Manufacturing method for pressed parts for vehicles

Abstract

To provide a manufacturing method of a vehicle press component which stably reduces or resolves spring back that occurs on a top plate part in the longitudinal direction and can reduce or resolve spring back or warpage that occurs on a side wall part in the short side direction in a long vehicle press component which has a substantial hat cross sectional shape and is bent such that the top plate part becomes convex to the plate outside in the longitudinal direction.SOLUTION: There is provided a manufacturing method of a long vehicle press component 10 which has a substantial hat cross sectional shape that connects a top plate part 1 and a flange part 2 by a side wall part 3 and is bent such that the top plate part becomes convex to the plate outside in the longitudinal direction. The manufacturing method comprises: a drawing step S1 of manufacturing an intermediate product 10a having a side wall expansion part 3a that is formed such that the length in the short side direction of the side wall part is longer than a production shape SK and a top plate expansion part 1a that is formed such that the length in the longitudinal direction of the top plate part is longer than the product shape; and a compression molding step S3 of compressing the side wall expansion part and the top plate expansion part in the intermediate product to restore it to the product shape.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a vehicle press part, and more particularly to a method for manufacturing a long vehicle press part having a substantially hat-shaped cross section and a top plate portion that is curved in the longitudinal direction so as to be convex toward the outside of the plate. [Background technology]

[0002] The pressed parts that make up an automobile body, especially the reinforcing pressed parts placed around the cabin, need to be both lightweight and strong from the standpoint of improving fuel efficiency and protecting occupants in the event of a collision, and so the use of high tensile steel plates is being promoted. For example, the B-pillar outer R / F (reinforcement) is a component that reinforces the B-pillar outer, which connects the floor and roof components from above and below between the openings of the front and rear doors (sliding doors), from the inside of the plate, so it needs to be strong enough to withstand collision loads from the side of the body while ensuring interior space and ease of getting in and out, and so even higher strength is being demanded.

[0003] In recent years, for parts that require high strength, such as B-pillar outer R / F, a manufacturing method has been adopted in which so-called ultra-high tensile material (steel plate) (for example, tensile strength: 1180 MPa or more) is heated and formed, and then heat-treated using hot stamping or other processes. However, because this method has low productivity and high processing costs, investigations are underway into manufacturing methods using cold presses, which can increase speed and reduce costs.

[0004] However, in a long pressed part such as a B-pillar outer R / F, which has a generally hat-shaped cross section that connects the top plate and the flange with the side wall and curves with a large radius of curvature in the longitudinal direction so that the top plate is convex toward the outside of the plate, springback and warping are likely to occur in the side wall in the short direction, and springback (also called "camber back") is likely to occur in the top plate in the longitudinal direction. In this regard, a manufacturing method in which a bending die or the like is used to estimate the springback and other inaccuracies has been generally used. However, there have been problems such as the large amount of springback, etc., making it difficult to set an accurate estimate, and the variation in material properties (e.g., yield point stress: Yp) of the steel plate making it difficult to ensure stable accuracy during mass production.

[0005] A manufacturing method for a pressed part that can reduce this springback and the like (a multi-stage press molding method with excellent shape freezing ability) is disclosed in, for example, Patent Document 1. That is, Patent Document 1 discloses a manufacturing method for a pressed part, as shown in Fig. 15 and Fig. 16, which "is a method for molding a metal member 100 having a U-shaped or hat-shaped cross section and a shape curved in the height direction when a ceiling surface 102 sandwiched between side walls 101 is placed on top, in which in a first molding step, an embossment 103 that is convex in the height direction is formed in the ceiling surface 102 sandwiched between the side walls 101 of the metal member 100, an intermediate product 100a is molded so that the line length in the longitudinal direction of the embossment is longer than the line length in the longitudinal direction of a final product, and in a second molding step, the intermediate product 100a is molded into the product shape while being pressed so that the embossment 103 disappears." It is described that this embossment 103 may consist of a plurality of convex protrusions that are discontinuous in the longitudinal direction of the intermediate product 100a, or may consist of a convex protrusion that is continuous in the longitudinal direction of the intermediate product 100a. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4709659 Summary of the Invention [Problem to be solved by the invention]

[0007] However, according to the manufacturing method for a pressed part described in Patent Document 1, "in a first forming step, an embossment 103 that is convex in the height direction is formed in a ceiling surface 102 sandwiched between side walls 101 of the metal member 100, and an intermediate product 100a is formed so that its longitudinal line length is longer than the longitudinal line length of the final product, and in a second forming step, the intermediate product 100a is formed into the product shape while being pressed so that the embossment 103 disappears." Therefore, while compressive stress can be applied to the ceiling surface 102, compressive stress cannot be applied to the side wall 101, and it is difficult to reduce or eliminate springback or warping that occurs in the side wall 101 in the short direction.

[0008] In addition, when the embossment 103 formed in the ceiling surface 102 is pressed, the ceiling surface 102 is easily deformed locally at its weaker portions, and in such cases, it is difficult to entirely reduce or eliminate the tensile stress in the ceiling surface 102. Therefore, it is not easy to stably reduce or eliminate the springback (camberback) that occurs in the longitudinal direction of the ceiling surface 102.

[0009] The present invention has been made to solve the above-mentioned problems, and aims to provide a manufacturing method for a vehicle press part that is long and has an approximately hat cross-sectional shape, with the top plate portion curved in the longitudinal direction so that it is convex toward the outside of the plate, and that can stably reduce or eliminate springback that occurs in the top plate portion in the longitudinal direction, and reduce or eliminate springback and warping that occurs in the side wall portion in the short direction. [Means for solving the problem]

[0010] In order to achieve the above object, a method for manufacturing a vehicle press part according to the present invention has the following configuration. (1) A method for manufacturing an elongated vehicle press part having a generally hat-shaped cross section in which a top plate portion and a flange portion are connected by a side wall portion, and the top plate portion is curved in a longitudinal direction so as to be convex toward an outer side of the plate, a drawing forming process for producing an intermediate product having a side wall extension portion in which the short-side length of the side wall portion is formed longer than the product shape and a top plate extension portion in which the long-side length of the top plate portion is formed longer than the product shape; and a compression molding process for compressing the side wall extension portion and the top plate extension portion of the intermediate product to restore the intermediate product to the product shape.

[0011] In the present invention, a drawing process is provided for manufacturing an intermediate product having a sidewall extension part in which the short-side length of the sidewall part is longer than the product shape and a top plate extension part in which the long-side length of the top plate part is longer than the product shape, and a compression molding process is provided for compressing the sidewall extension part and the top plate extension part in the intermediate product to restore them to the product shape, so that the short-side tensile stress generated in the sidewall extension part in the drawing process and the long-side tensile stress generated in the top plate extension part can be reduced or eliminated by the compressive stress applied in the compression molding process. Therefore, the springback generated in the top plate part in the long-side direction can be reduced or eliminated, and the springback and warpage generated in the sidewall part in the short-side direction can be reduced or eliminated.

