INTERNAL COMBUSTION ENGINE

Description

[0001] The present invention relates to an internal combustion engine for a motor vehicle.

[0002] An internal combustion engine typically has at least one cylinder, a cylinder head, and a piston that is movably mounted within the cylinder. These elements together define a combustion chamber of the internal combustion engine, in which a mixture consisting of at least air and fuel is burned.

[0003] During combustion, the piston moves up and down between top dead center and bottom dead center. As the piston moves upwards, particularly towards the cylinder head, the mixture in the combustion chamber is compressed. When the piston reaches top dead center, a spark plug located in the cylinder head ignites the mixture by creating an initial flame.

[0004] To achieve the fastest and most efficient combustion of the mixture, it is advantageous for the mixture to have the highest possible turbulent kinetic energy (TKE). The turbulent kinetic energy results from the flow behavior of the mixture and is significantly influenced by the geometry of the combustion chamber.

[0005] WO 2016 / 070291 A1 describes a combustion chamber geometry in which bulges are provided in a combustion chamber roof, extending into an area between an intake valve seat and an exhaust valve seat.

[0006] JP 2001059422 A discloses an internal combustion engine wherein a combustion chamber roof of a combustion chamber is provided with squish surfaces.

[0007] DE 10 2014 009 993 A1 describes a component for an internal combustion engine which is reinforced by a high-strength material applied by means of laser welding.

[0008] EP 3 617 473 A1 discloses a geometry of a combustion chamber for an engine, which is bounded by a bottom surface of a piston and a combustion chamber roof, wherein squish surfaces are provided in the combustion chamber roof.

[0009] US 6,502,540 B1 also describes a combustion chamber geometry for an engine, in which parabolically curved areas are provided in a combustion chamber roof.

[0010] It is therefore an object of the present invention to provide an internal combustion engine for a motor vehicle with an optimized combustion chamber.

[0011] This problem is solved according to the invention by an internal combustion engine for a motor vehicle, with at least one cylinder, a cylinder head and a piston movably mounted in the cylinder, which has a combustion chamber side that, together with the cylinder head and the cylinder, defines a combustion chamber, wherein the cylinder head has a combustion chamber roof in which at least two valve seats for at least one intake valve and at least one exhaust valve are provided, and wherein the combustion chamber roof has two curved cylinder head sections arranged between each valve seat for an intake valve and a valve seat for an exhaust valve, directed away from the combustion chamber.The cylinder head has squish areas in the form of circular area segments only on two opposing edge sections, wherein the squish areas are each bounded by one of two parallel transitions in the cylinder head, and wherein the squish areas are assigned to an intake side and an exhaust side of the cylinder head, wherein the squish area assigned to the intake side has a larger area than the squish area assigned to the exhaust side.

[0012] The curved cylinder head sections, directed away from the combustion chamber, allow the combustion chamber roof to have an almost hemispherical geometry. This results in a particularly advantageous combustion chamber geometry on the cylinder head side. Consequently, the flow behavior of the mixture during the intake process can be favorably influenced.

[0013] In particular, this results in a combustion chamber shape that is especially favorable with regard to the combustion process, namely a spherical shape. The two curved cylinder head sections are thus both located between the intake and exhaust sides of the cylinder head, so that they both contribute approximately equally to improving the flow characteristics.

[0014] According to one embodiment, an active area of ​​the combustion chamber roof is largely free of edges. This active area is the region that essentially comprises the hemispherical geometry of the combustion chamber roof. The edgeless design of the combustion chamber roof ensures that the tumble flow of the mixture is not disturbed. The turbulent kinetic energy of the air-fuel mixture can thus be generated and optimally maintained during compression.

[0015] The high turbulent kinetic energy allows for a high combustion velocity, enabling an initial flame to propagate particularly quickly through the mixture. This high combustion velocity also ensures that the mixture in the combustion chamber is burned as completely as possible during a combustion cycle, leaving virtually no unburned fuel.

[0016] Overall, the combustion engine according to the invention achieves a particularly good thermodynamic efficiency and reduced fuel consumption.

[0017] The combustion chamber roof is preferably manufactured entirely by machining. This improves the reproducibility of the combustion chamber roof, as machining is subject to lower manufacturing tolerances than a casting process. In particular, this allows the largely edge-free active area, which in turn results in the hemispherical geometry, to be produced with low variation.

