Spark plug for internal combustion engine
AssigneeDenso Corporation
InventorsMasamichi Shibata, Tsunenobu Hori
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Abstract
Carbon fouling adhered on an insulator tip of a spark plug of the present invention is burnt down by a leak current during an inductive discharge period, due to a promoted ionization before beginning a capacitive discharge, in such an arrangement of a central electrode that a border portion of a body and narrowed portion is positioned in an insulator. The carbon burning-down effect is further improved by a narrow projection provided with an earth electrode, due to increased inductive energy and extended inductive discharge time period. This is because an electric field in a discharge gap is raised, thereby decreasing a discharge voltage and suppressing an energy emitted from a coil during the capacitive discharge.
Claims15
A spark plug for an internal combustion engine comprising:
- a columnar central electrode;
- an insulator for holding said central electrode a hausing for holding said insulator;
- an earth electrode wherein one end thereof is connected with said hausing and the other end thereof is opposite to said central electrode,
- wherein:
- said earth electrode has a leg connected with said hausing and a projection smaller than said leg which projects from said leg toward said central electrode;
- said central electrode has a body held in said insulator and a narrowed portion smaller than said body which projects from said body toward said projection;
- and
- a first border portion (33) between said body and narrowed portion is positioned in said insulator.
Dependencies are inferred from the claim text.