DRIVE UNIT FOR A MOTOR VEHICLE DRIVETRAIN OF AN ELECTRIC VEHICLE

Description

[0001] The invention relates to a drive device for a motor vehicle drive train of an electric vehicle, in particular in the form of an off-road commercial vehicle, comprising a plurality of electric machines and a transmission in which different gear ratios can be switched between an input shaft and an output side, wherein a first electric machine is connected or connectable to the input shaft of the transmission, wherein the output side of the transmission is coupled to at least one output, which in the motor vehicle drive train serves to connect a respective drive axle of the electric vehicle, wherein a second electric machine is permanently connected to the output side, wherein in addition to the first electric machine and the second electric machine, at least one further electric machine is provided, which can each be connected to the input shaft via an intermediate clutch,and wherein a countershaft is provided in the transmission, axially offset from the input shaft. Furthermore, the invention relates to a motor vehicle drive train, an electric vehicle, and a method for operating a drive device according to the invention.

[0002] Electric vehicles are known to have drive systems that often consist of at least one electric motor and one or more downstream transmissions. In some cases, different gears can be engaged to translate the drive movement of the at least one electric motor with different transmission ratios.

[0003] DE 10 2016 006 208 A1 discloses a drive device for a motor vehicle drivetrain, which is designed for an electric vehicle in the form of a commercial vehicle. In one variant, this drive device comprises two electric motors, followed by a transmission. Different gear ratios can be selected in the transmission to couple one or both electric motors to an output side of the transmission. The output side is coupled to at least one output, to which a drive axle of the electric vehicle is connected within the motor vehicle drivetrain.

[0004] Furthermore, AT 522 931 A1 discloses a drive device comprising two electric motors and a transmission. Different gear ratios can be switched between an input shaft and an output side of the transmission. One electric motor is connected to the input shaft of the transmission, while the output side of the transmission is coupled to at least one output, which serves to connect a respective drive axle of an electric vehicle in the motor vehicle drive train. Furthermore, the other electric motor is permanently connected to the output side. Further drive devices are also disclosed in CN 2 06 781 515 U and EP 3 098 483 A1.

[0005] Furthermore, CN 206 329 684 U discloses a drive device, wherein a variant of CN 206 329 684 U provides several electric motors in addition to a transmission. Two of the electric motors can each be connected to an input shaft of the transmission, while two electric motors are permanently connected to an output side of the transmission. The transmission is designed as a spur gear and, in addition to the input shaft, also has a countershaft located axially offset therefrom.

[0006] Based on the prior art described above, it is now the object of the present invention to realize a drive device for an electric vehicle, wherein a high level of driving comfort can be realized via this drive device.

[0007] This object is achieved based on the preamble of claim 1 in conjunction with its characterizing features. The dependent claims that follow therefrom each represent advantageous developments of the invention. A motor vehicle drive train in which a drive device according to the invention is provided is further the subject of claims 7 and 8. Furthermore, claim 9 relates to an electric vehicle with the aforementioned motor vehicle drive train, while claims 10 and 11 relate to a method for operating a drive device according to the invention.

[0008] According to the invention, a drive device comprises a plurality of electric motors and a transmission in which different gear ratios can be switched between an input shaft and an output side. A first electric motor is connected to the input shaft of the transmission or can be connected to this input shaft, while the output side of the transmission is coupled to at least one output, which in the motor vehicle drive train serves to connect each drive axle of the electric vehicle.

[0009] In the drive device according to the invention, in addition to several electric motors, a transmission is provided which has an input shaft. This input shaft can be coupled to an output side of the transmission by switching one of several different gear ratios. Thus, different power flow paths with differing gear ratios can be implemented between the input shaft and the output side of the transmission, preferably by selectively actuating switching elements.

[0010] Within the drive device according to the invention, the output side of the transmission is coupled to at least one output, wherein this at least one output is provided in the installed state of the drive device in a motor vehicle drive train for connection to a respective drive axle of the electric vehicle.