[0018] The piston preferably has a recess that is rotationally symmetrical about a piston axis, particularly a lens-shaped one, wherein the diameter of the recess is smaller than the overall diameter of the piston. The recess allows for optimal flow development to generate tumble motion in the combustion chamber (even during inflow). In this respect, the recess helps maintain turbulent kinetic energy at the time of combustion. The recess, like the combustion chamber roof, also influences the combustion chamber and thus the compression ratio of the internal combustion engine.

[0019] The piston's recess preferably has a depth at its center of between 0.2 mm and 10 mm, particularly between 0.5 mm and 8 mm. This depth has proven especially advantageous with regard to charge motion and flame propagation. The depth of the recess is usually determined in combination with the combustion chamber roof according to a predetermined compression ratio of the internal combustion engine. The compression ratio corresponds to the ratio of the total combustion chamber volume before compression, when the piston is at bottom dead center, to the remaining volume after compression, when the piston is at top dead center.

[0020] The projected area of ​​the recess preferably covers 70% to 80% of the piston's surface area on the front face, i.e., the combustion chamber side. This geometry ensures a correspondingly high surface area of ​​the recess and its influence on the entire combustion chamber.

[0021] The recess, together with the combustion chamber roof, and especially with the active area of ​​the combustion chamber roof, can enclose an almost spherical volume that serves as the combustion chamber. This promotes flame propagation within the combustion chamber, resulting in particularly efficient combustion.

[0022] The spark plug is preferably positioned off-center in the cylinder head. This is due to the design of the combustion chamber, in particular the arrangement of valves in the cylinder head and the placement of an injector. When air or a mixture comprising at least air and fuel flows into the combustion chamber via an intake valve, it is typically accelerated towards the exhaust side of the combustion chamber.

[0023] A low flow velocity in the area of ​​the spark plug is advantageous because an initial flame can propagate particularly well at a low flow velocity. If the flow velocity is too high, the spark can be blown away and the corresponding flame extinguished, resulting in insufficient or no ignition of the mixture, which negatively affects the efficiency of the combustion process.

[0024] The piston preferably has piston squish surfaces on its combustion chamber side corresponding to the cylinder head. In particular, the piston has two piston squish surfaces that are radially opposite each other with respect to a longitudinal axis of the piston. In an alternative embodiment, the piston squish surfaces can be smaller than the squish surfaces of the cylinder head. This corresponds to an increased diameter of the recess.

[0025] The piston squish surfaces are preferably semicircular, in particular segmental or arc-shaped.

[0026] The piston squish area associated with the exhaust side of the cylinder head is approximately the same size as the corresponding squish area of ​​the cylinder head. The piston squish area associated with the intake side of the cylinder head can be smaller than the corresponding squish area of ​​the cylinder head.

[0027] Preferably, a masking element with a height of between 2 mm and 3.5 mm is arranged in the combustion chamber roof next to a valve seat, parallel to the valve axis of the intake valve. This masking element ensures that, particularly at small valve lifts, the intake valves are bypassed, resulting in a tumble motion of the mixture. This tumble motion increases the turbulence level.

[0028] The piston preferably has at least two recesses on its combustion chamber side, designed as valve pockets. The valve pockets serve as a mechanical safeguard to prevent a collision between the valve and the piston.

[0029] Further features and advantages of the invention will become apparent from the following description and from the following drawings, to which reference is made. The drawings show: Figure 1 schematically a combustion engine according to the invention, Figure 2a combustion chamber volume of an internal combustion engine according to the invention, Figure 3 a piston of an internal combustion engine according to the invention in a sectional view, Figure 4 the piston Figure 3 in a perspective view, and Figure 5 the combustion chamber of an internal combustion engine according to the invention in a top view, wherein the piston associated with the combustion chamber is shown transparently.

[0030] Figure 1 The figure schematically shows an internal combustion engine 10 with a cylinder 12, a cylinder head 14 and a piston 16 movably mounted in the cylinder 12.

[0031] The piston 16 has a combustion chamber side 18 which, together with the cylinder head 14 and the cylinder 12, defines a combustion chamber 20 of the internal combustion engine 10, the cylinder head 14 having a combustion chamber roof 21 facing the combustion chamber 20. Valve seats 22, 24 for at least one intake valve 26 and exhaust valve 28, respectively, as well as a spark plug 30, are arranged in the cylinder head 14, particularly in the combustion chamber roof 21. The spark plug 30 is arranged, in particular, off-center.

[0032] The in Figure 1 The schematically represented elements are explained in detail in the following figures.

[0033] The general operating principle of internal combustion engines is sufficiently known from the prior art, therefore it will not be discussed further here, since the geometry of the cylinder head 14 is of particular importance, especially the geometry of the side of the cylinder head 14 facing the combustion chamber 20.

