Patent ID: 7281505

Claim:
A variable lift valve operating system for an internal combustion engine comprising: an engine valve; a variable lift mechanism capable of changing a lift amount of the engine valve; and an actuator which is mounted on an engine body to rotatably drive a control shaft of the variable lift mechanism and which includes: an electric motor; a deceleration mechanism which decelerates output of the electric motor; a transmission mechanism interposed between the control shaft and the deceleration mechanism; and a default mechanism capable of rotatably biasing the control shaft to a position where a lift amount of the engine valve becomes a predetermined lift amount when the electric motor is not energized, wherein a deceleration mechanism accommodation part for accommodating the deceleration mechanism and a default mechanism accommodation part for accommodating the default mechanism are formed in a casing of the actuator so as to sandwich therebetween a thermally vulnerable part which is directly connected to the control shaft.