Prechamber spark plug and combustion chamber with prechamber spark plug

Abstract

The invention relates to a prechamber spark plug (1) having a housing (2) and a cap (80) arranged at the end of the housing (2) on the combustion chamber side, which together with the housing (2) forms a prechamber (81) and has at least one bore (30), an insulator (3) arranged inside the housing (2), a center electrode (4) arranged inside the insulator (3), and a ground electrode (5), wherein the ground electrode (5) and the center electrode (4) together form an ignition gap, characterized in that the cap has an outer geometry which is not rotationally symmetrical. In this arrangement, the cap has an outer geometry which is not rotationally symmetrical and / or the outer geometry of the cap (80) has at least one structural element (77) which makes the inflow of gas through the bore (30) into the prechamber (81) and / or the outflow of gas through the bore (30) from the prechamber (81) easier.

Description

Background Technology

[0001] The present invention is based on a pre-combustion chamber spark plug as described in the preamble of claim 1, as is known in principle, for example, from DE102017221517 A1. Summary of the Invention

[0002] This invention is based on the understanding that the cap of such a pre-combustion chamber spark plug, when used as intended, interacts strongly with the fuel-air mixture and its flow in the combustion chamber. In particular, it has been recognized that the external geometry of the cap can react to combustion within the engine, or that combustion within the engine can be optimized by designing the external geometry of the cap when using a pre-combustion chamber spark plug.

[0003] This related relationship can be based on the fact that the cap is designed to facilitate the flow of gas through the borehole into the pre-combustion chamber and / or the flow of gas through the borehole out of the pre-combustion chamber. Therefore, the ignition of the air-fuel mixture in the pre-combustion chamber, and subsequently in the combustion chamber, can be improved in terms of dynamics and efficiency by the ignition beam ejected from the pre-combustion chamber.

[0004] Therefore, according to the first aspect of the present invention, the spark plug cap has an external geometry without rotational symmetry. Thus, there is no axis of rotation and no N from {2, 3, 4, etc.}, such that the cap, including the bore introduced therein, transforms into itself when rotated 360° / N about this axis.

[0005] This breakthrough in overcoming all rotational symmetry provides degrees of freedom to optimize the external geometry of the cap in relation to dynamic flow conditions in the combustion chamber, which are not typically rotationally symmetric.

[0006] Furthermore, the present invention proposes a novel structural element according to the second embodiment, and the advantages described can be achieved by arranging the structural element on the outer side of the cap.

[0007] These structural elements are particularly the "spoiler" in the borehole region. Within the scope of this invention, the borehole region can be understood as a region defined by a circumference surrounding the borehole, the radius of which is equal to four times the radius of the borehole's opening on the outer surface of the cap. In modified embodiments, the region can be selected even smaller, for example, by using three times or two times the radius of the borehole's opening on the outer surface of the cap.

[0008] The structural elements, especially the following structural elements or flow guides, or combinations of these structural elements or flow guides, are: impact surface, flow divider edge, concave region, convex region.

[0009] The impact surfaces are characterized in that they are arranged in the area of ​​the borehole and at an angle relative to the borehole axis, said angle being less than 90°, and especially even less than 75°.

[0010] The impact surface can be directly adjacent to the borehole.

[0011] In the context of a combustion chamber, such as during the compression stroke, a flow direction dominates in the cap region, and an impact surface can be positioned downstream of the borehole to generate dynamic pressure that causes the flow to deflect into the borehole.

[0012] The shunt edge can be a sharp edge, having, for example, an edge radius of less than 150 μm, especially even less than 100 μm. The shunt edge can define the boundary of the impact surface and / or concave region, particularly defining the boundary of the impact surface and / or concave region on the side opposite to the borehole to which it is assigned if necessary.

[0013] The convex and concave regions are characterized in that their surface curvature radii are no greater than twice the radius of the borehole on the outer surface of the cap.

[0014] The convex and concave regions can be directly adjacent to the borehole.

[0015] In the context of a combustion chamber, such as during the compression stroke, a flow direction dominates in the cap region, and a concave region can be arranged downstream of the borehole to generate dynamic pressure that causes the flow to turn toward the borehole.

