TW201409819A - Fuel cell stack assembly - Google Patents

Abstract

A fuel cell stack assembly comprises a plurality of fuel cells in a stack, the stack defining two opposing parallel end faces. An end plate assembly is provided at each opposing end face of the stack. The end plate assemblies are coupled together to thereby maintain the fuel cells in the stack under compression. At least one, and preferably both, of the end plate assemblies comprises: a master plate defining a master compression face; a slave plate defining a slave compression face, the slave compression face facing the master compression face and being in compressive relationship therewith; and a plastic or viscoplastic interface disposed between the master compression face and the slave compression face. The plastic or viscoplastic interface may be bounded by a containment structure extending along a peripheral edge of the interface.

Description

Fuel cell stacking assembly

The present invention relates to a method and apparatus suitable for assembling an electrochemical fuel cell stack.

The fuel cell stack includes a series of individual fuel cells that are stacked in a stack. Each cell itself may include various layered elements such as a polymer electrolyte membrane, a gas diffusion layer, a fluid flow plate, and various active surfaces for maintaining fluid tightness and dispensing fluid fuel and oxidant to the membrane. Seal the air cushion. At each end face of the stack, a pair of pressure end plates coupled together by tie rods are conventionally used to hold the stack together and maintain compression on the stacked cells.

Most importantly, the pressure applied by the end plates to the ends of the stack of fuel cells is sufficiently uniform throughout the surface of the stack such that all of the individual components of the stack are maintained in proper compression relationship with each other. in. In particular, the sealing gasket must be maintained in proper compression throughout the entire area of each fuel cell to ensure that the flow path of the fluid can be properly defined so that the fuel and/or oxidant can be properly transported to each The active surface of the battery does not leak.

Traditionally, it has been possible to maintain a uniform pressure by providing a strong and robust end plate that maintains sufficient excess pressure throughout the entire surface of the stack end. This creates large and heavy end plates to ensure that these end plates do not create significant distortion under the necessary pressure and do not impart compressive forces unevenly. Using large, heavy end plates results in a heavier and larger fuel than needed Battery stack. An alternative approach is to use a lighter weight end plate, but provide an additional mechanism to mitigate the torsional effect of the end plate structure when compressive forces are applied. This can be a spacer that is centered between the end plate and a first internal stacked component.

One method described in U.S. Patent No. 6,004,072 is the use of a strap or strap around a stack of fuel cells for transporting loads via the end plates and an array of adjustable elements that control compression The distribution of the load is used to minimize the size and weight of the clamping mechanism.

Another method described in U.S. Patent No. US 2006/0194094 uses an end plate having a pressure shield and a carrier plate that is convexly curved toward the stack, the carrier plate acting as A transition element for transmitting a compressive force to a planar element of the stack of fuel cells.

Both documents acknowledge the importance of maintaining a uniform pressure distribution.

One problem with fuel cell operation is that the temperature of the fuel cell stack can be significantly increased. As a result, thermal expansion of the fuel cell stack can occur, causing a change in the load on the end plates, and thus changing the degree of twisting. This may adversely affect the mechanism of the torsional compensation of the end plates such that under all operating states of the fuel cell stack no uniform distribution of forces is applied throughout the stack.

It is an object of the present invention to provide an improved way to ensure a good pressure distribution throughout the end faces of the fuel cell stack in varying states.

According to one aspect, the present invention provides a fuel cell stack assembly comprising: a plurality of fuel cells in a stack, the stack defining two opposing parallel end faces; each phase of the stack An end plate assembly is provided at the end faces of the pair, the end plate assemblies being coupled together to thereby maintain the fuel cells in the stack in a compressed state; wherein the end plate assemblies are At least one of the following includes: a main board defining a main compression surface; a subordinate board defining a subordinate compression surface facing the main compression surface and in a compressed relationship with the main compression surface; A hydraulic, plastic or viscoplastic interface disposed between the primary compression surface and the secondary compression surface.

