| 摘要 |
PURPOSE:To restrain the generation of detrimental constituents, by controlling the atmospheric air pressure introduced in a pressure receiving chamber in a pneumatic control valve in an intake secondary air passage which is communicated with the downstream side of a throttle valve, in accordance the operating condition of an engine. CONSTITUTION:Gas pressure is fed, through a three-way solenoid valve 13, into a vacuum chamber 12a in a vacuum driven type pneumatic control valve 12 disposed in an intake secondary air passage 11 which is arranged bypassing a throttle valve 5 in an intake-air passage 3. The three-way solenoid valve 13 switchingly connects, under opening and closing operation of a valve element 13c the vacuum chamber 12a with a vacuum control part 31 for generating a first control pressure or with an atmospheric air passage 16 for introducing a second control pressure. The vacuum control part 31 is composed of a vacuum responsive type regulating valve 32 and a pneumatic valve 33, and actuates in such a way that the opening degree of the regulating valve 32 is increased when the amount of the main intake-air of an engine 4 is small, and a relatively low first control pressure (negative pressure) Pe is generated. The solenoid valve 13 is controlled by means of a control circuit 22 in accordance with the output of O2 sensor 23. |
