JP6777053B2 - Press molding equipment and method - Google Patents

Description

The present invention forms a molded product having a target shape having a groove-shaped portion extending in the longitudinal direction and having a flange portion curved along the longitudinal direction on at least one of a pair of vertical wall portions forming the groove-shaped portion. Regarding press molding equipment and methods.

Press molding is a method of transferring the shape of a die to a blank by pressing the die against the material (blank) which is the object thereof. In press molding, after the press-molded product is taken out from the mold, shape defects caused by elastic recovery of the residual stress in the press-molded product, so-called springback, occur, and the shape is different from the desired shape. Often occurs.

The extent to which springback occurs is largely influenced by the strength of the material. In recent years, especially in the automobile industry, there is a strong tendency to use high-strength steel plates for body parts from the viewpoint of weight reduction of automobile bodies, and the degree of springback caused by such high-strength materials is increasing. Is getting bigger.
For this reason, in order to bring the shape after springback closer to the target design shape, a skilled worker must modify the mold many times at the production site and repeat trials and errors, resulting in a production preparation period. Will be prolonged. Therefore, it can be said that developing a method that can effectively reduce springback is an increasingly important issue in reducing the development period and cost of automobiles.

In order to reduce springback, it is essential to control the stress that causes it. In a straight part in which the cross section of the part shape does not change in the longitudinal direction, the springback is limited to a two-dimensional change in the cross-sectional shape such as opening of the mouth, and stress control is relatively easy. On the other hand, in a curved part in which the cross section of the part shape changes in the longitudinal direction, in addition to the two-dimensional change in the cross-sectional shape, three-dimensional springback such as twisting and bending occurs. The stresses that cause three-dimensional springback are complex and difficult to control.
Patent Document 1 proposes a "press forming method and apparatus" as a technique for reducing three-dimensional springback of twisting and bending of curved parts.

In the same document, for example, as shown in FIG. 10, the punch bottom portion 51a, the vertical wall portion 51b, and the groove-shaped portion and the flange portion (curved outer flange portion 51c and curved inner flange portion 51d) are formed and along the longitudinal direction. The form of the springback that occurs in the molded product when the molded product 51 having the curved flange is foam-molded has been studied.
Since the present invention presupposes the mechanism of springback reduction examined in the same document, the mechanism examined in the same document will be outlined below.

In the conventional simple foam molding, as shown in the perspective view of FIG. 11 and the cross-sectional view of FIG. 12, the blank 69 (see FIG. 12) is sandwiched between the press molding dies 57 having the die 53 and the punch 55. Do. FIG. 13 is a diagram showing blank outlines before and after molding. The outer line corresponding to the flange (hereinafter referred to as the curved inner flange portion 51d) on the side with a large curvature of curvature (the side with a small radius of curvature) has a smaller curvature (the radius of curvature becomes larger) due to the inflow of blanks due to molding. Becomes longer (A ₀ B ₀ → A ₁ B ₁ ). That is, the curved inner flange portion 51d is formed with an elongated flange, and tensile stress remains in the longitudinal direction at the bottom dead center.

On the other hand, the opposite is true for the flange on the side with a small curvature of curvature (the side with a large radius of curvature) (hereinafter, the curved outer flange portion 51c), and the outer line has a large curvature (the radius of curvature is small) due to the inflow of blanks due to molding. Curvature) The line length becomes shorter. (C ₀ D ₀ → C ₁ D ₁ ). That is, the curved outer flange portion 51c is contracted and the flange is deformed, and the compressive stress remains in the longitudinal direction at the bottom dead center.
These residual stresses elastically recover at the time of mold release, and the curved inner flange portion 51d undergoes contraction deformation and the curved outer flange portion 51c undergoes elongation deformation. As a result, as shown in FIG. 14, the component has a large curvature curvature (radius of curvature). Springback occurs, which causes bending deformation. In FIG. 14, the broken line shows the shape before the springback, and the solid line shows the shape after the springback.

As described above, in the molded part having the flange portion curved in the longitudinal direction, the residual stress in the flange portion is released at the time of mold release, so that springback that bends and deforms the entire part is generated. From this, it can be said that in such a component, reduction of the residual stress of the flange portion is very important for reducing the springback of the component.

