JPH09259899A - Cooling plate of fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the corrosion of a cooling pipe or the electrolytic corrosion of a corner pert by the penetration of an electrolyte by providing a specified structure in the cooling plate for cooling a fuel cell having a prescribed structure. SOLUTION: In a cooling plate 3 for cooling a fuel cell formed of a plurality of laminated unit cells, which is laminated every lamination of a prescribed number of pieces of the unit cells, this cooling plate is formed of upper and lower cooling plate bases 4a, 4b vertically mounted opposite to each other, and a cooling pipe 7 for passing cooling water which is buried between the base materials 4a, 4b. A strip heat resisting and corrosion resisting resin layer 22 is provided on four side surfaces of the cooling plate, and they are simultaneously heated and pressure welded to integrate the whole body. Preferably, gas impermeable separators (A) 23 are laminated on both anti-fitting sides of the upper and lower cooling bases 4a, 4b, a heat resisting and corrosion resisting resin layer 25 is provided between A:24 and the upper and lower cooling plate bases 4a, 4b, and they are simultaneously heated and pressure welded to integrate the whole body.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell cooling plate for cooling a fuel cell, which is laminated on a cell stack formed by stacking single cells. Is. In general, a fuel cell is a hydrogen rich gas (fuel gas) obtained by reforming natural gas, methane gas or the like.
And air, which is an oxidant, are supplied into the main body of the fuel cell to cause an electrochemical reaction through an electrolyte such as phosphoric acid to generate electric energy. In addition, an efficient energy generation system is realized by recovering and utilizing the thermal energy generated during the power generation of the fuel cell. Such a fuel cell has a laminated structure (cell stack structure) in which a plurality of single cells (hereinafter referred to as single cells) having the above-mentioned power generation function are laminated. FIG. 6 shows a cell stack structure of a conventional fuel cell.
The unit cell 1 of the fuel cell body comprises a matrix layer 11 holding an electrolyte, a fuel electrode 12 to which hydrogen as a fuel is supplied in the direction of arrow A, and an oxidant electrode 13 to which air is supplied in the direction of arrow B. And electrode base materials 14 and 15 with ribs, and a separator 16. Every time a large number of these single cells are stacked, the water cooling cooling plate 3 is stacked to form one sub-stack 2. A large number of sub-stacks 2 are stacked to form a cell stack. This cell stack has clamping plates 17 arranged at the top and the bottom and held. In four directions of this cell stack, a hydrogen gas manifold 18 and an air manifold 19 are mounted orthogonal to each other and facing each other. A cooling pipe 7 is embedded in the cooling plate 3, and one end of the cooling pipe 7 has a water supply header 8
The other end is connected to the drainage head 9 and the insulation hose 1 respectively.
0. As a result, the cooling water is circulated and supplied to the cooling pipe 7 to cool the fuel cell. As shown in FIG. 7, the cooling plate 3 is composed of two upper and lower cooling plate bases 4a and 4b, and a cooling pipe 7 is embedded in the cooling plate 3. That is, the groove 5 is formed in a meandering loop shape on the inner surface side of the upper cooling plate base material 4a and the lower cooling plate base material 4b, and the cooling pipe 7 is housed in the groove 5. In this case, the gap with the cooling pipe 7 made of metal is filled with the good thermal conductive filler 6. In the cell stack having such a configuration, since the cooling pipe is not inside the hydrogen gas manifold 18, the cooling pipe 7 does not come into direct contact with the electrolyte such as phosphoric acid. However, even in such a fuel cell, in the hydrogen gas manifold 18, the ribbed electrode base materials 14, 1 adjacent to the cooling plate 3 are provided.
