Procedures for operating a motor vehicle

Abstract

Method for operating a motor vehicle comprising a powertrain with at least one electric machine and an internal combustion engine designed to jointly generate a required torque, wherein the method comprises the steps: - Determination of the operating point of the internal combustion engine, in particular depending on the required torque - Division of the required torque into a first target torque to be generated by the electric machine and a second target torque to be generated by the combustion engine. - Change in the distribution of the required torque between the first target torque and the second target torque depending on at least one first operating parameter of the drive train - Limiting the change in the distribution of the required torque as a function of at least one second operating parameter of the drive train, and wherein the limitation is changed as a function of at least one reset condition, in particular preventing a limitation, and to determine the reset condition, a current redistribution and limitation is calculated, whereby a predefined calculation path is performed twice, once for determining the reset condition and once for the calculation using the reset condition, and a reset condition is generated when there is a sudden reduction in the available maximum first and / or second target torque, in particular a reduction to values ​​below the currently limited first and / or second target torque.

Description

[0001] The invention relates to a method for operating a motor vehicle, comprising a drive train with at least one electric machine and an internal combustion engine, which are designed to jointly generate a required torque.

[0002] Motor vehicles with a drivetrain in which a required torque can be supplied jointly by an electric motor and an internal combustion engine are known as hybrid vehicles. For example, in a parallel hybrid configuration, a torque specified by the driver, a so-called driver-desired torque, can be provided either by the electric motor or by the internal combustion engine, or by a combination of both. In such a "hybrid mixed operation," part of the driver-desired torque is provided by the electric motor and the remaining part by the internal combustion engine, or vice versa.The individual components of the driver's desired torque, provided as the first target torque by the electric motor and as the second target torque by the combustion engine, are variable and can be adapted to the prevailing driving conditions. In other words, the total desired torque requested by the driver can be provided by any combination of a first target torque and a second target torque.

[0003] Operating states or driving situations may arise in which a redistribution between the first target torque and the second target torque is not possible at will. In such an operating state, deviations between the actual torque ultimately introduced into the drivetrain and the driver's desired torque may occur. Such operating states may occur, for example, if a change in the second target torque, i.e. the torque that is to be provided by the combustion engine, is changed too sharply or too quickly, so that the combustion engine can no longer keep up with the change in the torque to be provided. Such deviations can occur both in overrun mode and in traction mode, so that the actual torque that is ultimately introduced into the drivetrain deviates from the driver's desired torque.

[0004] Methods for operating drive devices of hybrid vehicles are known from the prior art. For example, DE102004044507A1 discloses a method and a device for operating a vehicle drive system that includes, among other things, an internal combustion engine and an electric motor. The electric motor and the internal combustion engine essentially jointly generate a requested drive target torque.

[0005] DE102006006107A1 also describes a method for operating a drive device of a hybrid vehicle, in which the torques of the internal combustion engine and the electric motor are added together. The electric motor is designed to compensate for the inertia of the internal combustion engine.

[0006] DE102007012303A1 discloses a method for operating a hybrid drive. The hybrid drive comprises an internal combustion engine, designed as a turbocharged engine, and an electric motor. The total target torque is filtered for comfort reasons. The rate of change of the filtered total target torque is specified as low during load changes and then high, ensuring a smooth torque build-up, especially during load changes. This is intended to enable high dynamics without jerking.

[0007] DE102016225953A1 discloses a method for operating a motor vehicle with a hybrid powertrain. The method involves compensating for a latency occurring in the torque generation of the combustion engine by an electric motor. A target torque is determined based on a desired torque. The difference is provided as additional torque by the electric motor and reduced within a specified time interval. The difference is initially provided as additional torque by the electric motor.

[0008] DE102007023164A1 discloses a method for operating a hybrid drive of a vehicle. The total torque of the drive motors is adjusted when the transmission is shifted in order to reduce the load on the transmission and change the speeds according to the new gear ratio. During a transition between traction and overrun mode, the torque gradient is particularly taken into account. Furthermore, the behavior of the drive motors in generator mode of the electric motor is described.

