JP7610908B2 - Press molding method - Google Patents

Description

The present invention relates to a press molding method.

For example, metal panel parts for automobile bodies are formed into a desired shape by applying press forming such as drawing to a blank material. Generally, the press forming device (mold) used for drawing includes a die that is the movable side, a punch that is the fixed side, and a blank holder that holds the end of the blank material.

Patent Document 1 discloses a press forming method for forming a convex bent portion and a vertical wall portion in a blank material using the above-mentioned press forming device. This press forming method includes a preforming process (extending process) in which the blank material is pressed against a punch while the end of the blank material is held by a die and a blank holder, thereby forming a convex protruding portion in the blank material, and a main forming process (drawing process) in which a formed product having a convex bent portion and a vertical wall portion is formed from the blank material (intermediate material) having the protruding portion after the preforming process.

In the above press molding method, the material in the center of the blank is stretched in advance in the preforming process, forming a thin-walled protruding portion. By forming this protruding portion into a convex bent portion in the main forming process, the thickness of the convex bent portion can be made thinner than the vertical wall portion, making the molded product lighter.

JP 2019-38025 A

In the above press forming method, if the vertical wall portion as well as the convex bent portion could be made thinner, the formed product could be made even lighter. However, in this case, it would be necessary to form a protruding portion over a wider area of the blank. This would result in a larger protruding portion, and when the blank is held by the die and blank holder in the main forming process, part of the protruding portion would come into contact with part of the die, which could interfere with the main forming process.

The present invention was made in consideration of the above circumstances, and its technical objective is to reduce the weight of molded products.

The present invention is intended to solve the above problems, and provides a press molding method including a preliminary forming process in which an intermediate product is formed from a blank by a first forming device, and a main forming process in which a final product is formed from the intermediate product by a second forming device, the first forming device including a first die and a first punch disposed below the first die, and the second forming device including a second die and a second punch disposed below the second die, the preliminary forming process forming a downward recess in the blank by the first die and the first punch to form an intermediate product having a recess, and the main forming process performing a drawing process on the intermediate product with the recess of the intermediate product facing downward so as to face the second punch of the second forming device.

With this configuration, the recesses formed in the blank in the preforming process are positioned facing downward so as to face the second punch of the second forming device in the main forming process, thereby preventing the recesses from coming into contact with the second die of the second forming device. Therefore, in the present invention, a wider range of the blank can be formed in the preforming process. This makes it possible to make the formed product lighter than before.

In the press molding method configured as above, the first die of the first molding device may have a recess molding surface for molding a recess in the intermediate molded product.

The present invention makes it possible to reduce the weight of molded products.

1 is a cross-sectional view of a blank and a formed product for explaining a press forming method. FIG. FIG. 4 is a cross-sectional view of a first molding device performing a pre-molding step. FIG. 4 is a cross-sectional view of a first molding device performing a pre-molding step. FIG. 4 is a cross-sectional view of a first molding device performing a pre-molding step. FIG. 4 is a cross-sectional view of a second molding device that performs the main molding step. FIG. 4 is a cross-sectional view of a second molding device that performs the main molding step. FIG. 2 is a cross-sectional view showing an example of an intermediate molded product.

The following describes an embodiment of the present invention with reference to the drawings. Figures 1 to 7 show one embodiment of the press molding method according to the present invention.

The press molding method according to the present invention includes a preforming process in which an intermediate product 2 is formed from a blank 1, and a main forming process in which a final product 3 is formed by drawing the intermediate product 2 formed in the preforming process.

Note that due to the preliminary molding process and the main molding process, there will be local differences in the thickness of the intermediate molded product 2 and the final molded product 3, and they will no longer be uniform, but for the sake of convenience, in Figures 1 to 7, the thickness is shown as being constant.

As shown in FIG. 1(a), the blank material 1 is, for example, a rectangular metal plate (e.g., a steel plate). The blank material 1 has a constant thickness over its entire length from one end 1a to the other end 1a. As shown in FIG. 1(b), the blank material 1 becomes an intermediate formed product 2 having uneven protruding portions through a preforming process.

