JP2021079408A - Press forming metallic mold - Google Patents

Abstract

To provide a press forming metallic mold that materializes reduction of forming load required for forming a press-formed product having, at a punch bottom portion, a shallow recessed-shape portion or a low projected-shape portion.SOLUTION: A press forming metallic mold 1 according to the present invention comprises a punch 3 and a die 5, and materializes press forming of a press-formed product 21 having a punch bottom portion 23 and a shallow recessed-shape portion 25 at the punch bottom portion 23. The punch 3 comprises a lower holder portion 9 and a block portion 11 provided above the lower holder portion 9. The block portion 11 has a punch bottom forming surface portion 11a that forms the punch bottom portion 23, a recessed-shape forming portion 11b that forms the recessed-shape portion 25 and a cavity portion 11c provided below the punch bottom forming surface portion 11a. The cavity portion 11c includes a range just below the recessed-shape forming portion 11b in the block portion 11, and a projection area in a press-forming direction, of the cavity portion 11c is 110% or more of a projection area of the recessed-shape forming portion 11b.SELECTED DRAWING: Figure 1

Description

The present invention relates to a press-molded die, and more particularly to a press-molded die for press-molding a blank into a punch bottom and a press-molded product having a shallow concave portion or a low-height convex portion at the punch bottom. ..
In the present application, the blank refers to hot-rolled steel sheet, cold-rolled steel sheet, surface-treated steel sheet obtained by subjecting the steel sheet to surface treatment (electrozinc plating, hot-dip galvanizing, organic film treatment, etc.), stainless steel, aluminum, magnesium, etc. A metal plate composed of various metals.
Further, in the present application, the punch bottom portion refers to a portion where the punch is pushed toward the die side and becomes the bottom in the press-molded product formed by the punch and the die.
Further, in the present application, terms such as "directly below", "downward", and "upward" represent the relative vertical direction of the punch and the die in the press forming direction. For example, the die is above the punch. In the case of, "directly below" and "downward" with respect to the punch mean the direction opposite to the die in the press forming direction, and "upper" with respect to the punch means the direction of the die side in the press forming direction. Means.

The application of high-strength steel sheets to automobile bodies is expanding due to growing needs for improving fuel efficiency and collision safety by reducing the weight of automobiles. However, when parts of automobile bodies are manufactured by press molding using high-strength steel sheets, there are problems such as deterioration of formability due to low ductility of high-strength steel sheets and deterioration of dimensional accuracy due to high material strength. There is. In addition to this, an increase in the forming load required for forming parts has also become a major problem, which has become an obstacle to the application of high-strength steel sheets, such as the need to change the press line and divide the parts. There is.

Therefore, some techniques for reducing the forming load in press forming using a high-strength steel plate have been proposed so far.
For example, in Patent Document 1, when forming a metal plate with a die and a punch, the punch is stopped until the punch contacts the metal plate and reaches the end of the stroke of the punch, and the metal plate is stopped after a lapse of a predetermined time. A method of relieving the stress of the metal plate and reducing the molding load by performing the operation of resuming the molding of the metal plate is disclosed.
Further, Patent Document 2 describes a method of reducing a molding load during press working by sequentially molding a blank material for each predetermined region by dividing and moving the punch in the press working of a blank material by a die and a punch. It is disclosed.

Japanese Unexamined Patent Publication No. 2011-245525 JP-A-2010-207907

However, in the method disclosed in Patent Document 1, a servo press is required to stop punching during molding, which is subject to equipment restrictions.
Further, in the method disclosed in Patent Document 2, the mold structure becomes complicated and expensive, and a high-strength steel plate having low formability may have problems such as cracks and wrinkles during molding.

