Recreational vehicle with a lifting support device and method for determining axle loads of the recreational vehicle

Abstract

1. A leveling device (2) for a recreational vehicle (1), in particular a motorhome or caravan, comprising at least one first leveling arrangement (6) comprising at least one, preferably two, hydraulically actuated leveling supports (8, 9), at least one hydraulic pump (15) for actuating the at least one leveling support (8, 9), at least one electric motor (16) for at least indirectly driving the hydraulic pump (15) and through which a motor current (I) dependent on the load on the pump (15) flows during operation, and a control device (20) for at least indirectly controlling the at least one electric motor (16). It is proposed that the control device (20) be configured to provide the first leveling arrangement (6) with measured values ​​(101) of a motor current (I) for an unloaded state (102) of the first leveling arrangement (6).to detect, in which, in the assembled state, a proportionate amount of the vehicle weight attributable to a first axle unit (4') of the recreational vehicle (1) is supported via the wheels (40) of the first axle unit (4'), that the control device (20) is configured, to detect measured values ​​(105) of the motor current (I) assigned to the first lifting support arrangement (6) for a state (106) lifted by the first lifting support arrangement (6), in which, during operation, at least one first axle unit (4') of the recreational vehicle (1) is lifted so that the wheels (40) of the first axle unit (4') are raised from the ground (42), and that the control device (20) is configured to determine a first axle load (114) of the recreational vehicle (1) on the first axle unit (4') as a function of the detected measured values ​​(101, 105) of the motor current (I). Furthermore, a recreational vehicle (1) with such a lifting support device (2) and a method for controlling a lifting support arrangement (2) are specified.

Description

[0001] The invention relates to a recreational vehicle, in particular a mobile home or caravan, a jack device, and a method for determining axle loads of the recreational vehicle. The recreational vehicle can be designed, in particular, as a campervan.

[0002] EP 3 498 548 A1 discloses a jack assembly for a preferably motorized road vehicle with a chassis, in particular for mobile homes, sales vehicles, or special-purpose vehicles, and a front and rear axle assembly. The jack assembly comprises several, in particular four, jacks with a control device. The jack assembly comprises a securing device for the jack assembly and / or the road vehicle, wherein the securing device comprises a detection device for weight characteristics of the road vehicle, in particular for the front and rear axle loads.

[0003] In the jacking support assembly known from EP 3 498 548 A1, the jacking supports are extended until ground contact is made to detect at least one weight characteristic. The axle assemblies are then lifted free, individually one after the other or together, until a constant pressure or force value is established at the jacking supports. The jacking supports are then retracted a short distance. If necessary, after a stability pause, the static pressure or force measurement is performed on the jacking supports, and the weight characteristic is calculated from the measured values. The hydraulic jacking support can have a sensor (pressure sensor) for detecting ground contact during extension. The same or a different sensor can also be used to detect an end stop in the retracted position of the jacking support.The same or a different sensor can also be used for other purposes, in particular for detecting the supporting force of the extended hydraulic jack or the load acting on the hydraulic jack.

[0004] The jack support assembly known from EP 3 498 548 A1 has the disadvantage that, for example, a pressure sensor is required for each jack support to detect the supporting force. Accordingly, it is disadvantageous that a separate pressure sensor is required for each jack support to detect ground contact or an end stop. Furthermore, the pressure sensors require transmission and evaluation of the measurement signals. Environmental influences can adversely affect the pressure measurement and thus the detection of the supporting force. The pressure sensors and any cables present must also be protected from damage and checked for damage if necessary.

[0005] The previously described state of the art is also known from DE 20 2018 006 636 U1.

[0006] The object of the invention is to provide a jack device, a recreational vehicle, and a method that have an improved design and functionality. In particular, the object of the invention is to determine a front axle load and a rear axle load of a recreational vehicle in an improved manner, particularly reliably and / or with reduced effort.

[0007] The object is achieved by a jack device having the features of independent patent claim 1, a recreational vehicle having the features of claim 14, and a method having the features of patent claim 15. Advantageous developments of the invention are specified in the subclaims.

[0008] The object is achieved by a jack stand device for a recreational vehicle, in particular a mobile home or a caravan, with at least one first jack stand arrangement, which comprises at least one, preferably two, hydraulically actuated jack stands, at least one hydraulic pump, which serves to actuate the at least one jack stand, at least one electric motor, which serves to at least indirectly drive the hydraulic pump and through which a motor current flows during operation, which depends on the load of the pump, and a control device, which serves to at least indirectly control the at least one electric motor, wherein the control device is designed to measure measured values ​​of a motor current assigned to the first jack stand arrangement for an unloaded state of the first jack stand arrangement,in which, in the mounted state, a vehicle weight proportionally attributable to a first axle unit of the recreational vehicle is supported via the wheels of the first axle unit, wherein the control device is designed to detect measured values ​​of the motor current assigned to the first jack support arrangement for a state in which, during operation, at least one first axle unit of the recreational vehicle is lifted such that the wheels of the first axle unit are lifted off the ground, and wherein the control device is designed to determine a first axle load of the recreational vehicle on the first axle unit as a function of the detected measured values ​​of the motor current.

[0009] Furthermore, the object is achieved by a recreational vehicle, in particular a mobile home and / or a caravan, with such a jack device.

[0010] Furthermore, the object is achieved by a method for controlling a jack device for recreational vehicles, in particular mobile homes or caravans, which jack arrangement comprises at least one first jack arrangement which comprises at least one, preferably two, hydraulically actuated jacks, at least one hydraulic pump which serves to actuate the jacks, at least one electric motor which serves to at least indirectly drive the hydraulic pump and through which a motor current flows during operation which is dependent on the load of the pump, and a control device which serves to at least indirectly control the at least one electric motor, wherein by means of the control device of the first jack arrangement, measured values ​​of a motor current for an unloaded state of the first jack arrangement,in which, in the mounted state, a vehicle weight proportionally attributable to a first axle unit of the recreational vehicle is supported via the wheels of the first axle unit, wherein measured values ​​of the motor current assigned to the first jacking support arrangement for a state in which at least one first axle unit of the recreational vehicle is lifted free during operation, wherein the wheels of the first axle unit are lifted off the ground, are recorded by means of the control device, and wherein a first axle load of the recreational vehicle on the first axle unit is determined by means of the control device as a function of the recorded measured values ​​of the motor current.

[0011] It is advantageous that the control device is configured to determine the first axle load of the recreational vehicle as a function of a differential value resulting from at least one measured value in the unloaded state and at least one associated measured value in the lifted state. Specifically in this configuration, the differential value formation results in compensation for environmental influences. In particular, the influence of an ambient or operating temperature can be fully or partially compensated.

[0012] It is advantageous for the control device to be configured to determine the first axle load of the recreational vehicle based on at least one vehicle-specific calibration value. One or more influencing variables can be taken into account. For example, mechanical influencing variables, such as the position of a jack relative to a wheel or axle or axle arrangement, can be fully or partially compensated.

