Vehicle suspension system

Abstract: A suspension system of a vehicle wheel set having an axle, comprising first, leaf spring suspension means (11, 13) arranged on opposed sides of an associated vehicle and connected to the axle and second suspension means (12) which is arranged in mechanical series with said first, leaf spring suspension means (15) and stabilising means (15) which is arranged generally transversely of the longitudinal axis of the vehicle and is arranged to act in conjunction with one or both of said first and second suspension means (11, 13: 12), to provide the vehicle with an anti-roll characteristic when operating under certain conditions, wherein said first, leaf spring suspension means (11, 13) is connected to the axle by mountings located generally centrally thereof in the longitudinal direction of the vehicle. In a preferred embodiment, the first suspension means comprises a pair of springs (21) and the second suspension means (22), a leaf spring, coil spring, hydraulic, pneumatic or rubber (elastomeric) suspension arrangement or any combination thereof, mounted upon an anti-roll bar or tube (25).

Description: This invention relates to a suspension system for a set of vehicle wheels, of the type including a stabiliser (anti-roll) bar or tube and is especially, but not exclusively, related to such a suspension system for heavy commercial vehicles, such as trucks, coaches, buses and plant. In existing vehicle suspensions, it is known to use a stabiliser (anti-roll) bar or tube mounted transversely of the vehicle frame (chassis), to act in a parallel sense to an associated pair of springs (leaf springs). Such an arrangement stiffens the vehicle suspension in roll but not during total axle movement. A typical stabiliser (anti-roll) bar or tube for, say, a truck, comprises a generally U-shaped torsion bar or tube with its otherwise free pair of ends connected to an associated axle of the truck by means of, say, shackles and with the base portion of its U connected to transversely spaced points on the vehicle frame (chassis). In the case of a torsion bar, this usually takes the form of a spring steel rod formed into the desired U-shape, although it can be of tubular construction. Although there are several variations of this known stabiliser (anti-roll) bar or tube arrangement, such as, having the bar or tube connected between pairs of leaf springs on opposed sides of an associated vehicle, the basic purpose of the bar or tube is to resist any axle rolling movement relative to the vehicle frame (chassis) and axle, or an associated spring assembly located at or adjacent the axle, by means of shackles which allow pivoting of the respective components with respect to each other and the chassis, thereby allowing for geometrical change in the configuration of the suspension during use thereof. Known in the art, from GB 255,729 (O'Neill), is a vehicle suspension system according to the preamble of claim 1 and having a first, leaf spring suspension means (2) arranged on opposite sides of the vehicle, a second suspension means (8) arranged in mechanical series with the first, leaf spring suspension means (2), and stabilising means (15) which is arranged generally transversely of the longitudinal axis of the vehicle and arranged to act in conjunction with the second suspension means (8) to provide the vehicle with an anti-roll characteristic. The stabilising means (15) is supported from the vehicle chassis (1) by a rigid bracket (16) at each end thereof. It is an object of the present invention to provide an improved vehicle suspension system with enhanced anti-roll characteristics which, in turn, provide better vehicle handling, particularly under adverse driving surface conditions. It is another object of the invention to provide an improved vehicle suspension system which affords a comparatively soft suspension during normal total axle movement which provides a comparatively stiff anti-roll characteristic capable of resisting at least a major proportion of any roll attempted by the associated vehicle. It is a further object of the invention to provide an improved vehicle suspension system which affords little or no anti-roll characteristic for an unladen vehicle, thereby providing a smoother and more comfortable ride, but which affords the required anti-roll characteristics when the vehicle is laden. It is yet a further object of the invention to provide an improved vehicle suspension system which affords a comparatively soft, low frequency ride and good inter-axle articulation with comparatively high roll resistance. Accordingly, one aspect of the invention resides in a suspension system of a vehicle wheel set having an axle, comprising first, leaf spring suspension means arranged on opposite sides of an associated vehicle and connected to the axle by mountings located generally centrally thereof in the longitudinal direction of the vehicle and second suspension means which is arranged in mechanical series with the first, leaf spring suspension means; and stabilising means which is arranged generally transversely of the longitudinal axis of the vehicle and is arranged to act in conjunction with one or both of said first and second suspension means to provide the vehicle with an anti-roll characteristic when operating under certain conditions, characterised in that said stabilising means is connected to the vehicle chassis by means of a pair of arms arranged on respective opposite sides, and extending generally longitudinally, of the vehicle, and in that an end of each arm is connected to the vehicle chassis by means of a controllable actuator or