DRIVE DEVICE FOR A MOTOR VEHICLE DRIVE TRAIN OF AN ELECTRIC VEHICLE

Abstract

A drive device (7) for a motor vehicle drive train of an electric vehicle has a plurality of electric machines (12, 13, 14) and a transmission, where different transmission ratios between an input shaft and an output side can be selected. In this case, a first electric machine (13) is connected to the input shaft of the transmission or can be connected thereto, and the output side of the transmission is coupled to at least one output drive (9, 10), which is used in the motor vehicle drive train to connect a respective drive axle of the electric vehicle. In order to achieve the highest possible driving comfort by means of this drive device (7), a second electric machine (14) is also permanently connected to the output side.

Claims

1. A drive device (7; 56; 58) for a motor vehicle drive train (2) of an electric vehicle (1), the drive device comprising a plurality of electric machines (12, 13, 14; 13, 14) and a transmission (26) having an input shaft (27) and an output side (41), wherein a plurality of transmission ratios between the input shaft (27) and the output side (41) can be selected, wherein the plurality of electric machines includes a first electric machine (13) connected or configured to be connected to the input shaft (27) of the transmission (26), wherein the output side (41) of the transmission (26) is coupled to at least one output drive (9, 10) of the motor vehicle drive train (2), the at least one output drive connecting the vehicle drive train to a respective drive axle (3, 4) of the electric vehicle (1), and wherein the plurality of electric machines includes a second electric machine (14) permanently connected to the output side (41).

2. The drive device (7; 56; 58) as claimed in claim 1, further comprising a countershaft (29) permanently coupled to the output side (41), the countershaft being axially offset with respect to the input shaft (27), wherein the input shaft (27) and the countershaft (29) can each be coupled to one another via a first spur gear stage (33) and a second spur gear stage (34) each having a fixed gear (35, 36) and a free gear (31, 32) meshing with the fixed gear, wherein in the first spur gear stage (33) and the second spur gear stage (34) the respective fixed gear (35, 36) is arranged for conjoint rotation on the input shaft or the countershaft (29), while the respective free gear (31, 32) of the respective first spur gear stage (33 or the second spur gear stage (34) is mounted rotatably on the countershaft or the input shaft (27) and can be fixed there via a respective associated shift element (37, 38).

3. The drive device (7; 56; 58) as claimed in claim 2, wherein, at least in one of the first spur gear stage (33) or the second spur gear stage (34), the respective fixed gear (35, 36) is located for conjoint rotation on the countershaft (29) and the respective free gear (31, 32) is mounted rotatably on the input shaft (27), wherein the respective fixed gear (36) also forms the output side (41) of the transmission (26) in that the respective fixed gear (36) couples the input shaft to the countershaft of the at least one output drive (9, 10).

4. The drive device (7; 56; 58) as claimed in claim 2 further comprising a first shift element (37) and a second shift element (38), the first shift element and the second shift element in combination form a shifting device (39) having an actuating element (40) configured in a first position to actuate the first shift element (37) and configured in a second position to actuate the second shift element (38).

5. The drive device (7; 56; 58) as claimed in claim 2, wherein the second electric machine (14) is connected to the countershaft (29) for conjoint rotation therewith.

6. The drive device (7; 56; 58) as claimed in claim 1, wherein the second electric machine (14) is a most powerful electric machine of the plurality of electric machines (12, 13, 14; 13, 14).

7. The drive device (7) as claimed in claim 1, further comprising an intermediate clutch (30), wherein, in addition to the first electric machine (13) and the second electric machine (14), the plurality of electric machines includes at least one further electric machine (12), each at least one further electric machine connected to the input shaft or configured to be connected to the input shaft (27) via the intermediate clutch (30).

8. The drive device (7; 56; 58) as claimed in claim 1, wherein the transmission (26) is followed on the output side (41) by a distributor device (42), a drive side of the distributor device being coupled to the output side (41) and to which a plurality of output drives (9, 10) is assigned, each of the plurality of output drives (9, 10) connecting the drive train to a respective drive axle (2, 3) of the electric vehicle (1).

9. The drive device (7; 56; 58) as claimed in claim 8, wherein the distributor device (42) comprises a differential (44), in particular a planetary differential, wherein a drive power introduced at the drive side of the distributor device (42) can be distributed via the differential (44) to output shafts (24, 25), which are each connected to one of the output drives (9, 10).

