METHOD FOR TRACTION CONTROL OF A VEHICLE OR VEHICLE TRAILER

Description

[0001] The invention relates to a method for traction control of a vehicle combination. The vehicle combination comprises a towing vehicle and at least one trailer coupled to it. The towing vehicle is a wheeled vehicle. The towing vehicle is equipped with a sensor device arranged on a coupling element of a trailer hitch, wherein the sensor device measures a coupling force transmitted from a counter-coupling element of the trailer to the coupling element of the towing vehicle in all vehicle directions and outputs it as a force signal, wherein the coupling force effective in the respective vehicle direction is determined from these force signals in an evaluation unit connected to the sensor device and transmitted to an electronic control unit of the towing vehicle, and wherein the traction of the towing vehicle is adapted to the properties of the road surface by means of the control unit.

[0002] The towing vehicle of the vehicle combinations considered here is preferably a tractor, such as a tractor, intended for use in agriculture and forestry, and equipped at the rear or front of the vehicle with a coupling element in the form of a trailer hitch, such as a ball hitch or jaw hitch. The associated trailer can be a rigid drawbar trailer, a center-axle trailer, or a work implement, which is equipped with a counter-coupling element, such as a coupling socket or a drawbar eye, arranged on a rigid drawbar or suspension.Similarly, the towing vehicle of the vehicle combinations considered here may be a semi-trailer tractor used in agriculture and forestry, such as an agrotruck, with a fifth wheel coupling as the coupling element, and the associated trailer vehicle may be a semi-trailer with a support plate equipped with a kingpin as the counter coupling element.

[0003] In a vehicle combination of the described type, it is assumed that the towing vehicle is equipped with a sensor device on the coupling element of its trailer coupling device, by means of which a coupling force FX , FY , FZ transmitted from a counter coupling element of the trailer to the coupling element of the towing vehicle or a coupling force FX , -FY , -Fz transmitted in the opposite direction can be detected as a force signal in all three vehicle directions x, y, z.

[0004] German patent application DE 10 2018 106 856 A1 describes such a sensor device for a trailer hitch, which has several sensor elements, each attached to the webs of a measuring plate. The webs of the measuring plate are elastically deformed under load from the trailer hitch. The sensor elements can be load cells, strain gauges, or SAW elements (SAW = Surface Acoustic Wave). In a tractor, the measuring plate is preferably arranged between a vehicle-mounted bolt-on plate and a hitch bracket, to which the respective coupling element, in the form of a jaw-pin coupling or a ball coupling, is attached. The transmitted forces and moments in all or around all three vehicle directions x, y, z can be detected by means of the sensor elements of the measuring plate.

[0005] From DE 10 2019 124 281 A1, a fifth wheel coupling of a semi-trailer truck with a sensor device for detecting the forces transmitted from a coupled semi-trailer to the semi-trailer truck via the fifth wheel coupling is known. The fifth wheel coupling has a bearing block that can be attached to the vehicle frame, on which a coupling plate is pivotably mounted about a horizontal transverse axis. For this purpose, the bearing block has two laterally arranged webs, each with a bearing block eye, into which a damping element, connected to the coupling plate via a clamping element and a bearing insert, engages. According to a first embodiment of the sensor device, sensors, which can be strain gauges or piezoelectric elements, are arranged on an intermediate element that is positioned between the damping element and the bearing insert and is elastically deformed when loaded by a coupled semi-trailer.According to a second embodiment of the sensor device, the sensors are arranged on the bearing insert, which is elastically deformed when subjected to a load from a coupled semi-trailer.

[0006] US 2020 / 102009 A1 discloses a method and apparatus for determining a vehicle's reset position for launching and loading a boat using a trailer hitch load. An exemplary apparatus includes a data analyzer to determine, based on the trailer hitch load of a vehicle coupled to a trailer, a reset position for launching a boat, where the boat is floating on a body of water, and an instruction generator to instruct the vehicle's braking system to stop the vehicle at the reset position to launch the boat.An exemplary procedure involves determining, based on a trailer hitch load of a vehicle coupled to a trailer, a reversing position of the vehicle in order to launch a boat at a body of water where a boat coupled to the trailer is floating, and instructing a braking system of the vehicle to stop the vehicle at the reversing position in order to launch the boat.

