Air-flow control device for engine

An air-flow control device for an engine having an intake passage and a fuel injector arranged in the intake passage for injecting fuel into the intake passage, the device comprising:

• an air-flow control valve arranged in the intake passage on the upstream of the fuel injector, the air-flow control valve being closed during an engine starting operation, and being open after the engine starting operation is finished;
• first and second vacuum sources;
• a driving apparatus for driving the air-flow control valve, the apparatus comprising:
• first and second vacuum chambers;
• a first vacuum control valve for selectively connecting the first vacuum chamber to either the first vacuum source or the atmosphere to introduce the negative pressure or the atmospheric pressure into the first vacuum chamber;
• and
• a second vacuum control valve for selectively connecting the second vacuum chamber to either the second vacuum source or the atmosphere to introduce the negative pressure or the atmospheric pressure into the second vacuum chamber, the apparatus driving the air-flow control valve so that a degree of opening thereof becomes larger as the negative pressure in the first and the second vacuum chamber becomes larger;
• and
• control means for controlling the apparatus so that each of the first and the second vacuum control valves introduces the atmospheric pressure into the corresponding vacuum chamber to thereby ensure that the air-flow control valve is closed during an engine starting operation, and that the first and the second vacuum control valves control the negative pressures in the corresponding vacuum chamber to thereby keep the air-flow control valve open and to thereby control a degree of opening of the air-flow control valve after the engine starting operation is finished.