AIR-FUEL RATIO CONTROL METHOD IN INTERNAL COMBUSTION ENGINE

• Main Authors: YANO TORU, YONEKURA HISAHIRO, KIMURA EISUKE, HAGA TSUYOSHI
• Format: Patent
• Language: English
• Published: 14.10.1997
• Edition: 6
• Subjects: BLASTING; COMBUSTION ENGINES; CONTROLLING COMBUSTION ENGINES; HEATING; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS; LIGHTING; MECHANICAL ENGINEERING; WEAPONS

PROBLEM TO BE SOLVED: To attempt compatibility between reduction of a fuel consumption and reduction of a NOx discharging rate by setting a target air-fuel ratio when speed of an internal combustion engine is in a low speed range near an idling engine speed, and when the load of the internal combustion engine is a prescribed rate or more. SOLUTION: In an electronic control unit U, a target air-fuel ratio is map- retrieved on the basis of each output signal of a throttle opening sensor 5 and an engine speed sensor 7. The target air-fuel ratio is set to a stoichiometric value in the normal operating range of an engine E, and it is set to a lean condition in the specified operating range of a decelerating time and the like. When the engine E is in an idling operating range, an air conditioner clutch is turned on, and the target air-fuel ratio is changed according to whether the load of an air conditioner 9 is applied or not. Namely, the engine speed is in a low speed range near the idling engine speed, and the target air-fuel ratio is set to a lean condition when the engine load is a prescribed value or more. It is thus possible to reduce a fuel consumption while ensuring idling safety.