[0012] In addition, the intermediate product manufactured in the drawing molding process has a side wall extension portion in which the short-side length of the side wall portion is longer than the product shape, so that when the side wall extension portion and the top plate extension portion are compressed in the compression molding process, the ridge portion where the side wall extension portion and the top plate extension portion intersect prevents local buckling or deformation in the longitudinal direction of the top plate extension portion, and the longitudinal tensile stress in the top plate extension portion can be stably reduced or eliminated.

[0013] Therefore, according to the present invention, a manufacturing method for a vehicle press part can be provided that can stably reduce or eliminate springback that occurs in the top plate portion in the longitudinal direction, and reduce or eliminate springback and warping that occurs in the side wall portion in the lateral direction, in a long vehicle press part that has an approximately hat-shaped cross-sectional shape and has a top plate portion that is curved in the longitudinal direction so that it is convex toward the outside of the plate.

[0014] (2) In the method for manufacturing a vehicle press part according to (1), The side wall extension portion is formed so as to be flared toward the pressing direction in the compression molding process, and is formed so that an intersection angle between the side wall extension portion and the top plate extension portion is an obtuse angle.

[0015] In the present invention, the side wall extension is formed to be flared toward the end with respect to the pressing direction in the compression molding process, and the crossing angle between the side wall extension and the top plate extension is formed to be an obtuse angle, so that when the side wall extension and the top plate extension are compressed in the compression molding process, the tip side of the side wall extension is pressed into the center of the top plate extension in the short direction, and a compressive stress in the short direction can be applied to the top plate extension. Therefore, the tensile stress in the short direction of the top plate extension can be reduced or eliminated, and in addition to reducing the springback in the longitudinal direction of the top plate, the springback in the short direction of the top plate can also be reduced or eliminated. As a result, the accuracy of the press part for the vehicle can be further improved.

[0016] (3) In the method for manufacturing a vehicle press part according to (1) or (2), The product shape includes a curved region in which the top plate portion is curved so as to be convex toward the outside of the plate in the longitudinal direction, and a linear region in which the top plate portion is formed substantially linearly in the longitudinal direction, The side wall extension and the tabletop extension are provided over substantially the entire curved area.

[0017] In the present invention, the product shape includes a curved region in which the top plate portion is curved so as to be convex toward the outside in the longitudinal direction, and a linear region in which the top plate portion is formed substantially linearly in the longitudinal direction, and the side wall extension portion and the top plate extension portion are provided over substantially the entire range of the curved region, so that compressive stress can be applied to substantially the entire range of the side wall extension portion and the top plate extension portion in the curved region in the compression molding process. Therefore, the springback in the longitudinal direction that occurs in the top plate portion of the curved region can be more effectively reduced or eliminated, and the curvature accuracy in the curved region of the vehicle press part can be further improved.

[0018] (4) In the method for manufacturing a vehicle press part according to (3), The top plate extension portion is formed approximately parallel to the top plate portion of the product shape, and is characterized in that its longitudinal length is expanded beyond the length of the product shape near both longitudinal ends of the curved region.

[0019] In the present invention, the top plate extension portion is formed substantially parallel to the top plate portion of the product shape, and is formed so that the longitudinal length is larger than the length of the product shape near both longitudinal ends of the curved region, so that compressive stress can be applied along the surface from both longitudinal ends of the top plate extension portion to the longitudinal center while pressing the top plate extension portion substantially parallel in the compression molding process. Therefore, the longitudinal tensile stress of the top plate extension portion can be reduced or eliminated as a whole, and the longitudinal springback generated in the top plate portion of the curved region can be reduced or eliminated more evenly. As a result, the curvature accuracy in the curved region of the pressed part for a vehicle can be improved more uniformly.

[0020] (5) In the method for manufacturing a vehicle press part according to (3) or (4), The compression molding process is characterized in that, while the top plate portion in the straight region is held, the side wall extension portion and the top plate extension portion in the curved region are compressed to restore the product shape.

[0021] In the present invention, in the compression molding process, the side wall extensions and the top plate extensions in the curved regions are compressed and restored to the product shape while the top plate portion in the straight region is held, so that compressive stress can be applied accurately to the side wall extensions and the top plate extensions in the curved regions without misalignment. Therefore, the springback in the longitudinal direction that occurs in the top plate portion can be more reliably reduced or eliminated without variation, and the curvature accuracy in the longitudinal direction of the pressed part for a vehicle can be further stably improved.

[0022] (6) A method for manufacturing a vehicle press part according to any one of (1) to (5), The intermediate product includes a side wall widening portion formed by widening the side wall portion toward the plate outer side from the product shape, The method is characterized in that in a bending process provided between the drawing process and the compression molding process, the side wall widening portion is bent to restore it to the product shape.

[0023] In the present invention, the intermediate product has a sidewall widening portion formed by widening the sidewall portion toward the plate outside from the product shape, and in a bending process provided between the drawing process and the compression molding process, the sidewall widening portion is bent to restore the product shape, so that a compressive stress associated with the bending process can be applied to the sidewall widening portion. Therefore, the tensile stress generated in the sidewall widening portion in the drawing process can be reduced or eliminated, the accuracy of the sidewall portion can be improved, and the curvature accuracy of the top plate portion can be improved. As a result, springback, warpage, and the like of the pressed parts for vehicles can be reduced or eliminated more stably.

[0024] (7) A method for manufacturing an elongated vehicle press part having a generally hat-shaped cross section in which a top plate portion and a flange portion are connected by a side wall portion, and the top plate portion is curved in a longitudinal direction so as to be convex toward an outer side of the plate, a drawing forming process for producing an intermediate product having a side wall extension portion in which the short-side length of the side wall portion is formed longer than the product shape and a top plate extension portion in which the long-side length of the top plate portion is formed longer than the product shape; a bending forming process in which the side wall extension portion of the intermediate product is bent to restore the base end side of the side wall extension portion to the product shape; and a compression molding process for compressing the tip side of the side wall extension portion and the top plate extension portion of the intermediate product to restore the intermediate product to the product shape.

[0025] In the present invention, the present invention includes a drawing process for manufacturing an intermediate product having a sidewall extension part in which the short-side length of the sidewall part is longer than the product shape and a top plate extension part in which the long-side length of the top plate part is longer than the product shape, a bending process for bending the sidewall extension part in the intermediate product to restore the base end side of the sidewall extension part to the product shape, and a compression process for compressing the tip end side of the sidewall extension part and the top plate extension part in the intermediate product to restore them to the product shape. Therefore, after the short-side tensile stress generated in the sidewall extension part in the drawing process is reduced or eliminated by the compressive stress applied in the bending process, the short-side tensile stress generated in the sidewall extension part in the drawing process and the long-side tensile stress generated in the top plate extension part can be reduced or eliminated by the compressive stress applied in the compression process. Therefore, by applying the compressive stress twice to the sidewall extension part, the compressive stress can be increased, and the curvature accuracy of the top plate part can be improved while further improving the accuracy of the sidewall part. As a result, springback occurring in the top plate portion in the longitudinal direction can be reduced or eliminated, and springback and warping occurring in the side wall portion in the lateral direction can be reduced or eliminated.