The interface can be a viscoplastic material. The viscoplastic material can be a Bingham plastic. The interface may comprise a substantially planar or curved profile layer bounded by a containment structure extending along a peripheral edge of the interface. The containment structure can be a surrounding seal coupled to the primary compression surface and coupled to the slave compression. The surrounding seal can include an O-ring seal.

The interface can include a hydraulic fluid disposed within a containment structure. The containment structure can be a bladder filled with hydraulic fluid. The pocket may be coupled to or integral with the slave plate. The slave plate can be integral with one of the end members of the stack. The slave board can include a collector board of the fuel cell stack.

The primary compression surface may have a first portion and a second portion that are at an excellent angle (ideal angle) relative to each other, and the dependent compression surface may have corresponding first and second portions that are obtuse with respect to each other, and The plastic or viscoplastic interface can include a first interface region between the respective first portions and a second interface region between the respective second portions. The first and second interface regions may be separate and each region Delimited by a separate containment structure. The superior and obtuse angles may be selected such that the main compression surface and the individual portions of the slave compression surface are non-parallel prior to applying a load to the end plate assemblies, however, the fuel cells are maintained at the application load In the compressed state, the bending moment in the main board causes the main compression surface and the sub-compression surface to become substantially parallel to each other or to a greater extent by the twist of the main board. The slave plate may include a pair of separate members, each of which is debited from one of the first portion and the second portion. The main compression surface may define a convex surface that is constructed such that the bending moment in the main plate causes the main compression surface in the case where the application load holds the fuel cells in a compressed state And the dependent compression faces become substantially parallel to each other or to a greater extent. The slave compression surface may define a convex surface that is constructed such that, in the case where the load is applied to the fuel cell in a compressed state, the bending moment in the main plate causes the main compression surface And the dependent compression faces become substantially parallel to each other or to a greater extent. The motherboard may be formed from a metal and the slave plate may be formed from a non-metallic material. The slave plate may extend laterally from the main plate on at least one side defining a laterally extending portion, the laterally extending portion including at least one fluid distribution channel coupled to a plurality of through the stack The fluid distribution channels of the fuel cells are in communication. The fuel cell stack assembly can include a tie rod that couples the end plate assemblies together to maintain the fuel cells in the stack in a compressed state, the tie rods extending through the main plate and the slave plate and configured to The interior of the laterally extending portion is oriented. The two end plate assemblies can each include a main plate and a sub-board, and a plastic or viscoplastic interface, as described above.

According to another aspect, the present invention provides a method of forming a fuel cell stack assembly, the method comprising: Forming a plurality of fuel cells in a stack defining two opposing parallel end faces; positioning a slave plate of the one end plate assembly at one end face of the stack, the slave plate having a slave facing outward from the stack a compression surface; positioning a hydraulic, plastic or a viscoplastic interface on the subordinate compression surface; positioning a main board defining a main compression surface on the plastic or viscoplastic interface Having the plastic or viscoplastic interface disposed between the primary compression surface and the slave compression surface; positioning a second end plate assembly at opposite end faces of the stack; coupling the end plate assemblies Together, the fuel cells and end plate assemblies are brought into compression and used to maintain the stack in a compressed state.

An example of the invention will now be described by way of example and with reference to the accompanying drawings, in which: FIG. 1 illustrates an exploded perspective view of a fuel cell end plate assembly including a fuel cell end plate assembly The main board, a slave board and a visco-plastic interface between the main board and the slave board; FIG. 1a illustrates a schematic cross-sectional view of the main board and the slave board, illustrating the angular relationship of the compression surface; FIG. 2 illustrates the combination A schematic perspective view of one end of a fuel cell stack incorporating an end plate assembly similar to the end plate assembly of FIG. 1; FIG. 3 illustrates a schematic, partial cut of an alternative fuel cell end plate assembly Stereo view, the fuel cell end plate assembly includes a main board, a slave board and a board between the slave board and the slave board Figure 10 illustrates a cross-sectional view of the fuel cell end plate assembly of Figure 3; Figure 5 illustrates a schematic perspective view of a combined fuel cell stack that is different from Figure 1 Alternative end plate assembly; Figure 6 illustrates (a) a perspective view of a hydraulic fluid bladder, (b) a partial cross-sectional view, (c) a plan view, and (d) an edge view; and Figure 7 illustrates integration into one (a) a perspective view of the hydraulic fluid bladder on the slave end plate, (b) a partial cross-sectional view, (c) an edge view, (d) a plan view, and (e) a cross-sectional view taken along line AA.

