TECHNICAL FIELD

The present disclosure relates to a bump stop arrangement for a vehicle. The present disclosure also relates to a vehicle comprising such a bump stop arrangement.

The invention can be applied in heavy-duty vehicles, such as trucks, buses and construction equipment. Although the invention will be described with respect to a truck, the invention is not restricted to this particular vehicle, but may also be used in other vehicles such as cars.

BACKGROUND

In suspensions, bump stops are used to limit the peak loads on spring elements. Bump stops may, for instance, be installed in connection to leaf spring suspensions as well as air suspensions. The bump stop protects the suspension and the vehicle from violent bottoming of the suspension, i.e. when the suspension runs out of upward travel without fully absorbing the energy of the stroke. The bump stop may be regarded as a cushion which absorbs the forces when engaged by the suspension. A problem with today’s solutions is that they lead to a compromise between spring travel, comfort and overload protection. The bump stop needs to be engaged early enough to prevent the suspension from being overloaded, but this can instead lead to a too early engagement which causes comfort problem and limits the levelling stroke.

SUMMARY

An object of the invention is to provide a bump stop arrangement which at least partly mitigates the drawbacks mentioned above. The object is achieved by a bump stop arrangement according to claim 1.

Thus, according to a first aspect of the general inventive concept, there is provided a bump stop arrangement for a vehicle, comprising: - a chamber containing a hydraulic fluid,

- a plunger movable within the chamber, wherein the plunger defines a proximal chamber portion provided on a proximal side of the plunger and a distal chamber portion provided on a distal side of the plunger, wherein movements of the plunger change the volumes of the proximal and distal chamber portions,

- a spring member biased to exert a proximally directed force to the plunger,

- a bump stop member provided proximally and externally of the chamber and being operatively connected to the plunger so as to follow the movements of the plunger, wherein the bump stop member is configured to operatively engage with a suspension of the vehicle for transferring forces from the suspension,

- a fluid transfer arrangement enabling fluid to be transferred from the proximal chamber portion to the distal chamber portion, and vice versa.

By the provision of a bump stop arrangement which comprises a bump stop member which is operatively connected to the plunger as indicated above, an arrangement is achieved which can engage the suspension early enough to avoid the suspension from being overloaded, and still provide comfort and satisfactory spring travel.

It should be understood that in this disclosure the terms proximal and distal are related to the intended installation of the bump stop arrangement on a vehicle. The bump stop arrangement is intended to be located distally of the suspension with which it is intended to engage. Thus, the bump stop member will always be located proximally of the spring member. In practice, when the bump stop arrangement is mounted to a vehicle, the proximal direction will normally correspond to a downwards direction, while the distal direction will normally correspond to an upwards direction. When the bump stop arrangement changes from an expanded state to a contracted state, then the bump stop member moves distally relative to the chamber. Conversely, when the bump stop arrangement changes from a contracted state to an expanded state, then the bump stop member moves proximally relative to the chamber.

The fluid provided in the chamber may be a Newtonian fluid such as any suitable hydraulic fluid, typically oil.

According to at least some exemplary embodiments, the spring member is provided in the distal chamber portion. In such cases, the spring member will be configured to push the plunger in the proximal direction. Conversely, when a force is transferred from the suspension via the bump stop member, there will be a distally directed force to the spring member. If that distally directed force is high enough it may urge the spring member into its fully compressed state, i.e. reaching its maximum elastic potential energy within the chamber portion in which it is arranged. According to at least some exemplary embodiments, the spring member is provided in the proximal chamber portion. In such cases, the spring member will be configured to pull the plunger in the proximal direction. In such cases, the maximum elastic potential energy of the spring member will be reached in its fully stretched state.

According to at least one exemplary embodiment, when the bump stop member is subjected to a distally directed force which exceeds the proximally directed force exerted by the spring member to the plunger, and fluid is allowed to flow between the chamber portions through the fluid transfer arrangement, then the bump stop arrangement will have a damper function in which the distally directed movement of the bump stop member is dampened by the spring member. By allowing the fluid to move between the chamber portions, even though the suspension may engages the bump stop member at an early stage, the suspension can continue its travel in a dampened manner. Thus, overloading of the suspension may be avoided, without compromising driver comfort. The maximum travel of the suspension is to a state in which the spring member is fully compressed. However, in at least some exemplary embodiments the travel of the fluid transfer arrangement may be controllable, such that fluid flow between the proximal chamber and the distal chamber becomes restricted or prevented. When the fluid flow is prevented, then the plunger is prevented from moving further in the distal direction. Thus, the travel of the plunger (and thus of the suspension) may be set to be shorter than to said state the spring member is fully compressed. This is at least partly reflected in some of the following exemplary embodiments.

