JP2007167886A - Method for forming metallic sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a metallic sheet by which a high-grade formed article without warping, waving or the like are obtained inexpensively by simple die composition. <P>SOLUTION: In the method of forming the metallic sheet for forming projecting and recessing parts on the metallic sheet by press working, the projecting and recessing parts are formed on the metallic sheet through a squeezing step where the metallic sheet is squeezed in the thickness direction by the projecting part of a punch between itself and a die and a fitting step where excess metal which is generated on the metallic sheet in the squeezing step is fitted into the recessed part of the die with the punch. By alternately repeating a plurality of times of the squeezing steps and the fitting steps, a corrugated-sheet part having a wavy cross section in which the projecting and recessing parts are continued alternately in the face direction are formed on the metallic sheet. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for forming a metal thin plate in which uneven portions are formed on the metal thin plate by press working.

  For example, a metal separator used in a polymer electrolyte fuel cell can be obtained by pressing a thin metal plate such as stainless steel or titanium alloy with a high corrosion resistance coating. A current collecting section having a corrugated cross section alternately formed in the plane direction is formed. Here, the concave portion of the current collecting portion becomes a gas flow passage or a flow passage such as generated water after reaction, and the convex portion becomes a portion in contact with the gas diffusion electrode plate of the electrode structure.

  By the way, when the current collector part of the fuel cell metal separator is formed by press working, stress is generated in the metal thin plate due to bending or extension, so that the formed separator is warped or wavy. If warpage or undulation occurs in the fuel cell metal separator, the convex part of the current collector does not contact the gas diffusion electrode plate with sufficient surface pressure, or the surface pressure becomes non-uniform, increasing the contact resistance and generating voltage. Will be reduced. Also, in the work of assembling a fuel cell stack by laminating a plurality of electrode structures with the separator in between, it is necessary to assemble while correcting the warp and undulation of the separator. There is a problem that the gas sealability is lowered.

  Thus, various methods for suppressing warpage and undulation of the fuel cell metal separator have been proposed.

  For example, in Patent Document 1, as shown in FIG. 9, a portion where a current collector WA ′ of a metal thin plate W ′ that is a material is formed is heated to 60 ° C. to 150 ° C., and a flat peripheral portion around it is heated. After a part or all of WB ′ is cooled to 0 ° C. to 20 ° C. to give a temperature gradient to the metal thin plate W ′, a current collecting portion WA ′ in which uneven portions are alternately continued in the surface direction is formed by stretch forming. A method has been proposed.

  Further, in Patent Document 2, as shown in FIG. 10, ribs WC ′ (hatched portions) are formed over the entire circumference at the edge portion WB ′ around the current collecting portion WA ′ of the separator W ′. A method has been proposed in which the rib WC ′ increases the rigidity of the edge WB ′ and suppresses the propagation of internal stress that causes warping to the edge WB ′.

Further, in Patent Document 3, as shown in FIG. 11, a peripheral portion WB ″ surrounding a central portion (molded portion) WA ″ of a press-processed product W ″ press-molded in a state where the peripheral portion is fixed is a central portion. A method has been proposed in which the press-worked product W ″ is plastically deformed by being relatively stretched in a direction away from WA ″, and the strain is removed from the press-worked product W ″.
JP 2004-134090 A JP 2002-175818 A JP 2003-230913 A

  However, in order to implement the method proposed in Patent Document 1, there is a problem that a large facility is required and temperature management is difficult.

  The method proposed in Patent Document 2 is more effective for warping as the rib WC 'is larger and thicker, but has a problem that it is difficult to apply to small products.

  Furthermore, the method proposed in Patent Document 3 has a problem that the mold structure is complicated, the mold is difficult to manufacture, and the cost is increased.

  The present invention has been made in view of the above problems, and the object of the present invention is a method for forming a thin metal plate that can obtain a high-quality molded product without warping or undulation with a simple mold configuration at low cost. Is to provide.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a metal sheet forming method in which an uneven portion is formed on a thin metal plate by press working. An uneven portion is formed in the metal thin plate through a crushing step of crushing and a step of inserting a surplus produced in the metal thin plate into the concave portion of the die by a punch.

