EP1792068A1 - Method for regulating the mixture of a multicylinder otto engine comprising cylinder-specific individual catalytic converters and a joint main catalytic converter mounted downstream of the individual catalytic converters - Google Patents

Method for regulating the mixture of a multicylinder otto engine comprising cylinder-specific individual catalytic converters and a joint main catalytic converter mounted downstream of the individual catalytic converters

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Publication number
EP1792068A1
EP1792068A1 EP05769792A EP05769792A EP1792068A1 EP 1792068 A1 EP1792068 A1 EP 1792068A1 EP 05769792 A EP05769792 A EP 05769792A EP 05769792 A EP05769792 A EP 05769792A EP 1792068 A1 EP1792068 A1 EP 1792068A1
Authority
EP
European Patent Office
Prior art keywords
cylinder
lambda
individual
control
catalysts
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP05769792A
Other languages
German (de)
French (fr)
Inventor
Alexander Ketterer
Gerd RÖSEL
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Continental Automotive GmbH
Original Assignee
Siemens AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens AG filed Critical Siemens AG
Publication of EP1792068A1 publication Critical patent/EP1792068A1/en
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
    • F02D41/1408—Dithering techniques
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/008—Controlling each cylinder individually
    • F02D41/0085—Balancing of cylinder outputs, e.g. speed, torque or air-fuel ratio
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1473—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the regulation method
    • F02D41/1474—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the regulation method by detecting the commutation time of the sensor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/32—Controlling fuel injection of the low pressure type
    • F02D41/34—Controlling fuel injection of the low pressure type with means for controlling injection timing or duration
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
    • F02D2041/1409—Introducing closed-loop corrections characterised by the control or regulation method using at least a proportional, integral or derivative controller
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
    • F02D2041/1413—Controller structures or design
    • F02D2041/142—Controller structures or design using different types of control law in combination, e.g. adaptive combined with PID and sliding mode
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/08—Exhaust gas treatment apparatus parameters
    • F02D2200/0816—Oxygen storage capacity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/008—Controlling each cylinder individually
    • F02D41/0082—Controlling each cylinder individually per groups or banks

Definitions

  • a lambda-controlled 3-way catalytic converter is usually used today, optionally preceded by a close-coupled precatalyst.
  • a conventional lambda control for the main catalyst common to all cylinders and optionally provided precatalyst is described, for example, in "Handbuch Verbrennungsmotor", 2nd edition, by Richard van Basshuysen / Fred Schifer, pages 559 to 561.
  • the lambda control regulates the air-fuel ratio lambda ( ⁇ ) with the aid of signals from a lambda probe (pre-catalyst probe) connected upstream of the main catalytic converter and, if appropriate, a lambda probe connected downstream from the main catalytic converter (aftercattern sensor) so-called
  • the lambda control furthermore usually comprises a so-called control or trim control, by means of which the signal of the pre-catalyst probe is corrected as a function of the signal of the post-cat probe in order to compensate for age-related measurement errors of the pre-cat probe.
  • control or trim control by means of which the signal of the pre-catalyst probe is corrected as a function of the signal of the post-cat probe in order to compensate for age-related measurement errors of the pre-cat probe.
  • a method for a cylinder-selective lambda control has already become known from DE 102 06 402 C1, in which the signal of the lambda probe (pre-catalyst probe) is cyclically resolved by a microcontroller, so that the lambda Signal to individual cylinders assigned and thus individual exhaust gas packets of these cylinders can be detected.
  • the present invention has for its object to provide a method for controlling the mixture of an Otto multi-cylinder Brenn ⁇ combustion engine with cylinder-related individual catalysts and the individual catalysts downstream common main catalyst, in which a cylinder-related Ge mixed control using a common lambda probe the individual catalysts is possible.
  • the present invention is based on a system configuration in which the individual cylinders are each assigned a single catalytic converter and a common main catalytic converter connected downstream of the individual catalytic converters is provided.
  • the individual catalytic converters are arranged as close as possible to the internal combustion engine and can, for example, be installed directly in the respective manifolds in order to achieve the shortest possible "light-off" of the individual catalytic converters provided the individual catalysts downstream common lambda probe.
  • the catalysts are each formed as 3-way catalysts Aus ⁇ , wherein the individual catalysts have a predetermined, but relatively low oxygen storage capacity.
  • the cylinder-related lambda control comprises a cylinder-related forced excitation, by means of which a mean lambda nominal value is modulated in each case by a periodic fluctuation in the form of lean-mixture and rich-compound half-waves.
  • the cylinder-related forced excitation if the number of cylinders of the entire internal combustion engine or at least one cylinder bank is even-numbered, is carried out in opposite directions to that of the other half for one half of the cylinders to compensate for the cylinder-related torque contributions to achieve the cylinder.
  • two cylinder-related torque contributions e.g. in a 4-cylinder engine
  • the oxygen charge of the individual catalysts caused by the forced excitation is expediently adapted to changes in the oxygen storage capacity which are due to aging. This adaptation is possible while maintaining the torque equalization position.
  • Another advantage of this solution is that the individual catalysts are within the range of their oxygen Storage capability can be operated; that is, the forced excitation does not necessarily have to be controlled until the individual catalytic converters reach the limit of their oxygen storage capacity in steady-state operation.
  • a trim control of the mixture is provided for each of the individual catalytic converters, the air-fuel ratio being detected downstream of the individual catalytic converters with only one common lambda probe. Since differences in the given system configuration between the air and / or fuel masses introduced into the individual cylinders (filling differences and differences in the injected fuel masses) influence the operation of the cylinder-related individual catalytic converters, operation of the individual catalytic converters with an air-fuel ratio ( ⁇ ) within the so-called catalyst window is not guaranteed. However, maximum utilization of the individual catalytic converters is known to be possible only if all individual catalytic converters are operated with optimized efficiency in the catalyst window. According to the invention, therefore, the mixture is subjected to a cylinder-related trim control for each of the catalysts.
  • cylinder-related lambda signals are reconstructed in a cycle-resolved manner from the signal of the common lambda probe, and a cylinder-related trim control is then carried out with the aid of these reconstructed cylinder-related lambda signals.
  • the procedure is preferably such that the zyzinderindividual forced excitation of the oxygen storage capacity of the individual catalytic converters is adjusted in advance so that the oxygen charge caused by the forced excitation the individual catalysts at the end of each lean mixture half-wave of the forced excitation reaches a target oxygen loading in the order of their SauerstoffSpeicherdozens, from constant curves of the reconstructed cylinder-related lambda signals over all cylinders a lying in the catalyst window mean reference value is obtained and this mean reference value as a reference variable and Signal deviations of the reconstructed cylinder-related lambda signals from the average lambda reference value can be used as the control deviation of the trim control.
  • the inventively provided trim control makes so ⁇ with the oxygen storage capacity of the individual catalysts advantage.
  • the constant courses of the cylinder-related lambda signals result from the oxygen storage of the individual catalytic converters, and to a certain extent form the reference point for the determination of the cylinder-related deviations of the air-fuel ratio.
  • the invention thus makes possible a stoichiometric mixture trimming of each of the cylinder-related individual catalytic converters with a single lambda probe in order to operate all the individual catalytic converters in the catalyst window and thus achieve the maximum efficiency of the individual catalytic converters for a long time.
  • the trim control is expediently carried out with a P and I component (high speed of the signal reconstruction) or with only one I component (ring speed of the signal reconstruction). If necessary, the cylinder-based trimming control for the individual catalytic converters can be superimposed on the mean value trim control that is standard today across all cylinders for correcting age-related measurement errors of the lambda probe.
  • a further advantage of the invention is that when determining the average lambda setpoint value from constant curves of the cylinder-related lambda signals over all cylinders, an offset error of the lambda probe does not affect the measurement result.
  • An additional lambda probe for offset error compensation is therefore not absolutely necessary, although it can of course be provided.
  • a third aspect of the invention relates to the lambda control for the individual catalysts downstream Haupt ⁇ catalyst.
  • the oxygen storage capacity of the individual catalytic converters is taken into account in the definition of the parameters of the lambda control for the main catalytic converter, which is designed in a conventional manner, and an optionally provided average trim control.
  • This consideration is expediently carried out by taking into account the time duration which elapses between a switching of the fuel injection caused by a rich mixture or lean mixture breakthrough of an individual catalytic converter and the signal deviation of the respective cylinder-related lambda signal caused thereby.
  • the lambda control for the main catalytic converter between operating states with constant signal curves (oxygen reservoir does not overflow) and operating states with signal deviations of cylinder-related lambda signals (oxygen storage überge ⁇ run) differs and adapts their behavior by a corre sponding ch adaptation of the controller parameters and / or controller structure to these two operating states.
  • a general advantage of the described aspects of the present invention is that the lambda probe common to the individual catalytic converters can be a binary or continuous probe and the signal of this lambda probe can be used as a guide variable for the mixture control of several cylinder-specific single catalysts can be used.
  • FIG. 1 is a schematic diagram of a Systemkonfigurati ⁇ on for the exhaust aftertreatment of a 4-cylinder internal combustion engine.
  • FIG. 2 shows a ⁇ pulse of a forced excitation and a reconstructed ⁇ signal for a first cylinder of the internal combustion engine
  • FIG. 3 shows a ⁇ pulse and a reconstructed ⁇ signal for a second cylinder
  • FIG. 4 shows the signal of a common lambda probe taking into account the two cylinders according to FIGS. 2 and 3.
