Abstract: 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 includes a central bore coincident with the axial centerline extending through the insulative core, and an insulative nose extending along the axial centerline at the firing end of the insulative core, the insulative nose having an axial length and defining an end surface of the insulative core, wherein a cross-sectional area of the insulative nose perpendicular to the axial centerline varies along the axial length of the insulative nose with a cross-sectional area along at least a portion of the axial length being less than a surface area of the end surface so that a perimeter surface along the portion of the axial length of the insulative nose has a concave profile.

Abstract: One example provides a spark plug including an insulative core having a central bore extending there through and including an insulative nose defining an end surface at a firing end of the spark plug, the insulative nose having a concave perimeter surface. An electrode includes an electrode wire extending into the central bore from an electrode head, the electrode head disposed beyond the insulative nose and having a perimeter edge disposed beyond a perimeter of the end surface of the insulative nose. A metal shell of a first material disposed circumferentially about the insulative core. A side electrode ring of a second material is attached to a firing end surface of the metal shell, wherein a perimeter edge of the side electrode ring forms a continuous spark gap with the perimeter edge of the electrode head, the second material having a hardness rating greater than the first material.

Abstract: One example provides a center electrode for a spark plug having an axial centerline. An electrode head of a first material has an upper side, a lower side, and a head cross-sectional area in a plane perpendicular to the axial centerline, with an outer edge of the lower side of the electrode head to provide a continuous spark edge about a perimeter of the lower side of the electrode head. An electrode wire extends from the lower side of the electrode head coaxially with the axial centerline and having a wire cross-sectional area in a plane perpendicular to the axial centerline less than the head cross-sectional area. The electrode wire includes a center core of a second material, and an outer sheath of the first material disposed about the center core, the electrode head and outer sheath of the electrode wire being a contiguous piece of the first material.

Abstract: One example provides a spark plug having an insulative core extending along an axial centerline between a terminal and a firing end and including a central bore extending there through, and an insulative nose at the terminal end having an end surface. A center electrode includes an electrode head having an outer edge extending about a perimeter of the electrode head beyond a perimeter of the end surface of the insulative nose and forming a spark gap with a side electrode. The electrode includes an electrode plate, at least a portion of which is positioned axially beyond the end surface of the insulative nose and has cross-sectional which is at least greater than a cross-sectional area of the central bore. An electrode wire extends from the electrode plate into the central bore, wherein the electrode plate and electrode wire are a contiguous piece of material.

Abstract: 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.

Abstract: 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 includes a central bore coincident with the axial centerline extending through the insulative core, and an insulative nose extending along and symmetrically about the axial centerline from an end surface of the insulative core at the firing end to a transition location along an axial length of the insulative core, wherein a perimeter surface of the insulative nose has a concave curvilinear shape between the end surface and the transition location.

Abstract: One example provides a spark plug including an axial centerline extending between a terminal end and a firing end, an insulative core including a central bore having a first diameter coincident with the axial centerline extending through the insulative core, an insulative nose proximate to the firing end, and a counter bore coincident with the axial centerline and extending axially into the insulative nose, the counter bore having a second diameter greater than the first diameter. A center electrode includes an electrode wire disposed within the central bore and having a first end extending into the counter bore, and an electrode head mechanically and electrically coupled to the first end of the electrode wire, a first portion of the electrode head seated within the counter bore to define an interface with the counter bore to provide a heat transfer path from the electrode head to the insulative core.

Abstract: 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.

Abstract: One example provides a spark plug including an axial centerline extending between a terminal end and a firing end, an insulative core including a central bore having a first diameter coincident with the axial centerline extending through the insulative core, an insulative nose proximate to the firing end, and a counter bore coincident with the axial centerline and extending axially into the insulative nose, the counter bore having a second diameter greater than the first diameter. A center electrode includes an electrode wire disposed within the central bore and having a first end extending into the counter bore, and an electrode head mechanically and electrically coupled to the first end of the electrode wire, a first portion of the electrode head seated within the counter bore to define an interface with the counter bore to provide a heat transfer path from the electrode head to the insulative core.