The present invention relates to a method and an apparatus for forming bulging portions on a metal plate by performing cold-pressing on the metal plate with a die including a die block and a punch.
A conventional fuel-cell separator includes bulging portions provided on a metal plate to form a flow passage through which gas such as hydrogen and oxygen, coolant, or the like flows. For example, Japanese Patent No. 5573511 and Japanese Laid-Open Patent Publication No. 2014-213343 disclose methods for forming a fuel-cell separator.
According to the forming method disclosed in Japanese Patent No. 5573511, as shown in
According to the forming method disclosed in Japanese Laid-Open Patent Publication No. 2014-213343, as shown in
To make the cross-sections of bulging portions more closely match rectangular shapes, more load is required to press the sidewalls of the bulging portions. As a result, a problem arises that the forming apparatus needs to be highly durable.
Particularly, it is preferable for a fuel-cell separator, for example, to have a large cross-sectional area in view of improving the output efficiency of the fuel cell so that gas such as hydrogen and oxygen easily flows through the flow passage. Thus, it is desired that the cross-sections of bulging portions closely match rectangular shapes.
It is an objective of the present invention to provide a method and an apparatus for forming a metal plate that allows the forming load to be reduced.
To achieve the above objective, a method for forming a metal plate is a method in which bulging portions are formed on a metal plate by performing cold-pressing on the metal plate using at least one die including a die block and a punch. The at least one die includes a first die and a second die. The method includes a first step of forming a pre-formed body including pre-formed bulging portions with the first die. Each pre-formed bulging portion includes sidewalls, and each sidewall includes a dent. The method further includes a second step of pressing the sidewalls with the second die so that the dents of the pre-formed body disappear.
To achieve the above objective, an apparatus for forming a metal plate includes at least one die including a die block and a punch. With the at least one die, bulging portions are formed on a metal plate by performing cold-pressing on the metal plate. The at least one die includes a first die and a second die. The first die forms a pre-formed body including pre-formed bulging portions. Each pre-formed bulging portion includes sidewalls, and each sidewall includes a dent. The second die presses the sidewalls so that the dents of the pre-formed body disappear.
With reference to
As shown in
Each of the bulging portions 31 includes a top 311 that is located at the front end in the projecting direction (the vertical direction of
The material used for the metal plate 30 is excellent in corrosion resistance, and is, e.g., titanium, titanium alloys, or stainless steel. In the present embodiment, titanium is used.
Such a fuel-cell separator is formed by cold-pressing on the flat sheet-shaped metal plate 30 shown in
As shown in
The first die block 11 includes recesses 111 and projections 112, which are alternately arranged on the upper surface. The first punch 12 includes projections 121 and recesses 122, which are alternately arranged on the lower surface. The projections 121 correspond to the respective recesses 111 of the first die block 11, and the recesses 122 correspond to the respective projections 112 of the first die block 11.
Each recess 111 and each projection 112 of the first die block 11 have curved surfaces. Each projection 112 and the adjacent recesses 111 are connected with oblique surfaces 113, each of which includes a first convex portion 114. The first convex portion 114 is located in the central portion of the oblique surface 113 in the projecting direction of the corresponding projection 112 (the vertical direction of
Each projection 121 and each recess 122 of the first punch 12 have curved surfaces. Each recess 122 and the adjacent projections 121 are connected with oblique surfaces 123, each of which includes a second convex portion 124. The second convex portion 124 is located in the central portion of the oblique surface 123 in the projecting direction of the corresponding projection 121 (the vertical direction of
In the present embodiment, the curvature radiuses of the first convex portions 114 of the first die block 11 and the curvature radiuses of the second convex portions 124 of the first punch 12 are set to be the same as each other.
As shown in
The second die block 21 includes recesses 211 and projections 212, which are alternately arranged on the upper surface. The second punch 22 includes projections 221 and recesses 222, which are alternately arranged on the lower surface. The projections 221 correspond to the respective recesses 211 of the second die block 21, and the recesses 222 correspond to the respective projections 212 of the second die block 21.
The central portion of each recess 211 of the second die block 21 has a planer shape that is perpendicular to the moving direction of the second punch 22 (the vertical direction of
The central portion of each projection 221 of the second punch 22 has a planer shape that is perpendicular to the moving direction of the second punch 22 (the vertical direction of
Therefore, the central portion of each recess 211 of the second die block 21 is parallel to the central portion of the corresponding projection 221 of the second punch 22. The central portion of each projection 212 of the second die block 21 is parallel to the central portion of the corresponding recess 222 of the second punch 22. In addition, each oblique surface 213 of the second die block 21 is parallel to the corresponding oblique surface 223 of the second punch 22.
A forming method according to the present embodiment and operation of the present embodiment will now be described together.
