JP2008146987A - Manufacturing method for fuel-cell sealing structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrict impregnation of a rubber material for gasket molding into the peripheral edge part 22 of each porous body 20, constituting both-side parts in the thickness direction of a power generation body 1, to a proper region in manufacturing of a fuel-cell sealing structure in which a gasket is integrally provided along the peripheral edge part of the power generation body 1 while being joined to the end face 1a of the power generation body. <P>SOLUTION: Each rubber-coating part 2, extending from the end face 1a of the power generation body 1 with a prescribed interval, is molded to each porous body 20 constituting both-side parts in the thickness direction of the power generation body 1. The power generation body 1 is set in a die 4. Each part located below the rubber-coating part 2 in each porous body 20 is pressed with the die inner face via the rubber-coating part 2 so as to clamp it in a properly compressed state. A low viscosity or liquid molding rubber material is filled into a cavity 43 defined between the end face 1a and the die inner face while it is partially impregnated into the peripheral edge part 22 of each porous body 20 so as to be crosslinked and cured. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention includes a gasket for sealing a flow path formed between fuel cells of a fuel cell stack, and a gasket integrated part in which GDLs on both sides in the thickness direction of the power generator of the fuel cell are integrated. It relates to a method of manufacturing.

  A fuel cell has GDL (Gas Diffusion Layer) on both sides in the thickness direction of MEA (Membrane Electrode Assembly) having a pair of electrode layers on both sides of an electrolyte membrane (ion exchange membrane). A stack in which a power generation body made of MEA in which a porous gas diffusion electrode layer is disposed on both surfaces of the power generation body disposed on the electrolyte membrane is sandwiched between separators to form a fuel cell, and a number of these fuel cells are stacked. It has a structure. Then, the oxidizing gas (air) is supplied from the oxidizing gas flow path formed on one surface of each separator to the cathode side of the power generator via one GDL, and the fuel gas (hydrogen) is supplied to each separator. The fuel gas flow path formed on the other surface is supplied to the anode side of the power generator through the other gas diffusion layer, and the electrochemical reaction, which is the reverse reaction of water electrolysis, that is, water from hydrogen and oxygen is removed. Electric power is generated by the reaction to be generated.

  For this reason, each fuel battery cell is integrally provided with a gasket for sealing a fuel gas, an oxidant gas, water generated by the above-described electrochemical reaction, surplus air, etc., for example, in the fuel cell. A fuel cell seal structure as a cell seal is formed. 6 and 7 are cross-sectional views showing an example of a conventional fuel cell seal structure.

  6 and 7, reference numeral 100 is a power generator composed of an electrolyte membrane 111 and an MEA 110 composed of a pair of electrode layers 112 and 112 provided on both sides thereof, and GDLs 120 and 120 provided on both sides thereof. The power generator 100 is integrally formed with a gasket 200 made of a rubber-like elastic material.

In the fuel cell seal structure shown in FIG. 6, the molding rubber material is shaped through the through-hole formed in the power generator 100, whereby the gaskets 200 and 200 each having the seal lip 201 are formed on the power generator 100. It is formed into a shape in which both sides in the thickness direction are connected to each other via a portion 202 in which the molding rubber material is cured in the through hole. Further, at the time of molding, a part of the molding rubber material having low viscosity or liquid is impregnated into GDL 120, 120 made of a porous body such as carbon fiber, whereby gaskets 200, 200 are provided on GDL 120, 120. The rubber-impregnated portions 121 and 121 are formed continuously so that there is no permeation leakage from the GDLs 120 and 120 (see, for example, the following patent document).
JP 2003-7328 A WO2002-43172

  However, in the structure shown in FIG. 6, the compressive load acting on the gaskets 200, 200 by the separators 300, 300 on both sides in the assembled state as a stack also acts on the GDLs 120, 120. Excessive load may be applied.

