Motor vehicle roll control system

A motor vehicle roll control system in a motor vehicle having a suspension system including one or more anti-roll bars, said motor vehicle being a dual-purpose vehicle for both road use and off-road use, which roll control system includes anti-roll force adjustment means whereby the action of said anti-roll bars can be eliminated or modified within predetermined limits, either manually or automatically, to compensate for changes in terrain traversed by said vehicle.

This invention relates to a motor vehicle roll control system to stabilise 
the tendency of a sprung portion of a motor vehicle to tilt laterally 
relative to an unsprung portion of said vehicle when said vehicle is in 
motion. In particular, it concerns a system applicable to an off-road 
vehicle to enable such a vehicle to exhibit suitable suspension 
characteristics for both on-road use and off-road use. 
According to the present invention, in a motor vehicle having a suspension 
system including one or more anti-roll bars, a motor vehicle roll control 
system includes anti-roll adjustment means whereby the action of said 
anti-roll bars can be eliminated or modified within predetermined limits, 
either manually or automatically, to compensate for changes in terrain 
traversed by said vehicle. 
With such an arrangement, the behaviour of the suspension system can be 
adjusted so that in conditions of very irregular terrain, the action of 
the anti-roll bars is eliminated or substantially reduced, so that the 
wheels of the vehicle can move into and out of ruts and gullies in the 
ground surface traversed by the vehicle without appreciable loss of 
traction between said wheels and the ground surface. 
Similarly, under good road conditions, the anti-roll bars can be made fully 
effective to give a vehicle ride characteristic appropriate to that 
expected for a vehicle intended for on-road use. 
Preferably the means controlling the action of said anti-roll bars are 
actuated automatically when the vehicle reaches a predetermined speed 
limit for off-road use. Alternatively, said controlling means may be 
actuated by selection of either a specific gear ratio or of two wheel 
drive instead of four wheel drive.

In a first embodiment of the invention shown in FIGS. 1 and 2, there is 
illustrated the rear axle 10 of a vehicle equipped with an anti-roll bar 
12, one end of which is coupled to an unsprung portion of the body of the 
vehicle (not shown) by means of a rigid pivoted link 14, and the other end 
of which is coupled to said unsprung portion of the body of the vehicle by 
means of a modified hydraulic suspension strut 16, shown in an enlarged 
cross-section in FIG. 2. The anti-roll bar 12, is pivotally coupled to a 
sprung portion of the vehicle, namely the rear axle 10, by the two bracket 
mountings 15. The remainder of the suspension system of the vehicle is a 
conventional one, and may include conventional suspension springs, either 
leaf springs or coil springs, and/or conventional hydraulic suspension 
struts. Such conventional suspension items are well known in the art and 
may be constructed and arranged as desired and, for these reasons, no 
detailed description of the construction or the arrangement of the 
remainder of the suspension will be given for any of the four embodiments 
of the invention hereinafter particularly described. The modified 
suspension strut shown in FIG. 2 comprises a cylinder 18 pivotally 
connected at one end to the body of the vehicle, in which cylinder can 
reciprocate a piston 20 carried on a connecting rod 22 pivotally connected 
at its free end 24 to the end of the anti-roll bar 12. The cylinder 18 is 
filled with hydraulic fluid above and below the piston 20, and there is a 
separate valved connection 26 between the top and the bottom of the 
cylinder. With the valve 26 in a closed condition, as shown in the main 
figure of FIG. 2, there is no interconnection between the top and the 
bottom of the hydraulic cylinder 18 and effective movement of the piston 
20 within the cylinder 18 is prevented. Consequently the modified 
suspension strut 16 exhibits the same physical effect on the anti-roll bar 
12 as would be achieved by a pivoted rigid strut. Thus, when the valve 26 
is in the closed position, the vehicle is provided with a fully operative 
anti-roll bar suspension arrangement, as required for driving the vehicle 
under good road conditions. 
On the other hand, if the valve 26 is placed in the open position, as shown 
in the scrap view of FIG. 2, then fluid communication is established 
between the top and the bottom of the hydraulic cylinder 18, and the 
piston 20 can move up and down the cylinder 18 without undue difficulty. 
