JP2000317535A - Die device for press forming - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a yield in press forming by eliminating wrinkles generated due to material excess in blank holding. SOLUTION: A die 1 forming the front hood inner of an automobile is arranged with a die face 2 to the upper face side and a recessed part 3 is formed in the center. A recessed side drawing bead 4 made of a step bead is formed to the periphery of the recessed part 3 of the die 1. The recessed side bead 4 is arranged with a bead groove of a fixed depth nearly to the whole periphery part and is formed with an enlarged width part 4a in which a depth of the bead groove of a portion positioned to a belly part (front side) 2a of the die face 2 is made larger than the other part. The belly part 2a is a portion where material excess is generated in the case of holding a blank. Further, the recessed side drawing bead 4 is formed so as to gradually (in curve) have the same depth as the other part more toward the periphery from the belly part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a press which suppresses wrinkles generated at the time of blank hold and secures surface quality of a product by devising a drawing bead shape formed in a press molding die. The present invention relates to a molding die apparatus. This is a technique that is particularly effective when a step bead is used as a draw bead in a mold having a concave part whose die face is convex downward.

[0002]

2. Description of the Related Art A basic shape of an automobile body panel is formed by press molding using a press mold apparatus 50 as shown in FIG. In the press molding die apparatus 50, a die die 54 is opposed to a split upper and lower blank holder dies 52 and 53 for pressing and holding a blank (material) 62 and a punch die 55 for forming the blank 62. Is provided. The upper blank holder mold 52 is formed with a convex draw bead 56 for holding the blank 62 together with the concave draw bead 57 formed in the lower blank holder mold 53.

FIGS. 9 (a) to 9 (d) show a single action type press molding die apparatus 61. FIG. The press molding die apparatus 61 includes a blank holder die 63 and a die die 64 for pressing and holding the blank 62, and a punch die 65 disposed opposite to the blank holder die 63 to form the blank 62. I have. As shown in FIG. 10, the press molding die apparatus 61 forms a concave draw bead 66 for holding the blank 62 in the die 64.
A convex side draw bead 67 is formed on the blank holder mold 63 facing this.

In order to manufacture an automobile body panel using the press molding die apparatus 61 shown in FIG.
First, as shown in FIG.
Place and set on top of Next, as shown in FIG. 9B, the blank holder mold 63 is pushed down, and the blank 62 is pressed and held between the die holder 64 and the die. Then, as shown in FIG. 9C, the blank 62 is pressurized by a punch die 65 to perform drawing. After a while, FIG.
As shown in (d), the punch mold 65 and the blank holder mold 63 are moved upward to be separated from the die mold 64, and the blank 62 is taken out from the press-molding mold device 61. And the press forming step is completed.

By the way, the press molding die apparatus 61
In the draw forming by the method, wrinkles are generated in the product, and the wrinkles occur when the movement in the in-plane direction around the blank 62 near the end of the draw forming becomes large, and it is a problem that it is not erased even in the final formed product. Often. The draw bead is
Moldability such as wrinkles and breaks that occur during the molding process,
It plays an important role in adjusting and improving the tension caused by the bending resistance as the material passes. As the sectional shape of the draw bead, various shapes as shown in FIG. 11 are used depending on the required tension.

[0006]

In recent years, step beads have been frequently used in order to improve the yield by using as small a material as possible for the purpose of cost reduction in press molding. However, as shown in FIG.
In a mold having a concave shape in which the die face of No. 4 is concave, that is, when a step bead having a cross-sectional shape as shown in FIG. 12 is used in a mold having a downwardly convex concave portion, fine wrinkles near the punch profile P as shown in FIG. 68 occurs at the time of blank hold. In a die such as a front hood inner where the concave shape of the die face is convex downward and the curvature is large as described above, and the blank to be pressed is relatively small, the blank does not fit into the die face when setting the blank. General. In particular, the mold center line (hereinafter,
OBL) and the punch profile P, which is the outer periphery of the punch, intersect with each other.

