JP4308088B2 - Automotive panel structure with excellent impact energy absorption - Google Patents

Description

  The present invention relates to an automobile panel structure that is installed on the side surface of a vehicle body and has excellent impact energy absorption.

  As is well known, in recent years, many structural materials that make up automobile bodies are required to have collision energy absorption with respect to vehicle body collisions, as well as rigidity and strength, which are basic characteristics. ing.

  Of these automobile body structural materials, relatively large panel structures (hollow structural members) such as doors, pillars such as center pillars, roof side rails, side sills, etc. An outer panel and an inner panel obtained by press-molding a plate of aluminum, aluminum alloy, or resin are joined to each other to form a hollow structure or a bag structure. Figure 9 schematically shows a front view of the automobile door. In FIG. 9, a door 1 is constituted by a panel structure having a hollow structure or a bag structure in which a press-molded outer panel 2 and a press-molded inner panel 3 are joined to each other.

  In recent years, with respect to global environmental problems caused by exhaust gas and the like, improvement in fuel efficiency has been pursued by reducing the weight of the body of a transport aircraft such as an automobile. With the trend toward reducing the weight of automobiles, the thickness of these molded panels has been reduced both for the outer panel and the inner panel. Along with this, steel plates and aluminum alloy plates used for molded panels have been strengthened. However, the reduction in the thickness of the molded panel is inevitably accompanied by a decrease in strength and rigidity as a panel structure and a decrease in impact energy absorption. For this reason, there is a big limit to weight reduction by increasing strength and reducing wall thickness.

  For this reason, the relatively large panel structure installed on the side surface of the vehicle body is required to have a function of protecting passengers in the passenger compartment even when the weight is reduced and the thickness is reduced. That is, there is a demand for a vehicle body structure in which this hollow structural member does not bend very much even when it receives a load due to a collision (side collision) and reduces the amount of bending or deformation toward the vehicle interior side.

  Conventionally, it has been typical to reinforce by installing a reinforcing member or the like in the hollow structure (inside) of a relatively large steel panel structure installed on the side surface of the vehicle body. .

  As an example, a reinforcing aluminum alloy having a curved shape in which a part of a hollow shape protrudes toward a side collision direction inside a steel panel structure such as a center pillar, a door, and a side sill constituted by a molded panel. It has been proposed to extend the hollow profile separately (see Patent Document 1).

  In addition, a technique has been proposed in which a load transmission portion is separately provided inside the panel structure of the steel center pillar to absorb the load at the time of collision (see Patent Document 2).

Furthermore, in order to prevent buckling deformation at the time of a side collision of a vehicle, a technique has been proposed in which a reinforcement made of steel or aluminum alloy is provided in a steel center pillar (see Patent Document 3).
Japanese Patent Laid-Open No. 2004-51065 (Claims, FIG. 1, pages 1 to 2) Japanese Patent Laid-Open No. 2003-2234 (Claims, FIG. 1, pages 1 to 2) Japanese Patent Laid-Open No. 2003-276639 (Claims, FIG. 1, pages 1 to 2)

  However, in order to suppress buckling deformation, a means for providing a reinforcing member or the like inside the panel structure has a problem that the weight increases due to these members and the shape of the center pillar itself is affected. Moreover, the shape of the load transmission part and reinforcement provided in a center pillar also has a limit on the design of a vehicle.

  Moreover, the demand level of buckling deformation suppression at the time of a collision is higher due to the enhancement of passenger protection. On the other hand, the means of providing a reinforcing member or the like inside these panel structures is actually limited in suppressing buckling deformation.

  By the way, if the thickness of the outer panel and inner panel in the automobile panel structure is increased, buckling deformation can be suppressed, but the panel structure cannot be reduced in weight, such as weight reduction, strength, rigidity, and impact energy absorption. It is impossible to achieve both characteristics.

  Accordingly, an object of the present invention is to provide an automobile panel structure in which the weight reduction of the automobile panel structure and characteristics such as strength, rigidity, and energy absorption are compatible.

