HK1247652B - Internal combustion engine and method for operating an internal combustion engine - Google Patents

Description

Internal combustion engine and method for operating an internal combustion engine

Technical Field

The invention relates to an internal combustion engine and a method for operating an internal combustion engine.

Background Art

In internal combustion engines operating with so-called multi-point injection (MPI), ignition characteristics are typically linked to the residual gas content in the engine's combustion chamber and the overall combustion air-fuel ratio (air-fuel ratio), also known as the lambda value. The area directly surrounding the ignition source is particularly important. To ensure that even significantly lean mixtures in the combustion chamber can be ignited, the combustion chamber is typically divided into a main combustion chamber and a pre-chamber. Reliable ignition is ensured in the smaller pre-chamber volume, while the torch light transferred from the pre-chamber into the main combustion chamber also ensures reliable ignition of the mixture in the larger volume of the main combustion chamber. Gas-purged pre-chambers directly connected to the gas supply require additional components, such as an additional gas compressor, a gas cooler, and a gas supply for each combustion chamber. It is also possible to connect the gas-purged pre-combustion chamber to the high-pressure side of the multi-point injection system, wherein the connection is respectively connected upstream of the controllable valve for the multi-point injection. The amount of fuel purged into the pre-combustion chamber thus depends on the supply pressure in the fuel line upstream of the controllable valve for the multi-point injection.

Summary of the Invention

The present invention is based on the object of creating an internal combustion engine and a method for operating an internal combustion engine in which the aforementioned disadvantages do not occur.

This object is achieved by providing the subject matter of the parallel claims. Advantageous embodiments are derived from the dependent claims.

This object is achieved, in particular, by providing an internal combustion engine having at least one combustion chamber, the combustion chamber being connected to an air flow path for supplying a combustion air-fuel mixture to the combustion chamber via the air flow path, wherein a fuel mixing region, preferably a combustion mixing chamber, is arranged in a section of the air flow path that is solely associated with the combustion chamber. The fuel mixing region is fluidically connected to the air flow path and to a fuel line, wherein the fuel line is configured to supply fuel to the fuel mixing region via a controllable valve. The combustion chamber comprises a main combustion chamber and a pre-combustion chamber, wherein the pre-combustion chamber is fluidically connected to the main combustion chamber via at least one bore. The internal combustion engine is characterized in that the pre-combustion chamber and the fuel mixing region are fluidically connected to each other via a check valve. Arranging the fuel mixing region in the section of the air flow path that is solely associated with the combustion chamber particularly means that the fuel mixing region is arranged downstream of a branching point at which the air flow path divides into intake manifold sections leading to different combustion chambers, if the internal combustion engine has more than one combustion chamber. This preferably means that the internal combustion engine is configured for operation with multi-point injection (MPI). For an internal combustion engine having multiple combustion chambers, the fuel quantity can be individually and chamber-by-chamber for each combustion chamber, to a section of the charge path associated with that combustion chamber. The fuel mixing area is fluidically connected to the fuel line via a controllable fuel valve, so that the fuel mixing area is particularly arranged downstream of the controllable valve. Consequently, the fuel mixing area is arranged on the low-pressure side of the multi-point injection system, i.e., downstream of the controllable valve. Since the pre-combustion chamber is fluidically connected to the fuel mixing area via a check valve, it is fluidically connected not to the high-pressure area of the multi-point injection system, but to the low-pressure area downstream of the controllable valve. This offers advantages over the prior art. In particular, the purged fuel quantity is independent of the supply pressure on the high-pressure side of the multi-point injection system, particularly in the fuel line. Rather, the purged quantity depends directly on the pressure difference between the pressure in the combustion mixing zone, on the one hand, and the temporary pressure in the precombustion chamber, on the other. Depending on this pressure relationship, the check valve can then be opened or closed, whereby, in particular, automatic purging of the precombustion chamber can be achieved depending on the temporarily prevailing pressure relationship. No additional components are required, in particular, no additional gas compressor, gas cooler, or additional gas supply for the precombustion chamber, since it is supplied with fuel directly from the fuel mixing zone. It is thus possible to achieve the properties of a gas-purged precombustion chamber using a simple check valve.

