JP2007130658A - Press forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a press molding method capable of ensuring the product quality of a press molding whose curved-hole shape is formed by press-molding a flat plate. <P>SOLUTION: A front cross member is formed by successively executing the following steps: a 1st drawing step, where the periphery of a prepared hole 2a is formed into a projecting shape 11 while drawing the periphery of the prepared hole 2a, which is formed in a flat plate 10, vertically in relation to the flat plate 10; a 2nd drawing step, where the periphery of the prepared hole 2a is drawn from a top part 13 of the projecting shape 11 and formed into a recessed shape; a punching step, where an odd-form prepared-hole is formed by punching the periphery of the prepared hole 2a; and a curved-hole machining step, where a curved-hole shape of an odd-form hole is formed by subjecting the odd-form prepared-hole to curved-hole machining. As a result, the portions of generating plate expansion at each of the 1st drawing step, the 2nd drawing step, and the curved-hole machining step are dispersed, so that the plate expansion is not concentrated on a specific portion of the curved-hole shape. Thereby, the generation of cracks at the edge of the curved-hole shape is prevented, so that the quality of the front cross member 1 is ensured. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a press molding method, and more particularly to a press molding method of a press molded product in which a hole bending shape is formed by pressing a flat plate.

  2. Description of the Related Art Generally, a truck frame of a cargo vehicle is formed by laying a plurality of cross members in a ladder shape between a pair of side rails extending in the longitudinal direction of the vehicle body. Such a front cross member 1 of the track frame (a cross member disposed at the front end portion of the track frame among the plurality of cross members) has a modified shape for inserting a steering shaft as shown in FIG. In some cases, a hole bending shape 2 is formed. Conventionally, when the front cross member 1 having such a hole bending shape 2 is formed by press molding, first, in a first drawing step, a flat plate-shaped molding material is drawn in a direction perpendicular to the molding material. Thus, as shown in FIGS. 11 and 12, the first work-in-process 3 in which the periphery of the pilot hole 2a is formed in a concave shape that is concave downward is formed. The pilot hole 2a shown in FIG. 11 is processed in advance. Next, in the second drawing step, the periphery of the pilot hole 2a of the first molding work piece 3 is drawn in a slanting direction (separated cam molding) by the offset cam molding die 4 shown in FIG. As shown in FIGS. 14 and 15, a second work-in-process 5 is formed in which the periphery of the pilot hole 2 a is formed in a concave shape 12 that is concave in an oblique direction.

  Next, the peripheral edge of the pilot hole 2a of the second work-in-process 5 is punched by a plurality of punches to form a pilot hole having a different shape (a pilot hole having a bent shape). Then, the irregularly shaped pilot hole is subjected to a hole bending process (burring process), and an irregularly shaped hole bending shape 2 is formed at the end of the front cross member 1 as shown in FIG. However, in the conventional press molding method, the periphery of the pilot hole 2a of the molding material is drawn in a direction perpendicular to the molding material in the first drawing process, and then the first drawing process is performed in the first drawing process. Since the periphery of the pilot hole 2a of the work-in-process 3 is drawn obliquely, the plate elongation rate of the A1 portion in the second work-in-process 5 shown in FIG. (Measured value of 1 is 24% elongation of A1 part.) This is because, as shown in FIG. 17, the second drawing step is an overhang forming in which material inflow from other parts cannot be expected. In the second drawing step, B in the first work-in-process 3 is performed. The line length L0 of the part is extended to L1 (line length difference L1-L0).

  In the conventional press molding method, the plate elongation maximum portion A1 at the time when the second drawing step is completed coincides with the plate elongation maximum portion A2 in the hole bending step. When the pilot hole is bent, the A1 part, which has a relatively large plate elongation rate, is further stretched, so the plate elongation rate of the A2 portion exceeds the allowable value and a crack occurs at the edge of the hole bending shape 2 There is a possibility (the plate elongation rate of A2 part is 33% with respect to the allowable value of 30%). Further, in the conventional press molding method, wrinkle pressers cannot be set at the C portion in the second drawing step because of the structure of the offset cam forming die 4, so that the C portion is likely to be wrinkled.

  Then, this invention is made | formed in view of the said situation, and it is providing the press molding method with which the quality of the press molded product by which a flat plate is pressed and a hole bending shape is formed is ensured.

