JPH10244955A - Collision energy absorbing structure of front side member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To thin the plate thickness of the front part of a front side member and lighten the front side member without reducing the energy absorption amount of the front side member. SOLUTION: In a front side member 10, the plate thickness of a front part 10A is thinner than that of a rear part 10B at its boundary line 34. Therefore, in comparison with the case in which the plate thickness of the front side member 10 is made to constant, a buckling load at the buckling time of a first buckling part 30 between a bead 24 and a bead 26 is lowered. Consequently, an initial irregularity (section deformation) on a second buckling part 32 generated by the shock when the front side member 10 is buckled at the first bulking part 30 is restrained to the minimum and reduced in comparison with the case in which the plate thickness of the front side member 10 is made to constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a collision energy absorbing structure for a front side member, and more particularly to a collision energy absorbing structure for a front side member disposed at a front portion of an automobile body.

[0002]

2. Description of the Related Art Conventionally, as an example of a structure for absorbing a collision energy of a front side member disposed at a front portion of a vehicle body, there is Japanese Utility Model Laid-Open No. 7-42737.

As shown in FIG. 10, in this front side member 100, first to third beads 102, 1 are provided on a front side wall 100A at predetermined intervals in the vehicle longitudinal direction.
Nos. 04 and 106 are formed, and a notch 10 continuous with each bead 102, 104 and 106 is formed in a corner below the side wall 100A.
8, 110 and 112 are provided. Notches 108, 11
The length in the vehicle front-rear direction of 0, 112 is set to be longer than the concave portion 114 forming each bead 102, 104, 106 at the corner above the side wall 100A. As a result, the lower side of the side wall 100A is more easily deformed than the upper side against the impact load at the time of a frontal collision, and the front portion of the front side member 100 is bent at the time of a frontal collision (hereinafter, referred to as a frontal collision). Instead, it is buckled and deformed so as to contract along the extending direction.

[0004]

However, in the collision energy absorbing structure of the front side member, at the time of a front collision, the front side member 100 is located between the first bead 102 and the second bead 104 at the forefront. The first buckling portion first starts buckling (at this time, the deceleration G
1) At this time, an impact is also applied to the second buckling portion between the second bead 104 and the third bead 106 located rearward of the first buckling portion, and the second buckling portion is applied. Deformation also occurs (initial irregularity). Therefore, as shown by the dashed line in FIG. 9, in the front side member 100, after the first buckling portion is deformed, the deceleration acceleration G2 when the second buckling portion is deformed decreases. Ensuring energy absorption is inefficient due to the size and thickness of the cross-section of the front side member, and it is necessary to enlarge the cross-section of the front side member and increase the thickness in order to ensure the required energy absorption. Also, to attach rigid members such as transport hooks and front cross members to the front end of the front side members,
As shown in FIG. 10, if the cross section of the front side member is reduced toward the front of the vehicle, or if a notch is provided in the front side member, the support rigidity of a rigid member such as a transport hook or a front cross member decreases.

In view of the above facts, the present invention provides a collision energy absorbing structure for a front side member that can reduce the thickness of the front portion of the front side member and reduce the weight of the front side member without reducing the amount of energy absorption. That is the purpose.

[0006]

According to the present invention, a rigid member is attached to a front end portion of a front side member extending in the front-rear direction of a vehicle, and the vehicle is referenced to a buckling portion provided behind the rigid member. A collision energy absorbing structure for a front side member in which a plurality of buckling portions are set at predetermined intervals along a front-rear direction, wherein a plate thickness of a first buckling portion immediately after the rigid member is set to the It is characterized in that it is thinner than the thickness of the second buckling portion behind the first buckling portion.

Therefore, at the time of a front collision, the peak value of the deceleration at the time of deformation at the first buckling portion on the vehicle front side of the thin side front member decreases, and the impact transmitted to the second buckling portion is reduced. Can be reduced. As a result, the peak value of the deceleration caused by the deformation of the first buckling portion on the vehicle front side of the front side member decreases, and the second buckling on the vehicle rear side of the thick front side member is reduced. The peak value of the deceleration caused by the deformation of the part increases. Therefore, it is possible to reduce the thickness of the front part of the front side member and reduce the weight of the front side member without reducing the amount of energy absorption.

