GEAR UNIT AND POWERTRAIN FOR A VEHICLE

Abstract

A gear unit for a powertrain and a powertrain including a stepped planetary gearset, a first gear shifting element and a second gear shifting element. The stepped planetary gearset has a first sun gear, a first ring gear, a second ring gear, and stepped planet gears rotatably mounted at a first planet carrier. The first ring gear is fixed with respect to rotation to an output shaft of the gear unit. The second ring gear is fixed with respect to rotation to a housing. The first gear shifting element drivingly connects the first sun gear to an electric machine in a closed state, and the second gear shifting element drivingly connects the first planet carrier to the electric machine in a closed state, and one of the two gear shifting elements is in the closed state for driving the output shaft in rotation.

Claims

1. A gear unit for a powertrain of an at least partially electrically driven vehicle, comprising: a housing; a first planet carrier; a stepped planetary gearset having: a first sun gear; a first ring gear fixedly connected with respect to rotation to an output shaft of the gear unit; a second ring gear is fixedly connected with respect to rotation to the housing; and a plurality of stepped planet gears rotatably mounted at the first planet carrier; a first gear shifting element configured to drivingly connect the first sun gear to an electric machine in a closed state; and a second gear shifting element configured to drivingly connect the first planet carrier to the electric machine in a closed state; wherein one of the first gear shifting element and the second gear shifting element is in the closed state for driving the output shaft in rotation.

2. The gear unit according to claim 1, wherein the first gear shifting element is a positively engaging shifting element.

3. The gear unit according to claim 1, wherein the first gear shifting element is a frictionally engaging shifting element.

4. The gear unit according to claim 1, wherein the second gear shifting element is a positively engaging shifting element.

5. The gear unit according to claim 1, wherein the second gear shifting element is a frictionally engaging shifting element.

6. The gear unit according to claim 1, wherein the first gear shifting element and the second gear shifting element are formed jointly as a double shifting element.

7. A powertrain for a vehicle that is at least partially electrically driven, comprising: an electric machine; a gear unit, comprising: a housing; a first planet carrier; a stepped planetary gearset having: a first sun gear; a first ring gear fixedly connected with respect to rotation to an output shaft of the gear unit; a second ring gear is fixedly connected with respect to rotation to the housing; and a plurality of stepped planet gears rotatably mounted at the first planet carrier; a first gear shifting element configured to drivingly connect the first sun gear to an electric machine in a closed state; and a second gear shifting element configured to drivingly connect the first planet carrier to the electric machine in a closed state; wherein one of the first gear shifting element and the second gear shifting element is in the closed state for driving the output shaft in rotation; and a differential that drivingly connects the gear unit to two driven shafts arranged coaxial to an output axis.

8. The powertrain according to claim 7, wherein the differential is a bevel gear differential.

9. The powertrain according to claim 7, further comprising a planetary gear assembly having at least a first planetary gearset, the planetary gear assembly drivingly connected to the output shaft of the gear unit.

10. The powertrain according to claim 9, wherein the first planetary gearset of the planetary gear assembly comprises: a second sun gear fixed with respect to the housing; a third ring gear; and a plurality of planet gears rotatably mounted at a second planet carrier, wherein the third ring gear is fixedly connected with respect to rotation to the first ring gear of the gear unit.

11. The powertrain according to claim 10, wherein a differential carrier (16a) of the differential is fixedly connected with respect to rotation to the second planet carrier of the planetary gear assembly.

12. The powertrain according to claim 7, wherein the gear unit and/or the differential are/is arranged at least partially or completely spatially inside of a rotor of the electric machine.

13. The powertrain according to claim 7, wherein at least a first transmission stage is drivingly arranged between the output shaft of the gear unit and the differential.

14. The powertrain according to claim 7, wherein the differential is an integral differential comprising: a second planetary gearset configured to transmit a first output torque to a first driven shaft; and a third planetary gearset drivingly connected to a respective driven shaft, wherein a supporting torque of the second planetary gearset is convertible in the third planetary gearset such that a second output torque corresponding to the first output torque is transmittable to a second driven shaft.

