JPS6323004B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a door guard bar that is attached between a door outer panel and a door inner panel in order to prevent the door from deforming and secure a vehicle interior space in the event of a side collision of an automobile. As shown in FIGS. 1 and 2, the door guard bar G is installed along the longitudinal direction of the vehicle body between the door outer panel 5 and the door inner panel 6 of the door D located on the side surface of the vehicle body B, and At times, it exhibits a certain bending strength and absorbs impact energy.
This is to ensure the safety of the passengers. Such a door guard bar G is basically formed into a substantially rectangular shape by a beam 1 having a hat cross-sectional structure with an appropriate number of ridges, and a ridge formed in the beam 1, which is attached to the center of the beam 1. When SP material is used as the material for these beams 1 and patches 3, the height of the peaks formed on the beam 1 must be increased to ensure a specified bending strength. It becomes necessary to make the thickness of the beam 1 and patch 3 relatively large (about 1.2 to 3.0 mm) relative to the width of the sheath (about 25 to 35 mm), which increases the weight of the door guard bar G itself and reduces the weight of the vehicle. It causes it to get bigger. Therefore, in the past, as a typical example of this type of door guard bar G, as shown in Figs. In addition to reducing the weight by reducing the plate thicknesses t _b and t _p of the beam 1 and the patch 3, the beam 1 has a substantially U-shaped cross section along its longitudinal direction so that it has a double-hat cross-sectional structure. In addition, a flat patch 3 is attached to the front side of the central part of the beam 1 by welding, and the patch 3 and the peak part 2 of the beam 1 form two approximately rectangular shapes. forming a cross-sectional portion, and further forming a beam 1
A bracket 7 made of mild steel is welded to both ends of the bracket 7 so that it can be easily drawn and welded to the door outer panel 5 or the door inner panel 6 during installation. (For example, Japanese Utility Model Application No. 52-48213) However, in such a conventional door guard bar G, when an impact load is applied to the door guard bar G from the direction of arrow A, both ends thereof are fixed. Therefore, the center part is deformed as shown by the imaginary line in Fig. 2, and as shown in Fig. 3, the center part is deformed from the center line O that vertically divides the approximate center of the approximately rectangular cross section, which mainly guarantees bending strength in terms of structure, as shown in Fig. 3. is also affected by compressive load on the left side, and
The right side part will be subjected to the action of a tensile load. Therefore, the height h _b and the width b _b of the crest 2 of the beam 1 are simply changed to the beam 1 and the patch 3.
When only the plate thicknesses t _{b and} t _p of the plate are made thinner, wall buckling peculiar to thin-walled structures occurs on the left side of the center line O, which is subjected to compressive load, and the wall surface buckling occurs, which is characteristic of thin-walled structures, and the plate passes the displacement point P indicating the peak load on the load-displacement curve. After the collision, the load decreases significantly, and in the event of a side collision, the amount of impact energy absorbed is insufficient, resulting in large deformation of the door D, making it impossible to ensure the safety of the occupants. In addition, b _p in the figure is patch 3
The distance between welding and beam 2 is shown. To explain this relationship based on FIGS. 4 _and 5, the load-displacement curve in the case of a single door guard bar G is shown as a solid line in _FIG . The load gradually decreases after passing the displacement point P indicating the peak load. However, if we simply reduce the plate thicknesses t _{b and} t _p using high-strength steel plates while ensuring the peak load value, the displacement point P indicating the peak load is almost the same, as shown by the broken line, but this After passing the displacement point P, the load decreases rapidly, and the absorption amount of impact energy corresponding to the area of the shaded portion becomes insufficient. This relationship is the fifth
As shown in the figure, almost the same tendency is observed when the door guard bar G is incorporated into the vehicle body B.