[0011] Of the electric machines, a first electric machine is either permanently connected to the input shaft of the transmission or can be connected to the input shaft of the transmission. In the former case, a constant speed ratio permanently prevails between the electric machine and the input shaft of the transmission, such that the input shaft and a rotor of the first electric machine cannot rotate independently of one another. In the latter case, however, the first electric machine can also be decoupled from the input shaft of the transmission and is specifically connected to the input shaft, wherein, according to the invention, this is preferably achieved via an intermediate switching clutch. This switching clutch is designed in particular as a positive-locking clutch, wherein the positive-locking clutch is particularly preferably designed as an unsynchronized dog clutch or as a locking synchronizer.Alternatively, an intermediate clutch can also be designed as a force-locking clutch, for example as a friction clutch or multi-disk clutch.

[0012] Within the scope of the invention, the first electric machine can be directly connected in a rotationally fixed manner to a connection point of the input shaft or can be connected to this connection point by arranging the first electric machine directly in the region of the connection point of the input shaft. Alternatively, however, an offset arrangement of the first electric machine relative to a connection point of the input shaft is also possible, in which case a cardan shaft is preferably provided in between for the rotationally fixed connection or the rotationally fixed connectability of the first electric machine to the input shaft of the transmission.

[0013] The multiple electric machines of the drive device according to the invention preferably each consist of a stator and a rotor. In this case, the individual electric machines can be operated, in particular, as generators, with the individual electric machine generating electricity in its generator mode. The individual electric machine can also be operated as electric motors, with a drive movement of the respective rotor being generated by the power supply during the electromotive operation of the individual electric machine.

[0014] The invention now comprises the technical teaching that a second electric machine is permanently connected to the output side. In other words, in addition to the first electric machine, which is connected to the input shaft or can be connected to it, a second electric machine is provided which is permanently coupled to the output side of the transmission and thus also to the at least one output. In addition to the first electric machine and the second electric machine, at least one further electric machine is provided, each of which can be connected to the input shaft via an intermediate clutch. Furthermore, the transmission is provided with a countershaft which is axially offset from the input shaft and is permanently coupled to the output side.The input shaft and the countershaft can be coupled to each other via a first spur gear stage and a second spur gear stage, each of which consists of a fixed gear and a meshing idler gear. In the spur gear stages, the respective fixed gear is mounted on the input or countershaft in a rotationally fixed manner, while the respective idler gear of the respective spur gear stage is rotatably mounted on the countershaft or input shaft and can be locked there via an associated shift element. Furthermore, the second electric motor is connected to the countershaft in a rotationally fixed manner.

[0015] Such a design of a drive device has the advantage that, due to the permanent connection of the second electric machine to the output side of the transmission and thus also to the at least one output in the installed state of the drive device according to the invention, a permanent connection to the drive wheels of the at least one drive axle of the electric vehicle is also established. As a result, the second electric machine can easily drive the electric vehicle without any interruption in tractive force. In addition, the first electric machine can also be integrated by switching one of the transmission ratios, whereby a drive movement of the first electric machine can be translated via the transmission in a suitable manner depending on requirements.Overall, this allows a wide driving range of the electric vehicle to be covered by the electric motors and by the transmission translating the drive movement of the first electric motor. The total available drive power can be further increased by the at least one additional electric motor, whereby the at least one electric motor can also be engaged via the intermediate clutch, if necessary, only in special situations where a particularly high drive power is required.

[0016] The first electric machine and the second electric machine can be used together to drive the electric vehicle by operating both electric machines as electric motors. Depending on the driving range to be achieved, a corresponding gear ratio is selected in the transmission in order to appropriately translate the drive movement generated by the first electric machine. If a change from one gear ratio of the transmission to another is then expedient or necessary, the tractive force can still be maintained via the second electric machine during the change and the associated, at least brief, separation of the first electric machine from the at least one output. Thus, a high level of driving comfort can be achieved when the drive device according to the invention is used in a motor vehicle drive train.

[0017] The at least one further electric machine can be connected to a connection point of the input shaft via the intermediate clutch, although alternatively intermediate components, such as a cardan shaft, can also be provided.

