DESCRIPTION
Title of Invention: Shock Absorbing Member
5 Technical Field
[OOOl] The present invention relates to a shock
absorbing member which absorbs externally-applied impact
energy while buckling.
10 Background Art
[0002] In recent years, in the automotive field, etc.,
improvement in fuel efficiency and motion performance
have been sought, while improvement in collision safety
has also been sought. As a chassis of a motorcar, in
15 order to balance reduced weight and high stiffness, a
chassis structure referred to as a "monocoque body,"
wherein a frame and a body are integrally formed, is
generally used. Further, in the chassis of a motorcar,
in order to maintain a survival space for a driver and a
20 passenger in a collision, a shock absorblmstructure is
i-- -
generally used, wherein a space (for example, an engine
room or a luggage room) other than a cabin is
preferentially collapsed, so that impact load applied to
the cabin is attenuated as much as possible and the
25 deformation of the cabin is minimized.
[0003] Therefore, in order to constitute a chassis
structure with high collision-safety performance, it is
important to effectively absorb the impact energy at the
time of collision. To this end, a shock absorbing member
30 for effectively absorbing the impact energy at the time
of collision has been strenuously developed (for example,
see Patent Literatures 1 to 15).
[0004] Generally, as a shock absorbing member, a
hollow columnar thin-walled structure (or a hollow
35 columnar member) manufactured by jointing press-formed
steel plates by welding, etc., is used. In order to
balance reduced weight and high stiffness, as described
above, the shock absorbing member is constituted by a
hollow member having a polygonal cross-section such as a
tetragon or a hexagon. Such a shock absorbing member is
used as a front-side member of a chassis, for example,
5 and absorbs the impact energy by buckling in an axial
direction (or axial crushing) when impact load is applied
to one end of the member at the time of collision.
Therefore, in order to improve the shock-absorbing
performance, it is important to effectively generate such
10 buckling and increase the buckling load thereof.
[0005] In the prior art, in order to solve the above
problems in terms of material, a relatively thick or
relatively high-strength steel plate is used to
manufacture a shock absorbing plate so as to increase the
15 buckling load. On the other hand, as a structural
measure, a dimple (or a bead) providing the origin of the
buckling is arranged so as to effectively generate the
buckling. Further, by forming a cross-section of the
hollow shock absorbing member as a polygonal shape, the
20 buckling load is increased.
[0006] However, when the plate thickness of the above
shock absorbing member is increased, the weight of the
member is increased, whereby the weight of a chassis
including the shock absorbing member is also increased.
25 As a result, fuel efficiency and driving performance of a
motorcar are deteriorated. Further, in a high-strength
steel plate, the degree of elongation is generally
decreased in inverse proportion to the strength thereof.
Therefore, the formability of a high-strength steel plate
30 is not good, and thus there are limitations to increasing
the strength of a steel plate for the shock absorbing
member at present.
[ 0 0 0 7 1 Incidentally, when the buckling load of the
shock absorbing member is solely increased, a minimum
35 impact load for generating the buckling is increased. In
this case, the impact load applied to the shock absorbing
member is not absorbed by the deformation of the shock
absorbing member, whereby the impact load with no change
is transmitted to another structure such as a cabin.
Further, a risk of injury to driver and a passenger is
increased, since a portion which is not to be deformed is
5 buckled; it is difficult to keep a survival space for the
drive and the passenger due to the deformation of the
cabin; or a significant change of acceleration is applied
to the driver and the passenger.
[ 0 0 0 8 ] Therefore, for example, the shock absorbing
10 member is configured as a straight member in order to
keep the cross-section from a start end of the buckling
constant as much as possible, and secure a certain amount
of deformation due to the buckling. Further, in order to
reduce an initial impact load applied to the shock
15 absorbing member, the shock absorbing member is stably
buckled into concertinas due to an arrangement of the
beads as described above.
[0009] However, there is no firm theory for
determining the above arrangement of the beads, and at
20 present, the arrangement is determined by repeatedly
buckling test or a computer simulation regarding the
shock absorbing member. Accordingly, it is necessary to
repeatedly carry out the above test or simulation in
relation to each kind of chassis, whereby design
25 efficiency is deteriorated. Moreover, since various load
conditions or buckling modes predicted when actual
collision cannot be dealt with, it is very difficult to
optimize the arrangement of the beads by using the above
techniques.
30
Citation List
Patent Literature
[ 0 0 10 ] PLT 1: Japanese Unexamined Patent Publication
(kokai) No. 2009-286221
35 PLT 2: Japanese Unexamined Patent Publication (kokai)
No. 2009-285668
PLT 3: Japanese Unexamined Patent Publication (kokai)
No. 2009-168115
PLT 4: Japanese Unexamined Patent Publication (kokai)
No. 2009-154587
PLT 5: Japanese Unexamined Patent Publication (kokai)
5 No. 2009-113596
PLT 6: Japanese Unexamined Patent Publication (kokai)
No. 2008-018792
PLT 7: Japanese Unexamined Patent Publication (kokai)
No. 2007-030725
10 PLT 8: Japanese Unexamined Patent Publication (kokai)
No. 2006-207726
PLT 9: Japanese Unexamined Patent Publication (kokai)
No. 2006-207724
PLT 10: Japanese Unexamined Patent Publication
15 (kokai) No. 2005-225394
PLT 11: Japanese Unexamined Patent Publication
(kokai) No. 2005-153567
PLT 12: Japanese Unexamined Patent Publication
(kokai) No. 2005-001462
20 PLT 13: Japanese Unexamined Patent Publication
(kokai) No. H10-138950
PLT 14: Japanese Unexamined Patent Publication
(kokai) No. H09-277954
PLT 15: Japanese Unexamined Patent Publication
25 (kokai) No. H09-277953
PLT 16: Japanese Unexamined Patent Publication
(kokai) No. 2011-056997
Summary of Invention
30 Problem to be Solved by the Invention
[OOll] Incidentally, in buckling modes (or compactmodes)
wherein the above shock absorbing member is
buckled into concertinas, a "concave-convex mixed mode"
and a "concave-convex independent mode" are included.
