DE102017009613A1 - Method for operating an internal combustion engine of a motor vehicle, in particular of 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 in at least one combustion chamber (12) of the internal combustion engine (10), a fuel-air mixture is formed, which by means of a pre-chamber spark plug (16), which one over several Overflow (13) with the combustion chamber (12) connected pre-chamber (18) is ignited, wherein an exhaust gas recirculation is performed, by means of which the combustion chamber (12) exhaust gas of the internal combustion engine (10) is supplied; and

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, for example, is already the US 8,925,518 B1 to be known as known. In the method, a fuel-air mixture is formed in at least one combustion chamber of the internal combustion engine, which is ignited by means of a third ignition device designed as Vorkammerzündkerze. The prechamber spark plug has a prechamber connected to the combustion chamber via a plurality of overflow openings. Since the fuel-air mixture is ignited not by auto-ignition, but by means of the pre-chamber spark plug, the internal combustion engine operates with spark ignition.

Object of the present invention is to develop a method of the type mentioned in such a way that a particularly low-emission operation of the internal combustion engine can be realized.

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

In order to develop a method specified in the preamble of claim 1 type such that a particularly low-emission operation of the internal combustion engine can be realized, it is inventively provided that an exhaust gas recirculation is carried out, by means of which the combustion chamber exhaust gas of the internal combustion engine is supplied. The exhaust gas supplied to the combustion chamber of the internal combustion engine is also referred to as an inert gas or can act as an inert gas in the combustion chamber, thereby being able to keep the nitrogen oxide emissions (NO _x emissions) particularly low, for example. In the context of the invention, supplying the exhaust gas into the combustion chamber means that the fuel-air mixture and the exhaust gas supplied to the combustion chamber and provided in addition to the fuel-air mixture are simultaneously accommodated in the combustion chamber, so that the fuel Air mixture ignited and is burned in the sequence, while the inert gas (the recirculated exhaust gas) is received in the example formed as a cylinder combustion chamber. In addition, in Otto engine stoichiometric operation in combination with high Inertgasbeimischung the combination of high efficiency, power density and the simultaneous use of a simple exhaust aftertreatment by 3-way catalyst is possible

Furthermore, it is provided according to the invention that an at least approximately stoichiometric fuel-air mixture is formed in the prechamber by introducing air and fuel directly into the prechamber via at least one feed element provided separately from the overflow openings. Thus, the air and the fuel are introduced directly from the overflow into the antechamber, so that also referred to as fuel fuel and the air not about the overflow, but on the different from the overflow, provided in addition to the overflow supply element and for example in addition to the possibly also inert gas having fuel-air mixture are introduced from the combustion chamber in the prechamber. In this way, a particularly advantageous ignition in the antechamber of the prechamber spark plug can be realized, wherein at the same time in the combustion chamber, also referred to as the main combustion chamber, a particularly high proportion of inert gas can be realized.

It has been found that with a high inert gas content in the antechamber of the prechamber spark plug, a high ignition delay as well as a slow flame propagation in the prechamber can occur. A resulting increase in pressure in the antechamber is therefore very small. Thus, torch jets emanating from the antechamber have only a small impulse and a low energy. As a result, the ignition of the fuel-air mixture in the combustion chamber or diesel-like combustion process of the gas jets in the combustion chamber by the emerging from the antechamber torch jets at high inert gas is only limited possible. These problems and disadvantages can be avoided by means of the method according to the invention, so that on the one hand a particularly low-emission operation of the internal combustion engine and on the other hand a reliable ignition of the fuel-air mixture can be realized. Thus, a particularly good smoothness of the internal combustion engine can be ensured at high inert gas in the main combustion chamber.

In particular, a significantly reduced inert gas content or a significantly reduced inert gas mass is provided in the prechamber, since the air and the fuel formed, for example, as fuel gas are introduced directly into the prechamber.

Preferably, the internal combustion engine is a gas engine used for a mobile application. It has proven to be particularly advantageous if the air and the fuel formed, for example, as fuel gas are provided at a high pressure to supply the prechamber, this provision of the air and of the fuel taking place, for example, from in-vehicle systems. For example, the air is provided as compressed air or introduced into the pre-chamber, in particular directly, wherein the compressed air is provided for example by a vehicle-side pneumatic system. The pneumatic system comprises, for example, at least one air compressor, which can be used in particular in a commercial vehicle. In particular, the air is provided, for example, with a pressure in a range of from 10 bar inclusive up to and including 15 bar and in particular introduced into the prechamber.

For example, the fuel formed as fuel gas, for example, is also provided by an in-vehicle system. In particular, as the fuel which is directly introduced into the prechamber, a gaseous fuel such as CNG (Compressed Natural Gas) or LNG (Liquefied Natural Gas) is used. It has proved to be advantageous if the fuel is introduced at a pressure of more than 5 bar in the prechamber.

