AGRICULTURAL TRAIN

Description

[0001] The present invention relates to an agricultural tractor according to the preamble of claim 1.

[0002] An agricultural combination consists of a tractor as the towing vehicle, which is powered by a drive engine interacting with a continuously variable transmission, and at least one trailer coupled to the tractor at a coupling point. The trailer can be an agricultural implement such as a baler or a transport wagon, loader wagon or the like. In addition to increasing maximum driving speeds of the tractors due to higher drive power, the weight ratios between the tractor and the towed trailer have changed. When loaded, the towed trailer can have a weight several times greater than the unladen weight of the tractor. If the driving speed of such a combination is to be reduced when driving downhill simply by adjusting the engine speed and the transmission ratio, the entire mass of the agricultural combination is decelerated by the tractor's drive axle.This poses the risk of over-braking the drive axle and significantly increasing slip, which in extreme cases can lead to the agricultural vehicle collapsing. Furthermore, in such driving situations, where deceleration is generated solely by the drag torque of the drive motor, there is a risk of the drive motor over-revving and thus being damaged.

[0003] An agricultural tractor-trailer of the type mentioned above is known from EP 2 269 880 B1. The tractor-trailer has a control device configured to determine the presence of overrun operation depending on at least one operating parameter of the transmission and / or the drive motor. For this purpose, a difference between an actual engine speed of the tractor-trailer and a predeterminable target engine speed, as well as a pressure difference across a hydrostatic drive, is determined as a measure of the overrun effect of a trailer at the coupling point.

[0004] When the agricultural tractor corners, the forces at the coupling point are distributed when the tractor and trailer collapse. By determining the forces at the coupling point based solely on the operating parameters of the transmission and / or the drive motor, only the force component acting in the longitudinal direction of the tractor is detected, resulting in the trailer's braking system being controlled using different parameters.

[0005] Another example of a generic agricultural train is known from EP 3 533 673 A1.

[0006] It is therefore the object of the invention to further develop an agricultural tractor of the type mentioned at the outset, with a tractor as a towing vehicle and at least one towed trailer, in such a way that it offers an improvement in driving safety.

[0007] The object is achieved according to the invention by the characterizing features of independent patent claim 1. Advantageous embodiments and further developments of the invention emerge from the following subclaims and the following description.

[0008] According to claim 1, an agricultural train is proposed, the train comprising a tractor as a towing vehicle, which is driven by a drive motor interacting with a continuously variable transmission and has a first braking system, and at least one trailer coupled to the tractor at a coupling point and having a second braking system, the tractor having a control device for controlling at least one braking system of the agricultural train, the control device being designed and configured to actuate at least one of the braking systems of the train as a function of a determined overrun operation of the train and / or towing vehicle, the control device further being configured to determine the presence of overrun operation as a function of at least one operating parameter of the transmission and / or the drive motor.According to the invention, the control device is configured to calculate a correction factor as a function of a steering angle detected during coasting operation in order to correct a coupling force at the coupling point determined from the at least one operating parameter, taking the steering angle into account.

[0009] The proposed invention is based on the finding that when cornering with a train that has already jackknifed, the forces occurring at the coupling point are divided into components that act in the longitudinal and transverse directions depending on the resulting jackknifing angle. When determining the presence of overrunning operation based on at least one operating parameter of the transmission and / or the drive motor, only the forces acting in the longitudinal direction of the train are detected. By calculating a correction factor depending on a steering angle detected during overrunning operation, the force component of the coupling force determined by the control device acting in the longitudinal direction is corrected in order to trigger the second braking system in a manner appropriate to the driving situation. In this way, critical driving situations, in particular the jackknifing of the train during overbraking, also known as jackknifing, can be avoided.The control unit can react to this driving situation accordingly sooner. The control unit can activate the braking systems of one or, if present, several towed trailers independently of the tractor's primary braking system. This decelerates the trailer and reduces the thrust on the tractor, thereby stretching the combination and preventing a critical driving condition.

[0010] To determine the steering angle, the invention provides a tractor steering wheel with an associated steering angle sensor, which specifies the steering angle as a control signal for the control device. According to the invention, the control device is configured to control the braking force generated by the second braking system proportionally to the detected steering angle when coasting.

[0011] In particular, the continuously variable transmission can be designed as a mechanical or hydrostatic transmission. A continuously variable transmission can be configured as a power-split hydraulic-mechanical transmission, an electric-mechanical transmission, a purely hydraulic transmission, or a purely electric transmission. Especially with a continuously variable hydrostatic transmission with power split, the occurrence of critical driving situations caused by sudden deceleration can be avoided by adjusting the engine speed and transmission ratio.

