JPH11260391A - Manifold for phosphoric acid type fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain airtightness and to prevent the corrosion of a manifold by forming a sheet provided with a heat resistance against the operation temperature of a cell, phosphoric acid resistance, and an insulating property into a box shape which matches the inside shape of the manifold and arranging it on the inside of the manifold. SOLUTION: A sheet 2 provided with heat resistance with respect to an operation temperature of a cell, phosphoric acid resistance, and an insulating property is formed into a box-shape matching the inside shape of a manifold 5, and this box-shaped sheet 2 is arranged on the inside of the manifold 5. The manifold 5 itself is provided with a function for keeping the box-shaped sheet 2 in a box-shape. In this process, the manifold 5 is constructed in a non- airtight structure, and a clearance is arranged between the box-shaped sheet 2 and the manifold 5, and a permeating gas or water vapor passes through the clearance to be discharged to the outside from an opening part such as a slit arranged in the manifold 5. In this way, adhesion to the inside face of the manifold 5 and retention of phosphoric acid in the permeating gas will not occur, and consequently, no corrosion is produced in the manifold 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a phosphoric acid type fuel cell which is formed by stacking a plurality of unit cells,
The present invention relates to a manifold used for distribution of a reaction gas.

[0002]

2. Description of the Related Art A fuel cell using an aqueous phosphoric acid solution can be operated at a lower temperature than a fuel cell using a solid oxide as an electrolyte, and therefore has been conventionally developed for consumer use. A unit cell of the phosphoric acid type fuel cell is configured by sandwiching a matrix holding phosphoric acid between a catalyst and a carbon electrode, and a plurality of such unit cells are stacked to form a fuel cell stack. For this reason, the entire surface of the fuel cell stack is a conductor, and the manifold incorporated for distributing the reactant gas to the side surface needs to ensure electrical insulation between the fuel cell stack and the manifold.

In a phosphoric acid type fuel cell, the phosphoric acid of the electrolyte evaporates and scatters from the matrix during operation and adheres to the inner surface of the manifold. Therefore, the manifold needs to have a phosphoric acid anticorrosion function. . Conventionally, a method of applying a fluororesin coating to a manifold has been generally used in consideration of these requirements and further considering heat resistance at an operating temperature. FIG. 9 is a perspective view of a conventional phosphoric acid fuel cell manifold showing a cut surface of the applied resin coating. In the figure, reference numeral 81 denotes a manifold, 83 denotes a resin coating, and 82 denotes a sealing surface which comes into contact with the fuel cell stack and keeps gas tightly.

As described above, in the conventional configuration in which the inner surface of the manifold is coated with the resin, the inner surface of the steel manifold serving as a base is not damaged in order to apply the resin coating having no defects such as pinholes. It is required to finish the welding beats smoothly and further increase the bending radius of the corners, so that many restrictions are imposed on the production of the manifold, and there is a problem that the production cost is increased. Further, in the applied resin coating, there is a variation in the formed film thickness, and there is a possibility that a portion where the film thickness is locally reduced may occur. When such a thin portion is formed, the mechanical strength is lower than that of other portions. Therefore, when the fuel cell is assembled in a fuel cell stack and operated for a long time, defects such as tearing or peeling of the film may occur. Will be higher. However, even when such a portion having a small film thickness occurs, a defect such as a pinhole does not exist, so that it is difficult to be found at the inspection stage, and it is difficult to take measures. For this reason, there was a problem that the reliability of the anticorrosion function was low in the resin coating.

[0005] As an anticorrosion method replacing resin coating, there is a resin lining method used for anticorrosion of various containers. FIG. 10 is a perspective view of a conventional phosphoric acid-type fuel cell manifold showing the applied resin lining by a cut surface. In the figure, reference numeral 91 denotes a manifold, 93 denotes a resin lining, and 92 denotes a sealing surface which comes into contact with the fuel cell stack and keeps gas tightly. As the lining material, a fluororesin is usually used in consideration of a use temperature of 150 to 200 ° C. As an example of this method, Japanese Patent Application Laid-Open No.
No. 7459 describes that at least a part of the inner surface of the manifold and the surface of the flange portion in contact with the fuel cell stack is provided with a heat-resistant, corrosion-resistant and sufficiently thick insulating film integrally with the manifold. I have.
Further, in this publication, as a means of integrating the insulating coating with the manifold, a method of punching a hole in the insulating coating and the manifold and mechanically integrating with a holding part, and penetrating a rivet made of insulating resin instead of the holding part. There is disclosed a method in which the wire is heated and welded, and a method in which a wire mesh is welded to the inner surface of the manifold hold, and an insulating film is heated and fused to the wire mesh.

