Press forming punch with air vent structure

Abstract

To provide a press molding punch having an air vent structure that does not affect the appearance quality. [Solution] A press molding punch 3 is configured to allow residual air 4 trapped between the forming punch 3 and the workpiece during press molding to escape, and an air groove 10 is provided on the peripheral edge of the forming surface of the forming punch 3, which corresponds to the peripheral edge of the workpiece 1 that does not affect the appearance quality of the final product, and one or more air vent holes 11 are provided in the air groove portion.

Description

[Technical Field]

[0001] This invention relates to a technology for improving press quality by arranging air vent holes, which remove air remaining between the press punch and the workpiece during press molding, in a location that does not impair the quality of the press molding. [Background technology]

[0002] Automotive exterior parts such as body panels and door panels are currently produced mainly by press-forming steel sheets. Since the appearance of such exterior parts is very important, high-quality press-forming is required.

[0003] However, when pressing exterior parts, panel-shaped parts consisting of complex curved surfaces are often formed, and air can become trapped between the workpiece and the molding die, adversely affecting molding quality. In particular, since the forming punch (convex) adheres to the workpiece from the early stages of processing, air often becomes trapped between the forming surface and the workpiece. Furthermore, in recent years, curved surfaces have become more common due to design requirements, and in particular in outer door panels, air can become trapped in the recessed surfaces of the curved surface, causing adverse effects such as preventing the intended shape from being formed due to the influence of residual air.

[0004] To avoid this, air vent holes are provided in areas where air is likely to remain in the forming punch. However, if the air vent holes are provided on the forming punch surface of the design surface of the door outer panel, traces of the air vent holes may be transferred, so it is necessary to select areas where the air vent holes will have as little effect as possible on the appearance quality.

[0005] In the past, the location of these air vent holes was determined through trial and error, which required time to adjust the molding die, and there were also cases where compromises had to be made when the appearance quality was affected by residual air or the air vent holes.

[0006] There are few patent applications related to the technology of this invention, but Patent Document 1 proposes an air vent structure in which a long groove 106 is provided on the press surface of the punch as shown in Figure 8, an insert material 107 is inserted into the groove and connected to an air hole inside the punch, and a slit 110 narrower than the thickness of the workpiece is provided in the insert material.

[0007] In the structure of Patent Document 1, a slit is provided on the processing surface of the punch that strongly presses the workpiece, which raises concerns that this may have a negative impact on the appearance quality and that the air venting function may not be sufficient. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Actual opening 1987-92023 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made in view of the above points, and its purpose is to provide a mold structure with an air vent structure that does not affect the appearance quality. [Means for solving the problem]

[0010] The invention of claim 1 is a press forming punch equipped with an air vent structure on the forming surface so that air trapped between the forming punch and the workpiece during press forming can be released, characterized in that an air groove is provided on the peripheral portion of the forming surface of the forming punch corresponding to the peripheral portion of the workpiece that does not affect the appearance quality of the final product, and one or more air vent holes are provided in the air groove portion. It is a press-molded punch.

[0011] During press molding, residual air trapped between the forming punch and the workpiece can prevent the accurate transfer of the punch shape to the workpiece, potentially degrading the appearance quality of the pressed product. Therefore, by providing an air vent structure that removes the residual air, the appearance quality of the pressed product can be improved.

[0012] However, if air vent holes are provided without sufficient consideration on the forming surface where the forming punch actually presses and forms the workpiece, the hole shape may be transferred to the product, degrading the appearance quality. Therefore, as shown in the configuration of claim 1, by providing air vent holes in areas that will not be visible from the outside when the workpiece becomes a final product, or in the peripheral areas of the press forming surface that correspond to areas that will be removed by trimming, it is possible to provide an air vent structure without affecting the appearance quality.

[0013] The invention of claim 2 is characterized in that, in addition to the configuration described in claim 1, the work is an outer panel that is joined to an inner panel by hemming the outer periphery, and the peripheral portion of the work that does not affect the appearance quality of the final product is the outer periphery of the outer panel hemming fold.

