Electric drive system and method of operation thereof

Abstract

The invention relates to an electric drive system for a motor vehicle (1), comprising an electric drive front axle (2) and an electric drive rear axle (3), the electric drive rear axle (3) having a first electric motor (5) with a first rotor (6) which is designed to drive a first rear wheel (7), the electric drive rear axle (3) having a third electric motor (8) which is designed to drive a second rear wheel (8). The electric drive front axle (2) has a third electric motor (17) having a third rotor (9) which is designed to drive a second rear wheel (10), and the electric drive front axle (2) has a second electric motor (17) having a second rotor (18) which is designed to drive a front wheel (20, 21) via a second axle reduction gear (67). According to the invention, the second rotor (18) is permanently coupled in a torque-transmitting manner to the first front wheel and to the second front wheel (21) by means of a second shaft reduction gear (67), a first switchable freewheel clutch (13) being provided, which is designed to couple in a torque-transmitting manner the first rotor (6) to the first rear wheel (7), and a second switchable freewheel clutch (13) being provided to couple in a torque-transmitting manner the second rotor (18) to the second front wheel (21). Wherein a second switchable freewheel clutch (14) is provided, which is designed to couple the second rotor (9) to the second rear wheel (6) in a torque-transmitting manner.

Description

Technical Field

[0001] The invention relates to an electric drive system for a motor vehicle having an electrically driven front axle and an electrically driven rear axle of the type defined in detail in the preamble of claim 1. Furthermore, a method for operating such an electric drive system is proposed. Background Art

[0002] Electric drive systems for motor vehicles are known from the general prior art. In this case, for example, both the front axle and the rear axle of the motor vehicle can be electrically driven. DE 10 2018 220 809 A1 describes a vehicle of this type, the focus of the specification of which is on the power electronic control of the electric drive system. The vehicle described therein by way of example shows a drive system in which a first electric motor drives a first rear wheel of the vehicle shown, a second electric motor drives a second rear wheel, and a third electric motor drives the front wheel via an axle reduction gear (e.g. a differential). DE 10 2016 218 717 B3 and the similar DE 10 2018 217 863 A1 also show electric drive systems for motor vehicles having two electric drive axles and a total of at least three electric motors.

[0003] DE 10 2019 202 207 A1 shows an electric drive axle of a motor vehicle, in which two electric machines are provided.

[0004] DE10 2011 080 236A1 describes an alternative to this. In this document, a single-wheel drive for a motor vehicle is described, which can also be used for two or more wheels of a motor vehicle. In this case, an electric motor is provided for each drive wheel. The rotor of the electric motor is coupled to the corresponding drive wheel via a planetary gear stage.

[0005] Reference is also made to DE 10 2020 127 790 A1 and DE 10 2019 121 215 A1. These documents each describe a switchable electric machine which can be switched via a planetary gear stage having a freewheel.

[0006] DE 38 01 351 A1 also describes a basic concept for a switchable four-wheel drive in a non-electric motor vehicle. Summary of the invention

[0007] The object of the present invention is to provide an improved electric drive system which can be operated in an energy-saving manner and at the same time improves driving performance, traction, dynamics and / or safety as required.

[0008] According to the invention, this object is achieved by an electric drive system having the features of claim 1, in particular the features in the characterizing part of claim 1. In addition, this object is achieved by a method having the features of claim 10. Advantageous embodiments and improvements of the electric drive system according to the invention are derived from the dependent claims of the above-mentioned claims.

[0009] The electric drive system according to the present invention uses a basic structure, which has been shown in principle in the literature of the same type mentioned in the background art. It mainly consists of an electric drive front axle and an electric drive rear axle and can be preferably used in cars, light commercial vehicles, etc. In principle, other application areas are also conceivable, such as heavy commercial vehicles, such as construction machinery, military vehicles, etc.

[0010] The electrically driven rear axle comprises a first motor with a first rotor, which is designed to drive a first rear wheel and / or a second rear wheel of the electrically driven rear axle. The electrically driven front axle comprises a second motor with a second rotor, which is designed to drive a front wheel of the electrically driven front axle via a second axle reduction gear (such as a differential or a transfer case).

[0011] Furthermore, in a known manner, the second rotor is permanently coupled to the first of the front wheels and to the second of the front wheels in a torque-transmitting manner via the second shaft reducer. Thus, the second motor drives the two front wheels of the electrically driven front axle via the second shaft reducer, without being disconnected therefrom. The electrically driven front axle is therefore the drive axle primarily responsible for the traction of the vehicle. In particular, in the case of low power demand or partial load, traction is provided by the electrically driven front axle or the electrically drivable front axle.

[0012] Furthermore, a first switchable freewheel clutch is provided in a known manner, which is designed to couple the first rotor to the first rear wheel and / or the second rear wheel in a torque-transmitting manner. Thus, unlike in the case of a permanently coupled front wheel, in the case of the two rear wheels of the electrically driven rear axle it is provided that the rear wheels can always be selectively driven when a drive of the rear wheels is desired.

