GB2189751A

GB2189751A - Vehicle suspension systems

Info

Publication number: GB2189751A
Application number: GB08709272A
Authority: GB
Inventors: Michael Anthony Mumford
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-04-15
Filing date: 1987-04-15
Publication date: 1987-11-04
Also published as: GB8609198D0; GB8709272D0

Abstract

A vehicle suspension system employs a torsion bar spring 15 which may be considered as a conventional "anti-roll bar". The torsion bar can be adjustably preloaded when the vehicle is in motion in order to limit roll angle during cornering manoeuvres. Pitch resistance may also or alternatively be controlled. Both aspects of the suspension are controlled by a servo arrangement which modifies suspension spring forces according to the demands of an acceleration-sensing control unit 27 (not shown). <IMAGE>

Description

SPECiFICATION Vehicle suspension systems This invention relates to vehicle suspension systems and more particularly, but not excl usiveiy, to the active control of vehicle suspension springs.

The prior art includes G.B. 1075481 (Mumford), and amongst other disclosures there have been proposals for the loading of individual suspension springs to be modified by servo-systems controlled buy a unit responsive to horizontal acceleration forces and to suspension feedback signals.

Such systems provide a degree of control overthe roll and pitch attitudes of a vehicle chassis. However, there is a need for improvements in these previous systems, including the need to simplify the task of the servo-system and its control unit, and an aim of the present invention is to provide improvements in one or more of these respects, or generally.

According to the invention there are provided vehicle suspension systems as defined in the accompanying claims.

The invention also provides a vehicle suspension system possessing any advantage ortechnical feature disclosed herein and further comprising any novel feature or novel combination offeatures disclosed herein.

In this specification and the claims thereof, references to changes in the loading ofthetorsion bar produced by loading means orthe like, are intended to refer to such changes in the torsional loading ofthe bar produced by such loading means as distinctfrom any changes arising, for example, from rolling ofthevehicleoritstendencytoroll.

Likewise, references to the provision of meansfor controlling the resilient resistance provided by resilient means of a suspension unit in a vehicle suspension system, are intended to referto changes in such resilient resistance caused by the control system as distinct from any such changes which may be caused, for example, merely by compression of the resilient means.

In an embodiment described below there is provided a vehicle suspension system in which the vehicle suspension springing means is divided into two parts. One part primarily supports the vehicle weight and provides pitch resistance, and the other part provides only roll resistance. Either one or both ofthese parts of the vehicle suspension system are controlled buy a servo arrangementwhich modifies the suspension spring forces according to the demand of a control unit. in this way, the task of the servo system and its control unit is simplified.

Likewise, in the embodiment described below, a vehicle suspension system includes wheel axles connected to a chassis th rough articu lated links and resilient suspension units which support the weight ofthe vehicle and provide pitch resistance, and may or may not provide some roll resistance. Torsion bar springs are adjustably mounted on the chassis and connect transverse pairs ofwheel axles such that the torsional loading of the bars or bar is changed when the wheels are differentially displaced about their articulating connections with the chassis. The adjustable mounts of the torsion bar springs are controlled by a servo arrangement such that the torsional loading of the bar may be changed according to the demands of a control unit.By means of a furtherservo servo arrangementthe control unit may also change the loading oftransverse pairs of resilient suspension units to modify the pitch attitude of the chassis.

Embodiments ofthe invention will nowbe described by way of example with reference to the accompanying drawings in which: Figure lisa diagrammatic front elevation of a wishbone suspension system for a transverse pair of wheel axles.

Figure2 is a plan view ofthe arrangement shown in figure 1.

Figure 3 is a schematic diagram ofthemain components of a suitable servo-system forthe control of chassis roll.

Figure 4 is a schematic diagram of the main components of a suitable servo-system forthe control of both roll and pitch attitude.

Figure 5is a diagrammaticfront elevation of a wishbone suspension system for a pair oftransverse wheel axles similarto figure 1 but substituting in place of coil springs coupled hydro-pneumatic springs of adjustable force for the purpose of controiling pitch attitude.

In the first embodiment illustrated in Figures 1,2 and 3 a vehicle comprises a chassis 10 having two pairs of wheel axles 11 each connected to itthrough a form ofwishbone linkage comprising a pair of normally horizontal wishbones 12, 13 one above the other. The upperwishbone 12 supports the chassis 10 through a spring 14. All the wishbones are pivotally connected to both their respective wheel axles and to the chassis.

Atorsion barspring 15, cranked at each endto form levers pivotally connected through rigid links 16 to the upperwishbones 12, is fitted in bearings 17 affording rotational freedom attached to an adjustable mounting plate 18. The adjustable mounting plate is connected at one end to the chassis by means of a pivot 19, and atthe other end a chassis mounted double acting hydraulic ram 20 controlsthe angular position ofthe mounting plate relative to the chassis. Normally the mounting plate is maintained in an horizontal position relative to the chassis such that no torsional load exists in the bar 15.

With referencetofigure 3 an hydraulic pump 23 receives fluid from a reservoir 24 and delivers it at higher pressure into an accumulator 25 which connects with a servo valve 26. Control unit 27 is proportionally sensitive to transverse accelerations of the vehicle and by means of servo valve 26will proportionally control the pressure in hydraulic lines 28 and 29.

