CN1328810C - End plates for a fuel cell stack structure - Google Patents

Abstract

An electro-chemical fuel cell stack (20) having a fuel cell assembly (24) disposed between upper and lower terminal plates (56) which are disposed between upper and lower end plates (45, 58). Optionally, spacer plates (52) can be inserted between the end plates (45, 58) and the terminal plates (56). The end plates (45, 58) and/or the spacer plates (52) may have contoured surfaces to apply a generally uniform compressive load on the fuel cell assembly (24). The terminal plates (56), spacer plates (52), and end plates (45, 58) may be connected together to form rigid end assemblies (32, 34) that compress the fuel cell assembly (24).

Description

End plates for fuel cell stacks

field of invention

The present invention relates to fuel cells, and more particularly to fuel cells arranged in a stack and held in compressed form.

Background of the invention

A fuel cell stack generally includes a plurality of fuel cells stacked one on top of the other in compressed form relative to each other. The plurality of stacked fuel cells form a fuel cell assembly that is compressed to allow the plurality of fuel cells to maintain a compressed relationship. In general, each fuel cell includes an anode layer, a cathode layer, and an electrolyte sandwiched between the anode layer and the cathode layer. The fuel cell assembly requires considerable compressive force to press the stack of fuel cells together. The need for compressive force is due to the pressure created by the internal gases of the reactants present within the fuel cell and the need to maintain good electrical contact between the internal components of the cell. Generally speaking, the force per area unit is generally about 195-205 psi, which is evenly distributed over the entire active area of the battery (typically 77-155 square inches for a car-sized stack). Thus, for a fuel cell area of about 80 square inches, the total compressive force for a stack of this size is typically about 15,500 to 16,500 pounds.

Typical fuel cell stack structures of the prior art focus on applying and maintaining compressive forces to the fuel cell assembly using rigid end plates. The fuel cell assembly to be compressed is sandwiched between a pair of rigid end plates. The end plates are then pressed together so that they are held in a spaced relationship to maintain compressive force. The end plates may be held in spaced relation in a number of ways. For example, a link extending through the end plates may be utilized to apply a compressive force to the end plates and maintain the spaced relationship of the end plates. The connecting rods are generally external to the fuel cell assembly and run along the outer edges of the end plates. The end plates may also be held in spaced relation with side plates extending along the length of the fuel cell assembly and connected to the end plates to maintain compressive forces on the fuel cell assembly.

Due to the large compressive forces that must be applied to the fuel cell assembly and the size of the effective area on the fuel cell assembly over which the compressive forces must be applied, the rigid end plates held in spaced relationship by various means along the outer edges of the rigid end plates are flexible. Therefore, a substantially uniform compressive force cannot be applied to the entire active area of the fuel cell assembly. That is, the central portion of the rigid end plate deflects, and the force applied to the active area below the central portion of the rigid end plate is not as great as the force applied to the active area at the outer edge of the rigid end plate.

Prior art attempts to provide substantially uniform compression distribution over the active area include very thick rigid end plates with external links, rigid end plates with internal links passing through the fuel cell assembly, semi-rigid end plates of the cavity, and employing a discreet force applying member, such as a screw, positioned over the central portion of the end plate, selectively movable relative to the end plate to apply compression along the central portion of the end plate force.

In rigid endplates with external links, threaded links extend along the exterior of the fuel cell assembly from the edge of the upper endplate to the edge of the lower endplate such that the link carries the entire compressive force. The end plates must be thick enough so that the total deflection is small (approximately less than 1 mil per cell). The disadvantage of this system is that, compared to all other options, since the entire end plate span is the largest, there is no other way to generate a uniform force over the entire active area, so the end plate must be very thick.

In rigid end plates with internal linkages passing through the fuel cell assembly, the linkages pass through the center of the fuel cell so that the linkages are located near the central portion of the end plate. The total span of the bending force then does not extend over the entire width of the upper end plate, but a shorter span is obtained. This solution has the advantage of shortening the span length of the end plates, thus enabling the use of thinner end plates, but it also has the disadvantage of requiring complex bipolar plate seal structures to allow the connecting rods to pass through the fuel cell assembly.

In semi-rigid end plates with bladder cavities, the lower surface of the upper end plate is hollowed out, and a bladder is placed in the cavity of the end plate to pressurize the bladder to provide the desired stack compressive load. Thus, some bending of the upper end plate itself may be allowed while the airbag maintains a uniform force distribution over the entire active area. This solution has the advantage of being able to make the upper end plate part thinner since it allows the upper end plate to bend significantly, but it also has the disadvantage that it requires a cavity in the end plate, so the overall thickness of the end plate is also significantly greater. Increase.

Where a force applying member is utilized, the force applying member is positioned above the central portion of the end plate and is selectively movable relative to the end plate to apply a compressive force along the central portion of the end plate. This solution has the advantage of being able to fine-tune the compressive force applied to various locations of the end plate above the force applying part, but it has the disadvantage that it requires additional mechanisms to hold the force applying part and fasten each force applying part. components to obtain a substantially uniform force distribution over the active area of the fuel cell assembly.

What is needed, then, is a fuel cell stack structure that has the ability to flow along the fuel cell without requiring excessively thick end plates, or without employing additional means to apply compressive forces to the central portions of the end plates. The end plates apply a substantially uniform compressive force to the active area of the battery assembly.

Summary of the invention

The present invention relates to a fuel cell stack structure that provides a fuel cell assembly capable of compressing and exerting a substantially uniform compressive force over the active area of the fuel cell assembly. More specifically, the present invention relates to improvements in end plate design that improve the distribution of compressive forces over the active area of a fuel cell assembly.

The electrochemical fuel cell stack of the present invention includes a plurality of fuel cells arranged in a stacked configuration to form a fuel cell assembly. The fuel cell assembly has opposing first and second ends. First and second ends having opposing inner and outer surfaces are disposed respectively adjacent to the first and second ends of the fuel cell assembly. The inner surface of the end plate faces the end of the fuel cell assembly. The first and second end plates are held in a spaced relationship such that the first and second end plates apply a compressive force to the fuel cell assembly. The inner surface of at least one of the first and second end plates is contoured to apply a substantially uniform compressive force to the fuel cell assembly. The profiled inner surface can be configured to allow the inner surface to extend from at least one end plate toward an end plate of the fuel cell assembly. Preferably, the profile of the end plate with the contoured inner surface is configured such that the thickness of the end plate increases from the edge of the end plate to the center of the end plate such that the thickness in the center of the end plate is the greatest. Optionally, the inner surface contours of both the first and second end plates may be configured to extend from the first and second end plates toward the first and second ends of the fuel cell assembly, respectively, such that the fuel cell The assembly applies a substantially uniform compressive load.

