ELECTRICAL POWER UNIT AND MOTOR VEHICLE

Abstract

An electric drive unit for driving at least two wheels of a motor vehicle, which has an exclusively electrically drivable wheel axle. The wheel axle is connected to at least one electric traction motor in order to transmit a drive torque and to a central brake in order to transmit a brake torque. A transmission gear having at least two gear stages and at least one intermediate gear shaft is arranged between the traction motor and the wheel axle and the central brake is integrated in an intermediate gear shaft of the transmission gear.

Claims

1.-21. (canceled)

22. An electric drive unit for driving at least two wheels of a motor vehicle, comprising: an exclusively electrically drivable wheel axle; a central brake; an electric traction motor connected to the wheel axle and configured to transmit a drive torque thereto and configured to transmit a brake torque to the central brake; and a transmission gear comprising at least two gear stages and at least one intermediate gear shaft arranged between the traction motor and the wheel axle; wherein the central brake is integrated in an intermediate gear shaft of the transmission gear.

23. The drive unit of claim 22 wherein the traction motor and transmission gear each comprise one or more shaft, said shafts constructed in an axially parallel manner with respect to an axle of the wheel drive.

24. The drive unit of claim 22 wherein of the gear stages of the transmission gear has an output shaft spaced apart from the wheel axle and which is connected to the central brake.

25. The drive unit of claim 22 wherein the transmission gear has a plurality of intermediate shafts, one of said intermediate shafts connected to the central brake.

26. The drive unit of claim 22 wherein the transmission gear is constructed to be switch-free.

27. The drive unit of claim 22 wherein the central brake is a dry-running friction brake.

28. The drive unit of claim 22 wherein the central brake forms the only vehicle brake

29. The drive unit of claim 22 wherein the wheel axle has individual wheel brakes in addition to the central brake.

30. The drive unit of claim 29 wherein the central brake and/or individual wheel brakes are an electromechanical brake.

31. The drive unit of claim 22 wherein the central brake is one or more of a service brake, a parking brake, or a holding brake.

32. The drive unit of claim 22 wherein the traction motor and the central brake have peripheral devices which are used together.

33. The drive unit of claim 22 wherein the central brake, the transmission gear, and the traction motor are arranged in a common housing.

34. The drive unit of claim 22 wherein the central brake and the traction motor have a common control device.

35. The drive unit of claim 34 wherein the control device is configured to control mixed braking.

36. The drive unit of claim 22 wherein the central brake comprises a fluid cooler.

37. The drive unit of claim 36 wherein the fluid cooler is connected to a motor cooling circuit.

38. The drive unit of claim 22 wherein the wheel axle has a torque vectoring unit.

39. The drive unit of claim 22 comprising a clutch arranged between the traction motor and the central brake.

40. The drive unit of claim 39 wherein the clutch and the central brake are configured to be controlled together.

41. The drive unit of claim 22 wherein the central brake comprises a brake dust collector.

42. The drive unit of claim 22 wherein the central brake is connected to a torsion damper.

43. A motor vehicle comprising the electric drive unit of claim 22.

Description

[0038] In the drawings:

[0039] FIG. 1 is a schematic illustration of a first embodiment according to the invention with the most important components, in which the transmission gear is provided with two gear stages and an intermediate gear shaft;

[0040] FIG. 2 is a schematic illustration of a second embodiment according to the invention, in which the transmission ratio has three gear stages and two intermediate gear shafts and in addition to the central brake individual wheel brakes are provided;

[0041] FIG. 3 is a schematic illustration of a third embodiment according to the invention in which the central brake is provided with an open filter device as a brake dust collector;

[0042] FIG. 4 is a schematic illustration of a fourth embodiment according to the invention in which the central brake is fluid-cooled and is encapsulated in a closed filter device as a brake dust collector;

[0043] FIG. 5 is a schematic illustration of a fifth embodiment according to the invention in which the central brake is combined with a torque vectoring unit and has a torsion damper, and

[0044] FIG. 6 is a schematic illustration of a sixth embodiment according to the invention, in which a clutch is arranged between the central brake and the traction motor;

[0045] FIG. 7 is a schematic illustration of a seventh embodiment according to the invention, in which the vehicle is constructed with two tracks and the drive unit is constructed as a twin drive.

