DE102016215394B4 - Method and device for controlling an internal combustion engine of a motor vehicle equipped with a fuel injection and an exhaust gas recirculation - Google Patents

Abstract

Method for controlling an internal combustion engine (1) of a motor vehicle equipped with a fuel injection and an exhaust gas recirculation, wherein a closed exhaust gas recirculation loop is formed in a deceleration _phase , a mass (m _circ ) of an air quantity trapped therein is determined, a first oxygen content (O _{2, exh1} , O _{2, man1} ) the amount of air is detected, with an injection valve, a test injection is performed, the fuel injected by the test injection fuel is burned within the closed circuit, a second oxygen content (O _{2, exh2} , O _{2, man2} ) of the air quantity is detected and from the mass (m _circ ) of the air quantity as well as the first and the second oxygen content (O _{2, exh1} , O _{2, man1} , O _{2, exh2} , O _{2, man2} ) the fuel _mass (m _fuel ) injected during the test injection is determined.

Description

The invention relates to a method for controlling an equipped with a fuel injection and exhaust gas recirculation engine of a motor vehicle and a corresponding device for controlling such an internal combustion engine.

Internal combustion engines, in particular internal combustion engines used in motor vehicles, are today generally equipped with fuel injection, for example direct injection. In this case, in particular the start and the end time of the fuel injection are determined by a control device of the internal combustion engine such that the injected fuel quantity corresponds to a desired fuel quantity, which is determined in particular from the respective operating conditions. In order to supply as much fuel as possible to all the cylinders provided under the relevant conditions, as well as all cylinders, the injection valves used are specified with narrow tolerances in the flow. Nevertheless, deviations from the desired fuel quantity may occur, for example due to deposits in the injection nozzles during the running time of the engine. Such deviations can cause, for example, an unfavorable for an exhaust gas treatment exhaust gas composition, can lead to unequal torques of the individual cylinders and thus to torsional vibrations in the drive train and can result in an increase in fuel consumption. Therefore, methods have been developed to determine the amount of fuel actually injected into a cylinder of the internal combustion engine and to adjust the injection parameters accordingly, for example, so that the intended fuel quantity can be supplied to the cylinder during operation of the internal combustion engine.

Out DE 10 2010 036 485 B3 a method for controlling an internal combustion engine with a fuel injection is known, wherein an injection duration of an injection valve of the internal combustion engine is changed, an exhaust gas composition of the internal combustion engine is measured, from the exhaust gas composition determines a deviation of a flow of the injector from a nominal value and the injection valve with a to compensate for determined deviation adjusted injection duration is controlled.

According to EP 1 336 745 A2 For example, in a method for controlling injection in an internal combustion engine of a motor vehicle, the intake mass flow rate and the air ratio in the exhaust gas are measured to estimate the amount of fuel that has actually been injected into the engine. By means of a closed loop it is achieved that the estimated amount of fuel is substantially equal to a desired amount of fuel calculated to meet the requirements of a user of the motor vehicle. Here, the difference between the target fuel amount and the estimated fuel amount is used for calculating a correction factor with which the target fuel amount is corrected.

In GB 2 475 521 A discloses a method for determining the amount of fuel actually injected in an internal combustion engine disclosed, wherein in an operating state without fuel supply, a desired test fuel quantity is injected into a cylinder, by means of an air mass flow sensor, the amount of air flowing into the cylinder during the test injection, with a lambda probe the air ratio in the exhaust gas is determined, and the amount of fuel injected in the test injection is calculated based on a function of the inflowed air amount and the air ratio. The amount of fuel injected during the test injection may be compared to a desired amount of fuel to correct the injection, for example, by appropriately adjusting the duration of activation of the injector.

From the DE 10 2010 046 703 A1 It is known to promote the exhaust gases in a closed cycle in a coasting phase of an internal combustion engine in order to prevent fuel or oil vapor from entering the environment.

The DE 603 06 697 T2 describes a method with an exhaust gas recirculation, with which the injected fuel mass is determined from the oxygen content of the air quantity.

It is an object of the present invention to provide an improved method for controlling an internal combustion engine equipped with a fuel injection and an exhaust gas recirculation of a motor vehicle and a corresponding device for controlling such an internal combustion engine.

This object is achieved by a method and by a device as specified in the independent claims.

The method according to the invention relates to an internal combustion engine which drives a motor vehicle and which is in particular a diesel engine or a gasoline engine. The internal combustion engine has a fuel injection and may comprise one or more cylinders, wherein each cylinder is provided with at least one injection valve for the supply of Fuel is associated with a combustion chamber of the cylinder. The invention particularly relates to a direct injection.

