Abstract: An igniter having a two-piece center electrode assembly that includes an upper electrode member and an iridium lower electrode member. The two electrode members are assembled together by insertion of an expanded head section of the iridium electrode into a blind hole within the upper electrode. The upper electrode is then swaged over the expanded head section to provide a positive mechanical interlock of the two electrode members together. Thereafter, the two components are brazed together by heating of a brazing compound that is pre-loaded into the blind hole prior to insertion of the expanded head section. This assembly results in both a mechanical and metallurgical bond between the two components without subjecting the iridium electrode to deformation that could otherwise result in axial cracking of the iridium material.

Abstract: A spark plug includes: a central electrode; an insulator surrounding the central electrode radially; a metallic shell surrounding the insulator radially; and a ground electrode having a first end connected to the metallic shell and a second end defining a side face. The ground electrode is so bent that the side face of the second end faces the central electrode. The ground electrode contains: a nickel in a range from 58% to 71% by weight, a chromium in a range from 21% to 25% by weight, an iron in a range from 7% to 20% by weight, and an aluminum in a range from 1% to 2% by weight. The ground electrode has a Vickers hardness in a range from Hv 140 to Hv 220 through a Vickers hardness test specified in Japanese Industrial Standard Z2244. A load 9.8 N is applied to the ground electrode in the hardness test.

Abstract: A spark plug including a center electrode which extends in the axial direction and is composed of a body and an electrode whose root end is joined to the end face of the body. The distance between a joined portion of the body and the electrode tip and the face of a free end of the electrode tip is at least 0.15 mm, particularly at least 0.2 mm. A diametral dimension of the electrode tip measured at a position located at the interface between the electrode tip and the joined portion and nearest to the free end of the electrode tip is at least 0.2 mm, particularly at least 0.25 mm, greater than a diametral dimension of the electrode tip measured at the free end. The spark plug suppresses lateral consumption of the electrode tip arising in the vicinity of a joined portion formed through welding.

Abstract: A method of manufacturing an electrode for the use of a spark plus is provided, in which a laser welding process is adopted. In the laser welding process, a tip (2a) is laser-welded to a center electrode (2) of a spark plug (1) at N (e.g., N=8) spots on the tip (2a). Practically, two laser radiation apparatuses (10, 11) are disposed around the tip (2a) at two positions mutually shifted by an angle of “180-360/N (=135 degrees).” Laser beams are radiated by the two radiation apparatuses (10, 11) so that a pair of selected two spots are simultaneously laser-welded (i.e., one welding process). When an even-numbered time of welding process is performed, two spots to be welded are shifted from the last two spots laser-welded in the last odd-numbered time of welding process, and welded simultaneously by the two laser beams.

Abstract: A method for manufacturing a spark plug that can calculate, in measurement of a gap, an accurate gap regardless of inclination of a workpiece (a spark plug) with respect to a measurement device and can manufacture the spark plug at high accuracy as well. Also disclosed is an apparatus for carrying out the same. A plurality of measurement points are determined on the outline (tip edge E2) of a ground electrode spark gap definition portion of a ground electrode W2 facing a spark gap and on the outline (tip edge E1) of a center electrode spark gap definition portion of a center electrode W1. The measurement points represent the outlines of the respective spark gap definition portions. A single measurement point on the outline of one spark gap definition portion is selected as a reference point. A measurement point on the outline of the other spark gap definition portion is found such that the distance between the measurement point and the reference point is the shortest.

Abstract: A spark plug fabricating machine and a method using the same are provided. The fabricating machine is designed to bend a plurality of electrode bars to fabricate L-shaped ground electrodes which have ends facing a center electrode through spark gaps, respectively. The fabricating machine includes a press mechanism and a holder supporting mechanism. The press mechanism works to press the electrode bars welded to a housing retained by a housing holder against a first die. The first die is held between the electrode bars and has curves each contoured to conform with an L-shape of the ground electrodes. Specifically, the press mechanism moves a second die to press each of the electrode bars against a corresponding one of the curves of the first die.

