U.S. patent number RE40,975 [Application Number 11/452,076] was granted by the patent office on 2009-11-17 for head suspension with resonance feedback transducer.
This patent grant is currently assigned to Hutchinson Technology Incorporated. Invention is credited to Robert B. Evans, Todd A. Krinke.
United States Patent |
RE40,975 |
Evans , et al. |
November 17, 2009 |
**Please see images for:
( Certificate of Correction ) ** |
Head suspension with resonance feedback transducer
Abstract
A head suspension assembly including a load beam having a rigid
region, a mounting region on a proximal end of the load beam, and a
flexure on a distal end of the load beam. The flexure has a
read/write head attachment region for supporting a read/write head
on the distal end of the load beam. Deformation of the head
suspension assembly displaces the head attachment region. A strain
transducer circuit that acts as a strain gauge is mounted on the
head suspension assembly. The resistance of the transducer circuit
varies with strain in the circuit, which, in turn, varies with
displacement of the read/write head. The magnitude of resistance
change of the transducer circuit indicates the magnitude of head
off-neutral motion.
Inventors: |
Evans; Robert B. (Hutchinson,
MN), Krinke; Todd A. (Rockford, MN) |
Assignee: |
Hutchinson Technology
Incorporated (Hutchinson, MN)
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Family
ID: |
21786603 |
Appl.
No.: |
11/452,076 |
Filed: |
June 9, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60018167 |
May 23, 1996 |
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Reissue of: |
08861530 |
May 22, 1997 |
05862015 |
Jan 19, 1999 |
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Current U.S.
Class: |
360/244.1;
360/75; 360/77.03; 360/78.05 |
Current CPC
Class: |
G11B
5/4833 (20130101) |
Current International
Class: |
G11B
21/02 (20060101); G11B 5/48 (20060101); G11B
5/596 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Yamaguchi, Y., et al.; Flow Induced Vibration of Magnetic Head
Suspension in Hard Disk Drive; IEEE Transactions on Magnetics; Sep.
1986; 1022-1024; MAG-22, #5; IEEE USA. cited by other .
D'Amico, "Disk Drives Go Micro", Berkley Engineering Forefront
1996, 3 pgs. cited by examiner .
Lee et al., "Piezoelectric model sensor/actuator pairs for critical
active damping vibrational control", J. Acoust. Soc. Am., vol. 90,
No. 1, Jul. 1991, pp. 374-384. cited by examiner.
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Primary Examiner: Olson; Jason C
Attorney, Agent or Firm: Faegre & Benson LLP
Parent Case Text
REFERENCE TO RELATED APPLICATION
This application claims the benefit of U.S. Provisional application
Ser. No. 60/018,167, filed May 23, 1996 abandoned.
Claims
What is claimed is:
1. A .Iadd.disk drive assembly, including: a .Iaddend.head
suspension assembly in which resonance mode motion can induce
strain, the head suspension assembly comprising: a load beam having
a proximal end, a distal end, a mounting region on the proximal
end, a rigid region adjacent to the distal end and a spring region
between the rigid region and the mounting region; a flexure for
supporting a read/write head at the distal end of the load beam;
and at least one strain transducer circuit on the head suspension
assembly for detecting strain therein such that the strain
transducer circuit detects resonance mode motion of the head
suspension assembly.Iadd.; a controller connected to the strain
transducer circuit, for providing drive signals as a function of
the strain detected by the transducer circuit; and an actuator
mechanically connected to the head suspension assembly and
electrically connected to the controller, for driving and
positioning the suspension assembly as a function of the drive
signals.Iaddend..
2. The .[.head suspension.]. .Iadd.disk drive .Iaddend.assembly of
claim 1 wherein the strain transducer circuit is located on the
load beam.
3. The .[.head suspension.]. .Iadd.disk drive .Iaddend.assembly of
claim 1 wherein the load beam includes a spring region between the
rigid region and the mounting region and further wherein the strain
transducer circuit is located in the spring region.
4. The .[.head suspension.]. .Iadd.disk drive .Iaddend.assembly of
claim 1 wherein the strain transducer circuit is located on the
rigid region of the load beam.
