Spindle Motor - Fujitsu M2361A Customer Engineering Manual

(3) Air system
The fundamental and important function of the air system is to maintain an
ultra-clean environment within the space of the DE to minimize the
possibility of head-disk interference. In this DE, a new type of self
circulating air system is provided. Features of the system are its
simplicity and maintenance free operation. Air flows through the disk
spacings from the center to outside of the disks by the pressure
difference between them, induced by the rotation of disks.
An
absolute
filter, whose efficiency is 99.97 percent above 0.3 um particle size dust,
is attached within the spindle hub and is rotating with the disks.
Particle count goes to nearly zero in a few minutes from the start of
rotation. Ferrofluidic seals are adopted to complete the elimination of
air contamination.
To enhance the cooling efficiency, the housing is made entirely of
aluminum casting with a high heat conductivity, and many fins formed
around it. Air circulation is completely symmetrical in the disk stacking
direction, and air flow is well intermingled at the inside hub for uniform
and efficient cooling around the read/write heads, along with the servo
head.
4.2.2 Spindle motor
(1) Features
By adopting the brushless DC spindle motor and connecting the motor
directly to the spindle shaft, the following are realized.
The device becomes compact.
Pulley and belts are unnecessary, therefore, no maintenance is
required.
Accuracy of rotational speed is improved.
Vibration is reduced.
Dynamic braking replaces mechanical brake
(2) Construction
Construction of the motor is shown in Figure 4.2.2. The rotor poles
generate torque by the revolving magnetic field, and are connected
directly to a single shaft to which magnetic disks are attached. The
stator winding generates the above mentioned revolving magnetic field by
successively switching the current in it.
The rotor pole position detector determines the switching time of the
current in the stator winding by detecting the position of rotor poles.
The stator winding and rotor pole position detector are fixed in the motor
housing, which is fixed on the DE base.
B03P-4825-0002A ••• 01
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