According to at least one exemplary embodiment, when the bump stop member is subjected to a distally directed force, and fluid is prevented from flowing between the chamber portions through the fluid transfer arrangement or the spring member has reached a fully compressed state (if provided in the distal chamber portion) or a fully stretched state (if provided in the proximal chamber portion), then the bump stop arrangement will have a bump stop function in which the bump stop member acts as a cushion. Thus, at the bottoming of the suspension (be it in a fully compressed state of the spring member or at an intermediate state when the plunger cannot move further distally because of the fluid path between the proximal and distal chambers is closed) the bump stop member may provide a normal bump stop function. Suitably, the bump stop member comprises a rubber portion which provides the cushioning effect. The rubber portion may be attached to a supporting portion of the bump stop member. Such a supporting portion may, for instance, be metallic, such as a steel or aluminium body. In case of the bump stop member having a rubber portion and a supporting portion, it will be the rubber portion that comes into contact with the suspension. According to at least one exemplary embodiment, the fluid transfer arrangement has a closed state in which no fluid is allowed to pass between the proximal and distal chamber portions, and at least one open state in which fluid is allowed to pass between the proximal and distal chamber portions. By being able to close the fluid transfer arrangement it is thus possible to limit the stroke of the plunger, and accordingly the travel of the suspension. In some situations it may be desirable to have a short travel of the suspension, i.e. a small bump stop height, which means that there is a small damping before the cushioning bump function is reached. In other situations it may be desirable to allow a longer travel of the suspension, i.e. a large bump stop height, which means that there is a larger damping before the cushioning bump function is reached. For instance, it is generally desirable to avoid that the cab dips during braking (i.e. it is desirable to have an anti-dive function). Therefore, when braking it may be suitable to have a relatively short allowable travel of the suspension in order to more quickly increase vertical force and thereby the possible longitudinal brake force. This also serves to protect the suspension during the brake event which may otherwise cause high stresses. The trade-off between comfort (low stiffness in general) and maximum brake force can be improved by the variability to the bump stop arrangement. For instance, when driving over bumps, comfort is desired and then a longer bump stop height may suitably be set.

According to at least one exemplary embodiment, the fluid transfer arrangement comprises a controllable valve, having a closed position and at least one open position. A valve provides a convenient and efficient way to switch between an open and closed state of the fluid transfer arrangement. The valve may, in at least some exemplary embodiments, be an on/off valve, having only two positions, either open or closed. However, in other exemplary embodiments, it may be provided with different sizes of orifices and/or passages, such that different degrees of openness may be selected. Thus, in some exemplary embodiments, the degree of openness may be set in a stepwise manner. In some exemplary embodiments, the degree of openness may be set in a continuous, i.e. stepless, manner.

According to at least one exemplary embodiment, the fluid transfer arrangement comprises a passage through the plunger, wherein the valve is provided in the passage in the plunger. An advantage of a such an integrated valve, is that it provides a compact fluid transfer arrangement without the need for additional conduits for passing the fluid between the proximal chamber and the distal chamber.

According to at least one exemplary embodiment, the fluid transfer arrangement comprises a flow passage, such as a pipe or tube, which extends at least partly outside the chamber, wherein the valve is located in said flow passage. An advantage of having such an external passage is that providing wiring for control of the valve may be facilitated. Furthermore, the valve may be more accessible for maintenance/service.

According to at least one exemplary embodiment, the bump stop arrangement comprises a control unit which is configured to control the state of the fluid transfer arrangement.

This is advantageous as the control unit may, suitably, adapt the state based on, for example, the current driving condition/situation. By providing a control unit which can open and close the fluid transfer arrangement, the effective bump stop height may be set, i.e. the length of travel of the suspension before the plunger stops moving and continued distally directed forces from the suspension are absorbed by the bump stop member.

Thus, according to at least one exemplary embodiment, the control unit is configured to set a bump stop height at which the plunger remains stationary in the chamber and the bump stop member will act as a cushion when subjected to a distally directed force. As explained above, adapting the bump stop height to different situations may be advantageous, such as the previous mentioned examples of anti-dive functionality or the ride comfort when driving over a bump.

