JP2955069B2 - Gas separator manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a gas separator used in a fuel cell, and more particularly to a method of manufacturing a gas separator having high rigidity using copper.

[0002]

2. Description of the Related Art Fuel cells do not need to use fossil fuels, which have a problem of resource depletion, and generate almost no noise.
Since it has excellent features such as an extremely high energy recovery efficiency as compared with other energy engines, it is used as a relatively small power plant, for example, in a building unit or a factory unit.

In recent years, it has been considered that this fuel cell is used as a power source for a motor that operates instead of a vehicle-mounted internal combustion engine, and a vehicle or the like is driven by this motor. In this case, it is important to recycle as much as possible the substances generated by the reaction. It is desirable that the fuel cell be as small as possible. In view of this, a solid polymer electrolyte membrane fuel cell has been receiving attention.

[0004] This solid polymer electrolyte membrane fuel cell (hereinafter referred to as “the fuel cell”)
As shown in FIG. 1 showing the concept of the main part of a fuel cell, the fuel cell 11 is a solid polymer electrolyte membrane 12.
A pair of gas reaction layers 13 and 14 joined to both sides of the solid polymer electrolyte membrane 12 by hot pressing or the like, and a solid polymer electrolyte membrane 12 sandwiching the gas reaction layers 13 and 14 therebetween.
And the gas diffusion layers 15 and 16 integrally joined to the gas reaction layers 13 and 14 to constitute a main part.

An oxygen gas supply plate 18 (oxygen gas supply plate) having an oxygen supply groove (oxidant gas supply passage) 17 is joined to the surface of one gas diffusion layer 15, and the other gas diffusion layer is similarly connected. A hydrogen gas supply plate (fuel gas supply plate) having a hydrogen supply groove (fuel gas supply passage) 19 on the surface of the layer 16
20 are joined to form an oxygen electrode and a hydrogen electrode.

Accordingly, when oxygen is supplied to the oxygen supply groove 17 and hydrogen is supplied to the hydrogen supply groove 19, the oxygen and hydrogen are supplied from the gas diffusion layers 15 and 16 to the gas reaction layer 1.
3, 14 side, mainly these gas reaction layers 13,
A battery reaction occurs at the contact interface between the solid polymer electrolyte membrane 14 and the solid polymer electrolyte membrane 12, and hydrogen ions (4H ⁺ ) flow from the hydrogen electrode to the oxygen electrode through the electrolyte membrane 12, but electrons (4e ⁻ ) flow to a load such as a motor. The fuel flows from the hydrogen electrode to the oxygen electrode through 21, and electric energy is supplied to the load 21.

As shown in FIG. 2, which shows the disassembly structure of a conventional gas separator in such a fuel cell, the conventional fuel cell has a copper plate having a thickness of about 0.5 mm and a slit shape having a width of about 0.5 mm. An oxygen gas supply plate 18 having oxygen supply grooves 17 formed at intervals of about 1 mm and a hydrogen supply groove 19 having a slit shape having a width of about 0.5 mm formed on a copper plate having a thickness of about 0.5 mm at an interval of about 1 mm. The formed hydrogen gas supply plate 20 and the oxygen supply manifold 22 formed of a copper plate having a thickness of about 0.5 mm and separating the oxygen gas supply plate 18 and the hydrogen gas supply plate 20 and communicating with the oxygen supply groove 17. In this structure, a hydrogen supply manifold 23 communicating with the hydrogen supply groove 19 and a partition plate 24 on which a hydrogen supply manifold 23 is formed are integrally joined.

The oxygen gas supply plate 18 and the hydrogen gas supply plate 20 are provided with an oxygen gas supply / discharge port 25 and a hydrogen gas supply / discharge port 26 communicating with the oxygen supply manifold 22 and the hydrogen supply manifold 23, respectively. I have. Further, the oxygen supply groove 17 and the hydrogen supply groove 19 are formed by a method such as etching, punching or electric discharge machining, and machining.

For this reason, unless these oxygen gas supply plate 18, hydrogen gas supply plate 20 and partition plate 22 are securely joined together, oxygen gas and hydrogen gas leak from these gaps, and a predetermined capacity is exhibited. There is a possibility that the operation cannot be performed. Therefore, conventionally, these oxygen gas supply plates 1
A method such as diffusion bonding or brazing is adopted as a means for joining the hydrogen gas supply plate 8, the hydrogen gas supply plate 20, and the partition plate 22, and care is taken so that no gap is generated between these joint surfaces.

