Internal combustion engine having spark plug and pre-chamber spark plug

Abstract

The present invention relates to an internal combustion engine (1) comprising at least one cylinder (10), four charge cycle openings (4) per cylinder (10), the first and second charge cycle openings (4) each being an intake opening (41), the third and fourth charge cycle openings (4) each being an exhaust opening (42), and a spark plug (2) and a pre-chamber spark plug (3) per cylinder (10).

Description

[Technical field]

[0001] The present invention relates to an internal combustion engine having a spark plug and a pre-chamber spark plug, and to a method of operating an internal combustion engine. [Background technology]

[0002] Internal combustion engines with pre-chamber spark plugs are known from the prior art. The pre-chamber spark plug, as known for conventional spark plugs, comprises a central electrode arranged in a housing and a ground electrode, between which an ignition gap is defined, in which the air-fuel mixture is ignited. This ignited air-fuel mixture is subsequently guided through an opening in a plug cap at the end of the pre-chamber spark plug facing the combustion chamber into the combustion chamber of the internal combustion engine, in which the actual combustion of the air-fuel mixture for the piston stroke takes place. For example, US Pat. No. 5,399,433 shows such a pre-chamber spark plug. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] DE 102019205478 Summary of the Invention

[0004] In contrast, the internal combustion engine according to the invention having the features of claim 1 is characterized by an improved operating configuration, which allows particularly high efficiency with a low tendency to knock and reliable operation in any operating state. This is realized according to the invention by an internal combustion engine comprising at least one cylinder, each cylinder including a spark plug and a pre-chamber spark plug. Furthermore, the internal combustion engine comprises four charge cycle openings per cylinder, where the first and second charge cycle openings are each intake openings and the third and fourth charge cycle openings are each exhaust openings.

[0005] What is considered here as an "ignition plug" is a conventional spark plug, in particular having exposed electrodes, set up to ignite the fuel-air mixture by an electric ignition spark between at least two electrodes. It is particularly preferred that the spark plug has a straight central electrode and at least one hook-shaped end electrode or roof-shaped electrode. In particular, such an ignition plug may alternatively be called a "spark plug". Alternatively, a laser device set up to ignite the fuel-air mixture by means of laser radiation may be used as an "ignition plug".

[0006] What is considered as a "pre-chamber spark plug" is a design with a pre-chamber formed inside the plug cap, which is fluidly connected with the combustion chamber of the internal combustion engine via a through hole in the plug cap. This allows the passage of gases from the pre-chamber through the plug cap into the combustion chamber and vice versa. The plug cap is preferably arranged at the end of the housing of the pre-chamber spark plug facing the combustion chamber, as viewed in the axial direction of the pre-chamber spark plug. The plug cap, the housing and the pre-chamber then form an integral component of the pre-chamber spark plug. Thus, in particular, the pre-chamber is inside the pre-chamber spark plug. Inside the pre-chamber, ignition of the fuel-air-mixture therein is then performed by an electrode, whereby a flame jet passes through the through opening in the plug cap and ignites the fuel-air-mixture in the combustion chamber. That is to say, the actual ignition of the fuel-air-mixture in the combustion chamber is performed by the flame jet generated by the pre-chamber spark plug. The pre-chamber spark plug is then preferably considered as an integral component that can be attached to the cylinder head of the internal combustion engine. The installation is preferably performed in such a way that when in the final position, the through holes of the plug cap are aligned in a predefined manner to generate, in particular, a properly aligned flame jet during operation. For example, the pre-chamber spark plug may be designed to be screwable into a standard thread of a cylinder head capable of receiving a normal spark plug.

[0007] The combination of a conventional spark plug with a pre-chamber spark plug then offers the advantage of a particularly flexible, efficient and reliable operating regime of the internal combustion engine, whereby the best possible and reliable ignition of the fuel-air-mixture can always be achieved in the combustion chamber in all operating states, for example during cold start, in the catalyst heating phase, at partial load and at full load. The operation of the internal combustion engine can preferably be designed in such a way that the pre-chamber spark plug is used as the sole ignition means in as wide an operating range as possible, in order to achieve an efficient knock reduction and low fuel consumption, especially under high loads. The spark plug can then be operated additionally or separately in operating ranges where the operation of the pre-chamber spark plug is unfavourable or impossible, for example during cold start, in order to achieve reliable ignition in these ranges as well. This has the further advantage that the pre-chamber spark plug can be specially optimized for as efficient an operation as possible, for example for a specific operating point of the internal combustion engine, while a reduced efficiency at other operating points can be ignored or accepted, since at such operating points the spark plug can for example be used solely or additionally for ignition. Furthermore, due to the ignition being always optimally adaptable to a wide variety of operating ranges, damage to the internal combustion engine, for example due to knocking, ignition failure or poor combustion, can be avoided and thus a particularly long service life of the internal combustion engine can be made possible.

[0008] The dependent claims indicate preferred developments of the invention.

[0009] The spark plug and / or the pre-chamber spark plug are preferably arranged on the combustion chamber roof of the combustion chamber of the cylinder. In particular, the combustion chamber roof forms the upper end of the combustion chamber along the stroke direction of the piston. The combustion chamber roof is preferably part of the cylinder head of the internal combustion engine. The pre-chamber spark plug and the spark plug preferably extend into the combustion chamber. Preferably, the plug cap of the pre-chamber spark plug and the electrode of the spark plug then extend into the combustion chamber. Alternatively, the end of the pre-chamber spark plug and the spark plug facing the combustion chamber can also be arranged inside the respective spark plug bore in which the corresponding pre-chamber spark plug or spark plug is arranged.

[0010] It is further preferred that the pre-chamber spark plug is arranged closer to the center point of the combustion chamber roof than the spark plug, so that a particularly uniform penetration of the combustion chamber by the generated flame jet for uniform ignition of the fuel-air mixture can be achieved in a simple manner. Alternatively, it is also preferred that the spark plug is arranged closer to the center point of the combustion chamber roof than the pre-chamber spark plug, so as to achieve a particularly efficient and uniform ignition by the spark plug.

