Non-right-angled parallelogram PZT for improving suspension resonance

Abstract

An embodiment of a suspension is provided. The suspension includes a mount plate attached to a load beam at a suspension assembly attachment site. The suspension may include first and second actuators located on the mount plate. The first actuator is in the shape of a non-right angled parallelogram that intersects a first opening in the mount plate. The second actuator is in the shape of a non-right angled parallelogram that intersects a second opening in the mount plate. The first and second actuators are configured to deflect a distal end of the mount plate, which causes the load beam to rotate about a center of rotation located along the load beam.

Description

[Technical field]

[0001] The present disclosure relates generally to a suspension that supports a read / write head over a storage medium. More specifically, the present invention is a head-suspension assembly having a pair of PZT milli-actuators mounted on a mounting plate. [Background technology]

[0002] Disk drives include suspension assemblies for supporting read / write heads over information tracks of a rotating disk. A well-known and widely used Watrous type suspension includes a load beam having a mounting region at a proximal end, a flexure at a distal end, a relatively rigid region adjacent the flexure, and a spring region between the mounting region and the rigid region. An air-bearing slider including the read / write head is attached to the flexure. The mounting region is typically attached to a mounting plate for mounting the load beam to an actuator arm. A motor controlled by a servo control system rotates the actuator arm to position the read / write head over a desired information track on the disk. This type of suspension is used with both magnetic and non-magnetic disks.

[0003] Disk drive manufacturers continue to develop drives that are smaller and have greater storage capacity. Increased storage capacity is achieved, in part, by increasing the density of information tracks on the disk (i.e., using narrower and / or more closely spaced tracks). However, as track density increases, it becomes more difficult for the motor and servo control systems to quickly and accurately position the read / write heads over the desired tracks.

[0004] The use of head suspensions with PZT actuators or fine tracking motors has been proposed to overcome these problems. Figures 1 and 2 show a conventional suspension assembly 50 with an exemplary triple-stage suspension 100. In general, the triple-stage suspension 100 includes three actuators, such as a voice coil motor (VCM) (not shown) generally configured to rotate a suspension arm, a pair of actuators mounted on a mounting plate generally configured to rotate a load beam, and a pair of microactuators generally configured to rotate a slider carrying a read / write head. In some embodiments, the milliactuator operation has a high stroke, so that the servo control can attenuate low-frequency vibration noise. Meanwhile, the gimbal microactuator operation has a cleaner PZT frequency response characteristic (FRF) that can be used to increase the servo bandwidth.

[0005] 1 and 2, suspension 100 may be swaged onto head stack arm 102. Suspension 100 includes a support arm 119 and a gimbal assembly 130. Gimbal assembly 130 includes a slider 154 having a read / write head configured to read digital information from and write digital information to a rigid rotating disk (not shown). Suspension 100 may be semi-rigid and may include a stainless steel load beam terminating in a hinge member 121 attached to a mounting plate 120. Mount plate 120 is connected to head stack arm 102 at attachment site 105.

[0006] Also attached to the load beam 116 is a flexure assembly that includes a flexible stainless steel flexure and a flex circuit 117 (shown in FIG. 2). The flex circuit 117 is made from upper and lower non-conductive polyimide layers with a number of conductive metal traces sandwiched between them.

[0007] The load beam 116 can be fabricated from a flat stainless steel sheet that is then chemically etched into nearly any two-dimensional structure, within the limits of process tolerances. Typical features that are etched are holes, slots, beams, and hinges. The patterned flat stainless steel sheet is then formed into the desired three-dimensional shape.

[0008] The suspension assembly 50 may include a servo-controlled actuator to position the slider 154 of the gimbal assembly 130 on a desired track. The actuator moves the slider 154 from one track to another in a process called seek. The actuator also maintains the position of the slider 154 on a desired track in a process called track following. The suspension assembly 50 may include a VCM (not shown) attached to the head stack arm 102 to control the positioning of the slider 154. As track density increases, limitations arise in the resolution and frequency response of the VCM. To increase track density while increasing storage capacity, three-stage actuators have been developed.

[0009] The triple stage actuator uses a VCM actuator for seeking and coarse track following, and a pair of actuators 110, 112 on the mounting plate 120 and a pair of micro-actuators 150, 151 on the gimbal assembly 130 for fine track positioning. Use of the terms motor, milliactuator and microactuator will be found throughout this specification. All three are types of actuators, which are command mechanisms for generating movement, but with different degrees of magnitude and / or precision of movement relative to the read / write heads.