The inventive method allows the use of the pre-chamber spark plug as rinsed Vorkammerzündkerze, since the prechamber is flushed with the provided in addition to the fuel-air mixture formed in the combustion chamber and the fuel provided in addition to the fuel-air mixture formed in the combustion chamber, by the fuel and the air separated from each other are introduced directly into the antechamber. Thus, the inventive method allows, for example, the use of the purged pre-chamber spark plug for realizing a diesel-like combustion process, in particular a diesel-like gas combustion process. In this case, for example, the internal combustion engine is operated as a gas engine, which is operated by means of a gaseous fuel. The gaseous fuel is used to form the fuel-air mixture in the combustion chamber. In this case, for example, the gaseous fuel is blown by means of a high-pressure direct injection, in particular directly, in the example designed as a cylinder combustion chamber. In order to keep the nitrogen oxide emissions particularly low, exhaust gas is recycled as inert gas mass and introduced or introduced into the combustion chamber designed as the main combustion chamber.

Furthermore, it is conceivable to use the prechamber spark plug for realizing an Otto engine combustion method, in particular a gas engine combustion method with a very high inert gas content in the combustion chamber. This allows a very high inert gas admixture, and it can be achieved by reducing heat loss efficiency improvement.

1. a) Zweistoffgasmotoren, welche auch als Dual-Fuel bezeichnet werden
2. b) dieselähnlich betriebene Gasmotoren
3. c) ottomotorisch betriebene Gasmotoren mit stöchiometrischem Kraftstoff-Luft-Verhältnis sowie magere, das heißt mit Luftüberschuss betriebene Gasmotoren.

In particular, the invention, the following findings are based on: Modern, working with spark ignition internal combustion engines, for example, for commercial vehicles and passenger cars use for increasing the thermodynamic efficiency and power density by lowering the component load and / or nitrogen oxide emission reduction charge dilution by recirculated exhaust gas, that is by implementation an exhaust gas recirculation (EGR). The use of the exhaust gas as an inert gas in the combustion chamber with the advantages mentioned allows the use of a stoichiometric fuel / air mixture whereby the use of a simple exhaust aftertreatment system by means of three-way catalyst is possible. The spark ignition of these mixtures in a pre-chamber is a particular challenge. For example, for mobile applications in commercial vehicles, the use of Vorkammerzündkerze with introduction or injection of air and fuel, in particular fuel gas, from a vehicle-side supply to reduce the inert gas in the antechamber proposed for optimized ignition. The following operations of gas engines are known from the general state of the art:

1. a) dual-fuel gas engines, which are also referred to as dual-fuel
2. b) diesel-powered gas engines
3. c) Otto engine gas engines with stoichiometric fuel-air ratio and lean, that is operated with excess air gas engines.

In the Otto engine combustion method, as mentioned above under c), an ignitable, for example, designed as a fuel gas-air mixture fuel-air mixture is either premixed introduced into the combustion chamber or during a compression phase in the combustion chamber by direct introduction, in particular injection, of the example formed as a gaseous fuel and also referred to as fuel or fuel gas produced fuel. The combustion of the fuel-air mixture is then initiated by spark ignition. Different ignition methods can be used. An option is the ignition by a Vorkammerzündkerze.

For diesel-like gas combustion processes, as mentioned above under b), can after EP 3 043 049 A1 or after US 2,799,255 a spark ignition of the high-pressure gas jets are used by a Vorkammerzündkerze.

For the improved ignition of lean mixtures, a pre-chamber spark plug is used as an alternative to a conventional spark plug, especially in stationary petrol engines, as it is, for example, in WO 03071644 or US 2016/0024994 A1 is described. In principle, this divides the combustion chamber into two individual combustion chambers connected by the overflow openings of the prechamber spark plug. A first of the individual combustion chambers is the antechamber, which is also referred to as pre-chamber combustion chamber. The second single combustion chamber is previously called combustion chamber and is also referred to as the main combustion chamber. The volume of the pre-chamber is significantly less than the volume of the main combustion chamber. The fuel-air mixture passes through the formed for example as overflow holes overflow into the antechamber, where it is ignited by spark ignition and passes through a resulting pressure increase as flame torches in the main combustion chamber. There, these flame torches ignite the fuel-air mixture or the premixed main fuel quantity for the following main combustion. In these passive antechambers without irrigation, the mixture composition in the prechamber corresponds to the mixture composition in the main combustion chamber.

