Manufacturing method of fuel cell separator and fuel cell separator

Abstract

Provided is a fuel cell separator manufacturing method and a fuel cell separator with which a reduction in sealing performance can be suppressed. The present invention is characterized by comprising: a layering step in which a first metal separator (21) and a second metal separator (22) are layered, each metal separator comprising a flat section (30) and bead sections (31) protruding from the flat section (30); and a welding step in which the layered flat sections (30) are welded to each other along the bead sections (31). The present invention is also characterized in that in the welding step, a welding merge section (Z) in which the welded sections merge with each other is formed at a position, on a welding route, which becomes a high rigidity section (U) where the rigidity is high, and / or at a position which is separated from the bead sections (31).

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a fuel cell separator and a fuel cell separator. [Background technology]

[0002] For example, as shown in Patent Document 1, a fuel cell is known in which an electrolyte membrane is sandwiched between a pair of bonded separators (hereinafter simply referred to as "separators") to ensure sealing. The separator is formed by welding together a first metal separator and a second metal separator, each of which has a flat portion and a convex bead portion. A sealing member made of rubber or the like is disposed at the tip of the bead portion. A sealing region is formed by the bead portions of the separators facing each other across the electrolyte membrane. The separator can improve sealing by utilizing the reaction force of the bead portions and the conformability of the sealing member.

[0003] A weld is formed on the overlapping flat portion along the extension direction of the bead portion. The weld can restrict the movement of the bead portion in the planar direction when pressure is applied in the thickness direction of the fuel cell. This makes it possible to maintain a high reaction force of the bead portion and maintain high sealing performance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6368807 Summary of the Invention [Problem to be solved by the invention]

[0005] It is preferable that the reaction force of the bead portion of the separator is uniform throughout. However, because the separator has multiple through-holes, embossments, ribs, protrusions, etc., the rigidity varies at each position. Therefore, it is difficult to make the reaction force of the bead portion uniform.

[0006] Furthermore, because welding is required along the bead portions around the entire circumferential direction of the separator and around the through holes, weld junctions where welded portions meet are inevitably formed. Because the heat input during welding at weld junctions is greater than at other locations, a force pulling the bead portions adjacent to the weld junctions in the planar direction is generated, which may reduce the height of the bead portions and reduce sealing performance. This phenomenon may also occur when welded portions meet on the front and back of the separator.

[0007] The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for manufacturing a fuel cell separator that can suppress deterioration of sealing performance, and a fuel cell separator. [Means for solving the problem]

[0008] In order to solve the above problem, the present invention provides a flat portion 、 A bead portion protruding from the flat portion and a sealing member disposed on the tip end surface of the bead portion. and a welding step of welding the flat portions of the overlapped metal separators together along the bead portions. a pair of fuel cell separators each having the same shape, the pair of opposing sealing members and bead portions sandwiching an electrolyte membrane therebetween to form a sealing region; In the welding step, a welding junction where the welded portions join together is positioned at a high rigidity portion on the welding route along the bead portion. and The welding junction is formed at a position away from the bead portion, the first metal separator and the second metal separator have ribs that connect to the bead portion, and the welding junction is formed at the high-rigidity portion that is formed at a position along the rib on the welding route, and the position away from the bead portion is a position where the effect of thermal contraction on the nearby bead portion is sufficiently small or where the effect of thermal contraction is eliminated.

[0009] In addition, the present invention provides a flat portion 、 A bead portion protruding from the flat portion and a sealing member disposed on the tip end surface of the bead portion. A fuel cell separator in which a first metal separator and a second metal separator are joined by welding, each of which has In the pair of fuel cell separators having the same shape, a seal area is formed by sandwiching an electrolyte membrane between a pair of opposing seal members and bead portions, A position where the weld junction where the welded parts formed by welding join together becomes a high-rigidity part on the weld route along the bead part. and The welding junction is formed at a position away from the bead portion, and the first metal separator and the second metal separator have ribs that connect to the bead portion, and the welding junction is formed at the high-rigidity portion that is formed at a position along the rib on the welding route, and the position away from the bead portion is a position where the effect of thermal contraction on the nearby bead portion is sufficiently small or where the effect of thermal contraction is eliminated.

