EP1132600A2 - Adapting method for the control of injection - Google Patents

Abstract

An adaption method for controlling the injection of a multi- cylinder internal-combustion (IC) engine, which is operated phase-wise stoichiometric and lean, involves a first stage (a) of continuously controlling the injection for each cylinder in stoichiometric and/or homogenous-lean operating phases, so that each cylinder on average is operated with stoichiometric or the required homogenous-lean mixture, where a first correction factor is continuously determined and stored, for the basic injection values, and which restores or reproduces the deviation of the actual injection from the desired injection. In a second stage (b), in the stratified-lean operating phases, control of injection for each cylinder is carried out so that each cylinder generates a given torque or that the running smoothness of the engine is maximal. A correction of the basic injection values then follows, during which the first correction factor stored finally in stage (a) is used.

Description

The invention relates to an adaptation method for control the injection of a multi-cylinder internal combustion engine, the phased stoichiometric, Lambda-1 controlled and operated lean becomes.

To continue the fuel consumption of Otto internal combustion engines to reduce, internal combustion engines come with lean Combustion is increasingly used. With such a skinny one Operating mode is between two basic operating modes distinguished.

In a lower load range, the internal combustion engine is used a heavily layered cylinder load and high excess air operated (hereinafter referred to as stratified-lean Operation designated). This will include through a late injection in the compression stroke shortly before the ignition point reached. The internal combustion engine is avoided of throttle losses largely when the throttle valve is open operated.

The internal combustion engine becomes lean in an upper load range and operated with homogeneous cylinder charge (hereinafter referred to as homogeneously lean operation called). The injection takes place already during the intake stroke to ensure thorough mixing to get fuel and air. The air mass sucked in is according to the requested torque, for example requested by a driver at an accelerator pedal is set via a throttle valve.

Finally, the internal combustion engine can also be used with stoichiometric Fuel-air mixture operated (in the following referred to as stoichiometric operation). Doing so the required amount of fuel from the inducted in a known manner Combustion air mass taking into account the Speed calculated and if necessary via a lambda control corrected.

The homogeneous, lean operation and the stoichiometric operation are summarized below under the term "homogeneous operation".

Fuel injectors naturally have a certain one Deviation of their actual behavior from the specified target behavior on. This deviation can be due to manufacturing tolerances be, or result from changes in operations, for example through deposits. It is therefore known in stoichiometric operation a so-called cylinder equality perform in the cylinder-specific differences of the injection valves are adaptively compensated. By correcting the control of the respective Injectors ensure that each cylinder is exactly in the stoichiometric operation with lambda 1 control is running. Each after tolerance or age-related deviation that the respective Injector shows, this equality can be a Excess or shortage of fuel mean that during operation of the respective injection valve is used as a correction must become.

This cylinder equation is for direct injection Internal combustion engines are particularly important because of their injectors directly into the combustion chamber of the internal combustion engine protrude and therefore subject to particularly strong aging influences are.

It is an object of the present invention to provide a method with that in an internal combustion engine that is both in stoichiometric as well as in lean operation, an adaptation the injection control is achieved to make changes of injectors in both stoichiometric and balance in lean operating phases.

This object is characterized by that in claim 1 Invention solved.

The invention is based on the knowledge that in the stratified-lean Operation for the behavior of the internal combustion engine essentially the spray characteristics of an injector emitted beam is determining. Are there individual changes in injector characteristics in stratified-lean operation mainly relevant to torque, whereas in homogeneous operation (both homogeneously lean and also stoichiometric) of the internal combustion engine mainly relevant to emissions are. According to the invention is therefore a known λ equality in homogeneous operation of the internal combustion engine carried out, a first correction factor for change predefined basic injection values for each injection valve determined and saved. With this first correction factor is achieved that the respective injectors all show the same actual behavior; tolerance or aging Deviations in the fuel mass delivered are balanced.

The engine now changes to the stratified-lean Operation, so here is also an equality carried out, now no longer a stoichiometric or Homogeneous, lean mixture for the individual cylinders but that emitted by the respective cylinder Torque; one therefore speaks of torque equalization. To determine the cylinder-specific correction factors the torque equalization is from respective last stored first correction factor of previous homogeneous operating phase, i.e. the first Correction factor is now for stratified-lean operation used, in addition a determination or adaptation of a second correction factor that is specific for the stratified and lean operation and together with that first correction factor is used. Starting from these The values are then adapted using an independent process the second correction factor in lean operation.