10. A motor vehicle drive train (2) for an electric vehicle (1), comprising a drive device (7; 56; 58) as claimed in claim 1.

11. The motor vehicle drive train (2) as claimed in claim 10, wherein the transmission (26) is followed on the output side (41) by a distributor device (42), a drive side of the distributor device being coupled to the output side (41) and to which a plurality of output drives (9, 10) is assigned, each of the plurality of output drives (9, 10) connecting the drive train to a respective drive axle (2, 3) of the electric vehicle (1); wherein at least one drivable front axle (5) is operatively connected to one output drive (9) of the plurality of output drives of the drive device (7; 56; 58) and at least one drivable rear axle (6) is operatively connected to another output drive (10) of the plurality of output drives of the drive device (7; 56; 58).

12. An electric vehicle (1), comprising a motor vehicle drive train as claimed in claim 10.

13. A method for operating a drive device (7; 56; 58) as claimed in claim 1, wherein changes between the plurality of transmission ratios of the transmission (26) are carried out in that, in the course of a respective change, a loss of drive torque of at least the first electric machine (13) is compensated for at least in part by increasing a drive torque of the second electric machine (14).

14. The method as claimed in claim 13, further comprising synchronizing rotational speeds at least via the first electric machine (13) in the course of the respective change.

15. The motor vehicle drive train of claim 10, wherein the electric vehicle is configured as an off-road utility vehicle.

16. The electric vehicle of claim 12, wherein the electric vehicle is configured as an off-road utility vehicle.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

[0033] Advantageous embodiments of the invention, which will be explained below, are illustrated in the drawings. In the drawings:

[0034] FIG. 1 shows a schematic illustration of an electric vehicle according to a preferred embodiment of the invention;

[0035] FIG. 2 shows a schematic illustration of a drive device of the electric vehicle from FIG. 1, corresponding to a first possible configuration of the invention;

[0036] FIG. 3 shows a schematic individual view of a part of the drive device from FIG. 2;

[0037] FIG. 4 shows diagrams with various parameter curves in the course of a change of a transmission ratio in a transmission of the drive device from FIGS. 2 and 3; and

[0038] FIGS. 5 and 6 show schematic views of drive devices according to further embodiments of the invention.

DETAILED DESCRIPTION

[0039] FIG. 1 shows a schematic view of an electric vehicle 1, which is, in particular, an off-road utility vehicle and, in this case, is preferably a truck. In this case, the electric vehicle 1 has a motor vehicle drive train 2, which is equipped with two drive axles 3 and 4. In this arrangement, drive axle 3 is a steerable front axle 5 and drive axle 4 is a nonsteerable rear axle 6. In this respect, the electric vehicle 1 is equipped with permanent all-wheel drive.

[0040] Within the motor vehicle drive train 2, the two drive axles 3 and 4 can be driven by means of a drive device 7, which is placed between the drive axles 3 and 4 in the longitudinal direction of the electric vehicle 1. Specifically, an axle differential 8 of drive axle 3 is here connected to an output drive 9 of the drive device 7, wherein the drive device 7 is furthermore connected at an output drive 10 to an axle differential 11 of drive axle 4.

[0041] FIG. 2 shows a schematic individual view of the drive device 7, which is designed according to a first embodiment of the invention. This drive device 7 comprises three electric machines 12, 13 and 14, each of which consists of a rotor and a stator (although this is not illustrated here). In addition, it is possible for each of the electric machines 12 to 14 to be operated, on the one hand, as a generator and, on the other hand, as an electric motor. Moreover, the drive device 7 is equipped with a transmission unit 15, which is illustrated only schematically in FIG. 2. The transmission unit 15 is equipped with a plurality of connection points 16, 17 and 18, to which in each case one of the electric machines 12 to 14 is connected for conjoint rotation therewith. In this case, connection points 16 and 17 are coaxial with respect to one another, while connection point 18 is placed axially offset with respect to the two connection points 16 and 17.

