Electric transmission with two switching elements

Abstract

The present invention relates to a transmission (18) for a motor vehicle drive train (12) of a motor vehicle (10), comprising: a first transmission input shaft (24) for operatively connecting the transmission (18) to a first drive engine (14) of the motor vehicle (10); a second transmission input shaft (26) for operatively connecting the transmission (18) to a second drive engine (16) of the motor vehicle (10); an output shaft (28) with an output (30); spur gear pairs (ST1, ST2, ST3, ST4) arranged in several gear set planes for forming gear ratios; and at least two gearshift devices with shifting elements (SE1, SE2) for engaging the gear ratios, wherein the output shaft (28) is arranged axially parallel to the first transmission input shaft (24) and / or to the second transmission input shaft (26); the first transmission input shaft (24) is an input shaft for a first partial transmission; the second transmission input shaft (26) is an input shaft for a second partial transmission;and all gear stages of the transmission (18) are usable for the first drive motor (14) and the second drive motor (16). The present invention further relates to a motor vehicle drive train (12) with such an electric transmission, a method for operating a motor vehicle drive train (12), and a motor vehicle.

Description

[0001] The present invention relates to a transmission, in particular an electric transmission, a motor vehicle drive train, a method for operating a motor vehicle drive train and a motor vehicle.

[0002] Spur gears have the advantage of a relatively simple design, as they use few moving parts and the externally toothed spur gears are comparatively easy to manufacture. A disadvantage is the small gear ratio that can be achieved in a single stage. In addition, a spur gear is larger and therefore heavier than, for example, a planetary gear with the same transmission power. To achieve large gear ratios with a pair of spur gears, the circumference of at least one gear is kept small, while the circumference of the second gear is kept large. The contact ratio, i.e. the number of meshing teeth, becomes smaller the smaller at least one of the meshing gears is. It is therefore important to ensure that the individual teeth always mesh.

[0003] Vehicles are increasingly being equipped with purely electric drives, i.e. with an electric prime mover as the power source. Electric drives can contribute to reducing pollutant emissions because the electrical energy can be generated in a way that is at least partially CO2-neutral. Drivetrains with an electric prime mover and a simple one- or two-speed gearbox have largely become the norm. Very high speed ranges can be covered, for example, when electric prime movers are used, electric prime movers are known to reach up to 15,000 or 20,000 revolutions per minute. The gearboxes are subjected to enormous stresses in this case. However, due to the high speed range, gearboxes with just a few gears are usually sufficient to cover the speed range of an electric vehicle, especially an electric passenger car.On the one hand, it is known to use powerful, heavy, and large electric motors as prime movers capable of generating high torque. It is also known to use smaller, high-speed electric motors that are reduced by a gearbox or a simple input gear. This allows for the creation of a weight-efficient automotive drivetrain.

[0004] One advantage of all-electric drives is that the high speed range requires only a few gear ratios in a transmission, allowing for comparatively simple transmissions. This leads to a loss of driving comfort, as high speeds are generally perceived as unpleasant. Furthermore, shifting comfort is reduced with simple transmissions. For cost and weight reasons, non-powershift transmissions are therefore usually used, resulting in a loss of drive power during gear changes in such a simple transmission.

[0005] Against this backdrop, a specialist faces the task of creating a cost-effective transmission, preferably for an electric drive. In particular, the goal is to achieve high transmission efficiency while maintaining technically simple operation.

[0006] This task is solved by a transmission for a motor vehicle drive train of a motor vehicle, with a first transmission input shaft for operatively connecting the transmission to a first drive engine of the motor vehicle; a second transmission input shaft for operatively connecting the transmission to a second drive engine of the motor vehicle; an output shaft with preferably a single output; spur gear pairs arranged in several gear set levels to form gear steps; and at least two gearshift devices with shifting elements for engaging the gear stages; wherein the gearshift devices are preferably always assigned to an input shaft; wherein the output shaft is arranged axially parallel to the first transmission input shaft and / or to the second transmission input shaft; the first transmission input shaft is an input shaft for a first partial transmission; the second transmission input shaft is an input shaft for a second partial transmission; and all gear stages of the transmission can be used for the first drive motor and the second drive motor.

