TECHNICAL FIELD
[0001] The present disclosure relates to an impact absorbing member.
BACKGROUND ART
[0002] There is known an impact absorbing member that absorbs an
10 impact by being crushed in an axial direction. When a load is input in such
an impact absorbing member in its axial direction, buckling proceeds
continuously in a bellows shape in the member, to thereby absorb the impact.
The impact absorbing member is arranged at a tip of a side member (a front
side member or a rear side member) as a crash box in a vehicle body of an
15 automobile, for example.
[0003] For example, Patent Document 1 discloses an impact absorbing
member having a groove portion that is recessed inward of a contour, in a part
of a region of at least one side of a basic cross section, at a position that is not
an end point of the side. Further, Patent Document 2 discloses a die-cast
20 aluminum alloy crash can in which a material modified portion is provided on
a peripheral wall of a cylindrical portion so as to partially reduce strength
against compression in a vehicle longitudinal direction. Further, Patent
Document 3 discloses an impact absorbing member in which corner wall
portions for forming a second closed cross section portion with a rectangular
25 cross section extending in a longitudinal direction, in cooperation with a part
of a lateral wall portion and a part of a vertical wall portion, are each provided
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in four corner portions of a first closed cross section portion, the corner wall
portions in the four corner portions being separated from each other. Further,
Patent Document 4 discloses a collision energy absorbing structure in which a
cross-sectional shape of a cross section perpendicular to an axial direction is a
5 polygonal shape that is symmetrical with respect to a center of the cross
section, and is not symmetrical with respect to a center line of the cross
section. In this energy absorbing structure, when an outside contour of the
above-described cross section is set to a quadrangle, an aspect ratio is less
than 1.5, and a ratio of lengths of adjacent sides among sides of the polygon
10 constituting the cross section is 2.3 or less.
PRIOR ART DOCUMENT
PATENT DOCUMENT
[0004] Patent Document 1: International Publication Pamphlet No. WO
15 2005-010398
Patent Document 2: Japanese Laid-open Patent Publication No.
2012-166641
Patent Document 3: Japanese Laid-open Patent Publication No.
2017-141860
20 Patent Document 4: Japanese Laid-open Patent Publication No.
2011-218935
SUMMARY OF THE INVENTION
PROBLEMS TO BE SOLVED BY THE INVENTION
25 [0005] An impact absorbing member is required to have both impact
absorbing performance and lightness in weight. The present disclosure was
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made in view of the above-described circumstances, and a main object thereof
is to provide an impact absorbing member with good balance between the
impact absorbing performance and the lightness in weight.
5 MEANS FOR SOLVING THE PROBLEMS
[0006] An aspect of the present disclosure is characterized in that it is an
impact absorbing member that absorbs an impact by being crushed in an axial
direction, the impact absorbing member having a cylindrical shape extending
along the axial direction, in which when a cross section perpendicular to the
10 axial direction of the impact absorbing member is set to a first cross section,
and a cross section defined by extension lines of a plurality of sides in the first
cross section is set to a second cross section, the second cross section is a
polygon, the first cross section includes a shared vertex that is shared by the
second cross section, and a recessed groove that is positioned to correspond to
15 a vertex of the second cross section, and an interior angle of at least one
vertex of the first cross section is 100° or more.
[0007] According to the present disclosure, the first cross section includes
the shared vertex and the recessed groove, so that it is possible to obtain an
impact absorbing member with good balance between impact absorbing
20 performance and lightness in weight (impact absorbing performance per
weight).
[0008] In the above disclosure, it is also possible that the first cross
section includes a plurality of the shared vertices and the recessed grooves,
and the shared vertex and the recessed groove are alternately arranged along a
25 peripheral direction of the first cross section.
[0009] In the above disclosure, it is also possible that the first cross
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section includes a plurality of the shared vertices and the recessed grooves,
and at least two of the recessed grooves are arranged at positions
corresponding to respective vertices on the same diagonal line in the second
cross section. The diagonal line is the longest diagonal line out of a plurality
5 of diagonal lines extending from one vertex.
[0010] In the above disclosure, it is also possible that lengths of adjacent
sides are different in the first cross section.
[0011] In the above disclosure, it is also possible that a non-planar
portion is provided to make widths of adjacent planar portions have mutually
10 different lengths.
[0012] In the above disclosure, it is also possible that, in the first cross
section, each interior angle of less than 180° is 75° or more and 135° or less,
and each angle of a bottom vertex in the recessed groove is 75° or more and
135° or less.
15 [0013] In the above disclosure, it is also possible that the first cross
section does not have a flange portion.
[0014] In the above disclosure, it is also possible that the first cross
section does not have a partition wall portion in the inside thereof.
20 EFFECT OF THE INVENTION
[0015] The impact absorbing member in the present disclosure brings
about an effect of providing a good balance between the impact absorbing
performance and the lightness in weight.
25 BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic perspective view exemplifying an impact
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absorbing member in the present disclosure.
FIG. 2 is a schematic sectional view exemplifying the impact
absorbing member in the present disclosure.
FIGS. 3(a) to 3(d) are schematic sectional views each exemplifying a
5 conventional impact absorbing member.
FIG. 4 is a schematic sectional view exemplifying the impact
absorbing member in the present disclosure.
FIG. 5 is a schematic sectional view exemplifying the impact
absorbing member in the present disclosure.
10 FIGS. 6(a) to 6(d) are schematic sectional views each exemplifying an
impact absorbing member in the present disclosure.
FIGS. 7(a) to 7(c) are schematic perspective views and schematic
sectional views exemplifying impact absorbing members in the present
disclosure.
15 FIGS. 8(a) to 8(c) are schematic sectional views exemplifying impact
absorbing members in an example 1 and comparative examples 1 and 2,
respectively.
FIG. 9 is a result of FEM analysis in the example 1 and the
comparative examples 1 and 2.
20 FIG. 10 is a result of FEM analysis in an example 2.
FIG. 11 is a result of FEM analysis in an example 3.
FIGS. 12(a) and 12(b) are schematic front views exemplifying
buckling deformation modes.