JP2007294136A - Separator for fuel cell and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator which prevents its deformation with high sealing performance. <P>SOLUTION: The manufacturing method includes a preforming step for forming a concavo-convex shaped flow path at a region contributing to the power generation by means of the press working of a metal plate, a finishing step for molding the flow path formed by the preforming step into the predetermined form, a trimming step for cutting off undesired portions of the metal plate which are generated in the finishing step, and a reforming step for forming a primary notch continuing along the longitudinal direction of the flow path simultaneously with the finishing step or the trimming step or after these steps. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a separator for a fuel cell and a method for manufacturing the same, and more particularly to a technique for correcting deformation (warping or undulation) of a separator that occurs when a flow path is formed by pressing a metal plate.

  For example, in a fuel cell in which hydrogen and oxygen are supplied to both sides of a polymer electrolyte membrane to generate electromotive force, a metal thin plate is pressed to form an uneven shape in order to further increase the electromotive force per unit volume. A so-called thin metal separator that forms a flow path has been developed (for example, see Patent Document 1).

Usually, a metal separator is formed by press molding using a press machine and a mold, and is manufactured through preliminary molding, finish molding, and trimming processes. Then, two metal separators obtained in this way are stacked so that the fuel gas, the oxidant gas, and the coolant (refrigerant) flow through the fuel gas channel, the oxidant gas channel, and the refrigerant channel, respectively. It is set as the separator formed.
JP 2002-367665 A

  However, since both the preforming and finishing steps of the press process are stretch forming in which the material is stretched and formed, the stretched material tends to return and deformation (warping and waviness) after press forming occurs.

  In particular, in a separator used in a fuel cell, since it has a regular flow path having an uneven shape, it is likely to bend greatly in a direction intersecting the flow path. When the separators thus deformed are overlapped and joined together, a gap may be formed at the joined portion, and gas or refrigerant may leak from the flow path.

  Then, an object of this invention is to provide the separator for fuel cells which can suppress the deformation | transformation of a separator, and can provide a separator with high sealing performance, and its manufacturing method.

  The fuel cell separator according to the present invention is a fuel cell separator in which a plurality of uneven channels are formed in a region that contributes to power generation by pressing a metal plate, and is continuous along at least the longitudinal direction of the channels. The 1st notch part which provides is characterized by the above-mentioned. Here, the part where the fuel gas, the oxidant gas and the refrigerant flow is defined as a flow path, and the opposite side of the part where the gas and the refrigerant flow is defined as the back surface of the flow path.

  The manufacturing method of a separator for a fuel cell according to the present invention includes a preforming step in which a metal plate is pressed to form an uneven channel in a region contributing to power generation, and a channel formed in the preforming step is predetermined. A finishing process for forming into a shape, a trimming process for cutting off unnecessary portions of the metal plate obtained in the finishing process, and a process continuous along the longitudinal direction of the flow path at the same time after or after the finishing process or the trimming process. And a shape correcting step for forming one notch.

  According to the fuel cell separator of the present invention, the first notch portion that is continuous along the longitudinal direction of the flow path is formed in the flow path portion. The formation of the notch cancels out the residual stress and suppresses the occurrence of warpage and undulation. Therefore, according to the present invention, it is possible to eliminate leakage of gas and refrigerant from the flow path by overlapping metal separators having no warpage or undulation.

  On the other hand, according to the method for manufacturing a separator for a fuel cell of the present invention, by forming the first notch continuous along the longitudinal direction of the flow path at the same time as the finishing step or the trimming step or after these steps, The residual stress of the tension remaining in the material during the press working is offset by forming the first notch, and the residual stress can be eliminated. Therefore, according to the method of the present invention, it is possible to obtain a fuel cell separator in which the occurrence of warpage and undulation is suppressed.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

"Overall structure of fuel cell stack"
First, the overall configuration of a fuel cell stack in which the fuel cell separator of the present invention is used will be briefly described. FIG. 1 is a perspective view showing the overall configuration of the fuel cell stack, FIG. 2 is an enlarged cross-sectional view of a single fuel cell, and FIG. 3 is an enlarged cross-sectional view of a main part of the single fuel cell.

