Abstract: A spark plug (10) for a spark ignited internal combustion engine includes a suppressor seal pack (54) interposed between an upper terminal stud (46) and a lower center electrode (60). The suppressor seal pack (54) includes a top layer of conductive glass (52) surrounding the bottom end (50) of the terminal stud (46) and a lower glass seal layer (58) surrounding a head (62) of the center electrode (60). A resistor layer (56) fills the space between the conductive glass layers (52, 58). The resistor layer (56) has a larger first cross-sectional area (76) at its upper end and a smaller second cross-sectional area (78) at its lower end. A reducing taper (80) establishes a progressive transition between the greater and lesser cross-sectional areas (76, 78). The reducing taper (80) is located in a large shoulder region (LS) which is defined as the longitudinal dimension between the theoretical reference point (70) at the filleted transition (26) and the theoretical reference point (68) at the upper seat (17).

Abstract: A method for producing a spark plug, the spark plug including: a center electrode; an insulator which holds the center electrode therein in a state where a tip end portion of the center electrode protrudes therefrom; a metal shell which holds the insulator therein; a ground electrode which is fixed to the metal shell, the ground electrode having an inner side face having a width that is smaller as it advances toward a tip end side, in a portion of the inner side face positioned between a pair of tapered faces; and a discharge portion which is bonded to the inner side face of the ground electrode by laser welding so as to attain a diameter of 0.8 mm or less and a height of 0.5 mm or more, a discharge gap being formed between the discharge portion and the tip end portion of said center electrode, the method including: forming the tapered faces before the discharge portion is laser-welded to the inner side face.

Abstract: A spark plug including: a cylindrical metal shell; a cylindrical insulator fixed to the metal shell; a center electrode having its leading end protruding from a leading end of the insulator and its trailing end fixed to the insulator; and a ground electrode having one end fixed to the metal shell and forming a discharge gap between the ground electrode and the center electrode. The ground electrode includes a precious metal alloy portion containing: 50 weight % or more of a first component of one of Rh and Pt; less than 50 weight % of a second component of the other of Rh and Pt; and optionally a third component containing at least one of: Ni in an amount of less than 7 weight %; and Zr in an amount of less than 2 weight % the content of the third component being less than that of the second component.

Abstract: A spark plug having a center electrode and a ground electrode wherein the spark portion of at least one of the center electrode and ground electrode includes a base material and a protective material that substantially prevents corrosion of the base material.

Abstract: A spark plug for an internal combustion engine is provided which includes a metal shell, a porcelain insulator, a center electrode, a main ground electrode, and auxiliary ground electrodes. Each of the auxiliary ground electrodes has an inner side surface facing the center electrode through the porcelain insulator to define an auxiliary spark gap between itself and a nose of the porcelain insulator so as to occupy a minimum distance between the porcelain insulator and the auxiliary ground electrode. This avoids a great local increase in electrical field strength on the auxiliary ground electrode to minimize excessive discharge within the auxiliary spark gap to enhance carbon fouling resistance and durability of the spark plug.

Abstract: A spark plug for an internal-combustion engine is provided wherein the central and ground electrodes exhibit a long service life and wherein the fatigue strength at high temperatures is improved. The ground electrode is made from an alloy comprised of nickel (Ni) as a primary component, chromium: 20-30% by weight, iron: 7-20% by weight, aluminum: 1-3% by weight, titanium: 0.05-0.5% by weight, manganese: not higher than 0.1% by weight, silicon: not higher than 0.1% by weight, and carbon: not higher than 0.5% by weight. The alloy further includes at least one specific element selected from zirconium, yttrium, neodymium, cerium, lanthanum and samarium. Further, the total content of the specific element group is 5% or more of the aluminum content and is not higher than 1% by weight.

Abstract: In a spark plug composed of a center electrode and an earth electrode, at least one of confronting portions of the center electrode and the earth electrode which are in opposed relation to each other is constructed with a noble metal chip containing Pt as a principal component. The noble metal chip is joined to an electrode base material of the center electrode or the earth electrode and is made of an alloy comprising Pt and another element. In this noble metal chip, Pt is contained as a first component, while Re is contained as a second component. The employment of this noble metal chip enables suppressing the growth of platinum balls even in a high-temperature atmosphere.

