pre-chamber spark plug

Abstract

Prechamber spark plug (10), comprising: a case (16); an insulator (14) located at least partially inside the housing (16); a central electrode (12) arranged at least partially within the insulator (14); a ground electrode forming a spark gap (G) with the central electrode (12); and a pre-chamber cover (20) which is connected to the housing (16) and forms a pre-chamber, wherein the pre-chamber cover (20) includes two or more openings (38); wherein the two or more openings (38) are configured such that at least one inflowing fuel-air mixture jet (J) is directed to a stepped wall section (32) to vent or remove gas from a previous ignition cycle that is present in a pre-chamber wall space, wherein the pre-chamber wall space is at least partially arranged between the insulator (14) and a pre-chamber wall which is an exposed inner wall (30) of the housing (16), wherein the stepped wall section (32) is at least partially arranged between the exposed inner wall (30) of the housing (16) and the pre-chamber cover (20) and inclines inwards from the inner wall in the direction of a central axis (A), wherein the two or more openings (38) are angled such that a first inflowing fuel-air mixture jet (J) from a first opening does not intersect with a second inflowing fuel-air mixture jet (J) from a second opening.

Description

TECHNICAL FIELD

[0001] This invention relates generally to spark plugs and more particularly to pre-chamber spark plugs. GENERAL STATE OF THE ART

[0002] Prechamber spark plug function in gasoline-powered engines depends on the intake of unburned gas and the exhaust or purge of residual gas after combustion. The exhaust of burned gas from the prechamber of a passive prechamber spark plug has a particular impact on the spark plug's thermal capability. Incomplete exhaust of residual gas can lead to irregular combustion caused by premature ignition in the prechamber of the spark plug. Premature ignition in the prechamber of the spark plug not only increases the temperatures of various spark plug components, such as the ground electrode, center electrode, insulator base, or prechamber cap, but can also lead to premature ignition in the main combustion chamber.

[0003] The document DE 37 09 976 A1 relates to a pre-chamber spark plug for igniting very lean fuel-air mixtures, in particular of gas engines, with an ignition chamber surrounding an ignition path, which has transfer channels leading to the main combustion chamber, preferably running tangentially, and with a valve-controlled supply channel supplying a rich additional fuel-air mixture or additional fuel, wherein at least one opening of the supply channel is provided outside the ignition chamber in the region of at least one transfer channel.

[0004] Further pre-chamber spark plugs are known from the documents DE 31 48 296 A1, US 8 181 617 B2 and US 2012 / 0 240 890 A1. SUMMARY

[0005] According to one embodiment, a prechamber spark plug with the features of claim 1 is provided, comprising: a housing or a shell; an insulator arranged at least partially within the housing; a center electrode arranged at least partially in the insulator; a ground electrode forming a spark gap with the center electrode; and a prechamber cover connected to the housing and forming a prechamber, wherein the prechamber cover includes two or more openings. The two or more openings are configured such that at least one incoming fuel-air mixture jet is directed to a prechamber wall gap or a prechamber wall spacing ora pre-chamber wall section to vent or remove gas from a previous ignition cycle, and the two or more openings are angled so that a first incoming fuel-air mixture jet of a first opening does not intersect a second incoming fuel-air mixture jet of a second opening.