• - mit einem Einblasventil direkt in die Vorkammer (zum Beispiel GB 9221970 , US 2012 103 302 und DE 11 2011 103 649 )
• - mit Direkteinblasung in den Hauptbrennraum und Einbringen von Brennstoff durch die Überströmöffnungen (zum Beispiel WO 2006/018291 )
• - Einbringen von Spülgas durch Kapillare (zum Beispiel DE 10 2005 005 851 und EP 1 143 126 ).

There are also pre-chamber variants that have the goal of making the mixture composition in the antechamber independent of the main combustion chamber. In the case of excess air, that is, lean-burn engines, fuel is added to the prechamber. Thus, the amount of air in the prechamber is reduced and the mixture composition in the prechamber approaches the ideal stoichiometric mixture composition for ignition. This method is also used in diesel-like gas combustion processes, as for example in the EP 3 043 049 A1 is described. Technically known variants are for the introduction of fuel in the antechamber continue:

• - with a blow-in valve directly into the antechamber (for example GB 9221970 . US 2012 103 302 and DE 11 2011 103 649 )
• - With direct injection into the main combustion chamber and introducing fuel through the overflow openings (for example WO 2006/018291 )
• - Introducing purge gas through capillary (for example DE 10 2005 005 851 and EP 1 143 126 ).

The mixture formation in the antechamber can be assisted by means of a swirl flow generated by eccentrically mounted transfer channels, as described, for example, in US Pat DE 10 2005 005 851 is described.

Furthermore, there is the possibility, in addition to or as an alternative to fuel, of introducing air or inert gas into the prechamber through the variants described above. This is to be diluted before introducing the fuel gas by introducing air or inert gas, the fuel-air mixture in the antechamber and thus pre-ignition before the actual spark or spark ignition can be prevented (for example DE 10 2008 015 744 . AT 134173 and JP 2002266643 ).

• - ansteigendem Zündverzug
• - Reduktion der in der Vorkammer enthaltenen Energiemenge
• - Verringerung der Brenngeschwindigkeit.

Otto-motor and diesel-like gas combustion processes are operated according to the current state of the art usually with inert gas in the main combustion chamber. The inert gas can originate from an internal exhaust gas recirculation as well as from an external exhaust gas recirculation. By operating with inert gas in the combustion chamber in the Otto engine combustion process, the combustion temperatures and thus the wall heat losses can be reduced. This is associated with an increase in the thermodynamic efficiency. The inert gas content in the main combustion chamber is, for example, in modern gasoline engines in the range of up to 30 percent by mass. In the diesel engine gas combustion process inert gas is used in the combustion chamber to reduce the oxygen partial pressure for the reduction of nitrogen oxide emissions. With increased inert gas in the combustion chamber, however, also increases the inert gas in the antechamber. The inert gas content in the antechamber leads to:

• - Increasing ignition delay
• - Reduction of the amount of energy contained in the antechamber
• - Reduction of burning speed.

Thus, the resulting pressure increase of the prechamber is reduced by the permanent connection with the main combustion chamber via the overflow. The momentum and the thermal energy of the exiting torch jets are lower. The ignition of the main fuel mixture resulting from the torch jets (Otto engine combustion method) or the high-pressure fuel jets (diesel-like combustion method) are deteriorated.

• - Bei stöchiometrischem Gemisch im Hauptbrennraum (ottomotorisches Brennverfahren mit AGR) ist die Einbringung von Brennstoff in die Vorkammer nicht zielführend. Es entsteht ein Brenngas-Luft-Gemisch mit zu hohem Brenngasanteil (fettes Gemisch), das schlechter zündet.
• - Bei dieselähnlichen Gas-Brennverfahren mit Vorkammerzündung liegen Luft und Inertgas im Hauptbrennraum und damit auch in der Vorkammer vor. Durch Zudosieren von Brenngas wird zündfähiges Gemisch in der Vorkammer erzeugt. Der Inertgasanteil in der Vorkammer verschlechtert jedoch auch hier die Zündbedingungen.

For engines with Inertgasbeimischung in the main combustion chamber, the sole admixture of fuel gas in the antechamber is not sufficient for better ignition conditions:

• - With a stoichiometric mixture in the main combustion chamber (Otto-cycle combustion process with EGR), the introduction of fuel into the pre-chamber is not expedient. The result is a fuel gas-air mixture with too high proportion of fuel gas (rich mixture), which ignites worse.
• - In diesel-like gas combustion process with prechamber ignition, air and inert gas are present in the main combustion chamber and thus also in the prechamber. By metering in fuel gas, an ignitable mixture is produced in the prechamber. However, the inert gas in the antechamber deteriorates the ignition conditions here.

