Ngk Spark Plug Company, Limited

Masahiro Ishikawa

Yoshihiro Matsubara

Kazumi Kawamura

Mamoru Kodera

Shinichi Hiramatsu

Terumasa Tomita

A method of making a spark plug having a noble metal chip joined to an electrode main body of a ground electrode by interposing therebetween an intermediate member. The method comprises the steps of prior to joining the noble metal chip to the electrode main body, joining the intermediate member and the noble metal chip together, placing a noble metal chip and intermediate member assembly on the electrode main body in a way as to allow the intermediate member to contact the electrode main body, and welding the electrode main body and the intermediate member together while restricting relative movement of the electrode main body and the intermediate member without applying an urging force to a joint between the intermediate member and the noble metal chip.

Method of making a spark plug

A front end portion of a center electrodeis a circular cylindrical center-electrode noble-metal ablation resistance portionwhose radius r mm and length l mm are determined so as to satisfy 5&#x2266;l/r&#x3c;20. An ignition-performance-improving ground electrodeis configured such that a distal end portion thereof is bent in a direction toward the center electrode; and a rear end-edgeof a distal end surfaceis located frontward in relation to a front end surfaceof the center-electrode noble-metal ablation resistance portion. In orthogonal projection on a projection plane P perpendicularly intersecting an axis O of the center electrode, the rear end-edgeis located outward in relation to the front end surfaceof the center-electrode noble-metal ablation resistance portion. A portion of the ignition-performance-improving ground electrodewhich includes at least the rear end-edgeis a ground-electrode noble-metal ablation resistance portion

Spark plug

An ion current detector device for an internal combustion engine, including: a spark plug having a metallic shell in which a tubular insulator is disposed, a center electrode extending in an axial direction of the tubular insulator and having a front end, a ground electrode which forms a spark gap (G1) with the front end of the center electrode, and at least one slanted bore provided in the metallic shell which is slanted inwardly against the axial direction with respect to the center electrode. An ion current detector electrode is provided within the slanted bore of the metallic shell and located proximate to the front end of the center electrode of the spark plug so as to form an ion current gap (G2) therebetween, the ion current gap (G2) being dimensionally wider than the spark gap (G1), and the spark plug being connected to an ignition circuit to be provided in a cylinder of the internal combustion engine. An operational rod is provided for initially moving the ion current detector in the axial direction within the slanted bore thereby to micro-adjust a width of the ion current gap (G2) and then firmly positioning the ion current detector electrode within the slanted bore. An ion current detector circuit is provided between the ion current detector electrode and the ground for detecting an ion current flowing between the center electrode and the ground through the ion current gap (G2) depending on a voltage difference therebetween.

Ion current detector device for use in an internal combustion engine

In a device of estimating heat resistivity for a spark plug, an ignition spark control circuit is provided to discontinue ignition spark across electrodes of a spark plug at a predetermined intervals. A counter circuit is provided to count the times of the ignition spark suppressed by the ignition spark control circuit. A self-ignition detection circuit is provided to detect the self-ignition from the spark plug when the ignition spark is suppressed by the ignition spark control circuit. A self-ignition counter circuit is provided to count the numbers of the self-ignition detected by the self-ignition detection circuit. A calculation circuit is provided to calculate occurrences rate of the self-ignition from the spark plug on the basis of the suppressing numbers of the ignition spark counted by the counter circuit and the detecting numbers of the self-ignition counted by self-ignition counter circuit. A self-ignition timing detection circuit is provided to detect a detection timing of the self-ignition detected by the self-ignition detection circuit. A preignition timing anticipating circuit is provide to anticipate an ignition timing when preignition of the internal combustion engine occurs on the basis of the occurrence rate of the self-ignition detected by the calculation circuit and detecting timing of the self-ignition detected by the self-ignition timing detection circuit.

Growing community of inventors

Aichi, Japan

Masahiro Ishikawa