U.S. patent application number 10/711502 was filed with the patent office on 2005-02-10 for method of improving impact absorbing and deformation control characteristics of vehicle components.
This patent application is currently assigned to FORD GLOBAL TECHNOLOGIES, LLC. Invention is credited to Caliskan, Ari Garo, Joaquin, Armando Mateo, Sanders, Paul George, Zaluzec, Matthew John.
Application Number | 20050029836 10/711502 |
Document ID | / |
Family ID | 33130083 |
Filed Date | 2005-02-10 |
United States Patent
Application |
20050029836 |
Kind Code |
A1 |
Caliskan, Ari Garo ; et
al. |
February 10, 2005 |
METHOD OF IMPROVING IMPACT ABSORBING AND DEFORMATION CONTROL
CHARACTERISTICS OF VEHICLE COMPONENTS
Abstract
A crush rail or other structural member of a vehicle is provided
with crush triggers. The crush triggers are formed by heating
localized areas of the crush rail or other part and allowing them
to cool slowly to provide increased ductility and reduced strength
in a localized region. The crush rail is designed to collapse in a
series of convolutions in a regular and repeated pattern. Crush
triggers may be provided on body pillars, steering columns, drive
shafts, engine support cradles, and other parts of a vehicle. A
plurality of crush triggers may be provided on a single structural
member depending upon impact absorption requirements.
Inventors: |
Caliskan, Ari Garo;
(Ypsilanti, MI) ; Sanders, Paul George; (Milan,
MI) ; Joaquin, Armando Mateo; (Rochester Hills,
MI) ; Zaluzec, Matthew John; (Canton, MI) |
Correspondence
Address: |
BROOKS KUSHMAN P.C./FGTL
1000 TOWN CENTER
22ND FLOOR
SOUTHFIELD
MI
48075-1238
US
|
Assignee: |
FORD GLOBAL TECHNOLOGIES,
LLC
One Parklane Blvd Suite 600 Parklane Towers East
Dearborn
MI
|
Family ID: |
33130083 |
Appl. No.: |
10/711502 |
Filed: |
September 22, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10711502 |
Sep 22, 2004 |
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10248350 |
Jan 13, 2003 |
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6820924 |
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Current U.S.
Class: |
296/193.06 |
Current CPC
Class: |
C21D 2221/00 20130101;
B62D 21/15 20130101; F16F 7/12 20130101 |
Class at
Publication: |
296/193.06 |
International
Class: |
B62D 024/04 |
Claims
What is claimed is:
1. A body pillar assembly of a vehicle comprising: an elongated
pillar formed of a heat treatable alloy, the pillar having a bottom
end attached to the chassis of the vehicle and a top end attached
to the body of the vehicle at a point spaced above the chassis of
the vehicle; and at least one crush trigger made by heat treating a
localized area of the pillar to reduce locally the yield strength
and increase the ductility of the pillar.
2. The body pillar assembly of claim 1 wherein the crush trigger is
created by means of induction heating.
3. The body pillar assembly of claim 1 wherein the crush trigger is
heated circumferentially.
4. The body pillar assembly of claim 1 wherein one crush trigger is
provided proximate the top end of the pillar, and a second crush
trigger is provided proximate the bottom end of the pillar which is
attached to the chassis.
5. A steering column assembly of a vehicle having improved crash
worthiness, comprising: steering column component made from a heat
treatable tube having circular cross section, the steering column
component having a first end that is closest to a steering wheel
and a second end that is closest to the steering gear; and a crush
trigger created by heat treating a localized area of the metal to
decrease the yield strength and increase the ductility of the
metal, the crush trigger being on the end of the elongated member
that is attached to the steering gear.
6. The steering column assembly of claim 5 wherein the crush
trigger is made by means of induction heating.
7. The steering column assembly of claim 5 wherein the crush
trigger is heat treated circumferentially.
8. A drive shaft for a rear wheel drive vehicle with improved crash
worthiness, comprising: an elongated member made from a heat
treatable metal, having a circular cross section, and having two
ends, one end being attached to a transmission, and the other end
being attached to a rear differential gear assembly; and a crush
trigger created by heat treating the metal to decrease the yield
strength and increase the ductility of the metal, the crush trigger
being on the end of the drive shaft that is connected to the rear
differential assembly.
