Patent ID: 6020742
Filing Date: 2000-02-01
Classification: F02D,F02P,G01L

Abstract:
A combustion monitoring apparatus for an internal combustion engine comprising:a voltage supply circuit supplying a voltage to opposed electrodes disposed within a combustion chamber of the engine;a combustion ion monitoring circuit monitoring a variation in amount of combustion ions existing between the opposed electrodes to determine a combustion condition of the engine based on a current flowing through the opposed electrodes produced by application of the voltage to the electrodes by said voltage supply circuit;wherein said combustion ion monitoring circuit includes an ion current monitoring circuit and a combustion condition analyzing circuit, said ion current monitoring circuit monitoring a combustion ion current flowing through the opposed electrodes which changes with the variation in amount of combustion ions to provide a combustion ion signal indicative thereof, said combustion condition analyzing circuit analyzing the combustion condition of the engine based on the combustion ion signal;wherein said combustion condition analyzing circuit determines that preignition has occurred when the combustion ion signal exceeds a given preignition reference value; anda control circuit controlling an operation of said voltage supply circuit so that the voltage is applied across the opposed electrodes prior to a discharge duration of a spark plug mounted in the combustion chamber of the engine;wherein the opposed electrodes are plug electrodes of the spark plug, and wherein said voltage supply circuit includes an ignition coil applying a dc voltage to the plug electrodes during the discharge duration of the spark plug to develop a spark between the plug electrodes, a variable dc power supply outputting a current to charge the ignition coil prior to the discharge duration for storing electrical energy used to develop the spark between the plug electrodes, an engine speed determining circuit determining a speed of the engine, a charged current control circuit controlling the variable dc power supply so that the current outputted to the ignition coil is decreased as the speed of the engine determined by said engine speed determining circuit is decreased, the variable dc power supply starting to charge the ignition coil at a fixed crank angle of the engine.