DE102017211163A1 - Method for blocking or enabling a fuel cutoff - Google Patents

Abstract

The invention relates to a method for blocking (51) or releasing (60) an overrun fuel cutoff for an internal combustion engine (2) of a motor vehicle (1). The overrun fuel cutoff is inhibited (51) if a driving state (50) with low emissions for fuel cut is detected

Description

The present invention relates to a method for disabling or enabling a fuel cutoff for an internal combustion engine of a motor vehicle. Furthermore, the invention relates to a computer program that performs each step of the method when it runs on a computing device, and a machine-readable storage medium that stores the computer program. Finally, the invention relates to an electronic control device which is set up to carry out the method according to the invention.

State of the art

Today, great efforts are being made to save fuel in internal combustion engines while reducing pollutant emissions. However, the reduction of pollutant emissions has a negative impact on fuel economy in many cases. However, in order to comply with current regulatory pollutant emission limits, it is anticipated that a catalyst, such as e.g. a three-way catalyst is always optimally operated or at least close to optimum.

For example, in a three-way catalyst, a reduction in nitrogen oxides (NOx), hydrocarbons (HC), and carbon monoxide (CO) emitted depends very much on exhaust gas flowing through the catalyst, particularly its oxygen content. If the oxygen content in the exhaust gas becomes too large, the nitrogen oxide emission of the internal combustion engine can no longer be converted in the catalytic converter. For this reason, phases in which the catalyst is purged with air are unfavorable for the rate of conversion of the catalyst.

In the overrun phase, the accelerator pedal is not actuated when used in a motor vehicle, wherein the current speed of the internal combustion engine is above a predefinable Widereinsetzdrehzahlschwelle, and the motor vehicle moves forward due to its previously built by the driving kinetic energy. In such overrun phases usually takes place a so-called overrun cutoff, in which an engine control for reasons of fuel economy interrupts the injection, whereby, however, oxygen is introduced into the catalyst.

Typically, at least one lambda probe is disposed in an exhaust line of the internal combustion engine, which measures the ratio of air to fuel (also referred to as the combustion air ratio or air ratio, λ). Through a so-called lambda control, which cooperates with the engine control, an air / fuel ratio required by the catalyst is adjusted via the mass of the injected fuel, in order to optimize the reduction of the expelled nitrogen oxides, hydrocarbons and carbon monoxide by means of the catalyst.

To re-activate the nitrogen oxide conversion through the catalyst after the booster phases, the oxygen from the catalyst must be "cleared" by a rich air / fuel mixture (ie, λ <1). This process of "catalyst evacuation" at least partially reverses the fuel savings previously achieved during overrun fuel cutoff. This method is for example from the DE 102 40 833 A1 known.

Disclosure of the invention

The method is used to block or enable a fuel cutoff for an internal combustion engine of a motor vehicle. In this case, the blocking of the overrun cutoff takes place when a low-emission driving state for the overrun fuel cutoff is detected. Such for the fuel cut emission-unfavorable driving conditions are in particular states in which a pollutant emission of a catalyst, which is assigned to the internal combustion engine, can not be set optimally. These driving conditions, which are low in emissions for fuel cutoff, can lead to an excessively high emissions of pollutants. Blocking the fuel cutoff avoids such low-emission driving conditions. For the sake of simplicity, the low-emission driving states for the fuel cut are referred to below as low-emission driving conditions.

If such a low-emission driving state is detected, the internal combustion engine can advantageously be operated with an optimum air / fuel mixture for the associated catalytic converter. In a three-way catalyst used by way of example, a combustion stoichiometric air / fuel mixture (λ = 1) is preferably set in which so much oxygen is present that the fuel reacts completely with the oxygen. As a result, the nitrogen oxide emission is minimized.

Typically, fuel cutoff is followed by "scavenging" of the catalyst in which a rich air / fuel mixture is introduced to lower the oxygen content in the catalyst. The "clearing" of the catalyst is only necessary if a fuel cut has previously been made and can preferably be avoided if the fuel cut is disabled.

In the following, a preferred selection of factors for the low-emission driving conditions and measures for their detection is shown. The selection is incomplete and other factors and measures may be included. Likewise, not all factors need to be considered. In addition, the measures for detecting the low-emission driving condition can be freely combined with each other.

• - Eine Fahrerdynamik;
• - eine Last- und/oder Drehzahldynamik des Verbrennungsmotors, d.h. eine Motordynamik; und
• - eine Fahrzeugdynamik.

The following factors can be used to detect an emission-poor driving state for the fuel cutoff:

• - a driver dynamics;
• - A load and / or speed dynamics of the internal combustion engine, ie an engine dynamics; and
• - a vehicle dynamics.

One measure provides that the low-emission driving state is detected when a driver's dynamic is above a driver's dynamic threshold. The driver dynamics can be determined by evaluating the driver's request. The following quantities can be included in the determination of the driver dynamics: The rate of change of an accelerator pedal position in the positive direction, i. to a higher acceleration, recorded and / or considered the frequency of each occurring rate of change within a predetermined time. From these variables, the driver's request and thus the driver's dynamics can be determined.

