JP2011206789A - Press forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a press forming method by which deformation of a formed parts in the mouth opening direction is suppressed after releasing pressurization.SOLUTION: The press forming method is provided for press-forming the formed parts 1 having a top surface portion 2 which is bent at a predetermined curvature in the longitudinal direction and two side surface portions 3 which are extended toward the inside of the bend from both longitudinal-direction ends of the top surface portion 2. The method has a preforming step and a normal forming step. In the preforming step, the preformed parts 31 is press-formed, the preformed parts 31 having a top surface portion 32 which is bent at a curvature different from the above predetermined curvature in the longitudinal direction and two side portions 33 which are extended toward the inside of the bend from both longitudinal-direction ends of the top surface portion 32 and which have an angle formed with the top surface portion 32 larger than that of the formed parts 1. In the normal forming step, after making the top surface portion 32 of the preformed parts 31 deform in a direction approaching the predetermined curvature by pressing, and in that state, press forming is performed so that the angle formed by the top surface portion 32 and the side portions 33 is made smaller than that of the preformed parts 31.

Description

  The present invention relates to a press molding method for molding a molded part having a top surface portion curved in the longitudinal direction and two side surface portions extending inwardly from both ends along the longitudinal direction of the top surface portion.

  2. Description of the Related Art Conventionally, press-molded parts used for automobile parts and the like have a top surface portion that is curved in the longitudinal direction and two side surface portions that extend inward from both ends along the longitudinal direction of the top surface portion. (For example, refer to Patent Document 1). As such a molded part, there is one in which a flange portion is provided at the tip of the side surface portion.

JP 2007-21568 A

  However, when a molded part as described above is press-molded, when the molded part is released from the mold, the bending angle of the connecting portion (corner portion) between the side surface portion and the top surface portion increases due to elastic recovery (spring back). It may be deformed and a mouth opening may occur. Further, in the case of a molded part having a flange portion, after releasing the pressure, the bending angle of the corner portion is increased by the spring back, and the side surface portion is warped by the spring back, thereby opening the mouth. There is a case. In addition, since the top surface portion of the molded part is curved, the top surface portion may be deformed in a direction in which the curvature is reduced by the spring back after the pressure is released. When a high-strength metal plate such as a high-tensile steel plate (high-tensile material) is used as the material of the molded part, the spring back is large, and the above-described dimensional accuracy defects are more likely to occur.

  Then, an object of this invention is to provide the press molding method which can suppress that a shaping | molding component deform | transforms in an opening direction after pressure cancellation.

Means for Solving the Problems and Effects of the Invention

  A press molding method according to a first aspect of the present invention is a molding having a top surface portion curved with a predetermined curvature in the longitudinal direction and two side surface portions extending from both ends along the longitudinal direction of the top surface portion toward the inside of the curve. A press molding method for press-molding a component, the top surface portion being curved with a curvature different from the predetermined curvature in a longitudinal direction, extending from both ends along the longitudinal direction of the top surface portion toward the inside of the curve, and A preforming step of press-molding a preformed part having two side parts with an angle formed with the top surface part larger than that of the molded part, and a direction in which the top surface part of the preformed part is pressed to approach the predetermined curvature And a main forming step of press forming so that an angle formed between the top surface portion and the side surface portion is smaller than that of the preformed part.

According to this configuration, when the molded part is released from the mold after the molded part is press-molded in the main molding process, the molded part is deformed in the opening direction (the direction in which the distance between the tips of the side surface portions increases). Can be suppressed.
In addition, since the top surface is pressed twice in the pre-molding process and the main molding process, the top surface of the molded part is deformed in a direction in which the curvature becomes smaller after the pressure is released compared to the case where the molded part is molded once. Can be suppressed.

  The press molding method of the second invention is characterized in that, in the first invention, the top surface portion of the preformed part is curved with a curvature larger than the predetermined curvature.

According to this configuration, in the main forming step, when the top surface portion of the preformed part is deformed in a direction approaching the predetermined curvature, that is, in a direction in which the curvature decreases, the side surface portion is stretched in the longitudinal direction of the top surface portion, so that the tension is applied. Stress is about to occur. Since the side portion is not pressed at this point, the side portion is deformed in the mouth closing direction so as to relieve the tensile stress. At this time, the deformation of the side surface portion remains even after the side surface portion is press-molded, and acts in the closing direction of the mouth, so that it is possible to prevent the molded part from being deformed in the opening direction after releasing the pressure.
Further, in the preforming step, the top surface portion is formed to have a curvature larger than the curvature of the top surface portion of the molded part, and in this forming step, the top surface portion is deformed in a direction in which the curvature decreases, so the curvature decreases. Springback of the top surface portion 2 in the direction of decreasing can be reduced. Therefore, it can suppress that the top | upper surface part of a molded component deform | transforms in the direction in which a curvature becomes small after pressure cancellation.

In the press molding method of the third invention, in the second invention, the curvature of the top surface portion at the time of pressing in the preforming step is ρ ₁ [1 / mm], and the angle formed by the top surface portion and the side surface portion. Is θ ₁ [°], the curvature of the top surface portion during pressing in the main forming step is ρ ₂ [1 / mm], and the angle between the top surface portion and the side surface portion is θ ₂ [°]. The following formulas (1) to (3) are satisfied.
1 <ρ ₁ / ρ ₂ ≦ 1.75 (1)
ρ ₁ / ρ ₂ ≦ 0.15 × (θ ₁ −θ ₂ ) −4.55 (2)
θ ₁ −θ ₂ ≦ 52 (3)

  According to this configuration, it is possible to prevent the molded part from being wrinkled and to more reliably suppress the molded part from being deformed in the opening direction after the pressure is released. Moreover, it can suppress more reliably that the top | upper surface part of a molded component deform | transforms in the direction where a curvature becomes small after pressure cancellation.