In order to achieve the above object, the invention described in claim 1 of the present invention is a press molding method of a press molded product in which a hole bending shape is formed by pressing a flat plate, and formed on the flat plate. A first drawing step of forming the periphery of the pilot hole in a convex shape while drawing the periphery of the pilot hole in a direction perpendicular to the flat plate, and a concave shape by drawing the periphery of the pilot hole from the top of the convex shape And a second bending step for forming the hole, and a hole bending step for bending the prepared hole to form a hole bending shape.
According to a second aspect of the present invention, in the press molding method according to the first aspect, a hole bending shape in the vicinity of the pilot hole is predicted in the first drawing step by predicting the plate elongation maximum portion of the hole bending shape. A convex top portion is formed including a portion corresponding to the maximum plate elongation portion.
The invention according to claim 3 includes a punching step of punching a peripheral edge of the prepared hole by a one-stroke operation of the punch after the second drawing process in the press molding method according to claim 1 or 2. It is characterized by.

  In order to achieve the above object, the invention according to claim 4 of the present invention is a cross member press molding method in which a flat plate is pressed to form a bent hole shape of an irregular hole at an end, A first drawing step of forming the periphery of the pilot hole in a convex shape while drawing the periphery of the pilot hole formed in the flat plate in a direction perpendicular to the flat plate, and drawing the periphery of the pilot hole from the top of the convex shape A second drawing step for forming a concave shape by machining, a punching step for punching the periphery of the pilot hole by a one-stroke operation of the punch to form a deformed hole, and a deformed hole formed by the punching step And a hole bending step of forming a hole bending shape by bending the hole.

Therefore, in the first aspect of the invention, the periphery of the pilot hole is drawn in the vertical direction in the first drawing step so as to form a convex shape, so that the plate elongation in the drawing processing in the second drawing step is achieved. The necessary material volume is secured. Moreover, the plate elongation maximum site | part at the time of completing the 2nd drawing process and the plate elongation maximum site | part in a hole bending process can be disperse | distributed.
In the second aspect of the present invention, it is possible to disperse the plate elongation maximum portion at the time when the second drawing step is completed and the plate elongation maximum portion in the hole bending step.
In invention of Claim 3, it can prevent that a crack generate | occur | produces in the edge of a hole bending shape.
In the invention according to claim 4, it is necessary for the plate elongation in the drawing process of the second drawing process by drawing the periphery of the pilot hole in the vertical direction to form a convex shape in the first drawing process. A large volume of material. Moreover, the plate elongation maximum site | part at the time of completing the 2nd drawing process and the plate elongation maximum site | part in a hole bending process can be disperse | distributed. Furthermore, it is possible to prevent cracks from occurring at the edge of the hole bending shape.

  It is possible to provide a press molding method in which the quality of a press molded product having a hole-bending shape of a deformed hole is ensured.

  An embodiment of the present invention will be described with reference to FIGS. In addition, the same name and code | symbol are provided about the same or an equivalent structure with respect to the said conventional press molding method. In the present press molding method, a flat cross section 10 (molding material) is pressed to form a front cross member 1 of a track frame in which a bent hole shape 2 having a deformed hole for inserting a steering shaft is formed at an end (see FIG. 10). ) In which the periphery of the pilot hole 2a formed in the flat plate 10 is drawn in a direction perpendicular to the flat plate 10 and the periphery of the pilot hole 2a is formed into a convex shape 11. The first drawing step, the second drawing step in which the periphery of the pilot hole 2a is drawn from the top portion 13 of the convex shape 11 to form the concave shape 10, and the peripheral edge of the pilot hole 2a is punched out. A hole punching process for forming a pilot hole 2b having a shape (a pilot hole for a bent hole shape 2), and a hole bending process for forming the bent hole shape 2 of the deformed hole by bending the deformed pilot hole 2b. Are sequentially performed. Thereby, in this press molding method, the plate elongation maximum site P1 at the time of completing the second drawing step and the plate elongation maximum site P2 in the hole bending step are dispersed, and the hole bending shape 2 is specified. This structure prevents the occurrence of cracking at the edge of the bent hole shape 2 due to the concentration of the plate elongation in the region.

