WO2005112160A1

WO2005112160A1 - Fuel cell separator

Info

Publication number: WO2005112160A1
Application number: PCT/IB2005/001301
Authority: WO
Inventors: Kei Morohoshi
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2004-05-17
Filing date: 2005-05-12
Publication date: 2005-11-24
Also published as: JP2005327670A

Abstract

A fuel cell separator (6) is formed by stacking two separator plates (20, 30) having the same shape on each other. Each of the two separator plates (20, 30) has corrugation portions (22, 32) formed with a predetermined pattern, and the corrugation portions (22, 32) have the same height. The two separator plates (20, 30) are stacked on each other such that convex portions (22a) of the corrugation portions (22) of one separator plate (20) are fitted in concave portions (32b) of the corrugation portions (32) of the other separator plate (30), and convex portions (32a) of the corrugation portions (32) of the other separator plate (30) are fitted in concave portions (22b) of the corrugation portions (22) of the one separator plate (20). Spaces are formed between the two separator plates (20, 30), and the spaces configure coolant passages (40, 42).

Description

FUEL CELL SEPARATOR BACKGROUND OF THE INVENTION

1. Field of the Invention [0001] The invention relates to a fuel cell separator. More particularly, the invention relates to a fuel cell separator formed by stacking two corrugated separator plates on each other. 2. Description of the Related Art [0002] Generally, a fuel cell is formed as a fuel cell stack that is formed by stacking multiple cells. Each of the cells includes a membrane electrode assembly (hereinafter, referred to as a "MEA") that is formed by sandwiching an ion conductive electrolyte membrane between two electrodes. Sandwiching the MEA between two separators forms the cell. Each separator has a gas passage through which fuel gas is supplied to the anode, a gas passage through which oxidizing gas is supplied to the cathode, and coolant passage through which coolant flows. [0003] One of the requests concerning a fuel cell is a downsizing of the fuel cell. Reduction in a thickness of each cell, especially, reduction in a thickness of each separator is an important factor in downsizing a fuel cell. In order to realize a separator having a reduced thickness, it has been suggested that a separator be prepared by pressing a thin metal plate. [0004] For example, Japanese Patent Application Publication No. JP(A) 2002- 100381 discloses a technology in which a separator is formed by integrally combining two separator plates each of which is prepared by shaping a metal plate into a corrugated plate. Two separator plates are different from each other in the height of a corrugation portion. However, the two separator plates are the same in a pattern with which the corrugation portions are formed. Convex portions of the separator plate whose corrugation portion has a smaller height are fitted in concave portions of the separator plate whose corrugation portion has a larger height. According to this technology, spaces formed between an anode of a MEA and the separator plate whose corrugation portion has a smaller height are used as fuel gas passages, spaces formed between a cathode of the MEA and the separator plate whose corrugation portion has a larger height are used oxidizing gas passages, and spaces formed between the concave portions and the convex portions are used as coolant passages. [0005] Japanese Patent Application Publication No. JP(A) 2003-151571 discloses a technology in which two separator plates, each of which is prepared by shaping a metal plate into a corrugated plate, are stacked on each other with a metal intermediate plate interposed therebetween. According to this technology, spaces formed between an anode of a MEA and the separator plate adjacent to the anode are used as fuel gas passages, spaces formed between a cathode of the MEA and the separator plate adjacent to the cathode are used as oxidizing gas passages, and spaces formed between each separator plate and the intermediate plate are used as coolant passages. [0006] However, in the technology disclosed in Japanese Patent Application Publication No. JP(A) 2002-100381, the coolant passages contact the MEA only on the cathode side. Therefore, the MEA cannot be cooled from the anode side, and therefore the MEA may not be cooled sufficiently. Also, two types of separator plates whose shapes are different from each other need to be prepared, which causes an increase in cost. [0007] In the technology disclosed in Japanese Patent Application Publication No. JP(A) 2003-151571, the coolant passages are formed on both the anode side and the cathode side of the MEA. Therefore, the cooling performance of the fuel cell is ensured. Also, the two separator plates have the same shape. Accordingly, the separator plates can be prepared at a low cost, as compared to the case where two or more types of separator plates whose shapes are different from each other need to be prepared. However, according to this technology, the thickness of the separator cannot be reduced sufficiently. Since the separator plates are stacked on each other with the intermediate plate interposed therebetween, the entire thickness of the separator becomes substantially equal to the total thickness of two separator plates.

