JP2008177089A - Fuel cell - Google Patents

Abstract

Provided is a fuel cell in which variation in surface pressure is suppressed while suppressing increase in size and weight.
A fuel cell according to the present invention includes a plurality of stacked cells, a pair of collector plates disposed on both outer sides in the stacking direction of the stacked cells, and a pair disposed on the outside of the collector plates. And a fastening member that fastens and fastens the cells stacked from the outside of the pair of end plates. Further, the cell has a curved shape in a cross section parallel to the stacking direction, and each of the cells is disposed on both sides of the electrolyte membrane and the electrolyte membrane, and on both sides of the pair of electrodes, The separator which comprises a fuel gas flow path and an oxidizing gas flow path is provided.
[Selection] Figure 1

Description

  The present invention relates to a fuel cell. More specifically, it is suitable as a fuel cell having a plurality of stacked cells.

  Conventionally, Japanese Patent Application Laid-Open No. 8-153525 discloses a fuel cell in which a plurality of single cells (cells) are stacked. Each cell of this fuel cell includes a membrane-electrode assembly including an electrolyte membrane and anode and cathode electrodes disposed on both sides thereof. Both sides of each electrode are sandwiched between carbon current collectors (separators). Here, the separator on the anode electrode side is formed with a fuel gas flow path through which the fuel gas flows through the anode electrode, and the oxidizing gas through which air serving as the oxidizing gas flows through the cathode electrode is formed in the cathode electrode separator. The flow path is formed in a groove shape.

  The separator of this fuel cell is formed in a shape curved with a predetermined curvature so that a vertical cross section (that is, a cross section parallel to the cell stacking direction) is an arc. The oxidizing gas channel is formed in a groove shape curved along the direction of the arc of the separator. On the other hand, the fuel gas channel is formed in a straight line in the direction perpendicular to the oxygen gas channel of the separator (that is, the direction perpendicular to the cross section). According to the above prior art, the oxidant gas flow path has a curved shape along the arc of the separator, thereby generating centrifugal force in the air flowing through the oxidant gas flow path. By this centrifugal force, the gas flowing through the oxidizing gas flow path can flow toward the cathode electrode. As a result, the diffusion of the gas in the oxidizing gas channel to the cathode electrode diffusion layer is promoted, and air containing more oxygen is supplied to the cathode electrode.

JP-A-8-153525 JP 2004-47155 A JP 2004-288539 A JP 2004-327105 A JP 2004-2104040 A JP 2001-93564 A

  By the way, the temperature change in a cell may become large during power generation of a fuel cell. For example, since a low-temperature cooling water flows when the fuel cell is started, a part of the cell may be rapidly cooled. In this case, there is a case where a large variation occurs in expansion in the cell due to a temperature difference, and the cell is deformed.

  In addition, the electrochemical reaction of the fuel cell is accompanied by heat generation. Therefore, the expansion of each cell increases as the calorific value of the fuel cell increases. Here, in general, in a fuel cell, cells are stacked as described above, end plates are arranged on both sides in the stacking direction, and are tightened by a fastening member from the outside with a predetermined fastening load. Therefore, when the cell expands due to heat generation of the fuel cell, it is conceivable that the cell bends greatly at a portion far from the tightening portion by the fastening member and deforms so that the cell expands toward the outside of the fuel cell.

  Thus, when the physique change by the temperature change of a fuel cell becomes large, it is possible that the fastening pressure (henceforth "surface pressure") applied in each cell surface will vary. Since variations in surface pressure lead to a decrease in power generation performance, it is preferable to stabilize the surface pressure uniformly.

  For example, in order to make the surface pressure constant, a spring is disposed outside the end plate, and the end plate is pressed in a direction perpendicular to the cell surface with a constant elastic force. However, in the case of using a structure using a spring in this way, there is a problem of an increase in size and weight of the fuel cell and an increase in cost due to a fastening member such as a spring.

  Even when the spring is used in this way, it may be difficult to keep the surface pressure within a certain level when the physique changes due to temperature changes. Further, in recent years, there is a strong demand for miniaturization of fuel cells, and for this reason, individual cells including separators tend to be thin. If the separator structure is thin, the deflection generated by heat increases and the physique changes more. Therefore, the variation in surface pressure increases, making it more difficult to stabilize the surface pressure more uniformly.

  The present invention has been made to solve the above-described problems, and is an improved fuel cell so that the surface pressure can be kept within a certain range while suppressing an increase in size and weight of the fuel cell. The purpose is to provide.

