NL2004548C2 - Suspension system for providing mobile support to a vehicle structure relative to a road surface and an anchoring system therefore. - Google Patents

Description

P91120NL00

Title: Suspension system for providing mobile support to a vehicle structure relative to a road surface and an anchoring system therefore.

5 FIELD

The invention refers to a suspension system for providing mobile support to a vehicle structure relative to a road surface and anchoring system therefore.

BACKGROUND

10 Improving driving comfort has long been an object of vehicle suspension systems. In this respect, US4687223 has been known to provide an active suspension wherein suspension arms are provided with bushings for connection with a vehicle body. Vehicle comfort is provided by reducing the pressure in the bushings when this is possible. When a steering movement is necessary a resistance 15 of the rubber bushings against a movement in a lateral direction of the vehicle is increased by increasing the hydraulic pressure in the bushings.

This mechanism will not provide the improved driving comfort results for wheel suspension systems in general where specifically longitudinal compliance is needed to isolate high frequency vibrations (typically > 8 Hz) related to the well 20 known harshness problem while riding over road irregularities. Moreover this need for good isolation becomes more pronounced commercial vehicles with heavier vehicle structures and application of longitudinal guiding arms in their suspension assemblies. In such systems wheel suspension of the axle is provided by attachment to one or more brackets or alternatively a central carrier fixed to the vehicle 25 structure. The linkage and radius rods common for such suspension structure are anchored to the vehicle structure, typically via a carrier and a connecting bushing which may be elastically in nature to provide some vibrational damping and resilience. This improves vehicle driving comfort and increases the life time of the suspension by fatigue prevention. However, such bushings are typically of a passive 30 nature, wherein the elastomer has progressive stiffness characteristics which are worsened due to high frequency dependency. This results in the suspension structure being more or less rigidly connected - even when resiliently coupled via 2 the elastomeric - in full load conditions often exceeding 10 tons of load conditions on the wheel with fully compressed bushings that altogether lack any elastic function and fail to dampen or absorb the vibrational loads transmitted via the wheel.

5 SUMMARY

It is a desire to improve driving comfort for such systems by increasing the coupling elasticity between the suspension arms and the vehicle structure. To this end, according to an aspect, a suspension system is provided for providing mobile support to a vehicle structure relative to a road surface; comprising guiding arms 10 allowing vertical movement of the axle, but restraining axle movement in a horizontal plane relative to the vehicle structure; an anchorage system that connects the guiding arms to the vehicle structure; said anchorage provided by a bushing having an elastomeric coupling part coupling at least one of the guiding arms to the vehicle structure. The coupling part defines a pressure reservoir in a 15 compression zone that is compressed due to a static wheel load; and a resilient system is provided external of the bushing arranged to pressurize the pressure reservoir so as to volumetrically relay any dynamic load vibrations in the pressure reservoir to the resilient system.

Accordingly, an anchorage is provided in the suspension system wherein 20 vehicle comfort can be increased and harshness is reduced.

EXEMPLARY EMBODIMENTS

Figure 1 shows a side elevation of a truck having an axle assembly according to the invention mounted at a rear end thereof; 25 Figure 2 shows a schematic embodiment of a suspension according to the invention;

Figure 3 shows a detailed perspective view of a central carrier and guiding sway bars;

Figure 4 shows a detailed view of the anchorage of the sway bar arms; 30 Figure 5 shows an exemplary pressure circuit for an active bushing anchoring system; 3

Figure 6 demonstrates three radial spring characteristics of different bushing anchorage systems;

Figure 7 shows an exemplary pressure circuit for an anchoring system for the guiding arms; 5 Figure 8 shows an alternative pressure circuit; and

Figure 9 shows a detailed construction of an active bushing.

Figure 10A-A and B-B show schematic cross sectional views of the bushing of Figure 9.

10 Where in this specification and its appended claims reference is made to ‘road’ or ‘road surface’, such references specifically do not exclude variations such as railroad, railroad tracks and rail surfaces, to which the invention may be equally adaptable.

