WO2020001860A1

WO2020001860A1 - Drive unit for a vehicle having two electrical machines and a common summation gearbox

Info

Publication number: WO2020001860A1
Application number: PCT/EP2019/062980
Authority: WO
Inventors: Bernard Hunold
Original assignee: Zf Friedrichshafen Ag
Priority date: 2018-06-25
Filing date: 2019-05-20
Publication date: 2020-01-02
Also published as: DE102018210329A1

Abstract

The invention relates to a drive unit (3) for a vehicle (1), the drive unit (3) comprising a first electrical machine (8) as a traction machine, a second electrical machine (9) as a traction machine and a summation gearbox (10) for summing the torques produced by the first and second electrical machines (8, 9) onto a common output shaft (7) of the summation gearbox (10), comprising a first inverter (11) for supplying electric current to the first electrical machine (8) and comprising a second inverter (12) separate from the first inverter (11) for supplying electric current to the second electrical machine (9).

Description

Drive unit for a vehicle with two electric machines and

a common summing gear

The invention relates to a drive unit for a vehicle, in particular for a motor vehicle, and a drive train for a vehicle with such a drive unit, and to a method for carrying out a switching operation in such a drive unit.

From DE 10 201 1 1 17 853 A1, an electric drive for transmitting the torques of two electric drive means via a gearbox to an output shaft is known. The transmission has a partial transmission for each drive means. Each sub-transmission is coupled to the corresponding drive means via a corresponding input channel. The sub-transmissions are designed to interact with one another and with the common output shaft in such a way that interruptions in the torque output of the output shaft are avoided during switching operations of one or the other sub-transmission.

The object of the invention is to improve the prior art.

This object is achieved by the objects specified in the main claims. Preferred embodiments thereof can be found in the subclaims.

Accordingly, a drive unit for a vehicle is proposed, as well as a drive train for a vehicle, as well as a method for performing a switching operation on a drive unit. The vehicle is preferably a motor vehicle, for example a truck or a passenger car or a bus.

The proposed drive unit has a first electric machine and a second electric machine as well as a summing gear. The summation gear is used for summing the torques generated by the first and second electric machines on a common output shaft of the summing gear. This output shaft also forms the output of the drive unit. The electric machines are designed as traction machines. In the installed state of the drive unit, they therefore both serve primarily for motor propulsion of the vehicle. This does not rule out that one or both of the electric machines can also be operated at least temporarily as a generator, for example for braking and / or for recuperation. Accordingly, the torques generated by the electric machines can be positive (motor operation) or negative (generator operation).

The electric machines are designed in particular as a rotating field machine, such as, for example, as synchronous or asynchronous machines. The electric machines can be configured identically to one another, that is to say they have identical performance data and / or identical stators and rotors. Alternatively, the electric machines can be designed differently from one another, that is to say they can have different performance data and / or different stators and rotors. Preferably, no further traction machine and / or no input for the torque of another traction machine, such as, for example, for an internal combustion engine, is provided in the drive unit. The drive unit is therefore, in particular, a purely electric drive unit. The drive unit is designed in particular for a purely electric vehicle, that is to say a vehicle which can be driven purely electrically.

The proposed drive unit is preferably present in the present case

(a) a first inverter for electrically energizing the first electric machine and a second inverter separate from the first inverter for electrically energizing the second electric machine.

This means that each of the e-machines has its own inverter. The two inverters are structurally separate from one another. The two inverters each have, in particular, at least the electrical power switches and the associated electrical driver circuit required for the complete electrical energization of the associated electric machine. The inverters each have their own housing, which houses the associated electrical components. The inverters can be electrically identical be designed differently, ie have identical performance data and / or have identical electrical components and assemblies. The inverters can be constructed identically to one another, that is to say essentially have an identical construction with identical components and assemblies. Alternatively, the inverters can be designed differently from one another, that is to say they can have different performance data and / or they can have different electrical components. The inverters can be designed to be operable independently of one another. The operation of one inverter is therefore not influenced by that of the other inverter. Accordingly, the electric machines can also be operated independently of one another.

In this way, existing and widely available inverters for a single electric machine can be easily accessed. The drive unit can thus be inexpensive. No further inverters are preferably provided for the electric machines.

Such an inverter is also referred to as an AC-DC converter. Such an inverter is used to convert a direct current into an alternating current and, if necessary, vice versa. In the present case, the inverters can be used to convert a direct current from a direct current source, for example a traction battery, into an alternating current for the electrical energization of the associated electric machines.

