Abstract: In a method of manufacturing a center electrode for a spark plug, a core member is press-fitted into a metal cup and, thereafter, a cold-forging process is performed to form a small-diameter portion at a closed end of the metal cup. The small-diameter portion is completely free from deformation which may occur during press-fitting operation. Thus, the small-diameter portion has excellent accuracy in shape. Furthermore, since the press-fitting is performed before the cold-forging of the small-diameter portion, it is possible to increase the press-fitting load or pressure to the extent that the core member and the metal cup are joined together with a sufficient degree of adhesion which will insure the a center electrode to have good thermal conductivity.

Abstract: A method of making an ignition device and center wire assembly that includes first, second and third electrode members, a conductive seal, and a noise suppressing seal. The method locates the first electrode member at an axial end of the center wire assembly near a spark gap and the third electrode member at an axial end of the center wire assembly such that it receives an electrical ignition pulse and a second electrode member between the first and third electrode members. Furthermore, the method locates the conductive seal between the first and second electrode members and the noise suppressing seal between the second and third electrode members.

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: 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: An object of the present invention is to efficiently adjust a positional difference (measured along the direction perpendicular to the center electrode axis) between the center electrode (CE) axis and the center of the earth electrode (EE). The CE tip and EE tip surface are illuminated from the front of the EE tip surface, thereby picking up their images. The image processing unit calculates the positional difference between the CE axis and EE center. Here, the EE center is defined by an area centroid of the EE tip surface area, thereby improving a measurement accuracy. The adjustment unit connected with the image processing unit causes the actual positional difference to decrease by moving EE by the that calculated positional difference, taking a prescribed spring-back into consideration. EE is moved by a jig moved by a screw rotated by a motor.

Abstract: A spark plug center wire assembly that includes a noise suppressing conductive seal with improved isolation of the seal from the heat generated at the firing end of the spark plug. The center wire assembly includes a firing electrode, a conductive glass seal, an intermediate electrode, the noise suppressing glass seal, and a terminal electrode. By locating the firing electrode, conductive seal and intermediate electrode between the noise suppressing seal and the spark gap, the center wire assembly is able to utilize the noise suppression attributes of the suppressive seal, while distancing the seal from the high temperatures created during the combustion process. A method of manufacturing the same is also disclosed in which the two glass seals are formed by sequential firing operations.

Abstract: A ground electrode for a spark plug has a through hole located adjacent a firing end of the electrode, with a precious metal firing tip extending through the hole. The firing tip is compressed axially to define a bulging portion extending radially outwardly from its longitudinal axis to mechanically retain the firing tip within the through hole. The firing tip additionally has an enlarged head or otherwise expanded portion at each axial end of the tip to provide a second mechanical interlock of the tip to the ground electrode. The firing tip can then also be welded to further strengthen its connection to the ground electrode. A method of manufacturing the ground electrode and a spark plug containing the ground electrode is also disclosed.

Abstract: A method for manufacturing a spark plug which reduces the generation of spatters and the possibility of insufficient weld strength resulting from penetration depth insufficiency of a weld metal portion is disclosed. In accordance with the method, a chip joint face formation portion of a center electrode is formed from a heat-resistant alloy predominantly containing Fe or Ni. A noble metal chip is attached to a chip joint face of the chip joint face formation portion to thereby form a chip-attached assembly. A full-circled laser-beam weld metal portion is formed on the chip-attached assembly in such a manner as to intrude into the noble metal chip and into the chip joint face formation portion. A graded-index-type fiber optic cable is used as an optical transmission path extending between a laser beam generator and an optical emission section. A laser beam which is transmitted from the laser beam generator through the cable irradiates the chip-attached assembly while being condensed.

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: A method of making a spark plug having a noble metal chip joined to an electrode main body of a ground electrode by interposing therebetween an intermediate member. The method comprises the steps of prior to joining the noble metal chip to the electrode main body, joining the intermediate member and the noble metal chip together, placing a noble metal chip and intermediate member assembly on the electrode main body in a way as to allow the intermediate member to contact the electrode main body, and welding the electrode main body and the intermediate member together while restricting relative movement of the electrode main body and the intermediate member without applying an urging force to a joint between the intermediate member and the noble metal chip.