35 The concave-convex mixed mode is a deformation mode
wherein both a concave portion and a convex portion of
concertinas are present in an arbitrary transverse crosssection
of a hollow columnar shock absorbing member which
is buckled into concertinas by impact load. On the other
hand, the concave-convex independent mode is a
deformation mode wherein only a concave portion or a
5 convex portion is present in the arbitrary transverse
cross-section. In this regard, a ratio of a deformed
portion to the entire member in the concave-convex
independent mode is larger than that in the concaveconvex
mixed mode. Therefore, in the concave-convex
10 independent mode, an amount of impact energy absorption
relative to an amount of deformation (or an amount of
crushing) is relatively high, and thus improved shockabsorbing
performance can be obtained.
[0012] In a conventional shock absorbing member,
15 various approaches have been made for increasing the
amount of impact energy absorption while buckling the
member into concertinas in the axial direction. However,
there has been no approach for purposely induce the above
concave-convex independent mode. In other words, in the
20 compact mode of the conventional shock absorbing member,
the concave-convex mixed mode is a major mode, and a
mechanism for generating the concave-convex independent
mode has not been found.
[0013] The present invention was made in view of the
25 above background, and an object of the invention is to
provide a shock absorbing member having improved shockabsorbing
performance, in particular, a shock absorbing
member capable of purposely inducing the concave-convex
independent mode.
30
Means for Solving the Problem
[0014] In order to solve the above problems, the
present invention provides a hollow columnar shock
absorbing member having an axis (0), a plurality of
35 rectangular walls extending parallel to the axis, and a
polygonal cross-section perpendicular to the axis, the
shock absorbing member extending in the direction of the
axis and absorbing externally-applied impact energy while
buckling in a direction of the axis, wherein the shock
absorbing member is provided with at least two flanges
protruding from at least two edges formed by at least two
5 sets of neighboring walls among a plurality of walls, and
the at least two flanges are arranged so that directions
of protrusion of the flanges from the edges are directed
to the same direction with respect to a circumferential
direction.
10 [0015] The shock absorbing member may be provided with
a bead on at least one of the walls. The bead may be a
dimple which dents from an outer surface of the shock
absorbing member or a bulge which bulges from the outer
surface. It is preferable that the dimple be positioned
15 so as to be deviated towards the edge positioned on a
side opposite to the direction of protrusion of the
flange with respect to the circumferential direction, and
the bulge be positioned so as to be deviated towards the
edge positioned on a side in the direction of protrusion
20 of the flange with respect to the circumferential
direction.
[0016] Further, the concave-convex independent mode
can be purposely induced by forming a buckling inducing
portion for determining a direction of inclination formed
25 on the wall and/or the edge of the shock absorbing
member, so that a ridge of each edge is inclined in the
same direction with respect to a circumferential
direction of the shock absorbing member at the beginning
of the buckling, when the shock absorbing member is
30 buckled in the direction of the axis.
Effects of Invention
[0017] According to the present invention, a shock
absorbing member having improved shock-absorbing
35 performance can be provided, in particular, the shock
absorbing member can be effectively buckled in the
direction of the axis by purposely inducing the concaveconvex
independent mode. As a result, the amount of
externally-applied impact energy absorption is increased,
and improved shock-absorbing performance can be obtained.
5 Brief Description of Drawings
[ 0 0 18 ] Fig. 1A is a perspective view of a hollow
columnar member having a square hollow cross-section,
wherein deformation of the member when impact load is
applied to one end thereof in an axial direction is
10 calculated by FEM numerical analysis, the view showing a
state in which the member is bent by local buckling.
Fig. 1B is a perspective view of a hollow columnar
member similar to Fig. lA, wherein deformation of the
member is calculated by FEM numerical analysis, the view
15 showing a non-compact mode in which the member is
irregularly buckled in the axial direction.
Fig. 1C is a perspective view of a hollow columnar
member similar to Fig. lA, wherein deformation of the
member is calculated by FEM numerical analysis, the view
20 showing a concave-convex mixed mode among compact modes
in which the member is buckled into concertinas in the
axial direction.
Fig. ID is a perspective view of a hollow columnar
member similar to Fig. lA, wherein deformation of the
25 member is calculated by FEM numerical analysis, the view
showing a concave-convex independent mode among the
compact modes in which the member is buckled into
concertinas in the axial direction.
Fig. 2A is a schematic view for exemplifying an
30 arbitrary transverse cross-section perpendicular to an
axis of the hollow columnar member in the concave-convex
mixed mode.
Fig. 2B is a schematic view for exemplifying a
transverse cross-section, other than the cross-section of
35 Fig. 2A, perpendicular to the axis of the hollow columnar
member in the concave-convex mixed mode.
Fig. 3A is a schematic view for exemplifying an
arbitrary transverse cross-section perpendicular to the
axis of the hollow columnar member in the concave-convex
independent mode.