  As shown in FIG. 1, a fuel cell stack 1 is a laminate in which a predetermined number of fuel cell single cells 2 as unit cells that generate an electromotive force by reaction of fuel gas (hydrogen gas) and oxidant gas (oxygen) are stacked. 3, the current collector plate 4, the insulating plate 5 and the end plate 6 are arranged at both ends of the laminate 3, the laminate 3 is fastened with a tie rod 7, and a nut 100 is screwed onto the end of the tie rod 7. It is composed of that.

  In this fuel cell stack 1, fuel gas introduction for allowing fuel gas, oxidant gas and refrigerant (cooling water) to flow through each flow path formed in a separator (not shown) of each fuel cell single cell 2. A port 8, a fuel gas outlet 9, an oxidant gas inlet 10, an oxidant gas outlet 11, a refrigerant inlet 12 and a refrigerant outlet 13 are formed in one end plate 6.

  In the fuel cell stack 1 having such a configuration, the fuel gas is introduced from the fuel gas inlet 8, flows through the fuel gas passage formed in the separator, and is discharged from the fuel gas outlet 9. The oxidant gas is introduced from the oxidant gas introduction port 10, flows through the oxidant gas flow path formed in the separator, and is discharged from the oxidant gas discharge port 11. The refrigerant is introduced from the refrigerant introduction port 12, flows through the refrigerant flow path formed in the separator, and is discharged from the refrigerant discharge port 13.

  As shown in FIG. 2, the fuel cell single cell 2 includes a membrane electrode assembly (MEA) 14 and fuel cell separators (hereinafter simply referred to as separators) disposed on both surfaces of the membrane electrode assembly 14, respectively. 15).

  The membrane electrode assembly 14 includes, for example, a solid polymer electrolyte membrane that is a polymer electrolyte membrane that passes hydrogen ions, an anode electrode that includes an anode catalyst and a gas diffusion layer, and a cathode electrode that includes a cathode catalyst and a gas diffusion layer (both are (Illustration is omitted). The membrane electrode assembly 14 has a laminated structure in which a solid polymer electrolyte membrane is sandwiched from both sides by an anode electrode and a cathode electrode.

  The separator 15 is made of, for example, a thin metal plate such as stainless steel, and the concave stripe portion 16 and the convex stripe portion 17 are formed by pressing in an active area contributing to power generation (a central area in contact with the membrane electrode assembly 14). Alternating concavo-convex shapes (so-called corrugated shapes) are formed.

  The recess 16 disposed in contact with the anode side of the membrane electrode assembly 14 forms a fuel gas flow path 18 through which fuel gas (hydrogen H) flows. On the other hand, the concave strip 16 disposed in contact with the cathode side of the membrane electrode assembly 14 forms an oxidant gas flow path 19 through which an oxidant gas (oxygen O) flows. . And the space part enclosed by the protruding strip parts 17 and 17 with which separators 15 and 15 were joined forms the refrigerant flow path 20 which distribute | circulates cooling water (LLC).

  The separator 15 communicates with the fuel gas inlet 8, fuel gas outlet 9, oxidant gas inlet 10, oxidant gas outlet 11, cooling water inlet 12, and cooling water outlet 13. The manifold (not shown) is formed. In particular, in this embodiment, in order to eliminate warpage and undulation of the separator 15, the concave and convex portions 16 and 17 having the concave and convex shapes are arranged in the longitudinal direction of the flow path (the surface of FIG. 3) as shown in FIG. The first notch portion 25 is formed along the direction perpendicular to the direction.

  The first notch 25 is formed as a groove having a substantially V-shaped cross section on the surface opposite to the side through which the fuel gas, oxidant gas or refrigerant flows, that is, on the back surface of the flow path. In this embodiment, the two first cutout portions 25 are formed in parallel to each other. Although not shown, a groove having a substantially V-shaped cross section is also used as the second notch in the direction intersecting the first notch 25 (the direction perpendicular to the gas and refrigerant flow direction). It is formed. When viewed from the whole, the concave strip portion 16 and the convex strip portion 17 are formed with a rhombus-shaped groove by the first cutout portion 25 and the second cutout portion.

  The fuel cell single cell 2 composed of the membrane electrode assembly 14 and the separator 15 configured as described above is stacked so that the membrane electrode assembly 14 is sandwiched between the pair of separators 15 and 15, and the membrane electrode assembly 14. The upper and lower separators 15 and 15 are coupled and integrated with each other through a first seal member 23 provided on the outer peripheral edge portion of the flat surface. The fuel cell single cell 2 is laminated in a plurality of layers by interposing the second seal member 24 at the outer peripheral edge portion to constitute the fuel cell stack 1.