The term "check valve" is understood here and below to mean, in particular, a valve device that can be displaced into an open position and a closed position depending on the pressure differential that develops across the valve device. The valve device thus opens and closes depending on the pressure conditions upstream of the valve device, on the one hand, and downstream of the valve device, on the other hand. In a particularly simple and cost-effective design of the check valve, it is provided that the valve element or valve body is pressed against the valve seat under preload, wherein the valve device only opens when the pressure differential that develops across it exceeds the preload force acting on the valve element or valve body in the opening direction.

The fuel mixing area is preferably designed as a fuel mixing chamber. The fuel mixing chamber has, in particular, a chamber wall that projects at least partially into the section individually associated with the charging path, wherein the wall of the fuel mixing chamber is preferably perforated by at least one connecting bore, via which the individually associated section of the charging path is in fluid connection with the fuel mixing chamber.

The internal combustion engine proposed herein combines the advantages of multi-point injection with a scavenged pre-chamber in a cost-effective manner, thus enabling the use of scavenged pre-chambers in previously uncommon applications, particularly marine applications, internal combustion engines for powering ships, applications in the construction and industrial sectors, applications for transporting raw materials, particularly oil and/or gas, and numerous other applications. A particular advantage, particularly in safety-critical areas such as marine, is that the combustible mixture no longer needs to be routed around the engine in the proposed internal combustion engine. Furthermore, the engine can be driven lean with the scavenged pre-chamber. This in turn increases the permissible spread of the lambda value (i.e., the air-fuel ratio), ultimately leading to improved design loads and, in particular, improved transient behavior of the internal combustion engine. The enleanment at the stationary cycle point can also reduce the engine's nitrogen oxide emissions. The ignition-enhancing effect of the pre-chamber improves engine efficiency. Furthermore, the internal combustion engine has improved ignition properties, so that misfires during idling can be avoided particularly effectively.

A preferred embodiment of an internal combustion engine is characterized in that a connecting path is provided, which opens into the fuel mixing area at a first end of its two ends, wherein the connecting path opens into the precombustion chamber at a second end of its two ends. A check valve is arranged in the connecting path. The connecting path is a particularly simple solution for realizing a fluid connection between the fuel mixing area and the precombustion chamber. It is possible to implement the connecting path as a conduit, in particular as a pipe or hose. The connecting path can be designed at least in sections or also completely as a channel, and in particular, at least in sections as a bore, wherein the bore can be at least partially formed in the cylinder head of the internal combustion engine. It is also possible that the connecting path is integrated at least in sections into the wall of the precombustion chamber. It is particularly preferred that the check valve is integrated into the wall of the precombustion chamber and/or into the cylinder head of the internal combustion engine. This enables similarly simple and cost-effective production of the internal combustion engine.

The connecting path preferably has exactly two ends, namely a first end and a second end, wherein the two ends are arranged opposite each other on the connecting path. The gas then flows, in particular, along the connecting path from the first end to the second end. The check valve is, in particular, arranged between the first and second ends of the connecting path.

Preferably, the non-return valve is preloaded into a closed position, wherein the non-return valve is particularly oriented in the connection path such that the pressure prevailing in the region of a first end of the connection path, i.e., upstream of the non-return valve, tends to press the non-return valve from its closed position into an open position, wherein, in addition to the preload force, the pressure prevailing in the region of the second end of the connection path, in contrast, tends to press the non-return valve into its closed position. Accordingly, the non-return valve preferably opens only when the pressure in the pre-combustion chamber is lower than the pressure in the fuel mixing region, wherein the pressure difference between the pressure in the fuel mixing region and the pressure in the pre-combustion chamber must in particular be greater than a predetermined limit pressure difference, which is determined in particular by the preload of the non-return valve.

It is shown here that the pressure in the fuel mixing area preferably corresponds at least approximately to the charge pressure, since the fuel mixing area is preferably fluidically connected to the charge path via at least one bore. In contrast, the pressure in the precombustion chamber depends approximately on the combustion chamber pressure and is therefore, in particular, a function of the engine crank angle, with the pressure varying periodically with the movement of the piston in the combustion chamber (in the case of an internal combustion engine designed as a reciprocating piston engine). Furthermore, the pressure difference also depends, in particular, on the position of the intake valve, which connects the main combustion chamber of the combustion chamber with the charge path, and/or the exhaust valve, which connects the main combustion chamber of the combustion chamber with the exhaust path.

