DE102005049069A1 - Internal combustion engine operating method, involves determining reference value of air ratio when fuel injection of cylinder is deactivated, and activating fuel injection of cylinder - Google Patents

Abstract

The method involves determining a reference value for an air ratio, and deactivating fuel injection of cylinders for a measuring time space. Another reference value of the air ratio is determined when the fuel injection of the cylinder is deactivated. The fuel injection of the cylinder is activated. A diagnostic information with respect to a component of an internal combustion engine is formed depending on the two references values, where the component influences accumulation of air-fuel-mixture. An independent claim is also included for a device for executing a method for operating an internal combustion engine.

Description

The The present invention relates to a method for operating a Internal combustion engine, in which the air-fuel mixture ratio characterizing Air ratio λ on the deviation is monitored from a predefinable setpoint becomes.

The The present invention further relates to a device according to the preamble of patent claim 11.

such Methods and devices are known and are used, for example. proper operation to monitor an internal combustion engine or to detect errors, in particular in a mixture formation.

It Object of the present invention, a method and a Specify device in which a differentiated than conventional systems Detection of errors in mixture formation, especially errors in the range of an injection valve of the internal combustion engine is possible.

• – Ermitteln eines ersten Referenzwerts für die Luftzahl λ,
• – Deaktivieren der Kraftstoffeinspritzung eines Zylinders für einen ersten Meßzeitraum,
• – Ermitteln eines zweiten Referenzwerts für die Luftzahl λ, während die Kraftstoffeinspritzung des Zylinders deaktiviert ist,
• – Aktivieren der Kraftstoffeinspritzung des Zylinders.

This object is achieved according to the invention in a method of the type mentioned by the following steps:

• Determining a first reference value for the air ratio λ,
• Deactivating the fuel injection of a cylinder for a first measurement period,
• Determining a second reference value for the air ratio λ, while the fuel injection of the cylinder is deactivated,
• - Activate the fuel injection of the cylinder.

Advantages of invention

By the targeted according to the invention Disable fuel injection and detection of reference values for the air ratio before and after deactivating the fuel injection of the cylinder is compared with conventional Systems - one precise Diagnosis of errors in a mixture formation, especially in the field given an injection valve of the internal combustion engine.

For example can thereby - possibly under execution further diagnostic steps - in particular between individual types of failure of an injector such as e.g. one open or closed clamping injection valve of the relevant Cylinders are distinguished, resulting in the conventional methods that occur Error without further differentiation only one fuel path or can assign to an air path, not possible is.

• – Ermitteln eines dem zeitlichen Verlauf der Luftzahl λ entsprechenden Lambdasignals,
• – Filtern des Lambdasignals, vorzugsweise mittels eines Bandpassfilters, um ein gefiltertes Lambdasignal zu erhalten,
• – Bilden einer Diagnoseaussage hinsichtlich einer die Bildung des Luft-Kraftstoff-Gemischs beeinflussenden Komponente der Brennkraftmaschine in Abhängigkeit des gefilterten Lambdasignals.

As a further solution to the object of the present invention, a method according to claim 7 is provided, which comprises the following steps:

• Determining a lambda signal corresponding to the time profile of the air ratio λ,
• Filtering the lambda signal, preferably by means of a bandpass filter, to obtain a filtered lambda signal,
• - Forming a diagnostic statement with respect to a formation of the air-fuel mixture influencing component of the internal combustion engine as a function of the filtered lambda signal.

The Bandpass filtering according to the invention Lambda signal allows the detection of a periodic change in the lambda signal, the example. Then occurs when a particular cylinder of the internal combustion engine e.g. due to a defective injector periodically from processed mixture different from the given air-fuel mixture or ejects into an exhaust tract of the internal combustion engine.

The Bandpass filtering according to the invention can very particularly advantageous with the above-described targeted Deactivation of the fuel injection of a single cylinder combined to the relevant cylinder, which is at the processing the faulty mixture is involved in isolation.

Yet another solution The object of the present invention is achieved by a device according to claim 11 indicated.

advantageous Embodiments of the invention are the subject of the dependent claims.