  Therefore, in the fuel cell seal structure shown in FIG. 7, the end face 100 a facing the planar extension direction of the power generator 100 is arranged so that the compressive load of the gasket 200 does not act on the GDLs 120 and 120. Are formed into a shape having a base 203 extending endlessly along the two sides and seal lips 201, 201 formed on both sides thereof. When the gasket 200 is molded using a low viscosity or liquid molding rubber material, a part of the molding rubber material is impregnated in the peripheral portion of the GDL 120 or 120 made of a porous body such as carbon fiber. Rubber impregnated portions 121, 121 are formed, and the gasket 200 is firmly joined to the GDLs 120, 120 via the rubber impregnated portions 121, 121, and there is no permeation leakage from the GDLs 120, 120.

  However, since the porosity of the GDL 120 made of a porous material such as carbon fiber varies, the structure shown in FIG. 7 has a gasket 200 with a mold using a low-viscosity or liquid molding rubber material. When molding, it is difficult to appropriately limit impregnation of the molding rubber material into the peripheral portion of the GDLs 120 and 120. For this reason, even if the filling pressure and viscosity of the molding rubber material are constant, the width W of the rubber-impregnated portions 121 and 121 becomes larger than necessary depending on the porosity and the like of the GDLs 120 and 120. There was a risk that the power generation area would be narrowed.

  The present invention has been made in view of the above points, and the technical problem is that the gasket is integrally formed in a state of being joined to the end face along the peripheral edge of the power generator. In the production of the provided fuel cell seal structure, the impregnation of the rubber material for molding a gasket into the peripheral portion of the porous body constituting both side portions in the thickness direction of the power generator is appropriately limited.

  As a means for effectively solving the technical problem described above, the method for manufacturing a fuel cell seal structure according to the present invention includes a gasket along the end face of the fuel cell generator facing the planar extension direction. In the production of the fuel cell seal structure provided integrally, the step of forming a rubber coating portion extending from the end face at a predetermined interval on the porous body constituting both side portions in the thickness direction of the power generator; A power generator is set in a mold, and a portion of the porous body located in a lower layer of the rubber coating portion is pressed by the inner surface of the mold through the rubber coating portion to be appropriately compressed. A mold clamping step, and a cavity defined between the end surface and the inner surface of the mold is filled with a low-viscosity or liquid molding rubber material, and a part of the cavity is formed on the periphery of the porous body. Immersed allowed, in which and a step of crosslinking and curing.

  Here, the power generation body means a power generation body in which a GDL made of a porous body is arranged on both sides in the thickness direction of the MEA provided with a pair of electrode layers on both sides of the electrolyte membrane, or a porous body on both sides of the electrolyte membrane. The power generator in which the gas diffusion electrode layer made of is disposed is generically named.

  In the method of the present invention, the molding rubber material filled in the cavity defined between the end face of the power generator and the inner surface of the mold becomes a gasket extending along the end face of the power generator by cross-linking curing. Yes, part of rubber material for molding is cross-linked and hardened while impregnated in the peripheral part of the porous body (for example, GDL or gas diffusion electrode layer) constituting both sides in the thickness direction of the power generator Thus, a fuel cell seal structure having a structure in which the gasket is firmly joined to the power generator via the rubber-impregnated portion is obtained.

  In the mold clamping process, when the power generator with the rubber coating portion provided on the porous body is set in the mold and the mold is clamped, the porous body is located at the lower layer of the rubber coating portion. Compressed by receiving a larger clamping pressure, the porosity is reduced. For this reason, when the cavity defined between the end face of the power generator and the inner surface of the mold is filled with a low-viscosity or liquid molding rubber material and a part thereof is impregnated into the peripheral edge of the porous body. The impregnation of the rubber material for molding into the porous body is effectively cut off at the compression part by the rubber coating part, and the rubber material for molding from the contact surface between the porous body and the inner surface of the mold also has a rubber coating. It is dammed by the intimate contact between the part and the inner surface of the mold.

  In the method for manufacturing a fuel cell seal structure according to the present invention, more preferably, the compressibility of the porous body compressed by the rubber coating portion pressed against the inner surface of the mold during clamping is 20 to 50%. The height of the rubber coating portion is set. This is because if the compressibility of the porous body is less than 20%, the limiting effect on the impregnation of the molding rubber material is not sufficient, and if it exceeds 50%, an excessive load is applied to the porous body such as GDL.