Furthermore, the internal combustion engine is equipped with exhaust gas recirculation. Due to the exhaust gas recirculation, a part of the exhaust gases of the internal combustion engine can be recirculated from the exhaust tract via an exhaust gas recirculation line in the intake tract, which in particular a reduction of pollutant emissions can be achieved. Preferably, the internal combustion engine has an exhaust turbocharger. The turbocharger has a turbine disposed in the exhaust stream and which drives a compressor disposed in the intake tract to compress the charge air supplied to the engine, which may be a mixture of fresh air and recirculated exhaust gas. As a result, an increase in performance can be achieved. The exhaust gas recirculation is preferably a low-pressure exhaust gas recirculation, exhaust gas being taken downstream of the turbine of the turbocharger and the intake air being sucked in upstream of the compressor of the turbocharger.

In the methods of the invention, in a deceleration phase, i. under such operating conditions of the internal combustion engine, in which no engine power is required to drive the motor vehicle, a closed exhaust gas recirculation loop is formed. In such a closed circuit, a complete exhaust gas recirculation takes place from the exhaust gas tract of the internal combustion engine in its intake tract. For this purpose, corresponding valves are brought into such a position that the entire exhaust gas flow of the internal combustion engine is guided through an exhaust gas recirculation line in the intake and no fresh air supply takes place in the intake. As long as the closed circuit exists, it is therefore included in this an amount of air that is not in exchange with the ambient air. Since in the deceleration phase the internal combustion engine is driven by the kinetic energy of the motor vehicle, a flow of the trapped air quantity takes place within the closed circuit. Here and in the following, "air" is mentioned, the enclosed gas being meant, which in particular also contains the exhaust gas produced by combustion.

According to the invention, the trapped in the closed exhaust gas recirculation loop air mass is determined, i. the mass of the enclosed air quantity is determined. For this purpose, sensor signals for detecting corresponding measured variables can be evaluated and the known, type-specific predetermined volume of the closed circuit and possibly other parameters taken into account. The detection of the measured variables and the determination of the trapped air mass can take place immediately after the creation of the closed exhaust gas recirculation circuit or at a later time, for example during the method steps described below, as long as the exhaust gas recirculation loop is closed.

Furthermore, according to the invention, at least a first oxygen content of the enclosed air quantity is detected at a first time. From the detected oxygen content can be concluded on the consumed by combustion of the fuel oxygen content and thus taking into account the trapped in the circulation air mass on a combusted fuel mass. Then, in a test injection with an injection valve associated with a cylinder of the internal combustion engine, fuel is injected into the cylinder, preferably a small amount of fuel. The other injection valves of the internal combustion engine are not activated for fuel injection. The fuel supplied by the test injection is combusted within the closed circuit, for example in the combustion chamber of the cylinder in question or else by means of a catalyst of the exhaust tract located within the closed exhaust gas recirculation loop. The burned fuel remains in the closed circuit and can be distributed therein. Furthermore, after the test injection has been carried out, at least a second oxygen content of the trapped air quantity is detected at a second time. From this, it is possible to deduce the oxygen content consumed by combustion of fuel at the second time and thus, taking into account the air mass trapped in the closed circuit, to the fuel mass burned at that time. After the second time or at a later time, such as the end of the deceleration phase, the closed exhaust gas recirculation loop can be opened again, i. the fresh air supply and the exhaust gas recirculation are adjusted again to the normal operation of the internal combustion engine.

According to the invention, the fuel mass injected in the test injection is determined from the mass of the enclosed air quantity as well as the at least one first and the at least one second oxygen content. In particular, taking into account the mass of the enclosed air quantity from the at least one first oxygen content of the fuel mass burned at the first time and from the at least one second oxygen content of the fuel mass burned at the second time closed, wherein the injected during the test injection fuel mass, the difference between the such determined burned fuel mass is. Since the injected fuel quantity by the corresponding Fuel mass can be specified, in the following also from "fuel quantity" the speech.

Characterized in that in a closed exhaust gas recirculation loop at a time before a test injection and at a time after a test injection in each case at least one oxygen content is measured, can thus be concluded on the consumed oxygen content in the trapped air and thus on the fuel injected during the test injection fuel mass. As a result, a determination of the amount of fuel actually injected during the test injection is possible in a simple manner. In particular, the actual amount of fuel injected may be determined without the use of a mass flow sensor; As a result, the injected fuel mass can be determined very accurately, because the trapped air mass can often be determined more accurately than the mass flow. The amount of fuel determined in this way can be used for improved control of the internal combustion engine and / or auxiliary units of the internal combustion engine.

