JP5730708B2 - Fuel cell - Google Patents

Description

  The present invention relates to a fuel cell, and more particularly to an internal structure of a fuel cell.

  The fuel cell has a structure in which an electrolyte membrane is sandwiched between both electrodes of a cathode and an anode, and a cathode gas containing oxygen such as air contacts the cathode, while an anode gas containing hydrogen contacts the anode. Thus, an electrochemical reaction occurs between both electrodes, and as a result, a voltage is generated between both electrodes.

  Various structures of such a fuel cell have been proposed. For example, Patent Document 1 prevents local current density concentration and temperature rise on the electrode surface to realize long-term stable operation. Therefore, a fuel cell having a structure in which a fuel gas inlet / outlet is alternately provided at one end of a separator and an air inlet / outlet is alternately provided at the other end of the separator (both ends not provided with a fuel gas inlet / outlet) is described. ing.

JP 7-249420 A

  By the way, when the above-described electrochemical reaction occurs, charge transfer occurs between the electrodes of the fuel cell via the electrolyte membrane. Therefore, in order to maintain power generation, the electrolyte membrane needs to be wet. Therefore, in general, an anode inlet (portion where the anode gas flows) is arranged at the cathode outlet (portion where the cathode gas flows), and a cathode inlet (cathode gas flows) into the anode outlet (portion where the anode gas flows). And the water generated on the cathode side is transported from the cathode outlet (anode inlet) to the anode outlet (cathode inlet) to maintain the wet state of the electrolyte membrane (that is, the water balance in the fuel cell). Is widely adopted.

  However, for example, if the fuel cell operation is continued under a high temperature condition called high temperature non-humidification operation, moisture transported from the anode inlet to the anode outlet is easily taken to the cathode side, or fuel gas consumption due to power generation As a result, the moisture on the anode side tends to be easily taken away. Then, the supply of moisture to the anode outlet becomes insufficient, and the electrolyte membrane in the vicinity thereof is locally dried. As a result, there is a problem that power generation cannot be performed at that portion and the output is reduced. This is a phenomenon that is also a concern in the fuel cell described in Patent Document 1.

  Therefore, the present invention has been made in view of such circumstances, and moisture (reaction product water) can be quickly and sufficiently transported and supplied from the cathode side to the anode side, thereby enabling high-temperature operation. An object of the present invention is to provide a fuel cell that can maintain a wet state of an electrolyte membrane well and suppress a decrease in output.

  In order to solve the above problems, a fuel cell according to the present invention includes a membrane electrode assembly in which a cathode and an anode are disposed on both surfaces of an electrolyte membrane, and a separator provided to face the membrane electrode assembly, The separator has a cathode inlet and a cathode outlet arranged side by side on a predetermined side, and an anode inlet provided on a side perpendicular to the predetermined side and arranged in the vicinity of the cathode outlet. In the vicinity of the cathode inlet and the cathode outlet, an anode gas flow path configured to allow anode gas to flow from the cathode outlet toward the cathode inlet is formed.

  In the fuel cell according to the present invention configured as described above, the anode gas flows from the anode inlet in the vicinity of the cathode outlet toward the anode outlet through the anode gas flow path, so that moisture (reaction) that tends to remain on the cathode outlet side is obtained. Product water) is transported together with the anode gas to the anode outlet, that is, the cathode inlet side. At this time, since the cathode inlet and the cathode outlet are arranged side by side on the predetermined side of the separator, the distance between the cathode inlet and the cathode outlet, that is, the transport distance of moisture by the anode gas can be effectively shortened, Before the moisture on the cathode outlet side is reduced, the moisture can be supplied to the cathode inlet side (anode outlet side).

  Therefore, according to the present invention, moisture (reaction product water) can be rapidly transported and supplied from the cathode side to the anode side, thereby suppressing the decrease in moisture even during high temperature operation. It becomes possible to maintain the wet state of the membrane satisfactorily, and as a result, it is possible to effectively prevent a decrease in the output of the fuel cell. Further, since the anode outlet and the cathode inlet to which moisture is transported are close to each other, drying near the cathode inlet can be prevented. Furthermore, since moisture can be quickly taken away from the cathode outlet, it is possible to prevent the occurrence of flooding at the cathode outlet.

