JP2010244913A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a gas sealing property at a gas diffusion layer in a fuel cell. <P>SOLUTION: Fuel cells 12 are fastened along a laminating direction by alternately laminating separators 60 and fuel cells 50 to form refrigerant flow passages 64 in a cell inside between end plates which are in opposite direction to a fuel cell 50. As for the separators 60 which are mutually neighboring pinching the fuel cells 50, one separator presses a gasket 67 which the other separator 60 has to an MEA 52 of the fuel cell 50 based on a fastening force. The other separator 60 receives the pressing force by the gasket 67 of the other separator 60 with an elastic member 68, via the MEA 52 and an anode gas diffusion layer 56. This elastic member 68, on being made convex by the refrigerant pumped by a refrigerant pumping pressure to the refrigerant passage in the cell 64, receives the pressing force by the gasket 67 by a pumping pressure of the refrigerant. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel cell in which battery cells that generate power upon receiving supply of a fuel gas and an oxygen-containing gas and separators having a refrigerant flow path through which a refrigerant is pumped and passed are alternately stacked.

  The fuel cell generates electricity by advancing an electrochemical reaction between a fuel, for example hydrogen, in the fuel gas supplied to the anode and oxygen in the oxygen-containing gas supplied to the cathode. A gas diffusion layer is bonded to both anode and cathode surfaces of a membrane electrode assembly (MEA) including an electrolyte membrane and a catalyst electrode bonded to both sides of the membrane. Is diffusely supplied.

  In such gas supply, sealing on the side of the gas diffusion layer joined to the electrode surface is indispensable, and various gas sealing techniques have been proposed (for example, Patent Document 1).

JP 2007-324114 A

  In the above-mentioned patent document, the seal member provided on the separator surface is pressed against the MEA to achieve a seal on the side where the seal member is located. At this time, the pressing force of the seal member is the gas diffusion layer facing the MEA. It will extend to. That is, the gas diffusion layer itself receives the pressing force of the seal member. By the way, since the gas diffusion layer is generally porous in order to supply and diffuse gas, it has low rigidity. For this reason, when the gas diffusion layer receives the pressing force as described above, there is a concern that the seal linear pressure on the pressing side of the seal member may be insufficient or unstable.

  In view of the above-described problems, an object of the present invention is to improve the gas sealing property on the gas diffusion layer side in a fuel cell.

  In order to achieve at least a part of the above object, the present invention adopts the following configuration.

[Application: Fuel cell]
A fuel cell in which fuel cells and oxygen-containing gas are supplied to generate power, and a separator having a refrigerant flow path through which a refrigerant is pumped and passed alternately,
The battery cell is
A membrane electrode assembly including an electrolyte membrane and a catalyst electrode bonded to both sides of the membrane;
An anode gas diffusion layer bonded to one surface of the membrane electrode assembly and supplying the fuel gas to the catalyst electrode on the anode side;
A cathode gas diffusion layer bonded to the other surface of the membrane electrode assembly and supplying the oxygen-containing gas to the catalyst electrode on the cathode side;
The separator is provided with a first seal member on one separator surface side and a second seal member on the other separator surface side back to back with the refrigerant flow path interposed therebetween,
The first seal member extends from the one separator surface and abuts on the membrane electrode assembly to exert a sealing force on the membrane electrode assembly,
The second seal member receives the pressure of the refrigerant passing through the refrigerant flow path, maintains the convex shape of the convex portion protruding from the other separator surface, and bonds the anode gas to the other separator surface. The gist is to press the layer or the cathode gas diffusion layer with the convex portion.

  In the fuel cell having the above configuration, in the state where the battery cells and the separators are alternately stacked, the separator includes the first seal member and the second seal member back to back with the refrigerant flow path interposed therebetween. The separators that are adjacent to each other face each other. In the first seal member and the second seal member that face each other in this manner, the first seal member in one separator extends from the surface of the one separator and contacts the membrane electrode assembly to seal the membrane electrode assembly. Exert the power of. On the other hand, the second seal member in the other separator receives the pressure of the refrigerant passing through the refrigerant flow path and maintains the convex shape of the convex portion protruding from the other separator surface, while the other separator surface The anode gas diffusion layer or the cathode gas diffusion layer bonded to the substrate is pressed by the convex portion. For this reason, in the fuel cell having the above-described configuration, the second sealing material that receives the pressure of the refrigerant and maintains the convex shape of the convex portion protruding from the separator surface while crushing the gas diffusion layer bonded to the separator surface, The pressing force by the first seal member of one separator is received by the pressure of the refrigerant. Therefore, the seal linear pressure when the first seal member is in contact with the membrane electrode assembly at the top increases, and the rigidity of the gas diffusion layer at the location where it is crushed by the convex second seal material under the pressure of the refrigerant Will rise. As a result, according to the fuel cell having the above-described configuration, the gas seal of the gas diffusion layer (either the anode gas diffusion layer or the cathode gas diffusion layer) on the side where the first seal member that contacts the membrane electrode assembly is present. It can be secured with high reliability.