The load dynamics and the speed dynamics can be summarized as engine dynamics. Another measure provides that the low-emission driving state is detected when the load and / or engine speed dynamics of the internal combustion engine is above an engine dynamics threshold. For this purpose, the rate of change of a positive (therefore towards higher values) speed and / or load change is determined. The speed can either be detected directly on the engine as the engine speed or indirectly determined, for example, from a camshaft speed, a transmission speed or the vehicle speed. For example, the load information can be derived in particular from an exhaust gas mass flow, an aspirated air mass flow, a mass flow of fuel, an in-cylinder pressure, an intake manifold pressure or from variables derived therefrom or from a combination of the aforementioned variables.

Yet another measure provides that the low-emission driving state is detected when the vehicle dynamics is above a vehicle dynamics threshold. The vehicle dynamics can be determined by evaluating the vehicle speed and the acceleration of the vehicle. For this purpose, on the one hand, the product of vehicle speed and positive acceleration, therefore towards greater speeds, can be determined. On the other hand, several products of vehicle speed and positive acceleration may be picked up for different times, then summed over them, and the result finally divided by the distance traveled to obtain Relative Positive Acceleration (RPA).

Preferably, filters are provided for the described measures. Here, the driver dynamics, the load and / or speed dynamics and the vehicle dynamics can be filtered as a whole. Alternatively, individual results of the evaluations can be filtered. For filtering, a moving average can also be formed for this purpose. The properties of the filtering and the time range used in the filtering can be adjusted to obtain an optimal significance of the filtered factors.

According to one aspect, the blocking of the overrun fuel cutoff can be canceled again if the driver dynamics, the load and / or rotational speed dynamics, the vehicle dynamics and the exhaust gas mass flow dynamics no longer exceed the respective associated threshold values.

In order to avoid that a constant change between locking and releasing the fuel cut occurs, which occurs in particular when the factors mentioned above are close to the associated threshold values, preferably a dead time after the lock and after the release of the fuel cut can be provided the fuel cut-off is not changed.

The computer program is set up to perform each step of the method, in particular when it is performed on a computing device or controller. It allows the implementation of the method in a conventional electronic control unit without having to make any structural changes. For this purpose it is stored on the machine-readable storage medium.

By loading the computer program on a conventional electronic control unit, the electronic control unit is obtained, which is configured to perform a control of the fuel cut.

list of figures

• 1 zeigt eine schematische Darstellung eines Kraftfahrzeugs mit einem Verbrennungsmotor, bei dem ein Schubbetrieb durch das erfindungsgemäße Verfahren gesteuert wird.
• 2 zeigt ein Ablaufdiagramm einer Ausführungsform des erfindungsgemäßen Verfahrens.

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

• 1 shows a schematic representation of a motor vehicle with an internal combustion engine, in which a pushing operation is controlled by the inventive method.
• 2 shows a flowchart of an embodiment of the method according to the invention.

Embodiments of the invention

1 shows a schematic representation of a motor vehicle 1 with an internal combustion engine 2 and an associated three-way catalyst 3 , which contributes to the reduction of pollutant emission, especially the nitrogen oxide emission. A driver 4 of the motor vehicle 1 actuates an accelerator pedal 5 to the motor vehicle 1 to accelerate. A position of the accelerator pedal 5 as well as its change can be detected and sent to an electronic control unit 6 are given. The electronic control unit 6 is set up, at least one rotational speed n of the internal combustion engine 2 , an exhaust gas mass flow q , a speed v and an acceleration a of the motor vehicle 2 to capture. In addition, the electronic control unit with an embodiment of the method according to the invention, a fuel cut-off of the internal combustion engine 2 Taxes.

Embodiments of the method according to the invention will be described with reference to a flowchart in FIG 2 explained in more detail. In the illustrated embodiment, there are three factors for detecting an emission-unfavorable driving condition for fuel cut 50 used that would be a driver dynamics FrDyn, an engine dynamics MoDyn and a vehicle dynamics FzDyn. In other embodiments, additional factors may be used or factors not taken into account.

For investigation 14 Driver Dynamics FrDyn is a rate of change of accelerator pedal position of the accelerator pedal 6 in the positive direction, ie towards a higher acceleration 10 , In addition, the frequency of each occurring rate of change within a predetermined time is considered 11 , These variables flow into the evaluation 12 a driver's request. By means of the evaluation 12 the driver's request is after a filtering 13 the driver dynamics FrDyn determined 14 , The properties of filtering 13 as well as the time range used are adaptable to obtain the highest possible information about the driver dynamics FrDyn. In some embodiments, individual results of the evaluation 12 filtered and in other embodiments a moving average for filtering 13 used. The driver dynamics FrDyn comes with a driver dynamics threshold S _Fr compared 15 ,

