US20210074892A1

US20210074892A1 - Method of manufacturing separator for fuel cell

Info

Publication number: US20210074892A1
Application number: US17/100,788
Authority: US
Inventors: Hideya KADONO; Shinya SUBE; Hajime KAWARASAK; Keisuke MIYANAGA; Kiyoyuki TANIGUCHI; Naohito Ohno
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2018-05-29
Filing date: 2020-11-20
Publication date: 2021-03-11
Also published as: US20210074891A1; US10879429B2; JP2023036729A; US11437549B2; JP7417153B2; US20190371972A1

Abstract

A method of manufacturing a separator for a fuel cell has a separator body arrangement process for arranging, through the use of a molding die equipped with a first die having a sealing member recess portion and a second die having a rib projection portion, a separator body in the second die before formation of a reinforcing rib, a die clamping for clamping the first die and the second die with the first die superimposed on the second die, and a sealing member molding for crosslinking an elastomer material into a sealing member and integrating the sealing member with a first surface of the separator body by injecting the elastomer material into the sealing member recess portion and heating the molding die. The reinforcing rib is formed on the separator body along the shape of the rib projection portion, between the die clamping and the sealing member molding.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2019-214106 filed on Nov. 27, 2019, incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The disclosure relates to a method of manufacturing a separator as a constituent of a fuel cell.

2. Description of Related Art

In a fuel cell, each of cells that is obtained by sandwiching an electrode member including a membrane electrode assembly (MEA) by separators serves as a unit of electric power generation. The fuel cell is configured by fastening a stack body of the cells from both outer sides thereof in a stacking direction with a predetermined force. A fuel gas such as hydrogen or an oxidant gas such as air flows on one side of each of the separators in a thickness direction (the stacking direction) thereof, and a coolant such as water flows on the other surface side of each of the separators in the thickness direction thereof. Each of the separators has a through-hole penetrating in the thickness direction thereof, and this through-hole serves as a flow passage through which reactive gases and the coolant flow. A frame-shaped sealing member made of rubber (a rubber gasket) is arranged around the electrode member and between the adjacent separators. The sealing member is glued to the separators, and is compressed with a fastening force from both the outer sides in the stacking direction. Thus, fluid is prohibited from moving into and out from the sealing member.
As a method of integrating each of the separators and the sealing member with each other, it is possible to mention a method according to which each of the separators is arranged in a molding die and a rubber material is injection-molded, or a method according to which a pre-molded body of the sealing member and each of the separators are arranged in a molding die, heated, and compressed to glue the pre-molded body through crosslinking.

