JP7697340B2 - Bending dies and manufacturing method for bending materials - Google Patents

Description

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

Bent materials obtained by bending forging materials, such as suspension arms, which are automobile parts, are generally manufactured by heating straight round bar-shaped materials, rolling and bending them, and then performing a two-stage forging process consisting of crush forging and finish forging (see, for example, Patent Documents 1 and 2).

In the conventional manufacturing process for suspension arms, it is believed that the generation of burrs during crush forging can be suppressed by first bending the straight round bar material before crush forging.

JP 2015-066572 A JP 2011-255404 A

However, the conventional manufacturing process for suspension arms requires multiple steps, such as roll forming, bending, crush forging, and finish forging, which increases manufacturing costs.

On the other hand, it is also possible to forge a straight round bar material directly while bending it using crush forging, without using roll forming or bending. However, in this case, many burrs are generated in the crush forging die, especially near the bent parts, resulting in poor yields and the possibility of not being able to obtain the desired product shape. Furthermore, because a large amount of burrs is generated, there is the issue that it is difficult to smoothly transport the material to the finish forging or trim the burrs, which is time-consuming.

This invention was proposed in consideration of the above problems, and aims to provide a bending die that can produce bent material with minimal burrs even when bending a round bar-shaped material by crush forging, and a manufacturing method for bent material using the same.

In order to solve the above problem, the bending die of the present invention is a bending die for bending a round bar-shaped material to form a bent material, and comprises a lower die having a mounting portion for mounting the material, and an upper die for pressing the material mounted on the mounting portion in a vertical direction, the lower die having a recess with a bending region that is bent in a horizontal direction, the mounting portion being formed in the bending region, and one side of the recess having an inclined region that is inclined outward from the vertical direction at an angle of 10° to 75°.

According to the present invention, when a round bar-shaped material is crushed and pushed below the lower die, the material is bent and shaped by plastic flow (metal flow), and during this process, the material is smoothly bent by metal flow due to an inclined region with a large inclination angle, such as 10° or more and 75° or less, relative to the vertical direction. This inclined region allows the material to easily undergo metal flow, suppressing the occurrence of burrs and other defects while forming a bent material of a specified shape.

In addition, in the present invention, the other side of the recess may be parallel to the vertical direction or inclined outward at an angle of 5° or less from the vertical direction.

In addition, in the present invention, the recess may be a molding area below the inclined area that is modeled after the outer shape of the bent workpiece.

In the present invention, the upper die may have a gap of a predetermined width between the surface facing the inclined region of the recess at bottom dead center along the vertical direction and the inclined region.

In addition, in the present invention, the bent material may be a suspension arm for an automobile.

The manufacturing method of the bent material of the present invention is a manufacturing method of the bent material using the bending die described in each of the above paragraphs, and includes a molding process in which a straight round bar-shaped material is placed on the aforementioned placement portion of the lower die of the bending die, and crushed forged by the upper die to obtain the bent material, and the molding process is characterized in that the material is subjected to metal flow by the inclined region.

1 is a side cross-sectional view showing a bending die according to a first embodiment of the present invention. FIG. FIG. 2 is a plan view of a lower die constituting a bending die as viewed from above. 3 is an enlarged cross-sectional view of a main portion taken along line A-A' in FIG. 2. FIG. 3 is an enlarged cross-sectional view of a main portion taken along line B-B' in FIG. 2 (with the upper die omitted). FIG. 11 is a plan view of a lower die constituting a bending die according to a second embodiment of the present invention, as viewed from above. Photographs showing the results of the examples.

Below, a bending die and a method for manufacturing a bent material according to one embodiment of the present invention will be described with reference to the drawings. Note that the embodiment shown below is specifically described to provide a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified. Also, the drawings used in the following description may show important parts enlarged for the sake of convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may not necessarily be the same as in reality.

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

The bending die 10 of this embodiment is used to bend (crush forge) a straight round bar-shaped material M to form a bent material, such as a suspension arm for an automobile, and has a lower die 11 and an upper die 12.

Suspension arms for automobiles often have non-axisymmetric and complex shapes, and while they require high strength and fatigue strength comparable to that of steel materials, they also need to have high impact resistance. Therefore, for example, JIS 6061 alloy or 6000 series aluminum alloy is used as material M.