Further Advantages, features and details emerge from the following Description in which referring to the drawing various embodiments the invention are shown. It can in the claims and mentioned in the description Features individually for each itself or in any combination essential to the invention.

drawing

In the drawing shows:

1 a block diagram of a first embodiment of the device according to the invention,

2 a simplified flow chart of a first embodiment of the method according to the invention,

3 a flowchart of another embodiment of the method according to the invention, and

4 a flowchart of a third embodiment of the method according to the invention.

description the embodiments

1 shows an internal combustion engine 1 a motor vehicle, which may be, for example, a gasoline engine. One in 1 not shown in detail combustion chamber of a cylinder of the internal combustion engine 1 is via an air supply 15 Fresh air supplied. The air supply 15 For example, an air mass meter 20 have, which measures one of the internal combustion engine or the combustion chamber supplied air mass flow and the corresponding measurement result to a the internal combustion engine 1 controlling control 45 forwards.

The flow direction of the fresh air in the air supply 15 is in 1 indicated by arrows. The air mass meter 20 is in the flow direction of the fresh air in the air supply 15 a throttle 5 downstream, with which the air mass flow can be adjusted.

The relevant combustion chamber of the internal combustion engine 1 is via at least one injection valve 10 Fuel supplied, wherein the amount of fuel supplied also from the controller 45 adjusted and corrected. In the present case is in the internal combustion engine 1 according to 1 a direct injection of the fuel in a combustion chamber indicated. Alternatively, however, the fuel could also be in an area of air supply, for example 15 be injected between the throttle 5 and a downstream intake valve of a cylinder of the internal combustion engine 1 lies.

That in the combustion chamber of the internal combustion engine 1 located air-fuel mixture is covered by at least one spark plug 25 ignited, wherein a determination of the ignition timing also by the controller 45 the internal combustion engine 1 he follows.

The internal combustion engine 1 is driven in a manner known in the art by the combustion of the air-fuel mixture in the combustion chamber. The resulting during combustion exhaust gas is at least one in 1 not shown exhaust valve from the combustion chamber in an exhaust line 40 the internal combustion engine 1 ejected, with in 1 the flow direction of the exhaust gas in the exhaust system 40 also marked by an arrow.

In the exhaust system 40 is a lambda sensor 35 arranged, which measures the oxygen content in the exhaust gas and the corresponding measured value to the controller 45 in the then from the measured oxygen content in the expert known manner an actual value for the air-fuel mixture ratio in the combustion chamber of the internal combustion engine 1 can be calculated. The air-fuel mixture ratio is also referred to as λ for short.

According to the invention, as by step 100 of the flowchart 2 indicated, a first reference value λ1 for the air ratio λ determined, and then a fuel injection into a specific cylinder of the internal combustion engine 1 deactivated for a first measurement period, cf. step 110 ,

Subsequently, according to step 120 a second reference value λ2 for the air ratio λ determined. That is, the second reference value λ2 is detected while the fuel injection of the cylinder under consideration is deactivated. After the determination of the second reference value λ2, in step 130 the fuel injection in the cylinder in question re-activated, whereby the internal combustion engine 1 returns to a normal operating state.

With knowledge of the first and second reference values for the air ratio λ ascertained according to the invention, it is advantageously possible to form an already relatively differentiated diagnostic statement relating to a component of the internal combustion engine which influences the formation of the air-fuel mixture 1 such as the injection valve 10 or the spark plug 25 refers.

That is to say, from the reference values λ1, λ2 determined according to the invention, cf. the steps 100 . 120 ( 2 ), a statement can be made, for example, if the injection valve 10 ( 1 ) has a malfunction and thus prevents the proper formation of an air-fuel mixture. The targeted shutdown of the fuel injection of the considered cylinder according to step 110 can take place for one or preferably several working cycles of the cylinder, so that the measuring period defined thereby is large enough to be able to reliably detect a possibly resulting change in the air ratio.

