Abstract: A spark plug and method of manufacturing the same. The spark plug includes a tubular insulator holding a center electrode, and a tubular metallic shell holding the insulator. The insulator is inserted into the metallic shell from the rear end side thereof until a portion of the insulator engages the metallic shell. In this state, the circumferential edge of the rear end portion of the metallic shell is crimped, whereby the insulator is unitarily fixed to the metallic shell. A talc charged layer is formed in a clearance portion between the insulator and the metallic shell, and a wire packing is placed on a rear end portion of the talc charged layer for engaging the crimp portion. A portion of the talc charged layer is interposed between the wire packing and the rear trunk portion of the insulator.

Abstract: A spark-ignited, internal combustion engine ignition device to increase electrical transfer efficiency of the ignition by peaking the electrical power of the spark during the streamer phase of spark creation and improving combustion quality, incorporating an electrode design and materials to reduce electrode erosion due to high power discharge, an insulator provided with capacitive plates to peak the electrical current of the spark discharge, and concomitant methods.

Abstract: A method of manufacturing a center electrode of a spark plug, comprising the steps of forming a cylindrical electrode member having a medium diameter portion and a small diameter portion and forming a barrel portion by extruding the medium diameter portion when the value of (S1?S2)/S1×100) is 30 or more, S1 being the cross-sectional area of a cross-section of the medium diameter portion perpendicular to an axial direction, and S2 being the cross-sectional area of a cross-section of each small diameter portion perpendicular to the axial direction.

Abstract: A spark plug (20) for igniting a mixture of fuel and air of an internal combustion engine comprises a center electrode (22) and a ground electrode (24). At least one of the electrodes (22, 24) includes a body portion (28, 30) formed of thermally conductive material and a firing tip (32, 34) disposed on the body portion (28, 30). The firing tip (32, 34) includes a ceramic material, providing an exposed firing surface (36, 38). The ceramic material is an electrically conductive, monolithic ceramic material. Examples of preferred ceramic materials include titanium diboride, silicon carbide, ternary carbide, and ternary nitride. The ceramic material can also include oxides, borides, nitrides, carbides, silicides, or MAX phases.

Abstract: A pre-chamber spark plug that includes a shell, and an end cap attached to the shell. Additionally, the pre-chamber spark plug includes an insulator disposed within the shell. In a particular embodiment, a center electrode has a first portion surrounded by the insulator, and a second portion that extends from the insulator into a pre-chamber. The pre-chamber defined by the shell and end cap. In a further embodiment, a ground electrode is attached to the shell. In particular embodiments, the ground electrode is tubular in shape and includes an inner spark surface ring spaced in surrounding relation to the center electrode to create a spark gap, an outer ring attached to the shell, and a plurality of rounded spokes connecting the inner and outer rings. In a particular embodiment, the ground and center electrodes accommodate attachment of precious metal alloys to increase electrode surface life.

Abstract: An alumina-based sintered body for a spark plug having enhanced mechanical strength and a method of manufacturing the same, as well as a spark plug having the alumina-based sintered body for a spark plug and a method of manufacturing the same.

Abstract: A spark plug for an internal combustion engine, the spark plug having: an elongated center electrode having a center electrode tip at one end and a terminal proximate the other end; an insulator substantially surrounding the center electrode, the insulator having a channel formed in an exterior surface of the insulator; an outer shell surrounding the insulator having: a jamb nut portion with a distal end extending thereform, the distal end being aligned with the channel such that the distal end of the outer shell is received within and engages the channel; a motor seat portion proximate to the jamb nut portion; and a threaded portion proximate to the motor seat portion, wherein the jamb nut portion, the motor seat portion, and the threaded portion are all integrally formed with the outer shell as a single component.