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: 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: Noble metallic tips, made of a Pt alloy or an Ir alloy, are fixed to electrode base materials. The electrode base materials are an alloy containing a chief element selected from the group consisting of Ni, Fe, and Co and a plurality of additive elements. At least two kinds of additive elements contained in this alloy have a standard free energy of formation smaller than that of the chief element.

Abstract: An electrode and spark plug for an internal combustion engine including an electrode of this type as a center electrode. The electrode includes an electrode base element made of a first material and an end section that is integrally joined to the electrode base element, with this end section including a first area that is integrally joined to the first material and is made of a platinum-containing material and including a second area that is integrally joined to the first area and is made of an iridium-containing and/or ruthenium-containing material. In a method for manufacturing an electrode of this type, a first recess is stamped in the electrode base element, a first preform is inserted into the first recess, the first preform is melted, thereby forming a first alloy, a second recess is stamped in an area of the first alloy, a second preform is inserted into the second recess, and the second preform is melted, thereby forming a second alloy.

Abstract: In a spark plug for an internal combustion engine oil is applied onto at least either the surface of an intermediate body portion of an insulator or the surface of an intermediate hole portion of a metallic shell, thereby forming an oil film. Since the oil film has a dielectric constant falling between those of the insulator and an ambient air layer, a great change in dielectric constant between the insulator and the ambient air layer is eased. Also, since the oil film is of liquid, the oil film smoothes a dent or protrusion or a fine defect such as crack present on the surface of the intermediate body portion of the insulator. Thus, electric field concentration is suppressed, thereby preventing dielectric breakdown caused by such a dent, protrusion or fine defect.

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: In a wire drawing process for forming a wire rod containing iridium as a main component and which further contains nickel and at least one of platinum, rhodium and ruthenium, and having a cross-sectional area of not smaller than 0.05 mm2 and not larger than 1.2 mm2. The worked material is continuously heated red hot and/or white hot in a heating region 103 extending up to 60 mm from the work inserting surface 101a of a die 101 in a direction opposite that in which the work 102 moves, the work being heated to a temperature of 1000 to 1150° C. at a temperature measuring position 105 which is removed from the work inserting surface 101a by 20 mm. Furthermore, the temperature in the region 106 extending from the temperature measuring position 105 to the work inserting surface 101a is set to not lower than 1000° C., and the wire drawing rate is set to 300 to 1600 mm/min.

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: The present application is to provide a spark plug where a marking layer 2m under a glaze layer 2d can form a color stably, even if the Pb amount is decreased in the glaze layer. The glaze layer 2d is formed on an insulator 2 of the spark plug, and the marking layer 2m is formed under the glaze layer 2d. The glaze layer 2d contains, e.g., 1 to 25 mol % of a Zn component in terms of Zno and 5 mol % or lower, e.g., 1 mol % or lower of a Pb component in terms of PbO. On the other hand, the marking layer 2m is adjusted in kinds and amounts of metallic element components in such manners that a tint seen through the glaze layer 2d is 3 or lower in brightness specified by JIS:Z8721 as well as 3 or lower in chroma specified by JIS:Z8721, or 4 or lower in the brightness specified by JIS:Z8721 as well as 2 or lower in the chroma specified by JIS:Z8721.

Abstract: In a method of manufacturing a spark plug in which a noble metal chip provisionally fixed to a center or ground electrode by resistance welding and finally bonded to the center or ground electrode by laser welding, a current supply time period of the resistance welding is controlled according to a transit moving amount of an upper or lower electrode of a resistance welding equipment, which corresponds to a transit embedding length of the noble metal chip to the center or ground electrode, to establish a predetermined final embedding amount of the noble metal chip to the center or ground electrode.

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 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, wherein the glaze layer comprises: 1 mol % or less of a Pb component in terms of PbO; 30 to 60 mol % of a Si component in terms of SiO2; 20 to 50 mol % of a B component in terms of B2O3; 0.5 to 25 mol % of a Zn component in terms of ZnO; 0.5 to 15 mol % in total of at least one of Ba and Sr components in terms of BaO and SrO, respectively; 2 to 12 mol % in total of at least two alkaline metal components of Na, K and Li, in terms of Na2O, K2O, and Li2O, respectively, wherein K and Li is essential; and 0.1 to 10 mol % of a F component in terms of F2.

