PURPOSE: To prevent reduction of output or the like by a constitution wherein a supercharging pressure is limited below a predetermined value upon the abnormality in which a relief valve in a bypassing path for the supercharger in an auxiliary suction system is left closed, in the titled system equipped with a main and the auxiliary suction systems.
CONSTITUTION: The air suction system is provided with the main suction system 2, supplying fresh air through a main suction port 4 opened in a combustion chamber 3, and the auxiliary suction system 5, supplying supercharged air through an auxiliary suction port 6, while the relief valve 22 is interopsed in the bypassing path 21 detouring the supercharger 18 provided in the auxiliary suction system 5. An abnormality detecting unit 34, detecting that relief valve 22 is left closed due to abnormality and consisting of an abnormality deciding circuit 36 inputting each outputs of an opening and closing sensor 37 and a pressure sensor 38, is provided in the suction system. Upon detecting the abnormality, the unit 34 feeds a signal to a supercharging pressure controlling unit 35 to put OFF a switching switch 49, cut a solenoid clutch 26 and stop the operation of the supercharger 18.
SATOU HARUHIKO
OKIMOTO HARUO
SAKURAI SHIGERU
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