15. The powertrain according to claim 14, wherein the integral differential and the two driven shafts are configured to be arranged coaxial to an output axis of the vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention will be described in the following with reference to drawings depicting the various embodiment forms of the invention. Like or similar elements are designated with consistent reference numerals. In particular, the drawings show:

[0036] FIG. 1 is a vehicle comprising a powertrain with a gear unit;

[0037] FIG. 2 is a schematic depiction of the gear unit shown in FIG. 1;

[0038] FIG. 3 is a schematic diagram of a shifting matrix relating to two shifting states for driving with a gear unit shown in FIG. 2;

[0039] FIG. 4 is a schematic depiction of the powertrain with the gear unit shown in FIG. 2;

[0040] FIG. 5 is a schematic depiction of the powertrain with the gear unit a;

[0041] FIG. 6 is a schematic depiction of the powertrain with the gear unit;

[0042] FIG. 7 is a schematic depiction of the powertrain with the gear unit; and

[0043] FIG. 8 is a schematic depiction of the powertrain with the gear unit.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0044] FIG. 1 shows an electrically driven vehicle 1 with a powertrain 2 according to one aspect of the invention. The powertrain 2 comprises an electric machine 11 that generates power and introduces this power into a gear unit 3. The gear unit 3 is shown in FIG. 2, and the associated shifting matrix is shown in FIG. 3. The gear unit 3 is drivingly connected to a planetary gear assembly 14 that increases an overall gear ratio and transmits the power to a differential 16 arranged downstream in the power flow, in this instance spatially inside of the electric machine 11. The differential 16 divides the motive power between a first driven shaft 18a and a second driven shaft 18b that are in turn operatively connected to a driven wheel 28 of the vehicle 1 in each instance. The vehicle 1 can further comprise an energy accumulator supplied with electrical energy by the electric machine 11 in generator mode when the power flow is reversed. The energy accumulator can be a battery or the like. Accordingly, in generator mode, by the electric machine 11, electrical energy is generated, stored, and conserved for resupplying the electric machine 11.

[0045] The gear unit 3 from FIG. 1 is shown in a detailed diagram in FIG. 2. The gear unit 3 according to FIG. 2 can be acted upon by a motive power in the powertrain 2 according to FIG. 4 via an input shaft 29 with a rotor 19 of the electric machine 11, which rotor 19 is mounted so as to be rotatable relative to a stator 30. The input shaft 29 can be connected to the rotor 19 integrally or in more than one part; in any case, a rotationally locked driving connection exists. The gear unit 3 comprises a stepped planetary gearset 4 with a first ring gear 8a connected to an output shaft 12 of the gear unit 3 so as to be fixed with respect to rotation relative to it, a second ring gear 8b which is connected to a housing 13 of the gear unit 3 so as to be fixed with respect to rotation relative to it, a first sun gear 7 and a plurality of stepped planet gears 10 rotatably mounted at a first planet carrier 9. The gear unit 3 further has a first gear shifting element 5 and a second gear shifting element 6. The first gear shifting element 5 is adapted to drivingly connect the first sun gear 7 to the electric machine 11 in a closed state, and the second gear shifting element 6 is adapted to drivingly connect the first planet carrier 9 to the electric machine 11 in a closed state. To drive the output shaft 12 in rotation, only one of the two gear shifting elements 5, 6 is in the closed state. Consequently, the drive is carried out via the first sun gear 7 or via the first planet carrier 9. The first sun gear 7 is in meshing engagement with a first toothed wheel 31a of the respective stepped planet gear 10, and the first ring gear 8a is also in meshing engagement with the first toothed wheel 31a of the respective stepped planet gear 10. The second ring gear 8b is in meshing engagement with a second toothed wheel 31b of the respective stepped planet gear 10. The two toothed wheels 31a, 31b of the respective stepped planet gear 10 are connected with one another so as to be fixed against relative rotation. The output is carried out via the first ring gear 8a which is in meshing engagement with the second toothed wheel 31b of the respective stepped planet gear 10. The two toothed wheels 31a, 31b have different diameters and numbers of teeth so that two different gear ratios can be realized depending on which gear shifting element 5, 6 is closed or open. In the present instance, the first toothed wheel 31a of the respective stepped planet gear 10 has a smaller diameter than the second toothed wheel 31b of the respective stepped planet gear 10.

