WO 2006/073884 PCT/US2005/046731
BUMPER SYSTEM WITH ENERGY ABSORBER
BACKGROUND OF THE INVENTION
This invention relates generally to automobile vehicle bumpers, and more particularly,
to energy absorbing vehicle bumper systems.
A known standard which bumper systems often are designed to meet is the United
States Federal Motor Vehicle Safety Standard (FMVSS). For example, some energy
absorbing bumper systems attempt to reduce vehicle damage as a result of a low speed
impact by managing impact energy and intrusion while not exceeding a rail load limit
of the vehicle. In addition, some bumper systems attempt to reduce pedestrian injury
as a result of an impact.
A bumper system typically includes a beam that extends widthwise across the front or
rear of a vehicle and is mounted to rails that extend in a lengthwise direction. The
beam typically is steel, and the steel beam is very stiff and provides structural strength
and rigidity. To improve the energy absorbing efficiency of a bumper system, some
bumper systems also include shock absorbers.
The efficiency of an energy absorbing bumper system, or assembly, is defined as the
amount of energy absorbed over distance, or the amount of energy absorbed over load.
A high efficiency bumper system absorbs more energy over a shorter distance than a
low energy absorber. High efficiency is achieved by building load quickly to just
under the rail load limit and maintaining that load constant until the impact energy has
been dissipated.
To improve the energy absorbing efficiency, shock absorbers sometimes are
positioned, for example, between the steel bumper beam and the vehicle rails. The
shock absorbers are intended to absorb at least some of the energy resulting from an
impact. Adding shock absorbers to a bumper assembly results in an added cost and
complexity as compared to a steel beam. The shocks also add weight to the bumper
assembly, which is also undesirable since such added weight may reduce the overall
fuel efficiency of the vehicle.
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Other known energy absorbing bumper systems include a W-shaped energy absorber.
However, the stack-up of the horizontal walls of the energy absorber is a problem.
Because of the stack-up issue, known W-shaped energy absorbers cannot be used in
pedestrian impact solutions.
BRIEF DESCRIPTION OF THE INVENTION
In one aspect, a bumper system for an automobile vehicle is provided. The bumper
system includes a beam configured to attach to the vehicle, and an energy absorber
coupled to the beam. The energy absorber includes a body having a first side and an
opposing second side with the second side facing the beam, an upper crushable
member extending from the first side of the body, and a lower crushable member
extending from the first side of the body and spaced apart from the upper crushable
member. The upper and lower crushable members each include an upper transverse
wall, a lower transverse wall, and an outer wall. Each upper transverse wall and each
lower transverse wall includes alternating solid portions and open portions. Each
solid and open portion extends from the body to the outer wall of a crushable member.
The solid portions of the lower transverse wall of the upper crushable member are
aligned with the open portions of the upper transverse wall of the lower crushable
member. Also, solid portions of the upper transverse wall of the lower crushable
member are aligned with the open portions of the lower transverse wall of the upper
crushable member.
In another aspect, a bumper assembly for an automobile vehicle is provided. The
bumper assembly includes a beam having a top surface and a bottom surface, with the
beam configured to attach to the vehicle, an energy absorber coupled to the beam, and
a fascia attached to the energy absorber to substantially envelop the beam and the
energy absorber. The energy absorber includes a body having a first side and an
opposing second side with the second side facing the beam, an upper crushable
member extending from the first side of the body, and a lower crushable member
extending from the first side of the body and spaced apart from the upper crushable
member. The upper and lower crushable members each include an upper transverse
wall, a lower transverse wall, and an outer wall. Each upper transverse wall and each
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lower transverse wall includes alternating solid portions and open portions. Each
solid and open portion extends from the body to the outer wall of a crushable member.
The solid portions of the lower transverse wall of the upper crushable member are
aligned with the open portions of the upper transverse wall of the lower crushable
member. Also, solid portions of the upper transverse wall of the lower crushable
member are aligned with the open portions of the lower transverse wall of the upper
crushable member.
In another aspect, an energy absorber for a vehicle bumper system is provided. The
energy absorber includes a body having a first side and an opposing second side, an
upper crushable member extending from the first side of the body, and a lower
crushable member extending from the first side of the body and spaced apart from the
upper crushable member. The upper and lower crushable members each include an
upper transverse wall, a lower transverse wall, and an outer wall. Each upper
transverse wall and each lower transverse wall includes alternating solid portions and
open portions. Each solid and open portion extends from the body to the outer wall of
a crushable member. The solid portions of the lower transverse wall of the upper
crushable member are aligned with the open portions of the upper transverse wall of
the lower crushable member. Also, solid portions of the upper transverse wall of the
lower crushable member are aligned with the open portions of the lower transverse
wall of the upper crushable member.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an exploded perspective schematic illustration of a bumper assembly in
accordance with an embodiment of the present invention.