It is explanatory drawing which shows schematic structure of the fuel cell system 10 as an Example of this invention. It is explanatory drawing which expands and shows the principal part of a fuel cell typically in cross section.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view showing a schematic configuration of a fuel cell system 10 as an embodiment of the present invention, and FIG.

  The fuel cell system 10 includes a fuel cell 12, and the fuel cell 12 is cooled by a cooling system 20. The cooling system 20 includes a circulation path 22 for circulating refrigerant from the radiator 30 to the fuel cell 12, an in-side valve 21a and an out-side valve 21b of the fuel cell 12 in the path, a bypass path 24 of the radiator 30, and a bypass. A three-way flow rate adjustment valve 26 at the path junction, a circulation pump 28, and a bypass path 32 having an ion exchanger 40 are provided. The cooling system 20 guides the refrigerant heat-exchanged by the radiator 30 to a later-described in-cell refrigerant flow path 64 (see FIG. 2) of the fuel cell 12 through the circulation path 22, and cools the fuel cell 12 to a predetermined temperature. To do. In this case, the driving amount of the circulation pump 28 during the operation of the fuel cell 12 (during power generation operation), that is, the circulation supply amount of the refrigerant and the radiator bypass flow rate by the three-way flow control valve 26 are based on the fuel cell temperature and the power generation status. Is determined by a control device (not shown). It is also possible to incorporate a three-way flow rate adjustment valve at the path junction of the bypass path 32 so as to determine the flow rate to the ion exchanger 40 based on the fuel cell temperature and the power generation status. The fuel cell system 10 includes a hydrogen gas supply system and an air supply system for supplying gas to the fuel cell 12 in addition to the cooling system 20 described above, but the description thereof is omitted because it is not directly related to the gist of the present invention. To do.

  As shown in FIG. 2, the fuel cell 12 includes battery cells 50 and separators 60 that are power generation units alternately stacked, and the battery cells 50 are sandwiched between the separators 60 on both sides thereof. The battery cell 50 includes a membrane electrode assembly (MEA) 52 in which both anode and cathode electrodes are bonded to both sides of an electrolyte membrane, and a cathode gas diffusion layer 54 and an anode gas diffusion layer 56 bonded to both sides thereof. With. Both gas diffusion layers are composed of members having gas permeability and electronic conductivity. For example, the gas diffusion layers are formed of a carbon material such as carbon paper, a metal member such as a foam metal, a metal mesh, and the like. The supplied gas (hydrogen gas, air) is diffused and supplied to the MEA 52. In the battery cell 50 of the present embodiment, for the convenience of using one gas diffusion layer, for example, the anode gas diffusion layer 56 for sealing the MEA 52, the formation range of the anode gas diffusion layer 56 reaches the vicinity of the end of the MEA 52. Thus, the cathode gas diffusion layer 54 is reserved before the end of the MEA 52.

  The separator 60 is called a so-called three-layer separator, and is configured by interposing an intermediate plate 63 between a first plate 61 and a second plate 62 and joining these plates. In this embodiment, the second plate 62 joined to the cathode gas diffusion layer 54 of the battery cell 50 includes a gasket 67 having a convex cross section on the outer surface thereof, and is joined to the anode gas diffusion layer 56. The plate 61 includes an elastic member 68 that protrudes from the outer surface thereof. The elastic member 68 is formed of a member such as rubber having heat resistance. The elastic member 68 is inserted into the through hole 69 formed in the first plate 61 from the inside of the separator, that is, the in-cell refrigerant flow path 64 formed by the intermediate plate 63 between the first plate 61 and the second plate 62. As described above, it is projected from the outer surface of the first plate 61. In this case, the gasket 67 and the elastic member 68 are positioned back to back with the in-cell refrigerant flow path 64 sandwiched between them in the same separator 60, and face each other between the separators 60 that sandwich the battery cell 50 therebetween.

  The manufacturing procedure of the separator 60 will be briefly described. First, the elastic member 68 is attached to the through hole 69 of the first plate 61. Next, the intermediate plate 63 is sandwiched between the first plate 61 and the second plate 62 to which the elastic member 68 is already attached, and these plates are joined and fixed by a technique such as welding. Thereby, the in-cell refrigerant flow path 64 is formed between the first plate 61 and the second plate 62, and the in-cell refrigerant flow path 64 is connected to the inside of the convex portion of the gasket 67. When the intermediate plate 63 is sandwiched or after the plates are joined and fixed, the elastic member 68 is bonded to the second plate 62 at a position where the gasket 67 is back to back. The separator 60 forms the above-described in-cell refrigerant channel 64, and also includes an in-cell gas channel for supplying hydrogen gas to the anode gas diffusion layer 56 and an in-cell gas channel for supplying air to the cathode gas diffusion layer 54. However, since these in-cell gas flow paths are not directly related to the gist of the present invention, the description thereof is omitted.

