JP7835526B2 - Deep drawing method - Google Patents

Description

This invention relates to a deep drawing method, and more particularly to a technique for forming deep product protrusions on a blank material by deep drawing.

For example, when forming the outer panels of an automobile body using press forming, deep drawing is often used due to its high degree of freedom in forming, reduced labor costs, and ultimately, lower costs.

A typical apparatus for performing deep drawing consists of an upper die called a die, a lower die called a punch, an upper blank holder, and a lower blank holder (see, for example, Patent Document 1). In this type of deep drawing apparatus, the upper and lower blank holders first hold a plate-shaped workpiece called a blank material before forming. Then, the upper and lower blank holders are brought closer to the punch, and the blank material is pressed against the punch, thereby forming the product shape onto the blank material.

Japanese Patent Publication No. 2021-159918

Incidentally, in the exterior body panels of automobiles, the spoiler portion of the back door outer panel, for example, has a shape that protrudes significantly from the surface of the product. Therefore, if this were to be formed using the deep drawing process described in Patent Document 1, a very large drawing depth would be required. As a result, it is difficult to accurately form this type of protrusion (convex portion). Furthermore, it becomes necessary to allow a large amount of surrounding blank material (material) to flow towards the convex portion, leading to a decrease in yield and, consequently, increased costs. There is also the problem that the more material is allowed to flow in, the more likely molding defects such as wrinkles and cracks are to occur.

In light of the above circumstances, this specification aims to address the technical problem of enabling high-precision and low-cost molding of press-formed products with large convex sections with significant drawing depth, while minimizing material inflow.

The aforementioned problem is solved by the deep drawing method according to the present invention. Specifically, this deep drawing method is a method for forming a product protrusion extending in a predetermined direction on a blank material by performing deep drawing as a press process on a plate-shaped blank material using an upper press die, a lower press die, an upper blank holder, and a lower blank holder. It is characterized by comprising: a protrusion forming step in which the upper and lower blank holders clamp the excess material located around the product portion of the blank material, and form protrusions corresponding to the product protrusion on a pair of portions of the excess material located on the extension line of the product protrusion; and a lower die forming step in which, after forming the protrusions, the lower press die forms the product protrusion on the blank material. In this specification, "protrusion" means a state where the product portion to be formed on the blank material protrudes toward the surface side, and "concave" means a state where the surface of the product portion to be formed on the blank material is concave.

In this way, the deep drawing method according to the present invention focuses on the fact that the product protrusion to be deep drawn has a rib shape. The upper blank holder and the lower blank holder first form protrusions corresponding to the product protrusion in a pair of areas of the excess material located on the extension line of the product protrusion, and then the lower press die forms the product protrusion in the blank material. In this way, by first forming predetermined protrusions in a pair of areas of the excess material located on the extension line of the product protrusion, bending deformation can be induced in the area located between these two protrusions to form a shape corresponding to the protrusion. Here, a product protrusion extending in a predetermined direction is provided between the pair of protrusions. Therefore, by applying bending deformation to the area of the product located between the pair of protrusions as described above, a protrusion corresponding to the product protrusion can be formed in the area that will become the product protrusion prior to the lower press die. This delays the start of forming the product protrusion by the lower press die (by raising the contact position of the lower press die), and thus reduces the depth of deep drawing of the product protrusion by the lower press die. Therefore, it becomes possible to significantly reduce or eliminate the inflow of material into the product's protruding portion. Based on the above, the deep drawing method according to the present invention makes it possible to form product protruding portions with large drawing depths accurately and at low cost.

Furthermore, in the drawing method according to the present invention, a lower die inner pad that can move up and down is provided on the inner circumference of the lower blank holder, and a connecting portion is provided on the inner circumference of the upper blank holder at a position corresponding to the lower die inner pad, connecting the two parts that make up the upper blank holder. In the convex portion forming step, the portion of the blank material close to the product's convex portion is held between the connecting portion and the lower die inner pad, and the convex portion is formed.

