheral apertures formed around a central aperture, the central aperture being intended to be superposed on an active area of a membrane electrode assembly, at least one portion of the border bounding the central aperture being common to the respective borders of the peripheral apertures, and in that the portions of the borders common to the central aperture and to the peripheral apertures consist only of a sealing bead.

16. The cell of claim 15, wherein the sealing device comprises at least one pair of adjacent peripheral apertures placed along two adjacent and perpendicular edges of the frame, respectively, the two adjacent peripheral apertures comprising a common portion that is not common to the central aperture and that consists only of a sealing bead, the sealing bead, without the frame, being T-shaped level with said two adjacent peripheral apertures.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Other particularities and advantages will become apparent on reading the following description, given with reference to the figures in which:

(2) FIG. 1 shows a top view of a sealing device according to one possible example embodiment of the invention;

(3) FIG. 2 shows a top view of a detail of the sealing device in FIG. 1, merely illustrating its rigid frame;

(4) FIG. 3 shows a perspective view of a detail of the sealing device in FIG. 1, merely illustrating the sealing bead (a hard or soft seal) and centering pins;

(5) FIG. 4 shows a schematic partial perspective view illustrating one example of a stack of fuel cells according to one possible embodiment of the invention;

(6) FIG. 5 shows a perspective view of a detail of the sealing device in FIG. 1, fitted to a stack plate;

(7) FIG. 6 shows a cross-sectional view of a detail of a detail of the sealing device in FIG. 1, fitted to a stack plate;

(8) FIG. 7 illustrates a cross-sectional view of a fuel-cell stack cell equipped with a sealing device according to the invention on either side of the proton exchange membrane;

(9) FIG. 8 schematically illustrates one example fuel-cell stack cell architecture in which the invention may be implemented; and

(10) FIG. 9 illustrates a cross-sectional view of a fuel-cell stack cell equipped with a sealing device according to the invention illustrating the fixture of a centering pin.

DETAILED DESCRIPTION OF THE INVENTION

(11) The sealing device illustrated in FIG. 1 comprises a preferably rigid (though possibly ductile) frame of generally flat shape (see FIG. 2). The frame 1 for example consists of at least one of the following materials: an elastomer, a thermoplastic, a thermoset, a thermoplastic elastomer, a metal, an alloy, graphite. Preferably, the frame 1 has a thickness smaller than 3 mm. For example, the frame 1 has a thickness comprised between 0.1 and 0.5 mm and preferably 0.2 mm. As illustrated, the frame 1 may have a substantially square shape. A sealing bead 2 is overmolded onto the frame 1 (see FIG. 3).

(12) The sealing bead 2 for example consists of at least one of: an elastomer, a thermoplastic, a thermoset, a thermoplastic elastomer. Preferably, the sealing bead 2 is overmolded on either side of the frame 1 (see FIGS. 5 and 6).

(13) As may be seen in FIGS. 5 and 6, the sealing bead 2 may be profiled in order to make it easier to compress. For example, the sealing bead 2 may be double lipped.

(14) FIG. 7 illustrates a cross-sectional view of a fuel-cell cell in which two stack plates 6, 66 sandwich an MEA (membrane electrode assembly) 5. A sealing device 3 is placed on either side of the membrane electrode assembly (MEA), between the MEA and the corresponding plate 6, 66. FIG. 7 also shows, placed on the upper plate 6, a cooling-circuit seal 14 and the lower plate 66 of the adjacent cell.

(15) As may especially be seen in FIG. 6 in transverse cross section, the rigid frame 1 is preferably located at the midpoint of the sealing bead 2. In this way, the frame 1 may be placed at distance from the adjacent elements of the stack (see FIGS. 6 and 7) and thus the frame 1 never makes contact with the reactive gases, the reaction products, the coolant and/or the active area of the cell. This makes it possible to considerably decrease the constraints on the chemical compatibility of the rigid frame 1 with the stack and to decrease significantly the cost thereof. The rigid frame 1 therefore does not make contact with the reactive elements of the cell because it is centered on the sealing bead and does not project therebeyond into the manifolds of the cell.

(16) The sealing bead 2 for example has a thickness on each side of the frame 1 preferably comprised between 0.2 mm and 2 mm and therefore has an overall thickness preferably comprised between 0.4 mm and 4 mm. The sealing bead 2 for example has a width (in the plane of the frame 1) for example comprised between 2 and 3 mm.

(17) The rigidity of the frame 1 makes it easier to manually position on a stack plate or on an MEA. The same rigidity makes it possible to envision automatization of the positioning of the seal during assembly without modification of the latter.

(18) As may be seen in FIG. 1, the frame 1 comprises, preferably near its periphery, clamping holes 10 provided for the passage of the clamping system of the stack, such as tie rods for example. For example, the frame comprises four clamping holes 10 placed near the midpoint of the four sides of the frame 1, respectively. The presence of clamping holes 10 through the frame 1 makes it possible, if needs be, to avoid using an adhesion promoter before the overmolding of the sealing bead 2 and thus allows the chemical integrity of the MEA 5 to be preserved.

