DE102012208456A1 - Method for correcting a quantity replacement signal - Google Patents

Abstract

The invention relates to a method for correcting a quantity replacement signal (ZFC), which displays an injection quantity burned in a cylinder of an internal combustion engine (100), wherein a quantity replacement signal (ZFC) is determined at a second, later time and the determined quantity replacement signal (ZFC) is based on at least an internal combustion engine parameter (x1, x2, x3) and a relationship (200) determined at a first, earlier time between the quantity replacement signal (ZFC) and the at least one internal combustion engine parameter (x1, x2, x3).

Description

The present invention relates to a method for correcting a quantity replacement signal as well as a computing unit for its implementation.

State of the art

In modern fuel injection systems of the type in question here, for example in common-rail diesel systems, partial injections which take place before or after the actual main injection are realized with relatively small fuel quantities in order to improve the mixture preparation. The mentioned main injections are usually calculated on the basis of a torque request of the driver. The injection quantities of said partial injections have to be as low as possible in order to avoid emission disadvantages. On the other hand, the injection quantities must be large enough so that even taking into account all sources of tolerance always the minimum amount necessary for the combustion process is discontinued. Such improved mixture preparation allows reduced exhaust emissions and reduced combustion noise.

The small amounts of fuel in these partial injections require a precise metering of the respective injection quantity. Falls a partial injection even completely away, for example, because a present injection component in common rail injection systems, a so-called. Injector, due to conventional tolerances at an underlying drive signal is not yet injected, this has a significant impact on the operation of the engine, which is, for example . Expressed by increased noise during combustion.

The metering of said small amounts is carried out on the basis of a zero quantity calibration, which, for example, in the DE 199 45 618 A1 is described. In the overrun mode of the internal combustion engine, a single injection valve (injector) is actuated and the actuation duration is increased stepwise until a change in a signal occurs at a minimum actuation time, for example a torque increase measurable on the internal combustion engine. The control duration then present corresponds to an operating state in which the injection for the respective combustion chamber (cylinder) of the internal combustion engine is just starting. This procedure is performed cyclically on all injectors and cylinders of the internal combustion engine accordingly. The control data obtained in this case are preferably stored in a characteristic map which is used in a subsequent control of the injectors in the context of an injection quantity correction.

In the DE 10 2008 002 482 A1 an embodiment of the zero quantity correction is described in which a plurality of measuring points including injection quantity, driving time and rail pressure approached and a relationship between the injection quantity and the driving time and the rail pressure mathematically from the measuring points is determined, for example. By linear or quadratic regression. The injection quantity can be obtained from a signal of the so-called quantity compensation control, as in DE 195 27 218 A1 described, since there is a linear relationship between this signal and the injection quantity in the relevant area here.

It is desirable to further improve injection quantity correction, especially for very small quantities.

Disclosure of the invention

According to the invention, a method for correcting a quantity replacement signal with the features of patent claim 1 is proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

Advantages of the invention

In the context of the invention, a correction and thus an increase in the accuracy of, for example, determined by a Laufruheregelung upper cylinder equalization quantity replacement signal. For the correction, at least one internal combustion engine parameter is taken into account, for which in particular an influence on the combustion of very small amounts (in particular in the range of 0.5-3 mm ³ ) has been determined. In this sense, the at least one internal combustion engine parameter is an internal combustion engine parameter influencing the combustion.

It has been shown that in overrun the volume replacement signal (especially in modern diesel engines with reduced compression, which makes the combustion difficult) not only of rail pressure and driving time, but also of other factors, such as prevailing in the engine pressures (boost pressure, ...) and temperatures (engine temperature, exhaust gas temperature, intake air temperature, ...). This is mainly because the amount of replacement signal is sensitive only to actually burned fuel, so that in cases where due to a changed engine parameter does not burn the entire amount of fuel injected, the determination of an actual injection amount from the quantity replacement signal is incorrect. Also effects of internal combustion engine parameters on the injection process itself, for example. Via a Shape change of the injector, play a role. The invention helps to compensate for disturbing environmental influences on the volume replacement signal. As a result, an increase in accuracy can be achieved by reducing the signal scattering, in particular under unfavorable environmental conditions such as altitude, cold, etc.

The set compensation signal corrected in the context of the invention can be used particularly advantageously for zero-quantity calibration. For example. results in the zero quantity calibration in overrun operation from test injections on the injector to be calibrated excitation of the drive train. From this, the speed signal evaluation determines the amplitude of the oscillation as a quantity replacement signal, which is regarded here as a raw signal. The quantity replacement raw signal is now corrected in the context of the invention, first taking into account the at least one internal combustion engine parameter, before it is used to determine the zero quantity. This increases the robustness of the zero-quantity correction relative to the engine parameter. As a result, injection quantity correction can be improved, especially for very small quantities, because a more accurate quantity replacement signal is taken into account.

