REGULATING A DRIVE SYSTEM FOR AN AXLE OF A MOTOR VEHICLE

Abstract

A drive system for an axle of a motor vehicle comprises at least one drive unit, a drive shaft driven by the drive unit, a first output shaft comprising a first wheel and a second output shaft comprising a second wheel, and a first clutch connecting the drive shaft to the first output shaft, and a second clutch connecting the drive shaft to the second output shaft, and furthermore, a control unit for regulating the clutches. In a stable first driving condition, the clutches are regulated such that a total locking power of the two clutches corresponds at least or substantially to a drive torque generated by the drive shaft; wherein a method comprises at least the following steps: a) determining an unstable second driving condition in which at least one first wheel has a first slip or a second wheel has a second slip; and b) modifying at least one locking ratio of the clutch connected to the at least one slipping wheel, wherein the first clutch has an adjustable first locking ratio and the second clutch has an adjustable second locking ratio.

Claims

1.-12. (canceled)

13. A method for controlling a drive system for an axle of a motor vehicle, wherein the drive system has at least one drive unit, a drive shaft driven by the drive unit, a first output shaft having a first wheel and a second output shaft having a second wheel, as well as a first clutch connecting the drive shaft to the first output shaft, and a second clutch connecting the drive shaft to the second output shaft, and further a control unit for controlling the clutches, wherein in a stable first travel state the clutches are controlled in such a way that a total locking torque of both clutches corresponds at least or substantially to a drive torque provided by way of the drive shaft, wherein the method comprises: a) establishing an unstable second travel state in which at least one first wheel has a first slip or a second wheel has a second slip; and b) varying at least one locking rate of the clutch connected to the at least one slipping wheel, wherein the first clutch has an adjustable first locking rate and the second clutch has an adjustable second locking rate.

14. The method of claim 13, wherein the clutches at least at certain operating points are operated with a micro-slip control in which a speed differential between the drive shaft and the output shaft at the respective clutch is set at more than zero revolutions per minute and at most 50 revolutions per minute.

15. The method of claim 13, wherein the drive unit is assigned exclusively to the axle such that only the wheels of the axle are drivable by way of the drive torque provided by the drive unit.

16. The method of claim 13, wherein the locking rate of a clutch connected to a non-slipping wheel is increased and the locking rate of a clutch connected to a slipping wheel is decreased.

17. The method of claim 13, wherein the drive torque is decreased when a total varied locking torque is less than the drive torque.

18. The method of claim 13, wherein a clutch on the outside of a curve is over-locked when the motor vehicle corners when varying the at least one locking rate of the clutch.

19. The method of claim 13, wherein the clutch on the outside of a curve is over-locked to an extent that corresponds to a torque setting accuracy of the clutches and of the drive unit.

20. The method of claim 13, wherein a distribution of the locking rates for forming the total locking torque for the first travel state is calculated as a function of at least one of the following parameters: a steering angle of a steering wheel of the motor vehicle; speed of the motor vehicle; yaw rate; or torque of the drive shaft.

21. The method of claim 13, wherein, by activating each clutch, wheels of the common axle of the motor vehicle are respectively connectable in a torque-transmitting manner to the drive unit.

22. The method of claim 13, wherein the drive unit is an electric machine.

23. The method of claim 13, wherein a torque differential between the drive shaft and the output shaft of more than zero revolutions per minute and of at most 5 revolutions per minute is set at the micro-slip control on the respective clutch.

24. An apparatus comprising a processor and a medium storing instructions executable by the processor, the apparatus provided for a drive system for at least one axle of a motor vehicle, the drive system having at least one drive unit, a drive shaft driven by the drive unit, a first output shaft having a first wheel and a second output shaft having a second wheel, and a first clutch connecting the drive shaft to the first output shaft, and a second clutch connecting the drive shaft to the second output shaft, wherein the instructions include instructions for controlling the clutches, the instructions including instructions to: a) establish an unstable second travel state in which at least one first wheel has a first slip or a second wheel has a second slip; and b) vary at least one locking rate of the clutch connected to the at least one slipping wheel, wherein the first clutch has an adjustable first locking rate and the second clutch has an adjustable second locking rate.

