KR19990037679A - Suspension with reduced torsional mode gain and sensitivity - Google Patents

Abstract

The present invention discloses an improved suspension for supporting a read / write head adjacent to a relatively moving storage medium in a disk drive. Suspension improves head position servo performance by reducing the magnitude of the gain in the first torsional resonance mode of vibration when the Z-axis height of the rod beam is configured as the minimum sensitivity of the first torsional gain as a function of the rod beam Z-axis height. And a curved rod beam 36 or curved flexure 45 to provide a suspension with improved manufacturing and assembly yield.

Description

Suspension with reduced torsional mode gain and sensitivity

The disk drive industry is competitive and therefore the demand for disk drives tends to be characterized as being very sensitive to price per unit storage capacity. In order to increase the capacity of data storage in a particular disk drive, multiple disks are typically mounted concentrically on the spindle motor and in conjunction with a set of ganged heads, each of which has a suspension member (hereafter referred to as a suspension disk). Supported on a gimbal structure that forms part of the suspension.

The suspension is then mounted to a rigid actuator arm that is connected to a common rotatable structure, typically known as an E-block. Rotation to selectively set the position of the collective head, attaching an E-block to the voice coil motor structure, mass-balanced at various radial positions or tracks with respect to the disc, and performing closed-loop servo positioning The actuator structure is formed. Since the suspension forms part of the mechanics within the servo loop, the dynamics of the suspension can thus limit the achievable servo system performance.

The title of the invention is a method of characterizing and controlling the in-plane stiffness of a load beam in a head-gimbal assembly of a hard disk drive and simultaneously continuing, the disclosure of which is described herein by reference. US patent application Ser. No. 08 / 249,525 discloses that the first torsional resonant mode can be geometrically constructed with the spring and rod beams of the suspension such that they have a minimum or optimum sensitivity of gain in terms of handling and manufacturing tolerances. In particular, the sensitivity of the first torsional gain can be reduced by adjusting the Z-axis height of the end of the rod beam zone against the spring. By reducing the sensitivity of the gain to the manufacturing process as described above, the manufacturing yield and headstack assembly operation of the rod beam assembly, for example, can be significantly improved. However, since the reduced gain sensitivity does not mean that the size of the gain itself is reduced, the suspension may not exhibit improved absolute performance despite improved performance consistency.

This unresolved need exists to date for suspensions that provide reduced magnitude of nominal gain to easily realize improved servo system performance while at the same time exhibiting reduced first torsional gain sensitivity to the manufacturing process.

The present invention generally relates to a suspension for supporting a read / write head adjacent to a recording medium relatively moving in a disk drive. More specifically, the present invention relates to a suspension comprising a structural member composed of an adjusted curvature that reduces both the gain of the torsional mode vibration and the sensitivity of the torsional mode gain to any suspension manufacturing variation.

1 is a schematic perspective view of an 8 head gimbal assembly (HGA) type according to the prior art.

2 is a schematic side view of an 8 HGA type according to the prior art.

3 is a schematic side view of an HGA with a negative sag imparted to a load beam in accordance with the principles of the present invention.

4 is a side view of an HGA end portion in accordance with an alternative embodiment of the present invention.

FIG. 5 is a graph showing the results of finite element modeling in which the maximum peak first torsional resonance gain (normalized at 1 Hz) is plotted as a function of suspension offset for various load beam and flexure configurations.

An alternative object of the present invention is to provide a suspension for supporting a read / write head in a disk drive that overcomes the limitations and drawbacks of the prior art.

A more specific object of the present invention is to provide a suspension for a disc drive which exhibits a reduced nominal gain in the first torsional mode of vibration.

It is another object of the present invention to provide a suspension that achieves a lower nominal gain at the minimum gain sensitivity point.

It is also an object of the present invention to provide a suspension comprising a rod beam or flexure with a curvature imparted or optimized to reduce the nominal gain at the minimum gain sensitivity point.

It is also an object of the present invention to provide a method of manufacturing a suspension combined with a load beam and flexure that provides a lower first torsional nominal gain at the minimum gain sensitivity point.

