JP2007026899A - Fuel cell and manufacturing method of separator therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell of less weight and smaller size by, relating to a separator formed with a metal plate, allowing the plate thickness of an inside gas flow channel to be thinner than the plate thickness of a gas seal that requires rigidity, and preventing increase in plate thickness of the entire separator as the plate thickness of the gas flow channel is equivalent to that of the gas seal part. <P>SOLUTION: A separator 1 is integrally molded from a metal plate. The plate thickness of a gas seal 35 at the periphery of it is so designed as not to be deformed by the reactive force of a compressed seal material 39 that is pressurized under an arbitrary load for preventing gas leakage. Gas communications 31 and 33 as well as a power generation channel 41 that are inside gas flow channels 24 are thinner than the plate thickness of the gas seal part 35. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention provides a gas diffusion layer having a fuel electrode on one side of an electrolyte membrane and a gas diffusion layer having an oxidizer electrode on the other side, and each gas diffusion layer is opposite to the electrolyte membrane. The present invention relates to a fuel cell and a method for manufacturing a fuel cell separator, in which a separator is disposed in each of which a gas flow path for supplying a fuel gas and an oxidant gas is provided between each separator and each gas diffusion layer.

  There are various types of fuel cells such as solid polymer fuel cells, phosphoric acid fuel cells, and molten carbonate fuel cells. These fuel cells consist of unit cells that generate an electromotive force by an electrochemical reaction between an oxidizing gas and a fuel gas such as hydrogen, and are provided with a separator that electrically connects the unit cells and separates the reaction gas.

  A plurality of unit cells may be stacked to obtain a predetermined output, and the number of unit cells stacked may be several hundreds. The separator used for this unit battery forms a gas flow path in a carbon or metal plate.

  The carbon separator is formed by cutting the gas flow path by cutting, etc., and the thickness is relatively thick, about several millimeters, to ensure strength. Therefore, technological developments using metals such as stainless steel and titanium are becoming popular.

  When a metal is used for the separator, the thickness can be reduced compared to carbon, and when a gas flow path is formed, the processing cost can be reduced by using press working.

This gas flow path is secured by processing the metal plate into a shape having a large number of irregularities, but by providing R at the corners of the irregularities, it prevents breakage due to an increase in bending strain, and during press working A method of preventing the cracking and breaking of the shoulder portion of the concavo-convex portion at the time of final molding by performing preliminary pressing, and further reducing the contact area by flattening the contact surface to the gas diffusion layer of the concavo-convex portion is described below. It is described in Patent Document 1.
JP 2002-313354 A

  By the way, it is necessary to gas-seal the peripheral part of the separator, and since this gas-sealed part receives compressive stress, it is necessary to ensure rigidity, and therefore a certain thickness is required.

  However, in the above-described conventional separator, since the overall plate thickness is uniform, a relatively thick plate similar to the gas seal portion is also used for a portion where a gas flow path that does not require a plate thickness as much as the gas seal portion is formed. As a result, the plate thickness of the entire separator increases, which increases the weight of the fuel cell or increases the pitch between unit cells, leading to an increase in the size of the fuel cell.

  Then, this invention aims at preventing the plate | board thickness increase of the whole separator.

  The present invention provides a gas diffusion layer having a fuel electrode on one side of an electrolyte membrane, and a gas diffusion layer having an oxidizer electrode on the other side, and the electrolyte membrane of each of the gas diffusion layers In the fuel cell in which separators are arranged on the opposite sides and gas flow paths for supplying fuel gas and oxidant gas are provided between the separators and the gas diffusion layers, the separators are formed of metal plates. The most important feature is that the thickness of the gas flow path portion forming the gas flow path inside the gas seal portion is made thinner than the thickness of the gas seal portion at the peripheral edge of the separator.

  According to the present invention, the separator formed of the metal plate is made thinner in the gas flow path portion on the inner side than the plate thickness of the gas seal portion requiring rigidity. According to the thickness, the gas flow path portion has the same plate thickness, thereby preventing an increase in the plate thickness of the entire separator, thereby achieving weight reduction and miniaturization as a fuel cell.

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

  FIG. 1 is a plan view of a separator 1 on the oxidizer electrode side used in a fuel cell according to an embodiment of the present invention. The separator 1 is formed of a metal plate made of, for example, stainless steel. FIG. 2 is a simplified cross-sectional view corresponding to the line AA of FIG. 1 of the fuel cell using the separator 1, in which a gas diffusion layer 5 having a fuel electrode is provided on one side of the electrolyte membrane 3, and the electrolyte A gas diffusion layer 7 having an oxidant electrode is provided on the other side of the film 3.

  Then, the separator 1 on the oxidant electrode side described above is disposed on the gas diffusion layer 7 side including the oxidant electrode, and the separator 9 on the fuel electrode side is disposed on the gas diffusion layer 5 including the fuel electrode.

  The above-described electrolyte membrane 3, both gas diffusion layers 5 and 7, the oxidant electrode side separator 1, and the fuel electrode side separator 9 constitute a unit cell of a fuel cell. Usually, a plurality of unit cells are stacked to form a fuel cell. Use as a stack.

