Press-formed product for vehicles and method of manufacturing the press-formed product

Abstract

A press-formed product of the present disclosure includes a plate-shaped portion, a wall, and a flange. The wall includes at least one curved surface having an arcuate cross-sectional shape that bulges radially outward in a cross-section taken along the plate-shaped portion. The at least one curved surface includes a first curved surface and a second curved surface. The second curved surface is a portion closer to the flange than the first curved surface. A radius of curvature of the second curved surface in the cross-section is configured to be smaller than a radius of curvature of the first curved surface in the cross-section.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of Japanese Patent Application No. 2024-015916 filed on Feb. 5, 2024 with the Japan Patent Office, the entire disclosure of which is incorporated herein by reference.BACKGROUND

[0002] The present disclosure relates to a press-formed product for vehicles and a method of manufacturing the press-formed product, and in particular, to a technique for improving its appearance quality.

[0003] Japanese Patent No. 5569609 discloses a press-forming method capable of inhibiting the formation of wrinkles in a press-formed product.SUMMARY

[0004] The inventor of the present disclosure studied techniques for improving the appearance quality of a press-formed product, such as techniques for reducing wrinkles. The press-formed product includes a plate-shaped portion, a wall, a flange, and a curved surface having an arcuate cross-sectional shape that bulges radially outward in a cross-section taken along the plate-shaped portion. As a result of the study, the inventor of the present disclosure found that wrinkles were easily formed on the curved surface in a region closer to the flange of the press-formed product.

[0005] In one aspect of the present disclosure, it is desirable to reduce the formation of wrinkles on the curved surface in the region closer to the flange of the press-formed product.

[0006] One aspect of the present disclosure is a press-formed product including a plate-shaped portion, a wall, and a flange. The wall has a plate shape and extends from the plate-shaped portion in a direction that intersects the plate-shaped portion. The flange has a plate shape and extends from an edge of the wall. The wall includes at least one curved surface having an arcuate cross-sectional shape that bulges radially outward in a cross-section taken along the plate-shaped portion. The at least one curved surface includes a first curved surface and a second curved surface. The second curved surface is a portion closer to the flange than the first curved surface. A radius of curvature of the second curved surface in the cross-section is smaller than a radius of curvature of the first curved surface in the cross-section.

[0007] In this configuration, a circumferential length of the wall in the region closer to the flange is longer than a circumferential length of the wall in the region farther from the flange. Thus, in the press-forming, the material flowing from the flange into the wall is dispersed in the circumferential direction, and the buckling of the material is inhibited. That is, an anti-buckling effect can be exhibited. As a result, the formation of wrinkles can be inhibited on the curved surface in the region closer to the flange.

[0008] In one aspect of the present disclosure, the wall may further include a stepped surface formed between the first curved surface and the second curved surface. The second curved surface may be located radially outside the first curved surface.

[0009] In this configuration, a length of an outer surface of the wall in its extension direction is longer by an amount of the stepped surface than a length of an outer surface of the wall in its extension direction without the stepped surface. This allows the material flowing from the flange to be dispersed also in the extension direction, thereby enhancing the anti-buckling effect achieved by the material. As a result, the formation of wrinkles can be further reduced on the curved surface in the region closer to the flange.

[0010] In one aspect of the present disclosure, the wall may include a plurality of stepped surfaces. In this configuration, a length of an outer surface of the wall in the extension direction is longer by an amount of the stepped surfaces than the length of the outer surface of the wall in the extension direction with one stepped surface. This facilitates the dispersion of the material flowing from the flange into the wall, further enhancing the anti-buckling effect achieved by the material. As a result, the formation of wrinkles can be further reduced on the curved surface in the region closer to the flange.

[0011] In one aspect of the present disclosure, the press-formed product may be a body component of an automobile. This configuration further reduces the formation of wrinkles on the curved surface in the region closer to the flange of the body component of the automobile.

[0012] In one aspect of the present disclosure, the press-formed product may have a bag shape with a recess. The wall may have a plurality of curved surfaces. The wall may further include a flat portion having a flat plate shape and connecting the plurality of curved surfaces. This configuration reduces the formation of wrinkles on the curved surface in the region closer to the flange of the bag-shaped press-formed product.

[0013] One aspect of the present disclosure may be a method of manufacturing a press-formed product for obtaining a press-formed product having a specified target shape using a first die and a second die. According to the method, the above-described press-formed product is obtained. Each of the first die and the second die includes a first forming portion, a second forming portion, and a third forming portion. The first forming portion is a portion for forming the plate-shaped portion. The second forming portion is a portion for forming the wall. The third forming portion is a portion for forming the at least one curved surface. The method of manufacturing the press-formed product includes: placing a blank between the first die and the second die that are spaced apart from each other; and bringing the first die and the second die closer to each other with the blank placed between the first die and the second die.