  According to the method for manufacturing a fuel cell seal structure according to the present invention, it is possible to obtain a fuel cell seal structure in which a gasket is firmly joined to a power generator via a rubber-impregnated portion. And, since the impregnation of the molding rubber material into the porous body in the gasket molding process is effectively limited at the compression portion of the porous body by the rubber coating portion, the rubber impregnation portion can be limited to a certain width. Therefore, it is possible to effectively prevent the power generation area of the MEA from being narrowed. In addition, rubber material for molding that tries to leak from the contact surface between the porous body and the inner surface of the mold to the power generation area side is also dammed by the rubber coating part, effectively preventing the occurrence of rubber burrs on the power generation area side. can do. Therefore, it is possible to improve the robustness by reducing the uncertainties necessary for various controls in the manufacturing process.

  Hereinafter, a preferred embodiment of a method for producing a fuel cell seal structure according to the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing a process of forming a rubber coating portion on GDL in a method for manufacturing a fuel cell seal structure according to the present invention, FIG. 2 is an explanatory view showing a mold clamping process, and FIG. It is explanatory drawing which shows the sealing structure for fuel cells manufactured by invention.

  In FIG. 1, reference numeral 1 denotes a power generator that constitutes a cell of a fuel cell, in which GDLs 20 are arranged on both sides in the thickness direction of an MEA 10 in which a pair of electrode layers 12 are provided on both surfaces of an electrolyte membrane 11. In the GDL 20, first, the rubber coating portion 2 extending at a predetermined interval L from the end face 1a facing the plane extending direction of the power generation body 1 is formed at a required height h. The distance L from the end surface 1a to the rubber coating portion 2 is appropriately determined in consideration of the width of a rubber-impregnated layer (described later) to be formed on the GDL 20. The GDL 20 corresponds to the “porous body” recited in claim 1, that is, is made of a porous body such as carbon fiber.

  The rubber coating part 2 uses a low-viscosity or liquid molding rubber material (including rubber ink in which an unvulcanized rubber compound is dispersed in an organic solvent), silk screen printing method, dispenser method, compression molding method, or injection. It can be formed by a forming method. Usable molding rubber materials include liquid EPDM, liquid fluororubber, liquid silicone rubber, liquid acrylic rubber, and the like, and are not particularly limited as long as they do not generate elution gas that adversely affects the power generation function in MEA10. However, the same material as the rubber material for molding the gasket 3 to be described later is preferable, and a flexible material having a rubber hardness after crosslinking and curing of Hs20 to 70, preferably Hs20 to 40 is preferable.

  The rubber coating portion 2 is firmly bonded to the GDL 20 because the rubber coating portion 2 is cured in a state where a part of the rubber material for molding is impregnated in the surface layer portion of the GDL 20 at the time of molding.

  The power generator 1 in which the rubber coating portion 2 is molded is set in a mold 4 as shown in FIG. That is, the mold 4 is composed of an upper mold 41 and a lower mold 42 that are brought into contact with and separated from each other, and the peripheral portion of the power generator 1 can be clamped together with the rubber coating portion 2 by mold clamping on the inner surfaces facing each other. Cavity 43 is defined between the inner surface extending toward the outer periphery and the end surface 1a of the power generator 1.

  In the upper die 41, a gate 44 for filling the cavity 43 with liquid rubber is opened toward the clamping surface 41a. The inner end opening of the gate 44 is located on the cavity 43 side of the clamping surface 41a of the upper die 41 with respect to the close contact position with the rubber coating portion 2 of the power generator 1.

  The cavity 43 is a space for molding the gasket 3 shown in FIG. 3, that is, a base molding portion 431 having a shape corresponding to the base portion 33 of the gasket 3 and a shape corresponding to the seal lips 32 and 33 of the gasket 3. It consists of seal lip forming parts 432 and 433. Further, the facing distance between the clamping surfaces 41a and 42a in the mold clamping state shown in FIG. 2 is substantially equal to the thickness t (see FIG. 1) of the power generator 1.

  For this reason, when the mold 4 is clamped as shown in FIG. 2, the rubber coating portion 2 protruding from the surface of the GDL 20 is pressed by the clamping surfaces 41 a and 42 a of the upper mold 41 and the lower mold 42, and the GDL 20 The part located in the lower layer of the rubber coating part 2 is compressed through this rubber coating part 2 (compression part 21).