Therefore, in both combustion process concepts with inert gas in the main combustion chamber in the pre-chamber air and fuel gas should be introduced to reduce the inert gas in the antechamber at ignition. This can be done according to the prior art ( US 5081969 ) by a direct introduction of externally premixed purge gas mixture with λ = 1 done. In the US 8,925,518 B1 For two-fluid engines, the introduction of two fuels and oxygen into the pre-chamber is described. The oxygen is produced consuming on the vehicle side via different separators or heat exchangers. In contrast, in the method according to the invention an on-board compressed air system is used to introduce the air directly into the prechamber. In addition, the object of the present invention is to improve the ignition in the pre-chamber with a high inert gas content in the main combustion chamber for Otto engine and diesel-like gas combustion processes in mobile vehicle applications.

In the context of the inventive method, a stoichiometric, for example, designed as a fuel gas-air mixture fuel-air mixture is formed with respect to the main combustion chamber significantly reduced inert gas in the antechamber of Vorkammerzündkerze, for example, designed as a gas engine internal combustion engine, further comprising an exhaust gas recirculation and thus a Inertgasbeimischung be performed, in the course of which inert gas or exhaust gas of the internal combustion engine is introduced into the main combustion chamber, so that not only the fuel-air mixture, but also inert gas is added in the main combustion chamber. As a result, a particularly advantageous ignition can be ensured.

• - ein erster der Ströme umfasst beispielsweise ein stöchiometrisches Brenngas-Luft-Gemisch mit λ = 1 und Inertgas beziehungsweise ein Luft-Inertgas-Gemisch, wobei der erste Fluidstrom über die Überströmöffnungen aus dem Hauptbrennraum in die Vorkammer einströmt
• - ein zweiter der Ströme umfasst den zuvor genannten, beispielsweise als gasförmiger Kraftstoff beziehungsweise Brenngas ausgebildeten Kraftstoff
• - der dritte Strom umfasst die zuvor genannte Luft

For example, three, in particular separate, streams or fluid streams enter the antechamber:

• - A first of the streams includes, for example, a stoichiometric fuel gas-air mixture with λ = 1 and inert gas or an air-inert gas mixture, wherein the first fluid flow flows through the overflow from the main combustion chamber into the prechamber
• - A second of the streams comprises the aforementioned, for example, formed as a gaseous fuel or fuel gas fuel
• - The third stream includes the aforementioned air

The first stream is introduced via the overflow from the main combustion chamber in the prechamber. However, the second and third stream is not introduced from the main combustion chamber and not via the overflow, but separately in the antechamber.

Gaseous fuels such as methane, natural gas (CNG or liquefied as LNG, for example propane), LPG, propane-butane mixture, ethane and / or hydrogen or preferably come as the said fuel and thus for example as the main fuel and for flushing the prechamber liquid fuels such as gasoline used. The material flows fuel gas and air should be metered separately into the prechamber for the following reasons: Premixing and provision of a combustible fuel gas / air mixture for the subsequent injection into the prechamber is disadvantageous in the vehicle for safety reasons. The removal of the fuel gas-air mixture from the intake manifold is problematic because the intake manifold pressure is insufficient even when charging for a sufficient injection into the prechamber. Furthermore, exhaust gas is already admixed in the intake manifold in engines with exhaust gas recirculation, so that when this exhaust gas air-fuel mixture is injected, no reduction of the inert gas portion in the prechamber is made possible.

• - über zwei einzelne Ventile direkt
• - zwei getrennte Leitungen beziehungsweise Kapillaren mit jeweils einem vorgelagerten Dosierventil
• - durch eine einzelne in die Vorkammer mündende Kapillare beziehungsweise Leitung, die durch ein T-Verbindungsstück mit zwei Dosierventilen verbunden ist.

The streams fuel gas or fuel and air can be metered into the pre-chamber in the following manner in the context of the method according to the invention:

• - directly via two individual valves
• - Two separate lines or capillaries, each with an upstream metering valve
• - By a single opening into the antechamber capillary or line, which is connected by a T-connector with two metering valves.

Furthermore, it is preferably provided, the fuel and the air under increased pressure bring in the antechamber, so that the example formed as a fuel gas fuel and the air at a pressure of more than 5 bar are introduced into the prechamber. The two individual entering into the antechamber streams of air and fuel gas mix preferably in the antechamber to a stoichiometric fuel gas-air mixture. Due to the respective high pressure of more than 5 bar, an inflow of inert gas mixture from the main combustion chamber into the pre-chamber is prevented over a wide range. Only when the pressure in the main combustion chamber exceeds the pressure in the pre-chamber or the Einblasedruck, with which the fuel gas and the air are introduced into the prechamber, passes inert gas from the main combustion chamber in the antechamber. There it mixes with the premixed stoichiometric fuel-air mixture without inert gas.