[0014] With this configuration, it is possible to produce the press-formed product described in detail above. That is, a press-formed product with reduced wrinkling can be obtained.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Some embodiments of the present disclosure will be described hereinafter by way of example with reference to the accompanying drawings, in which:

[0016] FIG. 1 is a perspective view of a press-formed product of a first embodiment;

[0017] FIG. 2A is a plan view of the press-formed product shown in FIG. 1;

[0018] FIG. 2B is a cross-sectional view taken along the line IIB-IIB of FIG. 2A;

[0019] FIG. 3A is a plan view conceptually illustrating a difference in radii of curvature and a difference in circumferential lengths in a corner of the press-formed product shown in FIG. 1;

[0020] FIG. 3B is a cross-sectional view taken along the line IIIB-IIIB of FIG. 3A;

[0021] FIG. 4 is a cross-sectional view of a press-forming device for manufacturing the press-formed product shown in FIG. 1;

[0022] FIG. 5 is a perspective view of an intermediate product formed by the press-forming device shown in FIG. 4;

[0023] FIG. 6A is a plan view of a press-formed product of a second embodiment;

[0024] FIG. 6B is a cross-sectional view taken along the line VIB-VIB of FIG. 6A; and

[0025] FIG. 7 is a perspective view of a press-formed product of a third embodiment.DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS1. First Embodiment[1-1. Configuration of Press-Formed Product]<Overview of Press-Formed Product>

[0026] The first embodiment relates to a press-formed product and a method of manufacturing the press-formed product.

[0027] FIG. 1 shows a perspective view of a press-formed product 10 formed by the method of manufacturing the press-formed product according to the first embodiment.

[0028] The press-formed product 10 serves as a component of an automobile body after being subjected to a drawing process according to the manufacturing method of the first embodiment and subsequent necessary additional processes (e.g., a trimming process and a bending process). The press-formed product 10 serves, for example, as a rear floor having a space for accommodating a spare tire. In addition to the spare tire, the space of the press-formed product 10 can also accommodate a tool, a safety vest, a charging cable (e.g., for electric vehicles), etc. The press-formed product 10 and its manufacturing method can be applied to various other components and products, including but not limited to the rear floor.

[0029] The press-formed product 10 is obtained by performing press-forming (drawing process), including drawing and bending, on a blank 50 made of steel sheet. The blank 50 that is used for the press-formed product 10 may be, for example, a steel sheet with an alloyed zinc coating. The blank 50 may have a sheet thickness of 0.6 mm to 1.4 mm. In the first embodiment, the blank 50 has a sheet thickness of 0.6 mm.<Overall Shape of Press-Formed Product>

[0030] The press-formed product 10 has a bag shape with depth. The bag shape is a shape capable of containing an object. The term “contain” here means that the object is held by a bottom wall and a side wall. In other words, the bag shape refers to a configuration that includes a bottom wall and one or more side walls.

[0031] The bag-shaped portion of the press-formed product 10 (a portion other than a flange 16 as described below) has dimensions of, for example, approximately 600 mm in width, approximately 200 mm in horizontal depth, and approximately 180 mm in vertical depth. Hereinafter, a direction along the vertical depth of the press-formed product 10 is referred to as a depth direction X (see also FIG. 1). The vertical depth of the press-formed product 10 is 80 mm or more. The press-forming method, in which the blank 50 is drawn into a bag shape with depth, is also referred to as “deep drawing”.

[0032] The press-formed product 10 includes a top plate 12, a vertical wall 14, and the flange 16. In FIG. 1, the top plate 12 is shown as an upper portion of the press-formed product 10 for illustrative purposes; however, the press-formed product 10 is used in a posture in which the top and bottom of FIG. 1 are reversed. Thus, the top plate 12 may be understood as a bottom wall in view of its state of use. In the first embodiment, the space surrounded by the top plate 12 and the vertical wall 14 is a space for accommodating a spare tire, a tool, a safety vest, a charging cable, etc.

[0033] The top plate 12 is a substantially flat plate. The top plate 12 has a substantially rectangular shape in its plan view, with two adjacent corners rounded to form top plate curvatures 18, as described below. However, the top plate 12 may generally have any other substantially polygonal shape in its plan view. The top plate 12 has two top plate curvatures 18 along its periphery. In the first embodiment, the top plate curvature 18 forms an arc of a perfect circle. However, the top plate curvature 18 may form an arc of an oval or a compound curve, etc. The top plate 12 may include a raised portion, a recessed portion, a hole, and the like as necessary. Hereinafter, a flat surface covering a large area of the top plate 12 may simply be referred to as “top plate 12”.

