JP7708725B2 - Manufacturing method of press-molded products - Google Patents

Description

This disclosure relates to a method for manufacturing press-molded products.

When a press-formed product is released from the load of the die after forming, springback occurs, which is a change in shape caused by the elastic recovery phenomenon of internal stress. Dies are designed taking the amount of springback into account. It is preferable for the amount of springback to be small.

For example, Patent Document 1 describes a method for manufacturing a press-molded product having a flange portion. In the method described in Patent Document 1, a crushed bead is formed in a portion of the workpiece that corresponds to the flange portion in a first step, and the crushed bead is crushed in a second step. This imparts compressive stress to the portion where the crushed bead was formed, reducing the tensile stress that was generated in the flange portion by press molding and reducing the amount of springback.

Patent No. 5380890

In press-molded products manufactured using the method described in Patent Document 1, bead marks remain in the areas of the flange where crushed beads were formed. The flange forms a joint surface with other components, and if the bead marks overlap the intended joint position on the joint surface, this can cause poor joining.

Therefore, from the perspective of preventing poor joining, it is possible to form crushed beads in areas of the workpiece that avoid the positions corresponding to the intended joining positions in the flange portion. However, in such limited areas, it can be difficult to form a crushed bead sufficient to reduce the amount of springback.

This issue can occur not only with crushed beads, but also with other excess material that is crushed during the manufacturing process of press-molded products.

One aspect of the present disclosure provides a technology that can reduce the amount of springback in a manufacturing method for a press-molded product having a flange portion, even when it is difficult to form a sufficient excess material portion in the portion of the workpiece that corresponds to the flange portion.

One aspect of the present disclosure is a method for manufacturing a press-molded product having a wall portion and a flange portion extending from the wall portion and forming a joint surface for joining to another member. The method for manufacturing a press-molded product includes forming an excess metal portion in a portion of the workpiece where a ridgeline between the wall portion and the flange portion is formed, and crushing the excess metal portion to impart compressive stress to the portion where the excess metal portion was formed.

This configuration makes it possible to reduce the amount of springback in the press-formed product even when it is difficult to form a sufficient excess material in the portion of the workpiece that corresponds to the flange portion.

In one aspect of the present disclosure, the excess pad portion may have a concave shape on the surface of the workpiece on which the ridge line is formed. With this configuration, the excess pad portion can be formed relatively easily.

In one aspect of the present disclosure, the flange portion may be curved in a direction along the ridge line. The excess material may be formed at least at a position corresponding to the center of the ridge line in the workpiece. With this configuration, the amount of springback in the press-formed product can be further reduced.

In one aspect of the present disclosure, the excess pad portion may be formed so as to be continuous from a position corresponding to one end of the ridge line in the workpiece to a position corresponding to the other end of the ridge line.

In one aspect of the present disclosure, the excess pad portion may be formed in multiple portions in the portion of the workpiece where the ridge line is formed.

In one aspect of the present disclosure, the workpiece may be made of high-tensile steel. With this configuration, it is possible to improve the forming accuracy of high-tensile steel, which tends to have a large amount of springback.

FIG. FIG. FIG. FIG. FIG. 11 is a schematic cross-sectional view for explaining a first bending step. FIG. 11 is a schematic cross-sectional view for explaining a second bending step. FIG. 2 is a top view of the workpiece after the first bending step has been performed. FIG. 4 is a schematic diagram for explaining an excess metal portion. FIG. 9 is a schematic diagram illustrating an excess metal portion, different from FIG. 8 . FIG. 13 is a schematic diagram for explaining a first modified example of the excess metal portion. FIG. 13 is a schematic diagram for explaining a second modified example of the excess metal portion. FIG. 13 is a schematic diagram for explaining a third modified example of the excess metal portion. FIG. 13 is a schematic diagram for explaining a fourth modified example of the excess metal portion. FIG. 13 is a schematic diagram for explaining a fifth modified example of the excess metal portion.

Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.
[1. Configuration of press-molded products]
The press-formed product 1 shown in Figures 1 to 4 is a roof reinforcement for a vehicle. A vehicle roof reinforcement is a skeletal component that constitutes the roof structure of the vehicle. The press-formed product 1 is disposed above the passenger compartment so as to extend in the vehicle width direction. The "up-down" and "left-right" directions shown in Figures 1 to 4 refer to the up-down and left-right directions when the press-formed product 1 is disposed in the vehicle. The press-formed product 1 of this embodiment is installed between the upper ends of left and right center pillars of the vehicle. The press-formed product 1 of this embodiment is a so-called roof center reinforcement.

In the vehicle, a roof panel is disposed above the press-formed product 1. The roof panel is an outer panel that constitutes the roof of the vehicle. The roof panel is joined to the press-formed product 1. In addition, in the vehicle, a roof reinforcing member may be disposed on the inside of the roof panel adjacent to the press-formed product 1. The roof reinforcing member is a member that reinforces the roof structure of the vehicle. When a roof reinforcing member is disposed, the roof reinforcing member may be joined to the press-formed product 1.

The press-formed product 1 has an elongated shape overall. As shown in FIG. 3, the press-formed product 1 has a shape that is curved like a bow in the longitudinal direction. As shown in FIG. 1, the press-formed product 1 has a main body portion 2, two wall portions 3, and two flange portions 4.

The main body 2 is a plate-like portion that is rectangular in plan view. The main body 2 is formed so that the central band-like portion is stepped higher than the band-like portions on either side of it.

The two walls 3 are plate-like portions extending from the short-side edge of the main body 2. The two walls 3 each stand up from the corresponding edge of the main body 2. Hereinafter, the angle θ1 between the main body 2 and the wall 3 is referred to as the first angle θ1. The first angles θ1 for the two walls 3 may be the same or different depending on the design. Hereinafter, the ridge line L1 between the main body 2 and the wall 3 is referred to as the first ridge line L1. The first ridge line L1 is located on the underside of the press-molded product 1, but in FIG. 1, the first ridge line L1 is shown at a corresponding position on the upper surface of the press-molded product 1 for convenience of illustration. The upper and lower surfaces of the press-molded product 1 refer to the upper and lower surfaces of the press-molded product 1 when the press-molded product 1 is placed on a vehicle.

The two flange portions 4 are plate-like portions that extend from the tips of the two wall portions 3. The two flange portions 4 extend from the tips of the two wall portions 3 to the outside of the press-molded product 1. In other words, each flange portion 4 protrudes to the opposite side of the main body portion 2 side, based on the adjacent wall portion 3. In the following, the angle θ2 between the wall portion 3 and the flange portion 4 is referred to as the second angle θ2. The second angles θ2 for the two flange portions 4 may be the same or different depending on the design. In the following, the ridge line L2 between the wall portion 3 and the flange portion 4 is referred to as the second ridge line L2.

As described above, the press-formed product 1 has a shape that is curved like a bow in the longitudinal direction. Therefore, as shown in FIG. 3, the flange portion 4 has a shape that is curved like a bow in the direction along the second ridge line L2. The second ridge line L2 is curved in the longitudinal direction of the press-formed product 1.

As shown in FIG. 1, the flange portion 4 forms a joint surface 41 for joining the press-formed product 1 to another member. In this embodiment, the upper surface of the flange portion 4 corresponds to the joint surface 41. The press-formed product 1 of this embodiment is intended to be joined to a roof panel and a roof reinforcing member.

Specifically, a plurality of mastic parts 42 are formed on the joint surface 41 of the flange portion 4. The mastic parts 42 are recessed parts of the joint surface 41. In this embodiment, the mastic parts 42 are groove-shaped parts (so-called beads) that extend along the second ridge line L2. When the mastic parts 42 are filled with an adhesive such as a mastic sealer, another member is superimposed on the joint surface 41 so as to cover the mastic parts 42, thereby joining the other member to the press-molded product 1. In other words, the mastic parts 42 correspond to the intended joining positions with the other members. In this embodiment, the roof panel is joined to the press-molded product 1 by the mastic parts 42.