[0042] In the present case, electric machine 12 is connected to connection point 16 for conjoint rotation therewith in that a rotor shaft 19 produces a rotational connection between the rotor of electric machine 12 and a connection point 20, at which the rotor shaft 19 and thus also the rotor of electric machine 12 are connected to a cardan shaft 21 for conjoint rotation therewith. Via the cardan shaft 21, the rotor shaft 19 is indirectly connected to connection point 16 of the transmission unit 15, for which purpose the cardan shaft 21 is fastened to connection point 16 at the end opposite to the rotor shaft 19. In this case, electric machine 12 is placed coaxially with connection point 16 of the transmission unit 15, but it could also be offset with respect to connection point 16 by means of the cardan shaft 21.

[0043] As can furthermore be seen in FIG. 2, electric machine 13 is connected to connection point 17 for conjoint rotation therewith by means of a rotor shaft 22, wherein here the rotor shaft 22 is connected to the rotor of electric machine 13 for conjoint rotation therewith within electric machine 13. In this case, electric machine 13 with the rotor shaft 22 is arranged coaxially with connection point 17.

[0044] In the case of electric machine 14, a rotor shaft 23 is connected to the rotor of electric machine 14 for conjoint rotation therewith, wherein the rotor shaft 23 is furthermore fastened to connection point 18 of the transmission unit 15 for conjoint rotation therewith by means of one shaft end. In the present case, electric machine 14 and thus also the rotor shaft 23 are arranged coaxially with connection point 18 of the transmission unit 15.

[0045] The transmission unit 15 is equipped with two output shafts 24 and 25, which are coaxial with one another and are axially offset with respect to the connection points 16 to 18. In this case, at mutually remote shaft ends, these output shafts 24 and 25 form the two output drives 9 and 10, at which the connection to the respectively associated drive axle 3 and 4 is in each case established within the motor vehicle drive train 2 of the electric vehicle 1, which can be seen in FIG. 1.

[0046] In FIG. 3, the transmission unit 15 is furthermore illustrated individually in a schematic way. As can be seen here, the transmission unit 15 comprises a transmission 26, in which, in addition to an input shaft 27, a connecting shaft 28 and a countershaft 29 are also provided. In this case, the connecting shaft 28 forms connection point 16 at one shaft end and can be connected to the input shaft 27, which is located coaxially with respect to it, for conjoint rotation therewith via an intermediate clutch 30. In this case, the clutch 30 is designed as a positive-locking clutch in the form of an unsynchronized claw clutch.

[0047] At an end located axially remote from the connecting shaft 28, the input shaft 27 forms connection point 17, wherein, in addition, two free gears 31 and 32, each of which is part of a spur gear stage 33 and 34, respectively, are rotatably supported on the input shaft 27. In this case, free gear 31 in spur gear stage 33 is permanently in mesh with a fixed gear 35, which is arranged for conjoint rotation on the countershaft 29. In this arrangement, the countershaft 29 is placed axially offset with respect to the input shaft 27 and also the connecting shaft 28 and forms connection point 18 at one shaft end. In addition to fixed gear 35, a fixed gear 36 of spur gear stage 34 is also arranged for conjoint rotation on the countershaft 29, wherein fixed gear 36 is in constant mesh with free gear 32 within spur gear stage 34.

[0048] In the transmission 26, two different transmission ratios can now be selected, in that, starting from the input shaft 27, a power flow is directed to the countershaft 29 either via spur gear stage 33 or via spur gear stage 34. For this purpose, the transmission 26 is equipped with two shift elements 37 and 38, of which shift element 37, when actuated, fixes free gear 31 to the input shaft 27 and accordingly effects guidance of the force flow from the input shaft 27 to the countershaft 29 via spur gear stage 33. On the other hand, shift element 38, when actuated, fixes free gear 32 to the input shaft 27 and accordingly ensures coupling of the input shaft 27 and the countershaft 29 via spur gear stage 34.

[0049] In the present case, the shift elements 37 and 38 are designed as positive-locking shift elements, wherein they are in the form of unsynchronized claw shift elements. In this case, the two shift elements 37 and 38 are combined to form a shifting device 39, to which an actuating element 40 is assigned, it being possible, by means of the actuating element 40, for shift element 37, on the one hand, and shift element 38, on the other hand, to be transferred from a neutral position to a respectively actuated state. In contrast, in the neutral position of the actuating element 40, which is preferably a sliding sleeve, neither of the shift elements 37 and 38 is actuated, as a result of which neither of the free gears 31 and 32 is fixed and, accordingly, the input shaft 27 is decoupled from the countershaft 29.

