JP4992048B2 - Press molding method for press molded parts with excellent shape freezing properties - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of press-forming a press-formed component excellent in a shape freezing property by which the press-formed component excellent in dimensional accuracy are stably mass-produced by appropriately suppressing occurrence of springback after press forming without using a complicated process when manufacturing the press-formed component having a U-shaped cross-sectional shape or a V-shaped cross-sectional shape. <P>SOLUTION: The cross-sectional shape of the joining part 12 of the press-formed component 10 comprises two curves and one straight line and is formed from a curve part 12a provided with a radius R of curvature between the starting point M of the connecting part 12 and a first intermediate point A, a straight line part 12b between the first intermediate point A and a second intermediate point B and a curve part 12a provided with the radius R of curvature between the second intermediate point B and the finish point N of the joining part 12. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a press molding method of a press molded part (particularly, a U-shaped cross-sectional shape or a V-shaped cross-sectional shape press-formed part) used for automobile parts and the like.

  In recent years, especially in the automobile industry, reduction in the thickness and strength of materials (metal plates) used for parts have been promoted by reducing the weight of the vehicle body due to environmental problems. For production of such parts, press molding with excellent production cost is often used, but in press molding using a material with reduced thickness or strength, the dimensional accuracy is greatly increased by the spring back after press molding. It becomes a problem at the time of assembling as a part.

In order to cope with such a problem, Patent Literatures 1 to 4 disclose a press molding method that suppresses spring back after press molding and has excellent shape freezing property.
JP 2005-177790 A JP 2001-314918 A JP-A-61-082929 JP 2004-314123 A

  However, the conventional press molding methods as disclosed in Patent Documents 1 to 4 have many complicated processes and unnecessary shapes, and have sufficiently solved the problem. I can't say that.

  For example, in Patent Document 1, warping of the punch R portion is reduced by two processes, but a process using a pad is necessary and complicated, and it is impossible to stably produce a component with high dimensional accuracy.

  Further, in Patent Document 2, the spring back is suppressed by duplicating the complicated movement of the mold and the die R, but the process becomes complicated and it is impossible to make a stable and highly accurate part.

  Moreover, in Patent Document 3, the spring back is corrected by forming with a large R after forming with a small R in the punch R. However, since the initial R is overhanging, the punch R is large. Variation occurs.

  Further, in Patent Document 4, a part having excellent shape freezing property is press-molded by providing a stepped shape on the vertical wall, but measures are taken for the R portion which is one of the factors of shape freezing property. Therefore, shape freezing property is insufficient. In addition, since a step shape is provided on the vertical wall, it is difficult to achieve consistency with other assembly parts of the automobile.

  Thus, in the prior art, there is no technique for producing a press-formed part that satisfies the dimensional accuracy without using a complicated process when mass-producing press-formed parts used in the automobile industry or the like.

  The present invention has been made in view of the circumstances as described above, and without using a complicated process, the spring back after press forming is accurately suppressed, and a press-formed part with good dimensional accuracy is stabilized. It is an object of the present invention to provide a press molding method of a press molded part having excellent shape freezing property that can be mass-produced.

  In order to solve the above problems, the present invention has the following features.

[1] A press molding method of a press-molded part having a U-shaped cross-sectional shape or a V-shaped cross-sectional shape, and when the press-molded part is press-molded by a one-step press molding process, A metal plate is formed by using a punch and a die , which are press-molding dies having a cross-sectional shape in which a connecting portion connecting two or more curves and one or more straight lines connecting the surface portions forming the V-shape. A press molding method of a press molded part having excellent shape freezing property, characterized by press molding.

[2] A press molding method of a press-molded part having a U-shaped cross-sectional shape or a V-shaped cross-sectional shape, wherein the first press molding is performed when the press-molded part is press-molded by a two-step press molding process. In the process, a metal plate is first formed by using a punch and a die, which are press-molding dies having a cross-sectional shape in which a connecting portion connecting the face portions forming a U-shape or a V-shape has a single curve. In the second press molding step, the cross-sectional shape is composed of two or more curves and one or more straight lines connecting the surface portions forming the U-shape or V-shape. A press-molding method for press-molded parts having excellent shape freezing properties, characterized in that a final press-molding is performed on a metal plate using a punch and a die, which are press-molding dies having the following.

