DE102012200659A1 - Method for correcting an injection quantity in a multiple injection by an injector of an internal combustion engine - Google Patents

Abstract

The invention relates to a method for correcting an injection quantity in a multiple injection, wherein at a second, later time a desired injection quantity of a multiple injection consisting of at least two individual injections each with a specific pause time between the at least two individual injections based on a first, earlier time determined relationship between an actual injection amount and a target injection quantity of a multiple injection for different pause times is corrected so that the resulting from the corrected target injection quantity of the multiple injection actual injection amount corresponds to a desired injection quantity.

Description

The present invention relates to a method for correcting an injection quantity in a multiple injection by an injector of an internal combustion engine and a computing unit for its implementation.

State of the art

In-use injectors (so-called injectors) for injecting fuel into the cylinder or the intake manifold of an internal combustion engine normally have to cover a wide range of quantities. This usually extends from the idle point or a fired overrun mode, whereby a minimum amount is defined, to full load at high speeds, whereby a maximum amount is defined.

Ideally, the injected fuel quantity correlates linearly with the duration of injection (activation duration of the injector). However, a very large linear range means a comparatively high production cost for the injector. This production cost is the higher, the less unwanted deviations from the linearity to be kept especially in the small amount range. Especially in this area, both the deviation from the linearity and the scattering between injectors with each other can be comparatively large, which makes a generally valid and non-injector-individual correction more difficult. This is u.a. because the injectors do not open identically and therefore the opening time deviates more or less from the specified injection duration. The shorter the duration of injection, the more these deviations have an effect. The specimen scatters in the small amount range lead to a poor running smoothness at idle and possibly also to a deterioration in the conversion of the pollutant components.

This behavior is exacerbated in multiple injections, since dynamic effects are important here.

It is therefore desirable to be able to make better use of the small quantity range of injectors for multiple injections.

Disclosure of the invention

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

Advantages of the invention

With the present invention, regardless of the combustion method used - whether port injection or direct injection - possible injector-specific relationships between the actual total injection quantity of a multiple injection and the pause time between the injections of the multiple injection particularly easy to determine (hereinafter also referred to as adaptation) and for the make use of later operation (also referred to as correction in the following). It is understood that the adaptation took place before the correction, which is based on this adaptation.

An adaptation method is proposed that allows the nonlinear (so-called ballistic) range of injection duration / injection quantity characteristics to be determined for different pause times. Thus, the entire usable Zumessbereich is larger, which can also affect the direction of a cheaper production of the injector. An adaptation is preferably carried out selectively for each injector.

The adaptation takes place at a first, earlier point in time and as a result delivers a relationship between an actual injection quantity and a desired injection quantity of a multiple injection for different pause times. The adaptation can be carried out regularly, for example. Depending on the operating time or mileage. It is expedient to go through several times in the vehicle / component life. The frequency can in particular be made dependent on the aging of the injector and / or adjusted by application. In the context of the invention, on the basis of such a relationship, a correction of an injection quantity in a multiple injection is carried out at a second, later point in time (usually during normal operation).

In the case of a multiple injection, a clear transverse influence of the pause time between the individual injections on the actual partial quantities actually injected can be recognized. The actual total injection quantity as the sum of the actual partial quantities is therefore usually greater than the sum of the desired partial quantities from which the individual injection periods are derived.

The transverse influence is based, on the one hand, on the residual magnetization of the coil, which is only slowly decreasing, and on the other hand on the dynamics effects of the needle and the armature, as well as on friction effects. The influence is also injector-specific for smaller break times (specimen spread), so functional consideration by application is hardly possible. It is therefore usual to limit the pause time down to unwanted quantity discrepancies to keep low. However, this limitation considerably limits the usable operating range, especially at higher speeds or with multiple injection. Safe startability at low temperatures with critical fuels is also impaired. The invention overcomes these disadvantages described by determining the deviation between the target total injection quantity and the actual total injection quantity injector-individually in an adaptation process and taken into account for the later activation in the context of a correction.

It is also to be assumed that a deviation measured during production will not remain constant over the entire service life of the injector with short pause times. For example. For example, the friction of the moving needle will change over time, affecting the needle movement and the amount of fuel delivered by the subsequent injections. Thus, an adaptation strategy proposed in the context of the present invention is a particularly advantageous solution, since a determination of the relationship can thus take place at arbitrary times during the lifetime. Thus, a precise metering injector-individual during the entire life is possible.