[0026] Furthermore, the intermediate product manufactured in the drawing molding process has a side wall extension portion in which the short-side length of the side wall portion is longer than the product shape, so that when the tip side of the side wall extension portion and the top plate extension portion are compressed in the compression molding process, the ridge portion where the side wall extension portion and the top plate extension portion intersect prevents local buckling or deformation in the longitudinal direction of the top plate extension portion, and the longitudinal tensile stress in the top plate extension portion can be stably reduced or eliminated.

[0027] Therefore, according to the present invention, a manufacturing method for a vehicle press part can be provided that can stably reduce or eliminate springback that occurs in the top plate portion in the longitudinal direction, and reduce or eliminate springback and warping that occurs in the side wall portion in the lateral direction, in a long vehicle press part that has an approximately hat-shaped cross-sectional shape and has a top plate portion that is curved in the longitudinal direction so that it is convex toward the outside of the plate. Effect of the Invention

[0028] According to the present invention, a manufacturing method for a vehicle press part can be provided that can stably reduce or eliminate springback that occurs in the top plate portion in the longitudinal direction and reduce or eliminate springback and warping that occurs in the side wall portion in the lateral direction in a long vehicle press part that has an approximately hat-shaped cross-sectional shape and has a top plate portion that is curved in the longitudinal direction so that it is convex toward the outside of the plate. [Brief description of the drawings]

[0029] [Figure 1] 1 is an external view of a vehicle press part formed by a method for manufacturing a vehicle press part according to an embodiment of the present invention, as viewed from a vehicle side surface. [Diagram 2] 2 is an external view of the vehicle press part shown in FIG. 1, as viewed from the vehicle front side. [Diagram 3] 2 is a perspective view of an intermediate product produced in a drawing process of the vehicle press part shown in FIG. 1. [Figure 4] 4 is a cross-sectional view taken along line AA in FIG. [Diagram 5] BB cross-sectional view shown in FIG. [Figure 6] 4 is a cross-sectional view taken along the line CC in FIG. [Figure 7] 4 is a cross-sectional view of a main part in a short direction at a bottom dead center of a press die (drawing die) that draws the intermediate product shown in FIG. 3. [Figure 8] FIG. 4 is a cross-sectional view of a press die (compression die) for compression molding the intermediate product shown in FIG. 3, and is a cross-sectional view of a main part in the short side direction during compression molding of a side wall extension portion and a top plate extension portion. [Figure 9]FIG. 4 is a cross-sectional view of a press die (compression die) for compression-molding the intermediate product shown in FIG. 3, and is a cross-sectional view of a main part in the longitudinal direction during compression molding of the top plate extension part. [Figure 10] 4 is a cross-sectional view of a main part in a short direction at bottom dead center of a press die (bending die) for bending the intermediate product shown in FIG. 3. [Figure 11] FIG. 2 is a flowchart of a method for manufacturing the vehicle press part shown in FIG. [Figure 12] 12A and 12B are stress distribution diagrams obtained by CAE analysis of a pressed product in the process shown in FIG. 11, in which (A) shows a stress distribution diagram of a pressed product (intermediate product) in a drawing process, and (B) shows a stress distribution diagram of a pressed product in a compression molding process. [Figure 13] 12A and 12B are surface position accuracy distribution maps obtained by CAE analysis of pressed products in the processes shown in FIG. 11 , in which (A) shows a surface position accuracy distribution map of a pressed product (intermediate product) in a drawing process, and (B) shows a surface position accuracy distribution map of a pressed product in a compression molding process. [Figure 14] 1A and 1B are conceptual cross-sectional views of a modified example of the manufacturing method for a vehicle press part of this embodiment, in which (A) shows a conceptual cross-sectional view at a drawing forming process, (B) shows a conceptual cross-sectional view at a bending forming process, and (C) shows a conceptual cross-sectional view at a compression forming process. [Figure 15] FIG. 1 is an external view of a metal member formed by the method for manufacturing a pressed part described in Patent Document 1 (a multi-stage press molding method with excellent shape freezing ability). [Figure 16] 16 is an external view of an embossment (an example in which an embossment is formed intermittently in the longitudinal direction) after the first molding in the multi-stage press molding method for manufacturing the metal member shown in FIG. 15. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Next, a manufacturing method for a vehicle press part according to an embodiment of the present invention will be described in detail with reference to the drawings. First, the configuration of a vehicle press part formed by the manufacturing method for a vehicle press part according to the present embodiment will be described. Then, a specific example of the manufacturing method for the vehicle press part will be described. Also, the evaluation results of the stress distribution and surface position accuracy of the press part formed by the manufacturing method for the vehicle press part according to the present embodiment will be described. Also, a modified example of the manufacturing method for the vehicle press part according to the present embodiment will be described.

[0031] <Structure of Vehicle Press Parts> First, the configuration of a vehicle press part formed by the manufacturing method for a vehicle press part according to this embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 shows an external view of the vehicle press part formed by the manufacturing method for a vehicle press part according to this embodiment, as seen from the vehicle side. Fig. 2 shows an external view of the vehicle press part shown in Fig. 1, as seen from the vehicle front side.

[0032] 1 and 2, the vehicle press part 10 is an elongated vehicle press part 10 having a generally hat-shaped cross section in which a top plate portion 1 and a flange portion 2 are connected by side wall portions 3 (31, 32) and in which the top plate portion 1 is curved in the longitudinal direction so as to be convex toward the outside of the plate. The vehicle press part 10 is formed by cold pressing a material of uniform plate thickness (for example, an ultra-high tensile material with a tensile strength of 1180 MPa).

[0033] Here, the vehicle press part 10 will be described in the case of, for example, a B-pillar outer R / F. The B-pillar outer R / F (vehicle press part 10) is a member that reinforces, from the inside of a plate, a B-pillar outer (not shown) that connects a floor member and a roof member vertically between the openings of the front door and the rear door (sliding door), and therefore needs to be strong enough to withstand a collision load from the side of the body while ensuring interior space and ease of getting in and out of the car.

[0034] Therefore, in the upper part of the vehicle in the B-pillar outer R / F (vehicle press part 10), the top plate 1 and the side wall 3 (31, 32) are formed as small as possible in the short direction (vehicle front-rear and vehicle inside-outside directions), while the top plate 1 is curved with a large radius of curvature R so as to be convex toward the outside of the plate (outside the vehicle) in the longitudinal direction (vehicle up-down direction). On the other hand, in the lower part of the vehicle in the B-pillar outer R / F (vehicle press part 10), the top plate 1 and the side wall 3 are formed with a substantially rectangular cross section that ensures the connection strength with the floor member and is large enough to accommodate a door lock member or the like, and the top plate 1 is formed substantially linearly to reduce the amount of protrusion toward the outside of the vehicle. Therefore, the product shape SK of the B-pillar outer R / F (vehicle press part 10) includes a curved region SK1 in which the top plate 1 is curved so as to be convex toward the outside of the plate in the longitudinal direction, and a linear region SK2 in which the top plate 1 is formed substantially linearly in the longitudinal direction. In addition, the curved region SK1 of the top plate portion 1 may be formed with a bead shape extending in the longitudinal direction in order to increase rigidity.