[0009] The invention is based on the object of providing an improved method for operating a motor vehicle. Advantageous embodiments are the subject of the dependent claims.

[0010] As described, the invention relates to a method for operating a motor vehicle having a drive train with an electric machine and an internal combustion engine, which are designed to generate a required torque, in particular a driver desired torque.

[0011] The procedure includes in particular the following steps: - Determination of the operating point of the combustion engine, especially depending on the required torque - Distribution of the required torque between a first target torque to be generated by the electric machine and a second target torque to be generated by the combustion engine - Changing the distribution of the required torque between the first target torque and the second target torque depending on at least one first operating parameter of the drive train - Limiting the change in the distribution of the required torque depending on at least one second operating parameter of the drive train, and wherein the limitation is changed depending on at least one reset condition, in particular a limitation is prevented, and to determine the reset condition, a current redistribution and limitation is calculated, wherein a predetermined calculation path is carried out twice and the calculation for determining the reset condition is carried out once and the calculation using the reset condition is carried out once, and a reset condition is generated in the event of a sudden reduction in the available maximum first and / or second target torque, in particular a reduction to values ​​below the currently limited first and / or second target torque.

[0012] In other words, an operating point of the internal combustion engine is first determined, for example as a function of the required torque. The operating point of the internal combustion engine can, in particular, provide information about the extent to which the required torque can be provided by the internal combustion engine, for example as a function of its current operating state. The required torque, i.e. the driver's desired torque, can then be divided between the first and second target torques. The first and second target torques are understood herein merely as examples of a first target torque that is or can be provided by the electric machine. The second target torque is understood to be a corresponding torque that is or can be provided by the internal combustion engine. The terms “first target torque” and “second target torque” are interchangeable.If the motor vehicle has more than one electric machine, it is also possible that several initial target torques can be provided by the individual electric machines.

[0013] In other words, at specific operating points, the driver's desired torque can be distributed between the electric motor and the combustion engine, or distributed such that the electric motor generates a first target torque and the combustion engine generates a second target torque, which together correspond to the driver's desired torque. In a further method step, the distribution of the required torque, i.e., the driver's desired torque, between the first target torque and the second target torque can be changed depending on an operating parameter of the first drivetrain. The first operating parameter can relate to various properties of the drivetrain or, in general, of the motor vehicle, which cause a change in the distribution of the required torque.For example, these may relate to driving parameters of the motor vehicle or other properties, such as a selection of an operating mode, a charge state of an electrical energy storage device from which the electric machine is fed or other parameters that influence the distribution of torque between the electric machine and the combustion engine.

[0014] In a further method step, the change can be limited so that the distribution of the required torque as a function of at least one second operating parameter of the drive train cannot be carried out without limits, but rather a change to the previous distribution is only possible within certain limits. The limitation can take into account characteristics of the electric machine and / or the combustion engine, for example as a second operating parameter. For example, it can be taken into account which maximum changes in the required torque the combustion engine can follow. It can also be taken into account whether and within which limits the electric machine or the combustion engine could follow a change in the previously provided first and second target torque. In particular, the dynamics with which the change is carried out can be limited.

[0015] The described design, in particular, prevents operating conditions from occurring, or specifically avoids operating conditions, in which the driver's desired torque may deviate from the actual torque actually introduced into the drivetrain. This effectively prevents situations in which the driver perceives that the actual torque actually generated deviates from the torque specified by the driver as the desired torque. As described, the limitation can be implemented both in overrun and traction mode, ensuring that the actual torque does not significantly exceed or fall below the required torque in all driving conditions.

[0016] According to one embodiment of the described method, it is provided that the limitation is changed, in particular a limitation is prevented, depending on at least one reset condition. The described reset condition can take into account different operating states or conditions of the drive train in which the previously described limitation of the change in the distribution of the driver's desired torque can be changed or a limitation can be prevented entirely. In other words, the embodiment proposes that the limitation can be changed, i.e., a different limitation can be implemented depending on the reset condition, or the limitation can be completely removed.This allows, in selected driving situations or operating states that are ultimately described by the reset condition or are confirmed by the presence of the reset condition, the limitation to be lifted or modified to enable different driving characteristics of the vehicle. For example, the limitation can intervene less strongly to enable a faster change in the actual torque and thus an adaptation to the driver's desired torque.

