JP2006228533A - Molding method of separator for fuel cell and separator shape correcting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding method of a separator for a fuel cell preventing warping of the separator and enhancing sealing capability without having recessed and projecting part in the periphery of a passage. <P>SOLUTION: Two separators 15, 15 in which each passage comprising a recessed line part 16 and a projecting line part 17 is formed in a region contributing to power generation by press work of a metal plate are superimposed, and superimposed two separators 15, 15 are pressed from the superimposed direction to bond them by plastic-deforming a part of at least the separator 15. By plastic-deforming a part of the separator 15 by pressing, the warping generated in press work can be suppressed, the contact parts of the separators 15, 15 are bonded with no gap, and the conductivity between the separators 15, 15 can be increased. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for forming a separator for a fuel cell and a separator shape correcting device, and more particularly to a technique for correcting a warp of a separator that occurs when a metal plate is pressed to form a flow path.

  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. The separator forms a fuel gas flow path, an oxidant gas flow path, and a refrigerant flow path through which the fuel gas, the oxidant gas, and the refrigerant circulate, respectively, by stacking the two sheet metal separators.

  However, when the uneven channel is formed in the central part of the metal plate by press processing, the uneven height of the uneven part is caused by the difference in local elongation (residual stress) between the front and back of the separator or the occurrence of springback. Variation or warpage of the entire separator.

  When such unevenness in the unevenness of the uneven part or warpage occurs in the separator as a whole, gaps are generated between the contact parts of the separators or between the separator and the membrane electrode assembly (MEA), and the contact resistance is reduced. The increase in conductivity deteriorates the power generation performance.

Therefore, after press forming a gas flow path having a concavo-convex shape on a metal plate, a flat portion formed around the gas flow path of the concavo-convex portion is elongated in a direction perpendicular to the longitudinal direction of the concavo-convex portion or A technique for preventing warpage of the separator by forming a strip-shaped concave portion or convex portion is disclosed (for example, see Patent Document 1).
JP 2003-338295 A (pages 3 to 5 and FIGS. 3 to 5)

  However, in the technique described in Patent Document 1, since the concave portion and the convex portion for preventing warpage are present in the peripheral portion surrounding the gas flow path, the seal member provided around the gas flow path is provided with these concave or convex portions. It is conceivable that they do not adhere to each other.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for forming a separator for a fuel cell and a separator shape correcting device having a separator with no irregularities around the flow path and having a high sealing property, while preventing the separator from warping.

  The method for forming a separator for a fuel cell according to the present invention includes a separator stacking step of stacking two separators each having a concavo-convex shape formed in a region contributing to power generation by pressing a metal plate, A pressurizing step of pressurizing the two stacked separators from the stacking direction and plastically deforming at least a part of the separators to bring them into close contact with each other.

  Further, the separator shape correcting device according to the present invention is a separator that presses a separator made of two metal plates each having a flow path having a concavo-convex shape from the overlapping direction, and plastically deforms at least a part of the separator so as to adhere to the separator. A shape correction apparatus, comprising: an upper mold having a molding die for pressing one separator; and a lower mold having a molding die for pressing the other separator.

  According to the method for molding a separator for a fuel cell of the present invention, two separators having unevenness in height and warpage generated during pressing are overlapped, and the overlapped separator is pressed from the overlapping direction. Since at least a part of the separator is plastically deformed and brought into close contact, there is no gap in the overlapping portion between the separators, and the contact resistance between them can be reduced and the conductivity can be increased. Further, according to the method of the present invention, by pressing the two stacked separators in the overlapping direction, a part of the separator is plastically deformed by the applied pressure, thereby reducing the warpage.

  In addition, according to the separator shape correcting device of the present invention, the upper and lower molds having a molding die for pressing the separator, the two separators having unevenness in height and warpage of the uneven shape generated during press processing. Since a part of the separator is plastically deformed and the separators are in close contact with each other without any gap, the contact resistance between them is reduced and the conductivity is reduced. Can be increased.

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

  First, the overall configuration of the fuel cell stack will be briefly described. FIG. 1 is a perspective view showing the overall configuration of the fuel cell stack, and FIG. 2 is an enlarged cross-sectional view of a main part showing a part of the laminated structure of the fuel cell stack.

