Land vehicles – Wheeled – Running gear
Reexamination Certificate
1998-10-16
2001-02-20
Mar, Michael (Department: 3619)
Land vehicles
Wheeled
Running gear
C280S124134, C267S149000, C267S047000
Reexamination Certificate
active
06189904
ABSTRACT:
TECHNICAL FIELD
The technical field of this invention is a vehicle wheel suspension and particularly such a suspension using a transverse leaf spring.
BACKGROUND OF THE INVENTION
A transverse leaf spring suspension, particularly using a composite leaf spring such as the fiberglass Liteflex® spring manufactured by Delphi Automotive Systems, can provide mass and space reduction in a vehicle wheel suspension. Such a suspension provides a single, transversely oriented leaf spring to provide both heave and roll compliance for a pair of wheels: one on each side of the vehicle. It is generally desirable that the ratio of spring rates in the roll and heave modes (roll ratio) be high, so that the suspension provides resistance to vehicle body roll in turns while remaining compliant in vertical motion to avoid harshness in ride. If a transverse leaf spring is used, each of these often conflicting goals must be addressed in the same spring.
The suspension apparatus of this invention is an improvement over the apparatus shown in U.S. Pat. No. 4,768,807 to McGibbon et al, in which a standard composite leaf spring of uniform cross-sectional area is supported by a pair of mounts having pivot studs projecting fore and aft from a retainer clamped on the spring into a receptacle on a vehicle body cross member to provide a pivoting support with respect to the vehicle body. The pivoting mount of McGibbon et al reduces restriction on the flexing of a leaf spring in heave mode but still provides some restriction due to its low longitudinal translation compliance. In addition, it is complicated to manufacture, due to the necessity of the pivot axis being aligned with the spring shear axis.
SUMMARY OF THE INVENTION
The suspension of this invention provides improvements to both the spring and the mounts of the prior art, which improve the roll ratio individually and in combination. The suspension comprises a composite, transversely oriented, leaf spring which is vertically thick and stiff in end regions extending inward from each end of the spring past the vehicle body support area but is vertically thin and compliant in a middle region between the end regions. This spring thus flexes easily in the heave mode, in which the thin middle region of the spring flexes vertically in opposition to each end. But the center of the spring resists flexing in the roll mode, in which the ends of the spring move vertically in opposition to each other and the spring attempts to flex in the thick end regions including the body support area. The spring thus provides a high spring rate in roll with a low spring rate in heave for a high roll ratio.
Preferably, the spring is constructed of a long, longitudinally aligned fiber and resin composite which is split at each outer end of the middle region into upper and lower horizontal layers separated by a core having a tapered inner end and extending through the end region. The inserts provide the additional vertical thickness in the end regions without widening the middle region and may be made of a different material, such as a short, randomly oriented fiber and resin composite.
The roll ratio is preferably additionally enhanced by providing pivoting and longitudinally translating body mounts for the spring; and two specific structures for such mounts are described herein. The pivoting body mounts permit the greatest possible central flexure of the spring in heave mode, without introducing any increase in compliance in roll mode.
REFERENCES:
patent: 4458918 (1984-07-01), Rumpel et al.
patent: 4768807 (1988-09-01), McGibbon et al.
patent: 4771997 (1988-09-01), Haldenwanger et al.
patent: 4969633 (1990-11-01), Ryan
patent: 4969634 (1990-11-01), Bellingham
patent: 5141209 (1992-08-01), Sano et al.
patent: 5826896 (1998-10-01), Baumann
Annequin Thierry
Blancher Jean-Marc
Derollepot Olivier M.
Gentry Johnny Ray
Graham Bruce Patrick
General Motors Corporation
Jasmin Lynda
Mar Michael
Sigler Robert M.
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