DE102021104691A1 - Method for operating an Otto engine internal combustion engine, comprising a spark plug assembly with a prechamber spark plug and a roof electrode spark plug - Google Patents

Abstract

The invention relates to a method for igniting a fuel/air mixture in a combustion chamber of a gasoline engine, which is defined by a cylinder head and a cylinder (Z), wherein the combustion chamber is assigned at least one inlet valve and at least one outlet valve and an ignition device which a roof electrode spark plug (DZ) and a prechamber spark plug (VZ), with the following steps: measuring or modeling the indicated mean pressure (pmi) within the at least one cylinder (Z) within a working cycle; Activation of an operating mode (B-VZ, B-DZ, B-DZ/VZ) of the ignition device in the next working cycle depending on an indicated mean pressure (pmi) measured or modeled in the previous working cycle above or below a predetermined limit value (PGrenz) within the at least one Cylinder (Z), depending on the activated operating mode (B-VZ, B-DZ, B-DZ/VZ) in the respective work cycle in a roof electrode spark plug operating mode (B-DZ) or a prechamber spark plug operating mode (B-VZ) only one of the two spark plugs (DZ, VZ) is actuated, or in a combined operating mode (B-DZ/VZ) both spark plugs (DZ, VZ) are actuated, with the top electrode spark plug (DZ) of the prechamber spark plug (VZ) being offset in time is previously controlled.

Description

The invention relates to a method for operating an Otto engine internal combustion engine, comprising a spark plug assembly with a prechamber and a roof electrode spark plug DZ.

The pamphlet EP 3 561 255 A1 describes an internal combustion engine comprising at least one cylinder, at least one intake valve acting on an intake port to control airflow entering the cylinder, at least one injector for supplying unburned fuel to the cylinder, at least one exhaust valve acting on a respective exhaust port acts to control the flow of exhaust gases at the outlet of the cylinder, a piston that slides linearly inside the cylinder, at least a first spark plug that is placed in a position adjacent to the injector and acts in the combustion chamber, a pre-chamber that communicates with the Combustion chamber is in communication, and a second spark plug, which acts in the pre-chamber. The first spark plug is located in an intermediate position between the pre-chamber and the injector. The publication discloses a method for controlling the internal combustion engine, comprising the steps of: driving the first spark plug in a first operating condition of the engine; and driving the second spark plug within the prechamber in a second operating condition of the engine different from the first operating condition, wherein the first operating condition is a certain operating condition of low load operation of the engine, wherein the IMEPH parameter is lower than 5 bar, in particular during the starting the engine; and wherein the second operating condition is a normal operating condition of the engine, wherein the IMEPH parameter is equal to or greater than 5 bar.

The pamphlet EP 3 453 856 B1 describes a gasoline internal combustion engine comprising an engine block having a plurality of cylinders and a cylinder head defining a combustion chamber associated with each cylinder, and at least one intake port and at least one exhaust port provided with respective intake and exhaust valves associated with each combustion chamber, one for each cylinder associated first spark plug mounted in a support element arranged in a seat of the cylinder head and having a combustion pre-chamber having a first end facing the electrodes of the first spark plug and a second end communicating via a plurality of openings with the respective combustion chamber, a second spark plug associated with each cylinder and having electrodes directly facing the combustion chamber, at least one electromagnetically controlled petrol injector associated with each cylinder of the engine, an electronic control unit, d a configured to control the first spark plug, the second spark plug, and the at least one gasoline injector for each cylinder of the engine. It is procedurally envisaged that the electronic control unit will be programmed such that the second spark plug is only activated at low and medium engine loads to stabilize combustion and is inactive or remains active but has no effect on combustion by e.g activated during the expansion or exhaust phase of the cylinder at higher loads.

The pamphlet DE 28 43 119 A discloses an internal combustion engine having a cylinder head, a cylinder block connected to the cylinder head, a piston disposed in the cylinder block and forming a combustion chamber therein with the cylinder head, an intake port for introducing an air/fuel mixture into the combustion chamber during an intake stroke of the internal combustion engine, an exhaust port for the exhaust of residual gases and an inlet valve arranged in the inlet opening for opening and closing it. It is provided that a first spark plug mounted in the cylinder head with its electrodes exposed with respect to the combustion chamber, a first spark advance control circuit connected to the spark plug and operable to cause sparking by the spark plug to form free radicals from the air/fuel mixture continuously supplies a relatively low voltage and through a second spark advance control circuit connected to the spark plug which supplies a relatively high voltage at a fixed frequency to facilitate the formation of the radicals. It is further provided that in the cylinder head there is also a secondary chamber connected to the combustion chamber for the formation of free radicals, with the electrodes of the first spark plug being arranged in the secondary chamber forming the free radicals. A second spark plug is fitted in the cylinder head, the electrodes of which protrude directly into the combustion chamber, the first spark plug being arranged in such a way that its electrodes protrude into the secondary chamber which is connected to the combustion chamber and serves to form the radicals, and that an ignition control circuit with the second spark plug is connected. In a known type of gasoline engine working with mixture compression, an ignition method is used in which a high voltage of 10 to 15 kV generated by the ignition system near the top dead center of the respective piston of the internal combustion engine is fed to the corresponding spark plug and a substantially capacitive discharge occurs between the electrodes of the spark plug is effected, resulting in an electric Ignition spark forms, which ignites the compressed air/fuel mixture. In the method presented in the publication, in one embodiment, an inductive discharge from the discharge electrodes or ignition electrodes arranged in the respective combustion chamber is initiated before explosive combustion or near bottom dead center during the transition from the intake stroke to the compression stroke, in order to convert a part of the air-fuel mixture into radicals and their chemical activation, thereby ensuring better ignition characteristics and stable combustion in cases where the mixture is lean or the amount of exhaust gas recirculation is greatly increased. In another embodiment of the method, the radicals are formed by a first spark plug located in the sub-chamber generating radicals, while the air/fuel mixture containing the radicals is ignited by a second spark plug located in the combustion chamber, which ensures better combustion.

