JP7246349B2 - Press molding method and press molding die - Google Patents

Description

The present invention relates to a press molding method and a press molding die.

BACKGROUND ART Panel parts constituting automobile bodies are often formed by press-molding a metal plate. For example, the side outer panel W shown in FIG. 11 is formed by press-molding a blank material W' indicated by a dotted line. Specifically, as shown in FIG. 12, a die 101 and blank holders 102 and 103 are lowered integrally with the ends of the blank W′ held therebetween to press the blank W′ against the punch 104. Then, the side outer panel W having the top plate portion W1, the vertical wall portion W2, and the flange portion W3 is formed (see FIG. 13). In this case, since the material of the flange portion W3 sandwiched between the die 101 and the blank holders 102 and 103 is formed while flowing into the vertical wall portion W2 (see arrows in FIG. 13), the end portion (edge) of the blank material W' ) moves toward the vertical wall portion W2.

By the way, holes W4 and W5 are formed in advance in regions corresponding to the door openings in the blank W' before molding indicated by dotted lines in FIG. When this blank material W' is formed, as indicated by arrows in the drawing, the material around the holes W4 and W5 forms a forming region (the top plate portion W1 and the vertical wall portion W2. The hatched regions in FIG. 11.). side, and the holes W4 and W5 widen. At this time, the flange portion W3 around the holes W4 and W5 flows into the vertical wall portion W2 while being pulled in the circumferential direction (such forming is also called "stretch flanging"). In this way, the tensile stress applied to the flange portion W3 may cause a crack P to occur at the end (edge) of the flange portion W3 (this end crack is also referred to as "edge crack").

For example, in Patent Literature 1 below, an excess thickness portion (preformed portion) is formed in advance in a portion of a blank material to be stretch-flanged. As a result, since the peripheral length of the blank material is increased, the tensile stress applied to the flange portion during stretch flange forming is alleviated, and edge cracks are prevented.

Further, in Patent Literature 2 below, of the pressing surfaces of a die and a blank holder, a portion to which stretch flanging is performed is provided with an extra-thickness imparting portion having a longer circumferential length than the flat surface.

JP 2015-139783 A JP 2008-119736 A

In Patent Literature 1, a new process is required to provide the excess thickness in the blank material before molding, which leads to an increase in cost due to an increase in the number of man-hours.

On the other hand, as in the above Patent Document 2, by providing an excess thickness imparting portion on the pressing surface of the die and the blank holder, it is possible to perform molding of the excess thickness portion and press molding of the product in the same mold. Therefore, there is no need for a separate process for forming the excess thickness.

However, even with the method of Patent Document 2, the following problems occur. That is, the blank is sandwiched between the flat portions of both pressing surfaces while the excess thickness is formed in the blank by the excess thickness imparting portions provided on the pressing surfaces of the die and the blank holder. At this time, when forming the excess thickness portion, since the periphery of the excess thickness portion is not sandwiched between the pressing surfaces, distortion (a slight curvature) occurs around the excess thickness portion. There is a risk that wrinkles (also referred to as “hold wrinkles”) may occur when the region around the excess thickness in which such distortion occurs is sandwiched between the flat portions of both pressing surfaces. If such hold wrinkles remain on the design surface of the product, the quality of the press-formed product is degraded.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to prevent edge cracks in stretch-flange-formed portions without increasing costs due to increased man-hours and reducing quality due to the occurrence of hold wrinkles.

In order to solve the above problems, the present invention provides a press molding die having a punch, a die, and a blank holder, and a method for subjecting a blank material to press molding including stretch flanging, wherein the die and a step of sandwiching the blank material with the blank holder; Provided is a press forming method comprising the steps of: forming an excess wall portion for increasing the actual length of the edge of the blank; and pressing the blank against a punch to perform press forming.

Further, in order to solve the above problems, the present invention provides a mold for press forming including stretch flange forming on a blank material, comprising a punch, a die and a blank holder, wherein the blank holder, the above A surplus portion forming die is provided adjacent to the punch on the opposite side, and the actual length of the edge of the blank is increased by the surplus portion forming die in a state in which the blank is sandwiched between the die and the blank holder. To provide a press-molding die for molding an excess wall portion to be formed.

As described above, in a state in which the blank is sandwiched between the die and the blank holder, the excess thickness is formed in the blank by the excess thickness molding die, thereby avoiding the occurrence of hold wrinkles around the excess thickness. After that, by pressing the blank material against the punch, the end of the blank material is pulled in the direction orthogonal to the material inflow direction while flowing into the forming area (stretch flanging). At this time, since the actual length of the edge of the blank is increased by the excess thickness, the tensile stress applied to the edge of the blank can be relaxed to prevent edge cracking.

As described above, according to the present invention, the edge of the portion to be stretch-flanged is formed while avoiding the occurrence of hold wrinkles around the excess wall portion without requiring a separate step for forming the excess wall portion. Cracking can be prevented.

