cylinder head

Abstract

The invention relates to a cylinder head (1) for an internal combustion engine, having a pre-chamber (2) which is arranged in the cylinder head (1) and is delimited by an inner wall surface (11) of a pre-chamber wall (5), wherein the pre-chamber (5) comprises a first chamber portion (3) and a second chamber portion (4), wherein the first chamber portion (3) has a greater maximum diameter (D) than the second chamber portion (4), wherein at least one ignition device (16) opens into the first chamber portion (3) and the second chamber portion (3) comprises at least one overflow channel (7) for the flow through into a combustion chamber (8) of an adjoining fire deck (6). Improved heat dissipation can be achieved if at least one inner wall surface (11) of the first chamber portion (3) comprises at least one first flat portion (13).

Description

Technical Field

[0001] The present invention relates to a cylinder head for an internal combustion engine, the cylinder head having a precombustion chamber, which is arranged in the cylinder head and is defined by the inner wall surface of the precombustion chamber wall, wherein the precombustion chamber includes a first chamber part and a second chamber part, wherein the first chamber part has a larger diameter than the second chamber part, wherein at least one ignition device opens into the first chamber part, and the second chamber part includes at least one overflow channel for flow through into the combustion chamber adjacent to the fireproof plate. Background Art

[0002] A common design for a pre-combustion chamber in a spark-ignition internal combustion engine is achieved by screwing a pre-combustion chamber sleeve into a hole in the cylinder head. An ignition device is screwed into the pre-combustion chamber sleeve, which closes the pre-combustion chamber at the top. The pre-combustion chamber sleeve and ignition device form the pre-combustion chamber, which is inserted or screwed into the cylinder head to position and retain the pre-combustion chamber in the combustion chamber.

[0003] JP 2018-172971 A discloses a partially integrated pre-combustion chamber, in which the chamber portion adjacent to the combustion chamber is formed by a separate component that is screwed into the cylinder head from the side of the combustion chamber. An overflow channel is formed in this separate component.

[0004] It is also known to form pre-combustion chambers without pre-combustion chamber sleeves and to integrate them directly into the cylinder head. Such pre-combustion chambers are known, for example, from DE 1 751 542 A1, US 2015 / 00220766 A1 or DE 2 308358 A.

[0005] A disadvantage of the known embodiments is that, particularly in cylinder heads with four gas exchange valves and a centrally arranged pre-combustion chamber, there are structural limitations and sufficient cooling of the pre-combustion chamber cannot always be ensured, especially when using a pre-combustion chamber sleeve. However, even in known cylinder heads with a pre-combustion chamber integrated into the cylinder head, the large wall thickness of the pre-combustion chamber and the accumulation of material between the pre-combustion chamber and the cooling jacket negatively affect heat dissipation. Summary of the Invention

[0006] The object of the present invention is to achieve improved heat dissipation in a cylinder head of the aforementioned type.

[0007] According to the invention, this is achieved in that at least one inner wall surface of the first chamber part comprises at least one first flat portion.

[0008] A flat portion is defined as an area of ​​the wall surface having a smaller curvature and / or a larger radius of curvature than adjacent wall surface areas.

[0009] Preferably, provision is made for at least one first flat portion to be arranged in the transition region to the second chamber portion.

[0010] According to one embodiment of the invention, the precombustion chamber is surrounded by a cooling jacket at least in the region of the first flat portion, wherein the precombustion chamber wall separates the cooling jacket from the precombustion chamber, and wherein at least one outer wall surface of the precombustion chamber wall has a second flat portion on the cooling jacket side in the region of at least one first flat portion.

[0011] A particularly compact design can be achieved if a plurality, preferably at least three or at least four, in particular exactly four, first and / or second flat portions are arranged, in particular evenly arranged, around the circumference of the first chamber part.

[0012] One embodiment of the present invention provides that the first chamber portion has a substantially rhombus-shaped cross-section in the region of the first flat portion. In a cross section orthogonal to the vertical axis of the pre-combustion chamber, the first chamber portion thus has a substantially rhombus-shaped shape. A rhombus is defined as a planar quadrilateral having four sides of equal length. The vertical axis of the pre-combustion chamber extends, for example, parallel to the vertical axis of the cylinder and may coincide with the vertical axis of the cylinder. In particular, the vertical axis of the pre-combustion chamber may form an axis of symmetry of the pre-combustion chamber. Thus, as viewed in a cross section about the cylinder axis and / or the vertical axis of the pre-combustion chamber, the first flat portion and / or the second flat portion may be arranged substantially in the form of a rhombus.

