ACTUATOR MOUNTING STRUCTURE FOR INTERNAL-COMBUSTION ENGINE HAVING VARIABLE COMPRESSION RATIO

A variable compression ratio internal combustion engine includes a variable compression ratio mechanism arranged to vary an engine compression ratio in accordance with a rotational position of a control shaft, and an actuator arranged to drivingly rotate the control shaft. The actuator is fixed to an actuator mounting portion (40) provided to a side wall of an upper oil pan (12) which is a main body of the engine, with a plurality of fixing bolts. A first rigidity improvement section (41) and a second rigidity improvement section (42) arranged to improve the rigidity of the actuator mounting portion (40) are provided within an intern-bolt distance (46) between the two fixing bolts positioned at both sides in a direction of a crank shaft, of the plurality of the fixing bolts.