Ngk Spark Plug Company, Limited

Iwao Kunitomo

Yoshihiro Matsubara

Wataru Matsutani

Yuichi Yamada

Yoshikuni Sato

Kenji Ban

Toru Nakamura

Daisuke Nakano

Kozo Amano

Hironobu Mizutani

A spark plug in which a front end portion of a ground electrode is positioned outside of a virtual outer circumferential face that is formed by extending a front and outer circumferential face of a center electrode in the axis direction, and positioned on a front end side in the axis direction with respect to a virtual face including a front end face of the center electrode. Further, the equation 1.1&#x2266;b/a&#x2266;1.6 is satisfied, where 'a' (mm) represents a first minimal distance between the front end portion of the center electrode and the front end portion of the ground electrode and, where 'b' (mm) represents a second minimal distance between the front end portion of a ceramic insulator and the front end portion of the ground electrode.

Spark plug for internal combustion engine

A plasma jet ignition plug capable of inhibiting occurrence of channeling while reducing removal of energy of plasma through a ground electrode at the time of emission of plasma. A ground electrode of a plasma jet ignition plug projects inward from a front end face of a metallic shell toward an opening end of a cavity which is open at a front end face of an insulator. A projecting distal end which forms a spark discharge gap between the same and a center electrode within a cavity is located inward, with respect to a diametral direction P orthogonal to an axis O, of a position which is located 0.5 mm radially outward from the opening end of the cavity.

Plasma jet ignition plug

A spark plug including: a cylindrical insulator having an axial hole extending through the insulator in an axial direction; a center electrode inserted in the axial hole; a metal shell provided around an outer periphery of the insulator and having a leading end surface, from which a leading end surface of the insulator protrudes; a ground electrode having a base end bonded to the leading end surface of the metal shell; and a noble metal tip disposed on a distal end of the ground electrode, an end of the noble metal tip protruding toward the center electrode in a radial direction, wherein: the spark plug forming a spark discharge path upon application of a discharging voltage between the protruding end of the noble metal tip and an end of the center electrode, the spark discharge path including an aerial discharge gap between a part of the protruding end of the noble metal tip and a part of the end of the insulator and a surface-creeping discharge path beginning at a part of the end of the insulator and a part of the center electrode and extending along the end surface of the insulator; and the noble metal tip protruding from the leading end of the ground electrode by a protruding length of more than 0.2 mm.

In a spark plug including a cylindrical metal shell whose inner wall has a ledge portion, an insulator having a seat portion which engages with a rear slope surface of the ledge portion to be supported within the metal shell, a center electrode supported with an axial bore of the insulator, and a ground electrode extended from the metal shell to form a spark gap with the center electrode. A dimensional relationship among (A), (B) and (g) is defined as follows: {(B-A)/2}.gtoreq.0.8.times.(g) or {(B-A)/2}.gtoreq.0.9.times.(g). Where B (mm) is an inner diameter of a metal shell portion which surrounds an insulator nose, A (mm) is a base diameter of the insulator nose, and g (mm) is a width dimension of the spark gap.

Spark plug in use for an internal combustion engine

In a multi-polarity type spark plug for an internal combustion engine, a tubular insulator is supported within a cylindrical metallic shell through which a spark plug is to be attached to an internal combustion engine. A center electrode is placed within the insulator, a front end of the center electrode being directed toward a combustion chamber of the internal combustion engine from a front end of the metallic shell so as to extend beyond a front end of the insulator. First and second ground electrodes are each connected to the front end of the metallic shell, the first ground electrode forming a first vertical spark gap with a front end surface of the center electrode which directly opposes an elevational side of the center electrode, and the second ground electrode forming a second horizontal spark gap with an elevational side of the center electrode. An angle .theta.a is limited as 60.degree..ltoreq..theta.a .ltoreq.150.degree. in which the angle .theta.a is taken when the first ground electrode forms against the second ground electrode with the center electrode as an axial center.

Growing community of inventors

Aichi, Japan

Iwao Kunitomo