DE10303705B4 - A method of operating a direct fuel injection internal combustion engine - Google Patents

Abstract

Method for operating an internal combustion engine (10)
The air supplied to the combustion chambers of the internal combustion engine (10) is precompressed by means of a charging device (25, 26),
- Fuel is injected directly into the combustion chambers of the internal combustion engine (10),
The exhaust gas of the internal combustion engine (10) is cleaned with the aid of at least one catalytic converter (21),
By means of a device (31) the valve overlap (VO) of the gas exchange valves of the internal combustion engine (10) can be varied,
The valve overlap (VO) of the gas exchange valves is set to stationary setpoint values (CAM_IN_FL_STAT_SP, CAM_EX_FL_STAT_SP) for full-load operation or at least operation of the internal combustion engine (10) close to full load by setting the gas exchange valve control times
A dynamic correction of the stationary setpoint values (CAM_IN_FL_STAT_SP, CAM_EX_FL_STAT_SP) takes place at an increased load request in the supercharged operation of the internal combustion engine (10),
- The dynamic correction values (CAM_IN_SP_DYN_COR, CAM_EX_SP_DYN_COR) depending on at least one of the operating variables of the engine speed (N), coolant temperature (TCO), inducted air mass (MAF_KGH) are determined and weighted by a factor (CAM_IN_DYN_COR_FAC, CAM_EX_DYN_COR_FAC), ...

Description

The The invention relates to a method of operating with a charging device provided with fuel direct injection internal combustion engine, which has a variable valve train.

Internal combustion engines With direct injection (DI, Direct Injection) involve a great potential to reduce fuel consumption with relatively low pollutant emissions. In contrast Intake manifold injection is fuel in a direct injection with high pressure directly into the combustion chambers of the internal combustion engine injected.

For this are injection systems with central pressure accumulator (common rail) known. In such common rail systems is by means of a high-pressure pump one from the electronic control unit the internal combustion engine over Pressure sensor and pressure regulator regulated fuel pressure in the distributor rail Constructed (common rail), the largely independent of speed and injection quantity is available. About an electric controllable injector, the fuel is injected into the combustion chamber. This one gets his signals from the controller. Due to the functional separation of pressure generation and injection the injection pressure can be independent largely free from the current operating point of the internal combustion engine chosen become.

It is known to increase the power and torque of internal combustion engines to provide a charging device, the amount of charge through Pre-compression increased. there promotes a supercharger the fresh air into the cylinder of the internal combustion engine. During mechanical charging, the compressor is taken directly from the Internal combustion engine driven (e.g., supercharger charging), while at an exhaust gas turbocharger one with the exhaust gas of the internal combustion engine acted upon turbine (exhaust gas turbine) one in the intake tract of the internal combustion engine lying compressor drives.

at Exhaust turbocharging is the dynamic start-up behavior partially delayed. The delay arises especially at the transition from part load operation to full load operation and occasionally too as "turbo lag" this transition of the operating point results in an uneven torque output.

modern Internal combustion engines have to reduce the charge cycle losses variable valve trains with single and multi-stage or stepless variability on. The variable valve control of the intake and exhaust valves offers the possibility the valve timing within the physical limits of the existing actuator principle (mechanical system, hydraulic System, electrical system, pneumatic system or a combination the said systems) more or less freely. Thereby can Consumption savings, lower raw emissions and higher torque be achieved. A variable camshaft adjustment is for example described in WO 99/43930.

From the DE 199 50 677 A1 a method is described for operating an internal combustion engine having at least one working piston guided in a cylinder, in which at least one inlet valve with variable closing time closes and releases an inlet opening of the cylinder and closes an outlet opening of the cylinder at least one outlet valve with variable opening time and constant closing time releases. It is envisaged that the internal combustion engine is operated with a geometric compression ratio that is raised to the specific partial load compression ratio.

Of the Invention has for its object to provide a method with the operation of a charged and with direct fuel injection working, a variable valve train having internal combustion engine, in particular, their response to instationary processes can be improved can, without causing damage the catalytic converter occurs due to high temperatures.

