Transmission Assembly for a Motor Vehicle Powertrain, and Method for Operating a Transmission Assembly

Abstract

A transmission assembly for a motor vehicle drive train may include a first input element, a second input element, a first sub-transmission associated with the first input element and including a first plurality of engageable gear-step gear sets, and a second sub-transmission associated with the second input element and including a second plurality of engageable gear-step gear sets. The transmission assembly may further include a first electric machine connected to the second input element and a second electric machine. Moreover, the transmission assembly may include a first clutch, the first input element being connectable to the second input element via the first clutch. Additionally, the transmission assembly may include a second clutch, the second electric machine being connectable to the first input element via the second clutch.

Claims

1-15. (canceled)

16. A transmission assembly (17) for a motor vehicle drive train (10), comprising: a first input element (32); a second input element (34); a first sub-transmission (26) associated with the first input element (32) and including a first plurality of engageable gear-step gear sets (40, 42); a second sub-transmission (28) associated with the second input element (34) and including a second plurality of engageable gear-step gear sets (44, 46); a first electric machine (22) connected to the second input element (34); a second electric machine (24); a first clutch (K1), the first input element (32) being connectable to the second input element (34) via the first clutch (K1); and a second clutch (K2), the second electric machine (24) being connectable to the first input element (22) via the second clutch (K2).

17. The transmission assembly of claim 16, further comprising: an internal combustion engine (12); an intermediate element (36) connectable to the first input element (32) via the second clutch (K2) and connected to the second electric machine (24); and a separating clutch (K0), the intermediate element (36) being connectable to the internal combustion engine (12) via the separating clutch (K0).

18. The transmission assembly of claim 16, further comprising a third clutch (E), the first sub-transmission (26) being connectable to the second sub-transmission (28) via the third clutch (E) to establish at least one winding-path gear step (V5, E1.1, E2.5).

19. The transmission assembly of claim 18, wherein the third clutch (E) is at an output shaft (30), the output shaft (30) being associated with the first sub-transmission (26) and the second sub-transmission (28).

20. The transmission assembly of claim 18, wherein the third clutch (E) is axially between the first sub-transmission (26) and the second sub-transmission (28).

21. The transmission assembly of claim 18, wherein one or both of: the first clutch (K1) is axially between the first sub-transmission (26) and the second sub-transmission (28); and the first clutch (K1) and the third clutch (E) are arranged in a plane.

22. The transmission assembly of claim 16, further comprising one or both of: a first gear set (54) connecting the first electric machine (22) to the second input element (34); and a second gear set (58) connecting the second electric machine (24) to an intermediate shaft (36).

23. The transmission assembly of claim 22, wherein the intermediate shaft (36) is coaxial to one or both of the first input element (32) and the second input element (34).

24. The transmission assembly of claim 16, further comprising a separating clutch (K0), the intermediate element (36) being connectable to the internal combustion engine (12) via the separating clutch (K0), wherein one or more of the separating clutch (K0), the second clutch (K2), and the first clutch (K1) is arranged coaxially to one or both of the first input element (32) and the second input element (34).

25. The transmission assembly of claim 16, further comprising an output shaft (30) connected to a differential (18) via an output gear set (66), the output gear set (66) and the second clutch (K2) being coplanar.

26. The transmission assembly of claim 16, wherein one or both of the first plurality of engageable gear-step gear sets (40, 42) and the second plurality of engageable gear-step gear sets (44, 46) comprises precisely two gear-step gear sets associated with regular forward gear steps.

27. The transmission assembly of claim 16, wherein ratios of the gear-step gear sets of one or both of the first plurality of engageable gear-step gear sets (40, 42) and the second plurality of engageable gear-step gear sets (44, 46) are matched such that one or both of: a first forward winding-path gear step (E1.1) has a lower ratio than all gear-step gear sets (40, 42, 44, 46) of the first and second pluralities of engageable gear-step gear sets associated with regular forward gear steps, and a second forward winding-path gear step (V5) has a higher ratio than all gear-step gear sets (40, 42, 44, 46) of the first and second pluralities of engageable gear-step gear sets.

28. The transmission assembly of claim 16, further comprising: a separating clutch (K0), the intermediate element (36) being connectable to the internal combustion engine (12) via the separating clutch (K0); a third clutch (E), the first sub-transmission (26) being connectable to the second sub-transmission (28) via the third clutch (E); and at least one gearshift clutch (A, B, C, D) for selectively engaging a gear-step gear set of the first and second pluralities of engageable gear-step gear sets (40, 42, 44, 46), wherein one or more of the separating clutch (K0), the second clutch (K2), the first clutch (K1), the third clutch (KK; E), and the at least one gearshift clutch (A, B, C, D) is a non-synchronized clutch or a dog clutch.

29. A transmission assembly (16) for a motor vehicle drive train (10), comprising: a first input element (32); a second input element (34); a first sub-transmission (26) associated with the first input element (32) and including a first plurality of engageable gear-step gear sets (40, 42); a second sub-transmission (28) associated with the second input element (34) and including a second plurality of engageable gear-step gear sets (44, 46); a first clutch (K1) selectively connecting the first input element (32) to the second input element (34); a first electric machine (22) connected to the second input element (34); a second electric machine (24) connectable to the first input element (32) via a second clutch (K2) or connected to the first input element (32); and a third clutch (E), the first sub-transmission being connectable to the second sub-transmission via the third clutch (E) to establish at least one winding-path gear step (V1, V6).

30. A method for operating the transmission assembly of claim 16, comprising: disengaging the second clutch (K2) during an electric operation by the first electric machine (22) in at least one gear step.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Exemplary embodiments of the invention are represented in the drawing and are explained in greater detail in the following description, wherein

[0078] FIG. 1 shows a schematic view of an embodiment of a hybrid drive train for a motor vehicle;

[0079] FIG. 2 shows a transmission diagram of a further embodiment of a hybrid drive train for a motor vehicle;

[0080] FIG. 3 shows a gearshift table of shift elements of the hybrid drive train from FIG. 2 in a purely internal combustion engine-driven operation;

[0081] FIG. 4 shows a gearshift table of shift elements of the hybrid drive train from FIG. 2 in a purely electric motor-driven operation by the first electric machine; and

[0082] FIG. 5 shows a gearshift table of shift elements of the hybrid drive train from FIG. 2 in a purely electric motor-driven operation by the second electric machine.

DETAILED DESCRIPTION

[0083] Reference will now be made to embodiments of the invention, one or more examples of which are shown in the drawings. Each embodiment is provided by way of explanation of the invention, and not as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be combined with another embodiment to yield still another embodiment. It is intended that the present invention include these and other modifications and variations to the embodiments described herein.

[0084] In FIG. 1, an embodiment of a hybrid drive train 10 for a motor vehicle is schematically represented.

[0085] The drive train 10 includes an internal combustion engine 12. Moreover, the drive train 10 includes a clutch assembly 14 with a series of clutches, including a separating clutch K0, a shaft coupling clutch K1, and a machine coupling clutch K2. The drive train 10 also includes a transmission 16, which, together with the clutch assembly 14, is part of a transmission assembly 17. An output of the transmission 16 is connected to a differential 18 (or another power distribution unit), by which input power is distributable to left and right driven wheels 20L, 20R of the motor vehicle.

[0086] Moreover, the transmission assembly 17 includes a first electric machine 22 and a second electric machine 24.

[0087] The transmission 16 includes a first sub-transmission 26, which is preferably associated with the odd forward gear steps, and a second sub-transmission 28, which is preferably associated with the even forward gear steps.

[0088] A shared output element of the two sub-transmissions 26, 28 is formed by an output shaft 30.

[0089] The sub-transmission 26 includes a first input shaft 32 as a first input element. The second sub-transmission 28 includes a second input shaft 34 as a second input element.

