JP2019181518A - Method for manufacturing automobile outer plate panel having concave portion, and press molding device - Google Patents

Abstract

To stably restrict formation of surface strain around a concave portion, while suppressing costs, in manufacturing an automobile outer plate panel having a concave portion, and thereby solve the problem of prior art that it has been difficult to stably restrict surface strain, while suppressing costs, in manufacturing an automobile outer plate panel, such as a door outer panel having a concave portion.SOLUTION: In manufacturing an automobile outer plate panel having a concave portion, the concave portion is formed under vibration of a die. The concave portion is a concave embossment or a portion interposed between adjacent character lines.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for manufacturing an automobile outer panel having a partially concave portion such as an outer door of an automobile, and a press molding apparatus.

  Among the outer plate panels constituting the automobile, for example, there is an outer plate panel having a concave embossed portion formed by overhanging like a door outer shown in FIG. The concave embossed part is usually formed by stretching a blank with a press molding device, but material flows into the concave embossed part during press molding. At the same time, in the corner portion of the concave embossed portion as viewed from the side facing the concave embossed portion as shown in FIG. 1, there is uneven movement of the material in the circumferential direction of the corner portion, and Compressive stress in the direction is generated. For this reason, surface distortion of about several tens of microns to several hundreds of microns occurs on the design surface of the outer panel. In the example shown in FIG. 1, the position of the black circle in the figure corresponds to the above-described corner portion, and surface distortion is likely to occur.

  Moreover, the door outer which arrange | positioned the several character line as shown in FIG. 1 is employ | adopted for the exterior panel of a motor vehicle in order to improve the external appearance design. An automobile skin panel having such a convex character line has a component shape in which the space between adjacent character lines is recessed. At the time of molding such a part, since the material flows toward a portion between adjacent character lines as in the case of the concave embossed portion, a compressive stress is generated around the portion. For this reason, even in such a part, surface distortion occurs on the design surface.

  When light strikes the outer panel where surface distortion has occurred, the surface distortion may appear in the appearance like a pattern, and the product appearance quality standard may not be satisfied. Such a problem of surface distortion is not limited to the outer door of the automobile, but can also occur in the other outer panel of the automobile. In particular, when surface distortion occurs on the design surfaces of outer panels such as side panels, front fenders, hoods, and back doors, the appearance quality of the automobile body is significantly impaired.

Until now, the shape of the press mold has been changed to suppress the occurrence of surface distortion itself, and surface distortion correction work has been carried out after press molding and before coating. And cost.
In recent years, there have been examples of using high-tensile steel plates to reduce the weight of outer panel panels such as door outers and back door panels. I need it.

  As a conventional countermeasure against surface distortion, Patent Document 1 discloses an invention relating to a press forming method and a press forming apparatus for performing press forming using a drawing press die having a movable punch having a concave portion and a die having a convex portion. ing. In the press molding method of Patent Document 1, after press forming a portion other than the recess first, the recess is formed with a movable punch, thereby reducing the material inflow into the recess and ensuring the surface quality of the recess. Yes.

  Further, Patent Document 2 discloses a press that reduces the friction coefficient between a blank and a mold by forming an oil film or optimizing a mold material for the purpose of suppressing surface distortion around the handle portion of the door outer. An invention relating to a molding die is disclosed.

Japanese Patent Laid-Open No. 62-131737 JP 2008-229637 A

  The invention disclosed in Patent Document 1 needs to perform press molding using a movable punch while pressing the panel surface after the panel surface is molded, and cannot be handled by a general press die. For this reason, in order to implement the press molding method of patent document 1, there existed a subject that enormous cost would be required in the case of introduction of a press molding apparatus.

  The invention disclosed in Patent Document 2 is a mold for reducing the friction coefficient between the handle portion and the blank during press molding to be smaller than the friction coefficient between the portion other than the handle portion and the blank. In addition, it is necessary to perform press molding by appropriately changing the mold material. Therefore, the optimum lubricating oil and mold material must be optimized depending on the material strength of the material to be molded and the plating type, and it is difficult to stably suppress the surface strain. Moreover, in the press molding method of Patent Document 2, it is necessary to partially change the mold material, and there are problems such as securing adjustment time and increasing costs.

