US Patent 9062488 Door opening and closing device

A door opening and closing device includes: a motor; an output shaft configured to output power of the motor; a transmission mechanism configured to transmit the power of the motor to the output shaft; and an accommodation member configured to accommodate the motor and the transmission mechanism. The door opening and closing device is installed in a vehicle main body or a door supported by the vehicle main body in an openable and closable manner, thereby opening and closing the door by the power that is output from the output shaft. The accommodation member is cylindrical in shape, and the motor and the transmission mechanism are accommodated in the accommodation member so that the motor, the transmission mechanism, and the output shaft are arranged in an axial direction of a rotary shaft of the motor.