[0011] The pre-chamber spark plug is preferably arranged closer to the side wall of the cylinder than the spark plug. In this case, the pre-chamber spark plug is preferably constructed and arranged in such a way that the flame jet generated by the pre-chamber spark plug during ignition is directed towards the centre of the combustion chamber. Alternatively, the spark plug is arranged closer to the side wall of the cylinder than the pre-chamber spark plug. This makes it possible to use more space for the pre-chamber spark plug in the region of the centre of the combustion chamber roof in order to enable a high efficiency of operation of the pre-chamber spark plug. The side wall considered in this case is the substantially cylindrical outer casing surface of the cylinder, which can also be called the running surface of the piston.

[0012] It is particularly preferred that the pre-chamber spark plug is arranged closer to at least one of the two intake openings than the spark plug, in particular closer to both intake openings, thereby enabling a particularly good supply of fresh combustion air to the pre-chamber spark plug and thus enabling the best ignition during its operation. Alternatively, it is also preferred that the pre-chamber spark plug is arranged closer to at least one of the two exhaust openings than the spark plug, in particular closer to both exhaust openings. In this case, the spark plug can be arranged particularly close to at least one of the intake openings, thereby enabling the best fresh air supply to the spark plug.

[0013] The spark plug is preferably arranged on the intake side or on the exhaust side with respect to the pre-chamber spark plug. Intake side or exhaust side is considered as a reference direction that describes the relative arrangement of the intake opening and the exhaust opening relative to each other and / or on the combustion chamber roof. In particular, the intake-side arrangement of the spark plug with respect to the pre-chamber spark plug means that the spark plug is arranged along an axis extending from the exhaust opening to the intake opening further towards the intake opening than the pre-chamber spark plug, i.e. the spark plug is arranged closer to the intake opening than the pre-chamber spark plug. It is then particularly preferred if the spark plug is arranged on the exhaust side of the pre-chamber spark plug, i.e. the spark plug is arranged closer to the exhaust opening than the pre-chamber spark plug. In particular in this case, the pre-chamber spark plug is arranged closer to the intake opening than the spark plug. As a result, the fresh air entering through the intake opening or the fuel-air-mixture entering can be ignited particularly precisely due to the proximity of the pre-chamber spark plug, especially when the pre-chamber spark plug is activated.

[0014] The charge cycle openings are further preferably arranged on the combustion chamber roof, which is subdivided into four quadrants by two mutually perpendicular cut planes. The combustion chamber roof is subdivided by both cut planes in such a way that in each of the four quadrants a respective one of the four charge cycle openings is arranged. The spark plug and / or the pre-chamber spark plug are then arranged in a particularly substantially manner in one of both cut planes. In other words, both cut planes are located centrally between the respective charge cycle openings. Both cut planes preferably intersect with one another on a cut line parallel to a piston direction in which the piston of the internal combustion engine is movable. In other words, the spark plug and / or the pre-chamber spark plug are located substantially symmetrically between the two charge cycle openings. It is particularly preferred that both cut planes form a symmetry plane of the combustion chamber roof. A particularly preferred arrangement can be achieved by arranging the spark plug and / or the pre-chamber spark plug in one of both cut planes. This is because in that case the area with the greatest free space is available in the combustion chamber roof and, moreover, allows for a virtually central ignition for uniform ignition of the fuel-air-mixture.

[0015] The spark plug and / or the pre-chamber spark plug are preferably arranged in the center point area of ​​the combustion chamber roof. The center point area is located substantially radially inside the charge cycle openings and in particular surrounds the center point of the combustion chamber roof or the area around the roof center. It is particularly preferred that the pre-chamber spark plug is then arranged exactly at the center point of the combustion chamber roof. It is particularly preferred that the center point area is defined by a circle of maximum size that is inscribed centrally between the respective charge cycle openings. That is to say, the spark plug and / or the pre-chamber spark plug are preferably arranged in the center of the combustion chamber roof, so that a particularly symmetrical and uniform penetration and therefore a simultaneous ignition are possible within the entire combustion chamber. In particular, a central pre-chamber spark plug can thereby enable a particularly uniform penetration of the combustion chamber by the flame jet that realizes ignition and therefore a uniform and efficient combustion.

[0016] It is particularly preferred that the spark plug and / or the pre-chamber spark plug are arranged between two adjacent charge cycle openings and the side wall of the cylinder. In particular, the spark plug and / or the pre-chamber spark plug are then located radially outside a center point circle on which the centers of the four charge cycle openings are located. In other words, the spark plug and / or the pre-chamber spark plug are arranged inside the free radially outer area of ​​the combustion chamber roof. In particular, these four free radially outer areas are distributed around the circumference of the combustion chamber roof. This allows the space available on the combustion chamber roof to be particularly favorably utilized for the arrangement of all components. It is particularly advantageous, for example, if one of the spark plug and the pre-chamber spark plug is arranged inside the center point area and the other is arranged radially outside. The distance between the side wall of the cylinder and the spark plug and / or between the side wall of the cylinder and the pre-chamber spark plug is then at most 30%, preferably at most 15%, of the cylinder radius of the cylinder. Furthermore, the lateral arrangement near the side wall allows the spark plug and / or pre-chamber spark plug to be spaced farther from the center of the combustion chamber, which results in a lower thermal load than, for example, a central arrangement, which favorably affects the long service life of the spark plug and / or pre-chamber spark plug.

[0017] Preferably, the internal combustion engine further comprises a combustion chamber fuel injector, particularly set up to inject liquid or gaseous fuel directly into a combustion chamber of the internal combustion engine.