According to a preferred embodiment of the invention, the exhaust tract of the internal combustion engine has an exhaust valve arranged downstream of a branch of an exhaust gas recirculation line, the intake tract of the internal combustion engine has an intake throttle valve and the exhaust gas recirculation line has an exhaust gas recirculation valve. Here, to form a closed exhaust gas recirculation loop, the exhaust valve is controlled such that the branch of the exhaust tract through which the exhaust gas exits into the environment is completely closed, so that the entire exhaust gas flow is guided into the exhaust gas recirculation line. Further, the intake throttle valve is driven to completely close the intake passage, so that no fresh air supply takes place, and the exhaust gas recirculation valve is opened. Alternatively, a three-way valve may be provided in the intake tract; In this case, the three-way valve is controlled such that the fresh air supply is completely closed and the exhaust gas recirculation line is fully opened to form the closed exhaust gas recirculation loop. Again, the exhaust valve is in such a position that the outlet of the exhaust gas from the exhaust system is completely sealed in the environment. In this way, with the valves provided for controlling the exhaust gas recirculation and the fresh air supply, a closed exhaust gas recirculation loop can be formed.

The mass of the quantity of air trapped in the closed exhaust gas recirculation loop is preferably determined by means of at least one pressure sensor and at least one temperature sensor. Furthermore, the known volume of the closed exhaust gas recirculation loop and the volumetric efficiency of the cylinders of the internal combustion engine can be taken into account. The pressure sensor and the temperature sensor are preferably arranged in the intake tract of the internal combustion engine, in particular in the intake manifold. For controlling the internal combustion engine or the exhaust aftertreatment system of the internal combustion engine, one or more further temperature sensors may be present, for example in the exhaust gas tract and / or in the exhaust gas recirculation line. If a plurality of pressure and / or temperature sensors are present, they can be used in an advantageous manner in each case for determining the mass of a corresponding subvolume of the trapped air quantity. When determining the mass of the air volume within or of the cylinder of the internal combustion engine, the volumetric efficiency of the cylinders may be taken into account. In this way, a particularly accurate determination of the trapped air mass is possible.

Preferably, after the formation of the closed exhaust gas recirculation loop and before the determination of the at least one first oxygen content, a first waiting time is maintained. Specifically, this waiting time is determined such that the engine has made a sufficient number of revolutions to evenly mix the amount of air trapped in and circulating in the closed circuit. In this case, an uneven filling of the cylinder, in which the test injection has been performed, contribute to the uniform mixing, just as in a multi-cylinder internal combustion engine, the remaining cylinders. Alternatively or additionally, after the test injection has been carried out and before the at least one second oxygen content has been determined, a second waiting time can be maintained, within which the internal combustion engine has likewise made enough revolutions to uniformly mix the amount of air trapped in the closed circuit. In a particularly preferred manner, both a first and a second waiting time are provided. As a result, a more accurate detection of the oxygen content of the trapped air quantity and thus a more accurate determination of the injected fuel mass is possible.

The first and the second oxygen content are preferably detected by means of at least one oxygen sensor arranged in the exhaust gas tract and / or at least one oxygen sensor arranged in the intake tract, for example in each case one lambda probe. According to a particularly preferred embodiment of the invention, it is provided that the first and the second oxygen content of the trapped air quantity by an oxygen sensor arranged in the exhaust tract and additionally by a in the intake arranged oxygen sensor can be measured. The oxygen sensor or the lambda probe is preferably arranged in the exhaust gas tract upstream of a catalytic converter. The oxygen sensor or the lambda probe in the intake tract is preferably arranged in the intake manifold of the internal combustion engine. In this way, in each case two independent measurements of the first and the second oxygen content of the trapped air quantity can be carried out, which enable a redundant determination of the amount of fuel injected during the test injection. In a particularly advantageous manner, it can be provided that an average value is formed from the respectively determined fuel masses. As a result, the actually supplied amount of fuel can be determined with increased accuracy.