Fig. 3B is a schematic view for exemplifying a
transverse cross-section, other than the cross-section of
Fig. 3A, perpendicular to the axis of the hollow columnar
member in the concave-convex independent mode.
Fig. 4A is a schematic cross-sectional view for
explaining a protruding direction of a flange, wherein
the flange extends along one wall.
Fig. 4B is a schematic cross-sectional view for
explaining a protruding direction of a flange, wherein
the flange is formed by bending walls by different
angles.
Fig. 5A is a schematic cross-sectional view for
explaining the buckling of a shock absorbing member
according to one embodiment of the invention.
Fig. 5B is a schematic cross-sectional view for
explaining the buckling of a shock absorbing member
according to another embodiment of the invention.
Fig. 5C is a schematic cross-sectional view for
explaining the buckling of a shock absorbing member
according to still another embodiment of the invention.
Fig. 6A is a schematic cross-sectional view for
explaining the buckling of a shock absorbing member
according to still another embodiment of the invention.
Fig. 6B is a schematic cross-sectional view for
explaining the buckling of a shock absorbing member
according to still another embodiment of the invention.
Fig. 7A is a perspective view of a shock absorbing
member according to one embodiment of the invention.
Fig. 7B is a perspective view of a shock absorbing
member according to one embodiment of the invention.
Fig. 7C is a perspective view of a shock absorbing
member according to one embodiment of the invention.
Fig. 8A is a perspective view of a shock absorbing
member according to one embodiment of the invention.
Fig. 8B is a perspective view of a shock absorbing
member according to one embodiment of the invention.
Fig. 9A is a perspective view of a shock absorbing
member of comparative example 1, showing a state before
5 impact load is applied thereto.
Fig. 9B is a perspective view of a shock absorbing
member of working example 1, showing a state before
impact load is applied thereto.
Fig. 9C is a perspective view of a shock absorbing
10 member of working example 2, showing a state before
impact load is applied thereto.
Fig. 9D is a perspective view of a shock absorbing
member of working example 3, showing a state before
impact load is applied thereto.
15 Fig. 9E is a perspective view of a shock absorbing
member of working example 4, showing a state before
impact load is applied thereto.
Fig. 10 is a perspective view of a shock absorbing
member of comparative example 1, wherein deformation
20 manner when impact load is applied to the shock absorbing
member is calculated by FEM numerical analysis.
Fig. 11 is a perspective view of a shock absorbing
member of working example 1, wherein deformation manner
when impact load is applied to the shock absorbing member
25 is calculated by FEM numerical analysis.
Fig. 12 is a perspective view of a shock absorbing
member of working example 2, wherein deformation manner
when impact load is applied to the shock absorbing member
is calculated by FEM numerical analysis.
30 Fig. 13 is a perspective view of a shock absorbing
member of working example 3, wherein deformation manner
when impact load is applied to the shock absorbing member
is calculated by FEM numerical analysis.
Fig. 14 is a perspective view of a shock absorbing
35 member of working example 4, wherein deformation manner
when impact load is applied to the shock absorbing member
is calculated by FEM numerical analysis.
Fig. 15A is a graph showing a measurement of a
relationship between a reactive force from the shock
absorbing member and an amount of deformation (crushing)
when impact load is applied to the shock absorbing
5 member, in relation to working example 1 and comparative
example 1.
Fig. 15B is a graph showing a measurement of a
relationship between a reactive force from the shock
absorbing member and an amount of deformation (crushing)
10 when impact load is applied to the shock absorbing
member, in relation to working example 2 and comparative
example 1.
Fig. 15C is a graph showing a measurement of a
relationship between a reactive force from the shock
15 absorbing member and an amount of deformation (crushing)
when impact load is applied to the shock absorbing
member, in relation to working example 3 and comparative
example 1.
Fig. 15D is a graph showing a measurement of a
20 relationship between a reactive force from the shock
absorbing member and an amount of deformation (crushing)
when impact load is applied to the shock absorbing
member, in relation to working example 4 and comparative
example 1.
25 Fig. 16A is a graph showing a measurement of a
relationship between an amount of energy absorption and
an amount of deformation (crushing) when impact load is
applied to the shock absorbing member, in relation to
working example 1 and comparative example 1.
30 Fig. 16B is a graph showing a measurement of a
relationship between an amount of energy absorption and
an amount of deformation (crushing) when impact load is
applied to the shock absorbing member, in relation to
working example 2 and comparative example 1.
35 Fig. 16C is a graph showing a measurement of a
relationship between an amount of energy absorption and
an amount of deformation (crushing) when impact load is
applied to the shock absorbing member, in relation to
working example 3 and comparative example 1.
Fig. 16D is a graph showing a measurement of a
relationship between an amount of energy absorption and
5 an amount of deformation (crushing) when impact load is
applied to the shock absorbing member, in relation to
working example 4 and comparative example 1.
Embodiments for Carrying out the Invention
10 [0019] Hereinafter, a shock absorbing member according
to the present invention will be explained in detail with
reference to the drawings.
A hollow columnar shock absorbing member of the
invention has an axis, a plurality of rectangular walls
15 extending parallel to the axis, and a polygonal crosssection
perpendicular to the axis, the shock absorbing
member extending in the direction of the axis and
absorbing externally-applied impact energy while buckling
in a direction of the axis. At least two flanges
20 protrude from at least two edges formed by at least two
sets of neighboring walls among the plurality of walls,
and the at least two flanges are arranged so that
directions of protrusion of the flanges from the edges
are directed to the same direction with respect to a
25 circumferential direction.
