A drive motor capable of being separated from a rotation member when the rotation member is restrained, the drive motor being configured to be coupled with the rotation member to transmit rotating force to the rotation member, and may include a power transmission control device provided on a junction between the drive motor and the rotation member and configured such that the rotating force can be transmitted from the drive motor to the rotation member, and such that when the rotation member is restrained and rotation thereof is not allowed, the power transmission control device is elastically deformed so that the coupling of the rotation member with the drive motor is released and only the drive motor is allowed to be rotated.