[0018] In its respective generator mode, the individual electric motor can also be used for braking through recuperation, whereby a suitable gear ratio can also be selected in the transmission with respect to the first electric motor in order to generate a high drive speed from the first electric motor. The second electric motor, on the other hand, can directly brake by operating as a generator due to its permanent coupling to at least one output.

[0019] The transmission is designed as a 2-stage transmission, in which two spur gear stages are provided between the input shaft and a countershaft permanently coupled to the output side, via which a power flow can be guided from the input shaft to the countershaft and thus to the output side by actuating a respective switching element. Particularly preferred is the one spur gear stage, which can be represented by a

[0020] The gear ratio is designed as a road gear, while the gear ratio shown when the other spur gear stage is integrated into the power flow forms an off-road gear for the electric vehicle. Within the scope of the invention, however, the transmission could also have more than two switchable spur gear stages.

[0021] Each spur gear stage features a fixed gear and an idler gear, each of which is constantly meshing with each other. Of these two spur gears, each preferably equipped with helical gearing, one is located on the input shaft and one on the countershaft. The fixed gear of the respective spur gear stage is mounted on the respective shaft in a rotationally fixed manner, while the idler gear is rotatably mounted on the respective shaft and can be locked there by actuating the corresponding shift element.

[0022] The rotationally fixed connection of the second electric machine to the countershaft allows for a permanent coupling of the second electric machine to the output side of the transmission and thus to the at least one output in a reliable manner. The second electric machine can be directly connected to the countershaft in a rotationally fixed manner by attaching a rotor of the second electric machine—possibly via a rotor shaft—directly to a connection point on the countershaft. Alternatively, the invention also provides for the rotationally fixed connection between the second electric machine and the countershaft to be realized via intermediate components, such as a cardan shaft.

[0023] In contrast, in DE 10 2016 006 208 A1, the electric machines can only be used to drive or brake the electric vehicle by switching one of the gear ratios in the transmission, since none of the electric machines is permanently coupled to at least one output of the electric vehicle.

[0024] In a further development, at least in one of the two spur gear stages, the respective fixed gear is mounted on the countershaft in a rotationally fixed manner and the respective idler gear is rotatably mounted on the input shaft, wherein the respective fixed gear of this spur gear stage also forms the output side of the transmission in that the coupling to the at least one output is established at this fixed gear. In this way, the fixed gear of this spur gear stage can advantageously be used to establish the output-side coupling of the transmission. For this purpose, the toothing of this fixed gear preferably not only engages with the idler gear of the spur gear stage but also with a further toothing, at which, in the installed state of the drive device according to the invention, a further power flow can then be guided to the at least one output and thus also to the respective drive axle.In particular, in the gearbox, the fixed gears of both spur gear stages are arranged in a rotationally fixed manner on the countershaft and the loose gears of both spur gear stages are rotatably mounted on the input shaft.

[0025] Alternatively or in addition to the aforementioned variant, a first switching element and a second switching element are combined to form a switching device, via whose actuating element the first switching element and the second switching element can be actuated. As a result, the two switching elements can be actuated via a common actuating element, which reduces manufacturing costs and also enables a compact design. Particularly preferably, this actuating element can be positioned in a neutral position in addition to a first switching position in which the first switching element is actuated and a second switching position in which the second switching element is actuated, in which neither the first switching element nor the second switching element is closed. This advantageously makes it possible toto decouple an additional electric motor provided here from the output side of the transmission and thus also from at least one output. This can prevent the first electric motor and any additional electric motor provided from being dragged along in certain driving conditions.

[0026] Within the scope of the invention, the shifting elements of the transmission are preferably designed as positive-locking shifting elements, with the shifting elements being present in particular as unsynchronized claw shifting elements or as locking synchronizers. Alternatively, however, one or more shifting elements can also be designed as non-positive shifting elements, and in this case, in particular as multi-disk shifting elements.