[0046] When the first gear shifting element 5 is in a closed state and the second gear shifting element 6 is in an open state, the first sun gear 7 is connected to the input shaft 29 so as to be fixed with respect to rotation relative to it so that a motive power of the electric machine 11 is conducted via the first sun gear 7 to the stepped planet gears 10 and then via the first ring gear 8a to the output shaft 12 of the gear unit 3. When the second gear shifting element 6 is in a closed state and the first gear shifting element 5 is in an open state, the first planet carrier 9 is connected to the input shaft 29 so as to be fixed with respect to rotation relative to it so that a motive power of the electric machine 11 is conducted via the first planet carrier 9 to the stepped planet gears 10 and then via the first ring gear 8a to the output shaft 12 of the gear unit 3. In an open state of the respective gear shifting element 5, 6, no torque is transmitted via the respective gear shifting element 5, 6. When both gear shifting elements 5, 6 are closed, a park lock function is realized because the stepped planetary gearset 4 is blocked in that the first sun gear 7 is connected to the first planet carrier 9 so as to be fixed with respect to relative rotation.

[0047] FIG. 3 shows the shifting matrix for a first gear step E1 and a second gear step E2 of the gear unit 3. The respective gear shifting element 5, 6 is closed where indicated by the “X” and open where there is no “X”. An electric forward drive of the vehicle 1 with respective gear ratio is realized via the respective gear step E1, E2. When the first gear shifting element 5 is closed and the second gear shifting element 6 is open, the first gear step E1 is engaged and a first gear ratio is accordingly realized. When the second gear shifting element 6 is closed and the first gear shifting element 5 is open, the second gear step E2 is engaged and a second gear ratio that is not equal to the first gear ratio is accordingly realized. This shifting matrix applies to all of the depicted embodiment examples of the invention. Traction power shifting and/or coasting power shifting may be realized depending on the construction of the gear shifting elements 5, 6. In such a case, the respective gear shifting element 5, 6 is formed as a powershift element.

[0048] According to FIG. 2, the first gear shifting element 5 is formed as a positively engaging shifting element, in this case as a jaw-type shifting element. In the closed state of the first gear shifting element 5, a positively engaging connection is accordingly produced between the first sun gear 7 and the input shaft 29 of the gear unit 3. If necessary, these parts are synchronized before entering the positively engaging connection. On the other hand, the second gear shifting element 6 is formed in the present case as frictionally engaging shifting element, in this instance as a disk-type shifting element. Accordingly, in the closed state of the second gear shifting element 6, a frictionally engaging connection is produced between the first planet carrier 9 and the input shaft 29 of the gear unit 3. A synchronization of the rotational speeds of the parts is not required, and a frictionally engaging shifting element is suitable as power shifting element. In other words, the second gear shifting element 6 realizes a traction power shifting from gear step E1 into gear step E2, or vice versa. The load during shifting processes between gear steps E1, E2 is supportable by the first gear shifting element 5 formed as positively engaging until the second gear shifting element 6 is completely open or closed to prevent a load decrease at the output particularly during shifting processes. Alternatively, the two gear shifting elements 5, 6 may be formed as in the respective embodiment form according to FIG. 5, FIG. 6 or FIG. 7.

[0049] FIG. 4 shows the powertrain 2 having the gear unit 3 described above. In this respect, reference is made to the statements referring to FIG. 1 to FIG. 3. FIG. 4 also shows the electric machine 11 connectible to the first sun gear 7 or to the first planet carrier 9 via the input shaft 29 and the respective gear shifting element 5, 6. Further, the powertrain 2 has a planetary gear assembly 14 with a first planetary gearset 15. In the present case, the first planetary gearset 15 is formed as a negative planetary gearset and comprises a second sun gear 20 connected to the housing 13 of the gear unit 3 so as to be fixed with respect to relative rotation, a third ring gear 21 connected to the output shaft 12 of the gear unit 3 so as to be fixed with respect to rotation relative to it, and a plurality of planet gears 23 rotatably mounted at a second planet carrier 22. The third ring gear 21 is connected via the output shaft 12 of the gear unit 3 to the first ring gear 8a of the gear unit 3 so as to be fixed with respect to rotation relative to it such that the planetary gear assembly 14 is subsequently operatively connected to the output shaft 12 on the drive side. The output of the planetary gear assembly 14 is carried out via the second planet carrier 22 drivingly connected to a differential 16. Total gear ratios between 6 and 13.5, for example, can be realized by such a combination comprising gear unit 3 and planetary gear assembly 14.