  The press molding method according to a fourth aspect of the present invention is characterized in that, in the first aspect, the top surface portion of the preformed part is curved with a curvature smaller than the predetermined curvature.

According to this configuration, when the molded part is released from the mold after press molding in the main molding process, the molded part is molded with a curvature smaller than a predetermined curvature (the curvature of the top surface of the molded part) in the preliminary molding process. The deformed jar remains. Due to this deformation wrinkle and the spring back by the press in the main forming step, the top surface portion of the molded part is deformed in a direction in which the curvature becomes smaller. Thereby, since the side surface portion is extended in the longitudinal direction of the top surface portion, a tensile stress tends to be generated on the side surface portion. The side portion is deformed in the mouth closing direction so as to relieve the tensile stress. Therefore, it is possible to suppress the molded part from being deformed in the opening direction after releasing the pressure.
In addition, as described above, after the pressure is released, the top surface portion of the molded part is deformed in a direction in which the curvature decreases, but the amount of deformation of the top surface portion is due to the spring back when the molded component is molded once. Small compared to the amount of deformation.

The press molding method of the fifth invention is the press molding method according to the fourth invention, wherein the curvature of the top surface portion is ρ ₁ [1 / mm] at the time of pressing in the preforming step, and the angle formed by the top surface portion and the side surface portion. Is θ ₁ [°], the curvature of the top surface portion during pressing in the main forming step is ρ ₂ [1 / mm], and the angle between the top surface portion and the side surface portion is θ ₂ [°]. The following formulas (1) to (4) are satisfied.
ρ ₁ / ρ ₂ <1 (1)
ρ ₁ / ρ ₂ ≦ 0.06 × (θ ₁ −θ ₂ ) −1.22 (2)
ρ ₁ / ρ ₂ ≧ 0.012 × (θ ₁ −θ ₂ ) +0.136 (3)
θ ₁ −θ ₂ ≦ 47 (4)

  According to this configuration, it is possible to prevent the molded part from being wrinkled and to more reliably suppress the molded part from being deformed in the opening direction after the pressure is released.

  In the press molding method of the sixth invention, in any one of the first to fifth inventions, the molded part has a flange portion extending from a tip portion of the side surface portion, and in the preliminary molding step, The preformed part is press-molded so that a flange portion is formed.

  According to this configuration, a molded part having a flange portion can be obtained.

It is a figure which shows the press molding process of 1st Embodiment, (a) is a perspective view of a preforming part, (b) and (c) are just after pressing only the top | upper surface part of a preforming part in this molding process. (D) is a perspective view of this molded part. It is a figure which shows the preforming die used with the press molding method of 1st Embodiment, Comprising: (a) is A2-A2 sectional view taken on the line of (b), (b) is the A1-A1 line of (a). It is sectional drawing. It is a figure which shows this shaping | molding die used with the press molding method of 1st Embodiment, Comprising: (a) is B2-B2 sectional view taken on the line of (b), (b) is the B1-B1 line of (a). It is sectional drawing. It is a figure which shows the press molding process of 2nd Embodiment, (a) is a perspective view of a preformed part, (b) is a perspective view of the molded part immediately after releasing pressure in this molding process, (C) is a perspective view of the final shaped molded part. It is a figure which shows the preforming die used with the press molding method of 2nd Embodiment, Comprising: (a) is C2-C2 sectional view taken on the line of (b), (b) is the C1-C1 line of (a). It is sectional drawing. It is a figure which shows this shaping | molding die used with the press molding method of 2nd Embodiment, Comprising: (a) is D2-D2 sectional view taken on the line of (b), (b) is D1-D1 line of (a). It is sectional drawing. (A) is sectional drawing at the time of the press of the preforming component of the example of this invention, (b) is sectional drawing at the time of the press of the shaping | molding component of the example of this invention. It is a figure which shows the state after the pressure release of the molded component of the example of this invention, Comprising: (a) is a figure of a longitudinal direction edge part, (b) is a side view. It is a graph which shows the relationship between curvature ratio (rho) ₁ / (rho) ₂ and an angle difference ((theta) _1- (theta) ₂ ).

<First Embodiment>
The first embodiment of the present invention will be described below.
The press molding method of the present embodiment is a method for press molding the molded part 1 shown in FIG. In the press molding method of this embodiment, the preforming part 31 shown in FIG. 1A is press-molded from the metal plate W using the preforming mold 10 (preliminary molding step), and then the preforming part 31 is formed. The molded part 1 is formed by press molding using the main molding die 20 shown in FIG. 3 (main molding step). As the metal plate W, a high-tensile steel plate (high-tensile material) is used, but a steel plate, an aluminum plate, or the like may be used. 2 and 3 omit cross-sectional hatching.

First, the molded part 1 will be described.
As shown in FIG. 1 (d), the molded part 1 is a long member having a hat-shaped cross section, and includes a top surface portion 2, two side surface portions 3, and two flange portions 4. Yes. The molded part 1 is formed symmetrically.

