JP3842109B2 - Fuel cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell in which a plurality of electrode structures each having an electrolyte sandwiched between a pair of electrodes are stacked via a separator.
[0002]
[Prior art]
The fuel cell constituting the fuel cell is configured in a flat plate shape by sandwiching a membrane electrode structure in which an anode electrode and a cathode electrode are respectively disposed on both sides of a solid polymer electrolyte membrane with a pair of separators. There is something. The fuel battery cells configured as described above constitute a fuel cell by being stacked in the thickness direction.
[0003]
In each fuel cell, a flow path of a fuel gas (for example, hydrogen) is provided on one surface of an anode separator disposed opposite to the anode electrode, and an oxidant gas (on the one surface of the cathode separator disposed opposite to the cathode electrode). For example, a flow path of air containing oxygen) is provided. A flow path for a cooling medium (for example, pure water) is provided between adjacent separators of adjacent fuel cells.
[0004]
When fuel gas is supplied to the electrode reaction surface of the anode electrode, hydrogen is ionized here, and this hydrogen ion moves to the cathode electrode through the solid polymer electrolyte membrane. Electrons generated during this time are taken out to an external circuit and used as direct current electric energy. Since the oxidant gas is supplied to the cathode electrode, hydrogen ions, electrons, and oxygen react to generate water. Since heat is generated when water is generated on the electrode reaction surface, the electrode reaction surface is cooled by a cooling medium circulated between the separators.
[0005]
In the fuel cell as described above, it is generally performed that the separator is made of carbon having excellent electrical characteristics such as conductivity and corrosion resistance, and also excellent in accuracy. In addition, there is a problem that strength and productivity are low. From such a point, it has been studied to use a metal separator that can be formed by press working and is thin and highly productive, and a technique related to the metal separator has already been disclosed (see Japanese Patent Application Laid-Open No. 2000-21419).
[0006]
That is, a fuel cell using a metal separator has a membrane electrode structure 4 having an anode electrode 2 and a cathode electrode 3 on both sides of a solid polymer electrolyte membrane 1 as shown in the sectional view of FIG. The fuel cell 7 is configured by arranging a pair of corrugated metal separators 5 and 6 on both sides. The fuel cell is configured by stacking a plurality of such fuel cells 7 so that the convex portions 8 and 9 of the adjacent metal separators 5 and 6 face each other and the concave portions 10 and 11 face each other. is there. The space between the recesses 10 and 11 facing the metal separators 5 and 6 is a cooling medium flow path 12, and the space between the recess 13 on the back side of the protrusion 8 of the metal separator 5 and the anode electrode 2. Is a fuel gas flow channel 14, and a space between the concave portion 15 on the back side of the convex portion 9 of the metal separator 6 and the cathode electrode 3 is an oxidant gas flow channel 16.
[0007]
[Problems to be solved by the invention]
However, since the metal separator formed by press working is thin, shape errors such as warpage and undulation are likely to occur. If it is used as it is, it is difficult to ensure the flatness of the metal separator. In particular, when a fuel cell is formed by fastening a plurality of stacked fuel cells in the stacking direction, when a tightening load is applied to the fuel cells, the shape error of the metal separator accumulates and warps the fuel cells. As a result, the surface pressure applied to the electrode surfaces of the adjacent anode electrode and cathode electrode may be non-uniform. Then, the contact resistance increases and the internal resistance of the fuel cell increases, which may make it difficult to obtain the intended performance.
[0008]
Therefore, by providing an intermediate plate (for example, a leaf spring) made of an elastic member between the separators, it is possible to absorb warpage, undulation, etc. generated in the fuel cell and apply an appropriate surface pressure to the fuel cell. Has been.
[0009]
When such an intermediate plate is used, if the intermediate plate is formed smaller than the separator in consideration of the reduction in size and weight of the fuel cell, positioning in the separator is difficult, while it is fixed to the separator with a knock pin or the like. However, there is a problem in that the degree of freedom of displacement of the intermediate plate is impaired and it becomes difficult to absorb the warp and swell described above.
