Abstract: A base end portion of a ground electrode of a spark plug includes a skin portion, an intermediate portion, and a core portion 52. A center cross section CP containing the center axis PX of the spark plug and the center axis EX of the base end portion includes a first multilayer portion in which the intermediate portion is disposed inward of the skin portion and the core portion is disposed inward of the intermediate portion, and a second multilayer portion in which the skin portion and the core portion are in direct contact with each other. The center cross section CP includes an intersection point PI at which a first boundary line BLa between the metallic shell and the skin portion and a second boundary line between the metallic shell and the core portion meet with a third boundary line BLc.

Abstract: A spark plug includes an insulator body and a central electrode having a spark-end and a terminal-end. The central electrode is disposed within the insulator body, with the spark-end and the terminal-end protruding from the insulator body at opposite ends thereof. A metal electrode surrounds the insulator body and extends to form a gap with the central electrode at the spark-end. A capacitor with metalized inner and outer surfaces is provided, with the metalized inner surface being connected to the central electrode and the metalized outer surface being connected to the metal electrode. A first resistive component is embedded within the central electrode between the capacitor and the terminal-end, and a second resistive component embedded within the central electrode between the capacitor and the spark-end.

Abstract: A spark plug includes an insulator; a center electrode; a metal shell; and a ground electrode whose base end is fixed to the metal shell. A distal end of the ground electrode includes a first surface facing the center electrode, a second surface facing a side opposite to the first surface, and an inclined surface that is inclined with respect to the second surface. A noble metal tip is partially buried in the inclined surface. A width of the inclined surface is larger than that of the noble metal tip. In this spark plug, A B is satisfied, where A is a distance from a distal end of the ground electrode to a proximal-end-side end portion of the inclined surface and B is a distance from the distal end of the ground electrode to a proximal-end-side end portion of the noble metal tip.

Abstract: A corona igniter including a hermetic combustion seal between an insulator and center electrode is provided. The combustion seal includes a metallic coating, such as a nickel-based layer applied to a layer of molybdenum-manganese, and the metallic coating is disposed on the insulator inner surface. Optionally, a shot of copper-based powder can be disposed on a head of the center electrode. The center electrode and/or the copper-based powder is then brazed to the metallic coating on the inner surface of the insulator. The process can include applying the metallic coating to the inner surface while applying a metal coating to an outer surface of the insulator. The method further includes brazing the center electrode and/or the copper-based powder to the metallic coating on the inner surface while brazing the metal coating on the outer surface to a metal shell.

Abstract: An electrode tip for a spark plug, wherein Pt is contained as a main component, 7% by mass or more of Rh is contained, and a total content of Pt and Rh is greater than or equal to 95% by mass. The electrode tip includes: a narrow portion having the same cross-sectional shape in a direction of an axis; and a wide portion which is adjacent to the narrow portion and has a cross-sectional area, in a radial direction, which is greater than the narrow portion.

Abstract: A system for testing an insulative material for a spark plug comprises a test spark plug having at least a center electrode and an insulator comprised of an insulative material surrounding at least a portion of the center electrode, wherein the insulator has an end that is closed, whereby the closed end of the insulator encloses an end of the center electrode. The system may further include a test engine that simulates engine conditions, wherein a conventional spark plug is installed in a first ignition port of the test engine and the test spark plug is installed in a second ignition portion of the test engine and a control system for controlling ignition signals to the test spark plug and the conventional spark plug.

Abstract: A spark plug wherein when a discharge tip is viewed from a direction of an axial line, a melted portion is formed in at least a region on a second-end side of an electrode base material from a center of a discharge layer, and wherein in a section that includes a center line along a longitudinal direction of a ground electrode and that is parallel to an axial line, a proportion of a length of the melted portion along the longitudinal direction to a length of the discharge tip along the longitudinal direction of the electrode base material is greater than or equal to 76.2%, with the length of the melted portion along the longitudinal direction being within a range in which the discharge tip exists along the longitudinal direction.

Abstract: An ignition plug includes a center electrode; a cylindrical insulator that surrounds at least the circumference of a front end portion of the center electrode and that includes a bottom portion at the front side; and a cylindrical metal shell that holds the insulator from the outer circumference side. The center electrode includes a shaft portion that extends along an axial line and a head portion disposed at a front end of the shaft portion. The head portion has a width greater than that of the shaft portion in the radial direction. The insulator includes a first and second insulator. The first insulator has an axial hole and a diameter smaller than the maximum diameter of the head portion. The second insulator is joined to the first insulator. The shaft portion is disposed in the axial hole of the first insulator. The second insulator encloses the head portion.