[0007] The above object is further achieved by a motor vehicle drive train for a motor vehicle with: a gearbox as previously defined; a first drive motor which is drivingly connected to the first transmission input shaft; and a second drive motor which is drivingly connected to the second transmission input shaft.

[0008] Furthermore, the problem is solved by a method for operating a motor vehicle drive train as previously defined.

[0009] The above object is finally achieved by a motor vehicle having a motor vehicle drive train as previously defined and an energy storage device for storing energy to supply the electric drive machine.

[0010] Preferred embodiments of the invention are described in the dependent claims. It is understood that the features mentioned above and those to be explained below can be used not only in the respective combinations specified, but also in other combinations or alone, without departing from the scope of the present invention. In particular, the motor vehicle drive train, the motor vehicle, and the method can be designed according to the embodiments described for the transmission in the dependent claims.

[0011] A first transmission input shaft and a second transmission input shaft make it technically easy to create a first and second partial transmission. Furthermore, the drive motors can be advantageously connected to the transmission. The spur gear pairs are preferably arranged between the first transmission input shaft or the second transmission input shaft and the output shaft. Preferably, no double gear planes are provided, so that the transmission has a radially compact design. It is understood that transmission input shafts can be provided to connect the drive motors. The transmission input shafts can be arranged coaxially or axially parallel to the transmission input shafts. The output is preferably connected to a differential, whereby the differential can also be arranged axially parallel or coaxially to the output shaft.Due to the axially parallel arrangement of the output shaft, an output gear, which serves to connect the output shaft to the differential, can be arranged nested with a switching element.

[0012] Nested means in particular that the output gear and the shifting element are arranged essentially in one gear set plane. Because all gear stages of the transmission can be used by both the first drive motor and the second drive motor, or by both drive motors simultaneously, a highly variable transmission with increased shifting comfort and a wide range of applications can be created. Both sub-transmissions can be drive-effectively connected to one another via a first shifting element and / or a second shifting element. Consequently, load-supported gear changes can be carried out with the transmission, in which a first drive motor provides drive power when a gear change is carried out for the second drive motor and vice versa.

[0013] Consequently, all gears can be operated with just one or both drive motors. Depending on the power requirements, an efficient operating point can be selected. The gearshifts are powershiftable using so-called electromotive shifts (EMS).

[0014] In a preferred embodiment, the output shaft comprises only fixed gears. This allows for cost-effective production of the output shaft. Furthermore, assembly of the transmission is technically simple.

[0015] In a further advantageous embodiment, the first transmission input shaft can be drive-effectively connected to the second transmission input shaft without a gear ratio. Preferably, the first transmission input shaft can be connected to a second transmission input shaft by means of a first shifting element. Furthermore, the second transmission input shaft can preferably be drive-effectively connected to the first transmission input shaft by means of a second shifting element. Due to the gear-free connection of the two transmission input shafts to each other, each gear stage can be used for each of the drive motors. In particular, the gear stages have the same gear ratio, i.e., regardless of whether the first drive motor or the second drive motor uses the gear stage.

[0016] In a particularly preferred embodiment, the second transmission input shaft is designed as a hollow shaft and surrounds the first transmission input shaft at least in sections. It is understood that the first transmission input shaft and the second transmission input shaft are arranged coaxially. This advantageous arrangement can increase the compactness of the transmission. Furthermore, with this arrangement, the two transmission input shafts can be advantageously connected; preferably, no additional shafts or gears are required to connect the transmission input shafts.

[0017] In a further advantageous embodiment, the shifting elements are designed as positive-locking shifting elements, in particular as claw shifting elements. This allows for the creation of an efficient and cost-effective transmission. In particular, it is conceivable for the drive motors to be used as synchronizing means. Positive-locking shifting elements enable the transmission to operate with low waste heat, thus reducing the lubricant volume for the transmission, since the lubricant has to absorb and dissipate less heat.

