Abstract: A spark plug, in particular for use in internal combustion engines, includes a spark plug casing and a ground electrode carrier casing. The ground electrode carrier casing has at least two ground electrode carrier casing portions having mutually different materials and/or the ground electrode carrier casing is of a different material from the spark plug casing.

Abstract: A spark plug including a cylindrical insulator having an axial hole extending in an axial direction; a center electrode held in the axial hole on a leading end side; a connecting terminal held in the axial hole on a trailing end side; and a sealing layer provided in the axial hole and including a glass sealing material containing a glass component and a metallic component, the sealing layer including a first sealing layer containing a first glass sealing material and a second sealing layer containing a second glass sealing material laminated in an axial direction of the axial hole, the first sealing layer contacting the center electrode, and the second sealing layer contacting the connecting terminal, wherein the second glass sealing material has a fluidity higher than that of the first glass sealing material at a temperature higher than a softening point of a glass component in the sealing layer.

Abstract: A spark plug has a compact structure where a threaded portion of a metal shell has a size of M10 or M12 and the width between any two opposite side surfaces of a polygonal prism-shaped portion of the metal shell is no greater than 14 mm. In the spark plug, a thickness A of the polygonal prism-shaped portion of the metal shell, a thickness B of a crimped portion of the metal shell, and a thickness C of a buckled portion of the metal shell are subject to a dimensional relationship of A>B>C. Through specifying such a relationship, the crimped portion of the metal shell exerts a large constricting force on sealing members provided in a gap between the inner surface of the polygonal prism-shaped portion of the metal shell and the outer surface of an insulator, thereby securing high gas tightness of the spark plug.

Abstract: A sparkplug having ground and center electrodes that include a firing tip formed from a noble metal or noble metal alloy by reflowing of a noble metal preform. The present invention also includes a method of manufacturing a metal electrode having an ignition tip for an ignition device, including forming a metal electrode having a firing tip portion; applying a noble metal preform to the firing tip portion; and reflowing the noble metal preform to form a noble metal firing tip.

Abstract: An object of the invention is to provide a spark plug having a discharge portion made of a precious metal tip, in which peeling of the precious metal tip from a surface of the discharge portion can be suppressed while spark abrasion, oxidation abrasion and abnormal abrasion of the discharge portion can be suppressed.

Abstract: A noble metal tip 20 for attachment to a spark plug center electrode 36 and/or a ground electrode. Noble metal tip 20 is a generally cylindrical component that includes a firing end 40, an attachment end 42, and one or more retention features 44, 46 and 60, 62. The retention features are generally conically shaped holes or recesses formed in the side of the noble metal tip, and are designed to receive molten material during a laser attachment process. Once the molten material has solidified in the retention features, a fusion layer is formed and acts as a mechanical bond or interlock between the noble metal tip and the electrode. Methods of manufacturing and attaching the noble metal tips are also provided.

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: A ground-electrode spark portion 32 is formed from a noble metal which contains Pt as a main component, and is joined to a main metal portion of the ground electrode 4 via an alloy layer which has a thickness ranging from 0.5 ?m to 100 ?m and in which the noble metal that constitutes the ground-electrode spark portion 32 and the metal that constitutes the main metal portion of the ground electrode 4 are alloyed with each other. The ground-electrode spark portion 32 is configured such that a distal end surface 32t facing a spark discharge gap g is smaller in diameter than a bottom surface 32u joined to the ground electrode 4; and the distal end surface 32t is protrusively located beyond the side surface 4s of the ground electrode 4.

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: The present invention provides a highly reliable spark plug used for an internal-combustion engine and including an insulator with a high withstand voltage, and a method for manufacturing the same. Namely, it provides a spark plug containing a cylindrical metal shell having an insulator holding hole, a cylindrical insulator including an axial hole therein which extends in an axial direction, and engaging with said insulator holding hole of said metal shell, and a center electrode held in said axial hole of said insulator, wherein said insulator has a texture in which one or more pores exposed in a judgment area with 50 ?m in diameter occupy 40% or less of said judgment area at any locations in an observation area, in the case where a predetermined mirror-finishing section of an enclosed portion surrounded by said metal shell is used as said observation area to observe pores exposed in said observation.

