U.S. patent application number 09/932673 was filed with the patent office on 2003-02-20 for taper and flare energy absorption system.
Invention is credited to Stull, Eric M., Summe, Todd L., Yeh, Jieh-Ren.
Application Number | 20030034659 09/932673 |
Document ID | / |
Family ID | 25462708 |
Filed Date | 2003-02-20 |
United States Patent
Application |
20030034659 |
Kind Code |
A1 |
Summe, Todd L. ; et
al. |
February 20, 2003 |
TAPER AND FLARE ENERGY ABSORPTION SYSTEM
Abstract
An energy absorption system and method comprised of a crush
tube, a taper component, and a flare component. The crush tube is
inserted into a matching hole in the taper component. As the taper
and flare components are moved down over the crush tube, the taper
component decreases the diameter of the crush tube and the flare
component splits the crush tube in a plurality of petals. The crush
tube may include a plurality of initiator slits to aid in the
flaring process. When mounted with the longitudinal axis of the
crush tube parallel to an axis of an impact, the present invention
is capable of absorbing some or all of the crash event by
dissipating energy by the tapering, flaring, friction, and other
methods.
Inventors: |
Summe, Todd L.; (Pittsburgh,
PA) ; Yeh, Jieh-Ren; (Pittsburgh, PA) ; Stull,
Eric M.; (Delmont, PA) |
Correspondence
Address: |
ALCOA INC
ALCOA TECHNICAL CENTER
100 TECHNICAL DRIVE
ALCOA CENTER
PA
15069-0001
US
|
Family ID: |
25462708 |
Appl. No.: |
09/932673 |
Filed: |
August 17, 2001 |
Current U.S.
Class: |
293/133 ;
188/371 |
Current CPC
Class: |
F16F 7/125 20130101;
B60R 19/34 20130101 |
Class at
Publication: |
293/133 ;
188/371 |
International
Class: |
B60R 019/34 |
Claims
What is claimed is:
1. An energy absorption assembly, comprising: a crush tube; a taper
component with an opening on a first end adapted to accept said
crush tube; and a flare component attached to a second end of said
taper component.
2. The energy absorption system of claim 1, wherein said taper
component and said flare component are manufactured as one single
component.
3. The energy absorption system of claim 1, wherein said crush tube
comprises a plurality of initiator slits in one end.
4. The energy absorption system of claim 3, wherein said plurality
of initiator slits is four slits.
5. The energy absorption system of claim 3, wherein each of said
plurality of initiator slits is approximately 6 mm deep and 1 mm
wide.
6. The energy absorption system of claim 1, wherein said taper
component, said flare component, and said crush tube have an
anodized coating thereon.
7. The energy absorption system of claim 1, wherein said crush tube
comprises a tube with a cross-sectional profile selected from the
group consisting of a circle, a square, an oval, a rectangle, a
hexagon, and a combination thereof.
8. The energy absorption system of claim 1, wherein said taper
component and said flare component are approximately 70 mm in
length combined.
9. The energy absorption system of claim 1, further comprising: a
vehicle bumper; and a vehicle chassis rail, wherein the crush tube,
taper component, and flare component are mounted between said
bumper and said chassis rail.
10. The energy absorption system of claim 1, wherein said flare
component includes a plurality of slots to allow a flared portion
of said crush tube to exit the energy absorption system.
11. The energy absorption system of claim 10, wherein said
plurality of slots is four.
12. The energy absorption system of claim 1, wherein said taper
component, said flare component and said crush tube are made of an
aluminum alloy.
13. The energy absorption system of claim 1, wherein said flare
component and said taper component are two separate pieces.
14. The energy absorption system of claim 13, wherein said taper
component and said flare component are made of two different
materials.
15. A taper and flare device, comprising: a hollow taper and flare
housing; a crush tube receiving profile at a first end of the
hollow housing adapted to receive a crush tube; a crush tube exit
profile including a plurality of slots adapted to allow flared ends
of a crush tube to leave the hollow housing; and a tapered inner
wall between said crush tube receiving profile and said crush tube
exit profile adapted to compress the crush tube in the radial
direction.
16. The device of claim 15, further comprising: a hollow crush tube
at least partially inserted into said crush tube receiving
profile.