[0014] According to the invention of claim 2, when press-molding the outer panel, which is joined to the inner panel by hemming the outer periphery, air grooves and air vent holes are provided on the molding punch molding surface along the outer periphery of the processed area corresponding to the hemmed folding portion of the outer panel.

[0015] With this configuration, the outer panel surface that is pressed against the air grooves and air vent holes becomes a part of the final product that cannot be seen from the outside due to the hemming process, so the air grooves and air vent holes do not affect the appearance quality.

[0016] The device of claim 3 is characterized in that, in addition to the configuration described in claim 2, the processing area corresponding to the outer panel hemming bending portion is a processing area of ​​the front edge or rear edge of the door.

[0017] According to the configuration of claim 3, air grooves and air vent holes are provided at the leading and trailing edges of the door outer panel, which are susceptible to the effects of residual air, thereby improving the appearance quality. Door outer panels are often shaped linearly in the longitudinal direction of the vehicle and curved in the vertical direction of the vehicle. For this reason, the leading and trailing edges of the door outer panel are prone to problems with residual air. According to the configuration of claim 3, residual air generated at the leading and trailing edges of the door outer panel can be efficiently discharged.

[0018] The invention of claim 4 is characterized in that, in addition to the configuration of claim 1, the peripheral portion of the workpiece that does not affect the appearance quality of the final product is the outer periphery of the trim line.

[0019] According to the invention of claim 4, air grooves and air vent holes are drilled on the press molded surface that corresponds to the outside of the trim line of the workpiece to be cut in the final product. With this configuration, the air vent structure acts on the workpiece molded surface of the part to be cut in the final product, so the air vent holes can be drilled without deteriorating the appearance quality of the final product, and the adverse effects of residual air can be eliminated. [Effects of the Invention]

[0020] According to this invention, residual air can be discharged using an air vent structure that does not affect the appearance quality, eliminating the adverse effects of residual air and improving the appearance quality of pressed products. [Brief explanation of the drawings]

[0021] [Figure 1] A cross-sectional view of a molding die showing the mechanism by which air remains during press molding. [Figure 2] (a) Cross-sectional view of the molding die and (b) front view of the molding die, showing the generation of residual air between the forming punch and the workpiece when forming a door outer panel using a forming punch. In the front view of (b), the forming die located at the front side is shown in perspective. [Figure 3] FIG. 1 is an external view of a forming punch for a door outer panel equipped with an air vent structure. [Figure 4] Photo of a forming punch for door outer panels with an air vent structure. [Figure 5] 1 is a cross-sectional view of a molding die for a door outer panel having an air vent structure according to a first embodiment. [Figure 6] A conceptual diagram showing the flow of residual air between the forming punch and the workpiece when forming using a forming punch for door outer panels equipped with an air vent structure. [Figure 7] FIG. 6 is a cross-sectional view of a press-molded product manufacturing die having an air vent structure according to a second embodiment. [Figure 8] Cross-sectional view of the mold showing the air vent structure of JP1987-92023 [Explanation of symbols]

[0022] 1 Work 2. Molding die 3. Forming punch 4 Residual air 5 Door outer panel 10 Air groove 11 Air vent hole 12 Trim Line 13 Hemming bend 20 Residual air flow DETAILED DESCRIPTION OF THE INVENTION

[0023] The following describes in detail the embodiments of the present invention with reference to the drawings. However, the present invention is not limited to the following embodiments. Furthermore, appropriate modifications can be made without departing from the scope of the effects of the present invention.

[0024] Figure 1 is a schematic diagram showing the mechanism by which residual air is generated when a workpiece is placed on a forming die and pressed against it by a forming punch to perform press forming. A forming punch 3 is fixed on the bolster of the press machine. A workpiece 1 is placed on the forming punch 3, and a forming die 4 fixed to the slide of the press machine presses the workpiece between the forming punch 3 and the forming die 4 by operating the press machine, thereby transferring the shape of the forming die to the workpiece. Steel plate is usually used for the workpiece.

