Abstract: The invention relates to a spark plug for igniting a combustible gas mixture in an internal combustion engine, comprising an ignition electrode (4), an electrical supply line (5), to which the ignition electrode (4) is connected, an insulator body (6), through which the supply line (5) is passed, a housing head (2), which rests in sealing fashion on the insulator body (6) and bears an outer thread (3) for the purpose of screwing it into an internal combustion engine, a tube housing (9), which is fixed on the housing head (2), surrounds the insulator body (6) and has a hexagon head (13). The invention provides that the tube housing (9) surrounds an insulator body holder (7), which is welded to the housing head (2) and presses the insulator body (6) with a prestress against the housing head (2).

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: A spark plug for an internal combustion engine, the spark plug having at least two electrodes, in which the electrodes are formed of a first part made of a substrate material and a surface part more durable than the substrate material. The surface part of the spark plug is joined to the first part via an intermediate part making use of explosion welding. The method also relates to a method for producing a spark plug for an internal combustion engine, the spark plug having at least two electrodes.

Abstract: A spark plug having a center electrode; an insulator having an axial hole extending in the direction of an axis; a metallic shell; a ground electrode extending from a front end portion of the metallic shell; a center-electrode-side noble metal chip joined to a distal end surface of the center electrode; and a ground-electrode-side noble metal chip joined to a distal end surface of the ground electrode, the ground-electrode-side noble metal chip having a distal end surface facing toward a side surface portion of the center-electrode-side noble metal chip, and the ground electrode being bent at an angle that falls within a range of 120° to 140° inclusive.

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 manufacturing method for an ignition plug is provided. The method includes: preparing an insulator having a cavity provided at a leading end portion thereof by disposing a leading end of the center electrode more inwards than a leading end of the insulator; building the insulator in an interior of the metal shell such that the leading end of the insulator is situated closer to a rear end side than the leading end of the metal shell; removing at least part of a leading end portion of the metal shell which projects from a leading end face of the insulator; and disposing the ground electrode at the leading end portion of the metal shell and welding the ground electrode and the metal shell together after the removal step.

Abstract: A method for manufacturing an ignition plug is provided. The method includes: preparing an insulator having a cavity provided at a leading end portion thereof by disposing a leading end of a center electrode more inwards in an axial hole than a leading end of the insulator; building the insulator in an interior of a metal shell; disposing a ground electrode at a leading end portion of the metal shell; positioning a center of a through hole of the ground electrode and a center of the cavity of the insulator; and welding the ground electrode and the metal shell together after the positioning step.

Abstract: A method and apparatus for manufacturing a spark plug, the spark plug being defined herein, the method including a center electrode position measuring step of measuring an X-directional position of the front end of the center electrode; a regulation member positioning step of positioning an X-directional position of a regulation member based on the X-directional position of the front end of the center electrode measured in the center electrode position measuring step, the regulation member regulating an X-directional position of a front end surface of the ground electrode when the ground electrode is pressed and bent in a Y direction; and a gap forming step of using the regulation member to regulate the X-directional position of the front end surface of the ground electrode while pressing and bending the ground electrode in the Y direction so as to form the spark discharge gap; wherein: the X direction and the Y direction are as defined herein.

Abstract: A method for manufacturing an insulator includes: preparing a press pin and a forming die having a cavity, the press pin including a pin-side spiral portion formed on a first position; filling a raw powder into the cavity; arranging the press pin within the cavity; pressing the raw powder within the cavity along with the press pin, and obtaining a green body formed with a green body-side spiral portion; releasing the green body along with the press pin from the cavity; retreating the press pin with respect to the green body while rotating the press pin relative to the green body around an axis, and extracting the press pin from the green body; and removing an unnecessary portion from the green body. The first position is positioned such that the green body-side spiral portion is located in the unnecessary portion of the green body.

