JP2008004291A - Manufacturing method of press metal separator for fuel cell - Google Patents

Abstract

A method of manufacturing a pressed metal separator for a fuel cell that generates the least amount of deformation such as warpage during power generation is provided.
In a method of manufacturing a pressed metal separator for a fuel cell, the method includes press-molding a thin metal plate member using a predetermined mold, and press-molding in a temperature band during power generation of the fuel cell. For example, the metal thin plate member is set in a temperature band during power generation of the fuel cell, and the mold is set in a temperature band during power generation of the fuel cell.
[Selection] Figure 2

Description

  The present invention relates to a method for producing a press metal separator for a fuel cell.

  A membrane-electrode assembly (MEA) in which an anode that reacts with a fuel gas such as hydrogen gas is formed on one surface of an electrolyte membrane and a cathode that reacts with an oxidizing gas such as oxygen gas is formed on the other surface ) Are sandwiched between a pair of separators (so-called solid polymer electrolyte fuel cells) are known.

  This type of fuel cell separator is made of a conductive material, and is placed in contact with the surface of the MEA to function as a current collector. Moreover, a separator is provided with uneven | corrugated shape on both surfaces. This uneven shape forms a groove arranged in parallel to the surface of the separator, and is used as a flow path for supplying hydrogen gas or oxidizing gas to the anode or cathode. In addition, since this type of fuel cell is normally used in a fuel cell stack in which a plurality of MEAs are stacked, a separator separates each MEA.

  As the separator, a metallic separator (metal separator) that is thin, has high strength, and is excellent in moldability is frequently used. As a method for producing a metal separator, for example, a metal thin plate member is produced by pressing. By press working, a recessed channel or the like is formed in the metal thin plate member, and a metal separator is obtained (see, for example, Patent Document 1).

JP 2004-296138 A JP 2004-241141 A JP 2005-339901 A

  Residual stress exists in the metal separator manufactured by press working. For this reason, the metal separator may be thermally expanded and deformed by heat generated during power generation by the fuel cell. If the metal separator is deformed and warps, the contact between the separator and the MEA becomes insufficient, and the function of the current collector of the separator is deteriorated. When the function of the current collector is reduced, the output of the fuel cell is eventually reduced. In addition, when the metal separator warps during power generation, the flow path on the metal separator may be deformed, and gas in the flow path may leak. In such a case, the output of the fuel cell becomes unstable, which is a problem.

  The above-mentioned Patent Documents 2 and 3 are metal separators having strips arranged in parallel, and a projection (bump) is provided between the strips to improve strength in a direction substantially perpendicular to the strips. Disclosed is a metal separator provided. By providing the protrusions and the like in this manner, the deformation (warping) of the metal separator can be prevented, but it is desirable to prevent the metal separator from being deformed without providing a special structure such as the protrusions.

  An object of the present invention is to provide a method for producing a pressed metal separator for a fuel cell that generates the least deformation such as warpage during power generation.

  A method for producing a press metal separator for a fuel cell according to the present invention is a method for producing a press metal separator for a fuel cell comprising a step of press-molding a thin metal plate member using a predetermined mold. It is characterized by press molding in a band. ADVANTAGE OF THE INVENTION According to this invention, the press-metal separator for fuel cells which hardly deform | transforms by a residual stress can be manufactured at the time of electric power generation.

  In the method for manufacturing a pressed metal separator for a fuel cell, the metal thin plate member is set to a temperature band during power generation of the fuel cell.

  In the method for manufacturing a press metal separator for a fuel cell, the mold is set in a temperature band during power generation of the fuel cell.

  The fuel cell press metal separator manufacturing apparatus used in the method for manufacturing a fuel cell press metal separator includes a heating means for heating at least one of the metal thin plate member and the mold.

  In addition, the fuel cell press metal separator manufactured by the above-described manufacturing method is characterized in that the flatness in the temperature band during power generation of the fuel cell is higher than the flatness in the temperature band other than the temperature band.

  According to the present invention, it is possible to manufacture a fuel cell press metal separator that generates the least amount of deformation such as warping during power generation.

