AIR/FUEL RATIO CONTROLLER FOR INTERNAL-COMBUSTION ENGINE

PURPOSE:To improve the control accuracy of an air/fuel ratio controller for lean combustion engine, by operating the air/fuel ratio on the basis of the insulation breakdown voltage of ignition means and the inner pressure of cylinder then performing feedback control of fuel supply on the basis of said air/fuel ratio. CONSTITUTION:Under engine operation, the combustion chamber pressure pig ignition and the peak level VB of ignition voltage vS variable with time are obtained respectively through cylinder inner pressure detecting means 20 and peak voltage decision means 21. While the instantaneous discharge resistance rS (=vS/ iS; where iS is the ignition current) is operated through discharge resistance operating means 22 then the average resistance RS is obtained from rS while the discharge time DS is decided in discharge time decision means 23 through variation of ignition current iS. Then actual air/fuel ratio A/F is operated 34 from pig and VB to operate 39 the correction factor (a) with correspondence to the comparison results between the absolute value of the difference DELTAA/F between said operated 34 value and the referential level and the referential level thus to correct the basic injection TP through correction operating means 40 with correspondence to said correction factor (a).