JP2008243499A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell for running a reaction gas along a gas passage without leaking the reaction gas from the gas passage. <P>SOLUTION: This fuel cell is provided with cells 11 each composed by sandwiching an MEA 22 including an electrolyte membrane 23 and electrodes 24 arranged on both its sides between two separators 21a and 21b. A passage partitioning rib 40 partitioning a gas passage 41a is formed on the MEA 22 side of the separator 21a; and a projecting part 51 suppressing deformation of the passage partitioning rib 40 in a direction separating from the MEA 22 by contacting the back surface of the passage partitioning rib 40 is formed on the separator 21b provided for the cell 11 arranged adjacently. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell that generates electric power by an electrochemical reaction between a fuel gas and an oxidizing gas.

In recent years, attention has been focused on fuel cell vehicles using fuel cells that generate power by an electrochemical reaction between a fuel gas and an oxidizing gas (hereinafter collectively referred to as “reactive gas”) as an energy source. The minimum unit of a fuel cell (referred to as a “cell”) has a structure in which a membrane-electrode assembly (MEA) having an electrolyte membrane and a pair of electrodes disposed on both sides thereof is sandwiched by a pair of separators. Have. These separators are formed with gas flow paths for supplying fuel gas and oxidizing gas to the MEA electrodes (anode and cathode), respectively. Practically, a fuel cell stack in which a required number of such cells are stacked is used.
JP-A-6-283181

  By the way, in a normal fuel cell, for example, a meandering gas flow path (also called a serpentine flow path) is provided by providing flow separator ribs on the separator so that the reaction gas spreads over almost the entire surface of the MEA. Is formed. However, when a gap is generated between the ribs for flow path partitioning and the MEA due to variations in the thickness of the MEA, the reactive gas passes through the gap and flows short-circuited from the inlet to the outlet of the gas flow path. That is, as a result of the reaction gas not flowing along the gas flow path, the reaction gas does not spread over the entire MEA, and power generation efficiency may be reduced.

As a related technique, in Patent Document 1, by inserting an elastic body in which a plurality of plate-like springs are overlapped in a flange at an end portion of a separator, a gas leak from a gas flow path due to a reduction in surface pressure is prevented. Suppressed. As described above, it is conceivable to increase the surface pressure of the flow path partitioning rib with respect to the MEA by the plate-like elastic body. However, the use of the elastic body having the complicated structure as described above increases the cost.
Therefore, there is a demand for a technique for easily increasing the surface pressure of the flow path partitioning rib with respect to the MEA and suppressing gas leakage in the gas flow path while suppressing cost.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a fuel cell capable of flowing along a gas flow path without leaking a reaction gas from the gas flow path while suppressing cost. To do.

  To achieve the above object, the fuel cell of the present invention is a fuel cell comprising a cell in which an ion exchanger including an electrolyte and electrodes disposed on both sides thereof is sandwiched between separators, and the ion exchange of the separator. On the body side, a flow path partition rib for partitioning the gas flow path is formed, contacting the back surface of the flow path partition rib, and deforming the flow path partition rib in a direction away from the ion exchanger. A pressing member to be suppressed is provided.

  According to this configuration, since the deformation of the flow path partition rib in the direction away from the ion exchanger is suppressed by the pressing member, the flow path partition rib even if the thickness of the ion exchanger varies. A large surface pressure is maintained at the contact surface with the ion exchanger. As a result, the flow path ribs can be brought into good contact with the surface of the ion exchanger, gas leakage in the gas flow path can be suppressed, and the reaction gas can flow along the gas flow path. Become.

Further, the pressing member may be formed of a convex portion formed in a separator adjacent to the flow path partitioning rib provided in a cell disposed adjacent to the pressing member.
According to this configuration, it is possible to easily reinforce the flow path partition ribs by forming convex portions on the adjacent separators constituting the stacked cells to form a pressing member.

  The fuel cell of the present invention is a fuel cell comprising a cell in which an ion exchanger including an electrolyte and electrodes disposed on both sides thereof is sandwiched between two separators, and at least one of the separators on the ion exchanger side. The channel partition ribs for partitioning the gas channel are formed, and the channel partition ribs are curved so as to protrude toward the ion exchanger.

  According to this configuration, the rigidity of the flow path partitioning rib is increased by curving the flow path partitioning rib. Thereby, even if there is variation in the thickness of the ion exchanger, a large surface pressure is maintained at the contact surface of the flow path partition rib with the ion exchanger. As a result, the ribs for the flow path section can be brought into good contact with the surface of the ion exchanger, gas leakage in the section of the gas flow path can be suppressed, and the reaction gas can flow along the gas flow path. Become.

  According to the fuel cell of the present invention, it is possible to flow the reaction gas along the gas flow path without using an expensive elastic body having a complicated structure, so that it is possible to obtain good power generation efficiency while suppressing cost. become.