9. The drive shaft of claim 8 wherein the elongated member is
formed by means of extrusion.
10. An engine support frame with improved crash worthiness,
comprising: an engine cradle made of a heat treatable metal; and a
crush trigger created by heat treating the engine cradle to locally
reduce the yield strength and increase the ductility of the engine
cradle.
11. A steering wheel for a vehicle, comprising: a hub assembly
adapted to be connected to a steering column assembly; a ring
formed of a heat treatable alloy and being secured to the hub
assembly; and at least one area being formed on the ring by locally
heating the area to reduce its strength and increase its ductility
so that local area will more easily bend in a collision than other
portions of the ring.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a division of U.S. application Ser. No.
10/248,350 filed Jan. 13, 2003.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method of selectively
modifying the physical characteristics of structural members to
improve control of part deformation and enhance impact energy
absorption.
[0004] 2. Background Art
[0005] Certain structural components of vehicles are designed to
improve crash worthiness of vehicles in the event of a collision.
Impact energy absorption characteristics of vehicle parts are
engineered to provide improved protection of vehicle occupants. For
example, bumpers, bumper support brackets, steering columns, drive
shafts and the like are designed, in part, to withstand the impact
of a collision and absorb impact loads through material
deformation.
[0006] It is preferable that some vehicle parts bend in a
controlled manner from the standpoint of improving impact energy
absorption because bending the part allows a part to absorb more
energy than if the part breaks or buckles in a single location.
Passenger compartment pillars, steering wheels and engine mounts
are parts that benefit from controlling deformation in the event of
a collision.
[0007] Protective crumple zones and selectively weakened structural
components are known to be enhanced by drilling, notching or
otherwise reducing the cross-sectional area of component parts.
Forming holes or slot to enhance the crush behavior structural
components adds to tooling and manufacturing costs. When structural
members are drilled, pierced or otherwise modified by conventional
methods, stress risers are created and work hardening of the metal
may lead to fatigue and tend to enhance the likelihood that a part
will be susceptible to fatigue cracks and breakage. Providing holes
or notches in impact absorbing members may also increase
susceptibility to corrosion.
[0008] Another method of controlling crushing is to provide
convolutions or ridges in an energy absorbing member. This
alternative requires expensive manufacturing steps and does not
facilitate the use of low-cost extruded parts.
[0009] Parts that are too strong are capable of transmitting higher
loads and are not easily crushed to absorb impacts. Structural
strength obtained by using high strength alloys of aluminum, steel
and other metals permits reduction in the weight of component
parts. However, increased strength of such parts causes them to
become more susceptible to fracture and less capable of absorbing
impact loads through deformation.
[0010] There is a need for a simple and inexpensive method for
improving the impact energy absorbing characteristics of structural
vehicle parts. There is also a need for structural components made
from high strength alloys that yield to impact forces in a
controlled manner. A need also exists for flexible design
alternatives that can be tuned for impact energy absorption and
controlled deformation. Tuning the impact energy absorbing
characteristics and deformation control characteristics of a part
is not easily accomplished with prior art techniques and could only
be provided with extensive tooling and complex manufacturing
processes. Other characteristics that are important to improve
include corrosion resistance, durability and improved noise,
vibration and harshness.
[0011] The above problems and shortcomings of the prior art
products and methods are addressed by applicants' invention as
summarized below.
SUMMARY OF THE INVENTION
[0012] According to one aspect of the present invention, a crush
rail having improved structural properties for improving the crash
worthiness of a vehicle is provided. The crush rail comprises an
elongated rail made from metal that is provided with a crush
trigger. The crush trigger is integrally formed on the rail and is
a localized part of the elongated member that is heat treated to
decrease the yield strength and increase the ductility of the
metal. The localized part of the elongated member is spaced from an
end of the rail.
[0013] According to other aspects of the invention, the crush
trigger is heat treated by means of induction heating. The
elongated rail may be made from aluminum, steel, or magnesium
alloys.
[0014] According to another aspect of the invention, a bumper
support bracket having improved crash worthiness is provided that
comprises an elongated metal member with a rectangular cross
section. The elongated member has a first end bolted to the frame
of the automobile and a second end spaced from the frame. At least
one crush trigger is formed by heat treating a localized area
spaced from but near the second end of the elongated member. The
crush trigger is an area of reduced yield strength and increased
ductility.