Figure 2 is a front schematic illustration of the energy absorber shown in Figure 1.
Figure 3 is a front schematic illustration of the energy absorber shown in Figure 1
after an impact event.
Figure 4 is a cross-sectional schematic illustration of the energy absorber shown in
Figure 1.
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Figure 5 is a cross-sectional schematic illustration of the energy absorber shown in
Figure 4 after an impact event.
Figure 6 is a cross-sectional schematic illustration of another embodiment of the
energy absorber shown in Figure 1.
Figure 7 is a cross-sectional schematic illustration of the energy absorber shown in
Figure 6 after an impact event.
DETAILED DESCRIPTION OF THE INVENTION
A bumper system that includes an energy absorber that is designed to provide
improved inner horizontal wall crushing that will eliminate the stack-up of the walls is
described below in detail. In an exemplary embodiment, an energy absorber having
inner horizontal walls that include alternating solid and open portions is attached to a
beam. The solid and open portions are arranged so that during an impact event, the
solid portions crush into the open portions so that the solid portions do not hit each
other which prevents a stack-up of material. The beams are fabricated, for example,
from steel, aluminum, or glass mat thermoplastic (GMT). The energy absorber, in the
exemplary embodiment, is fabricated from Xenoy® material and is tunable so as to
meet desired impact criteria, e.g., pedestrian and low speed impacts.
Although the bumper system is described below with reference to specific materials
(e.g. Xenoy® material (commercially available from General Electric Company,
Pittsfield, Massachusetts) for the energy absorber), the system is not limited to
practice with such materials and other materials can be used. For example, the beam
need not necessarily be a steel, aluminum, or GMT compression molded beam, and
other materials and fabrication techniques can be utilized. Generally, the energy
absorber is fabricated from materials that result in efficient energy absorption, and the
beam materials and fabrication technique are selected to result in a stiff beam.
Referring to the drawings, Figure 1 is an exploded perspective illustration of a bumper
assembly 20 in accordance with an exemplary embodiment of the present invention,
and Figure 2 is a front schematic illustration of energy absorber 22. Referring to
Figures land 2, bumper assembly 20 includes an energy absorber 22 and a beam 24.
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Energy absorber 22 is positioned between beam 24 and a fascia 26 which, when
assembled, form vehicle bumper assembly 20. As should be understood by those
skilled in the art, beam 24 is attached to lengthwise extending vehicle frame rails (not
shown).
Fascia 26 typically is generally formed from a thermoplastic material amenable to
finishing utilizing conventional vehicle painting and/or coating techniques. Generally,
fascia 26 envelops both energy absorber 22 and reinforcing beam 24 such that neither
component is visible once attached to the vehicle.
Beam 24, in the exemplary embodiment, is fabricated from extruded aluminum. In
other embodiments, beam 24 is fabricated from roll formed steel or a compression
molded glass mat thermoplastic (GMT). Beam 24 can have one of multiple
geometries, including being configured as a rectangular section, a B-section, a D-
section, an I-beam, or having a C or W cross-sectional shape. The geometry of beam
24 is selected to provide a desired section modulus depending on the particular
application in which the beam is to be used.
Energy absorber 22 includes a body 40 having a first side 42 and a second side 44.
First side 42 faces away from beam 24 and second side 44 faces toward beam 24.
Body 40 includes a flanged frame 45 for attaching energy absorber 22 to beam 24. An
upper crushable member 46 extends from first side 42 of body 40. Upper crushable
member 46 includes an upper transverse wall 48, a lower transverse wall 50, and an
outer wall 52. Upper transverse wall 48 includes alternating solid portions 54 and
open portions 56 along the length of upper crushable member 46. Solid portions 54
and open portions 56 extend from body 40 to outer wall 52. Similarly, lower
transverse wall 50 includes alternating solid portions 58 and open portions 60 along
the length of upper crushable member 46. Solid portions 58 and open portions 60
extend from body 40 to outer wall 52.
A lower crushable member 62 also extends from first side 42 of body 40 and is spaced
apart from upper crushable member 46. Lower crushable member 46 has a structure
similar to upper crushable member 46 and includes an upper transverse wall 64, a
lower transverse wall 66, and an outer wall 68. Upper transverse wall 64 includes
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alternating solid portions 70 and open portions 72 along the length of lower crushable
member 62. Solid portions 70 and open portions 72 extend from body 40 to outer
wall 68. Similarly, lower transverse wall 66 includes alternating solid portions 74 and
open portions 76 along the length of lower crushable member 62. Solid portions 74
and open portions 76 extend from body 40 to outer wall 68.