  • FIG. 1 shows an example of a system configuration according to the invention for a four-cylinder Otto internal combustion engine BKM with four cylinders Z1-Z4, individual cylinder-related catalysts K1-K4 and a main catalytic converter HK connected downstream of the individual catalytic converters.
  • a lambda sensor LS1 is arranged in the common exhaust gas tract, the signal of which is fed to an electronic operating control unit ECU.
  • the main catalytic converter HK is expediently followed by a further lambda sensor LS2 whose signal is likewise supplied to the operating control device ECU.
  • the electronic Commission Kunststoff ⁇ device performs a mixture control in the form of a cylinder-related lambda control to regulate the air-fuel ratio ⁇ ⁇ of the cylinder Z1-Z4.
  • the cylinder-related forced excitation for one half of the cylinders is in each case carried out in the opposite sense to that for the other half of the cylinders.
  • the lean-mixture half-waves of the cylinders Z1 and Z4 are assigned to the lean-mixture half-waves of the cylinders Z2 and Z4 (and vice versa), as becomes clear from a comparison of FIGS. 2 and 3. This allows complete compensation the torque contributions of the cylinder, provided that an even number of cylinders per bank or per entire internal combustion engine is provided.
  • the duration and amplitude of the ⁇ pulses of the forced excitation are selected to be the same for both groups of cylinders, as can be seen from FIGS. 2 and 3.
  • the oxygen charge of the individual catalysts caused by the forced excitation is adapted to changes in the oxygen storage capacity of the individual catalysts due to alteration (aging adaptation).
  • a cylinder-related trim control of the mixture is carried out for each of the individual catalytic converters K1 to K4.
  • the procedure is preferably as follows:
  • the cylinder-individual forced excitation is adapted to the oxygen storage capacity of the individual catalytic converters such that the oxygen charge of the individual catalytic converters caused by the forced excitation reaches a target oxygen charge in the order of magnitude of its oxygen storage capacity at the end of each lean mixture half-cycle.
  • the oxygen storage capacity of the individual catalysts is, for example, 10 mg
  • the probe signal ⁇ LS1 which in the example is shown only taking into account the two cylinders Z1 and Z2, has a constant course over the major part of the duration of a ⁇ pulse. This constant course results from the oxygen storage of the individual catalysts K1 to K4.
  • the signal of the lambda probe LS1 shown in FIG. 4 also shows signal deviations ⁇ , which result from lean mixture breakthroughs and fat mixture breakthroughs of the catalytic converters K1 and K2.
  • the oxygen storage of Kl and K2 have to some extent overflowed.
  • the signal from the lambda Probe LS1 Cycle-resolved Cylinder-related lambda signals ⁇ Zl and ⁇ Z2 reconstructed as shown in the lower halves of FIGS. 2 and 3 are shown.
  • the reconstructed signals ⁇ Z1 and ⁇ Z2 have constant waveforms as well as signal deviations ⁇ as shown in the lower halves of FIGS. 2 and 3 can be seen.
  • the trim control on the one hand it is necessary to determine from constant curves of the reconstructed signals ⁇ Z1 and ⁇ Z2 over all cylinders a mean reference value ⁇ ref, which forms the measure for the catalyst window.
  • the signal-like aberrations ⁇ of the reconstructed lambda signals ⁇ Z1, ⁇ Z2, which result from corresponding lean-mixture or rich-mixture breakthroughs of the individual catalysts, are to be interpreted as rich or lean interferences. These signal deviations ⁇ then cause a corresponding reaction of the trim control.
  • the reference value ⁇ ref determined from the constant signal curves of the reconstructed lambda signals thus serves as the reference variable and the signal deviations ⁇ as the control deviation.
  • the controller type used depends on the possible speed of the reconstruction of the cylinder-related lambda signals ⁇ Z1, ⁇ Z2. At high speed of Signalrekonstruk ⁇ tion a trim controller with P and I component is used, while at low speed of the signal reconstruction, a trim controller with I component is used.
  • An advantage of the described cylinder-related trim control of the mixture for the individual cylinders is that in obtaining the average lambda reference value ⁇ ref over all cylinders a possible offset error of the lambda probe LS1 does not affect the measurement result.
  • a Nachkat- probe as the lambda probe LS2 for offset error compensation is therefore not mandatory.
  • the cylinder-related trim control of a conventional and commonly used average trim control can be superimposed over all cylinders Z1 to Z4 in which the signal of the downstream lambda sensor LS2 serves as a monitor signal.
  • This superimposed average value trim control serves to stabilize the exhaust gas purification over the service life.
  • measures are provided to deactivate the cylinder-related trim control if, when monitoring the oxygen storage capacity of the individual catalytic converters K1-K4, it is determined that the oxygen storage capacity of one of the individual catalytic converters is less than its oxygen charge required by the forced excitation.
  • the cylinder-related trim control would lead to false results, since lean-mixture and fat mixture breakthroughs of the individual catalytic converters can not be distinguished from breakthroughs due to cylinder-specific differences due to the forced excitation.
  • the lambda control provided for the main catalytic converter HK which can be formed, for example, as described in the above-cited manual "Internal combustion engine manual", takes into account the oxygen storage capacity of the individual catalytic converters K 1 to K 4.
  • the lambda controller usually uses a PII 2 D controller with a P-component, an I-component, an I 2 component and a D-component, as well as a ne limitation due to non-stationary conditions.
  • the gas running time and the deceleration behavior of the lambda probe are also taken into account.
  • an average trim control can be provided for a characteristic shift of the signal of the lambda sensor LS1 by means of the signal of the downstream lambda sensor LS2.
  • the oxygen storage capacity of the individual catalytic converters K1 through K4 can be taken into account, for example, by detecting the time duration between a changeover of the fuel injection and a deviation ⁇ of the relevant cylinder-related lambda signal ⁇ 1 or X2 (FIGS. 2, 3) caused thereby. If a lean mixture or fat mixture breakthrough of a single catalyst takes place, this can be recognized by the corresponding switchover of the fuel injection. This time is thus known be ⁇ . In addition, the time of the change in the cylinder-related lambda signal caused thereby can be detected. Thus, the elapsed time between these two times can be detected.
  • the controller parameters of the lambda controllers can be adapted to the detected time duration. For example, the larger the corresponding time duration (dead time), the slower will be the e.g. the corresponding controller parameters (I-part) made.
  • Main catalyst HK between operating states with constant signal waveforms and operating states with signal deviations of the cylinder-related lambda signals ⁇ l, X2 differs and their behavior by a corresponding adjustment of the Regler ⁇ parameters and / or controller structure adapts to these two Radio- states.
  • the lambda control thus differentiates between that operating state in which oxygen is stored in the individual catalytic converters and therefore the signal of the lambda sensor LS1 is extremely sluggish (idealized assuming a constant course) and an operating state in which a lean mixture or Fat mixture breakthrough of the individual catalysts takes place and therefore a signal deviation of the lambda signal LSl can be detected immediately.
  • the lambda control performs a case discrimination by, for example, switching over the controller parameters.
  • Another or additional measure may be the switching over of the controller structure, for example, by making only one P controller from a PI controller and then switching on the I component subsequently.
  • the control quality of the lambda control for the main catalytic converter HK is increased by taking into account the different operating states of the lambda control in the form of parameter adaptations and / or structural changes.
  • the upstream lambda probe LSl is designed as a continuous probe. However, it can also be a binary lambda probe without any change in the basic principle of the present invention.

Abstract

According to one embodiment of the inventive method, half the cylinders of an in-line cylinder arrangement or the entire internal combustion engine are forcibly excited cylinder-specifically in opposite direction to the other half of the cylinders in order to balance the cylinder-specific total torque. According to another embodiment of the invention, trim regulation which compensates differences between the air quantities and/or fuel quantities introduced into the individual cylinders with the aid of the signal of a joint lambda probe is done cylinder-specifically for the individual catalytic converters. The invention also relates to lambda regulation for the joint main catalytic converter (HK) mounted downstream of the cylinder-specific individual catalytic converters (K1-K4).