[0025] During the processing process, air is sealed in on the forming surface of the forming punch 3 by the convex shape of the outer periphery of the forming punch, as shown in Figure 1, generating residual air 4. This residual air 4 acts on the workpiece 1 in addition to the pressure applied by the forming die 2, resulting in excessive pressure, which can have a negative effect on the appearance quality of the workpiece. To avoid this negative effect, air vent holes 11 are usually provided in appropriate locations on the surface of the die to release the residual air, as shown in Figure 3.

[0026] One of the conditions for this appropriate location is to provide an air vent hole in a location where residual air is likely to accumulate. As mentioned above, the forming surface of a forming punch has a convex shape around it, which makes it easy for air to be sealed in, and since the surrounding area tends to come into close contact with the workpiece from the beginning of the forming process, residual air is likely to accumulate there. Therefore, this is an appropriate location for providing an air vent hole. However, providing air vent holes on the forming surface of a forming punch presents the problem of the hole shape being transferred to the workpiece, which could cause scratches, so careful consideration is required when selecting the punching location and method.

[0027] Therefore, another condition for the appropriate location is to select a location where the hole shape will not be transferred to the workpiece and will not affect the appearance quality. The forming surface of the forming die is usually not pressed against the workpiece until the end of the forming process, so air vent holes are often provided on the forming die side. Even on the forming punch side, in areas where the forming surface is concave, the forming surface does not conform to the workpiece and no large pressure is applied, so hole marks often do not occur. Therefore, even on the punch side, air vent holes are often provided in areas where the forming surface is concave.

[0028] In practice, when locating air vent holes on the forming punch side, the position was carefully selected by predicting in advance through simulation the range in which surface pressure would be generated on the workpiece based on the shape of the forming surface, etc. However, because there were few suitable locations for setting air vent holes, it was not possible to sufficiently vent residual air, which could affect the appearance quality. The inventor wanted to solve this problem and came up with a method for providing a structure for discharging trapped air, primarily on the forming punch, without affecting the appearance quality.

[0029] Example 1 As Example 1 of the present invention, an example of a molding die for a door outer panel will be described. Figure 2 illustrates the location of residual air generation in the door outer panel molding punch 3. As shown in the cross section of the molding punch in Figure 2(a), residual air is trapped in the recessed portion of the door outer panel molding punch (the portion of the punch corresponding to the door handle attachment portion and the lower panel bottom, shown in the hatched area). In Figure 2(b), which is a front view, residual air is generated in the area shown in the hatched area.

[0030] Door outer panel forming punches often change shape linearly in the front-to-back direction of the door and curvedly in the up-and-down direction. In such shapes, residual air tends to flow easily in the front-to-back direction but not in the up-and-down direction. Therefore, providing an air vent structure at the front or rear end of the forming punch is expected to efficiently discharge residual air.

[0031] Therefore, we have considered a method in which the residual air trapped on the forming surface of the forming punch is collected in an air groove provided at the front or rear end of the forming punch and efficiently discharged through an air vent hole provided in the air groove.

[0032] Furthermore, when considering the impact on appearance quality, the locations where the air grooves and air vent holes are to be provided should be located in areas that cannot be seen from the outside when the workpiece is made into a final product, thereby preventing deterioration in appearance quality due to scratches.

[0033] Most outer door panels are joined to inner panels to form the final product, and this joining is often achieved by hemming the outer periphery, which means that the inner surface bent by hemming is not visible from the outside in the final product.

[0034] Figures 3 and 4 show a schematic diagram and a photograph of a forming punch 3 for an outer door panel that is actually equipped with an air vent structure. This diagram shows the rear end of the forming punch for an outer door panel, with an air groove 10 located at the rear end and multiple air vent holes 11 located at the bottom of the groove. These air vent holes 11 are connected to the outside air, and residual air is efficiently discharged by collecting in the air groove 10 and discharging through the air vent holes 11.

[0035] Conventionally, air vent holes are drilled directly into the molding surface of the forming punch, carefully selecting locations where scratches will not occur. However, the inventors have discovered from the results of experiments using an actual mold that a configuration in which air grooves 10 are formed on the edge of the forming punch in an area where residual air accumulates and does not affect the appearance quality, and air vent holes are drilled in the air groove to discharge the residual air, can efficiently discharge the residual air on the molding surface.