[0018] The combustion chamber fuel injector is preferably located in the combustion chamber roof, and in particular in proximity to the pre-chamber spark plug and / or spark plug, to generate a uniform fuel-air mixture, preferably aligned with the pre-chamber spark plug and / or spark plug position for uniform and even ignition.

[0019] It is particularly preferred that the combustion chamber fuel injector is arranged between two adjacent charge cycle openings and the side wall of the cylinder. In particular, the combustion chamber fuel injector is located radially outside the center circle on which the centers of the four charge cycle openings are located. In other words, the combustion chamber fuel injector is arranged inside the free radially outer area of ​​the combustion chamber roof. In particular, the combustion chamber fuel injector is then set up to inject fuel towards the center of the combustion chamber in order to obtain an even distribution and ignition. In this case, it is particularly preferred to arrange the combustion chamber fuel injector between both intake openings and the side wall of the cylinder in order to promote the best possible even mixture formation before combustion. Furthermore, the lateral arrangement causes a wider spacing of the combustion chamber fuel injector with respect to the combustion chamber center, which can favorably affect a lower thermal load of the combustion chamber fuel injector in order to enable a long service life.

[0020] The distance between the combustion chamber fuel injector and the side wall of the cylinder is preferably at most 30%, particularly preferably at most 15%, of the cylinder radius. In other words, the combustion chamber fuel injector is preferably located close to the side wall, i.e. not in the center, but on the side of the combustion chamber roof. In this case, the combustion chamber fuel injector is preferably aligned obliquely, so that the direction of the fuel to be injected is directed towards the center of the combustion chamber. The lateral arrangement of the combustion chamber fuel injector allows a particularly space-saving arrangement on the combustion chamber roof, whereby more space is available for the arrangement of the spark plug and / or the pre-chamber spark plug, especially in the central area of ​​the combustion chamber roof.

[0021] It is particularly preferred that the combustion chamber fuel injector and the pre-chamber spark plug are arranged on opposite sides of the combustion chamber roof. Alternatively or additionally, it is particularly preferred that the combustion chamber fuel injector and the spark plug are arranged on opposite sides of the combustion chamber roof. In particular, opposite is considered to be an arrangement opposite to the centre point of the combustion chamber roof, which allows a particularly favourable utilisation of the free space available on the combustion chamber roof for the arrangement of the respective components.

[0022] The combustion chamber fuel injector is preferably arranged within a center point area of ​​the combustion chamber roof, which center point area is located radially inside the charge cycle opening. It is particularly preferred that the combustion chamber fuel injector is arranged exactly at the center point of the combustion chamber roof. The central arrangement of the combustion chamber fuel injector on the combustion chamber roof allows a preferably symmetrical and particularly even injection into the combustion chamber in order to allow a particularly even fuel distribution in the combustion chamber and an efficient combustion.

[0023] It is particularly preferred that the pre-chamber spark plug is arranged closer to the combustion chamber / fuel injector than the spark plug. Such a close arrangement of the combustion chamber / fuel injector and the pre-chamber spark plug has a particularly favorable effect on the efficient and reliable operation of the pre-chamber spark plug. The closeness between the combustion chamber / fuel injector and the pre-chamber spark plug leads to improved flushing and mixture supply of the pre-chamber of the pre-chamber spark plug. Alternatively, it is preferred that the spark plug is arranged closer to the combustion chamber / fuel injector than the pre-chamber spark plug. In this case, a particularly good mixture supply can be provided in the area of ​​the spark plug. Such a close arrangement of the combustion chamber / fuel injector and the spark plug allows for a particularly robust operation of the internal combustion engine, for example during catalyst heating.

[0024] The combustion chamber fuel injectors and the pre-chamber spark plug are preferably spaced apart by a maximum of 50%, in particular a maximum of 30%, preferably a maximum of 10% of the cylinder radius of the cylinder.

[0025] The combustion chambers, fuel injectors and spark plugs are preferably spaced apart by a maximum of 50%, in particular a maximum of 30%, preferably a maximum of 10% of the cylinder radius.

[0026] It is particularly preferred that the injection direction of the combustion chamber fuel injector, i.e. the direction along which the fuel is injected substantially, is directed towards the pre-chamber spark plug, in particular towards the plug cap of the pre-chamber spark plug, whereby particularly good flushing and mixture supply of the pre-chamber of the pre-chamber spark plug can be achieved. Alternatively, it is preferred that the injection direction is directed substantially towards the spark plug.

[0027] The internal combustion engine further preferably comprises an intake manifold fuel injector set up for injecting fuel into an intake manifold of the internal combustion engine. In particular, the internal combustion engine comprises two intake manifolds each with an intake manifold fuel injector, each of which opens into the combustion chamber at one of both intake openings. Alternatively, the internal combustion engine can comprise just one intake manifold fuel injector set up for injecting fuel into both intake manifolds, or alternatively, the internal combustion engine can comprise just one intake manifold fuel injector set up for injecting fuel into a common intake manifold section, which section splits into both intake manifolds in the direction of the combustion chamber. The intake manifold fuel injector is preferably provided as an alternative to a combustion chamber fuel injector with direct injection, which is arranged in the combustion chamber. This allows particularly more space to be utilized in the combustion chamber roof for the spark plug and the pre-chamber spark plug for their best arrangement.

[0028] The invention further relates to a method of operating an internal combustion engine having at least one cylinder, four charge cycle openings per cylinder, a spark plug and a pre-chamber spark plug, the spark plug and / or the pre-chamber spark plug being operated to ignite a fuel-air mixture inside a combustion chamber of the cylinder, i.e. simultaneous operation of the pre-chamber spark plug and the spark plug during operation of the internal combustion engine, but also alternatively operation of either the spark plug or the pre-chamber spark plug alone to ignite a fuel-air mixture inside the combustion chamber of the cylinder, thereby allowing a particularly flexible and efficient operation of the internal combustion engine.