25. The apparatus of claim 24, wherein the instructions further include instructions such that clutches at least at certain operating points are operated with a micro-slip control in which a speed differential between the drive shaft and the output shaft at the respective clutch is set at more than zero revolutions per minute and at most 50 revolutions per minute.

26. The apparatus of claim 24, wherein the drive unit is assigned exclusively to the axle such that only the wheels of the axle are drivable by way of the drive torque provided by the drive unit.

27. The apparatus of claim 24, wherein the instructions further include instructions such that the locking rate of a clutch connected to a non-slipping wheel is increased and the locking rate of a clutch connected to a slipping wheel is decreased.

28. The apparatus of claim 24, wherein the instructions further include instructions such that the drive torque is decreased when a total varied locking torque is less than the drive torque.

29. The apparatus of claim 24, wherein the instructions further include instructions such that a clutch on the outside of a curve is over-locked at least one of (i) when the motor vehicle corners when varying the at least one locking rate of the clutch, or (ii) to an extent that corresponds to a torque setting accuracy of the clutches and of the drive unit.

30. The apparatus of claim 24, wherein the instructions further include instructions such that a distribution of the locking rates for forming the total locking torque for the first travel state is calculated as a function of at least one of the following parameters: a steering angle of a steering wheel of the motor vehicle; speed of the motor vehicle; yaw rate; or torque of the drive shaft.

31. The apparatus of claim 24, wherein the instructions further include instructions such that, by activating each clutch, wheels of the common axle of the motor vehicle are respectively connectable in a torque-transmitting manner to the drive unit.

32. The apparatus of claim 24, wherein the instructions further include instructions such that a torque differential between the drive shaft and the output shaft of more than zero revolutions per minute and of at most 5 revolutions per minute is set at the micro-slip control on the respective clutch.

Description

SUMMARY OF THE DRAWINGS

[0050] The invention as well as the technical field will be explained in more detail hereunder by means of the figures. It should be pointed out that the invention is not intended to be limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the substantive matter explained in the figures and to combine them with other constituent parts and knowledge from the present description and/or figures. The same reference signs denote the same objects and therefore where appropriate explanations from other figures can be used in a supplementary manner. In the figures, in each case schematically:

[0051] FIG. 1: shows a motor vehicle having a drive system for driving respective wheels of the motor vehicle;

[0052] FIG. 2: shows a further motor vehicle;

[0053] FIG. 3: shows a control unit for the drive system; and

[0054] FIG. 4: shows the control unit according to FIG. 3 in a more detailed illustration.

DESCRIPTION WITH REFERENCE TO THE FIGURES

[0055] FIG. 1 shows a motor vehicle 3 having a drive system 1 for driving respectively a first wheel 11 and a second wheel 12 of a common axle 2 of the motor vehicle 3. The drive system 1 comprises a drive unit 4, a drive shaft 5 driven by the drive unit 4, a first output shaft 6 and a second output shaft 7, as well as a first clutch 8 connecting the drive shaft 5 to the first output shaft 6, and a second clutch 9 connecting the drive shaft 5 to the second output shaft 7. Further provided is a control unit 10 for controlling the two clutches 8, 9.

[0056] Here, a drive system 1 in which two clutches 8, 9 are provided on a common axle 2 of the motor vehicle 3 is illustrated, wherein wheels 11, 12 of the motor vehicle 3 are respectively connected to the drive unit 4 of the motor vehicle 3 in a torque-transmitting manner by way of each of the two clutches 8, 9. The two clutches 8, 9 replace an otherwise usual differential 22 (illustrated here on the other axle 2 of the motor vehicle 3) by means of which different speeds of the wheels can be compensated.

[0057] A transmission 23 is disposed between the drive unit 4 and the output shafts 6, 7.

[0058] FIG. 2 shows a further motor vehicle 3. Reference is made to the explanations pertaining to FIG. 1. Here, the drive unit 4 transmits the torque directly by way of the drive shaft 5 to the axle 2, or by way of the first clutch 8 to the first output shaft 6, respectively, and by way of the second clutch 9 to the second output shaft 7. The first clutch 8 is controlled by way of a first valve 26 and the second clutch 9 by way of a second valve 27. The valves 26, 27 are actuated in a controlled manner by a pump 25 driven by a pump motor 24.

[0059] A steering angle 15 of the wheels of at least one axle can be controlled by way of a steering wheel 16.