"Configuration of fuel cell stack"
As shown in FIG. 1, the fuel cell stack 1 is a laminated body 3 in which a predetermined number of fuel cell single cells 2 as unit cells that generate an electromotive force by the reaction of fuel gas and oxidant gas are laminated. Current collector plate 4, insulating plate 5, and end plate 6 are arranged at both ends of 3, and a tie rod 7 is passed through a through-hole (not shown) penetrating through the laminated body 3. And a nut (not shown) are screwed together.

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

  The fuel gas is introduced from the fuel gas introduction port 8, flows through the fuel gas supply channel formed in the separator, and is discharged from the fuel gas discharge port 9. The oxidant gas is introduced from the oxidant gas introduction port 10, flows through the oxidant gas supply passage formed in the separator, and is discharged from the oxidant gas discharge port 11. The cooling water is introduced from the cooling water introduction port 12, flows through the cooling water supply passage formed in the separator, and is discharged from the cooling water discharge port 13.

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

  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 portion area in contact with the membrane electrode assembly 14). Alternating concavo-convex shapes (so-called corrugated shapes) are formed. In the present embodiment, a thin metal separator having a thickness of about 0.1 mm is used in order to further improve the power generation performance.

  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 item | line parts 17 and 17 with which separators 15 and 15 were joined forms the coolant 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. Further, the separator 15 is formed with a stacking hole (not shown) through which the tie rod 7 passes.

  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.

"Description of separator molding method and separator shape correction device"
Next, a method for forming the separator 15 will be described. When the metal gas plate 18, the oxidant gas channel 19, and the coolant channel 20 are formed in the active region contributing to power generation by pressing (press forming) the metal plate, as shown in FIG. Surface contact between the separators 15 and 15 (surface A in FIG. 3B) and contact portions between the separator 15 and the membrane electrode assembly 14 (region B in FIG. 3C) are in contact with each other. It may be a point contact instead. Alternatively, the height of the concave stripe portion 16 and the convex stripe portion 17 varies, and as shown in FIG. 4, a gap is formed in the overlapping portion between the separators 15, 15, or the separator 15 and the membrane electrode assembly 14 There may be gaps between them.

  In order to prevent this, in the present invention, the separator shape correcting device shown in FIG. 5 is used to eliminate the warp of the separator 15 and the variation in the heights of the concave stripe portion 16 and the convex stripe portion 17. The separator shape correcting device includes a lower die 31 set on a bolster bed 30 of a press machine and an upper die 33 set on a ram slide 32, and is overlapped between the lower die 31 and the upper die 33. The two separators 15, 15 are pressed with the lower mold 31 and the upper mold 33 to plastically process a part of the separator 15, thereby bringing the separators 15, 15 into close contact with each other.

  The lower die 31 includes a lower die set 34 fixed on the bolster bed 30, a lower die holder 35 fixed on the lower die set 34, and a lower die provided on the lower die holder 35. It consists of a die 36.

  The upper die 33 includes an upper die set 37 fixed to the ram slide 32, an upper die holder 38 fixed to the upper die set 37, and an upper die 39 provided on the upper die holder 38. Become.

  Note that the lower die 36 and the upper die 39 are divided (divided into three) in order to increase die dimensional accuracy. In the case of a single die, it is difficult to obtain a high processing dimensional accuracy. Therefore, by dividing the die, the processing dimensional accuracy of each die is made high.

  In order to eliminate the warpage of the two separators 15 and 15 using this separator shape correcting device, the two separators 15 and 15 are overlapped as shown in FIG. That is, the two separators 15 and 15 are overlapped so that the concave strips 16 and 16 are brought into contact with each other.

  Then, the two separated separators 15 and 15 are set on the lower die 31 of the separator shape correcting device, the upper die 33 is lowered, and the separators 15 and 15 are overlapped as shown in FIG. Pressurize from the direction. In the present embodiment, the pressing surfaces 36a and 39a of the lower die 36 and the upper die 39 are both flat surfaces.

  When a pressure is applied to the separators 15 and 15 with this separator shape correcting device, the inclined portions 15a connecting the concave strip portions 16 and the convex strip portions 17 are slightly plastically deformed, and the concave strip portions 16 and 16 are not spaced apart from each other. In addition to being in close contact, the contact portion between the ridge portion 17 and the membrane electrode assembly 14 is in close contact with no gap. The pressure applied to the separators 15 and 15 by the separator shape correcting device is set to a pressure that does not plastically deform the entire separator 15 but only a part of the separator 15 is plastically deformed.