[0029] The pre-chamber spark plug preferably operates alone during operation of the internal combustion engine under high load, in particular during which the spark plug is deactivated. High load is preferably considered to be operation under a torque of at least 20%, preferably at least 50%, particularly preferably at least 80% of the rated torque of the internal combustion engine. Such a torque threshold value may preferably be dependent on the engine speed or other characteristic values, such as the lambda value, the valve control time, the engine temperature, etc. By operating the pre-chamber spark plug alone under high load, a particularly efficient operation can be achieved as well as an efficient reduction in the knock tendency of the internal combustion engine.

[0030] It is further preferred that the spark plug operates alone during operation of the internal combustion engine under low load, in particular during which the pre-chamber spark plug is deactivated. Low load is preferably considered to be operation under torques below 80%, preferably below 50%, particularly preferably below 20% of the rated torque of the internal combustion engine, so that reliable ignition by the spark plug is possible even under low load.

[0031] It is particularly preferred that the spark plug is activated during the catalyst heating phase, in particular after a cold start of the internal combustion engine. An independent operation of the spark plug is preferred during the catalyst heating phase, in particular with the pre-chamber spark plug being deactivated during that time, in order to reliably guarantee optimal ignition of the fuel-air-mixture, for example after a cold start, when optimal conditions for the operation of the pre-chamber spark plug are not yet in place.

[0032] At low engine temperatures of the internal combustion engine, in particular at engine temperatures of up to 323 K, in particular up to 303 K, particularly preferably up to 293 K, an independent operation of the spark plug is preferably performed. For example, the temperature of the coolant of the internal combustion engine can be determined as the engine temperature, in order to obtain a particularly simple determination. Alternatively, a combined operation of the spark plug and the pre-chamber spark plug can be performed simultaneously, even at such low temperatures.

[0033] It is further preferred that during re-ignition of the internal combustion engine, in particular after the thrust phase, i.e. after towing of the internal combustion engine by the vehicle, and preferably under very low load, a sole operation of the spark plug is performed, or alternatively, a combined operation of the spark plug and the pre-chamber spark plug can be performed simultaneously during such a re-ignition of the internal combustion engine.

[0034] The spark plug and the pre-chamber spark plug preferably operate with different, preferably independent, ignition timings, in particular within a single operating stroke of the internal combustion engine. For example, the spark plug can preferably only be operated during the exhaust stroke under high loads, and preferably only the pre-chamber spark plug is used for ignition of the fuel-air mixture. This allows the best possible, complete and efficient combustion depending on the operating state of the internal combustion engine.

[0035] It is particularly preferred that the internal combustion engine is operated with a lambda value of at least 1 within at least one partial operating range. It is particularly preferred that a pre-chamber spark plug is operated within this partial operating range. Preferably, the spark plug can be deactivated within this partial operating range. Alternatively, a combined operation of the spark plug and the pre-chamber spark plug can also be performed. In a further alternative embodiment, an independent operation of the spark plug can also be performed within this partial operating range, i.e. the pre-chamber spark plug is deactivated during this. It is particularly preferred that the lambda value within at least one partial operating range of the internal combustion engine is at least 1.05. In this case, the internal combustion engine is operated with a lean fuel-air mixture within this partial operating range. During lean operation, it is preferred that a pre-chamber spark plug and / or a spark plug is operated. This allows a particularly fuel-saving operation, in particular the pre-chamber spark plug allows a reliable ignition of the fuel-air mixture with a low knock tendency.

[0036] BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the present invention will now be described in detail with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0037] [Figure 1] 1 is a cross-sectional view showing an internal combustion engine according to a first embodiment of the present invention. [Diagram 2] 2A-2C are simplified schematic detail views showing various preferred configurations of the internal combustion engine of FIG. [Diagram 3] FIG. 2 is a simplified schematic detail view showing another preferred configuration of the internal combustion engine of FIG. 1; [Figure 4] FIG. 4 is a cross-sectional view showing an internal combustion engine according to a second embodiment of the present invention. [Diagram 5] 5A-5C are simplified schematic detail views showing various preferred configurations of the internal combustion engine of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] FIG. 1 shows a simplified cross-sectional view of an internal combustion engine 1 according to a first embodiment of the invention. The internal combustion engine 1 comprises a number of cylinders 10, only one of which is shown in FIG. 1. The cylinders 10 have a combustion chamber 5 delimited at their upper end by a combustion chamber roof 50. The combustion chamber roof 50 is formed by the cylinder head 15 of the internal combustion engine 1. The combustion chamber roof 50 is preferably configured tapered or tapered upwards, with the roof edge forming in particular a centre point 54 (see FIG. 2) of the combustion chamber roof 50. The centre point 54 is then located centrally, in particular on the central axis 12 of the cylinder 10, which is preferably circular.

[0039] The internal combustion engine 1 comprises four charge cycle openings 4 per cylinder 10 (see also FIG. 2 ). The first and second charge cycle openings 4 each form an intake opening 41, via which fresh air can flow into the combustion chamber 5. The third and fourth charge cycle openings 4 each form an exhaust opening 42, via which the exhaust gases after combustion can flow out of the combustion chamber 5.

[0040] Furthermore, the internal combustion engine 1 includes a combustion chamber fuel injector 6 for each cylinder 10 which is set up to inject liquid or gaseous fuel directly into the combustion chamber 5. Here, the combustion chamber fuel injector 6 protrudes slightly into the combustion chamber 5. Alternatively, the combustion chamber fuel injector 6 may be recessed into the injector bore 60 in which it is located.

[0041] Furthermore, the internal combustion engine 1 includes, for each cylinder 10, a spark plug 2 and a pre-chamber spark plug 3.