[0010] According to the present invention, since the weld junction is located in a highly rigid portion, it is possible to ensure the surface pressure (linear pressure) required for sealing even if the reaction force of the bead portion decreases due to thermal contraction. Alternatively, by locating the weld junction at a position away from the bead portion, the effect of thermal contraction can be reduced or eliminated, thereby ensuring the surface pressure (linear pressure) required for sealing. Furthermore, according to the present invention, by forming the weld junction at a position along the rib of the bead portion, which is a high-rigidity portion, it is possible to prevent the height of the bead portion from decreasing.

[0011] It is also preferable that the bead portions of the first metal separator and the second metal separator have a straight portion and a curved portion, and the weld junction is formed in the high-rigidity portion formed at a position along the curved portion of the bead portion on the welding route. 。

[0012] Preferably, the first metal separator and the second metal separator have an embossment, and the weld junction is formed in the high-rigidity portion formed at a position along the embossment on the welding route.

[0013] According to the present invention, the curve of the bead portion, which is a high rigidity portion, Partmata By forming the weld junction at a position along the embossment, it is possible to prevent the height of the bead portion from becoming lower. [Effects of the Invention]

[0014] According to the fuel cell separator manufacturing method and the fuel cell separator of the present invention, deterioration of sealing properties can be suppressed. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 2 is a cross-sectional view of a separator according to Example 1. [Figure 2] FIG. 1 is a cross-sectional view of a fuel cell according to a first embodiment. [Figure 3] FIG. 2 is a plan view of the separator according to the first embodiment. [Figure 4] FIG. 4 is an enlarged plan view of a portion Q in FIG. [Figure 5] FIG. 4 is an enlarged plan view of a portion R in FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0016] The separator manufacturing method and separator according to the embodiment will be described in detail with reference to the drawings. As shown in Fig. 1, the first separator 3 (second separator 4) is a plate-like member used in a fuel cell, and includes a first metal separator 21, a second metal separator 22, and a plurality of sealing members 51. The first metal separator 21 and the second metal separator 22 are joined by welding. A welded portion W is formed by welding on each of the overlapping flat portions 30, 30.

[0017] In the separator manufacturing method according to this embodiment, the weld junction where the welded portions W join together is formed in a position that will become a high-rigidity portion of the first separator 3 (second separator 4) and / or in a position away from the bead portion. Examples will be described in detail below.

[0018] [Example 1] A fuel cell stack is formed by stacking a plurality of fuel cell cells 1 shown in Fig. 2 and applying a predetermined compressive load in the stacking direction of the fuel cell cells 1. Fig. 2 depicts the fuel cell cells 1 in a fastened state with the predetermined compressive load applied.

[0019] The membrane electrode assembly (MEA) 2 includes an electrolyte membrane 11, electrode catalyst layers 12, 12, and gas diffusion layers 13, 13. The electrolyte membrane 11 protrudes outward beyond the gas diffusion layer 13. Note that the portion protruding outward beyond the gas diffusion layer 13 may be a resin film (resin frame member).

[0020] The first separator 3 is a plate-like member arranged on one side (the lower side in FIG. 2) of the membrane electrode assembly 2. The second separator 4 is a plate-like member arranged on the other side (the upper side in FIG. 2) of the membrane electrode assembly 2. Since the first separator 3 and the second separator 4 have the same configuration in this embodiment, the second separator 4 is denoted by the same reference numeral as the first separator 3 and a detailed description thereof will be omitted.