Since in homogeneous operation it is primarily the injected fuel mass, in stratified and lean operation, however, essentially the beam characteristic determines the behavior the internal combustion engine, the second correction factor, that in the adaptation of a stratified-lean operating phase was hardly determined on the λ equality in homogeneous Operation. Therefore, the λ equality in homogeneous operation when changing the Operating mode from stratified-lean operation to homogeneous Operation again with that in the adaptation algorithm of the stratified-lean Operation unchanged first correction factor, which as a result of the adaptation in the previous homogeneous Operating phase was obtained, continued and the last value of the second correction factor for the homogeneous Operating phase not used. So there are two adaptation algorithms independent, one for homogeneous operation and one for the stratified and lean operation.

As a target for torque equalization in the stratified-lean Operation can preferably run smoothly of the internal combustion engine serve. You can do this using, for example of a knock sensor detect the smooth running cylinder selectively and Injection duration and / or start of injection for the individual Change the injection valves appropriately so that they run smoothly increases. One can in certain stratified lean operating phases Operating conditions do not capture the smooth running like it does for example with strong dynamics of the internal combustion engine Case, it is possible to adapt the second correction factor to suspend.

Of course, the deviation of the actual behavior of an injection valve must of his target behavior not in every phase be the same as the internal combustion engine. For example, it is conceivable that the deviation depends on the fuel pressure. It is therefore possible in a further training, the individual cylinder Correction factors of λ and / or torque equalization to design depending on the operating parameters. Instead of a single first and second correction factor for each cylinder then you will save for a given Operating parameter classification according to several first and Store second correction factors, for example in suitable ones Maps.

Have the separate first and second correction factors further the advantage that the adaptation algorithms acting on them slow in homogeneous and stratified-lean operation can be interpreted. In homogeneous operation only works the first correction factor, and only this is adapted, in stratified and lean operation act first and second correction factor, but only the second correction factor is through adaptation changed.

Advantageous developments of the invention are the subject of subclaims.

Fig. 1

eine schematische Darstellung einer Brennkraftmaschine mit Direkteinspritzung und

Fig. 2

einen Ablaufplan eines Verfahrens zur Adaption der Ansteuerung von Einspritzvehtilen der Brennkraftmaschine der Fig. 1.

The invention is explained in more detail below with reference to the drawing in an exemplary embodiment. The drawing shows:

Fig. 1

is a schematic representation of an internal combustion engine with direct injection and

Fig. 2

1 shows a flowchart of a method for adapting the control of injection systems of the internal combustion engine of FIG. 1.

Fig. 1 shows a schematic representation of an internal combustion engine with gasoline direct injection, both with stoichiometric as well as with a lean fuel-air mixture is operable. For reasons of clarity only those components of the internal combustion engine drawn in, necessary for understanding the invention; in particular is just one cylinder of a multi-cylinder internal combustion engine shown.

The internal combustion engine has a piston 10, which is in a Cylinder 11 delimits a combustion chamber 12. In the Combustion chamber 12 opens into an intake duct 13 at an inlet valve 14 through which the combustion air enters the combustion chamber 12 streams. An outlet valve 15 connects the Combustion chamber 12 with an exhaust tract 16, in the other Course an oxygen sensor in the form of a broadband Lambda probe 17 and a NOx storage catalytic converter 18 with not shown three-way pre-catalyst.

Using the signal from the lambda probe 17, a control unit 21 the fuel-air mixture accordingly the target specifications in different operating modes of the internal combustion engine regulated / controlled. For example, in stoichiometric operation a known lambda control.

For such a lambda control is located downstream of the NOx storage catalytic converter 18 a further lambda probe 32 which is used for control and setpoint control. The In this case, the oxygen probe is a binary lambda probe 32 (two-point lambda probe), which with a lambda value of λ = 1 jump characteristic shows. Instead of the lambda probe 32 a NOx sensor can also be used. Further located there is usually a temperature sensor in the exhaust tract 33.

The NOx storage catalytic converter 18 serves to operate during lean operation the exhaust gas limit values required for the internal combustion engine To be able to maintain NOx connections. It adsorbs due to its coating, those generated during lean combustion NOx compounds in the exhaust gas.

In particular for internal combustion engines with direct injection NOx emissions occurring in stratified, lean operation to reduce exhaust gas recirculation is provided. By mixing in exhaust gas, it is sucked in Fresh air lowered the temperature of the combustion, with what NOx emissions are reduced at the same time. Therefore from Exhaust tract 16 upstream of the NOx storage catalytic converter 18 Exhaust gas recirculation line 19 led to the intake duct 13, which between a throttle valve 20 and the inlet valve 14 in the Intake channel opens. In the exhaust gas recirculation line 19 is a controllable valve 22 switched, which is usually used as an exhaust gas recirculation valve referred to as. By controlling the valve 22, the amount of recirculated exhaust gas can be adjusted become.