"Manufacturing method of separator"
4A and 4B show a preforming process in the separator manufacturing process, FIG. 4A is a plan view of the separator in the process, FIG. 4B is an enlarged cross-sectional view of a main part of the flow path portion, and FIG. (A) is a plan view of a separator in the process, (B) is an enlarged cross-sectional view of a main part of the flow path portion, and FIG. 6 shows a trimming process in the separator manufacturing process. 7A and 7B show a mold used in the shape correction process, FIG. 7A is a perspective view of the mold, FIG. 7B is an enlarged view of a main part of a protrusion formed on the mold, and FIG. FIG. 9 is a diagram showing a state in which a tensile stress remains, FIG. 9 is a diagram showing a formation state of the first notch and the second notch, and FIG. 10 is a diagram showing stress remaining in the separator in the first notch and the second notch. The figure which shows the state canceled by the notch part, 11 is a diagram showing the relationship between the preforming height and distortion.

  In order to manufacture the separator 15 of the present embodiment, first, a preforming process is performed in which a metal plate is pressed to form a flow path having an uneven shape in the active region. In the preforming step, as shown in FIG. 4, a flow path having an uneven shape composed of the concave stripe portion 16 and the convex stripe portion 17 is gently formed in a metal plate 26 made of stainless steel.

  In this preforming step, the molding is performed with the molding height H1 sufficiently higher than the normal molding height (indicated by the dotted line in FIG. 4B). The molding height H1 at this time is such that the distortion is minimized when the circumference ratio (preliminary molding circumference / finish molding circumference), which is the ratio of the circumferences at the time of preliminary molding and finish molding, is around 100%. (Refer to FIG. 11) Preliminary molding is carried out at a preforming height H1 (0.8 mm) or more at that time.

  Next, the finishing process which shape | molds the flow path formed at the preforming process in a predetermined shape is performed. In the finishing process, since the molding height H1 is sufficiently increased in the preliminary molding process, the molding is not the tension molding but the compression molding while crushing the material as shown in FIG. For this reason, the residual stress of the tension remaining inside the workpiece is offset by the compression process, and the influence of distortion caused by the processed part trying to pull the unprocessed part is suppressed.

  Next, a trimming process for cutting off unnecessary portions of the metal plate 26 obtained in the finishing process is performed. In the trimming step, unnecessary portions (shaded portions in FIG. 6) of the metal plate 26 are cut off, and manifold holes 27 for supplying fuel gas, oxidant gas or refrigerant are formed in each flow path.

  Next, at the same time as the trimming step or after the trimming step, a first notch portion 25 that is continuous along the longitudinal direction of the flow path and a shape that forms the second notch portion in a direction intersecting the first notch portion 25. Perform the correction process. As shown in FIG. 7, the mold 27 used in the shape correction process intersects with the first protrusions 28 having two inverted V-shapes continuous in the direction along the flow path, and the first protrusions 28. And a second projecting portion 29 having an inverted V-shape that is continuous in the direction in which the second protrusion is formed. The first protrusions 28 are formed as many as the number of flow paths, and an appropriate number of second protrusions 29 are provided. The first protrusions 28 are formed with, for example, a protrusion height of 0.2 mm, a tip angle of 45 degrees, and a protrusion-to-projection pitch of 0.2 mm.

  After the trimming process, a tensile residual stress (indicated by an arrow in the figure) remains in the separator 15 as shown in FIG. 8 in the previous process. This is shown in FIG. The first notch portion 25 and the second notch portion 30 are formed in the separator 15 with the mold 27 in which the portion 28 and the second protrusion portion 29 are formed. If the first projecting portion 28 and the second projecting portion 29 are pressed against the workpiece to form a groove, a force acts in a direction to cancel the tensile residual stress, so that the separator 15 is deformed by warpage or undulation as shown in FIG. (Distortion) disappears. Thereby, the distortion that the processed part tries to pull the unprocessed part is eliminated.