An embodiment of the internal combustion engine is preferred, characterized in that the combustion chamber is fluidically connected to the charge path via at least one intake valve. In particular, the control times for the intake valve determine the pressure differential profile and thus the cleaning characteristics of the precombustion chamber. It is possible to achieve optimal cleaning of the precombustion chamber by adjusting the control times for the intake valve. Particularly preferably, the combustion chamber is fluidically connected to the charge path via at least one variably controllable intake valve, in particular an intake valve with a fully variable valvetrain. This makes it possible to vary the control times of the intake valve, in particular depending on the operating point, and thus achieve optimal cleaning of the precombustion chamber at any time and in particular at every operating point of the internal combustion engine via the pressure differential.

In the case of a particularly preferred embodiment, the combustion chamber is fluidically connected to the charge path via two intake valves, in particular via two variably controllable intake valves.

An embodiment of the internal combustion engine is also preferred, characterized in that the controllable fuel valve is designed as a metering valve for multi-point injection. The advantages already mentioned are achieved in this case.

Another preferred embodiment of an internal combustion engine is characterized in that a fuel line, configured to supply fuel to the fuel mixing area via a controllable fuel valve, opens into a connecting path. This design of an internal combustion engine is particularly simple and cost-effective to manufacture, as the connecting path can be used to perform two functions. On the one hand, the connecting path is regionally used to supply pure fuel from the fuel line to the fuel mixing area (particularly via its first end that opens into the fuel mixing area), while on the other hand, the connecting path (as previously described) serves as a fluid connection between the fuel mixing area and the precombustion chamber. In particular, the fuel line opens into the connecting path downstream of the controllable fuel valve. The connecting path is then connected not to the high-pressure region of the fuel line arranged upstream of the controllable fuel valve, but to the low-pressure region arranged downstream of the controllable valve. Therefore, the connecting path is particularly arranged on the low-pressure side of a system for multi-point injection. In this way, connecting the fuel line to the connecting path downstream of the controllable fuel valve (i.e., on the low-pressure side) can be easily achieved without additional measures. In particular, a passage into the fuel mixing region can be omitted, thereby eliminating corresponding production steps and the associated production costs. More precisely, the first end of the connecting path serves not only for supplying fuel into the fuel mixing region, but also for supplying fuel or a rich combustion air-fuel mixture from the fuel mixing region via the connecting path and the non-return valve into the pre-combustion chamber.

The internal combustion engine is preferably configured as a reciprocating piston engine. In a preferred embodiment, the internal combustion engine is used to drive particularly heavy land vehicles or ships (e.g., mining vehicles), trains, wherein the internal combustion engine is used in a locomotive or tractor, or to drive ships. The use of the internal combustion engine to drive vehicles used for defense, such as armored vehicles, is also possible. One embodiment of the internal combustion engine is also preferably used stationary, for example, for a stationary energy supply in emergency current operation, continuous load operation, or peak load operation, wherein the internal combustion engine preferably drives a generator in this case. The stationary use of the internal combustion engine to drive an auxiliary power unit, such as a fire pump on an offshore drilling platform, is also possible. In addition, the internal combustion engine is possible in the field of transporting fossil raw materials and, in particular, fuels (e.g., oil and/or gas). The use of this internal combustion engine in the industrial field or in the construction field, such as in construction or engineering machinery, such as cranes or excavators, is also possible. The internal combustion engine is preferably designed as a gasoline engine, a gas engine for operation with natural gas, biogas, special gas or other suitable gases, or as a dual-fuel engine for operation with two different fuels, in particular as a two-fuel engine or dual-fuel engine. In particular, when the internal combustion engine is designed as a gas engine, it is suitable for use in a combined heat and power plant for stationary energy generation.

An embodiment of the internal combustion engine configured as a gas engine, in particular as a lean gas engine, is particularly preferred. Here, the advantages of a purged pre-chamber for reliable ignition of a mixture that is also significantly lean in the main combustion chamber of the combustion chamber are particularly realized.