According to a second aspect of the present invention, there is provided the collision energy absorbing structure for a front side member according to the first aspect, wherein each of the buckling portions is provided on the front side member at a predetermined interval along the longitudinal direction of the vehicle. It is characterized by comprising a formed crush bead.

Therefore, the first buckling portion and the second buckling portion can be easily formed by the crash bead.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a collision energy absorbing structure for a front side member according to the present invention will be described with reference to FIGS.

In the drawings, an arrow FR indicates a vehicle forward direction, an arrow UP indicates a vehicle upward direction, and an arrow IN indicates a vehicle width inside direction.

As shown in FIG. 3, the front side members 10 of the present embodiment are arranged in a pair of right and left sides (the front right side member on the right side of the vehicle is not shown) along the longitudinal direction of the vehicle body in the vicinity of both lower ends in the vehicle width direction. I have.

As shown in FIG. 4, the front side member 10 includes a front side member outer panel 12 constituting an outer portion of the front side member 10 in the vehicle width direction;
The front side member 10 includes a front side member inner panel 14 that forms an inner portion in the vehicle width direction.

The cross-sectional shape of the front side member inner panel 14 as viewed from the vehicle front-rear direction is a U-shape with the opening directed outward in the vehicle width direction. It is a flange 14B. A flange 14D is formed downward at the outer end in the vehicle width direction of the lower wall portion 14C of the front side member inner panel 14.

As shown in FIG. 5, a flange 12A is formed at the upper end of the front side member outer panel 12 outward in the vehicle width direction.
A is joined to the lower surface of the flange 14B of the front side member inner panel 14. A lower edge 12B of the front side member outer panel 12 is joined to a vehicle width direction outer surface of a flange 14D of the front side member inner panel 14.

Accordingly, the front side member 10 has a closed cross-sectional structure having a rectangular cross section extending in the vehicle front-rear direction with the front side member outer panel 12, the front side member inner panel 14, and the vehicle front-rear direction.

As shown in FIG. 4, a front side member extension 16 for attaching a transport hook (not shown) is joined to the front end of the front side member outer panel 12, and the front side member extension 16 A front bumper mount bracket 18 is provided between the front side member 14 and the front end 14E of the front side member inner panel 14.

As shown in FIG. 3, the front bumper mount bracket 18 is fixed to the front end of the front side member 10 by two upper and lower bolts 20 and nuts (not shown). A bolt 20 for fixing the bumper reinforcement protrudes from the front surface 18A.

Crush beads 24, 26, 28 are formed at predetermined intervals in the vehicle longitudinal direction at upper and lower ridgelines 14F, 14G of the front side member inner panel 14.

As shown in FIG. 2, a crush bead 24 that triggers the first buckling of the front side member 10 is formed immediately after the front side member extension 16, and the front side member 10
Crash bead 24 and crash bead 26 at frontal collision
Is the first buckling portion 30, and the crush bead 2
The space between the bump 6 and the crush bead 28 is the second buckling portion 32.

As shown in FIG. 6, the cross-sectional deformation mode of the crush bead 24 when it buckles is a deformation mode in which the cross section expands from the original position (the position indicated by the two-dot chain line in FIG. 6) in the vehicle width direction. The cross-sectional deformation mode at the time of buckling at the intermediate position between the crush bead 24 and the crush bead 26 is shown in FIG.
As shown in FIG. 7, a deformation mode in which the cross section expands in the vertical direction from the original position (the position indicated by the two-dot chain line in FIG. 7). The cross-sectional deformation mode of the front side member 10 at the time of a front collision is a so-called axial compression mode in which the cross-sectional deformation modes shown in FIGS. 6 and 7 appear regularly along the vehicle front-rear direction.

Generally, the wavelength λ of the axial compression mode is λ = (L1 + L2) / 2, as shown in FIG. 5, by the width L1 and the height L2 of the cross section of the front side member 10.
Indicate with.

