JPS6483119A - Apparatus for detecting abnormal vibration of engine - Google Patents

Abstract

PURPOSE:To obtain an inexpensive apparatus having good detection accuracy, by converting the detected vibration of an engine to a component distribution signal at every predetermined frequency to compare the same with a reference value. CONSTITUTION:A programmable band-pass filter 35 divides as frequency band FB from 100 Hz to 10 kHz, for example, into 25 sections by the control of a CPU 32 and inputs the detection output of an electromagnetic pickup MP 4 while changes over the center frequency thereof at every one rotation of an engine in synchronous relation to the output of the MP. the passing signal of each FB is converted from a square average value to a smooth DC signal by an RMS/DC converter 36 while said DC signal is converted to a digital signal by an A/D converter and edited by a CPU 32a to be converted to a component distribution signal divided at every predetermined BF. At first, the vibration of the engine at a normal time is preliminarily detected by an MP 1 and processing is performed while the FB of the filter 35 is changed over to obtain a component distribution signal which is, in turn, stored in the CPU 32 as a reference value. By this method, the engine is operated under the same operating condition as that when the reference value is stored to detect the vibration thereof by a detector 1 and the detected value is compared with the corresponding waveform of the reference value and the presence of abnormality is judged from the difference between both of them.