17. The device of claim 16, wherein the inner profile of the crush
tube receiving profile and the outer profile of the crush tube are
approximately equivalent.
18. The device of claim 16 wherein said crush tube includes a
plurality of initiator slits.
19. A method of absorbing energy in a single direction, said method
comprising the steps of: providing a crush tube, a taper component,
and a flare component; inserting one end of said crush tube into
said flare component; and orienting said crush tube, said taper
component, and said flare component such that the taper component
reduces the diameter of the crush tube and the flare component
allows fragmented sections of the crush tube to leave the flare
component when the crush tube is displaced parallel to the
longitudinal axis of the crush tube in a direction towards the
taper and flare components.
20. The method of claim 19 wherein said step of inserting the crush
tube into the taper component occurs prior to a step in which the
crush tube, taper component, and flare component are installed
between a vehicle bumper and a vehicle chassis.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to systems and methods for
crash energy management and, more specifically, relates to systems
and methods for energy absorption in automotive applications
utilizing a taper and flare energy absorption system.
[0003] 2. Description of the Background
[0004] The design for crashworthiness is an extremely important
aspect of vehicle and structural design. The primary aspect of
crashworthiness design is providing a means to dissipate kinetic
energy through the work of deformation within the vehicle
structure. In the current energy absorption design systems, such as
axially collapsed or inverted crush tubes, highly ductile material
is critically important due to the severe strain states experienced
during the deformation. Also, the amount of energy absorption is
very sensitive to the quality and controls of the material. The
available materials that meet these requirements, especially for
non-ferrous metals, may be limited, and the resulting product cost
may be significantly increased.
[0005] A typical prior art application may utilize an axial folding
collapse technique, wherein a pre-dented hollow tube 100 is crushed
lengthwise into a regular pattern 110 (see, FIG. 1). These
triangular or other-shaped dents (not shown) force the crush tube
to collapse into the "natural mode" which can then produce expected
results. Typically, these prior art crush tubes 100 are made of
aluminum alloys, but many other materials are also used. Some
conventional crush tube assemblies may not contain any dents.
[0006] These conventional crush tubes are typically installed
behind the front bumper section of an automobile or truck. The tube
is affixed at one end to a rail on the chassis of the automobile
and at the other end to the bumper. Hence, the force of a resulting
collision that is perpendicular to the front face of the bumper
will cause an axial compressive force on the installed crush tube,
causing it to collapse. These tubes may also be installed in the
rear bumper of automobiles or in any other orientation or system in
which a spatially-confined absorption of an abrupt axial load is
desired.
[0007] The conventional crush tube applications may suffer from one
or more drawbacks that prevent their controlled use in many
applications. For example, because of the intense crushing action,
the tube must be made of a ductile metal, such as a special
aluminum alloy. Such highly ductile metals are typically more
expensive than less ductile materials. If materials with lower
ductility are used, they may crack or split and therefore lose some
or all of their energy absorption capacity.
[0008] Also, as seen in FIG. 1, the "crush zone" 110 into which the
tube 100 is compacted does not extend throughout the entire length
of the crush tube 100. Hence, the uncrushed portions of the crush
tube 100 are wasted in terms of energy absorption. Testing has
shown that the conventional crush tube application may crush only
approximately 70%-75% of the length of the crush tube.
[0009] Because of the intense and structured way in which the
conventional application is crushed in a natural mode pattern,
these crush tubes are typically made pursuant to very tight
tolerances. Even small variations in the thickness of the material
of the crush tube may cause a large variation in energy absorption
during a crash event. For example, a weakness in one area of the
tube may cause the tube to buckle in that area with a result that
the tube does not perform as designed and may not absorb the
requisite amount of energy for its intended application.
[0010] Even during normal operation, these conventional crush tube
applications are not ideal. For example, the force dissipated by
the "collapsing" process oscillates around the mean force
dissipation of the system. Therefore, high peaks of force are
created by the conventional methods. These peak loads may cause a
"jerking" sensation to the passengers of the vehicle and may
require that the backup structure be reinforced, thereby increasing
the peak loads when crushing the backup structure. This may reduce
passenger safety.