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

  FIG. 1 is a schematic plan view of a press metal separator 1 for a fuel cell. The separator 1 is provided with a flow path including a plurality of grooves arranged in parallel at the central portion. A gas or a refrigerant flows along the flow path 20. The cross section of the groove is substantially concave. The flow path 20 is formed on both the front surface and the back surface of the separator 1. Separator 1 is provided with a concavo-convex shape in which concave portions and convex portions are alternately repeated on both surfaces. The separator 1 is manufactured by pressing a metal thin plate member. The metal thin plate member is a known conductive thin plate member made of a metal such as aluminum, stainless steel, or titanium. In the present embodiment, the metal separator 1 manufactured by pressing a metal thin plate member is particularly referred to as a press metal separator. In addition, the outer side of the center part of the separator 1 is provided with a manifold 30 that is formed of a hollow portion and allows gas and refrigerant to pass therethrough. The manifold 30 is formed, for example, by punching a thin metal plate member after pressing.

  Hereinafter, the manufacturing method of the separator 1 is demonstrated. The separator 1 is manufactured by press molding using a predetermined mold. FIG. 2 is a schematic configuration diagram of the fuel cell press metal separator manufacturing apparatus 40. The apparatus 40 includes a chamber 42 and a mold 43 installed in the chamber 42. The mold 43 includes an upper mold 44 and a lower mold 47. The thin metal plate member 2 is disposed between the molds 44 and 47. The upper mold 44 and the lower mold 47 are movable in the vertical direction, and press the metal thin plate member 2 disposed between the both molds 44 and 47 from both sides. Convex portions 46 and 49 are provided on the pressing surfaces 45 and 48 of the upper mold 44 and the lower mold 47 facing the metal thin plate member 2, respectively. The convex portions 46 and 49 are elongated and parallel to each other on the pressing surfaces 45 and 48. When the metal thin plate member 2 is pressed by the mold 43, the convex portion 49 of the lower mold 47 enters between the convex portions 46 of the upper mold 44, and the metal thin plate member 2 follows the shape of the convex portions 46, 49. Can be bent. In this way, the convex portion 46 of the upper mold 44 and the convex portion 49 of the lower mold 47 are bent so that concave and convex shapes are formed on both surfaces of the metal thin plate member 2. Note that the inside of the chamber 42 can be set to a predetermined temperature by a heater or the like.

  In the present embodiment, the press molding is performed in a temperature band during power generation of the fuel cell. For example, if the temperature at the time of power generation of the fuel cell using the separator 1 is approximately 80 ° C., press molding is performed under the condition of approximately 80 ° C. Specifically, (I) the metal thin plate member 2 is warmed in advance, and the temperature of the metal thin plate member 2 is set to a temperature band during power generation of the fuel cell, and (II) a mold 43 used for press molding. Is set in advance, and the temperature of the mold 43 is set to a temperature band during power generation of the fuel cell, and (III) the temperature in the chamber 42 in which the metal thin plate member 2 and the mold 43 are installed is Set the temperature range during power generation. At least one of (I) to (III) is performed. It is preferable to perform all of (I) to (III).

  In the above (I), as a method for heating the thin metal plate member 2, for example, before the press molding, the thin metal plate member 2 is allowed to stand in a temperature-controlled room where the temperature is set in the temperature band during power generation of the fuel cell. There are a method of warming and a method of warming the thin metal plate member 2 by blowing warm air. Heating can be performed by a known method except that the temperature range is set at the time of power generation of the fuel cell. Moreover, in said (I), when heating the metal thin plate member 2 and installing temperature in the temperature range at the time of power generation of a fuel cell, it is preferable to warm the whole surface (all) of the metal thin plate member 2. This is because the thin metal plate member 2 is press-molded under substantially uniform conditions (temperature conditions).

  In the above (II), as a method for heating the mold 43, for example, there is a method in which an electric heater is built in the mold 43 and the mold 43 is heated by the electric heater. Heating can be performed by a known method except that the temperature range is set at the time of power generation of the fuel cell. As the mold, a known press working mold such as the mold 43 shown in FIG. 2 or a roll mold can be used. In addition, although it is preferable that the metal mold | die 43 heats both the upper metal mold | die 44 and the lower metal mold | die 47, depending on the case, you may heat only one side.

