Electrically driven actuator

An electrically driven actuator characterized by a gear device which performs a speed reduction of one step by means of two gears disposed between coaxially arranged input and output shafts, and which secures an axial dynamic balance in every individual rotating element in the electrically driven actuator which transmits the output of a motor through the gear device to a threaded shaft, and which generates a linear motion in a member engaged with the threaded shaft, the rotating elements including:

• (a) a disk which has a circular recess arranged to be eccentric with respect to the input shaft and which is fixed to the input shaft;
• (b) a ring gear which is rotatably supported by the circular recess and whose rotating motion is restricted to an eccentric motion within the circular recess when the disk rotates;
• and
• (c) a planetary gear which is coaxially fixed to the output shaft and engaged with the ring gear;
• wherein a weight portion is formed in the disk to recover an axial dynamic balance which is lost due to the circular recess and the ring gear.