  Here, the higher the height h (see FIG. 1) of the rubber coating portion 2 is, the higher the compression rate of the compression portion 21 in the GDL 20 is. Preferably, the rubber is adjusted so that the compression rate is 20 to 50%. The height h of the coating part 2 is set.

  Next, in the clamped state shown in FIG. 2, a low-viscosity or liquid molding rubber material (including rubber ink in which an unvulcanized rubber compound is dispersed in an organic solvent) is fed from a molding machine (not shown) through a gate 44. The cavity 43 is filled. Usable molding rubber materials include liquid EPDM, liquid fluororubber, liquid silicone rubber, liquid acrylic rubber, and the like, as with the rubber coating portion 2 material. If it does not generate | occur | produce, it will not specifically limit.

  Since the GDL 20 that is a porous body has innumerable continuous pores, a low-viscosity or liquid molding rubber material that is injected from the gate 44 at a required pressure is a compression portion formed by the rubber coating portion 2 of the GDL 20. The cavity 43 is filled through the outer peripheral side (peripheral portion 22) of 21. For this reason, the peripheral portion 22 of the GDL 20 is impregnated with the molding rubber material.

  Further, a part of the low-viscosity or liquid molding rubber material injected from the gate 44 toward the peripheral edge portion 22 of the GDL 20 tries to penetrate into the side opposite to the cavity 43, which is the rubber coating portion 2. Since the porosity is reduced by compression and the gap between the pores is reduced by the compression, the flow resistance is large and cannot easily penetrate. For this reason, impregnation of the molding rubber material into the GDL 20 is limited to the outer peripheral side region (peripheral portion 22) of the compression portion 21.

  When the molding rubber material filled in the mold 4 is cross-linked and cured, the upper mold 41 and the lower mold 42 are separated from each other to open the mold, and the product (fuel cell seal structure) is taken out. As shown in FIG. 3, the fuel cell seal structure includes a power generator 1 in which GDLs 20 and 20 are provided on both sides of an MEA 10 composed of an electrolyte membrane 11 and electrode layers 12 and 12 on both sides thereof, and a planar extension thereof. And a gasket 3 made of a rubber-like elastic material integrally formed along the end face 1a facing in the direction.

  Specifically, the gasket 3 has a shape having a base 31 extending endlessly along the end surface 1a facing the planar extension direction of the power generator 1, and seal lips 32, 33 projecting from both sides in the thickness direction. 2 is a portion formed in the cavity 43 of FIG. The base 31 of the gasket 3 is firmly joined to the GDL 20 and 20 via the rubber-impregnated portions 23 and 23 obtained by curing the molding rubber material impregnated in the peripheral portions 22 and 22 of the GDL 20 and 20 in the molding process described above. Has been.

  The portions on the opposite side (inner peripheral side) from the gasket 3 when viewed from the rubber-impregnated portions 23 and 23 are compression portions 21 and 21. Here, the rubber content in the GDL 20 is drastically reduced. Impregnation is blocked. Further, rubber coating portions 2 are present on the surface sides of the compression portions 21 and 21, respectively.

  In the fuel cell seal structure of FIG. 3 having the above-described configuration, the seal lips 32 and 33 of the gasket 3 are appropriately compressed by the separators 5 on both sides indicated by the one-dot chain line in the drawing in the assembled state as the fuel cell stack. In close contact with each other, a sealing function against fuel gas, oxidizing gas, etc. is achieved. And since this gasket 3 is provided so that the outer periphery may be extended along the end surface 1a which faced the planar extension direction of the electric power generation body 1, the reaction force by compression becomes an excessive load to GDL20 and 20 directly. There is no such thing as working.

  Further, the peripheral edge portion 22 of the porous GDL 20, 20 has a structure in which continuous pores do not exist due to the rubber-impregnated portions 23, 23, and the outer peripheral side thereof is surrounded by the gasket 3, so that the gas to be sealed Etc. can prevent the inside of the GDL 20 and 20 from moving in the plane extension direction and leaking out to the outside.