In addition, another member is placed on the joining surface 41, and spot-welded in the area of the joining surface 41 where the mastic portion 42 is not formed, thereby joining the other member to the press-formed product 1. In other words, the position where the spot-welding point is formed on the joining surface 41 also corresponds to the intended joining position with the other member. In this embodiment, the roof reinforcing member is joined to the press-formed product 1 by spot welding on the joining surface 41.

The press-formed product 1 is made of high-tensile steel material with high tensile strength. For example, the press-formed product 1 may be made of high-tensile steel material with a tensile strength of 980 MPa or more, or may be made of high-tensile steel material with a tensile strength of 1180 MPa or more. The press-formed product 1 of this embodiment is made of high-tensile steel material with a tensile strength of 1430 MPa.

[2. Manufacturing method of press-molded products]
Next, a description will be given of a manufacturing method of the press-formed product 1. The manufacturing method of the press-formed product 1 includes a first bending step shown in Fig. 5 and a second bending step shown in Fig. 6.

[2-1. First bending process]
As shown in Fig. 5, in the first bending step, a workpiece 10 is press-formed using an upper die 101 and a lower die 102. The workpiece 10 is a plate-like member that will be the material of the press-formed product 1. Before the first bending step is performed, the workpiece 10 is in the shape of a flat plate.

In the first bending process, the following preliminary bending process, main body forming process, mastic portion forming process, and excess material forming process are performed as a single process. In other words, these processes are performed simultaneously. Figure 7 shows the workpiece 10 from above after the first bending process has been performed, i.e., after all processes included in the first bending process have been performed.

<Pre-bending>
In the preliminary bending process, the workpiece 10 is bent at positions corresponding to the first ridge line L1 and the second ridge line L2 of the finished press-formed product 1. At this stage, the workpiece 10 is not bent to the first angle θ1 and the second angle θ2 described above, but is bent to an angle larger than the first angle θ1 and the second angle θ2.

<Main body molding process>
In the main body forming process, the portion of the workpiece 10 that corresponds to the main body 2 of the finished product is formed into the shape designed for the main body 2 .

<Molding process of mastic part>
In the mastic portion molding process, a mastic portion 42 is molded in a portion of the workpiece 10 that corresponds to the flange portion 4 of the finished product.

<Extra-thickness molding process>
In the excess metal portion forming process, excess metal portions 11 shown in Fig. 7 are formed in the portions of the workpiece 10 where the second ridge lines L2 are formed. The excess metal portions 11 are temporarily formed in the workpiece 10 in order to reduce tensile stress generated in the flange portion 4 of the finished product by press forming, and are crushed in the process of forming the workpiece 10 into the shape of the finished press-formed product 1. The workpiece 10 has two portions where the second ridge lines L2 are formed, corresponding to the two second ridge lines L2 in the finished press-formed product 1. In this embodiment, the excess metal portions 11 are formed in both of the two portions where the second ridge lines L2 are formed.

Figure 8 is a schematic diagram showing the shape of the portion of the workpiece 10 shown in Figure 7 that corresponds to the second ridge line L2 of the finished product when viewed from the front. In Figure 8, the shape of the workpiece 10 when the excess material portion 11 is not formed is shown by a two-dot chain line.

As shown in Figures 7 and 8, the excess pad portion 11 is a concave portion of the surface of the workpiece 10 where the second ridge line L2 is formed. More specifically, the excess pad portion 11 is a groove-shaped portion (a so-called bead) that extends along the direction corresponding to the second ridge line L2. The excess pad portion 11 is formed at a position corresponding to the center of the second ridge line L2 in the workpiece 10.