Abstract: A spark plug having a tip provided on at least one of a center electrode and a ground electrode. The tip includes a body portion, a coating layer, and a high specific resistance layer. The body portion contains mostly Ir. The high specific resistance layer is provided on a side peripheral surface of the body portion, has a Ni content greater than the Ni content of the body portion and less than 50 mass %, and has a thickness of 2 ?m or greater and 45 ?m or less. The coating layer is provided on a side peripheral surface of the high specific resistance layer, contains 50 mass % or more of Ni, and has a thickness of 3 ?m or greater and 20 ?m or less. The tip has a specific resistance of 20×10?8 ?m or less at room temperature.

Abstract: An ignition plug includes an insulator having an outer-diameter reduction surface and a metal shell. The metal shell includes a rear end portion, a curved deformation portion, and a stepped portion. In a section including an axial line, the average hardness of a surface layer portion, which extends along a specific surface, of a rear end surface of the stepped portion is higher than the average hardness of the rear end portion and the average hardness of the deformation portion.

Abstract: A method for manufacturing a spark plug includes pressing a tip in a first direction from a first surface thereof toward a second surface thereof via a jig when the tip is in contact with an electrode base material; and welding the electrode base material to the tip being pressed by the jig. The jig has a recessed portion which is brought into contact with an edge of the tip, and the recessed portion has a diameter-decreasing portion having an inner dimension that gradually decreases toward a second direction opposite to the first direction. The inner dimension of a first end portion in the first direction of the diameter-decreasing portion is larger than the outer dimension of the edge, and the inner dimension of a second end portion in the second direction of the diameter-decreasing portion is equal to the outer dimension of the edge.

Abstract: A method of inspecting a spark plug insulator that includes a collar portion, a rear body portion located in rear of the collar portion and a leg portion located in front of the collar portion. The inspection method includes: performing measurement of a distance in a radial direction of the insulator between an outer circumferential surface of the leg portion at a first measurement point and an outer circumferential surface of the any portion of the insulator other than the leg portion at a second measurement point, wherein the measurement is performed at a plurality of positions in a circumferential direction of the insulator with no contact to the measurement target; determining, as a circular runout, a difference between maximum and minimum values among measurement results of the distance; and making pass/fail judgment of the insulator based on the determined circular runout.

Abstract: A spark plug includes an insulator having an axial hole formed therethrough in the direction of an axis of the spark plug, a center electrode disposed in a front side of the axial hole and a metal shell disposed around an outer circumference of the insulator and having a collar-shaped tool engagement portion and a crimp portion located on a rear side of the tool engagement portion and reduced in diameter toward the rear, wherein the crimp portion of the metal shell is made of a carbon steel material having a grain size number equal to or greater than No. 11 as measured according to JIS G 0551.

Abstract: A spark plug includes a central electrode and a noble metal tip, which are joined together with a fusion portion interposed therebetween. A tip-adjoining boundary of the fusion portion has a shape that curves convexly toward the fusion portion. A central-electrode-adjoining boundary of the fusion portion has a shape that curves convexly toward the central electrode. The outline of a portion of the fusion portion exposed to the outer surface has a shape that curves concavely into the inner side of the fusion portion.

Abstract: A reversed-assembled corona igniter including an insulator, central electrode, and metal shell, wherein an outer diameter of the insulator increases adjacent a lower end of the metal shell to achieve an electrical advantage is provided. In addition, the insulator maintains strength because is not placed under tension during or after assembly, or once disposed in an engine. To achieve the increase in insulator outer diameter, the insulator includes a lower shoulder adjacent the shell firing end. An intermediate part, such as braze and/or a metal ring, is disposed between the insulator outer surface and the shell adjacent the shell firing end. To prevent tension in the insulator, the insulator can be supported at only one location between the insulator upper end and the insulator lower end, for example along the intermediate part.

Abstract: Disclosed herein is a spark plug capable of suppressing electrode consumption caused by a spark discharge and a method of manufacturing the same. A section except a welded section formed by welding a tip surface of a center electrode is defined as an unwelded section in side surfaces of a center chip, and a length of the unwelded section along a center axis of the center chip is defined as an unwelded section length. Under this definition, the welded section is formed in order for an unwelded section length in a side surface opposite to an inclination direction side of the center chip in the center chip to become longer than an unwelded section length in a side surface of the inclination direction side of the center chip in the center chip.