Abstract: A method for producing a spark plug, the spark plug comprising a center electrode, a metal shell and an alumina ceramic insulator disposed between the center electrode and the metal shell, wherein at least part of the surface of the insulator is covered with a glaze layer comprising oxides, the method comprising the steps of: preparing a coated glaze powder so that a surface of each particle of a glaze powder is covered by an elution-suppressing coating layer, the elution-suppressing coating layer suppressing an elution of water soluble component that is contained in each particle of the glaze powder; preparing a glaze slurry by suspending the glaze powder in a water solvent; applying the glaze slurry to a surface of the insulator so as to form a glaze powder-deposited layer; and baking the glaze powder-deposited layer to the surface of the insulator to form the glaze layer by heating the glaze powder-deposited layer.

Abstract: A spark plug has a tubular fitting which is assembled with a center electrode, a ground electrode and an insulator. The fitting has a reach length of at least 12 mm for use in high output-type engines. The fitting is formed with a thread part and a taper part so that the fitting is thread engaged with an engine head and seals a combustion chamber from an outside by a contact between the taper part and a seat surface of the engine head. The fitting is made by cold-forging a low carbon steel to provide the taper surface of a surface roughness of less than 10 &mgr;m and a column part. The column part is machine-cut to provide the thread part thereon. The deflection between the axes of the thread part and the taper part is limited to be less than 0.15 mm.

Abstract: A spark plug and a production method thereof is provided which is designed to improve the high temperature oxidation resistance of a ground electrode without sacrificing the mechanical strength of a weld of the ground electrode with a metal shell. The ground electrode is made of a Ni-based alloy containing 10% or more by weight of Cr and 1.5% or more by weight of Al and joined to the metal shell by resistance welding in a substantially oxygen free atmosphere.

Abstract: A metal member 55 (with a zinc plating layer 56 for prevention of corrosion) having a sliding expected surface that is expected to slide with the other member is immersed into a chromating bath containing a mixture of trivalent chromium salt and a complexing agent for trivalent chromium. And a chromate coat 57 having a film thickness of 0.2 to 0.5 &mgr;m and composed of trivalent chromium at 95 mass % or more of chromium component contained is formed at least on the sliding expected surface. Thereinafter, its chromate coat 57 is subjected to the heat treatment at temperatures from 85 to 255° C., thereby enhancing the sliding property of the chromate coat 57. As a result, the metal member 55 with chromate coat can be easily slid with the other member.

Abstract: A noble metal chip 31′ is superimposed on a surface of a central electrode 3 made of a heat resisting alloy, the main component of which is Ni or Fe, to which the chip is secured so that a superimposed assembly 70 is constituted. A perimeter laser weld portion 10 across the noble metal chip 31′ and a chip securing surface forming portion is formed around the outer surface of the chip of the superimposed assembly 70. Thus, the noble metal chip 31′ is secured to the chip securing surface so that a noble-metal igniting portion 31 is constituted. To form the perimeter laser weld portion 10 which has a maximum outer dimension dmax which is smaller than 2.

Abstract: A method of making a spark plug involves attaching a wear-resistant electrode tip to an electrode, in which the electrode tip incorporates two or more co-extruded metals, in which one of the metals is present in the form of one or more oriented strands disposed in a supportive matrix of the second metal. Preferably, one of the materials used in fabricating the tip is a noble metal, which may be selected from the group consisting of platinum, iridium, and alloys which include one or both of these metals. A wear-resistant spark plug electrode tip according to the invention is preferred to be made in a post or rivet shape, and a rivet is most preferred. A spark plug electrode tip according to the present invention may be attached to the center electrode of a spark plug, to the side electrode, or to both of the center and side electrodes.

Abstract: In a spark plug, an earth electrode (40) has a cladding member (43) made of a Ni-based alloy, a first core member (44) made of pure Cu and contained in the cladding member, and a second core member (45) made of pure Ni and contained in the first one. The second core member is protruded from the first one. A tip of the protruded portion is located to satisfy 0.3 mm≦L1≦L0, L1 being a distance between the protruded tip and a front end of the earth electrode and L0 being a distance between a farthest located edge of a melted portion (61 or 62) around a chip (60) from the front end of the earth electrode and the front end itself.

