|Publication number||USRE40975 E1|
|Application number||US 11/452,076|
|Publication date||Nov 17, 2009|
|Filing date||Jun 9, 2006|
|Priority date||May 23, 1996|
|Also published as||US5862015|
|Publication number||11452076, 452076, US RE40975 E1, US RE40975E1, US-E1-RE40975, USRE40975 E1, USRE40975E1|
|Inventors||Robert B. Evans, Todd A. Krinke|
|Original Assignee||Hutchinson Technology Incorporated|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (8), Non-Patent Citations (3), Referenced by (17), Classifications (10), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims the benefit of U.S. Provisional application Ser. No. 60/018,167, filed May 23, 1996 abandoned.
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.
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.
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
Transducer circuit lead 32 is fabricated of a material in which the electrical resistance varies with strain on the material. In the embodiment of
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.
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
Generally, the greater the motion of a head suspension assembly out of neutral position, the greater the strain thereon. Referring again to
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
In the embodiment shown in
In the embodiment shown in
Actuator arm 207 can be manufactured from a sheet of laminated material 40 as shown in
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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|US7813083 *||Jan 17, 2007||Oct 12, 2010||Maxtor Corporation||Disk drive load arm structure having a strain sensor and method of its fabrication|
|US8941951||Nov 27, 2013||Jan 27, 2015||Hutchinson Technology Incorporated||Head suspension flexure with integrated strain sensor and sputtered traces|
|US9001469||Mar 14, 2013||Apr 7, 2015||Hutchinson Technology Incorporated||Mid-loadbeam dual stage actuated (DSA) disk drive head suspension|
|US9007726||May 5, 2014||Apr 14, 2015||Hutchinson Technology Incorporated||Disk drive suspension assembly having a partially flangeless load point dimple|
|US9123371||Oct 10, 2013||Sep 1, 2015||Seagate Technology Llc||Methods and devices for head-media contact detection|
|US9147413||Nov 24, 2014||Sep 29, 2015||Hutchinson Technology Incorporated||Balanced co-located gimbal-based dual stage actuation disk drive suspensions|
|US9240203||Aug 25, 2014||Jan 19, 2016||Hutchinson Technology Incorporated||Co-located gimbal-based dual stage actuation disk drive suspensions with dampers|
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|US9431042||Oct 17, 2014||Aug 30, 2016||Hutchinson Technology Incorporated||Balanced multi-trace transmission in a hard disk drive flexure|
|US9524739||Jul 15, 2014||Dec 20, 2016||Hutchinson Technology Incorporated||Disk drive suspension assembly having a partially flangeless load point dimple|
|US9558771||May 22, 2015||Jan 31, 2017||Hutchinson Technology Incorporated||Piezoelectric disk drive suspension motors having plated stiffeners|
|US9564154||Mar 16, 2016||Feb 7, 2017||Hutchinson Technology Incorporated||Multilayer disk drive motors having out-of-plane bending|
|US9613644||Nov 4, 2014||Apr 4, 2017||Hutchinson Technology Incorporated||Two-motor co-located gimbal-based dual stage actuation disk drive suspensions with motor stiffeners|
|US9646638||May 13, 2016||May 9, 2017||Hutchinson Technology Incorporated||Co-located gimbal-based DSA disk drive suspension with traces routed around slider pad|
|US9715890||Jan 4, 2017||Jul 25, 2017||Hutchinson Technology Incorporated||Piezoelectric disk drive suspension motors having plated stiffeners|
|US9734852||Jun 22, 2016||Aug 15, 2017||Hutchinson Technology Incorporated||Disk drive head suspension structures having improved gold-dielectric joint reliability|
|US20070178746 *||Jan 17, 2007||Aug 2, 2007||Seagate Technology Llc||Disk drive load arm structure having a strain sensor and method of its fabrication|
|U.S. Classification||360/244.1, 360/78.05, 360/77.03, 360/75|
|International Classification||G11B21/21, G11B5/48, G11B21/02, G11B5/596|
|Apr 27, 2010||CC||Certificate of correction|
|Jul 19, 2010||FPAY||Fee payment|
Year of fee payment: 12
|Sep 30, 2013||AS||Assignment|
Owner name: HILLERICH & BRADSBY CO., KENTUCKY
Free format text: REASSINMENT AND RELEASE OF SECURITY INTEREST-PATENTS;ASSIGNOR:PNC BANK, NATIONAL ASSOCIATION;REEL/FRAME:031709/0923
Effective date: 20130809