METHOD FOR OPERATING A DRIVE TRAIN OF A WORKING MACHINE, DRIVE TRAIN FOR A WORKING MACHINE, AND WORKING MACHINE

Abstract

The disclosure relates to a method for operating a drive train of a working machine, wherein the drive train comprises a working drive and a travel drive. The working drive is driven by a first electric motor and the travel drive is driven by a second electric motor. The disclosed method includes that the travel drive is additionally driven by the first electric motor if at least one performance criterion of said travel drive has been met. The disclosure further relates to a corresponding drive train and to a working machine.

Claims

1. A method for operating a drive train of a working machine, wherein the drive train comprises a working drive and a traction drive, the method comprising driving the working drive by a first electric motor and driving the traction drive by a second electric motor, wherein the traction drive is additionally driven by the first electric motor if at least one power criterion of the traction drive is met.

2. The method as claimed in claim 1, wherein the power criterion is exceeding a limit speed.

3. The method as claimed in claim 1, wherein the power criterion is exceeding a limit time for which the second electric motor is operated in a peak power range.

4. The method as claimed in claim 1, wherein the power criterion is exceeding a limit gear stage of a traction transmission.

5. The method as claimed in claim 2, wherein the limit speed is a maximum of 20 km/h.

6. The method as claimed claim 1, wherein the working drive is permanently driven by the first electric motor.

7. The method as claimed in claim 6, wherein a power supply of the first electric motor to the working drive is adjusted or regulated via an adjustable piston stroke height of a hydraulic pump if the traction drive is additionally being driven by the first electric motor.

8. The method as claimed in claim 1, wherein the traction drive is additionally driven by the first electric motor only if a power required by the working drive can be supplied thereto by the first electric motor.

9. The method as claimed in claim 1, wherein the working drive is additionally driven by the second electric motor if at least one power criterion of the working drive is met.

10. A drive train for a working machine, wherein the drive train comprises a working drive having a working transmission and a first electric motor, and a traction drive having a traction transmission and a second electric motor, wherein the working drive can be driven by the first electric motor via the working transmission and wherein the traction drive can be driven by the second electric motor via the traction transmission, wherein a drive connection can be established between the working drive and the traction drive via a connecting clutch.

11. The drive train as claimed in claim 10, wherein the drive connection runs from the first electric motor to the traction drive via an intermediate shaft for adaptation of the direction of rotation.

12. The drive train as claimed in claim 11, wherein the intermediate shaft is an intermediate shaft of the traction transmission.

13. The drive train as claimed in claim 10, wherein a separate transmission stage is provided, via which an adaptation of the speed and/or an adaptation of the direction of rotation of the first electric motor to the second electric motor is made possible.

14. The drive train as claimed in claim 10, wherein the traction transmission is configured so as to be power-shiftable over a plurality of gear stages.

15. (canceled)

16. A working machine comprising a drive train as claimed in claim 10.

17. The drive train of claim 12, wherein a separate transmission stage is provided, via which an adaptation of the speed and/or an adaptation of the direction of rotation of the first electric motor to the second electric motor is made possible.

18. The drive train of claim 17, wherein the traction transmission (8) is configured so as to be power-shiftable over a plurality of gear stages.

19. The drive train of claim 11, wherein the traction transmission (8) is configured so as to be power-shiftable over a plurality of gear stages.

20. The method of claim 1, wherein the at least one power criterion of the traction drive includes both a limit speed and a limit time for which the second electric motor is operated in a peak power range.

21. The method of claim 20, wherein the limit speed is a maximum of 20 km/h.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The disclosure will be explained by way of example hereinbelow with reference to embodiments shown in the figures, by which:

[0053] FIG. 1 shows, by way of example and schematically, a possible exemplary arrangement of a drive train according to the disclosure of a working machine,

[0054] FIG. 2 shows, by way of example and schematically, a further possible exemplary arrangement of a drive train according to the disclosure,

[0055] FIG. 3 shows, by way of example and schematically, yet a further possible exemplary arrangement of a drive train according to the disclosure,

[0056] FIG. 4 shows, by way of example and schematically, a possible exemplary arrangement of a drive train 1 according to the disclosure in the form of a wheel diagram,

[0057] FIG. 5 shows, by way of example, various torque curves of the traction drive in dependence on a travelling speed, and

[0058] FIG. 6 shows, by way of example and schematically, a possible exemplary arrangement of a method according to the disclosure for operating a drive train of a working machine in the form of a flow diagram.

DETAILED DESCRIPTION

[0059] Identical objects, functional units and comparable components are designated with the same reference numerals throughout the figures. These objects, functional units and comparable components are identical in form in terms of their technical features, unless explicitly or implicitly apparent otherwise from the description.

