DE102008001180A1 - Method for controlling internal combustion engine, involves dividing fuel injection into partial injection of injector, where signal determining fuel quantity is corrected with correction value - Google Patents

Abstract

The method involves dividing fuel injection into a partial injection of an injector, where a signal determining fuel quantity is corrected with a correction value. The correction value is formed by a sum of a basic correction value adapted to an operating point of an internal combustion engine. An injector specific correction value (qm) that has a mechanical influence of the injector and an individual injector correction value (qL) are determined during the operation of the internal combustion engine. Independent claims are included for the following: (1) a computer program for running at computer, particularly a controller of an internal-combustion engine; and (2) a computer program product with program code stored on a machine-readable medium for the execution of the method.

Description

The The invention relates to a method for controlling an internal combustion engine according to the preamble of independent claim 1.

object The present invention also relates to a computer program a computer program product for carrying out the method when the program on a computer or a controller is performed.

State of the art

The increasing demands on direct-injection internal combustion engines, especially diesel engines with regard to noise and pollutant emissions require very high precision the amount of fuel injected by the injection system the entire life and in all operating conditions of the internal combustion engine. By Manufacturing tolerances due to wear / aging phenomena the internal combustion engine or the injection system of the internal combustion engine and the mutual influence in the case of multiple injections, namely pre, main and post injections can the actual injection quantities and injection times vary greatly from the applied setpoints. For example Disturbances caused by pressure waves caused by a first injection are triggered and during the the time of the second, the first injection immediately following injection in the injection system has not subsided yet are.

The injection quantity which is changed in a wave-like manner over the time interval of individual partial injections is referred to below as "quantity wave" for short. For their correction, various correction methods are known from the prior art. For example, the EP 1 303 693 B1 a method and a device for controlling an internal combustion engine, wherein for the pressure wave correction, the fuel injected at a second partial injection amount of fuel is corrected depending on a pressure variable that characterizes the fuel pressure, the fuel quantity and another size. The further variable may be, for example, a variable characterizing the fuel temperature.

From the DE 197 12 143 A1 For example, a method and a device for controlling an internal combustion engine have become known in which the fuel injection is divided into at least a first and a second partial injection. A signal determining the injected fuel quantity can be corrected with a correction value. This correction value is formed multiplicatively from a first value and a second value. The first value is predeterminable as a function of at least the measured fuel pressure value and / or the distance between the first and the second partial injection, and the second value is dependent on at least one injection quantity, which is metered in during the first partial injection, or can be predetermined by the duration of the first partial injection , The correction value takes into account fluctuations in the fuel pressure between a measurement of the fuel pressure value and the second partial injection. Based on the correction value and a measured fuel pressure value, a corrected fuel pressure value is formed.

Out In principle, these compensation methods achieve this but only a finite quality of correction. The remaining one Deviation of the actual quantity from the nominal value, which is referred to as residual quantity wave can not be easily compensated in this way.

Of the The invention is therefore based on the object, a method for pressure wave correction further develop the generic type such that Even such a residual amount wave can be compensated.

Disclosure of the invention

Advantages of the invention

These Task is performed by a procedure with the characteristics of the independent Claim 1 solved.

Characterized in that the correction value with which the fuel quantity determining signal is corrected, is formed from the sum of a base correction value adapted to an operating point of the internal combustion engine, a mechanical influences of injector-specific correction value taking into account at least one injector and an injector-individual correction value determined during operation of the internal combustion engine , can be compensated in a very advantageous manner, even errors caused by the above-mentioned residual quantity waves. As a result, a residual quantity deviation in multiple injections can be further reduced in time following an optionally used pressure wave correction method. An essential idea of the method is a grouping of residual quantity waves to describe the relationship between higher-frequency pressure oscillations, mechanical parameters and the injection quantity error during operation. As a result of this method, in addition to the reduction of higher-frequency oscillations, it is also possible to provide an intervention possibility for mechanical parameters, for example based on information about setting parameters and tolerances and the like. This can also be done in vector-specific and thus also cylinder-selective corrections are made. This is particularly and especially at short intervals between two partial injections of great advantage. Finally, a correction during operation of the internal combustion engine and thus a correction of injection quantity errors due to aging phenomena is possible.