Abstract: An igniter (20) of a corona ignition system emits a non-thermal plasma in the form of a corona (30) to ionize and ignite a fuel mixture. The igniter (20) includes an electrode (32) and a ceramic insulator (22) surrounding the electrode (32). The insulator (22) surrounds a firing end (38) of the electrode (32) and blocks the electrode (32) from exposure to the combustion chamber (28). The insulator (22) presents a firing surface (56) exposed to the combustion chamber (28) and emitting the non-thermal plasma. A plurality of electrically conducting elements (24) are disposed in a matrix (26) of the ceramic material and along the firing surface (56) of the insulator (22), such as metal particles embedded in the ceramic material or holes in the ceramic material. The electrically conducting elements (24) reduce arc discharge during operation of the igniter (20) and thus improve the quality of ignition.

Abstract: A buried portion (32B) buried from a junction target surface of a ground electrode (27) is provided in a noble metal tip (32). In a section, perpendicular to a central axis CL2 of the ground electrode (27), a large width portion (32W) is formed in the buried portion (32B), and a region between the junction target surface and a largest width region of the large width portion (32W) is formed into a shape which gradually increases in width, or into a shape having a region of the relevant shape and a constant width region. A region from the large width portion (32W) to a point of intersection P1, P2 is covered with a base material of the ground electrode (27) and a melt portion (35), and a thickness t1 (mm) of the noble metal tip (32) and a buried amount t2 (mm) satisfy 0.25?t2/t1.

Abstract: A method for manufacturing a spark plug having a central electrode and a ground electrode, the central electrode and the ground electrode being spaced apart from each other and a first planar electrode face being formed on the central electrode and a second planar electrode face being formed on the ground electrode by a separative manufacturing method.

Abstract: A plasma jet ignition plug that reliably prevents current leakage with restraint on variation in the position of a ground electrode relative to an insulator and on overheat of the ground electrode, for stable generation of plasma. The plug includes an insulator having an axial bore extending in the direction of an axis CL1, a center electrode inserted in the axial bore, a metallic shell disposed externally of the outer circumference of the insulator, and a ground electrode fixed to the metallic shell, and has a cavity defined by the wall surface of the axial bore and the front end surface of the center electrode. Supports intervene between the insulator and the ground electrode. A space formed radially outward of the supports and a space formed radially inward of the support communicate with each other.

Abstract: A spark plug having improved durability having a ground electrode comprised of a ground electrode base member and a noble metal tip. A center axis of the noble metal tip slants in relation to the center axis of the ground electrode base member at angle ? which satisfies a relation 2°???25°.

Abstract: An embodiment of the invention is a microtip microplasma device having a first metal microtip opposing a second metal microtip with a gap therebetween. The first and second metal microtips are encapsulated in metal oxide that electrically isolates and physically connects the first and second metal microtips. In preferred devices, the first and second metal microtips and metal oxide comprise a monolithic, unitary structure. Arrays can be flexible, can be arranged in stacks, and can be formed into cylinders, for example, for gas and liquid processing devices, air filters and other applications. A preferred method of to forming an array of microtip microplasma devices provides a metal mesh with an array of micro openings therein. Electrode areas of the metal mesh are masked leaving planned connecting metal oxide areas of the metal mesh unmasked.

Abstract: Provided is a manufacturing method for manufacturing a spark plug which produces a spark plug which mitigates misfire and improves gas mileage, peak engine performance, horsepower, and increases the RPM range of the host vehicle. The improved performance of the spark plug is, at least in part, attributable to the spacing between an electrode body and an electrode cage. In particular, the electrode cage extends over the electrode body such that the arcuate members of the electrode cage are equidistantly spaced from the bulbous or spherical electrode body. The manufacturing method described herein results in a spark plug having the above-described configuration, while being formed and assembled at an economical cost.

Abstract: A method for manufacturing an insulator for a spark plug is provided. The method includes: a preparing step; a press pin arranging step; a powder filling step after the press pin arranging step; a cavity blocking step after the powder filling step; a compression molding step after the cavity blocking step; a die releasing step after the compression molding step; and a press pin removing step after the die releasing step.

