Importance

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Abstract

A spark plug with a heat pipe in the centerbore of the insulator thereof for controlling the operating temperature of the spark plug firing end automatically. A vaporizable medium in the heat pipe vaporizes when the load on the engine causes the temperature of the engine cylinder in which the spark plug is installed to rise into a temperature range in which damage to its firing end can occur. In that temperature range, the change of state of the vaporizable medium extracts heat from the firing end to prevent its overheating. The vapor pressure of the vaporied medium moves the vapor to a condensation zone where it condenses and releases its heat by a change of state. The condensate is returned to the vaporization zone by capillary means and the cycle is repeated as long as the firing end is in the overheating range of the spark plug. When engine temperatures drop, the heat pipe becomes non-conducting but the design of the spark plug firing end is such that it runs hot to burn off fouling deposits that can settle thereon in the engine no-load phase of operation. In this invention, the capillary grooves of the heat pipe are incised directly into the insulator centerbore defining the side walls of the heat pipe such that heat transfer from the condensation zone of the heat pipe to the heat sink provided by the engine is optimized.

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First Claim