[0090] The first electric machine 22 is rotationally fixed to the second input shaft 34. The second electric machine 24 is connected to an intermediate element, which is preferably an intermediate shaft 36.

[0091] The intermediate shaft 36 is connectable to the internal combustion engine 12 via the separating clutch K0 of the clutch assembly 14. Moreover, the intermediate shaft 36 is connectable to the first input shaft 32 via the machine coupling K2 of the clutch assembly 14. The first input shaft 32 and the second input shaft 34 are connectable to each other via the shaft coupling K1. Moreover, the first sub-transmission 26 and the second sub-transmission 28 are connectable to each other via a bridge clutch E.

[0092] The connection by the above-described clutches is such that the elements connected to each other by a particular engaged clutch are also decoupled from each other when the particular clutch is disengaged. When the clutch is engaged, the particular elements are connected to each other in a rotationally fixed manner such that they rotate at proportional rotational speeds.

[0093] The clutches K0, K1, K2 are part of the clutch assembly 14 and are engageable individually and independently of one another by respective actuators. The bridge clutch E is part of the transmission 16 and is also engageable by a separate actuator.

[0094] By the hybrid drive train 10, essentially the following traveling modes are established: a purely internal combustion engine-driven operation, a purely electric motor-driven operation, or a hybrid operation (boost mode or recuperation mode). In the purely internal combustion engine-driven operation, input power of the internal combustion engine 12 is transmitted to the output shaft 30 via the separating clutch K0 and the machine coupling K2 and either the first input shaft 32 and the first sub-transmission 26, or the shaft coupling K1, the second input shaft 34 and the second sub-transmission 28.

[0095] In one preferred variant, a forward gear step is established in the internal combustion engine-driven mode by a so-called “winding-path gear step,” wherein power is initially supplied via the first input shaft 32 to the first sub-transmission 26, from the first sub-transmission 26 to the second sub-transmission 28 via the engaged bridge clutch E and, from the second sub-transmission 28 to the output shaft 30. The shaft coupling K1 is disengaged in this forward winding-path gear step.

[0096] In the hybrid operation, input power of the first electric machine 22 and/or the second electric machine 24 is provided in a so-called “boost” mode, where the particular electric machine 22, 24 is operated as a motor, or power is delivered to the particular electric machine 22, 24 via recuperation, where the particular electric machine 22, 24 is operated as a generator.

[0097] Moreover, a purely electric motor-driven operation is establishable by the first electric machine 22. In this case, essentially the gear steps of the second sub-transmission are utilized, and so input power from the first electric machine 22 is transmitted via the second input shaft 34 and the second sub-transmission 38 to the output shaft 30.

[0098] When the machine coupling K2 is disengaged, it is also possible, however, to guide input power of the first electric machine 22 via the engaged shaft coupling K1 and the first input shaft 32 to the first sub-transmission 26 and then to the output shaft 30.

[0099] Moreover, a winding-path gear step is also establishable in this purely electric motor-driven operation, wherein, when the shaft coupling K1 is disengaged, input power of the first electric machine 22 is guided via the second input shaft 34 to the second sub-transmission 28, from the second sub-transmission 28 via the bridge clutch E to the first sub-transmission 26 and, from the first sub-transmission 26 to the output shaft 30.

[0100] Finally, given a suitable design of the second electric machine 24, a purely electric motor-driven operation is also establishable by the second electric machine 24. Here, all gear steps are engageable, as during the internal combustion engine-driven operation. The separating clutch K0 is disengaged, however, in order not to have to entrain the internal combustion engine 12.

[0101] Input power of the first electric machine 22 and of the second electric machine 24 are used together in certain traveling modes to establish an electric motor-driven operation with maximum power.

[0102] Moreover, a so-called “serial operation” or “range extender operation” is also establishable by the drive train 10.