A first example of a fuel cell end plate assembly 1 is shown in exploded view in FIG. The end plate assembly 1 includes a main board 2 and a subordinate board 3. The main board 2 defines a main compression surface 4, which in this example comprises a first portion 5 and a second portion 6. The first and second portions form an obtuse angle relative to each other, and more particularly as shown in Figure 1a, at a vertex 7 between the first and second portions, at the first There is a good angle θ _M between the second part 5, 6. The slave plate 3 has a corresponding slave compression surface 8 that is facing away from the viewer of FIG. The slave compression surface 8 also includes a first portion 9 and a second portion 10, which portions only see the edges in FIG. The first and second portions of the slave compression surface 8 also form an obtuse angle with each other, and more particularly as shown in Figure 1a, at a vertex 11 between the first and second portions, the first and second portions There is an obtuse angle θ _S between 9,10. Although the slave plate 3 is shown as a single entity in Figure 1, it can be formed in two sections (e.g., two halves), each section defining a first portion 9 of the slave compression surface 8. And one of the second parts 10. The two halves can abut at the apex 11.

Between the main compression surface 4 and the subordinate compression surface 8, a viscoplastic interface 12 is provided. In the configuration of FIG. 1, the viscoplastic interface is divided into a first interface region 13 and a second interface region 14. In Figure 1, the second interface region is shown separated from the second portion of the primary compression surface 4 for purposes of clarity of illustration. The viscoplastic interface 12 is delimited by a containment structure. Among the examples shown, there are separate containment structures in the form of O-ring seals 15, 16 which respectively surround a peripheral edge of the respective interface regions 13, 14. And extending along the peripheral edge. Each of the O-rings is partially disposed in a recess, a retraction, a recess, a recess or a passage 17 in the respective main plate, and is also partially located in the recess, the retraction, the recess in the subordinate plate, Inside the recess or channel (cannot be seen in Figure 1). Each O-ring provides a peripheral seal against the primary compression surface and the secondary compression surface. More generally, an O-ring and a retaining feature (eg, a recess, a retraction, a recess, a recess or a channel of one of the primary compression surface or the secondary compression surface) may be considered a containment structure.

The slave plate 3 includes a planar surface 18 that is configured to engage an end face of a stack of fuel cells. The planar surface 18 may be unevenly flat or may comprise a series of pressure elements that themselves define a series of planar pressure surfaces distributed throughout the panel region that collectively define the plane Surface 18.

The slave plate 3 may also include fluid dispensing structures 19 for transporting fuel and/or oxidant among the batteries in the stack in a known manner. Both the main board 2 and the slave board 3 include apertures 20, 21 for the tie rods 22 (the ends of the tie rods can be seen in Figure 2) to pass through, for combining the stack sets Used to keep the stack in a compressed state. The main board 2 can be formed like an open battery structure having a cavity 23 and a connecting limb 24 for The given strength has a lighter weight construction.

Referring to Figure 2, an end plate assembly 1 is applied to each end of a stack of fuel cells 25, one end of which is shown in Figure 2. The fuel cell stack 25 includes a plurality of fuel cells 26 (not shown separately, but the fuel cell stack 25 is constructed such that each cell is parallel to the slave plate planar surface 18). The stack of cells thus defines two opposing parallel end faces, each of which is joined to a respective one of the slave plates. A set of tie rods 22 are passed through each end plate assembly 1 and the end assemblies are joined together, thereby compressing the battery 26 in the stack 25.

