Abstract: A spark plug includes: a center electrode; a metal shell that holds the center electrode in an insulated manner; and a rod-like ground electrode electrically connected to the metal shell and having one end opposed to the center electrode. The metal shell includes a tubular distal end portion inside which the one end of the ground electrode is located. The distal end portion has a hole into which the other end of the ground electrode is inserted. A value obtained by dividing a surface area of a portion of the ground electrode, the portion being located on an inner circumferential side of the distal end portion, by a side surface area of a portion of the ground electrode, the portion being located inside the hole, is less than or equal to 13.1.

Abstract: A spark plug includes: a cylindrical center electrode extending along an axial line; a metal shell that holds the center electrode in an insulated manner; and a ground electrode electrically connected to the metal shell. A spark gap is formed between a side surface of the center electrode and an end face of the ground electrode. The metal shell includes a tubular distal end portion inside which the spark gap is located. In a cross section perpendicular to the axial line and including a center of gravity of the end face, a distance between a center line of the ground electrode, the center line including the center of gravity, and a point of tangency of a tangent line to the side surface of the center electrode is greater than 0 and smaller than a distance between an edge of the end face and the center of gravity.

Abstract: A spark plug electrode includes an electrode tip that is attached to or formed on an electrode base so that the electrode tip is directly thermally coupled to a heat dissipating core through an opening in the electrode base. This direct thermal coupling may take place on a side surface of a ground electrode or a center electrode and removes thermal energy away from the electrode tip in order to reduce thermal and/or other stresses. The heat dissipating core may have one or more core extensions that diverge or branch off of a core main body and extend into the opening in the electrode base for better thermal coupling to the electrode tip. The electrode tip can be attached to the electrode base via welding or it can be formed on the electrode base using a suitable additive manufacturing process, such as a powder bed fusion technique.

Abstract: An ignition apparatus for an internal combustion engine includes at least one pre-chamber and at least one ignition source. The pre-chamber is coupled to the ignition source in the longitudinal extension direction of the ignition apparatus such that it can rotate about a center axis of the ignition apparatus without offset between at least two rotation direction positions of the pre-chamber relative to the ignition source. In at least one decoupling rotation direction position, the pre-chamber is reversibly detachable from the ignition source and can be spaced from the ignition source in the longitudinal extension direction.

Abstract: A spark plug electrode includes a thermally conductive core portion and a weldable core portion that are aligned in series within a multi-piece core assembly to improve the heat management and attachment characteristics of the electrode. The thermally conductive core portion, which can be made from a copper-based material, is located towards a firing end of the ground electrode. The weldable core portion can be made from a nickel-based material and is located towards a welding end of the ground electrode. A method of manufacturing is also described for extruding and forming the spark plug electrode with the multi-piece core assembly. The method is designed so that a core interface between the thermally conductive core portion and the weldable core portion does not substantially include any internal voids, and a welding surface where the electrode is attached to a spark plug shell has a nickel-to-nickel interface, but does not substantially include any copper.

Abstract: A spark plug and method of manufacturing, where the spark plug meets particular geometric relationships to maintain and potentially improve dielectric performance while downsizing other plug dimensions. The spark plug includes an insulator that can withstand higher voltages while having areas with a reduced cross-sectional thickness. In some embodiments, the insulator has a dielectric strength of 42 kV/mm or more with a radial thickness at the internal seal of 1.5 to 1.6 mm, inclusive, and a radial thickness at a gasket of 0.6 to 0.9 mm, inclusive.

Abstract: Spark plug has center electrode having leg portion extending in an axis direction, brim portion located at rear end side with respect to the leg portion and protruding outwards in a radial direction with respect to the leg portion and connecting portion connecting the leg portion and the brim portion; insulator having penetration hole and supporting the center electrode; and seal member filling the penetration hole and fixing the brim portion and the insulator. The center electrode satisfies “(D1-D2)/D1?0.06”, where a maximum value of a radius of the brim portion is D1, and a minimum value of the radius of the brim portion is D2, also satisfies “L2/L1?0.30”, where a size of the center electrode along the axis direction is L1, and a size along the axis direction from boundary between the connecting portion and the leg portion to a center of gravity of the center electrode is L2.

