Separator manufacturing method

Abstract

A method for producing a separator according to one embodiment of the present disclosure is for producing a separator that comprises a flow path part through which a gas for generating electrical energy passes and a bead part which is provided with a gasket at the top. This method for producing a separator comprises: a step in which a first projecting part corresponding to the flow path part is formed in a planar base material by means of press molding; a step in which a surface layer is formed on the surface of the base material in which the first projecting part has been formed; a step in which a gasket is provided in a planar bead part formation region, in which the bead part is to be provided, on the base material on which the surface layer has been formed; and a step in which a second projecting part corresponding to the bead part is formed in a position where the gasket has been provided.

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a separator. [Background technology]

[0002] Fuel cells are known that include a fuel cell stack in which multiple unit cells are stacked. This type of fuel cell is used in a wide range of applications, such as automobiles, industrial applications, and household applications. In general, in a fuel cell stack, each of the multiple unit cells includes a metal separator in which a gas flow path for fuel gas is formed (see, for example, Patent Documents 1 and 2).

[0003] Patent Document 3 shows that each separator has a bead portion surrounding the gas flow path, and that the bead portion prevents leakage of fuel gas. Patent Document 4 shows that an elastic member is provided at the top of the bead portion to ensure sealing of the gas flow path.

[0004] On the other hand, Patent Document 5 discloses that in order for the separator to maintain high conductivity even in a corrosive atmosphere within a unit cell, the substrate of the separator is surface-treated to provide a surface layer on the surface of the substrate to enhance resistance to the corrosive atmosphere. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-66817 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-251296 [Patent Document 3] Japanese Patent Publication No. 2020-198200 [Patent Document 4] Japanese Patent Publication No. 2021-143676 [Patent Document 5] Japanese Patent Publication No. 2022-85667 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in a separator having a surface layer on the surface and a gasket such as an elastic member in the bead portion, there is room for improvement in the quality of the surface layer and the gasket. In consideration of the above circumstances, the present disclosure aims to improve the quality of the surface layer and the gasket. [Means for solving the problem]

[0007] A method for manufacturing a separator according to one embodiment of the present disclosure is a method for manufacturing a separator having a gas flow path portion for generating electrical energy and a bead portion having a gasket at its top, and includes the steps of forming a first convex portion corresponding to the flow path portion on a flat substrate by press molding, forming a surface layer on the surface of the substrate on which the first convex portion is formed, providing the gasket in the flat bead portion forming region where the bead portion is to be formed on the substrate on which the surface layer is formed, and forming a second convex portion corresponding to the bead portion at the location where the gasket is provided. [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, the quality of the surface layer and gasket in the separator can be improved. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a plan view showing an example of a schematic configuration of a fuel cell stack according to a first embodiment of the present disclosure. [Figure 2] 2 is a partial cross-sectional view schematically showing a part of a cross section of a fuel cell stack taken along the thickness direction of a unit cell. FIG. [Figure 3] 3A to 3C are conceptual diagrams illustrating an example of a manufacturing process for the separator according to the first embodiment. [Figure 4] FIG. 6 is a conceptual diagram showing an example of a manufacturing process for the separator according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present disclosure will be described below with reference to the drawings. The dimensions and scale of each part in the drawings may differ from the actual dimensions and scale, and some parts may be shown schematically to facilitate understanding. Furthermore, unless otherwise specified to the effect that the present disclosure is limited in the following description, the scope of the present disclosure is not limited to the embodiments described below. The scope of the present disclosure includes equivalents of the embodiments described below.

[0011] 1. First embodiment [Fuel cell stack and unit cell configuration] Fig. 1 is a plan view showing an example of a schematic configuration of a fuel cell stack 10 according to this embodiment. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. Specifically, Fig. 2 is a partial cross-sectional view schematically showing a part of a cross section of the fuel cell stack 10 taken along the thickness direction Z of a unit cell 11.

[0012] The fuel cell stack 10 is one of the elements of a laminated solid polymer fuel cell, and as shown in FIG. 2, includes a plurality of unit cells 11. Each of the plurality of unit cells 11 generates electrical energy through a chemical reaction of a fuel gas. In this embodiment, the fuel gas is hydrogen, and each of the plurality of unit cells 11 converts the chemical energy of the hydrogen and oxygen, which is an example of an oxidant gas, into electrical energy through an oxidation-reduction reaction. In the fuel cell stack 10, the plurality of unit cells 11 are electrically connected to each other, and the electrical energy of each unit cell 11 is collected to increase the output of the fuel cell stack 10. Fuel cells including such a fuel cell stack 10 are used for various purposes, such as for vehicles, homes, and businesses.

