WO2008122393A1

WO2008122393A1 - Method for controlling the drive system of a motor vehicle

Info

Publication number: WO2008122393A1
Application number: PCT/EP2008/002609
Authority: WO
Inventors: Michael Back; Harald Braun; Norbert Ebner; Ralf KÖRBER; Martin-Claudio Schuler; Oliver Vollrath
Original assignee: Daimler Ag
Priority date: 2007-04-05
Filing date: 2008-04-02
Publication date: 2008-10-16
Also published as: DE102007016514A1

Abstract

The invention relates to a method for controlling a drive system (1) for a motor vehicle comprising an internal combustion engine (2) with a crankshaft (4) and at least one electric motor (3) that is or can be coupled to the internal combustion engine (2), in particular the crankshaft (4). According to the invention, when the vehicle is in overrun mode with the overrun cut-off activated (SAS), when said overrun cut-off (SAS (V3)) is deactivated, a target torque (MSoIlE) for the electric motor (3) is determined in the speed range approaching the idling range using a characteristic curve (K1 to Kn or L1 to Ln) that is determined from a characteristic curve field (F(K1 to Kn; L1 to Ln), in accordance with a speed gradient and/or a difference in speed.

Description

Method for controlling a drive system for a motor vehicle

The invention relates to a method for controlling a drive system for a motor vehicle with an internal combustion engine comprising a crankshaft and at least one electric motor which can be coupled to the internal combustion engine.

Such a drive system is commonly referred to as a hybrid drive. When developing and optimizing new drive systems for motor vehicles, emissions, fuel consumption, performance and ride comfort are taken into account. Today's internal combustion engines are generally equipped with engine management functions that can set different operating conditions.

For example, to reduce fuel consumption and pollutant emissions as an operating condition, coasting is adjustable when the driver takes his foot off the accelerator pedal while driving. In this case, the internal combustion engine is pushed by the inertia of the motor vehicle in overrun mode, the drive power of the internal combustion engine is no longer needed. By activating a so-called overrun fuel cutoff during coasting, especially above a lower speed limit, which is significantly above the idling speed limit, speed, usually the injection and the ignition of the internal combustion engine is switched off, wherein the motor vehicle is braked by the compression work to be performed by the internal combustion engine. A deactivation of the fuel cut is either at least indirectly by the driver, for example by this gas again, or automatically, for example, when the speed of the engine falls below a certain limit, which is above the idle speed. Then, fuel is supplied again and the ignition is switched on, so that the internal combustion engine again generates a drive torque.

The deactivation of the fuel cut and thus the injection usually takes place in a speed range well above the idle speed in a speed range of about 1500 U / min, while maintaining the fuel cut below this speed range would risk that the idle speed reached o - The falls below and not fast enough torque can be built so that the engine runs out (= so-called "stalling").

The invention is therefore based on the object of specifying an improved method for controlling a drive system of a motor vehicle, in which, in particular during overrun operation for fuel saving and comfort improvement, an extended fuel cut operation is made possible.

The object is achieved by a method having the features of claim 1.

Advantageous embodiments of the invention are the subject of the dependent claims. Reim inventive method for controlling a drive system for a motor vehicle with a comprehensive crankshaft internal combustion engine and at least one coupled to the internal combustion engine, in particular its crankshaft or coupled electric motor, when the vehicle is in overrun with activated overrun cutoff, when deactivating the fuel cut in the idling speed range determined on the basis of a characteristic field in response to a speed gradient and / or a speed difference characteristic curve a setpoint torque for the electric motor, which is set in particular on the electric motor for applying an additional torque to the crankshaft.