Abstract: It is an object of the invention to provide a method of producing a spark plug in which, in order to reduce the size of the spark plug, the diameter of a center electrode can be reduced while maintaining the heat dissipation property of the center electrode, and also such a spark plug. A columnar member 220 in which an outer skin member 21 made of a high refractory Ni alloy, and a core member 23 made of a copper alloy having a high thermal conductivity are clad, and which is columnarly extended can be configured by extrusion molding into a state where the thickness of the outer skin member 21 is substantially uniform (extrusion molding step). A flange portion 305 and a tip end portion 301 are formed in the columnar member 220 to obtain an electrode intermediate member 320 (tip end portion/flange portion forming step). In a middle trunk portion 303 of the electrode intermediate member 320, the thickness of the outer skin member 21 is maintained.

Abstract: A spark plug having a ground electrode with a precious metal pad welded to the ground electrode through a series of weld steps. The precious metal pad is a Pt-based pad which is attached to a side surface of the ground electrode via an attachment process that includes a resistance tack weld to initially secure the pad in place, a coining step to flatten the pad, a second resistance weld to form a permanent weld of the pad to the ground electrode, and a laser capping weld about the exposed periphery of the pad to seal the resistance weld. The laser capping weld comprises numerous overlapping weld spots that together form an annular weld bead located at or just below the discharge surface of the pad.

Abstract: A spark plug for an internal combustion engine is provided which includes a metal shell, a porcelain insulator, a center electrode, a main ground electrode, and auxiliary ground electrodes. Each of the auxiliary ground electrodes has an end face facing the insulator to define an auxiliary spark gap. The end face includes an increasing-radial distance surface which is located at a distance from a longitudinal center line of the spark plug in a radial direction thereof which increases as approaching to the metal shell. The insulator nose has a wall thickness T meeting a relation of 0.3 mm?T?0.7 mm. This avoids a great local increase in electrical field strength on the auxiliary ground electrode to minimize excessive discharge within the auxiliary spark gap to enhance carbon fouling resistance and durability of the spark plug.

Abstract: A noble-metal chip (30, 90) joined to at least either a center electrode or a ground electrode, the center and ground electrodes forming a spark discharge gap, and having a circumferential edge of its facing end surface (31, 91) removed so as to form an edge-removed portion (32, 92). The edge-removal length is 0.01 mm or more and a ratio of the edge-removal length to a radius of the noble-metal chip is less than 0.3. The noble-metal chip is made of iridium or an alloy that contains iridium man amount of 70% by weight or more, and crystal grains constituting the noble-metal chip (30, 90) extends in the axial direction. Also disclosed is a method for manufacturing the spark plug.

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: A spark plug including: a rod-shaped center electrode; an insulator; a metal shell; a ground electrode joined to the metal shell and bent toward the center electrode; a noble metal tip joined to an end portion of the ground electrode and opposing a leading end portion of the center electrode via a gap; and a bulge portion. A part of the noble metal tip is embedded in the ground electrode, and another part of the noble metal tip protrudes from a distal end surface of the ground electrode. A relationship A?0.25 mm is satisfied where A (mm) is a protruding length of the noble metal tip from the distal end surface. The bulge portion covers a center part of a boundary between the noble metal tip and the end surface in a width direction.

Abstract: A spark plug having a multilayer firing tip that minimizes the amount of precious metal used and a method of assembling a spark plug with a multilayer firing tip. The firing tip includes a discharge end and a weld end, with the weld end being connected to a center electrode, and more specifically to a base electrode on the center electrode. The weld end has a coefficient of thermal expansion, which is not between the values for the coefficients of thermal expansion for the discharge end and the base electrode. More specifically, the weld end has a coefficient of thermal expansion which is greater than the coefficients of thermal expansion for the discharge end and base electrode. The weld end is formed from Nickel and Chromium with a limited amount of additional elements. The spark plug is assembled by providing a first elongated material formed from the material used for the discharge end and a second elongated material formed from a material used for the weld end.

Abstract: The invention is a spark plug having multiple precise spark gaps (G} with a donut shaped electrode (20) attached to the firing end of the central electrode (32), as well as a cylindrical ground sleeve (40) that is pressed on to the primary shell (36) of the spark plug. The electrode donut (20) is generally flat and laded out in a radial direction towards the ground prongs (42) that protrude up towards the firing end from the ground sleeve (40). In conjunction with their structure, allow for the generation of a spark from every single ground prong (42) on the ground sleeve (40). This is spark potential area (G). Such multiple spark potential area along with the electrode donut (20) and ground sleeve (40) relation provides a more rapid and complete combustion of the air-fuel mixture within the internal combustion engine, which, in turn, results in more torque and more horse power.

