Multilayer actuator electrode configuration for improved resonance

Abstract

To provide a multi-layer actuator configuration to reduce out-of-plane motion and obtain good performance characteristics.SOLUTION: A multi-layer microactuator (PZT) 14 includes first to third active piezoelectric layers 131 to 133. The first active piezoelectric layer has a top surface and a bottom surface. The second active piezoelectric layer has a top surface and a bottom surface on the top surface of the first active piezoelectric layer. The third active piezoelectric layer has a top surface and a bottom surface on the top surface of the second active piezoelectric layer. The first and second active piezoelectric layers define a first effective electrode length 131D, and similarly the second and third active piezoelectric layers define a second effective electrode length 131D that is longer than the first effective electrode length.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate to the field of suspension devices for disk drives. More particularly, the present disclosure relates to the field of multi-layer actuator configurations for suspension devices. [Background technology]

[0002] A typical disk drive unit includes a rotating magnetic disk containing a pattern of ones and zeros on a magnetic storage medium. This pattern of ones and zeros on the magnetic storage medium constitutes the data stored on the disk drive. The magnetic disk is driven by a drive motor. The disk drive unit also includes a disk drive suspension with a magnetic read / write head mounted proximate to the tip of a load beam. The "base" end of the suspension or load beam is the supported end, i.e., the end closest to the base plate that is swaged or otherwise attached to the actuator arm. The "tip" end of the suspension or load beam is the end opposite the base end, i.e., the "tip" end is the cantilevered end.

[0003] The suspension is connected to an actuator arm, which is connected to a voice coil motor. The voice coil motor moves the suspension in an arc to position the head slider over the correct data track on the data disk. The head slider is mounted on a gimbal, allowing the slider to pitch and roll to follow the appropriate data track on the disk, while providing tolerance to variations such as disk vibrations, inertial events such as bumping, and irregularities in the disk's surface.

[0004] Both single stage actuation disk drive suspensions and dual stage actuation (DSA) suspensions are known, in which only the voice coil motor moves the suspension.

[0005] In a DSA suspension, a small actuator on the suspension moves the head slider to position it over the correct data track. The actuator positions the head slider more precisely than a voice coil motor can and provides higher servo bandwidth than a voice coil motor can. The actuators can be located in various locations on the suspension, depending on the specific DSA suspension design. Typically, the left and right actuators act in a push-pull fashion, rotating the load beam or the tip of the load beam. Summary of the Invention

[0006] A piezoelectric actuator assembly is described. The piezoelectric actuator assembly includes first, second, and third active piezoelectric layers. The first layer includes a top surface and a bottom surface. The second layer includes a top surface and a bottom surface disposed on the top surface of the first layer. The third layer includes a top surface and a bottom surface disposed on the top surface of the second layer. The first and second layers can define a first effective electrode length. Similarly, the second and third layers can define a second effective electrode length configured to be longer than the first effective electrode length.

[0007] In some embodiments, a first electrode is disposed on at least a portion of a bottom surface of the first single active piezoelectric layer, a second electrode is disposed between at least a portion of the first single active piezoelectric layer and the second single active piezoelectric layer, and a common length of the first electrode and the second electrode defines a first effective electrode length.

[0008] In some embodiments, a third electrode is disposed between at least a portion of the second layer and the third layer, a fourth electrode is disposed on at least a portion of a top surface of the third layer, and a common length of the third electrode and the fourth electrode defines a second effective electrode length.

[0009] In some embodiments, the second effective electrode length is 0.02 mm longer than the first effective electrode length. In some embodiments, the first effective electrode length is 0.59 mm. In some embodiments, the second effective electrode length is 0.61 mm.

[0010] A suspension is described. The suspension includes a flexure attached to a load beam, an electrical circuit attached to the flexure, and a multilayer piezoelectric microactuator PZT connected to the electrical circuit. The multilayer piezoelectric microactuator PZT includes first, second, and third active piezoelectric layers. The first layer includes a top surface and a bottom surface. The second layer includes a top surface and a bottom surface disposed on the top surface of the first layer. The third layer includes a top surface and a bottom surface disposed on the top surface of the second layer. The first and second layers can define a first effective electrode length. Similarly, the second and third layers can define a second effective electrode length configured to be longer than the first effective electrode length (e.g., 0.01 mm to 0.05 mm longer).