These The object is achieved by a method as defined in claim 1 is.

advantageous Further developments of the method according to the invention form the subject matter the dependent claims.

at the method according to the invention will be the combustion chambers the internal combustion engine supplied Air pre-compressed by means of a supercharger and fuel directly into the combustion chambers the internal combustion engine injected. The exhaust gas of the internal combustion engine is cleaned by means of a catalytic converter and with the help of a Device can valve overlap the gas exchange valves of the internal combustion engine can be varied. The valve overlap the gas exchange valves for a full load operation or at least full load close operation of the internal combustion engine is set to steady state setpoints by adjusting the gas exchange valve timing set. At an elevated Load request in the supercharged operation of the internal combustion engine a dynamic correction of the stationary setpoint values takes place in the direction of higher Values. The dynamic correction values are determined by means of a first Factor weighted, which depends on the pressure difference between pressure setpoint and actual Pressure in the intake duct is fixed and weighted by a second factor, which takes into account the temperature of the catalytic converter. Then be set the thus corrected setpoints.

Thereby results in an improved response of the exhaust gas turbocharger and thus an improved response of the internal combustion engine. The delayed at turbocharging Start-up behavior, especially during the transition from partial load operation for full load operation, sometimes referred to as "turbo lag", can thus safely prevented become.

Further Advantages of the method according to the invention tap from the description of the embodiment below closer to the drawing explained becomes. The single figure shows a simplified block diagram a supercharged and fuel direct injection ar Internal combustion engine with a variable valve train, in which the inventive method is applied.

In the figure, in the form of a block diagram, a supercharged Otto internal combustion engine 10 shown with direct fuel injection and an associated exhaust aftertreatment system. Only those components are shown which are necessary for the understanding of the invention. In particular, has been dispensed with the representation of the ignition system, the fuel circuit and the cooling circuit.

Via a suction channel 11 receives the internal combustion engine 10 the fresh air required for combustion. The supplied fresh air flows through an air filter 12 , an air mass meter 13 and a charge air cooler 14 to a throttle block 15 , The throttle block 15 includes a throttle 16 and a throttle valve sensor, not shown, which is the opening angle of the throttle valve 16 corresponding signal outputs. At the throttle 16 This is, for example, an electromechanically actuated throttle element (E-gas) whose opening cross-section, in addition to the actuation by the driver (driver request), depends on the operating range of the internal combustion engine via corresponding signals of a control device 17 is adjustable. The air mass meter 13 is used in a so-called air-mass-guided control of the internal combustion engine as a load sensor whose output signal MAF_KGH for further processing of the control device 17 is supplied.

The internal combustion engine 10 has a fuel metering device 18 on, the fuel KST is supplied under high pressure and includes one of the number of cylinders of the internal combustion engine corresponding number of injection valves, which are controlled via corresponding signals from the injection output stages, for example, in the electronic control device 17 the internal combustion engine are integrated. Fuel is injected directly into the cylinders of the internal combustion engine via the injection valves 10 injected. The injectors are supplied in an advantageous manner from a fuel pressure accumulator (common rail) with fuel. The amount of fuel injected by an injector is designated MFF. A pressure sensor 19 at the fuel metering device 18 detects the fuel pressure FUP, with which the fuel is injected directly into the cylinders of the internal combustion engine.

On the output side is the internal combustion engine 10 with an exhaust duct 20 connected, in which an exhaust gas catalyst 21 is arranged. In this case, a three-way catalytic converter or a NOx storage catalytic converter or a combination of the two can be provided. The exhaust gas aftertreatment sensor includes, for example, an upstream of the catalytic converter 21 arranged Abgasmessaufnehmer in the form of a lambda probe 22 ,

The temperature of the catalytic converter 21 More specifically, the monolith temperature T_MON is determined by means of a temperature sensor 34 detected, seen in the flow direction of the exhaust gas in the front part of the catalytic converter 21 is arranged. The signal T_MON is the control device 17 to further Ver supplied to processing. Alternatively, the monolith temperature T_MON can also be calculated from various input variables using any known exhaust gas temperature model, as described, for example, in US Pat DE 198 36 955 A1 is described.