Referring back to Figure 1, the viscoplastic interface 12 is preferably formed from any plastic or viscoplastic material to maintain the fuel cell stack in the correct configuration, i.e., in the proper contact state of all layers of the fuel cell stack. And all of the gasket seals are capable of restricting or inhibiting the flow of plastic between the primary compression surface 4 and the slave compression surface 8 in the desired compression state of operation. The term "limited plastic flow" is intended to cover several situations, including at least the following:

(i) The inherent plastic flow of the plastic or viscoplastic material layer 12 is constrained by the containment structure such that the material cannot escape from the primary compression surface 4, the dependent compression surface 5, and the containment structure (eg, O-ring 15) , 16) the defined boundaries, and thus the flow of plastic is limited to prevent material from escaping from between the main board and the subordinate board.

(ii) the inherent integrity of the plastic or viscoplastic material is sufficient to ensure that the plastic flow of the material is insufficient under the normal compressive forces applied to the fuel cell stack to allow the material to be removed from the main and sub-plates 2, 3 Escaped between.

(iii) a combination of the above (i) and (ii).

In each case, the plastic or viscoplastic interface is characterized by its ability to locally redistribute itself in the following cases: (a) applied to the compressive force during the assembly of the stack In the case of an end plate assembly; (b) in the case of any bending of the main plate or the subordinate plate under load; and (c) causing thermal expansion of the stack and subsequent distortion or distortion of the end plate structure during normal operation of the fuel cell The change includes reversal thermal expansion/contraction from the thermal cycle during a change in electrical load on the fuel cell.

The interface material 12 preferably has sufficient inherent structural integrity to allow the material to be fully positioned during assembly, and possibly also to be recombined into a single steerable self-supporting entity. The material can be removed and repositioned during this time.

Instead of plastic or viscoplastic materials, hydraulic interfaces can be used instead. The term "hydraulic interface" is intended to cover an interface containing a controlled volume of hydraulic fluid that can be applied to the controlled body under the compressive forces applied to the end plate assemblies. The itself is redistributed so that the pressure can be evenly transferred between the main board and the slave board in a similar manner as described above with the plastic or viscoplastic interface. Embodiments of the hydraulic interface include those that use water, glycerin, or other known hydraulic fluids, which are generally within a range of pressures experienced between the main plate and the slave plates, which fluids generally have very low compressibility or It is not compressible. Embodiments of containment structures suitable for use with hydraulic fluids (and also with plastic or viscoplastic materials) include flexible bladders that may be formed from any suitable flexible material, such as rubber or metal. An embodiment is shown in Figure 6.

Figure 6 shows a hydraulic fluid bladder 60 comprising a pair of foils 61, 62 which may be laser welded together to form a seam 63 at the peripheral edge 64. The foils 61, 62 thus together define a hydraulic fluid pocket 65 therebetween. The hydraulic fluid 66 fills the pocket 65. Such a pocket configuration can also be used to accommodate plastic or viscoplastic materials therein, as will be discussed further below. In the illustrated implementation, the pouch may be Manufactured from 0.2 mm thick foils 61, 62 to form a recess 65 having a thickness of 0.6 mm. These thicknesses can be adapted to fit any particular fuel cell assembly to provide sufficient compressive strength and thickness to accommodate buckling of the end plates.

The inclusion of a hydraulic, plastic or viscoplastic interface allows the material to locally redistribute itself to accommodate the divergence of the primary and secondary compression surfaces. Such localized divergence may result from changes in the compressive force as a result of varying thermal expansion. This localized material redistribution ensures that the resulting uneven pressure applied by the slave plate surface 18 to the fuel cell stack can be reduced, minimized, or even eliminated. The interface is such that the pressure of the distribution between the main board and the slave board is uniform.

