Patent ID: 8909459

Claim:
A knock control apparatus for an internal combustion engine, comprising: a sensor that outputs a signal corresponding to a combustion state of the internal combustion engine; a knock signal calculation portion that calculates, as a knock signal, a characteristic component of a knock using the output from the sensor at every spark timing; a knock signal normalization portion that normalizes the knock signal using a base statistic calculated on the basis of the knock signal; a knock determination threshold calculation portion that sets a knock determination threshold on the basis of the normalized knock signal; a knock determination portion that determines an occurrence of a knock in a case where the normalized knock signal exceeds the knock determination threshold set by the knock determination threshold calculation portion; and an operating state determination portion that determines an operating state of the internal combustion engine, wherein the knock signal normalization portion calculates, a base statistic 1 on the basis of a current value of the knock signal, a base statistic 2 on the basis of a last value of the knock signal, and a base statistic 3 by interpolating between the base statistic 1 and the base statistic 2 according to a determination result by the operating state determination portion; the knock signal normalization portion normalizes the knock signal using the calculated base statistic 3; and the base statistic 3 is calculated in reference to the base statistic 2 in a state in which the operating state determination portion determines that the internal combustion engine is not in an operating state such that accompanies a variance of the knock signal, and in a state in which the operating state determination portion determines that the internal combustion engine is in an operating state such that accompanies a variance of the knock signal, influences of the base statistic 1 are calculated more significantly into the base statistic 3 as a measure of the variance of the knock signal increases.