[0042] The spark plug 2 is a conventional spark plug set up to ignite the fuel-air mixture in the combustion chamber 5 by means of an electric spark. To this end, the spark plug 2 may have a central electrode 21 and a lateral hook-shaped end electrode 22, which in particular forms a ground electrode. An ignition spark can be generated between both electrodes 21, 22. The spark plug 2 may be arranged in a bore 20 inside the cylinder head 15, as shown in FIG. 1, which bore 20 communicates with the combustion chamber 5. Alternatively, the spark plug 2 may project into the combustion chamber 5.

[0043] The pre-chamber spark plug 3 has a plug cap 32 arranged at the axial end of a housing 34 of the pre-chamber spark plug 3. The plug cap 32 then forms a pre-chamber 35 inside the pre-chamber spark plug 3, which is connected to the combustion chamber 5 via a through-hole (not shown) passing through the plug cap 32. By means of the electrode 31, the fuel-air mixture can be ignited inside the pre-chamber 35, so that through the through-hole several, preferably four, flame jets 30 (see FIG. 2, FIG. 3 or FIG. 5; diagrammatically shown as club-shaped jets emanating from the pre-chamber spark plug 3) diffuse, in particular in the form of flames, into the combustion chamber 5 and ignite the fuel-air mixture therein. The pre-chamber spark plug 3 is screwed into a hole 33 in the cylinder head 15. Here, the pre-chamber spark plug 3 is screwed in such a way that the plug cap 32 protrudes into the combustion chamber 5.

[0044] The pre-chamber spark plug 3 is optimized for operation of the internal combustion engine 1 under high load and for operation while the internal combustion engine 1 is running with a stoichiometric or lean fuel-air mixture. The special ignition strategy of the pre-chamber spark plug 3 allows the fuel-air mixture to be ignited reliably and with a low knock tendency of the internal combustion engine 1. This makes it possible to operate the internal combustion engine 1 in a particularly fuel-saving manner without the risk of damage due to knocking.

[0045] The spark plug 2 operates in particular after a cold start, during catalyst heating operation and under low load, allowing reliable ignition of the fuel-air mixture in the combustion chamber 5 even in these operating ranges.

[0046] 2 and 3 show simplified schematic representations of several preferred variants of the arrangement of the combustion chamber fuel injector 6, the spark plug 2 and the pre-chamber spark plug 3 on the combustion chamber roof 50, which are explained below. Shown here are respective plan views of the combustion chamber roof 50 along the piston direction along which a piston (not shown) of the internal combustion engine 1 can move. The piston direction is parallel to the central axis 12 of the cylinder 10.

[0047] As can be seen in Figures 2 and 3, all four charge cycle openings 4 have the same cross section. Alternatively, the intake openings 41 and the exhaust openings 42 could each have a different cross section. It is particularly preferred that the intake openings 41 each have a larger cross section than the exhaust openings 42. Alternatively, the exhaust openings 42 each could have a larger cross section than the exhaust openings 41. The charge cycle openings 4 are each configured circular and inscribed in the combustion chamber roof 50 so that the maximum total cross section is available for the charge cycle. Alternatively, the charge cycle openings 4 could be smaller.

[0048] In order to simplify the description of the position of the components on the combustion chamber roof 50, two cutting planes 51, 52 perpendicular to each other and parallel to the piston direction are shown. Both cutting planes 51, 52 then subdivide the combustion chamber roof 50 into four quadrants 55, 56, 57, 58, in each of which one of the four charge cycle openings 4 is located. In particular, both cutting planes 51, 52 can also be considered as symmetry planes of the combustion chamber roof 50. As can be seen in Figures 2, 3 and 5, the components arranged on the combustion chamber roof 50, the spark plug 2, the pre-chamber spark plug 3 and the combustion chamber fuel injector 6, are each substantially located on one of the two cutting planes 51, 52, since in that case a maximum space is provided for these components.

[0049] 2 shows a variation of the arrangement of the components on the combustion chamber roof 50 with a central location of the combustion chamber fuel injector 6. A central location is considered here to be an arrangement within a central point area 53 surrounding a central point 54 of the combustion chamber roof 50 and located substantially radially within the respective charge cycle opening 4. Due to the central location of the combustion chamber fuel injector 6, a particularly even distribution of the injected fuel spray within the combustion chamber 5 can be achieved.

[0050] In the variant shown only in Fig. 2, the combustion chamber / fuel injector 6 is on the intake side of the midpoint 54, i.e. closer to both intake openings 41 than to the exhaust openings 42. In particular, the combustion chamber / fuel injector 6 is completely inside both intake side quadrants 55, 58. There is thus space inside the midpoint area 53 for other components, i.e. the spark plug 2 and the pre-chamber spark plug 3.

[0051] Furthermore, the combustion chamber roof 50 has four lateral regions 59 in which components can be arranged, each of which is arranged between two adjacent charge cycle openings 4 and the side wall 11 of the cylinder 10.

[0052] 2(a) shows an arrangement with the pre-chamber spark plug 3 inside the central area 53. This allows an ignition of the fuel-air mixture as centrally as possible by the pre-chamber spark plug 3, which allows a particularly uniform penetration of the combustion chamber 5 by the flame jet 30 and thus a particularly uniform ignition in the combustion chamber 5. Furthermore, this allows the distance 36 between the pre-chamber spark plug 3 and the combustion chamber fuel injector 6 to be reduced to a minimum, which has a favorable effect on the flushing of the pre-chamber 35 and the mixture supply.

[0053] Here, the pre-chamber spark plug 3 is constructed and arranged such that the flame jets 30 generated during its operation are directed substantially equally towards each of the four charge cycle openings 4. It should be noted here that the orientation of the flame jets 30 is shown in the figures only as an example. Rather, any orientation of the flame jets 30 is possible. For example, in another preferred embodiment, at least one of the flame jets 30 is directed parallel to one of the cutting planes 51, 52, in particular when the pre-chamber spark plug 3 lies on one of these cutting planes 51, 52. It is particularly preferred if at least one of the flame jets 30 is always directed towards the intake side of the combustion chamber 5, i.e. towards one of the intake openings 41.