[0013] Furthermore, it is provided in a known manner that the first switchable freewheel clutch has a first actuator, wherein, by means of the first switchable freewheel clutch, in forward traction operation of the first electric motor, a torque-transfer connection between the first rotor and the first rear wheel and / or the second rear wheel can be achieved without the action of the first actuator; and in forward coasting operation or reverse traction operation of the first electric motor, the torque-transfer connection can be achieved through the action of the first actuator.

[0014] Low-load driving, which accounts for the majority of many vehicle applications, now only drives the front axle via the second electric machine. This allows the electric drive system to be operated efficiently. The second electric machine can be designed ideally for low-load operating conditions, thereby achieving high efficiency.

[0015] In high-load driving situations, the rear axle wheels can now be switched on demand using the first electric machine and the first switchable freewheel clutch. The electrically driven rear axle is used here to improve driving performance, increase traction and, at the same time, enhance the driving experience and, ultimately, the dynamics.

[0016] A freewheel clutch is a clutch having a freewheel mechanism known per se with two rotatably mounted clutch halves. The two clutch halves can be coupled in a torque-transmitting manner, for example, when the first of the two clutch halves is driven, by means of the freewheel mechanism, wherein the two clutch halves are decoupled from one another when the first clutch half is not driven. The first clutch half is advantageously permanently coupled to the first electric machine in a torque-transmitting manner.

[0017] The first actuator is understood to be a mechanism which, based on an electrical signal or a plurality of different electrical signals, can achieve a mechanical coupling or decoupling or coupling capability or a coupling or decoupling capability of the clutch halves.

[0018] Forward traction operation of the first motor It refers to an operating mode of the first motor, in which the motor is operated in a driving manner in a rotational direction, thereby enabling the rear wheels to move forward.

[0019] The expression "without the action of an actuator" means that the two clutch halves are switched from the disengaged state to the coupled state without a signal change of the first actuator and without a position change of the first actuator component. Unlike a simple dog clutch operated by an actuator, this torque-transmitting coupling without the action of the first actuator does not require synchronization of the rotational speeds of the two clutch halves by means of a synchronization method. The synchronization required for closing the two clutch halves is achieved by means of the freewheel mechanism of the freewheel clutch with virtually no time loss.

[0020] Forward gliding operation relative to any of the motors This refers to the operation when the respective motor is coupled to the respective wheel in a torque-transmitting manner, and the respective rotor is pushed by the motor vehicle, ie in a direction of rotation for forward operation of the motor vehicle.

[0021] Reverse traction operation with respect to any of the motors refers to an operation in which, when the corresponding motor is coupled to the corresponding wheel in a torque-transmitting manner, the corresponding rotor is driven to operate, ie, in a rotational direction required for reverse operation of the motor vehicle.

[0022] Furthermore, it is provided in a known manner that the electrically driven rear axle comprises a third electric machine with a third rotor, which is designed to drive a second rear wheel and / or a first rear wheel of the electrically driven rear axle. In this case, a second switchable freewheel clutch with a second actuator is provided, which in turn is designed to couple the third rotor to the second rear wheel in a torque-transmitting manner.

[0023] In this way, the electrically driven rear axle can be driven with torque vectoring. The safety of the all-wheel drive can also be increased by this, which is achieved in the area of ​​the electrically driven rear axle by two electric machines and the rear wheels that can be driven independently by the electric machines.

[0024] According to the invention, it is provided that the first electric machine and the second electric machine are designed as axial flux machines, which are arranged in a common housing with a common oil chamber, wherein the housing can be, for example, a housing to which elements of the two planetary transmission stages can be fixed by means of a switchable freewheel clutch. However, it is also possible to use a plurality of separate housings or housing parts. According to the invention, the first planetary transmission stage, the second planetary transmission stage, the first switchable freewheel clutch and the second switchable freewheel clutch are arranged in a common housing and a common oil chamber.

[0025] According to another refinement of the electric drive system according to the present invention, a first planetary gear stage is provided which is arranged between the first rotor and the first rear wheel and / or the second rear wheel with respect to the torque flow from the first rotor.

[0026] Furthermore, the second planetary transmission stage is advantageously arranged between the third rotor and the second rear wheel with respect to the torque flow from the third rotor. The first rotor, the second rotor, the first planetary transmission stage and the second planetary transmission stage are all arranged coaxially with respect to one another. Coaxial in the context of the invention means that their axes of rotation are aligned, for example they are placed one after the other and their main axis of rotation is located on an axis in the axial direction. This allows a correspondingly compact design to be achieved.

[0027] According to a further development of this concept, it can be provided that the first switchable freewheel clutch is designed to couple the first output shaft of the first planetary gear stage to the first rear wheel in a rotationally fixed manner.

[0028] Accordingly, it can be provided that the second shiftable freewheel clutch is designed to couple the second output shaft of the second planetary gear stage to the second rear wheel in a rotationally fixed manner.

[0029] In this context, a rotationally fixed connection within the scope of the present invention is to be understood to mean that the coupled components rotate at the same angular speed after the coupling.

[0030] Therefore, the structure provides for the freewheel clutch to be between the corresponding planetary transmission stage and the corresponding rear wheel, so that it is located between the output shaft of the planetary transmission stage and the rear wheel.