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

Abstract: A spark plug according to the present invention includes a metal shell, an insulator, a cylindrical center electrode, a first ground electrode, and a second ground electrode. The first ground electrode is aligned with the center electrode in the axial direction of the center electrode to form a first spark gap, across which normal sparks are discharged when the insulator is not fouled with carbon. The second ground electrode is aligned with the center electrode in the radial direction of the center electrode to form a second spark gap, across which side sparks are discharged when the insulator is fouled with carbon. The spark plug has an improved structure where dimensional parameters A, T, B, C, L, D, and E are specified to be in suitable ranges that are determined through experimental investigation. The improved structure ensures a high ignition capability and a long service life of the spark plug.

Abstract: In a spark plug 100, the nickel content of a center electrode 20 is greater than that of a ground electrode 30. This enhances resistance to spark-induced consumption of the center electrode 20. Also, the ground electrode 30 to which a noble-metal chip 91 is joined exhibits high resistance to spark-induced consumption. Accordingly, the spark plug 100 can be attached to either of a negative-polarity cylinder in which the center electrode 20 assumes a negative polarity, and a positive-polarity cylinder in which the center electrode 20 assumes a positive polarity. The noble-metal chip 91 is joined only to the ground electrode 30, and a noble-metal chip is not joined to the center electrode 20.

Abstract: A spark plug comprises an electrically-insulating sleeve (12) extending along a central axis (14) of the plug, a first electrode (16) having a tip (20), an electrically-conducting shell (22), and a second electrode (26) mounted on the shell, the second electrode having a tip (28). The tips (20 and 28) have spark surfaces (30, 32) which define a spark gap (34) of the plug. The spark surfaces (30, 32) are inclined at different angles (?1, ?2) relative to a plane (36, 38) extending normally of said central axis (14) of the plug so that said spark gap (34) varies in width along the length of the gap with the narrowest point (X1) of the gap being further from the connection between the second electrode (26) and the shell (22) than the other end of the gap.

Abstract: A spark plug includes a metal shell, an insulator, a center electrode, and a ground electrode. The metal shell has a threaded portion with an outer diameter of equal to or less than 10 mm, or equal to 12 mm for installing the spark plug in an internal combustion engine. The dimensional parameters in the structure of the spark plug, such as a clearance X between the center electrode and the insulator, a surface-creeping distance Y outside the metal shell, a protruding length Y1 of the insulator, an air pocket size Z, and a surface-creeping distance W inside the metal shell satisfy the dimensional relationships defined through experimental investigation in the invention. The structure ensures a high capability of the spark plug to ignite the air-fuel mixture even when the insulator thereof is fouled with carbon.

Abstract: A spark electrode assembly has an elongate electrode with an inner insulator arranged for operable attachment to a support structure. The inner insulator surrounds the electrode with one end of the electrode positioned adjacent a ground element across a spark gap and another end of the electrode extending relative to the support structure for attachment to a source of electrical power. An outer insulator is spaced radially outwardly from the inner insulator and surrounds the inner insulator generally adjacent the end of the electrode adjacent the ground element. The inner and outer insulators cooperate to inhibit the formation of a continuous lubrication layer thereon, thereby establishing an area generally free from the lubrication layer between the end of the electrode adjacent the ground element and the support structure.

Abstract: Carbon fouling adhered on an insulator tip of a spark plug of the present invention is burnt down by a leak current during an inductive discharge period, due to a promoted ionization before beginning a capacitive discharge, in such an arrangement of a central electrode that a border portion of a body and narrowed portion is positioned in an insulator. The carbon burning-down effect is further improved by a narrow projection provided with an earth electrode, due to increased inductive energy and extended inductive discharge time period. This is because an electric field in a discharge gap is raised, thereby decreasing a discharge voltage and suppressing an energy emitted from a coil during the capacitive discharge.