Abstract: A spark plug electrode includes an electrode tip that is attached to or formed on an electrode base so that the electrode tip is directly thermally coupled to a heat dissipating core through an opening in the electrode base. This direct thermal coupling may take place on a side surface of a ground electrode or a center electrode and removes thermal energy away from the electrode tip in order to reduce thermal and/or other stresses. The heat dissipating core may have one or more core extensions that diverge or branch off of a core main body and extend into the opening in the electrode base for better thermal coupling to the electrode tip. The electrode tip can be attached to the electrode base via welding or it can be formed on the electrode base using a suitable additive manufacturing process, such as a powder bed fusion technique.

Abstract: Spark plugs are disclosed that include electrode arrangements to improve the charge flow into and out of the annular volume around the insulator nose and a pre-chamber volume of a pre-chamber device, thus directing a purge of exhaust gases trapped in the annular volume to a space formed by the exterior of the spark plug body and the interior of the pre-chamber device.

Abstract: A prechamber spark plug having a housing, which at its front end comprises a prechamber with an ignition electrode arranged therein, wherein the ignition electrode comprises a base and electrode legs protruding from the base, wherein the ignition electrode is machined from a sheet made of an iridium alloy and the legs are bent out of the plane of the base to form a basket shape, characterized in that the ignition electrode, in particular the electrode legs, is/are separated out of the sheet metal by means of laser cutting. Furthermore, a corresponding ignition electrode and a method for producing such an ignition electrode are claimed.

Abstract: Methods and systems are provided for a cylinder head. In one example, a system comprises cylinder head having a bore arranged therein. The bore comprises a coupling element therein configured to selectively receive an ignition plug.

Abstract: A spark plug includes a central electrode member and an outer electrode member. The central electrode member includes a central base and a plurality of electrode prongs extending in an axial direction from the central base. The outer electrode member surrounds the central electrode member. The outer electrode member includes a wall that is radially spaced from the plurality of electrode prongs to allow a series of electric arcs to form between the wall and the plurality of electrode prongs. The outer electrode member and the central electrode member are sized and positioned relative to one another such that a first rate of wear of the outer electrode member, along a longitudinal axis of the spark plug, is substantially equal to a second rate of wear of the central electrode member along the longitudinal axis.

Abstract: A spark plug is provided with a center electrode and a ground electrode. The ground electrode includes an electrode tip, an electrode base material, an intermediate member and a first melt portion. The intermediate member is disposed between the electrode tip and the electrode base material. The first melt portion contains components of the electrode base material and the intermediate member, and is disposed at least at a part of the boundary between the electrode base material and the intermediate member. In a cross section including the axis of the ground electrode, the boundary line between the intermediate member and the first melt portion has at least two first projection portions projecting toward the electrode tip side, and the boundary line between the electrode base material and the first melt portion has at least two second projection portions projecting toward the opposite side of the first projection portions.

Abstract: In a spark plug, a base material contains 50 mass % or more of Ni, 8 mass % or more and 40 mass % or less of Cr, 0.01 mass % or more and 2 mass % or less of Si, 0.01 mass % or more and 2 mass % or less of Al, 0.01 mass % or more and 2 mass % or less of Mn, 0.01 mass % or more and 0.1 mass % or less of C, and 0.001 mass % or more and 5 mass % or less of Fe. A discharge member contains at least Pt of a P group (Pt, Rh, Ir, and Ru) and Ni. The atomic concentration K of the P group of the discharge member, the atomic concentration L of the P group of the base material, the atomic concentration M of Ni of the discharge member, and the atomic concentration N of Ni of the base material satisfy (K+L)/(M+N)?1.14.