[0027] According to an advantageous embodiment of the invention, the second electric machine is the most powerful of the electric machines. This has the advantage that, during operation of the drive device according to the invention in a motor vehicle drive train, the drive of the electric vehicle can be maintained even when a change between gear ratios is currently being performed in the transmission and the first electric machine is accordingly disconnected from the at least one output. The drive power that can be provided by the second electric machine should be selected such that the electric vehicle can be driven alone to a sufficient extent, at least briefly.

[0028] According to one possible embodiment of the invention, a distribution device is connected downstream of the transmission on the output side. The drive side of the distribution device is coupled to the output side and is assigned to several outputs, each of which serves to connect a drive axle of the electric vehicle in the motor vehicle drive train. This allows the drive device to be used in an electric vehicle with all-wheel drive or selectable all-wheel drive, as the downstream distribution device can be used to distribute the power to several outputs and thus, in the installed state, to several drive axles.

[0029] In a further development of the aforementioned design option, the distribution device comprises a differential gear, which is particularly designed as a planetary differential. Via the differential gear, a drive power introduced at the input side of the distribution device can be distributed to output shafts, each of which is connected to one of the outputs. Particularly preferably, the differential gear is also assigned a locking device, the actuation of which results in a rigid distribution among the outputs. As an alternative to a planetary differential, the differential gear can also be designed as a bevel gear differential.In addition, within the scope of the invention, an embodiment of the distribution device is also considered in principle in which only one of the outputs is permanently coupled to the output side of the transmission, while one or more further outputs can only be coupled to the drive side of the distribution device by actuating an associated clutch.

[0030] The invention also relates to a motor vehicle drive train for an electric vehicle, wherein a drive device according to one or more of the aforementioned variants is provided in this motor vehicle drive train. When the drive device is designed with a distribution device, at least one drivable front axle is preferably connected to one output and at least one drivable rear axle is connected to another output. Overall, this makes it possible to realize a motor vehicle drive train in which, due to the permanent coupling of the second electric machine to the output or outputs, operation without interruption in traction and thus also a high level of comfort can be achieved.

[0031] The invention also relates to an electric vehicle equipped with the aforementioned motor vehicle drive train. This electric vehicle can, in particular, be an off-road commercial vehicle, such as a truck.

[0032] The invention also relates to a method for operating a drive device according to the invention. In this case, changes between gear ratios of the transmission are carried out by compensating, at least as far as possible, for a loss of drive torque of at least the first electric machine during the respective change by increasing the drive torque of the second electric machine. Therefore, if changes between gear ratios are carried out in the transmission, which, due to an interruption in the tractive force, results in a temporary decoupling of the first electric machine and possibly also at least one further electric machine, an attempt is made to compensate for a loss of drive torque of the first electric machine and possibly of the at least one further electric machine via the second electric machine by increasing its drive torque.

[0033] In a further development of the aforementioned method, during the respective change, rotational speeds are synchronized at least via the first electric motor. This is achieved within the scope of the invention, in particular, when shifting elements used to change between the gear ratios are designed as positive-locking and, in particular, as unsynchronized shifting elements. Synchronization via the first electric motor and, if applicable, the at least one additional electric motor can achieve rapid shifting between the gear ratios.

[0034] The invention is not limited to the specified combination of features of the main claim or the dependent claims. Furthermore, possibilities arise for combining individual features with one another, even if they emerge from the claims, the following description of preferred embodiments of the invention, or directly from the drawings. The reference of the claims to the drawings by the use of reference symbols is not intended to limit the scope of protection of the claims.

[0035] Advantageous embodiments of the invention, which are explained below, are illustrated in the drawings. It shows: Fig. 1 is a schematic representation of an electric vehicle according to a preferred embodiment of the invention; Fig. 2 is a schematic representation of a drive device of the electric vehicle from Fig. 1 , according to a first embodiment of the invention; Fig. 3 a schematic detailed view of a part of the drive device from Fig. 2 ; and Fig. 4 diagrams with different parameter curves in the course of a change of a transmission ratio in a gearbox of the drive device from the Fig. 2 and 3 .

