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AA511
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DESCRIPTION
Title of Invention: Metallic Hollow Columnar Member
Technical Field
[0001] The present invention relates to a thin-walled
hollow columnar member, which constitutes a frame and is
formed from a metal such as steel, aluminum, stainless
steel or titanium, etc.
Background Art
[0002] In recent years, in the automotive field, in
order to reduce the weight of a vehicle body of a
motorcar while maintaining or improving collision safety
15 of the motorcar and reduce carbon dioxide emissions so as
to improve the environmental performance of the motorcar,
there are many approaches for improving the rigidity of a
frame member such as a crash box, etc., of the motorcar,
by modifying a cross-section of the frame member. In
20 order to increase the rigidity of the frame member, a
distribution of sectional property (or strength balance)
of the frame member in the longitudinal direction thereof
is important. If the design of the frame member is
inappropriate, in the case of a forward collision of the
25 motorcar, a frame positioned at a rear side of the crash
box may be deformed before the deformation of the crash
box positioned at a front of a frame of the motorcar.
Further, in a collision experiment of a motorcar, a
boundary condition such as a loading direction is not
30 constant, whereby a certain degree of error occurs.
Therefore, it is necessary that an energy absorbing
member, a major deformation mode of which is a crushing
mode in the axial direction of the crash box, etc., be
highly robust, wherein impact-absorbing performance of
35 the member is not considerably changed due to a change in
the boundary condition.
[0003] In this regard, the "strength balance" means a
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second moment of area calculated from a plurality of
cross-sectional shapes perpendicular to the longitudinal
direction of the frame and characteristics of material
applied to the frame, and/or a distribution of maximum
5 tolerable buckling load in the longitudinal direction.
Further, the "impact-absorbing performance" means an
amount of energy absorption per unit amount of crushing
in the axial direction, and the "robustness" means
invariance of the impact-absorbing performance with
10 respect to the change in the dynamic boundary condition.
[0004] As prior art, patent literature 1 discloses an
impact absorbing member having a groove concaved toward
inside the member, wherein a cross-sectional shape in at
least a part in the axial direction is a closed cross-
15 section having a plurality of vertices.
[0005] Patent literature 2 describes an energy
absorbing member constituted by an extruded member of
aluminum alloy having a hollow rectangular cross-section,
wherein a rectangular cross-sectional projecting part is
20 arranged outside a wall surface part of the member.
[0006] Patent literature 3 discloses a front side
frame of a motorcar having beads on a lateral side
thereof, the beads extending in the axial direction and
projecting inside or outside the lateral side.
25 [0007] Patent literature 4 describes an impact
absorbing member having a generally C-shaped crosssection
which opens outward in the vehicle width
direction.
[0008] Further, patent literature 5 describes an
30 impact absorbing member having a polygonal cross-section,
wherein the length of one side of the polygonal crosssection,
the lengths of two sides which sandwiches the
one side, and a range of the angle constituted by the two
sides are limited.
35 Citation List
Patent Literature
[0009] PLT 1: Japanese Unexamined Patent Publication
f^ - 3 -
(kokai) No. 2006-207724
PLT 2: Japanese Unexamined Patent Publication (kokai)
No. 2002-12165
PLT 3: Japanese Unexamined Patent Publication (kokai)
5 No. H08-108863
PLT 4: Japanese Unexamined Patent Publication (kokai)
No. 2009-292340
PLT 5: International Publication No. WO 2005/010396
10 Summary of Invention
Problem to be Solved by the Invention
[0010] The techniques of PLTs 1 to 3 are intended to
increase the total number of vertices in the crosssection
so that cross-sectional force per unit length of
15 the member due to the compressive deformation is
significantly improved by forming the drastic concaveconvex
shape. Therefore, in PLTs 1 to 3, it is necessary
to redesign the entire frame in view of the strength
balance of the frame. If the technique is partially
20 applied to the frame, the overall strength balance of the
frame is deteriorated, and the frame is deformed at an
unexpected portion thereof, whereby the amount of energy
absorption of the member may be decreased. Further,
since the deformation mode may be unstable due to the
25 drastic concave-convex shape, the member may not be
stably crushed and deformed in the axial direction.
