CN1328810C

CN1328810C - End plates for a fuel cell stack structure

Info

Publication number: CN1328810C
Application number: CNB038096943A
Authority: CN
Inventors: J·A·罗克
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 2002-04-30
Filing date: 2003-04-09
Publication date: 2007-07-25
Anticipated expiration: 2023-04-09
Also published as: DE10392584B4; CN1650446A; DE10392585B4; AU2003230898A1; AU2003226325A1; CN100362685C; JP2008277303A; CN1650454A; DE10392584T5; DE10392585T5; JP2006501601A; CN1650460A; DE10392581T5; DE10392581B4; JP2005522857A; CN100499205C; AU2003223519A1; JP2005524214A

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

The end plate of fuel cell stack structure

Invention field

The present invention relates to fuel cell, be specifically related to arrange and keep the fuel cell of compressed format by the storehouse mode.

Background of invention

Fuel cell stack generally comprises a plurality of fuel cells, they one be stacked on another, keep compressed format each other.These a plurality of stacked fuel cells have formed and have been compressed into the fuel cell module that can allow a plurality of fuel cells keep compression context.Generally speaking, each fuel cell all comprise anode layer, cathode layer and be clipped in described anode layer and described cathode layer between electrolyte.This fuel cell module needs sizable compression stress that the fuel cell of this storehouse is forced together.Need compression stress to be because the needs that the internal gas of the reactant that exists in the fuel cell produces pressure and keeps excellent electric contact between the internal part of battery.Generally speaking, the power of each square measure totally is about 195-205psi, and this power is evenly distributed on the whole effective coverage (for the storehouse of automobile-used size, generally being the 77-155 square inch) of battery.So for the about 80 square inches fuel cell of area, the total compression power of this size storehouse generally is about 15500 to 16500 pounds.

The exemplary fuel cell stack stack architecture of prior art focuses on and adopts rigid end sheet to apply and keep compression stress to fuel cell module.The fuel cell module that compresses is clipped between a pair of rigid end sheet.Then end plate is forced together, it is held in a spaced relation to keep compression stress.Can be held in a spaced relation end plate in several ways.For example, can utilize the connecting rod that passes the end plate extension to apply compression stress, and keep the spaced relationship of end plate to end plate.Connecting rod is generally in the fuel cell module outside, and it is arranged along the outer rim of end plate.Also can utilize along the length direction extension of fuel cell module and the side plate that is connected with end plate and be held in a spaced relation end plate, to keep the compression stress on the fuel cell module.

Because it is very big be to the compression stress that fuel cell module applies must to apply the size of effective coverage of compression stress on the very big and fuel cell module, therefore the rigid end sheet that is held in a spaced relation by variety of way along the rigid end sheet outer rim has the deflection tendency, just can not apply basically compression stress uniformly thus to the whole effective coverage of fuel cell module.That is, the middle body generation deflection of rigid end sheet, the power that is applied on the effective coverage that is positioned at rigid end sheet middle body below neither be the same big with the power on being applied to effective coverage, rigid end sheet outer rim place.

Attempting is providing basically the prior art of compaction profile uniformly to comprise very thick rigid end sheet, the rigid end sheet that has the inner link of passing fuel cell module that has outer link, the semi-rigid end plate that has the air bag cavity and is adopting the certain force (discreet force) that is positioned at above the end plate middle body to apply parts such as screw on the effective coverage, described certain force applies parts and can move relative to the end plate selectivity, so that apply compression stress along the middle body of end plate.

In having the rigid end sheet of outer link, threaded rod extends to the bottom plate edge along the fuel cell module outside from the upper head plate edge, so just carries whole compression stress by connecting rod.End plate must be enough thick, so that allow total deflection very little (each battery is approximately less than 1mil).The shortcoming of this system is, compares with other all options, because whole end plate span maximum do not have other method can produce uniform power on whole effective coverage, so end plate must be very thick.

In the rigid end sheet that has the inner link of passing fuel cell module, connecting rod passes the fuel cell center, so that allow the position of connecting rod near the middle body of end plate.So the total span of bending force is not extended, but obtained shorter span on the whole width of upper head plate.This scheme has the advantage that can shorten the end plate length of span, therefore can utilize thin end plate, but it also has shortcoming, that is, need complicated bipolar plates hermetically-sealed construction so that allow connecting rod pass fuel cell module.

In having the semi-rigid end plate of air bag cavity, the lower surface of upper head plate is hollowed out, and is provided with an air bag in this end plate cavity, exerts pressure to this air bag, so that desirable storehouse compressive load to be provided.So, when air bag keeps uniform force to distribute on whole effective coverage, can allow upper head plate itself that a little bending takes place.Owing to can allow upper head plate crooked significantly, thus this scheme have the upper head plate parts can be done thin advantage, but it also has shortcoming, that is, it requires that cavity is arranged in the end plate, so the general thickness of end plate also will significantly increase.

When utilizing certain force to apply parts, this certain force applies the middle body top that parts are positioned at end plate, and it can move relative to the end plate selectivity, so that apply compression stress along the middle body of end plate.This scheme has to finely tune and is applied to the advantage of each locational compression stress that certain force applies the end plate of parts tops, but its shortcoming is, it needs additional mechanism to keep certain force to apply parts, and needs fastening each certain force to apply parts so that obtain the repetitive process of power distribution uniformly basically on the effective coverage of fuel cell module.

So, needed is a kind of like this fuel cell stack structure, it has and can need not under the situation of blocked up end plate, perhaps do not needing to adopt extra means to apply under the situation of compression stress, applying basically the end plate of compression stress uniformly along the effective coverage of fuel cell module to the middle body of end plate.