Abstract: The present disclosure relates to a spark plug for engines. The spark plug includes a center electrode and a ground electrode that includes a center void and a ground void respectively. An initial spark gap is formed between the center electrode and the ground electrode. A center electrode initial surface is disposed between the center void and the spark gap and a ground electrode initial surface is disposed between the ground void and the spark gap. The center void and ground void can become exposed through wear of the center electrode initial surface and ground electrode initial surface respectively. When the wear breaches center electrode initial surface and the ground electrode initial surface the wear creates a center first concentration edge and a ground first concentration edge that focus an electrical field and reduces the voltage required for fuel breakdown.

Abstract: An ignition plug for an internal combustion engine includes an electrode protrusion that protrudes from an electrode base material of a ground electrode toward a discharge gap. The electrode protrusion has a base part that is integrated with the electrode base material and a cover part that is joined to the base part and faces the discharge gap. The base part has an end surface facing a protrusion direction of the base part and a side peripheral surface. An outer edge of the end surface has a curved surface. The cover part is formed from a precious metal or a precious metal alloy having a lower linear expansion coefficient than that of a material for forming the base part and covers at least a part of the side peripheral surface and the end surface of the base part. While the ignition plug is attached to an internal combustion engine and the electrode protrusion is heated and then cooled, a projection is formed on an outer surface of a portion covering the side peripheral surface of the base part.

Abstract: An electrode base material of the spark plug contains not less than 50 wt. % of Ni. A discharge member contains not less than 45 wt. % of Pt, and at least one of Ni and Rh. An intermediate member contains Pt and Ni. In the discharge member, a content of Pt is highest, and a total content of Pt, Rh, and Ni is not less than 92 wt. %. In the intermediate member, a content of one of Pt and Ni is not less than 50 wt. %, a content of Ni is higher than a content of Ni in the discharge member, and a total content of Pt, Rh, and Ni is not less than 85 wt. %. A thickness of the diffusion layer formed between the discharge member and the intermediate member is not less than 0.002 mm and not more than 0.065 mm.

Abstract: A spark plug including a metallic shell having a ground electrode, an insulator held inside the metallic shell and having an axial hole having a small diameter portion, an intermediate diameter portion connected to a rear end of the small diameter portion via a step portion, and a large diameter portion disposed on the rear side of the intermediate diameter portion, a resistor disposed inside the large diameter portion, a center electrode having a flange portion which bulges in a radial direction inside the intermediate diameter portion and comes into contact with the step portion and a leg portion which extends forward from the flange portion and is disposed inside the small diameter portion, and a seal disposed on the rear side of the step portion and electrically connecting the center electrode and the resistor. The rear end of the seal is located inside the intermediate diameter portion.

Abstract: A spark plug comprises an insulator having a axial hole penetrating in a direction of an axis, a central electrode provided on the front end side of the axial hole, a tubular metal shell that holds the insulator, and a ground electrode including a surface layer and a core material that is surrounded by the surface layer and has a larger thermal conductivity than that of the surface layer. The metal shell of the spark plug has a protruding portion in which at least a part of the metal shell protrudes toward the front end side in the direction of the axis. The ground electrode has an end surface at one end portion thereof joined to the inside of the protruding portion and the other end portion thereof facing the central electrode.

Abstract: A spark plug has a firing pad attached to a center electrode or a ground electrode by way of a fused portion. In one or more embodiments, the firing pad is composed of a precious metal material. The fused portion can be formed in such a way that a material composition thereof at a sparking surface of the firing pad has a greater percentage of the precious metal material than a material of the underlying electrode to which the firing pad is attached.

Abstract: A spark plug includes a center electrode, a ceramic insulator provided with an axial hole, a metal shell, and a ground electrode having a facing surface that faces a leading end surface of the center electrode. An annular space is formed between an outer peripheral surface of the center electrode and an inner peripheral surface of the axial hole and is opened toward a leading end side, and when C (mm) is a distance between the outer peripheral surface of the center electrode and the inner peripheral surface of the axial hole in the opening of the annular space, C?0.2 mm is satisfied. In a cross-section which includes the axial line and is orthogonal to the center axis of the ground electrode, a contour line of lateral surfaces of the ground electrode has a curved shape convexed outward.

