JP3025023B2 - Vehicle impact beam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a door impact beam incorporated in a door of a vehicle such as an automobile.

[0002]

2. Description of the Related Art Door impact beams are known as means for reinforcing automobile doors. Conventional door impact beams are made by pressing a high-strength steel plate into an uneven shape and placing it inside the door in the front-rear direction.
The rigidity is increased with respect to the input from the side of the door.
The energy at the time of the side collision is absorbed by the deformation of the door impact beam, and the deformation of the door is minimized, thereby ensuring the safety of the occupant.

The conventional door impact beam described above is
To lay out inside a narrow door in order to satisfy a predetermined amount of energy absorption and door deformation, a considerably wide thing is required, and the weight per sheet is 5 to 8 kg.
There was a drawback that it became considerably heavy before and after.

[0004] Therefore, it has been conceived to reduce the mounting space and weight by using a heat-treated steel pipe for the door impact beam. However, since the round pipe has a lower secondary moment than that of a square pipe having the same cross-sectional area, the slope of the characteristic curve showing the relationship between load and deflection at the initial rise becomes gentler, so that it becomes unnecessary at the moment of collision. Will allow the deflection. For this reason, in order to obtain a desired strength with a round pipe, a larger cross-sectional area is required than with a square pipe, which causes problems such as an increase in weight.

From such a viewpoint, it has been studied to use a square pipe a having a square cross section as shown in FIG. The cross section of the conventional square pipe a is such that adjacent surfaces intersect at right angles at four corner portions b, or
The corner portion b was slightly rounded in an arc shape, and its radius of curvature R was almost the same as the plate thickness t.

[0006]

The conventional square pipe a described above may suddenly buckle when the bending progresses to some extent, and tends to lose the shock absorbing performance with a small bending as compared with the round pipe. Was.

[0007] The evaluation of the intensity of the door impact beam is performed using a test apparatus as shown in FIG. This test apparatus uses a ram c to apply a load W corresponding to the energy at the time of a side collision to the central portion in the longitudinal direction of the beam d. In this case, as the load W increases, the beam d bends as shown in FIG. 10, and plastic deformation proceeds in a U-shape. Therefore, the beam d is transmitted to the contact points A,
At B, they touch at a tangent angle θ.

When a beam made of a general pipe material is bent, a deformation behavior generally occurs as shown in FIG. That is, the initial stage of the bending is an elastic deformation region which is formed by three-point bending of the beam, which is governed by the secondary moment of section. The elasto-plastic deformation region is a region where the numerical value governing from the secondary moment of section to the section modulus shifts. The plastic deformation region is a region governed by the yield stress and the section modulus of the beam material. In this plastic deformation region, the material gradually flattens, and when the amount of deflection exceeds a certain value, the tendency becomes remarkable, and the characteristic curve starts to decrease. And the curvature of the beam became tight,
Sudden load drop or buckling begins and eventually breaks.

For example, a conventional (FIG. 8) square pipe (thickness 3 mm, span L = 700) having a square cross section of 32 mm on a side.
12), the characteristic curve shown by the solid line in FIG. 12 was obtained, and the wire was broken by about 100 mm. With this degree of deflection, the door cannot be sufficiently reinforced. On the other hand, in the case of a round pipe having the same cross-sectional area as the square pipe, the rising slope of the characteristic curve is gentle as shown by the dashed line in FIG. Will forgive. For this reason, there is a tendency to use round pipes having a large cross-sectional area, resulting in an increase in weight.

Accordingly, an object of the present invention is to provide a door impact beam capable of increasing the deflection up to the buckling point, not reducing the initial rising gradient of the characteristic curve, and exhibiting a desired strength at the moment of a collision. Is to provide.

[0011]

SUMMARY OF THE INVENTION A beam body of a door impact beam according to the present invention developed to achieve the above object has a rounded radius of curvature R outside a corner portion of a cross section thereof. Heat-treated steel with a square pipe shape
When the thickness of this hollow material is t,
A hollow material that satisfies the relationship 1.5t ≦ R ≦ 2.5t is used.

[0012]

When the beam main body is bent using the above-described test apparatus, it has been found from an experiment that the value of the deflection can be predicted by the following equation (1).

H × θ> (7-8) (1) H: length of one side of the pipe (mm) θ: tangent angle (radian) When the above θ is in the region satisfying the expression (1), the beam Tend to move away from the ram, the beam curvature becomes tight, and a sharp load drop begins.

The beam main body made of a square pipe-shaped hollow material gradually approaches the characteristics of a round pipe and becomes less likely to buckle if the R value of the corner portion is increased. The initial rising slope of the curve becomes gentler, allowing more deflection than necessary at the moment of the collision.

According to the present invention, by setting the relationship between R and t in the above-described range, it is possible to increase the deflection up to buckling while satisfying the rise of the characteristic curve.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. As shown in FIG.
Inside a door 1 of an automobile, a door impact beam 2 according to the present invention is arranged in the front-back direction of the door 1. The door impact beam 2 of this embodiment includes a beam main body 3 and mounting brackets 5 and 6 welded to both longitudinal ends of the beam main body 3. The beam main body 3 is made of a steel hollow member 20 having a cross-sectional shape (see FIG. 3) similar to a square pipe subjected to heat treatment such as quenching and tempering. The thickness t of the hollow member 20 is constant in the tube axis direction.

The brackets 5 and 6 are made of a high-tensile steel plate,
As shown in FIG. 2, one bracket 5 is fixed to the rear side frame 10 of the door by welding. The bracket 5 has a portion 5 a having a shape corresponding to the outer shape of the beam main body 3 and a flat portion 5 b fixed to the side frame 10. Reference numerals 11 and 12 in the figure indicate welded portions, respectively.

