DE102016209714B4 - Temporal stretching of an increase in drive torque when changing the operating mode of a hybrid drive - Google Patents

Abstract

Method for operating a hybrid drive in a motor vehicle (1), wherein the hybrid drive comprises an electric drive (5) with at least one electric motor and an internal combustion engine drive with at least one internal combustion engine (4), wherein - in a first, purely electric operating mode of the hybrid drive If a performance limit (Mem,max) of the electric drive (5) is exceeded by a power requirement (Msoll, asoll), the first, purely electric operating mode with operation of the electric drive (5) at the performance limit (Mem,max) of the electric drive (5) is initially maintained and - during a subsequent change from the first operating mode of the hybrid drive with operation of the electric drive (5) at the performance limit (Mem,max) and a power requirement (Msoll,asoll) that goes beyond the performance limit (Mem,max) into a second operating mode , in which the drive torque (Mist) of the hybrid drive is at least partially generated by the internal combustion engine drive (4), the increase in the drive torque (Mist) of the hybrid drive is artificially stretched in time; - the power requirement (Msoll, asoll) being a drive variable for controlling the power of the hybrid drive, whereby at the latest when changing from the first operating mode to the second operating mode, the drive variable (Msoll,asoll) is temporarily reduced in order to artificially extend the increase in the drive torque (Mist) of the hybrid drive over time and - the change in operating mode depends on State of charge of at least one energy storage unit supplying the electric drive (5): and/or- wherein the change in operating mode depends on a parameter indicating the driving mode selected by the driver.

Description

The invention relates to a method and a control system for operating a hybrid drive.

Today's motor vehicles often include several independent drive units that are controlled via a common torque coordinator. The total drive power of all drive units is greater than the drive power of each individual unit. For example, motor vehicles with hybridized drive trains that include at least one electric motor and at least one internal combustion engine are widespread. The task of this torque coordinator is, for example, to convert a target total torque for the entire drive, which is specified, for example, by the driver by operating the accelerator pedal or by a driver assistance system that influences the longitudinal guidance (e.g. a cruise control, an adaptive cruise control or a hill driving assistant), into target torques for each to transform individual drive units.

The specific design of this transformation in a specific operating point usually depends on a large number of factors, for example on factors that describe the operating state of the vehicle and/or the drive, or on factors that describe the current driver's request. A change in such a factor during driving can cause a significant change in the distribution of the target torques between the various drive units.

For example, in a vehicle with a hybridized drive train, the target torque for the electric motor can be maintained or reduced and the target torque for the combustion engine increased.

On the one hand, changing the drive operating mode can irritate the driver, as he may have consciously selected purely electric driving mode by setting an operating mode selector switch that may be present, but this is left without any conscious action by the driver. On the other hand, changing the operating mode can also pose a risk to the driver, since the actual torque of the internal combustion engine increases suddenly when changing the operating mode, since the target specifications of the assistance system are above the performance limit of the electric drive and therefore a high, possibly uncontrollable Acceleration of the vehicle can be caused.

From the disclosure document DE 10 2008 056 972 A1 a method is known that prevents driving comfort restrictions for the driver due to a sudden increase in the actual drive torque when changing the operating mode of a vehicle with a hybridized drive train, by predicting state changes that lead to a sudden increase in the actual drive torque and the drive torque in advance of the connecting drive unit is increased in the form of a ramp.

From the DE 10 2012 219 848 A1 a method for controlling or regulating a driver assistance system is known, wherein the driver assistance system requests a drive torque based on a driver specification and/or due to environmental conditions, which is provided either by the electric motor and/or electric motor if it can be seen based on a previous operator action by the driver that the Driver wants a consumption-oriented driving style.

From the DE 10 2011 005 803 A1 a method for operating a hybrid vehicle is known, wherein the vehicle is driven either in a first operating mode exclusively by the electric drive or in a second operating mode by the internal combustion engine and by the electric drive, or in a third operating mode is driven exclusively by the internal combustion engine, wherein the In the first operating mode, the driver specifies a desired drive torque via a selector element. The first operating mode is maintained even if the desired drive torque is greater than a maximum drive torque that can currently be provided by the electric machine.