Summarizing the prior art, operation with two individual spark plugs is known in principle. As is clear from the prior art, it can be advantageous for various reasons to operate a spark-ignition engine with a combination of two spark plugs in order to tap the full potential of the spark-ignition engine. In the case of small cylinder diameters in particular, however, the space conditions are so unfavorable that the use of two individual spark plugs and an associated ignition method for Otto engines with small cylinder diameters is structurally unknown.

The object of the invention is to provide an ignition method for a spark-ignition engine with a small cylinder diameter, ie for a small combustion chamber and a structural arrangement of two spark plugs associated with this combustion chamber.

The object is achieved by the structural design of a spark plug assembly, which is characterized in that it comprises a metallic base body with two receiving openings for arranging two spark plug insulator bodies with integrated center electrodes, the spark plug insulator bodies in the receiving openings are arranged plugged in, with one fastening element each, which is also arranged in and/or on the receiving openings of the base body, encompasses the respective spark plug insulator body at least in the respective upper area of the spark plug insulator body and the spark plug insulator body in fixed to the base body and aligned with respect to the base body, each center electrode being assigned a ground electrode which is connected to the base body. Advantageously, the subassembly prefabricated in this way can be easily installed in a cylinder head of an internal combustion engine.

Provision is preferably made for the base body to be designed in one piece or in multiple pieces.

The receiving openings are designed as through holes. In a preferred embodiment of the invention, the through bores have shoulder-like recesses.

The spark plug assembly includes the spark plug insulator bodies, each of which has an insulator central body with a first shoulder that is contacted in the assembled state by the end faces of the respective fastening element that are directed towards the insulator central bodies.

Preferably, the central insulator bodies of the spark plug insulator bodies each have a second shoulder, which rests on the shoulder-like indentations in the assembled state.

The base body preferably has an external thread that corresponds to an internal thread of a cylinder head.

The base body also preferably has an internal thread in each of the receiving openings, which corresponds to an external thread of the respective fastening element.

The spark plug assembly is characterized in that the first spark plug insulator body is formed as a prechamber spark plug completed and the second spark plug insulator body is formed as a roof electrode spark plug completed, the ground electrodes of which are connected to the base body near the center electrodes of the spark plug Insulator body lying, arranged and connected to the base body.

It is preferably further provided that the prechamber of the prechamber spark plug is connected to an underside of the base body and accommodates the ground electrode and the center electrode in their prechamber space formed opposite the underside.

Another essential aspect of the spark plug assembly is that a distance between the center electrodes arranged in the insulator tips of the spark plug insulator bodies in the main body is less than 20 mm in the assembled state of the spark plug assembly, preferably <15 mm, optimally <10 mm. This close arrangement of the center electrodes with a small spacing is possible in an advantageous manner, in particular by the arrangement in a common base body.

According to the invention, an internal combustion engine according to the invention is characterized in that at least one spark plug assembly, which has the aforementioned features, is arranged in the cylinder head of the at least one cylinder of a cylinder block. With several cylinders, several spark plug assemblies (one spark plug assembly per cylinder) are accordingly arranged.

• Ein Abstand der Mittelelektroden, die in den Isolator-Spitzen der Zündkerzen-Isolator-Körper angeordnet sind und in die Brennkammer des Zylinders ragen, betragen bevorzugt kleiner als 20 mm, bevorzugt < 15 mm, optimal < 10 mm.

Specific Preferred Embodiments:

• A distance between the center electrodes, which are arranged in the insulator tips of the spark plug insulator bodies and protrude into the combustion chamber of the cylinder, is preferably less than 20 mm, preferably <15 mm, optimally <10 mm.

A cylinder bore of a cylinder preferably has a diameter in a range between D=81 mm and 75 mm.

In relation to the range of diameters D of the cylinder bore, the cylinder preferably has between D = 81 mm and 75 mm (D = 81 mm, D = 81 mm, D = 79 mm, D = 77 mm, D = 75 mm) a cylinder stroke/bore ratio s/D > 1.05/1.1/1.15/1.2.

• 1 eine erste Verfahrensweise zum Betreiben einer ottomotorischen Brennkraftmaschine;
• 2 eine zweite Verfahrensweise zum Betreiben der ottomotorischen Brennkraftmaschine;
• 3 eine dritte Verfahrensweise zum Betreiben der ottomotorischen Brennkraftmaschine und
• 4 eine Zündkerzen-Baugruppe umfassend zwei Zündkerzen, die in einem Zylinderkopf eines Zylinders der ottomotorischen Brennkraftmaschine angeordnet ist.

The invention is explained below with reference to the associated drawing. It shows:

• 1 a first procedure for operating a spark-ignition internal combustion engine;
• 2 a second procedure for operating the spark-ignition internal combustion engine;
• 3 a third procedure for operating the Otto engine internal combustion engine and
• 4 a spark plug assembly comprising two spark plugs, which is arranged in a cylinder head of a cylinder of the internal combustion engine.

First shows 4 First of all, a spark plug assembly 100, which is characterized in that two spark plug insulator bodies 1, 2 are arranged next to one another in a metallic base body 10.

The base body 10 forms the metal housing for the two spark plug insulator bodies 1, 2, so that the spark plug assembly 100 according to the invention has two spark plugs in a housing or base body 10. The base body 10 is also referred to as a ground body since it forms the electrically conductive body (the negative ground of the spark plug assembly 100).