Abstract: Here in is disclosed a system of heat removal for the electrode part of a sparkplug that is used in the internal combustion engine. This is so as to use electrodes that have a very large mass as compared to the smaller, to very small electrodes, as in the case of using precious metals. Here in is further disclosed a sparkplug that is made using recycled parts from old used sparkplugs.

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 spark plug for an internal combustion engine, includes: a cylindrical insulating body; a center electrode; a cylindrical metal shell; and a ground electrode, as defined herein, wherein the noble metal tip is bonded to the ground electrode via a molten bond, and when viewed in a cross-section including a center axis of the noble metal tip along a longitudinal direction of the ground electrode, a sum of a cross-sectional area of a base-end-side molten bond (A) positioned at a base end side of the ground electrode and a cross-sectional area of a front-end-side molten bond (B) positioned at a front end side of the ground electrode is equal to or greater than 4 mm2, and the cross-sectional area of the front-end-side molten bond (B) is 1.1 to 1.3 times greater than that of the base-end-side molten bond (A).

Abstract: Protrudent matters caused by connecting metallic materials are detected with high precision and in turn offer products of high quality, and an increase of yield. The invention sets an allowable range and a non-allowable range around an outside outline (an outline of the work to be detected) of the connected work member on the basis of a shape of an outline of a reference work member (a reference outline) becoming a reference of the connected work member in order to judge presence or absence of the outline of the work to be detected in the non-allowable range, said allowable range allowing the existence of the outline of the work to be detected, and said non-allowable range not allowing the existence of the outline of the reference work.

Abstract: A spark plug for an internal combustion engine includes: a cylindrical insulator as defined herein; a center electrode as defined herein; a cylindrical metal shell as defined herein; and a ground electrode as defined herein, an annular gasket receiving portion projecting radially outward being provided on a rear end side of the externally threaded portion of the metal shell, and a metallic gasket capable of abutting against the gasket receiving portion being provided on the outer periphery of the metal shell, wherein the gasket has a solid annular shape, an inside diameter of the gasket is smaller than an outside diameter of the externally threaded portion, and a groove portion whose depth coincides with the direction of the axis is provided over an entire circumference of the gasket.

Abstract: The invention describes a spark plug having an outer electrode (12), a central electrode (10), an inner conductor (2) connected to the central electrode (10) and an insulator (3) enclosing the inner conductor (2). It is provided according to the invention that the insulator (3) is produced by extrusion. The invention further relates to a method for production of a spark plug of that kind.

Abstract: A spark plug (10) includes an intermediate connecting pin (54) disposed in the central passage (28) of an the insulator body (12). The connecting pin (54) seats in an intermediate taper section (72) within the central passage (28), which is generally frustoconical and establishes a transition between a first larger diameter of the central passage (28) and a second smaller diameter. The intermediate tapered section (72) is located longitudinally above a filleted transition (26) feature of the insulator body (12) exterior. A pin head (53) of the connecting pin (54) has a complementary tapered under-cut and seats against the intermediate tapered section (72) to provide self-centering of the connecting pin (54) without trapping gas during the assembly process. The intermediate taper section (72) also provides an increase in insulator wall thickness which improves dielectric capacity and structural integrity of the insulator (12).

Abstract: A spark plug is provided with a metal shell and a ceramic insulator to support therein a center electrode. The ceramic insulator includes a front portion with a stepped outer surface, a middle portion, a rear portion and a shoulder portion defined between the middle and rear portions. A difference between the outer diameters of the middle and rear portions of the ceramic insulator is 1.8 mm or smaller. The metal shell includes a radially inward protrusion to retain thereon the stepped outer surface of the ceramic insulator and a rear end portion crimped onto the shoulder portion of the ceramic insulator. An inner circumferential surface of the crimped shell portion has a region held in contact with the insulator shoulder portion with a radially innermost point of the crimped shell portion being spaced radially apart from the ceramic insulator and axially apart from the insulator shoulder portion.

