Die for bending and method for manufacturing bent workpiece

Abstract

To provide a bending die which can form a bending material which is suppressed in the generation of burrs even if a round rod-shaped raw material is bent by upset forging, and a manufacturing method of the bending material using the same.SOLUTION: A bending die for forming a bending material by bending a round rod-shaped raw material comprises a lower die having a placing part for placing the raw material thereon, and an upper die for pressing the raw material placed on the placing part along a vertical direction. The lower die comprises a recess having a bent region which is bent along a horizontal direction, the placing part is formed at the bent region, and one side face of the recess has an inclination region which is inclined toward the outside within a range of 10° or more and 75° or less with respect to the vertical direction at a cross section which is vertical to the recess in an elongation direction in the bent region.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a bending die for bending a round bar-shaped material to form a bent material, and a method for manufacturing a bent material using the same.

Background Art

[0002] A bent material obtained by bending a forging material, for example, a suspension arm which is an automobile part, is generally manufactured by two-stage forging such as upset forging and finish forging after heating a straight round bar-shaped material and performing roll forming and bending (see, for example, Patent Documents 1 and 2).

[0003] In such a conventional manufacturing process of a suspension arm, it is said that by previously bending a straight round bar-shaped material before performing upset forging, generation of burrs during upset forging can be suppressed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the conventional manufacturing process of a suspension arm, there is a problem that it is necessary to perform multi-stage processing such as roll forming, bending, upset forging, and finish forging, resulting in high manufacturing costs.

[0006] On the other hand, it is conceivable to directly forge a straight round bar-shaped material by upset forging while bending it without performing roll forming or bending. However, in this case, a large amount of burrs are generated particularly near the bent portion of the die for upset forging, resulting in poor yield and it may not be possible to obtain the desired product shape. Furthermore, due to the large amount of burrs generated, there are problems such as difficulty in smoothly transporting to finish forging and trimming the burrs, which takes time and effort.

[0007] The present invention has been proposed in view of the above problems, and an object thereof is to provide a bending die capable of forming a bent workpiece with less burr generation even when a round bar-shaped material is bent by upset forging, and a method for manufacturing a bent workpiece using the same.

Means for Solving the Problems

[0008] In order to solve the above problems, a bending die of the present invention is a bending die for bending a round bar-shaped material to form a bent workpiece, and includes a lower die having a placement portion for placing the material, and an upper die for pressing the material placed on the placement portion along the vertical direction. The lower die includes a concave portion having a bent region bent along the horizontal direction, and the placement portion is formed in the bent region. In a cross section perpendicular to the extension direction of the concave portion in the bent region, one side surface of the concave portion has an inclined region inclined outward in a range of 10° or more and 75° or less with respect to the vertical direction.

[0009] According to the present invention, when the round bar-shaped material is pushed downward into the lower die while being upset, the material is formed while being bent by plastic flow (metal flow). In this process, due to the inclined region having a large inclination angle in the range of 10° or more and 75° or less with respect to the vertical direction, the material smoothly undergoes metal flow and is bent. Due to such an inclined region, the material can easily undergo metal flow, suppress the generation of burrs, etc., and form a bent workpiece having a predetermined shape.

[0010] In the present invention, the other side surface of the concave portion may be parallel to the vertical direction or may be inclined outward within a range of 5° or less with respect to the vertical direction.

[0011] In the present invention, the lower side of the concave portion than the inclined region may be a molding region that imitates the outer shape of the bent workpiece.

[0012] In the present invention, a gap with a predetermined width may be formed between the surface of the upper die facing the inclined region of the concave portion and the inclined region at the bottom dead center along the vertical direction.

[0013] In the present invention, the bent workpiece may be an automotive suspension arm.

