Electric drive system for a motor vehicle

Abstract

Electric drive system (10) for a motor vehicle, comprising a first electric machine (16) with a first rotor (20), a second electric machine (24) with a second rotor (28), and a reduced coupling gear (30) comprising a first planetary gear set (32), a second planetary gear set (34), a first input shaft (36), a second input shaft (38), a first output shaft (40), and a second output shaft (42), wherein: - the first input shaft (36) is configured to transmit first torques (M1) emanating from the first electric machine (16) into the reduced coupling gear (30), - the second input shaft (38) is configured to transmit second torques (M2) emanating from the second electric machine (24) into the reduced coupling gear (30), - the first output shaft (40) is configured to transmit third torques (M3) from the reduced coupling gear (30),- the second output shaft (42) is configured to transmit fourth torques (M4) from the reduced coupling gear (30), - the first planetary gear set (32) has a first element that is rotationally fixed to or connectable to the first rotor (20), a second element that is rotationally fixed to the first output shaft (40), and a third element that is rotationally fixed to the second output shaft (42), - the second planetary gear set (34) has a fourth element that is rotationally fixed to the second rotor (28) and a fifth element that is rotationally fixed to the second element, wherein: - the second planetary gear set (34) has a sixth element that is rotationally fixed to the third element, and - a first stationary gear ratio of the first planetary gear set (32) has the same magnitude and an opposite sign compared to a second stationary gear ratio of the second planetary gear set (34), characterized in thatthat: - the first element of the first planetary gear set (32) is designed as a first ring gear (48), - the fourth element of the second planetary gear set (34) is designed as a second ring gear (52), - the third element of the first planetary gear set (32) is designed as a first sun gear (44), and - the sixth element of the second planetary gear set (34) is designed as a second sun gear (49).

Description

The invention relates to an electric drive system for a motor vehicle according to the preamble of claim 1 and a torque vectoring method according to claim 9. From US patent 2015 / 0065282A1, a drive system for a motor vehicle with two electric motors and a coupling device is known, in which it is possible to selectively generate different wheel torques by choosing different torques supplied by the electric motors. However, the controllability of the known system is very complex. From generic US 2007 / 0249456A1, an electric drive system with two electric machines and a planetary coupling gear is known, wherein the two electric machines are connected to different shafts of the coupling gear, thereby enabling a so-called torque shift function. The object of the present invention is to create an electric drive system for a motor vehicle in such a way that particularly good drivability, a particularly compact design and simple control and regulation can be achieved. This problem is solved by an electric drive system with the features of claim 1 and a torque vectoring method according to claim 9. Advantageous embodiments with expedient further developments of the invention are specified in the remaining claims. The invention relates to an electric drive system for a motor vehicle, in particular a car, also referred to as an electric drive device or designed as such. This means that the motor vehicle, in its fully manufactured state, has the electric drive system and can be driven, in particular purely electrically, by means of the electric drive system. In particular, the motor vehicle, in its fully manufactured state, has, for example, at least or exactly two axles, which are arranged consecutively in the longitudinal direction of the vehicle and thus one behind the other. Each axle has, for example, at least or exactly two wheels, also referred to as vehicle wheels, wherein preferably the wheels of each axle are arranged on opposite sides in the transverse direction of the vehicle.The wheels are ground contact elements by which the vehicle can be supported or is supported downwards against the ground in the vertical direction. For example, the electric drive system is assigned to at least one or exactly one of the axles, so that the wheels of at least or exactly one of the axles can be driven by the electric drive system. The wheels that can be driven by the electric drive system are also called drive wheels. If the drive wheels, and thus the vehicle, are driven by the electric drive system while the vehicle is supported downwards by the wheels against the ground in the vertical direction, the vehicle is driven along the ground, and the wheels roll along the ground. The electric drive system comprises a first electric machine with a first rotor. For example, the first electric machine has a first stator by means of which the first rotor can be driven and thus rotated about a first machine axis of rotation relative to the first stator. The electric drive system also comprises a second electric machine, which has a second rotor. For example, the second electric machine has a second stator by means of which the second rotor can be driven and thus rotated about a second machine axis of rotation relative to the second stator. The electric drive system also comprises at least one reduced coupling gear, which includes a first planetary gear set, a second planetary gear set, a first input shaft, a second input shaft, a first output shaft, and a second output shaft. The first input shaft is configured toThe first input shaft is configured to introduce initial torques emanating from the first electric machine, in particular from the first rotor, into the reduced coupling gear. This can be understood to mean, in particular, that the first electric machine, especially via its rotor, can provide the initial torques that can be introduced into the reduced coupling gear via the first input shaft. This allows, in particular, the reduced coupling gear to be driven. The second input shaft is configured to introduce secondary torques emanating from the second electric machine, in particular from the second rotor, into the reduced coupling gear. This can be understood to mean, in particular, that the second electric machine, especially via its second rotor, can provide the secondary torques that can be introduced into the reduced coupling gear via the second input shaft.in particular bypassing the first input shaft. This allows the reduced coupling gear to be driven. Furthermore, it is conceivable that the first torques can be introduced into the reduced coupling gear via the first input shaft, bypassing the second input shaft. This can be understood in particular as follows: The first torques that can be provided or are provided by the first electric machine, in particular by the first rotor, do not pass or flow, for example, via the second input shaft on their way from the first electric machine, in particular by the first rotor, into the reduced coupling gear; thus, the first torques bypass the second input shaft, so that, for example, the second input shaft, with respect to a first torque transmission path via which the torques provided by the first electric machine, in particular by the first rotor,The first torques from the first electric machine, in particular from the first rotor, can be transmitted to the first input shaft and introduced via the first input shaft into the reduced coupling gear, provided that the first input shaft is not located in the first torque transmission path, or at least not in the first torque transmission path between the first electric machine and the reduced coupling gear. The same applies to the second electric machine and the second torques. The second torques that can be provided or are provided by the second electric machine, in particular from the second rotor, do not pass or flow, for example, via the first input shaft on their way from the second electric machine, in particular from the second rotor, into the reduced coupling gear; thus, the second torques bypass the first input shaft.so that, for example, the first input shaft, with respect to a second torque transmission path via which the second torques provided by the second electric machine, in particular by the second rotor, can be transmitted from the second electric machine, in particular by the second rotor, to the second input shaft and introduced via the second input shaft into the reduced coupling gear, is not arranged in the second torque transmission path or at least not in the second torque transmission path between the second electric machine and the reduced coupling gear. The first output shaft is configured to transmit third torques from the reduced linkage. For example, the third torques result from the first torques and / or the second torques introduced into the reduced linkage. The second output shaft is configured to transmit fourth torques from the reduced linkage, particularly by bypassing the first output shaft, wherein, for example, the fourth torques result from the first torques and / or the second torques introduced into the reduced linkage. In particular, it is conceivable that the first output shaft is configured to transmit the third torques from the reduced linkage, bypassing the second output shaft. The first planetary gear set comprises a first sun gear, a first planet carrier (also called the first carrier), and a first ring gear. The first sun gear, the first planet carrier, and the first ring gear are also referred to as the first gear elements of the first planetary gear set. The second planetary gear set comprises a second sun gear, a second planet carrier (also called the second carrier), and a second ring gear. The second sun gear, the second planet carrier, and the second ring gear are also referred to as the second gear elements of the second planetary gear set. The first of the first gear elements of the first planetary gear set is also referred to as the first element, the second of the first gear elements of the first planetary gear set is also referred to as the second element, and the third of the first gear elements of the first planetary gear set is also referred to as the third element.The first of the second gear elements of the second planetary gear set is also referred to as the fourth element, the second of the second gear elements of the second planetary gear set is also referred to as the fifth element, and the third of the second gear elements of the second planetary gear set is also referred to as the sixth element. Within the context of this disclosure, ordinal numbers such as "first," "first," "second," "second," etc., are not necessarily used to indicate or imply a number or quantity, but rather to uniquely refer to terms to which the ordinal numbers are assigned or to which the ordinal numbers refer. Therefore, the first of the second gear elements is referred to as the fourth element, the second of the second gear elements as the fifth element, and the third of the second gear elements as the sixth element. The first element of the first planetary gear set is connected to the first rotor, in particular permanently and in a rotationally fixed manner, or the first element of the first planetary gear set can be connected to the first rotor in a rotationally fixed manner. Within the scope of the present disclosure, the feature that two components, such as the first element and the first rotor, are rotationally fixed to one another is