[0006]

By the way, the insulating coating disclosed in the above publication is a thick fluororesin sheet having a thickness of 3 mm in one example given in the embodiments. That is, in the lining construction method as described above, it is necessary to increase the thickness of the insulating coating in order to suppress the transmission and diffusion of gas and water vapor through the fluororesin.
However, when such a thick fluororesin sheet is used, the reliability is improved, but there is a drawback that the cost increases because the fluororesin is an expensive material.

Further, in the method disclosed in the above publication, in which the insulating film and the manifold are mechanically integrated, a hole is formed in the insulating film itself. The parts themselves need to be protected from corrosion, and the structure is complicated. Also, in the method of integrating the insulating film and the manifold by fusion, it is not necessary to make a hole, so that the gas sealing property and the anticorrosion reliability are high, but the fusion of the metal and the resin is difficult. And the manifold may peel off.

The present invention has been made in consideration of the problems of the prior art as described above, and an object of the present invention is to provide a method of anticorrosion which has a high anticorrosion reliability, is easy to manufacture a manifold, and the anticorrosion material itself is inexpensive. It is an object of the present invention to provide a phosphoric acid type fuel cell manifold capable of achieving reliability improvement and cost reduction by performing the above method.

[0009]

In order to achieve the above-mentioned object, according to the present invention, a reaction gas is supplied to a side surface of a phosphoric acid type fuel cell comprising a plurality of unit cells stacked. Alternatively, in a phosphoric acid fuel cell manifold provided for discharging, (1) a sheet having heat resistance, phosphoric acid resistance and insulating property with respect to the operating temperature of the phosphoric acid fuel cell is formed in the inside shape of the above-mentioned manifold. A suitable box-shaped configuration is provided inside the manifold.

(2) Further, in the above (1), the sheet cut in advance into a shape obtained by roughly expanding the above box shape is bonded to bonding portions provided at four corners thereof to form a box shape. The bonding is performed by heating and pressing the bonded portions. (3) Alternatively, in the above (1), the rectangular sheet is folded into a box shape without cutting and bonding.

(4) In the above (2), the sheet is formed from polytetrafluoroethylene, and the lamination is performed between the polytetrafluoroethylene of the lamination part with tetrafluoroethylene-perfluoroalkylvinyl ether polyether. It shall be constructed by sandwiching a plate made of united, heating and pressing. (5) Further, in the above (1), the sheet is formed of a fluororesin, and a fixing member made of a fluororesin fused to an outer surface thereof is provided, and the fixing member is mechanically fixed to the manifold, For example, the sheet is formed from polytetrafluoroethylene, the fixing member is a pin with a head made of perfluoroalkoxy resin, the sheet is incorporated into the manifold, and the pin with the head is fused and fixed to the sheet. .

As described in (1) above, a sheet having predetermined heat resistance, phosphoric acid resistance and insulation properties is formed into a box shape conforming to the inside shape of the manifold, and is disposed inside the manifold. For example, if the airtightness is formed as described in the above (2) and (3), the airtightness of the reaction gas supplied and discharged in the manifold portion is held by the sheet formed in a box shape. . Therefore, the manifold itself need only have a function of holding the sheet in a box shape, and does not need to have an airtight structure. At this time, if the thickness of the sheet is thin, the amount of gas and water vapor passing through the sheet increases, but if the manifold is made to have a non-hermetic structure and a gap is provided between the sheet and the manifold, the gas and water vapor passing therethrough can be obtained. Are discharged to the outside through openings such as slits provided in the manifold through the gap. Therefore, the situation in which phosphoric acid in the permeated gas adheres to the inner surface of the manifold and stagnates as in the case where the thickness of the insulating film is thin in the conventional airtight structure manifold does not occur. No corrosion occurs. Therefore, with this configuration, for example, 10
It is sufficient to use a thin fluororesin film such as polytetrafluoroethylene having a thickness of about 0 to 500 [mu] m, and it is possible to configure the apparatus at extremely low cost.