The plastic or viscoplastic material forming the interface 12 can be selected from any suitable material such as acrylic putty, enamel paste, mineral or artificial fat, and the like. One of the preferred grades of material for interface 12 is Bingham plastic. Preferably, the plastic or viscoplastic material is selected from a material having a rigid, semi-rigid or self-supporting body under low stress for easy assembly of the end plate, but the material acts as a viscous under high stress. Flows like fluid. However, other materials may be used, such as powders (eg, powdered marble, powdered plastic), and if desired, the material may be contained in a pouch or other containment structure as described above in connection with the hydraulic fluid. Inside. Materials that do not require rigid, semi-rigid or self-supporting properties can be provided as freezing elements for assembly, making automatic assembly of fuel cells easier.

In these preferred embodiments, the viscoplastic material 12 flows between the main plate 2 and the compression surfaces 4, 8 of the sub-plate 3 in a hydraulic state, and is accommodated in the O-rings 15, 16 Within the predetermined volume. Regardless of the relationship of the compression surfaces 4, 8 relative to each other, hydraulic pressure The forces are evenly distributed.

The substantial benefits of such a configuration may include (i) the integrity of the seal between each of the cells in the fuel cell stack assembly and within each of the fuel cell stack assemblies; Ii) even when varying loads are applied to the stack assembly, such as those caused by manufacturing variations and variations in the normal operating parameters of the fuel cell stack, there is a uniform interfacial impedance across the electrode area; A uniform interfacial impedance across the electrode area under the influence of thermal cycling.

The end plate assembly facilitates a lightweight end plate design that compensates for the distortion of the end plate structure under varying loads and will be evenly distributed as heat and other mechanical forces are circulating the overall compressive load. The force is supplied to a stacked assembly. The end plate assembly can accommodate compression trimming of a particular stack without compromising the parallel relationship of each battery relative to its adjacent cells.

The design of a large number of end plate assemblies benefits from the hydraulic, plastic or viscoplastic interfaces described above. Alternative designs for non-exhaustive selection are described below.

Figure 1 illustrates a design of a primary end plate and a secondary end plate, wherein the plates 2, 3 are faceted to include a first portion 5 and a second portion 6, each of the first and second portions being Flat, but formulated to form an obtuse angle relative to each other. In an alternative configuration, each of the first portion 5 and the second portion 6 need not be planar but may be a curved surface, for example, each portion may exhibit a convex surface in the y-direction. That is, a curve that extends outward as it progresses from the apex 7 to the peripheral edges of the panels close to the opening 21 is described. For example, when advancing along the surface in both the x and y directions as shown in Figure 1, the curved surfaces may be curved (e.g., convex or concave) in one direction or in two Bending in the orthogonal direction.

The transition region between the first portion 5 and the second portion 6 may be a smooth, circular transition portion 27 as shown in FIG. The primary compression surface 4 and the slave compression surface 8 may be flat The curved contour is smooth, and there is no flat portion in the x direction and/or the y direction.

The main board 2 and the sub-panel 3 can be pre-formed such that when the sheets are uncompressed, the main compression surface 4 and the sub-compression surface 8 can be non-parallel to each other. For example, the good angle θ _{M of the} main board 2 and the obtuse angle θ _{S of the} slave board may be non-cooperating angles that add up to more than 360 degrees, such that when the boards are uncompressed, the first sum of the main compression surfaces The second portion 5, 6 is separated from the first and second portions 9, 10 of the respective slave compression surfaces. The size of the separation can be calculated such that when the correct compression angle of the stack is applied by the main board 2 using the tie rods 22, the bending moment in the main board results in the compression surface 4, 8 or the compression surface 5, The individual parts of 6,9,10 become relatively close, substantially parallel or completely parallel by the distortion of the main board.

