JP2004141920A - Center pillar made from aluminum-alloy die casting and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a center pillar made from an aluminum-alloy die casting, which is lightweight and exhibits a very excellent energy absorptivity in a collision, and to provide its manufacturing method. <P>SOLUTION: A center pillar 10 made from an aluminum-alloy die casting includes a main body part 13, into which a center pillar part 11 and a side sill part 12 are integrally molded from an die casting aluminum-alloy by a die casting method, and a shock absorbing member 14, which consists of a foaming aluminum material and is cast-welded in the main body part 13. The shock absorbing member is cast-welded in the position ranging from the side sill part to the part at least 200 mm upper therefrom. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pillar made of an aluminum alloy die-cast casting and a method of manufacturing the same, and more particularly, to show a better energy absorption capacity than a conventional aluminum alloy die-cast cast center pillar in a side collision of an automobile. The present invention relates to a center pillar made of an aluminum alloy die-cast casting capable of forming a center pillar and a manufacturing method of manufacturing the center pillar by a die-casting method.
[0002]
[Prior art]
In recent years, attempts to apply aluminum alloys to vehicle bodies and chassis members have been widely made due to increasing demands for reducing the weight of automobiles. However, replacing the conventional steel vehicle body structure with an aluminum alloy as it is results in a significant increase in cost.
[0003]
For this reason, it is not possible for Audi to use large and complex parts, such as center pillars, which were manufactured by welding multiple parts in a steel car body, by using the features of aluminum alloys by die casting. It has been tried with the A2 series of all-aluminum body cars of the company (for example, see Non-Patent Document 1) and has been put to practical use.
[0004]
[Non-patent document 1]
W. Leiterman et. al, "Der Aluminum-Space-Frame des Audio A2", ATZ MTZ special (2002), 68
[0005]
[Problems to be solved by the invention]
Here, in applying an aluminum alloy die-casting to a body frame member such as a center pillar, from the viewpoint of ensuring safety at the time of a collision, a large crack is not generated even with an impact input such as a collision. It is required to deform and absorb large energy. From such a viewpoint, in order to improve the ductility of the aluminum alloy die casting, various die casting materials and die casting methods have been developed. However, in order to achieve both higher weight reduction and collision safety performance at a higher level in the future, it seems that there is a limit only to the continuation of material development and construction method development up to now.
[0006]
On the other hand, in recent years, application of a porous material has been studied as a measure for improving the collision performance of a vehicle body member, but there are still few examples of how to apply the method to a vehicle body member and a method of fastening the same.
[0007]
The present invention has been made in view of such circumstances, and when applied to an automobile, is a center pillar made of an aluminum alloy die-cast casting, which is lightweight and can exhibit extremely excellent energy absorbing ability at the time of collision. It is an object of the present invention to provide a manufacturing method thereof.
[0008]
[Means for Solving the Problems]
The object of the present invention is achieved by the following means.
[0009]
The present invention includes a main body in which a center pillar portion and a side sill portion are integrally formed by a die casting method from an aluminum alloy for die casting, and a shock absorbing member made of a foamed aluminum material and encapsulated in the main body portion, The shock absorbing member is a center pillar made of an aluminum alloy die-cast casting, which is cast in the side sill portion and at least 200 mm above the side sill portion of the center pillar portion.
[0010]
The present invention also provides a method of manufacturing the above-mentioned center pillar made of an aluminum alloy die-casting, wherein the center pillar is made of an aluminum alloy die-cast by casting a molten aluminum alloy for die casting by a high vacuum die casting method. It is.
[0011]
【The invention's effect】
In the aluminum alloy die-cast casting center pillar according to the present invention, the performance of the aluminum alloy die-cast casting and the foamed aluminum material are impaired at the portions where it is necessary to efficiently perform large deformation and absorb energy at the time of side collision. In addition, since the impact absorbing member made of a foamed aluminum material is cast-in, it is possible to exhibit more excellent energy absorbing ability as compared with a conventional aluminum alloy die-cast casting center pillar.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
FIG. 1A is a schematic view showing the appearance of a center pillar 10 made of an aluminum alloy die casting according to an embodiment of the present invention, and FIG. 1B is a center pillar 10 made of an aluminum alloy die casting according to an embodiment of the present invention. FIG. 4 is a schematic view showing a portion where the shock absorbing member 14 made of a foamed aluminum material is cast.