[0034] The vertical wall 14 is a portion extending from the top plate 12 in a direction that intersects the top plate 12. The vertical wall 14 has a plate shape. In this embodiment, the vertical wall 14 extends from a portion of the periphery of the top plate 12, the portion including the two top plate curvatures 18. Hereinafter, a direction in which the vertical wall 14 extends is referred to as an extension direction Y, as shown in FIG. 2B. In this embodiment, the extension direction Y is inclined relative to the depth direction X. When the vertical wall 14 is not inclined relative to the depth direction X, the extension direction Y is the same as the depth direction X. The vertical wall 14 is inclined to extend outward from the top plate 12.

[0035] The flange 16 extends from the edge of the vertical wall 14. In other words, the flange 16 extends outward from the edge of the vertical wall 14. The flange 16 extends substantially parallel to the top plate 12. The flange 16 has a plate shape. The flange 16 has a substantially partial annular shape in its plan view.

[0036] The vertical wall 14 includes three flat portions 20 and two corner portions 22. Each corner portion 22 is a band-shaped region extending from the top plate curvature 18 with a substantially constant width. Each flat portion 20 connects a plurality of curved surfaces 24, which is described below. Each flat portion 20 has a linear cross-sectional shape in a cross-section taken along the top plate 12. Each flat portion 20 is a portion of the vertical wall 14 other than the corner portions 22.

[0037] Since the press-formed product 10 of the first embodiment is symmetrical as shown in FIG. 1, one corner portion 22 is described below focusing on only one side. However, the press-formed product 10 is not necessarily symmetrical.

[0038] The corner portion 22 includes a first region 30 closer to the top plate 12 and a second region 32 closer to the flange 16. The first region 30 is connected to the top plate curvature 18 of the top plate 12, and the second region 32 is connected to the flange 16. In other words, the first region 30 is arranged adjacent to the top plate 12 and the second region 32 is arranged adjacent to the flange 16. The first region 30 and the second region 32 are arranged side by side along the extension direction Y, with a below-described stepped surface 38 interposed therebetween. In the corner portion 22 shown in FIG. 1, approximately 50% of the upper portion in the depth direction X constitutes the first region 30, and approximately 50% of the lower portion constitutes the second region 32.

[0039] The curved surface 24 includes a first curved surface 34 and a second curved surface 36.

[0040] The first curved surface 34 is included in the first region 30. The first curved surface 34 has a first arcuate cross-section that bulges radially outward in a cross-section taken along the top plate 12. The second curved surface 36 is included in the second region 32. The second curved surface 36 has a second arcuate cross-section that bulges radially outward in a cross-section taken along the top plate 12.

[0041] The cross-section taken along the top plate 12 is a cross-section perpendicular to the depth direction X. In the first embodiment, the shapes of the first arcuate cross-section and the second arcuate cross-section are constant at any position along the depth direction X. The shapes of the first arcuate cross-section and the second arcuate cross-section are not limited to the arcuate shapes of perfect circles, and may include other cross-sectional shapes, such as outward-curved oval arcs and compound curves.

[0042] The vertical wall 14 includes the stepped surface 38 formed between the first curved surface 34 and the second curved surface 36. The stepped surface 38 is a flat surface connecting the first curved surface 34 and the second curved surface 36, and extends substantially parallel to the top plate 12. In the first embodiment, the stepped surface 38 is formed at an intermediate position of the corner portion 22 along the depth direction X.

[0043] The second curved surface 36 is located radially outside the first curved surface 34. As used herein, the term “radially” refers to a radial direction of the arcs of the first arcuate cross-section and the second arcuate cross-section. As shown in FIG. 2B, when the corner portion 22 is viewed along the extension direction Y, the second curved surface 36 protrudes such that it is located outside the first curved surface 34 (i.e., to the right in FIG. 2B).

[0044] The radius of curvature R2 (described in detail below) of the second curved surface 36 in the cross-section taken along the top plate 12 is smaller than the radius of curvature R1 of the first curved surface 34 in the cross-section taken along the top plate 12. In the first embodiment, R1 and R2 are constant at any position along the depth direction X. However, the radii of curvature of the first curved surface 34 and the second curved surface 36 are not necessarily constant, and may vary along the depth direction X. In the first embodiment, R1 is 200 mm and R2 is 100 mm. However, R1 and R2 are not limited to these values and may take any values, provided that R2 is smaller than R1.[1-2. Press-Forming Device]

[0045] FIG. 4 is a cross-sectional view of a die set of a press-forming device for forming the press-formed product 10. The die set of the press-forming device includes a die 60, a punch 62, and a blank holder 64. The die 60 and the punch 62 are configured to be displaceable relative to each other in the depth direction X of the press-formed product 10 by a drive mechanism, which is not shown. For example, the die 60 may be displaced in the depth direction X, or the punch 62 may be displaced in the depth direction X, or both die 60 and punch 62 may be displaced in the depth direction X. In the first embodiment, the die 60 is displaced in the depth direction X. The blank holder 64 is configured to be displaceable in the depth direction X in conjunction with or independently of the die 60.

