| 摘要 |
PURPOSE:To feed appropriate quantity of secondary air to an exhaust system extending over the whole operative area, by a method wherein the secondary air is fed by making use of exhaust pulsation pressure in a low speed and an idling speed areas of an engine, while utilizing supercharged pressure in a medium and a high speed operative areas of the engine. CONSTITUTION:Booster pressure PB downstream a throttle valve 20 is high, and absorbs and displaces a diaphragm 40 against a bounce of a diaphragm spring 4 as an opening of a throttle valve 20 is in a low opening state, in a low speed, an idling speed and a reducing speed operating areas. With this, No.2 connecting opening 34 is opened by No.2 valve plug 36 and secondary air duct 31 is connected through an atmosphere duct 29 with the atmosphere. As the opening of the throttle valve is increased and the booster pressure PB is decreased in a medium and a high speed operating areas, the diaphragm 40 is displaced downward. With this, No.1 connecting opening 33 is opened by No.1 valve plug 35. Boosted air in a prechamber 21 is led to an exhaust port 6 through a boosted air duct 28. |