[0046] FIG. 1 shows a first embodiment of an electric drive unit 10 which is provided to drive at least two wheels 11 of a motor vehicle. The motor vehicle may, for example, be a passenger vehicle which has a wheel axle 12 which is driven exclusively electrically. Other vehicles are possible. The wheel axle 12 is connected or can be connected to the two driven wheels 11. The thick dashed line shows the system limit of the electric drive unit 10, the components of which form a module. In the context of the invention, a motor vehicle having such a drive unit 10 is further disclosed and claimed.

[0047] The drive unit 10 has an electric traction motor 13 which produces the drive torque required for driving the vehicle and which transmits it to the wheel axle 12 or the wheels 11. The drive unit 10 has a differential gear 15 which distributes the drive torque of the traction motor 13 to the wheels 11 and which compensates for the speed differences of the wheels 11. The drive unit 10 further has a central brake 14 which produces a brake torque and which transmits it to the wheel axle 12 or the two wheels 11. In contrast to the individual wheel brakes, the central brake 14 produces a central brake torque which acts on the wheels 11 together.

[0048] The central brake 14 is integrated in a transmission gear 16 which has at least two gear stages, in the embodiment according to FIG. 1 specifically a first gear stage 17 and a second gear stage 20a. The first and second gear stages are arranged between the traction motor and differential gear and coupled by means of a common intermediate gear shaft.

[0049] Specifically, the first gear stage 17 has a drive pinion 28 which is connected to the input shaft 19 of the first gear stage 17. The input shaft 19 forms at the same time the motor shaft of the traction motor 13. The first gear stage 17 further has an output toothed wheel 29 which is connected to an output shaft 18 of the gear stage 17. The output shaft 18 is in turn connected to the differential gear 15 by means of another gear stage, specifically a second gear stage 20a. The second gear stage 20a has on the output shaft 18 of the first gear stage 17 a first toothed wheel 33 which meshes with a second toothed wheel 34 which is connected to a differential cage of the differential gear 15 (not illustrated).

[0050] As can be seen in FIG. 1, the output shaft 18 of the first gear stage 17 is connected to the central brake 14. The output shaft 18 thus has two functions. On the one hand, the output shaft 18 transmits the drive torque of the traction motor 13 and, on the other hand, the drive torque of the central brake 14 in each case via the differential gear 15 to the wheels 11.

[0051] As a result of the above-described integration of the central brake 14 in an intermediate gear shaft 18 of the transmission gear 16, it is possible for the brake partners of the central brake 14 to be less heavily loaded with respect to the speed than in a central brake which is arranged directly on the motor shaft of the traction motor 13. With regard to the arrangement known per se of the central brake on the wheel axle, the torques which are intended to be braked are smaller. The central brake 14 may thus be constructed to be smaller and simpler. As a result of an appropriate selection of the transmission ratios of the gear stages 17, 20a, the central brake 14 and the relevant torque range or speed range during operation can be adapted. In this instance, the gear stages 17, 20a may have the same or different transmission ratios.

[0052] As can be seen in FIG. 1, the output shaft 18 is spaced apart in a parallel manner from the wheel axle 12. Consequently, and as a result of the integration of the central brake 14 in the transmission gear 16, structural space for the central brake 14 is obtained and structural space limitations are overcome. With a corresponding configuration of the central brake 14, the demands on the wheel brake power levels can sometimes be reduced so that the use of currently (in comparison with hydraulic wheel brakes) still very large electromechanical or electrohydraulic wheel brakes is possible.

[0053] Specifically, the central brake 14 may be constructed as a dry-running friction brake, in particular a disk brake.

[0054] The control of the central brake 14 is carried out by means of a control device 22, which takes over both the control of the traction motor 13 and the control of the central brake 14 and which is configured accordingly. It is further possible for the inverter of the traction motor 13 to be integrated in the control device 22. The signal line which connects the central brake 14 and the control device 22 is illustrated by the fine dashed line in FIG. 1.