[0011] Also, because the existing technologies typically utilize
only about 70% of the original crush tube length for energy
absorption, high loads are needed to absorb the required energy in
a given space. Therefore, in the case of automobiles, the
accelerations imparted to the passengers are correspondingly high
which may also adversely affect passenger safety.
[0012] These various limitations to the current implementation of
axially loaded crush tube absorption systems are preferably
addressed by one or more embodiments of the present invention.
SUMMARY OF THE INVENTION
[0013] In accordance with the present invention, there is provided
an energy absorption system and method generally comprised of a
crush tube, a taper component, and a flare component. The crush
tube is inserted into a matching hole in the taper component. As
the taper and flare components are moved over the crush tube, the
taper component decreases the diameter of the crush tube and the
flare component splits the crush tube into a plurality of petals.
When mounted with the longitudinal axis of the crush tube parallel
to an axis of an impact, the present invention is capable of
absorbing some or all of the crash event by dissipating energy by
the tapering, flaring, friction, and other methods.
[0014] The crush tube may include a plurality of initiator slits to
aid in the flaring process, and the crush tube may have a circular,
oval, square, rectangular, hexagonal, or other cross-sectional
profile. The taper and flare components are preferably adapted to
accept one or more of these crush tube orientations.
[0015] The present invention may utilize materials that are not
acceptable for use with conventional axial crush absorption
systems. For example, a material with less ductility may be
used.
[0016] In at least one presently preferred embodiment, the
invention is installed in a car, truck or other vehicle to
partially or wholly absorb the shock of a crash event. For example,
the energy absorption system may be mounted between a rail on the
chassis or frame of the car and a bumper. Because the present
absorption system generally dissipates energy along a single impact
axis, two or more of the present absorption systems may be
installed in a plurality of locations and orientations in a vehicle
to absorb crash shocks from various impact angles and locations.
The present invention may also be used in other axial load
applications such as trains, barriers, elevators, carriers, and the
like.
[0017] These and other features and advantages of the present
invention will become readily apparent to persons skilled in the
art from the following detailed description of the invention, the
abstract, and the attached claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] For the present invention to be clearly understood and
readily practiced, the present invention will be described in
conjunction with the following figures, wherein like reference
characters designate the same or similar elements, which figures
are incorporated into and constitute a part of the specification,
wherein:
[0019] FIG. 1 shows a conventional crush tube after partial
deformation;
[0020] FIG. 2 details one presently preferred embodiment of an
energy absorption assembly;
[0021] FIG. 3 shows a sectional view of a taper and flare energy
absorption system;
[0022] FIG. 4 shows a perspective view of a taper and flare energy
absorption system after a crash event; and
[0023] FIG. 5 shows a graph of the crush load versus crush distance
for an exemplary embodiment of the present invention and a
conventional axial collapsing crush tube.
DETAILED DESCRIPTION OF THE INVENTION
[0024] It is to be understood that the figures and descriptions of
the present invention have been simplified to illustrate elements
that are relevant for a clear understanding of the invention, while
eliminating, for purposes of clarity, other elements that may be
well known. Those of ordinary skill in the art will recognize that
other elements are desirable and/or required in order to implement
the present invention. However, because such elements are well
known in the art, and because they do not facilitate a better
understanding of the invention, a discussion of such elements is
not provided herein. The detailed description will be provided
hereinbelow with reference to the attached drawings.
[0025] In at least one presently preferred embodiment of the
invention, there is provided an energy absorption system comprising
a taper component, a flare component, and a crush tube component.
An axial load is initially absorbed by the crush tube as it is
compressed by the taper component and thereafter as it is split
apart by the flare component. The taper component and flare
component may be combined into a single "taper and flare
component." The present invention preferably combines the
advantages of tapering and flaring of crush tubes into a single
energy absorption system.
[0026] FIG. 2 details one presently preferred embodiment of an
energy absorption assembly 200 according to the present invention.
In FIG. 2, a cast, machined or fabricated taper and flare component
205 is oriented to accept the end of a crush tube 210 which is
shown broken because it is generally longer than that shown in FIG.
2. The crush tube 210 is depicted as a circular profile cylinder,
but the tube may be made in other orientations and profile shapes
as described below. When an impacting body imparts an axial load (a
load parallel to the longitudinal axis of the crush tube 210) on
the taper and flare assembly 200 (i.e., a "crash event"), the taper
and flare component 205 slides over the crush tube 210 and tapers
the tube (compresses the radial diameter of the tube).