Description

Beschreibungdescription
Verfahren zur Gemischregelung einer Otto-Mehrzylinder-Brenn¬ kraftmaschine mit zylinderbezogenen Einzelkatalysatoren und einem den Einzelkatalysatoren nachgeschalteten gemeinsamen HauptkatalysatorProcess for the mixture control of an Otto multi-cylinder internal combustion engine with cylinder-related individual catalysts and a common main catalyst downstream of the individual catalytic converters
Zur Reinigung des Abgases von Otto-Brennkraftmaschinen wird heute üblicherweise ein lambdageregelter 3-Wege-Katalysator verwendet, dem gegebenenfalls ein motornaher Vorkatalysator vorgeschaltet ist. Eine übliche Lambda-Regelung für den allen Zylindern gemeinsamen Hauptkatalysator und gegebenenfalls vorgesehenen Vorkatalysator ist beispielsweise in „Handbuch Verbrennungsmotor", 2. Aufl., von Richard van Basshuysen/Fred Schäfer, S. 559 bis 561 beschrieben. Die Lambda-Regelung re¬ gelt das Luft-Kraftstoff-Verhältnis Lambda (λ) mit Hilfe von Signalen einer dem Hauptkatalysator vorgeschalteten Lambda- Sonde (Vorkat-Sonde) und gegebenenfalls einer dem Hauptkata¬ lysator nachtgeschalteten Lambda-Sonde (Nachkat-Sonde) . Die Lambda-Regelung umfasst üblicherweise eine so genannteFor cleaning the exhaust gas of gasoline internal combustion engines, a lambda-controlled 3-way catalytic converter is usually used today, optionally preceded by a close-coupled precatalyst. A conventional lambda control for the main catalyst common to all cylinders and optionally provided precatalyst is described, for example, in "Handbuch Verbrennungsmotor", 2nd edition, by Richard van Basshuysen / Fred Schäfer, pages 559 to 561. The lambda control regulates the air-fuel ratio lambda (λ) with the aid of signals from a lambda probe (pre-catalyst probe) connected upstream of the main catalytic converter and, if appropriate, a lambda probe connected downstream from the main catalytic converter (aftercattern sensor) so-called
Zwangsanregung, die einem stöchiometrischen Lambda-Sollwert eine periodische Schwankung in Form eines λ-Pulses zur Opti¬ mierung des Katalysatorwirkungsgrades überlagert. Die Lambda- Regelung umfasst ferner üblicherweise eine so genannte Füh- rungs- oder Trimmregelung, durch die das Signal der Vorkat- Sonde in Abhängigkeit von dem Signal der Nachkat-Sonde korri¬ giert wird, um alterungsbedingte Mess-Fehler der Vorkat-Sonde auszugleichen. Wegen weiterer Einzelheiten einer derartigen herkömmlichen Lambda-Regelung mit Zwangsanregung und Füh- rungs- bzw. Trimmregelung sei auf die genannte Literatur¬ stelle Bezug genommen. Bei der vorbekannten Lambda-Regelung handelt es sich um eine über sämtliche Zylinder gemittelte Regelung, die zylinderspe¬ zifische Besonderheiten nicht berücksichtigen kann. Aus der DE 102 06 402 Cl ist bereits ein Verfahren für eine zylinder- selektive Lambda-Regelung bekannt geworden, bei dem das Sig¬ nal der Lambda-Sonde (Vorkat-Sonde) durch einen Mikrokontrol- ler zyklenaufgelöst wird, so dass das Lambda-Signal den ein¬ zelnen Zylindern zugeordnet und somit einzelne Abgaspakete dieser Zylinder erfasst werden können.Forced excitation, which superimposes a periodic variation in the form of a λ-pulse for optimizing the catalyst efficiency to a stoichiometric lambda desired value. The lambda control furthermore usually comprises a so-called control or trim control, by means of which the signal of the pre-catalyst probe is corrected as a function of the signal of the post-cat probe in order to compensate for age-related measurement errors of the pre-cat probe. For further details of such a conventional lambda control with forced excitation and guidance or trim regulation, reference should be made to the cited reference. In the previously known lambda control is averaged over all cylinders control, which can not take into account cylindrically specific features. A method for a cylinder-selective lambda control has already become known from DE 102 06 402 C1, in which the signal of the lambda probe (pre-catalyst probe) is cyclically resolved by a microcontroller, so that the lambda Signal to individual cylinders assigned and thus individual exhaust gas packets of these cylinders can be detected.
Der vorliegenden Erfindung liegt die Aufgabe zugrunde, ein Verfahren zur Gemischregelung einer Otto-Mehrzylinder-Brenn¬ kraftmaschine mit zylinderbezogenen Einzelkatalysatoren und einem den Einzelkatalysatoren nachgeschalteten gemeinsamen Hauptkatalysator anzugeben, bei dem eine zylinderbezogene Ge¬ mischregelung mit Hilfe einer den Einzelkatalysatoren gemein¬ samen Lambda-Sonde ermöglicht wird.The present invention has for its object to provide a method for controlling the mixture of an Otto multi-cylinder Brenn¬ combustion engine with cylinder-related individual catalysts and the individual catalysts downstream common main catalyst, in which a cylinder-related Ge mixed control using a common lambda probe the individual catalysts is possible.
Die Erfindung sowie vorteilhafte Ausgestaltungen der Erfin- düng sind in den Ansprüchen definiert.The invention and advantageous embodiments of the invention düng are defined in the claims.
Die vorliegende Erfindung geht von einer Systemkonfiguration aus, bei der den einzelnen Zylindern jeweils ein Einzelkata¬ lysator zugeordnet und ein den Einzelkatalysatoren nachge- schalteter gemeinsamer Hauptkatalysator vorgesehen ist. Die Einzelkatalysatoren sind möglichst nahe an der Brennkraftma¬ schine angeordnet und können z.B. in Direktmontage in den je¬ weiligen Krümmern installiert sein, um ein möglichst kurz¬ fristiges „Anspringen" der Einzelkatalysatoren zu erreichen. Zum Erfassen des Luft-Kraftstoff-Verhältnisses λ ist eine den Einzelkatalysatoren nachgeschaltete gemeinsame Lambda-Sonde vorgesehen. Die Katalysatoren sind jeweils als 3-Wege-Katalysatoren aus¬ gebildet, wobei die Einzelkatalysatoren eine vorgegebene, je¬ doch relativ geringe SauerstoffSpeicherfähigkeit haben. Die zylinderbezogene Lambda-Regelung umfasst eine zylinderbezoge- ne Zwangsanregung, durch die einem mittleren Lambda-Sollwert jeweils eine periodische Schwankung in Form von Magergemisch- und Fettgemisch-Halbwellen aufmoduliert wird.The present invention is based on a system configuration in which the individual cylinders are each assigned a single catalytic converter and a common main catalytic converter connected downstream of the individual catalytic converters is provided. The individual catalytic converters are arranged as close as possible to the internal combustion engine and can, for example, be installed directly in the respective manifolds in order to achieve the shortest possible "light-off" of the individual catalytic converters provided the individual catalysts downstream common lambda probe. The catalysts are each formed as 3-way catalysts Aus¬, wherein the individual catalysts have a predetermined, but relatively low oxygen storage capacity. The cylinder-related lambda control comprises a cylinder-related forced excitation, by means of which a mean lambda nominal value is modulated in each case by a periodic fluctuation in the form of lean-mixture and rich-compound half-waves.
Gemäß einem ersten Aspekt der Erfindung wird die zylinderbe- zogene Zwangsanregung, falls die Zylinderzahl der gesamten Brennkraftmaschine oder zumindest einer Zylinderbank gerad¬ zahlig ist, für eine Hälfte der Zylinder jeweils gegensinnig zu derjenigen der anderen Hälfte durchgeführt, um einen Aus¬ gleich der zylinderbezogenen Drehmomentbeiträge der Zylinder zu erzielen. So werden z.B. bei einem 4-Zylinder-Motor zweiAccording to a first aspect of the invention, the cylinder-related forced excitation, if the number of cylinders of the entire internal combustion engine or at least one cylinder bank is even-numbered, is carried out in opposite directions to that of the other half for one half of the cylinders to compensate for the cylinder-related torque contributions to achieve the cylinder. Thus, e.g. in a 4-cylinder engine two
Zylinder „angefettet" und gleichzeitig die anderen beiden Zy¬ linder „abgemagert". Hierdurch lässt sich ein vollständiger Drehmomentenausgleich realisieren. Ein weiterer Vorteil die¬ ser Lösung besteht darin, dass sich dies in einfacher Weise durch das an sich bekannte Verfahren der Zwangsanregung er¬ reichen lässt.Cylinder "greased" and at the same time the other two Zy¬ cylinder "emaciated". This makes it possible to realize a complete torque compensation. Another advantage of this solution is that this can be achieved in a simple manner by the per se known method of forced excitation.
Um die konvertierende Wirkung der zylinderbezogenen Einzelka¬ talysatoren auch bei dynamischen Gemischstörungen (z.B. bei instationären Betriebszuständen) aufrechtzuerhalten, wird die durch die Zwangsanregung hervorgerufene Sauerstoffbeladung der Einzelkatalysatoren zweckmäßigerweise an alterungsbe¬ dingte Änderungen der SauerstoffSpeicherfähigkeit angepasst. Diese Adaption ist unter Beibehaltung der Drehmomentengleich- Stellung möglich.In order to maintain the converting effect of the cylinder-related individual catalysts even in dynamic mixture disturbances (for example in transient operating conditions), the oxygen charge of the individual catalysts caused by the forced excitation is expediently adapted to changes in the oxygen storage capacity which are due to aging. This adaptation is possible while maintaining the torque equalization position.
Ein weiterer Vorteil dieser Lösung besteht darin, dass die Einzelkatalysatoren innerhalb des Bereiches ihrer Sauerstoff- Speicherfähigkeit betrieben werden können; d.h., die Zwangs¬ anregung muss nicht zwingend soweit ausgesteuert werden, bis die Einzelkatalysatoren an die Grenze ihrer SauerstoffSpei¬ cherfähigkeit im stationären Betrieb kommen.Another advantage of this solution is that the individual catalysts are within the range of their oxygen Storage capability can be operated; that is, the forced excitation does not necessarily have to be controlled until the individual catalytic converters reach the limit of their oxygen storage capacity in steady-state operation.