Abstract: A spark plug comprises a main metal fitting, a center electrode mounted to and held by the main metal fitting in a manner insulated therefrom and a grounding electrode having one end welded to the main metal fitting and another end opposing to the center electrode. A welding burr is further formed to the welded portion of the main metal fitting and the grounding electrode so as to have an area expanding outside the grounding electrode, and the main metal fitting of the main metal fitting is plated, whereas the grounding electrode and the welding burr are not plated.

Abstract: An object is to realize a spark plug which is less affected by “carbon fouling,” has a long service life, and exhibits excellent ignition characteristics. An air gap (&agr;) is formed between a parallel ground electrode 11 and an end face of a center electrode 2; a semi-creepage gap (&bgr;) is formed between an end face 12C of a semi-creeping discharge ground electrode 12 and a circumferential side surface 2A of the center electrode 2; and an insulator gap (&ggr;) is formed between the end face 12C and a circumferential side surface 1E of an insulator 1. The air gap (&agr;) and the semi-creepage gap (&bgr;) satisfy a relationship &agr;<&bgr;; and the air gap (&agr;) and the insulator gap (&ggr;) satisfy a relationship &agr;>&ggr;. The air gap (&agr;) is not greater than 1.1 mm; the insulator gap (&ggr;) falls within a range of 0.5 mm to 0.

Abstract: A method for manufacturing a spark plug which reduces the generation of spatters and the possibility of insufficient weld strength resulting from penetration depth insufficiency of a weld metal portion is disclosed. In accordance with the method, a chip joint face formation portion of a center electrode is formed from a heat-resistant alloy predominantly containing Fe or Ni. A noble metal chip is attached to a chip joint face of the chip joint face formation portion to thereby form a chip-attached assembly. A full-circled laser-beam weld metal portion is formed on the chip-attached assembly in such a manner as to intrude into the noble metal chip and into the chip joint face formation portion. A graded-index-type fiber optic cable is used as an optical transmission path extending between a laser beam generator and an optical emission section. A laser beam which is transmitted from the laser beam generator through the cable irradiates the chip-attached assembly while being condensed.

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: 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: A fabrication method of a metal shell to be installed on a park plug is provided which is made up of a small-diameter portion, a large-diameter portion, and a wrapping portion. The wrapping portion is to be wrapped by staking about the spark plug to achieve installation of the metal shell on the spark plug. The method comprises pressing a workpiece with a punch to shape the wrapping portion of the metal shell in a first cold forging process and processing the workpiece to shape the small-diameter portion of the metal shell in a second cold forging process different from the first cold forging process. This produces the metal shell which is less susceptible to cracks when installed on the spark plug and has an increased service life.

Abstract: The seal between the insulator and the center electrode is to be improved in a spark plug for an internal combustion engine comprising a shell (12), an insulator (16) located in the shell and composed of a sintered ceramic material, as well as a center electrode (18) and a terminal stud (22) that have an electrically conductive connection with each other and are located in the insulator. For this purpose, it is provided that a cermet (28) abuts the center electrode, the ceramic phase of which is composed of the same or a similar material as the insulator, and the metallic phase of which is composed of a material having good electrical conductivity. Since the material properties of the cermet are similar to those of the insulator—the thermal expansion, in particular, is same—a particularly good seal is created between the cermet and insulating body.

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 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: 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 &mgr;m to 0.5 &mgr;m.

Abstract: This invention relates to a method and apparatus for making a spark plug, in particular, for making a high-performance spark plug having a center electrode having a firing end made of Pt, Ir, Rh, Pd, Re, Os, Ru or alloy thereof, with its firing end diameter of about 0.3-1.0 mm. One of the embodiments provides a method comprising the steps of: extending a metal strip from an end of the metal shell; positioning a spacer above a firing end of the center electrode; preliminarily bending the metal strip toward the spacer so as to form an arc portion in the metal strip; and then precisely forming a gap-distance between the metal strip and the firing end of the center electrode by applying a force to the metal strip.

