System and method for operating a work machine

Abstract

The invention relates to a method for operating a work machine (1), comprising a drive device (5) having a hydrodynamic torque converter (2) and a power-shift transmission (3) having at least one first friction clutch (4) with power-shift capability, comprising the following steps:-during the following condition, a torque converter (2) is driven by the power-shift transmission (3), and the torque converter (2) is driven by the power-shift transmission (3) to be driven by the power-shift transmission (3) to be driven by the power-shift transmission (3) to be driven by the power-shift transmission (3); the transmission input shaft (6), which can be rotationally driven by the drive machine (1), is rotated at a constant unloaded operating speed, and wherein at least the first friction clutch (4) is in a first switching state in which at least one first torque converter slip is determined, and wherein the transmission input shaft (6), which can be rotationally driven by the drive machine (1), is rotated at a constant unloaded operating speed. No torque is transmitted via the at least first friction clutch (4), and a turbine wheel (8) of the torque converter (2), which turbine wheel (8) is operatively connected to the transmission input shaft (6), has a lower rotational speed than a pump wheel (7) of the torque converter (2); carrying out an inching adjustment mode, in which at least the first friction clutch (4) is actuated in order to adjust the ascertained first torque converter slip in such a way that friction partners (9, 10) of a respective friction pair of at least the first friction clutch (4) are brought into frictional contact with one another. The invention also relates to a system for operating a work machine (1), a processor unit (11), a drive train (12), a work machine (1) and a computer program product.

Description

Field of technology

[0001] The present invention relates to a method and a system for operating a work machine. In particular, a processor unit, a drive train, a work machine, and a computer program product are claimed herein. Background art

[0002] Modern motor vehicles in the form of work machines can be driven by a diesel engine and generally have a power-shiftable stepped transmission combined with a torque converter. These torque converters are equipped with one or more power-shift clutches that act as so-called direction clutches. With such power-shift clutches, it is possible to implement a so-called inch mode (Inchbetrieb). The (main) direction clutch is configured such that it can be used on the one hand for starting (engaging the gear) and on the other hand also for the inch mode (due to thermal load design, number of diaphragms, etc.).

[0003] "Inching" refers to the control process of a work machine with a hydraulic drive system, in which the system realizes a specific (mechanical or electronic) relationship between the braking or inching pedal position and the driving speed, which is required when the movement (e.g., driving speed) should be less than the movement corresponding to the engine speed. However, for a second movement of especially attached equipment, etc. (e.g., the forks in a forklift or the bucket in a wheel loader), a specific engine speed is required. This control process is called inching. During the inching process, the traction force of the driving drive can be arbitrarily changed from 100% to 0% via the corresponding pedal.

[0004] If the requirement is that a higher drive power is needed at the position of the work hydraulics rather than at the position of the driving drive, it is feasible to decouple the driving drive. For this purpose, the power-shiftable clutch in the stepped transmission either completely disengages the clutch or adjusts the transmitted power by clutch slip. Using a slipping clutch for traction modulation with limited power consumption is called "inching".

[0005] In "inching", a multi-disc clutch with power-shifting capability operates in a slipping state, in which a torque greater than or equal to 0 Nm is transmitted. However, the slipping clutch heats up quite significantly during operation, so the range in which the clutch can slip continuously is limited. In order to comply with the limit value of the clutch load capacity and avoid clutch damage, the predetermined hydraulic pressure and the resulting actual pressure need to be substantially consistent. To ensure this, a relatively high degree of measurement technology has been used so far, which ensures that the target pressure and the actual pressure at the clutch are as precisely consistent as possible. Despite adjusting the vehicle through measurement technology, the accuracy during the operation of the work machine is still not good enough, so clutch failures may occur due to excessive inching pressure. Summary of the invention

[0006] The object of the present invention may be to specify a method and a system for operating a work machine in an improved inching mode.

[0007] This object is achieved by the subject matter of the independent patent claims. Advantageous embodiments are the subject matter of the dependent claims, the following description and the drawings.

[0008] In order to achieve precise control of a power-shift-capable friction clutch for an inching mode of a work machine with as little additional measurement technology as possible, preferably without any additional measurement technology, it is proposed according to the invention to implement a traction force modulation at the power-shift transmission, which traction force modulation can also compensate for the influences of, for example, the state of wear, friction values and temperature. For this purpose, a so-called controlled inching mode is proposed, in which the torque converter slip is automatically learned and thus adapted to the various transmissions of the work machine.