15 Figure 1 shows a side elevation of a truck having an axle assembly according to the invention mounted at a rear end thereof, here in the form of a tractor unit, for pulling a trailer as an articulated lorry. The truck 1 includes a chassis 3 and pairs of front wheels, trailing rear wheels and leading rear wheels represented by road wheels 5, 7, 9, respectively. The chassis 3 together with a driver cab 11 forms a 20 vehicle structure that is in mobile support relative to a road surface 13 by at least a set of front wheels 5 and rear wheels 7. As shown in Figure 1, the leading rear wheels 9 may be lifted from the road surface 13 while the trailing set of rear wheels 7 are in contact with the road surface 13. The leading wheels are optional. The truck 1 also has a trailer coupling 15 supported by its chassis 3. It should be clear to 25 the skilled person that such a trailer coupling, popularly referred to as a “fifth wheel”, is optional and that various transport ancillaries could be supported by the chassis 3. Also the chassis could have a different length subject to requirement. It is further seen in Figure 1 that the trailing set of rear wheel 7 are part of a driven main axle 17, which is driven by a propeller shaft 19, itself driven from a change-30 speed gear transmission (not visible in drawing).

Figure 2 shows a schematic embodiment of the suspension system of trailing wheels 7. The system comprises an axle 17 containing a differential gear 4 (clockhouse) 95 and a pair of hubs (not visible in drawing) attached to a pair of wheels 7 to be driven by a motive force of the propeller shaft 19. A suspension means in the form of volumetric displacement devices represented by gas spring bellows 87 is operatively interposed between the main axle 17, i.e. through air 5 spring carriers 18, that are firmly connected an axle body (not shown) and the confronting nearest chassis rails 27. The airspring carriers additionally provide for attachment of the guiding arms 82 (typically referenced as radius rods or alternatively stabilinker blades). The guiding arms 82 are arranged for suspended relaying of a wheel load of wheels 7 to the vehicle structure 17 by allowing vertical 10 movement of the axle 17, but restraining axle movement in the horizontal plan, in particular, fore (A) and aft (B) direction relative to the vehicle structure 27. It is noted that in alternative embodiments, the guiding arms may have a different orientation in the horizontal plane, in particular, in a transverse direction relative to the vehicle structure. Suitably, a central carrier 101 may attached to the vehicle 15 structure 27 providing anchorage for the guiding arms 82 and linkage 41.

Alternatively, guiding arms may be coupled directly to a vehicle structure such as a chassis. Linkage 41 is associated with the axle 17 adapted for restraining longitudinal and lateral movement relative to the vehicle of axle 17, ie freeze of displacement in a horizontal plane parallel to the vehicle structure, while 20 permitting vertical movement and corresponding rotations in the three orthogonal directions (freedom provided by the applied ball joint on top of the axle clock house) thereof. The linkage 41 can be provided by various configurations, preferably, the linkage 41 is provided by a triangle configuration.

A trailer coupling 15 is arranged to be mounted by fasteners that also attach 25 the central carrier 101 to the vehicle structure.

Arrows A and B illustrate the main force directions of the reaction forces on the central carrier 101 due to the static wheel load 7. The suspension means 87 may include one of an active and a passive suspension element; a passive, resilient suspension element; the resilient suspension element including a mechanical 30 spring; the resilient suspension element including at least a volumetric displacement device; the volumetric displacement device being a gas spring. The suspension means may optionally be an active suspension element, which may 5 includes at least one second volumetric displacement device such as a shock absorber.

Figure 3 shows a detailed perspective view of a central carrier 101 and guiding bars 82 in the form of sway bars or stabilinkers 82. In this embodiment, a 5 stabilizer 83 is provided for stabilizing roll of the vehicle structure relative to a road surface, formed by a transverse anti-roll bar 83 interconnected to the guiding arms formed as flexible sway bar arms 82. The anti-roll bar 83 is connected to air spring carriers 18 providing air spring support faces 181 and axis support faces 182.