The composition of the mixture in the prechamber when it is ignited is preferably characterized by the fact that the proportion of inert gas in the prechamber is reduced compared to the portion of inert gas in the main combustion chamber (combustion chamber). The higher the existing during injection into the pre-chamber air or fuel gas pressure, the longer can be injected into the compression phase of the internal combustion engine during upward movement of the piston in the pre-chamber and reduced by preventing the influx of mixture from the main combustion chamber, the inert gas in the antechamber.

It has proven to be particularly advantageous if, particularly in the case of a mobile commercial vehicle application, the fuel gas is taken off from a vehicle-side gas supply under high pressure of, for example, more than 5 bar. The air is taken, for example, as compressed air under high pressure from a vehicle already existing pneumatic system. This pneumatic system is usually present in commercial vehicles for compressed air generation such as for brake, in particular service brake, air suspension and / or door operation in buses. The pneumatic system includes, for example, one of the internal combustion engine and / or alternatively electrically driven air compressor, which is designed for example as a piston compressor or compressor. Further, the pneumatic system includes, for example, a pressure accumulator in which the air compressed by means of the air compressor can be stored. Typical pressures provided by the air compressor are, for example, in a range of from 10 bar to 15 bar inclusive at a maximum delivery rate in a range of 170 to 380 liters per minute at operating pressure. The proportion of the air mass flow required by the prechamber to the capacity of the air compressor is estimated at a maximum of less than 3 percent.

For the formation of the fuel gas-air mixture in the pre-chamber different operating modes depending on the respective pressure ranges of the fuel gas and the air come into question. These are provided because at different pressures of air and fuel gas, especially in a common supply line in the antechamber, for example, the flows formed as gas streams can mutually influence or damming. In addition, inert residual gas can be blown out of the prechamber via an additional operating mode with the supplied air. In the diesel-like gas combustion process concept with high-pressure direct injection into the pre-chamber, a reduction of the fuel gas pressure before injection into the chamber is advantageous in the case of the vehicle-side gas branching. In this case, the use of the vehicle-side fuel gas system in combination with an additional pressure regulator for Vorkammereinblasung is still possible.

The method according to the invention is therefore characterized in particular by the fact that the spark ignition in the pre-chamber takes place at an inert gas fraction reduced in relation to the main combustion chamber and thus improved ignition conditions and increased energy content. The use is preferably in internal combustion engines for mobile and off-highway commercial vehicle applications. Preferably, the provision of the air formed as compressed air from a vehicle-side pneumatic system. The provision of the example formed as a fuel gas fuel is preferably carried out by a for the operation of, for example, designed as a gas engine internal combustion engine before a fuel gas system with a pressure of more than 5 bar.

To be particularly advantageous, it has been shown when the fuel gas and the air in parallel or synchronously, that is, at the same time introduced into the prechamber, in particular blown. Start and end of the respective injection can each be independent of each other. This operating mode is characterized in particular by the fact that an overlap of the injection periods takes place. The injection pressure of the two streams, which depends on the respective pressures, determines the fuel gas / air ratio in the prechamber. The injection of the two substances can also be done several times in succession as Mehrfacheinblasung. By varying the respective injection periods to each other, an advantageous mixture ratio in the antechamber can be adjusted by an engine control unit. This is especially true for all variants.

Alternatively, it is conceivable that the fuel gas and the air are introduced separately from each other in the antechamber. In this case, for example, first the fuel gas and then the air is blown with Einblasende before ignition for a sufficient mixture formation time. The pressure of the air is greater than the pressure of the gas in order to be able to blow against a gas pressure accumulated in the pre-chamber. This operating mode is characterized in particular by the fact that the injection of air takes place only after the injection of the fuel (fuel gas) is completed. The ratio of the two injection periods to each other determines the fuel-air ratio in the prechamber. By varying the respective injection periods to each other, an advantageous mixture ratio in the antechamber can be adjusted by an engine control unit. The sequential injection of the two substances (fuel and air) can also be done several times in succession as Mehrfacheinblasung.

Furthermore, in the context of the separate blowing of the fuel gas and air, it is possible to first carry out the air and then the fuel gas with Einblasende before ignition for a sufficient mixture formation time. The pressure of the fuel gas is greater than the pressure of the air in order to be able to blow against a pressure accumulated in the pre-chamber. This operating mode is characterized in particular by the fact that the injection of the fuel gas only starts after the injection of air has been completed. The ratio of the two injection periods to each other determines the fuel-air ratio in the prechamber. By varying the respective injection periods to one another, an advantageous mixture ratio in the antechamber can be set by the engine control unit. The sequential injection of the two substances can also be done several times in succession as Mehrfacheinblasung. Furthermore, it is conceivable that air is introduced into the prechamber after the main combustion, that is, after the top dead center, in order to blow out inert gas from the prechamber before refilling the prechamber.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or in the figures alone can be used not only in the respectively specified combination but also in other combinations or in isolation, without the scope of To leave invention.

