Spark plug with built-in resistor

A spark plug with a built-in resistor, which comprises:

• an insulator having an axially extending passing-through-hole;
• a terminal metal fitting fixed within the passing-through-hole at an end thereof;
• a center electrode fixed within the same passing-through-hole at the other end thereof;
• and
• a resistor provided between said terminal metal fitting and said center electrode within said passing-through-hole, said resistor comprising a resistor composition which is a mixture of a glass material portion and an electrically conductive material portion,
• wherein at least one of said terminal metal fitting and said center electrode is formed with a surface layer facing said resistor, said surface layer being an electrically conductive or semiconductive oxide having a thickness of 0.1 to 100 μm,
• wherein said at least one of said terminal metal fitting and said center electrode is directly in contact with said resistor on the surface of said oxide layer.

A spark plug with a built-in resistor, which comprises:

• an insulator having an axially extending passing-through-hole;
• a terminal metal fitting fixed within the passing-through-hole at an end thereof;
• a center electrode fixed within the same passing-through-hole at the other end thereof;
• and
• a resistor provided between said terminal metal fitting and said center electrode within said passing-through-hole, said resistor comprising a resistor composition which is a mixture of a glass material portion and an electrically conductive material portion,
• wherein at least one of said terminal metal fitting and said center electrode is formed with a surface layer facing said resistor, said surface layer being a Ni-based oxide layer having a thickness of 0.1 to 100 μm,
• wherein said at least one of said terminal metal fitting and said center electrode is directly in contact with said resistor on the surface of said oxide layer.

A spark plug with a built-in resistor, which comprises:

• an insulator having an axially extending passing-through-hole;
• a terminal metal fitting fixed within the passing-through-hole at an end thereof;
• a center electrode fixed within the same passing-through-hole at the other end thereof;
• and
• a resistor provided between said terminal metal fitting and said center electrode within said passing-through-hole, said resistor comprising a resistor composition which is a mixture of a glass material portion and an electrically conductive material portion, said resistor being directly in contact with at least one of said terminal metal fitting and said center electrode,
• wherein said resistor composition comprises at least one auxiliary elemental component selected from the group consisting of Zn, Sn, Ag and Ni in a total amount of 0.2 to 1.0 wt %.

A spark plug with a built-in resistor, which comprises:

• an insulator having an axially extending passing-through-hole;
• a terminal metal fitting fixed within the passing-through-hole at an end thereof;
• a center electrode fixed within the same passing-through-hole at the other end thereof;
• and
• a resistor provided between said terminal metal fitting and said center electrode within said passing-through-hole, said resistor comprising a resistor composition that has a structure comprising a mixture of a glass material portion with an electrically conductive material portion, said resistor being directly in contact with at least on of said terminal metal fitting and said center electrode,
• wherein said resistor composition comprises 0.2 to 1.0 wt % Zn as an auxiliary elemental component.

A spark plug with a built-in resistor, which comprises:

• an insulator having an axially extending passing-through-hole;
• a terminal metal fitting fixed within the passing-through-hole at an end thereof;
• a center electrode fixed within the same passing-through-hole at the other end thereof;
• and
• a resistor provided between said terminal metal fitting and said center electrode within said passing-through-hole, said resistor comprising a resistor composition which is a mixture of a glass material portion and an electrically conductive material portion, said resistor being directly in contact with at least one of said terminal metal fitting and said center electrode,
• wherein said resistor composition comprises a Ni-based metallic phase containing at least one selected from the group consisting of Cr, B, Si, C, Fe and P.

A spark plug with a built-in resistor, which comprises:

• an insulator having an axially extending passing-through-hole;
• a terminal metal fitting fixed within the passing-through-hole at an end thereof;
• a center electrode fixed within the same passing-through-hole at the other end thereof;
• and
• a resistor provided between said terminal metal fitting and said center electrode within said passing-through-hole, said resistor comprising a resistor composition which is a mixture of a glass material portion and an electrically conductive material portion,
• wherein at least one of said terminal metal fitting and said center electrode is formed with a surface layer facing said resistor, said surface layer being a metallic layer consisting essentially of at least one selected from the group consisting of Zn, Sn, Pb, Rh, Pd, Pt, Cu, Au, Sb and Ag, and a Ni alloy comprising at least one of B and P,
• wherein said at least one of said terminal metal fitting and said center electrode is directly in contact with said resistor on the surface of said metallic layer.

A spark plug with a built-in resistor, which comprises:

• an insulator having an axially extending passing-through-hole;
• a terminal metal fitting fixed within the passing-through-hole at an end thereof;
• a center electrode fixed within the same passing-through-hole at the other end thereof;
• and
• a resistor provided between said terminal metal fitting and said center electrode within said passing-through-hole, said resistor comprising a resistor composition which is a mixture of a glass material portion and an electrically conductive material portion,
• wherein at least one of said terminal metal fitting and said center electrode is formed with a surface layer facing said resistor, said surface layer consisting essentially of an electrically conductive or semiconductive oxide layer having a thickness at least 0.1 μm,
• wherein said at least one of said terminal metal fitting and said center electrode is directly in contact with said resistor on the surface of said oxide layer.

A spark plug with a built-in resistor, which comprises:

• an insulator having an axially extending passing-through-hole;
• a terminal metal fitting fixed within the passing-through-hole at an end thereof;
• a center electrode fixed within the same passing-through-hole at the other end thereof;
• and
• a resistor provided between said terminal metal fitting and said center electrode within said passing-through-hole, said resistor comprising a resistor composition which is a mixture of a glass material portion and an electrically conductive material portion,
• wherein at least one of said terminal metal fitting and said center electrode is formed with a surface layer facing said resistor, said surface layer consisting essentially of a Ni-based oxide layer having a thickness of at least 0.1 μm,
• wherein said at least one of said terminal metal fitting and said center electrode is directly in contact with said resistor on the surface of said oxide layer.