  As described above, in the conventional techniques disclosed in Patent Documents 1 and 2, when manufacturing an automobile skin panel having a concave shape portion such as a concave embossed portion or a portion between character lines as shown in FIG. It has been difficult to stably suppress surface distortion while suppressing cost.

  The present invention has been made in view of the above circumstances, and stably suppresses surface distortion generated around a concave portion while reducing the cost when manufacturing an automobile outer panel having a concave portion. The purpose is to do.

The cause of surface distortion in the concave part is
(I) the flesh due to the compressive stress in the circumferential direction accompanying the minute inflow of material around the concave shape part,
(Ii) bulge around the concave shape due to bending moment,
It is thought that there is.

  For this reason, with respect to the flesh due to the compressive stress of (i), the inflow of the material into the concave shape portion is suppressed as much as possible, that is, the tension for pulling the material into the concave shape portion generated by press molding is as much as possible. By making it small, generation | occurrence | production of a surface distortion can be suppressed. In order to reduce this tension, it is necessary to improve the sliding characteristics of the convex portion of the mold that contacts the portion where the concave portion of the blank is formed, that is, to reduce the friction coefficient of the convex portion of the mold corresponding to the concave portion. Good.

  Regarding the bulge around the concave embossed part due to the bending moment described in (ii) above, the contact range between the material being deformed and the mold should be as large as possible, that is, the material and the mold should be around the concave embossed part. Surface distortion can be reduced by making it contact in the state. In order to maintain this contacted state, it is only necessary to improve the adhesion between the material and the mold.

  One aspect of the present invention that solves the above-described problems based on the above knowledge is a method of manufacturing an automobile outer panel having a concave portion, wherein the concave portion is a concave embossed portion or an adjacent character line. It is an intermediate portion, and when the concave portion is formed, the concave portion is formed while vibrating a die.

  Another aspect of the present invention in another aspect is a press molding apparatus for an automobile skin panel having a concave portion, wherein the concave portion is a concave embossed portion or a portion between adjacent character lines, It is characterized by having a vibration device for vibrating the die.

  In the press molding according to one aspect of the present invention, by compressing the die when molding the concave portion, it is possible to reduce the compressive stress of the portion where the surface distortion of the blank occurs. You can improve the familiarity with. Thereby, while being able to reduce the tension | tensile_strength which draws material in a concave shape part, the rise | swell around the concave embossed part by a bending moment can be suppressed, and generation | occurrence | production of a surface distortion can be suppressed. Moreover, since such press molding can be implemented with a simpler structure than the press molding apparatuses disclosed in Patent Document 1 and Patent Document 2, the cost when introducing the press molding apparatus can be suppressed. .

  ADVANTAGE OF THE INVENTION According to this invention, when manufacturing the motor vehicle outer panel which has a recessed shape part, the surface distortion generate | occur | produced around a recessed shape part can be suppressed stably, suppressing cost.

It is a side view which shows an example of the motor vehicle outer panel which has a recessed part. It is a figure which shows schematic structure of the press molding apparatus which concerns on one Embodiment of this invention. It is a top view which shows the shape of the punch in the Example of this invention. It is AA sectional drawing in FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the present specification and drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 2, the press molding apparatus 1 according to the present embodiment is an apparatus that molds a concave embossed portion that is an example of a concave shaped portion. The press molding apparatus 1 includes a punch 2 provided as a lower die, a die 3 provided as an upper die, and a blank holder 4 provided so as to face the die 3 on the side of the punch 2. In the present embodiment, two blank holders 4 are arranged on the sides of the punch 2 so as to sandwich the punch 2. Moreover, in this embodiment, the dice | dies 3 and the blank holder 4 are comprised so that raising / lowering is possible by the raising / lowering mechanism (not shown). A concave portion 5 a is formed in the top portion 5 of the punch 2, and a convex portion 3 a having a shape corresponding to the concave portion 5 a of the punch top portion 5 is formed in a portion facing the punch top portion 5 of the die 3. At the time of press molding, a concave portion is formed in the blank by the convex portion 3 a of the die 3 and the concave portion 5 a of the punch 2.