In order to achieve the above object, a first invention is a fuel cell,
A plurality of stacked cells;
A pair of collector plates disposed on both outer sides in the stacking direction of the stacked cells;
A pair of end plates disposed outside the collector electrode plate;
From the outside of the pair of end plates, a fastening member that fastens and tightens the stacked cells;
With
Each of the cells has a curved shape in a cross section parallel to the stacking direction, and
An electrolyte membrane;
A pair of electrodes disposed on both sides of the electrolyte membrane;
The separators disposed on both sides of the pair of electrodes, respectively, constituting a fuel gas channel and an oxidizing gas channel;
Is provided.

  In a second aspect based on the first aspect, the plurality of cells are curved with the same curvature in the same direction in the cross section.

According to a third invention, in the first or second invention,
In a state before being fastened by the fastening member,
The plurality of cells are formed with different curvatures; and
In the cross-section, when the cell having the smallest curvature among the plurality of cells is a central cell, the cell disposed outside the central cell in the stacking direction has a recessed shape on the outside, and the central cell In addition, the curvature increases with increasing outside in the stacking direction.

  In a fourth invention according to any one of the first to third inventions, the curvature of the cell is in a range of 0.1 to 10.

  According to a fifth invention, in the first to fourth inventions, a pressure applied to each of the cells of the fuel cell is in a range of 0.1 MPa to 10 MPa.

  According to the first invention, each cell of the fuel cell has a curved shape in a cross section parallel to the stacking direction. According to this, each cell itself can have a certain amount of elastic force. Therefore, the surface pressure can be stabilized within a certain range without using an elastic body such as a spring. Moreover, since the electrode area can be increased by forming the cell in such a curved shape, the fuel cell can be reduced in size.

  According to the second invention, each cell has a curved shape with the same curvature in the same direction. Thereby, since the whole fuel cell can be given elastic force in the same direction, the surface pressure can be maintained within a certain range.

  According to the third invention, in a state before each cell is stacked and fastened, each cell has a cell having the smallest curvature as a central cell, and cells outside the central cell are curved toward the central cell. It is comprised and it is comprised so that a curvature may become large as it leaves outside a center cell. According to this, it can be set as the shape which considered the deflection | deviation by the pressure applied at the time of the fastening of a fuel cell, and the cell of the fuel cell after fastening can become a curved shape.

  According to the fourth invention, the curvature of the cell is 0.1-10. Thereby, the surface pressure of the fuel cell can be stabilized more reliably.

  According to the fifth invention, the surface pressure applied to each cell of the fuel cell is 0.1 to 10 MPa. As described above, a fuel cell having a stable surface pressure can be obtained by curving the cells of the fuel cell.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is simplified or omitted.

Embodiment 1 FIG.
FIG. 1 is a schematic diagram for illustrating a fuel cell according to Embodiment 1 of the present invention. FIG. 1 shows a cross section on one surface parallel to the stacking direction of each cell of the fuel cell. FIG. 2 is a schematic diagram for explaining a cell of this fuel cell, and shows a cross section in the same direction as FIG. FIG. 3 is a schematic diagram for explaining the separator of this cell.

  The fuel cell 10 of FIG. 1 is configured by stacking a plurality of cells 12. Terminals 14 (collector electrode plates) are disposed on both sides of the cell 12. The terminal 14 has a function of taking out the electric power generated by the power generation reaction of the plurality of stacked cells 12. An insulator 16 is disposed on both outer sides of the terminal 14, and an end plate 18 is disposed on the outer side thereof. The insulator 16 is an insulator that insulates between the terminal 14 and the end plate 18 disposed on both sides thereof. The fuel cell 10 is pressed and fastened by a fastening member 20 from the outside of the end plate 18 with a predetermined pressure.

  FIG. 2 is a diagram for explaining each cell in the fuel cell 10 of FIG. As shown in FIG. 2, an electrolyte membrane 22 is disposed in each cell 12. The electrolyte membrane 22 varies depending on the type of fuel cell, but here, a solid polymer electrolyte membrane 22 having proton conductivity is used. An anode electrode 24 and a cathode electrode 26 are arranged on both sides of the electrolyte membrane 22. The anode electrode 24 and the cathode electrode 26 are composed of, for example, a catalyst layer made of a catalyst in which platinum is supported on a carrier, and a diffusion layer formed on the surface of the catalyst layer.

  Separators 28 are disposed on both sides of the thus configured membrane-electrode assembly (MEA). The separator 28 is formed using carbon as a main material. The separator 28 in contact with the anode electrode 24 is configured with an anode flow channel for allowing a fuel such as hydrogen to flow through the anode electrode 24. On the other hand, the separator 28 in contact with the cathode electrode 26 is formed with a cathode channel for supplying the cathode electrode 26 with air as an oxidizing gas.