Summary of the invention

The present invention relates to a kind of provide can compressing fuel cells assembly, and can on the effective coverage of fuel cell module, apply basically the fuel cell stack structure of compression stress uniformly.Particularly, the present invention relates to the improvement to the end plate design, it has improved the compression force distribution on the fuel cell module effective coverage.

Electro-chemical fuel cell stack of the present invention comprises a plurality ofly arranges to form the fuel cell of fuel cell module according to the stacked structure mode.This fuel cell module has opposed first and second ends.Arranging first and second ends with the first and second end position adjacent of fuel cell module respectively with relative surfaces externally and internally.The inner surface of end plate is towards the end of fuel cell module.First and second end plates are held with spaced relationship, so that make first and second end plates apply compression stress to fuel cell module.The profile of the inner surface of at least one end plate is configured to and can applies basically compression stress uniformly to fuel cell module in first and second end plates.The profile of this contoured inner surface can be configured to allow the end plate of this inner surface from least one end plate towards fuel cell module extend.Preferably, the thickness of contour construction Cheng Nengrang end plate with end plate of contoured inner surface increases from the end plate edge to the end plate center, like this thickness maximum at end plate center.Optional is that the inner surface profile of first and second end plates all can be configured to the extension of first and second ends from first and second end plates towards fuel cell module respectively, so just can apply basically compressive load uniformly to fuel cell module.

Select among the embodiment of the present invention, electro-chemical fuel cell stack comprises a plurality of fuel cells that become fuel cell module according to the stacked structure arranged in form.This fuel cell module has opposed first and second ends.Arranging first and second dividing plates respectively with on the first and second end position adjacent of fuel cell module with opposed surfaces externally and internally.The inner surface of dividing plate is towards the end of fuel cell module.Arranging first and second end plates with the first and second dividing plate position adjacent respectively, and allowing dividing plate between the end of end plate and fuel cell module with relative surfaces externally and internally.The inner surface of end plate is towards the outer surface of dividing plate.First and second end plates are held with spaced relationship, so that make first and second end plates apply compression stress to dividing plate and fuel cell module.At least one surperficial profile of at least one in dividing plate or the end plate is configured to and can applies basically compression stress uniformly to fuel cell module.

In different selected embodiment of the present invention, electro-chemical fuel cell stack comprises according to the stacked structure mode arranges to form the fuel cell of fuel cell module.This fuel cell module has opposed first and second ends.Arranging first and second end brackets with the corresponding first and second end position adjacent of fuel cell module.Arranging first and second end plates with the first and second end bracket position adjacent respectively, allow end bracket between the end of end plate and fuel cell module.Have at least an end bracket to link to each other with one of first or second end plate in first and second end brackets, the rigidity of this at least one end bracket will help the rigidity of connected end plate like this.First and second end plates are held with spaced relationship, so that make first and second end plates apply compression stress to fuel cell module.Optional is that fuel cell stack also can comprise at least one dividing plate.This at least one dividing plate is clipped between at least one end bracket that links to each other with one of first or second end plate.This at least one dividing plate links to each other with one of first or second end plate with at least one end bracket, and the rigidity of this at least one dividing plate helps the rigidity of the end plate that connected like this.

To make other range of application of the present invention become obvious by the detailed description that provides below.Should be understood that,, attempt to think that they only are used for illustration purpose though detailed description and object lesson are all represented the preferred embodiments of the present invention, rather than limitation of the scope of the invention.

Brief description of drawings

By the detailed description and the accompanying drawings, will make the present invention become easier and fully understand, in the accompanying drawing:

Fig. 1 is the perspective view of electro-chemical fuel cell stack of the present invention;

Fig. 2 is the simplified cross-sectional view that the hatching 2-2 along electro-chemical fuel cell stack among Fig. 1 cuts open;

Fig. 3 is the part decomposition diagram of Fig. 1 electro-chemical fuel cell stack, and its expression side plate combines with this electro-chemical fuel cell stack of figure;

Fig. 4 is the incomplete view of the simplification of expression fuel cell details;

Fig. 5 A-5G is the cutaway view of the various structures of the end plate of electro-chemical fuel cell stack of the present invention and dividing plate;

Fig. 6 A is the plane graph according to the moulding inner surface of the end plate of the principle of the invention;

Fig. 6 B is the cutaway view that the hatching B-B along the end plate of Fig. 6 A cuts open;

Fig. 6 C is the cutaway view that the hatching C-C along the end plate of Fig. 6 A cuts open;

Fig. 7 A-7B is the incomplete cutaway view of the end assembly of electro-chemical fuel cell stack of the present invention, and its expression is in conjunction with the variety of way of the parts of these end board assemblies;

Fig. 8 is the perspective view of the dividing plate that adopts in the electro-chemical fuel cell stack of the present invention, and its expression utilizes the hole to alleviate separator;

Fig. 9 A-9B is the simple and easy cutaway view of the electro-chemical fuel cell stack of Fig. 1, and its expression utilizes the compression stress of pre-sizing F respectively fuel cell module and fuel cell stack to be compressed;

Figure 10 A-10B is the simple and easy cutaway view of the electro-chemical fuel cell stack of Fig. 1, and its expression has been compressed preset distance D with fuel cell module and fuel cell stack;

Figure 11 is the flow chart of expression according to the step of the predetermined force compression method of principle manufacturing fuel cell stack of the present invention;

Figure 12 is the flow chart of expression according to the step of the predetermined compression distance method of principle manufacturing fuel cell stack of the present invention;

Figure 13 represents that the manufacturing of use dividing plate is scheduled to or the flow chart of the step of the fuel cell stack of even length.

