METHOD AND UNIT FOR OPERATING A FUEL METERING SYSTEM IN AN INTERNAL COMBUSTION ENGINE

Abstract

A method and a unit for operating or for the operation of a fuel metering system of an internal combustion engine, in particular in a motor vehicle, and it being provided, in particular, that at least one operating variable of the internal combustion engine is detected, a dynamic operating state of the internal combustion engine is detected based on the at least one detected operating variable, and a dynamic correction to the fuel metering system of the internal combustion engine is carried out for a detected dynamic operating state of the internal combustion engine, taking into account the efficiency of an NOx exhaust gas aftertreatment system.

Claims

1-13. (canceled)

14. A method for operating a fuel metering system of an internal combustion engine, the method comprising: detecting at least one operating variable of the internal combustion engine; detecting a dynamic operating state of the internal combustion engine based on the at least one detected operating variable; and performing a dynamic correction to the fuel metering system of the internal combustion engine for a detected dynamic operating state of the internal combustion engine.

15. The method of claim 14, wherein the efficiency of an exhaust gas aftertreatment system of the internal combustion engine is determined and a dynamic corrective intervention on the fuel metering system of the internal combustion engine is carried out only when a predefined threshold value of the efficiency of the exhaust gas aftertreatment system is fallen below.

16. The method of claim 15, wherein the efficiency of the exhaust gas aftertreatment system is taken into account with a transfer characteristic map and an NOx exhaust gas aftertreatment factor derived from the transfer characteristic map.

17. The method of claim 16, wherein the NOx exhaust gas aftertreatment factor is formed from a transfer characteristic map including NOx emission levels plotted in one direction and average NOx emission values plotted in the other direction, a high value of the NOx emissions and a simultaneously high average emission value resulting in a value of the NOx exhaust gas aftertreatment factor of 1.

18. The method of claim 14, wherein average NOx emissions summed in a preceding time period are taken into account in the transfer characteristic map.

19. The method of claim 14, wherein a cited dynamic operating state of the internal combustion engine is characterized with a dynamic indicator, the dynamic indicator being standardized to values 0 and 1, the value 0 corresponding to a stationary operation of the internal combustion engine, and the value 1 corresponding to a dynamic operation of the internal combustion engine.

20. The method of claim 14, wherein the detection of a dynamic operating state of a charged internal combustion engine takes place on the basis of a change in the charge air pressure or a change in the manifold air pressure.

21. The method of claim 14, wherein the dynamic correction takes place by changing injection parameters, by changing the beginning of an injection or by changing a rail pressure, and/or by changing the position and quantity of partial injections.

22. The method of claim 14, wherein the dynamic corrective intervention on the fuel metering system of the internal combustion engine takes place by shifting a combustion center of gravity to retard.

23. A unit for operating a fuel metering system of an internal combustion engine, comprising: a control arrangement configured to perform the following: detecting at least one operating variable of the internal combustion engine; detecting a dynamic operating state of the internal combustion engine based on the at least one detected operating variable; and performing a dynamic correction to the fuel metering system of the internal combustion engine for a detected dynamic operating state of the internal combustion engine.

24. A non-transitory computer readable medium having a computer program, which is executable by a processor, comprising: a program code arrangement having program code for controlling a fuel metering system of an internal combustion engine, by performing the following: detecting at least one operating variable of the internal combustion engine; detecting a dynamic operating state of the internal combustion engine based on the at least one detected operating variable; and performing a dynamic correction to the fuel metering system of the internal combustion engine for a detected dynamic operating state of the internal combustion engine.

25. The computer readable medium of claim 24, wherein the efficiency of an exhaust gas aftertreatment system of the internal combustion engine is determined and a dynamic corrective intervention on the fuel metering system of the internal combustion engine is carried out only when a predefined threshold value of the efficiency of the exhaust gas aftertreatment system is fallen below.

26. An electronic control unit for controlling a fuel metering system of an internal combustion engine, comprising: a control arrangement configured to perform the following: detecting at least one operating variable of the internal combustion engine; detecting a dynamic operating state of the internal combustion engine based on the at least one detected operating variable; and performing a dynamic correction to the fuel metering system of the internal combustion engine for a detected dynamic operating state of the internal combustion engine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 shows one exemplary embodiment of the method according to the present invention on the basis of a flow chart.

[0031] FIG. 2 shows a combined flow chart/block diagram for illustrating the method according to the present invention, and a unit according to the present invention.

[0032] FIG. 3 shows exemplary embodiments of a dynamic injection correction according to the present invention.