[0018] In a particularly preferred embodiment, the transmission has exactly two shifting elements, which are preferably designed as triple shifting elements, each with a shift sleeve and an actuator, as well as five linear positions. This allows for a technically simple transmission with only two actuators. Shifting elements with a shift sleeve and five linear positions simplify the shifting process, preferably by only linearly displacing the shift sleeve. A compact and efficient transmission can be created.

[0019] The transmission preferably has exactly four spur gear pairs for establishing preferably exactly fifteen shifting states, particularly preferably with two additional optional shifting states. Precisely fifteen shifting states, which can be established using preferably exactly two shifting elements and only four spur gear pairs, allow for the creation of a compact, weight-optimized transmission with a wide range of functions and high variability. The fifteen shifting states allow for optimal operation of the two drive units and provide a high level of comfort for the driver.

[0020] In a further advantageous embodiment, preferably exactly two loose gears from two spur gear pairs are arranged on the first transmission input shaft. Additionally or alternatively, preferably exactly two loose gears from two further spur gear pairs are arranged on the second transmission input shaft. Further additionally or alternatively, the spur gear pairs arranged on the second transmission input shaft are surrounded by the spur gear pairs arranged on the first transmission input shaft. Surrounded is preferably to be understood in the axial direction. In other words, the spur gear pairs arranged on the second transmission input shaft are arranged centrally in the transmission and surrounded by the spur gear pairs arranged at both ends of the transmission, which are arranged on the first transmission input shaft. This advantageous arrangement of the spur gear pairs allows, on the one hand, preferential control of the individual switching points by means of the switching elements.On the other hand, this arrangement enables an extremely compact design of the gearbox, so that the gearbox can be created in a space-efficient manner.

[0021] In a particularly preferred embodiment, a central shaft of the first shifting element is designed to be drive-connected to the first drive motor. Additionally or alternatively, a central shaft of the second shifting element is designed to be drive-connected to the second drive motor. This enables additional axial nesting, thus reducing the axial installation space required for the transmission.

[0022] In a particularly preferred embodiment, the first shifting element is designed to drive-effectively connect the first transmission input shaft to the output shaft by means of a first spur gear pair in a first shifting position. Additionally or alternatively, a second shifting position of the first shifting element comprises a neutral position. Further additionally or alternatively, the first shifting element is designed to drive-effectively connect the first transmission input shaft to the second transmission input shaft in a third shifting position. Further additionally or alternatively, a fourth shifting position of the first shifting element comprises a further neutral position. Additionally or alternatively, the first shifting element is designed to drive-effectively connect the first transmission input shaft to the output shaft by means of a third spur gear pair in a fifth shifting position.Furthermore, additionally or alternatively, the second shifting element is designed to drive-effectively connect the second transmission input shaft to the output shaft by means of a second spur gear pair in a first shifting position. Furthermore, additionally or alternatively, a second shifting position of the second shifting element and a fourth shifting position of the second shifting element each comprise a neutral position. Furthermore, additionally or alternatively, the second shifting element is designed to drive-effectively connect the second transmission input shaft to the first transmission input shaft in a third shifting position. Finally, additionally or alternatively, the second shifting element is designed to drive-effectively connect the second transmission input shaft to the output shaft by means of a fourth spur gear pair in a fifth shifting position.Preferably, the shift positions of the first shift element can be selected independently of the shift position of the second shift element. Likewise, the shift positions of the second shift element can be selected independently of the shift position of the first shift element. With these advantageous shift positions, at least fifteen shift states can be established using only two shift elements and four spur gear pairs. This allows for mutual support of the drive power when a gear shift is performed in a sub-transmission. It is understood that both sub-transmissions, i.e., both drive motors, can also be used together in one gear stage to provide maximum drive power.

[0023] In a particularly preferred embodiment of the motor vehicle drive train, the drive motors are preferably designed as electric drive motors and can be controlled as synchronization means during a gear shift in the transmission. Electric drive motors offer the advantage that, on the one hand, they cover a wide speed range and, on the other hand, they provide high torque even at low speeds. A high level of comfort can be achieved by combining two electric drive motors with a transmission as defined above, i.e., a transmission with, in particular, four gears. By using the drive motors as synchronization means, positive-locking, i.e., cost-effective and efficient shifting elements can be used.On the other hand, an additional synchronizing agent can be dispensed with, so that the motor vehicle drive train can be constructed with fewer components while maintaining the same range of functions.

