Ngk Spark Plug Company, Limited

Kazuya Iwata

Akira Suzuki

Yoshihiro Matsubara

Takafumi Oshima

Tsutomu Okayama

Takahiro Suzuki

Mamoru Musasa

Makoto Yamaguchi

Kazumasa Yoshida

Akio Kokubu

Hiroshi Ono

Shoichiro Ito

Yuuji Hirano

Tetsushi 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 a spark plug, a main air gap (A) is formed between a parallel ground electrode (,) and the end face of a central electrode (,), a semi-surface gap (B) is formed between the end face (,C) of a semi-surface ground electrode (,) and the side face (,A) of the central electrode (,) and a semi-surface air gap (C) is formed between the end face (,C) and the side face (,E) of insulator. In addition, difference in a level E between the height of the lower end face (,D) of the insulator (,) and the height of the upper edge (,B) of the end face,C of the semi-surface ground electrode,is E&lE;&plus;0.7 mm, the distance B of the semi-surface gap (B) is longer than the distance A of the main air gap (A) and the distance C of the semi-surface air gap (C) and the insulator is shorter than the distance A of the main air gap (A).

Spark plug with specific gap between insulator and electrodes

A spark plug has a cylindrical metal shell, a ground electrode and an insulator fixedly supported within the metal shell with a front end of the insulator extended beyond a front end of the metal shell. The insulator has an axial bore in which a center electrode is placed to form a spark gap with the ground electrode. The front end of the metal shell is generally flush with or somewhat recessed into an inner wall of a combustion chamber of an internal combustion engine when the spark plug is mounted on a cylinder head of the engine. The front end of the insulator extends at least 4.0 mm from the front end of the metal shell.

Spark plug for an internal combustion engine

In a center electrode for a spark plug, the center electrode is made of a heat-conductor core cladded with a nickel-alloyed metal. A recess is provided on the front end surface of the nickel-alloyed matrix and the columnar tip is made of a precious metal and fit in the recess in such a manner that a front end of the tip protracts from the recess. The outer surface of the tip is welded to an inner surface of the recess. The dimensional relationship of the components of the spark plug A, B, C, D, E, F and G is as follows: 0.3 mm.ltoreq.A.ltoreq.0.8 mm, 1.2A.ltoreq.B.ltoreq.3A, 0.1 mm.ltoreq.(C-A)/2.ltoreq.0.5 mm, D.ltoreq.(C-A)/2, E.ltoreq.B/4, 0 mm.ltoreq.F.ltoreq.0.5 mm and A/5.ltoreq.G.ltoreq.A/2, where A: a diameter of the columnar tip, B: a length of the columnar tip, C: a diameter of a front end of the nickel-alloyed metal, D: a length of a front end of the nickel-alloyed metal, E: a length of the front end of the tip which is protracted from the recess, F: a distance between a rear end of the tip and a front end of the heat-conductor core, G: a distance of a welding portion penetrated from the outer surface of the tip into the inner surface of the recess.

Spark plug having an erosion resistant tip

In a method of making a spark plug, a recess is provided on an end surface of the electrode blank metal. A straight neck portion is provided around the recess, and forming a tapered surface connecting from the straight neck portion toward an opposite side of the recess. A disc-shaped tip is placed in the recess of the electrode blank metal. The disc-shaped tip is pressed against an inner bottom of the recess in the axial direction of the electrode blank metal, and a laser beam welding is applied to an outer wall of the recess substantially all through its circumferential length by rotating the electrode blank metal.

Method of making a spark plug

Growing community of inventors

Nagoya, Japan

Kazuya Iwata