SUMMARY

In the case where a sealing member is integrated with a separator through injection molding, there is a problem in that the separator warps. FIGS. 11 and 12 are schematic views of an injection molding process. FIG. 11 shows a die clamping state of a molding die, and FIG. 12 shows a state after injection of a rubber material. First of all, as shown in FIG. 11, a separator 90 is arranged between an upper die 91 and a lower die 92. A cavity 910 that is filled with the rubber material is formed in the upper die 91. The upper die 91 and the lower die 92 are clamped by applying a high pressure thereto as indicated by blank arrows in FIG. 11 such that the rubber material does not leak due to an injection pressure. Thus, a pressurized portion of the separator 90 is plastically deformed, and the material of the separator 90 flows to anon-pressurized portion as indicated by arrows in FIG. 11. As a result, the separator 90 is curved in such a manner as to deflect upward in the cavity 910. Subsequently, as shown in FIG. 12, a rubber material 93 is injected into the cavity 910. Then, as indicated by arrows in FIG. 12, the separator 90 is pressed downward due to an injection pressure of the rubber material 93, and returns to an original flat state thereof. Then, the injected rubber material 93 is glued to the separator 90 through crosslinking, and the integration of the separator with the sealing member is thus completed.
However, when the separator is taken out from the molding die, the separator is curved like a bow and warps due to springback. In the case of warped separators, when the separators and electrode members are stacked to assemble a stack body of cells, handling and positioning are difficult to carry out. In addition, the contact surface pressure of the sealing member is unevenly distributed, so the sealing performance of the sealing member may deteriorate.
For example, in Japanese Unexamined Patent Application Publication No. 2002-175818 (JP 2002-175818 A), it is described that in a separator for a fuel cell that is obtained by pressing a single metal plate to mold an electric power collector portion with an irregular cross-section, and an edge portion arranged around the electric power collector portion, a rib is formed at the edge portion (claims). In JP 2002-175818 A, the rib is formed at the edge portion to restrain the transmission of a stress caused in forming the electric power collector portion by pressing the separator. A sealing member 35 that is arranged in such a manner as to cover a rib 21 is disclosed in paragraph [0014] and FIG. 4 of JP 2002-175818 A. However, it is not mentioned in JP 2002-175818 A that the sealing member is injection-molded, or that a process of integrating the sealing member with the separator and a process of forming the rib are related to each other. On the contrary, it is described that the rib is preferably formed simultaneously with the electric power collector portion in press-molding the separator (paragraph [0010] of JP 2002-175818 A). For example, in the case where the sealing member is integrated with the separator after forming the rib, the sealing member needs to be stacked in accordance with the rib, positioning thereof is difficult to carry out. Besides, when the rib is formed in process separate from integration of the sealing member, the quantity of work increases correspondingly, the time required for manufacturing is prolonged, and the cost rises.
The disclosure has been made in view of these circumstances. It is an object of the disclosure to provide a method of manufacturing a separator for a fuel cell that makes it possible to easily manufacture the separator for the fuel cell with which a sealing member is integrated, while restraining the separator from warping.
In order to solve the aforementioned problem, the disclosure provides a method of manufacturing a separator for a fuel cell having a separator body that has a reinforcing rib protruding from a first surface as one of a pair of surfaces of the separator body in a thickness direction, that is, the first surface and a second surface, and a sealing member that is made of an elastomer and that is arranged on the first surface of the separator body. This method includes a separator body arrangement process for arranging, through the use of a molding die equipped with a first die having a sealing member recess portion for molding the sealing member and a second die having a rib projection portion for forming the reinforcing rib, the separator body in the second die, with the second surface of the separator body located on the second die side before formation of the reinforcing rib, and with an uncrosslinked material of the elastomer serving as an elastomer material, a die clamping process for clamping the first die and the second die with the first die superimposed on the second die, and a sealing member molding process for crosslinking the elastomer material into the sealing member and integrating the sealing member with the first surface of the separator body by injecting the elastomer material into the sealing member recess portion and heating the molding die. The reinforcing rib is formed on the separator body along a shape of the rib projection portion, between the die clamping process and the sealing member molding process.
With the method of manufacturing the separator for the fuel cell according to the disclosure, the reinforcing rib is simultaneously formed during a series of processes for integrating the sealing member with the separator body. The rigidity of the separator body increases through formation of the reinforcing rib. In consequence, when the separator body is taken out from the molding die, the separator body is unlikely to be subjected to springback, and is restrained from warping. As a result, when the separator and an electrode member are stacked on each other to assemble a cell stack body, handling and positioning are easy to carry out. In addition, the problem of a deterioration in sealing performance of the sealing member is also resolved. Besides, with the method of manufacturing the separator for the fuel cell according to the disclosure, the number of manufacturing processes can be made smaller, the manufacturing time can be made shorter, and the cost can be made lower than in the case of a method according to which the reinforcing rib is formed separately from a series of processes for integrating the sealing member with the separator body. Thus, the productivity of the separator for the fuel cell is enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein:

FIG. 1 is a top view of an anode-side separator of the first embodiment;

FIG. 2 is a cross-sectional view along a line II-II of FIG. 1;

FIG. 3 is a cross-sectional view of part of a molding die in a separator body arrangement process as one of processes of manufacturing the anode-side separator;

FIG. 4 is a cross-sectional view of part of the molding die in a die clamping process;

FIG. 5 is a cross-sectional view of part of the molding die in a sealing member molding process;

FIG. 6 is a top view of an anode-side separator of the second embodiment;

FIG. 7 is a cross-sectional view along a line VII-VII of FIG. 6;

FIG. 8 is a cross-sectional view of part of a molding die in a separator body arrangement process as one of processes of manufacturing the anode-side separator;

FIG. 9 is a cross-sectional view of part of the molding die in a die clamping process;

FIG. 10 is a cross-sectional view of part of the molding die in a sealing member molding process;

FIG. 11 is a cross-sectional schematic view showing a die clamping state of a molding die in a conventional injection molding process; and

FIG. 12 is a cross-sectional schematic view showing a state of the molding die after injection of a rubber material in the conventional injection molding process.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of a method of manufacturing a separator for a fuel cell according to the disclosure will be described hereinafter.