[0009] According to a first inventive aspect, a method for operating a working machine according to the present invention, wherein the working machine comprises a drive device, the drive device having a torque converter and a power shift transmission, the power shift transmission having at least one first friction clutch having power shifting capability, the method comprising the following steps:

[0010] - at least one first torque converter slip is determined during the following conditions, namely,

[0011] • The drive machine is in no-load operation, wherein the transmission input shaft, which can be driven by the drive machine, rotates at a constant no-load speed,

[0012] • at least the first friction clutch is in a first switching state, in which no torque is transmitted via at least the first friction clutch,

[0013] • The turbine wheel of the torque converter, which is operatively connected to the transmission input shaft, has a lower rotational speed than the pump wheel of the torque converter;

[0014] An inching control mode is implemented, wherein, in order to adjust the determined first torque converter slip, at least the first friction clutch is actuated in such a way that the friction partner parts of the respective friction pairing of at least the first friction clutch are brought into friction contact with one another.

[0015] Thus, the method generally consists of two steps. On the one hand, it is to learn the first torque converter slip, and on the other hand, it is to perform a controlled inching mode. The torque converter slip is understood as the difference between the engine speed or the impeller speed and the turbine speed while the engine is at the no-load running speed. The drive device is in no-load operation when no drive power is transmitted via the power shift transmission to the wheels of the work machine that are operatively connected to the transmission for driving the work machine.

[0016] At least the first friction clutch refers to a direction clutch or an inching clutch, and it is in the disengaged switching state during the learning of the first torque converter slip. More precisely, in any case, no torque is transmitted via this friction clutch. Thus, the learning of the torque converter slip can be carried out with the first friction clutch completely disengaged or with the so-called "preparing" friction clutch. The completely disengaged first friction clutch is understood as an unoperated friction clutch that has an actual pressure of 0 bar or a control current of 0 mA. The preparing friction clutch may already be operating at a specific pressure or a certain control current, yet it does not transmit torque. Thus, in the case of a friction clutch constructed as a multi-disc clutch, the diaphragm may be about to contact or has already contacted but does not transmit torque. Preferably, the learning of the torque converter slip is carried out with the friction clutch completely separated or unoperated.

[0017] The friction clutch in the sense of the present invention is provided for releasably transmitting torque between two component parts. The friction clutch is adjustable and can transmit torque between 0% and 100% depending on the squeezing pressure. The torque transmission is achieved via two friction pairs forming the friction pair of the friction clutch. When these friction pairs are pressed against each other by corresponding manipulation and / or displacement, a friction lock or a force lock for torque transmission is generated.

[0018] When the inching pedal of the work machine is 100% operated, there is an inching adjustment mode in the sense of the present invention. The 100%-operated inching pedal does not transmit torque or does not transmit significant torque to the driven end. In the inching adjustment mode, at least the first friction clutch is operated in such a way that the first torque converter slip obtained or learned is adjusted by means of a specific adjustment pressure, wherein the friction pairs of the respective friction pairs of at least the first friction clutch are brought into frictional contact with each other. This is understood as the so-called "contact point" of the friction clutch. The inching adjustment mode can be carried out at this point.

[0019] The first friction clutch is preferably configured as a multi-plate clutch, wherein each friction pair is a diaphragm of the multi-plate clutch. Thus, two diaphragms form each friction pair, and a form-locking force is generated by axially pressing the diaphragms. The friction clutch can have a plurality of friction pairs, which can be combined into a friction assembly in a known manner. Thus, due to the pressing force, a frictional force is obtained via the friction surface when the friction clutch is actuated, and the torque that can be transmitted is obtained by multiplying the frictional force by the average radius of the friction surface. The actuation of the friction clutch is achieved by means known in the prior art.

[0020] If starting from the contact point, the adjustment pressure applied to the first friction clutch is increased only to a minimum extent, the rotational speed of the turbine of the torque converter decreases. This is because each increase in pressure starting from the contact point pressure will result in torque transmission. If the slip of the torque converter at the contact point is known, it can be inferred therefrom when the first friction clutch transmits torque depending on the change in the slip of the torque converter. The contact point of the first friction clutch can theoretically be determined based on the structural data of the respective friction clutch.

