Spark plug
AssigneeNgk Spark Plug Co., Ltd.
InventorsKenji Nunome, Yoshikuni Sato
Life of this patent
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Abstract
A spark plug comprising a center electrode, a first noble metal tip joined to the center electrode, an insulator, a metallic shell, a ground electrode joined to the metallic shell and including an outer layer and an inner layer, and a second noble metal tip joined to the ground electrode by way of a melted portion, wherein in a cross section of the ground electrode, the protrusion height A of the second noble metal tip is 0.4 mm or more, the ground electrode includes a substantially flat joining surface to which the second noble metal tip is joined and an outwardly curved surface, the inner layer has at the joining surface side a substantially flat surface or recessed surface, and the minimum distance F between the melted portion and the inner layer is 0.1 mm or more.
Claims8
A spark plug comprising:
- a rod-shaped center electrode;
- a first noble metal tip joined to a front end of said center electrode;
- a substantially cylindrical insulator provided at an outer circumference of said center electrode;
- a tubular metallic shell provided at an outer circumference of said insulator;
- a ground electrode having a base end portion joined to a front end surface of said metallic shell, and a front end portion facing a front end portion of said center electrode, said ground electrode including an outer layer made of nickel alloy and an inner layer made of a material having a better thermal conductivity than the outer layer;
- and
- a second noble metal tip joined to said front end portion of said ground electrode by way of a melted portion formed by one of laser welding and beam welding and forming a spark discharge gap between said second noble metal tip and said first noble metal tip, wherein
- in a cross section of said ground electrode as viewed from the front end surface side of said ground electrode along the axis of said second noble metal tip;
- the protrusion height A of said second noble metal tip from said joining surface to said front end of said second noble metal tip is 0.4 mm or more;
- said ground electrode includes a substantially flat joining surface to which said second noble metal tip is joined and an outwardly curved surface;
- said inner layer has at said joining surface side one of a substantially flat surface and recessed surface;
- and
- the minimum distance F between the said melted portion and said inner layer is 0.1 mm or more.
A spark plug comprising:
- a rod-shaped center electrode;
- a first noble metal tip joined to a front end of said center electrode;
- a substantially cylindrical insulator provided at an outer circumference of said center electrode;
- a tubular metallic shell provided at an outer circumference of said insulator;
- a ground electrode having a base end portion joined to a front end surface of said metallic shell, and a front end portion facing a front end portion of said center electrode, said ground electrode including an outer layer made of nickel alloy and an inner layer made of a material having a better thermal conductivity than the outer layer;
- a second noble metal tip joined to the front end portion of said ground electrode by way of a melted portion formed by one of laser welding and beam welding and forming a spark discharge gap between the second noble metal tip and the first noble metal tip, wherein
- in a cross section of said ground electrode as viewed from the front end surface side of the ground electrode along the axis of said second noble metal tip,
- the protrusion height A of said second noble metal tip from said joining surface to the front end of said second noble metal tip is 0.4 mm or more;
- said ground electrode includes a substantially flat joining surface to which said second noble metal tip is joined and an outwardly curved surface;
- said inner layer has at a side of said joining surface one of a substantially flat surface and recessed surface;
- and
- said melted portion is disposed at a distant from said joining surface.
Dependencies are inferred from the claim text.