Circuit for detecting knocking for spark ignition engines

摘要

A circuit for detecting knocking for spark ignition engines, in which the combustion space of each cylinder has a spark plug connected to the secondary coil of an ignition transformer. The technical problem resides in designing the circuit in such a way that, without special measures, a positive measurement voltage can be used. The side of the secondary coil (31) conducting the positive voltage of the ignition pulse is connected via a pre-spark gap (4) to the high-voltage electrode of the spark plug (2). A high-voltage generator (8) for generating a positive high direct voltage which is substantially smaller than the ignition voltage is connected to at least one spark plug (2) via a measurement line (20) with a measuring resistor (10) and a high-voltage diode (11). A bandpass filter (13) which is tuned to the natural acoustic frequency of the respective combustion space is connected to the measurement line (20). A rectifier circuit (14) and a threshold value circuit (15) which emits a knocking signal (17) are connected downstream of the bandpass filter (13). <IMAGE>