[0024] In a particularly preferred embodiment, the first drive motor can be controlled as a support force means when gear shifts are performed for the second drive motor. Additionally or alternatively, the second drive motor can be controlled as a support force means when gear shifts are performed for the first drive motor. This allows for the creation of an efficient operating strategy for the motor vehicle drive train, which enables gear shifts without interruption in traction and thus increases driver comfort.

[0025] In this context, "drive-effectively connected" refers in particular to a non-switchable connection between two components, which is intended for the permanent transmission of a rotational speed, torque, and / or drive power. The connection can be established either directly or via a fixed transmission ratio. The connection can be established, for example, via a fixed shaft, a gearing, in particular a spur gear, and / or a belt drive, in particular a traction drive.

[0026] In this context, "drive-connectable," "can be connected to a drive," or "is designed for a drive-connected connection" refers, in particular, to a switchable connection between two components, which, in a closed state, is intended for the temporary transmission of a rotational speed, a torque, and / or a drive power. In an open state, the switchable connection preferably temporarily transmits essentially no rotational speed, no torque, and / or no drive power.

[0027] In this context, an actuator is, in particular, a component that converts an electrical signal into a mechanical movement. Actuators used with dual switching elements preferably perform movements in two opposite directions, switching one switching element of the dual switching element in the first direction and switching the other switching element in the second direction.

[0028] A gear change occurs, in particular, by disengaging a shifting element and / or a clutch from one shift position and simultaneously engaging another or the shifting element and / or the clutch with respect to a shift position for the next higher or lower gear. In the second shift position, the torque from the first shift position is preferably transferred gradually until, at the end of the gear change, the entire torque is transferred to the second shift position. With prior synchronization, a gear change can occur more quickly; positive-locking shift elements can preferably be used.

[0029] An electric vehicle axle, or simply an electric axle, is preferably a non-main drive axle of a motor vehicle, in which drive power can be transferred to the wheels of the motor vehicle by means of an electric drive motor. It is understood that the electric drive motor can also be connected via a transmission. Traction can be fully or partially maintained by means of an electric axle when a gear change occurs in the transmission for a main drive axle. Furthermore, all-wheel drive functionality can be implemented at least partially by means of an electric axle.

[0030] The invention is described and explained in more detail below using selected embodiments in conjunction with the accompanying drawings. They show: Fig. 1 a schematic plan view of a motor vehicle with a motor vehicle drive train according to the invention; Fig. 2 a schematic representation of the transmission according to the invention; Fig. 3 a schematic representation of a drive train according to the invention; Fig. 4 a schematic representation of another drive train according to the invention; Fig. 5 a schematic overview of the switching states of a transmission according to the invention; Fig. 6 a schematic overview of switching positions of the switching elements with respect to the switching states of a transmission according to the invention; and Fig. 7 a schematic overview of optional switching positions of the switching elements.

[0031] In Fig. 1 schematically shows a motor vehicle 10 with a motor vehicle drive train 12. The motor vehicle drive train 12 has a first electric drive motor 14, a second electric drive motor 16, and a transmission 18. The transmission 18 and the electric drive motors 14, 16 drive a front axle of the motor vehicle 10. An optional purely electric, combustion engine, or hybrid drive, in particular an electric axle 20, is operatively connected to the rear axle of the motor vehicle 10. In particular, the rear axle is designed as an electric axle 20. It is understood that a reverse connection can also be made, so that the electric axle 0 is connected to the front axle of the motor vehicle 10 and the rear axle of the motor vehicle 10 is assigned to the motor vehicle drive train 12. By means of the motor vehicle drive train 12, drive power of the electric drive motors 14, 16 is supplied to the wheels of the motor vehicle 10.The motor vehicle 10 further comprises an energy storage device 22 for storing energy that serves to supply the electric drive motor 14.