According to the illustrated embodiment, arranged next to one another means more precisely that the central axes 1M, 2M running in the longitudinal extension of the spark plug insulator bodies 1, 2 are arranged parallel to one another. However, it is pointed out that the principle of the invention can also be used for the arrangement of spark plug insulator bodies 1, 2 whose longitudinal extent, ie whose longitudinal axes do not run parallel to one another.

A central axis of the spark plug assembly 100 is indicated by reference numeral 100M. A cylinder head in which the spark plug assembly 100 is placed is not shown.

It is assumed that an underside 10.1 of the one-piece base body 10 of the spark plug assembly 100 together with an underside of the cylinder head form the combustion chamber roof of a combustion chamber in the cylinder Z of the internal combustion engine when the cylinder head is mounted on a cylinder Z of the internal combustion engine as intended.

The underside 10.2 of the base body 10 of the spark plug assembly 100 and the underside of the cylinder head are preferably in one plane or are arranged next to one another without any steps.

The base body 10 is also considered and referred to as a housing, since it essentially completely accommodates the spark plug insulator bodies 1, 2 in a housing-like manner according to the invention, as explained below.

The base body 10 of the spark plug assembly 100 has an upper side 10.1. In the base body 10, between the upper side 10.1 and the lower side 10.2, there are two continuous receiving openings 10.3, in a preferred way as through holes with a recess 10.31, in which the spark plug insulator bodies 1, 2 are arranged in the assembled state.

The through-holes 10.3 thus have the narrowing recesses 10.31, which are formed at a certain predetermined position, viewed in the longitudinal extension between the top side 10.1 and the bottom side 10.2.

The through holes 10.3 form in the base body 10 of the spark plug assembly 100 in the longitudinal extension of the spark plug Assembly 100 extending central web 10.4, which thickens at the height of the recesses 10.31 from the top 10.1 to the bottom 10.2. The central ridge 10.4 lies on the central axis 100M of the spark plug assembly.

Furthermore, the through-holes 10.3 in the upper area preferably have internal threads 10.32 adjoining the upper side 10.1 of the base body 10, the surface of the through-holes being provided with the internal threads 10.32 at least in the upper area, which are each connected to an external thread 20.1 of a fastening element 20, for example correspond in the manner of a hollow hole screw.

The hollow-hole screws each have a through hole, the inside diameter of which essentially corresponds to the outside diameter of the insulator heads 2.3 of the spark plug insulator bodies 1, 2, so that the insulator head 2.3 gripped by the respective through-hole 10.3 of the hollow hole screw is the spark plug insulator -Body 1, 2 is aligned in the intended assembled state in the through hole 10.3.

The respective insulator bodies 1.2 of the spark plugs are advantageously aligned in the through hole 10.3 of the spark plug assembly 100 and also fixed in their desired position, that is to say tightened, as will be explained below.

The spark plug insulator bodies 1, 2, which are preferably made of ceramic, each have an insulator tip 1.1, 2.1 and a central insulator body 1.2, 2.2 and, in the assembled state, above the central insulator body 1.2, 2.2 of the respective spark plug 1, 2 lying insulator heads 1.3, 2.3, with a lower insulator central body shoulder 1.2u being formed between the respective insulator tip 1.1 and 1.2 and the insulator central body 1.2, 2.2.

The respective insulator tip 1.1, 2.1 thus connects (seen from the top 10.2 to the bottom 10.2) to a lower insulator central body shoulder 1.2u, 2.2u of the insulator central body 1.2, 2.2.

Between the insulator central bodies 1.2, 2.2 and the insulator heads 1.3, 2.3, an upper insulator central body shoulder 1.2o, 2.2o is also formed. The insulator heads 1.3, 2.3 thus connect (from the bottom 10.2 to the top 10.2) on the insulator central body 1.2, 2.2.

In the assembled state, the lower insulator central body shoulders 1.2u, 2.2u of the spark plug insulator bodies 1, 2 rest on the recesses 10.31 narrowing the through bores 10.3.

This means that the spark plug insulator bodies 1, 2 are positioned with their lower insulator central body shoulders 1.2u, 2.2u opposite or on the indentations 10.31 provided in the receiving opening 10.3 of the base body 10 of the spark plug assembly 100 through their abutting one another Contact surfaces tightened gas-tight, in particular aligned with regard to the longitudinal extent by the hollow hole screws 20 and also tightened, the lower end faces, that is the end faces of the hollow hole screws 20 pressing on the upper insulator central body shoulders 1.2o, 2.2o.

It is provided that the geometric end contour of the hollow hole screws 20 on the central body side corresponds to the geometric contour of the upper insulator central body shoulder 1.2o, whereby an optimal contact surface pair of the respective contact surfaces is formed in which the force is transmitted less locally.

In addition, it is provided that the geometric contour of the lower insulator central body shoulders 1.2u, 2.2u correspond to the geometric shape of the recesses 10.31, which advantageously also forms an optimal contact surface pair of the respective contact surfaces, which also ensures gas-tight sealing of the environment against the combustion chamber.

The base body 10 also has, seen from the top 10.1 to the bottom 10.2, on its cylindrical lateral surface a flange-like shoulder 10.5, which protrudes from the underlying lateral surface, the underside of which serves as a stop on an upper side of the cylinder head when the spark plug assembly 100 in Cylinder head installed, in particular screwed, that is brought into the intended assembly state.

The flange-like shoulder 10.5 is preferably designed as a hexagon on the circumference, so that the spark plug assembly 100 can be assembled using a tool with a corresponding hexagon socket, screwed into the cylinder head and dismantled and unscrewed from the cylinder head.

