Ngk Spark Plug Company, Limited

Tomokatsu Kashima

Tatsunori Yamada

Katsutoshi Nakayama

Kenji Ban

Takashi Sekizawa

Yasushi Sakakura

Kazuyoshi Torii

Yuki Toumatsu

Yuya Ono

Yudai Kawaguchi

A spark plug that can reduce variation in a discharge point. The spark plug includes: a center electrode; a metal shell insulating and holding the center electrode; and a ground electrode including a base material having one end portion connected to the metal shell, and a tip connected to another end portion of the base material. The tip has a discharge surface opposed to the center electrode with a spark gap therebetween. The discharge surface has a quadrangular shape and is chamfered at four sides thereof. Only a first side which is one of the four sides is provided with a C chamfer.

Spark plug

A spark plug including a ground electrode including a base material, a tip having a discharge surface, and a melt portion interposed over an entire area between the tip and the base material and joining the tip to the base material; and a center electrode with a spark gap formed between the center electrode and the discharge surface. The tip has, in an inner area surrounded by an outer peripheral portion of the tip, a thin portion in which a distance between the discharge surface and the melt portion is shorter than a distance between the discharge surface and the melt portion in the outer peripheral portion. The thin portion extends from a part of the outer peripheral portion to a part other than the part of the outer peripheral portion.

A spark plug having a metal shell, center electrode and a ground electrode. The ground electrode includes an electrode base portion extending from a front end portion of the metal shell toward the front, a bent portion connected at one end thereof to a front end of the electrode base portion and an electrode distal end portion extending from the other end of the bent portion and forming a spark discharge gap with a center electrode. The ground electrode has a base material and a coating layer applied to the base material. The coating layer is formed on at least a front end face and an outer circumferential surface other than a center-electrode-side surface of the electrode distal end portion of the ground electrode. The base material of the ground electrode is exposed at least at a part of the electrode base portion.

An ignition system includes an ignition plug, a discharge power supply for applying a high voltage to the gap of the ignition plug, a high-frequency power supply for supplying a high-frequency current to the gap, a matching unit provided between the ignition plug and the high-frequency power supply, and a mixer through which currents output from the two power supplies flow. An oscillation frequency fs (Hz) which maximizes the current flowing between the matching unit and the mixer when spark discharge is generated and an oscillation frequency fo (Hz) which maximizes the current flowing between the matching unit and the mixer when spark discharge is not generated satisfy a relation fs/fo&#x2267;0.85. Thus, a current whose oscillation frequency is equal to the oscillation frequency fs flows between the matching unit and the mixer when spark discharge is not generated.

Ignition system

An ignition system that sufficiently utilizes the energy output from a power supply, to thereby realize excellent ignition performance. The ignition system includes an ignition plug having a spark discharge gap formed between a center electrode and a ground electrode, and a power supply for supplying electric energy to the spark discharge gap. Electric energy output from the power supply for producing spark discharge of one unit is set to 100 mJ or greater. S1&#x2267;[{&#x2212;30 (mm)&#xd7;G1+60}/100]&#xd7;S2 and G1&#x3c;2.0 are satisfied wherein G1 represents the size (mm) of the spark discharge, S1 represents an area (mm) defined with a region obtained by removing, from a projection region of the center electrode, a region where the projection region overlaps with a projection region of the ground electrode and S2 represents an area (mm) defined with the projection region of the center electrode.

A ground electrode includes a main body portion and a projecting portion having a width smaller than a width of the main body portion. A spark discharge gap is formed between a discharging surface of the projecting portion and a front end surface of a center electrode. When the front end surface and the ground electrode are projected on a first plane, at least a part of the projection region of the projecting portion overlaps the projection region of the front end surface. A width Le (mm), a width Lc (mm), a cross-sectional area Sg (mm), a cross-sectional area Sc (mm), an angle &#x3b8;1 (&#xb0;), an angle &#x3b8;2 (&#xb0;), an angle &#x3b8;3 (&#xb0;), and an angle &#x3b8;4 (&#xb0;) satisfy expressions Le&#x3c;Lc, 2.9&#x2266;Sc+Sg&#x2266;4.25, and 0.30&#x2266;(&#x3b8;1/&#x3b8;2)&#xd7;(&#x3b8;3/&#x3b8;4)&#x2266;0.67.

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Kiyosu, Japan

Tomokatsu Kashima