U.S. patent application number 11/242797 was filed with the patent office on 2006-09-14 for vehicle structural components made from tubular members and method therefor.
This patent application is currently assigned to COPPERWELD CANADA INC.. Invention is credited to Wayne Bland, Mamad Jahani, Stefano Lepre, Colin Newport, Livio D. Versolatto.
Application Number | 20060201227 11/242797 |
Document ID | / |
Family ID | 36121809 |
Filed Date | 2006-09-14 |
United States Patent
Application |
20060201227 |
Kind Code |
A1 |
Lepre; Stefano ; et
al. |
September 14, 2006 |
Vehicle structural components made from tubular members and method
therefor
Abstract
The invention provides rear suspension structures and engine
cradles involving tubular components. The tubular components have
variable wall thickness along the length for reducing materials
required. The tubular components also have mechanical properties
varying along the length of the tubular components, to meet the
requirements on strength and dynamic and static loads. The weight
of the tubular components can be further reduced by appropriately
varying the wall thickness and mechanical properties along the
length of the tubular components.
Inventors: |
Lepre; Stefano; (Canton,
MI) ; Jahani; Mamad; (Bremen, DE) ; Newport;
Colin; (Ayr, CA) ; Bland; Wayne; (Kitchener,
CA) ; Versolatto; Livio D.; (Dorchester, CA) |
Correspondence
Address: |
Michael L. Kenaga;DLA PIPER RUDNICK GRAY CARY LLP
P.O. Box 64807
Chicago
IL
60664-0807
US
|
Assignee: |
COPPERWELD CANADA INC.
|
Family ID: |
36121809 |
Appl. No.: |
11/242797 |
Filed: |
October 3, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60614494 |
Oct 1, 2004 |
|
|
|
Current U.S.
Class: |
72/370.14 |
Current CPC
Class: |
B21D 53/88 20130101;
B60G 2204/15 20130101; B60G 2206/8103 20130101; B60G 2206/20
20130101; B60G 2206/427 20130101; B21C 1/24 20130101; B60G 2200/42
20130101; B60G 2204/1246 20130101; B60G 2204/1226 20130101; B60G
2202/136 20130101; B60G 2204/148 20130101; B60G 2206/604 20130101;
B21C 37/16 20130101; B60G 2200/21 20130101; B60G 2202/134 20130101;
B60G 2206/8107 20130101; B60G 2206/8201 20130101; B60G 2206/012
20130101; B60G 2206/8106 20130101; B21K 1/12 20130101; B60G
2202/1362 20130101; B60G 2204/43 20130101; B62D 21/11 20130101;
B21D 26/033 20130101; B60G 2204/18 20130101; B60G 21/051 20130101;
B60G 2200/446 20130101; B60G 2206/50 20130101; B60G 2202/12
20130101; B60G 2204/4302 20130101 |
Class at
Publication: |
072/370.14 |
International
Class: |
B21D 26/02 20060101
B21D026/02; B21C 37/30 20060101 B21C037/30 |
Claims
1. A cross member for a rear suspension assembly, the cross member
comprising: a unitary tubular member, the tubular member having a
variable wall thickness along its length; the tubular member having
a generally elongated center portion, the center portion defining a
longitudinal axis along the center portion; the tubular member
including a pair of end portions and a pair of intermediate
sections each formed between the center portion and one of the end
portions, said pair of intermediate sections integrally connecting
the end portions to the center portion; each of the end portions
being displaced from and generally parallel with the longitudinal
axis, wherein the wall thickness at the end portions is smaller
than the wall thickness at the intermediate sections.
2. The cross member of claim 1, wherein the wall thickness is
larger at the center portion than at the bend portions.
3. The cross member of claim 1, wherein the wall thickness is
smaller at the center portion than at the bend portions.
4. An engine support structure for supporting an engine of a
vehicle, the engine support structure comprising: a pair of side
rails spaced from each other; and a front cross member and a rear
cross member spaced from the front member, the front and rear cross
members joining the side rails to form a general quadrilateral
shape, wherein each of the side rails is formed from a unitary
tubular member, the unitary tubular member having a variable wall
thickness along its length, the wall thickness monotonically
increasing along the unitary tubular member in a forward direction
in a substantial portion of the unitary tubular member.