SUMMARY OF THE INVENTION

[0008] The invention is made in order to solve the above-mentioned problems. It is therefore an object of the invention to realize a fuel cell separator having a reduced thickness without deteriorating cooling performance. [0009] In a fuel cell separator according to a first aspect of the invention, a first separator plate and a second separator plate which have the same shape and each of which has corrugation portions formed with a predetermined pattern, the corrugation portions of the first separator plate and the corrugation portions of the second separator plate having the same height, are stacked on each other such that convex portions of the corrugation portions of the first separator plate are fitted in concave portions of the corrugation portions of the second separator plate, and convex portions of the corrugation portions of the second separator plate are fitted in concave portions of the corrugation portions of the first separator plate, whereby spaces formed between the convex portions of the corrugation portions of the first separator plate and the concave portions of the corrugation portions of the second separator plate and spaces formed between the convex portions of the corrugation portions of the second separator plate and the concave portions of the corrugation portions of the first separator plate form coolant passages through which coolant flows. [0010] In the first aspect, the first separator plate and the second separator plate are stacked on each other such that the convex portions of the corrugation portions of the first separator plate are fitted in the concave portions of the corrugation portions of the second separator plate, and the convex portions of the corrugation portions of the second separator plate are fitted in the concave portions of the corrugation portions of the first separator plate. Accordingly, the entire thickness of the separator can be made smaller than the total thickness of the two separator plates. In addition, when the fuel cell separators are combined with MEAs, the coolant passages contact the MEAs on both the anode side and the cathode side. Therefore, each MEA can be cooled from both the anode side and the cathode side. According to the first aspect, it is possible to realize a fuel cell separator having a reduced thickness while ensuring sufficient cooling performance. [0011] In the first aspect, a stopper portion may be formed on a surface of at least one of the first separator plate and the second separator plate in order to reliably maintain the space. It is therefore possible to reliably maintain spaces for the coolant passages with a simple structure. [0012] In the first aspect, the corrugation portions may be formed at constant intervals. [0013] In the aspect, the stopper portion may be a protrusion. [0014] In the first aspect, a conductive spacer may be provided in the space in order to reliably maintain the space. It is therefore possible to reliably maintain spaces for the coolant passages with a simple structure. It is also possible to arbitrarily adjust a cross sectional area of each of the coolant passages. [0015] In the first aspect, a height of each of the coolant passages in a direction in which the first separator plate and the second separator plate are stacked on each other may be 0.1 to 0. 5 mm.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 is a cross sectional view of a fuel cell to which a fuel cell separator according to an embodiment of the invention is applied; [0017] FIG. 2 is an enlarged view of a cross section of a cell of the fuel cell according to the embodiment showing in FIG. 1 ; and [0018] FIG. 3 is a graph showing a relationship between a height h of coolant passage and a bending angle θ. [0019] FIG. 4A, 4B are an enlarged view of a cross section of a cell of a fuel cell showing another embodiment of the invention. [0020] FIG. 5 is an enlarged view of a cross section of a cell of a fuel cell showing another embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the invention will be described with reference to FIGS. 1 to 3. In the embodiment, a fuel cell separator according to the invention is applied to a polymer electrolyte fuel cell. FIG. 1 a cross sectional view of a fuel cell 2 to which the fuel cell separator according the invention is applied. The fuel cell 2 is formed by alternately stacking membrane electrode assemblies (hereinafter, referred to as "MEAs") 4 and separators 6. [0022] Each of the MEAs 4 is formed by sandwiching a polymer electrolyte membrane 10 between an anode 12 and a cathode 14. The polymer electrolyte membrane 10 is a non-conductive ion exchange membrane through which hydrogen ions permeate in a humid state. Each of the anode 12 and the cathode 14 includes a catalytic layer and a diffusion layer. The catalytic layer is formed of platinum, carbon and an electrolyte. The diffusion layer has gas permeability, and is formed of carbon. [0023] The separator 6 is formed by stacking two separator plates 20 and 30 on each other. Hereinafter, the separator plate which contacts the cathode 14 is referred to as the first separator plate 20, and the separator plate which contacts the anode 12 is referred to as the second separator plate 30. Corrugation portions 22 are formed in the first separator plate 20 with a predetermined pattern. Corrugation portions 32 are formed in the second separator plate 30 with the predetermined pattern. The corrugation portions 22 and the corrugation portions 32 have the same height. Each of the two separator plates 20 and 30 is formed, for example, by pressing a metal plate having a constant thickness into a corrugated plate. The two separator plates 20 and 30 have the same shape. [0024] FIG. 2 is an enlarged view of a cross section of a cell of the fuel cell 2 shown in FIG. 1. As shown in FIG. 2, the corrugation portions 22 of the separator plate 20 are formed by pressing a metal plate such that horizontal portions 24 and inclined portions 26 are alternately formed in the metal plate. The corrugation portions 32 of the separator plate 30 are formed by pressing a metal plate such that horizontal portions 34 and inclined portions 36 are alternately formed in the metal plate. In the separator plate 20, a convex bend surface formed by the horizontal portion 24 and the inclined portions 26 on both sides of the horizontal portion 24 forms a convex portion 22a of the corrugation portion 22, and a concave bend surface formed by the horizontal portion 24 and the inclined portions 26 on both sides of the horizontal portion 24 forms a concave portion 22b of the corrugation portion 22. In the separator plate 30, a convex bend surface formed by the horizontal portion 34 and the inclined portions 36 on both sides of the horizontal portion 34 forms a convex portion 32a of the corrugation portion 32, and a concave bend surface formed by the horizontal portion 34 and the inclined portions 36 on both sides of the horizontal portion 34 forms a concave portion 32b of the corrugation portion 32. [0025] The first separator plate 20 and the second separator plate 30 are integrally stacked on each other such that the convex portions 22a of the corrugation portions 22 of the first separator plate 20 