JP2009277521A - Fuel cell stack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell stack with a comparatively simple structure, less heat loss by heat dissipation, and with high heat recovery efficiency. <P>SOLUTION: The fuel cell stack is structured of a laminate body 11 with a plurality of unit cells, a pair of current collecting plates 12a, 12c arranged on either end of the laminate body 11, a pair of end plates 13a, 13c arranged at outer sides of the current collecting plates 12a, 12c, a plurality of elastic bodies 14 fitted so as to give pressing force between the current collecting plates 12a, 12c, and a thermal insulation 18 arranged so as to cover a periphery of the elastic bodies 14. The heat dissipation from the elastic bodies 14 is reduced, and degradation of heat recovery efficiency from the fuel cell stack is restrained due to heat loss by heat dissipation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell stack used for a portable power source, a power source for an electric vehicle, a stationary cogeneration system, and the like.

  In a polymer electrolyte fuel cell, a catalytic reaction layer mainly composed of carbon powder carrying a platinum-based metal catalyst is disposed on both sides of a polymer electrolyte membrane in close contact with each other. Basic structure of a fuel cell in which a membrane-electrode assembly (hereinafter referred to as MEA) in which a pair of gas diffusion electrode layers having characteristics is arranged to constitute an anode and a cathode is sandwiched between a pair of conductive separators This basic configuration is called a single cell.

  Gas separators are provided on the surfaces of the separators in contact with the anode and cathode of the MEA. Through these gas passages, the anode and cathode each contain hydrogen and other oxygen, such as hydrogen. An oxidant gas (hereinafter, fuel gas and oxidant gas may be collectively referred to as reaction gas) is supplied.

  At the anode, electrons are released from hydrogen atoms in the fuel gas by the electrode reaction to generate hydrogen ions, and these electrons reach the cathode through an external circuit (load) via the separator.

  On the other hand, hydrogen ions pass through the polymer electrolyte membrane and reach the cathode, where hydrogen ions, electrons, and oxygen in the oxidant gas are combined to generate water.

  Note that an MEA gasket having a seal structure is provided between the separator and the MEA so that the reaction gas does not leak from a predetermined region.

  In general, a fuel cell is used in a state (called a fuel cell stack) in which a plurality of single cells are electrically stacked in series and fastened in order to obtain necessary power. That is, a single-cell laminate is formed by overlapping the single-cell anode-side separator and the adjacent single-cell cathode-side separator so as to be electrically connected.

  In addition, a groove is provided in a region corresponding to the reaction region on the surface of the anode side separator and / or the cathode side separator where the gas flow path is not provided. Constitutes the road.

  In power generation, by circulating cooling water or antifreeze liquid through the cooling water flow path, the temperature of the fuel cell stack can be controlled to a predetermined temperature, and the generated heat can be used externally. A cooling water seal is arranged between adjacent single cells to prevent this cooling water from leaking from a predetermined area.

  The fuel cell stack includes current collecting plates provided with terminals for taking out electric power by connecting to an external circuit at both ends of a single cell stack, and further includes a pair of end plates on the outside thereof. And it is comprised by fastening between this pair of end plates with a fastening jig.

  In addition, an elastic body (for example, a coil spring or a disc spring) is disposed outside the current collector in the stacking direction, and there are differences in the holding structure and arrangement order depending on the fuel cell stack, but there is a difference between the separator and the MEA. Pressure is applied to improve adhesion.

  In addition, this elastic body exerts a pressing force on the MEA gasket and the cooling water seal to exhibit the sealing performance. In addition, the looseness of the fastening due to the thermal expansion / contraction of the fuel cell stack components due to the temperature difference between when the fuel cell stack generates power and when the power generation stops, and the deterioration of the sealing performance. It also functions to suppress loosening of the fastening and deterioration of sealing performance.

  The structure for holding the elastic body is, for example, a structure in which the elastic body is sandwiched between the end plate and the current collector plate, and the end plate is fastened with a fastening jig to compress the elastic body, or the end plate is fastened. Generally, an elastic body is disposed between the end portion of the rod and the end plate, and the elastic body is compressed between the end portion and the end plate of the fastening rod.