[0046] The die 60 and the punch 62 work together to perform press-forming. The die 60 and the punch 62 are spaced apart and face each other. The die 60 has a concave shape and includes a die hole 66 into which the top of the punch 62 is inserted. The punch 62 has a convex shape.

[0047] Each of the die 60 and the punch 62 has a shape that matches the shape of the press-formed product 10. Specifically, the die 60 has a first forming portion 70a, a second forming portion 72a, and a third forming portion 74a. The punch 62 has a first forming portion 70b, a second forming portion 72b, and a third forming portion 74b. The first forming portions 70a, 70b are for forming the top plate 12. The second forming portions 72a, 72b are for forming the vertical wall 14. The third forming portions 74a, 74b are for forming the first curved surface 34 and the second curved surface 36.

[0048] The blank holder 64 works with the die 60 to hold and secure the blank 50. The blank holder 64 faces the die 60. A through-hole corresponding to the punch 62 is formed at the center of the blank holder 64.[1-3. Method of Manufacturing Press-formed Product]

[0049] Next, a method of manufacturing the press-formed product 10 is described. In the first embodiment, the following press-forming is performed to manufacture the press-formed product 10.

[0050] In this first embodiment, the press-forming (forming process described below) is performed in a single step. The inventor has confirmed through simulation analysis that wrinkles and cracks were reduced even when the press-forming is performed in a single step. However, the press-forming may be performed in multiple steps rather than a single step. In the first embodiment, the press-forming is performed by lowering the die 60. However, the punch 62 may be moved upward, or both the die 60 and the punch 62 may be displaced.

[0051] The method of manufacturing the press-formed product 10 includes a placing step in which the blank 50 is placed between the die 60 and the punch 62 spaced apart from each other, and a forming step in which the die 60 and the punch 62 are brought closer to each other (e.g. engaged) with the blank 50 placed between the die 60 and the punch 62.

[0052] First, in the placing step, the blank 50 is mounted on the upper surface of the blank holder 64, placing the blank 50 between the die 60 and the punch 62, which are spaced apart.

[0053] Subsequently in the forming step, the die 60 is lowered and brought relatively closer to the blank holder 64, thereby securing the blank 50 in a state of being held between the blank holder 64 and the die 60.

[0054] The die 60 is lowered further, whereby the die 60 and the blank holder 64 are integrally lowered with the blank 50 held therebetween. As the die 60 is lowered further, the first forming portion 70b of the punch 62 comes into contact with the blank 50. As the die 60 is further lowered, the blank 50 is pushed into the die hole 66 by the punch 62. When the die 60 reaches the bottom dead center, the top plate 12 is formed by the first forming portions 70a, 70b. At this time, the vertical wall 14 is formed by the second forming portions 72a, 72b, and the first curved surface 34 and the second curved surface 36 are formed by the third forming portions 74a, 74b. The flange 16 is formed by the blank holder 64 and the die 60.

[0055] In this manner, an intermediate product 52 shown in FIG. 5 is formed. The intermediate product 52 is formed into the press-formed product 10 by undergoing subsequent steps such as a trimming process and / or a bending process etc., in which, for example, a bent portion for reinforcing the flange 16 is formed and / or a hole for attaching the press-formed product 10 to a specified location is formed.[1-4. Difference in Radii of Curvature and Difference in Circumferential Lengths in Corner Portion]

[0056] The difference in the radii of curvature and the difference in the circumferential lengths in the corner portion 22 are described below with reference to FIGS. 3A and 3B; however, a concept of “central angle”, which is the focus of the description, is explained first.

[0057] In the press-forming, the material that forms the blank 50 is stretched such that the material in a portion corresponding to the flange 16 flows into a portion corresponding to the vertical wall 14 along the extension direction Y. This movement of the material is described conceptually by focusing on the material in a target portion. The target portion is an area of the blank 50 that forms both a part of the flange 16 and a part of the vertical wall 14 near the corner portion 22. The target portion has a substantially partial annular shape in the blank 50. In the following description, the extension direction Y is also referred to as “axial direction”.

[0058] In the press-forming, the material of the target portion of the blank 50 flows from the portion corresponding to the flange 16 into the portion corresponding to the vertical wall 14, specifically into a region having the same central angle as the target portion. The material moves within a band-shaped region along the axial direction.