At this point, as shown in FIG. 2, at the position of the crush bead 26, the same cross-sectional deformation mode as the cross-sectional deformation mode of the crush bead 24 (cross-sectional deformation mode in FIG. 6) is taken. Is the wavelength λ. In this case, the width L1 and the height L2 of the cross section of the front side member 10 are obtained from the width L1 and the height L2 of the cross section at an intermediate position between the crush bead 24 and the crush bead 26. Since the width L1 and the height L2 are different from the width L1 and the height L2 of the cross section at the position of the crush bead 26, the experimental experience shows that the width L1 and the height L2 of the cross section at the position of the crush bead 24 are used. The constant a (a =
1.0 to 1.2, for example, a = 1.1))
(L1 + L2) / 2 is determined.

In the first buckling deformation region, a cross-sectional deformation generated by the crush bead 24 and a cross-sectional deformation generated between the crush bead 24 and the crush bead 26 are generated as a set. Deformation area F
1 is substantially λ from the crash bead 24 to the front of the vehicle.
From the position of / 4, a region of 3λ / 4 from the crash bead 24 to the rear of the vehicle is formed, and no cross-sectional deformation occurs at the front end and the rear end of this region.

The deformation area F2 rearward from the crash bead 24 to the rear of the vehicle by 3λ / 4 becomes a deformation area due to the second buckling.

Therefore, as shown in FIG. 1, 3λ / 4 from the crush bead 24 where no cross-sectional deformation occurs to the rear of the vehicle.
Is defined as a boundary line 34. At this boundary line 34, materials having different plate thicknesses are joined by laser welding or the like, so that the plate thickness of the front portion 10A of the front side member 10 is made smaller than the plate thickness of the rear portion 10B. I have.

Next, the operation of the present embodiment will be described. When the vehicle collides forward, the first side buckling portion 30 between the bead 24 and the bead 26 buckles in the front side member 10 triggered by the bead 24. At this time, in the front side member 10 of the present embodiment, since the plate thickness of the front portion 10A is smaller than the plate thickness of the rear portion 10B at the boundary line 34, when the plate thickness of the front side member 10 is constant. In comparison, the buckling load when the first buckling portion 30 between the bead 24 and the bead 26 buckles is reduced. As a result, the initial irregularity (cross-sectional deformation) at the second buckling portion 32 caused by the impact when the front side member 10 buckles at the first buckling portion 30 is minimized as shown by the solid line in FIG. This is smaller than the case where the thickness of the front side member 10 is made constant (the case shown by the two-dot chain line in FIG. 8).

Therefore, as shown by the solid line in FIG. 9, the deceleration G1 generated by the buckling of the first buckling portion 30 at the time of a front collision.
Thus, the deceleration G caused by the buckling of the second buckling portion 32
2 is larger. As a result, as the deformation stroke increases, the peak value of the deceleration increases without fail, and the energy absorption characteristics are stabilized.

At this time, the front side member 10
The reduction in the amount of energy absorption in the first buckling portion 30 caused by making the plate thickness of the front portion 10A smaller than that of the rear portion 10B of the front side member 10 is caused by the second buckling portion 32 Almost all can be covered by increasing the load when bending.
In addition, since the cross-sectional shape of the front side member 10 is not changed along the vehicle front-rear direction, the deformation wavelength along the vehicle front-rear direction does not change.

Further, since the deceleration G2 generated in the second buckling portion 32 is larger than the deceleration G1 generated in the first buckling portion 30, for example, the deceleration acceleration for starting the airbag device or the like. When G is detected by the acceleration sensor, the threshold value is set to the deceleration G1 generated in the first buckling portion 30.
And the deceleration G2 generated in the second buckling portion 32. For this reason, it is easy to detect the deceleration G of activation of the airbag device or the like, and the cost of the device can be reduced.

Further, in the collision energy absorbing structure of the front side member according to the present embodiment, the front side member 1
The thickness of the front portion of the front side member 10 can be reduced without reducing the energy absorption amount of zero, and the front side member 10 can be reduced in weight.

Further, in the collision energy absorbing structure of the front side member according to the present embodiment, the front side member 1
Since the cross-sectional shape of 0 is not changed in the vehicle longitudinal direction, the deformation wavelength along the vehicle longitudinal direction does not change. In addition, the cross section of the front end portion of the front side member 10 has a sufficient size, and sufficient rigidity for supporting a rigid member such as a transport hook or a front cross member can be secured.

