DE10354978A1 - Multicylinder internal combustion engine, has control device which operates knocking cylinder with richer fuel mixture, and non-knocking cylinders with leaner fuel mixture - Google Patents

Abstract

An ignition detector, a flue supply device and a knock detector are provided on the respective cylinders. In the event of a knock being detected in at least one cylinder, a control device changes the supplied quantity of fuel to the individual cylinders. The control device operates the knocking cylinder with a richer fuel mixture, and operates the remaining non-knocking cylinders with a leaner fuel mixture. Independent claims are included for further internal combustion engines; a control device; a motor vehicle; a method of operating an internal combustion engine; a computer program for implementing a microprocessor based control device; and a data carrier for the computer program.

Description

The The invention relates to a multi-cylinder internal combustion engine.

At such internal combustion engines are often spark generators and a fuel supply device intended. In operation, the condition sometimes arises that a so-called "knocking" is scanned.

The EP 0 725 393 B1 teaches that such knocking can be remedied by adjusting the spark timing of a knocking cylinder "late".

in the Operation is disadvantageous in that it sometimes leads to component failure in such equipped Engines is coming.

The Invention is based on the task of always reliable working Internal combustion engine, an improved control device for such Internal combustion engine and a method for operating such To provide internal combustion engine, for example in a motor vehicle.

The Task is solved by the independent claims. advantageous Further developments emerge from the respective dependent claims.

The Knock limit depends in gasoline engines according to the invention u. a. also of different fuel qualities (octane number) and motor tolerances (compression ratio) from. That's why these are equipped with a knock control, for optimum torque and performance can be. The current ignition timing can operate at a full throttle point with 91 RON fuel versus 98 RON by up to eight degrees crank angle change. In full load exists thereby between exhaust gas temperature and ignition a relatively linear dependence from about 5 to 10 K per degree crank angle. Especially near the engine arranged catalysts must the mixture at full load at high Speeds below the power-optimal air ratio of about lambda = 0.9 be greased so that the catalyst does not overheat. According to the o. g. dependence In temperature protection functions, the ignition returns the knock control or corrections of the ignition point considered as a function of engine and intake air temperature, To grease only so strong that the maximum permissible temperature is maintained becomes.

The dependence the knock limit of the air ratio (At lambda = 1, the tendency to knock is strongest) is in the invention considered. The invention makes use of the possibility To reduce the tendency to knock by fattening or leaning.

If the knock limits of the individual cylinders of an engine are different are (eg because of structural tolerances, air, fuel, blow-by, oil suction or worse "AGR distribution" = different Exhaust gas recirculation rates for the Single cylinder), the engine is a cylinder-individual Enrichment much better protected than by a global one Enrichment. The approach, not just the mixture of knocking cylinders to change, but also the mixture of possibly non-knocking cylinder opposite to modify, avoids increased Exhaust emissions and increased Fuel consumption.

The Concrete embodiment of the embodiments starts from the knowledge according to the invention from that in the known in the prior art internal combustion engines exhaust valves demolished during the endurance test, among other things, to excessive exhaust gas temperatures of the cylinder in question as a result of the ignition being canceled by the knock control are attributed.

The Invention looks dependent From the operating mode of the engine three very effective method before, from which two can be used alternatively to each other. there it is envisaged to use one of the two alternatively Method together with a third method according to the invention apply.

1st method:

in the Individual will be according to the invention at a substantially stoichiometric operated internal combustion engine when sensing a knock signal at least one cylinder or a cylinder group of the or knocking cylinder or cylinder groups each by a predetermined Amount of fuel enriched with simultaneous ignition reset. The remaining non-knocking are each by a predetermined amount of emaciation emaciated from the fuel.

