Abstract: An ignition plug having a center electrode, a grounding electrode, an insulator, and a metal shell. The center electrode is held by the insulator, and the insulator is held by metal shell. A cavity is formed between the grounding electrode and the center electrode. The grounding electrode is joined to the inner wall surface of the metal shell via a melting portion. In the melting portion, in a predetermined cutting surface MS including a melting deepest point DP and a central axis CX, a percentage ratio MDD of a melting depth MD of the melting portion with respect to a thickness of the grounding electrode is 5% or more, and an area Sm of a portion included in an outer circumferential side of the metal shell is 10% or more of the entire area S.

Abstract: A spark plug has a shell, an insulator, a center electrode, a ground electrode, and a firing pad. The firing pad is made of a precious metal material and is attached to the ground electrode. The firing pad has a side surface at a peripheral edge that can be flush or nearly flush with a free end surface of the ground electrode. This construction can help improve ignitability and flame kernel growth of the spark plug during a sparking event, and can provide better thermal management at the attached ground electrode and firing pad.

Abstract: A corona igniter (20) for emitting a radio frequency electric field and providing a corona discharge (24) includes a central electrode (22) at a positive voltage, a grounded metal shell (30), and an insulator (28) with an abruption (34) extending radially outward relative to the central electrode (22). The abruption (34) is typically an increase of at least 15% of a local thickness (t) of the insulator (28) over less than 25% of a nose length (el) of an insulator nose region (74). The abruption (34) is typically one flank (82) of a protrusion or a notch, and the flank (82) faces the shell (30). The abruption (34) reverses the electric field and voltage potential gradient along the insulator outer surface (32), repels charged ions away from the insulator (28), and thus prevents the formation of a conductive path between the central electrode (22) and the shell (22).

Abstract: A technique for lowering power loss involved in supply of high-frequency electric power to an ignition plug. The ignition plug includes a tubular insulator having an axial bore extending therethrough; a center electrode disposed in the axial bore; a metal terminal disposed rearward of the center electrode in the axial bore, electrically connected to the center electrode, and supplied with high-frequency electric power from an external source; a metallic shell disposed to circumferentially surround the insulator; and a ground electrode electrically connected to the metallic shell and adapted to generate plasma in cooperation with the center electrode through supply of high-frequency electric power to the metal terminal. At least a portion of the inner surface of the axial bore is coated with metal coating. The center electrode and the metal terminal are in electrical contact with the metal coating.

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

Abstract: An industrial spark plug (20) includes a central electrode (24) with a central base (30) formed of a nickel-based material and a central firing tip (32) formed of an iridium-based material. The central firing tip (32) has a tip thickness (tct) of 0.02 to 0.03 inches, a tip diameter (dct) of 0.1184 to 0.1776 inches, and an aspect ratio of 4.736 to 7.104. The central firing tip (32) is electron beam welded to the central base (30) to provide a robust joint therebetween. The central electron beam weld (36) includes a mixture of re-crystallized iridium-based material and re-crystallized nickel-based material extending continuously along and over the entire welding interface. The spark plug (20) also includes a ground electrode (26) with a ground firing tip (38) electron beam welded to a ground base (42).

Abstract: A spark plug for an internal combustion engine includes a center electrode, an insulator holding the center electrode inserted therein, a housing holding the insulator inserted therein, a ground electrode joined to the housing so as to form a spark discharge gap with the center electrode, and a stem electrically connected to the center electrode. The stem includes a stem body inserted and held inside the insulator and a terminal exposed from a proximal end of the insulator. The insulator includes a supported portion axially supported by the housing. A heat insulating member is interposed between the stem and the center electrode. A conductive member is disposed inside the insulator so as to pass through the heat insulating member for making electrical connection between the stem and the center electrode. The heat insulating member is located closer to a proximal side of the insulator than the supported portion is.

