Abstract: A spark plug includes an insulator, a terminal electrode, a center electrode, a resistor, and a glass seal layer. The terminal electrode has: a recess part opened to the front end side and having a depth in a center axis direction of the terminal electrode; and a flat part neighboring the recess part at its outer circumference side. The relationship 0.52?B/A?0.91 is satisfied, wherein A (mm2) represents an area of a region surrounded by an outline of an outer circumference surface of the terminal electrode, and B (mm2) which represents an area of a region of the terminal electrode surrounded by an outline of an inner surface of the recess part, in a cross section orthogonal to the center axis and located 0.1 mm away from a front end along the center axis to the rear end side.

Abstract: A spark plug with a particular configuration, particularly in the area of a gasket that seals between a shell and insulator, increases the mechanical strength of the spark plug and helps prevent breaking, cracking and/or other failures in the insulator. The spark plug is designed such that the shell, insulator and gasket, which may be in the form of a sleeve-like cylindrical gasket or a ring-like annular gasket, work together to provide better support for the insulator against axial and/or radial stresses. This improved support can offset certain stresses, such as radial stress RS that can be exerted against the insulator core nose when the engine experiences knocking or misfiring.

Abstract: An ignition plug having a ceramic insulator with an axial bore, a metallic shell provided around the ceramic insulator, and a terminal electrode having a leg portion inserted into a rear end portion of the axial bore and a head portion projecting from the rear end of the ceramic insulator, wherein the length L of a portion of the ceramic insulator projecting from the rear end of the metallic shell is not less than 28 mm but not greater than 34 mm. The thickness t of the thinnest portion of the ceramic insulator is 1.0 mm or greater within a region which extends 5.5 mm from the rear end of the ceramic insulator toward the forward end side with respect to the direction of the axis.

Abstract: A spark plug for a stationary, gas-powered internal combustion engine, having a metallic body, an insulator mounted in a passage of the body, a center electrode passing through the insulator, a ground electrode mounted on the body that, together with the center electrode, forms a spark air gap, and a cap attached to the body. The cap shields the center and ground electrodes from the combustion chamber after the spark plug is installed in a combustion chamber of the internal combustion engine, and that, together with the body of the spark plug, forms a prechamber in which the center and ground electrodes are located. The cap has at least one opening that permits gas exchange between the prechamber and the space outside of the prechamber.

Abstract: An ignition plug includes an insulator having an axial hole extending therethrough in the direction of an axis, a center electrode inserted into a forward end portion of the axial hole, and a metallic shell disposed externally of the insulator. The insulator includes a step portion engaged with an inner circumferential portion of the metallic shell and a leg portion extending forward from the forward end of the step portion. The porosity of the leg portion is 3.0% or less. Among three regions of the leg portion that are radially trisected in a cross section perpendicular to the axis, the outermost region is defined as a first region and the innermost region is defined as a second region. The porosity of the first region is equal to or more than 1.20 times the porosity of the second region.

Abstract: A spark plug includes a metal shell and a gasket. The metal shell includes a thread portion, a seat portion, and a thread root portion. The gasket has an inner diameter smaller than a thread size of the thread portion. The relationships 0.8L?C?L?2A and B?0.75L are satisfied in a case where: in the seat portion, an outer diameter of a seating portion is L (mm); the maximum value of a relatively shiftable distance is A (mm), the gasket is shiftable along a direction orthogonal to the axis relative to the metal shell by the maximum value; in the gasket, an outer diameter is C (mm); and in the gasket, an inner diameter is B (mm).

Abstract: A spark plug for an internal-combustion engine. The spark plug includes a central electrode, an insulator that holds the central electrode inside, a housing that holds the insulator inside, a ground electrode that forms a spark gap with the central electrode. The ground electrode includes a ground base member connected to the housing, and a ground protrusion protruding from a confronting face of the ground base member confronting the central electrode. The ground protrusion has a diameter of 0.9 to 1.4 mm. The spark plug is configured to satisfy ???53R+49, where R [mm] is a curvature radius of a base member corner and ?[degrees] is an angle formed by a shortest connecting line between the base member corner and a protrusion corner and a plane perpendicular to an axial direction of the ground protrusion.

Abstract: An ignition plug, wherein, when a relative density of a portion of an insulator, which is positioned between a radial virtual plane including a front end of the insulator and a radial virtual plane including a front end of a portion of the insulator which is in contact with a metal shell or the plate packing, is referred to as A (%), and a relative density of a portion of the insulator, which is positioned between the radial virtual plane including the front end of the portion of the insulator which is in contact with the metal shell or the plate packing and a radial virtual plane including a center of a resistor in an axial direction, is referred to as B (%), the following equations are satisfied: 93.90?A, and 0.10?A?B?0.90.

Abstract: A spark plug includes a center electrode, a ground electrode, and a ground-electrode-side tip joined to the ground electrode such that at least a portion of the tip along its thickness direction is embedded in the ground electrode. The ground-electrode-side tip is joined to the ground electrode through a fusion zone formed between the ground electrode and a proximal side of the tip. On a section containing a center axis of the ground electrode and in parallel with the thickness direction of the ground-electrode-side tip, E/F?1.1 is satisfied, where E (mm) is the longest distance along the thickness direction from an inner side of the ground electrode to a boundary between the fusion zone and the ground electrode, and F (mm) is the largest amount of embedment of the tip in the inner side surface along the thickness direction.

Abstract: A spark plug of internal combustion engine is disclosed. The spark plug includes: a main body having main thread on lower outer side; an insulator mounted in a hollow portion of the main body; a ground electrode to correspond to a central electrode extending from the lower end of the terminal rod; a primary combustion chamber forming shell having female thread to be screw-coupled with the main thread, male thread to fix a combustion chamber, and an ejection hole; the primary combustion chamber formed between the main body and the primary combustion chamber forming shell and having changeable volume; and a heat exchange member disposed between the main body and the insulator to exchange heat caused by flame and to block leak of volatile gas; wherein the main ejection hole has a single main ejection hole and at least two auxiliary ejection holes formed around the main ejection hole.

Abstract: A spark plug for an internal combustion engine includes a spark plug housing. An insulator is concentrically located within the housing and has a distal end extending from an outer surface of the housing. A center electrode extends from a proximal end of the insulator. A ground electrode is secured to the housing and has an electrode tip arranged a distance from the center electrode. A chamber cap fixedly secured to the housing and surrounding both the center and ground electrodes, includes a laminate shell and a plurality of orifices.

Abstract: A method of making an electrode material for use in a spark plug and other ignition devices including industrial plugs, aviation igniters, glow plugs, or any other device that is used to ignite an air/fuel mixture in an engine. The electrode material is a ruthenium-based material that includes a “fibrous” grain structure. The disclosed method includes hot-forming a ruthenium-based material into an elongated wire that includes the “fibrous” grain structure while intermittently annealing the ruthenium-based material as needed. The intermittent annealing is performed at a temperature that maintains the “fibrous” grain structure.

Abstract: Disclosed is an improved spark plug having an electrode extending from an insulator tip into a piston chamber in use. The improvement comprises a shell defining: a cavity; a cavity opening which couples the cavity with said piston chamber in use; a conduit extending from the cavity and into which the electrode extends in spaced relation to the shell; and, with the tip, a chamber surrounding the tip in spaced relation and coupled to the cavity by the conduit. The cavity includes: a concave portion presenting towards the opening such that the cavity narrows as it extends towards the conduit; and a cylindrical portion extending from the concave portion towards the opening. The chamber includes a cylindrical portion surrounding the tip in spaced relation and a frustoconical portion coupling the cylindrical portion to the conduit such that the chamber narrows as it extends from its cylindrical portion to the conduit.

Abstract: An ignition plug having enhanced seal performance, while suppressing deformation of a metallic shell thereof. The ignition plug includes a metallic shell having a crimp portion, a male screw portion, a seat portion, and a bent portion. The bent portion has a largest outer diameter (OD) portion, and first and second smallest OD portions, wherein 0.01?(L2+L3?L1)/(L2+L3)?0.3 is satisfied. L1 is distance between a point in the first smallest OD portion farthest from center axis and a point in the second smallest OD portion farthest from center axis, L2 is distance between the point in the first smallest OD portion farthest from center axis and a point in the largest OD portion farthest from center axis, and L3 is distance between the point in the second smallest OD portion farthest from center axis and the point in the largest OD portion farthest from center axis.

Abstract: A spark plug including a center electrode and a ground electrode having a core portion and an outer layer covering the core portion, the core portion being formed from a material having a thermal conductivity higher than that of the outer layer. At least a portion in which thickness of the outer layer is 0.5 mm or less is present at a cross-section perpendicular to a direction in which the ground electrode is extended. Further, the composition of the electrode material forming the outer layer is as follows: Ni is 96 mass % or more, total of at least one kind selected from Y and rare earth elements is 0.05 mass % or more, Al is 0.5 mass % or less, and Si is 0.5 mass % or more and 1.5 mass % or less, where the total of Ni, Y, rare earth elements, Al, Si does not exceed 100 mass %.

Abstract: A spark plug (20) for being threaded into a cylinder head (28) includes a shell (24) with threads (26) disposed at a predetermined angled relative to the ground electrode (34). The position of the threads (26) relative to the ground electrode (34) places the ground electrode (34) in a predetermined position in the combustion chamber (22) and relative to components of the engine, thus allowing the ground electrode (34) to provide a robust and reliable ignition. The threads (26) are formed by a thread forming apparatus (102) that includes an orientation tool (38) to position the ground electrode (34) relative to a thread forming apparatus (102), allowing the thread forming apparatus (102) to form the threads (26) at the desired angle (?).

Abstract: A spark plug and a method of forming the same. The spark plug having a rod-shaped center electrode extending in an axial direction, a tubular insulator having an axial hole and holding the center electrode in the axial hole, a tubular metallic shell having an end surface, an inner circumferential surface, and a gap formed between the inner circumferential surface and a forward end portion of the insulator, and a ground electrode welded to the end surface. A method of manufacturing the spark plug includes a welding step of welding the ground electrode to the end surface; and a shaping step which is performed after the welding step so as to form the inner circumferential surface, through shaping, on the metallic shell having the ground electrode welded to the end surface thereof.

Abstract: An igniter for igniting a fuel/air mixture using a corona discharge, generated by a high-frequency electric high voltage, in an internal combustion engine having one or more combustion chambers delimited by walls at ground potential, comprising an ignition electrode, which traverses in an electrically insulated manner one of the walls delimiting the particular combustion chamber and constitutes in cooperation with the walls of the combustion chamber, that are at ground potential, an electrical capacitance. Comprising a metallic or metallized outer member and an elongate passage extending through the outer member, through which extends the ignition electrode, and comprising an insulator which encloses the ignition electrode and insulates it electrically from the outer member, wherein the ignition electrode, the insulator, and the passage have a common longitudinal direction.

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 superior in salt corrosion resistance and stress corrosion cracking resistance is provided. The spark plug includes a metallic shell coated with a composite layer which includes a nickel plating layer and a chromate layer formed on the nickel plating layer. The spark plug is characterized in that the nickel plating layer has a thickness A which satisfies a relational expression 3 ?m?A?15 ?m and that the chromate layer has a thickness B which satisfies a relational expression 2 nm?B?45 nm.

Abstract: An ignition plug that reliably restrains generation of corona discharge for enhancing accuracy in detection of ionic current and method of manufacturing same. The ignition plug is configured such that a metallic shell and an insulator are fixed together by means of a crimped portion provided at a rear end portion of the metallic shell and bent radially inward. An electrically insulative filling member fills a space formed between the crimped portion and the insulator. The filling member covers at least a portion of an outer circumferential surface of a rear trunk portion of the insulator along the entire circumference and the entirety of a rear end surface of the metallic shell, which is a portion of the outer surface of the crimped portion and is visible from the rear side with respect to the direction of an axial line CL1.

