KR19990008454A - Suspension design supporting lightweight read / write heads - Google Patents

Abstract

An improved suspension is described that supports a read / write head adjacent to a storage medium that is relatively moved in a disk drive. Suspension 40 is mounted to an in-line rotary actuator arm and includes a reduced width side rail 48 load beam 44 with vent area 49. Suspensions exhibit improved modal performance, in particular for torsional operating modes.

Description

Suspension design supporting lightweight read / write heads

Field of invention

BACKGROUND OF THE INVENTION The present invention generally relates to suspensions which support a read / write head adjacent to a recording medium that is relatively moving in a disk drive. In particular, a suspension device which is particularly suitable for supporting a low-mass head at the end of a load beam, which reduces the mass of the load beam and the resonant mode characteristic of the combination of the head and the suspension device. Suspension device having a modified geometric shape that improves the.

background

With the advent of more powerful central processing units (CPUs) and higher bandwidth bus structures, disk drive performance has become a major limiting factor in overall computer system performance. Specifically, the disk drive imposes a data access delay of about 10 ^-3 seconds, in contrast to the 10 ^-9 seconds required to access data from the electronic storage device, and thus removes data from tracks on the recording surface of the disk drive. It is necessary to reduce the actuator access time in order to be able to search more quickly.

Current disc drives typically include a rotating rigid storage disc and a head positioner for positioning the data transducer at different radial positions relative to the axis of rotation of the disc, thereby storing a lot of concentric data on each recording surface of the disc. Form a track. Head positioners are commonly referred to as actuators. While many actuator structures are known in the art, in-line rotary actuators are most often employed today due to their simplicity, high performance, and mass balance around the axis of rotation, which makes the actuator less sensitive to disturbances. It is important to do. Closed loop servo systems are employed to operate the actuator, positioning the head relative to the disk surface. The dynamic nature of the hard disk drive actuator servo system allows higher servo system performance to be achieved when the inherent mechanical vibration modes of the head and suspension structures do not occur at or near the variable of the servo sampling frequency or alias. .

Typically, read / write transducers, which may be of single element or dual element design, are mounted on a ceramic slider structure having an air bearing surface that supports the transducer a small distance away from the surface of the moving medium. Combinations of air bearing sliders and read / write transducers are also known as write heads. By using an air bearing slider to support the head away from the disk surface, the head operates with hydrodynamic lubrication at the head / disk interface rather than boundary lubrication. The former approach creates additional space between the transducer and the medium and reduces transducer efficiency, but the prevention of direct contact significantly improves the reliability of the head and disk components. In the disc drive industry, the size and mass of the slider structure have been gradually reduced to reduce the moving mass of the actuator assembly and to allow the transducer to act close to the disc surface, the latter approach being associated with additional track density and Resulting in improved converter efficiency that can be exchanged.

In order to realize improved actuator access time, it is particularly important to reduce the undesired vibration levels of the components in the disk drive, because such vibrations can cause instability of the servo system of the disk drive. . Specifically, the resonant frequency of the first torsional vibration mode of the load beam structure of the suspension device is typically the first facing (ie lowest frequency) resonant mode that limits the actuator retrieval performance. The first torsional vibration mode significantly limits the access time achievable because the torsional vibration causes the supported data converter to move off the track relative to the data track on the storage disk. This off-track movement constrains servo system performance and causes delays in the transfer of data due to the settling time incurred so that the magnitude of the torsional vibration does not cause erroneous reading or writing of the data track.

Search performance may also be improved by reducing the mass of moving structures, such as suspensions. As is known in the art, the reduction of the mass of the suspension device tends to lower the stiffness of the structure with reduced mass, resulting in an undesirable reduction of the resonant frequency of the structure. As mentioned above, the reduced resonance frequency typically results in a bad result for servo performance. Thus, there is a need for a lightweight suspension structure with improved resonant frequency characteristics, particularly for the first torsional (1T) oscillation mode.

The present invention to be described provides a lightweight suspension device for an in-line rotary actuator with a load beam, in particular exhibiting improved modal performance with respect to the first torsional resonance mode, making it particularly suitable for use in high performance disk drive applications. do.

The suspension assembly according to the present invention incorporates a tapered spring section that supports a significantly narrowed load beam structure. The present invention presents substantial performance advantages over prior art suspension design. At the same time as the mass of the suspension is significantly reduced, the first torsional mode resonant frequency nearly doubles without sacrificing material performance in other modes, such as the first lateral vibration mode and the first bending vibration mode.

The overall object of the present invention is to overcome the limitations and shortcomings of the prior art and to provide a suspension device having a low load profile with an improved load beam structure supporting the read / write head in a disk drive.