First Embodiment

(Configuration of Separator for Fuel Cell)
First of all, the configuration of a separator for a fuel cell of the present embodiment will be described. In the present embodiment, the separator for the fuel cell is embodied as an anode-side separator as a constituent of a fuel battery cell. FIG. 1 is a top view of the anode-side separator of the first embodiment. FIG. 2 is a cross-sectional view along a line II-II of FIG. 1. Among directions in the drawings, the longitudinal and lateral directions indicate a plane direction of the separator, and the vertical direction indicates a thickness direction of the separator. As shown in FIG. 1, an anode-side separator 1 has a separator body 10 and a sealing member 20. For the convenience of explanation, in FIG. 1, the sealing member 20 is hatched by thin lines, and reinforcing ribs 16 a and 16 b that are arranged below the sealing member 20 are shown in a transparent manner.
The separator body 10 is made of titanium, and assumes the shape of a thin rectangular sheet. The separator body 10 has a thickness of 0.1 mm. The separator body 10 has six through-holes penetrating therethrough in the thickness direction thereof. That is, an air supply hole 11 a, a coolant supply hole 12 a, and a hydrogen supply hole 13 a are opened, in this sequence from a rear side, through the separator body 10 on a left side thereof, and a hydrogen discharge hole 13 b, a coolant discharge hole 12 b, and an air discharge hole 11 b are opened, in this sequence from the rear side, through the separator body 10 on a right side thereof.
The separator body 10 has an upper surface 14, a lower surface 15, and the reinforcing ribs 16 a and 16 b forming a pair. The upper surface 14 falls within the concept of “the first surface” in the disclosure, and the lower surface 15 falls within the concept of “the second surface” in the disclosure. A rectangular electric power generation region 21 is defined in a central part of the upper surface 14. The electric power generation region 21 corresponds to an arrangement region of an electrode member (an MEA or the like) stacked on the lower surface 15 side, in the case where the fuel battery cell is configured through the use of the anode-side separator 1. In the electric power generation region 21, a coolant flow passage 17 through which coolant flows is formed.
The reinforcing rib 16 a is rectilinearly arranged along the lateral direction (the longitudinal direction), at a rear edge portion of the separator body 10. The reinforcing rib 16 a is arranged below the sealing member 20 that extends in the lateral direction, also at the rear edge portion of the separator body 10. The reinforcing rib 16 b is rectilinearly arranged along the lateral direction (the longitudinal direction) at a front edge portion of the separator body 10. The reinforcing rib 16 b is arranged below the sealing member 20 that extends in the lateral direction, also at the front edge portion of the separator body 10. The reinforcing ribs 16 a and 16 b are identical in shape and size. Accordingly, the reinforcing rib 16 a will be described hereinafter.
As is apparent from FIG. 2 showing a cross-section of the rear edge portion of the separator body 10 in the thickness direction, the reinforcing rib 16 a is arranged in a protruding manner on the upper surface 14 side, and has a cross-section assuming the shape of a trapezoid. A groove portion 18 a is formed at the same position as the reinforcing rib 16a, in the lower surface 15 of the separator body 10. The groove portion 18 a assumes a shape symmetrical in a complementary manner to a rib projection portion 53 that will be described later. The reinforcing rib 16 a has a height (a length of protrusion from the upper surface 14) of 0.05 mm, and the ratio of the height of the reinforcing rib 16 a to the thickness of the separator body 10 is 0.5. The reinforcing rib 16 a is covered with the sealing member 20. The reinforcing rib 16 a is smaller in width (length in a transverse direction or length in a front-rear direction in FIG. 2) than the sealing member 20.
The sealing member 20 is arranged on a peripheral edge portion of the upper surface 14 of the separator body 10, and around the six through-holes (the air supply hole 11 a, the air discharge hole 11b, the coolant supply hole 12 a, the coolant discharge hole 12 b, the hydrogen supply hole 13 a, and the hydrogen discharge hole 13 b). The sealing member 20 is made of ethylene-propylene-diene rubber (EPDM), and assumes the shape of a rectangular frame. The sealing member 20 has a pedestal portion 200 that assumes the shape of a flat plate, and a mountain portion 201 that protrudes upward therefrom. A peak portion of the mountain portion 201 has a cross-section assuming the shape of a substantially semicircular curved surface in a thickness direction thereof. The sealing member 20 is elastically in contact with a partner member (a cathode-side separator of another cell) that is stacked on the upper surface 14 of the separator body 10 (the anode-side separator 1).
(Method of Manufacturing Separator for Fuel Cell)
Next, a method of manufacturing the separator for the fuel cell of the present embodiment will be described. The method of manufacturing the anode-side separator 1 has a separator body arrangement process, a die clamping process, and a sealing member molding process.
(1) Separator Body Arrangement Process
In the present process, the separator body is arranged in a second die, with the second surface of the separator body located on the second die side before formation of the reinforcing ribs. FIG. 3 is a cross-sectional view of part of a molding die in the present process. The cross-section of part of the molding die shown in FIG. 3 corresponds to the cross-section of the anode-side separator 1 shown in FIG. 1 along the line II-II (the same holds true for FIGS. 4 and 5 that will be described later). As shown in FIG. 3, a molding die 5 is equipped with a first die 50 and a second die 51. The first die 50 has a sealing member recess portion 52. The sealing member recess portion 52 is a cavity for molding the sealing member 20. The second die 51 has the rib projection portion 53 for forming the reinforcing rib 16 a. In a die clamping state of the molding die 5, the rib projection portion 53 is arranged at a position opposite the sealing member recess portion 52. In the present process, the separator body 10 where no reinforcing rib is formed is arranged on an upper surface of the second die 51 such that the lower surface 15 comes into contact with the rib projection portion 53.