[0013] Preferably, it is provided that the first flat portion and / or the second flat portion substantially forms the shape of a square pyramid.

[0014] The first and second flat sections can be of flat design, ie without curvature (curvature).In other embodiment variants of the invention, provision is made for the first and / or second flat sections to have a concave or convex curvature relative to the adjacent cavity.

[0015] Preferably, the at least one first flat portion and / or the second flat portion are arranged in a region between the cylinder axis or the vertical axis of the pre-combustion chamber and the at least one gas exchange channel. As viewed in a plan view along the cylinder axis, at least one surface normal of the at least one first flat portion and / or the second flat portion may be directed through the valve center of the nearest gas exchange valve.

[0016] The at least one first flat portion and / or second flat portion is preferably provided in a region of the inner and / or outer wall surface having the smallest distance from the adjacent gas exchange channel. Thus, the lower region of the inner and / or outer wall surface of the pre-combustion chamber having the smallest wall distance from the gas exchange channel or the corresponding seat ring has a flat shape.

[0017] Thus, the distance between the pre-chamber and the cooling jacket can be reduced and more cross-sectional area can be used for the coolant flow in the cooling jacket. Since no constriction is required at the gas exchange passage, a larger flow cross-section is also available for the gas exchange, and a larger raceway can also be used. This makes it possible to maximize the heat transfer into the coolant. In this way, the ignition device and in particular the pre-chamber can be cooled as required.

[0018] The first flat portion and / or the second flat portion is preferably formed symmetrically with respect to at least one vertical plane containing the vertical axis of the pre-chamber. It is particularly advantageous if the first flat portion and / or the second flat portion is formed symmetrically with respect to a first vertical plane containing the vertical axis of the pre-chamber and with respect to a second vertical plane containing the vertical axis of the pre-chamber and positioned orthogonally to the first vertical plane, wherein each vertical plane extends between the gas exchange valves of the internal combustion engine.

[0019] The first flat portion forms a flow guide surface for the fuel / air mixture flowing from the combustion chamber into the pre-chamber in the direction of the ignition device. The symmetrical arrangement of the first flat portion with respect to the first and second vertical planes makes it possible to flow into the pre-chamber substantially without eddy currents. Rotational movement of the flow around the vertical axis of the pre-chamber is thus avoided. The flow guidance of the gas exchange movement in the pre-chamber is thus not adversely affected.

[0020] If the pre-chamber is at least partially integrated in the cylinder head, preferably the pre-chamber is completely integrated in the cylinder head, components can be saved. Thus, there are no further components between the pre-chamber and the cylinder head, the cooling jacket and / or the gas exchange passage. This leads to a great degree of design freedom.

[0021] If the cylinder head and / or the pre-chamber is produced using an additive manufacturing process, the production can be simplified. An additive manufacturing process, also known as "3D printing", is a manufacturing process in which material is applied layer by layer under computer control according to specified dimensions and shapes.

[0022] The at least one overflow passage can be produced by a drilling operation.

[0023] An embodiment variant of the present application provides that a conical or crown-shaped sealing seat is formed between the ignition device and the pre-chamber wall. The portion accommodating the ignition device and spaced apart from the lateral pre-chamber wall can form the top of the pre-chamber. The remaining portion of the pre-chamber is advantageously formed by the cylinder head.

[0024] The design according to the present application allows a great degree of design freedom in terms of the pre-chamber geometry. BRIEF DESCRIPTION OF DRAWINGS

[0025] The application is explained in greater detail below with reference to the non-limiting exemplary embodiments shown in the drawings, which schematically show:

[0026] Figure 1 Based on Figure 2 The cross-sectional view taken along line II in FIG. 1 shows a cylinder head according to the present invention;

[0027] Figure 2 Based on Figure 1 The cross-sectional view taken along line II-II in FIG. 1 shows the cylinder head;

[0028] Figures 3a to 3d are based on Figure 1 The cross-sectional view taken along line II-II in FIG. 1 shows a pre-combustion chamber of a cylinder head according to various embodiment variations of the present invention;

