INTERNAL COMBUSTION ENGINE

An internal combustion engine comprises a variable compression ratio mechanism that changes the relative position of a cylinder block with respect to a crankcase and a controlling device that controls the variable compression ratio mechanism. The variable compression ratio mechanism contains a driving device that rotates a shaft that includes an eccentric axis, and the drive device includes a clutch that blocks reverse input and is disposed in a drive power transmission route that transmits the rotational power of a motor to the shaft. The control device fixes the mechanical compression ratio to a predetermined low mechanical compression ratio when the amplitude of the rotational power vibration applied to an output shaft of the clutch is less than a predetermined determination value.