[0013] As shown in Fig. 1, each of the plurality of unit cells 11 has a rectangular plate shape in a plan view, and as shown in Fig. 2, in a fuel cell stack 10, the plurality of unit cells 11 are stacked on top of each other in the thickness direction Z. Each of the plurality of unit cells 11 includes a membrane electrode assembly 100 called an MEA (Membrane Electrode Assembly) and a pair of separators 200. The pair of separators 200 sandwich the membrane electrode assembly 100 in the thickness direction Z. In other words, the pair of separators 200 form the surface of the unit cell 11.

[0014] In the following description, two directions defining a plane perpendicular to the thickness direction Z of the unit cell 11 are defined as the X direction and the Y direction. The X direction and the Y direction are perpendicular to each other. That is, the X direction, the Y direction, and the thickness direction Z correspond to the coordinate axes of an orthogonal three-dimensional coordinate system.

[0015] 2, the membrane electrode assembly 100 includes an electrolyte membrane 110 including, for example, a solid polymer membrane, an anode electrode layer 112, and a cathode electrode layer 114. The membrane electrode assembly 100 is a laminated structure in which the anode electrode layer 112 and the cathode electrode layer 114 sandwich the electrolyte membrane 110 in the thickness direction Z. Although not shown, each of the anode electrode layer 112 and the cathode electrode layer 114 is a laminated structure including a catalyst layer formed in the center of each side of the electrolyte membrane 110 and a gas diffusion layer formed on the catalyst layer.

[0016] Each of the pair of separators 200 is a metal plate-shaped member. The separator 200 facing the anode electrode layer 112 of the membrane electrode assembly 100 forms a first flow path 301 between itself and the anode electrode layer 112 for allowing hydrogen to flow. The separator 200 facing the cathode electrode layer 114 of the membrane electrode assembly 100 forms a second flow path 302 between itself and the cathode electrode layer 114 for allowing oxygen to flow. Hydrogen is supplied to the anode electrode layer 112 through the first flow path 301, and oxygen is supplied to the cathode electrode layer 114 through the second flow path 302, causing the membrane electrode assembly 100 to generate electrical energy through an oxidation-reduction reaction of hydrogen. Although not shown, the pair of separators 200 also have a flow path formed therein for allowing a coolant to flow.

[0017] 1, the pair of separators 200 are provided with a plurality of manifold holes 14 penetrating from the front to the back. A manifold hole 14 is provided for each of the first flow path 301, the second flow path 302, and the flow path of the coolant, and hydrogen, oxygen, and the coolant are introduced into the first flow path 301, the second flow path 302, and the flow path of the coolant through the individual manifold holes 14, respectively, and are discharged from the other individual manifold holes 14.

[0018] [Separator configuration] In this embodiment, the pair of separators 200 have the same configuration. More specifically, as shown in Fig. 2, each separator 200 includes a plurality of flow path portions 310 used for the first flow path 301, the second flow path 302, or the coolant flow path, one or more bead portions 320, and a gasket 330 provided in the bead portion 320.

[0019] The multiple flow path sections 310 are grooves with a concave (C-shaped) cross section that extend parallel to each other in the XY plane, and each separator 200 sandwiches the membrane electrode assembly 100 with the opening of each groove facing the anode electrode layer 112 or the cathode electrode layer 114 of the membrane electrode assembly 100.

[0020] The bead portion 320 is a ring-shaped portion surrounding all of the flow path portions 310 in a plan view of the separator 200, and has the function of sealing the internal space in a plan view. Specifically, as shown in FIG. 2 , in a cross-sectional view of the unit cell 11 in the thickness direction Z, the bead portion 320 has a convex shape that protrudes more in the thickness direction Z than other portions in the plane of the separator 200, and a gasket 330 is provided on the top of the convex shape. When the unit cells 11 are stacked, the gaskets 330 of the unit cells 11 come into contact with each other, and the contact between the gaskets 330 provides a seal. The bead portion 320 is also provided at a position surrounding each of the manifold holes 14.

[0021] The surface of the separator 200 is covered with a surface layer 350, which enhances resistance to a corrosive atmosphere.

