Internal combustion engine for a motor vehicle

Abstract

Internal combustion engine (1) for a motor vehicle, comprising at least one piston (4) movably arranged in a cylinder (2) of the internal combustion engine (1) with respect to a longitudinal central axis (3) of the cylinder (2), which together with a cylinder roof (6) and a cylinder wall (5) encloses a combustion chamber, wherein a piston bowl (7) extending through an end face (8) of the piston and open towards the combustion chamber is formed in the piston and an ignition device (9) is arranged on the cylinder roof (6), which has a pre-chamber (10) fluidically connected to the combustion chamber, wherein the end face (8) has a displacement surface (12) adjoining a piston bowl edge (11) of the piston bowl (7) and a displacement counter-surface (13) opposite the displacement surface (12) is formed on the cylinder roof (6),wherein the displacement surface (12) and the displacement counter-surface (13) together with the cylinder wall (5) define a displacement area of ​​the combustion chamber which surrounds the pre-chamber (10) in an annular manner, characterized in that a maximum diameter of the piston bowl (7) is at most 75% of a cylinder diameter of the cylinder (2).

Description

[0001] The invention relates to an internal combustion engine for a motor vehicle, with at least one piston movably arranged in a cylinder of the internal combustion engine with respect to a longitudinal central axis of the cylinder, which together with a cylinder roof and a cylinder wall encloses a combustion chamber, wherein a piston bowl extending through an end face of the piston and open towards the combustion chamber is formed in the piston and an ignition device is arranged on the cylinder roof, which has a pre-chamber fluidically connected to the combustion chamber, wherein the end face has a displacement surface adjoining a piston bowl edge of the piston bowl and a displacement counter-surface opposite the displacement surface is formed on the cylinder roof, wherein the displacement surface and the displacement counter-surface together with the cylinder wall define a displacement area of ​​the combustion chamber that surrounds the pre-chamber in an annular manner.

[0002] For example, the prior art includes the publication DE 10 2018 116 348 A1.This relates to an internal combustion engine comprising at least one main combustion chamber designed as a main chamber in a cylinder above the cylinder receiving a piston, wherein the main combustion chamber is supplied with fuel via a pre-chamber connected to a fuel supply system, wherein combustion air is supplied to the at least one main combustion chamber via at least one associated intake valve, wherein the pre-chamber is associated with an ignition source which ignites the fuel in the pre-chamber at a predetermined time, whereby ignited reactive gas jets are shot into the main combustion chamber and combusted in the main combustion chamber, after which the exhaust gas is discharged from the at least one main combustion chamber via an exhaust valve, wherein the pre-chamber has jet channels for the directed introduction of reactive gas jets into the main combustion chamber, which is bounded by a main combustion chamber roof of the cylinder and a piston bowl formed in the piston.It is intended that several reactive gas jets are directed at a primary ignition area of ​​the piston bowl of the piston at a predetermined position of the piston in the cylinder, which lies between a central area and a squish edge area located in the edge area of ​​the piston bowl of a geometrically specifically designed piston bowl.

[0003] The publication EP 3 056 710 B1 proposes a piston for a gas engine with a pre-chamber, wherein combustion jets are formed by burning a pre-chamber fuel in a pre-combustion chamber and introduced into a main combustion chamber through a plurality of through-holes. The piston comprises an end face with a surface section arranged in a first section extending in the direction of the longitudinal center axes of adjacent through-holes, the first section being arranged in a higher position than a second section extending in the direction of the longitudinal center axes. The surface section is formed in a recess in the end face of the piston.

[0004] The prior art documents US 2016 / 0 273 443 A1 , DE 10 2020 110 960 A1 and DE 102 61 333 A1 are also known.

[0005] The object of the invention is to propose an internal combustion engine for a motor vehicle which has advantages over known internal combustion engines, in particular reducing the tendency of the internal combustion engine to knock and increasing the efficiency of the internal combustion engine.

[0006] According to the invention, this is achieved with an internal combustion engine for a motor vehicle having the features of claim 1. It is provided that the maximum diameter of the piston bowl is at most 75% of the cylinder diameter.

[0007] In principle, it is provided that the end face has a displacement surface adjoining a piston bowl edge of the piston bowl and that a displacement counter-surface opposite the displacement surface is formed on the cylinder roof, wherein the displacement surface and the displacement counter-surface together with the cylinder wall define a displacement area of ​​the combustion chamber that surrounds the pre-chamber in a ring shape.

