초록 ▼

A method and system for controlling combustion engines by detection of the present air/fuel ratio within the cylinders of the combustion engine, using an analysis of the characteristics of the ionization current, as detected via a measuring gap with a bias voltage applied being arranged in the combu

A method and system for controlling combustion engines by detection of the present air/fuel ratio within the cylinders of the combustion engine, using an analysis of the characteristics of the ionization current, as detected via a measuring gap with a bias voltage applied being arranged in the combustion chamber, preferably using the spark plug gap in an Otto-engine. A measuring voltage corresponding to the degree of ionization is detected during the flame ionization phase and during a time- or crankshaft position dependent period A, B, C or D, which duration is dependent of the present air/fuel ratio, and will be finished by an amplitude maximum PF during the flame ionization phase. A parameter characteristic for the fundamental frequency of the measuring voltage during the period A, B, C or D is detected, which parameter indicates a tendency towards the rich direction of stoichiometric when the fundamental frequency increases, and inversely indicates lean tendency when the fundamental frequency decreases. The fundamental frequency is preferably detected from the differential value of the measuring voltage during the period A, B, C or D, in respect of time t or crankshaft degrees VC. dU.sub.ION /dt respectively dU.sub.ION /dVC. The differential value multiplied with a constant is used at least partly when determining a relative or absolute air/fuel ratio.

대표청구항 ▼

[ We claim:] [1.] A method for controlling combustion engines by detection of the present air/fuel ratio, A/F, within the combustion chambers of the combustion engine, the air/fuel ratio being determined at least partly from an evaluation of the output signal from an ionization sensor arranged withi

[ We claim:] [1.] A method for controlling combustion engines by detection of the present air/fuel ratio, A/F, within the combustion chambers of the combustion engine, the air/fuel ratio being determined at least partly from an evaluation of the output signal from an ionization sensor arranged within the combustion chamber, which method comprises:measuring an output signal, U.sub.ION, from the ionization sensor;determining from the output signal for each combustion of the combustion chamber a characteristic parameter characteristic of a fundamental frequency during at least a part of a flame ionization phase occurring during each combustion, a richer than a stoichiometric ratio of A/F being indicated when the characteristic parameter corresponds to a fundamental frequency higher than a predetermined value and a leaner than a stoichiometric ratio of A/F being indicated when the extracted parameter corresponds to a fundamental frequency lower than a predetermined value; andcontrolling the combustion engine in accordance with the characteristic parameter.