According to at least one exemplary embodiment, the control unit is configured to set said bump stop height by controlling the duration that the fluid transfer arrangement is in the open state and switching it to the closed state. The control unit may, suitably, depending on the current situation, determine an appropriate bump stop height. The bump stop height may suitable be based on available parameters (such as distally directed force, openness degree, vehicle speed, etc.) and the control unit may based on such parameters calculate (or access a lookup table to determine) the amount of time it takes for the plunger and/or bump stop member to reach the desired position, i.e. the amount of time before the control unit switches the fluid transfer arrangement to the closed state. It should be understood that, of course, other alternative ways of setting the bump stop height are also conceivably. For instance, the control unit may receive position signals from a position sensor operatively connected to the plunger, thus receiving information about the current position of the plunger and thereby being able to determine when to close the fluid transfer arrangement.

According to at least one exemplary embodiment, the control unit is configured to receive an input signal, such as a brake signal or a load signal, wherein the control unit is configured to set said bump stop height based on said input signal. Advantageously, the above-mentioned anti-dive situation may suitably be handled based on at least a brake signal. When driving over bump, a load signal may suitably be used by the control unit for appropriate setting of the bump stop height. Other input signals, such as vehicle speed signals may also be used by the control unit for determining an appropriate bump stop height.

From the above it can be understood that the control unit may be configured to set a bump stop height, which is different from the state in which the spring member has reached its maximum elastic potential energy (i.e. fully compressed if provided in the distal chamber portion or fully stretched if provided in the proximal chamber portion). The control unit may suitably set any such different bump stop height, including the fully expanded state of the bump stop arrangement. In the fully expanded state of the bump stop arrangement, when the suspension engages the bump stop member, the latter will immediately start absorbing the distally directed forces from the suspension, without first moving distally relative to the chamber.

The control unit may include a microprocessor, microcontroller, programmable digital signal processor or another programmable device. The control unit may also, or instead, include an application specific integrated circuit, a programmable gate array or programmable array logic, a programmable logic device, or a digital signal processor. Where it includes a programmable device such as the microprocessor, microcontroller or programmable digital signal processor mentioned above, the processor may further include computer executable code that controls operation of the programmable device.

According to at least one exemplary embodiment, the fluid transfer arrangement is configured to gradually increase its openness as the plunger moves in the distal direction and to gradually decrease its openness as the plunger moves in the proximal direction. This is advantageous as this may be provided as a passive control of the opening (in contrast to an active control in which a control unit controls a valve). Such passive control may, for instance, be achieved by allowing the plunger to follow a helical path in the chamber wall. For instance, the chamber wall may be provided with a helical groove which guides a protrusion of the plunger (or a helical ridge which guides a recess in the plunger). In some exemplary embodiments, the fluid transfer arrangement may closed similarly to a camera lens shutter or the like. In embodiments having this kind of passive control, the plunger may suitably move freely between a fully expanded stated of the bump stop arrangement and a contracted state at which the spring member is fully energized. Thus, in these embodiments, having a control unit for setting an intermediate bump stop height may be omitted.

According to a second aspect of the general inventive concept, there is provided a vehicle comprising a bump stop arrangement according to the first aspect, including any embodiment thereof. The advantages of the vehicle of the second aspect largely correspond to the advantages of the bump stop arrangement of the first aspect, including any embodiment thereof. Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realizes that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.

In the drawings:

Fig. 1 illustrates a vehicle in which a bump stop arrangement according to at least one exemplary embodiment may be implemented.

Fig. 2 illustrates schematically a bump stop arrangement according to at least one exemplary embodiment.

Figs. 3a and 3b illustrates different states of the bump stop arrangement of Fig. 2.

Fig. 4 schematically a bump stop arrangement comprising a valve, in accordance with at least one exemplary embodiment.

Fig. 5 schematically illustrates an exemplary configuration of a valve and some different states of the valve.

Fig. 6 schematically illustrates a bump stop arrangement according to at least another exemplary embodiment. Fig. 7 schematically illustrates a bump stop arrangement according to yet another exemplary embodiment. DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain aspects of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments and aspects set forth herein; rather, the embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Accordingly, it is to be understood that the present invention is not limited to the embodiments described herein and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims. Like reference numerals refer to like elements throughout the description.

Fig. 1 illustrates a vehicle 1 in which a bump stop arrangement according to at least one exemplary embodiment may be implemented. Although the vehicle 1 is illustrated in the form of a truck, other types of vehicles, such as busses, construction equipment, trailers or passenger cars may be provided in accordance with the invention.