  According to a second aspect of the present invention, in the first aspect of the invention, the corrugated corrugated plate section in which the concave and convex portions are alternately continued in the surface direction is obtained by alternately repeating the crushing step and the inserting step a plurality of times. It is characterized by being formed on a thin metal plate.

  The invention according to claim 3 is characterized in that, in the invention according to claim 2, the size of the convex portion of the punch in the crushing step and the concave portion of the die in the inserting step is gradually increased as each step is repeated. .

  According to the first aspect of the present invention, the surplus generated in the molded portion of the thin metal plate by the crushing process is inserted into the concave portion of the die and absorbed by the next insertion process, and only the molded portion is crushed like forging. In order to be extended, the movement of the material takes place only within the area of the forming part. For this reason, the cross-sectional area (volume) of the molded part does not change, so there is no inflow of material from the peripheral part to the molded part, stress and distortion associated with molding do not occur in the peripheral part, and warping, undulation, etc. A high-quality molded product can be obtained.

  In addition, troublesome temperature control and the like are not required for forming a thin metal plate, and since the forming is performed using a punch and die having a simple configuration, the die structure can be simplified and the processing cost can be kept low. .

  According to the second aspect of the present invention, since the corrugated portion and the corrugated portion are alternately repeated a plurality of times, the corrugated portion having the corrugated portion alternately continuous in the surface direction is formed on the thin metal plate. For example, a metal separator for a fuel cell or the like can be manufactured as a high-quality product free from undulations or the like.

  According to the third aspect of the present invention, the size of the convex portion of the punch in the crushing step and the size of the concave portion of the die in the inserting step are gradually increased as each step is repeated. A desired molded product can be obtained by repeating the steps until the dimensions (width and depth) of the uneven portions of the plate portion are gradually increased and the dimensions of the uneven portions become necessary values.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a perspective view of a metal separator for a fuel cell formed by the method of the present invention, and FIG. 2 is a sectional view taken along line XX of FIG.

  The metal separator W for a fuel cell shown in FIG. 1 is obtained by, for example, pressing (stretching) a thin metal plate having a thickness of 0.15 mm made of stainless steel, and a current collector WA is provided at the center. The current collector WA is surrounded by a flat peripheral WB.

  As shown in detail in FIG. 2, the current collector WA constitutes a corrugated plate having a corrugated cross section in which the concave portions Wa and the convex portions Wb are alternately continued in the plane direction. It becomes a flow path for later generated water and the convex portion Wb is a portion that contacts a gas diffusion electrode plate of an electrode structure (not shown). The fuel cell metal separator W shown in FIG. 1 is used for a polymer electrolyte fuel cell, and a fuel cell stack is assembled by laminating a plurality of electrode structures while sandwiching them. .

  Thus, the fuel cell metal separator W shown in FIG. 1 is obtained by the molding method of the present invention. Hereinafter, the molding method according to the present invention will be described with reference to FIGS. 3 to 8, (a) is a partial cross-sectional view of a mold showing the method of the present invention in the order of steps, and (b) is an enlarged view of main parts (E, F, G, H, I, and J are enlarged detailed views), which are shown for convenience, and the number of uneven portions is the uneven portion Wa of the actual fuel cell metal separator W shown in FIG. , Wb does not match.

  The forming method according to the present invention includes a crushing step in which a metal thin plate is crushed in the plate thickness direction between the die by a convex portion of the punch, and surplus material generated in the metal thin plate by the crushing step is put in the concave portion of the die by the punch. It is characterized by alternately repeating the insertion step. Here, the size of the convex portion of the punch in the crushing step and the concave portion of the die in the inserting step is gradually increased as each step is repeated. In each crushing process, the die used in the insertion process which is the preceding process is used, and in each insertion process, the punch used in the crushing process which is the preceding process is used.

  In the present embodiment, the fuel cell metal separator shown in FIG. 1 is obtained through the following six steps.

