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US 7,741,763 B2Granted
Spark plug
AssigneeNgk Spark Plug Co., Ltd.
InventorsKenichi Kumagai, Koji Mizoguchi
Life of this patent
Estimating the term…
Abstract
A spark plug including a center electrode; an insulator; a metal shell; a ground electrode; and an annular packing, all as defined herein, wherein the packing has a hardness greater than or equal to a hardness of the stepped portion of the metal shell or has a Vickers hardness of not less than 300 Hv. Preferably, a difference between the hardness of the packing and the hardness of the stepped portion of the metal shell is from 120 Hv to 160 Hv, and the packing has a Vickers hardness of not more than 500 Hv.
Claims11
A spark plug comprising:
- an insulator having an axial hole extending in an axial direction and a shoulder portion provided on an outer peripheral surface thereof;
- a center electrode held at a leading end side of the axial hole;
- a metal shell having a stepped portion provided on an inner peripheral surface thereof, the stepped portion retaining the shoulder portion of the insulator on a receiving surface thereof;
- a ground electrode having a rear end portion joined to a leading end portion of the metal shell and a leading end portion facing the center electrode;
- and
- an annular packing interposed between the shoulder portion of the insulator and the stepped portion of the metal shell,
- wherein the packing has a Vickers hardness greater than or equal to a Vickers hardness of the stepped portion of the metal shell.
4 more elements
A spark plug comprising:
- an insulator having an axial hole extending in an axial direction and a shoulder portion provided on an outer peripheral surface thereof;
- a center electrode held at a leading end side of the axial hole;
- a metal shell having a stepped portion provided on an inner peripheral surface thereof, the stepped portion retaining the shoulder portion of the insulator;
- a ground electrode having a rear end portion joined to a leading end portion of the metal shell and a leading end portion facing the center electrode;
- and
- an annular packing interposed between the shoulder portion of the insulator and the stepped portion of the metal shell,
- wherein the stepped portion has an indentation into which a portion of the packing is sunk.
4 more elements
Dependencies are inferred from the claim text.