PURPOSE: To make an air-fuel ratio promptly controllable as desired, by compensating an air-fuel ratio control reference value according to cooling water temperature in an engine, and calculating an air-fuel ratio control output value on the basis of the air-fuel ratio control reference value or the like after compensation.
CONSTITUTION: When an engine is driven, an air-fuel ratio control reference value is retrieved from a data map on the basis of each output of an absolute pressure sensor 10 and a crank angle sensor 11 at a control circuit 20. And, output of an oxygen content sensor 14 is compared with the reference value whereby whether an air-fuel ratio is more rich or lean that the theoretical air-fuel ratio is judged, and according to the judged result, a proportional value is added or subtracted to or from an air-fuel ratio compensation value, setting the calculated value down to a new air-fuel ratio compensation value. The air-fuel ratio control output value is calculated according to this air-fuel ratio compensation value and the said air-fuel ratio control reference value, controlling a linear type solenoid valve 9, and a secondary air quantity is controlled, then the air-fuel ratio is controlled. In this connection, the air-fuel ratio control reference value is made compensable according to cooling water temperature in a warming-up state.
KOSEKI JUNICHI
HASEBE HIROSHI
