Contour shape control of a universal joint assembly

Abstract

A suspension assembly has a load beam including a lower surface, a proximal end terminating at a hinge, a distal end, and a sag bend between the proximal and distal ends. A base plate includes a distal end connected to the hinge. A universal joint includes a base including a central strut, wherein the proximal end of the central strut is welded to the load beam at a location adjacent to the sag bend, and the distal end is welded to the distal end of the load beam. When the central strut is positioned in a neutral position, for any point along the central strut within a distance D of 0.5 mm from the sag bend, the gap G between the upper surface of the central strut and the plane defined by the lower surface of the load beam does not exceed 10 μm.

Description

Cross-references to related applications

[0001] This application claims the benefit and priority of U.S. Patent Application No. 18 / 972,546, filed December 6, 2024, which in turn claims the benefit and priority of U.S. Provisional Application No. 63 / 608,576, filed December 11, 2023, both of which are incorporated herein by reference in their entirety. Technical Field

[0002] This disclosure relates to hard disk drives, and more specifically to a suspension assembly for hard disk drives. Background Technology

[0003] A hard disk drive (HDD) is a non-volatile storage device that stores digitally encoded data on one or more circular disks with magnetic surfaces. During operation, each disk rotates rapidly. Data is read from and written to the disk using a read / write head positioned above a specific data track or location on the disk surface via a suspension assembly attached to an arm of a head stack assembly, which is rotated by a voice coil motor or actuator integrated into the head stack assembly. Maintaining the stability of the read / write head and aligning it with the target data track on the disk surface defines the primary function of the suspension assembly during HDD operation. Optimized suspension assembly design and manufacturing minimize the effects of mechanical, thermal, and other off-track interferences that can degrade HDD performance. The suspension assembly includes a load beam. During operation, an actuator positions the distal end of the load beam above the desired portion of the disk (e.g., one of the circular tracks on the disk surface). A gimbal assembly (also called a head gimbal assembly or flexure) is mounted to the distal end of the load beam. The gimbal assembly comprises components such as a slider containing a read / write head and PZT devices (piezoelectric devices) that rotate a portion of the gimbal assembly for fine positioning of the slider (as opposed to the coarser positioning of the slider by an actuator). Pressure caused by the air viscosity between the slider and the rotating disk causes the slider to levitate above (in close proximity to) the disk surface. While the load beam is relatively stiff, particularly on the lateral axis, the gimbal assembly is more flexible, allowing the slider to pitch and roll as it floats above the disk surface to maintain its operating distance close to the disk surface.

[0004] Dynamic load conditions within a hard disk drive, originating from rotating disks, actuator positioning, housing cooling fans, discrete impact loads, etc., can induce large vibrational responses in the drive and suspension assembly system. Resonance is the vibrational response in frequency and amplitude generated by external excitations input into the system. A mathematical transfer function can be created to correlate the load excitation conditions (or inputs) input into the system with a resonance or vibrational response (or output). This transfer function (called the forced resonance frequency function) visualizes the location and amplitude of multiple natural or modal frequencies, thus indicating high-energy conditions in the system represented by a set of wave-like structural motions called modes. The main modes of the suspension assembly system include load beam first bending, load beam first torsion, load beam second bending, load beam second torsion, and load beam sway, etc. These main modes are similarly represented by the gimbal assembly mode, which includes gimbal first torsion, gimbal second torsion, gimbal sway, etc. Suspension component design factors (such as material type, material thickness, component length, mass, rail geometry, spring stiffness, universal joint geometry, etc.) all play a role in determining the natural frequencies of the suspension components. Optimized suspension component design can minimize the resonant response amplitude at each modal frequency, or increase the resonant frequency, and support optimized system performance of hard drives.

[0005] Figure 1 A portion of the head stack assembly 1 is shown, while Figure 2-3 A head suspension assembly 2 is shown, comprising a load beam 4 terminating at its proximal end at a hinge 6 connected to a base plate 8. A head universal joint assembly 11, including a slider 14 with a read / write head and a universal joint 10, is mounted to the distal end of the load beam 4. The base plate 8 is connected to a head stack assembly 1. Figure 1 The actuator arm 12 is rotated by an integrated actuator (not shown). Figure 2 As best shown, the head gimbal assembly 11 includes a gimbal 10 composed of thin parts of laminated sheet metal (e.g., stainless steel) and polymer (e.g., polyimide), on which a slider 14 (e.g., by adhesive) is mounted. Circuitry 16 (i.e., electrical traces) extends along the load beam 4 and the head gimbal assembly 11 for electrical signal communication between the read / write head and the PZT.