The drive unit preferably has

(b) a common cooling system for the first and second electric machines, and / or

(c) a common lubrication system for the first and second electric machine and for the summation gear, and / or

(d) a common stator housing for the first and second electric machine,

and or

(e) a common control device for controlling (controlling and / or regulating) the first and second inverters.

One or more of these features (b) to (e) may be present in addition to the separate design of the inverters according to feature (a) mentioned above his. In alternative embodiments of the drive unit, one or more of these features (b) to (e) can also be present instead of the separate design of the inverter according to feature (a). In this case, the intended feature (b) to (e) replaces feature (a).

When using the common cooling system for the first and second electric machine according to feature (b), the cooling system of the drive unit can be made simpler overall and thus less expensive. In particular, only a common coolant pump for the coolant and / or a common coolant reservoir and / or a common coolant heat exchanger is then provided for releasing the coolant heat dissipated by the electric machines. The common cooling system can also serve to cool the first and second inverters.

When using the common lubrication system for the first and second electric machine and for the summation gear according to feature (c), the lubrication system of the drive unit can be made simpler overall. In particular, only a common lubricant pump for the lubricant and / or a common lubricant reservoir is then provided. Alternatively, it can be provided that a common lubrication system is provided, but that this has its own lubricant pump for each of the electric machines.

When using the common stator housing for the first and second electric machine according to feature (d), the housing of the drive unit can be made simpler overall. The common stator housing receives at least the stators of the first and second electric machines and carries them. In particular, it supports and encloses the stator windings and the stator laminations of the respective stator. The rotors of the electric machines are preferably also rotatably mounted in the stator housing by means of shaft bearings. The stator housing can form a first housing part of the drive unit, while a second housing part of the drive unit is used for housing the summing gear and for rotatably mounting the rotatable shafts of the summing gear. When the common control device is used to control the first and second inverters according to feature (e), the control of the drive unit can be simplified. In particular, each of the electric machines can be operated individually by means of the control device by means of a corresponding individual control of the first and second inverters. In particular, the control unit can be used to set the distribution of the torques generated by the electric machines. In particular, a switching operation of the summation gear can be effected by means of the control device. The control device is accordingly also designed in particular to control the summation gear. If the summing gear has switchable gear ratios (gears), the control device is therefore preferably designed to control one or more switching devices for switching the summing gear. In this case, the control unit effects the switching process in the summing gear by operating corresponding shifting elements of the summing gear, for example one or more switchable clutches.

The first electric machine has a rotor with a first axis of rotation. The second electric machine has a rotor with a second axis of rotation. It can now be provided that the output shaft of the summing gear is at a smaller (lateral) distance from one of said rotation axes than from the other of said rotation axes. In other words, the common output shaft is offset laterally towards one of the electric machines. The axis of rotation of the output shaft is thus closer to the axis of rotation of one e-machine than to the axis of rotation of the other e-machine. This can result in packaging advantages. As a result, the output shaft can be placed in the area of an input shaft of an axle differential gear coupled to the drive unit. This enables sufficient ground clearance and low bending angles to be achieved.

The first and second electric machines preferably each have an output shaft which is coupled to the rotor of the associated electric machine and which forms the output of the respective electric machine. The output shafts can therefore in particular also be rotated about the axes of rotation of the rotors. The first and second electric machines are then preferably arranged side by side in such a way that on the one hand the rotational axes sen the rotors or the output shafts of the e-machines are parallel and laterally spaced from each other and that on the other hand, the output shafts of the e-machines are coupled to the summing gear on a common output side of the e-machines. The output shafts of the e-machines thus protrude from the e-machines on the same end face, for example, and are parallel to one another. This can result in packaging advantages. As a result, two e-machines of identical or almost identical design can simply be arranged next to one another and coupled via the summation gear. As a result, the summation gear can be placed on the adjacent e-machines at the same time.

Shaft bearings designed as fixed bearings are preferably provided on the output side of the e-machines for the output shafts of the e-machines and / or for input shafts of the two partial transmissions. These shaft bearings absorb the axial forces of the partial transmissions and, if applicable, of the electric machines, in particular if they are designed as helical-toothed spur gear transmissions. The output side of the electric machine is arranged between the actual electric machine and the actual summing gear. In particular, an intermediate wall is provided at this point, which creates a spatial separation between the space for the stator and rotor of the respective electric machines and the space for the gear wheels of the summing gear. This partition is designed to be relatively rigid due to its construction and can therefore very well absorb the axial forces. This also minimizes airborne sound coupling to the outer housing surfaces of the electric machines and the summing gear. The drive unit is therefore quiet.