Abstract: There is provided a spark plug for an internal combustion engine, including: a center electrode extending in the direction of an axis of the spark plug and having a core of higher thermal expansion coefficient than that of a front end thereof, the center electrode including a flanged portion radially outwardly protruding on a rear side thereof and a cylindrical portion located closer to a front end of the spark plug than the flanged portion and being smaller in diameter than the flanged portion; an insulator having an axial hole in the direction of the axis to retain the flanged portion in the axial hole with the cylindrical portion held in a loose-fit state in the axial hole; and a metal shell accommodating the insulator, wherein the spark plug satisfies the following condition: Cb<Cf where Cb is a difference between an inner diameter of the axial hole and an outer diameter of the cylindrical portion at an arbitrary axial position B in the direction of the axis; and Cf is a difference between the inner di

Abstract: A spark plug includes a center electrode, an insulator holding the center electrode inserted thereinto, a housing holding the insulator inserted thereinto and a ground electrode joined to the housing so as to form a spark discharge gap with the center electrode . The center electrode includes a core member and a cover layer covering a surface of the core member. The core member includes a large-diameter portion made of a material having a thermal conductivity higher than that of the cover layer, a small-diameter portion extending from the large-diameter portion toward a distal end side of the core member, and a connecting portion connecting the large-diameter portion to the small-diameter portion. The cover layer is made of a material having a linear expansion coefficient lower than that of the core member, and covers between at least part of the connecting portion and a distal end of the small-diameter portion.

Abstract: A spark plug for an internal combustion engine includes a center electrode, an insulator holding the center electrode inserted therein, a housing holding the insulator inserted therein, a ground electrode joined to the housing so as to form a spark discharge gap with the center electrode, and a stem electrically connected to the center electrode. The stem includes a stem body inserted and held inside the insulator and a terminal exposed from a proximal end of the insulator. The insulator includes a supported portion axially supported by the housing. A heat insulating member is interposed between the stem and the center electrode. A conductive member is disposed inside the insulator so as to pass through the heat insulating member for making electrical connection between the stem and the center electrode. The heat insulating member is located closer to a proximal side of the insulator than the supported portion is.

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. The ceramic material of the firing tip (32, 34) includes at least one perovskite structure and/or at least one a spinel structure.

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

Abstract: A method of making a spark plug electrode includes several steps. One step includes providing an inner core of a ruthenium (Ru) based alloy or an iridium (Ir) based alloy. Another step includes providing an outer skin over a portion or more of the inner core in order to produce a core and skin assembly. The outer skin can be made of platinum (Pt), gold (Au), silver (Ag), nickel (Ni), or an alloy of one of these. Yet another step includes increasing the temperature of the core and skin assembly. And another step includes hot forming the core and skin assembly at the increased temperature.

Abstract: A spark plug in which a front end portion of a ground electrode is positioned outside of a virtual outer circumferential face that is formed by extending a front and outer circumferential face of a center electrode in the axis direction, and positioned on a front end side in the axis direction with respect to a virtual face including a front end face of the center electrode. Further, the equation 1.1?b/a?1.6 is satisfied, where “a” (mm) represents a first minimal distance between the front end portion of the center electrode and the front end portion of the ground electrode and, where “b” (mm) represents a second minimal distance between the front end portion of a ceramic insulator and the front end portion of the ground electrode.

Abstract: An igniter for an internal combustion engine includes a center electrode, an insulator disposed about the center electrode, and a ground shield or a threaded portion disposed about the insulator, wherein the insulator includes 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. The igniter further includes a cap secured to the center electrode, wherein the cap extends past and covers a distal end of the tip portion of the center electrode and a distal end of the tip portion of the insulator. A spark gap is disposed between a peripheral edge of the cap and the end portion of the ground shield or threaded portion wherein the peripheral edge of the cap is spaced away from a surface of the tip portion of the insulator.

Abstract: A sparkplug includes a ground electrode forming a gap with a front end surface of the center electrode. A front end portion of the ground electrode includes an opposed surface facing the center electrode, and a pair of tapered surfaces sandwiching the opposed surface. A shortest distance between the center electrode and a boundary formed by the opposed surface and the tapered surface is equal to or less than 1.2 times a distance of the gap. At least a part of a cross section of the core portion is disposed in a region at a front side of the straight line that passes a rear end of a line segment corresponding to the tapered surface and is vertical to the line segment. A shortest distance between the line segment and the cross section of the core portion is 0.2 mm or more and 1.5 mm or less.

Abstract: A plasma jet spark plug having increased capacitive discharge current, and thus improved plasma generation efficiency. The plasma jet spark plug includes an insulating body having an axial hole, a center electrode, a metal shell, and a cavity portion formed by the inner peripheral surface of the insulating body and the leading end face of the center electrode. A conductive layer formed from a conductive material is provided on at least one portion of at least one of: (a) a surface on the insulating body outer peripheral surface opposed to the inner peripheral surface of the metal shell, the conductive layer electrically connected to a ground electrode; and (b) a surface on the insulating body inner peripheral surface opposed to the outer peripheral surface of the center electrode, the conductive layer electrically connected to the center electrode.

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

Abstract: 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: A spark plug having a shell defining a cavity, an insulator disposed within the cavity, and an electrode at least partially encapsulated by the insulator. The electrode may be formed from a ruthenium (Ru) electrode material having a columnar grain structure. Further, the ruthenium (Ru) electrode material may have a purity greater than 99.90 wt. percentage.

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: A spark plug for internal combustion engines is provided, where the spark plug includes a cylindrical housing, a cylindrical insulation porcelain part, a center electrode, and a ground electrode. The insulation porcelain is housed in the housing and the center electrode is held inside the insulation porcelain. The ground electrode protrudes from a top end portion of the housing. A spark discharge gap is left between the ground and center electrodes. Further, first to third projections are formed on the top end portion. The first projection is opposed to the ground electrode with the center electrode therebetween. The second projection is closer to the ground electrode than to the first projection. The third projection is closer to the first projection than to the ground electrode.

Abstract: A spark plug is provided having a resistor. The resistor is made from resistor glass material containing an alkali free barium alumino-silicate glass mixed with mullite. In one embodiment, the resistor is a 15 to 30 wt % alkali free barium alumino-silicate glass and 10 to 25 wt % mullite. The resistor material provides for a greater processing kiln temperature range with reduced resistor variability and improved durability performance.

Abstract: A spark plug includes an insulator having an axial hole, a first inner circumferential surface, a second inner circumferential surface whose diameter is greater than that of the first inner circumferential surface, and a ledge portion connecting the first and the second inner circumferential surfaces. The spark plug also includes a center electrode having a large-diameter portion, a projection portion, and a circular columnar leg portion that projects into a space surrounded by the first inner circumferential surface. The spark plug includes a seal portion which fixes the center electrode within the axial hole. When C<A, A?C?B?A, where A represents a diameter of an imaginary cylinder having the minimum diameter required for surrounding the projection portion, B represents a maximum diameter of the large-diameter portion, and C represents an average diameter of the leg portion present in the space surrounded by the first inner circumferential surface.

Abstract: A spark plug and method of construction is provided. The spark plug has a generally annular ceramic insulator extending between a terminal end and a nose end. A conductive shell surrounds at least a portion of the ceramic insulator and a ground electrode having a ground electrode sparking surface is operatively attached to the shell. An elongate center electrode has a body extending between opposite ends. The body of the center electrode is formed of a compacted and sintered conductive or semi-conductive ceramic material. The ceramic material of the body comprises at least one oxide. For example, the body of the center electrode can be formed of a perovskite structure or a spinel structure.

Abstract: A combustor for a gas turbine engine includes a combustion chamber and a fuel igniter assembly. The combustion chamber is defined by an annular inner combustor liner and an annular outer combustor liner. The fuel igniter assembly is coupled to the combustor and extends radially outward from the outer combustor liner. The fuel igniter assembly includes an igniter housing configured to house a fuel igniter therein, and a heat-dissipating element coupled to the igniter housing. The heat-dissipating element includes a plurality of fins configured to dissipate heat from the fuel igniter assembly.

Abstract: It is an object of the present invention to provide a spark plug having a ground electrode joined securely by electric resistance welding. The spark plug includes a cylindrical metal shell and a ground electrode joined by electric resistance welding to an end portion of the metal shell. The metal shell has a high hardness region formed with a Vickers hardness of 3×102 to 5×102 Hv in the end portion thereof in such a manner that the high hardness region, when viewed in cross section along a plane including an axis of the spark plug and an axis of the ground electrode, has a length d of 0.3 to 0.8 mm from a ground electrode side welding boundary to a metal shell side welding boundary in a direction of load applied during the electric resistance welding.

Abstract: A spark plug includes a center electrode, an insulator, a metallic shell, and a ground electrode which has a noble metal tip at the other end portion. A gap is formed between a forward end portion of the center electrode and a discharge surface of the noble metal tip. When an acute angle formed by the forward end surface and the discharge surface is ?1, a point on the forward end surface closest to the noble metal tip is A, opposite ends of the discharge surface are B1 and B2, and an angle formed by a first line segment connecting A and B1 and a second line segment connecting A and B2 is ?2, 35°??1?55°, 85°??2?90°, and the difference in length between the first and second line segments is equal to or less than 10% of the longer line segment.