[0017] The method can further be developed such that, when a reset condition is met, a gradient limiter is initialized, in particular for temporarily deactivating the limitation. This allows the redistribution of the target torque between the combustion engine and the electric machine to be limited in its dynamics, for example in order to prevent sudden redistribution. Such a sudden redistribution could, under certain circumstances, mean that the actual torques actually generated by the individual units, especially by the combustion engine, could no longer be followed, meaning that the set target torques could no longer be achieved and ultimately a deviation of the total actual torque from the driver's desired torque would occur. The gradient limiter therefore limits the dynamics in which the redistribution of the target torque orThe target torque or the distribution can be changed. This further minimizes emissions from the combustion engine and reduces mechanical load on the system by avoiding sudden torque redistribution, as well as improving noise emissions and passenger comfort.

[0018] As already described, various parameters relating to the operating state of the drive train or motor vehicle can be used as the reset condition or reset conditions. To determine the reset condition, a current redistribution and limitation are calculated, among other things. A predefined calculation path is carried out twice, with the calculation to determine the reset condition being carried out once and the calculation using the reset condition being carried out once. In other words, a first calculation path can be used to generate the reset conditions or at least one reset condition. In the further calculation path, the distribution or change in the distribution of the target torque is effected using the reset condition. Depending on whether a reset condition exists or not,Depending on the reset condition, a deactivation of the limiting function, especially a temporary one, can be initiated, for example, as described by initializing the gradient limiter. The reset condition is generated, for example, when a specific operating state of the powertrain or the motor vehicle is present. In such operating states, the limitation of the dynamics is suspended.

[0019] For example, a reset condition can be generated when switching between push and pull operation. If a switch occurs between push and pull operation, the reset condition can be generated in the corresponding calculation path, as described. The reset condition results in the dynamic limitation not being applied when determining the distribution or changing the distribution. Thus, when switching between pull and push operation, no dynamic limitation occurs, and the distribution and change of the distribution can be performed as desired.

[0020] Another operating state that can cause a reset condition to be generated can be a sudden reduction in the available maximum first and / or second target torque, in particular a reduction to values ​​below the currently limited first and / or second target torque. For example, a sudden reduction in the maximum available or deliverable torque on the part of the electric machine and / or on the part of the combustion engine to values ​​below the corresponding torque currently limited in dynamics, in particular with respect to positive values, can lead to the generation of the reset condition. For example, in traction operation, the maximum torque that can be delivered by the electric machine, for example a second actual torque, can drop suddenly, for example due to an insufficient state of charge of the electrical energy storage device, so that the second target torque can no longer be met.In this case, a reset condition is generated that removes the limitation of the dynamics, so that a change in the distribution of the torques outside the limitation is possible.

[0021] A further reset condition, or alternatively, a reset condition is generated when the available minimum first and / or second target torque is suddenly reduced to values ​​above the currently limited first and / or second target torque. This could, for example, be the case during overrun, in which the minimum first and / or second target torque is above the first and / or second limited target torque. This could result in the driver's desired torque being overfulfilled, so that a limitation on the change in the distribution can be lifted, allowing the torque distribution to be adjusted more effectively to avoid overfilling.

[0022] In general, the driver's desired torque can suddenly fall below the dynamically limited total torque in the current driving situation, for example in traction mode, or exceed it, for example in overrun mode. For example, the driver can trigger such a sudden change by suddenly changing the driver's desired torque to smaller values, in particular by suddenly releasing the accelerator pedal. In this case, the reset condition can be generated which removes a limitation of the dynamics. In general, a reset condition can therefore be generated if the required torque deviates from a limited total torque. As already described, the required torque corresponds to the driver's desired torque. The limited total torque corresponds to the sum of the actual torques that can ultimately be introduced into the drivetrain by the combustion engine and the at least one electric machine together.If the driver's desired torque deviates from the limited total torque, the reset condition can be generated so that the limitation can be removed in order to provide the required torque.