[0027] As the taper and flare component 205 continues down the
crush tube 210 because of a continuous or additional axial load,
the tapered portion of the tube becomes split ("flared") into
multiple pieces ("petals"). The taper and flare component 205
continues to move down the crush tube 210 until all of the energy
from the crash event is absorbed or until the end of the crush tube
210 is reached.
[0028] More specifically, FIG. 3 shows a sectional view of a
preferred taper and flare assembly 300 cut parallel to the
longitudinal axis of the crush tube 310. The crush tube 310 enters
the taper and flare component 305 through an opening 315, which is
preferably just slightly larger than the profile of the crush tube
310. As the taper and flare component 305 is forced down over the
crush tube 310 (or similarly as the crush tube is forced up into
the taper and flare component), the crush tube enters the
"tapering" section 320 of the taper and flare component 305 which
is generally a gradual decrease in the size of the profile of the
crush tube 310.
[0029] For example, if the crush tube 310 was a circular profile
cylinder with a diameter of X millimeters, the taper and flare
opening 315 may be a circular opening with a diameter of just
greater than X millimeters, and the taper component 320 may
gradually reduce this diameter to approximately X-Y millimeters.
This tapering absorbs energy through the deformation of the crush
tube (described in greater detail below).
[0030] As shown in FIG. 2, the crush tube 210 is preferably
initiated with small slots 215 (shown as triangles in FIG. 2)
placed at various locations around the end of the tube 210 that
enters the taper and flare component 205. Forcing the split end of
the crush tube 210 onto the "cone" 325 (FIG. 3) of the flaring
component causes the tube to split into separate segments or
"petals" 330. These petals 330 then flare out away from the central
axis of the crush tube 310. In other words, as the taper and flare
component 305 continues to be forced down over the crush tube 310,
the "tapered" and split part of the tube will begin to flare into a
number of pieces 330 (dictated by the number of initiators 215 cut
into the tube). Preferably, no other guidance of the flares 330 is
necessary, but a guide slot 220 or other guiding mechanism may be
used in certain applications to better control the properties of
the flared crush tube.
[0031] For purposes of clarification, the small segments 313 shown
between the taper and flare components correspond to the small
amount of material between adjacent guide slots 220. If the FIG. 3
cross section is rotated slightly along the longitudinal axis (so
that the cross section is taken through the guide slots 220), these
segments 313 would not be present. The taper and flare components
are shown as one piece 305 in FIG. 3, but these components may also
be manufactured as two or more separate pieces that are then bolted
or otherwise attached together.
[0032] Preferred measurements for the initiator slots 215 may be
approximately 6 millimeters deep and 2 millimeters wide each. As
the taper and flare component 305 continues to push down over the
crush tube 310 and the flaring continues, the flared petals 330
will generally fold back over themselves ("curl") as the natural
(unguided) mode of deformation. The guide slots 220 in the flare
portion of the taper and flare component 305 may provide merely a
window or hole for the flared petals 330 to curl, but the petals
may be directed in any fashion to increase the resulting friction
(and therefore the resulting energy dissipation). The radial
compression of the tube 310 due to the taper component preferably
keeps the "split" from passing down into the non-tapered portion of
the crush tube and causing a failure or reduced energy absorption
in the system.
[0033] FIG. 4 shows a perspective view of one embodiment of a taper
and flare energy absorption system 400 after a crash event. The
taper and flare component 405 has been forced down over the
majority of the crush tube 410, and the various petals 430 (in this
case four) can be seen curled back over the taper and flare
assembly. From the outside of the assembly, the free end of the
crush tube and the resulting tapered and flared "ends" 430 of the
crush tube can be seen. The energy dissipated by the system
includes, among other sources, all of the energy used to deform the
cylinder between these two states (from tube 410 to split petals
430).
[0034] From a more technical point of view, the taper and flare
energy absorption system of the present invention is preferably
able to dissipate the energy from a crash event in a variety of
different manners. For example, during the tapering process, the
largest amount of energy is absorbed due to the reduction in the
crush tube's diameter. The amount of energy dissipated in the taper
is generally based on the decrease in the diameter of the tube
during compression and the plastic flow stress of the tube
material. The resulting crush tube will generally have a reduced
diameter, an increased thickness, and a decreased length.