[0015] According to other aspects of the invention as it relates to
a bumper support, the elongated rail is made from a heat treatable
metal alloy. The crush trigger may be heated circumferentially by
various heating processes, for example, by induction heating. The
crush trigger is created at a pre-determined distance from the free
edge with the distance being determined as a function of the
material characteristics, wall thickness and dimensions of the
rectangular tube. The crush trigger is located to control the
location and force required to initiate crush upon impact.
[0016] A plurality of crush triggers may be provided in addition to
the first crush trigger with a distance between each crush trigger
being substantially the same distance as the distance between the
second end and the first crush trigger. The first crush trigger is
preferably heat treated to obtain a particular yield strength and a
particular ductility. Each subsequent crush trigger may have a
relatively higher yield strength and relatively lower ductility
than the crush trigger adjacent to the crush trigger in the
direction of the second end.
[0017] According to another aspect of the invention, a body pillar
assembly for a vehicle is provided. The body pillar includes an
elongated pillar formed of a heat treatable alloy. The pillar has a
bottom end attached to the chassis or compartment pan of the
vehicle and a top end attached to the body of the vehicle at a
point spaced above the chassis of the vehicle. At least one crush
trigger is formed by heat treating a localized area of the pillar
to locally reduce yield strength and increase ductility of the
pillar.
[0018] According to other aspects of the invention, as they relate
to body pillars of a vehicle, the crush trigger may be created by
means of induction heating. For example, one crush trigger may be
provided near a top end of the b-pillar and a second crush trigger
may be provided proximate the bottom end of the b-pillar which is
attached to the chassis or compartment pan.
[0019] According to another aspect of the invention, a steering
column assembly of a vehicle having improved crash worthiness and
steering rigidity is provided. The steering column assembly
includes a steering column component made from a heat treatable
tube having a circular cross section. The steering column component
has a first end that is closest to the steering wheel and a second
end that is closest to the steering gear. A crush trigger is
created by locally heating an area of the heat treatable tube to
decrease the yield strength and increase the ductility of the
metal. The crush trigger is formed near the end of the heat
treatable tube that is attached to the steering gear.
[0020] According to another aspect of the invention, a drive shaft
for a rear wheel drive vehicle is provided. The drive shaft
includes an elongated member made from heat treatable metal having
a circular cross section. The drive shaft includes two ends with
one end being attached to a transmission and the other end being
attached to a rear differential assembly. A crush trigger is
created by heat treating the metal to decrease the yield strength
and increase the ductility of the metal. The crush trigger is
formed near the end of the drive shaft that is connected to the
rear differential assembly. The drive shaft may be made by an
extrusion process.
[0021] According to another aspect of the invention, an engine
support frame, or mount, is provided for improving the crash
worthiness of a vehicle. The engine mount may be made of a heat
treatable metal with a crush trigger being created by forming a
hole in the engine mount and heat treating an area rearward of the
hole in a localized area to reduce the yield strength and increase
the ductility thereof. In the event of an impact that involves the
engine, a fastener securing the engine to the engine mount can
deform the localized area on the engine mount and elongate the hole
that receives the fastener.
[0022] Another potential application of the invention is in the
manufacture of steering wheels. By using the present invention a
steering wheel can be made of a high strength alloy to obtain
weight savings. The steering wheel would then be locally heat
treated to reduce its strength around a portion of its periphery so
that the wheel would deform in the event of a collision that would
cause a driver's head to impact the wheel. Another advantage of
this application is that the rigidity of the steering wheel is
improved.
[0023] According to another aspect of the present invention, a
crush rail is prepared from an elongated member made from a heat
treatable metal having a first and a second end and intermediate
portions between the first and second ends. A crush trigger is
created by heat treating the elongated member with a continuously
varied yield strength and ductility being provided along the length
of the elongated member to provide progressively greater yield
strength and reduced ductility from the first end to the second end
of the elongated member. The yield strength and ductility are
modified by heat treating different areas of the elongated member
for different amounts of time. Yield strength and ductility may
also be modified applied along the length of the elongated member
by changing heat treat temperature or duration of heat treatment
along the length of the elongated member. The first end is heat
treated to have the lowest yield strength and the highest ductility
while the second end has the highest yield and the lowest ductility
with the yield strength of the intermediate portion of the
elongated member varying continuously from the first end to the
second end.