In an alternative embodiment of the invention, an electrochemical fuel cell stack includes a plurality of fuel cells arranged in a stacked configuration as a fuel cell assembly. The fuel cell assembly has opposing first and second ends. First and second separators having opposing inner and outer surfaces are disposed adjacent the first and second ends, respectively, of the fuel cell assembly. The inner surface of the separator faces the end of the fuel cell assembly. First and second end plates having opposing inner and outer surfaces are disposed adjacent the first and second separator plates, respectively, with the separator plates positioned between the end plates and the ends of the fuel cell assembly. The inner surface of the end plate faces the outer surface of the partition. The first and second end plates are held in a spaced relationship such that the first and second end plates apply a compressive force to the separator and fuel cell assembly. At least one surface of at least one of the separator or end plate is contoured to apply a substantially uniform compressive force to the fuel cell assembly.

In various alternative embodiments of the invention, an electrochemical fuel cell stack includes fuel cells arranged in a stacked configuration to form a fuel cell assembly. The fuel cell assembly has opposing first and second ends. First and second termination plates are disposed adjacent corresponding first and second ends of the fuel cell assembly. First and second end plates are disposed adjacent to the first and second end plates, respectively, such that the end plates are located between the end plates and the ends of the fuel cell assembly. At least one of the first and second end plates is connected to one of the first or second end plates such that the stiffness of the at least one end plate contributes to the stiffness of the connected end plate. The first and second end plates are held in a spaced relationship such that the first and second end plates apply a compressive force to the fuel cell assembly. Optionally, the fuel cell stack may also include at least one separator. The at least one bulkhead is sandwiched between at least one end plate connected to one of the first or second end plates. The at least one bulkhead is connected to at least one end plate and one of the first or second end plates such that the stiffness of the at least one bulkhead contributes to the stiffness of the connected end plate.

Other areas of applicability of the present invention will become apparent from the detailed description provided below. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

Brief description of the drawings

The present invention will be more easily and fully understood by the detailed description and accompanying drawings, in which:

Figure 1 is a perspective view of an electrochemical fuel cell stack of the present invention;

Figure 2 is a simplified cross-sectional view taken along section line 2-2 of the electrochemical fuel cell stack in Figure 1;

Figure 3 is a partially exploded perspective view of the electrochemical fuel cell stack of Figure 1 showing the combination of the side panels and the electrochemical fuel cell stack of Figure 1;

Figure 4 is a simplified fragmentary view showing details of a fuel cell;

5A-5G are cross-sectional views of various configurations of end plates and separators of an electrochemical fuel cell stack of the present invention;

Figure 6A is a plan view of the contoured inner surface of an end plate in accordance with the principles of the present invention;

Figure 6B is a cross-sectional view taken along section line B-B of the end plate of Figure 6A;

Figure 6C is a cross-sectional view taken along section line C-C of the end plate of Figure 6A;

7A-7B are fragmentary cross-sectional views of end assemblies of electrochemical fuel cell stacks of the present invention showing various ways of combining components of these end plate assemblies;

Figure 8 is a perspective view of a separator employed in the electrochemical fuel cell stack of the present invention showing the use of holes to reduce the weight of the separator;

9A-9B are simplified cross-sectional views of the electrochemical fuel cell stack of FIG. 1, which show that the fuel cell assembly and the fuel cell stack are respectively compressed using a compression force of a predetermined magnitude F;

10A-10B are simplified cross-sectional views of the electrochemical fuel cell stack of FIG. 1, showing that the fuel cell assembly and the fuel cell stack have been compressed by a predetermined distance D;

Figure 11 is a flowchart showing the steps of a predetermined force compression method for fabricating a fuel cell stack in accordance with the principles of the present invention;

Figure 12 is a flow chart illustrating the steps of a method of fabricating a fuel cell stack for a predetermined compression distance in accordance with the principles of the present invention;

FIG. 13 is a flowchart showing the steps of manufacturing a fuel cell stack of predetermined or uniform length using separators.

Detailed description of the preferred embodiment

The following descriptions of preferred embodiments are merely exemplary in themselves, they are in no way restrictive of the invention, its application or uses.

Referring to Figures 1 and 2, there is shown an electrochemical fuel cell stack 20 in accordance with a preferred embodiment of the present invention. The fuel cell stack 20 includes a plurality of fuel cells 22 arranged in a stacked structure as a fuel cell assembly 24 having opposite upper ends 26 and lower ends 28, as shown in FIG. length 30 and uncompressed length 31. The fuel cell assembly 24 is sandwiched between upper and lower end assemblies 32,34. The upper and lower end assemblies 32, 34 are held in fixed spaced relationship by the side walls. In the presently preferred embodiment, the side walls include at least one side panel 36 . Side plates 36 hold the upper and lower end assemblies 32 , 34 in a spaced relationship such that the upper and lower end assemblies 32 , 34 apply a compressive force to the fuel cell assembly 24 . Fuel cell stack 20 includes inlets 37 , outlets 38 and channels (not shown) for supplying and exhausting reactant and cooling fluid flows to and from fuel cell assembly 24 , in accordance with known fuel stack technology.

As shown in FIG. 4, the fuel cell assembly 24 includes a plurality of repeating units or fuel cells 22, each repeating unit having a membrane electrode assembly (MEA) 40 and a pair of bipolar plate assemblies 42 disposed on opposite sides of the MEA 40. . Each bipolar plate assembly 42 consists of a coolant distribution layer 42c sandwiched between two gas distribution layers 42g. Interposed between the coolant distribution layer 42c and the gas distribution layer 42g is an impermeable separator 44 which contains the coolant and separates the anode and cathode gas streams. The fuel cell 22 is formed when the MEA is sandwiched between the anode gas distribution layer 42ga of one cell and the cathode gas distribution layer 42gc of an adjacent cell. MEA 40 can take a variety of forms, which are known in the art. For example, MEA 40 may be a polymer electrolyte membrane. Preferably, the polymer electrolyte membrane is a thin reinforced membrane having a thickness on the order of about 0.018 microns. The thin reinforced polymer electrolyte membrane is much thinner than the approximately 0.007 inch thick polymer electrolyte membrane used in prior art fuel cells. The thin and reinforced polymer electrolyte membrane used in the present invention accounts for only a small percentage of the length 30 of the fuel cell assembly 24, compared to the thicker polymer electrolyte membrane used in prior art fuel cell stacks. Much less slippage or stress relaxation occurs.