Figure 9 is a schematic diagram showing the shape of the portion surrounded by circle IX in the cross section of the workpiece 10 after the first bending process shown in Figure 6 has been performed. In Figure 9, the cross section of the portion where the excess material portion 11 in the finished press-formed product 1 was formed is shown by a two-dot chain line. In reality, as described above, in the first bending process, the workpiece 10 is not bent to the first angle θ1 and the second angle θ2, so the workpiece 10 after the first bending process and the finished press-formed product 1 do not overlap neatly as shown in Figure 9.

As shown in FIG. 9, the length d1 along the surface of the excess material 11 in a cross section perpendicular to the direction corresponding to the second ridge line L2 in the workpiece 10 is longer than the length d2 along the surface of the portion where the excess material 11 was formed in a cross section perpendicular to the second ridge line L2 of the finished press-formed product 1. Therefore, when the excess material 11 is crushed as described below, compressive stress is applied to the portion where the excess material 11 was formed.

[2-2. Second bending process]
As shown in Fig. 6, in the second bending process, the workpiece 10 after the first bending process is press-formed using an upper die 201 and a lower die 202. In the second bending process, the main bending process and the crush forming process described below are performed as one process. In other words, these processes are performed simultaneously. The workpiece 10 after the first bending process is subjected to the second bending process, that is, all processes included in the second bending process are performed, thereby obtaining a press-formed product 1 from the workpiece 10.

<Main bending process>
In this bending process, the workpiece 10 is bent to a deeper angle at the location where it was bent in the preliminary bending process in the first bending step. The workpiece 10 is bent to an angle such that the angles in the completed press-formed product 1 are the first angle θ1 and the second angle θ2, which are design values.

<Crush molding process>
In the crush forming process, the excess metal portion 11 formed in the workpiece 10 is crushed. Crushing the excess metal portion 11 means that the excess metal portion 11 is formed so as to approximate the shape of the workpiece 10 that would have been obtained if the excess metal portion 11 had not been formed in the first bending step.

When the excess material 11 is crushed, compressive stress is applied to the portion of the workpiece 10 where the excess material 11 was formed. As a result, the tensile stress that was generated in the flange portion 4 by press molding is reduced in the finished press-molded product 1.

3. Effects
According to the embodiment described above in detail, the following effects can be obtained.

(3a) In the manufacturing method of the press-formed product 1, the excess material 11 is formed in the portion of the workpiece 10 where the second ridge line L2 is formed, and then crushed.

With this configuration, by crushing the excess metal portion 11, compressive stress is applied to the portion where the excess metal portion 11 was formed, so that the tensile stress generated in the flange portion 4 can be reduced in the finished press-formed product 1. Therefore, even if it is difficult to form a sufficient excess metal portion in the portion of the workpiece 10 that corresponds to the flange portion 4 of the finished product, the amount of springback can be reduced in the finished press-formed product 1.

(3b) The excess material portion 11 has a concave shape on the surface of the workpiece 10 where the second ridge line L2 is formed. With this configuration, the excess material portion 11 can be formed relatively easily.

(3c) The excess material portion 11 is formed at a position corresponding to the center of the second ridge line L2 in the workpiece 10.

In the finished press-formed product 1, the flange portion 4 has a bow-like curved shape in the direction along the second ridge line L2. For this reason, it is thought that the tensile stress generated by press forming tends to concentrate in the central area of the flange portion 4 in the direction along the second ridge line L2. With the above-mentioned configuration, the excess material portion 11 is formed and crushed in a position adjacent to the area in the finished flange portion 4 where the tensile stress tends to concentrate, so that the tensile stress generated in the flange portion 4 can be more effectively reduced. In other words, the amount of springback can be further reduced in the finished press-formed product 1.

(3d) In the above embodiment, the excess material 11 is formed and crushed in both of the two portions of the workpiece 10 where the second ridge line L2 is formed.

