Internal Combustion Engine Comprising at Least One Cylinder Equipped With a Pre-chamber, an Injector and Two Spark Plugs, and Method for Operating Same

Abstract

An internal combustion engine may include a combustion chamber which is delimited by a cylinder; an injector with which fuel can be injected into the combustion chamber, whereby a mixture comprising fuel and air can be generated in the combustion chamber; a pre-chamber, which is fluidically separate from the combustion chamber with the exception of a passage opening and which is fluidically connected to the combustion chamber via the passage opening; a first spark plug with which an ignition spark can be produced in the pre-chamber; and a second spark plug with which an ignition spark can be produced in the combustion chamber and outside of the pre-chamber, wherein the pre-chamber, the injector, and the second spark plug are arranged, in this order, in a direction extending in a plane that is perpendicular to the axial direction of the cylinder.

Claims

1.-15. (canceled)

16. An internal combustion engine, comprising: a combustion chamber which is at least partially delimited by a cylinder; an injector which is assigned to the combustion chamber and configured to inject a fuel directly into the combustion chamber such that a mixture comprising at least the fuel and an air is supplied to the combustion chamber; a pre-chamber that is fluidically connected via at least one passage opening to the combustion chamber and configured such that a portion of the mixture can be supplied via the at least one passage opening into the pre-chamber; a first spark plug which is configured to produce at least one ignition spark in the pre-chamber for igniting the portion of the mixture supplied via the at least one passage opening into the pre-chamber; and a second spark plug which is assigned to the combustion chamber and which is configured to produce at least one ignition spark in the combustion chamber and outside the pre-chamber for igniting the mixture received in the combustion chamber, wherein the pre-chamber, the injector, and the second spark plug are arranged in the following sequence along a direction running in a plane extending perpendicularly to an axial direction of the cylinder: the pre-chamber—the injector—the second spark plug.

17. The internal combustion engine according to claim 16, wherein a straight line which runs parallel to the direction or coincides with the direction and which runs in the plane intersects the pre-chamber, the injector and the second spark plug.

18. The internal combustion engine according to claim 17, wherein the straight line runs through the center axis of the cylinder.

19. The internal combustion engine according to claim 16, wherein the pre-chamber is arranged offset in relation to the injector toward an outlet side of the combustion chamber.

20. The internal combustion engine according to claim 19, wherein the pre-chamber is at least partially arranged between outlet valves of the internal combustion engine that are arranged on the outlet side and are assigned to the combustion chamber.

21. The internal combustion engine according to claim 16, further comprising: an ignition point at which the ignition spark can be produced with the second spark plug.

22. The internal combustion engine according to claim 21, wherein the ignition point is arranged in an edge region of the combustion chamber.

23. The internal combustion engine according to claim 21, wherein the ignition point is arranged between inlet valves of the internal combustion engine that are arranged on an inlet side of the cylinder and are assigned to the combustion chamber.

24. The internal combustion engine according to claim 16, wherein the injector is configured to inject the fuel directly into the combustion chamber with formation of one or more fuel jets formed by the fuel, such that a central longitudinal axis of at least one fuel jet bypasses the pre-chamber, wherein at least one of the fuel jets strikes directly against a tip of the second spark plug, the tip being a location where the ignition spark is produced by the second spark plug.

25. A method for operating an internal combustion engine according to claim 16.

26. The method according to claim 25, wherein within at least one operating cycle of the internal combustion engine, at least one first ignition spark for igniting the mixture in the combustion chamber is produced with the second spark plug, wherein after the at least one first ignition spark is produced, at least one second ignition spark is produced in the pre-chamber with the first spark plug, wherein production of an ignition spark by the first spark plug is suppressed within the operating cycle before the first ignition spark is produced with the second spark plug and during the production of the first ignition spark with the second spark plug.

27. The method according to claim 25, wherein in at least a first partial region of a characteristic map of the internal combustion engine, respective ignition sparks are produced within respective operating cycles of the internal combustion engine both with the first spark plug and with the second spark plug, wherein in at least a second partial region of the characteristic map, the second partial region, which comprises higher loads and higher rotational speeds than the first partial region, respective ignition sparks are produced within respective operating cycles of the internal combustion engine exclusively with the first spark plug.

28. The method according to claim 25, wherein ignition times at which respective ignition sparks are produced with the second spark plug are set with an electronic computing device of the internal combustion engine independently of ignition times at which respective ignition sparks are produced with the first spark plug.