Top surface portion 2 is curved in the longitudinal direction with a curvature kappa _1. The cross-sectional shape orthogonal to the longitudinal direction of the top surface portion 2 is flat, and the width in the direction orthogonal to the longitudinal direction of the top surface portion 2 is constant. The length in the longitudinal direction (length along the bending direction) of the top surface portion 2 is, for example, 900 mm. In this case, the curvature κ ₁ is, for example, 2.8 × 10 ^{−4 to} 2.9 × 10 ^{−. 4} [1 / mm].

The two side surface portions 3 extend from both ends along the longitudinal direction of the top surface portion 2 to the inside of the curve (downward in FIG. 3D). The side part 3 is substantially flat. The height of the side surface portion (the length in the curved radial direction) is constant. An angle α ₁ formed by the side surface portion 3 and the top surface portion 2 is, for example, 97 to 99 °.

The two flange portions 4 extend outward from the tips of the two side surface portions 3 (on the side opposite to the top surface portion 2). The flange portion 4 is curved substantially concentrically with the top surface portion 2. Flange 4 and the side surface portion 3 and the angle beta ₁ formed by is, for example, 97 to 99 °.

Next, the preforming mold 10 will be described.
As shown in FIG. 2A, the preforming die 10 is composed of a lower die punch 11, an upper die pad 12, and two upper die dies 13.

  The lower die punch 11 has a top surface molding surface 11a, two side surface molding surfaces 11b, and two flange portion molding surfaces 11c on the upper surface.

As shown in FIG. 2B, the top surface molding surface 11a is curved upward with a curvature ρ ₁₁ (corresponding to ρ ₁ of the present invention). The magnitude relationship between the curvature ρ ₁₁ , the curvature ρ ₁₂ (corresponding to ρ ₂ of the present invention) of a ceiling surface molding surface 21 a described later of the molding die 20, and the curvature κ ₁ of the ceiling surface portion 2 of the molded part 1 is as follows. Curvature ρ ₁₁ > curvature ρ ₁₂ ≈curvature κ ₁

Further, as shown in FIG. 2A, the two side surface molding surfaces 11b are connected to both ends in the longitudinal direction of the top surface molding surface 11a. An angle θ ₁₁ formed by the side surface molding surface 11 b and the top surface molding surface 11 a, an angle θ ₁₂ formed by a top surface portion molding surface 21 a and the side surface molding surface 21 b described later of the molding die 20, and the molded part 1 The magnitude relationship between the angle α ₁ formed by the top surface portion 2 and the side surface portion 3 is angle θ ₁₁ > angle θ ₁₂ ≈angle α ₁ .

The curvature ρ ₁₁ and the angle θ ₁₁ of the preforming mold 10 are set so as to satisfy the following expressions (1) to (3) with respect to the curvature ρ ₁₂ and the angle θ _{12 of the} forming mold 20. Is preferred. In the following formula, the unit of curvature is [1 / mm] and the unit of angle is [°].
1 <ρ ₁₁ / ρ ₁₂ ≦ 1.75 (1)
ρ ₁₁ / ρ ₁₂ ≦ 0.15 × (θ ₁₁ −θ ₁₂ ) −4.55 (2)
θ ₁₁ −θ ₁₂ ≦ 52 (3)

The flange part molding surface 11c is connected to the lower end of the side part molding surface 11b. The flange portion molding surface 11c is curved substantially concentrically with the top surface portion molding surface 11a. Even if the angle ψ ₁₁ formed by the flange portion forming surface 11c and the side surface forming surface 11b is the same as the angle ψ ₁₂ formed by the side surface forming surface 21b and the flange portion forming surface 21c of the main molding die 20 described later. Good but may be different. The angle ψ ₁₂ of the main mold 20 is substantially the same as the angle β ₁ of the molded part 1.

The upper die pad 12 is disposed above the top surface molding surface 11a of the lower die punch 11, and is driven in the vertical direction by a known driving means. As shown in FIG. 2 (b), the lower surface of the upper mold pad 12 is curved at a curvature [rho ₁₁ along the top portion forming surface 11a.

  The upper die 13 is disposed above the side surface molding surface 11b and the flange portion molding surface 11c of the lower die punch 11. The two upper dies 13 are simultaneously driven in the vertical direction by known driving means. Further, the two upper dies 13 and the upper die pad 12 are driven independently. The lower surface of the upper die 13 has a side surface molding surface 13a and a flange portion molding surface 13b formed along the side surface molding surface 11b and the flange portion molding surface 11c of the lower die punch 11.

Next, the main mold 20 will be described.
As shown in FIG. 3A, the main mold 20 includes a lower mold punch 21, an upper mold pad 22, and two upper mold dies 23.

The lower die punch 21 has a top surface molding surface 21a, two side surface molding surfaces 21b, and two flange portion molding surfaces 21c on the upper surface. As shown in FIG. 3 (b), the top surface portion forming surface 21a is curved upward with a curvature [rho _12. As shown in FIG. 3A, the two side surface molding surfaces 21b are connected to both ends in the longitudinal direction of the top surface molding surface 21a. The angle between the side surface portion forming surface 21b and the top surface portion forming surface 21a and theta _12. The flange part molding surface 21c is connected to the lower end of the side part molding surface 21b. The angle (same as flange forming surface 23b and the side portions forming surface 23a and the angle of the upper die 23) formed between the flange portion forming surface 21c and the side portions forming surface 21b is to [psi _12.