Further, in the collision energy absorbing structure of the front side member according to the present embodiment, the buckling portion is formed of the crash bead formed on the front side member 10 at a predetermined interval along the vehicle front-rear direction. It is. In addition, since the notch is not arranged, there is no need to increase the number of forming steps, and there is no possibility that muddy water or the like may enter the cross section of the front side member and accumulate during traveling. Further, in the collision energy absorbing structure of the front side member of the present embodiment, the thickness of the front portion 10A of the front side member 10 is
The structure is basically the same as that of the conventional structure except that the thickness of the rear portion 10B of the front side member 10 is smaller than that of the conventional structure.

In the above, the present invention has been described in detail with respect to a specific embodiment. However, the present invention is not limited to such an embodiment, and various other embodiments are included within the scope of the present invention. It is clear to a person skilled in the art that is possible.

[0035]

According to the first aspect of the present invention, a rigid member is attached to the front end portion of a front side member extending in the longitudinal direction of the vehicle, and the buckling portion provided behind the rigid member is used as a reference along the longitudinal direction of the vehicle. In a collision energy absorbing structure of a front side member in which a plurality of buckling portions are set at predetermined intervals, a plate thickness of a first buckling portion immediately after a rigid member is set to:
Since the thickness of the second buckling portion behind the first buckling portion is thinner than that of the second buckling portion, the thickness of the front portion of the front side member can be reduced without reducing the energy absorption of the front side member. It has an excellent effect that the front side member can be reduced in weight.

According to a second aspect of the present invention, in the collision energy absorbing structure for a front side member according to the first aspect, each buckling portion is formed on the front side member at a predetermined interval along the vehicle longitudinal direction. Since the crush bead is used, it has an excellent effect that manufacture is easy in addition to the effect described in the first aspect.

[Brief description of the drawings]

FIG. 1 is a side view showing a collision energy absorbing structure of a front side member according to an embodiment of the present invention.

FIG. 2 is a schematic side view showing a deformation mode of a collision energy absorbing structure of a front side member according to one embodiment of the present invention.

FIG. 3 is a perspective view showing the collision energy absorbing structure of the front side member according to the embodiment of the present invention, as viewed from obliquely inside the front of the vehicle.

FIG. 4 is an exploded perspective view showing the collision energy absorbing structure of the front side member according to the embodiment of the present invention, as viewed obliquely from the front inside the vehicle.

FIG. 5 is a sectional view taken along line 5-5 in FIG. 1;

FIG. 6 is a schematic cross-sectional view showing a deformation mode of the collision energy absorbing structure of the front side member according to one embodiment of the present invention.

FIG. 7 is a schematic cross-sectional view showing a deformation mode of the collision energy absorbing structure of the front side member according to one embodiment of the present invention.

FIG. 8 is a schematic plan view showing a deformation mode of the collision energy absorbing structure of the front side member according to one embodiment of the present invention.

FIG. 9 is a graph showing a relationship between a deformation stroke and a deceleration of the collision energy absorbing structure of the front side member according to the embodiment of the present invention.

FIG. 10 is a perspective view showing a collision energy absorbing structure of a front side member according to a conventional embodiment, as viewed obliquely from the front of the vehicle.

[Explanation of symbols]

 Reference Signs List 10 front side member 24 crush bead 26 crush bead 28 crush bead 30 first buckling part 32 second buckling part

Claims (2)

[Claims] 1. A rigid member is attached to a front end portion of a front side member extending in a front-rear direction of a vehicle, and a plurality of seats are provided at predetermined intervals along a vehicle front-rear direction with reference to a buckling portion provided behind the rigid member. A collision energy absorbing structure of a front side member having a bent portion, wherein a thickness of a first buckling portion located immediately after the rigid member is reduced by a second seat located behind the first buckling portion. A collision energy absorbing structure for a front side member, characterized in that it is thinner than a plate thickness of a bending portion. 2. The front side member according to claim 1, wherein each of the buckling portions is constituted by a crash bead formed on the front side member at a predetermined interval in the longitudinal direction of the vehicle. Construction.