DE102010011164A1 - Method for controlling fuel cut-off turn-off combustion engine in hybrid vehicle, involves increasing target moment of electric machine during fuel cut-off phase to increase target moment of drive - Google Patents

Abstract

The method involves activating a fuel cut-off phase with braking of a hybrid vehicle, and increasing the target moment of an electric machine during the fuel cut-off phase with an increase of the target moment of a drive to increase the target moment of the drive. The fuel cut-off phase is deactivated if the target moment of the drive is increased by the electric machine or if the amount of the remaining target moment of the electric machine reaches or falls below a lower limit. Independent claims are also included for the following: (1) an engine control device (2) a hybrid vehicle comprising a fuel cut-off turn-off combustion engine.

Description

The invention relates to a method for controlling the engine in a hybrid vehicle with an internal combustion engine which can be switched off via a fuel cut-off and at least one electric machine. In particular, the invention deals with engine control during the fuel cutoff phase of the internal combustion engine.

From the prior art hybrid vehicles are known which comprise a drive with an internal combustion engine and an electric machine, wherein a torque generated by the electric machine can act on the output. The electric machine can deliver torque both as a motor and as a generator as a generator. Here, different types of hybrid drives are known, for example, a mild hybrid drive, which allows both regenerative braking and torque assistance of the internal combustion engine, or a full hybrid, which also allows fully electric driving.

Furthermore, the fuel cut of an internal combustion engine is known from the prior art. This is a controlled interruption of the fuel supply of an internal combustion engine, in particular an interruption of the fuel injection.

Typically, in conventional non-hybrid, IC engine vehicles, as well as in hybrid vehicles, in the case of accelerator pedal actuation in a fuel cutoff phase, the fuel cutoff is immediately disabled in response and the engine is re-fired. The same applies to an external torque increase during a fuel cut-off phase. External torque increases are understood to mean an increase in the required drive torque, which does not directly result from driver's actuation of the accelerator pedal and is requested as external torque requests from ECUs (external to the engine control unit) such as transmission control or vehicle stabilization. Even in the case of an external torque increase, the fuel cut-off in response to this is immediately deactivated and the internal combustion engine is fired again.

A disadvantage of an immediate deactivation of the overrun fuel cutoff in the case of an accelerator pedal operation or in the case of an external torque increase is that when the fuel cutoff is deactivated, the internal combustion engine is re-fired and the instantaneous fuel consumption then increases again significantly.

From the publication DE 10 2004 052 786 A1 a method for controlling the overrun operation in a hybrid vehicle is known, which extends the fuel cut-off phase, that the fuel cut is only deactivated when the engine reaches or falls below a certain restarting speed, which is at most 200 revolutions per minute above the idling speed of the internal combustion engine.

It is an object of the invention to achieve an extension of the fuel cut-off phase in the case of an accelerator pedal operation or an external torque increase.

The object is solved by the features of the independent claims.

A first aspect of the invention relates to a method for controlling the engine in a hybrid vehicle with an internal combustion engine which can be switched off via a fuel cut-off and at least one electric machine. According to the method, the overrun fuel cutoff is initially activated during overrun operation of the hybrid vehicle. Should it then be determined that there is an increase in the desired torque of the drive (ie an increase in the torque required by the engine control to the drive), the setpoint torque of the electric machine during the fuel cut-off phase is increased by the increase of the desired torque to realize the drive. Typically, during the overrun cutoff phase, the electric machine is in recuperation mode; Therefore, increasing the target torque of the electric machine corresponds to decreasing the amount of the target recuperation torque of the electric machine.

The engine control thus tries to provide the requested torque increase - if possible - via the electric machine of the hybrid vehicle. This allows the engine to be left longer in the overrun fuel cutoff, thereby reducing fuel consumption.

Preferably, the internal combustion engine only then leaves the fuel cut-off phase (ie the fuel cut is deactivated) if the requested increase in the desired torque of the drive during the fuel cut-off phase can not or no longer be provided by the electric machine, that is no longer by reducing the amount of Target Rekuperationsmoments the electric machine can be applied. The deactivation of the overrun cutoff could also take place earlier, for example, depending on operating parameters of the drive, even if the setpoint recuperation torques are not completely exhausted. It may be provided that the internal combustion engine only then leaves the fuel cut-off phase, when the amount of remaining target recuperation torque equals or falls short of a minimum residual recuperation torque amount of the electric machine; This minimum remaining recuperation torque amount (ie, the lower limit) may also be set to zero.