  In the above (III), when the inside of the chamber 42 is warmed with a heater or the like and the temperature is set to a temperature band at the time of power generation of the fuel cell, the thin metal plate member 2 and the mold 43 installed in the chamber 42 are warmed. Further, in the above (I) or (II), it is possible to prevent the temperature of the metal sheet member 2 and the mold 43 that have been warmed in advance from decreasing.

  The separator 1 according to the present embodiment is molded into a predetermined shape desired during power generation in a temperature range during power generation of the fuel cell. FIG. 3 is a perspective view of the separator 1 under the temperature range during power generation of the fuel cell. FIG. 3 shows only a part of the uneven shape of the separator 1 used as the flow path 20 for convenience of explanation. Since the separator 1 is press-molded in the temperature range during power generation of the fuel cell, the separator 1 maintains a predetermined shape at least in this temperature range.

  By the way, since the separator 1 is manufactured by press molding, it has a state in which residual stress and strain energy are inherent. The separator 1 has a lower strength in the direction perpendicular to the groove (the direction of the arrow b) than the direction along the groove (the flow path 20) (the direction of the arrow a in FIG. 3), and is easily bent. Therefore, when affected by residual stress or the like, the separator 1 warps in the direction perpendicular to the groove.

  The temperature (band) at the time of power generation of the fuel cell is usually at room temperature or higher. Accordingly, after press molding, the temperature of the separator 1 is lower than that during press molding. The separator 1 that has fallen in temperature may undergo thermal shrinkage and warp. Therefore, when this separator 1 is used for a fuel cell, it is in a state where it can be warped due to thermal contraction except during power generation such as during standby. However, during power generation, the separator rises in temperature and thermally expands to restore the predetermined shape during press molding. The separator 1 according to the present embodiment maintains a predetermined shape at least during power generation, and is most unlikely to undergo deformation such as warping during power generation.

In the concavo-convex shape formed on both surfaces of the separator 1 during press molding, the height h ₁ (depth of each concave portion) of each convex portion is set to be the same. Further, in the separator 1 shown in FIG. 3, the surface S ₁ of the respective projecting portions of the upper surface is set to be substantially flush (horizontal plane). That is, the separator 1 has the highest flatness in the temperature range during power generation of the fuel cell.

  The separator 1 may be subjected to noble metal plating or conductive resin coating for the purpose of improving the corrosion resistance.

  Hereinafter, the fuel cell 50 using the separator 1 according to the present embodiment will be described. FIG. 4 is a schematic configuration diagram of a fuel cell 50 including the separator 1. The fuel cell 50 includes a membrane-electrode assembly 53 (MEA) including an ion conductive electrolyte membrane 51 and electrodes 52 disposed on both surfaces of the electrolyte membrane 51, and a set of separators disposed on both surfaces of the MEA 53. 1 (1A, 1B). The fuel cell 50 generates power by reacting hydrogen gas and oxidizing gas (oxygen) in the MEA 53. In FIG. 4, as the fuel cell 50, a fuel cell including one MEA 53 and one set of separators 1 is shown for convenience of explanation. A plurality of fuel cells are stacked and used as a fuel cell stack electrically connected in series.

  The electrolyte membrane 51 is made of a fluorine-based polymer material. It is a polymer membrane having an ion exchange group such as a sulfonic acid group or a carboxyl group in the side chain. As the electrolyte membrane 51, for example, a perfluorosulfonic acid polymer membrane (Nafion, registered trademark, manufactured by DuPont) is used. On one surface of the electrolyte membrane 51, an anode 52A that is an electrode 52 with which hydrogen gas reacts is provided. On the other surface, a cathode 52B, which is an electrode 52 that reacts with an oxidizing gas, is provided. These electrodes 52 include a catalyst layer 54 (54A, 54B) formed on the surface of the electrolyte membrane 51 and a diffusion layer 55 (55A, 55B) formed on the surface of the catalyst layer 54 (54A, 54B). Prepare. The catalyst layer 54 includes a catalyst-supporting carbon in which a noble metal catalyst such as platinum, gold, palladium, ruthenium, iridium and the like is supported by carbon, and a binder resin for binding the catalyst-supporting carbon. As the carbon, oil furnace black, channel black, thermal black, acetylene black and the like are used. As the binder resin, polyvinyl fluoride, polyvinylidene fluoride, polyhexafluoropropylene, or the like is used. The diffusion layer 55 is made of a conductive porous material such as carbon fiber (for example, carbon cloth, carbon paper). In the MEA 53 shown in FIG. 2, the electrode 52 disposed on the upper side of the electrolyte membrane 51 is the anode 52A, and the electrode 52 disposed on the lower side is the cathode 52B.