[0036] Fig. 1 shows a schematic view of an electric vehicle 1, which is in particular an off-road commercial vehicle, preferably a truck. The electric vehicle 1 has a motor vehicle drive train 2 equipped with two drive axles 3 and 4. The drive axle 3 is a steerable front axle 5, and the drive axle 4 is a non-steerable rear axle 6. In this respect, the electric vehicle 1 is equipped with permanent all-wheel drive.

[0037] Within the motor vehicle drive train 2, the two drive axles 3 and 4 can be driven via a drive device 7, which is positioned in the longitudinal direction of the electric vehicle 1 between the drive axles 3 and 4. Specifically, an axle differential 8 of the drive axle 3 is connected to an output 9 of the drive device 7, with the drive device 7 also being connected to an output 10 with an axle differential 11 of the drive axle 4.

[0038] Out of Fig. 2 1 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 - not further shown here - consists of a rotor and a stator. In addition, the electric machines 12 to 14 can each be operated as a generator or as an electric motor. In addition, the drive device 7 is equipped with a gear unit 15, which in Fig. 2 is shown only schematically. The gear unit 15 is equipped with several connection points 16, 17, and 18, to each of which one of the electric motors 12 to 14 is connected in a rotationally fixed manner. Connection points 16 and 17 are located coaxially to one another, while connection point 18 is positioned axially offset from the two connection points 16 and 17.

[0039] In the present case, the electric machine 12 is connected in a rotationally fixed manner to the connection point 16 in that a rotor shaft 19 establishes a rotationally fixed connection between the rotor of the electric machine 12 and a connection point 20, at which the rotor shaft 19 and thus also the rotor of the electric machine 12 are rotationally fixedly connected to a cardan shaft 21. The rotor shaft 19 is indirectly connected to the connection point 16 of the transmission unit 15 via the cardan shaft 21, for which purpose the cardan shaft 21 is fastened to the connection point 16 with an end opposite the rotor shaft 19. The electric machine 12 is positioned coaxially to the connection point 16 of the transmission unit 15, although it could also be offset from the connection point 16 via the cardan shaft 21.

[0040] As further stated in Fig. 2 As can be seen, the electric machine 13 is connected to the connection point 17 in a rotationally fixed manner by a rotor shaft 22, wherein the rotor shaft 22 is connected to the rotor of the electric machine 13 within the electric machine 13 in a rotationally fixed manner. The electric machine 13 is arranged with the rotor shaft 22 coaxially to the connection point 17.

[0041] In the electric machine 14, a rotor shaft 23 is non-rotatably connected to the rotor of the electric machine 14, with the rotor shaft 23 also being non-rotatably attached to the connection point 18 of the transmission unit 15 by one shaft end. In this case, the electric machine 14 and thus also the rotor shaft 23 are arranged coaxially with the connection point 18 of the transmission unit 15.

[0042] The gear unit 15 is equipped with two output shafts 24 and 25, which are coaxial to each other and axially offset from the connection points 16 to 18. These output shafts 24 and 25 form the two outputs 9 and 10 at opposite ends of the shaft, at which Fig. 1 visible motor vehicle drive train 2 of the electric vehicle 1, the connection to the respective associated drive axle 3 or 4 is established.

[0043] In Fig. 3 The transmission unit 15 is also shown schematically in detail. As can be seen here, the transmission unit 15 comprises a transmission 26, which, in addition to an input shaft 27, also has a connecting shaft 28 and a countershaft 29. The connecting shaft 28 forms the connection point 16 at one shaft end and can be connected in a rotationally fixed manner to the input shaft 27, which is located coaxially thereto, via an intermediate clutch 30. The clutch 30 is designed as a positive-locking clutch in the form of an unsynchronized claw clutch.

[0044] At an end axially remote from the connecting shaft 28, the input shaft 27 forms the connection point 17, with two idler gears 31 and 32 also being rotatably mounted on the input shaft 27, each of which is part of a spur gear stage 33 or 34. The idler gear 31 in the spur gear stage 33 is permanently in tooth engagement with a fixed gear 35, which is arranged in a rotationally fixed manner on the countershaft 29. The countershaft 29 is positioned axially offset from the input shaft 27 and also from the connecting shaft 28 and forms the connection point 18 at one shaft end. In addition to the fixed gear 35, a fixed gear 36 of the spur gear stage 34 is arranged in a rotationally fixed manner on the countershaft 29, with the fixed gear 36 constantly meshing with the idler gear 32 within the spur gear stage 34.

