DE10354102A1 - Process for operating a direct injection internal combustion engine with spark-ignition comprises injecting fuel during the compression phase in the event of a high load - Google Patents

Abstract

Process for operating a direct injection internal combustion engine with spark-ignition uses a combustion chamber in which a piston passes through at least one induction phase and one compression phase. An ignitable fuel/air mixture is ignited in a spark plug region. In the event of a high load, at least one fuel injection occurs during the compression phase. Preferred Features: The internal combustion engine is supercharged.

Description

The The invention relates to a method for operating an internal combustion engine according to the features in Preamble of claim 1.

she is based on WO 97/40356, in which an operating method for a direct injection Otto internal combustion engine is described, in which a control unit, the parameters determining the burning process in the combustion chamber adjusts that knocking combustion is avoided. When knocking Combustion does not burn off any part of the fuel / air mixture the spark plug starting evenly, but ignited by itself or by name surfaces and burns suddenly, with the pressure peaks occurring in the combustion chamber can have a performance-reducing effect. In the described Methods are used to detect a knocking combustion output signals evaluated by knock sensors. A microcomputer of the control unit calculates accordingly control signals for the ignition or the injection. When knocking is detected, the ignition timing becomes in the direction of "later ignition" during the work cycle the internal combustion engine adjusted. By this adjustment of the ignition timing after late To ensure that in the following combustion processes Knocking is avoided.

adversely in the method described is that only knocking occur must, so that the parameters for the internal combustion engine operation nachschüssig be readjusted so can, so that a knocking certainly avoided in the other Brennverläufen becomes.

task The present invention is an operating method for a direct-injection internal combustion engine show, in which a knocking largely avoided and a Readjustment is not necessary.

These The object is achieved by the feature in the characterizing part of the claim 1 solved.

By the inventive method, the preferably used in the upper part-load range and / or at full load is safely prevented during the compression phase, in the knocking areas can form, in the edge areas of the Combustion chamber an auto-ignitable fuel / air mixture is present. The ignition outside of the spark plug area located fuel evaporates after ignition, from combustion support and then burns completely due to the chemical reaction. Because of the late mixture preparation, d. H. Fuel evaporation in the areas outside the spark plug area, Forms at typical Klopforten, for example in the field of be called Exhaust valves, no knockout due to the significantly reduced pre-reaction time and the lower temperatures due to the late fuel evaporation. Thus, can also no auto ignition respectively. Next is by the inventive method in more advantageous Way the efficiency of the internal combustion engine increased and additionally cooler exhaust gas emitted.

By the injection according to claim 2 is advantageously avoided that before the ignition in the entire combustion chamber, a homogeneous fuel / air mixture, d. H. a uniformly mixed Fuel / air mixture is formed, which in advantageous Way the emergence of knocking is prevented.

Of the Field of application of the method according to the invention is extended by claim 3, since in particular charged Internal combustion engines tend to knock. Thus, the method is particularly suitable for charged Internal combustion engines or internal combustion engines with a compression ratio greater than 12.

• 1. Durch eine geeignete Kombination aus der geometrischen Form des Brennraums, der Kraftstoffstrahlform und der Kraftstoffstrahleindringtiefe, sowie der Ladungsbewegung im Brennraum, muss im Zündkerzenbereich innerhalb kürzester Zeit ein möglichst homogenes Gemisch erzeugt werden.
• 2. Der flüssige Kraftstoff muss im Zündkerzenbereich sehr schnell verdampfen, außerhalb des Zündkerzenbereiches bezogen auf die Ausbreitung der Flamme im Brennraum jedoch nicht zu schnell, damit an den kritischen Klopforten, wie oben beschrieben, kein Klopfherd entstehen kann. Dies heißt, dass zündfähiges Kraftstoff-/Luftgemisch, ausgehend von der Zündkerze, nach dem Zündzeitpunkt zum Brennen beginnt, während an den am weitesten von der Zündkerze entfernten Orten, bzw. an den klopfgefährdeten Orten, noch kein selbstzündfähiges Kraftstoff-/Luftgemisch vorliegt.
• 3. Vor dem Ende der Verbrennung muss auch in den noch nicht von der Flamme erfassten Gebieten ein zündfähiges Kraftstoff-/Luftgemisch vorliegen, so dass das gesamte Brennraumvolumen und somit auch der gesamte im Brennraum vorhandene Sauerstoff und Kraftstoff an der Verbrennung teilnimmt. Hier ist durch einen mageren Brennkraftmaschinenbetrieb eine Vereinfachung des Verfahrens möglich, indem weniger Kraftstoff in den Brennraum eingespritzt wird als Sauerstoff zur Verbrennung zur Verfügung steht. Somit wird das Verfahren der Gemischbildung vereinfacht.