By setting and applying a resulting from the target torque to the electric motor, which is guided by one of the characteristic behavior of the motor vehicle representing characteristic curves and has positive values and thus applied as a driving torque on the crankshaft, the deactivation of the fuel cut to the Be delayed range of idle speed, without the engine runs out (= "stalled"), since the actual rotational speed of the engine is held in the idling speed range by the additionally applied torque of the electric motor to the crankshaft. This delayed deactivation of the overrun fuel cutout with simultaneous connection of the electric motor and the connection of a torque of the electric motor to the crankshaft thus makes possible an anti-swelling function for the internal combustion engine. In this case, preferably by the continuous determination of speed characteristics of the internal combustion engine, such as the speed gradient and the speed difference, the target torque to from these speed characteristics Resulting Drehzahlschwankungcn or critical speed values of the internal combustion engine dynamically adjusted so that these occurring speed fluctuations of the actual speed of the engine are compensated by switching on the dynamically set torque of the electric motor and results in a largely uniform and quiet speed curve. In addition, fuel consumption and pollutant emissions are reduced by such an adjustable uniform driving behavior in overrun mode and especially in overrun with overrun fuel cutoff.

The method is preferably in one or more control devices, in particular in an already existing control device, e.g. an engine control unit, or in a controller, in particular an existing controller, e.g. an idle controller, implemented.

The characteristic curve field expediently comprises a number of first characteristic curves, which are designed as torque / rotational speed characteristic curves and each associated with a rotational speed gradient, each of the first characteristic curves describing a nominal torque for the electric motor as a function of a variable rotational speed difference. Additionally or alternatively, the characteristic field may comprise a number of second characteristic curves, which are designed as torque-rotational speed characteristics and each associated with a speed difference, wherein each of the characteristics describes a target torque for the electric motor in response to a variable torque gradient.

Preferably, the difference between idle target speed and instantaneous actual speed of the internal combustion engine is determined as the speed difference. As a torque gradient is preferred, the first derivative of the speed changes of the actual speed of the internal combustion engine per predetermined time unit determined. In this way, for example, a strong reduction of the actual speed can be detected when the overrun fuel cut is activated in overrun and the actual speed also drops sharply due to the deceleration of the motor vehicle due to the compression work to be done by the engine and it thus quickly falls below the idling speed range to below the Idle speed and could lead to a shutdown of the engine. The resulting determined speed gradients or speed differences are used to determine the first torque-speed characteristic curve and the second torque characteristic curve, whereby a correspondingly high torque for the electric motor is requested based on the first or second torque-speed characteristic.

Furthermore, the individual first and second characteristic curves, each designed as a torque-speed characteristic curve, can be dependent on the selected automatic program, on a gradient, a vehicle speed, a longitudinal acceleration, a lateral acceleration and / or a temperature of the internal combustion engine, the electric motor and / or a battery be determined. By taking into account such, the driving behavior and the total torque of the motor vehicle influencing factors such as automatic program, incline, engine speed, vehicle speed and / or different temperatures, a differentiated adaptation of the additional engaging torque of the electric motor is possible, creating a uniform ride of the motor vehicle and thus a quiet driving in overrun mode and especially in idle speed range is possible. By taking into account, for example, the different temperatures, such as temperature of the internal combustion engine, the electric motor and / or the battery, in the respective characteristic curve ensures that, for example, the electric motor at a too low temperature of the internal combustion engine, when it is still cold, no heavy load by a torque application by the electric motor to the internal combustion engine. If, alternatively or additionally, the temperature of the electric motor and / or the battery is too high, an adjustment of the additional torque on the electric motor is omitted in order to avoid consequential damage, eg due to excessive loading of the electric motor or the battery. In addition, different characteristics may additionally be dependent on the selected gear. In order to take account of different negative drag torques resulting from different gradients of the road, the characteristic curves are determined as a function of the gradient, which is determined for example by means of an acceleration and / or inclination sensor. This means that in addition to the speed dependency, various other parameters have been taken into account for different characteristics.

Advantageously, the instantaneous actual rotational speed of the internal combustion engine is detected continuously by means of a rotational speed sensor. In addition, for example, from a control unit, in which a Leerlaufregier is implemented, the idling target speed continuously determined.