  In order to achieve this object, the gist of an automobile panel structure excellent in collision energy absorption according to the present invention has a hollow structure composed of an outer panel and an inner panel joined to each other, and is provided on the side of the vehicle body. An aluminum panel having a thickness of 2 mm or less and an inner panel made of a high-tensile steel sheet with a thickness of 2 mm or less with an outer panel having a tensile strength of 900 MPa or more and an inner panel having a 0.2% proof stress of 250 MPa or more. It consists of a board.

  When a collision load is applied from the outer panel side, the automobile panel structure installed on the side surface of the vehicle body is subjected to compressive stress on the outer panel side and tensile stress on the inner panel side. On the other hand, in the present invention, as described in the above gist, the outer panel is made of a high-strength steel plate, and the inner panel is made of an aluminum alloy plate having a high strength but a low strength compared to the high-strength steel plate. It has a structure.

  For this reason, for example, when a collision load is applied from the outer panel side such as a side collision of an automobile, even if a compressive stress is applied to the outer panel side, the buckling strength of the high-tensile steel plate is high and the outer panel does not easily buckle. . On the other hand, the inner panel side made of an aluminum alloy plate has a lower strength than a high-tensile steel plate, but becomes a member that bears a tensile force. For this reason, load reduction due to buckling does not occur, and deformation occurs until the applied tensile force reaches the tensile strength of the aluminum alloy plate and breaks to absorb collision energy. That is, the inner panel aluminum alloy plate bearing the tensile force can absorb the collision energy as long as the tensile strength against the tensile force and the plate thickness are sufficient.

  Thus, when the outer panel is not easily buckled when a collision load is applied from the outer panel side, if an aluminum alloy plate that tends to deform relatively easily is used for the inner panel, the amount of collision energy absorption can be increased. can do. As a result, even when a relatively large panel structure installed on the side of the vehicle body, such as a center pillar, receives a load due to a collision (side collision), the panel structure is bent and deformed toward the vehicle interior side. Can be reduced.

  On the other hand, when the outer panel and the inner panel are both made of a high-strength steel plate as in the prior art, it is possible to obtain the same collision energy absorption as the combination of the high-strength steel plate and the aluminum alloy plate. However, the mass reduction effect (weight reduction effect) is lower than when the aluminum alloy plate is used. On the other hand, in order to reduce the weight to a mass equal to or less than the combination of the high-strength steel plate and the aluminum alloy plate, the high-tensile steel plate must be thinned. In this case, as described above, the collision energy absorption ability is reduced as compared with the combination of the high-tensile steel plate and the aluminum alloy plate.

  This phenomenon is the same when the outer panel is made of an aluminum alloy plate and the inner panel is made of a high-tensile steel plate. In this case, when an impact load is applied, the aluminum alloy outer panel buckles very easily (early), and the load drops at a stretch, taking advantage of the high tensile strength of the high strength steel inner panel. Absent. As a result, the amount of collision energy absorbed by the aluminum alloy outer panel is significantly reduced, the amount of bending of the high-strength steel inner panel (the amount of bending of the panel structure) is increased, and the amount of deformation toward the vehicle interior is increased.

  In addition, when both the outer panel and the inner panel are made of an aluminum alloy plate, a sufficient impact energy absorbing ability and a deformation suppression effect can be obtained by selecting a material and a plate thickness. However, an aluminum alloy plate is inferior in formability compared to a steel plate. For this reason, it is difficult to form an outer panel having a particularly complicated shape, and in some cases, it may not be possible to form the outer panel, and there is a difficulty in that the forming cost is higher than when a high-tensile steel plate is used.

  Therefore, according to the automobile panel structure of the present invention, it is possible to achieve both the weight reduction of the panel structure and the characteristics such as strength, rigidity, and collision energy absorption.

  Embodiments of the present invention will be specifically described below with reference to the drawings. 1 and 2 are each a cross-sectional view in a direction perpendicular to the axis of an automobile panel structure simulating a center pillar and the like, each showing an example of the invention (the automobile panel structure 1a stands in the front direction toward the figure). Iii). FIG. 1 shows the state of the automobile panel structure before the collision load is applied, and FIG. 2 shows the state of the automobile panel structure after the collision load is applied.