understood to mean that the two components are arranged coaxially and connected to one another in such a way that they rotate at the same angular velocity, in particular about a common axis of rotation and / or relative to a housing element of the drive system, especially when the components, or one of the components, or one of the components, or the other component is driven via one component, is driven or is driven.In other words, within the scope of this disclosure, the term or expression "rotationally fixed connection of two rotatably mounted components" means that the two components are arranged coaxially and connected to each other in such a way that they rotate at the same angular velocity. Furthermore, within the scope of this disclosure, the feature that two components are permanently rotationally fixed to each other means that these components are not associated with a switching element that can be switched between a coupled state in which the components are rotationally fixed to each other and a decoupling state in which the switching element allows a relative rotation between the components, particularly about the aforementioned axis of rotation of the components. Rather, the components are always, or always, that is, permanently, rotationally fixed to each other.Furthermore, within the scope of the present disclosure, the feature that two components, such as the first element of the first planetary gear set and the first rotor, can be connected to each other in a rotationally fixed manner, is to be understood as meaning that these components are associated with a switching element which can be switched between a coupled state and a decoupling state. In the coupled state, the components are connected to each other in a rotationally fixed manner by means of the switching element associated with them. In the decoupling state, the switching element associated with the components allows a relative rotation between the components, in particular about the aforementioned axis of rotation of the components. The second element of the first planetary gear set is, in particular, permanently and non-rotatably connected to the first output shaft. The third element of the first planetary gear set is, in particular, permanently and non-rotatably connected to the second output shaft. The fourth element of the second planetary gear set is, in particular, permanently and non-rotatably connected to the second rotor. The fifth element of the second planetary gear set is, in particular, permanently and non-rotatably connected to the second element of the first planetary gear set. To achieve particularly advantageous drivability of the motor vehicle, good controllability and regulating capabilities, and a particularly compact design of the electric drive system, it is provided, in a manner known per se, that the sixth element of the second planetary gear set is permanently and rotationally fixed to the third element of the first planetary gear set. Furthermore, it is also provided, in a manner known per se, that the first stationary gear ratio of the first planetary gear set has the same magnitude but an opposite sign compared to the second stationary gear ratio of the second planetary gear set. In other words, the first planetary gear set has a first stationary gear ratio, and the second planetary gear set has a second stationary gear ratio.The stationary gear ratios of the planetary gear sets have the same absolute value, but they have different mathematical signs. One stationary gear ratio has a positive sign (+) and the other a negative sign (-). It has been found that with the electric drive system according to the invention, it is particularly easy to individually adjust the third and fourth torques and to easily adjust them so that a constant sum torque results from the third and fourth torques.Furthermore, in the electric drive system according to the invention, the third and fourth torques depend on changes in the first and second torques in a very simple manner. It has also been found that when the gear ratios are set according to the invention, internal torques in the reduced coupling gear are minimal, so that the reduced coupling gear can be designed to be particularly lightweight and compact. Preferably, the second gear elements are provided in addition to the first gear element. Particularly when the respective first gear element is not rotationally fixed to a housing assembly, such as the aforementioned housing element of the drive system, the respective first gear element can be rotated about a first planetary gear set axis of rotation of the first planetary gear set relative to the housing assembly, which is, for example, the aforementioned housing element. Accordingly, the respective second gear element can be rotated about a second planetary gear set axis of rotation of the second planetary gear set relative to the housing assembly, particularly when the respective second gear element is not rotationally fixed to the housing assembly. It is conceivable that the planetary gear sets are arranged coaxially with each other, so that the planetary gear set axes of rotation coincide. According to the invention, the first element of the first planetary gear set is the first ring gear, the fourth element of the second planetary gear set is the second ring gear, the third element of the third planetary gear set is the first sun gear, and the sixth element of the second planetary gear set is the second sun gear. To achieve a particularly compact and thus space-saving design of the electric drive system, one embodiment of the invention provides that the second element of the first planetary gear set is the first planet carrier, which is preferably designed as a single planet carrier with first planet gears. This means, in particular, that the first planet gears are rotatably mounted on the first planet carrier, specifically such that each first planet gear is rotatable about a respective first planet gear axis of rotation relative to the first planet carrier. It is particularly provided that the first planet gear axes of rotation run parallel to each other and are spaced apart. Specifically, the first planet gear axes of rotation are uniformly spaced apart in pairs in the first circumferential direction of the first planetary gear set, which runs about the first planet gear set axis of rotation.It is preferably provided that the first planet gears are identical in construction to each other and, in particular, are arranged at the same height in the axial direction of the first planet gear set, and in particular start at the same first height and end at the same second height, especially in the axial direction of the first planet gear set. It has proven particularly advantageous if the fifth element of the second planetary gear set is the second planet carrier, which is most preferably designed as a double planet carrier with second planet gears and third planet gears. This means, in particular, that the second planet gears and the third planet gears are rotatably mounted on the second planet carrier, especially such that each second planet gear is rotatable about a respective second planet gear axis of rotation relative to the second planet carrier, and each third planet gear is rotatable about a respective third planet gear axis of rotation relative to the second planet carrier.It is particularly conceivable that the second planet gear axes of rotation run parallel to each other and are spaced apart, especially in the second circumferential direction of the second planet gear set, which runs around the second planet gear set axis of rotation. It is particularly conceivable that the second planet gear axes of rotation are uniformly or equally spaced apart in pairs in the second circumferential direction of the second planet gear set. Furthermore, it is conceivable that the third planet gear axes of rotation run parallel to each other and are spaced apart, especially in the second circumferential direction of the second planet gear set. Preferably, the third planet gear axes of rotation are uniformly or equally spaced apart in pairs in the second circumferential direction of the second planet gear set. For example, the second planet gears can be identical in construction. Furthermore, it is conceivable that the third planet gears are identical in construction.For example, the third planet gear axes of rotation run parallel to the second planet gear axes of rotation. Thus, for example, the second planet gears are arranged at the same height in the axial direction of the second planet gear set; therefore, the second planet gears begin and end at the same heights when viewed in the axial direction of the second planet gear set. Alternatively or additionally, for example, the third planet gears are arranged at the same height in the axial direction of the second planet gear set, so that preferably the third planet gears begin and end at the same heights when viewed in the axial direction of the second planet gear set. In particular, it is conceivable that the second planet gears are identical in construction. Alternatively or additionally, the third planet gears can be identical in construction.It is particularly conceivable that the respective second and third planet gears differ in their construction. Alternatively or additionally, it is conceivable that the respective second and third planet gears are arranged at the same or different heights in the axial direction of the planetary gear set, i.e., that they begin and / or end at the same or different heights. Furthermore, it is preferably provided that the first planet gears are designed separately from the second planet gears and separately from the third planet gears. Preferably, the second planet gears mesh with the second sun gear, with each second planet gear meshing with one of the third planet gears and not with the second ring gear. The third planet gears preferably mesh with the second ring gear, with each third planet gear meshing with one of the second planet gears and not with the second sun gear. In order to achieve a particularly compact design, a further embodiment of the invention provides that the third element of the first planetary gear set and the sixth element of the second planetary gear set have the same tooth diameters, in particular the same pitch circle diameters, and also the same number of teeth. In a further, particularly advantageous embodiment of the invention, the electric drive system comprises a first transmission stage. With respect to a first torque flow, along which the third torques can be transmitted from the reduced coupling gear via the first output shaft, the first transmission stage is arranged in the first torque flow and downstream of the first output shaft, thus connected downstream of the first output shaft. Conversely, the first output shaft is arranged in the first torque flow and upstream of the first transmission stage, thus connected upstream of the first transmission stage. It has proven particularly advantageous for the electric drive system to have a second transmission stage. With respect to a second torque flow, along which the fourth torques can be transmitted from the reduced coupling gear via the second output shaft, the second transmission stage is located in this second torque flow and downstream of the second output shaft. In other words, the second transmission stage is located in the second torque flow and is thus connected downstream of the second output shaft. Conversely, the second output shaft is located in the second torque flow and is thus connected upstream of the second transmission stage. It has proven particularly