Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
2002-03-15
2004-09-14
Sniezek, Andrew L. (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S294400
Reexamination Certificate
active
06791783
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic head device.
2. Description of the Related Art
FIG. 6
is a plan view of a conventional hard disk device. The hard disk device comprises a magnetic disk
101
, a spindle motor
102
which rotationally drives the magnetic disk
101
, a carriage
103
, a load beam
104
, a slider
105
, and a voice coil motor
106
. A magnetic head device is roughly formed by the load beam
104
and the slider
105
.
A base end portion
104
b
of the load beam
104
, which is a resilient supporting member, is connected to an end portion
103
a
of the carriage
103
, which is a rigid member. The slider
105
is mounted to an end
104
a
of the load beam 104 through a flexure (not shown).
The carriage
103
and the load beam
104
are driven in a radial direction of the magnetic disk
101
by the voice coil motor
106
in order to carry out a seek operation and a tracking operation. The seek operation is carried out to move a reproducing element and a recording element, which are mounted to the slider
105
, above any recording track. The tracking operation is carried out to achieve fine adjustment so as to maintain the positions of the reproducing element and the recording element above a centerline of a recording track.
In order to increase recording density, it is necessary to increase the precision of the tracking operation by increasing the driving frequency of the voice coil motor
106
. Since the driving frequency of the voice coil motor
106
is related to the resonant frequency of the load beam
104
, there is a limit as to how high the driving frequency of the voice coil motor
106
can be made. Thus, there is a limit as to how high the precision of the tracking operation can be made.
To overcome this problem, a magnetic head device which has a microactuator mounted to the load beam
104
has been developed. The magnetic head device can carry out a tracking operation as a result of moving only an end portion of the load beam
104
by the microactuator.
FIG. 7
is a perspective view of the load beam
104
.
FIG. 8
is a sectional view of the main portion of FIG.
7
.
The load beam
104
is formed of a stainless-steel plate spring material, and includes a stationary base end portion
111
a
and a swinging portion
111
b
. The stationary base end portion
111
a
is held by the carriage, and the swinging portion
111
b
can swing horizontally with respect to the stationary base end portion
111
a
. Arms
111
c
and
111
c
, which extend in the longitudinal direction of the stationary base end portion
111
a
, are formed on both sides of the front end portion of the stationary base end portion
111
a
. The swinging portion
111
b
is connected to the arms
111
c
and
111
c
through resilient supporting portions
111
d
and
111
d.
Piezoelectric elements
112
and
113
, which are microactuators, are placed on the swinging portion
111
b
and the stationary base end portion
111
a
by placing them over a gap
111
e.
The piezoelectric element
112
comprises a piezoelectric layer
112
a
and electrode layers
112
b
and
112
c
. The piezoelectric element
113
comprises a piezoelectric layer
113
a
and electrode layers
113
b
and
113
c
. The piezoelectric layers
112
a
and
113
a
are formed of, for example, lead zirconate titanate (PZT). The electrode layers
112
b
and
112
c
and
113
b
and
113
c
are formed of, for example, metallic films deposited onto the top and bottom sides of their corresponding piezoelectric layers
112
a
and
113
a.
As shown in
FIG. 8
, the electrode layers
112
c
and
113
c
of the corresponding piezoelectric elements
112
and
113
and the swinging portion
111
b
and the stationary base end portion
111
a
are joined together by an electrically conductive adhesive resin
115
.
In
FIG. 7
, reference numeral
121
denotes a slider which is mounted to an end of the swinging portion
111
b
through a flexure (not shown).
As shown in
FIG. 8
, the load beam
104
is connected to ground. As shown in
FIG. 7
, the electrode layer
112
b
of the piezoelectric element
112
and the electrode layer
113
b
of the piezoelectric element
112
are connected by a gold wire
114
a
. As shown in
FIGS. 7 and 8
, a different gold wire
114
b
is connected to the electrode layer
113
b
of the piezoelectric element
113
, and to a control circuit
114
c
. By virtue of this structure, a control voltage can be applied to the piezoelectric elements
112
and
113
from the control circuit
114
c.
The piezoelectric elements
112
and
113
are elements which get distorted when a voltage is applied through the electrode layers
112
b
and
112
c
, and
113
b
and
113
c
, respectively.
The piezoelectric layers
112
a
and
113
a
of the corresponding piezoelectric elements
112
and
113
polarize in the film thickness directions. However, the polarization directions are opposite each other. Therefore, when the same control voltage is applied to the electrode layers
112
c
and
113
c
, one of the piezoelectric elements expands in the longitudinal direction thereof, while the other piezoelectric element contracts in the longitudinal direction thereof.
As a result, the resilient supporting portions
111
d
and
111
d
get distorted, so that the position of the slider
121
, mounted to an end of the swinging portion
111
b
, changes. In other words, a precise tracking operation can be carried out by slightly moving the slider
121
, mounted to an end of the swinging portion
111
b
, in the widthwise direction of a track.
As the recording density of the magnetic disk
101
increases, it becomes necessary to increase the precision of the tracking operation. By the load beam
104
, it is possible to carry out a precise tracking operation, so that the recording density can be increased.
The electrically conductive adhesive resin
115
is required to maintain electrical conduction between the load beam
104
and the piezoelectric elements
112
and
113
, and to function so that the deformation of the piezoelectric elements
112
and
113
reliably causes deformation of the load beam
104
by increasing the bonding strength between the load beam
104
and the piezoelectric elements
112
and
113
.
However, the commonly used electrically conductive adhesive resin
115
is an epoxy adhesive resin mixed with, for example, a metal filler. Since the bonding strength is reduced by mixing the metal filler, the deformation of the piezoelectric elements
112
and
113
cannot reliably cause deformation of the load beam
104
, thereby giving rise to the problem that a precise tracking operation cannot be carried out.
The electrically conductive adhesive resin
115
tends to deteriorate at a high temperature. Therefore, when, for example, the magnetic head device is continuously operated for a long period of time, the temperature of the whole magnetic head device rises, so that the bonding strength of the electrically conductive adhesive resin
115
is reduced, thereby also resulting in the problem that a precise tracking operation cannot be carried out.
SUMMARY OF THE INVENTION
In view of the above-described situation, it is an object of the present invention to provide a magnetic head device which can precisely carried out a tracking operation as a result of increasing bonding strength between a piezoelectric element and a load beam.
To this end, the present invention uses the following structures.
According to the present invention, there is provided a magnetic head device comprising a slider having provided thereat a reproducing element and a recording element, with the reproducing element being used to detect a magnetic signal recorded on a recording medium and a recording element being used to record a magnetic signal on the recording medium; a resilient supporting member which supports the slider; and a piezoelectric element, mounted on the resilient supporting member, for changing the position of the slider by distorting the resilient supporting member. In the magnetic head device,
Alps Electric Co. ,Ltd.
Sniezek Andrew L.
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