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

Abstract

The disclosure relates to a method for operating a drive train for a working machine, in which a working drive of the working machine is driven by a first electric motor via a first gear arrangement, a travel drive of the working machine is driven by a second electric motor via a second gear arrangement and, in a shifting procedure of the second gear arrangement, the rotational speed of the second electric motor is synchronised and the temperature of said second electric motor is recorded. In the disclosed method, the rotational speed is synchronised by supplying current to the second electric motor, and in the event of a threshold temperature being exceeded, at least one measure is carried out to relieve the thermal load of the second electric motor. The disclosure further relates to a corresponding drive train and to a working machine.

Claims

1. A method for operating a drive train for a working machine, wherein a working drive of the working machine is driven by a first electric motor via a first transmission arrangement, wherein a traction drive of the working machine is driven by a second electric motor via a second transmission arrangement, wherein, during a shifting operation of the second transmission arrangement, a speed synchronization of the second electric motor is carried out, and wherein a temperature of the second electric motor is detected, wherein the speed synchronization is carried out by energization of the second electric motor, and in that, if a limit temperature is exceeded, at least one measure for relieving the thermal load of the second electric motor is carried out.

2. The method as claimed in claim 1, wherein the second transmission arrangement is in the form of an automated manual transmission, the at least one measure is the application of a shift hysteresis to a shifting point of the second transmission arrangement.

3. The method as claimed in claim 1 wherein the at least one measure is assistance of the speed synchronization by a clutch.

4. The method as claimed in claim 1 wherein the at least one measure is an intensification of a cooling of the second electric motor.

5. The method as claimed in claim 1, wherein the at least one measure is an establishment of a drive connection between the working drive and the traction drive, so that the traction drive is additionally or exclusively driven by the first electric motor.

6. The method as claimed in claim 5, wherein driving of the traction drive by the first electric motor is carried out while taking account of a temperature of the first electric motor.

7. The method as claimed in claim 1, wherein the at least one measure is a limitation of a permissible operating range of the second electric motor.

8. The method as claimed in claim 1, wherein the at least one measure is an upshift prevention in the second transmission arrangement.

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

10. The drive train as claimed in claim 9, wherein the first electric motor and the second electric motor are arranged in a common housing.

11. The drive train as claimed in claim 9 wherein the drive train is configured to implement a method as claimed in claim 1.

12. A working machine comprising a drive train as claimed in claim 9.

13. The method as claimed in claim 1 wherein the at least one measure includes the-assistance of the speed synchronization by a clutch and an intensification of a cooling of the second electric motor.

14. The method as claimed in claim 1, wherein the at least one measure includes the assistance of the speed synchronization by a clutch and establishment of a drive connection between the working drive and the traction drive, so that the traction drive is additionally or exclusively driven by the first electric motor.

15. The method as claimed in claim 1, wherein the at least one measure includes the assistance of the speed synchronization by a clutch and a limitation of a permissible operating range of the second electric motor.

16. The method as claimed in claim 1, wherein the at least one measure includes the assistance of the speed synchronization by a clutch and an upshift prevention in the second transmission arrangement.

17. The method as claimed in claim 8, wherein the at least one measure further comprises an upshift prevention in the second transmission arrangement.

18. The method of claim 1, wherein during the shifting operation of the second transmission arrangement, a previously closed clutch is opened and at the same time a previously open clutch is closed.

19. The method of claim 2, further comprising intensifying a cooling of the second electric motor.

20. The drive train of claim 9, wherein the second transmission arrangement further comprises three power-shiftable clutches and three shaft to provide three different spur gear stages.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The disclosure will be explained by way of example hereinbelow with reference to exemplary arrangements shown in the figures, in which:

[0052] FIG. 1 shows, by way of example, a possible exemplary arrangement of a drive train according to the disclosure for a working machine in the form of a wheel diagram,

[0053] FIG. 2 shows, by way of example, a further possible exemplary arrangement of a drive train according to the disclosure for a working machine in the form of a wheel diagram, and

[0054] FIG. 3 shows, by way of example, a curve of an energization of the second electric motor and an associated curve of a temperature of the second electric motor over time.

DETAILED DESCRIPTION

[0055] 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.

[0056] FIG. 1 shows, by way of example, a possible exemplary arrangement of a drive train 1 according to the disclosure for a working machine, not shown in FIG. 1, in the form of a wheel diagram. According to the example, the drive train 1 of FIG. 1 comprises a first electric motor 2 and a second electric motor 3, which are arranged in a common housing 11. Both the first electric motor 2 and the second electric motor 3 each have an associated temperature sensor 2′, 3′ for continuously detecting a temperature of the first or second electric motor 2, 3.

