JP2006027288A - Engine hood structure and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine hood structure and a method for manufacturing the same efficiently absorbing collision energy applied to an engine hood and mitigating an impact on a pedestrian's head when a vehicle collides with the pedestrian without using any complicated and expensive mechanism such as an airbag for protecting the head of the pedestrian and an engine hood flip-up device, and enhancing the degree of freedom of molding by narrowing the space between the engine hood and an object built in the engine room. <P>SOLUTION: The engine hood structure has a porous metal with continuously or stepwise reduced density in a space between a hood outer and a hood inner from the hood outer side to the hood inner side. The engine hood structure has a porous metal continuously or stepwise reduced density on a back side of the hood outer from the hood outer side to the hood inner side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an engine hood structure and a method for manufacturing the same, and more particularly, has excellent shock absorption performance, and efficiently protects a pedestrian's head with a smaller amount of deformation when the pedestrian collides with an automobile. ENGINE HOOD STRUCTURE AND METHOD FOR MANUFACTURING SAME.

  The engine hood of an automobile has a configuration in which a hood inner (inner plate) composed of a plurality of beam elements is combined with a hood outer (outer plate) in order to give tension rigidity, bending rigidity, and torsional rigidity. In recent years, in addition to conventional steel plates, the use of aluminum alloy plates of 5000 series, 6000 series, 7000 series, and the like according to JIS standards has been increasing as hood materials for these automobiles from the viewpoint of weight reduction.

Here, when the vehicle collides with a pedestrian, the pedestrian may be lifted up and the pedestrian's head or shoulder may be hit against the hood outer. Therefore, in addition to the above performance, the engine hood of an automobile is required to ensure head protection performance when colliding with a pedestrian.
As a means for improving the performance of such a pedestrian protection head, a measure of absorbing collision energy by taking a large deformation amount of the engine hood can be considered. Since there is a concern about an increase in head injury value due to a collision with a rigid body (for example, a rigid body such as an engine), it is necessary to increase the distance between the engine hood and the engine room built-in object. However, in recent years, there is a demand from the molding side of automobiles to keep the height of the engine hood as low as possible, and the conventional engine hood structure achieves both improved pedestrian head protection and molding. It is becoming increasingly difficult to do.
As another means for improving the pedestrian's head protection performance, for example, an impact absorbing means made of a synthetic resin material may be disposed between the engine hood and the chassis component in the engine room. It has been proposed (see, for example, Patent Document 1). Furthermore, a hood inner has also been proposed in which a plurality of protrusions are provided, and a shape irregular portion for deforming the protrusion surface locally in response to a load on the protrusion is provided in advance (see, for example, Patent Document 2). Furthermore, a hood inner and a reinforcing panel in which corrugated beads and convex shapes are formed have been proposed (see, for example, Patent Documents 3 to 5). In addition, a technology for detecting a collision between a vehicle and a pedestrian by a sensor disposed in the vehicle and deploying an air bag for protecting the pedestrian on the engine hood, or by raising (lifting) the engine hood Technology to prevent contact between a pedestrian and a built-in engine compartment is being energetically developed to increase the distance between the hood and the built-in engine compartment.
JP 2000-203378 A JP 2003-054449 A JP 2003-205866 A JP 2003-252246 A JP 2003-261070 A

  The present invention has been made in view of the above-described problems of the prior art, and the object of the present invention is to provide a complicated and high-lifting (lifting) device such as a pedestrian head protection airbag and an engine hood. Without using an expensive mechanism, the collision energy acting on the engine hood can be efficiently absorbed when the vehicle collides with the pedestrian, and the impact on the pedestrian's head can be mitigated. An object of the present invention is to provide an engine hood structure and a method for manufacturing the same that can narrow the interval between the built-in objects and improve the degree of freedom in molding.

  As a result of intensive studies to solve the above problems, the present inventor can solve the above problems by disposing a porous metal having a density gradient on the back surface of the hood outer or the gap between the hood outer and the hood inner. As a result, the present invention has been completed.

  According to the present invention, by filling or bonding a porous metal whose density is reduced from the hood outer side to the engine room side, an engine that can achieve both excellent pedestrian head protection performance and suppression of hood deformation. A food structure and a method for manufacturing the same can be provided.

  Hereinafter, the engine hood structure of the present invention will be described in detail. In the present specification, “%” indicates a mass percentage unless otherwise specified.