[0020] Further, in the shock absorbing member, a bead
may be formed on at least one of the walls. The bead may
be a dimple which dents from an outer surface of the
shock absorbing member or a bulge which bulges from the
30 outer surface. It is preferable that the dimple be
positioned so as to be deviated towards the edge
positioned on a side opposite to the direction of
protrusion of the flange with respect to the
circumferential direction, and the bulge be positioned so
35 as to be deviated towards the edge positioned on a side
in the direction of protrusion of the flange with respect
to the circumferential direction.
[0021] Hereinafter, a shock absorbing member according
to the present invention will be explained in detail with
reference to the drawings.
In Figs. 1A to ID, various deformation modes are
5 illustrated, which are generated when impact load is
applied to one end of a hollow linear columnar shock
absorbing member in a direction of an axis thereof (or an
axial direction), the shock absorbing member having a
square cross-section. The deformation modes as shown in
10 Figs. 1A to 1D are calculated by FEM (Finite Element
Method) numerical analysis (or computer simulation) when
the shock absorbing member is deformed by applied impact
load.
100221 Fig. 1A shows a state wherein the shock
15 absorbing member is bent by local buckling. On the other
hand, Fig. 1B shows a non-compact mode wherein the shock
absorbing member is irregularly buckled in the axial
direction. Figs. 1C and 1D show modes wherein the shock
absorbing member is buckled into concertinas in the axial
20 direction. In other words, Figs. 1C and ID shows compact
modes wherein the member is crushed so that a peak and a
valley are alternately formed in the axial direction. In
particular, Fig. 1C shows a concave-convex mixed mode of
the compact modes. In the concave-convex mixed mode,
25 both the valley (or a concave portion) and the peak (or a
convex potion) of the concertinas are included in an
arbitrary transverse cross-section of a hollow columnar
member, as schematically shown in Figs. 2A and 2B. To
the contrary, Fig. 1D shows a concave-convex independent
30 mode of the compact modes. In the concave-convex
independent mode, only the valley (or a concave portion)
or the peak (or a convex potion) of the concertinas is
included in an arbitrary transverse cross-section of a
hollow columnar member, as schematically shown in Figs.
35 3A and 3B. In addition, the "concave-convex independent
mode" and the "concave-convex mixed mode" may also be
referred to as an "extension mode" and an "inextension
mode," respectively.
COO231 In such a case, a ratio of a deformed portion
to the entire member is increased as the deformation mode
is shifted from Fig. 1A to Fig. ID. Therefore, in the
5 concave-convex independent mode as shown in Fig. ID, an
amount of impact energy absorption relative to an amount
of deformation (crushing) of the member is the highest.
In other words, in the concave-convex independent mode,
the member can be buckled in the axial direction most
10 effectively, whereby significantly high impact-absorbing
performance can be obtained.
COO241 As described above, in the present invention,
the flanges are formed on at least two edges, and the
flanges are arranged so that directions of protrusion of
15 the flanges from the edges are directed to the same
direction with respect to a circumferential direction.
By virtue of this, the concave-convex independent mode
can be purposely induced.
100251 In this regard, "the direction of protrusion of
20 the flange" means a direction towards one of two walls
constituting the flange having a smaller open angle. For
example, Fig. 4A schematically shows a flange 100A
constituted by walls 101 and 102, wherein an angle P
between wall 102 and flange 100A is smaller than an angle
25 a between wall 101 and flange lOOA (P < a). Therefore,
the direction towards wall 102 is determined as the
direction of protrusion of flange lOOA with respect to
the circumferential direction of the shock absorbing
member.
30 COO261 Although flange lOOA extends along wall 101 in
Fig. 4A (P < a = 180°), the flange is not limited as such.
For example, in a flange lOOB schematically shown in Fig.
4Bf walls 101 and 102 may be bent by different angles so
as to constitute flange lOOB (P < a < 180'). Otherwise, a
35 flange (not shown) wherein (P < 180' < a) is true may be
constituted.
[0027] As exemplified in Fig. 5A, a shock absorbing
member lA, constituted by a hollow member with a square
cross-section, has a center axis 0, four walls la, lb, lc
and Id positioned around center axis 0. By joining walls
5 la, lb, lc and Id to each other, four edges or corners
le, If, lg and lh and flanges 2a, 2b, 2c and 2d on
respective edges are formed. Flanges 2a, 2b, 2c and 2d
are arranged so that a direction (X) of protrusion of
each of flanges 2a, 2b, 2c and 2d from respective corners
10 le, If, lg and lh is directed to the same direction (Y)
with respect to the circumferential direction about axis
0.
[0028] In this case, by applying impact load to one
end of shock absorbing member 1A in a direction of the
15 axis (or the axial direction), the shock absorbing member
begins to be buckled while a ridge of each corner le, If,
lg and lh is inclined in the same direction Y with
respect to the circumferential direction about axis 0,
i.e., in the direction X towards walls lb, lc, Id and la,
20 respectively, wherein the open angle at each flange is
smaller. By virtue of this, the above concave-convex
independent mode can be purposely induced.