Abstract: An electrode material that may be used in spark plugs 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. In one embodiment, the electrode material is a ruthenium-based material that includes ruthenium (Ru) as the single largest constituent on a wt % basis, and at least one of rhenium (Re) or tungsten (W). The electrode material may further include one or more precious metals and/or rare earth metals. The electrode material may be used to form the center electrode, the ground electrode, firing tips, or other firing tip components.

Abstract: A spark plug having a tip formed of an alloy containing Pt. The tip contains not less than 6 mass % of Rh, at least one element selected from an R group consisting of Rh, Re, Ir, Ru, W, Mo, and Nb, not less than 5 mass % of Ni, and at least one element selected from an N group consisting of Ni, Co, Fe, and Cu. The tip contains Rh most among the elements of the R group, and contains Ni most among the elements of the N group. The total of contents of Pt, Rh, and Ni is not less than 91 mass %, and the total of contents of Pt, the R group, and the N group is not less than 95 mass %. A value obtained by dividing the content of the R group by the content of the N group is not less than 0.7 and not greater than 8.

Abstract: A spark plug having a center conductor, an insulator surrounding the center conductor, at least two electrodes forming a spark gap, and a spark plug body surrounding the insulator and having an external thread arranged at the front end of the spark plug for screwing in to an internal combustion engine. A component that is attached to the front end of the spark plug and comes into contact with fuel during operation is formed as a sintered powder injection molded part, referred to as a MIM component.

Abstract: A spark plug, including a housing, an insulator situated in the housing, a center electrode situated in the insulator and a ground electrode situated on the housing, the ground electrode and the center electrode being situated relative to one another in such a way that the ground electrode and the center electrode form a spark gap, and the ground electrode including a core and a sheath surrounding the core, the core being made of a material which has a higher thermal conductivity than the material of the sheath, and a cross sectional area of the ground electrode being not greater than 2.76 mm2, the sheath having a wall thickness c of not greater than 0.4 mm in a first region of the ground electrode.

Abstract: A spark plug having a center electrode, a ground electrode, and a noble metal tip that is joined to a part of the ground electrode near one end of the ground electrode via a fused portion. The fused portion extends outward beyond an outer shape of the noble metal tip so that a part of the fused portion is present at each of positions that are located inward from and separated from both side edges of the ground electrode in a width direction of the ground electrode. The fused portion includes a fused protrusion that is located near at least one of two side edges of the noble metal tip in the width direction of the ground electrode and that protrudes in a direction away from the one end of the ground electrode.

Abstract: A spark plug includes an insulator, a metal shell surrounding the insulator, a center electrode disposed in the insulator, with a front end thereof exposed outside from the insulator, a ground electrode having a fixed end portion fixed to the metal shell and a free end portion located at a predetermined gap apart from the center electrode, and a coating part formed of noble metal or noble metal alloy so as to cover at least a region of an inner surface of the ground electrode from a first intersection to a second intersection, where the first intersection is an intersection at which an imaginary line extending from an outer circumference of the center electrode intersects the ground electrode; and the second intersection is an intersection at which an imaginary plane extending through a midpoint of the predetermined gap in parallel with the front end intersects the ground electrode.

Abstract: This disclosure relates to a corona ignition device having: an insulator, which bears an electrically conductive coating, which forms a tubular face; a central electrode, which sits in the insulator and leads to at least one ignition tip; and a holder, in which the insulator sits. According to this disclosure, the insulator has an annular shoulder, on which is situated the end of the tubular face of the coating that faces away from the at least one ignition tip. A method for producing a corona ignition device is also described.

Abstract: A spark plug having a of center electrode, a ground electrode, and a noble metal tip that is laser-welded to at least one of the center electrode and the ground electrode The noble metal tip is joined to the electrode through a fused portion formed by laser welding, and the fused portion includes a first fused portion and a second fused portion.

Abstract: In the spark plug, at least one of the center chip and the ground chip is bonded with a center electrode or a ground electrode. The selected chip has a first part formed so as to linearly extend along a first center axis of an electrode bonded with the first part and a second part formed so as to extend linearly from a tip end of the first part along a second central axis inclined with respect to the first central axis.