This configuration makes it possible to reduce the tensile stress that occurs during press forming for both of the two flange portions 4 in the finished product. Therefore, the amount of springback for the entire finished press-formed product 1 can be further reduced compared to when the excess material portion 11 is formed and crushed only in one of the two portions where the second ridge line L2 is formed in the workpiece 10.

(3e) In this embodiment, the workpiece 10 is made of high-tensile steel. Therefore, the amount of springback in the finished press-formed product 1 is likely to be large compared to when the workpiece is made of steel with low tensile strength.

Even in such a case, the forming accuracy of the press-formed product 1 can be improved by forming and crushing the excess material 11 in the portion of the workpiece 10 where the second ridge line L2 is formed during the manufacturing process of the press-formed product 1.

4. Other embodiments
Although the embodiments of the present disclosure have been described above, it goes without saying that the present disclosure is not limited to the above-described embodiments and can take various forms.

(4a) In the above embodiment, the excess pad portion 11 is a groove-shaped portion extending along the direction corresponding to the second ridge line L2. In such a case, as shown in Figs. 10 and 11, the length of the excess pad portions 11a, 11b along the direction corresponding to the second ridge line L2 is not particularly limited. For example, as shown in Fig. 11, the excess pad portion 11b may be formed so as to be continuous from a position corresponding to one end of the second ridge line L2 in the workpiece 10 to a position corresponding to the other end of the second ridge line L2. Note that in Fig. 11, for convenience of illustration, the excess pad portion 11b does not extend to positions corresponding to both ends of the second ridge line L2, but the actual excess pad portion 11b extends to positions corresponding to both ends.

(4b) In the above embodiment, the excess pad 11 is formed at a position corresponding to the center of the second ridge line L2 in the workpiece 10. However, the excess pad does not necessarily have to be formed at a position corresponding to the center of the second ridge line L2 in the workpiece 10. For example, as shown in Figures 12 and 13, the excess pads 11c and 11d may not be formed at a position corresponding to the center of the second ridge line L2 in the workpiece 10, but may be formed at least on one of the positions corresponding to both sides of the center of the second ridge line L2.

(4c) In the above embodiment, one excess pad portion 11 is formed in each of the two portions of the workpiece 10 where the second ridge line L2 is formed. However, the number of excess pad portions formed corresponding to one second ridge line L2 is not particularly limited. For example, as shown in Figures 13 and 14, multiple excess pad portions 11d, 11e may be formed corresponding to one second ridge line L2.

(4d) For example, when multiple second ridges L2 are formed on the workpiece 10 as in the above embodiment, the excess material 11 does not necessarily have to be formed in all of the multiple portions of the workpiece 10 where the second ridges L2 are formed.

(4e) In the above embodiment, the excess metal portion 11 has a concave shape on the surface of the workpiece 10 where the second ridge line L2 is formed. However, the shape of the excess metal portion is not particularly limited. For example, the excess metal portion may have a bulging shape on the surface of the workpiece 10 where the second ridge line L2 is formed. Even in such a case, by forming the excess metal portion so that the length along the surface of the excess metal portion in a cross section perpendicular to the direction corresponding to the second ridge line L2 of the workpiece 10 is longer than the length along the surface of the part where the excess metal portion was formed in a cross section perpendicular to the second ridge line L2 of the finished press-formed product 1, compressive stress can be applied to the part where the excess metal portion was formed by crushing the excess metal portion.

(4f) In the above embodiment, the excess material 11 is formed in the portion of the workpiece 10 where the second ridge line L2 is formed. In such a case, an additional excess material may be formed in the portion of the workpiece 10 that corresponds to the flange portion 4 of the finished product.

(4g) In the above embodiment, the press-formed product 1 has an overall long shape, and is curved like a bow in the longitudinal direction. However, the shape of the press-formed product is not particularly limited. For press-formed products of other shapes having a wall portion and a flange portion extending from the wall portion, the amount of springback in the finished product can be reduced by forming an excess portion in the part of the workpiece where the ridge between the wall portion and the flange portion is formed during the manufacturing process and then crushing it.