[0035] The upper end of the B-pillar outer R / F (vehicle press part 10) is provided with a roof connecting part 10R formed in a substantially T-shape for connecting to a roof member (not shown). At the corners of the roof connecting part 10R, the side wall part 3R is formed in a curved shape so as to be concave toward the inside of the plate, resulting in stretch flange forming. At the location of the B-pillar outer R / F (vehicle press part 10) below the vehicle where the front door lock member is attached, the side wall part 3F is formed so as to be concave toward the inside of the plate, resulting in stretch flange forming.

[0036] <Manufacturing method for vehicle press parts> Next, the manufacturing method of the vehicle press part according to the present embodiment will be described in detail with reference to Figs. 3 to 11. Fig. 3 shows a perspective view of an intermediate product formed in the drawing process of the vehicle press part shown in Fig. 1. Fig. 4 shows the AA cross-sectional view shown in Fig. 3. Fig. 5 shows the BB cross-sectional view shown in Fig. 3. Fig. 6 shows the CC cross-sectional view shown in Fig. 3. Fig. 7 shows a cross-sectional view of the main part in the short direction at the bottom dead center of the press die (drawing die) for drawing the intermediate product shown in Fig. 3. Fig. 8 shows a cross-sectional view of the press die (compression die) for compression molding the intermediate product shown in Fig. 3, showing a cross-sectional view of the main part in the short direction during compression molding of the side wall extension part and the top plate extension part. Fig. 9 shows a cross-sectional view of the press die (compression die) for compression molding the intermediate product shown in Fig. 3, showing a cross-sectional view of the main part in the longitudinal direction during compression molding of the top plate extension part. Fig. 10 shows a cross-sectional view of the main part in the short direction at the bottom dead center of the press die (bending die) for bending the intermediate product shown in Fig. 3. FIG. 11 is a flowchart showing the method for manufacturing the vehicle press part shown in FIG.

[0037] As shown in Fig. 3 to Fig. 11, the method for manufacturing the vehicle press part 10 is a method for manufacturing the elongated vehicle press part 10 having a substantially hat-shaped cross section in which the top plate 1 and the flange portion 2 are connected by the side wall portions 3 (31, 32) and the top plate 1 is curved so as to be convex toward the outside in the longitudinal direction, and includes a drawing forming process S1 for manufacturing an intermediate product 10a having side wall extensions 3a (31a, 32a) in which the short-side length of the side wall portions 3 (31, 32) is longer than the product shape SK and a top plate extension 1a in which the longitudinal length of the top plate 1 is longer than the product shape SK, and a compression forming process S3 for compressing the side wall extensions 3a (31a, 32a) and the top plate extension 1a in the intermediate product 10a and restoring them to the product shape SK. Here, as shown in Fig. 5, the flange portion 2 in the intermediate product 10a is formed in a shape substantially the same as the flange portion 2 of the product shape SK. In addition, the side wall extension portion 3a (31a, 32a) in the intermediate product 10a has a base end shape that is connected to the flange portion 2 and is formed in a shape that is approximately the same as the side wall portion 3 (31, 32) of the product shape SK, and a tip end shape that is connected to the top plate extension portion 1a is formed by extending along the surface of the side wall portion 3 (31, 32) of the product shape SK.

[0038] As a result, the tensile stress δ1 in the short direction generated in the side wall extension portion 3a (31a, 32a) in the drawing process S1 and the tensile stress δ2 in the long direction generated in the top plate extension portion 1a can be reduced or eliminated by the compressive stresses γ1 and γ2 applied in the compression molding process S3. Therefore, the springback generated in the top plate portion 1 in the long direction of the present vehicle press part 10 can be reduced or eliminated, and the springback and warpage generated in the side wall portions 3 (31, 32) in the short direction can be reduced or eliminated.

[0039] Specifically, in the drawing process S1, as shown in Fig. 7, a press die 50 (drawing die) is provided which has a lower punch 51 formed in a substantially hat-shaped cross section, an upper die 52 arranged opposite the lower punch 51 and moving up and down in the pressing direction, and a lower cushion 53 arranged on the outer edge of the lower punch 51 and moving up and down while sandwiching the material outer edge W1 between the outer edge of the upper die 52. Also, as shown in Figs. 4 and 5, the lower punch 51 and the upper die 52 of the press die 50 (drawing die) are provided with forming surfaces 51S, 52S which form side wall extensions 3a (31a, 32a) in which the lateral length of the side wall 3 is longer than the product shape SK, and top plate extension 1a in which the longitudinal length of the top plate 1 is longer than the product shape SK.

[0040] Therefore, according to the present press die 50 (drawing die), for example, an ultra-high tensile material with a tensile strength of ≈1180 MPa is used as a raw material (steel plate) W, and the upper die 52 is lowered to press the raw material W against the lower punch 51 while applying tension to the raw material W, thereby manufacturing an intermediate product 10a shown in Figs. 3 to 6. The raw material W is handled and shaped in the short-side direction by the die R parts 521 and 522 of the upper die 52 in the side wall extension parts 3a (31a, 32a) of the intermediate product 10a, so that a tensile stress δ1 in the short-side direction is generated in the side wall extension parts 3a (31a, 32a) of the intermediate product 10a. In addition, the raw material W is curved and shaped in the long-side direction in the top plate extension part 1a of the intermediate product 10a, so that a tensile stress δ2 in the long-side direction is generated. The material W is elongated by the tensile stresses δ1 and δ2, but since the material W is an ultra-high tensile material and has a high yield stress, it cannot reach a completely plastic region. Therefore, large springback occurs in the side wall extensions 3a (31a, 32a) and the top plate extension 1a of the intermediate product 10a.

[0041] 8 and 9, the compression molding process S3 is provided with a press die 60 (compression die) having a lower punch 61 formed in a substantially hat-shaped cross section, an upper die 62 arranged opposite the lower punch 61 and moving up and down in the pressing direction, and an upper pad 63 that presses and holds the top plate 1 of the intermediate product 10a placed on the lower punch 61. The lower punch 61 and the upper die 62 are provided with molding surfaces 61S, 62S formed in substantially the same shapes as the side wall 3 (31, 32) and the top plate 1 of the vehicle press part 10 shown in FIGS. 1, 2, 4, and 5.