[0023] In addition to the method, the invention relates to a control device for a drive train of a motor vehicle, which is designed to carry out the method described above. The control device can, in particular, determine the reset condition and limit the change in the torque distribution. Furthermore, the control device can be designed to control the individual units. Furthermore, the method relates to a motor vehicle comprising such a control device. The motor vehicle further has the drive train, the at least one electric machine, and the internal combustion engine. The described method can thus be carried out on the motor vehicle, in particular using the control device described above.

[0024] The invention is explained below using exemplary embodiments with reference to the figures. The figures are schematic representations and show: Fig. 1 is a schematic flow diagram of the method according to a first embodiment; Fig. 2 is a schematic flow diagram of the method according to a second embodiment; and Fig. 3 a schematic simulation of different operating conditions of a motor vehicle.

[0025] Fig. Figure 1 shows a schematic flow diagram of a method for controlling the operation of a motor vehicle (not shown in detail). Such a motor vehicle has a drive train with at least one electric motor and an internal combustion engine.

[0026] The method can start in a block 1, in which an operating point, in particular an optimal one, of the internal combustion engine is determined. The operating point can be determined in particular in an efficiency map of the internal combustion engine. From this, in a block 2, the second target torque of the internal combustion engine is determined, i.e. the target torque that the internal combustion engine can provide at the current operating point. In a block 3, it is determined which first target torque, i.e. which target torque to be provided by the electric machine, must be applied in order to fulfill a driver's desired torque. In other words, the driver sets a driver desired torque, for example via a pedal position or pedal actuation, which is generated or is to be combined from the combination of the second target torque provided by the internal combustion engine and the first target torque provided by the electric machine.If it is known which second target torque the combustion engine can provide at its operating point, it can be determined which remaining torque is missing to reach the driver's desired torque, which ultimately has to be provided by the electric machine.

[0027] The operating limits of the electric machine can be considered in block 4. The extent to which the electric machine is capable of generating the first target torque in the current operating situation in order to meet the driver's desired torque together with the second target torque of the combustion engine can be taken into account in the first target torque. Block 5 therefore includes the driver's desired torque as well as the first target torque of the electric machine. Since the first target torque of the electric machine can take into account what the electric machine can provide in terms of first target torque in the current operating situation, this can be incorporated into block 6, which ultimately determines the operating limits of the combustion engine.In other words, in block 6 it can be determined which second target torque the combustion engine actually has to provide depending on the current ability of the electric machine to provide the first target torque.

[0028] When changing the distribution of the target torques, a limitation of the change can be implemented in block 7, for example, to ensure that the second target torque provided by the combustion engine can actually be provided or that the combustion engine can also follow the change in distribution. In block 8, the second target torque of the combustion engine that is to be provided can be added to the first target torque that can be provided via the electric motor.

[0029] In block 9, the limited second target torque can then be added to the first target torque of the electric machine. In other words, in block 9, the electric machine must compensate for what the combustion engine cannot achieve due to the limitation of the second target torque. In the event of a sudden change in the distribution of the target torque that the combustion engine could not follow, the change is limited in block 7, as described, for example based on a gradient limiter. The sudden change in the second target torque can therefore be implemented as a ramp. This creates a deficit in the total torque, which must be compensated for by the electric machine in block 9. In this case, it can then be determined in block 10 whether the electric machine, for its part, is exceeding its performance limits.If this is not the case, the distribution can be changed. If this is the case, a violation of the driver's desired torque may be unavoidable, and the corresponding target torques should only be set as close as possible to achieve the driver's desired torque as closely as possible.

[0030] By limiting the change in the distribution of the target torque in block 7, it is generally possible to prevent an actual torque or a sum torque from the target torques provided by the electric machine and the combustion engine based on the first target torque and the second target torque from deviating from the driver's desired torque or the required torque. The limitation can be implemented, for example, in the form of a gradient limiter. If the second target torque provided by the combustion engine is to be changed abruptly, the abrupt change can be converted into a ramp. The change in the distribution is thus limited in such a way that the ramp-shaped second target torque is compensated for by a corresponding adjustment of the first target torque, at least as far as possible.

