JP3016707B2 - Press forming method for thin work - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention relates to a press-molding how the thin plate work, in particular, by a simple method, a uniform elongation, while ensuring the shape fixability and tensile rigidity, given the small becomes blank about the press molding how the thin plate work can be obtained workpiece molded dimensions.

[0002]

2. Description of the Related Art FIG. 6 shows a conventional thin plate work press forming apparatus. This press molding apparatus is disclosed in
As disclosed in Japanese Unexamined Patent Publication No. 826, both sides of a thin plate workpiece 101 to which a predetermined tension in a plastic region has been applied in advance are clamped by clamp portions 103 of a blank holder 102, and the workpiece 101
Is pressed against the lower mold 104, and then the upper mold 105 is lowered and press-molded.

[0003]

However, since the work after forming has a partially different elongation, the elongation at each forming part becomes non-uniform, and the rigidity increase is small compared to the thin work after forming. Had an impact on quality.
Further, the material size before molding must be at least larger than the work size, and the yield has to be reduced.

[0004]

In order to solve the above-mentioned problems, first, both ends of a thin plate work are clamped by blank holders, and the thin plate work is pulled in both side directions to a plastic region, and is sufficiently removed. When the blank holder is lowered by a press forming method of a thin plate work in which the work is pressed by pressing the work against a lower mold having a large radius and having a curved surface, when the work is pressed against the lower mold, the blank holder is lowered. A press-forming method for increasing the elongation of the work as the work adapts to the lower mold by moving the clamp portion outward according to the position.
Is stretched at a predetermined elongation rate, and on the molding surface of the lower mold,
Unfamiliar area where the workpiece does not contact the familiar area where the workpiece contacts
And following the lowering of the blank holder
As the familiar area increases, the blank holder
Move the clamp part outward according to the lowered position
When the amount of movement is extended to one side length of the unfamiliar area
It was decided to multiply by the rate.

[0005] Second, the clamp portion of the blank holder is moved from the inside position of the side end of the lower die to the outside position of the same side end.

Third, after the blank holder is lowered and the work reaches the shoulder forming the edge of the lower die, the clamp portion of the blank holder is lowered while approaching the lower die. I made it.

Fourthly, the blank holder is configured to move the clamp portion so that an outer portion of the work from the shoulder portion to the tip portion of the clamp portion follows an arc centered on the shoulder portion.

[0008]

[0009]

[0010]

According to the first aspect of the present invention , since the clamp portion of the blank holder increases the elongation of the work as the blank holder is lowered,
The central portion of the work is stretched while its elongation is suppressed while receiving the frictional resistance due to the contact familiarity with the lower mold, so the elongation of the central portion of the work is suppressed, and the entire work is overhanged at a uniform elongation rate.

According to a second aspect of the present invention, the clamp portion of the blank holder is moved from an inner position of a side end of the lower die to an outer position of the same side end of the lower holder. A work of a predetermined molding size can be obtained by a small blank including the margin for clamping at the end.

According to a third aspect of the present invention, in the method for press-forming a thin plate work, the clamp portion of the blank holder is moved closer to the lower die after the blank holder is lowered and the work reaches the edge of the lower die. Since the workpiece is lowered, the extension of the workpiece during bending by the shoulder of the lower die can be suppressed.

According to a fourth aspect of the present invention, the blank is formed so that an outer portion of the work from the shoulder to the tip of the clamp portion follows an arc centered on the shoulder forming the edge of the lower die. Since the clamp portion of the holder is moved, the workpiece is bent by the lower shoulder without increasing the extension of the outer portion of the workpiece.

[0014]

[0015]

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described below with reference to the accompanying drawings. FIG. 1 is a partially cutaway perspective view of an apparatus for press-forming a thin plate work according to the present invention. The press forming apparatus includes a lower middle die 1 having a curved surface with a sufficiently large radius, and a blank holder 2 provided on a side portion of the lower die 1 so as to be vertically movable and clamping both side ends of a thin work (not shown). And

The blank holder 2 is provided with a bead 3 for securing a restraining force at the time of clamping, which clamps a side end portion of a work, and can slide outward in a clamp member 4a (the upper side is not shown). In addition, a guide mechanism is formed on the lower die 1 side by a cam groove 5 serving as advance / retreat control means for guiding the clamp portion 4 in accordance with the descending amount of the blank holder 2.