[0035] Additionally, the flaring of the crush tube into multiple
petals generally dissipates work by way of friction and metal
fracture or tearing. There is friction involved as the tube is
forced over the flaring apparatus. Energy is also dissipated by the
tearing of the material.
[0036] The present invention preferably allows the use of a much
higher percentage of the original length of the crush tube for
energy absorption, relative to conventional axial compression
technology. Testing has shown that the length utilization may be
approximately 90% instead of 70% for the existing technologies
described above. Given a specified space, for example between a
vehicle bumper and the frame, the present invention preferably
provides equal energy absorption with lower peak loads and
therefore provides better safety to the passengers in the vehicle.
In addition to the higher safety potential, this invention allows
the use of materials that have a much lower ductility than those
required for the conventional technologies. Therefore, the cost of
the present system may be decreased, and the reliability of the
present system may be increased.
[0037] FIG. 5 shows a graph of the energy absorption (the crush
load) versus crush distance in a taper and flare energy absorption
system according to the present invention as compared to the
conventional axial collapsing energy absorption system. FIG. 5
shows that the displacement of the crush tube through the taper
assembly is generally linearly related to the force applied to the
tube down its longitudinal axis. At the point where the compressed
end of the tube leaves the taper apparatus, the crush tube
displacement will proceed at an approximately steady level of force
(steady state). Since the assembly process preferably accounts for
the initial portion of the load curve which is due to tapering
only, the crush load experienced in an impact is initially
approximately equal to the steady state crush load. Therefore, high
energy absorption efficiency is achieved with lower peak load
requirements in the crush rail and supporting structure. This
results in improved passenger safety due to reduced peak
decelerations.
[0038] The highest point on the FIG. 5 curves is the peak load of
the energy absorption systems. Because it takes a greater initial
load to begin the crushing of the conventional system, the
conventional system has a greater peak load than the present
invention. In the FIG. 5 example, the peak load for the crush tube
and backup structure of the present invention is shown to be
approximately 15% less than the conventional assembly. These lower
peak loads preferably result in an automobile passenger "feeling"
less deceleration during a crash event, thereby increasing
passenger safety at lower vehicle speeds.
[0039] The steady state crush load for the present invention is
also significantly higher than that of the conventional energy
absorption systems. As seen in FIG. 5, after the "pre-loading" of
the taper component of the present invention (described more fully
below), the systems reach a steady state crush load throughout much
of the length of the crush tube. The conventional assembly has
comparatively wide oscillations with a mean steady state crush load
that is approximately 35-50% lower than the present invention.
Therefore, the present invention may be capable of absorbing more
energy per unit of displacement than the prior art. A higher total
crush load absorption may be further amplified because a greater
percentage of the length of the crush tube may be utilized with the
present invention when compared to conventional systems.
[0040] The prior art systems' ability to absorb loads is typically
based on the materials used, the geometry of the tubes, and the
thickness of the tubes. Preferably, the present invention may be
used with a wider variety of materials. Specifically, the present
invention may be used with the 6000 series aluminum alloys, such as
6260 and 6063-T6 temper. Many of these alloys are commonly
available and are among the cheapest metal alloys of this type
available. The present invention may also be used with steel. The
taper or the taper and flare components both may be made of steel,
aluminum, magnesium or other materials.
[0041] In one preferred embodiment of the present invention, the
taper and flare energy absorption assembly is installed behind the
bumper of a vehicle. Specifically, the crush tube and taper and
flare component are welded or otherwise affixed between a rail of
the vehicle chassis and the bumper of the vehicle. The taper and
flare component(s) may be oriented immediately behind the bumper or
between the crush rail and backup structure (the interior of the
vehicle frame). A "preloading" step of installation for the taper
and flare system involves inserting the end of the crush tube into
the taper component to the point just before flaring. In the
vehicle, the crush tube is preferably subassembled to the taper
component by simply pushing the tube into the taper. This
pre-insertion increases the energy capacity of the system (see,
FIG. 5).
