FREQUENCY COMPONENT ANALYZER

摘要

Provided is a frequency component analyzer which analyzes the frequency component in the detected value of the operating parameter of an internal combustion engine in synchronization with the rotation of the internal combustion engine.  The operating parameter is sampled at predetermined time intervals and the sampled value is converted into a digital value.  The intensity of a first element and the intensity of a second element of which the phase is shifted from that of the first element by 90 degrees are calculated with respect to a predetermined number of sampled values, said first element and said second element corresponding to a plurality of frequency components included in the detected value.  The intensities of the frequency components of a plurality of frequencies are calculated by using the intensity of the first element and the intensity of the second element in synchronization with the rotation of the internal combustion engine.  When the rotation speed of the internal combustion engine is not lower than a set threshold value, the calculation of the intensities of the frequency components is performed by substituting part of the integrated value of the intensities of the first elements by the previously calculated value thereof and substituting part of the integrated value of the intensities of the second elements by the previously calculated value thereof.