Detailed description of preferred embodiment

Following description of preferred embodiments itself only is exemplary, and they never are the restrictions to invention, its application, or uses.

With reference to Fig. 1 and 2, it shows the electro-chemical fuel cell stack 20 according to the preferred embodiment of the present invention.This fuel cell stack 20 comprises a plurality of fuel cells 22 that are arranged to fuel cell module 24 according to the stacked structure mode, described fuel cell module 24 has opposed upper end 26 and lower end 28, shown in Figure 10 A, in the middle of their reduction length 30 and reduction length 31 not.Fuel cell module 24 is clipped between the upper and lower end assembly 32,34.Upper and lower end assembly 32,34 is held with fixing spaced relationship by sidewall.In currently preferred embodiments, sidewall comprises at least one side plate 36.Side plate 36 is held in a spaced relation upper and lower end assembly 32,34, so that allow upper and lower end assembly 32,34 apply compression stress to fuel cell module 24.According to known fuel assembly stack technology, fuel cell stack 20 comprise to/from fuel cell module 24 supply, the inlet 37 of discharging reactant and chilled fluid flow, outlet 38 and passage (not shown).

As shown in Figure 4, fuel cell module 24 comprises a plurality of repetitives or fuel cell 22, and each repetitive all has the bipolar plate assembly 42 on the opposite flank of membrane electrode assembly (MEA) 40 and a pair of MEA of being arranged in 40.Each bipolar plate assembly 42 is all formed by being clipped in two coolant distribution 42c between the gas distribution layer 42g.Between coolant distribution 42c and gas distribution layer 42g, accompany the dividing plate 44 thoroughly that cooling agent is housed and anode and cathode flame are separated.In the time of between the cathode gas Distribution Layer 42gc of anode gas distribution layer 42ga that MEA is clipped in a battery and adjacent cell, just formed fuel cell 22.MEA40 can adopt various ways, and this is known in this area.For example, MEA40 can be a polymer electrolyte film.Preferably, polymer electrolyte film is slim the add strong film of thickness on 0.018 micron number magnitude.It is much thin that the thickness that adopts in the fuel cell of slim reinforcement polymer electrolyte film than prior art is about 0.007 inch polymer electrolyte film.The polymer electrolyte film that approaches and pass through again enhancing of the present invention only accounts for very little percentage in the length 30 of fuel cell module 24, with comparing than the thick polymer electrolytic thin-membrane that the fuel cell stack of prior art adopts, it occurs sliding or stress relaxation is wanted much less.

Fuel cell 22 according to the arranged in form of stacked structure to form fuel cell module 24.The number that is stacked adjacent one another to form the fuel cell 22 of fuel cell module 24 can change.The number that is used to form the fuel cell 22 of fuel cell module 24 depends on the needs of fuel cell stack 20.That is, when the bigger or more powerful fuel cell stack 20 of hope, the number of fuel cell 22 will increase in the fuel cell module 24.Well known in the artly be, need compressing fuel cells 22,, and produce more multipotency so that make fuel cell 22 more efficient.So, fuel cell module 24 is pressed between the upper and lower end assembly 32,34.Preferably, the effective coverage (not shown) of even compressing fuel cells assembly 24, make the maximizing efficiency of each fuel cell 22 in fuel cell module 24 and the fuel cell module 24.

Referring again to Fig. 2 and 3, upper module 32 is arranged in upper end 26 position adjacent with fuel cell module 24.Upper module 32 comprises the upper head plate 45 with opposed surfaces externally and internally 46,48.The inner surface 46 of upper head plate 45 is towards the upper end 26 of fuel cell module 24.Upper head plate 45 has a plurality of openings 50, so that each inlet 37, the outlet 38 that link to each other with the fluid passage extend to the outside of fuel cell stack 20 from fuel cell module 24.End with fuel cell stack 20 of the inlet that links to each other with these passages 37 and outlet 38 is also referred to as " green end ".

Lower end assembly 34 is arranged on the place adjacent with the lower end 28 of fuel cell module 24.Lower end assembly 34 comprises the bottom plate 58 with relative interior and outer surface 60,62.Bottom plate 58 is oriented to allow the inner surface 60 of bottom plate 58 towards the lower end 28 of fuel cell module 24.When the entrance and exit that does not link to each other with the fluid passage passed lower end assembly 34, the lower end 28 of fuel cell stack 20 was also referred to as " dry end ".

Optional but preferably, have one or more dividing plates 52 can fuel cell module 24 and above and/or under between the end plate 45,58.Dividing plate 52 allows the inner surface 54 of dividing plate 52 towards the end 26,28 of fuel cell module 24 between the end 26,28 of

end plate

45,58 and fuel cell module 24, allows the outer surface 55 of dividing plate 52 towards the inner surface 54,60 of end plate 45,58.When being provided with end bracket 56 on the end 26,28 of fuel cell module 24, dividing plate 52 is located between end bracket 56 and the

end plate

45,58, and the inner surface 54 of dividing plate 52 is towards end bracket 56.Dividing plate 52 separates

end plate

45,58 and end bracket 56.In end assembly 32,34, dividing plate 52 is oriented to allow the thickness 57 of dividing plate 52 and length 30 alignings of fuel cell module 24.Though preferred embodiment shows the dividing plate 52 that is associated with upper and lower end assembly 32,34, those of ordinary skills are cognoscible to be, but the design of the number of dividing plate 52 and position fuel cell storehouse 20 and application and change.