Further, for example, as shown in FIG. 2, when the press-molded product 21 having the concave concave portion 25 having a shallow depth on the punch bottom portion 23 is press-molded, the concave shape has a depth close to the plate thickness. Therefore, similar to the molding in which the plate thickness is thinned by a press, the molding load is remarkably increased in the vicinity of the bottom dead center of the molding, and it is an important issue to reduce the molding load. However, the methods described in Patent Document 1 and Patent Document 2 do not target such a press-molded product 21 as a molding target, and when press-molding into a concave shape or a convex shape having a depth close to the plate thickness. It was difficult to sufficiently reduce the molding load of the above. Therefore, a technique for reducing the molding load in the press molding process of the press-molded product 21 having the concave concave portion 25 having a shallow depth (or the convex convex portion having a low height in the press molding direction) on the punch bottom portion 23 is desired. It was rare.

The present invention has been made to solve the above-mentioned problems, and a concave concave portion or a convex convex portion in the press forming direction is formed on the bottom of the punch without requiring a complicated mechanism or structure. An object of the present invention is to provide a press molding die capable of reducing a molding load in a press molding process of a formed press molded product.

(1) The press-molded die according to the present invention is a press-molded product provided with a punch and a die, and having a punch bottom and a shallow concave portion or a low-height convex portion at the punch bottom. Is press-molded
The punch includes a lower holder portion constituting the lower portion of the punch and a block portion provided above the lower holder portion.
The block portion includes a punch bottom molding surface portion for molding the punch bottom portion, a concave shape forming portion provided on the punch bottom molding surface portion to form the concave shape portion, or a convex shape forming portion for forming the convex shape portion. , A hollow portion provided below the punch bottom molded surface portion, and
The hollow portion includes a range directly below the concave shape forming portion or the convex shape forming portion in the block portion, and the projected area in the press molding direction is 110% of the projected area of the concave shape forming portion or the convex shape forming portion. It is characterized by the above.

According to the present invention, when a press-molded product having a punch bottom portion and a concave-shaped portion having a shallow depth or a convex-shaped portion having a low height is press-molded on the punch bottom portion, the punch bottom portion on the punch block portion is molded. By providing a cavity below the punch bottom molding surface portion and allowing the punch bottom molding surface portion to bend toward the cavity portion in the press molding process, a concave shape forming portion or a convex shape forming portion in the punch bottom molding surface portion. It is possible to facilitate the familiarity between the blank and the blank, and suppress an increase in the molding load near the bottom dead center of molding.

It is a figure explaining the structure of the press molding die which concerns on embodiment of this invention. It is a figure which shows an example of the press-molded article which has the concave-shaped part formed concave in the press-molding direction in the punch bottom part which is the object of molding in this invention. It is a figure which shows the structure of the conventional press molding die. It is a schematic diagram which shows the deformation of a press molding die at the bottom dead center of molding when the conventional press molding die is used. It is a schematic diagram which shows the deformation and bending of the press molding die at the bottom dead center of molding when the press molding die which concerns on embodiment of this invention is used. In the Example, it is a figure which shows the press molding analysis result of the deformation amount in the vicinity of the molding bottom dead center of the press molding die which concerns on a conventional example. In the Example, it is a figure which shows the press molding analysis result of the deformation amount in the vicinity of the molding bottom dead center of the press molding die which concerns on the invention example. In the Example, it is a graph which shows the relationship between the molding stroke and the molding load in the press molding process obtained by the press molding analysis ((a) molding start-molding bottom dead center, (b) enlarged view near molding bottom dead center). .. It is a graph which shows the result of the conventional example and the invention example of the molding load in the vicinity of the bottom dead center of molding in an Example. In embodiments, a graph showing the ratio of the projected area A ₂ of the projected area A ₁ and the concave forming portions of the press-forming direction of the cavity, the relationship between the forming load.

