Spark plug and internal combustion engine provided with the same
First Claim
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1. A spark plug, comprising:
- a center electrode;
an insulator having therein an axial bore that extends in an axis direction of the center electrode and accommodating the center electrode in the axial bore;
a metal shell surrounding and holding the insulator in a radial direction, said metal shell having a threaded portion for mounting the spark plug on a mounting portion of an internal combustion engine;
a cylinder-shaped cylindrical portion extending from the threaded portion of the metal shell toward a front end portion of the center electrode; and
a ground electrode having one end joined to a front end of the cylindrical portion and another end disposed opposite to a front end portion of the center electrode to form a spark discharge gap therewith,wherein the insulator projects beyond the front end side of the cylindrical portion,wherein the cylindrical portion includes one or more ventilating portion which communicate with an inside and an outside of the cylindrical portion, said ventilating portion comprised of a notch.
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Accused Products
Abstract
A spark plug comprising a cylindrical portion which projects into a combustion chamber from an inner wall face of an engine head when the spark plug is fixed to the engine head, wherein the cylindrical portion has one or more ventilating portion comprised of a through hole or a notch in an outer circumferential face thereof. An igniting portion projecting into the combustion chamber improves ignitability. Further, because an air-fuel mixture fed from an inlet of the internal combustion engine flows to inside of the cylindrical portion through the ventilating portion, heat of an insulator is taken away and cooled down, whereby an occurrence of pre-ignition is prevented.
42 Citations
10 Claims
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1. A spark plug, comprising:
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a center electrode; an insulator having therein an axial bore that extends in an axis direction of the center electrode and accommodating the center electrode in the axial bore; a metal shell surrounding and holding the insulator in a radial direction, said metal shell having a threaded portion for mounting the spark plug on a mounting portion of an internal combustion engine; a cylinder-shaped cylindrical portion extending from the threaded portion of the metal shell toward a front end portion of the center electrode; and a ground electrode having one end joined to a front end of the cylindrical portion and another end disposed opposite to a front end portion of the center electrode to form a spark discharge gap therewith, wherein the insulator projects beyond the front end side of the cylindrical portion, wherein the cylindrical portion includes one or more ventilating portion which communicate with an inside and an outside of the cylindrical portion, said ventilating portion comprised of a notch. - View Dependent Claims (2, 3, 4, 7, 8, 9, 10)
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5. A spark plug, comprising:
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a center electrode; an insulator having therein an axial bore that extends in an axis direction of the center electrode, the center electrode being disposed in the axial bore; a metal shell surrounding and holding the insulator in a radial direction, said metal shell having a threaded portion for mounting the spark plug on a mounting portion of an internal combustion engine; a cylinder-shaped cylindrical portion formed extending from the threaded portion of the metal shell toward a front end portion of the center electrode; and a ground electrode having one end joined to a front end of the cylindrical portion and the other end disposed opposite to a front end portion of the center electrode to form a spark discharge gap therewith, wherein the cylindrical portion includes one or more ventilating portions which communicate with an inside and an outside of the cylindrical portion, said ventilating portion comprised of a through hole. - View Dependent Claims (6)
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Specification