When deep drawing is used for very large products such as back door outers, the blank material must also be of a correspondingly large size. In this case, as described above, even if one attempts to form a pair of protrusions on the extension of the product's protrusion to induce bending deformation in the area that will become the product's protrusion, the blank material is too large, making it difficult to stably deform it into the desired shape. In contrast, as described above, by providing a connecting portion that connects the two parts forming the upper blank holder on the inner circumference of the upper blank holder and at a position corresponding to the lower die inner pad, and then forming the protrusion while clamping the area near the product's protrusion between the connecting portion and the lower die inner pad during the protrusion forming step, it is possible to form the protrusion in the excess material while supporting the area near the product's protrusion, thereby imparting good bending deformation to the area that will become the product's protrusion. Therefore, it becomes possible to form the area that will become the product's protrusion with high precision and stability.

As described above, according to the present invention, it is possible to form press-formed products having protrusions with large drawing depths with high precision and low cost while minimizing material inflow.

This is a plan view of a press-formed product obtained by a deep drawing method according to one embodiment of the present invention. This is a cross-sectional view of the press-formed product shown in Figure 1, taken along line A-A. This is a cross-sectional view of the portion of a press working apparatus according to one embodiment of the present invention that corresponds to the section A-A in Figure 1. (a) A schematic perspective view of the upper blank holder shown in Figure 3, and (b) a schematic perspective view of the lower blank holder. Figure 3 shows an example of deep drawing using the press working apparatus shown, and is a cross-sectional view of the press working apparatus when a blank material is placed on the lower blank holder. Figure 3 shows an example of deep drawing using the press working apparatus shown, and is a cross-sectional view of the press working apparatus at the start of forming the convex portion relative to the excess material. Figure 3 shows an example of deep drawing using the press working apparatus shown, and is a cross-sectional view of the press working apparatus at the time when the formation of the convex part is completed. Figure 3 shows an example of deep drawing using the press working apparatus shown, and is a perspective view of the blank material after the formation of the convex portion is complete. Figure 3 shows an example of deep drawing using the press working apparatus shown, and is a cross-sectional view of the press working apparatus at the start of forming the product's raised portion by the lower press die. Figure 3 shows an example of deep drawing using the press working apparatus shown, and is a cross-sectional view of the press working apparatus at the time when the formation of the product's raised ridge is complete.

The following describes the drawing process according to one embodiment of the present invention, based on the drawings. In the following description, the vehicle width direction is defined as the X direction, the vehicle vertical direction as the Y direction, and the vehicle longitudinal direction as the Z direction.

Figure 1 is a plan view of an example of a press-formed product 1 obtained by a deep drawing method according to one embodiment of the present invention. As shown in Figure 1, in this embodiment, the press-formed product 1 is an intermediate part for the outer back door of an automobile, and integrally comprises a product portion 2 and an excess material portion 3 located around the product portion 2. In this embodiment, the excess material portion 3 consists of a first excess material portion 3a provided on the outer circumference of the product portion 2 and a second excess material portion 3b provided on the inner circumference of the product portion 2. Of these, the second excess material portion 3b is the part removed from the product portion 2 to form an opening in the back door where the window glass is installed. Both excess material portions 3a and 3b are removed by trimming or the like after the product portion 2 is formed by deep drawing.

Product section 2 integrally includes a spoiler section 4, which serves as a product protrusion, on its upper vertical end. This spoiler section 4 extends in the vehicle width direction of product section 2. Furthermore, as shown in Figure 2, the spoiler section 4 is the most protruding part on the surface 2a side of product section 2.

The press-formed product 1 with the above shape can be obtained, for example, by using the press-forming apparatus 20 shown in Figure 3 to perform a drawing process on a plate-shaped blank material 10 (see Figure 5, etc., described later).