Gemäß einem zweiten Aspekt der Erfindung ist eine Trimmrege¬ lung des Gemisches für jeden der Einzelkatalysatoren vorgese¬ hen, wobei das Luft-Kraftstoff-Verhältnis stromab der Einzel¬ katalysatoren mit nur einer gemeinsamen Lambda-Sonde erfasst wird. Da bei der gegebenen Systemkonfiguration Unterschiede zwischen den in die einzelnen Zylinder eingebrachten Luft- und/oder Kraftstoffmassen (Füllungsunterschiede und Unter¬ schiede der eingespritzten Kraftstoffmassen) den Betrieb der zylinderbezogenen Einzelkatalysatoren beeinflussen, ist ein Betrieb der Einzelkatalysatoren mit einem Luft-Kraftstoff- Verhältnis (λ) innerhalb des so genannten Katalysatorfensters nicht gewährleistet. Eine maximale Nutzung der Einzelkataly¬ satoren ist bekanntlich jedoch nur dann möglich, wenn alle Einzelkatalysatoren wirkungsgradoptimiert im Katalysatorfens- ter betrieben werden. Erfindungsgemäß wird daher das Gemisch für jeden der Katalysatoren einer zylinderbezogenen Trimmre¬ gelung unterzogen.According to a second aspect of the invention, a trim control of the mixture is provided for each of the individual catalytic converters, the air-fuel ratio being detected downstream of the individual catalytic converters with only one common lambda probe. Since differences in the given system configuration between the air and / or fuel masses introduced into the individual cylinders (filling differences and differences in the injected fuel masses) influence the operation of the cylinder-related individual catalytic converters, operation of the individual catalytic converters with an air-fuel ratio (λ ) within the so-called catalyst window is not guaranteed. However, maximum utilization of the individual catalytic converters is known to be possible only if all individual catalytic converters are operated with optimized efficiency in the catalyst window. According to the invention, therefore, the mixture is subjected to a cylinder-related trim control for each of the catalysts.
Bei dem erfindungsgemäßen Verfahren werden aus dem Signal der gemeinsamen Lambda-Sonde zyklenaufgelöst zylinderbezogene Lambda-Signale rekonstruiert, und mit Hilfe dieser rekon¬ struierten zylinderbezogenen Lambda-Signale wird dann eine zylinderbezogene Trimmregelung durchgeführt.In the method according to the invention, cylinder-related lambda signals are reconstructed in a cycle-resolved manner from the signal of the common lambda probe, and a cylinder-related trim control is then carried out with the aid of these reconstructed cylinder-related lambda signals.
Hierbei wird vorzugsweise so vorgegangen, dass vorab die zy¬ linderindividuelle Zwangsanregung an die SauerstoffSpeicher¬ fähigkeit der Einzelkatalysatoren so angepasst wird, dass die durch die Zwangsanregung hervorgerufene Sauerstoffbeladung der Einzelkatalysatoren am Ende jeder Magergemisch-Halbwelle der Zwangsanregung eine Ziel-Sauerstoffbeladung in der Grö¬ ßenordnung ihrer SauerstoffSpeicherfähigkeit erreicht, aus konstanten Verläufen der rekonstruierten zylinderbezogenen Lambda-Signale über alle Zylinder ein im Katalysatorfenster liegender mittlerer Referenzwert gewonnen wird und dieser mittlere Referenzwert als Führungsgröße und Signalabweichun¬ gen der rekonstruierten zylinderbezogenen Lambda-Signale von dem mittleren Lambda-Referenzwert als Regelabweichung der Trimmregelung verwendet werden.In this case, the procedure is preferably such that the zyzinderindividual forced excitation of the oxygen storage capacity of the individual catalytic converters is adjusted in advance so that the oxygen charge caused by the forced excitation the individual catalysts at the end of each lean mixture half-wave of the forced excitation reaches a target oxygen loading in the order of their SauerstoffSpeicherfähigkeit, from constant curves of the reconstructed cylinder-related lambda signals over all cylinders a lying in the catalyst window mean reference value is obtained and this mean reference value as a reference variable and Signal deviations of the reconstructed cylinder-related lambda signals from the average lambda reference value can be used as the control deviation of the trim control.
Die erfindungsgemäß vorgesehene Trimmregelung macht sich so¬ mit die SauerstoffSpeicherfähigkeit der Einzelkatalysatoren zunutze. Die konstanten Verläufe der zylinderbezogenen Lamb¬ da-Signale ergeben sich dabei infolge der Sauerstoffspei¬ cherung der Einzelkatalysatoren, und sie bilden gewissermaßen den Bezugspunkt für die Bestimmung der zylinderbezogenen Ab¬ weichungen des Luft-Kraftstoff-Verhältnisses.The inventively provided trim control makes so¬ with the oxygen storage capacity of the individual catalysts advantage. The constant courses of the cylinder-related lambda signals result from the oxygen storage of the individual catalytic converters, and to a certain extent form the reference point for the determination of the cylinder-related deviations of the air-fuel ratio.
Die Erfindung ermöglicht somit eine stöchiometrische Gemisch- trimmung jedes der zylinderbezogenen Einzelkatalysatoren mit einer einzigen Lambda-Sonde, um alle Einzelkatalysatoren im Katalysatorfenster zu betreiben und somit den maximalen Wir- kungsgrad der Einzelkatalysatoren langstabil zu erreichen.The invention thus makes possible a stoichiometric mixture trimming of each of the cylinder-related individual catalytic converters with a single lambda probe in order to operate all the individual catalytic converters in the catalyst window and thus achieve the maximum efficiency of the individual catalytic converters for a long time.
Je nach möglicher Geschwindigkeit der Rekonstruktion der zy¬ linderbezogenen Lambda-Signale wird die Trimmregelung zweck¬ mäßigerweise mit einem P- und I-Anteil (hohe Geschwindigkeit der Signalrekonstruktion) oder mit nur einem I-Anteil (ge¬ ringe Geschwindigkeit der Signalrekonstruktion) durchgeführt. Falls erforderlich, kann der zylinderbezogenen Trimmregelung für die Einzelkatalysatoren die heute übliche, standardmäßig eingesetzte Mittelwert-Trimmregelung über alle Zylinder zur Korrektur von altersbedingten Messfehlern der Lambda-Sonde überlagert werden.Depending on the possible speed of the reconstruction of the cylinder-related lambda signals, the trim control is expediently carried out with a P and I component (high speed of the signal reconstruction) or with only one I component (ring speed of the signal reconstruction). If necessary, the cylinder-based trimming control for the individual catalytic converters can be superimposed on the mean value trim control that is standard today across all cylinders for correcting age-related measurement errors of the lambda probe.
Ein weiterer Vorteil der Erfindung besteht darin, dass bei der Bestimmung des mittleren Lambda-Sollwertes aus konstanten Verläufen der zylinderbezogenen Lambda-Signale über alle Zy- linder ein Offset-Fehler der Lambda-Sonde das Messergebnis nicht beeinflusst. Eine zusätzliche Lambda-Sonde zur Offset- Fehlerkompensation ist daher nicht zwingend erforderlich, wenngleich sie natürlich vorgesehen werden kann.A further advantage of the invention is that when determining the average lambda setpoint value from constant curves of the cylinder-related lambda signals over all cylinders, an offset error of the lambda probe does not affect the measurement result. An additional lambda probe for offset error compensation is therefore not absolutely necessary, although it can of course be provided.
Ein dritter Aspekt der Erfindung betrifft die Lambda-Regelung für den Einzelkatalysatoren nachgeschalteten Haupt¬ katalysator. In diesem Zusammenhang ist erfindungsgemäß vor¬ gesehen, dass bei der Definition der Parameter der in übli¬ cher Weise ausgelegten Lambda-Regelung für den Hauptkatalysa- tor und einer gegebenenfalls vorgesehenen Mittelwert-Trimmre¬ gelung die SauerstoffSpeicherfähigkeit der Einzelkatalysato¬ ren berücksichtigt wird. Diese Berücksichtigung erfolgt zweckmäßigerweise durch eine Berücksichtigung der Zeitdauer, die zwischen einer durch einen Fettgemisch- oder Magerge- misch-Durchbruch eines Einzelkatalysators verursachten Um- schaltung der Kraftstoffeinspritzung und der hierdurch her¬ vorgerufenen Signalabweichung des betreffenden zylinderbezo¬ genen Lambda-Signals verstreicht.A third aspect of the invention relates to the lambda control for the individual catalysts downstream Haupt¬ catalyst. In this connection, it is provided according to the invention that the oxygen storage capacity of the individual catalytic converters is taken into account in the definition of the parameters of the lambda control for the main catalytic converter, which is designed in a conventional manner, and an optionally provided average trim control. This consideration is expediently carried out by taking into account the time duration which elapses between a switching of the fuel injection caused by a rich mixture or lean mixture breakthrough of an individual catalytic converter and the signal deviation of the respective cylinder-related lambda signal caused thereby.
Ferner ist zweckmäßigerweise vorgesehen, dass die Lambda-Re¬ gelung für den Hauptkatalysator zwischen Betriebszuständen mit konstanten Signalverläufen (SauerstoffSpeicher nicht ü- bergelaufen) und Betriebszuständen mit Signalabweichungen der zylinderbezogenen Lambda-Signale (SauerstoffSpeicher überge¬ laufen) unterscheidet und ihr Verhalten durch eine entspre¬ chende Anpassung der Reglerparameter und/oder Reglerstruktur an diese beiden Betriebszustände anpasst.Furthermore, it is expediently provided that the lambda control for the main catalytic converter between operating states with constant signal curves (oxygen reservoir does not overflow) and operating states with signal deviations of cylinder-related lambda signals (oxygen storage überge¬ run) differs and adapts their behavior by a corre sponding ch adaptation of the controller parameters and / or controller structure to these two operating states.
Diese Maßnahmen ermöglichen eine Erhöhung der Regelgüte der Lambda-Regelung für den Hauptkatalysator durch Berücksichti¬ gung der unterschiedlichen Betriebszustände der Lambda-Rege¬ lung in Form von Adaption der Reglerparameter und/oder Struk- turumschaltungen der Regelung.These measures make it possible to increase the control quality of the lambda control for the main catalytic converter by taking into account the different operating states of the lambda control in the form of adaptation of the controller parameters and / or structural switching of the control.