  As shown in FIG. 3, the separator 28 is configured in the curved shape of the cell shown in FIG. By being sandwiched between the separators 28, the membrane-electrode assembly is also curved along the separators 28, and each cell 12 is curved in an arc as shown in FIG.

  Referring again to FIG. 1, the cell 12 and the terminal 14 have an arcuate shape in which the vicinity of the center swells in the same direction in the cross section of FIG. 1. Here, the curvature of each cell 12 and terminal 14 is preferably in the range of 0.1 to 10. On the other hand, the insulator 16 and the end plate 18 outside the terminal 14 have a cross section that is linear, that is, a plane. The gap generated between the terminal 14 and the insulator 16 may be embedded with an insulating member having elasticity, or may not be embedded in particular.

  In the fuel cell 10, the pressure (surface pressure) applied to the MEA installation surface of each cell 12 is always in the range of 0.1 MPa to 10 MPa. That is, the variation in surface pressure is suppressed by the fastening pressure by the fastening member 20 and the elastic force of the curved separator 28 (cell 12), and is maintained within this range.

  As described above, according to the fuel cell 10 of Embodiment 1, the surface pressure of all the cells 12 is uniformly maintained by the fastening force and the elastic force of the curved cells 12. Here, for example, during the power generation of the fuel cell 10, when the heat is generated by the electrochemical reaction, both the MEA and the separator 28 expand. However, the cell 12 is in a curved state, and the cell 12 itself has an elastic force. Accordingly, an elastic force acts against the expansion, and the expansion by the MEA and the separator 28 is absorbed, so that the physique change of the fuel cell 10 is suppressed. Further, even when the cell 12 is expanded and deformed, the cell 12 as a whole is curved in the same direction and has an elastic force, so that stress can be exerted against the expansion. Therefore, the variation in the surface pressure in the cell 12 can be kept relatively small.

  Further, according to the fuel cell 10 of Embodiment 1 of the present invention, for example, a spring or the like is installed outside the end plate 18 and the cell 12 is given elastic force without applying pressure by the spring. Thus, the required surface pressure can be maintained. Therefore, the physique change of the fuel cell 10 can be suppressed to a small size without increasing the physique of the entire fuel cell 10 or increasing the thickness of the members such as the separator 28. Furthermore, since each cell 12 is formed in a curved shape, a larger electrode area can be secured for each cell 12 when compared with fuel cells of the same physique. Thereby, further miniaturization of the fuel cell 10 is achieved.

  In the first embodiment, the case where the cell 12 and the terminal 14 are curved and the insulator 16 and the end plate 18 are formed in a planar shape has been described. However, the fuel cell in the present invention is not limited to this, and the insulator 16 and the end plate 18 may be curved in the same shape as the cell 12. The same applies to the second embodiment.

  Moreover, the case where the cell 12 and the terminal 14 were formed with the same curvature was demonstrated. However, the present invention is not limited to this, and the curvature of the cell 12 and the terminal 14 may be different. Thereby, for example, when materials having different Young's moduli are used in the cell 12 and the terminal 14, the spring constant can be arbitrarily set by changing the curvature. Moreover, in Embodiment 1, the case where the curvature of the cell 12 and the terminal 14 is 0.1-10 was demonstrated. However, the curvature is not limited to this, and the curvature can be appropriately set in consideration of the expansion coefficient, Young's modulus, etc. of the material constituting each member. The same applies to the second embodiment.

Embodiment 2. FIG.
FIG. 4 is a schematic diagram for explaining a state when a conventional fuel cell is fastened. FIG. 5 is a diagram for illustrating a state before fastening by the fastening member of the fuel cell according to Embodiment 2 of the present invention. The fuel cell shown in FIG. 5 becomes a fuel cell having cells curved in one direction after the fastening of the fuel cell, like the fuel cell shown in FIG.

  As shown in FIG. 4, the fuel cell 110 is fastened and fastened by a fastening member 120 from the outside of the end plate 118. In the conventional fuel cell 110, the rigidity of the cell 112 cannot be secured with respect to the pressure at the time of fastening, and in the state shown in FIG. 4, the central portion of the cell 112 far from the fastening portion is greatly expanded outward. In some cases, the physique change of the fuel cell 110 may increase.

  On the other hand, in the second embodiment, in anticipation of the deflection generated in the cell 12 and the terminal 14 at the time of fastening, the fuel cell after fastening is finally a fuel cell 10 as shown in FIG. The shape of the cell 12 is configured as follows.

