General Description - Fujitsu M2361A Customer Engineering Manual

CHAPTER 4 THEORY OF OPERATION
4.1 General Description
The operation of the M2361A is divided into three parts. The first part
(Section 4.2) describes the mechanical assemblies of the unit. The second part
(Section 4.3 and 4.4) describes the magnetic heads and disks. The third part
(Section 4.5 and 4.6) describes the interface, servo circuit, R/W control, and
other electronic controls.
4.2 Mechanical Assemblies
4.2.1
Disk Enclosure (DE)
(1) Design concept
The mechanical configuration of the DE shown in Figure 4.2.1 was designed
to provide a compact, low power consumption, and maintenance-free file
with enhanced performance. It features six 10.5 inch diameter disks and a
rotary actuator with the fast average positioning time of 18 msec. The
rotary actuator is completely balanced statically and dynamically by using
a pair of moving coils, thereby avoiding undesired vibration that prolongs
settling time.
(2) Spindle and base casting
The primary function of the spindle is to maintain precise and constant
rotation of the assembled disks. The accuracy of rotation involves
concentricity, precision, thermal and dynamic stability; all of which
become more stringent as the track spacing gets tighter.
The dual-supported spindle construction reduces this problem. In this
design, the supporting casting is divided into two pieces in a plane
parallel to the spindle axis, with one of the divided pieces substantially
retaining the rotating bearings. Thus, precise concentricity can be
maintained.
With regard to the base casting, it is important to keep the relative
dimension between the spindle and rotary actuator very rigid, especially
in a dynamic mode. This has been given critical attention as track
spacing and access time become smaller and shorter.
In the present drive, the rotary actuator is designed so that the rotating
axis is pivoted at both ends, similar to the spindle. A pair of arms are
extended from the spindle bearing part to the pivoting element of the
rotary actuator. This technique, combined with the high rigidity of the
actuator, provides resonant-free seek operation.
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