METHOD FOR AUTOMATIC INTERNAL TIRE PRESSURE CONTROL OF WHEEL TIRES

Description

[0001] The present invention relates to a method for automatically controlling the internal tire pressure of wheel tires on an agricultural work vehicle according to the preamble of claim 1 and to an agricultural work vehicle for use in such a method according to claim 13.

[0002] When operating an agricultural work vehicle with wheeled tires, the tire pressure adjustment is particularly important when it comes to fuel consumption or soil compaction. The tire pressure adjustment of wheeled tires on agricultural work vehicles is done using a tire pressure control system. To adjust the tire pressure to suit the operating situation, various machine-specific parameters must be taken into account, including the mass of the work vehicle, the driving speed, and the tire type. The tire type determines which manufacturer-specific load pressures must be maintained to ensure the safe operation of the work vehicle both in the field and on the road.The mass of the work vehicle can vary, among other things, depending on the loading and unloading of crops, operating materials, or the like, and / or the presence and type of attachments on the work vehicle. In the simplest case, the control is based solely on a value for the target tire pressure during road travel and field travel.

[0003] EP 1 493 599 B1 discloses a method for automatically controlling the tire pressure of wheel tires on an agricultural vehicle. This method involves reducing the tire pressure below a minimum permissible tire pressure for a limited period of time, for example, to enable automatic freeing in a field situation in which the vehicle has become stuck in particularly soft ground. For this purpose, target value curves for tire pressures of various tire types are stored in the memory of a control device. These curves specify a minimum permissible tire pressure for a specific mass and speed.

[0004] DE 10 2009 025 494 B4 describes a method of the type mentioned above. To adjust the actual tire pressure, the deflection is determined by sensors and compared with stored target values ​​for the deflection, taking into account the soil properties and the ground pressure caused by the work vehicle. If a deviation between the actual tire pressure and the target tire pressure exceeds a threshold value, the tire pressure is adjusted to achieve optimal deflection of the wheels.

[0005] Further methods for automatic tire pressure control of wheel tires on agricultural work vehicles are known from US 2018 / 281535 A1, DE 20 2019 102183 U1 and WO 2020 / 131539 A1.

[0006] The invention is based on the problem of designing and developing the known method in such a way that the control system reacts better to dynamic changes in the driving condition, in particular to control an internal tire pressure that is optimally adapted to the respective driving situation.

[0007] The above problem is solved in a method according to the preamble of claim 1 by the features of the characterizing part of claim 1.

[0008] According to claim 1, a method for automatically regulating the tire pressure of wheel tires on an agricultural work vehicle is proposed, comprising a tire pressure control system controlled by a control device of the work vehicle in order to adjust the tire pressure of the wheel tires as a function of an actual spring deflection and an actual tire pressure, which are detected by sensors. A target tire pressure to be maintained by the tire pressure control system is determined taking into account a driving condition, at least one wheel-load-specific spring deflection characteristic curve, and a target spring deflection dependent on a wheel load and / or soil properties. By means of the method according to the invention, the tire pressure of the wheel tires can be optimally adjusted for a specific, in particular dynamically changing, operating situation.The tire pressure is optimally adjusted when the tire pressure is regulated to a value that is essentially at or immediately below the load limit of the permissible wheel deflection. The agricultural vehicle can be, among other things, a tractor, a self-propelled harvester, each with or without an attachment or front attachment, or, for example, a combination consisting of the agricultural vehicle and a trailer pulled by the agricultural vehicle. In this case, the wheel tires of the trailer can be coupled to the tire pressure control system of the agricultural vehicle or have a separate tire pressure control system that is controlled in the manner according to the invention.The procedure is used to regulate the tire pressure in such a way that a maximum load capacity is achieved while maintaining a constant tire pressure or a lower tire pressure while maintaining a constant load capacity.

[0009] The target tire pressure is specified depending on at least one selectable target spring deflection characteristic.

[0010] A memory unit of the control device can store several speed-dependent target spring deflection curves. At least one target spring deflection curve is stored for driving on a field to be worked and at least one target spring deflection curve is stored for driving on the road.