  That is, as shown in FIG. 4, the deflection that occurs at the time of fastening occurs in such a manner that the more outwardly arranged cells (or terminals) are, the larger the outward expansion occurs. Therefore, in the cross section of FIG. 1, the cell 12a (and the terminal 14a) disposed in the vicinity of the terminal 14a on the bulging side of the arc shape of the fuel cell 10 finally configured (left side in the drawing) is Is formed so as to swell inward (right in the drawing). On the other hand, the cell 12b (and the terminal 14b) disposed in the vicinity of the terminal 14b of the arc-shaped depression (right side of the drawing) is inward (left of the drawing) so that the curvature of the cell 12b is smaller than after the fastening. ) Curved toward the surface.

  In other words, before the fastening, when the cell having the smallest curvature arranged on the left side of the paper from the center of the fuel cell 10 is the center cell 12c, the cell arranged between the center cell 12c and the terminals 14a and 14b is Each has a shape in which the opposite side (outer side) from the center cell 12c is recessed. Further, the curvature of the cell is increased as the cell is located farther away from the center cell 12c and placed outside in the stacking direction.

  In the fuel cell 10 configured as described above before fastening, at the time of fastening, the cell 12a (and the terminal 14a) disposed on the left side of the paper with respect to the center cell 12c is bent toward the left side of the paper. Accordingly, the portion bent toward the center cell 12c (inner side) is canceled out, and the shape swells to the left side of the drawing. Further, with respect to the cell 12 arranged on the left side of the paper 12d than the cell 12d arranged at the actual center of the stacked cells 12 including the center cell 12c, the cell 12 is swelled toward the left side of the paper at the time of fastening. Deflection occurs. Accordingly, the cells in the vicinity of the center cell 12c are also curved toward the left side of the page as shown in FIG.

  Furthermore, the cell 12b (and the terminal 14b) on the right side of the paper surface from the cell 12d that is actually arranged at the center is formed to bend in the same direction as the bent direction after fastening. However, when these cells 12b are fastened, deflection occurs in the direction opposite to the bending direction of the cells 12 after fastening (right side of the drawing). Therefore, the curvature of these cells 12b is smaller than that before fastening.

  As a result, according to the second embodiment, all the cells 12 receive the fastening force at the time of fastening, and as shown in FIG. 1, the cells 12 are curved in the same direction with the same curvature. Thus, by adopting a shape that takes into account the deflection at the time of fastening, it is possible to reduce the variation in surface pressure due to the deflection that occurs when the fuel cell 10 is fastened.

  In the above embodiment, when the number of each element, number, quantity, range, etc. is mentioned, it is mentioned unless otherwise specified or clearly specified in principle. The number is not limited. The structures described in the embodiments are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

It is a schematic diagram for demonstrating the fuel cell in Embodiment 1 of this invention. It is a schematic diagram for demonstrating the cell of the fuel cell of Embodiment 1 of this invention. It is a schematic diagram for demonstrating the separator of the cell of Embodiment 1 of this invention. It is a figure for demonstrating the bending which generate | occur | produces at the time of the fastening of the conventional fuel cell. It is a figure for demonstrating the state before the fastening of the fuel cell of Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell 12 Cell 14 Terminal 16 Insulator 18 End plate 20 Fastening member 22 Electrolyte membrane 24 Anode 26 Cathode 28 Separator

Claims (5)

A plurality of stacked cells;
A pair of collector plates disposed on both outer sides in the stacking direction of the stacked cells;
A pair of end plates disposed outside the collector electrode plate;
From the outside of the pair of end plates, a fastening member that fastens and tightens the stacked cells;
With
Each of the cells has a curved shape in a cross section parallel to the stacking direction, and
An electrolyte membrane;
A pair of electrodes disposed on both sides of the electrolyte membrane;
The separators disposed on both sides of the pair of electrodes, respectively, constituting a fuel gas channel and an oxidizing gas channel;
A fuel cell comprising:   2. The fuel cell according to claim 1, wherein the plurality of cells are curved with the same curvature in the same direction in the cross section. In a state before being fastened by the fastening member,
The plurality of cells are formed with different curvatures; and
In the cross-section, when the cell having the smallest curvature among the plurality of cells is a central cell, the cell disposed outside the central cell in the stacking direction has a recessed shape on the outside, and the central cell 3. The fuel cell according to claim 1, wherein the curvature increases with increasing outside in the stacking direction.   The fuel cell according to any one of claims 1 to 3, wherein the curvature of the cell is in a range of 0.1 to 10.   The fuel cell according to any one of claims 1 to 4, wherein a pressure applied to each of the cells of the fuel cell is in a range of 0.1 MPa to 10 MPa.

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