Preferably, the output shaft of the summing gear is parallel and laterally spaced from the axes of rotation of the rotors of the electric machines or the output shafts of the electric machines. The output shaft is then not coaxial with the two axes of rotation. This can also result in packaging advantages.

The drive unit preferably has suspension points. These are used to attach the drive unit to a frame of the vehicle, for example via rubber-metal bearings. The suspension points can be, for example, as eyelets or screw-on points. In the present case, the suspension points are arranged at the level or above the first and second axes of rotation of the rotors of the electric machine. The output shaft of the summing gear is then in particular below these axes of rotation. This results in a stable mounting and suspension of the drive unit on the frame of the vehicle.

The summing gear for the first electric machine preferably has a first sub-gear. This is used to transfer the torque generated by the first electric machine to the output shaft of the summing gear. The summing gear then has a second sub-gear for the second electric machine. This is used to transfer the torque generated by the second electric machine to the output shaft of the summing gear. The first sub-transmission and / or the second sub-transmission has two switchable gear ratios (gears). In particular, exactly these two switchable transmission stages are provided in the respective partial transmission, that is, no more. The switchable partial transmission can thus be switched by means of a switching device between at least or exactly two different gear ratios which correspond to the gear ratios. For this purpose, the switching device has, in particular, at least one switching element, such as in particular one or more switchable clutches, in order to thereby insert the desired gear ratio during a switching operation. In the present case, the desired gear ratio, to which the partial transmission is to be shifted, is also referred to as the target gear. In particular, the respective partial transmission can also be switched to a neutral position, that is to say an idling. In the neutral position, the partial transmission does not transmit any torque between the associated electric machine and the output shaft of the summation transmission.

The sub-transmissions of the drive unit can be identical or almost identical, at least with regard to the wheel set used. At least one of the sub-transmissions can be designed as a spur gear. Both partial transmissions are preferably designed as spur gear transmissions. Gears of the summing gear or the partial gear are preferably designed with helical teeth for noise reduction. If both sub-transmissions have the switchable transmission stages, an independent switching device for shifting this sub-transmission is preferably provided for each sub-transmission. The switching devices are then not designed to shift the other sub-transmission. The partial transmissions can thus preferably be operated independently of one another. The torque flow to the output shaft in one of the sub-transmissions preferably does not also run through elements of the other sub-transmission.

The summing gear can have a power take-off, also called PTO (Power take-off). By means of such a auxiliary drive, auxiliary units arranged externally to the drive unit can be driven by the drive unit, such as a hydraulic oil pump, an air conditioning compressor or a coolant pump. The power take-off can be designed to be connected and disconnected. This means that by means of a switching device, a power take-off shaft serving as an output of the power take-off is optionally coupled or uncoupled to the summation gear. The power take-off can be part of one of the partial transmissions of the summing transmission. The torque flow to the power take-off therefore always takes place via this sub-transmission. The other sub-transmission then has in particular no auxiliary drive, and the torque flow to the auxiliary drive then does not take place via this other sub-transmission.

Said control unit for controlling the inverters can be designed to also control the switching device (s) of the switchable sub-gearbox (s). Thus, the control unit also serves to control the summing gear, that is to say to switch the gearbox or gearboxes that can be shifted.

The first and second sub-transmissions preferably have mutually different transmission ratios. In particular, the gear ratio difference between the sub-transmissions is slight. In particular, the gear ratio difference is less than 1, in particular less than 0.5, in particular less than 0.25, in particular less than 0.1. As a result, the e-machines rotate at corresponding (slightly) different speeds. This leads to different excitation frequencies and an improved acoustic signature of the drive unit.

The step change in the gear ratios of the switchable sub-gearbox or gearboxes is preferably relatively high, for example approximately 1.8. Thus, on the one hand, the full continuous output can be made available at maximum speed on the other hand, a high starting acceleration can be realized for starting. This means that the e-machines can quickly drive through the poor efficiency range at low speeds.

