The invention relates to a vehicle leveling system and use of it for leveling a recreational vehicle, for example a camper or caravan, with respect to an underground, wherein the vehicle leveling system comprises:

- at least a hydraulically operated front stabilizing support (38a) mountable to a front side of the recreational vehicle RV for supporting the front side and at least a hydraulically operated rear stabilizing support (39a) mountable to a rear side of the recreational vehicle for supporting the rear side;

- hydraulic lines for passing a hydraulic fluid;

- a pump unit including a pump (31) with an associated electric driving motor (32) for pressurising the hydraulic fluid;

- a reservoir (30) from which the pump (31) draws hydraulic fluid and to which hydraulic fluid is discharged;

- a leveling controller (ECU) electrically connected to a level sensor for detecting a vehicle level and electrically connected to the pump unit for controlling a flow of hydraulic fluid to at least one of the stabilizing supports (38,39) to level the recreational vehicle.

Hydraulic systems are known from the prior art, for example from EP1.000.828 or from EP1.026.057, which hydraulic systems serve to place a caravan or trailer in a stable horizontal position on uneven and/or inclined to terrain

EP2184211B1 discloses a hydraulic system for leveling a vehicle, in particular a towed vehicle, such as a caravan or a trailer having a chassis which is provided with a wheel axle, as well as a baseplate mounted on the chassis. The hydraulic system comprises a hydraulic pump assembly comprising a tank, a hydraulic pump with an electric driving motor, and a valve block for housing electrically actuable valves. Hydraulic lines are provided for interconnecting these components. The hydraulic system further comprises control electronics for controlling a leveling method.

Regarding the above-mentioned prior art, it is remarked that any discussion of documents, acts, materials, devices, articles or the like included in the present specification is for the purpose of providing a context for the present invention, and is not to be taken as an admission that any such matters form part of the prior art or were before the priority date of each claim of this application common general knowledge in the field relevant to the present invention.

A design of such a vehicle leveling system has to comply with several technical requirements. A main requirement is that the vehicle leveling system should be as compact and lightweight as possible for allowing an installation in a narrow buid-in space and for limiting an increase in weight of the vehicle. Additionally, the vehicle leveling system should carry out a leveling procedure quickly in for example 20 seconds. Lightweight and compact on the one hand, and a fast operation on the other hand are opposite demands. A very compact vehicle leveling system might contribute less in weight and build-in space, but will possibly operate slowly. Many known vehicle leveling systems do not satisfy to a right balancing of these requirements.

The general object of the present invention is to at least partially eliminate the above mentioned drawbacks and/or to provide a usable alternative. More specific, it is an object of the invention to provide a vehicle leveling system for leveling a recreational vehicle which only requires a small build-in space, which has a limited effect on an overall vehicle weight increase and which still satisfies operational speed requirements.

In an aspect of the invention, this object is achieved by a vehicle leveling system according to claim 1.

A vehicle leveling system is provided for leveling a recreational vehicle. The vehicle leveling system may also be called a recreational vehicle leveling system. Such a recreational vehicle may be a camper or a towed vehicle, like a caravan. When parking on a camping site, the recreational vehicle needs to be levelled with respect to an underground. To carry out a leveling method, the vehicle leveling system comprises at least one hydraulically operated front stabilizing support and at least one hydraulically operated rear stabilizing support. The front stabilizing support is configured to be mounted at a front side of the vehicle for supporting the front side. The rear stabilizing support is configured to be mounted at a rear side of the vehicle for supporting the rear side. In particular, each stabilizing support includes a double acting hydraulic cylinder having a housing and a piston rod protruding from the housing at one end.

The vehicle leveling system comprises a hydraulic circuit with hydraulic lines for the passage of a hydraulic fluid. The hydraulic fluid can be pressurized by a pump unit. The pump unit includes a pump with associated electric driving motor. A reservoir is provided for receiving and supplying hydraulic fluid. The pump draws hydraulic fluid from the reservoir and hydraulic fluid is discharged to the reservoir.

The vehicle leveling system comprises a leveling controller which is electrically connected to a level sensor. The level sensor is configured to detect a vehicle level. The level sensor is for example a tilt sensor which is arranged to measure a tilting angle about a centrally positioned wheel axle of a caravan.

The leveling controller is electrically connected to the pump unit for controlling a supply and discharge of hydraulic fluid to and from each stabilizing support to level the recreational vehicle.

According to the aspect of the invention, the vehicle leveling system has a main hydraulic circuit for leveling a vehicle which main hydraulic circuit is in fluid communication via at least one supply line and a return line with an auxiliary hydraulic circuit for carrying out other motions, which auxiliary hydraulic circuit includes at least one auxiliary hydraulic actuator which is arranged without an own pump unit, wherein the auxiliary hydraulic actuator is fluidly connected to be pressurised via the at least one supply line with at least one pump unit of the main hydraulic circuit.

Advantageously, a substantial weight reduction of a recreational vehicle can be obtained by controlling auxiliary on board motions by an available pump unit of the vehicle leveling system.

According to a first aspect of the invention an improvement is provided by the electric driving motor which is a brushless direct current motor. The brushless DC motor is beneficial in a vehicle leveling system, because of a high accuracy which can be obtained in controlling the vehicle leveling system. In addition, a brushless DC motor allows a compact arrangement of the vehicle leveling system which is beneficial in installing the system in a limited narrow build-in space.

The vehicle leveling system according to the invention may provide various benefits which will be further elucidated hereafter by presenting several embodiments which are according to one or more aspects of the invention.