[0013] It is advantageous for the control device to be configured to record measured values ​​of the motor current for the first jacking support arrangement as motor current calibration values ​​and to store these motor current calibration values ​​and / or a difference value resulting from the motor current calibration values ​​together with an externally measured first axle load. This allows for simple calibration. For example, an axle or axle arrangement can be lifted free at a time in order to store the values ​​for the jacking support arrangement with which the lifting is carried out.

[0014] It is advantageous for the control device to be configured to store an at least partially externally determined conversion factor, which specifies a factor for converting a unit of a measured value of the motor current or a difference value between measured values ​​of the motor current into a weight unit, as a vehicle-specific calibration value for the first axle unit. This allows for a conversion with minimal computational and storage effort.

[0015] It is advantageous that at least one device is provided which detects the current state of the first jack support arrangement during operation, and that the control device is designed to determine, by means of the detected state of the first jack support arrangement, whether the unloaded state of the first jack support arrangement exists or not and / or whether the state in which the first jack support arrangement is lifted freely exists or not. Such a device can be implemented in particular by a pressure sensor which is preferably arranged centrally, in particular on the hydraulic pump. In particular, exactly one pressure sensor can be used here. In this case, the hydraulic pump can be used to control, in particular, the jack supports of a jack support arrangement together or each jack support individually. Preferably, all jack supports of a jack support arrangement are controlled in each case.For control and / or pressure measurement for each jack assembly, a selective hydraulic connection to the hydraulic pump can be implemented. Accordingly, a selective hydraulic connection to a jack assembly can be implemented if necessary. Depending on the design, selective selection of a jack assembly from all jacks and / or, for example, a single jack assembly within a jack assembly may be possible. However, the device is not necessarily designed as a pressure sensor.

[0016] It is therefore also advantageous that at least one pressure sensor is provided which detects a system pressure dependent on the delivery pressure of the hydraulic pump, and that the control device is designed to determine by means of the detected system pressure whether the unloaded state of the first jacking support arrangement exists or not and / or whether the state in which the first jacking support arrangement is lifted freely exists or not.

[0017] It is advantageous that the control device is designed to determine, by means of a temporal progression of the measured values ​​of the motor current associated with the first jacking support arrangement, whether the unloaded state of the first jacking support arrangement exists or not, and / or that the control device is designed to determine, by means of a temporal progression of the measured values ​​of the motor current associated with the first jacking support arrangement, whether the state in which the first jacking support arrangement is lifted freely exists or not. In this embodiment, the states can also be detected without the corresponding use of a pressure sensor. However, a pressure sensor can still be provided for other purposes, for example to prevent overloading of the jacking support device.

[0018] It is advantageous for the control device to be configured to maintain a motor voltage of an electric motor at at least a specific motor voltage and to record at least some of the measured values ​​used to determine the first axle load of the recreational vehicle at the first axle unit simultaneously with controlling the electric motor with the specific motor voltage. The motor voltage can be controlled, in particular regulated, via pulse width modulation (PWM), for example.

[0019] It is advantageous that the control device is configured to reduce the motor voltage of an electric motor to a specific reduced motor voltage and to record at least some of the measured values ​​used to determine the first axle load of the recreational vehicle at the first axle unit simultaneously with the electric motor being controlled with the reduced motor voltage. This allows a lower flow rate of the hydraulic fluid to be achieved, at least for the measurement, which can improve the accuracy of the weight measurement. In particular, this can reduce the influence of the viscosity of the hydraulic fluid.In a preferred embodiment, in the case of a weighing process, the entire lifting process from the unloaded state to the freely lifted state takes place with the reduced motor voltage, while for another lifting operation in which no weight measurement takes place, a higher, conventional motor voltage is used instead of the reduced motor voltage. This allows the lifting process to be optimized depending on the operating mode, once with regard to the accuracy of the vehicle's weight measurement and once with regard to rapid raising or lowering of the vehicle. In another preferred embodiment, a higher motor voltage can be used between the measurements, in particular during the pure lifting process, as part of a weight measurement in order to lift the vehicle more quickly and thus reduce the overall duration of the weighing process.

[0020] It is therefore advantageous in a corresponding manner that the control device is designed to maintain a speed of an electric motor at at least a specific speed and to record at least some of the recorded measured values, which serve to determine the first axle load of the recreational vehicle at the first axle unit, simultaneously with controlling the electric motor at the specific speed. It is therefore also advantageous that the control device is designed to reduce a speed of an electric motor to a specific reduced speed and to record at least some of the recorded measured values, which serve to determine the first axle load of the recreational vehicle at the first axle unit, simultaneously with controlling the electric motor at the reduced speed.

[0021] It is advantageous that exactly one electric motor is provided for exactly one hydraulic pump. This enables a design in which all of the jacks can be controlled with just one hydraulic pump. This also simplifies the recording of the measured values. The control device can then be designed such that the measured values ​​of the motor current of exactly one electric motor are recorded, with an assignment being made to the respective jack arrangement that is controlled or the respective jack that is controlled. It is therefore also advantageous that exactly one electric motor is provided for exactly one hydraulic pump and that the control device is designed to record the measured values ​​of the motor current of the electric motor.

[0022] It is advantageous that a second jacking support arrangement is provided which comprises at least one, preferably two, hydraulically actuated jacking supports, that the control device is designed to detect measured values ​​of a motor current assigned to the second jacking support arrangement for an unloaded state of the second jacking support arrangement, in which, in the mounted state, a vehicle weight attributable to a second axle unit of the recreational vehicle is supported via the wheels of the second axle unit, that the control device is designed to detect measured values ​​of the motor current assigned to the second jacking support arrangement for a state in which, during operation, at least one second axle unit of the recreational vehicle is lifted free such that the wheels of the second axle unit are lifted off the ground, and that the control device is designedDetermine a second axle load of the recreational vehicle on the second axle unit based on the recorded motor current measurements. This allows for the advantageous determination of two axle loads. The total vehicle weight can also be determined.

[0023] It is advantageous that the control device is configured to determine the second axle load of the recreational vehicle as a function of a differential value resulting from at least one measured value in the unloaded state and at least one associated measured value in the lifted state. Specifically in this configuration, the differential value formation results in compensation for environmental influences. In particular, the influence of an ambient or operating temperature can be fully or partially compensated.

[0024] It is advantageous for the control device to be configured to determine the second axle load of the recreational vehicle based on at least one vehicle-specific calibration value. One or more influencing variables can be taken into account. For example, mechanical influencing variables, such as the position of a jack relative to a wheel or axle or axle arrangement, can be fully or partially compensated.

[0025] It is advantageous for the control device to be configured to record measured values ​​of the motor current for the second jacking support arrangement as motor current calibration values ​​and to store these motor current calibration values ​​and / or a difference value resulting from the motor current calibration values ​​together with an externally measured second axle load. This allows for simple calibration. For example, an axle or axle arrangement can be lifted free for this purpose in order to store the values ​​for the jacking support arrangement with which the lifting is carried out.