[0050] The fixed gear 36 of spur clear stage 34 also forms an output side 41 of the transmission 26, in that a connection to a distributor device 42 is established permanently at the fixed gear 36. In this case, this distributor device 42 is connected downstream of the transmission 26 within the transmission unit 15 and has a spur gear 43 which is in permanent mesh with fixed gear 36. The distributor device 42 furthermore has a differential 44, which is designed as a planetary differential in the present case and consists of a sun gear 45, a planet carrier 46 and a ring gear 47. In this case, a plurality of planet gears 48 is mounted rotatably in the planet carrier 46, and, more specifically, each is in mesh with both the sun gear 45 and the ring gear 47.

[0051] While, in the present case, the planet carrier 46 is connected to the spur gear 43 for conjoint rotation therewith, the sun gear 45 is connected to the output shaft 25 for conjoint rotation therewith, and the ring gear 47 is connected to the output shaft 24 for conjoint rotation therewith. In this case, a drive power introduced via the output side 41 of the transmission 26 is distributed to the two output shafts 24 and 25 via the differential 44, it being possible here for different rotational speeds of the output shafts 24 and 25 to be permitted by means of the differential 44. In this case, however, this effect of the differential 44 can be selectively blocked by way of a locking device 49, which is designed as a clutch and, when actuated, connects the spur gear 43 to the output shaft 25 for conjoint rotation therewith, resulting in locking up of the planetary differential.

[0052] Owing to the connection of electric machine 14 to connection point 18 of the transmission unit 15 for conjoint rotation therewith and the permanent coupling of the countershaft 29 to the output drives 9 and 10 via the distributor device 42, electric machine 14 is also permanently coupled to the output drives 9 and 10. Accordingly, electric machine 14 can be used continuously for driving the electric vehicle 1 in its electric motor mode or else for braking the electric vehicle in its generator mode. In this case, electric machine 14 of the electric machines 12 to 14 is embodied as the most powerful machine.

[0053] In contrast, the electric machine 13 connected to connection point 17 is coupled to the output drives 9 and 10 only when one of the shift elements 37 and 38 is actuated and, accordingly, one of the two transmission ratios of the transmission 26 is selected. The same is also the case with respect to electric machine 12, in which case clutch 30 has to be actuated in addition. Via the transmission ratios of the transmission 26, driving movements of one or both electric machines 12 and 13 can in this case be transmitted to the countershaft 29 in their respective electric motor mode, or else their respective braking action can be modified in their respective generator mode. As regards the transmission 26, one transmission ratio is here designed as a road gear, while the other transmission ratio is designed as an off-road gear.

[0054] FIG. 4 illustrates, by way of example, flow diagrams of various parameters in the course of a change between the transmission ratios of the transmission 26, this being shown for carrying out a downshift in the transmission 26 and for a state of the drive device 7 in which electric machine 12 is decoupled by means of clutch 30. In the uppermost diagram, drive torques M are here plotted against time t, a line 50 here representing a drive torque of electric machine 13, a line 51 representing a drive torque of electric machine 14, and a line 52 representing a sum of the drive torques of electric machines 13 and 14.

[0055] In contrast, it is rotational speeds n which are plotted against time tin the central diagram, line 53 of lines 53 and 54 here representing the rotational speed curve of electric machine 13 in the course of the change, while line 54 reproduces the rotational speed curve of electric machine 14. Finally, in the lowermost diagram, a shift position of the actuating element 40 is plotted against time t and is reproduced by means of line 55.

[0056] As can be seen from the diagrams in FIG. 4, at the beginning of the change, the actuating element 40 is in one of its shift positions, in which one transmission ratio is selected in the transmission 26, Δt a first time t.sub.1, there is then a request to change the transmission ratio in the transmission 26, whereupon the drive torque in electric machine 13 is reduced and the rotational speed is increased to a target rotational speed in order to be able to set synchronous rotational speeds with respect to the respective shift element 37 or 38 that is being actuated and is subsequently to be opened and to be able to design this without problems. At the same time, a drive torque of electric machine 14 is increased in order to keep the reduction of the sum of the drive torques as small as possible and thus to make the effect of the gear change as little noticeable as possible.