Abstract: A center electrode including an electrode base member having a cylindrical shape with a bottom and a core member embedded in the electrode base member. The core member has a thermal conductivity higher than that of the electrode base member. The center electrode includes a plurality of shoulder portions which each include a diameter reducing portion having a diameter that decreases toward a front end of the spark plug in a direction of an axial line, an outer side surface that extends in the direction of the axial line, and an edge disposed between the diameter reducing portion and the outer side surface. One of the shoulder portions closest to an inner surface of the axial hole has a cutting mark that extends in a circumferential direction over a region from the diameter reducing portion to the edge.

Abstract: In a spark plug, at a cross section of a ground electrode which is orthogonal to a longitudinal direction of an electrode base material and passes an axis of an electrode tip, a surface of the base material is exposed, and the following conditions are satisfied: 1.2E?F?1.9E; 0.05 mm?Da?0.30 mm; 0.05 mm?Db?0.30 mm; and 0.20 mm?J?0.70 mm2.

Abstract: The spark plug includes: an insulator having a through hole that penetrates therethrough along an axial direction; a center electrode disposed on one end side of the through hole; a metal terminal disposed on the other end side of the through hole; and a conductive seal layer connected to at least one of the center electrode and the metal terminal. The conductive seal layer contains glass and a Cu—Zn alloy. A volumetric percentage of the Cu—Zn alloy in the conductive seal layer is greater than or equal to 44% and not greater than 55%.

Abstract: A remanufactured sparkplug includes a housing, an insulator within the housing, and first and second electrodes. The first electrode and the second electrode form a plurality of spark gaps at a plurality of new spark gap locations, and a plurality of spark-induced erosions are formed in the second electrode at a plurality of former spark gap locations that are circumferentially offset from the new spark gap locations.

Abstract: A spark plug for an internal combustion engine provided with a cylindrical housing, a ceramic insulator, a center electrode and a ground electrode. The ground electrode has a body base disposed from a front end surface of the cylindrical housing to a front end-side thereof. The ground electrode has a spark discharge gap formed therebetween itself and the center electrode. The body base is provided with pair of side-connecting surfaces which connect the inner surface and the outer surface. Each of the side-connecting surfaces having a side flat surface which is a flat surface parallel to an aligning direction of the center electrode and the body base. A distance between the pair of the side flat surfaces is a maximum width of the body base. A minimum distance between the inner surface and the side flat surface satisfies a relationship of 0.1 mm?L?0.5 mm, in the aligning direction.

Abstract: A spark plug including an electrode having a cylindrical precious metal tip welded thereto, the electrode having a melt portion in which the precious metal tip and the electrode base material are melted, wherein the melt portion includes a melt sag over an entire circumference on a side surface of the precious metal tip.

Abstract: A tip that contains a noble metal is joined to a joining surface of an electrode base material of a ground electrode via a welded portion. On cross-sections of the tip and the electrode base material in a longitudinal direction of the joining surface, the welded portion has a void above the joining surface, and a continuous distance of the welded portion on the joining surface is less than or equal to 0.5 mm, whereby thermal stress due to a difference in thermal expansion between the tip and the electrode base material can be reduced. A total of continuous distances of the welded portions on the joining surface, are 0.4 times to 0.8 times a length from an end of the tip to another end thereof, whereby joining strength of the welded portion can be assured. Peeling at the tip or falling-off of the tip due to thermal stress can be less likely to occur, whereby durability of the ground electrode can be improved.

Abstract: An ignition plug includes an insulator that includes a through hole; a center electrode; a metal shell that holds the insulator; a bar-shaped ground electrode body; an electrode tip that is disposed along a side surface of the ground electrode body opposing a discharge surface of the center electrode; and a welding portion that is disposed between the ground electrode tip and the ground electrode body. Over ¼ of a range from a first end to a second end of the ground electrode tip, a length L1 of the ground electrode tip and a length L2 of the welding portion in the direction satisfy (L2/L1)?0.25.

Abstract: A spark plug capable of suppressing the occurrence and growth of a crack and oxide scale between an electrode tip and a melt portion, satisfies the relationships of C1?D1 and C2?D2, where C1 is a distance between a reference line RL and a point Pa5, D1 is a distance between the reference line RL and a point Pa1, C2 is a distance between the reference line RL and a point Pa6 and D2 is a distance between the reference line RL and a point Pa2.