The amount of absorption of impact energy corresponding to the area of the shaded portion is insufficient. By the way, if we consider the wall buckling characteristic of thin-walled structures, the thinner the plate thickness t is relative to the plate width b, and the higher the yield point of the material is by using high-tensile steel plates. It is understood that the higher the height, the more likely the material is to cause wall buckling, and that wall buckling means that the material deforms before it yields, which means that the expected load characteristics are not obtained. This means that the properties of the material are not fully utilized. Based on this viewpoint, the present inventors used high-strength steel plates as materials for beams and patches, and even if they tried to reduce the weight by thinning these plates, wall buckling would not occur and the specified level could be achieved. After many years of research into cross-sectional shapes that can ensure bending strength and absorb a large amount of impact energy, the following experimental results show that the patch should have a width that is approximately the same as the width of the crest, and that By forming a stepped portion that fits within the peak at the corresponding position, and forming a substantially rectangular cross section with the peak and the stepped portion, the width of the patch is substantially reduced, and the patch is made of high-strength steel. We have achieved a cross-sectional shape that can make the most of its properties. [Experimental Example] As a cross-sectional shape that does not cause wall buckling, a step portion 4 is formed in a patch 3 within a peak portion 2 of a beam 1 having a single-hat cross-sectional structure, as shown in Fig. 6A. A basic cross-sectional structure is set in which the peak part 2 and the step part 4 form a substantially rectangular cross section, and the beam 1 and the patch 2 are attached by welding. The relationship with the thickness, that is, the ratio of the plate thickness t _b to the height h _b of the peak 2 of the beam 1 t _b /
h _b and the plate thickness t _p relative to the width b _p of the stepped portion 4 of the patch 3
By varying the ratio t _p /b _p respectively, we investigated the conditions under which a sudden drop in load could be prevented after the displacement point indicating the peak load, and used a conventional flat patch 3 as shown in Figure 6 (b). The results of a comparative study with cross-sectional shapes are shown in the table below. In addition, since the flat patch 3 is restrained only at the position where it is welded to the beam 2, the dimension corresponding to the width b _p of the step shown in FIG. This is the distance between welds with 2. In the following table, the 〇 mark indicates a case where a sudden drop in load is not observed after the displacement point where the peak load occurs without causing wall buckling, and the × mark indicates a sudden drop in load due to wall buckling. △ indicates those that are considered to be in a transitional stage.

[Table] As a result of this experiment, in the basic cross-sectional structure shown in Figure 6A, the condition that the load does not drop suddenly after the displacement point at which the peak load occurs without wall buckling is determined at the crest of beam 1. For 2, t _b /h _b ≧
0.046, for step 4 of patch 3, t _p /b _p ≧
It turns out that the condition of 0.027 is necessary.
Furthermore, there was a tendency that as t _b /h _b became smaller, the impact energy absorption characteristics deteriorated, and as t _p /b _p became smaller, the peak load decreased. Furthermore, the height h _p and the plate thickness at the stepped portion 4 of the patch 3
As a result of various studies, we found that the relationship between t and _p is at least
h _p must be at least three times the plate thickness t _p . in this way,
The height h _p of the stepped portion 4 _is at least 3 of the plate thickness t _p
