Ngk Spark Plug Company, Limited

Terumasa Tomita

Yoshihiro Matsubara

Masahiro Ishikawa

Mamoru Kodera

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.

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Nagoya, Japan

Terumasa Tomita