It is provided according to the invention that the other cylinders or cylinder groups are operated so emaciated that in the exhaust gas originating from all cylinders or cylinder groups, a substantially stoichiometric composition is present. This makes it possible to effectively cool a particular cylinder or cylinder group, thereby avoiding knocking. By leaning out the remaining cylinders or cylinder groups is doing in the exhaust provided a mixture that can be easily stoichiometrically converted by a downstream catalyst.

at a four-cylinder engine with z. B. badly cooled and thus knock sensitive middle Cylinders could according to cylinders 1 and 4 without knocking activities with a middle mixture from Z. Lambda = 1.03, cylinder 2 (knocking the strongest, latest Ignition) with lambda = 0.96 and cylinder 3 with lambda = 0.98 run. The thermal or mechanical load of components of each cylinder is correspondingly more uniform. As a result the on average less necessary retardation on the the enrichment of simultaneously faster burning middle cylinders worsens as well the overall motor efficiency less strong.

In Embodiment of this method is preferably the one or the rest Cylinder or cylinder groups each operated emaciated, at the longest no knock has been detected. These cylinders are waiting for him that an additional Slimming process no additional Knocking will produce.

2nd method:

at the alternative to the above method training provided inventive method becomes substantially stoichiometric when sampling a knock signal Operation of the internal combustion engine on that cylinder or on that Cylinder group at which knocking is detected, a leaning operation causes. By leaning the knock tendency is slightly reduced. Independently and also in addition can the knocking cylinders or cylinder groups with a later ignition timing operated as cylinders or cylinder groups, where no Knocking signal has been sampled.

There in both processes a temperature rise in the catalyst occurs, it must be ensured that the permissible maximum catalyst temperature not exceeded is, for example, by temporarily providing a substoichiometric operation (Lambda <1) either for each Single cylinder or averaged over all cylinders.

3rd method:

A Alternative to the two methods explained above according to the invention suggest that in substantially substoichiometric operation of the Motors the knocking cylinders or cylinder groups respectively additionally be operated greased, with the knocking cylinder or Cylinder groups operated with the same ignition timing be like those cylinders or cylinder groups in which no knock signal is sampled.

As a general rule can to achieve the max. Torque or the max. Performance one Enrichment be provided. To protect cylinder-individual Components such. B. the exhaust valves or the exhaust system can also an enrichment for lowering the temperature can be used. In this case, in knock events to increase the knock limit only the Mixture of the relevant cylinder additionally, briefly enriched, to stop the knocking. The pre-ignition remains unchanged.

at Conventional systems are ignition returns usually for a period of 5 to 60 sec. active. In a cylinder-individual Enrichment to increase the knock limit only a few injection pulses are necessary to more To avoid knocking events safely because of the combustion chamber and all affected Components immediately cooled become. Accordingly, the engine power remains virtually unchanged, thereby an efficiency advantage over methods with ignition timing results.

The above-described method according to the invention can also be operated in combination with each other.

1 shows a program flowchart, which is adhered to in a control according to the invention in connection with an internal combustion engine, and

2 shows a diagram, with the curves of the cylinder-specific air ratios λ of a 6-cylinder engine and the associated, cylinder-specific ignition angle.

In the control device according to the invention is a commercially available industrial control, a predetermined computer program as in 1 displayed repeats periodically at a mark "start". In this case, contents of memory variables can be transferred from one program run to the next. This is known to the person skilled in the art and will not be explained in more detail here. In addition, the control device according to the invention can process signals from sensors, not shown here, wherein the sensor values are expressed in variable contents.

It is possible to use a plurality of control devices instead of a single control device, for. As a control device for the ignition, a further Steuerungsein Direction for the injection and another higher-level control device for the measurement and overall control.

The Control according to the invention uses the following variables:

α _z

basic ignition

Δα _{z, j}

cylinder-specific deviation from α _z

Δα _zd

Ignition angle change for gradual return to α _z per loop

λ _ges

Air ratio, averaged over all cylinder

λ _j

Air ratio of Single cylinder j

λ _Lim

individual cylinder lean limit

Δλ _j

cylinder-specific deviation of λ _ges

Δλ _d

Air ratio change for the stepwise return to λ _ges per loop

n

Number of cylinders

i

Number of cylinders, their mixture / ignition angle currently be influenced by the knock control

The Control means in the first step scans for the field "Start", whether on the internal combustion engine a knock has been recognized. It is also determined which the n cylinder is knocking. Therefor a knock sensor of a Knockferkennungssystems is used, the e.g. on ion current measurement or evaluation of the cylinder pressure signal based.

