Abstract: An ignition plug that promotes expansion of flame and enhances spark corrosion resistance, said plug includes a center electrode; a tubular insulator holding the center electrode; a tubular metallic shell holding the insulator; and a ground electrode having a bent portion and a facing end surface. A plurality of peak voltages can be applied to the center electrode after application of a voltage for trigger discharge thereto. When a forward end surface of the center electrode and the facing end surface are projected onto a plane orthogonal to axial direction of the center electrode, the projection of the center of the forward end surface and the projection of the facing end surface overlap with each other, and the projection of a remote-side edge portion of the facing end surface which is located on the side remote from the bent portion is located within the projection of the forward end surface.

Abstract: An ignition device (100) includes a power supply (2) for discharge; an AC power supply (3); an ignition coil (41) for generating a secondary voltage in a secondary coil (41B); an ignition plug (1) connected to the secondary coil (41B); an AC electrode (43) electrically connected to the AC power supply (3); a high-voltage electrode (42) located between the secondary coil (41B) and the ignition plug (1); an insulator (44) located between the two electrodes (42, 43); and a second insulator (47) which covers the ignition coil (41) and a capacitor (49) composed of the two electrodes (42, 43) and an insulator (44). The secondary voltage and AC power are supplied to the ignition plug (1) via the high-voltage electrode (42). Thus, excellent ignition performance can be implemented while the occurrence of misfire is restrained.

Abstract: A spark plug having a metal shell, center electrode and a ground electrode. The ground electrode includes an electrode base portion extending from a front end portion of the metal shell toward the front, a bent portion connected at one end thereof to a front end of the electrode base portion and an electrode distal end portion extending from the other end of the bent portion and forming a spark discharge gap with a center electrode. The ground electrode has a base material and a coating layer applied to the base material. The coating layer is formed on at least a front end face and an outer circumferential surface other than a center-electrode-side surface of the electrode distal end portion of the ground electrode. The base material of the ground electrode is exposed at least at a part of the electrode base portion.

Abstract: A superior ignitability is realized assuredly by specifying at least either of a relation in magnitude between absolute values of a plus-side voltage and a minus-side voltage and a relation in magnitude between absolute values of a plus-side current and a minus-side current when alternating current power is introduced. An ignition system includes a spark plug, a discharging power supply which applies a voltage to a spark gap of the spark plug to thereby generate an electric spark discharge and an alternating current power supply which introduces alternating current power to an electric spark generated by the electric spark discharge to generate an alternating current plasma.

Abstract: An ignition system includes an ignition plug, a discharge power supply for applying a high voltage to the gap of the ignition plug, a high-frequency power supply for supplying a high-frequency current to the gap, a matching unit provided between the ignition plug and the high-frequency power supply, and a mixer through which currents output from the two power supplies flow. An oscillation frequency fs (Hz) which maximizes the current flowing between the matching unit and the mixer when spark discharge is generated and an oscillation frequency fo (Hz) which maximizes the current flowing between the matching unit and the mixer when spark discharge is not generated satisfy a relation fs/fo?0.85. Thus, a current whose oscillation frequency is equal to the oscillation frequency fs flows between the matching unit and the mixer when spark discharge is not generated.

Abstract: A technique of improving the life of a spark plug which generates spark discharge and AC plasma. A plasma ignition device includes a power control section which reduces AC power P after generation of AC plasma in an AC power supply period Sa during which the AC power P is continuously supplied to a spark plug within a maintainable power range Rp within which the AC plasma can be maintained.

Abstract: An ignition system wherein creation of misfires is suppressed and excellent ignition ability is realized. The ignition system includes a spark plug; a discharge power source applying a voltage in order to generate a spark discharge at the spark plug; an AC power source supplying AC power to a spark generated by the spark discharge; and an ignition cable electrically connecting the spark plug, the discharge power source and the AC power source. The ignition cable includes a discharge electrode connecting the discharge power source and the spark plug, an AC electrode transmitting AC power from the AC power source to the spark plug, and an insulator interposed between the discharge and AC electrodes.

