GB2566699A

GB2566699A - Active suspension device

Info

Publication number: GB2566699A
Application number: GB1715195.2A
Authority: GB
Inventors: Neilson Robert
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2017-09-20
Filing date: 2017-09-20
Publication date: 2019-03-27
Anticipated expiration: 2037-09-20
Also published as: GB201715195D0; GB2566699B; DE102018215138A1

Abstract

An active suspension device 17 for a vehicle suspension system is provided. The active suspension device comprises a hydraulic shock absorber 21 having a first cylinder 30 and a working piston 40 dividing the first cylinder 30 into separate fluid chambers 42, 44. The active suspension device further comprises a second cylinder 22, arranged concentrically about the first cylinder 30 to form an actuation chamber 24 therebetween. The actuation chamber 24 is divided into a first fluid chamber C1 and a second fluid chamber C2 by an annular actuator piston 26. The first cylinder 30 is movable with respect to the second cylinder 22 in response to a pressure difference between the first and second fluid chambers C1, C2 acting on the annular actuator piston 26. The pressure difference is compensated via first ans second fluid ports 71, 75. An active suspension assembly 14, a vehicle comprising the active suspension device and a method for manufacturing the active suspension device are also disclosed.

Description

Figure 3

ACTIVE SUSPENSION DEVICE

TECHNICAL FIELD

The present disclosure relates to an active suspension device. Particularly, but not exclusively, the disclosure relates to an active suspension device of a vehicle suspension. Aspects of the invention relate to an active suspension assembly and a vehicle comprising an active suspension device as well as a method of manufacturing the active suspension device.

BACKGROUND

Suspension systems on vehicles are known to improve the ride quality of the vehicle compared to a vehicle without any suspension. As such, suspension systems are provided to filter or isolate the vehicle body from vertical road surface irregularities as well as to control body and wheel motion. They are also used to maintain stability during manoeuvring of a vehicle.

Passive suspension vehicles are known, wherein the system reacts to driver induced inputs and/or road induced inputs. This classic system includes a spring and a damping device, which are arranged in parallel and located between the vehicle body and the drive axis/wheels. The damping devices are typically shock absorbers, which are used in conjunction with conventional springs to absorb unwanted vibration during driving. To absorb vibration, the shock absorber includes a piston located within a pressure cylinder, which is connected to the body of the automobile via a piston rod. The piston divides the pressure cylinder into two separate chambers and is able to restrict the flow of damping fluid between these two chambers when the piston/piston rod is displaced. By means of restricting the flow of damping fluid between the chambers, the actuator is able to produce a damping force which counteracts the aforementioned, unwanted vibrations.

A known disadvantage of conventional passive suspension systems is that the damping force created by the damping device is dependent on the impact force and thereby the flow of damping fluid within the working chambers of the cylinder.

In view of the above, more recent vehicle suspension systems include active suspension systems, capable of electronically controlling the suppression forces generated by hydraulic actuators. The hydraulic actuators are independently controllable of the position of and the 1 forces acting on the vehicle suspension. That is, while the hydraulic actuators will be actuated in response to changes in the position of and the forces acting on the vehicle suspension, the forces generated by the hydraulic actuator are not directly determined by said position of/force acting on the suspension; rather, the forces generated by the actuator can actively be set to any desired value via an electronic control unit. In active suspension systems, the hydraulic actuators are arranged in parallel with the aforementioned springs and shock absorbers of the passive suspension systems. It is a known problem of current active suspension systems that the additional hydraulic actuator results in more package space and support structures required.

It is an aim of the present invention to address the disadvantages associated with the prior art. In particular, it is an object of the present invention to provide a vehicle suspension device for an active suspension, which comprises a significantly reduced packaging size.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a vehicle suspension device, a vehicle comprising the vehicle suspension device and a method of manufacturing a vehicle suspension device as claimed in the appended claims.

