Patent ID: 6931914
Filing Date: 2005-08-23
Classification: G01L

Abstract:
1. A combustion condition detecting apparatus for an internal combustion engine, comprising: an ignition coil for generating a high voltage for ignition on the basis of an ignition signal; an ignition plug which makes a spark to ignite a fuel-air mixture when the high voltage for ignition of the ignition coil is applied thereto; and an ion current detector which detects an ion current generated in a combustion chamber in the internal combustion engine immediately after ignition, extracts a knock vibration component from the detected ion current, outputs a knock pulse when the knock vibration component is larger than a knock detection threshold value, and inhibits detection of the ion current while a false ion current is being generated, wherein the ion current detector includes: a current distributor which distributes the ion current; a band pass filter which extracts the knock vibration component from an output from the current distributor; knock determination means of outputting the knock pulse if the extracted knock vibration component is larger than the knock detection threshold value; combustion determination means of outputting a combustion pulse when an output from the current distributor is larger than a combustion pulse threshold value; ignition signal determination means of making a determination on the basis of the ignition signal as to whether energization of the ignition coil for ignition in another cylinder is started; and ion current limiting means provided in front of the current distributor, the ion current limiting means limiting the output of the ion current to the current distributor during a predetermined time period after the start of energization of the ignition coil for ignition in the another cylinder.