[0029] Fig. 5B schematically shows a shock absorbing
member 1B with a square cross-section, wherein a panel
25 constituted by walls la and Id and another panel
constituted by walls lb and lc are joined at a site
between walls la and lb and at a site between walls lc
and Id so that flanges 2a and 2c are formed so as to
protrude from two corners le and lg, respectively. In
30 this case, flanges 2a and 2c are arranged so that a
direction (X) of protrusion of each of flanges 2a and 2c
from respective corners le and lg is directed to the same
direction (Y) with respect to the circumferential
direction about axis 0.
35 [ 0 0 3 0 1 Further, on walls la and lc, each wall being
one of the neighboring walls sandwiching corners If and
lh different from corners le and lg on which flanges 2a
and 2c are formed, dimples 3 denting from outer surfaces
of walls la and lc may be formed. In this case, dimples
3 are positioned so as to be deviated, in relation to
centers of walls la and lc, respectively, towards corners
5 If and lh which are positioned on the side opposite to
protruding direction X of flanges 2a and 2c with respect
to the circumferential direction about axis 0.
[0031] In this case, by applying impact load to one
end of shock absorbing member 1B in a direction of the
10 axis (or the axial direction), the shock absorbing member
begins to be buckled while ridges of corners le and lg
are inclined in the same direction Y with respect to the
circumferential direction about axis 0, i-e., in the
direction X towards walls lb and Id, respectively,
15 wherein the open angle at each flange is smaller.
Further, ridges of corners If and lh are inclined in the
same direction Y with respect to the circumferential
direction about axis 0, i.e., towards the side where
dimples 3 are formed (in the direction X). By virtue of
20 this, the above concave-convex independent mode can be
purposely induced.
LO0321 Fig. 5C schematically shows a shock absorbing
member 1C with a square cross-section, wherein a panel
constituted by walls la' and Id' and another panel
25 constituted by walls lb' and lc' are joined at a site
between walls la' and lb' and at a site between walls lc'
and Id' so that flanges 2' are formed so as to protrude
from two corners le' and lg', respectively. In this
case, flanges 2' are arranged so that a direction (X') of
30 protrusion of each of flanges 2' from respective corners
le' and lg' is directed to the same direction (Y') with
respect to the circumferential direction about axis 0.
[ 0 0 3 3 1 Further, on walls la' and lc', each wall being
one of the neighboring walls sandwiching corners If' and
35 lh' different from corners le' and lg' on which flanges
2' are formed, bulges 3' bulging from outer surfaces of
walls la' and lc' may be formed. In this case, bulges 3'
are positioned so as to be deviated, in relation to
centers of walls la' and lc' , respectively, towards
corners If' and lh' which are positioned on the side in
protruding direction X' of flanges 2' with respect to the
5 circumferential direction about axis 0.
[0034] In this case, by applying impact load to one
end of shock absorbing member 1C in a direction of the
axis (or the axial direction), the shock absorbing member
begins to be buckled while ridges of corners le' and lg'
10 are inclined in the same direction Y' with respect to the
circumferential direction about axis 0, i.e., in the
direction X' towards walls lb' and Id', respectively,
wherein the open angle at each flange is smaller.
Further, ridges of corners If' and lh' are inclined in
15 the same direction Y' with respect to the circumferential
direction about axis 0, i.e., towards a side opposite to
the side where bulges 3' are formed (in the direction
X ) By virtue of this, the above concave-convex
independent mode can be purposely induced.
20 100351 In another shock absorbing member to which the
present invention is applied, the flange is formed on one
corner, and the dimple denting from the outer surface or
the bulge bulging from the outer surface is formed on at
least one of the walls of the shock absorbing member.
25 When the dimple is formed, the dimple is positioned so as
to be deviated towards the corner which is positioned on
the side opposite to the direction of protrusion of the
flange with respect to the circumferential direction
about axis 0. When the bulge is formed, the bulge is
30 positioned so as to be deviated towards the corner which
is positioned on the side in the direction of protrusion
of the flange with respect to the circumferential
direction about axis 0. By virtue of this, the above
concave-convex independent mode can be purposely induced.
35 [0036] For example, Fig. 6A schematically shows a
shock absorbing member 1D with a square cross-section,
wherein a panel is constituted by walls la, Id, lc and
lb, and walls la and lb are joined so that a flange 2 is
formed so as to protrude from one corner le. In this
case, on walls la, lc and Id, each wall being one of the
neighboring walls sandwiching corners lh, If and lg
5 different from corners le on which flange 2 is formed,
dimples 3 denting from outer surfaces of walls la, lc and
Id may be formed. Further, dimples 3 are positioned so
as to be deviated, in relation to centers of walls la, lc
and Id, respectively, towards corners lh, If and lg which
10 are positioned on the side opposite to protruding
direction X of flange 2 with respect to the
circumferential direction about axis 0.
10037) In this case, by applying impact load to one
end of shock absorbing member 1D in a direction of the
15 axis (or the axial direction), the shock absorbing member
begins to be buckled while a ridge of corner le is
inclined in the same direction Y with respect to the
circumferential direction about axis Of i.e., in the
direction X towards wall lb, wherein the open angle at
20 the flange is smaller. Further, ridges of other corners
If, lg and lh are inclined in the same direction Y with
respect to the circumferential direction about axis 0,
i.e., towards the side where dimples 3 are formed (in the
direction X). By virtue of this, the above concave-
25 convex independent mode can be purposely induced.