The upper die pad 22 is disposed above the top surface molding surface 21a of the lower die punch 21 and is driven in the vertical direction by a known driving means. As shown in FIG. 3 (b), the lower surface of the upper die pad 22 are curved in the curvature [rho ₁₂ along the top face forming surface 21a.

  The upper die 23 is disposed above the side surface molding surface 21b and the flange portion molding surface 21c of the lower die punch 21. The two upper dies 23 are simultaneously driven in the vertical direction by known driving means. The two upper dies 23 and the upper die pad 22 are driven independently. The lower surface of the upper die 23 has a side surface molding surface 23 a and a flange portion molding surface 23 b formed along the side surface molding surface 21 b and the flange portion molding surface 21 c of the lower die punch 21.

  Hereinafter, the press molding process using the preforming mold 10 and the main molding mold 20 will be described.

[Preformation process]
First, as shown by a two-dot chain line in FIG. 2A, the upper die 13 of the lower die punch 11 and the upper die pad 12 with the upper die 13 of the preforming die 10 raised. The metal plate W is sandwiched therebetween, and the metal plate W is curved along the top surface forming surface 11a. Next, the upper die 13 is lowered, and the metal plate W is placed between the side surface molding surfaces 11b and 13a and between the flange surface molding surfaces 11c and 13b as shown by the solid line in FIG. Clamp and press mold.

By this press molding, as shown in FIG. 1 (a), the top surface portion 32 curved with a curvature larger than the curvature κ ₁ of the top surface portion 2 of the molded part 1, and the angle formed with the top surface portion 32 is A preformed part 31 composed of two side surface portions 33 larger than the angle α ₁ formed by the top surface portion 2 and the side surface portion 3 and two flange portions 34 is obtained. The curvature of the top surface portion 32 of the preformed part 31 after being released from the mold is slightly smaller than the curvature ρ ₁₁ of the preforming mold 10 due to the spring back. Further, the angle formed between the top surface portion 32 and the side surface portion 33 is slightly larger than the angle θ ₁₁ of the preforming mold 10 due to the spring back.

[Main molding process]
Next, as shown by a two-dot chain line in FIG. 3A, with the upper die 23 of the main mold 20 raised, the top surface molding surface 21a of the lower die punch 21 and the upper die pad 22 As shown in FIG. 1B, the top surface 32 is deformed in a direction in which the curvature decreases.

  Thereby, the side part 33 and the flange part 34 are extended in the longitudinal direction, and a tensile stress as shown by an arrow in FIG. 1B tends to be temporarily generated in the side part 33 and the flange part 34. At this time, the side surface portion 33 and the flange portion 34 are not in contact with the lower die punch 21 and the upper die 23 and can be freely deformed. Therefore, as shown in FIG. Deforms in a direction to relieve tensile stress. Specifically, the lower ends of the two side surface portions 33 are drawn in the mouth closing direction, and the upper portion of the side surface portion 33 is deformed to be bent outward.

  In this state, the upper die 23 is lowered, and preforming is performed between the side surface molding surfaces 21b and 23a and between the flange surface molding surfaces 21c and 23b as shown by a solid line in FIG. The side part 33 and the flange part 34 of the part 31 are clamped and press-molded. By this press molding, as shown in FIG. 1 (d), a molded part 1 including the top surface portion 2, the two side surface portions 3, and the two flange portions 4 is molded.

  When the molded part 1 is released from the mold, the molded part 1 tends to deform in the opening direction by springback (elastic recovery). More specifically, the connecting portion between the side surface portion and the top surface portion tends to be deformed so that the bending angle becomes large, and the side surface portion tends to be warped. At this time, a deformed wrinkle generated when only the top surface portion 32 is pressed in the main forming process remains on the side surface portion 3 of the molded part 1, and this deformed wrinkle acts in the mouth closing direction. Therefore, the deformation in the opening direction due to the spring back can be canceled (or alleviated) by this deformation flaw. Therefore, it is possible to suppress the molded part 1 from being deformed in the opening direction after the pressure is released.

Further, in the preforming step, and molding the top surface 2 of the top surface portion 32 to the curvature [rho ₁₁ greater than the curvature kappa ₁ of the molded part 1, in this molding step, is deformed in a direction in which the top face portion 32 curvature decreases Therefore, the spring back of the top surface part 2 in the direction in which the curvature decreases can be reduced. Therefore, it can suppress that the top | upper surface part 2 deform | transforms in the direction in which a curvature becomes small after pressure cancellation.

Further, by setting the curvatures ρ ₁₁ and ρ ₁₂ and the angles θ ₁₁ and θ ₁₂ of the preforming mold 10 and the main molding mold 20 to values within the ranges satisfying the above-described formulas (1) to (3), It is possible to prevent the molded part 1 from being wrinkled and to more reliably suppress the molded part 1 from being deformed in the opening direction after the pressure is released. Moreover, it can suppress more reliably that the top | upper surface part 2 of the molded component 1 deform | transforms in the direction in which a curvature becomes small after pressure release.