[0059] In the example shown in FIG. 3A, the region having the same central angle is a portion (e.g., the first curved surface 34) obtained by stacking fan-shaped arcs, which are at a specified distance from a center point O1, along the extension direction Y at arbitrary positions in the extension direction Y. However, the region having the same central angle includes not only the fan-shaped arcs, but also a portion formed from the target portion (e.g., a continuous portion that is a combination of the second curved surface 36 and two flat surfaces 40). In other words, the region having the same central angle is a band-shaped region extending from the flange 16 to the top plate 12 in the corner portion 22. In the first embodiment, the region having the same central angle is a band-shaped region Z between two dotted lines in the corner portion 22 (see FIG. 1).

[0060] Based on the above, a region of the corner portion 22 to be considered for wrinkle reduction can be defined as the region having the same central angle, including but not limited to the curved surfaces such as the first curved surface 34 and the second curved surface 36.

[0061] Next, with reference to FIGS. 3A and 3B, the difference in the radii of curvature in the corner portion 22 is described. FIG. 3A is a plan view of the corner portion 22, which is a model assuming that the outer surface of the corner portion 22 other than the stepped surface 38 extends in the depth direction X. The difference in the radii of curvature herein is a difference between a radius of curvature R1 of the first curved surface 34 and a radius of curvature R2 of the second curved surface 36. As described above, the radius of curvature R2 of the second curved surface 36 is set to be smaller than the radius of curvature R1 of the first curved surface 34.

[0062] The difference in the circumferential lengths due to the difference in the radii of curvature in the corner portion 22 is a difference between a circumferential length L2 of the second region 32 and a circumferential length L1 of the first region 30.

[0063] As shown in FIG. 3A, the first region 30 includes the first curved surface 34 that extends and forms, in its cross-section, an arc of a fan shape having a central angle θ1 (e.g. 90 degrees) and a specified R1 (e.g. 200 mm). The center point of the first curved surface 34 in the first region 30 thus defined is indicated by O1.

[0064] In the model shown in FIG. 3A, the first curved surface 34 coincides with the first region 30. Thus, the circumferential length L1 of the first region 30 is the same as the length of the arc that can be obtained by cutting the first curved surface 34 in a plane perpendicular to the depth direction X.

[0065] As shown in FIG. 3A, the second region 32 includes the second curved surface 36 that extends and forms, in its cross-section, an arc of a fan shape having a central angle θ2 (e.g. 90 degrees) and a specified R2 (e.g. 100 mm). The center point of the second curved surface 36 in the second region 32 thus defined is indicated by 02.

[0066] The second region 32 includes the two flat surfaces 40 located on both sides of the second curved surface 36 so as to sandwich the second curved surface 36 in a circumferential direction. Thus, the second region 32 is configured as a continuous portion that includes the second curved surface 36 and the two flat surfaces 40.

[0067] Thus, the circumferential length L2 of the second region 32 is a total length of the arc and two lines obtained by cutting the second curved surface 36 and the flat surfaces 40 in a plane perpendicular to the depth direction X.

[0068] As shown in FIG. 3A, the first region 30 and the second region 32 have the same central angle θ1, and R2 is smaller than R1. Thus, the circumferential length L2 of the second region 32 is longer than the circumferential length L1 of the first region 30.

[0069] The difference in the circumferential lengths between the first region 30 and the second region 32 has been described by focusing on the corner portion 22. However, instead of focusing on the corner portion 22, it is possible to focus on the entire press-formed product 10 and to describe the difference in the circumferential lengths between regions closer to the top plate 12 and closer to the flange 16 in the vertical wall 14.

[0070] Here, the differences in radius of curvature and circumferential length have been described in a hypothetical context assuming that the outer surface of the corner portion 22 is not inclined relative to the depth direction X. However, the relationship between the first region 30 and the second region 32, with respect to the difference in the radii of curvature and the difference in the circumferential lengths, can also be applied to a case where the outer surface of the corner portion 22 is inclined relative to the depth direction X. More specifically, in the corner portion 22, the circumferential length of the region closer to the flange 16 is longer than the circumferential length of the region closer to the top plate 12, while the radius of curvature in the region closer to the flange 16 is smaller than the radius of curvature in the region closer to the top plate 12. This characteristic configuration can also be applied to a case where the outer surface of the corner portion 22 is inclined relative to the depth direction X in a similar manner.[1-5. Effects]

[0071] The inventor conducted simulations to evaluate the effectiveness of various test products, including the press-formed product 10 of the first embodiment.

[0072] First, the inventor proposed a primary test product in which a radius of curvature of the corner portion 22, as a target shape, was uniformly set to 100 mm. As a result of the simulation analysis of the primary test product, it was found that cracking could occur along a boundary between the top plate 12 and the corner portion 22, and in the vicinity of the boundary, i.e., a punch shoulder.