[ 0 0 3 8 ] Fig. 6B schematically shows a shock absorbing
member 1E with a square cross-section, wherein a panel is
constituted by walls la', Id', lc' and lb', and walls la'
and lb' are joined so that a flange 2' is formed so as to
30 protrude from one corner le'. In this case, on walls
la', lc' and Id', each wall being one of the neighboring
walls sandwiching corners lh', If' and lg' different from
corners le' on which flange 2' is formed, bulges 3'
bulging from outer surfaces of walls la', lc' and Id' may
35 be formed. Further, bulges 3' are positioned so as to be
deviated, in relation to centers of walls la', lc' and
Id', respectively, towards corners lh', If' and lg' which
are positioned on the side in protruding direction X' of
flange 2' with respect to the circumferential direction
about axis 0.
COO391 In this case, by applying impact load to one
5 end of shock absorbing member 1E in a direction of the
axis (or the axial direction), the shock absorbing member
begins to be buckled while a ridge of corner le' is
inclined in the same direction Y' with respect to the
circumferential direction about axis 0, i.e., in the
10 direction X' towards walls la', wherein the open angle at
the flange is smaller. Further, ridges of other corners
If', lg' and lh' are inclined in the same direction Y'
with respect to the circumferential direction about axis
Of i.e., towards a side opposite to the side where bulges
15 3' are formed (in the direction XI). By virtue of this,
the above concave-convex independent mode can be
purposely induced.
COO401 As explained above, the flange and the bead of
the invention function as a buckling inducing portion,
20 capable of determining the direction of inclination, so
that the ridge of each edge or corner is inclined in the
same direction with respect to the circumferential
direction about axis 0 at the beginning of the buckling,
when the shock absorbing member is buckled in the
25 direction of the axis. In addition, unlike the
conventional bead having a function to provide the origin
of the buckling to the shock absorbing member, the bead
of the invention does not directly become the origin of
the buckling. Rather, the bead of the invention has a
30 function for rapidly making the transition to the
concave-convex independent mode after the ridge of the
corner is inclined (or after the buckling).
[0041] Therefore, the shock absorbing member according
to the present invention can be effectively buckled in
35 the axial direction thereof, by purposely inducing the
above concave-convex independent mode. As a result, the
amount of externally-applied impact energy absorption is
increased, whereby remarkable shock-absorbing performance
can be obtained.
100421 When such a shock absorbing member is used in a
chassis of a motorcar, etc., fuel efficiency and motion
5 performance are improved while balancing reduced weight
and high stiffness, and further, the chassis may have a
structure with high collision-safety performance.
100431 Although shock absorbing members 1A to 1E as
shown in Figs. 5A to 5C, 6A and 6B are exemplified, the
10 shock absorbing member of the invention is not limited as
such, and may have various configurations. In other
words, the invention may be widely applied to a hollow
columnar shock absorbing member with a polygonal crosssection,
which absorbs externally-applied impact energy
15 while buckling (or crushing) in the axial direction
thereof.
[0044] Concretely, as the shock absorbing member, for
example, a thin-walled structure having a flange, formed
as a hollow column (or a hollow columnar member),
20 constituted by joining a press-formed steel plates by
welding, etc., may be used. In this case, the bead may
be formed by press-forming, etc., before and/or after
joining the hollow columnar member.
[0045] A material of the shock absorbing member is not
25 limited to a steel plate as described above. For
example, the material may be a metal such as iron,
aluminum, copper or an alloy thereof; or a resin such as
an FRP, as long as the member can absorb externallyapplied
impact energy while buckling (or crushing) in the
30 axial direction thereof. Further, the shock absorbing
member is not limited to a member formed by joining
plates by welding, etc., and may be a hollow columnar
member formed by extrusion molding, etc. In this case,
the bead may be formed by press-forming, etc., after
35 forming the hollow columnar member.
[0046] In addition, it is preferable that the shock
absorbing member have a hollow cross-section with a
quadrangular, pentagonal, hexagonal, heptagonal or
octagonal shape, for example, in order to balance reduced
weight and high stiffness. In this case, as shown in
Figs. 7A to 7C, also in shock absorbing members each
5 having a hexagonal cross-section, the concave-convex
independent mode can be purposely induced by arranging
flanges 2 so that directions of protrusion of the flanges
are directed to the same direction with respect to the
circumferential direction about axis 0.
10 [ 0 0 4 7 ] As shown in Figs. 8A and 8B, dimples 3 may be
aligned in the axial direction, from a start end of the
buckling of the shock absorbing member. In this case, it
is preferable that dimples 3 be positioned at an interval
corresponding to a length of one side of the wall.
15 Further, it is preferable that dimple 3 closest to the
start end be positioned so as to be separated from the
start end by a distance which is more than a half of the
length of one side of the wall. By virtue of this, the
shock absorbing member can be stably buckled into
20 concertinas.
[ 0 0 4 8 ] The shape of the bead is not limited the above
dimple or bulge having a portion of a spherical surface,
as long as the bead has a function of the invention. For
example, the bead may have a V-shaped or U-shaped cross-
25 section. Dimple 3 as shown in Figs. 8A and 8B is
configured as a concave portion with a trough shape
extending in a direction (or a transverse direction)
perpendicular to the axial direction of the shock
absorbing member. In this case, the function of the bead
30 of the invention may be further improved. Preferably, a
length L1 of trough-shaped dimple 3, in a direction
perpendicular to axis 0 of the shock absorbing member, is
represented as below, wherein "W" is a width of the wall
(or a distance between the ridges of the shock absorbing
35 member) .
(l/lO)W I L1 I ( 3 / 4 ) W
Preferably, a length L2 of trough-shaped dimple 3, in
a direction of axis 0 of the shock absorbing member, is
represented as below.