This object is also achieved by providing a method for operating an internal combustion engine, in which a combustion air-fuel mixture is supplied via a charge path during the intake stroke to at least one combustion chamber divided into a main combustion chamber and a precombustion chamber, wherein the combustion air-fuel mixture is generated in a section of the charge path that is separately associated with the combustion chamber in such a way that fuel, particularly preferably pure fuel, is supplied via a fuel line via a controllable fuel valve to a fuel mixing region (particularly a fuel mixing chamber) arranged in the separate section, wherein when the pressure in the precombustion chamber is lower than the pressure in the fuel mixing region, the fuel is conducted directly from the fuel mixing region into the precombustion chamber. In this case, in particular, the advantages already described in connection with the internal combustion engine are achieved in conjunction with this method.

The fuel is conducted directly from the fuel mixing area into the precombustion chamber, meaning in particular that the fuel is conducted from the fuel mixing area into the precombustion chamber via the charge path without a detour. More precisely, the fuel is conducted into the precombustion chamber via the connection path between the fuel mixing area and the precombustion chamber, directly depending on the pressure in the precombustion chamber on the one hand and the pressure in the fuel mixing area on the other hand.

Because the fuel mixing area is fluidically connected to the charge path, it is possible for some combustion air to also reach the fuel mixing area. This allows for a richer combustion air-fuel mixture to form in the fuel mixing area than in the charge path of the main combustion chamber. In this case, the combustion air-fuel mixture is supplied directly from the fuel mixing area to the pre-combustion chamber.

The pressure in the fuel mixing area preferably corresponds to the charge pressure in the charge path, apart from any flow-induced pressure differences due to the boreholes between the fuel mixing area, in particular the fuel mixing chamber, and the charge path. In contrast, the pressure in the precombustion chamber (as already explained) is, in particular, a function of the crank angle of the internal combustion engine.

An embodiment of the method is preferred, characterized in that fuel or, if appropriate, a fuel-air mixture is conducted from the fuel mixing area directly into the precombustion chamber when the pressure difference between the pressure in the fuel mixing area and the pressure in the precombustion chamber exceeds a predetermined value. The predetermined value (in particular the limit pressure difference) is preferably determined by prestressing a check valve arranged in the connection between the fuel mixing area and the precombustion chamber.

A preferred embodiment of the method is characterized in that the intake valve connecting the main combustion chamber of the combustion chamber to the charge path is actuated using a Miller control time. This means, in particular, that the intake valve closes before the piston, which is displaceable in the combustion chamber, reaches bottom dead center during the intake stroke, or at any rate closes so early that, before the pressure in the combustion chamber rises above the charge pressure due to compression, the pressure in the combustion chamber remains below the charge pressure within a specific crank angle range even after closing the intake valve due to gas dynamics. Due to effective gas dynamics, it is possible to close the intake valve only when the piston reaches bottom dead center. This is due to the inertia of the air flow in the charge path and in the combustion chamber. Therefore, the closing of the intake valve upon reaching bottom dead center also serves as a Miller control time. The actuation of the intake valves, in particular intake valves with fully variable valvetrain, with Miller-controlled timing allows the formation of a pressure difference between the fuel mixing area and the precombustion chamber, which allows particularly efficient cleaning of the precombustion chamber with pure fuel, in particular gas, or a rich mixture from the fuel mixing area.

Finally, an embodiment of the method is preferred, characterized in that the internal combustion engine is operated with gas. Preferably, the internal combustion engine is operated with methane-containing gas, in particular natural gas, landfill gas, biogas, special gas, product gas from wood gas production, or other suitable gas as fuel. In particular, such internal combustion engines often operate with a significantly lean fuel-air mixture, wherein the advantages of the method are particularly realized.

It is clear that the characteristics of a gas-purged precombustion chamber can be achieved with the internal combustion engine and the method using a simple check valve. To this end, pure gas or a rich mixture is directed into the precombustion chamber downstream of a multi-point injection valve (i.e., a controllable fuel valve) via a connecting path in which the check valve is located. If a Miller control time is implemented for at least one intake valve, a particularly effective pressure differential is generated between the fuel mixing area on the one hand and the precombustion chamber on the other hand. The check valve then opens, and the precombustion chamber is purged with pure gas or a rich mixture from the fuel mixing area.