  Next, the operation of each of the above steps will be described. First, in the first drawing step, as shown in FIG. 1, an outer frame of dies 7 and 8 in which a flat plate 10 (molding material) in which a pilot hole 2a is previously formed is divided into two parts. It is set on the die 7 formed in a shape, and the punch 9 is lowered in this state. Then, in the first drawing step, in the course of the lowering operation of the punch 9, the flat plate 10 has a maximum elongation in a predetermined region (based on the experimental data, in the hole bending step, as shown in FIG. 9 and the front cross member 1 as shown in FIG. 9), and the periphery of the pilot hole 2a in the flat plate 10 is formed on the flat plate 10 as shown in FIG. On the other hand, it is drawn in the vertical direction (downward in FIG. 3). Thereby, in the first drawing step, as shown in FIGS. 3 to 5, the first work-in-process 3 in which the periphery of the pilot hole 2 a is formed in the convex shape 11 is formed. Next, in the second drawing step, the periphery of the pilot hole 2a of the first work-in-process 3 is subjected to a cam formation by the cam forming mold 4 shown in FIG. 13, and as shown in FIG. In addition, the second work-in-process 5 in which the periphery of the pilot hole 2a is formed in the concave shape 12 is formed.

  In the second drawing step, since the wrinkle pressing surface 14 shown in FIG. 4 is gripped by the wrinkle pressing pad, the generation of wrinkles can be prevented and the amount of plate extension can be adjusted as necessary. In the second drawing step, the convex shape 11 of the first work-in-process 3 is drawn from the top portion 13 of the convex shape 11 in an oblique direction (lower left oblique direction in FIG. 13) (composite cam forming). Thus, the periphery of the pilot hole 2a is formed in a concave shape 12. Thereby, in this press molding method, the volume of the material necessary for forming the concave shape 12 by drawing in the second drawing step is the material of the convex shape 11 formed by drawing in the first drawing step. Therefore, the position of the maximum plate elongation portion P1 at the time when the second drawing step is completed is intentionally shifted from the maximum plate elongation portion P2 in the hole bending step. Here, the plate elongation rate of the plate elongation maximum portion P1 at the time of completing the second drawing step is 25%, and the plate extension maximum portion P2 in the hole bending step at the time of completing the second drawing step. The plate elongation rate of the portion P1 corresponding to is smaller than that of the conventional press molding method.

  Next, in the hole punching step, as shown in FIGS. 7 and 8, the peripheral edge of the pilot hole 2a is punched by a one-stroke operation of the punch to form a pilot hole 2b having a different shape (hole bending shape 2). A pilot hole). Then, in the hole bending step, the irregularly shaped pilot hole 2b is subjected to a hole bending process (burring process), thereby forming a hole bending shape 2 of an irregular hole at the end of the front cross member 1, as shown in FIG. Is formed. Note that the plate elongation rate of the plate elongation maximum portion P2 in the hole bending shape 2 is 23%, which is below the allowable value (30%), so the quality of the product (in this embodiment, the front cross member 1) is ensured. Is done.

This embodiment has the following effects.
In this press forming method, a first drawing step of forming the periphery of the pilot hole 2a into a convex shape 11 while drawing the periphery of the pilot hole 2a formed in the flat plate 10 in a direction perpendicular to the flat plate 10. And a second drawing step in which the periphery of the pilot hole 2a is drawn from the top 13 of the convex shape 11 to form the concave shape 10, and the peripheral edge of the pilot hole 2a is punched to form a different shaped pilot hole 2b ( A hole punching process for forming a bent hole 2 of a bent shape and a hole bending process for forming a bent hole 2 of a deformed hole by bending a deformed pilot hole 2b in sequence. A front cross member 1 having a bent hole shape 2 having a deformed hole at the end is formed.
Therefore, in this press molding method, the volume of the material necessary for forming the concave shape 12 by drawing in the second drawing step is formed by drawing in the direction perpendicular to the flat plate 10 in the first drawing step. Since it is ensured by the volume of the material of the convex shape 11 to be formed, the molding in the second drawing step becomes easy (the stress applied to the material is small), which has been a problem in the conventional press molding method. The specific portion is not concentrated and stretched by the first drawing step and the second drawing step.

As a result, in this press molding method, the plate elongation occurrence sites in the first drawing step, the second drawing step, and the hole bending step are dispersed and the plate elongation maximum at the time when the second drawing step is completed. Since the portion P1 and the plate elongation maximum portion P2 in the hole bending process do not coincide with each other, the plate bending does not concentrate on a specific portion of the hole bending shape 2 even in the hole bending step. It is prevented that the edge of the shape 2 is cracked, and the quality of the product (front cross member 1) is ensured.
Moreover, in this press molding method, since the wrinkle pressing surfaces 14 are set on both sides in the width direction of the end portion of the second molded product 5 in the second drawing step, it is possible to prevent the product from being wrinkled. At the same time, the plate elongation can be adjusted.
Also, in this press forming method, in the punching process, the irregular shaped pilot hole 2b was punched by one stroke of the punch, so one punch hole (prepared hole 2b) was punched by multiple strokes. As in the case of punching, a notch shape is not formed on the end face of the prepared hole 2b, and it is possible to prevent the hole bending shape 2 from being cracked.