Ein genereller Vorteil der beschriebenen Aspekte der vorlie¬ genden Erfindung liegt darin, dass die für die Einzelkataly¬ satoren gemeinsame Lambda-Sonde eine binäre oder stetige Son- de sein kann und das Signal dieser Lambda-Sonde als Füh¬ rungsgröße für die Gemischregelung von mehreren zylinderbezo¬ genen Einzelkatalysatoren verwendet werden kann.A general advantage of the described aspects of the present invention is that the lambda probe common to the individual catalytic converters can be a binary or continuous probe and the signal of this lambda probe can be used as a guide variable for the mixture control of several cylinder-specific single catalysts can be used.
Anhand der Zeichnung werden weitere Einzelheiten der Erfin- düng erläutert. Es zeigt:With reference to the drawing, further details of the invention are explained düng. It shows:
Fig. 1 ein schematisches Diagramm einer Systemkonfigurati¬ on für die Abgasnachbehandlung einer 4-Zylinder- Brennkraftmaschine;1 is a schematic diagram of a Systemkonfigurati¬ on for the exhaust aftertreatment of a 4-cylinder internal combustion engine.
Fig. 2 einen λ-Puls einer Zwangsanregung und ein rekon¬ struiertes λ-Signal für einen ersten Zylinder der Brennkraftmaschine;FIG. 2 shows a λ pulse of a forced excitation and a reconstructed λ signal for a first cylinder of the internal combustion engine; FIG.
Fig. 3 einen λ-Puls und ein rekonstruiertes λ-Signal für einen zweiten Zylinder; Fig. 4 das Signal einer gemeinsamen Lambda-Sonde unter Be¬ rücksichtigung der beiden Zylinder entsprechend Fig. 2 und 3.FIG. 3 shows a λ pulse and a reconstructed λ signal for a second cylinder; FIG. 4 shows the signal of a common lambda probe taking into account the two cylinders according to FIGS. 2 and 3.
Fig. 1 zeigt ein Beispiel einer Systemkonfiguration gemäß der Erfindung für eine 4-Zylinder-Otto-Brennkraftmaschine BKM mit vier Zylindern Z1-Z4, zylinderbezogenen Einzelkatalysatoren K1-K4 und einem den Einzelkatalysatoren nachgeschalteten Hauptkatalysator HK. Zwischen den Einzelkatalysatoren K1-K4 und dem Hauptkatalysator HK ist im gemeinsamen Abgastrakt ei¬ ne Lambda-Sonde LSl angeordnet, deren Signal einem elektro¬ nischen Betriebssteuergerät ECU zugeführt wird. Dem Hauptka¬ talysator HK ist zweckmäßigerweise eine weitere Lambda-Sonde LS2 nachgeschaltet, deren Signal ebenfalls dem Betriebssteu- ergerät ECU zugeführt wird. Das elektronische Betriebssteuer¬ gerät führt eine Gemischregelung in Form einer zylinderbezo¬ genen Lambda-Regelung durch, um das Luft-Kraftstoff-Verhält¬ nis λ der Zylinder Z1-Z4 zu regeln.1 shows an example of a system configuration according to the invention for a four-cylinder Otto internal combustion engine BKM with four cylinders Z1-Z4, individual cylinder-related catalysts K1-K4 and a main catalytic converter HK connected downstream of the individual catalytic converters. Between the individual catalytic converters K1-K4 and the main catalytic converter HK, a lambda sensor LS1 is arranged in the common exhaust gas tract, the signal of which is fed to an electronic operating control unit ECU. The main catalytic converter HK is expediently followed by a further lambda sensor LS2 whose signal is likewise supplied to the operating control device ECU. The electronic Betriebssteuer¬ device performs a mixture control in the form of a cylinder-related lambda control to regulate the air-fuel ratio λ λ of the cylinder Z1-Z4.
Die Lambda-Regelung umfasst eine zylinderbezogene Zwangsanre¬ gung in Form eines λ-Pulses, der einem mittleren Lambda- Sollwert (0,998) aufmoduliert wird und somit Magergemisch- Halbwellen (λ = 1,028) und Fettgemisch-Halbwellen (λ = 0,968) erzeugt, siehe die oberen Kurven der Figuren 2 und 3.The lambda control comprises a cylinder-related Zwangsanre¬ supply in the form of a λ-pulse, which is modulated on a mean lambda setpoint (0.998) and thus produces lean-half-waves (λ = 1.028) and half-wave fat (λ = 0.968), see the upper curves of Figures 2 and 3.
Gemäß dem ersten Aspekt der Erfindung wird, wie bereits ein¬ gangs erläutert, die zylinderbezogene Zwangsanregung für eine Hälfte der Zylinder jeweils gegensinnig zu derjenigen für die andere Hälfte der Zylinder durchgeführt. So werden beispiels- weise den Magergemisch-Halbwellen der Zylinder Zl und Z3 die Fettgemisch-Halbwellen der Zylinder Z2 und Z4 zugeordnet (und umgekehrt) , wie durch einen Vergleich der Figuren 2 und 3 deutlich wird. Dies ermöglicht einen vollständigen Ausgleich der Drehmomentbeiträge der Zylinder, sofern eine geradzahlige Zylinderzahl pro Bank oder pro gesamter Brennkraftmaschine vorgesehen ist.According to the first aspect of the invention, as already explained in the introduction, the cylinder-related forced excitation for one half of the cylinders is in each case carried out in the opposite sense to that for the other half of the cylinders. Thus, for example, the lean-mixture half-waves of the cylinders Z1 and Z4 are assigned to the lean-mixture half-waves of the cylinders Z2 and Z4 (and vice versa), as becomes clear from a comparison of FIGS. 2 and 3. This allows complete compensation the torque contributions of the cylinder, provided that an even number of cylinders per bank or per entire internal combustion engine is provided.
Die Dauer und Amplitude der λ-Pulse der Zwangsanregung werden hierbei für beide Zylindergruppen gleich gewählt, wie eben¬ falls aus den Figuren 2 und 3 ersichtlich ist.The duration and amplitude of the λ pulses of the forced excitation are selected to be the same for both groups of cylinders, as can be seen from FIGS. 2 and 3.
Um die konvertierende Wirkung der zylinderbezogenen Einzelka- talysatoren Kl bis K4 auch bei dynamischen Gemischstörungen aufrechtzuerhalten, wird die durch die Zwangsanregung hervor¬ gerufene Sauerstoffbeladung der Einzelkatalysatoren an alte¬ rungsbedingte Änderungen der SauerstoffSpeicherfähigkeit der Einzelkatalysatoren angepasst (Alterungsadaption) .In order to maintain the converting effect of the cylinder-related individual catalysts K1 to K4 even with dynamic mixture disturbances, the oxygen charge of the individual catalysts caused by the forced excitation is adapted to changes in the oxygen storage capacity of the individual catalysts due to alteration (aging adaptation).
Bei der gegebenen Systemkonfiguration gemäß Fig. 1 beeinflus¬ sen Unterschiede der in die einzelnen Zylinder Zl bis Z4 ein¬ gebrachten Luft- und/oder Kraftstoffmassen den Betrieb der Einzelkatalysatoren Kl bis K4, so dass es zu Abweichungen der zylinderspezifisch eingeregelten Lambda-Werte von dem optima¬ len Lambda-Sollwert kommen kann. Diese Abweichungen können in der Größenordnung von + 3% liegen. Ohne zusätzliche Maßnahmen würden dann die Einzelkatalysatoren nicht mehr wirkungsgrad¬ optimiert im Katalysatorfenster betrieben werden.In the given system configuration according to FIG. 1, differences in the air and / or fuel masses introduced into the individual cylinders Z1 to Z4 affect the operation of the individual catalytic converters K1 to K4, so that there are deviations of the cylinder-specific adjusted lambda values from the Optimal Lambda setpoint can come. These deviations can be on the order of + 3%. Without additional measures, the individual catalysts would then no longer be operated in the catalyst window in an optimized manner.
Um diese Abweichungen der zylinderspezifischen Lambda-Werte von dem optimalen Lambda-Sollwert zu kompensieren, wird gemäß dem zweiten Aspekt der Erfindung eine zylinderbezogene Trimm¬ regelung des Gemisches für jeden der Einzelkatalysatoren Kl bis K4 durchgeführt. Hierbei wird vorzugsweise wie folgt vor¬ gegangen: Vorab wird die zylinderindividuelle Zwangsanregung an die SauerstoffSpeicherfähigkeit der Einzelkatalysatoren so ange- passt, dass die durch die Zwangsanregung hervorgerufene Sau¬ erstoffbeladung der Einzelkatalysatoren am Ende jeder Mager- gemisch-Halbwelle eine Ziel-Sauerstoffbeladung in der Größen¬ ordnung ihrer SauerstoffSpeicherfähigkeit erreicht. Beträgt die SauerstoffSpeicherfähigkeit der Einzelkatalysatoren bei¬ spielsweise 10 mg, die Amplitude der Zwangsanregung 0,3 (λ = 1,03) und eine Zylinderfüllung MAF = 200 mg/Hub, so lässt sich hieraus berechnen, dass ca. 7 Magerhalbwellen und somit 7 Arbeitsspiele erforderlich sind, um die Ziel-Sauer- stoffbeladung des betreffenden Einzelkatalysators unter den angenommenen Randbedingungen zu erzielen. Die Zwangsanregung wird daher in diesem Beispiel so ausgelegt, dass sich jede Magergemisch-Halbwelle und jede Fettgemisch-Halbwelle des X- Pulses über 7 Arbeitsspiele erstreckt.In order to compensate for these deviations of the cylinder-specific lambda values from the optimum lambda desired value, according to the second aspect of the invention, a cylinder-related trim control of the mixture is carried out for each of the individual catalytic converters K1 to K4. In this case, the procedure is preferably as follows: In advance, the cylinder-individual forced excitation is adapted to the oxygen storage capacity of the individual catalytic converters such that the oxygen charge of the individual catalytic converters caused by the forced excitation reaches a target oxygen charge in the order of magnitude of its oxygen storage capacity at the end of each lean mixture half-cycle. If the oxygen storage capacity of the individual catalysts is, for example, 10 mg, the amplitude of the forced excitation 0.3 (λ = 1.03) and a cylinder charge MAF = 200 mg / stroke, it can be calculated from this that approximately 7 lean half-waves and thus 7 working cycles necessary to achieve the target oxygen loading of the individual catalytic converter under the assumed boundary conditions. Forced excitation is therefore designed in this example so that each lean half-wave and each fat mix half-wave of the X-pulse extends over 7 cycles.