By way of example, iffigure 1 is considered to be a rear elevation of a vehicle which is cornering to the right, the vehicle will tend to roll to the left due to centrifugal force acting through it's centre of gravity which is normally above the vehicle's roll axis. The transverse acceleration is sensed by the control unit 27 which in turn operatesthe servo valve 26 changing the pressures existing in the hydraulic lines 28 and 29 so thatthe hydraulic ram 20 is caused to extend altering the angle of the mounting plate 18, together with torsion bar bearings 17, relative to the chassis 10. This establishes a torsional load in the ba r 1 5 which is reacted i nto the chassis th roug h pivots 19 and 30 causing a reduction in the roll angle which would otherwise have been obtained.

Similarly should the vehicle corner in the opposite direction the control unit 27 would cause the hydraulic ram to retract and load the torsion bar in the opposite sense.

In essencethetorsion bar spring 15 maybe considered as a conventional "anti-roll bar" which is capable of being adjustably preloaded when the vehicle is in motion in order to limit roll angle during cornering manoeuvres.

The second embodiment illustrated in figures 4 and Sis similar to thefirstwith two exceptions.

Firstly the chassis is supported by single acting hydraulic rams 21 instead of metal coil springs 14.

Transverse pairs of rams 21 are connected to a common gas charged pressure accumulator 22 or32 which acts as a resilient suspension spring.

Secondly, with reference to figure 4 which represents a schematic layout suitable for a vehicle having two pairs of transverse wheels, an additional servo valve 31, connected to accumulator 25 and proportionally controlled by a longitudinal acceleration sensor in control unit 27, is used to hydraulically modify the pressures in accumulators 22 and 32 in order to alterthe pitch attitude ofthe vehicle under acceleration or braking.

By way of example, and with reference to figure 4, if, with the vehicle at rest, the pressure in accumulator 32 is considered to be sufficientto support the weight of the front of the vehicle by means of the connected pair of rams 21, and similarly the pressure in accumulator 22 is sufficient to supportthe rear of the vehicle, when accelerating or decelerating weight transferred from front to rear or rear to front pairs of wheels respectively, due to the centre of gravity being above the road surface, will induce an angular pitching movement.

Longitudinal acceleration forces sensed bythe control unit 27 proportionally increases the pressure in accumulator 22 by means of the servo valve 31 and similarly decreases that in accumulator 32 to compensate forweighttransfer and thus reduce or eliminate pitch attitude changes.

Similarly deceleration forces are reacted to in the same way but in the opposite sense.

Amongst other advantages and features of the embodiments described above are the following, namely limitation of roll and pitch, and more constant ride height Moreover, the equipment can be designed as a factory fitted option without requiring major structural differences with respect to conventional layouts. Servicing is simple and the apparatus has certain fail safe characteristics.

Operation does not depend on displacement errors of the suspension. Because the car is suspended by "conventional " springs the control circuit responses becomefarsimplerto quantify.

Claims

1. Avehicle suspension system comprising an anti-roll torsion barcharacterised by loading means forthetorsion bar responsiveto vehicle motionto change the loading of the barandtherebyto reduce vehicle roll.

2. Avehiclesuspension system comprising wheel axles connected to a chassis through resilient suspension units to supportthe weight ofthe vehicle and provide pitch resistance, and a torsion bar connecting a transverse pair of wheel axles to provide roll resistance, characterised by means to adjust the torsional loading of the torsion bar in response to sensed aspects of vehicle motion.

3. Avehicle suspension system comprising wheel axles connectedto a chassisthrough articulated links and resilient suspension units which supportthe weight of the vehicle and provide pitch resistance and may or may not provide some roll resistance, and atorsion bar spring adjustably mounted on the chassis and connecting a transverse pair of wheel axles so that the torsional loading of the bar is changed when the wheels are differentially displaced abouttheirarticulating connections with the chassis.

4. A system according to claim 1 or claim 2 wherein said means for adjusting the loading of the torsion bar comprises a torque generating mechanism connected to the torsion bar between the ends of the torsion bar.

5. Asystem according to claim 4wherein said torque generating mechanism acts between the chassis and the torsion bar.

6. A system according to claim 4 or claim 5 wherein said torque generating mechanism comprises a hydraulic or pneumatic ram.

7. A system according to claim 6 wherein said ram actuates a mechanism to convert linear movement into rotary movement.

8. A system according to claim 7 wherein said mechanism comprises lever means.

9. A system according to claim 8 wherein said lever means comprises a pair of spaced bearings for said torsion bar and carried on a common mounting which is pivotally connected to the vehicle chassis and connected also to said ram for pivotal movement aboutthe axis of said pivotal connection to the chassis.

10. Asystem according to claim Swhereinsaid torsion bar extends generally horizontally between opposed wheel axles of said vehicle and said pivot axes of said ram and said common mounting extend generally horizontally in the travel direction of the vehicle.

11. A system according to any one ofthe preceding claims characterised in that said suspension units comprise spring units providing a controllable degree of resilient resistance to vehicle pitching, and means is provided to vary said degree of resilient resistance in accordance with sensed aspects of vehicle motion tending to cause pitching.

12. Avehicle suspension system comprising first resilient means primarily supporting vehicle weight and providing pitch resistance, and second resilient means providing substantially only roll resistance, characterised in that at least one of said resilient means is adapted to provide controlled resistance to its loads, and control means responsive to aspects of vehicle movement is connected to said resilient means to control said pitch and/or roll ofthevehicle.

13. A vehicle suspension system substantially as described herein with reference to Figures 1 to 3, or Figures 1 to 3 as modified by Figure 4 or by Figure 5, ofthe accompanying drawings.