JP5050697B2 - Separator for fuel cell - Google Patents

Description

  The present invention relates to a separator for a fuel cell. More specifically, the present invention has a plurality of protrusions that form a flow path of a fluid such as a fuel gas, an oxidizing gas, or a cooling medium together with electrodes and other members, and is laminated with the electrodes and the like. The present invention relates to a fuel cell separator that forms partition walls between unit cells when a fuel cell stack is formed.

  Conventionally, as a separator for this type of fuel cell, as shown as a conventional separator 320 in FIG. 6, a flow path of fuel gas or oxidizing gas formed by a gas diffusion electrode (not shown), The flow path forming ribs 334, 336, and 338 form two U-shapes as a whole, and the straight portions of the flow paths are guided by a plurality of straight ribs 340 to change the flow direction (that is, the U-shaped shape). As for the bent portion of the flow path, a plurality of convex portions 342 and 344 having a substantially square cross section have been proposed to increase the degree of freedom with respect to the directionality of the gas and change the flow direction of the fuel gas or the oxidizing gas (for example, JP, 10-106594, A, etc.). According to the separator 320 of this conventional example, the fuel gas and the oxidizing gas are more evenly supplied to the entire gas diffusion electrode by making the flow path of the fuel gas and the oxidizing gas into two U-shapes in this way. It is supposed to be possible.

  However, in the separator 320 of the conventional example, there is a problem that in the portion where the flow direction of the fuel gas or the oxidizing gas changes, the gas flows much on the inner peripheral side of the change in the flow direction and does not flow much on the outer peripheral side. It was. Since this problem hinders the uniform supply of fuel gas and oxidizing gas to the gas diffusion electrode, it also causes a problem that the performance of the fuel cell cannot be fully exhibited.

  Such a problem is caused when a cooling medium flow path is formed by using the same separator, and the temperature distribution of the separator caused by the cooling medium not flowing uniformly in the separator, that is, the temperature distribution is generated. It is grasped as a problem of deterioration of fuel cell performance.

  The separator for a fuel cell of the present invention aims to solve such problems and to supply fuel gas and oxidizing gas to the electrode more evenly or to flow the cooling medium more evenly in the separator.

  The fuel cell separator of the present invention employs the following means in order to achieve the above-described object.

  The separator for a fuel cell according to the present invention has a plurality of convex portions forming a fluid flow path, and forms a partition between unit cells when stacked with an electrode to form a fuel cell stack. And the said convex part which changes the flow direction of the said fluid has the convex part formed intermittently in the site | part which changes the flow direction of the said fluid.

  In the fuel cell separator, a plurality of the convex portions are formed toward an outer peripheral direction of the portion, and are collinear along a direction perpendicular to an extending direction of the intermittently formed convex portions. It is preferable that the intermittently formed convex portions adjacent to each other are arranged so as to be shifted from each other.

  Further, in the fuel cell separator, it is preferable that the intermittently formed convex portion is disposed on the downstream side with respect to the flow direction toward the outer peripheral direction of the portion.

  The separator for a fuel cell according to the present invention has a plurality of convex portions that form a fluid flow path, and forms a partition between unit cells when stacked with an electrode to form a fuel cell stack. The convex portion that changes the flow direction of the fluid has a flow passage through which the fluid flows between the inner periphery and the outer periphery of the convex portion at a portion that changes the flow direction of the fluid.

  Also, in the fuel cell separator, the plurality of convex portions are formed toward the outer peripheral direction of the portion, and the circulation is adjacent on the same straight line along a direction perpendicular to the extending direction of the flow passage. The paths are preferably arranged so as to be offset from each other.

  In the fuel cell separator, it is preferable that the communication path is disposed on the downstream side with respect to the flow direction toward the outer peripheral direction of the portion.