With the signal λ _{Ex of} the lambda probe 22 the mixture is regulated according to the setpoint specifications. This function is performed by a known lambda control device 23 , preferably in the, the operation of the internal combustion engine or regulating control device 17 is integrated. Such electronic control devices 17 , which usually include one or more microprocessors and in addition to the fuel injection and the ignition control take a variety of other control and regulating tasks are known per se, so that in the following only on the relevant in connection with the invention structure and its Functionality is received. In particular, the control device 17 with a storage device 24 in which, inter alia, various maps and threshold values are stored whose meaning will be explained.

To increase the cylinder filling and thus to increase the performance of the internal combustion engine 10 a charging device in the form of a known exhaust gas turbocharger is provided, the turbine 25 in the exhaust duct 20 is arranged and the dashed lines in the figure, unspecified wave with a compressor 26 in the intake channel 11 is in active connection. Thus, the exhaust gases drive the turbine 25 and this in turn the compressor 26 at. The compressor 26 takes over the suction and delivers the internal combustion engine 10 a pre-compressed fresh charge. The downstream of the compressor 26 lying intercooler 14 performs the heat of compression via the coolant circuit of the internal combustion engine 10 from. As a result, the cylinder filling can be further improved. Parallel to the turbine 25 is a bypass line (bypass line) 27 provided, via a so-called wastegate 28 can be opened differently wide. This results in a different sized part of the mass flow from the internal combustion engine to the turbine 25 bypassed, leaving the compressor 26 the exhaust gas turbocharger is driven to different degrees.

A temperature sensor 29 detects a the temperature of the internal combustion engine corresponding signal, usually the coolant temperature TCO. A speed sensor 30 detects the speed N of the internal combustion engine. A value PUT_MES for the pressure in the intake duct 11 at a location upstream of the throttle 16 and downstream of the intercooler 14 is by means of a pressure sensor 33 measured. All these signals are the controller 17 fed for further processing.

For switching off individual cylinders of the internal combustion engine 10 has the control device 17 An institution 32 on, with the aid of which the fuel supply to individual cylinders of the internal combustion engine according to a predetermined Abschaltmuster, the so-called Abschaltpattern NR_PAT_SCC off and is released again. Such a device is for example in the EP 0 614 003 B1 described. Single cylinder fuel cutoff increases utilization of the "fired" cylinders, ie those cylinders that continue to be fueled, thereby improving combustion quality and gas interaction efficiency torque limiting.

Furthermore, the internal combustion engine 10 An institution 31 with which the valve overlap of the intake valves and the exhaust valves can be adjusted and changed. Such variable valve controls can be realized with mechanical systems, hydraulic systems, electrical systems, pneumatic systems, or by a combination of said systems. A distinction can be made between so-called fully variable (continuously variable) valve trains and systems with valve drives that can be adjusted in stages.

The necessary for combustion Fuel injection quantity MFF is conventionally calculated from a load parameter, namely the intake air mass MAF_KGH and the rotational speed N calculated and several corrections (temperature influence, lambda control, etc.) subjected.

One turbocharged, homogeneously operated DI gasoline engine offers full load close Operation the possibility of fresh air to flush directly into the exhaust tract. Prerequisite is a positive pressure gradient between the inlet and outlet side at the time of the charge change OT (top dead center) and a sufficient valve overlap VO (valve overlap) between exhaust and inlet valve. The valve overlap VO, expressed in ° KW (crankshaft) let yourself in the described embodiment via a Infinitely variable IVVT system (Infinitely Variable Valve Timing). To identify this system, the following are used Parameters preceded by the term IVVT.

By The direct injection of fuel ensures that the Start of injection after closing the exhaust valve is done. It is flushed so only fresh air without fuel to the exhaust side.

By the extra purge air the mass flow is increased by the exhaust gas turbine disposed on the exhaust side, whereby the achievable maximum power and the dynamic behavior significantly improve an exhaust gas turbocharger. In particular for low Engine speeds improved the response of an exhaust gas turbocharger become.

