Exhaust gas control actuator

An exhaust gas control actuator wherein the feed of secondary air fed to an exhaust piping is controlled by a signal-emitting oxygen concentration detector disposed in the stream of exhaust gas of an internal combustion engine whereby an air-fuel ratio of the exhaust gas entering a catalyst disposed down-stream of the exhaust piping is maintained within a given range, said actuator comprising:

• a flow control valve having a housing provided with a valve chamber, a flow-in port communicating said chamber with an air pump, a flow-out port communicating said chamber with an exhaust piping, a bypass port communicating said chamber with an air cleaner, and a movable valve body in said chamber controlling flow out of said flow-out port and said bypass port;
• a flow control device for controlling said flow control valve comprising a housing partitioned by a diaphragm connected to said valve body into an actuating chamber and an atmospheric chamber, said actuating chamber having a vacuum introducing port communicating through a conduit with an intake manifold and an atmosphere introducing port constantly communicating with the atmosphere;
• a solenoid valve in said conduit having ON-OFF positions;
• an electronic circuit for controlling said solenoid valve in accordance with the signal from the detector;
• and a nozzle flapper mechanism in said actuating chamber for varying resistance to flow through said vacuum introducing port and said atmosphere introducing port in accordance with the position of said valve body in such a manner that the signal of the oxygen concentration detector is negatively fed back to control the feed of secondary air.