| 摘要 |
PURPOSE:To control a feed amount of a secondary air to an optimum according to a required amount and to effectively reduce the load of a supercharger during low load operation, by a method wherein the supercharging pressure of the supercharger and the pressure of a secondary air during supply of a secondary air are controlled in accordance with a load. CONSTITUTION:During low load operation of an engine E, an auxiliary throttle valve 20 is fully closed to effect no supercharging, and only a main throttle valve 16 is openable at a low opening. Thus, the engine E is operated by natural suction through a main suction passage 11, and an amount of fuel injected by a fuel injection valve 17 is controlled based on the output of an air flow meter 15 in the main suction passage 11. Meanwhile, with a control valve 27 opened, the air pressurized by a supercharger 18 is supplied to an exhaust passage 14 through a secondary air feed passage 26. A high suction negative pressure on the downstream side of the main throttle valve 16 is introduced through a negative pressure introduction passage 29 to a negative pressure chamber 25f of a pressure regulator 25, and through offset of the set load of a coil spring 25e, a relief valve 23 is reduced in a relief pressure. |