[0029] Figure 4 is similar to Figure 1 A cross-sectional view of FIG. 1 shows details of a pre-combustion chamber according to an embodiment variant of the present invention; and

[0030] FIG. 5 Flow curves (flow profiles) of the flow in the pre-combustion chamber during the compression stroke of an internal combustion engine. DETAILED DESCRIPTION

[0031] Figure 1 A cylinder head 1 of an internal combustion engine having at least one cylinder is shown, with a fully integrated precombustion chamber 2. The precombustion chamber 2 has a generally bottle- or pear-shaped configuration, with a barrel-shaped first chamber portion 3 and a substantially cylindrical second chamber portion 4. The precombustion chamber 2 is formed by a precombustion chamber wall 5 formed by the cylinder head 1. The upper first chamber portion 3 has a larger maximum diameter D than the lower second chamber portion 4, located in the area of ​​a fire shield 6 of the cylinder head 1. The maximum diameter of the lower second chamber portion 4 is indicated by d. The second chamber portion 4 is connected to the combustion chamber 8 of a cylinder of the internal combustion engine (not shown in greater detail) via an overflow channel 7. An ignition device 16 opens into the precombustion chamber 2 in the area of ​​a precombustion chamber cover surface 20 of the precombustion chamber 2, which closes the precombustion chamber at the top. Reference numeral 2 a denotes the vertical axis of the pre-combustion chamber, which in the exemplary embodiment coincides with the cylinder axis 1 a of the corresponding cylinder of the internal combustion engine.

[0032] According to the present invention, Figure 1 In an alternative embodiment of the partially integrated pre-combustion chamber 2 indicated by the dashed line, the second chamber part 4 can also be formed by a separate part 21 which is screwed into the cylinder head 1 from the combustion chamber 8 side. The overflow channel 7 is then provided in this separate part 21.

[0033] Figure 1 Reference symbol S in FIG. 5 represents the flow of the fuel / air mixture in the pre-combustion chamber 2 during the compression stroke. FIG. 5 also shows a detailed flow curve (flow profile, flow contour).

[0034] exist Figure 1 In the exemplary embodiment shown, the precombustion chamber 2 is surrounded in a central region 9 by a cooling jacket 10. A precombustion chamber wall 5 separates the cooling jacket 10 from the precombustion chamber 2.

[0035] The precombustion chamber wall 5 forms a lateral inner wall surface 11 facing the interior of the precombustion chamber 2 and an outer wall surface 12 facing the cooling jacket 10 .

[0036] The inner wall surface 11 has first flat portions 13 distributed around the periphery. Corresponding to the first flat portions 13, the outer wall surface 12 also has corresponding second flat portions 14. Therefore, in each case, the second flat portions 14 are provided on the coolant-side pre-combustion chamber wall 5 in the region of the first flat portions 13.

[0037] In this case, the first flat portion 13 is located in the central region 9 of the precombustion chamber 2 or in the central and / or lower region of the first chamber part 3 , in particular in the conical transition region 15 of the first chamber part 3 to the second chamber part 4 .

[0038] In the exemplary embodiment, four first flat portions 13 are evenly distributed around the periphery of the first chamber portion 3 and form a square cone. As viewed in a cross section perpendicular to the cylinder axis 1a and the pre-combustion chamber vertical axis 2a, the first flat portions 13 are arranged, for example, in the form of a rhombus. Thus, the first chamber portion has a rhombus-like cross section in the region of the first flat portions 13, as shown in FIG. Figure 2 shown.

[0039] As from Figure 2 As can be seen in the figure, similar to the first flat portion 13, the second flat portion 14 can also be arranged in a diamond shape. In this way, the distance between the pre-combustion chamber 2 and the cooling jacket 10 can be reduced or minimized. This minimizes heat transfer losses and maximizes heat transfer to the coolant. Therefore, the pre-combustion chamber 2, and specifically the ignition device 16, can be cooled as needed. The resulting compact pre-combustion chamber design further enables the optimized design of the gas exchange channels, namely the intake and exhaust channels IN and EX, and the seat ring dimensions.

