MICROSEAL FOR FUEL CELLS

Abstract

Micro seal (14) for a metal bead seal connection (40), the micro seal (14) comprising: a substantially horizontal surface (22); a first, substantially vertical surface (18) arranged at a first end (36) of the substantially horizontal surface (22), and a second, substantially vertical surface (20) arranged at a second end (38) of the substantially horizontal surface (22); and a contoured surface (32) arranged opposite the substantially horizontal surface (22), wherein the contoured surface (32) is an integral part of the first and second substantially vertical surfaces (18, 20) and is functionally configured to adhere to a section of a metal bead (16); wherein the contoured surface (32) and the substantially horizontal surface (22) define a micro-seal thickness (28); characterized by the fact that the micro-seal thickness (28) in a marginal region (26) is greater than the micro-seal thickness (28) in a central region (30), wherein the marginal region (26) is located near each of the first and second substantially vertical surfaces (18, 20) and the central region is located between the marginal region (26) for the first substantially vertical surface (18) and the marginal region (26) for the second substantially vertical surface (20).

Description

TECHNICAL AREA

[0001] The present invention relates to a micro-seal according to the preamble of claim 1 for fuel cells, as is known essentially from DE 10 2009 006 413 A1, and in particular a micro-seal for fuel cells to prevent buckling in the metal bead that is integrally incorporated into a fuel cell plate.

[0002] Further details of the state of the art can be found in DE 20 2014 004 456 U1. BACKGROUND

[0003] Fuel cells are used as an electrical energy source in many applications. In particular, their use as a replacement for internal combustion engines in automobiles has been proposed. A commonly used fuel cell design utilizes a solid polymer electrolyte (SPE) membrane or a proton exchange membrane (PEM) to ensure ion transport between the anode and cathode.

[0004] Fuel cells are generally electrochemical devices that convert the chemical energy of a fuel (hydrogen, methanol, etc.) and an oxidizer (air or pure oxygen) into electricity, heat, and water in the presence of a catalyst. Fuel cells produce clean energy during the electrochemical conversion of the fuel. This makes them environmentally friendly, as they produce no or very low emissions. Furthermore, fuel cells are high-performance systems that generate outputs ranging from a few watts to hundreds of kilowatts, with efficiencies far exceeding those of conventional combustion engines.

[0005] Furthermore, fuel cells produce quietly because they have few moving parts.

[0006] In proton exchange membrane (PEM) fuel cells, hydrogen is supplied to the anode as fuel, and oxygen is supplied to the cathode as an oxidant. The oxygen can be either in pure form (O₂) or as air (a mixture of O₂ and N₂). PEM fuel cells typically have a membrane electrode assembly (MEA) in which a solid polymer membrane has an anode catalyst on one side and a cathode catalyst on the opposite side. The anode and cathode layers of a typical PEM fuel cell are made of porous conductive materials, such as woven graphite, graphitized sheets, or carbon paper, so that the fuel can disperse across the surface of the membrane facing the fuel supply electrode.Each electrode has finely dispersed catalyst particles (e.g., platinum particles) supported by carbon particles, which promote the oxidation of hydrogen at the cathode and the reduction of oxygen at the anode. Protons flow from the anode through the ionically conductive polymer membrane to the cathode, where they combine with oxygen to form water, which is then discharged from the cell. The MEA is positioned between a pair of porous gas diffusion layers (GDLs), which are in turn sandwiched between a pair of non-porous, electrically conductive elements or plates (e.g., flow field plates). These plates act as current collectors for the anode and cathode and incorporate appropriate channels and openings for distributing the fuel cell's gaseous reactants over the surface of the respective anode and cathode catalysts.To efficiently produce electricity, the polymer electrolyte membrane of a PEM fuel cell must be thin, chemically stable, permeable to protons, non-electrically conductive, and gas-tight. In typical applications, individual fuel cells are connected in series to provide the required electrical power.