  Since the separator 9 on the fuel electrode side has the same structure as the separator 1 on the oxidant electrode side, the separator 1 on the oxidant electrode side shown in FIG. 1 will be described below.

  The separator 1 on the oxidizer electrode side in FIG. 1 has an oxidizing gas inlet through which oxidizing gas passes, outlet manifold holes 11 and 13, cooling water inlet through which cooling water passes, and outlet manifold holes 15 and 17. The fuel gas inlet and outlet manifold holes 19 and 21 through which the fuel gas passes are respectively formed to penetrate therethrough.

  These holes 11, 13, 15, 17, 19, 21 are also formed in the electrolyte membrane 3, which is another member constituting the fuel cell, and the separator 9 on the fuel electrode side. Each manifold is constituted by each hole located at a matching position.

  1, the holes 11 and 13 for the oxidizing gas inlet and the outlet manifold communicate with each other between the holes 11, 15 and 21 on the upper side and the holes 13, 17 and 19 on the lower side. A gas flow path 23 is provided. A portion including the gas flow path 23 is a gas flow path portion 24.

  The gas flow path 23 includes a plurality of power generation section gas flow paths 25 extending in parallel with each other in the vertical direction at the center position in the vertical direction in FIG. 1, and the power generation section gas flow paths 25 and the holes 11 for the oxidizing gas inlet manifold. , And a collective flow path 29 that communicates the power generation unit gas flow path 25 and the oxidant gas outlet manifold hole 13. The parts including the diffusion channel 27 and the collecting channel 29 described above are used as gas communication parts 31 and 33.

  Further, the periphery of the gas flow path 23 excluding the part corresponding to the holes 11 and 13, the periphery of the holes 1 and 13 excluding the part corresponding to the gas flow path 23, and the holes 15, 17, A gas seal portion 35 that prevents leakage of gas and cooling water is provided around the areas 19 and 21. As shown in FIG. 2, compression seal materials 37 and 39 are provided on both the front and back surfaces of the gas seal portion 35.

  As shown in FIG. 2, the gas seal portion 35 is thicker than the power generation flow path portion 41 that forms the power generation section gas flow path 25 on the inner side. That is, as shown in FIG. 3A showing a part of the separator 1 on the oxidizer electrode side as a single unit, assuming that the plate thickness of the gas seal portion 35 is T and the plate thickness of the power generation flow passage portion 41 is t1, T> t1.

  FIG. 3B is a cross-sectional view taken along the line BB in FIG. 1 and corresponds to the gas communication part 33 including the collecting flow path 29. When the thickness of the gas communication part 33 is t2, T> t2.

  FIG. 3C shows the CC cross-sectional view of FIG. 1 rotated 90 degrees in the clockwise direction, and corresponds to the gas communication part 33 having the holes 13 for the oxidizing gas outlet manifold. The plate thickness of the gas communication part 33 in the vicinity of the hole 13 is t2 similarly to the part including the collective flow path 29 described above, and is thinner than the plate thickness T of the gas seal part 35.

  Further, although not particularly shown, the thickness of the gas communication part 31 including the diffusion flow path 27 and the thickness of the gas communication part 31 in the vicinity of the hole 11 are also set to t2 similarly to the gas communication part 33 described above, and the gas seal part 35 The wall thickness is less than T.

  The above-described plate thickness T of the gas seal portion 35 is assumed not to be deformed by the reaction force of the compression seal members 37 and 39 pressed with an arbitrary load in order to prevent gas leakage.

  Thus, in this embodiment, the gas communication parts 31 and 33 and the power generation flow path that form the gas flow path 23 inside the gas seal part 35 with respect to the plate thickness of the gas seal part 35 at the peripheral edge part of the separator 1. The plate thickness of the gas flow path portion 24 including the portion 41 is reduced.

  3 (b) and 3 (c), the gas communication part 33 (31) having the plate thickness t2 is not limited to the roller that does not receive the reaction force from the compression seal materials 37 and 39, but also the power generation part gas flow path 25. Since the reaction force from the gas diffusion layer is not received unlike the power generation flow path portion 41 to be formed, it is possible to make the plate thickness thinner, and therefore, t1> t2.

  In the manufacture of the separator 1 as described above, an uneven portion continuous with the metal plate P having a thickness T is formed by press working, whereby a gas including the power generation unit gas flow path 25, the diffusion flow path 27, and the collective flow path 29. A flow path 23 is formed. FIG. 4A is a cross-sectional view after the press molding in the power generation flow path portion 41 including the power generation section gas flow path 25, and a metal mold is formed on the vertical wall portion 1a of the uneven portion of the separator 1 during the press molding. For the draft, the bent portion 1b needs to give R.

  Thereafter, as shown in FIG. 4B, the molded metal plate P is immersed in a solution that melts the metal in a state where the portion corresponding to the seal portion 35 is appropriately masked with the masking material 43, and the seal portion 35. Edging process is performed on other parts. FIG. 4C shows a state after the edging process in the power generation flow path portion 41. As a result, the separator 1 is obtained in which the plate thickness of the unmasked portion such as the press-formed portion (uneven shape portion) is t1 or t2 which is thinner than the plate thickness T of the seal portion 35.