[0021] The bead seal portion 41 is formed by bead portions 31 protruding from the flat portion 30 (see FIG. 1). The joining protrusions 42 are formed by protrusions 32 protruding from the flat portion 30. The bead seal portion 41 protrudes toward the electrolyte membrane 11 (or resin film) and is formed, for example, around the entire outer periphery of the fuel cell 1 so as to be endless. A seal member 51 is arranged at the tip of the bead seal portion 41 along the extension direction of the bead seal portion 41.

[0022] The sealing member 51 is made of an elastic material. The sealing member 51 of this embodiment is, for example, a gasket with a rectangular cross section. The sealing member 51 may be formed, for example, by applying a liquid material to the bead seal portion 41, or by attaching a strip-shaped material to the bead seal portion 41. The sealing member 51 may be made of an elastic material, and examples of materials that can be used include ethylene propylene diene rubber (EPDM), silicone rubber (VMQ), fluororubber (FKM), polyisobutylene (PIB), resin, etc., each having a rubber hardness Hs of 45 to 55.

[0023] A sealed area can be formed by sandwiching the electrolyte membrane 11 between the opposing bead seal portions 41, 41 and the sealing members 51, 51. As shown in Fig. 1, the bead seal portion 41 is formed of bead portions 31, 31 protruding from the flat portion 30, so that the reaction force of the bead portions 31 can be kept high, and high sealing performance can be maintained.

[0024] Next, a method for manufacturing the separator of this embodiment will be described. The method for manufacturing the separator of this embodiment includes a press-molding step, a stacking step, and a welding step.

[0025] 1, the press-molding process is a process in which a material is press-molded to form a first metal separator 21 and a second metal separator 22. The first metal separator 21 and the second metal separator 22 are, for example, thin metal plates with a thickness of about 0.03 to 0.5 mm and a hardness of Hv300 or less.

[0026] In this embodiment, the first metal separator 21 and the second metal separator 22 are made of a material having the same material properties. The molded first metal separator 21 and second metal separator 22 each have a flat portion 30, one or more bead portions 31, and one or more protruding portions 32. The bead portions 31 and the protruding portions 32 protrude from the flat portion 30 and, in this embodiment, have a hollow portion with a trapezoidal cross section. A seal member 51 is provided on the tip surface of the bead portion 31. Note that the shape, number, bead height, and arrangement of the bead portions 31 and the protruding portions 32 are merely examples and may be set as appropriate.

[0027] 3, a plurality of communication holes are formed on both sides in the width direction of the first metal separator 21 and the second metal separator 22. In this embodiment, from one end of the first metal separator 21 and the second metal separator 22, a fuel gas communication hole 61A, a coolant communication hole 62A, an oxygen-containing gas communication hole 63A, a coolant communication hole 62B, and a fuel gas communication hole 61B are formed in this order.

[0028] Additionally, the oxygen-containing gas passage 63B, the coolant passage 62C, the fuel gas passage 61C, the coolant passage 62D, and the oxygen-containing gas passage 63C are formed in this order from the other end of the first metal separator 21 and the second metal separator 22. Each passage is generally rectangular in shape and is made up of straight and curved portions.

[0029] Furthermore, a plurality of reaction gas flow channels 93 through which reaction gas flows are formed along the longitudinal direction in first metal separator 21 and second metal separator 22. Furthermore, an inlet buffer 92 and an outlet buffer 92 each made up of a plurality of embosses are formed on both sides of reaction gas flow channel 93.

[0030] 3, the bead portions 31 are formed at multiple locations on the first metal separator 21 and the second metal separator 22. The bead portions 31 are distinguished by assigning reference numerals such as bead portion 31A, bead portion 31B, bead portion 31C, . . . and bead portion 31K. The bead portion 31A extends around the entire outer periphery of the first metal separator 21 and the second metal separator 22, passing through each of the communication holes in a zigzag pattern, and is formed in an endless state.