[0016] In the context of a combustion chamber, such as during the compression stroke, a flow direction dominates in the cap region, and a convex region can be arranged upstream of the borehole. The negative pressure formed on the leeward side of the convex region can also help to divert the flow toward the borehole. Attached Figure Description

[0017] Figure 1 A schematic cross-sectional view of a pre-combustion chamber spark plug, which is known per se, is shown;

[0018] Figure 2 A schematic cross-section of the cap of the pre-combustion chamber spark plug according to the invention is shown in the combustion chamber. Detailed Implementation

[0019] Figure 1A pre-combustion chamber spark plug 1, known per se, is shown, and the present invention is based, for example, on this pre-combustion chamber spark plug. This pre-combustion chamber spark plug includes a housing 2. An insulator 3 is fitted into the housing 2. The housing 2 has an outer surface 24 and an inner surface 23. The longitudinal axis of the housing 2, the longitudinal axis X of the insulator 3, and the longitudinal axis of the spark plug 1 coincide. A center electrode 4 is fitted into the insulator 3. Furthermore, an electrical contact extends into the insulator 3, through which the spark plug 1 makes electrical contact with a voltage source. The electrical contact forms the end of the spark plug 1 opposite to the combustion chamber. The electrical contact is constructed, for example, by a connecting bolt 8 and a connecting nut 9.

[0020] The insulator 3 is typically divided into three regions: the insulator bottom 31, the insulator body 32, and the insulator head 33. The three regions differ, for example, in their different diameters. The insulator bottom 31 is the end of the insulator 3 facing the combustion chamber. The central electrode 4 is disposed inside the insulator bottom 31. Typically, the insulator bottom 31 is completely disposed inside the housing 2. Typically, the insulator bottom 31 has the smallest outer diameter on the insulator 3.

[0021] The insulator body 32 is arranged adjacent to the insulator bottom 31, and in this example, the insulator body is surrounded by the housing 2. The insulator body 32 has an outer diameter larger than the insulator bottom 31. The transition between the insulator bottom 31 and the insulator body 32 is configured as a shoulder, groove, or freeform surface. This transition is also referred to as a bottom groove or insulator seat 35.

[0022] The insulator head 33 is adjacent to the insulator body 32 at the end away from the combustion chamber and constitutes the end of the insulator 3 away from the combustion chamber. The insulator head 33 extends from the housing 2. The outer diameter of the insulator head 33 is between the outer diameter of the insulator bottom 31 and the outer diameter of the insulator body 32, wherein these regions typically do not have a constant outer diameter over their length, but rather the outer diameter can vary.

[0023] The housing 2 has a support 25 on its inner side. The insulator is placed on the housing support 25 with its shoulder or insulator seat 35. An internal seal 10 is arranged between the insulator seat 35 and the housing support 25.

[0024] Within the insulator 3, a resistive element 7, also known as a powder mixture (Panat), exists between the central electrode 4 and the connecting bolt 8. The resistive element 7 electrically connects the central electrode 4 to the connecting bolt 8. The resistive element 7 is, for example, constructed as a layer system consisting of a first contact powder mixture, a resistive powder mixture, and a second contact powder mixture. These layers of the resistive element differ in their material composition and the resulting resistance. The first and second contact powder mixtures can have different or the same resistance.

[0025] A ground electrode 5 is arranged in a through hole 52 on the inner side 23 of the housing 2, such that the ground electrode 5 extends radially from the inner side 23 into the through hole 52 along the longitudinal axis X of the housing 2. The ground electrode 5 and the center electrode 4 together form an ignition gap. The through hole 52 extends from the outer side 24 through the housing wall to the inner side 23 of the housing 2.

[0026] The housing 2 has a rod portion. A polygonal structure 21, a constriction groove, and a threaded portion 22 are constructed on this rod portion. The threaded portion 22 is used to screw the spark plug 1 into the internal combustion engine. An external sealing element 6 is arranged between the threaded portion 22 and the polygonal structure 21. In this embodiment, the external sealing element 6 is constructed as a corrugated seal.