A more specific object of the present invention is to provide a suspension for supporting a micro slider in an in-line rotary actuator which exhibits a higher first torsional resonance frequency than the suspension of the prior art.

Another object of the present invention is to provide a suspension device with reduced mass.

It is a further object of the present invention to provide an in-line, mass balanced, rotary voice coil actuator assembly comprising a reduced width and vented load beam with improved dynamic properties. To provide.

The above and other objects, advantages, aspects and features of the present invention will be fully understood upon consideration of the following detailed description of the preferred embodiments shown in connection with the accompanying drawings.

Brief description of the drawings

In the drawing,

1A is a schematic plan view of a picoslider suspension device of the prior art.

FIG. 1B is a cross-sectional view of the suspension device of FIG. 3A taken along section line 1B-1B in FIG. 1A.

2 is a schematic side view of a pico slider suspension of the prior art.

Figure 3A is a schematic plan view of an upswept rail pico slider suspension according to a preferred embodiment of the present invention.

3B is a sectional view of the suspension device of FIG. 3A taken along section line 3B-3B in FIG. 3A.

4A is a schematic plan view of an inverted rail pico slider suspension according to another preferred embodiment of the present invention.

4B is a cross-sectional view of the suspension device of FIG. 3A taken along section line 4B-4B in FIG. 4A.

5A is a graph of the frequency response characteristics of the prior art pico slider suspension.

FIG. 5B is a graph of the frequency response characteristics of the conventional pico slider suspension of FIGS. 3A and 3B.

Figure 6 is a graph of [...], i.e., negative offset and bump plots.

details

1A shows a prior art upwardly curved suspension device 10 supporting a 30 percent slider 15 (known as picoslider) adjacent to a disk surface (not shown). The illustrated suspension device 10 is generally known as a type 8 suspension device intended for use with a picoslider. The suspension device 10 comprises a base plate 20 which is conventionally attached to the mounting section 21 of the suspension device (at the cantilevered end). The base plate 20 is ultimately used to securely mount the suspension device 10 to an actuator arm (not shown), and typically the base plate is beaten onto the actuator arm. A spring (or hinge) section 22 fixed to the mounting section 21 and interconnecting the mounting section 21 with the load beam 24. The spring section 22 includes one or more holes 26 to adjust the spring constant of the spring section 22. In addition, the thickness of the spring section 22 may be varied to adjust the spring constant. The suspension device 20 has a small tool hole 27 which is used to facilitate the accurate manufacture and assembly of the suspension device.

The load beam 24 incorporates a pair of upwardly curved rails 28 along the side to increase the rigidity of the load beam. The shape of the rail 28 affects the resonant frequency of the beam 24, so the rail 28 may be designed to improve servo system performance by moving the resonant frequency of the suspension device 20 away from the servo sampling frequency. Can be. Importantly, the load beam is specifically designed according to the prior art to widen the vicinity of the spring section to improve the resonance characteristics. The proximal end of the load beam 24 is about _ mm wide. FIG. 1B shows a cross section of the upwardly curved rail 28 (taken along section line 1B-1B in FIG. 1A).

Returning now to FIG. 2, the suspension 10 is attached to the distal end of the load beam 24 and pivots to support the head 15 with respect to the load beam and to serve as a gimbal. 29). The spring section 22 shows the z-axis (height) required for the in-situ suspension structure to remain relatively straight while the suspension 10 applies a load force to the head 15 in the direction of the disk surface during operation. ) May optionally be pre-bent to reduce the gap.

In a preferred embodiment of the present invention, as shown in Figure 3A, the suspension device 40 has a total length (in the longitudinal direction) of about 20-30 mm and about _ mm in the widest region of the suspension device. Having the transverse width of the suspension, the widest area of the suspension is preferably located at or near the junction of the mounting section 44 and the spring section 42. The proximal end of the load beam 44 has a width of about _ mm. [Strict discussion about dimensions]

The main suspension body member is chemically etched from a flat stainless steel sheet having a thickness on the order of about 60-75 microns. The etching operation ultimately has a mounting section 41, a spring section 42 (including the holes 46), a load beam 44 (including the tool holes 27), and a rail 48. To form an area. After the suspension device 40 has been etched, the machine is shaped to impart a pair of upwardly curved rails 48 spaced laterally spaced in this case, generally at right angles to the flat region of the load beam structure 44. The job is adopted. Typical rail dimensions are 0.2-0.3 mm in height and about 0.2-0.5 mm in width. A separate base plate 20 is typically manufactured (eg, bent or shaped in gradual die operation) and attached to the suspension device 40 via conventional means, such as gluing or spot welding. In operating conditions, the height of the top surface of the load beam 44 is less than about 0. _ mm from the disk surface.