[0021] The contact point pressure is preferably adjusted by adjusting a specific drive current for actuating the friction clutch. Based on the drive current, an adjustment pressure is generated that brings the friction mating parts into frictional contact with each other but no torque is transmitted via the friction clutch. In this sense, at least the first friction clutch is actuated by adjusting the target drive current for implementing the jogging adjustment mode. By specifically adjusting the drive current, a specific actual pressure occurs at the first friction clutch. Thus, depending on the slip of the torque converter, the slip of the torque converter can be used as an indication parameter to determine the actual pressure of the respective friction clutch without measurement technology.

[0022] In the jogging adjustment mode, the drive current of the first friction clutch is adjusted such that the slip of the torque converter previously known during no-load operation occurs. Here, the drive current determined based on the target pressure acts as a feedforward control.

[0023] The "no-load operation" of at least the first friction clutch is prevented by the jogging adjustment mode. Thus, when the driver correspondingly actuates the jogging adjustment device, especially the jogging pedal, at least the first friction clutch is immediately ready to enter the adjusted jogging mode.

[0024] In one embodiment, an offset is determined in connection with the respectively known torque converter slip, wherein, in order to adjust the respectively known first torque converter slip, at least the first friction clutch is actuated in such a way that the friction counterparts of the respective friction pairs of the at least first friction clutch are brought into frictional contact with one another, taking into account the respective offset. Thus, the drive current for actuating the first friction clutch is supplemented by an additional drive current obtained from the offset. The offset can be known in advance by measurement technology.

[0025] The offset is a rotational speed deviation from the torque converter slip, which rotational speed deviation is superimposed on the respectively known torque converter slip, wherein the actuation of the first friction clutch is carried out taking into account the respectively known torque converter slip and the offset, more precisely preferably such that a minimum torque is transmitted via the first friction clutch. Thus, since the first friction clutch is also actuated depending on the offset, a very small torque is transmitted via the first friction clutch at the contact point of the first friction clutch in the jogging adjustment mode. Therefore, the transmitted torque is adjusted in particular by appropriately selecting the offset.

[0026] In the jogging adjustment mode, the drive current of the first friction clutch is adjusted such that the torque converter slip known previously during no-load operation plus a predetermined offset occurs. The additionally adjusted offset causes a slight increase in the actual pressure on the first friction clutch, such that the first friction clutch transmits a minimum torque. The control pressure is also slightly increased relative to the actual pressure without taking the offset into account. By means of the predetermined offset, the jogging mode can be directly initiated as soon as the driver actuates the jogging pedal accordingly.

[0027] Preferably, at least the first torque converter slip is known depending on at least one disturbance variable of the powershift transmission and / or the torque converter. The disturbance variable may in particular include the shrinkage behavior of the clutch lining, the condition of the clutch lining of the respective powershift clutch configured as a friction clutch, the condition of the lubricating medium and / or the cooling medium, the friction coefficient of the respective friction pairs of the respective powershift clutches configured as friction clutches and / or the lubricating medium temperature. The torque converter slip is in particular significantly temperature-dependent, such that the torque converter slip is known or learned at different temperatures respectively. In other words, depending on the respective disturbance variable, the respective torque converter slip can be known or automatically learned in the no-load operating state.

[0028] Preferably, the current offset is determined after reaching the target drive current. In other words, the regulator determines the current offset after reaching the target drive current, such that the desired torque converter slip occurs. The current offset is a current intensity deviation from the target drive current required to adjust the desired torque converter slip.

[0029] Furthermore preferably, the respective determined current offsets are stored. Thereby, the current offset values can also be used outside the jogging adjustment mode and / or after the work machine has been restarted. Thus, the respective stored current offsets can be used for various different jogging states. Outside the adjustment mode, the offset is fixed. Outside the adjustment mode, although the offset is output, it is not taken into account.