In addition, embodiment is not limited above, For example, you may comprise as follows.
The product need not be the front cross member of the track frame, and may be another press-formed product.
The dies 7 and 8 used in the first drawing step may be integrally formed.

It is explanatory drawing of this Embodiment, Comprising: It is a figure which shows the state which the punch contacted the flat plate (molding material) in the 1st drawing process. It is a figure which shows the state by which a punch is lowered | hung from the state shown by FIG. 1, and a flat plate is bent. It is a figure which shows the state which the punch was lowered | hung from the state shown by FIG. 2, and the shaping | molding in a 1st drawing process was completed. It is explanatory drawing of this Embodiment, Comprising: It is a figure which shows the one end part of a 1st molding work-in-process. It is an EE arrow line view in FIG. It is explanatory drawing of this Embodiment, Comprising: It is a figure which shows the one end part of the 2nd in-process product. It is explanatory drawing of this Embodiment, Comprising: It is a figure which shows the pilot hole just before being punched in a punching process. It is explanatory drawing of this Embodiment, Comprising: It is a figure which shows the prepared hole just before carrying out a hole bending process in a hole bending process. It is explanatory drawing of this Embodiment, Comprising: It is a figure which shows the hole bending shape formed in the end of the front cross member. It is a perspective view of a front cross member. It is explanatory drawing of conventional embodiment, Comprising: It is a perspective view which shows the one end part of a 1st molding work in process. It is explanatory drawing of conventional embodiment, Comprising: It is sectional drawing which shows the one end part of a 1st in-process product. It is explanatory drawing of a 2nd aperture_diaphragm | restriction process. It is explanatory drawing of conventional embodiment, Comprising: It is a figure which shows the one end part of a 2nd molding in-process item. It is explanatory drawing of conventional embodiment, Comprising: It is sectional drawing which shows the one end part of a 2nd molding in-process item. It is explanatory drawing of conventional embodiment, Comprising: It is a figure which shows the hole bending shape formed in the end of the front cross member. It is explanatory drawing of conventional embodiment, Comprising: It is a figure which shows the line length difference of a 1st aperture_diaphragm | restriction process and a 2nd aperture_diaphragm | squeeze process.

Explanation of symbols

1 Front cross member (press-molded product), 2 hole bending shape, 2a, 2b pilot hole, 3 1st molding work product, 5 2nd molding work product, 9 punch, 10 flat plate, 11 convex shape, 12 concave shape , 13 Top

Claims (4)

  A press-molding method of a press-molded product in which a flat plate is pressed to form a hole bending shape, wherein the lower part is formed by drawing a periphery of a pilot hole formed in the flat plate in a direction perpendicular to the flat plate. A first drawing step for forming the periphery of the hole into a convex shape; a second drawing step for drawing the periphery of the pilot hole from the top of the convex shape to form a concave shape; and bending the pilot hole And a hole bending step of processing to form the hole bending shape.   Predicting the plate elongation maximum portion of the hole bending shape, in the first drawing step, the convex shape including a portion corresponding to the plate bending maximum portion of the hole bending shape around the pilot hole. The press forming method according to claim 1, wherein a top portion is formed.   The press forming method according to claim 1, further comprising a punching step of punching a peripheral edge of the prepared hole by a one-stroke operation of a punch after the second drawing. A press method of a cross member in which a flat plate is pressed to form a hole-bending shape of a deformed hole at an end, and the periphery of a pilot hole formed in the flat plate is drawn in a direction perpendicular to the flat plate However, the first drawing step of forming the periphery of the pilot hole in a convex shape, the second drawing step of drawing the periphery of the pilot hole from the top of the convex shape to form a concave shape, A hole punching process for forming a deformed hole by punching the peripheral edge of the pilot hole by a one-stroke operation of the punch, and a hole for bending the deformed hole formed by the hole punching process to form the hole bending shape. A press forming method comprising: a bending step.