[0006] Universal joint 10 can be attached to load beam 4 via three weld points 18, 20, and 22. These weld points can be spot welds between load beam 4 and universal joint 10. Two of these weld points 18 and 20 (referred to herein as proximal weld points) are located at the base 10a of universal joint 10 (closer to the proximal end of load beam 4). Universal joint 10 includes intermediate supports 24 and 26, wherein the proximal weld points are located at the proximal ends of intermediate supports 24 and 26 of universal joint 10. Intermediate supports 24 and 26 can be components of universal joint 10 whose proximal ends are welded to load beam 4 at weld points 18 and 20. The third weld point 22 (referred herein as distal weld point) is located at the distal end of universal joint 10 and the distal end of load beam 4. External supports 25 and 27 can be components of universal joint 10 located between intermediate supports 24 and 26 and the third weld point 22.

[0007] Universal joint 10 is configured to exhibit lower stiffness than load beam 4, allowing it to bend (particularly the intermediate struts 24, 26 and outer struts 25, 27), which allows slider 14 to float above the disk surface during operation. Universal joint 10 of universal joint assembly 11 preferably withstands stresses caused by large deformation during unavoidable high-impact events, particularly when the suspension is parked away from the disk during non-operational periods. Load beam 4 may include a sag bend 28, which is a bend or crease of several degrees in the middle portion of load beam 4 (i.e., near the proximal weld points 18, 20). The sag bend 28 can be created by clamping a portion of load beam 4 and pressing another portion upward to bend the load beam along a line (i.e., a bend or crease extending along a line perpendicular to the length of the load beam). The drooping bend is advantageous because it minimizes the second torsional resonance gain amplitude of the head suspension assembly 2. This is achieved by introducing a lateral bend across the width of the load beam 4, with the bend angle aligning the head slider transducer gap with the longitudinal centerline rotation axis of the load beam 4 of the head suspension assembly 2, thereby minimizing the second torsional resonance gain amplitude of the head suspension assembly 2.

[0008] Further improvements are needed in the configuration of the load beams and intermediate supports to enhance performance and reduce the overall thickness of the combined load beam and universal joint assembly. Summary of the Invention

[0009] The aforementioned problems and requirements are addressed by a suspension assembly comprising a load beam, a base plate, and a universal joint. The load beam includes a lower surface, a proximal end terminating at a hinge, a distal end, and a drooping bend (bend) located between the proximal and distal ends. The base plate includes a distal end connected to the hinge. The universal joint includes a base comprising a central strut, wherein the proximal end of the central strut is welded to the load beam adjacent to the drooping bend, and the distal end is welded to the distal end of the load beam. Wherein, when the central strut is positioned in a neutral position, for any point along a distance D within 0.5 mm from the drooping bend, the gap G between the upper surface of the central strut and the plane defined by the lower surface of the load beam does not exceed 10 μm.

[0010] Other objects and features of this disclosure will become apparent from reading the specification, claims and drawings. Attached Figure Description

[0011] Figure 1 This is a partial 3D view of a conventional magnetic head stack assembly.

[0012] Figure 2 This is a partial bottom view of a conventional magnetic head suspension assembly.

[0013] Figure 3 This is a side view of a conventional head suspension assembly.

[0014] Figure 4 This is a bottom view of a first example of a head suspension assembly attached to the actuator arm of the head stack assembly.

[0015] Figure 5 This is a partial bottom view of the first example of the load beam of the magnetic head suspension assembly.

[0016] Figure 6 This is a partial side view of the load beam and universal joint of the head suspension assembly, showing... Figure 1-3 The standard universal joint center support 24, 26 and Figure 4-5 A comparison diagram of the outline shapes of the universal joint intermediate support pillars 54 and 56.

[0017] Figure 7 This is a side view of the load beam of the head suspension assembly, showing the gap G between the intermediate strut and the load beam within a distance D of the drooping bend.

[0018] Figure 8 This is a bottom-view perspective view of a second example of the load beam of the magnetic head suspension assembly.

[0019] Figure 9 This is a top view of the third example of a head suspension assembly.

[0020] Figure 10This is a bottom view of the third example of a head suspension assembly.

[0021] Figure 11 This is a top view of the fourth example of a head suspension assembly.