Patent documents describe a technique for reducing residual stress of a flange portion by changing the wire length of the flange portion larger than the target shape in the press forming process and then returning the flange portion line length to the target shape. It is an invention of 1.
FIG. 15 shows a cross section of the press molding apparatus disclosed in Patent Document 1 during molding. The press forming apparatus 59 includes a die 61, a flange forming die 63 arranged to face the die, a punch 67 movably supported by a support mechanism 65 up and down, and a pad 71 for pressing the blank 69 against the punch. ing.
In the press molding method of Patent Document 1, the punch bottom portion 51a and the vertical wall portion 51b are molded to the target shape to the first bottom dead point by the die 61 and the punch 67, and the curved outer flange portion 51c and the curved inner flange portion 51d are formed. The longitudinal line length of the curved outer flange portion 51c is shorter than the line length of the flange portion of the molded product 51, and the longitudinal line length of the curved inner flange portion 51d is shorter than that of the flange portion of the molded product 51. The first molding step (see FIGS. 15 (a) to 15 (c)) of molding so as to be longer than the line length, and the curved outer flange molded in the first molding step by the die 61 and the flange molding die 63. The first molding step and the first molding step are provided with a second molding step (see FIGS. 15C and 15D) for molding the portion 51c and the curved inner flange portion 51d into the target shape of the molded product 51 to the second bottom dead point. 2 It is characterized in that the molding step is performed by one press molding.

FIG. 16 is an explanatory diagram illustrating a change in line length between the curved inner flange portion 51d and the curved outer flange portion 51c from before the start of press molding to the first bottom dead center and the second bottom dead center. In FIG. 16, the part circled by the broken line is enlarged and shown about the inside and the outside of the curve. In each enlarged view, the broken line is the inner end 69a and the outer end 69b of the blank 69 before press forming, the dotted line is the inner end 69a and the outer end 69b at the first bottom dead center, and the solid line is the inner end 69a at the second bottom dead center. And the outer end 69b are shown respectively.

The points A ₀ and B ₀ at the inner end of the flange before the start of press molding are A ₁ point and B ₁ point at the first bottom dead center, and A ₂ points and B ₂ points at the second bottom dead center, respectively. , The line length changes from A ₀ B ₀ → A ₁ B ₁ → A ₂ B ₂ . During the first step from the start of molding to the first bottom dead center, A ₀ B ₀ at the inner end of the flange becomes A ₁ B ₁ due to the inflow of blanks, and the line length at the inner end of the flange is stretched and lengthened (extended flange). Deformation). Then, during the second step from the first bottom dead center to the second bottom dead center, the inner end of the flange is extruded (outflowed) to the outside, so that the line length of the inner end of the flange is slightly shortened ( A ₁ B ₁ → A ₂ B ₂ ), the line length corresponds to the target shape at the second bottom dead center.

At the outer end of the flange, the opposite phenomenon occurs at the inner end of the flange. The C ₀ and D ₀ points at the outer edge of the flange before the start of press molding are C ₁ and D _{1 at} the first bottom dead center, and C ₂ and D ₂ at the second bottom dead center, respectively. , The line length changes from C ₀ D ₀ → C ₁ D ₁ → C ₂ D ₂ . During the first step from the start of molding to the first bottom dead center, C ₀ D ₀ at the outer end of the flange becomes C ₁ D ₁ due to the inflow of blanks, and the line length at the outer end of the flange is shortened and shortened (shrinking flange). Deformation). Then, during the second step from the first bottom dead center to the second bottom dead center, the outer end of the flange undergoes a deformation that is pushed out (outflows), so that the line length of the outer end of the flange becomes slightly longer ( C ₁ D ₁ → C ₂ D ₂ ), the line length corresponds to the target shape at the second bottom dead center.

In this way, in the curved inner flange portion, in the first molding step, the line length is once made longer than the target shape of the molded product, and in the second molding step, the line length is returned to the target shape of the molded product. Perform molding. In the curved outer flange portion, in the first molding step, the line length is once shorter than the target shape of the molded product, and in the second molding step, the line length is returned to the target shape of the molded product. I have to. Therefore, in the curved inner flange portion and the curved outer flange portion, the strain generated in the first molding step is slightly returned in the second molding step, and the residual stress is significantly reduced.

This point will be described with reference to FIG. FIG. 17 is a stress-strain diagram in the longitudinal direction from the start of forming the flange portion to the second bottom dead center. As shown in FIG. 17, a large residual stress is accumulated in the flange portion of the first bottom dead center by the first molding step. However, the residual stress is significantly reduced by slightly returning the strain from the first bottom dead center to the second bottom dead center in the second molding step.
As described above, the invention of Patent Document 1 utilizes the feature that the residual stress changes significantly sensitively by returning the strain slightly.

JP-A-2015-27698

The mechanism of springback suppression disclosed in Patent Document 1 is that the residual stress is significantly reduced by slightly returning the strain in the process from the first bottom dead center to the second bottom dead center. It is important how much the return amount should be.
The strain return amount is the punch lowering amount (relative movement distance h) from the first bottom dead center (see FIG. 15 (c)) to the second bottom dead center (see FIG. 15 (d)) (FIG. 15 (see). It is related to a)), and it is important that the relative movement distance h can be adjusted reliably and accurately.

