JP2008171638A - Fuel cell separator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator for a fuel cell capable of improving flow easiness of a fluid between flow passages. <P>SOLUTION: This separator (12A) for the fuel cell is equipped with a first and a second flow passages (71A1, 71A2) which are extended and exist mutually in parallel and which are neighboring, and a third flow passage (72A1-2) which is communicated between the first and second flow passages so that the fluid flows between the first and the second flow passages. Then, the third flow passage (72A1-2) is inclined and has a small cross-sectional area against the first and second flow passages (71A1, 71A2). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell separator, and more particularly to a flow path structure of a fuel cell separator.

  Conventionally, a single cell of a polymer electrolyte fuel cell includes an MEA (Membrane Electrode Assembly) composed of an electrolyte membrane and a pair of electrodes that sandwich the electrolyte membrane, and a pair of separators that sandwich the MEA (for example, (See Patent Document 1).

In the separator described in Patent Document 1, the convex portion on the surface on the MEA side contacts the electrode to form a conductive passage, and the concave portion on the surface on the MEA side forms a flow path for the reaction gas. A plurality of the recesses extend in parallel to form a plurality of straight flow paths as reaction gas flow paths. A cross channel having a smaller cross-sectional area than the straight channel is formed in a groove shape on the convex portion, and the adjacent straight channels are connected to each other by the cross channel. According to such a separator, the reaction gas flows between the straight flow paths via the cross flow path, and it is expected that the straight flow path is prevented from being blocked by flooding.
Japanese Patent Laid-Open No. 2004-247061

  In such a patent document 1, although the thing compared with the straight flow path about the pitch and length of a cross flow path is examined, the ease of the flow of the reaction gas in a cross flow path is not fully examined. However, further improvements were required.

  An object of this invention is to provide the separator for fuel cells which can improve the ease of the flow of the fluid between flow paths.

  In order to achieve the above object, a fuel cell separator of the present invention includes a first flow path having a first cross-sectional area, and a second flow having a second cross-sectional area adjacent to the first flow path. A third flow path that communicates between the first and second flow paths so that fluid flows between the path and the first and second flow paths, and is smaller than the first and second cross-sectional areas. A third flow path having a cross-sectional area of The third flow path communicates between points where the fluid pressure difference occurs.

  According to this configuration, in the third flow path, the fluid flows from a point having a high pressure to a point having a low pressure among the points communicating with the first flow path and the second flow path. By adopting such a communication mode, the flow of fluid from one of the first and second flow paths to the other is promoted, so that the fluid easily flows between the first and second flow paths. Will improve. In addition, since the cross-sectional area of the third flow path is smaller than that of the first and second flow paths, the fluid flow in the first and second flow paths can be appropriately ensured.

  Preferably, the third channel is inclined with respect to the first and second channels.

  By doing so, the third flow path can be easily communicated between the points where the differential pressure of the fluid occurs without taking a complicated configuration.

  In order to achieve the above object, another fuel cell separator according to the present invention extends in parallel with each other and fluid flows between adjacent first and second flow paths and the first and second flow paths. And a third flow path communicating between the first and second flow paths. The third flow path is inclined and has a small cross-sectional area with respect to the first and second flow paths.

  According to this configuration, since the third flow path is inclined with respect to the first and second flow paths, the third flow path can communicate between the points where the differential pressure of the fluid occurs. Thereby, like the above-mentioned this invention, the easiness of the flow of the fluid between the 1st and 2nd flow paths via a 3rd flow path can be improved. Further, the flow of fluid in the first and second flow paths can be appropriately ensured by the relationship between the cross-sectional areas of the first, second, and third flow paths.

  Preferably, the third flow path may have a first opening end face that opens directly to the first flow path and a second opening end face that opens directly to the second flow path. The first opening end face is located upstream of the second opening end face in the fluid flow direction in the first and second flow paths, and has a larger cross-sectional area than the second opening end face. Good.

  According to this configuration, since the first opening end face is located upstream of the second opening end face, the fluid flows from the first flow path to the second flow path via the third flow path. It becomes easy. In addition, since the fluid flow is accelerated at the second opening end surface having a smaller cross-sectional area than the first opening end surface, the fluid between the first and second channels via the third channel is further increased. The ease of flow can be improved.

