A spark plug has a housing, an insulator, a central electrode and a ground electrode. At least one projection part is formed on an outer peripheral surface of the insulator at a location facing a distal end cylindrical surface of the insulator in a radial direction of the spark plug so that at least one projection part has a minimum distance measured from a plug central axis of the spark plug, which is longer than a distance of another part of the insulator measured from the plug central axis. On a cross section of the spark plug, at least one projection part is formed on the outer peripheral surface of the insulator in a direction between at least one projection part and the plug central axis which crosses to a direction between a rod-shaped part and the plug central axis.

A spark plug has a housing, an insulator, a central electrode and a ground electrode. At least one projection part is formed on an outer peripheral surface of the insulator at a location facing a distal end cylindrical surface of the insulator in a radial direction of the spark plug so that at least one projection part has a minimum distance measured from a plug central axis of the spark plug, which is longer than a distance of another part of the insulator measured from the plug central axis. On a cross section of the spark plug, at least one projection part is formed on the outer peripheral surface of the insulator in a direction between at least one projection part and the plug central axis which crosses to a direction between a rod-shaped part and the plug central axis.

An insulator arrangement for a spark plug arrangement, in particular for a prechamber spark plug, with an elongated body that has an insulator arrangement longitudinal bore for accommodating a center electrode arrangement and has a front end. A sealing shoulder is formed on an outer circumferential section of the body. An axial transition section is formed between the sealing shoulder and the front end of the body. The front end of the body is designed such that at least 50% of a gas flow impinging thereon in a first direction is deflected in a direction opposite to the first direction.

Spark plug has center electrode having leg portion extending in an axis direction, brim portion located at rear end side with respect to the leg portion and protruding outwards in a radial direction with respect to the leg portion and connecting portion connecting the leg portion and the brim portion; insulator having penetration hole and supporting the center electrode; and seal member filling the penetration hole and fixing the brim portion and the insulator. The center electrode satisfies (D1-D2)/D10.06, where a maximum value of a radius of the brim portion is D1, and a minimum value of the radius of the brim portion is D2, also satisfies L2/L10.30, where a size of the center electrode along the axis direction is L1, and a size along the axis direction from boundary between the connecting portion and the leg portion to a center of gravity of the center electrode is L2.

Spark plug has center electrode having leg portion extending in an axis direction, brim portion located at rear end side with respect to the leg portion and protruding outwards in a radial direction with respect to the leg portion and connecting portion connecting the leg portion and the brim portion; insulator having penetration hole and supporting the center electrode; and seal member filling the penetration hole and fixing the brim portion and the insulator. The center electrode satisfies (D1-D2)/D10.06, where a maximum value of a radius of the brim portion is D1, and a minimum value of the radius of the brim portion is D2, also satisfies L2/L10.30, where a size of the center electrode along the axis direction is L1, and a size along the axis direction from boundary between the connecting portion and the leg portion to a center of gravity of the center electrode is L2.

In a method for manufacturing a spark plug, a space on a proximal end side of a center electrode in a shaft hole of an insulator is filled with first electrically conductive glass powder. A space on the proximal end side of the first electrically conductive glass powder in the shaft hole is filled with resistor composition powder. A space on the proximal end side of the resistor composition powder in the shaft hole is filled with second electrically conductive glass powder. The first electrically conductive glass powder, the resistor composition powder, and the second electrically conductive glass powder are sintered in the shaft hole. Prior to filling of the resistor composition powder, at least one of the insulator and the first electrically conductive glass powder is placed in an uncharged state, or the insulator and the first electrically conductive glass powder are placed in the same charged state.

A spark plug has a housing, an insulator, a central electrode and a ground electrode. At least one projection part is formed on an outer peripheral surface of the insulator at a location facing a distal end cylindrical surface of the insulator in a radial direction of the spark plug so that at least one projection part has a minimum distance measured from a plug central axis of the spark plug, which is longer than a distance of another part of the insulator measured from the plug central axis. On a cross section of the spark plug, at least one projection part is formed on the outer peripheral surface of the insulator in a direction between at least one projection part and the plug central axis which crosses to a direction between a rod-shaped part and the plug central axis.

A spark plug that improves the heat resistance performance of an ignition plug.

A spark plug that improves the heat resistance performance of an ignition plug.

A spark plug for generating an axially extending surface spark between a sparking tip of the center electrode and a seal supporting sparking projection located at an internal step portion of the metal shell. In one embodiment, the spark plug is a pre-chamber spark plug having a pre-chamber cap attached to a distal end of the metal shell. The spark plug can allow for unobstructed flame propagation through the pre-chamber, without having the flame obstructed by narrow gaps or a separate ground electrode.