Press molding die and press molding method

Abstract

To suppress deformation of a long die during press molding and prevent deterioration of quality of formation, without increasing cost and size of a press forming die.SOLUTION: A press molding die 10 has long dies (bending dies 12, 13) and presses a workpiece (a side outer panel 1) in a direction crossing respective longitudinal directions of the bending dies 12, 13. Each of the bending dies 12, 13 is provided with driving means (an actuator 20) that applies compressive stress or tensile stress in the longitudinal direction.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a press molding die and a press molding method. [Background technology]

[0002] The side outer panel 1 of the vehicle body shown in Fig. 1 is usually formed by pressing from above and below while laid flat to perform drawing. The roof side rail 3 provided at the upper part of the door opening 2 of the side outer panel 1 has a negative corner 4 as shown by the dotted line in Fig. 2, and therefore cannot be formed by drawing in the vertical direction. For this reason, after the side outer panel 1 is drawn, the negative corner 4 is often formed by bending using a slide die (for example, see Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-164420 Summary of the Invention [Problem to be solved by the invention]

[0004] The slide die for forming the roof side rail 3 as described above has a long shape extending in the front-rear direction of the vehicle body along the roof side rail 3. When a workpiece is pressed in a direction perpendicular to the longitudinal direction using such a long slide die, the slide die may bend due to the reaction force of the press. When a long die is bent, the gap between the forming surfaces of the die becomes too large or too small, which may result in a deterioration in forming quality.

[0005] For example, if the strength (rigidity) of a long mold is improved, it is possible to suppress deflection during pressing. However, in order to increase the strength of the mold, it is necessary to make the mold from a high-strength material and to increase its size, which leads to increased costs and size of the press molding mold.

[0006] In view of the above circumstances, the present invention aims to suppress deflection of a long mold during press molding and prevent a decrease in molding quality without increasing the cost or size of the press molding mold. [Means for solving the problem]

[0007] In order to solve the above problem, the present invention provides a press molding die having a long die and pressing a workpiece in a direction intersecting the longitudinal direction of the die, the press molding die being provided with a driving means for applying longitudinal compressive stress or tensile stress to the die.

[0008] By applying compressive or tensile stress in the longitudinal direction to the long mold by the driving means, the mold can be deflected so that the intermediate portion in the longitudinal direction bulges. Therefore, by applying compressive or tensile stress in the longitudinal direction to the mold by the driving means so as to offset the deflection occurring in the mold during press molding, the deflection of the mold can be suppressed.

[0009] For example, if the part of a long die where bending occurs is pressed from behind (the side opposite the workpiece) with a cylinder or the like, the bending of the die can be suppressed. However, in this case, it is necessary to place a cylinder or the like behind the die, which leads to an increase in the size of the press molding die and requires a change in the design of the structure behind the die (for example, the cam mechanism that slides the die).

[0010] Therefore, it is preferable that the driving means has a first part and a second part that are relatively movable with respect to each other, and that the first part and the second part are attached to two places spaced apart in the longitudinal direction of the die. In this way, by attaching the driving means to the long die itself, it is not necessary to provide a cylinder or the like behind the die, so that it is possible to avoid an increase in size of the press molding die and a change in design.

[0011] For example, if a long die is designed in advance with the amount of deflection during pressing in mind, the deflection of the die during pressing can be suppressed. However, in the manufacturing process of the die, the molding surfaces of the die are aligned without a workpiece to check the gap between the molding surfaces, and if the gap is not appropriate, the shape of the molding surfaces of the die is corrected, and the molding surfaces of the die are aligned again to check the gap. This process is repeated. For this reason, if the die is formed with the deflection during pressing in mind, the molding surfaces of the die will not be aligned, and it may become impossible to carry out the above-mentioned work of correcting the molding surfaces.

[0012] Therefore, the present invention provides a press molding method in which a press molding die having a long die and a driving means for applying longitudinal compressive stress or tensile stress to the die is used to press a workpiece in a direction intersecting the longitudinal direction of the die, the press molding method comprising the steps of: checking the gap between the molding surface of the die and the molding surface of another die opposing it when no stress is applied to the die by the driving means; and pressing the workpiece when longitudinal compressive stress or tensile stress is applied to the die by the driving means.