The structure of the gas separator shown in FIG. 2 is completely the same as that of the solid polymer electrolyte membrane fuel cell using the ion exchange membrane described above, as well as the gas separators of a sulfuric acid fuel cell and an alkaline fuel cell. is there.

[0011]

When a gas separator for a fuel cell shown in FIG. 2 is manufactured, a bonding temperature of 80 is used because a method such as diffusion bonding or brazing is conventionally used.
Since the temperature reaches 0 ° C. or more, when this gas separator is formed of a copper plate, copper is in an annealed state, and it is difficult to secure a predetermined rigidity. For this reason, a reinforcing member must be added, which is a factor that hinders downsizing of the fuel cell itself.

Therefore, in order to avoid a problem that the rigidity of the gas separator is reduced by the heat treatment accompanying the joining, the gas separator is also formed using aluminum or the like in addition to brass or stainless steel. However, considering various physical characteristics required for the gas separator,
It is most desirable in current technology to form the gas separator from copper.

When a gas separator is manufactured by diffusion bonding, expensive equipment such as a hot isostatic pressing device is required, which may increase the manufacturing cost.

[0014]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a manufacturing method capable of forming a highly rigid gas separator used for a fuel cell from copper.

[0015]

A method of manufacturing a gas separator for a fuel cell according to the present invention comprises a fuel gas supply plate having a fuel gas supply passage formed therein, and an oxidant gas supply plate having an oxidant gas supply passage formed therein. And an oxidizing gas supply plate and a partition plate for partitioning the fuel gas supply plate are integrally joined, and the gas on one side is located between gas diffusion electrodes of a polymer electrolyte fuel cell. A gas separator for a polymer electrolyte fuel cell for supplying the fuel gas to the diffusion electrode and supplying the oxidant gas to the gas diffusion electrode on the other side ;
A method for manufacturing a copper fuel gas supply plate and a copper fuel gas supply plate;
A thin film of a low melting point brazing material having a weight ratio of tin to lead of 4: 1 to 3: 2 is formed on each of the joining surfaces of the oxidizing gas supply plate and the copper partition plate, and these are superimposed on each other.
Allowed, not exceeding 350 ° C. above the melting point of the low melting point brazing material
And the bonding pressure is 10 g / cm ² or less.
The fuel gas supply plate, the oxidizing gas supply plate, and the partition plate are integrally joined.

Here, when the thickness of the thin film of the low melting point brazing material is less than 3 micrometers, there is a possibility that the low melting point brazing material may not be interposed in a part of the joining portion. If the thickness of the thin film is greater than 6 micrometers, a portion of the low melting point brazing material may protrude from the joint and block the passage. Therefore, the thickness of the thin film of the low melting point brazing material is preferably in the range of 3 micrometers to 6 micrometers.

[0017]

When a thin film of a low melting point brazing material is formed on each of the joining surfaces of a fuel gas supply plate, an oxidizing gas supply plate and a partition plate, these are superimposed on each other and heated to a temperature higher than the melting point of the low melting point brazing material. The low-melting-point brazing material melts, and the joining surfaces of the fuel gas supply plate, the oxidizing gas supply plate, and the partition plate adhere to each other, and are joined without any gap.

Here, since the low melting point brazing material is in the form of a thin film, there is no danger that a part of the thin film will protrude into the fuel gas supply passage or the oxidizing gas supply passage and block them.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One side is 240 mm as shown in FIG.
Square fuel gas supply plate 18 and oxidant gas supply plate 2
0 and a partition plate 22 are prepared, and a thin film of a low melting point brazing material having a thickness of 3 μm to 6 μm, in this embodiment, a solder layer is formed on these joint surfaces 27.
In the present embodiment, the solder constituting the solder layer has a weight ratio of tin to lead of 4 to 1, and is formed on the joint surface 27 by a vacuum evaporation plating method or the like.