Abstract: In a bond step, one end of ground electrode is bonded to a metallic housing. In a provisional bending step performed after the bonding step, an intermediate portion of the ground electrode is bent with a pressing die so that the other end of the ground electrode is opposed to a distal end surface of a center electrode. In a regular bending step performed after the provisional bending step, the position of the other end of the ground electrode is adjusted so as to adjust the dimension of a spark gap. Receiving dies are prepared for regulating a shift range of a distal end surface of the other end of the ground electrode in a direction perpendicular to an axial line of the center electrode in the process of bending the intermediate portion of the ground electrode in the provisional bending step. In the provisional bending step, the intermediate portion of the ground electrode is bent until the distal end surface of the other end of the ground electrode is brought into contact with the receiving dies.

Abstract: A spark plug for an internal combustion engine is proposed, having at least two electrodes (9, 11), one of which at least two electrodes is at least one middle electrode (11) and another electrode of the at least two electrodes is at least one ground electrode (9), and between the at least one ground electrode (9) and the at least one middle electrode (11), a spark gap (13) is formed. Each of the at least two electrodes (9, 11) has an electrode base body (93, 113). At least one electrode has a region (95, 115) that is highly resistant to electrode erosion and that forms at least a part of the end face, oriented toward the spark gap, of the electrode (97, 117). The highly electrode-erosion-resistant region (95, 115) comprises an alloy which has at least the elements iridium and nickel.

Abstract: An ignition device such as a spark plug having ground and center electrodes, at least one of which includes a firing tip formed from an alloy containing iridium, rhodium, tungsten, and zirconium. With the inclusion of tungsten and zirconium in the alloy, the percentage of rhodium can be kept relatively low without sacrificing the erosion resistance or reduced sparking voltage of the firing tip. In one embodiment, the firing tip contains 2.5% rhodium, 0.3% tungsten, 0.07% zirconium, and the balance iridium.

Abstract: Ir alloy firing tips are bonded on opposed surfaces of a center electrode and a ground electrode facing to a discharge gap. The configuration of a cross-sectional area of the Ir alloy firing tip taken along a plane perpendicular to the axis of the Ir alloy firing tip is out of round. In this cross-sectional area of this Ir alloy firing tip, when it is assumed that a circumscribed circle has a largest diameter A among virtual circles each contacting at least three portions of a visible outline of the cross-sectional area and an inscribed circle has a largest diameter B among inscribed circles each being coaxial with the circumscribed circle, a ratio of the diameter B to the diameter A (i.e., B/A) is equal to or larger than 0.8 and is less than 1.0.

Abstract: The invention relates to a low-pressure gas discharge lamp which includes at least one discharge vessel and at least two capacitive coupling-in structures and operates at an operating frequency f. In order to achieve a better efficiency in combination with a small structural volume, a high luminous flux, a low operating voltage, a low electromagnetic emission, a high resistance against switching transients and a long service life for the low-pressure gas discharge lamp, it is proposed to form each capacitive coupling-in structure from at least one dielectric having a thickness d and a dielectric constant ?, each dielectric being subject to the condition d/(f.?)<10?8 cm.s. A substantially larger amount of light can thus be generated per lamp length (lumen/cm).

Abstract: An ignition device such as a spark plug having ground and center electrodes, at least one of which includes a firing tip formed from an alloy containing iridium, rhodium, tungsten, and zirconium. With the inclusion of tungsten and zirconium in the alloy, the percentage of rhodium can be kept relatively low without sacrificing the erosion resistance or reduced sparking voltage of the firing tip. In one embodiment, the firing tip contains 2% rhodium, 0.3% tungsten, 0.02% zirconium, and the balance iridium.

Abstract: A spark plug comprises an electrically-insulating sleeve (12) extending along a central axis (14) of the plug, a first electrode (16) having a tip (20), an electrically-conducting shell (22), and a second electrode (26) mounted on the shell, the second electrode having a tip (28). The tips (20 and 28) have spark surfaces (30, 32) which define a spark gap (34) of the plug. The spark surfaces (30, 32) are inclined at different angles (&thgr;1, &thgr;2) relative to a plane (36, 38) extending normally of said central axis (14) of the plug so that said spark gap (34) varies in width along the length of the gap with the narrowest point (X1) of the gap being further from the connection between the second electrode (26) and the shell (22) than the other end of the gap.