The intermediate molded product 2 has an end 4, a recess (concave protruding portion) 5 recessed at a position more inward than the end 4, and a protrusion (convex protruding portion) 6 protruding upward at a position more inward than the recess 5. The recess 5 is recessed downwardly than the end 4. In other words, the recess 5 can also be considered as a protrusion protruding downward. The recess 5 is configured to surround the periphery of the protrusion 6. The protrusion 6 protrudes upward beyond the end 4 and the recess 5. The thickness of the intermediate molded product 2 at the recess 5 and the protrusion 6 is thinner than that at the end 4.

As shown in FIG. 1(b), the recess 5 has a lower end 7 and side walls 8a and 8b. The side walls 8a and 8b include a first side wall 8a located inside the lower end 7 (toward the protrusion 6) and a second side wall 8b located outside the lower end 7 (toward the end 4).

As shown in FIG. 1(c), the final molded product 3 has a flange-shaped end 9 and a convex bent portion 10 that protrudes upward and inward from the end 9. The end 9 is a portion that can be removed by trimming after the main molding process (a portion to be removed). The convex bent portion 10 has an upper wall portion 11 and a side wall portion 12 that connects the upper wall portion 11 and the end 9. After the main molding process, this final molded product 3 is processed into, for example, a rear floor pan for an automobile or other parts.

2 to 4 show a first forming device that performs the preforming process. The first forming device 13 includes a first die 14, a first punch 15, and a first blank holder 16.

The first die 14 is a movable die configured to be raised and lowered by a drive device (not shown). The first die 14 has molding surfaces 14a, 14b that mold the blank piece 1. The molding surfaces 14a, 14b include a recess molding surface 14a for forming the recess 5 of the intermediate molded product 2 in the blank piece 1, and a convex portion molding surface 14b for forming the convex portion 6 of the intermediate molded product 2 in the blank piece 1. The recess molding surface 14a is configured as a convex curved surface that protrudes downward. The convex portion molding surface 14b is configured as a concave curved surface that is concave toward the upward direction.

The first punch 15 is disposed below the first die 14. The first punch 15 is a movable die configured to be raised and lowered by a drive device (not shown). The first punch 15 has molding surfaces 15a, 15b that mold the blank 1. The molding surfaces 15a, 15b include a recess molding surface 15a for forming the recess 5 of the intermediate molded product 2 in the blank 1, and a convex molding surface 15b for forming the convex 6 of the intermediate molded product 2 in the blank 1. The recess molding surface 15a is configured as a concave curved surface that is concave downward. The convex molding surface 15b is configured as a convex curved surface that protrudes upward.

The first blank holder 16 includes an upper blank holder 16a and a lower blank holder 16b, but is not limited to this configuration. Each blank holder 16a, 16b is configured to be movable up and down by a drive device (not shown).

As shown in FIG. 2, in the preforming process, the end 1a of the blank 1 is first gripped by the first blank holder 16 of the first forming device 13. The upper blank holder 16a and the lower blank holder 16b clamp the end 1a of the blank 1 with a predetermined cushion pressure so that the overall width (total length) of the blank 1 does not change before and after the preforming process.

Next, the first forming device 13 lowers the first die 14 located above the blank 1 and raises the first punch 15 located below the blank 1. This brings the forming surfaces 14a and 14b of the first die 14 and the forming surfaces 15a and 15b of the first punch 15 into contact with the blank 1.

As shown in Figures 3 and 4, by the operation of the first die 14 and the first punch 15, the recess forming surface 14a of the first die 14 and the recess forming surface 15a of the first punch 15 form a recess 5 in a part of the blank material 1. In addition, the convex portion forming surface 14b of the first die 14 and the convex portion forming surface 15b of the first punch 15 form a convex portion 6 in a part of the blank material 1. As shown in Figure 4, when the first die 14 reaches the bottom dead center and the first punch 15 reaches the top dead center, an intermediate molded product 2 having a recess 5 and a convex portion 6 is formed.