[0008] Advantageous embodiments with appropriate further developments of the invention are specified in the independent claims.

[0009] The internal combustion engine serves, for example, to propel the motor vehicle and thus to provide a drive torque directed towards propelling the motor vehicle. It is preferably a component of the motor vehicle, but can, of course, also exist separately. The internal combustion engine has a cylinder in which the piston is displaceably arranged, namely with respect to the longitudinal center axis of the cylinder. The piston is coupled to a crankshaft of the internal combustion engine, in particular via at least one connecting rod.

[0010] The piston, together with the cylinder wall and cylinder head, encloses the combustion chamber. The cylinder wall defines the outer boundary of the cylinder, or combustion chamber, in the radial direction with respect to the longitudinal center axis. The cylinder wall is a component of, or formed by, the cylinder crankcase of an internal combustion engine. For example, the cylinder is formed by a cylinder bore in the cylinder crankcase, which has radial dimensions that can also be referred to as the cylinder diameter.

[0011] The cylinder head defines the axial boundary of the cylinder, or combustion chamber, with respect to the longitudinal center axis, specifically on the side of the combustion chamber facing away from the piston. In other words, the combustion chamber is bounded axially by the cylinder head on one side and by the piston on the other. The cylinder head is, for example, a component of, or formed by, the cylinder head of an internal combustion engine. The internal combustion engine has a fresh gas intake system through which fresh gas is supplied to the engine, at least temporarily. This fresh gas preferably contains fresh air, which is drawn from the engine's external environment. At least one gas exchange valve is fluidically connected to the combustion chamber.The gas exchange valve is located between the fresh gas tract and the combustion chamber, whereby a flow connection between the fresh gas tract and the internal combustion engine is established when the gas exchange valve is at least partially open and is interrupted when the gas exchange valve is closed. The gas exchange valve is preferably arranged on the cylinder head.

[0012] The piston bowl is formed within the piston, extending through the piston's end face. The piston's end face is defined as the surface of the piston facing the combustion chamber. The piston's end face is preferably flat, but can also be convex or concave, particularly conical. Preferably, the end face is a surface of revolution, i.e., formed by rotating a planar curve around an axis of rotation, where the longitudinal center axis is used as the axis of rotation. The piston bowl is located on the side of the end face opposite the cylinder head, viewed axially with respect to the longitudinal center axis. The piston bowl extends through the end face, forming an opening. The piston bowl rim is formed by the end face and defines the opening through which the piston bowl is open towards the combustion chamber or the cylinder head.

[0013] The piston bowl is bounded axially, in the direction away from the cylinder head, by a piston bowl base formed by the piston. Opposite this, i.e., in the axial direction towards the cylinder head, it is bounded by the end face or an imaginary plane intersecting the end face. This imaginary plane is preferably perpendicular to the longitudinal center axis. It extends, in particular, through the piston bowl rim, preferably encompassing it completely in the circumferential direction.

[0014] The piston bowl is a hollow volume which—as already explained—is bounded on one side by the cylinder, in particular the piston bowl base, and on the other side by the end face or an imaginary plane. The piston bowl represents a first sub-volume of the combustion chamber and is fluidically connected to a second sub-volume of the combustion chamber, which is bounded axially on the one hand by the end face or imaginary plane and on the other hand by the cylinder head, and radially outwards by the cylinder wall. This means that the combustion chamber consists of the first sub-volume and the second sub-volume, in particular exclusively. The two sub-volumes adjoin each other at an imaginary dividing plane or are separated from each other by it. The dividing plane corresponds, for example, to the imaginary plane already mentioned.It should be noted that during a piston cycle, the volume of the first subvolume remains constant, while the volume of the second subvolume changes depending on the piston's position. The volume of the first subvolume, i.e., the piston bowl, is independent of the piston's position. The first and second subvolumes are fluidically connected via the piston bowl's outlet.

[0015] The ignition device is located on the cylinder roof. The ignition device serves to ignite a mixture of fuel and fresh gas present in the combustion chamber. The internal combustion engine is therefore a spark-ignition engine, in particular a gasoline engine. The ignition device includes a pre-chamber, which is fluidically connected to the combustion chamber via at least one through-opening, preferably exclusively via this one through-opening.

[0016] Preferably, the ignition device is a pre-chamber spark plug. However, the ignition device can also have a pre-chamber enclosed by the cylinder roof, into which a spark plug of the ignition device, for example a hook spark plug, projects in the usual way. In this case, the pre-chamber and the actual spark plug are thus designed separately from each other.