5. The engine support structure of claim 4, wherein the substantial
portion extends between the rear cross member and the front cross
member.
6. A method of making a unitary tubular component from a metallic
blank tube, the tubular component having a variable wall thickness
and a desired shape, the method comprising the steps of: placing
the blank tube in a die and mandrel assembly, passing the blank
tube through the die and mandrel assembly to form a tubular blank,
the tubular blank having a wall thickness varying along its length,
and placing the tubular blank in a forming die and forming the
tubular blank into the desired shape.
7. The method of claim 6, further comprising the step of: heat
treating the tubular blank at selected locations to adjust
mechanical properties of material thereat.
8. The method of claim 7, wherein the tubular blank is heat treated
at a location where a bend is formed.
9. The method of claim 7, wherein the tubular blank is heat treated
at a location where the wall thickness is reduced.
Description
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/614,494 filed on Oct. 1, 2004.
1. FIELD OF INVENTION
[0002] The present invention relates to structural components used
in vehicles and a method of forming same.
2. BACKGROUND OF INVENTION
[0003] In the automotive industry, various structural components
are of late made from tubular blanks. This is mainly due to the
fact that tubular components can often combine strength with
significant weight and material reduction.
[0004] In manufacturing the above mentioned structural components,
it is known to design the tubular blanks with a variable wall
thickness in order to, inter alia, have localized reinforcement in
regions of the components that are subject to stress. Various
methods have been suggested to provide such blanks with variable
wall thickness. For example, the method taught in U.S. Pat. No.
5,333,775 provides a blank comprised of tubular pieces of different
wall thickness that are welded together to form the blank. Although
resulting in the required variable wall blank, this method is not
entirely satisfactory for several reasons. Firstly, the method
involves the pre-forming step of creating the blank using a welding
procedure, which adds a considerable amount to the total processing
time. Secondly, the presence of welds may lead to weak spots in the
formed product. Thirdly, the sudden changes in wall thickness
associated with this method also tend to introduce undesirable
physical properties of the final product. The management of impact
energy and design of dynamic properties also tend to become more
difficult as a result.
3. SUMMARY OF INVENTION
[0005] The invention provides vehicle structural components, such
as rear suspension structures and engine cradles, made from tubular
blanks. In one aspect, the tubular blanks are provided with a
variable wall thickness along their lengths. In another aspect of
the invention, the tubular blanks also have variable mechanical
properties along their lengths.
[0006] In a first aspect of the invention, there is provided a
cross member for a rear suspension assembly. The cross member
comprises a unitary tubular member, the tubular member having a
variable wall thickness along its length. The tubular member has a
generally elongated center portion, a pair of end portions and a
pair of intermediate sections each formed between the center
portion and one of the end portions. The pair of intermediate
sections integrally connecting the end portions to the center
portion. The center portion defines a longitudinal axis along the
center portion and each of the end portions is displaced from and
generally parallel with the longitudinal axis. The wall thickness
at the end portions is smaller than the wall thickness at the
intermediate sections.
[0007] In another aspect, there is provided an engine support
structure for supporting an engine of a vehicle. The engine support
structure includes a pair of side rails spaced from each other, and
a front cross member and a rear cross member spaced from the front
member, the front and rear cross members joining the side rails to
form a general quadrilateral shape. Each of the side rails is
formed from a unitary tubular member. The unitary tubular member
has a variable wall thickness along its length, the wall thickness
monotonically increasing along the unitary tubular member in a
forward direction in a substantial portion of the unitary tubular
member.
[0008] In yet another aspect of the invention, there is provided a
vehicle seat support structure for mounting a seat to a vehicle.
The seat support structure includes an elongated side impact cross
member formed from a blank tube and a seat frame mounted on the
impact cross member for mounting the seat thereon. The side impact
cross member has an integral end portion, the end portion being
adapted to connect the side impact cross member to the vehicle. The
side impact cross member is tubular and has a variable wall
thickness along its length; wherein the wall thickness is smallest
at the end portion.