Consequently, this freedom of movement of the piston 20 within the 
cylinder 18 substantially eliminates the effectiveness of the anti-roll 
bar 12 in controlling the roll characteristics of the vehicle. With the 
valve 26 in this open position, the suspension of the vehicle is thus 
modified to a degree which allows a freedom of axle movement not limited 
in any way by the anti-roll bar 12; by allowing the wheels to maintain 
contact with the ground despite severe lateral irregularities, the vehicle 
can display the traction characteristics required when driving it under 
off-road conditions. The position of the valve 26 could be adjusted 
manually, preferably by making the valve 26 an electrically operated valve 
controlled by switch means (not shown) accessible to the driver of the 
vehicle. A preferred construction would incorporate this switch means 
within the gear box of the vehicle such that, on selecting a predetermined 
gear, switching of the valve 26 from one position to the other position 
would occur automatically. Alternative methods of operating the valve 26 
could be used, including, for example, pneumatic actuation and hydraulic 
actuation. 
In a second embodiment of the invention, illustrated in FIGS. 3 and 4 of 
the accompanying drawings, both ends of the anti-roll bar 12 are equipped 
with modified hydraulic suspension units 16 similar to that used in the 
first embodiment, the top and the bottom of each of the cylinders 18 
concerned being linked hydraulically to the corresponding top and bottom 
of the other cylinder 18 by means of a common shuttle valve 28, shown in 
cross-section in FIG. 4. When this common shuttle valve 28 is in the 
closed position shown in the full view of FIG. 4, then the hydraulic 
communication between the cylinders 18 is cut-off. In these circumstances, 
each of the modified suspension struts 16 acts as a rigid strut, and the 
anti-roll bar 12 becomes fully effective, as is required for on-road use 
of the vehicle. On the other hand, if the valve element 30 in the common 
shuttle valve 28 is opened, as shown in the scrap view of FIG. 4, then 
hydraulic communication is established between the tops and the bottoms of 
the cylinders 18, with the result that each piston 20 in each cylinder 18 
can move up and down its respective cylinder. This freedom of movement of 
the pistons 20 within the cylinders 18 of the modified suspension units 16 
effectively modifies the action of the anti-roll bar 12 so that the 
vehicle displays the desired traction characteristics for off-road use. 
Since the hydraulic communication between the cylinders 18 is such that 
the cylinders 18 are interconnected to one another, then, as one piston 20 
goes down in its cylinder 18, the other piston 20 rises the same amount in 
its respective cylinder 18. This means, in practice, that the effect of 
the anti-roll bar 12 upon the roll characteristics of the vehicle is, 
except for the resistance due to the motion of the fluid from one cylinder 
to the other, substantially eliminated. 
In a third embodiment of the invention shown in FIGS. 5, 6 and 7 of the 
drawings, the suspension system for the rear axle 10 of a motor vehicle is 
provided with an anti-roll bar 12 which can be mechanically engaged or 
dis-engaged when necessary. This anti-roll bar is made up of two separate 
L-shaped torsion bars 32, each one of which is pivotally connected at one 
end to the axle 10 of the vehicle and is pivotally connected to the body 
of the vehicle by a rigid link 34. The other ends 38, 40 of these torsion 
bars 32 are connected together by means of the splined coupling device 36 
shown in detail in FIGS. 6 and 7 of the drawings. Said other ends of the 
torsion bars are slidably socketed one within the other, and one 38 of 
said other ends of the torsion bars 32 has secured thereto a contoured 
sleeve portion 42. The other one 40 of said other ends of the torsion bars 
32 is provided with a splined periphery 44 upon which is slidably mounted 
a splined contoured sleeve portion 46 engageable with the contours of the 
fixed sleeve portion 42 on the other torsion bar 32. This slidable sleeve 
portion 46 can be moved backwards and forwards on the splined periphery 44 
in order to engage or disengage the torsion bars 32 with one another. FIG. 
6 shows the torsion bars 32 in a disengaged position, that is, in the 
position required for the vehicle to be used in off-road conditions. In 
the disengaged position shown in FIG. 6 the torsion bars 32 are free to 
move relative to one another as the vehicle moves over rough terrain 
without any torsional forces being transmitted from one torsion bar to the 
other. On the other hand, when the two torsion bars 32 are engaged with 
one another, as shown in FIG. 7, then any torsional movement induced in 
one of the torsion bars is transmitted to the other torsion bar, and the 
whole unit acts as a normal anti-roll bar. Thus the two torsion bars 32 
are maintained in this engaged position whenever the vehicle is used on a 
properly surfaced road. 