[0073] The inventor then proposed a secondary test product in which the radius of curvature of the corner portion 22 is uniformly set to 200 mm. As a result of the simulation analysis of the secondary test product, the possibility of cracking in the punch shoulder was reduced; however, it was found that wrinkles could occur in the second region 32 of the corner portion 22. The inventor thought that the wrinkles were caused by the material concentrating in the second region 32 when flowing from the flange 16 to the vertical wall 14, and consequently, by the excess material buckling in the second region 32.

[0074] Based on these test trials, the inventor focused on the differences in the movement of the material between the region closer to the top plate 12 (i.e., the first region 30) and the region closer to the flange 16 (i.e., the second region 32) in the corner portion 22. The inventor then considered setting different radii of curvature between the first region 30 and the second region 32. Specifically, the inventor set R1 to 200 mm in the first region 30 to reduce cracking and set R2 to 100 mm in the second region 32, as in the primary test product, to reduce wrinkling. The inventor also found that the circumferential length L2 of the second region 32 became longer than the circumferential length L1 of the first region 30 by setting the radii of curvature of the corner portion 22 as described above.

[0075] In this manner, the inventor developed the press-formed product 10 of the embodiment. As a result of the simulation analysis of the press-formed product 10, the inventor confirmed that the possibility of cracking in the punch shoulder and the formation of wrinkles in the second region 32 were both reduced.

[0076] According to the first embodiment described in detail above, the following effects can be achieved.

[0077] (1a) The press-formed product 10 of the first embodiment comprises the corner portion 22 in which the circumferential length L2 in the circumferential direction of the second region 32 is longer than the circumferential length L1 in the circumferential direction of the first region 30. Therefore, in the press-forming, the volume of the material occupying the second region 32 increases compared to that in the first region 30. Thus, the material flowing from the flange 16 to the vertical wall 14 is dispersed in the circumferential direction within the second region 32, thereby inhibiting the buckling of the material. As a result, the formation of wrinkles in the second region 32 can be inhibited.

[0078] (1b) In the press-formed product 10 of the first embodiment, the radius of curvature R1 of the first curved surface 34 is larger, and the radius of curvature R2 of the second curved surface 36 is smaller. This allows the material to flow more easily into the punch shoulder, dispersing the strain and inhibiting the formation of cracks in the punch shoulder.

[0079] (1c) In the press-formed product 10 of the first embodiment, R1 is 200 mm and R2 is 100 mm that is smaller than R1. This simultaneously inhibits both the formation of cracks in the punch shoulder and wrinkles in the second region 32 as described above.

[0080] (1d) The press-formed product 10 of the first embodiment includes the stepped surface 38 formed between the first curved surface 34 and the second curved surface 36. Thus, the length of the outer surface of the corner portion 22 in the extension direction Y is longer by the amount of the step compared to the case where the corner portion 22 does not include the stepped surface 38. This allows the material flowing from the flange 16 to the corner portion 22 to be dispersed also in the extension direction Y of the corner portion 221, thereby increasing the anti-buckling effect. As a result, the formation of wrinkles in the second region 32 can be further inhibited.

[0081] (1e) In the press-formed product 10 of the first embodiment, the length of the outer surface of the corner portion 22 in the extension direction Y (i.e., the length between the top plate curvature 18 and the flange 16 along the extension direction Y) is the longest when the circumferential centers of the corner portion 22 are connected along the extension direction Y. That is, the length of the outer surface of the corner portion 22 is the longest at the position shown in the cross-section of FIG. 2B. This effectively inhibits the formation of wrinkles in the center portion of the second region 32 in the circumferential direction, where wrinkles are most likely to occur.

[0082] (1f) In general, in deep drawing, to achieve a height in the depth direction X, it is necessary to divide the forming process into two or more steps to reduce wrinkles and cracks. In the method of manufacturing the press-formed product 10 of the first embodiment, the press-formed product 10 with reduced wrinkles and cracks can be formed in a single step.[1-6. Correspondence between Terms]

[0083] The top plate 12 in the first embodiment corresponds to an example of the plate-shaped portion in the present disclosure, and the vertical wall 14 corresponds to an example of the wall in the present disclosure. The die 60 in this embodiment corresponds to an example of the first die in the present disclosure, and the punch 62 corresponds to an example of the second die in the present disclosure.2. Second Embodiment[2-1. Configuration of Press-formed Product]

[0084] In the second embodiment, descriptions of elements same as those in the first embodiment are omitted by reference to the same numbers and names, while elements different from the first embodiment are described in detail.

