JPH0655231A - Press forming method for thin plate - Google Patents

Abstract

(57) [Abstract] [Purpose] When press-molding a press-formed product that locally has a concave portion such as a bead or a stepped portion on a curved surface, it is possible to minimize springback of the press-formed product, Provided is a press molding method capable of producing a curved product with a desired curved surface and obtaining a press-formed product with high accuracy. A press-formed product comprising a convex curved surface portion 1a and an outer peripheral flange portion 1b erected around the curved surface portion 1a, and having a concave portion 2 such as a bead or a step portion locally on the curved surface portion 1a. In the method of press-forming the blank 1 as a raw material, the curved surface portion 1a and the outer peripheral flange portion 1 of the blank 1 are
After applying a tensile force to b and the curved surface portion 1
While maintaining a and the outer peripheral flange portion 1b in a tensioned state,
The curved portion 1a is characterized by locally forming a concave portion 2 such as a bead or a step portion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for press-forming a thin plate.

[0002]

2. Description of the Related Art In recent years, a technique for realizing a complicated curved surface with high accuracy has been required for a thin plate press-formed product and a die for processing the same. Along with this, it is required to minimize the springback amount during press molding. Also, the radius of curvature of the curved surface is larger than that of the conventional one, and many products are closer to a flat surface.
In many cases, the prescribed shape accuracy cannot be obtained, including the peripheral portion of the curved surface portion.

An example of the solution is disclosed in Japanese Patent Laid-Open No. 63-
It is shown in Japanese Patent No. 188429.

The method will be described with reference to FIGS. In the figure, 73 is a punch, 74 is a wrinkle retainer, and 75 is
Is a pad, 76 is a die, and 77 is a blank which is a thin plate material having a predetermined shape. As shown in FIGS. 14 to 16, the blank 77 has its peripheral portion pressed between the wrinkle retainer 74 and the die 76, and is stretch-formed by the punch 73 and the pad 75 with a shallow drawing amount h. Is performed. At this time, the bead 78 is also formed on the curved surface portion 77a of the blank 77 at the same time.

Thereafter, as shown in FIG. 17, a wrinkle retainer 74
18, the outer peripheral flange portion 77b of the blank 77 is bent up by a drawing process with a deep drawing amount H as shown in FIG. 18, and then the outer peripheral flange portion is again covered with the wrinkle retainer 74 as shown in FIG. Outer peripheral edge 77c of 77b
20. Further, tension is applied to reduce the spring back of the outer peripheral flange 77b and the peripheral portion of the curved surface 77a by a drawing process (the drawing amount is indicated by H + α in FIG. 20) for further increasing the drawing amount as shown in FIG. To do.

After that, the wrinkle presser 74 is released again (see FIG. 2).
1) Then, the outer peripheral flange portion 77b is drawn to form a vertical wall (FIG. 22), and finally the press-formed product is taken out (FIG. 23).

[0007]

According to the above conventional example,
As shown in FIGS. 16 to 20, the curved surface 77 of the blank 77.
After the bead 78 is formed on a, the curved surface portion 77a is sandwiched between the punch 73 and the pad 75 until a drawing process of applying tension for reducing spring back by adding a drawing amount of α. It has been done. Therefore, in the drawing process of applying the tension shown in FIG. 20, the tensile force is not sufficiently transmitted to the curved surface portion inside the bead 78 of the curved surface portion 77a, and the springback of the curved surface portion 77a cannot be sufficiently reduced. It was

[0008]

In order to solve the above problems, the present invention comprises a convex curved surface portion and an outer peripheral flange portion standing upright around the curved surface portion, and a bead or the like is locally formed on the curved surface portion. In the method of press-forming a press-formed product having a concave portion or a stepped portion with a blank as a raw material, after applying a drawing force exerting a tensile force to the curved surface portion and the outer peripheral flange portion of the blank, the curved surface portion and the outer peripheral flange portion are It is characterized in that a concave portion such as a bead or a stepped portion is locally formed on the curved surface portion while maintaining the tensile state.

[0009]

According to the present invention, when press-molding a press-formed product having a concave portion such as a bead or a step portion locally on the curved surface portion, a drawing exerting a tensile force on the curved surface portion of the blank and the outer peripheral flange portion is performed. By applying a sufficient tensile force to the entire curved surface portion, a concave portion or a stepped portion such as a bead is formed locally on the curved surface portion while maintaining such a tensile state, so that Springback can be reduced sufficiently.

[0010]

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

FIG. 1 shows an example of a press-molded product obtained by the method of the present invention, where 1a is a convex curved surface portion, 1b is an outer peripheral flange portion raised around the curved surface portion 1a, and 2 is a curved surface portion 1a. The locally formed bead (concave portion) is shown in FIG.