Each all has the peripheral side wall 64 that inner surface 46,60 and outer surface were opened in 48,62 minutes upper and lower end plate 45,58.The peripheral side wall 64 of upper and

lower end plate

45,58 and length 30 alignings of fuel cell module 24.Preferably, as shown in the figure, the shape of fuel cell stack 20 is rectangular basically, and the shape of upper and

lower end plate

45,58 also is rectangular.The peripheral side wall 64 of rectangular upper and

lower end plate

45,58 is made up of the first and second pairs of

opposed side walls

66,68 that are perpendicular to one another basically.Each of first and second pairs of

opposed side walls

66,68 all has more than one screwed hole, in order to hold the threaded fastener 80 that side plate 36 can be fixed on the upper and

lower end plate

45,58.

Just as mentioned above, upper and lower end assembly 32,34 applies compression stress to fuel cell module 24.The compression stress that is applied on the fuel cell module 24 can produce by the upper and

lower end plate

45,58 of the spaced relationship that is maintained fixed.Preferably, the spaced relationship that is maintained fixed by side plate 36 of upper and lower end plate 45,58.Every block of side plate 36 has opposed first and second ends 72 and 74 and the length between the two 76.Every block of side plate 36 is positioned on the fuel cell stack 20, makes first end 72 adjacent with upper head plate 45, makes second end 74 adjacent with bottom plate 58, the length 76 of side plate 36 and length 30 alignings of fuel cell module 24.Optional but preferably, side plate 36 extends along the whole peripheral side wall 64 of end plate 45,58.First and second ends 72,74 of every block of side plate 36 all have more than one opening 78, and when compressing fuel cells assembly 24, these openings will align with the screwed hole 70 on the peripheral side wall 64 of upper and lower end plate 45,58.Preferably, the opening 78 of any end is a form of slits in first and/or second end 72,74 of every block of side plate 36, so just can keep upper and

lower end plate

45,58 with fixing spaced relationship.This slit still can keep upper and

lower end plate

45,58 with fixing spaced relationship in the change in size of each parts that allow fuel cell stack 20.Though preferably adopt screw thread machanical fastener 80 that side plate 36 is connected on the upper and

lower end plate

45,58, but experienced technical staff can recognize, under the situation of the invention scope that does not break away from claims and limited, also can adopt alternate manner that side plate 36 and upper and

lower end plate

45,58 are coupled together.On this meaning, the joint that is formed by side plate 36 and

end plate

45,58 should be enough to resist the relative rotation that meets the place, boundary between them.For example, on the

end plate

45,58, these modes were still in spiritual scope of the present invention above and/or under first end 72 of side plate 36 and/or second end 74 can or be fixed to accordingly by various bonding modes such as welding, soldering or binding agent bonding by other mechanical fasteners mode such as rivet or pin.In addition, should be understood that, end in the end 72,74 of side plate 36 can be crooked, to form the holding element (not shown) that can be positioned on one of

end plate

45,58, in order to maintain

end plate

45,58, allow the opposed end 72,74 of side plate 36 be connected on the

relative end plate

45,58 simultaneously, and keep end plate with fixing spaced relationship.

As required, every end plate 36 all can have more than one opening 82, in order to allow terminal block 83 on the end bracket 56 extend to the outside of fuel cell stack 20.Preferably, every side plate 36 electricity ground connection, thus protection fuel cell module 24 is not subjected to electromagnetic interference.In addition preferably, every block of side plate 36 is made of metal.To be used for keeping the size of the side plate 36 of upper and

lower end plate

45,58 to be configured to fixing spaced relationship: can be when keeping upper and

lower end plate

45,58 with fixing spaced relationship, allow upper and

lower end plate

45,58 apply and keep compression stress to fuel cell module 24.Because the width of side plate 36 is bigger, therefore need less thickness to provide the carrying compressive load necessary tensile strength.Compare with the situation of utilizing around the fuel cell module traditionally and/or run through the axial stem of fuel cell module, this scheme of the present invention has the effect of weight reduction.

Preferably, the side plate 36 more than is sealed at least a portion fuel cell module 24, is not subjected to accidental damage with protection fuel cell module 24.More preferably, side plate 36 is sealed whole fuel cell module 24, thereby provides protective cover for fuel cell module 24 and fuel cell stack 20.So; the size of side plate 36 is configured to allow side plate 36 stand these impacts, piping and druming and other strike, the infringement that can protect fuel cell module 24 and fuel cell stack 20 not produced by impact, piping and druming or other strike owing to various natural things simultaneously.In this way, side plate 36 not only is used for keeping upper and

lower end plate

45,58 so that apply and keep compressive load to fuel cell module 24 with fixing spaced relationship, and provides protective cover for fuel cell module 24 and fuel cell stack 20.Around fuel cell stack 20, the needs of additional structure are set utilizing side plate 36 execute protection functions to eliminate to resemble in the conventional fuel cell stack stack, fuel cell stack 20 are subjected to unexpected piping and druming, impact or the protection of other strike thereby provide.

The dividing plate 52 that comprises of choosing wantonly is used for multiple purpose in upper module 32 and/or the lower end assembly 34.That is, can be because of more than one former thereby dividing plate 52 covered in the fuel cell stack 20.For example, dividing plate 52 can be used for above and/or under

end plate

45,58 and end bracket 56 separate.According to recited above, end bracket 56 conducts electricity, and it is used for extracting electric current by terminal block 83 from fuel cell stack 20.When above and/or under during

end plate

45,58 conduction, above and/or under dividing plate 52 between

end plate

45,58 and the end bracket 56 upper head plate and/or

bottom plate

45,58 and end bracket 56 electric insulations can be separated.Dividing plate 52 also can be used for controlling the overall dimension of fuel cell stack 20.Promptly, to describe in detail according to following, can fuel cell module 24 and above and/or under dividing plate 52 more than one is set between the

end plate

45,58 so that in the fuel cell stack 20 that predetermined length is provided, still can allow end assembly 32,34 apply compression stress to fuel cell module 24.Preferably current, the thickness range of dividing plate (or a plurality of dividing plate) 52 is about the 8-18 millimeter, and electrical insulation capability is enough, the uniform fuel cell stack 20 of size thereby provide.But those of ordinary skill in the art can recognize that concrete application and design specification will determine the scope of the thickness 57 of dividing plate 52.To describe in detail according to following, dividing plate 52 also can with above and/or under

end plate

45,58 be used in combination, be used for applying basically compressive load uniformly to fuel cell module 24.