[0011] On the other hand, in PLTs 4 and 5, it is not
necessary to form the concave-convex shape, and the
cross-sectional force per unit length of the member due
30 to the compressive deformation is mildly improved,
whereby the crushing deformation mode may be stable in
the axial direction. However, in any of PLTs 4 and 5,
the arrangement of inside angles of the vertices of the
polygonal shape is inappropriate. In other words,
35 depending on the loading direction, the vertex may
disappear due to buckling of the polygonal shape be
eliminated, whereby the cross-sectional force may be
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significantly lowered.
[0012] The present invention was made in order to
provide a technique for improving the impact absorbing
performance without deteriorating the strength balance,
5 and a member to which the technique is applied.
Means for Solving the Problem
[0013] The inventors of this case examined the
relationship between the deformation mode and the impact
10 absorption performance (or the amount of energy
absorption) when a member was crushed, and found that
behavior of vertices in a transverse cross-section of the
member significantly contributes to the amount of energy
absorption when the crushing deformation. When the
15 vertex disappears or vanishes due to the deformation such
as flexion during the crushing, a reactive force is
significantly lowered. Therefore, although it is
effective to avoid the flexion at the vertex, it is
difficult to control the flexion in particular when the
20 crushing deformation in the axial direction. As a result
of analysis and experiments regarding the crushing of a
member in the axial direction, the inventors found that
the vanishment of the vertex when the crushing
deformation can be avoided by controlling the position of
25 the flexion. Since this technique is intended to lower a
reduction rate of the reactive force, the overall
strength balance is not deteriorated.
[0014] According to the present invention, a metallic
hollow columnar member with a polygonal cross-section
30 having at least five vertices and sides extending between
the vertices, is provided, wherein: the polygonal crosssection
is divided by two vertices (A, B) with small
inside angles into two perimeter segments with a
perimeter comprising one or more sides, the at least one
35 of the two perimeter segments containing at least four
sides, the respective inside angles of at least three
vertices (V(i) (1=1, 2, 3, ...)) included in the
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perimeter segment which includes the at least four sides
are equal to or less than 180 degrees, a distance (SS(i)
(i=l, 2, 3, ...)) between each of the at least three
vertices (V(i) (i=l, 2, 3, ...)) and a straight line (L)
5 connecting the two vertices (A, B) is shorter than 1/2 of
a distance between the two vertices (A, B), the inside
angle of a vertex (C) with the smallest inside angle
among the at least three vertices (V(i)) is larger than
the inside angles of the two vertices (A, B), and
10 vertices (VI) are present on the perimeter segment
including the at least four sides, respectively between
the vertex (C) with the smallest inside angle among the
at least three vertices (V(i)) and one (A) of the two
vertices (A, B), and between the vertex (C) with the
15 smallest inside angle and the other (B) of the two
vertices (A, B), said vertices (VI) having inside angles
larger than the inside angle of the vertex (C) with the
smallest inside angle.
[0015] According to another aspect of the present
20 invention, a metallic hollow columnar member with a
polygonal cross-section having at least five vertices and
sides extending between the vertices, is provided,
wherein: the metallic hollow columnar member comprises
two joined sections (J), the polygonal cross-section is
25 divided by two vertices (A, B) in the vicinity of the two
joined sections (J) into two perimeter segments with a
perimeter comprising one or more sides, the at least one
of the two perimeter segments containing at least four
sides, the respective inside angles of at least three
30 vertices (V(i) (i=l, 2, 3, ...)) included in the
perimeter segment which includes the at least four sides
are equal to or less than 180 degrees, a distance (SS(i)
(i=l, 2, 3, ...)) between each of the at least three
vertices (V(i) (i=l, 2, 3, ...)) and a straight line (L)
35 connecting the two vertices (A, B) is shorter than 1/2 of
a distance between the two vertices (A, B), and vertices
(VI) are present on the perimeter segment including the
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at least four sides, respectively between the vertex (C)
with the smallest inside angle among the at least three
vertices (V(i)) and one (A) of the two vertices (A, B),
and between the vertex (C) with the smallest inside angle
5 and the other (B) of the two vertices (A, B), said
vertices (VI) having inside angles larger than the inside
angle of the vertex (C) with the smallest inside angle.