By those listed in the dependent claims Measures are advantageous developments and improvements of the method specified in the independent claim possible.

So provides an advantageous embodiment of the method, the base correction value to take a previously determined reference map and with a the adjustment to the operating point characterizing scale factor to multiply. In the basic map lie reference curves, which determines when grouping in pressure stages for each pressure and were filed. From this map, a base correction value is calculated, which is then multiplied by the scaling factor. The scaling factor is preferably also a previously determined scaling map taken. This scale map contains factors for optimized adaptation of the reference curve to the respective measuring point, that is to the respective operating point.

alternative can to reduce the memory requirements of the maps of Base correction value including information about the scaling factor through a model-based approach, i. H. a suitable model based on several superimposed exponential damped sinusoids and a function term for Description of non-hydraulic vibration components can be determined.

Either the reference map as well as the scaling map or the model-based Approaches are determined on the basis of at least the following variables: the amount injected at a first injection, the rail pressure, the time difference between the first and the second injection and the injection amount of the post-injection.

Of the taking into account mechanical influences of the injector Injektorspezifische correction value is advantageously in the Production of the injector depending on operating point determined and in a data carrier assigned to the injector saved. This injector-specific correction value is taken into account for example, mechanical parameters.

hereby may be injector specific to the prior art and thus also cylinder-selective corrections are made. This is especially at short intervals between two partial injections helpful. The disk on which the injector-specific Correction values are stored, for example, the injector assigned data matrix code, such as when making a so-called injector quantity matching method (IMA) Installation of the injector is "communicated" to the engine control unit.

at Another very advantageous embodiment of the method is provided to "drive" individual injection pattern of the internal combustion engine and teach in. These values form the injector-specific correction values. Through them is a correction also over the lifetime the injectors possible.

The Method can be implemented as a computer program and on a Computer program product, for example on a machine-readable data carrier be saved. That way it can work in existing control devices be "read" for internal combustion engines and as it were "upgraded".

Brief description of the drawings

embodiments The invention is illustrated in the drawings and in the following Description explained in more detail.

It demonstrate:

1 a schematic representation of a known from the prior art common rail injection system;

2a schematically a block diagram for explaining an embodiment of the method according to the invention;

2 B schematically a block diagram for explaining a further embodiment of the method according to the invention and

3 schematically the injected amount over the time difference of two adjacent injections each with and without application of the method according to the invention.

embodiments the invention

In the 1 are components required for understanding the invention of a high-pressure-based fuel injection system using the example of a common rail system shown. With 100 is a fuel tank called. The fuel reservoir tank 100 is to pump fuel through a first filter 105 as well as a prefeed pump 110 with a second filter 115 in connection. From the second filter 115 out gets the power material via a line to a high-pressure pump 125 , The connection between the second filter 115 and the high pressure pump 125 also has a low pressure limiting valve 145 having connecting line with the reservoir 100 in connection. The high pressure pump 125 stands with a rail 130 in connection. The rail 130 is also referred to as (high pressure) memory and in turn is on fuel lines with different injectors 131 in pressure-conductive connection. Via a pressure relief valve 135 is the rail 130 with the fuel tank 100 connectable. The pressure relief valve 135 is by means of a coil 136 controllable.

The pipes between the outlet of the high-pressure pump 125 and the inlet of the pressure relief valve 135 are referred to as "high pressure area". In this area, the fuel is under high pressure. The pressure in the high pressure area is measured by means of a sensor 140 detected. The pipe between the fuel tank 100 and the high pressure pump 125 are referred to as "low pressure area".