  Next, embodiments of the present invention will be described using examples. FIG. 1 is a configuration diagram showing a schematic configuration of a fuel cell separator 20 according to an embodiment of the present invention. In addition, the bending part ribs 42a-42d and 44a-44c shown in FIG. 1 are reference examples. The separator 20 is formed of dense carbon that is impermeable to gas. As shown in the figure, near each side of the separator 20, a fuel gas introduction hole 22 for introducing a fuel gas (for example, a hydrogen rich gas containing hydrogen) into the surface of the separator 20, and other fuel gas A fuel gas communication hole 23 for communicating with the unit cell, a fuel gas discharge hole 24 for discharging the fuel gas from the separator 20, and a back surface of the separator 20 not shown with an oxidizing gas (for example, air containing oxygen). An oxidizing gas introduction hole 26 for introducing the oxidizing gas into the gas, an oxidizing gas communication hole 27 for communicating the oxidizing gas with other unit cells, an oxidizing gas discharge hole 28 for discharging the oxidizing gas from the separator 20, and cooling Cooling water holes 30 and 32 that form water channels are formed. Although these holes are not shown, when a fuel cell stack is formed by stacking, a flow path for inflow or discharge of fuel gas, oxidizing gas or cooling water in the stacking direction is formed in the fuel cell stack. The fuel gas and the oxidizing gas are supplied to each cell in the fuel cell stack, and the cooling water is supplied to each cooling member that is regularly stacked to cool the fuel cell stack.

  On the surface of the separator 20, the fuel gas introduced from the fuel gas introduction hole 22 flows in a U-shape as a whole to the fuel gas communication hole 23, and also flows in a U-shape from the fuel gas communication hole 23. Three flow path forming ribs 34, 36, and 38 that form a flow path discharged to the fuel gas discharge hole 24 are formed. A plurality of convex portions 40 having a square cross section are formed on the straight portions of the two U-shaped flow paths formed by the three flow path forming ribs 34, 36, and 38, to the fuel gas electrode. Ensures efficient diffusion and sufficient contact with the electrode. U-shaped bent portion ribs 42a to 42d (reference example) and 44a to 44c (reference example) for forming a plurality of equally spaced grooves are formed in the bent portions of the two U-shaped flow paths. Thus, the fuel gas is prevented from flowing toward the inner peripheral side of the bent portion, and the fuel gas is allowed to flow evenly on the outer peripheral side. In the bent portion, the upstream end of the outer side bent portion rib (for example, the bent portion ribs 42d and 44c) becomes closer to that of the inner peripheral side bent portion rib (for example, the bent portion ribs 42a and 44a) toward the outer peripheral side. The reason why it is formed on the downstream side is to make it easier for the fuel gas to flow into the outer peripheral portion. Considering the length of each groove formed by each bent rib, the amount of fuel gas supplied from each groove to the electrode, and the ease of flow of the hydrodynamic fuel gas, the groove on the outer peripheral side is more fueled. This is because it is necessary to flow more gas.

  Although not shown in the drawing, two U-shaped flow paths through which the oxidizing gas introduced from the oxidizing gas introduction hole 26 is discharged to the oxidizing gas discharge hole 28 via the oxidizing gas communication hole 27 are formed on the back surface of the separator 20. 1 is formed in the same manner as the two U-shaped flow paths of the fuel gas on the display surface of the separator 20 illustrated in FIG. Accordingly, the description of the configuration of the back surface of the separator 20 is omitted because it is redundant.

  The separator 20 of the embodiment thus configured includes an electrolyte membrane 50, a fuel gas side electrode 52, and an oxidizing gas side electrode 54 that constitute a cell illustrated in FIG. 2 as a unit cell configuration diagram of a solid polymer fuel cell. And a fuel cell stack (not shown). In the unit cell illustrated in FIG. 2, the electrolyte membrane 50 is formed of a proton conductive membrane formed of a solid polymer material such as a fluororesin, and the electrodes 52 and 54 are made of platinum or platinum and the like. It is made of carbon cloth in which an alloy catalyst made of one of these metals is kneaded.

  3 shows the performance of each unit cell when the unit cell of the fuel cell stack illustrated in FIG. 2 is configured using the separator 20 of the embodiment and the separator 320 of the conventional example illustrated in FIG. It is a graph shown by the relationship between a density and a voltage. Curve A represents the performance of the unit cell using the separator 20 of the example, and curve C represents the performance of the unit cell using the separator 320 of the conventional example. As shown in the figure, the unit cell using the separator 20 of the example shows better performance than the unit cell using the separator 320 of the conventional example in general in the current density, and the performance is remarkably improved particularly in the region where the current density is high. Is seen.