FIG. 2 is an exploded view schematically showing a part of the configuration of the first embodiment of the fuel cell according to the present invention. FIG. 2 is a perspective view schematically showing a structure of a cathode separator of the fuel cell shown in FIG. 1. FIG. 2 is a perspective view schematically showing a structure of an anode separator of the fuel cell shown in FIG. 1. It is a graph which shows typically distribution (at the time of high temperature operation) of the water inside the fuel cell by the present invention. FIG. 5 is an exploded view schematically showing a part of the configuration of a second embodiment of the fuel cell according to the present invention. It is a graph which shows typically distribution (at the time of normal operation) of the moisture inside the fuel cell of the conventional composition. It is a graph which shows typically distribution (at the time of high temperature operation) of the moisture inside the fuel cell of the conventional composition.

Hereinafter, embodiments of the present invention will be described in detail. The positional relationship such as up, down, left, and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios. Furthermore, the following embodiment is an illustration for explaining the present invention, and is not intended to limit the present invention only to the embodiment. Furthermore, the present invention can be variously modified without departing from the gist thereof.
(First embodiment)
FIG. 1 is an exploded view (by a one-point perspective view) schematically showing a part of the configuration of a preferred embodiment of a fuel cell according to the present invention. The fuel cell stack 10 is a solid polymer fuel cell (PEMFC) provided with a solid polymer separation membrane, and is mainly mounted on a fuel cell vehicle or the like. The fuel cell stack 10 has a stack structure in which a plurality of unit cells 20 are stacked (only one unit is shown in the figure). In the unit cell 20, a gas diffusion layer 22 is integrally formed by a seal gasket (not shown) outside an MEA 21 (Membrane Electrode Assembly) in which an anode and a cathode are arranged with an electrolyte membrane interposed therebetween. And a cathode separator 26 and an anode separator 28 made of a conductive metal material such as stainless steel or titanium for isolating the adjacent power generation bodies 23, 23.

  The separator that separates the adjacent power generators 23 is a three-layer structure in which the cathode separator 26, the intermediate plate (not shown; mainly used as a cooling water flow path), and the anode separator 28 are stacked. In this example, the unit cell 20 is defined as described above in order to match the drawing. Further, a cathode gas flow path 30 (described later) through which the cathode gas flows is defined between the cathode separator 26 and the power generator 23, and the anode gas flows between the anode separator 28 and the power generator 23. An anode gas flow path 40 (described later) is defined.

  Here, FIGS. 2 and 3 are perspective views schematically showing the structures of the cathode separator 26 and the anode separator 28 of the fuel cell stack 10 shown in FIG. 1, respectively. As shown in FIGS. 1 to 3, the power generator 23, the cathode separator 26, and the anode separator 28 are rectangular members having substantially the same outer shape, and the cathode separator 26 is a rib RC that extends in the illustrated vertical direction at the center thereof. In addition, the anode separator 28 has a frame shape having a rib RA extending in the horizontal direction in the figure at the center thereof.

  In the peripheral portions of the power generator 23, the cathode separator 26, and the anode separator 28, cathode inlets 31 and 31 communicating with a cathode gas flow path 30 indicated by white arrows in FIG. 32, and anode inlets 41 and 41 and anode outlets 42 and 42 communicating with the anode gas flow path 40 indicated by a solid line arrow in FIG. As described above, the cathode inlets 31 and 31 function as a cathode gas inlet manifold that is a supply port of cathode gas such as air, and the cathode outlets 32 and 32 function as a cathode gas outlet manifold that is a discharge port of cathode gas. . Similarly, the anode inlets 41 and 41 are anode gas inlet manifolds that are anode gas supply ports that are fuel gas containing hydrogen, and the anode outlets 42 and 42 are anode gas outlet manifolds that are anode gas outlets. Function as.