1) First step (crushing step 1):
As shown in FIG. 3A, a metal that is a material between a punch PA in which a plurality of mountain-shaped convex portions pa are formed on an upper surface that is a processing surface and a die DA that has a flat bottom surface that is a processing surface. A thin plate is set, and the metal thin plate is crushed between the die DA in the plate thickness direction by the convex portion pa of the punch PA. In addition, the diameter of the envelope circle which shows the magnitude | size of each convex part pa of punch PA used at this process is set to D1, as shown in FIG.3 (b).

  Then, as shown in detail in FIG. 3 (b), a recess W1a is formed in the portion crushed by the projection pa of the punch PA on the lower surface of the metal thin plate to obtain a semi-finished product W1, which is crushed and left over. The material appears as surplus W1b on both sides of each recess W1a.

2) Second step (insertion step 1):
In this second step, as shown in FIG. 4 (a), the surplus W1b (see FIG. 3 (b)) generated on the lower surface of the semi-finished product W1 in the first step is die-formed by the punch PA used in the first step. It inserts in the recessed part db of DB. Here, the mountain-shaped concave portion db is formed at a position corresponding to the convex portion pa of the punch PA on the lower surface which is the processed surface of the die DB.

  That is, if the semi-finished product W1 obtained in the first step (see FIG. 3) is set between the punch PA and the die DB, and the semi-finished product W1 is clamped between the punch PA and the die DB, The surplus W1b (see FIG. 3B) generated on both sides of each recess W1a on the lower surface is inserted into the recess db of the die DB.

3) Third step (crushing step 2):
In this third step, as shown in FIG. 5A, a second punch PB, which is different from the punch PA used in the first and second steps, and the die DB used in the second step are used. The semi-finished product W2 obtained in the process is set, and the semi-finished product W2 is crushed in the plate thickness direction by the convex portion pb of the punch PB with respect to the concave portion db of the die DB to obtain a semi-finished product W3. Note that the diameter D2 (see FIG. 5B) of the envelope circle indicating the size of each convex portion pb of the punch PB used in this step is the convex portion pa of the punch PA used in the first and second steps. Is set larger than the diameter D1 of the envelope circle (see FIG. 3B) (D2> D1).

  Then, as shown in detail in FIG. 5B, a concave portion W3a is formed in a portion crushed by the convex portion pb of the punch PB on the lower surface of the semi-finished product W3, and the material remaining after being crushed is each concave portion W3a. Appears as surplus W3b on both sides. In this third step, as shown in FIG. 5 (b), the convex portion W3c of the semi-finished product W3 is crushed by the convex portion pb of the punch PB, and the thickness t1 is the thickness of the metal thin plate as the material. It becomes thinner than t0 (t1 <t0).

4) Fourth step (insertion step 2):
In this fourth step, as shown in FIG. 6 (a), the surplus W3b (see FIG. 5 (b)) generated on the lower surface of the semi-finished product W3 in the third step is die-cut by the punch PB used in the third step. Insert into the DC recess dc. Here, the mountain-shaped concave portion dc is formed at a position corresponding to the convex portion pb of the punch PB on the lower surface, which is the processed surface of the die DC, and the size (width and depth) of the concave portion dc is as follows. The size (width and depth) of the concave portion db (see FIGS. 4 and 5) of the die DB used in the second and third steps is set.

  That is, if the semi-finished product W3 (see FIG. 5) obtained in the third step is set between the punch PB and the die DC, and the semi-finished product W3 is clamped between the punch PB and the die DC, The surplus wall W3b (see FIG. 5B) generated on both sides of each concave portion W3a on the lower surface is inserted into the concave portion dc of the die DC to obtain a semi-finished product W4 as shown in FIG. The semi-finished product W4 is provided with a corrugated plate portion W4A having a corrugated cross section in which the concave portions W4a and the convex portions W4b are alternately continued in the surface direction.

