DE10163894A1 - Internal combustion engine with direct injection - Google Patents

Abstract

To compensate for the tolerance differences in the production of injectors of a fuel injection device, the injectors of the individual cylinders are equalized by means of a Injektorhub- and / or injection time adjustment in an internal combustion engine with direct injection. The aim is to achieve the pre-control values of the application. The injection quantity of the individual injectors is changed in homogenous and / or in stratified operation until a desired fuel quantity is set in all injectors. This achieves a nominal equalization of fuel flow in all injectors.

Description

The invention relates to a method for operating a Internal combustion engine with direct injection according to claim 1 or 4.

In particular, direct-injection internal combustion engines with spark ignition optionally with charge stratification or homogeneous operated. The operation of an internal combustion engine with Charge stratification, the so-called shift operation, allows Low fuel consumption, especially due to the lower gas exchange and wall heat losses. At the Shift operation takes place the injection of the fuel during the compression stroke, preferably the Fuel / air mixture with significant excess air, d. H. λ> 1, is processed. In this case, the fuel is in the Burning chamber layered in front, leaving the fuel / air mixture can be reliably ignited despite excess air. in the Homogenous operation, the fuel injection takes place in Intake stroke, so that at the ignition a homogeneous Mixture cloud is present in the combustion chamber.

The aim of the newly developed gasoline engines with direct injection is the reduction of fuel consumption and Exhaust emissions. The advantages achieved are due to a defined control of injectors or injectors during the injection process, thereby optimizing the Burning process is achieved. This is done for example via the optimization of the injection jet characteristic. To drive injectors with adjustable opening stroke are suitable in particular piezo actuators, which make it possible to electrical signal virtually instantaneous in one to transform mechanical movement. This movement is in terms of deflection and timing through Setting a high voltage, with which the piezo actuator is applied, precisely controllable.

As in the production of piezoelectrically operated Injectors due to production-related Tolerance differences a different flow behavior come about, have the equipped with piezoelectric actuators Fuel injectors applied from one Injection parameters deviating injection behavior. This leads in particular with direct injection Internal combustion engines with spark ignition to a higher Consumption.

From DE 199 03 555 C2 a device is known, with the one power supply several different ones Voltage level provides between those for adjustment Switched directly to different valve opening positions can be, so that multiple required valve positions without additional control effort can be reliably adjusted can.

Since equality of the individual cylinders with the help of above-mentioned device is not enabled, and a Adjusting the fuel flow at the injector to a nominal fuel flow across the engines is needed, the present invention has the object underlying, a method for an internal combustion engine with Direct injection to create, with the equality the individual cylinder via functions in the engine control is possible.

According to the invention, this object is achieved by the features of Claim 1 or of claim 4 solved.

The inventive method provides that for metering a fuel quantity, in particular for a Direct injection internal combustion engine with spark ignition, the Fuel injection quantities adapted to the applied quantities become. As a rule, an internal combustion engine becomes load-dependent operated in a homogeneous and / or in a shift operation. An amount of fuel injected into a combustion chamber becomes by means of an injector by a variation of a Injection duration and / or a Injektornadelhubs dosed or set. At one operating point is in each cylinder the internal combustion engine, an injected amount of fuel as an actual amount of fuel determined. After that, the actual Fuel quantity with one in the control device for the respective operating point stored target fuel quantity compared, wherein one of the actual fuel quantities of the single cylinder average is formed. According to the invention is subsequently by means of the control device of the injector activated such that the injected amount of fuel the average value determined from the actual fuel quantities equivalent.

The injectors of the individual cylinders are known by Method via injector stroke and / or injection time adjustment equated with each other, d. h., in the respective Cylinder injected fuel amount is raised as long or lowered until it is adjusted to the mean value. The Adjustment to the mean value can be in the homogeneous or in the Shift operation take place.

In a further step, the injector is further so controlled that the injected fuel quantity in each Cylinder of the target fuel quantity corresponds. The adaptation to the target fuel quantity is such that a Difference value between the determined mean value and an in the control device for the respective operating point stored target fuel quantity is determined. After Setting the mean value is the one in the respective Combustion chamber injected fuel amount accordingly to this Difference value changed so that in the respective Combustion chamber injected fuel quantity of the target Fuel quantity corresponds.

According to the invention, the adaptation of the injected Amount of fuel in the individual cylinders to the target Fuel quantity in homogeneous operation instead. The level of Injectors will injector via and / or Injection time adjustment in Homgenbetrieb changed until, until a lambda control deviation has the value zero.