  The pressing force between the separator and the MEA is preferably uniform within the reaction surface. That is, since the pressing force in the reaction surface is closely related to the contact resistance between the separator and the MEA, it is conceivable that the distribution of the pressing force causes the distribution of power generation and reduces the durability of the MEA. . Therefore, in a general fuel cell stack, a plurality of elastic bodies are arranged with consideration given to a uniform pressing force on the reaction surface.

Further, another conventional fuel cell stack 31 shown in FIG. 5 includes a spring module 35 in which a plurality of coil springs 32 are assembled by a first casing 33 and a second casing 34 as shown in FIG. The contact pressure between the MEA and the separator is made uniform (see, for example, Patent Document 1).
JP 2004-288618 A

  However, the conventional fuel cell stack 31 has the following problems.

  That is, in particular, in the fuel cell stack 31 used in the cogeneration system, the efficiency of power generation is increased, and heat generated simultaneously with power generation is transferred to the outside of the fuel cell stack 31 by a cooling medium such as cooling water, and the heat In order to effectively use the fuel cell, it is required to reduce the heat loss due to heat radiation from the fuel cell stack 31 as much as possible and to improve the heat recovery efficiency.

  However, the conventional fuel cell stack 31 has a problem that heat loss occurs due to heat radiation from the elastic body, and heat recovery efficiency decreases. Further, in the fuel cell stack 31 using the spring module 35 in which the elastic body 32 is assembled by the casings 33 and 34 as in the conventional fuel cell stack 31, in addition to the direct heat dissipation from the elastic body 32, the elastic body 32 is elastic. There was a problem that heat transfer from the body 32 to the casings 33 and 34 caused heat loss due to heat radiation from the casings 33 and 34.

  The fuel cell stack of the present invention solves the above-described conventional problems, and an object thereof is to provide a fuel cell stack with little heat loss due to heat dissipation.

  In order to solve the above-described problems, the fuel cell stack of the present invention is configured such that the periphery of the elastic body is covered with a heat insulating material, thereby reducing heat dissipation from the elastic body.

  Since the fuel cell stack of the present invention can reduce the heat radiation from the elastic body, it can reduce the heat loss of the fuel cell stack and suppress the reduction of the heat recovery efficiency.

  A fuel cell stack according to a first aspect of the present invention includes a stack of a plurality of single cells, a pair of current collector plates disposed at both ends of the stack, a pair of end plates disposed outside the current collector plate, and a current collector plate. A plurality of elastic bodies provided so as to give a pressing force, and a heat insulating material arranged so as to cover the periphery of the elastic body. The decrease can be suppressed.

  The fuel cell stack according to the second invention is the fuel cell stack according to the first invention, in particular, in which the heat insulating material is formed in a substantially plate shape provided with a hole for accommodating the elastic body, and by suppressing heat dissipation from the elastic body. And the fall of the heat recovery efficiency by the heat radiation from an elastic body can be suppressed. In addition, since the elastic body is accommodated in the heat insulating material, the structure of the fuel cell stack does not increase.

  In the fuel cell stack according to the third invention, in particular, in the second invention, the elastic body is located between the current collector plate and the end plate, and is covered with the current collector plate and the end plate. Since the position of the elastic body can be regulated by the heat insulating material in addition to the effect of the invention, the elastic body can be positioned with a relatively simple configuration. Moreover, since the heat insulating material is covered with the current collector plate and the end plate, the heat insulating material can be protected.

  A fuel cell stack according to a fourth invention is the fuel cell stack according to the third invention, particularly in the third invention, wherein the end plate is provided with a recess in which at least a part of the elastic body can be accommodated. Since it becomes possible to regulate, the elastic body can be positioned with a relatively simple configuration. In addition, since the position of the heat insulating material is regulated by the end plate, the heat insulating material can be positioned.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiments.
(Embodiment 1)
FIG. 1 is an exploded view of a single cell constituting the fuel cell stack according to Embodiment 1 of the present invention.

