Spark plug temperature control

A spark plug for internal combustion engines, said spark plug having a terminal end and an inner firing end and comprising an annular metal shell carrying a ground electrode and having external threads for installing said spark plug for operation in an engine, an electrical insulator receiving in said shell with the insulator inner end nose portion being tapered and in a radially spaced relationship with the bore of said shell, a center conductor assembly received in a centerbore in said insulator, said center conductor assembly having at least said electrical terminal, a center conductor shank, a heat pipe, means for filling said heat pipe, and a center electrode having a firing end position with respect to said ground electrode such that a spark gap is formed therebetween, said heat pipe being hermetically sealed and containing a vaporizable heat pipe medium and having a vaporization zone and a condensation zone with an adiabatic zone therebetween, wicking means extending from said condensation zone to said vaporization zone, heat transferring means in thermal contact with said condensation zone for extracting heat therefrom for dissipation substantially into said engine, said electrical insulator being a relatively poor thermal conductor and having an annular necked-in region proximate said heat pipe condensation zone to reduce the thickness of relatively poor thermal conducting material in the path of heat dissipation from said heat pipe, said necked-in region being built up with a relatively good thermally conducting material, an annular sleeve of thermally conductive material interposed between said shell and said insulator in good thermal contact therewith, the lower end of said sleeve sealing said insulator in said shell, said heat pipe being thermally non-conducting below a design temperature such that said spark plug firing end runs hot to burn off fouling deposits settling thereon, said heat pipe being thermally conducting above said design temperature to conduct heat rapidly away from said firing end such that the overheating thereof is avoided.

A spark plug comprising an upper terminal end and a lower firing end adapted to be installed in the cylinder head of an engine, said spark plug including an annular metal shell with external threads proximate the firing end thereof for installing said spark plug for operation in said cylinder head, an elongated electrical insulator having its lower end received in the bore of said shell and including a nose portion spaced radially inwardly from said shell bore, means for sealing said insulator in a gas-tight relationship in said shell, an elongated center conductor assembly received in a centerbore in said insulator, said center conductor assembly comprising an electrical terminal, a center conductor head having a lower shank, a heat pipe, and a center electrode, said center electrode having a firing end positioned at the firing end of said insulator, said shell having ground electrode means disposed in an operative relationship with said firing end of said center electrode and forming a spark gap therebetween, means for sealing said center conductor assembly in a gastight relationship in said insulator, said electrical terminal being located at the upper end of said center conductor assembly for connecting said spark plug to the ignition system of said engine, said heat pipe being hermetically sealed and containing a vaporizable heat pipe medium, and having a vaporization zone near the firing end of said spark plug and a condensation zone distal therefrom with an adiabatic zone therebetween, capillary means extending from said vaporization zone to said condensation zone, heat transferring means in thermal contact with said condensation zone for extracting heat from said heat pipe for dissipation therefrom, said heat pipe being thermally non-conducting below a design temperature range, said vaporizable medium vaporizing above said design temperature such that its change of state extracts heat from said firing end, said vapor moving by vapor pressure to said condensation zone and condensing to release its heat by a change of state, the condensed medium returning by the capillarity of said capillary means to said vaporization zone, such that a circulation that transfers heat from said firing end is established when spark plug temperatures exceed said design temperature, said circulation ceasing below said design temperature to render the heat pipe thermally non-conducting, whereby said heat pipe controls the operative heat range of said spark plug automatically.

An internal combustion engine spark plug embodying dynamic convective heat transfer means for automatically varying its operative heat range according to changes in the combustion temperatures within the engine, said spark plug having an outer electrical terminal end and an inner firing end and comprising an annular metal shell carrying a ground electrode and having external threads for installing said spark plug for operation in an engine, an electrical insulator received in said shell with the insulator inner end nose portion being tapered and in a radially spaced relationship with the bore of said shell, a center conductor assembly received in a centerbore in said insulator, said center conductor assembly having at least said electrical terminal, a center conductor shank, reflux condenser heat transfer means, means for filling said reflux condenser, and a center electrode having a firing end positioned with respect to said ground electrode such that a spark gap is formed therebetween, means providing electrical continuity between said conductor shank and said center electrode, said reflux condenser being hermetically sealed and containing a vaporizable heat transfer medium and having a vaporization zone and a condensation zone with an adiabatic zone therebetween, heat transferring means in thermal contact with said condensation zone for dissipating heat therefrom substantially into said engine, said vaporizable medium in operation vaporizing above a design temperature such that its change of state extracts heat from said firing end, said vapor moving by vapor pressure to said condensation zone and condensing to release its heat by its change of state, the condensed vapor returning by gravity to said vaporization zone, such that a circulation that transfers heat from said firing end is established in operation when spark plug temperatures exceed said design temperature, said circulation ceasing below said design temperature to render the reflux condenser thermally non-conductive, whereby said reflux condenser controls the operative heat range of said spark plug automatically.