Hydrostatic Lock and Detonation: Spark Plugs as Pressure Relief Devices 980118

A spark plug for Internal Combustion (IC) engines is presented which incorporates structurally weakened regions. These weakened regions serve to rupture or break under excessive cylinder pressure, so that the cylinder to atmosphere seal is destroyed, and the cylinder contents are vented to atmosphere. The release of cylinder contents is to eliminate mechanical engine component damage from excessive cylinder pressures that develop under hydrostatic lock and detonation. Multiple stage release mechanisms are employed; pressures indicative of hydrostatic lock will effect a disintegration of the spark plug such that the insulator and center electrode are released and ejected, pressures indicative of detonation effect a small cylinder leak through the spark plug sidewall, such that compression is reduced by venting. These features may be imparted to existing spark plugs as a secondary manufacturing operation; only external machining and assembly modifications are required.