[0007] A vehicle combination used in agriculture and forestry typically travels to its work sites via paved roads and tracks from a farm or vehicle depot. The tire pressures of both the towing vehicle and the trailer are set relatively high to ensure safe handling and minimal fuel consumption. For this purpose, any drive axles that can be coupled or uncoupled are disconnected, unless the trailer is heavily loaded. Additionally, any lift axles that can be raised or lowered are raised, and the air springs of non-driven air-sprung axles are deflated.When leaving a paved road or track, the rolling resistance of the vehicle combination increases significantly due to the soft or loose, and possibly vegetated, soil of fields, meadows, or forests, and the traction of the towing vehicle decreases considerably. This leads to increased fuel consumption and the risk of the vehicle combination getting stuck. However, depending on the technical specifications of the towing vehicle and the trailer, various measures can be taken to increase the traction of the towing vehicle. These measures reduce the rolling resistance of the vehicle combination and increase the traction of the towing vehicle, thereby lowering fuel consumption and preventing the vehicle combination from getting stuck.The measures to increase traction can be carried out manually by the driver of the towing vehicle when leaving paved roads and paths, or automatically in conjunction with an assessment of the surface being traveled on.

[0008] A well-known measure to increase the traction of a towing vehicle in off-road use is to engage a non-permanently driven drive axle of the towing vehicle, provided it is equipped with a switchable all-wheel drive, and / or to engage a drive axle of the trailer that is driven via the power take-off of the towing vehicle, provided it is designed as a driven axle trailer.

[0009] German patent DE 10 2007 028 277 A1 describes a motor vehicle with a switchable all-wheel drive and a traction control system. An associated control method provides that a spinning drive wheel of a permanently driven drive axle is braked if its drive slip value exceeds a first slip limit, and that a switchable drive axle is engaged if the drive slip value of the spinning drive wheel subsequently exceeds a second slip limit.

[0010] German patent application DE 10 2016 208 792 A1 discloses a method for controlling an all-wheel drive coupling of a motor vehicle with selectable all-wheel drive. The method provides that, by means of a satellite navigation system and a digital road map, the road ahead of the motor vehicle is determined, and a selectable drive axle is engaged if there is an increased risk of wheel slip on the road ahead and the all-wheel drive coupling should therefore be closed.

[0011] Another known measure to increase the traction of a towing vehicle is to raise a non-driven axle located adjacent to the towing vehicle's drive axle, if it is designed as a lift axle, or to deflate its air springs if it is air-sprung. These measures each increase the axle load and thus the traction of the towing vehicle's drive axle. The same effect can also be achieved by raising an axle of the trailer, provided it is designed as a lift axle, or by deflating its air springs if it is air-sprung. These measures increase the vertical load transferred from the trailer to the towing vehicle's coupling point, and thus the axle load of the towing vehicle's drive axle, which is typically located close to the coupling point.

[0012] German patent application DE 10 2008 054 044 A1 discloses a method for controlling a lift axle on a semi-trailer of a tractor unit. In a starting aid mode, the lift axle of the semi-trailer is raised to increase the vertical load transferred from the fifth wheel of the semi-trailer to the fifth wheel coupling of the tractor unit, thereby increasing the axle load and traction of the tractor unit's drive axle. The maximum permissible axle loads of the other axles of the semi-trailer are not exceeded when starting on paved surfaces, but may be exceeded when starting off-road.

[0013] A method for controlling the starting assistance of a semi-trailer truck according to DE 10 2004 010 561 A1 provides that the air springs of an air-sprung axle of the semi-trailer are vented in order to increase the vertical load transferred from the fifth wheel of the semi-trailer to the fifth wheel coupling of the tractor unit, and thus the axle load and the traction of the drive axle of the tractor unit. If the tractor unit has a correspondingly load-relieving axle, this axle is first relieved by venting its air springs before the axle of the semi-trailer is relieved by venting its air springs.

[0014] To reduce the rolling resistance of the vehicle combination and increase the traction of the towing vehicle, the tire pressure of both the towing vehicle and the trailer can be lowered, provided they are equipped with a tire pressure monitoring system. Lowering the tire pressure increases the contact patch of the tires, so the vehicle wheels sink less into the ground, thus reducing the rolling resistance of the vehicle combination and increasing the traction of the towing vehicle. As a positive side effect, the lower ground pressure of the vehicle tires also reduces soil compaction in fields, meadows, or forests.

