| 摘要 |
PURPOSE:To obtain a rich air/furl ratio or a poor air/fuel ratio selectively by a method wherein a part of suction air can be introduced as bypass air from the upstream side of a variable venturi to a path between the variable venturi and a throttle valve in a variable venturi type carburettor in accordance with the operating condition of the engine. CONSTITUTION:When the operating condition of the engine is requesting the poor air/fuel ratio, an opening and closing valve 25 in a vacuum path 23 is opened. At this time, the diaphragms 32, 31 of a pressure control valve 24 are moved upwardly by a venturi vacuum in a fixed venturi 26 and an atmosphere port 38 is closed by a valve body 39. Therefore, a suction vacuum acts on an actuator 22a from the vacuum path 23 and a flow amount control valve 22 opens a bypass path 21. According to this operation, the air/fuel ratio may be set at the poor side thereof. On the other hand, when the operating condition is requesting the rich air/fuel ratio under a low-speed high load operation or the like, the opening and closing valve 25 is closed. Then, the flow amount control valve 22 is kept in closed condition, therefore, the rich air/fuel ratio, set by the variable venturi type carburettor 3, may be supplied to the engine. |