The truck (vehicle 1) comprises a cab 2 in which a driver may operate the vehicle 1. The vehicle comprises a number of road wheels 4, herein illustrated as two pairs of wheels, however, in other embodiments there may be a different number of wheels, such as three pairs, four pairs or more. The vehicle 1 may comprise various structural elements, such as suspensions, for smooth driving. At least some of the suspensions may be installed to be engageable with bump stop arrangements in accordance with the present disclosure. For instance, the bump stop arrangement may be as schematically exemplified in the remaining drawing figures and as discussed in connection therewith. Although Fig. 1 may illustrate a human-operated vehicle 1, in other exemplary embodiments, the vehicle 1 in Fig. 1 may represent an autonomous vehicle.

Fig. 2 illustrates schematically a bump stop arrangement 10 according to at least one exemplary embodiment. Fig. 2 illustrates a cross-sectional view, wherein the interior of the bump stop arrangement 10 is visible. The bump stop arrangement 10 comprises a chamber 12 containing a hydraulic fluid. The hydraulic fluid may suitably be an oil of the type generally used in dampers and similar devices. The chamber 12 may suitably form a substantially cylindrical space, although the general inventive concept is not limited to that particular shape.

The bump stop arrangement 10 comprises a plunger 14 which is movable within the chamber 12. More specifically, it is movable back and forth in an axial direction of the chamber 12. The plunger 14 defines a proximal chamber portion 12a provided on a proximal side 14a of the plunger 14 and a distal chamber portion 12b provided on a distal side 14b of the plunger 14, wherein movements of the plunger 14 changes the volumes of the proximal and distal chamber portions 12a, 12b.

In at least some exemplary embodiments, the plunger 14 may be sealingly arranged to the circumferential wall of the chamber, such that substantially no hydraulic fluid can pass between the plunger 14 and a circumferential wall 16 defining the chamber 12. In such cases, in order to enable the plunger 14 to be movable within the chamber 12, there may be provided a controllable fluid passage (not shown in Fig. 2) through the plunger 14 itself, whereby the plunger 14 can be moved in one direction (e.g. distally), and fluid will be forced to move through the passage in the other direction (e.g. proximally). The plunger 14 may remain stationary if said controllable fluid passage is closed. It is also conceivable to provide an external fluid passage (not shown in Fig. 2) passing through the circumferential wall 16, in order to enable movement of the plunger 14. Different examples of such fluid passages will be discussed later in connection with other drawing figures. In other exemplary embodiments, there may be a small opening/gap between the plunger 14 and the circumferential wall 16 to allow a small flow of fluid past the plunger 14, thereby enabling displacement of the plunger 14 within the chamber 12. In some exemplary embodiments such a small opening/gap may be of variable size.

The bump stop arrangement 10 comprises a spring member 18 which is biased to exert a proximally directed force to the plunger 14. In the exemplary illustration in Fig. 2, the spring member 18 is provided in the distal chamber potion 12b, whereby the spring member 18 is configured to provide a pushing (not pulling) force on the plunger 14. Although this location of the spring member 18 may be more practical than providing a pulling spring member in the proximal chamber portion 12a, the latter solution is also conceivable and encompassed by the general inventive concept. For simplicity, in the following discussions, it will be assumed that the spring member 18 is located as shown in Fig. 2, i.e. in the distal chamber portion 12b.

The bump stop arrangement 10 comprises a bump stop member 20 which is located proximally and externally of the chamber 12. The bump stop member 20 is operatively connected to the plunger 14 so as to follow the movements of the plunger 14. For instance, as illustrated in Fig. 2, the bump stop member 20 may be connected to the plunger 14 via a rod 22. It should be understood that in this disclosure and within the general inventive concept the terms plunger and piston are exchangeable. Thus, in Fig. 2, the bump stop member 20 may be considered to be connected to a piston 14 via a piston rod 22.

The bump stop member 20 is configured to operatively engage with a suspension of the vehicle for transferring forces from the suspension. The suspension is not illustrated in the drawings, as it does not form part of the bump stop arrangement 10 per se. However, it should be understood that a bump stop arrangement 10 according to the general inventive concept may suitably be used in relation to any suspension that is normally installed to interact with a bump stop.

