JP-2026076105-A - Shortening the bearing span by increasing the coil thickness to improve the structural dynamics of actuators in hard disk drives.

Abstract

[Problem] To improve non-repetitive runout (NRRO) associated with the structural dynamics and operating vibrations of the system. [Solution] A data storage device such as a hard disk drive (HDD) includes a rotary pivot bearing assembly of a rotary actuator configured with a bearing span smaller than the maximum available bearing span, thereby reducing the rotary pivot tilt (PT) gain of the corresponding acoustic transfer function relative to the rotational pivot tilt (PT) gain of the original acoustic transfer function corresponding to the maximum available bearing span. To counteract the resulting decrease in coil twist and rotational pivot tilt frequency, the voice coil is thickened vertically to increase the coil twist (CT) frequency and rotational pivot tilt frequency, bringing them closer to their values in the original acoustic transfer function. Combining a relatively short bearing span with a relatively thick voice coil ensures and improves performance by maintaining relatively high CT and PT frequencies while guaranteeing a relatively low PT gain. [Selection Diagram] None

Inventors

• シッデシュ ヴィベク サカルカール
• アルマン ブイ．ゴルゴラブ
• 江口 一
• 進藤 仁
• ダニエル グエン

Assignees

• ウェスタン デジタル テクノロジーズ インコーポレーテッド

Dates

Publication Date

20260511

Application Date

20250702

Priority Date

20241023

Claims (20)

