Ngk Spark Plug Company, Limited

Kazumasa Yoshida

Yoshihiro Matsubara

Akio Kokubu

Makoto Yamaguchi

Wataru Matsutani

Kazuyoshi Torii

Hiroyuki Kameda

Akira Suzuki

Katsutoshi Nakayama

Kenji Nunome

Satoshi Nagasawa

Hiroaki Kuki

Kazuya Iwata

Hiroshi Ono

Shoichiro Ito

Tetsusi Suzuki

Akio Kokubo

A spark plug including a center electrode and a ground electrode. A center electrode noble metal tip is joined to a leading end portion of a center electrode, and a ground electrode noble metal tip is joined to a center-electrode-side side surface of the ground electrode. A distal end portion of the ground electrode noble metal tip protrudes from a distal-end surface of the ground electrode by 0.1 mm to 1.5 mm. A center-electrode-side side surface of the ground electrode noble metal tip projects from a center-electrode-side side surface by 0.15 mm to 0.6 mm. The ground electrode includes chamfered portions. Thickness lengths and widthwise lengths of the respective chamfered portions achieved within a cross section perpendicular to a center axis of the ground electrode are set to 0.2 mm or more.

Spark plug for internal combustion engine and method for manufacturing spark plug

A spark plugcomprised of a metal shell, an insulator, a center electrodeand a ground electrode. A rear-end face of the ground electrodeis welded to a front-end face of the metal shell, and a bent portionlocated at the intermediated position in the longitudinal direction is bent toward the center of the spark plug. The ground electrodeassumes a circular-shape with a diameter of 2 mm or less whereby an inflow of an air-fuel mixture is not disturbed even when the air-fuel mixture directly flows into a back face of the ground electrode. The ground electrodeis comprised of an outer layerA made of a nickel alloy and an inner layerB made of pure copper with an excellent thermal conductivity, in which a ratio of a cross-sectional area of the inner layerB to the entire cross-sectional area of the ground electrodeis 10% or more to 35% or less. Thus, the spark plugwhich is excellent in heat sinking ability and can prevent a spring back phenomenon due to a difference in a coefficient of thermal expansion.

Spark plug for use in an internal-combustion engine with a bilayer ground electrode

A spark plug including: a center electrode as defined herein; a substantially cylindrical insulator as defined herein; a cylindrical metal shell as defined herein; and a ground electrode as defined herein, wherein a spark discharge gap is provided between the leading end portion of the center electrode and the leading end portion of the ground electrode, and the ground electrode has a bulging curved face on a side opposite to a side in which the center electrode is provided, and a maximum of width of the ground electrode within a range of &#xb1;1 mm from a center point of the spark discharge gap in the axial direction, as viewed in a direction where the center electrode and the ground electrode overlap, is 105% or less of a width of an ordinary portion having a substantially constant width.

Spark plug for internal combustion engine

A spark plug includes an outer electrode including an outer electrode tip of which a distal end surface is spaced from an outer peripheral surface of a leading end portion of a center electrode to define a spark discharge gap. A protruding insulator portion of a cylindrical insulator protrudes at least 1.0 mm from a leading end surface of a cylindrical metal shell. A protruding center electrode portion of the center electrode protrudes at least 3.5 mm from the leading end surface of the cylindrical metal shell. A relationship (&#x3b8;)/2&#x2267;75 degrees is satisfied where the angle &#x3b8;is defined as a central angle (degrees) of a first circular sector having a point Bas a center thereof, and the angle &#x3b8;is an average value (degrees) of the central angles of two second circular sectors having the point Bas a center thereof.

Spark plug having specific configuration of center electrode with respect to outer electrode

A spark plug comprising: a center electrode extending in a direction of an axis of said spark plug; a cylindrical insulator which has a shaft hole, and which holds said center electrode in said shaft hole in a state where a tip end of said center electrode is projected from a tip end face of said insulator; a metal shell which holds said insulator; and a ground electrode in which one end is joined to a tip end face of said metal shell, and which extends from said one end toward another end, wherein said ground electrode has an inner side face which faces said center electrode, and an outer side face which is a back face with respect to said inner side face, said outer side face is formed as an arcuately curved face when viewed from a side of said another end in an extending direction of said ground electrode, and a columnar noble metal tip is joined to said inner side face.

Spark plug including ground electrode with arcuately curved face

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;.

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

A spark plug having a center electrode, a ground electrode, and an insulator. The ground electrode has a firing surface formed in a tip end side, and the firing surface is opposed to a side face of the center electrode. The insulator covers the outside of the center electrode and is placed such that a tip end portion is between the side face of the center electrode and the firing surface of the ground electrode. A discharge high voltage is applied across the center electrode and the ground electrode such that a polarity of the center electrode is positive and that of the ground electrode is negative. The high voltage causes a spark discharge to be generated between the firing surface of the ground electrode and a tip end portion of the center electrode.

Spark plug and an internal combustion engine igniting system using the

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

Kazumasa Yoshida