[0006] According to various embodiments, the pre-chamber spark plug may further include one of the following features or a technically feasible combination of one or all of these features: • the two or more openings are evenly spaced along the pre-chamber cover such that each opening is offset from a center point of the pre-chamber cover by an offset distance; • the pre-chamber cover contains four or more openings; • a third incoming fuel-air mixture jet of a third opening and a fourth incoming fuel-air mixture jet of a fourth opening do not intersect with either the first incoming fuel-air mixture jet or the second incoming fuel-air mixture jet; • each opening is arranged at an angle with respect to the radial spark plug axis, each angle of each opening being the same with respect to a radial spark plug axis, such that the first, second, third and fourth incoming fuel-air mixture jets do not intersect a central spark plug axis; • the pre-chamber wall space has a width that extends beyond an axial bore of the housing; • the two or more openings are configured so that each incoming fuel-air mixture jet is directed to the stepped wall portion of the housing; • the two or more openings are configured such that each incoming fuel-air mixture jet is directed to the stepped wall portion and then travels along the exposed inner wall and to an upper portion of the pre-chamber wall space; • the two or more openings are each aligned at an angle with respect to the central axis of the spark plug and the stepped wall portion is aligned at an angle with respect to a central axis of the spark plug, each angle of the two or more openings being the same as the angle of the stepped wall portion; • the space between the antechamber walls is at least 1.5 mm wide; • the spark gap is a creeping discharge spark gap with an axial spark gap section; and / or • the center electrode includes a center electrode body and a center electrode tip that is angular and surrounds at least a portion of the center electrode body, wherein the ground electrode is a conductive seal at least partially aligned between an inwardly projecting portion of the housing and the insulator, and wherein the spark gap is a sliding discharge spark gap that is annular and located between the center electrode tip and the ground electrode along a surface of the insulator.

[0007] Further provided is a prechamber spark plug having the features of claim 11, comprising: a housing; an insulator disposed at least partially within the housing; a center electrode disposed at least partially within the insulator; a ground electrode forming a creeping discharge spark gap with the center electrode, the creeping discharge spark gap being located along an outer surface of the insulator; and a prechamber cover connected to the housing and forming a prechamber, the prechamber cover including two or more openings. The two or more openings are configured such that at least one incoming fuel-air mixture jet is directed to a prechamber wall gap to vent or remove gas from a previous ignition cycle.

[0008] According to various embodiments, the pre-chamber spark plug may further include one of the following features or a technically feasible combination of some or all of these features: • the pre-chamber wall space is at least partially disposed between the insulator and a pre-chamber wall that is an exposed inner wall of the housing, wherein the housing includes a stepped wall portion disposed between the exposed inner wall of the housing and the pre-chamber cover, and wherein the two or more openings are configured such that each incoming fuel-air mixture jet is directed to the stepped wall portion of the housing; and / or the center electrode includes a center electrode body and a center electrode tip, which is annular and surrounds at least a portion of the center electrode body, wherein the ground electrode is a conductive seal at least partially aligned between an inwardly projecting portion of the housing and the insulator, and wherein the spark gap is a creeping discharge spark gap which is annular and located between the center electrode tip and the ground electrode along a surface of the insulator.

[0009] According to various embodiments, the pre-chamber spark plug may further include one of the following features or a technically feasible combination of some or all of these features: • the two or more openings are angled so that an incoming fuel-air mixture jet from a first opening does not intersect an incoming fuel-air mixture jet from a second opening; and / or • the ground electrode is a conductive seal partially disposed between an inwardly projecting portion of the housing and the insulator. DRAWINGS

[0010] One or more embodiments are described below in conjunction with the accompanying drawings, wherein like designations indicate like elements, and wherein: Fig. 1 is a partial cross-sectional view of a spark plug according to one embodiment; Fig. 2 is a schematic view of a spark plug showing flow patterns according to one embodiment; Fig. Figure 3 is a partial side view of a pre-chamber cover; Fig. 4 is a side view of a pre-chamber cover and illustrating incoming fuel-air mixture jets corresponding to each opening of the pre-chamber cover; and Fig. 5 a plan view of a pre-chamber cover of Fig. 4 and illustrates incoming fuel-air mixture jets corresponding to each opening of the pre-chamber cover. DESCRIPTION

[0011] The pre-chamber spark plugs and operating methods described herein can be used to vent or remove residual gas present in the pre-chamber due to a previous ignition cycle. Pre-chamber spark plugs installed in a spark-ignition engine can experience erratic combustion caused by auto-ignition of the fuel-air mixture in the pre-chamber. For example, if the spark plug overheats, uncontrolled ignition can occur in the main combustion chamber prior to the ignition point. This can increase the risk of engine damage.

