Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
2001-12-12
2003-02-11
Arthur, Gertrude (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C280S124159, C280S005502, C280S005507, C280S005508
Reexamination Certificate
active
06519517
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to vehicle suspension systems, and in particular to suspension systems incorporating interconnected dampers and active roll control.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
not applicable
INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC
not applicable
REFERENCE TO “MICROFICHE APPENDIX”
not applicable
BACKGROUND OF THE INVENTION
In order to provide increased ride comfort and vehicle stability, a wide variety of solutions have been proposed. These can be categorised into several groups; damping systems; passive roll control and vehicle support; active roll control systems; active body control systems (also known as low-bandwidth active systems); and fully active (high bandwidth) suspension systems.
Damping systems proposed cover a wide range of concepts from passive, single wheel dampers (which provide damping forces determined in part by: position in the stroke, acceleration of the damper piston; load on the wheel) through passive interconnected dampers (which can provide different damping forces for the different suspension modes of roll, pitch and heave) up to electronically controlled “semi-active” dampers which modulate the damping force in dependence on sensed vehicle operating conditions (such as roll, yaw, etc.) to enable optimal damping to be provided at all times, giving increased comfort and stability. Without providing heave or roll stiffness, there is a limit to how effective these type of systems can be.
Passive roll control and vehicle support systems which decouple different suspension modes can vary from completely mechanical systems through to completely hydraulic systems. The ability to decouple the roll, warp and heave stiffness modes of a suspension allows more optimal tuning of each stiffness, allowing increased roll stiffness and stability and increased comfort. However, there is a limit to the amount of roll stiffness which can be provided before the ride comfort deteriorates. There is a trend towards suspension systems with very low roll angles, even at large lateral g, which to achieve passively can require excessive roll stiffness, thereby limiting ride comfort.
Active roll control systems usually rely on lateral stabiliser bars with hydraulic actuation to enable control of body roll angle through controlling the torsional force in the stabiliser bar. Packaging of the stabiliser bar including the hydraulic actuator can be difficult, especially at the front of a vehicle around the front subframe, suspension geometry and engine.
Active body control systems generally use conventional, soft springs for each wheel to improve comfort in conjunction with hydraulic actuators to control and limit body motion in roll and pitch. As these systems are controlling only body position, they do not need to respond to high frequency, small magnitude individual wheel inputs, which are generally absorbed by the low spring rate. The controllers can therefore be relatively low speed or “low bandwidth”. These types of systems do not generally provide vehicle damping.
Fully active suspension systems support the vehicle on hydraulic struts which are all controlled by a central computer. In order to react fast enough each wheel may have a local fluid source and a local computer to control small high frequency (high bandwidth) wheel inputs. The local computer usually senses actuator load and position, wheel and body acceleration, etc. This must communicate with the central computer which controls overall body position by communicating with the computers for each wheel and using additional inputs such as throttle, brake and steering positions, body accelerations, actuator positions. These systems are highly complex and expensive.
Most of the above types of suspension system have reached only limited production, due to varying reasons such as conflicts between cost, packagability, complexity, efficiency, weight and refinement
It is therefore preferable to provide a suspension system incorporating an interconnected damper arrangement providing damping and roll stiffness and further incorporating a low bandwidth active control of the vehicle roll angle.
BRIEF SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a vehicle suspension system incorporating an active roll control system including at least four wheel cylinders.
It is another object of the present invention to provide a combined damping and active roll control system.
With this in mind, the present invention provides a damping and roll control system for a vehicle suspension system, the vehicle having at least one pair of laterally spaced front wheel assemblies and at least one pair of laterally spaced rear wheel assemblies, each wheel assembly including a wheel and a wheel mounting locating the wheel to permit movement of the wheel in a generally vertical direction relative to a body of the vehicle, and vehicle support means for providing at least substantially all of the support for the vehicle; the damping and roll control system including;
wheel cylinders respectively locatable between each wheel mounting and the body of the vehicle, each wheel cylinder including an inner volume separated into first and second chambers by a piston supported within the wheel cylinder;
first and second fluid circuits respectively providing fluid communication between the wheel cylinders by fluid conduits, each said fluid circuit providing fluid communication between the first chambers of the wheel cylinders on one side of the vehicle and the second chambers of the wheel cylinders on the opposite side of the vehicle to thereby provide roll support decoupled from the warp mode of the vehicle suspension system by providing a roll stiffness about a level roll attitude whilst simultaneously providing substantially zero warp stiffness;
each fluid circuit including one or more fluid accumulators for providing roll resilience;
the or at least one of the accumulators on each fluid circuit including an accumulator damper means for controlling the rate of fluid flow into and out of the accumulator;
damper means for controlling the rate of fluid flow into and out of at least one chamber of each wheel cylinder; and
a fluid control means connected to said first and second fluid circuits for supplying or drawing fluid from each said fluid circuit as a function of the ride characteristics of the vehicle;
the damping and roll control system thereby providing substantially all of the damping of the vehicle suspension system.
The damper means of the damping and roll control system are being provided to control the rate of fluid flow into and out of at least one chamber of each wheel cylinder to thereby provide substantially all of the damping of the vehicle suspension system. The conduits may be sized to provide at least a portion of the high speed damping of the vehicle suspension system, but as they give a fixed, non-linear effects normally damper means are also necessary,
The vehicle support means may in certain embodiments of the present invention provide at least substantially all of the support for the vehicle.
The damping and roll control system therefore provides damping for the vehicle suspension and provides a roll stiffness without introducing a corresponding warp stiffness.
Each fluid circuit may in one preferred embodiment according to the present invention include a first fluid conduit providing fluid communication between the first chambers of the wheel cylinders on one side of the vehicle; and a second fluid conduit providing fluid communication between the second chambers of the wheel cylinders on the opposite side of the vehicle; the first and second fluid conduits being in fluid communication.
According to another preferred embodiment according to the present invention, each fluid circuit may include first and second diagonal fluid conduits, each respectively providing fluid communication between the first chamber of one wheel cylinder on one side of the vehicle and the second chamber of the diagonally opp
Heyring Christopher B
Longman Michael J.
Arthur Gertrude
Harness Dickey & Pierce PLC
Kinetic Pty. Ltd.
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