[0011] According to the invention, the target suspension characteristic curve is selected depending on the soil properties and / or the driving speed. Soil properties can be moisture, soil condition or soil type, and tillage condition. The driving speed varies depending on the operating situation. Higher speeds are achievable when driving on the road than when driving in the field. When driving in the field, a distinction must be made as to which type of work is to be carried out with the work vehicle. A work vehicle equipped with a soil cultivation implement such as a plow or cultivator is generally operated at a lower driving speed than a work vehicle designed as a harvester with a maize header as an attachment.

[0012] According to a preferred embodiment, selectable control strategies can be stored in the control device for tire pressure control. A "Load" control strategy can be applied to changes in the wheel load of the work vehicle, a "Soil" control strategy can be applied to changes in soil properties, an "Extreme Values" control strategy can be applied to determine a control range, and a "Dynamic" control strategy can be applied to simultaneous changes in soil properties and wheel load. To account for the different working conditions occurring during work, the control strategy that most closely matches the respective operating situation is selected, preferably automatically by the control device. Depending on the selected control strategy, the control device then regulates the tire pressure accordingly.This advantageously ensures that the operator of the agricultural vehicle is relieved of the burden of monitoring and / or adjusting the tire pressure, and that the tire pressure is automatically regulated to an optimized pressure based on the current operating situation. This also has the advantage that the tire inflation is independent of the operator's experience and / or subjective assessment of the situation.

[0013] The "Load" control strategy can be used to react to changes in wheel load, which can result, for example, from a change in the configuration of the agricultural work vehicle or a lower payload. For example, a work vehicle designed as a tractor may be carrying a seed drill, but the weight of the loaded seed is lower or higher than expected. A change in configuration can also be a change in an attachment, which can increase or decrease the wheel load. In a self-propelled harvester designed as a combine harvester, the grain tank can deliberately be filled less than its volume allows. Furthermore, a change in a working parameter on a soil cultivation tool, such as a plow or cultivator, can lead to a change in the wheel load on the work vehicle.The same applies if the work vehicle is towing a trailer, such as a transfer wagon or slurry tanker. In these cases, the wheel load can change continuously. Another factor that can lead to a change in the wheel load is the occurrence of significant dirt buildup on the work vehicle.

[0014] The "Soil" control strategy can be used to respond to changes in soil properties. Generally, a distinction can be made between hard and soft soil, for example, when driving on an asphalt road or on a field being worked. Hard and soft soil can also occur in fields with inhomogeneous soil properties. Soft soil can also be caused by stream meadows or damp patches in the field, which may require tire pressure adjustment. The same applies when driving on field soil after tillage, for example, after plowing. Hard soil can also occur when driving on gravel roads between fields if the working vehicle needs to be moved.

[0015] The "Extreme Values" control strategy can be used to determine a control range if the tire pressure is to be controlled within a permissible range between a minimum value and a maximum value for the tire pressure.

[0016] Preferably, the selection of one of the control strategies is carried out depending on at least one parameter change in one of the soil properties and / or the wheel load. A change in one of the soil properties can be detected by means of at least one sensor device, for example to determine a change between road travel and field travel. A change, in particular a sudden change, in the wheel load can result, for example, from the attachment or removal of an attachment or front attachment. The attachment or removal of an attachment or front attachment can, for example, be determined by a separate control unit of the work vehicle and transmitted to the control device. The separate control unit can be configured to determine attachment or removal automatically or through a manual input from an operator. However, it is also conceivable that the control device performs at least this task of the control unit.

[0017] In particular, according to the "Load" control strategy, upon detection of a change in wheel load under constant ground conditions and constant actual tire pressure, the target tire pressure can be adjusted until the actual deflection assumes a value that is at least approximately on the selected target deflection characteristic curve. The target deflection characteristic curve is selected according to the specific ground conditions, for example, hard ground or soft ground. Thus, a reduction in wheel load leads to a reduction in the actual deflection. With constant ground conditions, the target deflection characteristic curve remains unchanged, so that the target tire pressure is reduced until a pair of values ​​for the actual tire pressure and the actual deflection is reached that is at least approximately on the target deflection characteristic curve. An increasing wheel load leads to an increase in the actual deflection.If the soil properties remain constant, the target deflection characteristic curve remains unchanged, so that the target tire pressure is increased until a pair of values ​​for the actual tire pressure and the actual deflection is reached which is at least approximately on the target deflection characteristic curve.