  Here, in general, in a fuel cell, water is generated on the cathode side by a reaction between an oxidizing gas and a fuel gas. When the fluid flowing through the first, second, and third flow paths is an oxidant gas, the generated water is more likely to accumulate on the downstream side of the first, second, and third flow paths.

  Therefore, the third flow path has a gap between the first and second flow paths so that the distance is narrower on the downstream side than on the upstream side in the fluid flow direction in the first and second flow paths. It is good to communicate in several places.

  By doing so, the generated water is effectively discharged particularly when the fluid is an oxidizing gas.

  According to one aspect of the present invention, the fuel cell separator is preferably formed of metal. For example, the fuel cell separator may be formed by press-molding a sheet metal.

  According to the fuel cell separator of the present invention, it is possible to improve the ease of fluid flow between the flow paths via the third flow path.

  Hereinafter, a fuel cell separator according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings by taking a solid polymer fuel cell suitable for a fuel cell vehicle as an example.

FIG. 1 is a perspective view of a fuel cell.
The fuel cell 1 has a stacked stack structure in which a large number of single cells 2 that are basic units are stacked. The fuel cell 1 is configured by sequentially arranging a current collecting plate 5 with an output terminal 4, an insulating plate 6, and an end plate 7 outside the single cells 2 positioned at both ends of the stack structure. In the fuel cell 1, for example, a tension plate provided so as to bridge between both end plates 7 and 7 is bolted to each end plate 7 and 7, so that a predetermined compression is performed in the stacking direction of the single cells 2. It becomes a state where power is applied.

FIG. 2 is a cross-sectional view showing the single cell 2.
The single cell 2 includes an MEA 11 and a pair of separators 12A and 12B that sandwich the MEA 11. The MEA 11 includes an electrolyte membrane 15 made of an ion exchange membrane, and a pair of electrodes (anode and cathode) 16A and 16B sandwiching the electrolyte membrane 15. In the fuel cell 1, the separator 12A, the MEA 11, the separator 12B, the separator 12A, the MEA 11, the separator 12B, and so on are usually stacked in this order.

  Each of the electrodes 16A and 16B includes a diffusion layer 51 and a catalyst layer 52. The diffusion layer 51 faces the separator 12A or 12B and is made of, for example, a porous carbon material. The diffusion layer 51 is a conductor having a function of passing a fluid and a function of conducting the catalyst layer 52 and the separators 12A and 12B. The catalyst layer 52 is bound to the diffusion layer 51 and faces the electrolyte membrane 15. For example, platinum is preferably used as the catalyst of the catalyst layer 52.

  The separators 12 </ b> A and 12 </ b> B are members formed in a rectangular shape in plan view, both of which are not shown, but a fuel gas inlet / outlet port, an oxygen gas inlet / outlet port, and a refrigerant inlet / outlet port are formed therethrough. The fuel gas is supplied to the electrode (anode) 16A through the gas flow path 21A of the separator 12A. The oxygen gas is supplied to the electrode (cathode) 16B through the gas flow path 21B of the separator 12B.

  Here, the fuel gas means hydrogen gas containing hydrogen (anode gas). The oxygen gas means a gas (cathode gas) containing an oxidant typified by oxygen. Hydrogen gas and oxygen gas are generally collectively referred to as reaction gases.

  The separators 12A and 12B are made of a gas impermeable conductive material. For example, in addition to carbon, a metal such as aluminum, stainless steel, nickel alloy, titanium, or a conductive resin is used.

  Separator 12A, 12B of this embodiment has the structure where the concave part and convex part on a straight line continued alternately on the front and back each surface by press-molding the thin metal plate of substantially constant thickness. Therefore, the concave portion that functions as a fluid (hydrogen gas or refrigerant) flow path on one surface of the separator 12A becomes a convex portion that functions as a partition between adjacent flow paths on the other surface. This also applies to the separator 12B.

  Specifically, the separator 12A has a gas flow path 21A on the front surface and a refrigerant flow path 22A on the back surface, and the separator 12B has a gas flow path 21B on the front surface and the back surface due to the concave and convex portions. Has a refrigerant flow path 22B. In addition, a convex part can be paraphrased as a rib or a convex rib, and a recessed part can be paraphrased as a groove | channel or a concave groove.

  Each of the gas flow paths 21A and 21B and the refrigerant flow paths 22A and 22B includes a main flow path that is a plurality of straight flow paths, and a sub flow path that allows fluid to flow between adjacent straight flow paths, Consists of.

  Specifically, the gas flow path 21A includes a main flow path 71A and a sub flow path 72A. The gas flow path 21B includes a main flow path 71B and a sub flow path 72B, the refrigerant flow path 22A includes a main flow path 81A and a sub flow path 82A, and the refrigerant flow path 22B includes the main flow path 81B and the sub flow path. It consists of the road 82B. Between the adjacent single cells 2 and 2, the refrigerant main flow path 81 </ b> A and the main flow path 81 </ b> B substantially coincide with each other as viewed in the cell stacking direction to define a polygonal space, for example, a hexagon. The sub-channel 72A and the sub-channel 72B are preferably opposed to each other without being displaced in the cell stacking direction with the MEA 11 interposed therebetween. Setting the positional relationship is useful for stacking the single cells 2.

  The main flow path and the sub flow path have a common structure peculiar to the present invention although the flowing fluids are different. Here, in order to omit redundant description, the separator 12A will be described in detail focusing on the structure of the main flow path 71A and the sub flow path 72A of the gas flow path 21A.

  The separator 12A has a plurality of convex portions 91A that are convex with respect to the electrode 16A and a plurality of concave portions 92A that are concave with respect to the electrode 16A by the above-described press molding. The top surface of the convex portion 91A is in surface contact with the electrode 16A.

  The main flow path 71A is constituted by a recess 92A. There are a plurality of main flow paths 71A, and the plurality extend in parallel in one direction at an equal pitch. In each main flow path 71A, hydrogen gas is introduced from one end in the extending direction, and hydrogen gas is led out to the other end in the extending direction. Thereby, in the main flow path 71A, the fuel gas flows from the inlet of the fuel gas formed through the separator 12A toward the outlet.

  The sub-channel 72A is located between the adjacent main channels 71A and 71A, and communicates the main channels 71A and 71A so that hydrogen gas flows between the main channels 71A and 71A. The sub flow path 72A plays an auxiliary role in the flow of hydrogen gas in the fuel cell 1, and can be referred to as an auxiliary flow path or a cross flow path. Therefore, the amount of hydrogen gas flowing through the sub flow path 72A contributes to power generation of the single cell 2 is lower than the hydrogen gas flowing through the main flow path 71A.

Sub passage 72A is (see also 72A _2-3 of FIG. 3) which is formed in a groove shape so as to cross a part of the convex portion 91A, has a concave with respect to the electrode 16A. In addition, if the sub flow path 72A is expressed by the relationship between the convex portion 91A and the concave portion that is reversed, the sub flow channel 72A is configured by forming a part of the bottom rear surface of the concave portion into a concave shape. You can say that. The concave portion that is in a reverse relationship with the convex portion 91A constitutes the main flow channel 81A of the refrigerant flow channel 22A.

With reference to FIG. 3 and FIG. 4, the characteristic portion of the present invention will be further described in detail by taking the gas flow path 21 </ b> A as an example.
A plurality of main passages 71A are those comprising a main flow path 71A _1, 71A _2, 71A _3. Here, for convenience of explanation, a suffix is added to the reference numeral 71A, but the main flow paths 71A ₁ , 71A ₂ , 71A ₃ have the same structure.

The sub-channel 72A (third channel) includes a sub-channel 72A _1-2 and a sub-channel 72A _2-3 . Here, for convenience of explanation, a subscript is added to the reference numeral 72A, but the sub-channels 72A _1-2 and 72A _2-3 have the same structure.

Sub passage 72A _1-2 communicates with a plurality of locations in the extending direction between the main flow path 71A _1, 71A _2. Similarly, the sub-channel 72A _2-3 communicates with a plurality of locations in the extending direction between the main flow path 71A _2, 71A _3. Figure 3 shows the two sub-passages 72A _2-3, FIG. 4, each of the three sub-passages 72A _1-2, shows 72A _2-3. Note that the number of sub-channels 72A _1-2 and 72A _2-3 is arbitrary, but here they are plural.

Interval of a plurality of sub-passages 72A _1-2 is optional, in the flow direction of the hydrogen gas in the main flow passage 71A, it is preferable to narrow toward the downstream side of the upstream side. For example, as shown in FIG. 4, on the upstream side of the hydrogen gas to one form sub passage 72A _1-2, such as by two form a sub-channel 72A _1-2 on the downstream side, the sub the spacing of the passage 72A _1-2 and sparsely at the inlet of the hydrogen gas, may be densely at the outlet side. By doing so, the generated water can be effectively increased.

Specifically, in the fuel cell 1, water is generated on the cathode 16B side by the reaction between oxygen gas and hydrogen gas. A part of the generated water can also move to the anode 16A side through the electrolyte membrane 15. Since the generated water moves to the downstream side of the main flow path due to the flow of the reaction gas, the generated water tends to accumulate on the downstream side of the main flow path. Although a plurality of sub-passages 72A _1-2 can be formed at a constant pitch in the flow direction of the hydrogen gas, as described above, by closely spacing of the sub-channel 72A _1-2 toward the downstream side, The generated water that can be collected can be effectively discharged. In this regard, although not described in detail, the sub-channel 72A _2-3 is similar.

Sub passage 72A _1-2 has an open end face 101 which opens directly into the space of the main flow path 71A _1, an open end face 102 which opens directly into the space of the main flow channel 71A _2, a. Similarly, the sub-channel 72A _2-3 has an open end face 103 which opens directly into the space of the main flow channel 71A _2, the opening end face 104 which opens directly into the space of the main flow path 71A _3, the.

Open end surface 101 is located upstream of open end surface 102 in the direction of hydrogen gas flow in main flow path 71A. Therefore, the sub-channel 72A _1-2, to the main flow passage 71A _1, 71A _2, inclined at an angle other than 90 degrees. Similarly, the opening end surface 103 is located upstream of the opening end surface 104 in the hydrogen gas flow direction. Therefore, the sub-channel 72A _2-3, to the main flow passage 71A _1, 71A _2, inclined at an angle other than 90 degrees.

By adopting such a configuration, even if hydrogen gas having the same gas pressure is introduced into the adjacent main flow paths 71A ₁ and 71A ₂ , the hydrogen gas at the point of the opening end surface 101 and the point of the opening end surface 102 is reduced. A pressure difference occurs. That is, the sub-channel 72A _1-2 communicates between the point where the differential pressure of the hydrogen gas occurs. As a result, hydrogen gas flows from the point of the opening end surface 101 having a relatively high pressure to the point of the opening end surface 102 having a relatively low pressure. Thus, as compared with the case of orthogonal sub-channel to the main channel, the hydrogen gas flows easily from the main flow passage 71A ₁ via the sub-passage 72A _1-2 to the main flow channel 71A _2. This point is similar even sub passage 72A _2-3.

The cross-sectional shapes of the sub-channels 72A _1-2 and 72A _2-3 are arbitrary, and can be, for example, rectangular, trapezoidal, circular, or semicircular. The sub-channels 72A _1-2 and 72A _2-3 are formed, for example, in the range of 1/3 to 1/5 of the height of the convex portion 91A, and are not formed over the entire height of the convex portion 91A. The sub flow paths 72A _1-2 and 72A _2-3 have a smaller cross-sectional area than the main flow paths 71A ₁ , 71A ₂ , 71A ₃ , and preferably 1/3 of the main flow paths 71A ₁ , 71A ₂ , 71A ₃ . Has a cross-sectional area in the range of ~ 1/5. By setting it as such, the flow of hydrogen gas in the main flow paths 71A ₁ , 71A ₂ , 71A ₃ can be appropriately ensured.

In addition, the cross-sectional area of the flow path is obtained by multiplying the width by the depth (height). In order to make the cross-sectional area of the sub-channel 72A smaller than that of the main channel 71A, the depth or width of the sub-channel 72A may be made smaller than the depth or width of the main channel 71A. The main flow paths 71A ₁ , 71A ₂ , 71A ₃ may have different cross-sectional areas, but here have the same cross-sectional area.

