| 摘要 |
PURPOSE:To excellently protect an engine even if a drive demands a sever engine operating condition during cold-down of an engine, by a method wherein, during cold-down of an engine, an intake air amount is corrected in a direction, in which an intake air amount is controlled, at least in a high speed high load area. CONSTITUTION:A control unit 31 regulates the opening of an on-off valve 17 to a desired value through control of a pressure regulating valve 24 and a switching valve 25. Namely, with the switching valve 25 controlled, a pressure chamber 18a of an actuator 18 is released to the open air to bring the on-off valve 17 to a full closed state, and the pressure chamber 18a is communicated with a tank 20 to bring the on-off valve 17 into a full opening state. In order to adjust the opening of the on-off valve 17 to a desired value, based on a detecting pressure from a sensor 35, i.e., the magnitude of a negative pressure accumulated in the tank 20, duty control is applied on the pressure regulating valve 24 to escape a negative pressure in the tank 20 through a relief passage 22. Further, duty control is made on the switching valve 25 to control a ratio, in which the pressure chamber 18a of the actuator 18 is communicated with the open air or the tank 20, to control the opening of the on-off valve 17.
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