In a preferred embodiment, the deactivation of the fuel cutoff over conventional overrun operating method is only executed when the actual speed of the internal combustion engine is at least equal to or below the idling target speed. By such a delay of the deactivation of the fuel cut to the idle speed range of the internal combustion engine into the Fuel consumption of the motor vehicle significantly reduced. By connecting the determined on the basis of one of the first or second characteristic curves setpoint torque for the electric motor, a sufficiently good stalling protection is achieved. In the process, the electric motor is subjected to the determined dynamic setpoint torque while the speed range is close to idling until an upper speed limit for the internal combustion engine has been reached or exceeded. Alternatively or additionally, the deactivation of the fuel cut-off can be performed when the determined speed gradient exceeds a predetermined threshold. This ensures, in particular when reaching the idling speed range and large speed gradient, that by restarting the injection and the ignition supported by the connection of a requested torque for the electric motor quickly a sufficiently high torque is built up and the engine certainly does not run out.

In this case, for example, a request signal can be set to deactivate the fuel cut. The request signal is preferably determined as a function of the ascertained rotational speed characteristic values, such as the height of the rotational speed difference and the rotational speed gradient. In addition, the request signal for activation or deactivation of the overrun fuel cutoff can be formed as a function of the state of charge of a battery, of a gradient (= uphill drive), of a thrust operation or instantaneous thrust torque, and / or of the rotational speed of the internal combustion engine. In this case, the determination of the request signal for the fuel cutoff largely depends on the determined instantaneous speed characteristics. In a further preferred embodiment of the invention, the determined target torque for the electric motor is increased as a function of a currently possible maximum torque of the electric motor. This ensures that, in particular in a speed range below the idling speed, the electric motor is set with the maximum possible and available dynamic torque, which may be above the setpoint torque determined by the characteristic curve and then increased. In this case, the electric motor is set to reach or exceed a predetermined upper speed limit with the maximum possible torque, which is then applied to the crankshaft. The setting of the electric motor with the maximum possible torque is active only once per ignition run, unless the predetermined upper speed threshold is reached or exceeded. This avoids that the setting of the maximum torque is active more than once with an active anti-swelling function, eg with an empty tank.

Preferably, the currently possible maximum torque of the electric motor in dependence on the state of charge of a battery, the engine speed of the internal combustion engine, the temperature of the internal combustion engine, the temperature of the electric motor and / or the temperature of the battery can be determined. Thus, the electric motor is adjusted only with a currently allowable maximum torque, so that an overload of the electric motor is avoided.

In a further advantageous embodiment, the determined target torque for the electric motor is limited to a predetermined minimum torque of the electric motor. Is determined according to the method described above, a target torque for the electric motor to achieve an anti-ulcer, which is expediently above an effective minimum torque of the electric motor, this is preferably switched on, wherein the determined target torque for the electric motor is set at this. The determined setpoint torque is also set when the electric motor is already switched on. In detail, the Abwürgeschutzfunktion high so that he ^¬ mittelte target torque is set sufficiently quickly prioritized when the electric motor.

The electric motor is in particular a rotating electrical machine, which can be operated both as an electric motor and as an electric brake, starter generator and / or generator. In addition, a braking energy obtained in a conventional manner from a set and applied braking torque can be stored, for example in a battery, by the electric motor which can also be operated as a generator.

The electric motor can be coupled or coupled indirectly via an automated manual transmission or an automatic transmission with the internal combustion engine. Alternatively, the electric motor may also be directly coupled or couplable, e.g. when the rotor of the electric motor - similar to a flywheel - is arranged directly on the crankshaft of the internal combustion engine or on a couplable extension of this crankshaft.

Embodiments of the invention are explained in more detail below with reference to drawings.

Showing:

Fig. 1 shows schematically a control unit for controlling an on ^¬ drive system having an internal combustion engine and a to this coupled or coupled electric motor, and

FIG. 2 shows a schematic diagram with different speed curves as a function of time, FIG.