[0010] The actuators on the mount plate 120 (for rotating the load beam 116) include a first actuator 110 and a second actuator 112. The first actuator 110 and the second actuator 112 may be configured as suspension level actuators integrated with the load beam 116. These actuators may be rectangular piezoelectric elements that expand and contract in response to an electrical signal to rotate the load beam 116, with a slider assembled to the distal end of the load beam 116 to allow for large displacements on the recording element.

[0011] The microactuators on the gimbal assembly 130 include a first microactuator 150 and a second microactuator 151. The first microactuator 150 and the second microactuator 151 are integrated within the gimbal assembly 130. The first microactuator 150 and the second microactuator 151 operate in an extension mode and a contraction mode, respectively, to rotate a gimbal flexure tongue to which a head slider 154 is attached.

[0012] 1 and 2 configures the first actuator 110 and the second actuator 112 within a recessed region of the mount plate 120 to provide sufficient stroke. As the actuators 110, 112 expand and contract in response to an applied voltage, the actuators 110, 112 deflect the distal end of the mount plate 120 (to which the hinge member 121 is attached), thereby rotating the load beam 116. However, because the first actuator 110 and the second actuator 112 are very close to the tip of the head stack arm 102, an arm sway mode may be easily excited during actuation of the first actuator 110 and the second actuator 112.

[0013] 3 is a graph of the frequency response characteristics of the exemplary suspension 100 of FIGs. 1 and 2. The first actuator 110 and the second actuator 112 have a high gain at about 10 kHz, which is identified as the arm swing mode. Such a large peak at a low frequency band compromises the servo bandwidth of the triple stage suspension 100. Therefore, to maximize the servo bandwidth of the triple stage suspension 100, it is desirable to minimize the arm swing gain.

[0014] There is a continuing need for improved head suspensions with PZT actuators. Specifically, the head suspensions must be able to quickly and accurately position the read / write heads. The head suspensions must also be reliable and efficiently manufactured to be commercially viable. Summary of the Invention

[0015] An embodiment of a suspension is provided. The suspension includes a mount plate attached to a suspension assembly attachment site of a load beam. The suspension may include first and second actuators located on the mount plate. The first actuator is in the shape of a non-right angled parallelogram that traverses a first opening in the mount plate. The second actuator is in the shape of a non-right angled parallelogram that traverses a second opening in the mount plate.

[0016] In another embodiment, a suspension assembly is provided that includes a mount plate attached to a distal end of a load beam. A first actuator may be attached to the load beam, the first actuator having a non-right-angled parallelogram shape and configured to deflect the distal end of the mount plate. A second actuator may be attached to the load beam, the second actuator having a non-right-angled parallelogram shape and configured to deflect the distal end of the mount plate.

[0017] In some embodiments, the mounting plate may further include first and second actuators having a first set of parallel sides, a second set of parallel sides, and an acute angle of less than 45 degrees at an intersection of at least one of the first set of parallel sides and at least one of the second set of parallel sides. Optionally, the first actuator may be configured to extend toward a distal end and a first side edge of the mounting plate, and the second actuator may be configured to extend toward a distal end and a second side edge of the mounting plate.

[0018] Other features and advantages of the embodiments of the present disclosure will become apparent from the accompanying drawings and from the detailed description that follows. Embodiments of the present disclosure are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals indicate similar elements. [Brief description of the drawings]

[0019] [Figure 1] 1 shows a conventional suspension assembly having a three-stage suspension. [Diagram 2] FIG. 1 shows a gimbal assembly for a conventional three-stage suspension. [Diagram 3] 2 is a graph showing the frequency response characteristics of the three-stage suspension of FIG. 1. [Figure 4A] 1 illustrates a conventional mounting plate area for an exemplary three stage suspension. [Figure 4B] 1 illustrates an exemplary three stage suspension mounting plate area, according to one embodiment of the present disclosure. [Diagram 5] FIG. 4B shows the center of rotation of the conventional three-stage suspension. [Figure 6] 4C illustrates the center of rotation of the exemplary three-stage suspension of FIG. 4B, according to one embodiment of the present disclosure. [Figure 7] 4C shows a graphical representation of the frequency response characteristics of the conventional three-stage suspension of FIG. 1 and the exemplary three-stage suspension of FIG. 4B. [Figure 8] 1 illustrates a parallelogram PZT die casting according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] An embodiment of a suspension is provided. The suspension includes a mount plate attached to a load beam at a suspension assembly attachment site. The suspension may include first and second actuators located on the mount plate. The first actuator is in the shape of a non-right-angled parallelogram that traverses a first opening in the mount plate. The second actuator is in the shape of a non-right-angled parallelogram that traverses a second opening in the mount plate. Advantages of using actuators having non-right-angled parallelogram shapes are discussed in detail below.