• – Bei einem Lambdawert λ_EX = 1 findet bei Spülluft eine Verbrennung im Zylinder mit einem Lambdawert λ_Cyl < 1 statt. Durch die Verbrennung im Fetten wird die Klopfneigung reduziert.
• – λ_Cyl < 1 bewirkt einen sehr hohen CO- und HC-Anteil im Abgas. Gleichzeitig sorgt der Spülluftanteil für einen hohen Restsauerstoffgehalt und bewirkt so einen internen Sekun därlufteffekt. Die resultierende Abgaszusammensetzung bewirkt eine hohe Exothermie im Abgaskatalysator und beschleunigt so seine Aufheizung.
• – Durch Spülen wird der Restgasanteil im Brennraum und somit die Klopfneigung vermindert. Die Minimierung des Restgasanteils ist bei Betrieb an der Volllast von entscheidender Bedeutung um eine maximale Zylinderfüllung zu erreichen und diese Füllung auch effektiv, d.h. mit günstiger Verbrennungsschwerpunktlage, umzusetzen.
• – Die zusätzliche Spülluftmenge erhöht den Massenstrom durch die Turbine, wodurch bei niedrigen Motordrehzahlen sowohl das Ansprechverhalten, als auch die erreichbare Maximalleistung gesteigert werden können.

In full-load operation of a supercharged internal combustion engine causes a positive pressure difference between the inlet and outlet side in combination with a corresponding valve overlap VO that fresh air is flushed to the exhaust side. The purge air quantity increases the flow rate through the internal combustion engine without participating in the combustion. In particular, the following advantages for the operating behavior occur:

• For a lambda value λ _EX = 1, combustion in the cylinder takes place with a lambda value λ _Cyl <1. Combustion in fats reduces the tendency to knock.
• - λ _Cyl <1 causes a very high CO and HC content in the exhaust gas. At the same time, the scavenging air component ensures a high residual oxygen content and thus produces an internal second air effect. The resulting exhaust gas composition causes a high exotherm in the catalytic converter and thus accelerates its heating.
• - By rinsing the residual gas content in the combustion chamber and thus the tendency to knock is reduced. The minimization of the residual gas content is of crucial importance when operating at full load in order to achieve a maximum cylinder charge and to implement this charge effectively, ie with a favorable combustion center point.
• - The additional purge air volume increases the mass flow through the turbine, which at low engine speeds both the response, and the maximum achievable performance can be increased.

The relationship the remaining in the cylinder air mass to the entire during a Working cycle sucked air mass is called TE (Trapping Efficiency) designated.

The total intake air mass is composed of the air mass M _Cyl , which remains in the cylinder and the scavenging air mass M _Scav , ie the air mass that is flushed through the cylinder. From the above context, it follows that TE ≦ 1. The larger the scavenging air _mass M _Scav , the smaller the value for the trapping efficiency TE. Ie the air mass meter 13 ( 1 ) Measures the total air mass, which is sucked in total, but then divides the Trapping Efficiency TE in an air mass, which participates in the combustion and in an air mass, which is flushed through the cylinders of the internal combustion engine.

In an IVVT (Infinitely Variable Valve Timing) system, the trapping efficiency TE can be infinitely varied between a minimum value (maximum purge air) and the value 1 (no purge air, M _Scav = 0) via the intake and exhaust camshaft position ) adjust.

The lambda λ _Ex measured in the exhaust gas does not match the combustion _lambda λ _Cyl due to the scavenging air _mass M _Scav not participating in the combustion. The following relationship applies: TE · λ Ex = λ Zyl

The maximum permissible monolith temperature T_MON_MAX of the catalytic converter represents a limitation for the maximum permissible scavenging air quantity. By the lambda value λ _Ex = 1, by means of the lambda control device 23 is set and a trapping efficiency TE <1 (positive purge gradient, valve overlap VO> 0) results in a λ _Cyl <1. There is thus no complete combustion of the fuel in the combustion chamber instead. In the exhaust gas so occurs a high CO and HC concentration. The purge air content in the exhaust gas provides ideal conditions for a post-reaction in the exhaust gas catalytic converter. The high concentrations of unburned fuel constituents together with the high residual oxygen content lead to a strong exothermic reaction in the catalytic converter. The monolith temperature T_MON of the catalytic converter can thereby rise into critical ranges.