[0042] In typical energy absorption systems, material fracture is
an undesirable event, but with the present concept, the fracture is
limited to the free end of the tube because the compressive stress
field created by the taper component does not allow the fracture to
propagate past the taper. The taper component provides the
structural connection between the tube and the rest of the
structure. Therefore, the structural integrity is maintained
throughout the crash event.
[0043] Although the examples of the present disclosure have
involved the use of a hollow circular crush tube, it is also
possible to utilize other crush tube profiles such as oval, square,
rectangular, hexagonal, octagonal, etc. The taper and flare
component may be adapted to accept these various crush tube
profiles. Specifically, different taper and flare components may be
designed with different openings to accept different crush tube
profiles. These "alternative crush tubes" may also utilize common
aluminum alloys like air quenched 6063-T6 and 6060-T6 for primary
energy absorbing members or materials other than aluminum. The
taper and flare system has the potential to allow the use of more
common alloys, which may therefore improve the cost and supply base
issues.
[0044] In addition to the alloy-related issues, the existing energy
absorption technology typically utilizes 70-75% of the original
member length for energy absorption. Therefore, due to the
increased average crush load capability and crush length
efficiency, the present taper and flare concept has the potential
to significantly improve vehicle crashworthiness by absorbing more
energy with less intrusion into passenger compartments.
[0045] In the design concepts that utilize castings for the taper
and flare component, it is estimated that Advanced Green Sand
Casting (AGSC) or permanent mold castings will be best suited due
to the size, thickness and alloys available. Also, since the joints
connecting the taper, flare and crush tube are preferably
mechanical joints, it may be feasible to use any combination of the
design and materials of each component (e.g., a steel tube and
steel flare may be used with a cast taper) This added flexibility
is not generally available in the conventional energy absorption
system because of the design constraints described above.
[0046] An exemplary taper and flare component length may be
approximately 400 mm. The fracture initiators in the end of the
crush tube may be made by simple saw cuts approximately 6 mm deep
and as wide as the saw blade. In a preferred embodiment, the number
of initiators is four, however, a greater or lesser number of
initiators may be used for various applications and design
requirements. An isometric view of the exemplary initiators is
shown in FIG. 2.
[0047] The number of initiator slits may be adapted over a wide
range of values. Generally speaking, an increase in the number of
slits will increase the stability of the system during a crash
event. However, an increased number of slits may also decrease the
amount of energy that may be absorbed by the system. Hence,
depending on the desired performance of the taper and flare energy
absorption system in accordance with the present invention, the
number, size and orientation of the slits may be altered.
[0048] The present invention may be adaptable in a variety of
others ways. For example, due to the coefficient of static friction
between the tube and the taper component, significant surface
galling may occur on the taper and flare assembly which causes the
crush load to increase as the crash event progresses. This may
cause the tube to eventually collapse in an axial folding mode.
However, the surface galling may be eliminated by applying a common
hard anodize coating to the crush tube and taper and flare
components. It should be noted that the coating may affect the
coefficient of friction thus changing the crush loads. Although the
anodize coating may not be preferred, it demonstrates design
alterations that may not be feasible in the prior art which depends
more on material consistency and uniformity.
[0049] Because of the high efficiency of the energy absorption
system of the present invention, the taper and flare system may
preferably be used in other applications in addition to the
conventional front bumper orientation. For example, the present
invention may be used behind the instrument panels or in other
confined areas of the vehicle. Because of the adjustability and
high value of energy absorption, the present invention may be used
in higher inertial applications such as in trains or in elevators
as emergency braking apparatuses. The present invention may also be
less sensitive to tolerances in manufacture than conventional
applications.
[0050] Nothing in the above description is meant to limit the
present invention to any specific materials, geometry, or
orientation of parts. Many part/orientation substitutions are
contemplated within the scope of the present invention. The
embodiments described herein were presented by way of example only
and should not be used to limit the scope of the invention.
[0051] Although the invention has been described in terms of
particular embodiments in an application, one of ordinary skill in
the art, in light of the teachings herein, can generate additional
embodiments and modifications without departing from the spirit of,
or exceeding the scope of, the claimed invention. Accordingly, it
is understood that the drawings and the descriptions herein are
proffered by way of example only to facilitate comprehension of the
invention and should not be construed to limit the scope
thereof.
* * * * *