JP2003022815A - Manufacturing method of separator for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the time required for a separator manufacturing process, and enhance productivity of the separator by quickly raising the temperature of a preform with a first heating means and a second heating means during the compression molding of the preform, and accelerating curing, by keeping the raised temperature of the preform with the first heating means, after the second heating means has stopped. SOLUTION: The heating means, comprising electric heaters 21, 26 and a direct resistance heating device 28, in installed at the starting of heating, the electric heaters 21, 26 and the direct resistance heating device 28 are energized; and thus after the elapse of the specified time, or reaching a specified temperature, power supply to the direct resistance heating device 28 is stopped.

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, which is suitable for shortening the time required for a heat curing step and increasing the productivity of the separator.

[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.

[0006]

Although the above publication does not describe a method for manufacturing a separator, a general manufacturing method is to knead materials and mold the kneaded material into a mold to prepare a preform. A method is known in which this preform is compression-molded with a molding die and cured by heating during the compression molding to produce a separator.

When mass-producing separators by such a method, it is required to shorten the time required for each of the above steps in order to improve productivity. In particular, the above-mentioned heat curing step occupies a large time ratio in the separator manufacturing step because it takes a long time until the material is completely cured.

Therefore, an object of the present invention is to shorten the time required for the heating and curing step in the method for manufacturing a fuel cell separator and increase the productivity of the separator.

[0009]

In order to achieve the above object, the first aspect of the present invention is to form a preform from a kneaded material of a conductive material and a thermosetting resin, and compression-mold the preform into a predetermined shape. In addition to the above, in the method for manufacturing a fuel cell separator in which a separator is manufactured by heating with a heating means, a heating means including a first heating means and a second heating means is prepared, and at the start of heating, the first and second heating means are provided. Are operated together, and the second heating means is stopped when a predetermined time elapses or when a predetermined temperature is reached.

By operating both the first heating means and the second heating means as heating means, the temperature of the preform can be rapidly raised during compression molding of the preform, and the second heating means is stopped. By increasing the temperature of the preform by the first heating means, curing can be promoted, and the time required for the separator manufacturing process can be shortened.

According to a second aspect of the present invention, the first heating means performs indirect resistance heating, and the second heating means performs direct resistance heating for energizing the preform itself to generate heat. By directly passing an electric current to the conductive preform by the second heating means, the preform itself is heated, that is, direct resistance heating is performed to directly heat the preform during compression molding in a short time. be able to.

In addition, indirect resistance heating in which the first heating means is heated by passing a current through the first heating means as a conductor provided separately from the preform, and the preform is indirectly heated by the first heating means By performing the above, a large amount of heat can be supplied to the preform in cooperation with the second heating means, and the increased temperature of the preform can be maintained. Therefore, the preform can be efficiently cured by the two heating methods.

A third aspect of the present invention is characterized in that the start of heating is the time when the outer shape of the separator is completed in the compression mold. If heating is performed in a state where the preform is not sufficiently filled in the cavity after starting compression molding, the preform will start to harden and it will be difficult to fill the cavity. By starting heating when the filling is completed, that is, when the outer shape of the separator is completed, the quality of the separator after molding can be improved.

[0014]

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 flow of a method for manufacturing a fuel cell separator according to the present invention. Note that STXX indicates a step number. ST01 ... Blending thermosetting resin powder and carbon powder as a conductive material in a predetermined mixing ratio, adding an appropriate amount of binder, and kneading. 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 ... Heat curing treatment is carried out almost simultaneously with the start of the compression molding to produce a separator. The above-described separator manufacturing process (compression molding and heat curing treatment) will be described in detail with reference to FIGS. 3 to 5 below.

FIGS. 3 (a) and 3 (b) are first operation diagrams for explaining the separator manufacturing process according to the present invention.
In (a), the electric heater 21 as the first heating means.
And the preform 17 is placed on the separator forming lower die 25 including the lower die electrode 22 constituting the second heating means,
An upper die 32 for forming a separator including an electric heater 26 as a first heating means and an electrode 27 for an upper die that constitutes a second heating means is formed on the lower die 25 for forming a separator from above, as shown by a white arrow. To match.

The electric heaters 21 and 26 are devices for performing indirect resistance heating for indirectly heating the preform during compression molding, and the lower die electrode 22 and the upper die electrode 27 energize the preform. Thus, the direct resistance heating device 28 that heats the preform itself, that is, performs direct resistance heating of the preform is configured. The separator molding lower die 25 and the separator molding upper die 32 constitute a separator molding die 29 as a compression molding die.