The primary compression surface and the slave compression surface may be flat, that is, have no curved portions and do not have portions that are obtuse with each other. Referring to Figures 3 and 4, an end plate assembly 30 includes a main plate 32 and a subordinate plate 33. The main board 32 is a planar panel and includes a planar compression surface 34. The slave plate 33 is a planar plate member and includes a planar compression surface 38. An elastic or viscoplastic interface 12 is disposed between the compression surfaces 34, 38 and is bounded by an O-ring seal 15 disposed within a recess 37. In this configuration, the containment structure is shown as a retraction 39 in the slave plate that defines the effective edge of the slave compression surface. This retraction 39 limits the movement of the O-ring 15 and thereby confines the elastic or viscoplastic material 12. It will be seen that the peripheral edges of the main plate 32 and the subordinate plate 33 outside the boundary of the O-ring 15 do not form portions of the compression surface in a compressive relationship with each other because they do not meet and They are sufficiently separated to promote a non-parallel attitude of the respective panels when distortion occurs in the endplate assembly. Even if there is any such non-parallel relationship, it appears on the stack The planar surface 18 of the slave plate 33 can still provide uniform compression to the stack. The operation of the end plate assembly 30 and its viscoplastic interface 12 is similar to that described in connection with FIG.

The contour of one of the primary compression surface and the slave compression surface may be a curve. Referring to FIG. 5, an end plate assembly 50 includes a main plate 52 and a subordinate plate 53. The main board 52 is a flat panel when manufactured and includes a planar compression surface 54 when decompressed. The slave plate 53 is a curved raised plate member and includes a curved convex compression surface 58. When the main board 52 is coupled to the slave board 58 by the tie bar 22 and coupled to the board member 26 of the stack 25, the compressive force on the main board 52 causes the main board to circumscribe the convex surface of the slave board 53. Elastic twist. This brings the primary compression surface and the secondary compression surface into a substantially parallel relationship to each other. This provides a more uniform distribution of forces on the compression surface of the slave plate. Between the compression surfaces 54, 58 of the panels is placed an elastic or viscoplastic interface 12 which is similar to that of Figures 1 to 4 (not visible in Figure 5). The manner of description is delimited by an O-ring seal 15. In this case, the viscoplastic interface provides a curved interfacial layer that follows the contour of the convex surface of the sub-plate. In addition, the operation of the end plate assembly 30 and its viscoplastic interface 12 is similar to that described in FIG.

Although FIG. 5 shows a slave plate 53 having a compression surface 58 that is curved (eg, raised) in one direction (y-direction) and planar in the orthogonal (x) direction, The compression surface 58 can be curved in both the x- and y-directions. Considering the optimum pressure distribution of the fixed center of any tie rod 22 and the characteristics of the elastic main plate and/or the subordinate plate as well as the elastic or viscoplastic interface, the precise curved profile can be adjusted.

The elastic or viscoplastic interfaces described herein are particularly efficient for large fuel cell stacks. When a stack is formed from only a few batteries or even dozens of batteries, in the heat The cumulative effect of the battery on the pressure exerted by the end plates during cycling may be relatively small or moderate. However, in larger stacks, for example, in a stack of 192 cells, the total thickness variation from thermal cycling may be as much as 1 mm or more. This variation can be adjusted in a conventional manner by increasing the compression of the entire stack of pads and/or by the distortion in the end plates. The hydraulic, plastic or viscoplastic interface can be made thick enough to accommodate the desired amount of bending of the main board and/or the slave board regardless of the size of the fuel cell stack.

Preferably, both ends of a fuel cell stack have an end plate assembly as one of the examples described above, but it will be appreciated that if the end plate assembly described above is used At least some of the benefits can be achieved with only one end and the other end of the stacked assembly having conventional end plates.

In a preferred arrangement, the main board is formed from a metallic material for strength and rigidity, and may, in some instances, allow for modest and/or acceptable placement of the stack in a compressed state. The expected amount of elastic deformation. The slave plate is preferably formed from a rigid, non-elastic, non-metallic material that will retain its shape in the compressed state and distribute the compressive force evenly from the interface 12 to the planar surface 18.