[0030] According to a second aspect of the invention, in a system for operating a drive machine according to the invention, wherein the work machine comprises a drive device having a torque converter and a power shift transmission, the power shift transmission having at least one first friction clutch with power shift capability, during the following situations, at least one first torque converter slip can be ascertained, namely,

[0031] • the drive device is in no-load operation, wherein the transmission input shaft that can be rotated by the drive machine rotates at a constant no-load operating speed,

[0032] • the friction clutch is in a first switching state, in which no torque is transmitted via at least the first friction clutch,

[0033] • the turbine of the torque converter acting on the transmission input shaft has a lower rotational speed compared to the pump impeller of the torque converter;

[0034] and wherein a jogging adjustment mode can be implemented, wherein, in order to adjust the ascertained first torque converter slip, at least the first friction clutch can be actuated in such a way that the friction mating parts of the respective friction pairs of at least the first friction clutch are brought into frictional contact with one another.

[0035] Preferably, an offset can be determined in combination with the respective ascertained torque converter slip, wherein, in order to adjust the ascertained first torque converter slip, at least the first friction clutch can also be actuated in consideration of the respective offset in such a way that the friction mating parts of the respective friction pairs of at least the first friction clutch are brought into frictional contact with one another.

[0036] Preferably, at least the first torque converter slip can be ascertained as a function of at least one disturbance variable of the power shift transmission and / or the torque converter.

[0037] Furthermore preferably, by adjusting a target drive current, at least the first friction clutch can be actuated for implementing the jogging adjustment mode.

[0038] Furthermore preferably, the current offset can be determined after the target drive current has been reached. More preferably, the system has a data memory configured to store at least the determined current offset.

[0039] It should be clearly pointed out that in the sense of the present invention, a power shift transmission can have a plurality of friction clutches or direction clutches with power shift capabilities, and they can implement their respective inching adjustment modes. The power shift transmission should be understood as a stepped transmission that can be power shifted.

[0040] According to a third aspect of the present invention, a processor unit is proposed, wherein the processor unit is configured to implement the method according to the present invention according to the first aspect of the invention.

[0041] According to a fourth aspect of the present invention, a drive train for a work machine is provided. The drive train includes a processor unit according to the third aspect of the invention and a drive device having a power shift transmission operatively connected thereto and a torque converter also operatively connected thereto. The drive device is a drive motor, preferably an internal combustion engine, in particular a diesel engine, which is operatively connected via the power shift transmission to at least one wheel of a drivable axle.

[0042] According to a fifth aspect of the present invention, a work machine is provided, which includes a drive device according to the fourth aspect of the present invention. The work machine typically has at least one attachment device that can be operated by means of the system according to the present invention. The work machine is, for example, an agricultural machine, such as a tractor with a bucket or a fork, or a construction machine, such as a mobile excavator with a bucket, or a forklift with a fork. Other motor vehicles with attachment devices that can advantageously use the inching mode are also conceivable.

[0043] According to a sixth aspect of the present invention, a computer program product is provided, which contains machine-readable instructions that, when implemented on a computer and / or a processor unit, upgrade the computer and / or the processor unit to the control logic of the system for operating a work machine according to the second aspect of the invention, and / or cause the implementation of the method for operating a work machine according to the first aspect of the invention.

[0044] The above definitions and embodiments regarding the technical effects, advantages, and advantageous embodiments of the method according to the first aspect of the present invention meaningfully also apply to the system according to the second aspect of the present invention, the processor unit according to the third aspect of the present invention, the drive train according to the fourth aspect of the present invention, the work machine according to the fifth aspect of the present invention, and the computer program product according to the sixth aspect of the present invention, and vice versa. Description of the Drawings

[0045] The embodiments of the present invention are further elaborated below in conjunction with the schematic diagrams, wherein the same or similar elements are provided with the same reference numerals. In the figures:

[0046] Figure 1 A rough schematic diagram of the work machine is shown, and

[0047] Figure 2 A diagram is shown for schematically explaining the process of a method for operating a work machine according to the present invention according to Figure 1 the work machine. DETAILED DESCRIPTION

[0048] Figure 1 A motor vehicle in the form of a work machine 1 is shown. The work machine 1 can be, for example, a wheel loader having a bucket as an attachment device 17. The work machine 1 can be operated in a jogging mode. The work machine 1 includes a drive train 12, wherein the drive train 12 includes a processor unit 11 and a drive device 5 for driving the work machine 1. The drive device 5 is, for example, an internal combustion engine in the form of a diesel engine, which is operatively connected to a power shift transmission 3 or a power-shiftable stepped transmission and a torque converter 2. The exact structure of the power shift transmission 3 is not shown here. However, at least, the power shift transmission 3 includes a plurality of clutches, wherein at least the first clutch is a friction clutch 4 with power-shifting capability. The friction clutch 4 is understood as the direction clutch of the power shift transmission 3. The method according to the present invention for operating the drive machine 1 can be implemented by using the friction clutch 4, which will be described below.