[0016] The metallic hollow columnar member of the
invention is suitable for a frame member, in particular,
10 which constitutes a frame of a motorcar.
[0017] In the present invention, the "polygon" means a
diagram formed by intersection points of straight lines
corresponding to each extended side. The metallic hollow
columnar member with the polygonal cross-section includes
15 a member with vertices having curvatures.
[0018] According to the present invention, there is
provided a member wherein impact absorbing performance
and robustness are improved without deteriorating
strength balance.
20
Brief Description of Drawings
[0019] FIG. 1 is a diagram for schematically showing
reactive force and an amount of crushing when a member is
crushed, while explaining a method for improving impact
25 absorbing performance.
FIG. 2 is a schematic view for explaining the
relationship between maximum tolerable flexion load and
an inside angle.
FIG. 3 is a graph for explaining the relationship
30 between the maximum tolerable flexion load and the inside
angle.
FIG. 4 is a schematic view for explaining a dynamic
state when a hollow columnar member is crushed in an
axial direction.
35 FIG. 5 is a schematic view for explaining geometric
deformation and change in the inside angle when flexion.
FIG. 6 is a schematic view of a perimeter segment
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for explaining change in inside angles of vertices when a
polygonal cross-section is flexed at one vertex.
FIG. 7 is a schematic view of a perimeter segment of
a polygonal cross-section of the hollow columnar member
5 as an example of the invention.
FIG. 8 is a view of an example of a perimeter
segment of a polygonal cross-section of the invention,
schematically showing a transverse cross-section of the
hollow columnar member before and after the flexion,
10 wherein, among one or more vertices (VI) presenting on
approximate straight lines of an approximate polygon
between two vertices A, C and between two vertices B, C,
the inside angle of at least one vertex is larger than
the inside angle of vertex C. In this regard, mark (+)
15 indicates a vertex, among vertices between vertices A and
B, having the inside angle larger than the inside angles
of neighboring vertices, and mark (-) indicates a vertex,
among vertices between vertices A and B, having the
inside angle smaller than the inside angle of at least
20 one of the neighboring vertices.
FIG. 9 is a view schematically showing a transverse
cross-section of the hollow columnar member before and
after the flexion, wherein, three or more points do not
satisfy the condition of the invention, the points being
25 positioned on approximate straight lines of an
approximate polygon between two vertices A' and B' among
vertices of a perimeter segment of a transverse polygonal
cross-section having five or more vertices. In this
regard, mark (+) indicates a vertex, among vertices
30 between vertices A' and B', having the inside angle
larger than the inside angle of at least one of the
neighboring vertices, and mark (-) indicates a vertex,
among vertices between vertices A' and B', having the
inside angle smaller than the inside angles of
35 neighboring vertices.
FIG. 10 is an explanatory view schematically showing
a perimeter segment of a polygonal cross-section of the
m0
hollow columnar member as an example of the invention.
FIG. 11 is an explanatory view schematically showing
a perimeter segment of a polygonal cross-section of the
hollow columnar member as an example of the invention.
5 FIG. 12 is an explanatory view of a transverse
cross-section and dimensions of a member as a comparative
example.
FIG. 13 is an explanatory view of a transverse
cross-section and dimensions of a member as an embodiment
10 of the invention.
FIG. 14 is a comparison diagram of the relationship
between reactive force and an amount of crushing
generated when a thin-walled hollow columnar member is
crushed.
15 FIG. 15 is an explanatory view of a transverse
cross-section and dimensions of a member as a comparative
example.