[0031] 3, the bead portion 31B is formed so as to be endless around the entire outer periphery of the fuel gas communication hole 61A. The bead portion 31C is formed so as to be endless around the entire outer periphery of the coolant communication hole 62A. The bead portion 31D is formed so as to be endless around the entire outer periphery of the oxygen-containing gas communication hole 63A. The bead portion 31E is formed so as to be endless around the entire outer periphery of the coolant communication hole 62B. The bead portion 31F is formed so as to be endless around the entire outer periphery of the fuel gas communication hole 61B. The planar shape of each of these bead portions is formed to be one size larger along the corresponding communication hole.

[0032] Similarly, the bead portions 31G, 31H, 31I, 31J, and 31K are formed endlessly around the entire outer periphery of the oxygen-containing gas communication hole 63B, the coolant communication hole 62C, the fuel gas communication hole 61C, the coolant communication hole 62D, and the oxygen-containing gas communication hole 63C, respectively. The planar shape of each of these bead portions is formed to be slightly larger in size along the corresponding communication hole.

[0033] The overlapping process is a process of overlapping the first metal separator 21 and the second metal separator 22. In the overlapping process, the first metal separator 21 and the second metal separator 22 are arranged so that the surfaces opposite to the surfaces from which the bead portions 31 protrude face each other, and the flat portions 30, 30 are overlapped.

[0034] The welding process is a process of joining the first metal separator 21 and the second metal separator 22 by welding along a predetermined welding route. In the welding process, a welding device (welding torch) is moved over the flat portions 30 to weld the overlapping flat portions 30 together. A weld (weld bead) W is formed along the path of the welding device. The weld W is formed intermittently or continuously on the inside and / or outside of each bead 31 along each bead 31. The portion where the weld W intersects or where the start and end of the weld W overlap is the weld junction Z. The weld junction Z may also occur when the front and back of the first separator 3 (or the second separator 4) intersect or overlap. After the welding process is completed, a seal member 51 is attached to the leading end surface of each bead 31, completing the first separator 3 (or the second separator 4).

[0035] The welding process will be described in more detail. The welds W are distinguished by assigning reference symbols to the welds W1, W2, W3, . . . for each portion.

[0036] 4 is an enlarged plan view of portion Q (near the fuel gas hole 61A) in FIG. 3. An endless weld W1 is formed along the outer side of the bead 31A. An endless weld W12 is formed along the outer periphery of the fuel gas hole 61A (inside the bead 31A). A plurality of ribs 81 are formed on the bead 31B.

[0037] The ribs 81 are formed so as to intersect the bead portions 31B at right angles. The ribs 81 are formed to protrude from the flat portion 30, similar to the bead portions 31B. The height of the ribs 81 is the same as or smaller than that of the bead portions 31B. The ribs 81 are provided as flow paths for circulating the reaction gas and the coolant. A weld junction Z1 is formed on the weld portion W12 near the rib 81. Furthermore, an endless weld portion W13 is formed on the outside of the bead portion 31C along the bead portion 31C.

[0038] 5 is an enlarged plan view of portion R in FIG. 3 (near the oxidant gas passage 63C). An endless weld W21 is formed along the outer side of the bead 31K. A plurality of embossments 91 are formed on both sides of the weld W21. The embossments 91 protrude from the flat portion 30. The embossments 91 are provided to diffuse the reactive gas. A weld junction Z2 is formed on the weld W21 near the emboss 91. Furthermore, a weld junction Z3 is formed on the weld W21 near the curved portion of the bead 31K.

[0039] Additionally, an endless welded portion W1 is formed along the outer side of bead portion 31A, and an endless welded portion W20 is formed along the outer side of bead portion 31J.

[0040] Next, the effects of this embodiment will be described. Each bead portion 31 in first metal separator 21 and second metal separator 22 has a complex shape with linear portions and curved portions, and therefore has portions with high and low rigidity.

