DE102006033459B3 - Operating method for IC engines with fuel injection valves comprises determining point at which pressure fluctuations in fuel appear and calculating period from start of injection, correction being used to derive corrected injection time - Google Patents

Abstract

The operating method for IC engines with fuel injection valves (15) fed with fuel from a storage tank (29) supplied by a pump comprises determining a base value for the injection time. The point at which pressure fluctuations in the fuel first appear is determined and the period between the start point of injection and this point is calculated. A fluctuation correction is calculated from this period and a corrected injection time is derived from it. An independent claim is included for a mechanism for carrying out the method.

Description

The The invention relates to a method and an apparatus for operating an internal combustion engine with at least one injection valve for Metering of fuel and a fuel storage, the over a Fuel pump is fed and the fuel injectors with fuel provided. The need to meet more stringent legal Regulations regarding permissible Pollutant emissions from motor vehicles, in which internal combustion engines arranged, it makes the pollutant emissions necessary in the operation of the internal combustion engine as low as possible hold. A contribution to this can be made if the fuel is precisely metered by the injectors.

Increasingly internal combustion engines are used, in which the injection valves meter the fuel directly into the respective combustion chamber and at where a common fuel storage, also called common rail is designated for the injection valves is provided in which during operation of the internal combustion engine the fuel is kept under a very high pressure. at Diesel internal combustion engine amounts the pressure, for example, between 150 and 2000 bar, in gasoline internal combustion engines is he typically between 50 and 200 bar.

Out DE 103 16 811 A1 For example, there is known a method for correcting the injection period of injections due to the pressure fluctuations of previous injections. In this case, the injection period is determined from a map value and a correction value. The map value is read from a map depending on the fuel pressure and depending on the fuel mass to be injected. The correction value is calculated as a function of the time interval between the following injection and at least one last injection. The correction value has a vibration factor and a damping factor. The correction value is determined, for example, in the form of a sum of exponentially decreasing sine or cosine functions. In this case, an amplitude depends on the fuel pressure and on the injection duration of the last injection. A phase angle of the sine function is determined depending on the fuel pressure and injection duration of the last injection and the following injection. Moreover, in the calculation of the sine function, a time difference directly enters, which corresponds to the time difference between the end of injection of the last injection and the start of injection of the following injection.

From the EP 1 064 457 B1 For example, there is known a method for determining the injection time in a direct injection internal combustion engine having a high pressure accumulator containing fuel in communication with an injector. An occurring between two individual injections pressure fluctuations in the injector and in the line between high-pressure accumulator and injector is taken into account in determining the injection time for the next process. For this purpose, an estimation equation for the pressure fluctuations is taken into account, which represents a damped sinusoidal oscillation. The argument of the sine function is determined directly depending on the current time and the start time of the oscillation.

From the DE 102 17 592 A1 For example, an injector for injecting fuel is known, which has a compensation device in order to compensate for a pressure wave generated during the injection.

Out the publication Diesel Engine Management./Robert Bosch GmbH - 4th edition, Wiesbaden: Vieweg, 2004, ISBN 3-528-23873-9, Page 372, it is known that injections in common rail systems Trigger pressure waves in the lines between the nozzle and the rail. Further it is known from this that the deviations of later injections are dependent from the previously injected quantities and the time interval of the injections, the rail pressure and the fuel temperature.

From the DE 100 18 050 A1 It is known to calculate an opening duration of an injection valve taking into account a typical for the fuel metering periodic pulsation pattern of the accumulator pressure. This is done in relation to a delivery of fuel into the accumulator by a high-pressure pump. If an upcoming injection is the first injection after a delivery, a functional block will determine an upper value of the accumulator pressure using a compression equation.

From the DE 199 37 148 A1 It is known to correct the injection amount of the subsequent fuel injection with a fluctuation coefficient, which is determined as a function of an intended time interval since the previous partial injection and a pressure oscillation frequency in the pressure line.