[0103] During the serial or range extender operation, a purely electric operation is established by the first electric machine 22, as described above, with the machine coupling K2 disengaged. In this case, when the separating clutch K0 is engaged, input power of the internal combustion engine is guided to the second electric machine 24, which is operated as a generator to charge a battery. Preferably, during this serial operation, the first electric machine 22 withdraws electrical power from the same battery into which the second electric machine 24 delivers electrical energy.

[0104] A further embodiment of a hybrid drive train 10′ for a motor vehicle is described below, which generally corresponds to the drive train 10 from FIG. 1 with respect to configuration and mode of operation, except for differences explained in the following. Identical elements are therefore labeled with identical reference characters.

[0105] The representation of the hybrid drive train 10′ from FIG. 2 is a transmission diagram (in contrast to the power flow diagram from FIG. 1). First, the first input shaft 32 and the second input shaft 34 are concentric shafts, wherein the second input shaft 34 is a hollow shaft around the first input shaft 32. The shaft coupling K1 is arranged, in the axial direction, between the first sub-transmission 26 and the second sub-transmission 28 concentrically to the input shafts 32, 34.

[0106] On the axially opposite side of the first sub-transmission 26 (input side) from the shaft coupling K1, the first input shaft 32 is connected via the machine coupling K2 to the intermediate shaft 36, which is a hollow shaft around the first input shaft 32. Moreover, the intermediate shaft 36 is arranged coaxially to an input element of the separating clutch K0, which is connected on the input side to the internal combustion engine 12. Preferably, the input shaft (crankshaft) of the internal combustion engine 12, the separating clutch K0, the intermediate shaft 36, and the machine coupling K2 are arranged concentrically to the first input shaft 32.

[0107] The bridge clutch E is arranged, in the axial direction, between the first sub-transmission 26 and the second sub-transmission 28 and, in fact, concentrically to the output shaft 30. The bridge clutch E is axially aligned with the shaft coupling K1. In other words, the clutches E and K1 are situated in a radial plane. The first sub-transmission 26 has a first gear set 40 for a first, regular forward gear step 1 and a second gear set 42 for a third, regular forward gear step 3. The first and second gear sets 40, 42 each include a fixed gear, which is connected to the first input shaft 32, and an idler gear, which is rotatably mounted at the output shaft 30.

[0108] In a corresponding way, the second sub-transmission 28 has a third gear set 44 for a second, regular forward gear step 2 and a fourth gear set 46 for a fourth, regular forward gear step 4.

[0109] The third and fourth gear sets 44, 46 each also have a fixed gear, which is rotationally fixed to the second input shaft 34 in this case, and an idler gear, which is rotatably mounted at the output shaft 30.

[0110] The first sub-transmission 26 includes a first gearshift clutch assembly 48 with a first gearshift clutch A and a second gearshift clutch C, which are alternately engageable by an actuator of the first gearshift clutch assembly 48. The first gearshift clutch A is utilized for engaging the first gear set 40 and, consequently, for engaging the first, regular forward gear step 1. The second gearshift clutch C is utilized for engaging the second gear set 42 and, consequently, for engaging the third, regular forward gear step 3.

[0111] In a corresponding way, the second sub-transmission 28 includes a second gearshift clutch assembly 50 with a third gearshift clutch B and a fourth gearshift clutch D, which are alternately engageable by a further actuator. The gearshift clutch E is utilized for engaging the third gear set 44 and, consequently, for engaging the second, regular forward gear step 2. The fourth gearshift clutch D is utilized for engaging the fourth gear set 46 and, consequently, for engaging the fourth, regular forward gear step 4.

[0112] The first gearshift clutch assembly 48 and the second gearshift clutch assembly 50 are preferably arranged coaxially to the output shaft 30. The first gearshift clutch assembly 48 is arranged, in the axial direction, between the first and second gear sets 40, 42. The second gearshift clutch assembly 50 is arranged axially between the third and fourth gear sets 44, 46.