[0014] The method for manufacturing a bent workpiece according to the present invention is a method for manufacturing a bent workpiece using the bending die described in each of the above items, and includes a molding step of placing a linear round bar-shaped material on the placement portion of the lower die of the bending die and obtaining the bent workpiece by upset forging with the upper die. In the molding step, the material is metal-flowed by the inclined region.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0016] Hereinafter, with reference to the drawings, a bending die and a method for manufacturing a bent material according to an embodiment of the present invention will be described. Note that the embodiments described below are specifically described to better understand the gist of the invention, and do not limit the present invention unless otherwise specified. In addition, the drawings used in the following description may show the main parts enlarged for convenience of understanding the features of the present invention, and the dimensional ratios of each component are not necessarily the same as the actual ones.

[0017] (Bending Die: First Embodiment) FIG. 1 is a side cross-sectional view showing the bending die according to the first embodiment of the present invention. FIG. 2 is a plan view of the lower die constituting the bending die when viewed from above. FIG. 3 is an enlarged cross-sectional view of the main part taken along the line A-A' in FIG. 2. FIG. 4 is an enlarged cross-sectional view of the main part taken along the line B-B' in FIG. 2 (the upper die is omitted).

[0018] The bending die 10 of the present embodiment is, for example, for bending (upsetting forging) a linear round bar-shaped material M to form a bent material, for example, a suspension arm for an automobile, and includes a lower die 11 and an upper die 12.

[0019] Suspension arms for automobiles often have a non-axisymmetric and complex shape, and require high strength and fatigue strength similar to steel materials, while also requiring high impact resistance. Therefore, as the material M, for example, JIS6061 alloy, 6000 series aluminum alloy, etc. are used.

[0020] The lower die 11 is a fixed die fixed to a horizontal pedestal or the like, and includes a concave portion 21 having a bent region E1 bent along the horizontal direction. A placement portion 22 on which the material M can be placed is formed in the concave portion 21. In the present embodiment, the placement portion 22 is a portion where the linear round bar-shaped material M is placed between the inclined region E2 of one side surface 21a of the concave portion 21 described later and the other side surface 21b of the concave portion 21.

[0021] Further, in the concave portion 21, in a cross-section perpendicular to the extending direction of the concave portion 21 in the bending region E1, an inclined region E2 that inclines outward with respect to the vertical direction P is formed on one side surface 21a of the concave portion 21. This inclined region E2 is an inclined surface that widens outward from the lower side to the upper side of one side surface 21a of the concave portion 21. The inclination angle θ1 of the inclined region E2 is in the range of 10° or more and 75° or less, preferably 25° or more and 60° or less, with respect to the vertical direction P.

[0022] The other side surface 21b of the concave portion 21 may be parallel to the vertical direction P or may incline outward so as to incline upward at an inclination angle θ2. Such an inclination angle θ2 may be in the range of 5° or less.

[0023] The concave portion 21 of the lower die 11 has a molding region E3 that imitates the outer shape of the bending workpiece to be formed, such as a suspension arm, below the inclined region E2 of one side surface 21a. The material M placed on the placement portion 22 is pushed into this molding region E3 by the lowering of the upper die 12 and is thus formed into the shape of the bending workpiece.

[0024] The placement portion 22 is a region above the molding region E3 where the material M is stably placed between the inclined region E2 and the other side surface 21b of the concave portion 21. A straight portion E4 that abuts along the outer peripheral surface of the linear material M is formed on the other side surface 21b of the concave portion 21 in the bending region E1.

[0025] The upper die 12 is a movable die that can move up and down along the vertical direction P, and is moved up and down between the top dead center and the bottom dead center by a vertical movement mechanism (not shown) such as a hydraulic cylinder. The lower part of the upper die 12 is shaped like the molding region E3 of the lower die 11, and enters the concave portion 21 during molding to crush and forge the material M. The lower surface 12a of such an upper die 12 may be provided with a shape that imitates the shape of the upper surface of the bending workpiece to be formed.