[0015] German patent DE 20 2011 051 292 U1 describes a method for controlling a tire pressure control system of a vehicle or vehicle combination, in which a satellite navigation system and a digital road map are used to determine whether the vehicle or vehicle combination is currently on a paved road or off-road. Depending on the current driving position, the tire pressure control system is operated either in a road mode with higher tire pressures or in an off-road mode with lower tire pressures.

[0016] Furthermore, DE 10 2019 210 325 A1 discloses a method for controlling a tire pressure control system of a vehicle combination, in which the operating status of an implement coupled to a tractor unit is used to determine whether the vehicle combination is currently on a paved road or off-road. For example, if the coupled implement is a field sprayer with a laterally extendable and retractable spray boom, when the spray boom is extended, the system assumes that the vehicle combination is on a field, and the tire pressures are lowered accordingly. When the spray boom is retracted, the system assumes that the vehicle combination is traveling on a paved road, and the tire pressures are increased accordingly.

[0017] Furthermore, according to DE 697 18 290 T2, it is possible to switch the engine control of the drive motor and the transmission control of the drive transmission of a towing vehicle to characteristic curves that are intended for road use or for off-road use.

[0018] Since the known methods for traction control of a vehicle or vehicle combination do not determine the surface being driven on at all or only indirectly and therefore relatively imprecisely, the invention is based on the objective of providing a method for traction control of a vehicle combination of the type mentioned at the outset, with which the type or properties of the surface being driven on can be determined more directly than before and the traction of the vehicle or the towing vehicle can be adapted more precisely to this surface.

[0019] This problem is solved by a method that has the features of claim 1. Advantageous further developments of this method are defined in the dependent claims.

[0020] Accordingly, the invention relates initially to a method for traction control of a vehicle combination comprising a towing vehicle and at least one trailer coupled to it, wherein the towing vehicle is provided with a sensor device arranged on a coupling element of a trailer coupling device, wherein, by means of the sensor device, a coupling force FX, FY, FZ transmitted from a counter-coupling element of the trailer to the coupling element of the towing vehicle is measured in all vehicle directions x, y, z and output as a force signal, wherein, from these force signals, the coupling force FX, FY, Fz effective in the respective vehicle direction x, y, z is determined in an evaluation unit connected to the sensor device and transmitted to an electronic control unit of the towing vehicle, and wherein the traction of the towing vehicle is adapted to the properties of the surface driven on by means of the control unit.

[0021] To solve the given task, this method provides for the determination of the properties of the traversed surface based on the dynamics of the coupling forces FX, FY, Fz, such that in the evaluation unit the dynamic components are filtered out from successive sequences of the coupling forces FX, FY, Fz, that a characteristic value K Dyn, which characterizes the dynamics of the coupling forces FX, FY, Fz, is determined from these dynamic components of the coupling forces FX, FY, Fz and transmitted to the control unit, that in the control unit the characteristic value K Dyn is compared with a stored limit value K Dyn_Gr, and that at least one measure to increase the traction of the towing vehicle is carried out if the characteristic value K Dyn has exceeded the limit value K Dyn_Gr (K Dyn > K Dyn_Gr), and that the at least one measure to increase traction is reversed.when the characteristic value K Dyn has again fallen below the limit value K Dyn_Gr (K Dyn < K Dyn_Gr ).,

[0022] The method according to the invention assumes that the coupling forces FX, FY, FZ transmitted from the trailer to the coupling element of the towing vehicle exhibit significantly greater fluctuations and vibrations during off-road driving due to the uneven terrain than during driving on paved roads or paths due to the relatively smooth road surface. Thus, the nature of the terrain traversed by the vehicle combination can be determined directly and relatively accurately based on the dynamics of the coupling forces FX, FY, FZ, and a distinction can be made between road driving and off-road driving.

[0023] The method according to the invention can also be advantageously operated on a solo vehicle designed as a wheeled vehicle. Such a solo vehicle is operated either generally or only as needed without an attached trailer. A solo vehicle can be connected at the rear via a trailer hitch, for example, to an agricultural or forestry implement or machine, or be permanently connected. According to one embodiment, these implements or machines may not have their own chassis, so that they are raised off the ground when not in use.