In this third embodiment of the invention, it is not possible to have any 
degree of variation of the action of the anti-roll bar 12, since the 
mechanical linkage used is either fully engaged or fully disengaged, that 
is, the anti-roll bar 12 is either functioning or is substantially 
eliminated. This differs from the previous two embodiments, in which it is 
possible, if desired, by suitable adjustment of the valves 26, 28 
concerned, to arrange for a variation in the action of the anti-roll bar 
12 from a maximum to a minimum. Modifications to the coupling device used 
in this third embodiment can be made within the scope of the invention 
claimed. Thus, for example, engagement of the two torsion bars could be 
effected by tapered dogs in the manner of a dog clutch, the two bars being 
moved away from one another in order to disengage the tapered dogs. After 
disengagement, where the two torsion bars are independently movable 
relative to one another, re-engagement of the torsion bars with one 
another will be self aligning, even when the bars are rotationally 
displaced relative to one another, by reason of the tapered contours of 
the dogs. To avoid the necessity, in such an arrangement, of moving the 
torsion bars towards or away from one another and to maintain their 
concentricity, the engagement and disengagement could be effected by 
sliding splined components bearing the tapered dogs, similar to the 
contoured sleeve portions already described. 
In a fourth embodiment of the invention, shown in FIGS. 8 and 9 of the 
accompanying drawings, the anti-roll bar 12 is made up of two U-shaped 
torsion bars 48 each one of which has one end thereof pivotally connected 
to one end of an axle 10 of a motor vehicle, and is pivotally connected to 
a vehicle body by means of a rigid link 34. The other ends 50, 52 of these 
torsion bars are located parallel to one another and to the longitudinal 
axis of the vehicle by means of a rubber-filled coupling block 54. This 
rubber-filled coupling block 54 is in two parts 56, 58, one part 56 being 
anchored to the vehicle body by means of a rigid link 60, and the other 
part 58 being slidably mounted on the parallel sections of the two torsion 
bars 48 so that it can be slid between a position in which it is in 
contact with said anchored part 56 of the rubber-filled coupling block, as 
shown in FIG. 8, and a position in which it is adjacent the free ends 50, 
52 of the parallel portions of the torsion bars 48, as shown in FIG. 9. 
When the two portions 56, 58 of the rubber-filled coupling block 54 are in 
contact with one another, as shown in FIG. 8, then torsional deflection of 
one of the torsion bars can take place without producing any corresponding 
substantial torsional deflection in the other torsion bar. Thus, with the 
two portions 56, 58 of the rubber-filled coupling block 54 in the position 
shown in FIG. 8, the effective anti-roll bar 12 formed by the two torsion 
bars 48 has a minimal effect on the roll characteristics of the vehicle, 
that is, the suspension characteristics of the vehicle are adjusted for 
off-road conditions. On the other hand, when the slidable portion 58 of 
the rubber-filled coupling block 54 is in the position shown in FIG. 9, 
then deflection of one torsion bar 48 will result in deflection of the 
other torsion bar 48, that is, the two torsion bars are effectively 
coupled one with the other to form an overall anti-roll bar 12, so that 
the suspension characteristics of the vehicle are now suitable for on-road 
use. Alternatively, spherical jointed blocks could be used in place of the 
rubber-filled coupling block. 
The suspension system according to the invention provides a simple, yet 
effective, method of firstly inhibiting body roll of a vehicle relative to 
the axle of the vehicle when required and, secondly, allowing up to the 
maximum vertical differential road wheel movement on the vehicle for 
severe off-road conditions. By means of such a system, it is possible for 
the suspension characteristics of the vehicle to be readily adjusted for 
either off-road use or on-road use with little or no exertion on the part 
of the driver of the vehicle. The embodiments of the invention described 
specifically within the specification cover the basic concept of the 
suspension system according to the invention. In any of the embodiments, 
body and axle attachments could equally well be transposed, i.e., the 
centre section of the anti-roll bar could be attached either to the axle 
or to the body of the vehicle. It will be readily apparent that further 
modifications can be made in the system to render it more sophisticated in 
action. In particular, for example, with the first and second embodiments 
of the invention described hereinbefore, it would be possible to arrange 
that the valves used in the system are provided with bleed means to ensure 
that, on changing the roll control characteristics of the vehicle from the 
off-road setting to the on-road setting, the possibility of the anti-roll 
bar being brought into action with the vehicle canted over at an 
unacceptable angle can be avoided. 
Any one of the four of the embodiments specifically described herein could 
be utilised, if desired, in the suspension system of a trailer vehicle, 
since the concept of the roll control system according to the invention, 
is not limited solely to motor vehicles per se, but includes trailer 
vehicles as well.