29. The method according to claim 25, wherein ignition times at which respective ignition sparks are produced with the second spark plug are set with an electronic computing device on the basis of a first characteristic map which is independent of a second characteristic map, on the basis of which ignition times at which respective ignition sparks are produced with the first spark plug are set with the electronic computing device.

30. The method according to claim 25, wherein ignition times at which respective ignition sparks are produced with the second spark plug are set with an electronic computing device depending on at least one of a load, a temperature and a rotational speed of the internal combustion engine.

31. An internal combustion engine, comprising: a combustion chamber receiving a cylinder; an injector configured to inject a fuel into the combustion chamber such that a mixture comprising at least the fuel and an air is supplied to the combustion chamber; a pre-chamber that is fluidically connected via at least one passage opening to the combustion chamber and configured such that a portion of the mixture can be supplied via the at least one passage opening into the pre-chamber; a first spark plug which is configured to produce at least one ignition spark in the pre-chamber; and a second spark plug which is configured to produce at least one ignition spark in the combustion chamber and outside the pre-chamber, wherein the pre-chamber, the injector, and the second spark plug are arranged in sequence along a direction running in a plane extending perpendicularly to an axial direction of the cylinder such that the injector is located between the pre-chamber and the second spark plug.

32. The internal combustion engine according to claim 31, wherein a straight line which runs parallel to the direction or coincides with the direction and which runs in the plane intersects the pre-chamber, the injector and the second spark plug.

33. The internal combustion engine according to claim 32, wherein the straight line runs through the center axis of the cylinder.

34. The internal combustion engine according to claim 31, wherein the pre-chamber is arranged offset in relation to the injector toward an outlet side of the combustion chamber.

35. The internal combustion engine according to claim 34, wherein the pre-chamber is at least partially arranged between outlet valves of the internal combustion engine that are arranged on the outlet side and are assigned to the combustion chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Further details of the invention emerge from the description below of a preferred exemplary embodiment with the associated drawings, in which:

[0040] FIG. 1 shows a schematic sectional view of a detail of an internal combustion engine according to the invention;

[0041] FIG. 2 shows a schematic and sectioned side view of a detail of the internal combustion engine;

[0042] FIG. 3 shows a schematic illustration of a characteristic map, also referred to as engine characteristic map, of the internal combustion engine;

[0043] FIG. 4 shows a further schematic illustration of the characteristic map; and

[0044] FIG. 5 shows a further schematic illustration of the characteristic map.

[0045] Similar elements are provided with the same reference signs in the figures.

DETAILED DESCRIPTION OF THE DRAWINGS

[0046] FIG. 1 shows a schematic sectional view of a detail of an internal combustion engine 1. The internal combustion engine 1 has a housing element 2 which is preferably in the form of a crankcase, in particular a cylinder crankcase. The housing element 2 forms or delimits at least one cylinder 3 of the internal combustion engine 1. A piston, not illustrated in the figures, is accommodated in a translationally movable manner in the cylinder 3. In addition, the internal combustion engine 1 comprises an output shaft which is in the form of a crankshaft and which is mounted rotatably on the housing element 2. The piston arranged in the cylinder 3 is connected in an articulated manner to the crankshaft via a connecting rod such that the translational movements of the piston in the cylinder 3 can be converted into a rotational movement of the crankshaft. The cylinder 3 and the piston in each case partially delimit a combustion chamber 4 of the internal combustion engine 1. The cylinder 3 has a cylinder axis 5, also referred to as central axis, the cylinder 3 being at least substantially rotationally symmetrical, for example, with reference to the cylinder axis 5 which runs in the axial direction of the cylinder 3. In a first direction running parallel to the cylinder axis 5, the combustion chamber 4 is delimited by the piston. In a second direction which runs parallel to the cylinder axis 5 and is opposed to the first direction, the combustion chamber 4 is delimited by a combustion chamber roof 6. The combustion chamber roof 6 is formed, for example, by a cylinder head of the internal combustion engine 1. The cylinder head is formed separately from the housing element 2 and is connected to the housing element 2.