5. The .[.head suspension.]. .Iadd.disk drive .Iaddend.assembly of
claim 1 wherein the flexure includes a head attachment region for
supporting a read/write head at the distal end of the load beam and
wherein an elastic deformation of the head suspension assembly can
displace the head attachment region from a neutral position and
generate strain in the head suspension assembly.
6. The .[.head suspension.]. .Iadd.disk drive .Iaddend.assembly of
claim 5 wherein the strain transducer circuit has an electrical
resistance which varies with strain in the head suspension assembly
at a position of the strain transducer circuit thereon such that
the resistance in the strain transducer circuit varies with
deformation of the head suspension assembly to allow detection of
motion of the head mounting region out of the neutral position.
7. The .[.head suspension.]. .Iadd.disk drive .Iaddend.assembly of
claim 6 wherein the strain transducer circuit is located on the
load beam.
8. The .[.head suspension.]. .Iadd.disk drive .Iaddend.assembly of
claim 6 wherein the strain transducer circuit includes a single
strain gauge lead having an electrical resistance that varies with
strain on the lead.
9. The .[.head suspension.]. .Iadd.disk drive .Iaddend.assembly of
claim 8 wherein the strain gauge lead is formed of Constantan.
10. The .[.head suspension.]. .Iadd.disk drive .Iaddend.assembly of
claim 5 wherein the strain transducer circuit is located in the
spring region.
11. The .[.head suspension.]. .Iadd.disk drive .Iaddend.assembly of
claim 10 including a first strain transducer circuit and a second
train transducer circuit wherein the spring region has an open
region that divides the spring region into first and second radius
arms and the first strain transducer circuit is located on the
first radius arm and the second strain transducer circuit is
located on the second radius arm.
12. The .[.head suspension.]. .Iadd.disk drive .Iaddend.assembly of
claim 1 wherein the strain transducer circuit is on the
flexure.
13. The .[.head suspension.]. .Iadd.disk drive .Iaddend.assembly of
claim 1 including first, second, third and fourth strain transducer
circuits wherein the spring region has an open region that divides
the spring region into first and second radius arms and the first
and second strain transducer circuits are located on the first
radius arm, the third and fourth strain transducer circuits are
located on the second radius arm, and the first, second, third and
fourth strain transducer circuits are interconnected to form a
wheatstone bridge circuit.
14. A .Iadd.disk drive assembly, including: a .Iaddend.head
suspension assembly comprising: a load beam having a proximal end,
a distal end, a mounting region on the proximal end, a rigid region
adjacent to the distal end and a spring region between the rigid
region and the mounting region; a flexure having a head attachment
region for supporting a read/write head and at the distal end of
the load beam, the head attachment region displaceable from a
neutral position, such displacement causing strain in the head
suspension assembly; a microactuator on the head suspension
assembly between the mounting region and the head attachment region
and to displace the head attachment region from the neutral
position and along a transverse tracking axis; and at least one
strain transducer circuit on the head suspension assembly for
detecting strain in the head suspension assembly wherein
displacement of the head attachment region from the neutral
position caused by the microactuator is detected by the strain
transducer circuit.Iadd.; a controller connected to the strain
transducer circuit, for providing signals as a function of the
strain detected by the transducer circuit; and an actuator
mechanically connected to the head suspension assembly and
electrically connected to the controller, for driving and
positioning the suspension assembly as a function of the signals
provided by the strain transducer circuit.Iaddend..
15. The .[.head suspension.]. .Iadd.disk drive .Iaddend.assembly of
claim 14 wherein the strain transducer is located on the load
beam.
16. The .[.head suspension.]. .Iadd.disk drive .Iaddend.assembly of
claim 14 wherein the strain transducer circuit has an electrical
resistance which varies with strain in the head suspension assembly
at a position of the strain transducer circuit thereon.
17. The .[.head suspension.]. .Iadd.disk drive .Iaddend.assembly of
claim 16 wherein the strain transducer circuit includes a single
strain gauge lead having an electrical resistance that varies with
strain on the lead.