As shown in
As shown in
As shown in
At this time, as shown in
As shown in
The method and the apparatus for forming a metal plate according to the present embodiment, which is described above, achieve the following advantages.
(1) In the first step, the pre-formed body 33, which includes the pre-formed bulging portions 34, is formed with the first die 10. The pre-formed bulging portions 34 include the sidewalls 342, which include the dents 343. Subsequently, in the second step, the second die 20 presses the sidewalls 342 so that the dents 343 of the pre-formed body 33 disappear.
According to the method, in contrast to the case in which bulging portions are formed on a metal plate by pressing sidewalls without such recesses, the material inside the sidewall 342 smoothly moves with a small load. Therefore, a forming load is reduced.
In addition, in contrast to the case in which bulging portions are formed on a metal plate by pressing sidewalls without such recesses, the material inside the sidewall 342 smoothly moves with a small load, so that tension stress on the sidewalls 312 of the metal plate 30 after forming is reduced. Thus, warp of the metal plate 30 after forming, i.e., a fuel-cell separator, is minimized.
A fuel-cell separator is formed in two steps. Thus, the number of steps is reduced compared to the forming method disclosed in Japanese Laid-Open Patent Publication No. 2014-213343.
(2) In the first step, each sidewall 342 includes the corresponding dents 343 formed on the two surfaces. When the sidewalls 342 of the pre-formed body 33 are pressed by the oblique surfaces 213 of the second die block 21 and the oblique surfaces 223 of the second punch 22 in the second step, the ease in movement of the material inside the sidewall 342 rarely varies between the inner surface and the outer surface. Therefore, warp of the metal plate 30 is effectively minimized.
(3) In the first step, the dents 343 are formed to have curved surfaces. Thus, in the second step, when each sidewall 342 of the pre-formed body 33 is pressed by the corresponding oblique surface 213 of the second die block 21 and the corresponding oblique surface 223 of the second punch 22, material located on the opposite sides of the dents 343 smoothly moves to approach each other inside the sidewall 342. Thus, warp of the metal plate 30 is effectively minimized. In addition, the dents 343 of the pre-formed body 33 are restrained from leaving traces on the respective bulging portions 31 of the metal plate 30.
(4) In the first step, each sidewall 342 of the pre-formed body 33 includes the dents 343 in the central portion in the projecting direction of the pre-formed bulging portions 34.
Such a method limits the occurrence of a difference in the amount of material between one side and the other side of the dents 343 in each of sidewall 342 of the pre-formed body 33. Thus, when each sidewall 342 is pressed by the corresponding oblique surface 213 of the second die block 21 and the corresponding oblique surface 223 of the second punch 22 in the second step, material on one side of the dents 343 and material on the other side of the dents 343 inside the sidewall 342 move to approach each other. At this time, the occurrence of a difference in ease of the movement is limited. Therefore, warp of the metal plate 30 is effectively minimized.
Modifications
The above-illustrated embodiment may be modified, e.g., in the following forms.
The curvature radiuses of the first convex portions 114 of the first die block 11 may differ from the curvature radiuses of the second convex portions 124 of the first punch 12.
In each sidewall 342 of the pre-formed body 33, the dents 343 may be formed on the front side or the back side from the central portion in the projecting direction of the pre-formed bulging portions 34.
Each sidewall 342 of the pre-formed body 33 may include dents 343. The shape of each dent 343 may be modified as necessary.
Each sidewall 342 of the pre-formed body 33 may include a dent 343 on only one surface. Even this case achieves an advantage corresponding to advantage (1).
Number | Date | Country | Kind |
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2015-135536 | Jul 2015 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
2741834 | Reed | Apr 1956 | A |
8828622 | Fujimura | Sep 2014 | B2 |
9227239 | Hirata | Jan 2016 | B2 |
9630229 | Hirata | Apr 2017 | B2 |
9662700 | Taguchi | May 2017 | B2 |
20110229689 | Giang | Sep 2011 | A1 |
20120055223 | Watanabe et al. | Mar 2012 | A1 |
20140352395 | Hirata | Dec 2014 | A1 |
20150290692 | Hirata | Oct 2015 | A1 |
Number | Date | Country |
---|---|---|
2941635 | Aug 2010 | FR |
2000-317531 | Nov 2000 | JP |
5573511 | Aug 2014 | JP |
2014-213343 | Nov 2014 | JP |
Entry |
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EPO Machine Translation of FR 2941635 A1. |
JPO translation of JP 2000317531 A; dated Oct. 2018. |
Japanese Office Action issued in Japan Counterpart Patent Appl No. 2015-135536 dated Oct. 9, 2018, along with English translation thereof. |
Number | Date | Country | |
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20170008058 A1 | Jan 2017 | US |