[0032] In Fig. 2, a transmission 18 according to the invention is shown schematically.

[0033] The transmission 18 has a first transmission input shaft 24, which is designed as a solid shaft and penetrates a second transmission input shaft 26, which is designed as a hollow shaft. The second transmission input shaft 26 thus surrounds the first transmission input shaft 24, at least in sections.

[0034] An output shaft 28 having an output 30 is arranged axially parallel to the first transmission input shaft 24 and the second transmission input shaft 26. The output 30 is shown schematically in simplified form and is configured via an output gear, which is designed as a fixed gear and is assigned to the output shaft 28.

[0035] The transmission 18 further comprises four spur gear pairs, designated ST1 to ST4.

[0036] The spur gear pairs ST1 to ST4 each have a loose gear arranged on the first transmission input shaft 24 or the second transmission input shaft 26, which engages with a fixed gear arranged on the output shaft 28. The output shaft 28 therefore has only fixed gears. The first spur gear pair ST1 and the second spur gear pair ST2 are arranged on the first transmission input shaft 24.

[0037] The third spur gear pair ST3 and the fourth spur gear pair ST4 are arranged on the second transmission input shaft 26. The second transmission input shaft 26 is arranged approximately centrally in the transmission. Consequently, the fourth spur gear pair ST4 and the third spur gear pair ST3 are surrounded by the first spur gear pair ST1 and the second spur gear pair ST2.

[0038] Furthermore, a first connection fixed gear 32 is arranged on the first transmission input shaft 24 and is designed to be connected in a drivingly effective manner to a first electric drive machine 14.

[0039] In an analogous manner, the second transmission input shaft 26 has a second connecting gear 34 which is designed to be drive-effectively connected to a second electric drive machine 16.

[0040] The connection is preferably made via a gearwheel which is connected to the rotor shaft of the electric drive machine 14, 16 and meshes with the respective connecting gearwheel 32, 34.

[0041] In Fig. 2, a total of six switching points A to D and K3 as well as K3' are also marked, which can be controlled by two switching elements SE 1, SE 2. Controlled is to be understood in particular that the respective switching element connects the shaft assigned to the switching point or the gear pair assigned to the switching point to the respective transmission input shaft 24, 26 in a driving manner.

[0042] The first shifting element SE1 is assigned to the first transmission input shaft 24, and can therefore connect the first transmission input shaft 24 to the output shaft 28 via a first shifting point A by means of the first spur gear pair ST1. A second and fourth shifting position of the first shifting element SE1 each comprise a neutral position. The term neutral position is to be understood in particular as meaning that the first transmission input shaft 24 is not connected to any further shaft or any further spur gear pair. In a third shifting position, a third shifting point K3 is activated, with the first shifting element SE1 drivingly connecting the first transmission input shaft 24 to the second transmission input shaft 26. In a fifth shifting position, a fifth shifting point C is activated, with the first shifting element SE1 drivingly connecting the first transmission input shaft 24 to the output shaft 28 by means of the third spur gear pair ST3.

[0043] The first spur gear pair ST1 and the third spur gear pair ST3 therefore form a first partial transmission that can be shifted by means of the first shifting element SE1.

[0044] In a first shift position, the second shift element SE2 controls shift point B, with the second transmission input shaft 26 being drive-effectively connected to the output shaft 28 by means of a second spur gear pair ST2. A second shift position and a fourth shift position of the second shift element SE2 comprise a neutral position. In a third shift position, which controls shift point K3', the second shift element SE2 connects the second transmission input shaft 26 drive-effectively to the first transmission input shaft 24 without a gear ratio.

[0045] In a fifth switching position, which controls the switching point D, the second switching element SE2 connects the second transmission input shaft 26 to the output shaft 28 in a drive-effective manner by means of the fourth spur gear pair ST4.

[0046] The second spur gear pair ST2 and the fourth spur gear pair ST4 therefore form a second partial transmission, which can be shifted by means of the second shifting element SE2.