According to a second embodiment of the invention is in a Operating point in each cylinder of the internal combustion engine one injected fuel amount as an actual fuel amount determined, whereby from the actual fuel quantities of the individual Brennräume a first average is formed. Continue a difference value between the first mean and an in the control device for the respective operating point stored target fuel quantity determined. Then in each Cylinder the amount of fuel injected around the Difference value changed so that one from the Injected fuel quantities determined second average the target fuel amount corresponds. D. h., The injected Fuel quantity is adjusted until from the injected fuel quantities set an average which corresponds to the second mean. This Adaptation takes place in homogeneous operation.

According to the invention, in a final step, each Injector in the respective cylinder by means of the control device triggered such that the injected fuel amount of Target fuel quantity corresponds. This adaptation of changed fuel quantity in the individual cylinder to the Target fuel quantity can be in homogeneous and / or shift operation respectively.

According to the invention, the in the respective cylinder introduced amount of fuel in homogeneous operation by means of a Torque detection and / or a lambda single evaluation determined, the determination of the introduced Fuel quantity in shift operation by means of a torque Detection takes place.

It is preferred that the injection of the fuel in the combustion chamber by means of a piezoelectrically driven Injector takes place. The variation of the injection time and / or the Injektorhubs takes place at each operating point of the Internal combustion engine according to one in the control device stored injection map. When using a Piezoinjektors be through the in a control device stored injection maps based on the invention Procedure Voltage correction values for a piezo actuator determined, so the adjustment of the actual required injection quantities is achieved.

By the method according to the invention Tolerance differences, which are common in the production of injectors occur a fuel injection, balanced. This is important especially in spark-ignited ones Internal combustion engines with direct injection, where to achieve a better consumption a uniform and application-oriented Fuel supply is needed. By means of an injector lift and / or injection timing will be the injectors equal to each other. Thus, the pilot control values the application reached.

The injection quantity of the individual injectors becomes homogenous and / or in shift operation until a setpoint Fuel quantity is set at all injectors. Thereby becomes a nominal adjustment of fuel flow scored each injector of the internal combustion engine.

According to the invention, the present method can be the adaptation of fuel flow at each injector either through a cylinder equalization via the torque detection on the crankshaft and / or by the Einzellamda detection by means of a lambda probe in the exhaust system. At a Lambda Single evaluation is the injected fuel through the determination of the air ratios (λ) of the individual cylinders and Detection of the air mass determined. Alternatively, the Fuel quantity, for example by a Fuel meter or by values such as the opening time and the Pressure can be determined at the fuel injector.

In torque detection, those are on the crankshaft transmitted cylinder torques detected individually, whereby the Uneven injection of individual injectors determined is, wherein in the single-lambda detection, a correction of the injected fuel quantities by the air ratio of individual cylinder of the internal combustion engine can be done. It is possible, the injection quantities of each cylinder through to calculate the combustion air ratio accurately. Since that Air ratio in the individual cylinders due to Scattering in the production of injectors is not always is the same, such deviations occur accordingly Air ratios of the individual cylinders. A Lambda control compensates for such deviations by doing all Cylinder supplied with more or less fuel, so in Sum a desired air / fuel ratio in the exhaust gas is set, and the control deviation becomes zero.

But since the deviation does not depend on the target fuel quantity depends, this leads to that of a map calculated injection quantity not with the target fuel amount matches. By determining the λ values of the individual Cylinder it is thus possible, the deviations of to capture injected fuel quantities. This can be z. B. by a high temporal resolution of the with a λ control probe measured signal. In the exhaust gas is the firing order of Find internal combustion engine such that the λ-probe the Deviations of the individual cylinders from the desired air ratio detected.

Advantageous embodiments of the invention are in the Drawings are shown and described below. It demonstrate:

Fig. 1 shows the characteristics of the flow of the individual injectors and the associated deviation from a setpoint characteristic

Fig. 2 shows the characteristics of the flow of the individual injectors after an adjustment of the injected fuel quantities of the injectors with each other.

An unillustrated internal combustion engine with four cylinders preferably works according to the known four-stroke process, being the injection of the fuel into a combustion chamber directly done. To introduce the fuel Piezo injectors used. The Einspritzeitpunkt or the Injection quantity is varied depending on the load. It is also conceivable that the fuel main injection quantity in several Subsets is injected into the combustion chamber.

The characteristic curves shown in FIG. 1 show the differences of the individual injectors to a nominal value characteristic curve. The characteristics represent the injection behavior of the respective injectors, and how high the actual fuel flow of an injector deviates from a setpoint stored in a motor control.

The injectors used are actuated via a piezo actuator, wherein a voltage source provides the necessary voltage for setting a valve lift. A control device supplies corresponding information to the voltage source, whereby a specific opening stroke is set by means of the piezo actuator on the injector. Due to the differences in tolerance, a different fuel flow rate is established at the set stroke. In Fig. 1, for example, when injector 4 in the control of 50% of the maximum flow z. B. 60% of the maximum flow.