So that the spark plug assembly 100 can be screwed in the cylinder head according to the preferred embodiment, the outer surface lying under the shoulder 10.5 has at least in some areas an external thread 10.6 which corresponds to an internal thread (not shown) in the cylinder head.

Each spark plug insulator body 1, 2 has a contact for the center electrodes 1.4, 2.4 of the spark plug insulator bodies 1, 2 on the insulator head 1.3, 2.3, to which an ignition control circuit (not shown) is connected is.

Each spark plug insulator body 1, 2 is assigned a ground electrode 1.5, 2.5.

It is according to the invention in the 4 recognizable that the first spark plug 1 is preferably a prechamber spark plug VZ with a prechamber 1'.

According to the invention, the second spark plug 2 is a roof electrode spark plug DZ.

The center electrodes 1.4, 2.4 of the prechamber spark plug VZ and the roof electrode spark plug DZ are inserted into the base body 10 (not screwed) and from above from the top 10.1 - as already explained - each preferably with the hollow screw 20 in the base body 10 or in the housing of the spark plugs -Assembly 100 fixed and tightened gas-tight at the recesses 10.31 in the through holes 10.3.

The first ground electrode 1.5 of the prechamber spark plug VZ 1 is, as in 4 shown, connected to the combustion chamber-side underside 10.1 with the metallic base body 10, in particular welded.

The antechamber 1′ with the at least one antechamber opening to the combustion chamber (no reference number) is also connected, in particular welded, to the underside 10.1 of the metal base body 10 on the combustion chamber side.

The first hook ground electrode 2.5 of the roof electrode spark plug DZ 2 is also, as in 4 shown, connected to the combustion chamber side underside 10.1 of the metallic base body 10, in particular welded.

The described arrangement of the spark plug insulator bodies 1, 2 in a common base body 10 makes it possible to have two spark plugs or their spark plug insulator bodies 1, 2 and the associated components, in particular the ground electrodes 1.5, 2.5 and the prechamber 1' in easy to assemble and disassemble as a spark plug assembly 100, in particular a close arrangement (small distance A) of the insulator tips 1.1 and 2.1 of the spark plug insulator bodies 1, 2 with the integrated center electrodes 1.4, 2.4 is possible.

The spark plug insulator bodies 1, 2 are preferably arranged in an upstream manufacturing process, so that the assembly of the internal combustion engine is simplified in that the cylinder head is installed with the spark plug assembly 100 arranged therein, or the cylinder head is assembled without a spark plug assembly 100 , and then the spark plug assembly 100 is screwed into the cylinder head.

• Ein in 4 gezeigter Abstand A der Mittelelektroden 1.4, 2.4 in den Isolator-Spitzen 1.1, 2.1 beträgt kleiner als 20 mm, bevorzugt < 15 mm, optimal < 10 mm.

In detail, the following further configurations of the center electrode spacing of the center electrodes 1.4, 2.4 of the spark plug insulator bodies 1, 2 are provided as follows:

• a in 4 shown distance A of the center electrodes 1.4, 2.4 in the insulator tips 1.1, 2.1 is less than 20 mm, preferably <15 mm, optimally <10 mm.

• Die Zylinder-Brennräume der ottomotorischen Brennkraftmaschine weisen bevorzugt ZylinderBohrungen mit einem Durchmesser in einem Bereich zwischen D = 81 bis 75 mm, insbesondere D = 81 mm, D = 81 mm, D = 79 mm, D = 77 mm beziehungsweise D = 75 mm auf.

The following configurations of the cylinder bore diameter are also planned in detail:

• The cylinder combustion chambers of the Otto engine internal combustion engine preferably have cylinder bores with a diameter in a range between D=81 to 75 mm, in particular D=81 mm, D=81 mm, D=79 mm, D=77 mm or D=75 mm .

• Es wird weiter bevorzugt vorgesehen, dass im Zylinderkopf mindestens zwei Ventile (ein Einlass- und ein Auslassventil) pro Zylinder Z, bevorzugt vier Ventile (zwei Einlass- und zwei Auslassventile) zum Einsatz kommen, wobei insbesondere bei vier Ventilen pro Zylinder Z ein geringer beziehungsweise (im Vergleich zur Zwei-Ventilvariante) geringerer Bauraum zu Anordnung der Zündkerzen-Baugruppe100 im zugehörigen Zylinderkopf zur Verfügung steht.

The configurations of the number of valves per cylinder Z are also planned in detail:

• It is further preferably provided that at least two valves (one intake and one exhaust valve) per cylinder Z, preferably four valves (two intake and two exhaust valves) are used in the cylinder head, with four valves per cylinder Z in particular having a lower or (Compared to the two-valve variant) less installation space is available for arranging the spark plug assembly 100 in the associated cylinder head.

• Vorgesehen ist, dass die Zündkerzen-Baugruppe 100 insbesondere in der Brennkraftmaschine mit langhubigen Zylinderräumen eingesetzt wird, die ein Hub- (s = Hublänge in mm) Bohrungs-Verhältnis (Durchmesser in mm) von s/D > 1,05/1,1/1,15/1,2 in Bezug auf die oben genannten bevorzugten Durchmesser D = 81 mm, D = 81 mm, D = 79 mm, D = 77 mm beziehungsweise D = 75 mm aufweisen.

Finally, the following configurations of the stroke-bore ratio are planned in detail:

• Provision is made for the spark plug assembly 100 to be used in particular in internal combustion engines with long-stroke cylinder chambers that have a stroke (s=stroke length in mm) bore ratio (diameter in mm) of s/D>1.05/1.1 /1.15/1.2 in relation to the preferred diameters D=81 mm, D=81 mm, D=79 mm, D=77 mm and D=75 mm, respectively, mentioned above.