[0007] Conventional electrochemical fuel cell designs also include hardware components, such as plates, for reactant current separation, current collection, compression, and cooling (or heating). A bipolar plate performs several functions: (a) distributing the reactant current at the anode or cathode, (b) collecting the electrical current from the anode / cathode surfaces, and (c) preventing the mixing or crossing of the anode and cathode reactants in individual cells. An arrangement of two or more of these individual cells is called a stack. A cooling plate (often integrated with the bipolar plate) primarily distributes the coolant flow within a stack. The number and size of the individual cells in a fuel cell stack are generally chosen based on the system's power requirements.For convenient assembly and / or disassembly of a high-voltage or high-power fuel cell stack, several sub-stacks or modules can be combined into a single stack. The modules represent stacks of individual cells, a certain number fewer than those that ultimately comprise the finished stack, as understood by most professionals in this field. If the stack forms a PEM fuel cell, it is often referred to as a PEM stack.

[0008] In a conventional PEM stack configuration, sealing hardware components and active cells to effectively separate anode and cathode reactant streams and prevent leakage and mixing is a critical engineering challenge with a direct impact on stack performance and reliability. These factors, along with the design of the sealing system and manufacturing capabilities, directly affect the overall cost of the PEM fuel cell system.

[0009] Leakage or cross-mixing of reactants and coolant between different cells and multiple elements of a cell is typically prevented by pressure or adhesive seals, which sometimes employ elastomeric and / or adhesive materials. For example, as described in US Patent 6,080,503 A, the surfaces of the membrane electrode assembly (MEA) around the electroactive area are bonded to support plates. The adhesive bond consists of a bonding agent that encapsulates the edge portion of the MEA. In another example, US Patent 5,176,966 A, seals are formed by impregnating the back layer (gas diffusion layer or GDL) of the electrodes with a sealing material (silicone rubber) that surrounds the fluid flow orifices and the electroactive portion of the MEAs.Alternatively, the sealing material is deposited into the grooves that form on the outer surface of the MEA electrodes; the grooves enclose the fluid flow openings and the electroactive sections of the MEAs.

[0010] Regardless of whether printing or adhesive materials are used, the materials are generally applied, fastened, molded, or coated onto the surfaces to be sealed. These processes are labor-intensive, costly, and unsuitable for high-volume production. The variability of these processes can also affect the reliability and durability of the seals, which in turn negatively impacts production yields. Furthermore, these sealing processes and / or materials would exhibit compatibility and / or durability issues in high-temperature stacking applications due to highly concentrated acidic environments and / or high operating temperatures (e.g., 120°C to 250°C).

[0011] An adhesive-based PEM stack assembly process was described in a World Publication WO 02 / 43173 A1 based on US patent application US 2002 / 0068212 A1, which includes three sealant application steps to produce a resin-bonded (encapsulated) PEM stack. These three steps are as follows: (1) sealing the unused manifold openings / ports on each of the fluid flow plates with flow field structure (for example, on the cathode flow field surface, the ports for fuel and coolant flow are sealed around their perimeter to prevent mixing of these inlet flows); (2) sealing all ports within the MEAs to prevent reactants from leaking out within the MEA layers; and (3) sealing a remainder of the desired sealing surfaces in the stack assembly.Sealing the remaining sealing surfaces involves layering all pre-compacted components within a mold or fixture, applying a curable resin (sealant) around the perimeter, and injecting the resin into the stacked assembly (cassette) using vacuum transfer or injection molding technology. After curing, the resin provides structural support and edge sealing across the entire assembly. The resulting fuel cell cassette / stack is held between pressure plates with distributors and compression elements.

[0012] The further development of the three-stage PEM stack / cassette assembly process is described in US Patent 7,306,864 B2, which can be conveniently used for the high-volume production of stacks using a single-stage injection molding process. In this approach, all stack components, including support plates, stack cooling plates, compression and power pickup plates, and MEAs, are stacked accordingly and placed in a single mold. The sealing material (two-part silicone or other adhesive resin) is pressed into the complex openings (using pressure or vacuum) while the stacked assembly is held under optimal pressure to ensure minimal resistance between the individual electrical contact surfaces.Once the viscous sealant fills all desired sealing spaces (including the MEA edges) and the space around the stack assembly, the mold is placed in a low-temperature oven to cure the resin. The encapsulated stack is then removed from the mold.

