First and second air feeding means to regulate a/f ratio wherein second air feed requires two signals for actuation

摘要

An exhaust gas purifying device for an internal combustion engine, comprising a catalytic converter containing a three way catalyzer therein, a first oxygen sensor disposed in the exhaust passage, and an air-fuel ratio regulating means for regulating an air-fuel ratio of the mixture fed into the cylinder of the engine so as to conform it to the stoichiometric air-fuel ratio in response to an output signal of said first oxygen sensor over a larger range of running conditions of a vehicle. Said exhaust gas purifying device further comprises a second oxygen sensor located downstream of the catalytic converter, and a secondary air feeding device located upstream of the catalytic converter for regulating the feeding of a secondary air into the exhaust gas in response to an output signal of said second oxygen sensor so that the ratio of the air consisting of said secondary air and air contained in the mixture introduced into the cylinders of the engine to the fuel contained in the mixture introduced into the cylinders is made equal to the stoichiometric air-fuel ratio at the time of acceleration, deceleration and gear-shifting.