Method and apparatus for detecting knock in an internal combustion engine.

摘要

A method and apparatus of detecting knocking in an internal combustion engine having a crankshaft (4) uses a knock detecting sensor (17) to detect vibration caused by knocking. The signals from the knock detecting sensor (17) are detected between a first and a second moment of time (i.e. a measurement window) and at least one of the first and second moments of time are independently varied in dependence upon a vibration spectrum of frequencies to be detected. In a preferred embodiment a plurality of frequency spectra, each having a different first and second moment of time, are each separately analysed for determining knock intensity. The moments of time are represented by first and second angles of the crankshaft. A plurality of measurement windows are advantageously used to determine the level of knocking and if the level exceeds a predetermined level the ignition timing for the engine is retarded. The frequency of maximum amplitude is arranged in operation to be the centre frequency of a frequency spectrum determined by the measurement window. <IMAGE>