JP6459941B2 - Lightweight and highly rigid steel food panel parts for automobiles and methods for producing the same - Google Patents

Description

  The present invention relates to an automotive steel hood panel component, and more particularly to an automotive steel hood panel component that is lightweight and has sufficient tensile rigidity, and a method of manufacturing the same.

  In recent years, in the automobile field, in order to reduce the weight of a vehicle, there is an increasing need for reducing the thickness and weight of outer panel parts of an automobile such as a door and a hood. However, thinning of the outer panel parts causes a decrease in the rigidity of the outer panel, and the outer panel easily deforms when a person touches a door or hood, etc. Become.

  When such a phenomenon occurs, the sense of quality of the automobile is greatly impaired. Therefore, it is a major challenge for automobile manufacturers to ensure both the rigidity of the outer panel and the weight reduction.

  In addition, the hood parts are required to have pedestrian protection performance that is impact property when a pedestrian's head collides in a traffic accident and to have dent resistance when the hood is opened and closed by hand.

  From the background as described above, the following studies have been made for the purpose of reducing the weight, tension rigidity, and pedestrian protection performance of hood parts.

  With regard to weight reduction, studies have been made on parts made of conventional steel plates made of synthetic resin. For example, Patent Document 1 discloses an automobile panel in which a synthetic resin outer panel is joined to a steel plate inner panel. According to the technique described in Patent Document 1, since the inner panel is made of steel, it can be made to be a panel having higher rigidity than the case of all made of synthetic resin, which is a cause of sink marks generated on the outer surface of the outer panel. The ribs can be eliminated and the cost can be reduced.

  Further, in Patent Document 2, a honeycomb structure made of a light metal thin plate is stretched on the back surface of a panel body made of a resin material via a resin adhesive layer made of glass fiber as a base material, and the honeycomb structure A vehicle body panel structure is disclosed in which the surface is covered with a resin adhesive layer similar to that described above. According to the technique described in Patent Document 2, thermal strain is generated on the surface of the panel body, unlike a structure reinforced with ribs, by stretching a honeycomb structure made of a light metal thin plate on the back surface of the panel body made of a resin material. In addition to being able to remarkably increase the surface rigidity of the panel main body without being accompanied, since the resin adhesive layer is based on glass fiber, the resin adhesive layer itself has a reinforcing function, It is said that the surface rigidity can be further increased.

  Various techniques for improving the tension rigidity of an outer panel made of a steel plate have also been studied. For example, in Patent Document 3, the adhesive used in the method of imparting rigidity to the outer plate by heating and bonding the outer plate (outer panel) and the inner plate (reinforcing inner panel) is used as an expansion ratio of 1.03. A technique for obtaining high tensile rigidity without suppressing shrinkage during heating and curing by generating a thermosetting resinous foam of ˜1.30 times and without causing distortion in the outer plate is disclosed. .

  Further, Patent Document 4 discloses a first thermosetting resin composition layer containing a fine-part thermally expandable foaming agent in which a low-boiling hydrocarbon is embedded in a hollow body of a thermoplastic resin, and a first adhesive layer having adhesiveness. An adhesive sheet for reinforcing a thin plate in which two thermosetting resin composition layers are laminated is disclosed. According to the technique described in Patent Document 4, it is said that the foaming magnification can be controlled very easily, and a light-weight reinforcing adhesive sheet having an excellent reinforcing effect can be obtained.

  Patent Document 5 discloses a thermosetting resin sheet having adhesiveness on the back side of a coated steel sheet after press-molding a coated steel sheet formed by coating one or more organic coatings on at least both surfaces as an outer plate into a predetermined shape. A method of manufacturing an automotive panel is disclosed in which a top coat is applied to the front side of the sheet after the resin is applied, and a resin sheet is foamed and cured at the time of baking to provide sound absorption and panel reinforcement at the same time. According to the technique described in Patent Document 5, it is said that excellent corrosion resistance (corrosion of the foam sound absorbing panel mounting boundary) and excellent weight reduction (about 40%) can be achieved.