[0047] In Fig. 3 is a motor vehicle drive train 12 with a transmission 18 according to the Fig. 2. In contrast to the Fig. The embodiment shown in Figure 2 shows the two electric drive motors 14, 16 and their connection to the connecting gears 32, 34. Furthermore, the output 30 of the transmission 18 is formed by a differential.

[0048] It is understood that the representation of the differential is only an example. In addition to the illustrated embodiment, all differential types known in principle in the prior art can be used. It is also understood that the connection via the output gear is also only schematic. A person skilled in the art will recognize that the differential can also be arranged coaxially with the output shaft 28.

[0049] In Fig. 4 shows a further embodiment of a motor vehicle drive train 12 according to the invention. In contrast to the Fig. In the embodiment shown in Figure 3, the electric drive motors 14, 16 are not connected to the transmission input shafts 24, 26, but to a central shaft of the switching elements SE1, SE2, which is not designated in more detail.

[0050] Since the switching elements SE1, SE2 are always connected to the first transmission input shaft 24 and the second transmission input shaft 26, respectively, the functionality of the transmission 18 is according to the Fig. 4 identical to the gearbox 18 according to the Fig. 3. By connecting the electric drive motors 14, 16 to the central shafts of the switching elements SE1, SE2, a further nesting of the motor vehicle drive train 12 can be achieved, so that the axial installation space requirement can be reduced.

[0051] In the Fig. 4, the second electric drive motor 16 is connected to the central shaft of the second shift element SE2, for example, by means of a gear chain 36. It is understood that other connection options, such as a traction drive, may also be used.

[0052] In Fig. Figure 5 shows a schematic overview of 38 of a total of 15 switching states of the two switching elements SE1, SE2.

[0053] In the first column, the individual switching states are numbered from 1 to 15. The second to seventh columns list the individual switching points, where an X means that the respective switching point is closed, i.e. the shaft or spur gear pair assigned to the switching point is drivingly connected to the respective transmission input shaft 24, 26, as already described above.

[0054] The eighth and ninth columns indicate the gear ratios engaged for the electric drive motors 14 and 16.

[0055] In a first state, both shift elements SE1, SE2 are switched to neutral. Consequently, neither shift point is closed, so that the first electric drive motor 14 and the second electric drive motor 16 are switched to a neutral gear position B.

[0056] In a second switching state, only switching point A is closed, so that the second electric drive motor 16 is switched to neutral N and the first gear stage 1 is engaged for the first electric drive motor 14.

[0057] In a third switching position, the switching points A and K3' are closed, so that the first gear 1 is engaged for both electric drive motors 14, 16.

[0058] In a fourth shift position, only shift point A is closed, in which case the second shift element SE2 assumes a further neutral position. Consequently, the second electric drive motor 16 is shifted to neutral N, with the first electric drive motor 14 being assigned the first gear stage 1.

[0059] In a fifth switching position, the switching points A and B are closed, so that the first electric drive motor 14 is assigned the first gear stage 1 and the second electric drive motor 16 is assigned the second gear stage 2.

[0060] In a sixth switching position, only the second switching point B is closed, so that the first electric drive motor 14 is switched to neutral N and the second electric drive motor 16 is assigned the second gear stage 2.

[0061] In a seventh switching position, the switching points K3 and B are closed, so that both electric drive motors 14, 16 are assigned the second gear stage 2.

[0062] In an eighth shift position, only the second shift point B is closed, with the first shift element SE1 assuming another neutral position. In this shift state, the first electric drive motor 14 is shifted to neutral N, with the second electric drive motor 16 being assigned the second gear stage 2.

[0063] In a ninth switching state, the switching points C and B are closed, so that the first electric drive motor 14 is assigned the third gear stage 3 and the second electric drive motor 16 is assigned the second gear stage 2.

[0064] In a tenth switching position, only switching point C is closed, so that the second electric drive motor 16 is switched to neutral N and the first electric drive motor 14 is assigned the third gear stage 3.

[0065] In an eleventh switching position, the switching points C and K3' are closed, so that both electric drive motors 14, 16 are assigned the third gear stage 3.

[0066] In a twelfth shift position, only shift point C is closed, with the second shift element SE2 in a further neutral position. In this shift state, the first electric drive motor 14 is assigned the third gear stage 3, with the second electric drive motor 16 shifted to neutral N.