Abstract: A spark plug which includes an end at its combustion chamber end, and an end at its connecting end, as well as a housing and an insulator situated in the housing. The insulator has a longitudinal bore having a longitudinal axis, a center electrode situated in the longitudinal bore of the insulator, a first ground electrode which extends into the region of the longitudinal axis of the insulator, and a second ground electrode which is situated at a distance from the longitudinal axis of the insulator laterally next to the center electrode. The insulator has a front section, facing the first ground electrode, which has an end face. The insulator has an outside diameter d and an inside diameter c, d?c, that is, the difference between outside diameter d and inside diameter c, in the front section of the insulator being not greater than 1.9 mm.

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 includes a metal shell, an insulator, a center electrode, a ground electrode, and a terminal fixed to the insulator. The dimensional parameters in the structure of the spark plug, such as a maximum diameter A of the terminal and a diameter B of the insulator satisfy a dimensional relationship defined through experimental investigation. The structure facilitates an attachment of a plug cap to the spark plug.

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: A method of joining an electrode of a spark plug with a noble metal is described, the noble metal being joined locally with the electrode using a thermal input produced by a continuously operating laser beam.

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: In a glow plug and a spark plug, the surface of a main metal shell is coated with a chromate film in which the quantity of trivalent chrome is 95 wt % or more of the contained chrome components and which has a thickness of 0.2 ?m to 0.5 ?m.

Abstract: A spark plug includes a metallic housing, an insulator fixed in the metallic housing, a center electrode fixed in the insulator, a ground electrode opposed to the center electrode via a spark discharge gap, and a protective coat formed on the surfaces of a metallic housing and a gasket. The protective coat includes a galvanized film formed on the surfaces of the metallic housing and the gasket and a chromate film successively laminated on the galvanized film. The chromate film is hexavalent chromium-free and contains trivalent chromium as a major component. The chromate film has a film thickness not smaller than 0.05 ?m and not greater than 0.18 ?m, and the chromate film contains a metallic component which is robust against oxidation compared with zinc. Furthermore, the chromate film has a film hardness equal to or less than 1 GPa in the temperature range from a room temperature to 180° C.

Abstract: A spark plug is composed of a main metal fitting having a cylindrical structure, an insulator disposed inside the cylindrical main metal fitting, a center electrode fitted in the insulator in a manner that a front end portion of the center electrode projects outward over one end of the insulator, and a grounding electrode mounted to the main metal fitting and having one end portion opposing to the front end portion of the center electrode through a discharge gap therebetween. The front end portion of the center electrode includes a conical portion having a tapered surface having a taper angle of less than 80°, and a columnar portion formed to a top end portion of the conical portion so as to have a diameter in a range of 0.4 mm to 0.8 mm.

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: A ground-electrode spark portion 32 is formed from a noble metal which contains Pt as a main component, and is joined to a main metal portion of the ground electrode 4 via an alloy layer which has a thickness ranging from 0.5 ?m to 100 ?m and in which the noble metal that constitutes the ground-electrode spark portion 32 and the metal that constitutes the main metal portion of the ground electrode 4 are alloyed with each other. The ground-electrode spark portion 32 is configured such that a distal end surface 32t facing a spark discharge gap g is smaller in diameter than a bottom surface 32u joined to the ground electrode 4; and the distal end surface 32t is protrusively located beyond the side surface 4s of the ground electrode 4.