[0017] To ignite the mixture present in the combustion chamber, or combustion chamber mixture, by means of the ignition device, a pre-chamber mixture present in the pre-chamber is first ignited. The pre-chamber mixture is formed, for example, from the combustion chamber mixture, in particular by a piston stroke through at least one opening into the pre-chamber. Additionally or alternatively, the ignition device can have an injection device through which fuel is introduced into the pre-chamber to form the pre-chamber mixture. In the latter case, the introduction of fuel into the pre-chamber occurs independently of the supply of the combustion chamber mixture. Thus, fuel is introduced into both the combustion chamber and the pre-chamber, but this occurs separately, in particular by means of different fuel injectors.

[0018] Igniting the mixture present in the pre-chamber produces a flame jet, particularly a torch jet, which enters the combustion chamber through the through-hole and spreads out. This flame jet ignites the mixture in the combustion chamber. This results in a significantly faster combustion of the mixture compared to direct ignition of the combustion chamber mixture without a pre-chamber, especially in areas of the combustion chamber that are critical with regard to knocking. The use of the ignition system with the pre-chamber thus reduces the knocking tendency of the internal combustion engine.

[0019] A further improvement in efficiency can be achieved – optionally – by generating a so-called "tumble" motion of the combustion chamber mixture. This "tumble" motion is a rotational movement of the combustion chamber mixture, the axis of which is perpendicular to a vertical axis that is parallel to the longitudinal center axis of the cylinder. Specifically, the axis of rotation lies in an imaginary plane perpendicular to the longitudinal center axis. This rotational movement promotes thorough mixing and thus leads to an increase in the combustion velocity of the combustion chamber mixture and a reduction in the tendency to knock.

[0020] One measure to support the "tumble" motion is to increase the valve tilt angle of the gas exchange valve. The valve tilt angle is defined as the smallest angle between the longitudinal center axis of the gas exchange valve and a straight line parallel to that axis. The longitudinal center axis of the gas exchange valve is, for example, the center axis of a valve stem in a poppet-type gas exchange valve. Increasing the valve tilt angle of the gas exchange valve supports the "tumble" motion of the combustion chamber mixture described above.

[0021] However, this type of internal combustion engine design results in a relatively large axial extension of the combustion chamber to reliably prevent a collision between the gas exchange valve and the piston when the piston reaches top dead center. For a given combustion chamber volume, this in turn leads to a large distance that the flame jet must overcome to achieve reliable combustion of the fuel in the combustion chamber. Due to the finite propagation speed of the flame jet, the described measure cannot sufficiently reduce the engine's tendency to knock. In particular, at least partial auto-ignition of the mixture present in the piston bowl can occur.

[0022] The invention therefore provides that the displacement surface is formed on the end face of the piston. This surface adjoins, or forms, the edge of the piston bowl. In other words, the edge of the piston bowl defines the displacement surface in a radial direction inwards. The displacement surface extends radially outwards with respect to the longitudinal center axis from the edge of the piston bowl to a piston skirt. The piston skirt defines the piston in a radial direction outwards and is slidably mounted in the cylinder with respect to the cylinder wall. A seal is provided between the piston skirt and the cylinder wall, in particular by means of at least one piston ring.

[0023] Furthermore, it is provided that the displacement surface is formed on the cylinder roof. This surface is arranged opposite the displacement surface formed on the piston. This means that the displacement surface and the displacement surface overlap at least partially in the radial direction with respect to the longitudinal center axis. For example, the displacement surface overlaps the displacement surface completely in the radial direction. This means that the displacement surface extends radially from a first radial position located on the outer edge of the displacement surface to a second radial position located on the inner edge. The first radial position corresponds to the radial position of the outermost point of the displacement surface in the radial direction, and the second radial position corresponds to the radial position of the innermost point of the displacement surface in the radial direction.In the axial direction, the displacement surface and the counter-displacement surface are spaced apart from each other in every position of the piston that occurs during normal operation of the internal combustion engine, including top dead center. The displacement surface and the counter-displacement surface are arranged, for example, parallel and / or concentrically to each other.

[0024] The displacement surface and the opposing displacement surface, together with the cylinder wall, define a partial volume of the combustion chamber, also known as the displacement sub-region. The displacement sub-region is a part of the combustion chamber bounded axially by the displacement surface on one side and the opposing displacement surface on the other, and radially outward by the cylinder wall. Radially inward, the displacement sub-region extends to the piston bowl edge. The displacement sub-region surrounds the pre-chamber in a ring-like fashion with respect to its longitudinal center axis.