[0047] By way of example, the combustion chamber 4 is assigned precisely two inlet channels 7a, b which are formed or delimited, for example, by the cylinder head and open per se into the combustion chamber 4. In particular during fired operation of the internal combustion engine 1, air flows through the inlet channels 7a, b with which the air flowing through the inlet channels 7a, b is conducted into the combustion chamber 4. The respective inlet channel 7a, b is assigned a respective inlet valve 8a, b. The respective inlet valve 8a, b is movable relative to the cylinder head and/or translationally between a first closed position and at least one first open position. In the first closed position, the respective inlet valve 8a, b blocks the respectively associated inlet channel 7a, b such that the respective inlet channel 7a, b is fluidically separated from the combustion chamber 4 and air cannot flow out of the respective inlet channels 7a, b into the combustion chamber 4. However, in the respective first open position, the respective inlet valve 8a, b opens up the respectively associated inlet channel 7a, b such that the air which flows through the respective inlet channel 7a, b can flow out of the inlet channel 7a, b via the respective, opened inlet valve 8a, b and can flow or flows into the combustion chamber 4. An imaginary first plane E1 in which the cylinder axis 5 runs divides the combustion chamber 4, and therefore the cylinder 3, into an inlet side 9 and an outlet side 10. The plane E1 here divides the combustion chamber 4 or the cylinder 3 precisely in half into the inlet side 9 and the outlet side 10. It can be seen that the inlet channels 7a, b open on the inlet side 9 into the combustion chamber 4, with the inlet valves 8a, b being arranged on the inlet side 9.

[0048] Instead of the translationally movable inlet valves 8a, b, use could be made of rotary slide valves or other valves. The numbers and arrangements of the structural elements are shown and described by way of example and may vary. The previous and following statements can also be transferred to other engines, with it being possible for the internal combustion engine to be in the form of a two valve or three valve engine. A combustion method described below also functions in the case of two valve or three valve engines or other engines. Engines having five or six valves can also be equipped with pre-chambers and a second spark plug.

[0049] The combustion chamber 4 is assigned precisely two outlet channels 11a, b which are formed or delimited, for example, by the cylinder head. Furthermore, the combustion chamber 4 is assigned an injector 12 with which a liquid fuel can be injected directly into the combustion chamber 4 or is injected, in particular during the fired operation. By this means, a fuel-air mixture, also referred to simply as mixture, is formed in the combustion chamber 4, said mixture comprising the air which flows out of the inlet channels 7a, b and flows into the combustion chamber 4, consequently is conducted with the inlet channels 7a, b into the combustion chamber 4, and the fuel which is injected directly into the combustion chamber 4 with the injector 12. Alternatively or additionally, the fuel can be injected by an intake manifold injector, inter alia together with a direct-injection injector as a dual injection.

[0050] In particular, the mixture is formed within a respective operating cycle of the internal combustion engine 1. In addition, the mixture is ignited within the respective operating cycle and combusted as a result, with exhaust gas resulting from the internal combustion engine, which is preferably in the form of an Otto engine. The exhaust gas can flow into the outlet channels 11a, b and therefore can flow out of the combustion chamber 4, consequently can be removed from the combustion chamber 4 with the outlet channels 11a, b. The respective outlet channel 11a, b is assigned a respective outlet valve 13a, b. The respective outlet valve 13a, b is movable, in particular translationally and/or relative to the cylinder head, between a second closed position and at least one second open position. In the second closed position, the respective outlet valve 13a, b blocks the respective associated outlet channel 11a, b such that the respective outlet channel 11a, b is fluidically separated from the combustion chamber 4 and exhaust gas or gas cannot flow out of the combustion chamber 4 into the respective outlet channel 11a, b. However, in the respective second open position, the respective outlet valve 13a, b opens up the respectively associated outlet channel 11a, b such that the exhaust gas can flow via the respective outlet valve 13a, b into the respective outlet channel 11a, b and can therefore flow out of the combustion chamber 4. It can be seen that the outlet channels 11a, b open on the outlet side 10 into the combustion chamber 4, with the outlet valves 13a, b being arranged, in particular completely, on the outlet side 10. A further, imaginary second plane running perpendicularly to the first plane E1 is denoted by E2 in FIG. 1, the plane E2 also running through the cylinder axis 5. In addition, the internal combustion engine 1 has a pre-chamber 14 which is assigned to the combustion chamber 4 and, apart from a plurality of passage openings 15, is fluidically separated from the combustion chamber 4 and is fluidically connected via the passage openings 15 to the combustion chamber 4. For this purpose, the internal combustion engine 1 has, for example, an in particular single-piece chamber element 16 with which the pre-chamber 14, in particular the volume thereof, is at least predominantly, in particular completely, delimited. The pre-chamber 14 is fluidically separated from the combustion chamber 4 with the chamber element 16. The passage openings 15 are formed in the chamber element 16, and therefore the pre-chamber 14 is fluidically connected to the combustion chamber 4 via the passage openings 15 of the chamber element 16. By this means, at least a portion of the mixture can be conducted, that is to say can flow, out of the combustion chamber 4 via the passage openings 15 into the pre-chamber 14.