[0060] FIG. 3 shows a control unit 10 for the drive system 1.

[0061] In the drive system 1 described, the desired locking rate 13, 14 for each of the two clutches 8, 9 for the first travel state (none of the driven wheels 11, 12 is spinning or locked, thus has no slip 20, 21) is determined in particular as a function of at least one (preferably all) of the following parameters: a steering angle 15 of the motor vehicle 3 (thus of the wheels 11, 12 of an axle 2 controlled by way of a steering wheel 16), the torque 19 directed by way of the drive shaft 5 (drive torque or drag torque or recuperation torque, respectively), the speed 17 of the motor vehicle, and the measured yaw rate 18.

[0062] In an unstable (second) driving condition, this distribution of the torques or of the locking rates 13, 14 of the two clutches 8, 9 can be deviated from. This is the case when at least one of the wheels 11, 12 spins or locks (thus has a slip 20, 21). In this case, the locking rate 13, 14 of the spinning wheel 11, 12 can be decreased, or the locking rate 13, 14 of the spinning wheel 11, 12 can be increased. An increase in the locking rate 13, 14 should take place in conjunction with a reduction of the torque 19 directed by way of the drive shaft 5 (drive torque or drag torque or recuperation torque, respectively), for example.

[0063] FIG. 4 shows the control unit 10 according to FIG. 3 in a more detailed illustration. Reference is made to the explanations pertaining to FIG. 3. A first controller 28 is provided here for controlling the drive system 1 in the stable first travel state. A second controller 29 is provided for controlling the drive system 1 in the unstable travel state.

[0064] A desired distribution of the torques (the torque distribution 31 is determined as a function of at least one of the following parameters (preferably all of said parameters): a steering angle 15 of the motor vehicle, the torque 19 directed by way of the drive shaft (drive torque or drag torque or recuperation torque, respectively), the speed 17 of the motor vehicle 3, and the measured yaw rate 18. The desired distribution is indicated, for example, as a percentage distribution factor (e.g. 40/60: 40% of the torque 19 directed by way of the drive shaft 5 is transmitted by way of the first clutch 8 and 60% by way of the second clutch 9), which corresponds to the dynamic requirements of the desired driving behavior of the motor vehicle 3 for stable driving maneuvers. The distribution of the torques for the first clutch 8 can be set by way of the first locking rate 13 and for the second clutch 9 by way of the second locking rate.

[0065] As soon as one of the wheels 11, 12 slips (spins or locks), thus an unstable travel state is present, the desired torque distribution 31 can be corrected by a distribution correction 32. In order to increase the traction or to stabilize the motor vehicle 3, the torque distribution 31 is typically varied in such a way that the locking rate 13, 14 of the non-slipping wheel 11, 12 increases and/or the locking rate 14, 13 of the slipping wheel 12, 11 is reduced. If the locking rate 13, 14 in total (the total locking rate) is reduced, the torque 19 provided by the drive unit 4 should (also) be reduced.

[0066] The desired locking rate 13, 14 of the respective clutch 8, 9 for the first wheel 11, or the second wheel 12, respectively, can be calculated by way of the third controller 30 by means of the torque 19 (drive torque or drag torque or recuperation torque, respectively) directed by way of the drive shaft 5, as well as by means of the desired torque distribution 31 or the distribution correction 32.

LIST OF REFERENCE SIGNS

[0067] 1 Drive system [0068] 2 Axle [0069] 3 Motor vehicle [0070] 4 Drive unit [0071] 5 Drive shaft [0072] 6 First output shaft [0073] 7 Second output shaft [0074] 8 First clutch [0075] 9 Second clutch [0076] 10 Control unit [0077] 11 First wheel [0078] 12 Second wheel [0079] 13 First locking rate [0080] 14 Second locking rate [0081] 15 Steering angle [0082] 16 Steering wheel [0083] 17 Speed [0084] 18 Yaw rate [0085] 19 Torque [0086] 20 First slip [0087] 21 Second slip [0088] 22 Differential [0089] 32 Transmission [0090] 24 Pump motor [0091] 25 Pump [0092] 26 First valve [0093] 27 Second valve [0094] 28 First controller [0095] 29 Second controller [0096] 30 Third controller [0097] 31 Torque distribution [0098] 32 Distribution correction