JP2022016873A - Press-molding method and press-molding die - Google Patents

Abstract

To prevent ashlar crack of a site which is subjected to stretch flange-molding, without causing deterioration in quality due to cost increase caused by man-hour increase and to occurrence of wrinkles by holding.SOLUTION: A die 1 and a blank holder 4 hold a blank material W', and then an excess thickness portion Q which increases a real length of an edge of the blank material W' is molded in an area adjacent to the opposite side of an area molded with a punch 2, in an area held by the die 1 and the blank holder 4. Thereafter, the blank material W' is pressed against the punch 2 and subjected to press-molding.SELECTED DRAWING: Figure 7

Description

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

Panel parts that make up the body of an automobile 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 the blank material W'shown by the dotted line. Specifically, as shown in FIG. 12, the die 101 and the blank holders 102 and 103 hold the ends of the blank material W'to be lowered integrally, and the blank material W'is pressed 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 the arrow in FIG. 13), the end portion (edge) of the blank material W'is formed. ) Moves to the vertical wall portion W2 side.

By the way, in the blank material W'before molding shown by the dotted line in FIG. 11, holes W4 and W5 are formed in advance in the region corresponding to the door opening. When this blank material W'is molded, as shown by an arrow in the figure, the material around the holes W4 and W5 becomes a molding region (top plate portion W1 and vertical wall portion W2; the region hatched in FIG. 11). It flows into the side and the holes W4 and W5 expand. 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 molding is also referred to as “stretch flange molding”). As described above, when tensile stress is applied to the flange portion W3, crack P may occur at the end portion (edge) of the flange portion W3 (the crack at this end portion is also referred to as “edge crack”).

For example, in Patent Document 1 below, a surplus portion (preformed portion) is formed in advance at a portion of the blank material to which stretch flange molding is performed. As a result, the peripheral length of the blank material is increased, so that the tensile stress applied to the flange portion during stretch flange forming is relaxed and edge cracking is prevented.

Further, in Patent Document 2 below, a surplus thickness imparting portion having a circumference longer than that of a flat surface is provided at a portion of the holding surface of the die and the blank holder where the stretch flange molding is performed.

Japanese Unexamined Patent Publication No. 2015-139783 Japanese Unexamined Patent Publication No. 2008-119736

In Patent Document 1, a new step of providing a surplus portion in the blank material before molding is required, which leads to an increase in cost due to an increase in man-hours.

On the other hand, as in Patent Document 2, by providing the surplus thickness imparting portion on the pressing surface of the die and the blank holder, the surplus thickness portion can be formed and the product can be press-molded in the same mold. Therefore, a separate step for molding the surplus thickness portion is not required.

However, the method of Patent Document 2 also causes the following problems. That is, the blank material is sandwiched between the flat portions of both holding surfaces while forming the surplus wall portion on the blank material by the surplus wall applying portion provided on the holding surface of the die and the blank holder. At this time, when the surplus portion is formed, the periphery of the surplus portion is not sandwiched by the pressing surface, so that distortion (small curvature) occurs around the surplus portion. Wrinkles (also referred to as "hold wrinkles") may occur by sandwiching the region around the surplus wall where such distortion occurs between the flat portions of both holding surfaces. If such hold wrinkles remain on the design surface of the product, the quality of the press-molded product deteriorates.

Therefore, an object of the present invention is to prevent edge cracking at a portion to be stretch-flange formed without causing cost increase due to an increase in man-hours and quality deterioration due to the occurrence of hold wrinkles.

In order to solve the above problems, the present invention is a method for performing press molding including stretch flange molding on a blank material by a press molding die having a punch, a die, and a blank holder. The blank is formed in a step of sandwiching the blank material with the blank holder and in a region of the blank material sandwiched between the die and the blank holder, which is adjacent to a region opposite to the region formed by the punch. Provided is a press forming method including a step of forming a surplus portion for increasing the actual length of the edge of the material and a step of pressing the blank material against a punch to perform press forming.