[0031] In an alternative variant of the embodiment with a planetary gear stage, it can also be provided that the first switchable freewheel clutch is designed to connect, for example, an element of the first planetary gear stage, preferably its ring gear, to the housing in a rotationally fixed manner. Similarly, the second switchable freewheel clutch can be designed to connect an element of the second planetary gear stage, in particular the same element here, i.e. preferably also the ring gear, to the housing in a rotationally fixed manner. The freewheel clutch is thus integrated into the planetary gear stage and can make the corresponding element of the planetary gearbox, preferably but not limited to the ring gear, freely rotatable or keep it correspondingly fixed. Due to this design of the freewheel clutch, the rotationally fixed connection achieved by the switchable freewheel clutch is suitable for such a drive situation in which the rear wheels are not driven and are therefore correspondingly free to move, so that the vehicle movement can be achieved using only the drive by the electrically driven front axle.

[0032] Alternatively, another very advantageous embodiment of the electric drive system can provide that a superposition gear mechanism is arranged axially between the first rotor and the third rotor. The superposition transmission mechanism comprises a first drive shaft, a second drive shaft, a first driven shaft and a second driven shaft. The first rotor is connected to the first drive shaft in a rotationally fixed manner, and the third rotor is correspondingly connected to the second drive shaft in a rotationally fixed manner. The first driven shaft is in turn connected to the first input shaft of the first planetary transmission stage in a rotationally fixed manner, and the second driven shaft is connected to the second input shaft of the second planetary transmission stage in a rotationally fixed manner. This allows, for example, superposition of superimposed planetary gear sets to be achieved, so that the two rear wheels can be driven respectively by two electric motors connected to the planetary gear sets, namely the first and third electric motors.

[0033] Furthermore, a very advantageous embodiment can provide that the first planetary transmission stage, the second planetary transmission stage, the first switchable freewheel clutch and the second switchable freewheel clutch are all arranged in a common housing and a common oil chamber. This allows a very compact design, in which the advantages of the common oil chamber can now be shared by the planetary transmission stage and the switchable freewheel clutch, so that the entire transmission and drive technology of the electrically driven rear axle is placed in a common housing.

[0034] Now, according to an extremely advantageous improvement of the present invention, it can also be provided that between the first rotor and the third rotor, the rotor shaft of the first rotor is supported against the third rotor shaft of the third rotor. Therefore, the support of the rotor shaft relative to the housing can be eliminated between the first rotor and the third rotor in the axial direction. The first rotor shaft is therefore only supported on the third rotor shaft in the axial direction between the two rotors, and vice versa, thereby eliminating additional support technology and the friction losses caused by it. Since the rotor shafts are supported accordingly by mutual support, they can move independently relative to each other. However, if they move relative to each other at the same speed or very similar speeds, the relative support between the two rotor shafts minimizes the friction losses because the speeds of the rotor shafts relative to each other are very small or zero.

[0035] With regard to the electrically driven front axle, in the electric drive system of the present invention, according to a very advantageous improvement, it can be provided that the second electric motor, the shaft reducer, the third planetary transmission stage and the first front wheel are arranged in the order described relative to the torque flow from the second electric motor. Similarly, the second electric motor, the shaft reducer, the fourth planetary transmission stage and the second front wheel can also be arranged in the order described relative to the torque flow from the second electric motor. Therefore, in this very advantageous embodiment of the electric drive system according to the present invention, the second electric motor for the electrically driven front axle drives two planetary transmission stages via a shaft reducer (e.g. a differential), and the two planetary transmission stages are respectively permanently connected to the driven front wheels in a torque-transmitting manner.

[0036] As an alternative to arranging the planetary transmission stage between the shaft reducer and the respective drive wheels of the front axle, it can also be provided according to a very advantageous embodiment that the components are arranged in the following order with respect to the torque flow from the second electric machine: second electric machine, further planetary transmission stage, shaft reducer, first front wheel on the one hand after the shaft reducer and second front wheel on the other hand after the shaft reducer. In this alternative, only one of the third and fourth planetary transmission stages is used instead of the third and fourth planetary transmission stages. The planetary transmission stage is located directly after the electric machine, so that it is coupled to the input shaft of the further planetary transmission stage. The torque is thus transmitted to the shaft reducer via the output of the further planetary transmission stage, which distributes the power flow to the two driven front wheels. The order of the planetary transmission stages and the shaft reducer is thus reversed, whereby one of the planetary transmission stages can be omitted.

[0037] According to a very advantageous development of these two variants of the electrically driven front axle, it can also be provided that a parking lock is provided for the electrically driven front axle. Depending on the arrangement according to the torque flow, the parking lock can be arranged between the other planetary gear stage and the shaft reducer or between the shaft reducer and one or both of the third and / or fourth planetary gear stages, wherein in this case preferably only one parking lock is provided, namely between the shaft reducer and the third planetary gear stage or between the shaft reducer and the fourth planetary gear stage. By means of such a parking lock, the drive system can be correspondingly locked when the motor vehicle is parked in a manner known per se and known in function. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Further advantageous embodiments of the electric drive system according to the invention also result from the exemplary embodiments which are described in detail below with reference to the figures.