Diese Voraussetzungen führen zu einem Signal λLSl der Lambda- Sonde LSl, wie es beispielsweise in Fig. 4 dargestellt ist. Wie ersichtlich, hat das Sondensignal λLSl, das im Beispiel nur unter Berücksichtung der beiden Zylinder Zl und Z2 darge¬ stellt ist, über den größten Teil der Dauer eines λ-Pulses einen konstanten Verlauf. Dieser konstante Verlauf ergibt sich infolge der Sauerstoffspeicherung der Einzelkatalysato- ren Kl bis K4. Das in Fig. 4 dargestellte Signal der Lambda- Sonde LSl zeigt ferner Signalabweichungen Δλ, die von Mager¬ gemisch-Durchbrüchen und Fettgemisch-Durchbrüchen der Kataly¬ satoren Kl und K2 herrühren. Die SauerstoffSpeicher von Kl und K2 sind gewissermaßen übergelaufen.These prerequisites lead to a signal λ LS1 of the lambda sensor LS 1, as illustrated, for example, in FIG. 4. As can be seen, the probe signal λLS1, which in the example is shown only taking into account the two cylinders Z1 and Z2, has a constant course over the major part of the duration of a λ pulse. This constant course results from the oxygen storage of the individual catalysts K1 to K4. The signal of the lambda probe LS1 shown in FIG. 4 also shows signal deviations Δλ, which result from lean mixture breakthroughs and fat mixture breakthroughs of the catalytic converters K1 and K2. The oxygen storage of Kl and K2 have to some extent overflowed.
Für die zylinderbezogene Trimmregelung, die von dem elektro¬ nischen Betriebssteuergerät ECU oder auch einem gesonderten Regler durchgeführt wird, werden aus dem Signal der Lambda- Sonde LSl zyklenaufgelöst zylinderbezogene Lambda-Signale λZl und λZ2 rekonstruiert, wie sie in den unteren Hälften der Fign. 2 und 3 dargestellt sind. Die rekonstruierten Signale λZl und λZ2 haben konstante Verläufe sowie Signalabweichungen Δλ, wie in den unteren Hälften der Fign. 2 und 3 zu sehen ist.For the cylinder-related trim control, which is performed by the electronic operating control unit ECU or else a separate controller, the signal from the lambda Probe LS1 Cycle-resolved Cylinder-related lambda signals λZl and λZ2 reconstructed as shown in the lower halves of FIGS. 2 and 3 are shown. The reconstructed signals λZ1 and λZ2 have constant waveforms as well as signal deviations Δλ as shown in the lower halves of FIGS. 2 and 3 can be seen.
Für die Trimmregelung ist es zum einen erforderlich, aus kon¬ stanten Verläufen der rekonstruierten Signale λZl und λZ2 ü- ber alle Zylinder einen mittleren Referenzwert λref zu be¬ stimmen, der das Maß für das Katalysatorfenster bildet. Zum anderen sind die buckelartig dargestellten Signalabweichungen Δλ der rekonstruierten Lambda-Signale λZl, λZ2, die von ent¬ sprechenden Magergemisch- bzw. Fettgemisch-Durchbrüchen der Einzelkatalysatoren herrühren als fette bzw. magere Störungen zu interpretieren. Diese Signalabweichungen Δλ rufen dann ei¬ ne entsprechende Reaktion der Trimmregelung hervor.For the trim control, on the one hand it is necessary to determine from constant curves of the reconstructed signals λZ1 and λZ2 over all cylinders a mean reference value λref, which forms the measure for the catalyst window. On the other hand, the signal-like aberrations Δλ of the reconstructed lambda signals λZ1, λZ2, which result from corresponding lean-mixture or rich-mixture breakthroughs of the individual catalysts, are to be interpreted as rich or lean interferences. These signal deviations Δλ then cause a corresponding reaction of the trim control.
Bei der zylinderbezogenen Trimmregelung dienen somit der aus den konstanten Signalverläufen der rekonstruierten Lambda- Signale ermittelte Referenzwert λref als Führungsgröße und die Signalabweichungen Δλ als Regelabweichung.In the case of the cylinder-related trim control, the reference value λref determined from the constant signal curves of the reconstructed lambda signals thus serves as the reference variable and the signal deviations Δλ as the control deviation.
Der verwendete Reglertyp hängt von der möglichen Geschwindig- keit der Rekonstruktion der zylinderbezogenen Lambda-Signale λZl, λZ2 ab. Bei hoher Geschwindigkeit der Signalrekonstruk¬ tion wird ein Trimmregler mit P- und I-Anteil verwendet, wäh¬ rend bei geringer Geschwindigkeit der Signalrekonstruktion ein Trimmregler mit I-Anteil verwendet wird.The controller type used depends on the possible speed of the reconstruction of the cylinder-related lambda signals λZ1, λZ2. At high speed of Signalrekonstruk¬ tion a trim controller with P and I component is used, while at low speed of the signal reconstruction, a trim controller with I component is used.
Ein Vorteil der beschriebenen zylinderbezogenen Trimmregelung des Gemisches für die einzelnen Zylinder besteht darin, dass bei der Gewinnung des mittleren Lambda-Referenzwertes λref über alle Zylinder ein etwaiger Offset-Fehler der Lambda- Sonde LSl das Messergebnis nicht beeinflusst. Eine Nachkat- Sonde wie die Lambda-Sonde LS2 zur Offset-Fehlerkompensation ist daher nicht zwingend erforderlich.An advantage of the described cylinder-related trim control of the mixture for the individual cylinders is that in obtaining the average lambda reference value λref over all cylinders a possible offset error of the lambda probe LS1 does not affect the measurement result. A Nachkat- probe as the lambda probe LS2 for offset error compensation is therefore not mandatory.
Als zusätzliche Maßnahme kann jedoch der zylinderbezogenen Trimmregelung einer herkömmliche und üblicherweise verwendete Mittelwert-Trimmregelung über alle Zylinder Zl bis Z4 überla¬ gert werden, bei der das Signal der nachgeschalteten Lambda- Sonde LS2 als Monitorsignal dient. Diese überlagerte Mittel¬ wert-Trimmregelung dient der Stabilisierung der Abgasreini¬ gung über der Lebensdauer.As an additional measure, however, the cylinder-related trim control of a conventional and commonly used average trim control can be superimposed over all cylinders Z1 to Z4 in which the signal of the downstream lambda sensor LS2 serves as a monitor signal. This superimposed average value trim control serves to stabilize the exhaust gas purification over the service life.
Im übrigen werden Maßnahmen vorgesehen, um die zylinderbezo- gene Trimmregelung zu deaktivieren, wenn bei einer Überwa¬ chung der SauerstoffSpeicherfähigkeit der Einzelkatalysatoren K1-K4 festgestellt wird, dass die SauerstoffSpeicherfähigkeit eines der Einzelkatalysatoren kleiner als seine durch die Zwangsanregung geforderte Sauerstoffbeladung ist. In diesem Fall würde die zylinderbezogene Trimmregelung zu falschen Er¬ gebnissen führen, da Magergemisch- und Fettgemisch-Durchbrü¬ che der Einzelkatalysatoren aufgrund der Zwangsanregung nicht von Durchbrüchen aufgrund zylinderindividueller Unterschiede auseinandergehalten werden können.Incidentally, measures are provided to deactivate the cylinder-related trim control if, when monitoring the oxygen storage capacity of the individual catalytic converters K1-K4, it is determined that the oxygen storage capacity of one of the individual catalytic converters is less than its oxygen charge required by the forced excitation. In this case, the cylinder-related trim control would lead to false results, since lean-mixture and fat mixture breakthroughs of the individual catalytic converters can not be distinguished from breakthroughs due to cylinder-specific differences due to the forced excitation.