Abstract: A method for manufacturing a spark plug, the spark plug comprises: a cylindrical metal shell having a portion to be caulked and a tool-engaging portion that is to be attached on an engine; an insulator that is inserted into the metal shell and extends axially; and a caulking metallic mold, the method comprising caulking the portion to be caulked to be fixed to an outer circumferential face of the insulator with the caulking metallic mold, wherein the caulking metallic mold comprises a face, the face comprising a hard carbon film that comprises an amorphous carbon phase, and the face is contact with or sliding to the portion to be caulked.

Abstract: Electrode and spark plug (5) for an internal combustion engine, having an electrode of this type as a center electrode. The electrode includes an electrode base element (20) made of a first material and an end section (30) that is integrally joined to the electrode base element (20), with this end section having a first area (23) that is integrally joined to the first material and is made of a platinum-containing material and having a second area (26) that is integrally joined to the first area (23) and is made of an iridium-containing and/or ruthenium-containing material.

Abstract: A method for manufacturing a spark plug that can calculate, in measurement of a gap, an accurate gap regardless of inclination of a workpiece (a spark plug) with respect to a measurement device and can manufacture the spark plug at high accuracy as well. Also disclosed is an apparatus for carrying out the same. A plurality of measurement points are determined on the outline (tip edge E2) of a ground electrode spark gap definition portion of a ground electrode W2 facing a spark gap and on the outline (tip edge E1) of a center electrode spark gap definition portion of a center electrode W1. The measurement points represent the outlines of the respective spark gap definition portions. A single measurement point on the outline of one spark gap definition portion is selected as a reference point. A measurement point on the outline of the other spark gap definition portion is found such that the distance between the measurement point and the reference point is the shortest.

Abstract: A noble metal chip of which one end is welded to an earth electrode by laser has a sectional area of not less than 0.12 mm2 and not more than 1.15 mm2 at the other end. A length from the surface of the earth electrode to the top surface of the noble metal chip is not less than 0.3 mm and not more than 1.5 mm. An outer surface of the fused junction layer obtained by laser welding between the noble metal chip and the earth electrode has a concave surface, wherein the slope on the plane including the axis of the noble metal chip is curved with a radius R.

Abstract: A method for manufacturing a spark plug, which includes photographing a spark gap as to detect the edges of a center and ground electrode and performing a predetermined treatment on the basis of image information obtained from the photographing step. Also disclosed is an apparatus for carrying out the method. In performing the photographing step, an illumination device 200 is disposed opposite a tip portion of a spark plug, in which a spark gap is to be formed, such that illumination rays pass through the spark gap. A camera 4, which is disposed opposite the illumination device 200 with respect to the tip portion of the spark plug, photographs the spark gap formed between a center electrode W1 and a ground electrode W2.

Abstract: A spark plug fabricating machine and a method using the same are provided. The fabricating machine is designed to bend a plurality of electrode bars to fabricate L-shaped ground electrodes which have ends facing a center electrode through spark gaps, respectively. The fabricating machine includes a press mechanism and a holder supporting mechanism. The press mechanism works to press the electrode bars welded to a housing retained by a housing holder against a first die. The first die is held between the electrode bars and has curves each contoured to conform with an L-shape of the ground electrodes. Specifically, the press mechanism moves a second die to press each of the electrode bars against a corresponding one of the curves of the first die.

Abstract: A method of manufacturing an electrode for the use of a spark plus is provided, in which a laser welding process is adopted. In the laser welding process, a tip (2a) is laser-welded to a center electrode (2) of a spark plug (1) at N (e.g., N=8) spots on the tip (2a). Practically, two laser radiation apparatuses (10, 11) are disposed around the tip (2a) at two positions mutually shifted by an angle of “180-360/N (=135 degrees).” Laser beams are radiated by the two radiation apparatuses (10, 11) so that a pair of selected two spots are simultaneously laser-welded (i.e., one welding process). When an even-numbered time of welding process is performed, two spots to be welded are shifted from the last two spots laser-welded in the last odd-numbered time of welding process, and welded simultaneously by the two laser beams.