Abstract: A method of forming a spark plug for an internal combustion engine is provided, the method including the steps of: separately securing a ground electrode to a ground shield, the ground shield having an elongated base section being configured to substantially surround a first insulator section of an insulator configured to substantially surround a center electrode, the insulator having a substantially cylindrical body with at least the first insulator section and a second insulator section, the first and second insulator sections having first and second diameters respectively and being separated by an insulator shoulder; and the elongated center electrode having a center electrode tip at one end and a terminal proximate another end of the center electrode, wherein the ground shield has a frustoconical flange protruding from a first end of the elongated base section, the frustoconical flange being configured to engage the insulator shoulder, and wherein the ground electrode extends from a second end of the elon

Abstract: The invention describes a spark plug, which comprises an inner conductor, an insulator enclosing the inner conductor, a spark plug body enclosing the insulator and two electrodes forming a spark gap. The first electrode is a center electrode connected to the inner conductor in an electrically conductive manner and the second electrode is a ground electrode connected to the spark plug body in an electrically conductive manner. At least one of the electrodes has a precious metal region, adjoining the spark gap and consisting predominantly of platinum, iridium or an alloy of both and containing additionally at least one brittle metal. The precious metal region consists of a base material predominantly containing platinum and/or iridium, which comprises a coating with a brittle metal, which is more brittle than the base material.

Abstract: A spark plug in which an ignition portion of a ground electrode formed through joining of a noble metal chip to the ground electrode has high durability, and a method of manufacturing the spark plug.

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: In various embodiments, a spark plug includes an electrically conductive body disposed around an insulator, a tip of the insulator protruding from the body, a generally radially disposed annular groove formed by the insulator tip, a center electrode disposed within the insulator, a tip of the center electrode protruding from the insulator tip, and an annular auxiliary electrode disposed within the annular groove, the auxiliary electrode having a center portion thicker than an edge portion thereof. A longitudinal length of the auxiliary electrode may be greater than a radial thickness of the auxiliary electrode.

Abstract: A spark plug (100) including a center electrode (130) and a ground electrode (140), which is formed by joining a ground electrode chip (143) to a ground electrode base material (141) via an intermediate member (142). A method for producing the spark plug (100) includes providing a projecting portion (142p) on the intermediate member (142), and projection-welding the intermediate member (142) to the ground electrode base material (141) by means of the projecting portion (142p), to thereby join the intermediate member 142 to the ground electrode base material (141). Further, the intermediate member (142) of the spark plug (100) includes a cylindrical columnar portion (142e) which is joined to the ground electrode chip (143), and a flange portion (142d) which is joined to the ground electrode base material (141) and which flange portion (142d) has a diameter greater than that of the cylindrical columnar portion (142e).

Abstract: A decrease in yield and degradation of productivity can be avoided when a spark plug having an insulator with low mechanical strength is manufactured. In a second process, a terminal electrode 15 is inserted to a predetermined position in a state where an insulator 12 is heated to a temperature equal to or greater than the softening temperatures of first to third powder materials 16P, 17P, and 18P such that the first powder material 16P becomes a first conductive sealing material layer 16, the second powder material 17P becomes a resistor 17, and the third powder material 18P becomes a second conductive sealing material layer 18. In addition, a speed at which the terminal electrode 15 is inserted is reduced between the start and the end of the second process.

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: Provided is a technique for limiting the radial displacement between a metal shell and an insulator in a spark plug. At the time of manufacturing a spark plug with a metal shell and an insulator, the metal shell and the insulator are assembled together by, while allowing relative positional displacement between the metal shell and the insulator in an axial direction (O-O), limiting relative positional displacement between the metal shell and the insulator in a radial direction intersecting with the axial direction in such a manner that the amount of deviation between an axis of the metal shell and an axis of the insulator becomes less than or equal to a predetermined level.