[0031] In Fig. Figure 2 shows a schematic flow diagram of the described method in a second exemplary embodiment. In a first block 11, the presence of a reset condition is determined. For example, a calculation path can be used which determines whether the current operating situation or the operating state of the drive train or the motor vehicle requires the generation of a reset condition in order to remove or at least change the limitation of the change in the distribution of the target torques. A change in the limitation can, for example, represent an extension of the limits of the previous limitation. Likewise, the limitation can be removed entirely. If a reset condition exists, it is possible, for example, to start the described gradient limiter with the current torque or to perform the calculation with the currently available values. For example, the method according to Fig. 1 can be used for calculation or to determine whether a reset condition exists.

[0032] If no reset condition exists, the procedure can be continued as described in relation to Fig. 1. If a reset condition occurs, it can be determined or processed in block 12. Examples of reset conditions can be a change in operating mode, for example, a change between hybrid operation, purely combustion engine operation, or electric operation. Any change between two of the aforementioned operating modes is possible to generate a reset condition. Another example of an operating state that requires the generation of a reset condition can be a change from traction operation to overrun operation or vice versa.

[0033] Another example for generating a reset condition can occur when one of the units, for example the combustion engine or the electric machine, is limited in its ability to provide torque due to a specific operating condition, for example due to an insufficient charge level of an energy storage device, a fully charged energy storage device, a thermal event, an emergency operation program, and the like. If, for example, the limited second target torque is higher than the currently possible second target torque, the limitation can be lifted accordingly. If, for example, the limited second target torque is 200 Newton meters, but the currently adjustable second target torque is only 150 Newton meters, a reset condition must be generated that lifts the described limitation. The described reset condition can be transferred from the traction side to the push side accordingly.In particular, a minimum torque can be taken into account, which, for example, corresponds to a loss torque that cannot be undercut.

[0034] Another way to generate a reset condition is to compare a dynamically limited total torque with the driver's desired torque. If a deviation occurs between the driver's desired torque and the dynamically limited total torque, the reset condition can be generated to remove the limitation accordingly. It is also possible for the limited total torque to exceed or fall below the driver's desired torque. Generally, the reset condition can be generated if there is a deviation between the total torque and the driver's desired torque. In other words, if the difference between the limited total torque and the driver's desired torque is not equal to 0, the reset condition can be generated and the limitation removed.

[0035] In a block 13, the control of the drive train or the individual units, in particular the distribution of the target torques and the change in the distribution, can then be carried out, depending on whether a reset condition exists or which reset condition exists.

[0036] Fig. Figure 3 shows two diagrams arranged one above the other, showing various measured values ​​or various simulated or generated parameters of a motor vehicle. Different driving situations or operating conditions of the motor vehicle are illustrated as examples at different points in time. The implementation of the method will be explained below using these example situations. All torques and torque changes are to be understood purely as examples and can be adapted to the specific drivetrain. Both diagrams use the same time scale, which is represented by corresponding lines indicating the same points in time.

[0037] In the illustration shown, an upper diagram shows a curve 14 which represents the driver's desired torque, a curve 15 which represents the torque provided by the combustion engine, a curve 16 which represents the maximum torque that can be provided by the combustion engine, a curve 17 which represents the maximum torque that can be provided by the electric machine, and a curve 18 which represents the minimum torque that can be provided by the electric machine. The lower diagram shows three curves 19-21 which, in the case of curve 19, represent the total torque, in the case of curve 20 the torque requested by the combustion engine, and in the case of curve 21 the torque requested by the electric machine.

[0038] By way of example only, the driver's desired torque should be reduced at a time 22, which is represented by a ramp-like drop in curve 14. The torque drawn from the combustion engine, shown in curve 20, remains constant. The total torque, shown by curve 19, changes along with the driver's desired torque, shown in curve 14, so that the reduction in torque, for example from 400 Newton meters to 200 Newton meters, is brought about by a corresponding drop in the torque drawn from the electric machine, shown in curve 21. By way of example only, the power produced by the electric machine or the torque provided is reduced from 100 Newton meters to -100 Newton meters, so that in total with the torque of 300 Newton meters provided by the combustion engine, a total torque of 200 Newton meters is obtained.