18. A .Iadd.disk drive assembly, including: a .Iaddend.head
suspension assembly in which resonance mode motion can induce
strain, comprising: a load beam having a proximal end, a distal
end, a mounting region on the proximal end, a rigid region adjacent
to the distal end and a spring region between the rigid region and
the mounting region; an actuator arm having a proximal end and a
distal end, the proximal end of the load beam mounted to the distal
end of the actuator arm; a flexure for supporting a read/write head
and at the distal end of the load beam; and .[.at least one strain
transducer circuit on the head suspension assembly for detecting
strain in the head suspension assembly such that the strain
transducer circuit detects resonance frequency vibrations of the
head suspension assembly.]. .Iadd.at least a first strain
transducer circuit located on the actuator arm and at least a
second strain transducer circuit located on the load beam such that
at least one of the first strain transducer circuit and the second
strain transducer circuit detects resonance frequency vibrations of
the head suspension assembly; a controller connected to at least
the first and the second strain transducer circuits, for providing
drive signals as a function of the strain detected by at least the
first and the second strain transducer circuits; and an actuator
mechanically connected to the head suspension assembly and
electrically connected to the controller, for driving and
positioning the suspension assembly as a function of the drive
signals.Iaddend..
.[.19. The head suspension assembly of claim 18 wherein the strain
transducer circuit has an electrical resistance which varies with
strain in the head suspension assembly at a position of the strain
transducer circuit thereon..].
.[.20. The head suspension assembly of claim 18 wherein the strain
transducer circuit is located on the actuator arm..].
.[.21. The head suspension assembly of claim 18 including a first
strain transducer circuit and a second state transducer circuit
wherein the first strain transducer circuit is located on the
actuator arm and the second strain transducer circuit is located on
the load beam..].
.Iadd.22. The disk drive assembly of claim 1 wherein the controller
produces drive signals for reducing head off-neutral
motion..Iaddend.
.Iadd.23. The disk drive assembly of claim 14 wherein the
controller produces drive signals for reducing head off-neutral
motion..Iaddend.
.Iadd.24. The disk drive assembly of claim 14 wherein the
controller is electrically connected to the
microactuator..Iaddend.
.Iadd.25. The disk drive assembly of claim 18 wherein the
controller produces drive signals for reducing head off-neutral
motion..Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to suspensions for
supporting read/write heads over recording media. In particular,
the present invention relates to a head suspension assembly with a
strain transducer circuit thereon for detecting motion of the head
suspension assembly out of a neutral position.
2. Description of the Related Art
Information storage devices typically include a read/write head for
reading and/or writing data onto a storage medium such as a
magnetic disk within a rigid disk drive. An actuator mechanism
driven by a servo control is used to position the head at specific
radial locations or tracks on the magnetic disk. Both linear and
rotary type actuators are well known in the art. Between the
actuator and the head, a head suspension is required to support the
head in proper orientation relative to the disk surface.
The head suspension carries the read/write head so that the head
can "fly" over the surface of the rigid disk while the disk is
spinning. The head is typically located on a head slider having an
aerodynamic design so that the head slider flies on an air bearing
generated by the spinning disk. The combination of the head slider
and the head suspension is referred to as a head suspension
assembly. The head suspension includes a load beam which has a
radius or spring section, a rigid region, and a flexure. The
flexure is a spring or gimballing connection typically included
between the head slider and the rigid section of the load beam so
that the head slider can move in the pitch and roll directions of
the head to accommodate fluctuations of the disk surface. The
mounting region of the load beam is typically attached to an
actuator arm which supports the suspension assembly over the
rotating disk. A base of the actuator arm is coupled to an
actuator.
When no external forces (with the exception of gravity) are acting
on the head suspension assembly to deform it in any way, it is in a
"neutral un-loaded" state. When the head is flying over the
spinning surface of a disk, and is acted upon only by the force of
the air bearing generated by the spinning disk, the head suspension
assembly is in a "neutral loaded" state. However, the head
suspension assembly can experience deformations that cause motion
of the head away from either the neutral loaded or neutral
un-loaded positions.
One way these deformations can occur involves a head suspension's
tendency to bend and twist in a number of different modes, known as
resonant frequencies, when driven back and forth at certain rates.
Any such bending or twisting of a suspension can cause the position
of the head to deviate from its neutral loaded or neutral un-loaded
position.
Common bending and twisting modes of suspensions are generally
known and discussed, for example, in the Yumura et al. U.S. Pat.