[0024] Agricultural or forestry implements or machinery attached to the vehicle also generate forces in all three spatial directions at the vehicle's hitch, both when engaged and disengaged. These forces can be measured using the aforementioned sensor device. The measured values ​​obtained in this way can also be used to determine the properties of the surface or road the vehicle is currently traversing. This allows for adjustments to be made to the vehicle to optimize its traction.

[0025] The invention is therefore also advantageous for the operation of such solo vehicles. Not the subject of the present invention is a method for traction control of a vehicle which has a trailer hitch with a coupling element for attaching a counter-coupling element of an agricultural or forestry implement or an agricultural or forestry machine or other object, wherein the coupling element of the vehicle's trailer hitch is connected to a sensor device by means of which a coupling force FX, FY, Fz transmitted from the counter-coupling element to the coupling element of the vehicle's trailer hitch is measured in all vehicle directions x, y, z and output as a force signal, wherein the coupling force FX, FY, Fz effective in the respective vehicle direction x, y, z is determined from these force signals in an evaluation unit connected to the sensor device.The vehicle's speed is determined and transmitted to an electronic control unit of the vehicle, and the vehicle's traction is adapted to the properties of the surface by means of the control unit.

[0026] This method is characterized by the fact that properties of the road surface are determined based on the dynamics of the coupling forces FX, FY, Fz, such that in the evaluation unit the dynamic components are filtered out from successive sequences of the coupling forces FX, FY, Fz, that a characteristic value K Dyn, which characterizes the dynamics of the coupling forces FX, FY, Fz, is determined from these dynamic components of the coupling forces FX, FY, Fz and transmitted to the control unit, that in the control unit the characteristic value K Dyn is compared with a stored limit value K Dyn_Gr, that at least one measure to increase the traction of the vehicle is carried out if the characteristic value K Dyn has exceeded the limit value K Dyn_Gr (K Dyn > K Dyn_Gr), and that the at least one measure to increase traction is reversed if the characteristic value K Dyn falls below the limit value K Dyn_Gr again. K Dyn < K Dyn_Gr .

[0027] The defining characteristics of the procedure usable for a single vehicle are clearly the same as those of the procedure for a vehicle combination. Therefore, the same advantages described above also result.

[0028] The method described above can therefore also be advantageously used for operating a wheeled vehicle even when no trailer, implement, or machine is attached to it. In this case, a counter-coupling element of a separate coupling mass is attached to the coupling element of the trailer hitch before the vehicle begins its journey. This coupling mass assumes the process-related function of an agricultural or forestry implement or such an attached machine, because when the vehicle is in motion, this separate coupling mass is set into slight oscillations in all three spatial directions by the vehicle's movements and under the influence of inertia.These movements generate the aforementioned forces on the coupling element of the vehicle's trailer hitch, which are measured by the sensor device, then converted into relevant measured values ​​and used for traction control.

[0029] According to another variant of the procedure, it may be provided that the procedure is carried out without a trailer coupled to the coupling element of the vehicle's trailer hitch, without a coupled agricultural or forestry work tool or machine, and without a coupled coupling mass, wherein the coupling forces FX , FY , Fz measured by the sensor device are generated solely by the mass of the coupling element of the vehicle's trailer hitch.

[0030] Accordingly, for the execution of the method, it is sufficient if the vehicle is equipped only with a trailer hitch whose coupling element is connected to the vehicle's load-bearing structure via the described sensor device. Here, it is solely the mass of the trailer hitch's coupling device—for example, a coupling jaw with locking mechanism or a coupling hook with coupling ball—whose mass is connected to the vehicle's load-bearing structure via the sensor device in a limited manner, allowing for limited vibration. It is evident that the execution of the inventive method on a vehicle equipped in this way requires very high sensitivity from the sensor device, which is, however, achievable.

[0031] The characteristic value K Dyn, which characterizes the dynamics of the coupling forces FX, FY, FZ, is preferably determined as the averaged RMS value of the dynamic components of the coupling forces FX, FY, Fz. The RMS value of a dynamic signal represents an effective value of the fluctuations and oscillations in question and can be considered the average amplitude of the dynamic signal.