[0013] In this way, by checking the gap between the molding surfaces of the die without applying stress to the die with the driving means, it is possible to correct the molding surfaces of the die as necessary. Then, when pressing a workpiece using this die, it is possible to suppress the deflection of the die during pressing by applying a compressive stress or tensile stress in the longitudinal direction to the die with the driving means. Effect of the Invention

[0014] As described above, according to the present invention, it is possible to suppress the deflection of a long die during press molding without increasing costs or the size of the entire press molding die, thereby preventing a decrease in molding quality. [Brief description of the drawings]

[0015] [Figure 1] FIG. 2 is a plan view of the side outer panel when laid flat. [Diagram 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Diagram 3] FIG. 11 is a cross-sectional view showing a press molding die in a bending process, illustrating a state before an upper die starts to descend. [Figure 4] FIG. [Diagram 5] FIG. 4 is a plan view showing deformation of a bending die during press molding. [Figure 6] FIG. 11 is a cross-sectional view showing a press molding die in a bending process, illustrating a state in which an upper die is being lowered. [Figure 7] 11 is a cross-sectional view showing a press molding die in a bending process, illustrating a state in which an upper die has been lowered to a lower end position and bending has been completed. FIG. [Figure 8] 11 is a cross-sectional view showing a press molding die in a bending process, in which an upper die is raised to an upper end position. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] In this embodiment, a case where a side outer panel 1 of an automobile body shown in FIG. 1 is press-formed is shown. The side outer panel 1 is formed through a drawing process and a bending process. In particular, a roof side rail 3 provided at an upper portion of a door opening 2 of the side outer panel 1 is formed into a shape shown by a solid line in FIG. 2 in the drawing process, and then a negative corner portion 4 shown by a dotted line is formed in the bending process. The drawing process and the bending process are performed by lowering an upper mold (not shown) from above while the side outer panel 1 is laid flat. The right side of FIG. 2 is the upper side when the side outer panel 1 is assembled to the vehicle body, and the upper side is the outer side in the vehicle width direction when the side outer panel 1 is assembled to the vehicle body.

[0018] The bending process for forming the negative corner portion 4 of the roof side rail 3 will be described below. The bending process is performed using a press molding die 10 shown in Fig. 3. The press molding die 10 includes a lower die 11, an upper die (not shown), an inner bending die 12, and an outer bending die 13. In this embodiment, the lower die 11 is a fixed die, and the upper die is a movable die that can be raised and lowered in the vertical direction in the figure.

[0019] The inner bending die 12 and the outer bending die 13 are slide types that can slide in a direction that intersects with the movement direction of the upper die (the vertical direction in FIG. 3) and also intersects with the longitudinal direction of the inner bending die 12 and the outer bending die 13 (the direction perpendicular to the paper surface of FIG. 3). In the illustrated example, the inner bending die 12 and the outer bending die 13 can move in the vertical direction and in a direction perpendicular to the longitudinal direction (the horizontal direction in FIG. 3). The upper die is provided with a first cam (not shown) that drives the inner bending die 12 and a second cam (not shown) that drives the outer bending die 13.

[0020] The inner bending die 12 is provided with a forming surface 12a for forming the negative corner portion 4 and a cam surface (not shown) that comes into contact with a first cam provided on the upper die. The outer bending die 13 is provided with a forming surface 13a for forming the negative corner portion 4 and a cam surface (not shown) that comes into contact with a second cam provided on the upper die. The first cam and the second cam press down the cam surfaces of the inner bending die 12 and the outer bending die 13, causing the inner bending die 12 and the outer bending die 13 to move toward each other. The inner bending die 12 and the outer bending die 13 are biased toward the side moving away from each other by a biasing means such as a spring. When the first cam and the second cam are not in contact with the cam surfaces of the inner bending die 12 and the outer bending die 13, the inner bending die 12 and the outer bending die 13 come into contact with the lower die 11, and the movement toward the side moving away from each other is restricted.

[0021] As shown in FIG. 4, the inner bending die 12 and the outer bending die 13 are long dies extending in the front-rear direction of the vehicle body. A driving means for applying a compressive stress or a tensile stress in the longitudinal direction (the left-right direction in FIG. 4) is attached to the inner bending die 12 and the outer bending die 13. As the driving means, for example, an actuator 20 is provided. The actuator 20 has a cylindrical main body 21 (first part) and a pin 22 (second part) provided so as to be movable relative to the main body 21. As the actuator 20, a gas spring, a hydraulic cylinder, an electric cylinder, or the like can be used. The actuator 20 attached to the inner bending die 12 has the main body 21 and the pin 22 fixed to mounting parts 12b provided at two positions spaced apart in the longitudinal direction of the inner bending die 12. The actuator 20 attached to the outer bending die 13 has the main body 21 and the pin 22 fixed to mounting parts 13b provided at two positions spaced apart in the longitudinal direction of the outer bending die 13.

