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 of a working machine, wherein a traction drive of the drive train is driven by an electric traction motor via a transmission and wherein, when a gear stage of the transmission is changed, a rotational speed of the traction motor is synchronised with the gear stage being engaged. The method according to the disclosure further includes a computational model of the traction motor that is used for the rotational speed synchronisation. The model, taking into account a moment of inertia of the traction motor, describes a torque to be delivered for the rotational speed synchronisation. 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 a traction drive of the drive train is driven by an electric drive motor via a traction transmission and wherein, during a gear stage change of the traction transmission, a speed synchronization of the traction motor with the gear stage to be engaged is carried out, wherein there is used for the speed synchronization, a computational model of the traction motor which, while taking account of a moment of inertia of the traction motor, determines a torque to be applied for the speed synchronization.

2. The method as claimed in claim 1, wherein the speed synchronization is assisted, in accordance with the model, by an energization of the traction motor.

3. The method as claimed in claim 1, wherein the model takes into account a capacity for torque transmission of a clutch of the engaged gear which decreases over a duration of the gear stage change and a capacity for torque transmission of a clutch of the gear to be engaged which increases over the duration of the gear stage change.

4. The method as claimed in claim 1, wherein the torque to be applied is a torque curve which is specifiable by the model over the duration of the gear stage change.

5. The method as claimed in claim 4, wherein the torque curve is implemented in accordance with a specifiable speed ramp.

6. The method as claimed in claim 4, wherein an end torque of the torque curve is specified such that, when the gear stage change is complete, while taking account of a transmission ratio of the gear stage to be engaged to a transmission ratio of the engaged gear stage, the same output torque is provided at an output of the traction transmission as before the gear stage change.

7. The method as claimed in claim 1, wherein there are supplied to the model transmission speeds of the engaged gear stage and/or transmission speeds of the gear stage to be engaged and/or wheel speeds of the working machine and/or output speeds of the traction transmission and/or output torques of the traction transmission and/or a capacity for torque transmission of a clutch of an engaged gear stage and/or a capacity for torque transmission of a clutch of the gear stage to be engaged.

8. The method as claimed in claim 1, wherein a working drive of the drive train is driven by an electric working motor via a working transmission, wherein a drive connection is established between the working drive and the traction drive so that the traction drive is driven in a supporting manner by the working motor.

9. The method as claimed in claim 8, wherein the traction drive is driven in a supporting manner by the working motor whenever it is thereby possible to achieve an improvement in an overall efficiency of the drive train compared to when the traction drive is driven solely by the traction motor.

10. The method as claimed in claim 9, wherein the traction drive is not driven by the working motor, however, if the working motor must provide more than a threshold working power required by the working drive.

11. The method as claimed in claim 10, wherein the working drive comprises a hydraulic pump which can be driven by the working motor and has an adjustable piston stroke height, wherein the piston stroke height is first increased and only then is a speed of the working motor increased in order to provide the working power required by the working drive.

12. A drive train for a working machine, comprising a traction drive having an electric traction motor and a traction transmission, and a working drive having an electric working motor and a working transmission, wherein the traction drive can be driven by the traction motor via the traction transmission and wherein the working drive can be driven by the working motor via the working transmission, and wherein, during a gear stage change of the traction transmission, a speed synchronization of the traction motor with the gear stage to be engaged is carried out, wherein the drive train further comprises an electronic control unit which is configured to calculate a computational model of the traction motor which, while taking account of a moment of inertia of the traction motor, describes a torque to be applied for the speed synchronization.

13. The drive train as claimed in claim 11, wherein the drive train comprises a connecting clutch via which a drive connection can be established between the traction drive and the working drive.

14. The drive train as claimed in claim 12, wherein the drive connection leads from the working drive to an input of the traction transmission.

15. (canceled)

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

17. The method as claimed in claim 1, wherein the speed synchronization is assisted, in accordance with the model, by a generator mode of the traction motor.

18. The method as claimed in claim 2, wherein the model takes into account a capacity for torque transmission of a clutch of the engaged gear which decreases over a duration of the gear stage change and a capacity for torque transmission of a clutch of the gear to be engaged which increases over the duration of the gear stage change.

19. The method as claimed in claim 3, wherein the torque to be applied is a torque curve which is specifiable by the model over the duration of the gear stage change.