[0012] During the compression stroke, the fuel-air mixture must be delivered to the prechamber of the spark plug in such a way that an ignitable mixture is present at the spark gap. Due to the subsequent combustion and the resulting pressure increase, flares escape through the prechamber openings and ignite the mixture in the engine's main combustion chamber. In some cases, however, burnt fuel-air mixture may remain in the spark plug prechamber and cause auto-ignition of incoming fuel-air mixture from a subsequent ignition cycle. Thus, it is desirable to vent this remaining burnt fuel-air mixture from the prechamber. In at least some cases, this burnt fuel-air mixture remains in a space existing between the insulator (and / or the center electrode) and the prechamber wall, which may be a wall of the spark plug's metal shell or a wall of the prechamber cover.This gap may be referred to as the pre-chamber wall gap. Thus, according to at least one embodiment, the presently disclosed spark plug may include a pre-chamber cover with openings configured to direct an incoming fuel-air mixture to this pre-chamber wall gap, thereby venting or otherwise removing (or at least dispersing) the combusted fuel-air mixture.

[0013] Furthermore, in at least one embodiment, close clearances between the insulator and the pre-chamber wall can be avoided. Thus, the spark plug can include a pre-chamber wall gap large enough to increase the ability of the gas to flow within this gap. By using a pre-chamber wall gap of, for example, at least 1.5 mm, the gap allows the gas to move within this area, allowing the incoming fuel-air mixture to discharge or otherwise remove / disperse this combusted fuel-air mixture.

[0014] The pre-chamber spark plug assemblies described herein can be efficiently used in modern gasoline passenger car engines for igniting lean-burn main combustion mixtures. This can reduce nitrogen-containing oxide emissions by lowering overall combustion temperatures. Furthermore, the presently described arrangement can lead to a faster combustion process and thus contribute to the mitigation of knock noise. In some embodiments, the pre-chamber spark plug is a thermally robust, passive pre-chamber spark plug for boosted direct-injection gasoline engines, wherein the pre-chamber spark plug is used to precisely control the onset of combustion, increase engine efficiency, reduce pollutant emissions, and provide more stable combustion compared to conventionally initiated combustion with a J-shaped spark plug.A passive prechamber realizes its gas exchange exclusively through the pressure difference between the prechamber and the main chamber and through the local flow field in the vicinity of the prechamber cover openings.

[0015] An example pre-chamber spark plug is shown in Fig. 1, the prechamber spark plug 10 includes a center electrode 12, an insulator 14, a metal shell 16, a ground electrode 18, and a prechamber cover 20. The center electrode 12 includes a center electrode body 22 and a center electrode tip 24, which in the illustrated embodiment is shaped as a ring. The center electrode body 22 may be made of Inconel™ 600 or other suitable center electrode material, and the center electrode tip 24 may be made of a nickel alloy or a precious metal (e.g., platinum, iridium) or an alloy thereof. The center electrode body 22 is disposed within a central bore of the insulator 14 and protrudes from the insulator 14. The center electrode tip 24 is shaped as a ring or annular component that surrounds (at least a portion of) the protruding portion of the center electrode body 22.The center electrode tip 24 also adjoins and / or is disposed on an end portion of the insulator 14.

[0016] The insulator 14 may be made of a ceramic material, including any suitable spark plug insulator material. The insulator 14 includes an axial bore in which the center electrode body 22 is disposed. The insulator 14 includes an axially free end 26 (representing an end portion of the insulator) at which the center electrode tip 24 is disposed. The insulator 14 also includes a curved outer surface that joins a large diameter portion of the insulator to the axially free end 26 of the insulator 14, which portion has a smaller diameter than the large diameter portion of the insulator. The ground electrode 18 is disposed between the insulator 14 and the metal shell 16 and contacts the metal shell at an inwardly projecting portion 28 of the metal shell to be electrically grounded to the metal shell.The ground electrode 18 may be made of any suitable ground electrode material, including—in this embodiment—metal-based gasket-like materials that help create a gas-tight seal in the prechamber between the insulator 14 and the housing 16. The ground electrode 18 is annularly shaped and conforms to the curved outer surface of the insulator 14. The ground electrode 18 is held in place by the inwardly projecting portion of the metal housing and the curved outer surface of the insulator 14. The spark gap G is formed between a free end of the ground electrode 18 and the center electrode tip 24.

