VALVE ACTUATOR

Disclosed is a valve actuator including: a motor (120); a gear assembly including an input gear (131) rotated by the motor, an output gear (132) receiving rotational force of the input gear (131), and at least one power transmission gear (133, 134, 135) transmitting the rotational force of the input gear to the output gear; a valve output shaft (140) coupled to the output gear and actuated to close a path of a valve; and a selective power transmission unit interrupting rotation of the output gear after the output gear is rotated at a predetermined angle by the input gear, the selective power transmission unit including a lift member (150) releasing meshing of the first gear (133) and the second gear (134) by moving the first gear to an upper side after the output gear is rotated at the predetermined angle or a friction member provided in the output gear so as to brake the rotation of the first gear by contacting the first gear after the output gear is rotated at the predetermined angle. Accordingly, after the valve is actuated to close the path, the driving force of the motor is not transmitted to the valve output shaft.