Further, as a conventional press forming method, it anticipates the opening amounts mouth by spring back after the release of pressure, the angle of the bent portion of the mold (corresponding to the angle theta ₁₂ of the present embodiment), the target molding There is a method of press molding by setting it to be smaller than the angle of the part (for example, about 8 °), but in this case, the angle of the bending portion of the mold cannot be set to less than 90 °, so the top surface portion and the side surface For example, it is not possible to obtain a molded part having an angle of 90 to 95 ° with the portion.
On the other hand, in this embodiment, since opening deformation after pressure release can be suppressed, the molded part 1 in which the angle formed between the top surface portion and the side surface portion is approximately 90 ° can be obtained.

Second Embodiment
Next, a second embodiment of the present invention will be described.
The press molding method of the present embodiment is a method for press molding the molded part 101 shown in FIG. In the press molding method of the present embodiment, the preforming part 61 shown in FIG. 4A is press-molded from the metal plate W using the preforming mold 40 shown in FIG. 5 (preliminary molding step), and then this preliminary molding is performed. The molded part 61 is press-molded using the main molding die 50 shown in FIG. 6 to form the molded part 101 (main molding process). As the metal plate W, a high-tensile steel plate (high-tensile material) is used. A steel plate, an aluminum plate, or the like may be used. 5 and 6 omit cross-sectional hatching.

First, the molded part 101 will be described.
As shown by a solid line in FIG. 4C, the molded part 101 has substantially the same shape as the molded part 1 of the first embodiment (see FIG. 1D), and has a top surface portion 102 and two side surface portions. 103 and two flange portions 104. The curvature of the top surface portion 102 is κ ₁₀₁ , the angle formed by the side surface portion 103 and the top surface portion 102 is α _101, and the angle formed by the flange portion 104 and the side surface portion 103 is β ₁₀₁ . The curvature κ ₁₀₁ is slightly smaller than the curvature ρ ₂₂ of the lower surface of the upper pad 52 of the main molding die 50 described later (the curvature of the top surface molding surface 51a).

Next, the preforming mold 40 will be described.
As shown in FIG. 5 (a), the preforming mold 40 is similar to the preforming mold 10 of the first embodiment, in that a lower mold punch 41, an upper mold pad 42, two upper mold dies 43, It is composed of The curvature ρ ₂₁ (corresponding to ρ ₁ of the present invention) of the top surface molding surface 41 a of the lower mold punch 41 of the preforming mold 40 and the curvature (corresponding to the top surface molding surface 51 a of the present molding die 50). Contrary to the first embodiment, the magnitude relationship with the curvature of the lower surface ρ ₂₂ (corresponding to ρ ₂ of the present invention) is curvature ρ ₂₁ <curvature ρ ₂₂ . Other configurations of the preforming mold 40 are substantially the same as those of the preforming mold 10 of the first embodiment.

As shown in FIG. 5A, when the angle formed by the side surface molding surface 41b of the lower die punch 41 and the top surface molding surface 41a is θ ₂₁ , this angle θ ₂₁ and this molding die 50 will be described later. The magnitude relationship between the angle θ ₂₂ formed between the top surface forming surface 51a and the side surface forming surface 51b and the angle α ₁₀₁ formed between the top surface portion 102 and the side surface portion 103 of the molded part 101 is the same as in the first embodiment. Angle θ ₂₁ > angle θ ₂₂ ≈angle α ₁₀₁ .

Further, the angle between the flange portion forming surface 43b and the side portion forming surface 43a of the upper die 43 forms a [psi _21. The angle ψ ₂₁ may be the same as or different from the angle ψ ₂₂ formed by the side surface molding surface 51b and the flange portion molding surface 51c of the main molding die 50 described later, as in the first embodiment. Good.

The curvature ρ ₂₁ and the angle θ ₂₁ of the preforming mold 40 are set so as to satisfy the following expressions (1) to (4) with respect to the curvature ρ ₂₂ and the angle θ _{22 of the} forming mold 50. Is preferred. In the following formula, the unit of curvature is [1 / mm] and the unit of angle is [°].
ρ ₂₁ / ρ ₂₂ <1 (1)
ρ ₂₁ / ρ ₂₂ ≦ 0.06 × (θ ₂₁ −θ ₂₂ ) −1.22 (2)
ρ ₂₁ / ρ ₂₂ ≧ 0.012 × (θ ₂₁ −θ ₂₂ ) +0.136 (2)
θ ₂₁ −θ ₂₂ ≦ 47 (4)

Next, the main mold 50 will be described.
As shown in FIG. 6A, the main mold 50 includes a lower mold punch 51, an upper mold pad 52, and two upper dies 53. The main mold 50 has substantially the same shape as the main mold 20 of the first embodiment, but the curvature ρ ₂₂ of the top surface molding surface 51 a of the main mold 50 is the same as that of the top surface 102 of the molded part 101. In view of deformation due to springback, the value is set to be slightly larger than the curvature κ ₁₀₁ of the top surface portion 102. Other configurations of the main mold 50 are the same as those of the main mold 20 of the first embodiment. The angle between the side surface portion forming surface 51b and the top portion forming surface 51a of the lower punch 51 and theta _22, the angle between the flange portion forming surface 53b and the side portions forming surface 53a of the upper die 53 makes with the [psi ₂₂ .

  Hereinafter, the press molding process using the preliminary molding die 40 and the main molding die 50 will be described.