[0013] With reference to Fig. 1A The micro-gasket material 124 is transferred through a sieve 122 onto a metal bead 120. The final shape of the traditional micro-gasket 114 is controlled by the bead shape (gravity), the stencil design, the viscosity of the ink, and the surface energy. Unfortunately, as in Fig. As shown in Figure 1B, if the metal bead deforms, the sealing contact is not guaranteed, especially in the central area, where the metal bead 116 deforms. If the sealing contact is not maintained, the robustness against misalignment of the central axes 117 is reduced, as shown in Figure 1B. Fig. Figure 1C illustrates that for a number of metal properties and metal bead geometries, including metal thickness specifications, it may not be possible to sufficiently improve the buckling load of the metal bead by changing the metal shape itself.

[0014] Accordingly, there is a need for a new micro-seal design for fuel cells that improves the contact width of the seals and increases robustness against misalignment, further reducing the risk of leaks in the fuel cell. SUMMARY

[0015] According to the invention, a micro-seal with the features of claim 1 for a metal bead seal connection is presented.

[0016] Furthermore, a metal bead sealing connection for a fuel cell plate is presented, which is characterized by the features of claim 5.

[0017] The present invention and its special features and advantages will become more apparent from the following detailed description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] These and other features and advantages of the present invention will become apparent from the following detailed description, best mode, claims and accompanying drawings: Fig. Figure 1A is a schematic cross-sectional view of a conventional micro-seal for a metal bead seal, in which the seal is applied to the bead using a template method. Fig. 1B is a schematic cross-sectional view of the conventional micro-seal of Fig. 1A, when the bead and seal are pressed together. Fig. Figure 1C is a schematic cross-sectional view of the conventional metal bead gasket connection with the conventional micro-gaskets when the beads and gaskets are misaligned while not under pressure. Fig. Figure 2A is a schematic cross-sectional view of a first embodiment of a micro-seal according to the present invention, in which the metal bead and the micro-seal are not compressed together. Fig. Figure 2B is a schematic cross-sectional view of the first embodiment of a micro-seal in Fig. 2A, where the metal bead and the micro-seal are pressed together. Fig. Figure 3A is a schematic cross-sectional view of a micro-seal according to a first embodiment of the manufacturing process of the present invention, in which the micro-seal material is applied to the metal bead. Fig. Figure 3B is a schematic cross-sectional view of a microseal according to a first embodiment of the manufacturing method of the present invention, wherein a load is applied uniformly to the microseal material to form a substantially horizontal surface. Fig. Figure 4A is a schematic cross-sectional view of a micro-seal according to a second embodiment of the manufacturing process of the present invention, wherein the micro-seal material is applied to the metal bead in a first and second application. Fig. Figure 4B is a schematic cross-sectional view of a micro-seal according to the second embodiment of the manufacturing process of the present invention, wherein a substantially horizontal surface is formed in the micro-seal material. Fig. Figure 5 is a schematic cross-sectional view of the conventional metal bead seal connection with the micro-seals according to the various embodiments of the present invention, in which the beads and the seals are not compressed together and are misaligned. Fig. Figure 6 is an example of a process flow diagram that illustrates an example of a method for manufacturing the first embodiment of the micro-seal of the present invention. Fig. Figure 7 is an example of a process flow diagram that illustrates an example of a method for manufacturing the second embodiment of the micro-seal of the present invention.

[0019] Identical reference numbers refer to identical parts in the description of the different views of the drawings. DESCRIPTION

[0020] With reference to the Fig. 2A, Fig. 4B and Fig. Figure 5 of the present invention provides for an improved micro-seal design 14 which better maintains the connection between metal beads in a fuel cell plate. As shown, the micro-seal 14 comprises a substantially horizontal surface 22, first and substantially vertical surfaces, and a contoured surface 32. The first substantially vertical surface 18 can be arranged at a first end 36 of the substantially horizontal surface 22. The second substantially vertical surface 20 can be arranged at a second end 38 of the substantially horizontal surface 22. The contoured surface 32 can be arranged opposite the substantially horizontal surface 22, as shown in the preceding figures.The contoured surface 32 is an integral part of the first and second substantially vertical surfaces 18, 20 and is positioned between them, as shown in the cross-sectional images. The contoured surface 32 is configured to adhere to a section of a metal bead 16, while the metal bead 16, as shown in the cross-sectional images, Fig. 2B is shown, compressed under load 19.

