Knocking detection device for IC engine

摘要

The device includes an ignition coil (1), a switch arrangement (3) connected to the primary side of the ignition coil, and a spark plug (4) connected to the secondary side of the ignition coil, to ignite an air/fuel mixture in a cylinder using a high voltage induced in the secondary side of the ignition coil at a switch-off of a primary current through the switch arrangement. An ion current detection arrangement (10) forms an ion current path in combination with the secondary side of the ignition coil and the spark plug, to supply a voltage to the spark plug and to detect an ion current, which flows through the spark plug in response to an ignition of the air/fuel mixture in the cylinder. A processing arrangement (20) detects knocking through extracting a specific frequency component from an output signal of the ion current detection arrangement. An LC resonance frequency formed through the inductance of the secondary side of the ignition coil and a stray capacitance in the ion current path is adjusted in such way, that it does not overlap with the specific frequency component of the knocking.