FIG. 16 is an explanatory view of a transverse
cross-section and dimensions of a member as an embodiment
20 of the invention.
FIG. 17 is a comparison diagram of the relationship
between reactive force and an amount of crushing
generated when a thin-walled hollow columnar member is
crushed.
25 FIG. 18 is a comparison diagram of the relationship
between reactive force and an amount of crushing
generated when a thin-walled hollow columnar member is
crushed.
30 Embodiments for Carrying out the Invention
[0020] First, basis of the present invention will be
explained with reference to Figs. 1 to 6.
In order to improve impact absorbing performance of
a hollow columnar member with a polygonal cross-section,
35 it is necessary to increase an amount of energy
absorption per unit amount of crushing in the axial
direction of the hollow columnar member. In order to
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increase the amount of energy absorption, it is important
to maintain an average value of the reactive force
generated when crushing the member at a high level.
[0021] To this end, it is necessary to (1) increase
5 the reactive force which varies due to the deformation in
the crushing, as indicated by a dashed line in Fig. 1,
and (2) inhibit decrease in the reactive force which
varies due to the deformation in the crushing, as
indicated by a dotted line in Fig. 1.
10 [0022] As a result of analysis and experiments
regarding the crushing of a member in the axial
direction, the inventors found that (a) the increase in
the reactive force when the crushing is affected mainly
by the number of vertices of the transverse cross-section
15 of the member before the deformation; (b) the decrease in
the reactive force when the crushing is affected by the
number of vertices of the transverse cross-section of the
member during the deformation; and (c) the increase in
the reactive force affects another neighboring member
20 since the maximum reactive force is increase, while the
decrease in the reactive force does not affect another
neighboring member since the maximum reactive force is
not changed.
[0023] Generally, in the hollow columnar member with
25 the polygonal cross-section, the vertex of the polygonal
cross-section may disappear or vanish due to the flexion
during the crushing. In this case, the member is
deformed while having a cross-section with vertices fewer
than original vertices. When the vertex of the cross-
30 section vanishes, the length of a side of the polygonal
cross-section is increased, whereby a cycle of buckling
is extended. Since the cycle of buckling corresponds to
a fluctuation cycle of the reactive force, the number of
peaks of the reactive force during the crushing is
35 decreased when the cycle of buckling is extended.
Therefore, the maximum reactive force of the member
before the buckling may be raised by increasing the
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number of the vertices of the polygonal cross-section.
However, since an inside angle of the vertex is increased
when the number of the vertices of the polygonal crosssection
is increased, the member is easily to be flexed,
5 whereby the reactive force after the member is flexed may
be significantly decreased.
[0024] Since it is inevitable that the hollow columnar
member with the polygonal cross-section is flexed in the
crushing, it is important how the member is flexed, in
10 order to improve the impact absorbing performance of the
member. Further, since the reactive force is decreased
due to the flexion, an amount of decrease in the reactive
force may be controlled by controlling the flexion so as
to reduce the number of vertices which vanish when the
15 deformation occurs.
[0025] As a result of analysis and experiments
regarding the crushing of a hollow columnar member with a
polygonal cross-section, the inventors found that the
vanishment of the vertices can be avoided by controlling
20 the position of flexion, not by reducing a frequency of
flexion; and that the inside angle of the vertex is an
important factor for controlling the position of flexion.
[0026] Generally, in the hollow columnar member with
the polygonal cross-section, as the inside angle of the
25 vertex in the transverse cross-section is increased, the
hollow columnar member may be easily flexed. For
example, as shown in Fig. 2, in a system including two
elastic deformable bars, wherein each bar has a
longitudinal direction only and is connected to each
30 other at one end thereof at an angle 0 and the opposite
end of each bar is fixed, the maximum tolerable flexion
load immediately before the initiation of the flexion,
when a load is applied to the connecting part or a vertex
from the above as indicated by an arrow F, can be
35 analyzed in view of material mechanics. As shown in Fig.