[0085] The press-formed product 10 of the first embodiment includes one stepped surface 38. In contrast, a press-formed product 100 of the second embodiment shown in FIGS. 6A and 6B differs from the first embodiment in that the corner portion 22 includes a plurality of stepped surfaces 106.

[0086] In the second embodiment, the second region 32 is divided into two sub-regions arranged side by side along the extension direction Y. Thus, the corner portion 22 of the second embodiment is divided into three sub-regions arranged side by side along the extension direction Y. The stepped surfaces 38 and 106 are respectively formed between adjacent sub-regions of the three sub-regions.

[0087] In the second embodiment, the second region 32 is divided into a second A region 102 closer to the top plate 12 and a second B region 104 closer to the flange 16. The second A region 102 is located adjacent to the first region 30 with the stepped surface 38 interposed therebetween along the extension direction Y, and the second B region 104 is connected to the flange 16. The stepped surface 106 is formed between the second A region 102 and the second B region 104.

[0088] The second A region 102 and the second B region 104 include a second A curved surface 108 and a second B curved surface 110, respectively, similar to the first region 30 and the second region 32 in the first embodiment. The radius of curvature of the second B curved surface 110 is smaller than the radius of curvature of the second A curved surface 108. In addition, the second B curved surface 110 is located radially outside the second A curved surface 108.

[0089] Thus, the relationship between the second A region 102 and the second B region 104 of the second embodiment has similar features of the relationship between the first region 30 and the second region 32 of the first embodiment. That is, the radius of curvature of the region (the second B region 104) closer to the flange 16 in the second region 32 is smaller than a radius of curvature of the region (the second A region 102) closer to the top plate 12.

[0090] Thus, the relationship between the first region 30 and the second region 32 of the first embodiment with respect to the difference in the radii of curvature and the difference in the circumferential lengths can be applied to the relationship between the second A region 102 and the second B region 104 of the second embodiment with respect to the difference in the radii of curvature and the difference in the circumferential lengths. Thus, the circumferential length of the second B region 104 is longer than the circumferential length of second A region 102.

[0091] In the second embodiment, the second region 32 is divided into the two sub-regions arranged side by side along the extension direction Y. However, the second region 32 may be divided into three or more sub-regions. In this case, among the two sub-regions of the second region 32 (i.e., the second A region 102 and the second B region 104), the sub-region closer to the top plate 12 (the second A region 102) may be further divided into two subdivisions, and / or the sub-region closer to the flange 16 (the second B region 104) may be further divided into two subdivisions. These subdivisions have the feature similar to the relationship between the first region 30 and the second region 32 of the first embodiment. That is, among the subdivisions, the radius of curvature of a subdivision closer to the flange 16 is smaller than the radius of curvature of a subdivision closer to the top plate 12. Thus, among the subdivisions, the circumferential length of the subdivision closer to the flange 16 can be formed longer than the circumferential length of the subdivision closer to the top plate 12.[2-2. Effects]

[0092] (2a) In the press-formed product 100 of the second embodiment, the number of stepped surfaces in the corner portion 22 is greater than that in the first embodiment. Thus, the length of the outer surface of the corner portion 22 in the extension direction Y is longer than the length of the outer surface of the corner portion 22 in the first embodiment by the amount of the stepped surfaces. This facilitates the dispersion of the material flowing from the flange 16 into the corner portion 22, which further enhances the anti-buckling effect achieved by the material. As a result, the formation of wrinkles can be further reduced in the region of the curved surface 24 closer to the flange 16.

[0093] (2b) In the press-formed product 100 of the second embodiment, the regions closer to the flange 16 have longer circumferential lengths as in the first embodiment. Thus, the effects similar to those described in (1a) to (1f) above can be achieved.3. Third Embodiment[3-1. Configuration of Press-formed Product]

[0094] In the third embodiment, descriptions of elements same as those in the first and second embodiments are omitted by reference to the same numbers and names, while elements different therefrom are described in detail.

[0095] In the press-formed products 10 and 100 of the first and second embodiments, the first region 30 and the second region 32 are arranged side by side with the stepped surface 38 interposed therebetween along the extension direction Y in the corner portion 22 as shown in FIGS. 1 and 6. The second A region 102 and the second B region 104 are arranged side by side with the stepped surface 106 interposed therebetween. That is, in the press-formed products 10 and 100, the corner portion 22 has an uneven inclined surface with at least one stepped surface. In addition, in the press-formed products 10 and 100 of the first and second embodiments, the radius of curvature of each region in the curved surface 24 is constant at any position along the depth direction X.

[0096] In contrast, as shown in FIG. 7, in the press-formed product 200 of the third embodiment, the corner portion 22 does not include the stepped surfaces 38 and 106. The inclined surface of the corner portion 22 is flat along the extension direction Y.

