JP3368122B2 - Energy absorbing member - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energy absorbing member made of an aluminum or aluminum alloy extruded profile (hereinafter referred to as an aluminum extruded profile), and is particularly effective in a longitudinal direction of a vehicle frame or an automobile bumper stay. The present invention relates to an energy absorbing member suitable for use in a receiving part.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of environmental problems such as global warming and ozone layer destruction, weight reduction of automobiles has been seriously studied in order to suppress an increase in carbon dioxide gas in the atmosphere. There are various ways to reduce the weight, but by replacing the material, that is, by using aluminum extruded profile instead of the steel sheet that has been mainly used in the past, it is possible to reduce the weight and obtain a free cross-sectional shape. Utilizing the advantages of the extruded aluminum profile, it is being studied to improve performance, that is, to enhance energy absorption at the time of collision.

For example, in an automobile frame structure,
In order to improve the energy absorption, it has been attempted to provide an intermediate rib on the hollow cross section of the extruded aluminum profile. However, in this case, there is a problem that the difference between the initial load and the average load (see FIG. 5 described later) at the time of collision becomes large, and the impact on the occupant increases at the time of collision of the automobile. On the other hand, Japanese Laid-Open Patent Publication No. 64-67482 discloses a frame structure of an automobile in which a plurality of weld beads are formed at predetermined intervals on the outer periphery of a rectangular cross-section shaped member, and a notch is provided at a corner. Is listed. According to this structure, by forming such a low-rigidity portion in the longitudinal direction, the initial load at the time of collision can be reduced and the difference from the average load thereafter can be reduced, but the formation of weld beads and corner cutouts is possible. Is a factor of cost increase, and since the energy absorption amount per unit weight is reduced due to the formation of the low-rigidity portion, the wall thickness of the material must be increased to secure the desired energy absorption amount.
The weight had been increased. In addition, JP-A-7-10135
No. 4 discloses a side member of a vehicle frame in which a concave portion is formed at a corner portion of a U-shaped section material at a predetermined interval and a rib connecting between upper and lower walls of the section member is mounted. Has been done. In this structure, the recess reduces the initial load at the time of collision, and the rib improves the average load to compensate for the reduction in the initial load. However, providing the rib increases the weight and the cost. There was a flaw.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art. The initial load is not reduced and the average load is relatively increased, whereby a large energy absorption amount per unit weight is obtained. The object is to obtain an energy absorbing member having

[0005]

The inventors of the present invention have conducted various tests as a measure for improving the energy absorption amount of the aluminum extruded profile, and as a result, have found that the aluminum extruded profile is in the longitudinal direction, that is, in the direction of collision. It has been found that this can be done by applying a certain twist along. That is, the present invention relates to an energy absorbing member in which a twist is formed in the longitudinal direction of the profile in an aluminum extruded profile. In the present invention, the term “longitudinal direction” means the pushing of the extruded material.
Going out.

In general, aluminum extruded profiles are positively restrained from twisting, and such extruded aluminum extruded profiles have been conventionally used for automobile frames and bumper stays. On the other hand, the present invention remarkably improves the energy absorption amount when a shock is applied in the longitudinal direction by positively twisting the aluminum extruded profile (forming a twist in the longitudinal direction), and It is intended to improve passenger protection performance. The reason why such an effect appears in an aluminum extruded profile formed with a twist in the longitudinal direction is not always clear, but when an aluminum extruded profile is impacted in a direction parallel to the longitudinal direction, it repeatedly deforms like a bellows. It absorbs a compressive load, and when a twist is formed, it is considered that a force to eliminate the twist is required during the deformation, the average load increases, and as a result, the energy absorption amount increases. .

