DE102018200810A1 - Method for determining cylinder-specific lambda values and electronic control unit - Google Patents

Abstract

A method for determining the cylinder-specific lambda values of the individual cylinders of an internal combustion engine having a plurality of cylinders and an associated electronic control unit are described. In the method, the total lambda value of all the cylinders is kept lean or rich, and a single cylinder is abruptly loaded with a more lean-burned or enriched air-fuel mixture than the other cylinders. The air-fuel mixture supplied to the other cylinders is correspondingly enriched or emaciated for compensation. After the leaning of the single cylinder, the reaction is measured in the rough running for this cylinder. All cylinders are adjusted accordingly. Due to the rough running values, a conclusion can be drawn about the original lambda value.

Description

The present invention relates to a method for determining the cylinder-specific lambda values of the individual cylinders of an internal combustion engine having a plurality of cylinders.

Due to the current exhaust gas legislation, it has been necessary for some time to monitor the cylinder-specific air-fuel ratio of an internal combustion engine. It is not possible for cost reasons monitoring the air-fuel ratio of the individual cylinders by Einzellambdasonden or too expensive. Therefore, other methods have been developed.

From the DE 10 2006 026 390 A1 and the DE 10 2006 044 073 A1 It is known to carry out the determination of the individual lambda values by targeted emaciation of the combustion mixture in the context of an adaptation method. In this method, targeted leaning of individual cylinders and observation of the level of intervention on the cylinder-specific lambda value is concluded (CYBL_HOM method).

The DE 10 2009 027 822 A1 describes a method for determining a trimming of at least one cylinder of an internal combustion engine, wherein the at least one cylinder is operated in succession in at least one lean phase and at least one rich phase, to produce on average exhaust neutrality, wherein a rough running signal in a lean phase is evaluated to a cylinder-specific feature concerning the agreement.

In the DE 10 2010 035 365 A1 For example, a method for determining the oxygen storage capacity of a catalyst and a method for determining an oxygen sensor inherent time delay are described. This method involves varying the air-fuel ratio to perform a pre-catalyst lambda probe, post-catalyst lambda probe, and oxygen storage ability test of a catalyst.

The DE 10 2007 043 734 A1 discloses a method in which at least two cylinders are operated with a lambda value and here the associated rough running value is determined. Then the cylinders are operated with a different lambda value and again the associated running noise value is determined. For determining the lambda value of the individual cylinders, the difference of the rough running values is used.

The technical article "catalyst properties for diagnosability" (Motortechnische Zeitschrift / Issue 1/2016), the so-called CTG method (Close-the-gap) is described.

The object of the present invention is to provide a method for determining the cylinder-specific lambda values of the individual cylinders of an internal combustion engine having a plurality of cylinders, which can be carried out in a particularly efficient manner.

• - Halten des Gesamtlambdawertes aller Zylinder im mageren oder fetten Bereich;
• - sprunghaftes stärkeres Abmagern oder Anfetten des einem Einzelzylinder zugeführten Luft-Kraftstoff-Gemisches als das den anderen Zylindern zugeführten Gemisches;
• - Anfetten oder Abmagern des den anderen Zylindern zugeführten Luft-Kraftstoff-Gemisches zur Kompensation der durchgeführten zusätzlichen Abmagerung oder Anfettung unter Aufrechterhaltung des Gesamtlambdawertes aller Zylinder im mageren oder fetten Bereich;
• - nach Abmagern oder Anfetten des dem Einzelzylinder zugeführten Luft-Kraftstoff-Gemisches Messen der Reaktion in der Laufunruhe dieses Zylinders;
• - Prüfen aller anderen Zylinder entsprechend der Reihe nach und Ermitteln der jeweiligen Laufunruhewerte; und
• - nach der Verstellung aller Zylinder Ableiten des zylinderindividuellen ursprünglichen Lambdawertes aus den Laufunruhewerten.