Here, 33 is a copper piece embedded in each of the lower die electrode 22 and the upper die electrode 27, and the lower die electrode 22 and the upper die electrode 27 are made of copper pieces having a small electric resistance. The current is distributed between them.

Reference numeral 34 denotes an insulating plate provided in the separator molding lower die 25, which is a member for electrically insulating the separator molding lower die 25 from the outside. An insulating plate 35 is provided inside the separator molding upper die 32, and is a member that electrically insulates the separator molding upper die 32 from the outside. 36,3
Reference numerals 6, 37 and 37 denote insulating pieces, which are members that electrically insulate the lower mold 25 for separator molding and the upper mold 32 for separator molding. Reference numerals 41 and 42 are conductive wires for respectively energizing the lower die electrode 22 and the upper die electrode 27, 43 is a connector, 44
Is a bolt.

(B) is a plan view for explaining the electrothermal heater 21 and the lower die electrode 22 provided on the separator molding lower die 25. A plurality of electrothermal heaters 21 are arranged side by side on the separator molding lower die 25, It is shown that the lower mold electrode 22 is arranged above these electric heaters 21. The same applies to the electrothermal heater 26 and the upper mold electrode 27 of the separator molding upper mold 32, and a description thereof will be omitted.

FIG. 4 is a second action diagram for explaining the separator manufacturing process according to the present invention. The preform is compression-molded by the separator-forming lower mold 25 and the separator-forming upper mold 32 and heat-cured. Processing is performed to make the separator 50. The time course of this compression molding and heat curing treatment will be described with reference to the following figure.

FIG. 5 is a graph for explaining the change with time in the separator manufacturing process according to the present invention, in which the vertical axis represents the timing of material injection into the mold, the mold opening / closing timing in compression molding, and the time of electric heating. The energization state of the electric heater and the direct resistance heating device, the timing of demolding the molded product (separator) taken out of the mold, and the material temperature T are shown, and the horizontal axis shows the time t.

First, at time t1, the material (preform) is introduced into the separator molding lower die, and at time t2, the material is completed. Further, at this time t2, the separator forming upper die starts to descend, and the die starts to be closed. Then, when the compression molding of the material in the cavity is started at time t3, the material temperature T starts to rise at the time t3,
From time t4, the material temperature T becomes T2, which is level.

At time t5, the mold is completely closed, so that the cavity is completely filled with the material, that is, the outer shape of the separator is completed. At time t5, the electric heater serving as the first heating means is energized (ON; indicated by the solid line), and the direct resistance heating device serving as the second heating means is energized (ON, indicated by the broken line) to perform energization heating. I do. As a result, the material is rapidly heated by both heating means to raise the material temperature T in a short time, and when the predetermined time tst has passed from the time t5 (that is, when the time t6 is reached) or the material temperature T is cured. When the temperature reaches the upper limit temperature T3, the power supply to the resistance heating device is directly stopped (OFF).

After that, the material temperature T is maintained at T3 because it is heated only by the electric heater. Then, at time t7, the power supply to the electric heater is stopped (OFF). After that, since the heat capacity of the mold is large, the material temperature T gently drops.
The hardening of the material is accelerated by the amount of heat in the hatched area in the figure.

Then, at time t8 when the material temperature T drops to T2, it is judged that the curing of the material is completed, the compression molding is stopped and the mold starts to be opened, and the mold opening is finished at time t9. The product demolding is started at t9, and the product demolding is completed at time t10.

As described above with reference to FIGS. 2, 4 and 5, the present invention firstly forms a preform 17 from a kneaded material 13 of carbon powder and thermosetting resin powder, and the preform 17 is formed. In the manufacturing method of the fuel cell separator 50, in which the separator 50 is manufactured by compression-molding 17 into a predetermined shape and heating with a heating means, a heating means including electric heaters 21 and 26 and a direct resistance heating device 28 is prepared. However, the electric heaters 21 and 26 and the direct resistance heating device 28 are energized together at the start of heating, and the energization to the direct resistance heating device 28 is stopped when a predetermined time tst elapses or when a predetermined temperature T3 is reached. And

By operating both the electric heaters 21 and 26 and the direct resistance heating device 28 as heating means, the temperature of the preform 17 is rapidly increased to the temperature T3 which is the upper limit of the curing temperature during compression molding of the preform 17. The temperature can be increased, and the temperature T3 can be maintained after the power supply to the resistance heating device 28 is stopped, so that the curing can be accelerated.
The heat curing time th (see FIG. 5) of the preform, and eventually the molding time tp (see FIG. 5) can be shortened.
Therefore, the time required for the separator manufacturing process can be shortened, and the productivity of the separator 50 can be improved.