The resulting engine configuration(s) is/are ideal for direct-injection spark-ignition engines or direct-injection engines, as the case may be in combination with intake manifold injection. In addition, configuration(s) of the internal combustion engine is/are particularly suitable for internal combustion engines with external high and/or low pressure exhaust gas recirculation.

Preferably using the spark plug assembly 100 explained, which is suitable for a spark-ignition engine with a small cylinder diameter, i.e. a spark-ignition engine with small combustion chambers, an ignition method is created in which the two spark plugs VZ, DZ explained are used, which is explained below becomes.

In the following there is always talk of a combustion chamber with the main combustion chamber II, which is formed by a cylinder Z in a known manner. In the exemplary embodiment, the antechamber combustion chamber I is preferably arranged in the main combustion chamber II. The prechamber combustion chamber I can also be arranged in such a way that it is arranged in an integrated manner in the cylinder head. It is essential that the prechamber combustion chamber I is arranged near the ignition device of the roof electrode spark plug DZ in the main combustion chamber II, as will be explained below.

A fuel/air mixture is compressed in the main combustion chamber II in a known manner according to internal combustion engines that work according to the Otto principle, which is, for example, a four-cylinder, four-stroke internal combustion engine. Its main combustion chamber II is formed by the cylinder head, a cylinder block and a cylinder piston (all not shown). The piston 14 reciprocates in a cylinder Z provided in the cylinder block and outputs the work of the cylinder charge through a connecting rod and a crankshaft, also not shown.

The cylinder block is provided with an intake port and an intake valve so that the fuel/air mixture is sucked into the main combustion chamber II of the cylinder Z when the piston moves down on the intake stroke opening the intake valve. The spark plugs DZ and VZ are screwed into the cylinder head as a spark plug assembly.

If a cylinder Z is mentioned below, it goes without saying that it can preferably be a four-cylinder, four-stroke internal combustion engine with a plurality of cylinders and combustion chambers I, II formed therein. In other words, the spark plug assembly and associated ignition method discussed below may also be used in two-cylinder, three-cylinder, five-cylinder, six-cylinder, and multi-cylinder internal combustion engines.

• Der Betrieb eines Ottomotors mit einer passiven Vorkammerzündkerze VZ funktioniert in mittel- und hochlastigen Kennfeldbereichen besser als mit einer herkömmlichen DachelektrodenZündkerzen DZ und in anderen Bereichen, insbesondere im unteren Lastbereich (Teillast), im Leerlauf und beim Katalysator-Aufheizen heizen, schlechter. Um das volle Potential des Ottomotors zu erschließen, ist es gemäß dieser Erfindung von Vorteil den Ottomotor mit einer Kombination beider Zündkerzen VZ, DZ zu betreiben.

Starting point of the ignition method according to the invention:

• The operation of a gasoline engine with a passive prechamber spark plug VZ works better in medium and high load map areas than with a conventional roof electrode spark plug DZ and in other areas, especially in the lower load range (partial load), when idling and when heating up the catalyst, worse. In order to tap the full potential of the Otto engine, it is advantageous according to this invention to operate the Otto engine with a combination of both spark plugs VZ, DZ.

According to the invention, the ignition method is based on operating modes that differ from one another depending on an average load, with the average load being defined and set as a decision criterion for the selected operating mode using the measured or modeled indicated mean pressure p _mi within the at least one cylinder within a working cycle.

Provision is made for the indicated mean pressure p _mi to be measured or modeled within the at least one cylinder Z within a working cycle. The procedure for directly measuring or modeling the indicated mean pressure p _mi is known to the person skilled in the art, so that it is not discussed in any more detail here.

According to the invention, an operating mode B-VZ, B-DZ, B-DZ/VZ of the ignition device is then activated in the next working cycle depending on _whether the measured or modeled indicated mean pressure p _mi was above or below a predetermined limit value p limit in the previous working cycle within the at least a cylinder Z

• Die Betriebsweise B-DZ, bei der ausschließlich eine Dachelektrodenzündkerzen-Betriebsweise DZ angesteuert wird.

The following modes of operation, which are activated depending on the specified limit value p _limit of the average load in the respective work cycle, are provided:

• The operating mode B-DZ, in which only a roof electrode spark plug operating mode DZ is activated.

The operating mode B-VZ, in which only one prechamber spark plug VZ is controlled.

The combined mode of operation B-DZ/VZ, in which both spark plugs DZ, VZ are activated, with the roof electrode spark plug DZ being activated before the prechamber spark plug VZ with a time offset.

According to the 1 until 3 three procedures are explained in which the operating modes are combined in different ways.

• Die Vorkammerzündkerzen-Betriebsweise B-VZ wird aktiviert, sobald der indizierte Mitteldruck p_mi mit dem vorgegebenen Grenzwert p_Grenz übereinstimmt oder oberhalb des vorgegebenen Grenzwertes p_Grenz liegt.

the 1 shows a first procedure:

• The prechamber spark plug operating mode B-VZ is activated as soon as the indicated mean pressure p _mi matches the specified limit value p _limit or is above the specified limit value p _limit .

In the first procedure, the operating mode B-DZ, in which only a roof electrode spark plug operating mode DZ is activated, is activated as soon as the indicated mean pressure p _mi is below the specified limit value p _limit .

In this first procedure, the roof electrode spark plug operating mode B-DZ is also used when the internal combustion engine is idling L.

The second procedure is an alternative procedure.

