Land vehicles – Body elevation or tilt – Establishing riding or trim height
Reexamination Certificate
1999-02-08
2001-05-01
Swann, J. J. (Department: 3611)
Land vehicles
Body elevation or tilt
Establishing riding or trim height
C280S005514, C280S124160
Reexamination Certificate
active
06224069
ABSTRACT:
TECHNICAL FIELD
This invention relates to a body leveling system for a motor vehicle.
BACKGROUND OF THE INVENTION
A motor vehicle having a typical solid axle rear suspension system includes a rigid axle housing linked to a body of the motor vehicle for vertical suspension excursions, a pair of road wheels rotatably supported on the rigid axle housing, and a pair of suspension springs, e.g. leaf springs, coil springs, or air springs, between the body and the rigid axle housing. The elevation of the body above the rigid axle housing, typically referred to as the “trim height” of the body, decreases incrementally from a “curb trim” when the body is empty to a lower “GVW trim” when the body is fully loaded with passengers and/or cargo, i.e. at Gross Vehicle Weight (“GVW”). During a turn, the links between the body and the rigid axle housing turn the axle housing and the road wheels toward the center of the turn in response to pivotal movement of the body about its longitudinal roll axis, a performance characteristic commonly referred to as “roll understeer”. When the motor vehicle is further equipped with a body leveling system which maintains its body at curb trim regardless of the load on the body, the dynamic performance at GVW of the motor vehicle with its body at curb trim is relatively inferior to its dynamic performance with its body at GVW trim because the motor vehicle has more roll understeer and its center of gravity is lower at GVW trim than at curb trim.
SUMMARY OF THE INVENTION
This invention is a new and improved body leveling system for a motor vehicle including a rigid axle housing linked to a body of the motor vehicle for vertical suspension excursions, a pair of road wheels rotatably supported on the rigid axle housing, and a pair of suspension air springs between the body and the rigid axle housing. During a turn, the links between the body and the rigid axle housing effect roll understeer by turning the axle housing and the road wheels toward the center of the turn in response to pivotal movement of the body about its longitudinal roll axis. When the load on the vehicle body is in a moderate range from empty to four average passengers, the air springs are selectively inflated and deflated to maintain the body at curb trim. When the load on the body exceeds the moderate range in either a high range or an overload range, the air springs are sealed closed and incrementally vertically deflect as the load increases. The GVW trim of the vehicle body is below its curb trim and its center of gravity is lower at GVW than at curb trim for improved dynamic performance at GVW. In the overload range, an “overload trim” of the vehicle body is below its GVW trim to afford a visual alert of loading beyond GVW.
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Dunn David R.
General Motors Corporation
Sedlar Jeffrey A.
Swann J. J.
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