Flexible-disc drive spindle assembly with brushless DC motor

Claim 1

A flexible-disc drive spindle assembly including a flexible-disc for storing information and a brushless DC motor having a shaft member for providing rotation of the flexible-disc, comprising in combination: a driving hub having a top side on which a flexible-disc is mounted in a detachable manner and a bottom side; a brushless DC motor having a casing and stator coils; a driving shaft directly connected coaxially to said driving hub at said bottom side and being mounted within bearings positioned in a mounting frame in a manner permitting said driving shaft to rotate; a ring-shaped rotor magnet being affixed to said driving shaft to rotate therewith and having multipole magnets disposed in a radial alignment; a printed circuited plate being mounted to said casing of said motor by way of a yoke at a position facing said rotor magnet with a gap positioned in between, said printed circuited plate having a top side including a conductor pattern that detects the rotational speed of said rotor magnet and having a bottom side including magnetic pole position sensors mounted thereon for detecting the rotating magnetic pole position of said rotor magnet and stator coils of said motor; a comparator amplifier circuit for generating amplified deviation signals by comparing the detected speed signal from said conductor pattern with a reference speed signal; a motor driving means which distributes and supplies said stator coils with an excited current in response to said deviation signal upon receiving as input said deviation signal and a magnetic pole position signal from said magnetic pole position sensors; whereby a shaft bearing mechanism comprises two sets of bearings including a spring disposed therebetween wherein a pre-load is provided by the magnetic attractive force between said rotor magnet and said yoke as well as the spring force of said spring.