  As shown in FIG. 1, a unit cell 10 of a polymer electrolyte fuel cell includes an MEA 23 configured by sandwiching a polymer electrolyte membrane 21 between a pair of electrodes 22 that form a cathode and an anode, and an outer periphery of the MEA 23. The frame 1 formed of an electrically insulating resin integrated with the MEA 23 is sandwiched between carbon separators 24 each composed of a pair of anode side separators 24a and cathode side separators 24c. The frame 1 and the separator 24 are formed in a rectangular shape having the same main surface size.

  The anode side separator 24a, the cathode side separator 24c, and the upper part of one side portion (on the left side shown in FIG. 1, hereinafter referred to as the first side portion) of the main surface of the frame 1 contain hydrogen from the outside. A fuel gas inlet manifold hole 2 for introducing the fuel gas was formed, and the lower part of the other side part (on the right side shown in FIG. 1 and hereinafter referred to as the second side part) was not used for power generation. A fuel gas outlet manifold hole 3 for discharging the fuel gas to the outside is formed.

  An oxidant gas inlet manifold hole 4 for introducing an oxidant gas containing oxygen from the outside is formed in the upper part of the second side part, and the lower part of the first side part is used for power generation. An oxidant gas outlet manifold hole 5 for discharging the oxidant gas that has not been discharged to the outside is formed.

  Further, a cooling water inlet manifold hole 6 is formed inside the anode side separator 24 a, the cathode side separator 24 c, and the oxidant gas inlet manifold hole 4 inside the frame 1, and at the lower part of the oxidant gas outlet manifold hole 5. A cooling water outlet manifold hole 7 is formed inside.

  The fuel gas inlet manifold hole 2, the fuel gas outlet manifold hole 3, the oxidant gas inlet manifold hole 4, the oxidant gas outlet manifold hole 5, the cooling water inlet manifold hole 6 and the cooling water outlet manifold hole 7 are in the thickness direction of a single cell. Each of them is provided correspondingly.

  The fuel gas inlet manifold hole 2, the fuel gas outlet manifold hole 3, the oxidant gas inlet manifold hole 4, the oxidant gas outlet manifold hole 5, the cooling water inlet manifold hole 6 and the cooling water outlet manifold hole 7 will be described later. When a plurality of single cells are stacked to form a fuel cell stack, a fuel gas supply manifold, a fuel gas discharge manifold, an oxidant gas supply manifold, an oxidant gas discharge manifold, a cooling water supply manifold, and a cooling water discharge manifold, respectively. Configure.

  Further, on the cathode side of the frame 1, a region surrounding the electrode 22, the oxidant gas inlet manifold hole 4, and the oxidant gas outlet manifold hole 5, the fuel gas inlet manifold hole 2, and the fuel gas outlet manifold hole 3 The predetermined reaction gas or cooling water flowing in each region is prevented from leaking out of the region in the region surrounding the outer periphery of each of the cooling water inlet manifold hole 6 and the cooling water outlet manifold hole 7. An MEA gasket 25 is provided.

  On the anode side of the frame 1, similarly to the cathode side, a region surrounding the electrode 22, the fuel gas inlet manifold hole 2 and the fuel gas outlet manifold hole 3, an oxidant gas inlet manifold hole 4, and an oxidant The reaction gas or cooling water flowing in each region leaks out of the region into the region surrounding the outer periphery of each of the gas outlet manifold hole 5, the cooling water inlet manifold hole 6, and the cooling water outlet manifold hole 7. An MEA gasket (not shown) is provided for the purpose.

  A fuel gas inlet manifold hole 2 and a fuel gas outlet manifold hole 3 are connected to a surface of the anode side separator 24a in contact with the MEA 23 (hereinafter, this surface is referred to as a front surface of the anode side separator). Is provided.

  This fuel gas flow path 26 is connected to the outside by an MEA gasket (not shown for the rear surface of the frame 1) that surrounds the electrode 22 on the anode side of the frame 1, the fuel gas inlet manifold hole 2, and the fuel gas outlet manifold hole 3. A plurality of horizontal portions extending in the horizontal direction and vertical portions extending in the vertical direction are combined in a serpentine shape at a position corresponding to the sealed area.

