Ngk Spark Plug Company, Limited

Akio Kokubu

Yoshihiro Matsubara

Kazumasa Yoshida

Makoto Yamaguchi

Kazuya Iwata

Hiroshi Ono

Shoichiro Ito

Tetsusi Suzuki

An ignition system has a spark plug and a positive voltage applying unit. The spark plug includes a central electrode, a porcelain insulator for holding the central electrode, a main metallic shell for holding the porcelain insulator, and a ground electrode electrically connected to the main metallic shell. The positive voltage applying unit applies a positive voltage to the central electrode of the spark plug in comparison with the ground electrode, so that an ignition high voltage is applied between the central electrode and the ground electrode. In the spark plug, a spark discharge gap is formed between the ground electrode and a distal end portion of the central electrode. The ground electrode is positioned so that a rear edge of a mating face opposed to a peripheral side of the central electrode is positioned in the side of the distal end of the central electrode in comparison with an end face of the porcelain insulator.

Ignition system

In an internal combustion engine, an engine control device,judges based on a cooling water temperature of an engine in what state the engine is. When judged that the engine is in a cold state, the engine control device,produces an ignition signal to feed it to an igniter,so as to spark spark plugs,which are individually placed in cylinders at an exhaust stroke or expansion stroke.

Ignition device for internal combustion engines

A spark plug for an internal combustion engine is constituted by an insulating member (,) having an axial hole (,) formed along a central shaft (,); a rod-shape central electrode (,) accommodated in the axial hole; and a ground electrode (,) with which an igniting portion (,) opposite to the outer surface (,) of the central electrode is formed. In the spark plug, application of voltage between the central electrode and the ground electrode such that the polarity of the central electrode is made to be positive causes discharge to occur between the central electrode and the ground electrode. The spark plug satisfies at least one of the following conditions (a) and (b). (a) When the insulating member is cut along the central axis and a first extension line (,) in the form obtained by outwards extending a line (,) indicating an end surface of said insulating member adjacent to the igniting portion and a second extension line (,) in the form obtained by extending a line (,) indicating the outer surface of the insulating member in the vicinity of the igniting portion are drawn, the distance tp from an intersection (,) between the first and second extension lines to a line indicating an inner surface of the axial hole adjacent to the igniting portion is 1.0 mm or shorter (tp &lE;1.0 mm). (b) The difference (&phgr;d,&minus;&phgr;d,) between diameter &phgr;d,of the central electrode and diameter &phgr;d,of the axial hole is 0.08 mm or shorter &lcub;(&phgr;d,&minus;&phgr;d,) &lE;0.8 mm&rcub;.

Spark plug for internal combustion engine

In a semi-creeping discharge type spark plug, a cylindrical metal shell and an insulator are provided, the latter of which has an axial bore and placed within the metal shell so that a front end of the insulator extends beyond the metal shell. A center electrode is placed within the axial bore of the insulator so that a front end surface edge of the center electrode retracts by 0.1&tilde;0.6 mm behind from a front end surface of the insulator. A ground electrode, one end of which is connected to a front end of the metal shell, and the other end of which is bent to oppose an outer surface of the insulator so as to form an air-gap therebetween while permitting creeping spark discharges running along said front end surface of said insulator. A foward edge portion of a front end surface of the ground electrode extends by 0.0&tilde;1.0 mm forward from the front end surface of the insulator.

Semi-creeping discharge type spark plug

In a spark plug, a cylindrical metal shell (1) is provided whose inner wall has a rear section and a front section to respectively serve as a diameter-increased section and a diameter-decreased section with a seat portion (1) as a boundary therebetween. An insulator (2) is fixedly placed within the metal shell (1) so that a front end surface (21) of the insulator (2) extends beyond a front end surface (12) of the metal shell (1) with a shoulder portion (231) of an insulator nose (23) engaged against the seat portion (11) of the metal shell (1) by way of a packing (10). A center electrode (3) is fixedly placed within an axial bore (22) of the insulator (2), A ground electrode (4) is connected to the front end surface (12) of the metal shell (1), and bent so that a front end surface (41) of the ground electrode (4) opposes an outer surface (311) of the center electrode (3). The outer surface (311) and a front end surface (31) of the center electrode (3) are provided to respectively serve as a firing portion so as to form a spark discharge gap (Go) with the front end surface (41) of the ground electrode (4), the front end surface (41) of the ground electrode (4) forming an air gap (G) with an outer surface (25) of the insulator (2) so as to release creeping spark discharges along a front end surface (21) of the insulator (2).

Lateral electrode type spark plug with geometrical relationships with

In a spark plug in use for an internal combustion engine, a ground electrode is secured to a front end of the metal shell so that a front end surface of the ground electrode faces an elevational side of a front end of the center electrode to cause semi-creeping spark discharges therebetween along a front end surface of the insulator. A front end portion of the center electrode has an electrode base in the axial bore and an electrode front defined diametrically smaller than the electrode base by way of a diameter-variable portion. A diametrical difference between an initial point of the diameter-variable portion of the center electrode and the axial bore of the insulator is 1 mm or less, and the initial point of the diameter-variable portion is retracted by 0.0 mm-1.0 mm from the front end surface of the insulator.

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Nagoya, Japan

Akio Kokubu