[0012] Preferably, the control device can be configured to determine an output torque and / or a support torque of the continuously variable hydrostatic transmission from a pressure difference in a hydrostatic sub-transmission of the transmission. Thus, in a hydraulic-mechanical continuously variable transmission, the output torque, its magnitude and / or direction, can be determined as a transmission parameter using suitable sensors. The determined output torque can be used to detect overrun operation, for example, depending on the direction of the output torque. In a mechanical or hydrostatic continuously variable transmission and / or a powershift transmission, the support torque of the transmission can, for example, be determined as a transmission parameter.The support torque, which depends, for example, on the speed of the drive motor, a gear ratio, and / or the transmission efficiency, can be determined using a characteristic curve, particularly a drag characteristic curve. The advantage of such transmission parameters is the possibility of using existing components and / or cost-effectively retrofitting individual sensors, which enable simple and reliable determination of the operating parameter(s).

[0013] The output torque determined from the pressure difference of the hydrostatic sub-transmission can serve as a reference variable for controlling the second braking system. For example, a hydraulic-mechanical continuously variable transmission can feature a wide-angle hydrostatic actuator. This has the advantage that only one electronically controlled trailer brake valve is required to control the second braking system, since the output torque, which can be determined from the pressure difference of the hydrostatic sub-transmission, can be used as a reference variable for controlling the second braking system.

[0014] According to a preferred development, the control device can comprise an input / output unit configured to input and / or select at least one parameter influencing the braking behavior of the trailer. Thus, a tractor operator can influence the braking behavior of the tractor / trailer combination by inputting at least one parameter influencing the braking behavior of the trailer.

[0015] For this purpose, at least one parameter can be selected from the group consisting of trailer geometry, number of coupled trailers, load condition, environmental parameters, condition and / or performance of the second braking system. The term "trailer geometry" refers to the dimensions as well as the type of trailer. For example, the operator can manually enter and / or select manufacturer-specific information to select the coupled trailer(s) to be towed by the tractor. Environmental parameters such as the weather and the condition of the surface to be driven on can be entered. Furthermore, an input can be made regarding the condition and / or performance of the trailer's second braking system.

[0016] Furthermore, the at least one parameter can be a predeterminable gain factor for adjusting the braking force applied by the second braking system. The predeterminable gain factor can be used to influence the braking behavior.

[0017] The preset gain factor can have a value greater than zero. A gain factor between zero and less than one can be used to reduce the braking force, while a gain factor greater than one can increase the braking force. By setting the gain factor greater than one, more aggressive braking behavior can be achieved. The preset gain factor can be used to account for the influence of at least one parameter from the group of trailer geometry, number of coupled trailers, environmental parameters, condition, and / or performance of the trailer's second braking system.

[0018] According to the invention, the control device is designed to calculate a theoretical articulation angle at the coupling point using a mathematical model.

[0019] For this purpose, the control device comprises a memory for storing data and a computing unit for processing the data stored in the memory. The control device can be connected via signaling to a drive motor control unit of the drive motor and / or a transmission control unit of the transmission in order to receive additional information about the current operating status of the tractor and, if necessary, evaluate it.

[0020] The present invention is explained in more detail below with reference to an embodiment shown in the drawings.

[0021] They show: Fig. 1 shows a schematic representation of an agricultural train with a towing vehicle and a trailer coupled to it; Fig. 2(a) to (d) show, by way of example and schematically, an agricultural train with a towing vehicle and trailers coupled to it during a downhill journey in which a critical driving situation develops; and Fig. 3 shows schematically the train that has buckled during cornering according to Fig. 1 .

[0022] In Fig. 1is a schematic representation of an agricultural tractor 10 with a tractor 12 and a trailer 14 coupled thereto. The trailer 14 is coupled to a coupling 56 of the tractor 12. The tractor 12 is supported relative to the ground by ground engagement means 20 in the form of wheels arranged on a front axle 16 and a driven rear axle 18. The ground engagement means 20 can also be designed in the form of crawler tracks. To drive the ground engagement means 20, the tractor 12 has a drive motor 22, which is connected to a drive train 26 by a power-split transmission 24, which is preferably a continuously variable transmission.