The above and other objects of the present invention provide a data storage disk that rotates at a predetermined angular velocity relative to the base plate and an in-line rotary actuator structure that is rotatably mounted to the base, and different radial positions relative to the disk. And an in-line head mounting structure or suspension for supporting and moving the read / write head in the form of a fixed disk drive head and disk assembly that ultimately form a plurality of separate data tracks for recording information. According to the present invention, the disc drive comprises an improved suspension structure comprising a gimbal flexure attached to the distal end of a cantilevered long rod beam with rail-shaped reinforcement. The rod beam is connected to a leaf spring supported by a mounting zone disposed at the cantilever end of the suspension. The leaf spring may be pre-curved so that when the head is mounted to the drive, the suspension is drooping substantially straight, allowing the disk to be much closer to disk space. The rod beam has a curvature either formed directly during manufacture or imparted during the flexure mounting mechanism, which reduces the first torsional nominal gain of the suspension at the lowest gain sensitivity point.

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

Figure 1 shows a head-gimbal-assembly (HGA) according to the prior art comprising an "8 type" suspension 12 and a supported read / write head 14. The suspension 12 consists of a rigid flat base plate 16 and is an integral swaging boss 18, spring 20, rod beam 22 for mounting the suspension to an actuator arm (not shown). And a gimbal flexure 24 attached to the unsupported end of the distal end of the suspension that pivotally supports the read / write head 14. The rod beam 22 typically includes a pair of rails 26 along the lateral edges to reinforce the rod beam structure. Since the configuration of the rail 26 affects the resonant frequency of the HGA 10, the rail 26 typically has a higher resonant frequency of the HGA 10 (to improve the servo bandwidth) and the servo sampling frequency or its It is designed to improve servo system performance by moving away from other variables.

FIG. 2 shows a side view of the HGA shown in FIG. 1. The flexure 24 of FIG. 1 is omitted for clarity. The rod beam 22, however, is manufactured according to the prior art and is intended to operate in a nominally flat state. However, since the rail 26 is formed, there is an inductive stress that causes the rod beam to be somewhat curved. Spot welding operations may also affect rod beam flatness due to local annealing or recrystallization. Due to the uprail rod beam design as shown in FIGS. 1 and 2, the manufacturing method in which the beam bow is induced typically raises the center of the rod beam by about 1 mm relative to the end. Curve 50 of FIG. 5 shows a graph showing the kinetic behavior of the nominally flat rod beam of FIG. 2 operating in conjunction with a flexure mounted by the prior art. Curve 50 shows the maximum peak first torsional resonance gain (for 1 Hz to 0 Hz) as a function of imparted suspension offset. As such, the HGA 10 of FIG. 2 is manufactured such that its rod beam base is offset by -0.025 mm along the Z axis to minimize the sensitivity of the first torsional gain (since the rate of change of gain relative to the offset is approximately zero at -0.025 mm). Should be. Even if the operating point is not the point with the minimum gain, the operating system will ultimately obtain the minimum sensitivity of the gain, and the selected operating point may for example be offset at which the local minimum gain is achieved since there is a tendency to readjust the offset of the suspension during manufacture and during assembly operation. It is easy to provide a production yield that is significantly better than the point, because very small fluctuations in the offset at local minimums cause a dramatic and undesirable increase in the first torsional gain. The chosen operating point not only minimizes the variation in gain, but effectively sets an upper boundary to the gain so that a slight deviation from the optimal point will actually yield some good mechanical performance.

3 shows a side view of an HGA 30 in accordance with the preferred embodiment of the present invention. In this embodiment of the invention, the suspension 31 has a total length in the longitudinal direction of 20 to 30 mm and typically a width of about 5 mm in the widest area at or near the mounting end of the suspension. . The suspension body member is chemically etched into a flat stainless steel sheet having a thickness on the order of 60 to 75 μm. The etching operation ultimately forms an area that will include the mounting area 32, the spring 34, the load beam 36, and the rail 38.

After etching the suspension body member, a mechanical forming operation in this case imparts a feature which is in general in this case substantially perpendicular to the main surface of the rod beam 36 which is laterally isolated from the pair of rails 38 which are upwardly curved. . It also imparts a slight negative curvature (ie, a negative “sag” with a radius of curvature of about 236 mm) during the forming operation so that the center of the rod beam is ultimately weaker than the disk with a flat rod beam. It is arranged to be close to 3 mm. It should be noted that the curvature or sag imparted (according to the present invention) is in contrast to what normally occurs during uprail rod beam manufacturing according to the prior art. The size of the sag imparted is also about three times what occurs during normal rod beam manufacturing.

The rod plate 39, which is manufactured separately, is typically manufactured in advanced die operation and attached to the suspension 31 by conventional means, such as a spot. Similarly, the flexure (not shown) is spot welded or attached to the lower surface of the rod beam 36 in accordance with the prior art to complete the suspension 31. The read / write head 40 is attached to the flexure to terminate the manufacture of the HGA 30 in accordance with the preferred embodiment of the present invention.