[0039] The accompanying drawings show:

[0040] Figure 1 A schematic diagram showing a vehicle having an electric drive system according to the present invention,

[0041] Figure 2 A schematic diagram showing a vehicle having an electric drive system according to a second embodiment of the present invention,

[0042] Figure 3 shows a possible embodiment of the main elements of the electrically driven rear axle according to the second embodiment of the invention,

[0043] FIG. 4 shows two different variants of the mutual support of the rotor shafts of the first and second rotors,

[0044] Figure 5 shows a further possible embodiment of the main elements of the electrically driven rear axle according to the second embodiment of the invention; and

[0045] FIG. 6 shows two possible embodiments of an electrically driven front axle according to the invention. DETAILED DESCRIPTION

[0046] exist Figure 1 , a motor vehicle 1 is schematically shown, which in normal operation is to move from right to left in the diagram in a driving direction F, i.e., in forward driving. The motor vehicle 1 is equipped with an electric drive system 100 having an electrically driven front axle 2 and an electrically driven rear axle 3. The driving electrical energy of the electric drive system 100 is stored and supplied by a battery 4 or an alternative power storage system.

[0047] The electrically driven rear axle 3 comprises a first electric machine 5 with a first rotor 6 which is designed to drive a first rear wheel 7 and a second rear wheel 10 via a first shaft reducer 66 .

[0048] Furthermore, the electric drive system 100 includes a front portion in the driving direction F (i.e., Figure 1 The electrically driven front axle 2 comprises a second electric machine 17 with a second rotor 18, which is shown in FIG. Figure 6a and Figure 6b With the help of the second motor 17, the two front wheels 20 and 21 of the electric drive front axle 2, namely the first front wheel 20 and the second front wheel 21, can be driven simultaneously through the second shaft reducer 67. In addition, the electric drive front axle 2 Figure 1 The illustration includes the third and fourth planetary gear stages 22, 23 and the power electronics 24 connected to the battery 4. The two driven front wheels 20, 21 are permanently connected to the second rotor 18 of the second electric machine 17 via the second shaft reducer 67 and the planetary gear stages 22, 23, which is different from the case of the electrically driven rear axle 3, and the actuator device in the area of ​​the electrically driven front axle 2 can be completely omitted.

[0049] Furthermore, the electrically driven rear axle 3 comprises a first planetary gear stage 11 and a first switchable freewheel clutch 13, which is Figure 1 In the illustration of FIG. 3 , the electrically driven rear axle 3 further comprises a power electronics 15 (shown as being divided into two halves) and a schematically shown first actuator 13 a for actuating the first switchable freewheel clutch 13 .

[0050] By means of a first switchable freewheel clutch 13, the first rotor 6 can be coupled to the first rear wheel (7) and / or the second rear wheel 10 in a torque-transmitting manner, wherein the switchable freewheel clutch 13 is designed in a manner known per se so that, by means of the first switchable freewheel clutch 13, in a forward traction operation of the first electric machine 5, a torque-transmitting coupling of the first rotor 6 with the first rear wheel 7 and / or the second rear wheel 10 can be achieved without the action of the first actuator 13a (more precisely without a position change of the first actuator), and in a forward coasting operation or reverse traction operation of the first electric machine 5, a torque-transmitting coupling can be achieved by the action of the first actuator 13a (more precisely by a position change of the first actuator). The first actuator 13a advantageously has an electronic unit which generates an operating voltage based on an electronic signal. The first actuator 13a also advantageously has, for example, a servomotor or a hydraulic or pneumatic actuating element, by means of which the operating voltage can be converted into mechanical force to perform work.

[0051] Figure 2 The same existing features are given the same reference numerals, which shows a second embodiment of an electric drive system 100a, which has a third electric machine 8, which has a Figure 3 and Figure 5The third rotor 9 can be seen more clearly in the figure. The first motor 5 and the third motor 8 are designed to drive the first rear wheel 7 and the second rear wheel 10. Figure 3 and Figure 5 A possible embodiment of the electrically driven rear axle 3 is shown in detail. It should first be pointed out that for coupling / decoupling the third electric machine 8 with the first rear wheel 7 and / or the second rear wheel 10, a second switchable freewheel clutch 14 is provided, which itself includes a second actuator 14a. The second switchable freewheel clutch 14 and its associated two actuators 14a have the same construction as the first switchable freewheel clutch 13 and its first actuator 13a.

[0052] The electrically driven rear axle 3 in the second embodiment further comprises a first planetary transmission stage 11 and a second planetary transmission stage 12 , which are used for driving two rear wheels 7 , 10 respectively.

[0053] A first possible embodiment of the electrically driven rear axle 3 is now described in detail as follows. Figure 3 For this purpose, two electric machines 5, 8 are shown, which have a first rotor 6 and a third rotor 9. These rotors 6, 9 are connected in a rotationally fixed manner to the respective input shafts, namely a first input shaft 25 of the first planetary gear stage 11 and a second input shaft 26 of the second planetary gear stage 12. The first input shaft 25 is connected in a rotationally fixed manner to a first sun gear 27 of the first planetary gear stage 11. The second input shaft 26 is connected in a rotationally fixed manner to a second sun gear 28 of the second planetary gear stage 12.