In an embodiment of the vehicle leveling system according to the first aspect, the leveling controller (ECU) is programmed to control the pump unit based on a measured torque at a motor rotor of the brushless direct current motor. The leveling controller is programmed to level the vehicle based on a measured electrical torque at the brushless DC motor. The leveling controller ECU is programmed to control the at least one front stabilizing support and/or at least one rear stabilizing support based on a measured electrical torque provided by the brushless DC motor of the pump unit. The torque measured at the brushless DC motor is indicative of a load exerted on one of the stabilizing supports. The leveling controller may be programmed to adjust a phase and/or amplitude of the DC current pulses to control the torque of the motor within predetermined boundaries. Herewith, an overload of the vehicle leveling system or a deformation to a chassis of the vehicle can be prevented. By measuring a provided torque at the brushless DC motor, additional components, e.g. pressure sensors, in the hydraulic circuit of the vehicle leveling system may become redundant which beneficially may reduce a total weight of the vehicle system. The vehicle leveling system can be arranged without connected pressure sensors for each individual stabilizing support. Without all these sensors and their connections to the controller, the operational scheme can be considerably simplified. In addition, such a simplified system is less vulnerable to interferences.

Preferably, the brushless DC motor has a motor rotor provided with an amount of magnets forming magnetic poles, in which the motor rotor has at least 10 magnetic poles, more in particular at least 14 magnetic poles. The amount of poles contribute to an accuracy in driving a stabilizing support. Advantageously, a precise driving of the pump unit and a monitoring of an occurring load in the vehicle leveling system may prevent large fluctuations in displacements and occurring loads. Furthermore, a precise driving of the pump unit may reduce occurring vibrations during control.

Preferably, the brushless DC motor has a motor rotor provided with permanent magnets, in which the permanent magnets are of a rare-earth magnet material, preferably neodymium magnets. The permanent magnets provide a strong magnetic field which contributed to a high torque to be provided by a relative lightweight motor.

Preferably, the brushless DC motor is a sensor brushless DC motor including at least one Hall effect sensor for measuring a motor rotor rotational position. Advantageously, the Hall effect sensor contributes to a high accuracy in controlling the vehicle leveling system.

In an embodiment of the vehicle leveling system, the vehicle leveling system comprises a main hydraulic circuit which is arranged for controlling at least one front and at least one rear stabilizing support. The vehicle leveling system comprises in the main hydraulic circuit at least a first pump unit and a second pump unit. The first pump unit includes a first pump with an own associated electric driving motor for pressurizing hydraulic fluid. The second pump unit includes a second pump with an own associated electric driving motor. Preferably, the pumps are connected to a common reservoir. Each pump unit has an own dedicated separate electric driving motor. Each pump unit is provided with an own brushless DC motor for driving the pump. Beneficially, this arrangement allows an accurate control of each individual pump unit and its hydraulically connected front or rear stabilizing supports. By subdividing the hydraulic actuators in groups to be controlled by an own pump unit, the vehicle leveling system allows a groupwise anticipation on an occurring overload of a particular hydraulic actuator. Herewith, the level control has an improved accuracy and may at the same time achieve a high operational speed.

In an embodiment of the vehicle leveling system, the first and second pump units are fluidly interconnected. The second pump unit may be fluidly connectable to a supply line of the first pump unit by a control valve, in particular a solenoid actuated valve. The first pump unit in the main hydraulic circuit may be hydraulically connected to a first stabilizing support, e.g. a group of front stabilizing supports, and the second pump unit in the main hydraulic circuit may be hydraulically connected to a second stabilizing support, e.g. a group of rear stabilizing supports. By interconnecting the first and second pump unit, both groups of stabilizing supports can be operated simultaneously by both pump units which allows a high run-out speed of the supports.

The interconnecting valve may be a three way, two position valve to allow the vehicle leveling system to switch between an all-mode in which all stabilizing supports are operable by both the first and second pump unit and a split-mode in which an operation of the stabilizing supports is split in operable front and rear stabilizing supports. In the split-mode, an at least one front stabilizing support is then operable by the first pump unit, while an at least one rear stabilizing support is operable by the second pump unit.

Advantageously, in a method of leveling a vehicle, the method may comprise successive steps including a first step of lowering all stabilizing supports together until one of the stabilizing supports attaches an underground, and a second step of separately lowering stabilizing supports by one of the first pump unit and the second pump unit.

In the first step of the method, all stabilizing supports can be lowered by using both the first and second pump unit in which the vehicle leveling system is set in the all-mode. Advantageously, the stabilizing supports are then quickly lowered. When one of the stabilizing supports contacts the underground, a load will increase, and an electrical torque can be measured at the at least one brushless DC motor which electrical torque will also increase. An increase of the torque exceeding above a threshold value can be programmed in the leveling controller to switch from the all-mode to the split-mode to start the second step of the method of leveling.

Preferably, the control valve for interconnecting the first and second pump unit is of a same type as other control valves for actuating the stabilizing support in the main hydraulic circuit. By using the same control valve for switching the vehicle leveling system from an all-mode to a split-mode as the at least one control valves for actuating a stabilizing support, advantageously, a simple configuration of the vehicle leveling system may be obtained.

In an embodiment of the vehicle leveling system, the vehicle leveling system comprises a main valve block for housing a plurality of control valves. Preferably, all control valves of the main hydraulic circuit are mountable to a single main valve block. Preferably, the main valve block is block shaped in which all control valves for controlling stabilizing supports are arranged at a single side surface of the block shaped main valve block. Preferably, the main valve block is provided with at least one pump chamber for housing the at least one pump.