[0018] Furthermore, according to the "Soil" control strategy, an adapted target deflection characteristic can be determined for control purposes upon detection of a change in one of the soil properties at a constant wheel load and constant actual tire pressure. In response to a change in at least one soil property at a constant wheel load, for example, when the soil conditions change from harder to softer during field travel, such as upon reaching a wet patch, an adapted target deflection characteristic can be specified based on a known target deflection for the changed soil property at a constant wheel load.With constant wheel load, the system is controlled according to the adapted target deflection curve, so that the target tire pressure is reduced until a pair of values ​​for the actual tire pressure and the target deflection known for the ground properties is reached, which lies at least approximately on the adapted target deflection curve. This adjustment of the target deflection curve is carried out in a similar manner when transitioning from a softer to a harder ground, assuming constant wheel load and constant actual tire pressure.

[0019] According to a further development, the adapted target deflection characteristic curve can be specified as a function of a target deflection specific to the changed soil properties at constant wheel load.

[0020] In particular, by determining a change in the actual deflection at constant wheel load and constant actual tire pressure, a change in a soil property can be derived, and an adapted target deflection characteristic curve can be determined from the derived change in the soil property, on the basis of which an optimized target tire pressure is determined that is adapted to the changed operating situation due to the change in the soil property.

[0021] A preferred embodiment provides that, according to the "Extreme Values" control strategy, wheel load-tire pressure characteristic curves are specified as limits of a control range below the target spring deflection characteristic curve, with the target tire pressure being specified within the control range. This allows the tire pressure control to be adjusted so that the work vehicle always operates within a permissible range for load capacity and ground load.

[0022] Furthermore, according to the "Dynamic" control strategy, if changes in the wheel load and one of the ground properties occur simultaneously, in a first step, the previous target deflection characteristic can be determined as a function of a change in the ground property, which is determined by a change in the actual deflection, and a deflection characteristic adapted to the changed ground property. In a second step, a corresponding deflection characteristic can be determined as a function of a quantitatively determined change in the wheel load, assuming a constant ground property with a changed wheel load. In a third step, a comparison can be made between the set target tire pressure according to the target deflection characteristic before the change in wheel load and ground property and an expected target tire pressure according to the deflection characteristic after the determined change in the wheel load.so that a resulting shift between the deflection characteristic and the deflection characteristic can be used to shift the target deflection characteristic relative to the target deflection characteristic. In this way, a simultaneous change in wheel load and ground properties can be taken into account in tire pressure control.

[0023] Preferably, a change in a soil property can be determined by means of at least one sensor device or by manual input via an input unit of the control device. The at least one sensor device for determining soil properties can, for example, operate optically. Alternatively or additionally, a penetrometer can be used as a sensor device for determining soil properties.

[0024] Further preferably, a change in the wheel load can be detected by means of at least one sensor device and / or a change in the configuration of the work vehicle, which is automatically determined by a sensor device and / or manually transmitted to the control device via an input unit. For example, the attachment or removal of an implement or front attachment can be detected as a change in the configuration. In a work vehicle with a storage unit arranged thereon for crops, fertilizer, seeds, or the like, a change in the contents that affects the wheel load can be determined by level monitoring or weight determination.

[0025] Furthermore, the actual deflection can be determined directly by at least one sensor device assigned to the wheel tire or indirectly by a mathematical model. The at least one sensor device for determining the actual deflection can be configured to determine the actual deflection using acoustic measurement methods such as ultrasonic measurement, optical measurement methods such as laser measurement or a camera, electrical measurement methods such as strain gauges or piezoelectric sensors, or magnetic measurement methods.The object posed initially is further achieved by an agricultural work vehicle according to claim 13, comprising a tire pressure control system for automatically controlling the tire pressure of wheel tires, a control device with a computing unit and a memory unit for controlling the tire pressure control system, and sensor devices for detecting an actual spring deflection and an actual tire pressure of the wheel tires, designed for use in a method according to one of the preceding claims. The agricultural work vehicle can be designed as a tractor or as a self-propelled harvester.

[0026] The present invention is explained in more detail below with reference to an embodiment shown in the drawings.