[0022] Figure 12 This is a bottom view of the fourth example of the head suspension assembly. Detailed Implementation

[0023] It has been found that making the initial trajectory of the intermediate strut extending from the proximal weld point more closely follow the lower surface of the load beam provides improved resonant performance and a reduced total effective thickness of the load beam and universal joint assembly. Minimizing the spacing between the universal joint intermediate strut and the load beam along the vertical axis (i.e., towards the disk surface) results in a lower universal joint resonant mode gain amplitude. Minimizing the offset between the intermediate strut and the lower surface of the load beam over a certain longitudinal length in front of the drooping bend and similarly in front of the proximal weld point reduces the second universal joint torsional gain amplitude of the suspension assembly.

[0024] Specifically, it has been found that controlling the offset between the upper planar surface of the universal joint intermediate strut and the lower planar surface of the load beam along the vertical axis (i.e., towards the disk surface) to a value not exceeding 10 μm within a longitudinal length of 0.5 mm in front of the droop bend reduces the gain amplitude of the second torsional resonance mode of the universal joint in the suspension assembly. While there are benefits to placing the universal joint intermediate strut close to the load beam, the intermediate strut of the universal joint assembly still needs sufficient clearance from the lower surface of the load beam to minimize or prevent contact between the intermediate strut and the lower surface of the load beam at locations other than the proximal solder joint. Controlling the offset between the universal joint intermediate strut and the load beam can be achieved by clamping, shaping, adjusting, or any similar treatment of the head suspension assembly at or near the droop bend and proximal solder joint.

[0025] Furthermore, creating a gap between the proximal portion of the universal joint center strut and the plane of the load beam controls the offset between the universal joint center strut and the load beam by allowing the center strut to effectively pass through a large portion of the planar surface of the load beam along at least a portion of the universal joint center strut length after the sag bend, and also reduces the second torsional gain amplitude of the universal joint in the suspension assembly. The vertical, lateral, and longitudinal gaps between the universal joint center strut and the load beam can be created by patterning holes, voids, or through features in the load beam material to allow the center strut to maintain a minimum clearance or gap with the load beam, or even pass through the plane of the lower surface of the load beam. This measure of allowing the universal joint center strut to pass through the planar surface of the load beam effectively extends the length after the sag bend, in which the spacing between the universal joint center strut and the load beam on the vertical axis (i.e., towards the disk surface) is minimized.

[0026] Figure 4-5 A first example of a head suspension assembly 32 is shown. Similar to the head suspension assembly 2 discussed above, the head suspension assembly 32 includes a load beam 34, a hinge 36, a base plate 38, a universal joint 40 of a head universal joint assembly 41 attached to an actuator arm 42, and also includes a slider 44, circuitry 46, proximal solder points 48 and 50, distal solder points 52, intermediate struts 54 and 56, outer struts 55 and 57, and a drooping bend 58, generally configured as described above with respect to head suspension assembly 2. Furthermore, the lower surface 34a of the load beam 34 includes channels 60 and 62 that extend along and are aligned with the intermediate struts 54 and 56, respectively, such that the proximal portions of the intermediate struts 54 and 56 extending from the proximal solder points 48 and 50 are positioned above the channels 60 and 62, respectively. Channels 60 and 62 can be formed by subtractive etching of the lower surface 34a of the load beam 34 and extend from the region immediately adjacent to the side solder points 48 and 50 (the side solder points 48 and 50 are located between the drooping bend 58 and the starting point of the channel 60 and 62). Channels 60 and 62 provide additional clearance so that the proximal portions of the intermediate supports 54 and 56 can be effectively positioned adjacent to the lower surface 34a of the load beam 34 without contacting the lower surface of the load beam during operation (i.e., during operation, the proximal portions of the intermediate supports 54 and 56 can be at least partially deflected into the channels 60 and 62, but still do not contact the load beam 34). Furthermore, the proximal portions of the intermediate supports 54 and 56 can also be at least partially located in the channels 60 and 62 in a neutral position (i.e., an equilibrium position before any deflection caused by operation). Actuator 63 (e.g., a piezoelectric (PZT) actuator) may be included as part of head gimbal assembly 41 for fine positioning of slider 44 relative to load beam 34. Actuator 64 (e.g., a PZT actuator) may be included in an opening 66 formed in substrate 38 for deflecting the distal end of substrate 38 to achieve fine positioning of load beam 34 (and thus fine positioning of slider 44) in addition to positioning achieved by moving actuator arm 42.