The description of the internal combustion engine, on the one hand, and the method, on the other hand, is to be understood as complementary. Features of the internal combustion engine described explicitly or implicitly in connection with the method are preferably, individually or in combination, features of a preferred embodiment of the internal combustion engine. Method steps described explicitly or implicitly in connection with the internal combustion engine are preferably, individually or in combination, steps of a preferred embodiment of the method. This is preferably characterized by at least one method step that is determined by at least one feature of the internal combustion engine. The internal combustion engine is preferably characterized by at least one feature that is determined by at least one step of a preferred embodiment of the method.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further described below with reference to the accompanying drawings, wherein:

FIG1 shows a schematic illustration of a first embodiment of an internal combustion engine,

FIG2 shows a schematic diagram of a second embodiment of an internal combustion engine, and

FIG. 3 shows a schematic diagram of an embodiment of the method.

DETAILED DESCRIPTION

FIG1 shows a schematic illustration of an embodiment of an internal combustion engine 1. The internal combustion engine has a combustion chamber 3, which is divided into a main combustion chamber 5 and a pre-combustion chamber 7. The main combustion chamber 5 and the pre-combustion chamber 7 are fluidically connected to each other via a bore 9. The pre-combustion chamber 7 ensures the reliable ignition of a rich combustion air-fuel mixture within the relatively small pre-combustion chamber volume. When the mixture is ignited in the pre-combustion chamber 7, torch light enters the main combustion chamber 5 via the bore 9, whereby the relatively lean combustion air-fuel mixture present in the main combustion chamber 5 is reliably and completely ignited by the torch light. This makes it possible, in particular with a main combustion chamber 5 of a larger volume, to ignite a significantly leaner combustion air-fuel mixture.

The combustion chamber 3 , in particular the main combustion chamber 5 , is fluidically connected to a charge path 11 , wherein the charge path 11 is provided for supplying a combustion air-fuel mixture via the charge path 11 into the combustion chamber 3 , in particular into the main combustion chamber 5 .

In the section 13 of the charge path 11 which is separately associated with the combustion chamber 3, a fuel mixing region 14 (here a fuel mixing chamber 15) is arranged, which is in fluid connection with the charge path 11 on the one hand and with a fuel pipe 17 on the other hand, wherein the fuel pipe 17 is designed to supply particularly pure fuel to the fuel mixing region 14 via a controllable fuel valve 19.

To purge the precombustion chamber 7 with pure fuel or a rich combustion air-fuel mixture, the precombustion chamber 7 is in fluid communication with the fuel mixing chamber 15 via a nonreturn valve 21. Thus, achieving a gas-purged precombustion chamber 7 can be achieved in a very simple manner. In particular, no additional components are required for this purpose, and in particular, no separate gas compressor, gas cooler, and/or separate gas supply for the precombustion chamber 7 is required. Furthermore, the purge characteristics of the precombustion chamber are independent of the supply pressure in the fuel line 17 upstream of the controllable fuel valve 19.

The internal combustion engine 1 is preferably configured as a reciprocating piston engine, wherein a piston (not shown in FIG. 1 ) is displaceably accommodated in a main combustion chamber 5 of the combustion chamber 3 . The internal combustion engine 1 preferably has a plurality of combustion chambers 3 , in particular four, six, eight, ten, twelve, sixteen, eighteen, twenty, or twenty-four cylinders. Smaller, larger, or other numbers of cylinders are also possible. Furthermore, it is possible for the internal combustion engine 1 to be configured as an inline engine, a V-engine, a W-engine, or other configurations of combustion chambers 3 .

In particular, multi-point injection is provided for internal combustion engine 1, wherein the controllable fuel valve 19 is preferably designed as a metering valve for multi-point injection (MPI). This means that the fuel is metered into the sections 13 of charge path 11, each associated with the combustion chamber 3, downstream of the branching of the common charge path into the individual intake manifold sections for each cylinder and thus individually. Thus, an individually set fuel mass can be supplied to each cylinder by cylinder-specific control of the cylinder-associated controllable fuel valve 19.

The fuel mixing chamber 15 is fluidically connected to the charge air path 11, and in particular to the section 13, via a plurality of mixing bores 23. It is possible for the charge air to flow from the charge air path 11 through the mixing bores 23 into the fuel mixing chamber 15, so that no pure fuel is present in the fuel mixing chamber, but rather a very rich fuel-combustion air mixture. In this case, this rich mixture flows into the precombustion chamber 7 via the non-return valve 21 while purging the precombustion chamber 7.

