Patent Application
20240238900
The present invention relates to a manufacturing method of a fuel cell separator and the fuel cell separator.
For example, there is known a fuel cell which secures a sealing property by causing a pair of joining separators (hereinafter, also referred simply to as “separators”) to hold an electrolyte membrane therebetween, as described in JP6368807B. Each separator is formed by joining a first metal separator and a second metal separator by welding, the first metal separator and the second metal separator each including a flat portion and a bead portion having a protruding shape. A sealing member made of rubber or the like is arranged at a distal end of the bead portion. The bead portions of the separators are made to face each other while holding the electrolyte membrane therebetween, and a sealing region is thereby formed. Reaction force of the bead portions and a following capability of the sealing members can improve a sealing property of the separators.
A welded portion is formed along an extending direction of the bead portions in the flat portions laid one on top of another. The welded portion can restrict movement of the bead portions spreading in a planar direction in the case where pressure acts in a thickness direction of the fuel cell. This allows the bead portions to maintain high reaction force, and a high sealing property can be maintained.
The reaction force of the bead portions of the separators is preferably uniform over the entire bead portions. However, since multiple through-holes, embossed portions, ribs, protruding portions, and the like are formed in the separators, stiffness varies depending on the area. Accordingly, making the reaction force of the bead portions uniform is difficult.
Moreover, since the welding needs to be performed along the bead portions over the entire periphery of the separator in a circumferential direction and peripheries of the through-holes, weld meeting points where welded portions meet are inevitably formed. In each weld meeting point, heat input in the welding is excessive compared to the other portions. Accordingly, force pulling the bead portion adjacent to the weld meeting point in the planar direction is generated, and there is a risk that the height of the bead portion is reduced and the sealing property is also reduced. Such a phenomenon may occur also when the welded portions meet on the front and back sides of the separator.
The present invention has been made to solve such problems, and an object is to provide a manufacturing method of a fuel cell separator and a fuel cell separator that can prevent a reduction of a sealing property.
The present invention for solving the above problems includes: an overlaying step of overlaying a first metal separator and a second metal separator together, the first metal separator and the second metal separator each including a flat portion and a bead portion protruding from the flat portion, and a welding step of welding along the bead portion overlaid flat portions, and, in the welding step, a weld meeting point where welded portions meet is formed at an area which is away from the bead portion and/or which is to be a high stiffness part with a high stiffness on a welding path.
Moreover, the present invention is a fuel cell separator including a first metal separator and a second metal separator which are joined together by welding, the first metal separator and the second metal separator each including a flat portion and a bead portion protruding from the flat portion, and the fuel cell separator has a weld meeting point where welded portions formed by using welding meet, the weld meeting point being formed at an area which is away from the bead portion and/or is to be a high stiffness part with a high stiffness on a welding path.
According to the present invention, the weld meeting point is located in the high-stiffness part with a high stiffness. Accordingly, even if a reduction of reaction force of the bead portion due to thermal contraction occurs, surface pressure (linear pressure) required for sealing can be secured. Moreover, locating the weld meeting point at an area away from the bead portion can reduce or eliminate an effect of the thermal contraction. Accordingly, the surface pressure (linear pressure) required for sealing can be secured.
Moreover, it is preferable that the bead portion of each of the first metal separator and the second metal separator includes a linear portion with a linear shape and a curved portion with a curved shape, and the weld meeting point is formed at the high stiffness part formed at a position along the curved portion of the bead portion and on the welding path.
Furthermore, it is preferable that the first metal separator and the second metal separator include a rib coupled to the bead portion, and the weld meeting point is formed at the high stiffness part formed at a position along the rib and on the welding path.
Moreover, it is preferable that the first metal separator and the second metal separator include an embossed portion, and the weld meeting point is formed at the high stiffness part formed at a position along the embossed portion on the welding path.
According to the present invention, forming the weld meeting point at the position along the curved portion of the bead portion, the rib, or the embossed portion that are the high stiffness parts can prevent a reduction of the height of the bead portion.
According to the manufacturing method of a fuel cell separator and the fuel cell separator of the present invention, a reduction of a sealing property can be prevented.
A manufacturing method of a separator and the separator according to an embodiment are described in detail with reference to the drawings. As shown in
In the manufacturing method of the separator according to the present embodiment, a weld meeting point where the welded portions W meet is formed at an area which is to be a high stiffness part with a high stiffness and/or which is away from a bead portion in the first separator 3 (second separator 4). Examples are described below in detail.