3 shows a schematic diagram with a signal curve for fuel cutoff as a function of time with respect to the time diagram according to FIG. 2 according to the prior art,

4 shows a schematic diagram with a signal curve for fuel cutoff as a function of time with a delayed deactivation of fuel cutoff in relation to the time diagram according to FIG. 2, and FIG

Fig. 5 is a schematic diagram of a characteristic field with different examples of first and second characteristics, in particular torque-speed characteristics for determining a target torque for an electric motor.

Corresponding parts are provided in all figures with the same reference numerals.

FIG. 1 schematically shows a drive system 1 designed as a hybrid drive for a motor vehicle, comprising a combustion engine 2 and an electric motor 3. The electric motor 3 is connected or connectable with a crankshaft 4 of the internal combustion engine 2 and can drive these, ie exert positive or negative torques on them. To obtain recuperation energy, the electric motor 3 is connected to a battery 5. Depending on the type and structure of the Hyb Ridantriebs, eg serial hybrid, parallel hybrid or hybrid hybrid, the electric motor 3 directly or indirectly via a transmission 6, such as an automated manual transmission or an automatic transmission, with the crankshaft 4 coupled. In Ausführungsbeispiei of Figure 1, the electric motor 3 can be coupled directly to the crankshaft 4.

For controlling and / or regulating the drive system 1, an electronic control unit 7 is provided. The control unit 7 may be an already existing control unit, e.g. Brake control unit, engine control unit, Leerlaufregier, in which the method described below is implemented. In addition, other control and / or regulation techniques, e.g. for driving stability, idling control, engine control and / or brake control, be implemented in the control unit 7. By means of the control unit 7, both the internal combustion engine 2 and the electric motor 3, preferably only the electric motor 3 can be controlled and / or regulated.

In the operation of the motor vehicle, by removing an acceleration request, for example by the driver taking his foot off the accelerator pedal 8 and no longer actuating it, or by requesting an automatic traction drive control, for example a so-called cruise control, not acceleration, but a speed reduction, or a spacer for automatic compliance with a distance requesting a speed reduction, for the motor vehicle as the operating state, a pushing operation are set, in which the motor vehicle is pushed by its inertia and the driving power of the engine 2 is no longer needed. To control the Antriebssystcms 1 in such a coasting operation, the control unit 7 serve at least the following parameters, values and / or characteristics: a derived from a Aufspannungswert A pedal 9 of the accelerator pedal 8 torque request M, at least one rotational speed n of a speed sensor 10 (eg actual speed n _actual v of the internal combustion engine 2 and actual speed n _{IstE of} the electric motor), temperature _values T _v , T _E and T _B of temperature sensors 11 to 13 of the internal combustion engine 2, the electric motor 3 and the battery 5. In addition, the controller 7 further parameters supplied or from this is determined on the basis of other parameters: an idling nominal speed n _So ii _{empty /} momentary minimum actual torques M _minV and M _{minE of} the internal combustion engine 2 or of the electric motor 3 of the motor vehicle driving in overrun mode (which are referred to as thrust torques M _minV , M _m i _{nE hereinafter} ) , Speed limit values n _Gr enz, a request signal S _SA s for activating Activation or deactivation of a _fuel cut-off SAS and / or an effective minimum _torque M _effm i _{nE of} the electric motor 3 (= minimum limit).

In addition, for the consideration of operating and driving parameters when activating or deactivating the overrun fuel cutoff SAS further characteristic values are used: a state of charge value L of a state of charge SOC of the battery 5, an inclination value N of an inclination sensor 14, a program value P of an automatic program of the transmission selected by means of a switch 15 6, the vehicle speed v, a Längsbzw. Transverse acceleration a _{L / Q of} the motor vehicle.

By means of the control unit 7, a rotational speed gradient dn / dt representing the internal combustion engine 3 is used directly or indirectly for a given time period, directly or indirectly, on the basis of the ascertained or detected characteristic values, parameters and / or physical variables. , τ ~ π .J -

Speed gradient dn / dt and the speed difference Δn are continuously determined and are used to determine a characteristic curve Kl or Ll of a characteristic field F (Kl to Kn; Ll to Ln) for determining a desired _torque M _SOIIE for the electric motor 3. The each leading the electric motor 3 Torque characteristic Kl or Ll is as described in more detail below, determined by means of the control unit 7 on the basis of the detected and / or determined speed characteristics - the speed gradient dn / dt and the speed difference .DELTA.n - and possibly other parameters and / or parameters.