[Preformation process]
First, as indicated by a two-dot chain line in FIG. 5A, the upper die 43 of the lower die punch 41 and the upper die pad 42 with the upper die 43 of the preforming die 40 raised. The metal plate W is sandwiched therebetween, and the metal plate W is curved along the top surface forming surface 41a. Next, the upper die 43 is lowered, and the metal plate W is moved between the side surface molding surfaces 41b and 43a and between the flange surface molding surfaces 41c and 43b as shown by the solid line in FIG. Clamp and press mold.

By this press molding, as shown in FIG. 4A, the top surface portion 62 curved with a curvature smaller than the curvature κ ₁₀₁ of the top surface portion 102 of the molded component 101, and the angle formed by the top surface portion 62 is A preformed part 61 composed of two side surface parts 63 larger than the angle α ₁₀₁ formed by the top surface part 102 and the side surface part 103 and two flange parts 64 is obtained. Note that the curvature of the top surface portion 62 of the preformed part 61 after being released from the mold is slightly smaller than the curvature ρ ₂₁ of the preforming mold 40 due to the spring back. The angle formed between the top surface portion 62 and the side surface portion 63 is slightly larger than the angle θ ₂₁ of the preforming mold 40 due to the spring back.

[Main molding process]
Next, as shown by a two-dot chain line in FIG. 6A, with the upper die 53 of the main die 50 raised, the top surface molding surface 51a of the lower die punch 51 and the upper die pad 52 The top surface portion 62 of the preformed part 61 is sandwiched between the top surface portion 62 and the top surface portion 62 is deformed in a direction in which the curvature increases.

  Subsequently, the upper die 53 is lowered, and as shown by the solid line in FIG. 5A, a preformed part is formed between the side surface forming surfaces 51b and 53a and between the flange portion forming surfaces 51c and 53b. The side part 63 and the flange part 64 of 61 are clamped and press-molded. By this press molding, as shown in FIG. 4B, a molded part 101 including the top surface portion 102, the two side surface portions 103, and the two flange portions 104 is molded.

When the molded part 101 is released from the mold, a deformed wrinkle when the molded part 101 is molded to a curvature ρ ₂₁ smaller than the curvature ρ ₂₂ of the main molding die 50 remains in the top surface portion 102 of the molded part 101. The top surface portion 102 of the molded part 101 is deformed in a direction in which the curvature is reduced by the deformation wrinkle and the spring back by the press in the main forming step.

  Thereby, the side surface portion 103 and the flange portion 104 are extended in the longitudinal direction, and a tensile stress as indicated by an arrow in FIG. 4B tends to be temporarily generated in the side surface portion 103 and the flange portion 104. Then, as shown in FIG.4 (c), the side part 103 deform | transforms in the direction which relieves said tensile stress. Specifically, the side portion 103 is deformed so that the lower end of the side portion 103 is pulled in the closing direction. By this deformation, deformation in the opening direction due to the spring back (deformation in which the bending angle of the corner portion becomes wide and warpage of the side surface portion) is canceled (or mitigated). Therefore, it is possible to suppress the molded part 101 from being deformed in the opening direction after the pressure is released.

  Further, as described above, after releasing the pressure, the top surface portion 102 of the molded part 101 is deformed in a direction in which the curvature decreases, but the top surface portion 102 is pressed twice in the pre-forming step and the main forming step. Therefore, the amount of deformation is smaller than the amount of deformation due to springback when the molded part is formed by one-time molding. That is, as compared with the case where the molded part is molded by one-time molding, it is possible to suppress the top surface portion of the molded part from being deformed in a direction in which the curvature decreases after the pressure is released.

Further, by setting the curvatures ρ ₂₁ and ρ ₂₂ and the angles θ ₂₁ and θ ₂₂ of the preforming mold 40 and the main forming mold 50 to values within the ranges satisfying the above-described formulas (1) to (4), Wrinkles can be prevented from occurring in the molded part 101, and deformation of the molded part 101 in the opening direction after release of pressure can be more reliably suppressed.

  Moreover, in this embodiment, since it is possible to suppress the opening deformation after the release of pressure, the angle formed between the top surface portion and the side surface portion that cannot be manufactured when molding is performed in anticipation of the opening amount. Molded parts around 90 ° can be obtained.

  As mentioned above, although 1st Embodiment and 2nd Embodiment were described as suitable embodiment of this invention, said embodiment can be changed and implemented as follows.

  The molded part molded in the above embodiment has a shape having two flange portions, but may have a shape without one or both of the two flange portions.

  In the molded part molded in the above embodiment, the angle formed by one side surface portion and the top surface portion and the angle formed by the other side surface portion and the top surface portion are the same, but may be different.

  In the molded part molded in the above embodiment, the two side surface portions have the same height (length in the curved radial direction), but may be different from each other.

  In the molded part molded in the above embodiment, the lower side of the side part is a curved shape concentric with the top surface part, and the height of the side part (the length in the curved radial direction) is constant, As described above, when the flange portion is not provided, it may not be constant. For example, the height of the side surface portion may gradually increase from one end in the longitudinal direction toward the other end.

  The top surface portion of the molded part molded in the above embodiment is curved in an arc shape (that is, has a curvature in the entire longitudinal direction), but has a curvature only in a part in the longitudinal direction (preferably a substantially central portion). It may be a curved shape. In the present invention, the “top surface portion curved with a predetermined curvature in the longitudinal direction” is not limited to the case where it is curved with the same curvature in the entire longitudinal direction as in the above embodiment, but as in the present modified embodiment. In addition, it includes a case where a part of the longitudinal direction is curved with a predetermined curvature.