According to a preferred embodiment of the invention, in an internal combustion engine having a plurality of injectors associated with a plurality of cylinders, the measurement of the first oxygen content, the test injection and the measurement of the second oxygen content and the determination of the injected fuel quantity based thereon for each injection valve of the internal combustion engine, with the other injection valves between the measurement of the first oxygen content and the second oxygen content, no fuel is injected. It may be provided that after the creation of the closed exhaust gas recirculation loop, said steps for several or all injectors of the engine are performed sequentially before the closed exhaust gas recirculation loop is opened again. Preferably, it is provided that the closed exhaust gas recirculation loop is formed, said steps are performed for a first injection valve, then the closed exhaust gas recirculation loop is opened again and the injected fuel quantity for the first injection valve is determined; after a respective waiting time of a few revolutions of the internal combustion engine, particularly preferably in a respective further deceleration phase, a corresponding procedure is used to determine the injected fuel quantity for each further injection valve of the internal combustion engine. As a result, the injected fuel quantity can be determined precisely for all injection valves of the internal combustion engine.

An exhaust gas aftertreatment system of the internal combustion engine is preferably controlled on the basis of the fuel mass injected as determined during a test injection or the respective injected fuel mass determined for each injection valve of the internal combustion engine. For example, it can be provided that this is used to determine the fuel mass actually supplied in at least one further injection, in particular during the injections during normal operation. For example, it can often be assumed that the fuel mass actually injected during an injection in normal operation is changed by about the same ratio as a fuel mass actually injected during the test injection compared with a target fuel mass of the test injection. The determination of the actually injected amount of fuel allows an improved control of an exhaust aftertreatment system of the internal combustion engine and thus a reduction of pollutant emissions.

According to a preferred embodiment of the invention, a correction of the at least one injection parameter is determined from at least one injection parameter of the test injection and from the determined fuel mass, which was actually injected during the test injection. This is determined in particular such that with a correspondingly corrected injection parameter, the actually injected fuel mass would be equal to a desired fuel mass of the test injection. This correction is used in at least one further injection, in particular in the injections that take place after the end of the deceleration phase during normal operation of the internal combustion engine, in order to adapt the at least one injection parameter of the at least one further injection such that the fuel mass actually injected into the cylinder in each case from the required torque and the operating parameters of the internal combustion engine determined setpoint fuel mass is equal to or at least comes close. In particular, if the fuel mass injected during a respective test injection has been determined for all injection valves of the internal combustion engine, a separate correction can be determined for each injection valve, which is used in each case for the corresponding adaptation of the at least one injection parameter in the injections during normal operation. As a result, an improved control of the internal combustion engine and in particular a more economical operation can be achieved. If a corresponding adaptation of the at least one injection parameter takes place for each cylinder of the internal combustion engine in the case of the at least one injection valve associated with the respective cylinder, the generation of unequal torques by the individual cylinders and thus the formation of torsional vibrations can be avoided.

In particular, the at least one injection parameter may be the injection duration. The amount of fuel actually supplied to the combustion chamber in the test injection depends, inter alia, on the flow rate, ie on the amount of fuel flowing through the injection valve per unit time, and on Injection duration from. The amount of fuel actually injected may deviate from a predetermined target fuel quantity, in particular because the flow rate deviates from a nominal value, for example because of deposits in the injection nozzle. Since the quantity of fuel injected during operation of the internal combustion engine for driving the motor vehicle also depends on the flow rate, a deviation of the fuel quantity actually injected during operation from a desired fuel quantity can be concluded in most cases. By a corresponding correction or adaptation of the injection duration, therefore, a deviation of the actually injected fuel quantity can be corrected in a simple manner so that a respective desired fuel quantity is actually achieved with greater accuracy in the subsequent injections during operation of the internal combustion engine.

A device according to the invention for controlling an internal combustion engine of a motor vehicle, which has a fuel injection and an exhaust gas recirculation, comprises a control device, which is set up for carrying out the above-described method for controlling the internal combustion engine. For this purpose, the control device for controlling an exhaust valve and on the one hand a Ansaugdrosselventils and an exhaust gas recirculation valve or on the other hand, a three-way valve may be formed in the intake of the engine to provide a closed exhaust gas recirculation circuit in a deceleration phase of the motor vehicle. Furthermore, the control device is designed to control at least one injection valve of the cylinder for carrying out a test injection. Further, the control device for detecting the sensor signals of a arranged in the intake manifold and / or in the exhaust tract oxygen sensor, in particular a lambda probe, and a pressure sensor and a temperature sensor, which are arranged for example in the intake manifold of the internal combustion engine, and for determining the actually injected in the test injection fuel mass from the mass of trapped air and the first and second oxygen content. The controller may include processor means for calculating the amount of fuel actually injected. The control device may be part of an electronic engine control of the internal combustion engine and be designed, for example, for detecting a deceleration phase of the motor vehicle. The device for controlling the internal combustion engine may further comprise the sensors for detecting the first and the second oxygen content and for determining the trapped air mass.