Conventional gimbal means, such as bends (not shown), are secured to the distal end of the load beam 44, but the gimbal may optionally be formed as an integral part of the load beam 44, eg, via a chemical etching process. Suitable bends typically have planar dimensions on the order of 1.5x10.0 mm and thicknesses on the order of 25-30 microns. The bends are typically etched and attached to the underside of the load beam 44 using conventional means such as, for example, gluing or spot welding. A load button (not shown) may optionally be formed on or near the bend of the load beam 44 to establish a point at which the head 15 is balanced by the gimbal. Finally, prior to attaching the read / write head 15 to the underside of the bend, in order to maintain the low lateral shape while giving restoring force to the head 15 in the direction of the disk surface, the suspension device 40 has a spring zone. Plastic deformation or pre-bending at 42 allows the load beam 44 to remain essentially flat and generally parallel to the disk surface (not shown) when the resulting suspension 40 is installed in the drive. In the preferred embodiment shown in Fig. 3A, the load beam also includes an optional pressure equalization vent 49 between the load beam rails 48, which further reduces the mass of the load beam structure.

In contrast to the prior art indication that a wide suspension structure should be employed to improve the resonant mode characteristics of the suspension, the present invention includes a rail structure spaced along at least a portion of the lateral edges of the load beam. And a much narrower load beam, the maximum width of which is smaller than the width of the base plate. Surprisingly, significantly narrowing the width of the load beam did not alter the modal resonant frequency of the beam badly, but significantly increased the torsional mode resonant frequency. Table 1 shows the results of finite element modeling showing the modal resonance frequencies of each of the picosliders 10 and 40 of FIGS.

Table 1

Mode Description Pico Slider Suspension (Prior Art) Picoslider suspension system with narrow load beam 1st torsional mode 2.5 KHz 3.8 KHz Primary Bend Mode 1.9 KHz 1.9 KHz 2nd torsional mode 8.5 KHz 9.0 KHz 2nd bend mode _._ KHz _._ KHz 3rd Torsional Mode _._ KHz _._ KHz Primary lateral mode 10.0 KHz 9.5 KHz Heavy mode _._ KHz _._ KHz

Thus, tapered springs and narrow rod beam shapes significantly reduce the mass of the suspension, thereby significantly reducing the moment of inertia of the resulting actuator structure, which reduces search time. The masses of picosliders 10 and 40 in FIGS. 1A and 3A are shown in Table 2.

TABLE 2

TABLE 2

In disc drive applications, where high volumetric efficiency is the primary design goal, a reversing rail rod beam and pre-bent spring section are employed in the suspension to reduce the z-axis clearance necessary compared to conventional upward curved rail suspension designs. This can bring disk to disk space closer. In this situation, the mechanical suspension structure must remain relatively unmodified in rail depth to maintain adequate modal performance. 4A shows another preferred embodiment of the present invention for use in a drive requiring very close disk to disk space. Suspension 50 includes a reversing rail 58 and a pre-bent hinge section 42, both of which contribute to improved disk to disk space. The downwardly curved rail embodiment of the present invention requires an additional width (and eventually mass) at the distal end so that the rail 58 does not interfere with the gimbaling of the supported slider 15, but the prior art reverse type Significant improvements in modal performance and mass reduction are achieved compared to rail picoslider designs. In this downward curved rail embodiment, the dimensions of the hole 49 are important and must be carefully controlled to reduce both the vibration and the mass induced by the radial air flow. The vent zone 49 is at least _% of the load beam area.

(Bode Plot discussion of Figure 5)

[NOB Plot Discussion of Figure 6]

In summary, the present invention provides a lightweight suspension design with improved modal performance for use with a lightweight slider operating in an in-line rotary actuator assembly. Suspensions according to the teachings of the present invention provide better actuator servo system performance through improved modal performance. The combination of lower total mass and improved servo system performance provides improved search performance over drives incorporating prior art picoslider designs. Thus, the present invention facilitates the design and manufacture of high performance disk drives.

Although the present invention has been described by a preferred embodiment, ie a suspension device optimized for use with a picoslider or sub-pico slider, the invention can also be applied to a suspension device designed for use with a rather large slider, such as a nanoslider. Will be apparent to those skilled in the art. Accordingly, it should be understood that this description is not to be interpreted as limiting. There is no doubt that various changes and modifications will become apparent to those skilled in the art after reading the above description. Accordingly, the appended claims are to be construed as including all changes and modifications falling within the spirit and scope of the invention.