[0067] In a 13th switching position, the switching points C and D are closed, so that the first electric drive motor 14 is assigned the third gear stage 3 and the second electric drive motor 16 is assigned the fourth gear stage 4.

[0068] In the 14th switching position, only switching point D is closed, so that the first electric drive motor 14 is switched to neutral N and the second electric drive motor 16 is assigned the fourth gear stage 4.

[0069] In a 15th switching position, the switching points K3 and D are closed, so that both electric drive motors 14, 16 are assigned the fourth gear stage 4.

[0070] The individual switching states shown in a simplified overview 38 according to the Fig. 5 are in the Fig. 6 in a schematic overview 40 of positions of the switching elements in more detail, wherein for each switching position the corresponding position of the switching elements SE1, SE2 in the transmission 18 is shown.

[0071] The positions of the switching elements SE1, SE2 in the Fig. 6 correspond to the switching states according to the Fig. 5. The Fig. 6 is used for better understanding; the individual switching positions are not described again.

[0072] In Fig.7, two further optional switching states are shown in a schematic overview 42. In an optional 16th state, the second switching element SE2 engages switching point D in a drive-effective manner. It thus connects the second transmission input shaft 26 to the fourth spur gear pair ST4 in a drive-effective manner. The first switching element SE1 is in the neutral position. Consequently, in the optional state 16, only switching point D is closed. The first electric drive motor 14 is therefore in neutral N, with the second electric drive motor 16 being assigned the fourth gear stage 4.

[0073] In another optional switching position 17, the second switching element SE2 is in neutral. The first switching element SE1 is also in neutral. Consequently, both electric drive motors 14, 16 are also in neutral N.

[0074] In the patent claims, the words "comprising" and "having" do not exclude the presence of further elements or steps. The undefined article "a" or "an" does not exclude the presence of a plurality. A single element or a single unit can perform the functions of several of the units recited in the patent claims. The mere mention of some measures in several different dependent patent claims should not be understood to mean that a combination of these measures cannot also be used advantageously. Reference symbols in the patent claims are not to be understood as limiting. A method for operating a motor vehicle drivetrain 12 can, for example, be implemented in the form of a computer program that is executed on a control unit for the motor vehicle drivetrain 12.A computer program may be stored / distributed on a non-volatile storage medium, such as optical storage or a solid-state drive (SSD). A computer program may be distributed together with hardware and / or as part of hardware, such as via the Internet or via wired or wireless communication systems. Reference symbol 10 motor vehicle 12 Automotive powertrain 14 first drive machine 16 second drive machine 18 gearboxes 20 electric axles 22 energy storage units 24 first transmission input shaft 26 second transmission input shaft 28 Output shaft 30 downforce 32 first connecting gear 34 second connecting gear 36 sprocket chain 38 schematic overview of switching states 40 schematic overview of positions of the switching elements 42 schematic overview of optional positions of the switching elements