As described above, a drive train for a vehicle is also proposed. The proposed drive train has the proposed drive unit and an axle differential. The axle differential gear has an input shaft that is laterally offset with respect to a vehicle longitudinal axis. For this purpose, the input shaft is arranged, in particular, off-center on the axle differential. The output shaft of the drive unit, that is to say the said output shaft of the summing gear, is coupled in terms of drive technology to the input shaft of the axle differential gear. This coupling takes place in particular directly or by means of a cardan shaft or at least one homokinetic joint. The output shaft of the drive unit is now arranged in such a way that it is laterally offset to the same extent with respect to the longitudinal axis of the vehicle as the input shaft of the axle differential, at least when the drive train is installed. It follows that the output shaft of the drive unit and the input shaft of the axle differential gear are arranged on a common plane or even on a common line (coaxial). There is therefore no major misalignment between these shafts. The output shaft and the input shaft can, if necessary, even be firmly connected or made in one piece.

Such an axle differential is usually coupled on the output side to vehicle wheels in order to drive them with the torque generated on the input side by the drive unit. The axle differential usually also serves for speed compensation of the wheels driven thereby, which are arranged on opposite sides of the vehicle.

The installed state means the state and the associated component positions that exist when the drive train is installed in a vehicle or a frame of the vehicle for the intended operation. Then, at the latest, the drive unit and the axle differential gear assume predetermined installation positions with respect to one another. The axle differential and the drive unit are preferably arranged such that the output shaft of the drive unit and the input shaft of the axle differential are at the same height, at least in the installed state of the drive train. Together with the identical lateral offset of these shafts with respect to the longitudinal axis of the vehicle, this means that the output shaft and the input shaft are arranged on a common line (coaxial). A universal joint or a kinokinetic joint between these shafts may then not be required.

If an offset between the axle differential gear and the drive unit still has to be compensated for, a drive shaft can be provided in between. This can be made relatively short, in particular shorter than 1.5 m. A homokinetic joint is then preferably used for a low-vibration run in order to couple the output shaft of the drive unit to the drive shaft of the axle differential. Such a joint can also be integrated in the drive unit.

A method for performing a switching operation in the proposed drive unit is also proposed. This method provides that at least one of the sub-transmissions of the summing transmission has the two switchable transmission stages, that is to say gears. The gear ratios correspond to different gear ratios in the switchable partial transmission. As part of the method, one of the sub-transmissions is shifted from a gear ratio that has already been inserted into another desired gear ratio. This desired translation level is called the target gear.

The procedure involves the following steps:

• The one of the e-machines, whose partial transmission is not to be shifted, is energized electrically so that it generates a higher torque than before. The torque thus generated is raised in a targeted manner. This can include that this electric machine is overloaded in a targeted manner, at least for a short time. For this purpose, the power of the electric machine can be increased over the continuous power. • The one of the e-machines, whose partial transmission is to be shifted, is energized electrically so that it generates a torque which is lower than that previously. The torque thus generated is reduced in a targeted manner. In particular, no torque is then generated with this electric machine. In particular, the torque generated by the one electric machine is increased to such an extent that it compensates for the reduction in the torque generated by the other electric machine. The total torque of the e-machines applied to the output shaft therefore preferably remains constant during this time. Accordingly, the torque generated by one electric machine is preferably raised at the same time as the torque generated by the other electric machine is reduced.

• The partial transmission that is to be shifted is shifted into a neutral position. In the neutral position, also called idling, the sub-transmission does not transmit any torque between the associated electric machine and the output shaft of the summing gear. The electric machine of this sub-transmission cannot then be used as a drive source.

• The one of the electric machines whose partial transmission is to be shifted is energized electrically so that its speed changes to a target speed. Depending on the gear ratio of the target gear, the speed is increased or decreased. At the target speed, the speed ratio between the speed of the output shaft of the summing gear and the speed of the electric motor of the sub-gear that is to be shifted corresponds to the gear ratio of this sub-gear in the target gear. This means that by means of the electric machine whose partial transmission is to be shifted, the partial transmission is synchronized into the target gear before the actual shifting process.

The speeds of the shafts of this sub-transmission which are coupled to one another in the target gear are thus matched to one another. This sub-transmission can now be switched from neutral to target gear without any problems. It is therefore possible to dispense with an extra synchronization device for the switchable sub-transmission, such as synchronizer rings, or the synchronization device of the switchable sub-transmission can be made simpler. • Finally, the partial transmission that is to be shifted is shifted from the neutral position to the target gear.

The torques generated by the electric machines can then be matched to one another again, or a different distribution of the generated torques can be set by appropriate electrical energization of the electric machines. In particular, the torque of the electric machine whose sub-transmission was shifted into the target gear is raised again and the torque of the electric machine whose sub-transmission was not shifted is reduced again. The method enables a shifting process of the switchable gearbox or gearboxes without interruption of traction. It is equally suitable for an upshift and a downshift.