This is necessary since the step 4 is formed to suppress wall buckling, so the step 4 has an almost complete height wall formed as shown in Fig. 7A. Moreover, in the case of high-tensile steel plates, the plate does not elongate well, so when considering the bending radius of the stepped portion 4, it is necessary to have a plate thickness of about t _p at the inner radius r _i of the plate, and This is because the outer half warp r _p of the plate requires approximately twice the plate thickness t _p . If the height h _p of the stepped portion 4 is only about twice the plate thickness t _p , as shown in Fig. 7B, a wall in the height direction cannot be formed in the stepped portion 4. , this stepped portion 4 cannot exert a sufficient function to suppress wall buckling. However, if the height h _p of the step portion 4 is too large, the section modulus of the rectangular cross section formed by the peak portion 2 of the beam 1 will decrease, which will be disadvantageous in terms of bending strength. The height h _p is preferably 3t _p ≦h _p ≦5t _p . [Example] In the first example shown in FIGS. 8 and 9,
The door guard bar G uses high-tensile steel plates as the material for the beam 1 and the patch 3, and the beam 1 has two stripes with a U-shaped cross section along its longitudinal direction so that it has a double-hat cross-sectional structure. Forming the mountain part 2,
A patch 3 is attached to the front side of the central part of this beam 1 by welding, and a stepped part 4 is formed on this patch 3 at a position corresponding to the upper part 2 with approximately the same width as the width of the peak part 2. This stepped portion 4 is fitted into the inside of the peak portion 2 so as to protrude toward the beam 1 side, and furthermore, brackets 7 drawn and formed from a soft steel material are attached to both ends of the beam 1 by welding. It is what it is. Therefore, the peak portion 2 and the step portion 4 form a substantially rectangular cross section, and the rising portion 2a of the peak portion 2 and the rising portion 4a of the step portion 4 are located at substantially the same position. In this first embodiment, the beam 1 is formed such that the ratio t _b /h _b of the plate thickness t _b to the height h _b of the peak portion 2 is 0.046, and the patch 3 is as follows:
The ratio of the plate thickness t _p to the width b _p of the stepped portion 4 is t _p /b _p
0.027, and the height h _p of the stepped portion 4 is three times the plate thickness t _p . The results of drawing a load-displacement curve for the door guard bar G according to the first embodiment show almost the same tendency as shown by the solid line in FIG. It has been found that the present invention can also be applied to a beam 1 having a hat cross-sectional structure. Therefore, when an impact load is applied to the door guard bar G, a compressive load is applied to the part of the beam 1 on the patch 3 side and the patch 3, but since the peak part 2 and the step part 4 form a substantially rectangular cross section, Since the rising portion 2a of the mountain portion 2 and the rising portion 4a of the stepped portion 4 are located at the same position, both rising portions 2a and 4a are combined and work together to resist the compressive load. Since the mutual plate thicknesses of the beam 1 and the patch 3 are set to optimum conditions, wall buckling in combination with the above-mentioned rising portions 2a and 4a is prevented. Furthermore, as shown in FIG. 10A, when installing the conventional door guard bar G inside the door D, the door outer panel 5 and the patch 3 are required to make the overall thickness of the door D as thin as possible to increase the interior space of the vehicle. The gap d between the two is made as small as possible. For this reason, during the electrodeposition coating process for door D, it was difficult for the anti-corrosion paint to penetrate into the gap d, which sometimes caused unevenness in the anti-rust paint, and rainwater etc. easily accumulated in the gap d, causing rust. Although there was a problem that the door guard bar G of the first embodiment was
According to the above, even if the door guard bar G is attached close to the door outer panel 5, the gap d becomes large at the stepped portion 4 formed in the patch 3.
During the electrodeposition coating process, the anticorrosive paint is evenly distributed within the gap d, and rainwater and the like are less likely to accumulate, thereby preventing rust from forming within the gap d. Furthermore, in the door guard bar G of the conventional structure shown in FIG. According to the method, as shown in FIG. 10C, by matching the stepped portion 4 formed on the patch 3 with the accent line 8, it is possible to set the accent line 8 on the door outer panel 5, and the door outer panel It is possible to improve the rigidity of No. 5. Next, in the second embodiment shown in FIG.