[0034] Figure 2 Figure 1 shows a combustion chamber volume 31 of an internal combustion engine 10 according to the invention in a state in which the piston 16 is located at its upper maximum point. The combustion chamber volume 31 is limited by the cylinder head 14, in particular its combustion chamber roof 21, together with the cylinder 12 and the piston 16.

[0035] Thus, it shows Figure 2 essentially a negative impression of the cylinder head 14, in particular its combustion chamber roof 21, and of the piston 16.

[0036] The cylinder head 14, in particular the combustion chamber roof 21, has a round outer geometry in a top view and essentially comprises five surfaces 32, 34, 36, 38, 40 angled relative to each other. Surfaces 38, 40 and 36, 40 are each rounded relative to each other to avoid sharp edges in an active area 41 of the combustion chamber roof 21 at the corresponding transitions of surfaces 36-40. The active area 41 of the combustion chamber roof 21 preferably includes, among other things, surfaces 36, 38, 40.

[0037] The surfaces 32, 34 arranged laterally on the cylinder head 14 are each a squash surface. The shape of the squash surfaces 32, 34 corresponds to the shape of a circular segment, with each squash surface 32, 34 being bounded (radially) inwards by one of two parallel transitions 42, 44, whereas the outer edge of a cylinder bore bounds the squash surfaces 32, 34 (radially) outwards. The two squash surfaces 32, 34 are therefore arranged in opposite edge segments of the cylinder head 14.

[0038] Transitions 42 and 44 are located between the squish surfaces 32 and 34 and the adjacent surfaces 36 and 38, which extend from the squish surfaces 32 and 34 to the center of the cylinder head 14 and are part of the active area 41. Transitions 42 and 44 are at different distances from the center of the cylinder head 14.

[0039] In the embodiment shown, the squish area 32 assigned to the inlet side, i.e. the inlet valves 26, is larger in area than the squish area 34 assigned to the outlet side, i.e. the squish area 34 assigned to the outlet valves 28.

[0040] Between the valve seats 22, 24, in particular between each valve seat 22 for an intake valve 26 and each valve seat 24 for an exhaust valve 28, convex sections 46, 47 are arranged in the cylinder head 14. The convex sections 46, 47 are also part of the active area 41 of the combustion chamber roof 21, and are convex such that their curvature points away from the combustion chamber 20.

[0041] The curved sections 46 and 47, and in particular their curvature, allow the combustion chamber roof 21 to have a substantially hemispherical geometry. This promotes flame propagation in the combustion chamber 20, which in turn leads to thermodynamically optimal combustion, as will be explained below.

[0042] The cylinder head 14, in particular the combustion chamber roof 21, has a total of four valve seats 22, 24 for two intake valves 26 and two exhaust valves 28. Adjacent to the valve seat 22 of each intake valve 26 in the combustion chamber roof 21, a masking element 48 is arranged parallel to the valve axis, with a height between 2 mm and 3.5 mm. The masking element 48 ensures a high tumble motion of the mixture flowing in through the intake valves 26, which leads to an increase in the turbulent kinetic energy of the mixture and thus to an increased combustion velocity and optimized flame propagation.

[0043] Figure 3 shows a piston 16 in a sectional view, which has been manufactured, for example, using a die-casting process.

[0044] A recess 50, rotationally symmetrical and lenticular in shape, is provided on the combustion chamber side 18 of the piston 16, which together with the cylinder 12 and the cylinder head 14, in particular the combustion chamber roof 21, defines the combustion chamber 20 of the internal combustion engine 10. The recess 50 has a bottom surface 52 and a height h between 0.5 mm and 8 mm. The recess 50 of the piston 16 is rotationally symmetrical with respect to a longitudinal axis 54.

[0045] The curvature of the recess 50, for example, essentially corresponds to the curvature of the curved sections 46, 47 of the cylinder head 14, although it is oriented in the opposite direction. This allows the combustion chamber 20 to be as symmetrical as possible. Through the interaction of the active area 41, in particular the curved sections 46, 47 and the lens-shaped recess 50, the combustion chamber 20 is approximately spherical, which is optimal for combustion.

[0046] The tumble generated during the inflow of the mixture is supported and maintained due to this geometry of the combustion chamber 20.

[0047] The diameter d of the recess 50 is smaller than the overall diameter D of the piston 16, thus forming a circumferential rib 56 that radially surrounds the recess 50. Part of the circumferential rib 56 forms piston squish surfaces 58, 60 of the piston 16, which in conjunction with Figure 4This will be described in more detail. The overall diameter D of the piston 16 corresponds approximately to the inner diameter of the cylinder 12.