[0009] In another aspect, there is provided a method of making a
unitary tubular component from a metallic blank tube. The tubular
component has a variable wall thickness and a desired shape. The
method includes the steps of placing the blank tube in a die and
mandrel assembly, passing the blank tube through the die and
mandrel assembly to form a tubular blank, the tubular blank having
a wall thickness varying along its length, and placing the tubular
blank in a forming die and forming the tubular blank into the
desired shape.
[0010] In other aspects the invention provides various combinations
and subsets of the aspects described above.
4. BRIEF DESCRIPTION OF DRAWINGS
[0011] For the purposes of description, but not of limitation, the
foregoing and other aspects of the invention are explained in
greater detail with reference to the accompanying drawings, in
which:
[0012] FIG. 1 is a top perspective view showing a rear suspension
assembly having a tubular cross beam according to an embodiment of
the present invention;
[0013] FIG. 2A is a front elevation view showing the tubular cross
beam of the rear suspension assembly shown in FIG. 1;
[0014] FIG. 2B is a typical stress distribution map, showing the
stress distribution in a cross beam of FIG. 1;
[0015] FIG. 2C is a top perspective view showing another exemplary
cross beam having a different wall thickness variation along the
tube;
[0016] FIG. 3 is a longitudinal cross sectional view of a tubular
blank that can be further formed for making a tubular cross beam
shown in FIG. 2A;
[0017] FIG. 4A is a longitudinal cross sectional view of another
tubular blank according to an embodiment of the present
invention;
[0018] FIG. 4B is a longitudinal cross sectional view of yet
another tubular blank according to an embodiment of the present
invention;
[0019] FIG. 5 is a cross sectional view of a die and mandrel
apparatus for forming a tubular cross beam of FIG. 2A;
[0020] FIG. 6 is a perspective view of a hydroforming die for
forming a tubular cross beam shown in FIG. 2A;
[0021] FIG. 7 is an end view of the die of FIG. 6 in an open
position;
[0022] FIG. 8 is an end view of the die of FIG. 6 in an closed
position;
[0023] FIG. 9 is a perspective view of an engine cradle having
tubular side rails according to an embodiment of the present
invention;
[0024] FIG. 10 is a perspective view of a car seat support assembly
attached to a side of a vehicle body frame; and
[0025] FIG. 11 is a side view of the car seat support assembly of
FIG. 10.
5. DETAILED DESCRIPTION OF EMBODIMENTS
[0026] The description which follows and the embodiments described
therein are provided by way of illustration of an example, or
examples, of particular embodiments of the principles of the
present invention. These examples are provided for the purposes of
explanation, and not limitation, of those principles and of the
invention. In the description which follows, like parts are marked
throughout the specification and the drawings with the same
respective reference numerals.
[0027] FIG. 1 shows a rear suspension assembly 100. As is well
known, a rear suspension serves to connect a vehicle body to the
rear road wheels. FIG. 1 shows a rear suspension for a vehicle
whose rear wheels are not driven nor steerable. However, it will be
understood that the invention is not limited to such rear
suspensions.
[0028] As can be seen from FIG. 1, the rear suspension assembly 100
has a tubular cross member, or cross beam 102. Mounted to each end
of tubular cross beam 102 is an end plate 104. End plate 104 has a
spindle hole 106 for mounting a wheel assembly (only rotor 108 is
seen). As will be understood, a road wheel can be mounted to rotor
108 through wheel studs provided thereon. Near each end of the
tubular cross beam 102 and inboard thereof is attached a lower arm
110. At the distal end of the lower arm 110 is provided a
connection bracket 112 for connecting the rear suspension assembly
100 to the body or frame of the vehicle. Also attached to the
tubular cross beam 102 and near each end thereof is a spring seat
114. A coil spring 116 is positioned on the spring seat 114 to
provide cushioning between rear suspension assembly 100 and the
undersurface of the frame or floor of the vehicle.