The electrolyte of No. 5 permeates into the cooling plate 3 or adheres to the side surface of the cooling plate 3, permeates the relatively porous cooling plate base material 4 and reaches the cooling pipe 7 to corrode the cooling pipe 7 to corrode water. I have a concern about leakage. Further, according to the results of the research conducted so far, the side corners adjacent to the cooling plate 3 come into contact with oxygen to generate an electric potential, which is affected for a long period of time to cause electrolytic corrosion on the edge part of the end of the cooling plate 3. I also started to fear. An object of the present invention is to provide a cooling plate for a fuel cell which can prevent corrosion of a cooling pipe and electrolytic corrosion of a corner portion due to permeation of an electrolyte. According to a first aspect of the invention, a fuel cell formed by laminating a plurality of unit cells is laminated every time a predetermined number of unit cells are laminated to cool the fuel cell. A cooling plate for the upper and lower cooling plate bases, which are mounted in a pair of upper and lower cooling plates, and a cooling pipe embedded between the upper and lower cooling plate bases for passing cooling water. A band-shaped heat-resistant and corrosion-resistant resin layer is provided on the four sides of the cooling plate, and gas impermeable separators are laminated on the opposite mating surface sides of the upper and lower cooling substrates, respectively, between the gas impermeable separator and the upper and lower cooling plate base materials. A heat-resistant and corrosion-resistant resin layer is provided on the above, and they are heat-pressed at the same time to integrate the whole. According to the first aspect of the present invention, the strip-shaped heat-resistant and corrosion-resistant resin layers provided on the four side surfaces of the cooling plate are thermocompression bonded to the side surface portions of the upper and lower cooling plate base materials to integrate the whole. This prevents the electrolyte from penetrating from the side surface and prevents electrolytic corrosion of the edge portion. According to a second aspect of the present invention, in the first aspect of the present invention, gas impermeable separators are laminated on the opposite mating surface sides of the upper and lower cooling substrates, respectively, and a space between the gas impermeable separator and the upper and lower cooling plate substrates is provided. A heat-resistant and corrosion-resistant resin layer is provided on the above, and they are simultaneously heat-pressed to be integrated as a whole, and in addition to the action of the invention of claim 1, further permeation of the electrolyte in the vertical direction of the cooling plate is further suppressed. [0012] The invention of claim 3 is claim 1 or claim 2.
In the invention of, the carbon paper is laminated on the gas-impermeable separator, the heat-corrosion-resistant resin layer is provided between the carbon paper and the gas-impermeable separator, and they are simultaneously heat-pressed so that the whole is integrated. It was done,
In addition to the action of the invention of claim 1 or claim 2, further permeation of the electrolyte in the vertical direction of the cooling plate is further suppressed. Further, it works to reduce the contact resistance. The invention of claim 4 is the invention of claims 1 to 3.
The heat-corrosion-resistant resin layer in the form of a strip is provided in the peripheral portion and the central portion between the upper and lower cooling plate base materials, and is thermocompression bonded to integrate the entire cooling plate base material. In addition to the action of the invention, the opening of the upper and lower cooling plate base materials is suppressed. The invention according to claim 5 is any one of claims 1 to 3.