• 1 ein erstes Ausführungsbeispiel eines Abgasrückführungssystems, das zur Durchführung des erfindungsgemäßen Verfahrens geeignet ist;
• 2 ein zweites Ausführungsbeispiel eines Abgasrückführungssystems, das zur Durchführung des erfindungsgemäßen Verfahrens geeignet ist;
• 3 ein vereinfachtes Ablaufdiagramm für ein Ausführungsbeispiel eines erfindungsgemäßen Verfahrens.

The invention will be explained in more detail by way of example with reference to the drawings. Show it:

• 1 a first embodiment of an exhaust gas recirculation system, which is suitable for carrying out the method according to the invention;
• 2 a second embodiment of an exhaust gas recirculation system, which is suitable for carrying out the method according to the invention;
• 3 a simplified flowchart for an embodiment of a method according to the invention.

In the 1 and 2 two embodiments of an exhaust gas recirculation system of a motor vehicle are shown, wherein the exhaust gas recirculation system is suitable for carrying out the method according to the invention. The exhaust gas recirculation system is designed in each case as a low-pressure exhaust gas recirculation.

As in 1 exemplified symbolically, is an internal combustion engine 1 of a motor vehicle equipped with an exhaust gas turbocharger, which is a compressor 2 and a turbine 3 includes. The in the exhaust tract 4 of the internal combustion engine 1 arranged turbine 3 is from the exhaust gas flow of the internal combustion engine 1 go through and driven by it. About one in 1 not shown turbine shaft drives the turbine 3 in the intake tract 5 arranged compressor 2 to the internal combustion engine 1 supplies compressed charge air.

From the turbine 3 of the turbocharger, the exhaust gas passes through an exhaust pipe 6 in an exhaust aftertreatment system, which in the illustrated embodiment by a catalyst 7 is formed. The flow direction of the exhaust gas in the exhaust pipe 6 is in 1 through the arrow 8th shown. Downstream of the catalyst 7 branches off the exhaust pipe 6 an exhaust gas recirculation line 9 from, through which a portion of the exhaust gas into the intake tract 5 of the internal combustion engine 1 can be returned; the flow direction of the recirculated exhaust gas portion is indicated by the arrow 10 characterized. The remaining portion of the exhaust gas flows through the exhaust pipe 6 in the direction of the arrow 11 continue through the exhaust tract 4 , possibly by another exhaust aftertreatment system, and finally released to the environment. Downstream of the branch of the exhaust gas recirculation line 9 is on the exhaust pipe 10 an exhaust valve 12 arranged, which can be controlled by a control device, not shown, for adjusting the recirculated exhaust gas portion.

The exhaust gas recirculation line 9 opens upstream of the compressor 2 in a suction 13 so that the recirculated exhaust gas along with the via the intake pipe 13 sucked fresh air to the compressor 2 is supplied. The compressor 2 compresses the mixture of fresh air and recirculated exhaust gas and leads this as a compressed charge air via a charge air supply 14 and an intake manifold 15 the internal combustion engine 1 to. At the intake pipe 13 is upstream of the confluence of the exhaust gas recirculation line 9 an intake throttle valve 16 arranged, and at the exhaust gas recirculation line 9 is upstream of the confluence with the suction line 13 an exhaust gas recirculation valve 17 arranged. The intake throttle valve 16 and the exhaust gas recirculation valve 17 can by the controller for adjusting the fresh air content and the exhaust gas content and thus the mixing ratio of fresh air and exhaust gas in the internal combustion engine 1 supplied charge air to be controlled. As in 1 symbolically indicated is in the intake manifold 15 a plurality of charge air sensors 18 arranged that at least the temperature, pressure and oxygen content of the internal combustion engine 1 Enter supplied compressed charge air. The charge air sensors 18 include in particular a temperature sensor, a pressure sensor and a lambda probe. Next is at the exhaust pipe 6 downstream of the turbine 3 and upstream of the catalyst 7 another lambda probe 19 arranged to detect the oxygen content of the exhaust gas. The charge air sensors 18 and arranged in the exhaust stream further lambda probe 19 are with the in 1 Not shown control device connected.