Figure 3 shows a cross-sectional view of a press working apparatus 20 for performing the drawing process according to the present invention on a blank material 10. This cross-sectional view is a cross-sectional view of the press working apparatus 20 at the same position as the A-A cross-section along the longitudinal direction of the vehicle body at the center of the vehicle width direction of the press-formed product 1 obtained by the drawing process. This press working apparatus 20 mainly comprises an upper press die 21, a lower press die 22, an upper blank holder 23, and a lower blank holder 24.

The upper press die 21 and the lower press die 22 have corresponding first press forming surfaces 25 and 26 positioned opposite each other in the vertical direction. In this case, the first press forming surfaces 25 and 26 are configured to form the portion of the blank material 10 that will become the product part 2.

The upper blank holder 23 is positioned around the upper press die 21 and is configured to move up and down independently of the upper press die 21. The lower blank holder 24 is positioned around the lower press die 22 and is configured to move up and down independently of the lower press die 22. Here, the upper blank holder 23 and the lower blank holder 24 are configured to grip the excess material portion 3 of the blank material 10 (particularly the first excess material portion 3a located around the product portion 2) through their mutual proximity movement. Furthermore, the upper and lower blank holders 23 and 24 have corresponding second press forming surfaces 27 and 28 facing each other in the vertical direction. In this case, as shown in Figures 4(a) and 4(b), the second press-molded surfaces 27 and 28 have convex and concave shapes corresponding to the spoiler portion 4, respectively. A pair of portions 5 located on the extension of the spoiler portion 4, which serves as the product's raised ridge, are configured to allow the molding of convex portions 6 corresponding to the spoiler portion 4 (see Figures 1 and 7).

In this embodiment, a lower die inner pad 29 is provided on the inner circumference of the lower blank holder 24, capable of moving up and down independently of the lower blank holder 24. Furthermore, a connecting portion 30 is provided on the inner circumference of the upper blank holder 23, at a position corresponding to the lower die inner pad 29, connecting two predetermined parts of the upper blank holder 23 (see Figure 4(a)). These lower die inner pad 29 and connecting portion 30 are configured to grip the second excess material portion 3b located on the inner circumference of the product portion 2 of the blank material 10 through their mutual proximity movement.

In this case, the upper press die 21 is divided in the longitudinal direction of the vehicle body by the connecting portion 30 (see Figures 3 and 4(a)). Similarly, the lower press die 22 is divided in the longitudinal direction of the vehicle body by the lower die inner pad 29 (see Figures 3 and 4(b)). Of course, both these divided (multiple) upper press dies 21 and lower press dies 22 are configured to move up and down synchronously and integrally.

Next, an example of press working (deep drawing) using the press working apparatus 20 shown in Figure 3 will be explained based on Figures 1 to 10.

(S1) Convex Forming Step First, as shown in Figure 5, a plate-shaped blank material 10 is placed on the upper surface 24a of the lower blank holder 24. At this point, the blank material 10 is in contact only with the upper surface 24a of the lower blank holder 24, the second press molding surface 28, and the lower die inner pad 29, and is separated from the upper press die 21, the lower press die 22, and the upper blank holder 23. The shape of the blank material 10 before molding is arbitrary; the blank material 10 as a whole may be flat, or it may be curved so that it is convex upward when placed on the lower blank holder 24 and the lower die inner pad 29.

Subsequently, the upper blank holder 23 is moved downward relative to the upper press die 21. At this time, the blank material 10 is in contact with the second press forming surface 28 of the convex lower blank holder 24 at a relatively higher position (specifically, higher than the position where the blank material 10 contacts the upper surface 24a at both ends in the vertical direction of the vehicle body). Therefore, when the upper blank holder 23 is lowered, the portion of the blank material 10 supported by the second press forming surface 28 preferentially contacts the lower surface 23a of the upper blank holder 23 and is pushed downward (see Figure 6). Thus, by continuing the aforementioned pushing, the first excess material portion 3a is formed into a convex portion 6 of a predetermined shape, in this case a convex portion 6 corresponding to the spoiler portion 4 as the product's protruding ridge, by the second press forming surface 27 of the upper blank holder 23 and the second press forming surface 28 of the lower blank holder 24 (see Figure 7).