Abstract: A method for joining a precious-metal section to an electrode of a spark plug is provide, the precious-metal section being joined to the electrode by means of heat input generated by a laser beam. The laser beam is applied to the precious-metal section and optionally also to the electrode. During the heat introduction, the laser beam covers substantially the entire surface of the precious-metal section. No relative movement occurs between the laser beam and the precious-metal section during the heat introduction.

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 linear noble-metal member 32′, which is formed of a noble metal or noble metal alloy and will become a spark portion 32, is positioned on a distal end portion 4a (an attachment portion) of a ground electrode 4 of a spark plug work 100′; the positioned linear noble-metal member 32′ is fixed to the distal end portion 4a by resistance welding or laser welding; and the fixed linear noble-metal member 32′ is cut.

Abstract: In a method of manufacturing a center electrode for a spark plug, a core member is press-fitted into a metal cup and, thereafter, a cold-forging process is performed to form a small-diameter portion at a closed end of the metal cup. The small-diameter portion is completely free from deformation which may occur during press-fitting operation. Thus, the small-diameter portion has excellent accuracy in shape. Furthermore, since the press-fitting is performed before the cold-forging of the small-diameter portion, it is possible to increase the press-fitting load or pressure to the extent that the core member and the metal cup are joined together with a sufficient degree of adhesion which will insure the a center electrode to have good thermal conductivity.

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 &mgr;m to 100 &mgr;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 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 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: An iridium alloy firing tip, fixed to a center electrode, comprises a stem and a head. The firing tip head is integrally formed from one end of the stem. A distal end of the stem is opposed to an opponent electrode. The head is embedded in the opposing portion. The firing tip head is pointed or tapered in a direction opposite to the stem from a maximum diameter portion in such a manner that a cross-sectional area of the head continuously decreases with increasing distance from the maximum diameter portion. The maximum diameter portion is positioned deeply inside the opposing portion, and a base end of the stem extending from the maximum diameter portion is wrapped or surrounded by the opposing portion.

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 method for making a spark plug is provided. The method comprises the steps of, for adjustment of a spark gap, provisionally pressing a ground electrode toward a leading end surface of a center electrode and thereby decreasing the spark gap to a predetermined value larger than a final target gap gt, after the step of provisionally pressing the ground electrode, performing an adjustment bending process for eliminating an eccentricity &dgr; of the ground electrode in the widthwise direction thereof with respect to a target position, after the step of performing the adjustment bending process, measuring a spark gap g1 and measuring a difference (g1−gt) between the measured spark gap g1 and the final target gap gt, and pressing the ground electrode toward the center electrode when the difference (g1−gt) is positive. An apparatus for carrying out the method is also provided.

Abstract: A method for manufacturing a spark plug, the spark plug includes: 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 including caulking the portion to be caulked to be fixed to an outer circumferential face of the insulator with the caulking metallic mold, where in the caulking metallic mold includes a face, the face including a hard carbon film that includes an amorphous carbon phase, and the face is contact with or sliding to the portion to be caulked.

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 includes a sparking electrode with a firing tip and a ground electrode. The ground electrode includes a toroidal member, having a convex outer surface, coupled to a support portion of a sleeve of the ground electrode. The toroidal member forms an annular curve disposed generally transverse to and having a radial center coinciding with a central axis of the insulator body, whereby each differential segment of the toroidal member radially thereabout is generally equidistant to the firing tip. The toroidal member is a closest portion of the ground electrode relative to the firing tip. At least a portion of the outer surface of the toroidal member opposing the firing tip has a radius of curvature of about that of the firing tip for providing a spark path of least from the firing tip to a point of contact on the opposing surface defined by the toroidal member.

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 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: 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: Provided is a method of making a spark plug having a noble metal chip joined to an electrode main body of a ground electrode by interposing therebetween an intermediate member. The method comprises the steps of prior to joining the noble metal chip to the electrode main body, joining the intermediate member and the noble metal chip together, placing a noble metal chip and intermediate member assembly on the electrode main body in a way as to allow the intermediate member to contact the electrode main body, and welding the electrode main body and the intermediate member together while restricting relative movement of the electrode main body and the intermediate member without applying an urging force to a joint between the intermediate member and the noble metal chip.

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.