[0023] To decelerate the agricultural tractor 10, the tractor 12 has a first braking system 32, and the at least one trailer 14 has a second braking system 34. Multiple trailers 14 can each have their own braking system 34. The braking system 32 of the tractor 12 can include a service brake, which can be actuated, for example, by an operator pressing a brake pedal, a parking brake, and / or an auxiliary brake. The braking system 34 of the trailer 14 includes at least one brake 36, which acts on a trailer axle 38 and / or on a respective ground engagement means 20 of the trailer 14. In addition, the second braking system 34 can be controlled via at least one electronically controllable trailer brake valve 40, wherein the trailer brake valve 40 can be arranged on the trailer side or the towing vehicle side. A fluid required for braking, for example, compressed air, is conveyed from the tractor 12 to the trailer 14 via a brake line 66.The trailer 14 is connected to the towing vehicle 12 at the coupling point 72 by means of a drawbar 70 through the coupling 56. At least one brake 36 is arranged on each of the trailer axles 38, whereby, for example, the trailer axles 38 and / or the ground engagement means 20 can be braked independently of one another.

[0024] The first braking system 32 of the tractor 12 and the second braking system 34 of the trailer 14 are each connected to a control device 42 of the tractor 12 for controlling the braking systems 32, 34. An input / output unit 68 connected to the control device 42 can be arranged in a driver's cab 44 of the towing vehicle 12.

[0025] The continuously variable power-split transmission 24 has a mechanical sub-transmission 46 and a hydraulic or hydrostatic sub-transmission 48. Based on a drive torque input to the transmission 24, an output torque MA is provided to an output shaft of the transmission 24, which output torque MA is adjustable depending on the efficiency of the transmission 24 and the transmission ratio.

[0026] To split the power from the drive motor 22 entering the transmission 24, the transmission 22 has a planetary gear 50, through which part of the power is introduced into the drive train 26 via the mechanical sub-transmission 46 and another part via the hydrostatic sub-transmission 48. The power entering the hydrostatic sub-transmission 48 drives the first hydrostat 28, which acts as a pump, in particular depending on the direction of travel. This first hydrostat 28 is hydraulically connected by a first hydraulic line 52 and a second hydraulic line 54 to the second hydrostat 54, which then acts as a motor and also provides the power to the drive train 26. The continuously variable hydrostats 28, 30, in particular of wide-angle design, enable continuous control of the transmission ratio.

[0027] The output torque MA of the hydraulic-mechanical continuously variable transmission 24, in particular its direction and / or magnitude, can be determined by pressure sensors 58, 60 arranged on the hydraulic lines 52, 54 that hydraulically connect the hydrostats 28, 30. A first pressure sensor 58 is arranged on the first hydraulic line 52, and a second pressure sensor 60 is arranged on the second hydraulic line 54. If no overrun operation is present, for example, the pressure P 1 in the first hydraulic line 54 is greater than the pressure P 2 in the second hydraulic line 54. This pressure ratio is reversed as soon as overrun operation occurs, so that in overrun operation, with the direction of travel unchanged, the pressure P 2 is greater than the pressure P 1 . The magnitude of the pressure difference corresponds to the magnitude of the output torque MA at the output of the transmission 24.As a result, both the presence and magnitude of overrun operation can be determined based on the pressure difference in the hydraulic lines 52, 54. This is also conceivable in a continuously variable hydraulic-mechanical transmission 24 with hydrostats in a so-called back-to-back design. In a mechanical or hydrostatic continuously variable transmission 24 and / or a powershift transmission, for example, the support torque M St of the transmission 24 can be determined as a transmission parameter. The support torque M St , which depends, for example, on a speed of the drive motor 22, a transmission ratio, and / or a transmission efficiency, can be determined using a characteristic curve, in particular a drag characteristic curve. The support torque M St is the difference between the drive torque and the output torque MA of the transmission 24.The speed of the drive motor 22 can be measured by means of a first speed sensor 62, for example, on an input shaft of the transmission 24. A second speed sensor 64 on the output shaft of the transmission 24 can determine the output speed na and thus, together with the input speed ni or speed ni of the drive motor 22, the transmission ratio.

[0028] The detection of the presence of a coasting operation by the control device 42 causes it to automatically control the braking system 34 of the trailer 14.

[0029] In Fig. 2 (a) to (d)is an exemplary and schematic representation of an agricultural tractor-trailer combination 10 with a tractor 12 as the towing vehicle and two trailers 14 coupled to it during a downhill journey, in which a critical driving situation develops. Decelerating the tractor-trailer combination 10 solely by adjusting the engine speed and the gear ratio results in the entire mass of the tractor-trailer combination 10, whereby the mass of just one loaded trailer 14 may already exceed the mass of the tractor 12, being braked solely by the driven rear axle 18 of the tractor 12. Overbraking of the driven rear axle 18 can cause the slip on the ground contact means 20 or tires of the tractor 12 to increase significantly, which leads to a reduction in driving stability. In extreme cases, the tractor-trailer combination 10 may collapse during the resulting overrun, as shown in the Fig. 2(c) and 2(d) shown.