advantageous if the first transmission stage, the second transmission stage, the planetary gear sets, and the rotors are arranged in a common housing of the electric drive system. In particular, the housing can be the aforementioned housing element and / or housing assembly. Each transmission stage has, for example, at least or exactly two gears, which can be designed as spur gears. Preferably, the gears of each transmission stage are in direct meshing with one another, so that, for example, the gears form a spur gear stage or spur gear pair. By using the transmission stages, a particularly advantageous and, in particular, a particularly advantageously large transmission ratio can be achieved in a space-saving manner. To keep the installation space required for the electric drive system to a particularly low level, a further embodiment of the invention provides that the reduced coupling gear, the two rotors, and the two transmission stages are all arranged coaxially to one another. Preferably, the planetary gear sets are arranged coaxially to one another, so that the planetary gear set axes of rotation coincide. A coaxial arrangement of the rotors, meaning that the rotors are arranged coaxially to one another, means that the machine axes of rotation coincide. Thus, if the rotors are arranged coaxially to each other and coaxially to the planetary gear sets, and therefore coaxially to the reduced coupling gear, the machine axes of rotation coincide, the planetary gear set axes of rotation coincide, and each planetary gear set axis of rotation coincides with the respective machine axis of rotation. Furthermore, it is conceivable, for example, that each transmission stage has at least one transmission element, which can be designed, for instance, as a gear, in particular as a spur gear. The respective transmission element of each transmission stage can be rotated relative to the housing element or the housing, in particular about a respective transmission element rotation axis. If the transmission stages are arranged coaxially to each other, then the transmission elements of the transmission stages are arranged coaxially to each other, so that the transmission element rotation axes coincide. If, for example, the transmission stages are arranged coaxially to each other, coaxially to the reduced coupling gear, and coaxially to the motors, then the planetary gear set rotation axes, the machine rotation axes, and the transmission element rotation axes all coincide, thus enabling a particularly space-saving design. In order to keep the installation space requirement of the electric drive system to a particularly low level, it is provided in a further embodiment of the invention that the reduced coupling gear has exactly two planetary gear sets, namely the first planetary gear set and the second planetary gear set. Additionally and advantageously, the transmission stages downstream of the reduced coupling gear can each be designed as a further planetary gear set. It is advantageous for these additional planetary gear sets to be designed as simple planetary gear sets. To achieve particularly advantageous drivability in a space-saving manner, a further embodiment of the invention provides that the electric drive system includes a first switching element designed to connect the first rotor to the first ring gear in a rotationally fixed manner. This means, in particular, that the first switching element is switchable between a first coupling state and a first decoupling state. In the first coupling state, the first rotor and the first ring gear are rotationally fixed to one another by means of the first switching element, so that the first rotor and the first ring gear rotate together or simultaneously, i.e., at the same angular velocity, particularly about the first planetary gear set axis of rotation and / or relative to the housing element, especially when the reduced coupling gear is driven.In the first decoupling state, the first switching element allows relative rotations between the first rotor and the first ring gear, particularly about the first planetary gear set axis of rotation. For example, the switching element is movable, particularly translationally and / or relative to the housing element, between at least one first coupling position that effects the first coupling state and at least one first decoupling position that effects the first decoupling state. It has proven particularly advantageous if the electric drive system includes a second switching element designed to connect the first rotor to the second ring gear in a rotationally fixed manner. This means, in particular, that the second switching element is switchable between a second coupling state and a second decoupling state. In the second coupling state, the first rotor and the second ring gear are rotationally fixed to each other by means of the second switching element, so that the first rotor and the second ring gear rotate together, or at the same angular velocity, particularly about the first and second planetary gear set axis of rotation and / or relative to the housing element, especially when the reduced coupling gear is driven.In the second decoupling state, the second switching element allows relative rotations between the first rotor and the second ring gear, particularly around the first or second planetary gear set axis of rotation. For example, the second switching element is movable, particularly relative to the housing element and / or translationally, between at least one second coupling position that effects the second coupling state and at least one second decoupling position that effects the second decoupling state. In a further, particularly advantageous embodiment of the invention, the electric drive system comprises a locking switching element configured to force-fit two elements of the reduced coupling mechanism that are not permanently and rotationally fixed to one another. In other words, the locking switching element is assigned to two of the elements of the reduced coupling mechanism, wherein the elements to which the locking switching element is assigned are not permanently and rotationally fixed to one another. The locking switching element can, for example, be switched between a third coupling state and a third decoupling state. In the third coupling state, the two elements to which the locking switching element is assigned are force-fit to one another by means of the locking switching element.In the third decoupling state, the interlocking switching element allows relative rotations between the elements to which it is assigned, particularly around the first and / or second planetary gear set axis of rotation. The elements to which the interlocking switching element is assigned can, for example, be elements of the same planetary gear set, i.e., two of the first gear elements or two of the second gear elements. In particular, the interlocking switching element can be provided in addition to the first switching element and in addition to the second switching element. If the two elements to which the interlocking switching element is assigned are frictionally connected to each other by means of the interlocking switching element, this results in an equalization of the rotational speeds of the frictionally coupled elements, depending on the degree of friction.Advantageously, in the third coupling state, the two elements mentioned, to which the locking switching element is assigned, are not connected to each other in a rotationally fixed manner, but are only almost rotationally fixed to each other by the aforementioned force transmission. It is conceivable that each transmission stage is designed as a further planetary gear set. Thus, it is conceivable that the first transmission stage is designed as a third planetary gear set and the second transmission stage as a fourth planetary gear set, with the third planetary gear set being provided in addition to the first, second, and fourth planetary gear sets. For example, the respective transmission element mentioned above could be a sun gear, a ring gear, or a planet carrier of the respective third or fourth planetary gear set. Furthermore, it is preferably provided that each input of the respective further planetary gear set, and thus of the respective transmission stage, is a further sun gear of the respective further planetary gear set.Thus, for example, the third torques, which are routed from the reduced coupling gear via the first output shaft and, in particular, provided by the first output shaft, can be introduced into the first transmission stage via the input, i.e., via the sun gear, of the first transmission stage, which is designed as the third planetary gear set. Furthermore, for example, the fourth torques, which are routed from the reduced coupling gear via the second output shaft and, in particular, provided by the second output shaft, can be introduced into the second transmission stage via the input, i.e., via the sun gear, of the second transmission stage, which is designed as the fourth planetary gear set. It has also proven advantageous if the respective additional planet carrier of the respective additional planetary gear set, i.e., of the respective transmission stage, is a respective output or driven element of the respective transmission stage.Thus, for example, the first gear stage, designed as the third planetary gear set, can provide fifth torques via its additional planet carrier, and therefore derive or dissipate fifth torques from itself, whereby, for example, the fifth torques result from the third torques that are or were introduced into the first gear stage, particularly via the additional sun gear of the first gear stage. Furthermore, for example, the second gear stage, designed as the fourth planetary gear set, can provide sixth torques via its additional planet carrier, and therefore derive or dissipate sixth torques from itself, whereby, for example, the sixth torques result from the fourth torques that are or were introduced into the second gear stage, particularly via the additional sun gear of the second gear stage.It has also proven advantageous if the respective additional ring gear of the respective transmission stage, designed as the third or fourth planetary gear set, is fixed to the housing, i.e., in particular permanently and rotationally fixed to the housing, wherein the housing is, for example, the housing element and / or the housing assembly. It has proven particularly advantageous when the reduced coupling gear takes on the function of a planetary differential, especially one with a torque vectoring function. The torque vectoring function is also referred to as a torque distribution function. Specifically, this means that the electric drive system, and thus the planetary coupling gear, is assigned to one of the axles and therefore to the wheels of that axle, so that the drive wheels can be driven by the electric motor via the planetary coupling gear.Since the planetary coupling gear preferably functions or is designed as a planetary differential gear, the planetary coupling gear allows, for example, different speeds of the drive wheels when the motor vehicle is cornering, in particular such that the outer drive wheel rotates or can rotate at a higher speed than the inner drive wheel. It is conceivable that a differential lock of the reduced linkage designed as a planetary differential gear can be represented by means of the locking switching element, so that preferably at least or exactly two arbitrary elements of the reduced linkage and / or shafts of the reduced linkage that are not yet rotationally fixed to each other can be frictionally