[0057] The drive train 1 of FIG. 1 further comprises a first transmission arrangement 4 and a second transmission arrangement 5, wherein the first electric motor 2 and the first transmission arrangement 4 are associated with a working drive 6 of the drive train 1. The second electric motor 3 and the second transmission arrangement 5, on the other hand, are associated with a traction drive 7 of the drive train 1. The second transmission arrangement 5 further comprises according to the example three further, power-shiftable clutches 9, 9′ and 9″ and three shafts 5, 5′ and 5″ in order to provide, via three different spur gear stages 10, 10′, 10″, three shiftable gear stages of the second transmission arrangement 5.

[0058] During a shifting operation of the second transmission arrangement 5, a previously closed clutch 9, 9′ or 9″ is opened and at the same time a previously open clutch 9, 9′ or 9″ is closed. In order that a clutch 9, 9′ or 9″ is able to close, a speed synchronization of the elements of the gear stage to be shifted must first be carried out.

[0059] According to the example, the speed synchronization is carried out by corresponding energization of the second electric motor 3, which, however, owing to the necessary rapid speed change and the associated high current strengths, also leads to pronounced heat generation in the second electric motor 3. In order to relieve the thermal load of the second electric motor 3, a drive connection can be established between the first transmission arrangement 4 and the second transmission arrangement 5 via a connecting clutch 8, wherein the drive connection can be established according to the example from the first electric motor 2 to the shaft 5′ of the second transmission arrangement 5. The first electric motor 2 is thus able to drive the traction drive 7 when the connecting clutch 8 is closed. According to the example, this occurs whenever the thermal load of the second electric motor 3 has to be relieved. By driving the traction drive 7 additionally by the first electric motor 2, the second electric motor 3 can be operated at a lower operating point, whereby energization of the second electric motor 3 is reduced and thus a thermal load of the second electric motor 3 is also reduced.

[0060] FIG. 2 shows, by way of example, a further possible exemplary arrangement of a drive train 1 according to the disclosure for a working machine, not shown in FIG. 2, in the form of a wheel diagram. The drive train 1 of FIG. 2 differs from the drive train 1 only by the drive connection which can be established from the first electric motor 2 to the traction drive 7. According to the example, this drive connection runs from the first electric motor 2 to the shaft 5″ of the second transmission arrangement 5.

[0061] FIG. 3 shows, by way of example, a curve 20 of an energization (represented on the y-axis) of the second electric motor 3 and an associated curve 21 of a temperature (likewise represented on the y-axis) of the second electric motor 3 over time t (represented on the x-axis). At time t.sub.0, the second electric motor 3 is operated with current I.sub.0 and has temperature T.sub.0. Although the current I.sub.0 leads to constant heating of the second electric motor 3, the heat that develops is dissipated via a cooling system so that there is a dynamic thermal equilibrium. At time t.sub.1, a shifting operation takes place in the second transmission arrangement 5, and for this reason a speed synchronization is required. The speed synchronization is carried out by energization of the second electric motor 3 with current I.sub.1 for a short time. This also effects an abrupt rise in the temperature to value T.sub.1. The working machine then continues its journey uniformly until time t.sub.2, wherein at time t.sub.2 a shifting operation again takes place in the second transmission arrangement 5.

[0062] The speed synchronization which is again required and the high energization I.sub.2 of the second electric motor 3 required therefor results in a further rise in the temperature, this time to value T.sub.2. Temperature T.sub.2 is only just below the limit temperature T.sub.limit. At time t.sub.3, a further shifting operation takes place, which again leads to a short-time rise in the energization to current strength I.sub.3 and to a rise in the temperature to value T.sub.3. The temperature T.sub.3 of the second electric motor now also exceeds the limit temperature T.sub.limit. This has the result that, when the limit temperature T.sub.limit is exceeded, a number of measures for relieving the thermal load of the second electric motor 3 are carried out.

[0063] According to the example, a shift hysteresis is first applied to all the shifting points of the second transmission arrangement 5, in order to avoid or at least delay further shifting operations. Cooling of the second electric motor 3 is also intensified. Finally, a drive connection is established between the working drive 6 and the traction drive 7 so that the traction drive 7 is additionally driven by the first electric motor 2. As a consequence of the last-mentioned measure for relieving the thermal load of the second electric motor 3, the energization thereof can be reduced to value I.sub.4. The temperature of the second electric motor 3 thereupon reduces rapidly.