In this preforming process, the blank 1 is formed while the first blank holder 16 holds the end 1a immovably, so that the intermediate formed product 2 is elongated by the formation of the recesses 5 and protrusions 6, and has a longer linear length than the blank 1. As a result, the thickness of the recesses 5 and protrusions 6 is thinner than the thickness of the end 4. Because the intermediate formed product 2 has a longer linear length than the blank 1, it is possible to reduce the amount of material and reduce manufacturing costs compared to a normal forming method that does not involve a preforming process.

Figures 5 and 6 show the second forming device that performs this forming process. The second forming device 17 includes a second die 18, a second punch 19, and a second blank holder 20.

The second die 18 is a movable die that can be raised and lowered by a drive device (not shown). The second die 18 has concave forming surfaces 18a and 18b for forming the convex bent portion 10 of the final product 3 on the intermediate product 2, and a pressing surface 18c that clamps the end portion 4 of the intermediate product 2 together with the second blank holder 20.

The molding surfaces 18a, 18b include an upper surface 18a for mainly molding the upper wall portion 11 of the final molded product 3, and a side surface 18b for mainly molding the side wall portion 12 of the final molded product 3. The pressing surface 18c is configured as a flat surface facing downward.

The second punch 19 is a fixed die disposed below the second die 18. The second punch 19 has convex molding surfaces 19a, 19b for molding the final molded product 3 from the intermediate molded product 2. The molding surfaces 19a, 19b include an upper surface 19a for mainly molding the upper wall portion 11 of the final molded product 3, and a side surface 19b for mainly molding the side wall portion 12 of the final molded product 3.

The second blank holder 20 is disposed below the pressing surface 18c of the second die 18. The second blank holder 20 is configured to be movable up and down by a drive device (not shown).

As shown in FIG. 5, in this forming process, the end 4 of the intermediate product 2 is gripped by the pressing surface 18c of the second die 18 and the second blank holder 20 at a position above the second punch 19. In this case, the intermediate product 2 is positioned so that the recess 5 faces downward.

In the initial state in which the intermediate molded product 2 is held by the second die 18 and the second blank holder 20, the recessed portion 5 and the protruding portion 6 of the intermediate molded product 2 are separated from the molding surfaces 18a, 18b of the second die 18 and do not come into contact with them.

In this state, the upper surface 19a of the second punch 19 is located between the two recesses 5 in the cross section of the intermediate molded product 2. In other words, the width dimension W1 of the upper surface 19a of the second punch 19 is smaller than the distance W2 between the two recesses 5 (the distance between the two lower ends 7) in the cross section of the intermediate molded product 2. In addition, the recesses 5 of the intermediate molded product 2 are located away from the side surface 19b of the second punch 19 so as to face the side surface 19b (including the case where they are adjacent to each other).

The cushion pressure from the second die 18 and the second blank holder 20 is smaller than the cushion pressure from the first blank holder 16 in the preforming process. Therefore, the overall width of the intermediate molded product 2 before and after the main forming process is variable.

Next, the second die 18 and the second blank holder 20 are lowered together to bring the intermediate formed product 2 into contact with the second punch 19. In this case, the upper surface 19a of the second punch 19 contacts the convex portion 6 of the intermediate formed product 2 from its lower surface. Also, the side surface 19b of the second punch 19 contacts the concave portion 5 of the intermediate formed product 2 before the side surface 18b of the second die 18. Specifically, the side surface 19b of the second punch 19 contacts the first side wall portion 8a of the concave portion 5 before the second side wall portion 8b of the concave portion 5.

As the second die 18 and the second blank holder 20 descend, the intermediate formed product 2 is formed by the forming surfaces 18a, 18b of the second die 18 and the forming surfaces 19a, 19b of the second punch 19. As the forming progresses, some of the material at the end 4 of the intermediate formed product 2 that is clamped between the second die 18 and the second blank holder 20 flows between the second die 18 and the second punch 19.