[0036] Figure 5 shows a schematic cross section of the forming punch 3, forming die 2, and formed workpiece 1 (door outer panel) for a door outer panel. This figure shows a cross section of the outer periphery of the door outer panel, and the dotted line area on the right side of the figure where workpiece 1 is bent downward virtually represents the state where the outer periphery of the door outer panel has been hemmed. In this case, the air grooves 10 and air vent holes 11 shown in Figure 5 are located outside the hemmed bend 13. Even if the air grooves 10 and air vent holes 11 are transferred to the workpiece, the marks are located on the inside of the bent workpiece and do not affect the appearance quality.

[0037] Figure 6 shows a schematic diagram of the flow of residual air 4 discharged from the area shown in Figure 2. The forming die 2 is not shown in order to show the forming punch 3, but the results of an experiment using an actual mold show that pressure is applied to the forming die, and a flow like the arrow shown by the residual air flow 20 occurs, which can be seen from the tendency of the areas that affect appearance quality.

[0038] First, residual air 4 that has accumulated in the recessed portion of the door handle part of the door outer panel forming punch 3 is pushed by the forming die 2 and flows into the air groove formed on the edge of the forming punch 3 as shown by the arrow in Figure 6, and is then discharged through the air vent hole 11.

[0039] Next, residual air 4 that has accumulated on the recessed door outer panel molding surface below the molding punch is similarly forced by the pressure of the molding die 2 into the air groove 10 formed on the edge of the molding punch 3 and the air vent hole 11 drilled in the recessed portion of the molding surface. The residual air 4 that has flowed into the air groove 10 is discharged from the air vent hole 11 drilled at the bottom of the air groove.

[0040] It has been confirmed through experiments using an actual mold that by providing the air grooves 10 in this way, residual air that has accumulated in a plurality of areas can be collected and efficiently discharged.

[0041] Example 2 The second embodiment will be described with reference to a typical press-molded product such as a door outer panel, which is not joined by hemming around the periphery.

[0042] In the production of press-molded products, after the press molding process, a certain area is cut off around the periphery of the press-molded intermediate product in the trimming process. This is to remove the peripheral parts that are necessary for molding, such as the parts held by the blank holder during the molding process, but do not become part of the product. As long as the part is outside the trim line, which is the line to be cut, it will not affect the appearance quality of the final product.

[0043] Figure 7 shows a schematic cross section of a forming punch 3 used to produce press products, a forming die 2, and a formed workpiece 1. This figure shows a schematic cross section of the outer periphery of a forming punch 3 used to produce press products. In this case, the air grooves 10 and air vent holes 11 shown in Figure 7 are arranged outside the trim line 12, and even if the air grooves 10 and air vent holes 11 are transferred to the workpiece, the scars will not affect the appearance quality because they are parts that are cut away in the trimming process.

[0044] Although the flow of the residual air 4 being discharged is not shown in the figure in the second embodiment, it has been confirmed that, as in the first embodiment, the provision of the air groove 10 allows the residual air that has accumulated in a wide area to be collected and efficiently discharged.

Claims

1. A press forming punch having an air vent structure on the forming surface so that residual air trapped between the forming punch and the workpiece during press forming can be released, An air groove is provided on the peripheral portion of the forming surface of the forming punch corresponding to the peripheral portion of the workpiece that does not affect the appearance quality of the final product, and one or more air vent holes are provided in the air groove portion. Press forming punch.

2. The work is an outer panel that is joined to an inner panel by hemming the outer periphery, and the peripheral portion of the work that does not affect the appearance quality of the final product is the outer periphery of the hemmed bent portion of the outer panel. The press forming punch according to claim 1 .

3. The processing portion corresponding to the outer panel hemming bending portion is a processing portion of the door leading edge or the door trailing edge, The press-molding punch for an outer panel according to claim 2.

4. The peripheral portion of the workpiece that does not affect the appearance quality of the final product is the outer periphery of the trim line. The press forming punch according to claim 1 .

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