Abstract: A spark plug includes: a center electrode; an insulating member; a metal shell; a ground electrode; and a cap covers an opening of the metal shell on the front end side to define an auxiliary combustion space in which the gap is disposed, a first angle being formed by a second line and a first tangent line, a second angle being formed by the second line and a second tangent line, the second angle being greater than the first angle, and at least a portion of the opening of the specific through hole on the auxiliary combustion space side being positioned on a range of the second angle.

Abstract: A spark plug includes: an insulator with an axial hole; a center electrode held in a front end side of the axial hole; a cylindrical metal shell disposed around the insulator and having a seal part brought into contact with an outer circumferential surface of the insulator; a ground electrode arranged to form a gap with the center electrode; and a cap connected to a front end part of the metal shell to define therein an auxiliary combustion space in which the gap is formed, the cap having at least one through hole formed to provide communication between the auxiliary combustion space and the outside, wherein the condition (B/A)?0.25 is satisfied where A represents a volume of an imaginary space defined at a position frontward of the seal part; and B represents a volume of parts of the ground and center electrodes located in the imaginary space.

Abstract: A spark plug includes: a center electrode; an insulating member; a metal shell; a ground electrode; and a cap covers an opening of the metal shell on the front end side to define an auxiliary combustion space in which the gap is disposed, a first angle being formed by a second line and a first tangent line, a second angle being formed by the second line and a second tangent line, the second angle being greater than the first angle, and at least a portion of the opening of the specific through hole on the auxiliary combustion space side being positioned on a range of the second angle.

Abstract: An electrode base material of the spark plug contains not less than 50 wt. % of Ni. A discharge member contains not less than 45 wt. % of Pt, and at least one of Ni and Rh. An intermediate member contains Pt and Ni. In the discharge member, a content of Pt is highest, and a total content of Pt, Rh, and Ni is not less than 92 wt. %. In the intermediate member, a content of one of Pt and Ni is not less than 50 wt. %, a content of Ni is higher than a content of Ni in the discharge member, and a total content of Pt, Rh, and Ni is not less than 85 wt. %. A thickness of the diffusion layer formed between the discharge member and the intermediate member is not less than 0.002 mm and not more than 0.065 mm.

Abstract: An electrode tip for a spark plug, wherein Pt is contained as a main component, 7% by mass or more of Rh is contained, and a total content of Pt and Rh is greater than or equal to 95% by mass. The electrode tip includes: a narrow portion having the same cross-sectional shape in a direction of an axis; and a wide portion which is adjacent to the narrow portion and has a cross-sectional area, in a radial direction, which is greater than the narrow portion.

Abstract: An electrode base material of the spark plug contains not less than 50 wt. % of Ni. A discharge member contains not less than 45 wt. % of Pt, and at least one of Ni and Rh. An intermediate member contains Pt and Ni. In the discharge member, a content of Pt is highest, and a total content of Pt, Rh, and Ni is not less than 92 wt. %. In the intermediate member, a content of one of Pt and Ni is not less than 50 wt. %, a content of Ni is higher than a content of Ni in the discharge member, and a total content of Pt, Rh, and Ni is not less than 85 wt. %. A thickness of the diffusion layer formed between the discharge member and the intermediate member is not less than 0.002 mm and not more than 0.065 mm.

Abstract: A spark plug having a tip formed of an alloy containing Pt. The tip contains not less than 6 mass % of Rh, at least one element selected from an R group consisting of Rh, Re, Ir, Ru, W, Mo, and Nb, not less than 5 mass % of Ni, and at least one element selected from an N group consisting of Ni, Co, Fe, and Cu. The tip contains Rh most among the elements of the R group, and contains Ni most among the elements of the N group. The total of contents of Pt, Rh, and Ni is not less than 91 mass %, and the total of contents of Pt, the R group, and the N group is not less than 95 mass %. A value obtained by dividing the content of the R group by the content of the N group is not less than 0.7 and not greater than 8.

Abstract: A spark plug comprising a center electrode, a ground electrode disposed on the center electrode across a gap, and a tip joined to an opposed surface of the ground electrode that is opposed to the center electrode, the tip has a discharge layer and a relieving layer, the relieving layer is formed from a Pt—Ni alloy and joined to the opposed surface via a diffusion layer, the discharge layer is formed from a Pt—Rh alloy and joined via a clad diffusion layer to a side of the relieving layer opposite to a side of the relieving layer at which the ground electrode is joined, and 0.81?A/B?1.21 is satisfied when an average cross-sectional area of the discharge layer is A mm2 and an average cross-sectional area of the relieving layer is B mm2, and a method for producing the spark plug.

Abstract: An electrode tip for a spark plug, wherein Pt is contained as a main component, 7% by mass or more of Rh is contained, and a total content of Pt and Rh is greater than or equal to 95% by mass. The electrode tip includes: a narrow portion having the same cross-sectional shape in a direction of an axis; and a wide portion which is adjacent to the narrow portion and has a cross-sectional area, in a radial direction, which is greater than the narrow portion.

Abstract: A spark plug comprising a center electrode, a ground electrode disposed on the center electrode across a gap, and a tip joined to an opposed surface of the ground electrode that is opposed to the center electrode, the tip has a discharge layer and a relieving layer, the relieving layer is formed from a Pt—Ni alloy and joined to the opposed surface via a diffusion layer, the discharge layer is formed from a Pt—Rh alloy and joined via a clad diffusion layer to a side of the relieving layer opposite to a side of the relieving layer at which the ground electrode is joined, and 0.81?A/B?1.21 is satisfied when an average cross-sectional area of the discharge layer is A mm2 and an average cross-sectional area of the relieving layer is B mm2, and a method for producing the spark plug.