Spark plug with integrated center electrode

A spark plug comprising:

• a terminal end;
• a firing end;
• an axial centerline extending between the terminal end and the firing end;
• an insulative core extending between the terminal end and the firing end, the insulative core including:
• a central bore extending through the insulative core coincident with the axial centerline;
• and
• an insulative nose at the terminal end, the insulative nose having an end surface perpendicular to the axial centerline;
• a center electrode comprising:
• an electrode head including:
• an electrode plate having an upper surface, an opposing lower surface facing the insulative nose, and a diameter at least greater than a diameter of the central bore, wherein at least a portion of the electrode plate is disposed axially beyond the insulative nose toward the firing end;
• and
• a shield element disposed over surfaces of the electrode plate exposed from the insulative nose, the shield element mechanically and electrically coupled to at least the surfaces of the electrode plate exposed from the insulative nose, wherein a circumferential edge of a lower surface of the shield element facing the insulative nose forms a circumferential spark gap with a side electrode;
• and
• an electrode wire extending into the central bore from the electrode head, wherein the electrode plate and electrode wire are a contiguous piece of first material having a first hardness rating, and the shield element is of a second material having a second hardness rating greater than the first hardness rating.

A spark plug comprising:

• a terminal end;
• a firing end;
• an axial centerline extending between the terminal end and the firing end;
• an insulative core extending between the terminal end and the firing end, the insulative core including:
• an insulative nose at the terminal end, the insulative nose having an end surface perpendicular to the axial centerline;
• and
• a central bore extending through the insulative core, including through the insulative nose, the central bore disposed coincidently with and symmetrically about the axial centerline;
• and
• a center electrode comprising:
• an electrode head including:
• an electrode plate having an upper surface, an opposing lower surface facing the insulative nose, and a diameter at least greater than a diameter of the central bore, wherein at least a portion of the electrode plate is disposed axially beyond the insulative nose toward the firing end;
• and
• a shield element disposed over surfaces of the electrode plate exposed from the insulative nose, the shield element coupled via a metallurgical bond to at least the surfaces of the electrode plate exposed from the insulative nose, wherein a circumferential edge of a lower surface of the shield element facing the insulative nose forms a circumferential spark gap with a side electrode of the spark plug;
• and
• an electrode wire extending into the central bore from the lower surface of the electrode plate, wherein the electrode plate and electrode wire are a contiguous piece of first material having a first hardness rating, and the shield element is of a second material having a second hardness rating greater than the first hardness rating.

A spark plug comprising:

• a terminal end;
• a firing end;
• an axial centerline extending between the terminal end and the firing end;
• an insulative core extending between the terminal end and the firing end, the insulative core including:
• an insulative nose at the terminal end, the insulative nose having an end surface perpendicular to the axial centerline;
• a central bore coincident with the axial centerline extending through the insulative core, including through the insulative nose;
• and
• a center electrode comprising:
• an electrode head having an upper surface, an opposing lower surface, and a diameter greater than a diameter of the end surface of the insulative nose, wherein the electrode head is disposed axially beyond the insulative nose toward the firing end, and wherein a circumferential edge of the lower surface forms a circumferential spark gap with a side electrode;
• and
• an electrode wire extending into the central bore from the lower surface of the electrode head, wherein the electrode head and electrode wire are a contiguous piece of material.