According to a second aspect of the invention a vehicle leveling system for leveling a recreational vehicle, for example a camper or caravan, with respect to an underground is provided, wherein the vehicle leveling system comprises:

- at least one hydraulically operated front stabilizing support mountable to a front side of the recreational vehicle for supporting the front side and at least one hydraulically operated rear stabilizing support mountable to a rear side of the recreational vehicle for supporting the rear side;

- hydraulic lines for passing a hydraulic fluid;

- a pump unit including a pump with an associated electric driving motor for pressurising the hydraulic fluid;

- a reservoir from which the pump draws hydraulic fluid and to which hydraulic fluid is discharged;

- a leveling controller electrically connected to a level sensor for detecting a vehicle level and electrically connected to the pump unit for controlling a flow of hydraulic fluid to at least one of the stabilizing supports to level the recreational vehicle, wherein the vehicle leveling system comprises a main hydraulic circuit for controlling stabilizing supports, wherein the main hydraulic circuit comprises at least: a first pump unit including a first pump with an own associated electric driving motor for pressurising hydraulic fluid; and a second pump unit including a second pump with an own associated electric driving motor for pressurising hydraulic fluid.

According to the second aspect, multiple pump units in the main circuit may be beneficial to control each stabilizing support at a particular position independent of a stabilizing support at another position. Each pump unit may be positioned at a position of a stabilizing support to reduce a length of hydraulic lines. A pump unit may be incorporated in the stabilizing support to form a single mountable stabilizing unit. The stabilizing unit only needs an electrical connection with the leveling controller and a power supply. The leveling controller may be centrally positioned at the vehicle to control all pump units from a central position. Due to the incorporation of the pump unit in a stabilizing support, hydraulic lines may become redundant which is beneficial in upgrading existing vehicles by installation of a vehicle leveling system.

According to the second aspect of the invention, the electric driving motor for driving a pump is not necessarily a brushless DC motor. In an embodiment according to the first and second aspect, the electric driving motor for driving the pump is a brushless DC motor, preferably a sensored brushless DC motor. Preferably, the leveling controller is programmed to control the pump unit based on a measured electrical torque at a motor rotor of the brushless direct current motor.

In an embodiment according to the second aspect, the vehicle leveling system further comprises in the main hydraulic circuit at least one control valve in fluid communication with a stabilizing support, pump and reservoir, which control valve, in particular a solenoid actuated valves, is selectively actuable to extend or retract at least one stabilizing support by transferring hydraulic fluid, and wherein the main hydraulic circuit further comprises a control valve for fluidly interconnecting the first pump with the second pump. In particular, this control valve is of a same type as the control valves for actuating the stabilizing supports.

In an embodiment of the vehicle leveling system according to any aspect of the invention, the pump is a reversible pump. The reversible pump has a first and second port which depending on a rotational direction of the driving motor serve as a suction port or pressure port. Preferably, the pump of the pump unit is a gear pump. In particular, the pump is an internal gear pump.

In an embodiment of the vehicle leveling system according to any aspect of the invention, the vehicle leveling system has a main hydraulic circuit for leveling a vehicle which main hydraulic circuit is in fluid communication via at least one supply line and a return line with an auxiliary hydraulic circuit. The auxiliary hydraulic circuit is configured to carry out another motion, in particular on board of the vehicle. The auxiliary hydraulic circuit is configured to cooperate with the main hydraulic circuit. The auxiliary hydraulic circuit lacks a pump unit. The auxiliary hydraulic circuit has at least one auxiliary hydraulic actuator being arranged without an own pump unit. The auxiliary hydraulic actuator is fluidly connected to the main hydraulic circuit to be pressurized via the at least one supply line by the at least one pump unit of the main hydraulic circuit.

Advantageously, a substantial weight reduction of a recreational vehicle can be obtained by controlling auxiliary on board motions by an available pump unit of the vehicle leveling system.

According to a third aspect of the invention, the vehicle leveling system has an auxiliary hydraulic circuit which has a modular configuration comprising at least one sub-circuit module. Each sub-circuit module is arranged for carrying out a hydraulic function, e.g. a slide- out movement of a camper. Each sub-circuit module is formed by an auxiliary valve block section. The auxiliary valve block is mountable by assembling at least two valve block sections to each other. Preferably, the auxiliary valve block is mountable by assembling multiple valve block sections in series. The auxiliary valve block may for example be obtained by mounting three auxiliary valve block sections in a cascade arrangement.

In an embodiment of the vehicle leveling system according to third aspect of the invention, each auxiliary valve block section includes at least two flow channels in which a flow channel comprises a branch-line for connecting the auxiliary hydraulic actuator. In particular, each flow channel comprises a branch-line. Preferably, each flow channel linearly extends from a first end face to an opposite end face of the auxiliary valve block section. Herewith, the auxiliary hydraulic actuator is provided with a supply line and a return line for operation.

In an embodiment of the vehicle leveling system according to the third aspect of the invention, the auxiliary valve block section comprises a valve mounting surface for mounting at least one control valve, preferably a pair of control valves. Preferably, each control valve is a solenoid actuated 3/2 valve. In particular, the control valve is a normally closed valve. Herewith, each control valve is fluidly connectable to a branch-line of a flow channel for controlling the auxiliary hydraulic actuator.

In an embodiment of the vehicle leveling system according to the third aspect of the invention, the auxiliary valve block has a universal structure. This universal structure allows such an auxiliary valve block to be used in a variety of auxiliary hydraulic circuits. The universal structure of the auxiliary valve block comprises a configuration of flow channels in which each flow channel has a branch-line. Each branch-line extends from a flow channel to a valve mounting surface. To obtain a particular operation of a sub-circuit module, a branch-line can be plugged off to close the branch-line or can be provided with a control valve. By selectively closing off or using a branch-line, a required hydraulic configuration can be assembled for implementation in the auxiliary hydraulic circuit.

In an embodiment of the vehicle leveling system according to the third aspect of the invention, each flow channel of the auxiliary valve block forming a supply or a return fluid line is a permanent open flow channel. During operation of the vehicle leveling system, all in a cascade connected auxiliary actuators remain pressurized. No control valve is provided to temporary shut off one of the supply or return fluid lines. The flow channels are provided without control valves. Preferably, each flow channel forming a supply or return line, in particular the first supply line, second supply line and a common return line, extend parallel with each other from one end face of the valve block to an opposite end face of the valve block. Advantageously, herewith, a common rail is provided by the aligned flow channels of the auxiliary valve block sections for pressurizing the at least one auxiliary actuator.