Abstract: In an earth electrode apparatus, a cradle having first, second, and third shanks to which first, second, and third earth electrodes can be attached respectively is coupled to a shaft supported by a base. The cradle is coupled thereto in a tiltable manner. If the surface of a workpiece is irregular or inclined, the cradle tilts for balancing with the workpiece to ensure equal contact pressure for the contact of the first, second, and third earth electrodes with the workpiece, thereby offering stable contact irrespective of surface irregularity or inclination. Since a welding current is split to flow into the first, second, and third earth electrodes through respective points of contact thereof with the workpiece, it is possible to reduce current density at each of the points of contact and to avoid heat generation ascribable to conductive resistance at each of the points of contact.

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 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: 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 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 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 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 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: Described is a spark plug for gasoline engines with an elongated hollow body made of metal, said body having a forward end with an undercut formed by an interior annular shoulder of the body and a rear end, with an elongated ceramic insulator which is mounted in the body and has a rear end that projects beyond the rear end of the body and has a forward end beyond which the forward end of the body projects, with a center electrode which is inserted into the insulator, projects beyond the forward end thereof, and is connected to a metal connection pin in an electrically conductive manner, said connection pin projecting beyond the rear end of the insulator, and with at least one ground electrode which starts from the forward end of the body and is approached to the center electrode to an electrode distance (EA) to form a spark gap.

Abstract: A spark plug for an internal combustion engine is provided, which includes a housing, an insulation porcelain, a center electrode and a ground electrode. At least one of a tip portion of the center electrode and an opposing portion of the ground electrode is provided with a projection portion. At least one of the projection portions has a cross section perpendicular to the axial direction of the plug, the cross section having a minimum curvature radius portion and being in a specific shape that satisfies a predetermined requirement. The requirement is that, when a first straight line, a first line segment and a second straight line are provided, and when the cross section is divided into a first region and a second region by the second straight line, the second region has an area larger than the area of the first region.

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 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 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 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 includes a center electrode having an end portion, and an earth electrode having an opposing portion opposed to the end portion via a gap. The end portion has an end-projecting portion. The opposing portion has an opposing-projecting portion opposed to the end-projecting portion. The end-projecting portion and the opposing-projecting portion have non-projection direction opposing surfaces which are parallel to and opposed to each other with a minimum distance and in a direction other than a projection direction. A first opposing area of a portion which includes the non-projection direction opposing surfaces and where the end-projecting portion and the opposing-projecting portion are opposed to each other with the minimum distance is larger than a second opposing area obtained when a plane of the end-projecting portion and a plane of the opposing-projecting portion, which are orthogonal to the projection direction, are opposed to each other in the projection direction.

Abstract: A spark plug for internal-combustion engines equipped with a center electrode and a ground electrode is provided. In the spark plug, the ground electrode is fixed to a mount fitting, while the ground electrode has a convex portion. The convex portion is made of a part of base materials of the ground electrode where the part is facing the center electrode, and is projected toward the center electrode. The convex portion has a fusion solidification part made of precious metal materials and a part of the base materials melted together and solidified at least on part of an electric discharge surface facing the center electrode.

Abstract: An adhesion of a nickel plating layer to a metal shell is improved, and an effect of improving a corrosion resistance by providing the nickel plating layer is sufficiently exerted. A spark plug 1 includes a cylindrical metal shell 3 that extends in an axial CL1 direction, and a nickel plating layer 31 that is made of metal containing nickel as a main component and covers an outer surface of the metal shell. In a monochrome image of 256 gradations where black is 0 and white is 255, which is obtained by observing a cross-section perpendicular to an outer surface of the nickel plating layer by a transmission electron microscope with an acceleration voltage of 200 kV, an average value in 256 gradations of the monochrome image is 170 or larger and 230 or smaller.