[0039] Since the operation of the combustion engine does not need to be changed and the electric motor can implement the change in torque delivery, the described operating situation does not require the generation of a reset condition. Instead, the torque can be changed in a ramp-like manner, with the gradient limiter being able to be used as desired.

[0040] At a time 23, an operating situation reversed to that at time 22 is shown, in which the driver's desired torque is to be increased, for example, from 200 Newton meters to 400 Newton meters, as shown in curve 14. The combustion engine is to continue to operate at 300 Newton meters, as shown by curve 20. In order to increase the total torque, represented by curve 19, in accordance with the driver's desired torque, represented by curve 14, the torque requested by the electric machine, represented by curve 21, is increased in a ramp-like manner. Since the electric machine is readily capable of executing the ramp-like increase, the operating situation can also be executed without generating a reset condition.

[0041] Another operating situation is shown at time 24. In this operating situation, the driver's desired torque, represented by curve 14, is to be suddenly reduced from 400 Newton meters to 100 Newton meters, for example if the driver spontaneously releases the accelerator pedal. Accordingly, the total torque, shown in curve 19, is also reduced from 400 Nm to 100 Newton meters. In order to meet the total torque, the torque requested by the combustion engine is reduced as quickly as possible from 300 Newton meters to 200 Newton meters according to curve 20. To be able to execute the operating situation, a reset condition is therefore generated so that the gradient with which the torque generation can change is not limited by a gradient limiter.Accordingly, as shown by curve 21, the electric machine is also changed when generating the torque, so that the electric machine recuperates a torque of -100 Newton meters and the total torque is 100 Newton meters.

[0042] A reverse case is shown at a time 25, in which the driver's desired torque suddenly increases from 100 Newton meters to 400 Newton meters, for example when the driver suddenly depresses the accelerator pedal. The total torque, represented by curve 19, also increases accordingly from 100 Newton meters to 400 Newton meters. The total torque of 400 Newton meters is provided in this case by increasing the torque provided by the combustion engine from 200 Newton meters to 300 Newton meters, as shown in curve 20. In order to meet the total torque of 400 Newton meters, the torque generated by the electric machine, represented by curve 21, is increased from -100 Newton meters to 100 Newton meters. Since the change in torque occurs suddenly in this exemplary embodiment, a reset condition is generated which cancels or resets any limitation of the gradient.allows a change in the generation of torque without limitation.

[0043] Furthermore, the operating situation at times 26 and 27 is shown. The driver's desired torque, represented by curve 14, does not change. Here, a redistribution of the torques provided by the two units takes place. As shown in curves 15 and 20, the combustion engine's torque generation is ramped down in a ramp-like manner, for example from 300 Newton meters to 100 Newton meters, since the requested torque is reduced accordingly. Correspondingly, the torque requested by the electric machine, which is shown in curve 21, is increased from 100 Newton meters to 300 Newton meters. At time 27, the operating situation is reversed. Since a ramp-like change in the generated torque is sufficient in both operating situations, the generation of a reset condition is not necessary. The ramps can therefore be traversed with a limit provided by a gradient limiter.

[0044] Another operating situation is shown at time 28 or 29. At time 28, the driver's desired torque, shown in curve 14, does not change. The torque provided by the combustion engine, shown in curve 15, drops to 100 Newton meters. The torque requested by the combustion engine, shown in curve 20, is reduced in a ramp-like manner, from 300 Newton meters to 100 Newton meters. Conversely, the torque requested by the electric machine, shown by curve 21, can be increased in a ramp-like manner so that the total torque shown in curve 19 is not violated. Since the total torque is not violated, no reset condition is generated. The change in the requested torques or the generated torques can thus be limited and carried out in a ramp-like manner. The reverse operating situation is shown at time 29.This increases the torque generated by the combustion engine, with a corresponding ramp-like reduction in the torque required by the electric machine.

