Press molding method

Abstract

To achieve light weight of a molded article.SOLUTION: A press molding method comprises: a preliminary molding step of molding an intermediate molded article 2 from a blank material 1 by a first molding device 13; and a real molding step of molding an end molded article 3 from the intermediate molded article 2 by a second molding device 17. In the preliminary molding step, a recess 5 recessed downward is molded in the blank material 1, thereby molding the intermediate molded article 2 having the recess 5. In the real molding step, drawing processing is carried out for the intermediate molded article 2 in a state where the recess 5 of the intermediate molded article 2 is disposed to face downward oppositely to a second punch 19 of the second molding device 17.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a press forming method. [Background technology]

[0002] For example, metal panel parts for automobile bodies are formed into a predetermined shape by applying press forming such as drawing to a blank material. In general, a press forming device (mold) used for drawing includes a die that is a movable side, a punch that is a fixed side, and a blank holder that holds the end of the blank material.

[0003] 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 apparatus. This press forming method includes a preforming step (extending step) for forming a convex protruding portion in the blank material by pressing the blank material against a punch while holding an end portion of the blank material with a die and a blank holder, and a main forming step (drawing step) for forming a formed product having a convex bent portion and a vertical wall portion from the blank material (intermediate material) having the protruding portion after the preforming step.

[0004] In the above press forming method, the material in the center of the blank is stretched in advance in the preliminary forming process to form 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, thereby reducing the weight of the formed product. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-38025 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the above press forming method, if the vertical wall portion as well as the convex bent portion can be made thin, the weight of the formed product can be further reduced. However, in this case, it is necessary to form a protruding portion over a wider area of ​​the blank. This causes the protruding portion to become large, and when the blank is held by the die and the blank holder in the main forming process, a part of the protruding portion may come into contact with a part of the die, which may interfere with the main forming process.

[0007] The present invention has been made in view of the above circumstances, and has as its technical object to reduce the weight of a molded product. [Means for solving the problem]

[0008] The present invention is intended to solve the above-mentioned problems, and provides a press molding method comprising a preliminary forming process in which an intermediate molded product is formed from a blank material by a first forming device, and a main forming process in which a final molded product is formed from the intermediate molded product by a second forming device, wherein the first forming device comprises a first die and a first punch arranged below the first die, and the second forming device comprises a second die and a second punch arranged below the second die, and the preliminary forming process comprises forming a downwardly recessed recess in the blank material by the first die and the first punch to form an intermediate molded product having a recess, and the main forming process comprises applying a drawing process to the intermediate molded product while the recess of the intermediate molded product is positioned facing downwardly so as to face the second punch of the second forming device.

[0009] According to this configuration, the recesses formed in the blank in the preforming step are arranged facing downward so as to face the second punch of the second forming device in the main forming step, 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 can be formed in the blank in the preforming step. This makes it possible to reduce the weight of the formed product compared to conventional methods.

[0010] In the press molding method configured as described above, the first die of the first molding device may have a recess molding surface for molding a recess in the intermediate molded product. Effect of the Invention

[0011] According to the present invention, it is possible to reduce the weight of a molded product. [Brief description of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view of a blank and a formed product for explaining a press forming method. FIG. [Diagram 2] FIG. 4 is a cross-sectional view of a first molding device performing a pre-molding step. [Diagram 3] FIG. 4 is a cross-sectional view of a first molding device performing a pre-molding step. [Figure 4] FIG. 4 is a cross-sectional view of a first molding device performing a pre-molding step. [Diagram 5] FIG. 4 is a cross-sectional view of a second molding device that performs the main molding step. [Figure 6] FIG. 4 is a cross-sectional view of a second molding device that performs the main molding step. [Figure 7] FIG. 2 is a cross-sectional view showing an example of an intermediate molded product. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the press molding method according to the present invention will be described with reference to the drawings.

[0014] The press molding method of the present invention comprises a preforming process for molding an intermediate product 2 from a blank material 1, and a main molding process for molding a final product 3 by applying drawing to the intermediate product 2 formed in the preforming process.