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 is disclosed and comprises: a metal tube which interiorly defines an axis and is externally-threaded for engine block engagement; an insulator having a portion which is disposed inside the tube and extends therebeyond; a positive electrode extending through the insulator and projecting beyond the extending portion of the insulator; and an annular ground electrode coupled to the tube. The electrodes are configured such that a spark gap defined therebetween comprises an elongate channel which opens axially and away from said insulator and is substantially unobstructed in the axial direction.

Abstract: A spark plug includes a metal shell, a ground electrode joined to a front end portion of the metal shell and a nickel layer formed on the ground electrode, wherein the ground electrode has a base material exposed region in which a base material of the ground electrode is exposed; and wherein the nickel layer includes an outer-lateral-side nickel layer located on an outer lateral surface of the ground electrode at a position adjacent to the base material exposed region and satisfies a condition of LA?25 ?m, where LA is a length from a first part of the outer-lateral-side nickel layer having a thickness equal to 80% of a maximum thickness of the outer-lateral-side nickel layer to a second part of the outer-lateral-side nickel layer having a thickness equal to 20% of the maximum thickness of the outer-lateral-side nickel layer in a longitudinal direction of the ground electrode.

Abstract: A spark plug includes a center electrode, a ground electrode, and a tip joined to the center electrode and forming a spark discharge gap with the ground electrode. The tip is joined to the center electrode via a fusion zone, which has an exposed surface exposed to the external environment. In a section containing an axis and the center of the exposed surface, C?B?0.02 is satisfied, where C (mm) is the distance on the side surface of the tip between the fusion zone and the distal end of the tip, and B (mm) is the distance between a distal end surface of the tip and a portion of the fusion zone located closer to the axis than the side surface of the tip and located closest in the fusion zone to the distal end surface of the tip.

Abstract: A spark plug, including an insulator embedding a first metallic electrode axially extending therethrough from a high voltage outer end terminal to the center of the inner end of the insulator from which it protrudes; a metallic ground electrode isolated from the first electrode and having an extended inner termination facing toward the first electrode extending from the insulator tip for defining therebetween a spark gap, a resistive element connected to the ground electrode such that upon mounting the spark plug in an internal combustion engine, the ground electrode electrically connects to the engine body through the resistive element; and a second outer termination of the ground electrode, adapted to constitute an accessible sensing terminal.

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 method of manufacturing a spark plug that includes a metallic shell, an insulator, a center electrode, a ground electrode, and a firing pad. The method may include the steps of: applying a first laser beam to attach the firing pad to the ground electrode, and then using a second laser beam from the same laser beam welder to attach the ground electrode to the metallic shell. The laser beam welder may include a high energy density fiber laser for forming key-hole laser welds, as well as a programmable focusing optic (PFO) assembly for redirecting laser beams from one welding site to the other.

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 ground electrode includes a main body portion and a projecting portion having a width smaller than a width of the main body portion. A spark discharge gap is formed between a discharging surface of the projecting portion and a front end surface of a center electrode. When the front end surface and the ground electrode are projected on a first plane, at least a part of the projection region of the projecting portion overlaps the projection region of the front end surface. A width Le (mm), a width Lc (mm), a cross-sectional area Sg (mm2), a cross-sectional area Sc (mm2), an angle ?1 (°), an angle ?2 (°), an angle ?3 (°), and an angle ?4 (°) satisfy expressions Le<Lc, 2.9?Sc+Sg?4.25, and 0.30?(?1/?2)×(?3/?4)?0.67.

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: 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 (1) includes a metallic shell (3) and a ground electrode (27) resistance-welded to the metallic shell (3). The ground electrode (27) is formed from a metal material in which precipitates PR containing at least one of an oxide, an intermetallic compound, etc., are precipitated in grain boundaries. The diameter of an equivalent circle of a precipitate PR having the greatest area is 50 ?m or less, and the shortest distance between the precipitates PR is 2 ?m or greater. The area occupied by the precipitates PR on the section of the heat-affected zone 27A is equal to 65% or more the area occupied by the precipitates PR (the diameter of an equivalent circle of a precipitate PR having the greatest area) on a section of the normal zone 27B.