This central carrier 101 is preferably manufactured as a unitary piece having 10 a web portion 103 that effectively functions as a chassis cross member.

Alternatively, the central carrier 101 may also be composed of multiple brackets, effectively designed to transmit forces from the axle via suspension linkage and their corresponding anchorage systems to the vehicle structure. Opposite ends of the web portion 103 carry flanges 105 suitably drilled to receive fasteners for being 15 attached between webs of opposite chassis rails (such as chassis rails 27 of Figure 1). Depending from the web portion 103 are first and second bracket arms 113, 115 each having anchorage bores 117 at their lower ends. The anchorage bores 117 are adapted to receive an articulated connection of the sway bars 82 that are connected to air spring carriers 18 at the opposite side. Feasible articulated connections may 20 be based on elastomeric ball-and-socket joints, commonly referred to as so-called molecular joints and further exemplified in the figures below. The web portion 103 is provided with cavities (not shown) for receiving similar articulated connections of the upper linkage 41 (see previous Figure). The unitary central carrier 101 can be suitably formed as either a casting, such as an alloy casting, or as a forging from a 25 suitable metal, including steel and aluminum. Alternatively the central carrier 101 may also be formed by welding together of sheet and/or bar stock metal.

Linkage 41 may alternatively be in the form of a quadrangle. Such linkages are well known in the art and are amongst others described in WO 01/45972 Al; EP 1 057 665 Al; US 6,129,367; and US 2007/0284841 Al. These quadrangle type 30 linkages integrate the functions of a triangle linkage, a Watts linkage or a Panhard linkage, that is conventionally used to inhibit lateral movement of an axle relative to a vehicle structure, and of a stabilizer bar that reduces body roll of a vehicle 6 structure. The use of a quadrangle type linkage allows the elimination of a transverse torsion bar 83.

Figure 4 shows a further detailed view of the anchorage system. In this embodiment, the bushing 84 is anchored in anchoring bores 86 of the sway bar arms 5 82. The anchorage is provided by a bushing 84 having an elastomeric coupling part 846 coupling at least one of the guiding arms 82 to the central carrier 101 via a center shaft 845.

Figure 5 shows an exemplary pressure circuit 1000 for an active bushing anchoring system 84 for anchoring the guiding arms 82. In pressure circuit 1000 10 pressure supply terminal 1005 is provided. It is noted that for multiple anchoring systems 84 such as displayed in the left and right hand arms of the sway bar arms 82, a single supply terminal 1005 is in principal sufficient to provide the supply pressure in parallel to the active bushings 84.

In addition, the circuit 1000 comprises an electric motor 1012 driving 15 hydraulic fluid pump 1008; an additional pressure control module 1009; a pressure supply terminals 1004, arranged at a respective location in the circuit 1000; a resilient system 85 in the form of a gas accumulator and a hydraulic fluid reservoir840. It is noted that the resilient system 85 includes an elastic feature and an optional damping feature that complies with the relayed dynamic load vibrations 20 in the pressure reservoir 840. The controller 1007 is arranged to control pressure control modules 1006, 1009 in such a way that the desired pressure at supply terminal 1005 is adjusted. Advantageously, the hydraulic fluid pump 1008 is an electrically controlled hydraulic fluid pump; the pressure control modules may be solenoid controlled valves. The pump 1008 may be provided as an electro-hydraulic 25 power pack, having an Electronic Control Unit (ECU) power electronics (amplifiers) 1012 and hydraulic tank 1011 integrated into a single integrated assembly. The switching valve 1006 and the pressure control valves 1009 can be integrated in one valve block (housing, manifold). To increase the accuracy of the computer controlled pressure control system 1002 an additional pressure sensor (also integrated in the 30 valve block) at the pump port 1005 and/or a second pressure sensor at the consumer port 1004 between the pressure control valves can be provided. The valve block itself might even be part of the power pack, further reducing the package, weight 7 and complexity of the total system set up. The pump 1008 additionally enables complete shutting off of the system 1000; in particular, releasing the electric power from the pump when not used or switching into a low energy mode by lowering the pump flow when not full power needs to be made available, e.g. during straight-line 5 driving on the highway, thus avoiding unnecessary energy consumption.