According to an aspect of the invention, there is provided an active suspension device comprising a hydraulic shock absorber having a first cylinder and a working piston dividing the first cylinder into separate fluid chambers; a second cylinder, arranged concentrically about the first cylinder to form an actuation chamber therebetween, said actuation chamber being divided into a first fluid chamber and second fluid chamber by an annular actuator piston, wherein the first cylinder is movable with respect to the second cylinder in response to a pressure difference, between the first and second fluid chambers, acting on the annular actuator piston.

In simple terms, the hydraulic shock absorber and the active actuator of this active suspension device are constructed in an overlapping arrangement. Moreover, the housing structure, i.e. the first cylinder, of the hydraulic shock absorber is used as part of the actuation chamber. Accordingly, the active suspension device of the present invention exhibits a particularly compact arrangement and therefore is in line with ever decreasing availability of space within modern road vehicles.

In another embodiment of the present invention, the second cylinder comprises a first fluid port connected to the first fluid chamber and a second fluid port connected to the second fluid chamber. The first and second fluid ports may be constructed as bores extending through the wall of the second cylinder. The bores may be sized to receive hydraulic inlet/outlet connectors for supplying hydraulic fluids to or extracting hydraulic fluids from the first or second chambers.

In yet another embodiment, the first cylinder comprises a first open end and the second cylinder comprises a second open end, an opposite, third open end, and a cavity extending between the second and third open ends. In other words, the second cylinder is an open cylinder that can easily be put over an outside surface (or first cylinder) of a conventional shock absorber.

A first bearing element may be arranged between an inner surface of the second cylinder and an outer surface of the first cylinder, at the second open end of the second cylinder. Arranging the first bearing element at the second open end of the second cylinder also means that the first bearing element is located in such a way that the second open end of the second cylinder is arranged between the first bearing element and the annular actuator piston. The first bearing element will support relative movement of the first cylinder with respect to the second cylinder. In detail, the first bearing will support translatory and rotary movement of the first cylinder relative to the second cylinder.

In yet another embodiment, the first bearing element comprises a sealing member. According to this embodiment, the first bearing element not only facilitates movement of the first cylinder with respect to the second cylinder, but also defines a first end of the first fluid chamber of the actuation chamber. The second end, of course, will be defined by the annular actuator piston, as will be described below.

According to another embodiment, the third open end of the second cylinder, which is arranged opposite the second open end, has a larger diameter than the second open end. As such, the second cylinder may comprise a tapered transition portion arranged between the second and third open ends. Constructing the second cylinder with a third open end, which is larger than the second open, will simplify manufacture of the active suspension device according to the present invention.

In yet another embodiment, the second cylinder comprises a second fluid port connected to the second fluid chamber, wherein the second cylinder comprises a tapered transition portion arranged between the second fluid port and the third open end. The second fluid port will, therefore, be arranged between the transition portion and the annular actuator piston.

The active suspension device may comprise a third cylinder having a fourth open end arranged about the first open end of the first cylinder. The third cylinder may be part of a casing of the shock absorber, and thus may be connected to a piston rod of the shock absorber, as will be described herein below. The third cylinder may comprise a fourth open end and an opposite, second closed end, the fourth open end having a diameter substantially identical to a diameter of the second open end of the second cylinder. As such, the diameter of the fourth open end of the third cylinder is smaller than the diameter of the third open end of the second cylinder so that the third cylinder can be received within the third open end of the second cylinder. The transition portion of the second cylinder can then be used as a stop shoulder for the fourth open end of the third cylinder.

In yet another embodiment, a second bearing element is arranged between an inner surface of the third cylinder and the outer surface of the first cylinder at the fourth open end of the third cylinder. It will be appreciated that the second bearing element has to be arranged in a part of the third cylinder, which overlaps with the first cylinder of the shock absorber. Similar to the first bearing element, the second bearing element allows for the first cylinder to perform translatory and rotary movements with respect to the third and second cylinders.

The second bearing element may further comprise a sealing member. The second bearing element may, therefore, also define a first end of the second fluid chamber. The second end of the fluid chamber is then defined by the annular actuator piston. It will be appreciated that the second fluid opening of the second chamber is then arranged between the second bearing element and the annular actuator piston.