A controller 160 acts on the high pressure pump 125 with a drive signal AP, the injectors 131 each with a drive signal A and / or the pressure relief valve 135 with a drive signal AV. The control 160 processes different signals from different sensors 165 characterizing the operating state of the internal combustion engine (not shown) and / or of the motor vehicle driven by this internal combustion engine. Such an operating state is, for example, the rotational speed N of the internal combustion engine.

This in 1 shown injection system works as follows: The fuel, which is in the fuel tank 100 is, by means of the feed pump 110 through the first filter 105 and the second filter 115 promoted through. If the pressure in the low pressure range rises to impermissibly high values, the low pressure limiting valve opens 145 and gives the connection between the output of the feed pump 110 and the reservoir 100 free. The high pressure pump 125 promotes the amount of fuel Q1 from the low pressure area to the high pressure area. The high pressure pump 125 builds in the rail 130 a very high pressure. Usually, maximum pressure values of about 30 to 100 bar are achieved in injection systems for spark-ignited internal combustion engines and maximum pressure values of about 1000 to 2000 bar in the case of self-igniting internal combustion engines (diesel internal combustion engines). By means of injectors 131 The fuel can thus be metered under high pressure to the individual combustion chambers (cylinders) of the internal combustion engine.

By means of the sensor 140 the pressure P in the rail or in the entire high pressure range is detected. By means of the controllable high-pressure pump 125 and / or the pressure relief valve 135 the pressure is regulated in the high pressure area.

As pre-feed pump 110 Usually electric fuel pumps are used. For higher flow rates, which are particularly required for commercial vehicles, also several parallel feed pumps can be used.

injections in such internal combustion engines are during a Metering cycle divided into several partial injections. Usually are at least one or two pilot injections, one main injection and at least one post-injection provided. The distances the individual partial injections can be variably applied, they can depending on the system fixed or dependent be specified by the operating condition of the internal combustion engine.

Each injection in such multiple injections triggers vibrations in the line system of the common rail high pressure circuit, so-called pressure waves. These pressure waves systematically affect the amounts of subsequent injections. The over the time interval of individual partial injections wavy changed injection quantity is schematically in 3 based on the curve 310 shown. Such a disturbance, referred to below as "quantity wave" for short, is compensated by methods known per se for pressure wave correction in a control device of the internal combustion engine, in particular in the engine control unit. For reasons of principle, however, such a compensation achieves only a finite quality of correction. In addition to higher-frequency vibrations, the volume waves are also superimposed by mechanical influences, for example by an armature bladder in common-rail injectors, caused disturbances. These can not be compensated for principle reasons by per se known pressure wave correction method and remain as hereinafter referred to as "residual amount wave" left. Accordingly, there remains a deviation of the actual amount from the desired value in the form of these residual quantity waves. The basic idea of the invention is now also to compensate for these residual quantity waves and thus to further improve the measuring accuracy.

In order to compensate for such residual quantity waves also and so further improve the Zugmessgenauigkeit in multiple injections is in a first embodiment of the invention and in conjunction with 2a schematically explained method first in a first step 210 who called baseline correction who can, from the input quantities injected amount qRoh, rail pressure pRail, time difference between two adjacent injections t _diff and influenced subsequent partial injection quantity qE2 made a base correction to the effect that initially from the in a basic map 211 stored reference curves, which are previously determined in a grouping in pressure stages for each pressure, in particular calculated and stored, a base correction value is determined or calculated, which is then in one step 215 with a scaling factor corresponding to a scaling map 214 taken is multiplied. The scaling map 214 contains factors for the optimized adaptation of the reference curve of the basic map 211 to the respective operating point of the internal combustion engine, ie to the current measuring point.

