PURPOSE: To generate the maximum torque while preventing generation of knocking under the general driving condition by driving a valve timing adjusting device on the basis of the detected signal of a knock sensor and adjusting the compression ratio through a process of hastening the closing timing of a rotary valve in an intake passage.

CONSTITUTION: An engine 1 operates load through a differential gear mechanism 2 and a transmission 3. Moreover, in the differential gear mechansim 2, a ring gear 4 is attached to a flywheel 5, and power to the transmission 3 from a planetary gear 6 is taken out. And a supercharger 10 is driven by a driving gear 9 to be fitted to a gear 8 integrated with a sun gear 7. In this case, a rotary valve 12 is interposed in an intake passage 11, and the timing is adjusted by a valve timing adjusting mechanism composed of an adjusting piece 15 and an actuator 16. And the actuator 16 is driven on the basis of the detected signal of a knock sensor 17, and the compression ratio is adjusted by hastening the closing timing of the rotaty valve 12.