[ 3 ] According to the press molding method of a press-molded part having excellent shape freezing property according to [1] or [2] , the U-shaped cross section or the V-shaped cross section is formed. Press forming with excellent shape freezing characteristics, characterized in that a press forming part having a cross-sectional shape including two or more curves and one or more straight lines is formed by connecting the surface portion forming the character to the surface portion. Press molding method for parts.

  In the present invention, when manufacturing a press-molded part having a U-shaped cross-sectional shape or a V-shaped cross-sectional shape, the spring back after press molding is accurately suppressed without using a complicated process, Highly accurate press-molded parts can be stably mass-produced.

  Embodiments of the present invention will be described with reference to the drawings.

  First, the present invention is directed to a press-molded part having a U-shaped cross-sectional shape or a V-shaped cross-sectional shape, and FIGS. 1 shows a press-formed part 1 having a U-shaped cross-sectional shape, and FIGS. 2A and 2B show a press-formed part having a U-shaped cross-sectional shape with a collar. 2, what is shown in FIG. 3 is a press-formed part 3 having a V-shaped cross-sectional shape, and what is shown in FIG. 4 is a press-formed part 4 having a V-shaped cross-sectional shape provided with a flange. In addition, these figures are examples, Comprising: The thing in which the shape of FIGS. 1-4 is used for some components is also included.

  Then, the present invention provides a U-shaped cross-sectional shape or a V-shaped cross-sectional shape of the above-described press-formed parts 1 to 4 (collectively, press-formed parts 10) as shown in FIG. Or the cross-sectional shape of the site | part (connection part) 12 which connects between the surface part 11 and the surface part 11 which forms V character is prescribed | regulated. In other words, the cross-sectional shape of the connecting portion 12 is generally a cross-sectional shape made of one circular arc, whereas in the present invention, two or more curves and one or more straight lines are used. The cross-sectional shape is made of

  In FIG. 6, the cross-sectional shape of the connection part 12 in one Embodiment of this invention is shown. In this embodiment, the cross-sectional shape of the joint portion 12 of the press-formed part 10 is composed of two curves and one straight line, and the radius of curvature R is from the start point M of the joint portion 12 to the first intermediate point A. A curved portion (arc portion) 12a, a straight portion 12b from the first intermediate point A to the second intermediate point B, and a radius of curvature R from the second intermediate point B to the end point N of the connecting portion 12. It is formed by the curved part (arc part) 12a provided with.

  Corresponding to the above, as shown in FIG. 7, the press-molding dies (punch 20 and die 30) to be used also have the same cross-sectional shape. That is, with respect to the punch 20, the cross-sectional shape of the portion (connecting portion) 22 that connects between the surface portion 21 and the surface portion 21 that forms a U-shape or V-shape is a curved portion (arc portion) having a curvature radius R. 22a, a straight portion 22b, and a curved portion (arc portion) 22a having a radius of curvature R, and the die 30 is formed between the surface portion 31 and the surface portion 31 forming a U-shape or V-shape. The cross-sectional shape of the portion (connecting portion) 32 connecting the two is formed by a curved portion (arc portion) 32a having a curvature radius R, a straight portion 32b, and a curved portion (arc portion) 32a having a curvature radius R. Yes.

  FIG. 7 shows an example in which both the punch 20 and the die 30 have the cross-sectional shape as described above, but only the punch 20 is formed between the surface portion forming the U-shape or the V-shape. The die 30 may have a cross-sectional shape consisting of one arc as in the prior art, so that the connecting portion connecting the two has a cross-sectional shape consisting of two or more curves and one or more straight lines.

  Thus, in this embodiment, the spring back after press molding is suppressed by the mechanism shown below, and press-molded parts with good dimensional accuracy can be stably mass-produced.

