Method for manufacturing press-formed product

Abstract

To provide a method of manufacturing a press molding which can suppress a spring back when forming a bent projection strip part.SOLUTION: One embodiment of this disclosure is a method of manufacturing a press molding for obtaining a press molding having a projection strip part provided with a concave bead and keeping the projection strip part bent so that the top plate may expand in a projecting direction from a lateral side view. The method of manufacturing a press molding includes a step of pre-molding an intermediate molding having a pre-projection part and a step of mainly molding a press molding by pressing the intermediate molding. The pre-molding step enables the formation of an expansion part expanding in the projecting direction of the pre-projection part in the top plate of the pre-projection part and keeping an apex arranged outside in the pre-projection strip part in a width direction from a concave bead scheduled region working as the concave bead of the press molding.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a press-formed product.

Background Art

[0002] A method for manufacturing a press-formed product having a convex strip portion curved in the longitudinal direction by press working (i.e., drawing) of a metal plate is known (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above press-formed product, since the length in the longitudinal direction of the inner region of the curvature in the convex strip portion is smaller than the length in the longitudinal direction of the outer region of the curvature, tensile stress is generated on the inner side of the curvature during press working. Therefore, when the press-formed product is taken out of the die, springback occurs in which the inner side of the curvature extends due to residual stress. As a result, the dimensional accuracy of the product decreases.

[0005] One aspect of the present disclosure aims to provide a method for manufacturing a press-formed product capable of suppressing springback when forming a curved convex strip portion.

Means for Solving the Problems

[0006] One aspect of the present disclosure is a method for manufacturing a press-formed product for obtaining a press-formed product having a convex rib portion provided with a concave bead along the longitudinal direction on a top plate, and the convex rib portion is curved such that the top plate bulges in the protruding direction of the convex rib portion when viewed from the side of the convex rib portion. The method for manufacturing a press-formed product includes a step of pre-forming an intermediate formed product having a preliminary convex rib portion by pressing a flat blank material, and a step of final-forming the press-formed product by pressing the intermediate formed product.

[0007] In the pre-forming step, at least one bulging portion is formed on the top plate of the preliminary convex rib portion so as to bulge in the protruding direction of the preliminary convex rib portion, and the apex is disposed outside the width direction of the preliminary convex rib portion than the planned concave bead region that will become the concave bead of the press-formed product.

[0008] According to such a configuration, the bulging portion having an apex outside the planned concave bead region on the top plate of the preliminary convex rib portion is crushed in the final forming, so that the compressive stress in the concave bead is dispersed. As a result, the residual stress in the convex rib portion is reduced, and thus the springback of the press-formed product is suppressed.

[0009] In one aspect of the present disclosure, in the pre-forming step, the first bulging portion and the second bulging portion may be formed as at least one bulging portion. The apex of the first bulging portion and the apex of the second bulging portion may be arranged so as to sandwich the planned concave bead region in the width direction of the preliminary convex rib portion. According to such a configuration, since the compressive stress is dispersed on both sides of the concave bead in the final forming, the suppression effect of the springback of the press-formed product is promoted.

[0010] In one aspect of the present disclosure, in the pre-forming step, an apex that bulges in the protruding direction of the preliminary convex rib portion may be formed only in the region outside the width direction of the preliminary convex rib portion than the planned concave bead region in the preliminary convex rib portion. According to such a configuration, the concentration of the compressive stress on the concave bead can be suppressed, and thus the suppression effect of the springback of the press-formed product is promoted.

[0011] In one aspect of the present disclosure, in the preforming step, the concave bead planned area of the preliminary rib portion may be bulged in the protruding direction of the preliminary rib portion rather than the concave bead of the press-formed product. According to such a configuration, an increase in the perimeter of the preliminary rib portion can be suppressed, so that the difference between the perimeter of the preliminary rib portion and the perimeter of the rib portion in the press-formed product is reduced. As a result, the dimensional accuracy of the press-formed product can be improved.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments to which the present disclosure is applied will be described with reference to the drawings. [1. First Embodiment] [1-1. Configuration] <Press-formed product> The press-formed product 1 shown in FIGS. 1A, 1B, and 1C is a metal molded product obtained by press-working a blank material. The press-formed product 1 has a rib portion 2, a first flange portion 3, a second flange portion 4, and a concave bead 5.