The fuel cells 22 are arranged in a stacked configuration to form a fuel cell assembly 24 . The number of fuel cells 22 stacked adjacent to each other in a fuel cell assembly 24 may vary. The number of fuel cells 22 used to form the fuel cell assembly 24 depends on the needs of the fuel cell stack 20 . That is, when a larger or more powerful fuel cell stack 20 is desired, the number of fuel cells 22 in the fuel cell assembly 24 is increased. It is known in the art that the fuel cell 22 needs to be compressed in order for the fuel cell 22 to be more efficient and generate more power. Thus, the fuel cell assembly 24 is compressed between the upper and lower end assemblies 32,34. It is preferable to uniformly compress the active area (not shown) of the fuel cell assembly 24 to maximize the efficiency of the fuel cell assembly 24 and each fuel cell 22 in the fuel cell assembly 24 .

Referring again to FIGS. 2 and 3 , the upper end assembly 32 is disposed adjacent the upper end 26 of the fuel cell assembly 24 . The upper end assembly 32 includes an upper end plate 45 having opposing inner and outer surfaces 46 , 48 . An inner surface 46 of the upper end plate 45 faces the upper end 26 of the fuel cell assembly 24 . The upper end plate 45 has a plurality of openings 50 to allow the respective inlets 37 , outlets 38 associated with fluid passages to extend from the fuel cell assembly 24 to the exterior of the fuel cell stack 20 . The end of the fuel cell stack 20 having the inlet 37 and outlet 38 connected to these channels is also referred to as the "wet end".

The lower end assembly 34 is disposed adjacent the lower end 28 of the fuel cell assembly 24 . The lower end assembly 34 includes a lower end plate 58 having opposing inner and outer surfaces 60 , 62 . The lower end plate 58 is positioned such that the inner surface 60 of the lower end plate 58 faces the lower end 28 of the fuel cell assembly 24 . The lower end 28 of the fuel cell stack 20 is also referred to as the "dry end" when there are no inlets and outlets associated with fluidic channels passing through the lower end assembly 34 .

Optionally, but preferably, one or more separators 52 may be located between the fuel cell assembly 24 and the upper and/or lower end plates 45 , 58 . The separator 52 is positioned between the end plates 45, 58 and the ends 26, 28 of the fuel cell assembly 24 with the inner surface 54 of the separator 52 facing the ends 26, 28 of the fuel cell assembly 24 and the outer surface of the separator 52 55 faces the inner surfaces 54,60 of the end plates 45,58. When the ends 26, 28 of the fuel cell assembly 24 are provided with a terminal plate 56, the separator 52 is located between the terminal plate 56 and the end plates 45, 58, and the inner surface 54 of the separator 52 faces the terminal plate 56. . A bulkhead 52 separates the end plates 45 , 58 from the terminal plate 56 . In the end assemblies 32 , 34 , the separator 52 is positioned such that the thickness 57 of the separator 52 is aligned with the length 30 of the fuel cell assembly 24 . While the preferred embodiment shows separators 52 associated with the upper and lower end assemblies 32, 34, those of ordinary skill in the art will recognize that the number and location of separators 52 may vary depending on the design and application of the fuel cell stack 20. And change.

The upper and lower end plates 45,58 each have a peripheral side wall 64 separating the inner surface 46,60 from the outer surface 48,62. Peripheral sidewalls 64 of the upper and lower end plates 45 , 58 are aligned with the length 30 of the fuel cell assembly 24 . Preferably, as shown, the fuel cell stack 20 is substantially rectangular in shape, and the upper and lower end plates 45, 58 are also rectangular in shape. The peripheral sidewalls 64 of the rectangular upper and lower end panels 45, 58 are comprised of first and second pairs of opposing sidewalls 66, 68 that are substantially perpendicular to each other. Each of the first and second pairs of opposed side walls 66,68 has one or more threaded holes for receiving threaded fasteners 80 for securing the side panels 36 to the upper and lower end panels 45,58.

As mentioned above, the upper and lower end assemblies 32 , 34 apply a compressive force to the fuel cell assembly 24 . The compressive force exerted on the fuel cell assembly 24 may be generated by the upper and lower end plates 45, 58 held in a fixed spaced relationship. Preferably, the upper and lower end panels 45 , 58 are held in a fixed spaced relationship by the side panels 36 . Each side panel 36 has opposed first and second end portions 72 and 74, and a length 76 therebetween. Each side plate 36 is positioned on the fuel cell stack 20 with a first end 72 adjacent to the upper end plate 45 and a second end 74 adjacent to the lower end plate 58, the length 76 of the side plate 36 being the length 76 of the fuel cell assembly 24 30 lined up. Optionally, but preferably, the side panels 36 extend along the entire peripheral side walls 64 of the end panels 45 , 58 . The first and second ends 72, 74 of each side plate 36 have more than one opening 78 which, when the fuel cell assembly 24 is compressed, will engage with the outer edge side walls 64 of the upper and lower end plates 45, 58. The threaded holes 70 are aligned. Preferably, the opening 78 at either of the first and/or second ends 72, 74 of each side panel 36 is in the form of a slot so that the upper and lower end panels 45, 58 are held in a fixed spaced relationship. The slots allow the dimensions of the various components of the fuel cell stack 20 to vary while still maintaining the upper and lower end plates 45, 58 in a fixed spaced relationship. While threaded mechanical fasteners 80 are preferably used to connect the side panels 36 to the upper and lower end panels 45, 58, those skilled in the art will recognize that, without departing from the scope of the invention as defined in the appended claims, The side panels 36 can be joined to the upper and lower end panels 45, 58 in other ways. In this sense, the joint formed by the side plates 36 and the end plates 45, 58 should be sufficient to resist relative rotation at the interface between them. For example, the first end 72 and/or the second end 74 of the side panel 36 may be secured to the side plate 36 by other mechanical fastening means such as rivets or pins, or by various bonding means such as welding, brazing or adhesive bonding. On the respective upper and/or lower end plates 45, 58, these approaches are still within the spirit of the present invention. Furthermore, it should be understood that one of the ends 72, 74 of the side panels 36 can be bent to form a retaining member (not shown) that can be positioned on one of the end panels 45, 58 to retain the end panel 45. , 58, while connecting the opposite ends 72, 74 of the side panels 36 to the opposite end panels 45, 58 and maintaining the end panels in a fixed spaced relationship.

