Enhanced method of sensing ionization current in spark ignition internal combustion engines and related spark plug structures

A method of sensing ionization currents crossing electrodes of a spark plug, the method comprising:

• electrically connecting a resistive element between a ground electrode of the spark plug and an engine body of an internal combustion engine so that, upon mounting in the internal combustion engine, the ground electrode electrically connects to the engine body through the resistive element and has a second outer termination defining an accessible sensing terminal when the spark plug is mounted, the resistive element comprising a layer of resistive electrically conductive material between the ground electrode and a metal casing of the spark plug to be electrically coupled to the engine body upon mounting the spark plug in the internal combustion engine;
• mounting the spark plug in the internal combustion engine;
• and
• sensing a voltage between the accessible sensing terminal and the engine body.

A spark plug comprising:

• an insulator;
• a first electrode embedded within and axially extending through said insulator from a high voltage outer end terminal to a center of an inner end of the insulator from which said first electrode protrudes;
• a ground electrode isolated from said first electrode and comprising an extended inner termination facing toward said first electrode and extending from a tip of said insulator defining therebetween a spark gap;
• and
• a resistive element coupled to said ground electrode and configured so that upon mounting the spark plug in an internal combustion engine, said ground electrode electrically connects to an engine body through said resistive element;
• said ground electrode comprising a second outer termination configured to define an accessible sensing terminal and an outer threaded ground electrode surrounding an inner portion of said insulator;
• said resistive element comprising a threaded resistive element coupled to said outer threaded ground electrode.

A spark plug comprising:

• an insulator;
• a first electrode embedded within and axially extending through said insulator from a high voltage outer end terminal to a center of an inner end of the insulator from which said first electrode protrudes;
• a ground electrode isolated from the first electrode and comprising an extended inner termination facing toward the first electrode and extending from a tip of the insulator defining therebetween a spark gap;
• and
• a resistive element comprising at least one of molded conductive resin, a conductive ceramic coating, and a cermet coating, and having a resistance between 10 and 500 Ohms, coupled to said ground electrode and configured so that upon mounting the spark plug in an internal combustion engine, said ground electrode electrically connects to an engine body through said resistive element;
• said ground electrode comprising a second outer termination configured to define an accessible sensing terminal.

A method of making a spark plug comprising:

• embedding a first electrode within an insulator to axially extend therethrough from a high voltage outer end terminal to a center of an inner end of the insulator from which the first electrode protrudes;
• forming a ground electrode to be isolated from the first electrode and comprising an extended inner termination facing toward the first electrode and extending from a tip of the insulator defining therebetween a spark gap;
• and
• coupling a resistive element to the ground electrode so that upon mounting the spark plug in an internal combustion engine, the ground electrode electrically connects to an engine body through the resistive element;
• and
• the ground electrode comprising a second outer termination defining an accessible sensing terminal;
• the resistive element comprising a layer of resistive electrically conductive material between the ground electrode and a metal casing of the spark plug that is configured to be electrically coupled to the engine body upon mounting the spark plug in the internal combustion engine.

A method of making a spark plug comprising:

• embedding a first electrode within and axially extending through an insulator from a high voltage outer end terminal to a center of an inner end of the insulator from which the first electrode protrudes;
• forming a ground electrode to be isolated from the first electrode and comprising an extended inner termination facing toward the first electrode and extending from a tip of the insulator defining therebetween a spark gap;
• and
• coupling a resistive element to the ground electrode and so that upon mounting the spark plug in an internal combustion engine, the ground electrode electrically connects to an engine body through the resistive element;
• the ground electrode being formed to include a second outer termination defining an accessible sensing terminal and an outer threaded ground electrode surrounding an inner portion of the insulator;
• coupling the resistive element comprising coupling a threaded resistive element to the outer threaded ground electrode.

A method of making a spark plug comprising:

• embedding a first electrode within and axially extending through an insulator from a high voltage outer end terminal to a center of an inner end of the insulator from which the first electrode protrudes;
• forming a ground electrode to be isolated from the first electrode and comprising an extended inner termination facing toward the first electrode and extending from a tip of the insulator defining therebetween a spark gap;
• and
• coupling a resistive element comprising at least one of molded conductive resin, a conductive ceramic coating, and a cermet coating and having has a resistance between 10 and 500 Ohms, to the ground electrode and so that upon mounting the spark plug in an internal combustion engine, the ground electrode electrically connects to an engine body through the resistive element;
• forming the ground electrode comprising forming a second outer termination to define an accessible sensing terminal.