The present disclosure relates to a press die that is used to form, for example, a fuel cell separator.
A generally known separator that is used for a fuel cell includes a plate made of a hard metal material, such as titanium, in which concavo-convex portions through which hydrogen, oxygen, etc., are allowed to flow are formed.
Japanese Laid-Open Patent Publication No. 2015-131344 discloses a press die apparatus that has a press die to form the thus structured separator. This press die apparatus includes a lower die that has a concavo-convex upper surface serving as a forming surface and an upper die that has a concavo-convex lower surface corresponding to the forming surface of the lower die. The upper die is disposed so that it can move closer to and away from the lower die. The upper die is moved toward the lower die in a state in which a workpiece plate is placed on the forming surface of the lower die, and, as a result, the workpiece plate is pressed between the forming surfaces of both dies to form concavo-convex portions.
The conventional upper and lower dies disclosed by Japanese Laid-Open Patent Publication No. 2015-131344 each have a base and a plurality of quadrangular-prism-shaped die members that are disposed on the base and that are fitted in a frame in a mutually aligned state. The forming surface is defined by forward end surfaces of the die members.
This type of press die may be deformed by pressure applied during press forming so that its central part is dented more largely than its outer peripheral part. In other words, the amount of backward displacement of the central part of the forming surface of the die is large, and that of the outer peripheral part thereof is small. Therefore, there has been a case in which highly accurate processing becomes difficult because of the fact that the forming pressure of the central part becomes insufficient, the fact that the start timing or end timing of forming becomes asynchronous between the central part and the outer peripheral part, or the fact that a level difference in forming occurs in an area between the central part and the outer peripheral part of a shaped product.
An object of the present invention is to provide a press die in which the central part of the forming surface of the die is not easily displaced and that is capable of achieving highly accurate processing.
A press die according to one aspect of the present invention includes: a die base; a plurality of die members arranged on the die base so as to produce a forming surface; a plurality of shims each of which is interposed between the die base and each of the plurality of die members; and a frame that surrounds the die base, the plurality of die members, and the plurality of shims. Each of the plurality of shims has a hardness higher than the plurality of die members. A regulating means that carries out a regulation so that an amount of displacement of each of the plurality of die members caused by pressure applied during press forming becomes smaller in proportion to proximity of the die member to the frame is provided between the die base and the plurality of die members or provided on the die base.
Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the present invention.
Embodiments will be hereinafter described with reference to the drawings.
A press die apparatus 11 is to process and form a separator 100 for fuel cells shown in
As shown in
The upper die 14 is identical in configuration with the lower die 13 except for the fact that the forming surface 15 corresponds to the forming surface 12 of the lower die 13 in a concavo-convex relationship, and therefore the lower die 13 will be described in the present embodiment. The configuration, operation, and effects of the upper die 14 are identical with those of the lower die 13, and therefore a description of the upper die 14 is omitted.
As shown in
The outer die 24 includes a die base 29 and a die member 31 placed on the die base 29 with a shim 30 therebetween. The die base 29 is placed on the base 21, and is fixed by a bolt 28. The die member 31 is fixed to the base 21 by means of a bolt 32.
The inner die 27 includes a die base 34 and a plurality of block-shaped die members 36 respectively arranged on the die base 34 with shims 35 therebetween. The die base 34 is placed on the base 21, and is fixed by a bolt 33. Each die member 36 is fixed to the base 21 by means of a bolt 37. Each die member 36 and the shim 35 are temporarily positioned by a positioning pin 38 during assembly.
The forming surface 12 is defined by upper surfaces of the die members 31 and 36.
The die bases 29 and 34 are made of steel, and the shims 30 and 35 are made of cemented carbide (sintered hard alloy), and the die members 31 and 36 are made of high-speed steel. The shims 30 and 35 are harder than the die members 31 and 36, and hence are not easily deformed. As shown in
The shims 30 and 35 and the corresponding die members 31 and 36 are shaped similarly in a plan view, and, as shown in
As shown in
A pressing bolt 51 is inserted into the through-hole 41 and the through-concave 43, and its threaded portion 52 is screwed onto a female thread 42 of the through-hole 41. A lock nut 53 is screwed onto the threaded portion 52, and is tightened to an outer peripheral surface of the outer frame 22, so that the rotation of the pressing bolt 51 is blocked.
As shown in
Next, the operation of the present embodiment will be described.