In detail, in overrun mode, depending on the value of the control unit 7 supplied and / or determined by this characteristic, in particular depending on the achievement or falling below a predetermined idle speed n _L or the idling target speed n _So ii _Leer described below with reference to FIGS 2 to 6 Method for setting a target _torque M _{SOIIE carried out} for the electric motor 3.

Figure 2 shows three speed curves Vl to V3 of the actual speed ni _st v and / or the actual speed ni _{stE of} the engine V2 and the electric motor 3 in overrun operation as a function of time t.

In this case, the speed curve Vl represents the course of the actual speed ni _st v of the internal combustion engine 2 in overrun mode with a fuel cut-off SAS (see FIG. 3) activated up to the time t1, as is customary in the prior art today. At the point in time t1, the overrun cutoff SAS (V1) is deactivated, ie the injection and the ignition are switched on again, so that the internal combustion engine 2 generates a torque M _1St V and the speed n _Ist v in the further course of time. initially continues to fall and after the time t2 transiently rises and falls again. In this case, the deactivation of the fuel cut-off SAS in response to a predetermined speed _limit n _Gre n _z in a well above the idle speed _{L L} lying speed range, eg at a speed value of 1500 rev / min ^'1 .

The speed curve V2 shows the course of the actual speed n _{Istv of} the internal combustion engine 2 in the event that the _fuel cut SAS (V2) is delayed disabled, eg only at time t2, ie in a speed range in which the actual speed ni _st v idle speed n has _Sun IIL _ee r reached or exceeded. The only then performed late activation of the ignition and the injection is not sufficient for a rapid torque build-up, so that the engine 2 goes out (= "stalled").

In order to avoid the stalling of the internal combustion engine 2 in such a late deactivation of the fuel cutoff SAS, ie at a deactivation of fuel cut SAS in idling speed range, in the inventive method a stall protection function is implemented in the control unit 7, which is described in more detail by the speed curve V3. In this case, as with the speed curve V2 and the timing diagram of Figure 4, by means of the control unit 7, the fuel cutoff SAS (V3) is only deactivated when the current actual speed ni _st v of the engine 2 reaches the idling target speed n _So ii _empty and / or has fallen below. If this is the case, a setpoint _torque M _SOIIE for the electric motor 3 is determined by means of the control unit 7 on the basis of a first characteristic curve _K1 or second characteristic curve Ll determined from a characteristic field F (Kl to Kn; Ll to Ln), wel ^¬ ches by means of the control unit 7 set on the electric motor 3 becomes. That is, at time t2, both the ignition and the injection of the internal combustion engine 2 are turned on and the determined target _torque M _{SOIIE set} at the electric motor 3, wherein when the electric motor 3, this is possibly still switched on by means of the control unit 7.

In this case, positive torque _{values are applied} to the crankshaft 4 as a driving torque by means of the set desired torque M _OOIIE . By such a characteristic-guided, additionally applied to the crankshaft 4 actual torque M _Is tE of the electric motor 3, a drop in the actual speed ni _st v of the engine 2 is far below the idle speed n _L safely avoided in a switch-off for the engine 2 inside.

FIG. 6 shows the characteristic field F (Kl to Kn, Ll to Ln) for determining the first and second characteristic curves Kl to Kn or Ll to Ln. In this case, the first characteristic curves K1 through Kn represent torque / rotational speed characteristics, which are each assigned to a rotational speed gradient dn / dt. Each of the first characteristic curves _K1 through Kn describes a setpoint _torque M _SOIIE for the electric motor 3 as a function of the determined variable speed difference Δn. The second characteristics Ll to Ln show torque-speed characteristics, which are each associated with a speed difference .DELTA.n. Each of the second characteristic curves Ll to Ln describes a setpoint _torque M _SOII E for the electric motor 3 as a function of the determined speed gradient dn / dt.