If a knock has been detected, then the controller goes into a polling state in which it is determined whether the engine is operated stoichiometrically at λ _ges = 1 or substoichiometrically at λ _ges <1.

In stoichiometric operation with λ _ges = 1, both the angle of the pre-ignition and the cylinder-specific λ is adjusted in a particular embodiment of the invention. In the program in 1 is the first query "Knock recognized?" to query "λ _ges = 1?" branched. This condition is met in stoichiometric operation, so that the branch "yes" is passed.

In the present case, the value λ _{j is set} to the value λ _ges - Δλ _j . The value λ _{1 .. (n-1)} is set to the value (λ _ges + (Σ _1..i Δλ _j ) / (ni)), and this value should always be kept <λ _Lim (cylinder individual lean limit) , In the present case λ = 1, so that λ _{j is} calculated to be 1 - Δλ _j and λ _{1 .. (n-1)} = (1 + (Σ _1..i Δλ _j ) / (ni)).

By the Zündrücknahme and by the above-described simultaneous enrichment of the combustion mixture of the knocking cylinder while maintaining the component temperature limits for the one or more knocking cylinder effectively reduces the tendency to knock. The other cylinders are emaciated by an amount of (Σ _1..i Δλ _j ) / (ni), whereby a λ _ges of 1 can be obtained.

If it is recognized at the next pass that there is no more knock, then both the cylinder-specific deviation Δα _{z, j} and the cylinder-specific deviation Δλ _{j are} withdrawn. This is detected in the "Knocking?" equal to "No" accomplished. Alternatively, the program can _zd the value of Δα and / or Δλ and _d for a specific time to "0" set and thus a hold time for the ignition angle and / or enrichment provision. This possibility is not detailed in the program schedule.

2 FIG. 10 illustrates the retraction of ignition with the value Δα _{z, j} together with the enrichment of the knocking cylinder over the value λ _j = 1-Δλ _j, for example, on a six-cylinder internal combustion engine. As you can see very well, at the time t = 6 sec. sampled at the cylinder 1 that knocking is present. The internal combustion engine is operated stoichiometrically with λ _ges = 1 up to this time. As a result, the ignition angle is adjusted to "late", starting from a value α = 30 ° to a value α = 20 °. At the same time, the air ratio λ _{zyll is enriched} to a value of 0.93. In the present case, therefore, the air ratio of a knocking cylinder per 10 ° crankshaft angle at Zündzeitpunktspätverstellung by a value Δλ _j of 0.07 is lowered. The value λ _zyll then remains at the value 0.93. To the same extent, the air ratios for cylinders numbered 2 through n = 6 are raised to a value _greater than 1, each time by a value of (Σ _1..i Δλ _j ) / (ni) = 0, 07 / 5 = 0, 014. As a result, it is achieved that the air ratio, averaged over all six cylinders, is equal to 1, which corresponds to a stoichiometric combustion. The unburned fuel used in cylinder 1 for cooling is stoichiometrically reacted in a cylinder-installed catalyst together with the excess combustion air of cylinders 2 to n = 6.

In 2 is in addition to the time t = 10 sec. found that cylinder # 2 starts to knock. As a result, the ignition angle is retarded from a value of 30 ° to a value of 25 °. To the same extent, the air ratio for the cylinder 2 is set to a value of 0.965.

In order to further ensure a total air ratio of λ _ges = 1, the cylinders 3 to n = 6 must be further emaciated to compensate for the enrichment of cylinder 2, and in total by a value of (0.07 + 0.035 / 6-2) = 0 , 02625 to λ _{1 .. (ni)} = 1.02625

In another not shown here guidance analogous to 1 it is also provided in the case "λ _ges = 1", the cylinder or cylinder as a knocked scored cylinder with respect to their cylinder-individual air ratio so lean that the tendency to knock is reduced.