According to a further embodiment of the present invention, a lambda control of the internal combustion engine is particularly advantageous 1 before the investigation 100 of the first reference value deactivated. This ensures that a detected under shutdown of the cylinder considered two ter reference value for the air ratio λ not by one of the lambda control of the internal combustion engine 1 caused activation, for example, the injection valve is falsified. Accordingly, after activating 130 the fuel injection of the cylinder in question again activates the lambda control to ensure proper operation of the internal combustion engine 1 to enable.

The following is with reference to the in 3 flowchart shown another embodiment of the method according to the invention described in detail.

Before the actual start of the diagnostic method according to the invention with the step already described 100 However, first in step 90 checks whether the diagnostic procedure should be carried out. Individual criteria for this will be described later in detail.

If the decision according to step 90 indicates that the diagnostic procedure is to be performed is according to 3 in step 91 branches, in which possibly a the implementation of the diagnostic method representing flag in the controller 45 ( 1 ) or the like is set.

Subsequently, in step 95 , as already described, the lambda control of the internal combustion engine 1 deactivated in order to rule out a falsification of subsequently obtained measured values for the air ratio λ.

Thereafter, the process steps are sequentially 100 . 110 . 120 . 130 carried out the previously mentioned with reference to 2 described steps 100 to 130 match, so after step 130 of in 3 the two reference values λ1, λ2 for the air ratio are known.

In step 140 Finally, it is checked whether the second lambda reference value λ2 is greater by a predefinable factor S1 than the first lambda reference value λ1, λ2> λ1 S1, ie, whether the air-fuel mixture after switching off 110 fuel injection in the cylinder in question has become leaner.

If the inequality λ2> λ1 · S1 is not satisfied, it is concluded according to the invention that the injection valve 10 either completely jammed open or clamped closed, because in both these cases can also deactivate 110 Fuel injection into the respective cylinder cause no leaning of the mixture. Accordingly, the query becomes 140 to the further query 200 branched off, which allows a further differentiation of the aforementioned errors.

The method steps according to the invention 90 to 140 are too one from the 3 , group of process steps referred to as "step 1." The process steps of step 1 are described in 3 separated from the process steps of the subsequent stage 2 by a dashed line.

In a first step of the step 2, the query 200 , is checked with activated lambda controller, whether a difference between a given lambda setpoint λsoll and a current lambda actual value λist exceeds a predetermined difference Δ, ie λsoll - λist> Δ, and whether at the same time the actual lambda value λist falls below a predeterminable minimum threshold λmin , ie, λ is <λmin. If both criteria are not met, it is concluded that the injector 10 closed jammed and in step 210 a corresponding error or a flag symbolizing this error is set.

If the two criteria according to step 200 However, if λsoll - λ is> Δ and λ ist <λmin, it is concluded that the injection valve 10 open jammed and in step 220 a corresponding error or a flag symbolizing this error is set.

After the steps 210 . 220 will go straight to level 3 of the in 3 branched process, in which a verification of in the steps 210 . 220 set error is performed. This verification will be explained later in detail.

If after the query step 140 from Stage 1, the inequality λ2> λ1 · S1 is satisfied, the invention is closed for further errors, which are described in more detail below. In particular, if the inequality λ2> λ1 · S1 is satisfied, it is assumed that either a spray perforated disk of the injection valve 10 is clogged, or that there is a so-called ignition error.

For further differentiation between these two possible errors, the method steps described in more detail below 230 to 290 Level 2 executed.

First, in step 230 a first reference value LU1 for a running disturbance of the internal combustion engine 1 ( 1 ) running noise signal, based on the cylinder considered, determined.

An assessment of the running noise of the internal combustion engine 1 or the individual cylinder of the internal combustion engine 1 suitable signal or the Determining such Laufunruhesignals is, for example, in the DE 199 45 811 A1 described.

After the step 230 will be in step 240 an air-fuel mixture of the relevant cylinder of the internal combustion engine 1 enriched, ie the relative fuel content of the processed in the cylinder mixture is increased.

At the same time, the ignition angle of the corresponding cylinder in one of the enrichment 240 Appropriately be adjusted to the inventive enrichment of step 240 torque neutral to perform.

