Patent Grant
9165578
1. Field of the Invention
The present invention relates to disk head assemblies for supporting read/write heads adjacent rotating disks in disk drives and more particularly, to a swage mount for attaching a head suspension assembly to a head actuator arm.
2. Description of Related Art
In hard disk drives, data are stored on surfaces of a plurality of rotatable disks mounted on a housing of the drive. Transducer heads that write data to and read data from the disk surfaces are supported by an actuator that positions the transducer heads in alignment with concentric data tracks defined on the disks. Each transducer head is attached to one end of a head suspension that is connected to an actuator arm that extends from the actuator body.
It has been common practice for hard disk drives to incorporate dual stage actuation swage mounts, for example, as shown in
Primary actuation may be performed, for example, using a voice coil motor. In addition, at least one of a secondary actuation near the swage mount 15 or a direct movement of the head near the flexure 25 may be performed.
Piezoelectric transducers (PZTs) 17 may be provided as secondary actuators that mechanically position the head in a planar direction in response to applied electrical charge. The PZTs 17 actuate the head to move or vibrate in the x-z plane (see for example, the x, y and z axes shown in
In another embodiment, the swage mount 12 of
The swage mount 31 has a uniform thickness along the surface that extends from the flange portion 37 to the ‘T’ shaped tip 33. As the flange portion 37 and the tip 33 become thinner for providing additional clearance between the swage mount 31 and the disk underneath, the tip 33 becomes more susceptible to bending and/or twisting. The thin tip 33 lacks sufficient robustness for withstanding out-of-plane loads during shipping, handling, or assembly. Manufacturers in the art have sought to employ greater care in shipping, handling, or assembly methods, but such methods are costly and often ineffective in avoiding out-of-plane loads that cause permanent deformation of the swage mount and result in costly yield loss. Because the swage mounts known in the art have inadequate out-of-plane robustness, some manufacturers provide the swage mounts on a fret (a flat sheet for delivery of swage mounts) to help protect them, as shown in
Beyond concerns involving shipping, handling, or assembly, the swage mounts known in the art suffer from poor drive performance. More particularly, the thin ‘T’ shaped tip 33 often has out-of-plane mechanical resonance modes that are too low in frequency and/or too high in amplitude, and has high displacements due to mechanical shock on the drive, resulting in poor drive performance.
There is a need in the art for a swage mount with higher manufacturing throughput and lower cost handling, shipping, and assembly in order to decrease the likelihood of permanent deformation of the swage mount or the tip. There is a need in the art for a swage mount that on the one hand, has a relatively thin flange body for providing sufficient clearance for the disk, and on the other hand, has a thicker tip with high out-of-plane yield robustness. Beyond shipping, handling, or assembly, it is critical for the tip to have favorable compliance in an in-plane direction (for example, along the x-z plane as shown in
A swage mount is provided for attaching a head suspension assembly to a head actuator arm. The swage mount has a relatively thin flange body for providing sufficient clearance from the disk positioned underneath the swage mount. The swage mount has a tip for in-plane actuation. The tip extends from the flange body, and has a thickness greater than the thickness of the flange body. The thicker tip can be directed toward the middle of the actuator arm so as not to reduce the flange to disk clearance. The tip has a first part proximal to the flange body, and a distal part that is narrower than its proximal part. For example, the tip may be ‘T’ shaped with the stem part starting from the proximal end and with the cross-bar part positioned at the distal part. The swage mount maintains favorable in-plane compliance for actuation of the tip, yet withstands out-of-plane loads due to the greater thickness of the tip.
In one embodiment, a swage mount is provided that includes a planar flange body having a first flange body part and a second flange body part. The second flange body part has four sides and a predetermined thickness greater than a predetermined thickness of the first flange body part. A hub surrounds an aperture in the first flange body part. A tip extends from a side of the second flange body part substantially in the plane of the flange body. The tip has a predetermined thickness that is substantially the same as the predetermined thickness of the second flange body part.
The exact nature of this invention, as well as the objects and advantages thereof, will become readily apparent from consideration of the following specification in conjunction with the accompanying drawings in which like reference numerals designate like parts throughout the figures thereof and wherein:
Out-of-plane robustness is critical for withstanding out-of-plane loads during shipping, handling, or assembly and furthermore for optimal performance of the hard disk drive. Unlike the swage mounts known in the art with a uniform thickness along the flange body and the tip, the tip of the present invention can withstand significantly higher out-of-plane loads such as twisting or bending due to its greater thickness. The swage mount of the present invention maintains favorable in-plane compliance for actuation of the tip, yet withstands out-of-plane loads. The robust swage mount of the present invention can be shipped, handled, or assembled individually with a lower cost.