[0024] The above aspects of the different embodiments of the
present invention and additional aspects will be better understood
in view of the attached drawings and following detailed description
of the various embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a side elevation view of a vehicle having a crush
rail;
[0026] FIG. 2 is a perspective view of a rail having two crush
triggers formed therein by locally heat treating a portion of the
rail;
[0027] FIG. 2a is a perspective view of an alternative embodiment
of a crush rail with only the corners of the rail being heat
treated to form crush triggers;
[0028] FIG. 3 is a perspective view showing the deformation of a
crush rail similar to the rail shown in FIG. 2 after impact;
[0029] FIG. 4 is a cross-sectional view taken along the line 4-4 in
FIG. 3;
[0030] FIG. 5 is a cross-sectional view taken along the line 5-5 in
FIG. 3;
[0031] FIG. 6 is a graph showing the peak load of a untreated crush
rail compared to the peak load transmitted by a crush rail having a
crush trigger formed on the rail;
[0032] FIG. 7 is a diagrammatic side elevation view of a vehicle
having various parts formed with crush triggers according to the
present invention;
[0033] FIG. 8 is a perspective view of an engine mount having crush
triggers formed thereon;
[0034] FIG. 9 is an elevation view of a steering wheel having
weakened portions on its perimeter; and
[0035] FIG. 10 is a fragmentary perspective view of a crush rail
having a series of crush triggers formed thereon.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0036] Referring now to FIG. 1, a vehicle 10 having a frame 12 is
provided with a crush rail 14 that may be part of a bumper support
bracket. The crush rail could alternatively be connected to a
vehicle with a unibody type construction that does not have a
separate frame. The crush rail 14 connects the frame 12 of the
vehicle 10 to the front bumper 16. It should be readily appreciated
that variations of the crush rail 14 may be provided in other
locations in the vehicle 10 such as between the frame 12 and the
rear bumper 18, or the like. The crush rail 14 includes a first end
20 that is connected to the frame 12 and a second end 22 that is
connected directly or indirectly to the front bumper 16.
[0037] Referring now to FIG. 2, a crush rail 14 is shown in
isolation. One or more crush triggers 24 may be provided as
represented by the cross hatched band. The crush trigger 24 is
formed by locally heating the crush rail 14 and allowing it to
cool. The rail 14 is preferably formed of a high strength aluminum
alloy (such as 6XXX series alloy), steel alloy, or magnesium alloy.
The crush rail is a heat treated member. Heat treating is provided
to increase the strength of the crush rail. The crush trigger 24 is
preferably formed by induction heating the rail at a point that is
spaced from the second end 22 of the rail 14. Other methods of
heating may be used to form the crush trigger such as a gas torch,
electric radiant heat, or laser heating. After heating, the rail
may be allowed to cool. In aluminum, the objective of the heat
treatment is to overage the material to create a lower strength,
stable microstructure that does not age harden after processing.
This implies that solutionizing is not desired, and that the heat
treatment temperature should be kept below single phase (alpha)
region in the aluminum phase diagram. Depending on the alloy
composition, the maximum temperature could range from 350.degree.
C. to 600.degree. C.
[0038] Referring to FIG. 2a, an alternative embodiment of a crush
rail 14' is shown wherein only the corners of the rail are heated
to form a crush trigger 25. The crush trigger 25 may be formed by
inductively or otherwise heating the corners. By reducing the
strength and increasing the ductility of the corners it is thought
that impact absorption performance can obtained that is similar to
the embodiment of FIG. 2.
[0039] Referring now to FIGS. 3-5, a crush rail 14 is shown after a
simulated impact in a test fixture. The rail 14 is impacted at the
second end 22 while it is held in a fixture (not shown). After
impact, a series of outward convolutions 28 and inward convolutions
30 are formed in the area of the crush trigger 24. Once the
convolutions begin forming, they tend to be replicated as the rail
is further deformed. Even if only one crush trigger is provided, a
series of two, three, or more convolutions may stack up as the
crush rail 14 absorbs impact energy.
