Disc drive suspension assembly with PZT actuator having active and inactive regions

Abstract

The suspension assembly includes a load beam terminated by a hinge, a gimbal assembly attached to the load beam, and a base plate connected to the hinge and including an opening. The PZT actuator is positioned within the opening and includes first and second opposing ends. The PZT actuator includes an active region and an inactive region both extending between the first and second opposing ends, PZT material positioned in both the active region and the inactive region, and first and second electrodes configured to cause active expansion and contraction of the PZT material in the active region in response to a voltage difference applied to the first and second electrodes, and not to cause active expansion and contraction of the PZT material in the inactive region in response to a voltage difference applied to the first and second electrodes of the PZT actuator.

Description

[Technical Field]

[0001] The present disclosure generally relates to a suspension for supporting a read / write head on a recording medium. In particular, the present disclosure relates to a head suspension assembly having an actuator attached to a base plate. [Background Art]

[0002] A storage device such as a magnetic disk drive storage device ("disk drive") stores data on and reads data from a rotating disk medium using a read / write head disposed on a surface of the rotating disk medium. A suspension assembly is used to position the read / write head over concentric tracks of the rotating disk medium. As an example, as shown in FIG. 1, the suspension assembly 2 may include a load beam 4 having a gimbal assembly 6 (including a read / write head) attached near the distal end of the load beam 4, and the gimbal assembly 6 allows the read / write head to fly in close proximity over the surface of the rotating disk medium during operation. The proximal end of the load beam 4 terminates at a hinge 8 connected to a base plate 10. The base plate 10 is connected to an actuator arm 12, which is connected to an actuator motor (not shown) that rotates the actuator arm, thereby moving the entire suspension assembly 2 relative to the rotating disk medium. During operation, the actuator motor is used to position the read / write head over a desired concentric track of the rotating disk to write data to or read data from the desired concentric track.

[0003] As disk drive manufacturers continue to develop drives that are smaller but have higher storage capacity, the density of concentric tracks on the disk increases, becoming narrower and more closely spaced. However, as track density increases, it becomes increasingly difficult for the actuator motor to quickly and accurately position the read / write head on the desired concentric track. Therefore, it is known to use a pair of piezoelectric (PZT) actuators 14 and 16 mounted on an opening in a base plate 10, as shown in Figure 2. Conventional PZT actuators are fabricated from a material that expands in all directions in a plane when a forward voltage difference is applied (i.e., a voltage that is positive at the second terminal of the actuator or to ground is applied to the first terminal of the actuator) and contracts when a reverse voltage difference is applied (i.e., a voltage that is negative at the second terminal or to ground is applied to the first terminal). Thus, a pair of PZT actuators expand and contract in response to drive voltage signals of opposite polarity. For example, a forward voltage difference applied to the PZT actuator 14 causes it to expand, and a reverse voltage difference applied to the PZT actuator 16 causes it to contract. These two forces together bend the distal portion of the base plate 10, causing the load beam 4 to rotate clockwise (around the distal end of the base plate 10) to fine-tune the read / write head position. To bend the base plate 10 and rotate the load beam 4 counterclockwise (around the distal end of the base plate 10), a reverse voltage difference is applied to the PZT actuator 14 (contracting the PZT), while a forward voltage difference is applied to the PZT actuator 16 (expanding the PZT). Therefore, by complementing the coarse positioning of the actuator motor with the precise positioning of the PZT actuator, a higher track positioning resolution can be achieved.

[0004] While using a pair of PZT actuators can provide better positioning resolution, it has been found that driving a pair of PZT actuators to rotate the load beam around a rotation axis at the distal end of the base plate can induce undesirable arm sway modes, which are high-frequency deflections within the actuator arms. For example, driving a pair of conventional PZT actuators with the configuration shown in Figure 2 has been shown to excite arm sway modes at approximately 10.3 kHz, as shown in the graph of the actuator arm frequency response function in Figure 3.