  The press molding apparatus 1 includes a vibration device 6 that vibrates the die 3 and a control unit 10 that controls the operation of the vibration device 6. The control unit 10 sends a signal to the vibration device 6 so that the die 3 can be vibrated when the concave portion is formed. In the present embodiment, the vibration device 6 is incorporated in the die 3, but the installation method of the vibration device 6 is not particularly limited as long as the die 3 can be vibrated. As the vibration device 6, for example, an ultrasonic vibration device, a vibration device using a hydraulic liner, or the like may be employed. However, the device configuration is not particularly limited as long as the die 3 can be vibrated.

  The press molding apparatus 1 of the present embodiment is configured as described above. In this embodiment, the lower die 2 is fixed and the upper die 3 is movable. However, the punch 2 may be movable and the die 3 may be fixed. The upper die may be the punch 2 and the lower die may be the die 3. Moreover, about the convex part and recessed part by the side of a metal mold | die for forming a recessed shape part in a blank, the convex part may be formed in the punch 2, and the recessed part may be formed in the die | dye 3. FIG. That is, the configuration is not particularly limited as long as at least one of the punch 2 and the die 3 can move toward each other by moving up and down, and the mold configuration can mold the concave portion.

  Next, a method for manufacturing an automobile outer panel having a recessed portion in this embodiment will be described.

  First, the blank is fixed between the die 3 and the blank holder 4. At this time, the non-designed surface of the blank that appears on the appearance of the product (design surface) and the surface that does not appear on the appearance (non-design surface). The blank is fixed so that the surface side faces the punch 2 side. In addition, a blank is not limited to a steel plate, Other metal plates, such as an aluminum alloy plate and a titanium alloy plate, may be sufficient.

  Subsequently, the upper die (the die 3 in this embodiment) is lowered. Here, when the blank comes into contact with the convex portion 3 a of the die 3, the blank is deformed so as to be pushed into the concave portion 5 a of the punch top portion 5, and the material tries to move so as to be drawn into the concave portion 5 a of the punch top portion 5. . At this time, in the press molding method of this embodiment, press molding is performed while vibrating the die 3.

  By vibrating the dice 3 in this way, the compressive stress around the concave portion can be reduced, and further, the mating between the material and the mold can be improved. Thereby, the surface distortion in the circumference | surroundings of a concave shaped part can be suppressed.

  The vibration conditions are appropriately changed according to the type and hardness of the tool, the shape of the recessed portion, the material strength and plate thickness of the blank, the plating type and the plating thickness, and the like. From the viewpoint of effectively suppressing surface distortion, the vibration frequency is preferably 3 Hz or more, and more preferably 4 Hz or more. The upper limit of the vibration frequency is limited by the specification of the vibration device 6, but when the vibration frequency is high, wrinkles may occur, and therefore it is preferably 20 Hz or less. Further, from the viewpoint of effectively suppressing surface distortion, the larger the amplitude, the better, and it is preferably 1 μm or more, more preferably 2 μm or more. By satisfying the conditions that the vibration frequency is 3 Hz or more, preferably 4 Hz or more and 20 Hz or less, and the amplitude is 1 μm or more, preferably 2 μm or more, the effect of suppressing surface distortion is further increased.

  By lowering the die 3 to the bottom dead center while vibrating the die 3 as described above, it is possible to manufacture an automobile outer panel having a concave portion while suppressing surface distortion.

  According to the press molding method according to the present embodiment, for example, it is possible to stably suppress surface distortion that becomes a problem in an automobile outer panel having concave portions such as a door, a back door, a side panel, a front fender, and a hood. It becomes possible. Moreover, since the press molding apparatus 1 like this embodiment does not need to make a complicated mold structure in performing said press molding, it can suppress the cost accompanying introduction of a press molding apparatus. In particular, in the press molding apparatus 1 of the present embodiment, since the above press molding can be performed only by incorporating the vibration device 6 into the die 3, the apparatus structure does not become complicated.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to this example. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

  In the above-described embodiment, the concave embossed portion, which is an example of the concave-shaped portion, is a molding target. For example, when molding a portion between adjacent character lines, the mold is vibrated as in the above-described embodiment. By performing press molding, surface distortion can be suppressed.