[0029] The cross beam 102 is a unitary tubular component, produced
from a one-piece tubular blank, as will be described later. As can
be seen in FIG. 2A, the cross beam 102 has a generally straight
center section 120, which defines a longitudinal cross beam axis
122. At each end of the cross beam 102 are generally straight end
sections 124a, 124b. The end sections are shorter than the center
section 120. The longitudinal axes of the end sections 124a, 124b
generally lie in the same plane. As can also be seen, the plane
containing the longitudinal axes of the end sections 124a, 124b is
generally parallel to the plane containing the longitudinal axis of
the center section 120 but displaced therefrom at a distance d.
Intermediate sections 126a, 126b connect each end section 124a,
124b to the center section 120. The center section 120 and the
intermediate sections 126a, 126b form a generally `U` shaped
structure. The aforementioned profile of the rear suspension
provides the sufficient ground clearance between ground and the
vehicle body, or any components attached to the center section 120.
It will be appreciated that the center section 120 may not
necessarily be straight, as long as it can provide the required
clearance.
[0030] As will be known to person skilled in the art, a rear
suspension cross beam is subjected to uneven load distribution,
either static or dynamic, in normal use. To meet the maximum load
requirements, a tubular cross beam of uniform wall thickness can be
produced. Such a cross beam will require a wall thickness that is
based on the maximum load. However, such a cross beam tends to
require more material than necessary, which contributes to
unnecessary weight of the component and waste of material. To meet
the structural requirements, such stress and stress distributions
under various conditions are often analyzed and studied. FIG. 2B is
a typical stress distribution map from such studies. The map shows
concentrated strain energy, or stress, in the vicinity of bends
128. On the other hand, towards both ends of the cross beam, the
stress is shown to be lower.
[0031] According to the invention, the wall thickness of the cross
beam 102 can be varied along its length to provide localized
strengthening to meet these stress variations. Similarly, those
regions of the cross beam not subjected to stress can be provided
with reduced wall thicknesses. An example of such a variable wall
thickness is illustrated in FIG. 2A. As illustrated in FIG. 2A, the
end sections 124a, 124b of the tubular cross beam 102 are formed
with a first wall thickness t.sub.1. Both intermediate sections
126a, 126b are formed with a second wall thickness t.sub.2.
According to the invention, the thickness t.sub.2 is greater than
the first wall thickness t.sub.1, since the intermediate section
would typically be under greater stress. By way of example, the
first wall thickness t.sub.1 is 3.3 mm and the second wall
thickness t.sub.2 is 5.5 mm.
[0032] FIG. 2C shows another exemplary mass distribution, or wall
thickness variation along the cross beam. Tubular cross beam 102'
shown in FIG. 2C is similar to that shown in FIG. 2A, except that
the wall thickness is the largest in the center region of tubular
cross beam 102'.
[0033] As will be understood, for different vehicles and different
components, there may be a different stress distribution map. In
other words, the specific locations or regions of a tubular
component that require increased or reduced wall thickness will
vary from vehicle to vehicle and from component to component. The
examples provided herein are for illustrative purpose only.
[0034] FIG. 3 illustrates a tubular blank that can be further
formed for making a tubular cross beam 102. As illustrated, the
blank 200 comprises a tubular member having a generally uniform
outer surface 202 and a generally uniform outer diameter D.sub.1.
The blank 200 is formed with a variable wall thickness, as
described further below, such that at desired portions, the wall
thickness is either reduced or increased thereby resulting in a
larger or smaller inner diameter. FIG. 3 illustrates several
constant wall thickness regions, including two end regions 204, a
constant wall thickness center region 206. Also shown are two
enhanced wall thickness regions 208, each being formed between the
center region 206 and an end region 204. In the end regions 204,
the wall thickness is t.sub.4. In the enhanced wall thickness
regions 208, the wall thickness is increased to t.sub.5. In the
center region 206, the wall thickness is changed to t.sub.4. As
will be appreciated, the wall thickness of the center region
t.sub.5 can be larger or smaller than t.sub.4, depending upon the
specific characteristics of the required blank. The wall thickness
of each region is circumferentially uniform.