According to the invention, as shown in FIG. 1, an injected fuel quantity is determined as an actual fuel quantity at an operating point in each cylinder of the internal combustion engine. This is compared with a stored in the control device for the respective operating point target fuel quantity, and thus determines the injection behavior of the respective injector.

From the actual fuel quantities of the individual injectors an average value is formed. Subsequently, the injectors are controlled by means of the control device such that the injected fuel quantity corresponds to the mean value determined from the actual fuel quantities. The injectors then have the same injection behavior according to FIG. 2. Ie. the injectors 1 to 4 are equal to each other.

According to the adaptation of the Fuel flow at each injector either by one Cylinder equalization via the torque detection at the Crankshaft and / or by the Einzellamda detection means a lambda probe in the exhaust system. Before that is over Injector stroke and / or injection time adjustment in homogeneous operation the flow rate of each injector changed until one Lambda control deviation has the value zero. By the in a control device stored injection maps are for the adaptation of the actually required Injection quantities by the method according to the invention Correction values determined and used.

In a further step takes place for all four injectors a final correction by a difference value between the mean and the setpoint so that such Adjusting fuel flow behavior in all injectors, which allows the desired fuel amount. Thus, the desired fuel flow to an applied To achieve injection behavior in all injectors. Thereby becomes a nominal adjustment of fuel flow scored each of the four injectors.

Alternatively, the controller may change the Provide injection duration to at a certain Open position to achieve the desired flow. For this purpose, by means of the control unit aspired voltages on the piezo actuator based on stored in a map Voltage curves set a corresponding period of time.

In the internal combustion engine remains only a small Air error about the unequal distribution of the cylinder over the Air duct, but later in shift operation by the Equalization of injectors via Injektorhub- and / or Reduce injection time adjustment.

Claims (10)

1. A method for metering an amount of fuel, in particular for a direct injection internal combustion engine, with a plurality of combustion chambers, at least one fuel supply device having at least one injector in each combustion chamber, and a control device, wherein
at an operating point of the internal combustion engine, an amount of fuel injected into a respective combustion chamber is determined as an actual fuel quantity,
an average value is formed from the actual fuel quantities of the individual combustion chambers,
determining a difference value between the determined mean value and a desired fuel quantity stored in the control device for the respective operating point,
Further, by means of the control device, all injectors are controlled such that the amount of fuel injected into the respective combustion chamber corresponds to the determined mean value, and
then the amount of fuel injected into the respective combustion chamber is changed by the difference value such that the fuel quantity injected into the respective combustion chamber corresponds to the desired fuel quantity. 2. The method according to claim 1, characterized in that the adaptation of the into the respective combustion chamber injected fuel quantity to the mean in one Homogeneous or shift operation takes place. 3. The method according to claim 1 or 2, characterized that the change in the respective combustion chamber injected fuel quantity by the difference value for Adjustment of the injected fuel quantity to the target Fuel quantity is carried out in homogeneous operation. 4. A method for metering an amount of fuel, in particular for a direct injection internal combustion engine, with a plurality of combustion chambers, at least one fuel supply device, which has at least one injector in each combustion chamber, and a control device, wherein
at an operating point of the internal combustion engine, an amount of fuel injected into a respective combustion chamber is determined as an actual fuel quantity,
a first average is formed from the actual fuel quantities of the individual combustion chambers,
determining a difference value between the first mean value and a target fuel quantity stored in the control device for the respective operating point,
Further, all injectors are controlled by means of the control device such that the fuel quantity injected into the respective combustion chamber is changed by the difference value, so that a second average value determined from the injected fuel quantities corresponds to the desired fuel quantity, and
Subsequently, all injectors are controlled such that the fuel quantity injected into the respective combustion chamber corresponds to the desired fuel quantity. 5. The method according to claim 4, characterized in that the control of the respective injector for change the injected fuel quantity by the difference value in a homogeneous operation of the internal combustion engine takes place. 6. The method according to claim 4 or 5, characterized that the adaptation of the in the respective combustion chamber injected fuel amount to the target fuel amount in the homogeneous and / or shift operation of the internal combustion engine he follows. 7. The method according to any one of claims 1 to 6, characterized characterized in that the determination in the respective Brennraum injected fuel quantity by means of a Torque detection and / or a lambda Single evaluation done. 8. The method according to any one of claims 1 to 7, characterized characterized in that the injection of the fuel in the respective combustion chamber by means of a piezoelectric driven injector takes place. 9. The method according to any one of claims 1 to 8, characterized characterized in that the change in the respective Brennraum injected fuel quantity by means of a Variation of an injection duration and / or an injector stroke he follows. 10. The method according to any one of claims 1 to 9, characterized characterized in that the variation of the injection time and / or the Injektorhubs the internal combustion engine according to a stored in the control device Injection map is done.