As mentioned hereinbefore, the fourth open end of the third cylinder may be received within the third open end of the second cylinder. In this case, the transition portion of the second cylinder may be arranged as a stop surface (or shoulder) for engaging the fourth open end of the third cylinder.

According to yet another embodiment, the hydraulic shock absorber is an inverted-type shock absorber. The hydraulic shock absorber may be a mono-tube shock absorber. 4

Alternatively, it may also be feasible to construct the hydraulic shock absorber as a twin-tube shock absorber.

In yet another embodiment, the actuator piston is attached to an outer surface of the first cylinder and arranged to be moveable together with the first cylinder, relative to the second cylinder, or wherein the actuator piston is attached to an inner surface of the second cylinder and arranged to be moveable together with the second cylinder, relative to the first cylinder.

According to another aspect of the present invention, there is provided an active suspension assembly comprising an active suspension device as described hereinbefore and a spring arranged in parallel with the active suspension device. The spring may be attached at a first closed end of the first cylinder. Arranging a spring at the first closed end of the first cylinder is particularly useful for vehicle suspension devices that are located at the front end of the vehicle.

According to yet another aspect of the present invention, there is provided a vehicle comprising the active suspension device/assembly described hereinbefore arranged between a vehicle wheel and a vehicle body. In fact, the vehicle may comprise four of the aforementioned active suspension devices/assemblies, one for each wheel of the vehicle. The active suspension devices/assemblies are then part of an active suspension system, controlled by a central control unit of the vehicle.

The vehicle may comprise multiple vehicle wheels and one of said active suspension device or assemblies for each vehicle wheel, wherein the vehicle suspension devices are individually controllable by means of a central control unit.

In another aspect of the present invention, there is provided a method of manufacturing an active suspension device comprising providing a hydraulic shock absorber having a first cylinder;

attaching an actuator piston to an outer surface of the first cylinder;

arranging a second cylinder concentrically about the first cylinder such that an actuator space is formed between the first and second cylinder and that the actuator space is divided into first and second fluid chamber by the actuator piston, said first cylinder and actuator piston being moveable together, relative to the second cylinder.

In another embodiment, the method may include steps for providing a third cylinder, attaching a bearing element to an inner surface of the third cylinder, inserting the third cylinder into the annular space between the first and second cylinder such that the bearing element is in contact with an outer surface of the first cylinder.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic perspective view of a vehicle according to the present invention;

Figure 2 is a schematic circuit diagram of an active suspension assembly according to an embodiment of the present invention; and

Figure 3 shows a schematic cross section of an embodiment of the active suspension device according to the present invention.

DETAILED DESCRIPTION

Turning to Figure 1, there is shown a vehicle 10 having ground engaging structure, in this case in the form of four wheels 12. An active suspension assembly 14 is arranged between each wheel 12 and a body 16 of the vehicle 10. The vehicle, therefore, defines a sprung mass which includes a vehicle body 16 and further components which will be described below and an un-sprung mass which includes wheels 12 and further components which will be described below. Each of the four wheels 12 is connected to the body 16 by an individual 6 active suspension assembly 14. However, each active suspension assembly 14 is connected to a control unit 15 as indicated in Figure 1. The control unit 15 centrally controls each of the active suspension assemblies 14 so as to stabilise the vehicle body 16 during the entire journey. For example, if the vehicle 10 turns into a sharp left turn, the active suspension assemblies 14 on the right of the vehicle 10 may both be used to simultaneously produce an extension force via a control signal from a control unit 15. At the same time, the active suspension assemblies on the left of the vehicle (not shown in Figure 1) may be used to simultaneously produce a compression force to help the vehicle body 16 lean towards the bend.

Each active suspension assembly 14 includes an active suspension device 17 shown in Figure 2, for example. Each active suspension device 17 has an actuator 18, specifically a hydraulic actuator, and a damper/shock absorber 21. The damper/shock absorber 21 may be of any type, such as twin-tube or mono-tube types or upright/inverted shock absorbers. It will also be appreciated from the embodiment in Figure 2 that the actuator 18 and the damper 21 act in parallel.