20. The method as claimed in claim 5, wherein an end torque of the torque curve is specified such that, when the gear stage change is complete, while taking account of a transmission ratio of the gear stage to be engaged to a transmission ratio of the engaged gear stage, the same output torque is provided at an output of the traction transmission as before the gear stage change.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The disclosure will be explained by way of example hereinbelow with reference to exemplary arrangements shown in the figures:

[0045] FIG. 1 shows, by way of example and schematically, a possible exemplary arrangement of a drive train according to the disclosure,

[0046] FIG. 2 shows, by way of example and schematically, a gear stage change in the traction drive of the drive train according to the disclosure,

[0047] FIG. 3 shows, by way of example and schematically, a further gear stage change in the traction drive of the drive train according to the disclosure,

[0048] FIG. 4 shows, by way of example and schematically, a further gear stage change in the traction drive of the drive train according to the disclosure, and

[0049] FIG. 5 shows, by way of example and schematically, a further gear stage change in the traction drive of the drive train according to the disclosure.

DETAILED DESCRIPTION

[0050] 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.

[0051] FIG. 1 shows, by way of example and schematically, a possible exemplary arrangement of a drive train 1 according to the disclosure for a working machine, not shown in FIG. 1. The drive train 1 shown by way of example comprises an electric traction motor 2 and an electric working motor 3 and also a traction transmission 4 and a working transmission 5. Both the traction transmission 4 and the working transmission 5 each have a reduction stage 4′, 5′ for reducing an output speed of the working motor 3 or of the traction motor 2, respectively. The traction transmission 4 further has a power-shift part 4″ which according to the example is power-shiftable over three gear stages.

[0052] The working transmission 5, on the other hand, has only a single power-shiftable clutch 5″. An output speed of the traction transmission 4 is provided at an output shaft 6. An output speed of the working transmission 5 is provided at a power takeoff shaft 7. The traction motor 2, the traction transmission 4 and the output shaft 6 are associated according to the example with a traction drive 8 of the drive train 1, whereas the working motor 3, the working transmission 5 and the power takeoff shaft 7 are associated according to the example with a working drive 9 of the drive train 1.

[0053] The power flow directions in the working drive 9 and in the traction drive 8 are each represented by broken arrows. A drive connection can additionally be established between the working drive 9 and the traction drive 8 via a connecting clutch 10.

[0054] As can be seen, the drive connection runs from the power-shiftable clutch 5″ via the connecting clutch 10 to the traction transmission 4, namely to the input of the power-shift part 4″. It is thus possible to drive all the gear stages of the traction drive 8 in a supporting manner by the working drive 9. During a gear stage change of the traction transmission 8, a speed synchronization of the traction motor 2 must be carried out in order to match the speed of the traction motor 2 from the speed of the currently engaged gear stage to the speed of the gear stage to be engaged.

[0055] Since the traction motor 2 is in the form of an electric motor and electric motors have a comparatively high moment of inertia, a computational model of the traction motor 2 is used for the speed synchronization of the traction motor 2, wherein the model takes into account in particular the moment of inertia of the traction motor 2. Via the model it is possible to determine the magnitude of a moment that is necessarily to be applied for the speed synchronization and for what period of time it must be applied, and whether this torque can be generated solely by friction in the power-shift part 4″ or whether the application of an additional torque by energization or a generator mode of the traction motor 2 may be necessary. The drive train 1 therefore further also comprises an electronic control unit 11, which is configured to calculate the model.

[0056] FIG. 2 shows, by way of example and schematically, a gear stage change in the traction drive 8 of the drive train 1 according to the disclosure by the method according to the disclosure. According to the example, the gear stage change is from an engaged, higher gear stage to a lower gear stage that is to be engaged in coasting mode of the working machine. There are thereby shown in the form of a coordinate system a pressure curve 20 in a clutch of an engaged gear stage and a pressure curve 21 in a clutch of a gear stage to be engaged. A speed curve 23 of the traction motor 2 can likewise be seen. The x-axis in FIG. 2 shows the pressure in the clutches and the speed of the traction motor 2. The y-axis shows the time.