• 1 eine schematische Darstellung einer Verbrennungskraftmaschine gemäß einer ersten Ausführungsform, welche mittels eines erfindungsgemäßen Verfahrens betrieben wird;
• 2 eine schematische Darstellung der Verbrennungskraftmaschine gemäß einer zweiten Ausführungsform;
• 3 eine schematische Darstellung der Verbrennungskraftmaschine gemäß einer dritten Ausführungsform;
• 4 ein Diagramm zum Veranschaulichten einer ersten Ausführungsform des Verfahrens;
• 5 ein Diagramm zum Veranschaulichen einer zweiten Ausführungsform des Verfahrens; und
• 6 ein Diagramm zum Veranschaulichen einer dritten Ausführungsform des Verfahrens.

The drawing shows in:

• 1 a schematic representation of an internal combustion engine according to a first embodiment, which is operated by a method according to the invention;
• 2 a schematic representation of the internal combustion engine according to a second embodiment;
• 3 a schematic representation of the internal combustion engine according to a third embodiment;
• 4 a diagram for illustrating a first embodiment of the method;
• 5 a diagram illustrating a second embodiment of the method; and
• 6 a diagram illustrating a third embodiment of the method.

In the figures, the same or functionally identical elements are provided with the same reference numerals.

1 shows a schematic representation of a first embodiment of a generally designated 10 internal combustion engine for a motor vehicle, which by means of the internal combustion engine 10 is drivable. The internal combustion engine 10 has at least one as a cylinder 12 trained combustion chamber in which a piston 14 is recorded translationally movable. As is well known, the piston is 14 between a top dead center (TDC) and a bottom dead center (UT) translationally movable. The internal combustion engine 10 is designed as a gas engine and thus operable by means of a gaseous fuel, wherein the gaseous fuel is also referred to as the main fuel or main fuel or fuel gas. In a method of operating the internal combustion engine 10 be the cylinder 12 the fuel gas and air are supplied, causing in the combustion chamber 12 - Especially during a fired operation of the internal combustion engine 10 - A fuel-air mixture is formed. The cylinder 12 is also referred to as the main combustion chamber or main combustion chamber.

The cylinder 12 is a pre-chamber spark plug 16 trained prechamber spark plug associated with a prechamber 18 having. As in synopsis with 2 is recognizable, is the antechamber 18 over overflow openings 13 fluidic with the cylinder 12 (Main combustion chamber), the antechamber 18 a much smaller volume than the cylinder 12 having. By means of the prechamber spark plug 16 is the fuel-air mixture in the cylinder 12 ignited and burned in the sequence, resulting exhaust gas of the internal combustion engine 10 results. The internal combustion engine 10 or the motor vehicle has a on-board fuel gas supply 20 on, by means of which the gaseous fuel, in particular directly, into the cylinder 12 introduced, in particular injected, is. This includes the fuel gas supply 20 for example, a tank 22 for receiving and storing the gaseous fuel. By means of at least one line 24 the fuel gas supply 20 can the gaseous fuel (fuel gas) from the tank 22 to that and especially in the cylinder 12 be led and injected. It is in the line 24 for example, a valve element 26 the fuel gas supply 20 arranged, wherein by means of the valve element 26 one in the cylinder 12 amount of gaseous fuel to be introduced is adjustable.

To now a particularly low-emission operation of the internal combustion engine 10 and a low temperature load of the engine components of the internal combustion engine 10 It is within the scope of the method for operating the internal combustion engine 10 provided that an exhaust gas recirculation is performed, by means of which the cylinder 12 Exhaust gas of the internal combustion engine 10 is supplied. This exhaust gas recirculation (EGR) can be provided as internal and / or external exhaust gas recirculation (not shown). For example, an exhaust gas recirculation device is provided with an exhaust gas recirculation line. For example, the aforementioned exhaust gas flows out of the cylinder 12 from and is by means of an exhaust gas flow through the exhaust tract of the internal combustion engine 10 from the cylinder 12 dissipated. The air which enters the cylinder 12 is introduced, for example, flows through an intake tract of the internal combustion engine 10 and is by means of the intake tract to the and in particular into the cylinder 12 initiated. The exhaust gas recirculation line is on the one hand fluidly connected to the exhaust tract and the other fluidly to the intake, so that at least a portion of the exhaust gas flowing through the exhaust gas can be diverted from the exhaust system and returned to the and in particular in the intake by means of the exhaust gas recirculation line. The recirculated exhaust gas is introduced, for example, into the air flowing through the intake tract and is entrained by means of the air flowing through the intake tract and into the cylinder 12 transported. In the cylinder 12 the recirculated exhaust gas in the combustion of the fuel-air mixture, which is also referred to as fuel gas-air mixture, act as an inert gas, whereby the nitrogen oxide (NO _x ) emissions can be kept particularly low.