In an advantageous embodiment, starting from a known relationship between injection duration and actual injection quantity of an injection, at least two such injections are combined into a multiple injection with a pause time. Subsequently, the actual total amount is determined and the deviation of the actual total amount of the target total amount for different pause times, preferably relatively determined. The deviation is then used for the control of the injector, so that given a predetermined pause time, a smaller target total injection quantity corresponding to the deviation is predetermined in order to obtain the desired actual total injection quantity.

The adaptation of the mass dispersion with multiple injection with different pause times is preferably carried out separately for each injector, i. the adaptation process is run through separately for each injector and the result stored in a corresponding map. Also preferably, the ambient and operating conditions (e.g., fuel pressure, temperature) are taken into account.

It is advisable, in addition to the break time and the individual injection quantities, a fuel temperature and / or a fuel pressure to vary and take into account in a corresponding map. In this way, the applicability of the invention can be extended to large operating ranges. Depending on the configuration and required accuracy, individual variation parameters can also be omitted.

For each engine operating point that is specified by the driver, a total amount of fuel is required, which is determined by the engine control unit together with pause times of a multiple injection. In an advantageous embodiment of the invention, the actual required individual injection periods can now be determined based on at least these two variables, for example, from a map. A preferred characteristic field therefore contains individual injection periods as a function of the pause time and the actual total injection quantity.

In the post-published DE 10 2010 044 165 a particularly suitable possibility for determining a relationship between injection duration and injection quantity is disclosed in an injector of an internal combustion engine which uses a lambda measurement. The method disclosed therein is particularly suitable for determining the injection quantity in the context of this invention. In this regard, reference is made to this document and the content of which is hereby incorporated in full in this application. The method described there is expanded by determining the relationship between injection quantity and injection duration for a follow-up injection for different pause times in the manner described there. Thus, a relationship between injection quantity and injection duration is obtained for each break time investigated.

A determination of an injection quantity from a lambda signal is essentially based on the fact that the hydrocarbon emissions in the exhaust gas line rise when a single injector is activated in a coasting phase and no combustion is brought about. At the lambda probe, which is preferably a broadband probe, these emissions can be detected, since lambda is shifted by the hydrocarbon components to smaller values.

In such an advantageous embodiment, no additional sensor or a specifically designed manifold is needed. The method uses only the evaluation of a lambda signal of a lambda probe, preferably a broadband probe, which is usually installed in the system anyway. In addition, the effort for the construction of the injectors as well as the design of the final stage required for the control is minimized. This manifests itself directly in a minimization of the manufacturing costs.

The invention preferably uses the lambda signal in unfired overrun mode for evaluation. In overrun will be in Normally, the injections are hidden and the engine throttled (throttle almost closed). Accordingly, the mass flow of air through the engine is low, so that small amounts of fuel injected affect the lambda signal stronger than in de-throttled operation (throttle open).

The hydrocarbon fraction in the exhaust gas is preferably determined from the signal of the lambda probe, in order in turn to determine the injected fuel quantity therefrom. It has been found, in particular, that the relationship between lambda value and hydrocarbon fraction is substantially linear in all considered regions, so that this calculation can be carried out in a particularly simple manner, in particular using a linear relationship, which can be determined empirically, for example. The hydrocarbon fraction can be determined from the lambda value, in particular taking into account the air mass, which is determined, for example, by an air mass meter. In a simple embodiment, the air mass in the throttled operation can also be assumed to be constant, so that only the lambda signal must be used for the evaluation. However, with the knowledge of the air filling in the cylinder (from signals from the HFM or from the p-sensor), the process can also be carried out with decreasing or increasing air filling. Here then the filling must be included in the lambda value. As a result, calibration can also be carried out for longer injection periods.

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 a schematic representation of an internal combustion engine with intake manifold injection through an injector.

2 shows a diagram with a characteristic of the injector according to 1 , which links an injection duration with an injection quantity.

3 FIG. 15 is a diagram schematically showing a relationship between the injection amount of a following injection and the pause time. FIG.

4 shows a flowchart for explaining a preferred embodiment of the method according to the invention.