[0057] As can be seen, at the beginning of the gear stage change the pressure in the clutch of the engaged gear stage is initially at the fill pressure. The pressure in the clutch of the gear stage to be engaged, on the other hand, is initially zero. At time t.sub.1, the pressure in the clutch of the engaged gear stage is reduced in a ramp-like manner, so that the capacity for torque transmission between the clutch of the engaged gear stage and the traction motor 2 decreases. At the same time, the pressure in the clutch of the gear stage to be engaged is increased abruptly, whereby the capacity for torque transmission between the clutch of the gear stage to be engaged and the traction motor 2 increases abruptly. At time t.sub.2, the ramp-like pressure drop in the clutch of the engaged gear stage is stopped. The pressure in the clutch of the engaged gear stage is then kept constant to time t.sub.3. In the clutch of the gear stage to be engaged, on the other hand, the pressure is reduced again at time t.sub.2 and maintained at a constant level to time t.sub.3. This serves the purpose of fill compensation in the clutch of the gear stage to be engaged. From time t.sub.3, the pressure in the clutch of the gear stage to be engaged is then increased in a ramp-like manner and the pressure in the clutch of the engaged gear stage is reduced further in a ramp-like manner, so that at time t.sub.4 the pressure in the clutch of the gear stage to be engaged is greater than the pressure in the clutch of the engaged gear stage. Accordingly, at time t.sub.4, the capacity for torque transmission of the clutch of the gear stage to be engaged is greater than the capacity for torque transmission of the clutch of the engaged gear stage.

[0058] The speed curve 23 of the traction motor 2 was constant up to time t.sub.4. However, since the capacity for torque transmission of the clutch of the gear stage to be engaged is now greater than the capacity for torque transmission of the clutch of the engaged gear stage, the speed synchronization of the traction motor 2 begins here. The speed of the traction motor 2 already increases solely due to friction with the clutch of the gear stage to be engaged.

[0059] Since, according to the example, there is used for the speed synchronization a computational model of the traction motor 2 which, while taking account of a moment of inertia of the traction motor 2, determines a torque to be applied for the speed synchronization, it is recognized according to the example that it is not possible to apply sufficient torque for the speed synchronization via friction alone.

[0060] Accordingly, according to the example, energization of the traction motor 2 in the forward direction additionally takes place from time t.sub.4, in order to accelerate the speed synchronization by the additional torque and be able to complete it within the necessary time. The pressure in the clutch of the gear stage to be engaged is then slowly increased further in a ramp-like manner to time t.sub.5, whereby the friction between the clutch of the gear stage to be engaged and the traction motor 2 also increases further, which consequently correspondingly effects an increase in the applied torque for the speed synchronization. Therefore, according to the example, the torque additionally applied by energization is reduced to the same extent as the torque generated by friction with the clutch of the gear stage to be engaged increases. A uniform equalization of the speed, or a comparatively gentle increase in the speed until the end speed is reached thus takes place. The pressure in the clutch of the engaged gear stage, on the other hand, is kept constant from time t.sub.4. At time t.sub.5, the speed synchronization is complete according to the example. The traction motor 2 has reached its end speed. The pressure in the clutch of the engaged gear stage is then reduced to zero and the pressure in the clutch of the gear stage to be engaged is increased to the fill pressure. At time t.sub.6, the gear stage change is complete.

[0061] FIG. 3 shows, by way of example and schematically, a further gear stage change in the traction drive 8 of the drive train 1 according to the disclosure by the method according to the disclosure. In contrast to the gear stage change shown in FIG. 2, however, FIG. 3 shows a gear stage change from an engaged, lower gear stage to a higher gear stage to be engaged in traction mode of the working machine. The pressure curve in the clutch of the gear stage to be engaged 21 and the pressure curve in the clutch of the engaged gear stage 20 are unchanged from the illustration of FIG. 2. Only the speed curve 23 of the traction motor 2 differs from the speed curve 23 of FIG. 2 in that, in FIG. 3, a speed synchronization in the form of a speed reduction is carried out.

[0062] According to the example, the speed synchronization is again also carried out in FIG. 3 using the computational model of the traction motor 2 which, while taking account of the moment of inertia of the traction motor 2, determines a torque to be applied for the speed synchronization. In this case too, it is recognized according to the example that sufficient torque for the speed synchronization cannot be applied via friction in the clutch of the gear stage to be engaged alone. The start of the speed synchronization again begins at time t.sub.4.

[0063] In order to assist with the speed synchronization, energization of the traction motor 2 also takes place according to FIG. 3, but this time in the reverse direction, since a speed reduction is necessary for the speed synchronization. The speed of the traction motor 2 falls correspondingly until the speed synchronization is complete at time t.sub.5.

[0064] FIG. 4 shows, by way of example and schematically, a further gear stage change in the traction drive 8 of the drive train 1 according to the disclosure by the method according to the disclosure. FIG. 4 shows a gear stage change from an engaged, lower gear stage to a higher gear stage to be engaged in coasting mode of the working machine.

[0065] FIG. 4 shows the speed curve 23 of the traction motor 2, the pressure curve 20 in the clutch of the engaged gear stage, and the pressure curve 21 in the clutch of the gear stage to be engaged. As can be seen, the pressure in the clutch of the engaged gear stage is here too initially at the fill pressure at the start of the gear stage change. The pressure in the clutch of the gear stage to be engaged, on the other hand, is initially again zero. At time t.sub.7, the pressure in the clutch of the engaged gear stage is reduced in a ramp-like manner, so that the capacity for torque transmission between the clutch of the engaged gear stage and the traction motor 2 decreases. At the same time, the pressure in the clutch of the gear stage to be engaged is increased abruptly, whereby the capacity for torque transmission between the clutch of the gear stage to be engaged and the traction motor 2 correspondingly also increases.

[0066] The pressure in the clutch of the gear stage to be engaged is kept constant until time t.sub.8, then it is abruptly partially reduced again in order to effect fill compensation. The ramp-like pressure reduction in the clutch of the engaged gear stage is continued to time t.sub.9. During this time, the pressure in the clutch of the gear stage to be engaged is kept at a constant level to time t.sub.10. From time t.sub.9 to time t.sub.10, the ramp-like pressure reduction in the clutch of the engaged gear stage is continued, but slowed down. At time t.sub.10, on the one hand the pressure reduction in the clutch of the engaged gear stage is slowed further and on the other hand the pressure in the clutch of the gear stage to be engaged is increased slightly and then kept constant. From time t.sub.10, the speed synchronization of the traction motor 2 also takes place in the form of a speed reduction. According to the example, the speed synchronization is again also carried out in FIG. 4 using the computational model of the traction motor 2 which, while taking account of the moment of inertia of the traction motor 2, determines a torque to be applied for the speed synchronization. In this case too, it is recognized according to the example that sufficient torque for the speed synchronization cannot be applied via friction alone. The speed synchronization is therefore effected both by a torque applied by a friction between the traction motor 2 and the clutch of the gear stage to be engaged and by a torque applied by energization of the traction motor 2.

[0067] Energization of the traction motor 2 thereby takes place in the reverse direction, in order to accelerate the necessary speed reduction. At time the speed synchronization is complete and a ramp-like rise in the pressure in the clutch of the gear stage to be engaged and, at the same time, a ramp-like fall in the pressure in the clutch of the engaged gear stage take place. Since the pressure in the clutch of the gear stage to be engaged now exceeds the pressure in the clutch of the engaged gear stage, the capacity for torque transmission of the clutch of the gear stage to be engaged also exceeds the capacity for torque transmission of the clutch of the engaged gear stage.

[0068] At time t.sub.12, the pressure in the clutch of the engaged gear stage is finally reduced to zero and at time t.sub.13 the pressure in the clutch of the engaged gear stage is ultimately increased abruptly to the fill pressure. The gear stage change is thus complete.

[0069] FIG. 5 shows, by way of example and schematically, a further gear stage change in the traction drive 8 of the drive train 1 according to the disclosure by the method according to the disclosure. In contrast to the gear stage change shown in FIG. 4, however, FIG. 5 shows a gear stage change from an engaged, higher gear stage to a lower gear stage to be engaged in traction mode of the working machine. The pressure curve in the clutch of the gear stage to be engaged 21 and the pressure curve in the clutch of the engaged gear stage 20 are thereby unchanged from the illustration of FIG. 4. Only the speed curve 23 of the traction motor 2 differs from the speed curve 23 of FIG. 4 in that, in FIG. 5, a speed synchronization in the form of a speed increase is carried out.

[0070] According to the example, the speed synchronization is also carried out in FIG. 5 using the computational model of the traction motor 2 which, while taking account of the moment of inertia of the traction motor 2, determines a torque to be applied for the speed synchronization. According to the example, in accordance with the model, an additional torque is therefore applied via an energization of the traction motor 2 in the forward direction. The beginning of the speed synchronization again starts at time t.sub.10. The speed of the traction motor 2 correspondingly increases until the speed synchronization is complete at time t.sub.11.