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: A spark plug has a cylindrical housing case, a cylindrical glass insulator, a center electrode, and an earth electrode fixed to the cylindrical housing case. The earth electrode has a projected part which is projected toward the center electrode. The projected part has a facing surface which faces the center electrode and is most close to the center electrode in a spark discharge gap. This gap is formed between the center electrode and the earth electrode. The facing surface is covered with a plating layer. A base material, with which the earth electrode is made, is exposed on a side surface of the projected part around the facing surface of the projected part. The base material of the earth electrode is made of Ni alloy containing not less than 90 wt % Ni, and preferably, Ni within a range of 90 wt % to 98 wt %.

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 includes a ground electrode. The cross sectional area S of a ground electrode base member of the ground electrode satisfies a relation 1.8 mm2?S?3.2 mm2. The embedment depth A of a noble metal tip embedded in a second base member surface and the tip thickness B of the noble metal tip measured along the direction in which the noble metal tip is embedded in the second base member surface satisfy a relation 0.4?(A/B)?0.8.

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 method of manufacturing a spark plug includes a joining step of joining a first member and a second member which constitute the spark plug. In the joining step, a first welding electrode in contact with the first member and a second welding electrode which has an elastically deformable intermediate portion and which is in contact with the second member are electrically connected through the first member and the second member, whereby the first member and the second member are joined together by resistance welding.

Abstract: [Objective] To provide a spark plug which is configured such that an insulation member, from which a center electrode projects, is pressed frontward and held in a metallic shell, and is fixed by means of crimping the rear end of the metallic shell, and which can prevent a drop in gas tightness between the metallic shell and the insulation member due to a difference in thermal expansion therebetween. [Means for Solution] In a spark plug in which a mating shaft portion (10) of an insulation member (1) is loose-fitted into a mating hole portion (30) of a metallic shell (21), a filler (41) for maintaining gas tightness is charged between the outer circumferential surface of the mating shaft portion (10) and the inner circumferential surface of the mating hole portion (30). Despite the thermal expansion difference, the gas tightness is maintained, because the filler (41) for maintaining gas tightness is charged between the inner and outer circumferential surfaces.

Abstract: Disclosed is a spark plug having an insulator with good breakage resistance. A spark plug 1 contains a ceramic insulator 2, a plate packing 22 and a metal shell 3. The ceramic insulator 2 has, on an outer circumferential surface thereof, a step portion 14, a leg portion 13 and a curved surface portion 31 between the step portion 14 and the leg portion 13. The metal shell 3 has, on an inner circumferential surface thereof, a taper portion 21. The ceramic insulator 2 is fixed in the metal shell 3 with the step portion 14 retained on the taper portion 21 via the plate packing 22. Herein, 50% or more of an inner circumferential edge portion IP of the plate packing 22 is in contact with a part of the ceramic insulator 2 located front of a middle region CP of the curved surface portion 31.

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 includes a metallic shell, an insulator, a center electrode body, a ground electrode body, and a ground electrode tip. In one embodiment, the ground electrode tip includes a non-precious metal piece and a precious metal piece attached to each other. The non-precious metal piece has a side surface attached to a free end surface of the ground electrode body.

Abstract: A spark plug includes: a rod-shaped center electrode extending in an axial direction; an insulator including a shaft hole that holds the center electrode inside of the shaft hole; a metal shell surrounding and holding a part of the insulator; and a ground electrode including a base end welded to the metal shell. The metal shell and the ground electrode are joined via a fusion portion formed by welding the ground electrode and the metal shell together. When the smallest thickness of the fusion portion in the axial direction is A, when, in a cross section that includes a center line of the ground electrode and is parallel to the axis, a length of a ground-electrode-side melted boundary formed between the fusion portion and the ground electrode is B, and when the ground electrode thickness is C, conditions of A?0.2 mm and B >C are satisfied.