A spark plug is provided with a center electrode and a ground electrode. The ground electrode includes an electrode tip, an electrode base material, an intermediate member and a first melt portion. The intermediate member is disposed between the electrode tip and the electrode base material. The first melt portion contains components of the electrode base material and the intermediate member, and is disposed at least at a part of the boundary between the electrode base material and the intermediate member. In a cross section including the axis of the ground electrode, the boundary line between the intermediate member and the first melt portion has at least two first projection portions projecting toward the electrode tip side, and the boundary line between the electrode base material and the first melt portion has at least two second projection portions projecting toward the opposite side of the first projection portions.

A spark plug is provided with a center electrode and a ground electrode. The ground electrode includes an electrode tip, an electrode base material, an intermediate member and a first melt portion. The intermediate member is disposed between the electrode tip and the electrode base material. The first melt portion contains components of the electrode base material and the intermediate member, and is disposed at least at a part of the boundary between the electrode base material and the intermediate member. In a cross section including the axis of the ground electrode, the boundary line between the intermediate member and the first melt portion has at least two first projection portions projecting toward the electrode tip side, and the boundary line between the electrode base material and the first melt portion has at least two second projection portions projecting toward the opposite side of the first projection portions.

A spark plug electrode with an electrode tip formed on an electrode base using an additive manufacturing process, such as a powder bed fusion technique. The spark plug electrode includes an electrode base, an electrode tip that is formed on the electrode base and includes a precious metal-based material, and a thermally resilient joint that is located between the electrode base and the electrode tip, wherein the electrode tip and the thermally resilient joint together include a number of laser deposition layers.

A spark plug having a center electrode, a ground electrode, and a noble metal tip that is joined to a part of the ground electrode near one end of the ground electrode via a fused portion. The fused portion extends outward beyond an outer shape of the noble metal tip so that a part of the fused portion is present at each of positions that are located inward from and separated from both side edges of the ground electrode in a width direction of the ground electrode. The fused portion includes a fused protrusion that is located near at least one of two side edges of the noble metal tip in the width direction of the ground electrode and that protrudes in a direction away from the one end of the ground electrode.

A spark plug having a center electrode, a ground electrode, and a noble metal tip that is joined to a part of the ground electrode near one end of the ground electrode via a fused portion. The fused portion extends outward beyond an outer shape of the noble metal tip so that a part of the fused portion is present at each of positions that are located inward from and separated from both side edges of the ground electrode in a width direction of the ground electrode. The fused portion includes a fused protrusion that is located near at least one of two side edges of the noble metal tip in the width direction of the ground electrode and that protrudes in a direction away from the one end of the ground electrode.

A spark plug is provided that includes an improved jamb nut configuration, which provides improved torque transfer and prevents inadvertent separation of the jamb nut from the remaining components of the spark plug, particularly during removal from the engine head. The spark plug is configured for axial insertion into the plug hole, and may have a non-axisymmetric ground shield that fits into the plug hole, wherein the plug hole is also provided with a complementary non-axisymmetric shape. The spark plug includes a central insulator, which has an inner end surrounding a central electrode and supporting the ground shield, which is mounted on the insulator to support a ground strap adjacent the electrode for forming a spark therebetween. The insulator and ground shield are axially slidable into the plug hole, and the jamb nut is rotatable to fix the spark plug in position in a predefined orientation. The insulator includes a retaining clip outwardly of the jamb nut that permits rotation of the jamb nut relative to the insulator but prevents axial separation of the jamb nut during removal of the spark plug from the engine head. An improved tool is also provided which better distributes torque transfer to the jamb nut and includes a catch to facilitate pulling of the spark plug from the engine head.

The spark plug has a shaft shaped center electrode, insulator, terminal fitting, ground electrode and resistor. The insulator has an axially penetrating shaft hole, and the center electrode is held in a tip end side of the shaft hole. The terminal fitting has a shaft and a terminal part. The shaft is held in a base end side of the shaft hole. The terminal part is projected from a base end of the shaft hole to a base end side of the spark plug. The ground electrode faces the center electrode in a tip end side of the shaft hole. The resistor is disposed between the center electrode and the terminal fitting in the shaft hole. An axial length L of the resistor is 15 mm≦L≦22.5 mm. An axial length T of the shaft satisfies a relation of 1.25≦T/L.

A spark plug has an elongated center electrode, ground electrode, convex part and noble metal coating layer. The center electrode is held in a housing. The ground electrode has a tip end opposing part opposing the center electrode. The convex part is extended from the tip end opposing part to an opposing part face in an axial direction of the spark plug. A spark discharge gap is formed between a tip end part of the center electrode and the convex part. The noble metal coating layer covers a surface of the convex part. The noble metal coating layer has an end face coating layer covering a projecting end face of the convex part and a side face coating layer covering at least a part of a side face of the convex part extended from the projecting end face. A root part of the side face coating layer is buried in the tip end opposing part. An extension is formed so that at least a part of the root part is extended to an outside of the spark plug along the opposing part face.

A spark plug has an elongated center electrode, ground electrode, convex part and noble metal coating layer. The center electrode is held in a housing. The ground electrode has a tip end opposing part opposing the center electrode. The convex part is extended from the tip end opposing part to an opposing part face in an axial direction of the spark plug. A spark discharge gap is formed between a tip end part of the center electrode and the convex part. The noble metal coating layer covers a surface of the convex part. The noble metal coating layer has an end face coating layer covering a projecting end face of the convex part and a side face coating layer covering at least a part of a side face of the convex part extended from the projecting end face. A root part of the side face coating layer is buried in the tip end opposing part. An extension is formed so that at least a part of the root part is extended to an outside of the spark plug along the opposing part face.

A spark plug includes an insulator having an axial hole extending along an axial line, a center electrode disposed in the axial hole, a tubular metallic shell surrounding the insulator, a ground electrode whose proximal end is fixed to the metallic shell, and a cylindrical noble metal tip fixed to the ground electrode via an intermediate tip so as to form a gap between the noble metal tip and the center electrode. A weld portion is provided between the noble metal tip and the intermediate tip. The weld portion has a diameter larger than that of a portion of the intermediate tip which is adjacent to the weld portion. The noble metal tip is located inside a virtual tapered cylindrical surface which extends from a peripheral edge of a gap-side end of the center electrode so as to contact an outer circumferential edge of the weld portion.