[0010]
The present invention has been made in view of such circumstances, and provides a fuel cell in which positioning of the intermediate plate with respect to the separator is easy while ensuring a certain degree of freedom of displacement of the intermediate plate provided between the separators. Objective.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention described in claim 1 is directed to an electrolyte (for example, the solid polymer electrolyte membrane 21 in the embodiment) as a pair of electrodes (for example, the anode electrode 22 and the cathode electrode 23 in the embodiment). ) Are disposed on both sides of the electrode structure (for example, the membrane electrode structure 24 in the embodiment) sandwiched between the electrode structure and the separator on both sides, and the fuel is formed by the electrode structure and the separators on both sides. An intermediate plate in which a battery cell (for example, the fuel battery cell 27 in the embodiment) is configured, a plurality of the fuel battery cells are stacked, and a separator that abuts between the separators of adjacent fuel battery cells is elastically biased (e.g., an intermediate plate 36 in the embodiment) a fuel cell is provided, one of the separators of the adjacent fuel cell Resilient projections (e.g., the elastic projections 40 in the embodiment) set up, the intermediate plate, by engaging the resilient projections of the separator hole portion provided in the intermediate plate, characterized by securing It is a fuel cell.
[0012]
By configuring in this way, the intermediate plate is fixed to the elastic protrusion, and the elastic protrusion can be expanded and contracted within a certain range due to its property, so that the intermediate plate can slide relative to the separator. Therefore, it is possible to absorb warpage and undulation of the separator, the electrode structure, and consequently the fuel cell. Further, since the intermediate plate is provided inside the fuel cell, there is no risk of increasing the thickness in the stacking direction, and it does not hinder downsizing and weight reduction of the fuel cell.
[0013]
The intermediate plate can be applied not only when the cooling channel is defined but also when the gas channel is defined. Further, the elastic protrusion can be installed by bonding or baking to the separator. The fuel cell may be any of a solid polymer type, a solid electrolyte type, an alkali type, a phosphoric acid type, and a molten carbonate type.
[0014]
According to a second aspect of the present invention, there is provided a sealing member (for example, a seal member) that seals between an elastic protrusion (for example, the elastic protrusion 51 in the embodiment) installed on the one separator and a separator of the adjacent fuel cell. The fuel cell is characterized in that the cooling surface sealing member 52) in the embodiment is integrally formed .
[0015]
With this configuration, the elastic protrusion can be made of the same material as the seal member, and can be arranged together with the seal member, facilitating the molding process and reducing the number of parts. Can be lowered.
[0016]
The invention described in claim 3 is characterized in that the elastic protrusion (for example, the elastic protrusion 61 in the embodiment) includes a retaining portion (for example, the retaining portion 62 in the embodiment). It is.
By comprising in this way, it can prevent that an intermediate | middle board falls out from an elastic protrusion, and can improve the reliability with respect to an intermediate | middle board.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a fuel cell according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of an essential part showing a fuel cell according to a first embodiment of the present invention. The fuel cell 20 includes a membrane electrode structure 24 configured by arranging an anode electrode 22 and a cathode electrode 23 so as to sandwich the polymer electrolyte membrane 21 on both sides in the thickness direction. The membrane electrode structure 24 is further formed by stacking a plurality of fuel cells 27 sandwiched between a pair of metal separators 25 and 26, and power is taken out from both ends of the stacked fuel cells 27. ing.
[0018]
The metal separators 25 and 26 are, for example, a pair of stainless steel plate materials having a thickness of 0.1 to 0.5 mm that are formed by stamping and bending by press working. Corrugated plate portions 30 in which concave portions 28 and convex portions 29 are alternately arranged are provided. In the metal separator 26, convex portions 31 and concave portions 32 are alternately arranged in the center portions thereof. A corrugated plate portion 33 is provided. In addition, as a material of the metal separators 25 and 26, it is possible to use stainless steel or a stainless steel surface coated with a material having corrosion resistance.
[0019]
The metal separator 25 is disposed so that the plurality of concave portions 28 are in contact with the anode electrode 22 and the plurality of convex portions 29 are opposed to the anode electrode 22. Further, the metal separator 26 is disposed so that the plurality of convex portions 31 are in contact with the cathode electrode 23 and the plurality of concave portions 32 are opposed to the cathode electrode 23.
[0020]
An intermediate plate 36 is interposed between the separators 25 and 26. The intermediate plate 36 is made of a smooth metal plate, and elastically deforms when a load is applied, and gives an elastic force when the load is removed and the shape returns to its original shape. This bullet urging force ensures electrical contact between the separators 25 and 26 and by extension, the fuel cells 27. Details will be described later.
[0021]
A space between the anode electrode 22 and the convex portion 29 of the metal separator 25 adjacent to the anode electrode 22 serves as a fuel gas channel 34, and hydrogen gas is supplied to the fuel gas channel 34. On the other hand, the space between the cathode electrode 23 and the concave portion 32 of the metal separator 26 adjacent thereto is made an oxidant gas flow path 35, and air is supplied to the oxidant gas flow path 35. In addition, the space between the concave portion 28 of the metal separator 25 and the intermediate plate 36 and the space between the convex portion 31 of the metal separator 26 and the intermediate plate 36 serve as a cooling medium flow path 37 to form the cooling medium. A cooling liquid is supplied to the flow path 37 to cool the membrane electrode structure 24.
