A spark plug for an internal combustion engine includes a housing, an insulator, a center electrode, a ground electrode, and an auxiliary chamber forming portion. The ground electrode faces the center electrode from an outer peripheral side and forms a discharge gap between the ground electrode and the center electrode. An auxiliary chamber is formed inside the auxiliary chamber forming portion. A distance in an axial direction between the discharge gap and a distal end of the auxiliary chamber is equal to or greater than a maximum wall thickness of the auxiliary chamber forming portion. The auxiliary chamber forming portion includes injection holes. The injection holes are formed in a state where openings on an outer side are located closer to a distal end than openings on the auxiliary chamber side. At least one of the injection holes is an injection hole in the axial direction formed along an axial direction of a plug. When viewed in the axial direction of the spark plug, a center of the axial injection hole is eccentric from a central axis of the spark plug toward the discharge gap.

A spark plug for an internal combustion engine includes a housing, an insulator, a center electrode, a ground electrode, and an auxiliary chamber forming portion. The ground electrode faces the center electrode from an outer peripheral side and forms a discharge gap between the ground electrode and the center electrode. An auxiliary chamber is formed inside the auxiliary chamber forming portion. A distance in an axial direction between the discharge gap and a distal end of the auxiliary chamber is equal to or greater than a maximum wall thickness of the auxiliary chamber forming portion. The auxiliary chamber forming portion includes injection holes. The injection holes are formed in a state where openings on an outer side are located closer to a distal end than openings on the auxiliary chamber side. At least one of the injection holes is an injection hole in the axial direction formed along an axial direction of a plug. When viewed in the axial direction of the spark plug, a center of the axial injection hole is eccentric from a central axis of the spark plug toward the discharge gap.

A spark plug includes a central electrode member and an outer electrode member. The central electrode member includes a central base and a plurality of electrode prongs extending in an axial direction from the central base. The outer electrode member surrounds the central electrode member. The outer electrode member includes a wall that is radially spaced from the plurality of electrode prongs to allow a series of electric arcs to form between the wall and the plurality of electrode prongs. The outer electrode member and the central electrode member are sized and positioned relative to one another such that a first rate of wear of the outer electrode member, along a longitudinal axis of the spark plug, is substantially equal to a second rate of wear of the central electrode member along the longitudinal axis.

A spark plug includes a central electrode member and an outer electrode member. The central electrode member includes a central base and a plurality of electrode prongs extending in an axial direction from the central base. The outer electrode member surrounds the central electrode member. The outer electrode member includes a wall that is radially spaced from the plurality of electrode prongs to allow a series of electric arcs to form between the wall and the plurality of electrode prongs. The outer electrode member and the central electrode member are sized and positioned relative to one another such that a first rate of wear of the outer electrode member, along a longitudinal axis of the spark plug, is substantially equal to a second rate of wear of the central electrode member along the longitudinal axis.

A spark plug includes a central electrode member and an outer electrode member. The central electrode member includes a central base and a plurality of electrode prongs extending in an axial direction from the central base. The outer electrode member surrounds the central electrode member. The outer electrode member includes a wall that is radially spaced from the plurality of electrode prongs to allow a series of electric arcs to form between the wall and the plurality of electrode prongs. The outer electrode member and the central electrode member are sized and positioned relative to one another such that a first rate of wear of the outer electrode member, along a longitudinal axis of the spark plug, is substantially equal to a second rate of wear of the central electrode member along the longitudinal axis.

A spark plug includes a central electrode member and an outer electrode member. The central electrode member includes a central base and a plurality of electrode prongs extending in an axial direction from the central base. The outer electrode member surrounds the central electrode member. The outer electrode member includes a wall that is radially spaced from the plurality of electrode prongs to allow a series of electric arcs to form between the wall and the plurality of electrode prongs. The outer electrode member and the central electrode member are sized and positioned relative to one another such that a first rate of wear of the outer electrode member, along a longitudinal axis of the spark plug, is substantially equal to a second rate of wear of the central electrode member along the longitudinal axis.

A prechamber sparkplug includes a housing having a nozzle with a prechamber formed therein, and each of a first set and a second set of electrode prongs within the prechamber. The second set of electrode prongs downwardly depend from attachment points to the housing, and form, together with the first set of electrode prongs, spark gaps within the prechamber. Each of the anode-cathode pairs formed by the sets of electrode prongs is spaced radially inward a clearance distance from the prechamber wall to position the spark gaps in a flow of swirled gases. The flow of swirled gases displaces a flame kernel formed at the spark gaps to inhibit quenching.

A prechamber sparkplug assembly includes a sparkplug, and a sparkplug housing having a prechamber tip. The sparkplug housing includes a plug bore centered on a longitudinal axis of the sparkplug housing and receiving the sparkplug, an inside radial wall extending around the plug bore, and an outside radial wall. A cooling cavity is formed between the inside radial wall and the outside radial wall. Coolant ports extend through the outside radial wall and fluidly connect to the cooling cavity to place the cooling cavity in fluid communication with a water jacket in a cylinder head.

A spark plug capable of generating a sufficient volume of jet with an increased range is provided. The spark plug includes a metal shell having a tubular shape; a center electrode retained in the metal shell in an insulated manner; a ground electrode that is electrically connected to the metal shell and that defines a spark gap between the center electrode and an end portion of the ground electrode; and a cap portion that covers the center electrode and the end portion of the ground electrode from the front in a region in front of the metal shell and in which a through hole is formed. The cap portion includes a plurality of projections on an inner surface of the through hole. The projections extend in an extending direction in which the through hole extends.

A spark plug capable of generating a sufficient volume of jet with an increased range is provided. The spark plug includes a metal shell having a tubular shape; a center electrode retained in the metal shell in an insulated manner; a ground electrode that is electrically connected to the metal shell and that defines a spark gap between the center electrode and an end portion of the ground electrode; and a cap portion that covers the center electrode and the end portion of the ground electrode from the front in a region in front of the metal shell and in which a through hole is formed. The cap portion includes a plurality of projections on an inner surface of the through hole. The projections extend in an extending direction in which the through hole extends.