From the DE 603 17 605 T2 a hybrid vehicle is known that prevents the internal combustion engine from starting too often, starting unnecessarily or starting undesirably.

It is the object of the invention to provide an alternative method and a corresponding control system to reduce the problem described above:

The task is solved by the features of the independent patent claims. Advantageous embodiments are described in the dependent claims.

A first aspect of the invention relates to a method for operating a hybrid drive in a motor vehicle, wherein the hybrid drive has a Electric drive with at least one electric motor and an internal combustion engine drive with at least one internal combustion engine, wherein in a first, purely electric operating mode of the hybrid drive when a performance limit of the electric drive is exceeded due to a power requirement, the first, purely electric operating mode with operation of the electric drive at the performance limit initially is maintained. Both the performance requirement and the performance limit do not necessarily have to be a performance quantity in the physical sense. These can generally be variables that are characteristic of the performance of a drive, in particular a drive torque or vehicle acceleration.

During a subsequent change from the first operating mode of the hybrid drive with operation of the electric drive at the performance limit and a power requirement that goes beyond the performance limit to a second operating mode in which the drive torque of the hybrid drive is at least partially generated by the internal combustion engine drive, the increase in the drive torque of the hybrid drive artificially stretched in time. This artificial time extension preferably ensures that the increase in drive torque does not result in vehicle acceleration that is uncontrollable for the driver.

The change in the operating mode of the hybrid drive can be caused by a variety of reasons, which will be discussed in detail later. For example, only a fall below a minimum charge level of the energy storage supplying the electric drive should be mentioned at this point.

The second operating mode mentioned is, for example, an operating mode in which the drive torque of the hybrid drive is generated partly by the electric drive and partly by the internal combustion engine drive, or alternatively an operating mode in which the drive torque of the hybrid drive is essentially completely generated by the internal combustion engine drive is produced.

In the method according to the invention, the power requirement is a drive variable for controlling the power of the hybrid drive, for example a drive torque or vehicle acceleration.

When changing from the first operating mode to the second operating mode, the power requirement is temporarily reduced in order to artificially extend the increase in drive torque of the hybrid drive over time. Preferably, the power requirement is reduced to a value that corresponds to the performance limit of the electric drive. Following this reduction, the power requirement is then increased again, for example, to the value that it had before the reduction (provided the driver or a driver assistance system continues to have the same power requirement as before the reduction).

In a further advantageous embodiment, after the power requirement has been temporarily lowered, the power requirement is increased, the increase taking place in the form of a ramp with such a limited, preferably constant gradient that the motor vehicle remains in a state that the driver can control. A constant slope of the ramp is calculated, for example, from the amount of change in the power requirement and the duration of the increase in the power requirement. For example, either the slope of the ramp can be calculated analytically and specified explicitly, or the slope of the ramp can be specified implicitly by a control function that checks the change in the amount of the power requirement at discrete points in time and limits it if necessary.

Limit values that can be controlled by the driver for the change in acceleration acting on a vehicle and for the absolute amount of acceleration acting on a vehicle are known from the field of operational safety. These limit values can, for example, serve as the basis for parameterizing the ramp. According to the invention, the change in operating mode depends on the state of charge of at least one energy storage unit supplying the electric drive.

For example, changing the operating mode from a first, purely electric operating mode to a second operating mode, in which the drive torque of the hybrid drive is at least partially generated by the internal combustion engine drive, is advantageous if the state of charge reaches or falls below a lower threshold value, below which, for example, not There is enough energy available to power the electric drive. The change in operating mode can also be triggered, for example, for reasons of component protection, for example if the temperature of at least one electric motor rises sharply due to operation at the performance limit and reaches or exceeds an upper threshold value, above which, for example, damage to the electric motor is to be expected.