Curve 52 in FIG. 5 shows the first torsional gain of the suspension 31 shown in FIG. 3 as a function of the given suspension offset. The optimal operating point of the rod beam embodiment with the sag of the present invention is about 3 dB lower in the first torsional gain than the prior art eight type suspension.

4 illustrates an alternative preferred embodiment of an HGA 42 in accordance with the present invention. In this embodiment, the rod beam 43 is a flexure that protruding features 44 having a height of about 0.08 mm are made on both rod beams 43 (or optionally on flexure 45). It is manufactured in accordance with the prior art in a generally flat configuration except that it is disposed between the rod beam 43 and the flexure 45 in the middle of the longitudinal end of the 45. The flexure 45 is spot welded or attached to the rod beam at the joining point 46 of the flexure proximal end and at the protruding feature 45, resulting in a curved flexure structure that supports the head 47. The flexure attachment mechanism imparts a negative sag to the load beam 43. Although the curved flexure embodiment eventually exhibits a somewhat higher nominal gain than the curved rod beam embodiment, the implementation is about 2 kW for an 8 type suspension according to the prior art, as shown in curve 54 of FIG. It may be easier to use while also providing a first torsional gain reduction.

In summary, the present invention provides a suspension for an actuator in a disc drive that simultaneously provides both a reduced first torsional gain and a reduced first torsional gain sensitivity compared to a suspension in the prior art. Reduced first torsional gain improves potential head position servo system performance, while reduced gain sensitivity improves manufacturing yield. As such, the present invention facilitates the design and manufacture of lower cost, high performance disk drives.

Although the present invention has been described in terms of fairly good embodiments, it should not be construed as limiting the disclosed method of the present invention. Without doubt, those skilled in the art having read the disclosure will clearly understand that various modifications and variations can be made to the invention. For example, while the present disclosure has been presented in connection with an uprail suspension design, the disclosure is also applicable to downrail-type designs. Accordingly, the appended claims should be construed to cover all such variations and modifications as fall within the spirit and scope of the invention.

Claims (15)

A suspension for supporting a read / write head adjacent to a disk of a disk drive, The mounting zone at the end of the suspension, Leaf spring connected to the mounting area, A cross section of a rod beam connected to the leaf spring, having a proximal end and a distal end that abuts the leaf spring, and taken along the central longitudinal axis of the rod beam, is a long, generally planar rod beam that is concave toward the disc, And flexure means attached to the distal end of the load beam and comprising a gimbal for pivotally supporting the read / write head. The suspension of claim 1, wherein the rod beam further comprises reinforcing rail means along the lateral edge. A suspension according to claim 2, wherein the rail means extends away from the disk. The suspension according to claim 2, wherein the rail means extends toward the disk. The suspension of claim 1, wherein the radius of curvature of the cross section is about 236 mm. In a cantilevered suspension supporting a read / write head adjacent to a disk of a disk drive, The mounting area at the proximal end of the suspension, Leaf spring connected to the mounting area, A long, generally planar rod beam connected to the leaf spring, A long, generally planar flexure having a proximal end attached coplanarly to the bottom of the load beam and a distal end with a gimbal for pivotally supporting the read / write head, the bottom of the load beam being the bottom of the load beam. A projection interposed between a central portion of the flexure from and separating the flexure. 7. The suspension of claim 6, wherein the rod beam further comprises reinforcing rail means along the lateral edges. 8. The suspension of claim 7, wherein the rail means extends away from the disk. The suspension according to claim 7, wherein the rail means extends toward the disk. The suspension of claim 6, wherein the height of the protrusion is about 3 mm. In a cantilevered suspension supporting a read / write head adjacent to a disk of a disk drive, The mounting area at the proximal end of the suspension, Leaf spring connected to the mounting area, A long, generally planar rod beam with unsupported ends connected to the leaf springs, A long, generally planar flexure having a proximal end attached coplanarly to the bottom of the load beam and a distal end with a gimbal for pivotally supporting the read / write head, the top of the load beam being at the bottom of the load beam. A suspension interposed between the central portion of the flexure from a face and separating the flexure. 12. The suspension according to claim 11, wherein the rod beam further comprises reinforcing rail means along the lateral edges. The suspension according to claim 12, wherein the rail means extends away from the disk. The suspension according to claim 12, wherein the rail means extends toward the disk. 12. The suspension of claim 11, wherein the height of the projections is about 3 mm.