[0035] It will be understood by persons skilled in the art that
various other longitudinal cross sectional profiles will depend
upon the specific requirements of the blank. Further, although the
blank 200 is illustrated as being symmetric when viewed axially
from each end, it will be understood that this is not necessary as
different constant wall thickness regions may be provided along the
length of the tube according to the specific need.
[0036] FIGS. 4A and 4B provide further examples of tubular blanks
having variable wall thickness. FIG. 4A illustrates a tubular blank
200' that has a tapered section 212 with a gradually changing wall
thickness. FIG. 4B illustrates another tubular blank 200'' that has
a number of different wall thickness sections.
[0037] The tubes of the present invention having varying wall
thicknesses can be produced as described below. In a preferred
embodiment, the blank is formed by passing a tube of constant wall
thickness through a die and mandrel assembly. An example of a die
and mandrel assembly that can be used in the present invention is
illustrated in FIG. 5. As shown, the die and mandrel assembly 214
comprises a die 216 having die cavity 218. A mandrel 220 is
provided at one end of a rod 222. The rod 222 is attached, at its
other end, to a control mechanism that allows the mandrel to be
inserted and withdrawn from the die cavity 218 in a reciprocating
manner as indicated by the short arrow 224. An original tube 230 is
attached at a first end to a draw machine, not shown. The first end
of the tube is then drawn through the die cavity so as to result in
a drawn tube 232 having a constant outer diameter. The direction in
which the tube is drawn is indicated by the long arrow 234. The die
cavity 218 is provided with a first opening 236 having a diameter
to allow the passage of the original tube 230 and a second opening
238 having a diameter to allow the passage of drawn tube 232. As
can be seen, the diameter of second opening 238 is less than that
of first opening 236. Accordingly, the diameter of the drawn tube
232 is generally less than that of the original tube 230.
[0038] As shown, the mandrel 220 is positioned within the interior
of the original tube 230 and is generally co-axial therewith. A
ring gap is formed between the mandrel and the die. If the mandrel
is moved into the die cavity 218, the wall of the original tube 230
passing through the die cavity 218 is constricted. If the mandrel
is removed from the die cavity, such constriction is not effected.
Therefore, by reciprocating the mandrel 220 in and out of the die
cavity 218 while the original tube 230 is drawn therethrough, the
size of the ring gap can be varied so as to control the wall
thickness of the tube at desired locations along its length. As
illustrated in FIG. 4, the drawn tube 232 includes thin wall
regions 240 and 242, separated by a region where the wall thickness
is not affected, 246. As shown in FIG. 5, the mandrel 220 is
provided with a small diameter portion 221 and a large diameter
portion 223 joined by a tapered portion 225. The large diameter
portion 223 is connected to the rod 222.
[0039] As will be appreciated, it is possible to form the blank to
have a number of different wall thicknesses by varying the mandrel
used or the location of the mandrel within the die. By coordinating
the speed of the motion of the mandrel and the speed at which the
tube is drawn, sections of gradual change of wall thickness can
also be formed.
[0040] Once the drawn tube 232 described above is formed, the drawn
tube 232 may be subjected to localized heat treatment to vary local
mechanical properties, such as yield stress (YS), ultimate tensile
strength (UTS) or hardness, among others, along its length. Local
heat treatment may be performed in any suitable manner. In one
embodiment, induction heating is employed for its
controllability.
[0041] As will be appreciated, cold forming of a tubular component
tends to harden the material. This hardening will occur when
forming a tube blank of variable wall thickness as well as during
the stages of bending and hydroforming, as will be described later.