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the degree of twist (angle) formed in an aluminum extruded profile may be appropriately set according to the shape, size, material strength of the extruded profile, and balance with surrounding members. Good. However, the twist is 25
If it is less than 2 ° per 0 mm, the effect of improving the amount of energy absorption due to twisting is not clear, and if it exceeds 60 °, bellows-shaped deformation does not occur and buckling occurs due to concentrated load on the twisted part, resulting in energy absorption. Is reduced. Therefore, twisting of 2 to 60 degrees per 250 mm length is effective, and it is preferable to set the twist within that range. In the present invention, the twist of 2 to 60 ° per 250 mm length means that the degree of twist is within the above range regardless of the length direction. However, if it is within that range, it does not necessarily have to be a uniform twist,
There may be strong twists and weak twists.

Further, in the present invention, the range in which the twist is formed may be the entire length of the extruded profile or only a partial range in the longitudinal direction. In the latter case, if the range where the twist is formed is too short compared to the entire length of the extruded profile, the effect of improving the energy absorption amount due to the twist does not clearly appear, and especially in the case of a mild collision, the twist is not formed. The part is compressed and deformed first, and the effect of energy absorption due to torsion disappears, so 1/5 of the total length
The above is a guideline.

FIG. 1 schematically shows an example of the energy absorbing member according to the present invention. This is an extruded shape member (for example, a square pipe shape) in which the twist is uniformly formed over the entire length L ₁ (mm), and the entire twist angle θ is 250 mm.
Per 2 ° to 60 °, i.e. _{θ = (L 1/250)} ×
It is set to fall within the range of (2 ° to 60 °). In FIG. 2, a twist is formed in a part (length L ₁ ) of an extruded profile having a length L, and (L ₁ / L) is set to be ⅕ or more.

The present invention is applicable to aluminum extrusion profiles of various component systems and compositions. Further, as the aluminum extruded profile to which the present invention is applied, typically, a pipe-shaped product or a hollow product having a shape with a middle rib is provided, and the other part is provided with a hollow part having a closed cross section. A shape (see FIG. 3A) or a shape having a square pipe shape or a middle pipe connecting the opposite sides of the square pipe shape with a part of the side cut out (FIG. 3B to FIG. (D)) etc.
An aluminum extruded profile having a structure can be mentioned.

The energy absorbing member according to the present invention has a length direction which is expected to be the direction of the collision (front-rear direction) at a portion such as a front or rear side member of a vehicle frame which needs to absorb energy at the time of collision. Place it so that it is parallel to. At this time, it is assumed that the twist is formed over the entire straight portion of the front or rear side member or over a length range of 1/5 or more. If a side collision is taken into consideration, it can be applied to a cross member, and can also be applied to bumper stays and other various molded products that require energy absorption at the time of impact.

As means for forming a twist in the longitudinal direction of the aluminum extruded shape, a method of forming a twist by changing the position and size of the chamber portion of the extrusion die or the bearing length and angle, a method using a stretcher, Further, a method of adding a twist when bending with a multi-bender or a stretch bender, a method of bulge molding or a swaging molding can be mentioned. To briefly explain individually, in the case of extrusion, the metal flow balance during extrusion is changed by the above operation to form a twist, and in the case of a stretcher, pull one side of the chuck while twisting, or pull the chuck on both sides. Twist is formed by rotating in the opposite direction and pulling, in the case of a multi-bender, the twist is formed by controlling the θ axis that gives the rotation of the movable jig, and in the case of a stretch bender, the twist is processed in advance in the mold. The chuck can be rotated to form a twist during processing, and in the case of bulge molding or swaging, the mold can be processed in advance to form the twist during processing.

