Land vehicles – Wheeled – Running gear
Reexamination Certificate
1998-04-20
2001-10-16
English, Peter C. (Department: 3619)
Land vehicles
Wheeled
Running gear
C280S124152, C267S187000, C267S191000
Reexamination Certificate
active
06302417
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is generally directed to vehicular suspension systems, and in particular to suspension systems incorporating roll stabilisation mechanisms.
2. Description of the Background Art
Modem vehicles are normally provided with one or more roll stabilisation or “torsion” bars which transversely link the wheels of one or more axles in order to afford some containment of roll motion to prevent uncomfortable and sometimes dangerous swaying motions when cornering. Roll stabiliser bars are typically manufactured as spring steel bars which permit torsional resilience so that as one wheel on an axle is caused to move in a generally upward or downward direction the other wheel on the same axle is induced to move in a similar direction at the same time. The extent to which the two wheels of a single axle move in a common direction is defined in part by the torsional rigidity of the roll stabiliser bar which transversely couples the two wheels in response to the lateral roll force exerted on the vehicle resulting from cornering.
Vehicles with high centres of gravity (such as trucks which are prone to excessive roll motions) and vehicles which are required to ‘corner flat’ without exhibiting excessive roll motions (such as sports cars) are normally provided with stiff roll stabiliser bars to prevent roll motion. An unbeneficial consequence of providing stiffer roll stabilisers is that the ride quality becomes harsher as both wheels of an axle become functionally linked (to an extent) and single wheel inputs are therefore not resolved by that single wheel alone which impacts on a bump or pot-hole.
Luxury passenger vehicles are, therefore, normally equipped with more compliant roll stabiliser bars so that single wheel inputs are absorbed by that single wheel's associated spring and damper unit which are relatively free to move in response to the single input without the additional resistance resulting from the stabiliser's torsional rigidity.
Regardless of the torsional rigidity of the torsion bar, the provision of such bars do restrict the degree of movement of the wheels relative to each other. This can be a disadvantage in situations where a large degree of opposing vertical wheel motion is required, for example, when travelling over undulating surfaces. The limitations of the wheel movement due to the roll stabiliser bars interconnecting the wheels can lead to significant side to side jerking of the vehicle under such conditions. This movement limitation also restricts the amount of traction that the wheels will have when travelling over such surfaces.
When travelling over uneven ground, the points where the wheels contact the ground are not all in a single plane. This results in the suspension of two diagonally opposed wheels becoming compressed, with the wheels moving closer to the vehicle body, and the suspension of the other two diagonally opposed wheels becoming extended. This mode of suspension operation is known as ‘warp’ or alternatively ‘cross-axle articulation’.
It would be advantageous to have a vehicular suspension system which provides roll stability during cornering and also provides a comfortable ride when travelling in a near straight line or when traversing an undulating surface.
SUMMARY OF THE INVENTION
With this in mind, the present invention provides in one aspect a suspension system for a vehicle having at least one forward pair of surface engaging means and at least one rearward pair of surface engaging means connected to the body of the vehicle to allow substantially vertical relative motion of each surface engaging means with respect to the body, the suspension system including resilient support means for supporting the vehicle body with respect to the surface engaging means, a force transmitting means interconnecting at least one said forward pair of transversely adjacent surface engaging means and a force transmitting means interconnecting at least one said rearward pair of transversely adjacent surface engaging means, each force transmitting means including adjustment means, the adjustment means being longitudinally spaced and functionally linked such that the magnitude and the direction of the force transmitted between associated transversely adjacent surface engaging means by each of the force transmitting means varies progressively as a function of the relative positions of, and the load applied to, at least two pairs of the interconnected transversely adjacent surface engaging means, to thereby restrict roll motions of the vehicle whilst simultaneously facilitating warp motions of the surface engaging means.
Because of the functional linking of the adjustment means, this can provide “passive” control of the vehicle attitude. The suspension system can be self correcting without the need of any external control means. This avoids the need for components such as motion and displacement sensors, electronic control units for processing the sensor signals, and actuating components such as fluid pumps controlled by the electronic control units. Such arrangements are expensive and are relatively slow in their response to changes in surface conditions and vehicle motion.
The resilient support means may be provided between each said surface engaging means and the chassis of the vehicle. Alternatively, a said resilient support means may be provided for at least one said pair of transversely adjacent surface engaging means for carrying the load applied to both of the associated transversely adjacent surface engaging means. A said resilient support means may be provided for said at least one forward pair of transversely adjacent surface engaging means and a further said resilient support means may be provided for said at least one rearward pair of transversely adjacent surface engaging means for respectively providing substantially equal loading on each of the transversely associated surface engaging means.
The force transmitted by the force transmitting means may be a torsional force. To this end, means that allow torsional forces to be transmitted may be used. Therefore, each force transmitting means may include at least one transverse torsion bar. Preferably, each force transmitting means may include a pair of transverse torsion bars, each torsion bar being respectively connected to a said surface engaging means, the torsion bars being interconnected by the adjustment means. The torsion bars may be rotatable about their elongate axes, the adjustment means preferably progressively controlling the axial rotation of the associated torsion bars relative to each other such that the surface engaging means are permitted to move when undergoing warp motions while the roll attitude of the vehicle is simultaneously restrained by the torsion bars.
According to a preferred embodiment of the present invention, each adjustment means may provide a mechanical interconnection of the associated pair of torsion bars. The adjustment means interconnecting a said pair of transversely adjacent front surface engaging means and the adjustment means interconnecting a said pair of transversely adjacent back surface engaging means may be functionally linked by a mechanical connection. This mechanical connection may be a longitudinal shaft interconnecting said adjustment means, each adjustment means preferably including a pair of linkage members respectively connected at one end thereof to one of the torsion bars, the other end of each pair of linkage members being connected to an end of the longitudinal shaft such that torsional forces can be transmitted between said adjustment means.
According to another preferred embodiment of the present invention, the adjustment means may alternatively provide a hydraulic connection of the torsion bars. The adjustment means may be a double-acting ram, the ram having a cylinder and a piston assembly separating the cylinder into two fluid chambers therein. The cylinder may be connected to one of the torsion bars, and the piston assembly may be connected to the other torsion bar. A
Birch & Stewart Kolasch & Birch, LLP
English Peter C.
Kinetic Limited
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