The press-molded die 1 according to the embodiment of the present invention includes a punch 3, a die 5, and a blank holder 7, as shown as an example in FIG. 1, and has a punch bottom 23 as illustrated in FIG. A press-molded product 21 having a concave-shaped portion 25 formed in a concave shape on the punch bottom portion 23 and having a shallow depth is press-molded.
Here, the shallow depth of the concave portion 25 means that it is at least smaller than the molding height of the press-molded product 21, for example, the depth of the concave portion 25 is 10 mm or less and is close to the plate thickness. Suppose it is a thing.
Hereinafter, each configuration of the press molding die 1 according to the present embodiment will be described. In the following description, elements having the same function are designated by the same reference numerals, and the description is omitted.

The punch 3 includes a lower holder portion 9 that constitutes the lower portion of the punch 3, and a block portion 11 that is provided above the lower holder portion 9 and is detachably supported.

The block portion 11 includes a punch bottom molding surface portion 11a for molding the punch bottom portion 23 of the press-molded product 21, a concave shape forming portion 11b provided on the punch bottom molding surface portion 11a and forming a concave shape portion 25 on the punch bottom portion 23. It has a hollow portion 11c provided below the punch bottom molding surface portion 11a (opposite side to the die 5 in the press molding direction).

The hollow portion 11c includes a range directly below the concave shape forming portion 11b in the block portion 11, and the projected area in the press forming direction is 110% or more of the projected area of the concave shape forming portion 11b.

The die 5 is arranged so as to face the punch 3 with the blank 13 interposed therebetween, moves relative to the punch 3 side, and cooperates with the punch 3 to form the press-molded product 21. The punch of the press-molded product 21 It has a punch bottom molding surface portion 5a for molding the bottom portion 23, and a concave shape forming portion 5b for forming the concave shape portion 25 on the punch bottom portion 23.

The blank holder 7 is arranged on the punch 3 side facing the die 5 with the blank 13 sandwiched therein, and cooperates with the die 5 to sandwich the end portion of the blank 13 and move relative to the punch 3 side. ..

Next, FIG. 3 shows the operation of the press-molded die 1 and its action and effect when the press-molded product 21 is press-molded using the press-molded die 1 according to the present embodiment configured as described above. This will be described in comparison with the case where the conventional press molding die 31 shown as an example is used.

When the press-molded product 21 is press-molded using a conventional press-molding die 31 having a punch 33, a die 5, and a blank holder 7 as shown in FIG. 3, first, between the punch 33 and the die 5. The blank 13 is arranged in the blank 13 and both ends of the blank 13 are sandwiched between the die 5 and the blank holder 7. Subsequently, the punch bottom portion 23 is formed by relatively moving the die 5 and the blank holder 7 toward the punch 33 side while the blank 13 is sandwiched between the die 5 and the blank holder 7. Then, when the press-molded product 21 is fixedly pressed near the bottom dead center of molding, the concave-shaped forming portion 5b of the die 5 pushes the blank 13 toward the concave-shaped forming portion 37b of the punch 33, whereby the punch bottom portion 23 is pressed. The concave portion 25 is formed.

At this time, in the vicinity of the bottom dead center of molding, as shown in FIG. 4, the surfaces of the punch 33 and the die 5 are elastically deformed and crushed in the direction of the arrow in FIG. In FIG. 4, the broken line indicates the surface shape of the punch 33 and the die 5 before deformation, and the area hatched by the diagonal line is the punch 33 (punch bottom molding surface portion 37a) and the die 5 (punch bottom molding surface portion 37a) in the vicinity of the bottom dead point of molding. The concave shape forming portion 5b) shows a region crushed by elastic deformation.

However, since the punch 33 and the die 5 are hard to be elastically deformed, the amount of deformation thereof is small, and in order to fit the blank 13 into the concave shape forming portion 37b of the punch 33 to form the concave shape portion 25, the bottom dead center of molding is formed. It is necessary to push the blank 13 toward the punch 33 by applying a large molding load to the die 5 in the vicinity so as to press-mold the plate thickness to make it thinner.