[0015] Although the thicknesses of the intermediate product 2 and the final product 3 vary in parts and are not uniform due to the preforming process and main forming process, for the sake of convenience, the thicknesses are shown as being constant in FIGS.

[0016] As shown in Fig. 1(a), the blank piece 1 is, for example, a rectangular metal plate (for example, a steel plate). The blank piece 1 has a constant thickness over the entire length from one end 1a to the other end 1a. As shown in Fig. 1(b), the blank piece 1 becomes an intermediate formed product 2 having uneven protruding parts through a preforming process.

[0017] The intermediate molded product 2 has an end portion 4, a recess (concave protruding portion) 5 recessed at a position more inward than the end portion 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 portion 4. In other words, the recess 5 can also be considered as a protrusion protruding downwardly. The recess 5 is configured to surround the periphery of the protrusion 6. The protrusion 6 protrudes upward beyond the end portion 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 portion 4.

[0018] 1(b), the recess 5 has a lower end 7 and side walls 8a, 8b. The side walls 8a, 8b include a first side wall 8a located on the inner side (the protrusion 6 side) of the lower end 7 and a second side wall 8b located on the outer side (the end 4 side) of the lower end 7.

[0019] As shown in FIG. 1(c), the final formed 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 forming 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 forming process, this final formed product 3 is processed into, for example, a rear floor pan for an automobile or other parts.

[0020] 2 to 4 show a first forming device 13 for carrying out the preforming step. The first forming device 13 includes a first die 14, a first punch 15, and a first blank holder 16.

[0021] The first die 14 is a movable die configured to be movable up and down by a driving device (not shown). The first die 14 has molding surfaces 14a, 14b for molding 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 protrusion molding surface 14b for forming the protrusion 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 protrusion molding surface 14b is configured as a concave curved surface that is concave toward the upward direction.

[0022] The first punch 15 is disposed below the first die 14. The first punch 15 is a movable die configured to be movable up and down by a drive device (not shown). The first punch 15 has molding surfaces 15a, 15b for molding the blank piece 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 piece 1, and a convex portion molding surface 15b for forming the convex portion 6 of the intermediate molded product 2 in the blank piece 1. The recess molding surface 15a is configured as a concave curved surface that is concave downward. The convex portion molding surface 15b is configured as a convex curved surface that protrudes upward.

[0023] 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 of the blank holders 16a and 16b is configured to be movable up and down by a driving device (not shown).

[0024] 2, in the preforming step, first, an end portion 1a of the blank piece 1 is gripped by a first blank holder 16 of a first forming device 13. An upper blank holder 16a and a lower blank holder 16b clamp the end portion 1a of the blank piece 1 with a predetermined cushion pressure so that the overall width (total length) of the blank piece 1 does not change before and after the preforming step.

[0025] Next, the first forming device 13 lowers the first die 14 located above the blank piece 1, and raises the first punch 15 located below the blank piece 1. This brings the forming surfaces 14a, 14b of the first die 14 and the forming surfaces 15a, 15b of the first punch 15 into contact with the blank piece 1.

[0026] 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 protrusion forming surface 14b of the first die 14 and the protrusion forming surface 15b of the first punch 15 form a protrusion 6 in a part of the blank material 1. As shown in Fig. 4, when the first die 14 reaches the bottom dead center and the first punch 15 reaches the top dead center, an intermediate formed product 2 having a recess 5 and a protrusion 6 is formed.

[0027] In this preforming step, forming is performed with the first blank holder 16 gripping the end 1a of the blank 1 so that it cannot move, and therefore 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 thicknesses of the recesses 5 and protrusions 6 are thinner than the thickness of the end 4. Since the linear length of the intermediate formed product 2 is thus longer 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 perform a preforming step.

[0028] 5 and 6 show a second forming apparatus 17 for carrying out the main forming step. The second forming apparatus 17 includes a second die 18, a second punch 19, and a second blank holder 20.