[0050] In the present case, the differential 16 is formed as a bevel gear differential and drivingly connects the gear unit 3 via the planetary gear assembly 14 to the two driven shafts 18a, 18b arranged coaxial to an output axis 17, the second driven shaft 18b being guided through the gear unit 3 and the planetary gear assembly 14 in the present instance. The bevel gear differential 16 known from the prior art has two output elements on the wheel side which are formed as a first driven wheel 16b and second driven wheel 16c. The driven wheels 16b, 16c mesh, respectively, with a compensating element 16d, 16e. The compensating elements 16d, 16e are mounted in a differential carrier 16a so as to be rotatable around their own axes. The first driven wheel 16b is connected to the first driven shaft 18a so as to be fixed with respect to rotation relative to it, and the second driven wheel 16c is connected to the second driven shaft 18b so as to be fixed with respect to rotation relative to it. The differential carrier 16a of the differential 16 is connected via an intermediate shaft 32 to the second planet carrier 22 so as to be fixed with respect to rotation relative to it, the intermediate shaft 32 being guided through the gear unit 3 coaxial to the input shaft 29 and output shaft 12 of the gear unit 3 and connected to the differential carrier 16a. The differential 16 is arranged completely spatially inside of the rotor 19 of the electric machine 11 in order to save axial installation space. Accordingly, in this case the output axis 17 extends coaxial to an input axis 33 of the vehicle, and a rotational axis of the rotor 19, the input shaft 29 and the output shaft 12 of the gear unit 3 are arranged coaxial to the input axis 33. The gear unit 3 is arranged axially between the electric machine 11 and the differential 16 on one side and the planetary gear assembly 14 on the other side.

[0051] The powertrain 2 according to FIG. 5 comprises the gear unit 3 from FIG. 2 with the difference that the two gear shifting elements 5, 6 are formed as jaw-type shifting elements and are combined to form a double shifting element 41. Therefore, reference is made to the statements relating to the gear unit 3 from FIG. 2. Alternatively, the two gear shifting elements 5, 6 may be formed as in the respective embodiment form according to FIG. 4, FIG. 6 or FIG. 7. Reference is made to the description relating to FIG. 3 for the shifting between the first gear step E1 and second gear step E2. The gear unit 3 comprising the stepped planetary gearset 4 and the two gear shifting elements 5, 6 is arranged spatially completely inside of the rotor 19 of the electric machine 11 in order to save axial installation space and make the powertrain 2 more compact. The gear shifting elements 5, 6 are arranged directly adjacent one another coaxial to the input axis 33 and output axis 17 and together form the double shifting element 41 compactly comprised of the two gear shifting elements 5, 6. The gear shifting elements 5, 6 realize a positively engaging connection between the input shaft 29 of the gear unit 3 and the first sun gear 7 or first planet carrier 9 in the closed state. A particularly cost-optimized and efficiency-optimized clutch system is provided in this way.

[0052] The first planetary gearset 15 of the planetary gear assembly 14 is formed as a negative planetary gearset and comprises a third ring gear 21 connected to the output shaft 12 of the gear unit 3 so as to be fixed with respect to rotation relative to it, a stationary second sun gear 20 connected to the housing 13 so as to be fixed with respect to rotation relative to it, and a plurality of planet gears 23 rotatably mounted at a second planet carrier 22. The third ring gear 21 is connected to the first ring gear 8a of the gear unit 3 via output shaft 12 so as to be fixed with respect to rotation relative to it such that the planetary gear assembly 14 is subsequently operatively connected to the output shaft 12 of the gear unit 3 on the drive side. The output of the planetary gear assembly 14 is carried out via the second planet carrier 22 connected to a differential carrier 16a of the differential 16 so as to be fixed with respect to rotation relative to it. The differential 16 is formed as a bevel gear differential and is further identical to the differential 16 according to FIG. 4 so that the relevant statements apply here. Total gear ratios of between 6 and 13.5 can be achieved by such a combination comprising gear unit 3 and planetary gear assembly 14.