Preferably, dividing plate 52 is nonconducting, and it can be used for each parts electric insulation of fuel cell stack 20 is separated.So dividing plate 52 is preferably made by electrically non-conductive material such as plastics.More preferably, dividing plate 52 is made by the high performance plastics of technical grade.The technical grade high performance plastics that is used to make one or more dividing plate 52 under a certain size the compressive load effect that is applied on the fuel cell module 24 be incompressible relatively (promptly, stress relaxation is little), thus with compressive load from above and/or under

end plate

45,58 pass to the corresponding upper and lower end 26,28 of fuel cell module 24.Particularly, proved that utilizing polythenylene sulfide to make dividing plate 52 is effective especially materials.Polythenylene sulfide can be by Chenron Philips ChemicalCompany, and the FORTRON board that RYTON PPS board that L.P. sells and the Celanese AG of German Frankfurt sell obtains.Preferably, as shown in Figure 7, dividing plate 52 has the hole 84 that can alleviate dividing plate 52 weight more than.

Mention according to top, spaced relationship that upper and

lower end plate

45,58 is maintained fixed by side plate 36, and apply compressive load to fuel cell module 24.As described above, upper and

lower end plate

45,58 is held with fixing spaced relationship by side plate 36.The compressive load that produces at the upper and lower end 26,28 of fuel cell module 24 will change according to the distance of distance peripheral side wall 64, and it reaches maximum along peripheral side wall 64 place's compressive loads, and reaches minimum in the center of upper and lower end plate 45,58.Promptly, therefore because upper and

lower end plate

45,58 only is maintained along their peripheral side wall 64, upper and

lower end plate

45,58 peripheral side wall 64 that will respond compressive load on the fuel cell module 24 and upper and

lower end plate

45,58 can not further be removed and be out of shape or deflection.Because the efficient of fuel cell stack 20 depends in part on the even compressive load that applies on the whole effective coverage of fuel cell module 24, therefore it is desirable on the whole effective coverage of fuel cell module 24, keep basically compressive load uniformly.

Obtain basically that a kind of mode of uniform load is to become firm by the thickness that increases upper and

lower end plate

45,58 by them, the deflection that so just can allow upper and

lower end plate

45,58 produce reduces to minimum to the influence of the efficient of fuel cell module 24.But supposing can be for upper and

lower end plate

45,58 provides this thickness, and these end plates are just too thick, and this has increased too much weight for fuel cell stack 20, thereby has reduced the weight efficiency and the volume efficiency of fuel cell stack.Necessity for fear of the

end plate

45,58 that relative stiffness is provided,

end plate

45,58 can randomly be attached on dividing plate 52 and the end bracket 56, so that make the rigidity of the rigidity of dividing plate 52 and end bracket 56 help the global stiffness of end assembly 32,34, reduced the thickness that on the whole effective coverage of fuel cell module 24, applies basically the required

end plate

45,58 of compressive load uniformly thus.That is, shown in Fig. 7 A-7B, dividing plate 52 and

end plate

45,58 can be tightened together, their rigidity is combined, formation can apply basically the end assembly 32,34 of compressive load uniformly to the effective coverage of fuel cell module 24.Shown in Fig. 7 A, mode that end bracket 56 can be by machanical fastener 86 such as bolt or screw element link to each other with dividing plate 52, and the end bracket 56 that combines and dividing plate 52 can link to each other by in machanical fastener 87 and the end plate 45,58.What can replace is that one of end plate 56, dividing plate 52 and

end plate

45,58 all can link to each other by the mode that is clipped in the tack coat 88 between the corresponding component.So, the rigidity of the rigidity of the rigidity of end bracket 56 and dividing plate 52 and

end plate

45,58 combines, can apply basically the end assembly 32,34 of compressive load uniformly to the effective coverage of fuel cell module 24 to provide, so under situation about end bracket 56 or dividing plate 52 and

end plate

45,58 not being coupled together,

thin end plate

45,58 will be necessary.

What can replace is, and/or in addition,

end plate

45,58 and/or dividing plate 52 can have the moulding surface, and it can the deflection to

end plate

45,58 compensates and apply basically compressive load uniformly under the situation of blocked up

end plate

45,58 on the effective coverage of whole fuel cell module 24 need not to adopt.Promptly, by Fig. 5 A-5G that only shows a upper head plate 45 and a dividing plate 52 as can be seen, the size of the inner surface 46 of upper head plate 45 is configured to plate 45, towards upper end 26 bendings of fuel cell module 24, the thickness of upper head plate 45 is along peripheral side wall 64 place's minimums, in the center of upper head plate 45 maximum like this.Consider because the upper head plate 45 of the spaced relationship that is maintained fixed with bottom plate 58 is held, has applied the compressive load of desirable amount and the deflection that will produce to the effective coverage of fuel cell module 24 in upper head plate 45 again simultaneously along its peripheral side wall 64, the shape profile of the inner surface 46 of upper head plate 45 has also been done moulding.Fig. 6 A-6C represents the exemplary profile moulding of the inner surface 46 of upper head plate 45.Just as can be seen, the thickness of upper head plate 45 is greatly about the center of upper head plate 45 maximum.

