DE102021002192A1 - Method for operating an internal combustion engine of a motor vehicle, in particular a motor vehicle - Google Patents

Abstract

The invention relates to a method for operating an internal combustion engine (10) of a motor vehicle, in which the internal combustion engine (10) comprises at least one combustion chamber (20) and a prechamber spark plug (26) assigned to the combustion chamber (20) and having a plurality of openings (28) fluidically connected to the combustion chamber (20), the internal combustion engine (10) designed as a spark-ignition engine being operated in catalytic converter heating mode, in which an ignition point at which, within a respective working cycle of the internal combustion engine (10), an ignition spark is generated in the prechamber for igniting a Fuel-air mixture is generated, is retarded compared to normal operation, the last injection taking place within the respective working cycle, through which fuel is injected directly into the combustion chamber (20), in the catalytic converter heating operation in a range of 10 degrees inclusive Crank angle up to and including h Begins and/or ends 100 degrees crank angle before ignition timing.

Description

The invention relates to a method for operating an internal combustion engine of a motor vehicle, in particular a motor vehicle, according to the preamble of patent claim 1.

Such a method for operating an internal combustion engine of a motor vehicle, in particular a motor vehicle, is already known, for example DE 10 2018 000 706 A1 to be taken as known. In the method, the internal combustion engine has at least one combustion chamber and a prechamber spark plug which is assigned to the combustion chamber and comprises a prechamber which is fluidically connected to the combustion chamber via a plurality of openings. Furthermore, the DE 10 2010 010 109 A1 a prechamber spark plug. From the DE 102 46 505 A1 a method for operating an internal combustion engine is known. In addition, the DE 10 2020 000 353 A1 a method for operating an internal combustion engine of a motor vehicle.

The object of the present invention is to further develop a method of the type mentioned at the outset in such a way that particularly advantageous operation can be implemented.

This object is achieved by a method having the features of patent claim 1. Advantageous configurations with expedient developments of the invention are specified in the remaining claims.

In order to further develop a method of the type specified in the preamble of patent claim 1 in such a way that a particularly advantageous operation of the internal combustion engine can be implemented, it is provided according to the invention that the internal combustion engine designed as a spark-ignition engine is operated in catalyst heating mode, in which an ignition point at which within of a respective working cycle of the internal combustion engine in the antechamber, an ignition spark for igniting a fuel-air mixture received in the antechamber is generated, is retarded compared to normal operation of the internal combustion engine. By igniting the fuel-air mixture received in the prechamber, a fuel-air mixture received or remaining in the combustion chamber is also ignited, in particular in such a way that the fuel-air mixture received in the prechamber is ignited fuel-air mixture contained in the pre-chamber is ignited. This results in so-called burning flares, i.e. flames, which flow through the openings and thus flow or get out of the antechamber into the actual combustion chamber and thus ignite the fuel-air mixture received or remaining in the combustion chamber, which is then burned .

Furthermore, it is provided that in the catalytic converter heating mode, the last injection taking place within the respective working cycle, through which fuel is injected directly into the combustion chamber, takes place in a range from 10 degrees crank angle up to and including 100 degrees crank angle, in particular in a range from 20 Degrees of crank angle up to 60 degrees of crank angle before ignition timing starts and/or ends. For example, in the catalyst heating mode, several, i.e. in particular at least or exactly two, injections are carried out within the respective working cycle, which are consecutive and spaced apart in time, with the injections in each case of the liquid fuel, in particular, from which the fuel-air mixture is formed is injected directly into the combustion chamber. It is preferably provided that the last of the injections carried out within the respective working cycle in the catalytic converter heating mode, as described, is delivered at a distance of 10 degrees crank angle to 100 degrees crank angle, in particular 20 degrees crank angle to 60 degrees crank angle, before the ignition time or from the ignition time .