Further, according to the constitutions (4) and (5), a box-shaped sheet having predetermined heat resistance, phosphoric acid resistance and insulation properties is arranged on the inner surface of the manifold, Since it is kept airtight, it is particularly suitable as a manifold for a phosphoric acid type fuel cell.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific example of a phosphoric acid fuel cell manifold according to the present invention will be described below with reference to the drawings. <Example 1> FIG. 1 shows an example of an embodiment in which one sheet of a sheet of anticorrosive sheet is formed into a box shape that matches the inside shape of the manifold, and covers the inside of the manifold with this.
(A) is a plan view showing a developed state of the flat sheet,
(B) is a perspective view when assembled. FIG. 1 (a)
Anticorrosion sheet 1 has a working temperature of about 2
It is formed of a thin sheet of polytetrafluoroethylene having a thickness of 200 μm and having heat resistance capable of withstanding 00 ° C., phosphoric acid resistance and electric insulation. When assembled as shown in FIG. It is cut into a developed shape that matches the inside shape. The box-shaped sheet 2 shown in FIG. 1B is formed by folding the anticorrosion sheet 1 at a broken line portion shown in FIG.

Further, the anticorrosion sheet 1 is provided with gas supply / discharge holes 4 at a portion corresponding to the installation position of the gas supply / discharge nozzle of the manifold when formed on the box-shaped sheet 2.
In order to prevent the supply / exhaust gas from leaking between the box-shaped sheet 2 and the manifold, an airtight seal is provided between the edge of the gas supply / discharge hole 4 and the manifold. FIG. 2 is a side sectional view when the box-shaped sheet 2 is combined with a manifold. The end portion of the box-shaped sheet 2 is bent at a contact portion between the manifold 5 and the fuel cell stack 6, that is, outside the seal portion 5 a, and at the seal portion 5 a, the fuel cell stack In contact with body 6. Therefore, inside the manifold 5, the box-shaped sheet 2 and the sealing member 7 that are airtightly formed are held in an airtight manner, and the manifold 5 has a function of mechanically supporting the box-shaped sheet 2. . As described above, since the box-shaped sheet 2 is formed of a thin sheet of polytetrafluoroethylene having a thickness of 200 μm,
It is difficult to keep the gas and steam supplied and exhausted by the manifold 5 completely airtight, and a small amount of gas and steam leaks through the box-shaped sheet 2 and leaks into the gap with the manifold 5. Since these trace amounts of gas and water vapor are released to the outside of the manifold 5 through an opening (not shown) such as a slit provided in the manifold 5, the gas and water vapor may stay in the gap between the box-shaped sheet 2 and the manifold 5. Therefore, there is no danger of the manifold 5 being corroded and deteriorated by the staying phosphoric acid as seen in the related art.

In this embodiment, as shown in FIG.
The bent portion of the end portion of the box-shaped sheet 2 of the seal portion 5a is further extended outward from the end portion of the manifold 5 (indicated by A in the figure), and the electrical insulation between the fuel cell stack 6 and the manifold 5 is provided. To ensure the necessary edge distance. FIG. 3 is a side cross-sectional view showing another example of a method of mounting the box-shaped sheet 2 on a fuel cell stack 6 by combining the manifold with a manifold. In the configuration shown in FIG. 2, the sheet 7 is interposed in the seal portion. However, as shown in FIG. 3, if the U-shaped molding gasket 8 is used, the edges of the manifold and the box-shaped sheet 2 are fixed. As a result, deviation is prevented, and at the same time, the folded shape of the outer edge of the box-shaped sheet 2 is easily held.

FIG. 4 is a perspective view of an essential part showing an example of a method of bonding the bonding portions when the anticorrosion sheet 1 is formed on the box-shaped sheet 2. At the bonded portion 9a of the PTFE (polytetrafluoroethylene) sheet 9,
As shown in the figure, the PFA sheet 10 made of a tetrafluoroethylene-perfluoroalkylvinyl ether copolymer is sandwiched, and the bonding is performed by heating and pressing. If this method is adopted, the strength of the bonded portion is increased as compared with the case where the PTFE sheets 9 are directly contacted with each other and heated and pressed to adhere, and the box-shaped sheet 2 having high reliability is obtained.
Can be formed.

<Embodiment 2> In contrast to Embodiment 1 in which a cut anticorrosion sheet is bonded to form a box-shaped sheet, in this embodiment, a rectangular anticorrosion sheet is folded. This is to form a box-shaped sheet.
FIG. 5 is a developed view of the anticorrosion sheet before folding, and FIG. 5B is a perspective view showing the folded box-shaped sheet in association with the manifold.