damper to render the system "active" or "semi-active". Preferably, the second suspension means is connected to, and is mounted upon, the stabilising means. In one embodiment, the second suspension means is located on the longitudinal axis of the associated vehicle and can be secured to the chassis thereof. Preferred forms of the second suspension means include a leaf spring, coil spring, hydraulic, pneumatic or rubber (elastomeric) suspension arrangement or, indeed, any combination thereof. In other embodiments, the first suspension means is arranged on respective opposite sides of the associated vehicle, with the stabilising means being arranged to act in conjunction with the secondary suspension means. The first suspension means may also comprise spring means arranged on respective opposite sides of the vehicle, with the stabilising means connected therebetween. The "active" or "semi-active" arrangement of suspension system in accordance with this invention can use both powered actuators and cylinders acting as dampers and adjustable, by powered or switchable valves, from zero damping to virtually solid damping. The powered actuators or dampers may have control valves operated under microprocessor control. Preferably, the position of the stabilising means with respect to the first and second suspension means may be adjusted longitudinally of the vehicle. Also provided is a vehicle wheel set suspension systems as defined above, arranged in tandem or other multiple axle combinations thereof. In order that the invention may be more fully understood, various suspension systems will now be described with reference to the accompanying drawings in which each Figure includes a side elevational view and a plan view of a particular arrangement and wherein: Figure 1 is a first arrangement of suspension system for a vehicle wheel set, which is not in accordance with the invention; Figure 2 is a second arrangement of vehicle wheel set suspension system which may be embodied in the invention; Figures 3 and 4 are two modifications of the second arrangement of vehicle wheel set suspension system of Figure 2 and which also may be embodied in the invention; Figure 5 is a further modified form of the second arrangement of Figure 2 and which also may be embodied in the invention; Figure 6 is an embodiment of inventive vehicle suspension system; Figure 7 is another embodiment of inventive vehicle suspension system; Figure 8 is a modified form of the embodiment of Figure 7; and Figure 9 is a further arrangement of suspension system for a vehicle wheel set, which is not in accordance with the invention. Referring firstly to Figure 1 of the drawings, a description of a suspension system for a vehicle wheel set (not shown) is given for reference only; the suspension system comprises a first or primary suspension means 11 in the form of a single leaf spring 13 with an upturned eye 14 at an end thereof, such a spring 13 being mounted on either side of the frame or chassis (not shown) of an associated vehicle. A front axle wheel set suspension system is shown but, equally, the system can be associated with the rear and/or other axle wheel set of the vehicle. A stabilising anti-roll bar or tube 15 has its otherwise free ends 16 connected to respective ends of the leaf springs 13. Mounted upon the anti-roll bar or tube 15, centrally thereof, is secondary suspension means 12 in the form of a coil spring, pneumatic or other suitable suspension arrangement, which can be single, dual or multiple per axle and which acts between the leaf springs 13, via the anti-roll bar or tube 15, and the vehicle chassis to which it is secured. In this manner, with the primary suspension means 11 and the secondary suspension means 12 being employed in mechanical series with each other and with the anti-roll bar or tube 15 acting in conjunction with at least the primary suspension means 11, there is provided a comparatively soft suspension during normal, total axle movement but with a comparatively stiff anti-roll characteristic capable of resisting at least a major proportion of any roll attempted by the vehicle. Figures 2 to 4 show various forms of a vehicle wheel set suspension system which may be embodied in the present invention, as described later, and wherein secondary suspension means is employed, again in mechanical series with primary suspension means, but with the stabilising means acting in conjunction with the secondary suspension means, rather than the primary suspension means as in the case of the arrangement of Figure 1. Here again, the effect is to provide a comparatively soft suspension during normal, total axle movement. The secondary suspension means, which may be in any suitable form, for instance, another leaf spring, coil spring, hydraulic, pneumatic, rubber (elastomeric) suspension arrangement or any combination thereof, is associated with a comparatively stiff, stabilising anti-roll bar or tube capable of resisting at least a major proportion of any roll attempted by the vehicle. As a consequence, the secondary suspension means, in whatever suitable form, can, if the anti-roll effect is sufficient, be installed with less consideration for spacing across the vehicle chassis to provide the necessary anti-roll characteristic. Also, the second suspension unit can be single, dual or multiple per axle. In more detail and with reference to Figure 2, a first or primary suspension means 21 is constituted by a pair of leaf springs 23 disposed on opposed sides of a vehicle chassis (not shown) and having at respective ends thereof upturned eyes 24, 24', with the eyes 24 being connected to the