Various merits for performance of the swage mount are analyzed for designing the thicknesses of the swage mount. Mass properties of the swage mount, the twisting/bending yield load, modal frequency responses, in-plane/actuation direction stiffness and other performance metrics may be analyzed to design a swage mount with a relatively thin flange body and a thicker tip.
Even beyond shipping, handling, or assembly, it is desirable for the ‘T’ shaped tip 49 to be stiff/robust in an out-of-plane direction for optimal performance of the hard disk drive. More particularly, it is desirable for the ‘T’ shaped tip 49 to have high in-plane compliance to allow the PZTs to freely bias in-plane movement of the ‘T’ shaped tip 49. This allows the PZTs to effectively direct the head during, for example, a reading/writing process on the hard disk.
The ‘T’ shaped tip 49 has a thickness t2 that is greater than t1 for enhancing out-of-plane robustness of the ‘T’ shaped tip 49. A thickness step 48 may separate the flange body 42 into a first flange body part 42A having thickness t1 and a second flange body part 42B having thickness t2. Although a thickness step 48 is shown in
It is desirable to provide additional clearance between the flange body 42 and the disk positioned underneath it by providing a relatively thin flange body 42. This prevents or reduces the likelihood of contact between the swage mount 42 and the disk surface during a mechanical shock event. In one embodiment, when the thicker tip swage mount is utilized, the clearance between the flange body 42 and the disk can be maintained or increased. The maintained or additional clearance may advantageously allow incorporation of a higher number of actuator arms and/or heads into the same hard disk drive height, or allow for a shorter overall drive height which is critical for certain low profile devices.
For example,
Referring back to
In one embodiment, the swage mounts 41 may be manufactured on a fret 51, as shown in
In another embodiment, the swage mounts of the present invention can be individually processed without use of frets. Individual processing reduces costs associated with delivery on a fret. Furthermore, individual processing improves drive reliability because it prevents problems associated with cutting burrs and particles resulting from removing parts from a fret frame during processing.
Referring to
The ‘T’ shaped tip 49 is capable of withstanding twisting forces 55 and bending forces 57. An objective of the design is to prevent the swage mount 41 from being permanently deformed when an out-of-plane prescribed load is applied. It is desirable for the swage mount 41 to withstand a high load, when twisted or bent, before the swage mount 41 yields to the twisting/bending loads. For example, data may be generated by controlling displacement of a 1 millimeter (mm) diameter load pin that exerts the force, and by recording the resulting load reactions at various displacements. The load at yield may be measured, for example, in Newtons, by determining the point at which the load-displacement curve becomes non-linear and/or by applying and removing loads of various levels and measuring permanent swage mount deformation.
Measured or numerically modeled peak Von Mises stress (MPa) can also be plotted as a function of load to determine at what load value the known yield stress of the material is exceeded such that the swage mount is permanently deformed. It is also desirable to have high out of plane stiffness to keep mechanical resonance frequencies high during drive operation. Twisting stiffness (Ktwist) and bending stiffness (Kbend) can be measured before yielding in units of N/mm (Newtons/millimeter).
Table 1 below lists merits of performance set forth above of four swage mounts with different dimensions. The descriptions refer to different profiles and geometries of the compared swage mounts.
For example, swage mount −02 is a swage mount known in the art having a uniform thickness of 0.150 mm over the flange body 42 and the tip 43. This model was modified, according to an embodiment of the present invention, to increase the thickness of the tip 43 for improving out-of-plane robustness. w1 and w2 may also be altered to maintain or improve in-plane compliance of the tip 43.
For example, the twist yield load, the bending yield load, Ktwist, and Kbend all improve significantly when t1 is maintained to be as thin as the standard model (−02) and t2 is increased to 0.175 mm, as shown in model −001. Depending on the PZT performance and stroke requirements, the minor decrease in compliance in this range may prove beneficial for robustness.
As the standard model −02 is further altered to have a tip 49 with thickness t2 increased to 0.188 mm, the twist yield load, the bending yield load, Ktwist, and Kbend all improve significantly (as shown in model −015) even to a greater extent than −001.
