JP3480226B2 - Front side member collision energy absorption structure - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a collision energy absorbing structure of a front side member, and more particularly to a collision energy absorbing structure of a front side member disposed at a front portion of a vehicle body. 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 an automobile body, there is an actual open flat tire 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, the first bead 102 and the second bead 104 located at the forefront of the front side member 100 at the time of a frontal collision. The first buckling portion begins to buckle first (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. According to the present invention, a rigid member is attached to a front end of a front side member extending in the front-rear direction of a vehicle, and is provided behind the rigid member.
Multiple buckling triggers are placed at predetermined intervals along the vehicle longitudinal direction with respect to the crush bead that triggers buckling.
A collision energy absorbing structure for a front side member in which a crush bead is set, the crush bead serving as a trigger for a first buckling immediately after the rigid member.
Crash bi from over de that triggers the first buckling
The crush that trigger of the second buckling at the back of over de
When the length to the bead is wavelength λ, the first buckling occurs.
3λ from the crash bead to the rear of the vehicle
The position of / 4 is defined as a boundary line, and the thickness of the front part is smaller than the thickness of the rear part at the boundary line. [0007] Therefore, when the vehicle collides, the front side member becomes a crush that triggers the first buckling.
Yubido and crash Bee that triggers the second of buckling
Between the de buckles. At this time, at the front side member, at the boundary formed at a position of 3λ / 4 rearward of the vehicle from the crash bead that triggers the first buckling ,
Since the thickness of the front portion is smaller than the thickness of the rear portion, the first side member has a smaller thickness than the case where the thickness of the front side member is constant.
Crush bead and second buckle trigger buckling
The buckling load at the time of buckling of the first buckling portion between the first buckling portion and the crush bead which triggers the buckling is reduced. As a result, the initial irregularity (cross-sectional deformation) at the second buckling portion adjacent to the vehicle rear side caused by the impact when the front side member buckles at the first buckling portion is minimized, It is smaller than when the thickness of the front side member is constant.
Therefore, at the time of a front collision, the deceleration caused by the buckling of the second buckling portion is larger than the deceleration caused by the buckling of the first buckling portion. As a result, as the deformation stroke increases, the peak value of the deceleration increases without fail, and the energy absorption characteristics are stabilized. 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. An embodiment of a structure for absorbing a collision energy of 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 this 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, the deformation mode is such that 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, experimentally and experimentally, 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 made thinner. 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. According to the first aspect of the present invention, a rigid member is attached to the front end portion of the front side member extending in the front-rear direction of the vehicle, and is a trigger for buckling provided behind the rigid member.
Crash that triggers multiple buckling at predetermined intervals along the vehicle longitudinal direction based on the crash bead
A collision energy absorbing structure for a front side member having a bead , wherein a first buckling member immediately behind a rigid member is provided.
The first buckling trigger from the triggering bead
The second buckle behind the crush bead
Assuming that the length to the crush bead that triggers is a wavelength λ, the position of 3λ / 4 from the crush bead that triggers the first buckling to the rear of the vehicle is a boundary line. The thickness of the front part is made thinner than the rear part, so the front side member can be made thinner and the front side member can be made lighter without reducing the energy absorption of the front side member. Have. [0036]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view showing a collision energy absorbing structure of a front side member according to one 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. [Description of Signs] 10 Front side member 24 Crush bead 26 Crush bead 28 Crush bead 30 First buckling part 32 Second buckling part

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-26133 (JP, A) JP-A-7-329826 (JP, A) JP-A-7-165109 (JP, A) 319308 (JP, A) Japanese Utility Model 2-24777 (JP, U) Japanese Utility Model 7-42737 (JP, U) Japanese Utility Model 6-27439 (JP, U) Japanese Utility Model 5-12361 (JP, U) Shokai 61-67281 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B62D 21/15 B62D 25/00-25/08 B62D 25/14-25/22 B62D 17 / 00-23/00 B62D 27/00-29/04

Claims (1)

(1) 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 a buckling trigger provided at the rear of the rigid member and serving as a trigger for buckling is used as a reference. At predetermined intervals along the longitudinal direction of the vehicle,
A collision energy absorbing structure for a front side member in which a crush bead that triggers buckling is set, wherein a first buckling trigger immediately after the rigid member is provided.
Rush bead triggers the first buckle
The second buckle behind the rush bead
When the length to the crush bead is a wavelength λ, the position of 3λ / 4 from the crush bead which triggers the first buckling to the rear of the vehicle is defined as a boundary line, and the thickness of the front portion is determined at the boundary line. The collision energy absorbing structure of the front side member, characterized in that the thickness is smaller than the thickness of the rear part.