connected to each other by means of the locking switching element. Also disclosed is a motor vehicle, preferably designed as a motor car, in particular the aforementioned motor vehicle, wherein the motor vehicle has an electric drive system according to the invention. Advantages and advantageous embodiments of the electric drive system are to be regarded as advantages and advantageous embodiments of the motor vehicle and vice versa. The invention is based in particular on the following findings and considerations: The driving performance of any road vehicle is influenced by its respective drive concept in two respects. First, the installed and available power is crucial for the vehicle's acceleration during straight-line driving. Furthermore, the distribution of torque to the drive wheels, particularly when cornering, and thus to the inner and outer drive wheels, can be decisive for the vehicle's lateral and longitudinal dynamics in distinct phases of cornering.Cornering is defined as any continuous change of direction with a certain yaw rate, which the vehicle cannot complete at its maximum speed and / or during which the full installed and available power cannot be transferred from the drive wheels to the road because their grip is significantly affected by the centrifugal forces accompanying the corner. Regarding torque distribution, it is known in the art that a symmetrical axle differential should be used, which, during straight-line driving, distributes the torque equally to both drive wheels of the axle (also referred to as the drive axle) and allows the drive wheels to rotate at different speeds according to the following principle:For example, if such a different speed distribution occurs during cornering, a differential gear can no longer distribute the torque symmetrically, equally, to the individual drive wheels. This is because the relative rotational movement in the bearings and gears of such a differential generates frictional torque, resulting in a slightly higher torque being sent to the slower drive wheel and a slightly lower torque to the faster drive wheel. The difference corresponds to the frictional torque of the differential. A good guideline for typical vehicle differentials is approximately 6 percent frictional torque. However, such an open axle differential proves disadvantageous under certain circumstances, which is why, according to the current state of the art, two different systems for improving cornering dynamics have become established: Differential locks, which selectively increase the internal frictional torque of the differential, thereby always supplying the slower wheel with a higher torque corresponding to the locking value, and torque vectoring, i.e., torque distribution, which can distribute torque almost arbitrarily, independent of the speed difference between the drive wheels of an axle. It is also known that a combination of both systems can create a setup which, provided the driver has sufficient control of the vehicle, allows cornering at the vehicle's physical limits.Within the scope of this disclosure, a functionally comparable and at least partially equivalent axle drive family is presented in two basic versions, each with a different focus on driving dynamics and / or efficiency. Specifically, these versions feature two drive units acting on a single drive axle, in the form of electric motors of any design. These motors are coupled to one another via a linkage transmission, jointly ensuring the axle drive and thereby enabling so-called actuator-less torque vectoring solely through the control of the electric motors. In particular, the reduced linkage transmission is used.In particular, the invention provides that, instead of a simple axle differential, a reduced linkage transmission is used, which is designed or can be considered a reduced linkage transmission and comprises the planetary gear sets, which are designed in particular as spur gear planetary gear sets and are also simply referred to as planetary gear sets. In particular, it is preferably provided that the first stationary gear ratio of the first planetary gear set is -2, and preferably that the second stationary gear ratio of the second planetary gear set is +2. As previously explained, in a first variant, it is preferably provided that the first element is the first sun gear, the fourth element the second sun gear, the third element the first ring gear, and the sixth element the second ring gear. In a second variant, for example, it is provided that the first element is the first ring gear, the fourth element the second ring gear, the third element the first sun gear, and the sixth element the second sun gear. Both variants combine two, preferably differently powered, motors in the form of electric machines to form an axle drive, particularly in the form of an electric drive system, which is capable of torque vectoring.The electric machines are also referred to as drive machines, whose coupling in both variants, i.e., in both cases, is achieved via the essentially same, reduced coupling mechanism, whereby the coupled elements of the planetary gear sets in both variants, i.e., in the first variant, the ring gear and in the second variant, the sun gear, can be, for example, the carrier. This allows for a very compact coupling mechanism in the form of the reduced coupling mechanism in both variants. By means of a suitable control strategy, both variants can be symmetrized, meaning that the total drive torque delivered by the drive axle remains constant across the entire range of symmetrical torque vectoring, regardless of the fact that the applied level of torque vectoring and the opposing slopes of the torques of the two wheel drives have the same magnitude. This symmetrization not only changes the torque provided by the second electric motor, but also, synchronously, that of the first electric motor. For this purpose, it proves particularly advantageous that the fixed gear ratios of the two planetary gear sets—that is, the first and second planetary gear sets of the reduced coupling mechanism—are of the same magnitude but opposite signs and thus antisymmetric.This antisymmetry of the fixed gear ratios means that changes in the torques of the two electric machines with respect to the degree of torque vectoring can occur linearly, in opposite directions, and with the same slope. The resulting different wheel torques also change linearly, symmetrically, and in opposite directions. Overall, the reduced coupling gear according to the invention thus provides a torque vectoring system that is particularly easy to control. Due to the described symmetrical behavior, the total output torque, i.e., the sum of the two wheel torques of the axle, can be kept constant in a simple manner, even while individual wheel torques are being selectively changed. The total output torque is approximately equal to the sum of the third and fourth torques. The third torques correspond approximately to one wheel torque, and the fourth torques to another. The fact that the total output torque remains constant during symmetrical torque vectoring is particularly noteworthy, as torque vectoring systems are primarily intended to improve the longitudinal and lateral dynamics of the vehicle. Therefore, it is advantageous in torque vectoring systems that the drive power also remains constant at a constant accelerator pedal position, thus making it easier for the driver to control the vehicle, regardless of the applied torque vectoring level.Naturally, the symmetrical torque vectoring of both presented variants can be combined with an ESP system that can be deactivated, possibly even in stages, to help prevent a loss of vehicle stability. Such an ESP system can then also reduce the drive power, but the torque vectoring itself should not. Both variants can achieve a higher level of symmetrical torque vectoring across a wider range than concepts that divide the same total installed power equally between two independent, non-mechanically coupled motors, each driving one wheel. When driving straight ahead at the differential point, with both drive wheels of the axle rotating at the same speed, both variants achieve the maximum possible mechanical efficiency of a drive axle in this operating state. This efficiency distributes torque proportionally between the two drive wheels without preventing speed differences between them, as the entire reduced coupling mechanism of both preferred variants rotates en bloc, i.e., as a single unit, in this driving condition. Therefore, no gear losses occur.Since a final axle ratio is advantageous for both variants shown in most applications, particularly in the form of gear ratio stages, both variants feature a so-called fast differential (rotating faster than the drive wheels). This is especially beneficial when the drive axles are equipped with a differential lock, as the differential lock can be dimensioned smaller because the effectively achieved locking effect of the drive wheels must be multiplied by the final axle ratio. The first variant, in particular, is a drive system designed for maximum achievable driving dynamics with a given installed power output. In this configuration, both drive motors, i.e., both electric motors, are active in all driving situations. The second variant, however, operates differently.The variable connection of the first electric motor allows the driver to choose between driving dynamics or efficiency-prioritizing driving programs. In particular, the efficiency mode offers more extensive benefits than could be achieved through software measures alone, because the second electric motor can, for example, be completely disconnected from the rest of the powertrain or drive system. Furthermore, due to their largely identical design, a modular drive system can be assembled from both presented variants. This system, with its many shared components, can cover a wide range of products with diverse characteristics, meeting a broad spectrum of user expectations. Both variants allow for so-called actuator-less torque vectoring (torque distribution). This is achieved, for example, simply by selectively controlling the two electric motors, thereby generating torque vectoring, i.e., torque distribution, particularly the distribution of torque to the drive wheels. Additionally, the second variant enables switching between three different drive system states: a torque vectoring mode, a boost mode, and an efficiency mode. This is accomplished using a single actuator, specifically a three-state actuator, which allows for the selection of these three states. Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. The features and combinations of features mentioned above in the description, as well as those mentioned below in the figure description and / or shown in the figures alone, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention. The drawing shows in: Fig. 1 a schematic representation of an embodiment of an electric drive system for a motor vehicle, in particular for a car, not falling under claim 1, Fig. 2 a schematic representation of an embodiment of the electric drive system according to the invention and Fig. 3 a diagram to describe an example of a torque vectoring method. In the figures, identical or functionally equivalent elements are provided with the same reference numerals. Fig. 1 shows a schematic representation of a first embodiment of an electric drive system 10 for a motor vehicle, in particular for a car, which does not fall under claim 1. Thus, the motor vehicle, which is also simply referred to as the vehicle, in its fully manufactured state comprises the electric drive system 10, by means of which the motor vehicle can be driven, in particular purely, electrically. The motor vehicle has at least or exactly two axles arranged consecutively in the longitudinal direction of the vehicle. Each axle has at least or exactly two wheels, also referred to as vehicle wheels, wherein the respective wheels of each axle are arranged on opposite sides of the motor vehicle in the transverse direction.For example, the drive system 10 is assigned to at least or exactly one of the axles, such that at least or only the wheels of the axle to which the electric drive system 10 is assigned can be driven by means of the electric drive system 10. The wheels that can be driven by means of the electric drive system 10 are also referred to as drive wheels. The drive wheels are shown schematically in Fig. 1 and are labelled 12 and 14. By driving the drive wheels 12 and 14 electrically, in particular purely electrically, by means of the drive system 10, the motor vehicle can be driven electrically, in particular purely electrically. The drive system 10 has a first electric machine 16, which has a first stator 18 and a first rotor 20. The rotor 20 can be driven by means of the stator 18 and thereby rotated about a first machine axis of rotation relative to the stator 18. The drive system 10 has a [missing information] as shown in Fig.Figure 1 shows a particularly schematic representation of a housing 22, which is also referred to as a housing assembly or housing element. The rotor 20 is rotatable about the first machine axis of rotation relative to the stator 18 and relative to the housing 22. The drive system 10 also includes a second electric machine 24, which has a second stator 26 and a second rotor 28. The rotor 28 can be driven by means of the stator 26 and thereby rotated about a second machine axis of rotation relative to the stator 26 and relative to the housing 22. In the first embodiment shown in Figure 1, the electric machines 16 and 24 are arranged coaxially to each other, so that their machine axes of rotation coincide. The electric machine 16 can provide first torques via its rotor 20, and the second electric machine 24 can provide second torques via its second rotor 28. The drive system 10 comprises a reduced coupling gear 30, which includes a first planetary gear set 32 ​​and a second planetary gear set 34. The reduced coupling gear 30 also includes a first input shaft 36, a second input shaft 38, a first output shaft 40, and a second output shaft 42. The first input shaft 36 is configured to transmit the first torques emanating from the first electric machine 16, i.e., those supplied by the electric machine 16 via the rotor 20 and thus by the rotor 20, into the reduced coupling gear 30. The second input shaft 38 is configured to transmit the second torques emanating from the second electric machine 24, i.e., those supplied by the electric machine 24 via the rotor 28 and thus by the rotor 28, into the reduced coupling gear 30.The first output shaft 40 is configured to transmit third torques M3, which result, for example, from the first torques M1 and / or second torques M2 introduced into the reduced coupling mechanism 30, from the reduced coupling mechanism 30. The second output shaft 42 is configured to transmit fourth torques M4, which result, for example, from the first torques M1 and / or second torques M2 introduced into the reduced coupling mechanism 30, from the reduced coupling mechanism 30. The first planetary gear set 32 ​​comprises a first sun gear 44 and a first planet carrier 46. The first planetary gear set 32 ​​also comprises a first ring gear 48. The second planetary gear set 34 comprises a second sun gear 49, a second planet carrier 50, and a second ring gear 52. In the first embodiment, the first sun gear 44 is a first element of the first planetary gear set 32. Furthermore, in the first embodiment, the sun gear 44, or the first element, is permanently connected to the first rotor 20 in a rotationally fixed manner. In the first embodiment, the first planet carrier 46 is a second element of the planetary gear set 32. In the first embodiment, the first planet carrier 46, or the second element, is permanently connected to the first output shaft 40 in a rotationally fixed manner. In the first embodiment, the first ring gear 48 of the first planetary gear set 32 ​​is a third element of the first planetary gear set 32.In the first embodiment, the first ring gear 48 or the third element is permanently connected to the second output shaft 42 in a rotationally fixed manner. In the first embodiment, the second sun gear 49 of the second planet gear set 34 is a fourth element. In the first embodiment, the sun gear 49, or the fourth element, is permanently connected to the second rotor 28 in a rotationally fixed manner. In the first embodiment, the second planet carrier 50 is a fifth element. In the first embodiment, the planet carrier 50, or the fifth element, is permanently connected to the planet carrier 46, or to the second element, in a rotationally fixed manner. In the first embodiment, the second ring gear 52 is a sixth element. In the first embodiment, the second ring gear 52, or the sixth element, is permanently connected to the first ring gear 48 (third element) in a rotationally fixed manner. Furthermore, in the first embodiment, the first planetary gear set 32 ​​has a first stationary gear ratio, and the second planetary gear set 34 has a second stationary gear ratio. The stationary gear ratios have the same absolute value. However, the stationary gear ratios have opposite or different mathematical signs. For example, in the first embodiment, the first stationary gear ratio of the first planetary gear set 32 ​​is -2. Consequently, in the first embodiment, the second stationary gear ratio of the second planetary gear set 34 is +2. In the first embodiment, the first planet carrier 46 is designed as a single planet carrier on which first planet gears 54 are rotatably mounted. The respective first planet gear 54 meshes, for example, and in particular simultaneously, with the first sun gear 44 and with the first ring gear 48. In the first embodiment, the second planet carrier 50 is designed, for example, as a double planet carrier on which second planet gears 56 and third planet gears 58 are rotatably mounted. It is conceivable, for example, that the second planet gears 56 engage with the sun gear 49 and with the third planet gears 58, and it is conceivable that the third planet gears 58 engage with the ring gear 52 and with the second planet gears 56, but not with the sun gear 49.Thus, for example, the sun gear 49 meshes with the planet gears 56, and the planet gears 58 mesh with the ring gear 52, with, for example, the planet gears 56 and 58 meshing with each other. Furthermore, the planet gears 56 do not mesh with the ring gear 52, and the planet gears 58 do not mesh with the sun gear 49. In addition, the first planet gears 54 are designed separately from the second planet gears 56 and separately from the third planet gears 58. Preferably, the third element of the first planet gear set 32 ​​and the sixth element of the second planet gear set 34 have the same tooth diameters, in particular the same pitch circle diameters. Preferably, the third element and the sixth element also each have the same number of teeth. In the first embodiment, the third element is the ring gear 48, and the sixth element is the ring gear 52. The electric drive system 10 has a first transmission stage 60, which is located in the first torque flow and downstream of the first output shaft 40, along which the third torques M3 can be transmitted from the reduced coupling gear 30 via the first output shaft 40. For example, a first side shaft 62 is located in the first torque flow and downstream of the first transmission stage 60. The side shaft 62 can be driven by the output shaft 40 via the first transmission stage 60, whereby the drive wheel 12 can be driven by the side shaft 62 and thus, via the side shaft 62, by the transmission stage 60.The drive system 10 also comprises a second transmission stage 64, which is arranged in the second torque flow and downstream of the second output shaft 42, along which the fourth torques M4 can be transmitted from the reduced coupling gear 30 via the second output shaft 42. A second side shaft 66 is arranged downstream of the transmission stage 64 in the second torque flow, and the drive wheel 14 can be driven by the transmission stage 64 via the side shaft 66. Furthermore, the side shaft 66 can be driven by the output shaft 42 via the transmission stage 64. Consequently, the side shaft 62 can be driven by the output shaft 40 via the transmission stage 60. Preferably, the transmission stage 60 is a third planetary gear set, although it is conceivable that the transmission stage 64 is a fourth planetary gear set.Preferably, the third planetary gear set and the fourth planetary gear set are identical in construction, that is, identical or the same with regard to their design and thus, in particular, with regard to their gear ratio. Preferably the third planetary gear set and the fourth planetary gear set are arranged coaxially to the reduced coupling gear 30. It has proven particularly advantageous to arrange the transmission stages 60 and 64, the planetary gear sets 32 and 34, and the rotors 20 and 28 in the common housing 22 of the electric drive system 10. In the first embodiment, it is also provided that the reduced coupling gear 30, the rotors 20 and 28, and the two transmission stages 60 and 64 are arranged coaxially to one another. In the first embodiment, the drive system 10 optionally includes a locking switching element VS, which, since it is optional, can be omitted. The locking switching element VS allows the planet carrier 46 and the ring gear 48 of the planetary gear set 32 ​​to be positively connected to one another. Thus, the locking switching element VS can be used to provide a differential lock for the reduced coupling gear 30, which is designed or functions as a planetary differential gear. Fig. 2 shows a schematic representation of a second embodiment of the drive system 10 according to the invention. In the second embodiment, the first ring gear 48 of the first planetary gear set 32 ​​is the first element. In the second embodiment, the ring gear 48, or the first element, can be connected to the first rotor 20 of the first electric machine 16. For this purpose, a first switching element S1 is provided, by means of which the first ring gear 48, or the first element, can be connected to the rotor 20 in a rotationally fixed manner. In the second embodiment, the first planet carrier 46 of the first planetary gear set 32 ​​is the second element. In the second embodiment, the planet carrier 46, or the second element, is connected, in particular permanently, to the first output shaft 40 in a rotationally fixed manner. In the second embodiment, the first sun gear 44 of the first planetary gear set 32 ​​is the third element.In the second embodiment, the sun gear 44 or the third element is permanently connected to the second output shaft 42 in a rotationally fixed manner. In the second embodiment, the second ring gear 52 of the second planet gear set 34 is the fourth element. In the second embodiment, the second ring gear 52, or the fourth element, is permanently connected to the second rotor 28 in a rotationally fixed manner. In the second embodiment, the second planet carrier 50 of the second planet gear set 34 is the fifth element. In the second embodiment, the planet carrier 50, or the fifth element, is permanently connected to the planet carrier 46 (second element) in a rotationally fixed