The stationary IVVT setpoint CAM_IN_FL_STAT_SP for full-load operation for the adjustment The intake camshaft and the stationary IVVT setpoint CAM_EX_FL_STAT_SP for full-load operation for the adjustment of the exhaust camshaft are each tuned with regard to the achievable full load and the maximum permissible monolith temperature T_MON_MAX. This temperature T_MON_MAX must not be permanently exceeded for reasons of durability of the catalytic converter. It is particularly dependent on the mate rial used the catalytic converter. It is specified by the manufacturer and is typically 950 ° C for a commercial catalytic converter.

The Values CAM_IN_FL_STAT_SP and CAM_EX_FL_STAT_SP, as well as those resulting valve overlap VO thus represent the setpoints for the setting of the gas exchange valves for maximum performance of the internal combustion engine considering the maximum allowed Monolith temperature T_MON_MAX of the catalytic converter is that in steady state operation the internal combustion engine allowed are.

The value T_MON_MAX would be exceeded for low speeds (typically N <= 2000 1 / min) with minimal trapping efficiency (maximum purge air volume). Since at maximum purge air volume, achieved by maximum valve overlap VO after charge change - OT (top dead center) and a maximum monolith temperature T_MON_MAX is exceeded, the stationary IVVT setpoints must be limited.
CAM_IN_FL_STAT_SP = CAM_IN_FL_STAT_SP (N, TCO, MAF_KGH)
CAM_EX_FL_STAT_SP = CAM_EX_FL_STAT_SP (N, TCO, MAF_KGH)

The fixed set points (set point, SP) for full load (Full Load, FL) for setting the gas exchange valves, indicated in ° CA (crankshaft) are determined depending on the speed N, the coolant temperature TCO and the air mass MAF_KGH and are either in each a three-dimensional characteristic map KF_1 or KF_2 or in several, linked maps in the memory device 24 stored.

The monolith temperature T_MON can be determined as a function of basic parameters of the internal combustion engine by means of any known dynamic temperature model. A temperature model for the monolith temperature T_MON an exhaust gas catalyst is, for example, in the DE 199 31 223 C2 described.
T_MON = T_MON (N, MAF_KGH, IGA, λ _ex, VS, TCO, NR_PAT_SCC, TE)

• – Drehzahl N der Brennkraftmaschine
• – Luftmasse MAF_KGH,
• – Zündwinkel IGA,
• – Lambdawert im Abgas λ_Ex,
• – Fahrzeuggeschwindigkeit VS (wegen Fahrtwind-Kühlung),
• – Kühlmitteltemperatur TCO,
• – Abschaltpattern PAT_SCC, wenn die Brennkraftmaschine mit einer Einrichtung zur Zylinderabschaltung ausgestattet ist,
• – Trapping Effeciency TE.

Depending on the desired accuracy, all or a selection of the following parameters can be used as input variables for the temperature model:

• - Speed N of the internal combustion engine
• - Air mass MAF_KGH,
• Ignition angle IGA,
• Lambda value in the exhaust gas λ _Ex ,
• Vehicle speed VS (because of wind-wind cooling),
• Coolant temperature TCO,
• Shutdown pattern PAT_SCC when the internal combustion engine is equipped with a cylinder deactivation device,
• - Trapping Effeciency TE.

Alternatively, a direct measurement of T_MON in the monolith by means of the temperature sensor is also possible 34 possible.

The stationary IVVT setpoints are due to the maximum monolith temperature T_MON_MAX limited. With a positive load jump in the charged operation (Intake manifold pressure> ambient pressure) can However, IVVT setpoints are temporarily set, which off establish the maximum monolith temperature T_MON_MAX are not permanently possible.

Operation with the maximum possible valve overlap VO is possible for a short time (typically for a few seconds) because, due to the thermal inertia of the exhaust system, the value for the maximum monolith temperature T_MON_MAX is only reached and exceeded after a relatively long time. To improve the turbocharger and engine response but such a short-term operation with increased valve overlap VO is sufficient. The valve overlap VO is set via a temporary correction of the stationary full load IVVT setpoints CAM_EX_FL_STRT_SP, CAM_IN_FL_STAT_SP. The dynamic correction value for the intake valve is called CAM_IN_SP_DYN_COR, the dynamic correction value for the exhaust valve is called CAM_EX_SP_DYN_COR.
CAM_IN_SP_DYN_COR = CAM_IN_SP_DYN_COR (N, TCO, MAF_KGH)
CAM_EX_SP_DYN_COR = CAM_EX_SP_DYN_COR (N, TCO, MAF_KGH)

These correction values, indicated in ° CA (crankshaft), are determined as a function of the rotational speed N, the coolant temperature TCO and the air mass MAF_KGH and are either in a three-dimensional characteristic map KF_3 or KF_4, or in a plurality of linked characteristic diagrams in the storage device 24 stored.