[0022] The actuator 20 attached to the inner bending die 12 is attached at a position offset toward the molding surface 12a side from the center line L1 of the inner bending die 12 (a straight line passing through the center of gravity of the inner bending die 12 and running in the longitudinal direction). The actuator 20 attached to the outer bending die 13 is attached at a position offset toward the side away from the molding surface 13a from the center line L2 of the outer bending die 13 (a straight line passing through the center of gravity of the outer bending die 13 and running in the longitudinal direction).

[0023] The actuator 20 of the inner bending die 12 may be attached at a position offset from the center line L1 toward the side away from the molding surface 12a. The actuator 20 of the outer bending die 13 may be attached at a position offset from the center line L2 toward the molding surface 13a. Alternatively, the actuator 20 may be provided on both sides of the center lines L1, L2 of the bending dies 12, 13. The actuator 20 may be provided on only one of the inner bending die 12 and the outer bending die 13.

[0024] The number and positions of the actuators 20 provided on the inner bending die 12 and the outer bending die 13, and the expansion and contraction amount of each actuator 20 are set based on the stress applied to the inner bending die 12 and the outer bending die 13 during pressing. Specifically, a simulation is used to calculate the internal stress applied to the inner bending die 12 and the outer bending die 13 when bending the side outer panel 1 with the press molding die 10. Then, the number, positions, and expansion and contraction amount of the actuators 20 are set so as to relieve this internal stress.

[0025] For example, when pressing is performed with the long inner bending die 12 and outer bending die 13 shown in Fig. 5, if the bending dies 12, 13 are curved as shown by the dotted lines by the reaction force of the press (the curve is exaggerated in Fig. 5), a compressive stress F1 is applied to the molding surfaces 12a, 13a side of the center lines L1, L2, and a tensile stress F2 is applied to the side away from the molding surfaces 12a, 13a of the center lines L1, L2. In this case, if the actuator 20 is provided on the molding surface 12a side of the center line L1, as in the inner bending die 12 shown in Fig. 4, the pin 22 of the actuator 20 is extended to apply a tensile stress in the longitudinal direction to the die, thereby alleviating the compressive stress F1 applied during pressing and suppressing the curvature of the inner bending die 12. On the other hand, when the actuator 20 is provided on the side away from the molding surface 13a than the center line L2, as in the outer bending die 13 shown in Figure 4, the pin 22 of the actuator 20 is retracted to apply a longitudinal compressive stress to the die, thereby alleviating the tensile stress F2 applied during pressing and suppressing the curvature of the outer bending die 13.

[0026] After the press molding die 10 is installed in the factory, the molding surface 12a of the inner bending die 12 and the molding surface 13a of the outer bending die 13 are corrected before starting press molding. Specifically, in a state where the actuator 20 attached to the inner bending die 12 and the outer bending die 13 is not driven, that is, in a state where no longitudinal stress is applied to the inner bending die 12 and the outer bending die 13, the molding surface 12a of the inner bending die 12 and the molding surface 13a of the outer bending die 13 are fitted together without sandwiching the work (side outer panel 1). In this state, the size of the gap between the molding surfaces 12a and 13a and the presence or absence of interference are confirmed. Then, the molding surfaces 12a and 13a are cut to correct the shape as necessary. After that, the molding surfaces 12a and 13a are fitted together again without sandwiching the work, and the gap between the molding surfaces 12a and 13a is confirmed. By repeating the above, the gap between the molding surfaces 12a and 13a is set to an appropriate value.

[0027] Once the correction of the forming surfaces 12a, 13a of the bending dies 12, 13 has been completed in this manner, each actuator 20 is extended or retracted by the expansion / contraction amount set above, and a predetermined stress is applied to each part of the bending dies 12, 13 to deform (bend) the bending dies 12, 13. In this state, the bending process of the side outer panel 1 is performed. The procedure of the bending process will be described below.

[0028] First, as shown in Fig. 3, the side outer panel 1 that has been subjected to the drawing process is placed flat on the lower die 11. At this time, the inner bending die 12 and the outer bending die 13 of the press molding die 10 are retracted to positions where they come into contact with the lower die 11 or stoppers provided thereon. In this way, when the side outer panel 1 is set in the lower die 11, the outer bending die 13 is retracted to the side away from the inner bending die 12 (the right side in Fig. 3), thereby making it possible to avoid interference between the side outer panel 1 and the outer bending die 13.

