Abstract: 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 SiO2 and B2O3, 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 Na2O.

Abstract: 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 SiO2 and B2O3, 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 Na2O.

Abstract: A base end portion of a ground electrode of a spark plug includes a skin portion, an intermediate portion, and a core portion 52. A center cross section CP containing the center axis PX of the spark plug and the center axis EX of the base end portion includes a first multilayer portion in which the intermediate portion is disposed inward of the skin portion and the core portion is disposed inward of the intermediate portion, and a second multilayer portion in which the skin portion and the core portion are in direct contact with each other. The center cross section CP includes an intersection point PI at which a first boundary line BLa between the metallic shell and the skin portion and a second boundary line between the metallic shell and the core portion meet with a third boundary line BLc.

Abstract: A spark plug includes a tube-shaped metal shell, an insulator having an outer circumference, at least part of which is held by the metal shell, the insulator including an axial hole extending along an axial line, a center electrode disposed in the axial hole, and a ground electrode fixed to the metal shell. The ground electrode includes an outer layer and an inner layer covered with the outer layer, the inner layer having a thermal conductivity higher than a thermal conductivity of the outer layer. A ratio L of L2 to L1 (=L2/L1) falls within a range of 5% to 50% where a width of the inner layer in a width direction of the ground electrode is denoted with L1 and a dimension of an oxide located in an interlayer portion between the outer layer and the inner layer in the width direction is denoted with L2.

Abstract: A spark plug includes a tube-shaped metal shell, an insulator having an outer circumference, at least part of which is held by the metal shell, the insulator including an axial hole extending along an axial line, a center electrode disposed in the axial hole, and a ground electrode fixed to the metal shell. The ground electrode includes an outer layer and an inner layer covered with the outer layer, the inner layer having a thermal conductivity higher than a thermal conductivity of the outer layer. A ratio L of L2 to L1 (=L2/L1) falls within a range of 5% to 50% where a width of the inner layer in a width direction of the ground electrode is denoted with L1 and a dimension of an oxide located in an interlayer portion between the outer layer and the inner layer in the width direction is denoted with L2.

Abstract: An electrode material for at least one of a center electrode (5) and a ground electrode (27) provided with a chip (31, 32) for use in a spark plug (1). The electrode material contains Ni as a principal component, and has a Si content of from 0.50% to 1.0% by mass, an Al content of from 0.2% to 2.0% by mass, a Cr content of from 12% to 34% by mass, a rare-earth element or the like content of from 0.03% to 0.2% by mass, a Fe content of more than 0% but not more than 20% by mass, a C content of not more than 0.10% by mass, and a Mn content of not more than 1.0% by mass. The total content of Si and Al is not less than 0.80% by mass, and less than one tenth of the Cr content.

Abstract: A spark plug includes a ceramic insulator having an axial hole formed in an axis direction of the spark plug, a center electrode inserted in a front side of the axial hole, a metal shell disposed around the ceramic insulator and a ground electrode joined to a front end portion of the metal shell, wherein the ground electrode has a cross-sectional area of 2.0 mm2 or smaller in any arbitrary cross section thereof taken in a direction perpendicular to a center line of the ground electrode; the ground electrode is made of a metal material containing 93 mass % or more of nickel; and the ground electrode has a Vickers hardness of 130 to 260 Hv.

Abstract: A base end portion of a ground electrode of a spark plug includes a skin portion, an intermediate portion, and a core portion 52. A center cross section CP containing the center axis PX of the spark plug and the center axis EX of the base end portion includes a first multilayer portion in which the intermediate portion is disposed inward of the skin portion and the core portion is disposed inward of the intermediate portion, and a second multilayer portion in which the skin portion and the core portion are in direct contact with each other. The center cross section CP includes an intersection point PI at which a first boundary line BLa between the metallic shell and the skin portion and a second boundary line between the metallic shell and the core portion meet with a third boundary line BLc.

Abstract: A spark plug including a center electrode; an insulator; a metallic shell; and a ground electrode, wherein at least one of the center electrode and the ground electrode has thereon an intermediate member which connects the center electrode or the ground electrode to a noble metal tip. The intermediate member has a tip-bonding portion to which the noble metal tip is bonded, and an electrode-bonding portion which has a diameter greater than that of the tip-bonding portion, and which is bonded to the center electrode or the ground electrode. The intermediate member contains nickel (Ni) as a main component, and also contains chromium (Cr) in an amount of 15 to 25 wt. %. The intermediate member contains, in a surface portion thereof, silicon (Si) in an amount per unit volume of 0.04 mg/mm3 to 0.12 mg/mm3, and aluminum (Al) in an amount per unit volume of 0.03 mg/mm3 to 0.10 mg/mm3.

Abstract: An electrode material for at least one of a center electrode (5) and a ground electrode (27) provided with a chip (31, 32) for use in a spark plug (1). The electrode material contains Ni as a principal component, and has a Si content of from 0.50% to 1.0% by mass, an Al content of from 0.2% to 2.0% by mass, a Cr content of from 12% to 34% by mass, a rare-earth element or the like content of from 0.03% to 0.2% by mass, a Fe content of more than 0% but not more than 20% by mass, a C content of not more than 0.10% by mass, and a Mn content of not more than 1.0% by mass. The total content of Si and Al is not less than 0.80% by mass, and less than one tenth of the Cr content.

Abstract: It is an object of the present invention to provide a spark plug having a ground electrode joined securely by electric resistance welding. The spark plug includes a cylindrical metal shell and a ground electrode joined by electric resistance welding to an end portion of the metal shell. The metal shell has a high hardness region formed with a Vickers hardness of 3×102 to 5×102 Hv in the end portion thereof in such a manner that the high hardness region, when viewed in cross section along a plane including an axis of the spark plug and an axis of the ground electrode, has a length d of 0.3 to 0.8 mm from a ground electrode side welding boundary to a metal shell side welding boundary in a direction of load applied during the electric resistance welding.

