METHOD FOR OPERATING A MULTI-AXLE POWERTRAIN FOR A MOTOR VEHICLE, AND CORRESPONDING MULTI-AXLE POWERTRAIN

Abstract

A device and method for operating a multi-axle powertrain for a motor vehicle, with a first axle being permanently in operative connection and a second axle being at least temporarily in operative connection by a drive device via a clutch coupling. It is provided that, when the second axle is decoupled from the drive device and the starting clutch is disengaged, an expected wheel force is predictively ascertained. The determination of the wheel force takes into account a torque caused by a mass moment of inertia of the drive device, and the second axle is coupled with the drive device if the expected wheel force surpasses a maximum wheel force.

Claims

1-10. (canceled)

11. A method for operating a multi-axle powertrain for a motor vehicle, comprising: a first axle being permanently in operative connection and a second axle being at least temporarily in operative connection with a drive device via a clutch coupling, wherein, when the second axle is decoupled from the drive device and the starting clutch is disengaged, an expected wheel force is predictively ascertained, the determination of the wheel force taking into account a torque caused by a mass moment of inertia of the drive device, and wherein the second axle is coupled with the drive device if the expected wheel force surpasses a maximum wheel force.

12. The method according to claim 11, wherein the expected wheel force is determined from a rotational speed variable of the drive device and a course of the rotational speed variable over time.

13. The method according to claim 12, wherein a rotational speed gradient is used as the rotational speed variable.

14. The method according to claim 12, wherein the rotational speed variable is estimated as a function of a driver of the motor vehicle, a clutching behavior, and a driving situation.

15. The method according to claim 11, wherein an axle torque for the first axle is determined from the mass inertia and a powertrain transmission ratio.

16. The method according to claim 11, wherein the wheel force on one of the wheels is inferred from an axle torque and dimensions of wheels arranged on the first axle.

17. The method according to claim 11, wherein the maximum wheel force is ascertained from an axle load and a coefficient of friction existing between a wheel and a roadway.

18. The method according to claim 11, wherein the axle load is measured by at least one sensor arranged on a shock absorber of the first axle.

19. The method according to claim 11, wherein a manually activated starting clutch is used as the starting clutch.

Description

[0030] The invention shall be explained more closely below based on the exemplary embodiments represented in the drawing, without this limiting the invention. The single FIGURE shows:

[0031] FIGURE: a schematic representation of a multi-axle powertrain for a motor vehicle.

[0032] The FIGURE shows a multi-axle powertrain 1 for a motor vehicle, not otherwise represented. The multi-axle powertrain 1 has a multi-axle drive device 2, which serves for the alternative operation of only a first axle 3 or the first axle 3 as well as a second axle 4. Each of the axles 3 and 4 in the exemplary embodiment represented here has two wheels 5, which are arranged on axle members 6 and 7 of the first axle 3 and axle members 8 and 9 of the second axle 4. Now, it may be provided that the axle members 6 and 7 of the first axle 3 form a first output shaft 10. More preferably, however, they are connected via a differential gear, especially an axle differential gear, to the first output shaft 10, i.e., they are operatively connected to it, especially in rigid and/or permanent fashion. The axle members 8 and 9 can each be present as a second output shaft 11. Alternatively, it can be provided that the axle members 8 and 9 are connected via a differential gear, especially an axle differential gear, to the second output shaft 11.

[0033] The multi-axle drive device 2 has a connecting shaft 12, by which an operative connection can be produced between the first axle 3 and the second axle 4. The connecting shaft 12 is preferably designed as a Cardan shaft. A synchronizing clutch 13 is arranged in an operative connection between the first output shaft 10 and the connecting shaft 12. The synchronizing clutch 13 is preferably designed as a force-locking clutch. In particular, it allows for the transmitting of any given portion of the applied torque. Furthermore, a separating clutch 14 is also arranged in an operative connection between the connecting shaft 12 and the second output shaft 11. In the exemplary embodiment represented here, there are two separating clutches 14, each of the separating clutches 14 being arranged between a differential gear 15 and one of the two output shafts 11 or the axle members 8 and 9.

[0034] The connecting shaft 12 here is operatively connected in rigid and/or permanent manner to the differential gear 15. The operative connection between the differential gear 15 and thus the connecting shaft 12, on the one hand, and the second output shafts 11 in the form of the axle members 8 and 9, on the other hand, can be alternatively enabled or disabled with the aid of the separating clutch 14. Preferably, the separating clutches 14 are always found in the same position, so that either an operative connection between the connecting shaft 12, on the one hand, and the axle members 8 and 9, on the other hand, is enabled or disabled.

[0035] In a first operating state of the multi-axle drive device 2, the synchronizing clutch 13 and the separating clutch 14 are disengaged, so that the operative connection between the first output shaft 10 and the second output shaft 11 is disabled. Insofar as only one separating clutch 14 or one second output shaft 11 is mentioned in the following, both output shafts 11 or both separating clutches 14 are always meant in the context of the present exemplary embodiment. In a second operating state, the synchronizing clutch 13 and the separating clutch 14 are fully engaged. The separating clutch 14 is preferably designed as a form-locking clutch, especially as a dog clutch.

[0036] In the context of the multi-axle powertrain 1 presented here, the first axle 3 is in operative connection with a drive device, not represented here, or it is driven by it. The second axle, on the other hand, is only temporarily in operative connection with the drive device via a clutch coupling and accordingly is driven by it. The clutch coupling can be represented by the synchronizing clutch 13 and/or the separating clutches 14. It is only important that the operative connection between the drive device and the second drive shaft 11 can be disabled with the aid of the clutch coupling.

[0037] The multi-axle powertrain 1 is now operated such that, when the second axle is decoupled from the drive device and the starting clutch which is present between the drive device and both the first axle 3 and the second axle 4 is disengaged, an expected wheel force is predictively ascertained, the determination of the wheel force taking into account a torque caused by a mass moment of inertia of the drive device, and the second axle is coupled to the drive device if the expected wheel force surpasses a maximum wheel force. In this way, both the fuel consumption of the multi-axle powertrain 1 can be reduced, and an excellent traction can also be provided in every driving situation.