That is, in FIG. 8, as shown in the stress distribution schematic diagram of the plate thickness surface layer in the joint portion 12 after press molding,
(1) Between the curved portion 12a on the start point M side and the curved portion 12a on the end point N side, a line length difference from the press molding die occurs due to the familiarity of the metal plate with the press molding die. This induces reverse bending and reduces the stress that causes spring back after press forming (after unloading) of the straight portion 12b, resulting in a stress distribution that causes spring go, ensuring shape freezing properties and ensuring dimensional accuracy. improves. This is the biggest factor.
(2) Further, by forming the connecting portion 12 by two curved portions 12a and one straight portion 12b, the radius of curvature R of the curved portion 12a and the range (angle of R) of the curved portion 12a can be reduced. The springback-induced moment in the range where the curved portion 12a is formed is reduced, and the shape freezing property is improved.
(3) Furthermore, when the material (metal plate) is pushed out to the vertical wall side of the connecting portion 12, the dimensional accuracy is improved by the spring go utilizing the bending rod.

  Here, in the above press molding, it is possible to mold the press-molded part 10 from a blank (metal plate) in one process, but it is divided into two or more press molding processes, and the intermediate press molding process or final process. In the press molding step, dimensional accuracy can be further improved by using a press molding die (punch 20 and die 30) as shown in FIG.

  For example, as shown in FIG. 9, it is divided into two press forming steps. First, as shown in FIG. 9A, in the first press forming step, the connecting portion 22 is a curved portion (arc) as in the prior art. Part) 22a and the die 35 whose connecting part 32 consists only of a curved part (arc part) 32a is used to perform the first press forming on the blank (metal plate) 9, and FIG. ), In the second press molding step, the connecting portion 22 is formed of two curved portions 22a and one straight portion 22b, and the connecting portion 32 is formed of two curved portions 32a and one straight portion 32b. The final press molding is performed using the die 30.

  Hereinafter, the cross-sectional shape of the joint portion 12 of the press-formed part 10 will be described as an example, but the same applies to the cross-sectional shape of the joint portion (22, 32) of the press-molding die (punch 20, die 30). .

  In the embodiment shown in FIG. 7 and FIG. 9 described above, the cross-sectional shape of the connecting portion 12 of the press-formed part 10 has two curved portions 12a and one straight portion 12b (curved portion 12a-straight portion 12b-curved portion 12a). As shown in FIG. 10, it is formed by three curved portions 12a and two straight portions 12b (curved portion 12a-straight portion 12b-curved portion 12a-straight portion 12b-curved portion 12a). You may do it.

  As described above, when the cross-sectional shape is formed by combining two or more curved portions 12a and one or more straight portions 12b, it is started at the curved portion 12a and ends at the curved portion 12a. preferable.

  This is because it is possible to suppress the occurrence of cracking by arranging the curved portion 12a (R shape) at the position connecting the surface portion 11 and the straight portion 12b, and as described above, the curved portion 12a and the curved portion. This is because a reverse moment can be effectively generated by the straight portion 12b sandwiched between 12a.

  Further, in the cross-sectional shape of the press-molding die and the joint portion of the press-molded parts, the ratio R / t of the curvature radius R of the curved portions (12a, 22a) and the plate thickness t of the metal plate 9 is 0.1 or more and 80. The ratio L / t between the distance L from the start point M to the end point N of the joint portion (12, 22) and the thickness t of the metal plate 9 is preferably 100 or less.

  This is because when R / t is less than 0.1, the risk of cracking increases, and when R / t exceeds 80, the springback becomes large and is ineffective. Further, increasing L / t beyond 100 increases the number of curved portions and straight portions in the cross section, resulting in a decrease in the effect of shape freezing.

  In the press-molded parts 2 and 4 having the collar as shown in FIG. 2 and FIG. 4, the collar 11a may be handled in the same manner as the surface 11 as necessary. Applying the present invention to the 11 joints has the same effect.

  As Example 1 of the present invention, a press-molded part having a U-shaped cross-sectional shape having a collar portion as shown in FIG. 11 (a) and a cross-sectional shape in FIG. The press-molded part 2) shown in 2 (a) was press-molded. The materials subjected to press forming are 590 MPa grade steel plates and 780 MPa grade steel plates generally used for structural members of automobiles, and the material properties are as shown in Table 1.