Further, in order to solve the above-mentioned problems, the present invention comprises a punch, a die and a blank holder, and is a die for performing press molding including stretch flange molding on a blank material, wherein the blank holder is described. With the blank material sandwiched between the die and the blank holder having a surplus portion forming die adjacent to the punch, the surplus portion forming die increases the actual length of the edge of the blank material. Provided is a press forming die for forming a surplus portion to be formed.

As described above, by forming the surplus portion on the blank material with the surplus portion molding mold while the blank material is sandwiched between the die and the blank holder, it is possible to avoid the occurrence of hold wrinkles around the surplus portion. Then, by pressing the blank material against the punch, the end portion of the blank material is pulled in a direction orthogonal to the material inflow direction while flowing into the forming region (stretch flange forming). At this time, since the actual length of the edge of the blank material is increased by the surplus portion, the tensile stress applied to the end portion of the blank material is relaxed and edge cracking can be prevented.

As described above, according to the present invention, the edge of the portion where the stretch flange molding is performed while avoiding the occurrence of hold wrinkles around the surplus portion without requiring a separate step for forming the surplus portion. It is possible to prevent cracking.

It is a top view of the blank material. It is sectional drawing of the press-molding die which concerns on one Embodiment of this invention (cross-sectional view corresponding to the YY line of the press-molded article of FIG. 3, and shows the state before the start of press molding. It is a top view of the lower die (punch and blank holder) of the press molding die. It is a perspective view of the 2nd blank holder and the surplus portion molding die of the press molding die, and shows the state which the surplus part molding die is arranged at the lower end position. It is a perspective view of the 2nd blank holder and the surplus portion molding die of the press molding die, and shows the state which the surplus part molding die is arranged at the upper end position. It is sectional drawing of the said press molding die, and shows the state which the blank material is sandwiched between a die and a blank holder. It is sectional drawing of the said press molding die, and shows the state which the surplus part was molded in the blank material. It is a top view of the blank material which the surplus part was molded. It is a perspective view of a surplus part. It is sectional drawing of the said press molding die, and shows the state which the press molding is completed. It is a top view of the press-molded product molded by the conventional press-molding die. It is sectional drawing of the conventional press-molding die (cross-sectional view corresponding to XX line of the press-molded article of FIG. 11). It is sectional drawing of the conventional press molding die.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In the present embodiment, the panel parts of the vehicle body of the automobile, particularly the side outer panel W, are formed by press molding. Since the side outer panel W is the same as that shown in FIG. 11, duplicate description will be omitted.

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

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

The press forming die is provided with a surplus portion forming die 7 having a forming surface 7a. The surplus thickness forming die 7 is provided adjacent to the second blank holder 4 on the side opposite to 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 surplus thickness forming mold 7 is arranged in a vertically extending groove 4b provided on the inner peripheral surface of the second blank holder 4 in a state where it can be raised and lowered. 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 (FIG. 5). The surplus portion molding die 7 can be moved up and down between and from (see).

The forming surface 7a of the surplus portion forming die 7 is in the direction orthogonal to the material inflow direction of the blank material W', and in the present embodiment, in the extending direction of the edge of the blank material W'(horizontal direction in FIGS. 4 and 5). , Has a curved surface that is curved so as to be convex upward. In the illustrated example, the height of the molded surface 7a becomes lower as it approaches the punch 2 in the material inflow direction, that is, in the direction orthogonal to the edge of the blank material W'(left-right direction in FIG. 2). A recess 1b having a shape corresponding to the molding surface 7a is provided in a region of the lower surface of the die 1 that faces the molding surface 7a of the surplus portion molding die 7 in the vertical direction (see FIG. 2).

In the state before the die 1 is lowered, the holding surfaces 3a, 4a, and 5a of the blank holders 3, 4, and 5 are arranged above the punch 2. Further, the forming surface 7a of the surplus portion forming 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 holding surfaces 3a, 4a, 5a of the blank holders 3, 4, and 5 (see FIGS. 2 and 3).