Because compliance may decrease when thickness t2 and mass is increased without changing other parameters, w1 and w2 may be altered to compensate for the added mass and thickness. For example, w1 and w2 may be reduced to 0.750 mm and 0.450 mm, respectively, as shown in model −016−0.15w. This allows the compliance to improve significantly by 47%. The bending yield load, Ktwist, and Kbend improve as well with the foregoing modification.
As set forth above with respect to FIGS. 7 and 13-15 and Table 1, performance metrics may be defined, and t1 and t2 may be modified to achieve desirable out-of-plane robustness. w1 and w2 may be further modified to compensate for the added thickness of t2 to achieve desirable in-plane compliance and out-of-plane robustness.
In one embodiment, the following dimensions provided unexpected and superior performance results as defined by the foregoing performance metrics (including favorable out-of-plane robustness and in-plane compliance): 0.025 mm≦t1≦0.250 mm, 0.075 mm≦t2≦0.305, 0.20 mm≦w1≦5.0 mm, and 0.15 mm≦w2≦4.5. In one embodiment, t2 is designed to be at least 1.1 times greater than t1.
In addition to the metrics described above with respect to FIGS. 7 and 13-15 and Table 1, the natural frequencies and amplitudes of swage mount modes shapes that result in off-track head motion can be analyzed to further modify the dimensions of the swage mount. For example, the flange body thickness t1, the tip thickness t2 and/or the tip width portions w1 and w2 can be modified to move these frequencies higher or to lower the amplitudes of these modes.
Another design consideration for defining dimensions of the swage mount and the ‘T’ shaped tip 49 is related to mass properties. Referring back to
On the one hand, the thinner flange body (with thickness t1) results in lower mass, thereby providing more swage mount to disk clearance and improved performance. For example, the lower mass would decrease the seek time to get to the appropriate track. On the other hand, the out-of-plane robustness of the ‘T’ shaped tip 49 is not sacrificed because of the t2 thickness remains the same.
In sum, a swage mount is provided for attaching a head suspension assembly to a head actuator arm. The swage mount has a relatively thin flange body for providing sufficient clearance from the disk positioned underneath the swage mount. The tip extends from the flange body, and has a thickness greater than the thickness of the flange body.
Unlike the swage mounts known in the art that have a uniform thickness along the flange body and the tip, the tip of the present invention can withstand significantly higher out-of-plane loads such as twisting or bending due to its greater thickness. The swage mount of the present invention maintains favorable in-plane compliance for actuation of the tip, yet withstands out-of-plane loads. The robust swage mount of the present invention can be shipped, handled, or assembled individually with a lower cost.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5097584 | Cain et al. | Mar 1992 | A |
| 5142770 | Cain et al. | Sep 1992 | A |
| 5591277 | Braunheim | Jan 1997 | A |
| 5689389 | Braunheim | Nov 1997 | A |
| 5696653 | Lacey | Dec 1997 | A |
| 5796555 | Aoyagi et al. | Aug 1998 | A |
| 5844675 | Hayes et al. | Dec 1998 | A |
| 5948997 | Schmidt | Sep 1999 | A |
| 6183841 | Hanrahan et al. | Feb 2001 | B1 |
| 6231698 | Braunheim et al. | May 2001 | B1 |
| 6351349 | Braunheim et al. | Feb 2002 | B1 |
| 6417994 | Yim et al. | Jul 2002 | B1 |
| 7304824 | Brink et al. | Dec 2007 | B2 |
| 7324307 | Brink et al. | Jan 2008 | B2 |
| 8116038 | Zhang et al. | Feb 2012 | B1 |
| 8142638 | Brink et al. | Mar 2012 | B2 |
| 20020075605 | Nishida et al. | Jun 2002 | A1 |
| 20030202293 | Nakamura et al. | Oct 2003 | A1 |
| 20050128643 | Wobbe et al. | Jun 2005 | A1 |
| 20050152068 | Erpelding | Jul 2005 | A1 |
| 20060227463 | Wright et al. | Oct 2006 | A1 |
| 20090147406 | Otake et al. | Jun 2009 | A1 |
| 20090262463 | Yokota et al. | Oct 2009 | A1 |
| 20100208390 | Hanya et al. | Aug 2010 | A1 |
| 20110141625 | Fuchino | Jun 2011 | A1 |
| 20120087047 | Imuta | Apr 2012 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20150255095 A1 | Sep 2015 | US |