The invention is based in particular on the following findings: The use of a prechamber spark plug in a Otto direct injection combustion process should ensure that the function of the catalytic converter heating operation after a cold start to achieve exhaust gas limits is also guaranteed with this ignition technology. In the case of standard spark plugs, i.e. spark plugs without a prechamber, a so-called ignition injection is used to inject fuel directly before the ignition point at a constant distance from the ignition in order to stabilize a necessary, very late ignition. According to the invention, a special injection strategy solves the problem that an ignition injection in the prechamber spark plug cannot be delivered one-to-one directly into a spark area, as is the case with a standard spark plug. This means that the ignition spark is generated within the prechamber, but the fuel is injected directly into the combustion chamber, which is separated from the prechamber except for the openings, in particular in such a way that the fuel is injected directly into an area of the combustion chamber located outside of the prechamber becomes.

• - Besser aufbereitetes Kraftstoff-Luft-Gemisch liegt zum Zündzeitpunkt im Funkenbereich der Vorkammer vor. Dadurch werden die Entflammungsbedingungen im Vergleich zu herkömmlichen Lösungen verbessert, die Verbrennung wird stabilisiert.
• - keine Verbrennungsaussetzer, die zur Schädigung eines Katalysators führen, der durch den Katalysatorheizbetrieb besonders schnell erwärmt, das heißt aufgeheizt werden soll
• - Höhere Temperatur im Abgas kann erzeugt werden, da bis zu extrem späten Zündungszeitpunkten noch eine stabile Verbrennung stattfinden kann, um durch die späten Verbrennungslagen die Thermodynamik derart zu verschlechtern, dass der Katalysator so schnell wie möglich bis zu seinem Arbeitsbereich (Temperaturfenster) erwärmt wird.

So to ensure good ignition in the prechamber of the prechamber spark plug in the kata lysator heating mode, which is also referred to as catalytic converter heating mode, not to introduce too much fuel, some of which can also be poorly prepared, care should be taken to ensure that the last, particularly the second, injection before ignition, i.e. before the ignition point, takes place so late that that this injected portion of fuel either does not have enough time to get through the openings of the prechamber spark plug, also known as overflow bores or designed as overflow bores, into the prechamber and into a spark area in order to inject the fuel-air mixture located there, also simply called the mixture over-grease, or only partially penetrate to ensure rapid burnout after ignition in the spark area. According to the invention, this is applied, ie realized, via a constant differential angle or start of injection and ignition point, for example. The spark area is to be understood in particular as such an area or such a point in which or at which the ignition spark can be generated or is generated in the prechamber. In particular, at least the following advantages can be realized by the invention:

• - A better prepared fuel-air mixture is present in the spark area of the prechamber at the ignition point. This improves the ignition conditions compared to conventional solutions, and combustion is stabilized.
• - No combustion misfires that lead to damage to a catalytic converter that is heated particularly quickly by the catalytic converter heating operation, i.e. is to be heated up
• - Higher temperatures in the exhaust gas can be generated, since stable combustion can still take place up to extremely late ignition times, in order to deteriorate the thermodynamics due to the late combustion positions in such a way that the catalytic converter is heated up to its working range (temperature window) as quickly as possible.

Further findings on which the invention is based are that during catalyst heating operation, in particular after a cold start of the internal combustion engine, the thermodynamics of combustion are intentionally worsened in order to increase the exhaust gas temperature and to shorten the heating-up time to the working temperature (light-off temperature) of the catalyst. For this purpose, the ignition point is retarded compared to normal operation, and the combustion takes place at a thermodynamically unfavorable later point in time. Such late ignition of the mixture usually results in undesirable, increased cycle fluctuations or rough running, which in extreme cases can even lead to combustion misfires. In order to improve the ignition conditions even with these late ignition times, multiple injections are used with a standard spark plug, for example with a roof electrode, the last injection of which is usually coupled to the ignition time and with a constant interval of around 10 degrees crank angle to 20 degrees, for example crank angle at this ignition point, a small amount of fuel sprays into the spark area of the spark plug, where it ensures good and stable ignition as a rich mixture cloud.