[0013]

EXAMPLES Examples of the present invention will be described below. JIS6063
An aluminum alloy having the composition was extruded to obtain a square pipe shown in FIG. 4 having a side length of 40 mm and a wall thickness of 2 mm. This square pipe is subjected to a predetermined twisting process (0 ° to 70 ° per 250 mm) by a multi-bender, and 250 mm
Cut to length. Subsequently, in order to eliminate the effect of work hardening due to the twisting process, the sample was held at a temperature of 380 ° C. for 2 hours and then cooled into a furnace to obtain an O material, which was used as a test material (No. 1 to 6). As shown in FIG. 5, each of the test materials was compressed 150 mm axially at a speed of 30 mm / min using a compression tester,
A load-displacement diagram (schematically shown in FIG. 5) was obtained. In addition,
In the load-displacement diagram of FIG. 6, the initial load is the maximum load in the initial stage of compression, and the energy absorption amount is the area of the shaded area (TON.
mm), the average load is the energy absorption amount and the displacement amount (150
mm) divided by.

Table 1 shows the initial load and the energy absorption amount for each test material obtained from the load-displacement diagram. The numbers in parentheses in the column of energy absorption amount are the test material No.
It is the improvement rate when compared with the energy absorption amount of 1.
In addition, when the improvement rate of the energy absorption amount was less than 3%, x was evaluated as x, and 3% or more was evaluated as o, which is shown in the evaluation column of Table 1.

[0015]

[Table 1]

As shown in Table 1, the twist angle is from 2 ° to 6 °.
The test materials 2 to 4 set to 0 ° have the same initial load as the test material 1, and have improved energy absorption. But,
Although the initial load of the test material 5 in which the twist angle was set to 70 ° was the same as that of the test material, buckling occurred because the twist angle was too large.

[0017]

EFFECTS OF THE INVENTION According to the present invention, by forming a proper amount of twist in an extruded aluminum profile, the average load can be increased and the energy absorption amount per unit weight can be increased even with the same initial load. Conversely, if the amount of energy absorbed is the same, the initial load can be reduced and the weight of the member can be reduced. If the energy absorbing member according to the present invention is applied to, for example, a front or rear side member or a cross member of a vehicle frame, a bumper stay, or various molded products that need to absorb energy at the time of impact, thinning due to improved impact characteristics is achieved. Therefore, it can greatly contribute to the weight reduction of the product.

[Brief description of drawings]

FIG. 1 is a schematic perspective view (a) and a plan view (b) of an energy absorbing member according to the present invention.

FIG. 2 is a schematic perspective view of an energy absorbing member according to the present invention.

FIG. 3 is a diagram illustrating a cross-sectional shape of an extruded profile.

FIG. 4 is a diagram illustrating a cross-sectional shape and dimensions of an extruded shape material of an example.

FIG. 5 is a diagram illustrating a test procedure of an example using a compression tester.

FIG. 6 is a schematic diagram of a load-displacement diagram obtained in a compression test.

Continuation of front page (56) Reference JP-A-7-173584 (JP, A) JP-A-7-257426 (JP, A) JP-A-7-118782 (JP, A) JP-A-6-247337 (JP , A) JP 7-145842 (JP, A) JP 5-305876 (JP, A) JP 64-67482 (JP, A) JP 7-101354 (JP, A) 5-12361 (JP, U) Actual Kaihei 4-67577 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B62D 21/15 B62D 25/20

Claims (6)

(57) [Claims] 1. A bellows made of an extruded profile of aluminum or an aluminum alloy, when subjected to a shock in its longitudinal direction.
Energy absorbing member that deforms into a shape and absorbs a compressive load
In the energy absorbing member, a twist is formed in the longitudinal direction. 2. The energy absorbing member according to claim 1, wherein the twist is formed over a range of ⅕ or more of the length of the extruded profile. 3. The energy absorbing member according to claim 1, wherein the twist is formed over the entire length of the extruded profile. 4. The method according to claim 1, wherein the twist angle is 2 to 60 ° per 250 mm length.
The energy absorbing member described in any one of 1. 5. The energy absorbing member according to claim 1, wherein the twist is a twist that is forcibly formed during extrusion or bending. 6. A vehicle frame having the energy absorbing member according to any one of claims 1 to 5 as a part of its constituent elements, wherein the longitudinal direction of the energy absorbing member is arranged in parallel with the impact direction. A vehicle frame characterized by being