Generally, material hardening increases more notably in areas of
bends or in regions where the wall thickness has been significantly
reduced. As also will be understood, the stiffness of the tubular
component along its length tends to correlate with the local wall
thickness. These variations, namely the variation of mass,
stiffness and material hardening, along the tube tend to affect not
only the static, but also the dynamic physical properties of the
tubular component after it is finally formed. It is desirable to
vary the static and dynamic physical properties of the tube to meet
the requirements imposed by design objectives. While wall thickness
may be varied to meet the load bearing requirements, a further
selective heat treatment step can be applied where necessary to
control or target certain mechanical properties in selected areas,
such as bends or thin wall areas. Tubular components with this
controlled and combined variation in mass and mechanical properties
along the tube tend to more easily meet load and dynamic
characteristic requirements with further reduced mass. Although
frequent references are made to variations of mechanical properties
along the tube, it will be understood that a tubular component
having uniform mechanical properties along its length is but one
special case.
[0042] In a heat treatment step, heating is applied to selected
sections of the drawn tube 232 to adjust the local mechanical
properties along its length. More specifically, the cold forming
process used to vary the tube wall thickness generally results in a
hardening of the material. This hardening may adversely affect the
dynamic properties of an finished article. Some sections, such as
these that will eventually (after final forming) comprise bends in
the final article, may need to be rendered more malleable to
withstand the bending process, which also tends to adjust the
physical properties of the finished article at the same time. Such
malleability may be provided by a local heat treatment. Generally,
the amount of change in local mechanical properties after the tube
blank is bent and hydroformed is known. By appropriately heat
treating, or annealing these regions prior to the bending and
hydroforming stages, a desirable distribution of mechanical
properties in the final product may be obtained. Heat treating the
blank tube prior to bending or hydroforming also facilitates the
bending and hydroforming steps as annealing the tube generally
softens the tube at the annealed sections.
[0043] The drawn tube 232, or if heat treated, the heat treated
tube, may be cut to the desired length, if needed. In another
embodiment, the desired length may be cut prior to inserting into
the die and mandrel assembly, whereby the drawn tube 232 comprises
the tube blank itself. Alternatively, a cut tube blank may also be
pressed through the die and mandrel assembly. In any one of these
cases, the blank of varying wall thickness is then further
processed, where necessary, and formed to the desired final shape
as described further below.
[0044] After an appropriately cut drawn tube 232 is formed, and if
needed, heat treated, it is bent in the desired two or three
dimensional shape. A forming stage, such as a hydroforming stage,
may further be used to impart a desired cross sectional shape or
shapes. If the final tubular component is straight, no bending may
be needed. In the forming stage, the tube blank is delivered to a
forming station. In the preferred embodiment, such forming station
comprises a hydroforming station as is commonly known in the art.
An example of a typical hydroforming apparatus is illustrated in
FIG. 6.
[0045] As shown in FIG. 6, a hydroforming apparatus generally
includes a forming die 244 having two cooperating sections 246 and
248. Each of two cooperating sections 246 and 248 are provided with
one half of a forming die cavity 250. When the two cooperating
sections 246, 248 are in a closed position, they form a forming die
cavity 250. The forming die cavity 250 is formed with the desired
overall and cross sectional shape of the final component being
made.
[0046] As illustrated in FIG. 6, a pre-formed drawn tube blank 252
is placed within the forming die cavity when in the open position,
as shown in FIGS. 6 and 7. As can be seen, the drawn tube blank 252
is initially formed in the desired general shape of the desired
element, including the required bends etc. Once in the forming die
cavity 250, the two sections 246 and 248 are closed, wherein both
sections are in contact thereby forming and sealing the forming die
cavity 250. The ends of the drawn tube blank 252 are then sealed
and the interior of the drawn tube blank 252 is pressurized until
the blank assumes the desired shape defined by the forming die
cavity 250, including the cross sectional shape of the forming die
cavity, as illustrated in FIG. 8. A completely formed tubular
component 254 thus results.
[0047] It will be understood that the hydroforming apparatus
illustrated in FIGS. 6 to 8 is simplified so as to illustrate the
general principle. Various parts of the complete apparatus, such as
seals, valves, control and pumping units etc., have been omitted
for the purpose of clarity. However, such apparatus will be
apparent to persons skilled in the art. It will also be understood
by persons skilled in the art that although a hydroforming process
has been described, various other forming processes may also be
used in method of the present invention.