In the configuration of this embodiment, the anticorrosion sheet 1a made of a thin sheet of polytetrafluoroethylene having a thickness of 200 μm shown in FIG. 5A is folded along the folding line 11 shown in FIG. Folded part 12 shown
Are folded so as to form a rectangular box-shaped sheet 2a having a bent portion at the end as shown in FIG. 5B. Therefore, according to the configuration of the present embodiment, the bonding work as in the first embodiment becomes unnecessary, and a highly reliable box-shaped sheet 2a can be manufactured at low cost.

Although not shown in FIG. 5, the anticorrosion sheet 1a is also provided with the same gas supply / discharge holes as in the first embodiment, and can be combined with a manifold and mounted on a fuel cell stack. Performed as in Example 1. <Embodiment 3> FIG. 6 (a) is a developed view of the anticorrosion sheet before folding in Embodiment 3, and FIG. 6 (b) is a perspective view showing the folded box-shaped sheet in correspondence with the manifold. It is. In the present embodiment, a box-shaped sheet is formed by folding a rectangular anticorrosion sheet in the same manner as in the second embodiment, but the point is that the anti-corrosion sheet is formed in a box-shaped sheet according to the shape of the manifold to be applied. different.

That is, in this embodiment, the reaction gas is supplied from a part of the manifold mounted on one side of the fuel cell stack to flow through the cell, and the flow direction is controlled by the manifold mounted on the opposite side. Is used for a fuel cell adopting a return flow system in which the flow is reversed and the gas is passed through the cell again and discharged from the rest of the original manifold.The manifold has two spaces, a supply part and a discharge part for the reaction gas. It is applied to. Also in the present embodiment, the bending line 11 illustrating the anticorrosion sheet 1b made of the thin sheet of polytetrafluoroethylene shown in FIG.
6B, the folded portion 12 indicated by hatching is folded so as to overlap, thereby providing a bent portion at an end as shown in FIG. 6B, and a partition portion 14 of two spaces of the manifold 13. Is formed, a continuous box-shaped sheet 2b composed of two rectangular parallelepipeds divided at a portion opposed to. Also, corresponding to the gas supply / discharge nozzles of the manifold 13, a gas supply hole (not shown) is provided on the bottom surface of one of the rectangular parallelepiped, and a gas discharge hole (not shown) is provided on the bottom surface of the other rectangular parallelepiped. Further, since the gas supply / discharge nozzle is not incorporated in the manifold on the surface facing the manifold 13, the box-shaped sheet 2a shown in Embodiment 2 which does not have the gas supply / discharge holes is incorporated.

Although the present embodiment shows a box-shaped sheet 2a applied to a manifold having two spaces, a return flow system in which the direction of flow of a reaction gas is repeated a plurality of times is used. Even if the manifold is provided with three or more mutually partitioned spaces, a continuous box-shaped sheet having a plurality of rectangular parallelepipeds can be formed by folding one rectangular anticorrosion sheet in the same manner. The formation is easily inferred from the present embodiment.

<Embodiment 4> FIG. 7A is a cross-sectional view showing an embodiment of a method of fixing a box-shaped anticorrosion sheet to a manifold, and FIG. 7B is a sectional view of FIG. It is an enlarged view of the B section. As shown in FIG. 7A, an anticorrosion sheet 16 is disposed on the inner surface of the manifold 15, a plurality of fixed components 18 are fused to the surface of the anticorrosion sheet 16 on the side of the manifold 15, and one end thereof is stud bolted. It is fixed by being mechanically connected to the manifold 15 by using the reference numeral 19. That is, as shown in the enlarged view of FIG. 7B, the inner surface of one end of the fixing component 18 made of a fluororesin tape is overlapped with the outer surface of the anticorrosion sheet 16 made of a thin sheet of polytetrafluoroethylene, and the fixing component is formed. 18
The fixing component 18 is fused to the anticorrosion sheet 16 by applying heat and pressure from both sides of the anticorrosion sheet 16. The other end of the fixed component 18 is guided to the outside of the manifold 15 through a slit 17 provided in the manifold 15, and is mechanically fixed to an outer surface of the manifold 15 by a stud bolt 19.

In this configuration, since the anticorrosion sheet 16 is airtight, the manifold 15 does not need to be airtight. Therefore, it is not necessary to form the portion of the slit 17 through which the fixing component 18 penetrates airtightly. In addition, since the anticorrosion sheet 16 having airtightness in the present configuration is thin, water vapor passes through the anticorrosion sheet 16 when the operation is continued for a long time, but the anticorrosion sheet 16 and the manifold 15 do not adhere to each other, and Since the slits 17 are provided in the manifold 15, the water vapor that has passed through the anticorrosion sheet 16 easily escapes to the outside of the manifold 15. Therefore, the steam does not stay on the inner surface of the manifold 15, and there is no possibility that the manifold 15 may be corroded.

