Abstract: In a spark plug which has an electrode metal made from a heat- and erosion-resistant nickel alloy whose front end has a noble metal tip made of iridium or ruthenium, the electrode metal has a thermal conductivity of at least 30 W/m.multidot.K so as to avoid rapid temperature rise in the noble metal tip to thereby minimize oxidation-evaporation and attendant wear thereof.

Abstract: In a spark plug having a nickel-based electrode whose front end has a firing tip made from a ruthenium- or iridium-based metal in which an oxide of a rare earth metal group is dispersed, the firing tip is welded to the electrode by a solidified alloy layer having a component of the electrode and a component of the firing tip. The firing tip contains the oxide of the rare earth metal group in a range of 5.about.15% by volume (V), and an average grain size (D) of the oxide is in a range of 0.05.about.3.0 .mu.m with a quantitative relationship as D.ltoreq.-0.34V+5.1.

Abstract: In a spark plug, a nickel-alloyed center electrode has a front end which has a constricted end forming a spark gap with a ground electrode by way of a noble metal firing tip. The noble metal firing tip is secured to a front end surface of the constricted end by applying a laser beam welding to an interface between the constricted end and the firing tip all through their circumferential length so as to form a wedge-shaped welding solidification portion.

Abstract: In a center electrode for a spark plug, the center electrode is made of a heat-conductor core cladded with a nickel-alloyed metal. A recess is provided on the front end surface of the nickel-alloyed matrix and the columnar tip is made of a precious metal and fit in the recess in such a manner that a front end of the tip protracts from the recess. The outer surface of the tip is welded to an inner surface of the recess. The dimensional relationship of the components of the spark plug A, B, C, D, E, F and G is as follows: 0.3 mm.ltoreq.A.ltoreq.0.8 mm, 1.2A.ltoreq.B.ltoreq.3A, 0.1 mm.ltoreq.(C-A)/2.ltoreq.0.5 mm, D.ltoreq.(C-A)/2, E.ltoreq.B/4, 0 mm.ltoreq.F.ltoreq.0.5 mm and A/5.ltoreq.G.ltoreq.

Abstract: In a method of making a spark plug, a recess is provided on an end surface of the electrode blank metal. A straight neck portion is provided around the recess, and forming a tapered surface connecting from the straight neck portion toward an opposite side of the recess. A disc-shaped tip is placed in the recess of the electrode blank metal. The disc-shaped tip is pressed against an inner bottom of the recess in the axial direction of the electrode blank metal, and a laser beam welding is applied to an outer wall of the recess substantially all through its circumferential length by rotating the electrode blank metal.

Abstract: In a method of manufacturing a center electrode for a spark plug, a composite column is provided by enclosing a heat-conductor core into a nickel-alloyed clad by means of plastic working. A front end of the nickel-alloyed clad is severed to define a severing and surface with which an axial bore is provided to reach to a front end of the heat-conductor core. A straight neck portion around the axial bore is provided by diametrically reducing the front end of the nickel-alloyed clad. A firing tip made of precious metal is placed in the axial bore. A front end of the firing tip extends beyond the front end of the straight neck portion, while a rear end of the firing tip comes to be in thermally transferable contact with the front end of the heat-conductor core. An outer surface of the firing tip is bonded to an inner surface of the axial bore by means of laser beam welding or electron beam welding.

Abstract: In an outer electrode, a rear end of which is securely connected to a metallic shell of a spark plug by means of welding to form a spark gap between a front end of the outer electrode and a firing tip of a center electrode which is concentrically placed within the metallic shell through an insulator, a middle core which is provided which is made of copper, and the middle core is clad by a heat and spark-erosion resistant metal. A centermost core is clad by the middle core. The centermost core is made of a similar metal to the metallic shell, and rear end of the centermost core is welded to the metallic shell so as to reinforce a welding portion between the metallic shell and the outer electrode.

Abstract: A ceramic insulator structure for use in a spark plug is manufactured by mixing granular or powdery particles of AlN, Si3N.sub.4 or Al.sub.2 O.sub.3 with an organic binder and an auxiliary sintering agent, the average spherical diameter of the particles making up the resulting ceramic mixture being in the range 20-100 microns. The ceramic mixture is then pressed in a mold into a desired shape and sintered at a temperature of 1600.degree.-2000.degree. C.

