Abstract: In a device for purifying the exhaust gases discharged from an internal combustion engine of the type having a secondary air supply pipe for charging the secondary air from an air source such as an air pump into an exhaust pipe upstream of an exhaust gas reactor or the like, a three-way valve is inserted in the supply pipe in such a manner that the three-way valve may be displaced between a first position at which the air source and the exhaust pipe are communicated with each other and a second position at which the communication between them is interrupted and the secondary air is relieved or returned to the air source bypassing the exhaust pipe; an air-fuel ratio sensor is inserted into the exhaust pipe downstream of the opening of the secondary air supply pipe into the exhaust pipe; and means for controlling the three-way valve is provided so that when the air-fuel ratio detected by the sensor is lower than a reference or optimum ratio at which the best performance of the reactor is expected the three-way

Abstract: A secondary air supply pipe line is opened in the exhaust pipe of an internal combustion engine on the upstream side of an exhaust gas reactor which is mounted in the exhaust pipe, and an air-fuel ratio sensor for detecting the air-fuel ratio of exhaust gases is mounted in the exhaust pipe on the downstream side of the portion where the secondary air supply pipe line is open. An air flow control valve for on-off controlling the flow of air in the secondary air supply pipe line is operated in accordance with the output signal of the air-fuel ratio sensor.

Abstract: An engine exhaust gas purification system having an exhaust gas reactor mounted on the engine exhaust pipe, a secondary air supply system having a secondary air supply passage connected to the exhaust pipe upstream of the reactor, and an exhaust gas air-fuel ratio detector mounted on the exhaust pipe to detect air-fuel ratio of exhaust gases in the exhaust pipe. A secondary air supply control valve is provided in the secondary air supply passage and controlled by a valve actuator having a diaphragm to which positive pressure of the secondary air and the engine intake vacuum pressure can be applied. The application of the positive and vacuum pressures to the diaphragm is controlled by solenoid valves which are controlled in accordance with the air-fuel detector output voltage which represents the detected exhaust gas air-fuel ratio, whereby the secondary air supply control valve is controlled such that the secondary air is supplied to the engine exhaust gases at a continuously controlled, variable rate.