Pseudo contact type negative pressure air bearing slider

A negative pressure air bearing slider includes a slider body for flying above a surface of a recording disc during relative rotation of the recording disc. First and second projections extend from a lead portion of a principal surface of the slider body to define first and second air bearing surfaces, respectively, the first and second air bearing surfaces being spaced apart from each other in the lateral direction of said slider body. A third U-shaped projection extends from the principal surface and includes a curved front wall portion at least partially located between the first and second projections and first and second side wall portions extending from opposite ends of the curved front wall portion to a rear portion of the principal surface so as to define a rounded negative pressure cavity therein. A fourth projection extends from the rear portion of the principal surface of the slider body at a position centrally located in the lateral direction of the slider body, and a transducer is mounted on a rear edge of the third projection so as to establish pseudo contact with the disc surface while the slider body is flying above the disc surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic disk drive device, and in particular, to a pseudo contact type negative pressure air bearing slider for a transducer head assembly of a magnetic disk drive device.

2. Description of the Related Art

Transducer head assemblies have been designed to literally fly over a rapidly rotating disc, and include an air bearing slider for carrying a magnetic transducer proximate a rapidly rotating disc. The transducer, in the case of pseudo contact type sliders, is generally a thin-film head.

Computer disk drive technology evolution has focused on improvements in “areal density”, or the number of bits of information that can be stored in a given space on a magnetic disk. Over the last decade, the majority of progress has been gained through miniaturization of the recording heads and improving the magnetic efficiency of the write/read elements in the heads, and similar improvements in the magnetic and physical properties of the disks.

As suggested above, disk drives contain a plurality of recording heads that “fly” over rotating disks. The magnetic recording efficiency is a function of many physical characteristics of the heads and disks, the most significant of which is the spacing between the rotating disk surface and the recording head “pole” elements. The most straightforward method for manufacturers to improve areal density has been to reduce the spacing between the head disk, without sacrificing the long term reliability of the disk drive.

Across the previous disk drive industry product offerings, head-disk spacing had steadily decreased from several micro-inches to less than two micro-inches, until there came a point that further increases in areal density required the head to essentially touch the disk during flying. A new class of so-called “pseudo-contact” heads were developed in which the rear portion of the head, where the transducer poles are located, is in constant contact with the disk surface. Various design characteristics were developed to minimize friction and wear between the disk and head, and such “pseudo-contact” designs have proven to be as reliable over the long-term as the non-contact designs.

In magnetic disk technologies, it is generally desired to achieve higher data recording densities without a substantial change in form factor. In the context of the air bearing slider, increased recording densities are obtainable by maintaining the flying height, pitch angle and roll angle constant over the whole disk surface, to thereby enhance floating stability and contact start stop (CSS) reliability. In the case of the pseudo contact type slider, the “flying height” of the slider in effect refers to the pressure (or lack of pressure) applied to the disk surface by the assembly, and in particular, by the thin film transducer. Ideally, the slider should fly at a height in which the transducer makes pseudo contact with the disk surface at minimum pressure.

On the one hand, the magnetic head must fly at a sufficient height to avoid frictionally related problems caused by excessive physical contact during data communication between the magnetic head and the rapidly rotating disk. On the other hand, the head should be made to fly as low as possible to obtain the highest possible recording densities. As the magnetic head is fixed to the slider mechanism, the disk recording density increases as the flying height of the slider decreases. Accordingly, it is preferred that the slider fly as close as possible to the disk surface. A constant flying height is preferably maintained, regardless of variations in tangential velocity during flying, cross movements of the slider during data search operations, and changes in skew angle in the case of rotary type actuators.

To achieve stable flying characteristics, the slider should also fly at a pitch angle that falls within a safe range of a predetermined value. The pitch angle is defined as the tilt angle between the principal plane of the slider in the tangential direction of the rotating disc and the principal plane of the disc surface. The pitch angle is positive in the normal case in which the flying height of the rear portion of the slider is lower than that of the front portion of the slider. A transducer is generally situated at the lowest position of the rear portion of the slider for maximizing recording data capacity. If the designed pitch angle is too small, the possibility exists that a disturbance will cause the front end of the slidertodip down such that a negative pitch ensues resulting in a collision with the rapidly rotating disk. On the other hand, if the designed pitch angle is too large, the air stiffness needed for stable flying can be disadvantageously reduced. Therefore, to maintain stability while avoiding the situation of a negative pitch angle, the slider should be configured such that the pitch angle can be controlled to fall within an optimum value range. Another factor to consider regarding pitch angle is the general tendency for the pitch angle to increase with skew angle increases as the slider is positioned in a radially outward direction over the disc surface. Thus, the pitch angle should fall within the safe range regardless of skew angle variations.