  When the predetermined pressurizing force has been applied, the upper mold 33 is raised from the lower mold 31 and the separators 15 and 15 are removed from the mold. Since the pressurized separators 15 are pressed to such an extent that they are slightly plastically deformed from the overlapping direction in a state where they are overlapped with each other, they do not return to the state before being pressed, and each of the recesses 16 , 16 are in close contact with each other without a gap, and the membrane electrode assembly 14 and the separator 15 are also in close contact with each other when the fuel cell single cells 2 are stacked. Therefore, the contact portion between the separators 15 and 15 and the contact portion between the separator 15 and the membrane electrode assembly 14 are in surface contact, the contact resistance between them is reduced, and the conductivity is greatly improved.

  According to the method for molding a fuel cell separator of the present embodiment, the contact portions between the separators 15 and 15 that are warped by press working and the contact portions between the separator 15 and the membrane electrode assembly 14 are brought into close contact by surface contact. It is possible to improve the electric power generation performance of the fuel cell by increasing the conductivity between them.

  Further, according to the method for molding a separator for a fuel cell of the present embodiment, it is not necessary to form a warp preventing projection on the outer periphery of the active region where each flow path is formed. Adhesion can be achieved without a gap, and the sealing performance between the membrane electrode assembly 14 and the separator 15 can be enhanced.

  Further, according to the separator shape correction device of the present embodiment, since the lower separator 31 and the upper die 33 are simple devices that pressurize the two separators 15 and 15 from the overlapping direction, the warp of the separator 15 can be reduced at a low cost. Can be eliminated.

[Other embodiments]
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-described embodiment, the pressing surfaces 36a and 39a of the lower die 36 and the upper die 39 are flat surfaces. However, a molding die having an uneven portion corresponding to the uneven shape of the separator 15 may be used. .

  For example, as shown in FIG. 8 and FIG. 9, a lower die 36 and an upper die include a convex portion 40 that fits into the concave portion 16 formed in the separator 15 and a concave portion 41 that fits the convex portion 17. Formed on the pressing surfaces 36a and 39a of the die 39, respectively. As shown in FIG. 8, the protrusion 40 may be a protrusion that enters the middle of the concave portion 16 as shown in FIG. 8, or a protrusion that enters the entire concave portion 16 as shown in FIG. Also good.

  In this way, the lower mold 31 and the upper mold 33 are formed by forming the convex portions 40 and the concave portions 41 corresponding to the shapes of the concave strip portions 16 and the convex strip portions 17 formed by pressing the separator 15 on the pressing surfaces 36a and 39a. When the two stacked separators 15 and 15 are pressurized from the overlapping direction, the convex portions 40 and the concave portions 41 function as positioning guides, and the separator 15 can be accurately positioned during pressurization. At the same time, the shape of the separator 15 can be corrected by preventing the shape of the concave portion 16 and the convex portion 17 from collapsing. In particular, in FIG. 9, since the convex portion 40 fits perfectly into the concave strip portion 16 and the tip of the convex portion 40 is in contact with the contact portion of the separator 15, 15, the contact portion of the separator 15, 15 is It can be plastically deformed and completely adhered without any gaps. Thereby, if the lower mold | type 31 and the upper mold | type 33 of FIG. 9 are used, the electroconductivity between these separators 15 and 15 can be improved further.

  In addition, as shown in FIG. 10, a caulking forming portion 42 for forming a caulking portion that meshes with each other at a separator contact portion that is a portion where the two separators 15 and 15 are overlapped with each other is provided on the upper die 36 and the upper die 36. It may be formed on the mold die 39. The caulking forming portion 42 includes a protrusion 42a formed at the tip of the convex portion 40 of the upper die 39 and a concave portion 42b formed at the tip of the convex portion 40 of the lower die 36 that receives the protrusion 42a. It consists of.

  If the separators 15 and 15 that are overlapped by the separator shape correcting device in which the caulking forming portion 42 is formed are pressed, the contact portions of the separators 15 and 15 are engaged with each other to form caulking portions. The increase in the contact area between 15 further improves the conductivity between them. Further, the contact portions of the separators 15 and 15 are caulked, so that contact position shift due to deformation can be eliminated when the stacking load of the fuel cell single cell 2 is loaded.