In the invention described in (1), the heat and corrosion resistant resin layer is a tetrafluoroethylene-hexafluoropropylene copolymer or a tetrafluoroethylene-perfluoroalkylbihilethylene copolymer, which maintains heat and corrosion resistance. According to a sixth aspect of the present invention, in the first aspect of the invention, the thickness of the heat and corrosion resistant resin layer provided between the upper and lower cooling substrates and between the upper and lower cooling plate base materials and the gas impermeable separator is 0. The thickness is set to 02 to 0.1 mm, which suppresses the permeation of the electrolyte in the vertical direction, satisfies the contact resistance with the cells stacked above and below, and has the sealing property with the gas manifold. Try not to interfere. The invention according to claim 7 is that in the invention according to claim 2, the thickness of the heat and corrosion resistant resin layer between the gas impermeable separator and the carbon paper is 0.1 to 0.15 mm. This further suppresses vertical penetration of the electrolyte. According to an eighth aspect of the present invention, in the first aspect, the thickness of the strip-shaped heat-corrosion-resistant resin layer provided on the side surface of the cooling plate is 0.25 to 0.55 mm, and the polymer has a crystallinity. It is a material having a low resistance to cracks, has a crack resistance, and suppresses the electrolyte from penetrating in the lateral direction of the cooling plate to prevent electrolytic corrosion at the edge portion. According to a ninth aspect of the present invention, in the first aspect of the present invention, the width of the strip-shaped heat-resistant and corrosion-resistant resin layer provided on the side surface of the cooling plate is made 1 to 3 mm larger than the entire thickness of the cooling plate. The heat-resistant resin on the side surface is surely welded, the contact resistance with the cells stacked one above the other is satisfied, and the sealability with the gas manifold is not hindered. According to a tenth aspect of the invention, in the first aspect of the invention, the melt-out of the belt-shaped heat-corrosion-resistant resin layer provided on the side surface of the cooling plate after the thermocompression bonding is 0 to 1 mm in the horizontal direction,
The upper and lower surfaces are made to have a thickness of 0 to 0.2 mm to ensure the welding of the heat resistant resin and not to adversely affect the sealing surface. That is, the contact resistance with the cells stacked one above the other should be satisfied, and the sealability with the gas manifold should not be hindered. Embodiments of the present invention will be described below. FIG. 1 is an overall perspective view of a cooling plate 3 according to an embodiment of the present invention. A carbon paper 20 is attached to the outer surface of the cooling plate 3. The peripheral portion 21 of the carbon paper 20 is densified to enhance the sealing effect. This prevents the reaction gas from leaking from the contact surface in contact with the cooling plate 3. It should be noted that this densification treatment may be performed as necessary, and may be omitted depending on the configuration of the cell stack laminated member. A strip-shaped FEP (tetrafluoroethylene-hexafluoropropylene copolymer) film 22 is formed as a heat and corrosion resistant resin layer on the side surfaces (4 side surfaces) of the cooling plate 3.
Is heat-pressed. Since the side surface of the cooling plate 3 is not a current-carrying portion, the increase in contact resistance does not pose a problem even if the strip-shaped FEP film 22 is provided on the side surface. Also, the band-shaped FEP
When the thickness of the film 22 is about 0.5 mm or more, there is almost no permeation of phosphoric acid, which is the electrolyte. Therefore, the thickness of the strip-shaped FEP film 22 is 0.25 in the embodiment of the present invention. ˜0.55 mm, and the material is a polymer (L type) with low crystallinity, with an emphasis on mechanical strength, especially crack resistance. As the band-shaped FEP film 22,
If a commercially available product is used, its thickness should be 0.25 to
In order to make it 0.55 mm, a plurality of sheets may be stacked and used. The width of the strip-shaped FEP film 22 is set to be 1 to 3 mm larger than the width of the cooling plate 3 itself so as to eliminate the incompletely welded portion at the time of thermocompression bonding and prevent an excessive amount of melted out. . In addition, this strip-shaped FEP film 2
In both end portions of 2, the portions located outside the hydrogen gas manifold 18 (range of about 10 mm) are adjacent strip FEs.
The P films 22 and the side surfaces of the cooling plate may not be completely adhered. FIG. 2 is a partially cutaway plan view of cooling slope 7 according to the embodiment of the present invention. The lower cooling plate base material 4b is partially shown. A cooling pipe 7 is embedded and provided in a meandering loop shape on a mating surface between the upper cooling plate base material 4a and the lower cooling plate base material 4b. In the peripheral portion (4 peripheral portion) of the mating surface of the upper cooling plate base material 4a and the lower cooling plate base material 4b, and in the gap portion of the meandering cooling pipe 7 in the central part, the internal strip FE is formed.