Differing hydrodynamic forces support the inner and outer air bearing surface (ABS) rails of the slider, and resulting variations in side leakage air flow with skew angle changes can generate roll angle variations. Here, the inner and outer rails refer to those ABS rails of the slider positioned toward the inner periphery and outer periphery of the disc, respectively. Also, roll angle is defined as the tilt angle between the principal plane of the slider in the radial direction of the disc and the principal plane of the disc surface. As the transducer is usually centrally located on the rear slider edge in the case of pseudo contact slider, optimum performance is obtained by avoiding roll angle over the entire disk surface area.

FIG. 1is a schematic perspective view of a conventional tapered flat slider. InFIG. 1, two rails11a are formed in parallel at a predetermined height on a surface of a slim hexahedron body10a to thus form lengthwise extending ABS's. A tapered or sloped portion12a is formed at each leading edge portion of the ABS rails11a. In such a structure, air within a very thin boundary layer rotates together with the rotation of the disk due to surface friction. When passing between the rotating disk and the slider, the air is compressed by the ramp12a on the leading edge of the ABS11a. This pressure creates a hydrodynamic lifting force at the ramp section which is sustained through the trailing edge of the ABS, thus allowing the slider to fly without contacting the disk surface.

The conventional slider of this type suffers a drawback in that the flying height, pitch angle and roll angle vary considerably according to the skew angle of the rotary type actuator, i.e., according to the radial position of the slider over the disc surface. For flying heights of 3.0 millionths of an inch and greater, minor height and tilt fluctuations in the slider do not generally affect the read/write operations of the disk. However, current-day standards require flying heights below 2.0 millionths of an inch. At such small flying heights, even minor variations in flying height, pitch angle and roll angle can severely affect the reliability of the head read/write function of a hard disk drive.

An improved configuration aimed at countering flying height variations over the entire disc surface is the transverse pressure contour (TPC) slider, as described, for example, in U.S. Pat. No. 4,673,996. As shown inFIG. 2herein, this slider is also characterized by ABS rails11b formed on a slider body10b, and ramp portions12b formed at the leading edge of the ABS rails11b. In addition, however, a step-down111b is formed lengthwise on the both sides of each of the ABS rails11b. The slider of this TPC structure has the advantage of maintaining reasonably constant flying height regardless of skew angle variations. However, this TPC slider exhibitsreducereducedflying stability which is caused by insufficient air stiffness resulting in the reduction of the ABS surface area. Also, the TPC modification does not improve pitch and roll angle variations resulting from changes in skew angle.

In light of the above, to better realize a constant flying height and constant pitch and roll angles and to obtain an improve contact start stop (CSS) performance, most current air bearing sliders have adopted a negative pressure air bearing (NPAB) type of configuration with a variety of air bearing surface shape changes. A basic NPAB slider has the same structure of the slider shown inFIG. 1, together with a cross rail connecting the ABS rails. That is, as shown inFIG. 3, two ABS rails11c each having a slope12c at a leading edge thereof are formed in parallel on a surface of a body10c. A cross rail13c having the same height as the ABS rail11c is formed between the rails11c proximate the slopes12c. The cross rail13c creates a negative pressure cavity14c15cin proximity to the central surface portion of the body10c. Thus, since the pressure of the air passing over the cross rail is diffused as it passes the negative pressure cavity14c15c, a pulling or suction force is downwardly applied on the slider which reduces suspension gram load and provides the advantage of a fast take off from the disc surface. The counter action between the positive and negative forces reduces the sensitivity of the slider flying height relative to disc velocity and increases the slider stiffness characteristics.

Because of sub-ambient pressure of cavity14c15c, roll angle during a high skew condition can worsen, meaning that the NPAB slider ofFIG. 3exhibits more negative roll effects at high skew positions than the convention tapered flat slider of FIG.1. Also, there is a tendency for debris to gather at the cross-rail13c. Such debris can ultimately have an adverse effect on performance.

SUMMARY OF THE INVENTION

In consideration of the above, it is an object of the present invention to provide a negative pressure air bearing slider for a hard disk drive in which the application of negative pressure is stable, and the accumulation of debris is minimized.

It is another object of the present invention to provide a negative pressure air bearing slider for a hard disk drive which can maintain a relatively constant flying height regardless of skew angle.

It is still another object of the present invention to provide a negative pressure air bearing slider for a hard disk drive in which roll angle variations are minimized, sufficient air stiffness is maintained, and a constant optimum pitch angle is held.