Abstract: An ignition plug providing excellent ignition performance that can be maintained over a long period of time by restraining channeling. The ignition plug includes a ceramic insulator having an axial bore, a center electrode inserted into the axial bore, a metallic shell, and a ground electrode fixed to the metallic shell, and has a cavity defined by an inner circumferential surface of the axial bore and the forward end surface of the center electrode. The axial bore includes a first straight portion and a diameter-reducing portion. As viewed on a section which contains an axis (CL1) of the ignition plug, a relational expression ??10 is satisfied, where ? (°) is an acute angle formed by a straight line orthogonal to the axis (CL1) and the outline of the diameter-reducing portion.

Abstract: A spark plug includes a body and a center electrode. The body includes a first end, a second end, an insulating portion and a shell portion. The shell portion includes an exterior threaded section, a nut section below the threaded section, an electrically conductive, axially elongated firing ring above the threaded section and terminating at an upper surface. The center electrode extends through the body and includes a terminal end and a firing end. The firing end extends beyond the second end of the body and includes a plurality of tines. Each tine includes a first section and a second section. The first section extends radially from the firing end. The second section extends axially toward the upper surface of the firing ring and terminates at a tip. The insulating portion electrically isolates the shell portion from the center electrode.

Abstract: A spark plug includes a ceramic insulator, a center electrode, a metallic shell, and a ground electrode. The center electrode has a shoulder portion at a forward end portion, which tapers forward with respect to the axial direction. A noble metal tip is joined to the forward end portion of the center electrode through a fusion zone. A spark discharge gap is formed between the noble metal tip and the ground electrode. The shortest distance between the fusion zone and a forward end surface of the noble metal tip is 0.8-1.2 mm. The outside diameter of the fusion zone as measured at a forward end of the fusion zone is smaller than that as measured at a rear end of the fusion zone. An acute angle ?1 formed by a straight line L1 and a straight line L2 satisfies the relational expression ?1?72°.

Abstract: A spark plug for an internal combustion engine is provided which is equipped with an inward top end protrusion. The inward top end protrusion extends inwardly from a top end of a cylindrical housing within which a porcelain insulator is disposed. The porcelain insulator has a center electrode disposed therein. The inward top end protrusion is at least partially located to be closer to the top of the spark plug than a top end of the porcelain insulator is in an axial direction of the spark plug. This enhances the strength of an electric field surrounding the center electrode, which facilitates the ease with which an electron is emitted by the center electrode and thus permits an initial required voltage at the spark plug to be decreased, thereby resulting in an increase in service life of the spark plug.

Abstract: A spark plug for use with internal combustion engines includes a metallic shell housing having a semi-cylindrical shroud partially surrounding the insulator and the center electrode and to which the ground electrode is joined. The semi-cylindrical shroud promotes improved heat dissipation from the ground electrode to the shell housing.

Abstract: An ignition plug having enhanced seal performance, while suppressing deformation of a metallic shell thereof. The ignition plug includes a metallic shell having a crimp portion, a male screw portion, a seat portion, and a bent portion. The bent portion has a largest outer diameter (OD) portion, and first and second smallest OD portions, wherein 0.01?(L2+L3?L1)/(L2+L3)?0.3 is satisfied. L1 is distance between a point in the first smallest OD portion farthest from center axis and a point in the second smallest OD portion farthest from center axis, L2 is distance between the point in the first smallest OD portion farthest from center axis and a point in the largest OD portion farthest from center axis, and L3 is distance between the point in the second smallest OD portion farthest from center axis and the point in the largest OD portion farthest from center axis.

Abstract: A prechamber module for a laser spark plug, the prechamber module having a fastening region for the detachable fastening of the prechamber module to the laser spark plug. The prechamber module, in an end region, facing away from the combustion chamber, has a diaphragm arrangement, which borders on an inner chamber of the prechamber module in the axial direction, and has an orifice for the irradiation of laser radiation from the laser spark plug into the inner chamber of the prechamber module.