[0041] 4 and 5, for example, the thick solid circle indicates a region that becomes a low linear pressure region S (low linear pressure regions S1, S2). The low linear pressure region S is a region where the linear pressure is lower than the linear pressure required for sealing (the desired bead reaction force of the bead region 31). The bead reaction force of the bead region 31 decreases when the bead height is small or when the rigidity of the bead region 31 is low.

[0042] On the other hand, when welding is performed in the welding process, a weld junction Z is formed where the welds W join together. Because excessive heat input occurs at the weld junction Z during welding, a force pulling the adjacent bead portions 31 in the planar direction is generated, which may reduce the height of the bead portions 31 and reduce the sealing performance. For example, as shown in FIGS. 3 to 5 , in this embodiment, three weld junctions Z are formed (weld junctions Z1 to Z3). The weld junctions Z are unavoidable because the start and end of the welds (weld beads) W must overlap or the welds W must cross during the welding process. However, if the position where the welds W join is close to the low linear pressure portion S, the linear pressure of the low linear pressure portion S will be further reduced. Therefore, if possible in the welding process, it is preferable to form the weld junction Z at a position away from the low linear pressure portion S. Furthermore, if possible in terms of the welding process, it is more preferable to form the weld junction Z at a position that will become the high-rigidity portion U or at a position away from the bead portion 31.

[0043] For example, in Figure 4, the triangle mark V1 indicates the "previous weld junction." The previous weld junction V1 is located near the low linear pressure area S1. Therefore, if the previous weld junction V1 remains in its current position, there is a risk that the linear pressure of the bead 31B near the previous weld junction V1 will be further reduced.

[0044] On the other hand, the portion indicated by the dotted circle in Fig. 4 is a position that will become a high-rigidity portion U1. Because multiple ribs 81 are formed nearby, the high-rigidity portion U1 has higher rigidity than the conventional weld junction V1 on the welding route. Therefore, in this embodiment, the weld junction Z1 is formed at a position that will become the high-rigidity portion U1, replacing the position of the conventional weld junction V1.

[0045] Furthermore, the position indicated by high rigidity portion U1 is distant from bead portion 31B (the distance from bead portion 31B to weld junction Z1 is longer than the distance from bead portion 31B to the conventional weld junction V1), so the effect of thermal contraction on bead portion 31B can be reduced when welding weld junction Z1. In other words, the position of high rigidity portion U1 in this embodiment has high rigidity on the welding route and is sufficiently distant from bead portion 31B, so it is possible to prevent the bead height of bead portion 31B from decreasing and suppress a decrease in sealing performance.

[0046] In addition, in the claims, "forming the weld junction at a position away from the bead portion" means a position where, when the weld junction is welded, the effect of thermal contraction on the nearby bead portion is sufficiently small or is eliminated.

[0047] 5, the previous weld junction V2 is positioned close to the low linear pressure portion S2. Therefore, if the previous weld junction V2 remains in this position, there is a risk that the linear pressure of the bead portion 31K near the previous weld junction V2 will be further reduced.

[0048] On the other hand, the portion indicated by the dotted circle in Figure 5 is a position that will become a high-rigidity portion U2. Because multiple embossments 91 are formed nearby, high-rigidity portion U2 has higher rigidity than the previous weld junction V2 on the weld route. Therefore, in this embodiment, weld junction Z2 is formed at a position that will become the high-rigidity portion U2, replacing the previous weld junction V2. In other words, the position of high-rigidity portion U2 is a position on the weld route where the rigidity is high, preventing the bead height of bead portion 31A from decreasing and suppressing a decrease in sealing performance.

[0049] Furthermore, the position indicated by high rigidity portion U2 is far from bead portion 31K (the distance from bead portion 31K to weld junction Z2 is longer than the distance from bead portion 31K to the previous weld junction V2), so the effect of thermal contraction on bead portion 31K can be reduced when welding weld junction Z2. In other words, the position of high rigidity portion U2 has high rigidity on the welding route and is sufficiently far from bead portion 31K, so it is possible to prevent the bead height of bead portion 31K from decreasing and suppress a decrease in sealing performance.