[0055] The following synergistic effects arise in the integration of the central brake 14 in the electrical axle unit or drive unit:

[0056] The components mentioned above may be constructed in a common housing of the electric axle. The brake control device may be integrated in the motor control device or in a common control device 22 (control of the engine, inverter, brake, etc.) (see above). A more compact construction of the central brake 14 is possible by means of active fluid cooling of the brake unit, in particular by means of connection to the motor cooling circuit which is provided in any case (see below). It is further possible to operate blended braking (mixed braking) in the common control device, in particular when purely electromechanical/electrohydraulic brakes are used on the wheel and centrally. In a simple manner, it is thus possible for different operating modes of the drive train to be produced: for example, mechanical individual wheel brakes, regenerative motor brakes, central brakes or a combination thereof.

[0057] The structure of the electric drive unit 10 described in connection with FIG. 1 is accordingly implemented in the remaining embodiments and is also disclosed in connection with FIGS. 2 to 6. The invention is not limited to this specific structure.

[0058] The drive unit 10 according to FIG. 2 differs from the drive unit 10 according to FIG. 1, on the one hand, in that the transmission gear 16 is further constructed with multiple stages. Specifically, the transmission gear 16 has three stages, that is to say, the first and second gear stage 17, 20a, as in FIG. 1, and an additional third gear stage 20b. Furthermore, the drive unit 10 in provided in addition to the central brake 14 with two individual wheel brakes 21. It is also possible for the embodiment according to FIG. 1 to be provided with two individual wheel brakes 21.

[0059] The transmission gear 16 according to FIG. 2 is specifically constructed as follows. The input shaft 19 of the gear 16 is connected to the traction motor 13 and drives the first gear stage 17 by means of the drive pinion 28. The drive toothed wheel 29 of the first gear stage 17 is connected by means of an intermediate shaft 30 to the third gear stage 20b. The third gear stage 20b is arranged between the first gear stage and second gear stage 17, 20a and has a first toothed wheel 35 which is connected to the intermediate shaft 30, and a second toothed wheel 36 which is connected to the output shaft 18 of the gear 16. The output shaft 18 is, as in FIG. 1, connected, on the one hand, to the differential gear 15 and, on the other hand, to the central brake 14.

[0060] The three gear stages 17, 20a, 20b may have the same or different transmission ratios.

[0061] This embodiment has the advantage that the design freedom when the central brake 14 is positioned with respect to torque/speed range is further increased, which in particular enables the use of a central brake 14 with a slight pressing force, in particular of an electromechanical brake.

[0062] The gear 16 according to FIGS. 1, 2 cannot be switched. The same applies to the remaining embodiments of this application.

[0063] The embodiment according to FIG. 2 has in addition to the central brake 14 two individual wheel brakes 21 which are arranged close to the wheel and which are connected to the wheel axle 12. A redundant brake system is thereby provided, in which, in the event of failure of a partial system (central brake or individual wheel brakes), the other partial system can maintain a brake function at least to a limited extent. The control of the individual wheel brakes 21 is carried out by the common control device 22, which also controls the central brake 24. A mixed braking operation is thereby possible.

[0064] The drive unit 10 according to FIG. 3 is constructed in a similar manner to the drive unit 10 according to FIG. 1 and has in addition a brake dust collector 26 which in the example according to FIG. 3 is constructed as an open filter, that is to say, as a filter which is open toward the atmosphere. It is particularly advantageous for a brake dust intake or exhaust installation (impeller, ventilator, air acceleration means [37]) to be operated directly by a gear shaft.

[0065] In contrast to FIG. 3, the brake dust collector 26 according to FIG. 4 is constructed as a closed filter system which encapsulates the central brake 14. Furthermore, the central brake 14 has a device 23 for fluid cooling which is connected to the motor cooling circuit. This circuit is indicated by the double-headed arrow on the supply/discharge lines of the device 23. Another synergistic effect is achieved in that the device 23 for fluid cooling also cools the traction motor 13.

[0066] The drive unit 10 according to FIG. 5 has a torque vectoring unit 24 which is connected to the wheel axle 12 and which is arranged downstream of the differential gear 15. The torque vectoring unit 24 has an electric motor 31 and at least one torque vectoring gear mechanism 32 (distributor gear mechanism) which is connected to the wheel axle 12 for individual wheel influencing of the torque acting on the wheels 11. As a result of the combination of the central brake 14 with the torque vectoring unit 24, the individual wheel brakes can be omitted without being replaced without in this instance having to dispense with an individual wheel braking. In this instance, the main brake torque is applied by the central brake 14. The differential torque between the two wheels 11 of the drive axle 12 is produced by the torque vectoring unit 24.