Abstract: For producing a spark plug that has a high dimensional accuracy in the spark gap, a method is disclosed which comprises (a) preparing a semi-finished spark plug unit (100b) which comprises a center electrode (20) that has a leading end portion (22), a metal shell (50) that holds therein through an insulator (10) the center electrode (20) except the leading end portion (22) and a ground electrode (30) fixed to a leading end of the metal shell (50), (b) bending the ground electrode (30) so that a bent front portion (31) of the ground electrode (30) projects toward the leading end portion (22) of the center electrode (20), (c) putting an electrode tip (95) on a given part of the bent front portion (31) of the ground electrode (30) in such a manner that a front portion of the electrode tip (95) projects from the bent front portion (31) toward the leading end portion (22) of the center electrode (20) and (d) welding the electrode tip (95) to the given part of the bent front portion (31) of the ground electrode (30

Abstract: An objective is to provide a spark plug in which a ground electrode has a protrusion formed from the same material as that used to form the ground electrode and the heat transfer performance of the protrusion is improved to thereby improve erosion resistance. A spark plug 1 includes a rodlike center electrode 5 extending in the direction of an axis CL1; a substantially cylindrical insulator 2 provided externally of the outer circumference of the center electrode 5; a substantially cylindrical metallic shell 3 provided externally of the outer circumference of the insulator 2; and a ground electrode 27 extending from a front end portion 26 of the metallic shell 3 and forming a spark discharge gap 35 between a distal end portion thereof and a front end portion of the center electrode 5.

Abstract: A spark plug including a center electrode; an insulator; and a metal shell, the metal shell including: a tool engaging section; a body section; and a groove section formed between the tool engaging section and the body section, and having bulges which bulge in an outer peripheral direction and in an inner peripheral direction. When a portion of the groove section having a largest outer diameter is a first section, a thinnest portion from the first section to the body section is a second section, and a portion having a thickness that is the same as that of the first section is a third section, a relation between a thickness A of the second section and a radius of curvature R of an outer surface of the metal shell that continues from the second section to the third section satisfies R×A?0.20 mm2.

Abstract: A corona igniter (20) includes a metal shell (32) with a corona reducing lip (38) spaced from an insulator (26) and being free of sharp edges (40) to prevent arcing (42) in a rollover region and concentrate the electrical field at an electrode firing end (48). The corona reducing lip (38) includes lip outer surfaces (88) being round, convex, concave, or curving continuously with smooth transitions (90) therebetween. The corona reducing lip (38) includes lip outer surfaces (88) presenting spherical lip radii (r1) being at least 0.004 inches. The corona igniter (20) also includes shell inner surfaces (104) and insulator outer surfaces (75) facing one another being free of sharp edges (40).

Abstract: In a method for measuring deviation of a ground electrode from an optimal igniting position, a metallic shell is engaged with a female thread jig. Then the axis O of the metallic shell, a predetermined first measuring point P1 and a predetermined second measuring point P2 on a front end face of the ground electrode are detected. Then, a circumferential angle ?1 formed between a reference straight line “LS” connecting O to the optimal igniting position O1, and a first straight line L1 which connects O to P1 is measured, followed by a measurement of a circumferential angle ?2 formed between LS and a second straight line L2 connecting O to P2 Thereafter, the deviation of the ground electrode from O1 is measured as a circumferential angle “?” between “LS” and a third straight line L3 connecting the axis O to the center C of the front end face.

Abstract: A spark ignition device, ground electrode therefor, and methods of construction thereof are provided. The spark ignition device includes a generally annular ceramic insulator with a metal shell surrounding at least a portion of the ceramic insulator. A center electrode is received at least in part in the ceramic insulator and a ground electrode extends from the shell to a free end portion. A firing tip is attached adjacent the free end portion of the ground electrode to provide a spark gap between the center electrode and the firing tip. The free end portion is at least partially bounded by at least one “as laser cut” peripheral side extending adjacent the firing tip.

Abstract: A spark plug (100) including a center electrode (130) and a ground electrode (140), which is formed by joining a ground electrode chip (143) to a ground electrode base material (141) via an intermediate member (142). A method for producing the spark plug (100) includes providing a projecting portion (142p) on the intermediate member (142), and projection-welding the intermediate member (142) to the ground electrode base material (141) by means of the projecting portion (142p), to thereby join the intermediate member 142 to the ground electrode base material (141). Further, the intermediate member (142) of the spark plug (100) includes a cylindrical columnar portion (142e) which is joined to the ground electrode chip (143), and a flange portion (142d) which is joined to the ground electrode base material (141) and which flange portion (142d) has a diameter greater than that of the cylindrical columnar portion (142e).