• Bei der zweiten Verfahrensweise wird ebenfalls die Vorkammerzündkerzen-Betriebsweise B-VZ aktiviert, sobald der indizierte Mitteldruck p_mi mit dem vorgegebenen Grenzwert p_Grenz übereinstimmt oder oberhalb des vorgegebenen Grenzwertes p_Grenz liegt.

the 2 shows the second procedure:

• In the second procedure, the prechamber spark plug operating mode B-VZ is also activated as soon as the indicated mean pressure p _mi matches the specified limit value p _limit or is above the specified limit value p _limit .

In the second procedure, the combined operating mode B-DZ/VZ, in which both spark plugs DZ, VZ are activated, with the roof electrode spark plug DZ being activated before the prechamber spark plug VZ with a time offset, is activated as soon as the indicated mean pressure p _mi is below the specified one limit value p _limit .

In this first procedure, the combined operating mode B-DZ/VZ is also used when the internal combustion engine is idling L.

It is provided that in the combined mode of operation B-DZ/VZ, in a first step of the ignition process, the roof electrode spark plug DZ is ignited in the main combustion chamber II of the combustion chamber.

As a result of the onset of combustion in the main combustion chamber II, the pressure in the main combustion chamber II increases and a certain charge mass flows into the antechamber combustion chamber I, which is formed by the antechamber 1'.

In the exemplary embodiment, the prechamber 1′ with the prechamber combustion chamber I protrudes into the main combustion chamber II of the combustion chamber and is also arranged very close to the prechamber combustion chamber I with regard to the ignition position of the roof electrode spark plug DZ that ignites the fuel/air mixture in the main combustion chamber II. This means that the antechamber 1' and thus the antechamber combustion chamber I is only at a small distance A from the roof electrode spark plug DZ.

Due to the immediate proximity of the two spark plugs VZ, DZ to one another, which is defined by the distance A from one another in relation to their central axes 1M, 2M, combustion gas or its intermediate products and radicals are also advantageously transported in addition to the fresh fuel/air mixture Prechamber combustion chamber I of the prechamber 1' is transported or pressed into the prechamber combustion chamber I of the prechamber 1'.

The distance A or a distance range of the center axes 1M, 2M of the center electrodes 1.4 of the spark plugs VZ, DZ is, in addition to the previous information, preferably 0.1 to 0.2 multiplied by the diameter D (cylinder diameter) of the cylinder Z.

Because the fuel/air mixture and the combustion gas (with the reactive/more reactive intermediate products and radicals it contains) are pressed with a high charge mass into the antechamber combustion chamber I, the ignition conditions in the antechamber combustion chamber I of the antechamber 1' are advantageously improved significantly.

The ignition with the prechamber spark plug VZ takes place with the time delay after the roof electrode spark plug DZ.

Due to the ignition of the charge with the roof electrode spark plug DZ in the main combustion chamber II before the ignition of the prechamber spark plug VZ, a flame front spreads from the local ignition position of the roof electrode spark plug DZ in the main combustion chamber II. High temperatures prevail behind the flame front, in which the (first) combustion products, partly intermediate products and radicals, in particular individual atoms, of the otherwise diatomic or polyatomic (reactive/more reactive) gases are formed.

As the flame front progresses, initially still close to the spark plug (near the ignition position of the roof electrode spark plug DZ), the pressure in the main combustion chamber I of the combustion chamber increases and gases are released from the Area behind the flame front in the antechamber 1 'pressed, while the flame front also over the outer surface of the antechamber 1' runs. In this way, the charge mass in the prechamber 1' increases in a very short time and, due to the increasing pressure in the main combustion chamber II of the combustion chamber and the resulting pressure drop between the prechamber combustion chamber I of the prechamber 1' and the main combustion chamber II, more and more reactive particles are produced transported into the antechamber 1' (particularly due to the small distance A). As a result, the ignition conditions in the prechamber 1' improve continuously, with provision being made for the second ignition by means of the prechamber spark plug VZ in the prechamber combustion chamber of the prechamber 1 to occur in a predeterminable ignition interval, preferably after </= 1 ms after the first ignition with the roof electrode spark plug DZ ' he follows.

According to the invention, it is preferably provided that (only) at the end of the compression stroke at ignition angles, in particular between at the earliest 50° CA before ITDC and at the latest 30° CA after ITDC, ignition with the roof electrode spark plug DZ takes place.

A few degrees crank angle °KW later preferably </=1 ms after the ignition point of the roof electrode spark plug D, the ignition thus takes place, ie a further ignition with the prechamber spark plug VZ in the prechamber 1' with the time offset.

Due to the speed dependency of 600 rpm, for example, 1 ms corresponds to 3.6 °KW or 6000 rpm, then 1 ms corresponds to 36 °KW, as a time offset between the ignition of the roof electrode spark plug DZ and the subsequent ignition with the prechamber spark plug VZ a time specification of preferably </= 1 ms is given, which is thus selected independently of the speed, the starting point in time being the current ignition point of the roof electrode spark plug DZ at one end of the compression stroke, which is at ignition angles at one end of the compression stroke and in particular between at the earliest 50 °CA before ZOT and no later than 30 °CA after ZOT is selected.

It is of particular importance according to the invention, as illustrated in the preceding description, that due to the combined mode of operation B-DZ/VZ of two individual spark plugs DZ, VZ in a combustion chamber with a time offset from one another and due to the small distance A between the spark plugs DZ, VZ, improved transport of radicals into the antechamber 1′ and additional ignition in the antechamber 1′ is possible in particular next to one another in an advantageous manner. The combination of the arrangement of prechamber and roof electrode spark plugs VZ, DZ in the spark plug assembly and the combined procedure advantageously enables the production of short combustion paths in all directions for the realization of improved ignition conditions and a low knocking tendency of the internal combustion engine.