In an embodiment of the vehicle leveling system according to the third aspect of the invention, the auxiliary hydraulic circuit comprises at least one auxiliary actuator for controlling a motion on board of a vehicle. In an embodiment, the auxiliary actuator is arranged for controlling a slide-out mechanism in which the actuator is a slide-out actuator for sliding out a vehicle compartment or vehicle component. In an embodiment, the auxiliary actuator is arranged for controlling an elevation mechanism, e.g. for elevating a bike support. In an embodiment, the auxiliary actuator is arranged for controlling a closure mechanism, e.g. for closing and/or locking a vehicle compartment. In an embodiment, the auxiliary actuator is arranged for controlling a tensioning mechanism, e.g. for tensioning a belt.

In an embodiment of the vehicle leveling system according to any aspect of the invention, the vehicle leveling system further comprises an emergency circuit. The emergency circuit is a hydraulic circuit which can be operated in case of a breakdown of the main hydraulic circuit. The main hydraulic circuit may be in fluid communication with the emergency circuit by an OR-valve, in particular a shunt valve. The emergency circuit comprises a manually operable pump for operating at least one of the stabilizing supports. Embodiments described above with respect to a particular aspect can be combined to obtain an embodiment according to the invention including all these beneficial aspects.

Further, the invention relates to a vehicle, in particular a recreational vehicle, e.g. a camper, more in particular a recreational vehicle which can be towed, such as a caravan or tent trailer, comprising a chassis with at least one wheel axle, wherein the vehicle is provided with a vehicle leveling system according to the invention.

The invention also relates to a use of a vehicle leveling system according to the invention for leveling a vehicle with respect to an underground.

The invention will be explained in more detail with reference to the appended drawings. The drawings show a practical embodiment according to the invention, which may not be interpreted as limiting the scope of the invention. Specific features may also be considered apart from the shown embodiment and may be taken into account in a broader context as a delimiting feature, not only for the shown embodiment but as a common feature for all embodiments falling within the scope of the appended claims, in which:

Fig. 1 shows a perspective view of an undercarriage of a caravan and an exemplary embodiment of a vehicle leveling system according to the invention;

Fig. 2 shows a hydraulic circuit of the vehicle leveling system of Fig. 1 including a pump unit and several leveling actuators;

Fig. 3 shows a hydraulic circuit including auxiliary actuators but without a pump unit which can be hydraulically coupled to a main hydraulic circuit for leveling as shown in Fig.2;

Fig. 4 shows an embodiment of a leveling actuator, a so-called hydraulic stabilizing support of the vehicle leveling system;

Fig. 5-7 show a pump unit assembly for controlling leveling actuators from a certain position on board of the vehicle;

Fig. 8-9 show the pump unit assembly of figures 5-7 in respectively a front and top view;

Fig. 10-12 show the pump unit assembly including an auxiliary valve block of an auxiliary hydraulic circuit for controlling auxiliary actuators;

Fig. 13-14 show the pump unit assembly of figures 10-12 in respectively a top and side view. Identical reference signs are used in the drawings to indicate identical or functionally similar components.

According to the invention, a vehicle leveling system is provided which is in particular suitable for a leveling a recreational vehicle, like a camper or caravan. The vehicle leveling system is arranged for supporting and leveling a road vehicle, like a camper, trailer or caravan. The vehicle leveling system is mountable to an undercarriage 1 of such a vehicle.

Just to illustrate an exemplary embodiment of such a vehicle leveling system, Fig. 1 shows an undercarriage of a caravan. The undercarriage or chassis 1 comprises in this example, as usual, two metal longitudinal beams 1a, 1b which extend towards a front end to be connected to poles 1c, 1 d which are directed towards one another forming a V-shape. At the front end of the chassis 1, a towing hook is present (not shown) as well as a height-adjustable nose wheel 3.

The longitudinal beams 1a, 1b have a central portion having a height which is greater than that of the ends of that longitudinal beams 1a, 1b. At said central portion the wheel axle 4 with wheel 5 is attached to the longitudinal beams 1a, 1b.

A baseplate can be mounted to the chassis 1, which baseplate then forms a floor of a caravan. The baseplate is generally made from wooden material, such as plywood.

Furthermore, Fig. 1 diagrammatically shows a hydraulic system for levelling the caravan with respect to an underground. The hydraulic system is arranged to provide support at both ends of the longitudinal beams and to level the longitudinal beams about the wheel axle 4.

In this example, two hydraulically operated lifting supports 10, 11 are provided, each of which is in this case directly attached to the axle 5 by means of a bracket at positions which are arranged at a distance from one another in the width direction of the vehicle. Alternatively, the lifting supports 10, 11 could be attached to the section where the height of the longitudinal beams 1a, b is increased, as these sections are sufficiently rigid.

The lifting supports 10, 11 and the hydraulic system are designed in such a manner that a lifting support can preferably support at least the weight of the entire caravan.

The lifting supports 10, 11 are in this case have a telescopic design having a stationary part (which is attached to the axle 5) and a part which can be extended straight downwards and which has a footplate. A hydraulic cylinder, which is not visible in Fig. 1, is accommodated in each lifting support.

In a known alternative embodiment, the lifting support 10 can be a "knee-acting jack" as marketed by the US company Kwikee. This support has a bottom supporting part with a footplate which supporting part can be pivoted about a pivot 10 and is substantially horizontal when the lifting support is retracted and points downwards when the lifting support is extended. This embodiment allows for a greater ground clearance.