  FIGS. 3 and 4 each show a comparative example, and are longitudinal sectional views in a direction parallel to the axis of an automobile panel structure simulating a center pillar and the like (the automobile panel structures 1b and 1c are in the vertical direction of the figure) Standing up). 3 and 4 show the state of the automobile panel structure after the impact load is applied. FIG. 3 shows a state in which the automobile panel structure is bent. FIG. 4 shows a state in which the automobile panel structure is buckled. Show.

(Configuration of automobile panel structure)
First, the configuration of the automobile panel structure 1a in the invention example of FIG. 1 will be described. The configuration itself of the automobile panel structure 1a in the invention example is basically the same as that of the conventional panel structure as a premise. That is, it is basically composed of an outer panel 2 arranged outside the vehicle compartment and an inner panel 3 arranged inside the vehicle compartment.

  The outer panel 2 and the inner panel 3 are press-molded in advance into arbitrary shapes such as a HAT (cap) shape. Thus, the outer panel 2 has a flat top portion 2a, a wall portion 2b surrounding the top portion 2a, and a flat flange 2c extending outward from the outer panel 2 and surrounding the wall portion 2b. The inner panel 3 also has a flat top portion 3a, a wall portion 3b surrounding the top portion 3a, and a flat flange 3c extending outward from the inner panel 3 and surrounding the wall portion 3b.

  The outer panel 2 and the inner panel 3 are joined to each other by the flanges 2c and 3c, and are configured as a hollow structure or a bag structure having a hollow portion 4 or a closed cross-sectional structure.

  Reference numeral 5 denotes a joining means or joint of such an automobile panel structure 1a. That is, the flange 2c of the outer panel 2 and the flange 3c of the inner panel 3 are integrally joined by the joining means or the joining portion 5 over the outer periphery of the panel structure 1a. As the joining means 5 in this case, well-known mechanical joining means such as bolts and nuts, well-known welding means such as spot welding, and further, caulking means for the flange 3c tip by bending the flange 2c tip are suitably used. Or they are selected in combination.

  Examples of the automobile panel structure 1a having such a configuration include relatively large panel structures installed on the side of the automobile body, such as pillars other than the center pillar, roof side rails, doors, and side sills.

  The hybrid structure, in which the outer panel is made of a high-strength steel plate and the inner panel is made of an aluminum alloy plate having relatively large special irregularities on the surface, has already been adopted in automobile hoods and the like. However, this hybrid structure in the hood of an automobile is for weight reduction and pedestrian head protection at the time of a pedestrian collision. That is, in order to protect passengers in the vehicle interior as in the present invention, the panel structure is prevented from buckling and bending when a large collision load is applied, such as a collision between vehicles or a vehicle collision with an objective. There is no purpose.

  In addition, the hybrid structure of the present invention does not have a relatively large special unevenness on the surface like the aluminum alloy inner panel of the hood, and the walking is performed under a relatively small collision load such as a pedestrian collision. There is no head protection effect for the person.

  In the case of a car hood, whether it is a side collision or a frontal collision, the collision load is basically applied in a substantially horizontal direction from the end of the hood to the substantially horizontally disposed hood. That is, a compressive load in a substantially horizontal direction is simultaneously applied to both the outer panel and the inner panel. Accordingly, the compressive stress is applied to the outer panel side and the tensile stress is not applied to the inner panel side as in the case of the collision of the automobile panel structure installed on the side surface of the vehicle body of the present invention. For this reason, the hybrid structure of the present invention has a different object from buckling and bending prevention of the hood when a large collision load is applied to the hood of the automobile, such as a collision between vehicles or a vehicle body collision with an objective. .

  Given the configuration of the automobile panel structure 1a as described above, the features of the present invention will be described below. The feature of the present invention is that the outer panel is made of a high-tensile steel plate having a tensile strength of 900 MPa or more and a thickness of 2 mm or less, and the inner panel is made of an aluminum alloy plate having a 0.2% proof stress of 250 MPa or more and a thickness of 2 mm or less. is there.