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

Abstract: In a spark plug (100), at least one side face of the ground electrode (4) is made of an electrode base material comprising an Ni alloy containing 21-25% by mass of Cr, 1-2% by mass of Al, 7-20% by mass of Fe and 58-71% by mass of Ni. The noble metal wear resistant portion (32) is joined to the electrode base material via a welding portion (W). When the linear expansion coefficients at 800 K of the noble metal constituting the noble metal wear resistant portion (32) and the electrode base material are represented by &agr;1 and &agr;2, respectively, &Dgr;&agr;≡&agr;2−&agr;1 is adjusted to be 4.55×10−6/K or less. The outer diameter of the noble material wear resistant portion (32) is set from 0.6 mm to 1.5 mm.

Abstract: A method for manufacturing spark plugs with central and body electrode(s) armed with noble metal inserts, in which the tip of a central electrode which is pyramid or conic shaped with a base diameter (d), is liquefied by being pressed against a noble metal ball with diameter (d) that is mounted in the face of a welding electrode under a defined welding contact pressure and defined welding parameters. The liquefied material of the central electrode tip partially flows around the noble metal ball, and the welding electrode is separated from the central electrode after the liquefied material of the central electrode tip has solidified with noble metal ball embedded therein.

Abstract: A method for manufacturing a spark plug having a center electrode, an insulator disposed around the center electrode, a metallic shell disposed around the insulator, a ground electrode disposed in opposition to the center electrode so as to form a spark discharge gap therebetween, and a chip of a high melting point metal welded to at least the ground electrode. A zinc-based plating layer is formed on the surface of a metallic shell assembly composed of the metallic shell and the ground electrode, a root-end of which is welded to the metallic shell. Subsequently, the zinc-based plating layer is removed from a free-end portion of the ground electrode. The chip of a high melting point metal is welded to the free-end portion of the ground electrode from which the zinc-based plating layer has been removed.

Abstract: A spark plug having a center electrode 2 formed from an electrode base material 2n, which is made of an Ni alloy containing an alloy component (e.g., Cr) capable of forming an oxide semiconductor having a resistivity of negative temperature coefficient. Thus, a corrosion suppression layer originating from the components of the electrode base material is formed on the surface of a tip end portion of the insulator 3, so that corrosion (channeling) of the surface of the tip end portion of the insulator 3 due to creeping spark discharge can be effectively suppressed. In addition, when the constituent metal of the electrode base material 2n has a coefficient of thermal conductivity of 17 to 30 W/m·K, the heat transfer performance of the electrode is enhanced, so that durability against electrode consumption can be greatly improved.

Abstract: In a side ground electrode type of spark plug, sizes of discharge members are optimized to reduce a useless portion in discharging to improve discharge wear resistance. A first discharge member mainly comprising Ir alloy is welded to the central electrode. A second discharge member comprising Ir metal circle plate is welded to the ground electrode, wherein a side surface of the first discharge member confronts a surface of the second discharge member to form a spark discharge gap G≧0.2 mm, D(a width of the first discharge member)≧1.6 mm. |A−D|≦(G+0.5 mm). A is a width of the second discharge member. Moreover, D≦5.0 mm. A maximum cross-sectional area of weld portion between the first discharge member and the central electrode ≦8 mm2. This weld portion has distance L to the second discharge member. L≧G.

Abstract: At least one of a center electrode tip and a ground electrode tip is made of an iridium alloy. A discharge gap, formed between the center electrode tip and the ground electrode tip, is less than 1.1 mm. And, cross sections of the center electrode tip and the ground electrode tip are equal to or smaller than 0.95 mm2 in a spherical region where a distance from a midpoint of the discharge gap is within 0.6 mm.

Abstract: In producing a spark plug including a central electrode having a first chip including noble metal and an earth electrode having a second chip including the noble metal, a spark gap being disposed between the first and second chips, a chip including the noble metal. The chip is welded to an end of the central electrode and to an end of the earth electrode. The welded chip is cut to form the first and second chips and the spark gap.