[0042] Therefore, according to the present press die 60 (compression die), as shown in Figs. 8 and 9, when the upper die pad 63 and the lower die punch 61 hold the top plate portion 1 of the intermediate product 10a, and the side wall extension portion 3a (31a, 32a) and the top plate extension portion 1a in the intermediate product 10a are compressed by the upper die 62 and the lower die punch 61 to restore the intermediate product 10a to the product shape SK, compressive stresses γ1 and γ2 can be applied to the side wall extension portion 3a (31a, 32a) and the top plate extension portion 1a. These compressive stresses γ1 and γ2 can reduce or eliminate the tensile stress δ1 in the short direction generated in the side wall extension portion 3a (31a, 32a) of the intermediate product 10a and the tensile stress δ2 in the long direction generated in the top plate extension portion 1a. Therefore, the springback generated in the long direction in the top plate portion 1 can be reduced or eliminated, and the springback and warpage generated in the side wall portion 3 in the short direction can be reduced or eliminated.

[0043] Furthermore, as shown in Figure 5, the intermediate product 10a manufactured in the drawing molding process S1 has a side wall extension portion 3a (31a, 32a) in which the short-side length of the side wall portion 3 (31, 32) is formed longer than the product shape SK.Therefore, as shown in Figures 8 and 9, when the side wall extension portion 3a (31a, 32a) and the tabletop extension portion 1a are compressed in the compression molding process S3, local buckling or deformation in the longitudinal direction of the tabletop extension portion 1a is avoided by the ridge portion 4a extending in the longitudinal direction at the position where the side wall extension portion 3a (31a, 32a) and the tabletop extension portion 1a intersect, and the longitudinal tensile stress δ2 in the tabletop extension portion 1a can be stably reduced or eliminated.

[0044] Therefore, according to this manufacturing method for a vehicle press part 10, it is possible to provide a manufacturing method for a vehicle press part 10 that can stably reduce or eliminate springback that occurs in the top plate portion 1 in the longitudinal direction of a long vehicle press part 10 having an approximately hat cross-sectional shape and in which the top plate portion 1 is curved so as to be convex toward the outside of the plate in the longitudinal direction, and can reduce or eliminate springback and warping that occurs in the side wall portions 3 (31, 32) in the lateral direction.

[0045] As shown in Figs. 5 and 8, the side wall extensions 3a (31a, 32a) are preferably formed to be flared toward the end with respect to the pressing direction of the compression molding process S3, and the intersection angle θ (θ1, θ2) between the side wall extensions 3a (31a, 32a) and the top plate extension 1a is preferably formed to be an obtuse angle. Here, one (vehicle front side) side wall extension 31a is formed to be inclined at an opening angle α1 with respect to the pressing direction of the press die 60 (compression die), and the other (vehicle rear side) side wall extension 32a is formed to be inclined at an opening angle α2 (<α1) with respect to the same pressing direction. Also, the top plate extension 1a is formed perpendicular to the pressing direction of the compression molding process S3.

[0046] Therefore, when the side wall extensions 3a (31a, 32a) and the tabletop extension 1a are compressed in the compression molding process S3, the tip side 3A1 of the side wall extensions 3a (31a, 32a) is pressed into the short-side center side 1A of the tabletop extension 1a while bending, and a short-side compressive stress γ3 can be applied to the tabletop extension 1a. Therefore, the short-side tensile stress δ3 in the tabletop extension 1a can be reduced or eliminated, and in addition to reducing the springback in the long-side direction of the tabletop 1, the springback in the short-side direction of the tabletop 1 can also be reduced or eliminated.

[0047] In the above case, when the side wall extensions 3a (31a, 32a) and the top plate extensions 1a are compressed in the compression molding process S3, the base end sides 3A2 of the side wall extensions 3a (31a, 32a) are curved into an approximately S-shape and then compressed in the short-side direction by being pinched between the lower punch 61 and the upper die 62, so that the compressive stress γ1 in the short-side direction can be applied to the side wall extensions 3a (31a, 32a) in a larger amount. Therefore, the tensile stress δ1 in the short-side direction in the side wall extensions 3a (31a, 32a) can be further reduced or eliminated. As a result, the accuracy of the vehicle press part 10 can be further improved.

[0048] As shown in Figs. 1 and 2, the product shape SK of the vehicle press part 10 includes a curved region SK1 in which the top plate portion 1 is curved so as to be convex toward the outside of the plate in the longitudinal direction, and a linear region SK2 in which the top plate portion 1 is formed substantially linearly in the longitudinal direction. As shown in Figs. 3 to 5, it is preferable that the curved region SK1 has the side wall extension portion 3a (31a, 32a) and the top plate extension portion 1a in substantially the entire range. In this case, as shown in Figs. 8 and 9, in the compression molding step S3, the lower punch 61 and the upper die 62 of the press die 60 (compression die) can apply compressive stresses γ1, γ2, and γ3 to substantially the entire range of the side wall extension portion 3a (31a, 32a) and the top plate extension portion 1a in the curved region SK1. Therefore, the springback (camberback) in the longitudinal direction occurring in the top plate portion 1 in the curved region SK2 can be more effectively reduced or eliminated, and the curvature accuracy in the curved region SK2 of the vehicle press part 10 can be further improved.

[0049] 3 to 5, when the side wall extensions 3a (31a, 32a) and the tabletop extension 1a are formed over substantially the entire range of the curved region SK1, it is preferable that the tabletop extension 1a is formed substantially parallel to the tabletop 1 of the product shape SK and is formed so that its longitudinal length is larger than that of the product shape SK near both longitudinal ends 11a, 12a in the curved region SK1. Here, as shown in Figs. 4 and 5, the tabletop extension 1a is formed substantially parallel to the tabletop 1 of the product shape SK in the longitudinal and lateral directions. 4, the top plate extension 1a is formed longer than the length of the product shape SK by the amount of expansion (L1-L2, L3-L4) near both longitudinal ends 11a, 12a in a predetermined range (P1-P2) near the boundary between the curved region SK1 and the straight region SK2 and in a predetermined range (P3-P4) near the boundary between the curved region SK1 and the roof connecting portion 10R. In the range (P2-P3) other than the vicinity of both ends 11a, 12a, the top plate extension 1a is formed in a shape shifted in parallel by a predetermined distance d1 toward the outside of the vehicle from the product shape SK.

[0050] Therefore, as shown in Fig. 9, in the compression molding process S3, a lower punch 61 and an upper die 62 of a press die 60 (compression die) press the top plate extension portion 1a in a substantially parallel manner, while compressive stress γ2 can be applied along the surface from both longitudinal ends of the top plate extension portion 1a toward the longitudinal center side 1B. Therefore, the longitudinal tensile stress δ2 of the top plate extension portion 1a can be reduced or eliminated as a whole, and the longitudinal springback (camberback) occurring in the top plate portion 1 in the curved region SK1 can be reduced or eliminated more uniformly. As a result, the curvature accuracy in the curved region SK1 of the vehicle press part 10 can be improved more uniformly.

[0051] 9, in the compression molding step S3, it is preferable that the upper die pad 63 of the press die 60 (compression die) presses the top plate portion 1 of the straight region SK2 against the lower die punch 61 to compress the side wall extension portion 3a (31a, 32a) and the top plate extension portion 1a of the curved region SK1 while holding the top plate portion 1 of the straight region SK2, and restore the product shape SK. In this case, the compressive stresses γ1, γ2, and γ3 can be accurately applied to the side wall extension portion 3a (31a, 32a) and the top plate extension portion 1a of the curved region SK1 without positional deviation. Therefore, the springback (camberback) in the longitudinal direction generated in the top plate portion 1 can be more reliably reduced or eliminated without variation, and the curvature accuracy in the longitudinal direction of the press part 10 for a vehicle can be further stably improved.