[0027] Figure 6The advantages of utilizing channels 60, 62 in the lower surface 34a of the load beam 34 are illustrated. Line 34a represents the lower surface of the load beam 34, which includes a drooping bend 58. Lines 24 / 26 represent the side profile shape of conventional intermediate supports 24, 26 extending from the proximal solder point to the distal solder point, without benefiting from channels 60, 62. Specifically, without channels 60, 62, the proximal portions of intermediate supports 24, 26 are significantly deviated from the lower surface 34a of the load beam 34, such that the proximal portions of intermediate supports 24, 26 avoid contact with the lower surface 34a (which would adversely affect the bending and operation of the head gimbal assembly). Lines 54 / 56 represent the side profile of intermediate supports 54, 56 extending from the proximal solder points 48, 50 to the distal solder point 52, benefiting from channels 60, 62. Specifically, through channels 60 and 62, the proximal portions of the intermediate supports 54 and 56 can extend closer to the lower surface 34a of the load beam 34 and for a longer distance, while avoiding contact with the lower surface 34a. This results in the overall shape of the intermediate supports 54 and 56 being positioned closer to the load beam 34 in front of the slider 44. Specifically, this configuration allows the initial side profile trajectory of the proximal portions of the intermediate supports 54 and 56 extending from the proximal weld points 48 and 50 to be almost parallel to the load beam 34 and thus closer to the load beam 34 over a longer length extending from the drooping bend 58, without the risk of the intermediate supports 54 and 56 improperly contacting the load beam 34 during operation.

[0028] The inventors have discovered that this profile shape can reduce high-gain oscillating modes in the head gimbal assembly 41 that may be detrimental to its performance, thereby improving the resonant performance of the head suspension assembly 32. It has been determined that the improved performance by reducing high-gain oscillating modes is due to making the proximal portions of the intermediate struts 54, 56 extend more closely along the lower surface of the load beam 34 over a longer length extending from the drooping bend 58. Specifically, as... Figure 7 As shown, the inventors have discovered that when the universal joint 40 is in its neutral position (i.e., the equilibrium position before any deflection caused by operation), for any point along the intermediate supports 54, 56 within a distance D of 0.5 mm from the drooping bend 58, the gap G between the upper surface of the intermediate supports 54, 56 and the lower surface 34a of the load beam 34 (i.e., excluding the channel 62) does not exceed 10 μm, providing a beneficial profile shape that can reduce high-gain oscillation modes in the head universal joint assembly 41. The gap G within this distance D is... Figure 7 As shown in the image.

[0029] Channels 60 and 62 are provided in the lower surface 34a of the load beam 34, allowing the intermediate supports 54 and 56 to deflect more during operation without undesirable contact between the intermediate supports 54 and 56 and the load beam 34 during operation. Other advantages include reduced resonant performance variations, as intermittent contact conditions (where contact exists between some, but not all, portions of the load beam and intermediate supports due to normal process variations) are less likely to occur. Including channel 60 provides a smaller contact opportunity and still achieves the profile change benefit by keeping the intermediate supports 54 and 56 closer to the lower surface of the load beam. However, it should be understood that improved performance can also be achieved even without providing channels 60 and 62 by providing a gap G of no more than 10 μm for any point along the intermediate supports 54 and 56 within a distance D of 0.5 mm from the drooping bend 58. Therefore, channels 60 and 62 are optional. To accommodate the optional inclusion of channels 60, 62, the gap G at any point along the intermediate support is measured as the distance between the upper surface of the intermediate support 54, 56 at that point and the plane defined by the lower surface 34a of the load beam 34, such that for any given intermediate support configuration, whether or not channels 60, 62 are included, the gap G is the same.

[0030] Figure 8 Another example of load beam 34 is shown, which is similar to Figure 5 The example shown is the same, except that elongated openings 70, 72 replace channels 60, 62 extending into the lower surface 34a. These elongated openings 70, 72 are formed at the same location through the entire thickness of the load beam 34a, such that openings 70, 72 extend along and align with intermediate supports 54, 56 (i.e., intermediate supports 54, 56 are aligned with openings 70, 72). Openings 70, 72 also extend partially into guide rails 74, 76 (which extend perpendicularly from the edge of the load beam 34). Openings 70, 72 may extend into guide rails 74, 76 by a distance D, which is between 1 and 3 times the thickness T of the load beam 34. The openings 70 and 72 not only provide additional clearance to allow the intermediate supports 54 and 56 to deflect during operation without undesirable contact between them and the load beam 34, but they also provide passageways to the proximal portions of the intermediate supports 54 and 56 adjacent to the proximal weld points 48 and 50, allowing for mechanical and / or laser treatment of these proximal portions after they have been welded to the load beam 34. Specifically, the openings 70 and 72 provide passageways to the sides of the proximal portions of the intermediate supports 54 and 56 facing the load beam 34, enabling the profile of the intermediate supports 54 and 56 to be finely adjusted mechanically or by laser manipulation for better resonance performance.