3, when the maximum tolerable flexion load at angle 9 of
90 degrees is equal to 1.00, the maximum tolerable
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flexion load at angle 6 of 120 degrees and 150 degrees are
approximately 0.30 and 0.04, respectively.
[0027] As described above, it can be understood from
Fig. 3 that the maximum tolerable flexion load is very
5 sensitive to the inside angle of the vertex. Therefore,
by properly determining the magnitude of the inside angle
of each vertex in the polygonal cross-section, the
deformation mode of the hollow columnar member with the
polygonal cross-section can be controlled, and the
10 robustness thereof can be improved.
[0028] On the other hand, in the crushing deformation
of the hollow columnar member with the polygonal crosssection,
a force is applied to the hollow columnar member
in the axial direction thereof. Before the deformation,
15 as shown in Fig. 4, a tensile load is applied to each
vertex of the polygonal cross-section, wherein the
tensile load is directed to the neighboring vertices.
When the hollow columnar member is flexed, the inside
angle of the vertex at the flexed portion is increased
20 (+), while the inside angle of the vertices neighboring
the vertex at the flexed portion are decreased (-) under
the geometric condition. Therefore, the periphery of the
flexed portion is poorly flexed (Fig. 5). Similarly, the
inside angle of a further neighboring vertex is increased
25 (+). In other words, when the flexion occurs at one
vertex, the inside angles are alternately increased or
decreased ((+) or (-)), whereby the vertex having the
increased inside angle is likely to vanish or disappear
(Fig. 6).
30 [0029] In view of such flexion of the hollow columnar
member, the present invention can be applied to a hollow
columnar member with a polygonal cross-section having at
least five vertices. Although depending on the loading
direction when the crushing, the position in the
35 polygonal cross-section, where the flexion occurs and the
vertex vanishes, is mainly determined by the positions
and the magnitudes of the inside angles of the vertices.
^P - 12 -
and the existence of a connecting portion of a flange,
etc. In addition, it is preferable that the hollow
columnar member be made from metal, since it is important
that the material of the hollow column member has high
5 strength and ductility in order to improve energy
absorbing performance, and has small anisotropy (i.e.,
maintains the ductility even in a complicated stress
condition).
[0030] On the other hand, since the flexion easily
10 occurs in a "compact-type" crushing deformation in the
axial direction, it is preferable that the hollow
columnar member with the polygonal cross-section has
dimensions so that the "compact-type" crushing
deformation occurs in the axial direction. Concretely, a
15 ratio of a distance "D" between the vertices of the
polygonal cross-section and a plate thickness "t" (t/D)
is preferably 0.005 or more, more preferably, 0.010 or
more. Further, a ratio of a longitudinal length "H" of
the hollow columnar member and a minimum length "h" of
20 the polygonal cross-section (h/H) is preferably 0.10 or
more, more preferably, 0.15 or more. In this regard, the
"minimum length" of the polygonal cross-section means a
minimum distance between two parallel straight lines
which tangentially contact the transverse cross-section
25 of the hollow columnar member. In addition, the
"compact-type" is explained in a plurality of documents,
and means the deformation mode which is crushed by
repeating a constant pattern when the crushing
deformation in the axial direction.
30 [0031] Next, a first embodiment of the present
invention is explained.
First, in a polygonal cross-section having at least
five vertices and sides extending between the vertices,
two vertices "A" and "B" with small inside angles are
35 selected, and a perimeter of the polygonal cross-section
is divided by two vertices A and B into two perimeter
segments with one or more sides. In this regard, two
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vertices A and B are selected so that at least one of the
two perimeter segments contains at least four sides.