A connecting path 25 is provided, which opens into the fuel mixing chamber 15 at a first end 27 of its two ends, wherein it opens into the precombustion chamber 7 at a second end 29 of its two ends 27, 29. The non-return valve 21 is arranged in the connecting path 25. It is shown here that the connecting path 25 is partially integrated into the wall 31 of the precombustion chamber 7. In particular, the non-return valve 21 is integrated into the wall 31.

It is also shown that the check valve 21 is preloaded into a closed position, wherein it is arranged between a first end 27 and a second end 29 in the connecting path 25 in such a way that the pressure upstream of the check valve 21 on the side of the first end 27 in the connecting path 25 tends to squeeze the check valve 21 from its closed position into an open position, wherein the pressure downstream of the check valve 21 on the side of the second end 29 in the connecting path 25 loads the check valve 21 into its closed position in addition to the preload force.

The check valve 2 opens when the pressure in the precombustion chamber 7 is lower than the pressure in the fuel mixing chamber 15, in particular when the pressure difference between the pressure in the fuel mixing chamber 15 and the pressure in the precombustion chamber 7 is greater than a predetermined limit pressure difference, which is determined in particular by the preload of the check valve into its closed position and the geometric design of the effective area of the check valve 21. The cleaning properties of the precombustion chamber 7 can thus be coordinated or adjusted, in particular by adjusting the geometric design of the check valve 21 and its preload.

The combustion chamber 3, in particular the main combustion chamber 5, is fluidically connected to the charge path 11 via an intake valve 33. The intake valve 33 preferably has a fully variable valve train (not shown in FIG. 1 ), so that the actuation times of the intake valve 33 can be varied, in particular depending on the operating point. The combustion chamber 3, in particular the main combustion chamber 5, is also fluidically connected to an exhaust path 37 via an exhaust valve 35. In particular, by actuating the intake valve 33, preferably but also via actuating the exhaust valve 35, it is possible to influence the pressure conditions in the combustion chamber 3, in particular with respect to the pressure in the charge path 11, and thus, in particular, to influence the purge characteristics of the precombustion chamber 7, in a manner dependent on the operating point.

The internal combustion engine 1 is preferably configured as a gas engine, in particular as a lean gas engine. In this case, a gas, preferably a gas containing methane, is used as fuel.

It is also shown that an ignition device 39 for igniting the combustion air-fuel mixture is arranged in the pre-combustion chamber 7. Here, it can be, for example, an electric radio frequency spark plug, a corona spark plug, a laser spark plug or other suitable spark plugs or ignition devices.

FIG2 shows a schematic illustration of a second embodiment of an internal combustion engine 1. Identical and functionally identical elements are provided with the same reference numerals, so reference is made to the previous description in this regard. In this embodiment, it is particularly provided that the fuel line 17 opens into the connecting path 25 downstream of the controllable fuel valve 19 on the low-pressure side of the system for multi-point injection. This represents a particularly simple design for the internal combustion engine 1, as the connecting path 25 can thus, at least in some areas, perform two functions: firstly, the supply of pure fuel via the fuel line 17 and ultimately via the first end 27 to the fuel mixing area 14, and secondly, the supply of pure fuel or a rich combustion air-fuel mixture from the fuel mixing area 14 via the connecting path 25 and the non-return valve 21 to the pre-combustion chamber 7, as previously described. In this case, only one borehole or opening (in addition to the mixing borehole 23) is required, namely the borehole or opening at the first end 27 of the connecting path 25, through which, on the one hand, pure fuel can be supplied to the fuel mixing region 14, and, on the other hand, pure fuel or a rich combustion air-fuel mixture can flow from the fuel mixing region 14 into the precombustion chamber 7. This simplifies the design of the fuel mixing region 14 and, in particular, of the fuel mixing chamber 15, wherein, in particular, production or manufacturing steps for providing a further borehole or for providing a further line can be omitted.