The first engine hood structure of the present invention includes a hood outer that forms an outer plate, a hood inner that forms an inner plate, and a porous metal. Specifically, a porous metal is disposed in the gap between the hood outer and the hood inner, and the density of the porous metal is decreased continuously or stepwise from the hood outer side toward the hood inner side. The porous metal is filled or bonded to at least a part of the gap between the hood outer and the hood inner.
Thereby, compared with the case where the plate | board thickness of hood outer is enlarged or the case where a bulk material is filled, the raise of the head disorder value by the excessive deceleration of a head is suppressed. Immediately after the pedestrian's head collides with the engine hood, the head can be effectively decelerated due to the rigidity improvement effect as a hood structure and the mass effect in the vicinity of the hood outer. Can do. Further, in the latter half of the collision, energy can be absorbed with a small amount of deformation without increasing the head obstruction value due to the progress of uniform deformation of the porous metal with low reaction force. On the other hand, when the density of the porous metal increases from the hood outer side toward the engine room side, the head speed reduction is small because effective head deceleration cannot be performed at the beginning of the collision, resulting in a hood deformation amount. growing.
The “deceleration of the head” indicates a state in which the speed of the head is reduced after the head collides with the hood.

  In addition, the hood inner is preferably not a concavo-convex shape as in the prior art, but a substantially flat shape formed along the shape of the engine hood. As a result, the porous metal is easily compressed uniformly over a wide area, so that excellent pedestrian head protection performance can be obtained by compressive deformation of the porous metal.

Next, the second engine hood structure of the present invention is composed of a hood outer that forms an outer plate and a porous metal. Specifically, a porous metal is bonded to at least a part of the back surface of the hood outer, and the density of the porous metal is decreased continuously or stepwise from the hood outer side toward the engine room side.
Thus, similarly to the above-described first engine hood structure, energy can be absorbed with a small amount of deformation without increasing the head failure value.

A preferred embodiment common to the first and second engine hood structures will now be described.
As the hood outer and hood inner constituting the engine hood, for example, steel, 5000 series, 6000 series or 7000 series aluminum alloys according to JIS standards, and combinations thereof can be used as appropriate. In this case, rigidity and pedestrian head protection performance are more likely to be improved, which is preferable.
Further, as the porous metal, it is preferable to use one or both of foamed aluminum and an aluminum porous body. In this case, a mechanical property, in other words, a relatively low plateau stress can be easily obtained at a low cost. Here, the “plateau stress” refers to a stress value in a state in which deformation proceeds without increasing the stress value during the compression test. The foamed aluminum can be produced by mixing a foaming agent with aluminum and foaming. The aluminum porous body can be produced by sintering a hollow minute aluminum material.
Furthermore, it is preferable that the foamed aluminum or the aluminum porous body has a density in the vicinity of the hood outer of 0.1 g / cm ³ or more. If it is less than 0.1 g / cm ³ , the head protection performance of the pedestrian due to the rigidity improvement effect and the weight effect near the hood outer may be lowered.

The foamed aluminum and the aluminum porous body preferably have a laminated structure in which the density of each layer decreases from the hood outer side to the engine room side. For example, a layered foamed aluminum or porous aluminum body having two or more different densities may be stacked and bonded in order from the higher density toward the engine room side from the hood outer side.
Furthermore, when the foamed aluminum or aluminum porous body has a laminated structure, it is preferable that the strength of the adhesive used between the layers decreases from the hood outer side toward the engine room side. In this case, the pedestrian protection effect of the engine hood structure can be more effectively brought out. The strength at this time is the hardness after the adhesive is completely cured.
Furthermore, it is preferable that the strength of the adhesive is lower than the strength of foamed aluminum or aluminum porous body bonded to the hood outer side from the adhesive. This is because when the strength of the adhesive on the engine room side is stronger than the strength of foamed aluminum etc., the continuous deformation from the hood outer side of the foamed aluminum is obstructed by the strong adhesive layer, which is an effective effect It is because it becomes difficult to obtain. The strength at this time is the compressive strength after the adhesive is completely cured.
As the adhesive, for example, an acrylic or urethane structural adhesive, a urethane or epoxy foamed resin material, or the like can be used. Note that the laminated structure of the foamed aluminum or aluminum porous body may not use an adhesive. For example, each layer can be fixed by being sandwiched between the hood outer and the hood inner without bonding.