As a further measure, on the one hand, the rotational speed n from the engine speed of the internal combustion engine 2 determined 20 and on the other hand, the exhaust gas mass flow q determined 21 , from which on the load of the internal combustion engine 2 can be closed. These quantities flow into an evaluation 22 the load and speed dynamics. In further embodiments, the rotational speed n can also be determined via a camshaft rotational speed, a transmission rotational speed and / or the vehicle speed, or the load can be determined via an intake air mass flow, a mass flow of fuel and / or an in-cylinder pressure. In still other embodiments, only the load dynamics or the speed dynamics are evaluated. By means of the evaluation 22 the load and speed dynamics become after filtering 23 the motor dynamics MoDyn determined 24 , For the description of this filtering 23 is based on the filtering described above 13 related to the driver dynamics FrDyn. The engine dynamics MoDyn comes with a motor dynamics threshold S _Mo compared 25 ,

For investigation 33 the vehicle dynamics FzDyn will be an evaluation 32 the vehicle speed v and a positive vehicle acceleration a ⁺ , therefore, to greater speeds out running. For the evaluation 32 on the one hand, the product of the vehicle speed v and a positive vehicle acceleration a ⁺ educated. On the other hand, a relative positive acceleration RPA is previously calculated 30 by taking products from vehicle speed v and positive vehicle acceleration a ⁺ be summed up for different times and finally divided by the distance covered. Of course, only the relative positive acceleration RPA or only the product of vehicle speed v and positive acceleration a ⁺ at the evaluation 32 be used. By means of the evaluation 32 the vehicle speed v and the positive vehicle acceleration a ⁺ becomes after filtering 33 determines the vehicle dynamics FzDyn 34 , For the description of this filtering 33 will turn to the filtering described above 13 related to the driver dynamics FrDyn. The vehicle dynamics FzDyn comes with a vehicle dynamics threshold S _Fz compared 35 ,

In an exam 40 will be the results of the comparisons 15 . 25 and 35 evaluated. According to one embodiment, an unfavorable driving condition 50 detected if any of the factors FrDyn, MoDyn, FzDyn in one of the comparisons 15 . 25 or 25 its associated threshold S _Fr . S _Mo . S _Fz exceeds. In further embodiments, it may be provided that the unfavorable driving condition 40 is recognized when one of the factors FrDyn, MoDyn, FzDyn the associated threshold S _Fr . S _Mo . S _Fz exceeds a predefinable period. In still further embodiments, it may be provided that the unfavorable driving condition 50 is detected only if more than one of the factors FrDyn, MoDyn, FzDyn the associated threshold S _Fr . S _Mo . S _Fz exceeds.

Has been an unfavorable driving condition 50 If detected, a lock occurs 51 the fuel cutoff. As a result, a "clearing" of the three-way catalyst 3 exposed 52 , While fuel cut is disabled 51 is, is the internal combustion engine 2 with one for the associated three-way catalyst 3 operated optimal air / fuel mixture 53 , Following to the lock 51 the fuel cutoff becomes a dead time _dead Waited, in which the fuel cut-off locked 51 remains.

Will, however, in the exam 40 no unfavorable driving condition 50 recognized or is not an unfavorable driving condition 50 more, a release takes place 60 the fuel cut, in which also the blocking 51 the fuel cut is canceled, so that it can be executed again. Again, there will be a dead time _dead Waited, in which the fuel cut is released 60 remains.

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 10240833 A1 [0006]

Claims (11)

A method of disabling (51) or enabling (60) overrun fuel cutoff for an internal combustion engine (2) of a motor vehicle (1), characterized in that the overrun fuel cutoff is disabled (51) when a low fuel cut driving condition (50) is detected. Method according to Claim 1 , characterized in that the internal combustion engine (2) with a for an associated catalyst (3) optimal air / fuel mixture is operated (53), when a for the fuel cut emission-unfavorable driving condition (50) is detected. Method according to one of the preceding claims, characterized in that an emission-unfavorable driving state (50) for the overrun fuel cutoff is detected when a driver dynamics (FrDyn) is above a driver dynamic threshold value (S _Fr ). Method according to one of the preceding claims, characterized in that for the fuel cut emission-reducing driving condition (50) is detected when a load and / or speed dynamics of the internal combustion engine (MoDyn) is above an engine dynamics threshold (S _Mo ) is detected. Method according to one of the preceding claims, characterized in that an emission-unfavorable driving state (50) for the fuel cut is detected when a vehicle dynamics (FzDyn) is above a vehicle dynamics threshold (S _Fz ). Method according to one of Claims 3 to 5 , characterized in that the blockage (51) of the fuel cut-off is canceled when the driver dynamics (FrDyn), the load and / or speed dynamics (MoDyn) and the vehicle dynamics (FzDyn) the respective associated threshold values (S _Fr , S _Mo , S _Fz ) no longer exceed. Method according to one of Claims 3 to 6 , characterized in that the driver dynamics (FrDyn), the load and / or speed dynamics (MoDyn) and the vehicle dynamics (FzDyn) have each undergone a filtering (13, 23, 33). Method according to one of the preceding claims, characterized in that after the lock (51) and after the release (60) of the overrun fuel cutoff, a dead time (t _tot ) is provided in which the fuel cut-off is not changed. Computer program, which is set up, each step of the procedure according to one of Claims 1 to 8th perform. Machine-readable storage medium on which a computer program is based Claim 9 is stored. Electronic control unit (6), which is adapted to operate by means of a method according to one of Claims 1 to 8th to perform a control of the fuel cut-off.

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