Gemäß dem dritten Aspekt der Erfindung berücksichtigt die für den Hauptkatalysator HK vorgesehene Lambda-Regelung, die bei¬ spielsweise wie in der eingangs erwähnten Literaturstelle „Handbuch Verbrennungsmotor" ausgebildet sein kann, die Sau- erstoffSpeicherfähigkeit der Einzelkatalysatoren Kl bis K4. Wie in dieser Literaturstelle erwähnt, verwendet die Lambda- Regelung üblicherweise ein PII2D-Regler mit einem P-Anteil, einem I-Anteil, einem I2-Anteil und einem D-Anteil, sowie ei- ne Begrenzung aufgrund nicht-stationärer Bedingungen. Bei der Bestimmung eines gefilterten Lambda-Sollwertes wird ferner die Gaslaufzeit und das Verzögerungsverhalten der Lambda- Sonde berücksichtigt. Ferner kann eine Mittelwert-Trimmrege- lung für eine Kennlinien-Verschiebung des Signals der Lambda- Sonde LSl mittels des Signals der nachgeschalteten Lambda- Sonde LS2 vorgesehen sein.According to the third aspect of the invention, the lambda control provided for the main catalytic converter HK, which can be formed, for example, as described in the above-cited manual "Internal combustion engine manual", takes into account the oxygen storage capacity of the individual catalytic converters K 1 to K 4. As mentioned in this reference , the lambda controller usually uses a PII 2 D controller with a P-component, an I-component, an I 2 component and a D-component, as well as a ne limitation due to non-stationary conditions. When determining a filtered desired lambda value, the gas running time and the deceleration behavior of the lambda probe are also taken into account. Furthermore, an average trim control can be provided for a characteristic shift of the signal of the lambda sensor LS1 by means of the signal of the downstream lambda sensor LS2.
Die SauerstoffSpeicherfähigkeit der Einzelkatalysatoren Kl bis K4 kann beispielsweise dadurch berücksichtigt werden, dass die Zeitdauer zwischen einer Umschaltung der Kraftstoff¬ einspritzung und einer hierdurch verursachten Abweichung Δλ des betreffenden zylinderbezogenen Lambda-Signals λl bzw. X2 (Figuren 2, 3) erfasst wird. Wenn ein Magergemisch- oder Fettgemisch-Durchbruch eines Einzelkatalysators stattfindet, lässt sich dies an der entsprechenden Umschaltung der Kraft¬ stoffeinspritzung erkennen. Dieser Zeitpunkt ist somit be¬ kannt. Außerdem lässt sich der Zeitpunkt der hierdurch verur¬ sachten Änderung des zylinderbezogenen Lambda-Signals erken- nen. Somit lässt sich die zwischen diesen beiden Zeitpunkten verstrichene Zeit erfassen.The oxygen storage capacity of the individual catalytic converters K1 through K4 can be taken into account, for example, by detecting the time duration between a changeover of the fuel injection and a deviation Δλ of the relevant cylinder-related lambda signal λ1 or X2 (FIGS. 2, 3) caused thereby. If a lean mixture or fat mixture breakthrough of a single catalyst takes place, this can be recognized by the corresponding switchover of the fuel injection. This time is thus known be¬. In addition, the time of the change in the cylinder-related lambda signal caused thereby can be detected. Thus, the elapsed time between these two times can be detected.
Hieraus lassen sich dann entsprechende Schlussfolgerungen für die Lambda-Regelung ziehen. Insbesondere lassen sich die Reg- lerparameter der Lambda-Regler an die erfasste Zeitdauer an¬ passen. Je größer beispielsweise die entsprechende Zeitdauer (Totzeit) ist, umso langsamer werden z.B. die entsprechenden Reglerparameter (I-Anteil) gemacht.From this can then draw appropriate conclusions for the lambda control. In particular, the controller parameters of the lambda controllers can be adapted to the detected time duration. For example, the larger the corresponding time duration (dead time), the slower will be the e.g. the corresponding controller parameters (I-part) made.
Ferner ist vorgesehen, dass die Lambda-Regelung für denIt is further provided that the lambda control for the
Hauptkatalysator HK zwischen Betriebszuständen mit konstanten Signalverläufen und Betriebszuständen mit Signalabweichungen der zylinderbezogenen Lambda-Signale λl, X2 unterscheidet und ihr Verhalten durch eine entsprechende Anpassung der Regler¬ parameter und/oder Reglerstruktur an diese beiden Betriebszu- stände anpasst.Main catalyst HK between operating states with constant signal waveforms and operating states with signal deviations of the cylinder-related lambda signals λl, X2 differs and their behavior by a corresponding adjustment of the Regler¬ parameters and / or controller structure adapts to these two Betriebszu- states.
Die Lambda-Regelung unterscheidet somit zwischen demjenigen Betriebszustand, in dem Sauerstoff in den Einzelkatalysatoren gespeichert wird und daher das Signal der Lambda-Sonde LSl extrem träge ist (idealisiert als konstanter Verlauf angenom¬ men) , und einem Betriebszustand, bei dem ein Magergemisch- oder Fettgemisch-Durchbruch der Einzelkatalysatoren erfolgt und daher eine Signalabweichung des Lambda-Signals LSl sofort erkannt werden kann. Die Lambda-Regelung führt in Abhängig¬ keit von diesen beiden Betriebszuständen eine Fallunterschei¬ dung durch, indem sie beispielsweise die Reglerparameter um- schaltet. Eine andere oder zusätzliche Maßnahme kann die Um- schaltung der Reglerstruktur sein, indem beispielsweise aus einem PI-Regler nur ein P-Regler gemacht wird und der I-An¬ teil dann nachträglich zugeschaltet wird.The lambda control thus differentiates between that operating state in which oxygen is stored in the individual catalytic converters and therefore the signal of the lambda sensor LS1 is extremely sluggish (idealized assuming a constant course) and an operating state in which a lean mixture or Fat mixture breakthrough of the individual catalysts takes place and therefore a signal deviation of the lambda signal LSl can be detected immediately. As a function of these two operating states, the lambda control performs a case discrimination by, for example, switching over the controller parameters. Another or additional measure may be the switching over of the controller structure, for example, by making only one P controller from a PI controller and then switching on the I component subsequently.
Durch diese Maßnahmen wird die Regelgüte der Lambda-Regelung für den Hauptkatalysator HK durch Berücksichtigung der unter¬ schiedlichen Betriebszustände der Lambda-Regelung in Form von Parameteradaptionen und/oder Strukturumschaltungen erhöht.By these measures, the control quality of the lambda control for the main catalytic converter HK is increased by taking into account the different operating states of the lambda control in the form of parameter adaptations and / or structural changes.
Im beschriebenen Ausführungsbeispiel ist die vorgeschaltete Lambda-Sonde LSl als stetige Sonde ausgebildet. Sie kann je¬ doch auch eine binäre Lambda-Sonde sein, ohne dass sich am Grundprinzip der vorliegenden Erfindung etwas ändert. In the described embodiment, the upstream lambda probe LSl is designed as a continuous probe. However, it can also be a binary lambda probe without any change in the basic principle of the present invention.

Claims

Patentansprüche claims
1. Verfahren zur Gemischregelung einer Otto-Mehrzylinder- Brennkraftmaschine mit zylinderbezogenen Einzelkatalysatoren (K1-K4) und einem den Einzelkatalysatoren nachgeschalteten gemeinsamen Hauptkatalysator (HK) , die jeweils als 3-Wege-Ka- talysatoren ausgebildet sind und eine vorgegebene Sauerstoff¬ speicherfähigkeit haben, und einer allen Einzelkatalysatoren (K1-K4) gemeinsamen Lambda-Sonde (LSl) , die zwischen den Ein- zelkatalysatoren (K1-K4) und dem Hauptkatalysator (HK) ange¬ ordnet ist,1. A method for controlling the mixture of an Otto multi-cylinder internal combustion engine with cylinder-related individual catalysts (K1-K4) and a single catalysts downstream common main catalyst (HK), each of which are designed as 3-way catalysts and have a given Sauerstoff¬ storage capability, and a lambda probe (LS1) which is common to all the individual catalytic converters (K1-K4) and is arranged between the individual catalytic converters (K1-K4) and the main catalytic converter (HK),
welches Verfahren eine zylinderbezogene Lambda-Regelung mit einer zylinderbezogenen Zwangsanregung umfasst, durch die ei- nem mittleren Lambda-Sollwert jeweils eine periodischewhich method comprises a cylinder-related lambda control with a cylinder-related forced excitation, by means of which a mean lambda desired value is in each case periodic
Schwankung in Form von Magergemisch- und Fettgemisch-Halb¬ wellen (λ-Puls) aufmoduliert wird, undFluctuation in the form of lean mixture and fat mixture Halb¬ waves (λ-pulse) is modulated, and
bei welchem Verfahren für eine gerade Zylinderzahl der gesam- ten Brennkraftmaschine (BKM) oder einer Zylinderbank die zy¬ linderbezogene Zwangsanregung für eine Hälfte der Zylinder (Z1-Z4) jeweils gegensinnig zu derjenigen für die andere Hälfte der Zylinder durchgeführt wird, um einen Ausgleich der zylinderbezogenen Drehmomentbeiträge zu erzielen.In which method for a straight number of cylinders of the entire internal combustion engine (BKM) or a cylinder bank, the zy¬ cylinder-related forced excitation for half of the cylinder (Z1-Z4) is carried out in each case in opposite directions to that for the other half of the cylinder to compensate for the cylinder-related torque contributions to achieve.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass die Dauer und Amplitude der Magergemisch- und Fettgemisch- Halbwellen (λ-Puls) für beide Hälften der Zylinder jeweils gleich gewählt werden.2. The method according to claim 1, characterized in that the duration and amplitude of the lean mixture and fat mixture half-waves (λ-pulse) are chosen the same for both halves of the cylinder.
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die durch die Zwangsanregung hervorgerufene Sauerstoff¬ beladung der Einzelkatalysatoren (K1-K4) an alterungsbedingte Änderungen der SauerstoffSpeicherfähigkeit der Einzelkataly¬ satoren angepasst wird.3. The method according to claim 1 or 2, characterized in that caused by the forced excitation Sauerstoff¬ loading of the individual catalysts (K1-K4) due to aging Changes in the oxygen storage capacity of Einzelkataly¬ catalysts is adjusted.