Claims

[1] Transmission (18) for a motor vehicle drive train (12) of a motor vehicle (10), comprising: a first transmission input shaft (24) for operatively connecting the transmission (18) to a first drive engine (14) of the motor vehicle (10); a second transmission input shaft (26) for operatively connecting the transmission (18) to a second drive engine (16) of the motor vehicle (10); an output shaft (28) with an output (30); spur gear pairs (ST1, ST2, ST3, ST4) arranged in several gear set levels to form gear steps; and at least two gearshift devices with shifting elements (SE1, SE2) for engaging the gear stages, wherein the output shaft (28) is arranged axially parallel to the first transmission input shaft (24) and / or to the second transmission input shaft (26); the first transmission input shaft (24) is an input shaft for a first partial transmission; the second transmission input shaft (26) is an input shaft for a second partial transmission; and all gear stages of the transmission (18) can be used for the first drive motor (14) and the second drive motor (16). [2] Transmission (18) according to claim 1, wherein the output shaft (28) has exclusively fixed gears. [3] Transmission (18) according to one of the preceding claims, wherein the first transmission input shaft (24) can be connected to the second transmission input shaft (26) in a drive-effective, gear-free manner. [4] Transmission (18) according to one of the preceding claims, wherein the second transmission input shaft (26) is designed as a hollow shaft and surrounds the first transmission input shaft (24) at least in sections. [5] Transmission (18) according to one of the preceding claims, wherein the shifting elements (SE1, SE2) are designed as positive-locking shifting elements, in particular as claw shifting elements. [6] Transmission (18) according to one of the preceding claims, wherein the transmission (18) comprises exactly two switching elements (SE1, SE2), which are preferably designed as triple switching elements, each with a switching sleeve and an actuator as well as five linear positions. [7] Transmission (18) according to one of the preceding claims, wherein the transmission (18) comprises exactly four spur gear pairs (ST1, ST2, ST3, ST4) for establishing preferably exactly 15 switching states. [8] Transmission (18) according to the preceding claim, wherein two loose gears of two spur gear pairs (ST1, ST2) are arranged on the first transmission input shaft (24); two idler gears of two further spur gear pairs (ST3, ST4) are arranged on the second transmission input shaft (26); and / or the spur gear pairs (ST3, ST4) arranged on the second transmission input shaft (26) are surrounded by the spur gear pairs (ST1, ST2) arranged on the first transmission input shaft (24). [9] Transmission (18) according to one of the preceding claims, wherein the first drive machine (14) is drive-connectable to a central shaft of the first switching element (SE1); and / or the second drive machine (16) can be connected to a central shaft of the second switching element (SE2) in a drive-effective manner. [10] Transmission (18) according to one of the preceding claims, wherein the first shifting element (SE1) is designed to drive-effectively connect the first transmission input shaft (24) to the output shaft (28) by means of a first spur gear pair (ST1) in a first shift position; a second switching position of the first switching element (SE1) comprises a neutral position; the first shifting element (SE1) is designed to drive-effectively connect the first transmission input shaft (24) to the second transmission input shaft (26) in a third shift position; a fourth switching position of the first switching element (SE1) comprises a further neutral position; the first shifting element (SE1) is designed to drive-effectively connect the first transmission input shaft (24) to the output shaft (28) by means of a third spur gear pair (ST3) in a fifth shift position; the second shifting element (SE2) is designed to connect the second transmission input shaft (26) to the output shaft (28) in a first shifting position by means of a second spur gear pair (ST2); a second switching position of the second switching element (SE2) comprises a neutral position; the second shifting element (SE2) is designed to drive-effectively connect the second transmission input shaft (26) to the first transmission input shaft (24) in a third shift position; a fourth switching position of the second switching element (SE2) comprises a further neutral position; and / or the second shift element (SE2) is designed to drive-effectively connect the second transmission input shaft (26) to the output shaft (28) by means of a fourth spur gear pair (ST4) in a fifth shift position; wherein preferably the switching position of the first switching element (SE1) is independent of a switching position of the second switching element (SE2) and the switching position of the second switching element (SE2) is independent of a switching position of the first switching element (SE1). [11] Motor vehicle drive train (12) for a motor vehicle (10), comprising: a transmission (18) according to one of the preceding claims; a first drive motor (14) which is drivingly connected to the first transmission input shaft (24); and a second drive motor (16) which is drivingly connected to the second transmission input shaft (26). [12] Motor vehicle drive train (12) according to claim 11, wherein the drive machines (14, 16) are preferably designed as electric drive machines and can be controlled as synchronizing means during a gear shift in the transmission (18). [13] Motor vehicle drive train (12) according to claim 11 or 12, wherein the first drive machine (14) can be controlled as a supporting force means when switching operations for the second drive machine (16) are carried out; and / or the second drive machine (16) can be controlled as a supporting force means when switching operations for the first drive machine (14) are carried out. [14] Method for operating a motor vehicle drive train (12) according to one of claims 11 to 13. [15] Motor vehicle (10) with: a motor vehicle drive train (12) according to one of claims 11 to 13; and an energy storage device (22) for storing energy to supply the drive machines (14, 16).

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