[0017] The metal shell 16 is constructed of a suitable spark plug shell material and includes an axial bore in which the insulator 14 is disposed. The metal shell 16 includes the inwardly projecting portion 28, an exposed inner wall 30, and a stepped wall portion 32. In some embodiments, the inwardly projecting portion 28 is a portion of the metal shell 16 that contributes to forming a sliding discharge spark gap and also supports the insulator 14 via a gasket (e.g., an alternative embodiment wherein the inwardly projecting portion 28 forms the ground electrode rather than having a standalone gasket / ground electrode 18). In some embodiments, the inwardly projecting portion 28, as illustrated, is a gasket-supporting protrusion that supports the ground electrode 18, which also serves as a conductive gasket between the insulator 14 and the shell 16.The inwardly projecting portion 28 may include two angled surfaces, one of the angled surfaces abutting the ground electrode 18 such that the ground electrode 18 is held in place between the insulator 14 and the metal shell 16. The exposed inner wall 30 is a pre-chamber wall in that it partially defines the pre-chamber 36. This exposed inner wall 30 extends from the inwardly projecting portion 28 to the stepped wall portion 32 and is parallel to the central axis A. The exposed inner wall 30 extends axially past the axially free end 26 of the insulator 14 and the center electrode tip 24. The stepped wall portion 32 is disposed at or near one end of the metal shell 16 and slopes inwardly from the inner wall 30 toward the central axis A. In another embodiment, the stepped wall portion 32 is at least partially, or sometimes entirely, formed within the pre-chamber lid 20.A prechamber wall gap P is present between the exposed inner wall 30 of the housing and the insulator 14. The prechamber wall gap P includes a width d, as shown in . Fig. 1, where the width d is measured at an axial location along the outer surface of the insulator that is halfway between the center electrode tip 24 and the nearest end of the ground electrode 18. In one embodiment, this pre-chamber wall gap P is at least 1.5 mm. In another embodiment, this pre-chamber wall gap P is at least 2.0 mm, and in yet another embodiment, this pre-chamber wall gap P is at least 2.5 mm. In this embodiment, the exposed inner wall 30 is a radially expanded portion compared to the remainder of the axial bore of the housing 16, which contributes to creating a wider pre-chamber wall gap P.

[0018] The pre-chamber cover 20 is attached to the end of the metal housing 16 by a weld 34 and is used to at least partially define a pre-chamber 36. The pre-chamber cover 20 and the end of the metal housing 16 may have mating projections (as shown in Fig. 1) to facilitate and / or strengthen the attachment of the pre-chamber cover 20 to the metal shell 16. The pre-chamber cover 20 includes one or more openings 38, and in many embodiments includes a plurality of openings 38. In one embodiment, the pre-chamber cover 20 includes two openings 38 spaced 180° apart. In another embodiment, the pre-chamber cover 20 includes four openings 38 spaced 90° apart. And in another embodiment, the pre-chamber cover 20 includes six openings 38 spaced 60° apart or eight openings spaced 45° apart. The openings 38 enable fluid communication between the pre-chamber 36 and a main combustion chamber.In particular, a fuel-air mixture can be introduced into the pre-chamber 36 from the main combustion chamber via the openings 38, which can then be combusted by an electrical spark generated at the spark gap between the ground electrode 18 and the center electrode tip 24.

[0019] By way of non-limiting example, the spark gap G is a creeping discharge spark gap including an axial spark gap portion (e.g., the portion extending along an outer surface of the insulator nose) between the center electrode tip 24 and the ground electrode or conductive seal 18. Thus, the spark travels upward along the outer surface of the insulator 14 toward a terminal end of the spark plug 10. Combustion can propagate from the spark gap G through the openings 38 and into the main combustion chamber, igniting the fuel-air mixture in the combustion chamber. Because a surface discharge requires a lower voltage, a longer spark is possible.Furthermore, providing a sliding discharge spark gap, which does not have a discrete ground electrode extending into the space or prechamber area, can help minimize flow obstructions compared to typical air-gap spark plugs to better control internal aerodynamics. The sliding discharge spark gap can also reduce the overall thermal behavior of the bulk of the flow and surface temperatures. Furthermore, providing the spark point at the upper position within the prechamber 36 (away from the orifices 38) can be beneficial for flame propagation and subsequent prechamber pressure buildup, along with better mixing of the residual gas in the core nose region. Finally, this ignition arrangement allows all components to fit within a conventional M12 spark plug.

