JP2006185856A - Molding device and molding method of separator for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding device of a separator for a fuel cell capable of pressure-molding a separator with uniform density by molding the separator in uniform thickness. <P>SOLUTION: The molding device of the separator 10 for a fuel cell is provided with a molding mold 30 for pressure-molding a powdery molding material prepared by mixing graphite and thermosetting resin. Molding faces 31a, 32a are of convex shapes with a center protruded further toward a molding space side from a periphery part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell separator molding apparatus and molding method.

A single cell of a fuel cell has a separator that serves to extract electricity from an electrode. The separator is molded by pressure molding a powdery molding material obtained by mixing graphite and a thermosetting resin in a molding die (see Patent Document 1).
JP 2003-22814 A

  When a powdery molding material is pressure-molded with a molding die, the molding surface of the molding die may be distorted, and the thickness of the molded separator may not be uniform.

  In other words, hydrogen, oxygen, and cooling water channel grooves are formed in the separator, and the channel grooves have an uneven shape, so that they tend not to flow during pressure molding. Therefore, during pressure molding, the molding material located in the peripheral part flows to the outside and partly flows out as burrs, but the central part where the flow channel groove is located has a low fluidity, so it is locally Compressive stress increases.

  For this reason, the molding surface of the molding die is subjected to excessive stress at the central portion thereof, and the molding die is also less likely to release stress at the central portion than at the peripheral portion, so that the molding surface is distorted.

  For this reason, the thickness of the separator may not be uniform, and if it is not uniform beyond the specified dimensions, cracks may occur when multiple separators are stacked and pressed and stacked, or the sealing performance may be reduced. There is a possibility that it cannot be secured sufficiently, and there is a case where it must be discarded as a defective product in the inspection process.

  An object of the present invention is to provide a fuel cell separator molding apparatus and molding method capable of pressure-molding a separator that equalizes the thickness of the separator with high accuracy.

  In order to achieve the above object, the present invention has a molding die for pressure-molding a powdery molding material in which graphite and a resin are mixed, and the molding surface of the molding die is a central portion compared to the peripheral portion. Is a molding apparatus for a fuel cell separator having a convex shape protruding toward the molding space.

  In addition, a powdered molding material obtained by mixing graphite and resin is supplied to a molding die having a convex molding surface in which the central city protrudes toward the molding space as compared with the peripheral portion, and the molding die is This is a method for molding a fuel cell separator in which the convex shape of the molding surface is deformed so that the convex shape of the molding surface approaches the same surface as the peripheral portion by pressurizing when tightening and pressure molding.

  According to the present invention, since the molding surface of the molding die has a convex shape with the central portion protruding to the molding space side as compared with the peripheral portion, the powdery molding material in which graphite and resin are mixed is used. When supplying and clamping the mold and pressure forming, the convex shape of the molding surface is deformed so as to approach the same surface as the peripheral part by the applied pressure, so the thickness of the separator is uniformly molded, It becomes possible to press-mold a separator having a uniform density.

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

  FIG. 1 is a sectional view showing a molding die 30 of a fuel cell separator molding apparatus 20 according to an embodiment of the present invention. FIG. 2A is a sectional view showing a state in which a molding material 40 is put into the molding die 30. 2B is a cross-sectional view showing a state in which the separator 10 is pressure-molded by the molding die 30, and FIGS. 3A and 3B are separators 10 pressure-molded by the molding die 30 of the present embodiment. It is sectional drawing and a top view which show. 4A is a cross-sectional view showing a state in which the molding material 40 is put into the proportional mold 130, and FIG. 4B is a state in which the separator 110 is pressure-molded by the proportional mold 130. FIGS. 5A and 5B are a cross-sectional view and a plan view showing the separator 110 press-molded by the proportional mold 130, respectively.

  As is well known, a fuel cell is used in the form of a fuel cell stack in which a large number of single cells are stacked, for example, as a drive source for an automobile. A single cell is a battery that uses the reverse principle of electrolysis of water to obtain electricity in the process of obtaining water by reacting hydrogen and oxygen. For example, a unit cell of a solid polymer fuel cell includes a solid polymer electrolyte membrane as a cation exchange membrane, a pair of electrodes on which both sides of the solid polymer electrolyte membrane are formed and a catalyst layer is formed, And a pair of separators. The separator is provided with minute concavo-convex portions that form flow channel grooves for circulating fuel gas, air, cooling water, and the like.