[0053] The differential 16 drivingly connects the gear unit 3 to the driven shafts 18a, 18b via the planetary gear assembly 14. In the present case, the first driven shaft 18a is guided axially through the gear unit 3 and the electric machine 11. The planetary gear assembly 14 is arranged axially between the electric machine 11 and the gear unit 3 on the one hand and the differential 16 on the other hand. Alternatively, it is conceivable that the differential 16 is also arranged together with the gear unit 3 spatially inside of the rotor 19 of the electric machine 11 in order to save additional axial installation space. The differential 16 is drivingly connected to the second planet carrier 22 via an intermediate shaft 32. The intermediate shaft 32 is arranged coaxial to the output shaft 12 of the gear unit 3. In this instance, the output axis 17 is also arranged coaxial to an input axis 33.

[0054] The powertrain 2 according to FIG. 6 comprises the gear unit 3 from FIG. 2 with the difference that the two gear shifting elements 5, 6 are formed as jaw-type shifting elements. Therefore, reference is made to the statements pertaining to the gear unit 3 from FIG. 2. Reference is made to the description of FIG. 3 for the shifting between the first gear step E1 and the second gear step E2. FIG. 6 shows a third embodiment example of the powertrain 2 according to the invention. In the present instance, the gear unit 3 comprising the stepped planetary gearset 4 and the two gear shifting elements 5, 6 are arranged spatially completely inside of the rotor 19 of the electric machine 11 in order to save axial installation space of the powertrain 2. The gear shifting elements 5, 6 realize a positively engaging connection between the input shaft 29 of the gear unit 3 and the first sun gear 7 or first planet carrier 9 in the closed state. A particularly cost-optimized and efficiency-optimized clutch system is provided in this way. Alternatively, it is conceivable that the respective gear shifting elements 5, 6 formed in each instance as jaw-type shifting element are combined and formed as a double shifting element as in FIG. 5. Further alternatively, the two gear shifting elements 5, 6 can be formed as in the respective embodiment form according to FIG. 4 or FIG. 7.

[0055] In contrast to the powertrains 2 according to FIG. 4 and FIG. 5 which have a differential 16 formed as bevel gear differential, the powertrain 2 according to FIG. 6 comprises a differential 16 formed as integral differential 25 with a second planetary gearset 26 and a third planetary gearset 27. The two planetary gearsets 26, 27 are arranged either axially adjacent one another or radially one above the other depending on the requirements of the integral differential 25, particularly the gear ratio to be realized by the integral differential 25. In the present case, the planetary gearsets 26, 27 are arranged radially one above the other so that axial installation space of the powertrain 2 is saved. In other words, the planetary gearsets 26, 27 lie in a common plane perpendicular to the driven shafts 18a, 18b or output axis 17, respectively. Consequently, the integral differential 25 is constructed in a radially nested type of construction.

[0056] A first output torque can be transmitted to the first driven shaft 18a by the second planetary gearset 16. A supporting torque of the second planetary gearset 26 acting opposite the first output torque is transmitted to the third planetary gearset 27 and is convertible in the third planetary gearset 27 in such a way that a second output torque corresponding to the first output torque can be transmitted to the second driven shaft 18b. The integral differential 25 is formed as planetary gear assembly. The integral differential 25 is operatively connected to the gear unit 3 via the input shaft of the integral differential 25 which is simultaneously the output shaft 12 of the gear unit 3. The output at the integral differential 25 is carried out via the two driven shafts 18a, 18b. In other words, a motive power is distributed to two driven shafts 18a, 18b by the integral differential 25. In the present case, the first driven shaft 18a extends through the gear unit 3 and the electric machine 11. The second driven shaft 18b extends away from the powertrain 2 in the opposite direction. Due to the fact that the integral differential 25 which increases a torque coming from the gear unit 3 is arranged after the gear unit 3 at the end of the powertrain 2, the component parts arranged upstream thereof in the power flow can be formed comparatively small and slender so that production is more economical and the overall weight of the powertrain 2 is reduced. The driven shafts 18a, 18b, the integral differential 25, the electric machine 11 and the gear unit 3 are arranged coaxial to the input axis 33 of the gear unit 3 and to the output axis 17 of the vehicle 1.