are fitted in the concave portions 32b of the corrugation portions 32 of the second separator plate 30, and the convex portions 32a of the corrugation portions 32 of the second separator plate 30 are fitted in the concave portions 22b of the corrugation portions 22 of the first separator plate 20. As a result, the first separator plate 20 and the second separator plate 30 contact each other at the inclined portions 26 and the inclined portions 36, and spaces are formed between the horizontal portions 24 of the first separator plate 20 and the horizontal portions 34 of the second separator plate 30. In the separator 6, these spaces are used as coolant passages 40 and 42 through which coolant, for example, water flows. Spaces formed between the concave portions 22b of the corrugation portions 22 of the first separator plate 20 and the cathode 14 are used as oxidizing gas passages 46, and spaces formed between the concave portions 32b of the corrugation portions 32 of the second separator plate 30 and the anode 12 are used as fuel gas passages 44. [0026] In the embodiment, a thickness t of each of the separator plates 20 and 30 is set to 0.1 mm. Also, a height of each of the corrugation portions 22 and 32, that is a height H of each of the fuel gas passage 44 and the oxidizing gas passage 46 is set to 0.5 mm. At this time, a distance between the horizontal portion 24 and the horizontal portion 34, that is, a height h of each of the coolant passages 40 and 42 can be arbitrarily adjusted based on a bending angle θ of the inclined portions 26 and 36 with respect to the horizontal portions 24 and 34, respectively. If the height h of each of the coolant passages 40 and 42 is excessively small, a passage resistance increases, and a required flow rate cannot be obtained. Therefore, the height h of each of the coolant passages 40 and 42 needs to be a value in an appropriate range. As mentioned above, in the case where the height H of each of the fuel gas passage 44 and the oxidizing gas passage 46 is 0.5 mm, considering the flow rates of the fuel gas and the oxidizing gas, preferably, the height h of each of the coolant passages 40 and 42 is in a range of approximately 0.1 mm to approximately 0.5 mm. [0027] FIG. 3 is a graph showing a relationship between the height h of each of the coolant passages 40 and 42, and the bending angle θ. As can be seen from the graph, in order to set the height h of each of the coolant passages 40 and 42 to a value in the above-mentioned range, the bending angle θ needs to be set to a value in a range of approximately 60 degrees to approximately 80 degrees. When the bending angle θ is 60 degrees, the height h of each of the coolant passages 40 and 42 is 0.1 mm. When the bending angle θ is 80 degrees, the height h of each of the coolant passages 40 and 42 is 0.46 mm. In the embodiment, when a thickness t of each of the separator plates 20 and 30 is 0.1 mm, and the height H of each of the corrugation portions 22 and 32 is 0.5 mm, the range of approximately 60 degrees to approximately 80 degrees is the appropriate range for the bending angle θ. FIG. 2 shows the case where the bending angle θ is set to 75 degrees. In this case, the height h of each of the coolant passages 40 and 42 is 0.29 mm. [0028] With the above-mentioned structure, the two separator plates 20 and 30 are stacked on each other such that the corrugation portions 22 of the separator plate 20 and the corrugation portions 32 of the separator plate 30 are engaged with each other. As a result, the entire thickness of the separator 6 can be made smaller than the total thickness of the two separator plates 20 and 30. It is therefore possible to sufficiently reduce the thickness of the separator 6, thereby reducing the length of the fuel cell 2 in the direction in which cells are stacked. In addition, the separator plates 20 and 30 have the same shape. Therefore, it is also possible to suppress the unit price of the separator plates 20 and 30 in mass production, as compared to the case where two or more types of the separator plates whose shapes are different from each other need to be prepared. [0029] Also, the cathode 14 contacts the convex portions 22a of the corrugation portions 22 of the first separator plate 20. The coolant passages 40 are formed between the concave portions 22b, which are on the opposite side of the convex portions 22a, of the corrugation portions 22 of the first separator plate 20, and the convex portions 32a of the corrugation portions 32 of the second separator plate 30. Meanwhile, the anode 12 contacts the convex portions 32a of the corrugation portions 32 of the second separator plate 30. The coolant passages 42 are formed between the concave portions 32b, which are on the opposite side of the convex portions 32a, of the corrugation portions 32 of the second separator plate 30, and the convex portions 22a of the corrugation portions 22 of the first separator plate 20. Therefore, with the fuel cell 2 according to the embodiment, the MEA 4 can be efficiently cooled from both the anode 12 side and the cathode 14 side. It is therefore possible to achieve high cooling performance. [0030] While the invention has been described in detail with reference to the preferred embodiment, the invention is not limited to the above-mentioned embodiment, and the invention may be realized in various other embodiments within the scope of the invention. For example, the invention may be realized in the following modified examples. [0031] As shown in FIGS. 4A and 4B, in the structure according to the above- mentioned embodiment, a stopper portion (e.g., a protrusion 50, 52) may be formed on the surface of the inclined portion 26 of the first separator plate 20, which faces the second separator plate 30, and/or a stopper portion (e.g., a protrusion 50, 52) may be formed on the surface of the inclined portion 36 of the second separator plate 30, which faces the first separator plate 20. Then, the separator plates 20 and 30 may be stacked on each other with the stopper portion interposed therebetween. Each of the protrusions 50 and 52 is formed by bonding a conductive material, for example, carbon and metal, to the surface of the inclined portion 26 and/or bonding a conductive material to the surface of the inclined portion 36. Stacking the separator plates 20 and 30 on each other with the stopper portion interposed therebetween makes it possible to reliably maintain the spaces for the coolant passages 40 and 42. [0032] Also, as shown in FIG. 5, in the structure according to the above- mentioned embodiment, a spacer may be provided between the inclined portion 26 of the first separator plate 20 and the inclined portion 36 of the second separator plate 30, and the two separator plates 20 and 30 may be stacked on each other with the spacer provided therebetween. Each spacer is formed of a conductive material, for example, carbon and metal. Stacking the separator plates 20 and 30 on each other with the spacer provided therebetween makes it possible to reliably maintain the spaces for the coolant passages 40 and 42. Also, it is possible to arbitrarily adjust the cross sectional area of each of the coolant passages 40 and 42 by changing the thickness of the spacer.