Anchoring bushing system 84, further developed in the following figures comprises a pressure reservoir 840 in a compression zone P. A resilient system 85 external of bushing 84 is arranged to pressurize the pressure reservoir 840 so as to volumetrically relay any dynamic load vibrations in the pressure reservoir 840 to 10 the resilient system 85. A typical operating pressure of the hydraulic bushing embodiments of Figure 5 may be in the order of 200 bar. While the resilient system is depicted as an accumulator 85 known in the art, the resilient function may already be provided by compliance of the pressure lines 851 when the pressure supply terminal 1005 is shut from the fluid pump 1008. For multiple numbers of 15 hydraulically coupled active bushings 84 via a single pressure terminal, the elastomeric parts 846 can be designed to resist any undesirable fluid communication between pressure reservoirs 840 coupled in parallel. Indeed, for multiple coupled bushings 84, the elastomeric parts 846 form a spring in parallel to the encapsulated pressure reservoirs 840. Thus, the number of terminal 1005 may 20 be limited to one and the number of accumulators 85 may be limited to one or even zero when the compliance of the pressure lines 851 is properly designed. Once the bushing 84 is pressurized at the desired level the switching valve 1006 may be closed again and the power pack can be shut down, advantageously minimising the fuel consumption of the vehicle driveline which is caused by losses of auxiliaries.

25 Accordingly, in an active condition, the anchoring 84 may be switched off from the pressure circuit 1000.

It is noted that the compression zone P is located in a specified region relative to the centre and depends on the static load F on the bushing 84. In Figure 5 this is illustrated by the expansive force F exerted between shaft 845 and bushing wall 30 847. For example in the embodiment of Figure 4, for a bushing 84 anchored in anchoring bores 86 of the sway bar arms 82, in view of the static pull, the compression zone P 41 is arranged in a region of the elastomeric part 846 facing 8 away from the central carrier 101. Conversely, when a linkage is provided with a static push force, the compression zone P is arranged between shaft 845 and central carrier 101. When pressurizing the pressure reservoir 840, the elastomeric part 846 is compliant so that the shaft 845 is moved relative to the bushing wall 847 due to 5 expansion of the pressure reservoir 840. Accordingly, when subject to static load in anchored condition, due to the pressurized movement of the shaft relative to the bushing wall 847, a new working point with a reduced effective stiffness characteristic is provided allowing a movement path of the shaft when subject to dynamic loads.

10 This mechanism is graphically represented in Figure 6. Figure 6 demonstrates three radial spring characteristics of different bushing anchorage systems 84. These systems differ in design: the solid line corresponds to a conventional (passive) elastomeric bushing, the dotted line to an active pneumatic bushing according to the design of Figure 8 and the dash-dotted line corresponds to 15 an active hydraulic bushing according to designs of Figures 5 and 6. On the vertical axis the bearing force F is displayed and on the horizontal axis the compressed position x of shaft 845 relative the bushing wall 847 is displayed. The three curves intersect at location xo, Fo which depicts the actual working points of the individual anchorage systems when submitted to identical static loads. In this working point 20 different linearized stiffness coefficients ci, C2 and C3, being the tangent to the individual characteristics, can be recognized. Note that particularly the passive system (without pretension in unloaded condition) is strongly forced into its progression, resulting a very high effective stiffness (negative for comfort). Due to the higher achievable pressure of the hydraulic system a higher offset at the 25 vertical axis (= actively generated pretension) can be achieved and thus a lower effective stiffness. Depending on the application an appropriate design can be selected to optimally adjust the stiffness in the bushing working point for an ideal trade-off between ride comfort, packaging and anchorage stability (rigidity). Note that with the installed capacity of the external resilient system the effective 30 stiffness in the working point can be independently tuned from the pressure in the anchorage system. However, the lower the required stiffness, the more capacity and thus a larger accumulator is needed.