Here, the sub-channel 72A _1-2 are flow cross-section between the open end 101 and 102 may be constant, but may not be constant. For example, as shown in FIG. 5, in the sub flow channel A _1-2 , the opening end surface 101 may have a larger cross-sectional area than the opening end surface 102, and the flow channel is narrowed from the opening end surface 101 to the opening end surface 102. The cross-sectional area may be reduced. By doing so, the flow of hydrogen gas accelerates on the open end face 102 having a smaller cross-sectional area than the open end face 101. In this regard, the sub-channel 72A _2-3 can be similarly designed.

  As described above, according to the present embodiment, the hydrogen gas is passed through the sub-channel 72A through the simple channel by tilting the sub-channel 72A with respect to the adjacent main channels 71A, 71A. It becomes easy to flow from one of 71A and 71A to the other. Needless to say, the same effect can be obtained with respect to the main flow path and the sub flow path related to the oxidizing gas or the refrigerant. In the following description, hydrogen gas will be mainly described.

  Due to the above-described effects, the present embodiment has a useful effect even when the fuel cell 1 generates power and when power generation ends. For example, even when flooding occurs locally in the single cell 2 during power generation and one main flow path 71 is blocked, hydrogen gas flows through the sub flow path 72A to the adjacent main flow path 71A. At this time, the ease of flow can be ensured by the communication mode of the sub-channel 72A described above, so that it is possible to quickly suppress the fact that one main channel 71A cannot generate power over the entire length. On the other hand, if this is considered from the viewpoint of the refrigerant main flow paths 81A and 81B and the sub flow paths 82A and 82B, the heat distribution of the refrigerant can be made uniform quickly. For this reason, damage to the electrolyte membrane 15 due to the local high temperature of the single cell 2 can be appropriately suppressed.

  Further, the sub-channel 72A can also supply hydrogen gas to the portion of the MEA 11 where the top surface of the convex portion 91A of the separator 12A contacts. Thereby, since the effective power generation area of the electrode 16A contributing to the electrochemical reaction can be increased, the power generation efficiency of the MEA 11 can be improved.

  Generally, at the end of power generation of the fuel cell 1 (at the end of the fuel cell system), a scavenging process for drying the inside of the fuel cell 1 is executed. In this scavenging process, the water in the MEA 11 of each unit cell 2 is substantially discharged to dry the electrolyte membrane 15. There are various methods of scavenging treatment, but it is generally performed that a reactive gas is supplied to the fuel cell 1, and moisture in the fuel cell 1 is blown off with the reactive gas and is removed by evaporation.

  According to the present embodiment, the sub flow path 72 is formed in the convex portion 91A, and the ease of hydrogen gas flow in the sub flow path 72 is ensured, so the scavenging process is performed immediately below the convex portion 91A. The water in the diffusion layer 51 can be discharged efficiently. Therefore, the scavenging performance below the convex portion of the separator can be improved, and the next start of the fuel cell 1 below freezing point can be performed satisfactorily.

<Modification>
Next, a modified example of the separator 12A of the present embodiment will be briefly described. The separator 12B can be applied to the same modification as the separator 12A, but the description thereof is omitted here.

<Modification 1>
The main channels 71A and 81A of the separator 12A may be known serpentine channels. In this case, the hydrogen gas main channel 71A may be a serpentine channel, and the refrigerant main channel 81A may be a straight channel.

  When the main channel 71A is a serpentine channel, the main channel 71A has, for example, a structure in which a plurality of channels that are parallel to each other are folded back one or more times. In this case, the sub-channel 72A communicates two adjacent channels among the main channels 71A, but the position is arbitrary. However, since the generated water tends to stagnate at the place where the main flow path 71A is folded back, forming the sub flow path 72A at the turned-back position is effective in terms of drainage and the like.

<Modification 2>
FIG. 6A is a schematic plan view of a separator 12A according to another modification as viewed from the MEA 11 side. The convex portions 91A are hatched so that the regions of the main flow paths 71A ₁ , 71A ₂ , 71A ₃ and the convex portions 91A can be easily understood.
As shown in FIG. 6A, in the main flow paths 71A ₁ , 71A ₂ , 71A ₃ , pressure loss portions 120 are formed on the convex portions 91A so that the pressure loss of hydrogen gas occurs alternately.