[0027] The through hole 52 in the housing wall is constructed in the region of the threaded portion 22. Here, the through hole 52 for the ground electrode 5, and therefore the ground electrode 5, can be arranged at any height in the region of the threaded portion 22. Depending on the position of the ground electrode 5 in the region of the threaded portion 22, the center electrode 4, and consequently the bottom of the insulator 31, extend into the pre-combustion chamber 81 to a greater or lesser extent. Depending on the desired use of the pre-combustion chamber spark plug, the position of the drill hole in the region of the threaded portion 22 and the position of the ground electrode 5 on the inner surface 23 of the housing 2 can be selected.

[0028] The through hole 52 is arranged in a recess 51, such as a tapered groove or a circular groove. Here, the outer diameter of the housing 2 in the recess is smaller than the inner diameter of the threaded portion 22.

[0029] The recess 51 can be formed, for example, by stamping the housing 2 during the manufacture of the pre-combustion chamber spark plug 1. Here, not only is the outer diameter of the housing 2 reduced in the region of the recess 51, but the inner diameter of the housing 2 is also reduced in the region of the recess 51.

[0030] A cap 80 is arranged on the end face of the housing 2 on its combustion chamber side. The housing 2 and the cap 80 together constitute a pre-combustion chamber 81 with a pre-combustion chamber volume. The pre-combustion chamber 81 extends from the cap into the housing 2 and extends inside the housing 2 until it reaches the housing support 25, where the insulator 3 rests with its shoulder 35. In this position, the gap between the housing 2 and the insulator 3 is hermetically sealed by means of an internal seal 10. The pre-combustion chamber 81 and its volume can be divided into a front pre-combustion chamber 81a and a rear pre-combustion chamber 81b. The boundary between the front pre-combustion chamber 81a and the rear pre-combustion chamber 81b is determined by the position of the ground electrode, i.e., the front pre-combustion chamber 81a extends from the cap into a plane that extends perpendicular to the longitudinal axis X of the housing at the height of the ground electrode. Correspondingly, the rear pre-combustion chamber 81b extends from this plane into the housing support 25, where the insulator 3 and the internal seal 10 rest.

[0031] A plurality of drilled holes are provided in the cap 80, the drilled holes being configured as through holes. One of the plurality of drilled holes is arranged on the longitudinal axis XX of the pre-combustion chamber spark plug 1, and the other drilled holes are arranged relative to each other with a rotational angle of 72° about the axis XX. Therefore, the previously known cap 80 has five rotational symmetries.

[0032] Figure 2 A schematic cross-sectional view of a pre-combustion chamber spark plug 1 according to the invention is shown in a combustion chamber 200, in which the pre-combustion chamber spark plug 1 is installed. For better simplicity, Figure 2 Only the comparison with Figure 1 According to the invention, the cap 80 is modified and the arrow 100 points in the flow direction, which is dominant in the combustion chamber 200, for example, during the compression stroke, i.e. Figure 2 The middle point points from left to right.

[0033] The modified cap 80 according to the present invention has a structural element 77, which breaks through the limitations of... Figure 1 The rotational symmetry of the cap 80 is shown in the figure.

[0034] The structural element 77 is firstly an impact surface 77a, which is directly adjacent to the borehole 30 and arranged downstream of the borehole 30; secondly, a diversion edge 77b, which is constructed as a sharp edge with an edge radius of less than 50 μm and defines the boundary of the impact surface 77a on the side of the impact surface 77a away from the borehole 30; thirdly, a convex region 77c, whose surface curvature radius is not greater than twice the radius of the orifice of the borehole 30 on the outer surface of the cap 80 and is directly adjacent to the borehole 30 and arranged upstream of the borehole 30; and fourthly, a convex region 77c, whose surface curvature radius is not greater than twice the radius of the orifice of the borehole 30 on the outer surface of the cap 80 and is directly adjacent to the borehole 30 and arranged downstream of the borehole 30.