After the enrichment 240 will be in step 250 a second reference value LU2 for the running noise of the internal combustion engine 1 with respect to the same cylinder considered, which, together with the first reference value LU1 for the smooth running, allows the diagnosis of a diagnosis to be explained in more detail below.

This will be in the itself at the step 250 subsequent query 260 checks whether the second rough running reference value LU2 is smaller by a predefinable factor S2 than the first rough running reference value LU1, LU2 <LU1 * S2, ie whether the running noise of the internal combustion engine 1 ( 1 ) after enriching 240 of the mixture in the cylinder under consideration has not decreased or increased by more than the amount predetermined by the factor S2 with respect to the first uneven running reference value LU1.

If this is the case, it is concluded that a spray orifice plate of the injection valve 10 or their spray holes are clogged, and in step 270 a corresponding error or a flag symbolizing this error is set.

Otherwise, in the query 280 checks whether the enrichment according to the invention according to step 240 the mixture of the cylinder in question has already been made twice. If this condition is satisfied, it is concluded that there is an error in the area of the ignition system and in the step 290 a corresponding error or a flag symbolizing this error is set.

If at the query 280 shows that the enrichment according to the invention according to step 240 has not already been made twice, is again to the enrichment 240 and the subsequent steps 250, 260, and the corresponding queries are performed again.

The targeted enrichment according to the invention 240 the air-fuel mixture of the considered cylinder of the internal combustion engine 1 determining the first and second reference values LU1, LU2 for a running noise of the internal combustion engine 1 thus allows a further advantageous differentiation of possible errors in the mixture preparation in the cylinder in question.

After the steps 210 . 220 . 270 or 290 the stage 2, in each case on a special error of the injection valve 10 or the ignition system of the internal combustion engine 1 closed and a corresponding error entry is made, takes place in the step 300 According to the invention, a check as to whether the data determined in stages 1, 2 are valid and the corresponding errors can thus be confirmed, or whether, during the method steps of stages 1, 2, other malfunctions of the internal combustion engine 1 have occurred, which could have disturbed the process sequence of steps 1 and 2 according to the invention such that the respective determination of the error is not reliable.

In the context of the abovementioned check on the validity of the determined data, it is checked according to the invention whether an instantaneous rough-running value of the internal combustion engine 1 divided by one before the first deactivation according to the invention 110 of the considered cylinder in the step 111 stored rough running reference value is within predefinable limits.

In this case, the current uneven running is approximately comparable to the uneven running at the beginning of the diagnostic procedure, cf. step 111 , so that, for example, an intermittent occurrence of combustion misfires on other cylinders of the internal combustion engine 1 can be excluded and the errors detected in stage 2 can be confirmed. This is done in step 310 from level 3. still stored diagnostic requirements for the previously in the steps 110 to 290 considered cylinders can also be in step 310 to be deleted.

If in the query after step 300 However, it shows that the current running noise of the internal combustion engine 1 deviates more severely from the uneven running at the beginning of the diagnostic procedure, in step 320 previously as part of the process steps 90 to 290 has been invalidated so that the entire diagnostics process may need to be restarted. Accordingly, in contrast to the step 310 at the step 320 a still stored diagnostic request for the previously considered cylinder is not deleted.

Any existing enrichment (see step 240 ) or ignition angle early adjustment is then in step 330 reversed. Likewise, in step 330 possibly previously deactivated lambda control of the internal combustion engine 1 again activated, so that the internal combustion engine 1 initially returns to normal operation.

To Going through the stage 3 of the method according to the invention may possibly also one not closer also described as "Healing (Self-healing) " fourth stage are processed at the possibly detected errors under certain circumstances reset can be.

In a further particularly advantageous embodiment of the present invention, the inventive method is sequentially for different cylinders of the internal combustion engine 1 executed, whereby the cylinder or its components can be determined, which actually contributes to a faulty mixture formation. The selection of the respective cylinder to be considered is preferably carried out in step 91 ,

According to another advantageous embodiment of the present invention, the inventive method for a particular cylinder of the internal combustion engine 1 executed, as soon as by means of a rough running of the internal combustion engine 1 representing a misfire signal at the cylinder in question has been determined. Such a misfire during combustion can be detected, for example, by a particularly strongly varying Laufunruhesignal, and from this can directly the affected cylinder of the internal combustion engine 1 be determined. In this way, it is possible to further process steps of the invention targeted to those cylinders of the internal combustion engine 1 applied, which had a misfire in the combustion according to the Laufunruhesignal.

