JP2003022812A - Manufacturing method of separator for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To install a hole in a preform during a separator manufacturing process and prior to curing of the preform. SOLUTION: The working surface of the hole is made smooth, since generation of cracks on the working surface of the hole or the roughened working surface caused by increased hardness is prevented, unlike the case of cured preform. Fuel gas or oxidizing agent gas can be supplied stably from the hole to a gas passage, or exhausted from it formed in the preform, and the power generation performance of a fuel cell can be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a fuel cell separator suitable for forming a hole having a machined surface in a good condition.

[0002]

2. Description of the Related Art A fuel cell is a cell that utilizes the reverse principle of electrolysis of water to obtain electricity in the process of reacting hydrogen and oxygen to obtain water. In general, hydrogen is used to replace fuel gas, and oxygen is used to replace air and oxidant gas, so the terms fuel gas, air, and oxidant gas are often used.

As such a fuel cell, for example, Japanese Patent Laid-Open No. 2000-123848 "Fuel Cell" is known. According to FIG. 1 of the publication, the anode membrane 20 and the cathode membrane 22 are added to the electrolyte membrane 18 (the reference numerals are those described in the publication. The same applies hereinafter), and these are gaskets 24, 26. Through the first separator 1
The cell module is configured by being sandwiched by the fourth separator 16 and the second separator 16.

Specifically, the surface 14a of the first separator 14
A first flow path 38 serving as a fuel gas flow path is formed in the second
A second flow path 46, which serves as a flow path for the oxidant gas, is formed on the surface 16a of the separator 16, and has a structure in which the fuel gas and the oxidant gas face the electrolyte membrane 18 in the center.

Since the electric output obtained by one cell module shown in FIG. 1 is extremely small, a desired electric output can be obtained by stacking a large number of such cell modules. Therefore, the first and second separators 14 and 16 are called “separators” because they are separation members that prevent fuel gas and oxidant gas from leaking to the adjacent cells.

The first separator 14 has a flow path 38 for fuel gas on the surface 14a, and the second separator 16 has a surface 16a.
Although the flow path 46 for the oxidant gas is provided in a, it is necessary to effectively contact the gas with the anode electrode 20 and the cathode electrode 22, and therefore the flow paths 38 and 46 have a large number of shallow grooves. It is necessary to establish this article.

Then, the first and second separators 14 and 16
Is provided with a fuel gas supply hole 32a and an oxidant gas supply hole 34a in the upper part for supplying the fuel gas or the oxidant gas to the flow paths 38 and 46, respectively, and is provided in the lower part with the fuel gas discharge hole 32b and the oxidant gas, respectively. The agent gas discharge holes 34b are provided, the cooling water supply holes 36a for passing the cooling water are provided at the upper part of each, and the cooling water discharge holes 36b are provided at the lower part of each.

[0008]

Each of the holes 32a, 34 of the first separator 14 and the second separator 16 described above is solved.
When opening a, 32b, 34b, 36a, 36b, for example, after the material is completely hardened with a thermosetting resin, the hardness of the material is large, so that the punched surface may have a roughened or cracked surface when punched. Expected to occur. Further, if holes are drilled in a state where curing does not proceed, sufficient shearing will not occur and burrs will easily occur.

Therefore, an object of the present invention is to form, in the method of manufacturing a fuel cell separator, a hole having a processed surface in a good condition in the separator.

[0010]

In order to achieve the above object, the first aspect of the present invention is to provide a preform for producing a flat plate-like preform by adding a binder to carbon and a thermosetting resin, kneading and molding the mixture. In a method for manufacturing a fuel cell separator, which comprises a step and a separator manufacturing step in which the preform is compression-molded into a predetermined shape and heated to a curing temperature, a preform is cured during the separator manufacturing step. It is characterized in that the preform is perforated before being processed.

Smoothing of the machined surface of the hole without the occurrence of cracks on the machined surface of the hole or roughening of the machined surface such as after hardening of the preform. You can

According to a second aspect of the present invention, the boring process is performed when a predetermined time has elapsed since the separator manufacturing process was started. By controlling the timing of the drilling process by time, the machined surface of the hole can always be kept in a good state.

A third aspect of the present invention is characterized in that the perforating process is performed after a predetermined time has elapsed since the separator manufacturing process was started and when the temperature of the preform reached a predetermined temperature.

By controlling the timing of the punching process by the time and the temperature of the preform, for example, even if the temperature of the mold changes and the curing time of the preform changes, the cured state of the preform can be surely grasped. It is possible to make a hole having a good processed surface.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings should be viewed in the direction of the reference numerals. FIG. 1 is a manufacturing flow of a fuel cell separator according to the present invention. Note that STXX indicates a step number. ST01: Carbon powder and thermosetting resin powder are blended in a predetermined mixing ratio, an appropriate amount of binder is added, and kneading is performed. ST02 ... By molding the kneaded product in the following procedure,
Build a preform.