[0045] At time 30, the maximum torque available from the combustion engine, represented by curve 16, suddenly drops from 300 Newton meters to 200 Newton meters. This sudden reduction must be taken into account. The torque drawn by the combustion engine, represented by curve 20, is thus also suddenly reduced. This creates a reset condition to prevent the total torque of 400 Newton meters from being violated. This allows a sudden change in the torque drawn by the electric motor, which is represented by curve 21. By omitting the limitation of the gradients of the generated torques, sudden jumps are possible on the part of the electric motor of the combustion engine.

[0046] At time 31, a further operating situation is shown in which the maximum torque that can be provided by the combustion engine, represented by curve 16, is increased from 200 Newton meters to 400 Newton meters. The driver's desired torque, represented in curve 14, remains at 400 Newton meters. Likewise, the maximum torque that can be provided by the electric machine, represented in curve 17, is 400 Newton meters. The lower diagram shows that the torque called up by the combustion engine, represented by curve 20, is increased from 200 Newton meters to 300 Newton meters and, at the same time, the torque provided by the electric machine, represented by curve 21, is reduced from 200 to 100 Newton meters. Since the two changes can be carried out in a ramp-like manner, i.e. with limited dynamics, the generation of a reset condition is not necessary.

[0047] At time 32, the maximum torque that can be provided by the electric machine, shown by curve 17, drops to 0 Newton meters. At the same time, the minimum torque that can be provided by the electric machine, shown in curve 18, is also set to 0 Newton meters. The described condition can, for example, represent a failure of the electric machine or a limited availability of the electric machine, for example, due to an inappropriate charge state of the electrical energy storage device. In this case, a reset condition is generated so that the torque demanded by the combustion engine, shown in curve 20, can be increased from 300 Newton meters to 400 Newton meters.The reset condition is generated in particular because there is an unbalanced difference between the driver's desired torque of 400 Newton meters and the torque provided by the combustion engine, represented by curve 15, of 300 Newton meters.

[0048] At a time 33, an operating situation is shown in which the maximum torque available from the electric motor is increased to 400 Newton meters. In this case, the torque drawn from the combustion engine can be reduced from 400 Newton meters to 300 Newton meters, as shown in curve 20. Conversely, the torque drawn from the electric motor, shown in curve 21, can be increased from 0 Nm to 100 Newton meters, so that the driver's desired torque of 400 Newton meters is again met. The changes made to the drawn or supplied torque can, as shown, follow a ramp-like pattern, so that the generation of a reset condition is not necessary. Reference symbol 1-13 Blocks 14-21 curve 22-33 Time

Claims

[1] Method for operating a motor vehicle, comprising a drive train with at least one electric machine and an internal combustion engine, which are designed to jointly generate a required torque, the method comprising the steps of: - Determination of the operating point of the combustion engine, especially depending on the required torque - Distribution of the required torque between a first target torque to be generated by the electric machine and a second target torque to be generated by the combustion engine - Changing the distribution of the required torque between the first target torque and the second target torque depending on at least one first operating parameter of the drive train - Limiting the change in the distribution of the required torque depending on at least one second operating parameter of the drive train and wherein the limitation is changed depending on at least one reset condition, in particular a limitation is prevented, and to determine the reset condition, a current redistribution and limitation is calculated, whereby a given calculation path is carried out twice and the calculation to determine the reset condition is carried out once and the calculation using the reset condition is carried out once, and a reset condition is generated in the event of a sudden reduction in the available maximum first and / or second target torque, in particular a reduction to values ​​below the currently limited first and / or second target torque. [2] Method according to claim 1, characterized bythat when a reset condition is present, a gradient limiter is initialized, in particular to temporarily switch off the limitation. [3] Method according to one of the preceding claims, characterized by that a reset condition is generated when changing between push operation and pull operation. [4] Method according to one of the preceding claims, characterized by that a reset condition is generated when the available minimum first and / or second target torque is suddenly reduced to values ​​above the currently limited first and / or second target torque. [5] Method according to one of the preceding claims, characterized by that a reset condition is generated when the required torque deviates from a limited total torque. [6] Control device for a drive train of a motor vehicle, characterized bythat the control device is designed to carry out the method according to one of the preceding claims. [7] Motor vehicle comprising a control device according to the preceding claim.

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