Dynamic magnetic information storage or retrieval – Head mounting – For adjusting head position
Reexamination Certificate
2001-03-12
2004-05-04
Miller, Brian E. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
For adjusting head position
C360S244500
Reexamination Certificate
active
06731472
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-150004, filed May 22, 2000; and No. 2001-063010, filed Mar. 7, 2001, the entire contents of both of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a suspension for disc drive incorporated in an information processor such as a personal computer.
A magnetic head is used to record in or read data from a recording surface of a disc in a disc drive that is provided with a rotating magnetic or magneto-optical disc. The magnetic head includes a slider that is opposed to the recording surface of the disc, a transducer in the slider, etc. As the disc rotates at high speed, the slider is slightly lifted off the disc, whereupon an air bearing is formed between the disc and the slider. A suspension for holding the magnetic head is provided with a load beam, a flexure formed of a very thin plate spring fixed to the distal end portion of the load beam, a base plate on the proximal portion of the load beam, etc. The slider that constitutes the magnetic head is attached to the distal end portion of the flexure.
In a hard disc drive (HDD), the track center of the disc should be subjected to following control for ±10% or less of the track width. Most of modern high-density discs have a track width of 1 &mgr;m or less, so that it is hard to keep the slider in the track center. Accordingly, it is necessary to control the position of the slider more accurately as well as, for example, to increase the rigidity of the disc, thereby damping the oscillation.
In general, conventional disc drives are of a single-actuator type such that a suspension is moved by means of a voice coil motor only. According to this type, a lot of resonance peaks exist in a low-frequency band. It is difficult, therefore, to control the slider (head portion) at the distal end of the suspension in a high-frequency band by means of the voice coil motor only, and the bandwidth of servo cannot be increased.
Accordingly, there has been developed a dual-actuator suspension that is provided with actuator elements, such as piezo-electric elements that are formed of PZT (plumb zircon-titanate), as second actuators. According to this dual-actuator system, only the distal end portion of the suspension or the slider is slightly moved in the width direction (so-called sway direction) of the suspension by means of the actuator elements. A movable part that is driven by means of the actuator elements is considerably lighter in weight than that of the single-actuator system, so that the slider can be controlled in a high-frequency band. Thus, the band width of the servo for slider position control can be made several times as high as that of the single-actuator system, and tracking errors can reduced correspondingly.
FIG. 21
shows a part of a conventional dual-actuator suspension. A micro actuator mechanism
2
of this suspension
1
is formed having slits
4
and
5
in its base portion
3
. A pivot portion
7
and support walls
8
and
9
are formed on the proximal portion of a load beam body
6
. Actuator elements
10
such as PZT are provided individually on the opposite sides of the pivot portion
7
.
One end portion
10
a
of each actuator element
10
is bonded to the base portion
3
, and the other end portion
10
b
to the load beam body
6
. When supplied with current, the actuator elements
10
are distorted in opposite directions. The support walls
8
and
9
bend as this distortion causes the distal end portion of the suspension
1
to be displaced in the sway direction (direction indicated by arrow S) around the pivot portion
7
. The suspension of this type will hereinafter be referred to as a pivot-type suspension.
In the pivot-type suspension, the stiffness of the support walls
8
and
9
must be lowered in order to obtain satisfactory displacement in the sway direction. In this case, the torsional stiffness of the whole suspension is reduced, and the sway-mode resonance frequency lowers inevitably. In order to solve this problem, it is necessary to reduce length L′ and width B′ of the support walls
8
and
9
and increase the wall thickness.
Since the support walls
8
and
9
are formed integrally with the base portion
3
and the load beam body
6
, however, their width B′ can be reduced only limitedly. Further, their thickness is settled distinctly depending on the respective thicknesses of the base portion
3
and the load beam body
6
, so that it is hard to increase the thickness of the support walls
8
and
9
.
Since the thickness-direction stiffness of the micro actuator mechanism
2
is low, the PZT elements
10
may possibly undergo deformation such as warping as they are bonded to the base portion
3
and the load beam body
6
. If the elements
10
are deformed, their output characteristics may change, or accurate control may fail to be accomplished. Since the elements
10
share a high percentage of load on the micro actuator mechanism
2
, moreover, they are damaged heavily when shocked. In some cases, therefore, even a relatively small shock can destroy the elements
10
.
BRIEF SUMMARY OF THE INVENTION
Accordingly, the object of the present invention is to provide a suspension for disc drive, in which the resonance peak of the suspension with a micro actuator mechanism can be enhanced, and actuator elements can be made less destroyable.
In order to achieve the above object, a suspension according to the present invention comprises an actuator base including a base plate, a load beam provided with a flexure, and a micro actuator mechanism attached to the actuator base, the micro actuator mechanism including at least one pair of slits formed in the actuator base, a pivot portion situated between the slits, an actuator element provided on the actuator base and adapted to be distorted to cause displacement of the distal end portion of the load beam when supplied with current, and a support wall formed of a bent portion rising in the thickness direction of the actuator base from an edge portion of the actuator base.
In the suspension provided with the micro actuator mechanism of a pivot type, according to this invention, the sway-direction resonance frequency can be increased, so that the position of the suspension can be controlled with higher accuracy.
The pivot-type suspension of the present invention comprises a connecting plate for connecting the actuator base and the load beam, the connecting plate including a main plate portion formed of a plate material thinner than the base plate and superposed on the base plate and the support wall rising in the thickness direction of the main plate portion from an edge portion of the main plate portion, for example. According to this invention, the flexibility of the support wall in the sway direction can be secured.
Further, the connecting plate may be formed of a springy material and include a hinge portion flexible in the thickness direction between the base plate and the load beam. According to this invention, the support wall can be formed by utilizing a part of the connecting plate that integrally has the hinge portion. The support wall is composed of the bent portion that is formed at an end of the thin connecting plate. In this case, the thickness of the support wall can be increased depending on the height of the bent portion. Since the bent portion is thin, moreover, the width of the support wall that is formed of the bent portion can be reduced. Thus, the torsional stiffness and the sway-mode resonance frequency can be enhanced without lowering the flexibility the support wall.
Furthermore, a bending-type suspension for disc drive according to the present invention comprises an actuator base including a base plate having a thickness of 0.17 mm or more and formed integrally with a boss portion, a load beam provided with a flexure, and a micro actuator mechanism attached to the actuator base, the micro actuator mecha
Fujiwara Tetsuya
Hanya Masao
Iriuchijima Osamu
Okamoto Hiroshi
Shiigi Toshio
Frishauf Holtz Goodman & Chick P.C.
Miller Brian E.
NHK Spring Co. Ltd.
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