VARIABLE COMPRESSION RATIO INTERNAL COMBUSTION ENGINE

A variable compression ratio internal combustion engine includes a control shaft (13) rotatably supported by an engine body, a variable compression ratio mechanism (10) for changing an engine compression ratio in accordance with a rotational position of the control shaft (13), an actuator (21) that rotatively drives the control shaft (13), and a speed reducing mechanism (22) for reducing a rotational power of the actuator (21) and for transmitting the speed-reduced power to the control shaft (13). The speed reducing mechanism (22) has a rotation shaft (24) rotatably supported in a housing (26) fixed to the engine body and a lever (25) that connects the rotation shaft (24) and the control shaft (13). Located in the engine body is a first regulation part (42) for mechanically regulating the control shaft (13) to a position of maximum rotation on one side of a low compression ratio side and a high compression ratio side. Also located in the housing (26) is a second regulation part (41) for mechanically regulating the rotation shaft (24) to a position of maximum rotation on the other side of the low compression ratio side and the high compression ratio side.