Where the slave plate comprises at least one fluid distribution structure (channel) 19, as exemplified in Figures 1 and 2, these fluid distribution structures are preferably disposed laterally outside of the positioning of the tie rod 22. As shown, the slave plate 3 extends laterally from the compression surfaces 4, 5 (as shown in the y-direction) and extends laterally across the outer side of the main plate 2 defining a laterally extending portion. Outside the pole and outside the motherboard. This is beneficial because the compression system applied by the tie rods is kept close to the area where it is possible to approach the edge of the battery requiring a uniform pressure distribution. The fluid distribution channel 19 is in communication with a fluid distribution channel extending downwardly to the side of the stack, and And so the need for a precisely controlled uniform pressure distribution will be relatively small.

The function of the slave board 3 can be integrated with the endmost components of the fuel cell stack. In some configurations of fuel cell stacks, the last element in a stack may be a collector plate that is slightly more than other plates in the stack (eg, anode plates, cathode plates or bipolar plates) thicker. Such a collector plate, or other last element, in the stack can be used to form the function of a slave board as defined in the stack.

Figure 7 shows an arrangement in which a hydraulic fluid bladder is integral with a slave plate 70, for example, wherein the slave plate forms a wall portion of the bladder 71. In this configuration, a foil 72 is laser or impedance fused to the surface 74 of the slave plate 70 to form a seam 73. A pocket 75 is thereby formed and filled with hydraulic fluid. The pocket 75 can be filled with hydraulic fluid by using a filler port (not shown) that is drilled into the slave plate and the filler port is sealed after the filler. Alternatively, the pocket 75 can be filled prior to the final seam weld. For example, the recess 75 can be filled through a notch in a base weld, and then the weld is completed using the mass of the larger component to dissipate heat. The pocket can also be used to define a plastic or viscoplastic material as discussed above, rather than a hydraulic fluid. The slave board 70 can be a last component in the stack, such as the current collector panel as discussed above. Other flexible materials can be used in place of the foil.

While the examples described above are directed to a proton exchange membrane (PEM) fuel cell for converting hydrogen and oxidant to electrical energy, the concepts described above can be applied immediately to other fuel cell technologies. In particular, other types of fuel cells are typically operated at even higher temperatures than PEM fuel cells, and thus thermal cycling is an even greater problem that may be tuned.

Other examples are intended to fall within the scope of the appended claims.

1‧‧‧ fuel cell end plate assembly

2‧‧‧ motherboard

3‧‧‧Subordinate board

4‧‧‧Main compression surface

5‧‧‧Part 1

6‧‧‧Part II

7‧‧‧ vertex

8‧‧‧Subordinate compression surface

9‧‧‧Part 1

10‧‧‧Part II

11‧‧‧ vertex

12‧‧‧ interface

13‧‧‧First interface area

14‧‧‧two interface area

15‧‧‧O-ring seals

16‧‧‧O-ring seals

17‧‧‧ recesses, retractions, grooves, depressions or passages

18‧‧‧ planar surface

19‧‧‧ Fluid distribution structure

20‧‧‧opening

21‧‧‧Opening

22‧‧‧ tied

23‧‧‧ hollow

24‧‧‧Connected limbs

Claims (22)