As in the case of the first embodiment, the stepped portion 4 of the patch 3
is provided to protrude toward the beam 1 side, and a protrusion 9 is formed in the middle of this step 4 to protrude in the opposite direction to the protruding direction of the step 4, and this door guard bar G is assembled inside the door D. The patch 3 is arranged to be as close to the door outer panel 5 as possible to absorb the impact load efficiently. In the case of this second embodiment as well, it is possible to prevent the load from decreasing after the displacement point indicating the peak load in the load-displacement curve has passed. Further, a plurality of protrusions 9 may be provided. As described above, in the door guard bar of the present invention, the patch has a stepped portion having approximately the same width as the width of the crest of the beam and fitting into the ridge at a position corresponding to the ridge, The peak and the step form a substantially rectangular cross section, and the plate thickness of the peak and the step is set to optimal conditions to prevent the patch from buckling on the wall in the event of a collision. By using high-tensile steel plates as the material for the patch and the patch, the thickness of these plates can be reduced, making it possible to achieve weight reduction while ensuring the same bending strength and impact energy absorption performance as conventional ones. Also, if you use high-strength materials like high-strength steel plates,
By reducing the height of the peak of the beam and reducing the plate thickness, the overall thickness of the door can be made even thinner than before, thereby increasing the interior space of the vehicle. can. Furthermore, being able to reduce the height of the peaks of the beam makes it easier to draw the brackets attached to both ends of the beam, and the brackets can be made of stronger material. Additionally, if the height of the peak is sufficiently small, it is also possible to directly draw both ends of the beam and eliminate the bracket.

[Brief explanation of drawings]

Figure 1 is a side view of a vehicle body with a door guard bar attached, Figure 2 is an explanatory diagram showing a conventional door guard bar with the door shown in Figure 1 in cross section, and Figure 3 is a side view of a vehicle body with a door guard bar attached.
Figure 4 is a graph showing the load-displacement curve of a single door guard bar when only the plate thickness of a conventional door guard bar is simply made thinner. A graph showing the load-displacement curve when the door guard bar is incorporated into the vehicle body. Figure 6A is an explanatory diagram showing the basic cross-sectional shape adopted in the door guard bar of this invention. Figure 6B is the basics of the conventional door guard bar. 7A and 7B are enlarged explanatory views of the stepped portion in the basic sectional shape of FIG. 6A, and FIG. Figure 9 is a sectional view taken along the - line in Figure 8, and Figure 10.
Figure A is a cross-sectional view showing the conventional door guard bar installed inside the door, and Figure 10B is a cross-sectional view showing the door guard bar installed inside the door according to the first embodiment.
FIG. 10C is a cross-sectional view similar to FIG. 10B when an accent line is provided on the door outer panel, and FIG. 11 is a cross-sectional view showing the cross-sectional shape of the door guard bar according to the second embodiment. 1...Beam, 2...Beam peak, 3...Patch, 4...Stepped part of patch, D...Door, G...
Door guard bar, h _b ... Height of the peak of the beam, t _b
...Thickness of the beam, b _p ...Width of the stepped part of the patch,
t _p ...Thickness of the patch, h _p ...Height of the step.

Claims (1)

[Claims] 1. A beam 1 having a cross-sectional structure with a hat having an appropriate number of peaks;
A door guard bar G is formed of a patch 3 that forms a substantially rectangular cross section with a peak part 2 of a beam 1, and is disposed inside a door D to improve the side strength of the automobile.
In the patch 3, a stepped portion 4 having a width b _p that is approximately the same as the width of the ridge portion 2 and fitting into the ridge portion 2 is formed at a position corresponding to the ridge portion 2, and the step portion 4 is fitted into the ridge portion 2. 2 and the stepped portion 4 constitute the above-mentioned rectangular cross section, and the peak portion 2 has a ratio t _b /h _{b of the plate thickness t b to} its height h _b of 0.046 or more, and the stepped portion 4 has a A door guard bar for an automobile, characterized in that the ratio t _p /b _{p of the plate thickness t p to} the width b _p is 0.027 or more. 2 The step part 4 has a ratio of height h _p to its plate thickness t _p h _p /
The door guard bar for an automobile according to claim 1, characterized in that t _p is a numerical value of 3 or more. 3. The automobile according to claim 1 or 2, characterized in that a protrusion 9 is provided at an intermediate portion of the step 4 of the patch 3, the protrusion 9 projecting in a direction opposite to the direction in which the step 4 projects. door guard bar.