According to the invention, the change in operating mode depends on one or more parameters that can be influenced by the driver, in particular on a parameter indicating the driving mode selected by the driver. For example, includes These hybrid vehicles often have switching devices that allow the driver to select an operating mode of the hybrid drive from a plurality of selectable operating modes. Well-known options include, for example, “Hybrid” or “eDrive”. In the latter operating mode, the vehicle is usually operated in a purely electric operating mode, analogous to the first operating mode of the method according to the invention. In contrast to the “eDrive” driving mode, in the “Hybrid” driving mode the vehicle is operated in an operating mode in which the drive torque is generated by both the electric drive and the combustion engine drive. This can be, for example, the second operating mode of the method.

For example, the power requirement for the hybrid drive is specified depending on a driver specification, in particular depending on a variable that is characteristic of the actuation of an accelerator pedal connected to the hybrid drive, for example a driver's desired torque derived from the accelerator pedal position.

Alternatively, it is possible for the power requirement for the hybrid drive to be specified by a driver assistance system that influences the longitudinal guidance of the vehicle. These can be, for example, driver assistance systems with automatic longitudinal guidance such as distance or cruise control. This can also be, for example, driver assistance systems with only longitudinal guidance support, such as a hill driving assistant, which compensates for a driver's desired torque specified by the driver via the accelerator pedal with the help of slope detection, so that the vehicle has a constant speed regardless of the actual slope of the road with a constant accelerator pedal angle holds.

Exceeding the performance limit of the electric drive can also be triggered by the power requirement specified by a driver assistance system when the driving situation changes, in particular when the driving resistance increases. Typical examples of this are a change in the coefficient of friction of the road or an increase in the gradient of the road, for example at the foot of a mountain or a bridge.

Exceeding the performance limit of the electric drive due to the power requirement specified by the driver assistance system can also be triggered depending on a change in the driver specification for the driver assistance system, in particular when the speed specification of a speed control function of the driver assistance system increases. For example, the electric drive can be able to drive the vehicle alone when driving on the flat at a speed of 130 km/h. As soon as the driver increases the speed limit to, for example, 160 km/h, the performance limit of the electric drive, which allows a speed of 150 km/h when driving on the flat, for example, can be exceeded. In this situation, the vehicle would accelerate to 150 km/h, maintain that speed and remain in an all-electric mode during both acceleration and maintenance.

A second aspect of the invention relates to a control system for operating a hybrid drive in a motor vehicle, wherein the hybrid drive comprises an electric drive with at least one electric motor and an internal combustion engine drive with at least one internal combustion engine, the control system being set up in a first, purely electric operating mode Hybrid drive when a performance limit of the electric drive is exceeded due to a power requirement to maintain the first, purely electric operating mode with operation of the electric drive at the performance limit. During a subsequent change from the first operating mode of the hybrid drive with operation of the electric drive at the performance limit and a power requirement that goes beyond this to a second operating mode in which the drive torque of the hybrid drive is at least partially generated by the internal combustion engine drive, the control system is set up to detect the increase in the drive torque of the hybrid drive to artificially extend the time.

In an advantageous embodiment of the control system according to the invention, the control system comprises a first control unit for a driver assistance system that influences the longitudinal guidance and a second control unit for a drive control of the hybrid drive. The two control units are connected to one another via a communication connection and are, for example, distributed across different control devices. The first control unit is set up to receive a variable that is characteristic of the current operating mode of the hybrid drive and a variable that is characteristic of the current performance of the hybrid drive, in particular a drive torque and/or a vehicle acceleration, from the second control unit, and based on these two received signals from the second Control unit to send the power request.

The second control unit is set up to determine the operating mode of the hybrid drive, the current operating mode of the hybrid drive and the Size that is characteristic of the current performance of the hybrid drive to be sent to the first control unit and to receive the power request from the first control unit for implementation by the hybrid drive.