Near the front side of the base plate of the caravan, a pair of hydraulically operated front stabilizing supports 38a, 38b is provided. On the rear side of the base plate, a pair of hydraulically operated rear stabilizing supports 39a, 39b is provided, at a distance in front of and behind the axle 5, respectively, of which only the associated hydraulic cylinders 38a, b and 39a, b are shown in Fig. 1. Here, with each pair of stabilizing supports, the supports are arranged at a distance from one another in the width direction.

Figure 1 furthermore shows a box 20 which forms part of the leveling system for housing components at a central position in the hydraulic arrangement. The box 20 is designed to be fitted to the underside of the baseplate.

The box 20 contains a pre-assembled hydraulic pump assembly comprising a reservoir for hydraulic fluid, a hydraulic pump with an associated electric driving motor, and a valve block comprising one or more solenoid actuated valves.

The box 20 furthermore comprises assembled control electronics, also called a leveling controller, for driving the driving motor and the one or more solenoid actuated valves. The control electronics comprise a level sensor. The level sensor may be positioned in the box 20. The hydraulic vehicle leveling system furthermore comprises hydraulic lines, which lines are here passed through splash-proof ducts in the box. The hydraulic lines extend from the box to each stabilizing support.

When fitted to the base plate, the box 20 is splash-proof, with the electronics preferably being arranged so as to be waterproof. Said components may be pre-fitted to the body of the box 20, so that the box 20 ultimately serves as the mounting means for these components to the vehicle. As is preferred, these components are prefilled with hydraulic fluid and, as is furthermore preferred, the correct operation is tested before the pre-assembled box 20 containing the components is supplied as a single unit to the assembly process of the vehicle. As can be seen, the box 20 in this case has a peripheral edge with a mounting flange 20a provided with holes for screws and the like, which can, for example, be screwed directly into the plywood base plate. In this case, the box 20 is open at the top side, it being possible to provide further sealing along the top edge by means of a sealing ring and/or applying sealant/glue. In one variant, the box 20 has a lid.

An embodiment of the hydraulic vehicle leveling system according to the invention will now be explained in more detail with reference to the diagram in Fig. 2 which shows a main hydraulic circuit MC.

The main hydraulic circuit MC comprises a pump unit including a pump 31 and a motor 32. Here, besides a first pump unit, the main hydraulic circuit MC further comprises a second pump unit.

The pump 31 is a reversible pump having a first and a second port 31a, 31b which, depending on the direction of rotation of a driving motor, serve as suction port or pressure port.

The driving motor 32 is a brushless direct current motor, a so-called BLDC motor. The motor 32 has a motor rotor provided with permanent magnets of a neodymium material. The motor rotor has at least 10 permanent magnets defining at least 10 magnetic poles. The BLDC motor contributes to an accurate control of the pump unit.

Furthermore, a first pressure-relief valve 40.1 associated with the second port 31b is provided, which first pressure-relief valve 40.1 opens when a system pressure exceeds a threshold value, e.g. 210bar.

The main hydraulic circuits further includes a reservoir 30 for receiving discharged hydraulic fluid. The reservoir 30 is a central reservoir which serves all hydraulic actuators 38, 39.

Furthermore, the main hydraulic circuit MC comprises one or more solenoid actuated valves 47, 48. A first pair of solenoid actuated valves 47.1, 47.2 is provided for controlling a first pair of leveling actuators, also called front stabilizing supports 38a, 38b. A second pair of solenoid actuated valves 48.1, 48.2 is provided for controlling a second pair of leveling actuators, also called rear stabilizing supports 39a, 39b. The leveling controller ECU for driving the at least one electric driving motor 32 and the one or more solenoid actuated valves is not shown in Fig. 2.

Fig. 2 schematically shows double acting cylinders 68 of the front and rear stabilizing supports 38a, b, 39a, b respectively which are shown in further detail in figure 4.

The stabilizing supports 38, 39 in this case are provided with double-acting cylinders 68 with a housing 69 and a piston rod 70 which protrudes outwards at a single axial end of the housing. The piston rod 70 then forms a bottom-side chamber and a piston-rod-side chamber in each cylinder.

The cylinders 68 of each stabilizing support as shown in figure 2 is arranged in such a manner that a supply of hydraulic fluid to the bottom side chamber derived results in a lifting movement of the stabilizing support. Herewith, a large active system surface is available for the lifting movement. Figure 4 shows a mounting of a cylinder 68 in an inverse manner.

Between the second port 31b of the pump 31 and the bottom-side chamber of the cylinder 68, a separate solenoid actuated valve, in this case 47, 48, is provided for each cylinder 38, 39.

Furthermore, a hydraulically operated non-return valve 50, 51 (POCV; pressure operated control valve) is arranged between the second port 31b and the bottom-side chamber of the cylinder 68 of each stabilizing support, which hydraulically operated non-return valve 50, 51 (POCV) opens in a direction towards the first port 31a and opens on the basis of a control pressure when hydraulic fluid is supplied under pressure to the bottom-side chamber of the cylinder 68 of the stabilizing support (i.e. when the stabilizing support 38, 39 is extended on command).

As Figs. 1 and 2 show, the cylinders of each pair of stabilizing supports on the front side and on the rear side of the vehicle are connected in parallel by means of lines, with a separate solenoid actuated valve 47, 48 being associated with each support.

All solenoid actuated valves 47, 48 may be of a normally closed type, so that, when the electrical servo-mechanism of said valves fails, the supports can be moved upwards, preferably by operation of a manual pump 31.3 of an emergency circuit EC. For example, when a failure occurs in the control electronics or in one or more valves, all supports can be moved off the ground, provided the manual pump working in the direction of the second port 31b. The emergency circuit EC further comprises a relief valve 41 to present a pressure overload.