9

Figure 7 represents a system 2000 which is an alternative realization of the system according to Figure 5. In this application the active bushing system 84 is favorably added to the electro-hydraulic setup of an active steering system 2002 of an axle with steerable wheels. The steering configuration facilitates an actuator 5 1003 for adjustment of the positions of interconnected wheels using the in series connected pressure control valves 1009 and 1010 and an controllable pump 1008 as power source. The active bushing anchoring system 84 can simply be connected to this steering system using a controllable on/off valve 2006 (similar to the configuration of figure 5).

10 To accurately generate a correct pressure, a speed or flow control system may be provided (schematically illustrated as part of steering controller 1007) to control the pump flow. An electric motor driven pump 1008 enables, by speed of rotation feed back control, flow control in dependency of the actual vehicle state and required steering actuation performance. In the layout of Figure 7, pressure supply 15 terminal 2005 is coupled in parallel to first and second pressure control modules 1009, 1010 of an optional steering actuator 2002. In use, controller 1007 may control first and second pressure control modules 1009, 1010 to balance steering actuator 2002 while providing pressure to anchoring system 84. A pressure fluid controlled steering actuator 2002 is mechanically coupled to the steering 20 arrangements and comprises first and second actuator compartments 1002, 1003 hydraulically connected via respective first and second pressure supply terminals 1004, 1005.

The pressure supply terminals 1004, 1005 are connected via pressure control module 1009; the pressure control module 1009 is coupled in series with a second 25 pressure control module 1010 to control the pressure in the working compartments 1002, 1003 of the steering actuator 1001. The proportional valves 1009, 1010 are normally open. Furthermore oil reservoir 1011 is provided to buffer a certain amount of oil going in and out of the hydraulic assembly 1000; and a computer control system 1006 with sensors to accurately control the steering angles of the 30 wheel. In its simplest form this can be a sensor (not shown) to measure the position of the front wheels, acting as input for a control algorithm; and a sensor to measure 10 the angles of the wheels, e.g. linear measurement of actuator position, to be steered would suffice.

To change the (static) pressure in pressure reservoir of the anchoring system 84 the switching valve 2006 can be opened. Now the pressure in compartment 840 5 can be built up. To avoid simultaneous steering actions of steering actuator 2002, the pump pressure is generated with both valves activated simultaneously in proportion to the steering cylinder dimensions Al, A2. For the unique case that A2 = 2*A1 this means that the pressure drop which is generated by the first valve 1009 is equal to that of the second valve 1010, resulting in a situation where the 10 hydraulic forces acting on the piston 2023 compensate each other. Note that in this particular case the pressure in the piston sided compartment amounts half of the pump pressure and the rod sided piston is submitted to full pump pressure. Small deviations from this average point of equilibrium during lifting are allowed to enable a closed loop position control the steered wheels (feedback control using 15 information from the steering angle sensor).

Figure 8 shows an alternative embodiment of the active bushing anchoring system 84-A, including a pneumatic pressurizing system. Typical pressures and reaction forces (depending on busing dimensions) are a factor 10— 20 lower than the hydraulic system of Figures 5 and 6. An (optional) pressure vessel 85-A, pressurized 20 by a conventional pneumatic system 3000 including a pump 3001 and control means 3002, is provided connectable to the pressure reservoir 840 in the form of gas chamber. Note that the resilience of the enclosed gas medium (without the use pressure vessel 85-A might well be sufficient to design the desired effective spring stiffness.

25 Figure 9 shows a perspective view of an exemplary embodiment of the active bushing 84 previously referred. Figure 10A-A and B-B show schematic cross sectional views of the bushing along lines A-A and centerline B-B.