  Furthermore, for pedestrian protection performance, for example, in Patent Documents 6 and 7, in a bonnet having an outer panel and an inner panel, a plurality of substantially frustoconical dimples recessed toward the back surface of the outer panel are formed on the inner panel. A structure and a technique for absorbing an impact are disclosed. Patent Document 8 discloses a first inner material in which the inner panel is joined to the peripheral portion of the outer panel, and a second inner material that is disposed closer to the panel center than the first inner material and is joined to the first inner material and the outer panel. An automobile hood that is made of a material and has a structure in which a space portion is formed between the outer panel and the pedestrian protection performance is disclosed.

Japanese Patent Laid-Open No. 61-271174 JP-A-62-85767 Japanese Unexamined Patent Publication No. 63-258274 Japanese Patent Laid-Open No. 7-82535 JP-A-9-104365 JP 2006-103686 A JP 2006-131228 A JP 2007-245853 A

  However, although the technique described in Patent Document 1 achieves weight reduction and securing of rigidity, since an outer panel made of a synthetic resin is used, the cost is significantly increased compared to an outer panel made of a steel plate. In addition, the technique described in Patent Document 2 is a method that employs an outer panel and an inner panel made of resin, which increases the cost and is expected to reduce the weight when a honeycomb structure made of a lightweight metal thin plate is applied. However, there are concerns that it is difficult to match the upper surface of the structure to the shape of the outer panel, and that the bonding between the outer panel and the end face of the honeycomb structure becomes point contact, and the bonding strength cannot be secured sufficiently. In addition, it is considered difficult to achieve in consideration of mass production.

  With regard to the foamed adhesive applied between the outer panel and the inner panel described in Patent Document 3, the required level of weight reduction will increase in the future, and there is always a risk of surface damage when the outer panel is further thinned. Is expected.

  The adhesive sheet affixing to the outer panel in Patent Document 4 and Patent Document 5 is expected to improve the tension rigidity, but generally when the adhesive sheet is subjected to large deformations (load load) such as pedestrian protection performance, the adhesive sheet is generally cured. Considering that the later deformability is low, it is considered that the adhesive sheet is broken and a sufficient effect cannot be obtained.

  As for the method of disposing a frustoconical dimple on the inner panel in Patent Documents 6 and 7, and the method of making two inner panels in Patent Document 8, both use the inner panel and the head after the collision. In order to secure the pedestrian protection performance by controlling the acceleration change of the part, an inner panel is required. Therefore, it is disadvantageous in terms of component weight.

  An object of the present invention is to solve the above-described problems, to provide a steel hood panel component for automobiles that is light in weight and excellent in tensile rigidity, using a thin steel plate that is cost-effective, and a method for manufacturing the same. .

In order to solve the above-mentioned problems, the present inventor has intensively studied the structure of a steel hood panel for automobiles.
(1) A steel hood panel component for automobiles having parallel-line or lattice-shaped steel ribs on the back surface of the steel plate outer panel.
(2) The height H of the steel rib is 2 to 3 mm, the width W is 2 to 15 mm, and the pitch D of the steel ribs in the parallel line shape or the lattice shape is 30 to 60 mm. The steel hood panel part for automobiles as described in (1).
(3) A method for manufacturing a steel hood panel component for automobiles according to (1) or (2), wherein the outer panel made of steel plate and the steel rib are respectively pressed into a hood panel or stamped after press forming. Then, the steel plate outer panel and the steel rib are bonded to each other.

According to the present invention, it is possible to achieve a significant weight reduction as compared with conventional steel hood panel components and to maintain tension rigidity. Therefore, it greatly contributes to reducing the weight of the automobile and reducing the exhaust gas (CO ₂ ).