The other bracket 6 is welded to the front side frame 15 of the door 1. This bracket 6
This also has a portion 6 a having a shape corresponding to the outer shape of the beam main body 3 and a flat plate-shaped portion 6 b fixed to the side frame 15.

As shown in FIG. 3, the cross-sectional shape of the hollow member 20 forming the beam main body 3 has four flat portions 21 and
It is composed of four corner portions 22 and has a shape substantially similar to a square. The outer radius of curvature R of the corner portion 22 is described below when the plate thickness is t. For the reason, the value is set so as to satisfy the relationship of 1.5t ≦ R ≦ 4t.

According to the experiment, the characteristic of H = 34 mm, the thickness of the hollow member 20 of 3 mm, and the characteristic of R = 2t = 6 mm, as shown by the solid line in FIG. On the other hand, in the case of a hollow material with R = 1.5t = 4.5 mm,
As shown by the two-dot chain line in FIG. That is, at the same load, the larger the R value, the larger the deflection, and the required strength is secured.

According to the same experiment, when R = 1t = 3 mm, the deflection up to break is substantially the same as that of the conventional square pipe, and the rise of the characteristic curve is sharp, but the deflection is small. It has been found to cause buckling.

FIG. 5 shows how the initial resistance ratio and the intermediate resistance ratio change when R is changed from 1t to 4t. The initial resistance ratio is a value obtained by comparing the average of the sum of the loads required when bending the beam to 6 inches (15.24 cm) with a round pipe having the same external dimensions (1 in the case of a round pipe). ). The intermediate resistance ratio is a value obtained by comparing the average of the sum of loads required when bending the beam to 12 inches (30.48 cm) with a round pipe having the same external dimensions. As shown in FIG.
If it is 5t or more and 4t or less, any of the initial resistance ratio and the intermediate resistance ratio can be used for any pipe size (24 mm to 38 mm on one side) that can be practically used as a door impact beam. Can also be included. As can be seen from FIG. 5, when R becomes 1.5t or more with respect to the initial resistance ratio, the intermediate resistance ratio increases toward the maximum value even if the initial resistance ratio decreases, and the tendency is that the length of one side
Irrespective of the above, it continues at least until R reaches around 2.5t . When R exceeds 3t, both the initial resistance ratio and the intermediate resistance ratio decrease irrespective of the length of one side, so that the object of the present invention is not met. That is, if R is too large, the characteristics of the round pipe are too close to each other, and the above-mentioned drawbacks of the round pipe occur. Especially collision
In absorbing energy, practically an impact beam
The initial load (initial resistance) is as high as possible
Must be up. In contrast, the intermediate resistance is
Pact beam breaks or massive buckling or loading
If there is no decrease, change the magnitude of the initial resistance after the deformation stroke.
Can be maintained up to half. In other words, practically the first
The vicinity of the region where the initial resistance ratio takes the maximum value is desirable. For these reasons, the relationship between R and t is limited to the above range.

The present invention can be applied to a hollow member 30 having a substantially rectangular cross section as shown in FIG. Alternatively, a hollow member 31 having a cross section similar to a trapezoid as shown in FIG.
In short, the present invention can be similarly applied to any hollow material having a corner portion, such as a cross section resembling a triangle or a polygon.

[0024]

The door impact beam of the present invention is hardened.
Bead made of steel hollow material subjected to tempering heat treatment
By setting the relationship between R and the wall thickness t in the corner portion of the main body in the above-described range, the door impact beam is improved.
As long as the pipe size (the length of one side of the cross section) is within the range of the pipe that can be practically used as a system, regardless of the length of one side, the advantage of the round pipe that is hard to buckle and the advantage of the square pipe ( A large rise in the characteristic curve), and can increase the rise of the load (initial resistance ratio) at the initial stage of deformation, which is particularly important for absorbing collision energy. -A door impact beam exhibiting absorption performance is obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of a door provided with a door impact beam according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a mounting portion of the door impact beam shown in FIG.

FIG. 3 is a sectional view of the beam main body shown in FIG. 1;

FIG. 4 is a diagram showing a relationship between deflection of a door impact beam and a load.

FIG. 5 is a diagram showing a relationship between the magnitude of R of the beam main body and the resistance ratio.

FIG. 6 is a sectional view showing a modification of the beam main body.

FIG. 7 is a sectional view showing another modification of the beam main body.

FIG. 8 is a sectional view of a conventional beam main body.

FIG. 9 is a front view showing an outline of a test apparatus used for evaluating beam intensity.

FIG. 10 is a front view showing a state where a beam is bent.

FIG. 11 is a diagram showing a relationship between deflection and load of a general hollow material.

FIG. 12 is a diagram showing a relationship between load and deflection when a square pipe and a round pipe are bent.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Door, 2 ... Door impact beam, 3 ... Beam main body, 20 ... Hollow material, 22 ... Corner part, 30, 31 ...
Hollow material.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hidetoshi Ushito 1 Shinisogocho, Isogo-ku, Yokohama-shi, Kanagawa Japan (56) References JP-A-4-75715 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) B60J 5/00 B60J 5/04 E04C 3/04 B21C 37/15

Claims (1)

(57) [Claims] 1. A door impact beam having a beam body disposed inside a door in a front-rear direction and having both ends fixed to a frame of the door, wherein the beam body has a cross-section. The outside of the corner portion is made of a hollow steel material which has been subjected to a heat treatment of quenching and tempering in the shape of a square pipe having a roundness with a radius of curvature R. ≦ R ≦
A door impact beam for a vehicle, wherein a hollow material satisfying a relationship of 2.5t is used.