[0021] With reference to Fig. Figure 2A shows an uncompressed micro-seal 14 according to various embodiments of the present invention. The micro-seal material can be formed from any number of elastomer materials, including but not limited to EPDM, HNBR, NBR, VMQ, FVMQ and FKM; therefore, the micro-seal 14 generally compresses when a load is applied. Fig. Figure 2B illustrates the microseal 14 under pressure or in a compressed state. As in both Fig. 2A and Fig. As shown in Figure 2B, the substantially horizontal surface 22 is functionally configured to maintain a substantially flat surface orientation under vertical loading—both in the compressed and uncompressed states. The entire surface area of ​​the contoured surface 32 of the microseal 14 is functionally configured to flex, together with the advanced microseal 14, when a load 19 is applied, as shown in the Fig. 2A and Fig. 2B is shown.

[0022] The contoured surface 32 and the substantially horizontal surface 22 for all micro-seals 14 of the present invention define a micro-seal thickness 28, 28'. The micro-seal thickness 28 is the thickness in the uncompressed state, while the micro-seal thickness 28' is the thickness in the compressed state. As shown in Fig. As shown in Figure 2A, the micro-seal thickness 28 in a marginal region 26 is greater than the micro-seal thickness 28 in a central region 30 in the uncompressed state. The marginal region 26 can be defined as the area of ​​the micro-seal 14 that is near each of the first and second substantially vertical surfaces, and the central region 30 can be located between the marginal region 26 for the first substantially vertical surface 18 and the marginal region 26 for the second substantially vertical surface 20. As shown in Fig. 2A and Fig. As shown in Figure 5, the micro-gasket thickness 28 varies along a width of the substantially horizontal surface 22 when the micro-gasket is initially positioned on the metal bead 16. The micro-gasket thickness 28 is greater at or near each of the first and second substantially perpendicular walls (edge ​​region 26) than the micro-gasket thickness 28 in the central region 30 of the micro-gasket. However, as shown in Fig. As shown in Figure 2A, in the first embodiment the micro-seal 14 is a molded part that can be attached to a metal bead 16.

[0023] With reference to Fig. Figure 5 shows a metal bead sealing connection 40 for a fuel cell plate, wherein the micro-seals 14 of the Fig. 2A and Fig. 2B are implemented. As shown, a first metal bead 16 has a first micro-seal 14 that adheres to at least one section of the first metal bead 16. A second metal bead 16' with a second micro-seal 14 is also shown, the second micro-seal 14' adhering to at least one section of the second metal bead 16'. The second metal bead 16' and the second micro-seal 14' can be compressed against at least one section of the first micro-seal 14 and the first metal bead 16.

[0024] The micro-seals 14, 14', which are in the metal bead sealing connection 40 of Fig. The components used in Figure 5 also each include a substantially horizontal surface 22, first and second substantially vertical surfaces 18, 20, and a contoured surface 32. The first substantially vertical surface 18 can be located at a first end 36 of the substantially horizontal surface 22, and the second substantially vertical surface 20 can be located at a second end 38 of the substantially horizontal surface 22. As shown, the contoured surface 32 can be located opposite the substantially horizontal surface 22 at the opposite ends 42 of the first and second substantially vertical surfaces 18, 20. The contoured surface 32 can be an integral part of the first and second substantially vertical surfaces 18, 20.