[0022] The separator 200 of this embodiment is a bonded structure formed by bonding two metal plate-shaped substrates 400. Each of the two substrates 400 has a plurality of first convex portions 410 with a cross-sectional convex shape corresponding to the flow path portion 310 and one or more second convex portions 420 with a cross-sectional convex shape corresponding to the bead portion 320, provided on its surface. Here, if the front surface of the substrate 400 is defined as the surface located in the direction in which the first convex portions 410 and the second convex portions 420 protrude, and the back surface of the substrate 400 is defined as the surface opposite the front surface of the substrate 400, the separator 200 can be said to be a bonded structure formed by bonding the back surfaces of the two substrates 400 together, in other words, a bonded structure formed by bonding two substrates 400 back to back. In this bonded structure, the grooves formed by adjacent first convex portions 410 correspond to the flow path portion 310. Furthermore, the second protrusions 420 of the two base materials 400 are aligned vertically in the thickness direction Z, thereby forming bead portions 320 that are generally rectangular in cross section in both directions of the thickness direction Z. A gasket 330 is provided at the top of each bead portion 320. These bead portions 320 ensure sealing in both directions of the thickness direction Z. That is, sealing is ensured both between the membrane electrode assembly 100 and the separator 200 in each unit cell 11 and between the unit cells 11 themselves.

[0023] [Separator manufacturing method] FIG. 3 is a conceptual diagram showing an example of the manufacturing process for one separator 200. As shown in FIG. First, the substrate 400 is prepared (step Sa1). The substrate 400 may be made of any material as long as it is a plate material whose main component is metal. Typical examples of the plate material that constitutes the substrate 400 include a steel plate, a stainless steel plate, an aluminum plate, and a titanium steel plate. There are no limitations on the method for manufacturing the plate material that will become the substrate 400. The manifold holes 14 described above are formed in advance in the substrate 400 by appropriate processing.

[0024] Next, a plurality of first convex portions 410 are formed in a flow path portion forming region R1 of the substrate 400 where the flow path portion 310 is to be provided (step Sa2). The plurality of first convex portions 410 are formed, for example, by a first press molding. This first press molding is performed by sandwiching the substrate 400 between a first male die 611 and a first female die 612 and applying a pressing force between the first male die 611 and the first female die 612. The first male die 611 has convex portions corresponding to the first convex portions 410. The first female die 612 has concave portions that receive the convex portions of the first male die 611.

[0025] Next, a surface treatment is performed on the surface of the base material 400 (step Sa3). The surface treatment is a process for forming a surface layer 350 on the surface of the base material 400. Any method for the surface treatment can be used, and for example, a vapor deposition process or a reduction process described in Patent Document 5 can be used. FIG. 3 shows a form in which the base material 400 is placed in a chamber 700 and the surface layer 350 is formed by vapor deposition.

[0026] According to the manufacturing process of this embodiment, the surface layer 350 is formed on the substrate 400 after the first press molding for forming the first convex portion 410 that will become the flow path portion 310. Therefore, compared to when the surface layer 350 is formed before the first press molding, peeling or damage (e.g., cracks) does not occur in the surface layer 350 due to the first press molding, and the quality of the surface layer 350 can be maintained at a high level. As a result, it is possible to prevent a decrease in resistance to a corrosive atmosphere due to a decrease in the quality of the surface layer 350.

[0027] Next, prior to forming the second protrusions 420 corresponding to the bead portions 320, a gasket 330 is provided in the bead portion forming region R2 of the substrate 400 where the bead portions 320 are to be provided (step Sa4). The gasket 330 is made of a rubber material such as silicone, fluorine, or EPDM (ethylene propylene diene rubber). The width W and thickness of the gasket 330 are also appropriate. For example, the width W of the gasket 330 in this embodiment is 5 mm or less, and the thickness is 200 μm or less. For example, the gasket 330 is formed by applying a rubber material using a dispenser.

[0028] In step Sa4, the bead portion forming region R2 remains flat. Therefore, compared to providing the gasket 330 on a surface that may include curves or irregularities, such as the top of the second protrusion 420, the gasket 330 can be formed with high precision, and the quality of the gasket 330 can be maintained at a high level. As a result, a deterioration in sealing performance due to a deterioration in the quality of the gasket 330 can be prevented.

[0029] Next, in the bead portion forming region R2, the second convex portion 420 is formed at the location where the gasket 330 was provided (step Sa5). The second convex portion 420 is formed, for example, by second press molding. This second press molding is performed by sandwiching the base material 400 between the second male die 621 and the second female die 622 and applying a pressing force between the second male die 621 and the second female die 622. The second male die 621 has a convex portion corresponding to the second convex portion 420. The second female die 622 has a recess that receives the convex portion of the second male die 621 and a recess that receives the first convex portion 410 formed in step Sa2.