Abstract: In a spark plug insulator, an electrically conductive sealant in provided to connect a center electrode to a terminal electrode which are provided within an axial bore of the tubular insulator. The glass sealant being made from the following materials: (a) granular aluminosilicate glass consisting of silica (SiO.sub.2), alumina (Al.sub.2 O.sub.3), alkali metal oxides and alkali earth metal oxides, granular size of the aluminosilicate glass being more than 250.mu.; (b) granular silicate glass, granular size of which is less than 74.mu.; and (c) powdered metal, granular size of which is less than 74.mu., and selected from the group of nickel, chromium and nickel-chromium alloy.

Abstract: In a spark plug for use in an internal combustion engine, a nickel-alloy based center electrode is placed into a metallic shell through a tubular insulator. An outer electrode is depended from the metallic shell to from a spark gap with a front end of the center electrode. A spark portion is secured to the center electrode, and comprising a nickel-alloy based tubular clad tip and an iridium or iridium-alloy based inner core fit into the clad tip. A rear open end of the clad tip is welded to a front end surface of the center electrode. A dimensional relationship among the center electrode, the inner core and the clad tip being determined as follows: A.ltoreq.1.5mm, 0.2mm.ltoreq.B.ltoreq.0.8mm, C.gtoreq.0.1mm, where A is an outer diameter of the front end surface of the center electrode, B is an outer diameter of the inner core, while C is an outer diameter of the tubular clad tip.

Abstract: A rapid heat-dissipating type spark plug has a metallic shell which is made of material having a tensile stress of more than 40 Kg/mm.sup.2 with a thermal conductivity of more than 60 W/m.multidot.k.In another embodiment, there is provided a ground electrode which is made of nickel or nickel alloy.The ground electrode is connected to the metallic shell through a metallic ring which is made of different metal from the metallic shell such as steel, stainless steel or nickel alloy.

Abstract: A metal body has a heat- and corrosion-resistant surface which is composed of a layer of nickel plating applied to a surface of a metal base and an electrolytic chromate film formed over the nickel plating. Preferably, the chromate film has a thickness of 3 .mu.m or less. The chromate film may have a color imparted upon its formation by an electrolytic chromate treatment. A metal sheel of a spark plug may be mentioned as one example of the metal body.

Abstract: A spark plug structure comprising; a cylindrical metallic shell; a joint type insulator having a center bore, and including a front half piece and a rear half piece, each made of a tubular aluminum nitride (AlN), and the front and rear half pieces being joined at their respective end by means of a glass sealant, and encased into the metallic shell; a center electrode placed into the center bore of the insulator; an elongated terminal placed into the rear half piece of the insulator; an electrically conductive glass provided to seal respective spaces appeared between the center electrode, insulator and the terminal; the front half piece having an elongated projection, the length of which is more than 2.0 mm, and the rear half piece having a recess the depth of which is more than 2.0 mm, the front and rear half pieces being jointed at the projection and the recess by means of an annular glass sealant which has thickness of less than 2.0 mm and length of more than 2.0 mm.

Abstract: A spark plug in which a noble metal tip welded to the leading end face of a center electrode is in the form of a fine wire while a noble metal tip welded to the leading end face of a ground electrode is in the form of a wire or column; and when each of the noble metal tips is electrically welded to the leading end face of the center or ground electrode, the end of the noble metal tip in contact with the leading end face of the center or ground electrode is enlarged to form a flange. Therefore the strength between the welded joint between the noble metal tip and the center or ground electrode is satisfactorily increased.

Abstract: A spark plug is disclosed having central and ground electrodes made of a nickel-base alloy and a chip made of a platinum-nickel alloy having good bonding properties to the nickel-base alloy joined to the spark discharge surface of at least one of the central and ground electrodes. In another embodiment, the chip has an intermediate layer made of the platinum-nickel alloy and a top surface layer made of platinum or a platinum-base alloy having a higher spark wear resistance than the platinum-nickel alloy. Since the chip has good bonding properties to the nickel-base alloy, peeling of the chip from the central or ground electrode does not occur, and thus the spark plug has a high durability. If a chip having intermediate and top surface layers is used, since the top surface layer exhibits a higher spark wear resistance, the resulting spark plug is of higher durability.