Abstract: A spark plug having a discharge portion formed of a noble-metal chip, the spark plug being capable of restraining wear observed on a slenderized discharge portion in particular. Discharge portion (31) includes noble-metal chip (31′). Dimension D is 0.3-0.8 mm; and H is 0.4-2 mm, where D (mm) is a diameter representing the outside diameter of the noble-metal chip, and H (mm) is a discharge portion thickness representing the shortest distance between the periphery of a discharge face (31t) and a corresponding end edge of a weld zone W where a center electrode (3) and the noble-metal chip (31′) are welded. Further, the noble-metal chip (31′) contains a predominant amount of Ir and 0.5-8% by weight Ni.

Abstract: At least one of a center electrode tip and a ground electrode tip is made of an iridium alloy. A discharge gap, formed between the center electrode tip and the ground electrode tip, is less than 1.1 mm. And, cross sections of the center electrode tip and the ground electrode tip are equal to or smaller than 0.95 mm2 in a spherical region where a distance from a midpoint of the discharge gap is within 0.6 mm.

Abstract: A spark plug includes a metallic shell having a stepped portion an insulator disposed inside the metallic shell, while being engaged with the stepped portion of the metallic shell, and having an axially extending through hole; a center electrode fixed within the through hole of the insulator; and a ground electrode having a tip end portion bent toward the center electrode to thereby form a spark discharge gap. The insulator is formed such that the outer diameter of the insulator decreases toward the tip end side from an engagement position at which the insulator engages the stepped portion and such that the diameter decreases stepwise at an axial position between the engagement position and the tip end of the insulator. The diameter reduction ratio Y1=D1/d1 is 0.

Abstract: A tip portion of a center electrode 2 of a spark plug includes a tapered portion which is tapered such that the diameter reduces axially frontward. A convex portion 2k is formed at an axially intermediate position of the tapered portion so as to project radially outward with respect to an axis 30. The axially measured distance L2 between the vertex of the convex portion 2k (the convex vertex P) and the tip face 1D of an insulator is set to less than 0.5 mm. A heat release acceleration metal portion 2m, which is made of Cu or an alloy that contains a predominant amount of Cu, is present at a position located a distance L3 of 1.5 mm as measured axially rearward from the convex vertex P in order to suppress spark erosion by lowering the temperature of the center electrode 2. The heat release acceleration metal portion 2m is formed such that an electrode base material 2n, which encloses the heat release acceleration metal portion 2m, has a wall thickness W of not less than 0.

Abstract: In accordance with the present invention, there is provided a spark plug for producing a plurality of sparks which define a three-dimensional volume in a combustion chamber of an internal combustion engine. The spark plug is provided with an insulative body having a support end. The spark plug is further provided with a central positive electrode which extends through the insulative body. The central positive electrode has a spark ignition end. The spark plug is further provided with a conductive outer shell which is disposed about the insulative body. The spark plug is further provided with at least two neutral electrodes which are attached to the support end of the insulative body. One of the neutral electrodes is adjacent to the spark ignition end of the central positive electrode and spaced apart therefrom to form a spark gap therebetween. Another one of the neutral electrode is adjacent to the conductive outer shell and spaced apart therefrom to form a spark gap therebetween.

Abstract: A noble metal tip of a grounding electrode is inclinedly disposed with respect to a noble metal chip of a central electrode by an angle &agr; so that a discharging gap is narrow at a side closer to one end of the grounding electrode and wide at the opposite side closer to the other side of the grounding electrode. When the discharging gap has expanded to a certain extent due to exhaustion of the noble metal tips of the electrodes, the re-gapping adjustment is performed to decline or push the noble metal tip of the grounding electrode toward the noble metal tip of the central electrode so as to decrease the angle &agr;. Thus, the discharging gap can be adjusted to an adequate value.