[0005] A more stable suspension assembly design is needed to control the precise positioning of the read / write head without exciting undesirable arm sway modes. [Overview of the Initiative]

[0006] The aforementioned problems and needs are addressed by a suspension assembly comprising a load beam including a proximal end terminating at a hinge, a gimbal assembly attached to the load beam, a base plate connected to the hinge and having a distal end including a first opening, and a first PZT actuator including first and second opposing ends positioned within the first opening and attached to the first and second opposing ends of the first opening. The first PZT actuator includes an active region extending between first and second opposing ends of the first PZT actuator, an inactive region extending between first and second opposing ends of the first PZT actuator, a PZT material disposed in the active and inactive regions of the first PZT actuator, and a first electrode and a second electrode configured to cause active expansion and contraction of the PZT material in the active region of the first PZT actuator in response to a voltage difference applied to the first electrode and the second electrode of the first PZT actuator, and not to cause active expansion and contraction of the PZT material in the inactive region of the first PZT actuator in response to a voltage difference applied to the first electrode and the second electrode of the first PZT actuator. [Brief explanation of the drawing]

[0007] [Figure 1] This is a perspective view of a conventional suspension assembly. [Figure 2] This is a top view of a conventional suspension assembly. [Figure 3] This graph shows the actuator arm frequency response function of a conventional suspension assembly. [Figure 4] This is a top view of the suspension assembly according to the first embodiment. [Figure 5] This is a top view of a suspension assembly according to the first embodiment. [Figure 6A] This is a top view of the PZT actuator. [Figure 6B]Figure 6A is a side cross-sectional view of the PZT actuator. [Figure 6C] Figure 6A is another side cross-sectional view of the PZT actuator. [Figure 7A] This is a top view of a suspension assembly according to a first embodiment, showing the counterclockwise rotation of the load beam. [Figure 7B] This is a top view of a suspension assembly according to a first embodiment, showing the clockwise rotation of the load beam. [Figure 8] This graph shows the actuator arm frequency response functions for both a conventional suspension assembly and a suspension assembly according to the first embodiment. [Figure 9A] This is a top view of the PZT actuator. [Figure 9B] Figure 9A is a side cross-sectional view of the PZT actuator. [Figure 9C] Figure 9A is a side cross-sectional view of the PZT actuator. [Figure 10] This is a top view of a suspension assembly according to a second embodiment. [Figure 11A] This is a top view of a suspension assembly according to a second embodiment, showing the counterclockwise rotation of the load beam. [Figure 11B] This is a top view of a suspension assembly according to a second embodiment, showing the clockwise rotation of the load beam. [Modes for carrying out the invention]

[0008] This disclosure relates to a disk drive suspension assembly comprising an actuator having an active region and an inactive region to provide fine control over the positioning of a read / write head. A suspension assembly 20 is shown in Figure 4. A gimbal assembly 22 (including the read / write head) is mounted near the distal end of a load beam 24. The proximal end of the load beam 24 terminates with a hinge 26 connected to the distal end of a base plate 28. The proximal end of the base plate 28 is connected to an actuator arm (not shown), which is connected to an actuator motor (not shown) used to move the suspension assembly 20 to position the read / write head of the gimbal assembly 22 on a desired concentric track on the surface of a rotating disk (not shown).

[0009] As shown in Figures 4 and 5, the distal end of the base plate 28 includes an opening 30 to which a PZT actuator 32 is mounted. Each PZT actuator 32 has opposing ends 32a and 32b, which are attached to the opposing ends 30a and 30b of the respective opening 30 by, for example, adhesive 34. Each PZT actuator 32 has an active region 32c and an inactive region 32d. As best shown in Figures 5, 6A, 6B, and 6C, the active region 32c is the portion of the PZT actuator 32 that extends between the opposing ends 32a and 32b and actively expands and contracts in response to a voltage applied to the first and second electrodes 38 / 40 of the PZT actuator 32. Specifically, the PZT material layer 42 is positioned mostly or entirely between the first electrode 38 and the second electrode 40 in the active region 32c such that the voltage difference applied between the first electrode 38 and the second electrode 40 causes the portion of the PZT material layer 42 between the first electrode 38 and the second electrode 40 to expand and contract. The inactive region 32d is the portion of the PZT actuator 32 that extends between the opposing ends 32a and 32b where the PZT material layer 42 is not positioned between the first electrode 38 and the second electrode 40, and therefore does not actively expand and contract in response to the voltage difference applied between the first electrode 38 and the second electrode 40. The inactive region 32d is a dead zone by design that does not actively expand and contract in response to the voltage applied to the first and second electrodes 38 and 40. In one example, the active region 32c may be the part of the PZT actuator 32 closest to the center of the base plate 28, and the inactive region 32d may be the part of the PZT actuator 32 furthest from the center of the base plate 28. In one example, the inactive region 32d may be approximately 30% of the total area of ​​the PZT actuator 32.

