Abstract: A spark plug including a ground electrode including a base material, a tip having a discharge surface, and a melt portion interposed over an entire area between the tip and the base material and joining the tip to the base material; and a center electrode with a spark gap formed between the center electrode and the discharge surface. The tip has, in an inner area surrounded by an outer peripheral portion of the tip, a thin portion in which a distance between the discharge surface and the melt portion is shorter than a distance between the discharge surface and the melt portion in the outer peripheral portion. The thin portion extends from a part of the outer peripheral portion to a part other than the part of the outer peripheral portion.

Abstract: A spark plug including a ground electrode including a base material, a tip having a discharge surface, and a melt portion interposed over an entire area between the tip and the base material and joining the tip to the base material; and a center electrode with a spark gap formed between the center electrode and the discharge surface. The tip has, in an inner area surrounded by an outer peripheral portion of the tip, a thin portion in which a distance between the discharge surface and the melt portion is shorter than a distance between the discharge surface and the melt portion in the outer peripheral portion. The thin portion extends from a part of the outer peripheral portion to a part other than the part of the outer peripheral portion.

Abstract: An ignition plug includes a ground electrode tip disposed in through hole through a ground electrode base material, a discharge surface of the ground electrode tip being exposed to the center electrode side from the through hole; and a fixing member disposed in the through hole at a part on a second direction side with respect to the large diameter surface.

Abstract: A spark plug having an insulator that includes a fitted portion in contact with a rear end surface of a ledge portion of a metal shell. The insulator has a recessed portion recessed radially inward. The recessed portion is formed in an outer circumferential surface which is located on the rear side of the insulator relative to the fitted portion and which is disposed in the metal shell. The area of an outer circumferential surface of the insulator, from a front end of the recessed portion to a front end of the fitted portion, is larger than or equal to the area of a surface of the insulator which is exposed to combustion gas.

Abstract: A spark plug having an insulator that includes a fitted portion in contact with a rear end surface of a ledge portion of a metal shell. The insulator has a recessed portion recessed radially inward. The recessed portion is formed in an outer circumferential surface which is located on the rear side of the insulator relative to the fitted portion and which is disposed in the metal shell. The area of an outer circumferential surface of the insulator, from a front end of the recessed portion to a front end of the fitted portion, is larger than or equal to the area of a surface of the insulator which is exposed to combustion gas.

Abstract: An ignition plug includes a ground electrode tip disposed in through hole through a ground electrode base material, a discharge surface of the ground electrode tip being exposed to the center electrode side from the through hole; and a fixing member disposed in the through hole at a part on a second direction side with respect to the large diameter surface.

Abstract: A spark plug includes a center electrode, an electrode tip having a discharge surface, and an opposite surface having a diameter greater than that of the discharge surface and located opposite the discharge surface, a tip holding element having a through hole, a ground electrode body having a recess, and a fusion portion formed at at least a portion of the boundary between the outer side surface of the tip holding element and the inner side surface of the recess.

Abstract: A spark plug comprises an insulator having a axial hole penetrating in a direction of an axis, a central electrode provided on the front end side of the axial hole, a tubular metal shell that holds the insulator, and a ground electrode including a surface layer and a core material that is surrounded by the surface layer and has a larger thermal conductivity than that of the surface layer. The metal shell of the spark plug has a protruding portion in which at least a part of the metal shell protrudes toward the front end side in the direction of the axis. The ground electrode has an end surface at one end portion thereof joined to the inside of the protruding portion and the other end portion thereof facing the central electrode.

Abstract: A spark plug (1) includes an insulator (2) having an axial hole (4), a center electrode (5) inserted into the axial hole (4), a metallic shell (3) provided around the insulator (2), a ground electrode (27) whose base end portion is fixed to the metallic shell (3) and which has an annular portion (27A) formed at a forward end portion thereof, the center electrode (5) being disposed radially inward of the annular portion (27A), and an annular tip (32) which is joined to the inner circumference of the annular portion (27A) and which forms a spark discharge gap (28) between the center electrode (5) and the inner circumferential surface of the annular tip (32). Recesses (35) are provided on at least one of the inner and outer circumferences of the annular portion (27A).

Abstract: A spark plug including a center electrode, an insulator, a metal shell, a first ground electrode, and a second ground electrode. The center electrode extends in an axial direction. The insulator has an axial hole extending in the axial direction. The center electrode is to be inserted into the axial hole. The metal shell is arranged at an outer periphery of the insulator. The first ground electrode has electrical continuity with the metal shell, and forms a first gap with a front end surface of the center electrode. The second ground electrode has electrical continuity with the metal shell, is sealed to metal shell, extends from the metal shell to a position facing a side surface of the center electrode, and forms an annular second gap between the side surface of the center electrode and an inner peripheral surface of the second ground electrode.

Abstract: A spark plug (1) includes an insulator (2) having an axial hole (4), a center electrode (5) inserted into the axial hole (4), a metallic shell (3) provided around the insulator (2), a ground electrode (27) whose base end portion is fixed to the metallic shell (3) and which has an annular portion (27A) formed at a forward end portion thereof, the center electrode (5) being disposed radially inward of the annular portion (27A), and an annular tip (32) which is joined to the inner circumference of the annular portion (27A) and which forms a spark discharge gap (28) between the center electrode (5) and the inner circumferential surface of the annular tip (32). Recesses (35) are provided on at least one of the inner and outer circumferences of the annular portion (27A).