chassis. Opposed ends 26 of an anti-roll bar or tube 25 are connected to respective arms 27 which, at one end, are connected to the chassis by associated shackles 28 and, at the other end, to the respective eyes 24' by bushes 29. Although a single leaf spring arrangement is shown for the first or primary suspension means 21, any other suitable form of leaf spring arrangement may of course be used, such as a multiple one. Secondary suspension means in the form of, say, a coil spring 22, is mounted upon the bar or tube 25 to act in conjunction therewith. A modified form of the arrangement described with reference to Figure 2 can use a pneumatic (air) secondary suspension means, as referenced at 22, or any of the other secondary suspension means referred to above in relation to the arrangement of Figure 1. The arrangement shown in Figure 3 comprises a primary leaf spring suspension means 31 having upper leaves 33' and lower leaves 33'' with each end 36 of an anti-roll bar or tube 35 being connected by a bush 39 to each lower pair of leaves 33'' of the primary suspension means 31 and to the chassis via arms 37 and shackles 38. Associated with the anti-roll bar or tube 35 is a secondary suspension means in the form of a pneumatic (air) "spring" 32. Another arrangement, shown in Figure 4 which also includes a lowermost, rear elevational view as Figure 4A, comprises a vehicle wheel set suspension system similar to that described above in relation to Figure 3, with primary leaf spring suspension means 41 having, in this case, two upper leaves 43, 43' and a single lower leaf 43'' on opposed sides of the chassis. Secondary suspension means 42 is, however, in the form of a chevron-shaped rubber suspension block 42 or, rather, a pair thereof. Otherwise, the anti-roll bar or tube 45 and the other suspension components are substantially the same, namely the bushes 49 associated with the ends 46 of the bar or tube 45 the arms 47 and the shackles 48. An extension of the various forms of the wheel set suspension systems discussed above in relation to Figures 2 to 4, is to couple together two axles each incorporating such a suspension system with the secondary suspension means. For example, connection between secondary, pneumatic (air) spring suspension means 52 mounted on the anti-roll bars or tubes 55, such as those shown at 22 and 32 in Figures 2 and 3 would give equalised or controlled loads between axles, thereby producing an effective four spring tandem suspension, as shown in Figure 5. Here, this tandem arrangement comprises a pair of suspension systems each indicated generally at 50, as described above in relation to Figure 2, with their secondary, pneumatic spring suspension means 52 connected together by a conduit 150, although it can be seen that the arms 57, and associated bushes 59 and shackles 58, are oriented in the opposite sense to that of the corresponding components of Figure 2 but in the same sense as those components of Figures 3 and 4. Such an arrangement provides a comparatively soft, low frequency ride and good inter-axle articulation with comparatively high roll resistance. This improved axle articulation could be improved further by interconnecting, preferably hydraulically, the loads in the shackles connecting the anti-roll bars or tubes to the chassis. Such interconnection could also be effected pneumatically or mechanically. Only the same side of this tandem arrangement would be so-connected, thereby allowing each wheel on each side of the vehicle freedom to move relative to the other wheel, without anti-roll being brought into effect, whilst retaining full roll control when both wheels deflect together. Such an arrangement is shown in Figure 6, wherein a comparatively, very high articulating four spring suspension can be produced. In Figure 6, two inventive suspension systems 60, such as those constructed on the tandem arrangement described above in relation to Figure 5, have their secondary suspension means 62 connected together by a conduit 160 and their anti-roll bars or tubes 65 connected together via a hydraulic coupling 161 connected to a hydraulic piston/cylinder assembly 162 for each bar or tube 65. In accordance with the present invention, by replacing the bushes and/or shackles of the anti-roll bars or tubes of the arrangements described above with valve-controlled hydraulic actuators or dampers, the suspension arrangements described with reference to Figures 2 to 5 are rendered "active", with powered valves being controlled by a microprocessor fed with information relating to vehicle chassis motion. The valves would be operated when the vehicle sprung mass required support, either to maintain the vehicle upright or to lean as required dynamically. An active suspension of this nature is shown in Figure 7 wherein a suspension system 70 similar to that described above in relation to Figure 3 is shown, except that the shackles 38 between the anti-roll arms 37, 77 and the vehicle chassis of that previous Figure 3 are replaced by actuators or controlled dampers 78. If the vehicle chassis is stable, then the actuators 78 are free or in a damped mode, so that, on one bumps, they provide negligible or damped resistance to such wheel movement, thus effectively isolating the anti-roll arrangement from the vehicle. As soon as the sprung mass of the vehicle becomes subject to the influence of exterior forces, for instance, a strong side wind or camber, the actuator or controlled damper 78 is brought into operation or the damper setting is changed and, in conjunction with the secondary suspension means 72 and the anti-roll bar or tube 75, acts to support