In a further very advantageous embodiment of the method according to the invention, which in the form of in 4 is shown in a first step 400 a lambda signal corresponding to the time profile of the air ratio λ. The lambda signal is then in step 410 filtered, preferably by means of a bandpass filter, whereby a filtered lambda signal is obtained.

Subsequently, in step 420 of the method according to the invention a diagnostic statement with respect to a the formation of the air-fuel mixture influencing component of the internal combustion engine 1 be taken in response to the filtered lambda signal. If, for example, a particular cylinder of the internal combustion engine 1 - Especially due to a defective injector 10 or the like - permanently subject to incorrect mixture formation, this is reflected in the present invention bandpass filtered lambda signal by a corresponding periodic change of the bandpass filtered lambda signal, the period corresponds to a time interval between two successive cycles of the respective cylinder.

The inventive method is therefore initially given the opportunity to determine that a particular cylinder of the internal combustion engine 1 due to its periodically occurring, incorrect mixture formation may be a faulty component such as a defective injection valve 10 having. Due to runtime and Verwirbelungseffekten in an exhaust tract of the internal combustion engine 1 and further inaccuracies, however, can not yet be reliably ascertained, which is usually the number of cylinders of the internal combustion engine 1 actually has or causes the faulty mixture formation.

For this purpose - as already described - the inventive method after 3 successively for each cylinder of the internal combustion engine 1 be performed.

Another way to determine the affected by the faulty mixture formation cylinder is, separately for each cylinder of the internal combustion engine 1 a Laufunruhe signal representing the rough running of the respective cylinder, and as soon as the Laufunruhesignal a particular cylinder exceeds a predetermined threshold, for example, the method according to 3 be carried out for this cylinder. That is, the consideration according to the invention of the rough running of a cylinder also suggests whether there is a faulty mixture formation in the respective cylinder.

It is furthermore particularly advantageous to use an upper and / or lower limit frequency of a bandpass filter used for filtering the lambda signal as a function of a rotational speed of the internal combustion engine 1 to choose. As a result, the selectivity of the bandpass filter according to the invention is increased and in particular to an operating point or to the instantaneous speed of the internal combustion engine 1 adjusted, which are suppressed for the diagnosis of the invention uninteresting changes in the lambda signal.

Furthermore, the method according to the invention is particularly advantageously carried out only if it is not already a fault of a component of the internal combustion engine which influences the formation of the air-fuel mixture 1 has been determined. Such a decision can, as already described, eg in the step 90 out 3 be made.

Other errors that occur when the Implementation of the method according to the invention in step 90 are prohibited, for example: faults in an air system of the internal combustion engine, faults in a system for adjusting a camshaft, faults in an exhaust gas recirculation system, faults in a fuel supply, or faults in an ignition system.

For example, it is therefore not necessary or expedient to carry out the method according to the invention, if there is already an error in the lambda controller of the internal combustion engine 1 or a spark plug 25 or the like has been found.

The limit values or threshold values used in the context of the method according to the invention, such as, for example, S1, S2, etc., are preferably in the form of applicable quantities, for example in a memory of the controller 45 ( 1 ) filed. Furthermore, it is possible to provide characteristic curves or characteristic diagrams instead of individual values, in order to determine the dependence of the limit values on further variables, for example on other operating variables of the internal combustion engine 1 or the like.

The method according to the invention enables a differentiated diagnosis statement about possible errors, in particular of an injection valve 10 an internal combustion engine 1 and therefore facilitates and accelerates, for example, troubleshooting a supposedly defective internal combustion engine 1 , Furthermore, such an accurate error detection, as is possible with the present method, also avoid the unnecessary removal of error-free components, whereby testing and assembly times are further reduced, which also has a positive effect on the cost of maintenance and overall frequency reduced by workshop visits.