[0014] The rib portion 2 is formed along the longitudinal direction of the press-formed product 1. The cross-section perpendicular to the longitudinal direction of the rib portion 2 is U-shaped. The rib portion 2 has a top plate 21, a first side plate 22, and a second side plate 23.

[0015] The top plate 21 is a strip-shaped part extending along the longitudinal direction of the press-formed product 1. As shown in FIG. 1B, the top plate 21 bulges in the protruding direction of the rib portion 2 when viewed from the side of the rib portion 2. That is, the rib portion 2 is curved so that the top plate 21 bulges when viewed from the side of the rib portion 2, and the top plate 21 is located on the outer side of the bending of the rib portion 2 with respect to the first flange portion 3 and the second flange portion 4.

[0016] The first side plate 22 and the second side plate 23 are respectively connected to two ends in the width direction of the top plate 21 (that is, the direction perpendicular to the longitudinal direction) and face each other. The plate surfaces of the first side plate 22 and the second side plate 23 intersect the plate surface of the top plate 21.

[0017] The first flange portion 3 and the second flange portion 4 are respectively arranged continuously with the rib portion 2 on the outer side in the width direction of the rib portion 2 and constitute the end portions in the width direction of the press-formed product 1. Specifically, the first flange portion 3 extends from the end of the first side plate 22 of the rib portion 2 to the side opposite to the rib portion 2. The second flange portion 4 extends from the end of the second side plate 23 of the rib portion 2 to the side opposite to the rib portion 2.

[0018] The concave bead 5 is a groove provided along the longitudinal direction of the rib portion 2 on the top plate 21 of the rib portion 2. The concave bead 5 is recessed in the direction opposite to the protruding direction of the rib portion 2 (that is, toward the first flange portion 3 and the second flange portion 4). The concave bead 5 is arranged at a position away from each of the first side plate 22 and the second side plate 23 in the width direction of the rib portion 2.

[0019] Although the use of the press-formed product 1 is not limited, the press-formed product 1 is suitably used as a member (for example, a front pillar, a center pillar, etc.) constituting the skeleton of an automobile. By using the press-formed product 1, springback can be suppressed without restricting the material in the skeleton of an automobile that requires high strength and dimensional accuracy.

[0020] <Manufacturing method of press-formed product> As shown in FIG. 2, the manufacturing method of the press-formed product of the present embodiment includes a preliminary forming step S10 and a main forming step S20.

[0021] <Preliminary forming step> In this step, the flat blank material is sandwiched between dies in the plate thickness direction and pressed to preliminarily form the intermediate formed product 101 shown in FIG. 3A. Note that the intermediate formed product 101 may be formed by pressing several times.

[0022] The intermediate formed product 101 has a preliminary rib portion 102, a first flange portion 3, and a second flange portion 4. The preliminary rib portion 102 is a portion that is formed into the rib portion 2 in the main forming step S20. The preliminary rib portion 102 has a top plate 121, a first side wall 122, and a second side wall 123.

[0023] The top plate 121 has a concave bead planned region R that becomes the concave bead 5 of the press-formed product 1 in the main forming step S20. In addition, a first bulging portion 124 and a second bulging portion 125 are provided on the top plate 121.

[0024] The first bulging portion 124 and the second bulging portion 125 bulge outward in the protruding direction of the preliminary rib portion 102 (that is, the outer side) on the top plate 121, respectively. The first bulging portion 124 and the second bulging portion 125 are arranged side by side in the width direction of the preliminary rib portion 102.

[0025] Also, as shown in FIG. 3B, the first bulging portion 124 is divided into a plurality of portions in the longitudinal direction of the preliminary rib portion 102. The same applies to the second bulging portion 125. However, the first bulging portion 124 and the second bulging portion 125 may be continuously provided over the entire concave bead planned region R.