[0025] During a compression stroke of the piston, the volume of the displacement area decreases as the displacement surface on the piston moves towards the opposing displacement surface on the cylinder head. This causes a portion of the combustion chamber mixture within the displacement area to be forced radially inwards, particularly towards the pre-chamber, creating turbulent flow within the combustion chamber. This turbulent flow promotes the mixing of the mixture, especially during the ignition process described above.

[0026] The invention provides for the combustion chamber not being designed to support the "tumble" motion, but rather to minimize the maximum axial extent of the combustion chamber volume bounded by the cylinder head. For a given combustion chamber volume, the piston bowl is designed with a correspondingly larger volume. To minimize the combustion chamber volume bounded by the cylinder head, the valve tilt angle of the gas exchange valve is in a range of 0° to 6°. For example, it is greater than 0°, and in particular, it is at least 1°, at least 2°, or at least 3°. Additionally or alternatively, it is at most 6°, at most 5°, or at most 4°. Thus, the angle can be between 2° and 5°, between 3° and 4°, or approximately or exactly 3.5°, inclusive of the aforementioned values.

[0027] The area of ​​the displacement surface and / or the counter-displacement surface, viewed radially with respect to the longitudinal center axis, is at least 15%, at least 20%, or at least 25% of the cross-sectional area of ​​the piston. This results in a particularly high degree of turbulence in the turbulent flow within the combustion chamber.

[0028] It should be noted that the displacement area and the counter-displacement area do not necessarily have identical surface areas. Preferably, however, the surface area of ​​the displacement area formed on the piston is at least as large as the surface area of ​​the counter-displacement area formed on the cylinder head. Overall, this results in a reduced tendency to knock compared to known internal combustion engines, leading to an increase in efficiency and / or power output, particularly compared to known spark-ignition internal combustion engines, even if their combustion chamber is designed to support the "tumble" motion.

[0029] A further development of the invention provides that the volume of the piston bowl is larger than the volume of the combustion chamber volume bounded by the end face of the piston at top dead center and the cylinder head. As explained above, the combustion chamber comprises the first partial volume and the second partial volume; in particular, the combustion chamber consists of the first partial volume and the second partial volume. During operation of the internal combustion engine, the piston is periodically moved between bottom dead center and top dead center, and vice versa.

[0030] It is now provided that the volume of the piston bowl, and thus of the first partial volume, is larger than the volume of the second partial volume of the combustion chamber, which is bounded by the piston's end face and the cylinder head, when the piston is at top dead center. Specifically, when the piston is at top dead center, the volume of the piston bowl is at least 55%, at least 65%, or at least 75% of the total volume of the combustion chamber, consisting of the first and second partial volumes. This design achieves particularly efficient combustion of the mixture.

[0031] A further development of the invention provides that the prechamber is arranged radially centrally on the cylinder head with respect to the longitudinal center axis. The prechamber is part of the ignition device, which is arranged on the cylinder head. In addition to the prechamber, the ignition device further comprises the spark plug, the ignition device preferably being designed as a prechamber spark plug. The prechamber spark plug is, for example, inserted into a corresponding recess in the cylinder head. Alternatively, the spark plug and the prechamber are designed separately from each other. In this case, the prechamber is preferably formed in the cylinder head. For example, the prechamber is formed at least partially by the recess into which the spark plug is inserted.

[0032] The prechamber is fluidically connected to the combustion chamber via at least one through-opening. For this purpose, the ignition device projects at least partially into the combustion chamber, in particular such that the prechamber is located within the combustion chamber. Particularly preferably, when the piston is at top dead center, the ignition device projects partially into the piston bowl, in particular such that the prechamber is also located within the piston bowl. In particular, when the piston is at top dead center, the through-opening is located at least partially, and in particular completely, within the piston bowl. This results in particularly efficient combustion of the combustion chamber mixture and further reduces the tendency to knock.

[0033] A further development of the invention provides that the piston bowl, viewed in longitudinal section with respect to the longitudinal center axis, has a convex contour with a centrally formed elevation in the piston bowl. Viewed in longitudinal section, a concave region of the contour extends radially outwards from the elevation to the edge of the piston bowl. The contour is understood to be the shape of the piston bowl, in particular the piston bowl base, in longitudinal section. Viewed in longitudinal section, the contour is bounded on both sides of the longitudinal center axis by the edge of the piston bowl. The contour is preferably symmetrical about the longitudinal center axis in longitudinal section.