Preferably, the leveling controller ECU, which preferably comprise a microprocessor and a memory, are designed to produce an automatic levelling routine. This means that upon arrival at a campsite, said routine can be switched on and the caravan is then placed in the desired horizontal position in an automatic and stable manner.

Preferably, it is provided that there is a routine, the starting point of which is that the caravan is tilting slightly forwards, which can be adjusted using the nose wheel. At the start of the routine, the level sensor detects whether the caravan is in said starting position. If this is the case, the following routine is preferably carried out: a) operating the one or more front stabilizing supports 38a, 38b until the vehicle is level in the longitudinal direction; b) operating the one or more rear stabilizing supports 39a, 39b until the vehicle is stabilized in the longitudinal direction; c) in particular operating a lifting support 9,10 on the side of the vehicle which is lower, viewed in the width direction, until the vehicle is level in the width direction, and continuing said operation until the vehicle is slightly lifted up on that side; d) in particular operating the other lifting support until the vehicle is level in the width direction; e) operating the one or more stabilizing supports on the side which is lower, viewed in the longitudinal direction, until the vehicle is level in the longitudinal direction; f) operating the one or more other stabilizing supports until the vehicle is stable in the longitudinal direction.

By means of this routine, the vehicle is placed in the desired position in a reliable and safe manner, while avoiding excessive forces on the caravan.

Continued operation of the lifting support 9, 10 in step c), for example for a predetermined short period of time (for example 2 seconds), leads to the chassis being pushed "off the suspension". The same happens again by operating the other lifting support until the horizontal position is reached in the width direction. In addition, this ensures that "the weight" of the caravan is borne, as it were, by the lifting supports and not, therefore, by the stabilizing supports (which would result in undesirable torsion).

Preferably, the control electronics are furthermore designed to produce an automatic return routine, which comprises: a) briefly and partly lifting the one or more front and rear stabilizing supports on the front side and rear side, if desired in sequence, b) completely lifting both lifting supports; c) completing the lifting of the front and rear stabilizing supports.

[0061] The control electronics could furthermore be designed to carry out a calibration routine, in which the instantaneous position of the vehicle is stored in the memory of the control electronics as the desired level position. This may, in particular, in the electronics, make it also possible to operate each lifting support and/or (pair) of stabilizing supports separately and manually (by means of the remote control), so that it is possible to choose a position and then store this in the memory.

Further, the main hydraulic circuit comprises a control valve 43, in particular a solenoid actuated valve for switching from an all-mode to a split-mode during a leveling operation. The control valve 43 is arranged in between the first and second pump unit. The control valve 43 is in fluid communication with the second port 31b of the first pump 31.1 and the second port 31 b of the second pump 31.2.

The control valve 43 is a 3-way two-position solenoid actuated valve. In a first position (as shown in figure 2), the first and second pump unit are in fluid communication with each other. In the first position of the control valve, the vehicle leveling system is in the all-mode. Both or one of the first and second pump can be driven to actuate any of the leveling actuators 38, 39. Preferably, in the all-mode, all stabilizing supports 38, 39 are actuated together by both the first and second pump 31.1, 31.2.

In the second position of the control valve 43, the second pump unit is separated from the first pump unit. Herewith, the vehicle leveling system is in the split-mode, in which the first pump 31.1 is drivable by the first motor 32.1 to pressurize at least one of the front stabilizing supports 38a, 38b via the second port, and in which the second pump 31.2 is drivable by the second motor 32.2 to pressurize at least one of the rear stabilizing supports 39a, 39b. In the split-mode, the stabilizing supports 38, 39 are separately operable. Herewith, a front stabilizing support 38 can be adjusted independently of a rear stabilizing support 39. The motors being brushless DC motors are beneficial in the split-mode for accurately controlling each stabilizing support. A measured torque at the motor rotor is indicative of a load exerting on a stabilizing support and is useful in controlling the vehicle leveling system to prevent an overload. Advantageously, to simplify the main hydraulic circuit MC, the control valve 43 is of a same type as the solenoid actuated valves 47, 48 for controlling respectively the front and rear stabilizing supports 38, 39. In particular, all control valves in the main hydraulic circuit are of a same type which valves are preferably a three-way, two-position solenoid actuated valve. Preferably, all control valves included in the main hydraulic circuit MC are mountable to a single main valve block 44, as illustrated in figures 5-14.

Further, figure 2 shows a first supply line 36 originating from the second port of the first pump 31.1 and a second supply line 37 originating from the second port of the second pump 31.2. The first and second supply line 36, 37 are available for coupling an auxiliary hydraulic circuit AC.

Fig. 3 shows an embodiment of such an auxiliary hydraulic circuit AC which is fluidly connectable to the main hydraulic circuit MC as shown in figure 2.

The auxiliary hydraulic circuit AC has a modular configuration. Here, the auxiliary hydraulic circuit AC comprises three sub-circuit modules SC1, SC2, SC3. A sub-circuit module is marked with dashed lines in figure 3. Each sub-circuit module is connectable to at least one actuator, here each sub-circuit module SC is connectable to a pair of actuators. The at least one actuator is controlled by a control valve 49. The control valve 49 is mounted to an auxiliary valve block 45.

Here, the control valve 49 is a solenoid actuated control valve. The control valve 49 is normally closed, such that the actuator is normally disconnected from a supply of hydraulic fluid via one of the supply lines 36, 37.

Each auxiliary valve block 45 is provided with at least two through flow channel extending from a first end face to an opposing second end face. Here, each auxiliary valve block 45 includes a first, second and third through flow channel. The first through flow channel is configured to form a return line 35. The return line 35 is provided for discharging hydraulic fluid to a reservoir. The return line 35 in the auxiliary hydraulic circuit of figure 3 corresponds with the return line 35 in the main hydraulic circuit of figure 2.