The correction of the quantity replacement signal uses a relationship determined at a first, earlier point in time, in particular on a test bench at the manufacturer. There are (advantageously at fixed driving time and fixed rail pressure) determined numerous set value signal values for different engine parameters. The relationship can then be determined, for example, by regression. Depending on the number of engine parameters considered, a one-dimensional or multidimensional regression is performed. It is also possible to perform a Bayesian regression.

In a simple embodiment, a linear dependence is required. However, this approximation is not always valid. Therefore, a polynomial approach of arbitrary order or a logarithmic approach of arbitrary order can be chosen. This allows non-linear effects to be taken into account. A dependency can also be piecemeal from the mentioned.

In order to take better account of the deviation from a non-linearity, the at least one internal combustion engine parameter and / or the output value (in particular the correction factor) of the relationship can each be limited to a maximum value and / or minimum value.

In an alternatively preferred embodiment, it is possible to determine from a measured (ie uncorrected) quantity replacement signal ZFC an activation duration AD _theo to be expected for a reference _injector . The determination of the theoretical actuation duration AD _theo can preferably be based on a functional relationship f of the form AD _theo = f (ZFC, x _i , p _R ), where x _i , which is at least one internal combustion engine parameter and p _{R is} the rail pressure. In this case, preferably a reference injector is operated with different activation periods, internal combustion engine parameters and rail pressures and the resulting quantity replacement signal is detected. The relationship can be determined in a map or deposited or by regression, as described above. A reference injector is in particular an injector to which the control of the internal combustion engine is designed uncorrected. This relationship is determined in particular at a test bench.

By comparing this stored, theoretical actuation duration with the actuation time, which is actually necessary in the overrun operation on the special injector in order to obtain the same set substitute signal, a deviation can be determined, in particular a time difference for the actuation period. The time difference can be stored as a learning value and used in fired operation for the correction of injection times (known in the prior art). For example. the respective correction is added to the nominal injection time. The time difference can be stored using conventional smoothing / averaging methods, such as PT1 filter, moving average, ..., smoothed and non-volatile stored.

An arithmetic unit according to the invention, e.g. a control device of a motor vehicle is, in particular programmatically, configured to perform a method according to the invention.

The implementation of the method in the form of software is also advantageous, since this causes particularly low costs, in particular if an executing control device is still used for further tasks and therefore exists anyway. Suitable data carriers for providing the computer program are, in particular, floppy disks, hard disks, flash memories, EEPROMs, CD-ROMs, DVDs and the like. It is also possible to download a program via computer networks (Internet, intranet, etc.).

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically by means of exemplary embodiments in the drawing and will be described in detail below with reference to the drawing.

Brief description of the drawings

1 shows schematically a block diagram of an embodiment of the invention.

2 shows a diagram of a relationship between the quantity replacement signal and a boost pressure as internal combustion engine parameters.

Embodiment (s) of the invention

In 1 a preferred embodiment of the invention is shown schematically with reference to a block diagram. An internal combustion engine, in particular a diesel internal combustion engine is, with 100 designated. The internal combustion engine 100 has a crankshaft 101 on, for example, a toothed or segmented wheel 102 is arranged. The gear 102 is from a sensor 110 sampled, whose measurement signal an evaluation 120 is supplied. The measuring signal corresponds to a time-dependent speed signal. The evaluation unit processes the measurement signal and generates therefrom a cylinder-specific signal ZFC which indicates the amount of fuel burned in the respective cylinder. This signal can therefore be used as a so-called quantity replacement signal and is referred to below as the ZFC signal ZFC. The generation of the ZFC signal has long been known and, for example, in the DE 195 27 218 A1 which is referred to for further details.

The ZFC signal ZFC can be used for a zero-quantity correction and becomes a block for it 150 added, in which a zero-quantity correction, for example according to DE 199 45 618 A1 or DE 10 2008 002 482 A1 can be implemented.

In the context of the invention, these methods, which are known per se, are developed by carrying out a correction of the ZFC signal which takes into account the influence of one or more engine parameters on the ZFC signal. In accordance with the preferred embodiment described herein, the ZFC signal is multiplied by a correction factor f to produce a corrected ZFC signal ZFC ', which is then used for other methods, such as zero-set correction 150 is used.

For the correction of the ZFC signal is a correction unit 130 provided, to be considered internal combustion engine parameters x ₁ , x ₂ , ... are supplied. In the correction unit 130 For this purpose, a relationship between the internal combustion parameters x ₁ , x ₂ , ... and the correction factor f is stored, which has been determined at an earlier first time, in particular on a test bench at the manufacturer of the internal combustion engine. According to a preferred embodiment, the correction factor is limited to a maximum value and a minimum value, wherein the correction unit 130 instead of larger correction factors, the maximum value is output and the minimum value is output instead of smaller correction factors. Alternatively or additionally, a limitation of the supplied internal combustion engine parameter x ₁ , x ₂ , ... to a maximum value and a minimum value can also be carried out, so that the correction unit 130 instead of larger internal combustion engine parameters, the maximum value and, instead of smaller internal combustion engine parameters, the minimum value is taken into account.