[0040] Referring now to FIG. 6, a graph comparing the peak load of
a crush rail having no trigger represented by load line 36. Tests
of a rail having a crush trigger is represented by line 38. The
peak load transmitted in the test of the crush rail having no
trigger yielded a peak load of about 35,000 lbs. In comparison, the
crush rails having a crush trigger as shown in FIG. 2 yielded a
peak load of about 15,000 lbs. Based upon this test it is apparent
that the effect of potentially reducing the peak load by more than
half that may dramatically reduce the force transmitted to a
vehicle occupant in a collision as a result of superior impact
energy absorption of the crush rail.
[0041] Referring now to FIG. 7, a vehicle 10 is shown that includes
a crush trigger formed according to the present invention in a
variety of structural body parts. The invention could also be
applied to other vehicle parts. The vehicle 10 includes a body
pillar assembly 42 that is commonly referred to as the B pillar.
The body pillar 42 includes a lower crush trigger 44 near the
chassis or compartment pan 46 of the vehicle 10. An upper crush
trigger 48 may also be provided near the roof 50 of the vehicle.
Crush triggers 44, 48 permit the body pillar assembly 42 to absorb
impact energy in a controlled fashion. It is believed that the body
pillar assembly 42 with crush triggers 44, 48 is more likely to
bend at the top and bottom instead of the middle and thereby
improve occupant protection.
[0042] The vehicle 10 also includes a steering column assembly 56.
Steering column assembly 56 includes a steering column tube 58 that
is attached to a steering gear 60 of the vehicle on a steering gear
end 62. A steering wheel 64 is connected to the steering column
assembly 56 at a steering wheel end 66 of the steering column tube
58. A crush trigger 68 is preferably formed near the steering gear
end 62 of the steering column tube 58.
[0043] A drive shaft 70 is connected to the vehicle transmission
72. The drive shaft 70 includes a transmission end 74 that is
connected to the transmission 72. A differential 76 is provided in
a rear wheel drive vehicle with a differential end 78 of the drive
shaft 70 being connected to the differential 76. A crush trigger 80
is preferably provided near the differential end 78 of the drive
shaft 70.
[0044] Referring now to FIGS. 7 and 8, an engine support frame 86
is provided for an engine cradle or engine mount assembly 88 that
is formed from a heat treatable alloy. A hole 90 is provided on the
engine mount 88 through which a fastener may be inserted for
mounting the engine. A local area 92 represented by cross-hatched
lines rearward of the hole 90 is heated to reduce the strength of
the engine mount locally and increase its ductility. As the engine
mount in the local area becomes more ductile it will be more likely
to deform or bend instead of breaking in the event of a
collision.
[0045] Referring to FIG. 9, the steering wheel 64 is illustrated
that is made from a heat treatable material. The steering wheel has
two portions 96 of its periphery that are heated to reduce the
strength and increase the ductility of the upper portion 95 of the
wheel so that if a driver's head contacts the wheel 64 in an
impact, the top portion 95 of the steering wheel 64 will bend to
reduce the severity of the impact. By making the steering wheel 64
from a high strength alloy, the weight of the wheel may be reduced
and the rigidity increased to improve noise, vibration and
harshness performance. In addition, improved noise, vibration and
harshness characteristics may be achieved.
[0046] Referring now to FIG. 10, an alternative embodiment of a
crush rail 100 is provided that includes an end portion 102. A
first trigger 104 is provided on the crush rail 100 near the end
portion 102. Second, third and fourth triggers 106, 108, and 110
are provided at regularly or irregularly spaced intervals along
crush rail 100. By providing multiple crush triggers, it may be
possible to further tune the impact absorption capability of the
crush rail 100. The degree of modification of the hardness of the
crush triggers may be varied in a decreasing relationship by
sequentially reducing the heat applied for each crush trigger. The
crush rail could also be made with a section of continuously
reduced ductility by progressively reducing the heat applied.
[0047] While embodiments of the invention have been illustrated and
described, it is not intended that these embodiments illustrate and
describe all possible forms of the invention. Rather, the words
used in the specification are words of description rather than
limitation, and it is understood that various changes may be made
without departing from the spirit and scope of the invention.
* * * * *