[0031] Figure 9-10Another example of a suspension assembly 32 is shown, which includes most of the features described above, and additionally includes holes 80, 82 formed through the load beam 34 and tabs 84, 86 extending into the holes 80, 82, respectively. Holes 80, 82 are located adjacent to the drooping bend 58. Proximal weld points 48, 50 are located between the proximal ends of the universal joint 40 (i.e., the proximal ends of the intermediate struts 54, 56) and the tabs 84, 86. After the proximal ends of the intermediate struts 54, 56 have been welded to the tabs 84, 86, the tabs 84, 86 can be mechanically manipulated upwards or downwards by mechanical and / or laser processing, allowing the profile shape of the intermediate struts 54, 56 to be fine-tuned through mechanical manipulation of the tabs 84, 86 for better resonance performance. Proximity weld points 48, 50 on the tabs 84, 86 also reduce stress caused by any welding to the area of ​​the load beam 34 near the tabs 84, 86. Holes 80 and 82 with tabs 84 and 86 can, but do not necessarily, be connected to the holes mentioned above. Figure 4-6 The discussion focuses on channel 60 combinations.

[0032] Figure 11-12 Another example of a suspension assembly 32 is shown, which includes most of the features described above, and additionally includes holes 90, 92 formed through the load beam 34 and located proximal to the droop bend 58 (i.e., the droop bend 58 extends across or along the edges of the holes 90, 92). It has been found that forming the holes 90, 92 at the crease line of the droop bend 58 releases stress along the distal edges of the proximal weld points 48, 50, thereby making the profile shape of the intermediate struts 54, 56 more repeatable and allowing the intermediate struts 54, 56 to be positioned closer to the lower surface 34a of the load beam 34 over a longer distance extending proximally from the axis of the droop bend. The holes 90, 92 formed proximal to the droop bend 58 may, but do not necessarily, be aligned with the lower surface 34a of the load beam 34. Figure 4-10 Other example combinations.

[0033] It should be understood that this disclosure is not limited to the examples described above and shown herein, but covers any and all variations falling within the scope of any of the claims. For example, references to the invention, embodiments, or examples herein are not intended to limit the scope of any claim or claim terminology, but merely to refer to one or more features that may be covered by one or more claims. The examples of materials, processes, and numerical values ​​described above are merely exemplary and should not be construed as limiting the claims.

Claims

1. A suspension assembly comprising: A load-bearing beam, the load-bearing beam including a lower surface, a proximal end terminating at a hinge, a distal end, and a drooping bend between the proximal end and the distal end; A substrate, the substrate including a distal end connected to the hinge; as well as A universal joint, the universal joint comprising: The base includes an intermediate support column, wherein the proximal end of the intermediate support column is welded to the load-bearing beam at a location adjacent to the drooping bend. The distal end is welded to the distal end of the load-bearing beam. When the intermediate support is positioned in a neutral position, for any point along the intermediate support within a distance D of 0.5 mm from the drooping bend, the gap G between the upper surface of the intermediate support and the plane defined by the lower surface of the load beam does not exceed 10 μm.

2. The suspension assembly according to claim 1, further comprising: The slider is installed into the universal joint.

3. The suspension assembly according to claim 1, further comprising: Channels are formed in the lower surface of the load beam, wherein each channel extends along and is aligned with one of the intermediate supports.

4. The suspension assembly according to claim 1, further comprising: An opening is formed in the lower surface of the load beam, wherein each of the openings extends along and is aligned with one of the intermediate supports.

5. The suspension assembly according to claim 4, wherein: The load-bearing beam has a thickness T; The load beam includes guide rails extending from the edge of the load beam; and The opening extends into the guide rail by a distance D, which is between 1 and 3 times the thickness T of the load beam.

6. The suspension assembly according to claim 1, wherein, The load-bearing beam also includes: The hole formed near the drooping bend through the load beam; and A tab extending into the hole; The proximal end of the intermediate support is welded to the connector.

7. The suspension assembly according to claim 1, wherein, The load-bearing beam also includes: The drooping bend extends through the hole formed by the load beam adjacent to the drooping bend, wherein the drooping bend extends across the hole.

8. The suspension assembly according to claim 1, wherein, The load-bearing beam also includes: The drooping bend extends through a hole formed by the load beam adjacent to the drooping bend, wherein the drooping bend extends along the edge of the hole.

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