The active suspension assembly 14 of this particular embodiment also includes a spring 20. In some embodiments of the invention, the active suspension system may not include a spring 20. The spring 20 can be any type of spring, for example a helical spring or an airspring. As will be appreciated from Figure 2, the actuator 18 and damper/shock absorber 21 of the active suspension device 17 and the spring 20 act in parallel.

At a first end, the active suspension assembly 14 comprises a first connector 12a for securing the active suspension assembly to the un-sprung mass, including a corresponding wheel 12 of the vehicle. At an opposite, second end, the active suspension assembly 14 comprises a second connector 16a for securing the active suspension assembly 14 to the sprung mass, including a vehicle body 16. The actuator 18, the damper/shock absorber 21 and the spring 20 are arranged in parallel between the first and second connectors 12a, 16a.

Turning now to Figure 3, there is shown a schematic cross-section of an active suspension device 17 according to an embodiment of the present invention. In particular, the active suspension device 17 of Figure 3 is an active vehicle suspension device. The active suspension device 17 comprises a hydraulic shock absorber 21 and a hydraulic actuator 18. The shock absorber 21 and the hydraulic actuator 18 are arranged in parallel, as described hereinbefore with reference to Figure 2.

The hydraulic shock absorber 21 is an inverted mono-type shock absorber. The shock absorber 21 comprises a first cylinder 30 which has a first closed end 32 and an opposite, first open end 34. A floating piston 36 is arranged in the vicinity of the first closed end 32 and defines an air chamber 38 therebetween. On the other side of the floating piston 36, there is provided a working piston 40. The working piston 40 divides the remaining, inner volume of the cylinder 30 into a first fluid chamber 42 and a second fluid chamber 44. The first fluid chamber 42 is arranged between the floating piston 36 and the working piston 40. The second fluid chamber 44 is located between the working piston 40 and the first open end 34 of the cylinder 30. A piston rod 46 extends from the working piston 40 towards and through the first open end 34 of the cylinder 30. A plug 48 surrounds the piston rod 46 at the first open end 34 of the first cylinder 30 and sealingly closes the second chamber 44.

The end of the piston rod 46 that extends out of the first cylinder 30 is connected to the unsprung mass. The piston rod 46 may be connected to any suspension component including a steering knuckle or lower control arm (not shown). At the opposite, first closed end 32, the first cylinder 30 is connected to the sprung mass which may be directly to the vehicle body 16.

It will be understood that the working piston 40 comprises one or more piston valves, acting as a throttle between the first and second fluid chambers 42 and 44. If a force acts to compress the shock absorber 21, the pressure in fluid chamber 42 increases, resulting in a force acting on the floating piston 36. The floating piston 36, in turn, compresses the air in air chamber 38 and consequently moves towards the first closed end 32 of the first cylinder 30.

Since the pressure in the first chamber 42 is now higher than the pressure in the second chamber 44, hydraulic oil in the first chamber will start flowing towards the second chamber 44 via the piston valves (not shown), thereby creating a damping action.

A second cylinder 22 is arranged concentrically about the first cylinder 30. The second cylinder 22 is arranged between the first closed end 32 and the first open end 34 of the first cylinder. As such, the entire length of the second cylinder 22 overlaps the first cylinder 30. With the second cylinder 22 being arranged concentrically about the first cylinder 30, an actuation chamber 24 is created therebetween. The actuation chamber 24 is divided into a first fluid chamber C1 and a second fluid chamber C2 by an annular actuator piston 26. The first cylinder 30, the second cylinder 22 and the actuator piston 26 together form a housing 8 structure of the hydraulic actuator 18. The cylinder 22 is an open cylinder and so comprises a second open end 27 and an opposite third open end 28. The second open end 27 of the second cylinder 22 faces the first closed end 32 of the first cylinder 30. The third open end 28 of the second cylinder 22 faces the first open end 34 of the first cylinder 30. A cavity extending between the second open end 27 and the third open end 28 defines a space forming the actuation chamber 24.