[0025] With reference to Fig. 5 is the micro-seal 14 of Fig. 2A is shown in a metal bead sealing connection 40, wherein each of the first substantially horizontal surfaces 22 is functionally configured to maintain a substantially flat orientation in a compressed state (shown in Fig. 2B and Fig. 5) as well as an uncompressed state (represented in Fig. 2A). Consequently, the metal bead seal connection 40 maintains contact between each metal bead 16, 16' during the printing process, even if the central axes 17, 17' of the metal bead 16, 16' are not perfectly aligned, as in Fig. Figure 5 illustrates this. As shown, each of the first and second substantially vertical surfaces 18, 20 and the contoured surface 32 are functionally configured to have a surface orientation that may or may not change between the compression and non-compression states, while the substantially horizontal surface 22 maintains its orientation. It is understood that the orientation of the first and second substantially vertical surfaces 18, 20 and the contoured surface 32 can change, provided that each contoured surface 32 (for the first and second micro-seals 14, 14') is functionally configured to bond and bend with at least one section 44 of one of the first and second metal beads 16, 16'. Therefore, each contoured surface 32 is functionally configured to bend elastically under compression as the first and second metal beads 16, 16'.The vertical surfaces 18, 20 can bend, while the contoured surfaces 32 bend with the metal bead 16, 16', as in . Fig. 2B is shown.

[0026] Accordingly, the new micro-seal shape (formed from the first and second vertical surfaces 18, 20, the contoured surface 32, and the horizontal surface 22) distributes and transfers the vertical pressure load more effectively to the side walls 23 in the metal bead 16. Due to the redistribution of the load 19, the "essentially horizontal surface 22" of the micro-seal 14 remains "essentially horizontal" during compression. This improved load transfer and distribution also increases the buckling load of the sealing connection 40.

[0027] Again, with reference to Fig. Figure 5 defines the contoured surface 32 and the substantially horizontal surface 22 for each of the first and second micro-seals 14, 14', a micro-seal thickness 28. Furthermore, the micro-seal thickness 28 can vary along a width of the micro-seal 14, 14' before compression, with the thickness 28 increasing towards the first and second edges of the seal (“edge regions 26”), and the thickness 28 being comparatively less in the central region 30 of the micro-seal 14 than in the edge regions 26. During compression, the micro-seal thickness 28' can still vary along the width 45. However, the thickness 28' can vary less under pressure due to the compressive load (or vertical load).

[0028] At the in Fig. Figure 6 describes a first embodiment of method 62 for producing a micro-seal 14. The first embodiment of method 62 comprises the following steps: (1) applying a first application of a micro-seal material to a metal bead, wherein the micro-seal material is in a viscous state 70; (2) forming a substantially horizontal surface in the micro-seal material 74; and (3) curing the micro-seal material 78. These steps are described in Fig. Step 6 is shown as fixed, while the other steps are shown as phantoms to indicate additional steps that can be implemented.

[0029] The additional steps for the first embodiment of method 62 may include: (1) partial curing of the first application of the micro-seal material 76; (2) applying a compressive load over a width of the partially cured micro-seal material 72 – forming a substantially horizontal surface as described above – while the micro-seal material continues to cure; (3) removing the compressive load 78; and (4) complete curing of the first application of the micro-seal material, forming a micro-seal 80.

[0030] With reference to the Fig. 3A and Fig. Figure 3B shows the micro-seal 14 according to the first embodiment of the manufacturing process. As shown in Fig. 3A shows the micro-sealing material 24 produced according to the first embodiment (shown in Fig. 6) initially applied in liquid or viscous form to the metal bead, optionally via a sieve mesh template 50. Upon initial application and due to its viscosity, the surface 48 is initially not substantially horizontal (or straight), as in Fig. Figure 2A shows that the micro-sealing material 24 can partially harden, so that it is in a gel-like state. Once the gel-like state is reached, a pressure load (or plate) 46 can be applied uniformly to the top surface 48 of the micro-sealing material 24, forming a substantially horizontal surface 22, as shown in Figure 2A. Fig. 3B is shown. As described, the in Fig. The load 46 shown in Figure 3B is maintained while the micro-sealing material 24 continues to cure, or until the micro-sealing material 24 is fully cured, as shown in Figure 3B. Fig. 6 shown. In the micro-seal 14 of Fig. 3B, the essentially vertical surfaces 18, 20, as shown, exhibit a significant curve in each surface.