[0040] Apart from Figure 2 In addition to the flat shape shown, the first flat portion and / or the second flat portion can also be formed into a convex or concave shape. FIG3 shows various possible diamond-shaped configurations of the first flat portion 13 or the second flat portion 14. For example, FIG3a shows a convex configuration of the first flat portion 13, while FIG3d shows a concave configuration of the first flat portion 13. FIG3b and FIG3c show examples of diamond-shaped first flat portions 13 with flat surfaces, while FIG3c shows a square configuration of the first flat portion 13. FIG3d shows a substantially diamond-shaped first flat portion 13 with flat surfaces.

[0041] Figure 2 Also shown schematically is the coolant flow K through the cooling jacket 10, where the coolant flow takes place from the outlet side A to the intake side E of the cylinder head 1. The coolant from the outlet side A of the cylinder head 1 flows in the direction of the cylinder center, i.e., the cylinder axis 1a, flows in the region of the exhaust valve bridge AB between the two exhaust channels EX along the second flat portion 14 of the outer wall surface 12 of the pre-combustion chamber 2, around the pre-combustion chamber 2, and further flows in the region of the intake valve bridge EB between the two intake channels IN to the intake side of the cylinder head 1.

[0042] The first flat portion 13 and / or the second flat portion 14 are provided in a region between the pre-combustion chamber vertical axis 2a and at least one gas exchange channel (ie, the intake channel IN and / or the exhaust channel EX).

[0043] As seen in plan view, at least one surface normal n of at least one first flat portion 13 and / or second flat portion 14 is directed through the valve center M of the nearest gas exchange valve V of the intake channel IN or exhaust channel EX and intersects the pre-combustion chamber vertical axis 2a.

[0044] At least the first flat portion 13 is provided in a region of the inner wall surface 11 having a minimum distance from an adjacent gas exchange passage (ie, the intake passage IN or the exhaust passage EX).

[0045] Furthermore, at least the second flat portion 14 is provided in a region of the outer wall surface 12 having a minimum distance from the adjacent gas exchange passage (ie, the intake passage IN or the exhaust passage EX).

[0046] Each first flat portion 13 and / or each second flat portion 14 is symmetrical about a first vertical plane E1 containing the pre-combustion chamber vertical axis 2a and a second vertical plane E2 containing the pre-combustion chamber axis 2a and orthogonal to the first vertical plane E1. Each vertical plane E1 extends between the gas exchange valves V of the internal combustion engine.

[0047] As shown in Figure 4, the pre-combustion chamber covering surface 20 can also be formed by a separate covering element 17 accommodating the ignition device 16. The sealing surface 18 between the separate covering element 17 and the pre-combustion chamber wall 5 can be of conical or crowned design.

[0048] FIG5 shows the flow curve (flow profile) of the fuel / air mixture flow S in the precombustion chamber 2 during the compression stroke of the internal combustion engine. The fuel / air mixture from the combustion chamber 8 flows through the overflow channel 7 and, via the second chamber portion 4, reaches the first chamber portion 3 of the precombustion chamber 2, passing through the first flat portion 13 without causing turbulence or eddies. Rotational motion about the precombustion chamber's vertical axis 2a is thus avoided. The fuel / air mixture reaches the precombustion chamber cover surface 20 essentially turbulently, where it is ignited by the ignition device 16.

Claims

1. A cylinder head (1) for an internal combustion engine, the cylinder head having a pre-combustion chamber (2), the pre-combustion chamber being arranged in the cylinder head (1) and being defined by an inner wall surface (11) of a pre-combustion chamber wall (5), wherein: The precombustion chamber (5) comprises a first chamber portion (3) and a second chamber portion (4), wherein the first chamber portion (3) has a maximum diameter (D) that is larger than the second chamber portion (4), wherein at least one ignition device (16) leads to the first chamber portion (3), and the second chamber portion (4) comprises at least one overflow channel (7) for allowing air flow to pass through into a combustion chamber (8) adjacent to the fire protection plate (6), characterized in that at least one inner wall surface (11) of the first chamber portion (3) comprises at least one first flat portion (13), wherein the precombustion chamber (2) is surrounded by a cooling jacket (10) at least in the region of the first flat portion (13), wherein the precombustion chamber wall (5) separates the cooling jacket (10) from the precombustion chamber (2), and wherein at least one outer wall surface (12) of the precombustion chamber wall (5) has a second flat portion (14) on the cooling jacket side in the region of at least one first flat portion (13).

