One example provides a spark plug having a center electrode including at least one of a first material and a second material, the second material having a hardness rating greater than a hardness rating of the first material. The center electrode includes a region of first material disposed beyond an end surface of an insulative nose toward a firing end. The center electrode includes an electrode head, at least a portion of the electrode head disposed beyond the end surface of the insulative nose toward the firing end and having a cross-sectional area perpendicular to an axial centerline greater than a cross-sectional area of the end surface of the insulative nose. A shield element of the second material covers exposed surfaces of the region of first material disposed beyond the end surface of the insulative nose. An electrode wire extends from the electrode head into a central bore.

One example provides a spark plug including a terminal end, a firing end, an axial centerline extending between the terminal end and the firing end, and an insulative core extending between the terminal end and the firing end, the insulative core including an insulative nose proximate to the firing end, and a central bore coincident with the axial centerline extending through the insulative core. A center electrode includes an electrode wire and an electrode head. The electrode head includes an electrode plate, in a plane perpendicular to the axial centerline, the electrode plate having a cross-sectional area greater than a cross-sectional area of the insulative nose, the electrode wire mechanically and electrically connected to the electrode plate, the electrode wire extending from a bottom side of the electrode plate into the central bore at the insulative nose to form an electrical and thermal pathway with the electrode head.

One example provides a spark plug including a terminal end, a firing end, an axial centerline extending between the terminal end and the firing end, and an insulative core extending between the terminal end and the firing end, the insulative core including an insulative nose proximate to the firing end, and a central bore coincident with the axial centerline extending through the insulative core. A center electrode includes an electrode wire and an electrode head. The electrode head includes an electrode plate, in a plane perpendicular to the axial centerline, the electrode plate having a cross-sectional area greater than a cross-sectional area of the insulative nose, the electrode wire mechanically and electrically connected to the electrode plate, the electrode wire extending from a bottom side of the electrode plate into the central bore at the insulative nose to form an electrical and thermal pathway with the electrode head.

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 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 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 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 has an insulator having a through hole formed along an axial direction, a center electrode which is partially inserted into a portion of the through hole on a forward end side in the axial direction, and a glass seal portion which is in contact with the insulator and the center electrode within the through hole, in which the glass seal portion contains glass and an electrically conductive substance. The glass contains an Si component and a B component in a total amount of 50 mass % or more, as reduced to SiO.sub.2 and B.sub.2O.sub.3, a Zn component in an amount of 20 mass % to 35 mass % as reduced to ZnO, and an alkali metal component. The glass contains, as the alkali metal component, an Na component in an amount less than 1 mass % as reduced to Na.sub.2O.

A spark plug has an insulator having a through hole formed along an axial direction, a center electrode which is partially inserted into a portion of the through hole on a forward end side in the axial direction, and a glass seal portion which is in contact with the insulator and the center electrode within the through hole, in which the glass seal portion contains glass and an electrically conductive substance. The glass contains an Si component and a B component in a total amount of 50 mass % or more, as reduced to SiO.sub.2 and B.sub.2O.sub.3, a Zn component in an amount of 20 mass % to 35 mass % as reduced to ZnO, and an alkali metal component. The glass contains, as the alkali metal component, an Na component in an amount less than 1 mass % as reduced to Na.sub.2O.

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.