In a third approach, the modes of operation are combined with one another in yet another way, as explained below.

• Bei der dritten Verfahrensweise wird wiederum ebenfalls die Vorkammerzündkerzen-Betriebsweise B-VZ aktiviert, sobald der indizierte Mitteldruck p_mi mit dem vorgegebenen Grenzwert p_Grenz übereinstimmt oder oberhalb des vorgegebenen Grenzwertes p_Grenz liegt.

the 3 shows the third procedure:

• In the third procedure, the prechamber spark plug operating mode B-VZ is again activated as soon as the indicated mean pressure p _mi matches the specified limit value p _limit or is above the specified limit value p _limit .

In the third procedure, the combined operating mode B-DZ/VZ, in which both spark plugs DZ, VZ are activated, with the roof electrode spark plug DZ being activated before the prechamber spark plug VZ with a time offset, is activated as soon as the indicated mean pressure p _mi is below the predetermined limit p _limit is located. The advantages of the combined operating mode B-DZ/VZ described in this context in the second procedure also apply to this third procedure.

In contrast to the second procedure, the third procedure switches from the combined operating mode B-DZ/VZ to the roof electrode spark plug operating mode B-DZ as soon as the indicated mean pressure p _mi lying below the limit p limit _corresponds to the idling L of the internal combustion engine.

It applies to all procedures that the specified limit value p _limit of the indicated mean pressure p _mi within the at least one cylinder Z is between 0.2 MPa and 0.6 MPa, preferably 0.4 MPa.

Catalyst operation:

For catalytic converter operation in the operating modes B-DZ, B-VZ and B-DZ/VZ, it is provided that the roof electrode spark plug operating mode B-DZ or the prechamber spark plug operating mode or the combined operating mode B-DZ/VZ is independent of the limit value (of P _limit ). is chosen. In other words, one of the modes of operation is permanently assigned to the catalytic converter operation, into which there is a switchover as soon as the request for the catalytic converter operation is present on the control side and the catalytic converter operation is carried out.

In a preferred embodiment, limit value-dependent (P _limit ) catalytic converter operation is provided, with the limit value-dependent prechamber spark plug operating mode B-VZ being activated as soon as the indicated mean pressure corresponds to the specified limit value p _limit or is above the specified limit value p _limit , or the roof electrode spark plug Operating mode B-DZ or the combined operating mode B-DZ/VZ is activated as soon as the indicated mean pressure p _mi is below the specified limit value p _limit . In other words, the catalytic converter operation is carried out in the currently activated mode of operation, without switching over, as soon as there is a request for catalytic converter operation on the control side.

• Schließlich ist noch in allen Betriebsweisen B-DZ, B-VZ und B-DZ/VZ vorgesehen, dass eine lonenstromüberwachung durchgeführt wird. In allen Betriebsweisen B-DZ, B-VZ und B-DZ/VZ kann in vorteilhafter Weise mit den Elektroden 2.4, 2.5 der Dachelektrodenzündkerze DZ ein Ionenstromsignal S, insbesondere zur Überwachung des Klopfens und/oder von Verbrennungsaussetzern und/oder zur Korrektur des Lambda-Wertes (Lambdakorrekturen) erzeugt, ausgewertet und korrigierend eingesetzt werden.

Monitoring of the mode of operation by measuring the ion current:

• Finally, in all operating modes B-DZ, B-VZ and B-DZ/VZ, ion current monitoring is carried out. In all operating modes B-DZ, B-VZ and B-DZ/VZ, an ionic current signal S can advantageously be generated with the electrodes 2.4, 2.5 of the roof electrode spark plug DZ, in particular for monitoring knocking and/or combustion misfires and/or for correcting the lambda -value (lambda corrections) can be generated, evaluated and used for correction.

Due to the essentially central position of the two spark plugs DZ, VZ, especially due to the central position of the roof electrode spark plug DZ in the main combustion chamber II, it is possible to detect the ion current signal S in a central local area of the main combustion chamber II.

The invention thus achieves, on the one hand, that the roof electrode spark plug DZ is arranged relatively centrally in the main combustion chamber II of the cylinder Z, i.e. at a small distance from the central axis 100M of the spark plug assembly, which also corresponds to the central axis of the cylinder Z, while on the other hand the Distance A between the roof electrode spark plug DZ and the pre-chamber spark plug VZ is small, as a result of which the ignition conditions are influenced and improved accordingly in the sense of stable ignition that is always present.

In other words, the method according to the invention allows the desired stable ignition conditions to be achieved by selecting the operating modes B-VZ, B-DZ or B-DZ/VZ by using two spark plugs DZ, VZ depending on the indicated mean pressure p _mi and selection of the modes of operation as a function of the limit value p _limit , whereby at the same time the ion current signal S can be detected in an improved manner in the central local area of the main combustion chamber II by the central arrangement (compared to detection at the edge in a cylinder Z) in order to, in addition to the high ignition stability according to explained procedures to be able to influence the avoidance of knocking, combustion misfires or to correct the lambda value.

In terms of control and structure, the Otto engine internal combustion engine is set up to carry out the ignition method according to the invention. For this purpose, the internal combustion engine with the spark plug assembly includes, in particular, a control device in which a computer-readable program algorithm for executing the method and any necessary characteristic diagrams are stored.