[0014]
The aluminum alloy die-casting center pillar 10 according to the embodiment of the present invention can be summarized as follows: a main body portion 13 in which a center pillar portion 11 and a side sill portion 12 are integrally formed from a die-casting aluminum alloy by a die-casting method; A shock absorbing member 14 made of aluminum material and cast in the main body 13. The shock absorbing member 14 is cast in the side sill portion 12 and in a range of the center pillar portion 11 at least 200 mm above the side sill portion 12. The density of the shock absorbing member 14 to be cast is set to 0.2 g / cm ³ or more. In addition, the minimum thickness of the aluminum alloy die casting, which is the outer skin when the shock absorbing member 14 is cast-in, is 1 mm or more, and the range of the variation in the minimum thickness is 1 mm or less.
[0015]
Reference numeral 15 in the drawing indicates a roof rail portion joined to the upper end portion of the main body portion 13 by welding or the like.
[0016]
By the way, when a side collision of the vehicle is considered, the opponent vehicle collides with the side sill portion of the own vehicle or slightly above the side sill portion.
[0017]
Here, a case in which the side sill portion and the center pillar portion are individually manufactured by an aluminum alloy die casting method or extrusion molding, and then the two are joined to form a side body will be considered. In the side body having such a configuration, a joint portion between the side sill portion and the center pillar portion is present in a portion where it is required to undergo a large deformation upon receiving an input at the time of a side collision, and a discontinuous portion of strength is present. Will occur. For this reason, breakage and deformation are likely to be non-uniform, which hinders an improvement in energy absorbing ability.
[0018]
Therefore, in the center pillar 10 made of the aluminum alloy die-cast casting of the present embodiment, the main body portion 13 is formed by integrally forming the center pillar portion 11 and the side sill portion 12 from the aluminum alloy for die casting by die casting. .
[0019]
Further, in order to efficiently absorb energy at the time of side collision, a shock absorbing member 14 made of a foamed aluminum material is provided so as to be cast in the main body 13. As is well known, a foamed aluminum material is a material having excellent shock absorption performance. Here, the portion where the shock absorbing member 14 is cast-in is a portion where it is necessary to receive an input at the time of a side collision to absorb energy, and more specifically, the side sill portion 12 and the side sill portion 12 of the center pillar portion 11. It is preferable to set the range to at least 200 mm above. With this configuration, it is possible to deform more uniformly with a smaller amount of deformation and to perform efficient energy absorption. In the illustrated example, the impact absorbing member 14 is cast in a part of the side sill portion 12 in the longitudinal direction. However, the impact absorbing member 14 can be cast over the entire length in the longitudinal direction.
[0020]
Further, when the density of the shock absorbing member 14 to be cast, that is, the foamed aluminum material is extremely small, that is, less than 0.2 g / cm ³ , the strength of the foamed aluminum material itself becomes low, and the energy absorbing ability and the deformation control function are sufficiently improved. Do not have. Furthermore, the possibility that the foamed aluminum material itself is deformed by the casting pressure when casting by the die casting method is increased. Therefore, the density of the shock absorbing member 14, that is, the foamed aluminum material is preferably 0.2 g / cm ³ or more.
[0021]
Further, when the thickness of the aluminum alloy die-casting, which is the outer skin when the shock absorbing member 14 is cast-in, is less than 1 mm, the strength of the casting itself is not sufficient, and sufficient energy absorption by the die-casting casting cannot be expected. . Therefore, it is preferable that the thickness of the aluminum alloy die casting, which is the outer skin when the shock absorbing member 14 is cast, is 1 mm or more.
[0022]
In addition, when the variation of the thickness of the aluminum alloy die-cast casting as the outer skin when the shock absorbing member 14 is cast-in exceeds 1 mm, the deformation tends to concentrate on the thin portion, and the deformation is uneven. Therefore, there is a possibility that efficient energy absorption cannot be performed. Therefore, it is preferable that the variation in the thickness of the aluminum alloy die-casting as an outer shell when the shock absorbing member 14 is cast-in is 1 mm or less.
[0023]
When the center pillar 10 made of the above-mentioned aluminum alloy die-casting is cast by the ordinary die-casting method, the aluminum alloy die-casting as the outer skin is easy to entrain air, and the properties of the alloy (for example, elongation and toughness, etc.) Mechanical properties). In addition, due to the inclusion of air, welding of the aluminum alloy die casting becomes difficult, and it becomes difficult to incorporate the aluminum alloy into the vehicle body by welding. Therefore, when manufacturing the center pillar 10 made of an aluminum alloy die-cast casting, it is preferable to maintain the pouring system including the mold cavity in a vacuum (reduced pressure) atmosphere and cast the aluminum alloy melt for die casting by a high vacuum die casting method. .