Abstract: An igniter for an internal combustion engine, the igniter comprising: a center electrode; an insulator disposed about the center electrode; a ground shield disposed about the insulator, the insulator having a tip portion extending past an end portion of the ground shield and a tip portion of the center electrode extending through and away from the tip portion of the insulator; and a spark gap disposed between the tip portion of the center electrode and the end portion of the ground shield.

Abstract: A method for manufacturing a spark plug which includes: (a) preparing a metal shell; (b) preparing an insulator; (c) inserting the insulator in an insertion hole of the metal shell; (d) forming an intended crimping portion of the metal shell into a crimping portion; and (e) pressing a lower side portion of the metal shell closer to a position lower than the intended compressive deformation portion, and pressing the crimping portion of the metal shell in an axial direction to compressively deform the intended compressive deformation portion of the metal shell and thus seal a space between a stepped portion of the metal shell and a stepped portion of the insulator, wherein step (e) controls a pressing amount of a press in a constant value from the start of compressive deformation to the end thereof.

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 ignition device, metal shell, and methods of construction are provided. The spark ignition device has a ceramic insulator extending along a longitudinal axis and a metal shell. The metal shell extends along the longitudinal axis to a distal end. A center electrode is received in the ceramic insulator and extends along the longitudinal axis. A ground electrode has an attachment end fixed by a weld joint to the distal end of the shell and a free end extending from the distal end to provide a spark gap. The weld joint includes a resistance weld joint and a laser weld joint, which in combination inhibit material expulsion; provide a reliable, strong attachment of the ground electrode to the shell; provide an improved heat transfer path between the ground electrode and the shell, and facilitate repeatable and accurate positioning of the ground electrode to the shell.

Abstract: A spark plug for an internal combustion engine, the spark plug having an elongated center electrode having a center electrode tip at one end and a terminal proximate to another end of the center electrode; an insulator surrounding a portion of the center electrode, the insulator having a channel formed in an exterior surface of the insulator; and a jamb nut surrounding the insulator, the jamb nut being aligned with the channel such that a distal end of the jamb nut does not contact the insulator.

Abstract: A spark plug for an internal combustion engine includes a housing having a distal end, a proximal end, and an outer periphery extending therebetween. A mounting thread formed on the outer periphery at the proximal end of the housing secures the spark plug to the engine. A center electrode fixedly secured along a central axis of the housing has a first end extending outwardly from the proximal end of the housing. A ground electrode secured to the proximal end of the housing has an electrode tip at a first distance from the center electrode. The electrode tip has a central aperture extending through the ground electrode from an upper surface to a lower surface. A protruding edge circumscribes the aperture and extends a second distance from the upper surface of the electrode tip towards the center electrode.

Abstract: A spark plug comprises a shell having a substantially cylindrical threaded portion for threadable engagement in a cylinder head of an internal combustion engine, an insulator disposed coaxially in the shell, a center electrode disposed coaxially in the insulator, a side ground electrode having a first end coupled to the shell and a second end facing an end of the center electrode to define a spark discharge gap therebetween, and an electrode tip portion secured to either the side ground electrode or the center electrode proximate the spark discharge gap. The tip portion is formed from an alloy comprising from about 60 to about 70 percent by weight iridium, from about 30 to about 35 percent by weight rhodium, from 0 to about 10 percent by weight nickel, from about 3500 to about 4500 parts per million tantalum, and from about 100 to about 200 parts per million zirconium.

Abstract: An ignition device for an internal combustion engine and method of construction therefore includes a housing with an insulator secured therein. A center electrode is mounted within the insulator. A ground electrode extends from the housing with a portion of the ground electrode defining a spark gap across from the center electrode. The center electrode has a firing tip, wherein a resistance weld joint initially bonds the firing tip to the center electrode and a continuous bead of overlapping first weld pools formed substantially from the material of the firing tip further bonds the firing tip to the electrode. A continuous bead of overlapping second weld pools formed radially outwardly from the first weld pools forms a rounded shoulder surface extending from the first weld pools to an outer surface of the center electrode.