Is now in coasting mode on the basis of the determined speed characteristics, such as the speed gradient dn / dt and Drehzahldif ^¬ ference Δn, the fuel cutoff SAS (V3) only in an empty has been deactivated, a current first or second characteristic curve Kl or Ll is determined based on the implemented in Steuergerat 7 and Abwurgeschutzfunktion described above, based on a corresponding target torque Ms _o ii _{E is set} by means of the control unit 7 on the electric motor 3. In this case, the electric motor 3, _{which is} guided by the setpoint torque M _SOIIE, engages the crankshaft 4 of the internal combustion engine 2 with associated positive torque values, so that the actual speed n _actual v of the internal combustion engine 2 is reliably maintained in a speed range above a switch-off range, wherein the characteristic curve - Guided dynamic setting of the target _torque M _{SOIIE a gleichmaßiges} and quiet speed _{behavior of} the internal combustion engine 2 is set simultaneously.

In order to enable the fastest possible torque build-up, the characteristic-guided setpoint torque M _SOIIE for the electric motor 3 can additionally be increased to a corresponding value as a function of a currently possible maximum torque M _ma χ _{E of} the electric motor 3. This ensures that in the speed range below the idling speed n _L, the electric motor 3 is set with its maximum possible and available dynamic torque M _maxE , which may be above the setpoint torque M _SOIIE determined by the characteristic curve _{K 1} or _{L 1} , for example. Here, the E is set lektromotor 3 with the possible Maxi ^¬ maldrehmoment M _maxE until reaching or exceeding a predetermined upper rotational speed limit n _boundary. In addition, the currently possible maximum torque M _{maxE of} the electric motor 3 can be determined and predetermined as a function of the state of charge SOC of the battery 5, the actual number n _Ist v of the internal combustion engine 2 and / or the temperatures T _v , T _E , T _B. ^Hereby , it is ensured that the electric motor 3 is only connected to a is set at the currently permissible maximum torque M _maxE .

Further, further, the speed behavior of the motor vehicle influencing parameters can be considered. For this purpose, the relevant first and second characteristic curves Kl to Kn or Ll to Ln, for example, depending on the selected automatic program P, from the determined slope N and / or the temperatures T _{V /} T _E , T _B , for a speed-dependent characteristic control of the target torque M. _SOIIE the electric motor 3 determines. The consideration of these dependencies by a determined characteristic curve Kl or Ll in the determination of the setpoint _torque M _{SOIIE to be set} serves in particular for improved ride comfort and / or vehicle safety and / or vehicle stability.

Thus, for example, for vehicle safety at an excessively high engine temperature T _{E of} the electric motor 3, the setpoint torque Ms _o iiE is not activated in order to avoid an excessive load on the electric motor 3.

In a further embodiment of the invention, the request signal S _SAS for activating the overrun fuel cutoff SAS can be automatically formed depending on the state of charge SOC of the battery 5, the gradient N, the engine speed n of the internal combustion engine 2 and / or the value of a requested fuel cut-off torque M _SAS , The requested overrun fuel deceleration torque M _SAS is a torque M which is dependent on the minimum thrust or actual torque Mi _st v of the internal combustion engine 2 and the braking power of the internal combustion engine 2 and the inertia of the motor vehicle, for example by means of the control unit 7 on the basis of the parameters and parameters is determined. LIST OF REFERENCE NUMBERS

1 drive system

2 internal combustion engine

3 electric motor

4 crankshaft

5 battery

6 gears

7 control unit

8 accelerator pedal

9 accelerator pedal

10 speed sensor

11 Temperature sensor for internal combustion engine

12 temperature sensor for electric motor

13 temperature sensor for battery

14 tilt sensor

15 switches for selecting an automatic program

A clamping on the accelerator pedal a _L longitudinal acceleration a _Q lateral acceleration

