U.S. patent application number 11/170473 was filed with the patent office on 2005-10-27 for suspension component having localized material strengthening.
This patent application is currently assigned to Visteon Global Technologies, Inc.. Invention is credited to Cai, Haimian, Li, Hang.
Application Number | 20050236794 11/170473 |
Document ID | / |
Family ID | 32712181 |
Filed Date | 2005-10-27 |
United States Patent
Application |
20050236794 |
Kind Code |
A1 |
Cai, Haimian ; et
al. |
October 27, 2005 |
Suspension component having localized material strengthening
Abstract
A suspension component for an automobile, such as a stabilizer
bar, is provided and includes at least one localized portion having
a strengthened outer surface. The localized portion is positioned
at a location of highest stress along the suspension component. A
method of forming the suspension component is also disclosed.
Inventors: |
Cai, Haimian; (Ann Arbor,
MI) ; Li, Hang; (Farmington Hills, MI) |
Correspondence
Address: |
VISTEON
C/O BRINKS HOFER GILSON & LIONE
PO BOX 10395
CHICAGO
IL
60610
US
|
Assignee: |
Visteon Global Technologies,
Inc.
|
Family ID: |
32712181 |
Appl. No.: |
11/170473 |
Filed: |
June 29, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11170473 |
Jun 29, 2005 |
|
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10346580 |
Jan 17, 2003 |
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Current U.S.
Class: |
280/124.107 |
Current CPC
Class: |
B60G 2206/427 20130101;
B60G 21/055 20130101; B21D 53/84 20130101 |
Class at
Publication: |
280/124.107 |
International
Class: |
B60G 021/055 |
Claims
What is claimed is:
1. A suspension component for an automobile comprising: a member
having opposing first and second distal ends; an attachment point
located at each of said first and second distal ends; and at least
one localized portion having a strengthened outer surface, said
localized portion being positioned at a location of highest stress
along the suspension component.
2. The suspension component of claim 1 wherein said member is
formed from steel.
3. The suspension component of claim 1 wherein said member is
formed from one of micro-alloyed boron steel and vanadium
steel.
4. The suspension component of claim 1 wherein said outer surface
of said localized portions is shot peened.
5. The suspension component of claim 1 wherein said outer surface
of said localized portions is heat treated.
6. The suspension component of claim 5 wherein said outer surface
of said localized portions is quenched and tempered.
7. The suspension component of claim 5 wherein said outer surface
of said localized portions is induction case hardened.
8. The suspension component of claim 1 wherein said member is a bar
and said suspension component is a stabilizer bar.
9. The suspension component of claim 1 wherein said localized
portion is located at a bend that is cold formed within said
member.
10-20. (canceled)
Description
BACKGROUND OF INVENTION
[0001] 1. Technical Field of the Invention
[0002] The present invention generally relates to a suspension
component for an automobile. More specifically, the present
invention relates to a stabilizer bar having localized material
strengthening, and a method of manufacturing the stabilizer
bar.
[0003] 2. Description of the Prior Art
[0004] In an automotive vehicle, suspension components, such as a
stabilizer bar, helps to keep the vehicle level, particularly when
the vehicle is traveling through a curve. The ends of the
stabilizer bar are connected to the right and left wheel assemblies
of the vehicle. A pair of brackets, positioned between the ends of
the stabilizer bar, secure the stabilizer bar to a structural
component of the vehicle. Rubber bushings positioned between the
stabilizer bar and the brackets provide limited torsional, axial
and radial movement of the stabilizer bar relative to the bracket.
The rubber bushings also dampen the movement of the stabilizer
bar.
[0005] Typically, the goal of the material selection and
manufacturing process used to make a stabilizer bar is to form a
stabilizer bar with homogenous material properties that meet the
highest required yield and fatigue strengths, as determined by
calculated finite element analysis procedures. In many cases, cold
forming, hot forming, heat treatments, and shot peening operation
are performed on the stabilizer bar to achieve the yield and
fatigue strength properties. The heat treatments must be applied to
the entire stabilizer bar.
[0006] In actual use the highest stresses within the stabilizer bar
are realized in specific localized areas along the stabilizer bar,
not along the entire length. Therefore, stabilizer bars made by
more traditional methods, where the entire stabilizer bar is heat
treated, present several disadvantages. One disadvantage is that
the stabilizer bar is heavier than it needs to be, because the
stabilizer bar is homogenous. Another disadvantage is that the
process involves unnecessary cost, as the entire stabilizer bar is
subjected to heat treatment, when only a localized area must meet
the high stress requirements. Finally, the facilities needed to
process the stabilizer bar are larger, and require more energy,
than needed, because they must be adapted to treat the entire
stabilizer bar.
[0007] Additionally, typical manufacturing methods for suspension
components such as stabilizer bars include heating the bar to a
high temperature, bending the bar to the desired shape, and then
quenching and tempering the bar. These steps are typically required
to maintain the strength of the bar after the bar is bent.