[0060] FIG. 1 shows, by way of example and schematically, a possible exemplary arrangement of a drive train 1 according to the disclosure in the form of a functional diagram for a working machine, not shown in FIG. 1. The drive train 1 shown by way of example comprises a working drive 2 having a first electric motor 3, a working transmission 4 and a working hydraulics system 5 operated by an electro-hydraulic pump 5. The drive train 1 further comprises a traction drive 6 having a second electric motor 7, a traction transmission 8 and a drive shaft 9. According to the example, the traction transmission 8 includes an auxiliary transmission 8′ and a power-shift part 8″. The working drive 2 is driven by the first electric motor 3, the traction drive 6 is driven by the second electric motor 7. A drive connection can additionally be established between the working drive 2 and the traction drive 6 via a connecting clutch 10. The traction drive 6 can thus additionally be driven by the first electric motor 3. Likewise, the working drive 6 can, however, additionally also be driven by the second electric motor 7.

[0061] According to the exemplary embodiment of FIG. 1, this additional drive connection leads from the first electric motor 3 via the working transmission 4, via the connecting clutch 10 to an intermediate shaft, not shown in greater detail, of the power-shift part 8″. Alternatively, the additional drive connection leads from the second electric motor 7 via the auxiliary transmission 8′, the mentioned intermediate shaft of the power-shift part 8″ and the connecting clutch 10 to the working hydraulics system 5. Thus, in this case, a separate intermediate shaft does not have to be provided for adaptation of the direction of rotation of the first electric motor 3.

[0062] Adaptation of the direction of rotation likewise takes place via the intermediate shaft of the power-shift part 8″. According to the example, the intermediate shaft selected for establishing the drive connection is chosen such that an output speed of the comparatively more slowly rotating working transmission 4 is adapted to an output speed of the comparatively more quickly rotating traction transmission 8.

[0063] FIG. 2 shows, by way of example and schematically, a further possible exemplary arrangement of a drive train 1 according to the disclosure in the form of a functional diagram for a working machine, not shown in FIG. 2. The exemplary arrangement illustrated in FIG. 2 differs from the exemplary arrangement shown in FIG. 1 by the path of the drive connection from the working drive 2 to the traction drive 6 and vice versa. According to the example, the drive connection in FIG. 2 runs from the first electric motor 3 via the working transmission 4, via the connecting clutch 10 and further to a separate intermediate shaft 11, which permits an adaptation of the direction of rotation, to an output shaft of the power-shift part 8″. The drive connection from the second electric motor 7 correspondingly runs via the traction transmission 8, the separate intermediate shaft 11 and the connecting clutch 10 to the working hydraulics system 5.

[0064] FIG. 3 shows, by way of example and schematically, yet a further possible exemplary arrangement of a drive train 1 according to the disclosure in the form of a functional diagram for a working machine, not shown in FIG. 3. The exemplary arrangement shown in FIG. 3 likewise differs from the exemplary embodiment shown in FIG. 1 by the path of the drive connection. According to the example, the drive connection in FIG. 3 runs from the first electric motor 3 via the working transmission 4, via the connecting clutch 10 and further to a separate transmission stage 12, which in addition to permitting an adaptation of the direction of rotation also permits an adaptation of the speed, to an output shaft of the power-shift part 8″. The drive connection from the second electric motor 7 correspondingly runs via the auxiliary transmission 8′, via the separate transmission stage 12 and the connecting clutch 10 to the working hydraulics system 5.

[0065] FIG. 4 shows, by way of example and schematically, a possible exemplary arrangement of a drive train 1 according to the disclosure in the form of a wheel diagram. The drive train 1 shown in FIG. 4 comprises a working drive 2 having a first electric motor 3, having a working transmission 4 in the form of a planetary transmission 4, and a working hydraulics system 5. The working hydraulics system 5 can be separated from the first electric motor 3 in terms of drive via a clutch 13.

[0066] The drive train 1 further comprises a traction drive 6 having a second electric motor 7, having a traction transmission 8, likewise in the form of a planetary transmission, and having an output shaft 9. A drive connection can be established from the working drive 2 to the traction drive 6 and vice versa via the connecting clutch 10 and a transmission stage 12, 12′. As can be seen, the drive connection in the example of FIG. 4 runs, starting from the first electric motor 3, via the working transmission 4, via the connecting clutch 10 and the transmission stage 12, 12′ to the output shaft 9 of the traction drive 6. The transmission stage 12, 12′ is thereby arranged on the intermediate shaft 11. Both an adaptation of the speed and an adaptation of the direction of rotation of the first electric motor 3 is thereby made possible.

