Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2001-12-19
2004-05-25
Budd, Mark (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
Reexamination Certificate
active
06741012
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric actuator, more precisely relates to a piezoelectric actuator capable of precisely positioning a magnetic head.
These days, capacity of magnetic disk units are made greater but size of them are made smaller. Therefore, memory density of magnetic disks are made greater. To make the memory density greater, number of tracks in a unit length (TPI) must be made greater. Namely, width of each track must be made narrower. To correctly read data from and write data in the narrow tracks, a magnetic head must be highly precisely positioned.
To precisely position the magnetic head, the inventors of the present invention tried to actuate an actuator arm by a head actuating mechanism, further they tried to slightly move the magnetic head or a head suspension so as to correctly position the magnetic head or the head suspension. The inventors found that deformation of piezoelectric elements and a specific structure of a carriage arm are capable of moving the head suspension and precisely positioning the magnetic head. The piezoelectric actuator of the present invention employs the deformation of the piezoelectric elements.
An exploded perspective view of a conventional piezoelectric actuator, which employs the deformation of the piezoelectric elements, is shown in FIG.
21
. The piezoelectric actuator has a flat actuator base
10
, which is connected to a carriage arm, and a hinge plate
14
, which sandwich the piezoelectric elements
12
with the actuator base
10
. A first electrode member
16
is provided between the actuator base
10
and the piezoelectric elements
12
; a second electrode member
18
is provided between the piezoelectric elements
12
and the hinge plate
14
. The electrode members
16
and
18
input electric voltage to the piezoelectric elements
12
so as to apply shear stress to the piezoelectric elements
12
and deform them.
The electrode members
16
and
18
input electric voltage to the piezoelectric elements
12
sandwiched between the actuator base
10
and the hinge plate
14
, so the actuator base
10
and the first electrode member
16
are electrically insulated each other, and the hinge plate
14
and the second electrode member
18
are also electrically insulated each other. One side face of the first electrode member
16
, which contacts the actuator base
10
, is covered with an insulating layer; the other side face of the first electrode member
16
, which contacts the piezoelectric elements
12
, is covered with an electric conductive layer. One side face of the second electrode member
18
, which contacts the hinge plate
14
, is covered with an insulating layer; the other side face of the second electrode member
18
, which contacts the piezoelectric elements
12
, is covered with an electric conductive layer.
A plan view of a magnetic head assembly, to which the piezoelectric actuator shown in
FIG. 22
is assembled, is shown in FIG.
21
. The head suspension
20
is connected to the hinge plate
14
. The deformation of the piezoelectric elements
12
move the hinge plate
14
, in a plane, in the right-left directions, so that the head suspension
20
is also moved in the right-left directions and the magnetic head, which is mounted on the head suspension
20
, can be correctly positioned. Side edges of the electrode members
16
and
18
are bent, and terminals
16
a
and
18
a
, which will be connected to a flexible printed circuit, are formed therein.
As shown in
FIG. 22
, in the magnetic head assembly including the conventional piezoelectric actuator, a terminal section
24
, to which cables connecting to the magnetic head will be connected, is formed at one side edge of the head suspension
20
; terminals
16
a
and
18
a
for actuating the piezoelectric elements
12
are formed at the other side edge thereof. With this structure, a flexible printed circuit, which will be connected to the terminal section
24
of the suspension
20
, and another flexible printed circuit, which will be connected to the terminals
16
a
and
18
a
, must be required. Namely, manufacturing cost of the head assembly must be high. In the case that the terminal section
24
and the terminals
16
a
and
18
a
are provided on the same side of the head suspension
20
and one flexible printed circuit is connected thereto, positions of the terminal section
24
and the terminals
16
a
and
18
a
must be highly precisely located. If the are slightly shifted from the predetermined positions and a step-shaped section is formed between the terminal section
24
and the terminals
16
a
and
18
a
, it is very difficult to correctly connect the flexible printed circuit to the terminal section
24
and the terminals
16
a
and
18
a
, so that manufacturing cost of the head assembly must be higher.
In the conventional piezoelectric actuator shown in
FIG. 21
, the actuator base
10
and the hinge plate
14
are electrically insulated from the piezoelectric elements
12
, and the electrode members
16
and
18
are provided between the actuator base
10
and the hinge plate
14
so as to input voltage to the piezoelectric elements
12
. As described above, size of magnetic disk units are made smaller, so the piezoelectric actuator must be smaller and lighter. Mechanical characteristics of the piezoelectric actuator depends on its mass. If mass of the piezoelectric actuator is great, the carriage arm vibrates and badly influences the characteristics. Further, number of parts of the piezoelectric actuator must be reduced so as to reduce the manufacturing cost.
SUMMARY OF THE INVENTION
The present invention was invented to solve the disadvantages of the conventional piezoelectric actuator.
An object of the present invention is to provide a small and light piezoelectric actuator, which is capable of highly precisely positioning magnetic head assemblies, reducing number of parts and manufacturing cost, and improving characteristics.
To achieve the object, the present invention has following structures.
A first basic structure of the piezoelectric actuator of the present invention comprises: a movable member to which a head suspension is fixed; a fixed member being fixed to a carriage arm; a plurality of piezoelectric elements being provided between the movable member and the fixed member, the piezoelectric elements being capable of adjusting a position of the head suspension by their deformation; and an electrode member being provided to a part of the fixed member on which the piezoelectric elements are provided, the electrode member having an electric conductive layer, which is electrically insulated from the fixed member and electrically connected to one of electrodes of each of the piezoelectric elements, wherein the movable member is adhered on the piezoelectric elements and electrically insulated from the other electrodes of the piezoelectric elements, and the electric conductive layer of the electrode member and the other electrode of each of the piezoelectric elements are electrically connected to cables, which are provided to the head suspension so as to actuate the piezoelectric elements.
A second basic structure of the piezoelectric actuator comprises: a movable member to which a head suspension is fixed; a fixed member being fixed to a carriage arm; and a plurality of piezoelectric elements being provided between the movable member and the fixed member, the piezoelectric elements being capable of adjusting a position of the head suspension by their deformation, wherein the piezoelectric elements are fixed to the fixed member, and one of electrodes of each of the piezoelectric elements is electrically connected to the fixed member, the movable member is adhered on the piezoelectric elements and electrically insulated from the other electrodes of the piezoelectric elements, and the other electrode of each of the piezoelectric elements is electrically connected to a cable, which is provided to the head suspension so as to actuate the piezoelectric elements.
A third basic structure of the piezoel
Heya Shuichi
Hiraoka Shinji
Koganezawa Shinji
Makino Kenichi
Budd Mark
Fujitsu Limited
Greer Burns & Crain Ltd.
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