DETAILED DESCRIPTION

[0033] In the present exemplary embodiment, the detection of a dynamic operating state of the internal combustion engine takes place in the case of an internal combustion engine including a turbocharger by monitoring a relative control deviation of a charge air pressure or a manifold air pressure. In cases in which the charge air pressure is adjusted purely in a precontrolled way, or in which there is no active charge air pressure control available, a comparison may be alternatively carried out between a present charge air pressure and a reference charge air pressure which is predefined or which was empirically determined, for example, in advance. In this case, environmental conditions such as, e.g., the ambient temperature or the ambient air pressure, may also be taken into account. In the latter-mentioned cases, in turn, as an alternative, the charge air pressure itself and/or the engine load may also be monitored and utilized for the dynamic detection.

[0034] As illustrated in the flow chart shown in FIG. 1, in order to detect an aforementioned dynamic operating state on the basis of a charge air pressure detected 100 in a way known per se, a check is carried out 105 to determine whether an aforementioned relative charge air pressure deviation exceeding a predefined threshold value is present. If a corresponding charge air pressure deviation is not present, the method returns to the beginning of the procedure. Otherwise, a dynamic factor, which is described in detail in the following, or a dynamic indicator (standardized to continuous values between 0 (=stationary) and 1 (=dynamic)) is determined 110. In this case, the value 0 means there is no or only a slight charge air pressure deviation, i.e., essentially a stationary operation of the internal combustion engine, and the value 1 means there is a relatively great charge air pressure deviation, i.e., essentially a dynamic operation of the internal combustion engine in the aforementioned sense.

[0035] The dynamic correction of the injection parameters is activated or deactivated on the basis of the particular value of the dynamic indicator which is present. In addition, on the basis of a transfer characteristic map shown in FIG. 2, the present efficiency of the NOx exhaust gas aftertreatment is converted 115 into a so-called NOx exhaust gas aftertreatment factor (standardized to continuous values between 0=sufficient efficiency of NOx exhaust gas aftertreatment, and 1=support required by engine-related measures). In this case, the value is 0 when the efficiency of the particular NOx exhaust gas aftertreatment system is sufficient for an effective exhaust gas aftertreatment or, in the present case, in particular, for an effective NOx reduction, and the value is 1 when support for such an effective exhaust gas aftertreatment is required by measures applied to the operation of the internal combustion engine.

[0036] As shown in FIG. 1, a check 120 is therefore carried out on the basis of the result of the multiplication of the dynamic factor 110 and the NOx exhaust gas aftertreatment factor 115 to determine whether a dynamic correction, which was mentioned above and which will be described herein in detail in the following, should be carried out or not. If not, the method returns to the beginning of the procedure. Otherwise, in the present exemplary embodiment, a dynamic correction, which is described in the following, is carried out 130 on the basis of correction data provided 125 by an offset characteristic map.

[0037] An aforementioned dynamic correction takes place by changing injection parameters, e.g., the beginning of injection, the rail pressure, and the timed position or phase angle with respect to the crankshaft angle and the injection quantity of pre- and post-injections. In the exemplary embodiment, corresponding dynamic correction values are determined on the basis of an offset characteristic map or are taken from such a characteristic map, and these correction values are multiplied by the standardized dynamic indicator, and the resultant standardized correction value is added to a particular stationary setpoint value (see also FIG. 2). By accurately activating the aforementioned interventions or corrections on an injection system, NOx emissions may be reduced and, simultaneously, the negative influences of the correction on fuel consumption may be minimized.

[0038] FIG. 2 shows one exemplary embodiment of the method according to the present invention or a unit according to the present invention for dynamic injection correction on the basis of a combined flow chart/block diagram. The efficiency of the NOx reduction, in particular, which is achievable or which has already been achieved by the exhaust gas aftertreatment with the aid of an NOx exhaust gas aftertreatment system, is taken into account in this unit. The input variables for the calculation shown are standardized values 0 to 1 which are provided by an aforementioned transfer characteristic map 200 and which are taken into account 205 as an NOx exhaust gas aftertreatment factor. In the present exemplary embodiment, these values of the NOx exhaust gas aftertreatment factor are entered or plotted in the transfer characteristic map 200, with the level of the NOx emission NOx.sub.out plotted in the vertical direction over average NOx emission values NOx.sub.avg in the horizontal direction. A high value of the NOx emission corresponds to an aforementioned emission spike (peak) and corresponds to a value 1 when an average value NOx.sub.avg is simultaneously high.

[0039] In order to account for the efficiency of an NOx exhaust gas aftertreatment, a dynamic factor 210 is additionally determined and correction values are provided by or read from a dynamic offset characteristic map 215 (see also FIG. 3 and associated description). The values resulting according to 210 and 215 are subsequently multiplied 220 by the aforementioned dynamic correction value 205.

[0040] The aforementioned dynamic factor 210 has the value 0 when only a very slight charge air pressure deviation, i.e., a stationary operation of the internal combustion engine, is present, and has the value 1 when a relatively great charge air pressure deviation, i.e., a dynamic operation of the internal combustion engine in the aforementioned sense, is present.