[0026] The vertex P1 of the first bulging portion 124 is disposed in a portion closer to the first side wall 122 in the region outside the width direction of the preliminary convex strip portion 102 than the concave bead planned region R. The vertex P2 of the second bulging portion 125 is disposed in a portion closer to the second side wall 123 in the region outside the width direction of the preliminary convex strip portion 102 than the concave bead planned region R.

[0027] In the present embodiment, the vertex P1 of the first bulging portion 124 is a point on the ridge line of the first bulging portion 124 extending along the longitudinal direction of the preliminary convex strip portion 102. Further, the vertex P2 of the second bulging portion 125 is a point on the ridge line of the second bulging portion 125 extending along the longitudinal direction of the preliminary convex strip portion 102. The ridge line of the first bulging portion 124 and the ridge line of the second bulging portion 125 are each located outside the width direction of the preliminary convex strip portion 102 than the concave bead planned region R.

[0028] The vertex P1 of the first bulging portion 124 and the vertex P2 of the second bulging portion 125 are arranged so as to sandwich the concave bead planned region R in the width direction of the preliminary convex strip portion 102. In the present embodiment, the heights (i.e., the bulging amounts) of the vertex P1 of the first bulging portion 124 and the vertex P2 of the second bulging portion 125 from the top plate 21 in the press-formed product 1 are the same.

[0029] A part of the first bulging portion 124 and a part of the second bulging portion 125 are provided in the concave bead planned region R. Specifically, the connecting portion (i.e., the valley) between the first bulging portion 124 and the second bulging portion 125 exists in the concave bead planned region R. Therefore, the concave bead planned region R bulges outside the preliminary convex strip portion 102 than the concave bead 5 in the press-formed product 1. On the other hand, there is no vertex of the bulge in the concave bead planned region R.

[0030] In this way, in this step, the first bulging portion 124 and the second bulging portion 125 are formed as a part of the top plate 121 of the preliminary rib portion 102. Also, in this step, no vertex that bulges in the protruding direction of the preliminary rib portion 102 is formed within the concave bead planned region R. That is, in this step, vertices that bulge in the protruding direction of the preliminary rib portion 102 are formed only in the region outside the width direction of the preliminary rib portion 102 with respect to the concave bead planned region R of the preliminary rib portion 102. Further, in this step, the concave bead planned region R of the preliminary rib portion 102 is bulged in the protruding direction of the preliminary rib portion 102 more than the concave bead 5 of the press-formed product 1.

[0031] <This forming step> In this step, the press-formed product 1 is finally formed by further sandwiching the intermediate formed product 101 with a die and pressing it. Specifically, by pressing the preliminary rib portion 102 so as to crush the first bulging portion 124 and the second bulging portion 125, the rib portion 2 and the concave bead 5 are formed.

[0032] The top plate 121 of the preliminary rib portion 102 is formed into the top plate 21 provided with the concave bead 5 at the center in the width direction while dispersing the compressive stress when the first bulging portion 124 and the second bulging portion 125 are crushed.

[0033] [1-2. Effect] According to the embodiment described in detail above, the following effects can be obtained. (1a) By crushing the bulging portions 124 and 125 having vertices outside the concave bead planned region R on the top plate 121 of the preliminary rib portion 102 in the final forming, the compressive stress in the concave bead 5 is dispersed. As a result, the residual stress in the rib portion 2 is reduced, so that the springback of the press-formed product 1 is suppressed.

[0034] (1b) By arranging the vertex P1 of the first bulging portion 124 and the vertex P2 of the second bulging portion 125 so as to sandwich the concave bead planned region R, the compressive stress is dispersed on both sides of the concave bead 5 in the final forming, so that the suppression effect of the springback of the press-formed product 1 is promoted.

[0035] (1c) By not forming a vertex that bulges in the protruding direction of the preliminary rib portion 102 within the planned area R of the concave bead, the concentration of compressive stress on the concave bead 5 can be suppressed, so that the springback suppression effect of the press-formed product 1 is promoted.

[0036] (1d) Since an increase in the perimeter of the preliminary rib portion 102 can be suppressed, the difference between the perimeter of the preliminary rib portion 102 and the perimeter of the rib portion 2 in the press-formed product 1 is reduced. As a result, the dimensional accuracy of the press-formed product 1 can be improved.