Claims (20)

A cantilevered suspension device having a proximal end and a distal end, which supports a read / write head on an in-line rotary actuator assembly for use in a disc drive, comprising: The mounting zone at the proximal end of the suspension device, A base plate fixed to the mounting area for mounting the suspension device to the actuator assembly, A spring section-spring section fixed at the distal end of the mounting zone and having a generally wide trapezoidal section adjacent to the mounting zone has a maximum width zone and a minimum width zone at the distal end of the spring section and is arranged along the side of the suspension device. With spring edges, At the distal end of the load beam for attaching the read / write head, the proximal end of the long, generally flat load beam-load beam comprising a gimbal means is connected to the distal end of the spring section, and the load beam is connected to With generally straight major lateral edges, each major lateral edge of the load beam forming an obtuse outer shell with adjacent ones of the lateral spring edges; Suspension device comprising a. The suspension device of claim 1, wherein the load beam also includes a pair of laterally spaced rail members extending along at least a portion of each major lateral edge of the load beam. The suspension device according to claim 1, wherein the load beam also includes inverted rail means for increasing the rigidity of the load beam, the inverted rail means extending at least partially along each lateral edge of the load beam. . 4. The suspension of claim 3, wherein the load beam also includes an outer boundary defining the first zone and an inner boundary defining the hole, the inner boundary surrounding an area greater than about 20% of the first zone. Device. The load beam of claim 4, wherein the holes are substantially trapezoidal. A suspension device for supporting a read / write head, A long load beam having a pair of substantially straight major lateral edges that converge at a first rate along the central longitudinal axis of the suspension from the proximal end to the distal end of the load beam, A delta spring section connected to the proximal end of the load beam, Triangular springs have a pair of lateral spring edges that converge along the longitudinal axis at a rate greater than a first ratio. 7. The suspension of claim 6, wherein the total length of the suspension is about 20 mm to 30 mm, the maximum spring section width is about 6.0 mm, and the maximum load beam width is about 3.2 mm. 7. The load beam according to claim 6, wherein the load beam also includes upwardly curved rail means for increasing the rigidity of the load beam, wherein the upwardly curved rail means extends at least partially along each major lateral edge of the load beam. Suspension device. 7. The suspension of claim 6, wherein the load beam also includes inverted rail means to increase the rigidity of the load beam, the inverted rail means extending at least partially along each major lateral edge of the load beam. Device. 10. The method of claim 9, wherein the pair of substantially straight major lateral edges includes an outer boundary defining the first zone, the load beam also includes an inner boundary defining the aperture, and the inner boundary is about 25 of the first zone. Suspension device characterized by surrounding the area larger than%. The suspension of claim 10, wherein the aperture is substantially trapezoidal. A suspension device which supports a lightweight magnetic read / write head on an actuator assembly for a hard disk drive and is substantially symmetrical about a central longitudinal axis, A base plate for mounting the suspension device to the actuator assembly, A mounting area fixed to the base plate at the proximal end of the suspension device, The load beam-load beam, which is located at the distal end of the suspension and supports the head and has a maximum width adjacent the proximal end of the load beam, has a pair of substantially straight major lateral edges, each major lateral edge Forms an angle of 0 to 10 degrees with respect to the central longitudinal axis—and The generally flat spring section-spring section interconnecting the mounting zone and the proximal end of the load beam has a pair of converging lateral spring edges defining a maximum width zone and a minimum width zone, the maximum width zone being connected to the mounting zone. Adjacent, minimum width zone adjacent to the load beam Including; Suspension device, characterized in that each converging lateral spring edge forms an acute angle greater than about 25 degrees with respect to the central longitudinal axis. 13. The suspension of claim 12, wherein the load beam also includes a pair of laterally spaced rail members extending along at least a portion of each major lateral edge of the load beam. The suspension of claim 13, wherein the total length of the suspension is about 20 mm to 30 mm and the maximum width of the load beam is about 3.2 mm. A suspension device for supporting a read / write head, A long load beam-load beam having a pair of substantially straight converging main lateral edges has a maximum width at the proximal end of the load beam, has a proximal end for attachment of the read / write head, and is substantially straight. Major lateral edges define a first interior angle; The generally trapezoidal spring section attached to the proximal end of the load beam has a pair of lateral spring edges tapering towards the load beam, and the cabinet between the pair of lateral spring edges is greater than the first cabinet angle. Suspension device comprising a. 16. The suspension device of claim 15, wherein the load beam has a width that varies substantially linearly from the proximal end to the distal end. 16. Suspension device according to claim 15, wherein the load beam comprises flanges along the major lateral edges to increase the rigidity of the load beam. 16. Suspension device according to claim 15, wherein the load beam also includes rails located along major lateral edges to increase the rigidity of the load beam. 19. The suspension of claim 18 wherein the rail is upwardly curved. 19. A suspension system according to claim 18, wherein the rail is an inverted rail.