It is a top view of a blank material. FIG. 4 is a cross-sectional view of the press-molding die according to one embodiment of the present invention (a cross-sectional view corresponding to line YY of the press-molded product in FIG. 3), showing a state before the start of press-molding. Fig. 3 is a plan view of a lower die (punch and blank holder) of the press molding die; FIG. 4 is a perspective view of the second blank holder and the extra-wall portion molding die of the press molding die, showing a state in which the excess-wall portion molding die is arranged at the lower end position. FIG. 4 is a perspective view of the second blank holder and excess wall portion molding die of the press molding die, showing a state in which the excess wall portion molding die is arranged at the upper end position. It is a cross-sectional view of the press molding die, showing a state in which a blank material is sandwiched between a die and a blank holder. It is a sectional view of the above-mentioned press-molding metallic mold, and shows the state where an excess thickness part was formed in a blank material. FIG. 4 is a plan view of a blank material with an excess thickness portion formed; It is a perspective view of an excess meat part. It is a sectional view of the above-mentioned press molding die, and shows the state where press molding was completed. FIG. 3 is a plan view of a press-molded product molded with a conventional press-molding die; FIG. 12 is a cross-sectional view of a conventional press-molding die (a cross-sectional view corresponding to line XX of the press-molded product in FIG. 11); It is a cross-sectional view of a conventional press molding die.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In this embodiment, the panel components of the automobile body, particularly the side outer panel W, are formed by press molding. Note that the side outer panel W is the same as that shown in FIG. 11, so redundant description will be omitted.

First, a flat metal plate (steel plate) is punched to form a blank W' shown in FIG. Holes W4 and W5 are provided in a region of the blank W' corresponding to the door opening.

Next, the above blank material W' is set in the press molding die shown in FIG. This press molding die has a die 1 , a blank holder and a punch 2 . In this embodiment, as shown in the plan view of FIG. 3, as blank holders, a first blank holder 3 provided along the outer circumference of the blank material W' and a blank holder provided along the edge of the hole W4 on the rear side. A second blank holder 4 is provided, and a third blank holder 5 is provided along the edge of the hole W5 on the front side. Flat pressing surfaces 3a, 4a, 5a are provided on the upper surfaces of the blank holders 3, 4, 5, respectively. A flat pressing surface 1a is provided in a region of the lower surface of the die 1 that vertically faces the pressing surfaces 3a, 4a, and 5a of the blank holders 3, 4, and 5 (see FIG. 2). The pressing surfaces 3a, 4a, 5a of the blank holder and the pressing surface 1a of the die 1 may be provided with beads for controlling the material inflow.

The press-molding die is provided with a surplus portion molding die 7 having a molding surface 7a. The surplus portion forming die 7 is provided adjacent to the second blank holder 4 on the opposite side of the punch 2 (see FIG. 2). The surplus portion molding die 7 is movable in the mold opening/closing direction (vertical direction in this embodiment) independently of the second blank holder 4 . In the present embodiment, as shown in FIG. 4, the excess wall portion forming die 7 is arranged in a vertically extending groove 4b provided in the inner peripheral surface of the second blank holder 4 and extending in the vertical direction. Specifically, the position where the forming surface 7a is arranged below the pressing surface 4a of the second blank holder 4 (see FIG. 4) and the position where the forming surface 7a protrudes above the pressing surface 4a (see FIG. 5). ), the surplus portion molding die 7 can be moved up and down.

The molding surface 7a of the excess wall portion molding die 7 is formed in a direction orthogonal to the material inflow direction of the blank material W', which in this embodiment is the extending direction of the edge of the blank material W' (horizontal direction in FIGS. 4 and 5). , has a curved surface that is convex upward. In the illustrated example, the height of the forming surface 7a becomes lower as it approaches the punch 2 in the material inflow direction, that is, the direction perpendicular to the edge of the blank W' (horizontal direction in FIG. 2). A concave portion 1b having a shape corresponding to the molding surface 7a is provided in a region of the lower surface of the die 1 that vertically faces the molding surface 7a of the excess thickness molding die 7 (see FIG. 2).

Before the die 1 is lowered, the pressing surfaces 3 a , 4 a , 5 a of the blank holders 3 , 4 , 5 are arranged above the punch 2 . Further, the molding surface 7a of the extra-wall portion molding die 7 is arranged below the pressing surface 4a of the second blank holder 4 (see FIG. 4). In this state, the blank material W' is placed on the pressing surfaces 3a, 4a and 5a of the blank holders 3, 4 and 5 (see FIGS. 2 and 3).

Then, the die 1 is lowered, and the pressing surface 1a of the die 1 and the pressing surfaces 3a, 4a, 5a of the blank holders 3, 4, 5 are pressed together to form a region along the outer edge of the blank material W' and the edges of the holes W4, W5. is sandwiched (see FIG. 6). Thereafter, the die 1 is further lowered, and the die 1, the blank holders 3, 4, 5, and the blank material W' are lowered together while pushing down the blank holders 3, 4, and 5. At this time, as the second blank holder 4 is pushed down, the excess wall portion molding die 7 rises relative to the second blank holder 4, and the molding surface 7a of the excess wall portion molding die 7 moves toward the second blank holder. 4 protrudes upward from the pressing surface 4a (see FIG. 5). As a result, an excess thickness portion Q is formed in a region of the blank material W′ sandwiched between the die 1 and the second blank holder 4, adjacent to the region opposite to the region formed by the punch 2. (See FIG. 7).