[0054] 2(a) also provides a particularly efficient operating regime for the internal combustion engine 1 during operation of the pre-chamber spark plug 3 due to the close proximity of the combustion chamber / fuel injector 6 to the pre-chamber spark plug 3, since the spray generated can be ignited particularly precisely and reliably by the flame jet 30. Furthermore, the close proximity of the combustion chamber / fuel injector 6 to the pre-chamber spark plug 3 allows for an efficient flushing of the pre-chamber 35 of the pre-chamber spark plug 3 and an optimal mixture supply, which acts particularly favorably for a robust and efficient operation of the pre-chamber spark plug 3.

[0055] 2(a), the spark plug 2 is arranged laterally near the side wall 11 of the cylinder 10. In particular, the spark plug 2 is arranged in a lateral area 59 on the intake side, which is located in both intake side quadrants 55, 58, i.e. near both intake openings 41. As a result, a good supply of fresh air can be provided in the area of ​​the spark plug 2 when the spark plug 2 is activated.

[0056] 2(b) shows an arrangement which substantially corresponds to the arrangement in FIG. 2(a), but with the difference that the spark plug 2 is arranged in a lateral area 59 on the exhaust side, i.e. in the vicinity of both exhaust openings 42. Thereby, the combustion chamber fuel injector 6 can be directed further towards the exhaust openings 42, for example in order to bring the fuel spray closer to the plug 3 and to the spark plug 2.

[0057] 2(c) shows a similar arrangement to FIG. 2(a), but with the positions of the spark plug 2 and the pre-chamber spark plug 3 swapped: the spark plug 2 is arranged in the center point area 53 near the combustion chamber / fuel injector 6, and the pre-chamber spark plug 3 is arranged on the intake side near the side wall 11. In this case, the central arrangement of the spark plug 2 near the center point 54 and near the combustion chamber / fuel injector 6 may allow a particularly robust and efficient operation of the internal combustion engine during ignition by the spark plug 2, preferably under low loads and / or during catalyst heating phases.

[0058] The pre-chamber spark plug 3 is here constructed and arranged in such a way that the flame jet 30 is directed towards the centre of the combustion chamber roof, which makes it possible to achieve a particularly fuel-saving operation, even when the pre-chamber spark plug 3 is operated alone, for example in the medium or high load range of the internal combustion engine 1. Furthermore, the lateral arrangement of the pre-chamber spark plug 3 offers the advantage that, due to its distance from the centre of the combustion chamber 5, a comparatively lower temperature acts on the plug cap 32, which therefore makes possible a lower load and a longer service life of the pre-chamber spark plug 3.

[0059] Figure 2(d) shows an arrangement which substantially corresponds to the arrangement in figure 2(c), but with the difference that the pre-chamber spark plug 3 is arranged in the lateral area 59 on the exhaust side, i.e. on the exhaust side of the spark plug 2 and the combustion chamber / fuel injector 6. In this case the flame jet 30 generated by the pre-chamber spark plug 3 is directed towards the intake opening 41.

[0060] FIG. 2(e) shows an arrangement similar to FIGS. 2(a) and (b) with a central pre-chamber spark plug 3, but the spark plug 2 is arranged in a lateral region 59 located in the second cutting plane 52. In this case, the lateral region 59 is located in one of the two intake-side quadrants 55, 58 and in one of the two exhaust-side quadrants 56, 57. This provides a particularly favorable mounting position of the spark plug 2 in the cylinder head 15, since the intake and exhaust pipes connected to the intake and exhaust openings 41 and 42 often point away from each other inside the cylinder head 15. As an alternative to the position shown in FIG. 2(e) in the right-hand lateral region 59 of the quadrants 55 and 56, the spark plug 2 can also be arranged in the left-hand lateral region 59 of the quadrants 57 and 58.

[0061] FIG. 3 shows a variant in which the combustion chamber fuel injector 6 is arranged laterally on the combustion chamber roof 50, i.e. in a lateral area 59 on the intake side. Here, the combustion chamber fuel injector 6 is arranged at a small distance 61 from the side wall 11. Due to the lateral arrangement of the combustion chamber fuel injector 6, a large space for the spark plug 2 and the pre-chamber spark plug 3 can be used in the central center point area 53 of the combustion chamber roof 50 around the center point 54, so that they can be arranged as centrally as possible for improved uniform ignition. The spray direction of the combustion chamber fuel injector 6 is then directed towards the center of the combustion chamber in order to achieve as uniform a distribution of the fuel spray as possible in the combustion chamber 5.

[0062] In this case, Figures 3(a) and 3(b) show variants in which the spark plug 2 and also the pre-chamber spark plug 3, respectively, are arranged within the central point area 53. As a result, both the spark plug 2 and the pre-chamber spark plug 3 are located as close as possible to the central point 54 of the combustion chamber roof 50, which allows for the best possible operation for both with as central and even ignition as possible. Here, Figure 3(a) shows a variant in which the spark plug 2 is arranged on the intake side of the pre-chamber spark plug 3, and Figure 3(b) shows a variant in which the spark plug 2 is arranged on the exhaust side of the pre-chamber spark plug 3.

[0063] 3(c) and 3(d) furthermore show variants in which the spark plug 2 is arranged centrally and the pre-chamber spark plug 3 is arranged laterally on the combustion chamber roof 50. This is particularly preferred if there is not enough space in the midpoint area 53 for the spark plug 2 and the pre-chamber spark plug 3. In this case, the spark plug 2 is arranged in both variants exactly at the midpoint 54 of the combustion chamber roof 50, which allows a particularly robust operation of the internal combustion engine 1 when the spark plug 2 is activated, for example during a catalyst heating phase.

