Dynamic magnetic information storage or retrieval – Head mounting – For adjusting head position
Reexamination Certificate
2002-03-05
2004-05-18
Davis, David (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
For adjusting head position
Reexamination Certificate
active
06738230
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to information recording and/or playback devices and methods of positioning of magnetic heads of the devices, and more particularly, to an information recording and/or playback device and a method of positioning of a magnetic head of the device, in which the magnetic head is positioned by dual-stage actuators.
2. Description of the Related Art
There is great demand to improve the speed and accuracy of positioning a magnetic head of a magnetic disk device. Because of this, a magnetic disk device which has a dual-stage servo system comprising a slight movement actuator and a rough movement actuator is proposed.
For instance, a magnetic disk device having such the dual-stage servo system comprising a slight movement actuator and a rough movement actuator is described in Japanese Laid-Open Patent Application No. 11-031368.
A magnetic disk device having a dual-stage servo actuator will be described.
FIG. 1A
is a plan view of the magnetic disk device having the dual-stage actuator.
FIG. 1B
is a vertical sectional-view taken on line A—A in FIG.
1
A.
FIG. 2
is a block diagram of the magnetic disk device having the dual-stage actuator.
The magnetic disk device
1
includes a disk enclosure
11
and a circuit board assembly
12
.
The disk enclosure
11
has a case
21
and a cover
22
. A magnetic disk
31
, a spindle motor
32
, a magnetic head
33
, a suspension
34
and an arm
35
, a slight movement actuator
36
, and a rough movement actuator
37
are built in a space between the case
21
and the cover
22
of the disk enclosure
11
.
The magnetic disk
31
is clamped to the spindle motor
32
. The magnetic disk
31
rotates as the spindle motor
32
rotates. The spindle motor
32
is connected to the circuit board assembly
12
and rotates based on a driving signal provided by the circuit board assembly
12
.
A magnetic head
33
is fixed on a head end part of the suspension
34
. The magnetic head
33
faces the magnetic disk
31
. The suspension
34
is provided on a head end part of the arm
35
. The suspension
34
is capable of circular movement driven and in a disk radius direction (an arrow A direction). The suspension
34
and arm
35
are connected to each other by the slight movement actuator
36
. The slight movement actuator
36
, for example, is comprised of a shear type piezo actuator and makes the suspension
34
move circularly and in the arrow A direction. The other end part of the arm
35
is connected with the rough movement actuator
37
. The rough movement actuator
37
, for example, is comprised of a voice coil motor (VCM) and makes the arm
35
move circularly and in the arrow B direction.
The magnetic head
33
is connected to a flexible print wire board
38
by a print wire in the suspension
34
and the arm
35
or a lead line wired along the arms
34
and
35
. A head IC
39
is mounted on the flexible print wire board
38
. The head IC
39
is connected to the magnetic head
33
. The head IC
39
amplifies a recording signal which is supplied to the magnetic head
33
and a playback signal which is played back by the magnetic head
33
. In addition, the flexible print wire board
38
is connected with the slight movement actuator
36
and the rough movement actuator
37
.
The head IC
39
is extended to a bottom surface side of the case
21
by the flexible print wire board
38
, and connected to the circuit board assembly
12
. The flexible print wire board
38
is connected to the spindle motor
32
, the slight movement actuator
36
, and the rough movement actuator
37
. The flexible print wire board
38
is extended from an inside part of the case
21
to an outside part of a bottom surface of the case
21
, that is, piercing the bottom surface.
The circuit board assembly
12
is provided at an outside part of the bottom surface of the case
21
. Furthermore, the circuit board assembly
12
is connected to the flexible print wire board
38
. The circuit board assembly
12
has a structure in which a hard disk controller (HDC)
41
, a random access memory (RAM)
42
, a read only memory (ROM)
43
, a digital signal processor (DSP)
44
, a micro processor unit (MPU)
47
, a read channel (RDC)
45
, and a servo controller (SVC)
46
are mounted on the print wire board
38
.
The HDC
41
is connected to a high ranked controller
51
, and thereby the HDC
41
controls a communication with the high ranked controller
51
. The RAM
42
is used as a buffer memory in which data communicated with the high ranked controller
51
are stored temporarily. The RDC
45
modulates the recording signal recorded in the magnetic disk
31
and demodulates the playback signal played back from the magnetic disk
31
, by the magnetic head
33
.
The SVC
46
is connected to the spindle motor
32
, the slight movement actuator
36
, the rough movement actuator
37
, and the DSP
44
. The SVC
46
drives the spindle motor
32
, as a relative speed of the magnetic head
33
and the magnetic disk
31
becomes a designated value based on the playback signal which is played back by the magnetic head
33
. In addition, the SVC
46
controls the slight movement actuator
36
and the rough movement actuator
37
based on instructions from the MPU
44
. And thereby, the magnetic head
33
follows a track formed in the magnetic disk
31
.
The MPU
44
controls the HDC
41
, the RDC
45
, and the SVC
46
by firm ware stored permanently in the ROM
43
, and thereby the MPU
44
controls an action of the whole of the device.
It is required for the slight movement actuator
36
of the above-mentioned dual-stage servo actuator of the magnetic disk device to have a high speed ability. Because of this, a shear type piezo actuator is used as the slight movement actuator
36
.
FIG. 3
is a plan view of the dual-stage actuator in which the shear type piezo actuator is used as the slight movement actuator
36
and the VCM is used as the rough movement actuator
37
. The piezo actuator has a movable area of “a”(a plus direction of “a” to a minus direction of “a”) where “a” is defined as a distance of 0.5 &mgr;m from a center position of the movable area. The rough movement actuator
37
has a movable area of “b” (a plus direction of “b” to a minus direction of “b”) where “b” is defined as a distance of 12 mm from a center position of the movable area.
FIG. 4
is a view showing a frequency response of the piezo actuator namely the slight movement actuator
36
.
FIG. 5
is a view showing a frequency response of the VCM namely the rough movement actuator
37
.
The piezo actuator has a main resonance frequency of 9 kHz, as shown in FIG.
4
. On the other hand, the VCM has a main resonance frequency of 5 kHz, as shown in FIG.
5
. Therefore, the piezo actuator can act with a higher speed than the VCM.
FIG. 6
is a block diagram of a track following control system of the dual-stage actuator.
At the time of track following, a tracking error signal is necessary. The tracking error signal represents a difference between an information of an objective position of the head and an information of a present position of the head. The tracking error signal is supplied to a controller
62
for controlling the slight movement actuator
36
and a controller
63
for controlling the rough movement actuator
37
.
The controller
62
controls the slight movement actuator
36
based on the tracking error signal. The controller
63
controls the rough movement actuator
37
based on the tracking error signal.
The magnetic head
33
is moved a total amount by the slight movement actuator
36
and the rough movement actuator
37
. A position of the magnetic head
33
is fed back as information providing a present head position. With the above-mentioned operation, the magnetic head
33
is positioned at the objective position.
FIG. 7
is a block diagram of a track seek control system of the dual-stage actuator.
As shown in
FIG. 7
, in this system, a control by the slight movement actuator
36
and a control by the rough
Davis David
Greer Burns & Crain Ltd.
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