Next, a straight line connecting two vertices A and B is
determined as "L," and the length of straight line L
5 (i.e., a distance between two vertices A and B) is
determined as "S." Further, a distance between straight
line L and each of the at least three vertices (V(i)
(i=l, 2, 3, ...)) included in the perimeter segment which
includes the at least four sides is determined as "SS(i)"
10 (i=l, 2, 3, . . . ) . In this regard, if SS(i)<0.5S is true
(i.e., the inside angle is larger than 90 degrees) and
the inside angles of vertices V(i) in the polygonal
cross-section are all equal to or less than 180 degrees
(Fig. 7), then at least one of vertices V(i) on the
15 perimeter segments between vertices A and B is likely to
vanish due to the flexion.
[0032] When at least three vertices V(i) includes a
vertex with the inside angle of 180 degrees or more, the
side extends outward from the vertex. As a result, when
20 the hollow columnar member is crushed, the vertex with
the inside angle of 180 degrees or more is deformed in a
manner significantly different from the other vertices.
Therefore, the deformation of the hollow columnar member
during the crushing is complicated, whereby it is
25 difficult to control the deformation.
[0033] On the other hand, when SS(i)0) is true,
as a is decreased (i.e., as the inside angles of vertices
V(i) are increased), at least one of vertices V(i) is
likely to vanish due to the flexion.
30 [0034] Further, in the present embodiment, the inside
angle of vertex C with the smallest inside angle among
vertices V(i) is larger than the inside angles of the two
vertices A, B. Also, among the vertices presenting on
the selected perimeter segment and between vertices A and
35 B or between vertices B and C, vertices having inside
angles larger than the inside angle of vertex C are
referred to as vertices V(I). Vertex V(I) preferentially
^1 - 14 -
becomes a starting point of the flexion when the hollow
columnar member is crushed and deformed, and vertices A,
B and C other than vertices V(I) are hardly flexed,
whereby the vanishment of vertices A, B and C can be
5 avoided. In other words, in this embodiment, (j)A<(|)C<())VI is
true, and (t)B<(t)C<(t)VI is true. In this regard, (|)A, 0) is true,
as a is decreased (i.e., as the inside angles of vertices
V(i) are increased), at least one of vertices V(i) is
likely to vanish due to the flexion.
[0042] Further, in the present embodiment, the inside
10 angle of vertex C with the smallest inside angle among
vertices V(i) is larger than the inside angles of the two
vertices A, B. Also, among the vertices presenting on
the selected perimeter segment and between vertices A and
B or between vertices B and C, vertices having inside
15 angles larger than the inside angle of vertex C are
referred to as vertices V(I). Vertex V(I) preferentially
becomes a starting point of the flexion when the hollow
columnar member is crushed and deformed, and vertices A,
B and C other than vertices V(I) are hardly flexed,
20 whereby the vanishment of vertices A, B and C can be
avoided. In other words, in this embodiment, (j)A< - 17 -
inside angles of vertices VI and C be as large as
possible. Preferably, the difference is 10 degrees, and
more preferably, 20 degrees. In addition, when a
plurality of vertices C having the same inside angle
5 exist, vertices C are adjacent to each other. If they
are not adjacent to each other (i.e., two points having
small inside angles in Fig. 9 correspond to vertices C),
the number of vanishing vertices cannot be reduced as
shown in Fig. 9.
10 [0045] In addition, it is important that the above
relationship between vertices A, B, C and VI be satisfied
in at least a part of the transverse cross-section of the
hollow columnar member, and it is not necessary that the
above relationship be satisfied in all of the vertices of
15 the cross-section. For example, in the case that the
member partially has a longitudinal bead and the crosssection
includes the vertex with the inside angle of 180
degrees or more, if the relationship relating to the
inside angle of the invention is satisfied in the other
20 area, the reduction in the varying reactive force due to
the deformation when the crushing can be avoided.
[0046] By creating an area including two joint
sections J such as flanges, where the distribution and
the positional relationship of the inside angles of the
25 vertices in the transverse cross-section as described
above are satisfied, the position of flexion in the
polygonal cross-section can be controlled, whereby the
number of vanishing vertices can be reduced.