1. A data storage device, A disk medium rotatably mounted on a spindle, A head slider equipped with a read-write head configured to write to and read from the disk media, A rotary actuator configured to move the head slider around a rotary pivot, the rotary pivot comprising: a rotary actuator having a rotary pivot bearing and accessing a portion of the disk medium via operation by a voice coil motor assembly (VCMA); and an enclosure having a cover coupled to a base, A data storage device in which the rotating pivot bearing is configured with a bearing span smaller than the maximum available bearing span, based on the vertical distance between the base and the cover.
2. The data storage device according to claim 1, wherein the bearing span is configured to reduce the second rotational pivot tilt gain of a second corresponding acoustic transfer function, defined as the off-track displacement of the head slider due to unit sound pressure excitation applied to the enclosure, with respect to the first rotational pivot tilt gain of a first corresponding acoustic transfer function corresponding to the maximum available bearing span.
3. The data storage device according to claim 1, wherein the bearing span is within the range of 5 mm or more and 13 mm or less.
4. The data storage device according to claim 1, wherein the bearing span is configured to reduce the second rotational pivot tilt gain of a second corresponding acoustic transfer function, defined as the off-track displacement of the head slider due to a unit sound pressure excitation on the enclosure, with respect to the first rotational pivot tilt gain of a first corresponding acoustic transfer function corresponding to the maximum usable bearing span and the first vertical thickness of the voice coil of the VCMA, and the second acoustic transfer function is configured to further correspond to the second vertical thickness of the voice coil, wherein the second vertical thickness is greater than the first vertical thickness of the voice coil, and increases the second coil torsion frequency of the second acoustic transfer function to near the first coil torsion frequency of the first acoustic transfer function.
5. The data storage device according to claim 4, wherein the second vertical thickness is configured to increase the second rotational pivot tilt frequency of the second acoustic transfer function to near the first rotational pivot tilt frequency of the first acoustic transfer function.
6. The data storage device according to claim 5, wherein the second vertical thickness of the voice coil is within the range of 3.4 mm or more and 4.0 mm or less.
7. The data storage device according to claim 6, wherein the bearing span is within the range of 5 mm or more and 13 mm or less.
8. The data storage device according to claim 5, wherein the bearing span is within the range of 5 mm or more and 13 mm or less.
9. The bearing span is configured to reduce the second rotational pivot tilt gain of a second corresponding acoustic transfer function, defined as the off-track displacement of the head slider due to a unit sound pressure excitation applied to the enclosure, with respect to the first rotational pivot tilt gain of a first corresponding acoustic transfer function corresponding to the maximum usable bearing span and the first vertical thickness of the voice coil of the VCMA. The bearing span is configured to individually reduce the second coil torsion frequency of the second acoustic transfer function with respect to the first coil torsion frequency of the first acoustic transfer function, The bearing span is configured to individually reduce the second rotational pivot tilt frequency of the second acoustic transfer function with respect to the first rotational pivot tilt frequency of the first acoustic transfer function, The second acoustic transfer function corresponds to the second vertical thickness of the voice coil, and the second vertical thickness is greater than the first vertical thickness of the voice coil. The data storage device according to claim 1, wherein the second vertical thickness is configured to individually increase the second coil torsion frequency of the second acoustic transfer function to a position closer to the first coil torsion frequency of the first acoustic transfer function than the coil torsion frequency of the bearing span, and the second vertical thickness is configured to individually increase the second rotational pivot tilt frequency of the second acoustic transfer function to a position closer to the first rotational pivot tilt frequency of the first acoustic transfer function than the rotational pivot tilt frequency of the bearing span.
10. The data storage device according to claim 1, wherein the data storage device is configured as a hard disk drive with a thickness of substantially one inch from the base to the cover, and comprises ten or more disk media.
11. A data storage device, A rotary actuator configured to move a read-write transducer around a rotary pivot, the rotary pivot comprising: a rotary actuator having a rotary pivot bearing and accessing a portion of a disk medium via actuation by a voice coil motor assembly (VCMA); and an enclosure having a cover coupled to a base, The rotational pivot bearing is configured with a bearing span smaller than the maximum usable bearing span based on the vertical distance between the base and the cover, and reduces the second rotational pivot tilt gain of the second corresponding acoustic transfer function with respect to the first rotational pivot tilt gain of the first corresponding acoustic transfer function corresponding to the maximum usable bearing span and the first vertical thickness of the voice coil of the VCMA, and the second acoustic transfer function further corresponds to the second vertical thickness of the voice coil, wherein the second vertical thickness is configured to be greater than the first vertical thickness of the voice coil. A data storage device in which the second coil torsion frequency of the second acoustic transfer function is increased to a value close to the first coil torsion frequency of the first acoustic transfer function, and the second rotational pivot tilt frequency of the second acoustic transfer function is increased to a value close to the first rotational pivot tilt frequency of the first acoustic transfer function.
12. The data storage device according to claim 11, wherein the bearing span is within the range of 5 millimeters or more and 13 millimeters or less.
13. The data storage device according to claim 11, wherein the second vertical thickness of the voice coil is within the range of 3.4 mm or more and 4.0 mm or less.
14. The data storage device according to claim 13, wherein the bearing span is within the range of 5 millimeters or more and 13 millimeters or less.
15. The data storage device according to claim 11, wherein the data storage device is configured as a hard disk drive substantially one inch thick in the direction from the base to the cover, and further comprises ten or more disk media.
16. It is a hard disk drive (HDD), A disk medium rotatably mounted on a spindle, A means for reading from and writing to one of the aforementioned disk media, A rotary actuator configured to move the reading and writing means around a rotary pivot, wherein the rotary pivot includes a rotary pivot bearing that accesses a portion of the disk medium via an actuation by a voice coil motor assembly (VCMA), A hard disk drive (HDD) comprising an enclosure with a cover coupled to a base, and means for reducing the second rotational pivot tilt gain of a second corresponding acoustic transfer function with respect to the first rotational pivot tilt gain of a first corresponding acoustic transfer function corresponding to the maximum usable bearing span.
17. The first acoustic transfer function further corresponds to the first voice coil of the VCMA, and the second acoustic transfer function further corresponds to the second voice coil of the VCMA. The HDD according to claim 16, further comprising means for increasing the second coil torsion frequency of the second acoustic transfer function to near the first coil torsion frequency of the first acoustic transfer function.
18. The HDD according to claim 17, further comprising means for increasing the second rotational pivot tilt frequency of the second acoustic transfer function to near the first rotational pivot tilt frequency of the first acoustic transfer function.
19. The first acoustic transfer function further corresponds to the first voice coil of the VCMA, and the second acoustic transfer function further corresponds to the second voice coil of the VCMA. The HDD according to claim 16, further comprising means for increasing the second rotational pivot tilt frequency of the second acoustic transfer function to near the first rotational pivot tilt frequency of the first acoustic transfer function.
20. The disk media comprises 10 or more disk media, The HDD according to claim 16, wherein the HDD has a substantially 1-inch thickness between the base and the cover.