In the event that the internal combustion engine and each individual cylinder is operated substoichiometrically, ie λ _ges <1, Δα _{z ,, j is set} to 0, ie there is no Zündwinkelrücknahme (see 1 ). In this case, the control device is influenced in such a way that Δλ _{j is set} to a value of, for example, approximately 0.1 in order to reliably avoid repeated knocking. This value can be made dependent on the knock intensity in a particular embodiment and thus adapted to the respective prevailing conditions and also be different from cylinder to cylinder.

In the next run of the program is again checked whether the corresponding change has already caused a disappearance of knocking. Optionally, the enrichment is further increased to z. B. Δλ _j about 0.15. If the knock on the cylinder in question ceases, then the program branches according to 1 at the first query on the branch "no". Then it is checked whether Δλ _j is still> 0. If so, the next injection quantity is determined so that the next Δλ _j results from the difference between the instantaneous Δλ _j and the value Δλ _d . Alternatively, the program may also set the value for Δλ _d to "0" for a certain time and thus provide a hold time for enrichment, which option is not detailed in the program schedule.

If Δλ _j already has the value 0 in this check, then the loop is continued at "Start" without changing Δλ _j .

On this way is in substoichiometric Always ensuring that knocking is avoided, wherein an adjustment of the current ignition angle does not occur.

Of course, according to 1 all changes made in the branch "Knock recognized?" = "No" gradually returned to baseline if knocking is no longer detected.

Claims (26)