Embodiment (s) of the invention

In 1 is an internal combustion engine, as can be based on the present invention, shown schematically and in total with 10 designated. The internal combustion engine 10 usually includes several cylinders, of which in 1 however, only one with the reference numeral 11 is shown. Via an inlet valve 14 (or more) can the combustion chamber 12 of the cylinder 11 with a suction pipe 16 get connected. In the present embodiment, this fuel is injected through an injector 18 injected. However, the operating principles and methods described below are also applicable to internal combustion engine with direct fuel injection, for example, gasoline direct injection. In the suction pipe 16 is also a throttle 20 arranged. The in the intake manifold 16 flowing air mass is in the present embodiment of an air mass sensor 22 detected.

That in the combustion chamber 12 existing fuel-air mixture is in normal operation of a spark plug 24 ignited. Hot combustion exhaust gases then pass out of the combustion chamber 12 via an exhaust valve 26 (or more) in an exhaust pipe 28 , In this are a catalyst 30 and a lambda probe 32 , which detects a lambda value, through which the fuel-air mixture in the combustion chamber 12 is characterized, arranged.

One from the injector 18 in the suction pipe 16 injected fuel quantity Q is, at constant fuel pressure, mainly by the injection duration ti of the injector 18 affected. It is used in the design of the injector 18 put emphasis on that the relationship between injection duration ti and injected fuel quantity Q, which as 2 can be seen by a characteristic curve 34 is expressed in a wide operating range of the injector 18 is linear. Such a linear characteristic or the parameters for determining such a necessary slope and zero crossing are in a control unit 36 ( 1 ) which stores the injector 18 but also the throttle 20 as well as the spark plug 24 depending on different sensor signals, for example the signals of the lambda probe 32 and the air mass sensor 22 , drives.

For manufacturing reasons, an injector has a non-linear behavior with short injection periods ti <ti _G or small injection quantities Q. This area is commonly referred to as the "ballistic area". The corresponding area is in 2 shown dotted and with 38 designated. Due to manufacturing tolerances, behavior in this area also varies from one injector to another.

How farther 2 shows that in this area a smaller amount of fuel Q is injected as it is the linear characteristic 34 would correspond. In principle, however, deviations in the other direction are conceivable, ie the injection of a larger amount of fuel.

In 3 the effect of the explained small quantity dispersion on multiple injections is shown. A diagram shows the relative actual injection quantity Q of a subsequent injection (second injection of a multiple injection) for a fixed injection duration ti over the pause time Δt between the first and the second injection of the multiple injection. A relative actual injection quantity of 100% corresponds to the target injection quantity expected for the given injection duration ti. It becomes clear that the actual injection quantity for small pause times can deviate very clearly from the target injection quantity.

With reference to 4 Now, a preferred embodiment of the invention will be explained, with which this deviation can be taken into account in the control of the injector. The method is preferably by the programmatically set up control unit 36 carried out.

The execution of the preferred method during the operation of an internal combustion engine can be subdivided in two parts, an adaptation in which at a first, earlier time a relationship between actual injection quantity and target injection amount is determined injector individually as a function of the pause time, and a Correction in which, at a second, later time, a desired injection quantity is corrected on the basis of this relationship in such a way that the correct actual injection quantity results.

The adaptation to the first time begins in one step 400 in which the internal combustion engine is brought into a defined operating state. In this operating state should prevail a certain operating temperature, be completed an adaptation of a lambda control, expediently no errors in the controller present, a certain voltage in the electrical system of the motor vehicle may be present, etc. Furthermore, the internal combustion engine must be in overrun.

Depending on the accuracy requirement, different variations can be performed during the adaptation.

In the present example, the optional variations of fuel temperature T and / or fuel pressure P are in an outer variation step 401 shown. Each time the process is run, the quantities T _~ and Q _{~ are} varied.

In a subsequent step 402 First, a first (general) relationship between injection duration ti and injection quantity Q is determined. This determination is preferably made in accordance with the reference DE 10 2010 044 165 , In this case, the lambda signal is detected and evaluated in an unfired overrun mode. As a result of this determination, a dependency Q (ti) of an injection amount is obtained from an injection period for a single injection.

In a further variation step 403 is also the optional variation of the single injection amount Q shown. Each time this step is executed, the single injection amount Q _{~ is} varied. Out of the step 402 determined relationship Q (ti) is in each case the associated injection duration ti (Q _~ ) obtained.

In a next step 404 the variation of the pause time Δt is shown. Each time this step is executed, the pause time Δt _{~ is} varied, preferably from a long pause time to a short pause time. In particular, the invention makes it possible to use pause times of less than 5 ms up to 0.1 ms.