The bump stop arrangement 10 further comprises a fluid transfer arrangement (not shown in Fig. 2) enabling fluid to be transferred from the proximal chamber portion 12a to the distal chamber portion 12b, and vice versa. The above briefly mentioned possible fluid passages are thus some examples which may be included in such fluid transfer arrangements. From the previous explanations, it should now be understood that when the plunger 14 moves distally, then hydraulic fluid is configured to move from the distal chamber portion 12b, via the fluid transfer arrangement, to the proximal chamber portion 12a (the volume of the distal chamber portion 12b thus decreasing while the volume of the proximal chamber portion 12a is increasing). Conversely, when the plunger 14 moves in the proximal direction, then hydraulic fluid is configured to move from the proximal chamber portion 12a, via the fluid transfer arrangement, to the distal chamber portion 12b (the volume of the proximal chamber portion 12a thus decreasing while the volume of the distal chamber portion 12b is increasing).

Figs. 3a and 3b illustrates different states of the bump stop arrangement 10 of Fig. 2. Figs. 3a and 3b are schematic side views. In Fig. 3a the bump stop arrangement 10 is in a contracted state, while in Fig. 3b the bump stop arrangement 10 is in an extended state. The bump stop arrangement 10 may, for instance, be controlled to be in the extended state in order to be ready to engage the suspension when the suspension approaches the bump stop arrangement 10. Thus, turning back to Fig. 2, when the bump stop member 20 is subjected to a distally directed force which exceeds the proximally directed force exerted by the spring member 18 to the plunger 14, and fluid is allowed to flow between the chamber portions 12a, 12b through the fluid transfer arrangement, then the bump stop arrangement 10 will have a damper function in which the distally directed movement of the bump stop member 20 is dampened by the spring member 18. Thus, the damper function of the bump stop arrangement 10 may be controlled by controlling how far proximally the plunger 14 and bump stop member 20 are located relative to the chamber 12 when subjected to the distally directed force of the suspension, and also by controlling how far distally the plunger 14 and the bump stop member 20 are allowed to travel when subjected to said distally directed force.

When the bump stop member 20 is subjected to a distally directed force, and fluid is prevented from flowing between the chamber portions 12a, 12b through the fluid transfer arrangement or the spring member 18 has reached its maximum elastic potential energy (in this case the fully compressed state of the spring member 18), then the bump stop arrangement 10 will have a bump stop function in which the bump stop member 20 acts as a cushion. Thus, by controlling the flow between the chamber portions 12a, 12b, it is possible to control when the bump stop arrangement 10 will go from having a damper function to having a bump stop function. For instance, the fluid transfer arrangement may be controlled to prevent flow therethrough when the bump stop member 10 has moved part-way from the position in Fig. 3b, i.e. to an intermediate state between the extended state (Fig. 3b) and the contracted state (Fig. 3a) of the bump stop arrangement 10. Thus, depending on the current driving situation, the bump stop height (i.e. the height of the bump stop member 20 at which it remains substantially stationary relative to the chamber 12) can be controlled by controlling the closing of the fluid transfer arrangement.

From the above it should be understood that, in at least some exemplary embodiments, the fluid transfer arrangement may suitably have a closed state in which no fluid is allowed to pass between the proximal chamber portion 12a and the distal chamber portion 12b, and at least one open state in which fluid is allowed to pass between proximal and distal chamber portions 12a, 12b.

Fig. 4 schematically a bump stop arrangement comprising a valve 24, in accordance with at least one exemplary embodiment. Thus, the fluid transfer arrangement may comprise a passage 26 through the plunger 14, wherein the valve 24 is provided in the passage 26 in the plunger 14. Although not illustrated in Fig. 4, the valve 24 may suitably be controllable by a control unit for selectively opening/closing the valve 24. The valve 24 may be an on/off valve or may be set in different degrees of openness. Fig. 5 schematically illustrates an exemplary configuration of a valve 24’ and some different states of the valve 24’. The valve 24’ may suitably be located within a plunger 14’ which may be of the type previously discussed or a different type. In this exemplary embodiment, the plunger 14’ has first openings 27. The valve 24’ has relatively small second openings 28 and relatively large third openings 30. The valve 24’ has three different states 101, 102, 103. In the first state 101, neither the second opening 28 nor the third openings 30 are aligned with the first openings 27. Thus, in this state 101, the fluid transfer arrangement is closed, i.e. the valve 24’ does not permit any passing of fluid therethrough. This may, for example, be a “sport mode” of the bump stop arrangement. In the second state 102, the relative small second openings 28 of the valve 24’ are aligned with the first openings 27 of the plunger 14’, thus allowing a certain flow therethrough. This may, for example, be a “normal mode”. In the third state 103, the relative large third openings 30 of the valve 24’ are aligned with the first openings 27 of the plunger 14’, thus allowing a larger flow threrethrough. This may, for example, be a “comfort mode”.