Abstract: An ignition plug that reliably restrains generation of corona discharge for enhancing accuracy in detection of ionic current and method of manufacturing same. The ignition plug is configured such that a metallic shell and an insulator are fixed together by means of a crimped portion provided at a rear end portion of the metallic shell and bent radially inward. An electrically insulative filling member fills a space formed between the crimped portion and the insulator. The filling member covers at least a portion of an outer circumferential surface of a rear trunk portion of the insulator along the entire circumference and the entirety of a rear end surface of the metallic shell, which is a portion of the outer surface of the crimped portion and is visible from the rear side with respect to the direction of an axial line CL1.

Abstract: A spark plug includes an insulator, and a metal shell disposed at an outer periphery of the insulator and including a shoulder. The insulator includes a trunk portion, and a leg formed at the tip end side of the trunk portion. The shoulder of the metal shell includes a first shoulder, and a second shoulder formed at the tip end side of the first shoulder. A distance Da between the tip end of the second shoulder and the leg and a distance Db between the tip end of the trunk portion and the second shoulder satisfy a relationship of Da/Db?1.1. A distance T between the rear end of the first shoulder and the tip end of the second shoulder and a distance L between the rear end of the first shoulder and a tip end face of the metal shell satisfy a relationship of T/L?0.5.

Abstract: A ground electrode is provided having a ground electrode body, the ground electrode body having an anchored end and a non-anchored end opposite the anchored end. The ground electrode includes a plateau extending from a surface of the ground electrode body adjacent the non-anchored end. In illustrative embodiments, the plateau is formed by removing a portion of the ground electrode body near the non-anchored end. The plateau is configured to be exposed around its periphery. A noble metal tip is fixably attached to the plateau.

Abstract: An ignition plug includes a ceramic insulator having an axial bore, a metallic shell, and a terminal electrode. The terminal electrode has a leg portion inserted into a rear side of the axial bore, and a head portion formed on a rear side of the leg portion and having an outside diameter greater than that of the leg portion. The insulator includes a rear trunk portion exposed from the rear end of the metallic shell, which has a maximum outside diameter of 9.5 mm or less. The insulator has an end-surface seat portion located forward of its rear end and being in contact with the forward end surface of the head portion, and an outer circumferential portion into which at least a forward end portion of the head portion is inserted and which is located externally of the outer circumference of the head portion.

Abstract: A task of this invention is to provide a spark plug that is superior in withstand voltage characteristics at high temperatures. A spark plug of this invention is equipped with a center electrode, an insulator, and a metal shell, and is characterized by that the insulator is equipped with an alumina-based sintered body containing silicon component (Si component), magnesium component (Mg component), at least one component of calcium component, strontium component, and barium component, and a rare earth element component (RE component), that a grain boundary phase of the alumina-based sintered body has a hexaaluminate crystal containing the RE component, that, in the alumina-based sintered body, the weight ratio of the RE component to the Mg component is 5.4?RE oxide/MgO?17.5, and that the content of an alkali metal component in terms of oxide in a spot having a diameter of 0.

Abstract: Described is an HF ignition device for igniting a fuel in an internal combustion engine, comprising a ceramic insulator which carries an ignition electrode and encloses an inner conductor leading to the ignition electrode, and an outer conductor which encloses the insulator and, together with a section of the inner conductor, forms a capacitor which is part of a circuit for the HF excitation of the ignition electrode. According to the invention, the insulator is part of a ceramic body which comprises an inner region which is composed of an electrically conductive ceramic and is enclosed by the insulator, and an outer region which is composed of an electrically conductive ceramic and encloses the insulator.

Abstract: A spark plug includes a metal shell and a gasket. The metal shell includes a thread portion, a seat portion, and a thread root portion. The gasket has an inner diameter smaller than a thread size of the thread portion. The relationships 0.8L?C?L?2A and B?0.75L are satisfied in a case where: in the seat portion, an outer diameter of a seating portion is L (mm); the maximum value of a relatively shiftable distance is A (mm), the gasket is shiftable along a direction orthogonal to the axis relative to the metal shell by the maximum value; in the gasket, an outer diameter is C (mm); and in the gasket, an inner diameter is B (mm).