The press-formed product is obtained by forming the blank 1 which is a thin plate material having a predetermined shape by the press-forming process shown in FIGS.

2 to 12, 3 is a punch, 4 is a wrinkle retainer, 5 is a pad, 6 is a die, and 7 is a bead forming tool.

As shown in FIGS. 2 to 4, the blank 1 is lowered in the peripheral portion thereof between the wrinkle retainer 4 and the die 6 to lower the punch 3 to obtain a shallow drawing amount h.
Overhang molding is performed. The aperture amount h at this time is 1 m
m or less. Also, the bead forming tool 7 is in the retracted position,
Only the curved surface is formed on the curved surface portion 1a of the blank 1, and the bead 2 is not formed.

After that, as shown in FIG. 5, the wrinkle retainer 4 is once lifted to release the clamped state, and then the punch 3 is lowered as shown in FIG. The flange portion 1b is bent upright, then the wrinkle retainer 4 is lowered again as shown in FIG. 7, and the outer peripheral edge 1c of the outer peripheral flange portion 1b is clamped by the wrinkle retainer 4, and as shown in FIG. In the drawing step of increasing the drawing amount by slightly lowering 3 (the drawing amount is indicated by H + α in FIG. 8), tension is applied to reduce the springback of the outer peripheral flange portion 1b and the curved surface portion 1a.

Next, as shown in FIG. 9, the outer peripheral edge 1c is sandwiched between the wrinkle retainer 4 and the die 6, and the punch 3 applies tension to the curved surface portion 1a and the outer peripheral flange portion 1b. Then, the bead forming tool 7 is raised to form the bead 2.

After that, as shown in FIG. 10, the wrinkle retainer 4 is raised again to release the sandwiched state, and then the punch 3 is lowered to bend the outer peripheral flange portion 1b upright as shown in FIG. Next, as shown in FIG. 12, when the wrinkle retainer 4 and the punch 3 are raised to a height higher than the height of the outer peripheral flange portion 1b of the press-formed product, the pad 5 and the bead forming tool are raised to take out the press-formed product.

In the above embodiment, the concave portion such as the bead is formed on the curved surface portion, but as shown in FIG. 13, the step portion 2a is formed.
The present invention can be applied to the case where the curved surface 1a is formed.

[0019]

According to the present invention, when press-molding a press-molded product having a concave portion such as a bead or a stepped portion locally on a curved surface, it is possible to minimize springback of the press-molded product. Therefore, a curved product can be manufactured into a desired curved surface, and a press-molded product with high accuracy can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a press-formed product obtained by the method of the present invention.

FIG. 2 is a sectional view showing an embodiment of the present invention.

FIG. 3 is a sectional view showing an embodiment of the present invention.

FIG. 4 is a sectional view showing an embodiment of the present invention.

FIG. 5 is a sectional view showing an embodiment of the present invention.

FIG. 6 is a sectional view showing an embodiment of the present invention.

FIG. 7 is a sectional view showing an embodiment of the present invention.

FIG. 8 is a sectional view showing an embodiment of the present invention.

FIG. 9 is a sectional view showing an embodiment of the present invention.

FIG. 10 is a sectional view showing an embodiment of the present invention.

FIG. 11 is a sectional view showing an embodiment of the present invention.

FIG. 12 is a sectional view showing an embodiment of the present invention.

FIG. 13 is a sectional view showing another example of the press-formed product obtained by the method of the present invention.

FIG. 14 is a sectional view showing a conventional example.

FIG. 15 is a sectional view showing a conventional example.

FIG. 16 is a sectional view showing a conventional example.

FIG. 17 is a sectional view showing a conventional example.

FIG. 18 is a sectional view showing a conventional example.

FIG. 19 is a sectional view showing a conventional example.

FIG. 20 is a sectional view showing a conventional example.

FIG. 21 is a sectional view showing a conventional example.

FIG. 22 is a sectional view showing a conventional example.

FIG. 23 is a sectional view showing a conventional example.

[Explanation of symbols]

 1 blank 1a curved surface part 1b outer peripheral flange part 2 bead 2a step part 3 punch 4 wrinkle retainer 5 pad 6 die 7 bead forming tool

Claims (1)

[Claims] 1. A blank of a press-formed product comprising a convex curved surface portion and an outer peripheral flange portion erected around the curved surface portion, and locally having a concave portion or a stepped portion such as a bead on the curved surface portion. In the method of press-molding, after applying a drawing force to the curved surface portion and the outer peripheral flange portion of the blank, while maintaining the curved surface portion and the outer peripheral flange portion in a tensile state, a bead or the like is locally formed on the curved surface portion. 2. A method for press-forming a thin plate, characterized in that the concave portion or the step portion is formed.