Micrometric actuation, hard disk read/write unit with a...

Details Micrometric actuation, hard disk read/write unit with a... Micrometric actuation, hard disk read/write unit with a...

2000-02-23

2003-09-23

Renner, Craig A. (Department: 2652)

Dynamic magnetic information storage or retrieval

Head mounting

For adjusting head position

C360S244200, C360S245600

Reexamination Certificate

active

06624981

ABSTRACT:

TECHNICAL FIELD
The present invention relates to hard disk systems, and in particular to a micrometric actuation, hard disk read/write unit.
BACKGROUND OF THE INVENTION
As known, hard disks are the most commonly used means of storing data in personal computers. Consequently they are produced in very large volumes, and the maximum data storage density is increasing year by year. Hard disks are read and written by actuator devices, the general structure whereof is shown in
FIGS. 1 and 2
and is described hereinafter.
In particular,
FIG. 1
shows a known actuator device
1
of a rotary type, comprising a motor
2
(also called a voice coil motor), secured to a support body
3
, generally called E-block, owing to its shape as an “E” in lateral view (see, e.g., FIG.
2
). The support body
3
has a plurality of arms
4
, each of which supports a suspension
5
, formed from a steel plate, and secured in a projecting manner. At an end not secured to the support body
3
, each suspension
5
supports a coupling
8
(called a gimbal or a flexure), also made of steel, which in turn supports a read/write transducer
6
(called a slider), which (in the operative condition) faces a surface of a hard disk
7
.
The slider
6
comprises a support body, a bearing secured thereto, and a magneto/resistive and inductive read/write (R/W) head
91
that forms the actual reading and writing device. Electric wires (not shown) extend from the R/W head
91
, along a coupling
8
and the suspension
5
, as far as a signal processing device (also not shown), secured to a main board of a personal computer or other device that contains hard disks for data storage.
To prevent the read/write signal from becoming excessively attenuated, to ensure that it has sufficient amplitude for reading/writing of the hard disk
7
, and also to prevent the hard disk
7
from being damaged by the slider
6
, the slider
6
must be maintained at a predetermined distance (which at present is 20-30 nm) from, and parallel to, the hard disk
7
. Consequently, the suspension
5
has a degree of freedom in a vertical direction, to regulate the distance of the slider
6
from the hard disk
7
. The coupling
8
has two degrees of freedom around two axes &phgr; and &psgr; in a horizontal plane, and can carry out pitch and roll movements, to maintain the slider
6
parallel to the hard disk
7
even in presence of roughness and non-planar points. In particular, the suspension
5
should support the weight of the slider
6
(now 1.5 mg), and should also be able to oppose pressure generated on the surface of the slider
6
by air interposed between the hard disk
7
and the slider
6
and biasing the slider
6
away from the disk
7
during movement of the hard disk
7
and/or the actuator device
1
.
For this purpose, after assembling the various components, the suspension
5
is permanently bent, exploiting plastic deformation characteristics of steel. If the suspension is bent too much or too little, the bending error cannot be corrected, and it is necessary to scrap the suspension
5
and the elements secured to it (e.g., the flexure
8
and the slider
6
). Now, the assembly process, including the above-described bending step, has an output efficiency of 65-75%, giving rise to high costs for scrap. Furthermore, in some cases, the bending error is detected only upon completion of installation on the hard disk
7
, thus further aggravating the problem of costs.
In currently commercially available hard disk read/write devices, the slider
6
is glued directly to the coupling
8
. To obtain more accurate and finer control of the position of the slider
6
, it has already been proposed to use a double actuation step, with a first, courser actuation stage, including the motor
2
, displacing the assembly formed by support body
3
, suspension
5
, flexure
8
and slider
6
, across the hard disk
7
, during the approximate track search, and a second actuation stage, effecting a finer control of the position of the slider
6
, during tracking.
Hitherto, two solutions have been proposed. According to a first solution, the suspension
5
or the support body
3
is modified, such as to control in a micrometric manner the position of the suspension
5
. According to a second solution, the position of the slider
6
with respect to the end of the suspension
5
is controlled through a microactuator, interposed between the slider
6
and the coupling
8
.
An example of an embodiment of a microactuator
9
of a rotary electrostatic type, usable for the second micrometric actuation solution, is represented schematically in
FIG. 3
, wherein only part of the microactuator
9
is completely shown, owing to the axial symmetry. The microactuator
9
comprises a stator
17
, integral with a dice integrating the microactuator
9
and glued to the coupling
8
, and a rotor
11
, capacitively connected to the stator
17
, to be glued to the slider
6
(see, e.g., FIG.
2
).
The rotor
11
comprises a suspended mass
12
, of a substantially circular shape, and a plurality of mobile arms
13
, extending radially towards the exterior from the suspended mass
12
. Each mobile arm
13
supports a plurality of mobile electrodes
14
, extending in a substantially circumferential direction and equidistant from one another. The rotor
11
also comprises resilient suspension and anchorage elements (spring
15
), to support and bias the rotor
11
via fixed regions
16
.
The stator
17
comprises a plurality of fixed arms
18
,
19
, extending radially and supporting each a plurality of fixed electrodes
20
. In particular, each mobile arm
13
is associated to a pair of fixed arms, formed by a fixed arm
18
and a fixed arm
19
. The fixed electrodes
20
of each pair of fixed arms
18
,
19
extend towards the associated mobile arm
13
, and are intercalated or interdigitated with the mobile electrodes
14
. The fixed arms
18
are all arranged on a single side of the respective mobile arms
13
(on the right, in the example of FIG.
3
), and are all biased to the same potential, via biasing regions
21
. Similarly, the fixed arms
19
are all arranged on the other side of the respective mobile arms
13
(on the left, in the example of FIG.
3
), and are all biased to the same potential via biasing regions
22
.
The fixed arms
18
and
19
are biased to different potentials, so as to generate two different potential differences with respect to the mobile arms
13
, and to cause rotation of the rotor
11
in one direction or the other.
However, the insertion of the microactuator
9
between the coupling
8
and the slider
6
causes a reduction in the assembly output of the read/write device, because of the criticalities of the microactuator
9
.
SUMMARY OF THE INVENTION
An embodiment of the invention provides a read/write unit not affected by the above-described disadvantages.
According to embodiments of the present invention, a read/write unit for hard disks and a manufacturing method are provided, as defined in the claims.


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patent: 5793571 (1998-08-01), Jurgenson et al.
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patent: 6198145 (2001-03-01), Ferrari et al.
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patent: 0 955 629 (1999-11-01), None
Ohwe, T. et al., “Development of Integrated Suspension System for a Nanoslider with an MR Head Transducer,”IEEE Transactions on Magnetics29(6): 3924-3926, Nov. 1993.
Ohwe, T. et al., “A New Integrated Suspension for Pico-Sliders (Pico-Caps),”IEEE Transactions on Magnetics32(5):3648-3650, Sep. 1996.

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