Method of Manufacturing a Formed Component

This application claims the benefit of Japanese Patent Application No. 2024-084142 filed on May 23, 2024 with the Japan Patent Office, the entire disclosure of which is incorporated herein by reference.

The present disclosure relates to a method of manufacturing a formed product.

WO2017/006793 describes a method of manufacturing a press-formed product, in which a blank is press-formed with a die and a punch to produce a product having a curved portion curved orthogonally to a top plate, in plan view. In this manufacturing method, the formed product is manufactured such that a material of the blank is invited by a material inflow facilitating portion to flow into an inner circumference of the curved portion, where a so-called stretch flange is to be formed. The material inflow facilitating portion has a shape formed by a raised portion of the blank, allowing the material of the blank to locally flow into the inner circumference of the curved portion.

However, according to the manufacturing method described above, inviting the material of the blank to flow into the inner circumference of the curved portion is possible only when manufacturing a component such as an L-shaped component in which the curved portion is only partially formed in the entire component. In other words, when manufacturing a component that is curved orthogonally to the top plate portion in side view, such as a mostly curved component, there is a problem such that cracks easily occur in an area where a stretch flange is formed because the material is flowed in only a part of the area where the stretch flange is formed.

In one aspect of the present disclosure, in the press-formed product, it is preferable to provide a technique to inhibit occurrence of cracks in the area where the stretch flange is formed.

One aspect of the present disclosure is manufacturing a formed product by pressing a blank with a first press mold and a second press mold. The method comprising: arranging the blank between the first press mold and the second press mold spaced apart from each other; and forming a top plate portion, a vertical wall portion, and a flange portion while forming a fold on an extension portion by bringing the first press mold and the second press mold close to each other in a state where the blank is arranged between the first press mold and the second press mold to thereby press the blank by the first press mold and the second press mold. The blank includes a top plate corresponding portion that corresponds to the top plate portion of the formed product, a vertical wall corresponding portion that corresponds to the vertical wall portion of the formed product, and the extension portion. The extension portion is an area extending to an outer side from an outer-side edge of a vertical wall corresponding portion. The outer side is a downstream side in a direction from the vertical wall corresponding portion to a side opposite where a top plate corresponding portion is located, in a plane parallel to the blank. The flange portion is a portion that is formed of the extension portion and that extends from an outer-side edge of the vertical wall portion in a direction intersecting with the vertical wall portion, the flange portion having a shape curved to form a stretch flange. The fold extends along a longitudinal direction of an outer-side edge of the flange portion.

Here, in the flange portion having a shape curved to form the stretch flange, tensile stress is generated during its forming step, and cracks may occur. However, the aforementioned configuration makes it possible to obtain the following actions and effects. Specifically, the fold extends along a longitudinal direction of the outer-side edge of the flange portion and is thus curved in the same way as the flange portion. Therefore, the extension portion on the outer side relative to the fold is also a portion where the stretch flange is formed. Since tensile stress is also generated in the extension portion, as a reaction to this, compressive stress is generated in proximity to the fold. Compressive stress may relieve tensile stress in the flange portion. Accordingly, it is possible to inhibit the occurrence of cracks in the area where the stretch flange is formed.

In one aspect of the present disclosure, the method may include removing a portion of the extension portion that is on the outer side relative to the fold after forming the flange portion. According to this configuration, a part that is no longer required has been removed in the formed product, so that it is easy to perform an optional processing on the formed product in subsequent steps.

In one aspect of the present disclosure, the top plate portion may include a recessed portion recessed in a thickness direction of the top plate portion. This configuration makes it possible to manufacture various formed products.

In one aspect of the present disclosure, the recessed portion may be formed in advance in the blank before arranging the blank between the first press mold and the second press mold spaced apart from each other. This configuration makes it possible to manufacture various formed products.

In one aspect of the present disclosure, the formed product may be an automobile component.

A press-formed productshown inis formed by press forming a blank. The press-formed productis used, as one example, as a rear floor side member mounted on a vehicle. The manufacturing method according to the present embodiment can be used for manufacturing press-formed products of various shapes without being limited to the press-formed productshown in. For example, the manufacturing method according to the present embodiment can be used for manufacturing press-formed products of any shape having a stretch flange. The stretch flange is a part of a flange where tensile stress is generated and a material is stretched. For example, the flange including the stretch flange has a shape formed by bending the blank in which a ridge line, that is a bent portion, has a concave arc shape relative to the blank.

As one example, the blankis made of high-tensile steel. However, without being limited to high-tensile steel, the blankmay be made of stainless steel or iron, for example.

The press-formed productincludes a top plate portion, a first vertical wall portion, a second vertical wall portion, a first flange portion, and a second flange portion.

