Patent ID: 8727926

Claim:
A vehicle door driving device comprising a driving mechanism, which is fixed to a vehicle body or to a vehicle door and includes a motor and an output member rotated by the motor, the vehicle door driving device being configured to open and close the vehicle door by rotating the output member, wherein the output member is arranged to have at least a part thereof accommodated in a space corresponding to an external shape of the motor, the space being a space corresponding to a dimension in a radial direction of the motor, and the driving mechanism includes a pinion arranged on a rotary shaft of the motor and including a thread portion, a transmission gear, which is arranged at a skew position with respect to the rotary shaft of the motor and has an axis extending in the radial direction, the transmission gear being freely rotational about an axis of the transmission gear, the transmission gear including a disk gear portion having a plurality of teeth and a sun gear, the disk gear portion being arranged to be annular on a surface facing the pinion of the transmission gear and capable of being meshed with and rolling relative to the thread portion of the pinion, and the sun gear being arranged on the same side as the pinion with respect to the disk gear portion, a ring gear, which is coaxial with the transmission gear and arranged on an outer peripheral side of the sun gear, the ring gear forming a fixed shaft, a carrier coupled to the output member to rotate with the output member, the carrier including a planet gear meshed with both the sun gear portion and the ring gear, and a case that accommodates at least the output member, the transmission gear, the ring gear, and the carrier, wherein a rolling member is rotationally supported by the case, and the rolling member rotationally makes contact with a surface of the transmission gear on a side opposite to the pinion.