Abstract: A spark plug used in an automotive internal combustion engine. The spark plug includes a center electrode. An insulator is disposed around the center electrode. A metal main body is disposed around the insulator. A ground electrode has a first end section connected to the metal main body, and a second end section located opposite to the center electrode. Additionally, a tip is formed of an alloy whose main component is Ir. The tip is secured to the ground electrode and serving as a spark consumption-resistant electrode material. The tip has an axis directed to the center electrode. In the spark plug, a molten and solidified section formed of alloy is disposed to fix the tip to the ground electrode. The molten and solidified section includes a surrounding molten and solidified section located surrounding a peripheral surface of a major part of the tip embedded in the ground electrode.

Abstract: An improved structure of a spark plug is provided for improving the mechanical strength of joints between a noble metal member made of Ir-alloy and a ground electrode which withstands intense heat. The noble metal member is welded to the ground electrode through laser-fused portions. Each of the fused portion contains less than 40% by weight of Ir in a range defined inside an imaginary plane coinciding with an outer peripheral wall of the noble metal member before welded to the ground electrode, thereby enhancing the strength of the joints between the noble metal member made and the ground electrode.

Abstract: A noble metallic firing tip includes a protruding portion which is formed partly on its outer circumferential surface so as to protrude in the direction substantially normal to the axis of a center electrode. The protruding portion is disposed in confronting relationship via a discharge gap with a distal end of an opposed portion of a ground electrode far from its leg portion.

Abstract: A spark plug of an internal combustion engine, in particular for use in Otto-cycle gas engines, having an insulator body, at least one fixed ground electrode carrier arrangement and at least one fixed central electrode carrier, wherein a spark plug housing having at least two parts encloses the insulator body, wherein the spark plug housing has a lower housing portion and an upper housing portion, wherein at least the combustion chamber-side part of the insulator body is pressure-resistantly, preferably completely, enclosed by the lower housing portion jointly with the upper housing portion.

Abstract: An insulator (2) is inserted into a metallic shell (1) in the direction of an axis O, and a sealing material powder (160) is charged into a circumferential gap (20) formed between the inner circumferential surface of a rear end portion of the metallic shell (1) and the outer circumferential surface of the insulator (2). The compressed sealing-material-powder layer (61) contains talc in an amount of from 75% to 99.7% by mass and at least one of magnesite and dolomite in an amount of from 0.3% to 25% by mass, and satisfies 0.5?M?1.3 and 0.5?L?2×(M×4.5), wherein L in mm represents height as measured in the direction of the axis O, and M in mm represents thickness as measured radially with respect to the axis O.

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: A spark plug having a ground electrode in the shape of a horn nozzle defined by an enlarged mouth and a reduced throat joined together, a conical inner wall tapered from the mouth to the throat. An ignitor electrode terminates at its distal end in a spherical tip disposed in the throat in spaced-apart relationship with respect to the tapered inner wall. An insulative body supports the ignitor electrode with a conductive body supporting the ground electrode. The horn nozzle is joined with the conductive body by a pair of posts so as to define a pair of slots for venting exhaust gasses from the ignition site.

Abstract: In an ignition device for an internal combustion engine which is mounted in a cylinder head in a state where a spark plug and an ignition coil are integrated with each other, the plug side tube section is made of ceramics and internally accommodates a center electrode and the coil side tube section is made of ceramics, with one of a primary winding and a secondary winding being wound around the coil side tube section. The plug side tube section and the coil side tube section are constructed as separate bodies and then combined with each other. This shortens the overall lengths of both the tube sections, thus preventing the occurrence of cracks or bends at calcining and improving the dimension accuracy after the calcining.

Abstract: A spark plug configured such that a metallic shell is joined to an insulator through hot-crimping. The metallic shell is firmly joined to the insulator by means of a sufficient fastening force even when the diameter of the spark plug is reduced, to thereby enhance gastightness and vibration resistance. A rear end portion of a metallic shell (1) is hot-crimped toward an insulator (2) to form a curved, crimped portion (1d). The inside diameter of an insulator insertion hole (40) of the metallic shell (1) is 8-12 mm.