However, in the press forming apparatus 59 disclosed in Patent Document 1, it is the flange forming die 63 that is fixed, and the entire punch 67 is supported by the support mechanism 65, and the entire punch is supported during press forming. It has a moving structure. For this reason, the movement of the punch during press molding may become unstable due to variations in the material strength of the blank and the influence of mechanical play.
If the movement of the punch is not the same for each shot of press molding, the relative movement distance h described above changes for each shot, and the amount of strain return changes. Therefore, the shape after springback may fluctuate for each shot, and in this respect, there is a concern that the target shape after springback may vary in the press forming apparatus 59 of Patent Document 1.

Further, in the press molding apparatus 59 disclosed in Patent Document 1, the relative movement distance h is set only by the position of the punch at the first bottom dead center, and if it takes time to finely adjust the punch position, the springback is surely performed. There is a problem that it is difficult to prevent.
Furthermore, since the positions of the curved inner flange and the curved outer flange in the pressing direction are the same, and the relative movement distance h cannot be adjusted individually for the curved inner flange and the curved outer flange, a complicated three-dimensional spring such as twisting or bending occurs. There was also the problem that it was difficult to respond flexibly to the back.

The present invention has been made to solve the above-mentioned problems, and it is possible to stably perform adjustment so that the amount of strain returned during molding becomes constant, and to stably suppress springback. The purpose is to obtain press molding equipment and methods.
Another object of the present invention is to provide a press forming apparatus and method capable of stably reducing three-dimensional springback such as twisting and bending.

(1) The press molding apparatus according to the present invention has a groove-shaped portion extending in the longitudinal direction, and has a flange portion curved in the longitudinal direction at least one of a pair of vertical wall portions forming the groove-shaped portion. A press molding device that molds a molded product with a target shape.
The groove portion for forming the groove-shaped portion, a die having die shoulder portions on both sides of the groove portion, a lower punch for forming the lower portion of the vertical wall portion and the flange portion in cooperation with the die, and the lower punch. On the other hand, the punch gap between the upper punch and the lower punch, which are provided so as to be detachable (so that they can be separated and touched) in the height direction and form the upper part of the vertical wall portion, is adjusted. It is characterized by having an upper punch support mechanism that supports the upper punch and is installed in the lower punch.

(2) The press molding apparatus according to the present invention has a groove-shaped portion extending in the longitudinal direction, and has a flange portion curved along the longitudinal direction on at least one of a pair of vertical wall portions forming the groove-shaped portion. It molds a molded product with a target shape,
A groove portion for forming the groove-shaped portion, a die having die shoulder portions on both sides of the groove portion, and a flange forming die arranged facing the die shoulder portion and forming the flange portion in cooperation with the die shoulder portion. A lower punch that is inserted into the groove of the die to form the lower portion of the vertical wall portion and a lower punch that can be separated from the lower punch in the height direction (so that they can be separated or contacted) are provided. It is provided with an upper punch that forms the upper part of the vertical wall portion, and an upper punch support mechanism that supports the upper punch so that the punch gap between the upper punch and the lower punch can be adjusted and is installed in the lower punch. At least one of the flange forming dies is configured to be movable in the height direction independently of the other.

(3) The press molding method according to the present invention has a groove-shaped portion extending in the longitudinal direction, and has a flange portion curved in the longitudinal direction at least one of a pair of vertical wall portions forming the groove-shaped portion. A molded product having a target shape is molded using the press molding apparatus according to (1).
A step of forming a part of the groove-shaped portion by the upper punch and the die in a state where the upper punch is supported by providing a predetermined punch gap with respect to the lower punch, and the die is moved to the lower punch side. This is characterized by including a step of pressing the upper punch against the lower punch so that the lower punch does not have the punch gap, and forming the groove-shaped portion and the flange portion into the target shape.

(4) The press molding method according to the present invention has a groove-shaped portion extending in the longitudinal direction, and has a flange portion curved in the longitudinal direction at least one of a pair of vertical wall portions forming the groove-shaped portion. A molded product having a target shape is molded using the press molding apparatus described in (2).
The upper punch is supported by providing a predetermined punch gap with respect to the lower punch, and the height of the flange forming die that can move in the height direction is adjusted to a predetermined height by the upper punch and the die. In the step of forming a part of the groove-shaped portion and by moving the die to the lower punch side, the upper punch is pressed against the lower punch so that there is no punch gap, and the groove-shaped portion is made into the target shape. It is characterized by including a step of forming and a step of moving the flange forming die to the die side to form the flange portion into the target shape.

In the present invention, a groove portion for forming a groove-shaped portion, a die having die shoulder portions on both sides of the groove portion, and a lower punch for forming the lower portion of the vertical wall portion and the flange portion in cooperation with the die. Between the upper punch, which is provided so as to be detachable (separate and contactable) with respect to the lower punch in the height direction and forms the upper part of the vertical wall portion, and the upper punch and the lower punch. The upper punch is supported so that the punch gap can be adjusted, and the upper punch support mechanism installed in the lower punch is provided. By adjusting the punch gap, the amount of strain returned during molding becomes constant. Such adjustments can be made stably, and springback can be suppressed stably.