[0052] As shown in Figs. 3, 6, 10, and 11, the intermediate product 10a is provided with a side wall widening portion 3b (31b, 32b) formed by widening the side wall portion 3 (31, 32) toward the plate outside from the product shape SK, and it is preferable to bend the side wall widening portion 3b (31b, 32b) to restore it to the product shape SK in the bending forming process S2 provided between the drawing forming process S1 and the compression forming process S3. Here, as shown in Fig. 6, the top plate portion 1 in the intermediate product 10a is formed in a shape substantially identical to the top plate portion 1 of the product shape SK. Also, the flange portion 2 in the intermediate product 10a is formed in a shape substantially identical to the flange portion 2 of the product shape SK, and is formed so that the distance between them is expanded. And, the side wall widening portion 3b (31b, 32b) is formed in a curved shape between the top plate portion 1 and the flange portion 2 so that the widening amount gradually increases from the tip side connected to the top plate portion 1, and the widening amount at the center is maximized.

[0053] 10, the bending process S2 is provided with a press die 70 (bending die) having a lower punch 71 formed in a substantially hat-shaped cross section, an upper die 72 arranged opposite the lower punch 71 and moving up and down in the pressing direction, and an upper pad 73 that presses and holds the top plate 1a of the intermediate product 10a placed on the lower punch 71. The lower punch 71 and the upper die 72 are provided with forming surfaces 71S, 72S formed in substantially the same shape as the side wall portions 3 (31, 32) of the product shape SK of the vehicle press part 10 shown in FIGS.

[0054] Therefore, according to the present press die 70 (bending die), as shown in FIG. 10, while the upper die pad 73 and the lower die punch 71 hold the top plate portion 1 of the intermediate product 10a, the upper die 72 descends to bend the side wall widened portion 3b (31b, 32b), thereby applying a compressive stress γ4 associated with the bending to the side wall widened portion 3b (31b, 32b). Therefore, the tensile stress δ4 generated in the side wall widened portion 3b (31b, 32b) in the drawing process S1 can be reduced or eliminated, and the accuracy of the side wall portion 3 (31, 32) can be improved. As a result, the springback, warpage, and the like of the vehicle press part 10 can be reduced or eliminated more stably.

[0055] It is preferable that the side wall widening portions 3b (31b, 32b) are provided at locations where the side wall portion 3 is formed to be concave toward the plate inner side and stretch flange forming is performed. For example, as shown in Fig. 1 and Fig. 3, in the case of a B-pillar outer R / F (vehicle press part 10), it is preferable that the side wall widening portions 3b (31b, 32b) are provided at locations where the side wall portion 3F is formed to be curved so as to be concave toward the plate inner side and stretch flange forming is performed in order to attach a front door lock member below the vehicle, and at locations where the side wall portion 3R is formed to be curved so as to be concave toward the plate inner side and stretch flange forming is performed at corners of the roof connecting portion 10R.

[0056] As shown in Fig. 11, the manufacturing method of the present vehicle press part includes an outer shape punching or outer shape hole punching process S4 after the compression molding process S3. The outer shape punching or outer shape hole punching process S4 is a process for finally forming the present vehicle press part into a product shape SK, but since it is the same as a conventional outer shape punching or outer shape hole punching process, a detailed description will be omitted. The hole punching method in the outer shape punching or outer shape hole punching process S4 includes a method of punching holes in the press direction and a method of cam hole punching using a cam mechanism at a predetermined inclination direction with respect to the press direction. When cam hole punching is used, the outer shape punching or outer shape hole punching process S4 may be divided into two processes.

[0057] <Stress distribution and surface position accuracy of pressed products> Next, the evaluation results of the stress distribution and the surface position accuracy of the pressed product formed by the manufacturing method of the present vehicle pressed part by CAE analysis will be described with reference to Figs. 12 and 13. Fig. 12 shows stress distribution diagrams by CAE analysis of the pressed product in the process shown in Fig. 11, where (A) shows the stress distribution diagram of the pressed product (intermediate product) in the drawing process, and (B) shows the stress distribution diagram of the pressed product in the compression molding process. Fig. 13 shows surface position accuracy distribution diagrams by CAE analysis of the pressed product in the process shown in Fig. 11, where (A) shows the surface position accuracy distribution diagram of the pressed product (intermediate product) in the drawing process, and (B) shows the surface position accuracy distribution diagram of the pressed product in the compression molding process. Here, the subject of the CAE analysis is a vehicle pressed part 10 (B-pillar outer R / F) press-formed using ultra-high tensile steel with a tensile strength of ≈1180 MPa as a material. The stress distribution is expressed by the density of the dots, with the side with high dot density (+) being tensile stress and the side with low dot density (-) being compressive stress. The unit of stress is kg / mm 2 The surface position accuracy indicates the amount of displacement of the pressed part relative to the product shape SK, where (+) indicates displacement toward the outside of the plate and (-) indicates displacement toward the inside of the plate. The unit of surface position accuracy is millimeters (mm).

[0058] (Stress distribution in pressed products) As shown in Fig. 12(A), in the pressed product (intermediate product 10a) in the drawing process S1, a region X1 of high tensile stress occurs over a wide area in the longitudinal direction in the top plate extension 1a of the curved region SK1. This region X1 of high tensile stress is also distributed in the side wall extension 3a (31a, 32a) of the curved region SK1. In contrast, in the top plate portion 1 of the straight region SK2, tensile stress and compressive stress occur in a dispersed manner, and there is no region of concentrated high tensile stress. Meanwhile, in the side wall widening portion 3b (31b, 32b) of the straight region SK2 that will be stretch flanged, a region X2 of high tensile stress exists.

[0059] As shown in FIG. 12(B), in the pressed product in the compression molding process S3, a region Y1 of high compressive stress occurs over a wide area in the longitudinal direction in the top plate extension 1a of the curved region SK1. This region Y1 of high compressive stress is also distributed in the side wall extension 3a (31a, 32a) of the curved region SK1. In contrast, in the top plate portion 1 of the straight region SK2, tensile stress and compressive stress occur in a dispersed manner, and there is no region of concentrated high tensile stress. This is approximately the same as the pressed product (intermediate product) in the drawing process S1. Meanwhile, in the side wall widening portion 3b (31b, 32b) of the straight region SK2 that will be stretch flanged, the region X2 of high tensile stress is reduced.

