SUPERCHARGER OF ENGINE

PROBLEM TO BE SOLVED: To prevent the occurrence of knocking by restraining a rise of intake temperature when the operating condition of an engine is within a pre-rotation region in a supercharger of the engine. SOLUTION: This supercharger of an engine includes: a motor-driven supercharger provided in an intake passage; a by-pass passage for communicating the upstream and the downstream of the motor-driven supercharger with each other in the intake passage; a by-pass valve opening and closing the by-pass passage; and an intake system controller for controlling the rotational frequency of the motor-driven supercharger and the by-pass valve to obtain a predetermined supercharging pressure when the operating condition of the engine is in the supercharging region. When the operating condition of the engine is determined to be within the pre-rotation region, the intake system controller controls the rotational frequency of the motor-driven supercharger and the by-pass valve to obtain lower supercharging pressure than that when the operating condition is within the supercharging region, performs the cylinder cut-off operation to stop the fuel supply to a specified cylinder, and circulates the fresh air discharged from the cylinder where the supply of fuel is stopped to an intake passage on the upstream side of the motor-driven supercharger. COPYRIGHT: (C)2006,JPO&NCIPI