[0034] The raised section is formed in the center of the piston bowl. The central arrangement refers specifically to an arrangement centered with respect to the radial direction. The raised section extends from the piston bowl base towards the combustion chamber. Adjoining the raised section in the radial direction is the concave portion of the contour, which extends to the edge of the piston bowl. Within this concave portion, the depth of the piston bowl, measured axially with respect to the longitudinal center axis and the end face or imaginary plane, is at least partially greater than the depth at the raised section. In particular, the maximum depth of the piston bowl is found in this concave portion.

[0035] According to the invention, the maximum diameter of the piston bowl is at most 75%, preferably at most 70%, or preferably at most 65% of the cylinder diameter. The maximum diameter of the piston bowl is understood to be the largest diameter of the piston bowl in the radial direction with respect to the longitudinal center axis along its axial extent. For example, the maximum diameter of the piston bowl is located at the cylinder outlet. A piston bowl designed in this way enables particularly efficient combustion and reduces the tendency to knock.

[0036] A further development of the invention provides that the prechamber is fluidically connected to the combustion chamber via at least one through-opening, the through-opening being oriented towards the concave region. The through-opening has already been mentioned above. The through-opening is arranged on the prechamber such that the flame jet propagates towards the concave region of the contour or the piston bowl base.

[0037] In particular, a longitudinal center axis of the through-opening intersects the contour of the piston bowl or the piston bowl floor in the concave area when the piston is at top dead center. The pre-chamber preferably has several through-openings arranged circumferentially with respect to the longitudinal center axis of the cylinder, and especially uniformly, so that when the pre-chamber mixture is ignited, several flame jets propagate into the combustion chamber, particularly in a star-shaped pattern. This arrangement of the through-opening(s) ensures optimal combustion of the combustion chamber mixture.

[0038] A further development of the invention provides that the concave area forms an undercut of the piston bowl rim, such that the diameter of the piston bowl in the concave area is larger than the diameter of the piston bowl rim. As explained above, the concave area of ​​the piston bowl contour extends from the piston bowl rim to the raised section located centrally in the piston bowl.

[0039] It is now planned that the diameter of the piston recess in the concave area is at least partially larger than the diameter of the muzzle opening. This design allows for a maximum volume of the piston recess with a maximum surface area of ​​the displacement surface.

[0040] A further development of the invention provides that at least one gas exchange valve, fluidically connected to the combustion chamber, is arranged on opposite sides of an imaginary plane on the cylinder roof, wherein at least one outlet opening of a fuel injector for introducing fuel into the combustion chamber is arranged in the imaginary plane. In other words, at least two gas exchange valves are arranged in the cylinder roof, located on opposite sides of the imaginary plane.

[0041] The fuel injector serves to introduce fuel into the combustion chamber. The internal combustion engine is therefore a direct-injection engine. The fuel injector has at least one outlet opening through which the fuel is introduced into the combustion chamber. The outlet opening is located in the plane of the combustion chamber. The fuel is thus introduced into the combustion chamber between the two gas exchange valves located on opposite sides of this plane. This allows for a particularly compact design of the fuel injector.

[0042] Additionally or alternatively, a longitudinal center axis of the fuel injector is arranged in the imaginary plane. Specifically, the longitudinal center axis of the fuel injector intersects the longitudinal center axis of the cylinder at an angle. The fuel injector is therefore not parallel to the longitudinal center axis of the cylinder. This allows the fuel to be injected into the combustion chamber in a targeted manner, heading towards the piston bowl.

[0043] A further development of the invention provides that, in addition to the gas exchange valve, at least one further gas exchange valve is provided on each of the opposite sides, wherein the gas exchange valve is an inlet valve and the further gas exchange valve is an outlet valve. Thus, at least two gas exchange valves are arranged on each of the opposite sides, namely the gas exchange valve and the further gas exchange valve. The gas exchange valve is configured as an inlet valve and the further gas exchange valve as an outlet valve.

[0044] In other words, there are at least two intake valves and at least two exhaust valves, with a first intake valve and a first exhaust valve located on one side of the imaginary plane. Similarly, a second intake valve and a second exhaust valve are located on the opposite side of the imaginary plane. As explained above, the fuel injector outlet is located in this imaginary plane. The fuel injector, or rather its outlet, is thus positioned between the first intake valve and the first exhaust valve on the one hand, and the second intake valve and the second exhaust valve on the other. This allows for a particularly compact design of the cylinder head.