(4h) In the above embodiment, in the first bending step, the preliminary bending process, the main body forming process, the mastic portion forming process, and the excess portion forming process are performed simultaneously, but these processes do not necessarily have to be performed simultaneously. Also, for example, if these processes are performed in sequence rather than simultaneously, the order is not particularly limited.

Similarly, in the above embodiment, in the second bending step, the main bending process and the crushing process are performed simultaneously, but these processes do not necessarily have to be performed simultaneously. Also, for example, if these processes are performed in sequence rather than simultaneously, the order is not particularly limited.

(4i) The functions of one component in the above embodiments may be distributed among multiple components, or the functions of multiple components may be integrated into one component. In addition, part of the configuration of the above embodiments may be omitted. In addition, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[Technical idea disclosed in this specification]
[Item 1]
A method for manufacturing a press-molded product having a wall portion and a flange portion extending from the wall portion and forming a joining surface for joining to another member,
forming an excess portion at a portion of the workpiece where a ridge line between the wall portion and the flange portion is formed;
crushing the excess part to impart compressive stress to a portion where the excess part was formed;
A method for manufacturing a press-molded product comprising the steps of:

[Item 2]
A method for producing a press-molded product according to item 1,
A method for manufacturing a press-molded product, wherein the excess material portion has a concave shape on a surface of the workpiece on which the ridge line is formed.

[Item 3]
A method for producing a press-molded product according to item 1 or 2,
The flange portion has a shape curved in a direction along the ridge line,
A method for manufacturing a press-formed product, wherein the excess metal portion is formed at least at a position corresponding to a center portion of the ridge line of the workpiece.

[Item 4]
A method for producing a press-molded product according to any one of items 1 to 3,
A method for manufacturing a press-formed product, wherein the excess pad portion is formed so as to be continuous from a position corresponding to one end of the ridge line of the workpiece to a position corresponding to the other end of the ridge line.

[Item 5]
A method for producing a press-molded product according to any one of items 1 to 3,
A method for manufacturing a press-molded product, wherein the excess pad portion is molded in a plurality of portions in a portion of the workpiece where the ridge line is formed.

[Item 6]
A method for producing a press-molded product according to any one of items 1 to 5,
A method for manufacturing a press-formed product, wherein the workpiece is made of high-tensile steel.

1... Press-molded product, 10... Workpiece, 11... Excess material, 2... Main body, 3... Wall, 4... Flange, 41... Joint surface, 42... Mastic, L1... First ridge, L2... Second ridge.

Claims (6)

A method for manufacturing a press-molded product having a wall portion and a flange portion extending from the wall portion and forming a joining surface for joining to another member,
forming an excess portion at a portion of the workpiece where a ridge line between the wall portion and the flange portion is formed;
crushing the excess part to impart compressive stress to a portion where the excess part was formed;
A method for manufacturing a press-molded product comprising the steps of: A method for producing a press-molded product according to claim 1,
A method for manufacturing a press-molded product, wherein the excess material portion has a concave shape on a surface of the workpiece on which the ridge line is formed. A method for producing a press-molded product according to claim 1 or 2,
The flange portion has a shape curved in a direction along the ridge line,
A method for manufacturing a press-formed product, wherein the excess metal portion is formed at least at a position corresponding to a center portion of the ridge line of the workpiece. A method for producing a press-molded product according to claim 1 or 2,
A method for manufacturing a press-formed product, wherein the excess pad portion is formed so as to be continuous from a position corresponding to one end of the ridge line of the workpiece to a position corresponding to the other end of the ridge line. A method for producing a press-molded product according to claim 1 or 2,
A method for manufacturing a press-molded product, wherein the excess pad portion is molded in a plurality of portions in a portion of the workpiece where the ridge line is formed. A method for producing a press-molded product according to claim 1 or 2,
A method for manufacturing a press-formed product, wherein the workpiece is made of high-tensile steel.