The second and third through flow channel are configured to form a part of a supply line for pressurizing a connected actuator. The second and third through flow channel 36, 37 of the auxiliary hydraulic circuit as shown in figure 3 respectively correspond with the first and second supply line 36, 37 of the main hydraulic circuit as shown in figure 2. Multiple auxiliary valve blocks 45.1, 45.2, 45.3 of sub-circuit modules can be mounted to each other, such that the through flow channels 35, 36, 37 align with each other to form a common fluid line, also called a common rail. The common fluid lines 36, 37 are configured to be interconnected with the supply line 36 or 37 of the main hydraulic circuit MC as shown in figure 2.

As shown in figure 3, the control valve 49 is positioned outside of the common fluid line 36, 37. The control valve 49 is connected to a branch-line originating from the common fluid line 36, 37. Opening or closing the control valve 49 does not open or close any of the common supply lines, but only opens or closes the branch-line. The common fluid line 36, 37 remains always open to further sub-circuit module connected in series. Advantageously, the common fluid lines 36, 37 can serve as a common rail to pressurize a cascade of sub-circuit modules SC1, SC2, SC3.

The auxiliary valve block 45 includes at least two branch-lines respectively originating from the at least two through flow channels. A first branch-line 351 , a return branch-line, originates from a through flow channel serving in the auxiliary hydraulic circuit as a common return line 35. A next branch-line, a supply branch-line 361 ;371 , originates from a through flow channel serving in the auxiliary hydraulic circuit as a common supply line 36 or 37. In case of a presence of more than one pump in the main hydraulic circuit MC which have to be connected to multiple auxiliary hydraulic actuators, each sub-circuit module SC1, SC2 contain more than two flow channels and is in that way selectively connectable to a first, second or further supply line, and one return line.

Here, the auxiliary hydraulic actuator is double-acting and operable by controlling two control valves 49. When opening the control valves, the auxiliary hydraulic actuator is fluidly connected with either the first supply line 36 or the second supply line 37.

As shown in figure 3, the first sub-circuit module SC1 schematically differs from the second sub-circuit module SC2 by a first supply branch-line 361 originating from the common supply line 36 instead of a second supply branch-line 371 in SC2 originating from the second common supply line 37. The third sub-circuit module SC3 has the same configuration as the first sub-circuit module SC1 and is also pressurized from the first common supply line 36.

In an embodiment of an auxiliary valve block 45, each flow channel may be provided with a branch-line extending to a valve mounting surface for mounting at least one valve. The difference between sub-circuit modules as presented in a scheme like Fig. 3 can be arranged by plugging off non-used branch-lines by an end plug. Herewith, each auxiliary valve block 45 for each sub-circuit module SC1, SC2, SC3 may have a same configuration of channels. Different types of sub-circuit modules correspond with each other in that each module include at least one flow channel to allow a particular pump connection. Each flow channel has a branche-line extending to a valve mounting surface for mounting a valve. In embodying a particular auxiliary hydraulic circuit, one of the branche-lines will be used for operation and provided with a control valve while remaining branch-lines will be plugged. Sub-circuit modules then differ from each other by a positioning of a valve on a particular branche-line and an end plug on remaining brache-lines. Herewith, the auxiliary hydraulic circuit can easily be configured by assembling sub-circuit modules SC by identical auxiliary valve blocks 45 to control a plurality of hydraulic actuators by more than one pump unit. By selecting a particular configuration of a sub-circuit module, a designer can easily select which pump should be operated for actuating a particular actuator in the auxiliary hydraulic circuit AC.

The auxiliary hydraulic circuit AC may be configured for operating any mechanism on board of a recreational vehicle. Multiple on-board mechanisms can be driven by using the at least one pump of the vehicle leveling system which makes an own dedicated pump unit for each on-board mechanism redundant. Advantageously, a recreational vehicle like a camper may get more luxury on board by implementing electronically controlled functionality without substantially increasing a weight of the vehicle.

Typically, the auxiliary hydraulic circuit AC includes a slide-out mechanism including a slide- out actuator for sliding out a vehicle compartment or vehicle component. In an embodiment, the auxiliary hydraulic circuit AC may comprise an actuator for controlling a closure mechanism, e.g. for closing/opening/locking a vehicle compartment like a camper garage. In an embodiment, the auxiliary hydraulic circuit AC may comprise an actuator for controlling an elevation mechanism, e.g. for elevating a bike support or a lift platform. In an embodiment, the auxiliary hydraulic circuit AC may comprise an actuator for operating a tensioning mechanism, e.g. for tensioning a belt.

Fig. 4 shows the hydraulically operated stabilizing support 55 which is preferably used for a caravan and which can be fitted in the positions indicated in Fig. 1. The support 55 is intended to be fitted directly on the bottom of the base plate of the caravan.

The cylinder 68 in this case is arranged in such a manner that, in order to move the stabilizing support in question towards the ground, hydraulic fluid is supplied to the rod-side chamber, that is to say, the piston rod slides inwards. Thus, the relatively small piston surface is therefore available, which, as is preferred, has been done in order to limit the force which is to be exerted by the stabilizing supports 38a, b and 39a, b. This, in combination with a suitable design of the stabilizing support, can result in the stabilizing support not being able to overload and/or twist the caravan.

The stabilizing support 55 has a guide 60 which is to be attached to the base plate, a pivotable stabilizing arm 61 which, at its top end, is attached around a pivot axis 62 to the guide 60 and which is designed to rest on the ground with its bottom end 64.

The support 55 furthermore has an intermediate arm 65 which, at one end, at 66, is hingedly attached to the stabilizing arm 61, in this case in a middle region of this arm 61, and, at the other end, is slidably guided with respect to the guide 60, in this case by means of a sliding element 67.