Reference List

100

spark plug assembly

100M

Central axis of the spark plug assembly

10

Body of the spark plug assembly

10.1

top

10.2

bottom

10.3

through hole

10.31

confiscation/s

10.32

inner thread

10.4

center bar

10.5

Unit volume

10.6

external thread

20

fastener

20.1

external thread

vz

Prechamber spark plug VZ

1

Insulator body of the prechamber spark plug VZ

1'

antechamber

1.1

Insulator Tip

1.2

insulator core

1.2o

shoulder

1.2.u

shoulder

1.3

head

1.4

center electrode

1.5

ground electrode

1M

central axis

double room

roof electrode spark plug

2

Insulator body roof electrode spark plug

2.1

Insulator Tip

2.2

insulator core

2.2o

shoulder

2.2u

shoulder

2.3

insulator head

2.4

center electrode

2.5

ground electrode

2M

central axis

Z

cylinder

A

Distance

B-VZ

Mode of operation exclusively with prechamber spark plug

B-DZ

Mode of operation exclusively with roof electrode spark plug

B- DR/VZ

Mode of operation with roof electrode spark plug and prechamber spark plug

S

ionic current signal

I

prechamber combustion chamber

II

main combustion chamber

pmi

indicated mean pressure

plimit

Indicated mean pressure limit

L

Neutral

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

• EP 3561255 A1 [0002]
• EP 3453856 B1 [0003]
• DE 2843119 A [0004]

Claims (12)

Method for igniting a fuel/air mixture in a combustion chamber of an Otto engine internal combustion engine, which is defined by a cylinder head and a cylinder (Z), wherein the combustion chamber is assigned at least one inlet valve and at least one outlet valve as well as an ignition device, which is a roof electrode spark plug (DZ ) and a prechamber spark plug (VZ), with the following steps: • Measuring or modeling the indicated mean pressure (p _mi ) within the at least one cylinder (Z) within a working cycle, • Activating an operating mode (B-VZ, B-DZ, B -DZ/VZ) of the ignition device in the next working cycle as a function of an indicated mean pressure (p _mi ) within the at least one cylinder (Z) measured or modeled above or below a predetermined limit value (P _limit ) in the previous working cycle, • depending on the activated Mode of operation (B-VZ, B-DZ, B-DZ/VZ) in the respective working cycle ◯ in one day n electrode spark plug operating mode (B-DZ) or a prechamber spark plug operating mode (B-VZ) only one of the two spark plugs (DZ, VZ) is activated, or ◯ in a combined operating mode (B-DZ/VZ) both spark plugs (DZ, VZ ) are activated, with the roof electrode spark plug (DZ) being activated before the prechamber spark plug (VZ) with a time offset. procedure after claim 1 , characterized in that the prechamber spark plug mode of operation (B-VZ) is activated as soon as the indicated mean pressure (p _mi ) matches the specified limit value (P _limit ) or is above the specified limit value (P _limit ). procedure after claim 1 , characterized in that the roof electrode spark plug operating mode (B-DZ) is activated as soon as the indicated mean pressure (p _mi ) is below the specified limit value (P _limit ). procedure after claim 1 , characterized in that the combined mode of operation (B-DZ/VZ) is activated as soon as the indicated mean pressure (p _mi ) is below the specified limit value (P _limit ). procedure after claim 4 , characterized in that the combined mode of operation (B-DZ/VZ) is maintained as soon as the indicated mean pressure (p _mi ) lying below the predetermined limit value (P _Grenz ) corresponds to the idling (L) of the internal combustion engine. procedure after claim 4 , characterized in that there is a switchover from the combined mode of operation (B-DZ/VZ) to the roof electrode spark plug mode of operation (B-DZ) as soon as the indicated mean pressure (p _mi ) lying below the specified limit value (P _Grenz ) corresponds to idling (L ) corresponds to the internal combustion engine. procedure after claim 1 , characterized in that in a catalytic converter operation, the roof electrode spark plug operating mode (B-DZ) or the prechamber spark plug operating mode (B-VZ) or the combined operating mode (B-DZ/VZ) is selected regardless of the limit value. procedure after claim 1 , characterized in that in catalytic converter operation, the prechamber spark plug operating mode (B-VZ) is activated as a function of the limit value as soon as the indicated mean pressure (p _mi ) matches the specified limit value (P _limit ) or is above the specified limit value (P _limit ), or the roof electrode spark plug operating mode (B-DZ) or the combined operating mode (B-DZ/VZ) is activated as soon as the indicated mean pressure (p _mi ) is below the specified limit value (P _limit ). procedure after claim 1 , characterized in that the predetermined limit value (p _limit ) of the indicated mean pressure (p _mi ) within the at least one cylinder (Z) is between 0.2 MPa and 0.6 MPa, preferably 0.4 MPa. Process according to at least one of claims 2 until 4 , characterized in that the ignition timing of the prechamber spark plug (VZ) in the prechamber spark plug mode (B-VZ) and the ignition timing of the roof electrode spark plug (DZ) in the roof electrode spark plug mode (B-DZ) or the combined mode (B-DZ/VZ ) at the end of the compression stroke, in particular at ignition angles between at the earliest 50° CA before ZOT and at the latest 30° CA after ZOT and controlled. procedure after claim 9 , characterized in that the time offset between the specified and controlled ignition point of the roof electrode spark plug (DZ) and the subsequent ignition point of the prechamber spark plug (VZ) in the combined operating mode (B-DZ/VZ) is between 0.1 ms and 2 ms, preferably smaller /equal to </= 1 ms. procedure after claim 1 , characterized in that in all operating modes (B-VZ, B-DZ, B-DZ/VZ) by means of the roof electrodes spark plug (DZ) to monitor and avoid knocking and/or to avoid combustion misfires and/or to correct the lambda value, an ionic current signal (S) is recorded, evaluated and used to correct it.

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