Fig. 6 schematically illustrates a bump stop arrangement 10’ according to at least another exemplary embodiment. The circumferential wall 16 of the chamber is provided with a spiral groove or track 32. The plunger 14 has a mating protrusion (not shown) which is guided by the spiral groove 32 so that when the plunger 14 moves distally or proximally it will also rotate. Such a rotating motion may be used to configure a fluid transfer arrangement to gradually increase its openness as the plunger 14 moves in the distal direction and to gradually decrease its openness as the plunger 14 moves in the proximal direction. Such an opening or closing motion may, for instance, resemble to the motion of a camera lens shutter. In this exemplary embodiment, the plunger is allowed to move freely, i.e. there is no control unit which controls the opening/closing of the fluid transfer arrangement. It should be noted that instead of a spiral groove 32, the wall 16 may instead be provided with a spiral ridge which can guide a notch or recess in the plunger 14.

Fig. 7 schematically illustrates a bump stop arrangement 10” according to yet another exemplary embodiment. In this exemplary embodiment, the fluid transfer arrangement comprises a flow passage 26’, such as a pipe or tube, which extends at least partly outside the chamber, wherein the valve 24 is located in said flow passage 26’. Thus, the flow passage 26’ extends through the circumferential wall of the chamber (at two locations, suitably near opposite ends of the chamber) in order to fluidly interconnect the distal chamber portion and the proximal chamber portion when the valve 24 is open. The bump stop arrangement further comprises a control unit 40 which is configured to control the state of the fluid transfer arrangement, i.e. in this exemplary embodiment, to control the opening/closing of the valve 24. Such a control unit 40 may suitably be used to control any other controllable valve discussed in this disclosure. The control unit 40 may thus be configured to set a bump stop height at which the plunger 14 remains stationary in the chamber and the bump stop member will act as a cushion when subjected to a distally directed force. For instance, the control unit 40 may be configured to set the bump stop height by controlling the duration that the fluid transfer arrangement is in the open state (i.e. in this embodiment the duration during which the valve 24 is open) and switching it to the closed state. In other exemplary embodiments, the control unit 40 may, for instance, receive position signals from a position sensor at the plunger, to determine when to close the valve 24. The control unit 40 may suitably receive an input signal 42, such as a brake signal or a load signal, wherein the control unit 40 is configured to set said bump stop height based on said input signal 42. As previously explained, an anti-dive situation may suitably be handled based on at least a brake signal, or when driving over bump, a load signal may suitably be used by the control unit 40 for appropriate setting of the bump stop height. Other input signals, such as vehicle speed signals may also be used by the control unit 40 for determining an appropriate bump stop height. It should be understood that the input signal 42 in Fig. 7 may include several types of input signals. For instance, the control unit may be configured to receive two, three or more input signals simultaneously, such as those exemplified above.

The control unit 40 may be comprised in a vehicle, such as illustrated schematically in Figs. 1. The control unite may comprise processing circuitry. The processing circuitry may be provided using any combination of one or more of a suitable central processing unit CPU, multiprocessor, microcontroller, digital signal processor DSP, etc., capable of executing software instructions stored in a computer program product, e.g. in the form of a storage medium. The processing circuitry may further be provided as at least one application specific integrated circuit ASIC, or field programmable gate array FPGA. Particularly, the processing circuitry may be configured to cause the control unit 40 to perform a set of operations, or steps, such as receiving input signals, calculating a bump stop height based on the received input signals, and opening/closing a valve based on such calculation, etc. For example, the storage medium may store the set of operations, and the processing circuitry may be configured to retrieve the set of operations from the storage medium to cause the control unit 40 to perform the set of operations. The set of operations may be provided as a set of executable instructions. The storage medium may also comprise persistent storage, which, for example may be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory. The control unit 40 may further comprise an interface for communications with at least one external device such as the brake actuators, load sensors, speed sensors, etc.. As such, the interface may comprise one or more transmitters and receivers, comprising analogue and digital components and a suitable number of ports for wireline or wireless communication. The processing circuitry may control the general operation of the control unit 40, e.g. by sending data and control signals to the interface and the storage medium, by receiving data and reports from the interface, and by retrieving data and instructions form the storage medium. Other components, as well as the related functionality, of the control unit 40 are omitted in order not to obscure the concepts presented herein.

It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.