On the other hand, even when the press-molded product 21 is press-molded using the press-molded die 1 provided with the punch 3 and the die 5 according to the present embodiment as shown in FIG. 1, the die 5 and the blank holder are also used. When the die 5 and the blank holder 7 are relatively moved toward the punch 3 side while both ends of the blank 13 are sandwiched by the blank 13, the surfaces of the punch 3 and the die 5 become visible near the bottom dead point of molding as shown in FIG. It deforms in the direction of the arrow in FIG. Here, the broken line in FIG. 5 indicates the surface shapes of the punch 3 and the die 5 before deformation.

At this time, in the die 5, the surface (concave shape forming portion 5b) of the die 5 is crushed by elastic deformation near the bottom dead center of molding as in the conventional press molding die 31 (in the die 5 in FIG. 5). Areas hatched by diagonal lines).
On the other hand, in the punch 3, since the hollow portion 11c is provided below the punch bottom forming surface portion 11a in the block portion 11 and including directly below the concave shape forming portion 11b, the punch bottom molding is performed near the bottom dead point of molding. When the surface portion 11a bends toward the cavity portion 11c, the surfaces of the punch bottom molded surface portion 11a and the concave shape forming portion 11b in the block portion 11 are deformed (the hatched region in the punch 3 in FIG. 5).

Since the amount of deformation due to the deflection of the concave shape forming portion 11b of the punch bottom molding surface portion 11a is larger than the amount of deformation due to the elastic deformation of the punch 33 in the conventional press molding die 31, the concave shape forming portion of the block portion 11 The 11b and the blank 13 easily fit together.
As a result, according to the press-molded die 1 according to the present embodiment, the press-molded product 21 in which the concave portion 25 is formed can be press-molded by suppressing an increase in the molding load near the bottom dead center of molding. it can.

In particular, the present invention has a remarkable effect of suppressing an increase in the forming load near the bottom dead center of forming when press forming using a high-strength steel plate of 590 MPa class or higher as a blank.

Further, as described above, in the present invention, the projected area of the hollow portion of the punch in the press molding direction is set to 110% or more of the projected area of the concave shape forming portion, so that the punch bottom molded surface portion is bent in the press molding process. However, the thickness of the punch bottom molded surface portion in the press molding direction may be appropriately set so that the punch bottom molded surface portion can be bent. The projected area of the concave shape forming portion is an area projected from the bottom portion of the concave shape forming portion 11b of the punch bottom forming surface portion 11a.

The above description is for molding a press-molded product 21 having a concave-shaped portion 25 formed in a concave shape on the punch bottom portion 23 and having a shallow depth. However, the press-molded die according to the present invention has been described. May be a press-molded product (not shown) having a punch bottom portion and a convex-shaped portion having a convex shape formed on the punch bottom portion and having a low height.

Here, the low height of the convex portion means that it is at least smaller than the molding height of the press-molded product. For example, the height of the convex portion is 10 mm or less, and the height press is close to the plate thickness. The present invention can be suitably applied to molded products.

Even when a press-molded product having a convex portion formed on the bottom of the punch is press-molded using the press-molding die according to the present invention, the die is relatively moved to the punch side to be near the bottom dead point of molding. When the convex shape portion is formed in the above, the die is pushed toward the punch side and the punch bottom molding surface portion in the punch block portion bends toward the lower cavity portion, so that the punch bottom molding surface portion and the convex shape forming portion are deformed. The blank becomes more familiar with the convex shape forming portion of the block portion, and the increase in the press forming load near the bottom dead point of forming can be suppressed to form the convex shape portion.

Further, in the press molding die 1 according to the present embodiment, as shown in FIG. 1, the die 5 is arranged above the punch 3, and the direction in which the die 5 is lowered toward the punch 3 is the press molding direction. However, in the present invention, the direction in which the punch 3 is raised toward the die 5 may be the press forming direction.

Further, the press molding die according to the present invention may be one in which a die is arranged below the punch (not shown) and the punch is lowered to the die side, a die is raised to the punch side, or the like. The positional relationship between the punch and the die and the press forming direction are not particularly limited.