Each end plate 36 may have more than one opening 82 for extending the terminal plate 83 on the end plate 56 to the outside of the fuel cell stack 20 as required. Preferably, each side plate 36 is electrically grounded to protect the fuel cell assembly 24 from electromagnetic interference. It is also preferred that each side panel 36 is made of metal. The side panels 36 for holding the upper and lower end plates 45, 58 in a fixed spaced relationship are sized to allow the upper and lower end plates 45, 58 to 58 applies and maintains a compressive force to fuel cell assembly 24 . Because of the greater width of the side panels 36, less thickness is required to provide the necessary tensile strength to carry the compressive loads. This aspect of the invention has the effect of reducing weight compared to the conventional use of axial rods around and/or through the fuel cell assembly.

Preferably, one or more side panels 36 enclose at least a portion of the fuel cell assembly 24 to protect the fuel cell assembly 24 from accidental damage. More preferably, the side panels 36 enclose the entire fuel cell assembly 24 , thereby providing a protective cover for the fuel cell assembly 24 and the fuel cell stack 20 . Thus, the side panels 36 are sized to allow the side panels 36 to withstand these impacts, blows, and other blows while protecting the fuel cell assembly 24 and the fuel cell stack 20 from impacts, blows, or other blows due to various elements of nature. damage caused by blows. In this manner, the side plates 36 not only serve to hold the upper and lower end plates 45, 58 in a fixed spaced relationship to apply and maintain compressive loads to the fuel cell assembly 24, but also provide a more robust and robust environment for the fuel cell assembly 24 and the fuel cell stack 20. protective cover. Utilizing the side plates 36 to perform the protective function eliminates the need for additional structures around the fuel cell stack 20 as in conventional fuel cell stacks, thereby providing protection of the fuel cell stack 20 from accidental blows, impacts or other impacts.

The partitions 52 optionally included in the upper end assembly 32 and/or the lower end assembly 34 serve a variety of purposes. That is, the separator 52 may be included in the fuel cell stack 20 for more than one reason. For example, a spacer 52 may be used to separate the upper and/or lower end plates 45 , 58 from the termination plate 56 . Termination plate 56 is electrically conductive and is used to draw current from fuel cell stack 20 via terminal plate 83, as described above. When the upper and/or lower end plates 45,58 are electrically conductive, the partition 52 between the upper and/or lower end plates 45,58 and the terminal plate 56 can connect the upper end plate and/or the lower end plates 45,58 to the terminal plate. 56 are separated by electrical insulation. Separator 52 may also be used to control the overall dimensions of fuel cell stack 20 . That is, more than one separator 52 may be provided between the fuel cell assembly 24 and the upper and/or lower end plates 45, 58, as will be described in detail below, to provide a fuel cell stack 20 of predetermined length while still being able to Let the end assemblies 32 , 34 apply a compressive force to the fuel cell assembly 24 . It is presently preferred that the separator (or separators) 52 have a thickness in the range of about 8-18 millimeters to provide a fuel cell stack 20 with adequate electrical insulation and uniform size. However, one of ordinary skill in the art will recognize that the specific application and design specifications will dictate the range of thickness 57 of the separator 52 . Separator 52 may also be used in combination with upper and/or lower end plates 45, 58 to apply a substantially uniform compressive load to fuel cell assembly 24, as described in detail below.

Preferably, the separator 52 is electrically non-conductive and can be used to electrically isolate the various components of the fuel cell stack 20 . Thus, the spacer 52 is preferably made of a non-conductive material such as plastic. More preferably, the separator 52 is made of industrial-grade high-performance plastics. The industrial grade high performance plastic used to make the one or more separators 52 is relatively incompressible (i.e., has little stress relaxation) under a certain amount of compressive load applied to the fuel cell assembly 24, thereby reducing the compressive load From the upper and/or lower end plates 45 , 58 to the respective upper and lower ends 26 , 28 of the fuel cell assembly 24 . In particular, the use of polythienyl sulfide for the separator 52 has proven to be a particularly effective material. Polythiophene sulfides are available under the brand RYTON PPS sold by Chenron Philips Chemical Company, L.P. and under the brand FORTRON sold by Celanese AG of Frankfurt, Germany. Preferably, as shown in FIG. 7 , the partition 52 has more than one aperture 84 for reducing the weight of the partition 52 .

As noted above, the upper and lower end plates 45 , 58 are held in a fixed spaced relationship by the side plates 36 and apply a compressive load to the fuel cell assembly 24 . As previously described, the upper and lower end panels 45, 58 are held in fixed spaced relationship by the side panels 36. The compressive loads generated at the upper and lower ends 26, 28 of the fuel cell assembly 24 will vary according to the distance from the outer edge sidewall 64, where the compressive load is at its maximum along the outer edge sidewall 64 and at the upper and lower end plates 45. , The center of 58 reaches the minimum. That is, because the upper and lower end plates 45, 58 are retained only along their outer peripheral sidewalls 64, the upper and lower end plates 45, 58 will respond to compressive loads on the fuel cell assembly 24 and the outer edges of the upper and lower end plates 45, 58. The rim sidewall 64 cannot be moved further apart to deform or flex. Because the efficiency of the fuel cell stack 20 depends in part on a uniform compressive load applied across the active area of the fuel cell assembly 24 , it is desirable to maintain a substantially uniform compressive load across the active area of the fuel cell assembly 24 .

One way to achieve substantially uniform loading is to stiffen the upper and lower end plates 45, 58 by increasing their thickness so that the deflection of the upper and lower end plates 45, 58 has no effect on the deflection of the fuel cell assembly 24. Efficiency impact is minimized. However, given this thickness could be provided for the upper and lower end plates 45, 58, these end plates would be too thick, adding excessive weight to the fuel cell stack 20, thereby reducing the fuel cell stack's weight efficiency and volumetric efficiency. To avoid the necessity of providing relatively rigid end plates 45, 58, end plates 45, 58 may optionally be bonded to bulkhead 52 and termination plate 56 so that the stiffness of bulkhead 52 and the stiffness of termination plate 56 Contributes to the overall stiffness of the end assemblies 32 , 34 thereby reducing the thickness of the end plates 45 , 58 required to exert a substantially uniform compressive load across the active area of the fuel cell assembly 24 . That is, as shown in FIGS. 7A-7B , the separator 52 and end plates 45, 58 can be fastened together to combine their stiffness into a structure capable of applying a substantially uniform compressive load to the active area of the fuel cell assembly 24. The end assembly 32,34. As shown in Figure 7A, the terminal plate 56 can be connected to the partition plate 52 by means of mechanical fasteners 86, such as bolts or screw parts, and the combined terminal plate 56 and partition plate 52 can be connected to the end plate 52 by means of mechanical fasteners 87. One of the plates 45, 58 is connected. Alternatively, end plate 56, bulkhead 52, and one of end plates 45, 58 may all be connected by means of an adhesive layer 88 sandwiched between the respective components. Thus, the stiffness of the termination plate 56 and the stiffness of the separator plate 52 combine with the stiffness of the end plates 45, 58 to provide an end assembly 32, 34 capable of applying a substantially uniform compressive load to the active area of the fuel cell assembly 24. , then the thinner end plates 45, 58 would be necessary without connecting the end plate 56 or the bulkhead 52 to the end plates 45, 58.