[0057] The output shaft 12 of the gear unit 3 is connected to a third sun gear 34a of the second planetary gearset 26 so as to be fixed with respect to rotation relative to it. Accordingly, the first ring gear 8a is connected to the third sun gear 34a so as to be fixed with respect to rotation relative to it. The transmission of power from the second planetary gearset 26 to the third planetary gearset 27 is carried out via a coupling shaft 35 connected to a fourth ring gear 36a of the second planetary gearset 26 so as to be fixed with respect to rotation relative to it on the one hand and, on the other hand, is connected to a fourth sun gear 34b of the third planetary gearset 27 so as to be fixed with respect to rotation relative to it. In particular, the coupling shaft 35, the fourth ring gear 36a and the fourth sun gear 34b are connected integral with one another. The coupling shaft 35 with the fourth ring gear 36a and the fourth sun gear 34b can also be formed as a ring gear which has not only an inner toothing but also an outer toothing. A plurality of second planetary gears 37a is arranged spatially between the third sun gear 34a and the fourth ring gear 36a, in the present instance so as to be rotatable on a rotatably mounted third planet carrier 38a. Further, a plurality of third planetary gears 37b which are arranged in the present case so as to be rotatable on a fourth planet carrier 38b fixed with respect to the housing are arranged on the same radially extending plane and radially outside of the second planetary gearset 26 spatially between the fourth sun gear 34b and a fifth ring gear 36b of the third planetary gearset 27. The first output on the first driven shaft 18a is carried out via the third planet carrier 38a of the second planetary gearset 26, which third planet carrier 38a is connected to the first driven shaft 18a so as to be fixed with respect to rotation relative to it. The second output on the second driven shaft 18b is carried out via the fifth ring gear 36b of the third planetary gearset 27, which fifth ring gear 36b is connected to the second driven shaft 18b so as to be fixed with respect to rotation relative to it.

[0058] According to a fourth embodiment example of the powertrain 2 shown in FIG. 7, the gear unit 3 is arranged axially between the electric machine 11 and the differential 16, the differential 16 being arranged on the output axis 17 arranged paraxial to the input axis 33 in the present case. Accordingly, the input shaft 29 and the output shaft 12 of the gear unit 3 are arranged on the input axis 33. In the present case, the gear unit 3 is formed substantially identical to the embodiment example according to FIG. 2a with respect to its functioning. The direct drive of the stepped planetary gearset 4 is realized by shifting the second gear shifting element 6 into the closed state with the attendant rotationally fixed connection between the first ring gear 8a and the first planet carrier 9. The output shaft 12 is drivingly connected via a transmission stage 24 which, in the present case, is formed to be single-stage and comprises a third toothed wheel 39a connected to the output shaft 12 so as to be fixed with respect to rotation relative to it and a fourth toothed wheel 39b connected to a differential carrier 16a of the differential 16 so as to be fixed with respect to rotation relative to it. In particular, the fourth toothed wheel 39b can be formed directly as toothing at the differential carrier 16a. In the present case, the toothed wheels 39a, 39b are formed as spur gears so that the transmission stage 24 is consequently a spur gear stage. The transmission stage 24 influences the overall gear ratio of the powertrain 2 by a suitably configured toothed wheel diameter and number of teeth. In this respect, an additional planetary gear assembly 14 corresponding to the embodiment examples according to FIG. 4 and FIG. 5 can be dispensed with. However, depending on the requirements of the powertrain, it may be useful to provide a further gear unit for increasing a total gear ratio. As a result of the paraxial arrangement of the powertrain components, axial installation space is economized in the powertrain 2, that is, in particular in that the electric machine 11 together with the gear unit 3 are arranged radially adjacent the differential 16. In this way, the electric machine 11 can also be made more slender, which in turn has a positive effect on the axial spacing between the input axis 33 and output axis 33. In the present case, the differential 16 is formed as a bevel gear differential and, further, is identical to the differential 16 according to FIG. 4. Reference is made to the relevant statements.

