JP2005243424A - Manufacturing method of separator for fuel cell, and separator for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the aggravation of conductivity in a separator for a fuel cell. <P>SOLUTION: The separator for the fuel cell is obtained by making graphite and a resin as components and by compression molding these into a prescribed shape. The graphite component is made to be anisotropic graphite particles 15 having the short diameter part d1 and the long diameter part d2, while the resin component is made to be a resin base material 9 provided with a plurality of graphite particle insertion holes 11. A hole diameter of the graphite insertion holes 11 is set to be larger than the short diameter part d1 of the graphite particles 15 and smaller than the long diameter part d2, the graphite particles 15 are incorporated into the graphite particle insertion holes 11 in such a condition that the long diameter part d2 becomes the axis line direction of the graphite particle insertion holes 11, and the graphite containing resin base material 17 is formed. This graphite containing resin base material 17 is laminated in plurality in a molding die, compressed, and molded. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a fuel cell separator that contacts a pair of electrodes that sandwich an electrolyte membrane, and a fuel cell separator.

  A fuel cell is a device that converts the chemical energy of fuel directly into electrical energy by electrochemically reacting a fuel gas such as a hydrogen-containing gas that is a reactive gas with an oxidant gas such as air. It has excellent characteristics such as high energy efficiency compared to other energy engines and no generation of exhaust gas because there is no need to use fossil fuels that have a problem of resource depletion.

  In such a fuel cell, an electrolyte membrane is sandwiched between a pair of electrodes, used to collect electricity from the electrodes in contact with the electrodes, and a gas flow path for supplying gas is provided on the electrode side, and a cooling water flow is provided on the opposite side of the electrode. A separator having a path is provided.

As such a fuel cell separator, as shown in FIG. 6 (a), carbon powder for ensuring conductivity and a thermosetting resin for maintaining moldability and ensuring strength were mixed. A material 101 is known that is compression-molded into a predetermined shape using a molding die 103 (a lower die 103a and an upper die 103b) (see, for example, Patent Document 1 below).
JP 2003-17085 A

  By the way, in the above-described conventional fuel cell separator, as shown in FIG. 6B, which is an enlarged view of the portion A in FIG. 6A, the granular carbon powder 107 contained in the resin molded body 105 has an elliptical cross section. It has so-called anisotropy in shape, and when it is put into the lower mold 103a, its major axis direction is directed in a direction parallel to the surface of the separator including the arrow B direction under the influence of gravity.

  Therefore, in the granular carbon powder 107, the vertical direction indicated by the arrow C in FIG. 6B is the short diameter direction, and when the separator is considered to have the same thickness as compared with the case where the long diameter direction is the vertical direction, The number of the granular carbon powders 107 arranged along the direction increases, and the contact portion between the granular carbon powders 107 increases along the vertical direction (electrical conduction direction), and the electrical resistance increases. Causes deterioration.

  Even when an isotropic granular carbon powder having a small difference between the major axis and the minor axis is used as the granular carbon powder, the granular carbon powder is compressed by the load during compression molding, and the vertical direction is the minor axis direction. Thus, the material is deformed to have anisotropy. Therefore, even in this case, the electrical resistance increases as described above.

  Then, this invention aims at preventing the deterioration of the electroconductivity in the separator for fuel cells.

  The present invention provides a method for producing a separator for a fuel cell in which graphite and a resin as components are compression-molded into a predetermined shape, wherein the graphite component is an anisotropic graphite particle having a short diameter portion and a long diameter portion, The resin component is a resin base material having a plurality of graphite grain insertion holes, the pore diameter of the graphite grain insertion holes is set larger than the minor axis part of the graphite grain and smaller than the major axis part, and the graphite grain has its major axis The graphite containing resin base material is made by entering the graphite grain inserting hole in a state where the portion is in the axial direction of the graphite grain inserting hole, and a plurality of the graphite containing resin base materials are formed along the axial direction of the graphite grain inserting hole. The most important feature is to laminate and compression mold.