It is a figure which shows typically the structure of the steel food panel components for motor vehicles of this invention. It is a figure which shows typically the structure of the steel hood panel components for motor vehicles which have the outer periphery reinforcement frame of this invention. It is a figure which shows the steel hood panel components which have the inner panel which analyzed tension rigidity as a comparative example. It is a figure which shows typically the dimension and arrangement | positioning of a parallel-line-shaped steel rib. It is a figure which shows typically the dimension and arrangement | positioning of a grid | lattice-like steel rib. It is a true stress-true plastic strain diagram of a steel plate used for an outer panel. It is a figure which shows typically the load position in the outer surface of the food panel component used for tension rigidity analysis, and the shape of a rigid body indenter. It is the figure which compared the load-displacement curve of the food panel component of this invention which has a parallel-line-shaped steel rib on the back surface of an outer panel, and the conventional food panel component. It is the figure which compared the load-displacement curve of the food panel component of this invention which has a grid | lattice-like steel rib on the back surface of an outer panel, and the conventional food panel component.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram schematically showing the configuration of an automotive steel hood panel component according to the present invention. The steel hood panel part for automobiles of the present invention is formed in a parallel line shape with a slit-processed steel plate on the back surface of a steel plate outer panel 1 press-molded into a hood panel shape, and is produced by press molding and punching into a hood panel shape. After the parallel line rib member 2 or the steel plate processed into a lattice shape and the lattice rib member 3 produced by press forming and punching into a hood panel shape are bonded together, the outer peripheral edge of the steel plate outer panel 1 is It has a configuration in which the strength of the outer peripheral edge is reinforced by hem processing (bending processing) on the back surface side.
The steel plate outer panel 1 is manufactured by press-forming a thin steel plate in the same manner as the conventional method, and the parallel line rib member 2 and the lattice rib member 3 are each slitted or stamped. After being made of a steel plate, it is press-molded. Moreover, it is desirable that the thickness of the parallel-line-shaped rib member 2 and the lattice-shaped rib member 3, that is, the height H of the steel rib is 2 to 3 mm. When the height H of the steel rib is less than 2 mm, it is difficult to secure the tension rigidity. When the height H exceeds 3 mm, not only the weight of the hood panel member is increased, but also the tension rigidity is excessively improved. Further, the width W of the steel rib is preferably 2 to 15 mm. If the width W of the steel rib exceeds 15 mm, the weight of the hood panel member becomes heavy, and if it is less than 2 mm, a sufficient tension rigidity improvement effect cannot be obtained. Moreover, it is preferable that the pitch D of the said steel rib of the said parallel line shape or the said grid | lattice form is 30-60 mm. If the pitch D of the steel ribs is less than 30 mm, not only the weight of the hood panel member is increased, but also the tension rigidity is excessively increased, and if it exceeds 60 mm, a sufficient tension rigidity improvement effect cannot be obtained. It is also possible to produce the parallel linear rib member 2 and the lattice-shaped rib member 3 by applying casting, lath metal, honeycomb, or steel wire.

  The adhesive used when the back surface of the steel plate outer panel 1 and the parallel-line-shaped rib member 2 or the lattice-shaped rib member 3 are bonded together is conventionally used mastic adhesive, resin sheet, metal. Although it does not specifically limit an adhesive agent etc., in order to prevent the surface shrinkage of the said steel plate outer panel 1, a thing with small shrinkage | contraction by thermosetting as much as possible is desirable. Further, in order to maximize the effect of the steel ribs, the back surface of the steel plate outer panel 1 and the entire mating surface of the parallel line rib members 2 or the lattice rib members 3 are bonded with an adhesive. It is preferable to adhere.

  If the hood panel parts are not sufficiently rigid or torsionally rigid, a reinforcing frame 4 having a shape along the contour of the steel plate outer panel 1 is added as shown in FIG. It doesn't matter. The reinforcing frame 4 is made of a steel material that is molded into a hat cross-sectional shape or a rectangular closed cross-sectional shape. However, since the displacement of the outer edge of the hood panel is restrained by the vehicle body when the hood panel component is attached to the vehicle body, the reinforcing frame 4 basically does not contribute to the tension rigidity of the hood panel.