Solid portions 58 of lower transverse wall 50 of upper crushable member 46 are
aligned with open portions 72 of upper transverse wall 64 of lower crushable member
62. Also, solid portions 70 of upper transverse wall 64 of lower crushable member 62
are aligned with open portions 60 of lower transverse wall 50 of upper crushable
member 46. As illustrated in Figure 3, this arrangement permits solid portions 58 of
lower transverse wall 50 of upper crushable member to buckle into open portions 72
of upper transverse wall 64 of lower crushable member 62 and solid portions 70 of
upper transverse wall 64 of lower crushable member 62 to buckle into open portions
60 of lower transverse wall 50 of upper crushable member 46 during an impact event.
With the solid portions of the transverse walls bucking into the open portions of the
opposing transverse wall, stack-up of the opposing transverse walls 50 and 64 is
eliminated. A stack-up of the opposing transverse walls 50 and 64 could adversely
affect the ability of energy absorber 22 to absorb energy.
In the example embodiment, transverse walls 48, 50, 64 and 66 vary linearly in
thickness from a first front-most portion 82 to a rearmost portion 86. In one
embodiment, the wall thickness varies from about 1 millimeter (mm) to about 7 mm,
in another embodiment, from about 1.5 mm to about 5 mm, and still another
embodiment, from about 2.5 mm to about 3.5 mm. In further embodiments, the
thickness of the walls is constant from front-most portion 82 to rearmost portion 86
and is between about 1 mm to about 7 mm. In still further embodiments, the
thickness of the walls are stepped. Particularly, the thickness of the walls of front-
most portion 82 is constant and the thickness of the walls of rearmost portion 86 is
constant with the walls of rearmost portion 86 thicker than the walls of front-most
portion 82.
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Energy absorber 22 is tunable in that by selecting a thickness of each portion 82 and
86, the response of energy absorber 22 can be altered depending on the application in
which absorber 22 is used. For example, front portion 82 of energy absorber 22 is
tuned, and tunable, to absorb pedestrian leg form impact, and rear portion 86 is tuned,
and tunable, for low speed and pendulum impact.
Another aspect in appropriately tuning energy absorber 22 is the selection of the
thermoplastic resin to be employed. The resin employed may be a low modulus,
medium modulus or high modulus material as needed. By carefully considering each
of these variables, energy absorbers meeting the desired energy impact objectives can
be manufactured.
The characteristics of the material utilized to form energy absorber 22 include high
toughness/ductility, thermally stable, high energy absorption capacity, a good
modulus-to-elongation ratio and recyclability. While the energy absorber may be
molded in segments, the absorber also can be of unitary construction made from a
tough plastic material. An example material for the absorber is Xenoy material, as
referenced above. Of course, other engineered thermoplastic resins can be used.
Typical engineering thermoplastic resins include, but are not limited to, acrylonitrile-
butadiene-styrene (ABS), polycarbonate, polycarbonate/ABS blend, a
copolycarbonate-polyester, acrylic-styrene-acrylonitrile (ASA), acrylonitrile-
(ethylene-polypropylene diamine modified)-styrene (AES), phenylene ether resins,
blends of polyphenylene ether/polyamide (NORYL GTX® from General Electric
Company), blends of polycarbonate/PET/PBT, polybutylene terephthalate and impact
modifier (XENOY® resin from General Electric Company), polyamides, phenylene
sulfide resins, polyvinyl chloride PVC, high impact polystyrene (HIPS), low/high
density polyethylene (1/hdpe), polypropylene (pp) and thermoplastic olefins (tpo).
As shown in Figure 4, lower transverse wall 50 of upper crushable member 46 and
upper transverse wall 64 of lower crushable member 62 have a concave shape or
profile between a front-most portion 82 and a rearmost portion 86. The concave shape
encourages the deflection of transverse walls 50 and 64 away from each other during
an impact. This deflection of transverse walls 50 and 64 away from each other during
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impact prevents a stack-up of material which could adversely affect the ability of
energy absorber 22 to absorb energy. Figure 5 shows energy absorber 22 during an
impact and the deflection of transverse walls 50 and 64.
In another embodiment, shown in Figure 6, lower transverse wall 50 of upper
crushable member 46 and upper transverse wall 64 of lower crushable member 62
have a convex shape or profile between a front-most portion 82 and a rearmost portion
86. The convex shape encourages the deflection of transverse walls 50 and 64 away
from upper crushable member 46 and lower crushable member 62 respectively. This
deflection of transverse walls 50 and 64 away from upper crushable member 46 and
lower crushable member 62 during impact directs solid portions 58 of lower
transverse wall 50 of upper crushable member to buckle into open portions 72 of
upper transverse wall 64 of lower crushable member 62 and solid portions 70 of upper
transverse wall 64 of lower crushable member 62 to buckle into open portions 60 of
lower transverse wall 50 of upper crushable member 46 and prevents a stack-up of
material which could adversely affect the ability of energy absorber 22 to absorb
energy. Figure 7 shows energy absorber 22 during an impact and the deflection of
transverse walls 50 and 64.