<Embodiment 5> FIG. 8 is an enlarged sectional view of a main part showing another embodiment of a method of fixing a box-shaped anticorrosion sheet to a manifold. In this embodiment, the headed pin 1
The anticorrosion sheet 16 is fixed to the manifold 15 using the fixing ring 8a and the retaining ring 18b. That is,
PFA on the surface of the anticorrosion sheet 16 on the manifold 15 side
(Perfluoroalkoxyl) resin pin 18a
Hole 2 having one end fused and the other end provided in the manifold 15.
0 to the outside of the manifold 15 through the retaining ring 18
The anticorrosion sheet 16 is fixed to the manifold 15 by fitting b.

In the present construction, since the head-mounted pins 18a are made of PFA resin having a good fusion property, the head-mounted pins 18a are arranged in contact with the anticorrosion sheet 16 and heat and pressure are applied only from the inner side of the anticorrosion sheet 16. Thereby, the headed pin 18 a can be firmly fused to the anticorrosion sheet 16. Therefore, a head-mounted pin 18a is previously installed in the hole 20 provided in the manifold 15, a box-shaped anticorrosion sheet 16 is installed from above, and then a trowel is applied from the inner surface side of the anticorrosion sheet 16. By performing the treatment, the headed pin 18a can be fused to the anticorrosion sheet 16, so that the pin 18a can be fixed at an appropriate position without being affected by the manufacturing error of the manifold 15 or the box-shaped anticorrosion sheet 16. There is an advantage that you can.

In the first to fifth embodiments described above,
In each case, a thin sheet of polytetrafluoroethylene is used as the anticorrosion sheet, but the present invention is not limited to this as long as the sheet has heat resistance to the operating temperature of the phosphoric acid type fuel cell, phosphoric acid resistance, and electric insulation. . In the above embodiments, a thin sheet having a thickness of 200 μm was used as the anticorrosion sheet. However, if the thickness of the thin sheet is too small, the risk of breakage during operation increases. It becomes difficult, costly, and rigid.As a result, the number of fixed parts must be increased to avoid damage to the fixed part due to the difference in thermal expansion between the seat and the manifold.
It is necessary to increase the strength. In consideration of these, a thin sheet having a thickness of about 100 to 500 μm is preferable, but it is needless to say that the present invention is not limited to this.

[0028]

As described above, the phosphoric acid type fuel cell manifold according to the present invention is airtight by disposing a thin anticorrosion sheet formed in a box shape in advance in accordance with the shape of the manifold on the inner surface of the manifold. The characteristic feature is that the manifold is held to prevent corrosion of the manifold.

An airtight anticorrosion sheet is incorporated inside the non-airtight manifold, and the gas and water vapor permeating the anticorrosion sheet are easily discharged to the outside of the manifold. This eliminates the risk of corrosion of the manifold, and makes it possible to incorporate a thin anticorrosion sheet. This makes it possible to obtain an anticorrosion film with a uniform thickness that is less expensive than conventional coating methods and lining with a thick anticorrosion sheet, and has no defects such as pinholes, and high anticorrosion reliability. became. Also, unlike the conventional method of applying resin coating, a thin anticorrosion sheet formed in a box shape in advance is arranged and fixed on the inner surface of the manifold to maintain airtightness, so the finishing accuracy of the inner wall surface of the manifold etc. The manufacturing restrictions have been relaxed, and it has become possible to manufacture at low cost. In particular, since the box-shaped anticorrosion sheet is formed not by molding with a mold but by laminating or folding a flat sheet, a large capital investment is not required, and the cost can be further reduced.

Further, since the box-shaped anticorrosion sheet is attached to the manifold by a method of mechanically fixing the resin-made fixing part, which is attached to the box-shaped anticorrosion sheet by fusion, to the manifold. There is no problem of peeling that occurs when using the conventional method of fusing the anticorrosion sheet directly to the metal manifold, and also as in the case of using the method of mechanically fixing the conventional anticorrosion sheet directly to the metal manifold. In addition, since there is no possibility that the anticorrosion sheet is damaged or the fixed parts are corroded, both high gas sealing properties and anticorrosion reliability can be obtained.