Abstract: A spark plug having ground and center electrodes that include a firing tip formed from an alloy containing platinum, tungsten, and yttrium oxide. The firing tip can take the form of a pad, rivet, ball, wire, or other shape and can be welded in place on the electrode. The firing tip provides good erosion resistance, a reduced sparking voltage, good welding and forming characteristics, as well as a minimal occurrence of oxidation of the alloy at the weld area. Desirable ranges of the relative amounts of platinum, tungsten, and yttrium are also disclosed.

Abstract: First and second guides of a guide jig are removed from a tip in a direction normal to an axial direction of the tip. This surely prevents the guide jig from touching and moving the tip when the guide jig departs from the tip. Accordingly, the welding operation can be performed properly under a condition that the tip is accurately positioned on a ground electrode. Thus, it becomes possible to reduce a manufacturing error of the discharge gap formed between a center electrode and the ground electrode.

Abstract: A spark plug includes a metal shell, an insulator coaxially disposed within the metal shell, and a center electrode coaxially disposed in the insulator. The metal shell has a substantially cylindrical base portion, and the base portion has a lower surface with a recess formed therein. A bimetallic ground electrode is affixed to the lower surface of the base portion at the recess thereof. The ground electrode has a central core formed of a first thermally conductive metal which may include copper, and an external sheath surrounding the core, the sheath being made of a second metal which includes nickel. The recess in the lower surface of the metal shell is preferred to be provided as an annular grove extending therearound. The present invention also encompasses a method of making a spark plug, including a step of placing a ground electrode adjacent a lower surface of a spark plug shell, aligned with a recess thereof, such that a tip end of the ground electrode enters into the recess.

Abstract: A firing tip for a spark plug assembly comprises an iridium-rhodium alloy. The firing tip is resistance welded to an electrode for use with a long life spark plug. A thermal expansion dividing layer can be bonded between the electrode surface and iridium-rhodium firing tip to prevent peeling, cracking and/or spalling due to thermal stress fatigue. The thermal expansion dividing material can be a platinum-nickel alloy having a coefficient of thermal expansion compatible with both the electrode material and iridium-rhodium alloy.

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 comprises: a center electrode (3); an insulator (2) provided around the center electrode (3); a metal shell (1)provided around the insulator (2); a ground electrode (4) disposed in opposition to the center electrode (3) so as to form a spark discharge gap; and a sealing-material layer (61) comprising a sealing material, wherein the sealing material comprises talc, and the sealing material is filled in a space between the inner face of the metal shell (1) and the outer face of the insulator (2), so as to seal the space, wherein the sealing material has a filling density of 1.5 g/cm3 to 3.0 g/cm3, or the sealing-material layer (61) comprises at least one of an inorganic material and a silicone binder in an amount of 2 to 7 wt %.

Abstract: A spark plug derives an extended lifetime because a large plurality of sharp edges are provided on the center electrode, the ground electrode, or both to enhance spark propagation. In a first embodiment, the ground electrode has a conventional cantilever shape, but the center electrode extends into coplanar relation to a distal surface of the electrode so that sparks propagate from the cylindrical side walls of the center electrode. In variations of the first embodiment, the number of cantilevered ground electrodes is increased, with the ground electrodes being circumferentially and equidistantly spaced about the center electrode. In another embodiment, the ground electrode has an annular configuration and includes a cylindrical annular wall spaced radially outwardly of the cylindrical sidewall of the center electrode, in concentric relation to the center electrode.

Abstract: A spark plug gap adjustment system is provided which is designed to adjust a spark gap between a ground electrode and a center electrode installed in a spark plug to a target value. The system determines the position of the ground electrode in a given coordinate system to calculate a target distance required to move an end of the ground electrode toward an end of the center electrode for bringing the spark gap into agreement with the target value and moves the ground electrode under pressure by the target distance to define a desired spark gap. This achieves the spark gap adjustment precisely at high speeds.

Abstract: A method of manufacturing a sheathed glow plug, the glow plug comprising: a cylindrical main metal shell; a heat resisting tube mounted to a leading end of a through hole of the main metal shell; a center electrode, that comprises a leading end axial shaft and a rear end axial shaft coaxially welded each other, disposed in a center portion of the through hole of the main metal shell; and an electric heat generator received in the heat resisting tube, the electric heat generator having one end electrically connected to the center electrode, which comprises a process of manufacturing the center electrode comprising the steps of. making a diameter of a connecting end of one of the axial shafts smaller than a diameter of a connecting FR7 end of the other axial shaft; disposing the leading end axial shaft and the rear end axial shaft on the same axis; bringing the connecting ends into contact; and connecting them by a resistance welding after bringing of the connecting ends.

