Stabilizer bars with variable cross-sectional properties

A stabilizer bar is provided having a varying cross-section along the length of the bar. In particular, the stabilizer bar includes a first cross-sectional area and a second cross-sectional area that is different than the first cross-sectional area. A first surface at least partially defines the second cross-sectional area. The first surface has a non-circular shape with primary and secondary load bearing directions bearing different maximum loads in each of the directions. The shape of the second cross-sectional area may be arranged so that the primary load bearing direction is generally aligned with the highest load. Similarly, the shape of the second cross-sectional area may be arranged in a manner to bear the highest torsional load. The stabilizer bar may be solid or hollow. Preferred shapes may include egg-shaped or elliptical shaped surfaces. Alternatively, the stabilizer bar may have a generally uniform cross-sectional area along its length with the non-circular shape described above.

BACKGROUND OF THE INVENTION
 This invention relates to a stabilizer bar for a vehicle, and more
 particularly, the invention relates to a stabilizer bar having a
 cross-sectional shape for better enduring stresses in that particular
 cross-sectional area.
 Stabilizer bars for vehicles are increasingly being required to withstand
 higher loads and stresses. Stabilizer bars are typically formed from a bar
 having a circular cross-section. The bar is bent into the required shape
 for the particular vehicle application. For higher load and stress areas,
 the thickness along the entire length of the bar may be increased.
 However, much of the stabilizer bar experiences a lower load and stress
 and therefore the increased bar thickness is unnecessary along much of the
 length of the bar. Alternatively, the thickness of the bar has been
 increased in the area of the higher loads and stresses. But, only a
 circular cross-section has been used in the thicker area of the bar. By
 using stabilizer bars having only circular cross-sections, unnecessary
 weight and costs is added to the bar. That is, a circular cross-section is
 not necessarily the most effective shape for enduring the loads and
 stresses in the particular area. Accordingly, what is needed is a
 stabilizer bar having a variable cross-section designed to better endure
 the loads and stresses in the particular area.
 SUMMARY OF THE INVENTION AND ADVANTAGES
 The present invention provides a stabilizer bar having a varying
 cross-section along the length of the bar. In particular, the stabilizer
 bar includes a first cross-sectional area and a second cross-sectional
 area that is different than the first cross-sectional area. A first
 surface at least partially defines the second cross-sectional area. The
 first surface has a non-circular shape with primary and secondary load
 bearing directions bearing different maximum loads in each of the
 directions. The shape of the second cross-sectional area may be arranged
 so that the primary load bearing direction is generally aligned with the
 highest load. Similarly, the shape of the second cross-sectional area may
 be arranged in a manner to bear the highest torsional load. The stabilizer
 bar may be solid or hollow. Preferred shapes may include egg-shaped or
 elliptical shaped surfaces. Alternatively, the stabilizer bar may have a
 generally uniform cross-sectional area along its length with the
 non-circular shape described above.
 Accordingly, the above invention provides a stabilizer bar having a
 variable cross-sectional area along its length to more efficiently endure
 the different loads and reduce weight and costs of the stabilizer bar.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 A stabilizer bar 10 is shown in FIG. 1. The stabilizer 10 includes a
 lateral portion 11 extending along the width of the vehicle. Lateral
 portion 11 is received in a bushing 12 that is secured to a frame of the
 vehicle. The lateral portion 11 extends to a leg portion 13 which
 terminates in an end 14 that is secured to a suspension component. As the
 suspension component moves up and down during the operation of the
 vehicle, the stabilizer bar 10 absorbs some of the load from the
 suspension component by deforming the stabilizer bar. The stabilizer bar
 10 is deformed by bending and torsional stresses. Typically, the leg
 portion 13 undergoes primarily bending stresses while the lateral portion
 11 and the portion of the stabilizer connecting the lateral portion 11 and
 the leg portion 13 undergo torsional stresses.
 Since the different cross-sectional areas of the stabilizer bar 10 undergo
 different stresses, it is more efficient to design the cross-sectional
 area of the stabilizer bar 10 to endure the maximum stress for that
 particular cross-sectional area. That is, it is not necessary to
 unnecessarily add material to a portion of the stabilizer bar that
 undergoes a lower stress than another area of the stabilizer bar 10. In
 particular, the leg portion 13 typically requires less material than the
 lateral portion 11 because the leg portion 13 undergoes lower stresses
 than the lateral portion 11. Previously, the leg portion 13 had a circular
 cross-section and the lateral portion 11 also had a circular
 cross-section, which was larger than the circular cross-section of the leg
 portion 13.
 The stabilizer bar 10 of the present invention has a first cross-sectional
 area 16 and a second cross-sectional area 18. Preferably, the
 cross-sectional areas are different from one another to more efficiently
 accommodate the stresses experienced in the particular area of the
 stabilizer bar 10. Referring now to FIG. 2, the second cross-sectional
 area 18 includes a first non-circular surface 20. The surface 20 is
 egg-shaped and includes a primary load bearing direction P and a secondary
 load bearing direction S, which is transverse to the primary load bearing
 direction P. The second cross-sectional area 18 is able to endure a
 greater load in the primary load bearing direction P than the secondary
 load bearing direction S. As a result, it is desirable to arrange the
 second cross-sectional area 18 such that the primary load bearing
 direction P is generally aligned with the maximum bending load experienced
 in the cross-sectional area 18. By utilizing a non-circular shape,
 stabilizer bar material and weight may be reduced.
 Other configurations of the cross-sectional areas may be used, as shown in
 FIGS. 3-6. The cross-sectional area shown in FIG. 3 is a solid bar having
 an elliptical shape. The wider portion of the cross-sectional area is
 capable of enduring a greater load than the narrower portion of the
 cross-sectional area. This elliptical cross-sectional area is particularly
 suitable for the leg portion 13 of the stabilizer bar 10. The primary load
 bearing direction P is preferably arranged generally vertically, which is
 the direction of movement of the suspension component.
 The stabilizer bar 10 may also be formed from a hollow bar which is defined
 by a first surface 20 and a second surface 22 which defines an inner
 cavity 24. The cross-sectional area may have a generally uniform wall
 thickness and may be egg-shaped, as shown in FIG. 4. Another possible
 configuration is utilizing an egg-shaped outer surface 20 and a circular
 inner surface 22, as shown in FIG. 5. Yet another suitable embodiment is
 shown in FIG. 6. The cross-sectional area includes a circular outer
 surface 22 and an elliptical inner surface 20.
 The shapes of the surfaces and the wall thicknesses may be varied to adjust
 the load bearing capacity of the cross-sectional area in the direction
 needed. As a result, the material needed to form the stabilizer bar 10 may
 be reduced and the weight and cost reduced.
 The stabilizer bar 10 may be formed using any suitable method such as
 extrusion, upset forging, swaging, and/or machining. Additionally, the
 stabilizer bar 10 may be cold or hot formed.
 The invention has been described in an illustrative manner, and it is to be
 understood that the terminology that has been used is intended to be in
 the nature of words of description rather than of limitation. Obviously,
 many modifications and variations of the present invention are possible in
 light of the above teachings. It is, therefore, to be understood that
 within the scope of the appended claims the invention may be practiced
 otherwise than as specifically described.