Here, the portion 5 formed by the second press-forming surfaces 27 and 28 within the first excess material 3a is positioned on the extension of the portion that will become the spoiler portion 4 of the product portion 2 of the blank material 10 (see Figure 1). Therefore, as described above, when the protrusions 6 are formed on the first excess material 3a by the second press-forming surfaces 27 and 28, the portion of the product portion 2 between the pair of protrusions 6 undergoes bending deformation in a shape that conforms to the protrusions 6, and a protruding ridge portion 7 extending in the vehicle width direction is integrally formed with the pair of protrusions 6 (see Figure 8).

In this embodiment, since the blank material 10 is in contact with the lower die inner pad 29 at a relatively high position, when the upper blank holder 23 is lowered, the portion of the blank material 10 supported by the upper surface 29a of the lower die inner pad 29 preferentially contacts and is clamped by the lower surface 30a of the connecting portion 30, which is integrally provided with the upper blank holder 23 (see Figure 6). Therefore, by configuring the connecting portion 30 and the blank material 10 to contact at least during the molding of the convex portion 6 by the second press molding surfaces 27 and 28 (preferably at the start of molding), the molding of the convex portion 6 can be performed with the vicinity of the portion of the blank material 10 that will become the spoiler portion 4 being clamped between the lower die inner pad 29 and the connecting portion 30.

(S2) Lower die forming step After a part of the spoiler portion 4 (the raised portion 7) is formed in this way, the upper and lower blank holders 23, 24 and the lower die inner pad 29 are lowered together with the upper press die 21 to press the blank material 10 against the first press forming surface 26 of the lower press die 22. This forms the portion of the blank material 10 that will become the product portion 2 into a shape that conforms to the first press forming surface 26 of the lower press die 22. In this case, the portion of the product portion 2 that will become the spoiler portion 4 already has a raised portion 7 formed in a shape similar to the spoiler portion 4 but smaller than the spoiler portion 4 (see Figures 8 and 9). Therefore, the first press forming surface 26 is first pressed against the center of the raised portion 7 in the width direction, which is the highest part of the product portion 2 of the blank material 10, and the drawing process continues until it comes into contact with the first press forming surface 25 of the upper press die 21 (see Figure 10). Therefore, if the maximum drawing depth of the spoiler portion 4 is H, the maximum drawing depth H is equal to the sum of the depth H1 of the protrusion 7 formed on the product portion 2 in the protrusion forming step S1 and the drawing depth H2 of the spoiler portion 4 formed by the lower press die 22 in the lower die forming step S2. From the above, the press-formed product 1 shown in Figure 1 is obtained.

As described above, in the deep drawing method according to this embodiment, by first forming predetermined protrusions 6 on a pair of parts 5 located on the extension of the spoiler part 4, which will become the product's protruding ridge, the product part 2 located between these two protrusions 6 can also be subjected to bending deformation corresponding to the shape of the protrusions 6. Here, since a spoiler part 4 extending in a predetermined direction is provided between the pair of protrusions 6, by applying bending deformation to the part of the product part 2 located between the pair of protrusions 6 as described above, a protruding ridge 7 having a shape corresponding to the spoiler part 4 can be formed on the part that will become the spoiler part 4 prior to the press lower die 22. This makes it possible to delay the start of forming the spoiler part 4 by the press lower die 22 (by raising the contact position of the press lower die 22), so that the drawing depth H2 of the spoiler part 4 by the press lower die 22 can be reduced by the depth H1 of the protruding ridge 7 compared to the conventional drawing depth H. Therefore, it becomes possible to significantly reduce or eliminate the inflow of material into the spoiler part 4. Based on the above, the deep drawing method according to this embodiment makes it possible to form even spoiler portions 4 with large deep drawing depths H accurately and at low cost.

