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 includes: a metallic shell having a through hole extending in a direction of an axis; a cap covering an opening in the metallic shell; a melt portion formed between the cap and the metallic shell to join the cap and the metallic shell to each other; and a gap extending from a specific space which is surrounded by the metallic shell and the cap to the melt portion and interposed between the metallic shell and the cap.

A batch of spark plugs. Each spark plug has a longitudinal axis, a central electrode oriented in the direction of the longitudinal axis, a ground electrode oriented at an angle to the longitudinal axis, such that a spark gap is formed between a tip of the central electrode and a tip of the ground electrode, and an outer thread for screwing the spark plug in the longitudinal direction into an inner thread of a cylinder head of a combustion chamber of an internal combustion engine, and has an annular contact surface oriented perpendicularly to the longitudinal axis and intended for bringing the spark plug to rest against the cylinder head. After the spark plugs have been screwed into the inner thread of the cylinder head, the ground electrodes have the same orientation with regard to a rotation about the longitudinal axis of the spark plug relative to the combustion chamber.

A pre-chamber spark plug that includes a shell, and an end cap attached to the shell. Additionally, the pre-chamber spark plug includes an insulator disposed within the shell. In a particular embodiment, a center electrode has a first portion surrounded by the insulator, and a second portion that extends from the insulator into a pre-chamber. The pre-chamber defined by the shell and end cap. In a further embodiment, a ground electrode is attached to the shell. In particular embodiments, the ground electrode is tubular in shape and includes an inner spark surface ring spaced in surrounding relation to the center electrode to create a spark gap, an outer ring attached to the shell, and a plurality of rounded spokes connecting the inner and outer rings. In a particular embodiment, the ground and center electrodes accommodate attachment of precious metal alloys to increase electrode surface life.

A pre-chamber spark plug that includes a shell, and an end cap attached to the shell. Additionally, the pre-chamber spark plug includes an insulator disposed within the shell. In a particular embodiment, a center electrode has a first portion surrounded by the insulator, and a second portion that extends from the insulator into a pre-chamber. The pre-chamber defined by the shell and end cap. In a further embodiment, a ground electrode is attached to the shell. In particular embodiments, the ground electrode is tubular in shape and includes an inner spark surface ring spaced in surrounding relation to the center electrode to create a spark gap, an outer ring attached to the shell, and a plurality of rounded spokes connecting the inner and outer rings. In a particular embodiment, the ground and center electrodes accommodate attachment of precious metal alloys to increase electrode surface life.

A spark plug having an insulating body defining a longitudinal axis and including a base portion and an obstruction portion, a first electrode including a proximal portion, a sheathed portion and a distal portion, the sheathed portion of the first electrode extending through the base portion of the insulating body, and a second electrode including a proximal portion, a sheathed portion and a distal portion, the sheathed portion of the second electrode extending through the base portion and the obstruction portion of the insulating body, wherein the obstruction portion axially extends beyond the distal portion of the first electrode.

An internal combustion engine includes a spark plug which protrudes into a combustion chamber. The spark plug has a central electrode and a ground electrode, and is configured such that a spark is generated between the central electrode and the ground electrode by electrical discharge. The spark plug has a vortex generator that separates an air flow near the ground electrode from the ground electrode and generates a vortex at a downstream side. The central electrode and the ground electrode are placed in a manner such that a spark or a flame deformed by an air flow flowing between the central electrode and the ground electrode enters the trailing vortex, or the spark penetrates through the inside of the trailing vortex.

A spark plug includes a metal shell and a cap member joined to the metal shell to define a pre-chamber. The cap member includes an overlapping surface that overlaps the metal shell along the axial line direction, an inner facing surface positioned closer to the pre-chamber than is the overlapping surface, the inner facing surface facing the metal shell in the axial line direction, and an outer facing surface positioned closer to an outer periphery than is the overlapping surface, the outer facing surface facing the metal shell in the axial line direction. A portion of the cap member that is closer to the pre-chamber than is the overlapping surface s spaced from the metal shell. The metal shell and the cap member are joined together at at least one of the outer facing surface and the overlapping surface.

A spark plug includes a metal shell and a cap member joined to the metal shell to define a pre-chamber. The cap member includes an overlapping surface that overlaps the metal shell along the axial line direction, an inner facing surface positioned closer to the pre-chamber than is the overlapping surface, the inner facing surface facing the metal shell in the axial line direction, and an outer facing surface positioned closer to an outer periphery than is the overlapping surface, the outer facing surface facing the metal shell in the axial line direction. A portion of the cap member that is closer to the pre-chamber than is the overlapping surface s spaced from the metal shell. The metal shell and the cap member are joined together at at least one of the outer facing surface and the overlapping surface.