Abstract: A spark plug including a center electrode, an insulator, a metal shell, a first ground electrode, and a second ground electrode. The center electrode extends in an axial direction. The insulator has an axial hole extending in the axial direction. The center electrode is to be inserted into the axial hole. The metal shell is arranged at an outer periphery of the insulator. The first ground electrode has electrical continuity with the metal shell, and forms a first gap with a front end surface of the center electrode. The second ground electrode has electrical continuity with the metal shell, is sealed to metal shell, extends from the metal shell to a position facing a side surface of the center electrode, and forms an annular second gap between the side surface of the center electrode and an inner peripheral surface of the second ground electrode.

Abstract: A ground electrode comprised of a noble metal tip having an outer circumferential surface, a holder having an inner circumferential surface defining a through hole for the noble metal tip thereon, and a body to which the holder is joined. At least one of a) the inner circumferential surface of the holder which forms the through hole, and b) the outer circumferential surface of the noble metal tip which is disposed in the through hole, continuously reduces in diameter toward the forward side. A forward end surface of the noble metal tip is located on a forward side with respect to a forward end surface of the holder.

Abstract: A spark plug includes a tip joined to a center electrode. The coefficient of linear thermal expansion of the center electrode is greater than that of the tip. The tip has a gap-forming portion having a maximum width of 1.2 mm or greater and forming a gap in cooperation with the ground electrode and a to-be-joined portion joined to the center electrode. At a position A which is shifted 0.1 mm from the forward end of the outer surface of the fusion portion toward the forward end side, the width of the to-be-joined portion measured on the cross section is smaller than the width of the gap-forming portion. The to-be-joined portion satisfies Dtw/Dw?1.1, where Dtw represents the width of the to-be-joined portion at the position A, and Dw represents the width of the fusion portion at the forward end of the outer surface thereof.

Abstract: A spark plug includes an electrode wherein a plurality of fusion regions are formed by melting to each other a circular noble metal tip having a diameter of not less than 2 mm and a base material disposed around an outer periphery of the noble metal tip. In a particular tip cross section, a total length of the portions passing the fusion region on the circumference of a circle A concentric to an outline of the tip and having a diameter of 90% of the length of the tip is not less than 30% of the length of the circumference of the concentric circle A, and a total length of the portions on which a circumference of a concentric circle B, having the same diameter as that of the outline passes, is not less than 30% of the length of the circumference of the concentric circle B.

Abstract: An ignition plug having a metallic shell with a through hole extending therethrough in an axial direction, an insulator fitted into the through hole of the metallic shell and having an axial hole extending in the axial direction, and a center electrode fitted into the axial hole of the insulator. The ignition plug further includes a cap member which covers a front end opening of the metallic shell, provided on a front end side thereof where the center electrode is disposed, to thereby form an ignition chamber at the front end portion of the metallic shell, and a ground electrode disposed within the ignition chamber and facing a circumferential surface of the center electrode directly or indirectly.

Abstract: A ground electrode comprised of a noble metal tip having an outer circumferential surface, a holder having an inner circumferential surface defining a through hole for the noble metal tip thereon, and a body to which the holder is joined. At least one of a) the inner circumferential surface of the holder which forms the through hole, and b) the outer circumferential surface of the noble metal tip which is disposed in the through hole, continuously reduces in diameter toward the forward side. A forward end surface of the noble metal tip is located on a forward side with respect to a forward end surface of the holder.

Abstract: A spark plug includes an electrode wherein a plurality of fusion regions are formed by melting to each other a circular noble metal tip having a diameter of not less than 2 mm and a base material disposed around an outer periphery of the noble metal tip. In a particular tip cross section, a total length of the portions passing the fusion region on the circumference of a circle A concentric to an outline of the tip and having a diameter of 90% of the length of the tip is not less than 30% of the length of the circumference of the concentric circle A, and a total length of the portions on which a circumference of a concentric circle B, having the same diameter as that of the outline passes, is not less than 30% of the length of the circumference of the concentric circle B.

Abstract: A technique of reducing occurrence of multiple discharge in a spark plug. The spark plug has a main ground electrode and three auxiliary ground electrodes. The position at which first auxiliary ground electrode is joined to a metallic shell is located opposite the position at which main ground electrode is joined to the metallic shell, with respect to a center electrode. The positions at which second and third auxiliary ground electrodes are joined to the metallic shell are located opposite to each other with respect to the center electrode. When the width of first auxiliary ground electrode is represented by W, the shortest distance between second auxiliary ground electrode and third auxiliary ground electrode is represented by T, and a distance which is a component of the shortest distance T in a direction orthogonal to first auxiliary ground electrode is represented by Tp, a relation W?Tp is satisfied.

Abstract: An electrode-attached insulator having an insulator provided with an axial hole extending in the direction of an axis and a center electrode which is disposed on a distal-end side of the axial hole and has a front end portion that is exposed from a front end of the insulator. The electrode-attached insulator includes a locking member having a collar portion which is locked on a step portion. The center electrode and the locking member are joined together in the axial hole.