| 摘要 |
PURPOSE:To stabilize engine operation by interrupting feedback control when the difference between the second coefficient that is the long term average of the first coefficients obtained on the bases of the output of an O2 sensor and the third coefficient that is the short term average thereof exceeds a specified value. CONSTITUTION:A control circuit 5 constituted of a microcomputer calculates the standard fuel injection period from absolute pressure of intake air and engine rpm. detected by sensors 8 and 11, respectively, and compensates the calculated period by the temperatures of intake air and cooling water detected by sensors 9 and 10, respectively. At the time of feedback control, the circuit finds the air- fuel ratio compensating coefficients according to concentration of O2 measured by an O2 sensor 15 so as to make compensation of the ratio. The averages of the compensating coefficients obtained for both terms determined long and short by the frequencies of generating TDC signals from a crank angle sensor 11 are computed and if the difference between both the averages if found in excess of the specified value, the circuit interrupts feedback control. Since air-fuel mixture is prevented from getting lean in the operating condition of low load, idling or the like, the engine may be operated stably. |