[0031] With reference to Fig. 7 includes a second embodiment of method 62' for producing a fuel cell micro-seal comprising the following steps: (1) applying a first application of a micro-seal material to a metal bead, wherein the micro-seal material is in a viscous state 82; (2) applying a second application of the micro-seal material to the metal bead adjacent to the first application of the micro-seal material, wherein the micro-seal material from the first and second applications is in a viscous state 84; (3) forming a substantially horizontal surface in the micro-seal material 86; and (4) curing the micro-seal material 88. It is understood that in the step of forming a substantially horizontal surface in step 86, the first and second applications of the micro-seal material (elements 52 and 54 in Fig. 4A) are functionally configured to flow against each other, thereby forming the substantially horizontal surface 22 (shown in Fig. 4B).

[0032] With reference to Fig. Figure 4A shows the first and second applications 52, 54 of the viscous micro-sealing material 24, wherein the first application 52 and the second application 54 are arranged adjacent to each other. Fig. 4A a sieve 50 is used to feed the micro-sealing material 24 to the metal bead 16. Fig. Figure 4B illustrates the final result of the micro-seal 14 once the first and second applications 52, 54 of the viscous micro-seal material flow against each other, forming an essentially horizontal surface 22. It is understood that the final result of the micro-seals 14 in the Fig. 2A, Fig. 3B and Fig. 4A have the same or similar configurations, wherein the micro-seal thickness 28 varies along a width 56 of the substantially horizontal surface 22 when the micro-seal thickness 28 is arranged on the metal bead 16 in an uncompressed state (shown in the Fig. 2A and Fig. 4B). The micro-seal thickness 28 is greater at or near each of the first and second substantially perpendicular walls (edge ​​region 26) than the micro-seal thickness 28 in the middle region 30 of the micro-seal.

Claims

[1] Micro seal (14) for a metal bead seal connection (40), comprising the micro seal (14): a substantially horizontal surface (22); a first, substantially vertical surface (18) arranged at a first end (36) of the substantially horizontal surface (22), and a second, substantially vertical surface (20) arranged at a second end (38) of the substantially horizontal surface (22); and a contoured surface (32) arranged opposite the substantially horizontal surface (22), wherein the contoured surface (32) is an integral part of the first and second substantially vertical surfaces (18, 20) and is functionally configured to adhere to a section of a metal bead (16); wherein the contoured surface (32) and the substantially horizontal surface (22) define a micro-seal thickness (28); characterized by , that the micro-seal thickness (28) in a marginal region (26) is greater than the micro-seal thickness (28) in a central region (30), wherein the marginal region (26) is located near each of the first and second substantially vertical surfaces (18, 20) and the central region is located between the marginal region (26) for the first substantially vertical surface (18) and the marginal region (26) for the second substantially vertical surface (20). [2] Micro seal (14) for a metal bead seal connection (40) according to claim 1, wherein the substantially horizontal surface (22) is configured to maintain a substantially flat surface orientation when subjected to a vertical load. [3] Micro seal (14) for a metal bead sealing connection (40) according to claim 2, wherein a total surface area of ​​the contoured surface (32) is configured to bend together with a metal bead (16). [4] Microseal (14) for a metal bead seal connection (40) according to claim 1, wherein the microseal thickness (28) varies along a width of the substantially horizontal surface (22). [5] Metal bead sealing connection (40) for a fuel cell plate, comprising the metal bead sealing connection (40): a first metal bead (16) with a first micro-seal (14); and a second metal bead (16') with a second micro-seal (14) which is compressed against at least one section of the first micro-seal (14) and the first metal bead; wherein each of the first and second micro-seals (14) is designed according to claim 1. [6] Metal bead sealing connection (40) for a fuel cell according to claim 5, wherein each of the first substantially horizontal surfaces (22) is functionally configured to maintain a substantially flat orientation in a compressed state as well as in an uncompressed state. [7] Metal bead sealing connection (40) for a fuel cell according to claim 6, wherein each of the first and second substantially vertical surfaces (18, 20) and the contoured surface (32) are operationally configured to have a surface orientation that alternates between the compressed state and the uncompressed state.

Images