It is explanatory drawing of the press molding apparatus which concerns on Embodiment 1 of this invention. It is explanatory drawing of the press molding method using the press molding apparatus shown in FIG. It is explanatory drawing of the press molding apparatus which concerns on Embodiment 2 of this invention. It is explanatory drawing of the press molding method using the press molding apparatus shown in FIG. It is explanatory drawing of the target shape of the press-molded article which concerns on Examples 1 and 2 (the 1). It is explanatory drawing of the target shape of the press-molded article which concerns on Examples 1 and 2 (the 2). It is explanatory drawing of the evaluation method of the springback amount which concerns on Examples 1 and 2. It is explanatory drawing of the evaluation method of the springback amount which concerns on Example 2. FIG. It is a graph which shows the evaluation result of the springback amount which concerns on Example 2. FIG. It is explanatory drawing of the subject of this invention, and is the perspective view of the press-molded article molded by the conventional press molding method. It is explanatory drawing of the subject of this invention, and is the perspective view of the die of the conventional press forming apparatus. It is explanatory drawing of the subject of this invention, and is explanatory drawing of the conventional press molding method. It is explanatory drawing of the subject of this invention, and is explanatory drawing of the generation mechanism of the springback in the molded article molded by the conventional press molding method. It is explanatory drawing of the subject of this invention, and is explanatory drawing of the spring back in the molded article molded by the conventional press molding method. It is explanatory drawing of the conventional press forming apparatus and press forming method. It is explanatory drawing of the mechanism of the springback suppression in the press forming method shown in FIG. 15 (the 1). It is explanatory drawing of the mechanism of the springback suppression in the press forming method shown in FIG. 15 (the 2).

[Embodiment 1]
The press forming apparatus 1 as an example according to the present embodiment has a groove-shaped portion extending in the longitudinal direction and a punch bottom portion 51a shown in FIG. 5, and is provided on both sides of a pair of vertical wall portions 51b forming the groove-shaped portion. A molded product 51 having a target shape having flange portions 51c and 51d curved in the longitudinal direction is molded, and as shown in FIG. 1, a die 3, a lower punch 5, an upper punch 7, and an upper portion are formed. It includes a punch support mechanism 9 and a pad 11.
Hereinafter, each configuration will be described in detail.

<Die>
The die 3 has a groove portion 15 for forming a groove-shaped portion and die shoulder portions 13 on both sides of the groove portion 15, and can be relatively moved to the punch side by a die driving device (not shown).
Above the groove 15 of the die 3, a pad accommodating portion 17 accommodating the pad 11 and a pad pressing mechanism accommodating portion 19 for accommodating the pad pressing mechanism 35 described later are provided.

<Lower punch>
The lower punch 5 cooperates with the die 3 to form the lower portion and the flange portion of the vertical wall portion 51b having the target shape. As shown in FIG. 1, the lower punch 5 is provided with a vertical wall lower molding portion 21 for molding the lower portion of the vertical wall portion 51b in the central portion, and is continuously in the horizontal direction from the lower end of the vertical wall lower molding portion 21. A flange forming portion 23 overhanging is provided.
A hollow portion 25 is formed in the lower punch 5, and a communication groove 27 is formed from the hollow portion 25 to the upper surface of the vertical wall lower molded portion 21 through the center of the vertical wall lower molded portion 21.

<Upper punch>
The upper punch 7 is provided so as to be detachable (separate and contactable) with respect to the lower punch 5 in the height direction, and forms the upper portion of the vertical wall portion 51b.

<Upper punch support mechanism>
The upper punch support mechanism 9 is installed in the cavity 25 so as to adjust the punch gap G between the lower surface of the upper punch 7 and the upper surface of the vertical wall lower forming portion 21 in the lower punch 5 to support the upper punch 7. A support member 29 that is vertically movable in the communication groove 27 and whose upper end is connected to the lower surface of the upper punch 7 to support the upper punch 7 from below, and a cavity portion that is connected to the lower end of the support member 29. A stopper 31 that regulates the upward movement position of the support member 29 by abutting against the upper wall of the 25, and a support device 33 such as an air cylinder that is connected to the lower part of the stopper 31 and supports the stopper 31 with a predetermined bearing force. I have.

The support device 33 supports the upper punch 7 in a state where the upper surface of the stopper 31 is pressed against the upper surface of the cavity 25 by pushing up the lower surface of the stopper 31 with a predetermined supporting force, whereby the upper punch 7 is supported. A punch gap G at a predetermined interval is formed between the lower surface of No. 7 and the upper surface of the lower punch 5.
This punch gap G corresponds to the relative movement distance h (FIG. 15), but can be easily finely adjusted by disposing a shim or the like between the stopper 31 and the upper surface of the cavity 25.