The top plate portionis a plate-shaped portion where many of its portions, except for small ones, extend in the same plane. When describing the press-formed productbelow, a thickness direction of the top plate portionis referred to as an up-down direction. The top plate portionis curved in the thickness direction. Specifically, the top plate portionis curved so as to recess downward. The top plate portionis curved also in plan view. More specifically, the top plate portionis curved such that the first vertical wall portionis recessed toward the second vertical wall portion.

The top plate portionincludes a first downward recessed portion, an upward recessed portion, and a second downward recessed portion

The upward recessed portionis a portion on the top plate portionthat is recessed upward when the top plate portionis viewed from below. The first downward recessed portionand the second downward recessed portionare portions on the top plate portionthat are recessed downward when the top plate portionis viewed from above. Positions where the first downward recessed portion, the upward recessed portion, and the second downward recessed portionare arranged are not particularly limited as long as they are on the top plate portion.

The first vertical wall portionis a plate-shaped portion extending from an end of the top plate portionin a direction intersecting with the top plate portion. In the present embodiment, the first vertical wall portionextends substantially downward from the end of the top plate portion. A portion where the top plate portionand the first vertical wall portionare joined to each other forms a first ridge line. The first ridge linehas a concave arc shape recessed downward and has a partially curved arc shape in plan view. The first vertical wall portionis curved along the first ridge line

The second vertical wall portionis a plate-shaped portion extending from the other end of the top plate portion, which is opposite to the end from which the first vertical wall portionextends, in a direction intersecting with the top plate portion. In the present embodiment, the second vertical wall portionextends substantially downward from the other end of the top plate portion. A portion where the top plate portionand the second vertical wall portionare joined to each other forms a second ridge line. The second ridge linehas a concave arc shape recessed downward. The second vertical wall portionis curved along the second ridge line. The term “along” as used herein refers not only to cases where there is complete alignment, but also to cases where there is substantial alignment. For example, a direction in which the second vertical wall portionextends may be completely aligned with a direction in which the second ridge lineextends, or it may be approximately aligned a direction in which the second ridge lineextends.

The first flange portionis a plate-shaped portion extending from an end of the first vertical wall portionon the side opposite where the first ridge lineis, in a direction intersecting with the first vertical wall portion. The first flange portionextends in a direction opposite to a direction in which the top plate portionextends relative to the first vertical wall portion. The portion where the first vertical wall portionand the first flange portionare joined to each other forms a third ridge line. The third ridge linehas a concave arc shape recessed downward and has a partially curved arc shape in plan view. The first flange portionis curved along the third ridge line. In other words, the first flange portionis formed to have a stretch flange having a shape that is curved in a thickness direction of the first flange portionand curved in plan view. The first flange portionis substantially parallel to the top plate portion.

The second flange portionis a plate-shaped portion extending from an end of the second vertical wall portionon the side opposite where the second ridge lineis, in a direction intersecting with the second vertical wall portion. The second flange portionextends in a direction opposite to a direction in which the top plate portionextends relative to the second vertical wall portion. The portion where the second vertical wall portionand the second flange portionare joined to each other forms a fourth ridge line. The fourth ridge linehas a concave arc shape recessed downward. The second flange portionis curved along the fourth ridge line. The second flange portionis substantially parallel to the top plate portion.

In summary, the press-formed productis substantially U-shaped and is curved so as to recess downward as a whole, as shown in. In addition, the press-formed productis partially curved in plan view. For example, the press-formed productmay have an L-like curve in plan view.

An intermediate productA shown inincludes a preliminary top plate portionA, a preliminary first vertical wall portionA, a preliminary second vertical wall portionA, a preliminary first flange portionA, a preliminary second flange portionA, and an excess portionA. The press-formed productis a formed product obtained by performing, on the intermediate productA, processing in a trimming step and a forming step, which are described in detail below. The preliminary top plate portionA, the preliminary first vertical wall portionA, the preliminary second vertical wall portionA, the preliminary first flange portionA, and the preliminary second flange portionA of the intermediate productA respectively correspond to the top plate portion, the first vertical wall portion, the second vertical wall portion, the first flange portion, and the second flange portionof the press-formed product. In addition, a fifth ridge lineAa formed by the preliminary top plate portionA and the preliminary first vertical wall portionA, a sixth ridge lineAb formed by the preliminary top plate portionA and the preliminary second vertical wall portionA, a seventh ridge lineAa formed by the preliminary first vertical wall portionA and the preliminary first flange portionA, and an eighth ridge lineAb formed by the preliminary second vertical wall portionA and the preliminary second flange portionA respectively correspond to the first ridge line, the second ridge line, the third ridge line, and the fourth ridge lineof the press-formed product.