  A steel hood panel of a commercially available SUV vehicle (sports multipurpose vehicle) is used as a model case, and a steel having a steel inner panel as shown in FIG. 3 is used by using an FEM model that is freely disclosed on the National Crash Analysis Center website. A conventional hood panel, a steel hood panel having only an outer panel without an inner panel, a comparative example, and a back surface of a steel outer panel as shown in FIG. As an example of the present invention, a steel hood panel having a steel rib was used to verify the effect of the present invention by FEM analysis of tension stiffness. In the analysis model, the thickness of the outer panel in the conventional steel hood panel is 0.70 mm, the thickness of the inner panel is 0.60 mm, and the thickness of the outer panel in the comparative example and the example of the present invention is also 0.70 mm. did. In addition, the SUV car hood panel was used as a model case because the SUV car hood is larger in size than other car models, and the hood panel has a smaller (flat) shape and has a higher rigidity. This is because the hood panel is likely to be lowered, and a significant difference in tension rigidity due to the structure of the hood panel appears significantly. 4 or 5, the steel rib width W is 2 mm, the height H is 2 mm or 3 mm, and the steel rib pitch D is 30 mm or 60 mm. The outer panel of the present invention was taken as an example of the present invention.

  FEM analysis of tension stiffness was performed using LS-DYNA ver. As shown in FIG. 7, a 45 mmφ × 40 mmH rigid body indenter is attached to the center of the outer panel (boundary condition of using 9.71, mesh size of 15 mm, and restraining translational movement about the entire circumference of the outer panel. This was done by obtaining a load-displacement curve when the load was applied to the part with the smallest curvature. At this time, the true stress-true plastic strain curve shown in FIG. 6 was used for the FEM analysis as the tensile characteristics of the outer panel. The true stress-true plastic strain curve shown in FIG. 6 is obtained by applying a tensile strain of 2% to a 340 MPa class BH steel plate (YP: 244 MPa, TS: 350 MPa, El: 42%) used as an outer panel material, and then painting. This is a true stress-true plastic strain curve obtained by a tensile test after baking heat treatment (170 ° C. × 20 minutes). The outer layer is subjected to press molding strain and heat treatment during paint baking during manufacturing. Represents the tensile properties of the panel material.

  The load-displacement curve of each hood panel model obtained by FEM analysis of the tension stiffness is shown in FIGS. FIG. 8 is a diagram comparing the present invention example having parallel linear steel ribs, a conventional example, and a comparative example, and FIG. 9 is a diagram comparing the present invention example having grid-like steel ribs, the conventional example, and the comparative example. FIG. In addition, in the example of this invention of each figure, the weight reduction rate (total weight reduction rate) S at the time of comparing with the prior art example which has an inner panel was shown. As apparent from FIGS. 8 and 9, it was confirmed that the present invention can achieve a significant weight reduction and improve the tension rigidity compared to the conventional steel hood panel parts.

DESCRIPTION OF SYMBOLS 1 Outer panel 2 Parallel wire rib member 3 Grid rib member 4 Reinforcement frame 5 Inner panel 6 Parallel wire steel rib 7 Grid steel rib

Claims (5)

It consists of a steel plate outer panel and a parallel line or grid steel rib bonded to the back surface of the steel plate outer panel, and the thickness of the parallel line or grid steel rib member is steel. automobile steel hood panel part, wherein the height H der Rukoto ribs.   The height H of the steel rib is 2 to 3 mm, the width W is 2 to 15 mm, and the pitch D of the steel ribs in the parallel line shape or the lattice shape is 30 to 60 mm. Item 2. A steel hood panel part for automobiles according to Item 1. 3. The steel for automobile according to claim 1, wherein the parallel-line or lattice-shaped steel ribs are bonded together with an adhesive on the entire mating surface with the back surface of the steel plate outer panel. Food panel parts. The steel steel hood panel component according to any one of claims 1 to 3, wherein a reinforcing frame having a shape along the contour of the steel plate outer panel is added. It is a manufacturing method of the steel steel hood panel components in any one of Claims 1-4, Comprising: After punching after the said steel plate outer panel and the said steel rib are press-molded or press-molded in the shape of a hood panel, respectively. A method for manufacturing a steel hood panel component for automobiles, comprising bonding the steel plate outer panel and the steel rib.

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