Patent ID: 7243569

Claim:
A power transmission device, comprising: a motor section having a rotational shaft, a rotor attached to an inner end side of the rotational shaft, and a stator positioned opposite to the rotor; a driving gear attached to a distal end side of the rotational shaft with respect to the motor section; a driven gear engaged with the driving gear; and a fixed-side member for rotatably supporting the driven gear, wherein the rotational shaft is a single member and is rotatably supported by a first bearing and a second bearing, the first bearing is held by the fixed-side member at a distal end side of the rotational shaft with respect to the driving gear, and the second bearing is held by the fixed-side member between the driving gear and the rotor so that the driving gear is sandwiched between the first bearing and the second bearing, wherein the motor section has a brushless motor structure comprising a rotation detecting device for detecting rotation of the rotational shaft provided at a distal end side of the rotational shaft with respect to the first bearing. the rotation detecting device has a movable member mounted on the distal end side of the rotational shaft with respect to the first bearing, and a detector for detecting rotation of the movable member mounted on the fixed-side member. the fixed-side member is formed with a cylindrical part having a first opening on a first end, and a second opening on a second end, the first opening of the cylindrical part is configured to accept the first bearing and the rotation detecting device, and the second opening of the cylindrical part is configured to accept the distal end side portion of the rotational shaft and the second bearing.