FIG3 shows a schematic diagram of an embodiment of the method. FIG3a) shows the plotting of the pressure p against the crank angle of the crankshaft of the internal combustion engine 1 in degrees of crank angle (°KW). The first curve K1, as a solid line, shows the pressure curve in the combustion chamber 3, in particular in the main combustion chamber 5, wherein the pressure in the main combustion chamber 5 roughly corresponds to the pressure in the precombustion chamber 7. The second curve K2, as a dotted line, shows the charge pressure, which is present in the charge path 11 and in particular in the section 13 associated solely with the combustion chamber 3. This shows that the charge pressure is roughly constant and, in particular, depends only slightly on the momentary crank angle changes of the internal combustion engine 1. The third curve K3, as a dashed line, shows the control curve for the exhaust valve 35. The fourth curve K4, as a dot-dash line, shows the control curve for the intake valve 33.

If we examine the solid first curve K1 of the cylinder pressure, it is clear that during the cylinder's expansion stroke, and particularly at the moment when the exhaust valve 35 opens, the cylinder pressure drops until it ultimately falls below the level of the charge pressure, indicated by the dotted second curve K2. If the exhaust valve 35 is closed again, the pressure rises again, particularly above the level of the charge pressure. The dashed first surface area F1 shows the surface between the solid first curve K1 of the cylinder pressure and the dotted second curve K2 of the charge pressure, in the region where the cylinder pressure is less than the charge pressure. Here, a positive purging pressure drop occurs, thereby generating a first purging process. The check valve 21 then opens, and fuel or a rich mixture is directed from the fuel mixing chamber 15 into the precombustion chamber 7. However, the fuel mass purged into the precombustion chamber 7 in the first surface area F1 is relatively small compared to the total purged mass, so that overflow into the main combustion chamber 5 is preferably avoided.

The first surface area F1 can also be omitted. In particular, it is possible to select at least one parameter from the group consisting of exhaust back pressure, the geometric design of the effective surface of the check valve 21, the preload of the check valve, and the actuation of the inlet valve 33 and/or the exhaust valve 35, or a plurality of these parameters and/or other or additional parameters, so that the cylinder pressure in the crank angle range of the first surface area F1 shown in FIG. 3 a ) does not drop below the charge pressure, or in any case only in the range where the check valve 21 is not open. Such a design can have advantages. In particular, it can prevent unburned fuel from flowing through the open exhaust valve 35, which could potentially increase the CO2 emissions of the internal combustion engine 1 (possibly to an impermissible degree). Furthermore, the risk of self-ignition of the entrained fuel due to the still relatively hot combustion chamber in the crank angle range of the first surface area F1 shown in FIG. 3 a ) can be prevented by avoiding the design of this surface area F1.

As indicated by the dashed control curve K3 of the exhaust valve 35 and the dashed control curve K4 of the intake valve 33, the intake valve 33 is already open while the exhaust valve 35 is still closing, resulting in an overlap between the opening of the intake and exhaust valves 33 and 35. The piston reaches top dead center at 360° KW, with the piston's intake stroke, i.e., its downward movement in the combustion chamber 3, following at this point for a greater crank angle. Consequently, the pressure in the combustion chamber 3 now drops below the charge pressure indicated by the dotted curve K2, as indicated by the dashed second surface area F2. The dashed control curve of the intake valve 33 indicates that it closes at 540° KW, i.e., when the piston reaches bottom dead center. This corresponds to the Miller control time, in which the pressure difference (i.e., a positive scavenging pressure drop) between the charge pressure in the fuel mixing chamber 15 and the pressure in the combustion chamber 3 persists due to the inertia of the gas flow, causing the scavenging process to continue beyond the closing of the intake valve 33. A certain compression due to the upward movement of the piston is then required until the pressure in the combustion chamber 3 and, consequently, in the precombustion chamber 7 rises again above the charge pressure level and, consequently, the pressure level in the fuel mixing chamber 15. The scavenging process then ends at the last intersection point on the right in the diagram of the solid curve K1 of the cylinder pressure and the dotted curve K2 of the charge pressure. During the opening of the intake valve 33 and also after its closure, the main fuel scavenging process takes place, where the main amount of fuel or a rich mixture is introduced into the precombustion chamber 7. The check valve 21 is always closed when the pressure in the precombustion chamber 7, i.e., in particular the cylinder pressure, is greater than the charge pressure and, therefore, the pressure in the fuel mixing chamber 15.