If the drive unit has a low power requirement, it can be provided that only one of the electric machines is driven. The other electric machine can then be uncoupled by switching the associated partial transmission to the neutral position. An efficiency of the drive unit in the partial load range can thus be optimized. This procedure can also be used if a fault has been detected in one of the e-machines and this e-machine is brought into its safe state. The vehicle can thus continue to be driven with the remaining electric machine.

Said control device is in particular designed to carry out this method. For this purpose, the switching device of the partial transmission that is to be shifted is controlled accordingly by the control unit. Likewise, the inverters of the e-machines are controlled accordingly by the control unit, so that the e-machines set the required torques and speeds.

The invention is explained in more detail below with reference to figures, from which further preferred embodiments and preferred features of the invention can be gathered. Each shows in a schematic representation:

1 is a vehicle with a drive unit, 2 is a view of a drive unit in the vehicle longitudinal direction,

3 is a sectional view through the drive unit according to FIG. 2,

4 is a sectional view through the drive unit according to FIG. 2,

5 shows a switching sequence for switching the drive unit according to FIG. 2.

In the figures, identical or at least functionally identical components or elements are provided with the same reference symbols.

1 shows a side view of a vehicle 1 designed as a truck, for example. The vehicle 1 has a frame 2. The frame 2 carries, among other things, a drive unit 3 which is used for the electrical propulsion of the vehicle 1. In particular, no further drive unit, such as an internal combustion engine, is provided. The drive unit 3 thus forms a central component of the drive train of the vehicle 1. An output shaft 7 of the drive unit 3 is coupled to an input shaft 4, which in turn is coupled to an input shaft 5A of an axle differential 5 (shown in broken lines). The axle differential gear 5 is in turn coupled in a manner known per se to wheels 6 of the vehicle 1 in terms of drive technology. These wheels 6 can thus be driven by means of the drive unit 3. In FIG. 1, these are, for example, the wheels 6 of a rear axle of the vehicle 1. The wheels 6 of a front axle are, for example, not driven. The axle differential 5 is also part of the drive train of the vehicle 1. The drive unit 3 is arranged between the front axle and the rear axle. In principle, the drive unit 3 can be used in any other vehicle (for example a watercraft) or motor vehicle (for example a motor bus).

FIG. 2 shows an exemplary embodiment of a proposed drive unit 3, such as that from FIG. 1. Here, the drive unit 3 is viewed in the longitudinal direction of the vehicle. The view is thus directed towards the output shaft 7 of the drive unit 3, which is designed for coupling to an input shaft 4 (see FIG. 1).

The drive unit 3 has a first electric machine 8 and a second electric machine 9. Both are designed as traction machines and are therefore used for Driving a vehicle 1. The drive unit 3 also has a summing gear 10. This is used for summing the torques generated by the electric machines 8, 9 on the (common) output shaft 7. The summing gear 10 is designed to be switchable. It therefore has switchable gear ratios (gears). The summing gear 10 has a switching device for inserting the selected gear ratios.

In addition, the drive unit 3 has a first inverter 11 for the electrical energization of the first electric machine 8, and a second inverter 12 for the electrical energization of the second electric machine 9. The inverters 11, 12 are designed separately from one another. For this purpose, the inverters 11, 12 each have, in particular, their own housings, which house the components required for the electrical energization of the associated electric machine 8, 9, in particular the electrical circuit breakers and driver circuits required for this. The inverters 11, 12 are in particular constructed identically to one another.

The inverters 11, 12 are preferably controlled by a control unit 13. This therefore determines the operating mode of the respective electric machine 8, 9 and accordingly controls the respective inverter 11, 12. The control device 13 is also used to control the switching device of the summing gear 10, that is to say to effect the engagement and disengagement of the gear ratios.

The control device 13 has at least one input via which it receives information. It controls the inverters 11, 12 and the switching device of the summing gear 10 on the basis of the information. Such information can be, for example, an accelerator pedal position. Such information can also be, for example, a road gradient. Such information can also be, for example, a brake pedal position.

Alternatively or in addition to the separate inverters 11, 12, a common cooling system for the electric machines 8, 9 and for the inverters 11, 12 can be provided. And / or a common lubrication system can be provided for the first and second electric machines 8, 9 and the summation gear 10. And or a common stator housing can be provided for the first and second electric machines 8, 9. And / or the common control device 13 can be provided for controlling the inverters 11, 12. All of these features are preferably implemented together.

