BIPOLAR PLATE WITH IMPROVED SEAL CONTACT PRESSURE UNIFORMITY

Abstract

A fuel cell stack assembly comprising at least one bipolar plate (12) including at least one first raised bead (14) comprising a first split corner (26); characterized in that the split corner (26) comprises a first concave joint (22) in the center.

Description

TECHNICAL FIELD

[0001] The present invention relates to bipolar plates and in particular to a fuel cell stack arrangement according to the preamble of claim 1 and a bipolar plate according to the preamble of claim 5, as essentially known from DE 11 2015 004 742 B4 or from WO 2009 / 043 600 A1. BACKGROUND

[0002] Fuel cells are electrochemical devices that combine a fuel, such as hydrogen, and an oxidizer, such as oxygen, to generate electricity. The term fuel cell is typically used to refer to either a single cell or a plurality of cells, depending on the context. A plurality of individual cells are typically bundled to form a stack, with the plurality of cells usually arranged in electrical series.

[0003] To reduce unwanted leakage of fluids between the plates, a seal is often used. The seal is disposed along a peripheral edge of the plates and / or around a perimeter of an opening through the plates. The seal may comprise an elastomeric seal, or alternatively, the metal plates may be molded to form a raised bead seal. The raised bead may be formed on a flat metal sheet adjacent to an outer edge of the sheet or adjacent to an edge surrounding an opening formed in the sheet. The raised bead may be formed in the metal sheet by a stamping operation, although other methods may be used. The raised bead seal may be substantially symmetrical about a longitudinal centerline of the raised bead seal. It should be noted, however, that the raised bead seal may be non-symmetrical about the longitudinal centerline.The raised bead seal may have a generally arcuate cross-sectional shape perpendicular to the longitudinal centerline. The generally arcuate cross-sectional shape of the raised bead seal provides an elastic response to a load in a direction normal to the flat metal sheet.

[0004] The raised bead seal can be compressed against an adjacent plate to form a seal against the adjacent plate. If sections of the raised bead seal have high stiffness and others have lower stiffness, the high-stiffness regions of the raised bead seal may prevent the lower stiffness regions of the raised bead seal from forming a tight seal. Accordingly, the raised bead seals should have uniform stiffness throughout all sections of the raised bead seal to form a tight seal around the entire peripheral edge of the plates and / or around the entire perimeter of the adjacent opening.

[0005] Sealant beads can prevent fluid leakage from adjacent plates within a fuel cell stack and facilitate the flow of reactants within the fuel cell stack. Under extreme loads, such as a vehicle crash, the bead can become overcompressed, leading to leakage within a fuel cell or fuel cell stack failure. In particular, sealant beads can have corners that can experience high contact pressure. Incorporating compounds at the corners of the beads can reduce the contact pressure. SUMMARY OF ILLUSTRATIVE VARIATIONS

[0006] According to the invention, a fuel cell stack arrangement is presented which is characterized by the features of claim 1.

[0007] Furthermore, according to the invention, a bipolar plate is presented which is characterized by the features of claim 5. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Selected examples of variations of the invention will be more fully understood from the detailed description and the accompanying drawings, wherein: Fig. 1 shows a variation of the bipolar plate; Fig. Figure 2 shows a variation of the bipolar plate with raised ridges; Fig. 3 shows a variation of the bipolar plate with raised ridges; Fig. 4 shows a variation of the bipolar plate with raised ridges; Fig. Figure 5 shows a variation of the bipolar plate with a raised ridge; Fig. Figure 6 shows a variation of a finite element analysis of the contact pressure measured at the corner of a raised bead of a bipolar plate; and Fig. Figure 7 shows a variation of a finite element analysis of the contact pressure measured at the corner of a raised bead of a bipolar plate. DETAILED DESCRIPTION OF THE ILLUSTRATIVE VARIATIONS

[0009] With reference to the Fig. 1-4; a fuel cell stack 10 may include at least one bipolar plate 12, which may include a first bead 14 and a second bead 18, wherein the first bead 14 and the second bead 18 may be parallel, and wherein the first and second bead are constructed and arranged to create a seal between the at least one bipolar plate 12 and an adjacent bipolar plate (not shown) within the fuel cell stack 10. The first bead 14 may include a first corner 16 and may include a first joint 22, which may be constructed and arranged to split the first corner 16 into a first split corner 26, wherein the first split corner 26 is constructed and arranged to reduce bead contact pressure and improve the uniformity of the seal contact pressure along the seal path.The second bead 18 may include a second corner 20 and may include a second joint 24 that may be constructed and arranged to split the second corner 20 into a second split corner 28, the second split corner 28 being constructed and arranged to reduce bead contact pressure and improve the uniformity of the seal contact pressure along the seal path.

[0010] With reference to Fig. 5, a fuel cell stack 10 may include at least one bipolar plate 12, which may include a first bead 14, wherein the first bead 14 may be constructed and arranged to create a seal between the at least one bipolar plate 12 and an adjacent bipolar plate (not shown) within the fuel cell stack 10. The first bead 14 may include a first corner 16 and may include a first joint 22, which may be constructed and arranged to split the first corner 16 into a first split corner 26, wherein the first split corner 26 is constructed and arranged to reduce bead contact pressure and improve the uniformity of the seal contact pressure along the seal path.

[0011] With reference to the Fig. 6 and Fig.7; and as an example, a bipolar plate having a sealing raised bead 14 including a corner 16 may have an average corner contact pressure (A) of approximately 3.13 MPa. A bipolar plate having a sealing raised bead 14 with a corner 16, which may include a joint 22 constructed and arranged to split the corner into a split corner 26, may have an average corner contact pressure (B) of approximately 2.71 MPa, thereby reducing bead contact pressure and improving the uniformity of the seal contact pressure along the seal path.

Claims

[1] A fuel cell stack assembly comprising at least one bipolar plate (12) including at least one first raised bead (14) comprising a first split corner (26); characterized by that the split corner (26) comprises a first concave connection (22) in the middle. [2] The fuel cell stack assembly of claim 1, further comprising a second raised bead (18) including a second split corner (28) including a second joint (24). [3] The fuel cell stack assembly of claim 1, further comprising a second raised bead (18) parallel to the at least one first raised bead (14). [4] The fuel cell stack assembly of claim 3, wherein the second raised bead (18) includes a second split corner (28) including a second joint (24). [5] Bipolar plate (12) having at least one first raised bead (14) comprising a first split corner (26); characterized bythat the first split corner (26) comprises a first concave connection (22) in the middle. [6] The bipolar plate (12) of claim 5, further comprising a second raised bead (18) comprising a second split corner (28) comprising a second joint (24). [7] The bipolar plate (12) of claim 5, further comprising a second raised bead (18) parallel to the at least one first raised bead. [8] The bipolar plate (12) of claim 7, wherein the second raised bead (18) includes a second split corner (28) including a second joint (24).

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