Alternatively, and/or in addition, the end plates 45, 58 and/or the bulkhead 52 may have contoured surfaces that allow for deflection of the end plates 45, 58 without the need for excessively thick end plates 45, 58. Compensation occurs and a substantially uniform compressive load is applied across the active area of the fuel cell assembly 24 . That is, as can be seen from FIGS. 5A-5G , which only show the upper end plate 45 and one separator 52, the inner surface 46 of the upper end plate 45 is sized to face away from the upper end plate 45 toward the upper end 26 of the fuel cell assembly 24. Curved so that the thickness of the upper end plate 45 is at a minimum along the peripheral sidewall 64 and is greatest at the center of the upper end plate 45 . Considering that the upper end plate 45 is held in a fixed spaced relationship with the lower end plate 58 along its peripheral sidewall 64 while applying a desired amount of compressive load to the active area of the fuel cell assembly 24, the upper end plate 45 The deflection produced in the process also shapes the shape profile of the inner surface 46 of the upper end plate 45. 6A-6C illustrate exemplary contouring of the inner surface 46 of the upper end plate 45 . As can be seen, the thickness of the upper end plate 45 is greatest approximately at the center of the upper end plate 45 .

Alternatively, and/or in addition, the bulkhead 52 may have contoured inner and/or outer surfaces 54 , 55 to account for the deflection that would occur at the upper end plate 45 . That is, the thickness of the bulkhead 52 is configured to be smallest along the outer edges of the bulkhead 52 and greatest at the center of the bulkhead 52 . For example, as shown in FIG. 5G, the inner surface 54 of the separator 52 is contoured to extend from the separator 52 toward the upper end 26 of the fuel cell assembly 24, or as shown in FIG. 5E, the outer surface 55 of the separator 52 is contoured. The profile is configured to extend from the separator 52 towards the upper end plate 45 such that a substantially uniform compressive load is applied through the end plate 45 to the active area of the fuel cell assembly 24 . Alternatively, as shown in FIG. 5F, the contours of the inner and outer surfaces 54, 55 of the separator 52 are configured to extend from the separator 52 toward the upper end 26 of the fuel cell assembly 24 and the inner surface 46 of the upper end plate 45, respectively, by This enables a substantially uniform compressive load to be applied to the active area of the fuel cell assembly 24 .

Variations in the configuration of the inner and outer surfaces 54, 55 of the bulkhead 52 and the inner surface 46 of the upper end plate 45 are shown in Figures 5A-5G. To allow for deflection of not only the upper end plate 45, but also the lower end plate 58, the surface contours of the upper end plate 45 and/or the separator 52 can be shaped such that the upper and lower ends 26, 28 of the fuel cell assembly 24 are A substantially uniform compressive load can be received. Likewise, it should be understood that the inner surface 60 of the lower end plate 58 and the inner and outer surfaces 54, 55 of the separator 52 in the lower end assembly 34 can also be configured or shaped in the same manner so that the components of the lower end assembly 34 can be aligned with the fuel cell. The active area of assembly 24 exerts a substantially uniform compressive load. Experienced practitioners of the art will recognize that the inner surface 46 has various localized features formed therein to achieve more uniform compressive loading across the active area of the fuel cell assembly 24 . Thus, it should be appreciated that the surface topography of components of upper end assembly 32 and/or components of lower end assembly 34 may, individually or together, be configured or shaped to apply a substantially uniform compressive load to the active area of fuel cell assembly 24 . It should also be understood that the dimensions shown in the various figures are exaggerated for exemplary purposes and should not be considered relative to the dimensions of each component of the fuel cell stack 20 . That is, it should be understood that the deflection of the end plates 45, 58 and the correction by shaping the surface shape of the end plates 46, 58 and/or the diaphragm 52 are exaggerated to better illustrate the advantages of the present invention. principle. It should also be understood that the use of the terms "upper and lower" to describe various components of the fuel cell stack 20 is not to be construed as an absolute reference but rather to provide a relative relationship of the components of the fuel cell stack 20 .

Although the fuel cell stack 20 has been described and shown as having a substantially rectangular configuration, it should be understood that the shape of the fuel cell stack 20 may take various configurations while remaining within the scope of the invention as defined in the claims. For example, the fuel cell stack 20 may be cylindrical, as may the fuel cell assembly 24 and the upper and lower end assemblies 32, 34. When the fuel cell stack 20 is cylindrical, the side plate 36 is a cylindrical sleeve in which the upper and lower end assemblies 32, 34 and the fuel assembly 24 are inserted. The side plate 36 may also be a partial cylindrical sleeve that houses the components of the fuel cell stack 20 . Thus, the use of the term "side plate" should not be limited to flat plates, but should be understood to be flat or curved, or various shapes dictated by the particular shape of the fuel cell stack 20 .

As mentioned earlier, the fuel cell stack 20 has the fuel cell assemblies 24 retained using compressive loads, thereby making the fuel cell assemblies 24 more efficient. The present invention also includes various fabrication methods for fabricating the fuel cell stack 20 having the fuel cell assemblies 24 under compressive loading conditions. In the first method, the predetermined compressive load method, as shown in FIGS. external compressive load to compress. The side plates 36 are then secured to the upper and lower end plates 45, 58 so that the upper and lower end plates 45, 58 remain fixed when external compressive loads on the fuel cell assembly 24 and/or fuel cell stack 20 are removed. interval relationship. Because the upper and lower end plates 45, 58 remain in a fixed spaced relationship after the external compressive loads are removed, the upper and lower end plates 45, 58 continue to apply internal compressive loads to the fuel cell assembly 24 as discussed in more detail below.