  According to the present invention, a graphite-containing resin base material is prepared by inserting graphite grains into the graphite grain insertion holes of the resin base material in a state where the major axis portion is in the axial direction of the graphite grain insertion holes. Since the base material is laminated and compression molded along the axis direction of the graphite grain insertion hole, the major axis side of the graphite grain matches the load direction at the time of compression molding, and the contact in the direction intersecting the separator surface between the graphite grains The number of portions can be reduced, and the electrical resistance can be reduced to prevent deterioration of conductivity.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of a fuel cell including a separator 1 manufactured by the method for manufacturing a fuel cell separator according to the first embodiment of the present invention. This fuel cell is a solid polymer fuel cell, and has a structure in which a solid polymer electrolyte membrane 3 is sandwiched between a pair of electrodes 5 from both sides, and the separator 1 is disposed on both sides thereof. A large number of batteries 7 are stacked and used as a fuel cell stack.

  The separator 1 is a resin molded body containing graphite, and includes a gas flow path 1 a for supplying gas on the electrode 5 side and a cooling water flow path 1 b on the side opposite to the electrode 5. Hydrogen serving as a fuel is supplied to the gas flow path 1a of one separator 1, and air serving as an oxidant is supplied to the gas flow path 1a of the other separator 1.

  The manufacturing method of such a separator 1 is demonstrated below.

  What is shown to Fig.2 (a) is the sheet-like resin base material 9 which consists of a thermoplastic resin material. The resin base material 9 is injection-molded by an injection molding machine (not shown), and then, by laser processing, for example, as shown in FIG. A plurality of graphite grain insertion holes 11 are formed. The thickness of the sheet-like resin base material 9 is about 0.05 mm to 0.1 mm.

  Then, as shown in FIG. 3A, the sheet-like resin base material 9 provided with the graphite grain insertion holes 11 is put into the graphite grains 15 deposited in the container 13, and the container 13 is placed in this state. By vibrating, the graphite particles 15 are caused to enter the graphite particle insertion holes 11 as shown in FIG.

  Here, the above-described graphite particles 15 are anisotropic graphite particles having an elliptical cross section having a short diameter portion d1 and a long diameter portion d2, and the hole diameter d of the graphite particle insertion hole 11 is set to be the short diameter portion of the graphite particles 15. It is set to be larger than d1 and smaller than the long diameter portion d2.

  Therefore, the graphite particles 15 are vibrated by vibrating the container 13 so that the long diameter portion d2 thereof is in the axial direction of the graphite particle insertion hole 11 (vertical direction in FIG. 3B) as shown in FIG. In this state, it enters the graphite particle insertion hole 11, whereby a graphite-containing resin substrate 17 composed of the resin substrate 9 and the graphite particles 15 is obtained.

  Thereafter, as shown in FIG. 3, the heater 19 installed at the lower part of the container 13 causes the graphite-containing resin base material 17 to be reacted with the reaction temperature (about 180 ° C.) of the thermoplastic resin so that the resin does not thermally cure. ) Until heated.

  After the heating, as shown in FIG. 4, compression molding is performed using the lower mold 21 and the upper mold 23. At this time, the opposing surfaces of the lower mold 21 and the upper mold 23 are shown in FIG. Protrusions 21a and 23a for forming the gas flow path 1a and the cooling water flow path 1b of the separator 1 are provided, respectively. Moreover, the lower mold | type 21 is provided with the side wall part 21b which protrudes toward the upper mold | type 23 over the perimeter on the outer peripheral side.

  And as shown to Fig.4 (a), many above described graphite containing resin base materials 17 after a heating are set inside the side wall part 21b of the lower mold | type 21 in a laminated state. At this time, as shown in FIG. 3B, the graphite particles 15 are in a state in which the long diameter portion d2 faces in a direction substantially perpendicular to the surface of the graphite-containing resin base material 17. Thereafter, as shown in FIG. 4B, a large number of graphite-containing resin base materials 17 are compression-molded between the lower mold 21 and the upper mold 23, so that the separator 1 shown in FIG. obtain.