[0054] The ring gears 29, 30 of the respective planetary gear stages 11, 12, i.e. the first ring gear 29 of the first planetary gear stage 11 and the second ring gear 30 of the second planetary gear stage, are both connected in a rotationally fixed manner here to a housing 31 indicated by hatching, preferably a common housing 31 of the electrically driven rear axle 3. The first electric machine 5 and the third electric machine 8, as well as the first planetary gear stage 11 and the second planetary gear stage 12, can preferably be arranged in the common housing.

[0055] The first output shaft 32 of the first planetary gear stage 11 is coupled to the first planetary gears 34 of the first planetary gear stage 11 or forms its planetary gear carrier or is connected to it in a rotationally fixed manner. The second output shaft 33 of the second planetary gear stage 12 is coupled to the second planetary gears 35 of the second planetary gear stage 12 or forms its planetary gear carrier or is connected to it in a rotationally fixed manner.

[0056] The respective output shaft 32 , 33 of the respective planetary gear stage 11 , 12 is coupled to the respective driven rear wheel 7 , 10 via the respective switchable freewheel clutch 13 , 14 with the respective actuator 13 a and 14 a , wherein the rear wheels 7 , 10 are merely indicated here by arrows symbolizing the torque flow.

[0057] The two motors 5 and 8 of the rear axle 3 can preferably be designed as axial flux motors, which are arranged in a preferably common housing 31 with a common oil chamber. The two planetary gear stages 11 and 12 and the switchable freewheel clutches 13 and 14 can also be designed to be integrated in a common housing. The rotors 6 and 9 of the rear axle 3 and the planetary gear stages 11 and 12 of the rear axle 3 are preferably all arranged coaxially with each other. In other words, the rotors 6 and 9 and the planetary gear stages 11 and 12 of the rear axle 3 preferably have a common axis of rotation. Observed in the axial direction relative to the axis of rotation, the first planetary gear stage 11, the first motor 5, the third motor 8 and the second planetary gear stage 12 are arranged in sequence. They are preferably arranged in sequence in the axial direction according to the order described here. Alternatively, the coaxial arrangement can also be provided with a structure in which one of the planetary gear stages 11 and 12 is arranged at the same height in the axial direction and arranged radially inside the corresponding motor 5 and 8.

[0058] In the diagram of FIG4, Figure 4a and Figure 4b 2 shows two examples of how two rotor shafts, namely the first rotor shaft 36 of the first electric machine 5 and the third rotor shaft 37 of the third electric machine 8, can be supported against one another in the axial region 16 between the two electric machines 5, 8. Figure 2 Shown in.

[0059] The two rotor shafts 36 , 37 of the first rotor 6 and of the third rotor 9 are preferably supported only against one another in the axial region 16 between the two electrical machines and not with respect to the housing 31 .

[0060] according to Figure 4a In order to provide a support for the rotor shaft 36, a sleeve 38 is provided in which the ends of the two rotor shafts 36, 37 are supported via a bearing arrangement 39. The end of the rotor shaft 36 is arranged radially inside the bearing arrangement 39, and the bearing arrangement 39 is arranged radially inside the sleeve 38. The bearing arrangement 39 preferably has two separate bearings.

[0061] according to Figure 4b An alternative embodiment provides that one of the rotor shafts (here the third rotor shaft 37) is designed as a hollow shaft at least at its end and the first rotor shaft 36 is accommodated in the hollow shaft via an alternative bearing device 40, so that the first rotor shaft 36 is arranged radially inside the alternative bearing device 40 and the alternative bearing device 40 is arranged radially inside the hollow shaft end of the third rotor shaft 37. As a result, the sleeve 38 as a separate component can be omitted.

[0062] exist Figure 5 In the diagram, compared to Figure 3, now we can see an alternative possible embodiment of the electrically driven rear axle, which is indicated here by 3a. This structure basically corresponds to Figure 3 structure, so all Figure 3 Components known from the prior art have the same reference numerals. Therefore, only the differences are described in detail below.

[0063] The first difference is that the positions of the first switchable freewheel clutch 13 and the second switchable freewheel clutch 14 have changed. The output shafts 32, 33 of the planetary gear stages 11, 12 are permanently connected to the drive wheels 7, 10 or their shafts. The switchable freewheel clutches 13, 14 are now located between the corresponding ring gears 29, 30 of the respective planetary gear stages 11, 12 and the common housing 31. With this arrangement of the switchable freewheel clutches 13, 14, although slightly higher losses occur when driving with the freewheel clutches 13, 14 in the disconnected state, the connection behavior of the freewheel clutches 13, 14 is improved because less torque is generated when connected. Figure 5 The arrangement of the freewheel clutches 13, 14 shown can also be used in an otherwise unchanged Figure 3 In this arrangement of the first switchable freewheel clutch 13, the first clutch half of the switchable freewheel clutch 13 is connected to the housing 31 in a rotationally fixed manner, and the second clutch half of the switchable freewheel clutch 13 is connected to the first ring gear 29 in a rotationally fixed manner. The second switchable freewheel clutch 14 is arranged in a similar manner between the housing 31 and the second ring gear 30.