Quenching and tempering, however, causes de-carbonization of the
entire bar and deformation of the bar, which must be later
corrected.
[0008] Therefore, there is a need for an improved stabilizer bar,
made from a material that can be cold formed to the required shape
without requiring heating, quenching and tempering operations, and
that includes localized area that are treated to withstand high
stresses. Further, there is a need for an improved method of
forming a suspension component that allows the suspension component
to be cold formed to the required shape and to have localized areas
that are treated to withstand high stresses, while the remaining
areas of the suspension component are not treated.
[0009] A principle object of this invention is to provide a
suspension component that is made from a material that can be cold
formed to the needed shape and can be cold work hardening
strengthened or heat treated to withstand stress levels that will
be experienced by the suspension component.
[0010] Another object of this invention is to provide a suspension
component that has localized portions that are specially treated
with cold work hardening, shot peening and/or heat treatment to
withstand localized stresses that the suspension component will
experience, while the remaining portions of the suspension
component remain untreated.
[0011] It is also an object of this invention to provide a method
of manufacturing a suspension component having localized portions
that are work hardening strengthened, shot peened or heat treated
to withstand localized stresses that the suspension component will
experience, while the remaining portions of the suspension
component remain untreated.
SUMMARY OF THE INVENTION
[0012] The disadvantages of the prior art are overcome by providing
a suspension component, in accordance with the present invention,
in which the suspension component includes localized portions that
are specially treated using cold work hardening, shot peening
and/or heat treatment to withstand localized stresses that the
suspension component will experience, while the remaining portions
of the suspension component left untreated.
[0013] In a first aspect of the present invention the suspension
component is formed from one of micro-alloyed boron steel and
vanadium steels containing relatively low levels of carbon, such
that the suspension component will have good ductility and fracture
toughness, to allow the suspension component to be cold formed, and
yet still allow the suspension component to be readily heat treated
thereafter if heat treatment localized material strengthening is
desired.
[0014] In another aspect of the present invention the suspension
component includes localized portions that are shot peened or heat
treated after the suspension component has been cold formed into a
desired shape.
[0015] In still another aspect of the present invention, the
localized portions of the suspension component are induction case
hardened.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a plan view of a stabilizer bar of the present
invention;
[0017] FIG. 2 is a plan view similar to FIG. 1;
[0018] FIG. 3 is a sectional view taken along line 3-3 of FIG. 2,
wherein the stabilizer bar is solid;
[0019] FIG. 4 is a sectional view similar to FIG. 3, wherein the
stabilizer bar is hollow;
[0020] FIG. 5 is a flow chart of a method of manufacturing the
stabilizer bar of the present invention, including a shot-peeing
process; and
[0021] FIG. 6 is a flow chart of a method of manufacturing the
stabilizer bar of the present invention, including a heat treating
process.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] Referring to FIG. 1, a suspension component for an
automotive vehicle is shown generally at 10. The suspension
component shown is a stabilizer bar, however, it is to be
understood, that the teachings of the present invention are
applicable to other suspension components. The stabilizer bar
assembly 10 includes a stabilizer bar 12 having opposing first and
second distal ends 14, 16. The stabilizer bar 12 is generally made
from steel, and can be solid or hollow between the ends 14, 16. The
stabilizer bar 12 further includes at least one bushing assembly 18
mounted thereon. The bushing assemblies 18 are adapted to mount the
stabilizer bar 12 to the structure of the automobile.
[0023] Each of the first and second distal ends 14, 16 have an
attachment point 20. The attachment points 20 are adapted to
connect the distal ends 14,16 to wheel assemblies (not shown) on
the automobile. The attachment points 20 can be attached to the
distal ends 14, 16, by welding. Alternatively, the attachment
points 20 can be formed unitary with the distal ends 14, 16,
whereby the distal ends 14, 16 are heated, and/or otherwise formed
into the shape of the attachment points 20.
[0024] In operation, the stabilizer bar 12 is adapted to keep the
wheels on opposite sides of the automobile level to one another
with respect to the automobile. The shape of the stabilizer bar 12
includes a generally straight center section 22 and two arms 24, 26
extending generally angularly from opposite ends of the straight
section 22.
[0025] The arms 24, 26 are formed by bending the stabilizer bar 12,
such that the arms 24, 26 are integral with the center section 22.
The arms 24, 26 extend at and angle to the center section 22. When
the distal ends 14 of a first of the two arms 24 is forced upward
or downward vertically, the arm 24 acts as a moment arm, thereby
transferring torque to the center section 22. The center section 22
transfers the torque to the opposite arms 26, to correspondingly
force the second distal end 16 upward or downward.
[0026] Referring to FIG. 2, a finite element analysis identifies
localized areas 28, 30 immediately around the bends between the
arms 24, 26 and the straight section 22 as the point of highest
stress within the stabilizer bar 12 during operation of an
automobile. To withstand the higher stresses experienced within the
localized areas 28, 30, these localized areas 28, 30 include a
strengthened outer surface.