The supporting force of the support device 33 is sufficiently increased as compared with the pressing force of the pad pressing mechanism 35 described later. In other words, the supporting force of the support device 33 is made larger than the sum of the pressing force of the pad pressing mechanism 35 and the force required for processing the blank 69 from the start of processing of the blank 69 to the first bottom dead center. By supporting the upper punch 7 with such a bearing force, the upper punch 7 is firmly fixed to the lower punch 5, so that the instability of the punch during processing as in the technique of Patent Document 1 is eliminated.

<Pad>
The pad 11 presses the blank 69 against the upper punch 7 in the molding process, and is pressed against the upper punch 7 by a pad pressing mechanism 35 composed of an air cylinder or the like provided inside the die 3. There is.
Although the method of the present invention can be carried out without using the pad 11, it is desirable to hold the blank 69 with the pad 11 and the upper punch 7 so that the blank 69 does not move during molding.

A press forming method using the press forming apparatus 1 configured as described above will be described with reference to FIG.
At the start of press molding, as shown in FIG. 2A, the upper punch 7 is supported in a state of being pushed up to the uppermost position by the support device 33, and in this state, the lower surface of the upper punch 7 and the lower punch 7 are supported. A predetermined punch gap G is formed between the vertical wall lower portion 21 and the upper surface of the vertical wall forming portion 21. The blank 69 is gripped by the upper punch 7 and the pad 11.

From the state before press molding in FIG. 2 (a) to the state of the first bottom dead center in FIG. 2 (b), the die 3 is lowered while the pad 11 is pressed against the blank surface, and the blank 69 is the punch bottom portion. It is molded on the upper part of the vertical wall. As described above, from the start of press molding to the state of the first bottom dead center in FIG. 2B, the upper punch 7 is supported and fixed by the support device 33 so as not to move.

At the first bottom dead center in FIG. 2B, the upper punch 7 is pushed up by the punch gap G above the second bottom dead center. Therefore, when the upper part of the vertical wall is formed in this state, The blank width direction end portions (portions 69a and 69b corresponding to the flange end portions) enter inside the state of the second bottom dead center. Therefore, the line length of the flange inner end 69a before the start of press molding is stretched and lengthened (extended flange deformation on the curved inner side), and the line length of the flange outer end 69b is shortened and shortened (contracted flange deformation on the curved outer side). ..

At the first bottom dead center, the pad pressing mechanism 35 is accommodated in the pad pressing mechanism accommodating portion 19, and the pad 11 is accommodated in the pad accommodating portion 17. In this state, the upper surface of the pad 11 abuts on the upper portion of the pad accommodating portion 17, and thereafter, when the die 3 is lowered, the upper punch 7 is pressed downward by the die 3 via the pad 11.

From the first bottom dead center in FIG. 2 (b) to the second bottom dead center in FIG. 2 (c), the die 3 further descends, during which the upper punch 7 is pushed down and the punch gap G becomes smaller. At the second bottom dead center, the punch gap G becomes zero, and the curved outer flange portion 51c and the curved inner flange portion 51d are formed. In the process from the first bottom dead center to the second bottom dead center, the inner end of the flange is extruded (outflowed) and deformed, so that the line length of the inner end 69a of the flange is slightly shorter than the first bottom dead center. The line length corresponds to the target shape at the second bottom dead center, which is offset by the tension applied to the flange end corresponding portion at the first bottom dead center. On the other hand, the flange outer end 69b is deformed to be pushed out (outflow) in the process from the first bottom dead center to the second bottom dead center, so that the line length of the flange outer end is longer than the first bottom dead center. It becomes slightly longer, and a tensile force is applied to offset the compressive force acting on the flange end corresponding portion at the first bottom dead center, resulting in a line length corresponding to the target shape at the second bottom dead center.

As described above, according to the press forming apparatus 1 of the present embodiment, the strain returning operation as shown in FIG. 16 is performed on the flange portions 51c and 51d, and the residual stress can be reduced.
Then, in the press forming apparatus 1 of the present embodiment, the punch for forming the vertical wall portion 51b is divided into upper and lower parts so that the punch gap G between the upper punch 7 and the lower punch 5 can be adjusted. By biting, the punch gap G can be finely adjusted. By finely adjusting the punch gap G, the amount of strain return can be controlled, so that the punch gap G most suitable for reducing springback can be obtained, and springback can be effectively prevented.
Further, although the above shows an example in which both the inner flange and the outer flange are curved, the above means can be applied to a target shape in which either the inner flange or the outer flange is curved, and springback can be prevented.