[0027] They show: Fig. 1 shows a schematic representation of an agricultural work vehicle with a tire pressure control system; Fig. 2 shows a simplified overview of a control process; Fig. 3 shows an example of a spring deflection-pressure diagram for an application according to a "load" control strategy; Fig. 4 shows an example of a spring deflection-pressure diagram for an application according to a "ground" control strategy; Fig. 5 shows an example of a spring deflection-pressure diagram for an application according to an "extreme values" control strategy; and Figs. 6a, 6b show an example of a spring deflection-pressure diagram for an application according to a "dynamic" control strategy.

[0028] In Fig. 11 shows an agricultural work vehicle 1 designed as a self-propelled harvesting machine, here a combine harvester 1a. The agricultural work vehicle can also be designed as a tractor. The combine harvester 5 is equipped with a tire pressure control system 6, with which the internal tire pressure of air-filled wheel tires 7 can be changed. This tire pressure control system 6 consists of an air compressor 11 as the pressure source, which is connected to the wheel tires 7 via supply lines 12. Adjustable valves 17 are installed in the supply lines 12, which enable controlled filling and emptying of the wheel tire 7 and maintaining the internal tire pressure. The valves 17 are connected to a control device 20, which regulates the position of the valves 17. With the help of the control unit 20, the internal tire pressure is regulated depending on the machine mass of the combine harvester 1, as will be explained in more detail later.

[0029] An input / output unit 19, which is connected to a control unit 13 via a communication means 21 such as a wireless or wired bus system, can input, for example, specific data of the wheel tires 7 mounted on the combine harvester 1 as well as information about the type and weight of an attached attachment 10, which according to the exemplary embodiment is designed as a cutting unit 15. Alternatively, the mass of the attachment 10 can also be measured using pressure sensors 16 on a support hydraulic system 18 for the attachment 10. Using the input / output unit 19, information about current and / or changed soil properties 31 can also be manually entered by an operator.

[0030] Crops picked up from the field soil 22 by the combine harvester 5a with the front attachment 10 are conveyed by a grain elevator 2 into a grain tank 3 in the combine harvester 5, where the crops are temporarily stored. Once the grain tank 3 is filled, the crops are transferred into a loader wagon (not shown) by means of a transfer device 4.

[0031] At least one sensor device 8 is arranged in the grain elevator 2, which detects a volume of crop conveyed into the grain tank 3 within a limited period of time and / or is configured to determine a mass flow and generates an associated signal. Level sensors 9.1, 9.2, 9.3, 9.4 can be arranged at various heights in the grain tank 3. These sensors detect the fill level at, for example, 20%, 70%, 100%, and when the grain tank 3 is empty and generate an associated signal. The sensors 8, 9.1, 9.2, 9.3, 9.4, 16 are also connected to the control unit 13. Based on the known empty weight of the combine harvester 5, the weight of the harvested material in the grain tank 3 determined by means of the at least one sensor device 8 and the determined weight of the front attachment 10 adapted to the combine harvester 5, a respective wheel load 30 occurring on the wheel tires 7 can be determined.

[0032] The control unit 13 is connected to the control device 20 of the tire pressure control system 6, which changes the tire pressure depending on a signal generated by the control device 20. The control unit 13 can also assume the function of the control device 20, or vice versa, so that only one control device is required. At least one sensor device 23 is arranged on the combine harvester 5, which is configured to determine at least one soil property. The at least one sensor device 23 is connected to the control unit 13 and / or the control device 20, so that a change in a soil property 31 can be determined by evaluating the signals from the at least one sensor device 23. Furthermore, each wheel tire 7 is assigned a sensor device 24, by means of which an actual spring deflection 28 can be determined.The actual spring deflection 28 is determined directly by the respective sensor device 24 assigned to the wheel tires 7 or indirectly by a mathematical model which is stored in a memory unit 25 of the control device 20 and / or a memory unit 14 of the control unit 13.