No. 5,339,208 and the Hatch et al. U.S. Pat. No. 5,471,734. Modes
which result in lateral or transverse motion (also known as
off-track motion) of the head slider are particularly detrimental
since this motion causes the head slider to move from the desired
track on the disk toward an adjacent track. The three primary modes
which produce this transverse motion are known as the sway, first
torsion, and second torsion modes. The sway mode is a lateral
bending mode in which the suspension bends in a transverse
direction along its entire length. The first and second torsion
modes are twisting modes during which the suspension twists about a
rotational axis which extends along the length of the
suspension.
Deformation of the suspension can also be caused by a
secondary-actuation or microactuation device designed to move the
head relative to the remainder of the head suspension assembly.
Such a microactuation device is disclosed in U.S. patent
application Ser. No. 08/457,432 filed Jun. 6, 1995 by Jurgenson et
al. for a Head Suspension with Tracking Microactuator now U.S. Pat.
No. 5,657,188.
Whether generated by motion during resonant modes, a secondary
actuation device, or other causes, it can be useful to monitor
motion of the head away from a neutral loaded or neutral un-loaded
position, that is, read/write head off-neutral motion. Information
about head off-neutral motion caused by undesirable resonant
vibrations can be used to actively damp such vibrations. Further,
monitoring of the displacement of the head caused by a first
actuator can be important to correct placement of the head by a
second actuator.
SUMMARY OF THE INVENTION
The present invention provides a means for detecting the
off-neutral motion of a head mounted on a head suspension assembly.
This information can be used to correct head off-neutral motion, if
necessary, so that read/write operations can be accomplished
relatively quickly and accurately. It can also be used to determine
the displacement of a magnetic head caused by a microactuation
device to allow accurate placement of the head by a primary
actuator. The head suspension assembly includes a load beam having
a proximal end, a distal end, a mounting region on the proximal
end, and a rigid region adjacent to the distal end. A flexure is at
the distal end of the load beam. A strain transducer circuit is
located on the head suspension assembly and detects strain in the
head suspension assembly. In one embodiment, the flexure includes a
head attachment region where the read/write head is attached.
Deformation of the head suspension assembly displaces the head
attachment region from a neutral position and subjects the head
suspension assembly to strain. The strain transducer circuit
detects the strain which allows detection of motion of the head
attachment region out of the neutral position.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an isometric view of a head suspension assembly including
a strain transducer circuit on a load beam in accordance with the
present invention.
FIG. 2a is an isometric view of the suspension assembly shown in
FIG. 1 undergoing twisting motion in the first torsion mode.
FIG. 2b is an isometric view of the suspension assembly shown in
FIG. 1 undergoing twisting motion in the second torsion mode.
FIG. 2c is an isometric view of the suspension assembly shown in
FIG. 1 undergoing bending motion in the sway mode.
FIG. 3 is a block diagram showing a system for detecting motion of
a head suspension assembly out of neutral position in accordance
with the present invention.
FIG. 4 is a side view of laminated sheet material from which the
head suspension shown in FIG. 1 can be fabricated.
FIG. 5 is a sectional view of the head suspension assembly shown in
FIG. 1 taken along line 5--5.
FIG. 6 is a sectional view of the head suspension assembly shown in
FIG. 1 taken along line 6--6.
FIG. 7 is an isometric view of a head suspension assembly including
first and second strain transducer circuits in accordance with a
second embodiment of the present invention.
FIG. 8 is an isometric view of a head suspension assembly including
an actuator arm and first and second strain transducer circuits in
accordance with a third embodiment of the present invention.
FIG. 9 is an isometric view of a head suspension assembly including
an actuator arm and first, second, third, and fourth strain
transducer circuits in accordance with a fourth embodiment of the
present invention.
FIG. 10 is a top view of a head suspension assembly including a
microactuation device and strain transducer circuit in accordance
with a fifth embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A head suspension assembly 8 which includes a strain transducer
circuit 10 in accordance with the present invention is illustrated
generally in FIG. 1. As shown, head suspension assembly 8 includes
a load beam 12 having a base or mounting region 14 on a proximal
end, a flexure 16 on a distal end, a relatively rigid region 17
adjacent to the flexure, and a radius or spring region 18 between
the base 14 and rigid region 17. The flexure 16 supports a head
slider (not shown) which is mounted on a head attachment region 13
and which "flies" on an air bearing created by a spinning magnetic
disk (not shown). The head slider supports a read/write head (not
shown) for transferring data to, and reading data from the spinning
magnetic disk. A base plate 20 is welded to base 14 for mounting
the load beam 12 to a disk drive actuator arm (not shown). Flexure
16 is a spring connection provided between a head slider and the
distal end of the load beam 12 which permits the head slider to
move in pitch and roll directions so that it can compensate for
fluctuations of the spinning disk surface above which the slider
flies. Many different types of flexure, also known as gimbals, are
known to provide the spring connection allowing for pitch and roll
movement of the head slider and can be used with the present
invention. First and second edge rails 23 and 24 are formed in
transversely opposite sides of the rigid region 17 of load beam 12.