Abstract: A spark plug having a metal shell, center electrode and a ground electrode. The ground electrode includes an electrode base portion extending from a front end portion of the metal shell toward the front, a bent portion connected at one end thereof to a front end of the electrode base portion and an electrode distal end portion extending from the other end of the bent portion and forming a spark discharge gap with a center electrode. The ground electrode has a base material and a coating layer applied to the base material. The coating layer is formed on at least a front end face and an outer circumferential surface other than a center-electrode-side surface of the electrode distal end portion of the ground electrode. The base material of the ground electrode is exposed at least at a part of the electrode base portion.

Abstract: A technique for lowering power loss involved in supply of high-frequency electric power to an ignition plug. The ignition plug includes a tubular insulator having an axial bore extending therethrough; a center electrode disposed in the axial bore; a metal terminal disposed rearward of the center electrode in the axial bore, electrically connected to the center electrode, and supplied with high-frequency electric power from an external source; a metallic shell disposed to circumferentially surround the insulator; and a ground electrode electrically connected to the metallic shell and adapted to generate plasma in cooperation with the center electrode through supply of high-frequency electric power to the metal terminal. At least a portion of the inner surface of the axial bore is coated with metal coating. The center electrode and the metal terminal are in electrical contact with the metal coating.

Abstract: There is provided a spark plug for an internal combustion engine, including: a center electrode extending in the direction of an axis of the spark plug and having a core of higher thermal expansion coefficient than that of a front end thereof, the center electrode including a flanged portion radially outwardly protruding on a rear side thereof and a cylindrical portion located closer to a front end of the spark plug than the flanged portion and being smaller in diameter than the flanged portion; an insulator having an axial hole in the direction of the axis to retain the flanged portion in the axial hole with the cylindrical portion held in a loose-fit state in the axial hole; and a metal shell accommodating the insulator, wherein the spark plug satisfies the following condition: Cb<Cf where Cb is a difference between an inner diameter of the axial hole and an outer diameter of the cylindrical portion at an arbitrary axial position B in the direction of the axis; and Cf is a difference between the inner di

Abstract: An ignition system having a spark plug, a discharge power supply, and an AC power supply. Voltage from the discharge power supply and AC power from the AC power supply are supplied to a spark discharge gap through an electrode of the spark plug. The AC power from the AC power supply is applied to a spark generated by the voltage from the discharge power supply in the spark discharge gap.

Abstract: A spark plug includes a center electrode, a ground electrode, and a tip joined to the center electrode and forming a spark discharge gap with the ground electrode. The tip is joined to the center electrode via a fusion zone, which has an exposed surface exposed to the external environment. In a section containing an axis and the center of the exposed surface, C?B?0.02 is satisfied, where C (mm) is the distance on the side surface of the tip between the fusion zone and the distal end of the tip, and B (mm) is the distance between a distal end surface of the tip and a portion of the fusion zone located closer to the axis than the side surface of the tip and located closest in the fusion zone to the distal end surface of the tip.

Abstract: A ground electrode includes a main body portion and a projecting portion having a width smaller than a width of the main body portion. A spark discharge gap is formed between a discharging surface of the projecting portion and a front end surface of a center electrode. When the front end surface and the ground electrode are projected on a first plane, at least a part of the projection region of the projecting portion overlaps the projection region of the front end surface. A width Le (mm), a width Lc (mm), a cross-sectional area Sg (mm2), a cross-sectional area Sc (mm2), an angle ?1 (°), an angle ?2 (°), an angle ?3 (°), and an angle ?4 (°) satisfy expressions Le<Lc, 2.9?Sc+Sg?4.25, and 0.30?(?1/?2)×(?3/?4)?0.67.

Abstract: A ground electrode includes a main body portion and a projecting portion having a width smaller than a width of the main body portion. A spark discharge gap is formed between a discharging surface of the projecting portion and a front end surface of a center electrode. When the front end surface and the ground electrode are projected on a first plane, at least a part of the projection region of the projecting portion overlaps the projection region of the front end surface. A width Le (mm), a width Lc (mm), a cross-sectional area Sg (mm2), a cross-sectional area Sc (mm2), an angle ?1(°), an angle ?2(°), an angle ?3(°), and an angle ?4(°) satisfy expressions Le<Lc, 2.9?Sc+Sg?4.25, and 0.30?(?1/?2)×(?3/?4)?0.67.