[0113] The first electric machine 22 is arranged axially parallel to the shafts of the sub-transmissions 26, 28 and is rotationally fixed to the second input shaft 34 via a first machine gear set 54. The first machine gear set 54 includes a first machine pinion 56, which is rotationally fixed to a rotor of the first electric machine 22 and is in engagement, directly or via an intermediate gearwheel, with the fixed gear of the fourth gear set 46 for the fourth, regular forward gear step 4. Consequently, the first machine gear set 54 is formed by the machine pinion 56, an intermediate gear, if necessary, and the fixed gear of the fourth gear set 46. Alternatively, the first machine pinion 56 is also connected at the third gear set 44 in the same manner.

[0114] The fourth gear set 46 for the fourth forward gear step 4 is arranged at an axial end of the transmission 16, more precisely at the end positioned axially opposite the internal combustion engine 12. The first electric machine 22 extends in the axial direction preferably starting from the first machine gear set 54 in the direction toward the input side of the transmission 16. The first electric machine 22, consequently, is arranged in axial overlap with the sub-transmissions 26, 28.

[0115] The second electric machine 24 is rotationally fixed to the intermediate shaft 36 via a second machine gear set 58. The second machine gear set 58 includes a second machine pinion 60, which is rotationally fixed to a rotor of the second electric machine 24. The second machine pinion 60 is in engagement with a fixed gear 62 of the second machine gear set 58 directly or via an intermediate gearwheel. The fixed gear 62 is rotationally fixed to the intermediate shaft 36.

[0116] The second electric machine 24 extends in the axial direction starting from the second machine gear set 58 in the direction toward the end of the transmission 16, at which the fourth gear set 46 for the fourth forward gear step 4 is arranged, i.e., preferably toward the end of the transmission 16 positioned axially opposite the internal combustion engine 12. The second electric machine 24 is preferably arranged in axial overlap at least with the first sub-transmission 26 and, if necessary, also with the second sub-transmission 28.

[0117] The electric machines 22, 24 preferably overlap in the axial direction.

[0118] The bridge clutch E connects the sub-transmissions 26, 28, by connecting the idler gears of the second and third gear sets 42, 44 to one another.

[0119] On the side of the first sub-transmission 26 facing the internal combustion engine 12, the output shaft 30 is connected to an output pinion 64, which is part of an output gear set 66. Via the output gear set 66, the differential 18 is driven, by which input power is distributable to the driven wheels 20L, 20R.

[0120] The drive train 10′ is preferably for front-mounted transverse installation in a motor vehicle. The drive train 10′ is axially compact and provides a high variability with regard to internal combustion engine-driven and electric motor-driven traveling modes. This is explained with reference to FIGS. 3, 4, and 5.

[0121] FIGS. 3, 4, and 5 are gearshift tables, which represent the condition of shift elements of the drive train 10′ from FIG. 2 in various conditions and/or gear steps. The affected shift elements are the separating clutch K0, the shaft coupling K1, the machine coupling K2, the gearshift clutches A, B, C, and D, and the bridge clutch E.

[0122] FIG. 3 shows the condition of these shift elements in five different gear steps V1-V5 in the internal combustion engine-driven mode, including a first forward gear step V1, a second forward gear step V2, a third forward gear step V3, a fourth forward gear step V4, and a fifth forward gear step V5.

[0123] For the first four forward gear steps V1, V2, V3, V4, a respective one of the gearshift clutches A, B, C, D is engaged, and the bridge clutch E is not engaged. In all of these first four forward gear steps V1, V2, V3, V4, the separating clutch K0 and the machine coupling K2 are also engaged in order to transmit internal combustion engine-generated input power from the internal combustion engine 12 to the first input shaft 32.

[0124] In the second and fourth forward gear steps V2, V4 of the second sub-transmission 28, the shaft coupling K1 is also engaged in order to transmit internal combustion engine-generated input power to the second input shaft 34.