Abstract: Process for producing a middle electrode with precious metal reinforcement, a middle electrode being used with an ignition tip which 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 tip and such that this precious metal wire is cut off at the desired height, with a sharp edge.

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 spark plug configured such that a metallic shell is joined to an insulator through crimping. The metallic shell is firmly joined to the insulator by means of a sufficient fastening force even when the diameter of the spark plug is reduced, to thereby enhance gastightness and vibration resistance. A method for manufacturing the spark plug is also disclosed.

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 spark plug is described having a partially cylindrical insulator element and a housing surrounding the insulator element on the side of a base part. The insulator element and the housing are connected with one another by at least one material bond and/or one friction-lock connection aligned in the radial direction. A compact spark plug can be produced using this type of connection. In particular, the diameter of the spark plug is smaller than the diameter of known spark plugs having the same characteristics.

Abstract: A spark plug having a tubular metallic shell (1), an insulator (2) fitted into the metallic shell (1), a center electrode (3) provided in the insulator (2), and a ground electrode (4), one end of the ground electrode (4) being joined to the metallic shell (1) by means of welding or a like process, and a spark discharge gap (g) being formed between the other end portion of the ground electrode (4) and the center electrode (3), the spark plug being further characterized in that: the ground electrode (4) has an electrode base metal (4a), a Cu-based heat transfer acceleration element (4c) embedded in the electrode base metal (4a) and formed predominantly from Cu, and a noble metal chip (32) welded to the electrode base metal (4a) at a position facing the spark discharge gap (g); and the electrode base metal (4a) is an Ni alloy containing Cr in an amount of 14%-17% by mass, Mo in an amount of 0.8%-3.5% by mass, and Ni in an amount of 68%-85.2% by mass.

Abstract: A spark plug fabricating method and a spark plug fabricated by the same are provided. The spark plug is equipped with a piezoelectric sensor working to measure the pressure of combustion of fuel in an engine and required to apply a given preload to the piezoelectric sensor at all the time. The piezoelectric sensor is disposed within a holder and retained between the holder and a porcelain insulator. The fabrication method includes the steps of pressing the holder to apply a required preload to the piezoelectric sensor in a longitudinal direction of the porcelain insulator and joining the holder to a metal shell while maintaining the preload applied to the piezoelectric sensor as it is.

Abstract: A noble metallic tip of a ground electrode protrudes from an opposed surface of the ground electrode by a protrusion amount ‘t’ not less than 0.3 mm. The noble metallic tip of the ground electrode possesses excellent oxidative and volatile resistance compared with a noble metallic tip of a center electrode.

Abstract: A spark plug is disclosed in which, in a cross-section of the metallic shell of the spark plug, a crimped portion of the metallic shell is curved such that an end-side part of the crimped portion approaches the insulator, such that an exterior outline of the crimped portion has an outwardly convex crimped curve portion at the end-side part, and such that a tangent to the exterior outline at a base point of the crimped curve portion and a radial line perpendicular to the axis of the insulator form an angle of 50°-110°. Accordingly, most of a crimping force is imposed in the axial direction of the metallic shell during crimping, and stress generated in the metallic shell in a radial direction is very small. Thus, the metallic shell can be thin-walled and can maintain its shape with high accuracy after crimping.

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: A spark plug of the present invention is made of an Ir alloy including a specific amount of (1) Rh, (2) Pt, or (3) Rh and Pt or Rh and Ru. The spark plug comprises tips for a center electrode and for a ground electrode that are each 0.6 to 1.8 mm in diameter and 0.2 to 0.7 mm in thickness and for an interlayer made of an Ir alloy including Ni of 40 mass % that has a diameter slightly larger or smaller than that of each tip for the center electrode and for the ground electrode and has a thickness of 0.1 to 0.6 mm. These tips can be manufactured according to the powder processing method, the dissolution method, and so on. The tip for the center electrode is joined to the end surface of the basic body of the center electrode, which is made of a Ni alloy (Inconel 600), according to laser welding. The tip for the interlayer and the tip for the ground electrode are brought into contact with a predetermined position of the ground electrode, and are joined while being pressed according to electric resistance welding.