[0037] [2. Other Embodiments] As described above, the embodiments of the present disclosure have been described. Needless to say, the present disclosure can take various forms without being limited to the above embodiments.

[0038] (2a) In the method for manufacturing a press-formed product according to the above embodiment, it is not necessarily required to form two bulging portions in the preliminary forming step. For example, as shown in FIGS. 4A and 4B, only one bulging portion 124 may be formed in the preliminary forming step. That is, only one vertex P1 may be provided outside the planned area R of the concave bead.

[0039] In addition, in FIG. 4B, the vertex P1 of the first bulging portion 124 is located at the center in the width direction of the top plate 121. However, since the planned area R of the concave bead is shifted from the center in the width direction, the vertex P1 is not arranged in the planned area R of the concave bead.

[0040] (2b) In the method for manufacturing a press-formed product according to the above embodiment, a vertex that bulges in the protruding direction of the preliminary rib portion may be formed within the planned area of the concave bead in the preliminary forming step. For example, as shown in FIG. 5A, in the preliminary forming step, a third bulging portion 126 in which the vertex P3 is arranged in the planned area R of the concave bead may be formed.

[0041] (2c) In the method for manufacturing the press-formed product of the above-described embodiment, in the preliminary forming step, it is not necessarily required to bulge the planned concave bead region in the protruding direction of the preliminary protruding strip portion more than the concave bead of the press-formed product. For example, as shown in FIG. 5B, the planned concave bead region R may be formed in the same shape as the concave bead 5 in the preliminary forming step.

[0042] (2d) The functions of one component in the above-described embodiment may be distributed among a plurality of components, or the functions of a plurality of components may be integrated into one component. Also, a part of the configuration of the above-described embodiment may be omitted. Further, at least a part of the configuration of the above-described embodiment may be added to, replaced with, etc., the configuration of other above-described embodiments. Note that all aspects included in the technical idea specified from the language described in the claims are embodiments of the present disclosure.

Explanation of Reference Numerals

[0043] 1... Press-formed product, 2... Protruding strip portion, 3... First flange portion, 4... Second flange portion, 5... Concave bead, 21... Top plate, 22... First side plate, 23... Second side plate, 101... Intermediate formed product, 102... Preliminary protruding strip portion, 121... Top plate, 122... First side wall, 123... Second side wall, 124... First bulging portion, 125... Second bulging portion, 126... Third bulging portion, P1, P2, P3... Vertices, R... Planned concave bead region.

Claims

1. A method for manufacturing a press-formed product, the press-formed product having a rib portion provided with a concave bead along the longitudinal direction on the top plate, and the rib portion being curved such that the top plate bulges in the protruding direction of the rib portion when viewed from the side of the rib portion, comprising: a step of pre-forming an intermediate formed product having a preliminary rib portion by pressing a flat blank material; a step of main-forming the press-formed product by pressing the intermediate formed product; and comprising: In the step of pre-forming, at least one bulging portion is formed on the top plate of the preliminary rib portion, bulging in the protruding direction of the preliminary rib portion, and having a vertex disposed outside the width direction of the preliminary rib portion than a concave bead planned region that will become the concave bead of the press-formed product. A method for manufacturing a press-formed product.

2. The method for manufacturing a press-formed product according to Claim 1, wherein: in the step of pre-forming, a first bulging portion and a second bulging portion are formed as the at least one bulging portion; and the vertex of the first bulging portion and the vertex of the second bulging portion are arranged so as to sandwich the concave bead planned region in the width direction of the preliminary rib portion. A method for manufacturing a press-formed product.

3. The method for manufacturing a press-formed product according to Claim 1 or Claim 2, wherein: in the step of pre-forming, a vertex that bulges in the protruding direction of the preliminary rib portion is formed only in a region of the preliminary rib portion that is outside the width direction of the preliminary rib portion than the concave bead planned region. A method for manufacturing a press-formed product.

4. The method for manufacturing a press-formed product according to Claim 1 or Claim 2, wherein: in the step of pre-forming, the concave bead planned region of the preliminary rib portion is bulged in the protruding direction of the preliminary rib portion more than the concave bead of the press-formed product. A method for manufacturing a press-formed product.

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