  A pair of fuel cell press metal separators 1 (1A, 1B) is disposed on both surfaces of the MEA 53. In FIG. 4, the separator 1 disposed on the upper side of the MEA 53 is the anode-side separator 1A, and the separator 1 disposed on the lower side is the cathode-side separator 1B. These separators 1 (1A, 1B) are arranged to face each other via the MEA 53. In addition, these separators 1 (1A, 1B) are press-molded (processed) under conditions of approximately 80 ° C.

  The separator 1 (1A, 1B) has an uneven shape. This uneven shape consists of a plurality of grooves arranged in parallel and is used as a flow path. In the anode-side separator 1A, the groove (recess 22A) facing the MEA 53 is used as a hydrogen gas flow path for supplying hydrogen gas to the anode 52A of the MEA 53. Further, the groove (recess 23A) on the opposite side of the hydrogen gas flow path is used as a refrigerant flow path for passing a refrigerant (cooling water). On the other hand, in the cathode side separator 1B, the groove (recess 22B) facing the MEA 53 is used as an oxidizing gas flow path for supplying oxidizing gas to the cathode 52B of the MEA 53. Further, the groove (recess 23B) on the opposite side of the oxidizing gas channel is used as a refrigerant channel. A cathode separator 1B 'of another fuel cell is disposed on the upper surface of the anode separator 1A, and an anode separator 1A "of another fuel cell is disposed on the lower surface of the cathode separator 1B. Separator 1 (1A, 1B) separates MEA 53 of fuel cell 50 from MEAs of other fuel cells.

  In this fuel cell 50, hydrogen gas is supplied to the anode 52A of the MEA 53 via the hydrogen gas flow path of the separator 1A, and the oxidizing gas (usually air) is supplied to the cathode 52B via the oxidizing gas flow path of the separator 1B. Is supplied. The supplied hydrogen gas is subjected to a chemical reaction of the following formula (1) at the anode 52A. Further, the oxidizing gas (oxygen) is subjected to a chemical reaction of the following formula (2) at the cathode 52B.

H ₂ → 2H ⁺ + 2e ⁻ (1)
^{_{(1/2) O 2 + 2H +}} + 2e - → H 2 O ··· (2)

  At the anode 52A, protons and electrons are generated from hydrogen. The generated protons move through the electrolyte membrane 51 to reach the cathode 52B and are subjected to the chemical reaction represented by the above formula (2). The proton moves through the electrolyte membrane 51 with water molecules. The electrons generated in the anode 52A move in the anode side separator 1A, move in the adjacent cathode side separator 1B ', and move to the cathode of another fuel cell. The electrons used in the cathode 52B of the fuel cell 50 are supplied from the anode of the fuel cell adjacent to the cathode separator 1B through the anode separator 1A ″. The fuel cell 50 generally generates power under a temperature condition of approximately 80 ° C.

  The hydrogen gas supplied to the anode 52A and the oxidizing gas supplied to the cathode 52B are not all consumed for the reaction. Unconsumed hydrogen gas passes through the hydrogen gas flow path of the anode-side separator 1A, and unconsumed oxidizing gas passes through the oxidizing gas flow path of the cathode-side separator 1B and is discharged as off-gas to the outside of the fuel cell 50. . Further, as shown in the above equation (2), water is generated at the cathode. The produced water is discharged to the outside of the fuel cell 50 together with the off gas through the oxidizing gas flow path of the cathode side separator 1B.