[0033] In Fig. 2A simplified overview of a control process for setting a target tire pressure 33 is shown. Input variables are a driving condition 26, in particular the driving speed of the work vehicle 1 and the general distinction between road travel and field travel, the sensor-determined actual tire pressure 27, the sensor-determined actual spring deflection 28, a target spring deflection characteristic curve 29, the current wheel load 30 and / or the current soil properties 31. From the current wheel load 30 and / or the current soil properties 31, a target spring deflection 32 can be determined which is specific for the respective wheel load 30 and the soil properties 31. Thus, a target tire pressure 33 to be set and maintained by the tire pressure control system 6 is determined taking into account the driving speed 26, the target deflection characteristic curve 29 and a target deflection 32 dependent on the wheel load 30 and / or ground properties 31.

[0034] Various target spring deflection curves 29 are stored in the memory unit 25 of the control device 20 and / or the memory unit 14 of the control unit 13. The target tire pressure 33 is specified as a function of at least one selectable target spring deflection curve 29. The target spring deflection curve 29 is selected as a function of the determined ground properties 31 and / or the current driving speed.

[0035] For tire pressure control, selectable control strategies 34, 35, 36, 37 are stored in the control device 20. A "Load" control strategy 34 is applied to changes in the wheel load 30 of the work vehicle 1, a "Soil" control strategy 35 is applied to changes in soil properties 31, a "Extreme Values" control strategy 36 is applied to determine a control range, and a "Dynamic" control strategy 37 is applied to simultaneous changes in soil properties 31 and wheel load 30. The selection is preferably made automatically by the control device 20 based on a detected parameter change for the wheel load 30 or one of the soil properties 31, or a simultaneous change in the wheel load 30 and one of the soil properties 31.

[0036] The representation in Fig. 3shows an example of a deflection-pressure diagram for an application according to control strategy 34 "Load." Control strategy 34 "Load" comes into effect when a change in wheel load 30 is determined, for example, due to the attachment or removal of the front attachment 10 or the filling or emptying of the grain tank 3.

[0037] Shown are Fig. 3the target deflection characteristic curve 29, which represents the load limit for a permissible actual deflection 28 of the wheel tire 7 at a given actual tire pressure 27. Above the target deflection characteristic curve 29 is the range within which the conditions for the operation of the wheel tires 7 are inadmissible. Furthermore, a first deflection characteristic curve 38 for a specific wheel load 30 and a second deflection characteristic curve 39 for a lower wheel load 30 are shown. Immediately before a change in the wheel load 30, the value pair of actual tire pressure 27 and actual deflection 28 lies, in the optimal case, directly on the target deflection characteristic curve 29 at the operating point 40. The operating point 40 is located at the intersection point of the first deflection characteristic curve 38 and the target deflection characteristic curve 29. The actual tire pressure 27 corresponds to the target tire pressure 33, which is set according to the target deflection characteristic curve 29.When the wheel load 30 is reduced, a new operating point 41 is established which, with the actual tire pressure 27 remaining constant, is below the previous operating point 40 on the second compression characteristic curve 39.

[0038] According to the "Load" control strategy 34, upon detection of a change in the wheel load 30 with otherwise constant ground properties 31 and constant actual tire pressure 27, the target tire pressure 33 is adjusted until the actual spring deflection 28 at least approximately assumes a value lying on the selected target spring deflection characteristic curve 29, here a new operating point 42, which, in the optimal case, is located at the intersection point of the second spring deflection characteristic curve 39 and the target spring deflection characteristic curve 29. In the illustrated embodiment, this is achieved when reducing the wheel load 30 by lowering the actual tire pressure 27 to a target tire pressure 33a adapted to the changed wheel load 30. An increase in the wheel load 30 results in the actual tire pressure 27 being adjusted analogously to the new conditions by means of an adapted target tire pressure 33a.

[0039] The representation in Fig. 4shows an example of a deflection-pressure diagram for an application according to control strategy 35 "Soil." Control strategy 35 "Soil" can be used to respond to changes in soil properties 31. Generally, a distinction can be made between hard soil and soft soil, for example, when driving on an asphalt road or on a field to be worked. Hard and soft soil can also occur in a field with inhomogeneous soil properties 31. Soft soil can also be caused by stream meadows or damp patches in the field, which may require an adjustment of the tire pressure. The same applies to driving on field soil 22 after soil cultivation, for example, after plowing. Hard soil can also occur when driving on gravel roads between two fields if the work vehicle 1 has to be moved.