FIG. 2 is a cross-sectional view of a press forming apparatus for a thin plate work according to the present invention. The press forming apparatus includes an upper member 4b of a clamp portion 4 opposed to a side end of the lower die 1. The lower clamp member 4a is slidably abutted against the blank holder 2 by the bead 3 restrained between the clamp members 4a and 4b. It is provided with a follower unit 8 serving as advance / retreat control means.

The cam groove 5 causes the clamp portion 4 to advance and retreat according to the lowered position of the blank holder 2, that is, the work from contact with the molding surface 9 of the lower mold 1 to the shoulder 10 of the lower mold 1. The clamp portion 4 is moved outward in the overhanging process of the work main body portion, and is moved inward in the bending process of the periphery of the work by the shoulder portion 10 of the lower die 1.

FIG. 3 is an explanatory view of the method of overhanging the work body according to the present invention. In FIG. 3, the position where the work 11 comes into contact with the top (not shown) of the lower mold 1 is lowered after clamping the work 11. Between the upper mold 1 and the shoulder 10 of the lower mold 1 (stroke H).
The clamp unit 4 is moved outward by the advance / retreat control means so that the point 12 on the workpiece 11 before processing corresponding to the above-mentioned condition follows a predetermined path.

Specifically, from the apex of the molding surface 9 to the shoulder 1
A is the creepage length on one side up to 0, and α is the predetermined elongation percentage of the work.
Then, the distance B from the center of the lower mold to the point 12 on the work 11 before processing corresponding to the shoulder 10 of the lower mold 1 is B = A /
(1 + α). Considering the range from the central portion on the work 11 to the point 12, the one-sided elongation C after forming is α × B.

The blank holder 2 is lowered and the work 11
Is brought into contact with the molding surface 9 of the lower mold 1, and when the familiar region 13 having the stroke Hi of the blank holder 2 and the one-side creeping length Di is formed on the molding surface 9, the subsequent one-sided elongation Ci However, in order to determine the position of a new point 12i with respect to the above point 12, a clamp is formed so as to form a length α × Bi obtained by multiplying the creepage length Bi of one side of the unfamiliar area 14 of the work 11 by the extension rate α. The part 4 is moved to the side. In this case, the clamp portion 4 of the blank holder 2 is moved from an inner position of the shoulder portion 10 forming a side end of the lower die 1 to an outer position thereof.

In this way, as the work 11 fits on the molding surface 9, the elongation of the work 11 is sequentially increased, so that the central portion of the work receives the frictional resistance due to the contact with the lower mold and the elongation. The work is stretched while being suppressed, so that the elongation at the center of the work is suppressed, and the entire work is overhanged at a uniform elongation. According to this bending method, when the target elongation α was set to 10% for a 0.75 t thin plate, an actually measured elongation along the target value could be obtained.

FIG. 4 is an explanatory view of the method for bending the peripheral portion of the work according to the present invention. After the work reaches the shoulder portion 10 of the lower mold 1, the clamp portion 4 is moved in accordance with the lowering position of the blank holder 2. The clamp unit 4 is moved inward by the advance / retreat control means so that the distal end 21 of the clamp unit forms an arc 22 centered on the shoulder 10.

In this case, since the length of the work outer portion 23 from the shoulder portion 10 to the tip portion 21 of the clamp portion 4 is kept substantially constant, the work outer portion 23 does not receive excessive elongation. The peripheral edge of the work is bent by the shoulder of the lower mold without increasing the height.

FIG. 5 shows a plan view of the shape of the workpiece after molding and the material taken. The blank dimension E is determined by F / (1 + α) + G, where α is the target elongation rate of molding, F is the dimension of the workpiece after molding, and G is the length of the clamping margin on both sides. The blank dimension E is smaller than the workpiece dimension F after molding by moving the clamp portion of the blank holder from the inner position of the shoulder portion 10 forming the side end of the lower die to the outer position of the same side end. As for the blanks, both ends 11a and 11
Since b can be arranged and press-formed, there is no need for the conventional material taking length Eq, and an improvement in the yield can be ensured.