[Embodiment 2]
In the actual press molding process, a press try is performed before the press molding of a certain part is continuously performed, and the mold is finely adjusted based on the result of measuring the shape of the molded product. At that time, if the amount of strain return in the curved outer flange portion 51c and the curved inner flange portion 51d can be adjusted individually, three-dimensional springback such as twisting and bending can be effectively prevented.
However, in the press forming apparatus 1 of the first embodiment, the flange heights of the die 3 and the lower punch 5 are the same, and the curved outer flange portion 51c and the curved inner flange portion 51d cannot be individually adjusted.
Therefore, it is an object of the second embodiment to provide a press forming apparatus capable of individually adjusting the amount of strain return in the curved outer flange portion 51c and the curved inner flange portion 51d.

The press forming apparatus 37 according to the second embodiment will be described with reference to FIG. In FIG. 3, the same parts as those in FIG. 1 showing the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.
In the press forming apparatus 37 according to the present embodiment, the lower punch 39 has the vertical wall lower forming portion 21 but does not have the flange forming portion 23 of the first embodiment, and the flange forming portion 23 does not have the flange forming portion 23. Instead, flange forming dies that can move in the height direction (curved inner flange forming die 41 (left side in the figure) and curved outer flange forming die 43 (right side in the drawing)) are provided on both sides of the lower punch 39. The curved inner flange forming die 41 and the curved outer flange forming die 43 can be vertically positioned and moved up and down by the die moving mechanism 45.
The heights of the curved inner flange forming die 41 and the curved outer flange forming die 43 do not have to be the same, and the springback of bending and twisting is controlled more precisely by setting both independently to the optimum heights. can do.
In the following description, regarding the heights of the curved inner flange forming die 41 and the curved outer flange forming die 43, as shown in FIG. 3, the die gap is the vertical distance from the lower end of the vertical wall lower forming portion 21 in the lower punch 39. It is called g (the die gap of the curved inner flange forming die is g ₁ , and the die gap of the curved outer flange forming die is g ₂ ).

A press molding method using the press molding apparatus 37 of the present embodiment configured as described above will be described with reference to FIG. 4 (a) is before the start of molding, FIG. 4 (b) is the first bottom dead center, FIG. 4 (c) is on the way from the first bottom dead center to the second bottom dead center, and FIG. 4 (d) is the first. 2 Shows bottom dead center.
At the start of molding in FIG. 4A, the height of the curved inner flange forming die 41 on the left side in the drawing is set to be slightly lower than that on the curved outer flange forming die 43 on the right side in the drawing. That is, the die gap g ₁ of the curved inner flange forming die 41 is set to be larger than the die gap g ₂ of the curved outer flange forming die 43. This is because the amount of strain returned from the curved inner flange portion 51d is larger than that of the curved outer flange portion 51c.

The operation from the state before press molding in FIG. 4 (a) to the state of the first bottom dead center in FIG. 4 (b) is the same as in the first embodiment, in which the die is lowered with the upper punch 7 fixed. However, since the position of the curved inner flange forming die 41 is lower than the position of the curved outer flange forming die 43, at the first bottom dead center, the curved inner flange end portion is more inside (lower punch) than the curved outer flange forming end portion. 39 side).
In the process from FIG. 4 (b) to FIG. 4 (c), the die 3 is further lowered and the punch gap G becomes zero. After that, both the curved inner flange forming die 41 and the curved outer flange forming die 43 rise, and the die gap g becomes smaller, and the die gap g becomes zero in the state of the second bottom dead center shown in FIG. 4 (d). ..

In the process from the first bottom dead center to the second bottom dead center, the amount of strain returned at the curved inner flange portion 51d is larger than the amount of strain returned at the curved outer flange portion 51c.
As described above, in the present embodiment, the curved inner flange forming die 41 and the curved outer flange forming die 43 can be individually moved in the height direction, so that the curved inner flange portion does not change the shape of the mold itself. The amount of return of each strain of the 51d and the curved outer flange portion 51c can be controlled individually, and the springback of bending and twisting can be controlled more precisely.
It can be said that such flexibility of the embodiment of the present invention has a great advantage in a press shop where fine adjustment is repeated.

In the above example, both the curved inner flange forming die 41 and the curved outer flange forming die 43 are movable in the height direction, but the press forming apparatus 37 of the present invention is not limited to this and is curved. At least one of the inner flange forming die 41 and the curved outer flange forming die 43 may be configured to be height-adjustable independently of the other. For example, only the curved inner flange forming die 41 can move in the height direction. The curved outer flange forming die 43 may be fixed.
Further, as in the first embodiment, the above means can be applied to a target shape in which either the inner flange or the outer flange is curved. It is necessary to change the die gap g on the curved side.