[0057] At a time t.sub.2, synchronous rotational speeds have then been established at the shift element 37 or 38 to be opened, whereupon the actuating element 40 is moved in the direction of its neutral position. In this case, drive torques of the two electric machines 13 and 14 are kept constant from this point in time. From a point in time t.sub.3, the actuating element 40 is then moved into its neutral position and, accordingly, the input shaft 27 and thus also the electric machine 13 coupled thereto are decoupled from the countershaft 29. As soon as the neutral position is reached, a rotational speed of electric machine 13 is increased in order to set synchronous rotational speeds at the shift element 38 or 37 which is subsequently to be actuated.

[0058] In this case, these synchronous rotational speeds are reached at a time t.sub.4, whereupon the actuating element 40 is now moved out of the neutral position in the direction of the shift position in which the shift element 38 or 37 is actuated. Here, this process is completed at a point in time t.sub.5, with the result that the transmission ratio in the transmission 26 is now selected. From time t.sub.5, the drive torque of drive machine 13 is now also increased again, as a result of which the sum of the drive torques is correspondingly increased as well. In this case, a driving motion of electric machine 13 is now transmitted with the selected transmission ratio via the transmission 26.

[0059] Furthermore, FIG. 5 shows a schematic view of a drive device 56 which is designed according to a second possible embodiment of the invention and can likewise be used in the electric vehicle 1 from FIG. 1, In this case, this possible configuration corresponds substantially to the variant according to FIGS. 2 to 4, with the difference that now only electric machines 13 and 14 are provided. Because of this reduced number of electric machines, a transmission unit 57 of a drive device 56 is also equipped only with connection points 17 and 18. Furthermore, it is preferable if no clutch is provided within the transmission unit 57 either. In other respects, the possible configuration according to FIG. 5 corresponds to the variant according to FIGS. 2 to 4, and therefore attention is drawn to what is described in relation thereto.

[0060] Finally, FIG. 6 shows a schematic illustration of a drive device 58, which is embodied according to a third embodiment of the invention and can be used in the electric vehicle 1 from FIG. 1. Here, this embodiment corresponds substantially to the preceding variant according to FIG. 5, although, in contrast to this, electric machine 13 and electric machine 14 are now not connected directly to the respective connection point 17 or 18 but are fastened via interposed cardan shafts 59 and 60. As a result, electric machines 13 and 14 can also be placed with an offset with respect to the respective connection point 17 or 18. In other respects, the possible configuration according to FIG. 6 corresponds to the variant according to FIG. 5, and therefore attention is drawn to what is described in relation thereto.

[0061] It is possible to achieve a high level of driving comfort in an electric vehicle by means of the embodiments of a drive device according to the invention.

REFERENCE SIGNS

[0062] 1 electric vehicle [0063] 2 motor vehicle drive train [0064] 3 drive axle [0065] 4 drive axle [0066] 5 front axle [0067] 6 rear axle [0068] 7 drive device [0069] 8 axle differential [0070] 9 output drive [0071] 10 output drive [0072] 11 axle differential [0073] 12 electric machine [0074] 13 electric machine [0075] 14 electric machine [0076] 15 transmission unit [0077] 16 connection point [0078] 17 connection point [0079] 18 connection point [0080] 19 rotor shaft [0081] 20 connection point [0082] 21 cardan shaft [0083] 22 rotor shaft [0084] 23 rotor shaft [0085] 24 output shaft [0086] 25 output shaft [0087] 26 transmission [0088] 27 input shaft [0089] 28 connecting shaft [0090] 29 countershaft [0091] 30 clutch [0092] 31 free gear [0093] 32 free gear [0094] 33 spur gear stage [0095] 34 spur gear stage [0096] 35 fixed gear [0097] 36 fixed gear [0098] 37 shift element [0099] 38 shift element [0100] 39 shifting device [0101] 40 actuating element [0102] 41 output side [0103] 42 distributor device [0104] 43 spur gear [0105] 44 differential [0106] 45 sun gear [0107] 46 planet carrier [0108] 47 ring gear [0109] 48 planet gears [0110] 49 locking device [0111] 50 line [0112] 51 line [0113] 52 line [0114] 53 line [0115] 54 line [0116] 55 line [0117] 56 drive device [0118] 57 transmission unit [0119] 58 drive device [0120] 59 cardan shaft [0121] 60 cardan shaft [0122] drive torque [0123] n speed [0124] t time [0125] t.sub.1 to t.sub.5 times