US-12624528-B2 - 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.

Inventors

• Rico Glöckner
• Migen Bebeti
• Jan Döring

Assignees

• ZF FRIEDRICHSHAFEN AG

Dates

Publication Date

20260512

Application Date

20200317

Priority Date

20190319

Claims (18)

1. 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 active measure during the shift operation to relieve the the thermal load of the second electric motor, the measure comprising at least one of clutch-assisted synchronization, intensification of cooling, application of shift hysteresis, or drive reconfiguration to reduce load on the second electric motor.
2. 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. 3 . The method of claim 2 , further comprising intensifying a cooling of the second electric motor.
4. 4 . The method as claimed in claim 1 wherein the at least one measure is assistance of the speed synchronization by a clutch.
5. 5 . The method as claimed in claim 1 wherein the at least one measure is an intensification of a cooling of the second electric motor.
6. 6 . 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.
7. 7 . The method as claimed in claim 6 , 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.
8. 8 . 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.
9. 9 . The method as claimed in claim 1 , wherein the at least one measure is an upshift prevention in the second transmission arrangement.
10. 10 . 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.
11. 11 . 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.
12. 12 . 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.
13. 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 upshift prevention in the second transmission arrangement.
14. 14 . 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, wherein the clutch switching is coordinated with the execution of a thermal relief measure when the temperature of the second electric motor exceeds a threshold.
15. 15 . 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, a traction drive including a second transmission arrangement and a second electric motor, a connecting clutch configured to selectively establish a drive connection between the working drive and the traction drive, a first temperature sensor associated with the first transmission arrangement and a second temperature sensor associated with the second transmission; wherein the first and second temperature sensors are each configured to continuously detect a temperature of the respective first and second electric motors; and wherein, upon detection that the temperature of the second electric motor exceeds a predefined threshold, the connecting clutch is configured to be engaged to enable the first electric motor to drive the traction drive, thereby relieving thermal load on the second electric motor.
16. 16 . The drive train as claimed in claim 15 , wherein the first electric motor and the second electric motor are arranged in a common housing.
17. 17 . A working machine comprising the drive train as claimed in claim 15 .
18. 18 . The drive train of claim 15 , wherein the second transmission arrangement further comprises three power-shiftable clutches and three shaft to provide three different spur gear stages.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is a national stage of International Application No. PCT/EP2020/057279, filed Mar. 17, 2020, the disclosure of which is incorporated herein by reference in its entirety, and which claimed priority to German Patent Application No. 102019203730.5, filed Mar. 19, 2019, the disclosure of which is incorporated herein by reference in its entirety. TECHNICAL FIELD The present disclosure relates to a method for operating a drive train for a working machine, to a drive train for a working machine, and to a corresponding working machine. BACKGROUND Electrically driven working machines, such as, for example, wheel loaders, compact loaders, telescopic handlers, dumpers or excavators, are known in the prior art. Such electrically driven working machines are either driven purely electrically, that is to say they have only an electric battery or an electric accumulator for their energy supply, or they are driven diesel-electrically, which means that the required energy is provided by a diesel-driven generator, usually in conjunction with an electric buffer store, such as, for example, a correspondingly dimensioned capacitor. In all cases, the mechanical power required for the traction drive and the working drive is generated by one or more electric motors. Furthermore, hybrid-electric working machines are also known, in which the required mechanical power is generated primarily by a combustion engine, usually a diesel engine. An electric motor which is additionally provided here typically performs a so-called boost function. Power-shiftable transmissions for working machines are likewise known, in which, during a shifting operation, a speed synchronization between the speed of the drive unit and the speed of the gear stage to be engaged is carried out. In the case of an upshift operation, the speed of the drive unit is correspondingly reduced, and in the case of a downshift operation it is correspondingly increased. The synchronization of the speed thereby takes place via friction work between the clutch elements. In this context DE 20 2014 000 738 U1 describes a wheel loader which is driven purely electromotively, which has a first electric motor for a traction drive and a second electric motor for a working drive. From DE 10 2010 063 503 A1 there is further known a multistage transmission of the planetary type of a working machine. The multistage transmission comprises a housing, in which four planetary gear sets and a plurality of shafts are received, and shifting elements which are formed by at least one brake and clutches and by a targeted actuation of which eight different transmission ratios between a drive shaft and an output shaft can be described. The transmission of DE 10 2010 063 503 A1 permits power-shiftability. From DE 10 2007 046 735 A1 there is known a method for preventing overloading of a starting clutch during a starting operation in a higher gear of an automated manual transmission. In the event of actual or possible overheating of the starting clutch, an emergency downshift is carried out. The known electrically driven working machines are, however, disadvantageous in that a speed synchronization of the gear stages involved in a shifting operation under power is more difficult compared to an identical operation in a working machine driven by a combustion engine. The reason for this is on the one hand the comparatively greater moment of inertia of an electric motor compared to a combustion engine, but primarily the significantly greater speed spectrum of the electric motor, as a result of which there may be correspondingly greater speed differences, which must correspondingly be synchronized. In the case of repeated shifting, in particular at short time intervals, this can also lead to high thermal loading of the electric motor. Accordingly, an improved method for operating a drive train for a working machine is needed. SUMMARY The disclosure herein provides for a method for operating a drive train for a working machine. The disclosure relates to 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. The method according to the disclosure is distinguished by the fact that the speed synchronization is carried out by energization of the second electric motor and that, if a limit temperature is exceeded, at least one measure for relieving the thermal load of the second electric motor is carried out. The method according to the disclosure thus provides the operation of a drive train for a working