  In the fuel cell 50 during power generation, the separator 1 (1A, 1B) is under the same temperature condition of about 80 ° C. as in the press molding. When present under this temperature condition, the separator 1 (1A, 1B) exerts a force to restore the shape during press molding. For this reason, the separator 1 (1A, 1B) is prevented from warping at least during power generation, so that the separator 1 (1A, 1B) is lifted from the surface of the MEA and gas etc. leaks from the gas flow path. And problems such as deterioration of the function of collecting electrons do not occur.

In addition, in the separator 1 of this embodiment, you may provide a reinforcement part in the groove | channel arranged in parallel in order to prevent a curvature etc. more reliably. That is, the reinforcing portion may be formed so as to pass between the convex portions in the concave portion formed between the convex portions. FIG. 5 is a perspective view of a part of the separator 11 including the reinforcing portion 15. The reinforcing portion 15 is formed on both the front surface and the back surface of the separator 11. FIG. 6 is a side view of the separator as viewed from the direction of the arrow A shown in FIG. Reinforcing portion 15 has a height h ₃ corresponds to the depth of about half of the recess of depth h _2. This reinforcing portion 15 improves the strength in the direction (in the direction of arrow b) perpendicular to the direction along the recess (strip) (in the direction of arrow a in FIG. 5). Note that spaces (S ₁₀ , S ₂₀ ) for ensuring the flow of fluid such as gas or refrigerant are provided in the recesses (slots) in which the reinforcing portions 15 are formed.

FIG. 7 is an explanatory diagram of a separator 61 having uneven shapes with different sizes on each surface. FIG. 7A is an explanatory diagram showing the state of the separator 61 in the fuel cell during press molding and during power generation. The separator 61 has a width L ₁ of the projecting portion 62 projecting to the upper surface side is set larger than the width L ₂ of the convex portion 63 projecting on the lower surface side. In other words, the width L ₃ of the bottoms of the recesses 64 on the upper surface side is set smaller than the base width L ₄ of the lower surface side recessed portion 65 of the. FIG. 7B is an explanatory diagram showing a state in which the separator 61 shown in FIG. 7A is deprived of heat, the temperature is lowered, and the separator 61 is thermally contracted. Since the width L ₁ (width L ₃ ) is longer than the width L ₂ (width L ₄ ), the amount of heat shrinkage is the width L ₂ (width L ₄ ) in the width L ₁ (width L ₃ ). Bigger than. Therefore, the heat shrinkage amount in the width L ₁ (width L ₃ ) exceeds the heat shrinkage amount in the width L ₂ (width L ₄ ), and as a result, the separator as a whole warps downward. On the other hand, FIG.7 (c) is explanatory drawing which shows a mode that heat is added to the separator 61 shown by Fig.7 (a), temperature rises, and the separator 61 expands thermally. As for the amount of thermal expansion, the width L ₁ (width L ₃ ) is larger than the width L ₂ (width L ₄ ). Therefore, the thermal expansion amount in the width L ₁ (width L ₃ ) exceeds the thermal expansion amount in the width L ₂ (width L ₄ ), and as a result, the entire separator warps upward. Thus, by appropriately setting the width of the concavo-convex shape, the warping direction of the separator 61 after thermal expansion or thermal contraction can be controlled.

  In another embodiment, the separator may be manufactured by pressing a metal sheet material at a temperature higher than the temperature range during power generation of the fuel cell. For example, when a separator having the shape shown in FIG. 7 is manufactured under this temperature condition, the standby separator is thermally contracted and warped downward as shown in FIG. 7B. At the time of power generation of the fuel cell, although the degree of warpage is smaller than that at the time of standby, the separator is still in a state where the central portion is warped downward. By the way, in this type of fuel cell, the central portion of the MEA is exclusively used for power generation. Therefore, there is a case where it is desired to make the central portion of the separator particularly strongly contact with the central portion of the MEA. In such a case, a separator in which the MEA and the central portion are in strong contact during power generation is useful.