At the in 2 also symbolically illustrated second embodiment of an exhaust gas recirculation system is instead of Ansaugdrosselventils 16 and the exhaust gas recirculation valve 17 a three-way valve 20 provided at the confluence of the exhaust gas recirculation line 9 in the intake pipe 13 is arranged. The three-way valve 20 can be controlled to adjust the mixing ratio of fresh air and recirculated exhaust gas in the charge air from the control device, not shown. Incidentally, this is in 2 embodiment shown as in 1 shown trained.

In 3 an embodiment of the method according to the invention is shown in simplified form in a flow chart. If, for example, it is determined on the basis of the signal of a speed sensor of the motor vehicle and the position of the accelerator pedal and possibly the brake pedal of the motor vehicle that the motor vehicle is in a deceleration or overrun phase, a closed exhaust gas recirculation loop is produced, ie an exhaust gas recirculation loop with exhaust gas recirculation of 100%. For this purpose, the control device, the exhaust valve 12 closed (s. 1 and 2 ). In the in 1 The embodiment shown, the intake throttle valve 16 closed and the exhaust gas recirculation valve 17 open; in the embodiment according to 2 becomes the three-way valve 20 so controlled that the suction line 13 closed on the inlet side and the exhaust gas recirculation line 9 is open.

wobei R die spezifische Gaskonstante ist. Der Druck p und die Temperatur T werden mittels der Ladeluftsensoren 18 gemessen. Das Volumen V des geschlossenen Abgasrückführungskreislaufs ist bekannt, wobei der ebenfalls bekannte volumetrische Wirkungsgrad der Zylinder des Verbrennungsmotors berücksichtigt wird. Die Bestimmung der Luftmasse m_circ kann auch zu einem anderen Zeitpunkt erfolgen. Weiter werden der Sauerstoffanteil O_2,exh1 (in Prozent) im Abgastrakt 4 mittels der Lambdasonde 19 sowie der Sauerstoffanteil O_2,man1 (in Prozent) im Ansaugtrakt 5 mittels der Lambdasonde der Ladeluftsensoren 18 gemessen. Hieraus wird jeweils der verbrauchte Sauerstoffanteil der eingeschlossenen Luftmenge im Abgastrakt (f_exh1) sowie im Ansaugtrakt (f_man1) gemäß $${\text{f}}_{\text{exh1}}=1-{\text{O}}_{\mathrm{2,}\text{exh1}}/21$$

$${\text{f}}_{\text{man}}=1-{\text{O}}_{\mathrm{2,}\text{man1}}/21$$

berechnet.After a first waiting time t ₁ , which comprises a few revolutions of the internal combustion engine, so that the amount of air trapped in the closed exhaust gas recirculation loop is uniformly mixed, the mass m _{circ of} the trapped air quantity is estimated from the general gas law for ideal gases: $${\text{m}}_{\text{circ}}=\text{pv}/\text{R T}.$$

where R is the specific gas constant. The pressure p and the temperature T are determined by means of the charge air sensors 18 measured. The volume V of the closed exhaust gas recirculation loop is known, whereby the likewise known volumetric efficiency of the cylinders of the internal combustion engine is taken into account. The determination of the air mass m _circ can also take place at another time. Next, the oxygen content O _{2, exh1} (in percent) in the exhaust system 4 by means of the lambda probe 19 and the oxygen content O _{2, man1} (in percent) in the intake tract 5 by means of the lambda probe of the charge air sensors 18 measured. From this, in each case the consumed oxygen content of the enclosed air quantity in the exhaust gas tract (f _exh1 ) and in the intake tract (f _man1 ) according to $${\text{f}}_{\text{EXH1}}=1-{\text{<figure-callout id="2" label="O" filenames="DE102016215394B4\_0011.png,DE102016215394B4\_0012.png" state="{{state}}">O</figure-callout>}}_{\mathrm{2,}\text{EXH1}}/21$$

$${\text{f}}_{\text{you}}=1-{\text{<figure-callout id="2" label="O" filenames="DE102016215394B4\_0011.png,DE102016215394B4\_0012.png" state="{{state}}">O</figure-callout>}}_{\mathrm{2,}\text{man1}}/21$$

calculated.