From the DE 103 28 789 A1 It is known to split a fuel metering into a first partial injection and at least a second partial injection and to correct a control signal determining the fuel quantity to be injected by means of the at least two injection elements as a function of a pressure wave influencing of the at least two partial injections. For this purpose, it is provided that a collective pressure wave correction is carried out for the at least two injection elements and a collective correction function is determined. It is further provided that individual characteristics of the at least two injection elements are detected and that the collective correction function is amplitude-modulated by means of detected individual characteristics of the at least two injection elements.

From the DE 10 2005 001 428 A1 It is known to use a neural network to correct the fuel quantity of a second partial injection, wherein the input quantity which defines the time difference of the successive injections is dispensed with.

From the DE 103 02 806 A1 It is known to apply the method of Fourier analysis to analyze a resulting fuel pressure oscillations in an injection system. Depending on the Fourier analysis, a correction value for an intended actuation time, an intended actuation duration and / or the injection volume is then calculated.

The The object of the invention is a method and a device to provide for operating an internal combustion engine, the or which is simply a precise one Dosing of fuel allows.

The Task is solved by the characteristics of the independent Claims. Advantageous embodiments of the invention are characterized in the subclaims.

The Invention is characterized by a method and a corresponding Device for operating an internal combustion engine with at least one Injector for metering fuel, a fuel storage, the over a fuel pump is fed and the at least one injection valve fueled. A basic value of an injection period for the injection valve for metering Fuel is determined. This is preferably done depending on at least one operating variable of the internal combustion engine. A vibration excitation reference point of a fuel pressure vibration with respect to Injection valve becomes dependent determined by a previous metering of fuel. there it may be a previous metering of fuel of the same Injector or in the case of several injectors also to to act that of another injector. The vibration excitation reference point thus has a fixed relationship to the previous metering of fuel, such as a beginning or an end of appropriate metering of the fuel.

One Period reference point of the fuel pressure vibration is relative to a Beginning value of the base value of the injection period, starting from the vibration excitation reference point determined. The period reference point thus characterizes the respective position of the initial value of the underlying the duration of injection within the fuel pressure oscillation and that the respective oscillation period, within which the initial value the basic value of the injection duration with respect to the vibration excitation reference point located. Dependent from the period reference point and the base value becomes a vibration correction value determined. Dependent from the base value and the vibration correction value becomes an injection value the injection duration determined.

On this way is a particularly simple and extremely precise consideration of fuel pressure oscillations, caused by the metering of fuel allows. About that In addition, the course of the fuel pressure oscillations, for example, due to simulations or measurements on one Engine test stand, very precise be simulated and at the same time a low computational effort in terms of determining the vibration correction value based on the determining of the period reference point are guaranteed. All Points or durations can in this context and also with regard to all beneficial Embodiments of the invention, either time-related or angle-related, so be particularly crankshaft angle related.

On This way, therefore, in particular, for example, in several Metering of fuel into the respective combustion chamber of each cylinder per working cycle a particularly high accuracy in the dosage simply guaranteed become and so a high reproducibility of working play to working play and also ensures absolute accuracy of the metered metering of fuel become. In particular, you can so also very low fuel masses during an injection metered be, for example, in the order of magnitude of a milligram. It can thus pressure waves in the fuel reservoir and towards the injectors sufficiently precise be compensated.

According to an advantageous embodiment of the invention, the period reference time is determined depending on at least one period change value based on a respective period of the fuel pressure oscillation. This particularly makes it possible to suitably take into account a period of the fuel pressure vibration changing with the number of periods in a given manner. This has proven to be particularly effective in practice with regard to a particularly accurate mapping of the real behavior of the fuel pressure oscillation. That way, that way very easy and precise at the same time a very accurate metering of fuel can be ensured.

According to one further advantageous embodiment of the invention correlates the Vibration correction value to an integral of the oscillation over the Injection period starting with the period reference point. To this Way is a very precise and at the same time easy to consider the pressure fluctuations with respect to the base value of the injection duration possible.