[0050] As shown in FIG. 5, the weld junction Z3 is formed in a high-rigidity portion U3. The high-rigidity portion U3 is located on the weld route near the curved portion of the bead portion 31K, and therefore has high rigidity. This prevents the height of the bead portion 31K from decreasing, thereby preventing a decrease in sealing performance. The curved portion of the bead portion 31 generally has higher rigidity than the straight portion. The curved portion of the bead portion 31 also includes, for example, a portion where the shape of the bead portion 31 is wavy in plan view.

[0051] Although the above describes the embodiments, appropriate design modifications are possible. For example, in the above embodiments, the weld junction Z is located at the position of the high-rigidity portion U and at a position sufficiently distant from the bead portion 31. However, to the extent possible in the welding process, the weld junction Z may be located at the position of the high-rigidity portion U, or may be located at a position sufficiently distant from the bead portion 31. Furthermore, in the present embodiments, the case where the rib communicates with the bead portion 31 has been illustrated, but in cases where the rib and the bead portion 31 do not communicate with each other, the weld junction Z may be located near the rib.

[0052] In addition, in the examples, the high rigidity portion U is exemplified as being near the curved portion of the bead portion 31 on the welding route, near the rib, and near the embossment, but any point on the welding route that has higher rigidity than that point may be set as the high rigidity portion U. [Explanation of symbols]

[0053] 1 Fuel cell 2 Electrolyte membrane / electrode structure 3 First separator (separator) 4 Second separator (separator) 11 Electrolyte membrane (film) 21 First metal separator 22 Second metal separator 81 Ribs 91 Emboss S Low linear pressure section U High rigidity part W welded section Z-weld junction

Claims

1. a laminating step of laminating a first metal separator and a second metal separator, each of which has a flat portion, a bead portion protruding from the flat portion, and a sealing member disposed on a tip end surface of the bead portion; a welding step of welding the overlapped flat portions together along the bead portions, In a pair of fuel cell separators having the same shape, a seal area is formed by sandwiching an electrolyte membrane between a pair of opposing seal members and bead portions, In the welding step, a weld junction where the welded portions join together is formed at a position that becomes a high-rigidity portion on a welding route along the bead portion and at a position away from the bead portion, the first metal separator and the second metal separator each have a rib connected to the bead portion, and the weld junction is formed in the high-rigidity portion formed at a position along the rib on the welding route; A method for manufacturing a fuel cell separator, characterized in that the position away from the bead portion is a position where the effect of thermal contraction on the nearby bead portion is sufficiently small or where the effect of thermal contraction is eliminated.

2. the bead portions of the first metal separator and the second metal separator each include a linear portion that is linear and a curved portion that is curved, 2. The method for manufacturing a fuel cell separator according to claim 1, wherein the weld junction is formed in the high-rigidity portion formed at a position along the curved portion of the bead portion on the welding route.

3. the first metal separator and the second metal separator have embossments; 2. The method for manufacturing a fuel cell separator according to claim 1, wherein the weld junction is formed in the high-rigidity portion formed at a position along the embossment on the welding route.

4. A fuel cell separator formed by welding a first metal separator and a second metal separator, each of which has a flat portion, a bead portion protruding from the flat portion, and a sealing member disposed on a tip end surface of the bead portion, In a pair of fuel cell separators having the same shape, a seal area is formed by sandwiching an electrolyte membrane between a pair of opposing seal members and bead portions, a weld junction where welded portions formed by welding join together is formed at a position that becomes a high-rigidity portion on the weld route along the bead portion and at a position away from the bead portion, the first metal separator and the second metal separator each include a rib connected to the bead portion, and the weld junction is formed in the high-rigidity portion formed at a position along the rib on the welding route; The position away from the bead portion is a position where the influence of thermal contraction on the adjacent bead portion is sufficiently small or is eliminated.

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