  And in this Example 1, said press-molded part was shape | molded by the press molding of 1 process (Comparative example 1, this invention example 1-3).

  In that case, it formed using the punch which has the cross-sectional shape of a joint part as shown in Table 2 and FIG. 12 (FIG. 12 is a figure which shows the cross-sectional shape of the joint part of a press-molded part. Is also the same as FIG. In Comparative Example 1, the cross-sectional shape of the joint portion is only a curved portion (R9) having a radius of curvature of 9 mm, and Example 1 of the present invention has a cross-sectional shape of the joint portion having a radius of curvature of 3 mm, a straight portion, and a radius of curvature of 3 mm. It is a curved part (R3-straight part-R3), and the present invention example 2 is also a curved part having a radius of curvature of 3 mm, a straight part, and a curved part having a curvature radius of 3 mm (R3-straight part-R3). In the present invention example 3, the cross-sectional shape of the connecting portion is a curved portion having a curvature radius of 3 mm, a straight portion, a curved portion having a curvature radius of 3 mm, a straight portion, and a curved portion having a curvature radius of 3 mm (R3-straight portion-R3-straight portion). -R3). Note that the die had a shape with only a curved portion (R10) having a radius of curvature of 10 mm (die R = 10).

  For such Comparative Example 1 and Invention Examples 1 to 3, the amount of deformation (spring back amount) when extracted from the press die after press molding was measured. As shown in FIG. 11 (b), the measurement location is the angle θ between the surface portion and the surface portion in the joint portion and the width W of the opening portion, and the angle change amount Δθ and the width deformation amount ΔW were calculated. The angle change amount Δθ and the width deformation amount ΔW are positive in the springback direction and negative in the spring go direction.

  The results are shown in Table 2.

  As shown in Table 2, in Examples 1 to 3 of the present invention, compared to Comparative Example 1, the angle change amount Δθ and the width deformation amount ΔW are small, the shape freezing property is excellent, and the press-molded part with good dimensional accuracy. Was able to create.

  As Example 2 of the present invention, like Example 1, it has a U-shaped cross-sectional shape with a collar portion as shown in a perspective shape in FIG. 11 (a) and a cross-sectional shape in FIG. 11 (b). Press molding of press molded parts was performed. The materials used for the press forming are also 590 MPa grade steel plates and 780 MPa grade steel plates that are generally used for structural members of automobiles, as in Example 1. The material characteristics are shown in Table 1.

  In Example 2, the above-mentioned press-molded part was molded by two-step press molding as shown in FIG. 9 (Comparative Example 2, Invention Examples 4 to 6).

  Incidentally, here, in the first press molding step, the cross-sectional shape shown in FIG. 13A is molded, and in the second press molding step, the cross-sectional shape shown in FIG. 13B (that is, in FIG. 11B). (Cross-sectional shape).

  At that time, in the first press molding step, both the comparative example 2 and the inventive examples 4 to 6 have the same pressing mold (the cross-sectional shape of the joint portion is a curved portion having a radius of curvature of 9 mm (punch) and 10 mm (die)). After forming using a die having a shape only of R9, R10) (punch R is 9 and die R is 10)), in the second press molding step, the cross-sectional shape of the joint portion is different as in Example 1. Molding was performed using a pressing die.

  That is, as shown in Table 3, the cross-sectional shape of the joint portion of the punch is that the comparative example 2 is only a curved portion (R9) in which the cross-sectional shape of the joint portion has a radius of curvature of 9 mm. The cross-sectional shape is a curved portion having a radius of curvature of 3 mm, a straight portion, and a curved portion having a radius of curvature of 3 mm (R3-straight portion-R3). A straight line portion and a curved portion having a curvature radius of 3 mm (R3-straight portion-R3). In the present invention example 6, the cross-sectional shape of the joint portion is a curved portion having a curvature radius of 3 mm, a straight portion, a curved portion having a curvature radius of 3 mm, and a straight line. Part and a curved part having a radius of curvature of 3 mm (R3-linear part-R3-linear part-R3). Note that the die had a shape with only a curved portion (R10) having a radius of curvature of 10 mm (die R = 10).