In In this context, it is particularly advantageous if the vibration correction value correlates to an integral of the oscillation beginning over the duration of injection with the Perio denbezugspunkt and standardized to the Underlying. In this way, such an even more precise and easier and also ensures very simple correction and so a very precise metering of fuel.

According to one Another advantageous embodiment of the invention is an initial amplitude correction value dependent from the metered fuel mass of the previous metering of Fuel determined. In this way can also be a very precise metering be made of fuel and so be used to the knowledge that the Initial amplitude of the fuel pressure oscillation decisively depends from the metered fuel mass of the previous metering of fuel.

According to one Another advantageous embodiment of the invention is a vibration damping value dependent from the vibration excitation reference point and the initial value of the base value the injection duration and / or the fuel pressure determined. Also in this way can be an even more precise metering of fuel taking advantage of the knowledge that such a dampening excited pressure oscillation subsides.

embodiments The invention are explained in more detail below with reference to the schematic drawings.

It demonstrate:

1 an internal combustion engine with a control device,

2 a block diagram of a program that is executed in the control device,

3 a first flow chart of another program that is executed in the control device,

4 a second flowchart of another program that is executed in the control device and

5 Fuel pressure gradients.

elements same construction or function are cross-figurative with the same Reference number marked.

An internal combustion engine ( 1 ) comprises an intake tract 1 an engine block 2 , a cylinder head 3 , an exhaust tract 4 and a feeder for fuel 5 , The cylinder head 3 includes a valvetrain with a gas inlet valve 11 and a gas outlet valve 13 , The drive of the gas inlet valve 11 and the gas outlet valve 13 takes place by means of a camshaft. The cylinder head 3 further comprises an injection valve 15 and optionally a spark plug. In principle, the injection valve 15 also in the intake tract 1 be arranged.

The feeder 5 for fuel includes a fuel tank 20 that is via a first fuel line with a low pressure pump 21 connected is. On the output side is the low-pressure pump 21 towards an inlet of a high-pressure pump 27 operatively connected. The feed 25 is going to a valve 31 guided, which is designed as a 3/2-way valve.

Furthermore, the high pressure pump 27 provided, which is designed as a reciprocating pump and with the valve 31 connected is. Furthermore, with the valve 31 another feed 33 to a fuel storage 29 connected. The high pressure pump 27 thus promotes depending on the switching position of the valve 31 Fuel into the fuel tank 29 in which the fuel is stored under high pressure during operation of the internal combustion engine.

The injectors 15 are with the fuel storage 29 connected. The fuel is so with the injectors 15 over the fuel storage 29 fed.

A disturbance factor in this connection is the formation and propagation of pressure waves in the high-pressure region of the feed device 5 for fuel, ie in the supply line 33 , the fuel storage 29 and to the injectors 15 , The pressure waves are triggered by any form of excitation, such as in particular by metering of fuel through the respective injectors. As a rule, the greater the injected fuel mass, the stronger the excitation. The pressure waves, also referred to as fuel pressure vibration, propagate throughout the high pressure area of the feeder 5 for fuel off. After a short time, for example, after a millisecond, form stand de pressure waves in the high pressure area of the feeder 5 for fuel whose time course by natural frequencies of the high pressure area of the feeder 5 is intended for fuel. The associated natural oscillations often have a vibration node in the energy storage 29 , They spread between the fuel tank 29 and the respective injection valve 15 off and have in the area of the injector 15 often an antinode. The frequency of these vibrations is determined by the dimensions of the connecting lines between the fuel tank 29 and the respective injectors 15 significantly influenced. Thus, in this context, in particular their diameter, length and the Volumi na in the injector prevail. The decay of the vibrations is determined by the damping, which is influenced by the viscosity of the fuel, cross-sectional constrictions in the inlets or lines to the injection valves 15 ,

