Patent ID: 7788022

Claim:
A control apparatus for an internal combustion engine, comprising: knock detection means for determining occurrence of knock based on an output signal from at least one of a knock sensor and a cylinder internal pressure sensor provided for the internal combustion engine; and knock control means for performing knock control to avoid the knock in detection of the knock by the knock detection means; wherein the knock detection means includes: a lowpass filter for eliminating a high frequency component of the output signal from the at least one of the knock sensor and the cylinder internal pressure sensor; A/D conversion means for performing A/D conversion on the output signal from the lowpass filter for each predetermined time; and digital signal processing means for performing digital signal processing on the data obtained by the A/D conversion performed by the A/D conversion means to perform a time-frequency analysis, the knock detection means performing knock detection based on a result of the digital signal processing by the digital signal processing means, wherein the digital signal processing means includes: observation interval setting means for dividing the data obtained by the A/D conversion performed by the A/D conversion means to set observation intervals each containing a predetermined number of samples; and multi-frequency simultaneous analysis means for simultaneously analyzing multiple frequencies by a discrete Fourier transform for each of the observation intervals set by the observation interval setting means, and wherein the observation interval setting means changes the number of samples contained in each of the observation intervals according to a frequency to be analyzed.