If a positive load jump occurs in the boosted operation (intake manifold pressure> ambient pressure), the desired pressure value, for example given by an intake manifold model, upstream of the throttle valve PUT_SP will abruptly rise to the target value, which is higher than the ambient pressure level. The actual pressure PUT_MES upstream of the throttle 16 However, initially remains at the ambient pressure level and begins to increase only when the compressor 26 over the turbine 25 is driven at a higher speed. If the pressure PUT-MES now reaches the value PUT_SP (PUT_DIF = PUT_SP - PUT_MES the value 0), ie the pressure setpoint has been reached, the dynamic corrections CAM_EX_SP_DYN_COR, CAM_IN_SP_DYN_COR must be reset to zero.

The correction takes place via the factors
CAM_EX_DYN_COR_FAC and CAM_IN_DYN_COR_FAC.

These factors are dependent on the pressure difference PUT_DIF = PUT_SP - PUT_MES in corresponding maps KF_5 or KF_6 in the memory device 24 stored.
CAM_EX_DYN_COR_FAC = CAM_EX_DYN_COR_FAC (PUT_DIF)
CAM_IN_DYN_COR_FAC = CAM_IN_DYN_COR_FAC (PUT_DIF),
where:
CAM_EX_DYN_COR_FAC ∈ [0, 1]
CAM_IN_DYN_COR_FAC ∈ [0, 1]

ever smaller the pressure difference PUT_DIF = PUT_SP - PUT_MES is the closer the factors CAM_EX_DYN_COR_FAC and CAM_IN_DYN_COR_FAC to the value Zero introduced.

As already mentioned, is a longer one Operation with dynamic corrections CAM_EX_SP_DYN_COR, CAM_IN_SP_DYN_COR for reasons the maximum monolith temperature T_MON_MAX not possible. Depending on Temperature level in the monolith at the time of load jump, can it happens that exceeded T_MON_MAX before the set load value has been reached. In this case, the dynamic corrections CAM_EX_SP_DYN_COR, CAM_IN_SP_DYN_COR early set to zero. The target load value is also in this case set, but not with the highest possible Dynamics.

The correction takes place via the factors CAM_EX_TEMP_COR_FAC and CAM_IN_TEMP_COR_FAC. These factors depend on the monolith temperature T_MON in corresponding maps KF_7 and KF_8 in the memory device 24 stored.
CAM_EX_TEMP_COR_FAC = CAM_EX_TEMP_COR_FAC (T_MON)
CAM_IN_TEMP_COR_FAC = CAM_IN_TEMP_COR_FAC (T_MON),
where:
CAM_EX_TEMP_COR_FAC ∈ [0, 1]
CAM_IN_TEMP_COR_FAC ∈ [0, 1]

The corrected IVVT setpoint for the exhaust camshaft CAM_EX_FL_SP thus results from the sum of the steady-state setpoint for full load CAM_EX_FL_STAT_SP and the dynamic correction of the setpoint CAM_EX_SP_DYN_COR weighted with the correction factor CAM_EX_DYN_COR_FAC dependent on the pressure difference and the temperature-dependent correction factor CAM_EX_TEMP_COR_FAC. CAM_EX_FL_SP = CAM_EX_FL_STAT_SP + CAM_EX_SP_DYN_COR · CAM_EX_DYN_COR_FAC · CAM_EX_TEMP_COR_FAC