[0064] Here, in FIG. 3(c), the pre-chamber spark plug 3 is arranged in the left side region 59 located between the side wall 11 and, respectively, one of the intake openings 41 and one of the exhaust openings 42.

[0065] Furthermore, FIG. 3( d ) shows a variant in which the pre-chamber spark plugs 3 are arranged in the lateral areas 59 on the exhaust side, i.e. in the vicinity of both exhaust openings 42 .

[0066] It should be noted that, as an alternative to the variant shown in FIGS. 3(c) and 3(d), an arrangement of the pre-chamber spark plug 3 in each of the other lateral regions 59 is also possible.

[0067] 3(e) furthermore shows a variant in which the pre-chamber spark plug 3 is arranged centrally, i.e. exactly at the center point 54 of the combustion chamber roof 50. This makes it possible for a particularly even and symmetrical ignition to occur in the combustion chamber 5 when the pre-chamber spark plug 3 is activated. The spark plug 2 is arranged in this case in the right-hand side area 59, i.e. between the side wall 11 and one of the two intake openings 41 and one of the two exhaust openings 42. Alternatively, an arrangement of the spark plug in the respective other side area 59 is also possible.

[0068] FIG. 4 shows a cross-sectional view of an internal combustion engine 1 according to a second embodiment of the invention. The second embodiment corresponds substantially to the first embodiment of FIGS. 1 to 3, with the difference that instead of the combustion chamber fuel injector 6 arranged in the combustion chamber roof 50 and with direct injection, a suction pipe fuel injector 7 is provided. The suction pipe fuel injector 7 is arranged in the cylinder head 15 in a suction pipe 70 and is set up to inject liquid or gaseous fuel into the suction pipe 70. The suction pipe 7 then communicates with the combustion chamber 5 at an intake opening 41 and thus guides the fuel-air-air mixture into the combustion chamber 5. In particular, one suction pipe 70 is provided for each intake opening 41, and each suction pipe 70 is provided with one suction pipe fuel injector 7 (not shown).

[0069] Figure 5 shows a variation of the arrangement of the spark plug 2 and the pre-chamber spark plug 3 on the combustion chamber roof 50 of the internal combustion engine 1 of the second embodiment of Figure 4. In the second embodiment, the fuel injectors are not arranged on the combustion chamber roof 50, which has the advantage that more space is available for the spark plug 2 and the pre-chamber spark plug 3. The arrangement of Figure 5 here is similar to Figure 3, which offers substantially the same advantages.

[0070] It is particularly preferred that the spark plug 2 and the pre-chamber spark plug 3 can both be arranged in the central point area 53. Such an arrangement is shown in the variants of Figures 5(a) and (b), where in Figure 5(a) the spark plug 2 is arranged on the intake side of the pre-chamber spark plug 3 and in Figure 5(b) the spark plug 2 is arranged on the exhaust side of the pre-chamber spark plug 3.

[0071] 5(c) and 5(d) furthermore show a variant having a central spark plug 2 located exactly at the midpoint 54 of the combustion chamber roof 50. In the embodiment shown in FIG.

[0072] In this case, in FIG. 5(c), the pre-chamber ignition plug 3 is arranged in the left side region 59, and in FIG. 5(d), it is arranged in the exhaust side region 59.

[0073] 5(e) furthermore shows a variant with a central pre-chamber spark plug 3 arranged exactly at the midpoint 54. In this variant the spark plug 2 is arranged in the right-hand side region 59.

[0074] As with FIG. 3, it should be noted here that the laterally positioned spark plugs 2 and / or pre-chamber spark plugs 3 may be positioned in any of the four lateral regions 59, respectively, as an alternative to the positions shown in FIGS. 5(c) to 5(e).

[0075] It should be noted that all distances cited are to be regarded as minimum distances in each case, i.e. for example "the distance between the pre-chamber spark plug and the combustion chamber fuel injector" is to be regarded as the minimum distance in particular from the outer circumference of the spark plug to the outer circumference of the combustion chamber fuel injector substantially in the plane of the combustion chamber roof. [Explanation of symbols]

[0076] 1. Internal combustion engine 2 Spark plugs 3 Pre-chamber spark plug 4 Charge cycle opening 5. Combustion chamber 6 Combustion chambers and fuel injectors 7 Suction pipe / fuel injector 10 Cylinders 11 Side wall 41 Intake opening 42 Exhaust opening 50 Combustion chamber roof 51,52 Cutting plane 53 Center point area 54 Center point 55,56,57,58 quadrant 65 Direction of injection 70 Suction pipe

Claims

1. In an internal combustion engine, At least one cylinder (10); four charge cycle openings (4) for each cylinder (10), each of the first and second charge cycle openings (4) being an intake opening (41), each of the third and fourth charge cycle openings (4) being an exhaust opening (42); and one spark plug (2) and one pre-chamber spark plug (3) for each cylinder (10), the spark plug (2) and / or the pre-chamber spark plug (3) being arranged in a combustion chamber roof (50) of the combustion chamber (5) of the cylinder (10), 1. An internal combustion engine, wherein the spark plug (2) is positioned closer to a center point (54) of the combustion chamber roof (50) than the pre-chamber spark plug (3), or the pre-chamber spark plug (3) is positioned closer to a side wall (11) of the cylinder (10) than the spark plug (2), and the pre-chamber ignition plug (3) has a plug cap (32) that forms a pre-chamber (35).

2. 2. The internal combustion engine of claim 1, wherein the pre-chamber spark plug (3) is positioned closer to at least one of the intake openings (41) or closer to at least one of the exhaust openings (42) than the spark plug (2).

3. 3. An internal combustion engine according to claim 1 or 2, wherein the spark plug (2) is arranged on the intake side or on the exhaust side with respect to the pre-chamber spark plug (3).