FIG. 3 shows a sectional view of the drive unit 3 from FIG. 2 along the section line X-X shown there. The electric machines 8, 9 each have a stator 8A, 9A fixed to the housing and a rotor 8B, 9B which can be rotated about an axis of rotation. The rotor 8B, 9B is firmly coupled to an associated output shaft 8C, 9C, which forms the output of the respective electric machine 8, 9. The electric machines 8, 9 are arranged in parallel and side by side. The axes of rotation of the rotors 9B, 8B and the output shafts 8C, 9C are thus also parallel and laterally spaced apart.

As can be seen in FIG. 3, the stators 8A, 9A are fixedly arranged in a common stator housing. The output shafts 8C, 9C are rotatably supported in the stator housing. The stator housing can have a common cooling structure in order to cool both electric machines 8, 9. This cooling structure forms part of the common cooling system. The same can apply to the common lubrication system. The stator housing can be made in one or more parts. The end of the stator housing can have end shields which rotatably support the rotors 8C, 9C or the output shafts 8B, 9B by means of shaft bearings. The stator housing itself can form a first housing part of a housing of the drive unit 3 or it can form part of a first housing part of the drive unit 3 surrounding the electrical machines 8, 9. Another housing part of the drive unit 3 can be assigned to the summing gear 10 and at least partially or completely house it.

The output shafts 8C, 9C are coupled to the summing gear 10 on a common output side of the electric machines 8, 9. In detail, the output shafts 8C, 9C are coupled to an associated sub-transmission 10A, 10B of the summing transmission 10. Each of the electric machines 8, 9 is accordingly coupled in terms of drive technology to the common output shaft 7 via the respectively assigned partial transmission 10A, 10B. The shaft bearings for the output shafts 8B, 9B of the electric machines 8, 9 or for the respective input shafts of the partial transmissions 10A, 10B are preferably designed as fixed bearings on the output side of the electric machines 8, 9. In FIG. 3 and FIG. 4, these shaft bearings are designed as grooved ball bearings by way of example. These fixed bearings guide an axial force of the summing gear 10 into an intermediate wall 3A of the drive unit 3, which separates the actual electric machines 8, 9 and the actual summing gear 10 from one another.

As can be seen in FIG. 2, the suspension points 14 of the drive unit 3 for fastening the drive unit 3 to the frame 2 of the vehicle 1 are preferably arranged at the level or above the axes of rotation of the rotors 8B, 9B. There, the drive unit 3 is thus attached to the frame 2.

The partial transmissions 10A, 10B are only indicated in FIGS. 3 and 4. The partial transmissions 10A, 10B are preferably designed as helical-toothed spur gear transmissions. At least one of the partial transmissions 10A, 10B is switchable in two stages, in particular both of the partial transmissions 10A, 10B. The two-stage sub-transmission 10A, 10B thus has two gear ratios (gears), which can be selectively engaged. A neutral position (idle) can then also be engaged. The partial transmissions 10A, 10B preferably have slightly different ratios.

A power take-off 15 is provided in the area of the electric machine 8. The power take-off shaft 15A can be releasably coupled to the input shaft of the partial transmission 10A via a switching element (here a clutch). This input shaft is in turn coupled to the output shaft 8C of the electric machine 8. In the coupled state, the power take-off shaft 15A thus rotates at the same speed as the rotor of the electric machine 8.

FIG. 4 shows a sectional view of the drive unit 3 from FIG. 2 along the section line X-Y shown there. The second electric machine 9 is therefore not visible in FIG. 4.

It can be seen from FIGS. 3 and 4 that the summing gear 10 has an intermediate shaft 10C which is coupled to the two subgear 10A, 10B. This intermediate shaft 10C is connected via a further (common) sub-transmission 10D, which is also preferably designed as a helical spur gear (Common) output shaft 7 of the summing gear 10 coupled in terms of drive technology. The output shaft 7 of the summing gear 10 simultaneously forms the output shaft of the unit 3.

Alternative embodiments are possible in which no intermediate shaft 10C or no common partial transmission 10D is required. In this case, the electric machines 8, 9 can thus be coupled with the output shaft 7 directly via the respectively assigned partial transmission 10A, 10B.

4, the output shaft 7 is coupled, for example, via a constant velocity joint 16 to the end of the drive shaft 4 assigned to the drive unit 3. As an alternative to this, a universal joint can also be used, for example, or the shafts 4, 7 can be firmly connected to one another.