Typically, the internal combustion engine in addition to the cylinder Z1 also has additional cylinders Z2 to Z4, so for example, six cylinders which, in principle, also a single fuel storage 29 can be assigned. In particular, in the case of multiple meterings of fuel within a working cycle of a cylinder, a separation time T_DLY is therefore the interval between two meterings of fuel, in this case one and the same injection valve 15 so brief that the pressure oscillations caused by the previous metering of fuel have not yet decayed to the extent that they are intended to be metered so far that they would be irrelevant. In particular, in connection with the use of multiple cylinders Z1-Z4, such as six cylinders Z1-Z4, the one single fuel tank 29 are assigned, the separation time periods T_DLY between associated successive metering of fuel in different combustion chambers of different cylinders Z1-Z4 are so low that also corresponding excited pressure oscillations are relevant.

The internal combustion engine is also a control device 37 assigned, the sensors are assigned, which detect different variables and each determine the measured value of the measured variable. Operating variables include not only the measured variables but also variables derived from the measured variables. The control device 37 determined depending on at least one of the operating variables manipulated variables, which are then converted into one or more control signals for controlling the actuators by means of appropriate actuators. The control device 37 may also be referred to as a device for operating the internal combustion engine.

she includes in particular corresponding input / output interfaces, the For example, include A / D converter, and corresponding data or also program memory, which is part of a computing unit can.

The sensors are a pedal position transmitter 41 , which is a pedal position of an accelerator pedal 39 detected, a crankshaft angle sensor 43 , which detects a crankshaft angle, a fuel pressure sensor 47 that is a pressure in the fuel tank 29 detected. Preferably, the detection point of the fuel pressure sensor 47 For example, directly to the fuel storage 29 and thus locally spaced from the injectors 15 , Furthermore, a first temperature sensor 49 provided, which detects a coolant temperature of the internal combustion engine, and a second temperature sensor 51 , which has a fluid temperature T_FU in the fuel reservoir 29 detected.

ever according to embodiment There may be any subset of said sensors or it can also additional Sensors be present.

The actuators are, for example, a throttle valve, the gas inlet and gas outlet valves 11 . 13 , the injection valve 15 , the spark plug or the valve 31 ,

Next explained in detail Cylinder Z1 are in the internal combustion engine usually also additional cylinders Z2 to Z4 present, which then corresponding actuators or sensors are assigned.

To operate the internal combustion engine are programs in the control device 37 stored during operation of the internal combustion engine in the control device 37 be processed.

A program that during the operation of the internal combustion engine in the control device 37 will be described in more detail below with reference to the block diagram of 2 explained. A metered fuel mass MFF (k) of a previous metering of fuel is input to a map MAP_A whose output value is an initial amplitude correction value A. In this case, "k" designates the preceding metering of fuel, that is, for example, that within the current working cycle via the same injection valve 15 one and the same combustion chamber has already been metered, while "k + 1" then refers to a subsequent and immediately following metering of fuel, and preferably during the current cycle. However, depending on the design and application of the program, "k" can also affect the metering of fuel over another refer to injection valve associated with another combustion chamber, and thus "k + 1" and "k" refer to calculations for metering fuel via different injectors.

By the initial amplitude correction value A thus becomes a magnitude of stimulating fuel metering that is relevant on the initial amplitude of the fuel pressure oscillation. The map MAP_A is preferably determined empirically.

Further a map MAP_B is preferably provided on the input side with the detected fuel pressure FUP and the separation time T_DLY is charged. On the output side depends on the map MAP_B a vibration damping correction value B available then set in block B1 with the initial amplitude correction value A multiplicatively linked is and then a block B2 is supplied. By means of the map MAP_B and the derived therefrom vibration damping correction value B can thus a damping the pressure oscillation over takes into account a progressive separation time T_DLY become. About that In addition, a pressure dependency of the damping can be considered as well become.

The determination of the separation time period T_DLY is described in more detail with reference to the flowchart of FIG 3 explained. The program is started in a step S1, and in each case preferably in correspondingly small time intervals, in order to ensure that a current and newly determined separation time period T_DLY is present whenever possible for each determination of the injection duration TI.