Claims

1. A pre-chamber spark plug (1) having a housing (2) and a cap (80) arranged at the end of the housing (2) on the combustion chamber side, which cap together with the housing (2) forms a pre-chamber (81) and has at least one bore (30), having an insulator (3) arranged inside the housing (2), having a center electrode (4) arranged inside the insulator (3), and having a ground electrode (5), wherein the ground electrode (5) and the center electrode (4) together form an ignition gap, characterized in that, The outer geometry of the cap (80) has at least one structural element (77) which makes the inflow of gas through the bore (30) towards the pre-chamber (81) and / or the outflow of gas through the bore (30) from the pre-chamber (81) easier, wherein the structural element (77) is an impact face (77a), a flow-splitting edge (77b) and / or a convex region (77c).

2. The pre-chamber spark plug (1) according to claim 1, characterized in that The structural element (77) is a concave region (77d).

3. The pre-chamber spark plug (1) according to claim 1 or 2, characterized in that The structural element (77) is an impact face (77a) which is arranged in the region of the bore (30) and which is arranged at an angle (a) with respect to the axis (Y-Y) of the bore (30), the angle being less than 90°.

4. The pre-chamber spark plug (1) according to claim 3, characterized in that The impact face (77a) directly adjoins the bore (30).

5. The pre-chamber spark plug (1) according to claim 1 or 2, characterized in that The structural element (77) is a flow-splitting edge (77b) which is configured as a sharp edge having an edge radius of less than 150 pm.

6. The pre-chamber spark plug (1) according to claim 3, characterized in that The structural element (77) is a flow-splitting edge (77b) which is configured as a sharp edge having an edge radius of less than 150 pm, and wherein the flow-splitting edge (77b) defines the boundary of the impact face (77a) on the side of the impact face (77a) facing away from the bore (30), or, The impact face (77a) directly adjoins the bore (30), and wherein the structural element (77) is a flow-splitting edge (77b) which is configured as a sharp edge having an edge radius of less than 150 pm, and wherein the flow-splitting edge (77b) defines the boundary of the impact face (77a) on the side of the impact face (77a) facing away from the bore (30).

7. The pre-chamber spark plug (1) according to claim 2, characterized in that The structural element (77) is a concave region (77d) which has a face curvature radius which is not more than twice the radius of the aperture of the bore (30) on the outer surface of the cap (80).

8. The pre-chamber spark plug (1) according to claim 7, characterized in that The concave region (77d) directly adjoins the bore (30).

9. The pre-chamber spark plug (1) according to claim 1 or 2, characterized in that The structural element (77) is a convex region (77c) which has a face curvature radius which is not more than twice the radius of the aperture of the bore (30) on the outer surface of the cap.

10. The pre-chamber spark plug (1) according to claim 9, characterized in that The convex region (77c) directly adjoins the bore (30).

11. The pre-chamber spark plug (1) according to claim 1, 2, 7 or 8, characterized in that The cap (80) has an outer geometry which has no rotational symmetry.

12. The pre-chamber spark plug (1) according to claim 1 or 2, characterized in that The structural element (77) is an impact face (77a) which is arranged in the region of the bore (30) and which is arranged at an angle (a) with respect to the axis (Y-Y) of the bore (30), the angle being less than 75°.

13. Combustion chamber (200) having a pre-chamber spark plug (1) according to any one of claims 1 to 12, wherein in the combustion chamber (200) a flow direction (100) prevails in the region of the cap (80).

14. The combustion chamber (200) according to claim 13, wherein in the combustion chamber (200) during a compression stroke of the combustion chamber (200) a flow direction (100) prevails in the region of the cap (80).

15. A combustion chamber (200) having a pre-chamber spark plug (1) according to claim 3, 4 or 6, characterized in that, In the combustion chamber (200) a flow direction (100) prevails in the region of the cap (80), and wherein the impact surface (77a) is arranged downstream of the bore (30).

16. A combustion chamber (200) having a pre-chamber spark plug (1) according to claim 7 or 8, characterized in that In the combustion chamber (200) a flow direction (100) prevails in the region of the cap (80), and wherein the concave region (77d) is arranged downstream of the bore (30).

17. A combustion chamber (200) having a pre-chamber spark plug (1) according to claim 9 or 10, characterized in that In the combustion chamber (200) a flow direction (100) prevails in the region of the cap (80), and wherein the convex region (77c) is arranged upstream of the bore (30).

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