Brushless motor having coreless coil assembly

A brushless motor having a stator and a rotor in a clean chamber of contaminant-free atmosphere, the stator comprising a motor base, shaft means provided on the motor base and a plurality of coils mounted on the motor base, the rotor comprising a bearing holder having a center hole for supporting bearing means, a hub connected to the bearing holder for mounting information storage discs and a magnet having magnetic poles provided on an inner wall of the hub facing to the plurality of coils, the rotor including the hub being rotated around the shaft means through the bearing means by causing a magnetic field of the magnetic poles of the magnet to interact with a magnet field generated by the coils in the clean chamber, the brushless motor comprising:

• a top cover made of a plate placed on a top of the bearing holder to close the center hold thereof;
• a cylindrical chamber defined by an outer wall of the bearing holder and an inner wall of the hub of the rotor;
• and
• a cylindrical coreless coil assembly comprising a cylindrical flexible support provided with printed circuits having lands for soldering, and the plurality of the coils disposed at least on one surface of the cylindrical flexible support, winding ends of the plurality of coils being soldered to the lands, the cylindrical coreless coil assembly being erected from the motor base in such a manner that the cylindrical coreless coil assembly protrudes into the cylindrical chamber so as to form a labyrinth path having predetermined clearances narrow and long enough to prevent contaminant particles from invading the clean chamber without providing any magnetic fluid seal in cooperation with the top cover made of the plate.