JP4568077B2 - Press mold with excellent shape freezing - Google Patents

Description

  The present invention relates to a press forming apparatus for a metal plate, and more particularly to a press die for preventing a spring back that occurs in the case of a high-strength steel plate or an aluminum alloy plate and ensuring good shape freezing. is there.

In recent years, high-strength steel plates and aluminum alloy plates have been frequently used for automobile parts, but shape freezing defects that occur when molding them into automobile parts have become a problem. That is, when a hat-shaped cross-sectional part is formed using a U-shaped bending mold, a shape freezing defect called a spring back occurs, and dimensional accuracy cannot be obtained. Yes.
In addition, this shape freezing defect not only significantly deteriorates the appearance quality of the final product, but also causes welding defects in assembly operations performed after molding, so it is possible to prevent shape freezing defects especially in structural parts such as members and frames. It is important.

Springback, which is known as a shape defect frequently observed in bending, is a phenomenon that occurs because the residual stress generated in the mold plate during bending is elastically restored and deformed during unloading. This is because the residual stress is unevenly distributed in the thickness direction. In general, when bent from the mold, it is opened at the shoulder of the punch due to the spring back of the metal plate.
In order to solve this problem, Patent Document 1 discloses a press molding method and a molded product for simultaneously molding a concave step portion recessed in a direction opposite to the molding direction on a bending shoulder. This is to counterbalance the spring back and balance it to prevent the angle near the punch shoulder from opening.

  However, as shown in FIG. 1, the springback not only changes the angle of the shoulder 1 but also manifests a phenomenon called “wall warpage” in which the wall 2 deforms from a flat surface to a curved surface with curvature as the material strength increases. Therefore, the invention disclosed in Patent Document 1 cannot prevent the wall from warping.

In addition, since an actual part such as an automobile part has a very complicated shape, not only “angular change” and “wall warp” which are two-dimensional springbacks, but also “ “Twist” and “ridge warp” occur, which is an important problem when press forming.
JP 7-185663 A

  An object of this invention is to provide the press molding die which prevents the shape freezing defect in a press molded component.

In order to solve this problem, the gist of the present invention is as follows.
(1) A press mold for press-molding a hat-shaped molded part from a metal plate having a punch, a die and a wrinkle presser,
The punch is divided into three or more in the longitudinal direction, and the heights of the divided punches are different from each other, and the divided punches located at both ends in the longitudinal direction are lower than the heights of the other divided punches. These divided punches have the function of having a constant height at the molding bottom dead center, and the divided punches are further divided in the stroke direction. A press die excellent in shape freezing property, characterized in that an elastic body is arranged.
(2) punch, having a die and a pad, a hat-shaped parts from a metal plate a press die for press-molding, punch is divided into three or more in the longitudinal direction and the divided punch height The divided punches located at both ends in the longitudinal direction are configured to be lower than the heights of the other divided punches, and these divided punches have a height at the bottom dead center. A press die that has a constant function and has excellent shape freezing characteristics, in which the divided punch is further divided in the stroke direction, and an elastic body is arranged at the divided portion in the stroke direction. .
(3) The press mold excellent in shape freezing property as described in (1) or (2) above, wherein the load resistance of the elastic body is different.

  According to the present invention, a good hat-shaped molded part having excellent dimensional accuracy can be obtained.

Hereinafter, the present invention will be described in detail.
The punches for press molding that have been used in the past are, for example, a die shape having an integral structure such as a shape warped in the height direction (Z direction) shown in FIG. 4, and divided in the longitudinal direction and the stroke direction. Was not.

As shown in FIG. 5, the inventors divide the punch in the longitudinal direction, further divide the divided punch in the stroke direction as necessary, and dispose the elastic body at the divided portions in the stroke direction. Thus, as shown in FIG. 6, it is possible to provide a step in the punch.
In FIG. 6, the punch is also divided in the stroke direction, but it is not always necessary to divide in the stroke direction. Punches having different heights are provided for each longitudinal direction, and the height is constant at the bottom dead center for molding. It is good also as a structure movable in a stroke direction so that it may become.
It was also found that the springback can be further reduced by changing the load resistance of the arranged elastic bodies.

The invention according to (1) is a press die having a punch, a die and a wrinkle presser, wherein the punch is divided into two or more in the longitudinal direction, and the heights of the divided punches are different from each other, The divided punch has a function of having a constant height at the bottom dead center of molding.
By dividing the punch in the longitudinal direction, the height of the punch can be set partially, and the contact timing between the product and the punch can be set freely. As a result, it is possible to control twisting and ridge warping by controlling too much of the material (sag at the bottom of the punch) and crushing it at the bottom dead center.

The invention according to (2) is a press die having a punch, a die and a pad, wherein the punch is divided into two or more in the longitudinal direction, and the heights of the divided punches are different from each other, The divided punch has a function of having a constant height at the bottom dead center of molding.
Spring back can be reduced even with a structure that does not have a wrinkle presser. The material that does not use the wrinkle presser can generate a lot of material flesh (punch bottom sagging), and it can be crushed at the bottom dead center of molding. This is because twisting and ridge warping can be reduced.

The inventions according to (1) and (2) are characterized in that the divided punch is further divided in the stroke direction, and an elastic body is arranged at the divided portion.
As shown in FIG. 7, when the elastic body is arranged at the divided portion, the step difference of the punch disappears due to the pressing effect with the die bottom at the bottom dead center (FIG. 7B), which is the same as the original punch shape. Become height. However, when the wrinkle holding force and the back pressure are large, the level difference of the punch cannot be maintained up to the molding bottom dead center, so the load resistance of the elastic body must be more than that.
As an elastic body, a metal spring, a urethane material, etc. can be used.