Abstract: Problem is to enhance the welding strength when a projecting shape section is resistance-welded to a around electrode. A ground electrode 30 includes a ground electrode base material 35 and a projecting shape section 36. The projecting shape section 36 is connected by resistance welding to an opposite surface 32 of the ground electrode 30 so as to be opposite and project towards the leading end of a center electrode 20. The ground electrode base material 35 and the projecting shape section 36 are formed from a material that is composed of the same metal (for example, nickel) as a main component and have a relation of formulas (1) and (2) described below. In formula (1), the specific resistance of the ground electrode base material 35 is R (??cm) and the specific resistance of the projecting shape section 36 is S (??cm). The specific resistance R>the specific resistance S . . . (formula 1), the specific resistance R?specific resistance S?20 . . . (formula 2).

Abstract: An insulator for a spark plug is provided having an insulator tip. The insulator tip includes a feature extending radially inward from an exterior surface of the insulator tip.

Abstract: A spark plug comprises an insulator and a metal shell. The insulator includes a nose length portion at the forward end, and a tapered portion, extending from the rear end of the nose length portion toward the rear end of the insulator, increased in diameter toward the rear end. The metal shell includes a shoulder portion, protruding inward and having a retaining surface by which the tapered portion is retained, and a male thread portion on the outer peripheral side of the shoulder portion, and the thread diameter of the male thread portion is set to M12 or less. When the insulator's cross-sectional area, perpendicular to an axis, passing through the boundary between the nose length section and tapered portion is B (mm2), and the metal shell's cross-sectional area, perpendicular to the axis, passing through the tip of the retaining surface is C (mm2), 2.80?C/B?3.50 is satisfied.

Abstract: A spark plug includes a tubular metallic shell extending in the direction of an axis and having a tool engagement portion formed through extrusion. The tool engagement portion has a 12-point shape which is a sectional shape taken orthogonally to the axis and has a plurality of protrusions and recesses provided alternately. As viewed in a section taken orthogonally to the axis, when D (mm) represents the diameter of a circle which passes radially through the outermost positions on the protrusions, and d (mm) represents the diameter of a circle which passes radially through the innermost positions on the recesses, the relational expression 0.45?(D?d)/2?0.75 is satisfied. The spark plug can provide a more reliable restraint on the slippage of a tool at the time of mounting and enables the tool engagement portion to be reliably formed so as to form a desired shape.

Abstract: A spark plug having a metallic shell covered with a nickel plating layer and having a groove portion formed between a tool engagement portion and a gas seal portion and having an orthogonal-to-axis sectional area of 36 mm2 or less.

Abstract: A spark plug having improved load life performance and fixing strength of a metallic terminal to an insulator, and which reduces the incidence of breakage of the insulator when the metallic terminal is inserted into the axial hole of the insulator. The spark plug of the present invention is characterized in that the distance ((B?A)/2) between the forward end portion of the metallic terminal and the wall surface of an intermediate diameter portion of the axial hole of the insulator falls within a range of 0.02 mm to 0.2 mm, the shrinkage amount (D?C) of a connecting portion falls within a range of 6 mm to 27 mm, and the Vickers hardness of the metallic terminal at ordinary temperature falls within a range of 100 Hv to 430 Hv.

Abstract: A spark plug includes an insulator extending along an axis and a metal shell provided on the outer periphery of the insulator. The metal shell includes a thread portion for threadedly engaging with a mounting hole of an internal combustion engine and a seat portion having a tapered surface whose outer diameter decreases gradually toward a leading end side. The tapered surface contacts with a bearing surface of the internal combustion engine when the thread portion is engaged with the mounting hole. Annular protruding portions or a helical protruding portion are formed within a range on the tapered surface from an outermost peripheral portion to a part forming an outer diameter occupying 95% of the diameter of the outermost peripheral portion. The arithmetic mean roughness of a surface of the tapered surface within the range is set to 1-5 ?m on a section including the axis.