(Panel thickness)
In the automobile panel structure of the present invention, as a premise, both the outer panel and the inner panel have a thickness of 2 mm or less for the purpose of reducing the weight of the automobile panel structure. When these plate thicknesses exceed 2 mm, buckling deformation of the automobile panel structure can be suppressed, but as described above, the panel structure cannot be reduced in weight, and it is reduced in weight and strength, rigidity, and impact energy absorption. It is not possible to achieve characteristics such as sex.

(Hybrid structure)
The automobile panel structure of the present invention also has a hybrid structure in which the outer panel is made of a high-strength steel plate, and the inner panel is made of an aluminum alloy plate that has a high strength but has a lower strength than a high-strength steel plate. Yes.

  The effect of this hybrid structure will be described with reference to FIG. Fig. 3 shows a collision load (indicated by the arrow pointing to the right in the figure) applied to the center of the outer panel 2 such as a side collision with the center of the center pillar, and the automobile panel structure 1b is linearly shown by the original dotted line. The figure shows a state in which the entirety is bent and deformed (curved deformation) in the vehicle interior direction from the arrangement state.

  Here, the smaller the deformation allowance (displacement amount) d from the original state due to the bending of the automobile panel structure 1b, the higher the protection for passengers in the vehicle.

  In addition, when a collision load as shown in FIG. 3 is applied, compressive stress indicated by an arrow facing in the figure is applied to the outer panel 2 side, while the inner panel 3 side is indicated by an arrow separating from the figure. The indicated tensile stress is applied.

  On the other hand, in the hybrid structure, as shown in FIG. 2, when a collision load (indicated by a right-pointing arrow in the figure) is applied from the outer panel 2 side such as a side collision with the center pillar, the hybrid structure is compressed to the outer panel 2 side. Even when stress is applied, the buckling strength of the high-tensile steel plate is high, and the outer panel does not easily buckle. More specifically, the flat top 2a, wall 2b, and flange 2c of the outer panel 2 are not buckled, and only the bending deformation (curvature deformation) of the entire outer panel 2 as shown in FIG. Arise.

  On the other hand, the inner panel side made of an aluminum alloy plate has a lower strength than a high-tensile steel plate. As a result, when a tensile stress due to a collision is applied to the inner panel side, the inner panel is deformed relatively easily and absorbs the collision energy. More specifically, in particular, the inner panel wall 3b parallel to the collision load direction is deformed into a bellows shape as shown in FIG. Although the collision energy absorption by the inner panel is also caused by deformation of other parts, the collision energy absorption by the inner panel largely depends on the bellows-like deformation of the inner panel wall 3b.

(Panel strength)
However, in order to exert the effect of such a hybrid structure, the outer panel is made of a high-tensile steel plate having a tensile strength of 900 MPa or more, and the inner panel It is necessary to be made of an aluminum alloy plate having a 0.2% proof stress of 250 MPa or more.

  When the tensile strength of the high-tensile steel plate of the outer panel is less than 900 MPa, the strength of the outer panel is too low, which is not much different from the case where the outer panel and the inner panel are made of an aluminum alloy plate. That is, when a collision load is applied from the outer panel side, both the outer panel and the inner panel have a low buckling strength and are easily buckled. As a result, according to the collision load, the panel structure is buckled, damaged or destroyed, and is more likely to be scattered into the passenger compartment.

  This will be further described with reference to FIG. In FIG. 4, as in FIG. 3, a collision load is applied from the outer panel 2 side, such as a side collision with the center pillar, and the automobile panel structure 1b moves from the linear arrangement shown by the original dotted line toward the vehicle interior. It shows a bent (curved) state. However, FIG. 4 shows a state in which buckling (crushed cross section) has occurred in the central portion of the automobile panel structure 1b in addition to bending. When the tensile strength of the high strength steel plate of the outer panel is less than 900 MPa, such a panel structure is buckled, and the panel structure is damaged or broken from the buckled portion (central portion) to the vehicle interior side. The possibility of scattering increases.

  When both the outer panel and the inner panel are made of an aluminum alloy plate, the possibility of the phenomenon shown in FIG. 4 increases.