That can replace is, and/or in addition, considers that dividing plate 52 can have profile by the interior and/or

outer surface

54,55 of moulding in the deflection of upper head plate 45 with generation.That is, the thickness of dividing plate 52 is configured to along dividing plate 52 outer rim minimums, in the center of dividing plate 52 maximum.For example, shown in Fig. 5 G, the profile of the inner surface 54 of dividing plate 52 is configured to be extended towards the upper end 26 of fuel cell module 24 by dividing plate 52, perhaps shown in Fig. 5 E, the profile of the outer surface 55 of dividing plate 52 is configured to be extended towards upper head plate 45 by dividing plate 52, so just can apply basically compressive load uniformly to the effective coverage of fuel cell module 24 by end plate 45.What can replace is, shown in Fig. 5 F, the profile of the surfaces externally and internally 54,55 of dividing plate 52 is configured to be extended towards the upper end 26 of fuel cell module 24 and the inner surface 46 of upper head plate 45 by dividing plate 52 respectively, just can apply basically compressive load uniformly thus to the effective coverage of fuel cell module 24.

The various variations of the moulding of the surfaces externally and internally 54,55 of dividing plate 52 and the inner surface 46 of upper head plate 45 are shown among Fig. 5 A-5G.Consider the deflection that upper head plate 45 is not only arranged, and the deflection of bottom plate 58 is arranged, the surface profile shape of upper head plate 45 and/or dividing plate 52 can be by moulding, and the upper and lower end 26,28 of fuel cell module 24 can both be received basically compressive load uniformly like this.Equally, should be understood that, the shape of the surfaces externally and internally 54,55 of the inner surface 60 of bottom plate 58 and dividing plate 52 also can be constructed or moulding according to same way as in the lower end assembly 34, and the parts of lower end assembly 34 can apply basically compressive load uniformly to the effective coverage of fuel cell module 24 like this.Experienced engineering practice personnel can recognize that inner surface 46 has the various local features that wherein are formed for realizing uniform more compressive load on the effective coverage of fuel cell module 24.So, should be understood that the surface configuration of the parts of the parts of upper module 32 and/or lower end assembly 34 can be constructed or be shaped to separately or together can apply uniform basically compressive load to the effective coverage of fuel cell module 24.It is to be further understood that for exemplary object, the size shown in each figure has been done exaggerative processing, they should not regarded as the size of each parts of relative fuel cell stack 20.That is, should be understood that, done exaggerative processing to the deflection of

end plate

45,58 with by the correction that the surface configuration of moulding

end plate

46,58 and/or dividing plate 52 is carried out, so that illustrate principle of the present invention better.It is to be further understood that each parts that will not utilize term " upper and lower " to describe fuel cell stack 20 are interpreted as it is absolute reference, be interpreted as it it is the relativeness that the parts of fuel cell stack 20 will be provided.

Though fuel cell stack 20 described and is expressed as basically rectangle structure, should be understood that the shape of fuel cell stack 20 can adopt various structures, they are still in the invention scope that claims limited.For example, fuel cell stack 20 can be columniform, and fuel cell module 24 and upper and lower end assembly 32,34 also can be columniform.When fuel cell stack 20 when being cylindrical, side plate 36 is exactly a cylindrical sleeve, and the inside is inserted with upper and lower end assembly 32,34 and fuel assembly 24.Side plate 36 can also be the part cylindrical sleeve, and it is covering the parts of fuel cell stack 20.So the use of term " side plate " should not be limited to flat board, and to should be understood to can be flat or crooked, or by the different shape of the given shape defined of fuel cell stack 20.

According to what mention previously, fuel cell stack 20 has the fuel cell module 24 that the compressive load utilized keeps, and can allow fuel cell module 24 more efficient thus.The present invention also is included in the various manufacture methods of making the fuel cell stack 20 with fuel cell module 24 under the compressive load condition.In first method, predetermined compressive load method, shown in Fig. 9 A-9B and 11, fuel cell module 24 and/or fuel cell stack 20 utilizable energies produce the external compressive load of the internal compressive load of pre-sizing F and compress on fuel cell module 24.Side plate 36 is fixed on the upper and

lower end plate

45,58 then, so that still can keep the fixing spaced relationship of upper and

lower end plate

45,58 during the external compressive load on laying down fuel cell module 24 and/or fuel cell stack 20.Because still can keep upper and

lower end plate

45,58 with fixing spaced relationship after laying down external compressive load, therefore according to following discussed in detail, upper and

lower end plate

45,58 continues to apply internal compressive load to fuel cell module 24.

In second method, predetermined compression distance method, shown in Figure 10 A-10B and 12, fuel cell module 24 and/or fuel cell stack 20 can be by external compressive load C compression preset distance D.In other words, the size of external compressive load is enough to fuel cell module 24 compression preset distance D.Then side plate 36 is connected to up and down end plate 45,58 (will describe in further detail) as following.Then lay down external compressive load.Upper and

lower end plate

45,58 keeps its fixing spaced relationship.Fuel cell module 24 keeps being compressed basically the state of preset distance D, applies internal compressive load thus in the above.