[0125] The fifth forward gear step V5 is established as a winding-path gear step. Here, the separating clutch K0 and the machine coupling K2 are engaged, and input power is transmitted to the first input shaft 32. Moreover, the fourth gearshift clutch D for the fourth, forward gear step 4 is engaged, as well as the bridge clutch E. The shaft coupling K1 is disengaged. Here, input power (i) flows from the internal combustion engine 12 via the clutches K0, K2 to the first input shaft 32, (ii) from the first input shaft 32 via the second gear set 42 and the bridge clutch E to the third gear set 44, and (iii) from the third gear set 44 via the second input shaft 34 to the fourth gear set 46, and then via the engaged fourth gearshift clutch D to the output shaft 30, so the input power is transmitted from the gear set 46 to the output shaft 30, and finally (iv) from the output shaft 30 to the differential 18.

[0126] The fifth forward gear step V5 has a higher (i.e., longer) ratio than the fourth, regular forward gear step V4.

[0127] In the internal-combustion-engine gear steps V1-V5, input power is added or withdrawn via the electric machines 22, 24 depending on the driving mode, wherein the electric machines 22, 24 therefore operate either as a motor or as a generator.

[0128] In FIG. 4, a gearshift table of the shift elements is shown for three electric-motor gear steps, including a first electric-motor gear step E1.1, a second electric-motor gear step E1.2, and a third electric-motor gear step E1.3 for an electric motor-driven operation by the first electric machine 22.

[0129] In the second electric-motor gear step E1.2, only the third gearshift clutch B is engaged, so input power is transmitted from the first electric machine 22 via the machine gear set 54 to the second input shaft 34 and, from the second input shaft 34 via the third gear set 44 and the engaged third gearshift clutch B to the output shaft 30. The fourth gearshift clutch D is engaged in the third electric-motor gear step E1.3, so input power is transmitted from the first electric machine 22 via the machine gear set 54 and the fourth gear set 46 for the fourth regular forward gear step 4 and the engaged fourth gearshift clutch D to the output shaft 30.

[0130] The first electric-motor gear step E1.1 is a winding-path gear step. Here, the first gearshift clutch A and the bridge clutch E are engaged.

[0131] In the first electric-motor gear step E1.1, power flows from the first electric machine 22 and the first machine gear set 54 to the second input shaft 34 and, from there, via the third gear set 44 and the bridge clutch E to the second gear set 42. From the second gear set 42, the input power flows via the first input shaft 32 to the gear set 40, which is connected to the output shaft 30 by engagement of the first gearshift clutch A, and so the input power is then transmitted to the output shaft 30.

[0132] The machine coupling K2 is disengaged in all three of these electric-motor gear steps E1.1, E1.2, E1.3. In this condition, the internal combustion engine 12 is disengageable. In this case, the position of the separating clutch K0 is essentially irrelevant. Alternatively, the separating clutch K0 is engaged and the internal combustion engine 12 is started, for example, by the second electric machine 24, in order to subsequently drive the second electric machine 24 in the internal combustion engine-driven operation, so that the second electric machine 24, operating as a generator, generates electrical power for charging a battery. This so-called serial operation therefore makes it possible to supply the battery by the second electric machine 24, while a purely electric motor-driven operation is simultaneously established by the first electric machine 22.

[0133] In FIG. 5, a gearshift table is shown for a purely electric motor-driven operation by utilizing the second electric machine 24, which operates as a motor in this case.

[0134] The gearshift table from FIG. 5 is identical to the gearshift table from FIG. 3, as is readily apparent, with the exception that the separating clutch K0 is disengaged in all these gear steps, including a first forward gear step E2.1 (corresponding to the first forward gear step V1), a second forward gear step E2.2 (corresponding to the second forward gear step V2), a third forward gear step E2.3 (corresponding to the third forward gear step V3), a fourth forward gear step E2.4 (corresponding to the fourth forward gear step V4), and a fifth forward gear step E2.5 (corresponding to the fifth forward gear step V5), and is not engaged as in the internal combustion engine-driven operation. In the gear steps E2.1-E2.5, additional input power is able to be provided by the first electric machine.