(2) Die Clamping Process
In the present process, the first die is superimposed on the second die, and is clamped. FIG. 4 is a cross-sectional view of part of the molding die in the die clamping process. As shown in FIG. 4, the first die 50 is superimposed on the second die 51, and is pressurized from above as indicated by blank arrows in FIG. 4. Thus, the molding die 5 is clamped at a die clamping pressure equal to or higher than a yield stress of the separator body 10. In this case, the separator body 10 is curved in the sealing member recess portion 52 due to plastic deformation of a pressurized portion and the flow of material to a non-pressurized portion.
(3) Sealing Member Molding Process
In the present process, an elastomer material as an uncrosslinked material of elastomer is injected into the sealing member recess portion, and the molding die is heated. Thus, the elastomer material is crosslinked into the sealing member, and the sealing member is integrated with the first surface of the separator body. FIG. 5 is a cross-sectional view of part of the molding die in the sealing member molding process. As shown in FIG. 5, first of all, an uncrosslinked material of solid rubber containing EPDM as a rubber component (an elastomer material 54) is injected into the sealing member recess portion 52 from a nozzle of an injection molding machine (not shown) through a runner and a gate of the first die 50. The molding die 5 is heated to a temperature equal to or higher than 150° C. to crosslink the elastomer material 54.
When the elastomer material 54 is injected, the upper surface 14 of the separator body 10 is pressed downward in the sealing member recess portion 52, and is about to return to an original flat state thereof, due to an injection pressure of the elastomer material 54 and an expansion pressure of the elastomer material 54 resulting from the heating of the molding die 5. In this case, the separator body 10 is deformed along the shape of the rib projection portion 53, so the reinforcing rib 16 a and the groove portion 18 a are formed. That is, in the die clamping process and the sealing member molding process, the separator body 10 is pressed in the sealing member recess portion 52 by both the rib projection portion 53 and the elastomer material 54, so the reinforcing rib 16 a and the groove portion 18 a are formed. Besides, the elastomer material 54 with which the sealing member recess portion 52 is filled is crosslinked into the sealing member 20, and is glued to the upper surface 14 of the separator body 10. In this manner, the formation of the reinforcing rib 16 a for the separator body 10 and the integration of the sealing member 20 with the separator body 10 are completed.
(Operation and Effect)
Next, the operation and effect of the method of manufacturing the separator for the fuel cell according to the present embodiment will be described. According to the method of manufacturing the anode-side separator 1, the reinforcing ribs 16 a and 16 b are simultaneously formed in a series of processes for integrating the sealing member 20 with the separator body 10. The rigidity of the separator body 10 increases through the formation of the reinforcing ribs 16 a and 16 b. In consequence, when the molding die 5 is opened and the separator body 10 is taken out after the sealing member 20 is molded, the separator body 10 is unlikely to be subjected to springback, and is retrained from warping. In particular, the reinforcing ribs 16 a and 16 b are arranged along the longitudinal direction of the anode-side separator 1. Therefore, the separator body 10 is effectively restrained from warping to the extent of being curved like a bow.
When the amount of warpage of the anode-side separator 1 is small, handling and positioning are easy to carry out when the anode-side separator 1 and the electrode member are stacked on each other to assemble a cell stack body. In addition, the contact surface pressure between the sealing member 20 and the partner member (the cathode-side separator of another cell) is homogenized, so the sealing performance is also unlikely to deteriorate. Besides, according to the method of manufacturing the anode-side separator 1, the number of manufacturing processes can be made smaller, the manufacturing time can be made shorter, and the cost can be made lower than in the case where the reinforcing ribs 16 a and 16 b are formed separately from a series of processes for integrating the sealing member 20 with the separator body 10. Thus, the productivity of the anode-side separator 1 is enhanced.
In the method of manufacturing the anode-side separator 1, the sealing member 20 is molded through the use of the injection molding method, and the reinforcing ribs 16 a and 16 b are formed below the sealing member 20. Thus, in the sealing member molding process, the upper surface 14 of the separator body 10 can be pressed through the use of the injection pressure and expansion pressure of the elastomer material 54. Therefore, the reinforcing ribs 16 a and 16 b that assume the same shape as the rib projection portion 53 of the second die 51 can be easily formed. Conventionally, in the case where the sealing member is integrally molded, the separator body 10 is rolled to cause material excess in the die clamping process, so a dimensional deviation is caused. However, according to the method of manufacturing the anode-side separator 1, the excess material is absorbed by the reinforcing ribs 16 a and 16 b, so dimensional accuracy can be ensured. The height of the reinforcing ribs 16 a and 16 b is half of the thickness of the separator body.
Therefore, even in the case where the separator body 10 is small in thickness, the reinforcing ribs 16 a and 16 b can be formed without destroying the separator body 10. In the anode-side separator 1, the reinforcing ribs 16 a and 16 b are smaller in width than the sealing member 20. Therefore, the influence on the sealing performance of the sealing member 20 is small.