Mention according to top, the predetermined compressive load method of making the fuel cell stack 20 with fuel cell module 24 under the compressive load condition of pre-sizing F comprises to fuel cell stack 20 and to apply external compressive load.Predetermined compressive load method may further comprise the steps: 1) fuel cell module 24 is arranged between the upper and

lower end plate

45,58, makes the upper end 26 of fuel cell module 24 adjacent with upper head plate 45, the lower end 28 of fuel cell module 24 is adjacent with bottom plate 58; 2) at least one end plate in

end plate

45,58 applies external compressive force, so that compressing fuel cells assembly 24 makes it be subjected to the internal compression power effect of pre-sizing F; 3) side plate is combined with

end plate

45,58, allow side plate 36 first and second ends 72,74 respectively with corresponding upper and

lower end plate

45,58 combinations; And 4) lay down external compressive force at least one end plate that is applied in the

end plate

45,58, keep upper and

lower end plate

45,58 with fixing spaced relationship thus, thereby on fuel cell module 24, keep being substantially equal to the compression stress of pre-sizing F.Predetermined compressive load method just provides the fuel cell stack 20 that is applied with the compression stress that is substantially equal to pre-sizing F on fuel cell module 24 thus.

On the contrary, when utilizing predetermined compression distance method fuel cell stack assembly stack 20, compress with the compression stress of utilizing pre-sizing F and opposite to be, be with fuel cell stack 20 and/or fuel cell module 24 compression preset distance D.The datum mark of preset distance D can be the length overall of fuel cell module 24 itself.Therefore, another benchmark is only fuel cell module 24 to be compressed preset distance D, rather than compressing fuel cells storehouse 20.But, should be understood that, also can be with fuel cell module 24 compression preset distance D by fuel cell stack 20 compression preset distance D are realized.Preferably, preset distance D is corresponding to 24 that apply to fuel cell module, as to cause fuel cell stack 20 efficient operations compression stress.The preset distance D of compressing fuel cells assembly 24 can determine in several ways.For example, to go through according to following, but the fixed range of each fuel cell 22 that preset distance D fuel cell stack part 24 is comprised compresses and calculates, and perhaps the empirical data of experience of fuel cell module 24 that has a fuel cell 22 of dose known amounts according to compression is in the past determined.In case determined preset distance D, just apply external compressive load, so that with fuel cell stack 20 and/or fuel cell module 24 compression preset distance D to fuel cell stack 20.Then side plate 36 and upper and

lower end plate

45,58 are coupled together, lay down external compressive load.Gained fuel cell stack 20 just has the fuel cell module 24 that has been compressed preset distance D, and has the internal compressive load corresponding to the valid function of fuel cell stack 20.

When determining compression distance D, each fuel cell 22 is compressed to set a distance according to calculating (that is, the fixed range based on each battery compresses).The preset distance D of compressing fuel cells assembly 24 can multiply by each fuel cell 22 by the number n with the fuel cell in the fuel cell module 24 22 wants compressed fixed range d to calculate.In other words, calculate by equation D=n * d.The fixed range of each fuel cell 22 of compression to be chosen as and can provide size to correspond essentially to the compression stress of the valid function that fuel cell module 24 can be provided to fuel cell 22.That is, to want compressed fixed range d be based on the required decrement of the physical characteristic of fuel cell 22 and fuel cell 22 valid functions to each fuel cell 22.The fuel cell stack 20 of gained has the fuel cell module 24 that has been compressed preset distance D, and has the compressive load that realizes valid function corresponding to fuel cell module 24.

With with each fuel cell 22 compression fixed ranges opposite be that when data rule of thumb, the fixed range D of compressing fuel cells assembly 24 can determine by the experience in the past of utilizing known compressive load compressing fuel cells assembly 24.For these two kinds of methods, final preset distance D equates.Because the homogeneity basically of the composition of the fuel cell 22 that comprised of fuel cell module 24, just can for every type fuel cell 22 set up the number of fuel cell 22 and be subjected to the fuel cell module 24 of compression force generation of known dimensions at fuel cell module 24 and/or the compression distance of fuel cell stack 20 between general correlation.This correlation can be used for determining compressing fuel cells assembly 24 so that apply the preset distance D of the compression stress of desirable amount on fuel cell module 24 according to the number that comprises the fuel cell 22 of fuel cell module 24.For example, empirical data represents that the fuel cell module that will have 50 to 200 fuel cells has been compressed distance X and 4X respectively, thereby has applied the compression stress of desirable amount.The fuel cell stack 20 that has the fuel cell module of being made up of 100 equal fuel batteries 22 24 can be compressed apart from 2X, and according to above-mentioned correlation, it should apply the compression stress of the basic desirable amount that equates to fuel cell module 24.

Because the composition of the fuel cell of any given type 22 all has some to change, therefore the final compression stress that is applied on the fuel cell module 24 can change.The variable quantity of final compression stress will depend on the precision of correlation and the variation of fuel cell 22.Preferably, final compression stress will change near the tolerance interval desirable amount, and therefore this variation is insignificant to the influence of the efficient of fuel cell stack 20.So the empirical data method provides such fuel cell stack 20 with fuel cell module 24: with fuel cell module 24 compression preset distance D the time, described fuel cell module be substantially equal to desirable amount, corresponding to the compression force of fuel cell 24 valid functions.

Mention according to top, dividing plate 52 can be used for providing the fuel cell stack 20 of predetermined or homogeneous length L.That is, in fuel cell stack 20, dividing plate 52 can be used for occupying the space that allows fuel cell stack 20 reach predetermined or homogeneous length L.The homogeneous length L provides a plurality of advantages.For example, the homogeneous length L allows the replacing of fuel cell stack become easily, and allows and adopted the device of fuel cell stack 20 to have the normed space that is used for fuel cell stack 20.