Abstract: A spark plug electrode is disclosed. The electrode comprises, based upon the total weight of the electrode, about 83 wt. % to about 96.8 wt. % copper, about 3.0 wt. % to about 9.0 wt. % chromium, and about 0.2 wt. % to about 8.0 wt. % niobium. A spark plug is also disclosed. The spark plug comprises a shell disposed in contact with an insulator body. A center electrode is disposed at a lower end of the insulator body. A side electrode is also disposed at a lower end of the shell. This side electrode is coaxially aligned with the center electrode. At least one of the center electrode and the side electrode comprises a core composition of about 83 wt. % to about 96.8 wt. % copper, about 3.0 wt. % to about 9.0 wt. % chromium and about 0.2% to about 8.0% niobium, based upon the total weight of the composition. A resistor section is also disposed in electrical communication with the center electrode.

Abstract: A spark plug for an engine comprises a mounting member to be mounted to an engine, an insulator disposed inside the mounting member and formed with an axial hole, a center electrode formed of a metal material and disposed in the axial hole of the insulator in a manner insulated from the mounting member, and an earth electrode disposed so as to oppose to the center electrode. At least one of the center electrode and earth electrode is formed as a base material having one surface to which a tip composed, as a discharge member, of a noble metal or alloy thereof is welded and fixed thereto through a fused portion. The fused portion between the tip and the base material has an area of a maximum sectional area portion of a size of not more than 1.5 times a sectional area of a portion of the tip positioned at a boundary portion to the fused portion, and the sectional area of the tip positioned at the boundary portion is not less than 2 mm2 and not more than 7 mm2.

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: An improved structure of a spark plug is provided for improving heat dissipation from an Ir-alloy chip attached to a ground electrode. The Ir-alloy chip works to a sequence of sparks between itself and the tip of a center electrode mounted in a metal shell and is embedded in a center electrode-facing surface of the ground electrode, thereby enhancing the transmission of heat produced in the Ir-alloy chip to the metal shell through the ground electrode.

Abstract: A spark plug electrode having a welded-on noble-metal part for a longer service life of the spark plug. Prior to the welding process, the noble-metal part is provided with a profiling on the side facing the spark plug electrode.

Abstract: A spark plug having a ceramic insulator, which contains a precious-metal center electrode in a cylindrical, axial opening, at the end on the side of the combustion chamber. A contact pin is arranged in the cylindrical opening, downstream from the precious-metal center electrode, in the direction of the insulator end away from the combustion chamber. To reduce corrosion, the surface of the contact pin is provided with a layer of one or more metal aluminides.

Abstract: A spark plug having a tip composed of an iridium alloy essentially consisting of iridium is resistance welded through a relieving layer to a front end of a center electrode having an iron-based alloy and a facing portion of a ground electrode and wherein the material of the relieving layer has a coefficient of linear expansion between the iridium alloy and the iron-based alloy and has a Young's modulus of elasticity smaller than that of the two alloys.

Abstract: A ceramic sheathed-element glow plug is proposed in which a metallic tubular holder holds a ceramic U-shaped heating device in a cantilevered fashion at its combustion chamber side end and has a terminal stud for applying a voltage to the ceramic heating device on the end remote from the combustion chamber. At its end enclosed by the holder, the ceramic heating device has a segment of greatest diameter and is coated with an insulating layer which has recesses for an electrical contacting. One recess is provided at the end of the ceramic heating device remote from the combustion chamber and a second recess is provided on the external wall of the ceramic heating device. A for an electrically conductive sealing compound is provided between the external wall of the ceramic heating device and the internal wall of the holder.

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.