Tab 26 which extends from base 14 is used to position and support
read/write head lead wires (not shown), transducer circuit lead
wires 28a and 28b, and electrical contacts 30.
The strain transducer circuit 10 is located in the transverse
center of load beam 12 and functions as a strain gauge. Strain
gauges are well known in the art and any suitable strain gauge is
contemplated to be used with the present invention. In the
embodiment of FIG. 1, individual transducer circuit lead 32 of
transducer circuit 10 is formed from a single electrical lead which
extends longitudinally back and forth in parallel sections
connected at ends of the sections. Other orientations and
configurations of circuit lead 32 are also within the ambit of the
present invention. For example the electrical lead can be
configured in a circular spiral or other non-parallel
configurations. FIG. 5 is a sectional view of load beam 12 taken
along line 5--5 and showing transducer circuit lead 32. Lead wires
28a and 28b are connected to opposite ends of circuit lead 32 to
form a continuous closed circuit between lead wires 28a and 28b.
FIG. 6 is a sectional view of load beam 12 taken along line 6--6
and showing lead wires 28a and 28b. Lead wires 28a and 28b are
connected to contacts 30 on tab 26.
Transducer circuit lead 32 is fabricated of a material in which the
electrical resistance varies with strain on the material. In the
embodiment of FIG. 1, circuit lead 32 is formed of Constantan, a
commercially available nickel-copper alloy. Transducer circuit lead
32 can also be formed of any other material in which electrical
resistance varies as the strain on the material varies.
When head suspension assembly 8 is acted upon by no external forces
it is in a neutral un-loaded position. When the head suspension
assembly 8 is acted on only by the force of the air bearing on
which the slider flies, the head suspension assembly is in a
neutral loaded (fly-height) position. Hereinafter, the term
"neutral" will be used to refer to either the neutral un-loaded
position or neutral loaded position. When the head suspension
assembly 8 is in a neutral position, it holds the read/write head
attachment region 13, and thereby the read/write head (not shown),
in a neutral position with respect to a base 14 of the load beam
12. However, head suspension assembly 8 can elastically deform out
of neutral position moving the head attachment region 13 out of
neutral position. This causes read/write head off-neutral
motion.
This kind of motion can occur as a result of motion in resonant
modes causing oscillatory excursions of a head suspension assembly
about its neutral position. As is discussed generally in the
Description of the Related Art section of this document, when in
operation, head suspension assemblies such as 8 bend and twist in a
number of different modes, known as resonant frequencies, when
driven back and forth at certain rates of speeds. FIG. 2a is an
illustration of suspension assembly 8 undergoing twisting motion in
what is known as the first torsion mode. FIG. 2b is an illustration
of suspension assembly 8 undergoing twisting motion in what is
known as the second torsion mode. In both the first and second
torsion modes the load beam 12 of suspension assembly 8 twists or
rotates about a central, longitudinally oriented rotational axis.
FIG. 2c is an illustration of suspension assembly 8 undergoing
bending motion in what is known as the sway mode. In the sway mode
the load beam 12 bends about an axis that is perpendicular to the
base of the load beam. Typically, the sway mode exhibits a slight
twisting motion as well.
Read/write head off-neutral motion can also be caused by a
microactuation device on a head suspension assembly, such as
microactuator 338 shown in FIG. 10, intentionally designed to move
a portion of the suspension assembly out of its neutral
position.
Generally, the greater the motion of a head suspension assembly out
of neutral position, the greater the strain thereon. Referring
again to FIG. 1, because transducer circuit 10 is mounted to head
suspension 8, strain in head suspension 8 causes strain in
transducer circuit lead 32 of transducer circuit 10, varying the
electrical resistance of transducer circuit 10. In this way, the
electrical resistance of transducer circuit 10 varies with motion
of the head attachment region 13 out of neutral position. This
variation in resistance can be converted into an electrical signal
using a wheatstone bridge or other methods known in the art, and
used to monitor motion of the head attachment region out of neutral
position, that is, read/write head off-neutral motion.
