Spark plug
First Claim
1. A spark plug, wherein a cylindrical metallic shell having a tool engagement portion for mounting said spark plug on an engine is fixedly attached to an axially extending insulator inserted into said metallic shell, by crimping a protrusion formed at one opening portion of said metallic shell toward a crimp rest portion formed on an outer circumferential surface of said insulator to thereby form said protrusion into a crimped portion of said metallic shell, and wherein a distance between opposed sides of said tool engagement portion is not greater than 14 mm;
- and said crimped portion as projected orthogonally on a virtual plane in parallel with an axis of said insulator is curved such that an end-side part of said crimped portion approaches said insulator, such that an exterior outline of said crimped portion has an outwardly convex crimped curve portion at the end-side part, and such that a tangent to said exterior outline at a base point of said crimped curve portion and a line perpendicular to the axis projected on the virtual plane form an angle of 50°
-110°
.
1 Assignment
0 Petitions
Accused Products
Abstract
A spark plug is disclosed in which, in a cross-section of the metallic shell of the spark plug, a crimped portion of the metallic shell is curved such that an end-side part of the crimped portion approaches the insulator, such that an exterior outline of the crimped portion has an outwardly convex crimped curve portion at the end-side part, and such that a tangent to the exterior outline at a base point of the crimped curve portion and a radial line perpendicular to the axis of the insulator form an angle of 50°-110°. Accordingly, most of a crimping force is imposed in the axial direction of the metallic shell during crimping, and stress generated in the metallic shell in a radial direction is very small. Thus, the metallic shell can be thin-walled and can maintain its shape with high accuracy after crimping.
9 Citations
7 Claims
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1. A spark plug, wherein a cylindrical metallic shell having a tool engagement portion for mounting said spark plug on an engine is fixedly attached to an axially extending insulator inserted into said metallic shell, by crimping a protrusion formed at one opening portion of said metallic shell toward a crimp rest portion formed on an outer circumferential surface of said insulator to thereby form said protrusion into a crimped portion of said metallic shell, and
wherein a distance between opposed sides of said tool engagement portion is not greater than 14 mm; - and said crimped portion as projected orthogonally on a virtual plane in parallel with an axis of said insulator is curved such that an end-side part of said crimped portion approaches said insulator, such that an exterior outline of said crimped portion has an outwardly convex crimped curve portion at the end-side part, and such that a tangent to said exterior outline at a base point of said crimped curve portion and a line perpendicular to the axis projected on the virtual plane form an angle of 50°
-110°
. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- and said crimped portion as projected orthogonally on a virtual plane in parallel with an axis of said insulator is curved such that an end-side part of said crimped portion approaches said insulator, such that an exterior outline of said crimped portion has an outwardly convex crimped curve portion at the end-side part, and such that a tangent to said exterior outline at a base point of said crimped curve portion and a line perpendicular to the axis projected on the virtual plane form an angle of 50°
Specification