ELECTRONIC PARKING BRAKE ACTUATOR ASSEMBLY

An actuator assembly for an electromechanical parking brake greatly reduces vibration and noise. A casing (132) of a motor (130) and a gear housing (180) of a planetary gear set (170) are coupled to a lower surface of an inner housing (110) in parallel, a reduction gear train having a pinion gear (140) and a drive gear (160) for transmitting a power from a rotary shaft (131) of the motor (130) to the planetary gear set (170) is received in an upper surface of the inner housing (110), and an inner cap (120) covering the outer portion of the reduction gear train is coupled to the upper surface of the inner housing (110), thereby configuring a primary module (100) which is a single small independent assembly in which the motor (130), the reduction gear train, the planetary gear set (170), the inner housing (110) and the inner cap (120) are combined. The primary module (100) is inserted into an outer housing (210) while keeping a gap at a circumference thereof, an outer cap (220) is coupled to an upper portion of the outer housing (210) to cover the primary module (100), and the primary module (100) is surrounded by the outer housing (210) and the outer cap (220), thereby configuring a final module (50) which is a single large independent assembly in which inner components of the motor (130), the reduction gear train and the planetary gear set (170) are surrounded doubly. A final output shaft (176) of the planetary gear set (170) is exposed from a lower through hole (214a) of the outer housing (210) and connected to a parking brake.