FIG3 b) shows the mass flow plotted against the crank angle. A first scavenging process can be seen in the region of the first surface area F1 shown in FIG3 a) and a second scavenging process in the region of the second surface area F2 shown in FIG3 a) This also shows that the main amount of fuel is introduced into the precombustion chamber 7 during the second scavenging process. The scavenging occurs in particular due to pressure losses in the intake manifold, with the pressure in the cylinder thus being below the charge pressure level.

To implement this method, it is not absolutely necessary to actuate the intake valve 33 with a Miller control time. However, the method can also be implemented effectively with other control times. However, the Miller control time increases the efficiency of the method and improves the cleaning of the precombustion chamber 7.

Overall, it is shown that the internal combustion engine 1 and the method make it possible to realize a gas-purged precombustion chamber 7 by means of a simple non-return valve 21. Here, the pressure difference between the charge pressure and therefore the pressure in the fuel mixing region 14 downstream of the controllable fuel valve 19 and the pressure in the combustion chamber 3 containing the precombustion chamber 7 is utilized in order to cause the non-return valve 21 to open and purge the precombustion chamber 7 with pure fuel or a rich mixture of combustion air and fuel.

Claims (13)

1. An internal combustion engine (1), equipped with - At least one combustion chamber (3) having a main combustion chamber (5) and a pre-combustion chamber (7), wherein the pre-combustion chamber (7) is in fluid connection with the main combustion chamber (5) via at least one borehole (9), wherein, - The at least one combustion chamber (3) is connected to an air supply path (11) for supplying a combustion air-fuel mixture to the combustion chamber (3) via the air supply path (11), wherein, - A fuel mixing zone (14) is arranged in a separate section (13) of the charging path (11) associated with the combustion chamber (3), which - On the one hand, with the inflation path (11) and - On the other hand, it is in fluid connection with the fuel pipe (17) for supplying fuel to the fuel mixing zone (14) via a controllable fuel valve (19). The pre-combustion chamber (7) and the fuel mixing zone (14) are fluidly connected to each other via a check valve (21). 2. The internal combustion engine (1) according to claim 1, characterized in that it is provided with a connection path (25) which leads to the fuel mixing region (14) at the first end (27) of the two ends (27, 29) and to the pre-combustion chamber (7) at the second end (29) of the two ends (27, 29), wherein the check valve (21) is arranged in the connection path (25). 3. The internal combustion engine (1) according to claim 1 or 2, characterized in that the combustion chamber (3) and the charging path (11) are fluidly connected via at least one intake valve (33). 4. The internal combustion engine (1) according to claim 1 or 2, characterized in that the controllable fuel valve (19) is configured as a metering valve for multi-point injection. 5. The internal combustion engine (1) according to claim 2, wherein the fuel pipe (17) leads to the connection path (25). 6. The internal combustion engine (1) according to claim 1 or 2, characterized in that the internal combustion engine (1) is configured as a gas engine. 7. The internal combustion engine (1) according to claim 3, wherein the intake valve (33) is variablely controllable. 8. The internal combustion engine (1) according to claim 6, characterized in that the internal combustion engine (1) is configured as a lean gas engine. 9. A method for operating an internal combustion engine (1), wherein, - During the intake stroke, the combustion air-fuel mixture is supplied via the charging path (11) to at least one combustion chamber (3) divided into a main combustion chamber (5) and a pre-combustion chamber (7), wherein - The combustion air-fuel mixture is generated in a separate section (13) of the charging path (11) associated with the combustion chamber (3) in such a manner that fuel is supplied via a fuel pipe (17) through a controllable fuel valve (19) to a fuel mixing zone (14) arranged in the separate section (13), wherein, When the pressure in the pre-combustion chamber (7) is less than the pressure in the fuel mixing zone (14), fuel is directly guided from the fuel mixing zone (14) into the pre-combustion chamber (7). 10. The method according to claim 9, characterized in that when the pressure difference between the pressure in the fuel mixing zone (14) and the pressure in the pre-combustion chamber (7) exceeds a predetermined value, fuel is directly guided from the fuel mixing zone (14) into the pre-combustion chamber (7). 11. The method according to claim 9 or 10, characterized in that the intake valve (33) connecting the main combustion chamber (5) and the charging path (11) is operated with Miller-control time. 12. The method according to claim 9 or 10, wherein the internal combustion engine (1) operates using gas as fuel. 13. The method according to claim 12, wherein the gas is a methane-containing gas.