Since the action and effect of the press molding method of the first embodiment have been verified by conducting a press molding experiment, this will be described below.
As shown in FIGS. 5 and 6, the press-formed target shape has a hat cross section, both flanges are curved in the horizontal direction of the top plate along the longitudinal direction, the length is 1000 mm, and the cross section height is high. The width of the punch bottom is 30 mm, the width of the curved inner flange and the curved outer flange is 25 mm, and the radius of curvature of the longitudinal curve at the center of the width of the shape is 1000 mm. As a blank, a steel plate having a tensile strength of 980 MPa with a plate thickness of 1.2 mm was used. A 1000 tonf hydraulic press was used as the press.

As an example of the present invention, using the press forming apparatus 37 shown in FIG. 3, the punch gap G between the upper punch 7 and the lower punch 5 is set to 10 mm, and the heights of the curved inner flange forming die 41 and the curved outer flange forming die 43 are both set. The lowermost position of the vertical wall lower molding portion 21 of the lower punch 5 was set. This is equivalent to setting the punch gap G between the upper punch 7 and the lower punch 5 to 10 mm in the press forming apparatus 1 shown in FIG.
As a comparative example, the method of Patent Document 1 in which the relative movement distance h was 10 mm was used using the press molding apparatus 59 shown in FIG. A pad was used in both the comparative example and the example of the present invention, and the pad pressure was 50 tonf. In both the comparative example and the example of the present invention, 20 blanks were press-molded.

The molded target shape was measured with a three-dimensional shape measuring device. After that, the measurement data is aligned on the CAD software so that the curved portion in the center of the longitudinal direction matches the design shape, and then the Y coordinate difference between the measurement shape data and the design shape data at the component end (bending amount Δy, FIG. 7). (See) was calculated, and this bending amount Δy was used as an index of bending deformation due to springback.
The amount of bending Δy is that if it is positive, it bends and deforms in the direction in which the curvature of curvature of the part increases (the radius of curvature decreases), and if it is negative, it bends and deforms in the direction that the curvature of curvature decreases (the radius of curvature increases). Means that. And if the absolute value is small, it means that the amount of springback is small.

The bending amount Δy of 20 panels after press molding was measured.
The minimum value of Δy in the example of the present invention was −0.6 mm, and the maximum value was 1.4 mm. On the other hand, the minimum value of Δy in the comparative example was -1.7 mm, and the maximum value was 1.5 mm. The difference between the maximum value and the minimum value of Δy was 2.0 mm in the example of the present invention and 3.2 mm in the comparative example, demonstrating that the variation in shape is reduced by the present invention.

The effects of the press molding method of the second embodiment of the present invention have also been verified by conducting a press molding experiment, and will be described below. The press-molded target shape is shown in FIGS. 5 and 6 as in the first embodiment, and the blank and the press-molding apparatus are also the same as in the first embodiment.
As an example of the present invention, using the press forming apparatus 37 shown in FIG. 3, the punch gap G between the upper punch 7 and the lower punch 5 is set to 10 mm, and the heights of the curved inner flange forming die 41 and the curved outer flange forming die 43 (die). A method of individually setting the gap g) was used. As a comparative example, the relative movement distance h was changed by using the method of Patent Document 1 using the press molding apparatus 59 shown in FIG. A pad was used in both the comparative example and the example of the present invention, and the pad pressure was 50 tonf.

The evaluation of the molded product was performed by comparing the bending amount Δy shown in FIG. 7 with the twist amount Δθ in FIG. The amount of bending Δy was measured by the same method as in Example 1 shown in FIG. A method for measuring the twist amount Δθ will be described with reference to FIGS. 5 and 8. After aligning the measurement data so that the curved portion matches the design shape, the cross-sectional shapes of the center and the end of the curved portion were extracted as shown in FIG. The extracted cross-sectional shape is as shown in the schematic view of FIG. The angle formed by the punch bottom portion of the measurement shape and the punch bottom portion of the design shape (rotation angle due to springback) is measured with the direction of the rotation angle (counterclockwise) in FIG. 8 as positive, and the punch bottom at the center of the curved portion is measured. From the rotation angle θ _C and the punch bottom rotation angle θ _E at the end, the twist amount was calculated as Δθ = θ _E − θ _C.

When the punch gap G is 10 mm, the die gap g ₁ of the curved inner flange forming die 41 is 6 mm, and the die gap g ₂ of the curved outer flange forming die 43 is 4 mm by the method of the present invention, the bending amount Δy and the twisting amount Δθ is shown in FIG. 9 by ● and ▲, respectively. In FIG. 9, the vertical axis represents Δy (mm) and Δθ degree, and the horizontal axis represents the relative movement distance h (mm).
The relative movement distance h at this time corresponds to 15 mm (h = 10 + (6 + 4) / 2 = 15), and in the example of the present invention, both the bending amount Δy and the twisting amount Δθ can be set to values close to zero.