A fuel cell according to a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a part of a cell of a fuel cell that generates power by receiving supply of fuel gas and oxidizing gas. A cell is one unit constituting a fuel cell. FIG. 1 shows two cells 11 arranged adjacent to each other. A fuel cell stack is formed by stacking a required number of such cells 11 in the thickness direction. Fuel cell stacks are used for in-vehicle power generation systems for fuel cell vehicles, power generation systems for all moving objects such as ships, airplanes, trains, and walking robots, as well as stationary power generation equipment for buildings (housing, buildings, etc.). It can be applied to power generation systems.

As shown in FIG. 1, each cell 11 includes an MEA (Membrane Electrode Assembly) 22 and a pair of separators 21 a and 21 b arranged so as to sandwich the MEA 22 from both sides.
The separators 21a and 21b partition adjacent MEAs 22 and have a flow path for fuel gas (for example, hydrogen gas) or oxidizing gas (for example, air) supplied to the MEA 22 and a flow path for cooling water. The separators 21a and 21b are made of, for example, a metal formed of aluminum, carbon steel, tungsten, or the like, and surface treatment is performed on the side facing the MEA 22 in order to ensure conductivity and corrosion resistance. .

  The MEA 22 is an ion exchanger including an electrolyte membrane 23 made of, for example, a polymer material and a pair of electrodes 24 arranged on both surfaces thereof. The electrode 24 has a structure in which a catalyst layer and a diffusion layer are laminated from the electrolyte membrane 23 side. The catalyst layer is formed of, for example, carbon particles carrying platinum or a platinum alloy, and the diffusion layer uses carbon as a substrate. In the present embodiment, the ion exchanger is formed using a membrane electrolyte, but the form of the electrolyte is not limited to a membrane.

  FIG. 2 is a plan view showing the inside of the cell 11 shown in FIG. As shown in FIG. 2, an oxidizing gas inlet manifold 31, a fuel gas inlet manifold 32, and a cooling water inlet manifold 33 are formed in the vicinity of one end of the cell 11 (on the left side in FIG. 2). An oxidizing gas outlet manifold 34, a fuel gas outlet manifold 35, and a cooling water outlet manifold 36 are formed near the other end of the cell 11 (on the right side in FIG. 2).

In the separator 21a, a flow path partitioning rib 40 that contacts the MEA 22 is formed. A gas composed of a serpentine flow path bent at a plurality of locations on the surface of the MEA 22 from one end side to the other end side in a plan view (upper left to lower right in FIG. 2) by the flow path dividing rib 40. A flow path 41a is formed. Although not shown, the other separator 21b is also provided with a flow path partitioning rib 40, and a gas flow path 41b (see FIG. 1) formed of a serpentine flow path is formed.
Further, the separators 21a and 21b are formed with a plurality of ribs 43 that are narrower than the channel partitioning ribs 40 so as to come into contact with the MEA 22 along the straight portions of the gas channel.

  Both ends of the gas flow path 41a on one surface of the MEA 22 are connected to the oxidizing gas inlet manifold 31 and the oxidizing gas outlet manifold 34, respectively. Further, both ends of the gas flow path 41b on the other side of the MEA 22 are connected to the fuel gas inlet manifold 32 and the fuel gas outlet manifold 35, respectively.

  As shown in FIG. 1, the two adjacent cells 11 are arranged such that the separators 21a and 21b are in contact with each other on the back surface. Thereby, between the adjacent cells 11, the cooling water flow path 44 which abuts the recessed part formed in the back surface side of the rib 43 of each separator 21a and 21b is formed. The cooling water passage 44 communicates with the cooling water inlet manifold 33 and the cooling water outlet manifold 36.

In such a cell 11, the oxidizing gas sent into the oxidizing gas inlet manifold 31 flows through the gas flow path 41 a formed by the separator 21 a and then is sent out from the oxidizing gas outlet manifold 34. Further, the fuel gas sent into the fuel gas inlet manifold 32 flows through the gas flow path 41b formed by the separator 21b, and then is sent out from the fuel gas outlet manifold 35.
Then, the oxidizing gas and the fuel gas respectively supplied to the two electrodes 24 of the MEA 22 through the gas flow paths 41a and 41b cause an electrochemical reaction to generate electric power.

  Further, the cooling water sent to the cooling water inlet manifold 33 flows through the cooling water flow path 44 and then is sent out from the cooling water outlet manifold 36. Each cell 11 is cooled by the cooling water flowing through the cooling water flow path.