[0032] The duration of the sequences in which the dynamic components of the coupling forces FX , FY , Fz are determined and evaluated can range between 5 and 90 seconds.

[0033] The possible measures to increase the traction of the solo vehicle or the towing vehicle, which were already mentioned earlier in the explanation of the state of the art, can each be executed individually or summatively automatically as soon as an off-road journey that has just begun has been detected based on the dynamics of the coupling forces FX , FY , Fz.

[0034] However, it is also possible that the measures to increase the traction of the solo vehicle or the towing vehicle are displayed to the driver on a display of a display and control device, and that at least one of these possible measures is only carried out after confirmation by the driver.

[0035] Furthermore, it may be provided that the confirmation of at least one of the measures by the driver is carried out by pressing an OK button on the display and control device or by touching an OK keypad in a touchscreen display of the display and control device.

[0036] The selection of measures to be implemented to increase traction can also be made, for example, by repeatedly pressing a scroll button until a marker of the respective measure is displayed and then pressing the OK button of the display and control unit, or by touching a selection keypad on the measure display in the touchscreen display of the display and control unit.

[0037] The method according to the invention is explained in more detail below with reference to an embodiment shown in the accompanying drawing. In the drawing shows Fig. 1 a block diagram of the procedure for the traction control of a vehicle combination, Fig. 2a a first vehicle combination with a towing vehicle and a trailer with a first operating position of a lift axle of the trailer, Fig. 2b the first vehicle combination according to Fig. 2a with a second operating position of the lift axle of the trailer vehicle, Fig. 3a a second vehicle combination with a towing vehicle and a trailer with a first operating position of a lift axle of the trailer, Fig. 3b the second vehicle combination according to Fig. 3a with a second operating position of the lift axle of the trailer, and Fig. 4 a solo vehicle designed as a tractor, not according to the invention, with a separate coupling mass attached to its trailer hitch.

[0038] In Fig. 2a The figure shows a first vehicle combination 24, consisting of a tractor as the towing vehicle 26 and a central axle trailer coupled to it as the trailer 34. The towing vehicle 26 has a front axle 28 and a rear axle 30 with wheels and is equipped at its rear with a trailer coupling 32, shown only schematically. The front axle 28 is shown here as an example of a switchable drive axle, whereas the rear axle 30 is shown as a permanently driven drive axle. The trailer coupling 32 can be a ball coupling, a jaw coupling, or a hook coupling. The trailer 34 is equipped with a tipper body 36, which can be tipped at least to the rear for unloading. The trailer 34 also has two adjacent central axles 38, 40 with wheels arranged one behind the other.The front first central axle 38 is designed as a lift axle, which can be raised as required, whereas the rear second central axle 40 is rigidly suspended from the frame of the trailer 34. A drawbar 42 is rigidly attached to the front of the trailer 36, which is connected via an end-mounted coupling (in . Fig. 2a (not visible) is articulatedly connected to the trailer coupling 32 of the towing vehicle 26. The counter coupling of the trailer 34 is adapted to the design of the trailer coupling 32 of the towing vehicle 26 and is therefore designed as a ball coupling or as a drawbar eye.

[0039] In the operating position according to Fig. 2a The front central axle 38 or lift axle of the trailer 34 is in its lowered normal position, in which the weight of the trailer 34 is distributed over the two central axles 38, 40 and the vertical load Fz transferred to the trailer coupling 32 of the towing vehicle 26 is relatively low.

[0040] In the operating position according to Fig. 2b The front central axle 38 of the trailer 34 is in its raised functional position, in which the weight of the trailer 34 is only supported by the rear central axle 40 and the vertical load Fz transferred to the trailer coupling 32 of the towing vehicle 26 is increased.

[0041] In Fig. 3a A second vehicle combination 44 is shown, consisting of a tractor unit 46 and a semi-trailer 56 coupled to it. The tractor unit 44 has a frame 48, a front axle 50, and a rear axle 52 with wheels. At the rear of the frame 48, it is equipped with a fifth-wheel coupling 54. The front axle 50 is shown here as an example of a switchable drive axle, while the rear axle 52 is a permanently driven drive axle. The semi-trailer 56 is fitted with a tipper body 58, which can be tipped at least to the rear for unloading, and has three adjacent semi-trailer axles 60, 62, 64 with wheels.The front, first semi-trailer axle 60 is designed as a lift axle, which can be raised as required, whereas the two rear semi-trailer axles 62, 64 are rigidly suspended from the frame of the trailer 56. A fifth wheel coupling 66 with a kingpin (in . ) is located in the front area of ​​the trailer 56. Fig. 3a (not recognizable) arranged, which is pivotably connected to the fifth wheel coupling 54 of the towing vehicle 46 about a vertical axis.