In a second method, the predetermined compression distance method, as shown in FIGS. 10A-10B and 12 , the fuel cell assembly 24 and/or the fuel cell stack 20 may be compressed a predetermined distance D by an external compressive load C. In other words, the magnitude of the external compressive load is sufficient to compress the fuel cell assembly 24 by the predetermined distance D. The side panels 36 are then connected to the upper and lower end panels 45, 58 (as will be described in further detail below). Then remove the external compressive load. The upper and lower end plates 45, 58 maintain their fixed spaced relationship. The fuel cell assembly 24 remains in a state of being substantially compressed by a predetermined distance D, thereby exerting an internal compressive load thereon.

As noted above, the predetermined compressive load method of manufacturing the fuel cell stack 20 having the fuel cell assemblies 24 under a compressive load condition of the predetermined magnitude F includes applying an external compressive load to the fuel cell stack 20 . The predetermined compressive load method comprises the following steps: 1) the fuel cell assembly 24 is arranged between the upper and lower end plates 45, 58, the upper end 26 of the fuel cell assembly 24 is adjacent to the upper end plate 45, and the lower end 28 of the fuel cell assembly 24 is adjacent to the upper end plate 45. 2) applying an external compressive force to at least one of the end plates 45, 58 so as to compress the fuel cell assembly 24 so that it is subjected to an internal compressive force of a predetermined magnitude F; 3) aligning the side plates with The end plates 45, 58 are joined such that the first and second ends 72, 74 of the side plates 36 are joined to the corresponding upper and lower end plates 45, 58, respectively; and 4) removing at least one of the end plates 45, 58 applied to the The external compressive force on the end plates, thereby maintaining the upper and lower end plates 45, 58 in a fixed spaced relationship, maintains a compressive force on the fuel cell assembly 24 substantially equal to a predetermined magnitude F. The predetermined compressive load method thus provides the fuel cell stack 20 with a compressive force substantially equal to the predetermined magnitude F exerted on the fuel cell assembly 24 .

On the contrary, when the fuel cell stack 20 is assembled by the predetermined compression distance method, the fuel cell stack 20 and/or the fuel cell assembly 24 should be compressed by a predetermined distance D, contrary to compressing with a predetermined compression force F. The reference point for the predetermined distance D may be the overall length of the fuel cell assembly 24 itself. Therefore, another benchmark is to compress the fuel cell assembly 24 only the predetermined distance D, rather than compressing the fuel cell stack 20 . However, it should be understood that compressing the fuel cell assembly 24 by the predetermined distance D may also be achieved by compressing the fuel cell stack 20 by the predetermined distance D. Preferably, predetermined distance D corresponds to a compressive force applied to fuel cell assembly 24 that results in efficient operation of fuel cell stack 20 . The predetermined distance D to compress the fuel cell assembly 24 may be determined in a number of ways. For example, as will be discussed in detail below, the predetermined distance D may be calculated based on a fixed distance compression of each fuel cell 22 contained in the fuel cell assembly 24, or based on historical compression of a fuel cell assembly 24 having a known number of fuel cells 22. to determine from empirical data. Once the predetermined distance D is determined, an external compressive load is applied to the fuel cell stack 20 to compress the fuel cell stack 20 and/or fuel cell assembly 24 by the predetermined distance D. The side panels 36 are then joined to the upper and lower end panels 45, 58 to relieve the external compressive load. The resulting fuel cell stack 20 then has the fuel cell assembly 24 compressed by the predetermined distance D with an internal compressive load corresponding to efficient operation of the fuel cell stack 20 .

Each fuel cell 22 is compressed a given distance when the compression distance D is determined according to calculations (ie, based on a fixed distance compression for each cell). The predetermined distance D to compress the fuel cell assembly 24 may be calculated by multiplying the number n of fuel cells 22 in the fuel cell assembly 24 by the fixed distance d that each fuel cell 22 is to be compressed. In other words, it is calculated by the equation D=n×d. The fixed distance to compress each fuel cell 22 is selected to provide a compressive force to the fuel cells 22 substantially corresponding in magnitude to provide efficient operation of the fuel cell assembly 24 . That is, the fixed distance d by which each fuel cell 22 is to be compressed is based on the physical characteristics of the fuel cell 22 and the amount of compression required for the fuel cell 22 to operate efficiently. The resulting fuel cell stack 20 has the fuel cell assembly 24 compressed by the predetermined distance D and has a compression load corresponding to the fuel cell assembly 24 for efficient operation.

As opposed to compressing each fuel cell 22 a fixed distance, when based on empirical data, the fixed distance D to compress the fuel cell assembly 24 may be determined by past experience compressing the fuel cell assembly 24 with known compression loads. The final predetermined distance D is equal for both methods. Due to the substantially uniform composition of the fuel cells 22 contained in the fuel cell assembly 24, the relationship between the number of fuel cells 22 produced when the fuel cell assembly 24 is subjected to a known magnitude of compressive force can be established for each type of fuel cell 22. A general correlation between the compression distance of the fuel cell assembly 24 and/or the fuel cell stack 20. This correlation can be used to determine a predetermined distance D to compress the fuel cell assembly 24 to apply a desired amount of compressive force on the fuel cell assembly 24 based on the number of fuel cells 22 comprising the fuel cell assembly 24 . For example, empirical data indicates that a fuel cell assembly with 50 to 200 fuel cells will be compressed by distances X and 4X, respectively, thereby applying a desired amount of compressive force. A fuel cell stack 20 having a fuel cell assembly 24 composed of 100 identical fuel cells 22 can be compressed a distance 2X, which should apply substantially equal compressive forces to the fuel cell assemblies 24 according to the above correlation.

Because of some variation in the composition of any given type of fuel cell 22, the resulting compressive force applied to fuel cell assembly 24 may vary. The amount of change in the final compressive force will depend on the accuracy of the correlation and the variation of the fuel cell 22 . Preferably, the final compressive force will vary within an acceptable range around the ideal magnitude, so that the variation has a negligible effect on the efficiency of the fuel cell stack 20 . The empirical data method then provides a fuel cell stack 20 having a fuel cell assembly 24 that, when the fuel cell assembly 24 is compressed by a predetermined distance D, is substantially equal to the ideal size corresponding to the fuel cell 24 effective Operating compressive force.