5) Fifth step (crushing step 3):
In this fifth step, as shown in FIG. 7A, the punch PC, which is different from the punch PB used in the third step and the fourth step, and the die DC used in the fourth step, The semi-finished product W4 (see FIG. 6) obtained in the four steps is set, and the semi-finished product W4 is crushed in the plate thickness direction by the convex portion pc of the punch PC with respect to the concave portion dc of the die DC to obtain the semi-finished product W5. The diameter D3 (see FIG. 7B) of the envelope circle indicating the size of each convex part pc of the punch PC used in this step is the convex part pb of the punch PB used in the third and fourth processes. Is set to be larger than the diameter D2 of the envelope circle (see FIG. 5B) (D3> D2).

  Then, as shown in detail in FIG. 7B, a recess W5a is formed in a portion crushed by the convex portion pc of the punch PC on the lower surface of the semi-finished product W5, and the material remaining after being crushed is left in each recess W5a. Appears as surplus W5b on both sides. In this fifth step, as shown in FIG. 7B, the convex portion W5c of the semi-finished product W5 is crushed by the convex portion pc of the punch PC, and the thickness t2 thereof is the convex portion W3c of the semi-finished product W3. It becomes thinner than the thickness t1 (see FIG. 5B) (t2 <t1).

6) Sixth step (insertion step 3):
In this sixth step, as shown in FIG. 8 (a), the surplus W5b (see FIG. 7 (b)) generated on the lower surface of the semi-finished product W5 in the fifth step is die-formed by the punch PC used in the fifth step. Insert into the recess dd of DD. Here, the mountain-shaped concave portion dd is formed at a position corresponding to the convex portion pc of the punch PC on the lower surface, which is the processed surface of the die DD, and the size (width and depth) of the concave portion dd is as follows. The size (width and depth) of the recess dc (see FIGS. 6 and 7) of the die DC used in the fourth and fifth steps is set.

  That is, if the semi-finished product W5 (see FIG. 7) obtained in the fifth step is set between the punch PC and the die DD, and the semi-finished product W5 is sandwiched between the punch PC and the die DD, The surplus metal W5b (see FIG. 7B) generated on both sides of each concave portion W5a on the lower surface is inserted into the concave portion dd of the die DD, and the metal for the fuel cell as the final product as shown in FIG. A separator W (see FIG. 1) is obtained. In the fuel cell metal separator W as the final product, a current collecting part WA having a corrugated cross section in which the concave portions Wa and the convex portions Wb are alternately continued in the surface direction is formed.

  The metal separator W for a fuel cell shown in FIG. 1 is manufactured through the above first to sixth steps, but according to the molding method according to the present invention, the first, third and fifth steps which are crushing steps. The surplus portions W1b, W3b, W5b generated in the molded parts of the semi-finished products W1, W3, W5 by the second, fourth, and sixth steps, which are the next insertion steps, are recessed portions db, dc, Each of them is inserted into dd and absorbed, and the crushing process and the insertion process are repeated to form a current collecting part WA that is a corrugated plate part, and only the current collecting part WA that is a forming part is crushed like forging. In order to be extended, the movement of the material is performed only within the range of the current collector WA. For this reason, the cross-sectional area (volume) of the current collector WA does not change. Therefore, there is no inflow of material from the peripheral portion WB to the current collector WA, and stress and strain associated with molding do not occur in the peripheral portion WA. Thus, a high-quality metal separator W for a fuel cell free from warpage or undulations can be obtained.

  Moreover, troublesome temperature control and the like are not necessary for forming a thin metal plate, and the forming is performed using punch PA, PB, PC and die DA, DB, DC, DD having a simple structure. However, the processing cost can be kept low.

  Further, the protrusions pa, pb, pc of the punches PA, PB, PC used in the first, third and fifth processes which are crushing processes are used in the second, fourth and sixth processes which are insertion processes. Since the sizes of the recesses db, dc, and dd of the die DB, DC, and DD are gradually increased as each process proceeds, the dimensions (width and depth) of the corrugated part of the corrugated sheet formed as the processes are repeated. The metal separator W for a fuel cell, which is a desired molded product, can be obtained by repeating the respective steps until the dimension of the concave and convex portions reaches a required value.