The P films 23 are inserted and arranged. Then, these inner band-shaped FEP films 23 are integrated with the upper and lower cooling plate base materials 4a and 4b by thermocompression bonding. FIG. 3 is a sectional view taken along the line AA of FIG. 2 and shows a state before thermocompression bonding. Upper cooling plate base material 4
The meandering loop groove 5 is formed in the a and the lower cooling plate base material 4b, and the good thermal conductive filler 6 is injected into the bottom portion of the groove 5. The cooling pipe 7 is assembled thereon, and the filling amount of the filling material 6 is determined so as to fill the gap between the groove 5 and the cooling pipe 7 when the cooling plate 4 is thermocompression bonded. Therefore, the excess filling material 6 overflows into the escape groove 5a. A gas impermeable separator 24 and a carbon paper 20 are laminated on the opposite side of the cooling plate substrate 4 and the outside thereof, and a flat FEP having substantially the same size as the cooling plate substrate 4 is provided between them. Films 25 and 26 have been inserted. The inner strip-shaped FEP film 23 inserted between the upper cooling plate base material 4a and the lower cooling plate base material 4b, and between the respective cooling plate base materials 4a and 4b and the gas impermeable separator 24. The flat FEP film 25 is
Since the cooling plate base materials 4a and 4b have a medium porosity, the film thickness thereof is set to 0.02 to 0.1 mm in consideration of the penetration amount and the contact electric resistance value. Since the planar FEP film 26 inserted between the gas impermeable separator 24 and the carbon paper 20 has a relatively high porosity of the carbon paper 20, the penetration amount and the contact electric resistance value are taken into consideration in the same manner. Film thickness is 0.1-0.15mm
And FIG. 4 is a sectional view after the thermocompression bonding of FIG. Upper and lower cooling plate base materials 4a and 4b and carbon paper 20
Is a porous graphitized carbon plate, and the gas impermeable separator 24 is a high density carbon plate. Therefore, the strip FEP film 22, the flat FEP films 25, 2
6 is melted into the pores of the carbon paper 20 and the upper and lower cooling plate base materials 4a and 4b mainly by thermocompression bonding, and the cooling plate base material 4 is
The carbon paper 20 and the gas impermeable separator 24 are integrated. Band-shaped FEP film 22 on the side surface of the cooling plate 3
Is welded to the cooling plate substrate 4, the carbon paper 20, the gas impermeable separator 24, and the FEP films 25 and 26 over the entire thickness. FIG. 5 is a sectional view of the end portion of the cooling plate 3 after thermocompression bonding. Band-shaped FEP film 2 melted by hot pressing
Two burrs 27 are shown. The burr 27 is formed in a range in which the corner portion of the cooling plate 3 is completely covered with the band-shaped FEP film 22 and the adjacent cell stack base material is not locally applied with a surface pressure higher than the allowable value. To do so. The burr 27a is 0 to the upper surface of the carbon paper 20.
The burrs 27b formed on the side face are formed within the range of 0.2 mm, and the allowable range of the protrusions 0-1 from the plane is as a range that does not adversely affect the sealing surface of the hydrogen gas manifold 18.