  In FIG. 10, a single caulking portion is formed at the contact portion of the separators 15, 15, but a plurality of caulking portions may be formed at the contact portions of the separators 15, 15 as shown in FIG. 11. . In this way, the contact area between the separators 15 and 15 can be further increased as compared with the case where pressure is applied by the separator shape correcting device of FIG. 10, and further improvement in conductivity can be achieved.

  In addition, as shown in FIG. 12, you may make it form the protrusion part 43 of a scissors shape on the surface of the concave part 16 of the separator 15 after a press work by scratching or machining. At this time, the protrusions 43 and 43 are formed so that the positions of the protrusions 43 and 43 are shifted at equal intervals so that the protrusion 43 of one separator 15 and the bottom 43a of the other separator 15 face each other. Thereafter, the separators 15 and 15 are overlapped with each other and pressed by the separator shape correcting device shown in FIG. 5, so that the protrusions 43 and 43 of one and the other separators 15 and 15 are crushed and joined. You may do it. By carrying out like this, the protrusions 43 and 43 formed in the contact part of the separators 15 and 15 are crushed and entangled, the contact area between them increases, and the electroconductivity can be aimed at.

It is a perspective view which shows the whole structure of a fuel cell stack. It is a principal part expanded sectional view which shows a part of laminated structure of a fuel cell stack. It is a principal part expanded sectional view which shows a part of fuel cell stack of the conventional structure formed using the separator which only formed the flow path by press work. FIG. 5 is an enlarged cross-sectional view of a main part showing another example of a fuel cell stack having a conventional configuration formed by using a separator having a flow path formed by press working. It is a figure which shows an example of the separator shape correction apparatus of this Embodiment. It is a principal part expanded sectional view which shows the state which piled up the separators after press work. It is an important section expanded section of a separator shape straightening device which pressurizes with a lower die and an upper die which made the overlapped separator flat. It is a principal part expanded sectional view of the separator shape correction apparatus pressurized while correcting the shape of a separator with the shaping | molding die which has an uneven | corrugated | grooved part according to the uneven | corrugated shape of a separator. It is a principal part expanded sectional view of the separator shape correction apparatus which pressurizes, correcting the shape of a separator in the state which made the concave part and convex part formed in the separator fit completely. It is a principal part expanded sectional view of the separator shape correction apparatus which pressurizes a separator with the shaping | molding die which forms the crimping part which mutually meshes | engages in the part with which two separators are overlapped. It is a principal part expanded sectional view of the separator shape correction apparatus which pressurizes a separator with the shaping | molding die which forms a some crimping part in a separator contact part. It is a principal part expansion perspective view of the separator which formed the sacrificial-shaped protrusion part in the contact part of separators.

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)
31 ... Lower die 33 ... Upper die 36 ... Lower die 39 ... Upper die 40 ... Convex part (concave part)
41 ... concave portion (concave / convex portion)
42 ... caulking formation part

Claims (7)

A separator stacking step of stacking two separators each formed with a flow path having a concavo-convex shape in a region contributing to power generation by pressing a metal plate;
A method of forming a separator for a fuel cell, comprising: a pressurizing step of pressurizing the two stacked separators from the stacking direction and plastically deforming at least a part of the separators to bring them into close contact with each other. A method for forming a fuel cell separator according to claim 1,
A method for forming a separator for a fuel cell, comprising applying pressure while correcting the shape of the separator with a forming die having an uneven portion according to the uneven shape of the separator. A method for molding a fuel cell separator according to claim 1 or 2,
A method for forming a separator for a fuel cell, wherein a caulking portion that meshes with each other is formed in a portion where the two separators are overlapped. A separator shape correcting device that presses a separator made of two metal plates each having a concavo-convex shape and presses it in the overlapping direction to plastically deform at least a part of the separator, thereby closely contacting the separator.
A separator shape correction device comprising: an upper die having a molding die for pressing one separator; and a lower die having a molding die for pressing the other separator. The separator shape correction device according to claim 4,
A separator shape correction device, wherein the pressing surfaces of the upper die and the lower die are flat surfaces. The separator shape correction device according to claim 4,
The separator shape correction device, wherein the pressing surface of the upper die and the lower die is formed with an uneven portion that fits in accordance with the uneven shape of the separator. The separator shape correction device according to claim 4,
A separator shape correcting device, wherein a press forming surface of the upper die and the lower die is formed with a caulking forming portion where the separators are engaged with each other at a portion where the two separators are overlapped.

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