[0026] It is advantageous for the control device to be configured to store an at least partially externally determined conversion factor, which specifies a factor for converting a unit of a measured value of the motor current or a difference value between measured values ​​of the motor current into a weight unit, as a vehicle-specific calibration value for the second axle unit. This allows for a conversion with minimal computational and storage effort.

[0027] It is advantageous that at least one device is provided which detects the current state of the second jack support arrangement during operation, and that the control device is designed to determine, by means of the detected state of the second jack support arrangement, whether the unloaded state of the second jack support arrangement exists or not and / or whether the state in which the second jack support arrangement is lifted freely exists or not. Such a device can be implemented in particular by a pressure sensor which is preferably arranged centrally, in particular on the hydraulic pump. In particular, exactly one pressure sensor can be used here. In this case, the hydraulic pump can be used to control, in particular, the jack supports of a jack support arrangement together or each jack support individually. Preferably, all jack supports of a jack support arrangement are controlled in each case.For control and / or pressure measurement for each jack assembly, a selective hydraulic connection to the hydraulic pump can be implemented. Accordingly, a selective hydraulic connection to a jack assembly can be implemented if necessary. Depending on the design, selective selection of a jack assembly from all jacks and / or, for example, a single jack assembly within a jack assembly may be possible. However, the device is not necessarily designed as a pressure sensor.

[0028] It is therefore also advantageous that at least one pressure sensor is provided which detects a system pressure dependent on the delivery pressure of the hydraulic pump, and that the control device is designed to determine by means of the detected system pressure whether the unloaded state of the second jack assembly is present or not and / or whether the state in which the second jack assembly is lifted freely is present or not.

[0029] It is advantageous that the control device is designed to determine, by means of a temporal progression of the measured values ​​of the motor current assigned to the second jack support arrangement, whether the unloaded state of the second jack support arrangement exists or not. It is also advantageous that the control device is designed to determine, by means of a temporal progression of the measured values ​​of the motor current assigned to the second jack support arrangement, whether the state in which the second jack support arrangement is lifted freely exists or not. In this embodiment, the states can also be detected without the corresponding use of a pressure sensor. However, a pressure sensor can still be provided for other purposes, for example to prevent overloading of the jack support device.

[0030] It is advantageous for the control device to be configured to maintain a motor voltage of an electric motor at at least a specific motor voltage and to record at least some of the measured values ​​used to determine the second axle load of the recreational vehicle at the second axle unit simultaneously with controlling the electric motor with the specific motor voltage. The motor voltage can be controlled, in particular regulated, via pulse width modulation (PWM), for example.

[0031] It is advantageous that the control device is configured to reduce the motor voltage of an electric motor to a specific reduced motor voltage and to record at least some of the measured values ​​used to determine the second axle load of the recreational vehicle at the second axle unit simultaneously with the electric motor being controlled with the reduced motor voltage. This allows a lower flow rate of the hydraulic fluid to be achieved, at least for the measurement, which can improve the accuracy of the weight measurement. In particular, this can reduce the influence of the viscosity of the hydraulic fluid.In a preferred embodiment, in the case of a weighing process, the entire lifting process from the unloaded state to the freely lifted state takes place with the reduced motor voltage, while for another lifting operation in which no weight measurement takes place, a higher, conventional motor voltage is used instead of the reduced motor voltage. This allows the lifting process to be optimized depending on the operating mode, once with regard to the accuracy of the vehicle's weight measurement and once with regard to rapid raising or lowering of the vehicle. In another preferred embodiment, a higher motor voltage can be used between the measurements, in particular during the pure lifting process, as part of a weight measurement in order to lift the vehicle more quickly and thus reduce the overall duration of the weighing process.

[0032] It is advantageous for the control device to be configured to maintain the speed of an electric motor at at least one specific speed and to simultaneously capture at least some of the acquired measured values, which serve to determine the second axle load of the recreational vehicle at the second axle unit, while controlling the electric motor at the specific speed. The control device can then be configured to capture the measured values ​​of the motor current of precisely one electric motor, with an assignment being made to the respective jack assembly being controlled or the respective jack being controlled.

[0033] Accordingly, it is advantageous that the control device is designed to reduce a speed of an electric motor to a specific reduced speed and to record at least some of the recorded measured values, which serve to determine the second axle load of the recreational vehicle on the second axle unit, simultaneously with a control of the electric motor at the reduced speed.

[0034] Depending on the design, the following disadvantages can be avoided and the features and advantages mentioned can be realized.

[0035] During operation, the motor current can vary, with measured values ​​of the current being recorded at different times. In a motor-pump unit, the motor current can also be referred to as the pump current. In one possible design, the pump current can therefore be considered, although other applications arise accordingly. For example, a gearbox can also be provided between the electric motor and the hydraulic pump.

[0036] To explain an exemplary embodiment, the pump flow can be observed, for example, over time as the jacks move downwards. During the idle travel, until the associated jack(s) reach the ground, the pump resistance can be essentially determined by the viscosity (η).

[0037] During the lifting process until the axle is free, an approximately linear increase in the pump flow can be observed. During further lifting in the already free-raised state, a maximum pump flow occurs when the jack stand(s) are extended far enough that the recreational vehicle is at least positioned above them. This means that there is a jump, for example, between a first measurement on the ground and a second measurement in the free-raised state or in the course of the pump flow. The jump between the lower value and the upper value then corresponds to the weight in relation to the jack stand(s). Through calibration, the difference value corresponding to the jump can indicate a weight on an assigned axle arrangement.Since viscosity affects the pump load equally both in the unloaded state, when the recreational vehicle is on the ground, and in the free-lifted state (and in this context also during "further lifting"), the influence of viscosity is compensated. This means that viscosity changes that occur, for example, due to different outside or operating temperatures are already compensated.

[0038] Although viscosity may increase with pressure, this can also cancel itself out and is then no longer a noticeable influence. The correlation between the temperature dependence of viscosity and the pressure dependence is generally negligible. The main influencing factor is then the temperature dependence of viscosity. However, this is already compensated for by evaluating the jump between the upper and lower values.

[0039] It is also conceivable, however, that the change in viscosity is at least approximately measured from the lower current value. In the respective application area, a further increase in accuracy may then be possible. If necessary, measured values ​​for the motor speed and / or the motor voltage, in particular a measurement of the voltage drop, can also be taken into account. The product of current and voltage, i.e., the motor power, can also be considered to further improve accuracy. Furthermore, in addition to the current, the motor speed can also be considered as a factor.

[0040] In a preferred embodiment, the voltage of the electric motor is electronically controlled. The voltage is then, in particular, independent of the vehicle electrical system voltage. Furthermore, the voltage of the electric motor is preferably kept constant. This means that the same voltage is always provided. Since the voltage factor does not change, its influence does not need to be considered, or changes in it need not be taken into account.