[Brief description of the drawings]

FIG. 1 shows an example of a box-shaped sheet applied to a phosphoric acid type fuel cell manifold based on a first embodiment of the present invention, wherein (a) is a developed plan view and (b). Is a perspective view of the assembled state

FIG. 2 is a side cross-sectional view showing an example of a state in which a box-shaped sheet applied to the phosphoric acid type fuel cell manifold according to the first embodiment of the present invention is mounted on a fuel cell stack.

FIG. 3 is a side sectional view showing another example of a state in which a box-shaped sheet applied to the phosphoric acid type fuel cell manifold according to the first embodiment of the present invention is mounted on a fuel cell stack.

FIG. 4 is a perspective view showing an example of a box-shaped sheet bonding portion applied to the phosphoric acid type fuel cell manifold according to the first embodiment of the present invention.

FIG. 5 shows an example of a box-shaped sheet applied to a phosphoric acid type fuel cell manifold according to a second embodiment of the present invention, wherein (a) is a developed plan view and (b). Is a perspective view of the assembled state

FIG. 6 shows an example of a box-shaped sheet applied to the phosphoric acid type fuel cell manifold according to the third embodiment of the present invention, wherein (a) is a developed plan view and (b). Is a perspective view of the assembled state

FIG. 7A is a cross-sectional view showing an example of a method of fixing a box-shaped sheet to a manifold applied to a phosphoric acid type fuel cell manifold according to a fourth embodiment of the present invention,
(B) is an enlarged view of part B of (a).

FIG. 8 is an enlarged sectional view of a main part showing an example of a method of fixing a box-shaped sheet to a manifold applied to a phosphoric acid fuel cell manifold according to a fifth embodiment of the present invention.

FIG. 9 is a perspective view showing a resin coating applied to a conventional phosphoric acid type fuel cell manifold.

FIG. 10 is a perspective view showing a resin lining applied to a conventional phosphoric acid type fuel cell manifold.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1a, 1b Anticorrosion sheet 2, 2a, 2b Box-shaped sheet 3 Bonding part 4 Gas supply / discharge hole 5 Manifold 5a Seal part 6 Fuel cell stack 7 Sheet material 8 Molded gasket 9 PTFE sheet 9a Bonding part 10 PFA Sheet 11 Bending line 12 Folding part 13 Manifold 14 Partition part 15 Manifold 16 Anticorrosion sheet 17 Slit 18 Fixed part 18a PFA headed pin 18b Retaining ring 19 Stud bolt 20 Hole

Claims (8)

[Claims] 1. A phosphoric acid fuel cell manifold provided on a side surface of a phosphoric acid fuel cell formed by stacking a plurality of unit cells for supplying or discharging a reaction gas to the unit cell, The sheet having heat resistance, phosphoric acid resistance and insulation properties with respect to the operating temperature of the phosphoric acid type fuel cell is formed in a box shape conforming to the inside shape of the manifold, and this is disposed inside the manifold. Phosphoric acid type fuel cell manifold. 2. The box-shaped sheet obtained by cutting the sheet preliminarily cut into a shape obtained by roughly expanding the box-shaped shape, by bonding the bonding portions provided at four corners thereof. 2. The manifold for a phosphoric acid type fuel cell according to 1. 3. The phosphoric acid type fuel cell manifold according to claim 2, wherein the bonding is performed by heating and pressing the bonded portions. 4. The phosphoric acid type fuel cell manifold according to claim 1, wherein the rectangular sheet is folded into a box shape without cutting and bonding. 5. The phosphoric acid fuel cell manifold according to claim 1, wherein the sheet is made of a fluororesin, preferably polytetrafluoroethylene. 6. The sheet is made of polytetrafluoroethylene, and the bonding is such that a plate made of a tetrafluoroethylene-perfluoroalkylvinyl ether polymer is sandwiched between polytetrafluoroethylenes in a bonding portion, The phosphoric acid type fuel cell manifold according to claim 2, wherein the manifold is constructed by heating and pressurizing. 7. The sheet according to claim 1, wherein the sheet is made of a fluororesin,
2. The phosphoric acid type fuel cell manifold according to claim 1, further comprising a fixing member made of a fluororesin fused to an outer surface thereof, wherein the fixing member is mechanically fixed to the manifold. 8. The sheet is made of polytetrafluoroethylene, the fixing member is made of a pin with a head made of perfluoroalkoxyl resin, and after the sheet is assembled in a manifold, the pin with a head is fused to the sheet. The phosphoric acid type fuel cell manifold according to claim 7, wherein the manifold is formed.