(1/20) L1 I L2 I L1
Preferably, a distance L3 between dimple 3 and the
5 ridge is represented as below, wherein "T" is a thickness
of the plate.
T I L3 I (1/5)T
[0049] According to the invention, by arranging the
bead on at least one of the walls of the shock absorbing
10 member so that the bead is deviated towards one corner of
the wall, the above concave-convex independent mode can
be purposely induced. In other words, in the invention,
the bead deviated towards one corner of at least one wall
functions as the origin for determining the direction of
15 the inclination of the ridge on the side towards which
the bead is deviated. Similarly, the other ridges are
induced to incline in the same direction as the ridge of
the corner which becomes the origin.
[OOSO] However, in order for the corners to be stably
20 inclined in the same direction, it is preferable that the
bead be deviated towards the corner in two walls. More
preferably, the bead is deviated towards the corner in
all of the walls. A portion, to which the bead is
provided, will become a valley (or a concave portion) of
25 the concertinas after the buckling. Therefore, when the
bead is arranged on all of the walls, a corner in the
transverse cross-section, to which the bead is not
provided, can be prevented from being a peak (or a convex
portion) of the concertinas after the buckling. In
30 addition, when the bead is positioned so as to be
deviated towards the corner on the plurality of walls, it
is preferable that the wall constituting an opposing
corner of the cross-section of the polygonal shape is
preferentially provided with the bead, in view of the
35 balance of arrangement of the beads.
[0051] In the invention, "the bead is positioned so as
to be deviated towards the corner" means that the bead is
displaced towards the corner so that the center of the
wall does not exist in the bead (i.e., the center is not
deformed). Further, it is preferable that the beads be
positioned in the vicinity of the corners which are
5 located on the same sides with respect to the
circumferential direction. In this regard, "in the
vicinity of the corner" means the position near the
corner so that the ridge of the corner does not exist in
the bead (i.e., the corner is not deformed), and a
10 distance between the center of the bead and the corner is
equal to or smaller than a quarter of a width of the
wall. In the invention, by positioning the bead in the
vicinity of the corner, the ridge of the corner can be
stably inclined.
15 [0052] On the other hand, when the bead is formed on
the corner, the buckling is stably carried out, whereas
the load supported by the corner is decreased. However,
since the corner having the flange corresponds to a joint
section between the neighboring walls sandwiching the
20 corner, the corner has high deformation resistance and
the load is not significantly decreased. Therefore, when
buckling stability is required, the flange and the bead
on the corner where the flange is formed, may be
arranged. Further, the bead may be elongated between the
25 flange and the wall.
[00531 In addition, in the invention, by conforming
the direction of the deviation of the bead to a direction
of a torsional load applied to the shock absorbing
member, the impact absorbing performance of the shock
30 absorbing member is also effective for the torsional
load.
Examples
[0054] Hereinafter, the effect of the present
35 invention will be more clearly explained. The invention
is not limited to following examples, and numerous
modifications could be made thereto, without departing
from the basic concept and scope of the invention.
[0055] First, in relation to shock absorbing members
of working examples 1 to 4 and a comparative example 1,
deformation states thereof were calculated by FEM
5 numerical analysis (computer simulation), when the impact
load is applied to one end of the member in the axial
direction of the member. As an analysis condition of the
FEM numerical analysis, a linear hollow columnar member
with a square cross-section, having a plate thickness of
10 1.4 mrn, a side length of 50 mm and an axial length of 300
mm, was used as a model. Material constants of the model
are indicated in table 1 as follows.
COO561
[Table 11
15
[0057] Then, the deformation state was calculated,
when a rigid wall with a weight of 1000 kg fell at a rate
of 4.44 m/s towards one end (or an upper end) of the
hollow columnar member. In this regard, a constitutive
20 equation used in the FEM numerical analysis was a Swift-
Cowper-Symonds equation, as follows. In addition, an
analysis time was 50 ms (milliseconds).
[0058]
Base Material
25
COO591 Comparative example 1
As shown in Fig. 9A, comparative example 1 was a
hat-shaped hollow columnar member, wherein two flanges
were directed to different directions with respect to the
30 circumferential direction. Dimensions of the hat-shaped
hollow columnar member are indicated in Fig. 9A. In this
K [GPa]
1.5
Eo
0.001
n
0.2
D [l/ms]
1.0~10'~
D [l/ms]
3.0
case, as shown in Fig. 10, the buckling of the member
progressed in the concave-convex mixed mode from initial
stage of the buckling.
[0060] Working example 1
5 As shown in Fig. 9B, in working example 1, a flange
was formed on each of two opposing corners of the hollow
columnar member (a protruding length of each flange was
20 rnm), so that the two flanges were directed in the same
direction with respect to the circumferential direction.
10 In this case, as shown in Fig. 11, the bucking of the
member progressed in the concave-convex independent mode
from initial stage of the buckling.
[0061] Working example 2
As shown in Fig. 9C, in working example 2, in
15 addition to the configuration of working example 1,
dimples were formed on one of the neighboring walls
sandwiching the corner on which the flange was not
formed. Each dimple dented from an outer surface of the
shock absorbing member, and was positioned so as to be
20 deviated towards the corner, relative to the center of
the wall, which was positioned on the side opposite to
the direction of protrusion of the flange with respect to
the circumferential direction. In this case, as shown in
Fig. 12, the bucking of the member progressed in the
25 concave-convex independent mode from initial stage of the
buckling.