Next, the manufacturing method of the engine hood structure of the present invention will be described in detail.
In the production method of the present invention, two or more precursors (precursors) are heated and foamed with a porous metal disposed on the back surface of the hood outer to obtain the engine hood structure described above. Specifically, two or more types of precursors obtained by adding a foaming aid to one or both of aluminum powder and aluminum alloy powder are produced by changing the amount of the foaming aid added. Then, the porous metal which the said foaming auxiliary agent foamed is obtained by laminating | stacking and heating these precursors. In addition, although it can arrange | position on the back surface of a hood outer after porous metal formation, you may form a porous metal after arrange | positioning a precursor.
In this way, by forming precursors with different amounts of addition of foaming aids in a laminated structure, a porous metal having a density distribution can be obtained from the difference in foaming rate when heated to a predetermined temperature. Here, the bubbles generated by the foaming aid have a lighter specific gravity than aluminum or an aluminum alloy, and thus exhibit a property of floating upward in a molten aluminum or aluminum state. Therefore, in order to obtain a more ideal density distribution of the porous metal, in the heating furnace, the precursor with a low content of foaming aid is heated below and the precursor with a high content is stacked on top. It is desirable.
Further, as the foaming auxiliary agent, for example, can be used, such as TiH ₂ and CaCO _3, it can be heated in the range of 600 ° C. to 800 ° C..

Next, the suitable form of the engine hood structure of this invention is demonstrated using drawing.
FIG. 1 is a top view of a hood structure of an automobile. Moreover, FIG. 2 is a figure explaining 1 aspect of this invention about the AA cross section of this food | hood structure. In FIG. 2, the hood outer 1 is made of a steel plate or an aluminum alloy plate. A porous metal 2 whose density decreases continuously or stepwise from the hood outer 1 side to the hood inner 3 side is disposed on the inner side (engine room side). A hood inner 3 having no irregularities is provided further inside the porous metal 2 and is fastened to the hood outer 1 by a hem at the edge.
The hood inner 3 is preferably a substantially flat plate shape having no irregularities as shown in FIG. 2, but it may be subjected to a normal press work as shown in FIG. Further, the porous metal 2 disposed in the gap between the hood outer 1 and the hood inner 3 is bonded to one or both of the hood outer 1 side and the hood inner 3 side with a structural adhesive or a foamed resin material. However, it may be mechanically sandwiched between the hood outer 1 and the hood inner 3 without being bonded.

  In the hood structure shown in FIGS. 2 and 3, the porous metal 2 is disposed over the entire back surface of the hood outer 1. The region where the porous metal 2 is disposed is illustrated in FIG. 4. As shown in the perspective view from the hood outer side, the same effect can be locally obtained even if it is a part of the hood structure. Note that the position where the porous metal 2 is locally disposed is not limited to the position shown in FIG. 4.

  FIG. 5 is a diagram illustrating another aspect of the present invention with respect to the AA cross section of FIG. 1. This hood structure is the same as that shown in FIGS. 2 and 3 except that the porous metal 2 is bonded to the back surface of the hood outer 1 using a structural adhesive or foamed resin material without using a hood inner. It has the same configuration as. Also in this embodiment, the porous metal 2 is not limited to the one adhered to the entire back surface of the hood outer 1, and may be disposed locally.

  FIG. 6 shows an enlarged cross section of a hood structure having a porous metal 2 whose density gradually decreases from the hood outer 1 side toward the engine room side. That is, porous metals 4 to 6 having different densities are bonded to the inside of the hood outer 1 with the adhesives 7 and 8 so that the density decreases from the hood outer side toward the engine room side. At this time, it is desirable that the strength of the adhesive 7 is lower than the strength of the porous metal 4 to be bonded, and the strength of the adhesive 8 is lower than the strength of the porous metal 5 to be bonded. Although FIG. 6 shows an example in which three types of porous metals having different densities are bonded, the number of porous metal layers is not particularly limited as long as it is a laminated structure of two or more types. The adhesive may be of any type, such as a structural adhesive, a foamed resin agent, or a sealer agent.

  In the present invention, by configuring the engine hood structure as described above, immediately after the head of the pedestrian collides with the engine hood, the rigidity improvement effect as the hood structure is exhibited, and the weight effect in the vicinity of the hood outer is achieved. Thus, the head can be decelerated more efficiently, and head problems can be reduced. Further, in the latter half of the collision, energy can be absorbed with a small amount of deformation without increasing the head damage value due to the progress of uniform deformation of the porous metal with a low reaction force. Furthermore, since the distance between the engine hood structure and the engine room can be narrower than in the prior art, a vehicle or the like can be designed more freely.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.