[0021] Although one suspension structure is referenced herein, it should be understood that any number of suspensions may be implemented herein. Additionally, although a three stage suspension 100 is illustrated herein, it should be understood that the disclosure that follows may be implemented in a two stage suspension.

[0022] To achieve the desired operation of servo bandwidth, a three-stage suspension has been introduced in the industry, where a PZT milliactuator is assembled on a mounting plate and a PZT microactuator is assembled on a flexure tongue. The PZT milliactuator serves to provide a larger stroke and coarser head position adjustment, while the PZT microactuator serves to provide better resonance performance and finer head position adjustment.

[0023] 4A shows another embodiment of a conventional triple stage suspension 200. The conventional triple stage suspension 200 uses a pair of rectangular shaped milliactuators 210, 212 and includes a gimbal assembly with a slider 254 having a read / write head configured to read and write digital information from and to a rigid rotating disk (not shown). Similar to the suspension 100 of FIG. 1, the suspension 200 can be semi-rigid and can include a stainless steel load beam 216 terminating in a hinge member 221 connected to a mount plate 220. The mount plate 220 is connected to an arm 202 at a suspension assembly attachment site 205.

[0024] The load beam 216 can be fabricated from flat stainless steel that is then chemically etched into nearly any two-dimensional structure, within the limits of process tolerances. Typical features that are etched are holes, slots, beams, and hinges. The patterned flat stainless steel sheet is then formed into the desired three-dimensional shape.

[0025] The suspension 200 may include a pair of milliactuators 210, 212 in the openings 243, 244 in the mounting plate 220, and may also include a pair of microactuators 250, 251 for fine track position adjustment in a gimbal assembly 252. The microactuators in the gimbal assembly 252 include a first microactuator 250 and a second microactuator 251. The first microactuator 250 and the second microactuator 251 have microactuators that are integrated within the gimbal assembly 252.

[0026] FIG. 4B illustrates an embodiment of the present invention including the features of FIG. 4A, except as noted below. The suspension 300 includes a pair of milliactuators, including a first actuator 312 and a second actuator 312, mounted on a mounting plate 320. The first actuator 310 is a piezoelectric element that is shaped as a non-right-angled parallelogram that traverses an opening 343 in the mounting plate 320. The non-right-angled parallelogram shape of the first actuator 310 helps optimize the gain of the arm swing of the first actuator 310. The second actuator 312 is a piezoelectric element that is shaped as a parallelogram that traverses an opening 344 in the mounting plate 320. The non-right-angled parallelogram shape of the second actuator 312 helps optimize the gain of the arm swing of the second actuator 312.

[0027] A parallelogram is a quadrilateral with four straight sides, with opposite sides of equal length and parallel to each other. In the present disclosure, a non-right-angled parallelogram is a parallelogram in which adjacent sides do not meet at right angles (i.e., two of the opposite interior angles are equal and acute (less than 90 degrees), and the other two opposite interior angles are equal and obtuse (greater than 90 degrees)). As shown in FIG. 4B, the first actuator 310 may include a first set of parallel sides A and C, and a second set of parallel sides B and D. The first actuator 310 includes acute interior angles at the intersections of sides A and D and sides B and C, and obtuse interior angles at the intersections of sides A and B and sides C and D. Thus, even if side B is parallel to the distal end of the mount plate 320, the first actuator 310 extends (and is configured to extend) from the suspension assembly attachment site 305 in a direction parallel to sides A and C. Similarly, the second actuator 312 includes acute interior angles at the intersections of sides A and D and sides B and C, and obtuse interior angles at the intersections of sides A and B and sides C and D. Thus, even if side B is parallel to the distal end of the mount plate 320, the second actuator 312 extends (and is configured to extend) from the suspension assembly attachment site 305 toward the distal end in a direction parallel to sides A and C.