[0048] The method described above can be used to make other tubular
structural members. FIG. 9 shows an engine support structure, or
engine cradle 300. Engine cradle 300 provides a support structure
for supporting an engine and securing it to a vehicle frame. The
engine cradle 300 has a front cross member 302 and a rear cross
member 304, extending between a pair of longitudinally extending
side rails, left side rail 306 and right side rail 308. Front cross
member 302 and rear cross member 304 are secured to side rails by
secure brackets, namely front secure brackets 310 and rear secure
brackets 312. Secure brackets may be welded to side rails and cross
members, or secured to side rails in any other suitable manner such
as by bolting. Engine cradle 300 is connected to vehicle body or
frame through resilient connectors 314 to reduce vibration
transmitted to the vehicle.
[0049] Side rails 306, 308 are shown to be spaced from each other
and are generally parallel with each other as well. Similarly,
front and rear cross members 302, 304 are also shown to be spaced
from each other and are generally parallel with each other as well.
Side rails and cross members, when joined together, form a general
rectangular shape. However, it will be appreciated that these four
components may be joined to form any other quadrilateral shape and
is not restricted to a general rectangular shape as shown. Further,
the quadrilateral shape is not necessarily restricted to a two
dimensional shape as the side rails and front and rear cross
members may not necessarily be straight. A general three
dimensional shape having four sides may result.
[0050] Each end of the side rails extend beyond the general
rectangular shape and diverges from the corresponding end of the
opposite side rail, for providing better stability to the engine
rested upon the engine cradle 300. As shown, resilient connectors
314 are provided in the end portions of side rail for connecting
the engine cradle 300 to a vehicle frame or body.
[0051] In general, in a crash, front end of an engine cradle takes
more load than its rear end. It is therefore advantageous to
provide side rails that are stronger in the front than in the rear
section. Side rails shown in FIG. 9 has a substantial portion,
namely a portion approximately corresponding to a side of the
general rectangular shape, enhanced with the wall thickness thereof
increasing gradually and monotonically towards the front. A tube
blank such as that shown in FIG. 4A may be conveniently used for
producing such a side rail. Such a gradual and continuous increase
in wall thickness toward the front end helps to achieve the desired
strength without having to add unnecessary weight to the engine
cradle 300.
[0052] FIG. 10 shows a car seat support assembly 400. The car seat
support assembly 400 is shown as attached to the side of a car body
frame 402. The car seat support assembly 400 has a side impact
cross member 404 for supporting a car seat frame 406 thereon. A
pair of track bars 408 are provided between the side impact cross
member 404 and the car seat frame 406 to allow a car seat to be
moved along the track bars 408 back and forth.
[0053] As shown more clearly in FIG. 11, side impact cross member
404 defines a general beam center axis 410. The side impact cross
member 404 has a center tunnel mount area 412. A bend area 414 is
formed on each side of the center tunnel mount area 412 to displace
it from but keeps it generally parallel with the general beam
center axis 410.
[0054] During a side impact, it is important that the side impact
cross member 404 does not buckle in the tunnel mount area 412, nor
the track mount area 416. Any crush in the bend area 414 is also to
be avoided. Preferably, the impact energy is directed toward either
or both ends such that the impact energy is absorbed by the
deformation of the end portions 418. FIG. 11 also shows the
variation of wall thickness along the side impact cross member for
achieving the energy management and stress requirements described
above. As can be seen, the wall thickness is reduced in the end
portions 418 of the side impact cross member 404. This promotes the
deformation of the side impact cross member 404 in the end
portions, but not other sections. Preferably, as can be seen in
FIG. 11, wall thickness is also increased in the bend area 414 to
discourage buckling and crush.
[0055] Various embodiments of the invention have now been described
in detail. Those skilled in the art will appreciate that numerous
modifications, adaptations and variations may be made to the
embodiments without departing from the scope of the invention.
Since changes in and or additions to the above-described best mode
may be made without departing from the nature, spirit or scope of
the invention, the invention is not to be limited to those details
but only by the appended claims.
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