  On the other hand, if the 0.2% proof stress of the aluminum alloy plate of the inner panel is less than 250 MPa, even if the outer panel does not buckle easily when a collision load is applied from the outer panel side, the inner panel easily buckles and absorbs collision energy. The amount cannot be increased. That is, even when a collision load from the outer panel side to the inner panel is relatively gradually applied including a delay in the transmission time, the inner panel easily buckles and the amount of collision energy absorption cannot be increased. As a result, the deformation allowance (displacement amount) d from the original state due to the bending of the automobile panel structure 1b shown in FIG. 3 becomes large.

  In the case where both the outer panel and the inner panel are made of high-strength steel plates as in the past, or when the outer panel is made of an aluminum alloy plate and the inner panel is made of a high-strength steel plate, the phenomenon shown in FIG. 3 can also occur. Increases nature.

  Therefore, as described above, according to the automobile panel structure of the present invention, it is possible to achieve both the weight reduction of the panel structure and the characteristics such as strength, rigidity, and collision energy absorption.

  In addition, in the automobile panel structure of the present invention, in order to further improve characteristics such as strength, rigidity and energy absorption at the time of collision within a range that does not hinder weight reduction, the inside of the hollow structure of the panel structure is provided as necessary. It is permissible to provide reinforcement members, load transmission parts, reinforcements, etc. (to be used in combination).

(High tensile steel plate)
The high-strength steel sheet for the outer panel used in the present invention has a tensile strength of 900 MPa or more after the tempering treatment, and a normal high-tensile cold-rolled steel sheet can be applied if the thickness is 2 mm or less. However, the present invention preferably has a composition and a structure excellent in press formability (extrusion formability), bending formability, corrosion resistance, and the like among high-tensile cold-rolled steel sheets on the premise of press forming on an outer panel.

(Aluminum alloy plate)
If the aluminum alloy plate for an inner panel used in the present invention has a 0.2% proof stress of 250 MPa or more and a thickness of 2 mm or less after the tempering treatment, a normal aluminum alloy cold-rolled plate can be applied. However, as in the case of the steel plate, on the premise of press forming on the inner panel, among aluminum alloy plates, those having a composition and structure excellent in press formability (drawing formability) and the like are preferable. In this respect, aluminum alloys such as 3000 series, 5000 series, and 6000 series specified in AA or JIS standards or similar to the specifications are preferably used.

  Among these, 6000 series aluminum alloy sheets ensure formability by reducing the yield strength during press forming on panels, and during relatively low-temperature artificial aging (hardening) processing, such as paint baking processing of panels after press forming. It is age-hardened by heating to improve the yield strength and has the BH property that can secure the required strength. In addition, since the amount of alloying elements is small, there are advantages such as excellent recyclability of the waste material to the original 6000 series Al alloy.

Examples of the present invention will be described below.
When the door shape is modeled as shown in Fig. 1 and the conditions of the outer panel 2 and the inner panel 3 are changed for various materials and strengths as shown in Table 1, load (kN)-displacement (mm ) Relationship, energy absorption (J) -displacement (mm) relationship, respectively, were obtained by FEM analysis. These results are shown in FIGS.

  5 is an explanatory diagram showing the load-displacement relationship from Invention Example A to Comparative Example F in Table 1. FIG. 6 is an explanatory diagram showing the load-displacement relationship from Comparative Example G to Comparative Example J in Table 1. FIG. Is an explanatory diagram showing the energy absorption amount-displacement relationship from Invention Example A to Comparative Example F in Table 1. FIG. 8 is an explanatory diagram showing the energy absorption amount-displacement relationship from Comparative Example G to Comparative Example J in Table 1. It is.

  In Table 1, “HITEN” is a high-tensile steel plate, and the described strength is tensile strength (MPa). Aluminum is a 6000 series (Al-Si-Mg series) aluminum alloy sheet, and the stated strength is 0.2% proof stress (MPa).

  As FEM analysis conditions, the analysis was performed using a general-purpose dynamic explicit software LS-DYNA3D using a three-point bending analysis model.

  As is clear from Table 1 and FIGS. 5 and 7, Invention Examples A and B are made of a high-tensile steel plate with an outer panel of 590 MPa or more, a tensile strength of 900 MPa and a thickness of 2 mm or less, and an inner panel of 250 MPa with 180 MPa or more. The aluminum alloy plate has a 0.2% proof stress and a thickness of 2 mm or less. For this reason, Invention Examples A 1 and B have a large energy absorption amount and a small displacement amount as compared with Comparative Examples C 1 to J 3 that do not satisfy these requirements.