Press forming is performed with respect to the workpiece plate 101 between the lower die 13 and the upper die 14, and the separator 100 is formed. In other words, the upper die 14 descends, and then the workpiece plate 101 is pressed between both dies 13 and 14 to form the separator 100.
When press forming pressure acts, the base 21 of the lower die 13, the die base 29 of the outer die 24, and the die base 34 of the inner die 27 become more deformable so as to be moved backwardly in proportion to proximity to their central parts, and become less deformable in proportion to proximity to their outer peripheral parts. Therefore, the forming surface 12 of the lower die 13 becomes more displaceable backwardly in proportion to proximity to its central part. However, the shims 30 and 35 made of cemented carbide having higher hardness than the die members 31 and 36 made of high-speed steel are used in the present embodiment. Furthermore, the shims 30 and 35 become larger in thickness in proportion to proximity to a central part of the lower die 13. As a result, the central part of the forming surface 12 is restrained from being displaced.
According to the present embodiment, it is possible to obtain the following effects.
(1) When press forming pressure acts on the lower die 13, the central part of the forming surface 12 of the lower die 13 is restrained from being deformed backwardly because of a difference in thickness between the shims 30 and 35. Therefore, it is possible to keep the forming surface 12 in a flat state even when the area of the forming surface 12 is large. This advantage is obtained in the upper die 14 as well. Therefore, a deviation between a central part and an outer peripheral part of a press position with respect to the workpiece plate 101 is small over the whole area of the forming surface 12 from the beginning to the bottom dead center of a press step. In other words, press forming pressure evenly acts on the entirety of the workpiece. Therefore, a level difference is less likely to occur in the forming surface 12, and a difference in the amount of press or a difference in the timing of the start or end of press forming is less likely to occur between the central part and the outer peripheral part of the forming surface 12, and therefore it becomes possible to apply highly-accurate processing to the workpiece plate 101.
(2) The advantageous effects stated above can be obtained only by adjusting the thicknesses of the shims 30 and 35. This means that the number of components of the press die does not increase, and the structure is simple.
(3) The external shapes of the shims 30 and 35 in a plan view are similar to the external shapes of the corresponding die members 31 and 36 in a plan view, and are smaller than the external shapes of the corresponding die members 31 and 36 in a plan view. Therefore, corner portions of the die members 31 and 36 closer to the shims 30 and 35 do not hit against the shims 30 and 35. This makes it possible to prevent stress caused by the corner portions of the die members 31 and 36 from concentrating at the shims 30 and 35. Therefore, it is possible to prevent cracks caused by the concentration of stress from occurring in the shims 30 and 35.
The present embodiment may be modified as follows.
As shown in
As shown in
The shims 30 and 35 may be made identical with the die members 31 and 36 in shape and in size in a plan view.
Without providing the lower-side shims 72, the die members 36 may become smaller in thickness in proportion to their proximity to the outer peripheral side so that the die member 36 disposed closer to the outer peripheral side is more easily displaced.
The shims 30 and 35 may be a layered piece consisting of thin shims, and the thicknesses of the shims 30 and 35 may be adjusted in proportion to the number of stacked shims.
The die bases 29 and 34 may be made integrally with the base 21.
The die base 34 of the inner die 27 may be divided correspondingly to the die members 36. In this case, preferably, the die base 34 has a greater shape in a plan view than the shim 35 so that a corner portion of each die base 34 does not hit against the shim 35.
The die bases 29 and 34 may be made of cemented carbide. In this case, the hardness of each of the die bases 29 and 34 increases, and therefore it is possible to make the die bases 29 and 34 smaller in thickness, and hence make the outer frame 22 smaller in thickness. This makes it possible to thin the press die apparatus 11, i.e., makes it possible to make the press die apparatus 11 compact.
The above embodiments are intended to be illustrative, and the present invention is not limited to the above-described embodiments. Various alternatives, modifications and variations are possible to the disclosed exemplary embodiments without departing from the spirit and scope of the present invention. For example, the subject matter of the present invention may exist in fewer features than all of the features of the particular embodiments disclosed. The claims are incorporated into the detailed description and each claim by itself claims a separate embodiment. The scope of the invention is intended to embrace all such alternatives, modifications and variations, along with all equivalents thereof, within the scope of the claims.
Number | Date | Country | Kind |
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2016-244463 | Dec 2016 | JP | national |