[0067] Furthermore, the output shaft 18 of the gear 16 is provided with a torsion damper 27, which connects the output shaft 18 to the central brake 14. The use of the central brake 14 may have a positive effect on the noise emissions, on the one hand, as a result of the positioning inside the vehicle itself, on the other hand, as a result of possible encapsulation of the central brake 14 in a housing. The interposition of the torsion damper 27 between the central brake 14 and the output shaft 18 as a result of the higher degree of design freedom with respect to individual wheel brakes leads to a further improved NVH ratio (noise vibration harshness).

[0068] FIG. 6 shows an embodiment in which the output shaft 18 has a clutch 25 which decouples the traction motor 13 from the central brake 14 during the braking operation. Specifically, the coupling 25 is arranged on the intermediate gear shaft of the first gear stage 17 and second gear stage 20a and in the force path closer to the traction motor than the central brake. As a result of the clutch 25, the motor drag torque (moment of inertia in the event of braking) is decoupled, which leads to improved response behavior and higher dynamics (for example, for EPS) and/or to further downsizing potential. Advantageously, the clutch 25 and central brake 14 are in this instance acted on via a common actuator so that, in the event of braking, the clutch 25 is automatically opened. As a result of this mechanical coupling of the brake 14 and clutch 25, it is possible in particular to dispense with a separate clutch control device or an individual clutch control.

[0069] FIG. 7 shows an embodiment in which the drive unit 10 is constructed for a dual-track vehicle and is provided with a twin drive. The wheel axles (semi-axles) 12a, 12b are driven independently. Both wheels 11 of the drive axle are driven by a traction motor 13. They are not connected by means of a differential gear. A compensation for wheel speeds when travelling on bends can be carried out by controlling the traction motors. Each twin motor is connected to the wheel by means of a transmission gear 16; each transmission gear has a central brake 14. The vehicle has in the example no brakes (individual wheel brakes) which are fitted to the wheel axle 12a, 12b.

[0070] Preferably, the invention relates to an electric drive unit 10 for driving at least two wheels 11 of a motor vehicle, which has an exclusively electrically drivable wheel axle 12, wherein the wheel axle 12 is connected to at least one electric traction motor 13 in order to transmit a drive torque and to a central brake 14 in order to transmit a brake torque and has a differential gear 15 which is distinguished in particular by a transmission gear 16 having at least two gear stages 17, 20a, 20b and at least one intermediate gear shaft 18, 20 being arranged between the traction motor 13 and the differential gear 15, wherein the central brake 14 is integrated in an intermediate gear shaft 18, 30 of the transmission gear 16.

LIST OF REFERENCE NUMERALS

[0071] 10 Drive unit

[0072] 11 Wheels

[0073] 12 Wheel axle

[0074] 12a Left wheel axle (semi-axle)

[0075] 12b Right wheel axle (semi-axle)

[0076] 13 Traction motor

[0077] 14 Central brake

[0078] 15 Differential gear

[0079] 16 Transmission gear

[0080] 17 First gear stage

[0081] 18 Output shaft

[0082] 19 Input shaft

[0083] 20a Second gear stage

[0084] 20b Third gear stage

[0085] 21 Individual wheel brakes

[0086] 22 Control device

[0087] 23 Device for fluid cooling

[0088] 24 Torque vectoring unit

[0089] 25 Clutch

[0090] 26 Brake dust collector

[0091] 27 Torsion damper

[0092] 28 Drive pinion

[0093] 29 Output toothed wheel

[0094] 30 Intermediate shaft

[0095] 31 Electric motor

[0096] 32 Torque vectoring gear mechanism

[0097] 33 First toothed wheel of the second gear stage

[0098] 34 Second toothed wheel of the second gear stage

[0099] 35 First toothed wheel of the third gear stage

[0100] 36 Second toothed wheel of the third gear stage

[0101] 37 Air conveying means