[0030] Then, the two substrates 400 that have been processed in steps Sa1 to Sa5 are joined together (step Sa6). Specifically, the back surfaces of the two substrates 400 are joined together. Any joining method may be used, for example, welding. By this step Sa6, one separator 200 is obtained that includes a plurality of flow path portions 310 and bead portions 320 with gaskets 330. Note that steps Sa1 to Sa5 are an example of a "first step," and step Sa6 is an example of a "second step."

[0031] As described above, the manufacturing process of the separator 200 in this embodiment includes a step of press-molding the first convex portion 410 corresponding to the flow path portion 310 onto the base material 400 of the separator 200 (step Sa2), a step of forming a surface layer 350 on the surface of the base material 400 on which the first convex portion 410 has been formed (step Sa3), a step of providing a gasket 330 in the flat bead portion forming region R2 where the bead portion 320 will be provided on the base material 400 on which the surface layer 350 has been formed (step Sa4), and a step of forming a second convex portion 420 corresponding to the bead portion 320 at the location where the gasket 330 has been provided (step Sa5), and these steps are performed in this order.

[0032] According to this manufacturing process, peeling or damage (e.g., cracks) does not occur in the surface layer 350 when the first convex portion 410 is press-molded, as compared to when the surface layer 350 is formed before the first convex portion 410 is press-molded, and a decrease in resistance to a corrosive atmosphere can be prevented.

[0033] Additionally, in this embodiment, the gasket 330 is formed in the flat bead portion forming region R2 with little curvature or unevenness. As a result, the gasket 330 can be accurately provided in the location where the bead portion 320 is to be formed, and a decrease in sealing performance due to insufficient precision of the gasket 330 can be prevented.

[0034] The manufacturing process of separator 200 in this embodiment also includes a step of joining two base materials 400, each having first protrusions 410 and second protrusions 420 with gaskets 330 provided on their tops.

[0035] This manufacturing process provides a separator 200 having bead portions 320 with a generally rectangular cross section that protrude in both directions in the thickness direction Z and have gaskets 330 provided at each apex. With this separator 200, the bead portions 320 ensure sealing in both directions in the thickness direction Z. That is, sealing is ensured both between the membrane electrode assembly 100 and the separator 200 in each unit cell 11 and between the unit cells 11 themselves.

[0036] 2. Second embodiment Fig. 4 is a conceptual diagram showing an example of a manufacturing process for one separator 200 according to the first embodiment. In Fig. 4, the same elements as those described in the first embodiment are denoted by the same reference numerals, and their description will be omitted. In addition, in the second embodiment, steps Sa1 and Sa2 are performed in the same manner as in the first embodiment, but steps Sa1 and Sa2 are not shown in Fig. 4 for convenience.

[0037] As shown in FIG. 4, the manufacturing process of this embodiment includes a step (step Sb1) of forming third protrusions 430 in the bead portion forming region R2 by third press molding after the step (step Sa3) of forming the surface layer 350 and before the step (step Sa4) of forming the gasket 330. The third protrusions 430 are portions with a convex cross section and a flat top. Specifically, the height H of the third protrusions 430 is equal to or greater than the height of the first protrusions 410 and equal to or less than the height of the second protrusions 420. Note that FIG. 4 shows a case where the height H of the third protrusions 430 is approximately equal to the height of the first protrusions 410. After the above-described step Sb1, the gasket 330 is formed in step Sa4.

[0038] The third press molding in step Sb1 is performed by sandwiching the base material 400 between the third male die 631 and the third female die 632 and applying a pressing force between the third male die 631 and the third female die 632. The third male die 631 has a convex portion corresponding to the third convex portion 430. The third female die 632 has a concave portion that receives the convex portion of the third male die 631 and a concave portion that receives the first convex portion 410 formed in step Sa2.