[0028] The use of non-rectangular parallelogram shaped piezoelectric (PZT) elements for each of the actuators 310, 312 is useful for optimizing the arm swing gain of the PZT actuator frequency response characteristics compared to the rectangular shaped actuator of FIG. 4A. The first actuator 310 and the second actuator 312 may be configured as suspension level non-rectangular parallelogram actuators that are integrated with the load beam 316 of the suspension. For each of the actuators 310, 312, sides B and D engage with sides of respective openings 343, 344, thereby deflecting the distal end of the mounting plate 320 (to which the hinge member 321 is attached) and thereby rotating the load beam 316 when the actuator is extended by a voltage applied between its top and bottom surface electrodes.

[0029] FIG. 5 shows the rotation center of the conventional triple stage suspension 200 of FIG. 4A using a rectangular shaped milliactuator. The rectangular shaped first actuator 210 and the second actuator 212 deflect the distal end of the mount plate 220 to rotate the load beam 216 about the rotation center 501 located near the distal end 522 of the mount plate 220. The coincidence of the rotation center 501 and the distal end 522 is due to the fact that the rectangular actuator is arranged parallel to the longitudinal axis AA of the suspension to rotate the load beam 216 about the distal end 522. Since the rotation center 501 is at the proximal end of the load beam 216, the magnetic head slider assembled at the distal end of the load beam 216 can stroke or displace on the track greatly. However, since the rotation of the load beam 216 is centered on the tip of the mount plate 220, the arm swing mode can be easily excited under the operating mode of the conventional rectangular shaped actuator configured parallel to the longitudinal axis AA of the suspension. Changing the angle between the two actuators 210, 212 can help change the center of rotation of the load beam 216, but this requires modifying the geometry of each of the openings 243, 344. Modifying the geometry of the openings 243, 344 will generally tend to weaken the stiffness of the mounting plate 220 and adversely affect the resonant performance of the suspension, especially the critical low frequency modes, including the first bending mode, the first torsional mode, etc.

[0030] FIG. 6 shows the center of rotation of the exemplary triple suspension of FIG. 4B. The first and second actuators 310 and 312 of the non-right-angle parallelogram deflect the distal end 622 of the mount plate 320 to rotate the load beam 316 about the center of rotation 601 located near the center of the load beam 316. The coincidence of the center of rotation 601 and the center of the load beam 316 is due to the fact that the two actuators 310, 312 are configured to be at a constant angle with respect to each other without the need to modify the openings 343, 344. In the non-right-angle parallelogram shape, the proximal ends of the actuators 310, 312 can be configured closer to the center of the suspension and the distal ends of the actuators 310, 312 can be configured toward the lateral side edges of the suspension while maintaining the design of the mount plate 320. As the angle of attack of the PZT actuators 310, 312 increases, or the obtuse included angle at the intersection of sides A and B increases, the center of rotation of the PZT actuation is moved from the tip of the mount plate 320 toward the distal end of the load beam 316. Such center of rotation movement allows the head slider to rotate about the center of rotation in an opposite direction to the head stack arm 302. As a result, the arm vibration gain can be optimized by properly tuning the center of rotation to balance the mass moment of inertia about the center of rotation.

[0031] FIG. 7 is a graph of the frequency response characteristics of the exemplary three-stage suspension of FIG. 4A and FIG. 4B. The frequency response characteristics of the rectangular shaped first actuator 210 and the second actuator 212 and the non-right angle parallelogram shaped first actuator 310 and the second actuator 312 are shown in FIG. 7. The non-right angle parallelogram shaped first actuator 310 and the second actuator 312 are shown in two shapes, one shape having an acute angle equal to 32 degrees and the second shape having an acute angle equal to 22 degrees. As shown in FIG. 7, the suspension incorporating the non-right angle parallelogram shaped actuator with an acute angle of 32 degrees reduces the arm swing gain at 10 kHz, but the suspension incorporating the non-right angle parallelogram shaped actuator with an acute angle of 22 degrees reduces the arm swing gain more significantly at 10 kHz. The non-right-angled parallelogram shaped actuator can be mounted to a conventional mounting plate with only minor modifications to the conventional mounting plate (ideal since conventional mounting plates can have tight geometric tolerances). As shown in Figure 7, the frequency response characteristics for a non-right-angled parallelogram shaped actuator with an acute angle equal to 22 degrees shows a significant reduction in arm swing gain. However, it has been found that a reduction in arm swing gain can be achieved with a PZT acute angle less than 45 degrees.