100621 Working example 3
As shown in Fig. 9E, in working example 3, in
addition to the configuration of working example 2,
30 dimples were formed on one of the neighboring walls
sandwiching the corner on which the flange was formed.
Each dimple dented from an outer surface of the shock
absorbing member, and was positioned so as to be deviated
towards the corner, relative to the center of the wall,
35 which was positioned on the side opposite to the
direction of protrusion of the flange with respect to the
circumferential direction. In this case, as shown in
Fig. 13, the bucking of the member progressed in the
concave-convex independent mode from initial stage of the
buckling.
[0063] Working example 4
5 As shown in Fig. 9D, in working example 4, in
addition to the configuration of working example 2,
dimples were formed on the flanges. In this case, as
shown in Fig. 14, the bucking of the member progressed in
the concave-convex independent mode from initial stage of
10 the buckling.
[0064] Next, Figs. 15A to 15D indicate a result of
measurement of the relationship between a reactive force
from the shock absorbing member (or a resistive force of
the member against the impact energy) and an amount of
15 deformation (or an amount of crushing) when impact force
was applied to one end of the member in the axial
direction thereof, in relation to working examples 1 to 4
and comparative example 1. Figs. 15A to 15D indicate the
results of working examples 1 to 4, respectively, and
20 each result is compared to a result of comparative
example 1. In this regard, since a product of the
reactive force from the shock absorbing member and the
amount of crushing corresponds to an amount of energy
absorption, the impact absorbing performance of the
25 member is improved as the reactive force is increased.
[0065] Further, Figs. 16A to 16D indicate a result of
measurement of the relationship between the amount of
deformation (or the amount of crushing) and an amount of
energy absorption when impact force was applied to one
30 end of the member in the axial direction thereof, in
relation to working examples 1 to 4 and comparative
example 1. Figs. 16A to 16D indicate the results of
working examples 1 to 4, respectively, and each result is
compared to a result of comparative example 1.
35 [0066] As shown in Figs. 15A to 15D and 16A to 16D, in
the shock absorbing member of working examples 1 to 4, by
inducing the concave-convex independent mode, a ratio of
the amount of energy absorption relative to the amount of
deformation (or crushing) was higher than comparative
example 1 having the concave-convex mixed mode. In other
words, the shock absorbing member of working examples 1
5 and 2 had improved shock absorbing performance.
[Reference Signs List]
[0067]
1A
1B
1C
ID
1E
la
lb
lc
Id
la '
lb '
lc'
Id'
le
If
lg
lh
le '
If'
lg '
lh '
2a
2b
2c
2d
2a'
2b'
2c'
2d'
shock absorbing member
shock absorbing member
shock absorbing member
shock absorbing member
shock absorbing member
wall
wall
wall
wall
wall
wall
wall
wall
corner
corner
corner
corner
corner
corner
corner
corner
flange
flange
flange
flange
flange
flange
flange
flange
dimple
bulge

[Claim 11
A hollow columnar shock absorbing member having an
axis, a plurality of rectangular walls extending parallel
to the axis, and a polygonal cross-section perpendicular
to the axis, the shock absorbing member extending in the
direction of the axis and absorbing externally-applied
impact energy while buckling in a direction of the axis,
wherein the shock absorbing member is provided
with at least two flanges protruding from at least two
edges formed by at least two sets of neighboring walls
among a plurality of walls, and the at least two flanges
are arranged so that directions of protrusion of the
flanges from the edges are directed to the same direction
with respect to a circumferential direction.
[Claim 21
The shock absorbing member according to claim 1,
wherein a bead is formed on at least one of the walls,
the bead being a dimple which dents from an outer surface
of the shock absorbing member or a bulge which bulges
from the outer surface, and wherein the dimple is
positioned so as to be deviated towards the edge
positioned on a side opposite to the direction of
protrusion of the flange with respect to the
circumferential direction, and the bulge is positioned so
as to be deviated towards the edge positioned on a side
in the direction of protrusion of the flange with respect
to the circumferential direction.
[Claim 31
The shock absorbing member according to claim 2,
wherein the bead is positioned in the vicinity of the
edge positioned on the side opposite to the direction of
protrusion of the flange.
[Claim 41
The shock absorbing member according to claim 2 or
3, wherein the bead is a dimple formed into a trough
shape extending in a direction perpendicular to the
yr%.f,t t
O R ~ ~ ~ ~ ~ ~ f i ~ e - 29 - o(\6Y7 KU@1 4 - directLon of the axis.
[Claim 51 3 Q JAM
The shock absorbing member according to any one of
. .
-. .
claims 2-to -47-w h-erein the--beadsa re aligned in the-
5 direction of the axis from an end of the shock absorbing
-. member-wher-e--the=-buckl-ing -i-s- init-iated7--
[Claim 61
A hollow columnar shock absorbing member .having an
axis and a polygonal cross-section, the shock absorbing
10 member absorbing externally-applied impact energy while
buckling in a direction of the axis,
wherein a buckling inducing portion for
determining a direction of inclination is formed on a
wall and/or an edge of the shock absorbing member, so
15 that a ridge of each edge is inclined in the same
direction with respect to a circumferential direction of
the shock absorbing member at the beginning of the
buckling, when the shock absorbing member is buckled in -
the direction of the axis.
Dated this 30/01/2014
OF REMFRY & SAGAR
ATTORNEY FOR THE APPLICANTS