manner. In the second embodiment, the second sun gear 49 of the second planet gear set 34 is the sixth element. In the second embodiment, the second sun gear 49, or the sixth element, is permanently connected to the sun gear 44, or to the third element, in a rotationally fixed manner.In the second embodiment, the drive system 10 has a second switching element S2 by means of which the first rotor 20 of the first electric machine 16 is connected to the second ring gear 52 in a rotationally fixed manner. In particular, for example, the first input shaft 36 is connected to the rotor 20 in a rotationally fixed manner, especially permanently. Alternatively or additionally, for example, the input shaft 38 is connected to the rotor 28 in a rotationally fixed manner, especially permanently. In the second embodiment, the electric drive system 10 has the locking switching element VS, which is optional and can therefore be omitted. By means of the locking switching element VS, the sun gear 44 and the planet carrier 46 of the first planet gear set 32 ​​can be positively connected to each other in the second embodiment, so that a differential lock of the reduced coupling gear 30 can also be represented in the second embodiment by means of the locking switching element VS. In the first embodiment, for example, the planet gear sets 32 and 34, which are designed in particular as spur gear planetary stages, have a common web, in particular because the planet carriers 46 and 50 are permanently and rotationally fixedly connected to one another. Furthermore, in the first embodiment, the planet gear sets 32 and 34 have, so to speak, a common ring gear, since the ring gears 48 and 52 are permanently and rotationally fixedly connected to one another. The sun gear 49 can be driven by the electric machine 24, and the sun gear 44 can be driven by the electric machine 16. The type of electric machines 16 and 24, which can be operated or function as motors or electric motors, is irrelevant.Outputs to the two drive wheels 12 and 14 are provided via the common link of the reduced coupling gear 30 (designed as a reduced coupling gear) for drive wheel 12 and via the common ring gear for drive wheel 14. This allows for a particularly advantageous, very compact design of the reduced coupling gear, since none of the planetary gear sets 32 and 34 (also referred to as planetary sets) are enclosed by a shaft, enabling all connections to be made directly via the shortest possible path. A reduced coupling gear designed in this way allows the total torque of the two motors to be distributed in different proportions to the side shafts 62 and 66 of the two drive wheels 12 and 14, which are designed as drive shafts, when the applied drive torque of the electric motors 16 and / or 24 is changed.Assuming that one of the electric machines 16 and 24 is more powerful than the other electric machine 24 or 16, and thus a more powerful main drive machine, then, for example, the distribution of the drive torques to the two wheels (drive wheels 12 and 14) of the axle can be changed by modulating the drive torque of the other electric machine 24 or 16. The other electric machine 24 or 16 is therefore also referred to as an auxiliary machine or auxiliary drive machine. For example, the main drive motor is initially operated at a constant 50 percent of its peak torque, specifically under the assumption that the main drive motor reaches 100 percent peak torque. It is also assumed, for example, that the auxiliary drive motor delivers 50 percent of the main drive motor's peak torque without any throttling. Now, with the main drive motor maintaining a constant torque, the auxiliary drive motor's torque is gradually throttled or increased. This allows the drive torque acting on the respective drive wheels 12 and 14 to be changed in either direction.If this is represented in a diagram using two straight lines intersecting at a point, this point is the so-called differential point. At this point, the total output torque is distributed equally between the drive wheels 12 and 14, also referred to as outputs. When driving straight ahead, the reduced coupling gear rotates within the unit and acts like a symmetrical differential. It should be noted that torque distributions to the outputs may occur independently of the wheel speeds, solely due to the different torques of the electric motors 16 and 24 driving the reduced coupling gear. This enables targeted torque vectoring. Against this background, a so-called symmetrization is advantageous. This involves not only changing the torque provided by the auxiliary drive motor, but also, synchronously, that of the main drive motor. For this purpose, it proves particularly advantageous that the fixed gear ratios of the two coupled planetary gear sets 32 and 34 are antisymmetric, meaning they have the same absolute value but opposite mathematical signs. Therefore, the changes in the torques of the two electric motors 16 and 24 can be made in opposite directions with the same slope (positive for one of the electric motors 16 and 24, and negative for the other electric motor 24 or 16). Consequently, the total torque transmitted to the axle remains constant across the entire range of variation of the torques of the electric motors 16 and 24, which are also referred to as drive torques. Fig. 3 shows a diagram describing an example of a torque vectoring method with a symmetrical control method for the electric drive system 10 according to the invention, for the variant shown in Fig. 1. In the diagram of Fig. 3, the ordinate represents a percentage torque M, based on a total drive torque or a total output torque Mges, during torque vectoring operation. The abscissa represents a percentage extent of torque vectoring TV. +100% TV means, for example, that 100% of the total drive torque applied during the torque vectoring process is directed to the right wheel, while -100% TV means that 100% of the total drive torque applied during the torque vectoring process is directed to the left wheel. At the start of an application of the method, for example, a torque distribution between both drive wheels (TV = 0%) can be assumed. In this initial state, the third torques M3 and the fourth torques M4 each amount to 50% of the instantaneous total drive torque. Figure 3 shows that in this initial state with TV = 0%, the first torques M1 and the second torques M2 are not equal. The first torques M1 amount to approximately 63%, and the second torques to approximately 37%. If torque vectoring behavior, i.e., an unequal distribution of the total drive torque between the two wheels, is desired, this can be achieved by increasing the first torques M1 by a certain amount and decreasing the second torques M2 by the same amount.The electric drive system 10 according to the invention is designed such that, when this method is applied, the third torques M3 and the fourth torques M4 each change by the same amount, but with opposite signs, thus ensuring that the total output torque Mges remains constant, which is essential for the drivability of the motor vehicle. The total output torque Mges is approximately, namely, neglecting friction losses, the sum of the third torques and the fourth torques, as well as the sum of the first torques M1 and the second torques M2. Thus, for the purpose of torque vectoring, to adjust a torque difference between the third torques M3 and the fourth torques M4, starting from an equality of torques between the third torques and the fourth torques (at TV = 0), the first torques M1 and the second torques M2 are each changed simultaneously, whereby the first torques M1 and the second torques M2 are each changed by the same amount, but with opposite signs. Such behavior of the drive system is advantageous, or rather essential for a driver, since the driver expects constant drive power with a constant accelerator pedal position, regardless of the resulting degree of torque vectoring. As a further, decidedly positive effect of symmetrizing the behavior of the axle drive, the slopes of the lines shown in the diagram of Fig. 3 for the third torques M3 and the fourth torques M4, as well as for the first torques M1 and the second torques M2, are in opposite directions. This significantly simplifies the control of the drive's behavior. It should also be noted that the differential point shifts due to the symmetrization. Furthermore, it is advantageous that when driving straight ahead, at the differential point—the operating point of the drive where the same drive torque is applied to the outputs—the electric motors 16 and 24 operate with different torques. Therefore, it can prove beneficial to integrate electric motors 16 and 24 with different power ratings into the drive system. Any question regarding the most suitable combination of performance characteristics, particularly assuming the main drive motor's performance is always considered to be 100 percent regardless of its nominal value, can be most easily answered by considering cornering. The basis for this is the so-called Kamm circle, which, in the case of modern tires, is an ellipse. This graphical representation illustrates the relationship between a tire's ability to absorb longitudinal and lateral forces based on its grip. For a given tire on a given road surface, the Kamm circle scales linearly with the tire's vertical contact force, especially when the tire pressure is adjusted. The tire can only be loaded up to the respective elliptical contour; beyond this point, the tire loses grip.At high driving forces, the resulting high slip means that only minimal lateral forces can be transmitted, and at low slip angles, these forces remain within the slip limit, whose envelope is represented by the Kamm circle. Similarly, at high centrifugal forces, which place considerable demands on the tire's lateral grip at high slip angles, only minimal driving forces can be reliably transmitted. The physical limiting speed of a vehicle through a curve is influenced by many other vehicle parameters, but it can be determined with sufficient approximation by the point at which, after absorbing the centrifugal forces induced by cornering, the tires can still compensate for the equivalent of the driving resistances to prevent the vehicle from slowing down, thus maintaining a quasi-steady cornering position.When exiting a curve, with a progressively reduced steering angle, centrifugal forces decrease, while the lateral grip required for transmitting drive force increases as lateral grip diminishes. The curve radius increases continuously, allowing for increasingly strong acceleration. Therefore, if the goal is to enhance both the longitudinal and lateral components of vehicle dynamics, a high degree of torque vectoring can be effectively implemented at low power outputs during quasi-stationary cornering with low drive torques. However, with increasing power output, a progressively lower degree of torque vectoring is still sufficient to meaningfully improve vehicle dynamics in most applications.However, driving situations can arise, for example on a handling course, which are often used for spectacular vehicle tests, where even with high power outputs a high degree of torque vectoring can still be useful. The determination of the limit up to which sufficient torque vectoring should be enabled can also be used to determine the still reasonable ratio of the power outputs of the electric motors 16 and 24. It has been found that a power output of approximately 63 percent of the power output of the auxiliary motor is ideal with regard to overall efficiency and performance. Even with a high utilization of the drive capacity of the electric