The combustion air for the cylinder 11 flows through one Air mass meter 23 in the intake duct 13. The arranged therein Throttle valve 20 is controlled by an electric motor Throttle body (E-gas system), whose opening cross section next to actuation by a driver (driver's pedal position) too can be influenced by the control unit 21. With that you can For example, reduce disturbing load change reactions. In addition, the throttle valve 20 is controlled by the control unit 21 almost completely opened in stratified lean operation. The control device 21 also provides appropriate intervention on the throttle valve 20 for a smooth transition from stoichiometric to homogeneously lean and from there to stratified-lean Business.

Finally, there is a temperature sensor in the intake duct 13 24, which is connected to the control unit 21. Of course, the temperature sensor 24 can also be used in the air mass meter 23 be integrated.

A spark plug 25 and an injection valve protrude in the combustion chamber 12 26, which is used for fuel injection from a High-pressure accumulator 27 is fed, which is part of a known Fuel supply for direct petrol injection is. The control unit 21 is finally with a knock sensor 28 connected, the mechanical vibrations on the housing the internal combustion engine detects and a corresponding signal delivers. The speed of the internal combustion engine is over a the crankshaft or a sensor wheel attached to it Sensor 29 detected. Others for operating the internal combustion engine necessary control parameters, e.g. accelerator pedal position, Signals from temperature sensors etc. are sent to the control unit 21 are also supplied and are general in FIG. 1 identified by reference numeral 30.

Finally, there is a block 31 in the control unit 21 for determining the torque and monitoring provided, its function will be explained later.

Furthermore, the control device 21 is connected to a memory 34, in which different threshold values TQI_SW1, TQI_SW2 as well at least the maps KF1 and KF2 are stored, whose meaning will be discussed later.

The control unit 21 determines, depending on the operation, whether the internal combustion engine stoichiometric, homogeneously lean or stratified-lean to be operated.

In each operating mode, the control device 21 continuously determines the control data for the injection valve 26, that is, the start of injection and the injection duration or the injection end. The injection starts on the crankshaft position related, known to the control unit 21 by means of the sensor 29 is. Individuals due to aging and production tolerance Deviations of the individual injection valves 26 at to compensate for a multi-cylinder internal combustion engine is from Control unit 21 performed an adaptation process, the Flow chart is shown in Fig. 2, in which those beginning with S. Reference numerals denote steps of the process sequence.

In a step S1, corresponding sizes are first initialized. In particular, the map KF1 is either with Default values, or with the last execution values determined during the adaptation process.

Subsequently, a query is made in a step S2 as to whether the Internal combustion engine is in the homogeneous operating mode (λ = 1). If this is the case, the is marked with a "+" sign designated branch continued. Is the Internal combustion engine not in homogeneous operating mode, is with the branch marked with a "-" sign. This Query is necessary if the adaptation process as independent process in control unit 21 is running. It is against it The query can be integrated into the operating mode control omitted in step S2, since it is then always known which operating mode is present.

In the case of homogeneous operation, in a step S4 Signal of the lambda probe 32 recorded individually for each cylinder. This cylinder-specific detection makes it possible to assess which mixture each cylinder receives on average. Doing so the internal combustion engine with the currently valid control values operated for injection. The currently valid control values consist of a basic control value and a current value of a first correction factor to be described from the map KF1 together. Then in Step S5 queries whether there is a change in operating mode in the meantime took place. If this is the case, before step S2 jumped back, otherwise it is in the branch labeled "-" continued.

Then, in step S6, it is next checked whether it turns out recognize the cylinder-specific detection in step S4 leaves that all cylinders with the target mixture, at stoichiometric Operation was operated on average with λ = 1.

If this is the case, the system jumps back in a loop before step S4.

The query in step S6 shows that individual cylinders not on average with the target mixture through their injectors 26 have been supplied, becomes cylinder-selective in step S7 a fuel quantity correction is calculated. The to be metered to the cylinders via their injection valves 26 Corrected the fuel quantity to the target mixture. For cylinders, that were operated with too rich a mixture, so calculates a fuel shortage; for cylinders with were operated to a lean mixture, a fuel excess.

This fuel quantity correction is the first mentioned above Correction factor. It is stored in the map KF1 in step S8.

Then jump back before step S4. In step S4 is then instructed to control unit 21 during activation of the injection valves 26 the corresponding fuel quantity corrections map KF1 to be taken into account. This will usually happen by the injection duration is reduced or extended accordingly. Through the sequence these steps achieve cylinder equality. As mentioned, the loop only becomes a step S5 jumped out if there is an operating mode change.