4. Verfahren zur Gemischregelung einer Otto-Mehrzylinder- Brennkraftmaschine mit zylinderbezogenen Einzelkatalysatoren (K1-K4) und einem den Einzelkatalysatoren nachgeschalteten gemeinsamen Hauptkatalysator (HK) , die jeweils als 3-Wege-Ka- talysatoren ausgebildet sind und eine vorgegebene Sauerstoff¬ speicherfähigkeit haben, und einer allen Einzelkatalysatoren (K1-K4) gemeinsamen Lambda-Sonde (LSl) , die zwischen den Ein¬ zelkatalysatoren (K1-K4) und dem Hauptkatalysator (HK) ange¬ ordnet ist,4. A method for controlling the mixture of an Otto multi-cylinder internal combustion engine with individual cylinder-related catalysts (K1-K4) and a common main catalytic converter downstream of the individual catalytic converters (HK), which are each designed as 3-way catalysts and have a predetermined oxygen storage capacity, and a lambda probe (LS1) common to all individual catalysts (K1-K4), which is arranged between the individual catalysts (K1-K4) and the main catalyst (HK),
welches Verfahren eine zylinderbezogene Lambda-Regelung mit einer zylinderbezogenen Zwangsanregung umfasst, durch die ei¬ nem mittleren Lambda-Sollwert jeweils eine periodische Schwankung in Form von Magergemisch- und Fettgemisch-Halb¬ wellen (λ-Puls) aufmoduliert wird, undwhich method comprises a cylinder-related lambda control with a cylinder-related forced excitation, by means of which a mean lambda nominal value is modulated in each case by a periodic fluctuation in the form of lean-mixture and rich-compound half-waves (λ-pulse), and
bei welchem Verfahren aus dem Signal (λLSl) der Lambda-Sonde (LSl) zyklenaufgelöst zylinderbezogene Lambda-Signale (λl, λ2) rekonstruiert werden und mit Hilfe dieser rekonstruierten Lambda-Signale (λl, λ2) eine zylinderbezogene Trimmregelung durchgeführt wird.in which method, cylinder-related lambda signals (λ1, λ2) are reconstructed from the signal (λSL1) of the lambda probe (LS1), and with the aid of these reconstructed lambda signals (λ1, λ2), a cylinder-related trim control is performed.
5. Verfahren nach Anspruch 4, dadurch gekennzeichnet, dass die zylinderbezogene Trimmregelung in der Weise durchgeführt wird, dass5. The method according to claim 4, characterized in that the cylinder-related trim control is carried out in such a way that
vorab die zylinderindividuelle Zwangsanregung an die Sauer¬ stoffSpeicherfähigkeit der Einzelkatalysatoren (K1-K4) so an¬ gepasst wird, dass die durch die Zwangsanregung hervorgerufe¬ ne Sauerstoffbeladung der Einzelkatalysatoren (K1-K4) am Ende jeder Magergemisch-Halbwelle der Zwangsanregung eine Ziel- Sauerstoffbeladung in der Größenordnung ihrer SauerstoffSpei¬ cherfähigkeit erreicht,in advance, the cylinder-individual forced excitation to the oxygen storage capacity of the individual catalytic converters (K1-K4) is adapted so that the oxygen charge of the individual catalytic converters (K1-K4) caused by the forced excitation occurs at the end each lean half-wave of the forcible excitation reaches a target oxygen loading in the order of its oxygen storage capacity,
aus konstanten Verläufen der rekonstruierten zylinderbezoge¬ nen Lambda-Signale (λl, λ2) über alle Zylinder (Z1-Z4) ein im Katalysatorfenster liegender mittlerer Referenzwert (λref) gewonnen wird undfrom constant progressions of the reconstructed cylinder-related lambda signals (λ1, λ2) over all cylinders (Z1-Z4), a mean reference value (λref) lying in the catalyst window is obtained, and
Signalabweichungen (Δλ) der rekonstruierten zylinderbezogenen Lambda-Signale (λl, λ2) von dem mittleren Lambda-Referenzwert (λref) als Regelabweichung der Trimmregelung dienen.Signal deviations (Δλ) of the reconstructed cylinder-related lambda signals (λl, λ2) from the average lambda reference value (λref) serve as a control deviation of the trim control.
6. Verfahren nach Anspruch 4 oder 5, dadurch gekennzeichnet, dass in Abhängigkeit von der Geschwindigkeit der Rekonstruk¬ tion der zyklenbezogenen Lambda-Signale (λl, λ2) die zylin¬ derbezogene Trimmregelung mit einem P- und I-Anteil oder mit nur einem I-Anteil durchgeführt wird.6. The method of claim 4 or 5, characterized in that depending on the speed of Rekonstruk¬ tion of the cycle-related lambda signals (λl, λ2) zylin¬ derbezogene trim control with a P and I component or with only one I Share is performed.
7. Verfahren nach einem der Ansprüche 4 bis 6, dadurch ge¬ kennzeichnet, dass der zylinderbezogenen Trimmregelung für die Einzelkatalysatoren (K1-K4) eine Mittelwert-Trimmregelung über alle Zylinder (Z1-Z4) zur Korrektur von alterungsbeding¬ ten Messfehlern der Lambda-Sonde (LSl) überlagert wird.7. The method according to any one of claims 4 to 6, characterized ge indicates that the cylinder-related trim control for the individual catalysts (K1-K4) an average trim control over all cylinders (Z1-Z4) for the correction of age-related Messfehler the lambda Probe (LSl) is superimposed.
8. Verfahren nach einem der Ansprüche 4 bis 7, dadurch ge¬ kennzeichnet, dass die zylinderbezogene Trimmregelung deakti¬ viert wird, wenn bei einer Überwachung der SauerstoffSpei¬ cherfähigkeit der Einzelkatalysatoren (K1-K4) festgestellt wird, dass ihre SauerstoffSpeicherfähigkeit kleiner als ihre durch die Zwangsanregelung geforderte Sauerstoffbeladung ist. 8. The method according to any one of claims 4 to 7, characterized ge indicates that the cylinder-related trim control is deactivated if, when monitoring the SauerstoffSpei¬ cherfähigkeit the individual catalysts (K1-K4) is determined that their oxygen storage capacity is smaller than their by the forced control required oxygen loading is.
9. Verfahren nach einem der Ansprüche 4 bis 8, dadurch ge¬ kennzeichnet, dass eine Lambda-Regelung für den Hauptkata¬ lysator (HK) vorgesehen ist und bei der Definition der Para¬ meter dieser Lambda-Regelung und einer gegebenenfalls vorge- sehenen Mittelwert-Trimmregelung die SauerstoffSpeicherfähig¬ keit der Einzelkatalysatoren (K1-K4) berücksichtigt wird.9. The method according to any one of claims 4 to 8, characterized ge indicates that a lambda control for the Hauptkata¬ analyzer (HK) is provided and in the definition of the parameters of this lambda control and an optionally provided mean value Trim regulation, the oxygen storage capacity of the individual catalytic converters (K1-K4) is taken into account.
10. Verfahren nach Anspruch 9, dadurch gekennzeichnet, dass die Berücksichtigung der SauerstoffSpeicherfähigkeit der Ein- zelkatalysatoren (K1-K4) durch Berücksichtigung der Zeitdauer erfolgt, die zwischen einer durch einen Fettgemisch- oder Ma¬ gergemisch-Durchbruch eines Einzelkatalysators (K1-K4) verur¬ sachten Umschaltung der Kraftstoffeinspritzung und der hier¬ durch verursachten Signalabweichung (Δλ) des betreffenden zy- linderbezogenen Lambda-Signals (λl, λ2) verstreicht.10. The method according to claim 9, characterized in that the consideration of the oxygen storage capacity of the individual catalysts (K1-K4) takes place by taking into account the time duration between a by a mixture of fat or Ma¬ merger breakthrough of a single catalyst (K1-K4) However, the fuel injection and the signal deviation (Δλ) caused thereby are switched over by the respective cylinder-related lambda signal (λ1, λ2).
11. Verfahren nach Anspruch 9 oder 10, dadurch gekennzeich¬ net, dass die Lambda-Regelung für den Hauptkatalysator (HK) zwischen Betriebszuständen mit konstanten Signalverläufen und Betriebszuständen mit Signalabweichungen der zylinderbezoge¬ nen Lambda-Signale (λl, λ2) unterscheidet und ihr Verhalten durch eine entsprechende Anpassung der Reglerparameter und/oder Reglerstruktur an diese beiden Betriebszustände an- passt. 11. The method according to claim 9 or 10, characterized gekennzeich¬ net, that the lambda control for the main catalyst (HK) between operating states with constant signal waveforms and operating states with signal deviations of the cylinder-related lambda signals (λl, λ2) and their behavior adapted by a corresponding adaptation of the controller parameters and / or controller structure to these two operating states.
EP05769792A 2004-09-08 2005-08-05 Method for regulating the mixture of a multicylinder otto engine comprising cylinder-specific individual catalytic converters and a joint main catalytic converter mounted downstream of the individual catalytic converters Withdrawn EP1792068A1 (en)

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PCT/EP2005/053877 WO2006027303A1 (en) 2004-09-08 2005-08-05 Method for regulating the mixture of a multicylinder otto engine comprising cylinder-specific individual catalytic converters and a joint main catalytic converter mounted downstream of the individual catalytic converters

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