  Next, in order to verify the effect of the present invention, a simulation analysis by a finite element method (FEM) was performed. The software used was JSTAMP / NV 2.2.0.

As an example of the present invention, a cold-rolled high-tensile steel plate having a thickness of 1.2 mm, a 980 MPa class (yield strength (YP) 712 MPa, tensile strength (TS) 1090 MPa, elongation at break (EL) 13.9%) is used. A simulation for press-molding a molded part as shown in FIG. 1D was performed in the same procedure as in the first or second embodiment. The length of the molded part in the longitudinal direction was 900 mm. This length is the same in the comparative example described later. 7A and 7B show the cross-sectional shape and the cross-sectional dimensions of the preformed part and the molded part before releasing the pressure. The curvature ρ _{1 of} the top surface portion of the preformed part and the angle θ ₁ formed by the top surface portion and the side surface portion at the time of pressing in the preforming step were values shown in Table 1. Further, the curvature ρ ₂ of the top surface portion of the molded part at the time of pressing in the main forming step was 2.86 × 10 ⁻⁴ [1 / mm], and the angle θ ₂ formed by the top surface portion and the side surface portion was 98 °.
As shown in Table 1, in Invention Examples 1 and 2, as in the first embodiment described above, in the preforming step, the preformed part is molded to a curvature larger than the curvature of the top surface portion of the molded part, In Invention Examples 3 and 4, as in the second embodiment described above, in the preforming step, the preformed part is molded with a curvature smaller than the curvature of the top surface portion of the molded part.

  As Comparative Example 1, a simulation was performed in which a molded part was press-molded by one-time molding using a main mold having the same shape as the present invention.

As Comparative Example 2, the curvature ρ ₁ of the top surface portion of the preformed part at the time of pressing in the preforming step and the curvature ρ ₂ of the top surface portion of the molded component at the time of pressing in the main forming step are both 2.86 × 10 ⁻⁴ [ 1 / mm], and the angle θ ₁ formed between the top surface portion and the side surface portion during pressing in the preforming step is set to the value shown in Table 1, and the angle θ ₂ formed between the top surface portion and the side surface portion during pressing in the main forming step. A simulation of press-molding a molded part was performed with the angle of 98 °.

  For the molded parts of the inventive examples and comparative examples, the wrinkles of the side plate portions were evaluated. Specifically, when the upper die (see the upper dies 23 and 53 in FIGS. 3 and 6) is raised 1 mm from the bottom dead center (the lowest point during pressing), the side surface portion is aligned with the lower die punch. When wavy so as to come into contact with both upper dies, it was judged as “wrinkle large”. The results are also shown in Table 1. When it was not determined that the wrinkle was large, a circle mark was displayed in Table 1.

  Further, for a molded part that has not been determined to be wrinkle large (hereinafter referred to as a molded part without wrinkle), the opening amount of the side surface portion before and after the release of pressure (the horizontal displacement amount of the lower end of the side surface portion) ΔD ( 8A) and a displacement amount ΔH (see FIG. 8B) in the height direction of the longitudinal end portion of the top surface part before and after releasing the pressure. The results are also shown in Table 1. The opening amount ΔD is an average value of values measured at one end and the center in the longitudinal direction of the molded part, and the displacement in the opening direction is positive, and the displacement in the closing direction is negative. In addition, the displacement amount ΔH is defined as positive for upward displacement (displacement in the direction in which the curvature of the top surface becomes smaller) and negative for downward displacement.

As shown in Table 1, among the inventive examples, the inventive examples 2-3 to 3, 3-1 to 4, and 4 to 1 having no wrinkles are compared to the comparative example 1 of single molding, The opening amount ΔD is small.
In addition, the above-described inventive examples 2-3 to 5, 3-1 to 4, 4-1 to 3 and the comparative examples 2-2 to 5 having no wrinkles have an angular difference (ρ ₁ −ρ ₂ ). When the same case is compared, the opening amount ΔD is smaller in the example of the present invention.

Further, in the inventive examples 2-3 to 5, 3-1 to 4, and 4-1 to 3, the displacement amount ΔH of the top surface portion is smaller than that of the first comparative example 1.
Further, Invention Examples 2-3 to 5 in which the curvature ratio ρ ₁ / ρ ₂ is larger than 1 have a smaller displacement ΔH of the top surface portion than the comparative example 2 in which the curvature ratio ρ ₁ / ρ ₂ is 1. ing.

Next, based on the results of the present invention example and the comparative example, conditions for the curvature ratio ρ ₁ / ρ ₂ and the angle difference (θ ₁ −θ ₂ ) that are free of wrinkles and can suppress the opening amount ΔD are obtained. It was. FIG. 9 shows the results of Examples 2-3 to 5, 3-1 to 4, 4-1 to 3 and Comparative Examples 2-2 to 5 of the present invention in which no wrinkles and a small opening amount ΔD were obtained. It is a graph which shows the relationship between curvature ratio (rho) ₁ / (rho) ₂ and an angle difference ((theta) _1- (theta) ₂ ).