mm. In the embodiment of the present invention configured as described above, the electrolyte held by the electrode base materials 14 and 15 dents into the upper portion of the carbon paper 20 in the vertical direction, but By melting the planar FEP film 26 between the paper 20 and the gas impermeable separator 24, the carbon paper 20 becomes richer in FEP resin than the gas impermeable separator 24, and becomes the electrolyte permeation preventive layer of the first stage. Next, the gas impermeable separator 24 itself becomes the second electrolyte permeation preventive layer, and the upper and lower cooling substrates 4a, 4
b between the b and the gas impermeable separator 24
Due to the melting of the P film 25, the surface layer portions of the cooling substrates 4a and 4b become a resin rich layer, and this becomes a third electrolyte permeation prevention layer. For the electrolyte attached to the side surface of the cooling plate 3 or transmitted in the stacking direction, the carbon paper on the surface of the cooling plate 3 is formed by the thick strip-shaped FEP film 22 which is thermocompression bonded to the side surface. It is possible to completely prevent the permeation of the electrolyte, since it is integrated over the entire length in the thickness direction up to the side surface of 20. That is, according to this embodiment, it is possible to prevent the electrolyte from penetrating into the inside of the cooling plate 3, to prevent the corrosion and water leakage of the cooling pipe 7 due to the adhesion of the electrolyte, and also to prevent the side surface of the cooling plate 3 from being entirely heat-resistant. Since it is covered with the corrosion-resistant resin layer, it does not come into contact with oxygen and can prevent electrolytic corrosion. Therefore, the quality of the cooling plate 3 can be maintained for a long period of time. Further, since carbon paper 20 made of a relatively flexible material is used for the upper and lower surfaces of the cooling plate 3 which are the contact surfaces with the adjacent cell stacks, it is necessary to bring them into close contact with the cell stack in contact with the cooling plate 3. The fuel is highly reliable and free from problems such as damage to the electrode substrates 14 and 15 and the cooling plate 3 due to uneven surface pressure and no leakage of reaction gas, and increase in contact resistance and uneven heat conduction. A battery stack can be provided. As described above, with the cooling plate 3 according to this embodiment, cooling due to corrosion of the cooling pipe 7 due to the permeation of the electrolyte into the cooling plate 3 expected in the operation of the fuel cell and generation of a local potential. It is possible to prevent electrolytic corrosion of the plate 3. As a result, a highly reliable fuel cell capable of stable operation over a long period of time can be provided. In the above-mentioned embodiments, the FEP film is used as the heat and corrosion resistant resin. However, a PFA (tetrafluoroethylene-fluorofluoroalkylbihilethylene copolymer) film having the same function is used. It is also possible to use, and it is also possible to use a fluororesin. When an FEP film is used, it is heated and pressed at about 330 ° C., and when a PFA film is used, it is heated and pressed at about 350 ° C., and at the same time, the upper and lower side surfaces are integrated. Then, the FEP film or the PFA film is melted by pressurization and melts into the pores of the cooling substrate 4, the carbon paper 20 and the gas impermeable separator 24 in the upper and lower surfaces (lamination surface) direction. Then, the contact is a mixture of graphite plates and FEP films or PFA films. Since the side surface portion has a small pressure-bonding load and is thick, a part thereof melts into the side surface of the cooling plate 3, but almost all remains in a film state. In this way, the cooling plate 3 is completely covered with the film of the heat-resistant and corrosion-resistant resin on the upper and lower surfaces and the side surface of the cooling plate inside the sealing portion of the hydrogen gas manifold 18. Thereby, the cooling plate 3
It is possible to prevent the penetration of electrolytes such as phosphoric acid into the interior. As described above, according to the present invention, the cooling plate of the fuel cell stack is provided with the heat-resistant and corrosion-resistant resin layer in the lateral direction so that the cooling plate of the fuel cell can be operated during operation of the fuel cell. It is possible to prevent the electrolyte from penetrating into the inside of the cooling plate. Therefore, it is possible to prevent the corrosion of the cooling pipe due to the permeation of the electrolyte and the electrolytic corrosion of the cooling plate due to the generation of the partial potential, and it is possible to provide a highly reliable fuel cell capable of stable cicada rotation for a long period of time. Further, when the heat-resistant and corrosion-resistant resin layer is additionally provided on the plane direction or the contact surface with the cell stack, not only the side direction of the electrolyte but also the upper and lower surfaces are prevented from permeating. Improves reliability.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a cooling plate according to an embodiment of the present invention. FIG. 2 is a front view of the cooling plate according to the embodiment of the present invention. FIG. 3 is a cross-sectional view of the cooling plate taken along the line AA in FIG. 2 before thermocompression bonding. 4 is a cross-sectional view of the cooling plate taken along the line AA of FIG. 2 after thermocompression bonding. FIG. 5 is a sectional view of the corner portion of the cooling plate after thermocompression bonding according to the embodiment of the present invention. FIG. 6 is a perspective view showing a conventional cell stack structure diagram. FIG. 7 is a cross-sectional view of a conventional cooling plate. [Description of Reference Signs] 1 single cell 2 sub-stack 3 cooling plate 4 cooling plate base material 5 groove 6 filler 7 cooling pipe 8 water supply head 9 drainage head 10 insulating hose 11 matrix layer 12 fuel electrode 13 oxidizer electrode 14, 15 rib Electrode base material 16 Separator 17 Tightening plate 18 Hydrogen gas manifold 19 Air manifold 20 Carbon paper 21 Peripheral part 22 Strip FEP film 23 Internal strip FEP film 24 Gas impermeable separator 25, 26 Planar FEP film 27 Burr

Continuation of front page    (72) Inventor Kazuhisa Tanaka             2-4 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa               Toshiba Keihin Office (72) Inventor Toshiro Kanano             2-4 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa               Toshiba I-Tech Co., Ltd.