[0011] The above summary is not intended to represent each embodiment or every aspect of the present disclosure. Rather, the foregoing summary provides only an example of some of the novel aspects and features described herein. The above features and advantages, as well as other features and advantages of the present disclosure, will be readily apparent from the following detailed description of exemplary embodiments and modes for carrying out the invention when taken in conjunction with the accompanying drawings and appended claims.

[0012] To describe how the advantages and features of the present disclosure are obtained, embodiments of the present disclosure will be described with reference to specific examples illustrated in the accompanying drawings. These drawings depict only exemplary aspects of embodiments of the present disclosure and are therefore not to be considered limiting of its scope. Principles will be described and explained with additional specificity and detail through the use of the following drawings. [Brief explanation of the drawings]

[0013] [Figure 1] 1A and 1B show microactuators undergoing deformation. [Figure 2A] 2A and 2B illustrate torsion-related modes of the suspension with the microactuator of FIG. 1. [Figure 2B] 2 illustrates the load beam torsional mode and the gimbal flexure torsional mode of the suspension with the microactuator of FIG. 1. [Figure 3] FIG. 1 illustrates a suspension with an actuator according to one embodiment of the present disclosure. [Figure 4] 1 is a cross-sectional view of a multi-layer piezoelectric microactuator (PZT) according to one embodiment of the present disclosure. [Figure 5] 1 is a graphical representation of the vertical profile of a multi-layer PZT according to one embodiment of the present disclosure under 1 volt actuation. [Figure 6] 1 is a graphical representation of the resonant frequency (FRF) of a multi-layer PZT according to one embodiment of the present disclosure under 1 volt actuation. [Figure 7] Graphical representation of the resonant frequency (FRF) of a known multilayer PZT under 1 volt actuation. DETAILED DESCRIPTION OF THE INVENTION

[0014] Embodiments of the present disclosure will be described with reference to the accompanying drawings, in which like reference numerals are used throughout to indicate like or equivalent elements. The drawings are not drawn to scale and are provided as an illustrative illustration. Some aspects of the embodiments are described below with reference to exemplary applications, which are not intended to limit the scope of the disclosure. It will be understood that numerous specific details, relationships, and methods are described to provide a thorough understanding of the embodiments.

[0015] Embodiments described herein are directed to a multi-layer microactuator that overcomes problems associated with current microactuators, for example, the left and right microactuators act in a push-pull manner to rotate the load beam or the tip of the load beam, and both microactuators bend vertically.

[0016] 1 shows the deformation of microactuators 110 and 120. Microactuator 110 is pushed out and bends convexly, while microactuator 120 is pulled back and bends concavely. Such puddling out-of-plane motion can easily excite torsion-related modes of the entire suspension, such as the load beam torsion mode and the gimbal flexure torsion mode.

[0017] FIG. 2A shows the torsion-related modes of the entire suspension 2. FIG. 2B shows the load beam and gimbal flexure torsion modes of the entire suspension 2. Excitation of these torsion modes can cause lateral motion of the head slider, resulting in off-track issues for read / write operations. For example, the resonant frequency (FRF) of a conventional multilayer PZT has a high T1FX mode (gimbal flexure torsion mode) peak of ~3 dB at 11 kHz with a z-ht variation of ±0.2 mm, as shown in supplemental FIG. 3. Such a low-frequency peak requires a drive servo design to place a notch filter at the T1FX mode frequency, which in turn affects the drive servo bandwidth. The present disclosure provides a multilayer actuator configuration to reduce this out-of-plane motion, enabling better performance characteristics for current multilayer actuators.

[0018] However, those skilled in the art will readily recognize that the present invention can be practiced without one or more of the specific details or with other methods. In other instances, well-known structures or operations have not been shown in detail to avoid obscuring the embodiments. Embodiments of the present disclosure are not limited by the depicted order of acts or events, as some acts may occur in different orders and / or concurrently with other acts or events. Furthermore, not all depicted acts or events are required to implement a methodology in accordance with the present invention.