[0029] The second die 18 is a movable die configured to be able to move up and down by a driving device (not shown). The second die 18 has concave forming surfaces 18a, 18b for forming the convex bent portion 10 of the final product 3 on the intermediate product 2, and a pressing surface 18c for clamping the end portion 4 of the intermediate product 2 together with the second blank holder 20.

[0030] 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.

[0031] 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.

[0032] 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 driving device (not shown).

[0033] 5, in this forming step, the end portion 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 arranged so that the recess 5 faces downward.

[0034] 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 concave portion 5 and the convex 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.

[0035] 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. That is, 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).

[0036] The cushion pressure by the second die 18 and the second blank holder 20 is smaller than the cushion pressure by the first blank holder 16 in the preforming step. Therefore, the overall width of the intermediate product 2 before and after the main forming step is variable.

[0037] Next, the second die 18 and the second blank holder 20 are lowered integrally 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 comes into contact with the convex portion 6 of the intermediate formed product 2 from its lower surface. Also, the side surface 19b of the second punch 19 comes into contact with the concave portion 5 of the intermediate formed product 2 before the side surface 18b of the second die 18 comes into contact with the first side wall portion 8a of the concave portion 5 before the second side wall portion 8b of the concave portion 5 comes into contact with the first side wall portion 8a of the concave portion 5.

[0038] As the second die 18 and the second blank holder 20 move down, the forming of the intermediate formed product 2 by the forming surfaces 18a, 18b of the second die 18 and the forming surfaces 19a, 19b of the second punch 19 progresses. As the forming progresses, some of the material at the end 4 of the intermediate formed product 2 held between the second die 18 and the second blank holder 20 flows between the second die 18 and the second punch 19.

[0039] As shown in FIG. 6, when the second die 18 reaches the bottom dead center, the final formed product 3 having the convex bent portion 10 is formed.

[0040] FIG. 7 shows another example of an intermediate product formed by the preforming step.

[0041] 7(a) is different from the above embodiment in the shape of the protrusion 6. The protrusion 6 in this intermediate product 2 does not protrude upward from the end 4 and the recess 5, and is composed of a flat portion that is at the same position as the end 4 in the up-down direction.

[0042] 7(b) does not include the convex portion 6 in the above embodiment. That is, the intermediate product 2 only has the concave portion 5 protruding downward.

[0043] According to the press molding method of this embodiment described above, the recess 5 formed in the blank 1 by the preliminary forming process is positioned facing downward so as to face the second punch 19 of the second forming device 17 in the main forming process, thereby preventing the recess 5 and the protrusion 6 from contacting the forming surfaces 18a, 18b of the second die 18.

[0044] Therefore, in the preforming process, a wider range of the blank 1 can be formed than in the past. That is, in the intermediate product 2, not only the convex portion 6 corresponding to the upper wall portion 11 in the final product 3 (convex bent portion 10) but also the concave portion 5 corresponding to the side wall portion 12 can be stretched to a thin shape.

[0045] This reduces the material cost of the intermediate molded product 2, and also reduces the weight of not only the upper wall 11 but also the side wall 12 of the final molded product 3, making the final molded product lighter than ever before. This makes it possible to reduce the manufacturing cost of the final molded product as much as possible.

[0046] The present invention is not limited to the configuration of the above embodiment, nor is it limited to the above-mentioned effects and advantages. Various modifications of the present invention are possible without departing from the spirit and scope of the present invention.

[0047] In the above embodiment, the convex bent portion 10 is illustrated in a simplified form, but the present invention is not limited to the above embodiment and is applicable to the formation of various panel parts in automobiles.

[0048] In the above embodiment, an example has been 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. [Explanation of symbols]

[0049] 1 Blank material 2 Intermediate molded product 3 Final molded product 5. Recesses in intermediate molded products 13 First forming device 14 First Die 14a: Concave forming surface of first die 15 First Punch 17 Second molding device 18 Second Die 19 Second Punch

Claims

1. 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.

2. 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.

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