A third aspect of the invention relates to a control unit of a driver assistance system that influences the longitudinal guidance for a vehicle with a hybrid drive, the hybrid drive comprising an electric drive with at least one electric motor and an internal combustion engine drive with at least one internal combustion engine. The control unit is set up to specify a power requirement for the hybrid drive and to receive a quantity that is characteristic of the current performance of the hybrid drive. When changing the operating mode of the hybrid drive from a purely electric operating mode to an operating mode in which the drive torque of the hybrid drive is at least partially generated by the internal combustion engine drive, the control unit is able to temporarily lower the power requirement in order to artificially increase the power of the hybrid drive to extend in time if the power requirement exceeds the size that is characteristic of the current performance of the hybrid drive.

The above statements regarding the method according to the invention according to the first aspect of the invention also apply in a corresponding manner to the control system according to the invention according to the second aspect of the invention and the control unit according to the invention according to the third aspect of the invention. Advantageous exemplary embodiments of the control system according to the invention and the control unit according to the invention that are not explicitly described at this point and in the patent claims correspond to the advantageous exemplary embodiments of the method according to the invention described above or described in the patent claims.

• 1 eine schematische Darstellung eines beispielhaften Kraftfahrzeugs;
• 2 eine schematische Darstellung einer beispielhaften Schnittstelle zwischen einer Steuereinheit für ein Fahrerassistenzsystem mit automatischer Längsführung und einer Steuereinheit für eine Antriebssteuerung;
• 3 ein Ausführungsbeispiel des erfindungsgemäßen Verfahrens;
• 4 beispielhafte Zeitverläufe bei einem Ausführungsbeispiel des erfindungsgemäßen Verfahrens; und
• 5 beispielhafte Zeitverläufe bei einem konventionellen Verfahren.

The invention is described below using an exemplary embodiment with the aid of the accompanying drawings. Show in these:

• 1 a schematic representation of an exemplary motor vehicle;
• 2 a schematic representation of an exemplary interface between a control unit for a driver assistance system with automatic longitudinal guidance and a control unit for a drive control;
• 3 an embodiment of the method according to the invention;
• 4 exemplary time courses in an exemplary embodiment of the method according to the invention; and
• 5 exemplary time courses for a conventional process.

1 shows a schematic representation of an exemplary motor vehicle 1. Wheels 2 are driven via an axle 3, the axle 3 being driven by an internal combustion engine drive 4 and an electric drive 5. Both the internal combustion engine drive 4 and the electric drive 5 are connected to a control unit 6 for drive control, which is also connected to a control unit 7 for a driver assistance system. In principle, other drive topologies are also conceivable, for example so-called axle hybrids, in which the two axles of a hybrid vehicle are each driven by a separate drive unit.

In 2 is a schematic representation of an exemplary interface between a control unit 7 for a driver assistance system with automatic longitudinal guidance and a control unit 6 of a drive control. The control unit 7 of the driver assistance system gives the control unit 6 of the drive control a current setpoint for a power-determining drive variable, for example a setpoint drive torque M _should or a setpoint vehicle acceleration a _should . The control unit 6 of the drive control transmits to the control unit 7 of the driver assistance system the current actual value for a power-determining drive variable, for example an actual drive torque M _or an actual vehicle acceleration _a , and the currently active mode BA of the hybrid drive, for example purely electric, hybrid or pure -combustion engine drive.

3 shows an exemplary embodiment of the method according to the invention, for which in 4 Time courses of relevant variables are shown.

• - verschiedene Antriebsmomente (Koordinatensystem 1),
• - der Antriebsmodus (Koordinatensystem 2),
• - die Ist- und die Soll-Fahrzeuggeschwindigkeiten (Koordinatensystem 3) und
• - die Fahrbahnsteigung (Koordinatensystem 4).