[0022]
A cooling surface sealing member 38 that seals the peripheral portions of the separators 25 and 26 is provided between the separators 25 and 26. In addition, a gas seal member (not shown) is provided between the membrane electrode structure 24 and the separators 25 and 26, and a reaction gas and a coolant are supplied to or discharged from the membrane electrode structure 24 and the separators 25 and 26. There are provided communication holes (both not shown), but the description thereof will be omitted.
[0023]
The intermediate plate 36 is formed to have a smaller planar dimension than the separators 25 and 26, and is provided inside the cooling surface sealing member 38 between the separators 25 and 26. A cooling medium flow path 37 formed between the separators 25 and 26 is partitioned by a cooling surface sealing member 38. Further, the intermediate plate 36 has an engagement hole 39 formed on the periphery thereof, and the engagement hole 39 engages with a rubber elastic protrusion 40 disposed on the inner side of the cooling surface seal member 38. ing. Accordingly, the intermediate plate 36 is positioned and held between the separators 25 and 26 by being fixed to the elastic protrusions 40. In addition, due to the nature of the elastic protrusion 40, the intermediate plate 36 has a degree of freedom that allows the intermediate plate 36 to move following the displacement of the separators 25 and 26. In the present embodiment, in order to position the intermediate plate 36, two engagement holes 39 are provided on the outer periphery of the intermediate plate 36. Further, the intermediate plate 36 is formed with a step portion 41 between the outer peripheral portion where the engagement hole 39 is formed and the inside thereof. By forming the step portion 41 in the intermediate plate 36 in this way, the engagement hole 39 can be engaged on the proximal end side (back side) of the elastic protrusion 40, and thus the engagement hole 39 is formed by the elastic protrusion 40. Therefore, the intermediate plate 36 can be positioned and held more reliably.
[0024]
Thus, even when the separators 25 and 26 and the membrane electrode structure 24 undergo thermal expansion along the stacking direction during operation of the fuel cell 20, the intermediate plate 36 is elastically deformed at this time. The separators 25 and 26 that come into contact with each other are elastically energized. For this reason, the surface pressure applied to the electrode surfaces of the anode electrode 22 and the cathode electrode 23 adjacent to the separators 25 and 26 can be kept uniform. Since the increase in the internal resistance of the fuel cell 20 due to the increase in contact resistance can be suppressed, the target performance can be sufficiently obtained from the fuel cell 20.
[0025]
Further, when the operation of the fuel cell 20 is stopped and the temperature is lowered and the fuel cell 27 contracts in the stacking direction, the intermediate plate 36 returns to the original shape. At this time, the intermediate plate 36 elastically biases the separators 25 and 26. That is, the separators 25 and 26 are pressed by the intermediate plate 36, thereby maintaining the pressure holding force for the fuel cell 27. Similarly, when a so-called sag occurs in the fuel cell 27, the intermediate plate 36 elastically biases the separators 25 and 26 to maintain the pressure holding force on the fuel cell 27. Further, even when a shape error such as warpage or undulation occurs in the separators 25 and 26, the intermediate plate 36 imparts an elastic force in a direction in which the separators 25 and 26 have an appropriate shape. 25, 26, the membrane electrode structure 24, and thus the warp and undulation of the fuel cell 27 can be absorbed.
Since the intermediate plate 36 is fixed to the elastic protrusion 40, even if the intermediate plate 36 is deformed once as described above, it can return to the predetermined position again.
[0026]
As described above, the intermediate plate 36 is positioned while ensuring the degree of freedom of displacement to the predetermined positions of the separators 25 and 26, so that the intermediate plate 36 is generated in the separators 25 and 26, the membrane electrode structure 24, and eventually the fuel cell 27. The intermediate plate 36 can absorb dimensional changes due to deformation (the above-described thermal expansion and contraction, sag and shape error, etc.). Further, since the intermediate plate 36 is positioned inside the fuel cell, it does not hinder the miniaturization and weight reduction of the fuel cell 20.
[0027]
Next, the fuel cell 50 according to the second embodiment will be described with reference to FIG. In the following description, the same members as those in the above embodiment are given the same reference numerals, and the description thereof is omitted as appropriate.
