Abstract: An electrical self-purification ignition plug comprising a porcelain insulator ignition leg provided at its end surface opposed to a grounded electrode with a conical depression, and a center electrode exposed to the base surface of said conical depression and made integral with said porcelain insulator.

Abstract: A spark plug with a spark electrode prepared by mixing at least a matrix material of a titanium compound (e.g., TiO.sub.2, TiC, TiN, etc.) with an electrical conductivity-imparting substance (e.g., Pt and Pd, or a mixture of Pt, Pd and a noble metal, e.g., Au, Ru, Ag, Rh, etc.) and sintering the resulting mixture.

Abstract: A spark plug with a rivet-like tip center discharge electrode is obtained by melting powdery metal essentially consisting of noble metal Au, Ag and/or alloys thereof with Pd or the like charged in a small end bore formed at a discharge end bottom of a ceramic insulator then allowing to cool. Sealing and/or resistor incorporation together with setting (sealing) of a terminal rod may be done one-stepwise with the center electrode formation or two-stepwise after the center electrode formation. A resultant space in the center bore may be utilized for various purposes.

Abstract: A spark plug including an insulator body provided with a center bore and a bottom end defining a discharge end of the insulator body and a discharge center electrode formed in a region of the discharge end of the insulator body; a spark plug including thermal conductivity-controling material comprising spherical metal powder as an essential element thereof in the center bore providing function to control thermal conductivity of the spark plug. The conductivity controling material further comprises refractory powder and glass powder. The controling material is also composed of spherical metal powder coated with a ceramic layer of a mixture thereof with the spherical metal powder. The spark plug with the controling material permits an increasing conductance according to temperature rise to provide a thermally wide-ranged spark plug.

Abstract: A spark plug with a sphere-like center discharge electrode is obtained by pressing a sphere-like metal essentially consisting of noble metal Au, Ag and/or alloys thereof with Pd or the like set on a small end bore formed at a discharge end bottom of a ceramic insulator. Sealing of a sealing material and/or resistor material together with setting (sealing) of a terminal body may be done simultaneously with the pressing of the sphere-like metal on the small end bore by means of hot-pressing applied on the terminal rod head.

Abstract: An ignition system for creeping discharge spark plugs for producing a spark discharge at least one portion of which slidably moves along a creeping discharge path is disclosed. The system comprises producing a spark discharge operative to ignite a mixed gas in an usual manner and selectively producing a purifying and sweeping spark discharge operative to remove carbon deposited on said creeping discharge path. An ignition circuit for carrying out the system is also disclosed.

Abstract: An ignition plug insulator provided at its front end with a closed ignition portion. The closed front end of the ignition portion is impregnated with an electric conductivity imparting material to form a ceramic electrode. Alternatively, the ceramic electrode may be incorporated in the closed front end of the ignition portion or filled in an axial bore provided in the insulation.

Abstract: A spark plug incorporating a winding type inductor has a low noise level from a low frequency range to a high frequency range. The spark plug comprises a ceramic insulator having a bore, a metal fitting surrounding the insulator, a center electrode, a terminal electrode and a noise-attenuation element arranged in the bore of the ceramic insulator and sealed to the center and terminal electrodes through glass, said noise-attenuation element consisting of an inductance component alone or a combination of an inductance component and a resistance component, and said inductance component being arranged extending to both sides of a sealed level for the noise-attenuation element formed by an end of the metal fitting which is connected to the insulator.

Abstract: An ignition circuit for self-purifying creeping discharge spark plugs is disclosed. The ignition circuit comprises a creeping discharge spark plug including a center electrode and a concentric ground electrode between which is formed a spark gap having a creeping surface along which sparks are slidably moved, a capacitor located near said spark gap and connected in parallel therewith, and an impedance element connected in series with said capacitor and not impeding the movement of the electric charge discharged from said capacitor.

Abstract: An internal combustion engine ignition device comprises a radio noise preventing device for suppressing the capacity discharge current which flows in the low voltage side circuit of an ignition circuit and is generated during the spark discharge of a spark plug in order to prevent the radio noise generated by the ignition system of the internal combustion engine.

Abstract: A spark plug is disclosed which is used for an internal combustion engine such as an automobile. The spark plug has a carbonaceous resistance sandwiched between its spark rod electrode and its terminal rod in the central through hole of an elongated hollow cylindrical ceramic insulator. The spark electrode is made of a heat and spark resisting semiconductive resistance material, is sealed integrally with the carbonaceous resistance in the central through hole of the insulator, and produces a spark discharge between a grounded electrode spaced therefrom by a predetermined gap. The spark plug of the above-mentioned construction enables the intensity of a noise wave produced upon the spark discharge to be suppressed to the lowest possible level.