A fuel cell stack is a stack in which multiple fuel cells 1 shown in
A membrane electrode assembly (MEA) 2 is configured to include an electrolyte membrane 11, electrode catalyst layers 12, 12, and gas diffusion layers 13, 13. The electrolyte membrane 11 protrude out of the gas diffusion layers 13. Note that a portion of the electrolyte membrane 11 protruding out of the gas diffusion layers 13 is a resin film (resin frame member) in some cases.
The first separator 3 is a plate shaped member arranged on one side (lower side in
Bead sealing portions 41 are formed of bead portions 31 protruding from flat portions 30 (see
The sealing members 51 are made of an elastic material. The sealing members 51 of the present example are, for example, gaskets with a rectangular cross section. The sealing members 51 may be formed by, for example, applying a liquid-state material to the bead sealing portions 41 or by attaching a strip shaped material to the bead sealing portions 41. The sealing members 51 only need to be made of an elastic material, and, for example, ethylene propylene diene rubber (EPDM) with a rubber hardness of Hs 45 to 55, silicone rubber (VMQ), fluoro-rubber (FKM), polyisobutylene (PIB), a resin, or the like may be used.
The bead sealing portions 41, 41 and the sealing members 51, 51 facing one another can form sealing regions by holding the electrolyte membrane 11 therebetween. Since the bead sealing portions 41 are formed of the bead portions 31, 31 protruding from the flat portions 30 as shown in
Next, the manufacturing method of the separator in the present example is described. In the manufacturing method of the separator in the present example, a press forming step, an overlaying step, and a welding step are performed.
As shown in
The first metal separator 21 and the second metal separator 22 use materials with the same material properties in the present example. The formed first metal separator 21 and second metal separator 22 each include the flat portion 30, single or multiple bead portions 31, and single or multiple protruding portions 32. The bead portions 31 and the protruding portions 32 protrude from the flat portion 30, and include hollow portions with trapezoidal cross sections in the present example. The sealing members 51 are provided on distal end surfaces of the bead portions 31. Note that the shapes, numbers, bead heights, and arrangement of the bead portions 31 and the protruding portions 32 are merely examples, and may be set as appropriate.
As shown in
Moreover, an oxidizer gas communication hole 63B, a fuel cooling medium communication hole 62C, a gas communication hole 61C, a cooling medium communication hole 62D, and an oxidizer gas communication hole 63C are formed in this order in an end portion on the other side of each of the first metal separator 21 and the second metal separator 22. The shape of each communication hole is formed of linear portions and curved portions, and has a substantially rectangular shape.
Moreover, multiple reaction gas flow passages 93 through which a reaction gas flows are formed in the first metal separator 21 and the second metal separator 22 along a longitudinal direction. An entrance buffer 92 and an exit buffer 92 formed of multiple embossed portions are formed on both sides of the reaction gas flow passages 93.
As shown in
Moreover, as shown in
Similarly, the bead portions 31G, 31H, 31I, 31J, and 31K are formed over the entire circumferences of outer peripheral edges of the oxidizer gas communication hole 63B, the cooling medium communication hole 62C, the fuel gas communication hole 61C, the cooling medium communication hole 62D, and the oxidizer gas communication hole 63C, respectively, to be in endless states. A plan shape of each of these bead portions is formed to be slightly larger than the corresponding communication hole to extend along the corresponding communication hole.
The overlaying step is a step of overlaying the first metal separator 21 and the second metal separator 22 together. In the overlaying step, surfaces of the first metal separator 21 and the second metal separator 22 on the opposite sides to surfaces where the bead portions 31 protrude are made to face each other, and the flat portions 30, 30 are overlaid one on top of the other.
The welding step is a step of joining the first metal separator 21 and the second metal separator 22 by welding along welding paths set in advance. In the welding step, a welding device (welding torch) is made to run from above the flat portion 30 to weld the overlaid flat portions 30, 30. Welded portions (welding bead) W is formed along movement trajectories of the welding device. The welded portions W are intermittently or continuously formed the inner side and/or the outer side of each bead portion 31 to extend along the bead portion 31. Portions where the welded portions W intersect each other or portions where a start end and a terminal end of the welded portion W overlap each other are weld meeting points Z. The weld meeting points Z include cases where the welded portions W intersect or overlap each other on the front and back sides of the first separator 3 (or the second separator 4). When the welding step is completed, the sealing member 51 is installed on the distal end surface of each bead portion 31, and the first separator 3 (second separator 4) is thereby completed.