[0045] In the transmission 26, two different gear ratios can now be selected by routing the power flow from the input shaft 27 either via the spur gear stage 33 or via the spur gear stage 34 to the countershaft 29. For this purpose, the transmission 26 is equipped with two shifting elements 37 and 38, of which the shifting element 37, when actuated, fixes the idler gear 31 to the input shaft 27 and accordingly guides the power flow from the input shaft 27 via the spur gear stage 33 to the countershaft 29. In contrast, the shifting element 38, when actuated, fixes the idler gear 32 to the input shaft 27 and accordingly ensures a coupling of the input shaft 27 and the countershaft 29 via the spur gear stage 34.

[0046] In the present case, the shift elements 37 and 38 are designed as positive-locking shift elements, whereby they are present as unsynchronized claw shift elements. The two shift elements 37 and 38 are combined to form a shift device 39, to which an actuating element 40 is assigned. Via the actuating element 40, the shift element 37 and the shift element 38 can be transferred from a neutral position into an actuated state. In the neutral position of the actuating element 40, which is preferably a sliding sleeve, however, neither of the shift elements 37 and 38 is actuated, whereby none of the idler gears 31 and 32 are locked and, accordingly, the input shaft 27 is decoupled from the countershaft 29.

[0047] The fixed gear 36 of the spur gear stage 34 also forms an output side 41 of the transmission 26, in that a permanent connection to a distributor device 42 is established at the fixed gear 36. This distributor device 42 is connected downstream of the transmission 26 within the transmission unit 15 and has a spur gear 43 that is permanently meshed with the fixed gear 36. The distributor device 42 also has a differential gear 44, which in this case is designed as a planetary differential and is composed of a sun gear 45, a planetary carrier 46, and a ring gear 47. Several planetary gears 48 are rotatably mounted in the planetary carrier 46, each of which is individually meshed with both the sun gear 45 and the ring gear 47.

[0048] While the planetary gear 46 is here connected in a rotationally fixed manner to the spur gear 43, the sun gear 45 is connected in a rotationally fixed manner to the output shaft 25, and the ring gear 47 is connected in a rotationally fixed manner to the output shaft 24. The differential gear 44 distributes the drive power introduced via the output side 41 of the gear 26 to the two output shafts 24 and 25, whereby different speeds of the output shafts 24 and 25 can be permitted via the differential gear 44. This effect of the differential gear 44 can, however, be specifically blocked via a locking device 49, which is designed as a clutch and, when actuated, connects the spur gear 43 in a rotationally fixed manner to the output shaft 25, resulting in the planetary differential locking.

[0049] Due to the rotationally fixed connection of the electric motor 14 to the connection point 18 of the transmission unit 15 and the permanent coupling of the countershaft 29 to the outputs 9 and 10 via the distribution device 42, the electric motor 14 is also permanently coupled to the outputs 9 and 10. Accordingly, the electric motor 14 can be continuously used to drive the electric vehicle 1 in its electric motor mode or to brake the electric vehicle in its generator mode. In this case, the electric motor 14 is designed as the most powerful of the electric motors 12 to 14.

[0050] In contrast, the electric motor 13 connected to connection point 17 is only coupled to the outputs 9 and 10 when one of the shift elements 37 and 38 is actuated and, accordingly, one of the two gear ratios of the transmission 26 is engaged. The same applies to the electric motor 12, although in this case the clutch 30 must also be actuated. Via the gear ratios of the transmission 26, drive movements of one or both electric motors 12 and 13 can be transferred to the countershaft 29 in their respective electromotor mode, or their respective braking effect can be changed in their respective generator mode. In the transmission 26, one gear ratio is designed as a road gear, while the other gear ratio is designed as an off-road gear.