In a next step 405 is based on the currently valid injection quantity Q _~ (or the associated injection duration ti (Q _~ )) and the currently valid pause time .DELTA.t _~ a multiple injection issued. It is preferably a double injection comprising a first single injection Q _~ followed by a pause time Δt _~ followed by a second single injection Q _~ .

In a next step 406 the resulting actual total injection amount Q _is determined. The determination is made in accordance with the determination of the individual injection quantity in step 402 ,

In a next step 407 is a relative deviation of the actual total injection quantity Q _{is to} the target total injection quantity Q (which in the present example to 2Q _~ results) is determined and in a map 500 depending on the relevant parameters Δt _~ (and possibly P _~ , T _~ , Q _~ or ti (Q _~ )) stored. The map preferably contains at least one relationship of the form (Q _ist , Δt, ti (Q)).

The steps 408 . 409 and 410 complete the respective variation. Optionally, a variation of the number of single injections per multiple injection may also take place.

The procedure ends in one step 411 , This is an adaptation for an injector.

The determination of the relationship between total injection quantity and pause time is expediently carried out separately for each injector. For this purpose, the adaptation process is performed separately for each injector and each cylinder. The order is arbitrary.

In the context of the invention, a particular relationship determined in this way is used to perform a correction of the injection durations during operation (ie at the second, later time), preferably a map 500 containing at least one relationship of the form (Q _ist , .DELTA.t, ti) is used. The correction is used when multiple injection is required.

In one step 600 an engine operating point is specified by the driver.

In one step 601 For example, a target total injection amount Q _ges and appropriate pause times Δt are determined based on the engine operating point request.

In one step 602 becomes the map 500 taken from the associated control period ti for the respective individual injections of the multiple injection.

In one step 603 the multiple injection is carried out accordingly.

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 102010044165 [0017, 0042]

Claims (13)

Method for correcting an injection quantity in a multiple injection, wherein at a second, later time a desired injection quantity of a multiple injection consisting of at least two individual injections, each with a specific pause time (At) between the at least two individual injections based on a first, earlier time determined Context ( 500 ) between an actual injection amount (Q _ist ) and a target injection quantity (Q _soll ) of a multiple injection for different pause times (Δt _~ ) is corrected such that the actual injection quantity resulting from the corrected target injection quantity of the multiple injection of a desired injection quantity (Q _tot ) corresponds. The method of claim 1, wherein the correction of the target injection quantity of the multiple injection comprises a correction of the respective injection duration of the at least two individual injections. Method according to claim 1 or 2, wherein at the first, earlier point in time the relationship ( 500 ) between an actual injection quantity (Q _ist ) and a desired injection quantity (Q _soll ) of a multiple injection for different pause times (Δt _~ ) in an unfired overrun operation of the internal combustion engine ( 10 ) is determined. Method according to one of the preceding claims, wherein as a target injection quantity (Q _soll ) a sum of the individual injection quantities (Q _~ ) which would result for the individual injections is used. Method according to one of the preceding claims, wherein the relationship between an actual injection quantity (Q _ist ) and a desired injection quantity (Q _soll ) of a multiple injection for different pause times (Δt _~ ) in a characteristic field ( 500 ) is stored. Method according to one of the preceding claims, wherein based on a determined relationship between injection duration and actual injection quantity of a single injection, at least two such injections are combined into a multiple injection with a pause time. Method according to one of the preceding claims, wherein at the first, earlier point in time the relationship ( 500 ) between an actual injection quantity (Q _ist ) and a desired injection quantity (Q _soll ) of a multiple injection for different pause times (Δt _~ ) for different individual injection quantities, fuel temperatures and / or a fuel pressure is determined. Method according to one of the preceding claims, wherein an actual injection quantity is determined based on a current lambda value. The method of claim 8, wherein in the determination of the injection quantity and a current air mass value received. The method of claim 9, wherein from the respective lambda value and an air mass of the respective hydrocarbon content in the exhaust gas is determined. The method of claim 9 or 10, wherein the respective hydrocarbon fraction is determined in the exhaust gas via a correlation measurement. Method according to one of the preceding claims, for each injector ( 18 ) at least one cylinder ( 11 ) of the internal combustion engine ( 10 ) is performed sequentially and / or for each injector ( 18 ) of each cylinder ( 11 ) of the internal combustion engine ( 10 ) is performed sequentially. Arithmetic unit ( 36 ), which is adapted to perform a method according to any one of the preceding claims.

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