Land vehicles – Wheeled – Running gear
Reexamination Certificate
1999-09-27
2001-04-17
Rice, Kenneth R. (Department: 3611)
Land vehicles
Wheeled
Running gear
Reexamination Certificate
active
06217047
ABSTRACT:
FIELD OF THE INVENTION
The present invention is generally related to vehicular suspension systems, and in particular to suspension systems incorporating roll control mechanisms.
DESCRIPTION OF THE BACKGROUND ART
The objectives of many suspension systems are to provide a high level of roll control, independent of the pitch and four wheel bounce stiffness rates, and also to provide control over the attitude of the body whilst providing a minimal stiffness to cross-axle articulation motions as the vehicle traverses rough terrain. These systems are especially suitable for use on vehicles which have high centres of mass and consequently experience high roll moments when cornering, so benefit from the combination of superior roll control, comfort and traction provided by suspension systems having the above characteristics.
One way that has been attempted for achieving the abovenoted suspension characteristics is to use active suspension systems which use fast-acting, closed loop control systems to determine how to modify their characteristics in response to ground surface inputs. This enables them to eliminate some of the compromises forced on the designers of conventional passive suspension systems and thereby achieve enhanced dynamic performance. The disadvantage of active systems is that they consume large amounts of power to provide a supply of fluid under pressure to drive the actuators as dictated by the control systems. The actuators are usually double acting hydraulic cylinders which are connected through control valves to the pressurised fluid supply or to a return to the reservoir. A hydropneumatic accumulator is often provided to reduce harshness and the need to operate the control valves for each cylinder for smaller wheel motion. To resist roll for example, fluid is supplied to the cylinders on one side of the vehicle. To return to level straight line running, fluid must be exhausted from the cylinders on the first side and supplied to the opposite cylinders.
In order to reduce the power consumption requirements of active suspension systems, there is a trend towards combining conventional support springing with active roll control systems, such as coil springs with active, powered anti-roll bar adjustment systems. Although these systems reduce the power requirements of the suspension system, they still need to have pumps, supply accumulators, reservoirs, supply plumbing and a control system. The pumps still draw power to provide pressurised fluid to the control system and can generate noise, as can the valves in the control system. Systems such as these demand detailed design and development to reach the levels of refinement required by vehicle manufacturers, yet their off road performance is still not entirely satisfactory as the support springs compress in cross-axle articulation, generating uneven wheel loadings and limiting performance.
There is disclosed in International Application Number PCT/AU96/00528 a roll stabilisation system linked front to rear to passively resist roll motions of the vehicle, without introducing substantial cross-axle articulation stiffness. In the above noted patent application there is disclosed a number of arrangements, some of which are improved roll stabilisation systems which can be applied to conventionally suspended vehicles, others include improved support means to suspend the vehicle body thereby conveying all the desirable characteristics discussed above. A potential limitation of the systems disclosed in the above patent application is that the packaging requirements of the combined freely cross-axle articulating roll stabilisation and support systems may not always be compatible with many typical modern, space-efficient vehicle designs.
Other mechanical systems with the same objections of resilient support, roll control and free cross-axle articulation are disclosed in International Application Number PCT/AU95/00135 and in U.S. Pat. No. 2,099,819.
SUMMARY OF THE INVENTION
It would therefore be advantageous to provide an improved passive suspension system combining a freely cross-axle articulating roll stabilisation system with a separate support system. The individual systems may then be located quite separately, giving the designer more freedom and a greater range of possible package envelopes to choose from while maintaining all of the desirable characteristics discussed above. Furthermore, the separate roll stabilisation and support systems may be designed to package into similar areas to existing conventional anti-roll bars and coil springs or torsion bars for example, allowing the improved suspension system to be packaged into modern vehicle designs with little alteration necessary. Such systems can however also have applications on other forms of land and sea transport where the packaging requirements are not as limiting, such as agricultural tractors. For ease of reference, throughout the specification, the term chassis will be used for the vehicle body. It should be noted that the “chassis” may, for example, be a monocoque or spaceframe structure.
With this in mind, the present invention provides in one aspect a suspension system for a vehicle having a chassis supported on at least one forward pair of laterally spaced wheels and at least one rear pair of laterally spaced wheels, including
vehicle support means for supporting the chassis above each said pair of wheels, and
roll moment reaction means for providing location of the chassis about a substantially level roll attitude, said roll moment reaction means including a respective roll attitude control mechanism for each pair of at least two said pairs of laterally spaced wheels for passively controlling the position of the wheels relative to each other and the chassis, each roll attitude control mechanism being connected to at least one other roll attitude control mechanism by roll mechanism interconnection means,
said roll mechanism interconnection means being arranged such that the roll moment reaction means resists roll of the vehicle chassis with respect to the wheels, whilst simultaneously permitting cross-axle articulation motions of the wheels,
wherein the vehicle support means for at least one pair of wheels includes at least a first support means for supporting at least a portion of the load on said vehicle support means, said first support means providing substantially zero roll stiffness for the vehicle,
the roll moment reaction means being separate from the vehicle support means thereby providing substantially zero load carrying capacity.
The roll moment reaction means do not afford any form of load carrying capability, and are provided to locate the vehicle body about its roll axis whilst introducing substantially zero cross-axle articulation stiffness. An advantage of this suspension system is that the support means and the roll moment reaction means are effectively physically and functionally independent. This allows alternative vehicle support means to be readily interchanged and used in conjunction with separately located alternative roll moment reaction means, giving a wide range of available combinations and packaging alternatives.
It should be noted that the term “wheel” can also refer to other forms of surface engaging means such as skis, the term being used herein in this broad manner.
The vehicle support means for at least one pair of laterally spaced wheels may provide substantially zero roll stiffness.
Alternatively, the vehicle support means for each said pair of wheels may provide substantially zero roll stiffness, thereby providing substantially equal wheel loading for non-dynamic wheel displacements, regardless of the cross-axle articulation, up to the limit of travel of at least one of the vehicle support means or the roll moment reaction means.
It is also possible for the vehicle support means for at least one pair of wheels further include additional independent second support means, the second support means including resilience and being arranged to provide a degree of support and a degree of roll stiffness for the vehicle.
Each roll
Heyring Christopher B.
Longman Michael J
Monk Richard
Robertson Alexander John
Birch & Stewart Kolasch & Birch, LLP
Kinetic Limited
Rice Kenneth R.
LandOfFree
Passive vehicular suspension system including a roll control... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Passive vehicular suspension system including a roll control..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Passive vehicular suspension system including a roll control... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2515678