  Specifically, from the fuel gas inlet manifold hole 2 on the first side portion side, it extends toward the second side portion in the horizontal direction, in the vicinity of the second side portion in the region surrounded by the MEA gasket, After changing the direction downward in the vertical direction and extending downward by a predetermined distance, it extends horizontally again toward the first side. From there, the flow path pattern is repeated a predetermined number of times within the region surrounded by the MEA gasket, and finally reaches the fuel gas outlet manifold hole 3.

  The region where the fuel gas channel 26 is provided substantially overlaps the region in contact with the electrode 22 except for a part of the horizontal portion connected to the fuel gas inlet manifold hole 2 and the fuel gas outlet manifold hole 3. As a result, the fuel gas can be spread over the entire surface of the electrode 22.

  Further, on the surface of the cathode side separator 24c in contact with the MEA 23 (hereinafter, this surface is referred to as the front side of the cathode side separator), the oxidant gas inlet manifold hole 4 and the oxidant gas outlet are provided as in the front side of the anode side separator 24a. An oxidant gas flow path (not shown) for connecting the manifold hole 5 and supplying the oxidant gas to the electrode 22 is provided in a serpentine shape.

  The region where the oxidant gas flow path is provided substantially overlaps the region in contact with the electrode 22 except for a part of the horizontal portion connected to the oxidant gas inlet manifold hole 4 and the oxidant gas outlet manifold hole 5. As a result, the oxidant gas can be spread over the entire surface of the electrode 22.

  A cooling water flow path 8 connecting the cooling water inlet manifold hole 6 and the cooling water outlet manifold hole 7 is formed on the main surface of the cathode side separator that is not the front surface (hereinafter, this surface is referred to as the back surface of the cathode side separator). It is provided.

  Further, on the back surface of the cathode separator, a region surrounding the cooling water flow path 8, the cooling water inlet manifold hole 6, and the cooling water outlet manifold hole 7, the fuel gas inlet manifold hole 2, the fuel gas outlet manifold hole 3, A cooling water seal 9 is provided to surround the outer periphery of each of the oxidant gas inlet manifold hole 4 and the oxidant gas outlet manifold hole 5 so that a predetermined reaction gas and cooling water flowing through each region do not leak to the outside. It is like that.

  The cooling water flow path 8 is substantially composed of a horizontal portion extending in the horizontal direction and a vertical portion extending in the vertical direction.

  Specifically, the cooling water flow path 8 extends a predetermined distance vertically downward from the cooling water inlet manifold hole 6 on the upper side of the second side, and then turns to the first side to change the second side. Reach the side and turn again vertically downwards.

  And after extending downward for a predetermined distance, this time it extended horizontally toward the second side to reach the second side, and turned downward for a predetermined distance on the second side. Later, it now extends horizontally towards the first side. The horizontal and vertical flow path patterns are repeated a predetermined number of times, and finally connected to the cooling water outlet manifold hole 7 below the first side portion.

  The area where the cooling water flow path 8 is provided is the area where the oxidant gas flow path is provided in front of the cathode side separator, and the area where the fuel gas flow path 26 is provided in front of the anode side separator, that is, the electrode 22. It almost overlaps with the area.

  However, a part of the vertical part connected to the cooling water inlet manifold hole 6 and the cooling water outlet manifold hole 7 is located outside the region.

  2 is a perspective view of a fuel cell stack formed by stacking a plurality of single cells shown in FIG. 1, and FIG. 3 is a cross-sectional view taken along line AA in FIG. However, the left side surface in FIG. 2 is shown as the top in FIG.

  As shown in FIG. 2, the fuel cell stack is formed by stacking a plurality of single cells shown in FIG. 1 so that the anode separator 24a of the single cell and the cathode separator 24c of the adjacent single cell are electrically connected. A pair of current collector plates (first current collector plate 12a, second current collector plate 12c) are arranged at both ends of the laminated body 11, and a pair of end plates (first end plate 13a, second 2 end plates 13c), and the first end plate 13a and the second end plate 13c are fastened with fastening bolts (not shown).