[0010] Figures 7A and 7B show the expansion and contraction of a PZT actuator 32 for deflecting the load beam 24 in a counterclockwise direction. One of the two PZT actuators may be referred to as the first PZT actuator 32-1, located within one of the two openings, which may be referred to as the first opening 30. The other PZT actuator may be referred to as the second PZT actuator 32-2, located within the other of the two openings, which may be referred to as the second opening 30. During operation, the active region 32c may be actively expanded by applying a voltage difference to the first and second electrodes 38, 40 of the PZT actuator 32-1. The inert region 32d of the PZT actuator 32-1, which does not actively expand in response to the applied voltage difference, bends the active region 32c of the PZT actuator 32-1 toward the inert region 32d of the PZT actuator 32-1 in approximately the same plane as the base plate 28 as the active region 32c of the PZT actuator 32-1 actively expands. Any expansion and bending of the inert region 32d of the PZT actuator 32-1 is passively induced by the expansion and bending of the active region 32c of the PZT actuator 32-1. At the same time, the active region 32c is contracted by applying a voltage difference to the first and second electrodes 38, 40 of the PZT actuator 32-2. The inert region 32d of the PZT actuator 32-2, which does not actively contract in response to the applied voltage difference, bends the active region 32c of the PZT actuator 32-2 toward the inert region 32d of the PZT actuator 32-1 in approximately the same plane as the base plate 28 as the active region 32c of the PZT actuator 32-2 actively contracts. Any contraction and bending of the inert region 32d of the PZT actuator 32-2 is passively induced by the contraction and bending of the active region 32c of the PZT actuator 32-2.

[0011] As shown in Figures 7A and 7B, the direction of bending of both PZT actuators 32-1 and 32-2 is the same, even when one actuator is expanding and the other is contracting. The amount of bending of the PZT actuators can be increased by attaching only the outer portion of the distal end 32b of the PZT actuator 32 to the corresponding distal end 30b of the opening 30 with adhesive 34, while attaching the entire proximal end 32a of each PZT actuator 32 to the corresponding proximal end 30a of the opening 30 with adhesive 34. The expansion and contraction of the PZT actuators 32-1 and 32-2 bend the distal portion of the base plate 10 so that the load beam 24 rotates counterclockwise around a center of rotation located along the load beam 24, as shown in Figure 7A, or clockwise around a center of rotation located along the load beam 24, as shown in Figure 7B.

[0012] The bending of the PZT actuators 32-1 and 32-2, due to the lateral movement caused by the bending of the PZT actuators, which involves expansion and contraction of the PZT actuators 32-1 and 32-2, moves the center of rotation of the load beam 24 further away from the base plate 28 compared to when there is no bending. This displacement of the center of rotation away from the base plate 28 results in a reduction of the arm sway gain around 10 kHz, as shown in Figure 8, which compares the conventional suspension assembly design in Figure 2 with the suspension assembly designs in Figures 4 and 5, and shows actuator arm vibration.

[0013] Figures 9A to 9C show another example in which the PZT actuator 32 includes multiple layers of PZT material 42. The illustrated example includes three layers of PZT material 42 (i.e., an intermediate layer below the top layer and above the bottom layer), but more or fewer layers of PZT material 42 may be used. In this example, the first electrode 38 has a first portion positioned above the top layer of PZT material 42 and a second portion positioned between the intermediate and bottom layers of PZT material 42. The second electrode 40 has a first portion positioned between the top and intermediate layers of PZT material 42 and a second portion positioned below the bottom layer of PZT material 42. In the active region 32c, each layer of PZT material 42 has a portion of one electrode extending along the top surface and a portion of the other electrode extending along the bottom surface. In contrast, the inert region 32d lacks the first and second electrodes 38 and 40 (i.e., no portion of the first and second electrodes 38 / 40 is located within the inert region 32d).

[0014] Figure 10 shows another example of the suspension assembly 20, which is the same as the example of the suspension assembly 20 shown in Figure 4, except that the opening 30 is completely enclosed by the base plate 28 (compared to the example shown in Figure 4, where the opening 30 is not completely enclosed by the base plate 28). Figures 11A and 11B show the expansion and contraction of the active regions 32c of the PZT actuators 32-1 and 32-2, respectively, and the expansion and contraction of the active regions 32c rotate the load beam 24 counterclockwise as shown in Figure 11A or clockwise as shown in Figure 11B by bending the distal portion of the load beam 24.