An alternative embodiment of the method will be described below in connection with 2 B are described in which the same elements are denoted by the same reference numerals as in 2a , to the description of which reference is made. Alternatively to the above-described determination of the base correction by means of the basic map 211 and scaling using the scaling map 214 The basic correction can also be done by a mathematical model, in 2 B through a function 212 : q = f (x) based on several superimposed exponentially damped sinusoids and a function term describing the non-hydraulic oscillations. This mathematical model describes the basic map 211 , the scaling map 214 and the step 215 analytically.

Then follow in the steps 223 . 233 two additions of variables explained below qm and qL to the correction value thus determined. A first addition 223 takes into account the superimposed injector-specific mechanical component. This proportion of sqm will be in one step 220 determined and based on injector-specific parameters, for example, in a data matrix code associated with the injector 221 are stored and informed when injector installation an engine control unit. "Shared" means as much as consideration of the corresponding data.

Another addition 233 considers learning points during operation of the internal combustion engine. These values are also injector-individual, they are determined, for example, by "approaching" learning points during operation of the internal combustion engine. The correction value qL becomes in one step 230 calculated. The advantage of this consideration is that a better adaptation between measurement and driving operation can be realized thereby and that, in particular, a consideration during operation of the internal combustion engine, ie over its lifetime, can thereby be realized. This makes it possible to compensate for errors caused by aging effects, for example, of the injectors.

The result of this calculation is a corrected injection quantity q _corr . In 3 is schematically based on the curve 320 an example of a correction of a signal generated in this way 310 shown. As can be seen from this figure, the residual quantity wave is largely compensated, the positive and negative quantity deviations are significantly reduced.

The The method described above can be used, for example, as a computer program on a computing device, in particular a control device of a Internal combustion engine to be implemented and run there. The program code can be stored on a machine-readable carrier, which the controller can read. That's the way it is Method also to some extent "retrofittable" with existing control units.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 1303693 B1 [0004]
• - DE 19712143 A1 [0005]

Claims (9)

Method for controlling an internal combustion engine, wherein the fuel injection into at least a first and a second partial injection of at least one injector ( 131 ) and wherein a signal determining the fuel quantity can be corrected with a correction value, characterized in that the correction value is formed from the sum of a base correction value adapted to an operating point of the internal combustion engine, a mechanical influence of the at least one injector ( 131 ) and an injector-specific correction value (qL) determined during operation of the internal combustion engine. Method according to Claim 1, characterized in that the base correction value corresponds to a previously determined reference characteristic map ( 211 ) and multiplied by a scaling factor characterizing the adjustment to the operating point. Method according to Claim 2, characterized in that the scaling factor corresponds to a previously determined scaling map ( 214 ) is taken. Method according to claim 2 or 3, characterized in that the reference characteristic field ( 211 ) and the scaling map ( 214 ) represent the relationship between the amount (qRoh) injected at a first injection, the rail pressure (pRail), the time difference between the first and second injections (t _diff ) and the injection amount of the post injection (qE2). Method according to Claim 1, characterized in that the basic correction value is determined by a mathematical model ( 212 ) on the basis of a plurality of specifiable, superimposed and exponentially damped sinusoids and a vorgeb ble, the non-hydraulic vibration components descriptive function term is determined. A method according to claim 1, characterized in that the mechanical influences of the injector ( 131 Injektorspezifische correction value (qm) in the manufacture of the injector ( 131 ) is determined depending on the operating point and in a the injector ( 131 ) associated volumes ( 221 ) is stored. Method according to claim 1, characterized in that that determined during operation of the internal combustion engine Injector-individual correction value (qL) through targeted start-up determined by specifiable operating points of the internal combustion engine and in a memory of a control device of the internal combustion engine, in particular a control device is stored. Computer program that shows all the steps of a procedure according to one of claims 1 to 7 executes when it on a computing device, in particular a control unit an internal combustion engine, expires. Computer program product with program code based on a machine-readable carrier is stored for execution The method according to any one of claims 1 to 7, when said Program on a computer or a control unit of the internal combustion engine is performed.