As mentioned above, the separator 52 may be used to provide a predetermined or uniform length L of the fuel cell stack 20 . That is, in the fuel cell stack 20, the separator 52 may be used to occupy a space for the fuel cell stack 20 to a predetermined or uniform length L. Referring to FIG. The uniform length L provides several advantages. For example, the uniform length L facilitates replacement of the fuel cell stack and allows a device employing the fuel cell stack 20 to have a standard space for the fuel cell stack 20 .

As shown in Figures 13a-13b, the present invention provides various assembly sequences of fuel cell stacks having a uniform length L. The desired predetermined or uniform length L of the fuel cell stack 20 can be either a known length, such as an industry standard, or a selected length. In either case, the total length L is a known quantity. The thicknesses of the upper and lower end plates 45, 58, all end plates 56 employed in the fuel cell stack 20, and all other components of the end assemblies 32, 34 can be measured and therefore are also known quantities. Based on these known quantities/dimensions, the space within the fuel cell stack 20 where the fuel cell assembly 24 is to be placed can be calculated, so this space is also a known quantity. That is, the length of the space in the fuel cell stack 20 in which the fuel cell assembly 24 is to be placed is equal to the predetermined or uniform length L of the fuel cell stack 20 minus the end plates 45, 58, all end plates 56 and the components that make up the end assemblies 32, 34. Dimensions of all other components. The only unknown dimension is the compressed length 30 of the fuel cell assembly 24 . The compressed length 30 of the fuel cell assembly 24 may vary depending on the method used to fabricate the fuel cell stack 20 and the number of fuel cells 22 included in the fuel cell assembly 24 discussed above.

As set forth above, the separator 52 can be used in conjunction with the predetermined compressive loading method to produce a fuel cell stack 20 of predetermined or uniform length L in which a load substantially equal to the predetermined size is applied to the fuel cell assembly 24. Compression load of F. To accomplish this, it is necessary to determine the compressed length 30 of the fuel cell assembly 24 or the compressed length of the fuel cell stack 20 so that the desired combined thickness of the one or more separators 52 can be determined.

The compressed length 30 of the fuel cell assembly 24 can be determined in the following ways: (1) As shown in FIG. 9A , compress the fuel cell assembly 24 with an external compressive load so as to obtain an internal compressive load of a predetermined size F, and then measure the compressed length 30; Or (2) compress the fuel cell stack 20 with an external load as shown in FIG. 9B so as to apply an internal compressive load of a predetermined magnitude F to the fuel cell assembly 24, and then or (A) measure the compressed length 30 of the fuel cell assembly 24; or (B) Measure the compressed length of the fuel cell stack 20 and then calculate the degree of compression 30 of the fuel cell 24 by subtracting the known dimensions of the end plates 45,58, end plate 56 and all other components of the end assemblies 32,34. Once the compressed length 30 of the fuel cell assembly 24 is determined, the external compressive loads are removed from the fuel cell assembly 24 or fuel cell stack 20 . The desired combined thickness of the separators 52 is calculated using the compressed length 30 of the fuel cell assembly 24 to produce a predetermined or uniform length L of the fuel cell stack 20 . The desired combined thickness of the separator 52 is equal to the difference between the length of the space in which the fuel cell assembly 24 is to be placed (as discussed above) and the compressed length 30 of the fuel cell assembly 24 . From this, the required combined thickness of the separators 52 is calculated.

Alternatively, a compressed length of the fuel cell stack 20 with an internal compressive load of a predetermined magnitude F on the fuel cell assembly 24 may be employed. The compressed length of the fuel cell stack 20 can be obtained by compressing the fuel cell stack 20 with an external compressive load to apply an internal compressive load of a predetermined magnitude F to the fuel cell assembly 24 and then measuring the compressed length of the fuel cell stack 20 . The external compressive loads on the fuel cell stack are then relieved. The difference between the predetermined or uniform length L of the fuel cell stack 20 and the measured compressed length of the fuel cell stack 20 is calculated. The calculated difference is the desired combined thickness of the separators 52 .

Once the desired combined thickness of the separators 52 is determined, one or more separators 52 having the desired combined thickness are selected. Selected separators 52 are positioned between the upper and/or lower end plates 45 , 58 and the corresponding upper and/or lower ends 26 , 28 of the fuel cell assembly 24 . Separator 52 is positioned such that the combined thickness of separator 52 is aligned with length 30 of fuel cell assembly 24 . The fuel cell stack 20 is then compressed by applying an external compressive load to the fuel cell stack 20, whereby the fuel cell stack 20 has substantially a predetermined or uniform length L. The final internal compressive load of a fuel cell stack 20 having a predetermined or uniform length L should be substantially equal to the predetermined size F. The side plates 36 are then secured to the upper and lower end plates 45, 58 such that the upper and lower end plates 45, 58 substantially maintain the fuel cell stack 20 at a predetermined or uniform length L. Finally, the external compressive loads are removed from the fuel cell stack 20 . The length of the final fuel cell stack 20 is substantially equal to the predetermined or uniform length L, while the fuel cell assembly 24 is substantially compressed with a force F of the predetermined magnitude.

The predetermined compression distance method for fabricating the fuel cell stack 20 can also utilize the separator 52 to fabricate the fuel cell stack 20 of a predetermined or uniform length L. The desired combined thickness of the separator 52 is based on the desired predetermined or uniform length L of the fuel cell stack 20 , the compressed length 30 of the fuel cell assembly 24 , and the thickness of various components including the end assemblies 32 , 34 . The compressed distance 30 of the fuel cell assembly 24 may be calculated by subtracting the predetermined distance D from the uncompressed length 31 of the fuel cell assembly 24 . Subtracting the compressed length 30 of the fuel cell assembly 24 and the thickness of the ends 45, 58, the termination plate 56 and all other components including the end assemblies 32, 34 from the predetermined or uniform length L of the fuel cell stack 20, The desired combined thickness of the separator 52 is obtained. Separators 52 are then selected such that the combined thickness of the separators 52 is substantially equal to the desired total thickness. The selected separator 52 is then added to the fuel cell stack 20 as discussed above. The resulting fuel cell stack 20 has substantially a desired predetermined or uniform length L, the fuel cell assembly 24 substantially compressed a predetermined distance D, and an internal compressive load corresponding to efficient operation of the fuel cell assembly 24 .

The use of the adverb "substantially" to quantify a term herein should be understood to mean that the size of the element in question is within acceptable tolerances of the desired size.

The description of the invention is exemplary in nature and, therefore, variations that may be made without departing from the gist of the invention are intended to be considered as being within the scope of the invention. Such changes should not be regarded as a departure from the spirit and scope of the invention.