The preliminary top plate portionA, the preliminary first vertical wall portionA, the preliminary second vertical wall portionA, the preliminary first flange portionA, and the preliminary second flange portionA of the intermediate productA have substantially the same configurations as the top plate portion, the first vertical wall portion, the second vertical wall portion, the first flange portion, and the second flange portionof the press-formed product, respectively. Similarly to the press-formed product, the intermediate productA is also substantially U-shaped and is curved so as to recess downward as a whole, as shown in. In addition, the intermediate productA is also partially curved in plan view. For example, the intermediate productA may have an L-like curve in plan view.

Similarly to the top plate portion, the preliminary top plate portionA includes the first downward recessed portion, the upward recessed portion, and the second downward recessed portion

Hereinafter a description will be given of differences between the intermediate productA and the press-formed product.

Although the excess portionA is formed in the intermediate product, the excess portionA is cut off when the intermediate productA is processed into the press-formed product, and thus the excess portionA does not exist in the press-formed product. The excess portionA is a plate-shaped portion extending from an end of the preliminary first flange portionA on the side opposite where the seventh ridge lineAa is. The end of the preliminary first flange portionA opposite to the seventh ridge lineAa corresponds to a trim line, which is shown in a dashed line. The trim lineis an outer-side edge of the preliminary first flange portionA and indicates a reference position when cutting the intermediate productA in the trimming step, which will be described in detail later. The excess portionA has a foldA that extends along a longitudinal direction of the outer-side edge of the preliminary first flange portionA. In other words, the foldA is formed in the excess portionA and extends along the longitudinal direction of the trim line. In short, the foldA extends along the preliminary first flange portionA where the stretch flange is formed. The foldA is formed to be a mountain fold. In the present embodiment, the foldA extends to a position that is approximately the same distance from the preliminary first vertical wall portionA, thus forming a ridge line along the seventh ridge lineAa. From the outer-side edge of the preliminary first flange portionA to the foldA, the excess portionA extends in a curved shape substantially identical with a shape of the preliminary first flange portionA, and then extends downward in a slope from the foldA. In other words, the foldA is formed on an outer side relative to the preliminary first flange portionA and the trim line. The foldA has a concave arc shape recessed downward, that is, an arc shape partially curved in plan view. The foldA may have a gentle ridge line. It is sufficient for the foldA to be formed in a way suitable for a material of the blank.

In addition, the fifth ridge lineAa, the sixth ridge lineAb, the seventh ridge lineAa, and the eighth ridge lineAb of the intermediate productA are formed in a slightly gentler shape than the first ridge line, the second ridge line, the third ridge line, and the fourth ridge lineof the press-formed product, respectively. The press-formed productis slightly larger in the up-down direction than the intermediate productA.

As shown in, the method of manufacturing the press-formed productincludes an intermediate forming step, the trimming step, and the forming step.

The intermediate forming step in Sis a step for press forming the blankto form the intermediate productA. As shown in, the blankused for the present manufacturing method includes a top plate corresponding portionB, a first vertical wall corresponding portionB, a second vertical wall corresponding portionB, and an extension portionB.

The top plate corresponding portionB is a portion corresponding to the preliminary top plate portionA of the intermediate productA. Specifically, the top plate corresponding portionB is an area in the blankwhere the preliminary top plate portionA is to be formed when the intermediate productA is formed.

The first vertical wall corresponding portionB is a portion corresponding to the preliminary first vertical wall portionA of the intermediate productA. Specifically, the first vertical wall corresponding portionB is an area in the blankwhere the preliminary first vertical wall portionA is to be formed when the intermediate productA is formed.

The second vertical wall corresponding portionB is a portion corresponding to the preliminary second vertical wall portionA of the intermediate productA. Specifically, the second vertical wall corresponding portionB is an area in the blankwhere the preliminary second vertical wall portionA is to be formed when the intermediate productA is formed.

In the present embodiment, in the blank, the first vertical wall corresponding portionB and the second vertical wall corresponding portionB extend with the top plate corresponding portionB between them. Hereinafter, on a plane parallel to the blank, a downstream side in directions from the first vertical wall corresponding portionB and the second vertical wall corresponding portionB to the top plate corresponding portionB is referred to as an inner side, and a downstream side in directions from the first vertical wall corresponding portionB and the second vertical wall corresponding portionB to a side opposite where the top plate corresponding portionB is located is referred to as an outer side.

The extension portionB is an area extending further outward from an outer-side edge of the first vertical wall corresponding portionB.

In the intermediate forming step in S, a press forming device is used. The press forming device includes an upper press mold, an upper pad, a gas cushion, and a lower press mold.

The upper press moldshown inis a press mold for press forming. The upper press moldincludes a ceiling face, an upper first wall forming portion, an upper second wall forming portion, an upper first flange forming portion, an upper second flange forming portion, and an upper fold forming portion. In, only a shape of a lower face of the upper press moldis shown schematically and the ceiling faceis omitted.

The ceiling faceis a face facing down in the upper press moldand extends in a direction perpendicular to the up-down direction.

