Spark plug with electrode head shielding element

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 coaxial with the axial centerline extending through the insulative core;
• an insulative nose proximate to the firing end;
• and
• a counter bore coaxial with the axial centerline and extending into the insulative nose toward the terminal end, the counter bore having a diameter greater than a diameter of the central bore;
• and
• a center electrode including:
• an electrode wire of a first material having a first hardness rating;
• and
• an electrode head comprising:
• an electrode plate of a second material having a second hardness rating greater than the first hardness rating, the electrode plate having a bottom surface and a top surface and having a cross-sectional area greater than a cross-sectional area of the insulative nose in a plane perpendicular to the axial centerline;
• a collar extending from the bottom surface of the electrode plate and seated in the counter bore;
• and
• a collar bore coaxial with the axial centerline, the collar bore extending through the collar and electrode plate to a pocket in the top surface of the electrode plate, the pocket coaxial with and having a diameter greater than a diameter of the collar bore, wherein a first end of the electrode wire extends through the collar bore to an electrode wire head seated and within and mechanically secured to the electrode plate within the pocket via a staked connection, and wherein the electrode wire is electrically and mechanically connected to an interior of the collar bore via a brazed connection;
• and
• a shield element disposed to cover a surface of the electrode wire head exposed from the electrode plate, the shield element of a material having a 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:
• a central bore coaxial with the axial centerline extending through the insulative core;
• an insulative nose proximate to the firing end;
• and
• a counter bore coaxial with the axial centerline and extending into the insulative nose toward the terminal end, the counter bore having a diameter greater than a diameter of the central bore;
• and
• a center electrode of a first material having a first hardness rating, the center electrode including:
• an electrode wire;
• and
• an electrode head comprising:
• an electrode plate having a bottom surface and a top surface and, in a plane perpendicular to the axial centerline, having a cross-sectional area greater than a cross-sectional area of the counter bore and less than a cross-sectional are of the end surface of the insulative nose;
• a collar extending from the bottom surface of the electrode plate and seated in the counter bore such that the bottom surface of the electrode plate is seated on the end surface of the insulative nose;
• and
• a collar bore coaxial with the axial centerline and extending into the collar toward the electrode plate, wherein a first end of the electrode wire extends into the collar bore and is electrically and mechanically connected to an interior of the collar bore via a crimp connection and a braze connection;
• and
• a shield element disposed to cover exterior surfaces of the electrode plate exposed from the insulative nose, the shield element of a second material having a second hardness rating greater than the first hardness rating, wherein the shield element extends laterally beyond the end surface of the insulative nose such that an edge extending about a perimeter of a bottom surface of the shield element facing the terminal end forms a spark gap with a metal shell of the spark plug.

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;
• and
• a center electrode comprising:
• an electrode head including:
• an electrode plate having a cross-sectional area perpendicular to the axial centerline which is greater than a diameter of the central bore and less than a diameter of the end surface of the insulative nose, wherein at least a portion of the electrode plate is positioned beyond the end surface of the insulative nose;
• and
• a shield element disposed over surfaces of electrode plate exposed from the insulative nose, wherein the shield element extends laterally beyond the end surface of the insulative nose such that an edge extending about a perimeter of a bottom surface of the shield element facing the terminal end forms a spark gap with a metal shell of the spark plug;
• and
• an electrode wire extending from electrode plate into the central bore, wherein the electrode head and electrode wire comprise a contiguous homogeneous piece of first material having a first hardness rating and the shielding element comprises a second material having a second hardness rating greater than the first hardness rating.