  For such Comparative Example 2 and Invention Examples 4 to 6, the amount of deformation (spring back amount) when extracted from the press die after press molding was measured. As shown in FIG. 13B, the measurement location is the angle θ between the surface portion and the surface portion of the joint portion and the width W of the opening portion, as shown in FIG. 13B, and the angle change amount Δθ and the width deformation amount ΔW are calculated. did. The angle change amount Δθ and the width deformation amount ΔW are positive in the springback direction and negative in the spring go direction.

  The results are shown in Table 3.

  As shown in Table 3, in Examples 4 to 6 of the present invention, compared to Comparative Example 2, the angle change amount Δθ and the width deformation amount ΔW are small, the shape freezing property is excellent, and the press-molded part with good dimensional accuracy. Was able to create.

It is a figure which shows the press-molding component which has a U-shaped cross-sectional shape. It is a figure which shows the press molding component which has a U-shaped cross-sectional shape provided with the collar part. It is a figure which shows the press-molded part which has V character type cross-sectional shape. It is a figure which shows the press molding component which has a V-shaped cross-sectional shape provided with the collar part. It is explanatory drawing of the connection part of a press-molded component. It is a figure which shows the cross-sectional shape of the connection part of the press-molded component in one Embodiment of this invention. It is a figure which shows the cross-sectional shape of the connection part of the metal mold | die for press molding in one Embodiment of this invention. It is a figure explaining the shape freezing mechanism in one Embodiment of this invention. In one Embodiment of this invention, it is the figure which performed the case where it implements by the press molding process of 2 processes. It is a figure which shows the other cross-sectional shape of the connection part of the press-molded component in one Embodiment of this invention. It is a figure which shows the press molded component in Example 1 of this invention. It is a figure which shows the cross-sectional shape of the connection part of the press molded component in Example 1 of this invention. It is a figure which shows the press molded component in Example 2 of this invention.

Explanation of symbols

1 Press-formed part having a U-shaped cross-sectional shape 2 Press-formed part having a U-shaped cross-sectional shape with a collar 3 Press-formed part having a V-shaped cross-sectional shape 4 V-shaped with a collar Press-formed parts with mold cross-section 9 Metal plate (blank)
DESCRIPTION OF SYMBOLS 10 Press-molded part 11 Surface part 11a Ridge part 12 Connection part 12a Curved part 12b Straight line part 20 Punch 21 Surface part 22 Connection part 22a Curved part 22b Linear part 25 Punch 30 Die 31 Surface part 32 Connection part 32a Curved part 32b Linear part 35 Die

Claims (3)

A method for press-forming a press-formed part having a U-shaped cross-sectional shape or a V-shaped cross-sectional shape , wherein the U-shaped or V-shaped is formed when press-molding a press-formed part by a one-step press forming process. A metal plate is press-molded using a punch and a die , which are press-molding dies having a cross-sectional shape in which a connecting portion connecting two or more curves and one or more straight lines is formed between the surface portions forming the surface. A press molding method of a press molded part having excellent shape freezing characteristics characterized by the above. A press-forming method of a press-formed part having a U-shaped cross-sectional shape or a V-shaped cross-sectional shape, and when press-molding a press-formed part by a two-step press forming process, First press molding on a metal plate using a punch and a die, which is a die for press molding having a cross-sectional shape in which a connecting portion connecting the surface portions forming a U-shape or V-shape has a single curve Then, in the second press forming step, the press part having a cross-sectional shape in which the connecting part connecting the face part and the face part forming the U-shape or V-shape is composed of two or more curves and one or more straight lines. A press molding method of a press molded part having excellent shape freezing property, characterized by performing final press molding on a metal plate using a punch and a die which are molding dies. According to the press molding method of a press-molded part having excellent shape freezing property according to claim 1 or 2 , the U-shaped cross section or the V-shaped cross section is formed, and a U-shaped or V-shaped is formed. A press forming method of a press formed part having excellent shape freezing characteristics, characterized in that a press formed part having a cross-sectional shape having two or more curves and one or more straight lines is formed by connecting the surface portions to each other. .