However, when using a prechamber spark plug, this mixture cloud cannot get directly into the spark area. In the prechamber spark plug, the mixture cloud is diverted through the openings and a deflection when it enters the prechamber and in the prechamber into the spark area located there. A longer period of time is required for this, depending on the free path length from the injection valve to the spark gap in the prechamber, the speed and the injection pressure. Reliable ignition of the mixture in the pre-chamber, also known simply as the chamber, requires that this mixture does not consist of too much fuel (lambda<1) or poorly prepared fuel. According to the invention, for the catalytic converter heating operation with the prechamber spark plug, it is to be avoided that the injections, and in particular the last injection, are discontinued in such a way that they reach the prechamber and there in the area of the spark gap between the electrodes poorly prepared shortly before the ignition point. However, it is advantageous for ignition if the last injection produces a somewhat richer mixture cloud at the exit from the prechamber or in the immediate vicinity of the prechamber. An ignition-coupled, final injection should therefore be carried out at a distance defined according to the invention of 10 degrees crank angle to 100 degrees crank angle, in particular 20 degrees crank angle to 60 degrees crank angle, from the ignition point.

Further advantages, features and details of the invention result from the following description of a preferred exemplary embodiment and from the drawing. The features and combinations of features mentioned above in the description and the features and combinations of features mentioned below in the description of the figures and/or shown alone in the single figure can be used not only in the combination specified in each case, but also in other combinations or on their own, without the frame to abandon the invention.

In the single figure, the drawing shows a detail of a schematic sectional view of an internal combustion engine of a motor vehicle, the internal combustion engine being operated in accordance with a method according to the invention.

The only figure shows a detail in a schematic sectional view of an internal combustion engine 10 of a motor vehicle, in particular a motor vehicle, designed as a reciprocating piston machine or reciprocating piston engine. This means that the motor vehicle has the internal combustion engine 10 in its fully manufactured state and can be driven by the internal combustion engine 10 . The internal combustion engine 10 has a housing element, not shown in the figure, which is designed, for example, as a crankcase, in particular as a cylinder crankcase, by which at least one cylinder 12 is formed or delimited. The internal combustion engine 10 has at least one piston 14 which is arranged in the cylinder 12 so that it can move in a translatory manner and can therefore be moved between a bottom dead center and a top dead center. The internal combustion engine 10 also has a second housing element 16 which, for example, is formed separately from the first housing element and is connected to the first housing element. The housing element 16 is, for example, a cylinder head, through which a combustion chamber roof 18 is formed. The cylinder 12, the piston 14 and the combustion chamber roof 18 each form or partially delimit a combustion chamber 20 of the internal combustion engine 10 designed as a reciprocating piston machine or reciprocating engine 24 a fuel, in particular a liquid fuel, can be injected directly into the combustion chamber 20 . The injector 22 is also referred to as an injection valve. The direct injection of the fuel into the combustion chamber 20 is also referred to as direct injection or direct fuel injection or simply as injection. Internal combustion engine 10 is designed as an Otto engine and also has a prechamber spark plug 26 assigned to combustion chamber 20, which has a prechamber that cannot be seen in more detail in the figure. The prechamber of prechamber spark plug 26 is also referred to simply as a chamber and is fluidically connected to combustion chamber 20 via respective openings 28 embodied, for example, as bores, and is preferably otherwise separated from combustion chamber 20 . An electrode arrangement is arranged in the antechamber, by means of which at least one ignition spark can be generated in particular in a spark region arranged in the antechamber, which is also referred to as a spark gap.