A first bearing element 51 is arranged along the second open end 27 of the second cylinder 22. The first bearing element 51 is adapted to allow translatory and rotary movement of the first cylinder 30 with respect to the second cylinder 22. To this end, the first bearing element 51 can be constructed in any form that will allow for said movement.

In a second function, the first bearing element 51 also provides a fluid seal between the first cylinder 30 and the second cylinder 22 along the second open end of the second cylinder 22. As such, the first fluid chamber C1 extends between the first bearing/sealing element 51 and the annular actuator piston 26.

A third cylinder 60 is arranged about the first open end 34 of the first cylinder 30. The third cylinder 60 has a fourth open end 62 and an opposite, second closed end 64. As can be seen from Figure 3, the third cylinder 60 overlaps the first open end 34 of the first cylinder 30 along the fourth open end 62.

The third cylinder 60 is received within the third open end 28 of the second cylinder 22. To this end, the third open end 28 of the second cylinder 22 has a larger diameter than the second open end 27. Consequently, the second cylinder 22 comprises a tapered transition portion 25 located between the second open end 27 and the third open end 28 of the second cylinder 22. The transition portion 25 acts as a stop shoulder for the fourth open end 62 of the third cylinder 60. As can be derived from Figure 3, the diameter of the third cylinder 60 is substantially the same as the diameter of the second cylinder 22 along the second open end 27. The diameter of the third open end 28 of the second cylinder 22 is slightly larger than the diameter of the third cylinder 60 and adapted to receive the fourth open end 62 of the latter. As such, the widened, third open end 28 of the second cylinder 22 overlaps the fourth open end 62 of the third cylinder 60 and the overlapping parts are joined together by any means that provide a fluid tight seal between the outer surface of the third cylinder 60 and the inner surface of the second cylinder 22, such as welding or gluing.

A second bearing element 53 is arranged between the inner surface of the third cylinder 60 and the outer surface of the first cylinder 30 along the overlapping section between the first and third cylinders 30, 60. Similar to the first bearing element 51, the second bearing element 53 allows for translatory and rotary movement of the first cylinder 30 with respect to the third cylinder 60. At the same time, the second bearing element 53 also acts as a sealing element, which defines one end of the second fluid chamber C2. The second fluid chamber C2, therefore, extends between the first bearing element 53 and the annular actuator piston 26.

A first fluid port 71 is connected to the second cylinder 22. The first fluid port 71 connects a hydraulic fluid supply with the first fluid chamber C1. A second fluid port 75 is connected to the second cylinder 22. The second fluid port 75 connects a hydraulic fluid supply to the second fluid chamber C2.

In operation, the hydraulic actuator 18 is an active part and, therefore, controlled by an electronic control unit 15. Depending on determined or predicted compression/extraction forces, the control unit 15 will regulate the hydraulic fluid supply for fluid chambers C1 and C2.

In a first example, the wheel 12 (shown in Figure 2) is a front left wheel. The vehicle is being driven along a straight, generally smooth road. The front left of the vehicle is being supported entirely by its spring 20 and shock absorber 21, and as such actuator 18 is not creating any force, i.e. it does not create an extension force nor does it create a contraction force. In these circumstances, the first and second fluid chambers C1 and C2 will not be provided with pressurised hydraulic fluid. Rather, the road vibrations are compensated by the spring 20 and the shock absorber 21.

The driver then creates a driver induced input, by turning the steering wheel clockwise, which causes the vehicle to turn to the right, which in turn will tend to cause the vehicle to roll to the left. In order to prevent, minimise or control roll to the left, the active suspension device 17 causes the second fluid chamber C2 to be pressurised to a target pressure, which causes an extension force to be generated by the actuator 18, thereby reducing leftward roll. The target pressure is determined by the electronic control unit 15 and dependent on a variety of factors, such as the vehicle weight, vehicle speed, road conditions, radius of the bend, etc. The electronic control unit 15 will cause the hydraulic fluid supply to increase the pressure in chamber C2, which will result in a force acting on the annular actuator piston 26, 10 forcing the actuator piston 26 towards the first chamber C1. On the opposite side of chamber C2, the pressurised hydraulic fluid acts against the second bearing element 53, thereby pushing the latter in a downwards direction, that is, away from the annular actuator piston 26.