$${\text{f}}_{\text{man2}}=1-{\text{O}}_{\mathrm{2,}\text{man2}}/21$$

und daraus jeweils eine bei der Testeinspritzung tatsächlich zugeführte Kraftstoffmasse berechnet: $${\text{m}}_{\text{fuel}\text{,exh}}=\left({\text{f}}_{\text{exh2}}-{\text{f}}_{\text{exh1}}\right){\text{m}}_{\text{circ}}/\left(1+{\mathrm{\phi }}_{\text{stoech}}\right)$$

$${\text{m}}_{\text{fuel}\text{,man}}=\left({\text{f}}_{\text{exh}2}-{\text{f}}_{\text{exh1}}\right){\text{m}}_{\text{circ}}/\left(1+{\mathrm{\phi }}_{\text{stoech}}\right)$$

wobei φ_stoech das stöchiometrische Luft-Kraftstoff-Verhältnis ist. Aus den beiden auf diese Weise ermittelten Werten kann die tatsächlich zugeführte Kraftstoffmasse m_fuel genauer bestimmt werden, beispielsweise durch Mittelwertbildung: $${\text{m}}_{\text{fuel}}=\left({\text{m}}_{\text{fuel},\text{exh}}+{\text{m}}_{\text{fuel},\text{man}}\right)/2$$

A test injection into a cylinder of the internal combustion engine is now carried out, the injection _{parameters being} known, and in particular the injection _duration T _{inj, test} for supplying a desired fuel _mass m _{test, is} selected. After a second waiting time t ₂ , which again comprises a few revolutions of the internal combustion engine, so that the amount of air trapped in the closed exhaust gas recirculation loop is uniformly mixed and corresponding combustion has taken place, the lambda probe is used 19 the oxygen content O _{2, exh2} in the exhaust gas tract 4 and with the lambda probe of the charge air sensors 18 the oxygen content O _{2, man2} in the intake tract 5 measured. From this, in each case, the consumed oxygen content of the enclosed air quantity in the exhaust gas tract (f _exh1 ) or in the intake tract (f _man1 ) $${\text{f}}_{\text{exh2}}=1-{\text{<figure-callout id="2" label="O" filenames="DE102016215394B4\_0011.png,DE102016215394B4\_0012.png" state="{{state}}">O</figure-callout>}}_{\text{2}\text{, exh2}}/21$$

$${\text{f}}_{\text{man2}}=1-{\text{<figure-callout id="2" label="O" filenames="DE102016215394B4\_0011.png,DE102016215394B4\_0012.png" state="{{state}}">O</figure-callout>}}_{\mathrm{2,}\text{man2}}/21$$

and from each of these a fuel mass actually supplied during the test injection is calculated: $${\text{m}}_{\text{fuel}\text{, exh}}=\left({\text{f}}_{\text{exh2}}-{\text{f}}_{\text{EXH1}}\right){\text{m}}_{\text{circ}}/\left(1+{\mathrm{\phi }}_{\text{Stoich}}\right)$$

$${\text{m}}_{\text{fuel}\text{, you}}=\left({\text{f}}_{\text{exh}2}-{\text{f}}_{\text{EXH1}}\right){\text{m}}_{\text{circ}}/\left(1+{\mathrm{\phi }}_{\text{Stoich}}\right)$$

where φ _{stoech is} the stoichiometric air-fuel ratio. From the two values determined in this way, the actually supplied fuel mass m _{fuel can} be determined more accurately, for example by averaging: $${\text{m}}_{\text{fuel}}=\left({\text{m}}_{\text{fuel}.\text{exh}}+{\text{m}}_{\text{fuel}.\text{you}}\right)/2$$

ermittelt, der angibt, um welchen Faktor die tatsächlich zugeführte Kraftstoffmenge gegenüber der Soll-Kraftstoffmenge verändert ist.This will be a correction factor $${\text{F}}_{\text{corr}}={\text{m}}_{\text{flood fill}}/{\text{m}}_{\text{test}.\text{should}}$$

determined, which indicates by what factor the actually supplied amount of fuel is changed from the target amount of fuel.

Now, if the deceleration phase is completed, for example by pressing the accelerator pedal by the driver of the motor vehicle, the exhaust valve 12 as well as the intake throttle valve 16 and the exhaust gas recirculation valve 17 (S. 1 ) or the three-way valve 20 (S. 2 ) is controlled, as it corresponds to the normal operation of the internal combustion engine, ie usually for a partial exhaust gas recirculation. For an injection into the combustion chamber of the cylinder, a desired fuel _{mass to be supplied} and a corresponding injection _duration T _{inj, should be} determined from the required torque and the instantaneous rotational speed of the internal combustion engine. This is corrected with the correction factor in order to determine a corrected or adjusted injection _duration T _inj : $${\text{T}}_{\text{inj}}={\text{T}}_{\text{inj}.\text{should}}/{\text{F}}_{\text{corr}}$$

This correction is used for the normal operation of the internal combustion engine, ie for the operation outside the deceleration _phase , and the injections are each carried out with an adapted injection _duration T _inj . In this way, in particular a reduction of the flow rate of an injection valve can be compensated by a corresponding extension of the injection duration.