[0060] (Surface position accuracy distribution of pressed products) As shown in FIG. 13(A), in the pressed product (intermediate product 10a) in the drawing process S1, in the top plate extension portion 1a of the curved region SK1, the surface position at the bottom of the vehicle is slightly lower than the normal size, but the surface position becomes significantly higher toward the top of the vehicle. Therefore, it can be seen that the springback (camber back) amount in the longitudinal direction is considerably large in the top plate extension portion 1a of the curved region SK1. In contrast, as shown in FIG. 13(B), in the pressed product in the compression molding process S3, in the top plate extension portion 1a of the curved region SK1, the surface position at the top of the vehicle is lower than the normal size, and it can be evaluated that the springback amount in the longitudinal direction has been significantly reduced. Also, as shown in FIG. 13(A), in the pressed product (intermediate product 10a) in the drawing process S1, the surface position of the flange tip portion in the short-side direction of the straight region SK2 is significantly elevated, whereas, as shown in FIG. 13(B), in the pressed product in the compression molding process S3, the surface position of the flange tip portion in the short-side direction of the straight region SK2 is close to the normal size.

[0061] From the above CAE analysis results, it can be inferred that when the upper die 62 and the lower punch 61 compress the side wall extension 3a (31a, 32a) and the top plate extension 1a of the intermediate product 10a in the compression molding process S3 to restore them to the product shape SK, compressive stresses γ1 and γ2 can be applied to the side wall extension 3a (31a, 32a) and the top plate extension 1a, and these compressive stresses γ1 and γ2 can reduce or eliminate the short-side tensile stress δ1 generated in the side wall extension 3a (31a, 32a) of the intermediate product 10a and the longitudinal tensile stress δ2 generated in the top plate extension 1a, respectively. As a result, it can be inferred that the longitudinal springback (camber back) of the top plate portion 1 in the curved region SK1 has been significantly improved. Furthermore, in the side wall widening portion 3b (31b, 32b) which is the stretch flange forming of the straight region SK2, the region X2 of high tensile stress can be reduced by the compressive stress γ4 applied in the bending forming process S2, and it can be estimated that the springback in the short direction of the side wall portion 3 (31, 32) has been significantly improved.

[0062] <Action and effect> As described in detail above, the manufacturing method for a vehicle press part in this embodiment includes a drawing forming process S1 for manufacturing an intermediate product 10a having a side wall extension portion 3a (31a, 32a) in which the short-side length of the side wall portion 3 (31, 32) is longer than the product shape SK and a top plate extension portion 1a in which the longitudinal length of the top plate portion 1 is longer than the product shape SK, and a compression molding process S3 for compressing the side wall extension portion 3a (31a, 32a) and the top plate extension portion 1a in the intermediate product 10a to restore them to the product shape SK.Therefore, the short-side tensile stress δ1 generated in the side wall extension portion 3a (31a, 32a) in the drawing forming process S1 and the longitudinal tensile stress δ2 generated in the top plate extension portion 1a can be reduced or eliminated, respectively, by the compression stresses γ1 and γ2 applied in the compression molding process S3. Therefore, it is possible to reduce or eliminate springback (camber back) occurring in the top plate portion 1 in the longitudinal direction, and to reduce or eliminate springback and warping occurring in the side wall portion 3 in the lateral direction.

[0063] Furthermore, the intermediate product 10a manufactured in the drawing molding process S1 has a side wall extension portion 3a (31a, 32a) in which the short-side length of the side wall portion 3 (31, 32) is formed longer than the product shape SK. Therefore, when the side wall extension portion 3a (31a, 32a) and the top plate extension portion 1a are compressed in the compression molding process S3, local buckling or deformation in the longitudinal direction of the top plate extension portion 1a is avoided by the ridge portion 4a where the side wall extension portion 3a (31a, 32a) and the top plate extension portion 1a intersect, and the longitudinal tensile stress δ2 in the top plate extension portion 1a can be stably reduced or eliminated.

[0064] Therefore, according to this embodiment, a manufacturing method can be provided for a long vehicle press part 10 that has an approximately hat-shaped cross-sectional shape and in which the top plate portion 1 is curved in the longitudinal direction so as to be convex toward the outside of the plate, which can stably reduce or eliminate springback that occurs in the top plate portion 1 in the longitudinal direction, and can reduce or eliminate springback and warping that occurs in the side wall portions 3 (31, 32) in the lateral direction.

[0065] In addition, according to this embodiment, the side wall extension 3a (31a, 32a) is formed to be flared toward the end with respect to the pressing direction in the compression molding process S3, and the intersection angle θ (θ1, θ2) between the side wall extension 3a (31a, 32a) and the top plate extension 1a is formed to be an obtuse angle. Therefore, when the side wall extension 3a (31a, 32a) and the top plate extension 1a are compressed in the compression molding process S3, the tip side 3A1 of the side wall extension 3a (31a, 32a) is pressed into the short-side central side 1A of the top plate extension 1a, and a short-side compressive stress γ3 can be applied to the top plate extension 1a. Therefore, the short-side tensile stress δ3 in the top plate extension 1a can be reduced or eliminated, and in addition to reducing the springback (camber back) in the longitudinal direction of the top plate portion 1, the springback in the short-side direction of the top plate portion 1 can also be reduced or eliminated. As a result, the precision of the vehicle press part 10 can be further improved.

[0066] According to the present embodiment, the product shape SK includes a curved region SK1 in which the top plate portion 1 is curved so as to be convex toward the outside of the plate in the longitudinal direction, and a linear region SK2 in which the top plate portion 1 is formed substantially linearly in the longitudinal direction, and the side wall extensions 3a (31a, 32a) and the top plate extensions 1a are provided in substantially the entire range of the curved region SK1, so that the compression stresses γ1, γ2, and γ3 can be applied to substantially the entire range of the side wall extensions 3a (31a, 32a) and the top plate extensions 1a in the curved region SK1 in the compression molding process S3. This makes it possible to more effectively reduce or eliminate the springback in the longitudinal direction that occurs in the top plate portion 1 in the curved region SK1, and further improve the curvature accuracy in the curved region SK2 of the vehicle press part 10.

[0067] In addition, according to this embodiment, the top plate extension portion 1a is formed substantially parallel to the top plate portion 1 of the product shape SK, and is formed so that the longitudinal length is larger than the length of the product shape SK near both longitudinal ends 11a, 12a in the curved region SK1. Therefore, while pressing the top plate extension portion 1a substantially parallel in the compression molding process S3, a compressive stress γ2 can be applied along the surface from both longitudinal ends of the top plate extension portion 1a toward the longitudinal center. Therefore, the longitudinal tensile stress δ2 of the top plate extension portion 1a can be reduced or eliminated as a whole, and the longitudinal springback occurring in the top plate portion 1 in the curved region SK2 can be reduced or eliminated more uniformly. As a result, the curvature accuracy in the curved region SK2 of the vehicle press part 10 can be improved more uniformly.

[0068] According to this embodiment, in the compression molding step S3, while the top plate portion 1 in the straight region SK1 is held, the side wall extension portion 3a (31a, 32a) in the curved region SK2 and the top plate extension portion 1a are compressed and restored to the product shape SK, so that the compressive stresses γ1, γ2, and γ3 can be accurately applied to the side wall extension portion 3a (31a, 32a) in the curved region SK2 and the top plate extension portion 1a without positional deviation. Therefore, the springback in the longitudinal direction generated in the top plate portion 1 can be more reliably reduced or eliminated without variation, and the curvature accuracy in the longitudinal direction of the vehicle press part 10 can be further stably improved.