[0045] A further development of the invention provides that the fuel injector is arranged on a side facing the intake valve of a further imaginary plane that incorporates the longitudinal center axis and is arranged perpendicular to the imaginary plane. The imaginary plane and the further imaginary plane thus intersect at an angle of 90°. Preferably, the first intake valve and the second intake valve are arranged on a first side of the further imaginary plane, and the first exhaust valve and the second exhaust valve are arranged on a side of the further imaginary plane opposite the first side.

[0046] The fuel injector, or rather its outlet, is located on the first side, or the side facing the intake valves, of the further imaginary plane. Thus, the fuel is introduced into the combustion chamber on the side of this further imaginary plane facing the intake valves. Specifically, the fuel injector, or rather its outlet, is located between the first intake valve and the second intake valve.

[0047] Alternatively, the fuel injector, or rather its outlet, is located on the second side, or the side facing the exhaust valves, of the further imaginary plane. In this case, the fuel is introduced into the combustion chamber on the side opposite the intake valves. Positioning the fuel injector between the intake or exhaust valves allows for a particularly compact cylinder head design.

[0048] A further development of the invention provides that an annular collar extending into the combustion chamber extends from a valve seat of the gas exchange valve and / or from a valve seat of the further gas exchange valve, wherein a valve disc of the gas exchange valve and / or a valve disc of the further gas exchange valve is partially encompassed by the annular collar in a first position of the gas exchange valve and / or the further gas exchange valve, and is located away from the annular collar in a second position of the gas exchange valve and / or the further gas exchange valve. The gas exchange valve and the further gas exchange valve are preferably identically designed, so that the following descriptions apply to both the gas exchange valve and the further gas exchange valve.

[0049] The gas exchange valve comprises a valve disc from which a valve stem extends. The valve stem is displaceably arranged in the cylinder head of the internal combustion engine by one valve stroke. The longitudinal center axis of the gas exchange valve and a longitudinal center axis of the valve stem are preferably identical or correspond to each other. The valve stroke describes a displacement of the gas exchange valve in the axial direction with respect to its longitudinal center axis, relative to a closed position. Preferably, the gas exchange valve is in the closed position in the first position, with a valve stroke of zero. The second position of the gas exchange valve preferably corresponds to an open position, with a non-zero valve stroke.

[0050] In the closed position, the valve seat completely surrounds the valve disc in the circumferential direction. The cross-sectional area of ​​the gas exchange valve between the valve seat and the valve disc is completely closed in the closed position. Therefore, in the closed position, the gas exchange valve has a cross-sectional area of ​​zero. In the open position, however, the gas exchange valve has a non-zero cross-sectional area. To open the gas exchange valve, the valve stem is displaced axially. When a maximum valve stroke is reached, the gas exchange valve is fully open.

[0051] The valve seat features an annular collar that extends into the combustion chamber, particularly in the axial direction with respect to the longitudinal center axis of the gas exchange valve. The annular collar only partially surrounds the valve seat in the circumferential direction. In the axial direction, the annular collar has a length that is preferably less than the maximum valve stroke of the gas exchange valve. When the gas exchange valve moves from the closed position towards the open position, the flow cross-sectional area is initially at least partially obscured by the annular collar. Thus, when the gas exchange valve is only partially open, flow through the cross-sectional area in the radial direction with respect to the longitudinal center axis of the gas exchange valve is at least partially prevented. If, however, the gas exchange valve is fully open, the valve head is located away from the annular collar.

[0052] The annular collar is preferably arranged on the side of the valve seat facing away from the pre-chamber. Due to the annular collar, the flow velocity across the cross-sectional area is greater on the side of the valve seat facing the pre-chamber than on the side facing away from the pre-chamber. This, particularly when the gas exchange valve is the intake valve, promotes the "tumble" motion in the combustion chamber described above. This further improves the mixing of the mixture in the combustion chamber and further reduces the tendency to knock.

[0053] The features and combinations of features described in the description, in particular those described in the following figure description and / or shown in the figures, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention. Thus, embodiments that are not explicitly shown and explained in the description and / or the figures, but which emerge from or can be derived from the explained embodiments, are also to be considered as encompassed by the invention.