A fuel cell stack assembly comprising: a plurality of fuel cells in a stack, the stack defining two opposing parallel end faces; an end plate assembly at each of the opposite end faces of the stack, the end plates The assemblies are coupled together to thereby maintain the fuel cells in the stack in a compressed state; wherein at least one of the end plate assemblies includes: a main board defining a primary compression a subordinate plate defining a dependent compression surface facing the main compression surface and in a compressive relationship with the main compression surface; and a hydraulic, plastic or viscoplastic interface, configured Between the main compression surface and the slave compression surface. The fuel cell stack assembly of claim 1, wherein the interface is a viscoplastic material. The fuel cell stack assembly of claim 2, wherein the viscoplastic material is a Bingham plastic. The fuel cell stack assembly of claim 1, wherein the interface comprises a substantially planar or curved profile layer surrounded by a containment structure extending along a peripheral edge of the interface Demarcation. The fuel cell stack assembly of claim 4, wherein the containment structure is coupled to the main compression surface and coupled to the surrounding seal of the slave compression surface. The fuel cell stack assembly of claim 5, wherein the peripheral seal comprises an O-ring seal. The fuel cell stack assembly of claim 1, wherein the interface comprises a hydraulic fluid disposed within a containment structure. The fuel cell stack assembly of claim 7, wherein the containment structure is a bladder filled with the hydraulic fluid. A fuel cell stack assembly according to claim 8 wherein the bladder is coupled to or integral with the slave plate. The fuel cell stack assembly of claim 1, wherein the slave plate is integral with the one end member of the stack. The fuel cell stack assembly of claim 10, wherein the slave plate comprises a collector plate of the fuel cell stack. The fuel cell stack assembly of claim 1, wherein the main compression mask has a first portion and a second portion, the first and second portions being at an excellent angle to each other; and wherein the subordinate compression surface Having a corresponding first portion and a second portion, the first and second portions being at an obtuse angle to each other, and wherein the plastic or viscoplastic interface comprises a first interface region between the individual first portions and a second interface region between the respective second portions. The fuel cell stack assembly of claim 12, wherein the first and second interface regions are separated and each region is delimited by a separate containment structure. The fuel cell stack assembly of claim 12, wherein the superior angle and the obtuse angle are selected such that the main compression surface and the individual portions of the slave compression surface are applied before the load is applied to the end plate assemblies Non-parallel, however, where the load is applied to maintain the fuel cell in a compressed state, the bending moment in the main plate causes the main pressure to be twisted by the main plate The reduced faces and the dependent compressed faces become a substantially, or even greater, parallel relationship to each other. The fuel cell stack assembly of claim 13, wherein the slave plate comprises a pair of separate members, each element gap defining at least one of the first portion and the second portion. The fuel cell stack assembly of claim 1, wherein the main compression surface defines a convex surface configured to allow a load to be applied to maintain the fuel cell in a compressed state, The bending moment in the main plate causes the main compression surface and the subordinate compression surface to become substantially, or even to a greater extent, parallel to each other. The fuel cell stack assembly of claim 1, wherein the slave compression surface defines a convex surface configured to apply a load to maintain the fuel cell in a compressed state. Next, the bending moment in the main plate causes the main compression surface and the subordinate compression surface to become a substantially or greater parallel relationship with each other. The fuel cell stack assembly of claim 1, wherein the main plate is formed from a metal and the sub-plate is formed from a non-metallic material. The fuel cell stack assembly of claim 1, wherein the slave plate extends laterally from the main plate on at least one side defining a laterally extending portion, the laterally extending portion comprising at least one fluid distribution The tunnel is in communication with a fluid distribution tunnel through a plurality of fuel cells in the stack. The fuel cell stack assembly of claim 19, further comprising a plurality of tie rods, the tie rod assemblies being coupled together to maintain the fuel cell in the stack in a compressed state Next, the tie bars extend through the main plate and the slave plate and are disposed inside the laterally extending portion. The fuel cell stack assembly of claim 1, wherein the end plate assemblies comprise a main plate and a sub-board and a plastic or viscoplastic interface as defined in claim 1 of the patent application. . A method of forming a fuel cell stack assembly, the method comprising: forming a plurality of fuel cells into a stack, the stack defining two opposing parallel end faces; positioning a slave plate of the end plate assembly at one end of the stack Wherein the slave plate has a slave compression surface facing away from the stack; a hydraulic, plastic or a viscoplastic interface is positioned on the slave compression surface; a motherboard defining a main compression surface Positioning at the hydraulic, plastic or viscoplastic interface such that the hydraulic, plastic or viscoplastic interface is disposed between the main compression surface and the slave compression surface; positioning a second end plate assembly at The opposite end faces of the stack; the equal end plate assemblies are coupled together to bring the fuel cells and end plate assemblies into compression and to maintain the stack in a compressed state.