[0059] In the present case, the two gear shifting elements 5, 6 of the gear unit 3 are formed as disk-type shifting elements and realize in each instance a frictionally engaging connection between the input shaft 29 of the gear unit 3 and the first sun gear 7 or first planet carrier 9 in the closed state. In this regard, it is advantageous that both traction shifts and coasting shifts can be power-shifted between gear steps E1 and E2, or vice versa. The load during shifting processes between the gear steps E1, E2 can be supported by the first gear shifting element 5 until the second gear shifting element 6 is completely open or closed, or vice versa, thereby preventing a load decrease at the output particularly during shifting processes. In other words, the gear shifting elements 5, 6 are power shifting elements in the present case. Consequently, the powertrain 2 according to FIG. 7 comprises the gear unit from FIG. 2 with the difference that the two gear shifting elements 5, 6 are formed as disk-type shifting elements. Therefore, reference is made to the statements relating to the gear unit 3 from FIG. 2. As regards the shifting between the first gear step E1 and second gear step E2, reference is made to the description relating to FIG. 3. Alternatively, the two gear shifting elements 5, 6 can be formed as in the embodiment form according to FIG. 4, FIG. 5 or FIG. 6.

[0060] FIG. 8 shows a fifth embodiment example of the powertrain 2 in which the gear unit 3 is arranged axially between the electric machine 11 and the differential 16. Analogous to FIG. 7, the differential 16 formed as a bevel gear differential is arranged on the output axis 17 paraxial to the input axis 33 on which the input shaft 29 and the output shaft 12 of the gear unit 3 lie. The output shaft 12 of the gear unit 3 is operatively connected to the differential 16 via two transmission stages 24, 40. The first transmission stage 24 comprises a third toothed wheel 39a which is connected to the output shaft 12 so as to be fixed with respect to rotation relative to it and a fourth toothed wheel 39b which is connected to an intermediate shaft 32 arranged paraxial to the input axis 33 and output axis 17 so as to be fixed with respect to rotation relative to the intermediate shaft 32. Axially adjacent the fourth toothed wheel 39b, a fifth toothed wheel 39c of the second transmission stage 40 is arranged on the intermediate shaft 32 so as to be fixed with respect to rotation relative to it, this intermediate shaft 32 being in meshing engagement with a sixth toothed wheel 39d which is operatively connected to the differential 16. The two transmission stages 24, 40 influence the overall gear ratio of the powertrain 2 by correspondingly configuring the toothed wheel diameters and number of teeth of the toothed wheels 39a-39d. The toothed wheels 39a-39d are formed in the present instance as spur gears, and the transmission stages 24, 40 are consequently spur gear stages. Axial installation space is saved in the powertrain 2 through paraxial arrangement of the powertrain components, particularly in that the electric machine 11 together with the gear unit 3 are arranged radially adjacent the differential 16. Accordingly, the electric machine 11 can also be made more slender, which in turn has a positive effect on the axial spacing between the input axis and output axis.

[0061] The two gear shifting elements 5, 6 of the gear unit 3 are arranged directly adjacent one another coaxial to the input axis 33 and together form a double shifting element 41 which combines the two gear shifting elements 5, 6. In the present case, the two gear shifting elements 5, 6 are formed as jaw-type shifting elements as in the embodiment example according to FIG. 5 to which reference is made. For shifting between the first gear step E1 and second gear step E2, reference is made to the description relating to FIG. 3. Further, reference is made to the statements relating to FIG. 7 and the reference numerals used therein, particularly to FIG. 2 and FIG. 5. Alternatively, the two gear shifting elements 5, 6 can be formed as in the respective embodiment form according to FIG. 4, FIG. 6 or FIG. 7. As a further alternative, the gear unit 3 can be arranged inside of the rotor 19 as in the embodiment forms according to FIG. 5 and FIG. 6.

[0062] Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.