[0015] It should be understood that this disclosure is not limited to the embodiments described above and illustrated herein, but encompasses any and all modifications within the scope of any claim. For example, in the PZT actuator of Figures 6A–6C, the inert region 32d lacks both the first and second electrodes 38 / 40 so that no active expansion / contraction occurs in the PZT material 42 between them when a voltage difference is applied to the first and second electrodes 38 / 40, but the inert region 32d may include the other of the first and second electrodes 38 / 40, insofar as one of the first and second electrodes 38 / 40 is lacking, so that no active expansion / contraction occurs in the inert region 32d when a voltage difference is applied to the first and second electrodes 38 / 40. References to this disclosure or inventions or embodiments herein are not intended to limit any claim or the scope of the terminology of any claim, but rather to refer to one or more features that may be covered by one or more claims. The materials, processes, and numerical examples described above are illustrative and should not be considered to limit the scope of the claims.

Claims

1. A suspension assembly, A load beam including a proximal end terminated by a hinge, A gimbal assembly attached to the aforementioned road beam, A base plate connected to the hinge and having a distal end including a first opening, The first PZT actuator is disposed within the first opening and includes first and second opposing ends attached to the first and second opposing ends of the first opening, wherein the first PZT actuator is The active region extending between the first and second opposing ends of the first PZT actuator, An inert region extending between the first and second opposing ends of the first PZT actuator, A PZT material disposed in the active region and the inactive region of the first PZT actuator, A suspension assembly comprising: a first electrode and a second electrode, configured to cause active expansion and contraction of the PZT material in the active region of the first PZT actuator in response to a voltage difference applied to the first electrode and the second electrode of the first PZT actuator, and configured not to cause active expansion and contraction of the PZT material in the inactive region of the first PZT actuator in response to a voltage difference applied to the first electrode and the second electrode of the first PZT actuator.

2. The second opening having the distal end of the base plate, The system comprises a second PZT actuator, which is positioned within the second opening and includes first and second opposing ends attached to the first and second opposing ends of the second opening, wherein the second PZT actuator is The active region of the second PZT actuator extends between the first and second opposing ends, The inert region extending between the first and second opposing ends of the second PZT actuator, A PZT material disposed in the active region and the inactive region of the second PZT actuator, The suspension assembly according to claim 1, comprising: a first electrode and a second electrode, configured to cause active expansion and contraction of the PZT material in the active region of the second PZT actuator in response to a voltage difference applied to the first electrode and the second electrode of the second PZT actuator, and configured not to cause active expansion and contraction of the PZT material in the inactive region of the second PZT actuator in response to a voltage difference applied to the first electrode and the second electrode of the second PZT actuator.

3. The inert region of the first PZT actuator lacks the first electrode and the second electrode of the first PZT actuator. The suspension assembly according to claim 2, wherein the inert region of the second PZT actuator lacks the first electrode and the second electrode of the second PZT actuator.

4. The inert region of the first PZT actuator lacks at least one of the first electrode and the second electrode of the first PZT actuator. The suspension assembly according to claim 2, wherein the inert region of the second PZT actuator lacks at least one of the first electrode and the second electrode of the second PZT actuator.

5. The first opening is completely enclosed by the base plate. The suspension assembly according to claim 2, wherein the second opening is completely enclosed by the base plate.

6. The first opening is not completely enclosed by the base plate. The suspension assembly according to claim 2, wherein the second opening is not completely enclosed by the base plate.

7. For each of the first and second PZT actuators, The PZT material within the active region is placed between the first electrode and the second electrode. The suspension assembly according to claim 2, wherein the PZT material in the inert region is not located between the first electrode and the second electrode.

8. Each of the first and second PZT actuators is: The intermediate layer of the PZT material, The uppermost layer of the PZT material is disposed on the intermediate layer of the PZT material, The PZT material comprises the bottom layer of the PZT material, which is disposed below the intermediate layer of the PZT material, In the active region, the first electrode has a first portion disposed on the uppermost layer of the PZT material and a second portion disposed between the intermediate layer of the PZT material and the lowermost layer of the PZT material. The suspension assembly according to claim 2, wherein in the active region, the second electrode has a first portion disposed between the uppermost layer of the PZT material and the intermediate layer of the PZT material, and a second portion disposed below the lowermost layer of the PZT material.

9. For each of the first and second PZT actuators, None of the portions of the first electrode are located within the inert region. The suspension assembly according to claim 8, wherein none of the portions of the second electrode are located within the inert region.

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