[0049] The drive device 5 drives the front axle 14 via the power shift transmission 3 and, depending on the jogging state, also drives the attachment device 17. It is conceivable that, alternatively or additionally, the drive device can also drive the rear axle 13 of the work machine 1. Wheels, tracks or the like for propelling the work machine 1 can be mounted on the front axle 14 and the rear axle 13. The power shift transmission 3 communicates with the processor unit 11 and also includes a torque converter 2. The torque converter 2 includes a pump impeller 7 and a turbine 8, which are operatively connected or can be operatively connected to the transmission input shaft 6 of the drive device 5. The torque converter 2 is part of the system according to the present invention for operating the drive machine 1, wherein the friction clutch 4 can be actuated in the jogging control mode in such a way that "idling" of the friction clutch 4 is prevented and, conversely, the friction clutch 4 can be immediately used to implement the jogging mode of the work machine 1.

[0050] Figure 2 A diagram is shown, in which the upper part respectively plots a first rotational speed curve 18 of the pump impeller 7 or the transmission input shaft 6 and a second rotational speed curve 19 of the turbine 8 over time. In accordance with Figure 2In the middle part of the diagram, a torque curve 20 of the torque transmitted by the friction clutch 4 is plotted against time. In the lower part of the diagram, a first pressure curve 21 of the friction clutch 4 and a second pressure curve 22 of the second friction clutch 15 are plotted. The second friction clutch 15 connects the power shift transmission 3 to the wheels of the driven end or the drive train 12. The second pressure curve 22 shows that the second friction clutch 15 is closed during the no-load operation (phases P1 and P2) and during the jogging adjustment mode (phase P3). It can also be seen that the rotational speed of the pump impeller 7 or the transmission input shaft 6 does not change in phases P1 to P3.

[0051] According to Figure 2 , in a first phase P1 of the method according to the invention, the torque converter slip is determined or automatically learned. This is done during the no-load operation of the drive device 5, in which the transmission input shaft 6 driven by the drive machine 1 rotates at a constant no-load operating speed according to a first rotational speed curve 18, while the friction clutch 4 is in a first switching state of being fully disengaged, so that no torque is transmitted via the friction clutch 4, see the first pressure curve 21 in phase P1. In addition, when the drive device 5 is operating without load, the turbine 8 of the torque converter 2 acting on the transmission input shaft 6 has a lower rotational speed than the pump impeller 7 of the torque converter 2. The torque converter slip is affected by various different interference variables of the drive train 12, in particular of the power shift transmission 3, and the torque converter slip of the torque converter 2 is determined in combination with these interference variables. Since the torque converter slip is particularly significantly temperature-dependent, the torque converter slip at different temperatures can be determined or learned. For example, and for better understanding, here, when the lubricant temperature is 70 °C, the torque converter slip is determined to be 30 revolutions per minute in the no-load operation mode of the drive device 5. In the first phase P1, the torque converter slip is automatically learned as a reference value.

[0052] Subsequently, in the no-load operation mode of the drive device 5, a jogging adjustment mode can be implemented, in which, in order to adjust the determined first torque converter slip, the friction clutch 4 is first actuated in such a way that the friction mating parts 9, 10 of the respective friction pairs of the friction clutch 4 are brought into frictional contact with each other. This corresponds to phase P2 and is understood as the "Touchpoint" of the friction clutch 4. Here, the pressure is increased to a specific value according to Figure 2 the pressure curve 21. At the contact point, each increase in the torque converter slip can be detected by the friction clutch 4 as the transmissible torque. In addition, each increase in the pressure in the friction clutch 4 results in the transmission of torque, while the rotational speed of the turbine 8 decreases. This is evident in the transition region between phase P2 and phase P3.