[0048] In general, the compression ratio of the internal combustion engine 10 can (additionally) be adjusted via the depth of the recess 50, provided that the mechanical boundary conditions or limitations are taken into account, for example with regard to the stability of the piston 16.

[0049] Figure 4 Figure 16 shows piston 16 in a perspective view. This view shows that piston 16, in addition to the one in Figure 16, also has a perspective view. Figure 3 The already discernible depression 50 has recesses 62 formed as valve pockets. The recesses 62 serve as a mechanical safeguard 64 to prevent a collision of the valves 26, 28 with the piston 16.

[0050] Figure 5 shows the combustion chamber 20, in particular the combustion chamber volume 21 in a top view, with the piston 16 shown transparently.

[0051] The piston squish surfaces 58, 60 are aligned with the squish surface 34 of the cylinder head 14 associated with the exhaust side; in particular, the piston squish surfaces 58, 60 at least partially overlap the squish surfaces 32, 34 of the cylinder head 14. In an alternative embodiment, the piston squish surfaces 58, 60 can be smaller in area than the squish surfaces 32, 24 of the cylinder head 14.

[0052] As already explained, the geometry of the combustion chamber 20 ensures that both the generated tumble and the turbulent kinetic energy of the intake mixture are maintained for as long as possible, thus enabling a high combustion speed to be achieved. This allows an initial flame originating from the spark plug 30 to propagate quickly through the mixture. This, in turn, increases the efficiency of the combustion engine 10.

[0053] The necessary geometry of the combustion chamber 20 is achieved, among other things, by the essentially edgeless active area 41 of the combustion chamber roof 21, which interacts with the recess 50 in the piston 16.

[0054] To form the combustion chamber roof 21 in this way, it is machined (exclusively) by machining.

Claims

1. Internal combustion engine (10) for a motor vehicle, having at least one cylinder (12), a cylinder head (14) and a piston (16) which is mounted movably in the cylinder (12) and has a combustion chamber side (18) which delimits a combustion chamber (20) with the cylinder head (14) and the cylinder (12), the cylinder head (14) having a combustion chamber roof (21), in which at least two valve seats (22, 24) for at least one inlet valve (26) and at least one outlet valve (28) are provided, and the combustion chamber roof (21) having two domed cylinder head sections (46, 47) which are arranged between in each case a valve seat (22) for an inlet valve (26) and a valve seat (24) for an outlet valve (28) and are directed away from the combustion chamber (20), the cylinder head (14) having squish faces (32, 34) in the form of circular face sections merely on two edge sections which lie opposite one another, characterized in that the squish faces are delimited in each case by way of one of two transitions (42, 44) in the cylinder head (14) which run parallel to one another, the squish faces (32, 34) being assigned to an inlet side and an outlet side of the cylinder head (14), the squish face (32) which is assigned to the inlet side having a greater area than the squish face (34) which is assigned to the outlet side.

2. Internal combustion engine (10) according to Claim 1, characterized in that an active region (41) of the combustion chamber roof (21) is of substantially edge-free configuration.

3. Internal combustion engine (10) according to either of the preceding claims, characterized in that the combustion chamber roof (21) has been produced completely by machining.

4. Internal combustion engine (10) according to any one of the preceding claims, characterized in that the piston (16) has a depression (50) which is, in particular, lenticular and is rotationally symmetrical with respect to a piston axis (54), a diameter (d) of the depression (50) being smaller than an overall diameter (D) of the piston (16).

5. Internal combustion engine (10) according to Claim 4, characterized in that, at its centre point, the depression (50) has a depth of between 0.2 mm and 10 mm, in particular of between 0.5 mm and 8 mm.

6. Internal combustion engine (10) according to either of Claims 4 and 5, characterized in that the depression (50) encloses an approximately spherical volume together with the combustion chamber roof (21), in particular with the active region (41) of the combustion chamber roof (21) .

7. Internal combustion engine (10) according to any one of the preceding claims, characterized in that a masking (48) is arranged parallel to the valve axis of the inlet valve (26) in the combustion chamber roof (21) next to a valve seat (22), which masking (48) has a height of between 2 mm and 3.5 mm.

8. Internal combustion engine (10) according to any one of the preceding claims, characterized in that two domed cylinder head sections (46, 47) are provided which are arranged in each case between two valve seats (22, 24) which are assigned to an inlet valve (26) and an outlet valve (28).