Internal combustion engine

Abstract

An internal combustion engine for a motor vehicle has at least one cylinder, a cylinder head, and a piston which is movably mounted in the cylinder and has a combustion chamber side which delimits a combustion chamber with the cylinder head and the cylinder. The cylinder head has a combustion chamber roof, in which at least two valve seats for at least one inlet valve and at least one outlet valve are provided. The combustion chamber roof has at least one arched cylinder head section which is arranged between the at least two valve seats and points away from the combustion chamber.

Claims

1. An internal combustion engine for a motor vehicle, comprising: at least one cylinder; a cylinder head; a piston which is mounted movably in the cylinder and has a combustion chamber side which delimits a combustion chamber with the cylinder head and the cylinder, wherein the cylinder head has a combustion chamber roof, in which at least two valve seats for at least one inlet valve and at least one outlet valve are provided, the combustion chamber roof has at least one domed cylinder head section which is arranged between the at least two valve seats and points away from the combustion chamber, the cylinder head has squish faces in a form of circular face sections merely on two edge sections which lie opposite one another, said squish faces are delimited in each case by way of one of two straight line transitions in the cylinder head which run parallel to one another, the two squish faces having a different area size, the squish faces are assigned to an inlet side and an outlet side of the cylinder head, the squish face which is assigned to the inlet side has a greater area than the squish face which is assigned to the outlet side, and an active region of the combustion chamber roof is comprised of a first face, a second face, and a third face, wherein the first face and the third face are rounded with respect to one another at a transition between the first face and the third face and wherein the second face and the third face are rounded with respect to one another at a transition between the second face and the third face such that the combustion chamber roof has an edge-free configuration without sharp edges in the active region.

2. The internal combustion engine according to claim 1, wherein the combustion chamber roof is an exclusively machined combustion chamber roof.

3. The internal combustion engine according to claim 1, wherein the piston has a depression which is lenticular and is rotationally symmetrical with respect to a piston axis, a diameter of the depression being less than an overall diameter of the piston.

4. The internal combustion engine according to claim 3, wherein at a center point, the depression has a depth of between 0.2 mm and 10 mm.

5. The internal combustion engine according to claim 3, wherein at a center point, the depression has a depth of between 0.5 mm and 8 mm.

6. The internal combustion engine according to claim 3, wherein the depression encloses a spherical volume together with the combustion chamber roof.

7. The internal combustion engine according to claim 3, wherein the depression encloses a spherical volume together with the active region of the combustion chamber roof.

8. The internal combustion engine according to claim 1, further comprising: a masking arranged parallel to the valve axis of the inlet valve in the combustion chamber roof next to a valve seat, which masking has a height of between 2 mm and 3.5 mm.

9. The internal combustion engine according to claim 1, wherein two domed cylinder head sections are provided which are arranged in each case between two valve seats which are assigned to an inlet valve and an outlet valve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 diagrammatically shows an internal combustion engine according to an embodiment of the invention.

(2) FIG. 2 shows a combustion chamber volume of an internal combustion engine according to an embodiment of the invention.

(3) FIG. 3 shows a piston of an internal combustion engine according to an embodiment of the invention in a sectional view.

(4) FIG. 4 shows the piston from FIG. 3 in a perspective view.

(5) FIG. 5 shows the combustion chamber of an internal combustion engine in a plan view, the piston which is assigned to the combustion chamber being shown in a transparent manner.

DETAILED DESCRIPTION OF THE DRAWINGS

(6) FIG. 1 diagrammatically shows an internal combustion engine 10 having a cylinder 12, a cylinder head 14 and a piston 16 which is mounted movably in the cylinder 12.

(7) The piston 16 has a combustion chamber side 18 which delimits a combustion chamber 20 of the internal combustion engine 10 together with the cylinder head 14 and the cylinder 12, the cylinder head 14 having a combustion chamber roof 21 which is directed toward the combustion chamber 20. Valve seats 22, 24 for at least one inlet valve 26 and outlet valve 28 and a spark plug 30 are arranged in the cylinder head 14, in particular in the combustion chamber roof 21. The spark plug 30 is arranged eccentrically, in particular.

(8) The elements which are shown diagrammatically in FIG. 1 are described in detail in the following figures.

(9) The general method of operation of internal combustion engines is sufficiently known from the prior art; therefore, this is not described in further detail at this point, since the geometry of the cylinder head 14 is important in the following, in particular the geometry of that side of the cylinder head 14 which is directed toward the combustion chamber 20.

(10) FIG. 2 shows a combustion chamber volume 31 of an internal combustion engine 10 in a state in which the piston 16 is situated at the top maximum point. The combustion chamber volume 31 is delimited by way of the cylinder head 14, in particular its combustion chamber roof 21, together with the cylinder 12 and the piston 16.

(11) Therefore, FIG. 2 shows essentially a negative image of the cylinder head 14, in particular its combustion chamber roof 21, and the piston 16.

(12) In a plan view, the cylinder head 14, in particular the combustion chamber roof 21, has a round external geometry and has substantially five faces 32, 34, 36, 38, 40 which are angled away with respect to one another. The faces 38, 40 and 36, 40 are in each case rounded with respect to one another, in order to avoid sharp edges in an active region 41 of the combustion chamber roof 21 at the corresponding transitions of the faces 36-40. The active region 41 of the combustion chamber roof 21 preferably comprises, inter alia, the faces 36, 38, 40.