[0047] The metallic hollow columnar member of the
30 present invention is particularly suitable for a frame
member which constitutes a frame of an automobile. In
the automotive field, many designers and researchers
address many problems: improving safety performance of
collision, reducing vehicle body weight for improving
35 fuel efficiency, and shortening a developing period for
many vehicle types in view of globalization, etc.
[0048] Regarding the safety performance of collision.
- 18 -
in Japan, a standard equivalent to UN uniform criteria
(ECE rule), R94 (the protection of an occupant in the
event of an offset collision) has been established, and
applied to new models on or after 2007. This standard
5 has also been applied to commercial vehicles weighing 2.5
tons or less. In the United States, a side pole impact
at the speed of 32 km/h be added to FMVSS214 has been
planned since 2009. Further, FMVSS301 has been revised
so that an offset rear impact at the speed of 80 km/h has
10 been used since 2006.
[0049] Regarding the fuel efficiency of an automobile,
in Japan, the "Act on the Rational Use of Energy" has
been revised and put in force since April, 2006, wherein
the "Fuel Efficiency Standard for Heavy Duty Vehicles"
15 should be achieved by 2015. In the United States, the
federal government published a draft revision regarding a
CAFE system for 2008-2011 model small trucks. In both
the federal government and California, tightening of
limitations in the next period is in discussion.
20 [0050] Regarding globalization, the amount of export
of automobiles has significantly increased in recent
years. For example, the amount of export in 2005 was
rapidly increased by 22% in comparison to 2001. It is
expected that overseas production will exceed domestic
25 production of all makers in Japan, due to Japanese makers
advancing into Russia, etc.
[0051] In view of such a situation, in order to
shorten the design time, reduce in weight of the vehicle
body, and improve the safety performance of collision at
30 a rapid rate, the present invention may contribute the
reduction of a burden of a car designer and the weight
saving of the vehicle body, since the safety performance
of collision may be improved only by arranging the
distribution of the inside angles without changing the
35 strength balance of the entire frame in the present
invention. There are many components in the automobile
to which the dynamic load is applied when the collision.
- 19 -
In particular, the present invention may significantly
contribute when designing an energy absorbing member,
such as a crash box and a front side member which
significantly contribute an amount of energy absorption
5 when frontal collision, or a rear side member which
significantly contribute an amount of energy absorption
when rear collision.
Example
10 [0052] Hereinafter, the effect of the present
invention will be explained with reference to examples.
First, as shown in Figs. 12 and 13, in relation to
thin-walled hollow columnar members 100 and 200 having
two kinds of generally decagonal cross-sections, the
15 inventors compared the relationship between a reactive
force when crushing and an amount of crushing. The
dimensions of the cross-sections are indicated in Fig. 12
(member 100) and Fig. 13 (member 200). Member 200
corresponded to the shape of one example of the present
20 invention. Both members 100 and 200 were made from
JSC590Y steel, had a length of 300mm, a plate thickness
of 1.6mm. Further, all of the corners of the members had
a curvature of 1.35mm""'". When an impact body having the
weight of 700kg collided with each member in the axial
25 direction (or the direction perpendicular to the sheet of
Figs. 12 and 13) and in the compressive direction at an
initial speed of 5.0m/s, the relationship between the
reactive force when crushing and the amount of crushing
was evaluated by analysis, and compared between members
30 100 and 200 (Fig. 14).
[0053] Next, in relation to thin-walled hollow
columnar members 300 and 400 having two kinds of
generally decagonal cross-sections, the inventors
compared the relationship between a reactive force when
35 crushing and an amount of crushing. The dimensions of
the cross-sections are indicated in Fig. 15 (member 300)
and Fig. 16 (member 400). Member 400 corresponded to the
- 20 -
shape of one example of the present invention. Both
members 300 and 400 were made from JSC590Y steel, had a
length of 150mm, a plate thickness of 1.6mm. Further,
all of the corners of the members had a curvature of
5 1.35mm''''. When an impact body having the weight of 700kg
collided with each member in the axial direction (or the
direction perpendicular to the sheet of Figs. 15 and 16)
and in the compressive direction at an initial speed of
5.0m/s, the relationship between the reactive force when
10 crushing and the amount of crushing was evaluated by
analysis, and compared between members 300 and 400 (Fig.