[0041] In an advantageous embodiment, the entire weighing process is carried out at a reduced speed. This reduces the influence of viscosity, since the viscosity influence increases with the volume flow of the hydraulic fluid. At standstill, the change in viscosity no longer has any influence. Therefore, to further reduce the influence of viscosity, the weighing section, at least in the lower and upper regions of the line determined by the temporal progression of the pump flow, or even the entire process, can be carried out at the lowest possible travel speed.

[0042] In a further development, for example, it is possible to briefly travel at two different speeds only during the free travel of the jack(s), i.e., in the unloaded state, in order to determine information about the viscosity from the differential current. This can serve to further increase accuracy.

[0043] One possible configuration for the weighing process is as follows. The weight of recreational vehicles or special vehicles, especially mobile homes, can be determined using a hydraulic jack assembly by measuring the pump current while the respective axle or axle assembly is being lifted free, with the current consumption being used as the weight characteristic. The current consumption can increase proportionally to the load.

[0044] In particular, the following possible disturbances may occur: temperature, oil viscosity, aging of the motor and permanent magnets, friction, and the specific positioning of the supports on the vehicle. One or more of these disturbances and / or one or more other disturbances may occur.

[0045] To completely or partially eliminate such disturbances, a reference current measurement is performed and stored during the process in the no-load state. Further compensation for the viscosity disturbance is preferably achieved by significantly reducing the motor speed during the weighing process. This significantly reduces friction losses at hydraulic throttle points to improve the quality of the measurement results. The axle is then lifted free, and a current measurement is also performed. The delta (the difference) between the two current measurements is preferably used to determine the weight. In one possible design, the delta between the two current measurements is equivalent to the support force.

[0046] Each vehicle is preferably calibrated individually after initial assembly so that mechanical influences such as the position of the support relative to the wheel can be eliminated. In addition, a vehicle-specific conversion factor for current to weight is preferably stored. This vehicle-specific factor is preferably determined by weighing on an external scale. The determined weight is then preferably assigned to the current measured when the axle is lifted free.

[0047] A pressure or force sensor integrated into the system is no longer required for weight determination. It can still be included in a possible design, but then preferably serves only to detect the position of an extension and retraction limit stop and / or to detect ground contact of the supports, or for other purposes, such as an overpressure protection device to protect against overload.

[0048] The unloaded state can be characterized by the failure path of the respective jack until it reaches the ground.

[0049] Between the unloaded state and the free-lifted state, there is usually another state in which the recreational vehicle is lifted while the wheels of the respective axle unit are in contact with the ground.

[0050] The measurements can therefore be performed at a reduced speed compared to the speed possible with power or used during lifting, over at least a period of time / distance in the unloaded / loaded state, especially during idle travel. Since viscosity is a quadratic factor in the flow velocity, this results in further optimization with regard to the accuracy of determining the respective axle load.

[0051] The same speed can be used in free stroke or idle travel. In particular, the reduced speed can be used in the entire free stroke or idle travel.

[0052] Regardless of the number of electric motors, the voltage of at least one electric motor can be reduced.

[0053] Depending on the design, the voltage of the electric motor or the speed of the electric motor can be stabilized. The controller can also enable different operating modes, allowing weight determination with stabilized voltage and / or stabilized speed.

[0054] Further advantages and details of the invention are explained in more detail with reference to the exemplary embodiment illustrated in the schematic figures. Herein: Fig. 1 a recreational vehicle with a jack device according to an embodiment in a schematic representation in the freely raised state, wherein a view from the side is shown; Fig. 2 is a partial schematic representation of the jack device of the recreational vehicle, showing, by way of example, a front jack arrangement with two jacks, which is mounted near a front axle, and a rear jack arrangement with two jacks of the Fig. 1, mounted near a rear axle, and showing further elements of the jacking device, such as a hydraulic pump and an electric motor for driving the hydraulic pump, which are hydraulically connected to the jacking supports; Fig. 3 that in Fig. 1 recreational vehicle shown in the unloaded state of the jacks; Fig. 4 a diagram showing the time course of a motor current of the Fig. 2 shows a schematic representation of the electric motor shown during at least one weighing process according to a possible embodiment; and Fig. 5 a diagram showing the time course of a motor current of the Fig. 2 shows a schematic representation of the electric motor shown during two weighing processes with different viscosities of a pressure fluid according to a possible embodiment.

[0055] Fig. Figure 1 shows a recreational vehicle 1 with a jack support device 2 according to an exemplary embodiment in a schematic representation, depicting a side view. The recreational vehicle 1 can be configured, in particular, as a mobile home or caravan. The recreational vehicle 1 can be configured, in particular, as a camper van. The jack support device 2 is particularly suitable for such recreational vehicles 1.

[0056] The recreational vehicle 1 has a chassis 3. The jack support device 2 can be connected to the chassis 3 as part of series production. However, the jack support device 2 can also be designed as a retrofittable jack support device 2 that can be subsequently installed in an already registered recreational vehicle 1.

[0057] In this exemplary embodiment, the recreational vehicle 1 has a first axle 4 and a second axle 5. Here, the first axle 4 and the second axle 5 are preferred embodiments for a first axle unit 4' and a second axle unit 5'. In a modified configuration, at least one axle unit 4', 5' can also be designed as a multiple axle, in particular a double axle. In this exemplary embodiment, the first axle 4 is the front axle 4 or front axle 4. The second axle 5 is the rear axle 5 or rear axle 5.

[0058] The jack support device 2 comprises a first jack support arrangement 6 and a second jack support arrangement 7. The first jack support arrangement 6 is the front jack support arrangement 6 in this exemplary embodiment. The second jack support arrangement 7 is the rear jack support arrangement 7 in this exemplary embodiment.

[0059] The design of the recreational vehicle 1 and the design of the jack device 2 are described below with reference to the Fig. 2 further described.

[0060] Fig. Figure 2 shows a partial, schematic representation of the jack support device 2 of the recreational vehicle 1. In this exemplary embodiment, the front jack support assembly 6 has two jack supports 8, 9 mounted near the front axle 4. Furthermore, the rear jack support assembly 7 in this exemplary embodiment has two jack supports 10, 11 mounted near the rear axle 5.

[0061] The jacks 8, 9, 10, 11 are connected to a switching unit 13 of the jack device 2 via hydraulic lines 12A, 12B, 12C, 12D. The switching unit can have at least one electrohydraulic switching valve. This allows the jacks 8, 9, 10, 11 to be controlled individually and / or in pairs. In particular, the jacks 8, 9 of the front jack assembly 6 can be controlled in pairs. Accordingly, the jacks 10, 11 of the rear jack assembly 7 can be controlled in pairs. In principle, it is also conceivable for all jacks 8, 9, 10, 11 to be controlled jointly, at least in one operating mode.