M _maxE maximum torque of the electric motor

Mmi _nE minimum _{torque of} the electric motor

Me _ffm i _nE effective minimum torque of the electric motor

Msoii _E target torque of the electric motor

M _SAS overrun cutoff torque

N slope n rotation speed _Actual speed of the electric motor nis _t v Actual speed of the combustion engine n _L Idling speed ns _o ii _Le e _r idle idle speed

P automatic program

S _SAS demand signal for fuel cut-off

SAS overrun cutoff

SOC State of charge of the battery

Claims

claims

1. A method for controlling a drive system (1) for a motor vehicle with a crankshaft (4) comprising an internal combustion engine (2) and at least one with the internal combustion engine (2), in particular the crankshaft (4) coupled or koppeibaren electric motor (3), wherein when the vehicle is in overrun mode with overrun fuel cutoff (SAS) activated, when overrun fuel cutoff (SAS (V3)) is deactivated in the idling speed range using a characteristic field (F (Kl to Kn; Ll to Ln) depending on a speed gradient (dn / dt) and / or a rotational speed difference (Δn) determined characteristic (Kl to Kn or Ll to Ln) a target torque (M _So i _1E ) for the electric motor (3) is determined.

2. The method according to claim 1, characterized in that the characteristic field (F (Kl to Kn; Ll to Ln) comprises a number of first characteristic curves (Kl to Kn) formed as torque-speed characteristics and each a speed gradient (dn / dt), each of the first characteristic curves (Kl to Kn) describing a setpoint torque (M _So n _E ) for the electric motor (3) as a function of a variable speed difference (Δn).

3. The method according to claim 1 or 2, characterized in that the characteristic field (F (Kl to Kn; Ll to Ln) comprises a number of second characteristic curves (Ll to Ln) formed as torque-speed characteristics and each a speed difference (Δn) are assigned, wherein each of the characteristic curves (Ll to Ln) describes a target _torque (M _SOIIE ) for the electric motor (3) in response to a variable torque _gradient (dn / dt).

4. The method according to any one of claims 1 to 3, characterized in that as a speed difference (Δn), the difference between idle target speed (n _So iiLeer) and instantaneous actual speed (n _is v) of the internal combustion engine (2) is determined.

5. The method according to any one of claims 1 to 4, characterized in that as a torque gradient (dn / dt), the first derivative of the speed changes (dn) of the actual speed (ni _st v) of the internal combustion engine (2) per predetermined time unit (dt) is determined ,

6. The method according to any one of claims 1 to 5, characterized in that by means of a speed sensor (10) the instantaneous actual speed (n _Istv ) of the internal combustion engine (3) is _detected continuously.

7. The method according to any one of claims 1 to 6, characterized in that the idling target speed (n _So ii _Lee r) is determined continuously.

8- method according to one of claims 1 to 7, characterized in that the deactivation of the fuel cut-off (SAS (V3)) is executed when the actual speed (ni _st v) of the internal combustion engine (2) is at least equal to the idling speed target (nsoiiLeer) or this falls below.

9. The method according to any one of claims 1 to 8, characterized in that the deactivation of the fuel cut-off (SAS (V3)) is executed when the determined speed gradient (dn / dt) exceeds a predetermined threshold.

10. The method according to any one of claims 1 to 9, characterized in that the determined target _torque (M _SOIIE ) for the electric motor (3) in dependence on the currently possible maximum torque (M _maxE ) of the electric motor (3) is increased.

11. The method according to claim 10, characterized in that the currently possible maximum torque (M _maX E) of the electric motor in dependence on the state of charge (SOC) of a battery (5), of the actual speed (ni _st v) of the internal combustion engine (2), of the temperature (T _v ) of the internal combustion engine (2), the temperature (T _E ) of the electric motor (3) and / or the temperature (T _B ) of the battery (5) is determined.

12. The method according to any one of claims 1 to 11, characterized in that the determined target _torque (M _SOIIE ) for the electric Tor (3) to a vorqegebenes minimum torque (M _e rfm-.nE/ of the electric motor (3) is limited.