Spark plug with a wide discharge gap
First Claim
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1. A spark plug with a wide discharge gap comprising:
- a plug shell;
a cylindrical center electrode disposed along a spark plug axis;
an insulator of substantially cylindrical shape disposed so as to surround and electrically insulate said center electrode from said plug shell;
at least one ground electrode grounded through said plug shell and disposed to face and be spaced from said center electrode to form a gap therebetween; and
an outer insulating layer comprising a material having a resistance to heat and high voltage formed on one of said electrodes so as to expose a portion of said one electrode, said outer insulating layer being extended into the gap between said electrodes to define a shortest gap between a surface of said insulating layer and the other of said electrodes, and further including an inner insulating layer of material having a high dielectric constant, said outer insulating layer being formed on said inner insulating layer so that said inner insulating layer is substantially covered thereby to substantially prevent said inner insulating layer from being exposed to sparks.
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Abstract
A spark plug with a wide discharge gap includes an insulating layer formed on one or the other of its center and ground electrodes and disposed in the gap between the electrodes. The insulating layer includes an inner insulating layer of a material having a high dielectric constant and an outer insulating layer of a material having an excellent resistance to heat and high voltage, which surrounds the inner insulating layer, whereby ensuring a reduced discharge voltage, an improved ignition performance and improved heat resistance and durability.
41 Citations
14 Claims
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1. A spark plug with a wide discharge gap comprising:
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a plug shell; a cylindrical center electrode disposed along a spark plug axis; an insulator of substantially cylindrical shape disposed so as to surround and electrically insulate said center electrode from said plug shell; at least one ground electrode grounded through said plug shell and disposed to face and be spaced from said center electrode to form a gap therebetween; and an outer insulating layer comprising a material having a resistance to heat and high voltage formed on one of said electrodes so as to expose a portion of said one electrode, said outer insulating layer being extended into the gap between said electrodes to define a shortest gap between a surface of said insulating layer and the other of said electrodes, and further including an inner insulating layer of material having a high dielectric constant, said outer insulating layer being formed on said inner insulating layer so that said inner insulating layer is substantially covered thereby to substantially prevent said inner insulating layer from being exposed to sparks. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification