In the present invention, an internal combustion engine is provided with a variable-compression-ratio mechanism with a variable mechanical compression ratio and the variable-compression-ratio mechanism comprises a drive device for changing the volume of a combustion chamber when a piston reaches top dead center. The drive device comprises a reverse input blocking clutch disposed in a drive power transmission path for transmitting the rotational force of a rotator. A control device estimates the reverse input torque applied to an output shaft of the reverse input blocking clutch and sets a gradient for torque output by the rotator and a continuation duration for continuing the torque increase on the basis of the reverse input torque.

In the present invention, an internal combustion engine is provided with a variable-compression-ratio mechanism with a variable mechanical compression ratio and the variable-compression-ratio mechanism comprises a drive device for changing the volume of a combustion chamber when a piston reaches top dead center. The drive device comprises a reverse input blocking clutch disposed in a drive power transmission path for transmitting the rotational force of a rotator. A control device estimates the reverse input torque applied to an output shaft of the reverse input blocking clutch and sets a gradient for torque output by the rotator and a continuation duration for continuing the torque increase on the basis of the reverse input torque.