[0026] The upper die 12 is preferably designed such that a gap Δt with a predetermined width is formed between the surface 12b facing the inclined region E2 of the concave portion 21 and the inclined region E2 at the bottom dead center along the vertical direction P. In this embodiment, the bottom dead center of the upper die 12 is the boundary portion between the inclined region E2 and the forming region E3.

[0027] In this embodiment, in the concave portion 21 of the lower die 11, the region below the inclined region E2 is the forming region E3 that imitates the outer shape of the bent workpiece. However, a configuration in which a part of the inclined region E2 forms a part of the forming region E3 may also be employed. In this case, a part of the shape of the inclined region E2 becomes a part of the shape of the bent workpiece obtained after forging.

[0028] (Method for manufacturing a bent workpiece) The operation, effects, and method for manufacturing a bent workpiece using the bending die 10 of this embodiment configured as described above will be described. When performing upset forging on the round bar-shaped material M using the bending die 10 of this embodiment, first, the material M is placed on the placement portion of the lower die 11. The linear material M is stably supported between the inclined region E2 of one side surface 21a of the concave portion 21 and the straight portion E4 of the other side surface 21b of the concave portion 21.

[0029] Next, the upper die 12 is lowered and the upper die 12 is inserted into the concave portion 21. Then, the linear material M is pushed downward while being crushed (forming process). At this time, the material M is bent by plastic flow (metal flow) and formed into the shape of the forming region E3. In this process, due to the inclined region E2 having a large inclination angle in the range of 10° or more and 75° or less with respect to the vertical direction P, the material M smoothly undergoes metal flow and is bent. As a result, the material M easily undergoes metal flow from the inclined region E2 toward the forming region E3, and it is possible to obtain a bent workpiece formed in a shape following the forming region E3 while suppressing the generation of burrs and the like.

[0030] After that, by performing finish forging, which is a subsequent process, using the bent material formed by the bending die 10 of this embodiment, it becomes possible to obtain an automotive suspension arm, for example, with only two forging operations without performing roll forming or bending on the material as was done conventionally.

[0031] (Bending Die: Second Embodiment) FIG. 5 is a plan view of the lower die constituting the bending die of the second embodiment of the present invention as viewed from above. In addition, the same components as those in the above-described first embodiment are denoted by the same reference numerals, and redundant explanations are omitted. In the concave portion 41 of the lower die 31 constituting the bending die 30 of this embodiment, an inclined region E2 that forms one side surface 41a of the concave portion 41 in a cross section perpendicular to the extending direction of the concave portion 41 in the bending region E1 is formed. Such an inclined region E2 is an inclined surface that widens outward from the lower side to the upper side of one side surface 41a of the concave portion 41, and the inclination angle thereof is in the range of 10° or more and 75° or less, preferably 25° or more and 60° or less with respect to the vertical direction.

[0032] And, a placement portion 42 on which a linear round bar-shaped material M can be placed is formed in the concave portion 41 of the lower die 31. The placement portion 42 of this embodiment is formed in a part of the inclined region E2, and a substantially triangular material placement region E5 is formed in which both end regions of the linear material M can enter the concave portion 41 respectively.

[0033] In this embodiment, by forming such a substantially triangular material placement region E5, the linear material M can be stably placed in the concave portion 41, and during forging by the upper die (not shown), the material M can be metal-flowed toward the forming region E3 without displacement. Therefore, a bent material with suppressed generation of burrs and the like can be obtained.

[0034] The embodiments of the present invention have been described above. However, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, as well as in the invention described in the claims and the equivalent scope thereof.

Example

[0035] The effects of the present invention were verified. In the verification, assuming the bending die of the first embodiment shown in FIGS. 1 and 2, forging simulations were performed when the inclination angle θ1 (see FIG. 4) of the inclined region E2 was set to 30° (Example 1), 45° (Example 2), and 60° (Example 3) with respect to the vertical direction P, respectively.