The excess wall portion Q is provided in a region of the blank material W' where stretch flanging is performed or in the vicinity thereof. Specifically, of the edge of the blank material W', the excess thickness portion Q is formed at or in the vicinity of a concave curve that is concave toward the forming region side (punch 2 side). In the present embodiment, two extra thickness portions Q are formed in the vicinity of the portion (lower end) where the curvature is the largest in the hole W4 on the rear side of the blank W' (see FIG. 8).

The surplus portion Q has a curved surface that is convex upward (see FIG. 9). In the illustrated example, the height of the excess wall portion Q is highest at the edge of the hole W4 of the blank material W', and gradually decreases toward the molding region side (back side in FIG. 9). By providing the excess thickness portion Q, the actual length of the edge of the hole W4 of the blank W' is increased compared to the flat state before the excess thickness portion Q is formed.

When the excess thickness portion Q is formed in the blank material W' in this way, there is a possibility that the periphery of the excess thickness portion Q will be distorted (slightly deformed). In the present embodiment, as described above, the excess thickness portion Q is formed in a state in which the blank material W' is clamped and restrained by the die 1 and the blank holder 4, so that the periphery of the excess thickness portion Q is distorted. It is less likely to occur, and the occurrence of hold wrinkles is avoided. In particular, in the present embodiment, all regions of the blank material W′ adjacent to the excess thickness portion Q are sandwiched between the pressing surface 1a of the die 1 and the pressing surface 4a of the blank holder 4, so that the excess thickness portion Q Distortion around is less likely to occur.

After that, by further lowering the die 1, the blank material W' is pressed against the forming surface 2a of the punch 2, and the side outer panel W having the top plate portion W1, the vertical wall portion W2, and the flange portion W3 is formed ( See Figure 10). At this time, as the molding progresses while the die 1 is lowered, the material near the end of the blank material W' (the outer edge and the edges of the holes W4 and W5) moves toward the molding region (the top plate portion W1 and the vertical wall portion W2). flow into At this time, the area near the concave curve of the edge of the blank material W' is subjected to "stretch flanging" in which it is stretched to both sides in a direction orthogonal to the inflow direction. In this embodiment, an excess wall portion Q is provided in the vicinity of the portion where this stretch flanging is performed, particularly the portion where the edge has a large curvature (in this embodiment, the lower part of the hole W4 of the rear door opening). be done. Due to this excess wall portion Q, the actual length of the edge of the blank material W' is increased compared to the flat surface, so the tensile stress due to stretch flanging is alleviated, and edge cracks (edge cracks) are avoided.

The invention is not limited to the above embodiments. For example, the excess wall portion Q may be provided not only in the vicinity of the stretch-flanging portion, but also in the stretch-flanging portion. Further, the excess thickness portion Q may be provided in the upper portion of the hole W4 on the rear side, in the hole W5 on the front side, or in a region along the outer edge of the blank material. Further, the shape of the excess thickness portion Q is not limited to the above, and may be a concave curved surface shape or a corrugated shape in a direction perpendicular to the material inflow direction (direction along the edge) of the end portion of the blank material W'.

In the above embodiment, the punch 2 is fixed and the die 1 is movable. Conversely, the die 1 may be fixed and the punch 2 movable. In addition, the present invention can be applied to the case of forming press-formed products other than automobile panel parts as long as it is press-forming including stretch flanging.

1 Die 2 Punch 3 First blank holder 4 Second blank holder 5 Third blank holder 7 Extra-thickness molding die 7a Molding surface Q Extra-thickness W Side outer panel W' Blank material

Claims (2)

A press molding die having a punch, a die, a blank holder, and an excess wall portion molding die, and performs press molding including stretch flanging on the blank material by pressing a molding area spaced from the edge of the blank material against the punch. a method for
sandwiching a region along the edge of the blank with the die and the blank holder;
In this state, by relatively moving the excess wall portion forming die with respect to the blank holder, the excess wall portion forming die forms a concave curve recessed toward the forming region side of the edge of the blank material, or forming an excess wall portion in the vicinity thereof to increase the actual length of the edge of the blank;
and then pressing the forming region of the blank against the punch to perform press forming while holding the region along the edge of the blank between the die and the blank holder . A punch, a die, and a blank holder are provided, and with the die and the blank holder holding an area along the edge of the blank material, the forming area spaced apart from the edge of the blank material is pressed against the punch. A mold for press forming including stretch flange forming on a blank material,
an excess thickness molding die adjacent to the blank holder on the opposite side of the punch and movable relative to the blank holder ;
In a state in which the blank is sandwiched between the die and the blank holder, by relatively moving the surplus portion molding die with respect to the blank holder, the edge of the blank is recessed toward the molding region. A press-molding mold for forming an excess wall portion that increases the actual length of the edge of the blank material on or near the concave curve .

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