| 摘要 |
PURPOSE:To make it possible to introduce auxiliary air in an amount corresponding to engine load, by opening and closing a valve disposed in an auxiliary air introduction passage, in association with the timing of opening and closing of an intake valve to control the amount of auxiliary air in accordance with the amount of intake-air. CONSTITUTION:During low speed and low load operation, the dynamic pressure of intake-air in an intake-air passage 2 is low even through an intake valve 4 is opened, and therefore, a spool valve only opens a second auxiliary air introduction passage 16 slightly, while the amount of second auxiliary air from a first auxiliary air introduction passage 15 is also small, and therefore, the amount of auxiliary air is set to a value corresponding to the amount of fuel injection from an injection nozzle 9. Meanwhile, during high speed and high load operation when the intake valve 4 is opened, the spool valve 12 is moved leftward under a high dynamic intake-air pressure overcoming a spring 13 so that the second auxiliary air introduction passage 16 is largely opened, and therefore, the amount of auxiliary air greatly increases and in therefore jetted from an air injection hole 18 to promote the atomization of fuel. Thus, it is possible to promote the atomization of fuel without deteriorating the control ability of air-fuel ratio.
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