Spark plug for igniting a combustible fuel in an internal combustion engine, wherein the spark plug has an igniter arranged at an end of the spark plug facing the combustion chamber, when the spark plug is mounted in the internal combustion engine. The spark plug includes a wall and a sealing area. The wall at least partially surrounds the igniter. The sealing area is used for sealing the combustion chamber against the environment. The wall has the sealing area located at an end of the wall, which end faces the combustion chamber when the spark plug is mounted in the internal combustion engine.

Spark plug for igniting a combustible fuel in an internal combustion engine, wherein the spark plug has an igniter arranged at an end of the spark plug facing the combustion chamber, when the spark plug is mounted in the internal combustion engine. The spark plug includes a wall and a sealing area. The wall at least partially surrounds the igniter. The sealing area is used for sealing the combustion chamber against the environment. The wall has the sealing area located at an end of the wall, which end faces the combustion chamber when the spark plug is mounted in the internal combustion engine.

A spark-ignited reciprocating piston internal combustion engine may include a pre-chamber ignition system which is arranged in the cylinder head of the reciprocating piston internal combustion engine and in which an ignition device is arranged, comprising an ignition electrode in a housing, said ignition electrode protruding into a cavity of the pre-chamber ignition system. The cavity is covered from the combustion chamber of the reciprocating piston internal combustion engine by a cover, and the cover has at least one first opening which connects the cavity and the combustion chamber together so as to conduct gas. A metal transverse brace with at least one second opening, which connects opposite sides of the housing together, is arranged in the cavity in the region of the ignition electrode, wherein the metal transverse brace is made of a first metal material in a central region and a second metal material in a region contacting the housing.

A spark-ignited reciprocating piston internal combustion engine may include a pre-chamber ignition system which is arranged in the cylinder head of the reciprocating piston internal combustion engine and in which an ignition device is arranged, comprising an ignition electrode in a housing, said ignition electrode protruding into a cavity of the pre-chamber ignition system. The cavity is covered from the combustion chamber of the reciprocating piston internal combustion engine by a cover, and the cover has at least one first opening which connects the cavity and the combustion chamber together so as to conduct gas. A metal transverse brace with at least one second opening, which connects opposite sides of the housing together, is arranged in the cavity in the region of the ignition electrode, wherein the metal transverse brace is made of a first metal material in a central region and a second metal material in a region contacting the housing.

This spark plug includes a cap portion covering a center electrode and an end of a ground electrode from a front side. In a cross section including an axial line, where a pitch of an external thread of a metal shell is X (mm), an axial-line-direction distance between a crest of a rear-end ridge of a full thread portion of an external thread and a rear end of a contact portion of an insulator with which the metal shell contacts directly or via another member is A (mm), an axial-line-direction distance between the rear end of the contact portion and a front end of the insulator is B (mm), and an axial-line-direction distance between the rear end of the contact portion and a seating surface of the metal shell is C (mm), 0<A<4×, B≤15, and C≤3.6 are satisfied.

A spark plug, including a housing, an insulator situated in the housing, a center electrode situated in the insulator and a ground electrode situated on the housing, the ground electrode and the center electrode being situated relative to one another in such a way that the ground electrode and the center electrode form a spark gap, and the ground electrode including a core and a sheath surrounding the core, the core being made of a material which has a higher thermal conductivity than the material of the sheath, and a cross sectional area of the ground electrode being not greater than 2.76 mm.sup.2, the sheath having a wall thickness c of not greater than 0.4 mm in a first region of the ground electrode.

A spark plug, including a housing, an insulator situated in the housing, a center electrode situated in the insulator and a ground electrode situated on the housing, the ground electrode and the center electrode being situated relative to one another in such a way that the ground electrode and the center electrode form a spark gap, and the ground electrode including a core and a sheath surrounding the core, the core being made of a material which has a higher thermal conductivity than the material of the sheath, and a cross sectional area of the ground electrode being not greater than 2.76 mm.sup.2, the sheath having a wall thickness c of not greater than 0.4 mm in a first region of the ground electrode.

A plasma jet plug includes a rod-shaped central electrode, an insulator having an axial hole, a metal shell disposed around the insulator, an orifice electrode electrically connected to the metal shell and located at a distal end side of the insulator, and a gasket that contacts an outer surface of the insulator and an inner surface of the metal shell. The insulator includes a first member, a second member and an inorganic seal layer. The first member has the axial hole and includes a large-diameter portion and a small-diameter portion. The second member has a through hole into which the small-diameter portion is inserted. The second member has an outer surface that contacts the gasket. The inorganic seal layer seals a gap between the first member and the second member. In a section including the axis, the sum of seal lengths is greater than or equal to 3 mm.

A plasma jet plug includes a rod-shaped central electrode, an insulator having an axial hole, a metal shell disposed around the insulator, an orifice electrode electrically connected to the metal shell and located at a distal end side of the insulator, and a gasket that contacts an outer surface of the insulator and an inner surface of the metal shell. The insulator includes a first member, a second member and an inorganic seal layer. The first member has the axial hole and includes a large-diameter portion and a small-diameter portion. The second member has a through hole into which the small-diameter portion is inserted. The second member has an outer surface that contacts the gasket. The inorganic seal layer seals a gap between the first member and the second member. In a section including the axis, the sum of seal lengths is greater than or equal to 3 mm.

A spark plug having a housing, an insulator situated in the housing, a center electrode situated in the insulator and a ground electrode situated on the housing, the ground electrode and the center electrode being situated toward each other in such a way that the ground electrode and the center electrode form a spark gap, and the center electrode rest with a center electrode head on a seat developed on an inner side of the insulator, and the center electrode having an electrode base body and a core situated in the electrode base body, the core being made from a material that has a higher heat conductivity than the material of the electrode base body, the electrode base body having a diameter that is not greater than 1.7 mm.