Abstract: A spark plug and method of construction thereof is provided. The spark plug includes a metal shell having a through cavity, a lower insulator and a plastic upper insulator. The lower insulator is received in the through cavity and has a through passage with a center electrode received therein. A ground electrode is operatively attached to the shell in spaced relation from the ground electrode to provide a spark gap. The plastic upper insulator has a distal end received in the through cavity of the shell and a terminal end extending axially outwardly from the shell. The upper insulator has a through passage extending between the terminal end and the distal end. An elongate conductive member is received in the through passage of the upper insulator and is configured for electrical communication with the center electrode.

Abstract: A method for producing a spark plug which contains an inner conductor, an insulator surrounding the inner conductor, a spark plug body surrounding the insulator, and two electrodes forming an ignition gap. The first electrode is a center electrode connected to the inner conductor in an electrically conducting manner and the second electrode is a ground electrode connected to the spark plug body in an electrically conducting manner. An iridium component which contains more than 95 percent by weight of iridium is welded onto one of the electrodes. An iridium component that is punched out of an iridium sheet and has a thickness that is less in size than its diameter is also employed.

Abstract: A spark plug manufacturing method providing a spark plug equipped with an insulator having dielectric strength by means of judging whether or not the insulator has a defect. A defect judgement step judges whether or not the insulator has a defect, by generating an electric potential difference between the center electrode and the metallic shell under conditions such that an assembly of the center electrode, metallic shell, and insulator is disposed within a pressure vessel; a high-pressure atmosphere higher in pressure than the atmospheric pressure is established within the pressure vessel; a space allowing the presence of insulating oil is a space surrounded by the packing, the metallic shell, the insulator, and an imaginary plane containing a forward end surface of the metallic shell; and the insulating oil is present at least in a region of the space where the distance between the ledge and insulator becomes shortest.

Abstract: A spark plug includes a ceramic insulator having a tapered rear end stepped portion whose diameter decreases from front to rear and a metal shell having a crimp portion which crimps the rear end stepped portion from the rear end. An area defined by an outer edge of the rear end stepped portion and an inner edge of the crimp portion is 5-25 mm2 when the spark plug is projected on a plane perpendicular to an axial line. An angle formed by a tapered surface of the rear end stepped portion and a plane perpendicular to the axial line is 20-60 degrees. A distance along the axial line from a front end of a proximal portion of the crimp portion to a frontmost position of a contact portion between an inner surface of the crimp and the rear end stepped portion is 0.4-1.8 mm.

Abstract: A spark plug including a center electrode and a ground electrode having a gap between the center electrode and the ground electrode, the ground electrode has an outer layer which is formed from an Ni-based alloy and a core portion which is covered by the outer layer and formed from a material having a thermal conductivity higher than that of the outer layer. Further, the melting point of the Ni-based alloy forming the outer layer is 1150° C. or more and 1350° C. or less.

Abstract: A spark plug having an insulator with improved breakage resistance. The spark plug has a cross-section that satisfies the following relationship: 0.6 mm<=L, where “A” represents a connection point between a support portion of the insulator and an insulator trunk portion formed at a front end side with respect to the support portion, where “B” represents a position closer to the outer circumference side among the positions of (a) an innermost position of a contact portion where the support portion and a packing are in contact with each other and (b) an intersection of the support portion and a virtual straight line that is parallel to an axial line of the spark plug and extends from an innermost circumferential end of a stepped portion of a metal shell, and where “L” represents a length of a path from point “A” to point “B” along a surface of the insulator.

Abstract: A spark plug (20) includes an insulator seat angle (?i) of 35° to 50° and an increased insulator thickness (ti) in selected areas around the insulator seat (28). The insulator seat angle (?i) is greater than or equal to a boundary value provided by the equation: 90°?a cos [1?(R1?R2)÷(R4+R5)], and preferably not greater than 150% of the boundary value. The radii (R1, R2, R3, R4, R5) can be adjusted to maximize R4 while maintaining an acceptable R2. A gasket is compressed between the insulator (22) and shell (58), and the inner gasket thickness (tg2) is greater than or equal to 70% of the outer gasket thickness (tg1).

Abstract: A halogen free contact arranged a between an insulation body of a spark plug and a resilient protective cap of a spark plug connector.