[0036] The setting conditions common to each example are as follows. (1) The material was set as a round bar, and the diameter of the material was set to 80 mm so that the cross-sectional area was 10% larger than that at the position where the cross-sectional area was the largest as shown in FIG. 4. (2) The length of the material was set to 260 mm so that the volume was 5% larger than the volume of the desired bent material. Therefore, the material is a straight round bar-shaped material of φ80×L260 (mm). (3) The inclination angle θ2 (see FIG. 4) of the other side surface 41b of the concave portion 41 was set to 5°.

[0037] FIG. 6 shows the shape changes of the material before forging (top dead center), during forging 1, during forging 2, and after forging completion (bottom dead center) when the upper die is lowered from the top dead center to the bottom dead center in Examples 1 to 3. Also, Table 1 shows the results of the material yield and the crushed shape of the bent material after forging.

[0038]

Table 1

[0039] According to the simulation results shown in FIG. 5 and Table 1, in any of Examples 1 to 3, although forging burrs were observed near the contact portions at both ends of the material, a bent workpiece close to the assumed crushed shape was obtained, and the amount of the generated forging burrs was also limited. In Examples 2 and 3, although there were slightly parts that did not reach the assumed crushed shape, it was a range that could be improved by slightly extending the material length, and it was confirmed that the material needed to fit within the recess of the lower die up to both ends in the inclined region E2.

[0040] Also, the smaller the inclination angle θ2 of the inclined region E2, the more efficiently forging can be performed. However, if the inclination angle θ2 becomes too small, the material will not fit into the recess of the lower die unless the diameter of the material used is reduced. If the diameter of the material is reduced, the material volume becomes insufficient, so it is necessary to increase the length of the material. In this case as well, the material will not fit into the recess of the lower die. Therefore, it was confirmed that the inclination angle θ2 of the inclined region E2 is in the range of 10° or more and 75° or less, preferably 25° or more and 60° or less with respect to the vertical direction.

Industrial Applicability

[0041] The bending die and the method for manufacturing a bent workpiece of the present invention can directly manufacture a bent workpiece, for example, a suspension arm for an automobile, by two-stage forging such as upset forging and finish forging from a round bar-shaped material without performing pretreatment processes such as roll forming and bending. Therefore, it has industrial applicability.

Explanation of Reference Numerals

[0042] 10... Bending die 11... Lower die 12... Upper die 21... Recess 21a... One side surface 21b... The other side surface E1... Bending region E2... Inclined region E3... Forming region E4... Straight portion M... Material P... Vertical direction

Claims

1. A bending die for bending a round bar-shaped material to form a bent workpiece, comprising: a lower die having a placement portion for placing the material, and an upper die for pressing the material placed on the placement portion along the vertical direction; the lower die includes a concave portion having a bent region bent along the horizontal direction; the placement portion is formed in the bent region; A bending die, wherein in a cross-section perpendicular to the extension direction of the concave portion in the bent region, one side surface of the concave portion has an inclined region inclined outward in a range of 10° or more and 75° or less with respect to the vertical direction.

2. The bending die according to claim 1, wherein the other side surface of the concave portion is parallel to the vertical direction or inclined outward in a range of 5° or less with respect to the vertical direction.

3. The bending die according to claim 1 or 2, wherein a lower side of the inclined region of the concave portion is a molding region imitating the outer shape of the bent workpiece.

4. The bending die according to any one of claims 1 to 3, wherein a gap with a predetermined width is formed between a surface of the upper die facing the inclined region of the concave portion at the bottom dead center along the vertical direction and the inclined region.

5. The bending die according to any one of claims 1 to 4, wherein the bent workpiece is an automotive suspension arm.

6. A method for manufacturing a bent workpiece using the bending die according to any one of claims 1 to 4, comprising: a molding step of placing a straight round bar-shaped material on the placement portion of the lower die of the bending die and obtaining the bent workpiece by upset forging with the upper die; In the molding step, the material is metal-flowed by the inclined region. A method for manufacturing a bent workpiece.

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