[0029] Then, when the upper die is lowered, the first cam comes into contact with the cam surface of the inner bending die 12. When the upper die is further lowered, the first cam causes the inner bending die 12 to slide to the right in the figure and is disposed at a predetermined position. In this embodiment, as shown in FIG. 6, the inner bending die 12 is disposed at a position where it comes into contact with the side outer panel 1 set on the lower die 11 (or at a position immediately before coming into contact). At this position, the first cam restricts the inner bending die 12 from moving to the left in the figure.

[0030] After that, when the upper die is further lowered, the second cam comes into contact with the cam surface of the outer bending die 13. When the upper die is further lowered, the second cam causes the outer bending die 13 to slide to the left in the figure, and the roof side rail 3 of the side outer panel 1 is clamped between the forming surface 12a of the inner bending die 12 and the forming surface 13a of the outer bending die 13, and the negative angle portion 4 is formed (see FIG. 7).

[0031] In this way, by pressing the side outer panel 1 in a direction intersecting the longitudinal direction of each of the long bending dies 12 and 13 (in this embodiment, a direction substantially perpendicular to the longitudinal direction), there is a risk that the bending dies 12 and 13 may bend due to the reaction force at the time of pressing (see dotted lines in FIG. 5). In this embodiment, the actuator 20 applies compressive stress or tensile stress in the longitudinal direction to the long bending dies 12 and 13 in advance to deform them, thereby forming a shape that anticipates the bending at the time of pressing. During pressing, the bending due to the stress of the actuator 20 and the bending due to the reaction force at the time of pressing are offset, so that the bending of the bending dies 12 and 13 is suppressed. As a result, the gap between the forming surfaces 12a and 13a of the bending dies 12 and 13 becomes close to a preset appropriate size, improving the quality of the bending process. Furthermore, even when molding parts that experience a large reaction force during pressing, the bending of the bending dies 12, 13 can be suppressed without providing a structure to reinforce the bending dies 12, 13, which contributes to simplifying the die structure and reducing the weight of the die.

[0032] When the upper die is raised after being lowered to the bottom end position, the inner bending die 12 and the outer bending die 13 move away from the negative corner portion 4 of the side outer panel 1 due to the biasing force of the biasing means. Then, when the upper die is raised to the top end position, the inner bending die 12 and the outer bending die 13 are retreated to positions where they do not overlap with the negative corner portion 4 in the press direction (the up-down direction in the figure) (see FIG. 8). This allows the side outer panel 1 with the negative corner portion 4 formed therein to be separated from the lifted lower die 11.

[0033] In the above embodiment, a slide type long mold is used to apply compressive or tensile stress in the longitudinal direction using a driving means (actuator 20). However, the present invention is not limited to this and may be, for example, a long mold that is integral with an upper or lower mold.

[0034] Furthermore, the present invention is not limited to application to press molding dies that perform bending, but can also be applied to press molding dies that perform other processes such as drawing and punching. [Explanation of symbols]

[0035] 1 Side outer panel (work) 2 Door opening 3 Roof side rail 4 Negative corner 10 Press molding dies 11 Lower mold 12 Inner bending die (long die) 13 Outer bending die (long die) 20 Actuator (driving means) 21 Main body (1st part) 22 pin (second part)

Claims

1. A press molding die having a long die and pressing a workpiece in a direction intersecting a longitudinal direction of the die, providing a driving means for applying a compressive stress or a tensile stress in a longitudinal direction to the die; the drive means has a first part and a second part movable relative to each other; A press molding die in which the first portion and the second portion are fixed at two locations spaced apart in the longitudinal direction of the die.

2. 2. The press molding die according to claim 1, wherein the driving means is attached to the die on a side away from the molding surface with respect to a center line of the die, or at a position offset toward the molding surface.

3. A press molding method for pressing a workpiece in a direction intersecting a longitudinal direction of a press molding die having a long die and a driving means for applying a compressive stress or a tensile stress in a longitudinal direction to the die, comprising: the drive means has a first part and a second part movable relative to each other; The first portion and the second portion are fixed at two locations spaced apart in the longitudinal direction of the mold, a step of checking a gap between a molding surface of the mold and a molding surface of another mold opposed thereto, in a state where no stress is applied to the mold by the driving means; and pressing the workpiece while applying compressive or tensile stress in the longitudinal direction to the die using the driving means.

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