  In addition, what is necessary is just to machine the recessed part of the installation site | part of the compression sealing materials 37 and 39 in the seal part 35 after an edging process.

  As described above, the separator 1 used in the fuel cell according to the present embodiment integrally forms a metal plate and forms a gas flow path 23 on the inner side with respect to the plate thickness of the gas seal portion 35 that requires rigidity. Since the plate thickness of the flow passage portion 24 is reduced, the gas flow passage portion 24 that forms the other portion, that is, the gas flow passage 23 in accordance with the plate thickness of the gas seal portion 35 that requires rigidity has the same plate thickness. Accordingly, an increase in the thickness of the separator as a whole can be prevented, thereby reducing the weight of the fuel cell, and reducing the pitch between the unit cells, thereby reducing the size of the fuel cell.

  Further, as shown in FIG. 5 (a), the bent portion 1b of the concavo-convex portion after the edging process maintains the R shape after the press forming, and this is further shown in FIG. 5 (b) by the edging process. As described above, R of the bent portion 1b can be eliminated or R can be reduced. Thereby, the contact area with the gas diffusion layer of the separator 1 increases, the contact resistance decreases, and the power generation efficiency can be increased.

  In this case, as shown by a two-dot chain line in FIG. 5 (a), a masking material 45 is provided at a portion to be a concave portion, and the convex portion opposite to the concave portion is melted by edging to reduce the plate thickness. Thereby, R of the bending part 1b can be eliminated or R can be made small.

  Further, by reducing the plate thickness of the power generation flow path portion 41 including the power generation section gas flow path 25 in contact with the gas diffusion layer, deformation due to thermal expansion such as when the fuel cell is started up is prevented from being generated as described above. The portion 41 is easily deformed by being elastically deformed, which can contribute to improving the performance of the fuel cell.

  In addition, the plate thickness of the separator 1 can be changed in two steps, pressing and edging, so the processing time is shortened compared to, for example, changing the plate thickness by partially attaching carbon to the surface of a metal plate. can do.

It is a top view of the separator by the side of the cathode used for the fuel cell which shows one Embodiment of this invention. FIG. 2 is a simplified cross-sectional view of a fuel cell corresponding to line AA in FIG. 1. 2A is a sectional view showing a part of the separator in the fuel cell of FIG. 2 alone, FIG. 2B is a sectional view taken along the line BB in FIG. 1, and FIG. FIG. It is explanatory drawing which shows the manufacturing method of the separator of FIG. 1, (a) is sectional drawing after press molding, (b) Sectional drawing which shows the state masked after press molding, (c) is edging in the masking state It is sectional drawing which shows a state. (A) is sectional drawing which shows the masking state at the time of edging the bending part of the separator after press molding, (b) is sectional drawing which shows the state which eliminated the R shape of the bending part of the separator by edging.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cathode side separator 3 Electrolyte membrane 5 Gas diffusion layer provided with fuel electrode 7 Gas diffusion layer provided with oxidant electrode 9 Separator on anode side 23 Gas flow path 24 Gas flow path section 31, 33 Gas communication section 35 Gas seal Part 41 Power generation flow path

Claims (5)

  A gas diffusion layer having a fuel electrode is provided on one side of the electrolyte membrane, a gas diffusion layer having an oxidant electrode is provided on the other side, and a separator is provided on the opposite side of each gas diffusion layer from the electrolyte membrane. In the fuel cell in which gas flow paths for supplying fuel gas and oxidant gas are provided between each separator and each gas diffusion layer, the separator is formed of a metal plate, and the separator A fuel cell characterized in that the plate thickness of the gas flow path portion forming the gas flow path inside the gas seal portion is made thinner than the plate thickness of the gas seal portion at the peripheral edge of the fuel cell.   The gas flow path portion of the separator is located outside the gas diffusion layer, and is a gas communication portion that communicates the gas diffusion layer and a gas manifold outside the gas diffusion layer. Fuel cell.   The fuel cell according to claim 1, wherein the gas flow path portion of the separator is a power generation flow path portion corresponding to the gas diffusion layer.   The fuel cell according to any one of claims 1 to 3, wherein the separator formed of the metal plate has a plate thickness changed by melting the metal with a meltable solution.   A gas diffusion layer provided with a fuel electrode is provided on one side of the electrolyte membrane, and a gas diffusion layer provided with an oxidant electrode is provided on the other side, and each of the gas diffusion layers is opposite to the electrolyte membrane. In the method for manufacturing a separator for a fuel cell, wherein the separator is formed of a metal plate, and the separator is formed with a metal plate. The separator is formed of a metal plate. The metal plate is melted with a meltable solution so that the plate thickness of the gas flow path portion forming the gas flow path inside the gas seal portion is thinner than the thickness of the gas seal portion at the periphery. A method for producing a separator for a fuel cell, characterized in that the plate thickness is changed.

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