Abstract: A spark plug is provided which comprises a center electrode and a ground electrode having at a free end portion thereof a discharge surface which is opposite to an axial end surface of the center electrode to provide therebetween a spark gap, wherein the center electrode has a center electrode tip forming the axial end surface thereof, the center electrode tip being made of a material containing Ir as a major constituent, and wherein G≦2A+0.5 where G is a spark gap (mm) and A is the distance (mm) between a first imaginary line and a second marginal line.

Abstract: An insulator for spark plug comprises an alumina-based sintered body comprising: Al2O3 as a main component; and at least one component (hereinafter referred to as “&bgr; component”) selected from the group consisting of Ca component, Sr component and Ba component, wherein the alumina-based sintered body comprises particles comprising a compound comprising the &bgr; component and Al component, the compound having a molar ratio of the Al component to the &bgr; component of 4.5 to 6.7 as calculated in terms of oxides thereof, and has a relative density of 90% or more.

Abstract: A first gap discharge gap is located between a front end of a center electrode and a front side of a first ground electrode of a spark plug. A second discharge gap is located between a front end of a second ground electrode and a front side of the center electrode. Respective dimensional relationships between various of these elements are established to promote self-cleaning of the spark plug.

Abstract: A spark plug includes a chip made of iridium. The distance E between the chip and a copper core of a core rod of the center electrode is not greater than 3.5 mm. The core rod has a diameter D1 of 1.4 mm to 2.6 mm. The ratio of a chip diameter D2 to the core rod diameter D1, or D2/D1, is not greater than 0.50.

Abstract: The present invention relates to improved spark plugs for igniting a fuel charge in an internal combustion engine, and is particularly concerned with an improved spark plug construction which improves combustion pressure and fuel mileage and diminishes exhaust pollution. The spark plug includes a center electrode and a ground electrode. In one embodiment, the ground electrode has an elongate edge that extends past the major dimension of the center electrode. The elongate edge can either be positioned substantially tangentially to or within a “zone” outside of the center electrode's periphery. Preferably, the edge of the center electrode and the lower interior edge of the ground electrode will be presented towards one another such that the edges are or are among the closest portions within the sparking region.

Abstract: A gasket for a threaded element such as a spark plug to be screwed into a threaded hole of a support such as a cylinder head is provided. The threaded element has a threaded portion and an annular seat portion. The gasket is installed on the threaded element and compressed between the seat portion and an outer surface of the support around a threaded hole, when the threaded element is screwed into the threaded hole, to provide a seal between the threaded portion and the threaded hole. The gasket is formed from an annular sheet metal and in the form of an annular strip of a cross section including a plurality of bent portions. The cross section is made by a plane including a center axis of the gasket and of a such a bent shape as to enable an imaginary reference line which is located on the above described plane and parallel with the center axis, to cross at least three portions of the cross section. The initial axial size of the gasket, i.e.

Abstract: In a spark plug for an internal combustion engine, having a fitting screw portion with a diameter of M10. An axial distance A between an end surface of a fitting piece and an other end surface of a noble metal chip is set within a range of 3 mm to 8 mm, and the other end surface has an area S set within a range of 0.07 mm2 to 0.55 mm2. One end portion of a ground electrode is a fitted to the end surface of the fitting piece, and the other end portion is inclined toward the noble metal chip at a slant angle of &thgr; with respect to an axial length so as to provide a discharge gap G between the noble chip and the other end portion. The slant angle &thgr; is set within a range of 40°to 70°, and the discharge gap G is set within a range of 0.7 mm to 0.9 mm. According to the structure, it is possible to sufficiently protrude the spark position of the spark plug.

Abstract: A spark plug is disclosed. The spark plug has no iron tower electrode. A lower end of the spark plug is directly formed with a circular edge electrode. A predetermined gap is formed between the edge electrode and the central electrode. The end surface of the insulating ceramic enclosed by the electrode head is lower than the height of the end surface of the edge electrode. The electrode head of the central electrode ignites to the edge electrode at the housing. One or more conductive rings are installed on the insulating ceramic so as to be formed with a multiple ignition way. Thereby, a preferred explosion may be generated and thus no coal will be accumulated.