[0042] In the operating position according to Fig. 3a The lift axle 60 of the trailer 56 is in its lowered normal position, in which the weight of the semi-trailer 56 is distributed over the three semi-trailer axles 60, 62, 64 and the vertical load Fz transferred to the fifth wheel coupling 54 of the towing vehicle 46 is relatively low.

[0043] In the operating position according to Fig. 3b The lift axle 60 of this trailer 56 is in its raised functional position, in which the weight of the semi-trailer 56 is only supported by the two rear semi-trailer axles 62, 64 and the vertical load Fz transferred to the fifth wheel coupling 54 of the towing vehicle 46 is increased.

[0044] The following will be based on the in Fig. 1 The block diagram shown describes the inventive method for traction control of a vehicle combination 24, 44 of the type described. A sensor device 2 is arranged on the coupling element of the trailer hitch 32, 54 of the towing vehicle 26, 46, by means of which a coupling force FX, FY, Fz transmitted from a counter-coupling element of the trailer 34, 56 to the coupling element of the towing vehicle 26, 46 is detected as a force signal in all vehicle directions x, y, z, from which the coupling force FX, FY, Fz effective in the respective vehicle direction x, y, z can be determined in a connected evaluation unit 4 and transmitted to an electronic control unit 6 of the towing vehicle 26, 46.

[0045] According to the invention, the surface traversed by the vehicle combination 24, 44 is determined based on the dynamics of the coupling forces FX, FY, Fz. For this purpose, in the evaluation unit 4, the dynamic components are filtered out from successive sequences of the coupling forces FX, FY, Fz with a duration between 5 and 90 seconds, and a characteristic value K Dyn, which characterizes the dynamics of the coupling forces FX, FY, Fz, is determined from these and transmitted to the control unit 6 of the towing vehicle 26, 46. In the control unit 6, the characteristic value K Dyn is compared with a limit value K Dyn_Gr stored in an associated data memory 8. If the characteristic value K Dyn exceeds the limit value K Dyn_Gr (K Dyn > K Dyn_Gr), at least one measure to increase the traction of the towing vehicle 26, 46 is implemented.If the characteristic value K Dyn falls below the limit value K Dyn_Gr again (K Dyn < K Dyn_Gr), at least one measure to increase traction is reversed.

[0046] The characteristic value K Dyn, which characterizes the dynamics of the coupling forces FX, FY, FZ, is preferably determined as the averaged RMS value of the dynamic components of the coupling forces FX, FY, Fz. The RMS value of a dynamic signal represents an effective value of the fluctuations and oscillations in question and can be considered the average amplitude of the dynamic signal.

[0047] For the purposes of this example, it is assumed that the towing vehicle 26, 46 and the trailer 34, 56 each have several devices that can be used to increase the traction of the towing vehicle 26, 46. As already shown above, based on the Figuren 2a bis 3b As previously described, the front axle 28, 50 of the towing vehicle 34, 56 can each be configured as a switchable drive axle. The traction of the towing vehicle 26, 46 can then be increased by a corresponding control of a transmission control unit 12, which engages a clutch to engage the respective front axle 28, 50 for drive. Likewise, it was previously determined based on the Figuren 2a bis 3b As already described, the front axle 38, 60 of the trailers 34, 56 can each be configured as a lift axle. The traction of the towing vehicle 26, 46 can then be increased by a corresponding control of a lift axle control unit 20 from an electronic control unit 18 of the trailer 34, 56, which is connected to the control unit 6 of the towing vehicle. This control unit activates a lifting actuator to raise the respective lift axle 38, 40. By raising the lift axle 38, 40, the vertical load Fz transferred to the trailer hitch 32, 54 of the towing vehicle 26, 46, and thus the axle load of the adjacent drive axle 30, 52 of the towing vehicle 26, 46, is increased, resulting in improved traction of the towing vehicle 26, 46.The same effect could also be achieved by venting the relevant air springs if the front axles 38, 60 of the trailers 34, 56 were air-sprung instead of being designed as lift axles on the respective vehicle frame of the trailers 34, 56.