[0019] FIG. 3 illustrates a suspension 10 including an actuator according to one embodiment of the present disclosure. Suspension embodiments include, but are not limited to, dual-stage actuation (DSA) suspensions, triple-stage actuation suspensions, and other configurations of actuators in suspensions. The suspension 10 includes a flexure 20 attached to a load beam 12. The flexure 20 further includes an electrical circuit 22 including copper contact pads 24. The DSA suspension 10 further includes two multilayer piezoelectric microactuators (PZTs) 14 attached near the gimbal. The copper contact pads 24 are configured to carry drive voltages to the multilayer PZTs 14. The suspension 10 further includes a grounded copper contact pad 28 for each multilayer PZT 14.

[0020] The gimbal allows the slider to pitch and roll to follow the appropriate data track on the disk, providing tolerance for variations such as disk vibration, inertial events such as bumping, and irregularities in the disk's surface. The multilayer PZT 14 acts directly on the gimbal through a flexible connector. Such a suspension is sometimes called a gimbaled DSA suspension, or simply a GSA suspension. A GSA suspension is a type of DSA suspension. Other configurations of the multilayer PZT 14 can be used to actuate the suspension, including, but not limited to, a three-stage actuation suspension. Under a drive voltage, one multilayer PZT 14 expands and the other contracts, causing the gimbal to rotate around a dimple on the load beam to position the head-slider write / read head over the rotating disk. The multilayer PZT 14 in Figure 3 is annotated by cross section A-A' and is described in more detail below with reference to Figure 4.

[0021] FIG. 4 illustrates a cross-sectional view (A-A') of a multilayer microactuator (PZT) 14 according to an embodiment of the present disclosure. While electrostatic microactuators and other types of microactuator motors have been proposed and used, piezoelectric elements are often used as microactuator motors. A commonly used piezoelectric material is lead zirconate titanate (PZT), although other piezoelectric materials are also used and known. In the following disclosure, for simplicity, piezoelectric devices that are microactuators may be referred to simply as "PZT" as a shorthand, and it is recognized that the piezoelectric material need not be lead zirconate titanate. Thus, as used herein, the term "PZT" may refer to any piezoelectric material or any piezoelectric device formed from any piezoelectric material.

[0022] It is understood that the multilayer PZT 114 can be arranged in a suspension having a configuration other than that shown in FIG. 3 . The multilayer PZT 114 can include a first electrode 131A disposed on at least a portion of the bottom surface of the first PZT layer 131. The second electrode 132A can be disposed between at least a portion of the first PZT layer 131 and the second PZT layer 132. The third electrode 133A can be disposed between at least a portion of the second PZT layer 132 and the third PZT layer 133. Finally, the fourth electrode 134A can be disposed on at least a portion of the top surface of the third PZT layer 133. The common length of the first electrode 131A and the second electrode 132A can define an effective electrode length 131D. Furthermore, the common length of the third electrode 133A and the fourth electrode 134A can define an effective electrode length 133D.

[0023] The effective electrode length 131D of the first PZT layer 131 can be 0.59 mm. It is understood that, in some embodiments, the electrode length can be configured to have any desired length. The effective electrode length 133D of the third PZT layer 133 can be increased between 0 mm and 0.05 mm, according to some embodiments. In this case, the effective electrode length 133D of the third PZT layer 133 can be increased by 0.02 mm to 0.61 mm. In this case, the electrode dead zone 133C decreases as the effective electrode length 133D of the third PZT layer 133 increases. Thus, the described embodiments are configured to reduce the gain of the T1FX mode in the z-ht transition by reducing the bending of the multilayer PZT 114 when an actuation voltage is applied.

[0024] Figure 5 is a graphical representation of the vertical profile of a multilayer PZT according to embodiments described herein under 1 volt actuation. As shown in Figure 5, a shorter electrode dead zone 133C reduces the bending of the PZT at the hinge end by approximately 12.5%. For example, the resonant frequency (FRF) of the multilayer PZT in T1FX mode is reduced by ∼2 dB over a z-ht change of + / −0.20 mm when compared to current multilayer microactuators. The improved T1FX gain in the low frequency range also benefits the drive servo bandwidth.