The units 120 . 130 and 150 are for example in a so-called engine control unit 160 implemented.

The relationship is preferably determined on a reference internal combustion engine on the test bench. For this purpose, the reference internal combustion engine is operated in overrun mode and numerous small-quantity injections are carried out with fixed injection duration and fixed injection pressure (eg rail pressure), but with changed engine parameters, whereby the resulting ZFC signal is determined in each case. The resulting ZFC signal is normalized to an ideal ZFC signal ZFC ₀ , which corresponds to a fully burnt injection quantity, so that a factor f = ZFC / ZFC ₀ can be determined, which is a deviation of the ZFC result for certain engine parameters. Describes signals from the ideal ZFC signal. This factor is expediently used for the correction at a second, later point in time, in particular in the field. The factor can show a dependency on the engine parameters f = f (x ₁ , x ₂ , x ₃ , ...). In this way, a relationship between the ZFC signal and the varied engine parameters for a fixed drive duration and a fixed injection pressure can be determined according to ZFC (x ₁ , x ₂ , x ₃ , ...) = f (x ₁ , x ₂ , x ₃ , ...) · ZFC ₀ .

As a connection, according to a preferred embodiment, the correction factor itself is determined and used. The backing is conveniently carried out in the control unit 160 the internal combustion engine, for example. In the form of a map or in the form of a mathematical function. The determination of the function is expediently carried out by regression of the measured values, in particular by multidimensional regression. In this case, a linear relationship, a piecewise linear relationship, a polynomial relationship, an exponential relationship and / or assume a logarithmic relationship.

In 2 is as context 200 the correction factor f is plotted against a varied engine parameter x ₁ , here the charge pressure. It becomes clear that the relationship can be approximated particularly well by linear regression. The measuring points are taken from the measurement of a reference internal combustion engine on a test bench. According to a preferred embodiment, the correction factor is limited to a maximum value f _max and a minimum value f _min .

If the relationship between the correction factor f and the at least one further engine parameter has been determined at the first time, the control unit becomes known 160 the internal combustion engine gedatet so that the relationship in the field, ie at a second, later time, for the correction of the measured ZFC signal can be used.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19945618 A1 [0004, 0024]
• DE 102008002482 A1 [0005, 0024]
• DE 19527218 A1 [0005, 0023]

Claims (13)

Method for correcting a quantity substitute signal (ZFC), which is one in a cylinder of an internal combustion engine ( 100 ), wherein at a second, later time a quantity replacement signal (ZFC) and the determined quantity replacement signal (ZFC) based on at least one internal combustion engine parameter (x ₁ , x ₂ , x ₃ ) and a determined at a first, earlier time relationship ( 200 ) between the set replacement signal (ZFC) and the at least one engine parameter (x ₁ , x ₂ , x ₃ ) is corrected. The method of claim 1, wherein the at least one engine parameter (x ₁ , x ₂ , x ₃ ) is one in the internal combustion engine ( 100 ) is the prevailing temperature or a pressure prevailing in the internal combustion engine. The method of claim 1 or 2, wherein the at least one engine parameter (x ₁ , x ₂ , x ₃ ) is selected from the group comprising a boost pressure, an intake air temperature, a heat integral, an exhaust gas temperature, an engine temperature, a rotational speed, and a fuel temperature , Method according to one of the preceding claims, wherein the quantity replacement signal (ZFC) is determined in the overrun mode. Method according to one of the preceding claims, wherein from the context ( 200 ) a correction value (f) is determined and the set replacement signal (ZFC) is applied to the correction value, in particular multiplicatively or additively. Method according to claim 5, wherein the correction value (f) is limited to a minimum value (f _min ) and / or maximum value (f _max ). Method according to one of the preceding claims, wherein the relationship is determined by regression of measurement points of the set replacement signal for different values of the at least one engine parameter (x ₁ , x ₂ , x ₃ ), wherein each completely or piecewise linear, polynomial, logarithmic or exponential dependence of the set spare signal (ZFC) from the at least one engine parameter (x ₁ , x ₂ , x ₃ ) is used. The method of claim 7, wherein the at least one engine parameter (x ₁ , x ₂ , x ₃ ) is limited to an engine parameter minimum value and / or an engine parameter maximum value. Method according to one of the preceding claims, wherein the corrected quantity replacement signal (ZFC ') is used for zero-quantity calibration. Method according to one of the preceding claims, wherein from the determined quantity replacement signal (ZFC) a theoretical activation duration is determined, which a reference injector requires to obtain the determined quantity replacement signal (ZFC), and determines a difference between the theoretical activation duration and an actual activation duration and for a zero quantity calibration and / or a cylinder equalization is used. Arithmetic unit which is adapted to carry out a method according to one of the preceding claims. Computer program with program code means which cause a computer unit to carry out a method according to one of claims 1 to 10 when executed on the corresponding computer unit. A machine readable storage medium having a computer program stored thereon and having program code means for causing a computing unit to perform a method according to any one of claims 1 to 10 when executed on the computing unit.

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