A spark plug which is capable of further improving load life performance and a resistor material for a spark plug are provided.

A spark plug includes a center electrode, a terminal fitting, and a resistor disposed between the center electrode and the terminal fitting. The resistor contains glass, a zirconia-based material and an electrically conducting material. The zirconia-based material contains at least stabilized zirconia.

The spark plug includes: an insulator having an axial hole formed along an axial line; and a metal terminal provided on a rear side of the axial hole of the insulator. The metal terminal has, at a rear end portion thereof, a bottom surface facing rearward and a projection projecting rearward from an outer edge of the bottom surface, and a mark is provided to at least a part of the bottom surface. The Vickers hardness of the projection is 100 HV or higher. A rear end surface of the projection is positioned on a rear side with respect to a rear end of the mark. An area of the rear end surface is 3 mm.sup.2 or greater.

A prechamber spark plug having a thermally enhanced prechamber cap with a thermally conductive core, such as one made from a copper-, aluminum- and/or silver-based material. Due to its location and function, a prechamber cap is exposed to thermal energy from a pre-combustion process taking place within a prechamber, as well as thermal energy from a combustion process taking place in a main combustion chamber. Thus, the prechamber cap is being heated on both its interior and its exterior and, if not sufficiently cooled, can become so hot that it undesirably triggers preignition events in the engine. The thermally enhanced prechamber cap may include a main body with an interior surface and an exterior surface, a thermally conductive core with one or more thermal segments and insert segments, and one or more openings extending between a prechamber and a main combustion chamber, where each opening extends through an insert segment that is designed to resistant to corrosion and/or erosion.

A spark plug having an insulating body defining a longitudinal axis and including a base portion and an obstruction portion, a first electrode including a proximal portion, a sheathed portion and a distal portion, the sheathed portion of the first electrode extending through the base portion of the insulating body, and a second electrode including a proximal portion, a sheathed portion and a distal portion, the sheathed portion of the second electrode extending through the base portion and the obstruction portion of the insulating body, wherein the obstruction portion axially extends beyond the distal portion of the first electrode.

A spark plug having an insulating body defining a longitudinal axis and including a base portion and an obstruction portion, a first electrode including a proximal portion, a sheathed portion and a distal portion, the sheathed portion of the first electrode extending through the base portion of the insulating body, and a second electrode including a proximal portion, a sheathed portion and a distal portion, the sheathed portion of the second electrode extending through the base portion and the obstruction portion of the insulating body, wherein the obstruction portion axially extends beyond the distal portion of the first electrode.

Disclosed is a spark plug including: an insulator having an axial through hole formed with a first hole region and a second hole region larger in inner diameter than the first hole region; a center electrode having a collar portion disposed in the second hole region; a resistor disposed in the second hole region, with a front end of the resistor being located apart from a rear end of the center electrode; and a conductive seal material arranged at least between the center electrode and the resistor within the second hole region, wherein the center electrode has a recess recessed from the rear end thereof toward the front, wherein the recess is provided at least at a location of a maximum outer diameter section of the collar portion, and wherein the conductive seal material is filled into the recess from the rear end of the center electrode.

Disclosed is a spark plug including: an insulator having an axial through hole formed with a first hole region and a second hole region larger in inner diameter than the first hole region; a center electrode having a collar portion disposed in the second hole region; a resistor disposed in the second hole region, with a front end of the resistor being located apart from a rear end of the center electrode; and a conductive seal material arranged at least between the center electrode and the resistor within the second hole region, wherein the center electrode has a recess recessed from the rear end thereof toward the front, wherein the recess is provided at least at a location of a maximum outer diameter section of the collar portion, and wherein the conductive seal material is filled into the recess from the rear end of the center electrode.

A spark plug includes: an insulator having an axial hole formed therein in an axial direction; a center electrode extending in the axial direction and having a rear end located within the axial hole; a metal terminal extending in the axial direction and having a front end located rearward of the rear end of the center electrode within the axial hole; a resistor arranged between the center electrode and the metal terminal within the axial hole; and a conductive seal layer that fills a space between the resistor and the center electrode in the axial. The conductive seal layer has a first layer portion located adjacent to the center electrode and a second layer portion located between the first layer portion and the resistor. The second layer portion has a thermal expansion coefficient different from and falling between those of the first layer portion and the resistor.

A spark plug suppressor and a method of producing a spark plug suppressor from a suppressor precursor liquid that may be cured at a temperature below 300 C. The spark plug suppressor may include particles or grains dispersed in a matrix of electrically conducting material, electrically semiconducting material, or electrically non-conducting material. The suppressor may include a conductive glass seal component and a resistive suppressor component. The resistive suppressor component may be at least partially embedded in the glass seal component, and the glass seal component may seal a center electrode of the spark plug, a terminal of the spark plug, or both the center electrode and the terminal.

A spark plug suppressor and a method of producing a spark plug suppressor from a suppressor precursor liquid that may be cured at a temperature below 300 C. The spark plug suppressor may include particles or grains dispersed in a matrix of electrically conducting material, electrically semiconducting material, or electrically non-conducting material. The suppressor may include a conductive glass seal component and a resistive suppressor component. The resistive suppressor component may be at least partially embedded in the glass seal component, and the glass seal component may seal a center electrode of the spark plug, a terminal of the spark plug, or both the center electrode and the terminal.