Ngk Spark Plug Company, Limited

Niterra Co., Ltd.

Kohei Katsuraya

Katsutoshi Nakayama

Tatsunori Yamada

Hiroyuki Kameda

A plasma ignition deviceincludes a spark plug, a DC power supply, an AC power supply, and a coupling section. The coupling sectionincludes a capacitorwhich electrically connects the AC power supplyto the spark plug. The coupling sectionreduces the capacitance of the capacitorin the second ignition mode in which transmission of AC power is halted, as compared with that in the first ignition mode in which AC power is transmitted to the spark plug

Plasma ignition device and plasma ignition method

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

Ignition device and structure for mounting same

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.

Ignition system

A spark plug has a metal shell and a cylindrical ceramic insulator disposed in an inner circumference of the metal shell. An axial hole extends in an axial line CL direction through the insulator, and has a tip located more to a tip side of the spark plug than a tip of the metal shell, and a distance along the axial line CLfrom the tip of the metal shell to the tip of the ceramic insulator is 0.5 mm or more. The insulator satisfies C &#x2267;1.07 mm and V &#x2266;3.9 mm, where C is a thickness of the insulator in a cross section passing an inner circumference surface tip of the metal shell and orthogonal to the axial line CL,and V is a volume of the ceramic insulator within a range of 0.5 mm from the tip of the ceramic insulator to a rear end side in the axial line CLdirection.

Ignition plug

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.

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.

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.

Ignition plug and ignition apparatus

An ignition plug includes an insulator having an axial bore extending in the direction of an axis and an electrode inserted into the axial bore, and generates plasma discharge through supply, to the electrode, of high-frequency power generated by a predetermined high-frequency power supply. The electrode includes a center electrode inserted into the forward side of the axial bore and a terminal electrode inserted into the rear side of the axial bore. In the axial bore, the terminal electrode and the center electrode are fixed to the insulator by means of a glass seal which contains a glass component, and are in direct contact with each other. Thus, ignition performance can be further improved.

High-frequency spark plug with center electrode and terminal electrode in direct contact

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.

Ignition system and spark plug

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&#x2212;B&#x2267;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.

Spark plug having fusion zone

An ignition plug () includes a center electrode () extending in the direction of an axis (CL), an insulator () having an axial hole () into which the center electrode () is inserted, a tip () joined to a forward end portion of the center electrode () by a fusion portion (), and a ground electrode () forming a gap () in cooperation with the tip (). The ignition plug generates high-frequency plasma at the gap () when high-frequency electric power is supplied to the gap (). The forward end of the tip () is located forward of the forward end of the insulator () with respect to the direction of the axis (CL). Also, at least a portion of the outer surface of the fusion portion () is located within the axial hole (), and, the distance between a forward-end-side opening of the axial hole () and the rearmost end of the outer surface of the fusion portion (), measured along the axis (CL), is equal to or greater than 0.1 mm. Thus, in the ignition plug () which generates high-frequency plasma, corrosion of the fusion portion can be suppressed effectively, whereby durability is improved.

High-frequency plasma spark plug

A spark plug includes a center electrode extending in an axial direction; an insulator formed externally of the outer circumference of the center electrode; a metallic shell formed externally of the outer circumference of the insulator and having a ledge which supports the insulator; and a ground electrode joined to the metallic shell. The insulator has a support portion which faces the ledge. A 'frontward direction' is defined as the direction parallel to the axial direction toward a spark portion formed between the center electrode and the ground electrode. The insulator has a diameter reduction portion whose outside diameter reduces along the frontward direction from the support portion, and a diameter increase portion whose outside diameter increases along the frontward direction from the front end of the diameter reduction portion. This restrains the generation of leak current while maintaining heat resistance of the spark plug.

Spark plug having shaped insulator

High-frequency plasma spark plug includes an insulator which has an axial hole extending in the axis direction, a center electrode inserted into a distal end side of the axial hole, a terminal electrode inserted into a rear end side of the axial hole, and being electrically connected to the center electrode, and a cylindrical main fitting mounted on an outer periphery of the insulator. With respect to a coaxial cable, the inner conductor is connected to the terminal electrode and the outer conductor is connected to the main fitting. High frequency power generated by a predetermined high-frequency power source is supplied via the coaxial cable thus generating high frequency plasma. The main fitting includes a large diameter portion which bulges radially outward and a connection portion which is brought into contact with the outer conductor.

There is provided a spark plugwith a ground electrode, wherein a protrusion amount A of a protruding portionsatisfies a relationship of 0.4 mm&#x2266;A&#x2266;1.0 mm and wherein a width B from a front end surfaceto a press recessed portionsatisfies a relationship of 0.4 mm&#x2266;B&#x2266;2.5 mm.

Spark plug and manufacturing method thereof

It is an object of the present invention to provide a spark plug that can be produced at low cost and secure compatibility between ignition performance and durability. The spark plug according to the present invention includes a center electrode and a ground electrode having an inner surface facing the center electrode, characterized in that; the ground electrode has a protrusion and a hole; the protrusion protrudes from the inner surface by a protruding length A of 0.4 to 1 mm and has a first straight portion with a projected first straight portion area Sof 1.5 to 3 mm; the hole has an opening at an outer surface of the ground electrode, a second straight portion, a bottom portion and a transition portion; the opening is formed in such a manner that the ratio (S/S) of a projected opening area Sof the opening to the projected first straight portion area Sis not less than 1.2; and the transition portion is in the form of a taper portion.

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Nagoya, Japan

Kohei Katsuraya