[0040] Shown are Fig. 4the target deflection characteristic curve 29, which represents the load limit for a permissible actual deflection 28 of the wheel tire 7 at a given actual tire pressure 27. The target deflection characteristic curve 29 represents the load limit for hard ground at a constant wheel load 30. For softer ground, an adapted second target deflection characteristic curve 45 is shown as an example as the load limit at a constant wheel load 30. Furthermore, a first deflection characteristic curve 43 for a constant wheel load 30 and hard ground as ground property 31 and a second deflection characteristic curve 44 for the same wheel load 30 and softer ground as ground property 31 are shown.

[0041] Immediately before a change in a ground property 31, due to a transition from harder ground to softer ground, the value pair of actual tire pressure 27 and actual deflection 28 lies, in the optimal case, directly on the target deflection characteristic curve 29 at the operating point 46, whereby the actual deflection 28 then corresponds to the target deflection 32. Due to the transition to softer ground, the actual deflection 28 decreases to a lower actual deflection 28a, so that a new operating point 47 is established which, with the actual tire pressure 27 remaining constant, lies below the previous operating point 46 on the second deflection characteristic curve 44.

[0042] According to the "Soil" control strategy 34, upon detection of a change in the soil properties 31 with an otherwise constant wheel load 30 and constant actual tire pressure 27, the target tire pressure 33 is adjusted by using the adapted target deflection characteristic curve 45 for control. In response to the change in at least one soil property 31 with a constant wheel load 30, for example, when the soil condition changes from harder to softer soil during field travel, such as upon reaching a wet spot, the adapted target deflection characteristic curve 45 is specified based on a known target deflection 28 for the changed soil property 31 with a constant wheel load 30 by selecting from target deflection characteristics stored in the memory unit 14 or 25.With constant wheel load 30, control is carried out on the adapted target deflection characteristic curve 45, so that a reduction of the constant actual tire pressure 27 to a new target tire pressure 33a is carried out until a pair of values ​​for the actual tire pressure 27 and the target deflection 28 known for the ground properties is reached, which lies at least approximately on the adapted target deflection characteristic curve 45, here the adapted operating point 48. This adaptation of the target deflection characteristic curve 45 is carried out in an analogous manner with constant wheel load 30 and constant actual tire pressure 27 during a transition from a softer to a harder ground.

[0043] The representation in Fig. 5shows an example of a spring deflection-pressure diagram for an application according to control strategy 36 "Extreme Values." Control strategy 36 "Extreme Values" can be used to determine a control range 51 if the tire pressure is to be controlled within a permissible range between a minimum value 49 as the lower limit and a maximum value 50 as the upper limit for the actual tire pressure 27. The control range 51 is specified by the target spring deflection characteristic curve 29 as well as the minimum value 49 and the maximum value 50 for the actual tire pressure 27 to be set as the target tire pressure 33. An operating point 52 is shown as an example, at which the actual tire pressure 27 lies outside the control range 51.The actual tire pressure 27 at operating point 52 is too low for the sensor-determined actual deflection 28 for permissible operation of the wheel tires 7, so that the target tire pressure 33 is increased until an operating point 53 is reached, which lies at least at the lower limit of the control range 51. The actual tire pressure 27 at operating point 54 is too high for the sensor-determined actual deflection 28, so that the target tire pressure 33 is reduced until an operating point 55 is reached, which lies at least at the upper limit of the control range 51. This achieves control of the tire pressure that always lies within the permissible range for the operation of the wheel tires 7 under prevailing operating conditions. As an example, the operating point 40 is shown, which lies on the target compression characteristic curve 29 and in which the optimal target tire pressure 33 is given.

[0044] In the Fig. 6a and 6bAn exemplary deflection-pressure diagram is shown for an application according to a "Dynamic" control strategy. With the "Dynamic" control strategy, when changes in the wheel load 30 and one of the ground properties 31 occur simultaneously, in a first step the previous target deflection characteristic 29 is determined as a function of a change in the ground property 31, which is determined by a change in the actual deflection 28, and a second target deflection characteristic 56 corresponding to the changed ground property 31 is determined. The second target deflection characteristic 56 is shifted parallel to the previous target deflection characteristic 29 by an amount 61 to be determined.Starting from the operating point 57, which lies at the intersection of the target deflection curve 29 and the deflection curve 38 for a specific wheel load 30 and hard ground, a simultaneous change in the wheel load 30 to a reduced wheel load in the illustrated embodiment and in the ground properties 31 from hard ground to softer ground at a constant actual tire pressure 27 results in the establishment of a new operating point 58. The operating point 58 lies on a deflection curve 60 for softer ground with a reduced wheel load 30.