This object is achieved according to the invention by a method of the type indicated, which comprises the following steps:

• - keeping the total lambda value of all cylinders in the lean or rich area;
• - Greater heavy leaning or enrichment of a single cylinder supplied air-fuel mixture as the other cylinders supplied mixture;
• Enriching or leaning the air-fuel mixture supplied to the other cylinders to compensate for the additional leaning or enrichment while maintaining the total lambda value of all cylinders in the lean or rich region;
• - After leaning or enriching the air supplied to the single cylinder air-fuel mixture measuring the reaction in the rough running of this cylinder;
• - checking all other cylinders in sequence and determining the respective rough running values; and
• - After the adjustment of all cylinders, deriving the cylinder-specific original lambda value from the rough running values.

The correction requirement of the cylinder-specific lambda value can be determined from the difference between the determined rough running values and the current operating point.

The current operating point is usually determined by load (torque or air mass) and the engine speed, the above relationship is usually read from a map.

Preferably, in the method according to the invention, the total lambda value of all the cylinders is kept in the lean range and the individual cylinder is charged with a more highly depleted air-fuel mixture. The mixture fed to the other cylinders is enriched for compensation.

An advantage of the method according to the invention is that it with a Diagnosis for the Vorkat probe, Nachkat probe and / or oxygen storage ability can be combined. In such a diagnosis (CTG method or "close-the-gap method"), the corresponding lambda setpoint value is dimmed several times to "lean" or "rich" in order to evaluate the dynamics of the Vorkat probe. In addition, the switch from lean to rich and vice versa is performed due to the post-cat probe signal. In this case, the breakdown of the catalyst is evaluated on the basis of the binary lambda probe signal.

In such a diagnosis (CTG method), the lean or rich phase may be several seconds. Such a phase is preferably used according to the invention for an evaluation of the cylinder-specific lambda values of the individual cylinders. In this case, the method according to the invention is preferably used in the lean phase of such a diagnosis. For this purpose, a cylinder is suddenly emaciated more heavily than other cylinders. By enriching the mixture of other cylinders, this additional erratic weight loss is compensated. However, the total lambda is still in the lean range, as required for the diagnosis made (CTG diagnosis).

According to the invention, an abrupt increase in leaning or enrichment of the air-fuel mixture fed to a single cylinder takes place as the mixture supplied to the other cylinders.

The Gesamtabmagerung or Gesamtanfettung (lambda target point + additional leaning or enrichment) of a single cylinder is stored, preferably in an intermediate buffer, and the adjustment of all cylinders is determined, which, as mentioned, can be deduced from the corresponding Verstellweite to the respective original lambda value.

In the method according to the invention, all other cylinders are checked in sequence, and preferably the rough running value is stored in each case. After performing the adjustment of all cylinders, a conclusion can be drawn on the original lambda value due to the rough running values.

Preferably, therefore, according to the invention, a CYBL_HOM method is combined with a CTG diagnosis, so that a separation of the two methods is no longer necessary.

The present invention further relates to an electronic control unit for controlling an internal combustion engine with a running irregularity determination unit and an injection quantity correction unit, wherein a group of cylinders of the internal combustion engine is associated with a lambda probe. The control unit according to the invention is characterized in that it is designed to carry out the method described above.

Specifically, the electronic control unit is designed so that it uses a lean or rich phase of a diagnosis for a Vorkat probe, Nachkat probe and / or oxygen storage capability for determining the cylinder-specific lambda values of the individual cylinder, in particular for performing a correspondingly modified CTG diagnosis Determining the cylinder-specific lambda values of the individual cylinder is formed.

The electronic control unit is designed to carry out an abruptly greater emptying or enrichment of the mixture fed to a single cylinder than to other cylinders and, after the exhausting of the test cylinder, to measure the reaction in the rough running for this cylinder. Furthermore, it is preferably set up for the storage of the respectively determined rough running values.

• 1 ein Diagramm, das den typischen Verlauf des Lambdasollwertes einer CTG-Diagnose zeigt;
• 2 ein Diagramm, das die Durchführung des erfindungsgemäßen Verfahrens wiedergibt, wobei oben die Abmagerung und unten der Laufunruhewert eines Einzelzylinders dargestellt ist; und
• 3 ein Diagramm, das den Lambda-Unterschied in Abhängigkeit vom Laufunruhe-Zielwertunterschied für verschiedene Arbeitspunkte zeigt.