If the upper die contacts the unfamiliar blank at the beginning of the blank hold, a large excess of the blank is generated. After that, it gradually changes into small wrinkles, but because of the downwardly projecting die face shape, the excess thickness is driven inward (in the direction of OBL), and especially near the OBL, it breaks even after drawing. Leave. The wrinkles are generated because the excess thickness of the material is trapped inside during blank hold, and may remain as folds even after drawing, which is likely to cause a problem in product quality.
Conventionally, such a problem has generally been dealt with by changing the shape of the die face and the like, and the man-hour and cost have been increased. The present invention has been made in view of the above problems, and an object of the present invention is to provide a press-molding die capable of reducing wrinkles caused by excess thickness generated during blank holding.

[0008]

In order to achieve the above object, the present invention provides a press-molding die apparatus comprising a pair of dies for pressing and holding a blank, one of which has a concave side. In a press forming die apparatus in which a drawing bead is formed and a convex drawing bead is formed on the other side of the die so as to face the concave drawing bead, the press blank corresponds to the excess portion generated when the blank is pressed and held. Thus, the depth of the concave-side draw bead was increased to form the convex-side draw bead in a shape corresponding to the concave-side draw bead.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a press molding apparatus according to an embodiment of the present invention. FIG. 1 shows one side from the center of a die 1 for molding a front hood inner of an automobile. The die 1 is provided with a die face 2 on the upper side and a concave part 3 having a convex lower side in the center. A concave draw bead 4 made of a step bead is formed around the concave portion 3 of the die 1. The concave-side draw bead 4 is provided with a bead groove having a constant depth almost all around the circumference, and the bead groove at a portion located on the abdomen (front side) 2a of the die face 2 is made wider than other portions. The portion 4a is formed. And, as it goes around, it is formed so as to have a constant depth gradually (curvilinearly) like the other parts.

FIG. 3 shows a die 1 and a blank holder 5 which is arranged to face the upper part of the die 1. The blank holder mold 5 has a convex draw bead 6 formed on the punch profile P side. The convex draw bead 6 is provided with a rib-shaped bead having a constant thickness almost all around the periphery thereof. The thickness of a portion corresponding to the abdomen 2a is made thicker than other portions to form a thick portion 6a. The thick portion 6a
The rib-shaped bead of the convex side draw bead 6 of the blank holder die 5 and the groove of the concave side draw bead 4 of the die 1 are formed so as to mesh with each other.

In the present embodiment, with such a configuration,
When the blank holder mold 5 is lowered to a blank (not shown) placed on the die 1, the concave and convex draw beads 4, 6 press and hold the blank. At the stage before the entire die face 2 comes into contact with the blank positioned at the widest part 4a of the concave side draw bead 4 at the abdomen of the die face 2, the tip of the thick part 6a of the convex side draw bead 6 Contact. Thereafter, contact starts around the tip of the thick portion 6a, and at this time, a deformation mode is set in which the excess thickness of the blank is pushed outward. To some extent, after the excess thickness is pushed outward, the die face 2 and the other concave and convex draw beads 4 and 6 of the blank holder mold 5 start to come into contact with each other.
In the vicinity of the center of the mold, folds are less likely to remain.

FIG. 4 shows a concave drawing bead 4 of the die 1.
And a state after the blank 7 is held by the convex side draw bead 6 of the blank holder mold 5. O in the figure
BL is a mold center line, a chain line P is a punch profile, and a chain line a is an evaluation line offset 10 mm inward from the line of the punch profile a. FIG. 5 shows a change in the level of the cross-sectional shape A of the blank 7 in the present embodiment and the cross-sectional shape B of the conventional blank 62 on the evaluation line. 200m from center axis OBL
Difference (amplitude) HA, H between the top and the valley of the waveform near m
B is the size of wrinkles. It can be seen that the wrinkle amplitude HA at the time of holding of the present embodiment is smaller than the conventional wrinkle amplitude HB, and the degree of wrinkles (amplitude) is greatly reduced. FIG. 6 shows a more detailed cross-sectional shape of the conventional blank 62 when pressed and held, and FIG. 7 shows a cross-sectional shape of the blank 7 in the present embodiment. Blank 7
It can be seen that the degree of wrinkling is smaller in the present embodiment for each of the components.