(13) The faces 32, 34 which are arranged laterally on the cylinder head 14 are in each case a squish face. The shape of the squish faces 32, 34 corresponds to the shape of a circular section, the squish faces 32, 34 being delimited (radially) to the inside in each case by way of one of two transitions 42, 44 which run parallel to one another, whereas the outer edge of a cylinder liner delimits the squish faces 32, 34 (radially) to the outside. Accordingly, the two squish faces 32, 34 are arranged in opposite edge sections of the cylinder head 14.

(14) The transitions 42, 44 are provided in each case between the squish faces 32, 34 and the adjoining faces 36, 38 which, starting from the squish faces 32, 34, extend to the center point of the cylinder head 14 and are part of the active region 41. The transitions 42, 44 are at a different spacing from the center point of the cylinder head 14.

(15) In the embodiment which is shown, the squish face 32 which is assigned to the inlet side (that is to say, the inlet valves 26) is greater in terms of area than the squish face 34 which is assigned to the outlet side, that is to say the squish face 34 which is assigned to the outlet valves 28.

(16) Domed sections 46, 47 are arranged in each case in the cylinder head 14 between the valve seats 22, 24, in particular between in each case a valve seat 22 for an inlet valve 26 and a valve seat 24 for an outlet valve 28. The domed sections 46, 47 are likewise part of the active region 41 of the combustion chamber roof 21, said sections 46, 47 being domed in such a way that their curvature points away from the combustion chamber 20.

(17) As a result of the domed sections 46, 47, in particular their curvature, the combustion chamber roof 21 can have a substantially hemispherical geometry. By way of this, a flame propagation in the combustion chamber 20 is aided, which in turn leads to a thermodynamically optimum combustion, as will still be described in the following text.

(18) The cylinder head 14, in particular the combustion chamber roof 21, has a total of four valve seats 22, 24 for two inlet valves 26 and two outlet valves 28. A masking 48 is arranged in each case parallel to the valve axis in the combustion chamber roof 21 in a manner which adjoins the valve seat 22 of the inlet valves 26, which masking 48 has a height of between 2 mm and 3.5 mm. The masking 48 ensures a high tumble movement of the mixture which flows in via the inlet valves 26, which leads to an increase in the turbulent kinetic energy of the mixture and therefore to an increased burning speed and an optimized flame propagation.

(19) FIG. 3 shows a piston 16 in a sectional view, which piston 16 has been produced, for example, in a high pressure die casting process.

(20) A depression 50 which is rotationally symmetrical and lenticular is made on the combustion chamber side 18 of the piston 16, which combustion chamber side 18 delimits the combustion chamber 20 of the internal combustion engine 10 together with the cylinder 12 and the cylinder head 14, in particular the combustion chamber roof 21. The depression 50 has a bottom face 52 and a height h of between 0.5 mm and 8 mm. The depression 50 of the piston 16 is of rotationally symmetrical configuration with regard to a longitudinal axis 54.

(21) The curvature of the depression 50 corresponds, for example, substantially to the curvature of the domed sections 46, 47 of the cylinder head 14, said curvature being oriented in an opposed manner. As a result, the combustion chamber 20 can be configured to be as symmetrical as possible. As a result of the interplay of the active region 41, in particular of the curved sections 46, 47 and the lenticular depression 50, the combustion chamber 20 is approximately spherical, which is optimum with regard to the combustion.

(22) The tumble which is generated during the inflow of the mixture is assisted and maintained on account of said geometry of the combustion chamber 20.

(23) The diameter d of the depression 50 is smaller than the overall diameter D of the piston 16, as a result of which a circumferential web 56 is formed which surrounds the depression 50 radially. A part of the circumferential web 56 forms piston squish faces 58, 60 of the piston 16 which will be described in greater detail in conjunction with FIG. 4. The overall diameter D of the piston 16 corresponds approximately to the internal diameter of the cylinder 12.

(24) In general, the compression ratio of the internal combustion engine 10 can be set (additionally) via the depth of the depression 50, as long as the mechanical boundary conditions and/or limits are taken into consideration, for example with regard to the stability of the piston 16.

(25) FIG. 4 shows the piston 16 in a perspective view. It is apparent from this view that, in addition to the depression 50 which can already be seen in FIG. 3, the piston 16 has cutouts 62 which are configured as valve seat pockets. The cutouts 62 serve as a mechanical securing elements 64, in order to avoid a collision of the valves 26, 28 with the piston 16.

(26) FIG. 5 shows the combustion chamber 20, in particular the combustion chamber volume 21 in a plan view, the piston 16 being shown in a transparent manner.

(27) The piston squish faces 58, 60 are oriented on that squish face 34 of the cylinder head 14 which is assigned to the outlet side; in particular, the piston squish faces 58, 60 overlap the squish faces 32, 34 of the cylinder head 14 at least partially. In one alternative embodiment, the piston squish faces 58, 60 can be smaller in area terms than the squish faces 32, 24 of the cylinder head 14.

(28) As has already been described, both the generated tumble and the turbulent kinetic energy of the mixture which is sucked in are maintained for as long as possible on account of the geometry of the combustion chamber 20, as a result of which a high burning speed can be achieved, with the result that an initial flame which emanates from the spark plug 30 can propagate rapidly in the mixture. As a result, the efficiency of the internal combustion engine 10 rises correspondingly.

(29) The geometry necessary for this purpose of the combustion chamber 20 is achieved, inter alia, by way of the active region 41 of the combustion chamber roof 21, which active region 41 is of substantially edge-free configuration and interacts with the depression 50 in the piston 16.

(30) In order to configure the combustion chamber roof 21 in this way, it is (exclusively) machined.

(31) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.