Then, the die 1 is lowered, and the holding surface 1a of the die 1 and the holding surfaces 3a, 4a, and 5a of the blank holders 3, 4, and 5 form an outer edge of the blank material W'and a region along the edges of the holes W4 and W5. (See FIG. 6). After that, the die 1 is further lowered, and the die 1, the blank holders 3, 4, 5, and the blank material W'are integrally lowered while pushing down the blank holders 3, 4, and 5. At this time, by pushing down the second blank holder 4, the surplus portion molding die 7 rises relatively with respect to the second blank holder 4, and the molding surface 7a of the surplus portion molding die 7 is the second blank holder. It protrudes upward from the holding surface 4a of No. 4 (see FIG. 5). As a result, the surplus portion Q is formed in the region of the blank material W'that is sandwiched between the die 1 and the second blank holder 4 and is adjacent to the region opposite to the region formed by the punch 2. (See FIG. 7).

The surplus portion Q is provided in or near the region of the blank material W'where the stretch flange molding is performed. Specifically, of the edge of the blank material W', the surplus portion Q is formed at or near the concave curve recessed on the molding region side (punch 2 side). In the present embodiment, of the holes W4 on the rear side of the blank material W', the surplus portion Q is formed at two locations near the portion (lower end) having the largest curvature (see FIG. 8).

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

When the surplus portion Q is formed on the blank material W'in this way, distortion (slight deformation) may occur around the surplus portion Q. In the present embodiment, as described above, since the surplus portion Q is formed in a state where the blank material W'is sandwiched and restrained by the die 1 and the blank holder 4, distortion is generated around the surplus portion Q. It is less likely to occur and the occurrence of hold wrinkles is avoided. In particular, in the present embodiment, in the blank material W', all the regions adjacent to the surplus 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 surplus portion Q Distortion around the 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 FIG. 10). At this time, as the molding proceeds while lowering the die 1, the material near the end portion (outer edge and edge of the holes W4 and W5) of the blank material W'is on the molding region (top plate portion W1 and vertical wall portion W2) side. Inflow to. At this time, the region near the concave curve at the edge of the blank material W'is subjected to "elongation flange forming" in which the blank material W'is pulled on both sides in a direction orthogonal to the inflow direction. In the present embodiment, the surplus portion Q is provided in the vicinity of the portion where the stretch flange molding is performed, particularly, the portion where the curvature of the edge is large (in the present embodiment, the lower portion of the hole W4 of the rear door opening). Be done. Since the actual length of the edge of the blank material W'is increased by this surplus portion Q as compared with the flat surface, the tensile stress due to the stretch flange molding is relaxed, and the edge crack (edge crack) is avoided.

The present invention is not limited to the above embodiment. For example, the surplus portion Q may be provided not only in the vicinity of the portion where the stretch flange molding is performed, but also in the portion where the stretch flange molding is performed. Further, the surplus portion Q may be provided in the upper portion of the hole W4 on the rear side, the hole W5 on the front side, or the region along the outer edge of the blank material. Further, the shape of the surplus portion Q is not limited to the above, and may be a concave curved surface or a corrugated shape in a direction orthogonal to the material inflow direction (direction along the edge) of the end portion of the blank material W'.

Further, in the above embodiment, the case where the punch 2 is a fixed type and the die 1 is a movable type is shown, but conversely, the die 1 may be a fixed type and the punch 2 may be a movable type. Further, the present invention can be applied to the case of molding a press-molded product other than an automobile panel part as long as it is press-molded including stretch flange molding.

1 Die 2 Punch 3 1st blank holder 4 2nd blank holder 5 3rd blank holder 7 Extra wall forming mold 7a Molding surface Q Extra wall W Side outer panel W'Blank material

Claims (2)

A press forming die having a punch, a die, and a blank holder, which is a method for performing press forming including stretch flange forming on a blank material.
The step of sandwiching the blank material between the die and the blank holder, and
Of the blank material, a surplus portion that increases the actual length of the edge of the blank material is provided in a region adjacent to the region formed by the punch in the region sandwiched between the die and the blank holder. The molding process and
A press molding method comprising a step of pressing the blank material against the punch to perform press molding. A die provided with punches, dies and blank holders for performing press forming including stretch flange forming on a blank material.
The blank holder has a surplus forming die adjacent to the opposite side of the punch.
A press-molded die for forming a surplus portion that increases the actual length of the edge of the blank material by the surplus portion molding die in a state where the blank material is sandwiched between the die and the blank holder.

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