  In the separator 1 for a fuel cell manufactured in this way, the long diameter portion d2 of the graphite particle 15 in each graphite-containing resin base material 17 is in the vertical direction (a direction substantially perpendicular to the surface of the separator 1) in FIG. When the separator is considered to have the same thickness as compared with the case where the short diameter portion d1 is oriented in the vertical direction in FIG. 4, the graphite grains 15 arranged along the vertical direction Accordingly, the number of graphite particles 15 in the electrical conduction direction is reduced by that amount, and the electrical resistance is lowered, thereby preventing deterioration of conductivity.

  Further, even if the graphite particles 15 are compressed by a load at the time of compression molding, since the vertical direction is the major axis direction, compared to the case where the minor axis part is the vertical direction, after the compression molding Even if there are, the size of the graphite grains 15 in the vertical direction is large. For this reason, when the separator is considered to have the same thickness, the number of graphite grains 15 arranged along the vertical direction is reduced. The contact portion between the grains 15 is reduced, the electrical resistance is lowered, and the deterioration of conductivity can be prevented.

  As a second embodiment of the method of forming the graphite grain insertion hole 11 described above, a foamable material is mixed into the thermoplastic resin material when the sheet-like resin base material 9 is injection-molded. As a result, the sheet-like resin base material 9 becomes so-called porous including a large number of graphite grain insertion holes 11.

  After the sheet-like porous resin base material 9 having the graphite grain insertion holes 11 is formed, the manufacturing process is the same as that of the first embodiment shown in FIGS.

  FIG. 5 is a manufacturing process diagram corresponding to FIG. 4A according to the third embodiment.

  Since the fuel cell separator 1 includes the gas flow path 1a and the cooling water flow path 1b as shown in FIG. 1, the recesses that become the flow paths 1a and 1b when compression molding is performed in FIG. The compression rate is different between the portion 25 corresponding to, and the portions 27 corresponding to the convex portions on both sides thereof.

  Therefore, in order to make the compression ratio uniform throughout, the portion corresponding to the protruding portion 27a of the portion 27 corresponding to the convex portion is made convex with the graphite-containing resin base material 17 as shown in FIG. A plurality of base material pieces 17a appropriately cut according to the width dimension of the part are set in a laminated state in accordance with the difference in the compression rate described above.

  In this state, the separator 1 having the same shape as in FIG. 4C is obtained by performing compression molding in the same manner as in FIG. 4B.

  In this embodiment, since the base material piece 17a appropriately cut is laminated on the portions 27 corresponding to the convex portions on both sides of the gas flow path 1a and the cooling water flow path 1b before compression molding, The compression ratio can be made equal to each other at the portion 25 corresponding to 1a and 1b and the portion 27 corresponding to the convex portions on both sides thereof. For this reason, the density distribution of the graphite grains 15 with respect to the resin can be made uniform as a whole, which can contribute to the improvement of conductivity.

  According to the present invention, simply by laminating a sheet-like resin base material causes a difference in compression rate due to the uneven part of the separator during compression molding, but the sheet-like resin base material is appropriately cut. By laminating the cut pieces of the base material on the part corresponding to the convex part of the separator, the compressibility can be made equal between the concave part and the convex part, and the density distribution of the graphite grains relative to the resin is as a whole. Uniformity can contribute to the improvement of conductivity.

  Since the graphite grain insertion hole is processed after the resin base material is molded, the hole shape can be made highly accurate.

  The resin base material is prepared by injection molding a thermoplastic resin containing a foaming material, and the holes generated at this time are used as graphite grain insertion holes. Therefore, it is easy to manufacture a resin base material having graphite grain insertion holes. It will be a thing.

  The sheet-like resin substrate is put into a container in which the graphite particles are deposited, and the container is vibrated, whereby the graphite particles easily enter the graphite particle insertion holes of the sheet-like resin substrate.

  Since the graphite-containing resin base material is heated after the graphite grains are inserted into the graphite grain insertion holes of the resin base material, the resin and the graphite grains are reliably bonded.