To ignite the fuel-air mixture particularly well and thus a particularly high smoothness of the internal combustion engine 10 to ensure that it is also provided in the process that in the antechamber 18 a stoichiometric fuel-air mixture, in particular fuel gas-air mixture, is formed by air and fuel, in particular fuel gas, via at least one of the overflow openings 13 different, in addition to the overflow openings 13 provided feed element 28 directly into the antechamber 18 be introduced. The fuel gas and the air, which directly into the antechamber 18 are introduced so are not out of the cylinder 12 over the overflow openings 13 in the antechamber 18 introduced, but over that of the overflow 13 different feed element 28 in the antechamber 18 blown.

At the in 1 shown first embodiment, the fuel gas, via the supply element 28 directly into the antechamber 18 is injected, the fuel gas supply 20 , especially the tank 22 taken from. In this case, the fuel gas, that is, the aforementioned gaseous fuel in the tank 22 stored and with the pressure p _G in the antechamber 18 , in particular directly blown. In this case, the pressure of the fuel gas in the tank 22 be higher than the pressure p _G of more than five bar in the injection of the fuel gas into the antechamber 18 , This is a line 30 of the feeding element 28 intended. About the line 30 the fuel gas gets out of the tank 22 in the antechamber 18 blown. It is in the line 30 a valve element 32 of the feeding element 28 arranged. By means of the valve element 32 can be a lot of in the antechamber 18 directly einzubasenden fuel (fuel gas) can be adjusted as needed.

The motor vehicle further includes a pneumatic system 34 by means of which at least one of the internal combustion engine 10 different and also referred to as compressed air consumers 36 can be supplied with compressed air. This includes the pneumatic system 34 an example of the internal combustion engine 10 and / or by an electric motor drivable air compressor 38 , by means of which air can be conveyed and compressed. This allows the air compressor 38 provide the compressed air as compressed air, with the consumer 36 can be supplied. This includes the pneumatic system 34 For example, designed as a compressed air accumulator accumulator 40 in which the air can be stored as compressed air at a pressure p _L. The air can thus with the pressure p _L the consumer 36 be supplied. Further, a line 42 of the feeding element 28 intended. About the line 42 Can be used as compressed air in the accumulator 40 stored air of the antechamber 18 fed and in particular directly into the antechamber 18 be blown. It is in the line 42 a valve element 44 of the feeding element 28 arranged. By means of the valve element 44 can be a lot of in the antechamber 18 directly einzublasenden and from the accumulator 40 originating air (compressed air) can be adjusted as needed.

2 shows a second embodiment of the internal combustion engine 10 , Out 2 is an ignition element 46 the prechamber spark plug 16 recognizable. By means of the ignition element 46 can in the antechamber 18 at least one spark be generated, by means of which the fuel gas-air mixture in the prechamber 18 ignited and can be burned. In the second embodiment, it is provided that the air at the pressure p _L and the fuel gas at the pressure p _G via the two separate lines 30 and 42 in the antechamber 18 be blown. The lines open 30 and 42 separated from each other in the antechamber 18 ,

Based on 2 is particularly clear that, for example, in the second embodiment of the internal combustion engine 10 the antechamber 18 three fluid streams, in particular separately from each other, are supplied, these fluid streams are also referred to as streams or streams and into the prechamber 18 be initiated or inflow. A first of the fluid streams flows out of the cylinder 12 over the overflow openings 13 in the antechamber 18 and includes the fuel-air mixture and the recirculated exhaust gas from the cylinder 12 , A second of the fluid streams is, for example, the air formed as compressed air and flows over the line 42 in the antechamber 18 one. The third fluid stream is the fuel gas and flows over the conduit 30 in the antechamber 18 one. The second and the third fluid flow thus do not flow over the overflow openings 13 in the antechamber 18 and do not come from the cylinder 12 , Preferably, the respective pressure p _G or p _{L is} more than 5 bar. Preferably, the pressure p _{L is} in a range of from 10 bar to 15 bar inclusive.

