초록 ▼

A misfire detecting apparatus for an internal combustion engine detects only an ion current due to combustion of an air/fuel mixture regardless of a leakage current when combustion: takes place normally. The apparatus includes circuitry for detecting an ion current generated within the engine cylind

A misfire detecting apparatus for an internal combustion engine detects only an ion current due to combustion of an air/fuel mixture regardless of a leakage current when combustion: takes place normally. The apparatus includes circuitry for detecting an ion current generated within the engine cylinder immediately after combustion, circuitry 21, 24, 26 for detecting a leakage current occurring between electrodes of a spark plug 14, a first waveform shaper 18 for shaping the ion current into a pulse signal indicating a combustion or misfire event by comparing the pulse signal with a first threshold value for deciding the ion current, the first threshold value being set on the basis of a level of the ion current upon rising thereof, the ion current being superposed on the leakage current, a second waveform shaper 20 for shaping the ion current as detected into a pulse signal through comparison with a second fixed threshold value which is fixed at a value smaller than the first threshold value, and a selector 22 for selectively outputting as the combustion pulse signal either a shaped pulse signal outputted from the first waveform shaper 18 upon detection of occurrence of the leakage current or a shaped pulse signal outputted from the second waveform shaper 20 when no leakage current is detected.

대표청구항 ▼

1. A misfire detecting apparatus for an internal combustion engine for detecting combustion of an air/fuel mixture or occurrence of misfire event within an engine cylinder of an internal combustion engine on the basis of an ion current which makes appearance upon combustion of the air/fuel mixture,

1. A misfire detecting apparatus for an internal combustion engine for detecting combustion of an air/fuel mixture or occurrence of misfire event within an engine cylinder of an internal combustion engine on the basis of an ion current which makes appearance upon combustion of the air/fuel mixture, comprising:ion current detecting means for detecting an ion current which depends on an amount of ions generated within said engine cylinder immediately after combustion of the air/fuel mixture within said engine cylinder; first waveform shaping means for shaping the ion current as detected into a pulse signal indicating combustion/misfire event by comparing with a first threshold value for deciding occurrence of the ion current, said first threshold value being set on the basis of a bottom-hold value of said ion current; and means for outputting said pulse signal as a combustion pulse signal indicating either combustion of the air/fuel mixture or occurrence of misfire event.