[0024]
When the foamed aluminum material forming the shock absorbing member 14 is cast-in, if the outer skin of the foamed aluminum material does not remain at the portion in contact with the die-casting aluminum alloy melt at the time of casting, the heat of the die-casting aluminum alloy melt is reduced. Due to the pressure and pressure, the surface of the foamed aluminum material is melted or broken, and the thickness variation of the aluminum alloy die casting becomes large. Further, the air contained inside is released due to the erosion of the surface of the foamed aluminum material, and this air is taken into the aluminum alloy die casting, thereby increasing the possibility that the characteristics of the aluminum alloy die casting decrease. Therefore, it is preferable that at least a portion of the foamed aluminum material forming the shock absorbing member 14 to be in contact with the molten aluminum alloy for die-casting at the time of the casting-in so that the skin of the foamed aluminum material remains. desirable.
[0025]
In addition, when the temperature of the aluminum alloy melt for die casting at the time of die casting is a high temperature exceeding 700 ° C., the surface of the aluminum foam material is melted when the aluminum foam material is cast. . For this reason, as described above, the problem that the thickness of the aluminum alloy die-casting becomes non-uniform or that air released from the foamed aluminum material is taken into the aluminum alloy die-casting tends to occur. Therefore, it is desirable that the temperature of the aluminum alloy melt for die casting at the time of die casting is 700 ° C. or less.
[0026]
【Example】
An embodiment of the present invention will be described.
[0027]
As an embodiment of the present invention, as shown in FIGS. 1 (A) and 1 (B), a body portion 13 in which a center pillar portion 11 and a side sill portion 12 are integrally formed by die casting from an aluminum alloy for die casting, A center pillar 10 made of an aluminum alloy die-cast casting including an impact absorbing member 14 made of an aluminum material and cast in a main body 13 was manufactured. The impact absorbing member 14 was cast into the side sill portion 12 and a range of the center pillar portion 11 up to 200 mm above the side sill portion 12.
[0028]
A mold was used which was processed to hold the shock absorbing member 14 so that the shock absorbing member 14 was cast in a predetermined position. After setting the shock absorbing member 14 in the mold, high vacuum die casting was performed. Casting by the high vacuum die casting method was performed under the conditions of a casting pressure: 35 MPa, a degree of cavity vacuum: 40 hPa, an injection speed: 5 m / s, and a molten metal temperature: 690 ° C. As an aluminum alloy for die-casting, an alloy composed of Si: 1.5%, Mg: 3.5%, Mn: 1.3%, the balance being Al and inevitable impurities was used in a mass ratio.
[0029]
The impact absorbing member 14 to be cast was formed using a foamed aluminum material having a density of 0.34 g / cm ³ . Further, a foamed aluminum material having a surface skin left on the side to be cast and used was used.
[0030]
When the thickness of the obtained center pillar 10 made of an aluminum alloy die-casting was examined, the thickness of the aluminum alloy die-casting, which was the outer skin of the portion enclosing the shock absorbing member 14, was 2 to 2.3 mm. Further, the thickness variation was within a range of ± 0.3 mm.
[0031]
As a comparative example, a center pillar made of an aluminum alloy die casting without casting the shock absorbing member 14 was manufactured. The manufacturing conditions of the comparative example were the same as those of the example except that the shock absorbing member 14 was not cast.
[0032]
FIG. 2A is a schematic diagram showing a support position P1 of a center pillar made of an aluminum alloy die-cast casting during a falling weight impact test, and FIG. 2B is a schematic diagram showing a falling position P2 of a weight during a falling weight impact test. FIG.
[0033]
After trimming the aluminum alloy die-cast center pillars obtained in Examples and Comparative Examples so as to have predetermined dimensions, the steel inner panels were joined by rivets and adhesion, and subjected to a drop weight impact test. .
