Land vehicles – Wheeled – Running gear
Reexamination Certificate
1999-06-07
2001-01-30
Culbreth, Eric (Department: 3611)
Land vehicles
Wheeled
Running gear
C280S124106, C280S124160, C280S005506
Reexamination Certificate
active
06179310
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
This invention relates to vehicle roll stabilising systems of the kind in which an actuator operatively connected to sprung and unsprung portions of the vehicle is arranged so that roll of the vehicle due to lateral acceleration of the vehicle tends to cause displacement of the actuator, the actuator is operable in use to exert an effort in opposition to such displacement and so counteract the roll. Such a system is known for example from WO-A-89/04262.
It is an object of the invention to provide an improved roll stabilising system for a vehicle.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided a roll stabilising system for a vehicle having front and rear wheels, a front suspension resiliently supporting vehicle weight on the front wheels and a rear suspension resiliently supporting vehicle weight on the rear wheels, the stabilising system including an actuator operatively connected to sprung and unsprung portions of the vehicle and arranged so that roll of the vehicle due to lateral acceleration of the vehicle tends to cause displacement of the actuator, the actuator being operable in use to exert an effort in opposition to such displacement and so counteract the roll, the system further including electronic control means operatively connected to the actuator to control the actuator effort in response to the lateral acceleration such that the actuator effort generally increases with increasing lateral acceleration, the increase in actuator effort being at a rate which is variable according to the magnitude of the lateral acceleration.
Preferably the actuator effort increases in direct proportion to the vehicle lateral acceleration up to a predetermined magnitude of lateral acceleration, in which case the actuator effort can be substantially equal to that required to maintain the vehicle level during cornering. Beyond said predetermined magnitude, the actuator effort can remains constant when lateral acceleration is increased, i.e. the rate of increase of actuator effort with the lateral acceleration reduces to zero. However, in a preferred arrangement, the actuator effort continues to increase in direct proportion to the lateral acceleration but at a reduced rate. In this case the actuator effort may be arranged to remain constant when the lateral acceleration is increased beyond a second predetermined magnitude. The predetermined magnitude of lateral acceleration is typically in the range 0.3 to 0.6 g, e.g. around 0.5 g in the case where the actuator effort remains constant when lateral acceleration is increased and around 0.4 g in the case where the actuator effort continues to increase in direct proportion to lateral acceleration at the reduced rate. Where the actuator effort is arranged to remain constant when lateral acceleration is increased beyond a second predetermined magnitude, the second predetermined magnitude of lateral acceleration is typically 1.0 g.
There may be a first actuator associated with the front wheels and a second actuator associated with the rear wheels. This enhances the vehicle stability during cornering by keeping the proportional share of the vehicle weight carried by each of the front wheels substantially the same as that of each of the rear wheels.
Conveniently the or each actuator comprises a double acting hydraulic device having first and second inlet/outlet ports, valve means being provided for controlling flow of hydraulic fluid from a source of hydraulic pressure to a drain, the valve means being operable in a first mode in which the first inlet/outlet port is connected to the source and the second inlet/outlet port is connected to the drain and in a second mode in which the second inlet/outlet port is connected to the source and the first inlet/outlet port is connected to the drain, and pressure modulating means is provided to modulate the pressure of the hydraulic fluid supplied by the source to the valve means and thereby control the actuator effort. The first and second modes are the normal operating modes for the valve means when the stabilising system is active to reduce or prevent roll, the first and second modes being selected according to the direction of cornering.
Where there is a first actuator associated with the front wheels and a second actuator associated with the rear wheels, said valve means can be common to both actuators. This arrangement equalises the pressures at both actuators, thereby keeping the proportional share of the vehicle weight carried by each of the front wheels the same as that of each of the rear wheels, as discussed earlier.
If the flow rate of the hydraulic fluid supplied by the source is limited, the pressure modulating means may conveniently comprise a diverter valve which diverts some of the hydraulic fluid supplied by the source to the drain. The diverter valve may comprise an electrically driven proportional valve in which the restriction to hydraulic flow from the source to the drain varies proportionally with the driving electrical current.
Preferably, the valve means comprises first and second selector valves, each selector valve having a supply port for connection to the source, a return port for connection to the drain, a first control port connected to one of the inlet/outlet ports of the or each actuator and a second control port connected to the other of the inlet/outlet ports of the or each actuator, each selector valve having an off condition in which communication between the supply and drain ports and the control ports is prevented and an on condition in which, in the first selector valve, the supply port is connected to the first control port and the second control port is connected to the return port and, in the second selector valve, the supply port is connected to the second control port and the first control port is connected to the return port, the arrangement being such that, in the first mode, the first selector valve is in the on condition and the second selector valve is in the off condition and, in the second mode, the first selector valve is in the off condition and the second selector valve is in the on condition.
Such an arrangement of first and second selector valves can be used in other vehicle roll stabilising systems. Hence, according to a second aspect of the invention, there is provided a roll stabilising system for a vehicle having front and rear wheels, a front suspension resiliently supporting vehicle weight on the front wheels and a rear suspension resiliently supporting vehicle weight on the rear wheels, the stabilising system including an actuator operatively connected to sprung and unsprung portions of the vehicle and arranged so that roll of the vehicle tends to cause displacement of the actuator, the actuator comprising a double acting hydraulic device having first and second inlet/outlet ports and being operable in use to exert an effort in opposition to such displacement and so counteract the roll, the system further including valve means for controlling flow of hydraulic fluid from a source of hydraulic pressure to a drain, the valve means being operable in a first mode in which the first inlet/outlet port is connected to the source and the second inlet/outlet port is connected to the drain and in a second mode in which the second inlet/outlet port is connected to the source and the first inlet/outlet port is connected to the drain, and pressure modulating means to modulate the pressure of the hydraulic fluid supplied by the source to the valve means and thereby control the actuator effort, the valve means comprising first and second selector valves each having a supply port for connection to the source, a return port for connection to the drain, a first control port connected to one of the inlet/outlet ports of the actuator and a second control port connected to the other of the inlet/outlet ports of the actuator, each selector valve having an off condition in which communication between the supply and drain ports and the control ports is prevented and an on conditio
Burdock William
Clare David Andrew
Green Phillip James
Pask Mark
Culbreth Eric
Davis and Bujold
Lum L.
Rover Group Limited
LandOfFree
Vehicle roll stabilizing system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vehicle roll stabilizing system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vehicle roll stabilizing system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2545479