Outer electrode for spark plug and a method of manufacturing thereof
AssigneeNgk Spark Plug Co., Ltd.
InventorsTakafumi Oshima, Minoru Ando
Life of this patent
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Abstract
In an outer electrode, a rear end of which is securely connected to a metallic shell of a spark plug by means of welding to form a spark gap between a front end of the outer electrode and a firing tip of a center electrode which is concentrically placed within the metallic shell through an insulator, a middle core which is provided which is made of copper, and the middle core is clad by a heat and spark-erosion resistant metal. A centermost core is clad by the middle core. The centermost core is made of a similar metal to the metallic shell, and rear end of the centermost core is welded to the metallic shell so as to reinforce a welding portion between the metallic shell and the outer electrode.
Claims7
An outer electrode, a rear end of which is securely connected to a metallic shell of a spark plug by means of welding to form a spark gap between a front end of the outer electrode and a firing tip of a center electrode which is concentrically placed within the metallic shell through an insulator,
- the outer electrode comprising:
- a middle core which is made of copper to have a heat-conductive property, the middle core being clad by a heat and spark-erosion resistant metal;
- and
- a centermost core clad by the middle core, the centermost core being made of a metal weld-intense to that of the metallic shell, and a rear end of the centermost core being welded to the metallic shell so as to reinforce a welding portion between the metallic shell and the outer electrode.
A method of manufacturing an outer electrode for a spark plug comprising the steps of:
- forcing a centermost core into an upper recess provided with a metallic column which is made of copper to form a first body, a rear end of the centermost core terminating at that of the metallic column, while a front end of the centermost core terminates short of that of the metallic column;
- forcing the first body into a cup-shaped metal until an upper end of the first body reaches to an upper end of the cup-shaped metal to form a second body;
- forcing the second body into a circular hole provided with a die to extrude the second body so as to form an elongated bar;
- removing an upper end of the elongated bar;
- forcing the elongated bar into a rectangular hole provided with a rectangular die to extrude the elongated bar so as to form a rectangular bar;
- cutting a rear portion of the rectangular bar so that a rear end of the rectangular bar is flush with that of the metal cladding the metallic column;
- and
- thermally annealing the rectangular bar;
- a cross sectional area of the metallic column being within a range from 20% to 40% of that of the outer electrode.
Dependencies are inferred from the claim text.