If the thickness of the solder layer exceeds 6 μm, a part of the solder will
Therefore, the thickness of the solder layer is desirably set to 6 μm or less, since the solder layer may protrude into the hydrogen supply groove 19 or the like and block these. Conversely, if the thickness of the solder layer is less than 3 micrometers, a region where solder does not exist is formed in a part of the bonding surface 27 at the time of heating, and this portion serves as a gap to perform perfect bonding. Therefore, the thickness of the solder layer is desirably set to 3 micrometers or more.

Thereafter, these are superposed and heated at a temperature of 350 ° C. for 15 minutes while applying a pressure of 10 grams per square centimeter in a heating furnace to melt the solder layer, and then gradually cooled. Thereby, the joining surfaces 27 are in close contact with each other, and the fuel gas supply plate 18, the oxidizing gas supply plate 20, and the partition plate 22 are joined without any gap.

In this case, since the heating temperature for the gas separator may be about 350 ° C., the copper constituting the gas separator does not reach an annealed state, the initial rigidity can be maintained as it is, and a special reinforcing material is used. A fuel cell can be manufactured without additional components.

As described above, in this embodiment, the solder having a weight ratio of tin to lead of 4: 1 was used as the low melting point brazing material. Etc. can also be adopted. In this case, although the melting point of the solder becomes lower as the weight ratio of tin becomes smaller, there is a possibility that the joint portion of the gas separator may be peeled off due to thermal stress due to repeated operation of the fuel cell. Melting point brazing materials cannot be used.

In the present embodiment, when the fuel gas supply plate 18, the oxidizing gas supply plate 20, and the partition plate 22 are joined by heating, they are lightly pressurized. It is desirable to pressurize at an appropriate pressure while giving the tendency that the pressure increases as the thickness increases. Further, in this embodiment, the gas separator made of copper has been described, but it is of course possible to form the gas separator using aluminum or the like in addition to brass or stainless steel.

The gas separator according to the present invention can be used as a gas separator for a sulfuric acid type fuel cell, an alkaline type fuel cell and the like, in addition to a solid polymer electrolyte membrane fuel cell.

[0026]

According to the method of manufacturing a gas separator of the present invention, a thin film of a low melting point brazing material is formed on each of the joining surfaces of a fuel gas supply plate, an oxidizing gas supply plate and a partition plate, and these are superimposed on each other. Thus, even when a gas separator is used with copper, it is possible to maintain the rigidity without the copper being in an annealed state. As a result, the fuel cell can be made extremely compact without using a reinforcing material.

Further, it is not necessary to use an expensive hot isostatic pressurizing apparatus, and the production cost of the gas separator can be reduced.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating the operation principle of a solid polymer electrolyte membrane fuel cell.

FIG. 2 is an exploded perspective view of a conventional gas separator.

[Explanation of symbols]

17 is an oxygen supply groove, 18 is a fuel gas supply plate, 19 is a hydrogen supply groove, 20 is an oxidizing gas supply plate, 22 is an oxygen supply manifold, 23 is a hydrogen supply manifold, 24 is a partition plate, and 25 is hydrogen gas. The supply / discharge port 26 is an oxygen gas supply / discharge port.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01M 8/00-8/24

Claims (2)

(57) [Claims] 1. A fuel gas supply plate having a fuel gas supply passage formed therein, an oxidant gas supply plate having an oxidant gas supply passage formed therein, and a partition between the oxidant gas supply plate and the fuel gas supply plate. a partition plate made by integrally joined, solid high
A polymer electrolyte fuel cell for supplying the fuel gas to the gas diffusion electrode on one side and supplying the oxidant gas to the gas diffusion electrode on the other side located between the gas diffusion electrodes of the molecular fuel cell; For manufacturing method of gas separator for fuel cell
A copper fuel gas supply plate and a copper oxidant gas supply plate;
The weight division of tin and lead is applied to each joint surface of the copper partition plate.
If the 4: 1 to 3: 2 after forming a thin film of low melting point brazing material, bonding with them superimposed on each other and heated so as not to exceed 350 ° C. above the melting point of the low melting point brazing material
A method for producing a gas separator for a polymer electrolyte fuel cell , wherein the pressure is set to 10 g / cm ² or less and the fuel gas supply plate, the oxidant gas supply plate, and the partition plate are integrally joined. 2. The method of claim 1, wherein the thin film of the low melting point brazing material has a thickness in a range of 3 micrometers to 6 micrometers.