  By the way, there is a method in which punches PA, PB, PC and dies DA, DB, DC, DD used in the above first to sixth steps are integrated and juxtaposed, and a thin metal plate is sequentially fed between them. If employed, continuous processing by progressive feeding is possible, and the metal separator W for a fuel cell, which is the final molded product, can be efficiently formed in one apparent process (one punching).

  In the above embodiment, the fuel cell metal separator W, which is the final molded product, is formed through the first to sixth steps. However, the number of steps is arbitrary, and the uneven portions Wa, It can be increased or decreased according to the size of Wb.

  The present invention can be similarly applied not only to the metal separator for a fuel cell but also to the formation of any other product formed by forming a concavo-convex portion on a metal thin plate by pressing.

It is a perspective view of the metal separator for fuel cells formed by the forming method concerning the present invention. FIG. 2 is an enlarged sectional view taken along line XX in FIG. 1. (A) is the fragmentary sectional view of the metal mold | die which shows the 1st process (crushing process 1) of this invention, (b) is the E section enlarged detail drawing of (a). (A) is the fragmentary sectional view of the metal mold | die which shows the 2nd process (insertion process 1) of this invention, (b) is F section enlarged detail drawing of (a). (A) is the fragmentary sectional view of the metal mold | die which shows the 3rd process (crushing process 2) of this invention, (b) is the G section enlarged detail drawing of (a). (A) is the fragmentary sectional view of the metal mold | die which shows the 4th process (insertion process 2) of this invention, (b) is the H section enlarged detail drawing of (a). (A) is the fragmentary sectional view of the metal mold | die which shows the 5th process (crushing process 3) of this invention, (b) is the I section enlarged detail drawing of (a). (A) is the fragmentary sectional view of the metal mold | die which shows the 6th process (insertion process 3) of this invention, (b) is the J section enlarged detail drawing of (a). It is a top view explaining the conventional shaping | molding method (The shaping | molding method of patent document 1). It is a top view explaining the conventional shaping | molding method (The shaping | molding method of patent document 2). It is a top view explaining the conventional shaping | molding method (The shaping | molding method of patent document 3).

Explanation of symbols

DA, DB, DC, DD Dies db, dc, dd Die recesses PA, PB, PC Punches pa, pb, pc Punch projections W Metal separator for fuel cell WA Current collector for metal separator for fuel cell (corrugated plate) Part)
WB Peripheral part of metal separator for fuel cell Wa Concave part of current collecting part Wb Convex part of current collecting part W1 Semi-finished product W1a Concave part of semi-finished product W1 W1b Semi-finished product W1 W2, W3 Semi-finished product W3a Concave part of semi-finished product W3 W3b Semi Product W3 surplus W3c Semi-finished product W3 convex portion W4 Semi-finished product W4A Semi-finished product W4 corrugated plate W4a Semi-finished product W4 concave portion W4b Semi-finished product W4 convex portion W5 Semi-finished product W5a Semi-finished product 5 concave portion W5b Semi-finished product 5 Surplus W5c Projection of semi-finished product 5

Claims (3)

In the forming method of the metal thin plate that forms the uneven portion on the metal thin plate by pressing,
The metal thin plate is subjected to a crushing process in which the metal thin plate is crushed between the die and the die by the convex portion of the punch, and the surplus generated in the metal thin plate by the crushing step is inserted into the concave portion of the die by the punch. A method for forming a metal thin plate, comprising forming an uneven portion.   2. The metal according to claim 1, wherein the crushing step and the inserting step are alternately repeated a plurality of times to form a corrugated plate portion having a corrugated portion in which the concavo-convex portions are alternately continued in the plane direction on the metal thin plate. Thin plate forming method.   3. The method for forming a thin metal plate according to claim 2, wherein the size of the convex portion of the punch in the crushing step and the size of the concave portion of the die in the inserting step are gradually increased as each step is repeated.

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