The lower mold 11 is a fixed mold that is fixed to a horizontal base or the like, and has a recess 21 with a bending region E1 that is bent along the horizontal direction. The recess 21 is formed with a mounting portion 22 on which a material M can be placed. In this embodiment, the mounting portion 22 is a portion on which the straight round bar-shaped material M is placed, between an inclined region E2 on one side surface 21a of the recess 21 (described later) and the other side surface 21b of the recess 21.

In addition, in a cross section perpendicular to the extension direction of the recess 21 at the bending region E1, an inclined region E2 is formed on one side 21a of the recess 21, inclining outward with respect to the vertical direction P. This inclined region E2 is an inclined surface that widens outward from the lower side to the upper side of one side 21a of the recess 21. The inclination angle θ1 of the inclined region E2 is in the range of 10° or more and 75° or less with respect to the vertical direction P, and preferably in the range of 25° or more and 60° or less.

The other side 21b of the recess 21 may be parallel to the vertical direction P or may be inclined outwardly at an inclination angle θ2 toward the upper side. Such an inclination angle θ2 may be in the range of 5° or less.

The recess 21 of the lower die 11 has a molding area E3 below the inclined area E2 on one side 21a, which is the outer shape of the bent workpiece to be formed, for example a suspension arm. The material M placed on the loading section 22 is pressed into this molding area E3 by the lowering of the upper die 12, and is formed into the shape of the bent workpiece.

The placement section 22 is an area above the molding area E3, between the inclined area E2 and the other side surface 21b of the recess 21, where the material M is stably placed. The other side surface 21b of the recess 21 has a straight section E4 formed in the bent area E1 that abuts along the outer peripheral surface of the linear material M.

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 to resemble the molding region E3 of the lower die 11, and during molding, the upper die 12 enters the recess 21 to crush and forge the material M.
The lower surface 12a of the upper die 12 may be provided with a shape that corresponds to the shape of the upper surface of the workpiece to be bent.

It is preferable that the upper die 12 is designed so that, at the bottom dead center along the vertical direction P, a gap Δt of a predetermined width is formed between the surface 12b facing the inclined region E2 of the recess 21 and the inclined region E2. In this embodiment, the bottom dead center of the upper die 12 is the boundary between the inclined region E2 and the molding region E3.

In this embodiment, the recess 21 of the lower die 11 is configured such that the area below the inclined area E2 is a molding area E3 that resembles the outer shape of the bent workpiece, but a portion of the inclined area E2 may also be configured to form a portion of the molding area E3. In this case, a portion of the shape of the inclined area E2 becomes a portion of the shape of the bent workpiece obtained after forging.

(Method of manufacturing bent material)
The operation and effect of the bending die 10 of this embodiment configured as above, and a method for manufacturing a bent workpiece using the bending die 10 will be described below.
When the bending die 10 of this embodiment is used to perform crush forging of a round bar-shaped material M, the material M is first placed on the placement portion of the lower die 11. The linear material M is stably supported between the inclined region E2 on one side surface 21 a of the recess 21 and the linear portion E4 on the other side surface 21 b of the recess 21.

Next, the upper die 12 is lowered and inserted into the recess 21. The linear material M is then crushed and pressed downward (molding process). At this time, the material M is bent by plastic flow (metal flow) and molded into the shape of the molding region E3, and during this process, the material M is smoothly bent by metal flow due to the inclined region E2, which has a large inclination angle of 10° or more and 75° or less with respect to the vertical direction P. This allows the material M to easily metal flow from the inclined region E2 toward the molding region E3, and a bent material molded into a shape that imitates the molding region E3 can be obtained while suppressing the occurrence of burrs, etc.

Then, by performing the post-processing finish forging using the bent material formed by the bending die 10 of this embodiment, it becomes possible to obtain an automobile suspension arm, for example, with only two forging steps, without the need for roll forming or bending of the material as was conventionally done.

(Bending die: second embodiment)
FIG. 5 is a plan view of a lower die constituting a bending die according to a second embodiment of the present invention, as viewed from above.
The same components as those in the first embodiment described above are given the same reference numbers, and duplicated explanations will be omitted.
In the recess 41 of the lower die 31 constituting the bending die 30 of this embodiment, an inclined region E2 is formed which forms one side surface 41a of the recess 41 in a cross section perpendicular to the extension direction of the recess 41 in the bending region E1. The inclined region E2 is an inclined surface which widens outward from the lower side to the upper side of the one side surface 41a of the recess 41, and the inclination angle is in the range of 10° to 75°, preferably 25° to 60°, with respect to the vertical direction.