The bushing comprises a center shaft 845, an elastomeric coupling part 846 defining a pressure reservoir 840 in a compression zone P compressed due to a 30 static load and an outer bushing wall 847 arranged around the elastomeric part 846, wherein the pressure reservoir 840 is arranged to define a counter force to the static load. The center shaft 845 provides a practical realisation of the connection 11 between the encapsulated pressure reservoir 840 and the external resilient pressure control system. A recess 848 may be provided in a part away from the pressure reservoir 840 to comply with the expansion movement of the shaft 845 (relative to the bushing wall 847). These expansion movements are either caused by fore and 5 aft movements of the guiding arms 82 or actively generated pressure changes in the resilient system 85. The recess 848 may be formed as an open -air axial bore that is aligned with the bushing wall 847 and that is in direct communication with the ambient atmosphere. The recess increases the compliance of the region opposite the shaft, away from the pressure reservoir which might be relevant to decrease the 10 influence of the elastomeric material on the effective radial and torsional stiffness of the anchorage system.

In an embodiment the center shaft 845 is comprised with a fluid channel 8451 and having a channel exit 8452 in pressure reservoir 840. The elastomeric 15 part 846 may be vulcanized substantially around the shaft 845, so that a pressure reservoir 840 is asymmetrically formed relative to the shaft 845.

The axle assembly according to the invention may have exemplary embodiments in which one or more of the following features are present: a second pair of hubs are articulated to an ancillary axle to render a 20 second pair of wheels steerable; the second pair of wheels is adapted to be controlled by a supply of pressurised hydraulic fluid; the ancillary axle includes a steering linkage; the first pair of hubs on the main axle is arranged to be driven by a 25 motive force; the axle assembly is adapted for mounting to a rear portion of a vehicle structure; the axle assembly is adapted to be attached as a unit to a vehicle structure comprising a pair of opposite chassis rails, so as to act as a chassis cross 30 member; the ancillary axle is adapted to form a leading axle and the main axle is adapted to form a trailing axle; 12 the suspension means includes one of an active and a passive suspension element; the suspension means is a passive, resilient suspension element; the resilient suspension element includes a mechanical spring; 5 the resilient suspension element includes at least one second volumetric displacement device; the at least one second volumetric displacement device is a gas spring; a first pair of second volumetric displacement devices formed as gas springs is associated with the main axle and a second pair of second volumetric 10 displacement devices in the form of gas springs is associated with the ancillary axle; the suspension means is an active suspension element, which includes at least one second volumetric displacement device;

The pump- when not already protected by e.g. an internal pressure relief 15 valve - is preferably be protected against overpressure. Moreover, the pump should be provided with energy saving means, viz. by limiting the pump’s pressure to the requested pressure at each moment. Both, overpressure protection and energy saving can be realized by means of a pressure relief valve connected with the pump’s outlet and inlet (so in parallel with the pump 3) or with the pump’s outlet 20 side and the tank’s inlet side (so in parallel to the series connection of pump 3 and tank 4). Such a protecting pressure relief valve could be comprised by the pressure control module 8, or could be separate from it.

The pressure reservoir 840 may have reinforced walls, for example by a membrane of a fiber reinforced fabric that is enclosed in the elastomeric material.

25 Alternative to the disclosed fluid channel 8451 arranged in the shaft 845, a fluid connector may be arranged in the bushing wall.

It is thus believed that the operation and construction of the present invention will be apparent from the foregoing description. The skilled person will recognize that the invention is not limited to the embodiment represented and 30 described here, but that within the framework of the appended claims a large number of variants are possible. The disclosed anchoring concept may be applicable for any anchoring that is subject to static and dynamic loads. In particular, the 13 anchoring concept may be applied in other vehicle structures that have separate axles or suspension systems that directly couple to a vehicle chassis. Also, in addition to for-aft driving comfort, also lateral (relative to a vehicle length axis) dynamic vibrations may be compensated by the disclosed structures. The 5 description is deemed to encompass all variants combining features of the hereabove embodiments. Also kinematic inversions are considered inherently disclosed and to be within the scope of the present invention. The terms comprising and including when used in this description or the appended claims should not be construed in an exclusive or exhaustive sense but rather in an inclusive sense.