Abstract: What is described is a spark plug (1) comprising an inner conductor (6), an ignition tip (7) connected to the inner conductor (6), an insulator (8) surrounding the inner conductor (6) and having a front end (9) and a rear end (10), a spark plug body (2) having a front end (3) and a rear end (4), and at least one ground electrode (5) connected to the front end (3) of the spark plug body (2). The spark plug (1) has a longitudinal direction extending parallel to the inner conductor (6). The spark plug body (2) comprises a passage (12) extending in the longitudinal direction and in which the insulator (8) is disposed. A sleeve composed of metal is disposed between the insulator (8) and the spark plug body (2). The sleeve is tightly connected to the insulator (8) and the spark plug body (2) and is referred to below as the “first sleeve” (13). At least one second sleeve (14) is disposed at a distance from the first sleeve (13) and, in fact, between the first sleeve (13) and the rear end (10) of the insulator (8).

Abstract: The invention relates to a pre-chamber spark plug with a housing which, at its forward end, comprises a pre-chamber with a plurality of openings, an insulator arranged in the housing, a center electrode which is surrounded by the insulator and supports an ignition electrode arranged in the pre-chamber which comprises a plurality of electrode arms, wherein the electrode arms each comprise a rear section which extends in a transverse direction in relation to the longitudinal direction of the center electrode and a forward section which extends along a pre-chamber wall and forms a spark gap between itself and the pre-chamber wall. It is provided according to the invention that the electrode arms are embedded in the center electrode and project from a lateral surface of the center electrode. Furthermore, the invention relates to a method according to the invention.

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 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: Provided are a spark plug in which the occurrence of spark blowout or the like is restrained for improvement of ignition performance, and a method of manufacturing the spark plug. A ground electrode 27 of the spark plug has a protrusion 28 which faces a center electrode 5. The distal end surface of the protrusion 28 has a noble metal tip 32 provided at the center thereof and includes an annular fusion portion 33 adjacent to the periphery of the noble metal tip 32, and an annular electrode base metal surface located externally of the annular fusion portion 33. A spark discharge gap 35 is formed between the center electrode 5 and the distal end of the protrusion 28 including the noble metal tip 32.

Abstract: A spark plug capable of increasing a welding strength between a leading end of a metal shell and a base end of a ground electrode to avoid fracture of a welded part due to vibrations and the like even when making the metal shell smaller. The spark plug satisfies a relation of S2?S wherein S2 is a sectional area of the welded part between the metal shell and the ground electrode, the sectional area S2 being cut off by a plane including a leading end surface of the metal shell, and S is a sectional area of the ground electrode, the sectional area S being cut off by a plane passing to the most axial leading end of a boundary between the ground electrode and the welded part and perpendicular to the axial direction.

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 in which the center electrode is formed by laser welding along the circumference of a joint surface between a center electrode base metal and a noble metal tip in excess of full circumference. When G represents a spark gap and A represents a shortest gap between a laser weld bead and a line drawn parallel with axis X, A?3G. Straight lines S1 and S2 which connect the center of the noble metal tip 1 and the circumferential center of a proximal end 52 of the ground electrode 51 and vertex 8 of a protrusion 7 formed at a final end portion 6e of a bead 6 formed by circumferential laser welding, respectively, form an angle ? of 45 degrees. Since the protrusion 7 of the bead is the angle ? away from the ground electrode 51, an abnormal discharge is unlikely to be generated.

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 metal shell assembly for a spark plug including a cylindrical metal shell that extends in a direction of a central axis and which has a screw portion formed in an outer peripheral surface thereof, and a bar-shaped ground electrode that extends from a front end portion of the metal shell, the method including: disposing an intermediate assembly, having the ground electrode provided in a metal shell intermediate body, between a plurality of rolling dies having process surfaces facing each other; forming the screw portion by performing a rolling process on the intermediate assembly by the plurality of rolling dies while the intermediate assembly is interposed between the plurality of rolling dies; and positioning the ground electrode in a circumferential direction about a central axis of the intermediate assembly between the disposing and forming steps.