[0053] The torque converter slip corresponds to the state when the friction clutch 4 transmits a torque of 0 Nm. In the present text, the friction clutch 4 is a multi-plate clutch, in which the friction pairs 9, 10 are Figure 1 understood as the diaphragm of the multi-plate clutch. Whenever the diaphragm is mentioned hereinafter, it is always understood as the friction pairs 9, 10, and vice versa. Similarly, whenever the multi-plate clutch is mentioned hereinafter, it always means the friction clutch 4, and vice versa. It should be noted that all types of clutches with frictional capacity can be used for the present invention, regardless of whether they are pneumatically, hydraulically or otherwise actuated.

[0054] There is a jogging adjustment mode when a jogging adjustment device (not shown here), such as a jogging pedal, is fully actuated, i.e., no torque is transmitted or a negligible torque is transmitted to the attachment device of the working machine 1. The jogging adjustment mode takes place in the third phase P3.

[0055] In the jogging adjustment mode, the target drive current of the friction clutch 4 is adjusted such that the torque converter slip previously known during no-load operation plus an empirically known and predetermined offset occurs. Thus, the slip in the torque converter 2 is set to the target value. Once the torque converter slip is reached, the actual pressure in the friction clutch 4 (by which the friction clutch 4 is actuated) can be determined according to physical relationships. The offset is, for example, 5 revolutions per minute, so that a drive current corresponding to 35 revolutions per minute is adjusted for actuating the friction clutch 4. The drive current determined according to the target pressure serves as feedforward control. The additionally adjusted offset causes the actual pressure of the friction clutch 4 to increase slightly, so that the friction clutch 4 transmits a minimum torque. The control pressure also increases slightly relative to the "0 Nm pressure". In this example, the control pressure for adjusting the first torque converter slip or for actuating the friction clutch 4 is 1.5 bar, so that the friction pairs 9, 10 are in contact with each other but do not transmit torque. This pressure roughly corresponds to the spring force in the friction clutch 4.

[0056] Taking the offset into account, the friction clutch 4 is controlled to a target pressure of, for example, 1.6 bar in the jogging adjustment mode. The drive current therefor corresponds to 220 mA. After the target drive current is reached, the regulator determines the current offset, so that the desired torque converter slip occurs. This torque converter slip can be stored in the storage unit 16 for various different jogging states. In other words, the currently used current can be stored as a value on the proportional pressure regulator, where the basic parameters are used for various different jogging states by forming the current offset. The torque converter slip speed can be stored on the storage unit 16 depending on the aforementioned disturbance parameters and is used for operating states different from the adjustment mode.

[0057] The jogging adjustment mode can be carried out by means of a computer program product for operating the working machine 1, wherein the computer program product can contain corresponding program code for this purpose. For example, a regulator for adjusting the drive current can be stored on the computer program product. The processor unit 11 can access and execute the computer program product. For example, the computer program product can be stored in the storage unit 16 of the processor unit 11.

[0058] It should be noted that the present invention is not only applicable to torque converters, but also to main clutches or hydrostatic devices. Only the indication parameters for torque transmission change.

[0059] Of course, different torque converters have different characteristic curves and torque converter slip speeds. With the present invention proposed here, an automatic recognition function for the torque converter slip can be achieved. By learning the torque converter slip speed, the torque converter characteristics can be learned and equalized for any transmission. Similarly, tolerances such as friction values can be compensated, and the aging effects of friction surfaces and lubricants can also be compensated.