As described above, according to the present embodiment, when a relatively small blank is formed by a press die having a downwardly projecting die face, wrinkles which are likely to cause a problem are reduced. Surface quality defects can be improved. In addition, when step beads are used, the yield can be maximized while satisfying the above-described quality improvement, and the number of man-hours required for die processing is not increased, so that the schedule of automobile development can be shortened. The embodiments of the present invention have been described above. However, the present invention is not limited to the embodiments, and various modifications and changes can be made based on the technical idea of the present invention. For example, in the above embodiment,
Although the draw bead is a concave bead and a convex draw bead using a step bead, the shape of the draw bead is not limited to the step bead. Also, the extension 4 of the concave side draw bead 4
Although a is defined as a portion where the OBL and the punch profile P intersect, the present invention is not limited to the other portions as long as wrinkles occur, and the shape of the extended portion 4a is symmetric or asymmetric. Alternatively, it can be changed as appropriate according to the shape of the mold.

[0014]

As described above, according to the present invention, a pair of dies for pressing and holding a blank are provided, and a concave drawing bead is formed on one of the dies, and the concave bead is formed on the other of the dies. In a press-molding die apparatus in which a convex drawn bead is formed in opposition to a side drawn bead, the depth of the concave drawn bead is formed to be large in correspondence with an excess portion generated when the blank is pressed and held, Since the convex side drawing bead is formed in a shape corresponding to the concave side drawing bead, wrinkles generated at the time of holding the blank can be reduced, and poor quality of the press surface can be improved. In addition, the yield can be maximized, and the number of required mold processing steps is not increased, so that the schedule for vehicle development can be shortened.

[Brief description of the drawings]

FIG. 1 is a perspective view of a die of a press molding apparatus according to an embodiment of the present invention.

FIG. 2 shows a concave drawing bead located at the center of the center of a die of a die apparatus for press molding according to an embodiment of the present invention, and a convex drawing bead of a blank holder corresponding to the concave drawing bead. It is the figure which looked at from the inside to the outside.

FIG. 3 is a sectional view taken along line XX in FIG.

FIG. 4 is a perspective view showing a state in which a blank is held by the press molding die apparatus according to the embodiment of the present invention.

FIG. 5 is a diagram showing a difference in height of a cross-sectional shape of a blank between the present embodiment and a conventional blank when the blank is held.

FIG. 6 is a diagram showing a difference in height of a cross-sectional shape of a blank when a conventional blank is held.

FIG. 7 is a diagram showing a cross-sectional shape height difference of a blank when the blank of the present invention is held.

FIG. 8 is a perspective view of a conventional press die for forming a basic shape before draw press forming.

9A and 9B are cross-sectional views illustrating a pressing step of a conventional press molding die apparatus, in which FIG. 9A is a cross-sectional view in which a blank is placed on a die, and FIG. Sectional view of a state where the mold and the blank holder mold are sandwiched,
(C) is a cross-sectional view in a state where drawing is performed by a punch die, and (d) is a cross-sectional view in a state where the blank holder die and the punch die are released.

FIG. 10 is an enlarged view of the concave and convex draw beads of the mold of FIG. 9;

FIG. 11 is a cross-sectional view showing a basic shape of a drawing bead used in a conventional press molding die apparatus.

FIG. 12 is a sectional view showing a concave side and a convex side draw bead in a conventional step bead.

FIG. 13 is a perspective view of a blank showing a place where wrinkles occur when a blank is held by a draw bead using a step bead in the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Die die 2 Die face 3 Concave part 4 Concave side draw bead 4a Wide part 5 Blank holder mold 6 Convex side draw bead 6a Thick part

Claims (2)

[Claims] 1. A pair of dies for pressing and holding a blank, wherein a concave drawing bead is formed on one of the dies and a convex drawing bead is formed on the other of the dies so as to face the concave drawing bead. In the press molding die apparatus formed with
The concave draw bead is formed to have a large depth corresponding to the excess portion generated when the blank is pressed and held, and the convex draw bead is formed in a shape corresponding to the concave draw bead. Press molding die equipment. 2. The concave drawing bead is formed in a die, and the convex drawing bead is formed in a blank holder. The blank holder is disposed above the die. The die apparatus for press molding according to claim 1, wherein the concave side drawing bead and the convex side drawing bead are formed in a stepped shape.