Furthermore, in this embodiment, a connecting portion 30 is provided on the inner circumference of the upper blank holder 23 and at a position corresponding to the lower die inner pad 29, connecting the two parts that make up the upper blank holder 23. In the convex portion molding step S1, the convex portion 6 is molded while the vicinity of the spoiler portion 4 is supported (clamped) by the connecting portion 30 and the lower die inner pad 29. This avoids situations such as the spoiler portion 4 bending, and allows for good bending deformation of the spoiler portion 4. Therefore, it becomes possible to stably mold the spoiler portion 4 into a good shape that conforms to the product shape (shape of the spoiler portion 4).

In this embodiment, the portion clamped between the lower die inner pad 29 and the connecting portion 30 is the second excess material portion 3b (the portion that will become the opening of the window glass), so even if it cannot be molded with high precision, there is no particular problem. In other words, by using this excess material portion on the inner circumference (second excess material portion 3b) to support the vicinity of the spoiler portion 4, which will serve as the product's protruding part, it becomes possible to mold a portion of the spoiler portion 4 prior to the deep drawing process by the lower press die 22 without impairing the moldability of the product portion 2 other than the spoiler portion 4.

Although one embodiment of the present invention has been described above, the deep drawing method according to the present invention may also adopt configurations other than those described above, without departing from the spirit of the invention.

For example, in the above embodiment, the lower die inner pad 29 and the connecting portion 30 come into contact with the blank material 10 at the start of forming the protrusion 6 by the second press forming surfaces 27 and 28 (i.e., the lower die inner pad 29 and the connecting portion 30 begin to clamp the blank material 10) (see Figure 6). However, this is not the only example. For instance, the connecting portion 30 may come into contact with the blank material 10 when the forming of the protrusion 6 has progressed to a certain extent. Alternatively, the connecting portion 30 may come into contact with the blank material 10 before the formation of the protrusion begins.

Of course, depending on the material, thickness, and dimensions of the blank material 10, if it is not necessary to form the protrusion 6 while supporting the area near the spoiler portion 4, the connecting portion 30 may be eliminated, or the lower mold inner pad 29 and the connecting portion 30 may be eliminated.

1 Press-formed product 2 Product part 2a Surface 3 Excess material 3a First excess material 3b Second excess material 4 Spoiler part 5 A pair of parts 6 located on the extension line of the product's protruding part within the excess material 7 Protruding part 10 Blank material 20 Pressing apparatus 21 Upper press die 22 Lower press die 23 Upper blank holder 24 Lower blank holders 25, 26 First press forming surface 27, 28 Second press forming surface 29 Lower die inner pad 30 Connecting part S1 Protruding part forming step S2 Lower die forming step

Claims (2)

A method for forming a product protrusion extending in a predetermined direction on a blank material by performing a deep drawing as a press process on the blank material using an upper press die, a lower press die, an upper blank holder, and a lower blank holder,
A convex forming step is performed by sandwiching the excess material located around the product portion of the blank material between the upper blank holder and the lower blank holder, and forming convex portions corresponding to the product convex portion on a pair of portions of the excess material located on the longitudinal extension of the product convex portion, while the lower press die is not in contact with the portion of the blank material that will become the product convex portion.
A drawing method comprising a lower die forming step of forming the product protrusion on the blank material using the lower press die after forming the aforementioned protrusion. A lower mold inner pad that can move up and down is provided on the inner circumference of the lower blank holder,
A connecting portion is provided on the inner circumference of the upper blank holder at a position corresponding to the lower mold inner pad, connecting the two parts that make up the upper blank holder.
The drawing method according to claim 1, wherein in the step of forming the protrusion, the portion of the blank material closest to the product protrusion is held between the connecting portion and the lower die inner pad while the protrusion is formed.