Furthermore allows the inventive method a better differentiation of possible errors also a more effective fulfillment future Requirements for a diagnosis of the fuel or injection system an internal combustion engine.

According to a further variant of the method according to the invention, the method steps according to 3 for example, at the same time on several cylinders of the internal combustion engine 1 be applied.

A Extension of the method according to the invention by active intervention in other systems of the internal combustion engine such as. in an exhaust gas recirculation system or a valve control is also possible.

Another, very particular advantage of the method according to the invention is that for carrying out the method no additional actuators or sensors in the internal combustion engine 1 must be provided. A conventionally equipped internal combustion engine 1 already has all the components required for carrying out the method according to the invention. Alone the controller 45 the internal combustion engine 1 is to be equipped with a modified program that allows implementation of the method steps according to the invention.

Claims (11)

Method for operating an internal combustion engine ( 1 ), in which the air-fuel mixture ratio characterizing air ratio λ is monitored for the deviation from a predefinable setpoint, characterized by the following steps: - determining ( 100 ) of a first reference value for the air ratio λ, - disable ( 110 ) the fuel injection of a cylinder for a first measurement period, - determining ( 120 ) of a second reference value for the air ratio λ, while the fuel injection of the cylinder is deactivated, - activate ( 130 ) the fuel injection of the cylinder. A method according to claim 1, characterized in that a diagnostic statement regarding an influencing the formation of the air-fuel mixture component of the internal combustion engine ( 1 ) is formed depending on the first reference value and the second reference value. Method according to one of the preceding claims, characterized in that a lambda control of the internal combustion engine ( 1 ) before the investigation ( 100 ) of the first reference value and / or after activation ( 130 ) of the fuel injection of the cylinder is activated. Method according to one of the preceding claims, characterized by the following steps: - determining ( 230 ) of a first reference value for a running noise of the internal combustion engine ( 1 ), - enrichment ( 240 ) of the air-fuel mixture of a cylinder of the internal combustion engine ( 1 ), - Determine ( 250 ) of a second reference value for the uneven running, - forming a diagnosis statement with regard to a component of the internal combustion engine which influences the formation of the air-fuel mixture ( 1 ) depending on the first reference value for the running noise signal and the second reference value for the Uneven running signal. Method according to one of the preceding claims, characterized in that the method successively for different cylinders of the internal combustion engine ( 1 ) is performed. Method according to one of claims 1 to 5, characterized in that the method for a particular cylinder of the internal combustion engine ( 1 ) is executed, as soon as by means of one of the rough running of the internal combustion engine ( 1 ) or a single cylinder representing Laufunruhesignals a misfire of the relevant cylinder has been determined. Method for operating an internal combustion engine ( 1 ), in which the air-fuel mixture ratio characterizing air ratio λ is monitored for the deviation from a predefinable setpoint, characterized by the following steps: - determining ( 400 ) a lambda signal corresponding to the time profile of the air ratio λ, - filters ( 410 ) of the lambda signal, preferably by means of a bandpass filter, in order to obtain a filtered lambda signal, 420 ) a diagnostic statement with regard to a component of the internal combustion engine which influences the formation of the air-fuel mixture ( 1 ) as a function of the filtered lambda signal. Method according to claim 7, characterized in that an upper limit frequency and / or a lower limit frequency of a filter ( 410 ) of the lambda signal used in accordance with a speed of the internal combustion engine ( 1 ) is selected. Method according to one of claims 7 or 8, characterized in that separately for each cylinder of the internal combustion engine ( 1 ), a running disturbance of the respective cylinder representing Laufunruhesignal is determined, and that for the cylinder whose Laufunruhesignal exceeds a predetermined threshold, the method is carried out according to one of claims 1 to 6. Method according to one of the preceding claims, characterized in that the method is carried out only if not already an error of the formation of the air-fuel mixture influencing component of the internal combustion engine ( 1 ) has been determined. Contraption ( 45 ) for operating an internal combustion engine ( 1 ), characterized in that the device ( 45 ) is suitable for carrying out the method according to one of the preceding claims.