  According to the separator 20 of the embodiment described above, the U-shaped bent portion ribs 42a to 42d (reference example) and 44a to 44c (reference example) are formed at the bent portions in the two U-shaped flow paths. As a result, the fuel gas and the oxidizing gas can be prevented from flowing toward the inner peripheral side of the bent portion, and can flow sufficiently to the outer peripheral side. As a result, when the fuel cell stack is configured, the fuel gas and the oxidizing gas can be supplied uniformly by the electrodes 52 and 54, and the performance of the fuel cell can be improved. Further, by forming the upstream end of the outer peripheral side bent portion rib in the bent portion so as to be downstream from that of the inner peripheral side bent portion rib, the fuel gas and the oxidizing gas can easily flow into the outer peripheral portion. be able to. As a result, a necessary amount of fuel gas or oxidizing gas can be supplied to the outer peripheral portion, and the performance of the fuel cell can be further improved.

  In the separator 20 of the example, the upstream end portion of the outer side bent portion rib in the bent portion of the two U-shaped flow paths is formed downstream of that of the inner peripheral side bent portion rib. 4, as illustrated in the bent portion ribs 142 a to 142 d (reference example) of the reference example, the upstream end of the bent portion rib on the outer peripheral side in the bent portion is the same position as that of the bent portion rib on the inner peripheral side. It can be formed as follows. The performance of the unit cell when the unit cell is configured using the separator of this modification is shown as a curve B in FIG. As shown in the figure, the unit cell using the separator of the modification is not as large as the separator 20 of the embodiment, but the performance is remarkably improved as compared with the unit cell using the separator 320 of the conventional example.

  In the separator 20 of the embodiment, the U-shaped bent portion ribs 42a to 42d (reference example) so as to form a plurality of equally-shaped U-shaped grooves in the bent portions in the two U-shaped flow paths, 44a to 44c (reference example) are formed, but the straight portion formed on the outer peripheral side of the bent portion does not need to be formed in a U shape by an integral continuous rib, and the bent portion of the embodiment of FIG. As illustrated in the ribs 242a to 242d, a plurality of convex portions 243 may be formed in the U-shaped linear portion.

  In the embodiment, the present invention is applied to the flow path for supplying the fuel gas and the oxidizing gas to the electrode. However, in order to cool the fuel cell stack, a cooling medium (for example, a cooling medium regularly stacked in the stack) , Water) flow path may be applied. By so doing, the cooling medium flows more evenly in the cooling member, whereby the temperature distribution of the cooling member can be reduced, and as a result, the fuel cell performance can be improved.

  The embodiments of the present invention have been described using the embodiments. However, the present invention is not limited to these embodiments, and can be implemented in various forms without departing from the gist of the present invention. Of course you get.

It is a block diagram which shows schematic structure of the separator 20 for fuel cells which is one Example of this invention. It is a block diagram which illustrates schematic structure of the unit cell at the time of comprising a polymer electrolyte fuel cell using the separator 20 of an Example. It is a graph shown by the relationship between the current density and voltage of the unit cell of the fuel cell stack comprised using the separator of an Example and a prior art example. It is explanatory drawing which shows the bending part ribs 142a-142d of a reference example. It is explanatory drawing which shows the bending part ribs 242a-242d of an Example. It is a block diagram which illustrates the structure of the separator 320 of a prior art example.

Explanation of symbols

  20 Separator, 22 Fuel gas introduction hole, 23 Fuel gas communication hole, 24 Fuel gas discharge hole, 26 Oxidation gas introduction hole, 27 Oxidation gas communication hole, 28 Oxidation gas discharge hole, 30, 32 Cooling water hole, 34, 36, 38 flow path forming rib, 40 convex portion, 42a to 42d bent portion rib, 44a to 44c bent portion rib, 50 electrolyte membrane, 52, 54 electrode, 142a to 142d bent portion rib, 242a to 242d bent portion rib, 243 convex portion , 320 Conventional separator, 334, 336, 338 Channel forming rib, 340 Linear rib, 342, 344 Projection.

Claims (1)

A separator for a fuel cell having a plurality of convex portions forming a fluid flow path, and forming a partition wall between unit cells when the fuel cell stack is formed by being laminated with an electrode,
A convex rib that forms the fluid flow path is formed with a bent rib at a U-shaped bent portion that changes the flow direction of the fluid, and a plurality of the bent ribs are formed in the outer peripheral direction of the portion. ,
The bending rib has a convex portion that is intermittently formed in a straight portion of the U-shaped bending portion ,
The convex portion is intermittently formed on the bending rib is arranged in a straight line, in and adjacent the bent ribs, do not overlap on the same straight line along a direction perpendicular to the arrangement direction of the linear convex portion A separator for a fuel cell, wherein the separator is disposed so as to be shifted.

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