  Here, FIG. 4 is explanatory drawing which shows the manufacturing method of the sealing structure for fuel cells as a comparative example. That is, as shown in FIG. 4, the rubber material for molding is also formed on the GDL 20 by projecting the throttle portions 41 b and 42 b on the inner surface of the mold (the holding surfaces 41 a and 42 a of the upper mold 41 and the lower mold 42). It is possible to form the compression part 21 for restricting the impregnation of the resin. Therefore, also with this method, the impregnation of the rubber material for molding into the GDL 20 (rubber impregnated portion 23) can be limited to the peripheral portion 22.

  However, the clamping force for the GDL 20 is low, and there are innumerable fine continuous gaps due to the pores of the GDL 20 between the inner surface of the mold and the contact surface of the GDL 20. Moreover, the pressure of the molding rubber material injected from the gate 44 increases due to a decrease in porosity due to the water repellent treatment of the GDL 20. Therefore, according to the method of the comparative example shown in FIG. 4, a part of the molding rubber material is formed between the contact surfaces of the throttle portions 41 b and 42 b on the inner surface of the mold and the compression portion 21 of the GDL 20 by the continuous gap. The rubber burr 34 is liable to be generated by passing through the surface portion of the region inside the compression portion 21 (power generation region). In order to prevent the occurrence of such rubber burrs 34, it is difficult to appropriately select and control the properties (porosity, etc.) of the GDL 20, the fluidity of the molding rubber material, and the molding pressure.

  Moreover, since the compression rate of the GDL 20 varies, there is a possibility that the difference in compression rate becomes large at the boundary between the compression unit 21 by the throttle unit 41b and the other part, and the boundary part may be damaged.

  On the other hand, according to the method of the present invention, in the mold clamping state shown in FIG. 2, the rubber coating portions 2, 2 are applied to the holding surfaces 41 a, 42 a of the upper mold 41 and the lower mold 42 with their own elasticity or GDL 20. Therefore, the low-viscosity or liquid molding rubber material flowing from the gate 44 to the peripheral portion 22 of the GDL 20 is connected to the rubber coating portions 2 and 2. It is dammed by the contact surface with the clamping surfaces 41a and 42a and does not leak to the inner peripheral side. Moreover, since the rubber coating part 2 and the compression part 21 are mutually joined, a leak path | route is not formed between both.

  Therefore, when the gasket 3 is molded with the mold 4 using a low-viscosity or liquid molding rubber material, the impregnation region of the molding rubber material on the peripheral portions 22 and 22 of the GDLs 20 and 20 is reliably controlled. For this reason, it is possible to effectively prevent the width of the rubber-impregnated portions 23 and 23 from becoming unnecessarily large due to variations in the porosity of the GDL 20 and 20 made of a porous material such as carbon fiber. A predetermined power generation area in the MEA 10 can be secured. Moreover, since the molding rubber material that leaks to the power generation region side along the contact surface between the power generation body 1 and the inner surface of the mold is also dammed by the rubber coating portion 2, the power generation region as shown in FIG. It is possible to prevent the rubber burr 34 from being generated or damaged.

  In the embodiment shown in FIGS. 1 to 3 described above, the power generator 1 has the GDL 20 made of a porous material disposed on both sides in the thickness direction of the MEA 10 in which the electrode layers 12 and 12 are provided on both surfaces of the electrolyte membrane 11. However, the present invention can also be implemented when the power generator 1 is made of MEA. FIG. 5 is an explanatory view showing another embodiment of the method for manufacturing a fuel cell seal structure according to the present invention as an example.

  That is, in FIG. 5, the power generation body 1 includes a gas diffusion electrode layer 13 that carries an electrode catalyst on at least an electrolyte membrane contact surface of a porous body made of carbon fiber or the like used for GDL or the like on both surfaces of an electrolyte membrane 11. , 13 are provided in a stacked state. Also in this case, the fuel cell seal structure can be manufactured basically by the same steps as those described above.