[0051] The combustion chamber 4 is assigned a first spark plug 17 which is illustrated particularly schematically in FIG. 2 and is also referred to as pre-chamber spark plug and with which at least one ignition spark can be produced in the pre-chamber 14, in particular within the respective operating cycle. By this means, the portion of the mixture conducted via the passage openings 15 into the pre-chamber 14 can be ignited in the pre-chamber 14 and consequently combusted. Furthermore, the combustion chamber 4 is assigned a second spark plug 18 with which at least one ignition spark can be produced in the combustion chamber 4, and therefore outside the pre-chamber 14, in particular within the respective operating cycle, for igniting the mixture received or remaining in the combustion chamber 4.

[0052] In order then to be able to realize particularly advantageous and in particular efficient operation of the internal combustion engine 10, provision is made that the pre-chamber 14, the injector 12 and the second spark plug 18 are arranged one behind another or consecutively along a rectilinear direction running in a plane extending perpendicularly to the axial direction of the cylinder 3 and therefore perpendicularly to the planes E1 and E2 and running in the plane E2 and shown in FIG. 1 by an arrow 19, in the following sequence: the pre-chamber 14—the injector 12—the second spark plug 18. The direction shown by the arrow 19 coincides here with a straight line G which runs in the plane E2 and therefore perpendicularly to the plane E1 and intersects the pre-chamber 14, the injector 12 and the second spark plug 18. The straight line G runs here through the cylinder axis 5 (central axis) of the cylinder 3.

[0053] It can be seen from FIG. 1 that the injector 12 is an injector which is arranged at least substantially centrally with respect to the cylinder 3 or the combustion chamber 4, with the pre-chamber 14 being arranged offset in relation to the injector 12 toward the outlet side 10. The pre-chamber 14 is at least predominantly arranged here on the outlet side 10, with the injector 12 being at least predominantly, in particular completely, arranged on the inlet side 10. The spark plug 18 or the tip S thereof, at which an ignition spark can be produced in the combustion chamber 4 and outside the pre-chamber 14 with the spark plug 18, is also arranged completely on the inlet side 9. Furthermore, the pre-chamber 14 is at least partially, in particular at least predominantly, arranged between the outlet valves 13a, b arranged on the outlet side 10. In addition, an ignition point Z at which the ignition spark can be produced with the second spark plug 18 is arranged on the inlet side 9. The ignition point Z and therefore the tip S are arranged, as can be seen particularly readily from FIG. 2, in an edge region R of the combustion chamber 4, and therefore the second spark plug 18, the longitudinal axis or direction of longitudinal extent of which is shown in FIG. 2 by a chain-dotted line 20, is also referred to as an edge spark plug. The ignition point Z or the tip S is arranged here between the inlet valves 8a, b.

[0054] As can furthermore be seen particularly readily from FIGS. 1 and 2, the injector 12 is designed to inject the fuel directly into the combustion chamber 4 with formation of fuel jets K1, K2, K3, K4 and K5, which are formed by the fuel and are also referred to as injection jets, in such a manner that the fuel jets K1-5, in particular the respective central longitudinal axes thereof, bypass the pre-chamber 14 or the chamber elements 16, and consequently do not strike directly against the pre-chamber 14 or the chamber elements 16. Injectors with significantly more spray jets are also possible, e.g. seven or eight hole injectors. It is advantageous that the pre-chamber 14 is not struck by any injection jet and at least one jet is injected toward the edge spark plug.