  1 and 2, a molding apparatus 20 used for molding a fuel cell separator 10 press-molds a powdery molding material 40 in which graphite and a thermosetting resin are mixed. A mold 30 is provided. The thermosetting resin is, for example, a phenol resin or an epoxy resin. The resin contained in the molding material 40 preferably has a small diameter, thereby increasing the reaction rate and reducing the space between the graphite, thereby improving the strength of the separator 10 obtained. .

  The mold 30 has an upper mold 31 and a lower mold 32 that are relatively close to and away from each other. The molding material 40 filled in the cavity in the molding die 30 is pressure-molded by the upper die 31 and the lower die 32. Although not shown in the drawings, on the molding surface 31 a of the upper mold 31 and the molding surface 32 a of the lower mold 32, minute ridges and ridges for forming the concavo-convex parts forming the flow path grooves of the separator 10 are formed. ing. The molding die 30 has a mechanism for clamping the upper die 31 and the lower die 32, a pressure mechanism for pressurizing the molding material 40, and a separator 10 after molding is pushed out from the lower die 32 and taken out. A known mechanism or member such as an extraction rod is provided.

  At the time of pressure molding, the molding surfaces 31a and 32a of the mold 30 may be distorted, and the thickness of the molded separator may not be uniform.

  With reference to FIGS. 4 (A), 4 (B) and FIGS. 5 (A), (B) showing the proportionality, it is necessary to consider that distortion d occurs on the molding surfaces 131a, 132a of the molding die 130 during pressure molding. The thickness of the molded separator 110 is not uniform, and the separator 110 is formed with a thick portion 110a located at the center and a thin portion 110b located at the periphery. For this reason, the molded separator 110 has an appropriate portion 111a in which the molding material 40 is pressurized with an appropriate pressure, and an overpressure in which the molding material 40 is pressurized with an excess pressure beyond the appropriate pressure. Part 111b occurs. Here, the flow path groove 1 of hydrogen, oxygen (air), and cooling water is formed in the separator 110, and the flow path groove 1 has an uneven shape. It tends to be difficult to flow. Therefore, at the time of pressure molding, the molding material 40 located in the peripheral portion flows to the outside, and a part of the molding material 40 flows out from the joining surface of the upper and lower molding dies 130 as the burr 110c, but the flow channel 1 is located. Since the central portion has low fluidity, the compressive stress locally increases. Therefore, the molding surfaces 131a and 132a of the molding die 130 are subjected to excessive stress at the central portion thereof, and the molding die 130 is also less likely to release the stress at the central portion than the peripheral portion, so that the molding surface is distorted. It happens. For this reason, the thickness of the separator 110 may not be uniform, and if it becomes more than the specified dimension, it may be unavoidable to be discarded as a defective product.

  In addition, 2, 3, and 4 shown in FIG. 5 are manifolds through which hydrogen, cooling water, and oxygen (air) are conducted, respectively, and hydrogen, cooling water, and oxygen (air) are selectively used depending on the shape of the seal member outside the figure. It is made to conduct to the channel groove 1.

  Therefore, in the present embodiment, as shown in FIGS. 1 and 2, the molding surfaces 31 a and 32 a of the molding die 30 have a planar shape located on the outer peripheral side of the portion where the uneven channel groove 1 is formed. Compared to the peripheral portions 31b and 32b, the central portion n has a convex shape protruding toward the molding space.

  These convex shapes are obtained by a simulation which will be described later. As shown in FIG. 1, the convex shapes have curvatures so as to gently protrude from the peripheral portions 31b and 32b toward the central portion n toward the molding space side. As shown in FIG. 2, a long axis along the longitudinal direction of the circular molding surface, more specifically, a circular shape inscribed in the outer periphery of the flow channel groove 1 is formed at a portion where the flow channel groove 1 of the separator is formed. It has an elliptical shape.