The results of measuring the bending amount Δy and the twisting amount Δθ by changing the relative movement distance h from 2.5 mm to 25 mm by the method of the comparative example are plotted in FIG. 9 with the bending amount Δy being ○ and the twisting amount Δθ being Δ. Shown. In the comparative example, there is no relative movement distance h that makes the bending amount Δy and the twisting amount Δθ zero at the same time.
As can be seen from the second embodiment, in the method of the present invention, the curved inner flange forming die 41 and the curved outer flange forming die 43 can be set independently, and the bending amount and the twisting amount are both close to zero. It is possible to search for and set the operating conditions such that

1 Press forming apparatus (Embodiment 1)
3 Die 5 Lower punch 7 Upper punch 9 Upper punch support mechanism 11 Pad 13 Die shoulder 15 Groove 17 Pad accommodating part 19 Pad pressing mechanism accommodating part 21 Vertical wall lower forming part 23 Flange forming part 25 Cavity part 27 Communication groove 29 Support member 31 Stopper 33 Support device 35 Pad pressing mechanism 37 Press molding device (Embodiment 2)
39 Lower punch 41 Curved inner flange molding die 43 Curved outer flange molding die 45 Die movement mechanism <molded product>
51 Molded product 51a Punch bottom 51b Vertical wall 51c Curved outer flange 51d Curved inner flange <Conventional example>
53 Die 55 Punch 57 Press molding die 59 Press molding device 61 Die 63 Flange forming die 65 Support mechanism 67 Punch 69 Blank 69a Flange inner end 69b Flange outer end 71 Pad G Punch gap g Die gap g ₁ Curved inner flange forming die Die gap g ₂ Die gap of curved outer flange forming die h Relative movement distance

Claims (4)

A press molding apparatus that has a groove-shaped portion extending in the longitudinal direction and has a flange portion curved along the longitudinal direction on at least one of a pair of vertical wall portions forming the groove-shaped portion to form a molded product having a target shape. There,
A groove portion for forming the groove-shaped portion, a die having die shoulders on both sides of the groove portion, a lower punch for forming the lower portion of the vertical wall portion and the flange portion in cooperation with the die, and a lower surface of the lower portion. an upper punch in the height direction relative to the upper surface of the punch provided disjunction possible (to allow or contact or away) forming the upper portion of the vertical wall portion, the upper surface of the lower punch and the lower surface of the upper punch A press molding apparatus characterized in that the upper punch is supported so that a punch gap between the two and the punch can be adjusted, and an upper punch support mechanism is provided in a cavity formed in the lower punch. A press molding apparatus that has a groove-shaped portion extending in the longitudinal direction and has a flange portion curved along the longitudinal direction on at least one of a pair of vertical wall portions forming the groove-shaped portion to form a molded product having a target shape. There,
A groove portion for forming the groove-shaped portion, a die having die shoulder portions on both sides of the groove portion, and a flange forming die arranged facing the die shoulder portion and forming the flange portion in cooperation with the die shoulder portion. The lower punch, which is inserted into the groove of the die to form the lower part of the vertical wall portion, and the lower surface can be separated from or detached from the upper surface of the lower punch in the height direction (so that they can be separated or touched). an upper punch provided for forming an upper portion of the vertical wall portion, adjustably supporting the upper punch punches gap between the lower surface of the upper punch and the upper surface of the lower punch, are formed on the lower punch Equipped with an upper punch support mechanism installed in the cavity
A press forming apparatus characterized in that at least one of the flange forming dies is configured to be movable in the height direction independently of the other. The press according to claim 1 is a molded product having a groove shape extending in the longitudinal direction and having a flange portion curved along the longitudinal direction on at least one of a pair of vertical wall portions forming the groove shape. It is a press molding method that molds using a molding device.
A step of forming a part of the groove-shaped portion by the upper punch and the die while supporting the lower surface of the upper punch with a predetermined punch gap with respect to the upper surface of the lower punch, and the lower punch of the die. and characterized by comprising a step of molding the groove-shaped portion and the flange portion in the target shape is pressed against the lower surface of the upper punch by moving to the side in the absence the punch gap on the upper surface of the lower punch Press molding method. A molded product having a target shape having a groove-shaped portion extending in the longitudinal direction and having a flange portion curved along the longitudinal direction on at least one of a pair of vertical wall portions forming the groove-shaped portion, is pressed by claim 2. It is a press molding method that molds using a molding device.
The upper punch is supported by providing a predetermined punch gap with respect to the upper surface of the lower punch , and the height of the flange forming die that can move in the height direction is adjusted to a predetermined height. And the step of forming a part of the groove-shaped portion by the die, and by moving the die to the lower punch side, the lower surface of the upper punch is pressed against the upper surface of the lower punch so that there is no punch gap. A press molding method comprising a step of forming a groove-shaped portion into the target shape and a step of moving the flange forming die to the die side to form the flange portion into the target shape.

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