Abstract: A spark plug of the present invention includes a cylindrical metal shell, a cylindrical ceramic insulator retained in the metal shell, a center electrode retained in the ceramic insulator and extending in an axial direction, and a ground electrode formed into a bent shape and having a rear end portion fixed to the metal shell and a front end portion facing a front end portion of the center electrode with a gap left therebetween. The ground electrode contains a large thickness region formed on a rear end side thereof with a large thickness, a small thickness region formed on a front end side thereof with a smaller thickness than that of the large thickness region, a protruding region formed on the small thickness region and facing the center electrode and a thickness changing region formed between the large thickness region and the small thickness region and located at a different position from a position of a minimum curvature radius region of the bent shape of the ground electrode.

Abstract: There is provided a spark plug 100 with a ground electrode 30, wherein a protrusion amount A of a protruding portion 36 satisfies a relationship of 0.4 mm?A?1.0 mm and wherein a press recessed portion 37 extends to a front end surface 31 of the ground electrode 30.

Abstract: A spark plug includes an insulator, a center electrode, a metal shell, a ground electrode, and a noble metal tip joined to at least one of the two electrodes. The noble metal tip is joined to the electrode via a melt portion formed by using a laser or electron beam from a side surface of the noble metal tip. In a predetermined section, including a central axis of the noble metal tip, ¾ or more of one end face of the noble metal tip is joined to the electrode. When the thickness of the melt portion is taken to be TX (mm), and the length in a direction of irradiation with the laser beam is taken to be LX (mm), TX and LX satisfy 1.5?LX/TX, and an angle ?X or angle ?Y, formed by two predetermined straight lines, satisfies ?15??X (?Y)?25.

Abstract: A center electrode includes a tapered electrode base member mount and a noble metal tip joined to the electrode base member mount via a fused portion in which the component of the noble metal tip and the component of the electrode base member mount are fused. In this state, the cross section area S1 at a tip side boundary between the fused portion and the noble metal tip and the cross section area S2 at a base member side boundary between the fused portion and the electrode base member mount satisfy the relational expression of S1<S2. Regarding the cross section area S3 at the base portion of the electrode base member mount, (S3?S2)/D satisfies the relational expression of 5?(S3?S2)/D?50. D is the shortest distance in the axis line direction from the base member side boundary to the base portion.

Abstract: High-frequency plasma spark plug includes an insulator which has an axial hole extending in the axis direction, a center electrode inserted into a distal end side of the axial hole, a terminal electrode inserted into a rear end side of the axial hole, and being electrically connected to the center electrode, and a cylindrical main fitting mounted on an outer periphery of the insulator. With respect to a coaxial cable, the inner conductor is connected to the terminal electrode and the outer conductor is connected to the main fitting. High frequency power generated by a predetermined high-frequency power source is supplied via the coaxial cable thus generating high frequency plasma. The main fitting includes a large diameter portion which bulges radially outward and a connection portion which is brought into contact with the outer conductor.

Abstract: A spark plug includes a center electrode extending in an axial direction; an insulator formed externally of the outer circumference of the center electrode; a metallic shell formed externally of the outer circumference of the insulator and having a ledge which supports the insulator; and a ground electrode joined to the metallic shell. The insulator has a support portion which faces the ledge. A “frontward direction” is defined as the direction parallel to the axial direction toward a spark portion formed between the center electrode and the ground electrode. The insulator has a diameter reduction portion whose outside diameter reduces along the frontward direction from the support portion, and a diameter increase portion whose outside diameter increases along the frontward direction from the front end of the diameter reduction portion. This restrains the generation of leak current while maintaining heat resistance of the spark plug.

Abstract: Peeling resistance of a noble metal chip is improved by reducing a difference in the thermal stress generated between the noble metal chip and a ground electrode. A spark plug 1 includes an insulator 2, a center electrode 5, a metal shell 3, and a ground electrode 27, wherein a spark discharge gap 33 is formed between the center electrode 5 and the noble metal chip 41 bonded to the ground electrode 27. The ground electrode 27 is provided with a concave hole portion 43, and 70% or more of the noble metal chip 41 is bonded to the hole portion 43 of the ground electrode 27 through a fusion portion 35 formed by fusing the noble metal chip and the ground electrode 27 to each other by emitting a laser beam or the like from the side surface of the noble metal chip. A gap 45 is formed between the noble metal chip 41 and at least a part of an inner wall surface 43 S of the hole portion 43 so as to be more than 0 mm and equal to or less than 1.

Abstract: A method for improving welding strength between a ground electrode and a noble metal tip on a spark plug. A fusion zone is formed along at least a portion of the boundary between the ground electrode and the noble metal tip through fusion of a portion of the ground electrode and a portion of the noble metal tip.

Abstract: A spark plug having a ground electrode that includes a press-formed recess portion comprised of a first portion with which a working pin has come into contact, and a second portion with which the working pin has not come into contact. A relation B1/B2?0.05 is satisfied, where B1 represents the depth of the second portion, and B2 represents the depth of the press-formed recess portion.

Abstract: A method of manufacturing a spark plug having an insulator, a center electrode, a metallic shell, a ground electrode, and a noble metal tip provided on the ground electrode and having a discharge surface forming a spark discharge gap in cooperation with the center electrode. The method of manufacturing includes a fusion-zone formation step of forming a fusion zone through radiation of a high-energy beam to the boundary between the ground electrode and the noble metal tip.