Second Embodiment

The method of manufacturing the separator for the fuel cell according to the present embodiment is different from the method of manufacturing the separator for manufacturing the separator for the fuel cell according to the first embodiment in that the reinforcing ribs are formed at different positions, and that the reinforcing ribs are formed through press molding in the die clamping process. The differences will be mainly described hereinafter.
(Configuration of Separator for Fuel Cell)
First of all, the configuration of the separator for the fuel cell of the present embodiment will be described. FIG. 6 is a top view of an anode-side separator of the second embodiment. FIG. 7 is a cross-sectional view along a line VII-VII of FIG. 6. FIG. 6 corresponds to FIG. 1 mentioned earlier. In FIG. 6, members identical to those of FIG. 1 are denoted by the same reference symbols respectively. As shown in FIG. 6, an anode-side separator 3 has a separator body 30 and the sealing member 20.
The separator body 30 has an upper surface 31, a lower surface 32, and a pair of reinforcing ribs 33 a and 33 b. The upper surface 31 falls within the concept of “the first surface” in the disclosure, and the lower surface 32 falls within the concept of “the second surface” in the disclosure. The separator body 30 is made of titanium, and has a thickness of 0.1 mm. The reinforcing rib 33 a is rectilinearly arranged along the lateral direction (the longitudinal direction) at a rear edge portion of the separator body 30. The reinforcing rib 33 a is arranged outside (behind) and parallel to the sealing member 20 that extends in the lateral direction also at the rear edge portion of the separator body 30. The reinforcing rib 33 b is rectilinearly arranged along the lateral direction (the longitudinal direction) at a front edge portion of the separator body 30. The reinforcing rib 33 b is arranged outside (in front of) and parallel to the sealing member 20 that extends in the lateral direction also at the front edge portion of the separator body 30. The reinforcing ribs 33 a and 33 b are identical in shape and size. Accordingly, the reinforcing rib 33 a will be described hereinafter.
As is apparent from FIG. 7 showing a cross-section of the rear edge portion of the separator body 30 in the thickness direction, the reinforcing rib 33 a is arranged in a protruding manner on the upper surface 31 side, and has a cross-section assuming the shape of a trapezoid. The reinforcing rib 33 a is arranged outside (behind) the sealing member 20, and is not covered with the sealing member 20. A groove portion 34 a is formed at the same position as the reinforcing rib 33 a, on the lower surface 32 of the separator body 30. The groove portion 34 a assumes a shape symmetrical in a complementary manner to a rib projection portion 64 that will be described later. The reinforcing rib 33 a has a height (a length of protrusion from the upper surface 31) of 0.05 mm, and the ratio of the height of the reinforcing rib 33 a to the thickness of the separator body 30 is 0.5.
(Method of Manufacturing Separator for Fuel Cell)
Next, the method of manufacturing the separator for the fuel cell according to the present embodiment will be described. The method of manufacturing the anode-side separator 3 has a separator body arrangement process, a die clamping process, and a sealing member molding process, as is the case with the first embodiment.
(1) Separator Body Arrangement Process
FIG. 8 is a cross-sectional view of part of a molding die in the present process. The cross-section of part of the molding die shown in FIG. 8 corresponds to a cross-section of the anode-side separator 3 shown in FIG. 6 along the line VII-VII (the same holds true for FIGS. 9 and 10 that will be described later). As shown in FIG. 8, a molding die 6 is equipped with a first die 60 and a second die 61. The first die 60 has a sealing member recess portion 62 and a rib recess portion 63. The sealing member recess portion 62 is a cavity for molding the sealing member 20. The second die 61 has the rib projection portion 64. In a die clamping state of the molding die 6, the rib projection portion 64 is arranged at a position different from a position opposite the sealing member recess portion 62 of the first die 60. The rib projection portion 64 and the rib recess portion 63 constitute a structure for forming the reinforcing rib 33 a. The rib recess portion 63 is arranged at a position opposite the rib projection portion 64, and assumes a shape symmetrical in a complementary manner to the rib projection portion 64. In the present process, the separator body 30 where no reinforcing rib is formed is arranged on the upper surface of the second die 61 such that the lower surface 32 comes into contact with the rib projection portion 64.
(2) Die Clamping Process