[0030] The representation in Fig. 3shows schematically the train 10 which has buckled during cornering due to a steering command according to Fig. 1 MP denotes an instantaneous center of gravity, which serves as the reference point of the train 10 moving on a curved path KB. A two-dimensional coordinate system serves to illustrate a longitudinal direction x and a transverse direction y.

[0031] The tractor-trailer combination 10 moves along a curved path KB which results from a set steering angle α Lenk. The tractor 12 has a longitudinal axis 74 and the trailer 14 has a longitudinal axis 76. The velocity vector v T of the tractor 12 and v A of the trailer 14 act at the center of the tractor 12 and the trailer 14 respectively. The steering angle α Lenk is illustrated on the ground engagement means 20 of the front axle 16 on the inside of the curve. As a result of the steering movement with the steering angle α Lenk, the tractor-trailer combination 10 buckles at the coupling point 72. The longitudinal axis 74 of the tractor 12 and the longitudinal axis 76 of the trailer 14 run at an angle α Knick to one another, inclined to one another. A coupling force generated at the coupling point 72 in a thrust drive, represented by the force vector F coupling , acts in the direction of the longitudinal axis 76 of the trailer 14. Due to the articulation angle α kink, the coupling force F coupling only acts proportionally with a force component F coupling,x in the longitudinal direction x, ieDirection of the longitudinal axis 74 of the tractor 12. A further force component F coupling,y acts in the transverse direction y, ie perpendicular to the longitudinal axis 74 of the tractor 12.

[0032] The determination of the presence of a pushing operation of the tractor 10 described above only records the force component F coupling,x , which acts in the longitudinal direction x of the tractor 12. Thus, the actual coupling force F coupling at the coupling point 72 is greater than the force component F coupling,x determined to determine the presence of a pushing operation. The coupling force F coupling at the coupling point 72 can be calculated according to the equation F Koppel = F Koppel , x α knick <none / > <mprescripts / > <none / > cos determine.

[0033] The articulation angle α articulation is an unknown if no additional means for detecting the articulation angle α articulation are provided. This makes it impossible for the control device 42 to detect all critical driving situations in which strong active steering is required, regardless of whether the vehicle is traveling downhill or on level ground.

[0034] In order to be able to determine the coupling force F coupling without the need for an additional sensor, such as a camera, and the evaluation unit required for this, the invention provides that the control device 42 is set up to calculate a correction factor K as a function of the steering angle α Lenk detected when coasting is present, in order to correct the coupling force F coupling,x acting in the longitudinal direction x in the coupling point 72, which is determined from the at least one operating parameter, output torque MA or support torque M St , taking into account the steering angle α Lenk and a theoretical articulation angle α Knick,t in the coupling point 72.

[0035] Thus, the coupling force F coupling at the coupling point 72 can be generalized according to the equation F Koppel = F Koppel , x ∗ K α Lenk α Knickk , t calculate.

[0036] In particular, the control device 42 is configured to calculate the theoretical articulation angle α Knick,t at the coupling point 72 using a mathematical model that takes into account the steering angle α Lenk detected by a steering angle sensor. The steering angle α Lenk , which is decisive for setting the target trajectory curve KB, is preferably the steering angle α Lenk of a steering wheel of the tractor 12. The steering angle sensor assigned to the steering wheel makes it possible to derive the respective steering angle α Lenk of the steering wheel.

[0037] When coasting operation is present, the control device 42 is configured to control the braking force generated by the second braking system 34 of the trailer 14 in proportion to the detected steering angle α Lenk.

[0038] Furthermore, the input / output unit 68 of the control device 42 is configured to input and / or select at least one parameter influencing the braking behavior of the train 10. The at least one parameter is selected from the group consisting of the geometry of the working device, the number of coupled working devices, the loading condition, environmental parameters, and the condition and / or performance of the second braking system 34.

[0039] In addition, the at least one parameter can be a predeterminable gain factor for adjusting the braking force applied by the second braking system 34. The predeterminable gain factor has a value greater than zero. A gain factor between zero and one results in less aggressive braking, while a gain factor greater than one results in more aggressive braking behavior.

