Appeal No. 1997-1162
Application 08/200,455
11. In a magnetic disk unit comprising a disk drive
unit (22), including a rotor (9) on which a magnetic disk
(18) is loaded, a motor rotatably driving said rotor (9),
the motor having a spindle (5) fixedly mounted on a base
portion (1a) of a casing (1), and a ball bearing unit,
said ball bearing unit including a sleeve portion (10)
concentrically surrounding said spindle (5),
the improvement wherein:
said disk unit comprises a one-piece integrally
formed unit including therein said rotor (9) and said
sleeve portion (10) of said ball bearing unit, wherein
said sleeve portion (10) is integrally formed in a
central portion of a lower surface of said rotor (9);
said spindle (5) is a stepped shaft having a
large-diameter shaft portion and a small-diameter shaft
portion;
said small-diameter shaft portion is fitted in an
inner ring (8);
said integrally formed sleeve portion (10) operating
as double-row outer rings of said ball bearing unit and
eliminating outer rings therefrom, and including an inner
peripheral surface having a pair of ball-running grooves
therein;
a first plurality of balls (14) are disposed between
a ball-running groove (7) of an outer peripheral surface
of said inner ring and a first ball-running groove (12)
of said pair of ball-running grooves of said inner
peripheral surface of said sleeve portion (10) and free
of any outer ring therefor; and
a second plurality of balls (13) disposed between a
ball-running groove (6) of an outer peripheral surface of
said large-diameter shaft portion and a second
ball-running groove (11) of said pair of ball-running
grooves of said inner peripheral surface of said sleeve
portion (10) and free of any outer ring therefor, said
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