  The current collector plate 12 includes two types, a first current collector plate 12a and a second current collector plate 12c. The first current collector plate 12a includes a fuel gas discharge manifold, an oxidant gas discharge manifold, and a cooling device. Through holes corresponding to the water discharge manifold are provided, and through holes corresponding to the fuel gas supply manifold, the oxidant gas supply manifold, and the cooling water supply manifold are provided in the second current collecting plate 12c.

  In addition, a part of the current collector plates (first current collector plate 12a, second current collector plate 12c) protrudes from the main surface shape of the laminate 11, and forms a terminal portion 12d to form an external load (not shown). Connected with.

  By the way, the current collector plate takes out the electric power generated in the fuel cell stack to an external circuit over a long period of time with a small electric loss, so that the contact resistance with the laminated body 11 is small, the corrosion resistance is excellent, and the conductive material is conductive. It must be good.

  Therefore, a metal current collector plate is generally used. However, when a metal current collector plate is formed into a complicated shape, the metal plate having a relatively thin plate thickness (thickness is increased) because the molding and processing costs are increased and the weight of the fuel cell stack is increased. It is desirable to use one having a relatively simple shape, such as punching out about 1 to 5 mm.

  In the fuel cell stack according to the present embodiment, a brass plate (thickness 2 mm) punched into a current collector plate shape by press working is subjected to gold plating, and a current collector with improved flatness, corrosion resistance, and conductivity is collected. Used as a plate.

  The end plates (the first end plate 13a and the second end plate 13c) are formed of an electrically insulating resin, and a fuel gas supply manifold, an oxidant gas supply manifold, and a cooling water supply are supplied to the second end plate 13c. A through hole corresponding to the manifold is provided, and a fuel gas inlet for introducing fuel gas into the fuel cell stack is provided on the opposite surface of the second end plate 13c to the main surface facing the second current collector plate 12c. A pipe 15, an oxidant gas inlet pipe 16 for introducing oxidant gas into the fuel cell stack, and a cooling water inlet pipe 17 for introducing cooling water into the fuel cell stack are provided.

  The first end plate 13a is provided with through holes corresponding to the fuel gas discharge manifold, the oxidant gas discharge manifold, and the cooling water discharge manifold, and further the first current collecting of the first end plate 13a. On the opposite side of the surface facing the plate 12a, there are a fuel gas outlet pipe for discharging fuel gas from the stack, an oxidant gas outlet pipe for discharging oxidant gas from the stack, and a cooling water outlet pipe for discharging cooling water. Is provided.

  Further, as shown in FIG. 3, a plurality of coil springs 14 are provided between the current collecting plate 12 and the end plate 13 by stress distribution analysis or the like so that the contact pressure between the MEA and the separator is uniform within the reaction surface. It is provided in a considered arrangement. Further, a recess 13d into which a part of the coil spring 14 is inserted is provided at a position where the coil spring 14 of the end plate 13 is disposed, and the coil spring 14 is displaced from a predetermined position when the fuel cell stack is assembled. Is preventing.

  Further, as shown in FIG. 3, a plate-like heat insulating material 18 is provided between the current collector plate 12 and the end plate 13. The heat insulating material 18 is provided with a through hole 18a in which the coil spring 14 compressed by the current collector plate 12 and the end plate 13 is accommodated. The inner wall of the through hole 18a holds the coil spring 14 so as not to fall by its own weight. The

  Moreover, the thickness of the heat insulating material 18 has a thickness equivalent to a gap generated between the end plate and the current collector plate when the fuel cell stack is fastened. That is, when laminating the members constituting the fuel cell stack, which is thinner than the natural length of the coil spring, even if the coil spring is inserted into the heat insulating material, the coil spring is not completely buried in the heat insulating material, and a part of It comes out of the heat insulating material.

  In the fuel cell stack shown in the first embodiment, a hard plate-like vacuum heat insulating material using glass wool as a core material is used as the heat insulating material 18, but it is relatively soft and compressible like a silicone sponge. In this case, the thickness of the heat insulating material may not be the above relationship.

  With this configuration, since the surface of the current collector plate facing the end plate and the outer peripheral surface of the coil spring are covered with a heat insulating material, the heat generated by the laminate is reduced, and the heat recovery by the cooling water is reduced by the heat dissipation. It can suppress that efficiency falls.