[0020] However, as mentioned above, combusted fuel-air mixture may remain in the pre-chamber 36, and particularly in the pre-chamber wall space P. This remaining combusted fuel-air mixture may cause auto-ignition of the fuel-air mixture entering the pre-chamber 36 during a subsequent engine cycle. To prevent this auto-ignition problem, the openings 38 of the pre-chamber cover 20 are configured to direct an incoming fuel-air jet toward the pre-chamber wall space P. Thus, the openings 38 of the pre-chamber cover 20 cause the incoming fuel-air mixture to expel the remaining combusted fuel-air mixture located in and around the pre-chamber wall space P.In one embodiment, the openings 38 are configured such that each incoming fuel-air mixture jet is directed toward the stepped wall portion 32 and such that each incoming fuel-air mixture jet is directed along the exposed inner wall 30 and toward a top portion P. oberer of the antechamber wall space.

[0021] In one embodiment, the openings 38 of the pre-chamber cover 20 may be angled so that the incoming fuel-air mixture jet is directed toward or aimed at the exposed inner wall 30 near the stepped wall portion 32. The stepped wall portion 32 is angled to lead to the exposed inner wall 30 of the pre-chamber wall gap P. Thus, the stepped wall portion 32 may help guide the incoming fuel-air mixture jet J toward the pre-chamber wall gap P. Fig. 2 illustrates an incoming fuel-air mixture jet J entering the opening 38. As in Fig. 2, the angles of the openings 38 are configured to correspond to the angle of the stepped wall section 32 so that the incoming fuel air jet J is directed to the upper section P obererof the prechamber wall gap P near the ground electrode 18 and / or the inwardly projecting portion 28 of the metal housing 16. This configuration causes the incoming fuel-air jet J to scatter, expel, or otherwise remove combusted fuel-air mixture from the prechamber wall gap P. The configuration of the openings 38 can be achieved by drilling through the prechamber cover 20 at a predetermined angle, which can, for example, correspond to the stepped wall portion 32. The “predetermined angle” or the “same angle” includes two angles that are within 10° of each other, for example, to allow for manufacturing tolerances. In one embodiment, the openings 38 are configured so that an outer peripheral portion J äußererof the incoming fuel-air mixture jet(s) J contacts or slides along an angled surface of the stepped wall section 32. Configuring the openings to orient the jet J involves either direct flow to the gap P or indirect flow to the gap P (e.g., the jet J encounters the stepped wall section 32 before reaching the gap P).

[0022] With reference to Fig. 3 and Fig. 4, the prechamber lid 20 is shown together with a first opening 38a. The opening is cylindrical, with the cylindrical axis of the opening 38a being arranged at an angle α from the central axis A. The other openings 38 are also arranged at the same angle α, at least in one embodiment. In addition, the stepped wall portion 32 may also be aligned at this same angle α with respect to the central axis A. Again, the "predetermined angle" or the "same angle" includes two angles that are within 10° of each other, for example, to allow for manufacturing tolerances. With reference to Fig. 4, the prechamber cover 20 includes four openings 38 (three are shown and labeled 38a,b,c). As shown, for each opening 38, an incoming fuel-air mixture jet J1-J4 is directed to the stepped wall portion 32 and the prechamber wall (or exposed inner wall 30), and in at least one embodiment, incoming fuel-air mixture jets J1-J4 contact an angled surface of the stepped wall portion 32. Each of the openings 38 is offset from the central axis A by an offset distance, which can be determined based on the number of openings 38, the geometry of the prechamber, etc. In many embodiments, the openings 38 are offset from the central axis A by the same offset distance.

