Polygonal type optical deflector

DETAILED DESCRIPTION An object of the present invention is to provide an electric motor unit which permits rotating a polygonal mirror at a high speed, which can be processed, assembled and adjusted easily, and which permits optionally changing the rotating direction of the motor shaft.
According to the present invention, there is provided an electric motor unit, comprising: a motor housing; a fixed shaft extending within the motor housing and having a smooth outer surface; a rotatable hollow cylindrical spindle having the cylindrical shaft coaxially and detachably inserted thereinto and having a smooth inner surface facing the outer surface of the cylindrical shaft with a gap provided therebetween; a thrust bearing serving to suspend the hollow cylindrical spindle in its axial direction; a motor rotor fixed to the hollow cylindrical spindle; and a motor stator fixed to the housing and serving to rotate the motor rotor.
According to the present invention, there is also provided an electric motor unit, comprising: a motor housing; a fixed shaft extending within the motor housing; a rotatable hollow cylindrical spindle having the shaft coaxially and detachably inserted thereinto, the inner surface of the spindle facing the outer surface of the shaft with a gap provided therebetween; a dynamic pressure type radial bearing consisting of a smooth plane formed on one of the inner surface of the spindle and the outer surface of the shaft and parallel grooves extending in parallel with the axis of the shaft and formed on the other of the inner surface of the spindle and the outer surface of the shaft; a thrust bearing serving to suspend the hollow cylindrical spindle in its axial direction; a motor rotor fixed to the hollow cylindrical spindle; and a motor stator fixed to the housing and serving to rotate the motor rotor.