PRECHAMBER SPARK PLUG HAVING AN OPTIMIZED CAP, AND INTERNAL COMBUSTION ENGINE

Abstract

A prechamber spark plug. The spark plug includes a housing, a cap, which defines a prechamber at least partially, and which includes a plurality of through holes that are configured to produce a connection between the prechamber and a combustion chamber of an internal combustion engine; the through holes each having a hole center line; the cap including a recess at a region pointed towards the housing, the recess abutting the housing at a combustion-chamber-side end of the housing; a distance from an exit point of a through hole lying on the hole center line, to a recess, being in a range of 2 mm to 7 mm; and a first angle between a center axis of the prechamber spark plug and the hole center line being in a range of 30° to 70°. An internal combustion engine including such a prechamber spark plug is also described.

Claims

1-10. (canceled)

11. A prechamber spark plug, comprising: a housing; and a cap, which defines a prechamber at least partially, and which includes a plurality of through holes that are configured to produce a connection between the prechamber and a combustion chamber of an internal combustion engine, the through holes each having a hole center line; wherein the cap includes a recess at a region pointed towards the housing, the recess abutting the housing at a combustion-chamber-side end of the housing, wherein a distance from an exit point of a through hole that lies on the hole center line, to a recess, being in a range of 2 mm to 7 mm, and wherein a first angle between a center axis of the prechamber spark plug and the hole center line is in a range of 30° to 70°.

12. The prechamber spark plug as recited in claim 11, wherein: the distance is in a range of 4 mm to 7 mm, and the first angle is in a range of 30° to 50°, or the distance is in a range of 5 mm to 7 mm, and the first angle is in a range of 30° to 40°.

13. The prechamber spark plug as recited in claim 11, wherein in an installed state, the distance is determined at the through hole which is set up to be closest to a conical spray of fuel in the combustion chamber.

14. The prechamber spark plug as recited in claim 11, wherein respective exit points of all of the through holes are situated in a common plane, each of the exit points lying on respective hole center lines.

15. The prechamber spark plug as recited in claim 13, wherein in the installed state, the through hole is configured to be oriented for tumble flow in the combustion chamber in such a manner that a portion of the tumble flow streams directly into the through hole.

16. The prechamber spark plug as recited in claim 13, wherein the hole center line of the through hole, a beginning of an external thread on the housing, and the center axis lie in a common plane.

17. An internal combustion engine, comprising: a combustion chamber; a piston configured to move back and forth; an injector configured to introduce a fuel into the combustion chamber; and a prechamber spark plug, including: a housing, and a cap, which defines a prechamber at least partially, and which includes a plurality of through holes that are configured to produce a connection between the prechamber and a combustion chamber of an internal combustion engine, the through holes each having a hole center line, wherein the cap includes a recess at a region pointed towards the housing, the recess abutting the housing at a combustion-chamber-side end of the housing, wherein a distance from an exit point of a through hole that lies on the hole center line, to a recess, being in a range of 2 mm to 7 mm, and wherein a first angle between a center axis of the prechamber spark plug and the hole center line is in a range of 30° to 70°.

18. The internal combustion engine as recited in claim 17, wherein a center axis of a conical spray of the injector is situated at a second angle to the center axis of the prechamber spark plug, the second angle being in a range of 30° to 70°.

19. The internal combustion engine as recited in claim 18, wherein the second angle is approximately 60°.

20. The internal combustion engine as recited in claim 17, wherein a tumble flow is generated in the combustion chamber in such a manner that at least a portion of the tumble flow is pointed directly at a through hole of the prechamber spark plug which lies closest to the conical spray in the combustion chamber.

21. The internal combustion engine as recited in claim 17, wherein the prechamber spark plug is positioned substantially centrally at the combustion chamber, and the injector is positioned laterally to the prechamber spark plug, at the combustion chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In the following, a preferred exemplary embodiment of the present invention is described in detail with reference to the figures.

[0016] FIG. 1 show a schematic sectional view of an internal combustion engine including a prechamber spark plug according to a preferred exemplary embodiment of the present invention.

[0017] FIG. 2 show a part-sectional view of a cap of the prechamber spark plug of FIG. 1.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0018] In the following, a prechamber spark plug 1 of an internal combustion engine according to a preferred exemplary embodiment of the present invention is described in detail with reference to FIGS. 1 and 2.

[0019] As is shown in FIG. 1, prechamber spark plug 1 includes a prechamber 2, which is defined by a cap 3 having a U-shaped section. Cap 3 is fixed to a housing 6 of the prechamber spark plug, for example, with the aid of a welded connection.

[0020] In addition, prechamber spark plug 1 includes an electrode 5 and an insulator 7. An external thread is provided at the circumference of housing 6, at an end 60 pointing towards combustion chamber 11. External thread 4 is formed up to the installed cap 3 and is used for fixing prechamber spark plug 1 in a cylinder head 10.