The invention will be explained below with reference to an embodiment in conjunction with the drawings in detail. Show it:

• 1 a diagram showing the typical course of the lambda setpoint of a CTG diagnosis;
• 2 a diagram showing the implementation of the method according to the invention, wherein the upper leaning and below the rough running value of a single cylinder is shown; and
• 3 a graph showing the lambda difference as a function of the turbulence target difference for different operating points.

The diagram of 1 represents the upstream lambda value on the ordinate as a function of time on the abscissa. The solid line shows the typical course of the diagnosis for a Vorkat probe, Nachkat probe and oxygen storage capability, wherein the lambda setpoint shown several times from lambda = 1 (middle dashed line) to "lean" (upper dashed line) and "bold" (lower dashed line) dashed line) was trimmed.

This profile of the lambda value serves as the basis for carrying out the method according to the invention, which is shown in the diagram of FIG 2 is shown, with the case of leaning and below the corresponding rough running value are shown above. In the upper diagram is shown, as in the lean phase, a test cylinder 1 is dramatically more emaciated than other cylinders. Furthermore, a second test cylinder 2 shown. Furthermore, it is shown like the other cylinders 3 compensate for this extra emaciation by enrichment. However, overall lambda is still lean, as needed for CTG diagnosis.

The corresponding total leaning (lambda target point + additional leaning) marked 4 here corresponds to the length of the straight line from the lambda = 1 corresponding dashed line to the highest point.

The bottom diagram of 2 shows the corresponding rough running value of the test cylinder 1 and the test cylinder 2 , The corresponding rune difference 5 corresponds to the distance indicated by arrows.

If all individual cylinders have been emaciated to achieve the corresponding uneven running, the respective cylinder individual original lambda values are derived from the corresponding Verstellweiten.

By combining the test procedure of the cylinder-specific lambda values of the individual cylinders with the CTG diagnosis, a faster run of the "Imbalance Monitoring" can be achieved. A temporal separation of both methods is no longer necessary.

3 shows in a diagram the lambda difference depending on the rough running target value difference for different operating points.

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• DE 102006026390 A1 [0003]
• DE 102006044073 A1 [0003]
• DE 102009027822 A1 [0004]
• DE 102010035365 A1 [0005]
• DE 102007043734 A1 [0006]

Claims (6)

Method for determining the cylinder-specific lambda values of the individual cylinders of an internal combustion engine having a plurality of cylinders, comprising the following steps: - keeping the total lambda value of all cylinders in the lean or rich area; - Greater heavy leaning or enrichment of a single cylinder supplied air-fuel mixture as the other cylinders supplied mixture; Enriching or leaning the air-fuel mixture supplied to the other cylinders to compensate for the extra leaning or enrichment while maintaining the total lambda value of all cylinders in the lean or rich region; - After leaning or enriching the air supplied to the single cylinder air-fuel mixture measuring the reaction in the rough running of this cylinder; - checking all other cylinders in sequence and determining the respective rough running values; and - After the adjustment of all cylinders, deriving the cylinder-specific original lambda value from the rough running values. Method according to Claim 1 , characterized in that the correction requirement of the cylinder-specific lambda value is determined from the difference between the determined rough running values and the current operating point. Method according to Claim 1 or 2 , characterized in that the total lambda value of all cylinders kept in the lean range and the individual cylinder is acted upon with a more depleted air-fuel mixture. Method according to one of the preceding claims, characterized in that the lean or rich phase of a diagnosis for the Vorkat probe, Nachkat probe and / or oxygen storage capability for determining the cylinder-specific lambda values of the individual cylinder is used. Method according to one of the preceding claims, characterized in that the required Gesamtabmagerung or Gesamtanfettung a single cylinder is stored in an intermediate buffer. Electronic control unit for controlling an internal combustion engine having a rolling irregularity determination unit and an injection amount correction unit, wherein a group of cylinders of the internal combustion engine is associated with a lambda probe, characterized in that the control unit for performing the method according to one of Claims 1 to 5 is trained.

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