  As a result, when the molding die is clamped and pressure-molded, the convex shape of the molding surface is deformed by the applied pressure so that it approaches the same surface as the peripheral portion, and the thickness of the separator is highly accurate as a whole. It becomes possible to make uniform.

  In addition, 32c shown in FIG. 1 is an outflow passage through which the molding material 40 flows out as burrs when the molding die 30 is clamped and pressure-molded, and further outside is a storage chamber 32d for storing burrs. Is formed. In particular, the burr outflow passage 32c and the storage chamber 32d are formed in a direction extending to the molding surface, so that the molding material is actively flowed out to make the pressure of the molding material more uniform. It is possible to mold the separator with higher accuracy.

  Therefore, in the present embodiment, as shown in FIGS. 1 and 2, the molding surfaces 31 a and 32 a of the mold 30 have deformation amounts predicted for the deformation of the molding surfaces 31 a and 32 a during pressure molding. It has a reflected shape. For example, when a result is obtained by simulation that the center part of the molding surfaces 31a and 32a is deformed so as to be recessed compared to the peripheral part during pressure molding (see the shape shown in FIG. 4B). The molding surfaces 31a and 32a are formed so as to reflect the simulation result and have a shape in which the central portion is convex compared to the peripheral portion. The predicted deformation amount is d (FIG. 4B), and the symbol L in FIG. 1 is the convex amount of the molding surface reflecting the predicted deformation amount d. The convex dimension L can be adopted as appropriate, but is, for example, in the range of 0.01 to 0.5 mm. The convex dimension L varies depending on the type of the molding material 40. For this reason, in predicting the amount of deformation for the deformation of the molding surfaces 31a and 32a during pressure molding, a simulation is performed with the type of the molding material 40 as one of the conditions.

  This simulation is performed by a well-known FEM analysis. The elastic modulus of the mold 30, the dimensions of the mold 30 including the molding surfaces 31 a and 32 a and the channel grooves, the pressure applied when the mold 30 is clamped, and the molding material The amount of deformation (especially the uneven portion of the channel groove) is input and calculated to determine whether the molding surface is distorted so as to recede from the molding surface, and the convex shape is designed so that the molding surface becomes flat by the applied pressure .

  In addition, since the central part of the molding material is more stressed than the peripheral part during pressure molding, depending on the applied pressure, there may be cases where the central part greatly springs back. Thus, the spring back amount may be obtained and reflected in the design of the convex shape.

  Separator molding apparatus 20 further includes known heating means and cooling means (both not shown).

  The heating means is used to heat the molding die 30 to increase the temperature of the molding material 40 and to thermoset the thermosetting resin contained in the molding material 40. The heating means is disposed inside the upper mold 31 and the lower mold 32 and has a heat medium passage through which a heat medium is introduced. The heat medium is not particularly limited, but high-temperature oil is preferable in consideration of cost and handleability. Since the heat medium has a large heat capacity and good heating performance, the molding material 40 can be rapidly heated to the thermosetting temperature of the resin contained in the molding material 40.

  The cooling means is used for lowering and taking out the temperature of the molded separator 10 by cooling the molding die 30 after completion of thermosetting. The cooling means is disposed inside the upper mold 31 and the lower mold 32 and has a refrigerant passage into which a refrigerant is introduced. The refrigerant is not particularly limited, but low temperature water is preferable in consideration of cost and handleability.

  Next, the operation will be described.

  As shown in FIG. 2 (A), the upper and lower molds 31 and 32 are opened, and a powdery molding material 40 in which graphite and a thermosetting resin are mixed is discharged from a nozzle (not shown) and is evenly distributed in the cavity of the lower mold 32. To supply. When the supply of the molding material 40 is continued and the required amount is reached, the discharge of the molding material 40 from the nozzle is stopped.

  Next, as shown in FIG. 2B, the upper and lower molds 31 and 32 are closed, and the separator 10 is pressure-molded from the molding material 40 by the upper and lower molds 31 and 32. In the present embodiment, considering that the molding surfaces 31a and 32a of the molding die 30 are distorted during pressure molding, the molding surfaces 31a and 32a are reflected by predicting the deformation amount during pressure molding, The central part has a convex shape as compared with the peripheral part (see FIGS. 1 and 2A). For this reason, at the time of pressure molding, the molding surfaces 31a and 32a become flat, and the separator 10 having a uniform thickness is pressure molded. Reference sign n in FIG. 2B indicates a range in which the molding surfaces 31a and 32a are deformed and become flat from the convex shape. As a result of the uniform thickness of the separator 10, the separator 10 having a uniform density can be pressure-molded.