Internal combustion engine with multiple cylinders, wherein at least one spark generator each at the cylinders, a fuel supply device and a Knockferkennungssystem is provided, and with a control device, the at substantially stoichiometric Operation of the internal combustion engine during the sampling of a knock signal on at least one cylinder through the knock detection system supplied in the individual cylinders Fuel quantity changed as follows: - The control device operates the knocking cylinders each by a predetermined Anfettungsmenge fueled by fuel; - The control device operates the remaining non-knocking Cylinder each by a predetermined amount of lean fuel emaciated. Internal combustion engine according to claim 1, characterized the control device emaciates the remaining cylinders in such a way operates in that in the exhaust of all cylinders exhaust one stoichiometric Composition is present. Internal combustion engine according to one of the preceding claims, characterized in that the control device for the knock detection system has a time measuring device that detects how long no Knocking was detected more, wherein the control means those other cylinders each emaciated by a predetermined amount of lean fuel operates the longest no knock was detected. Internal combustion engine according to one of the preceding claims, characterized characterized in that the control device with the knocking cylinder a later one ignition timing operates as in cylinders where no knock signal is sampled is. Internal combustion engine with several cylinders, where on at least one spark generator each of the cylinders, a Kraftstoffstoffzuführeinrichtung and a knock sensor is provided, and with a control device, those at substantially stoichiometric Operation of the internal combustion engine during the sampling of a knock signal at least one cylinder through the Knockferkennungssystem the in fed to the individual cylinders Fuel quantity changed as follows: - The control device each operates the knocking cylinders by a predetermined amount of leaning emaciated from fuel. Internal combustion engine having a plurality of cylinders, wherein at least one ignition spark generating device, a Kraftstoffstoffzuführeinrichtung and a knock sensor is provided on the cylinders, and with a control device which supplied in substoichiometric operation of the internal combustion engine when sensing a knock signal to at least one cylinder by the knock detection system in the individual cylinders Amount of fuel changed as follows: the control means operates the knocking cylinders respectively by a predetermined amount of enrichment of fuel; - The controller operates the knocking cylinder with the same ignition timing as the cylinders in which no knock signal is sampled. Internal combustion engine according to claim 6, characterized that the control means the knocking cylinder with a later ignition point operates as the cylinders where no knock signal is sampled is. Internal combustion engine with the characteristics of either one of the claims 1 to 4 or 5 and in addition with the features of one of the claims 6 or 7. Control device for an internal combustion engine with a plurality of cylinders, wherein at least one of the cylinders Zündfunkenerzeugungseinrichtung, a Kraftstoffstoffzuführeinrichtung and a knock detection system is provided, and wherein the control means at substantially stoichiometric Operation of the internal combustion engine during the sampling of a knock signal on at least one cylinder through the knock detection system supplied in the individual cylinders Fuel quantity changed as follows: - The control device operates the knocking cylinders each by a predetermined Anfettungsmenge fueled by fuel; - The control device operates the rest Cylinder each by a predetermined amount of lean fuel emaciated. Control device according to claim 9 and with the Features of one or more of claims 2 to 4. Control device for an internal combustion engine with a plurality of cylinders, wherein at least one of the cylinders Zündfunkenerzeugungseinrichtung, a Kraftstoffstoffzuführeinrichtung and a knock detection system is provided, wherein the control device, those at substantially stoichiometric Operation of the internal combustion engine during the sampling of a knock signal on at least one cylinder through the knock detection system supplied in the individual cylinders Fuel quantity changed as follows: - The control device each operates the knocking cylinders by a predetermined amount of leaning emaciated from fuel. Control device for an internal combustion engine with a plurality of cylinders, wherein at least one of the cylinders Zündfunkenerzeugungseinrichtung, a Kraftstoffstoffzuführeinrichtung and a knock sensor is provided, wherein the control device those at substoichiometric Operation of the internal combustion engine during the sampling of a knock signal at least one cylinder by the or the knock sensors the in the individual cylinders or cylinder groups supplied amount of fuel changed as follows: - The control device operates the knocking cylinders each by a predetermined Anfettungsmenge fueled by fuel; - The control device operates the knocking cylinders with the same ignition timing as the cylinders, where no knock signal is sampled. Control device according to claim 12 and with the Features of one or both of claims 6 and 7. Control device with the features either one of the claims 9 to 10 or 11 and in addition with the features of one of the claims 12 or 13. Motor vehicle with an internal combustion engine after a the claims 1 to 8. Method for operating an internal combustion engine with multiple cylinders, wherein when sampling a knock signal on at least one cylinder, the knocking cylinders each one predetermined amount of fuel enrichment, wherein the remaining each emaciated by a predetermined amount of lean fuel become. Method according to claim 16, characterized in that that the rest non-knocking cylinders are operated so emaciated that in the exhaust gas from all cylinders, one substantially stoichiometric Composition is present. Method according to claim 16 or 17, characterized that others are left Cylinder each by a predetermined amount of lean fuel be degraded, where the longest no knocking is detected. Method according to one of Claims 16 to 18, characterized that the knocking cylinders are operated at a later ignition point as the cylinders where no knock signal is sensed. Method for operating an internal combustion engine having a plurality of cylinders at substantially stoichiometric operation, wherein Sampling a knock signal to at least one cylinder in the fed to individual cylinders Fuel quantity, the knocking cylinders each by a predetermined Emaciation amount of fuel to be emaciated operated. Method of operating a burn Multi-cylinder engine in which, in substoichiometric operation, when sensing a knock signal on at least one cylinder, the amount of fuel supplied in each cylinder is changed as follows: - the knocking cylinders are each enriched by a predetermined amount of fuel; - The knocking cylinders are operated at the same ignition timing as the cylinders where no knocking is sensed. Method according to claim 21, characterized that the knocking cylinders are operated at a later ignition point as the cylinders where no knock signal is sensed. Method with the features of either of claims 16 to 19 or 20 and in addition with the features of one of the claims 20 or 21. Computer program for implementation in a microprocessor-driven Control device for an internal combustion engine having a plurality of cylinders, wherein on the cylinders at least one ignition spark device each, a Kraftstoffstoffzuführeinrichtung and a knock detection system is provided, wherein the computer program so is formed, that a method according to any one of claims 16 to 23 executable is. Computer program according to claim 24, which is on a Storage medium, in particular in a semiconductor memory or in a direct access memory. disk with a computer program according to claim 24.