Abstract: A plasma jet spark plug and a manufacturing method therefor are disclosed. In a state in which a noble-metal chip having a flange-like outwardly projecting portion is disposed in a communication section of a ground electrode, an electrode base metal of the ground electrode is disposed in a stepped engagement portion of a metallic shell, which retains an insulator therein. While being pressed against a front end portion of the insulator, the noble-metal chip is joined to the electrode base metal, whereby a clearance between the ground electrode (electrode base metal) and the front end portion of the insulator can be closed. Therefore, energy of plasma generated within the cavity does not leak.

Abstract: A method for manufacturing a spark plug and a spark plug manufactured by the method in which a gasket used for securing the air-tightness when mounting the spark plug on an internal-combustion engine is prevented from falling out from the metal shell with a simple step.

Abstract: A spark plug and method for making. The spark plug comprises a center electrode, an insulator surrounding the center electrode, and a metallic shell surrounding the insulator. The spark plug also includes a ground electrode engaged with the metallic shell. The ground electrode has a first surface facing the center electrode for defining a spark gap and a second surface opposite the first surface. A cross-section of the ground electrode between the first and second surfaces includes a first zone of a non-noble metallic base material extending a distance from the second surface toward the first surface and a second zone of a blend of the non-noble base material and a noble metallic material extending from the first zone to the first surface. A method of making the spark plug includes the step of disposing a quantity of noble metallic material on an electrode blank formed of a non-noble metallic base material.

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: 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. At least a selected one of the center electrode or ground electrode has a platinum or platinum-based alloy firing tip. A resistance weld joint bonds the firing tip to the selected electrode and defines a lower surface of the firing tip that is embedded a first distance beneath an outer surface of the selected electrode. A continuous bead of overlapping laser weld pools is formed over an outer periphery of the firing tip. The overlapping weld pools extend a second distance beneath the outer surface of the selected electrode, with the second distance being greater than the first distance.

Abstract: A sparkplug having ground and center electrodes that include a firing tip formed from a noble metal or noble metal alloy by reflowing of a noble metal preform. The present invention also includes a method of manufacturing a metal electrode having an ignition tip for an ignition device, including forming a metal electrode having a firing tip portion; applying a noble metal preform to the firing tip portion; and reflowing the noble metal preform to form a noble metal firing tip.

Abstract: A spark plug having a protrusion amount t of not smaller than 0.3 mm and satisfying a relation ?1+?2?93° in which ?1 is an included angle between virtual lines s1 and s2, and ?2 is an included angle between virtual lines s3 and s4 when the virtual line s1 is taken as a line parallel to a direction of an axis and including the other end side edge on a leading end surface of a first precious metal tip, the virtual line s2 is taken as a line connecting the other end side edge and a point of intersection between an inner circumferential surface of a ground electrode body and the other end surface of the ground electrode body, the virtual line s3 is taken as a line parallel to the direction of the axis and including the other end side edge on a leading end surface of a center electrode, and the virtual line s4 is taken as a line including the other end side edge and tangent to an insulator.

Abstract: A spark plug is provided, for a provisional bending process for manufacturing the spark plug, as a work in a condition where an earth electrode is straight and substantially in parallel with an axial line of a center electrode. In the provisional bending process, two searchers individually facing the tip of the center electrode with the tip located therebetween are arranged, positions of the searchers in a first direction perpendicular to the axial line being adjusted for every spark plug. Then a bending punch is driven to press a second end-surface of the other end of the earth electrode down to the searchers so that the earth electrode is provisionally bent at a substantially perpendicular angle to the axial line, the second end-surface being opposite to the first end-surface. Preferably, before the provisional bending process, positioning the work and correcting the position and tilt of the work are performed.

Abstract: A spark plug for an internal combustion engine comprising a centre electrode and an earth electrode serving as a spark discharge section, as well as a noble metallic chip, which is inserted into one end of at least one of said electrodes along part of its length and which is subsequently welded thereto by irradiation with energy-condensing light, characterized in that said noble metallic chip is provided with a profile for holding said noble metallic chip onto said at least one electrode on at least part of the outer periphery of said part of its length, wherein a fusion layer extending between said profile and an inner region of the end of said at least one electrode locks said noble metallic chip onto said at least one electrode.