[0041] The aforementioned NOx exhaust gas aftertreatment factor 205 is ascertained from a transfer characteristic map which, in the present exemplary embodiment, covers the mass flow rate of NOx after NOx exhaust gas aftertreatment (NOx.sub.out) or, if available, covers the efficiency of the NOx exhaust gas aftertreatment, and the average NOx emissions NOx.sub.avg summed in a preceding time period. The aforementioned preceding time period may be 10 min to 30 min before the particular actual time. It should be noted that the NOx exhaust gas aftertreatment factor according to one simplified variant may also be ascertained with the aid of a characteristic curve via the NOx exhaust gas temperature which determines the efficiency of the exhaust gas aftertreatment.

[0042] In the exemplary embodiment shown in FIG. 2, it is assumed that an aforementioned dynamic correction is carried out. For this purpose, the value resulting from the multiplication 220 is added 230 to a stationary injection parameter 225. The result of the addition 230, therefore, is a dynamically optimized injection parameter 235.

[0043] The aforementioned transient corrective interventions into the injection system may be fully activated in the event of a high mass flow rate of NOx after NOx exhaust gas aftertreatment (or the aforementioned low efficiency of NOx exhaust gas aftertreatment) and high NOx emissions already in the aforementioned preceding time period or, if these conditions are not present, the corrective interventions may be attenuated or completely deactivated.

[0044] FIG. 3 shows one first exemplary embodiment of a transient control affected here, in which an aforementioned offset characteristic map covers the operating variables of speed and load 300 of the internal combustion engine, aforementioned critical emission spikes mostly occurring only at higher loads. Due to a dynamic correction which takes place only at high loads, NOx emission spikes may be reduced without the fuel consumption increasing too greatly.

[0045] In the present exemplary embodiment, offset values for the transient control of injection timing 305 and rail pressure 310 and the transient control of injection pattern 315 for the aforementioned pre-injections and/or post-injections are ascertained on the basis of the operating variables speed and load 300. In addition, information regarding transient operating conditions of the internal combustion engine 320 are read out, e.g., from a control unit of the internal combustion engine.

[0046] A calculation 325 of setpoint values of the injection parameters for the stationary operation, from which injection parameters which are suitable for the stationary operation are derived 330, is additionally carried out on the basis of the operating variables of speed and load 300.

[0047] The three variables 305, 310, 315 are jointly 333 processed further and, together with variables 320, 330, are supplied to a transient adaptation 335 which, in the end, delivers setpoint values of the injection parameters 340 which are desired or required for the dynamic correction.

[0048] According to one second exemplary embodiment of a transient control, which is not shown here, an aforementioned offset characteristic map does not cover the aforementioned operating variables of load and speed 300, but rather covers the two air system variables of inert gas rate and charge coefficient. In dynamic operating states, due to the absence of charge air pressure, the charge coefficient initially assumes low values which are increased as the charge air pressure increases (and, therefore, as the cylinder charge increases). If the EGR quantity is reduced due to insufficient cylinder charge, the inert gas rate decreases (no EGR means inert gas rate=0 or O2 concentration=O2 fresh air). As soon as the charge is sufficiently high enough to reactivate the EGR, the inert gas rate also increases. Since the O2 concentration and, therefore, the inert gas rate at the cylinder inlet correlate well with the NOx emissions, the aforementioned measures in the injection system may be accurately controlled or activated by accounting for the present state of the air system (inert gas rate and charge coefficient). In this case, input variables 300 represented in the upper left in FIG. 3 for the offsets of injection timing 305 and rail pressure 310 and the control of injection pattern 315 are replaced by the aforementioned inert gas rate and the aforementioned charge coefficient. The input variables for aforementioned setpoint value calculation 325 represented in the lower left in FIG. 3 remain unchanged, i.e., the load and the speed of the internal combustion engine.

[0049] In this second exemplary embodiment, an activation of aforementioned injection system interventions or corrections are made possible on the basis of air system variables which are decisive for the combustion and occur at the cylinder inlet. The aforementioned charge coefficient includes the value of a cylinder charge which has been standardized with the injection quantity and therefore allows for a parameterization which is essentially independent of the operating point of the internal combustion engine or the injection system. Due to a dynamic correction which takes place only at a low inert gas rate, in turn, NOx emission spikes may be reduced without the fuel consumption exceeding a maximally permissible limit value of increased fuel consumption of 0.5%. An aforementioned relatively low inert gas rate results in a cylinder of the internal combustion engine at a relatively low or even completely suppressed exhaust gas recirculation.

[0050] As compared to the exemplary embodiment shown in FIG. 3, the second exemplary embodiment has the further advantage that it is possible to respond immediately to the state of the gas mixture in the cylinder or in the corresponding combustion chamber, whereby an even more accurate activation of the aforementioned injection corrections is made possible and, therefore, further advantages with respect to the reduction of NOx, particulates, and fuel consumption way result.

[0051] The described method may be implemented in the form of a control program for an electronic control unit for controlling an internal combustion engine or in the form of one or several corresponding electronic control units (ECUs).