[0051] In Fig. 4 Flow diagrams of various parameters during a change between the gear ratios of the transmission 26 are shown by way of example, wherein this is shown for the execution of a downshift in the transmission 26 and for a state of the drive device 7 in which the electric machine 12 is decoupled via the clutch 30. In the uppermost diagram, drive torques M are plotted against time t, wherein a line 50 represents a drive torque of the electric machine 13, a line 51 represents a drive torque of the electric machine 14, and a line 52 represents a sum of the drive torques of the electric machines 13 and 14.

[0052] In contrast, in the middle diagram, speeds n are plotted against time t, with line 53 representing the speed curve of electric motor 13 during the changeover, while line 54 represents the speed curve of electric motor 14. Finally, in the bottom diagram, a switching position of the actuating element 40 is plotted against time t and represented by line 55.

[0053] As can be seen from the diagrams in Fig. 4 As can be seen, at the start of the change, the actuating element 40 is in its one switching position, in which one gear ratio is engaged in the transmission 26. At a first time t 1 , there is then a request to change the gear ratio in the transmission 26, whereupon the drive torque of the electric machine 13 is reduced and the speed is increased to a target speed in order to set synchronous speeds with regard to the respectively actuated switching element 37 or 38 to be opened and to be opened subsequently, and to be able to design this without problems. At the same time, a drive torque of the electric machine 14 is increased in order to keep the reduction in the total of the drive torques as small as possible and thus to make the effect of the gear change as unnoticeable as possible.

[0054] At a time t 2 , synchronous speeds have been established at the switching element 37 or 38 to be opened, whereupon the actuating element 40 is moved toward its neutral position. Drive torques of the two electric motors 13 and 14 are kept constant from this time onward. From a time t 3 , the actuating element 40 is then moved into its neutral position, and accordingly, the input shaft 27, and thus also the electric motor 13 coupled thereto, are decoupled from the countershaft 29. Once the neutral position is reached, the speed of the electric motor 13 is increased in order to set synchronous speeds at the switching element 38 or 37 to be actuated subsequently.

[0055] These synchronous speeds are reached at a time t 4 , whereupon the actuating element 40 is now moved from the neutral position toward the switching position in which the switching element 38 or 37 is actuated. This process is completed at a time t 5 , so that the gear ratio in the transmission 26 is now engaged. From time t 5 , the drive torque of the drive motor 13 is also increased again, whereby the sum of the drive torques also increases accordingly. A drive movement of the electric motor 13 is now transmitted via the transmission 26 with the engaged gear ratio.

[0056] By means of the inventive designs of a drive device, a high level of driving comfort can be achieved in an electric vehicle. Bezuaszeichen

[0057] 1 Electric vehicle 2 Motor vehicle drive train 3 Drive axle 4 Drive axle 5 Front axle 6 Rear axle 7 Drive device 8 Axle differential 9 Output 10 Output 11 Axle differential 12 Electric motor 13 Electric motor 14 Electric motor 15 Gear unit 16 Connection point 17 Connection point 18 Connection point 19 Rotor shaft 20 Connection point 21 Propshaft 22 Rotor shaft 23 Rotor shaft 24 Output shaft 25 Output shaft 26 Gearbox 27 Input shaft 28 Connection shaft 29 Countershaft 30 Clutch 31 Idler gear 32Idler gear 33Spur gear stage 34Spur gear stage 35Fixed gear 36Fixed gear 37Shift element 38Shift element 39Shift device 40Actuator 41Output side 42Distributor device 43Spur gear 44Differential gear 45Sun gear 46Planetary carrier 47Ring gear 48Planet gears 49Locking device 50Line 51Line 52Line 53Line 54Line 55Line MDrive torque nSpeed ​​tTime t 1 to t 5 points in time