  That is, in the cathode separator 26 and the anode separator 28, the cathode inlet 31 and the cathode outlet 32 are arranged in parallel on predetermined one side (the upper side and the lower side in the drawing), and the side perpendicular to the predetermined one side (the right side and the right side in the drawing). An anode inlet 41 is disposed in the vicinity of the cathode outlet 32 on the left side (the corner near the cathode outlet 32). The anode gas channel 40 is formed in the vicinity of the cathode inlet 31 and the cathode outlet 32 so that the anode gas flows from the cathode outlet 32 toward the cathode inlet 31.

  According to the fuel cell stack 10 configured in this way, the anode gas flows from the anode inlet 41 in the vicinity of the cathode outlet 32 toward the anode outlet 42 through the anode gas flow path 40, thereby remaining on the cathode outlet 32 side. Moisture (reaction product water) that is easily generated is transported together with the anode gas to the anode outlet 42, that is, the cathode inlet 31 side. At this time, since the cathode inlet 31 and the cathode outlet 32 are arranged side by side on a predetermined side of the cathode separator 26 and the anode separator 28, the distance between the cathode inlet 31 and the cathode outlet 32, that is, the transport distance of moisture by the anode gas. Can be effectively shortened, and the moisture can be supplied to the cathode inlet 31 side (the anode outlet 42 side) before the moisture on the cathode outlet 32 side does not decrease.

  As a result, moisture (reaction product water) can be quickly transported and supplied from the cathode side to the anode side, and even during high-temperature operation, the reduction of moisture can be suppressed and the electrolyte membrane of MEA 21 can be kept wet. As a result, it is possible to effectively prevent a decrease in the output of the fuel cell stack 10. Further, since the anode outlet 42 to which moisture is transported and the cathode inlet 31 are close to each other, it is possible to prevent the vicinity of the cathode inlet 31 from being dried. Furthermore, since moisture can be quickly taken away from the cathode outlet 32, the occurrence of flooding at the cathode outlet 32 can be prevented.

  Here, FIG. 4 is a graph schematically showing the distribution of moisture (during high temperature operation) inside the fuel cell stack 10 according to the present invention. FIGS. 6 and 7 are graphs schematically showing the moisture distribution inside the fuel cell having the conventional structure, and show the moisture distribution during normal operation (non-high temperature) and during high-temperature operation, respectively. . The horizontal axis in the illustrated graph indicates the relative positions of the cathode inlet / outlet and the anode inlet / outlet, and the vertical axis indicates the relative humidity (%). A thick solid line indicates the cathode relative humidity distribution LC, and a broken line indicates the anode relative humidity distribution LA.

  As shown in FIG. 6, the relative humidity of the cathode tends to be high on the cathode outlet side and the anode inlet side and low on the cathode inlet side and the anode outlet side during the normal operation of the fuel cell of the conventional configuration. The relative humidity tends to be low on the cathode outlet side and anode inlet side and high on the cathode inlet side and anode outlet side. In this case, as conceptually indicated by the white arrows in the figure, moisture is supplied from the cathode to the anode on the cathode outlet side and the anode inlet side, and moisture is supplied from the anode to the cathode on the cathode inlet side and the anode outlet side. Thus, the overall moisture balance and the wet state of the electrolyte membrane can be maintained.

  On the other hand, as shown in FIG. 7, the relative humidity of the cathode is high at the cathode outlet and the anode inlet and tends to decrease toward the cathode inlet side and the anode outlet side during the high temperature operation of the fuel cell of the conventional configuration. Further, the relative humidity of the anode is low at the cathode outlet and the anode inlet, and slightly increases near the cathode inlet and the anode outlet, but tends to decrease toward the cathode inlet side and the anode outlet side. In this case, as conceptually indicated by the white arrows in the figure, moisture is supplied from the cathode to the anode on the cathode outlet side and the anode inlet side, and moisture is removed from the anode to the cathode on the cathode inlet side and the anode outlet side. However, at the cathode inlet and the anode outlet (the region indicated by the two-dot chain line in the drawing), the electrolyte membrane tends to dry and the state tends to be difficult to be improved.