  Specifically, first, the rubber coating portion 2 extending at a predetermined interval L from the end surface 1a facing the planar extension direction of the power generator 1 is formed on the gas diffusion electrode layer 13 at a required height. Next, the power generator 1 is set in a mold, clamped, and a low-viscosity or liquid molding rubber material is filled in a cavity defined between the end face 1a and the inner surface of the mold. At the same time, a part of the gas diffusion electrode layer 13 is impregnated into the peripheral edge of the gas diffusion electrode layer 13 and cured by crosslinking.

  As shown in FIG. 5, the fuel cell seal structure manufactured by this method includes a power generation body (MEA) 1 including an electrolyte membrane 11 and gas diffusion electrode layers 13 and 13 on both sides thereof, and a planar extension direction thereof. And a gasket 3 made of a rubber-like elastic material integrally formed along the end surface 1a facing the gas. The gasket 3 has a base 31 formed in the above-described forming process in the gas diffusion electrode layer 13. , 13 are firmly joined to the gas diffusion electrode layers 13, 13 through rubber-impregnated portions 13b, 13b formed by curing the molding rubber material impregnated in the peripheral portion.

  And according to this embodiment, the part located in the lower layer of the rubber coating part 2 among the gas diffusion electrode layers 13 of the power generator 1 set in the mold in the mold clamping step is more than the other parts. Since the porosity is reduced by receiving a large clamping pressure, the peripheral portion of the gas diffusion electrode layer 13 is impregnated with a low-viscosity or liquid molding rubber material in the compression portion 13a by the rubber coating portion 2. Effectively cut off. For this reason, the rubber-impregnated portion 13b can be limited to a certain width, and the power generation region can be effectively prevented from being narrowed.

  In addition, leakage of the molding rubber material from between the contact surfaces of the gas diffusion electrode layer 13 and the inner surface of the mold is blocked by the close contact portion between the rubber coating portion 2 and the inner surface of the mold. Rubber burr is not generated on the region side.

It is explanatory drawing which shows the process of shape | molding a rubber coating part in GDL in the manufacturing method of the sealing structure for fuel cells which concerns on this invention. It is explanatory drawing which shows the clamping process in the manufacturing method of the sealing structure for fuel cells which concerns on this invention. It is explanatory drawing which shows the sealing structure for fuel cells manufactured by this invention. It is explanatory drawing which shows the comparative example of the manufacturing method of the sealing structure for fuel cells. It is explanatory drawing which shows the other form in the manufacturing method of the sealing structure for fuel cells which concerns on this invention. It is sectional drawing which shows an example of the conventional sealing structure for fuel cells. It is sectional drawing which shows an example of the conventional sealing structure for fuel cells.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power generation body 1a End surface 10 MEA
11 Electrolyte membrane 12 Electrode layer 13 Gas diffusion electrode layer (porous body)
20 GDL (porous material)
21 Compression part 22 Peripheral part 23 Rubber impregnation part 2 Rubber coating part 3 Gasket 4 Mold 41 Upper mold 42 Lower mold 41a, 42a Clamping surface 43 Cavity 44 Gate

Claims (2)

In the production of a fuel cell seal structure in which a gasket (3) is integrally provided along an end surface (1a) facing the planar extension direction of a power generator (1) of a fuel cell,
Forming a rubber coating portion (2) extending from the end face (1a) at a predetermined interval on the porous bodies (20, 13) constituting both sides in the thickness direction of the power generation body (1);
The power generation body (1) is set in a mold (4), and a portion of the porous body (20, 13) located below the rubber coating portion (2) is defined as the rubber coating portion (2). A mold clamping step that is appropriately compressed by pressing on the inner surface of the mold via
A cavity (43) defined between the end face (1a) and the inner surface of the mold is filled with a low-viscosity or liquid molding rubber material, and a part of the cavity (43) is filled with the porous body (20, 13). A step of impregnating the peripheral edge of the resin and crosslinking and curing;
The manufacturing method of the sealing structure for fuel cells characterized by the above-mentioned.   The height of the rubber coating portion (2) is set so that the compressibility of the porous body (20, 13) compressed by the rubber coating portion (2) pressed against the inner surface of the mold during clamping is 20 to 50%. The method for manufacturing a fuel cell seal structure according to claim 1, wherein length (h) is set.

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