Abstract: A method of coating a metal spark plug shell with a titanium-containing compound involves placing the shell into a vacuum chamber, lowering the pressure in the chamber to a level below atmospheric pressure, and applying a protective coating, containing a titanium compound, to a portion of the exterior of the spark plug shell by physical vapor deposition. A preferred titanium compound is titanium nitride. The coating on the spark plug shell improves corrosion resistance thereof, provides a pleasing appearance, and resists seizing of the spark plug in place in a cylinder head portion of an engine. A spark plug incorporating the coated shell is also disclosed.

Abstract: An improved structure of an ignition sparking plug having a grounding electrode and a central electrode is disclosed. The grounding electrode has a tip end with respect to the central electrode so that the only a small part of the central electrode is shielded by the grounding electrode. Thereby, mixed gas enters into the space between the grounding electrode and the central electrode rapidly so as to be ignited and then explode quickly to push the piston. Therefore, the piston can move reciprocally. Since the grounding electrode has a smaller volume, the generated spark has a large volume and absorbs a little thermal energy. Since electric discharging occurs in a tip point, the efficiency of ignition is high so as to improve the air to oil ratio in the cylinder and thus oil is saved and exhausted waste is reduced.

Abstract: In a spark plug, a chip or a plurality of chips made of Ir alloy are bonded by resistance welding through a stress releasing layer on the respective chip mounting portions of the center and ground electrodes made of Ni base alloy. At the temperature of 900° C., the value of Young's modulus of the stress releasing layer is less than those of the Ir alloy and the Ni base alloy and, further, the value of linear expansion co-efficient of the stress releasing layer is intermediate between those of the Ir alloy and the Ni base alloy. The bonded junction of the chip and the stress releasing layer is shaped as a curved surface.

Abstract: The shortest distance (F, F′) from an end face (11A) of each ground electrode (11, 11′) to a porcelain insulator (1) is made smaller than the shortest distance (G, G′) from the end face (11A) of each ground electrode (11, 11′) to the peripheral side surface of a central electrode (2, 2′). An anti-spark consumption member (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32) is secured to a portion of the central electrode (2, 2′) in such a way that it is spaced at least a specified distance (H) of from the end face of the porcelain insulator (1).

Abstract: A spark plug includes a spark portion of an Ir-based metal and a resistor disposed between a center electrode and a metallic terminal and adapted to establish an electric resistance of not less than 10 k&OHgr;, preferably not less than 15 k&OHgr;, but not greater than 25 k&OHgr; as measured between the center electrode and the metallic terminal. Thus, even in a system in which an ignition coil is connected directly to the spark plug without use of a high tension cable, an electrical discharge with a relatively weak current, such as a glow discharge, can be maintained stably, so that even at high speed or heavy load operation, consumption of the spark portion caused by volatilization of Ir through oxidation can be suppressed, thereby extending spark plug life.

Abstract: A spark plug for attachment to a cylinder head includes a metallic shell including a tip-end side having an open tip end and a tail-end side having an open tail end. The metallic shell has an attachment screw portion peripherally formed at the tip-end side thereof. The spark plug also includes a ground electrode attached onto the tip-end side of the metallic shell, and an insulator including an axial through-hole formed therein and a tail end portion having a tail end. The insulator is disposed within the metallic shell such that the tail end portion of the insulator substantially projects from the tail end of the metallic shell. A center electrode has a tip end and being disposed within the through-hole and facing the ground electrode to define a spark discharge gap therebetween, and a metallic terminal has a tail end and being disposed within the through-hole of the insulator such that the tail end of the metallic terminal is set back from the tail end of the insulator into the through-hole.

Abstract: In a spark plug, molten portions formed by bonding by laser welding a leading end of an Ir alloy element to a leading end of a Ni base alloy base element of a ground electrode to overlap with each other, where Ir alloy and Ni base alloy are mixed with each other, are located outside a region within which the spark is regularly discharged. Another leading end of the Ni base alloy base element is fixed to the housing and both of the Ir alloy element and the Ni base alloy base element extend perpendicular to a housing so that another leading end of the Ir alloy element may face a leading end of the center electrode with the spark discharge gap therebetween.