Accordingly, to achieve the above and other objects, there is provided according to the invention a negative pressure air bearing slider, comprising: a slider body for flying above a surface of a recording disc during relative rotation of the recording disc, the slider body having a principal surface for confronting the disc surface, said principal surface having a lead portion, a rear portion, a first side portion and a second side portion, wherein the lead portion is spaced upstream of the rear portion relative to a longitudinal direction of said slider body which is coincident with a tangential rotational direction of the recording disc, and wherein the first side portion is spaced from the second side portion relative to a lateral direction of said slider body; first and second projections extending from said lead portion of said principal surface of said main body to define first and second air bearing surfaces, respectively, wherein said first and second air bearing surfaces are spaced apart from each other in the lateral direction of said slider body; and athirdU-shapedthirdprojection extending from said principal surface and having a curved front wall portion at least partially located between said first and second projections andcurvedfirst and second side wall portions extending from opposite ends of said curved front wall portion to said rear portion of said principal surface so as to define a rounded negative pressure cavity therein, said curved front wall portion and said first and second curved side wall portions being spaced apart from said first and second projections, wherein the first and second curved side wall portions respectively extend along said first and second side portions of said principal surface and define third and fourth air bearing surfaces located at said rear portion of said principal surface andspacespacedapart from each other relative to the radial direction of said slider body; a fourth projection extending from said rear portion of said principal surface of said slider body at a position centrally located in the lateral direction of said slider body; and a transducer mounted on a rear edge of said third projection so as to establish pseudo contact with the disc surface while said slider body is flying above said disc surface.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 4 and 5respectively illustrate a perspective view and a plan view of one embodiment of a negative pressure slider for a hard disk driver according to the present invention.

As shown inFIGS. 4 and 5, first and second lead ABS platforms110a and110b are provided at a lead surface portion of a slider body100projecting from a principal surface111thereof. The lead ABS platforms110a and110b are symmetrically or unsymmetrically disposed on opposite sides of a longitudinal axis L of the slider body100and are aligned with one another along alongitudinallateralaxis H, and thus in a lateral direction of the slider body100, and provide a positive lifting force at an air inlet between the slider body100and the disc surface (not shown). Also, a ramp portion120extends from a lead edge121of the slider body100to the ABS platforms110a and110b.

Trailing ABS110c and110d are provided at the rear surface portion of the slider body100adjacent a rear edge123thereof. These trailing ABS platforms110c and110d are symmetrically disposed on opposite sides of a central longitudinal axisLof the slider body100and are aligned with one another inalateral direction of the slider body100, and provide a positive lifting force at an air outlet between the slider body100and the disc surface (not shown). In operation, the front and rear ABS platforms110a,110b,110c and110d generate sufficient positive pressure to support the slider body100in a suspended state above a rotating disk of a hard disk drive.

In addition, as shown inFIGS. 4 and 5, an arcuate cross rail130extends across the principal surface111of the slider100and between the rear ABS platforms110c and110d and lead ABS platforms110a and110b and generally along the latitudinal axis H. The arcuate cross rail130and the rear ABS platforms110c and110d together define a substantially U-shaped projection that extends from theprincipleprincipalsurface111of the slider100. The curvature of the cross rail130forms a negative pressure cavity150, that may be somewhat rounded, at the center of the slider body100.

Additionally, a forwardmost portion131of the arcuate cross rail130may be generally aligned with the longitudinal axis L of the slider body100and positioned partially between the lead ABS platforms110a,110b. However, the cross rail130is positioned a distance from a rear edge133a133b of each of the lead ABS platforms110a,110b to form a pair of wide passage135a,135b therebetween. The wide passages135a,135b coact with a wide space135c extending from the lead edge121and interposed between the lead ABS platforms110a,110b and generally aligned with the longitudinal axis L, to form a wide air flow channel135that terminates along the sides of the slider body100. The configuration of the air flow channel135enhances the stability of the slider100, particularly as the skew angle of air flowing past the slider body100increases. The configuration of the air flow channel135and cross rail130provide further advantages to be discussed more thoroughly hereinafter. It is noted that the arcuate cross rail130should be made as thin as possible to avoid adverse influence on the positive pressure areas created by the four separate and distinct air bearing surfaces110a,110b,110c,110d, while simultaneously providing a stable and centrally located negative pressure area150.

The negative pressure cavity150functions to provide a downward pulling action on the slider body100, which in turn creates a gram load equivalent effect that enhances stability. The rounded configuration of both the negative pressure cavity150and the cross rail130reduces the skew angle dependency on the magnitude of gram load equivalency. Since the negative pressure cavity is rounded, angular variations in the direction of air flow resulting from skew angle changes do not substantially alter the action of the negative pressure cavity150. This results in reduced flying characteristic (flying height and roll angle) variations as the slider is positioned at different diameters along the disc surface. Skew angle related variations are further minimized by the four stable positive lifting forces positioned at each corner around the centrally located negative pressure cavity.

