JP2005243415A - Manufacturing method of separator for fuel cell, and separator for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the reduction of conductivity of the whole separator without carrying out repeatedly heating-cooling of a molding die in continuously carrying out molding. <P>SOLUTION: A mixed powder material 13 in which thermosetting resin and graphite powder are mixed and kneaded at a prescribed proportion, is preliminarily molded by a preliminary molding die composed of a lower die 9 and an upper die 11 so as to become to have a larger dimension than the compression direction dimension of the finished product, and the finished product is obtained by heating and compression molding this preformed product 1A molded preliminarily by a final molding die heated beforehand. <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. Some cooling water passages are not provided.

As such a fuel cell separator, a material in which carbon for ensuring conductivity and a thermosetting resin for maintaining moldability and ensuring strength are mixed in a predetermined shape by heat compression molding Is described in Patent Document 1 below.
JP 2003-17085 A

  By the way, when molding the above-described fuel cell separator, if the material is put into a heated mold, the resin touching the mold reacts and cures prior to the resin inside, and the pressurization is not sufficient. There is a problem that the surface layer of the separator is covered with a resin having low conductivity, and the conductivity of the entire separator is lowered.

  In addition, it is possible to suppress the above-described resin film formation on the separator surface layer by heating the mold after the material is charged. In this case, when the molding is continuously performed, A control mechanism for repeatedly performing heating and cooling is required, and the manufacturing time is increased due to a longer molding time.

  Therefore, an object of the present invention is to prevent a decrease in the conductivity of the entire separator without repeatedly heating and cooling the molding die when continuously molding.

  The present invention relates to a method for manufacturing a fuel cell separator in which a mixed powder material made of a resin and graphite powder is compression-molded into a predetermined shape. The main feature is that the preform is preliminarily molded and the preform is preliminarily heated and compression-molded by a preheated main mold to form a finished product.

  According to the present invention, after preforming with a preforming die so as to have a size larger than the dimension in the compression direction of the finished product, this preformed product is heated and compression-molded with the pre-heated mold so that heating is performed. Resin material mixed with graphite powder at the time of preforming not performed can be kept dispersed throughout without being collected on the surface layer, and heat compression molding in this state prevents deterioration of the conductivity of the entire separator can do.

  In addition, since heat compression molding is performed with a preheated main mold after pre-molding, there is no need to repeatedly heat and cool the mold when performing continuous molding, and therefore no control mechanism is required In addition, the molding time can be shortened, and an increase in manufacturing cost can be prevented.

  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 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.

  A first embodiment of a method for manufacturing such a separator 1 will be described with reference to FIGS. FIG. 2 shows a preforming step, and FIG. 3 shows the main forming step.

  First, as shown in FIG. 2, preforming is performed using the lower mold 9 and the upper mold 11 constituting the preforming mold. At this time, the surfaces of the lower mold 9 and the upper mold 11 facing each other are Protrusions 9a and 11a for forming the gas flow path 1a and the cooling water flow path 1b of the separator 1 shown in FIG. 1 are provided. Moreover, the lower mold | type 9 is provided with the side wall part 9b which protrudes toward the upper mold | type 11 over the perimeter on the outer peripheral side.

  Then, as shown in FIG. 2A, after the mixed powder material 13 in which the thermosetting resin and the graphite powder are kneaded at a predetermined ratio is introduced into the inside of the side wall portion 9b of the lower mold 9 described above, As shown in FIG. 2B, the mixed powder material 13 is compressed between the lower mold 9 and the upper mold 11 to perform preforming. At this time, the preforming die is not heated.

  The preform 1A shown in FIG. 2 (c) obtained by the above preforming has grooves 1Aa and 1Ab corresponding to the gas flow path 1a and the cooling water flow path 1b of the separator 1 shown in FIG. The thickness dimension t1 in the compression direction in each part is larger than the same dimension t2 of the finished product shown in FIG.

  In addition, the part which makes the vertical dimension in FIG.2 (c) larger than the same dimension in FIG.3 (c) is not only the part shown as t1 in FIG.2 (c), but also the part corresponding to other groove | channels 1Aa and 1Ab. It is the same.

  In addition, the vertical dimension of each part of the preform 1A is at least twice as long as the long diameter part of the graphite powder.