[0027] Referring to FIG. 3, a cross section of a solid stabilizer
bar 12 shows an outer surface portion 32 and an inner portion 34.
The outer surface portion 32 is strengthened by shot peening the
outer surface of the stabilizer bar 12 within the localized areas
28, 30. Alternatively, the surface of the stabilizer bar 12 within
the localized areas 28, 30 can be heat treated. The heat treatment
used to strengthen the outer surface of the stabilizer bar 12
within the localized areas 28, 30 can be a traditional quench and
temper. However, it is typically difficult to perform a quench and
temper operation on a localized portion of an object. To resolve
this difficulty, the localized areas 28, 30 of the stabilizer bar
are preferably induction case hardened, using an eddy current
applied to the surface of the stabilizer bar 12 within the
localized areas 28, 30. By using an eddy current process to
induction case harden the stabilizer bar 12, the area that is
treated, and the depth of the treatment can be closely controlled.
Alternatively, the stabilizer bar can be hollow, as shown in FIG.
4.
[0028] The material of the stabilizer bar 12 is preferably steel,
however, the particular steel used is important. Preferably the
steel selected has good ductility and fracture toughness and high
yield strength. This is necessary to allow the stabilizer bar 12 to
be bent to the desired shape. The stabilizer bar 12 is cold worked,
meaning the stabilizer bar 12 is bent when it is at ambient
temperature, rather than at an elevated temperature.
[0029] Further, the steel will be treated to harden the surface
within the localized areas 28, 30. Typically, low carbon steels
cannot be hardened to the equivalent strength of high carbon
steels. With the above in mind, the stabilizer bar 12 of the
present invention is preferably formed from a micro-alloyed boron
steel, such as 15B21, a vanadium steel, such as 1541V, or other
material of similar characteristics. These steels are low carbon
steels, but because of the addition of Boron or Vanadium, can be
heat treated to hardness and strengths equivalent to high carbon
steels. Therefore, the stabilizer bar 12 possesses good ductility
and toughness that allows the stabilizer bar 12 to be cold bent to
the desired shape, and the localized areas 28, 30 can be heat
treated to harness and strength levels that meet the requirements
of the application.
[0030] Referring to FIGS. 5, the localized areas 28, 30 will be
localized work hardened during the cold forming process, due to the
work hardening material strengthening mechanism. The shaded areas
indicate material plastic flow during cold forming, regardless of
sold or hollow bars. Material cold plastic flow will induce work
hardening effects further localized strengthening the material.
[0031] Referring to FIG. 6, a flow chart illustrating method of
manufacturing the stabilizer bar 12 according to the present
invention is shown generally at 36. After the steel is received, as
shown in block 37 of FIG. 6, the attachment points 20 are formed
onto the distal ends 14, 16 of the stabilizer bar 12. Preferably,
the distal ends 14, 16 are heated, and the attachment points are
formed therein by a process known as "Double Eye", as shown in the
blocks indicated by reference numerals 38 and 40. Then the
stabilizer bar 12 is cold formed into the desired shape as shown in
block 42. After the stabilizer bar 12 is cold formed, localized
areas of the outer surface are strengthened. In one method, the
localized areas of the outer surface of the stabilizer bar 12 are
shot peened, to provide compressive forces into the surface of the
stabilizer bar 12 which further strengthens the stabilizer bar.
This step is illustrated in block 44 of FIG. 6. This step provides
the added strength that the localized portions 28, 30 need to
withstand the high stresses placed on the stabilizer bar 12 within
the localized portions 28, 30. After the shot peening, the
stabilizer bar 12 can be painted and shipped.
[0032] Referring to FIG. 7, in an alternative process the
stabilizer bar 12 is received, as shown in Block 37 of FIG. 6. The
attachment points 20 are formed onto the distal ends 14, 16 of the
stabilizer bar 12, as shown in blocks 38 and 40, and , and the
stabilizer bar 12 is cold formed into the desired shape, as shown
in Block 42. However, in the alternative process, after the
stabilizer bar 12 is cold formed, the outer surface of the
stabilizer bar 12 is heat treated within the localized areas 28,
30, which further strengthens the stabilizer bar 12. This step is
illustrated in block 46 of FIG. 7. The heat treatment can consist
of a quenching and tempering procedure, an induction case hardening
process whereby an eddy current is applied to the surface of the
stabilizer bar 12, or other heat treating method. After the heat
treatment, the stabilizer bar 12 can be painted and shipped.
[0033] The foregoing discussion discloses and describes the
preferred embodiments of the invention. One skilled in the art will
readily recognize from such discussion, and from the accompanying
drawings and claims, that changes and modifications can be made to
the invention without departing from the fair scope of the
invention as defined in the following claims. The invention has
been described in an illustrative manner, and it is to be
understood that the terminology which has been used is intended to
be in the nature of words of description rather than of
limitation.
* * * * *