10 Expressions such as: "means for ...” should be read as: "component configured for ..." or "member constructed to ..." and should be construed to include equivalents for the structures disclosed. The use of expressions like: "critical", "preferred", "especially preferred" etc. is not intended to limit the invention. Features which are not specifically or explicitly described or claimed may be additionally included in 15 the structure according to the present invention without deviating from its scope.

Claims (16)

1. Suspension system for providing a mobile support to a vehicle structure relative to a road surface, comprising: guide arms that allow vertical movement of the axle, but prevent movement of the axle in a horizontal plane with respect to the vehicle structure; - an anchoring system that connects the guide arms to the vehicle structure; - the anchoring is formed by a bush with an elastomeric coupling part that couples at least one of the guide arms to the vehicle structure; -the coupling part defines a pressure reservoir in a pressure zone which is depressed as a result of a static wheel load; and a resilient system external to the bushing arranged to pressurize the pressure reservoir to volumetically transmit any dynamic load vibration in the pressure reservoir to the resilient system. The suspension system of claim 1, further comprising a shaft comprising a pair of hubs and a pair of wheels to be driven by a driving force. 20 The suspension system of claim 1, further comprising - a central carrier attached to the vehicle structure for providing an anchor for the guide arms; - a stabilizer for stabilizing a rolling movement of the vehicle structure relative to the road surface; and - a connection suitable for preventing axial movement of the shaft, while allowing lateral movement. The suspension system of claim 3, wherein the stabilizer is formed by a transverse anti-roll bar connected to the guide arms formed as flexible rocker bar arms. Suspension system according to claim 4, wherein the bush is anchored in anchoring holes in the rocker bar arms. Suspension system according to claim 3, wherein the connection is formed by a triangle. 10 Suspension system according to claim 3, wherein the stabilizer is formed by the connection in the form of a quadrangle. 8. Suspension system according to claim 1, wherein the resilient system is hydraulic or pneumatic. 9. Suspension system as claimed in claim 1, wherein the resilient system further comprises a pressure circuit which comprises a liquid pump, a liquid reservoir and a suitable pressure supply point which is connected to the pressure reservoir by pressure lines. 10. Suspension system according to claim 9, wherein the hydraulic fluid pump is electrically controlled for pressurizing the reservoir, and wherein in operation, the resilient system is formed by a reaction of the pressure lines closing off the pressure supply point from the fluid pump. The suspension system of claim 9, wherein the resilient system comprises an accumulator. The suspension system of claim 1, further comprising a trailer coupling adapted to be mounted by fasteners which also fix the central carrier on the vehicle structure. A method for suspending a vehicle structure relative to a road surface; which vehicle structure provides an anchor for the suspension system; wherein the anchoring is carried out by a bushing having an elastomeric coupling part that couples at least one of the guide arms 5 to the central carrier; which method comprises: - providing a suspension system comprising guide arms for conductively transmitting a wheel load to the vehicle structure; - providing in the coupling part a pressure reservoir in a pressure zone that is pressurized as a result of a static wheel load; 10. providing a resilient system external to the bus; and depressurizing the pressure reservoir to volumetically transmit any dynamic load vibration in the pressure reservoir to the resilient system. An anchoring system comprising an external resilient system and a sleeve, which sleeve is loaded with static load in an anchored condition, and comprising a centrally located shaft, an elastomeric coupling part that forms a pressure reservoir in a pressure zone and is pressurized by the static load and an outer sleeve disposed around the elastomeric part, the pressure reservoir being arranged to form a counterforce against the static load and coupled to the spring system to transmit dynamic loads in the pressure reservoir to the spring system. The anchoring system of claim 14, wherein the centrally located shaft is provided with a fluid channel coupled to the pressure reservoir and wherein the elastomeric portion is vulcanized substantially around the axis, so that a pressure reservoir is asymmetrically shaped with respect to the axis . The anchoring system of claim 14, wherein an open-air recessed recess is provided in the elastomer portion opposite the fluid reservoir, which recess is configured to follow a pressure reservoir expansion.