3 shows a third embodiment of the internal combustion engine 10 , In the third embodiment, the leads are 30 and 42 based on a flow direction of the compressed air from the pressure accumulator 40 to the antechamber 18 and based on a flow direction of the fuel gas from the tank 22 to the antechamber 18 at an upstream of the pre-chamber 18 arranged point S fluidly connected to each other and open into a common feed line 50 of the feeding element 28 , The feed line 50 leads into the antechamber 18 , Thus, in the third embodiment, that of the pneumatic system 34 provided and designed as compressed air with the air from the fuel gas supply 20 Provided fuel gas not only in the antechamber 18 mixed, as is the case in the 2 illustrated second embodiment, but that of the pneumatic system 34 Provided air is already upstream of the prechamber 18 at the point S fluidly with that of the fuel gas supply 20 Provided fuel gas mixed, so that a supply line 50 flowing fuel gas-air mixture is formed, which is not from the cylinder 12 and not about the overflow openings 13 out of the cylinder 12 in the antechamber 18 flows in, but by means of the overflow 13 different feeding element 28 in the antechamber 18 , in particular directly, is blown.

4 shows a diagram illustrating a first embodiment of the method for operating the internal combustion engine 10 , An in 4 shown course 52 illustrates the cylinder 12 prevailing cylinder pressure p _cyl , being on the abscissa 54 of the diagram is plotted crank angle. At the in 4 shown embodiment of the method are those of the pneumatic system 34 provided compressed air and that of the fuel gas supply 20 Provided fuel gas during at least a period Z at the same time, that is, synchronously or in parallel, in the antechamber 18 blown. The period Z and thus the injection of the fuel gas and the air start at a first time t1. The period Z and thus the respective injection of the compressed air and the fuel gas end at a second time t2 following the first time t1. It illustrates in 4 a block 56 the injection of air into the antechamber 18 , where a block 58 the injection of the fuel gas into the pre-chamber 18 illustrated.

5 shows a second embodiment of the method. Also in the second embodiment, the compressed air and the fuel gas during the period Z in the prechamber 18 blown. In the second embodiment, however, it is provided that within the period Z, the fuel gas and the air in succession in the antechamber 18 be blown. In the second embodiment, a sequential injection of the fuel gas and the air thus takes place in the antechamber. In the second embodiment, only the fuel gas in the prechamber 18 blown. Only after the end of the injection of the fuel gas into the antechamber 18 will be the injection of air into the antechamber 18 started.

Also at a in 6 illustrated third embodiment of the method, there is a sequential blowing of the compressed air and the fuel gas. In contrast to the second embodiment, it is provided in the third embodiment that first the air in the prechamber 18 blown. Only when the injection of air into the antechamber 18 is finished, the injection of the fuel gas is in the antechamber 18 started.

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

• US Pat. No. 8925518 B1 [0002, 0023]
• EP 3043049 A1 [0015, 0017]
• US 2799255 [0015]
• WO 03071644 [0016]
• US 2016/0024994 A1 [0016]
• GB 9221970 [0017]
• US 2012103302 [0017]
• DE 112011103649 [0017]
• WO 2006/018291 [0017]
• DE 102005005851 [0017, 0018]
• EP 1143126 [0017]
• DE 102008015744 [0019]
• AT 134173 [0019]
• JP 2002266643 [0019]
• US 5081969 [0023]

Claims (9)

Method for operating an internal combustion engine (10) of a motor vehicle, in which in at least one combustion chamber (12) of the internal combustion engine (10) a fuel-air mixture is formed, which by means of a Vorkammerzündkerze (16), which via a plurality of overflow openings (13) with the combustion chamber (12) connected antechamber (18), is ignited, characterized in that - an exhaust gas recirculation is performed, by means of which the combustion chamber (12) exhaust gas of the internal combustion engine (10) is supplied; and - in the pre-chamber (18) a stoichiometric fuel-air mixture is formed by air and fuel via at least one of the overflow openings (13) different, additionally provided feed element (28) are introduced directly into the prechamber. Method according to Claim 1 Characterized in that the fuel at a pressure (p _G) of more than five bar above the feeding member (28) directly into the antechamber (18) is introduced. Method according to Claim 1 or 2 , characterized in that the air with a pressure (p _L ) of more than five bar, in particular with a pressure (p _L ) in a range of ten bar inclusive including 15 bar, via the feed element (28) directly into the prechamber (18) is introduced. Method according to one of the preceding claims, characterized in that the air is introduced as a first fluid flow and the fuel as a separate from the first fluid flow, second fluid flow directly into the prechamber (18). Method according to one of Claims 1 to 3 , characterized in that the air and the fuel at a upstream of the prechamber (18) arranged point (S) are mixed to form a mixture which is introduced directly into the prechamber (18). Method according to one of the preceding claims, characterized in that the air and the fuel are introduced simultaneously into the pre-chamber (18). Method according to one of Claims 1 to 5 , characterized in that the air and the fuel are introduced in succession in the antechamber (18). Method according to one of the preceding claims, characterized in that the fuel from an existing pressure-fuel gas system and the air is taken from an existing pneumatic system of the motor vehicle Method according to one of the preceding claims, characterized in that the method is used in a mobile application.

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