The internal combustion engine runs in stratified, lean operation so can equality by adapting the injectors 26 not with steps S4 to S8, because then no longer predominantly determining the injected fuel mass for the behavior of the internal combustion engine, but Consider the beam characteristics too is. Therefore, the first correction factor, i.e. the Fuel quantity and quantity of the map KF1 not be used more alone. Rather, an independent, Additional adaption for torque equalization in the stratified-lean Operation of the internal combustion engine necessary. Therefore is in lean operation of the internal combustion engine in Step S9 first on a further map KF2 with a second correction factor accessed. For torque equalization the injection takes place with two correction values, the first correction value that occurs during the stratified-lean Mode of operation remains unchanged, and the second Correction factor that is changed by adaptation.

Then the injection with currently valid control values performed. These consist of a basic control value, the first correction factor and the current one Value of the second correction factor from the map KF2 together.

Then, in step S10, the smooth running is detected cylinder-selectively. This takes place in the above-mentioned block 31 of the control unit 21 by suitable evaluation of the signal from the knock sensor 28 to the torque delivered by each cylinder capture. This block 31 can for example also on the Signals from a torque sensor (not shown in FIG. 1) Take recourse.

The detection in step S10 provides the difference of the torques delivered to the individual cylinders.

Subsequently, in step S11 it is again queried whether a Operating mode change is present. If this is the case, will Step S2 jumps back, otherwise step S12 continued.

This step S12 checks whether the difference of the Torques given torques below a threshold lies. Depending on the operating mode, this can be the Threshold value TQI_SW1 for the case of homogeneously lean operation or the threshold value TQI_SW2 for the case stratified-lean Act. If the difference is less than Threshold value for all cylinders, is jumped back before step S10, otherwise proceed to step S13.

In step S13, the second correction factor becomes cylinder-selective for taking the beam characteristics of the Injector 26 updated. This adaptation of the second Correction factor takes place on a torque equalization the cylinder 11 out. The so adapted or second correction factor is changed in for each cylinder the map KF2 entered.

Now the injection takes place with corrected values. In the Injection correction can be a change in injection duration act, but it is also an injection start correction or a combination of the two possible. For correction both correction factors used. Doing so in step S14 the control device 21 instructed the second correction factor of the map KF2 together with the unchanged first Correction factor from the map KF1 when controlling the Injectors 26 to be considered. Then before step S10 jumped back.

The adaptation of the control of the injection valves 26 is used thus in stratified and lean operation of the internal combustion engine the first correction factor from λ equality, but not the second correction factor in homogeneous operation. This is because the results the λ equalization for homogeneous operation to the torque equalization used for stratified and lean operation can be because in λ equality in the homogeneous Operation differences in injected fuel mass are taken into account, both there and in the stratified-lean Operation of the internal combustion engine validity have. The second correction factor, that of torque equalization is adapted in stratified-lean operation, resembles a change in the jet characteristics of the injection valves 26, for example due to coking. This Differences in the jet characteristics of the injection valves 26, however, are in homogeneous operation of the internal combustion engine not or hardly relevant, which is why the results of the Torque equality in the adaptation process in the stratified-lean Operation of the engine is not the first correction factor of λ equality in the adaptation process react in homogeneous operation of the internal combustion engine allowed to.

Claims (6)

Adaptation process for controlling the injection of a multi-cylinder internal combustion engine, which is operated stoichiometrically and lean in phases, in which process the following stages are carried out: a) In stoichiometric and / or homogeneously lean operating phases, the control of the injection is continuously effected for each cylinder in such a way that each cylinder is operated on average with stoichiometric or desired homogeneous-lean mixture, with a first correction factor being continuously determined and stored for basic injection values , which shows the deviation of an actual injection from the target injection, and b) in stratified, lean operating phases, the control of the injection is effected continuously for each cylinder in such a way that each cylinder generates a predetermined torque or that the smooth running of the internal combustion engine becomes maximum, a correction of basic injection values being carried out, the last being in stage a) stored first correction factor is used. Method according to Claim 1, characterized in that a second correction factor is obtained in stage b), which is used together with the first correction factor stored last in stage a) and which reproduces the deviation of the actual injection from the target injection for the stratified-lean operation. Method according to one of the preceding claims, characterized in that after a transition from a stratified-lean operating phase to a stoichiometric or homogeneous-lean operating phase when the injection is controlled in stage a), the last stored value of the first correction factor is continued. Method according to one of the preceding claims, characterized in that in stage a) the first correction factor reflects the deviation of the injected fuel mass. Method according to Claim 2, characterized in that the second correction factor is adapted in stage b), but the first correction factor remains unchanged. Method according to one of the preceding claims, characterized in that the first and / or second correction factor is selected as a function of the operating parameters and is stored in an operating parameter-dependent map.

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