  As described above, according to the present embodiment, after the trimming step, the first cutout portion 25 and the second cutout portion 30 that are continuous along the longitudinal direction of the flow path are formed, and thus the material is obtained by pressing these materials. The residual stress of the remaining tension is offset by forming the first cutout portion 25 and the second cutout portion 30, and the residual stress can be eliminated. Therefore, according to the method of the present invention, it is possible to obtain a fuel cell separator in which the occurrence of warpage and undulation is suppressed.

  In addition, according to the present embodiment, the tensile residual stress can be sufficiently canceled only by the first cutout portion 25, but in addition to the first cutout portion 25, the second cutout portion 30 is formed to form a rhombus. By adopting the shape, it is possible to further suppress the deformation of the separator.

  In addition, according to the present embodiment, unlike normal preliminary molding, since the molding height is sufficiently high and molding is performed after molding, this final molding is not tensile molding but compression molding. It is possible to eliminate the force of shrinking remaining inside the workpiece, and it is possible to eliminate the distortion of the separator.

  Further, according to the present embodiment, the first cutout portion 25 is formed on the surface of the flow path opposite to the side through which the fuel gas, the oxidant gas, or the cooling water flows (the back surface opposite to the surface through which the fluid flows). And since the 2nd notch part 30 is formed, fluid resistance is not applied to the gas and cooling water which flow through a flow path.

  Although specific embodiments to which the present invention is applied have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made.

  In the above embodiment, the shape correction process is performed after the trimming process. However, the shape correction process may be performed simultaneously with the trimming process, or the shape correction process may be performed simultaneously with the finishing process or after the finishing process. good.

It is a perspective view which shows the whole structure of a fuel cell stack. It is an expanded sectional view of a fuel cell single cell. It is a principal part expanded sectional view of a fuel cell single cell. A preforming process is shown among separator manufacturing processes, (A) is a top view of the separator in the process, (B) is a principal part expanded sectional view of the flow-path part. A finishing process is shown among separator manufacturing processes, (A) is a top view of the separator in the process, and (B) is an important section expanded sectional view of the channel part. It is a top view of the separator in the process which shows a trimming process among separator manufacturing processes. The metal mold | die used at a shape correction process is shown, (A) is the perspective view of the metal mold | die, (B) is the principal part enlarged view of the processus | protrusion formed in the metal mold | die. It is a figure which shows that the tensile stress remains in a workpiece | work. It is a figure which shows the formation state of a 1st notch part and a 2nd notch part. It is a figure which shows the state by which the stress which remain | survives in a separator was canceled by the 1st notch part and the 2nd notch part. It is a figure which shows the relationship between preforming height and distortion.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell stack 2 ... Fuel cell single cell 14 ... Membrane electrode assembly 15 ... Separator 16 ... Concave part (concavo-convex shape)
17 ... ridge (uneven shape)
18 ... Fuel gas flow path (flow path)
19 ... Oxidant gas channel (channel)
20: Refrigerant flow path (flow path)
25 ... 1st notch part 27 ... Metal mold | die used by a shape correction process 28 ... 1st projection part 29 ... 2nd projection part 30 ... 2nd notch part

Claims (6)

In the fuel cell separator in which a plurality of channels having irregularities are formed in a region that contributes to power generation by pressing a metal plate,
A fuel cell separator, comprising at least a first cutout portion continuous along a longitudinal direction of the flow path. The fuel cell separator according to claim 1,
A fuel cell separator, wherein a second notch is provided in a direction intersecting with the first notch. The fuel cell separator according to claim 1 or 2,
The fuel cell separator, wherein the first notch and the second notch are formed on the back surface of the flow path through which the fuel gas, the oxidant gas, or the cooling water flows. A preforming step of forming a flow path having a concavo-convex shape in a region contributing to power generation by pressing a metal plate;
A finishing step of forming the flow path formed in the preforming step into a predetermined shape;
A trimming process for cutting off unnecessary portions of the metal plate obtained in the finishing process;
A fuel cell separator characterized by comprising a shape correcting step for forming a first notch continuous along the longitudinal direction of the flow path at the same time after the finishing step or the trimming step or after these steps. Method. It is a manufacturing method of the separator for fuel cells according to claim 4,
In the shape correction step, a second notch is formed in a direction intersecting with the first notch. A method for manufacturing a fuel cell separator, wherein: A method for producing a fuel cell separator according to claim 4 or 5, wherein
In the finishing step, compression molding is performed by crushing and molding the metal plate. A method for producing a fuel cell separator.

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