FIG. 3 shows a block diagram of a system to monitor read/write head
off-neutral motion using the transducer circuit 10 in accordance
with the present invention. A deformation of head suspension
assembly 8 causes read/write head off-neutral motion. Deformation
of head suspension assembly 8, as explained above, also causes
strain in transducer circuit lead 32 which changes the electrical
resistance of transducer circuit 10. The resistance of transducer
circuit 10 can be detected across contacts 30 and can then be
converted into a voltage by a resistance to voltage converter 17,
such as a wheatstone bridge or other well known means. The
converter 17 can then be electrically connected to a servo control
system 19. In this way, the servo control system 19 can be provided
with the head off-neutral motion information. If necessary, servo
control system 19 can then act to correct or minimize head
off-neutral motion through appropriate control of actuator system
21, which can include a primary and/or secondary or micro-actuator
which actuate head suspension 8. This would be desirable if, for
example, head off-neutral motion was caused by resonance vibrations
in head suspension assembly 8. Correction of head off-neutral
motion may not be desirable, however, if it is intentionally caused
by a micro-actuation device as shown in the embodiment shown in
FIG. 10. In such a case, monitoring head off-neutral motion can
still be important for correct placement of the load beam 12 by a
primary actuator.
It should be noted that converter 17 can be incorporated onto the
head suspension assembly itself by forming a wheatstone bridge on
the suspension assembly from four strain transducer circuits as
shown in FIG. 9.
The position at which transducer circuit 10 is located can be
determined on the basis of the specific types of deformations that
are desired to be monitored. As noted above, it is possible to use
the transducer circuit 10 to detect whether the head suspension
assembly 8 is undergoing motion in a resonant mode that could cause
off-track error and increase read/write function time. Different
resonant modes more severely strain different sections of the head
suspension assembly. For monitoring off-neutral head motion in a
resonant mode, it is desirable to locate the transducer circuit 10
at a location of relatively high strain for that particular
resonant mode.
The location on a head suspension assembly that a particular mode
strains more severely is dependent upon the design of the
particular suspension assembly. Which section of a given suspension
assembly is most strained for a given resonant mode (i.e. the
location of the nodes for that mode) is generally known, can be
determined empirically, or can be determined using methods of
computer modeled finite element analysis known in the art. The
transducer circuit can then be placed on the section of the
suspension assembly that experiences relatively high strain during
a condition of resonance in a chosen mode.
A method for manufacturing load beam 12 and transducer circuit 10
can be described with reference to FIGS. 4, 5 and 6. In the
embodiment of FIG. 1, all the features of load beam 12 with the
exception of the flexure 16 and baseplate 20 are manufactured from
a single sheet of laminated material 40 shown in FIG. 4. FIG. 5
shows a sectional view of load beam 12 taken along line 5--5. FIG.
6 shows a sectional view of load beam 12 taken along line 6--6.
Material 40 includes a lower layer 42 of stainless steel or other
resilient material; an intermediate layer 44 of polyimide or other
dielectric material overlaying the lower layer; and an upper layer
46 of Constantan or other material in which the resistance varies
in relation to strain. Using etching or otherwise known techniques,
blanks having the desired external dimensions of load beam 12 are
formed from the sheet of material 40. The lower layer 42 is
patterned and etched to form base 14, spring region 18, rigid
region 17, and first and second edge rails 23 and 24. Intermediate
layer 44 and upper layer 46 are then patterned and etched to form
transducer circuit lead 32, lead wires 28a and 28b, and contacts
30. First and second edge rails 23 and 24 are then formed in the
edges of load beam 17. In other embodiments (not shown), transducer
circuit 10 can be separately fabricated and bonded by adhesive or
other means to a conventional or otherwise manufactured load beam.
Also, additive processes, such as plating, sputtering, or vapor
deposition, or other processes known in the art may be used to form
the transducer circuit 10 on suspension 8.