[0045] In a second step, a corresponding deflection characteristic curve 64 is determined for the constant ground property 31, i.e., the hard ground, with a reduced wheel load 30, as a function of a quantitatively determined change in the wheel load 30. A comparison is then made between the originally set target tire pressure 33 according to the target deflection characteristic curve 29 before the change in the ground property 31 and an expected target tire pressure 62 according to the deflection characteristic curve 64 after the determined change in the wheel load 30. A resulting shift 63 between the deflection characteristic curve 38 and the deflection characteristic curve 64 is used to shift the target deflection characteristic curve 56 relative to the original target deflection characteristic curve 29.To this end, in a third step, the previous target spring deflection characteristic curve 29 is shifted in parallel by the amount determined based on the pressure difference in order to adapt the target tire pressure 33. In this way, a simultaneous change in wheel load 30 and ground properties 31 can be taken into account in the tire pressure control. A new operating point 59 is established, which lies at the intersection of the target spring deflection characteristic curve 56 and the spring deflection characteristic curve 60. This results in a new, in this case lower, target tire pressure 33a. Using the "Dynamic" control strategy 37, the influences on the spring deflection and the tire pressure caused by a simultaneous change in wheel load and ground properties can be taken into account when determining and setting the optimal target tire pressure. List of reference symbols 1 Work vehicle 30 Wheel load 2 grain elevator 31 Soil properties 3 grain tank 32 Target spring deflection 4 Overloading device 33 Target tire pressure 5 Combine harvester 33a Target tire pressure 6 Tire pressure control system 34 Control strategy "Load" 7 Wheel tires 35 Ground control strategy 8 Sensor device 36 Control strategy "Extreme values" 9.1 Level sensor 37 Dynamic control strategy 9.2 Level sensor 38 Suspension characteristic curve 9.3 Level sensor 39 Suspension characteristic curve 9.4 Level sensor 40 Operating point 10 Attachment 41 Operating point 11 air compressor 42 Operating point 12 supply line 43 Suspension characteristic curve 13 Control unit 44 Suspension characteristic curve 14 storage unit 45 Target spring deflection curve 15 Cutting unit 46 Operating point 16 pressure sensor 47 Operating point 17 valve 48 Operating point 18 Support hydraulics 49 Minimum value 19 Input-output unit 50 Maximum value 20 Control unit 51 Control range 21 means of communication 52 Operating point 22 field soil 53 Operating point 23 Sensor device 54 Operating point 24 Sensor device 55 Operating point 25 storage unit 56 Target spring deflection curve 26 Driving condition 57 Operating point 27 Actual tire pressure 58 Operating point 28 Actual deflection 59 Operating point 28a Actual deflection 60 Suspension characteristic curve 29 Target spring deflection curve 61 Amount 62 Target tire pressure 63 shift 64 Suspension characteristic curve

Claims

1. A method for the automatic internal tyre pressure regulation of wheel tyres (7) on an agricultural working vehicle (1, 5), with a tyre pressure regulation system (6), which is controlled by a control device (20), for adjusting the internal tyre pressure of the wheel tyres (7) as a function of an actual deflection (28) and an actual internal tyre pressure (27) which is detected via a sensor, characterized in that a target internal tyre pressure (33) to be maintained by the tyre pressure regulation system (6) is determined in consideration of a driving status (26), at least one deflection characteristic (38, 39, 43, 64), as well as a target deflection (32) which is a function of a wheel load (30) and / or ground properties (31), wherein the target internal tyre pressure (33, 33a) is specified as a function of at least one selectable target deflection characteristic (29, 45, 56), wherein the target deflection characteristic (29, 45, 56) is selected as a function of the ground properties (31) and / or the driving speed.