Corresponding correction factors can be determined in succession for all cylinders of the internal combustion engine and taken into account in the injection during normal operation. The described method can be repeated on a regular basis, for example after a period of operation of the motor vehicle, within which a change in the flow rate of an injection valve can occur, a renewed execution of the method upon detection of a deceleration phase can be started.

LIST OF REFERENCE NUMBERS

1

internal combustion engine

2

compressor

3

turbine

4

exhaust tract

5

intake system

6

exhaust pipe

7

catalyst

8th

arrow

9

Exhaust gas recirculation line

10

arrow

11

arrow

12

exhaust valve

13

suction

14

Charge air supply

15

intake

16

intake throttle valve

17

Exhaust gas recirculation valve

18

Charge air sensors

19

lambda probe

20

Three-way valve

Claims (11)

Method for controlling an internal combustion engine (1) of a motor vehicle equipped with a fuel injection and an exhaust gas recirculation, wherein a closed exhaust gas recirculation loop is formed in a deceleration _phase , a mass (m _circ ) of an air quantity trapped therein is determined, a first oxygen content (O _{2, exh1} , O _{2, man1} ) the amount of air is detected, with an injection valve, a test injection is performed, the fuel injected by the test injection fuel is burned within the closed circuit, a second oxygen content (O _{2, exh2} , O _{2, man2} ) of the air quantity is detected and from the mass (m _circ ) of the air quantity and the first and the second oxygen content (O _{2, exh1} , O _{2, man1} , O _{2, exh2} , O _{2 , man2} ) the fuel _mass (m _fuel ) injected during the test injection is determined. Method according to Claim 1 , characterized in that an exhaust valve (12) and on the one hand a Ansaugdrosselventil (16) and an exhaust gas recirculation valve (17) or on the other hand, a three-way valve (20) of the intake tract (5) are controlled to form the closed exhaust gas recirculation loop. Method according to Claim 1 or 2 , characterized in that the mass (m _circ ) of the trapped air quantity is determined by means of at least one pressure sensor and at least one temperature sensor. Method according to one of the preceding claims, characterized in that after formation of the closed exhaust gas recirculation loop and before the detection of the first oxygen content (O _{2, exh1} , O _{2, man1} ) a first waiting time t ₁ and / or after carrying out the test injection and before detecting the second oxygen content (O _{2, exh2} , O _{2, man2} ) a second waiting time t _{2 is} maintained. Method according to one of the preceding claims, characterized in that the first and the second oxygen content (O _{2, exh1} , O _{2, man1} , O _{2, exh2} , O _{2, man2} ) by means of at least one oxygen sensor in the exhaust tract (4) and / or at least one oxygen sensor in the intake tract (5) are measured. Method according to Claim 5 , characterized in that from the oxygen content (O _{2, exh1} , O _{2, exh2} ) in the exhaust gas tract (4) and from the oxygen content (O _{2, man1} , O _{2, man2} ) in the intake tract (5) in each case one injected during the test injection Fuel _mass (mf _{uel, exh} , m _{fuel, man} ) is calculated and to determine the fuel injected during the test injection fuel _mass (m _fuel ) an average value is formed. Method according to one of the preceding claims, characterized in that the internal combustion engine (1) has a plurality of injection valves and that the fuel mass injected at a respective test injection (m _fuel ) is determined for each injection valve. Method according to one of the preceding claims, characterized in that an exhaust aftertreatment system of the internal combustion engine (1) is controlled on the basis of the determined fuel mass (m _fuel ). Method according to one of the preceding claims, characterized in that from at least one injection parameter of the test injection and from the determined fuel mass (m _fuel ) a correction of the at least one injection parameter for adapting the injected fuel mass (m _fuel ) to a desired fuel mass (m _{test, is} ) is determined and that in at least one further injection, the injection valve is driven in accordance with the determined correction. Method according to Claim 9 , characterized in that the at least one injection _parameter is the injection _duration (T _inj ). Device for controlling an internal combustion engine (1) of a motor vehicle equipped with a fuel injection and an exhaust gas recirculation, comprising a control device, characterized in that the control device is arranged to carry out the method according to one of the preceding claims.

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