While the invention has been described in terms of various specific embodiments,
those skilled in the art will recognize that the invention can be practiced with
modification within the spirit and scope of the claims.
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WHAT IS CLAIMED IS:
1. A bumper system (20) for an automobile vehicle, said bumper system
comprising:
a beam (24) configured to attach to the vehicle; and
an energy absorber (22) coupled to said beam, said energy absorber comprising:
a body (40) having a first side (42) and an opposing second side (44), said second side
facing said beam,
an upper crushable member (46) extending from said first side of said body; and
a lower crushable member (62) extending from said first side of said body and spaced
apart from said upper crushable member;
said upper and lower crushable members each comprising an upper transverse wall
(48, 64), a lower transverse wall (50, 66), and an outer wall (52, 68), each said upper
transverse wall and each said lower transverse wall comprising alternating solid
portions (54, 58) and open portions (56, 60), each solid and open portion extending
from said body to said outer wall,
wherein said solid portions of said lower transverse wall of said upper crushable
member are aligned with said open portions of said upper transverse wall of said
lower crushable member, and said solid portions of said upper transverse wall of said
lower crushable member are aligned with said open portions of said lower transverse
wall of said upper crushable member.
2. A bumper system in accordance with Claim 1 wherein said lower transverse
wall (50) of said upper crushable member (46) has a concave cross-sectional shape
and said upper transverse wall (64) of said lower crushable member (62) has a
concave cross-sectional shape.
3. A bumper system (20) in accordance with Claim 1 wherein said lower
transverse wall (50) of said upper crushable member (46) has a convex cross-sectional
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shape and said upper transverse wall (64) of said lower crushable member (62) has a
convex cross-sectional shape.
4. A bumper system (20) in accordance with Claim 1 wherein said body (40)
comprises a flanged frame (45) for attachment to said beam (24).
5. A bumper system (20) in accordance with Claim 1 wherein said energy
absorber (22) comprises a thermoplastic material.
6. A bumper system (20) in accordance with Claim 1 wherein said beam (24)
comprises at least one of steel, aluminum, thermoplastic, and glass mat thermoplastic.
7. A bumper assembly (20) for an automobile vehicle, said bumper assembly
comprising:
a beam (24) having a top surface and a bottom surface, said beam configured to attach
to the vehicle;
an energy absorber (22) coupled to said beam; and
a fascia (26) attached to said energy absorber to substantially envelop said beam and
said energy absorber;
said energy absorber comprising:
a body (40) having a first side (42) and an opposing second side (44), said second side
facing said beam,
an upper crushable member (46) extending from said first side of said body; and
a lower crushable member (62) extending from said first side of said body and spaced
apart from said upper crushable member;
said upper and lower crushable members each comprising an upper transverse wall
(48, 64), a lower transverse wall (50, 66), and an outer wall (52, 68), each said upper
transverse wall and each said lower transverse wall comprising alternating solid
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portions (54, 58) and open portions (56, 60), each solid and open portion extending
from said body to said outer wall,
wherein said solid portions of said lower transverse wall of said upper crushable
member are aligned with said open portions of said upper transverse wall of said
lower crushable member, and said solid portions of said upper transverse wall of said
lower crushable member are aligned with said open portions of said lower transverse
wall of said upper crushable member.
8. A bumper assembly (20) in accordance with Claim 7 wherein said lower
transverse wall (50) of said upper crushable member (46) has a concave cross-
sectional shape and said upper transverse wall (64) of said lower crushable member
(62) has a concave cross-sectional shape.
9. A bumper assembly (20) in accordance with Claim 7 wherein said lower
transverse wall (50) of said upper crushable member (46) has a convex cross-sectional
shape and said upper transverse wall (64) of said lower crushable member (62) has a
convex cross-sectional shape.
10. A bumper assembly (20) in accordance with Claim 7 wherein said body (40)
comprises a flanged frame (45) for attachment to said beam (24).
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A bumper system (20) for an automobile vehicle includes, in an exemplary embodiment, a beam (24) configured to
attach to the vehicle, and an energy absorber (22) coupled to the beam. The energy absorber includes a body (40), an upper crushable
member (46) extending from the body, and a lower crushable member (62) extending from the body and spaced apart from the upper
crushable member. The upper and lower crushable members each include an upper transverse wall (48, 64), a lower transverse wall
(50, 66), and an outer wall (52, 68). Each upper transverse wall and each lower transverse wall includes alternating solid portions
(54, 58) and open portions (56, 60). Each solid and open portion extends from the body to the outer wall of a crushable member. The
solid portions of the lower transverse wall of the upper crushable member are aligned with the open portions of the upper transverse
wall of the lower crushable member.