| 摘要 |
PROBLEM TO BE SOLVED: To solve a delay of closure of an exhaust control valve when shifting an operating state from a twin turbo state to a single turbo state, to thereby improve the controllability. SOLUTION: When an operating region is within the twin turbo region (S160 to S163), switching solenoid valves SOL. 1, 2 are set ON, a supercharged pressure relief value is held in a closed state and a suction control valve is held in a fully opened state (S169, S170). Further, a switching solenoid valve SOL. 3 for a first exhaust control valve is set OFF, and the atmospheric air is introduced into a positive pressure chamber of an actuator for operating the exhaust control valve (S171). A switching solenoid valve SOL. 4 for a second exhaust control valve is set ON (S172), the exhaust control valve is held in a fully opened state by the negative pressure introduced into a negative pressure chamber of the actuator for operating the exhaust control valve, thereby maintaining the twin turbo state. Thus, when the operating state is shifted from the twin turbo state to the single turbo state, under such a condition that the force in the valve-opening direction does not remain in the positive pressure chamber of the actuator for operating the exhaust control valve, the atmospheric air is introduced into the negative pressure chamber to quickly attenuate the force in the valve-opening direction so that the valve-closing responsibility of the exhaust control valve is raised so as to improve the controllability. |