  In the configuration according to the first embodiment, the heat escaping from the current collector plate through the coil spring to the end plate cannot be expected to decrease, but the direct current from the current collector plate close to the laminate as a heat source is not expected. Compared to heat radiation, the heat radiation amount is expected to be small, and one of the through holes provided in the heat insulating material of the first embodiment is closed, and the coil spring is compressed at the bottom of the hole instead of the through hole. In this case, it is possible to reduce the heat that escapes from the end plate through the coil spring. However, also in that case, it is expected that the effect of reducing the influence of heat radiation can be expected by heat insulation on the side of the current collector plate close to the heat source.

  Insulation also plays an important role in assembling the fuel cell stack. That is, when assembling a fuel cell stack, a plurality of single cells prepared in advance are stacked with a cooling water seal interposed therebetween, and a plurality of coil springs and heat insulating materials are placed at predetermined positions on one end plate. After the arrangement, one current collector plate is placed thereon, and a single cell laminate is formed thereon.

  Under the present circumstances, the recessed part provided in the end plate and the through-hole provided in the heat insulating material make it easy to arrange | position the position of a coil spring in a predetermined position. Furthermore, when arranging the coil spring after arranging the other current collector plate on the laminate, by arranging the coil spring in the through hole after arranging the heat insulating material on the current collector plate first, It is possible to easily arrange the coil spring at a predetermined position.

  In the fuel cell stack of the first embodiment, the coil spring and the heat insulating material are disposed between the current collector plate and the end plate. However, as shown in FIG. 4, the coil spring is disposed outside the end plate and between the end plates. Even in the fuel cell stack that is held in a state where the inner hole of the coil spring is penetrated by the fastening rod 19 for fastening the coil spring, it is possible to suppress a decrease in heat recovery efficiency due to heat dissipation by covering the periphery of the coil spring with a heat insulating material. is there.

  In the first embodiment, the coil spring is used as the elastic body. However, the elastic body of another form such as a leaf spring or a disc spring does not hinder the effect of the present embodiment.

  As described above, the polymer electrolyte fuel cell according to the present invention can be applied to uses such as a portable power source, a power source for an electric vehicle, and a stationary cogeneration system.

1 is an exploded view of a single cell of a fuel cell stack according to Embodiment 1 of the present invention. The perspective view of the fuel cell stack of Embodiment 1 AA sectional view of FIG. Partial sectional view showing another form of the fuel cell stack of the first embodiment Side view of conventional fuel cell stack Sectional view of a conventional fuel cell stack spring module

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Frame 2 Fuel gas inlet manifold hole 3 Fuel gas outlet manifold hole 4 Oxidant gas inlet manifold hole 5 Oxidant gas outlet manifold hole 6 Cooling water inlet manifold hole 7 Cooling water outlet manifold hole 8 Cooling water flow path 9 Cooling water seal 10 Single cell 11 Laminated body 12 Current collector plate 12a First current collector plate 12c Second current collector plate 12d Terminal portion 13 End plate 13a First end plate 13c Second end plate 13d Recessed portion 14 Coil spring 15 Fuel gas inlet piping 16 Oxidant gas inlet piping 17 Cooling water inlet piping 18 Heat insulating material 18a Through hole 21 Polymer electrolyte membrane 22 Electrode 23 MEA
24 Separator 24a Anode-side separator 24c Cathode-side separator 25 MEA gasket 26 Fuel gas flow path

Claims (4)

A pressing force is applied between the stacked body of a plurality of single cells, a pair of current collector plates disposed at both ends of the stacked body, a pair of end plates disposed on the outer P side of the current collector plate, and the current collector plate. A fuel cell stack comprising a plurality of elastic bodies provided as described above and a heat insulating material arranged to cover the periphery of the elastic bodies. The fuel cell stack according to claim 1, wherein the heat insulating material is formed in a substantially plate shape provided with a hole in which the elastic body is accommodated. The fuel cell stack according to claim 2, wherein the elastic body is located between the current collector plate and the end plate and is covered with the current collector plate and the end plate. The fuel cell stack according to claim 3, wherein the end plate is provided with a recess in which at least a part of the elastic body is received.

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