In the above description, the press-molded die 1 shown in FIG. 1 includes a blank holder 7, and both ends of the blank 13 are sandwiched between the die 5 and the blank holder 7 to press-mold the press-molded product 21 by draw molding. However, the present invention may be a press-molding die that does not include a blank holder, includes a punch 3 and a die 5, and press-molds a press-molded product 21 by foam molding.

In the press molding die 1 according to the present embodiment, the punch 3 has a structure in which the block portion 11 is stacked on the upper surface portion of the lower holder portion 9 and the block portion 11 is directly held. The present invention is not limited to a punch having a structure in which a block portion stacked on a lower holder portion is held, but a punch having a structure or shape in which the lower holder portion holds the block portion from below and the block portion is removable. All you need is.

An experiment for verifying the action and effect of the press molding die according to the present invention has been conducted, and this will be described below.

In the experiment, the press molding analysis in the process of press molding the press molded product 21 shown in FIG. 2 was performed, and the deformation and molding load of the press molding die in the press molding process were evaluated.

In the press forming analysis, a high-strength steel plate having a tensile strength of 1180 MPa class and a plate thickness of 1.2 mm was used as the blank 13. As shown in FIG. 2, the press-molded product 21 to be molded has a cross-sectional hat shape having a punch bottom portion 23 and a concave-shaped portion 25 formed in a concave shape in the press molding direction on the punch bottom portion 23 and having a shallow depth. , The dimensions of each part are as shown in FIG.
The depth of the concave portion 25 formed on the punch bottom portion 23 was set to 3 mm, which was smaller than the molding height (= 20 mm) of the press-molded product 21 and was close to the plate thickness.

In the experiment, an invention was invented in which a punch 3, a die 5, and a blank holder 7 shown in FIG. 1 were provided, and a press molding analysis was performed in a process of press molding a press molded product 21 using a press molding die 1 made of a steel material. As an example.
In an example of the invention, the punch 3 includes a lower holder portion 9 constituting a lower portion of the punch 3 and a block portion 11 provided above the lower holder portion 9, and the block portion 11 is a punch of a press-molded product 21. From a steel material having a punch bottom forming surface portion 11a for forming the bottom portion 23, a concave shape forming portion 11b for forming a concave shape portion 25 on the punch bottom portion 23, and a cavity portion 11c provided below the punch bottom forming surface portion 11a. It will be. The hollow portion 11c includes a range directly below the concave shape forming portion 11b, and the projected area A _{1 in the} press forming direction is 110% _{of the projected area A 2} of the concave shape forming portion 11b.

Further, as a comparison target, press molding analysis in the process of press molding the blank 13 into the press molded product 21 using the conventional press molding die 31 including the punch 33, the die 5 and the blank holder 7 shown in FIG. Was used as a conventional example.

Here, the punch 33 according to the conventional example includes a lower holder portion 35 constituting below the punch 33 and a block portion 37 provided above the lower holder portion 35, and the block portion 37 includes a punch bottom portion 23. It is made of a solid steel material having a punch bottom forming surface portion 37a for forming the punch bottom forming surface portion 37a and a concave shape forming portion 37b forming the concave shape portion 25, and no cavity is provided below the punch bottom forming surface portion 37a. It shall be.

6 and 7 show the results of conventional examples and invention examples of the amount of deformation of the punch and die in the press molding direction near the bottom dead center of molding.
In the conventional example shown in FIG. 6, deformation in the press molding direction is observed near the edges of the concave shape forming portion 37b of the block portion 37 and the concave shape forming portion 5b of the die 5, and the maximum value of the deformation amount is about 0.02 mm. Met.
On the other hand, in the example of the invention shown in FIG. 7, deformation in the press molding direction is observed in each range below the concave shape forming portion 11b of the block portion 11 and above the concave shape forming portion 5b of the die 5, and the amount of deformation is increased. The maximum value was about 0.05 mm, which was a result of an increase in the range of deformation and the amount of deformation as compared with the conventional example.