4. The charge cycle opening (4) is disposed in the combustion chamber roof (50); said combustion chamber roof (50) being subdivided into four quadrants (55, 56, 57, 58) by two mutually perpendicular cutting planes (51, 52) such that in each of said quadrants (55, 56, 57, 58) a respective one of said four charge cycle openings (4) is located; 4. An internal combustion engine according to claim 1, wherein the spark plug (2) and / or the pre-chamber spark plug (3) is arranged in one of the cutting planes (51, 52).

5. 5. An internal combustion engine according to claim 1, wherein the spark plug (2) and / or the pre-chamber spark plug (3) are arranged within a centre point region (53) of the combustion chamber roof (50) located substantially radially inside the charge cycle opening (4).

6. the spark plug (2) and / or the pre-chamber spark plug (3) are disposed within a center point region (53) of the combustion chamber roof (50) located substantially radially inside the charge cycle opening (4); 5. An internal combustion engine according to claim 1, wherein the pre-chamber spark plug (3) or the spark plug (2) is positioned exactly at a centre point (54) of the combustion chamber roof (50).

7. 5. The internal combustion engine according to claim 1, wherein the spark plug (2) and / or the pre-chamber spark plug (3) are arranged between two adjacent charge cycle openings (4) and the side wall (11) of the cylinder (10).

8. 8. An internal combustion engine according to any one of the preceding claims, further comprising a combustion chamber fuel injector (6) set up for injecting fuel directly into the combustion chamber (5).

9. 9. An internal combustion engine according to claim 8, wherein the combustion chamber fuel injector (6) is arranged in the combustion chamber roof (50).

10. 10. An internal combustion engine according to claim 8 or 9, wherein the combustion chamber fuel injector (6) is arranged between two adjacent charge cycle openings (4) and the side wall (11) of the cylinder (10).

11. 10. An internal combustion engine according to claim 8 or 9, wherein the combustion chamber / fuel injector (6) is arranged between both the intake openings (41) and the side wall (11) of the cylinder (10).

12. 10. An internal combustion engine according to claim 8 or 9, wherein the combustion chamber fuel injector (6) is arranged within a centre point region (53) of the combustion chamber roof (50) located substantially radially inside the charge cycle opening (4).

13. the combustion chamber fuel injector (6) is disposed within a center point region (53) of the combustion chamber roof (50) located substantially radially inside the charge cycle opening (4); 10. An internal combustion engine according to claim 8 or 9, characterized in that the combustion chamber fuel injector (6) is arranged exactly at the centre point (54) of the combustion chamber roof (50).

14. the pre-chamber spark plug (3) is located closer to the combustion chamber / fuel injector (6) than the spark plug (2); or 14. An internal combustion engine according to any one of claims 8 to 13, wherein the spark plug (2) is arranged closer to the combustion chamber / fuel injector (6) than the pre-chamber spark plug (3).

15. 15. An internal combustion engine according to any one of claims 8 to 14, wherein the injection direction (65) of the combustion chamber fuel injector (6) is directed towards the spark plug (2) or towards the pre-chamber spark plug (3).

16. An internal combustion engine according to any one of the preceding claims, further comprising an intake manifold fuel injector (7) set up for injecting fuel into an intake manifold (70) of the internal combustion engine (1).

17. A method for operating an internal combustion engine (1) as described in any one of claims 1 to 16, wherein the internal combustion engine (1) has at least one cylinder (10), four charge cycle openings (4) per cylinder (10), a spark plug (2) and a pre-chamber spark plug (3), and the spark plug (2) and / or the pre-chamber spark plug (3) operate to ignite a fuel-air-mixture inside a combustion chamber (5) of the cylinder (10).

18. The method described in claim 17, wherein the pre-chamber spark plug (3) operates alone during operation of the internal combustion engine (1).

19. 18. The method according to claim 17, wherein the pre-chamber spark plug (3) operates alone during operation of the internal combustion engine (1) under a torque of at least 20% of the rated torque of the internal combustion engine (1).

20. 18. The method according to claim 17, wherein the pre-chamber spark plug (3) operates alone during operation of the internal combustion engine (1) under a torque of at least 50% of the rated torque of the internal combustion engine (1).

21. 18. The method according to claim 17, wherein the pre-chamber spark plug (3) operates alone during operation of the internal combustion engine (1) under a torque of at least 80% of the rated torque of the internal combustion engine (1).

22. A method according to any one of claims 17 to 21, wherein the spark plug (2) operates alone during operation of the internal combustion engine (1).

23. 22. The method according to any one of claims 17 to 21, wherein the spark plug (2) operates alone during operation of the internal combustion engine (1) under a torque lower than 80% of the rated torque of the internal combustion engine (1).

24. 22. The method according to any one of claims 17 to 21, wherein the spark plug (2) operates alone during operation of the internal combustion engine (1) under a torque lower than 50% of the rated torque of the internal combustion engine (1).

25. 22. The method according to any one of claims 17 to 21, wherein the spark plug (2) operates alone during operation of the internal combustion engine (1) under a torque lower than 20% of the rated torque of the internal combustion engine (1).

26. 26. The method according to any one of claims 17 to 25, wherein the spark plug (2) is activated during a catalyst heating phase.

27. 27. The method according to any one of claims 17 to 26, wherein the spark plug (2) is activated after a cold start of the internal combustion engine (1).

28. 28. The method according to any one of claims 17 to 27, wherein the spark plug (2) and the pre-chamber spark plug (3) operate with different ignition timings.

29. 29. The method according to any one of claims 17 to 28, wherein the spark plug (2) and the pre-chamber spark plug (3) operate with independent ignition timing from each other.

30. 30. The method according to any one of claims 17 to 29, wherein the internal combustion engine (1) is operated with a lambda value of at least 1 at least within a partial operating range.

31. 31. The method according to any one of claims 17 to 30, wherein the internal combustion engine (1) is operated with a lambda value of at least 1 during operation of the spark plug (2) and / or the pre-chamber spark plug (3).

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