FIG. 6B is a graph showing the relationship between the pressure of hydrogen gas and the position in the main flow path. As shown in FIG. 6B, the main flow paths 71A ₁ and 71A ₃ and the main flow path 71A ₂ have different pressures depending on their positions downstream from the pressure loss portion 120. That is, a differential pressure is generated downstream of the pressure loss part 120 between the two adjacent main flow paths 71A ₁ and 71A _{2 and} between the main flow paths 71A ₂ and 71A ₃ .

As shown in FIG. 6 (A), also in this modified example, communication between the point where the differential pressure of the main flow path 71A _1, 71A ₂ occurs in the sub passage 72A _1-2, The main flow path between the point where the differential 71A _2, 71A ₃ occurs in communication with the sub-channel 72A _2-3. Therefore, even if it is such a modification, there can exist the same effect as embodiment of above-described this invention.

<Modification 3>
When the separator 12A is formed of carbon, the main channels 71A and 81A and the sub channels 72A and 82A may be formed by cutting, injection molding, compression molding, ultrasonic processing, or the like. However, the main channels 71A and 81A and the sub channels 72A and 82A may be formed in the separator 12A by using etching.

  The above-described fuel cell separator of the present invention can be applied not only to a polymer electrolyte fuel cell but also to a phosphoric acid fuel cell. A fuel cell system equipped with a fuel cell can be mounted on a train other than a two-wheeled or four-wheeled vehicle, an aircraft, a ship, a robot, or other moving objects or vehicles. The fuel cell system can also be stationary and can be incorporated into a cogeneration system.

1 is a perspective view of a fuel cell according to an embodiment. It is sectional drawing which shows the structure of the single cell which concerns on embodiment. It is a perspective view which expands and shows a part of separator which concerns on embodiment. It is a figure which shows the flow-path structure of the separator which concerns on embodiment. It is a figure which shows the flow-path structure of the separator which concerns on a modification. It is a figure explaining the separator which concerns on another modification, (A) is the schematic plan view which looked at the separator from the MEA side, (B) shows the relationship between the pressure of hydrogen gas, and the position in a main flow path. It is a graph.

Explanation of symbols

1: Fuel cell, 2: single cell, 11: MEA, 12A, 12B: Separator, 21A, 21B: gas passage, 22A, 22B: refrigerant passage, 71A, 71A _1, 71A _2, 71A _3: Main flow path , 72A, 72A _1-2 , 72A _2-3 : Sub flow path (third flow path)

Claims (6)

A first flow path having a first cross-sectional area;
A second flow path adjacent to the first flow path and having a second cross-sectional area;
A third flow path communicating between the first and second flow paths so that a fluid flows between the first and second flow paths and having a smaller cross-sectional area than the first and second cross-sectional areas; A third flow path having a cross-sectional area of 3;
A fuel cell separator comprising:
The third channel is a fuel cell separator that communicates between points where the differential pressure of the fluid is generated.   2. The fuel cell separator according to claim 1, wherein the third flow path is inclined with respect to the first and second flow paths. First and second flow paths extending parallel and adjacent to each other;
A third flow path communicating between the first and second flow paths so that a fluid flows between the first and second flow paths;
A fuel cell separator comprising:
The fuel cell separator, wherein the third flow path is inclined and has a small cross-sectional area with respect to the first and second flow paths. The third flow path has a first opening end face that opens directly to the first flow path, and a second opening end face that opens directly to the second flow path,
The first opening end surface is located upstream of the second opening end surface in the fluid flow direction of the first and second flow paths, and is cut off from the second opening end surface. The fuel cell separator according to any one of claims 1 to 3, having a large area.   The first flow path and the second flow path are arranged such that the downstream side is narrower than the upstream side in the fluid flow direction of the first and second flow paths. The fuel cell separator according to any one of claims 1 to 4, wherein a plurality of portions communicate with each other.   The fuel cell separator according to any one of claims 1 to 5, wherein the fluid flowing through the first, second, and third flow paths is a reaction gas.

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