As shown in FIG. 9, the straight line connecting the point of Invention Example 2-3 and the point of Comparative Example 2-2 is ρ ₁ / ρ ₂ = 0.15 × (θ ₁ −θ ₂ ) −4.55. It is represented by Therefore, in the graph of FIG. 9, the range indicated by hatching is represented by the following formulas (1) to (3).
1 <ρ ₁ / ρ ₂ ≦ 1.75 (1)
ρ ₁ / ρ ₂ ≦ 0.15 × (θ ₁ −θ ₂ ) −4.55 (2)
θ ₁ −θ ₂ ≦ 52 (3)

A straight line connecting the point of Invention Example 3-1 and the point of Comparative Example 2-2 is represented by ρ ₁ / ρ ₂ = 0.06 × (θ ₁ −θ ₂ ) −1.22. A straight line connecting the point of Invention Example 4-3 and the point of Invention Example 3-4 is represented by ρ ₁ / ρ ₂ = 0.012 × (θ ₁ −θ ₂ ) +0.136. Therefore, in the graph of FIG. 9, the range indicated by the lattice-like hatching is expressed by the following formulas (4) to (7).
ρ ₁ / ρ ₂ <1 (4)
ρ ₁ / ρ ₂ ≦ 0.06 × (θ ₁ −θ ₂ ) −1.22 (5)
ρ ₁ / ρ ₂ ≧ 0.012 × (θ ₁ −θ ₂ ) +0.136 (6)
θ ₁ −θ ₂ ≦ 47 (7)

The curvature ratio ρ ₁ / ρ ₂ and the angle difference (θ ₁ −θ ₂ ) are set so as to satisfy all of the above formulas (1) to (3), or all the above formulas (4) to (7) are set. By setting so as to satisfy, it is considered that the generation of wrinkles can be suppressed and the opening of the mouth after releasing the pressure can be suppressed.
In addition, since Examples 2-3 to 5 of the present invention have a small amount of displacement ΔH of the top surface portion, the curvature ratio ρ ₁ / ρ ₂ and the angle difference (θ ₁ −θ ₂ ) are set to the above formulas (1) to (3). It is considered that by setting so as to satisfy all of the above, it is possible to suppress the top surface portion from being deformed in a direction in which the curvature decreases after the pressure is released.

1,101 molded parts 2,102 top face portion 3, 103 side portion 4, 104 flanges 31 and 61 preformed parts 32 and 62 the top face portion 33,63 side portions 34, 64 flange portion kappa _1, kappa ₁₀₁ curvature (present invention "Predetermined curvature")
ρ ₁₁ , ρ ₁₂ curvature (curvature ρ _{1 of the} present invention)
ρ ₂₁ , ρ ₂₂ curvature (curvature ρ _{2 of the} present invention)
θ ₁₁ , θ ₁₂ angles (angle θ _{1 of the} present invention)
θ ₂₁ , θ ₂₂ angles (the angle θ _{2 of the} present invention)

Claims (6)

A press molding method for press molding a molded part having a top surface curved with a predetermined curvature in the longitudinal direction and two side surfaces extending from both ends along the longitudinal direction of the top surface toward the inside of the curve. And
A top surface portion that curves in a longitudinal direction with a curvature different from the predetermined curvature, and an angle that extends from both ends along the longitudinal direction of the top surface portion toward the inside of the curve and forms with the top surface portion is larger than that of the molded part. A preforming step of press molding a preformed part having two side portions;
The top surface portion of the preformed part is pressed and deformed in a direction approaching the predetermined curvature, and in that state, an angle formed between the top surface portion and the side surface portion is made smaller than that of the preformed component. A press forming method comprising: a main forming step of press forming.   The press molding method according to claim 1, wherein the top surface portion of the preformed part is curved with a curvature larger than the predetermined curvature. The curvature of the top surface portion at the time of pressing in the preforming step is ρ ₁ [1 / mm], the angle formed by the top surface portion and the side surface portion is θ ₁ [°],
When the curvature of the top surface portion at the time of pressing in the main forming step is ρ ₂ [1 / mm], and the angle formed by the top surface portion and the side surface portion is θ ₂ [°],
The press molding method according to claim 2, wherein the following formulas (1) to (3) are satisfied.
1 <ρ ₁ / ρ ₂ ≦ 1.75 (1)
ρ ₁ / ρ ₂ ≦ 0.15 × (θ ₁ −θ ₂ ) −4.55 (2)
θ ₁ −θ ₂ ≦ 52 (3)   The press molding method according to claim 1, wherein the top surface portion of the preformed part is curved with a curvature smaller than the predetermined curvature. The curvature of the top surface portion at the time of pressing in the preforming step is ρ ₁ [1 / mm], the angle formed by the top surface portion and the side surface portion is θ ₁ [°],
When the curvature of the top surface portion at the time of pressing in the main forming step is ρ ₂ [1 / mm], and the angle formed by the top surface portion and the side surface portion is θ ₂ [°],
The press molding method according to claim 4, wherein the following formulas (1) to (4) are satisfied.
ρ ₁ / ρ ₂ <1 (1)
ρ ₁ / ρ ₂ ≦ 0.06 × (θ ₁ −θ ₂ ) −1.22 (2)
ρ ₁ / ρ ₂ ≧ 0.012 × (θ ₁ −θ ₂ ) +0.136 (3)
θ ₁ −θ ₂ ≦ 47 (4) The molded part has a flange portion extending from a tip portion of the side surface portion,
6. The press molding method according to claim 1, wherein, in the preforming step, the preformed part is press-molded so that a flange portion is formed.