  Here, as described above, the diffusion layer constituting a part of the electrode 24 of the MEA 22 is usually made of carbon as a base material. Therefore, the MEA 22 may vary in the thickness direction, which may cause a gap between the flow path partition rib 40 and the MEA 22. Further, the flow path partitioning rib 40 is less rigid because the width dimension is larger than the other ribs 43. In addition, the flow path partitioning rib 40 is relatively large on the back side (adjacent cell side) of the flow path partitioning rib 40. A space is formed. Therefore, when the cells 11 are stacked and fastened, the flow path dividing rib 40 is deformed in a direction away from the MEA 22, and a gap is easily generated between the cells 11. Then, the predetermined reaction gas flowing through the gas flow paths 41a and 41b may pass through the region partitioned by the flow path partition ribs 40 and may not flow so as to meander through the gas flow paths 41a and 41b. .

  Therefore, in this embodiment, the convex part (pressing member) 51 formed in the separator 21b of the adjacent cell 11 is disposed on the back surface of the flow path partitioning rib 40 of the separator 21a. The front end portion of the flow path is brought into contact with the substantially central portion of the flow path dividing rib 40.

  Thereby, the deformation in the direction away from the MEA 22 of the flow path dividing rib 40 formed in the separator 21 a is suppressed by the convex portion 51 formed in the separator 21 b of the adjacent cell 11. Further, the surface pressure by the flow path partition rib 40 at the contact surface between the flow path partition rib 40 and the MEA 22 is maintained, so that even if the cells 11 are stacked and fastened, the flow path partition rib 40 remains in the MEA 22. The state of being in good contact with the surface is maintained. As a result, leakage at the partition portion forming the serpentine flow path (gas flow paths 41a and 41b) is suppressed.

  As described above, according to the fuel cell according to the present embodiment, the flow path partition rib 40 formed in the separator 21a is deformed in the direction away from the MEA 22 in the separator of the adjacent cell 11. It can suppress by pressing the flow path division rib 40 from the back surface by the convex part 51 formed in 21b. Thereby, even if the thickness of the MEA 22 varies, a large surface pressure is maintained on the contact surface with the MEA 22 in the flow path partition rib 40 without using an expensive elastic body having a complicated structure. It is possible to maintain a good contact with the surface. Therefore, gas leakage at the partition portion forming the gas flow paths 41a and 41b can be suppressed, and the reaction gas can be distributed over the entire surface of the MEA 22 along the gas flow paths 41a and 41b, thereby obtaining good power generation efficiency. It becomes possible.

Next, a fuel cell according to a second embodiment of the present invention will be described.
As shown in FIG. 3, the separator 60a used in the present embodiment is provided with a channel partitioning rib 61 curved toward the MEA 22 instead of the channel partitioning rib 40 shown in FIG. The tip of the flow path partitioning rib 61 is formed so as to protrude to the MEA 22 side from the other part (rib 43).

Thus, by curving the flow path partition rib 61 of the separator 60a, the rigidity of the flow path partition rib 61 is increased. As a result, as shown in FIG. 4, when the cells 11 are configured, stacked, and fastened, the flow path can be obtained without using an expensive elastic body having a complicated structure even if the thickness of the MEA 22 varies. A large surface pressure can be maintained at the contact surface of the partition rib 61 with the MEA 22, and the flow path partition rib 61 can be in good contact with the surface of the MEA 22. In the present embodiment, it is not necessary to press the flow path dividing rib 61 by the separator 60b provided in the adjacent cell 11.
As a result, gas leakage at the partition portion forming the gas flow path 41 can be suppressed, and the reaction gas can be distributed over the entire surface of the MEA 22 along the gas flow path 41, thereby obtaining good power generation efficiency. become.

It is sectional drawing which shows a part of fuel cell which concerns on 1st Embodiment. It is a top view which shows the structure inside the fuel cell which concerns on 1st Embodiment. It is sectional drawing which shows a part of separator used in the fuel cell which concerns on 2nd Embodiment. It is sectional drawing which shows a part of fuel cell which concerns on 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Cell, 21a, 21b, 60a, 60b ... Separator, 22 ... MEA (membrane-electrode assembly), 23 ... Electrolyte membrane, 24 ... Electrode, 40, 61 ... Channel partition rib, 41, 41a, 41b ... Gas flow path, 51 ... convex portion (pressing member)

Claims (3)

A fuel cell comprising a cell in which an ion exchanger including an electrolyte and electrodes disposed on both sides thereof is sandwiched between two separators,
On the ion exchanger side of at least one of the separators, a flow path partition rib that partitions the gas flow path is formed,
A fuel cell provided with a pressing member that abuts against a back surface of the flow path partition rib and suppresses deformation of the flow path partition rib in a direction away from the ion exchanger.   2. The fuel cell according to claim 1, wherein the pressing member includes a convex portion provided in a separator adjacent to the flow path partitioning rib provided in a cell disposed adjacent to the pressing member. A fuel cell comprising a cell in which an ion exchanger including an electrolyte and electrodes disposed on both sides thereof is sandwiched between two separators,
On the ion exchanger side of at least one of the separators, a flow path partition rib that partitions the gas flow path is formed,
The fuel cell is curved so that the flow path partition rib protrudes toward the ion exchanger.