FIG. 7 is an illustration of a suspension assembly including
another embodiment of the present invention. Elements in FIG. 7
which are functionally similar to those of FIG. 1 are labeled with
like numerals incremented by 100. As shown in FIG. 7, a head
suspension assembly 108 includes a load beam 112 having a base or
mounting region 114 on a proximal end, a flexure 116 on a distal
end, a relatively rigid region 117 adjacent to the flexure, and a
radius or spring region 118 between the base 114 and rigid region
117. Flexure 116 includes read/write head attachment region 113. An
open region 111 is formed in the transverse center of spring region
118 forming a pair of spring arms 119a and 119b. In the embodiment
of FIG. 7, strain transducer circuits 110a and 110b, which act as
strain gauges, are mounted on spring arms 119a and 119b,
respectively. Individual transducer circuit lead 132a of transducer
circuit 110a is a single connected lead that extends longitudinally
back and forth in parallel sections connected at ends of the
sections. Lead wires 128a connect transducer circuit 110a to
contacts 130a and lead wires 128b connect transducer circuit 110b
to contacts 130b. Tab 126 supports contacts 130a and 130b. Head
suspension assembly 108 can be manufactured in a manner similar to
that of head suspension assembly 8 shown in FIG. 1.
In the embodiment shown in FIG. 7, the transducer circuits 110a and
110b are placed in a position of relatively high strain for either
the first and second torsion modes or the sway mode.
FIG. 8 is an illustration of a head suspension assembly 208
including another embodiment of the present invention. In FIG. 8,
the head suspension assembly 208 includes an actuator arm 207 to
which the mounting region 14 of load beam 12 is attached. Actuator
arm 207 is connected at base 206 to a servo actuator (not shown)
and carries and positions load beam 12 above a spinning magnetic
disk (not shown). A strain transducer circuit 234 which acts as a
strain gauge is located on the actuator arm 207. In the embodiment
of FIG. 8, individual transducer circuit lead 242 of transducer
circuit 234 is a single connected lead which crosses longitudinally
back and forth in parallel sections connected at the ends of the
sections. As noted previously, other configurations of circuit lead
242 are also within the ambit of the present invention. Lead wires
236a and 236b connect to opposite ends of transducer circuit 234 to
form a closed circuit between lead wires 236a and 236b. Tab 238
supports electrical contacts 240.
In the embodiment shown in FIG. 8, transducer circuit 10, as
discussed above, detects deformation in load beam 12. Further,
deformation of actuator arm 207 can cause motion of head attachment
region 13 on flexure 16 out of a neutral position with respect to
base 206 of actuator arm 207. Transducer circuit 242 detects
deformation of actuator arm 207 and thereby detects read/write head
off-neutral motion with respect to base 206 caused by deformation
in actuator arm 207. The signals from transducer circuits 10 and
242 can be fed to a servo controller (not shown) to facilitate
correction or control of head off-neutral motion as necessary.
Actuator arm 207 can be manufactured from a sheet of laminated
material 40 as shown in FIG. 4 having a lower layer 42 of stainless
steel or other resilient material, an intermediate layer 44 of
polyimide or other dielectric, and an upper layer 46 of Constantan
or other material in which electrical resistance varies with
strain. Using etching or otherwise known techniques, blanks having
the desired external dimensions of actuator arm 207 are formed from
the sheet of material 40. The lower layer 42 is patterned and
etched to form base 206 and tab 238. Intermediate layer 44 and
upper layer 46 are then patterned and etched to form transducer
circuit lead 242, lead wires 236a and 236b, and contacts 240. In
other embodiments (not shown), transducer circuit 234 can be
separately fabricated and bonded by adhesive or other means to a
conventional or otherwise manufactured actuator arm. Load beam 12
can be mounted to actuator arm 207 by welding or other known means.
Also, additive processes, such as plating, sputtering, or vapor
deposition, or other processes known in the art may be used to form
the transducer circuit 234 on actuator arm 207.
FIG. 9 is an illustration of a suspension assembly showing another
embodiment of the present invention. Elements .[.if.]. .Iadd.in
.Iaddend.FIG. 9 which are functionally similar to those of FIG. 1
are shown with like numerals incremented by 400. As shown in FIG.
