In an ignition device having an ignition plug for igniting a fuel mixture gas introduced in a combustion chamber, a super hydrophilic membrane is formed on a surface at the combustion chamber side of a plug forming member of the ignition plug. The super hydrophilic membrane contains super hydrophilic particles and thermal excitation catalyst particles, and satisfies a relationship of .sub.W2<.sub.W1, where .sub.W1 indicates a water contact angle between water and the plug forming member on which no super hydrophilic membrane is formed, and .sub.W2 indicates a water contact angle between water and the plug forming member on which the super hydrophilic membrane is formed.

Methods and systems are provided for controlling spark plug fouling in newly manufactured vehicles. In one example, an engine is operated with a first, more aggressive spark discharge schedule when in a pre-delivery state and transitioned to a second, less aggressive spark discharge schedule when in a post-delivery state. In each spark discharge schedule, a spark plug ignition coil is repeatedly discharged when the engine is off, such as when the engine is spinning down to rest on a shutdown event or before the engine is fueled on an engine restart event.

A center electrode including an electrode base member having a cylindrical shape with a bottom and a core member embedded in the electrode base member. The core member has a thermal conductivity higher than that of the electrode base member. The center electrode includes a plurality of shoulder portions which each include a diameter reducing portion having a diameter that decreases toward a front end of the spark plug in a direction of an axial line, an outer side surface that extends in the direction of the axial line, and an edge disposed between the diameter reducing portion and the outer side surface. One of the shoulder portions closest to an inner surface of the axial hole has a cutting mark that extends in a circumferential direction over a region from the diameter reducing portion to the edge.

A center electrode including an electrode base member having a cylindrical shape with a bottom and a core member embedded in the electrode base member. The core member has a thermal conductivity higher than that of the electrode base member. The center electrode includes a plurality of shoulder portions which each include a diameter reducing portion having a diameter that decreases toward a front end of the spark plug in a direction of an axial line, an outer side surface that extends in the direction of the axial line, and an edge disposed between the diameter reducing portion and the outer side surface. One of the shoulder portions closest to an inner surface of the axial hole has a cutting mark that extends in a circumferential direction over a region from the diameter reducing portion to the edge.

A center electrode including an electrode base member having a cylindrical shape with a bottom and a core member embedded in the electrode base member. The core member has a thermal conductivity higher than that of the electrode base member. The center electrode includes a plurality of shoulder portions which each include a diameter reducing portion having a diameter that decreases toward a front end of the spark plug in a direction of an axial line, an outer side surface that extends in the direction of the axial line, and an edge disposed between the diameter reducing portion and the outer side surface, One of the shoulder portions closest to an inner surface of the axial hole has a cutting mark that extends in a circumferential direction over a region from the diameter reducing portion to the edge.

A center electrode including an electrode base member having a cylindrical shape with a bottom and a core member embedded in the electrode base member. The core member has a thermal conductivity higher than that of the electrode base member. The center electrode includes a plurality of shoulder portions which each include a diameter reducing portion having a diameter that decreases toward a front end of the spark plug in a direction of an axial line, an outer side surface that extends in the direction of the axial line, and an edge disposed between the diameter reducing portion and the outer side surface, One of the shoulder portions closest to an inner surface of the axial hole has a cutting mark that extends in a circumferential direction over a region from the diameter reducing portion to the edge.

A spark plug for an internal combustion engine is provided which includes a housing, a porcelain insulator, a center electrode, and an annular ground electrode. The housing has a small-diameter portion which has a smaller inner diameter and defines a front end thereof. The ground electrode is secured to a front end surface of the small-diameter portion and forms a spark gap between itself and an outer periphery of the center electrode. A pocket is formed between the inner periphery of the housing and a portion of the porcelain insulator which is located closer to a front end of the porcelain insulator than the mounting shoulder is. An air vent extends from outside the ground electrode in a radial direction of the spark plug to the pocket to establish communication between the pocket and the combustion chamber of the internal combustion engine.

Embodiments of the present technology relate to a temperature controllable and variable spark plug, and method of use. An example thermally controlled ignition device may comprise at least one sensor communicatively coupled to a control module for determining whether an engine characteristic is within a desired operating range and at least one heating element for adjusting the temperature of the ignition device.

In a spark plug, an annular gap is formed between a metallic shell and an outer surface of a leg portion of an insulator. A contact end position is provided at a front most position of a contact portion formed between a packing and the metallic shell. A radial distance between the outer surface of the leg portion and an inner surface of the metallic shell is a gap distance. A maximum end position is provided at the rear end of the annular gap maximum portion. The gap distance at a front end of the metallic shell is larger than the gap between the center electrode and the ground electrode. The metallic shell includes an increased inner diameter portion having an inner diameter at the front side relative to the contact end position. The maximum end position is located at the rear side relative to an intermediate position.

A spark plug for an internal combustion engine is provided which includes a housing, a porcelain insulator, a center electrode, and an annular ground electrode. The housing has a small-diameter portion which has a smaller inner diameter and defines a front end thereof. The ground electrode is secured to a front end surface of the small-diameter portion and forms a spark gap between itself and an outer periphery of the center electrode. A pocket is formed between the inner periphery of the housing and a portion of the porcelain insulator which is located closer to a front end of the porcelain insulator than the mounting shoulder is. An air vent extends from outside the ground electrode in a radial direction of the spark plug to the pocket to establish communication between the pocket and the combustion chamber of the internal combustion engine.