The lower press moldas shown inis also a press mold for press forming. The lower press moldincludes a lower top plate forming portion, a lower first wall forming portion, a lower second wall forming portion, a lower first flange forming portion, a lower second flange forming portion, and a lower fold forming portion. In, only a shape of an upper face of the lower press moldis shown schematically and portions to be arranged on the lower top plate forming portion, such as recesses, are omitted.

The lower top plate forming portionis a portion for forming the preliminary top plate portionA. An upper side of the lower top plate forming portionis provided with recesses and protrusions each corresponding to the first downward recessed portion, the upward recessed portion, and the second downward recessed portion. The lower top plate forming portionis curved to so as to recess downward.

The upper first wall forming portionand the lower first wall forming portionhave shapes similar to that of the preliminary first vertical wall portionA of the intermediate productA, and are portions for forming the preliminary first vertical wall portionA. The upper second wall forming portionand the lower second wall forming portionhave shapes similar to that of the preliminary second vertical wall portionA of the intermediate productA, and are portions to form the preliminary second vertical wall portionA.

The upper first flange forming portionand the lower first flange forming portionhave shapes similar to that of the preliminary first flange portionA of the intermediate productA, and are portions for forming the preliminary first flange portionA. The upper second flange forming portionand the lower second flange forming portionhave shapes similar to that of the preliminary second flange portionA of the intermediate productA, and are portions for forming the preliminary second flange portionA.

The upper fold forming portionis a portion for forming the excess portionA. The upper fold forming portionis a portion extending from an end of the upper first flange forming portion. A foldis formed in the upper fold forming portionand extends along a longitudinal direction of an outer-side edge of the upper first flange forming portion. More specifically, the foldextends along the upper first flange forming portionfor forming the preliminary first flange portionA where the stretch flange is formed. The foldis formed to be a valley fold. From the outer-side edge of the upper first flange forming portionto the fold, the upper fold forming portionextends in a curved shape substantially identical with a shape of the upper first flange forming portion, and then extends downward in a slope from the fold. In other words, the foldis formed on the outer side relative to the upper first flange forming portion. An angle formed by the upper first flange forming portionand the upper fold forming portionis substantially coincident with an angle formed by the preliminary first flange portionA and the excess portionA in the intermediate productA.

The lower fold forming portionis also a portion for forming the excess portionA. The lower fold forming portionis a portion extending from an end of the lower first flange forming portion. A foldis formed in the lower fold forming portionand extends along a longitudinal direction of an outer-side edge of the lower first flange forming portion. Specifically, the foldextends along the lower first flange forming portionfor forming the preliminary first flange portionA where the stretch flange is formed. The foldis formed to be a mountain fold. From the outer-side edge of the lower first flange forming portionto the fold, the lower fold forming portionextends in a curved shape substantially identical with a shape of the lower first flange forming portion, and then extends downward in a slope from the fold. In other words, the foldis formed on the outer side relative to the lower first flange forming portion. An angle formed by the lower first flange forming portionand the lower fold forming portionis substantially coincident with the angle formed by the preliminary first flange portionA and the excess portionA in the intermediate productA.

The upper padis a pad for press forming. In the present embodiment, a cross section of the upper padalong its up-down directions is substantially rectangular in shape. Recesses corresponding to the first downward recessed portion, the upward recessed portion, and the second downward recessed portionare provided on a lower surface of the upper pad.

The gas cushionis a cushion utilizing a reaction force of compressed gas. The gas cushionexpands or contracts in its up-down direction according to pressure.

An upper surface of the gas cushioncomes in contact with a lower surface of the ceiling face. A lower surface of the gas cushioncomes in contact with an upper surface of the upper pad.

The blankis arranged between the upper press moldand the lower press moldspaced apart from each other, although the illustration is omitted. More specifically, the blankis arranged between the upper pad, which is arranged above the blankand below the upper press mold, and the lower press mold, which is arranged below the blank. At this point of time, the upper first wall forming portion, the upper second wall forming portion, the upper first flange forming portion, the upper second flange forming portion, and the upper fold forming portionof the upper press moldare substantially parallel with the lower first wall forming portion, the lower second wall forming portion, the lower first flange forming portion, the lower second flange forming portion, and the lower fold forming portionof the lower press mold, respectively.

The upper padcomes in contact with an upper surface of the blank. The lower top plate forming portionof the lower press moldcomes in contact with a lower surface of the blank. The blankis clamped from above and below by and between the upper padand the lower press mold. Specifically, the top plate corresponding portionB of the blankis clamped by and between the upper padand the lower press mold. Of the blankclamped therebetween, the first vertical wall corresponding portionB, the second vertical wall corresponding portionB, and the extension portionB are not in contact with the upper padand the lower press mold.

The upper press moldis moved from above the upper paddownward to the blankclamped by and between the upper padand the lower press moldto perform press forming.