[0034]
In the drop weight impact test, the center pillar made of an aluminum alloy die-cast casting was supported at three positions P1 shown in FIG. 2A on the inner panel side. Then, a weight having a weight of 500 kg was dropped on a center pillar made of an aluminum alloy die-cast casting at a speed of 8 m / s, and a load-displacement diagram and an absorbed energy-displacement diagram at that time were measured. As shown in FIG. 2B, the falling position of the falling weight was set to a position P2 slightly above the side sill portion 12, as shown in FIG. The size of the contact surface of the falling weight with respect to the center pillar made of the aluminum alloy die casting is 200 mm × 150 mm. In addition, a weight whose corner was chamfered with R20 was used.
[0035]
FIG. 3 is a diagram showing a comparison of a load-displacement diagram obtained as a result of performing a falling weight impact test in Examples and Comparative Examples of the present invention, and FIG. 4 is a diagram showing Examples and Comparative Examples of the present invention. FIG. 7 is a diagram showing a comparison between an absorbed energy amount-displacement diagram obtained as a result of performing a falling weight impact test.
[0036]
As shown in FIGS. 3 and 4, when comparing the embodiment of the present invention and the comparative example, there is almost no difference in the load and the amount of absorbed energy at the very early stage of the deformation. And the difference between Comparative Example and Comparative Example. When the amount of displacement reached 150 mm, the example could absorb about 1.5 times the energy of the comparative example. This is due to the effect of the foamed aluminum material cast in a portion where large deformation occurs in the drop weight test.
[0037]
Thus, the impact absorbing member 14 made of the foamed aluminum material can be provided in a portion where it is necessary to efficiently perform large deformation and absorb energy at the time of a side collision, without impairing the performance of the aluminum alloy die-cast casting and the foamed aluminum material. It has been confirmed that the effect of the present invention is that by encapsulating the aluminum alloy, it is possible to exhibit more excellent energy absorbing ability as compared with a conventional aluminum alloy die-casting center pillar.
[Brief description of the drawings]
FIG. 1A is a schematic view showing an appearance of a center pillar made of an aluminum alloy die casting according to an embodiment of the present invention, and FIG. 1B is a diagram showing an aluminum alloy die casting made according to an embodiment of the present invention. It is a schematic diagram which shows the site | part which encases the shock absorption member which consists of a foamed aluminum material in a center pillar.
FIG. 2A is a schematic view showing a support position of a center pillar made of an aluminum alloy die-cast casting during a falling weight impact test, and FIG. 2B is a diagram showing a falling position of a weight during a falling weight impact test. FIG.
FIG. 3 is a diagram showing a comparison of load-displacement diagrams obtained as a result of performing a falling weight impact test in Examples and Comparative Examples of the present invention.
FIG. 4 is a diagram showing a comparison between an absorbed energy amount-displacement diagram obtained as a result of performing a falling weight impact test in Examples and Comparative Examples of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Center pillar 11 made of an aluminum alloy die-cast casting 11 ... Center pillar part 12 ... Side sill part 13 ... Body part 14 ... Shock absorbing member 15 made of aluminum foam material ... Roof rail part

Claims (6)

A main body in which a center pillar portion and a side sill portion are integrally formed by die casting from an aluminum alloy for die casting;
Comprising a shock absorbing member made of foamed aluminum material and cast in the main body,
A center pillar made of an aluminum alloy die-cast casting, wherein the shock absorbing member is cast in the side sill portion and a range of at least 200 mm above the side sill portion of the center pillar portion. The density of the shock absorbing member is an aluminum alloy die cast iron center pillar according to claim 1, characterized in that 0.2 g / cm ³ or more wrapped cast. 2. The aluminum alloy die-cast casting as an outer shell when the impact absorbing member is cast-in, has a minimum thickness of 1 mm or more, and a variation range of the minimum thickness is 1 mm or less. Or the center pillar made of an aluminum alloy die-casting product according to claim 2. It is a manufacturing method of the center pillar made from the aluminum alloy die-casting according to any one of claims 1 to 3,
A method for manufacturing a center pillar made of an aluminum alloy die-casting, comprising casting a molten aluminum alloy for die-casting by a high vacuum die-casting method. The skin of the foamed aluminum material is left at least in a portion of the shock absorbing member to be cast in contact with the molten aluminum alloy for die casting at the time of casting. Manufacturing method of center pillar made of aluminum alloy die casting. The method for manufacturing a center pillar made of an aluminum alloy die-cast casting according to claim 4 or 5, wherein the temperature of the aluminum alloy melt for die-casting at the time of die-casting is 700 ° C or less.

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