[0040] This allows the operator of tractor 12 to influence the braking behavior of the tractor-trailer combination 10. In addition to the specific conditions that depend on the coupled trailer(s) 14, the operator's individual needs can also be taken into account. Preferably, the input / output unit 68 can have its own menu structure for setting and / or selecting the at least one parameter that influences the braking behavior of the tractor-trailer combination 10. The menu structure can assist the operator in the input and / or selection process. List of reference symbols

[0041] 10 Agricultural train 76 Longitudinal axis of 14 12 tractor α Lenk Steering angle 14 Trailer α kink bending angle 16 front axle α kink,t Theoretical bending angle 18 rear axle F coupling Coupling force 20 Ground intervention equipment F coupling,x Coupling force 22 drive motor F Koppel,y Coupling force 24 Gearbox KB Curved track 26 Powertrain MA Output torque 28 Hydrostat M St Support moment 30 Hydrostat MP Instantaneous pole 32 First braking system n / a Output speed 34 Second braking system no Input speed 36 brake P 1 Pressure 38 trailer axle P 2 Pressure 40 Trailer brake valve va Velocity vector 42 Control device vt Velocity vector 44 Driver's cab 46 Mechanical partial transmission 48 Hydrostatic partial transmission 50 planetary gear 52 hydraulic line 54 hydraulic line 56 coupling 58 pressure sensor 60 pressure sensor 62 Speed ​​sensor 64 Speed ​​sensor 66 brake line 68 Input-output unit 70 drawbar 72 dome point 74 Longitudinal axis of 12

Claims

1. An agricultural vehicle combination (10), comprising a tractor (12) as a traction vehicle which is driven by a propulsion engine (22) cooperating with a continuously variable transmission (24) and has a first braking system (32), and at least one trailer (14) coupled to the tractor (12) in a coupling point (72) and which has a second braking system (34), wherein, in order to regulate at least one braking system (32, 34) of the agricultural vehicle combination (10), the tractor (12) has a control device (42) which is constructed and configured to actuate at least one of the braking systems (32, 34) of the vehicle combination (10) as a function of a determined engine braking operation of the vehicle combination (10) and / or traction vehicle (12), wherein the control device (42) is configured to determine the presence of an engine braking operation as a function of at least one operating parameter of the transmission (24) and / or of the propulsion engine (22), characterized in that the control device (42) is configured to calculate a correction factor (K) as a function of a steering angle (αLenk) detected when an engine braking operation is present, in order to correct a coupling force (FKoppel,x) in the coupling point (72) from the at least one operating parameter taking the steering angle (αLenk) into consideration, wherein, in order to determine the steering angle (αLenk), a steering wheel of the tractor (12) is provided with an associated steering angle encoder which specifies the steering angle (αLenk) as a control signal for the control device (42), wherein, when an engine braking operation is present, the control device (42) is configured to control the braking force produced by the second braking system (34) in proportion to the detected steering angle (αLenk), wherein the control device (42) is configured to use a mathematical model in order to calculate a theoretical buckling angle (αKnick,t) in the coupling point (72), which is fed into the calculation of the correction factor (K).

2. The agricultural vehicle combination (10) according to claim 1, characterized in that the continuously variable transmission (24) is configured as a mechanical or hydrostatic transmission.

3. The agricultural vehicle combination (10) according to claim 2, characterized in that the control device (42) is configured to determine an output torque (MA) and / or a drag torque (MSt) of the continuously variable hydrostatic transmission (24) from a pressure difference in a hydrostatic sub-transmission (48) of the transmission (24).

4. The agricultural vehicle combination (10) according to claim 3, characterized in that the output torque (MA) determined from the pressure difference of the hydrostatic sub-transmission (48) serves as a reference variable in the control of the second braking system (34).

5. The agricultural vehicle combination (10) according to one of claims 1 to 4, characterized in that the control device (42) comprises an input / output unit (68) which is configured for inputting and / or selecting at least one parameter influencing the braking behaviour of the trailer (14).

6. The agricultural vehicle combination (10) according to claim 5, characterized in that the at least one parameter is from the group: trailer (14) geometry, number of coupled trailers (14), loading status, environmental parameters, status and / or performance of the second braking system (34).

7. The agricultural vehicle combination (10) according to claim 5 or claim 6, characterized in that the at least one parameter is a specifiable gain factor for adjusting the braking force applied by the second braking system (34).

8. The agricultural vehicle combination (10) according to claim 7, characterized in that the specifiable gain factor has a value greater than zero.