A spark plug for an internal combustion engine includes insulating glass having a tubular shape, a central electrode including a tip protruding portion, a housing having a tubular shape, and a plug cover provided over an auxiliary combustion chamber. The plug cover is provided with injection holes through which the auxiliary combustion chamber communicates with the exterior. The central electrode includes a base material and a core material disposed inside the base material and having a higher thermal conductivity than the base material. The core material includes a large diameter portion and a small diameter portion continuously formed on a tip side of the large diameter portion. The small diameter portion has a smaller diameter than the large diameter portion, and includes, in a part of the small diameter portion in an axial direction, a small-diameter columnar portion having a constant diameter. At least a part of the small-diameter columnar portion is disposed further on the tip side of the spark plug than a tip of the insulating glass.

A pre-chamber spark plug includes a shell extending along a longitudinal axis and comprising an inner surface. The pre-chamber spark plug further includes an insulator including an outer surface. The pre-chamber spark plug further includes a pre-chamber cap connected to the shell. The pre-chamber cap and the shell together forms a pre-chamber. The pre-chamber spark plug further includes an annular reservoir defined between the outer surface of the insulator and the inner surface of the shell. The annular reservoir is spaced apart from the pre-chamber with respect to the longitudinal axis. The pre-chamber spark plug further includes a plurality of projections disposed between the annular reservoir and the pre-chamber with respect to the longitudinal axis. The plurality of projections at least partially define a plurality of flow passages therebetween.

A spark plug includes: a cylindrical insulator; a center electrode that is held on an inner circumferential side of the insulator and includes a tip-end protruding portion that protrudes from the insulator toward a tip end side; a cylindrical housing that holds the insulator on an inner circumferential side; and a plug cover that is provided in a tip end portion of the housing so as to cover a pre-combustion chamber in which the tip-end protruding portion is arranged. The plug cover is provided with an injection hole that communicates the pre-combustion chamber to the outside. A positioning portion that performs positioning of the housing and the plug cover in a plug circumferential direction is provided in the housing and the plug cover.

A spark plug electrode with an electrode tip formed on an electrode base using an additive manufacturing process, such as a powder bed fusion technique. The spark plug electrode includes an electrode base that at least partially surrounds a heat dissipating core, an electrode tip that is formed on the electrode base and includes a precious metal-based material, and a thermal coupling zone that directly thermally couples the electrode tip to the heat dissipating core. In some examples, the electrode tip is formed on an electrode base that has been cut or severed to expose a portion of the heat dissipating core, such that the electrode tip is formed directly on the heat dissipating core using additive manufacturing.

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.

In a spark plug, at least one injection hole serves as a ground-directed injection hole arranged to face a facing side of a ground electrode. An extension line of the center axis of the at least one ground-directed injection hole intersects with the facing side of the ground electrode at an intersection point. The facing side of the ground electrode has a closer region closer to the projection-end edge of the ground electrode than the intersection point is. The closer region of the facing side intersects with the extension line of the center axis of the ground-directed injection hole at a predetermined angle as viewed in the axial direction of the spark plug. The predetermined angle being an obtuse angle.

A spark plug for an internal combustion engine includes insulating glass having a tubular shape, a central electrode including a tip protruding portion, a housing having a tubular shape, and a plug cover provided over an auxiliary combustion chamber. The plug cover is provided with injection holes through which the auxiliary combustion chamber communicates with the exterior. The central electrode includes a base material and a core material disposed inside the base material and having a higher thermal conductivity than the base material. The core material includes a large diameter portion and a small diameter portion continuously formed on a tip side of the large diameter portion. The small diameter portion has a smaller diameter than the large diameter portion, and includes, in a part of the small diameter portion in an axial direction, a small-diameter columnar portion having a constant diameter. At least a part of the small-diameter columnar portion is disposed further on the tip side of the spark plug than a tip of the insulating glass.

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.