Furthermore, a double-acting hydraulic cylinder 68 (in accordance with the cylinders 38a, b and 39a, b) with a housing 69 and a piston rod 70 protruding from the housing at one end is provided, in which the housing 69 is attached by its bottom side, at 63, to the guide 60, near the hinged attachment of the stabilizing arm 61, and wherein the piston rod 70 is attached to the slidably guided end with sliding element 67 of the intermediate arm 65.

Thus, the piston rod 70 will be extended in the "folded-away position" of the stabilizing support. Preferably, in this case, it is provided that the intermediate arm and/or the stabilizing arm are partially U-shaped and then cover the piston rod, so that the piston rod is (to some degree) protected.

In this case, a hydraulically operated non-return valve 50, 51 (POCV) is in each case provided in the connection between the respective valve 47, 48 and the rod-side chambers of the cylinder pairs 38a, b and 39a, b, which hydraulically operated non-return valve 50, 51 (POCV) closes in the direction towards the first port 31 a and opens on the basis of a control pressure when hydraulic fluid is supplied under pressure to the bottom-side chambers of the cylinder pair.

Fig. 5-9 show in several views and embodiment of a pump unit assembly 21 for implementation in a main hydraulic circuit HC. The pump unit assembly 21 is mountable as a certain position to a chassis 1 of a vehicle. The pump unit assembly 21 can be mounted in a box 20 together with a leveling controller ECU for controlling at least one main hydraulic actuator. The pump unit assembly 21 includes a pump unit with a pump 31 and a driving motor 32 for driving the pump.

Here, the pump 31 is housed in a main valve block 44 which has a valve mounting surface for mounting at least one control valve 47. The driving motor 32 is mounted at one end face of the main valve block 44. Further, the pump unit assembly 21 comprises a reservoir 30 which is fluidly connected to the main valve block 44 for mounting at least one control valve 47. The reservoir 30 is fluidly connected to the pump 31 and mounted to an opposite end face of the main valve block 44.

Figure 8 shows in a frontal view a first and second motor 32. Here, the first and second motor 32 are brushless DC motors. Each motor 32 drives a pump 31. A control valve 43 is fluidly connected to the main valve block 44. The control valve 43 is fluidly connected in a fluid line in between the first and second pump 31.1, 31.2 to allow the second pump 31.2 to be in cooperation with or disconnected from the first pump 31.1 as explained above with reference to figure 2.

Figure 9 shows a top view of the pump assembly 21. A first pair of control valves 47, and a second pair of control valves 48 are positioned in a row at a common valve mounting surface. As shown in figure 2, the first pair of control valves 47 are arranged to operate the front stabilizing supports 38a, and the second pair of control valves 48 are arranged to operate the rear stabilizing supports 39. The control valve 43 can be switched to operate both the front and rear stabilizing supports together by both the first and second pump or to operate the front and rear stabilizing support independent from each other.

Fig. 10-14 show a further embodiment of the pump unit assembly 21 as presented in figures 5-9 further comprising an auxiliary valve block 45 for fluidly connecting an auxiliary hydraulic circuit AC to the main hydraulic circuit and the MC.

An auxiliary valve block 45 is mounted to the main valve block 44. Here, the auxiliary valve block 45 is mounted to a side surface of the main valve block 44. The auxiliary valve block 45 is modular and structured by valve block sections. Here, the auxiliary valve block 45 comprises valve block sections 45.1, 45.2, 45.3 corresponding with the three sub-circuit modules SC1, SC2, SC3 as explained with reference to figure 3. Each valve block section has a valve mounting surface for connecting at least one control valve 49. In figure 13 which shows a top view of the pump unit assembly 21, the control valves 43, 47, 48 and 49 are referred in correspondence with figure 2 and figure 3.

It will be clear that the invention has in this case only been explained with reference to a caravan by way of illustration. It is also possible to use one or more aspects of the invention for a vehicle which is not towed. The invention is, for example, also suitable for a trailer or a camper.

Although the present invention has been described in detail, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the invention as hereinafter claimed. It is intended that all such changes and modifications be encompassed within the scope of the present disclosure and claims.

Reference signs list:

RV recreational vehicle 32 motor; BLDCmotor

ECU electronic control unit; leveling 32.1 first motor controller 32.2 second motor

MC main hydraulic circuit EC emergency circuit 35 return line AC auxiliary hydraulic circuit 351 return branch-line

36 first supply line; first common supply line

SC sub-circuit 361 first supply branch-line SC1 sub-circuit 1 37 second supply line; second common SC2 sub-circuit 2 supply line SC3 sub-circuit 3 371 second supply branch-line

1 chassis; undercarriage 38 front stabilizing support 1a beam 39 rear stabilizing support 1b beam

3 nose wheel 40 pressure-relief valve

4 wheel axle 40.1 first pressure relief valve

5 wheel 40.2 second pressure relief valve

9 lifting support 41 EC pressure relief valve

10 lifting support 42 shuttle valve

43 control valve

20 box

21 pump unit assembly 44 main valve block

45 auxiliary valve block

30 reservoir 45.1 valve block section

45.2 valve block section

31 pump 45.3 valve block section 31a first port 31b second port 47 solenoid actuated valve; normally closed

31.1 first pump 48 solenoid actuated valve; normally closed

31.2 second pump 49 SC solenoid actuated valve; normally

31.3 third pump; manual pump closed 49.1 SC1 solenoid actuated valve; normally closed 52.1 SC1 non-return valve; POCV

49.2 SC2 solenoid actuated valve 52.2 SC2 non-return valve; POCV

49.3 SC3 solenoid actuated valve 52.3 SC3 non-return valve; POCV

52.1 SC1 non-return valve; POCV

52.2 SC2 non-return valve; POCV

50 non-return valve; POCV (pressure operated control valve) 68 cylinder

51 non-return valve; POCV 69 housing

52 non-return valve; POCV 70 piston rod