The increase in the desired torque of the engine may be based on accelerator operation during the fuel cut phase to accelerate the vehicle. When accelerator pedal operation during Schubabschaltephasen the internal combustion engine is preferably not re-fired until the desired torque of the drive can not be made by reducing the amount of recuperative torque of the electric machine. In conventional hybrid vehicles, on the other hand, when the accelerator pedal is actuated, the fuel cut-off phase is immediately ended and the internal combustion engine is re-fired.

The increase in the setpoint torque of the drive may alternatively also correspond to an external torque increase, for example by the transmission control, the driving stabilization or the temporal. In the case of an external torque increase during the fuel cut-off phase, the internal combustion engine is preferably only re-fired when the electric machine can not independently set the torque increase. In conventional hybrid vehicles, the internal combustion engine is stopped with external torque increases the fuel cut-off phase and the internal combustion engine re-fired.

For example, an external torque increase may occur when the electronic transmission control requests an external torque intervention for a push downshift or clutch adaptation, such as when an automatic transmission controller shifts from one gear to another gear (eg, from fourth gear to third gear). An external torque increase can also be requested by a drive stabilization system or cruise control (both systems can be part of the DCS, DCS - Dynamic Stability Control). An increase in torque can be used for example for a reduction of the drag torque. In this case, the internal combustion engine is often commanded to re-fire, in order to get from the unspotted drag torque of the internal combustion engine to a fired drag torque (eg unfired drag torque = -40 Nm, fired drag torque = -10 Nm, drag torque reduction by 30 Nm). However, the DSC can also request an increasing torque intervention from the point of view of the cruise control (eg the desired speed can not be maintained due to uphill driving).

It can be checked whether the increase of the desired torque of the drive (for example due to a torque increase) can be applied by the electric machine. The increase of the target torque of the electric machine takes place when the increase of the desired torque of the drive can be applied by the electric machine. Alternatively, the fuel cut-off phase is deactivated immediately.

Preferably, the desired torque of the drive substantially corresponds to the sum of the desired torque of the internal combustion engine and the desired torque of the electric machine. The moment of the electric machine is preferably integrated in the adjustment range of the drive. The integration of the torque of the electric machine in the control range of the drive is described in the German patent application "Method for controlling a drive system in a motor vehicle", which was filed by the same Applicant on March 12, 2010. The disclosure of the above-mentioned application (in particular the explanations on the integration of the torque of the electric machine into the actuating range of the drive) is hereby incorporated by reference in the disclosure content of the present application.

A second aspect of the invention is directed to an engine control apparatus which is arranged to carry out the method described above. All explanations regarding the method described above and its preferred embodiments apply correspondingly to the engine control unit.

A third aspect of the invention is directed to a hybrid vehicle having an overrun fuel cut-off engine and at least one electric machine. The hybrid vehicle includes the engine control apparatus according to the second aspect of the invention.

The invention will be described below with reference to the accompanying drawings with reference to several embodiments. In these show:

1a an exemplary course of the internal combustion engine drag torque 1 and the driver's request torque 2 at an accelerator pedal request during the Schubabschaltephase;

1b the exemplary course of the moment 3 the electric machine;

1c the one in 1a illustrated driver request torque underlying exemplary course of the accelerator pedal request 4 ;

2a an exemplary course of the internal combustion engine drag torque 11 and the driver's request torque 12 at an external torque request;

2 B the one in 1a illustrated driver request torque underlying exemplary course of the external torque intervention 13 ; and

2c an exemplary maximum adjustable moment 15 and minimal adjustable moment 16 the electric machine and the torque curve 14 the electric machine including the moment intervention.

In conventional drives, the internal combustion engine leaves the fuel cut-off phase directly with an accelerator pedal request. In the method according to the invention, the internal combustion engine can leave the fuel cut-off phase later. By means of the invention, the internal combustion engine can thus remain longer in the fuel cut-off phase. This can reduce fuel consumption.