The corrected IVVT setpoint for the intake camshaft CAM_IN_FL_SP thus results from the sum of the stationary setpoint value for full load CAM_IN_FL_STAT_SP and the dynamic correction of the setpoint value CAM_IN_SP_DYN_COR weighted with the correction factor CAM_IN_SP_DYN_COR_FAC dependent on the pressure difference and the temperature-dependent correction factor CAM_IN_TEMP_COR_FRC. CAM_IN_FL_SP = CAM_IN_FL_STAT_SP + CAM_IN_SP_DYN_COR · CAM_IN_DYN_COR_FAC · CAM_IN_TEMP_COR_FAC

is both the pressure difference dependent correction factor, as also the temperature-dependent correction factor equal to zero (pressure difference P_DIF = zero and T_MON = T_MON_MAX), so also the dynamic correction is zero and it becomes the IVVT setpoint on the stationary Setpoint set for Continuous operation possible is.

An IVVT position controller of the facility 31 Sets the current intake and exhaust camshaft position to the specified IVVT setpoints. From the measured actual Po positions CAM_EX, CAM_IN results in the current valve overlap VO, which assigns the respective Trapping Efficency (TE).

The The invention has been explained by way of example, in the valve overlap VO by means of a so-called IVVT system, i. through stepless adjustment set both the intake and the exhaust camshaft becomes.

to execution the method according to the invention But every facility is suitable, with the help of the valve overlap changed can be.

Claims (4)

Method for operating an internal combustion engine ( 10 ) wherein - the combustion chambers of the internal combustion engine ( 10 ) supplied air by means of a charging device ( 25 . 26 ) is pre-compressed, - fuel directly into the combustion chambers of the internal combustion engine ( 10 ) is injected, - the exhaust gas of the internal combustion engine ( 10 ) with the aid of at least one catalytic converter ( 21 ), - by means of a device ( 31 ) the valve overlap (VO) of the gas exchange valves of the internal combustion engine ( 10 ) can be varied, - the valve overlap (VO) of the gas exchange valves for a full load operation or at least full load close operation of the internal combustion engine ( 10 ) is set to stationary setpoint values (CAM_IN_FL_STAT_SP, CAM_EX_FL_STAT_SP) by setting the gas exchange valve control times, - at an increased load requirement in the supercharged operation of the internal combustion engine ( 10 ) a dynamic correction of the stationary setpoint values (CAM_IN_FL_STAT_SP, CAM_EX_FL_STAT_SP) takes place, - the dynamic correction values (CAM_IN_SP_DYN_COR, CAM_EX_SP_DYN_COR) depending on at least one of the operating variables of the internal combustion engine speed (N), coolant temperature (TCO), inducted air mass (MAF_KGH) are determined and by of a factor (CAM_IN_DYN_COR_FAC, CAM_EX_DYN_COR_FAC) which is weighted as a function of the pressure difference between the pressure setpoint (PUT_SP) and the actual pressure (PUT_MES) in the intake duct (FIG. 11 ) and by means of a factor (CAM_IN_TEMP_FAC, CAM_EX_TEMP_COR_FAC), which determines the temperature (T_MON) of the catalytic converter ( 21 ), - the thus corrected setpoint values (CAM_IN_FL_SP, CAM_EX_FL_SP) are set. Method according to claim 1, characterized in that that the stationary Setpoints (CAM_IN_FL_STAT_SP, CAM_EX_FL_STAT_SP) depending on at least one of the operating variables of the internal combustion engine Speed (N), coolant temperature (TCO), inducted air mass (MAF_KGH). Method according to claim 1, characterized in that that the weighting factors (CAM_IN_DYN_COR_FAC, CAM_EX_DYN_COR_FAC; CAM_IN_TEMP_FAC, CAM_EX_TEMP_COR_FAC) Values between zero and one exhibit. Method according to Claim 1, characterized in that the corrected setpoint values (CAM_IN_FL_SP, CAM_EX_FL_SP) are calculated according to the following relationship: CAM_IN_FL_SP = CAM_IN_FL_STAT_SP + CAM_IN_SP_DYN_COR · CAM_IN_DYN_COR_FAC · CAM_IN_TEMP_COR_FRC CAM_EX_FL_SP = CAM_EX_FL_STAT_SP + CAM_EX_SP_DYN_COR · CAM_EX_DYN_COR_FAC · CAM_EX_TEMP_COR_FAC