Another advantage of the arcuate configuration of the cross rail130resides in the fact that contaminates will have less of a tendency to accumulate against the front wall of the cross rail. That is, contaminates will instead tend to travel along the arcuate front wall and exit off the side of the slider body between the gaps formed by the front corner ABS projections. This also enhances read/write performance of the slider100over the long run.

Reference numeral180ofFIG. 4denotes a centrally located rail for mounting of the transducer. In particular, the transducer is mounted on the rear edge123of the rail180, so as to make pseudo contact with the recording disc during flight of the slider body100. As shown, the rear edge123of the rail180is located further to the rear of the slider body100than is the rear edges of the ABS platforms100c110cand100d110d.

As shown inFIG. 6FIGS.6(b),6(a), the cross rail130may berespectivelysmoothly configured without inner or outer corners, or it instead may be formed by a series of connected straight sidewall segments, or a combination thereof. In any case, a substantially rounded negative pressure region is formed in proximity to the geometrical center of the slider bodyby negative pressure cavity150.

Referring again toFIG. 4, the air that supports lead ABS platforms110a and110b is initially compressed through action of the respective ramp regions120positioned at the front edge121of the slider body100. The amount of air can be adjusted by changing the inclination angle of the ramp120. Lithography techniques are used to create complex NPAB-type sliders, and a typical inclination of the etched surface obtained through lithography is around 18 degrees. Also, as shown inFIG. 7, the slider ramp regions120can be completely replaced by shallow recessed edge steps121120through a lithography process.

FIG. 8illustrates an approach for minimizing side air flow leakage and increasing the amount of air supporting the rear ABS platform. In this embodiment, an interface region between the ABS rail110c and the cross rail130includes a stepped down surface portion112extending between the ABS platform110c and an edge of the slider body100, and a stepped down surface portion113extending between the ABS platform110c and said negative pressure cavity150. Similarly, an interface region between the ABS platform110d and the cross rail130includes a stepped down surface portion115extending between the ABS platform110c and another edge of the slider body100, and a stepped down surface portion114extending between the ABS platform110d and said negative pressure cavity150. Particularly under the condition of a skew angle variation, additional pressure is accumulated at the step portions112,113,114and115, and as a result, more compressed air is applied to the rear ABS platform and the effects of skew angle variations can be reduced. It may also be useful to prepare unsymmetrical shallow edge steps so as to maximize the effects of the edge step functions.

Further modifications of the invention will now be described with reference toFIGS. 9-12.

Characteristics of the negative pressure cavity150may in some instances retard the take-off of the slider during an initial operational phase. This problem is largely overcome by the provision of a shallow recessed step131on the cross rail130as shown in FIG.9. The recessed step131allows sufficient air flow through the negative pressure cavity150to prevent delay in the slider take-off period. This recessed step can also reduce debris accumulation on the cross rail130.

As an alternative to the recess131, a gap132in the cross rail130may instead be provided as shown in FIG.10. This configuration provides similar results of relieving the negative pressure during take-off and reducing debris accumulation.

The recess131and the gap132ofFIGS. 9 and 10are symmetrically disposed on opposite sides of a central longitudinal axis of the slider body.FIGS. 11 and 12illustrate alterative configurations in which the recess133and the gap134are offset from the longitudinal axis. In addition to the advantages of relieving negative pressure during take-off and reducing debris accumulation, these offset configurations provide a mechanism for biasing the aerodynamic characteristics to combat the problem of negative roll.

Referring once again toFIGS. 4,8,9and12, it is noted that the rear rail180,181,182and183can be configured any number of ways. Moreover, these rails can function as an additional ABS to enhance flying stability. The particular configuration chosen should have the dual functions of providing a hydrodynamic lifting force and minimizing debris accumulation. The sharpened or rounded leading edge of the rear rail will avoid debris accumulation, while the size of its ABS surface will dictate the degree of lifting force.

As described above, the NPAB type slider of the invention provides a relatively constant flying height, minimized roll and pitch angle variations, and excellent reliability. During operation, most of the positive pressure is generated at the four corner ABS's, and since the cross rail has a curved configuration, negative pressure is generated at a geometrical central area. This results in stable flying characteristics without substantial variations in the flying height and pitch and roll angles throughout the entire data range. Additionally, the arcuate configuration of the cross rail minimizes contaminant accumulation.

While the present invention has been described in terms of the embodiments described above, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims and their equivalents.