Sealed magnetic fluid bearing for polygon mirror drive motor

A motor comprising:

• a cylindrical portion provided on an end bracket;
• radial bearings disposed in said cylindrical portion;
• a magnetic fluid filled in the interior of said cylindrical portion accommodating said radial bearings;
• a shaft rotatably supported by said radial bearings;
• a rotor fixed to said shaft;
• a stator arranged oppositely to said rotor;
• and
• a housing enclosing said rotor and said stator,
• wherein said rotor is provided with a rotor magnet of a seal magnet, and said housing is provided with a stator magnet of the seal magnet in the vicinity of said rotor magnet, and
• wherein said rotor magnet of the magnetic bearing is a cylindrical body.

A polygon mirror motor comprising:

• a cylindrical portion provided on an end bracket;
• radial bearings disposed in said cylindrical portion;
• a magnetic fluid filled in the interior of said cylindrical portion accommodating said radial bearings;
• a shaft rotatably supported by said radial bearings;
• a rotor fixed to said shaft and carrying a polygon mirror;
• a stator arranged oppositely to said rotor;
• and
• a housing enclosing said rotor and said stator,
• wherein said rotor is provided with a rotor magnet fashioned as a seal magnet for forming a magnetic seal, and said housing is provided with a stator magnet fashioned as a the seal magnet for forming a magnetic seal in the vicinity of said rotor magnet.

A polygon mirror drive motor comprising as main components:

• a rotor having a polygon mirror mounted thereon;
• a stator unit having driving coils, a rotor position detector and a rotor revolution detector attached thereto;
• a magnetic fluid bearing unit having magnetic and dynamic pressure seals attached thereto;
• and
• a seal magnet, and
• wherein a triple seal structure for magnetic fluid is provided which includes a first fluid seal constituted by the seals of the bearing unit, a second fluid seal constituted by a magnet of the rotor and a third fluid seal constituted by a magnet of the seal magnet.

A motor comprising:

• a driving coil unit;
• a fluid bearing unit;
• a position sensor;
• a revolution detecting portion;
• and
• a rotor, and
• wherein said rotor is constituted mainly by a shaft, a collar made of a material having a larger coefficient of thermal expansion than said shaft and shrinkage fitted or fitted by heating of said shaft, and a magnet made of a material having a larger coefficient of thermal expansion than said collar and shrinkage fitted or fitted by heating on said collar.

A polygon mirror drive motor for laser scanning, comprising:

• a driving coil unit;
• a fluid bearing unit;
• a position sensor;
• a revolution detecting portion;
• and
• a rotor having a polygon mirror attached thereto, and
• wherein the rotor is constructed such that a collar made of a material having a better machinability and a larger coefficient of thermal expansion than a shaft is shrinkage fitted on the shaft, a magnet made of a material having a larger coefficient of thermal expansion than the collar is shrinkage fitted on the collar, and a base of the polygon mirror is made of a material having substantially the same coefficient of thermal expansion as the collar and a portion of said base which is fitted on said collar has an out of roundness equal to or less 2 .mu.m.