DRIVE DEVICE FOR A MOTOR VEHICLE

Abstract

A drive device for a motor vehicle includes a primary powertrain and a secondary powertrain, wherein the primary powertrain includes a combustion engine for generating a total torque; a torque distribution device coupled to the combustion engine and including a first and a second output, wherein the torque distribution device is designed to provide a first partial torque in mechanical form at its first output derived from the total torque, and to provide a second partial torque in electrical form at its second output derived from the total torque; and a transmission which is coupled to the first output of the torque distribution device; wherein the secondary powertrain includes an electric machine which is coupled to the second output of the torque distribution device; wherein the torque distribution device includes a torque limiting device which is designed to limit the first partial torque to a presettable threshold value.

Claims

1.-13. (canceled)

14. A drive device for a motor vehicle, comprising: a first drivetrain comprising an internal combustion engine for generating a total torque, a torque distribution device coupled with the internal combustion engine, said torque distribution device having a first output and a second output and being configured to provide at the first output a mechanical first partial torque derived from the total torque, and to provide at the second output an electrical second partial torque derived from the total torque, said torque distribution device comprising a torque limitation device configured to limit the first partial torque to a predeterminable threshold value; a secondary drivetrain comprising an electric machine which is coupled with the second output of the torque distribution device; and a transmission which is coupled with the first output of the torque distribution device;

15. The drive device of claim 14, wherein the torque distribution device is configured to provide a difference between the total torque and the predeterminable threshold value for the first partial torque as second partial torque.

16. The drive device of claims 14, wherein the predeterminable threshold value for the first partial torque is variable.

17. The drive device of claim 16, wherein the predetermineable threshold value for the first partial torque is variable in dependence on at least one of a control by at least one driving dynamics system and a control by a user.

18. The drive device of claim 17, wherein the control by the at least one driving dynamics system is a function of at least one of a target efficiency, a road friction value, a speed of the motor vehicle, a yaw rate, and a transverse dynamic influence.

19. The drive device of claim 14, wherein the torque distribution device is configured to limit a value range for the predetermineable threshold value for the first partial torque to a maximal value, which corresponds to a nominal maximal torque of the transmission.

20. The drive device of claim 14, wherein the torque distribution device is configured to limit the predeterminable threshold value to a maximal value which corresponds to a nominal maximal torque of the transmission.

21. The drive device claim 19, wherein the internal combustion engine is configured to provide a maximal total torque which corresponds to the sum of the maximal value for the first partial torque and the maximal value for the second partial torque (Mel) wherein the maximal value for the first partial torque and the maximal value for the second partial torque are not zero.

22. The drive device of claim 14, wherein the electric machine of the secondary drivetrain is adapted for coupling with the second output of the torque distribution device so that the second partial torque can be provided in real-time to a supply input of the electric machine.

23. The drive device of claim 22, wherein the second partial torque can be provided to the supply input of the electric machine without an intermediate storage in an electrical energy storage.

24. The drive device of claim 14, further comprising an electrical energy storage, wherein the electrical energy storage is adapted for coupling with the second output of the torque distribution device.

25. The drive device of claim 24, further comprising a controllable switch for switching between a coupling of the second output of the torque distribution device with the electrical energy storage and a coupling of the second output of the torque distribution device with the electric machine of the secondary drivetrain.

26. The drive device of claim 25, wherein the controllable switch is configured to switch in dependence on at least one of a driving situation and a control by the user.

27. The drive device of claim 26, wherein the controllable switch is configured to couple the second output of the torque distribution device with the electric machine of the secondary drivetrain when at least one of a road friction value a yaw rate and a speed of the motor vehicle exceed or fall below predeterminable threshold values.

28. The drive device of claim 26, wherein the controllable switch is configured to couple the second output of the torque distribution device with the electric energy storage when a residual range is to be increased purely electrically.

29. The drive device of claim 14, wherein the internal combustion engine is coupled with the transmission via an input shaft, and wherein the torque distribution device is arranged on the input shaft and is configured as an electric machine.

30. The drive device of claim 29, wherein the electric machine is assigned to the primary drivetrain.

31. The drive device of claim 30, wherein the electric machine is adapted for coupling with an electrical energy storage.

Description

[0020] In the following an exemplary embodiment of the present invention is described in more detail with reference to the included drawing in which the sole FIGURE shows a schematic representation of an exemplary embodiment of a drive device according to the invention.

[0021] The FIGURE schematically shows a drive device 10 according to the invention. The drive device includes a primary drivetrain 12 and a secondary drivetrain 14. The primary drivetrain 12 includes an internal combustion engine 16, which is configured to provide the entire torque for the primary drivetrain 12 and the secondary drivetrain 14. The internal combustion engine 16 is coupled with a transmission 20 via an input shaft 18, wherein the output shaft 22 of the transmission, as is known, can be coupled with a primary axle 24, which is not shown for reasons of simplicity.