Abstract: A spark plug is provided which ensures the reliability of a weld between a noble metal chip and a ground electrode as well as higher durability and ignitability of fuel. The ground electrode is joined to a metal shell, after which the noble metal chip is laser-welded to the ground electrode. The laser welding is achieved by emitting laser beams around an interface between the noble metal chip and the ground electrode outside a given angular range within which the metal shell will be an obstruction to the traveling of the laser beams. Specifically, the laser beams are emitted without any optical interference with the metal shell. This permits the angle between the orientation of each of the laser beams and the surface of the ground electrode to be minimized regardless of the metal shell, thus ensuring a desired depth of the fused portions in the noble metal chip.

Abstract: The spark plug manufacturing apparatus includes a holding plate formed with a plurality of mounting holes penetrating from a front surface to a rear surface thereof for holding therein hollow tubular insulators of spark plugs, each of which is fitted therein with a center electrode and a metal stem provided with a terminal part, and is charged with a powder resistance material between the center electrode and the stem, and an electric furnace for heating the insulators held in the mounting holes of the holding plate. The holding plate is made of a ceramic material containing not less than 50 wt % of silicon nitride.

Abstract: Spark plug devices are formed of a conductive loaded resin-based material. The conductive loaded resin-based material comprises micron conductive powder(s), conductive fiber(s), or a combination of conductive powder and conductive fibers in a base resin host. The percentage by weight of the conductive powder(s), conductive fiber(s), or a combination thereof is between about 20% and 50% of the weight of the conductive loaded resin-based material. The micron conductive powders are metals or conductive non-metals or metal plated non-metals. The micron conductive fibers may be metal fiber or metal plated fiber. Further, the metal plated fiber may be formed by plating metal onto a metal fiber or by plating metal onto a non-metal fiber. Any platable fiber may be used as the core for a non-metal fiber. Superconductor metals may also be used as micron conductive fibers and/or as metal plating onto fibers in the present invention.

Abstract: A method for manufacturing a starting element, in particular a sheathed-element glow plug, for the combustion process in an internal combustion engine having a ceramic element (1, 3) is proposed, which substantially improves the glazing of the ceramic element (1, 3). According to the present invention, this is achieved by a dry glaze (2) being applied on the ceramic element (1, 3).

Abstract: A method of joining an electrode of a spark plug with a noble metal is described, the noble metal being joined locally with the electrode using a thermal input produced by a continuously operating laser beam.

Abstract: In a first embodiment a spark plug satisfying the relations: t?0.3 mm and St/Sw?7 in which t is the axial-direction shortest distance between a leading end surface 41a of a precious metal tip 41 and a joint portion 43, St is the surface area of the precious metal tip 41 and a joint portion 43 between the precious metal tip 41 and the ground electrode body 4a, and Sw is the area of the joint portion 43 between the ground electrode body 4a and the precious metal tip 41. In a second embodiment, the spark plug satisfies the relations t?0.3 mm and La>Lb; and in a third embodiment the spark plug satisfies the relations t>T and La>Lb, where T, La and Lb are as defined in the specification. The relation t?0.3 mm is specific to the first and second embodiments, and the relation St/Sw?7 is specific to the first embodiment only.

Abstract: A method of making a metallic shell for a spark plug. The metallic shell includes a multi-stepped through hole, an intermediate tubular portion, a tip end side tubular portion and a base end side tubular portion. The through hole includes a large diameter hole section, an intermediate diameter hole section and a small diameter hole section. The method includes the steps of cutting a metal pipe that is used as a starting material to a predetermined length and thereby preparing a pipe-shaped blank, and subjecting the blank to a deformation process and thereby forming the blank into the metallic shell. A spark plug and a method of making the same are also disclosed.

Abstract: In a wire drawing process for forming a wire rod containing iridium as a main component and which further contains nickel and at least one of platinum, rhodium and ruthenium, and having a cross-sectional area of not smaller than 0.05 mm2 and not larger than 1.2 mm2. The worked material is continuously heated red hot and/or white hot in a heating region 103 extending up to 60 mm from the work inserting surface 101a of a die 101 in a direction opposite that in which the work 102 moves, the work being heated to a temperature of 1000 to 1150° C. at a temperature measuring position 105 which is removed from the work inserting surface 101a by 20 mm. Furthermore, the temperature in the region 106 extending from the temperature measuring position 105 to the work inserting surface 101a is set to not lower than 1000° C., and the wire drawing rate is set to 300 to 1600 mm/min.