In the example of Figure 3, the annular actuator piston 26 is rigidly connected to the outer surface of the first cylinder 30, whereas the first and second bearing elements 51, 53 are connected to the inner surface of the second or third cylinders 22, 60 respectively. As such, the force created by the pressurised hydraulic fluid in chamber C2 acts to push the first cylinder upwards via the annular actuator piston 26. At the same time, the pressurised fluid in chamber C2 pushes the second and third cylinders 22, 60 downwards relative to the first cylinder 30 via the force applied to the second bearing element 53. As a result an expansion force is created by the hydraulic actuator 18 of the active suspension device 17, which acts against the roll momentum created by the vehicle when negotiating the turn.

It will be understood that the annular actuator piston 26 does not necessarily have to be rigidly connected to the outer surface of the first cylinder 30. Alternatively, it is also feasible to rigidly attach the annular actuator piston 26 to the inner surface of the second cylinder 22. In this case, however, the first and second bearing elements 51, 53 would have to be rigidly connected to the outer surface of the first cylinder 30 in order to create a compression or extension force. It should also be noted that, in this scenario, an extension force would be created by supplying pressurised fluid to chamber C1 rather than C2. A compression force would be created if chamber C2 is pressurised.

Returning to the arrangement of the annular actuator piston 26 and the first and second bearing elements 51,53 shown in Figure 3, a compression force is created by pressurising the first fluid chamber C1.

In a second example, if the wheel 12 in Figure 2 is still a front left wheel and the operator rotates the steering wheel in an anti-clockwise direction, the car will turn left. As a consequence of the vehicle 10 negotiating a left-hand turn, a roll momentum towards the right-hand side of the vehicle will result in a compression of the right sided vehicle suspension and an extension of the suspension devices on the left-hand side of the vehicle. In order to counteract the extension forces on the left-hand side, the suspension device 14 shown in Figure 2 may utilise the hydraulic actuator 18 to produce a compression force to stabilise the vehicle.

If the electronic control unit 15 of the vehicle determines or predicts that the aforesaid compression force is required to stabilise the vehicle, it will regulate a hydraulic fluid supply to supply the first fluid chamber C1 with pressurised fluid. As the pressure increases in the first fluid chamber C1, a pressure differential builds up between the first and second fluid chambers C1 and C2. As a result of this pressure differential, a net force will act on the annular actuator piston 26, pushing the latter downwards in Figure 3. At the same time, the pressurised fluid within the first fluid chamber C1 acts on the first bearing element 51, pushing the latter upwards in Figure 3. Since the annular actuator piston 26 is rigidly connected to the outer surface of the first cylinder 30, the force created by the fluid within chamber C1 will also act to introduce a compression force (downwards force in Figure 3) on the first cylinder 30. The force acting on the first bearing element 51, in turn, will be transferred to the second and third cylinders 22 and 60 and create an upwards momentum in Figure 3. This compression force acts against the extension force introduced by the roll momentum when negotiating the corner.

The skilled person will understand that the use of the hydraulic actuator 18 of the active suspension device 17 may not only be used to counteract driver induced forces. Rather, the hydraulic actuator 18 can also be used to compensate for road induced forces, such as loads created by road holes or road bumps. For example during a straight journey or when negotiation a corner, if the vehicle encounters a road hole, the hydraulic actuator 18 may be used to generate an extension force as described hereinbefore. Otherwise, if the vehicle encounters a road bump, the hydraulic actuator 18 may be used to generate a compression force as mentioned above.

