Patent ID: 7219006

Claim:
A knock determining apparatus for an internal combustion engine, comprising: a sensor outputting a waveform signal which corresponds to a knock state of the internal combustion engine; and at least one of a first knock determining means, a second knock determining means, and a third knock determining means, for determining the knock state based on a vibration intensity distribution of the waveform signal which is outputted from the sensor during a predetermined number of times of combustions; wherein the first knock determining means includes: a calculating means for calculating a center value of the vibration intensity distribution and a dispersion index relating to the center value in a region where the vibration intensity is smaller than the center value; and a reference determining means for determining a statistical reference level based on the center value and the dispersion index, the first knock determining means determines the knock state based on a number of times the vibration intensity exceeds the statistical reference level during the predetermined number of times of combustions, the second knock determining means includes: an average calculating means for calculating an average of the vibration intensity distribution and a dispersion index relating to the average; a region establishing means for dividing the vibration intensity distribution in such a manner as to establish a plurality of regions based on the average and the dispersion index relating to the average; and a counter means for respectively counting a number of the vibration intensity in each region, the second knock determining means determines the knock state based on the number of the vibration intensity in each region and/or a ratio of the numbers of the vibration intensity between in each region, and the third knock determining means includes an index average calculating means for calculating an average of the dispersion index, the third knock determining means determines the knock state based on the average of the dispersion index.