[0023] As also in Fig. 5, the openings 38 may be configured so that the incoming fuel air jets J1-J4 are each arranged at an angle β taken from a reference axis BC which is oriented with respect to the central axis A when viewed from above as in Fig.5. This reference axis BC may be referred to as the "radial spark plug axis," and each of B and C is perpendicular to each other, and the central spark plug axis A is perpendicular with respect to the radial spark plug axis. Further, as shown, B and C intersect at a center point of the pre-chamber cover 20. The openings 38 are thus configured so that incoming fuel-air jets J1-J4 generally do not intersect or overlap each other. This prevents incoming fuel-air jets J1-J4 from interfering with each other. By configuring the openings 38 in this manner, the fuel-air mixture can be directed to the pre-chamber wall gap P without impedance or interference caused by the flow of the fuel-air mixture from another incoming fuel-air jet.

[0024] The following CLAUSES define embodiments of the present disclosure, wherein each of the clauses may be combined with any of the appended claims.

[0025] CLAUSE 1. Pre-chamber spark plug, comprising: a housing; an insulator disposed at least partially within the housing; a center electrode arranged at least partially within the insulator; a ground electrode forming a spark gap with the center electrode; and a pre-chamber cover connected to the housing and forming a pre-chamber, the pre-chamber cover including two or more openings; wherein the two or more openings are configured such that at least one incoming fuel-air mixture jet is directed to a pre-chamber wall space to vent or remove gas from a previous ignition cycle, wherein the two or more openings are angled such that a first incoming fuel-air mixture jet of a first opening does not intersect a second incoming fuel-air mixture jet of a second opening.

[0026] CLAUSE 2. A pre-chamber spark plug according to CLAUSE 1, wherein the two or more openings are equally spaced along the pre-chamber cover such that each opening is spaced an offset distance from a center point of the pre-chamber cover.

[0027] CLAUSE 3. Pre-chamber spark plug according to CLAUSE 2, wherein the pre-chamber cover includes four or more openings.

[0028] CLAUSE 4. A pre-chamber spark plug according to CLAUSE 3, wherein a third incoming fuel-air mixture jet of a third opening and a fourth incoming fuel-air mixture jet of a fourth opening do not intersect the first incoming fuel-air mixture jet or the second incoming fuel-air mixture jet.

[0029] CLAUSE 5. A pre-chamber spark plug according to CLAUSE 4, wherein each opening is arranged at an angle with respect to a spark plug radial axis, each angle of each opening being the same with respect to the spark plug radial axis, such that the first, second, third and fourth incoming fuel-air mixture jets do not intersect a central spark plug axis.

[0030] CLAUSE 6. A pre-chamber spark plug according to any one of CLAUSES 1 to 5, wherein the pre-chamber wall space is at least partially disposed between the insulator and a pre-chamber wall, the pre-chamber wall being an inner wall of the housing or an inner wall of the pre-chamber cover.

[0031] CLAUSE 7. A pre-chamber spark plug according to CLAUSE 6, wherein the pre-chamber wall space has a width extending beyond an axial bore of the housing.

[0032] CLAUSE 8. A pre-chamber spark plug according to CLAUSE 6 or 7, wherein the pre-chamber wall is an exposed inner wall of the housing, the housing including a stepped wall portion disposed between the exposed inner wall of the housing and the pre-chamber cover, and wherein the two or more openings are configured such that each incoming fuel-air mixture jet is directed to the stepped wall portion of the housing.

[0033] CLAUSE 9. The pre-chamber spark plug of CLAUSE 8, wherein the two or more openings are configured such that each incoming fuel-air mixture jet is directed to the stepped wall portion and then travels along the exposed inner wall and to an upper portion of the pre-chamber wall gap.

[0034] CLAUSE 10. A pre-chamber spark plug according to CLAUSE 8 or 9, wherein the two or more openings are each oriented at an angle with respect to a central axis of the spark plug and the stepped wall portion is oriented at an angle with respect to a central axis of the spark plug, each angle of the two or more openings being the same as the angle of the stepped wall portion.

[0035] CLAUSE 11. A pre-chamber spark plug according to any one of CLAUSES 1 to 10, wherein the pre-chamber wall gap is at least 1.5 mm wide.