  Thereafter, the heat medium is introduced into the heat medium passage and the mold 30 is heated, whereby the temperature of the molding material 40 is raised and the resin contained in the molding material 40 is thermoset. When the heating rate of the molding material 40 is slow, the resin in the middle of curing moves to the surface and corners and concentrates locally, thereby forming a resin-rich portion, resulting in poor graphite dispersion. In the present embodiment, since the molding material 40 is rapidly heated by the heat medium, formation of a resin-rich portion is prevented, and poor graphite dispersion is suppressed.

  The thermosetting is completed and the introduction of the heat medium into the heat medium passage is stopped, while the refrigerant is introduced into the refrigerant passage and the mold 30 is cooled. When the temperature of the separator 10 falls to, for example, room temperature, the upper and lower molds 31 and 32 are opened, and the separator 10 is taken out.

  As described above, according to the present embodiment, in consideration of the occurrence of distortion on the molding surfaces 31a and 32a of the molding die 30 during pressure molding, the deformation amounts of the molding surfaces 31a and 32a during pressure molding are predicted. Since the shape reflects this, the thickness of the separator 10 can be uniformly formed, and the separator 10 having a uniform density can be pressure-molded.

It is sectional drawing which shows the shaping | molding die of the shaping | molding apparatus of the separator for fuel cells which concerns on embodiment of this invention. FIG. 2A is a cross-sectional view showing a state in which a molding material is charged into a mold, and FIG. 2B is a cross-sectional view showing a state in which a separator is pressure-formed by the mold. FIGS. 3A and 3B are a cross-sectional view and a plan view showing a separator press-molded by the molding die of the present embodiment. FIG. 4A is a cross-sectional view showing a state in which a molding material is put into a proportional mold, and FIG. 4B is a cross-sectional view showing a state in which a separator is pressure-formed by a proportional mold. . 5A and 5B are a cross-sectional view and a plan view showing a separator press-molded by a proportional mold.

Explanation of symbols

10 separator,
20 Separator molding device,
30 Mold,
31 Upper mold,
31a molding surface,
31b peripheral part,
32 Lower mold,
32a molding surface,
32b peripheral part,
40 molding materials,
n Central part,
d The amount of deformation predicted for deformation of the molding surface during pressure molding,
L Projection amount of the molding surface reflecting the predicted deformation amount.

Claims (7)

It has a molding die that press-molds a powdery molding material in which graphite and resin are mixed
The molding surface of the said shaping | molding die is a shaping | molding apparatus of the separator for fuel cells in which the center part has the convex shape which protruded in the shaping | molding space side compared with the peripheral part.   2. The fuel cell separator molding apparatus according to claim 1, wherein the convex shape of the molding surface has a curvature so as to project gently toward the molding space from the peripheral part toward the central part.   3. The fuel cell separator molding apparatus according to claim 1, wherein the convex shape of the molding surface is formed at least at a portion where a flow path groove of the separator is formed. 4.   4. The apparatus for forming a separator for a fuel cell according to claim 3, wherein the convex shape of the molding surface is formed so as to surround a part of the separator that forms a flow channel groove with a circle.   5. The fuel cell separator according to claim 4, wherein the molding surface is rectangular as a whole, and the convex shape is an ellipse having a major axis along a longitudinal direction of the molding surface. Molding equipment. Supplying a powder-free molding material in which graphite and resin are mixed to a molding die having a convex molding surface whose central part protrudes toward the molding space compared to the peripheral part,
A method for molding a fuel cell separator, wherein when the molding die is clamped and pressure-molded, the convex shape of the molding surface is deformed so as to approach the same surface as a peripheral portion by pressure.   The convex shape of the molding surface is formed on the basis of a deformation amount predicted for deformation of the molding surface due to a pressing force when the molding die is clamped and pressure-molded. A method for forming a fuel cell separator as described in 1. above.

Images