[0022] On the input shaft 18 an electric machine 26 is arranged which is configured as torque distribution device. Via its first output, i.e., the input shaft 18, the torque distribution device provides a first partial torque M.sub.mech in mechanical form, which is derived from the total torque M.sub.ges generated by the internal combustion engine 16. On the second output 28 the torque distribution device provides a second partial torque M.sub.ef in electrical form, which is derived from the total torque M.sub.ges. The transmission 20 is configured for a maximal mechanical torque M.sub.mech-max, where. M.sub.mech-max is smaller than M.sub.ges. The electric machine 26 is configured to limit the torque M.sub.mech provided by the transmission 20 in any event to the value M.sub.mech-max. In the cases in which the actual torque M.sub.ges actually provided by the internal combustion engine 16 is greater than M.sub.mech-max the electric machine 26 starts to brake the input shaft 18, generates thereby the electric torque M.sub.el, which is conducted to an electric machine 30 of the secondary drivetrain 14 in the manner of a cardanic shaft, where it purely electrically drives a secondary axle 32 in a known manner. The electric machine 26 thus realizes a drivetrain generator.

[0023] In this way the entire drive device 10 can provide a greater torque M.sub.ges provided by the internal combustion engine 16 for the thrust of the motor vehicle wherein the transmission 20 can still be configured small and lightweight.

[0024] As a result of the variability of the threshold value for the mechanical partial torque M.sub.mech the transmission of a second partial torque M.sub.el to the secondary drivetrain 14 can be enabled even when the total torques M.sub.ges are smaller than M.sup.mech-max, for example by corresponding control by at least one driving dynamics system, in particular in dependence on a target efficiency, a road friction value a speed of the motor vehicle, a yaw rate or by control by the user.

[0025] While in the approach described above the second partial torque is provided to the electric machine 30 of the secondary drivetrain 14 in real-time, i.e., in particular without intermediate storage in an electrical energy storage, it is also possible to provide this partial torque M.sub.el to an electrical energy storage 34. This may be due to the fact that the internal combustion engine 16 operates more efficiently at another operating point than at an operating point at which it generates the exact torque that is currently requested for thrust. Because the operating point can only be changed so that the desired torque is generated the efficiency can only be increased by increasing the total torque M.sub.ges generated by the motor 16, so that a momentarily not requested torque is available that can be stored in the electrical storage 34 to be used at a later point in time. For this purpose a controllable switch 33 is provided in order to switch back an forth between a coupling of the second output 28 of the torque distribution device 26 with the electric energy storage 34 and the electric machine 30 of the secondary drivetrain 14.

[0026] However, it may also be considered to intentionally select a different operating point of the internal combustion engine 16 in order to increase the energy stored in the electrical energy storage 34, for example when a range that is to be achieved purely eclectically is to be increased. Vice versa it can be provided that for example the second output 28 of the electric machine 26 is coupled with the electric machine 30 when the road friction value and/or the yaw rate exceed or fall below predeterminable threshold values.

[0027] The design of the primary axle 24 has to taken into account that the total torque at this axle 24 consisting of a partial torque provided by the internal combustion engine 16 and a partial element optionally provided by the battery 34 must not exceed the mechanical limits at this axle 24.

[0028] The drive device 10 according to the present invention enables different drive concepts, which means [0029] drive of the primary axle 24 purely mechanically; [0030] drive of the primary axle 24 purely electrically [0031] drive of the secondary axle purely electrically; [0032] drive of the primary axle 24 and the secondary axle 32 purely electrically; [0033] drive of the primary axle 24 purely mechanically and drive of the secondary axle 32 purely electrically; [0034] drive of the primary axle 24 mechanically and electrically; [0035] drive of the primary axle 24 mechanically and electrically and the secondary axle 32 purely electrically.

[0036] A combination of electrical and mechanical drive of the primary axle 24 is useful in particular in the following cases: [0037] dynamically in order to compensate dead times of the internal combustion engine; [0038] stationary in order to fill torque gaps up to the mechanical limit of the primary axle 24

[0039] The corresponding controls can be realized in a motor control unit or a control provided in the electric machine 26.

[0040] In summary the internal combustion engine 16 is configured so that it can provide the maximal total torque or the maximal total power for the primary axle 24 and the secondary axle 32, wherein the transmission 20 is designed only for the maximal torque that is to be provided at the primary axle 24 (which is smaller than the maximal total torque of the internal combustion engine 16). However the transmission 20 is protected in the case of outputting the maximal power of the internal combustion engine 16 in that the excess torque is redirected via the electrical cardanic shaft to the electric machine 30 of the secondary drivetrain 14 or the energy storage 34.