As can be seen from FIGS. 2 and 4, the output shaft 7 is laterally displaced in the direction of the second electric machine 9. In the installed state of the drive unit 3 shown in FIG. 1, the output shaft 7 is thereby laterally offset with respect to a vehicle longitudinal axis of the vehicle 1. The output shaft 7 thus runs off-center of the vehicle 1 and the frame 2. The input shaft 5A of the axle differential 5 is preferably also laterally offset with respect to the longitudinal axis of the vehicle. The output shaft 7 and the input shaft 5A can also be arranged at substantially the same height.

5 shows a process sequence for performing a shifting process in the drive unit 3 according to FIGS. 2 to 4. It is assumed here that at least the sub-transmission 10A assigned to the first electric machine 8 has two switchable gear ratios (gears), and a neutral position (idle). It is also assumed that one of the gear ratios of this sub-transmission 10A is engaged. As part of the switching process, the other gear stage of the partial transmission 10A, which is referred to below as the target gear, is now switched. The switching process is effected by the control unit 4. This therefore issues corresponding commands to the inverters 11, 12 and the switching device of the partial transmission 10A. Step A:

First, the second electric machine 9 is energized electrically by means of the associated inverter 12 in such a way that it generates a higher torque than in the previous case. The partial transmission 10B assigned to the second electric machine 9 is not to be shifted in the present case. It can therefore also be non-switchable.

Step B:

Subsequently or preferably at the same time as step A, the first electric machine 8 is energized electrically by means of the associated inverter 11 so that it generates a torque which is reduced in comparison with that previously. In particular, torque is no longer generated. Thus, the sub-transmission 10A that is to be shifted is relieved. In particular, the torque generated by the first electric machine 8 is reduced to the same extent that the torque generated by the second electric machine 9 is increased. The total torque generated by the electric machines 8, 9 on the output shaft 7 can thus be kept constant.

Step C:

The partial transmission 10A is now switched to its neutral position. It then no longer transmits torque.

Step D:

The electric machines 8 are now energized electrically by means of the assigned inverter 11 so that their speed changes to a target speed. The target speed corresponds to the speed that the partial transmission 10A would have at the present speed of the output shaft 7 with the target gear engaged. In other words, at the target speed, the speed ratio between the speed of the output shaft 7 and the speed of the rotor 8A of the electric machine 8 corresponds to that gear ratio of the partial transmission 10A in the target gear. To determine the speed of the output shaft 7, for example, a speed sensor can be provided. The gear ratios of the partial transmission 10A in the two gear ratios are fixed and known. They are stored in the control unit 4 in particular. The required target rotational speed can thus be determined from the known transmission ratio of the partial transmission 10A in the target gear and the determined rotational speed of the output shaft 7. number can be determined. The sub-transmission 10A is thus specifically synchronized for the target gear.

Steps:

The partial transmission 10A is switched from the neutral position to the target gear.

Step F: The electric machines 8, 9 are energized electrically by means of the respective inverter 11, 12 in such a way that the torque generated by the electric machine 8 is increased and that the torque generated by the electric machine 9 is reduced. This results in a specific torque ratio between the torques generated by the electric machines 8, 9.

This switching sequence can be used for upshifts and downshifts. In the case of a downshift, the target speed is increased compared to a previously existing speed of the electric machine 8. In the case of an upshift, the target speed is reduced compared to a previously existing speed of the electric machine 8. This switching sequence can also be used for switching operations of the other sub-transmission 10B if it has two switchable gear ratios and a neutral position.

Bezuaszeichen

1 vehicle, truck

frame

power unit

A partition

drive shaft

5 axle differential gear

5A input shaft

6 wheel

7 output shaft

8 electric machine

8A stator

8B rotor

8C output shaft

9 electric machine

9A stator

9B rotor

9C output shaft

10 summation gears

10 / partial transmission

101 partial transmissions

10 (intermediate shaft

101 partial transmissions

11 inverters

12 inverters

13 control unit

14 suspension point

15 power take-off

15 / PTO shaft

16 joint

step

Claims

claims

1. Drive unit (3) for a vehicle, in particular for a motor vehicle (1), the drive unit (3) having

a first electric machine (8) as a traction machine and

a second electric machine (9) as a traction machine and

a summing gear (10) for summing the torques generated by the first and second electric machines (8, 9) onto a common output shaft (7) of the summing gear (10), characterized by

(a) a first inverter (11) for electrically energizing the first electric machine (8) and a second inverter (12) separate from the first inverter (11) for electrically energizing the second electric machine (9).