[0054] The invention is explained in more detail below with reference to the exemplary embodiments shown in the drawings, without limiting the invention. The drawings show... Fig. 1 a schematic representation of an internal combustion engine and the Fig. 2 another schematic representation of the internal combustion engine.

[0055] The Fig. Figure 1 shows a schematic representation of an internal combustion engine 1 for a motor vehicle not shown in detail. The internal combustion engine 1 has at least one piston 4 movably arranged in a cylinder 2 of the internal combustion engine 1 with respect to a longitudinal central axis 3. The piston 4, together with a cylinder wall 5 and a cylinder roof 6, encloses a combustion chamber. The cylinder wall 5 is, for example, part of a cylinder crankcase of the internal combustion engine 1, while the cylinder roof 6 is part of a cylinder head of the internal combustion engine 1.

[0056] The piston 4 has a piston bowl 7 that extends through an end face 8 of the piston and is open towards the combustion chamber, particularly towards the cylinder head 6. An ignition device 9 is arranged on the cylinder head 6, which has a pre-chamber 10 fluidically connected to the combustion chamber. In the illustration, the piston 4 is at top dead center. The volume of the piston bowl 7 is larger than the volume of the combustion chamber bounded by the end face 8 of the piston 4 at top dead center and the cylinder head 6.

[0057] The end face 8 of the piston 4 has a displacement surface 12 adjoining a piston bowl rim 11 that defines the piston bowl 7. A displacement counter-surface 13 is formed on the cylinder roof 6, opposite the displacement surface 12. The displacement surface 12 and the displacement counter-surface 13, together with the cylinder wall 5, define a displacement region of the combustion chamber that surrounds the pre-chamber 10 in an annular manner. During a compression stroke of the piston 4, the volume of the displacement region bounded by the displacement surface 12 and the displacement counter-surface 13 decreases. A mixture of fuel and fresh gas present in this displacement region is forced towards the pre-chamber 10, creating turbulent flow.

[0058] The piston bowl 7 has a piston bowl base which, viewed in longitudinal section with respect to the longitudinal center axis 3, has a convex contour with a raised section 14 formed centrally in the piston bowl 7. Adjoining the raised section 14 is a concave area 15 of the contour, which extends to the piston bowl edge 11. The piston bowl 7 is open towards the cylinder roof 6 via a vent opening.

[0059] The prechamber 10 is arranged centrally in the cylinder roof 6 with respect to the longitudinal axis 3. The prechamber is fluidically connected to the combustion chamber via at least one through-opening 16. The through-opening 16 is oriented towards the concave region 15. In the illustration shown, the piston bowl 7 has a maximum diameter in the region of the piston bowl rim 11. In an alternative embodiment (not shown in detail), the concave region 15 forms an undercut of the piston bowl rim 11, such that the diameter of the piston bowl 7 in the concave region 15 is larger than the diameter of the piston bowl rim 11.

[0060] A fuel injector 17 is arranged in the cylinder roof 6, which has at least one outlet opening 18. The fuel injector 17 serves to introduce fuel into the combustion chamber.

[0061] The Fig.Figure 2 shows a further schematic representation of the internal combustion engine 1 as a sectional view perpendicular to the longitudinal center axis 3 in the area of ​​the displacement counter-surface 13. The area of ​​the displacement counter-surface 13 is at least 15%, at least 20% or at least 25% of the area of ​​a cross-sectional area of ​​the cylinder bore of the cylinder 2 bounded by the cylinder wall 5.

[0062] On the cylinder roof 6, at least one valve seat 20 of a gas exchange valve fluidically connected to the combustion chamber is arranged on opposite sides of an imaginary plane 19 which accommodates the longitudinal center axis 3. The at least one outlet opening 18 of the fuel injector 17 is arranged in the imaginary plane 19.

[0063] In addition to the valve seat 20 of the gas exchange valve, at least one valve seat 21 of a further gas exchange valve is arranged on each of the opposite sides of the imaginary plane 19, wherein the first gas exchange valve is an inlet valve and the second gas exchange valve is an exhaust valve. The fuel injector 17 is arranged on a side of a further imaginary plane 22 facing the valve seat 20 of the inlet valve. The plane 22 contains the longitudinal center axis 3 and is arranged perpendicular to the imaginary plane 19.

