초록 ▼

An exhaust gas purifying device including a first O2 sensor, a first three-way catalyst, a secondary air feed port, a second O2 sensor, and a second three-way catalyst, which are arranged in the exhaust passage in that order. When not increasing the fuel supplied, the feeding of secondary air is sto

An exhaust gas purifying device including a first O2 sensor, a first three-way catalyst, a secondary air feed port, a second O2 sensor, and a second three-way catalyst, which are arranged in the exhaust passage in that order. When not increasing the fuel supplied, the feeding of secondary air is stopped and feedback control is performed based on the output signals of the first O2 sensor and the second O2 Sensor so that the air-fuel ratio of the mixture fed to the engine cylinders becomes the stoichiometric air-fuel ratio. When increasing the fuel supplied, the feedback control of the air-fuel ratio is stopped, secondary air is fed from the secondary air feed port, and the amount of secondary air is controlled so that the air-fuel ratio of the gas flowing into the second three-way catalyst becomes the stoichiometric air-fuel ratio.

대표청구항 ▼

An engine having an exhaust passage, comprising: a first catalyst arranged in the exhaust passage; a second catalyst arranged in the exhaust passage downstream of said first catalyst; a secondary air feed port open to the exhaust passage between said first catalyst and said second catalyst; a first

An engine having an exhaust passage, comprising: a first catalyst arranged in the exhaust passage; a second catalyst arranged in the exhaust passage downstream of said first catalyst; a secondary air feed port open to the exhaust passage between said first catalyst and said second catalyst; a first air-fuel ratio sensor arranged in the exhaust passage upstream of said first catalyst to detect an air-fuel ratio; a second air-fuel ratio sensor arranged in the exhaust passage downstream of said secondary air-feed port to detect an air-fuel ratio; enrichment means for increasing an amount of fuel fed into the engine to make an air-fuel ratio of a mixture, burned in the engine, the rich side of the stoichiometric air-fuel ratio when the engine is operating in a predetermined operating state; an air-fuel ratio control means for carrying out feedback control of said air-fuel ratio of the mixture on the basis of an output signal of said first air-fuel ratio sensor so that an air-fuel ratio of gas flowing into said first catalyst becomes equal to the stoichiometric air-fuel ratio when an increasing operation of the amount of fuel by said enrichment means is not carried out, said air-fuel ratio control means stopping said feedback control when the increasing operation of the amount of fuel by said enrichment means is carried out; and a secondary air feed control means for stopping the supply of secondary air to the exhaust passage from said secondary air feed port when the increasing operation of the amount of fuel by said enrichment means is not carried out, said secondary air feed control means causing the secondary air to flow into the exhaust passage from said secondary air feed port and carrying out feedback control of an amount of secondary air fed into the exhaust passage on the basis of an output signal of said second air-fuel ratio sensor so that an air-fuel ratio of gas flowing into said second catalyst becomes equal to the stoichiometric air-fuel ratio when the increasing operation of the amount of fuel by said enrichment means is carried out.