FIG. 8 shows the relationship between the forming stroke and the forming load in the press forming process.
From FIG. 8, in both the conventional example and the invention example, the molding load gradually increased at the start of molding (molding stroke 0 mm), and rapidly increased near the bottom dead center of molding (molding stroke of about 21 to 23 mm).
Then, as shown in FIGS. 8A and 8B, the molding loads of the conventional example and the invention example from the start of molding to the vicinity of the bottom dead center of molding (molding stroke of about 22.7 mm) were almost the same.
However, as shown in FIG. 8B, it can be seen that in the vicinity of the bottom dead center of molding, the molding load of the invention example is lower than that of the conventional example.

FIG. 9 shows a graph comparing the molding loads of the conventional example and the invention example at the bottom dead center of molding (molding stroke 23 mm).
From FIG. 9, in the invention example, the molding load was reduced by about 2.1 tonf as compared with the conventional example.

Next, by changing the size of the concave shape forming portion 11b in the punch 3, the projected area A _{1 in} the press forming direction of the hollow portion 11c including the range directly below the concave shape forming portion 11b and the projected area of the concave shape forming portion 11b. The molding load at the bottom dead center of molding was compared by changing the ratio with A _{2, and the result is shown in FIG.}

Than 10, the ratio of the projected area A ₂ of the projected area A ₁ and the concave forming portion 11b of the cavity 11c in the range of the present invention it is understood that the forming load is 110% or more significantly reduced.
When the hollow portion 11c deviates from directly below the concave shape forming portion 11c, _{the ratio of the projected areas A 1} and A ₂ shown in FIG. 10 is equivalent to less than 100%, and the molding load is sufficiently reduced. Couldn't.

The above result was intended for a press-molded product in which a concave portion having a concave shape in the press-molding direction was formed on the bottom of the punch, but the present invention is convex in the press-molding direction and has a height. It was also confirmed that even when a press-molded product having a low convex portion formed on the bottom of the punch is targeted for molding, the result of suppressing an increase in the molding load near the bottom dead point of molding can be obtained.

As described above, according to the press molding die according to the present invention, when a press-molded product in which a concave concave portion or a convex convex portion is formed on the bottom of the punch in the press molding direction is press-molded, the punch block is used. By bending the punch bottom molding surface portion of the portion toward the cavity portion provided below the punch bottom molding surface portion, it is possible to press-mold the press-molded product while suppressing an increase in the molding load near the bottom dead point of molding. Was demonstrated.

1 Press molding die 3 Punch 5 Die 5a Punch bottom molding surface 5b Concave shape forming part 7 Blank holder 9 Lower holder 11 Block part 11a Punch bottom molding surface 11b Concave shape forming part 11c Cavity 13 Blank 21 Press molding 23 Punch Bottom 25 Concave shape 31 Press molding die (conventional structure)
33 Punch 35 Lower holder 37 Block 37a Punch bottom molded surface 37b Concave shape forming part

Claims (1)

A press-molding die comprising a punch and a die, and press-molding a press-molded product having a punch bottom portion and a concave-shaped portion having a shallow depth or a convex-shaped portion having a low height at the bottom of the punch.
The punch includes a lower holder portion constituting the lower portion of the punch and a block portion provided above the lower holder portion.
The block portion includes a punch bottom molding surface portion for molding the punch bottom portion, a concave shape forming portion provided on the punch bottom molding surface portion to form the concave shape portion, or a convex shape forming portion for forming the convex shape portion. , A hollow portion provided below the punch bottom molded surface portion, and
The hollow portion includes a range directly below the concave shape forming portion or the convex shape forming portion in the block portion, and the projected area in the press forming direction is 110% of the projected area of the concave shape forming portion or the convex shape forming portion. A press-molded die characterized by the above.

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