On the other hand, as shown in FIG. 4, when the fuel cell stack 10 according to the present invention is operated at a high temperature, the relative humidity of the cathode is high at the cathode outlet 32 and the anode inlet 41 and to the cathode inlet 31 side and the anode outlet 42 side. The relative humidity of the anode is low at the cathode outlet 32 and the anode inlet 41, slightly increases near the cathode inlet 31 and the anode outlet 42, and further decreases toward the cathode inlet 31 side. There is a tendency to go. However, as described above, the moisture at the cathode inlet 31 is transported and supplied by the anode gas, so that the relative humidity increases. Therefore, as conceptually indicated by the white arrow in the figure, the cathode inlet 31 (two-dot chain line in the figure). Water is supplied from the anode to the dried electrolyte membrane in the region indicated by (2), and the wet state of the electrolyte membrane is suitably maintained.
(Second Embodiment)
FIG. 5 is an exploded view (by a one-point perspective view) schematically showing a part of the configuration of another preferred embodiment of the fuel cell according to the present invention. The fuel cell stack 110 is a fuel cell having a serpentine-shaped cathode flow path, and is the same as the fuel cell stack 10 except that the unit cell 120 includes a cathode separator 126 and an anode separator 128 instead of the unit cell 20. It is composed of. In the peripheral portions of the power generator 23, the cathode separator 126, and the anode separator 128 of the unit cell 120, the cathode inlet 131 communicating with the cathode gas channel 130, the cathode outlet 132, and the anode gas channel 140 are connected. A communicating anode inlet 141 and anode outlet 142 are provided. Thus, the fuel cell stack 110 is provided with a set of cathode inlet 131 and cathode outlet 132 and a set of anode inlet 141 and anode outlet 142.

  The fuel cell stack 110 configured in this manner also has the same effects as the fuel cell stack 10 described above, and has the advantage that the structure of the cathode separator 126 and the anode separator 128 can be simplified. .

  In addition, as above-mentioned, this invention is not limited to said each embodiment, A various deformation | transformation is possible in the limit which does not change the summary. For example, the shapes of the cathode gas passages 30 and 130 and / or the anode gas passages 40 and 140 are not limited to those illustrated.

  As described above, since the present invention can effectively prevent a decrease in the output of the fuel cell, it is widely and effectively used for the entire fuel cell, devices, systems, facilities, etc. equipped with the fuel cell, and their production. can do

  DESCRIPTION OF SYMBOLS 10,110 ... Fuel cell stack, 20, 120 ... Unit cell, 21 ... MEA, 22 ... Gas diffusion layer, 23 ... Power generation body, 26, 126 ... Cathode separator, 28, 128 ... Anode separator, 30, 130 ... Cathode gas Channel, 40, 140 ... anode gas channel, RA, RC ... rib, 31, 131 ... cathode inlet, 32, 132 ... cathode outlet, 41, 141 ... anode inlet, 42, 142 ... anode outlet, LC ... cathode relative Humidity distribution, LA ... anode relative humidity distribution.

Claims (1)

A membrane electrode assembly in which a cathode and an anode are disposed on both sides of the electrolyte membrane;
A rectangular separator provided facing the membrane electrode assembly;
With
The separator is arranged along a predetermined one side, the cathode inlet and a cathode outlet, and the separator is provided along one side of the vertical sides with respect to said predetermined side adjacent to each other An anode inlet disposed adjacent to the cathode outlet without an opening through which a fluid flowing along the surface of the anode flows, and along the other side of the sides perpendicular to the predetermined side And an anode outlet disposed adjacent to the cathode inlet,
In the vicinity of the cathode inlet and the cathode outlet, an anode gas flow path is formed through which anode gas flows from the cathode outlet toward the cathode inlet.
Fuel cell.

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