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: Process for producing a middle electrode with precious metal reinforcement, a middle electrode being used with an ignition tipwhich is tapered relative to the middle electrode body, such that a precious metal wire with a cross section which corresponds to the tapered ignition tip is welded flat onto the tapered ignition tipand such that this precious metal wire is cut off at the desired height, with a sharp edge.

Abstract: A spark plug derives an extended lifetime because a large plurality of sharp edges are provided on the center electrode, the ground electrode, or both to enhance spark propagation. In a first embodiment, the ground electrode has a conventional cantilever shape, but the center electrode extends into coplanar relation to a distal surface of the electrode so that sparks propagate from the cylindrical side walls of the center electrode. In variations of the first embodiment, the number of cantilevered ground electrodes is increased, with the ground electrodes being circumferentially and equidistantly spaced about the center electrode. In another embodiment, the ground electrode has an annular configuration and includes a cylindrical annular wall spaced radially outwardly of the cylindrical sidewall of the center electrode, in concentric relation to the center electrode.

Abstract: In a spark plug (100), the resistor composition constituting a resistor (15) contains semiconductive ceramic particles, offering a superior load life characteristic. Also, the value of (&agr;2−&agr;1)/&agr;1>=−0.30, where a value of electric resistance between a terminal (13) and a center electrode (3) is &agr;1 at 20° C. and &agr;2 at 150° C., so that deterioration of the radio frequency noise prevention performance at high temperatures can be effectively suppressed. The resistor composition contains semiconductive ceramic particles whose temperature coefficient of electric resistance shows a positive value, or a negative value of relatively small absolute value, (e.g., TiO2 particles having a rutile type crystalline structure, titanate or zirconate of alkali earth metal elements, titanium suboxide, etc.), or titanium metal.

Abstract: A spark plug assembly is produced in the following manner. Namely, an insulator having an axial through-hole with a metallic terminal fixed at an end thereof and a center electrode fixed at the other end and with packing layers of bulk powders of a conductive glass seal layer, a resistor and the like being formed in the through-hole between the metallic terminal and the center electrode. Subsequently, the spark plug assembly is heated so that the temperature of the side closer to the center electrode is higher than that of the side closer to the metallic terminal along the longitudinal axis of the insulator. Then, the packing layers of the bulk powders within the through-hole are pressed between the center electrode and the metallic terminal by applying pressure to the heated spark plug assembly so that the metallic terminal comes closer to the center electrode along the axis of the through-hole with the position of the center electrode being fixed relative to the through-hole.

Abstract: In a method of manufacturing a ground electrode for spark plug having a better heat conductive core metal such as Cu, Cu alloy or composite metal of Cu and Ni and a better erosion and oxidization resistant coating metal, a composite body of the core and coating metals in which an outer circumference of the core metal with the coating metal is wrapped with the coating metal and an end of the core metal is completely embedded into the coating metal on an end side thereof is prepared. Then, the composite body is cut to form a bar type body having a predetermined length from the end of the coating metal. Simultaneously, the bar type body on a cut end side thereof is formed in each of the core and coating metals to have a narrow portion whose cross sectional area is reduced during a given length thereof extending up to each another end of the core and coating metals.

Abstract: A spark plug has at least two electrodes having ends facing toward one another so as to produce an electrical discharge when an electrical potential is applied to said electrodes, and a layer of an erosion-resistant material applied on each of said electrodes by electro-spark deposition so the lifetime of the spark plug comparing to existing is substantially increased.

Abstract: A spark plug defines a spark gap G in a range of 0.2 mm≦G<0.4 mm, between a noble metal chip disposed on a central electrode and an earth electrode. The noble metal chip has a groove portion facing the earth electrode so that a space, which is larger than a sphere having a diameter equal to or larger than 0.4 mm, is provided in the spark gap G. As a result, a flame core having a diameter equal to or larger than 0.4 mm can be held in the space not to be quenched, resulting in high ignition property of the spark plug.