The invention according to (3) is characterized in that the load resistance of the elastic body is different.
The spring back can be reduced by partially changing the load resistance of the elastic body, because the load resistance to crush the step of the punch at the bottom dead center can be changed, so the pushing load on the punch shoulder is increased. It is because it can also.

  The effect of the present invention is not influenced by the vertical wall angle of the molded product, and is effective when the vertical wall is vertical or inclined. In addition, the effect of the present invention can be obtained even when lubrication is performed during molding.

As an example of the present invention, a hat-type press molding test was performed using a steel plate having a thickness of 1.2 mm and a tensile strength of 590 MPa. As shown in FIGS. 8A to 8C, the part shape is curved (R330) in the longitudinal direction of the part on the XY plane (FIG. 8C) and in the height direction (Z direction). Is not warped (see FIG. 8B). The test piece is a mold having a width of 200 mm and a length of 500 mm, a punch width of 60 mm, a punch shoulder R of 5 mm, and a die width of 62.4 mm. As shown in FIG. A hat bending test with a molding height of 40 mm was performed by changing the height to 10 mm or 20 mm. The wrinkle pressing force during molding was 200 kN or none (indicated by “−” in Table 1). The load capacity of the elastic body arranged on the punch 2 was made of a metal spring of 300 kN.
As a comparative example, a hat bending test was performed using the same steel plate as in Example 1 and a mold that does not divide the punch.

  The test pieces subjected to the bending test were measured for the shape of the ceiling surface in the longitudinal direction using a three-dimensional shape measuring apparatus, and evaluated by the twist angle α on the ceiling surface as shown in FIG. The evaluation criteria were ◎ for those having a twist angle of 0 ° to 2 °, 以下 for those having a twist angle of 2 ° to 4 °, and △ to 4 ° to 6 °.

As an example of the present invention, a hat-type press molding test was performed using a steel plate having a plate thickness of 1.6 mm and a tensile strength of 780 MPa. As shown in FIGS. 11A to 11C, the component shape is curved (R1000) in the product inflow direction, that is, in the longitudinal direction in the YZ plane (FIG. 11C), X- The shape projected onto the Y plane is straight in the longitudinal direction (see FIG. 11B). The test piece is a mold having a width of 160 mm and a length of 400 mm, a punch width of 40 mm, a punch shoulder R of 5 mm, and a die width of 43.2 mm. As shown in FIG. 12, the height of the punch 3 is 2.5 mm from the punch. , 5 mm and 10 mm, and the height of the punch 2 was changed to 2.5 mm and 5 mm higher, and a hat bending test with a molding height of 40 mm was performed. The load capacity of the elastic body arranged on the punches 2 and 3 was made of metal springs of 100 kN and 200 kN.
As a comparative example, a hat bending test was performed using the same steel plate as in Example 2 and a mold that does not divide the punch.

  The test piece subjected to the bending test was measured for the cross-sectional shape at both ends with a three-dimensional shape measuring device, and as shown in FIG. Evaluated. The evaluation criteria were as follows: ◎ when the warp angle was 0 ° or more and 2 ° or less, ○ if 2 ° or more and 4 ° or less, and △ if 4 ° or more and 6 ° or less.

  The measurement result of the said Examples 1-2 is shown to Tables 1-2. According to the present invention, it was possible to obtain a hat-shaped molded part having excellent dimensional accuracy regardless of the part shape.

It is sectional drawing which shows the conventional hat bending component. It is a figure which shows the twist of a hat-shaped molded component. It is a figure which shows the ridgeline curvature of a hat-shaped molded component. It is a figure which shows the conventional punch shape. It is a figure which shows the punch shape which concerns on this invention. It is a figure which shows the punch shape which concerns on this invention. (A) of the punch according to the present invention is a sectional view showing a state at the initial stage of molding, and (b) is a state at the bottom dead center of molding. (A) is a conceptual diagram, (b) is a plan view in the XZ plane, and (b) is an example of a hat-shaped molded part in which the ridgelines of the flange portion and the ceiling portion according to the present invention are bent continuously or discontinuously horizontally. c) is a plan view in the XY plane. It is a figure explaining the punch shape used in the Example of this invention. It is sectional drawing of the both ends of the test piece which measures a twist angle. (A) Conceptual diagram of an example of a hat-shaped molded part in which the ridge lines of the flange portion and the ceiling portion according to the present invention are bent continuously or discontinuously in the vertical direction, (b) a plan view in the XZ plane, (c) It is a top view in a YZ plane. It is a figure which shows the punch shape used in the Example of this invention. It is a side view of the test piece which measures a ridgeline curvature angle.

Explanation of symbols

1 shoulder
2 walls

Claims (3)

A press die for press-molding a hat-shaped molded part from a metal plate having a punch, a die, and a wrinkle presser, wherein the punch is divided into three or more in the longitudinal direction, and the height of the divided punch is The divided punches which are different from each other and located at both ends in the longitudinal direction are configured to be lower than the heights of the other divided punches, and these divided punches have a constant height at the bottom dead center. A press die excellent in shape freezing property, characterized in that the divided punch is further divided in the stroke direction, and an elastic body is arranged at the divided portion in the stroke direction. Punch, having a die and a pad, a hat-shaped parts from a metal plate a press die for press-molding, punch is divided into three or more in the longitudinal direction and the height of the divided punch are each The divided punches that are different and located at both ends in the longitudinal direction are configured to be lower in height than the other divided punches, and these divided punches have a constant height at the bottom dead center. A press die that has a function and has a shape freezing property, wherein the divided punch is further divided in a stroke direction, and an elastic body is arranged at a divided portion in the stroke direction.   The press die having excellent shape freezing property according to claim 1 or 2, wherein the load resistance of the elastic body is different.

Images