Claims (20)

1. electro-chemical fuel cell stack, this storehouse comprises:

A plurality ofly arrange that in the stacked structure mode described fuel cell module has opposed first and second ends to form the fuel cell of fuel cell module;

First and second end plates with relative surfaces externally and internally, described first and second end plates are arranged in the described first and second end position adjacent with described fuel cell module, and make described inner surface towards described fuel cell module, described first and second end plates are held with fixing spaced relationship, so that apply compression stress to described fuel cell module; With

At least one the moulding surface that forms on the described inner surface of at least one end plate in described first and second end plates can apply basically compression stress uniformly to described fuel cell module thus.

2. storehouse according to claim 1, wherein:

Extend towards described fuel cell module from described at least one end plate on described at least one moulding surface.

3. storehouse according to claim 2, wherein:

The profile on described at least one moulding surface is a convexity, and the thickness of described like this at least one end plate increases to the center of described end plate from the outer rim of described end plate, reaches maximum at the described center of described end plate thickness.

4. storehouse according to claim 1, wherein:

Described at least one moulding surface is formed on each described inner surface of described first and second end plates, and extends towards described fuel cell module thus.

5. electro-chemical fuel cell stack, this storehouse comprises:

A plurality of fuel cells that have the fuel cell module of opposed first and second ends with formation of arranging in the stacked structure mode;

First and second dividing plates with relative surfaces externally and internally, a plurality of flat lateral vertical are in described inner surface and outer surface, described first and second dividing plates are arranged in the described first and second end position adjacent with described fuel cell module, and the described inner surface that makes described first and second dividing plates is respectively towards first and second ends of described fuel cell module;

First and second end plates with relative surfaces externally and internally, described first and second end plates are arranged in and the described first and second dividing plate position adjacent, and allow the described inner surface of described first and second end plates respectively towards the described outer surface of described first and second dividing plates, and described first and second end plates are held with fixing spaced relationship by fixing first and second end plates by described side, so that make described first and second end plates apply compression stress to described first and second dividing plates and described fuel cell module; And

At least one the moulding surface that forms at least one plate in described first end plate, described second end plate, described first dividing plate and described second partition can apply basically compression stress uniformly thus on described fuel cell module.

6. storehouse according to claim 5, wherein:

Described at least one moulding surface is formed on the described outer surface of at least one dividing plate in described first and second dividing plates, and extends towards described adjacent end plate thus.

7. storehouse according to claim 6, wherein:

Described at least one moulding surface is formed on each described outer surface of described first and second dividing plates, and extends towards first and second end plates of correspondence thus.

8. storehouse according to claim 5, wherein:

Described at least one moulding surface is formed on the described inner surface of at least one dividing plate in described first and second dividing plates, and extends towards described fuel cell module thus.

9. storehouse according to claim 8, wherein:

Described at least one moulding surface is formed on each described inner surface of described first and second dividing plates, and extends towards described fuel cell module thus.

10. storehouse according to claim 5, wherein:

Described at least one moulding surface is formed on the described outer surface of at least one dividing plate in described first and second dividing plates, and extends towards described adjacent end plate thus; And

Described at least one moulding surface is formed on the described inner surface of at least one dividing plate in described first and second dividing plates, and extends towards described fuel cell module thus.

11. storehouse according to claim 5, wherein:

Described at least one moulding surface is formed on the described inner surface of at least one end plate in described first and second end plates, and extends towards described fuel cell module thus.

12. storehouse according to claim 11, wherein:

Described at least one moulding surface is formed on each described inner surface of described first and second end plates, and extends towards described fuel cell module thus.

13. storehouse according to claim 5, wherein:

Described at least one moulding surface is formed on the described inner surface of at least one end plate in described first and second end plates, and extends towards described fuel cell module thus; And

Described at least one moulding surface is formed on the described outer surface of at least one dividing plate in described first and second dividing plates, and extends towards described adjacent end plate thus.

14. storehouse according to claim 5, wherein:

Described at least one moulding surface is formed on the described inner surface of at least one end plate in described first and second end plates, and extends towards described fuel cell module thus; And

Described at least one moulding surface is formed on the described inner surface of at least one dividing plate in described first and second dividing plates, and extends towards described fuel cell module thus.

15. an electro-chemical fuel cell stack, it comprises:

A plurality ofly arrange that in the stacked structure mode described fuel cell module has opposed first and second ends to form the fuel cell of fuel cell module;

Be arranged in first and second end brackets on the described first and second end position adjacent with described fuel cell module;

Be arranged in the described first and second end bracket position adjacent on first and second end plates, and allow described end bracket be inserted between described fuel cell module and described first and second end plates respectively;

At least one end bracket in described first and second end brackets is fixedly attached on the adjacent end plate, and the rigidity of described like this end bracket helps the rigidity of described adjacent end plate; And

Described first and second end plates have a plurality of flat side perpendicular to the described adjacently situated surfaces of described end bracket and described end plate,

Described first and second end plates are held with fixing spaced relationship by fixing first and second end plates by described side, so that described first and second end plates apply compression stress to described fuel cell module.

16. storehouse according to claim 15, wherein:

Each all securely is fixed to respectively on the adjacent end plate in described first and second end brackets, and the rigidity of described like this first and second end brackets helps the rigidity of described first and second end plates respectively.

17. storehouse according to claim 15, wherein:

Described at least one end bracket utilizes at least one machanical fastener securely to be fixed on the described adjacent end plate.

18. storehouse according to claim 15, wherein:

Described at least one end bracket utilizes binding agent securely to be fixed on the described adjacent end plate.

19. storehouse according to claim 15, it also comprises:

Be clipped at least one dividing plate between described at least one end bracket and the described adjacent end plate, described at least one dividing plate securely is fixed on described at least one end bracket and the described adjacent end plate, and the rigidity of described like this at least one dividing plate helps the described described rigidity that is connected end plate.

20. storehouse according to claim 19, it also comprises:

First and second dividing plates, described first dividing plate are clipped between described first end bracket and described first end plate, and described second partition is clipped between described second end bracket and described second end plate;

Described first end bracket, described first dividing plate and described first end plate securely are fixed together, and the rigidity of the rigidity of described like this first end bracket and described first dividing plate helps the rigidity of described first end plate; And

Described second end bracket, described second partition and described second end plate securely are fixed together, and the rigidity of described like this second end bracket and the rigidity of described second partition help the rigidity of described second end plate.

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