The recess 41 of the lower die 31 is formed with a mounting section 42 on which a straight rod-shaped material M can be placed. In this embodiment, the mounting section 42 is formed in a part of the inclined region E2, and a substantially triangular material mounting region E5 is formed in which both end regions of the straight material M can enter the recess 41.

In this embodiment, the formation of the approximately triangular material placement area E5 allows the linear material M to be stably placed in the recess 41, and during forging with the upper die (not shown), the material M can be metal-flowed toward the molding area E3 without misalignment. This makes it possible to obtain a bent material with reduced burrs and other defects.

Although the embodiments of the present invention have been described above, 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, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are within the scope of the invention and its equivalents as set forth in the claims, as well as the scope and gist of the invention.

The effect of the present invention was verified.
For the verification, assuming the bending die of the first embodiment shown in Figures 1 and 2, a forging simulation was performed in which the inclination angle θ1 (see Figure 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.

The set conditions common to all the examples are as follows.
(1) The material was a round bar, and the diameter of the material was set to 80 mm so that the cross-sectional area was 10% larger than the position in Figure 4 where the cross-sectional area was maximum.
(2) The length of the material was set to 260 mm so that the volume was 5% larger than the volume of the bent material to be obtained. Therefore, the material was a straight round bar material with a diameter of 80 mm and a length of 260 mm. (3) The inclination angle θ2 (see FIG. 4) of the other side surface 41b of the recess 41 was set to 5°.

Figure 6 shows the change in the shape of the material before forging (top dead center), during forging 1, during forging 2, and at the end of forging (bottom dead center) when the upper die is lowered from top dead center to bottom dead center in Examples 1 to 3. Table 1 also shows the material yield and the crushed shape of the bent material after forging.

According to the simulation results shown in Figure 5 and Table 1, in all of Examples 1 to 3, forging burrs were observed near the contact points at both ends of the material, but the bent material was close to the expected crushed shape, and the amount of forging burrs was limited. In Examples 2 and 3, some parts did not reach the expected crushed shape, but this could be improved by slightly extending the material length, and it was confirmed that the material needs to fit into the inclined region E2 to both ends.

In addition, the smaller the inclination angle θ2 of the inclined region E2, the higher the forging yield, but if the inclination angle θ2 is too small, the material used will not fit into the recess in the lower die unless the diameter is reduced. If the diameter of the material is reduced, the material volume will be insufficient, so the length of the material must be increased, but in this case too, the material will not fit into the recess in 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, and preferably 25° or more and 60° or less, relative to the vertical direction.

The bending die and bending material manufacturing method of the present invention make it possible to manufacture bending materials, such as suspension arms for automobiles, directly from round bar-shaped material through two-stage forging, namely crush forging and finish forging, without pretreatment such as roll forming and bending. Therefore, it has industrial applicability.

REFERENCE SIGNS LIST 10: bending die 11: lower die 12: upper die 21: recess 21a: one side surface 21b: other side surface E1: bending region E2: inclined region E3: molding region E4: straight section M: material P: vertical direction

Claims (6)

A bending die for bending a round bar-shaped material to form a bent material,
a lower die having a placement portion on which the material is placed, and an upper die configured to press the material placed on the placement portion in a vertical direction,
the lower die includes a recess having a bent region bent along a horizontal direction,
The placement portion is formed in the bending region,
A bending die characterized in that, in a cross section perpendicular to the extension direction of the recess in the bending region, one side of the recess has an inclined region that is inclined outward at an angle of 10° or more and 75° or less with respect to the vertical direction. The bending die according to claim 1, characterized in that the other side of the recess is parallel to the vertical direction or inclined outward at an angle of 5° or less from the vertical direction. The bending die according to claim 1 or 2, characterized in that the recessed portion is a molding area below the inclined area that is modeled after the external shape of the bent workpiece. The bending die according to any one of claims 1 to 3, characterized in that the upper die has a gap of a predetermined width between the surface facing the inclined region of the recess at bottom dead center along the vertical direction and the inclined region. The bending die according to any one of claims 1 to 4, characterized in that the bending workpiece is a suspension arm for an automobile. A method for manufacturing a bent workpiece using the bending die according to any one of claims 1 to 4,
A molding process includes placing a straight round bar-shaped material on the placement portion of the lower die of the bending die, and crush forging the material by the upper die to obtain the bent material,
A method for manufacturing a bent material, characterized in that in the forming step, the material is subjected to metal flow by the inclined region.

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