The fuel cell 50 shown in the cross-sectional view of FIG. 2 is different from the fuel cell 20 in that the elastic protrusion 51 is integrally formed with the cooling surface sealing member 52. As a result, the elastic protrusion 51 can be made of the same material as the cooling surface sealing member 52 and can be disposed together with the cooling surface sealing member 52, thereby facilitating the molding process and reducing the number of components. it can.
[0028]
Next, a fuel cell 60 according to a third embodiment will be described with reference to FIG. The fuel cell 60 shown in the cross-sectional view of FIG. 3 is different from the fuel cell 50 in that the elastic protrusion 61 includes a retaining portion 62. Thus, even when the intermediate plate 36 moves in the stacking direction, the portion of the engagement hole 39 is held in contact with the retaining portion 62, so that the intermediate plate 36 is held more securely. Therefore, the reliability of the intermediate plate 36 can be improved.
[0029]
Next, a fuel cell 70 according to a fourth embodiment will be described with reference to FIG. In the fuel cell 70 shown in the sectional view of FIG. 4, a separator 71 is further provided in addition to the separators 25 and 26. The separator 71 has a plurality of projections 72 abutted against the recesses 28 of the separator 25, and a plurality of recesses 73 opposed to the projections 29 of the separator 25 and abutted with the anode electrode 22. Has been placed. Thus, in addition to the fuel gas flow path 34 formed in the space between the intermediate plate 36 and the recess 28 of the separator 25, the fuel gas is also present in the space between the protrusion 72 of the separator 71 and the anode electrode 22. A flow path 74 can be formed. As described above, by providing the intermediate plate 36, fuel gas flow paths 34 and 74 different in the stacking direction can be formed, and the fuel gas can be folded and flown between these flow paths. A cooling medium flow path 75 is formed in the space between the concave portion 73 of the separator 71 and the convex portion 29 of the separator 25. In the present embodiment, the case where the fuel gas flow path is folded back has been described. However, the present invention can also be applied to the case where the oxidant gas flow path is folded back.
[0030]
In addition, in the above embodiment, although the case where a separator was metal was demonstrated, it is not restricted to this, A carbon-made separator may be sufficient. The intermediate plate has been described as having a size smaller than that of the separator, but may be the same size or larger than that of the separator as long as there is no problem in reducing the size and weight of the fuel cell. Further, as described above, it is preferable to use an elastic member such as a leaf spring in order to prevent deformation due to thermal expansion or contraction of the fuel cell, sag or shape error, etc. When it does, it does not need to be an elastic member.
[0031]
【The invention's effect】
As described above, according to the first aspect of the present invention, it is possible to prevent deformation of the separator, the electrode structure, and the fuel cell. Further, since the intermediate plate is provided inside the fuel cell, there is no risk of increasing the thickness in the stacking direction, and it does not hinder downsizing and weight reduction of the fuel cell.
[0032]
According to the second aspect of the present invention, the same material as that of the seal member can be used and can be disposed at a time. Therefore, the molding process is facilitated and the number of parts can be reduced.
[0033]
According to the invention described in claim 3, it is possible to prevent the intermediate plate from falling off the elastic protrusion, and it is possible to improve the reliability of the intermediate plate.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a main part of a fuel cell according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view of a main part showing a fuel cell according to a second embodiment of the present invention.
FIG. 3 is a cross-sectional view of a principal part showing a fuel cell according to a third embodiment of the present invention.
FIG. 4 is a cross-sectional view of a main part showing a fuel cell according to a fourth embodiment of the present invention.
FIG. 5 is a cross-sectional view of an essential part showing a conventional fuel cell.
[Explanation of symbols]
20 Fuel Cell 21 Solid Polymer Electrolyte Membrane 22 Anode Electrode 23 Cathode Electrode 24 Membrane Electrode Structures 25 and 26 Separator 36 Intermediate Plate 37 Cooling Medium Channel 39 Engagement Holes 40, 51 and 61 Elastic Protrusion 62 Retaining Part

Claims (3)

Separators are disposed on both sides of an electrode structure in which an electrolyte is sandwiched between a pair of electrodes, and a fuel battery cell is configured by the electrode structure and separators on both sides.
A fuel cell in which a plurality of the fuel cells are stacked, and an intermediate plate is provided between the separators of the adjacent fuel cells to elastically bias the abutting separator ,
Installing an elastic protrusion on one separator of the adjacent fuel cells;
A fuel cell, wherein the intermediate plate is fixed by engaging the elastic protrusion of a separator with a hole provided in the intermediate plate. A fuel cell, wherein an elastic protrusion installed on the one separator and a seal member for sealing between the separators of the adjacent fuel cells are integrally formed .   The fuel cell according to claim 1, wherein the elastic projection includes a retaining portion.

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