Claims (1)

Claim: What is claimed is: 1. A cooling plate for cooling a fuel cell, the fuel cell being formed by stacking a plurality of single cells, the stack being stacked every time a predetermined number of the single cells are stacked. And a cooling plate comprising upper and lower cooling plate base materials mounted in a pair of upper and lower sides, and a cooling pipe embedded between the upper and lower cooling plate base materials for passing cooling water. 4 on the side
A cooling plate for a fuel cell, characterized in that a belt-shaped heat-resistant and corrosion-resistant resin layer is provided on a surface thereof, and they are simultaneously heat-pressed to be integrated as a whole. 2. A gas impermeable separator is laminated on each of the opposite mating surface sides of the upper and lower cooling substrates, and a heat resistant and corrosion resistant resin layer is provided between the gas impermeable separator and the upper and lower cooling plate base materials. 2. The cooling plate for a fuel cell according to claim 1, wherein the cooling plates are heated and pressure-bonded at the same time to integrate the whole. 3. A carbon paper is laminated on the gas impermeable separator, a heat and corrosion resistant resin layer is provided between the carbon paper and the gas impermeable separator, and they are heated and pressure bonded at the same time to form an integrated body. The cooling plate for a fuel cell according to claim 1 or 2, wherein 4. A belt-shaped heat-resistant and corrosion-resistant resin layer is provided in a peripheral portion and a central portion between the upper and lower cooling plate base materials, and is thermocompression bonded to integrate the entire cooling plate base material. Item 5. A cooling plate for a fuel cell according to item 3. 5. The heat and corrosion resistant resin layer contains a tetrafluoroethylene-hexafluoropropylene copolymer or a tetrafluoroethylene-perfluoroalkylbihiruethylene copolymer.
The cooling plate for the fuel cell described. 6. The thickness of the heat and corrosion resistant resin layer provided between the upper and lower cooling substrates and between the upper and lower cooling plate base materials and the gas impermeable separator is 0.02 to 0.1 mm. The cooling plate for a fuel cell according to claim 1, wherein: 7. The thickness of the heat and corrosion resistant resin layer between the gas impermeable separator and the carbon paper is 0.1 to 10.
The cooling plate for a fuel cell according to claim 2, wherein the cooling plate has a thickness of 0.15 mm. 8. The strip-shaped heat-corrosion-resistant resin layer provided on the side surface of the cooling plate has a thickness of 0.25 to 0.55 mm,
The cooling plate for a fuel cell according to claim 1, wherein the cooling plate is a polymer and has a low crystallinity. 9. The cooling plate for a fuel cell according to claim 1, wherein the width of the belt-shaped heat-resistant and corrosion-resistant resin layer provided on the side surface of the cooling plate is 1 to 3 mm larger than the total thickness of the cooling plate. 10. The melt-out of the strip-shaped heat-corrosion-resistant resin layer provided on the side surface of the cooling plate after thermocompression bonding is 0 in the horizontal direction.
The cooling plate of the fuel cell according to claim 1, wherein the cooling plate has a width of ˜1 mm and a height of 0 to 0.2 mm on the upper and lower surfaces.