motors 16 and 24 configured in such a way that they are operated at 94 percent of the maximum total drive torque of both motors, a level of 33.33 percent of the output drive torque, considered sufficient, can still be provided as symmetrical torque vectoring.This amount is limited by the torque capacity of the main drive motor, which, for example, cannot further increase the drive torques beyond a certain point and therefore marks the limit of symmetrical torque vectoring. Beyond this point, torque vectoring may be possible, but it will no longer be symmetrical. It follows that it can be advantageous if the auxiliary drive motor has a torque capacity of 63 percent relative to the torque capacity of the main drive motor. For example, with total drive torques lower than the aforementioned 94 percent, torque vectoring of up to 100 percent of the drive torque delivered by the two electric motors 16 and 24 is possible in a wide range using the first embodiment; that is, the entire delivered drive torque can be directed to any single wheel of the axle. The first embodiment, by coupling the two drive machines (electric machines 16 and 24), can offer a more extensive, symmetrical torque vectoring capability than can be guaranteed with an arrangement of two machines acting independently on one wheel each, even with the power output of the main drive machine. This is because the ability of two identical electric machines, each acting independently on one wheel, to utilize 100 percent of the delivered torque as torque vectoring inevitably ends at the 50 percent combined drive torque of both machines. This means, among other things, that if torque vectoring behavior, which, for example, accounts for approximately half of the yaw moment around the vehicle's vertical axis during cornering, is to be maintained until the end of the corner, the first variant of the drive according to the invention only requires a maximum reduction of 6% in the sum of the torque of both motors. This reduction is then reduced progressively less as the corner radius increases, ensuring that a sufficient level of torque vectoring can be maintained even into straight-line driving. This is particularly important because it prevents significant understeer of the vehicle should the torque vectoring level drop during cornering. This provides an advantage over torque vectoring drives with individual wheel motors, which require a torque reduction of approximately 17% to achieve comparable cornering behavior. As a further criterion for the suitability of the 100 percent / 63 percent ratio of electric machines 16 and 24, the torque output of such a drive during acceleration at the differential point while driving straight ahead can also be considered. For example, the main drive machine is ramped up from 0 percent to 100 percent, while the auxiliary drive machine, to remain at the differential point at all times, ramps up from 0 percent to 60 percent. Thus, their combined output reaches 160 percent of the main drive machine's capacity, which is 98.16 percent of the total installed power output of electric machines 16 and 24 (100 + 63 = 163 percent of the main drive machine's). Considering the enhanced torque vectoring capabilities of this drive, this can be considered quite acceptable. Therefore, the first embodiment proves to be quite suitable for high-performance vehicles.Therefore, it seems appropriate to provide a differential lock, or the aforementioned differential lock, in addition to the torque vectoring capabilities to ensure cornering ability right up to the physical limit. This is especially true because, thanks to the favorable arrangement, it can be easily integrated, as can be seen in Figures 1 and 2. Such a differential lock is also particularly compact and lightweight because, in most applications, an axle ratio can be incorporated at the two outputs, which multiplies the effective locking effect of the differential lock's coupling. This is another particularly advantageous feature of the electric drive system 10. It should also be noted that the described drive system 10, in its two shown variants, behaves in a mirror-symmetric manner with respect to the sign of the torques (M1 to M4). If drive torques are designated as positive and thrust torques as negative, then the behavior of both described variants of the drive system 10 is mirror-symmetric in drive and overrun modes. It follows that the behavior of the electric drive system 10, which is present for torque vectoring during drive operation, can be transferred in a mirror-symmetric manner to overrun mode. As a result, the thrust torques M3 and M4 yield thrust torques according to the same principle as thrust torques M1 and M2 in drive operation, which can be used for recuperating electrical energy and thus for charging the vehicle battery.Of particular note is the possibility of adjusting the amount of recuperated energy at each individual wheel, analogous to the torque vectoring described above, solely by controlling the recuperation level of the two electric motors. This also opens up extensive possibilities for designing electric anti-lock braking system (eABS) and electronic stability program (ESP) functions to improve driving stability. Thus, an electric anti-lock braking system (eABS) and / or an electronic stability program (eESP) for the vehicle in critical driving situations can be implemented solely through the electronic control of the electric motors.The significantly higher clock frequency that the eABS and eESP systems can achieve via the vehicles' hydraulic-mechanical braking system, compared to their classic, state-of-the-art counterparts, proves to be particularly advantageous for the driving feel and the drivability of the vehicle. In the first embodiment of the electric drive system 10, which is also referred to as axle drive, with the two electric machines 16 and 24 designed or functioning as driving machines and connected or connectable to each other via the reduced coupling gear 30, a simultaneous drive of the electric machines 16 and 24 can be provided in at least almost any driving condition. The second embodiment allows one of the drive units to be switched off in driving situations where only a fraction of the installed power is required, such as in city traffic, and the other drive unit to operate in normal differential mode. In the second embodiment, the planetary gear sets 32 and 34, preferably designed as spur gear planetary stages, have the aforementioned common web, since the planet carriers 46 and 50 are permanently and rotationally fixed to one another. In the second embodiment, the planetary gear sets 32 and 34 have a common sun gear, since the sun gears 44 and 49 are permanently and rotationally fixed to one another. It is particularly conceivable that the planet carriers 46 and 50 are formed integrally. Alternatively or additionally, the sun gears 44 and 49 can be formed integrally, particularly in the second embodiment.With regard to the first embodiment, it is conceivable that the ring gears 48 and 52 are formed integrally. In the second embodiment, the ring gear 52 can be driven by the electric machine 24. The electric machine 16 can selectively drive either the ring gear 52 or the ring gear 48. In particular, to enable symmetrical torque vectoring, the ring gear 48 can be driven by the electric machine 16. A special feature of the second embodiment is that the electric machine 16, in particular its rotor 20, can be selectively connected to either the ring gear 48 or the ring gear 52 in a rotationally fixed manner by means of the switching elements S1 and S2. In particular, the switching elements S1 and S2 are formed by a three-state actuator or a three-state switching element, in particular of any design. Preferably, the switching element S1 and / or S2 is designed as a positive-locking switching element, in particular as a jaw coupling.In other words, it is conceivable that the first switching element S1 and / or the second switching element S2 are designed as a jaw coupling or as a positive-lock coupling, i.e., as a positive-locking switching element. Thus, for example, the rotor 20 can be connected to the ring gear 48 or to the ring gear 52, particularly in a positive-locking manner, by means of the switching elements S1 and S2. It is also conceivable that the switching element S1 and / or S2 are designed as a friction-locking switching element, i.e., for example, as a multi-plate clutch or friction-lock coupling. In particular, in a switching state where the ring gear 48 is rotationally fixed to the rotor 20 by means of the switching element S1, a torque-vectoring state results for the electric drive system 10, which functions or is designed as an axle drive. In another switching state, the rotor 20 is rotationally fixed to the ring gear 52 by means of the switching element S1, resulting in a so-called boost state of the axle drive by simply summing the power outputs of the two electric machines 16 and 24. The boost state is also referred to as an acceleration state or support state.In the boost state, the planetary gear set 34, which is preferably configured as a positive planetary stage (since, for example, the second stationary gear ratio is positive and the first stationary gear ratio is negative), operates like a symmetrical axle differential, with the planetary gear set 32, also referred to as the negative planetary gear set, being uninvolved in this case. Finally, the electric machine 16 can be completely decoupled from the reduced coupling gear 30, particularly in a third switching state. In other words, if the switching element S1 is in its coupled state while the switching element S2 is in its decoupling state, the rotor 20 is rotationally fixed to the ring gear 48 by means of the switching element S1. If the switching element S2 is in its coupled state while the switching element S1 is in its decoupling state, the rotor 20 is rotationally fixed to the ring gear 52 by means of the switching element S2.If the switching elements S1 and S2 are in their decoupling states, particularly simultaneously, the rotor 20 is decoupled from both the ring gear 48 and the ring gear 52, so that the electric machine 16 is, in particular, completely decoupled from the reduced coupling gear 30. It is preferably provided that the switching elements S1 and S2 comprise a common switching part which is movable, particularly relative to the housing 22, between a first switching position, a second switching position, and a third switching position. For example, the switching part is movable translationally or rotationally between the switching positions relative to the housing 22. In the first switching position, for example, the switching element S1 is in its coupled state, while the switching element S2 is in its decoupling state.In the second switching position, for example, switching element S2 is in its coupled state, while switching element S1 is in its decoupled state. In the third switching position, for example, switching elements S1 and S2 are in their decoupled states, particularly simultaneously. If the electric machine 16 is completely decoupled from the reduced coupling gear 30, the other electric machine 24 is active on its own, thus opening up efficiency potential in the range of low power demands. The outputs to the two drive wheels 12 and 14 of the drive axle are provided via the common web of the reduced coupling gear for drive wheel 14 and via the common sun gear for drive wheel 12. This allows for an advantageous, compact design of the reduced coupling gear. The three different operating modes of the second embodiment are described below.One of the operating