In the 1a - 1c Illustrated courses relate to an embodiment of the invention, in which an accelerator pedal operation takes place during the overrun fuel cut-off phase in order to accelerate the vehicle. 1a - 1b show an exemplary course of the internal combustion engine drag torque 1 , the driver's torque 2 (ie, the desired torque of the drive) and the torque 3 the electric machine. 1c shows the exemplary course of the accelerator pedal request 4 , At the in 1a - 1c illustrated example of the method according to the invention begins at time A, the accelerator pedal request by pressing the pedal. In a conventional drive, the engine would leave the fuel cut-off phase at time A and re-fire the engine. In a hybrid drive, the internal combustion engine can later be re-fired, namely, for example, only when the accelerator pedal request of the driver can not be realized by reducing the amount of recuperative torque of the electric motor. In 1a represents the difference between the engine drag torque 1 and the driver's request moment 2 the recuperative moment of the electric machine, z. B. the moment of Schubrekuperation and / or Bremsrekuperation. The moment of the electric machine is in 1b shown. As it turned out 1b , the torque of the electric machine during the overrun cut-off phase is increased (ie, the amount of recuperative torque is reduced) to increase the driver's desired torque 2 to realize. Only when the driver's request torque 1 at time B, the internal combustion engine drag torque 1 exceeds, the internal combustion engine is re-fired. Alternatively, it would also be conceivable to re-fire the engine a little earlier. To 1a It should be noted that at time B, the actual torque of the internal combustion engine increases although it is not shown (in FIG 1a is the engine drag torque 1 shown, which remains constant).

By means of the invention, the internal combustion engine can remain in the fuel cut-off mode for a longer period of time, ie, at the maximum until time B.

In the 2a - 2c shown courses relate to an embodiment of the invention, in which during the fuel cut-off phase, an external torque request (s. 2 B ) at time A begins. 2a - 2 B show the exemplary course of the internal combustion engine drag torque 11 , the driver's torque 12 (ie, the desired torque of the drive, in which an external torque intervention is also included) and the external torque intervention 13 , 2c shows an exemplary maximum adjustable torque 15 and an exemplary minimal adjustable moment 16 the electrical machine and the torque curve 14 the electric machine including the moment intervention. In conventional drives, the internal combustion engine leaves the fuel cut-off phase as soon as there is an increasing torque intervention. In the example shown, the internal combustion engine would leave the fuel cut-off phase at time A and the internal combustion engine would be re-fired. In a hybrid drive, the combustion engine can later be re-fired, namely, for example, only when the increasing torque intervention 13 exceeds the torque potential of the electric machine and can not be realized by the electric machine. Only when the positive moment requirement 13 (S. 2 B ) can no longer be realized by the electric motor, the internal combustion engine is re-fired in this example.

By means of the invention, the internal combustion engine can remain in the fuel cut-off operation during an external torque request.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102004052786 A1 [0006]

Claims (10)

Method for controlling the engine in a hybrid vehicle with an internal combustion engine which can be switched off via a fuel cut and at least one electric machine, comprising the steps of: activating overrun fuel cutoff of the hybrid vehicle; and - increasing the desired torque ( 3 . 14 ) of the electric machine during the Schubabschaltephase with an increase of the desired torque ( 2 . 12 ) of the drive to realize the increase of the target torque of the drive. Method according to Claim 1, with the further step of: deactivating the fuel cut-off when the increase in the desired torque ( 2 . 12 ) of the drive can not or can no longer be applied by the electric machine or the amount of the remaining setpoint torque of the electric machine reaches or falls below a lower limit. Method according to one of the preceding claims, wherein increasing the desired torque ( 3 . 14 ) of the electric machine by reducing the amount of the target recuperation torque of the electric machine. Method according to claim 3, wherein the fuel cut-off is deactivated when the increase of the desired torque ( 2 . 12 ) of the drive can no longer be made by reducing the amount of the desired recuperation torque of the electric machine or the amount of the remaining target recuperation torque reaches or falls below a lower limit. Method according to one of the preceding claims, wherein the increase of the desired torque ( 2 . 12 ) of the drive based on accelerator operation during the overrun cutoff phase. Method according to one of claims 1-4, wherein the increase of the desired torque ( 2 . 12 ) on an external torque increase ( 13 ), in particular due to an external torque request from the transmission control, the driving stabilization system or the cruise control based. Method according to one of the preceding claims, with the step: - checking whether the increase of the setpoint torque ( 2 . 12 ) of the drive can be applied by the electric machine, wherein the increase of the desired torque ( 3 . 14 ) of the electric machine takes place when the increase in the desired torque of the drive can be applied by the electric machine. Method according to one of the preceding claims, wherein the desired torque of the drive ( 2 . 12 ) the sum of - the target torque of the internal combustion engine and - the desired torque of the electric machine ( 3 . 14 ) corresponds. Motor control device, which is set up for carrying out the method according to one of the preceding claims. Hybrid vehicle having an internal combustion engine which can be switched off via fuel cut-off and at least one electric machine, comprising the engine control device according to claim 9.

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