FIG. 9 is a cross-sectional view of part of the molding die in the die clamping process. As shown in FIG. 9, the second die 61 is superimposed on the first die 60, and is pressurized from above as indicated by blank arrows in FIG. 9. Thus, the molding die 6 is clamped at a die clamping pressure equal to or higher than a yield stress of the separator body 30. In this case, the separator body 30 is curved in the sealing member recess portion 62 due to plastic deformation of a pressurized portion and the flow of material to a non-pressurized portion. At the same time, the separator body 30 is pressed while being sandwiched between the rib projection portion 64 and the rib recess portion 63. Thus, the reinforcing rib 33 a and the groove portion 34 a are formed.
(3) Sealing Member Molding Die
FIG. 10 is a cross-sectional view of part of the molding die in the sealing member molding process. As shown in FIG. 10, first of all, the elastomer material 54 is injected into the sealing member recess portion 62 from a nozzle of an injection molding machine (not shown) through a runner and a gate of the first die 60. The molding die 6 is heated to a temperature equal to or higher than 150° C. to crosslink the elastomer material 54. When the elastomer material 54 is injected, the upper surface 31 of the separator body 30 is pressed downward in the sealing member recess portion 62, and returns to an original flat state thereof, due to an injection pressure of the elastomer material 54 and an expansion pressure of the elastomer material 54 resulting from the heating of the molding die 6. The elastomer material 54 with which the sealing member recess portion 62 is filled is crosslinked into the sealing member 20, and is glued to the upper surface 31 of the separator body 30. In this manner, the formation of the reinforcing rib 33 a for the separator body 30 and the integration of the sealing member 20 with the separator body 30 are completed.
(Operation and Effect)
Next, the operation and effect of the method of manufacturing the separator for the fuel cell according to the present embodiment will be described. The method of manufacturing the separator for the fuel cell according to the present embodiment has the same operation and effect as the method of manufacturing the separator for the fuel cell according to the first embodiment, as far as the common components are concerned. That is, according to the method of manufacturing the anode-side separator 3, the reinforcing ribs 33 a and 33 b are simultaneously formed during a series of processes for integrating the sealing member 20 with the separator body 30. Each of the reinforcing ribs 33 a and 33 b is arranged along the longitudinal direction of the anode-side separator 3. Thus, when the molding die 6 is opened and the separator body 30 is taken out after the sealing member 20 is molded, the separator body 30 is unlikely to be subjected to springback, and is effectively restrained from warping to the extent of being curved like a bow. Besides, according to the method of manufacturing the anode-side separator 3, in the die clamping process, the separator body 30 is press-molded by the rib recess portion 63 of the first die 60 and the rib projection portion 64 of the second die 61 to form the reinforcing ribs 33 a and 33 b. Therefore, the reinforcing ribs 33 a and 33 b can be easily manufactured regardless of the position of the sealing member 20. Besides, the reinforcing ribs are not formed in the cavity for molding the sealing member 20 (the sealing member recess portion 62). Therefore, the width of the reinforcing ribs 33 a and 33 b is not restricted by the width of the sealing member 20.
(Others)
The embodiments of the method of manufacturing the separator for the fuel cell according to the disclosure have been described above. However, the disclosure is not limited to the aforementioned embodiments in particular. The disclosure can also be carried out in a variety of modified or improved modes that can be realized by those skilled in the art.
In each of the aforementioned embodiments, the separator for the fuel cell is embodied as the anode-side separator, but the separator for the fuel cell to which the manufacturing method according to the disclosure is applied may be a cathode-side separator. In each of the aforementioned embodiments, the first surface of the separator body is a surface on which the cathode-side separator of another cell is stacked in the case where the fuel battery cell is configured. However, the first surface and the second surface may be interchanged with each other. That is, the first surface may be a surface that is in contact with the electrode member. The material of the separator body is not limited to that of the aforementioned embodiments. Iron, stainless steel, aluminum, or the like can be mentioned as the material of the separator body, instead of titanium. Besides, the flow passage, the through-holes, and the like that are formed in the separator body are not limited in configuration either. The thickness of the separator body is desired to be equal to or larger than 0.1 mm and equal to or smaller than 0.3 mm, from the standpoint of the performance of electric power generation.