  Here, a method for producing a fuel cell metal separator using the roll forming apparatus 60 will be described. FIG. 8 is a schematic configuration diagram of the roll forming apparatus 60. The roll forming apparatus 60 includes a pair of forming rolls 61A and 61B arranged close to each other in the vertical direction. The upper forming roll 61A includes a forming die 64A fixed to the outer periphery of the intermediate portion in the axial direction of the upper roll shaft 62A, split dies 66A and 66C fixed to both ends in the axial direction of the forming die 64A, and a roll shaft. A dummy 68A that does not participate in molding fixed to the opposite side of the molding die 64A across the diameter of 62A is combined. The lower forming roll 61B includes a forming die 64B fixed to the outer periphery of the intermediate portion in the axial direction of the lower roll shaft 62B, split molds 66B and 66D fixed to both ends in the axial direction of the forming die 64B, A dummy 68B that does not participate in molding fixed to the opposite side of the molding die 64B across the diameter of the roll shaft 62B is combined. Both end portions of the roll shafts 62 </ b> A and 62 </ b> B are rotatably held by a bearing holder 74 with respect to a frame 76 that supports the entire apparatus. A reduction gear 72 is connected to the roll shafts 62A and 62B. Furthermore, a motor 71 is connected via a speed reducer 72. By driving the motor 71, the forming rolls 61A and 61B rotate in the opposite direction at the same speed. A thin metal plate member is fed between the upper forming roll 61A and the lower forming roll 61B, and the mold (64A, 66A, 66C) of the forming roll 61A and the mold (64B, 66B, 66D), the metal thin plate member is roll-formed into a predetermined shape. The roll forming apparatus 60 includes heaters (heating means) 69A and 69B inside the forming roll 61A and the forming roll 61B. The temperature of the mold heated by the heater is the temperature (band) during power generation of the fuel cell. The roll forming apparatus 60 may include a heater that heats the thin metal plate member.

It is a schematic plan view of the press metal separator for fuel cells. It is a schematic block diagram of the press metal separator manufacturing apparatus for fuel cells. It is a perspective view of the separator (part) under the temperature zone at the time of power generation of the fuel cell. It is a schematic block diagram of a fuel cell. It is a perspective view of a separator (part) provided with a reinforcement part. It is a side view of the separator of FIG. It is explanatory drawing of a separator provided with the uneven | corrugated shape of a different magnitude | size. (A): It is explanatory drawing which shows the state of the separator in the fuel cell at the time of press molding and during electric power generation. (B): It is explanatory drawing which shows the state which the separator of Fig.7 (a) thermally contracted. (C): It is explanatory drawing which shows the state which the separator of Fig.7 (a) thermally expanded. It is a schematic block diagram of the press metal separator manufacturing apparatus (roll forming apparatus) for fuel cells.

Explanation of symbols

  1, 1A, 1B, 11, 61 Fuel cell press metal separator, 2 metal thin plate member, 40 fuel cell press metal separator manufacturing apparatus, 42 chamber, 43 mold, 50 fuel cell.

Claims (5)

In the manufacturing method of a press metal separator for a fuel cell comprising a step of press-molding a thin metal plate member using a predetermined mold,
A method for producing a pressed metal separator for a fuel cell, which is press-molded in a temperature range during power generation of the fuel cell. In the manufacturing method of the press metal separator for fuel cells of Claim 1,
A method for producing a pressed metal separator for a fuel cell, wherein the metal thin plate member is set in a temperature band during power generation of the fuel cell. In the manufacturing method of the press-metal separator for fuel cells of Claim 1 or Claim 2,
A method for manufacturing a press metal separator for a fuel cell, wherein the mold is set in a temperature band during power generation of the fuel cell. In the press metal separator manufacturing apparatus for fuel cells used for the manufacturing method of the press metal separator for fuel cells of any one of Claims 1-3,
An apparatus for producing a pressed metal separator for a fuel cell, comprising heating means for heating at least one of a metal thin plate member and a mold. A press metal separator for a fuel cell manufactured by the manufacturing method according to any one of claims 1 to 3,
A press metal separator for a fuel cell, wherein the flatness in a temperature zone during power generation of the fuel cell is higher than the flatness in a temperature zone other than the temperature zone.

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