9, a head suspension assembly 408 includes a load beam 412 having a
base or mounting region 414 on a proximal end, a flexure 416 on a
distal end, a relatively rigid region 417 adjacent to the flexure,
and a radius or spring region 418 between the base 414 and rigid
region 417. Flexure 416 includes read/write head attachment region
413. An open region 411 is formed in the transverse center of
spring region 418 forming a pair of spring arms 419a and 419b. In
the embodiment of FIG. 9, first and second strain transducer
circuits 410a and 410c are mounted on spring arm 419a and third and
.[.forth.]. .Iadd.fourth .Iaddend.strain transducer circuits 410b
and 410d are mounted on spring arm 419b. Transducer circuits 410a,
410b, 410c and 410d are electrically connected together by
electrical lead 421 to form a wheatstone bridge circuit. This
wheatstone bridge circuit is then connected by electrical leads
428a, 428b, 428c, and 428d to electrical contacts 430a, 430b, 430c,
and 430d, respectively. In this way, read/write head off neutral
motion of suspension assembly 408 can be detected directly as a
voltage and the need for an external resistance to voltage
converter is obviated. Head suspension assembly 408 can be
manufactured in a manner similar to that of head suspension
assembly 8 shown in FIG. 1.
FIG. 10 is an illustration of a suspension assembly showing yet
another embodiment of the present invention. Elements in FIG. 10
which are functionally similar to those of FIG. 1 are shown with
like numerals incremented by 300. FIG. 10 shows a head suspension
assembly 308 including a load beam 312 having a base or mounting
region 314 on a proximal end, a T-type flexure 316 on a distal end,
a relatively rigid region 317 adjacent to the flexure, and a spring
region 318 between the base 314 and the rigid region 317.
Flexure 316 includes a mounting portion 327, a pair of spaced arms
329a and 329b which extend from the mounting portion 327, and a
cross member 331 which extends between the distal ends of arms 329a
and 329b. The arms 329a and 329b and cross member 331 form gap 333
through the distal end of flexure 316. A tongue 334 extends from
the cross member 331 into gap 333 toward load beam base 314. Cross
member 331 is offset from arms 329a and 329b so the plane of the
cross member 331 and tongue 334 are offset from the plane of the
arms 329a and 329b. Tongue 334 also includes a conventional load
point dimple 335. A slider (not shown) with a read/write head (not
shown) is adhesively bonded or otherwise mounted to tongue 334 to
form a head suspension assembly from suspension 308.
A microactuator 338 is positioned at the distal end of tongue 334
and is configured to move tongue 334 laterally between arms 329a
and 329b in response to tracking control signals. The details of
such a microactuator is disclosed in U.S. patent application Ser.
No. 08/457,432 filed Jun. 6, 1995 by Jurgenson et al. for a Head
Suspension with Tracking Microactuator. Any other suitable
microactuator is also contemplated to be used in conjunction with
the present invention. As microactuator 338 moves tongue 334, the
read/write head (not shown) is moved beneath load point dimple 335
to be placed above a correct information track in a spinning
magnetic disk (not shown).
As tongue 334 is moved between arms 329a and 329b the distal end of
tongue 334 elastically deforms and causes strain in tongue 334. A
strain transducer circuit 310 which acts as a strain gauge is
located at the distal end of tongue 334. Individual transducer
circuit lead 332 is configured to extend longitudinally back and
forth in parallel sections connected at ends of the sections. As
above, other configurations of circuit lead 332 are also within the
ambit of the present invention. Lead wires 328a and 328b connect to
opposite ends of transducer circuit 310 to form a continuous closed
circuit between lead wires 328a and 328b. Lead wires 328a and 328b
connect to contacts 330 on tab 326.
Deformation of the distal end of tongue 334 causes strain therein.
This strain causes strain in circuit lead 332 and increasing the
resistance of transducer circuit 310. The resistance of transducer
circuit 310 can be detected across contacts 330 and may be
converted into a voltage by a resistance to voltage transducer (not
shown) such as a wheatstone bridge or other known means. This
signal can then be provided to a servo controller (not shown) and
even fed back to microactuator 338 to monitor the position of the
read/write head over information tracks (not shown). Head
suspension assembly 308 can be manufactured in a manner similar to
that of head suspension assembly 8 shown in FIG. 1.
Though the present invention has been described with reference to
preferred embodiments, those skilled in the art will recognize that
changes can be made in form and detail without departing from the
spirit and scope of the invention.
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