[0048] Another way to increase the traction of the towing vehicle 26, 46 is to lower the tire pressure of the vehicle wheels on all axles 28, 30, 38, 40; 50, 52, 60, 62, 64 when driving off-road, provided that the towing vehicle 26, 46 and the trailer 34, 56 are each equipped with a tire pressure control system. By lowering the tire pressure, which is achieved by appropriately controlling a tire pressure control unit 14 of the towing vehicle 26, 46 and a tire pressure control unit 22 of the trailer 34, 56, the contact area of ​​the tires is increased, so that the vehicle wheels sink less into the ground. This reduces the rolling resistance of the vehicle combination 24, 44 and increases the traction of the towing vehicle 26, 46. As a positive side effect, the lower ground pressure of the vehicle wheels results in less compaction of the arable, meadow or forest soil.

[0049] Furthermore, to increase the traction of the towing vehicle 26, 46 and to prevent the vehicle combination 24, 44 from getting stuck, it is possible to

[0050] The engine control unit of the drive motor and the transmission control unit of the drive transmission of the towing vehicle 26, 46 are switched to characteristic curves intended for off-road use, resulting in a higher engine speed and power output of the drive motor as well as a higher gear ratio of the drive transmission. The switch to characteristic curves for off-road use is effected by corresponding control of an engine control unit 10 and the transmission control unit 12.

[0051] The possible measures to increase the traction of the towing vehicle 26, 46 can be executed automatically as soon as an off-road journey that has just begun has been detected based on the dynamics of the coupling forces FX , FY , FZ.

[0052] However, it is also possible that the measures for increasing the traction of the towing vehicle 26, 46 are displayed to the driver on a display of a display and control unit 16 connected to the control unit 6 and are only executed after confirmation by the driver. Confirmation by the driver can be given, for example, by pressing an OK button on the display and control unit 16 or by touching an OK keypad on a touchscreen display of the display and control unit 16.

[0053] It is also possible that not all possible measures for increasing the traction of the towing vehicle 26, 46 are implemented, but rather that the driver can select from the available measures those to be implemented. The selection of the measures to be implemented can be made, for example, by repeatedly pressing a scroll button until a marker is displayed for the respective measure and then pressing the OK button on the display and control unit 16, or by touching a selection button on the measure's display in the touchscreen display of the display and control unit 16.

[0054] The Fig. 4Figure 1 shows a vehicle 70, designed as a tractor but not according to the invention, at the rear of which a trailer hitch 72 with a coupling element 74 in the form of a coupling jaw is arranged. The coupling element 74 is connected to a supporting structure of the vehicle 70 via the sensor device 2 described in detail above. A separate coupling mass 78 is connected to the trailer hitch 72 of the vehicle 70. For this purpose, the separate coupling mass 78 has a counter-coupling element 76, which is inserted into the coupling element 74 of the trailer hitch 72 and locked there. When the vehicle 70 travels over a surface 25 with varying properties, the coupling mass 78 is excited to oscillate at different amplitudes due to its inertia relative to the vehicle 70, which introduce corresponding coupling forces into the trailer hitch 72 in all three spatial directions. This is detected by the sensor device 2 by generating measured values.These measurements are then used, as already described, to implement measures on the vehicle side that result in optimized vehicle traction for the specific surface being driven on. These measures can be selected and triggered automatically or manually by the driver, as described above. Reference symbol list (part of the description)