Abstract: A spark plug includes a center electrode, a ground electrode opposing the center electrode in such a manner as to define a spark discharge gap between the center electrode and the ground electrode, and an igniter fixed to at least one of the center electrode and the ground electrode in such a manner as to face the spark discharge gap. The igniter is composed of a metallic material whose principal component is one of a platinum and an iridium. One type of the metallic material of the igniter contains an oxygen content of not more than 120 ppm. Another type of the metallic material of the igniter has a crystal grain of not less than 50 ?m in mean diameter, and contains the oxygen content of not more than 300 ppm.

Abstract: A spark plug includes a ceramic component, whose surface is at least in part coated with a glaze, with the glaze containing 0.6% to 4% by weight of fluoride and 6% to 11.2% by weight of zinc oxide.

Abstract: A method for making a spark plug is provided. The method comprises the steps of, for adjustment of a spark gap, provisionally pressing a ground electrode toward a leading end surface of a center electrode and thereby decreasing the spark gap to a predetermined value larger than a final target gap gt, after the step of provisionally pressing the ground electrode, performing an adjustment bending process for eliminating an eccentricity ? of the ground electrode in the widthwise direction thereof with respect to a target position, after the step of performing the adjustment bending process, measuring a spark gap g1 and measuring a difference (g1?gt) between the measured spark gap g1 and the final target gap gt, and pressing the ground electrode toward the center electrode when the difference (g1?gt) is positive. An apparatus for carrying out the method is also provided.

Abstract: A spark plug is provided after a provisional bending process, during which the earth electrode is provisionally bent at almost 90 degrees. The earth electrode, one of both ends is joined to a housing member, has first and second end-side surfaces located mutually back to back and a tip surface connecting both end-side surfaces. A noble metal chip is mounted on the first end-side surface. A bending punch is set, which has a first pressing surface to be fitted to the second end-side surface located and a second pressing surface to be fitted to a tip surface. The bending punch is first moved so that the second pressing surface comes in contact with the tip surface of the earth electrode, and then moved so that the first pressing surface presses the second end-side surface in the axial direction of the center electrode. Accordingly, a main bending process is performed.

Abstract: A method and apparatus for manufacturing a spark plug which avoids depth insufficiency of the weld metal portion or thickness insufficiency of the spark portion and which thus enhances the weld strength and service life of the spark portion. According to the method, a noble metal chip is attached to a chip joint face formed on a distal end of a center electrode of a spark plug workpiece, along the direction of the longitudinal axis of the workpiece, so as to form a chip-attached assembly. The chip-attached assembly is irradiated with a laser beam LB so as to form a laser-beam weld metal portion intruding into the noble metal chip and into the chip joint face, thereby forming a noble-metal spark portion having a discharge face.

Abstract: A ground-electrode spark portion 32 is formed from a noble metal which contains Pt as a main component, and is joined to a main metal portion of the ground electrode 4 via an alloy layer which has a thickness ranging from 0.5 ?m to 100 ?m and in which the noble metal that constitutes the ground-electrode spark portion 32 and the metal that constitutes the main metal portion of the ground electrode 4 are alloyed with each other. The ground-electrode spark portion 32 is configured such that a distal end surface 32t facing a spark discharge gap g is smaller in diameter than a bottom surface 32u joined to the ground electrode 4; and the distal end surface 32t is protrusively located beyond the side surface 4s of the ground electrode 4.

Abstract: A method for producing a spark plug, the spark plug comprising a center electrode, a metal shell and an alumina ceramic insulator disposed between the center electrode and the metal shell, wherein at least part of the surface of the insulator is covered with a glaze layer, the method comprising the steps of: preparing a plurality of kinds of element glaze powders wherein each kind of the element glaze powders has a different dilatometric softening point and a different linear expansion coefficient compared to other kinds of element glaze powders; coating a surface of the insulator with the plurality of kinds of element glaze powders so as to form a glaze powder layer; and baking the glaze powder layer to the surface of the insulator so as to form the glaze layer by heating the glaze powder layer.