Abstract: A spark plug including a center electrode and a ground electrode having a gap between the center electrode and the ground electrode, the ground electrode has an outer layer which is formed from an Ni-based alloy and a core portion which is covered by the outer layer and formed from a material having a thermal conductivity higher than that of the outer layer. Further, the melting point of the Ni-based alloy forming the outer layer is 1150° C. or more and 1350° C. or less.

Abstract: A spark plug including a center electrode; an insulator; a metallic shell; and a ground electrode, wherein at least one of the center electrode and the ground electrode has thereon an intermediate member which connects the center electrode or the ground electrode to a noble metal tip. The intermediate member has a tip-bonding portion to which the noble metal tip is bonded, and an electrode-bonding portion which has a diameter greater than that of the tip-bonding portion, and which is bonded to the center electrode or the ground electrode. The intermediate member contains nickel (Ni) as a main component, and also contains chromium (Cr) in an amount of 15 to 25 wt. %. The intermediate member contains, in a surface portion thereof, silicon (Si) in an amount per unit volume of 0.04 mg/mm3 to 0.12 mg/mm3, and aluminum (Al) in an amount per unit volume of 0.03 mg/mm3 to 0.10 mg/mm3.

Abstract: A spark plug which exhibits improved resistance to high-temperature oxidation of an electrode, and improved resistance to spark-induced erosion of, improved resistance to oxidation of, and improved joining reliability of a tip joined to the electrode. A spark plug has spark members; each of the spark members has a weight of 1.5 mg or more; and a center electrode and a ground electrode contain Ni as a main component, C in an amount of 0.005% by mass to 0.10% by mass, Si in an amount of 1.05% by mass to 3.0% by mass, Mn in an amount of 2.0% by mass or less, Cr in an amount of 20% by mass to 32% by mass, and Fe in an amount of 6% by mass to 16% by mass.

Abstract: It is an object of the present invention to provide a spark plug having a ground electrode joined securely by electric resistance welding. The spark plug includes a cylindrical metal shell and a ground electrode joined by electric resistance welding to an end portion of the metal shell. The metal shell has a high hardness region formed with a Vickers hardness of 3×102 to 5×102 Hv in the end portion thereof in such a manner that the high hardness region, when viewed in cross section along a plane including an axis of the spark plug and an axis of the ground electrode, has a length d of 0.3 to 0.8 mm from a ground electrode side welding boundary to a metal shell side welding boundary in a direction of load applied during the electric resistance welding.

Abstract: A spark plug includes a ceramic insulator having an axial hole formed in an axis direction of the spark plug, a center electrode inserted in a front side of the axial hole, a metal shell disposed around the ceramic insulator and a ground electrode joined to a front end portion of the metal shell, wherein the ground electrode has a cross-sectional area of 2.0 mm2 or smaller in any arbitrary cross section thereof taken in a direction perpendicular to a center line of the ground electrode; the ground electrode is made of a metal material containing 93 mass % or more of nickel; and the ground electrode has a Vickers hardness of 130 to 260 Hv.

Abstract: A spark plug which exhibits improved resistance to high-temperature oxidation of an electrode, and improved resistance to spark-induced erosion of, improved resistance to oxidation of, and improved joining reliability of a tip joined to the electrode. A spark plug has spark members; each of the spark members has a weight of 1.5 mg or more; and a center electrode and a ground electrode contain Ni as a main component, C in an amount of 0.005% by mass to 0.10% by mass, Si in an amount of 1.05% by mass to 3.0% by mass, Mn in an amount of 2.0% by mass or less, Cr in an amount of 20% by mass to 32% by mass, and Fe in an amount of 6% by mass to 16% by mass.

Abstract: A spark plug provides a reduced production cost by forming a tip from a metallic material containing Ni that exhibits excellent erosion resistance. The spark plug comprises an insulator having an axial hole extending in an axial direction; a center electrode inserted into the axial hole at a front end thereof; a metallic shell provided around the insulator; a ground electrode whose proximal end portion is fixed to a front end portion of the metallic shell; and a tip bonded to a distal end portion of the ground electrode such that a spark discharge gap is formed between the tip and a front end portion of the center electrode. The tip is formed of a metallic material containing Ni in an amount of 93 mass % or more, and has a Vickers hardness of 163 Hv or less.

Abstract: A spark plug including a center electrode and a ground electrode having a gap between the center electrode and the ground electrode, the ground electrode has an outer layer which is formed from an Ni-based alloy and a core portion which is covered by the outer layer and formed from a material having a thermal conductivity higher than that of the outer layer. Further, the melting point of the Ni-based alloy forming the outer layer is 1150° C. or more and 1350° C. or less.

Abstract: The object of the invention is to provide a spark plug including a central electrode and/or a ground electrode with a gap, which can suppress generation of corrosion-like generated foreign substances while maintaining high thermal conductivity and high strength. The gap between the central electrode and the ground electrode with at least one of the central electrode and the ground electrode formed from an electrode material including 96% by mass or more of Ni, in which the electrode material includes a total content of from 0.05% by mass to 0.45% by mass of at least one selected from a group consisting of Y and rare earth elements, 0.05% by mass or more of Mn, and a total content of 0.01% by mass or more of at least one selected from a group consisting of Ti, V, and Nb, and the ratio (a/b) of the total content (a) of Ti, V, and Nb to the content (b) of Mn is from 0.02 to 0.40.