(Examples 1-4 and Comparative Examples 1-3)
As shown in FIG. 7, three types (9 to 11) of foaming precursors with different contents of the foaming aid in the aluminum powder or aluminum alloy powder are stacked, and this is filled into a mold having a predetermined shape. By heating to 650 ° C. to 800 ° C., foamed aluminum whose density was continuously changed in the thickness direction was obtained. Table 1 shows the specifications of each example.
A head impactor 15 equipped with an accelerometer is sandwiched between an outer equivalent material 12 and an inner equivalent material 13 with a 10 mm thick foamed aluminum 14 having a density changed in two steps from the hood outer 12 side toward the hood inner 13 side. Was collided at a speed of 35.7 km / hr, and the HIC value (head injury value) and the maximum displacement of the hood at that time were measured. An outline of the model experiment is shown in FIG. Moreover, FIG. 9 shows a schematic shape of the hood structure material used in the model experiment. In addition, the shape and the support method have no correlation with the actual automobile hood structure, and superiority or inferiority was judged by relative comparison with a steel plate model (Comparative Example 1) and an aluminum plate material model (Comparative Example 2) as comparative materials. . The results of the model experiment are shown in FIGS.

  From the graphs shown in FIG. 10 and FIG. 11, the hood structure material which is a preferred embodiment of the present invention is a steel plate alone, an aluminum plate alone, or a case where foamed aluminum having no density distribution is sandwiched. It can be seen that the HIC is reduced and the displacement is also suppressed.

It is the schematic which shows the plan view of a food structure. It is the schematic which shows the one aspect | mode of this invention in the AA cross section of FIG. It is the schematic which shows another aspect of this invention in the AA cross section of FIG. It is the schematic which shows the one aspect | mode of this invention with the perspective view from the plan view of a hood structure material. It is the schematic which shows another aspect of this invention in the AA cross section of FIG. It is the figure which expanded locally one aspect | mode of this invention from which the density changed in steps toward the engine room side from the hood outer side. It is the schematic which shows the one aspect | mode of the foaming precursor (precursor) at the time of producing the foamed aluminum in which the density changed continuously by the powder method. It is a schematic diagram which shows embodiment of model experiment. It is a figure which shows the general shape of the hood structure used for the model experiment. It is a graph which shows the result regarding HIC of a model experiment. It is a graph which shows the result regarding the maximum displacement amount of a model experiment.

Explanation of symbols

1 Food outer 2 Porous metal (foamed aluminum, aluminum porous body)
3 Food inner 4 Porous metal (density: high)
5 Porous metal (density: medium)
6 Porous metal (density: low)
7 Adhesive 8 Adhesive 9 Foam precursor (foaming aid content: many)
10 Foam precursor (foaming aid content: medium)
11 Foam precursor (foaming aid content: low)
12 Hood outer equivalent material 13 Hood inner equivalent material 14 Foamed aluminum 15 Head impactor

Claims (9)

An engine hood structure in which a porous metal is filled or bonded to a part or all of a gap between a hood outer forming an outer plate and a hood inner forming an inner plate,
The engine hood structure according to claim 1, wherein the density of the porous metal decreases continuously or stepwise from the hood outer side toward the hood inner side. An engine hood structure comprising a hood outer forming an outer plate and a porous metal bonded to part or all of the back surface thereof,
An engine hood structure characterized in that the density of the porous metal decreases continuously or stepwise from the hood outer side to the engine room side.   The engine hood structure according to claim 1, wherein the hood inner has a substantially flat plate shape formed along the shape of the engine hood.   The engine hood structure according to any one of claims 1 to 3, wherein the hood outer and / or the hood inner is made of steel and / or an aluminum alloy.   The engine hood structure according to any one of claims 1 to 4, wherein the porous metal is foamed aluminum and / or an aluminum porous body. 6. The engine hood structure according to claim 5, wherein the foamed aluminum and / or the porous aluminum body has a density in the vicinity of the hood outer of 0.1 g / cm ³ or more.   The engine hood structure according to claim 5 or 6, wherein the foamed aluminum and / or the aluminum porous body has a laminated structure in which the density of each layer decreases from the hood outer side toward the engine room side.   The engine hood structure according to claim 7, wherein the strength of the adhesive used between the layers of the foamed aluminum and / or the porous aluminum body decreases from the hood outer side toward the engine room side. In manufacturing the engine hood structure according to any one of claims 1 to 8,
The porous metal is prepared by preparing two or more precursors containing aluminum and / or an aluminum alloy and a foaming aid by changing the amount of the foaming aid added. A method for producing an engine hood structure obtained by foaming an auxiliary agent.

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