[0027]

According to the present invention, the following effects are exhibited by the above configuration. In the method for press-forming a thin plate work according to the first aspect, the clamp portion of the blank holder increases the elongation of the work as the blank holder descends, so that the center portion of the work is formed by the contact with the lower mold. Since the workpiece is stretched while being restrained from being stretched due to the frictional resistance, the stretch at the center of the workpiece is restrained, and the entire workpiece is stretched at a uniform stretch rate.

According to a second aspect of the present invention, the clamp portion of the blank holder is moved from an inner position of a side end of the lower die to an outer position of the same side end of the lower die. A work of a predetermined molding size can be obtained by a small blank including the margin for clamping at the end.

According to a third aspect of the present invention, in the method for press-forming a thin work, the clamp portion of the blank holder is moved closer to the lower die after the blank holder is lowered and the work reaches the edge of the lower die. Since the workpiece is lowered, the extension of the workpiece during bending by the shoulder of the lower die can be suppressed.

According to a fourth aspect of the present invention, there is provided a method for press-forming a thin sheet work, wherein the outer side of the work from the shoulder to the tip of the clamp is formed along an arc centered on the shoulder forming the edge of the lower mold. Since the clamp portion of the holder is moved, the workpiece is bent by the lower shoulder without increasing the extension of the outer portion of the workpiece.

[0031]

[0032]

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view of a press forming apparatus for a thin plate work according to the present invention.

FIG. 2 is a cross-sectional view of a press forming apparatus for a thin plate work according to the present invention.

FIG. 3 is an explanatory view of a method for overhanging a work body according to the present invention.

FIG. 4 is an explanatory view of a method for bending a peripheral portion of a work according to the present invention.

FIG. 5 is a plan view of a workpiece shape after forming and material picking thereof.

FIG. 6 shows a conventional thin plate work press forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Lower mold, 2 ... Blank holder, 3 ... Bead, 4 ... Clamp part, 4a, 4b ... Clamp member, 5 ... Cam groove (Advance / retreat control means), 8 ... Follower part (Advance / retreat control means), 9 ...
Forming surface, 10 ... shoulder, 11 ... work, 11a, 11b ...
Both ends, 12, 12i: point, 13: familiar area, 14: unfamiliar area, 21: tip, 22: arc, 23: outside of work, α: elongation, A: creepage length on one side, B: distance, B
i: creepage length on one side, C, Ci: elongation on one side, Di: creepage length on one side, H, Hi: blank holder stroke, E: blank dimension, F: workpiece dimension after molding, G: length of clamp on both sides .

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichiro Fukutomi 1-10-1, Shinsayama, Sayama-shi, Saitama Honda Engineering Co., Ltd. 44-11014 (JP, B1) JP-B-47-43735 (JP, B1) JP-B-51-1571 (JP, Y1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21D 25/02 , 25/04 B21D 24/04

Claims (4)

(57) [Claims] 1. A method in which both ends of a thin plate work are clamped by a blank holder, and the thin plate work is pulled in both directions to a plastic region and pressed against a lower mold having a curved surface having a sufficiently large radius. When the blank holder is lowered by a press forming method of a thin work to be pressed by a work against a lower mold, the clamp portion is moved outward according to the lowered position of the blank holder, thereby forming the work. Is a press forming method that increases the elongation of the work as it comes in contact with the lower mold.
To stretch the work at a predetermined elongation rate, and
And the contact area does not contact the work area
Follow the lowering of the blank holder against the unfamiliar area
As the familiar area increases, the clamp portion of the blank holder according to the lowered position of the blank holder
The amount of movement when moving to the outside is determined by the unfamiliar area.
Characterized in that it is determined by multiplying the length of one side by the elongation.
Press molding method of the thin plate workpiece to be. 2. The method according to claim 1, wherein the clamp portion of the blank holder is moved from an inner position of the lower die to an outer position of the lower end. 3. After the blank holder is lowered and the work reaches the shoulder forming the edge of the lower die, the clamp portion of the blank holder is lowered while approaching the lower die. The method of press-forming a thin plate work according to claim 1. 4. The blank holder according to claim 3, wherein the clamp portion is moved such that an outer portion of the work from the shoulder portion to a tip portion of the clamp portion follows an arc centered on the shoulder portion. A press forming method for the thin plate work described in the above.