SUPERCHARGING DEVICE FOR ENGINE

PROBLEM TO BE SOLVED: To suppress temperature rise of intake air in a pre-rotation region in a supercharging device for an engine provided with an electric supercharger. SOLUTION: The supercharging device for the engine includes a supercharging passage provided with the electric supercharger, and a bypass passage bypassing an upstream side and a lower stream side of the supercharger in the supercharging passage and provided with a bypass control valve, operates the supercharger and operates the bypass control valve to close when an operation condition of the engine is in a predetermined supercharging region, and operates the supercharger and operates the bypass control valve to open when the operation condition of the engine is in the pre-rotation region in a lighter load side than the supercharging region. The supercharging device is provided with an intake pressure control valve provided between a branch part of the bypass passage in the supercharging passage and the electric supercharger, controls opening of the intake pressure control valve and drops pressure in a downstream of the supercharger in the supercharging passage to roughly atmospheric temperature (step S10) at a time of the pre-rotation region. COPYRIGHT: (C)2007,JPO&INPIT