Abstract: An ignition plug (1) includes a center electrode (5) extending in the direction of an axis (CL1), an insulator (2) having an axial hole (4) into which the center electrode (5) is inserted, a tip (31) joined to a forward end portion of the center electrode (5) by a fusion portion (35), and a ground electrode (27) forming a gap (33) in cooperation with the tip (31). The ignition plug generates high-frequency plasma at the gap (33) when high-frequency electric power is supplied to the gap (33). The forward end of the tip (31) is located forward of the forward end of the insulator (2) with respect to the direction of the axis (CL1). Also, at least a portion of the outer surface of the fusion portion (35) is located within the axial hole (4), and, the distance between a forward-end-side opening of the axial hole (4) and the rearmost end of the outer surface of the fusion portion (35), measured along the axis (CL1), is equal to or greater than 0.1 mm.

Abstract: An ignition plug that promotes expansion of flame and enhances spark corrosion resistance, said plug includes a center electrode; a tubular insulator holding the center electrode; a tubular metallic shell holding the insulator; and a ground electrode having a bent portion and a facing end surface. A plurality of peak voltages can be applied to the center electrode after application of a voltage for trigger discharge thereto. When a forward end surface of the center electrode and the facing end surface are projected onto a plane orthogonal to axial direction of the center electrode, the projection of the center of the forward end surface and the projection of the facing end surface overlap with each other, and the projection of a remote-side edge portion of the facing end surface which is located on the side remote from the bent portion is located within the projection of the forward end surface.

Abstract: An ignition plug (1) includes a center electrode (5) extending in the direction of an axis (CL1), an insulator (2) having an axial hole (4) into which the center electrode (5) is inserted, a tip (31) joined to a forward end portion of the center electrode (5) by a fusion portion (35), and a ground electrode (27) forming a gap (33) in cooperation with the tip (31). The ignition plug generates high-frequency plasma at the gap (33) when high-frequency electric power is supplied to the gap (33). The forward end of the tip (31) is located forward of the forward end of the insulator (2) with respect to the direction of the axis (CL1). Also, at least a portion of the outer surface of the fusion portion (35) is located within the axial hole (4), and, the distance between a forward-end-side opening of the axial hole (4) and the rearmost end of the outer surface of the fusion portion (35), measured along the axis (CL1), is equal to or greater than 0.1 mm.

Abstract: In a spark plug, a fusion zone where a ground electrode and a noble metal tip are fused together is formed in at least a portion of an interfacial region between the ground electrode and the noble metal tip. When the fusion zone is projected in the axial direction, the projected fusion zone overlaps 70% or more of the area of the noble metal tip. As viewed on a section which passes through the center of gravity of the noble metal tip and is perpendicular to the longitudinal direction of the ground electrode, the relational expression 1.3?B/A is satisfied, where A is the greatest thickness of the fusion zone along the axial direction, and B is the length from a portion having the greatest thickness of the fusion zone to the inner end of the fusion zone.

Abstract: A spark plug has a center electrode having an electrode base member and a core material which is disposed in the electrode base member and which predominantly contains copper, and a noble metal tip disposed at a forward end of the center electrode, and a fusion portion formed between the noble metal tip, and the electrode base member and the core material. The fusion portion is in contact with the core material in a cross section which is parallel to the center axis of the center electrode and which passes through the center axis and the fusion portion. The fusion portion contains a component of the noble metal tip, a component of the electrode base member, and a copper component forming the core material.

Abstract: A spark plug has a center electrode having an electrode base member and a core material which is disposed in the electrode base member and which predominantly contains copper, and a noble metal tip disposed at a forward end of the center electrode, and a fusion portion formed between the noble metal tip, and the electrode base member and the core material. The fusion portion is in contact with the core material in a cross section which is parallel to the center axis of the center electrode and which passes through the center axis and the fusion portion. The fusion portion contains a component of the noble metal tip, a component of the electrode base member, and a copper component forming the core material.