[0025] Figure 6 shows the FRF of a multilayer PZT according to embodiments described herein under 1 volt actuation. Figure 7 shows the FRF of a known multilayer PZT under 1 volt actuation. Compared to the known multilayer PZT, the T1FX peak at a z-ht variation of + / - 0.20 mm is reduced to less than 1 dB. As a result, a high servo bandwidth can be achieved without the need for a notch filter to be located in this low frequency range.

[0026] The present disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments and designs described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. 1. A piezoelectric actuator assembly comprising: a first single active piezoelectric layer having a top surface and a bottom surface; a second single active piezoelectric layer having a top surface and a bottom surface disposed on the top surface of the first single active piezoelectric layer; a third single active piezoelectric layer having a top surface and a bottom surface disposed on the top surface of the second single active piezoelectric layer; a first electrode disposed on at least a portion of the bottom surface of the first single active piezoelectric layer and enveloping a first side surface of the first single active piezoelectric layer on a fixed end side; a second electrode disposed between at least a portion of the first single active piezoelectric layer and the second single active piezoelectric layer, disposed on at least a portion of the bottom surface of the first single active piezoelectric layer, and enveloping a second side surface of the first single active piezoelectric layer on a hinge end side; the first single active piezoelectric layer and the second single active piezoelectric layer have a first effective electrode length, and the first effective electrode length is defined by a common length portion of the first electrode and the second electrode; a second effective electrode length of the second single active piezoelectric layer and the third single active piezoelectric layer is configured to be longer than the first effective electrode length; a third electrode disposed between at least a portion of the second single active piezoelectric layer and the third single active piezoelectric layer; a fourth electrode disposed on at least a portion of a top surface of the third single active piezoelectric layer; a common length of the third electrode and the fourth electrode defines the second effective electrode length.

2. The piezoelectric actuator assembly of claim 1 , wherein the second effective electrode length is 0.02 mm longer than the first effective electrode length.

3. The piezoelectric actuator assembly of claim 1 , wherein the first effective electrode length is 0.59 mm.

4. 2. The piezoelectric actuator assembly according to claim 1, wherein the second effective electrode length is 0.01 mm to 0.05 mm longer than the first effective electrode length.

5. A suspension, a flexure attached to the load beam; an electrical circuit attached to the flexure; a piezoelectric actuator assembly connected to the electrical circuit, the piezoelectric actuator assembly comprising: a first single active piezoelectric layer having a top surface and a bottom surface; a second single active piezoelectric layer having a top surface and a bottom surface disposed on the top surface of the first single active piezoelectric layer; a third single active piezoelectric layer having a top surface and a bottom surface disposed on the top surface of the second single active piezoelectric layer; a first electrode disposed on at least a portion of the bottom surface of the first single active piezoelectric layer and enveloping a first side surface of the first single active piezoelectric layer on a fixed end side; a second electrode disposed between at least a portion of the first single active piezoelectric layer and the second single active piezoelectric layer, disposed on at least a portion of the bottom surface of the first single active piezoelectric layer, and enveloping a second side surface of the first single active piezoelectric layer on a hinge end side; the first single active piezoelectric layer and the second single active piezoelectric layer have a first effective electrode length, and the first effective electrode length is defined by a common length portion of the first electrode and the second electrode; a second effective electrode length of the second single active piezoelectric layer and the third single active piezoelectric layer is configured to be longer than the first effective electrode length; a third electrode disposed between at least a portion of the second single active piezoelectric layer and the third single active piezoelectric layer; a fourth electrode disposed on at least a portion of a top surface of the third single active piezoelectric layer; a piezoelectric actuator assembly, wherein the second effective electrode length is defined by a common length portion of the third electrode and the fourth electrode.

6. The suspension according to claim 5 , wherein the second effective electrode length is 0.02 mm longer than the first effective electrode length.

7. The suspension of claim 5 , wherein the first effective electrode length is 0.59 mm.

8. 6. The suspension according to claim 5, wherein the second effective electrode length is longer than the first effective electrode length by 0.01 mm to 0.05 mm.

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