Direct-current brushless motor, and polygon scanner and image forming apparatus having the same and a method thereof

DETAILED DESCRIPTION The present invention has been made to solve the problems as mentioned above.
In particular, it is an object of the present invention to provide a small direct-current brushless motor which is capable of realizing a variety of operational improvements including: an easy winding operation; a flat shape; effective utilization of a magnetic force generated by a permanent magnet fixed on the rotor over the entire periphery thereof; improved magnetic characteristics of a stator core; and a good rotation driving efficiency particularly at a higher rotational speed region.
It is another object of the present invention to provide a polygon scanner and an image forming apparatus which employ the improved direct-current brushless motor as described above.
To achieve the above and other objects, the present invention provides a direct-current brushless motor for switching conduction to windings wound around a stator core fixedly disposed corresponding to a rotatable rotor on which a permanent magnet is fixed, to generate a rotating magnetic field which causes the rotor to rotate.
The direct-current brushless motor includes a permanent magnet having n magnetized poles, where n is an even number, a rotatably held rotor on which the permanent magnet is fixed, a stator core having T-shaped pole shoes corresponding to the magnetic poles of the permanent magnet, windings fixed on the stator core and including a plurality of phases for selectively generating magnetic polarities in sequence, a driver circuit for switching conduction to the windings, and a rotating position detecting mechanism for detecting a rotating position of the permanent magnet.
The windings are divided into a plurality of winding groups for generating magnetic polarities in a plurality of the windings so as to produce a magnetic repellent force or a magnetic attractive force between all of the magnetic poles of the permanent magnet and T-shaped pole shoes of the stator core associated with selected phases by the driver circuit based on a rotating position detected by the rotating position detecting mechanism