Claims

1. An active suspension device comprising:

a hydraulic shock absorber having a first cylinder and a working piston dividing the first cylinder into separate fluid chambers;

a second cylinder, arranged concentrically about the first cylinder to form an actuation chamber therebetween, said actuation chamber being divided into a first fluid chamber and a second fluid chamber by an annular actuator piston, and wherein the first cylinder is movable with respect to the second cylinder in response to a pressure difference, between the first and second fluid chambers, acting on the annular actuator piston.

2. The active suspension device of claim 1, wherein the second cylinder comprises a first fluid port connected to the first fluid chamber and a second fluid port connected to the second fluid chamber.

3. The active suspension device of claim 1 or 2, wherein the first cylinder comprises a first open end and the second cylinder comprises a second open end, an opposite, third open end, and a cavity extending between the second and third open ends.

4. The active suspension device of claim 3, wherein a first bearing element is arranged between an inner surface of the second cylinder and an outer surface of the first cylinder, at the second open end of the second cylinder.

5. The active suspension device of claim 4, wherein the first bearing element comprises a sealing member.

6. The active suspension device of any claims 3 to 5, wherein the third open end of the second cylinder has a larger diameter than the second open end.

7. The active suspension device of any of claims 3 to 6, wherein the second cylinder comprises a second fluid port connected to the second fluid chamber, and wherein the second cylinder comprises a tapered transition portion arranged between the second fluid port and the third open end.

8. The active suspension device of any of claims 1 to 7, wherein the active suspension device comprises a third cylinder having a fourth open end arranged about a first open end of the first cylinder.

9. The active suspension device of claim 8 when dependent on claim 3, wherein the third cylinder comprises the fourth open end and an opposite, second closed end, the fourth open end having a diameter substantially identical to a diameter of the second open end of the second cylinder.

10. The active suspension device of claim 9, wherein a second bearing element is arranged between an inner surface of the third cylinder and the outer surface of the first cylinder at the first end of the third cylinder.

11. The active suspension device of claim 10, wherein the second bearing element comprises a sealing member.

12. The active suspension device of any of claims 9 to 11, wherein the fourth open end of the third cylinder is received within the third open end of the second cylinder.

13. The active suspension device of claim any of claims 9 to 12 when dependent on claim 7, wherein the transition portion of the second cylinder is arranged as a stop surface for engaging the fourth open end of the third cylinder.

14. The active suspension device of any of claims 1 to 13, wherein the hydraulic shock absorber is an inverted-type shock absorber.

15. The active suspension device of any of claims 1 to 14, wherein the hydraulic shock absorber is a mono-tube shock absorber.

16. The active suspension device of any of claims 1 to 15, wherein the actuator piston is attached to an outer surface of the first cylinder and arranged to be moveable together with the first cylinder, relative to the second cylinder, or wherein the actuator piston is attached to an inner surface of the second cylinder and arranged to be moveable together with the second cylinder, relative to the first cylinder.

17. A vehicle suspension assembly comprising an active suspension device of any of claims 1 to 16 and a spring arranged in parallel with the active suspension device.

18. A vehicle comprising the active suspension device of any of claims 1 to 16 or the vehicle

5 suspension assembly of claim 17 arranged between a vehicle wheel and a vehicle body.

19. The vehicle of claim 18, wherein the vehicle comprises multiple vehicle wheels and one of said active suspension devices for each vehicle wheel, wherein the active suspension devices are individually controllable by means of a central control unit.

20. A method of manufacturing an active suspension device, comprising:

providing a hydraulic shock absorber having a first cylinder;

attaching an actuator piston to an outer surface of the first cylinder;

arranging a second cylinder concentrically about the first cylinder such that an

15 actuator space is formed between the first and second cylinder and that the actuator space is divided into first and second fluid chambers by the actuator piston, said first cylinder and actuator piston being moveable together, relative to the second cylinder.

21. The method of claim 20, including steps for providing a third cylinder; attaching a

20 bearing element to an inner surface of the third cylinder; and inserting the third cylinder into the annular space between the first and second cylinder such that the bearing element is in contact with an outer surface of the first cylinder.