[0097] In addition, in the press-formed product 200 of the third embodiment, the radius of curvature of the curved surface 24 gradually decreases from the top plate 12 to the flange 16. That is, the radius of curvature of the curved surface 24 continuously varies to become smaller from the top plate 12 to the flange 16 along the depth direction X. Thus, the curved surface 24 has a tapered shape that tapers toward the flange 16. For example, the curved surface 24 may be a part of a conical surface having an apex in the vicinity of the flange 16.

[0098] The third embodiment also has the feature that the radius of curvature of a region closer to the flange 16 is smaller than the radius of curvature of a region closer to the top plate 12 in the corner portion 22, as in the first embodiment. Therefore, the relationship between the first region 30 and the second region 32 of the first embodiment with respect to the difference in the radii of curvature and the difference in the circumferential lengths can be applied to the corner portion 22 of the third embodiment that does not include the stepped surfaces 38 and 106. Thus, in the corner portion 22, the circumferential length of the region closer to the flange 16 is longer than the circumferential length of the region closer to the top plate 12.[3-2. Effects]

[0099] In the press-formed product 200 of the third embodiment, the circumferential length of the region closer to the flange 16 is longer than the circumferential length of the region closer to the top plate 12 in the corner portion 22, as in the first and second embodiments. Therefore, the effects of (1a) to (1c), and (1e) to (1f) can be achieved.4. Other Embodiments

[0100] The embodiments of the present disclosure have been described; however, it is to be understood that the present disclosure is not limited to the above-described embodiments, and that the present disclosure can be embodied in various forms.

[0101] A function of a single component in the aforementioned embodiments may be distributed to a plurality of components, and functions of a plurality of components may be achieved by a single component. A part of the configurations of the aforementioned embodiments may be omitted. At least a part of the configurations of the aforementioned embodiments may be added to or replaced with the configuration of another embodiment.

Claims

1. A press-formed product comprising:a plate-shaped portion;a wall having a plate shape and extending from the plate-shaped portion in a direction that intersects the plate-shaped portion; anda flange having a plate shape and extending from an edge of the wall,wherein the wall includes at least one curved surface having an arcuate cross-sectional shape that bulges radially outward in a cross-section taken along the plate-shaped portion,wherein the at least one curved surface includes a first curved surface and a second curved surface that is closer to the flange than the first curved surface, andwherein a radius of curvature of the second curved surface in the cross-section is smaller than a radius of curvature of the first curved surface in the cross-section.

2. The press-formed product according to claim 1,wherein the wall further includes a stepped surface formed between the first curved surface and the second curved surface, andwherein the second curved surface is located radially outside the first curved surface.

3. The press-formed product according to claim 2,wherein the stepped surface includes a plurality of stepped surfaces and the wall includes the plurality of stepped surfaces.

4. The press-formed product according to claim 1,wherein the press-formed product is a body component of an automobile.

5. The press-formed product according to claim 1,wherein the press-formed product has a bag shape with a recess,wherein the at least one curved surface includes a plurality of curved surfaces and the wall includes the plurality of curved surfaces, andwherein the wall further includes a flat portion having a flat plate shape and connecting the plurality of curved surfaces.

6. A method of manufacturing a press-formed product for obtaining a press-formed product having a specified target shape using a first die and a second die,the press-formed product comprising:a plate-shaped portion;a wall having a plate shape and extending from the plate-shaped portion in a direction that intersects the plate-shaped portion; anda flange having a plate shape and extending from an edge of the wall,wherein the wall includes at least one curved surface having an arcuate cross-sectional shape that bulges radially outward in a cross-section taken along the plate-shaped portion,wherein the at least one curved surface includes a first curved surface and a second curved surface that is closer to the flange than the first curved surface, andwherein a radius of curvature of the second curved surface in the cross-section is smaller than a radius of curvature of the first curved surface in the cross-section,each of the first die and the second die comprising:a first forming portion for forming the plate-shaped portion;a second forming portion for forming the wall; anda third forming portion for forming the at least one curved surface,the method comprising:placing a blank between the first die and the second die that are spaced apart from each other; andbringing the first die and the second die closer to each other with the blank placed between the first die and the second die.

7. The method of manufacturing the press-formed product according to claim 6,wherein the wall further includes a stepped surface formed between the first curved surface and the second curved surface, andwherein the second curved surface is located radially outside the first curved surface.

8. The method of manufacturing the press-formed product according to claim 7,wherein the stepped surface includes a plurality of stepped surfaces and the wall includes the plurality of stepped surfaces.

9. The method of manufacturing the press-formed product according to claim 6, wherein the press-formed product is a body component of an automobile.

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