  The fuel cell 12 is manufactured by alternately stacking the separators 60 and the battery cells 50 obtained as described above between opposing end plates and exerting a fastening force along the stacking direction. In the fuel cell 12 thus obtained, the separators 60 adjacent to each other with the battery cell 50 pressed against the MEA 52 of the battery cell 50 with the force based on the above-described fastening force, the gasket 67 included in one separator 60. The other separator 60 receives the pressing force by the gasket 67 of the one separator 60 through the MEA 52 and the anode gas diffusion layer 56 by the elastic member 68 that the other separator 60 has.

  By the way, in the fuel cell system 10 having the above-described configuration, during the power generation operation, the refrigerant is pumped by the circulation pump 28 to the separator 60 of each battery cell 50 of the fuel cell 12 through the circulation path 22. The refrigerant thus pressure-fed always passes through the in-cell refrigerant flow path 64 over the power generation operation period, and the elastic member 68 is convex toward the anode gas diffusion layer 56 by the refrigerant pressure. For this reason, of the separators 60 adjacent to each other with the battery cell 50 interposed therebetween, the other separator 60 is pressed against one of the separators while the anode gas diffusion layer 56 is crushed by the elastic member 68 convex by the refrigerant pressure. The pressing force of the 60 gaskets 67 is received by the pressure of the refrigerant. As a result, the seal linear pressure when the gasket 67 is in contact with the MEA 52 at the top is increased, so that the gas sealing performance on the cathode gas diffusion layer 54 side and its reliability can be improved. In this case, since the anode gas diffusion layer 56 at the location crushed by the elastic member 68 has high rigidity, the anode gas diffusion layer 56 also contributes to an improvement in the seal linear pressure of the gasket 67. Therefore, even if the pumping pressure of the refrigerant fluctuates for some reason, it is possible to secure the sealing linear pressure and, in turn, secure the gas sealing property on the cathode gas diffusion layer 54 side.

  Further, in the fuel cell system 10 of the present embodiment, when the power generation operation is stopped, the valve is opened and closed in the circulation path 22 shown in FIG. 1 as follows. First, when the operation is stopped, the out side valve 21b is closed while the operation of the circulation pump 28 is continued, and the in side valve 21a is closed after the valve is stopped. Thus, the circulation pump 28 is stopped after both the out-side and in-side valves are closed. By such valve / pump control, the refrigerant is sealed in the in-cell refrigerant flow path 64 of each separator 60 in the fuel cell 12 with the above-described refrigerant pressure, and the elastic member 68 is provided even during system shutdown. It can be made convex by this refrigerant pressure. For this reason, according to the fuel cell system 10 of the present embodiment, maintenance of the sealing linear pressure by the gasket 67 during the operation stop of the system and securing of gas sealing performance on the cathode gas diffusion layer 54 side accompanying this are achieved. Can be planned.

  The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, after the formation range of the anode gas diffusion layer 56 is refrained, the gasket 67 can be provided on the in-cell refrigerant flow path 64 side, and the elastic member 68 can be provided on the second plate 62 side. 2 has an elastic member 68 on the first plate 61 and a gasket 67 on the second plate 62 to seal the cathode gas diffusion layer 54 on the upper side in the figure. The first plate 61 may be provided with a gasket 67, and the second plate 62 may be provided with an elastic member 68. In this way, gas sealing can be achieved with high reliability even on the anode gas diffusion layer 56 side.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 12 ... Fuel cell 20 ... Cooling system 21a ... In side valve 21b ... Out side valve 22 ... Circulation path 24 ... Bypass path 26 ... Three-way flow control valve 28 ... Circulation pump 30 ... Radiator 32 ... Bypass path 40 ... Ion exchanger 50 ... battery cell 54 ... cathode gas diffusion layer 56 ... anode gas diffusion layer 60 ... separator 61 ... first plate 62 ... second plate 63 ... intermediate plate 64 ... in-cell refrigerant flow path 67 ... gasket 68 ... elastic member 69 ... through hole

Claims (1)

A fuel cell in which fuel cells and oxygen-containing gas are supplied to generate power, and a separator having a refrigerant flow path through which a refrigerant is pumped and passed alternately,
The battery cell is
A membrane electrode assembly including an electrolyte membrane and a catalyst electrode bonded to both sides of the membrane;
An anode gas diffusion layer bonded to one surface of the membrane electrode assembly and supplying the fuel gas to the catalyst electrode on the anode side;
A cathode gas diffusion layer bonded to the other surface of the membrane electrode assembly and supplying the oxygen-containing gas to the catalyst electrode on the cathode side;
The separator is provided with a first seal member on one separator surface side and a second seal member on the other separator surface side back to back with the refrigerant flow path interposed therebetween,
The first seal member extends from the one separator surface and abuts on the membrane electrode assembly to exert a sealing force on the membrane electrode assembly,
The second seal member receives the pressure of the refrigerant passing through the refrigerant flow path, maintains the convex shape of the convex portion protruding from the other separator surface, and bonds the anode gas to the other separator surface. A fuel cell, wherein the layer or the cathode gas diffusion layer is pressed by the convex portion.

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