The welding step is described in further detail. The welded portions W are distinguished according to parts by being denoted by reference signs such as welded portion W1, welded portion W2, welded portion W3, and so on.
The ribs 81 are each formed orthogonal to the bead portion 31B. The ribs 81 are formed to protrude from the flat portion 30 like the bead portion 31B. The height dimension of the ribs 81 is the same as that of the bead portion 31B or is smaller than that of the bead portion 31B. The ribs 81 are provided as flow passages that allow the reaction gas and the cooling medium to flow. A weld meeting point Z1 is formed on the welded portion W12, near the ribs 81. Moreover, a welded portion W13 with an endless shape is formed outside the bead portion 31C, along the bead portion 31C.
Moreover, the welded portion W1 with the endless shape is formed outside the bead portion 31A, along the bead portion 31A. Furthermore, a welded portion W20 with an endless shape is formed outside the bead portion 31J, along the bead portion 31J.
Next, operations and effects of the present example are described. Each bead portion 31 has a complex shape including the linear portion having a linear shape and the curved portion having a curved shape, in the first metal separator 21 and the second metal separator 22. Accordingly, the bead portion 31 has a portion with a high stiffness and a portion with a low stiffness.
For example, in
Meanwhile, when the welding is performed in the welding step, the weld meeting points Z where the welded portions W meet are formed. Since excessive heat is inputted in each weld meeting point Z in the welding, force pulling the adjacent bead portion 31 in a planar direction is generated, and there is a risk that the height of the bead portion 31 is reduced and the sealing property is also reduced. For example, as shown in
For example, in
Meanwhile, a portion shown by a dotted line circle in
Moreover, since the area shown by the high-stiffness part U1 is away from the bead portion 31B (a distance from the bead portion 31B to the weld meeting point Z1 is larger than a distance from the bead portion 31B to the prior weld meeting point V1), the effect of thermal contraction on the bead portion 31B in the welding of the weld meeting point Z1 can be reduced at this area. Specifically, since the area of the high-stiffness part U1 in the present example is an area with a high stiffness on the welding path and is sufficiently away from the bead portion 31B, it is possible to prevent the reduction of the bead height of the bead portion 31B and prevent the reduction of the sealing property.
Note that “the weld meeting point is formed at an area away from the bead portion” in the claims means an area where the effect of the thermal contraction on the nearby bead portion is sufficiently small or an area where the effect of the thermal contraction is eliminated when the welding is performed on the weld meeting point.
Moreover, in
Meanwhile, a portion shown by a dotted line circle in
Moreover, since the area shown by the high-stiffness part U2 is away from the bead portion 31K (a distance from the bead portion 31K to the weld meeting point Z2 is larger than a distance from the bead portion 31K to the prior weld meeting point V2), the effect of thermal contraction on the bead portion 31K in the welding of the weld meeting point Z2 can be reduced at this area. Specifically, since the area of the high-stiffness part U2 is an area with a high stiffness on the welding path and is sufficiently away from the bead portion 31K, it is possible to prevent the reduction of the bead height of the bead portion 31K and prevent the reduction of the sealing property.
Moreover, as shown in
Although the example has been described above, design changes can be made as appropriate. For example, in the above example, the weld meeting point Z is at the area that is at the high-stiffness part U and that is sufficiently away from the bead portion 31. However, the weld meeting point Z may be formed at an area at the high-stiffness part U, or may be formed at an area sufficiently away from the bead portion 31, within a range where this is possible in terms of the welding step. Moreover, although the case where the ribs communicate with the bead portion 31 is given as an example in the present example, the weld meeting point Z may be set near the ribs in the case where the ribs and the bead portion 31 do not communicate with each other.
Moreover, although the portion near the curved portion of the bead portion 31, the portion near the ribs, and the portion near the embossed portions and on the welding path are given as examples of the high-stiffness part U in the present example, an area that has a higher stiffness than a certain area on the welding path may be set as the high-stiffness part U.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-082987 | May 2021 | JP | national |
This application is a 371 U.S. National Phase of International Application No. PCT/JP2022/010239, filed on Mar. 9, 2022, which claims priority to Japanese Patent Application No. 2021-082987, filed May 17, 2021. The entire disclosures of the above applications are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/010239 | 3/9/2022 | WO |