[0021] Cap 3 includes a plurality of through holes 30, which are each situated at a first angle α to a center axis X-X of prechamber spark plug 1. Through holes 30 are used, on one hand, to allow purging of prechamber 2 and, on the other hand, to enable, after ignition by electrode 5, a fuel-air mixture to ignite initially within prechamber 2 and then in combustion chamber 11 via through holes 30, with the aid of so-called torch jets. An injector 8, which produces a conical fuel spray 80 in combustion chamber 11, is represented schematically in FIG. 1.

[0022] Through hole 30 is a through bore having a stepless diameter.

[0023] In addition, a cylinder 13 having a piston 12, which moves back and forth in cylinder 13, as indicated by double arrow B, is shown schematically in FIG. 1. Furthermore, an intake valve 14 and an exhaust valve 15 are provided. In this context, injector 8 is positioned between exhaust valve 15 and prechamber spark plug 1.

[0024] As is further shown in FIG. 2, which shows cap 3 of prechamber spark plug 1 in detail, cap 3 includes a radial recess 32 directed inwards. In this context, cap 3 rests against front-side end 60 of housing 6 at recess 32. Fixation may be accomplished, for example, with the aid of a welded connection.

[0025] In addition, a hole center line 31 of a through hole 30 is represented in FIG. 2. This through hole 30 shown is one of a plurality of through holes 30 in cap 3 and is situated at the shortest distance from injector 8. Due to that, this through hole 30 is used to allow purging of prechamber 2 during a stroke of the piston, in order to introduce an ignitable mixture into prechamber 2.

[0026] As is further shown in FIG. 2, an exit point 33 is defined on hole center line 31; the exit point being situated on the side of through hole 30 pointing towards combustion chamber 11. As already explained above, hole center line 31 determines first angle α. Angle α is preferably in a range of 30° to 50° and is, in this exemplary embodiment, 35°.

[0027] As is further shown in FIG. 1, a distance A between exit point 33 and recess 32 in the axial direction of center axis X-X is defined. This distance A is in a range of 2 mm to 7 mm and is, in this exemplary embodiment, 6 mm.

[0028] In addition, combustion chamber 11 is geometrically configured in such a manner, that tumble flow 16 is produced in response to movement of piston 12. This tumble flow 16 ensures that exchange of gas between combustion chamber 11 and prechamber 2 is rendered possible, in particular, in order to introduce an ignitable mixture into prechamber 2 again after an occurring ignition. As is apparent from FIG. 2, tumble flow 16 is generated in such a manner, that a portion of tumble flow 16 is aimed directly at through hole 30 of cap 3. Therefore, gas mixture from combustion chamber 11 may be introduced directly through through hole 30 into prechamber 2.

[0029] In this context, prechamber spark plug 1 is positioned centrally at combustion chamber 11 and, particularly preferably, exactly on a center axis of piston 12.

[0030] In addition, hole center line 31 of the through hole 30, which is positioned closest to injector 8, as well as center axis X-X of prechamber spark plug 1, and the beginning 40 of external thread 4, lie in a common plane. This plane is the sectional plane in FIG. 2.

[0031] Conical spray 80 produced by injector 8 has a center axis 81. As is apparent from FIG. 1, center axis 81 of conical spray 80 is positioned at a second angle β to the center axis of prechamber spark plug 1. As is further apparent from FIG. 1, in this instance, a center axis of the injector and center axis 81 of conical spray 80 diverge. In this exemplary embodiment, second angle β is 60°.

[0032] In addition, all of the through holes 30 of cap 3, which include their respective exit points 33 on their respective hole center lines 31, lie in a common plane E, which is perpendicular to axial direction X-X of the prechamber spark plug.

[0033] Consequently, in comparison with the related art, prechamber 2 of prechamber spark plug 1 may be purged more effectively, and an ignitable fuel-air mixture may be introduced more effectively into prechamber 2 in cap 3.

[0034] This produces improved ignition within prechamber 2, which results in more rapid combustion of the fuel-air mixture in prechamber 2. Due to the markedly more rapid combustion in prechamber 2, the torch jets may then reach earlier and further into combustion chamber 11 of internal combustion engine 100. This produces more rapid and more effective inflammation of the fuel-air mixture in combustion chamber 11 and results in more rapid and more complete combustion in combustion chamber 11. In this manner, fuel utilization in combustion chamber 11, as well as exhaust gas characteristics of the internal combustion engine, are improved markedly.

[0035] In addition, due to the orientation of the through hole 30 situated closest to injector 8, in conjunction with the beginning 40 of external thread 4 of prechamber spark plug 1, exact positioning of this through hole 30 is rendered possible. Exact positioning of the exit points 33 at through holes 30 is achieved by screwing prechamber spark plug 1 completely into cylinder head 10.