17) .
[0054] Further, in relation to members 300 and 400,
the inventors carried out the similar crushing analysis
15 wherein the collision angle was inclined by one degree
relative to the axial direction (i.e., inclined by one
degree toward the right side relative to the direction
perpendicular to the sheet of Figs. 15 and 16), and
observed the effect due to change in the boundary
20 condition of the relationship between the reactive force
and the amount of crushing (Fig. 18).
[0055] In any of the examples, in the member of the
present invention, although an initial peak of the
reactive force was the same as the member which was not
25 included in the invention, the significant reduction of
the reactive force from the initial peak when the flexion
was limited more than the member out of the invention.
Further, even when the boundary condition was changed, it
was observed that the relationship between the reactive
30 force and the amount of crushing (i.e., the impact
absorbing performance) was not substantially changed in
the member of the invention. According to the present
invention, the impact absorbing performance and the
robustness may be improved while maintaining the maximum
35 reactive force of the member.

f§ - 21 -
CLAIMS
Claim 1
A metallic hollow columnar member with a polygonal
cross-section having at least five vertices and sides
5 extending between the vertices, wherein:
the polygonal cross-section is divided by two
vertices (A, B) with small inside angles into two
perimeter segments with a perimeter comprising one or
more sides, the at least one of the two perimeter
10 segments containing at least four sides,
the respective inside angles of at least three
vertices (V(i) (i=l, 2, 3, ...)) included in the
perimeter segment which includes the at least four sides
are equal to or less than 180 degrees,
15 a distance (SS(i) (1=1, 2, 3, ...)) between
each of the at least three vertices (V(i) (1=1, 2, 3,
.. . ) ) and a straight line (L) connecting the two vertices
(A, B) is shorter than 1/2 of a distance between the two
vertices (A, B ),
20 the inside angle of a vertex (C) with the
smallest inside angle among the at least three vertices
(V(i)) is larger than the inside angles of the two
vertices (A, B), and
vertices (VI) are present on the perimeter
25 segment including the at least four sides, respectively
between the vertex (C) with the smallest inside angle
among the at least three vertices (V(i)) and one (A) of
the two vertices (A, B), and between the vertex (C) with
the smallest inside angle and the other (B) of the two
30 vertices (A, B), said vertices (VI) having inside angles
larger than the inside angle of the vertex (C) with the
smallest inside angle.
Claim 2
35 A metallic hollow columnar member with a polygonal
cross-section having at least five vertices and sides
extending between the vertices, wherein:
22 -
the metallic hollow columnar member comprises
two joined sections (J),
the polygonal cross-section is divided by two
vertices (A, B) in the vicinity of the two joined
5 sections (J) into two perimeter segments with a perimeter
comprising one or more sides, the at least one of the two
perimeter segments containing at least four sides,
the respective inside angles of at least three
vertices (V(i) (i=l, 2, 3, ...)) included in the
10 perimeter segment which includes the at least four sides
are equal to or less than 180 degrees,
a distance (SS(i) (i=l, 2, 3, ...)) between
each of the at least three vertices (V(i) (i=l, 2, 3,
...)) and a straight line (L) connecting the two vertices
15 (A, B) is shorter than 1/2 of a distance between the two
vertices (A, B), and
vertices (VI) are present on the perimeter
segment including the at least four sides, respectively
between the vertex (C) with the smallest inside angle
20 among the at least three vertices (V(i)) and one (A) of
the two vertices (A, B), and between the vertex (C) with
the smallest inside angle and the other (B) of the two
vertices (A, B), said vertices (VI) having inside angles
larger than the inside angle of the vertex (C) with the
25 smallest inside angle.
30
Claim 3
The metallic hollow columnar member according to
claim 1 or 2, wherein an intended purpose of the metallic
hollow columnar member is a frame of a motorcar.