[0036] CLAUSE 12. A pre-chamber spark plug according to any one of CLAUSES 1 to 11, wherein the spark gap is a creeping discharge spark gap having an axial spark gap section.

[0037] CLAUSE 13. The pre-chamber spark plug of CLAUSE 12, wherein the ground electrode is a conductive seal disposed at least partially between an inwardly projecting portion of the housing and the insulator.

[0038] CLAUSE 14. Pre-chamber spark plug, comprising: a housing; an insulator arranged at least partially within the housing; a center electrode arranged at least partially within the insulator; a ground electrode forming a creeping discharge spark gap with the center electrode, the creeping discharge spark gap being arranged along an outer surface of the insulator; and a pre-chamber cover connected to the housing and forming a pre-chamber, the pre-chamber cover including two or more openings; wherein the two or more openings are each configured such that at least one incoming fuel-air mixture jet is directed to a pre-chamber wall space to purge or remove gas from a previous ignition cycle.

[0039] CLAUSE 15. The pre-chamber spark plug of CLAUSE 14, wherein the two or more ports are configured such that the incoming fuel-air mixture jet of a first port does not intersect the incoming fuel-air mixture jet of a second port.

[0040] CLAUSE 16. A pre-chamber spark plug according to CLAUSE 14 or 15, wherein the pre-chamber wall space is at least partially disposed between the insulator and a pre-chamber wall that is an exposed inner wall of the housing, the housing having a stepped wall portion disposed between the exposed inner wall of the housing and the pre-chamber cover, and wherein the two or more openings are configured such that each incoming fuel-air mixture jet is directed to the stepped wall portion of the housing.

[0041] CLAUSE 17. A pre-chamber spark plug according to any one of CLAUSES 14 to 16, wherein the ground electrode is a conductive seal disposed at least partially between an inwardly projecting portion of the housing and the insulator.

[0042] CLAUSE 18. Pre-chamber spark plug comprising: a housing; an insulator arranged at least partially within the housing; a center electrode arranged at least partially within the insulator; a sliding discharge spark gap with the center electrode forming a ground electrode; and a pre-chamber cover connected to the housing and forming a pre-chamber, the pre-chamber cover including two or more openings; wherein a pre-chamber wall space is at least partially between the insulator and a pre-chamber wall, wherein the pre-chamber wall is an exposed inner wall of the housing or an exposed inner wall of the pre-chamber cover, and wherein the prechamber wall includes a stepped wall section.

[0043] CLAUSE 19. A pre-chamber spark plug according to CLAUSE 18, wherein the two or more openings are angled with respect to a radial spark plug axis such that an incoming fuel-air mixture jet of a first opening does not intersect an incoming fuel-air mixture jet of a second opening.

[0044] CLAUSE 20. A pre-chamber spark plug according to claim 18 or 19, wherein the creeping discharge spark gap has an axial spark gap portion, and wherein the ground electrode is a conductive seal at least partially disposed between an inwardly projecting portion of the housing and the insulator.

[0045] It should be understood that the foregoing is not a definition of the invention, but a description of one or more embodiments of the invention. The invention is not limited to the particular embodiment(s) but is defined solely by the claims below. Furthermore, the statements contained in the foregoing description refer to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, unless a term or phrase is expressly defined above. Various other embodiments and various changes and modifications of the disclosed embodiment(s) will be apparent to those skilled in the art. All such other embodiments, changes, and modifications are within the scope of the appended claims.

[0046] As used in this specification and the claims, the terms "for example," "e.g.," "for example," "such as," and "like," and the verbs "comprising," "having," "including," and their other verb forms, when used in connection with a list of one or more components or other items, are each to be construed as open-ended, meaning that the list is not to be considered exclusive of other additional components or items. Other items are to be construed in their broadest, reasonable meaning, unless used in a context that requires a different interpretation.