Abstract: A spark plug for an internal combustion engine comprises a noble metallic firing tip laser welded on the opposing surface of either a central electrode or a grounded electrode. A fused junction layer, formed between the noble metallic firing tip and the base electrode member, contains 40˜70 wt % noble metallic firing tip component. The noble metallic firing tip has a non-fused portion axially extending by a length “L”, where 0.2 mm ≦L≦0.7 mm. The fused junction layer axially extends by a length “M”, where 0.2 mm ≦M≦0.7 mm. And, the relationship B≧1.3A is established when “A” represents the diameter of the noble metallic firing tip and “B” represents the diameter of a contact area at the boundary between the fused junction layer and the base electrode member, where 0.3 mm ≦A≦0.6 mm.

Abstract: In a transfer sheet and a method of transferring a figuration to a ceramic product, an ink is provided by mixing a chromophoric pigment for expressing a desired coloration, a vitreous powder and thermoplastic resin. A sheet of paper or plastic film is prepared on which an appropriate figuration is screen printed with the use of the ink to transfer it to an outer surface of a ceramic product. A thermoplastic separable layer is provided between the mount sheet and a pigment layer. The pigment layer is coated with an adhesive layer.

Abstract: In a method or an apparatus for adequately securing a predetermined distance of a spark discharge gap of a spark plug by means of an image data processing, the image data taken by a camera are processed in a manner that a measurement is made on the image data along each of a plurality of measurement lines nearly parallel to each other connecting the center and ground electrodes so as to cover an entire range of a width length of the center electrode in order to obtain a plurality of values of the distance of the spark discharge gap along the measurement lines.

Abstract: A method of affixing a precious metal to an electrode includes placing a length edge of a generally cylindrical, precious metal wire on an electrode surface and resistance welding the wire to the electrode surface. The precious metal may include platinum.

Abstract: A spark plug derives an extended lifetime because a large plurality of sharp edges are provided on the center electrode, the ground electrode, or both to enhance spark propagation. In a first embodiment, the ground electrode has a conventional cantilever shape, but the center electrode extends into coplanar relation to a distal surface of the electrode so that sparks propagate from the cylindrical side walls of the center electrode. In variations of the first embodiment, the number of cantilevered ground electrodes is increased, with the ground electrodes being circumferentially and equidistantly spaced about the center electrode. In another embodiment, the ground electrode has an annular configuration and includes a cylindrical annular wall spaced radially outwardly of the cylindrical sidewall of the center electrode, in concentric relation to the center electrode.

Abstract: A process of producing a spark plug having an improved consumption resistance is provided. The spark plug comprises a noble metal chip composed of an Iridium (Ir) alloy material and includes an insulator enclosing a center electrode and a ground electrode, which has a facing portion facing the tip of the center electrode. The chip may be disposed on the tip of the center electrode, the facing portion of the ground electrode or both. The Ir alloy material consists of Ir and a metal that has a higher oxidation resistance than Ir and forms a solid solution with Ir at all proportions to prevent oxidation evaporation of Ir. In order to prevent surface cracking, the chip is produced by elongating an ingot of the Ir alloy material through hot forging to form a bar having a fine fiber texture. Then, the chip is hot rolled, hot wire drawn and cut to the desired length.

Abstract: A spark plug for an internal combustion engine is provided with a double ringed ground electrode permanently affixed to the spark plug base. One ring is used for the attachment and the other, held apart by one or more legs, is suspended circumferentially and perpendicular to the longitudinal axis of the spark plug a set distance from the center electrode. The method of manufacturing a spark plug comprises the steps of providing a spark plug base, providing a ring shaped ground electrode with enhancements to accomplish shielding and centering of the piece, providing a welding apparatus for rotable welding of said ring shaped ground electrode to said spark plug base, providing an alignment tool for aligning said ring shaped ground electrode with said spark plug base, aligning the ring shaped ground electrode with said spark plug base and welding the ring shaped ground electrode to said spark plug base to form a spark plug.