  The fuel cell separator includes a plurality of convex portions on at least one surface, and includes a concave portion serving as a gas flow path between the convex portions, and the portion corresponding to the convex portion has the sheet-like resin base. Since the base material piece made by cutting the graphite-containing resin base material made of a material is laminated, the compressibility can be made equal between the concave portion and the convex portion, and the density distribution of the graphite particles relative to the resin can be made as a whole. Uniformity can contribute to the improvement of conductivity.

It is sectional drawing of the fuel cell provided with the separator manufactured by the manufacturing method of the separator for fuel cells concerning the 1st Embodiment of this invention. (A) is a side view which shows a sheet-like resin base material, (b) is sectional drawing which expanded the part. (A) is a manufacturing process diagram showing a state in which a sheet-like resin base material is put into a container in which graphite particles are deposited, and (b) is a graph showing a state in which graphite particles are inserted into the graphite particle insertion holes of the resin base material according to (a). It is sectional drawing which shows the state which entered. FIG. 3 is a manufacturing process diagram following FIG. 3, (a) is a state in which the graphite-containing resin base material obtained as shown in FIG. 3 (b) is laminated and set on the lower mold, and (b) is from the state of (a). A state where compression molding is performed, (c) shows a separator after compression molding. It is a manufacturing process figure corresponding to Drawing 4 (a) by a 3rd embodiment. (A) is sectional drawing which shows the manufacturing method of the conventional separator for fuel cells, (b) is an enlarged view of the A section of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell separator 9 Sheet-like resin base material 11 Graphite grain insertion hole 13 Container 15 Graphite grain 17 Graphite-containing resin base material 25 Part corresponding to a concave part 27 Part corresponding to a convex part d1 Short diameter part of a graphite grain d2 Graphite Long diameter part of grain

Claims (8)

  In a method for producing a separator for a fuel cell in which graphite and a resin are used as components and compression-molded into a predetermined shape, the graphite component is an anisotropic graphite particle having a short diameter portion and a long diameter portion, while the resin component is A resin base material having a plurality of graphite grain insertion holes, the pore diameter of the graphite grain insertion hole is set larger than the short diameter part of the graphite grain and smaller than the long diameter part, and the long diameter part of the graphite grain is the graphite A graphite-containing resin base material is created by entering the graphite grain insertion hole in a state where the grain insertion hole is in the axial direction, and a plurality of graphite-containing resin base materials are laminated along the axial direction of the graphite grain insertion hole and compressed. A method for producing a separator for a fuel cell, comprising molding.   2. The method for producing a fuel cell separator according to claim 1, wherein the resin base material is formed into a sheet shape, and the graphite grain insertion hole is formed through the sheet-shaped resin base material.   3. The method for producing a separator for a fuel cell according to claim 1, wherein the graphite grain insertion hole is processed after the resin base material is molded.   The fuel cell according to claim 1 or 2, wherein the resin base material is prepared by injection molding a thermoplastic resin containing a foam material, and the holes generated at this time are used as the graphite grain insertion holes. Separator manufacturing method.   The sheet-shaped resin base material is put into a container in which the graphite particles are deposited, and the container is vibrated to allow the graphite particles to enter the graphite particle insertion holes of the sheet-shaped resin base material. The method for producing a fuel cell separator according to claim 2.   6. The method for producing a fuel cell separator according to claim 5, wherein the graphite-containing resin base material is obtained by heating the graphite grains after inserting the graphite grains into the graphite grain insertion holes of the resin base material.   The fuel cell separator includes a plurality of convex portions on at least one surface, and includes a concave portion serving as a gas flow path between the convex portions, and the portion corresponding to the convex portion has the sheet-like resin base. The method for producing a fuel cell separator according to claim 2, wherein the base material piece is made by laminating the graphite-containing resin base material made of a material.   A fuel cell separator manufactured by the method for manufacturing a fuel cell separator according to any one of claims 1 to 7.

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