Claims

[1] Pre-chamber spark plug (10), comprising: a housing (16); an insulator (14) disposed at least partially within the housing (16); a center electrode (12) arranged at least partially within the insulator (14); a ground electrode forming a spark gap (G) with the center electrode (12); and a pre-chamber cover (20) connected to the housing (16) and forming a pre-chamber, the pre-chamber cover (20) including two or more openings (38); wherein the two or more openings (38) are configured such that at least one incoming fuel-air mixture jet (J) is directed to a stepped wall portion (32) to vent or remove gas from a previous ignition cycle present in a prechamber wall space, wherein the prechamber wall space is arranged at least partially between the insulator (14) and a prechamber wall, which is an exposed inner wall (30) of the housing (16), wherein the stepped wall section (32) is arranged at least partially between the exposed inner wall (30) of the housing (16) and the prechamber cover (20) and inclines inwardly from the inner wall in the direction of a central axis (A), wherein the two or more openings (38) are angled such that a first incoming fuel-air mixture jet (J) of a first opening does not intersect with a second incoming fuel-air mixture jet (J) of a second opening. [2] The pre-chamber spark plug (10) of claim 1, wherein the two or more openings (38) are evenly spaced along the pre-chamber cover (20) such that each opening is spaced an offset distance from a center point of the pre-chamber cover (20). [3] Pre-chamber spark plug (10) according to claim 2, wherein the pre-chamber cover (20) includes four or more openings (38). [4] Pre-chamber spark plug (10) according to claim 3, wherein a third inflowing fuel-air mixture jet (J) of a third opening and a fourth inflowing fuel-air mixture jet (J) of a fourth opening intersect neither the first inflowing fuel-air mixture jet (J) nor the second inflowing fuel-air mixture jet (J). [5] The pre-chamber spark plug (10) of claim 4, wherein each opening (38) is disposed at an angle relative to a spark plug radial axis, each angle of each opening being the same relative to the spark plug radial axis, such that the first, second, third, and fourth incoming fuel-air mixture jets (J) do not intersect a central spark plug axis (A). [6] Pre-chamber spark plug (10) according to claim 1, wherein the pre-chamber wall gap (P) has a width (D) extending beyond an axial bore of the housing (16). [7] Pre-chamber spark plug (10) according to claim 1, wherein the housing (16) includes the stepped wall portion (32) disposed between the exposed inner wall (30) of the housing (16) and the pre-chamber cover (20), and wherein the two or more openings (38) are configured such that each incoming fuel-air mixture jet (J) is directed to the stepped wall portion (32) of the housing (16). [8] Pre-chamber spark plug (10) according to claim 7, wherein the two or more openings (38) are configured such that each incoming fuel-air mixture jet (J) is directed to the stepped wall portion (32) and then travels along the exposed inner wall (30) and to an upper part of the pre-chamber wall gap (P). [9] Pre-chamber spark plug (10) according to claim 7 or 8, wherein the two or more openings (38) are each oriented at an angle with respect to a central axis (A) of the spark plug and the stepped wall portion (32) is oriented at an angle (α) with respect to a central axis (A) of the spark plug, each angle of the two or more openings (38) being the same as the angle of the stepped wall portion (32). [10] Pre-chamber spark plug (10) according to claim 1, wherein the pre-chamber wall gap (P) is at least 1.5 mm wide. [11] Pre-chamber spark plug (10), comprising: a housing (16); an insulator (14) disposed at least partially within the housing (16); a center electrode (12) arranged at least partially within the insulator (14); a ground electrode forming a spark gap (G) with the center electrode (12); and a pre-chamber cover (20) connected to the housing (16) and forming a pre-chamber, the pre-chamber cover (20) including two or more openings (38); wherein the two or more openings (38) are configured such that at least one incoming fuel-air mixture jet (J) is directed to a pre-chamber wall space to vent or remove gas from a previous ignition cycle, wherein the two or more openings (38) are angled so that a first incoming fuel-air mixture jet (J) of a first opening does not intersect with a second incoming fuel-air mixture jet (J) of a second opening, and wherein the spark gap (G) is a sliding discharge spark gap with an axial spark gap section. [12] Pre-chamber spark plug (10) according to claim 11, wherein the ground electrode is a conductive seal arranged at least partially between an inwardly projecting portion (28) of the housing (16) and the insulator (14).

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