Claims

1. Drive device (7) for a motor vehicle drivetrain (2) of an electric vehicle (1), in particular in the form of an off-road commercial vehicle, comprising a plurality of electric machines (12, 13, 14) and a transmission (26) in which different gear ratios between an input shaft (27) and an output side (41) are able to be selected, wherein a first electric machine (13) is connected, or connectable, 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 (9, 10) which in the motor vehicle drivetrain (2) serves in each case to link in each case one drive axle (3, 4) of the electric vehicle (1), wherein a second electric machine (14) is permanently connected to the output side (41), wherein provided apart from the first electric machine (13) and the second electric machine (14) is also at least one further electric machine (12) which is in each case connectable to the input shaft (27) by way of an intervening shifting clutch (30), and wherein provided in the transmission (26) is a layshaft (29) which is axially offset from the input shaft (27), characterized in that the layshaft (29) is permanently coupled to the output side (41), in that the input shaft (27) and the layshaft (29) are in each case able to be coupled to one another by way of a first spur gear stage (33) and a second spur gear stage (34), which each are composed of in each case one fixed gear (35, 36) and in each case one idler gear (31, 32) meshing with the latter, wherein in the spur gear stages (33, 34) the respective fixed gear (35, 36) is co-rotationally disposed on the input shaft or layshaft (29), while the respective idler gear (31, 32) of the respective spur gear stage (33, 34) is rotatably mounted on the layshaft or input shaft (27) and is able to be fixedly established thereon by way of in each case one assigned switching element (37, 38), and in that the second electric machine (14) is co-rotationally connected to the layshaft (29).

2. Drive device (7) according to Claim 1, characterized in that at least one of the two spur gear stages (33, 34) places the respective fixed gear (35, 36) so as to be rotatable on the layshaft (29), and the respective idler gear (31, 32) is rotatably mounted on the input shaft (27), wherein the respective fixed gear (36) of this spur gear stage (34) moreover forms the output side (41) of the transmission (26) in that the coupling to the at least one output (9, 10) is established on this fixed gear (36).

3. Drive device (7) according to Claim 1 or 2, characterized in that a first switching element (37) and a second switching element (38) are combined so as to form a switching device (39), the first switching element (37), on the one hand, and the second switching element (38), on the other hand, being able to be activated by way of the activating element (40) of said switching device (39).

4. Drive device (7) according to one of the preceding claims, characterized in that of the electric machines (12, 13, 14; 13, 14), the second electric machine (14) is the electric machine with the highest output.

5. Drive device (7) according to one of the preceding claims, characterized in that disposed downstream of the transmission (26) on the output side (41) is a transfer device (42), the drive side of the latter being coupled to the output side (41) and being assigned a plurality of outputs (9, 10) which in the motor vehicle drivetrain serve in each case to link in each case one drive axle (2, 3) of the electric vehicle (1).

6. Drive device (7) according to Claim 5, characterized in that the transfer device (42) comprises a differential gearbox (44), in particular a planetary differential, wherein a drive output which by way of the differential gearbox (44) is introduced on the drive side of the transfer device (42) is able to be transferred to output shafts (24, 25) which each are connected in each case to one of the outputs (9, 10).

7. Motor vehicle drivetrain (2) for an electric vehicle (1), in particular in the form of an off-road commercial vehicle, comprising a drive device (7) according to one or a plurality of Claims 1 to 6.

8. Motor vehicle drivetrain (2) according to Claim 7, and having a drive device according to Claim 5 or 6, characterized in that operatively connected to an output (9) of the drive device (7) is at least one drivable front axle (5), and operatively connected to another output (10) of the drive device (7) is at least one drivable rear axle (6).

9. Electric vehicle (1), in particular in the form of an off-road commercial vehicle, comprising a motor vehicle drivetrain according to Claim 7 or 8.

10. Method for operating a drive device (7) according to one or a plurality of Claims 1 to 6, characterized in that changes between gear ratios of the transmission (26) are carried out in that in the course of the respective change a shortfall of in each case one drive torque at least of the first electric machine (13) is at least ideally largely compensated for by increasing a drive torque of the second electric machine (14).

11. Method according to Claim 10, characterized in that in the course of the respective change a synchronization of rotating speeds is performed at least by way of the first electric machine (13).