[0064] Figure 5 Examples and Figure 3 Another difference of the embodiment of the present invention is that a superposition transmission mechanism is provided between the first rotor 6 and the third rotor 9. 41, which comprises a first drive shaft 42, a second drive shaft 43, a first driven shaft 44 and a second driven shaft 45, wherein the first rotor 6 is connected to the first drive shaft 42 in a rotationally fixed manner, and wherein the third rotor 9 is connected to the second drive shaft 43 in a rotationally fixed manner. The first driven shaft 44 is itself connected to the first input shaft 25 of the first planetary gear stage 11 in a rotationally fixed manner, and the second driven shaft 45 is connected to the second input shaft 26 of the second planetary gear stage 12 in a rotationally fixed manner. Figure 5 In the embodiment of the invention, the superposition gear mechanism 41 is arranged axially between the two electric machines 5, 8. However, it is also possible that the superposition gear mechanism 41 is arranged axially beside the two electric machines 5, 8, wherein one of the two rotor shafts 36, 37 of the rear axle 3a then extends radially in the other of the two rotor shafts 36, 37.

[0065] Figure 5 The structure of the design corresponds in other respects to Figure 3 The structure, wherein the two switchable freewheel clutches 13, 14 are arranged according to Figure 5 In the structure of the planetary gear stage 11, 12, the position can also be changed to the area of ​​the output shaft 32, 33 (similar to the Figure 3 structure).

[0066] In the diagram of FIG6, Figure 6a and Figure 6b Two possible alternative embodiments for electrically driving the front axle 2 are shown. Figure 6a In the illustration of the electric drive front axle 2, the electric drive is designed so that the second electric machine 17 with the second rotor 18 is arranged centrally in the axial direction. The second shaft reducer 67 is designed as a differential transmission mechanism, which is driven by the second rotor 18 of the second electric machine 17. In particular, the input shaft of the second shaft reducer 67 can be coupled to the second rotor 18 in a rotationally fixed manner. The input shaft of the second shaft reducer 67 can be designed, for example, as a differential cage of a bevel gear differential. The output shafts of the second shaft reducer 67 respectively form the input shafts, namely the third input shaft 46 of the third planetary gear stage 48 on the one hand and the fourth input shaft 47 of the fourth planetary gear stage 49 on the other hand.

[0067] Similar to the above description of the electrically driven rear axle 3, the input shafts 46 and 47 can be connected to the sun gears, namely the third sun gear 50 of the third planetary gear stage 48 and the fourth sun gear 51 of the fourth planetary gear stage 49. The ring gears of the two planetary gear stages 48 and 49, namely the third ring gear 52 and the fourth ring gear 53, are fixed relative to another housing 54.

[0068] The planetary gear carriers of the respectively rotating planetary gears 66 , 67 respectively form the third output shaft 55 of the third planetary gear stage 48 and the fourth output shaft 56 of the fourth planetary gear stage 49 and respectively drive one of the two front wheels 20 , 21 , which are also indicated here only by corresponding directional arrows, similar to the above-mentioned illustrations.

[0069] The two planetary gear stages 48, 49, the second shaft reduction gear 67 and the second electric machine 17 can here again preferably be arranged coaxially with respect to the axis of rotation of their structure, wherein here too, as in Figure 3 and Figure 5 , only the upper half of the structure which is rotationally symmetrical with respect to the rotation axis is shown accordingly. Here, the sequence in the axial direction is particularly such that the first driven front wheel 20 is followed by the third planetary gear stage 48, the second shaft reducer 67, the fourth planetary gear stage 49 and the second driven front wheel 21. The second motor 17 surrounds the second shaft reducer 67, so that the second shaft reducer 67 is arranged coaxially with the second motor 17 and is arranged to overlap axially with respect to the second motor and radially inside it.

[0070] Figure 6b , an alternative structure for the front axle 2 is shown, in which the second electric machine 17 or the second rotor 18 first transfers the torque to the further planetary gear stage 57. The further planetary gear stage 57 is configured in the example shown here so that the second rotor 18 is connected to its input shaft (here in the form of the fifth sun gear 58) in a rotationally fixed manner, while the fifth ring gear 59 of the further planetary gear stage 57 is connected to the further housing 54 in a rotationally fixed manner. The output shaft of the further planetary gear stage 57 in turn forms a planetary gear carrier 60 for the fifth planetary gear 61. The planetary gear carrier 60 is connected to the sixth ring gear 62 of the planetary differential as the second shaft reducer 67a, which drives the first driven front wheel 20 via the double planetary gear carrier 63 and drives the second driven front wheel 21 via the sixth sun gear 64.

[0071] You can also Figure 6b The parking lock 65 can be seen in the illustration. The parking lock 65 is arranged between the other planetary gear stage 57 and the second shaft reducer 67a and is used to fix the drive device when the motor vehicle 1 is parked. In this case, the planetary gear carrier 60 can be connected to the other housing 54 in a rotationally fixed manner via the parking lock 65 when the parking lock 65 is locked. In principle, this parking lock 65 can also be used for Figure 6a In the structure shown, for example, between the second shaft reducer 67a and the third planetary gear stage 48, or alternatively (or additionally) between the second shaft reducer 67a and the fourth planetary gear stage 49. From the perspective of the overall system of the electric drive system 100, 100a, it is advantageous to integrate the parking lock 65 into the electric drive front axle 2, 2a rather than into the electric drive rear axle 3, 3a, because the electric drive front axle 2, 2a provides more space in the overall system, and the electric drive front axle 2, 2a designed in this way can also be used as a module in other conceivable overall systems.

