| 摘要 |
PURPOSE:To improve the operation performance and exhaust gas purifying performance by dividing the ordinary operation region of an engine into the theoretical air-fuel ratio operation region at a relatively low speed and the lean air-fuel ratio operation region at a relatively high speed and carrying out the transition to each operation region according to the cooling water temperature. CONSTITUTION:When the intake negative pressure is judged to be over a certain value P0 or the revolution speed is judged to be below a certain value N0 from each output of a pressure sensor 19 and a revolution speed sensor 20 in the ordinary operation of an engine, a control unit 16 judges the theoretical air-fuel ratio operation region A, and a control valve 15 in a corrected fuel passage 14 is controlled on the basis of the output of an O2 sensor 22. When the intake negative pressure is below the certain value P0 or the revolution speed is over the certain value N0, the lean air-fuel ratio operation region B is judged, and the control valve 15 is closed. The transition from the region A to the region B is carried out on the set boundary on the high temperature side according to the output of a temperature sensor 21, and the transition from the region B to the region A in the case when the cooling water temperature is lower than the set temperature on the high temperature side is carried out on the set boundary on the low temperature side.
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