Abstract: An internal combustion engine is described and includes a combustion chamber formed by cooperation of a cylinder bore formed in a cylinder block, a cylinder head and a piston. A plasma ignition controller is electrically connected to a groundless barrier discharge plasma igniter that includes a tip portion disposed to protrude into the combustion chamber. A current sensor is disposed to monitor secondary current flow between the plasma ignition controller and the groundless barrier discharge plasma igniter. The plasma ignition controller is disposed to execute a plasma discharge event. A controller is disposed to monitor a magnitude of the secondary current flow via the current sensor during the plasma discharge event. The controller includes an instruction set executable to evaluate integrity of the groundless barrier discharge plasma igniter based upon the magnitude of the secondary current flow during the plasma discharge event.

Abstract: The present invention relates to a tape material for manufacturing an ignition plug electrode, the tape material being a member for forming an electrode chip, in which a base metal layer and a precious metal layer are cladded, on a bonded region set on an electrode base material of an ignition plug, the member is in the form of a long tape in which the base metal layer being in contact with the bonded region is cladded with the precious metal layer being in contact with the base metal layer, the base metal layer has a width substantially equal to one of the longitudinal width, lateral width and diameter of the bonded region. According to the present invention, bonding between a precious metal chip and a substrate can be reliably maintained to prolong the life of an ignition plug. Accordingly, precious metals can be efficiently used to save resources.

Abstract: A spark plug having at least one center or ground electrode that includes a first base metal or a first base metal alloy and a precious metal or a precious metal alloy. The at least one electrode has a surface bordering a spark gap that is made of a composite material in which crystalline particles of the precious metal or precious metal alloy are mixed with the first base metal or the first base metal alloy, and a portion of the particles of the precious metal or precious metal alloy forms a portion of the surface that borders the spark gap.

Abstract: An electrode material for at least one of a center electrode (5) and a ground electrode (27) provided with a chip (31, 32) for use in a spark plug (1). The electrode material contains Ni as a principal component, and has a Si content of from 0.50% to 1.0% by mass, an Al content of from 0.2% to 2.0% by mass, a Cr content of from 12% to 34% by mass, a rare-earth element or the like content of from 0.03% to 0.2% by mass, a Fe content of more than 0% but not more than 20% by mass, a C content of not more than 0.10% by mass, and a Mn content of not more than 1.0% by mass. The total content of Si and Al is not less than 0.80% by mass, and less than one tenth of the Cr content.

Abstract: A spark plug having a ground electrode, a noble metal tip having a front end that projects forward of a front end portion of the ground electrode, and a center electrode. When S1 represents an area of an overlap region in which a region onto which the center electrode is projected overlaps a region onto which the noble metal tip is projected when the center electrode and the noble metal tip are projected onto an imaginary plane perpendicular to a center line of the center electrode, and S2 represents an area of an overlap region in which a region onto which the noble metal tip is projected overlaps a region onto which the ground electrode is projected when the noble metal tip and the ground electrode are projected onto the imaginary plane, 0.22?S1/S2?0.68 is satisfied.

Abstract: A spark plug includes a ceramic insulator having an axial hole formed in an axis direction of the spark plug, a center electrode inserted in a front side of the axial hole, a metal shell disposed around the ceramic insulator and a ground electrode joined to a front end portion of the metal shell, wherein the ground electrode has a cross-sectional area of 2.0 mm2 or smaller in any arbitrary cross section thereof taken in a direction perpendicular to a center line of the ground electrode; the ground electrode is made of a metal material containing 93 mass % or more of nickel; and the ground electrode has a Vickers hardness of 130 to 260 Hv.

Abstract: A spark plug includes an insulator made of an alumina sintered body containing Al2O3 as a principal component and additional components including; an Si component, a Ba component, an Mg component, a Ca component, an Sr component, and a rare earth element component. When the additional components are expressed as oxides including RSiO2, RBaO, RMgO, RCaO, RSrO, and RRE2O3, contents (mass %) of the sub-component satisfy expressions (1) to (6) as follows: (1) 1.0?RSiO2?5.0; (2) 0.5?RBaO?5.0; (3) 0?RMgO?0.18; (4) 0?RMgO/RBaO?0.36; (5) 0.3?(RMgO+RCaO+RSrO)?1.8; and (6) 0?RRE2O3?0.1.

Abstract: Disclosed is a spark plug with improved lifetime. The spark plug includes a first electrode and a second electrode having an electrode base and an electrode tip joined to the electrode base with a gap defined between the first electrode and the electrode tip. The electrode tip has a flat surface located apart from the electrode base and is joined to the electrode base at a side opposite to the flat surface by laser welding with emission of laser beam in a plane direction from one to the other end of the flat surface. A fused part is formed by the laser welding at the opposite side of the electrode tip. A cross-sectional shape of the fused part taken along a plane perpendicular to the flat surface and parallel to the plane direction has a constricted section at a position from one side to the other side in the plane direction.