The sealing member is not limited in material, shape, mode of arrangement, and the like. In addition to the rubber component, the sealing member may contain a crosslinking agent, a co-crosslinking agent, a processing aid, a softener, a reinforcing material, and the like. As the preferable rubber component, instead of EPDM, it is possible to mention silicone rubber, fluorine-containing rubber, butyl rubber (IIR), ethylene propylene rubber (EPR), acrylic nitrile-butadiene rubber (NBR), hydrogenated acrylic nitrile-butadiene rubber (H-NBR), styrene-butadiene rubber (SBR), butadiene rubber (BR), or the like.
Although the positions where the reinforcing ribs are formed are not limited, it is desirable to arrange the reinforcing ribs at positions outside the electric power generation region, from the standpoint of enhancing the performance of electric power generation by reducing the contact resistance between the separator body and the electrode member. While only a single reinforcing member may be provided, it is also possible to provide two or more reinforcing ribs. The reinforcing ribs may be rectilinear or curved, and may be scattered about at a plurality of locations. For example, the reinforcing ribs may be annularly arranged along an outer peripheral edge of the separator body. When the reinforcing ribs are arranged along the longitudinal direction of the separator body, the separator body can be effectively restrained from warping.
The cross-sectional shape of the reinforcing ribs is not limited. As the cross-sectional shape of the reinforcing ribs, it is possible to mention a quadrilateral shape such as a trapezoidal shape or an oblong shape, a curved shape such as a semicircular shape or an elliptical shape, a V-shape, or the like. The height (the length of protrusion from the first surface) of the reinforcing ribs may be appropriately determined in accordance with the thickness of the separator body, the position where the separator body is formed, the shape of the separator body, and the like. When the height of the reinforcing ribs is too high for the thickness of the separator body, the separator may be destroyed. In consequence, the ratio of the height of the reinforcing ribs to the thickness of the separator body (the height of the reinforcing ribs/the thickness of the separator body) is desired to be equal to or smaller than 0.6.
For example, in the case where each of the reinforcing ribs is formed in such a manner as to be superimposed on the sealing member, the center of each of the reinforcing ribs in the width direction thereof and the center of the sealing member in the width direction thereof may or may not coincide with each other. In the case where the centers in the width direction do not coincide with each other as in the aforementioned first embodiment, the influence on the sealing performance can be reduced. Besides, in order to form the reinforcing ribs through the use of the injection pressure of the elastomer material and the expansion pressure of the elastomer material at the time of heating in the sealing member molding process, the width of the reinforcing ribs may be made smaller than the width of the sealing member.
In the aforementioned embodiment, the sealing member is molded through injection molding. Instead of injection molding, however, compression molding, transfer molding, or the like may be adopted as the method of molding the sealing member. Besides, the temperature to which the molding die is heated may be appropriately determined in consideration of the crosslinking reaction and crosslinking time of the elastomer material. The die clamping pressure of the molding die may be appropriately determined such that the injected elastomer material does not leak. The die clamping pressure may be equal to or higher than the yield stress of the separator body or 0.2% of the proof stress of the separator body. “0.2% of the proof stress” corresponds to a point where 0.2% of permanent distortion is caused, and serves as an indicator of plastic deformation of the separator body. “0.2% of the proof stress” may be measured according to an offset method prescribed in JIS Z2241: 2011.
The reinforcing ribs may be formed somewhere between the die clamping process and the sealing member molding process. That is, the reinforcing ribs may be formed in both the processes. Alternatively, the reinforcing ribs may be formed only in the sealing member molding process, or may be formed only in the die clamping process as in the case of press molding.