Abstract: A spark plug includes an insulator, a center electrode, a metal shell, a ground electrode, and a noble metal tip joined to at least one of the two electrodes. The noble metal tip is joined to the electrode via a melt portion formed by using a laser or electron beam from a side surface of the noble metal tip. In a predetermined section, including a central axis of the noble metal tip, ¾ or more of one end face of the noble metal tip is joined to the electrode. When the thickness of the melt portion is taken to be TX (mm), and the length in a direction of irradiation with the laser beam is taken to be LX (mm), TX and LX satisfy 1.5?LX/TX, and an angle ?X or angle ?Y, formed by two predetermined straight lines, satisfies ?15??X (?Y)?25.

Abstract: There is provided a spark plug 100 with a ground electrode 30, wherein a protrusion amount A of a protruding portion 36 satisfies a relationship of 0.4 mm?A?1.0 mm and wherein a width B from a front end surface 31 to a press recessed portion 37 satisfies a relationship of 0.4 mm?B?2.5 mm.

Abstract: A spark plug including: a ground electrode including a thick portion provided on a base end side, a thin portion provided on a distal end side, and a stepped portion provided on an inner peripheral surface between the thick portion and the thin portion; a noble metal tip partially embedded in an inner peripheral surface of the thin portion; and a bulge portion provided on the inner peripheral surface of the thin portion between the stepped portion and the noble metal tip. When viewed from a side surface of the ground electrode, a relationship [a protruding height of the noble metal tip from the inner peripheral surface of the thin portion]?[a protruding height of the bulge portion from the inner peripheral surface of the thin portion].

Abstract: A spark plug including: a center electrode; a substantially cylindrical insulator; a cylindrical metal shell; a ground electrode having a base end joined to a leading end portion of the metal shell and a distal end bent toward the axis line. The ground electrode includes: a thick portion provided on a base end side, a thin portion provided on a distal end side, and a stepped portion provided on an inner peripheral surface between the thick portion and the thin portion. A noble metal tip is joined to and partially embedded in the inner peripheral surface of the thin portion and disposed to form a gap between the noble metal tip and the leading end portion of the center electrode.

Abstract: A spark plug having a ground electrode that includes a press-formed recess portion comprised of a first portion with which a working pin has come into contact, and a second portion with which the working pin has not come into contact. A relation B1/B2?0.05 is satisfied, where B1 represents the depth of the second portion, and B2 represents the depth of the press-formed recess portion.

Abstract: There is provided a spark plug 100 with a ground electrode 30, wherein a protrusion amount A of a protruding portion 36 satisfies a relationship of 0.4 mm?A?1.0 mm and wherein a press recessed portion 37 extends to a front end surface 31 of the ground electrode 30.

Abstract: Separation of a noble metal tip is prevented and wear resistance is enhanced, while the increase in manufacturing cost is suppressed. A spark plug 1 includes a center electrode 5 and a noble metal tip 31. The center electrode 5 and the noble metal tip 31 are joined to each other through a molten portion 35. An area of an interface between the noble metal tip 31 and the center electrode 5 is set to be 5% or less with respect to a cross-sectional area of the noble metal tip 31 which is perpendicular to an axial line CL1 at a portion of an outer surface of the noble metal tip 31 which is nearest to the molten portion 35. In the cross section including the axial line CL1, supposing that a length of the portion of the molten portion 35 in the axial line CL1 which is exposed to the outer surface is A (mm), and a width of the noble metal tip 31 is B (mm), B/A?6 is satisfied. The portion of the molten portion 35, of which a length along the axial line CL1 is A/1.

Abstract: A spark plug (1) including a noble metal tip joined to a ground electrode and forming a spark discharge gap in cooperation with a center electrode. A surface of the noble metal tip which forms the gap has an area of 0.9 mm2 or greater. The noble metal tip (32) is joined to the ground electrode (27) via a fusion zone (35) formed by irradiating at least one surface among a distal end surface and side surfaces of the ground electrode with a laser beam or an electron beam. Further, as viewed on a projection plane orthogonal to a center axis of the noble metal tip and on which the noble metal tip and the fusion zone are projected along the center axis, an overlapping region between the noble metal tip (32) and the fusion zone accounts for 70% or more of a projected region of the noble metal tip.

Abstract: A spark plug includes a ground electrode formed with a flat region and a convex curved region on an outer peripheral surface thereof. The flat region is located on a front end of the ground electrode and has a length of 0.2 mm or more from a front end face of the ground electrode in a longitudinal direction of the ground electrode. The ground electrode satisfies the following dimensional condition (1) with respect to first and second cross sections of the ground electrode taken through the convex curved region and the flat region in directions perpendicular to the longitudinal direction of the ground electrode, 0.950?(S2/L2)/(S1/L1)?0.995 ??(1) where S1 is the area of the first cross section; L1 is the perimeter of the first cross section; S2 is the area of the second cross section; and L2 is the perimeter of the second cross section.

Abstract: A spark plug includes a center electrode extending along an axial line, a ground electrode, and a noble metal tip. A center axis of the noble metal tip is displaced from a center axis of the ground electrode toward a base-end side in the axial line. The ground electrode includes an outer layer and an inner layer, and a distal end of the inner layer is closer to the axial line than a base end of the ground electrode. An overlap area between the inner layer and the noble metal tip occupies a ratio of 25% or more in a projective plane defined by projecting, along the center axis, a plane of the ground electrode viewed from a distal-end face on a cross section of the ground electrode in which a maximum cross-sectional area of the inner layer is achieved, among cross sections orthogonal to the center axis.