[0069] According to the present embodiment, the intermediate product 1a includes the sidewall widened portion 3b (31b, 32b) formed by widening the sidewall portion 3 from the product shape SK toward the plate outside, and in the bending process S2 provided between the drawing process S1 and the compression process S3, the sidewall widened portion 3b (31b, 32b) is bent to restore the sidewall widened portion 3b (31b, 32b) to the product shape SK, so that the compressive stress γ4 associated with the bending process can be applied to the sidewall widened portion 3b (31b, 32b). Therefore, the tensile stress δ4 generated in the sidewall widened portion 3b (31b, 32b) in the drawing process S1 can be reduced or eliminated, the accuracy of the sidewall portion 3 can be improved, and the curvature accuracy of the top plate portion 1 can be improved. As a result, the springback and warpage of the vehicle press part 10 can be reduced or eliminated more stably.

[0070] <Modification> The above-described embodiment may be appropriately modified within the scope of the present invention. For example, according to this embodiment, the manufacturing method of the vehicle press part 10 is a manufacturing method of a long-shaped vehicle press part 10 having a substantially hat-shaped cross section in which the top plate part 1 and the flange part 2 are connected by the side wall parts 3 (31, 32) and the top plate part 1 is curved so as to be convex toward the outside in the longitudinal direction, and includes a drawing forming process S1 for manufacturing an intermediate product 10a having side wall extension parts 3a (31a, 32a) in which the short-side length of the side wall parts 3 (31, 32) is formed longer than the product shape SK and a top plate extension part 1a in which the longitudinal length of the top plate part 1 is formed longer than the product shape SK, and a compression forming process S3 for compressing the side wall extension parts 3a (31a, 32a) and the top plate extension part 1a in the intermediate product 10a to restore them to the product shape SK. Also, as shown in FIG. 5, the flange part 2 in the intermediate product 10a is formed in a shape substantially the same as the flange part 2 in the product shape SK. In addition, the side wall extensions 3a (31a, 32a) in the intermediate product 10a have a base end connected to the flange 2 formed in substantially the same shape as the side wall 3 (31, 32) of the product shape SK, and a tip end connected to the top plate extension 1a formed by extending along the surface of the side wall 3 (31, 32) of the product shape SK. However, the side wall extensions 3a (31a, 32a) in the intermediate product 10a are not necessarily limited to the above shape.

[0071] For example, as shown in Fig. 14(A), in the drawing forming process S1, an intermediate product 10c is manufactured having a side wall extension 3c in which the short-side length of the side wall 3 is longer than the product shape SK and expanded toward the outside of the plate, and a top plate extension 1c in which the long-side length of the top plate 1 is longer than the product shape SK, and as shown in Fig. 14(B), in the bending forming process S2, the side wall extension 3c is bent to restore the base end side 3A2 of the side wall extension 3c to the product shape SK, and as shown in Fig. 14(C), in the compression forming process S3, the tip end side 3A1 of the side wall extension 3c and the top plate extension 1c are compressed to restore the product shape SK. According to the above manufacturing method, the compressive stress applied to the side wall extension 3c can be increased, so that the accuracy of the side wall 3 can be further improved while the curvature accuracy of the top plate 1 can be increased. [Industrial Applicability]

[0072] INDUSTRIAL APPLICABILITY The present invention can be used as a manufacturing method for a long vehicle press part having a substantially hat-shaped cross section and a top plate portion that is curved in the longitudinal direction so as to be convex outward. [Explanation of symbols]

[0073] 1 Top plate 1a Top extension 2 Flange 3 Side wall 3a Sidewall extension 3b Side wall widening section 3A1 Tip side 3A2 Proximal side 10 Vehicle press parts 10a Intermediate product 11a, 12a end 31a, 32a Side wall extensions 31b, 32b Side wall widening part S1 Drawing process S2 Bending process S3 Compression molding process SK product shape SK1 Curved Area SK2 Linear area θ, θ1, θ2 intersection angle

Claims

1. A method for manufacturing a long vehicle press part having a generally hat-shaped cross section in which a top plate portion and a flange portion are connected by a side wall portion, and the top plate portion is curved in a longitudinal direction so as to be convex toward an outer side of the plate, a drawing forming process for producing an intermediate product having a side wall extension portion in which the short-side length of the side wall portion is formed longer than the product shape and a top plate extension portion in which the long-side length of the top plate portion is formed longer than the product shape; A compression molding process is provided in which the side wall extension portion and the top plate extension portion of the intermediate product are compressed to restore the intermediate product to the product shape. The intermediate product includes a side wall widening portion formed by widening the side wall portion toward the plate outer side from the product shape, A manufacturing method of a pressed part for a vehicle, characterized in that in a bending forming process provided between the drawing forming process and the compression forming process, the side wall widening portion is bent to restore it to the product shape.

2. The method for manufacturing a vehicle press part according to claim 1, A method for manufacturing a pressed part for a vehicle, characterized in that the side wall extension portion is formed to be wider toward the press direction of the compression molding process, and an intersection angle between the side wall extension portion and the top plate extension portion is an obtuse angle.

3. In the method for manufacturing a vehicle press part according to claim 1 or 2, The product shape includes a curved region in which the top plate portion is curved so as to be convex toward the outside of the plate in the longitudinal direction, and a linear region in which the top plate portion is formed substantially linearly in the longitudinal direction, A method for manufacturing a press part for a vehicle, comprising the steps of: forming the side wall extension portion and the top plate extension portion over substantially the entire range of the curved region;

4. The method for manufacturing a vehicle press part according to claim 3, A manufacturing method for a vehicle press part, characterized in that the top plate extension portion is formed approximately parallel to the top plate portion of the product shape and has a longitudinal length that is expanded beyond the length of the product shape near both longitudinal ends of the curved region.

5. In the method for manufacturing a vehicle press part according to claim 3 or 4, A manufacturing method for a vehicle press part, characterized in that in the compression molding process, while holding the top plate portion in the straight region, the side wall extension portion and the top plate extension portion in the curved region are compressed to restore them to the product shape.

6. A method for manufacturing a long vehicle press part having a generally hat-shaped cross section in which a top plate portion and a flange portion are connected by a side wall portion, and the top plate portion is curved in a longitudinal direction so as to be convex toward an outer side of the plate, a drawing forming process for producing an intermediate product having a side wall extension portion in which the short-side length of the side wall portion is formed longer than the product shape and a top plate extension portion in which the long-side length of the top plate portion is formed longer than the product shape; a bending forming process in which the side wall extension portion of the intermediate product is bent to restore the base end side of the side wall extension portion to the product shape; and a compression molding process for compressing the tip side of the side wall extension portion and the top plate extension portion in the intermediate product to restore it to the product shape.

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