[0062] The jack support device 2 comprises a hydraulic pump 15 and an electric motor 16, which serves to drive the hydraulic pump 15. The hydraulic pump 15 delivers hydraulic pressurized fluid from a tank 17 to the switching unit 13. In this exemplary embodiment, the switching unit 13 has a return line 18, via which hydraulic pressurized fluid can be returned to the tank 17. Depending on the design, the hydraulic pump 15 can deliver in one or both directions. Accordingly, the jack supports 8, 9, 10, 11 can be actuated in one direction, i.e., for extension, or in both directions, i.e., for retraction and extension.

[0063] The electric motor 16 serves to at least indirectly drive the hydraulic pump 15. In this exemplary embodiment, the electric motor 16 directly drives the pump 15. However, the electric motor can also drive the pump 15, for example, via a transmission.

[0064] In a modified embodiment, it is also conceivable to provide multiple pumps 15. For example, one pump can be provided for the jacks 8, 9 of the first jack assembly 6, while another pump is provided for the jacks 10, 11 of the second jack assembly 7. A separate electric motor can then be provided for each pump. However, preferably, exactly one hydraulic pump 15 and exactly one electric motor 16 are provided for the hydraulic pump 15.

[0065] A control device 20 serves to at least indirectly control the electric motor 16. In this exemplary embodiment, the control device 20 controls the electric motor 16 with a voltage U. The voltage U can be regulated, for example, via pulse width modulation (PWM).

[0066] During operation, a motor current I flows through the electric motor 16, which depends on the load on the pump 15. If the voltage U is kept constant, then changes in the motor current I indicate changes in the load on the pump 15. In a modified embodiment, however, the control device 20 can also take the instantaneous voltage U into account.

[0067] The jack device 2 can have a pressure sensor 30. The control device 20 can detect a pressure p measured by the pressure sensor 30. Furthermore, in one possible embodiment, the control device can detect a rotational speed D of the electric motor 16 (M).

[0068] The design of the recreational vehicle 1 and the design of the jack device 2 are described below with reference to Fig. 3 further described.

[0069] Fig. 3 shows that in Fig. 1 shows the recreational vehicle 1 in the unloaded state of the jacks 8, 9, 10, 11. In contrast, Fig. 1 shows the recreational vehicle 1 in an extended state of the jacks 8, 9, 10, 11, in which the recreational vehicle 1 is freely raised on both axles 4, 5. For an initial measurement of the motor current, for example, the electric motor 16 can be operated at a reduced speed while the unloaded state 102, 104 initially exists. The initial measurement can therefore be taken before one of the jacks 8, 9, 10, 11 touches the ground.

[0070] The recreational vehicle 1 has wheels 40 on the first axle unit 4', i.e., in this embodiment, on the first axle 4, of which only one wheel 40 is visible. The recreational vehicle 1 has wheels 41 on the second axle unit 5', i.e., in this embodiment, on the second axle 5, of which only one wheel 41 is visible.

[0071] In the unloaded state of the jacks 8, 9, 10, 11, the vehicle weight is supported at the front partially by the first axle 4, with the wheels 40 touching the ground 42, and at the rear partially by the second axle 5, with the wheels 41 touching the ground 42. In the freely raised state 106, 108, the wheels 40, 41 each have no contact with the ground 42.

[0072] In one possible embodiment, during one process, a free lift on the first axle 4 can be carried out in such a way that the wheels 40 have no contact with the ground 42 and, at the same time, the wheels 41 are on the ground 42 and the jacks 10, 11 of the second jack assembly 7 have no contact with the ground 42. Furthermore, in one possible embodiment, during another process, a free lift on the second axle 5 can be carried out in such a way that the wheels 41 have no contact with the ground 42 and, at the same time, the wheels 40 are on the ground 42 and the jacks 8, 9 of the first jack assembly 6 have no contact with the ground 42.

[0073] In one possible embodiment, free lifting can be carried out in such a way that all wheels 40, 41 have no contact with the ground 42 at the same time.

[0074] The jack support device 2 can be operated by a user via an operating device 31. For example, the operating device 31 can be designed as a handheld device, in particular a mobile phone. Software adapted to the jack support device, in particular in the form of an app downloaded via the Internet, can be installed on the operating device 31. The control device can also be partially implemented via the software on the operating device 31.

[0075] The design of the recreational vehicle 1 and the design of the jack device 2 are described below with reference to Fig. 4 further described.

[0076] Fig. 4 shows a diagram showing the time course of a motor current of the Fig. 2 during at least one weighing process according to a possible embodiment in a schematic representation. Here, a time profile 100 of the motor current I for an actuation of the pump 15 to raise the jacks 8, 9 of the first jack assembly 6 and a time profile 120 of the motor current I for an actuation of the pump 15 to raise the jacks 10, 11 of the second jack assembly 7 are considered. For illustration, a case is shown in which the recreational vehicle 1 is subjected to a greater load on the rear axle 5 than on the front axle 4. For simplification, it is assumed that the time profiles 100, 120 begin at the same level 121 of the motor current I in the unloaded state.However, in the case of the rear axle 5, the motor current I reaches a level 122 corresponding to the time curve 120, which is higher than the level 123 corresponding to the curve 100 on the front axle 4, since the rear axle is more heavily loaded.

[0077] The control device 20 records measured values ​​101 of a motor current I assigned to the first jack support arrangement 6 for an unloaded state 102 of the first jack support arrangement 6. Furthermore, the control device 20 can record measured values ​​103 of a motor current I assigned to the second jack support arrangement 7 for an unloaded state 104 of the second jack support arrangement 7. The recording of the measured values ​​101, 103 can take place during a joint weighing process in which all jack supports 8, 9, 10, 11 are temporarily extended together. In this case, only the front jack support arrangement 6 or only the rear jack support arrangement 7 can be actuated by the pump 15 for a certain period of time in order to record the measured value 101 or the measured value 103, respectively.

[0078] However, the recording of the measured values ​​101, 103 can also take place in separate weighing processes at different times, so that in a preferred embodiment, a joint extension of only the jacks 8, 9 of the first jack arrangement 6 and, separately therefrom, a joint extension of only the jacks 10, 11 takes place, as in Fig. 4 is illustrated.

[0079] The control device 20 also records measured values ​​105 of the motor current I assigned to the first jack support arrangement 6 for a state 106 in which the first jack support arrangement 6 is raised, in which at least the first axle unit 4' of the recreational vehicle 1 is raised. The control device 20 can further record measured values ​​107 of the motor current I assigned to the second jack support arrangement 7 for the state 108 in which the second jack support arrangement 7 is raised, in which at least the second axle unit 5' of the recreational vehicle 1 is raised.