In a step S2, a vibration excitation reference point T_REF of the fuel pressure vibration with respect to each injection valve becomes 15 determined and depending on a previous metering of fuel. It may be in the previous metering of fuel, as already explained above, to a previous metering of fuel via the same injection valve 15 act or even via a previous metering of fuel through another injection valve 15 act. The oscillation excitation reference time T_REF can thus correspond, for example, to a start o of one end of the previous metering of fuel or of another value which is correspondingly firmly connected with the previous metering of fuel.

In In step S4, the separation period T_DLY is then used as the difference a start value SOI of a basic value TI_B (k + 1) of an injection period the fuel mass to be metered and the vibration excitation reference point T_REF determined. The base value TI_B (k + 1) of an injection duration A fuel mass to be metered is preferably at least dependent on an operating variable of the internal combustion engine determined in a known manner.

Subsequently, will the program ends in a step S6.

In a block B3 becomes a basic period T_PER of the fuel pressure oscillation dependent from the fuel temperature T_FU and the detected fuel pressure FUP determined and preferably over another map. In this case, alternatively, the determination of the basic period T_PER can also dependent of either the detected fuel pressure FUP or the fuel temperature T_FU done. In this way, so the different speed of sound considered in particular in the propagation of the fuel pressure oscillation suitable become.

In a block B5 ( 2 ), a period reference point T_PER_REF of the fuel pressure oscillation is determined depending on the basic period T_PER and the separation period T_DLY. For this purpose, another program is started, which is described below on the basis of 4 is explained in more detail. The program is started in a step S8 in which variables are initialized if necessary.

In a step S10, an intermediate time period T_TEMP, which is essentially only an arithmetic variable for the execution of the program in accordance with the 4 represents the separation period T_DLY assigned.

following In a step S12, a "while" loop is processed, the "while" loop being so go through as long as the intermediate time T_TEMP is greater as a product of the basic period T_PER with a period change value F_i with respect to the respective period of the fuel pressure oscillation. In this case, "i" represents a period counter and thus the respective period of the fuel pressure oscillation. The period change value F_i can for each period of the fuel pressure shrinkage, for example, fixed and if necessary, be specified differently, but he can preferably also dependent predetermined by a suitable operating size be.

In this way, in particular very good influence of delivery strokes of the high-pressure pump 27 be considered very precisely. Furthermore, by the period change value F_i also a dynamics of a possibly existing pressure control valve can be taken into account.

Of the Period variation value F_i can thus for Each period of the fuel pressure oscillation different values accept. Within the "while" loop is the Intermediate duration T_TEMP respectively reduced by the basic period duration T_PER multiplied by the current period change value F_i and the period counter i increments by one until the condition of the while loop stops Fulfills is.

In a step S14 is then a period reference point T_PER_REF the fuel pressure oscillation assigned the interim period T_TEMP. Subsequently the program is ended in a step S16.

In a block B7 ( 2 ), the quotient of the period reference point T_PER_REF of the fuel pressure oscillation and the base period duration T_PER multiplied by the period change value F_i is determined, which is then the input variable into a characteristic MAP_C. In this way, a relative position of the period reference point T_PER_REF can thus be determined within the period of the fuel pressure oscillation which is assigned to the starting time SOI of the base value of the injection duration of the fuel quantity to be metered.

a Block B9 becomes the base value TI_B (k + 1) of the duration of the injection supplied to be metered fuel mass. In block B9, the Ratio of the basic period T_PER multiplied by the period change value F_i and the base value TI_B (k + 1) of the injection duration determined and also as an input to the map MAP_C used. The output value of the map MAP_C is on Vibration correction value C. Preferably, the vibration correction value corresponds C by appropriate Bedatung the map MAP_C an integral the fuel vibration over the base value TI_B of the injection duration starting with the period reference point T_PER_REF. About that In addition, this integral is preferably normalized to the underlying TI_B (k + 1) of injection duration.