modes is a torque-vectoring mode, in which, for example, the switching element is in its first switching position, meaning that switching element S1 is in its coupled state and switching element S2 is in its decoupling state. For the torque-vectoring mode, the electric machine 16 is thus rotationally fixed to the ring gear 48. This results in a corresponding behavior when the output torque of the electric machine 16 changes from the initially identical and opposite torque of the electric machine 24, past the zero point, to the same but opposite torque, regardless of its actual power output.For this purpose, the electric machine 24 is operated, for example, at a constant 50 percent of its capacity. The electric machine 16 is continuously varied, for example, through iterative steps from the same torque in the same direction to the same torque in the opposite direction. This results in corresponding, opposing torque curves at the outputs of the axle drive, i.e., at the drive wheels 12 and 14, and their sum constitutes the total output torque of the drive. As in the first embodiment, the slopes of the two outputs, or rather the respective straight lines representing the torques of all outputs, have different gradients, and the total torque corresponds solely to the differential point, at the zero crossing of the torque output by the electric machine 16, which is the actual target output of 50 percent torque of the electric machine 24. This may be undesirable in some cases.Therefore, the second embodiment also uses a method for symmetrizing the axle drive, which is slightly different but achieves the same goal: a constant total output torque across the entire possible torque-vectoring range, as well as equal and opposite slopes of the output torques. The different approaches, each achieving the same result of complete symmetrization, are both possible and advantageous. When driving straight ahead at the differential point, the electric motor 16 runs at axle speed; when driving around a curve at the differential point, it runs at a speed dependent on the differential speed of the drive wheels 12 and 14, in each case without load. Thus, with this initial state, symmetrical torque vectoring of still 29.33 percent of that achieved by the electric motor 24 alone in this state at its 87 percent torque utilization can be achieved, which is advantageous.The limit of symmetrical torque vectoring is reached at full load of the electric machine 24. The torque of the torque-reduced drive reverses after passing through zero. A negative torque, directed against the direction of travel, is present, which may not be desirable for road vehicles in typical driving situations. Therefore, the range exceeding 100 percent resulting from this torque reversal can be ignored. The second embodiment can also utilize a wider, symmetrical torque-vectoring range than would be possible with the use of two motors equivalent to the electric machine 24, each independently driving one of the two drive wheels 12 and 14 of the axle. The rationale is the same as the previous one.To reduce the energy consumption of the electric machine 16, which is roughly equivalent to its internal losses and bearing friction in all driving situations where torque vectoring is neither desired nor expected, the electric machine 16 can be switched off by deactivating the switching element S1 or S2, which couples the electric machine 16 to the ring gear 48 for torque vectoring mode. This effectively shuts down the electric machine 16. As a result, the second embodiment can be operated in a particularly efficient mode using only the electric machine 24.If driving conditions are to be covered in which the power of the electric machine 24 is considered insufficient, the additional power of the electric machine 16 can be used together with the electric machine 24 in the so-called boost mode or boost operation by switching the electric machine 16 to the ring gear 52 using the switching element S1 or S2. In order to utilize a symmetrical torque vectoring that is considered sufficient in the second embodiment, it is advantageous if the first electric machine 16 can achieve at least approximately 15 to 20 percent of the torque capacity of the second electric machine 24, i.e., the main drive machine. However, the final design of the power output of the first electric machine 16 can exceed this as desired if a higher boost power is required. This makes the second embodiment particularly versatile.High driving dynamics can be achieved through the alternating operation of the arrangement in torque-vectoring and boost modes. Therefore, it is also recommended to provide a differential lock for this second embodiment. The advantages listed at the beginning and in the discussion of the first embodiment also largely apply to this second embodiment. Furthermore, it can also be noted that when the drive is operated in boost mode with the combined power of electric motors 16 and 24, or with electric motor 24 alone, the axle drive is via an open differential, the capabilities of which are known to be enhanced by a locking differential. This also demonstrates that when electric motor 16 is decoupled from the reduced coupling gear 30, the vehicle can be operated particularly efficiently at lower power output. This condition underscores the exceptionally wide conversion capability of the axle drive. Reference symbol list 10 Drive system 12 Drive wheel 14 Drive wheel 16 First electric machine 18 First stator 20 First rotor 22 Housing 24 Second electric machine 26 Second stator 28 Second rotor 30 Reduced coupling gear 32 First planetary gear set 34 Second planetary gear set 36 First input shaft 38 Second input shaft 40 First output shaft 42 Second output shaft 44 First sun gear 46 First planet carrier 48 First ring gear 49 Second sun gear 50 Second planet carrier 52 Second ring gear 54 First planet gear 56 Second planet gear 58 Third planet gear 60 First transmission stage 62 First side shaft 64 Second transmission stage 66 Second side shaft M Torque component M1 First torques M2 Second torques M3 Third torques M4 Fourth torques Mtotal output torque TV Torque vectoring extent S1 Switching element S2 Switching element VS Interlocking switching element

Claims

Electric drive system (10) for a motor vehicle, comprising a first electric machine (16) with a first rotor (20), a second electric machine (24) with a second rotor (28), and a reduced coupling gear (30) comprising a first planetary gear set (32), a second planetary gear set (34), a first input shaft (36), a second input shaft (38), a first output shaft (40), and a second output shaft (42), wherein: - the first input shaft (36) is configured to transmit first torques (M1) emanating from the first electric machine (16) into the reduced coupling gear (30), - the second input shaft (38) is configured to transmit second torques (M2) emanating from the second electric machine (24) into the reduced coupling gear (30), - the first output shaft (40) is configured to transmit third torques (M3) from the reduced coupling gear (30),- the second output shaft (42) is configured to transmit fourth torques (M4) from the reduced coupling gear (30), - the first planetary gear set (32) has a first element that is rotationally fixed to or connectable with the first rotor (20), a second element that is rotationally fixed to the first output shaft (40), and a third element that is rotationally fixed to the second output shaft (42), - the second planetary gear set (34) has a fourth element that is rotationally fixed to the second rotor (28) and a fifth element that is rotationally fixed to the second element, wherein: - the second planetary gear set (34) has a sixth element that is rotationally fixed to the third element, and - a first stationary gear ratio of the first planetary gear set (32) has the same magnitude and an opposite sign compared to a second stationary gear ratio of the second planetary gear set (34), characterized in thatthat: - the first element of the first planetary gear set (32) is designed as a first ring gear (48), - the fourth element of the second planetary gear set (34) is designed as a second ring gear (52), - the third element of the first planetary gear set (32) is designed as a first sun gear (44), and - the sixth element of the second planetary gear set (34) is designed as a second sun gear (49). Electric drive system (10) according to claim 1, characterized in that: - the second element of the first planet gear set (32) is designed as a first planet carrier (46) in the form of a single planet carrier with first planet gears (54), - the fifth element of the second planet gear set (34) is designed as a second planet carrier (50) in the form of a double planet carrier with second planet gears (56) and third planet gears (58), and - the first planet gears (54) are designed separately from the second planet gears (56) and separately from the third planet gears (58). Electric drive system (10) according to claim 1 or 2, characterized in that the third element of the first planetary gear set (32) and the sixth element of the second planetary gear set (34) have the same tooth diameters and the same number of teeth. An electric drive system (10) according to one of the preceding claims, characterized by: - ​​a first transmission stage (60), which, with respect to a first torque flow along which the third torques (M3) are to be transmitted via the first output shaft (40) from the reduced coupling gear (30), is arranged in the first torque flow downstream of the first output shaft (40), and - a second transmission stage (64), which, with respect to a second torque flow along which the fourth torques (M4) are to be transmitted via the second output shaft (42) from the reduced coupling gear (30), is arranged in the second torque flow downstream of the second output shaft (42), wherein the first transmission stage (60), the second transmission stage (64), the reduced coupling gear (30) and the rotors (20, 28) are arranged in a common housing (22) of the electric drive system (10). Electric drive system (10) according to claim 4, characterized in that the reduced coupling gear (30), the two rotors (20, 28) and the two transmission stages (60, 64) are arranged coaxially to each other. Electric drive system (10) according to one of the preceding claims, characterized in that the reduced coupling gear (30) has exactly two planet gear sets (32, 34), namely the first planet gear set (32) and the second planet gear set (34). Electric drive system (10) according to claim 1, characterized by: - ​​a first switching element (S1) which is configured to connect the first rotor (20) to the first ring gear (48) in a rotationally fixed manner, and - a second switching element (S2) which is configured to connect the first rotor (20) to the second ring gear (52) in a rotationally fixed manner Electric drive system (10) according to one of the preceding claims, characterized by a locking switching element (VS) which is designed to connect two of the elements of the reduced coupling gear (30) to each other in a force-locking manner. Torque vectoring method for controlling an electric drive system (10) according to one of claims 1 to 8, characterized in that, to adjust a torque difference between the third torques (M3) and the fourth torques (M4), starting from an equality of torques of the third torques (M3) and the fourth torques (M4), the first torques (M1) and the second torques M(2) are changed simultaneously, wherein the first torques (M1) and the second torques (M2) are each changed by the same amount, but with opposite signs.

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