  Next, as shown in FIG. 3, the preform 1A described above is subjected to main molding using a lower mold 15 and an upper mold 17 constituting the main mold. Also in this main mold, convex portions 15a and 17a for forming the gas flow path 1a and the cooling water flow path 1b of the separator 1 shown in FIG. 1 are formed on the surfaces of the lower mold 15 and the upper mold 17 facing each other. , Respectively. Moreover, the lower mold | type 15 is provided with the side wall part 15b which protrudes toward the upper mold | type 17 over a perimeter on the outer peripheral side. Further, a heater 19 is installed below the lower mold 15 to heat the main mold.

  In the main molding using the main molding die, as shown in FIG. 3A, the preform 1 </ b> A is set on the lower die 15 that has been heated in advance by the heater 19. At this time, the convex portion 15a of the lower mold 15 enters the groove 1Ab of the preform 1A, and the convex portion 17a of the upper mold 17 enters the groove 1Aa of the preform 1A.

  And as shown in FIG.3 (b), the finished product shown in FIG.3 (c), ie, the separator 1 for fuel cells, is obtained by performing heat compression molding between the lower mold | type 15 and the upper mold | type 17. .

  According to the above-described embodiment, since the preforming mold is not heated at the time of preforming, the resin touching the lower mold 9 and the upper mold 11 is not reacted and cured prior to the internal resin, Therefore, the resin can be kept dispersed throughout the surface of the finished product (separator 1) without being collected, and heat compression molding in this state can prevent a decrease in conductivity of the separator 1 as a whole. it can.

  In addition, since heat compression molding is performed with a preheated main mold after pre-molding, there is no need to repeatedly heat and cool the mold when performing continuous molding, and therefore no control mechanism is required In addition, the molding time can be shortened, and an increase in manufacturing cost can be prevented.

  FIG. 4 shows a method of manufacturing a fuel cell separator according to the second embodiment of the present invention. In this embodiment, as shown in FIG. 4 (a), in the preforming step of FIG. 2 or in the main forming step of FIG. 3 as shown in FIG. The powder 21 is sprayed in a state of containing moisture to adhere to the mold surface.

  Then, by performing preforming or main molding in this state, a large amount of graphite powder 21 is present on the surface of the preformed product 1A or the finished product (separator) 1 as compared with the first embodiment. . As a result, as the fuel cell separator 1, the graphite powder 21 at the portion in contact with the electrode 5 shown in FIG.

  According to the present invention, before the molding operation of at least one of the preforming step and the main molding step, the graphite powder is supplied to the mold surface that is in contact with the surface of the molded product. More graphite powder is present on the surface, and the conductivity of the fuel cell separator is further improved.

  By spraying the graphite powder containing water and adhering it to the mold surface, the graphite powder can be reliably supplied to the mold surface.

  Moreover, the electroconductivity fall of the separator for fuel cells using the thermosetting resin as a resin material can be prevented.

It is sectional drawing of the fuel cell provided with the separator manufactured by the manufacturing method of the separator for fuel cells of this invention. It is a preforming process figure in the manufacturing method of the separator for fuel cells concerning the 1st Embodiment of this invention. FIG. 3 is a main molding process diagram following the preliminary molding process of FIG. 2. FIGS. 3A and 3B are manufacturing process diagrams showing a method for manufacturing a fuel cell separator according to a second embodiment of the present invention, wherein FIG. 3A is a state in which graphite powder is supplied to the mold surface during the pre-molding of FIG. 2, and FIG. The state of supplying graphite powder to the mold surface at the time of the main molding is shown.

Explanation of symbols

1 Separator 9 Lower mold (Preliminary mold)
11 Upper mold (preliminary mold)
15 Lower mold (main mold)
17 Upper mold (main mold)
21 Graphite powder

Claims (5)

  In a method of manufacturing a fuel cell separator in which a mixed powder material made of resin and graphite powder is compression-molded into a predetermined shape, the resin and graphite powder are preformed so as to have a size larger than the size in the compression direction of the finished product by a preforming mold. A method for manufacturing a separator for a fuel cell, wherein the preformed preform is heat-compressed with a preheated main mold to obtain a finished product.   2. The fuel cell separator according to claim 1, wherein the graphite powder is supplied to a mold surface in contact with a surface of a molded product before at least one of the preforming step and the main forming step. Method.   The method for producing a separator for a fuel cell according to claim 2, wherein the graphite powder is sprayed with water contained therein and adhered to the mold surface.   The method for producing a fuel cell separator according to any one of claims 1 to 3, wherein the resin is a thermosetting resin.   A fuel cell separator manufactured by the method for manufacturing a fuel cell separator according to any one of claims 1 to 4.

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