Exhaust gas re-circulation control device for internal combustion engines

Abstract

An exhaust re-circulation control device for gasoline engines is provided, which realizes efficient reduction of NOx in the low-temperature idling ranges before the catalytic converter is activated while preventing deterioration of driveability and engine stalling. Normally, an exhaust re-circulation control device comprises a re-circulation passage which re-circulates a portion of exhaust gas from an engine to an intake system and an exhaust re-circulation valve which opens and closes the re-circulation passage. Also, the engine has a bypass passage which controls idling rpm and an idling rpm control valve. In the engine, the low-temperature idling range before the catalytic converter is activated is detected exhaust re-circulation ratio is obtained and based on a target idling speed during that time to prevent deterioration of driveability and engine stalling and to efficiently reduce NOx emissions, even when the catalytic converter is not active.

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