Description

Embodiments of the present invention generally relate to data storage devices such as hard disk drives, and more particularly to approaches for improving the structural dynamics of actuator assemblies within hard disk drives. 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, housed in a protective enclosure. When the HDD is operating, each magnetic recording disk is rapidly rotated by a spindle system. Data is read from and written to the magnetic recording disk using a read-write transducer (or read-write "head") positioned on a specific location on the disk by an actuator. The read-write head uses a magnetic field to write data to the surface of the magnetic recording disk and read data from this surface. The write head functions by generating a magnetic field using an electric current flowing through its coils. Electrical pulses are sent to the write head with different patterns of positive and negative currents. The current in the write head's coils generates a localized magnetic field across the gap between the head and the magnetic disk, which then magnetizes a small area on the recording medium. An HDD typically includes at least one head gimbal assembly (HGA) containing a slider and suspension that house the read-write heads. Each slider is mounted to the free end of the suspension, which is then cantilevered from the rigid arms of the actuators. Several actuator arms may be combined to form a single movable unit, typically a head stack assembly (HSA) with a rotary pivot bearing system. Conventional HDD suspensions typically include a relatively rigid load beam with a mounting plate at its base end, the mounting plate being mounted to the actuator arms, and its free end mounting a flexure that supports the slider and its read-write heads. As the number and capabilities of networked computing systems increase, more data storage system capacity is required. Cloud computing and large-scale data processing further increase the need for digital data storage systems capable of transferring and holding large amounts of data. For this purpose, increasing the storage capacity of HDDs is one of the ongoing goals in the evolution of HDD technology. In one form, this goal manifests as increasing the number of disks and read-write heads within a given HDD. In modern HDDs, operational vibration (also called "customer box vibration") is one of the most important factors in track misalignment (TMR), which generally refers to the variation in the deviation of the track-following/servo head from its intended position, i.e., the deviation of the read-write head from the center of the data track. The main causes of operational vibration are (a) acoustic excitation caused by air pressure fluctuations from the cooling fan, and (b) structurally transmitted external vibrations. Any approach described in this section is a possible approach, but not necessarily a previously conceived or pursued method. Therefore, unless otherwise indicated, none of the approaches described in this section should be assumed to be eligible as prior art simply by their inclusion in this section. Embodiments are shown in the accompanying drawings as examples, not as limitations, and similar reference numerals refer to similar elements. This is a plan view showing a hard disk drive (HDD) according to one embodiment. This is a cross-sectional side view showing the HDD rotational pivot bearing assembly. This is a side view showing the HDD voice coil actuator assembly. Figure 2B is a top view showing the HDD voice coil actuator assembly. This is a cross-sectional side view showing a shortened span HDD rotational pivot bearing assembly according to one embodiment. This figure shows the acoustic transfer function of the head stack assembly (HSA) corresponding to the HDD rotational pivot bearing assembly in Figure 2A. This figure shows the HSA acoustic transfer function corresponding to the shortened span HDD rotational pivot bearing assembly shown in Figure 3, according to one embodiment. This is a side view showing an increased-thickness voice coil of an HDD voice coil actuator assembly according to one embodiment. This is a top view showing the increased-thickness voice coil of the HDD voice coil actuator assembly of Figure 5A, according to one embodiment. Figures 2B and 2C show the HSA acoustic transfer function corresponding to the HDD voice coil actuator assembly. This figure shows the HSA acoustic transfer function corresponding to the increased-thickness voice coil in Figures 5A to 5B, according to one embodiment. This figure shows the HSA frequency response function corresponding to the operating vibration of the HDD rotational pivot bearing assembly in Figure 2A and the HDD voice coil actuator assemblies in Figures 2B to 2C. This figure shows the HSA frequency response function corresponding to the operating vibration of the shortened span HDD rota