[0072] Advantageously, the overall system of the electric drive system 100, 100a can be used to operate a motor vehicle equipped with the system so that when the forward traction operation of the first electric machine 5 is switched to the forward coasting operation by means of the first actuator 13a, if the vehicle speed before the switch is greater than a speed threshold and no vehicle motion operation mode selectable by the vehicle driver is present and the charge level of the battery 4 is less than a charge level threshold, then a torque-transmitting connection of the first rotor 6 with the first rear wheel 7 and / or the second rear wheel 10 is achieved under the action of the first actuator 13a. The action of the first actuator 13a, as described above, refers, for example, to a position change of a hydraulic piston or a pneumatic piston or a servomotor of the first actuator 13a. The speed threshold may preferably be in the range of 100 km / h. The charge level threshold may preferably be in the range of 90% of the total charge capacity of the battery 4.

[0073] Reference numerals list

[0074] 1 Motor Vehicle

[0075] 2.2a Front axle

[0076] 3 Rear axle

[0077] 4 Batteries

[0078] 5 First Motor

[0079] 6 First rotor

[0080] 7 First rear wheel

[0081] 8 Third motor

[0082] 9 Third rotor

[0083] 10 Second rear wheel

[0084] 11 First planetary gear stage

[0085] 12 Second planetary gear stage

[0086] 13 First switchable freewheel clutch

[0087] 13a First actuator

[0088] 14 Second switchable freewheel clutch

[0089] 14a Second actuator

[0090] 15 Power Electronics

[0091] 16 Axial region

[0092] 17 Second Motor

[0093] 18 Second rotor

[0094] 20 First front wheel

[0095] 21 Second front wheel

[0096] 22 Third planetary gear stage

[0097] 23 Fourth planetary gear stage

[0098] 24 Power Electronics

[0099] 25 First input shaft

[0100] 26 Second input shaft

[0101] 27 First sun gear

[0102] 28 Second sun gear

[0103] 29 First gear ring

[0104] 30 Second gear ring

[0105] 31 Shell

[0106] 32 First output shaft

[0107] 33 Second output shaft

[0108] 34 First planetary gear

[0109] 35 Second planetary gear

[0110] 36 First rotor shaft

[0111] 37 Second rotor shaft

[0112] 38 Casing

[0113] 39 Bearing assembly

[0114] 40 Alternative bearing arrangements

[0115] 41 Superposition transmission mechanism

[0116] 42 First drive shaft

[0117] 43 Second drive shaft

[0118] 44 First driven shaft

[0119] 45 Second driven shaft

[0120] 46 Third input shaft

[0121] 47 Fourth input shaft

[0122] 48 Third planetary gear stage

[0123] 49 Fourth planetary gear stage

[0124] 50 Third sun gear

[0125] 51 Fourth sun gear

[0126] 52 Third gear ring

[0127] 53 Fourth gear ring

[0128] 54 Another shell

[0129] 55 Third output shaft

[0130] 56 Fourth output shaft

[0131] 57 Another planetary gear stage

[0132] 58 Fifth sun gear

[0133] 59 Fifth gear ring

[0134] 60 Planetary gear carrier

[0135] 61 Fifth planetary gear

[0136] 62 Sixth gear ring

[0137] 63 Double planetary gear carrier

[0138] 64 Sixth sun gear

[0139] 65 Parking lock

[0140] 66 First axis reducer

[0141] 67, 67a Second axis reducer

[0142] 100, 100a Electric drive system.

Claims

1. An electric drive system for a motor vehicle (1), comprising an electrically driven front axle (2) and an electrically driven rear axle (3), wherein The electrically driven rear axle (3) has a first motor (5), the first motor has a first rotor (6), and the first rotor is designed to drive a first rear wheel (7) and / or a second rear wheel (10) of the electrically driven rear axle (3), wherein: The electrically driven front axle (2) has a second motor (17), the second motor has a second rotor (18), and the second rotor is designed to drive the front wheels (20, 21) of the electrically driven front axle (2) via a second shaft reducer (67, 67a). wherein the second rotor (18) is permanently coupled to the first front wheel (20) and to the second front wheel (21) via the second shaft reducer (67, 67a) in a torque-transmitting manner, wherein the first switchable freewheel clutch (13) is designed to couple the first rotor (6) to the first rear wheel (7) and / or the second rear wheel (10) in a torque-transmitting manner, The first switchable freewheel clutch (13) has a first actuator (13a), wherein, by means of the first switchable freewheel clutch (13), under the forward traction operation of the first motor (5), the first rotor (6) can be connected to the first rear wheel (7) and / or the second rear wheel (10) by torque transmission without the action of the first actuator (13a); and under the forward sliding operation or reverse traction operation of the first motor (5), the first rotor (6) can be connected to the first rear wheel (7) and / or the second rear wheel (10) by torque transmission under the action of the first actuator (13a), The electrically driven rear axle (3) has a third motor (8), the third motor has a third rotor (9), and the third rotor is designed to drive the second rear wheel (10) and / or the first rear wheel (7) of the electrically driven rear axle (3). A second switchable freewheel clutch (14) is provided, which has a second actuator (14a) and is designed to couple the third rotor (9) to the second rear wheel (10) in a torque-transmitting manner. It is characterized in that The first motor (5) and the third motor (8) are designed as axial flux motors and are arranged in a common housing (31) having a common oil chamber. The first planetary transmission stage (11), the second planetary transmission stage (12), the first switchable freewheel clutch (13) and the second switchable freewheel clutch (14) are arranged in the common housing (31) and the common oil chamber.