2. Drive unit (3) according to claim 1, with

(b) a common cooling system for the first and second electric machine (8, 9), and / or

(c) a common lubrication system for the first and second electric machine (8, 9) and for the summation gear (10), and / or

(d) a common stator housing for the first and second electric machine (8, 9), and / or

(e) a common control device (13) for controlling the first and second inverters (11, 12).

3. Drive unit (3) according to one of the preceding claims, wherein the first electric machine (8) has a rotor (8B) with a first axis of rotation and the second electric machine (9) has a rotor (9B) with a second axis of rotation , in which

the output shaft (7) of the summing gear (10) is closer to one of the axes of rotation than to the other of the axes of rotation.

4. Drive unit (3) according to one of the preceding claims, wherein the first electric machine (8) has a rotor (8B) with a first axis of rotation and the second electric machine (9) has a rotor (9B) with a second axis of rotation , in which the first and second e-machines (8, 9) each have an output shaft (8C, 9C) which is coupled to the respective rotor (8B, 9B) and which forms the output of the respective e-machine (8, 9), in which

the first and second e-machines (8, 9) are arranged next to one another such that the axes of rotation of the rotors (8B, 9B) and / or the output shafts (8C, 9C) are parallel and laterally spaced apart and

that the output shafts (8C, 9C) are coupled to the summing gear (10) on a common output side of the electric machines (8, 9).

5. Drive unit (3) according to claim 4, wherein the output shaft (7) parallel and laterally spaced to the axes of rotation of the rotors (8B, 9B) and / or to the output shafts (8C, 9C) of the electric machines (8, 9) lies.

6. Drive unit (3) according to one of claims 3 to 5, wherein suspension points (14) of the drive unit (3) for fastening the drive unit (3) to a frame (2) of the vehicle (1) at the level or above the axes of rotation of the rotors (8B, 9B) of the first and second electric machine (8, 9) are arranged.

7. Drive unit (3) according to one of the preceding claims, wherein the summing gear (10) for the first electric machine (8) has a first sub-gear (10A) for transmitting the torque generated by the first electric machine (8) the output shaft (7) of the summing gear (10), and

wherein the summing gear (10) for the second electric machine (9) has a second partial gear (10B) for transmitting the torque generated by the second electric machine (9) to the output shaft (7) of the summing gear (10), wherein the first sub-transmission (10A) and / or the second sub-transmission (10B) has two switchable gear ratios.

8. Drive unit (3) according to claim 7, wherein the first and second sub-transmission (10A, 10B) have mutually different transmission ratios.

9. Drive train for a vehicle (1), the drive train having

an axle differential gear (5) which has an input shaft (5A) laterally offset with respect to a vehicle longitudinal axis and a drive unit (3), wherein

an output shaft (7) of the drive unit (3) is coupled to the input shaft (5A) of the axle differential gear (5),

characterized in that the drive unit (3) is designed according to one of the preceding claims, wherein

the output shaft (7) of the drive unit (3) is arranged in such a way that, at least in the installed state of the drive train (3), it is laterally offset to the same extent with respect to the vehicle longitudinal axis as the input shaft (5A) of the axle differential gear (5).

10. The drive train according to claim 9, wherein the axle differential gear (5) and the drive unit (3) are arranged such that the output shaft (7) of the drive unit (3) and the input shaft (5A) of the axle differential gear (5 ) are at the same height.

11. A method for performing a switching operation of a drive unit (3) according to claim 7 or 8, wherein one of the sub-transmissions (10A, 10B) of the summing gear (10) of the drive unit (3) is switched to a target gear, wherein

• The electric machines (8, 9), the partial transmission (10A, 10B) of which is not to be shifted, are energized electrically so that they generate a higher torque than previously, and

• The electric machine (8, 9), the partial transmission (10A, 10B) of which is to be shifted, is energized electrically so that it generates a torque which is reduced in comparison to that previously generated, in particular does not generate any torque, and

• The sub-transmission (10A, 10B) to be shifted is switched to a neutral position in which this sub-transmission (10A, 10B) has no torque between the associated electric machine (8, 9) and the output shaft (7) of the summation transmission (10) transmits, and

The electric machine (8, 9) whose partial transmission (10A, 10B) is to be shifted is energized electrically so that its speed changes to a target speed,

a speed ratio between the output shaft (7) of the summing gear (10) and the speed of the electric machine (8, 9) depending on the target speed. few sub-transmission (10A, 10B) to be shifted corresponds to the gear ratio of this sub-transmission (10A, 10B) in the target gear, and • the sub-transmission (10A, 10B) to be shifted is switched from the neutral position to the target gear.