In a block B2, the product of the vibration correction value C and the product of the initial amplitude correction value A and the vibration damping correction value B is then determined, to which a value one is added in a block B1 and thus results in a total correction value FAC_TI. The basic value TI_B (k + 1) of the injection duration is then corrected by means of the total correction value FAC_TI and thus results in the injection value TI, with which then the respective injection valve 15 is controlled accordingly.

By the procedure according to blocks B5 to B7 can thus correct any periodic oscillations and the course of the vibration during The respective period can be adjusted accordingly. It can be like this also phase shifts over taken into account for several periods be corrected and preferably also speed influences in single injections become.

Based on 5 are exemplary curves over the time t represented by typical fuel pressure oscillations plotted against an actual fuel pressure p.

Claims (7)

Method for operating an internal combustion engine with at least one injection valve ( 15 ) for metering fuel, a fuel storage ( 29 ), which is fed by a fuel pump and the at least one injection valve ( 15 ), in which - a base value (TI_B) of an injection duration for the injection valve ( 15 ) is determined for fuel to be metered, - a vibration excitation reference point (T_REF) of a fuel pressure vibration with respect to the injection valve ( 15 ) is determined dependent on a previous metering of fuel, - a period reference point (T_PER_REF) of the fuel pressure oscillation with respect to a starting value (SOI) of the injection duration is determined as a function of the oscillation excitation reference point (T_REF), the period reference point (T_PER_REF) determining the respective position of the initial value (SOI ) of the basic value (TI_B) of the injection duration within the fuel pressure oscillation, namely the respective oscillation period, within which the initial value (SOI) of the basic value (TI_B) of the injection duration is relative to the oscillation excitation reference point (T_REF), - dependent on the period reference point (T_PER_REF) and the base value (TI_B) a vibration correction value (C) is determined and - depending on the base value (TI_B) and the vibration correction value (C) an injection value (TI) of the injection duration is determined. The method of claim 1, wherein the period reference time (T_PER_REF) of at least one period change value (F_i) with respect to a respective period of the fuel pressure vibration is determined. Method according to one of the preceding claims, in the vibration correction value (C) correlates to an integral the fuel pressure oscillation over the injection duration starting with the period reference point (T_PER_REF). Method according to one of the preceding claims, in which the vibration correction value (C) is correlated to an integral of the fuel pressure oscillation over the duration of injection starting from the period reference point (T_PER_REF) and normalized to the base value (TI_B) of the injection duration. Method according to one of the preceding claims, in an initial amplitude correction value (A) depending on the metered fuel mass (MFF) of the previous metering of fuel is determined. Method according to one of the preceding claims, in a vibration damping correction value (B) dependent from the vibration excitation reference point (T_REF) and the initial value (SOI) the base value (TI_B) of the injection duration and / or the fuel pressure (FBD) is determined. Device for operating an internal combustion engine with at least one injection valve ( 15 ) for metering fuel, a fuel storage ( 29 ), which is fed by a fuel pump and the at least one injection valve ( 15 ), wherein the device is designed to - a base value (TI_B) of an injection period for the injection valve ( 15 ) for fuel to be metered, - a vibration excitation reference point (T_REF) of a fuel pressure oscillation with respect to the injection valve ( 15 ) to determine a period reference point (T_PER_REF) of the fuel pressure oscillation with respect to an initial value (SOI) of the injection duration as a function of the oscillation excitation reference point (T_REF), the period reference point (T_PER_REF) determining the respective position of the initial value (SOI ) of the basic value (TI_B) of the injection duration within the fuel pressure oscillation, namely the respective oscillation period, within which the initial value (SOI) of the basic value (TI_B) of the injection duration is relative to the oscillation excitation reference point (T_REF), - dependent on the period reference point (T_PER_REF) and the base value (TI_B) to determine a vibration correction value (C) and - depending on the base value (TI_B) and the vibration correction value (C) to determine an injection value (TI) of the injection duration.