[0032] 8 illustrates a method for cutting a non-right-angled parallelogram PZT actuator wafer 800. The non-right-angled parallelogram PZT actuator wafer 800 is cut into a plurality of non-right-angled parallelogram PZT pieces after dielectric poling. The method for manufacturing a non-right-angled parallelogram PZT actuator is substantially the same as a conventional rectangular shaped PZT actuator, except for the non-perpendicular cutting of the wafer. In some embodiments, a quartz crystal element may be implemented instead of a piezoelectric material to form a non-right-angled parallelogram shaped actuator.

[0033] It should be understood that terms such as "upper," "lower," "above," "best," and x-, y-, and z-directions used herein are terms of convenience to indicate the spatial relationship of parts relative to one another, rather than any particular spatial or gravitational orientation. These terms are therefore intended to encompass an assembly of components, whether the assembly is oriented in the particular orientation shown in the drawings and described herein, or upside down from that orientation, or any other rotational variation.

[0034] It should be understood that the term "the present disclosure" as used herein is not to be interpreted as meaning that only a single disclosure having a single essential element or group of elements is presented. Similarly, it should be understood that the term "the present disclosure" encompasses several separate innovations, each of which may be considered as a separate disclosure. Although the present disclosure has been described in detail with reference to the preferred embodiment and drawings thereof, it will be apparent to those skilled in the art that various adaptations and modifications of the embodiments of the present disclosure may be accomplished without departing from the spirit and scope of the present disclosure.

Claims

1. a mounting plate attached to a distal end of the load beam; a first actuator having a non-right angled parallelogram shape and spanning a first opening in the mounting plate; a second actuator having a non-right angled parallelogram shape and spanning a second opening in the mounting plate; A suspension assembly comprising a three-stage suspension having:

2. The suspension assembly of claim 1 , further comprising a gimbal assembly attached to the load beam, the gimbal assembly including a slider configured to write digital information to a rigid rotating disk.

3. The suspension assembly of claim 2 , further comprising a first micro-actuator and a second micro-actuator integrated within the gimbal assembly.

4. The suspension assembly of claim 3 , wherein the first and second micro-actuators are in the shape of a non-right angle parallelogram.

5. The suspension assembly of claim 1 , wherein said first and second actuators are integral with said load beam.

6. Each of the first and second actuators comprises: a first set of parallel sides; and a second set of parallel sides; and 2. The suspension assembly of claim 1, including an acute angle of less than 45 degrees at an intersection of at least one of the first set of parallel sides and at least one of the second set of parallel sides.

7. the first actuator is configured to extend toward a distal end and a first side edge of the mounting plate; The suspension assembly of claim 1 , wherein the second actuator is configured to extend toward the distal end and a second side edge of the mounting plate.

8. 8. The suspension assembly of claim 7, wherein expansion of the first actuator causes the load beam to rotate about a center of rotation located along the load beam.

9. a mounting plate attached to a distal end of the load beam; a first actuator attached to the load beam, the first actuator being shaped as a non-right angle parallelogram and configured to deflect a distal end of the mounting plate; a second actuator attached to the load beam, the second actuator being shaped as a non-right angle parallelogram and configured to deflect the distal end of the mount plate.

10. the first actuator traverses a first opening in the mounting plate; The suspension assembly of claim 9 , wherein the second actuator traverses a second opening in the mounting plate.

11. 10. The suspension assembly of claim 9, further comprising a gimbal assembly attached to the load beam, the gimbal assembly including a slider configured to write digital information to a rigid rotating disk.

12. The suspension assembly of claim 11 , further comprising a first micro-actuator and a second micro-actuator integrated within the gimbal assembly.

13. The suspension assembly of claim 12 , wherein the first and second micro-actuators are in the shape of a non-right angle parallelogram.

14. The suspension assembly of claim 9 , wherein the first and second actuators are integral with the load beam.

15. Each of the first and second actuators comprises: a first set of parallel sides; and a second set of parallel sides; and 10. The suspension assembly of claim 9, including an acute angle of less than 45 degrees at an intersection of at least one of the first set of parallel sides and at least one of the second set of parallel sides.

16. the first actuator is configured to extend toward the distal end and a first side edge of the mounting plate; The suspension assembly of claim 9 , wherein the second actuator is configured to extend toward the distal end and a second side edge of the mounting plate.

17. 10. The suspension assembly of claim 9, wherein deflection of the distal end by the first actuator causes the load beam to rotate about a center of rotation located along the load beam.

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