[0080] The measured values ​​101, 103, 105, 107 can thus be recorded during one or more processes for extending the jacks 8, 9, 10, 11 and for raising the recreational vehicle 1. The control device 20 determines a first axle load 114 of the recreational vehicle 1 on the first axle unit 4' and a second axle load 115 of the recreational vehicle 1 on the second axle unit 5' depending on the recorded measured values ​​101, 103, 105, 107 of the motor current I. In this case, the axle loads 114, 115 can also be determined separately from one another, each with a process for recording the measured values ​​101, 105 and the measured values ​​103, 107, respectively. When the axle loads 114, 115 are recorded together, the recreational vehicle 1 is lifted freely on both axles 4, 5 at the two upper levels 122, 123 at the same time to record each measured value 105, 107.

[0081] The control device 20 determines the first axle load 114 of the recreational vehicle 1 and the second axle load 115 of the recreational vehicle 1 as a function of difference values ​​124, 125, which each result from at least one measured value 101, 103 in the unloaded state 102, 104 and at least one associated measured value 105, 107 in the raised state 106, 108. In a preferred embodiment, the axle loads 114, 115 at least approximately indicate the respective proportion of the total mass of the recreational vehicle 1 attributable to the respective axle 114, 115. Furthermore, the sum of the axle loads 114, 115 indicates at least an approximate value for the total mass of the recreational vehicle 1.

[0082] The axle loads 114, 115 and, if applicable, the total mass can be displayed on the control unit 30. A user can then check the load of the recreational vehicle 1.

[0083] In one possible embodiment, exactly one measured value 101, 103, 105, 107 can be recorded for each axle unit 4', 5' in the unloaded state 102, 104 and in the free-lifted state 106, 108. However, in a modified embodiment, multiple measured values ​​can also be recorded in order to improve reliability and / or accuracy, for example, by averaging.

[0084] Furthermore, by recording the temporal profiles 100, 120, for example, with a fine temporal resolution, it is possible to determine whether the unloaded state 102, 104 or the free-lifted state 106, 108 is present. In this case, a pressure sensor 30 is not required.

[0085] Furthermore, electrical elements, in particular electrical contact switches, can also be used to detect whether the jacks 8, 9, 10, 11 are at least largely retracted, so that the unloaded state 102, 104 exists, or whether the jacks 8, 9, 10, 11 are at least extended far enough to create a freely raised state 106, 108. This also eliminates the need for a pressure sensor 30.

[0086] The control device 20 can determine the first axle load 114 of the recreational vehicle 1 and the second axle load 115 of the recreational vehicle 1 depending on at least one vehicle-specific calibration value. The vehicle-specific calibration value can be used to take into account, in particular, different equipment configurations. Furthermore, tolerance errors or deviations that may arise, for example, due to the mounting positions of the jacks 8, 9, 10, 11 on the chassis 3 can be taken into account.

[0087] The control device 20 can record measured values ​​101, 103, 105, 107 of the motor current I for the first jack support assembly 6 and the second jack support assembly 7 as motor current calibration values ​​and store these motor current calibration values, or the difference values ​​resulting from the motor current calibration values, together with an externally measured first axle load and an externally measured second axle load. The external measurement can be performed, for example, using a vehicle scale.

[0088] For example, measured calibration values ​​and the corresponding externally measured axle loads enable the conversion of the subsequently determined differential values ​​124, 125 into axle loads 114, 115. A proportional conversion can be performed with or without a non-zero reference value. However, other, particularly non-linear, functions can also be stored for the conversion. One or more vehicle-specific parameters, particularly calibration values, can be stored here.

[0089] The control device 20 can store an at least partially externally determined conversion factor, which specifies a factor for converting a unit of a measured value 101, 103, 105, 107 of the motor current I or a difference value 124, 125 from measured values ​​101, 103, 105, 107 of the motor current I into a weight unit, as a vehicle-specific calibration value. The external determination can relate at least to a measurement of the total mass of the recreational vehicle 1 or a measurement of the axle loads of the recreational vehicle 1 using a vehicle scale.

[0090] In certain possible embodiments, at least one device 30 can be provided which, during operation, detects the current state 102, 106 of the first jack support arrangement 6 and the current state 104, 108 of the second jack support arrangement 7. Such a device 30 can be designed as a pressure sensor 30, as an electrical contact switch, or the like. The control device 20 can determine, by means of the detected state 102, 106 of the first jack support arrangement 6 and the detected state 104, 108 of the second jack support arrangement 7, whether the unloaded state 102 of the first jack support arrangement 6 exists and / or whether the unloaded state 104 of the second jack support arrangement 7 exists. Accordingly, the control device 20 can additionally or alternatively determine whether the state 106 in which the first jacking support arrangement 6 is raised freely and / or whether the state 108 in which the second jacking support arrangement 7 is raised freely is present.

[0091] If the at least one device 30 is designed as a pressure sensor 30, then in a preferred embodiment, a system pressure p dependent on the delivery pressure of the hydraulic pump 15 is detected. The control device 20 then uses the detected system pressure p to determine whether the unloaded state 102 of the first jack assembly 6 exists and / or whether the unloaded state 104 of the second jack assembly 7 exists. Additionally or alternatively, the control device 20 then determines whether the state 106 in which the first jack assembly 6 is lifted free and / or whether the state 108 in which the second jack assembly 7 is lifted free.

[0092] In a further possible embodiment, the control device 20 determines whether the unloaded state 102 of the first jack support arrangement 6 exists by means of a time profile 100 of the recorded measured values ​​101, 105 of the motor current I assigned to the first jack support arrangement 6. Additionally or alternatively, the control device 20 determines whether the unloaded state 104 of the second jack support arrangement 7 exists by means of a time profile 120 of the recorded measured values ​​103, 107 of the motor current I assigned to the second jack support arrangement 7. Additionally or alternatively, the control device 20 determines whether the state 106 in which the first jack support arrangement 6 is lifted free is present by means of a time profile 100 of the recorded measured values ​​101, 105 of the motor current I assigned to the first jack support arrangement 6.Additionally or alternatively, the control device 20 determines by means of a time profile 120 of the measured values ​​103, 107 of the motor current I assigned to the second jack support arrangement 7 whether the state 108 in which the second jack support arrangement 7 is lifted freely is present.

[0093] The control device 20 can maintain a motor voltage U of the electric motor 16 at at least a specific motor voltage U and record at least some of the recorded measured values ​​101, 103, 105, 107, which serve to determine the first axle load 114 of the recreational vehicle 1 on the first axle unit 4' and the second axle load 115 of the recreational vehicle 1 on the second axle unit 5', simultaneously with a control of the electric motor 16 with the specific motor voltage U.

[0094] Additionally or alternatively, the control device 20 can reduce a motor voltage U of an electric motor 16 to a specific reduced motor voltage U and record at least some of the recorded measured values ​​101, 103, 105, 107, which serve to determine the first axle load 114 of the recreational vehicle 1 on the first axle unit 4' and the second axle load 115 of the recreational vehicle 1 on the second axle unit 5', simultaneously with a control of the electric motor 16 with the reduced motor voltage U.