Secondly, in the present invention, the first heating means, that is, the electric heaters 21 and 26 perform indirect resistance heating, and the second heating means, that is, the direct resistance heating device 28 energizes the preform 17 itself to generate heat. However, it is characterized by performing direct resistance heating. By performing direct resistance heating with the direct resistance heating device 28, it is possible to heat the preform 17 during compression molding in a short time by the Joule heat generated in the conductive preform 17, and the electric heater 21, By performing indirect resistance heating at 26, a large amount of heat can be supplied to the preform 17 in cooperation with the direct resistance heating device 28, and the increased temperature of the preform 17 can be maintained. Therefore, the preform 17 can be efficiently cured by the two heating methods.

Thirdly, according to the present invention, the heating start time is defined as the time when the outer shape of the separator 50 is completed in the separator forming lower die 25 as the compression forming die and the separator forming upper die 32 as the compression forming die. It is characterized by having done.

If heating is performed after the compression molding is started, for example, in a state where the preform 17 is not sufficiently filled in the cavity, the preform 17 begins to harden and it becomes difficult to fill the cavity. By starting heating at the time when the filling of the preform into the cavity is completed, that is, when the outer shape of the separator is completed,
The quality of the separator after molding can be improved.

In the present invention, the resistance heating is directly performed by the second heating means. However, the present invention is not limited to this, and each electrode plate of the second heating means is replaced with a coil, and the coil is energized. Alternatively, induction heating may be performed to generate an induction current in the conductive material and heat the conductive material itself. Induction heating
Since the conductive material can be entirely heated in a short time and the heating efficiency is high, it is suitable for the heat curing treatment of the preform.

[0034]

The present invention has the following effects due to the above configuration. A method for manufacturing a fuel cell separator according to claim 1,
A heating means including a first heating means and a second heating means is prepared, and both the first and second heating means are operated at the start of heating,
Since the second heating means is stopped when a predetermined time has elapsed or when the temperature reaches a predetermined temperature, it is possible to rapidly raise the temperature of the preform by both the first heating means and the second heating means during compression molding of the preform. Therefore, after the second heating means is stopped, the elevated temperature of the preform can be maintained by the first heating means to accelerate the curing. Therefore, the time required for the separator manufacturing process can be shortened, and the productivity of the separator can be improved.

In the method for manufacturing the fuel cell separator according to the second aspect, since the first heating means performs the indirect resistance heating and the second heating means performs the direct resistance heating, the second heating means conducts the conductive preform itself. By heating the preform, the preform during compression molding can be heated in a short time. Moreover, since the temperature of the preform can be maintained by the first heating means after the second heating means is stopped, the preform can be efficiently cured by two heating methods.

In the method for manufacturing the fuel cell separator according to the third aspect of the present invention, since the start of heating is the time when the outer shape of the separator is completed in the compression mold, the time when the filling of the preform into the cavity is completed. The heating can be started at, and the quality of the separator after molding can be improved.

[Brief description of drawings]

FIG. 1 is a flow of a method for 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 illustrating a separator manufacturing process according to the present invention.

FIG. 4 is a second action diagram illustrating a separator manufacturing process according to the present invention.

FIG. 5 is a graph illustrating changes over time in a separator manufacturing process according to the present invention.

[Explanation of symbols]

13 ... Kneaded product, 17 ... Preform, 21, 26 ... First
Heating means (electrothermal heater), 28 ... Second heating means (direct resistance heating device), 29 ... Compression molding die (separator molding die), 50 ... Separator, t5 ... Heating start time.

Claims (3)

[Claims] 1. A fuel cell for producing a separator by molding a preform from a kneaded material of a conductive material and a thermosetting resin, compression-molding the preform into a predetermined shape, and heating by a heating means. In the method for manufacturing a separator, a heating means including a first heating means and a second heating means is prepared, and both the first and second heating means are operated at the start of heating,
A method for manufacturing a fuel cell separator, characterized in that the second heating means is stopped after a lapse of a predetermined time or when a predetermined temperature is reached. 2. The fuel according to claim 1, wherein the first heating means performs indirect resistance heating, and the second heating means performs direct resistance heating for energizing the preform itself to generate heat. Method for manufacturing battery separator. 3. The method for producing a fuel cell separator according to claim 1, wherein the heating is started at the time when the outer shape of the separator is completed in the compression mold.