Claims

What is claimed is:

1. A method of manufacturing a separator for a fuel cell having a separator body that has a reinforcing rib protruding from a first surface as one of the first surface and a second surface of the separator body in a thickness direction, and a sealing member that is made of an elastomer and that is arranged on the first surface of the separator body, the method comprising:

a separator body arrangement process for arranging, through use of a molding die equipped with a first die having a sealing member recess portion for molding the sealing member and a second die having a rib projection portion for forming the reinforcing rib, the separator body in the second die, with the second surface of the separator body located on the second die side before formation of the reinforcing rib, and with an uncrosslinked material of the elastomer serving as an elastomer material;

a die clamping process for clamping the first die and the second die with the first die superimposed on the second die; and

a sealing member molding process for crosslinking the elastomer material into the sealing member and integrating the sealing member with the first surface of the separator body, by injecting the elastomer material into the sealing member recess portion and heating the molding die, wherein

the reinforcing rib is formed on the separator body along a shape of the rib projection portion, between the die clamping process and the sealing member molding process.

2. The method of manufacturing the separator for the fuel cell according to claim 1, wherein

the rib projection portion of the second die is arranged opposite the sealing member recess portion of the first die, in a die clamping state of the molding die, and

the reinforcing rib is formed along the shape of the rib projection portion, due to pressing of the first surface of the separator body through an injection pressure of the elastomer material and an expansion pressure of the elastomer material at time of heating, in the sealing member molding process.

3. The method of manufacturing the separator for the fuel cell according to claim 2, wherein

the reinforcing rib is smaller in width than the sealing member.

4. The method of manufacturing the separator for the fuel cell according to claim 1, wherein

the rib projection portion of the second die is arranged at a position different from a position opposite the sealing member recess portion of the first die, in a die clamping state of the molding die,

the first die has a rib recess portion that is arranged at a position opposite the rib projection portion and that assumes a shape symmetrical in a complementary manner to the rib projection portion, and

the reinforcing rib is formed by pressing the separator body in the die clamping process.

5. The method of manufacturing the separator for the fuel cell according to claim 1, wherein

the separator body is made of iron, stainless steel, titanium, or aluminum.

6. The method of manufacturing the separator for the fuel cell according to claim 1, wherein

a die clamping pressure in the die clamping process is equal to or higher than a yield stress of the separator body or 0.2% of a proof stress of the separator body.

7. The method of manufacturing the separator for the fuel cell according to claim 1, wherein

the reinforcing rib is arranged along a longitudinal direction of the separator body.

8. The method of manufacturing the separator for the fuel cell according to claim 1, wherein

the sealing member molding process is carried out through injection molding of the elastomer material.

9. The method of manufacturing the separator for the fuel cell according to claim 1, wherein

the separator body has a thickness that is equal to or larger than 0.1 mm and that is equal to or smaller than 0.3 mm.

10. The method of manufacturing the separator for the fuel cell according to claim 1, wherein

a ratio of a height of the reinforcing rib to a thickness of the separator body is equal to or smaller than 0.6.