As shown in FIG. 6, when the second die 18 reaches the bottom dead center, the final molded product 3 having a convex bent portion 10 is formed.

Figure 7 shows another example of an intermediate molded product formed by the preforming process.

In the intermediate molded product 2 shown in FIG. 7(a), the shape of the protrusion 6 is different from that of the above embodiment. The protrusion 6 in this intermediate molded product 2 does not protrude upward from the end 4 and the recess 5, but is composed of a flat portion that is at the same position as the end 4 in the vertical direction.

The intermediate molded product 2 shown in FIG. 7(b) does not have the convex portion 6 in the above embodiment. In other words, the intermediate molded product 2 only has a concave portion 5 that protrudes downward.

According to the press molding method of this embodiment described above, the recess 5 formed in the blank 1 in the preliminary molding process is positioned facing downward so as to face the second punch 19 of the second molding device 17 in the main molding process, thereby preventing the recess 5 and the protrusion 6 from contacting the molding surfaces 18a, 18b of the second die 18.

Therefore, in the preliminary forming process, a wider range of the blank 1 can be formed than in the past. In other words, in the intermediate formed product 2, not only the convex portion 6 corresponding to the upper wall portion 11 in the final formed product 3 (convex bent portion 10) but also the concave portion 5 corresponding to the side wall portion 12 can be stretched thin.

This reduces the material cost of the intermediate molded product 2, and also reduces the weight of not only the upper wall portion 11 but also the side wall portion 12 of the final molded product 3, making it possible to make the final molded product lighter than before. This makes it possible to reduce the manufacturing cost of the final molded product as much as possible.

The present invention is not limited to the configuration of the above embodiment, nor is it limited to the above-mentioned effects. Various modifications of the present invention are possible without departing from the spirit of the present invention.

In the above embodiment, the convex bend portion 10 is simplified, but the present invention is not limited to the above embodiment and can be applied to the molding of various panel parts in automobiles.

In the above embodiment, an example is shown in which the first punch 15 of the first molding device 13 is configured as a movable type, but the configuration of the first molding device 13 is not limited to the above embodiment. For example, the first punch 15 of the first molding device 13 may be a fixed type.

REFERENCE SIGNS LIST 1 Blank 2 Intermediate formed product 3 Final formed product 5 Recess in intermediate formed product 13 First forming device 14 First die 14a Recess forming surface of first die 15 First punch 17 Second forming device 18 Second die 19 Second punch

Claims (2)

A press molding method including a preforming step of forming an intermediate product from a blank by a first forming device, and a main forming step of forming a final product from the intermediate product by a second forming device,
the first molding device includes a first die and a first punch disposed below the first die;
the second molding device includes a second die and a second punch disposed below the second die;
In the preforming step, a recess is formed downward in the blank by a first die and a first punch, thereby forming an intermediate formed product having a recess;
In the main forming step, the intermediate formed product is subjected to drawing while the recess of the intermediate formed product is facing downward so as to face the second punch of the second forming device,
The intermediate molded product has an end portion, a recessed portion recessed at a position more inward than the end portion, and a protruding portion protruding upward at a position more inward than the recessed portion,
The recess is recessed downward from the end portion and configured to surround the periphery of the protrusion,
The protrusion protrudes upward from the end and the recess,
The final molded product has a flange-shaped end portion and a convex bent portion that protrudes upward and is located inside the end portion,
A press molding method , characterized in that the convex bent portion has an upper wall portion and a side wall portion connecting the upper wall portion and the flange-shaped end portion . a first die of the first forming device having a forming surface for forming the blank;
The press molding method according to claim 1 , wherein the molding surfaces include a recess molding surface for forming the recess of the intermediate product in the blank, and a protrusion molding surface for forming the protrusion of the intermediate product in the blank .

Images