[0060] List of reference signs

[0061] 1 Working machine

[0062] 2 Torque converter

[0063] 3 Power shift transmission

[0064] 4 First friction clutch or multi-disc clutch

[0065] 5 Drive device

[0066] 6 Transmission input shaft

[0067] 7 Pump impeller

[0068] 8 Turbine

[0069] 9 First friction mating part or first diaphragm of the friction clutch

[0070] 10 Second friction mating part or second diaphragm of the friction clutch

[0071] 11 Processor unit

[0072] 12 Drivetrain

[0073] 13 Rear axle

[0074] 14 Front axle

[0075] 15 Second friction clutch

[0076] 16 Storage unit

[0077] 17 Additional equipment

[0078] 18 First speed curve

[0079] 19 Second rotational speed curve

[0080] 20 Torque curve

[0081] 21 First pressure curve

[0082] 22 Second pressure curve

[0083] P1 First stage

[0084] P2 Second stage

[0085] P3 Third stage

Claims

1. A method for operating a work machine (1), said work machine (1) including a drive device (5), said drive device having a torque converter (2) and a power shift transmission (3), said power shift transmission having at least one first friction clutch (4) with power shift capability, the method comprising the following steps: - During the following conditions, obtaining at least one first torque converter slip, • The drive device (5) is running without load, wherein, the transmission input shaft (6) that can be rotationally driven by the drive machine (1) rotates at a constant no-load running speed, • said at least first friction clutch (4) is in a first switching state, in which no torque is transmitted via said at least first friction clutch (4), • the turbine (8) of the torque converter (2) acting on the transmission input shaft (6) has a lower speed compared to the pump impeller (7) of the torque converter (2); - Implementing a jog adjustment mode, wherein, in order to adjust the obtained first torque converter slip, said at least first friction clutch (4) is manipulated in such a way that the friction mating parts (9, 10) of the respective friction pairs of said at least first friction clutch (4) are placed in frictional contact with each other.

2. The method according to claim 1, wherein, Determining an offset in combination with the respective obtained torque converter slip, wherein, in order to adjust the obtained first torque converter slip, said at least first friction clutch (4) is further manipulated in consideration of the respective offset in such a way that the friction mating parts (9, 10) of the respective friction pairs of said at least first friction clutch (4) are placed in frictional contact with each other.

3. The method according to claim 1 or claim 2, wherein Said at least first torque converter slip is obtained depending on at least one disturbance parameter of the power shift transmission (3) and / or the torque converter (2).

4. The method according to any one of the preceding claims, wherein, Manipulating said at least first friction clutch (4) by adjusting a target drive current for implementing the jog adjustment mode.

5. The method according to claim 4, wherein Determining a current offset after reaching the target drive current.

6. The method according to claim 5, wherein Storing the determined current offset.

7. A system for operating a work machine (1), the work machine (1) including a drive device (5) having a hydrodynamic torque converter (2) and a power shift transmission (3), the power shift transmission having at least one first friction clutch (4) with power shift capability, wherein, During the following conditions, it is possible to obtain at least one first torque converter slip, that is, • said drive device (5) is in no-load operation, wherein the transmission input shaft (6) that can be rotationally driven by the drive machine (1) rotates at a constant no-load running speed, • said at least first friction clutch (4) is in a first switching state, in which no torque is transmitted via said at least first friction clutch (4), • the turbine (8) of the torque converter (2) acting on the transmission input shaft (6) has a lower speed compared to the pump impeller (7) of the torque converter (2); and wherein, it is possible to implement a jog adjustment mode, wherein, in order to adjust the obtained first torque converter slip, said at least first friction clutch (4) can be manipulated in such a way that the friction mating parts (9, 10) of the respective friction pairs of said at least first friction clutch (4) are placed in frictional contact with each other.

8. The system according to claim 7, wherein, It is possible to determine an offset in connection with the respectively known torque converter slip. Herein, in order to adjust the respectively known first torque converter slip, the at least first friction clutch (4) can also be actuated taking into account the respectively determined offset in such a way that the friction mating parts (9, 10) of the respective friction pairs of the at least first friction clutch (4) are brought into frictional contact with one another.

9. The system according to claim 7 or claim 8, wherein, The at least first torque converter slip can be determined as a function of at least one disturbance variable of the power shift transmission (3) and / or the torque converter (2).

10. The system according to any one of the preceding claims, wherein, The at least first friction clutch (4) can be actuated by adjusting a target drive current for implementing a jogging adjustment mode.

11. The system according to claim 10, wherein, An offset current can be determined after the target drive current has been reached.

12. A processor unit (11) which is set up to carry out the method according to any one of claims 1 to 6.

13. A drive train (12) for a work machine (1), comprising the processor unit (11) according to claim 12 and a drive device (5) which has a power shift transmission (3) operatively connected thereto and a hydrodynamic torque converter (2) also operatively connected thereto.

14. A work machine (1) comprising the drive train (12) according to claim 13.

15. A computer program product which contains machine-readable instructions which, when the machine-readable instructions are carried out on a computer and / or a processor unit (11), upgrade the computer and / or the processor unit (11) to the control logic of a system for operating a work machine (1) according to any one of claims 7 to 11, and / or cause the method for operating a work machine (1) according to any one of claims 1 to 6 to be carried out.

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