the vehicle, thereby providing high dynamic stability. Thus, this active suspension does not bear loads under steady state operation, which is in contrast to known active systems which act directly upon the wheel(s). Accordingly, the inventive active suspension system 70 has an advantage over the normal active ride suspension systems in that its response and sophistication need not be as sensitive as the known systems which act directly upon the wheel(s). Also, the system could be more failsafe for longer term durability situations. Figure 8 shows such an active suspension of the tandem type, which is similar to the suspension described above in relation to Figure 6, with control lines 181 connecting actuators 182 together. These actuators 182 are associated with the arms 87 of the anti-roll bars or tubes 85 connected between the leaf spring 83 of primary suspension means 81 and bearing secondary suspension means 82. Also, further control lines 183 link the control lines 181 to microprocessor-controlled valves (not shown) with a conduit 180 linking the two secondary suspension means 82 together. Figure 9 shows another type of active suspension not in accordance with the present invention, wherein the anti-roll bar or tube is replaced by other stabilising (anti-roll) means in the form of actuators 95 which are linked directly to the vehicle chassis and which simulate the action of an anti-roll bar or tube and secondary suspension means. The primary suspension means is represented here by respective lower and upper leaf springs 91, 92, to the former of which the actuators 95 are attached. Thus, it can be seen that the invention provides a vehicle wheel set suspension system which is capable of improving the anti-roll characteristic of a vehicle.

Claims: A suspension system of a vehicle wheel set having an axle, comprising first, leaf spring suspension means (70) arranged on opposite sides of an associated vehicle and connected to the axle by mountings located generally centrally thereof in the longitudinal direction of the vehicle and second suspension means (72) which is arranged in mechanical series with the first, leaf spring suspension means (70); and stabilising means (75) which is arranged generally transversely of the longitudinal axis of the vehicle and is arranged to act in conjunction with one or both of said first and second suspension means (70,72) to provide the vehicle with an anti-roll characteristic when operating under certain conditions, characterised in that said stabilising means (75) is connected to the vehicle chassis by means of a pair of arms (77) arranged on respective opposite sides, and extending generally longitudinally, of the vehicle, and in that an end of each arm (77) is connected to the vehicle chassis by means of a controllable actuator or damper (78) to render the system "active" or "semi-active". A suspension system according to claim 1, characterised in that said second suspension means (72) is mounted upon said stabilising means (75). A suspension system according to claim 1 or 2, characterised in that said second suspension means (72) is located on the longitudinal axis of the associated vehicle. A suspension system according to claim 1, 2 or 3 characterised in that said second suspension means (72) is secured to the chassis of the associated vehicle. A suspension system according to any preceding claim, characterised in that said second suspension means (72) comprises a leaf spring, coil spring, hydraulic or pneumatic or rubber (elastomeric) suspension arrangement or any combination thereof. A suspension system according to any preceding claim, characterised in that said stabilising means (75) is connected between said first, leaf spring suspension means (70) on opposite sides of the vehicle. A suspension system according to any preceding claim, characterised in that said stabilising means (75) comprises an anti-roll bar or tube. A suspension system according to any preceding claim, characterised in that the position of said stabilising means (75) with respect to said first and second suspension means (70,72) is adjustable longitudinally of the vehicle. A vehicle having a wheel set incorporating a suspension system according to any preceding claim. Two or more vehicle wheel set suspension systems according to any of claims 1 to 8 arranged in tandem or multiple axle combinations thereof. The suspension system combination according to claim 10, characterised in that the second suspension means (82) comprises a hydraulic or pneumatic spring, said spring of one wheel set suspension system being connected to said spring of a second wheel set suspension system by a hydraulic or pneumatic line (180). The suspension system combination according to claim 10 or claim 11, characterised in that the controllable actuator or damper (182) connecting an end of each arm (87) of one wheel set suspension system to the vehicle chassis is connected by a control line (181) to the controllable actuator or damper (182) of a second wheel set suspension system on the same side of the vehicle. A suspension system according to any of claims 1 to 8, or a suspension system combination according to any of claims 10 to 12, characterised in that the controllable actuators or dampers (78,182) are valve controlled each with a powered valve controllable by a microprocessor arranged to receive information relating to vehicle chassis motion.

Inventors: REAST JOHN BOLLAND, REAST, JOHN BOLLAND
Applicants: DETROIT STEEL PRODUCTS CO INC, DETROIT STEEL PRODUCTS CO.INC.
Application year: 1990
Main classification: B60G21
IPC codes: B60G11, B60G21, B60G17, B60G5