Abstract: A spark plug includes an insulator having a through hole formed in the direction of an axis, a rod-shaped center electrode inserted in the through hole and extending in the direction of the axis, a metal shell disposed around an outer circumference of the insulator, and a ground electrode electrically conducted with the metal shell and adapted to define a gap between the ground electrode and the center electrode. A front end part of the insulator has a front end surface, an outer circumferential surface and a curved surface region formed between the front end surface and the outer circumferential surface. In a cross section including the axis, a front end of an inner circumferential surface of the metal shell faces the curved surface region in a direction perpendicular to the axis. The curved surface region has a curvature radius of 0.2 mm to 0.8 mm.

Abstract: A method for manufacturing a spark plug includes: a joining step of joining a rod-shaped ground electrode member to a front end portion of a metal shell; a tilt step of tilting the ground electrode member in a radial direction of the metal shell; a correction step of decreasing a tilt angle of the ground electrode member to an allowable tilt angle or less; and a welding step of welding a ground electrode tip to the ground electrode member.

Abstract: A spark plug comprising a center electrode, a ground electrode disposed on the center electrode across a gap, and a tip joined to an opposed surface of the ground electrode that is opposed to the center electrode, the tip has a discharge layer and a relieving layer, the relieving layer is formed from a Pt—Ni alloy and joined to the opposed surface via a diffusion layer, the discharge layer is formed from a Pt—Rh alloy and joined via a clad diffusion layer to a side of the relieving layer opposite to a side of the relieving layer at which the ground electrode is joined, and 0.81?A/B?1.21 is satisfied when an average cross-sectional area of the discharge layer is A mm2 and an average cross-sectional area of the relieving layer is B mm2, and a method for producing the spark plug.

Abstract: An electrically conductive glass seal for providing a hermetic bond between an electrically conductive component and an insulator of a corona igniter is provided. The glass seal is formed by mixing glass frits, binder, expansion agent, and electrically conductive metal particles. The glass frits can include silica (SiO2), boron oxide (B2O3), aluminum oxide (Al2O3), bismuth oxide (Bi2O3), and zinc oxide (ZnO); the binder can include sodium bentonite or magnesium aluminum silicate, polyethylene glycol (PEG), and dextrin; the expansion agent can include lithium carbonate; and the electrically conductive particles can include copper. The finished glass seal includes the glass in a total amount of 50.0 to 90.0 weight (wt. %), and electrically conductive metal particles in an amount of 10.0 to 50.0 wt. %, based on the total weight of the glass seal.

Abstract: A spark plug includes a tubular housing, a tubular insulator, a center electrode, a ground electrode, a resistor, and a stem. The insulator is supported inside the housing. The center electrode is supported inside the insulator so as a distal end portion thereof protrudes. The ground electrode forms a spark discharge gap G between the ground electrode and the center electrode. The resistor is supported inside the insulator at a proximal side of the central electrode. The stem is supported inside of the insulator at a proximal side of the resistor. Of an outer peripheral surface of the insulator, and closer to a distal end side than a proximal portion of the resistor is, there is formed a high emissivity surface of which thermal emissivity is at least 0.7 on at least a part of a portion facing an inner circumferential surface of the housing.

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 packing between an insulator and a metal shell of a spark plug. A length between a first position of a contact portion of the packing and the insulator and a second position of a contact portion of the packing and the insulator parallel to an axial line direction is set as a first length. In the case where a load perpendicular to the axial line direction is applied to the second position, a ratio of stress at a surface position that is a position on a surface of the insulator to stress at the first position is set as a stress ratio. In a range of the surface position where the stress ratio is 0.8 or more to 1.15 or less, a length in a continuous range from the first position toward a front end side parallel to the axial line direction is set as a second length. A ratio of the second length to the first length is 0.7 or more.

Abstract: A method of converting a diesel engine to a natural gas engine comprising inserting a spark plug into a diesel fuel injector opening in a cylinder head; installing a throttle body on the diesel engine; installing a throttle body adaptor between a throttle body and an intake manifold of said diesel engine; and modifying a piston, whereby the compression ratio of said piston is decreased during operation of said piston. The method also includes installation of a waste gate and waste gate adaptor and a timing mask.