Abstract: In a spark plug for an internal combustion engine, a noble metal chip such as an iridium alloy chip is bonded on the tip of a center electrode made of a material such as nickel by laser beam welding. The noble metal chip contains another noble metal such as rhodium having a melting point lower than that of the noble metal chip. By laser welding, a molten bond containing the noble metal melted thereinto from the noble metal chip is formed at the junction of the noble metal chip and the center electrode. Alternatively, the noble metal to be melted into the molten bond may be supplied by a separate noble metal plate. The molten bond thus made has a high bonding strength and a small thermal stress, and thereby durability of the spark plug is improved.

Abstract: An electrode is secured and sealed in an insulator having a bore. The electrode has a shaft and an end plate, with the shaft having a cross section smaller than a cross section of the bore and the end plate having a cross section larger than the cross section of the bore. The shaft of the electrode is inserted into the bore and secured in the bore. A compressive force is applied between the end plate and an opposite end of the electrode, and an electrical current is applied between the end plate and the opposite end of the electrode to heat the electrode while the compressive force is applied. The electrical current and the compressive force are removed after being applied for a time sufficient to heat and expand the electrode so that, upon removing the electrical current, the electrode contracts to establish a seal between the electrode and the insulator.

Abstract: A wear-resistant electrode tip for a spark plug, and a spark plug which incorporates the wear-resistant tip. The wear-resistant tip includes an alloy of platinum, iridium, and tungsten. Surprisingly, by addition of a small amount of tungsten to platinum-iridium alloy, the wear-resistance of a resultant spark plug is greatly improved. The spark plug electrode tip according to the invention is either spherical or rivet-shaped. During manufacture, the spark plug electrode tip is annealed in an annealing furnace. The annealing furnace is preferably either charged with an inert gas such as argon or nitrogen, or is subjected to a vacuum. The electrode tip is, optionally, further externally coated with platinum or a compatible bonding metal alloy before attachment to the electrode. Subsequent to annealing and, where used, to external coating, the spark plug electrode tip is placed in a welding fixture. The tip is then aligned with a spark plug electrode and is resistance welded thereto.

Abstract: A spark plug, especially one for a gas-fueled internal combustion engine has an electrically conducting spark plug body (1), a central electrode (3) which is located in the spark plug body (1) and which is electrically insulated from and projects away from the spark plug body (1), and a ground electrode (4) which is electrically connected to the spark plug body (1) and is made in the form of an annular electrode. The annular electrode (4) surrounds the front part of central electrode (3) such that an annular ignition gap (ZS) is formed between them. Surfaces of the central electrode (3) and the annular electrode (4) bordering the ignition gap (ZS) are provided with precious metal armorings in the form of sleeves (5, 6,), especially of platinum or a platinum alloy. This yields a spark plug with an extremely long service life.

Abstract: A heater-equipped spark plug comprises an insulator having an insulator nose which holds thereon a center electrode in the vicinity of a free end of an axial bore, a lead wire arranged along a surface of the insulator, a heater formed on the insulator nose by baking a metal paste and connected to the lead wire; and a high softening-point glass layer covering and holding the heater in place with an alumina layer interposed between the high softening-point glass and the heater. Preferably, the alumina layer can have a thickness of 20-200 .mu.m and the high softening-point glass layer can have a thickness of 30-500 .mu.m.

Abstract: A spark plug and method of making same, wherein the spark plug includes a platinum alloy tip portion which takes the form of a rivet or a sphere. The tip portion is annealed in an annealing furnace at a temperature between about 700.degree.-1400.degree. C. for a time between about 5-30 minutes. The annealed tip portion is then resistance welded to an electrode of the spark plug. The annealing provides the tip portion with added resistance to corrosion and attack by lead. Preferred embodiments of the spark plug tip material comprise 80% platinum--20% rhodium; 80% platinum--20% iridium; 96% platinum--4% tungsten; and Pt (bal)-Ir(a)%-W(b)%, where "a" ranges from about 15 to 19 percent by weight, "b" ranges from about 1 to 4 percent by weight, and the balance is comprised of platinum and incident impurities, and wherein the sum of iridium and tungsten present ranges from about 16 to 19.