Shown in Figure 13 a-13b, the invention provides the various assembling sequences of fuel cell stack with homogeneous length L.The ideal of fuel cell stack 20 is scheduled to or the homogeneous length L both can be known length such as industrial standard, also can be designated length.No matter under which kind of situation, total length L all is a known quantity.The thickness of all end brackets 56 that adopt in upper and

lower end plate

45,58, the fuel cell stack 20 and all other parts of end assembly 32,34 can be measured, so they also are known quantities.According to these known quantities/dimensions, the spaces that just can the computing fuel cell stack will place fuel cell module 24 in 20 are so this space also is a known quantity.That is, the space length that will place fuel cell module 24 in the fuel cell stack 20 predetermined or homogeneous length L that just equals fuel cell stack 20

deducts end plate

45,58, all end brackets 56 and forms the size of all other parts of end assembly 32,34.And unknown dimension only is the reduction length 30 of fuel cell module 24.The reduction length 30 of fuel cell module 24 can change according to the number of the included fuel cell 22 of the method that is used to make fuel cell stack 20 discussed above and fuel cell module 24.

According to top illustrated, dividing plate 52 can be used from the fuel cell stack 20 of making predetermined or homogeneous length L with predetermined compressive load method one, in this fuel cell stack 20, has applied the compressive load that is substantially equal to pre-sizing F to fuel cell module 24.In order to realize this purpose, need to determine the reduction length 30 of fuel cell module 24 or the reduction length of fuel cell stack 20, so that can determine the required combination thickness of one or more dividing plates 52.

All can determine the reduction length 30:(1 of fuel cell module 24 in the following manner) shown in Fig. 9 A, utilize external compressive load compressing fuel cells assembly 24, so that obtain the internal compressive load of pre-sizing F, measure reduction length 30 then; Perhaps (2) utilize external load compressing fuel cells storehouse 20 shown in Fig. 9 B, so that apply the internal compressive load of pre-sizing F to fuel cell module 24, then or (A) measure the reduction length 30 of fuel cell module 24; Perhaps (B) measures the reduction length of fuel cell stack 20, and the known dimensions of all other parts by cutting end plate 45,58, end bracket 56 and end assembly 32,34 is calculated the compression degree 30 of fuel cell 24 then.In case determined the reduction length 30 of fuel cell module 24, just laid down external compressive load from fuel cell module 24 or fuel cell stack 20.Utilize the reduction length 30 of fuel cell module 24 to calculate the required combination thickness of dividing plate 52 to make the fuel cell stack 20 of predetermined or homogeneous length L.The required combination thickness of dividing plate 52 equals reduction length 30 poor that the space length (as discussed above) of fuel cell module 24 and fuel cell module 24 will be placed in the inside.Calculate the required combination thickness of dividing plate 52 thus.

What can replace is to adopt the reduction length of the fuel cell stack 20 of the internal compressive load that pre-sizing F is arranged on fuel cell module 24.The reduction length of fuel cell stack 20 can obtain by following steps: utilize external compressive load compressing fuel cells storehouse 20, to apply the internal compressive load of pre-sizing F to fuel cell module 24, measure the reduction length of fuel cell stack 20 then.Then lay down the external compressive load on the fuel cell stack.Calculate institute's measured compressed length poor of predetermined or the homogeneous length L and the fuel cell stack 20 of fuel cell stack 20.Calculate difference be exactly the required combination thickness of dividing plate 52.

In case determined the required combination thickness of dividing plate 52, will select to have one or more dividing plate 52 of required combination thickness.Hold between 26,28 above and/or under

end plate

45,58 and fuel cell module 24 corresponding above and/or under the dividing plate of selecting 52 placed.With dividing plate 52 location, make the combination thickness of dividing plate 52 and length 30 alignings of fuel cell module 24.Come compressing fuel cells storehouse 20 by applying external compressive load to fuel cell stack 20 then, fuel cell stack 20 has predetermined or homogeneous length L basically thus.Final internal compressive load with fuel cell stack 20 of predetermined or homogeneous length L should be substantially equal to pre-sizing F.Then side plate 36 is fixed on the upper and

lower end plate

45,58, upper and lower like this

end plate

45,58 remains essentially in fuel cell stack 20 on predetermined or the homogeneous length L.At last, lay down external compressive load from fuel cell stack 20.The length of final fuel cell stack 20 is substantially equal to predetermined or homogeneous length L, and fuel cell module 24 is basically with the force compresses of pre-sizing F simultaneously.

Making the predetermined compression distance method of fuel cell stack 20 also can utilize dividing plate 52 to make the fuel cell stack 20 of predetermined or homogeneous length L.The reduction length 30 of the required combination thickness of dividing plate 52 predetermined or homogeneous length L, fuel cell module 24, comprise the thickness of a plurality of parts of end assembly 32,34 based on the ideal of fuel cell stack 20.The compression distance 30 of fuel cell module 24 can calculate by cut preset distance D from the not reduction length 31 of fuel cell module 24.The thickness that cuts the reduction length 30 of fuel cell module 24 and end 45,58, end bracket 56 and comprise all other parts of end assembly 32,34 from the predetermined or homogeneous length L of fuel cell stack 20 obtains the required combination thickness of dividing plate 52.Select the dividing plate 52 that can allow the combination thickness of dividing plate 52 be substantially equal to required gross thickness then.According to discussed above, selected dividing plate 52 is added on the fuel cell stack 20 then.The fuel cell stack 20 that finally obtains have basically desirable predetermined or homogeneous length L, basically be compressed preset distance D fuel cell module 24 and with the corresponding internal compressive load of the valid function of fuel cell module 24.

Quantize term at this with adverbial word " basically ", the size that it should be interpreted as the described key element of expression is in the range of tolerable variance accepted of desirable amount.

The description of this invention all is exemplary in essence, therefore, attempts to think that the variation made all within the scope of the present invention under the situation that does not break away from main points of the present invention.Not will be understood that these variations have broken away from the spirit and scope of the present invention.

Claims

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

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:

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

14. storehouse according to claim 5, wherein:

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

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.