[0067] As can further be seen in FIG. 4, the intermediate shaft 11 is lengthened and has at one axial end a PTO (power take off) interface 14, which is in non-separable drive connection with the traction drive 6, or the second electric motor 7. Conversely, the drive connection runs, starting from the second electric motor 7, via the traction transmission 8, the output shaft 9, the transmission stage 12, 12′ and the connecting clutch 10 and the clutch 13 to the working hydraulics system 5.

[0068] According to a further exemplary arrangement, not shown, of a drive train 1 according to the disclosure, the PTO interface 14 shown in FIG. 4 is in non-separable drive connection not with the traction drive 6, or the second electric motor 7, but with the working drive 2, or the first electric motor 3.

[0069] FIG. 5 shows, by way of example, various torque curves 20, 21, 22, 23 of the traction drive (shown on the y-axis) in dependence on a travelling speed (shown on the x-axis) of a working machine, not shown. Torque curve 20 describes the torque at maximum power of the second electric motor 7 in a low gear stage of the traction transmission 8 with increasing speed. As can be seen, the torque, as expected, decreases as the speed of the working machine increases. Torque curve 21, on the other hand, describes the torque at continuous operating power of the second electric motor 7 in a low gear stage of the traction transmission 8 with increasing speed. In this case, the torque is comparatively lower than in the case of torque curve 20 and likewise falls as the speed increases.

[0070] Torque curve 22 describes the torque at maximum power of the second electric motor 7 in a comparatively higher gear stage of the traction transmission 8 with increasing speed. In this case too, the torque, as expected, decreases as the speed of the working machine increases.

[0071] Finally, torque curve 23 describes the torque at continuous operating power of the second electric motor 7 in the same gear stage as torque curve 22 with increasing speed. Owing to the falling torque curves 20, 21, 22, 23 at higher speeds, sharp acceleration is accordingly no longer possible at higher speeds. Even small inclines of the ground can lead to a loss of speed. By implementing the method according to the disclosure in a drive train 1 according to the disclosure, it is recognized, on reaching a specific speed, which is indicated in FIG. 5 by a dotted line 24, that a specified power criterion has been met. Accordingly, a connecting clutch 10 is closed, so that the traction drive 6 is additionally driven by the first electric motor 3. As a result, the torque according to torque curves 20 and 22 increases from line 24 to a torque curve corresponding to curve 25. The torque according to torque curves 21 and 23 increases from line 24 to a torque curve corresponding to curve 26.

[0072] FIG. 6 shows, by way of example and schematically, a possible exemplary arrangement of a method according to the disclosure for operating a drive train 1 of a working machine in the form of a flow diagram. The drive train 1 comprises a working drive 2 and a traction drive 6, wherein the working drive 2 is driven by a first electric motor 3 and the traction drive 6 is driven by a second electric motor 7.

[0073] In a first method step 30, state values of the traction drive are continuously detected as comparison values for comparison with specified power criteria. According to the example, the specified power criteria are the exceeding of a limit speed, the exceeding of a limit time for which the second electric motor 3 is operated in a peak power range, and the exceeding of a limit gear stage of the traction transmission 8.

[0074] In step 31, the detected speed of the working machine is compared with the specified limit speed. If it is detected that the limit speed has been exceeded, the corresponding power criterion of the traction drive 6 is met and in step 34 the connecting clutch 10 is closed so that the traction drive 6 is additionally driven by the first electric motor 3. If, however, it is not detected that the limit speed has been exceeded, the method starts again at step 30.

[0075] In step 32, which is carried out at the same time as step 31, a detected period of time for which the second electric motor 7 has been operating in the peak power range is compared with a specified limit time. If it is detected that the limit time has been exceeded, the corresponding power criterion of the traction drive 6 has been met and in step 34 the connecting clutch 10 is closed so that the traction drive 6 is additionally driven by the first electric motor 3. If, however, it is not detected that the limit time has been exceeded, the method here too starts again at step 30.

[0076] In step 33, which is carried out at the same time as steps 31 and 32, a detected and engaged gear stage of the traction transmission 8 of the traction drive 6 is compared with a specified limit gear stage of the traction transmission 8. If the detected and engaged gear stage is higher than the limit gear stage, that is to say the limit gear stage has been exceeded, the corresponding power criterion of the traction drive 6 has been met. Accordingly, in step 34, the connecting clutch 10 is closed so that the traction drive 6 is additionally driven by the first electric motor 3. If, however, it is not detected that the limit gear stage has been exceeded, the method here too starts again at step 30.