Spark plug
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.
1. A spark plug comprising:
a center electrode extending in an axial direction; and
a ground electrode forming a gap between the ground electrode and the center electrode,
wherein at least one of the center electrode and the ground electrode includes:
an electrode base material;
a discharge member having a discharge surface that forms the gap;
an intermediate member disposed between the discharge member and the electrode base material; and
a diffusion layer formed between the discharge member and the intermediate member,
the electrode base material contains not less than 50 wt. % of nickel (Ni),
the discharge member contains not less than 45 wt. % of platinum (Pt), and at least one of nickel and rhodium (Rh),
the intermediate member contains platinum and nickel,
in the discharge member, a content of platinum is highest, and a total content of platinum, rhodium, and nickel is not less than 92 wt. %,
in the intermediate member, a content of one of platinum and nickel is not less than 50 wt. %, a content of nickel is higher than a content of nickel in the discharge member, and a total content of platinum, rhodium, and nickel is not less than 85 wt. %, and
a thickness of the diffusion layer is not less than 0.002 mm and not more than 0.065 mm.
2. The spark plug according to claim 1 , wherein
the thickness of the diffusion layer is not less than 0.005 mm and not more than 0.065 mm.
3. The spark plug according to claim 1 , wherein
in the case where D 1 represents a distance between the diffusion layer and the discharge surface of the discharge member, and G represents a length of the gap,
D 1 ≥0.1 mm and (D 1 /G)≥0.1 are satisfied.
4. The spark plug according to claim 1 , wherein
in the discharge member, a total content of platinum, rhodium, and nickel is not less than 96 wt. %.
5. The spark plug according to claim 1 , wherein
in the intermediate member, a total content of platinum, rhodium, and nickel is not less than 96 wt. %.
6. The spark plug according to claim 1 , wherein
a content of nickel in the intermediate member is higher than a content of nickel in the discharge member by not less than 2.5 wt. %.
7. The spark plug according to claim 4 , wherein
in the discharge member, a total content of platinum and rhodium is not less than 88 wt. %.