2. The method according to claim 1, characterized in that in order to regulate the internal tyre pressure, control strategies (34, 35, 36, 37) which are to be selected are stored in the control device (20), wherein a "Load" control strategy (34) is used for variations in the wheel load of the working vehicle (1, 5), a "Ground" control strategy (35) is used for variations in the ground properties (31), an "Extreme values" control strategy (36) is used for the determination of a control range (51) and a "Dynamic" control strategy (37) is used in the case of a simultaneous variation of ground properties (31) and wheel load (30).

3. The method according to claim 2, characterized in that the selection of one of the control strategies (34, 35, 36, 37) is made as a function of at least one parametric variation of one of the ground properties (31) and / or of the wheel load (30).

4. The method according to claim 2 or claim 3, characterized in that according to the "Load" control strategy (34), upon detection of a variation in the wheel load (30) for constant ground properties (31) and constant actual internal tyre pressure (27), the target internal tyre pressure (33) is adjusted until the actual deflection (28) at least approximately takes a value lying on the selected target deflection characteristic (29).

5. The method according to one of claims 2 to 4, characterized in that according to the "Ground" control strategy (35), upon detection of a variation in one of the ground properties (31) for constant wheel load (31) and constant actual internal tyre pressure (27), an adapted target deflection characteristic (45) is determined for the regulation.

6. The method according to claim 5, characterized in that the adapted target deflection characteristic (45) is specified as a function of a target deflection (28) for constant wheel load (30) which is specific to the varied ground property (31).

7. The method according to claim 5 or claim 6, characterized in that a variation in a ground property (31) is derived by the determination of a variation in the actual deflection (28a) for constant wheel load (30) and constant actual internal tyre pressure (27), and in that from the derived variation in the ground property (31), an adapted target deflection characteristic (45) is determined, with the aid of which an optimized target internal tyre pressure (33a) is determined.

8. The method according to one of claims 2 to 7, characterized in that according to the "Extreme values" control strategy (36), wheel load - internal tyre pressure characteristics are specified as boundaries of a control range (31) below the target deflection characteristic (29), within which control range the target internal tyre pressure (33) is specified.

9. The method according to one of claims 2 to 8, characterized in that according to the "Dynamic" control strategy (37), upon the simultaneous occurrence of variations in the wheel load (30) and one of the ground properties (31), in a first step, the previous target deflection characteristic (29), as a function of a variation in the ground property (31) which is determined by means of a variation in the actual deflection (28), is determined as an adapted deflection characteristic (60) corresponding to the varied ground property (31), in that in a second step, as a function of a quantitatively determined variation in the wheel load (30), a corresponding deflection characteristic (64) is determined assuming a constant ground property (31) for a varied wheel load (30), in that in a third step, a comparison between the adjusted target internal tyre pressure (33) according to the target deflection characteristic (29) before the variation in the ground property (31) and an expected target internal tyre pressure (62) according to the corresponding deflection characteristic (64) after the determined variation in wheel load (30) is carried out, and an offset (63) resulting therefrom between a first deflection characteristic (38) and the corresponding deflection characteristic (64) is used in order to offset the target deflection characteristic (56) with respect to the original deflection characteristic (29).

10. The method according to one of the preceding claims, characterized in that a variation in a ground property (31) is determined by means of at least one sensor device (23) or by a manual input via an input / output unit (19) of the control device (20).

11. The method according to one of the preceding claims, characterized in that a variation in the wheel load (30) is detected by means of at least one sensor device (8, 9.1, 9.2, 9.3, 9.4, 18) and / or a variation in the configuration of the working vehicle (1, 5), which is automatically determined by a sensor device and / or by manual transmission through an input / output unit (19) of the control device (20) on the working vehicle.

12. The method according to one of the preceding claims, characterized in that the determination of the actual deflection (28) is carried out directly by at least one of the sensor devices (24) associated with the wheel tyres (7) or indirectly by a mathematical model stored in a memory unit (25) of the control device (20).

13. An agricultural working vehicle, comprising a tyre pressure regulation system (6) for the automatic regulation of the internal tyre pressure of wheel tyres (7), a control device (20) with a processing unit and a memory unit (25) for controlling the tyre pressure regulation system (6), sensor devices (24) for detecting an actual deflection (28) and an actual internal tyre pressure (27) of the wheel tyres (7), designed for use in a method according to one of the preceding claims.