For implementing the method in the upper part-load operation and / or full-load operation of the internal combustion engine, the following points must be ensured:

• 1. By a suitable combination of the geometric shape of the combustion chamber, the fuel jet shape and the fuel-jet penetration depth, as well as the charge movement in the combustion chamber, the most homogeneous mixture must be generated in the spark plug within a very short time.
• 2. The liquid fuel must evaporate very quickly in the spark plug area, but not too fast outside the spark plug area with respect to the propagation of the flame in the combustion chamber, so that no knocking hearth can develop at the critical knock locations as described above. This means that ignitable fuel / air mixture, starting from the spark plug, begins to burn after the ignition, while at the furthest removed from the spark plug locations, or at the knock-prone locations, yet no auto-ignitable fuel / air mixture.
• 3. Before the end of combustion, an ignitable fuel / air mixture must be present even in the areas not yet covered by the flame, so that the entire combustion chamber volume and thus also the total amount of oxygen and fuel present in the combustion chamber burns participate. Here is a lean internal combustion engine operation, a simplification of the method possible by less fuel is injected into the combustion chamber as oxygen is available for combustion. Thus, the method of mixture formation is simplified.

• – Vorreaktionszeit: Die Zeit, die für den Ablauf von chemischen Vorreaktionen bis zur Selbstzündung erforderlich ist. Sie ist abhängig von Temperatur, Druck und der Kraftstoff-/Luftgemischzusammensetzung.
• - selbstzündfähig: Ein Kraftstoff-/Luftgemisch ist selbstzündfähig, wenn die Bedingungen für Selbstzündung erfüllt sind, d.h. wenn die Vorreaktionszeit kürzer ist als die Zeit, die eine Flammenfront zum Erfassen des Endgases, das noch nicht verbrannte Kraftstoff-/Luftgemisch, benötigt.
• - Hohe Last: Zu einer hohen Last einer Brennkraftmaschine sind alle Betriebspunkte zu zählen, bei denen Klopfen auftreten kann.
• - Zündkerzenbereich: Ein Bereich um den Zündort einer Zündquelle mit maximal dem halben Durchmesser eines Kolbens.

The following definitions also apply to the proposed procedure:

• - Pre-reaction time: The time required for the passage of chemical pre-reactions to auto-ignition. It depends on temperature, pressure and the fuel / air mixture composition.
• - autoignitable: A fuel / air mixture is auto-ignitable when the conditions for auto-ignition are met, that is, when the pre-reaction time is shorter than the time that a flame front for detecting the final gas, the not yet burned fuel / air mixture needed.
• - High load: To a high load of an internal combustion engine are all operating to count, where knocking can occur.
• - Spark plug area: An area around the ignition location of an ignition source with a maximum of half the diameter of a piston.

Around Achieving above points can have different parameters for the Operation of the internal combustion engine can be adjusted. Regarding the Fuel injection, these are: The injection timing, eventually a multiple injection, the fuel injection pressure and the Fuel injection history, d. H. the opening stroke of the injector over the Time. Furthermore, the hole geometry of the fuel injector, for example the bore diameter, adapted accordingly or the hole geometry over the Scope of the fuel injector to be changed. As further parameters are also the ignition point to name, which determines the beginning of the burn and a purposeful Charge movement over the inlet channels and the piston shape, which affect the mixture formation.

Summarized can be said that the invention is a strong reduction up to prevent the tendency to knock and thus allows high compression ratios with simultaneously improved ignition timing and resulting improved center of gravity of the combustion allowed. This is especially true for supercharged internal combustion engines who work according to the Otto principle.

• – Einen besseren Wirkungsgrad der Brennkraftmaschine und/oder
• – ein höheres Verdichtungsverhältnis, wodurch
• – niedrigere Abgastemperaturen bei gleicher Motorlast und gleichem Kraftstoff-/Luftverhältnis erzielt werden, wodurch
• – keine bzw. eine stark verringerte Volllastanreicherung mit Kraftstoff zum Schutz des Katalysators erforderlich wird, was
• – zu einer zusätzlichen Kraftstoffeinsparung führt.

Thus, the invention allows in addition to the high security against self-ignition (knocking) of the fuel / air mixture:

• - A better efficiency of the internal combustion engine and / or
• - a higher compression ratio, which
• - Lower exhaust gas temperatures are achieved with the same engine load and the same fuel / air ratio, which
• - No or a greatly reduced full load enrichment with fuel to protect the catalyst is required, what
• - leads to additional fuel savings.

Claims (3)

Method for operating a spark-ignited, direct-injection internal combustion engine with at least one combustion chamber in which a piston undergoes at least one intake phase and one compression phase, wherein an ignitable fuel / air mixture is ignited in a spark plug region, characterized in that at high load at least one fuel injection during the compression phase. The method of claim 1, wherein the piston from the crankshaft in the compression phase towards an upper one Zündtodpunktes is moved, characterized in that the fuel injection only at a smaller distance of the piston than 100 degrees crank angle from the top dead center starts. Method according to claim 1 or 2, characterized that the internal combustion engine is charged.