  A molding test simulating a car door outer was carried out. The concave part formed in the molding test is a concave embossed part. A 2000 kN servo press was used as the press molding apparatus. In the press molding apparatus of the present embodiment, the lower die punch is fixed, and the upper die is movable. The blank is a 340 MPa class bake hardened steel plate (BH steel plate) having a square thickness of 0.70 mm and 600 mm square.

FIG. 3 is a plan view of the punch 20 in this embodiment, and FIG. 4 is a cross-sectional view taken along the line AA in FIG. The surface 20a facing the die of the punch 20 has a curved shape with a radius of curvature of 1200 mm in the cross section shown in FIG. 4, and a concave portion 21a is formed on the top 21 of the punch 20 as shown in FIG. Although not shown, the surface 20a facing the die of the punch 20 in a cross section orthogonal to the AA cross section is not curved but linear.

  In this molding test, a blank was held with a die and a blank holder, 50 tons of wrinkle pressing pressure was applied, and then the die was lowered to form a panel having a recessed portion having a depth of 5 mm. Further, the molding test is performed under the condition 1 where the die is not vibrated during press molding and the condition 2 where the die is vibrated during press molding.

  And the surface of the panel after shaping | molding was grind | polished with the oil grindstone, and the surface distortion which generate | occur | produced in the panel was evaluated quantitatively. The quantitative evaluation of the surface strain was performed based on the amount of change in curvature around the concave shape portion. The amount of change in curvature is 3 with a gauge length of 50 mm when the longitudinal direction of the concave portion, that is, the longitudinal direction L of the concave portion 21a of the punch 20 shown in FIG. Using a point gauge, the strain in a direction parallel to the longitudinal direction of the concave portion at a position 15 mm below the concave portion was measured, and the calculation was made based on the measurement result. The molding test results under the above conditions 1 and 2 are shown in Table 1 below.

Table 1 shows a comparison of average values of the amount of change (δ) in curvature (1 / ρ) (maximum value of curvature−minimum value of curvature) under various conditions. The amount of change in curvature correlates with the uneven state of the panel surface, and the smaller the amount of change in curvature, the smaller the surface distortion.

  As shown in Table 1, the change in curvature is smaller in condition 2 in which the die is vibrated during press molding than in condition 1 in which the die is not vibrated during press molding, resulting in a panel with good surface quality. I was able to get it. That is, it is possible to suppress surface distortion generated around the concave portion by vibrating the die during press molding.

  INDUSTRIAL APPLICABILITY The present invention can be used for manufacturing an automobile outer panel having a concave portion.

DESCRIPTION OF SYMBOLS 1 Press molding apparatus 2 Punch 3 Dies 3a Dice convex part 4 Blank holder 5 Punch top part 5a Punch top part recessed part 6 Vibrating device 10 Control part 20 Punch 20a Surface 21 facing a die Punch top part 21a Punch top part recessed part L Punch recessed part Longitudinal direction

Claims (7)

A method of manufacturing an automobile skin panel having a concave portion,
The concave shape portion is a concave embossed portion or a portion between adjacent character lines,
The method for manufacturing an automobile outer panel, wherein the concave portion is formed while vibrating a die when the concave portion is formed.   2. The method of manufacturing an automobile outer panel according to claim 1, wherein a vibration frequency when the die vibrates is 3 Hz or more.   The method of manufacturing an automobile outer panel according to claim 1 or 2, wherein an amplitude of the die when vibrating is 1 µm or more. An automotive outer panel press forming apparatus having a concave portion,
The concave shape portion is a concave embossed portion or a portion between adjacent character lines,
A press molding apparatus comprising a vibration device for vibrating a die.   The press forming apparatus according to claim 4, wherein the vibration device is incorporated in the die.   6. The press molding apparatus according to claim 4, wherein the vibration device is configured to generate vibration having a vibration frequency of 3 Hz or more. The press molding apparatus according to any one of claims 4 to 6, wherein the vibration device is configured to generate a vibration having an amplitude of 1 µm or more.

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