Abstract: A spark plug having a center electrode, a ground electrode, and a ground electrode side tip. The tip partially projects from a front end face and an inner circumference-side side surface of the ground electrode. The ground electrode has a center of the front end face, which center is located at a front end side in a direction of the axis with respect to a front end of the center electrode.

Abstract: A method of producing an electrode support for a spark plug is provided. The method includes providing the electrode support. The method includes brazing a chip to the electrode support.

Abstract: A spark plug including: a center electrode which extends in an axial direction; a cylindrical insulator which is disposed around an outer circumference of the center electrode; a cylindrical metal shell which is disposed around an outer circumference of the insulator; and a ground electrode having one end connected to the metal shell, and an end surface of the other end being positioned between the one end and the center electrode or on the center electrode, when viewed in the axial direction of the center electrode, wherein the end surface has a maximum width portion which is formed only at a position where a distance from a center position of the end surface is 12% to 88% of a distance from the center position to an outer side surface of the ground electrode.

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 ???53 R+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: A spark plug for an internal combustion engine includes a center electrode, a tubular insulator, a tubular metal shell, a ground electrode and an overvoltage preventer. The insulator has the center electrode inserted and held therein. The metal shell has the insulator inserted and held therein such that a proximal part of the insulator is exposed from the metal shell. The ground electrode is joined to a distal end of the metal shell and faces the center electrode through a spark gap formed between the center and ground electrodes. The overvoltage preventer prevents a voltage higher than or equal to a threshold voltage from being applied across the spark gap. The overvoltage preventer is arranged in the proximal part of the insulator so as to be positioned outside the metal shell and farther than the metal shell from the spark gap.

Abstract: A ground electrode includes a main body portion and a projecting portion having a width smaller than a width of the main body portion. A spark discharge gap is formed between a discharging surface of the projecting portion and a front end surface of a center electrode. When the front end surface and the ground electrode are projected on a first plane, at least a part of the projection region of the projecting portion overlaps the projection region of the front end surface. A width Le (mm), a width Lc (mm), a cross-sectional area Sg (mm2), a cross-sectional area Sc (mm2), an angle ?1(°), an angle ?2(°), an angle ?3(°), and an angle ?4(°) satisfy expressions Le<Lc, 2.9?Sc+Sg?4.25, and 0.30?(?1/?2)×(?3/?4)?0.67.

Abstract: An ignition plug (1) includes a center electrode (5) extending in the direction of an axis (CL1), an insulator (2) having an axial hole (4) into which the center electrode (5) is inserted, a tip (31) joined to a forward end portion of the center electrode (5) by a fusion portion (35), and a ground electrode (27) forming a gap (33) in cooperation with the tip (31). The ignition plug generates high-frequency plasma at the gap (33) when high-frequency electric power is supplied to the gap (33). The forward end of the tip (31) is located forward of the forward end of the insulator (2) with respect to the direction of the axis (CL1). Also, at least a portion of the outer surface of the fusion portion (35) is located within the axial hole (4), and, the distance between a forward-end-side opening of the axial hole (4) and the rearmost end of the outer surface of the fusion portion (35), measured along the axis (CL1), is equal to or greater than 0.1 mm.

Abstract: The plug comprises a nut, a coupling extending from the nut and adapted to receive an ignition wire and an insulator extending from the nut and away from the coupling. A positive electrode extends through the insulator. An externally-threaded tubular portion extends from the nut in surrounding relation to the insulator and terminating, short of the insulator end, in a cap that is disposed in spaced relation to the insulator. The cap defines a void having: a central portion into which the positive electrode extends; an annular channel surrounding the central portion; and a plurality of lobes, each positioned with respect to the central portion as the planet gears are positioned with respect to the sun gear in a planetary gear. The cap has a central surface that is axially spaced from the insulator and a convex surface that surrounds and extends to the central surface.

Abstract: A spark plug, a center electrode therefore and method of construction is provided. The spark plug has a generally annular ceramic insulator extending between a terminal end and a nose end. A conductive shell surrounds at least a portion of the ceramic insulator and a ground electrode having a ground electrode sparking surface is operatively attached to the shell. An elongate center electrode has a body extending between opposite ends, wherein the body is compacted and sintered of a conductive or semi-conductive ceramic material. One of the electrode ends provides a center electrode sparking surface to provide a spark gap between the center electrode sparking surface and the ground electrode sparking surface.

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.