Claims

CLAIMS:

1. A fuel cell separator, characterized in that a first separator plate and a second separator plate which have the same shape and each of which has corrugation portions formed with a predetermined pattern, the corrugation portions of the first separator plate and corrugation portions of the second separator plate having the same height, are stacked on each other such that convex portions of the corrugation portions of the first separator plate are fitted in concave portions of the corrugation portions of the second separator plate, and convex portions of the corrugation portions of the second separator plate are fitted in concave portions of the corrugation portions of the first separator plate, whereby spaces formed between the convex portions of the corrugation portions of the first separator plate and the concave portions of the corrugation portions of the second separator plate and spaces formed between the convex portions of the corrugation portions of the second separator plate and the concave portions of the corrugation portions of the first separator plate form coolant passages through which coolant flows.

2. The fuel cell separator according to claim 1, characterized in that the corrugation portions formed at constant intervals.

3. The fuel cell separator according to claim 1 or 2, characterized in that a stopper portion is formed on a surface of at least one of the first separator plate and the second separator plate in order to reliably maintain the space.

4. The fuel cell separator according to claim 3, characterized in that the stopper portion is a protrusion.

5. The fuel cell separator according to any one of claims 1 to 4, characterized in that a conductive spacer is provided in the space in order to reliably maintain the space.

6. The fuel cell separator according to any one of claims 1 to 5, characterized in that a height of each of the coolant passages in a direction in which the first separator plate and the second separator plate are stacked on each other is 0.1 to 0. 5 mm.