  In particular, in the load-displacement relationship of FIG. 5, the amount of displacement is smaller in Invention Example A where the tensile strength of the outer panel is higher than in Invention Example B where the tensile strength is low. In Comparative Example C, the tensile strength of the outer panel is too low, and the displacement amount is larger than that of Invention Example B. Therefore, the critical significance of the tensile strength of the outer panel for reducing the displacement amount can be understood.

  Contrary to the present invention, Comparative Examples D, E, and F in which the outer panel side is made of an aluminum alloy plate buckle very easily (early) when a collision load is applied, and the load decreases at a stretch. The high tensile strength steel inner panel does not take advantage of the high tensile strength. For this reason, the collision energy absorption amount is remarkably reduced, the bending amount of the high-strength steel inner panel is increased, and the displacement amount (the amount of deformation toward the vehicle interior side) is increased.

  In Comparative Examples G, H, I, and J, in which the outer panel and the inner panel are made of high-strength steel plates, the collision energy absorption amount is the same as in the invention examples A and B of the combination of the high-strength steel plates and the aluminum alloy plates. Energy absorption can be obtained. However, in Comparative Examples G 1, H 2, I 1, and J, the high-tensile steel sheet is thinned to reduce the weight to the same mass as Invention Examples A 1 and B. As a result, the amount of displacement is larger than that of Invention Examples A 1 and B 2.

  ADVANTAGE OF THE INVENTION According to this invention, the automotive panel structure which made compatible the characteristics, such as weight reduction of a panel structure, intensity | strength, rigidity, a collision energy absorption property, can be provided. For this reason, it is applied to relatively large panel structures such as doors, pillars such as center pillars, roof side rails, and side sills that are installed on the side of the vehicle body. It contributes to improvement and coexistence.

It is a transverse cross section of the direction orthogonal to the axis of the automobile panel structure concerning the present invention. FIG. 2 is a lateral cross-sectional view in a direction perpendicular to the axis of the panel structure, showing a deformation state at the time of collision of the panel structure of FIG. 1. It is a longitudinal direction sectional view of a direction parallel to an axis of a panel structure showing a load applied and a deformation state at the time of collision of an automobile panel structure. It is a longitudinal direction sectional view of the direction parallel to the axis of a panel structure showing the buckling state at the time of a collision of an automobile panel structure. FIG. 3 is an explanatory diagram showing a load-displacement relationship from Invention Example A to Comparative Example F in Table 1. FIG. 3 is an explanatory diagram showing a load-displacement relationship from Comparative Example G to Comparative Example J in Table 1. FIG. 2 is an explanatory diagram showing an energy absorption amount-displacement relationship from Invention Example A to Comparative Example F in Table 1. FIG. 3 is an explanatory diagram showing an energy absorption amount-displacement relationship from Comparative Example G to Comparative Example J in Table 1. It is a schematic diagram which shows a motor vehicle door.

Explanation of symbols

1: automotive panel structure, 2: outer panel, 2a: flat top, 2b: wall,
2c: flange, 3: inner panel, 3a: flat top, 3b: wall, 3c: flange,
4: Hollow part, 5: Joint part,

Claims (3)

  An automotive panel structure having a hollow structure composed of an outer panel and an inner panel joined to each other and installed on the side surface of the vehicle body. The outer panel has a tensile strength of 590 MPa or more and a thickness of 2 mm or less. An automobile panel structure excellent in impact energy absorption, characterized in that it is made of a tension steel plate and the inner panel is made of an aluminum alloy plate having a 0.2% proof stress of 180 MPa or more and a thickness of 2 mm or less.   The automobile panel structure excellent in impact energy absorption according to claim 1, wherein the application is selected from pillars, roof side rails, doors, and side sills. 3. The automobile panel structure excellent in collision energy absorption according to claim 1, wherein the aluminum alloy plate is a 6000 series aluminum alloy.

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