2 (a) and 2 (b) are operation diagrams for explaining the procedure of preform molding according to the present invention. First,
In (a), molding surface 1 of preform molding lower mold 11
Place the kneaded product 13 on 2. Then, the preform molding upper die 15 is lowered as shown by the white arrow, and the kneaded material 13 is pressure-molded. Next, in (b), it is shown that the preform lower mold 11 and the preform upper mold 15 mold the preform 17 into a desired shape.

Returning to FIG. 1, the description of the separator manufacturing flow will be continued. ST03 ... Start compression molding of the preform. ST04 ... The heat curing treatment is performed almost at the same time as the start of the compression molding. ST05 ... The preform which has been compressed and heated is subjected to perforation processing in a manner described later, and then completely cured to form a separator.

FIGS. 3 (a) and 3 (b) are first operation diagrams for explaining the procedure for molding the separator according to the present invention.
In (a), first, the preform 17 is placed on the molding surface 23 of the separator molding lower die 22 including the heater 21. Then, the separator molding upper mold 2 including the heater 25
6 is aligned as shown by the white arrow.

Here, 28 is a convex portion (only one of a plurality is shown) for forming a fuel gas flow passage or an oxidant gas flow passage in the separator, and 31 is a separator for performing a perforating process. Punch provided on the upper die 26, 32 is a punch 31
The pad 33 holds the material to be punched by, and 33 is a thermocouple inserted in the pad 32 so as to be vertically movable.

In (b), while the heaters 21 and 25 are heating the separator lower mold 22 and the separator upper mold 26, press molding is performed into a desired shape. The preform 17 in a compressed and heated state before being completely cured is referred to as a compression molded product 40P.

FIGS. 4 (a) to 4 (c) are second operational views for explaining the procedure of the separator molding according to the present invention, and the drilling process will be described. First, in (a), immediately after compressing the preform, the thermocouple 33 is placed in the compression molded product 40P.
Then, the temperature of the compression molded product 40P is measured.

In (b), when a predetermined time elapses from the time when the compression molding is started and the temperature of the compression molded product 40P reaches a predetermined temperature, the punch 31 is lowered to punch out the compression molded product 40P and the hole 41 is formed. Open. Along with this, the pad 32 is lowered. Since the temperature detecting portion at the tip of the thermocouple 33 is thin, the inside of the pad 32 is lowered and retracted immediately before the punch 31 is lowered in order to prevent the tip from being bent or broken. In (c), compression molded product 4
When the 0P is completely cured, the separator molding upper die 26 is raised and the separator 40 is taken out.

FIG. 5 is a graph showing the relationship between the molding time and the material temperature of the separator according to the present invention. The vertical axis represents the material temperature T (unit: ° C) of the compression molded product 40P, and the horizontal axis represents the molding time t from the start of compression molding. The compression molding is started at time t0, the material temperature T gradually rises, and the material temperature T reaches T1 and becomes almost constant. This material temperature T1 is a preset molding temperature. The perforation described with reference to FIG. 4 is performed in a period between the molding time t1 and the molding time t2 immediately after the material temperature T reaches the molding temperature T1. The molding temperature T1, the molding time t1, and the molding time t2 described above are, for example, T1 = 185 ° c, t1 = 65 sec, t2 = 84.
sec.

If the compression-molded product is perforated between the molding time t1 and the molding time t2, the machined surface of the perforated hole can be smoothly formed without causing cracks or burrs. That is, if the holes are punched before the molding time t reaches t1, the material temperature T is low, so that the curing does not proceed so much, the shearing is not sufficiently performed, and burrs are easily generated. If drilling is performed after the molding time t exceeds t2,
The hardening of the compression molded product progresses considerably, or it completely hardens to increase the hardness, and when punching with a punch, the machined surface becomes rough and cracks occur.

As described above, the present invention firstly includes a preform process for producing a flat plate-like preform by adding a binder to carbon and a thermosetting resin, kneading the mixture, and molding the same. In a method for manufacturing a fuel cell separator, which comprises a separator manufacturing step of manufacturing a separator by compression-molding a reform into a predetermined shape and heating it to a curing temperature, a compression-molded product 40P (Fig. 4 (c )) Is hardened, the compression molded product 40P is subjected to perforation processing.

According to the above-mentioned manufacturing method, the hardness is increased and the hole 41 (see FIG. 4) is formed after the preform is cured.
The processed surface of the hole 41 can be made smooth without cracking or roughening of the processed surface (see (c)).

Therefore, the hole 41 is used as a supply hole for supplying the fuel gas or the oxidant gas to the fuel gas passage or the oxidant gas passage, or the fuel gas or the oxidant gas passage is supplied with the fuel gas or the oxidant gas passage. When the discharge hole for discharging the oxidant gas is used, by smoothing the processed surface of the hole 41, the moisture contained in the fuel gas and the oxidant gas and the moisture generated during the power generation are
It can be made difficult to adhere to the processed surface of the supply hole and the drain hole.