2. The electric drive system according to claim 1, It is characterized in that A first planetary gear stage (11) is provided, which is arranged between the first rotor (6) and the first rear wheel (7) with respect to the torque flow from the first rotor (6), wherein the first rotor (6) and the first planetary gear stage (11) are arranged coaxially with each other.

3. The electric drive system according to claim 2, It is characterized in that The first switchable freewheel clutch (13) is designed to connect the first output shaft (32) of the first planetary gear stage (11) to the first rear wheel (7) in a rotationally fixed manner.

4. The electric drive system according to claim 2, It is characterized in that The first switchable freewheel clutch (13) is designed to connect an element (29) of the first planetary gear stage (11) to a housing (31) in a rotationally fixed manner.

5. The electric drive system according to claim 2, It is characterized in that A superposition transmission mechanism (41) is arranged axially between the first rotor (6) and the third rotor (9), the superposition transmission mechanism comprising a first drive shaft (42), a second drive shaft (43), a first driven shaft (44) and a second driven shaft (45), wherein the first rotor (6) is connected to the first drive shaft (42) in a rotationally fixed manner, the third rotor (9) is connected to the second drive shaft (43) in a rotationally fixed manner, the first driven shaft (44) is connected to the first input shaft (25) of the first planetary gear stage (11) in a rotationally fixed manner, and the second driven shaft (45) is connected to the second input shaft (26) of the second planetary gear stage (12) in a rotationally fixed manner.

6. The electric drive system according to claim 1, It is characterized in that Axially between the first rotor (6) and the third rotor (9), a first rotor shaft (36) of the first rotor (6) is supported against a third rotor shaft (37) of the third rotor (9).

7. An electric drive system according to any one of the preceding claims, It is characterized in that With respect to the torque flow from the second motor (17), the second motor (17), the second shaft reducer (67), the third planetary transmission stage (48) and the first front wheel (20) are arranged in the stated order, and With respect to the torque flow from the second motor (17), the second motor (17), the second shaft reducer (67), the fourth planetary gear stage (49) and the second front wheel (21) are sequentially arranged in the stated order.

8. The electric drive system according to any one of claims 1 to 6, It is characterized in that With respect to the torque flow from the second electric machine (17), the following components are arranged in the following order: the second electric machine (17), another planetary transmission stage (57), the second shaft reducer (67a), the first front wheel (20) after the second shaft reducer (67a) on the one hand and the second front wheel (21) after the second shaft reducer (67a) on the other hand.

9. The electric drive system according to claim 8, It is characterized in that With respect to the torque flow, a parking lock (65) is engaged between the further planetary gear stage (57) and the shaft reducer (67a).

10. A method for operating a motor vehicle, the motor vehicle having an electric drive system (100, 100a) and a battery (4), in, The electric drive system (100, 100a) comprises an electric drive front axle (2) and an electric drive rear axle (3), The electrically driven rear axle (3) has a first motor (5), the first motor has a first rotor (6), and the first rotor is designed to drive a first rear wheel (7) and / or a second rear wheel (10) of the electrically driven rear axle (3). The electrically driven front axle (2) has a second motor (17), the second motor has a second rotor (18), and the second rotor is designed to drive the front wheels (20, 21) of the electrically driven front axle (2) through a second shaft reducer (67, 67a). wherein the second rotor (18) is permanently coupled to the first front wheel (20) and to the second front wheel (21) via the second shaft reducer (67, 67a) in a torque-transmitting manner, wherein the first switchable freewheel clutch (13) is designed to couple the first rotor (6) to the first rear wheel (7) and / or the second rear wheel (10) in a torque-transmitting manner, The first switchable freewheel clutch (13) has a first actuator (13a), wherein, by means of the first switchable freewheel clutch (13), under the forward traction operation of the first motor (5), the first rotor (6) can be connected to the first rear wheel (7) and / or the second rear wheel (10) by torque transmission without the action of the first actuator (13a); and under the forward sliding operation or reverse traction operation of the first motor (5), the first rotor (6) can be connected to the first rear wheel (7) and / or the second rear wheel (10) by torque transmission under the action of the first actuator (13a), It is characterized in that In the case of switching from the forward traction operation of the first motor (5) to the forward gliding operation, when the vehicle speed of the motor vehicle is greater than a speed threshold before the switching is performed and there is no motor vehicle motion operation mode that can be selected by the motor vehicle driver and the power of the battery (4) is less than a power threshold, the first rotor (6) is connected to the first rear wheel (7) and / or the second rear wheel (10) through torque transmission under the action of the first actuator (13a).

Images