[0095] Fig. 5 shows a diagram showing the time course 100, 100' of a motor current of the Fig.2 during two weighing processes with different viscosities of a pressure fluid according to a possible embodiment, in a schematic representation. To simplify the illustration, only the time profile 100 or the time profile 100' of the motor current I for the front axle 4 is shown. The situation at the rear axle 5 arises in a corresponding manner.

[0096] For the sake of explanation, it is assumed that the temporal progression 100 corresponds to a progression at a comparatively low temperature of the hydraulic fluid (pressure fluid). The temporal progression 100' then corresponds to a progression at a comparatively high temperature of the pressure fluid. This can lead to a change in viscosity. To illustrate this, the viscosity is higher in the comparatively cold application than in the warm application. For example, the temporal progression 100 can occur in more northern latitudes in the northern hemisphere, and the temporal progression 100' can occur in more southern latitudes in the northern hemisphere, so that such a change can occur even during a journey.

[0097] The two levels 121 and 123 of the time profile at low temperature are each higher than the corresponding levels 121' and 123' of the time profile at high temperature, since the load on pump 15 depends on the viscosity. However, with the same load on recreational vehicle 1, the resulting difference values ​​124, 124' are at least approximately equal, since the temperature influence is at least approximately compensated by the subtraction.

[0098] Preferably, the hydraulic fluid (pressure fluid) used is a pressure fluid whose viscosity has a low dependence on temperature.

[0099] In a corresponding manner, other influences on the viscosity of the hydraulic fluid can be at least approximately compensated.

[0100] The weighing process for determining the axle loads 114, 115 can be carried out with a constant or variable voltage U of the electric motor 16. The weighing process can be carried out with a constant or variable speed D of the pump 15. In particular, the voltage U or the speed D can be reduced in order to record the measured values ​​101, 103, 105, 107. Furthermore, the entire weighing process can also be carried out with a reduced voltage U or a reduced speed D compared to another operating mode used for free lifting of the recreational vehicle 1. Free lifting without weight determination can then be carried out in a shorter time.

[0101] When determining the weight, the voltage U and / or the speed D can be taken into account if necessary.

[0102] The invention is not limited to the described embodiments.