All four in 4 The coordinate systems 1, 2, 3 and 4 shown describe the time t on their respective abscissa axis. Different sizes are shown on their respective ordinate axes:

• - different drive torques (coordinate system 1),
• - the drive mode (coordinate system 2),
• - the actual and target vehicle speeds (coordinate system 3) and
• - the road gradient (coordinate system 4).

In the coordinate system 1, _exemplary curves for a _{predetermined} target total drive torque M, an actual actual total drive torque M and a performance limit M _em,max of the electric drive are given. The coordinate system 2 shows a change in the drive mode from the purely electric EV mode to a hybridized hybrid mode, in which the actual torque of the drive is generated by both the electric drive 5 and the internal combustion engine drive 4. The coordinate system 3 shows exemplary curves of a target vehicle speed v _target , which can be specified in particular by the driver assistance system, and an actual vehicle speed v _is . The coordinate system 4 shows the course of an increase in the road gradient with an associated increase in driving resistance.

At the beginning of the in 3 shown exemplary flowchart (see step 100), the vehicle 1 is in a purely electric operating mode with the target drive torque M set _being specified by the control unit 7 of the driver assistance system. The control unit 7 of the driver assistance system determines the target drive torque M _target based on a target vehicle speed v _target desired by the driver at the current driving resistance. The target drive torque M _should is according to 4 below the performance limit M _em,max of the electric drive 5, which is why the actual drive torque M _ist corresponds to the target drive torque M _target and the actual vehicle speed v _ist also corresponds to the target vehicle speed v _target .

In step 200, for example, the driving resistance increases due to an incline in the road. This increase begins from time t ₁ .

In order to be able _to maintain the speed specification v target, the control unit 7 of the driver assistance system increases the specification of the target drive torque M _target , which the actual drive torque M _ist follows with a small time delay.
Due to the continuous increase in the target total drive torque M _shall , the target total drive torque M _shall reaches and exceeds the performance limit M _em,max of the electric drive 5 in step 300 at time t ₂ .

Analogously, at time t ₂ the actual drive torque M _is would have to exceed the performance limit M _em,max of the electric drive 5 in order to continue to be able to follow the target drive torque M _should . Instead of starting the internal combustion engine 4, the drive remains in a purely electric operating mode EV at the performance limit M _em,max of the electric drive 5, which leads to the actual vehicle speed v _is falling and from the target vehicle speed v _should differs.

In step 400, at time t ₃ , for example due to the state of charge of an energy storage supplying the electric drive 5 falling below a threshold, the operating mode of the hybrid drive changes from purely electric EV operation to hybrid hybrid operation, in which the drive torque of the hybrid drive is both of Electric drive 5, as well as the internal combustion engine drive 4 is generated.

In step 500, as part of the change of operating mode in the control unit 7 of the driver assistance system, a temporary reduction in the target drive torque M target _is triggered, for example to the performance limit M _em,max of the electric drive. This reduction in the target drive torque M _should takes place at time t ₃ , essentially at the same time as the operating mode of the hybrid drive changes.

In the subsequent step 600, the control unit 7 of the driver assistance system increases the target total drive torque M _target again. However, this increase is spread over time so that it does not result in acceleration that the driver cannot control.

The target total drive torque M _shall is ramped up by the control unit 7 of the driver assistance system from time t _{3 to} time t ₄ , starting from the target drive torque M target which is reduced to the performance limit M _em,max of the electric drive. Due to the internal combustion engine drive 4, which is also active in the hybrid operating mode, the actual total drive torque M _can exceed the performance limit M _em,max of the electric drive and the specified target total drive torque M _should follow. As a result, the actual vehicle speed v _is getting closer and closer to the target vehicle speed v _should .

From time t ₄ onwards, the actual vehicle speed v _ist essentially corresponds again to the target vehicle speed v _target .

In 5 are, compared to 4 , the time curves are shown with a conventional control system. The four coordinate systems shown therein describe the same sizes as the four in 3 coordinate systems shown.