[0064] A ring collar (not shown) extends from valve seat 20 and / or valve seat 21 into the combustion chamber. In a first position of the gas exchange valve or the additional gas exchange valve, the ring collar partially encompasses a valve disc of the gas exchange valve and / or a valve disc of the additional gas exchange valve, respectively. In a second position of the gas exchange valve or the additional gas exchange valve, the valve disc lies away from the ring collar. REFERENCE MARK LIST: 1 internal combustion engine 2 cylinders 3 Longitudinal center axis 4 pistons 5 cylinder wall 6-cylinder roof 7 piston bowl 8 Front surface 9 Ignition device 10 Antechamber 11 Piston bowl edge 12 Displacement area 13 Displacement counter-surface 14 Survey 15 concave areas 16 Passage opening 17 Fuel injector 18 Exit opening 19 imagined levels 20 Valve seat 21 Valve seat 22 further imaginary levels

Claims

[1] Internal combustion engine (1) for a motor vehicle, comprising at least one piston (4) movably arranged in a cylinder (2) of the internal combustion engine (1) with respect to a longitudinal central axis (3) of the cylinder (2), which together with a cylinder roof (6) and a cylinder wall (5) encloses a combustion chamber, wherein a piston bowl (7) extending through an end face (8) of the piston and open towards the combustion chamber is formed in the piston and an ignition device (9) is arranged on the cylinder roof (6), which has a pre-chamber (10) fluidically connected to the combustion chamber, wherein the end face (8) has a displacement surface (12) adjoining a piston bowl edge (11) of the piston bowl (7) and a displacement counter-surface (13) opposite the displacement surface (12) is formed on the cylinder roof (6),wherein the displacement surface (12) and the displacement counter-surface (13) together with the cylinder wall (5) define a displacement area of ​​the combustion chamber which surrounds the pre-chamber (10) in an annular manner, characterized by , that a maximum diameter of the piston bowl (7) is at most 75% of a cylinder diameter of the cylinder (2). [2] Internal combustion engine (1) according to claim 1, characterized by , that the volume of the piston bowl (7) is greater than the volume of the combustion chamber volume bounded by the front surface (8) of the piston (4) at top dead center and the cylinder roof (6). [3] Internal combustion engine (1) according to any one of the preceding claims, characterized by , that the pre-chamber (10) is arranged centrally on the cylinder roof (6) in the radial direction with respect to the longitudinal central axis (3). [4] Internal combustion engine (1) according to any one of the preceding claims, characterized by, that the piston recess (7) in longitudinal section with respect to the longitudinal central axis (3) has a curved contour with a raised area (14) formed in the center of the piston recess (7), wherein a concave area (15) extending to the edge of the piston recess (11) adjoins the raised area (14). [5] Internal combustion engine (1) according to claim 4, characterized by , that the pre-chamber (10) is fluidically connected to the combustion chamber via at least one through-opening (16), wherein the through-opening (16) is oriented in the direction of the concave area (15). [6] Internal combustion engine (1) according to claim 4 or 5, characterized by , that the concave area (15) forms an undercut of the piston bowl edge (11), such that a diameter of the piston bowl (7) in the concave area (15) is larger than a diameter of the piston bowl edge (11) [7] Internal combustion engine (1) according to any one of the preceding claims, characterized by, that on the cylinder roof (6) on opposite sides of an imaginary plane (19) receiving the longitudinal central axis (3) at least one gas exchange valve fluidically connected to the combustion chamber is arranged, wherein at least one outlet opening (18) of a fuel injector (17) for introducing fuel into the combustion chamber is arranged in the imaginary plane (19). [8] Internal combustion engine (1) according to claim 7, characterized by , that on each of the opposite sides, in addition to the gas exchange valve, there is at least one further gas exchange valve, wherein the gas exchange valve is an inlet valve and the further gas exchange valve is an outlet valve. [9] Internal combustion engine (1) according to claim 7 or 8, characterized by, that the fuel injector (17) is arranged on a side facing the inlet valve of a further imaginary plane (22) which accommodates the longitudinal central axis (3) and is arranged perpendicular to the imaginary plane (19). [10] Internal combustion engine (1) according to any one of claims 7 to 9, characterized by , that an annular collar extending into the combustion chamber extends from a valve seat (20) of the gas exchange valve and / or from a valve seat (21) of the further gas exchange valve, wherein a valve disc of the gas exchange valve and / or a valve disc of the further gas exchange valve is partially enclosed by the annular collar in a first position of the gas exchange valve and / or the further gas exchange valve and is located away from the annular collar in a second position of the gas exchange valve and / or the further gas exchange valve.

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