As a result, the supply holes are partially blocked to reduce the supply amount of the fuel gas and the oxidant gas, and the drain holes are partially blocked to cause the fuel gas passage and the oxidant gas passage. There is no need to worry about not being able to fully drain the water. Thereby, the fuel gas and the oxidant gas can be stably supplied, and the power generation performance of the fuel cell can be improved.

Secondly, the present invention is characterized in that the perforating process is carried out when a predetermined time has elapsed from the start of the separator manufacturing process, that is, between the molding time t1 and the molding time t2. By controlling the timing of the drilling process by time, the machined surface of the hole can always be kept in a good state. Therefore, the separator 40 of stable quality can be easily manufactured.

Thirdly, in the present invention, the punching process is performed after a predetermined time has elapsed from the start of the separator manufacturing process, that is, between the molding time t1 and the molding time t2, and the compression molded product 40P.
It is performed when the material temperature T of 1 reaches the molding temperature T1 as a predetermined temperature.

By controlling the timing of punching by the molding time t and the direct material temperature T of the compression molded product 40P, for example, even if the mold temperature changes and the curing time of the compression molded product 40P changes. The cured state of the compression molded product 40P can be accurately grasped, the timing suitable for drilling can be determined, and a hole having a good machined surface can be drilled. Therefore, the quality of the separator 40 can be improved.

In the embodiment of the present invention, as shown in FIG. 4, the temperature of the compression molded product 40P is directly measured to determine the timing of punching.
Not limited to this, if the temperature of the separator molding lower mold 22 or the separator molding upper mold 26 close to the compression molded product 40P is measured to determine the timing of punching, a suitable structure is obtained with a simple structure. Pores can be obtained.

[0033]

The present invention has the following effects due to the above configuration. A method for manufacturing a fuel cell separator according to claim 1,
Add a binder to carbon and thermosetting resin, knead,
A preform step of manufacturing a flat plate-like preform by molding, and a separator for fuel cell comprising a separator manufacturing step of manufacturing a separator by compressing and molding this preform into a predetermined shape and heating to a curing temperature. In the manufacturing method, since the preform is perforated during the separator manufacturing process and before the preform is cured, the hardness becomes large and cracks occur on the machined surface of the hole, such as after the preform is cured. The machined surface of the hole can be made smooth without causing the machining or roughening of the machined surface. Therefore, the fuel gas and the oxidant gas can be stably supplied to and discharged from the above-described holes in the gas flow path formed in the separator, and the power generation performance of the fuel cell can be improved.

In the fuel cell separator manufacturing method according to the second aspect, since the hole forming process is performed when a predetermined time has elapsed since the separator manufacturing process was started, the hole forming process is controlled by time. The processed surface of the hole can always be in a good state. Therefore, a separator of stable quality can be easily manufactured.

In the fuel cell separator manufacturing method of the third aspect of the present invention, the perforating process is performed after a lapse of a predetermined time from the start of the separator manufacturing process and when the temperature of the preform reaches a predetermined temperature. By controlling the timing of punching with time and direct temperature of the preform, for example, even if the mold temperature changes and the curing time of the preform changes, the cured state of the preform can be accurately grasped. It is possible to make a hole having a good processed surface. Therefore, the quality of the separator can be improved.

[Brief description of drawings]

FIG. 1 is a flow chart of manufacturing a fuel cell separator according to the present invention.

FIG. 2 is an operation diagram for explaining the procedure of preform molding according to the present invention.

FIG. 3 is a first operation diagram for explaining the procedure for forming a separator according to the present invention.

FIG. 4 is a second operation diagram for explaining the procedure for forming a separator according to the present invention.

FIG. 5 is a graph showing the relationship between the molding time and the material temperature of the separator according to the present invention.

[Explanation of symbols]

17 ... Preform, 40 ... Separator, 40P ... Compression molded product, 41 ... Hole, T1 ... Predetermined temperature (molding temperature), t1
Molding time, t2 Molding time.

Claims (3)

[Claims] 1. A preform step of producing a flat plate-like preform by adding a binder to carbon and a thermosetting resin, kneading and molding the mixture, and compression molding the preform into a predetermined shape and curing temperature. In a method for manufacturing a fuel cell separator comprising a separator manufacturing step of manufacturing a separator by heating the preform, during the separator manufacturing step and before the preform is cured, the preform is perforated. Method for manufacturing a fuel cell separator. 2. The method for manufacturing a fuel cell separator according to claim 1, wherein the perforating process is performed when a predetermined time has elapsed after the separator manufacturing process was started. 3. The method according to claim 1, wherein the perforating process is performed after a predetermined time has elapsed from the start of the separator manufacturing process and when the temperature of the preform reaches a predetermined temperature. Method for manufacturing fuel cell separator.