At the beginning, the vehicle 1 is in a purely electric operating mode with the target drive torque M set _being specified by the driver assistance system. The driver assistance system determines the target drive torque M _{should is} based on a target vehicle speed v target _desired by the driver and the currently existing driving resistance. At the beginning of the exemplary embodiment _, the target drive torque M _should is below the performance limit M _em,max of the electric drive 5, which is why the actual drive torque M _is the target drive torque M target and the actual vehicle speed v _is also the target vehicle speed v _should correspond.

At time t _1, the driving resistance increases due to an increase in the gradient of the road. In order to be able to maintain the speed specification v _target , the driver assistance system A increases the specification of the target drive torque M _target , which the actual drive torque M _ist follows with a time delay.

At time t ₂ , the actual drive torque M _is would have to exceed the performance limit M _em,max of the electric drive 5 in order to continue to follow the target drive torque M _should . For this purpose, the drive control 6 changes the operating mode from purely electric EV operation to hybrid hybrid operation, in which the drive torque of the hybrid drive is generated by both the electric drive 5 and the internal combustion engine drive 4. As a result, the actual drive torque M _is can follow the target drive torque M _should even over the performance limit M _em,max and the actual vehicle speed v _is remains essentially the same as the target vehicle speed v _should .

Claims (10)

Method for operating a hybrid drive in a motor vehicle (1), wherein the hybrid drive comprises an electric drive (5) with at least one electric motor and an internal combustion engine drive with at least one internal combustion engine (4), wherein - in a first, purely electric operating mode of the hybrid drive If a performance limit (M _em,max ) of the electric drive (5) is exceeded due to a power requirement (M _target , a _target ), the first, purely electric operating mode with operation of the electric drive (5) at the performance limit (M _em,max ) of the electric drive ( 5) _is initially maintained, and - in the event of a subsequent change from the first operating mode of the hybrid drive with operation of the electric drive (5) at the performance limit (M _em,max ) and a power requirement (M set) that goes beyond the performance limit (M _em,max ). _, a _shall ) in a second operating mode in which the drive torque (M _ist ) of the hybrid drive is at least partially generated by the internal combustion engine drive (4), the increase in the drive torque (M _ist ) of the hybrid drive is artificially stretched in time; - where the power requirement (M _target , a _target ) is a drive variable for controlling the performance of the hybrid drive, with the drive variable (M _target, a _target ) being temporarily lowered at the latest when changing from the first operating mode to the second operating mode in order to reduce the increase in the Drive torque (M _is ) of the hybrid drive to be artificially stretched in time and - where the change in operating mode depends on the state of charge of at least one energy storage unit supplying the electric drive (5): and / or - where the change in operating mode depends on a parameter indicating the driving mode selected by the driver . Procedure according to Claim 1 , where the drive variable (M _should , a _should ) is a drive torque (M _should ) or a vehicle acceleration (a _should ). Method according to one of the preceding claims, wherein after the temporary reduction of the drive variable (M _target , a _target ) the drive variable (M _target , a _target ) is increased and the increase takes place in the form of a ramp with a limited gradient such that the motor vehicle ( 1) remains in a condition that the driver can control. Method according to one of the preceding claims, wherein the power requirement (M _target , _asoll ) is specified for the hybrid drive depending on a driver specification, in particular depending on a variable that is characteristic of the actuation of an accelerator pedal connected to the hybrid drive. Method according to one of the preceding claims, wherein the performance requirement (M _target , a _target ) for the hybrid drive is specified by a driver assistance system (7) which influences the longitudinal guidance. Procedure according to Claim 5 , whereby the exceeding of the performance limit (M _em,max ) of the electric drive (5) is triggered by the power requirement (M _target , a _target ) specified by the driver assistance system (7) when the driving situation changes, in particular when the driving resistance increases. Procedure according to Claim 6 wherein the exceeding of the performance limit (M _em,max ) of the electric drive (5) is triggered by the power requirement (M _target , a _target ) specified by the driver assistance system (7) depending on a change in the driver specification for the driver assistance system (7), in particular depending an increase in the speed specification (v _target ) of a speed control function of the driver assistance system (7). Control system (6, 7) for operating a hybrid drive of a motor vehicle, wherein the hybrid drive comprises an electric drive (5) with at least one electric motor and an internal combustion engine drive (4) with at least one internal combustion engine, wherein - the control system (6, 7) is set up, In a first, purely electric operating mode of the hybrid drive, when a performance limit (M _em,max ) of the electric drive (5) is exceeded due to a power requirement (M _target , a _target ), the first, purely electric operating mode with operation of the electric drive (5) is activated the performance limit (M _em,max ) is initially maintained, - with a subsequent change from the first operating mode of the hybrid drive with operation of the electric drive (5) at the performance limit (M _em,max ) and one that goes beyond the performance limit (M _em,max ). Power requirement (M _target , a _target ) in a second operating mode, in which the drive torque (M _is ) of the hybrid drive is at least partially generated by the internal combustion engine drive (4), the increase in the drive torque (M _is ) of the hybrid drive is artificially stretched in time, - where the power requirement (M _target , a _target ) is a drive variable for controlling the performance of the hybrid drive, whereby when changing from the first operating mode to the second operating mode, the drive variable (M _target , a _target ) is temporarily reduced in order to increase the drive torque ( M _is ) of the hybrid drive to be artificially extended in time and - where the change in operating mode depends on the state of charge of at least one energy storage unit supplying the electric drive (5): and / or where the change in operating mode depends on a parameter indicating the driving mode selected by the driver. Control system (6, 7). Claim 8 , wherein the control system (6, 7) comprises - a first control unit (7) for a driver assistance system that influences the longitudinal guidance and - a second control unit (6) for drive control of the hybrid drive, the two control units being connected to one another via a communication connection, and - the first control unit (7) is set up, - a variable (BA) characteristic of the current operating mode of the hybrid drive and a variable characteristic of the current performance of the hybrid drive, in particular a drive torque (M _is ) and / or a vehicle acceleration (a _is ), of to receive the second control unit (6), and - based on this to specify the power requirement (M _target , a _target ) to the second control unit (6), and - the second control unit (6) is set up to - determine the operating mode of the hybrid drive, which is for current operating mode of the hybrid drive characteristic variable (BA) and the variable (M _is , a _is ), which is characteristic of the current performance of the hybrid drive, to the first control unit (7), and - from the first control unit (7) the power requirement (M _should, a _should ) for implementation by the hybrid drive. Control unit (7) of a driver assistance system which influences the longitudinal guidance for a vehicle with a hybrid drive, the hybrid drive comprising an electric drive (5) with at least one electric motor and an internal combustion engine drive (4) with at least one internal combustion engine, the control unit (7) being set up, - to specify a power requirement (M _should , a _should ) for the hybrid drive, - to accept a quantity (M _is , a _is ) that is characteristic of the current performance of the hybrid drive, and - when changing the operating mode of the hybrid drive from a purely electric one Operating mode in an operating mode in which the drive torque of the hybrid drive is at least partially generated by the internal combustion engine drive (4); and the power requirement (M _should , a _should ) exceeds the size (M _is , a _is ) that is characteristic of the current performance of the hybrid drive, the power requirement (M _should , _{a should} ) is temporarily reduced in order to reduce the increase in power (M _is , a _is ) of the hybrid drive to be artificially stretched in time, - where the power requirement (M _should, a _should ) is a drive variable for controlling the performance of the hybrid drive, whereby when changing from the first operating mode to the second operating mode, the drive variable (M _should, a _should ) is temporarily lowered in order to artificially stretch the increase in the drive torque (M _is ) of the hybrid drive in time and - where the change in operating mode depends on the state of charge of at least one energy storage unit supplying the electric drive (5): and / or - where the change of Operating mode depends on a parameter indicating the driving mode selected by the driver.

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