2. The cylinder head (1) according to claim 1, characterized in that The at least one first flat portion (13) is arranged in a transition region (15) to the second chamber portion (4).

3. The cylinder head (1) according to claim 1 or 2, characterized in that A plurality of the first flat portions (13) and / or the second flat portions (14) are arranged to be distributed around the circumference of the first chamber portion (3).

4. The cylinder head (1) according to claim 1 or 2, characterized in that At least three or at least four of the first flat portions (13) and / or the second flat portions (14) are arranged to be distributed around the circumference of the first chamber portion (3).

5. The cylinder head (1) according to claim 1 or 2, characterized in that The first flat portion (13) and / or the second flat portion (14) are arranged to be evenly distributed around the circumference of the first chamber portion (3).

6. The cylinder head (1) according to claim 1 or 2, characterized in that The first chamber portion (3) has a substantially rhombus-shaped cross section in the region of the first flat portion (13).

7. The cylinder head (1) according to claim 1 or 2, characterized in that Each of said first flat portions (13) is associated with a second flat portion (14).

8. The cylinder head (1) according to claim 1 or 2, characterized in that As viewed in a cross section perpendicular to the cylinder axis (1a) and / or the pre-combustion chamber vertical axis (2a) of the pre-combustion chamber (2), the first flat portion (13) and / or the second flat portion (14) are substantially arranged in a rhombus form.

9. The cylinder head (1) according to claim 1 or 2, characterized in that The first flat portion (13) and / or the second flat portion (14) are substantially in the form of a square pyramid.

10. The cylinder head (1) according to claim 1 or 2, characterized in that At least one first flat portion (13) and / or second flat portion (14) has a flat, convex or concave design.

11. The cylinder head (1) according to claim 1 or 2, characterized in that At least one first flat portion (13) and / or a second flat portion (14) is provided in a region between a vertical axis (2a) of the pre-combustion chamber and at least one inlet passage (IN) or exhaust passage (EX).

12. The cylinder head (1) according to claim 1 or 2, characterized in that As viewed in plan, at least one surface normal (n) of at least one first flat portion (13) and / or second flat portion (14) is directed through a valve center (M) of the closest gas exchange valve (V).

13. The cylinder head (1) according to claim 1 or 2, characterized in that At least one first flat portion (13) is provided in a region of the inner wall surface (11) where the distance to an adjacent intake passage (IN) or exhaust passage (EX) is minimum.

14. The cylinder head (1) according to claim 1 or 2, characterized in that At least one second flat portion (14) is provided in a region of the outer wall surface (12) where the distance to an adjacent intake passage (IN) or exhaust passage (EX) is minimum.

15. The cylinder head (1) according to claim 1 or 2, characterized in that At least two first flat portions (13) and / or at least two second flat portions (14) are formed symmetrically with respect to at least one vertical plane (E1, E2) containing a vertical axis (2a) of the pre-combustion chamber.

16. The cylinder head (1) according to claim 1 or 2, characterized in that The first flat portion (13) and / or the second flat portion (14) are formed symmetrically with respect to a first vertical plane (E1) containing the vertical axis (2a) of the pre-combustion chamber and with respect to a second vertical plane (E2) containing the vertical axis (2a) of the pre-combustion chamber and positioned orthogonal to the first vertical plane (E1), wherein the vertical planes (E1, E2) extend between the gas exchange valves (V) of the internal combustion engine.

17. The cylinder head (1) according to claim 1 or 2, characterized in that The pre-combustion chamber (2) is at least partially integrated into the cylinder head (1).

18. The cylinder head (1) according to claim 1 or 2, characterized in that The pre-combustion chamber (2) is completely integrated into the cylinder head (1).

19. The cylinder head (1) according to claim 1 or 2, characterized in that The pre-combustion chamber (2) is closed by a separate covering element (17) accommodating the ignition device (16), wherein a conical or crown-shaped sealing surface (18) is formed between the covering element (17) and the pre-combustion chamber wall (5).

20. The cylinder head (1) according to claim 1 or 2, characterized in that The cylinder head (1) and / or the pre-combustion chamber (2) are manufactured using an additive manufacturing process.

21. The cylinder head (1) according to claim 1 or 2, characterized in that At least one overflow channel (7) is formed by drilling.

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