Dynamic magnetic information storage or retrieval – Head mounting – For shifting head between tracks
Reexamination Certificate
2001-10-23
2003-04-15
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
For shifting head between tracks
Reexamination Certificate
active
06549381
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to disk drives. More particularly, the present invention relates to disk drives in which the motion of the actuator assembly is damped using a damping magnet placed within the magnetic field of the voice coil motor.
2. Description of the Prior Art
A typical hard disk drive includes a head disk assembly (“HDA”) and a printed circuit board assembly (“PCBA”). The HDA includes at least one magnetic disk (“disk”), a spindle motor for rotating the disk, and a head stack assembly (“HSA”) that includes a head with at least one transducer for reading and writing data. The HSA is controllably positioned by a servo system in order to read or write information from or to particular tracks on the disk. The typical HSA has three primary portions: (1) an actuator assembly that moves in response to the servo control system; (2) a head gimbal assembly (“HGA”) that extends from the actuator assembly and biases the head toward the disk; and (3) a flex cable assembly: that provides an electrical interconnect with minimal constraint on movement.
A typical HGA includes a load beam, a gimbal attached to an end of the load beam, and a head attached to the gimbal. The load beam has a spring function that provides a “gram load” biasing force and a hinge function that permits the head to follow the surface contour of the spinning disk. The load beam has an actuator end that connects to the actuator arm and a gimbal end that connects to the gimbal that carries the head and transmits the gram load biasing force to the head to “load” the head against the disk. A rapidly spinning disk develops a laminar airflow above its surface that lifts the head away from the disk in opposition to the gram load biasing force. The head is said to be “flying” over the disk when in this state.
Within the HDA, the spindle motor rotates the disk or disks, which are the media to and from which the data signals are transmitted via the head on the gimbal attached to the load beam. The transfer rate of the data signals is a function of rotational speed of the spindle motor; the faster the rotational speed, the higher the transfer rate. A spindle motor is essentially an electro-magnetic device in which the electromagnetic poles of a stator are switched on and off in a given sequence to drive a hub or a shaft in rotation.
FIG. 1
shows the principal components of a magnetic disk drive
100
constructed in accordance with the prior art. With reference to
FIG. 1
, the disk drive
100
is an Integrated Drive Electronics (IDE) drive comprising a RDA
144
and a PCBA
114
. The HDA
144
includes a base
116
and a cover
117
attached to the base
116
that collectively house a disk stack
123
that includes a plurality of magnetic disks (of which only a first disk
111
and a second disk
112
are shown in FIG.
1
), a spindle motor
113
attached to the base
116
for rotating the disk stack
123
, an HSA
120
, and a pivot bearing cartridge
184
(such as a stainless steel pivot bearing cartridge, for example) that rotatably supports the HSA
120
on the base
116
. The spindle motor
113
rotates the disk stack
123
at a constant angular velocity. The HSA
120
comprises a swing-type or rotary actuator assembly
130
, at least one HGA
110
, and a flex circuit cable assembly
180
. The rotary actuator assembly
130
includes a body portion
140
, at least one actuator arm
160
cantilevered from the body portion
140
, and a coil portion
150
cantilevered from the body portion
140
in an opposite direction from the actuator arm
160
. The actuator arm
160
supports the HGA
110
with a head. The flex cable assembly
180
includes a flex circuit cable and a flex clamp
159
. The HSA
120
is pivotally secured to the base
116
via the pivot-bearing cartridge
184
so that the head at the distal end of the HGA
110
may be moved over a recording surface of the disks
111
,
112
. The pivot-bearing cartridge
184
enables the HSA
120
to pivot about a pivot axis, shown in
FIG. 1
at reference numeral
182
. The storage capacity of the HDA
111
may be increased by including additional disks in the disk stack
123
and by an HSA
120
having a vertical stack of HGAs
110
supported by multiple actuator arms
160
.
The “rotary” or “swing-type” actuator assembly comprises a body portion
140
that rotates on the pivot bearing
184
cartridge between limited positions, a coil portion
150
that extends from one side of the body portion
140
to interact with one or more permanent magnets
192
mounted to back irons
170
,
172
to form a voice coil motor (VCM), and an actuator arm
160
that extends from an opposite side of the body portion
140
to support the HGA
110
. The VCM causes the HSA
120
to pivot about the actuator pivot axis
182
to cause the read write heads of the HSA
120
to sweep radially over the disk(s)
111
,
112
.
Dynamic load/unload (LUL) of flying heads in rigid disk drives offers many technical advantages along with new engineering challenges. Among these challenges are 1) methods of retaining the actuator in the non-operational position on the ramp and 2) ensuring that upon loss of power, the flying heads are not unloaded at too high of a velocity.
Many solutions for retaining the actuator in the non-operational position on a contact-start-stop (CSS) drive are well known such as magnetic, air-vane, spring detent, and the like. Furthermore, the contact friction of the heads resting on the CSS area (an annular region on each of the disks
111
,
112
that is typically located at the inner diameter -ID) of the disks of a CSS drive helps retain the actuator assembly
120
in the non-operational position. These solutions work quite well to retain the actuator assembly
120
in the non-operational position during mechanical shocks. Controlled, low-velocity unloads are required to ensure that neither the heads nor media are damaged. The critical unload operation occurs when power is suddenly removed from the drive. The actuator may be moving at a high velocity towards the ramp; neither normal servo control nor full power is available to brake the actuator assembly
120
before loading onto the ramp. In this case, some means of slowing the actuator prior to reaching the ramp would aid in unload velocity control.
For dynamic LUL drives, a controlled, low-velocity loading of the heads onto the rotating disks is necessary to eliminate the potential of head/media contact and damage during the load. In a LUL drive, portions of the head suspension contact a ramp during non-operation, and the friction between the ramp and suspension are designed to low values to allow low-velocity motion control. This low friction offers little retaining force to the actuator and may allow the actuator to move under the influence of even small mechanical shocks. A detent on the ramp is usually employed to increase the retaining force, but the angle of detent is similarly limited to low values and hence offers little improvement.
What are needed, therefore, are improved head stack assemblies and drives that include a structure to slow the actuator prior to reaching the ramp or the CSS area of the disk or disks.
SUMMARY OF THE INVENTION
Accordingly, this invention may be regarded as a disk drive including a disk having a recording surface, a ramp structure defining a ramp surface and a head stack assembly. The head stack assembly includes an actuator body, an actuator arm cantilevered from the actuator body and including a head for reading and writing on the recording surface, the head resting on the ramp surface when the disk drive is non-operational, a coil cantilevered from the actuator body in an opposite direction from the actuator arm, the coil defining a first leg and a second leg and a damping magnet disposed between the first leg and the second leg. The damping magnet may be configured to exert a damping force on the head stack assembly, the damping force being greater when the head is on the ramp surface than when the head is over the recordin
Kim Esq. W. Chris
Shara, Esq. Milad G.
Tupper Robert S.
Western Digital Technologies Inc.
Young Law Firm
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