Claims

[1] Jack device (2) for a recreational vehicle (1), in particular a mobile home or a caravan, with at least one first jack arrangement (6) which comprises at least one, preferably two, hydraulically actuated jacks (8, 9), at least one hydraulic pump (15) which serves to actuate the at least one jack (8, 9), at least one electric motor (16) which serves to at least indirectly drive the hydraulic pump (15) and through which a motor current (I) flows during operation, which depends on the load of the pump (15), and a control device (20) which serves to at least indirectly control the at least one electric motor (16), characterized bythat the control device (20) is designed to detect measured values ​​(101) of a motor current (I) assigned to the first jack support arrangement (6) for an unloaded state (102) of the first jack support arrangement (6), in which, in the mounted state, a vehicle weight attributable to a first axle unit (4') of the recreational vehicle (1) is supported via the wheels (40) of the first axle unit (4'), that the control device (20) is designed to detect measured values ​​(105) of the motor current (I) assigned to the first jack support arrangement (6) for a state (106) in which, during operation, at least one first axle unit (4') of the recreational vehicle (1) is raised such that the wheels (40) of the first axle unit (4') are lifted off the ground (42), and that the control device (20) is designed,to determine a first axle load (114) of the recreational vehicle (1) on the first axle unit (4') as a function of the recorded measured values ​​(101, 105) of the motor current (I). [2] Jack device according to claim 1, characterized by in that the control device (20) is designed to determine the first axle load (114) of the recreational vehicle (1) as a function of a difference value (124) which results from at least one measured value (101) in the unloaded state (102) and at least one associated measured value (105) in the freely raised state (106). [3] Jack device according to claim 1 or 2, characterized by that the control device (20) is designed to determine the first axle load (114) of the recreational vehicle (1) as a function of at least one vehicle-specific calibration value. [4] Jack device according to claim 3, characterized byin that the control device (20) is designed to record measured values ​​(101, 105) of the motor current (I) for the first jack assembly (6) as motor current calibration values ​​and to store these motor current calibration values ​​and / or a difference value resulting from the motor current calibration values ​​together with an externally measured first axle load. [5] Jack device according to claim 3 or 4, characterized by in that the control device (20) is designed to store an at least partially externally determined conversion factor, which indicates a factor for converting a unit of a measured value (101, 105) of the motor current (I) or a difference value (124) from measured values ​​(101, 105) of the motor current (I) into a weight unit, as a vehicle-specific calibration value for the first axle unit (4'). [6] Jack device according to one of claims 1 to 5, characterized by , a) that at least one device (30) is provided which detects the current state of the first jacking support arrangement (6) during operation, and that the control device (20) is designed to determine, by means of the detected state of the first jacking support arrangement (6), whether the unloaded state (102) of the first jacking support arrangement (6) is present or not, or whether the state (106) lifted freely by the first jacking support arrangement (6) is present or not, and / or b) that at least one pressure sensor (30) is provided which detects a system pressure (p) dependent on the delivery pressure of the hydraulic pump, and that the control device (20) is designed to determine by means of the detected system pressure (p) whether the unloaded state (102) of the first jack assembly (6) is present or not, or whether the state (106) lifted freely by the first jack assembly (6) is present or not. [7] Jack device according to one of claims 1 to 6, characterized by in that the control device (20) is designed to determine, by means of a time profile (100) of the measured values ​​(101, 105) of the motor current (I) recorded and assigned to the first jack support arrangement (6), whether the unloaded state (102) of the first jack support arrangement (6) is present or not, and / or in that the control device (20) is designed to determine, by means of a time profile (100) of the measured values ​​(101, 105) of the motor current (I) recorded and assigned to the first jack support arrangement (6), whether the state (106) in which the first jack support arrangement (6) is lifted free is present or not. [8] Jack device according to one of claims 1 to 7, characterized byin that the control device (20) is designed to maintain a motor voltage (U) of an electric motor (16) at at least one specific motor voltage (U) and to record at least some of the recorded measured values ​​(101, 105) which serve to determine the first axle load (114) of the recreational vehicle (1) on the first axle unit (4') at the same time as controlling the electric motor (16) with the specific motor voltage (U). [9] Jack device according to one of claims 1 to 8, characterized by in that the control device (20) is designed to reduce a motor voltage (U) of an electric motor (16) to a specific reduced motor voltage (U) and to record at least some of the recorded measured values ​​(101, 105), which serve to determine the first axle load (114) of the leisure vehicle (1) on the first axle unit (4'), simultaneously with a control of the electric motor (16) with the reduced motor voltage (U). [10] Jack device according to one of claims 1 to 9, characterized by in that the control device (20) is designed to maintain a rotational speed (D) of an electric motor (16) at at least one specific rotational speed (D) and to record at least some of the recorded measured values ​​(101, 105), which serve to determine the first axle load (114) of the recreational vehicle (1) on the first axle unit (4'), simultaneously with a control of the electric motor (16) at the specific rotational speed (D). [11] Jack device according to one of claims 1 to 10, characterized byin that the control device (20) is designed to reduce a rotational speed (D) of an electric motor (16) to a specific reduced rotational speed (D) and to record at least some of the recorded measured values ​​(101, 105), which serve to determine the first axle load (114) of the leisure vehicle (1) on the first axle unit (4'), simultaneously with a control of the electric motor (16) at the reduced rotational speed (D). [12] Jack device according to one of claims 1 to 11, characterized by that exactly one electric motor (16) is provided for exactly one hydraulic pump (15) or that exactly one electric motor (16) is provided for exactly one hydraulic pump (15) and that the control device (20) is designed to record the measured values ​​(101, 103, 105, 107) of the motor current (I) of the electric motor (16). [13] Jack device according to one of claims 1 to 12, characterized bythat a second jack stand arrangement (7) is provided, which comprises at least one, preferably two, hydraulically actuated jack stands (10, 11), that the control device (20) is designed to detect measured values ​​(103) of a motor current (I) assigned to the second jack stand arrangement (7) for an unloaded state (104) of the second jack stand arrangement (7), in which, in the mounted state, a vehicle weight proportionally attributable to a second axle unit (5') of the recreational vehicle (1) is supported via the wheels (41) of the second axle unit (5'), that the control device (20) is designed to detect measured values ​​(107) of the motor current (I) assigned to the second jack stand arrangement (7) for a state (108) in which, during operation, at least one second axle unit (5') of the recreational vehicle (1) is raised such that the wheels (41) of the second axle unit (5') are lifted from the ground (42),and that the control device (20) is designed to determine a second axle load (115) of the recreational vehicle (1) on the second axle unit (5') as a function of the detected measured values ​​(103, 107) of the motor current (I). [14] Jack device according to claim 13, characterized by , a) that the control device (20) is designed to determine the second axle load (115) of the recreational vehicle (1) as a function of a difference value (125) resulting from at least one measured value (103) in the unloaded state (104) and at least one associated measured value (107) in the freely raised state (108), and / or b) that the control device (20) is designed to determine the second axle load (115) of the recreational vehicle (1) as a function of at least one vehicle-specific calibration value, and / or c) that the control device (20) is designed to record measured values ​​(103, 107) of the motor current (I) for the second jack arrangement (7) as motor current calibration values ​​and to store these motor current calibration values ​​and / or a difference value resulting from the motor current calibration values ​​together with an externally measured second axle load, and / or d) that the control device (20) is designed to store an at least partially externally determined conversion factor, which indicates a factor for converting a unit of a measured value (103, 107) of the motor current (I) or a difference value (125) from measured values ​​(103, 107) of the motor current (I) into a weight unit, as a vehicle-specific calibration value for the second axle unit (5'). [15] Jack device according to claim 13 or 14, characterized by , a) that at least one device (30) is provided which detects the current state (104, 108) of the second jacking support arrangement (7) during operation, and that the control device (20) is designed to determine, by means of the detected state (104, 108) of the second jacking support arrangement (7), whether the unloaded state (104) of the second jacking support arrangement (7) is present or not, or whether the state (108) lifted freely by the second jacking support arrangement (7) is present or not, and / or b) that at least one pressure sensor (30) is provided which detects a system pressure (p) dependent on the delivery pressure of the hydraulic pump, and that the control device (20) is designed to determine by means of the detected system pressure (p) whether the unloaded state (104) of the second jack assembly (7) is present or not, or whether the state (108) in which the second jack assembly (7) is raised freely is present or not. [16] Jack device according to one of claims 13 to 15, characterized by , a) that the control device (20) is designed to determine, by means of a time profile (120) of the measured values ​​(103, 107) of the motor current (I) recorded and associated with the second jack support arrangement (7), whether the unloaded state (104) of the second jack support arrangement (7) is present or not, and / or b) that the control device (20) is designed to determine, by means of a time profile (120) of the measured values ​​(103, 107) of the motor current (I) recorded and associated with the second jack support arrangement (7), whether the state (108) in which the second jack support arrangement (7) is lifted free is present or not. [17] Jack device according to one of claims 13 to 16, characterized by , a) that the control device (20) is designed to maintain a motor voltage (U) of an electric motor (16) at at least one specific motor voltage (U) and to record at least some of the recorded measured values ​​(103, 107) that serve to determine the second axle load (115) of the recreational vehicle (1) on the second axle unit (5') simultaneously with a control of the electric motor (16) with the specific motor voltage (U), and / or b) that the control device (20) is designed to reduce a motor voltage (U) of an electric motor (16) to a specific reduced motor voltage (U) and to record at least some of the recorded measured values ​​(103, 107) that serve to determine the second axle load (115) of the recreational vehicle (1) on the second axle unit (5') simultaneously with a control of the electric motor (16) with the reduced motor voltage (U), and / or c) that the control device (20) is designed to maintain a rotational speed (D) of an electric motor (16) at at least one specific rotational speed (D) and to record at least some of the recorded measured values ​​(103, 107) that serve to determine the second axle load (115) of the recreational vehicle (1) on the second axle unit (5') simultaneously with a control of the electric motor (16) at the specific rotational speed (D), and / or d) that the control device (20) is designed to reduce a speed (D) of an electric motor (16) to a specific reduced speed (D) and to record at least some of the recorded measured values ​​(103, 107), which serve to determine the second axle load (115) of the recreational vehicle (1) on the second axle unit (5'), simultaneously with a control of the electric motor (16) at the reduced speed (D). [18] Recreational vehicle (1), in particular a mobile home and / or caravan, with a jack device (2) according to one of claims 1 to 17. [19] Method for controlling a jack device (2) for recreational vehicles (1), in particular mobile homes or caravans, which jack arrangement (2) comprises at least one first jack arrangement (6) which comprises at least one, preferably two, hydraulically actuated jacks (8, 9), at least one hydraulic pump (15) which serves to actuate the jacks (8, 9), at least one electric motor (16) which serves to at least indirectly drive the hydraulic pump (15) and through which a motor current (I) flows during operation, which depends on the load of the pump (15), and a control device (20) which serves to at least indirectly control the at least one electric motor (16), characterized bythat measured values ​​(101) of a motor current (I) assigned to the first jack support arrangement (6) for an unloaded state (102) of the first jack support arrangement (6), in which, in the mounted state, a vehicle weight attributable to a first axle unit (4') of the recreational vehicle (1) is supported via the wheels of the first axle unit (4'), are detected by means of the control device (20), that measured values ​​(105) of the motor current (I) assigned to the first jack support arrangement (6) for a state (106) raised by the first jack support arrangement (6), in which, during operation, at least one first axle unit (4') of the recreational vehicle (1) is raised such that the wheels of the first axle unit (4') are lifted off the ground, are detected by means of the control device (20), and that a first axle load (114) of the recreational vehicle (1) on the first axle unit (4') depending on the measured values ​​(101,105) of the motor current (I).

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