[0055] 2 Sensor device 4 Evaluation unit 6 Electronic control unit 8 Data storage 10 Engine control unit 12 Transmission control unit 14 Tire pressure control unit of a towing vehicle 16 Display and operating unit 18 Electronic control unit 20 Lift axle control unit 22 Tire pressure control unit of a trailer 24 First vehicle combination 26 First towing vehicle, tractor 28 Front axle, drive axle (switchable) 30 Rear axle, drive axle 32 Trailer hitch, trailer coupling 34 First trailer, center axle trailer 36 Tipper body of the trailer 34 38 First center axle, lift axle 40 Second center axle 42 Drawbar (with counter coupling) 44 Second vehicle combination 46 Second towing vehicle, semi-trailer tractor 48 Vehicle frame 50 Front axle, drive axle (switchable) 52 Rear axle, drive axle 54 Trailer hitch, fifth wheel coupling 56 Second trailer, semi-trailer 58 Tipper body of the trailer 56 60 First semi-trailer axle,Lift axle 62 Second semi-trailer axle 64 Third semi-trailer axle 66 Fifth wheel (with concealed kingpin) 70 Vehicle, tractor, solo vehicle 72 Trailer hitch on solo vehicle 70 74 Coupling element of the trailer hitch 72 76 Counter-coupling element 78 Coupling mass with counter-coupling element 75 FX Coupling force in x-direction FY Coupling force in y-direction Fz Coupling force in z-direction, support load K Dyn characteristic value K Dyn_Gr limit value x Vehicle longitudinal direction y Vehicle transverse direction z Vehicle vertical direction

Claims

1. Method for traction control of a vehicle combination (24, 44), which comprises a tractor vehicle (26, 46) and at least one trailer vehicle (34, 56) coupled to this tractor vehicle, wherein the tractor vehicle (26, 46) is provided with a sensor device (2) arranged on a coupling element of a trailer device (32, 54), wherein a coupling force Fx, Fy, Fz transmitted by a mating coupling element of the trailer vehicle (34, 56) to the coupling element of the tractor vehicle (26, 46) is measured by means of the sensor device (2) in all vehicle directions x, y, z in each case and output as a force signal, wherein the coupling force Fx, Fy, Fz acting in the respective vehicle direction x, y, z is determined from these force signals in an evaluation unit (4) connected to the sensor device (2) and is transmitted to an electronic control device (6) of the tractor vehicle (26, 46), and wherein the traction of the tractor vehicle (26, 46) is adapted to the properties of the ground surface (25) by means of the control device (6), characterized in that properties of the ground surface (25) being driven on are determined on the basis of the dynamics of the coupling forces Fx, Fy, Fz, specifically in such a way that the dynamic components are each filtered out from successive sequences of the coupling forces Fx, Fy, Fz in the evaluation unit (4), in that a characteristic value KDyn, which characterizes the dynamics of the coupling forces Fx, Fy, Fz, is determined from these dynamic components of the coupling forces Fx, Fy, Fz and transmitted to the control device (6), in that the characteristic value KDyn is compared with a stored limit value KDyn_Gr in the control device (6), in that at least one measure for increasing the traction of the tractor vehicle (26, 46) is carried out if the characteristic value KDyn has exceeded the limit value KDyn_Gr (KDyn > KDyn_Gr), and in that the at least one measure for increasing the traction is reversed if the characteristic value KDyn has again fallen below the limit value KDyn_Gr (KDyn < KDyn_Gr).

2. Method according to Claim 1, characterized in that the characteristic value KDyn, which characterizes the dynamics of the coupling forces Fx, Fy, Fz, is determined as the average RMS value of the dynamic components of the coupling forces Fx, Fy, Fz.

3. Method according to either of Claims 1 and 2, characterized in that the duration of the sequences in which the dynamic components of the coupling forces Fx, Fy, Fz are ascertained and evaluated is between 5 and 90 seconds.

4. Method according to any of Claims 1 to 3, characterized in that, when a ground surface (25) that is off-road or away from a paved path has been identified, the motor controller of the drive motor and the transmission controller of the transmission of the vehicle (70) or of the tractor vehicle (26, 46) are switched over to characteristic maps that are intended for off-road use and result in a higher motor speed and motor power of the drive motor and a greater transmission ratio of the transmission in order to increase the traction of the vehicle (70) or of the tractor vehicle (26, 46) and prevent the vehicle combination (24, 44) from becoming stuck.

5. Method according to any of Claims 1 to 4, characterized in that the possible measures for increasing the traction of the vehicle (70) or of the tractor vehicle (26, 46) are displayed to the driver in a display of a display and operating device (16), and in that at least one of these measures is carried out only after confirmation by the driver.

6. Method according to any of Claims 1 to 5, characterized in that confirmation of at least one of the measures by the driver is performed by pressing an OK button of the display and operating device (16) or by touching an OK touch area in a display of the display and operating device (16) in the form of a touchscreen.