[0135] The clutches K0, K1, K2, and E and the gearshift clutches A, B, C, D are each preferably non-synchronized clutches or dog clutches. A synchronization takes place by the first electric machine 22 and/or the second electric machine 24, depending on the mode of operation.

[0136] During gear changes in the internal combustion engine-driven mode, a support of tractive force is also provided, in order to prevent an interruption of tractive force. The drive torque necessary therefor is provided by the first electric machine 22 or by the second electric machine 24, according to demand.

[0137] During a gear change from the first forward gear step V1 to the second forward gear step V2, the following procedure is generally carried out. Initially, the third gearshift clutch B in the still inactive, second sub-transmission 28 is preliminarily engaged, if necessary, by synchronization by the first electric machine 22.

[0138] Thereafter, the shaft coupling K1 is synchronized and engaged, which, in the ideal case, takes place in overlap with the disengagement of the gearshift clutch A, while the input power of the internal combustion engine 12 is reduced. The necessary torque is then already provided via the first electric machine 22. Thereafter, the power of the internal combustion engine 12 is increased again and guided via the shaft coupling K1 to the engaged gear set 44 for the second forward gear step 2. In a corresponding way, the power of the first electric machine 22 is decreased.

[0139] Starting from the above-described serial operation, in which an operation is carried out in the electric forward gear step E1.1 by utilizing the bridge clutch E, a transition into the gear step V1 is possible when the clutch K2 is initially engaged. Thereafter, the internal combustion engine 12, together with the second electric machine 24, supports the tractive force and the bridge clutch E is disengageable, wherein the first electric machine 22 is load-free. The first electric machine 22 then synchronizes the shift element B, so the gearshift clutch B is engageable. As a result, the gear E1.2 is effectively engaged for the first electric machine. As a result, the first electric machine supports the tractive force and switches the internal combustion engine, together with the second electric machine 24, into a no-load condition, for example, into the forward gear step V2 (by disengaging the gearshift clutch A and engaging the shaft coupling K1). The machine coupling K2 always remains engaged.

[0140] Modifications and variations can be made to the embodiments illustrated or described herein without departing from the scope and spirit of the invention as set forth in the appended claims. In the claims, reference characters corresponding to elements recited in the detailed description and the drawings may be recited. Such reference characters are enclosed within parentheses and are provided as an aid for reference to example embodiments described in the detailed description and the drawings. Such reference characters are provided for convenience only and have no effect on the scope of the claims. In particular, such reference characters are not intended to limit the claims to the particular example embodiments described in the detailed description and the drawings.

REFERENCE CHARACTERS

[0141] 10 drive train [0142] 12 internal combustion engine [0143] 14 clutch assembly [0144] 16 transmission [0145] 17 transmission assembly [0146] 18 differential [0147] 20L, 20R driven wheels [0148] 22 first electric machine [0149] 24 second electric machine [0150] 26 first sub-transmission [0151] 28 second sub-transmission [0152] 30 output shaft [0153] 32 first input element (first input shaft) [0154] 34 second input element (second input shaft) [0155] 36 intermediate element (intermediate shaft) [0156] 40 first gear-step gear set for V1 [0157] 42 second gear-step gear set for V3 [0158] 44 third gear-step gear set for V2 [0159] 46 fourth gear-step gear set for V4 [0160] 48 first gearshift clutch assembly [0161] 50 second gearshift clutch assembly [0162] 54 first gear set (first machine gear set) [0163] 56 first machine pinion [0164] 58 second gear set (second machine gear set) [0165] 60 second machine pinion [0166] 62 fixed gear of 58 [0167] 64 output pinion [0168] 66 output gear set [0169] A first gearshift clutch of 48 [0170] C second gearshift clutch of 48 [0171] B third gearshift clutch of 50 [0172] D fourth gearshift clutch of 50 [0173] K0 separating clutch [0174] K1 first clutch (shaft coupling) [0175] K2 second clutch (machine coupling) [0176] E third clutch (bridge clutch)