[0039] By performing step Sb1, the height H of the area where the gasket 330 is formed becomes equal to or greater than the height of the first convex portion 410. Here, when screen printing is used to form the gasket 330 instead of the dispenser described in the first embodiment, a screen with pre-openings corresponding to the areas where the material for the gasket 330 needs to be applied is pressed against the area where the gasket 330 is to be formed with a squeegee, and the film is formed with the screen in close contact. However, if the first convex portion 410 is taller than the gasket 330, the first convex portion 410 interferes with the screen, making it impossible to close the screen to the area where the gasket 330 is to be formed. In contrast, in this embodiment, the height H of the area where the gasket 330 is to be formed is equal to or greater than the height of the first convex portion 410, so the gasket 330 can be formed by screen printing on the substrate 400 without being obstructed by the first convex portion 410. Therefore, the material for the gasket 300 can be applied over a wide area at once using a screen with pre-openings corresponding to the areas where the gasket needs to be applied. As a result, the cycle time required to form the gasket 330 can be shortened.

[0040] Here, the bead portion forming region R2 has a width sufficient to contain at least the bead portion 320 when viewed in cross section in the thickness direction Z. Furthermore, when multiple bead portions 320 are arranged side by side, the bead portion forming region R2 has a width sufficient to contain all of the multiple bead portions 320. In other words, the width of the bead portion forming region R2 is sufficiently wider than each of the individual bead portions 320, and the shape of the top of the third protrusion 430 formed by the third press molding is maintained as a flat plate.

[0041] That is, in the manufacturing process of this embodiment, as in the first embodiment, the gasket 330 is provided in the flat bead portion forming region R2, and then the second convex portion 420 corresponding to the bead portion 320 is formed. Therefore, the gasket 330 can be provided with high precision, and a decrease in sealing performance due to insufficient precision of the gasket 330 can be prevented.

[0042] 3. Variations Specific modified forms that can be added to the first and second embodiments exemplified above are shown below. Two or more forms arbitrarily selected from the following examples may be combined as appropriate within the scope of not contradicting each other.

[0043] (1) In each embodiment, the separator 200 is illustrated as being formed by bonding two substrates 400. However, the separator 200 may be formed by a single substrate 400. In this case, the first convex portion 410 corresponds to the flow path portion 310, and the second convex portion 420 corresponds to the bead portion 320.

[0044] (2) The materials and manufacturing methods described in each embodiment can be modified as appropriate without departing from the spirit of this disclosure.

[0045] (3) The term "nth" (n is a natural number) in this application is used only as a formal and convenient label to distinguish each element in the description and does not have any substantive meaning. Therefore, there is no room for restrictive interpretation of the position of each element or the order of manufacture, etc., based on the term "nth." [Explanation of symbols]

[0046] 10...fuel cell stack, 11...unit cell, 100...membrane electrode assembly, 200...separator, 310...flow path portion, 320...bead portion, 330...gasket, 350...surface layer, 400...substrate, 410...first convex portion, 420...second convex portion, 430...third convex portion, H...height, R2...bead portion forming region, Z...thickness direction.

Claims

1. A method for manufacturing a separator having a gas flow path for generating electrical energy and a bead portion having a gasket provided at the top thereof, comprising: forming a first protrusion corresponding to the flow path portion on a flat substrate by press molding; forming a surface layer on the surface of the base material on which the first convex portions are formed; providing the gasket in a flat bead portion forming region where the bead portion is to be provided in the base material on which the surface layer is formed; forming a second protrusion corresponding to the bead portion at the location where the gasket is provided; A method for manufacturing a separator comprising:

2. The step of providing the gasket includes: forming a third convex portion having a height equal to or less than that of the second convex portion and a flat top portion in the bead portion forming region by press molding; providing the gasket on a flat top of the third protrusion; forming the second protrusion corresponding to the bead portion at the location where the gasket is provided; Including, A method for producing the separator of claim 1.

3. The step of providing the gasket includes: forming a third convex portion having a height equal to or greater than the height of the first convex portion and equal to or less than the height of the second convex portion, and having a flat top portion, in the bead portion forming region by press molding; providing the gasket on a flat top of the third protrusion; forming the second protrusion corresponding to the bead portion at the location where the gasket is provided; Including, A method for producing the separator of claim 1.

4. a first step of forming a gas flow path for generating electrical energy and a bead portion having a gasket provided on the top of each of two flat substrates; a second step of joining the two base materials together after the first step is performed, The first step includes, for each of the two substrates: a step of press-molding a first protrusion corresponding to the flow path portion onto the base material; forming a surface layer on the surface of the base material on which the first convex portions are formed; providing the gasket in a flat bead portion forming region where the bead portion is to be provided in the base material on which the surface layer is formed; and forming a second protrusion corresponding to the bead portion at the location where the gasket is provided. A method for manufacturing a separator.

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