(19) The frame 1 may also comprise one or more centering pins 12 and centering holes 11. These centering pins 12 make it possible in the assembly step to align the MEA on a stack plate 6, and vice versa. These centering pins 12 also make it possible to poka yoke the seal 3 on the plate 6, 66 and to poka yoke the MEA on the plate 6, 66 so that the anode side of the MEA is correctly located on the anodic side of the plate and so that the cathode side of the MEA is correctly located on the cathodic side of the plate.

(20) Advantageously, each sealing device 3 comprises centering holes 11 and centering pins 12. In this way, and as illustrated in FIG. 9, the centering pins 12 of one of the sealing devices 3 of a cell may interact with centering holes 11 formed in the other sealing device 3 of the cell (and vice versa). The centering pins 12 may especially pass through orifices formed through the membrane electrode assembly 5 located between the two sealing devices. As illustrated in FIG. 9, the one or more pins 12 may also interact with a corresponding housing in the plates 6, 66 of the cell.

(21) This makes it possible to precisely align and position the MEA 5 with respect to the plates 6, 66.

(22) As may be seen in FIGS. 1 to 3, the sealing device 3 comprises a plurality of apertures 7, 8, 9, 13 bounded by the sealing bead 2. These apertures 7, 8, 9, 13 form respective passages for fluids. For example, the device comprises a plurality of peripheral apertures 7, 8, 9 formed around a central aperture 13. The central aperture 13 is intended to be superposed on an active area of a membrane electrode assembly. The peripheral apertures 7, 8, 9 for example comprise two radially opposite apertures 7 forming air inlet and outlet manifolds, respectively, two other radially opposite apertures 8 forming hydrogen inlet and outlet manifolds, respectively, and two opposite pairs of apertures 9 forming coolant inlet/outlet manifolds.

(23) As illustrated, the border bounding the central aperture 13 may be common to the respective borders of the peripheral apertures 7, 8, 9. Preferably, as may be seen in FIGS. 2 and 3, the border portions common to the central aperture 13 and to the peripheral apertures 7, 8,9 consist only of a sealing bead 2, i.e. the frame 1 is not present in these locations. As may be seen in FIG. 5, this configuration allows, in the assembled position, the sealing bead 2 to be placed in a seal groove of a plate 6, as close as possible between a manifold and the active area of a cell.

(24) As may be seen in FIG. 6, in order to prevent the frame 1 from being stressed during the clamping of the stack and in order to make it easier to position the sealing device 3, the area of the (for example monopolar) plate facing the frame 1 may be locally recessed or set back. This is preferably possible only for the zones of the plate that extend from the periphery of the sealing bead 2 as far as toward the exterior of the cell (to the left in FIG. 5). Specifically, decreasing the height of the area of the plate 6 facing the MEA would risk promoting internal gas leaks. In addition, in order to isolate electrically the two polar plates 6, 66, between which the MEA is located, and as may be seen in FIGS. 6 and 7, the peripheral ends of said plates may be beveled. This makes it possible to avoid the MEA projecting beyond the seal and makes it possible to align elements of the stack during assembly.

(25) FIG. 4 schematically illustrates an elementary fuel-cell stack cell comprising two polar or bipolar stack plates 6, 66 sandwiching a membrane electrode assembly 5. Two sealing devices 3 such as described above are placed on either side of the membrane electrode assembly 5, respectively, and facing a corresponding plate 6, 66.

(26) The sealing devices 3 thus ensure the various reactive-fluid circuits are sealably separated in the cell.

(27) The absence of contact with the MEA 5 during the assembly greatly decreases the risk of chemical contamination of the stack core. The architecture of the device and if needs be the materials used also contribute thereto.

(28) By placing the rigid frame 1 at the midpoint of the height of the sealing bead 2, an identical sealing device 3 may be used anode-side and cathode-side. The number of different constituent parts of the stack may thus be decreased and the risk of fitting errors is decreased.

(29) In one possible variant, the two sealing devices 3 on the two sides of the MEA may be connected by a flexible material and thus form a single part.

(30) For example, two sealing devices 3 are securely fastened via a demountable joint (on the exterior or through centering pins 12). This makes it possible to imprison elements and thus form fuel-cell stack subassemblies.

(31) It may therefore easily be conceived that, while having a simple and inexpensive structure, the device allows not only: a constant distance to be maintained between two (for example composite) stack plates 6, 66; but also leak tightness to be ensured and the fuel-cell stack to be easily and precisely assembled and disassembled.

(32) The device is compatible with various MEAs.

(33) The device also allows the MEA to be aligned on the plate 6, 66 or vice versa (via the system of pins 12 and holes 11).

(34) This type of sealing device may also be used to seal a liquid cooling network.

(35) While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

(36) The singular forms a, an and the include plural referents, unless the context clearly dictates otherwise.

(37) Comprising in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing i.e. anything else may be additionally included and remain within the scope of comprising. Comprising is defined herein as necessarily encompassing the more limited transitional terms consisting essentially of and consisting of; comprising may therefore be replaced by consisting essentially of or consisting of and remain within the expressly defined scope of comprising.

(38) Providing in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

(39) Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

(40) Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

(41) All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.