At least during fired operation of internal combustion engine 10, the aforementioned fuel and air are introduced into combustion chamber 20 within a respective working cycle of internal combustion engine 10, as a result of which a fuel-air mixture, also referred to as charge or mixture, is formed in combustion chamber 20. At least a first part of the fuel-air mixture can flow out of the combustion chamber 20 via the openings 28 into the antechamber. If the ignition spark is then generated, for example, in the antechamber and in particular at an ignition point, the first part of the fuel-air mixture accommodated in the antechamber is thereby ignited and thereby burned. This results in burning flares that flow through the openings 28 and thus flow out of the antechamber into the actual combustion chamber 20 . As a result, a second portion of the fuel-air mixture remaining in combustion chamber 20 is ignited and subsequently burned. Thus, for example, the fuel-air mixture in the combustion chamber, ie the second part, is also ignited at the ignition point mentioned.

The figure also shows a gas exchange valve 30 of internal combustion engine 10 that is associated with combustion chamber 20 and is designed, for example, as an inlet valve. For example, the above-mentioned air can flow into combustion chamber 20 via the intake valve, in particular forming a tumble-shaped flow illustrated by arrow 32 in the figure, which results in a tumble-shaped charge movement in combustion chamber 20, for example.

In order to now implement a particularly advantageous operation of the internal combustion engine 10, the internal combustion engine 10 is operated according to a method which is explained below. In the method, internal combustion engine 10 embodied as an Otto engine is operated in catalytic converter heating operation, which is specifically provided or carried out in order to heat at least one catalytic converter through which exhaust gas from internal combustion engine 10 can flow. In the catalytic converter heating mode, the ignition point at which the ignition spark for igniting the fuel-air mixture received in the prechamber is generated in the prechamber within the respective working cycle of internal combustion engine 10 is retarded compared to normal operation of the internal combustion engine that follows, for example, catalytic converter heating mode .

For example, in particular in the catalyst heating mode, several and therefore preferably at least or in particular exactly two consecutive and spaced apart injections are carried out within the respective working cycle, through which the fuel is injected directly into the combustion chamber. It is also provided that the last injection taking place within the respective working cycle, through which the fuel is injected directly into the combustion chamber 20, in the catalytic converter heating operation in a range from 10 degrees crank angle up to and including 100 degrees crank angle, in particular in a range from 20 degrees crank angle inclusive up to and including 60 crank angle degrees inclusive, before the ignition timing is discontinued, ie begins and/or ends. As a result, the catalytic converter can be heated up particularly quickly. This also makes it possible to avoid combustion misfires and thus undesired rough running of the internal combustion engine 10 .

reference list

10

internal combustion engine

12

cylinder

14

Pistons

16

housing element

18

combustion chamber roof

20

combustion chamber

22

injector

24

beam

26

prechamber spark plug

28

opening

30

gas exchange valve

32

Arrow

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was 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.

Patent Literature Cited

• DE 102018000706 A1 [0002]
• DE 102010010109 A1 [0002]
• DE 10246505 A1 [0002]
• DE 102020000353 A1 [0002]

Claims (3)

Method for operating an internal combustion engine (10) of a motor vehicle, in which the internal combustion engine (10) comprises at least one combustion chamber (20) and a prechamber spark plug (26) assigned to the combustion chamber (20), which is fluidically connected to the combustion chamber via a plurality of openings (28). (20) has a connected antechamber, characterized in that the internal combustion engine (10) designed as an Otto engine is operated in a catalyst heating mode, in which an ignition point at which within a respective working cycle of the internal combustion engine (10) in the antechamber an ignition spark for igniting a fuel -air mixture is generated, is retarded compared to normal operation, the last injection taking place within the respective working cycle, through which fuel is injected directly into the combustion chamber (20), in the catalytic converter heating operation in a range of 10 degrees crank angle inclusive up to and including 1 00 degrees crank angle before ignition timing starts and/or ends. procedure after claim 1 , characterized in that the last injection taking place within the respective working cycle in the catalytic converter heating operation begins and/or ends in a range of 20 degrees crank angle inclusive up to and including 60 crank angle degrees before the ignition point. procedure after claim 1 or 2 , characterized in that in the catalyst heating operation within the respective working cycle exactly two consecutive and spaced apart injections are carried out, through which fuel is injected directly into the combustion chamber (20).

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