[0055] At least or precisely one of the fuel jets K1-5, in the present case the fuel jet K5, is oriented in such a manner that it strikes directly against the second spark plug 18, in particular against the tip S thereof. The respective fuel jet K1-5 is, for example, a spray jet. It can be seen from FIG. 2 that the largest angle which the spark plug 18, in particular its longitudinal axis or direction of longitudinal extent, encloses with the plane E2 or with the cylinder axis 5 is greater than 90 degrees and less than 100 degrees. As a result, the spark plug 18 can be arranged particularly flatly, and therefore its tip S can be arranged particularly close to the injector 12, the longitudinal axis or direction of longitudinal extent of which is shown in FIG. 2 by a chain-dotted line 21. The spark plug 17, the longitudinal axis or direction of longitudinal extent of which is shown in FIG. 2 by a chain-dotted line 22 can also be advantageously arranged and in particular oriented relative to the combustion chamber 4 and relative to the injector 12 and relative to the spark plug 18. It can be seen from FIG. 2 that the longitudinal axes of the injector 12 and of the spark plug 17 each enclose the same angle with the plane E2 or with the cylinder axis 5 and run obliquely with respect to the plane E2 or obliquely with respect to the cylinder axis 5.

[0056] FIG. 3 shows a diagram, on the abscissa 23 of which the rotational speed of the internal combustion engine 1 or of the crankshaft thereof is plotted. The load of the internal combustion engine 1 is plotted on the ordinate 24. A or the characteristic map K, also referred to as engine characteristic map, of the internal combustion engine 1 is entered in the diagram shown in FIG. 3. The characteristic map K has at least or precisely two partial regions T1 and T2, wherein the partial region T2 adjoins the partial region T1, in particular directly, in the direction of higher rotational speeds and higher loads. A dual ignition is provided, for example, in the partial region T1. The dual ignition should be understood as meaning that in each case at least one ignition spark is produced, and therefore ignition brought about, both with the spark plug 17 and with the spark plug 18 in the partial region T1 within the respective operating cycle of the internal combustion engine 1. For example, first of all the edge spark plug is used to bring about ignition, whereupon the pre-chamber spark plug is used to bring about ignition in the pre-chamber 14. A single ignition is provided in the partial region T2, and therefore ignition is brought about with the pre-chamber spark plug in the partial region T2 within the respective operating cycle, and, consequently, at least one ignition spark is produced in the pre-chamber 14 with the first spark plug 17, and an ignition brought about by the edge spark plug, consequently production of an ignition spark brought about by the edge spark plug, is suppressed.

[0057] FIG. 4 shows the characteristic map K with further partial regions T3 and T4, wherein the partial region T4 can comprise the partial region T2 and/or the partial region T1 can comprise the partial region T3. A dual injection is provided in the partial region T3. This means that precisely two temporally consecutive injections which are spaced apart from one another are carried out with the injector 12 within respective operating cycles of the internal combustion engine 1 belonging to the partial region T3 of the characteristic map K, the respective injection causing the fuel to be directly injected into the combustion chamber 4 with the injector 12. It can be seen that the partial region T4 directly adjoins the partial region T3 in the direction of higher loads and optionally in the direction of higher rotational speeds.

[0058] Finally, FIG. 5 shows the characteristic map K with two further partial regions T5 and T6, wherein the partial region T4 can comprise the partial region T6, and/or the partial region T5 can comprise the partial region T3. A triple injection is provided here in the partial region T6. This should be understood as meaning that precisely three temporally consecutive injections which are spaced apart from one another are carried out with the injector 12 within respective operating cycles of the internal combustion engine 1 belonging to the partial region T6, the respective injection causing the fuel to be injected directly into the combustion chamber 4 with the injector 12. Furthermore, it can be seen from FIG. 5 that the partial region T6 directly adjoins the partial region T5 in the direction of higher loads and/or rotational speeds.

LIST OF REFERENCE SIGNS

[0059] 1 Internal combustion engine [0060] 2 Housing element [0061] 3 Cylinder [0062] 4 Combustion chamber [0063] 5 Cylinder axis [0064] 6 Combustion chamber roof [0065] 7a, b Inlet channel [0066] 8a, b Inlet valve [0067] 9 Inlet side [0068] 10 Outlet side [0069] 11a, b Outlet channel [0070] 12 Injector [0071] 13a, b Outlet valve [0072] 14 Pre-chamber [0073] 15 Passage openings [0074] 16 Chamber element [0075] 17 First spark plug [0076] 18 Second spark plug [0077] 19 Arrow [0078] 20 Chain-dotted line [0079] 21 Chain-dotted line [0080] 22 Chain-dotted line [0081] 23 Abscissa [0082] 24 Ordinate [0083] E1 Plane [0084] E2 Plane [0085] G Straight line [0086] K Characteristic map [0087] K1-5 Fuel jet [0088] R Edge region [0089] S Tip [0090] T1-6 Partial region [0091] Z Ignition point