HK1038634B

HK1038634B - Subambient pressure slider

Info

Publication number: HK1038634B
Application number: HK01108980.4A
Authority: HK
Inventors: E‧T‧查
Original assignee: 新科工业中心
Priority date: 1998-11-03
Filing date: 1999-10-27
Publication date: 2005-05-06

Description

Low-pressure sliding body

Technical Field

The present invention is directed to the design of air bearing sliders in disk drives. In particular, the present invention relates to a multi-layer surface structure for a low pressure air bearing slider.

Background

Hard disk drives are common information storage devices that basically comprise a series of rotating magnetic disks or platters that are accessible by magnetic read/write elements. Such data transfer members, commonly referred to as transducers, are typically carried and engaged by a slider body which is held in relatively close proximity over discrete data tracks formed on the disk. In order to properly position such transducers relative to the disk surface, an Air Bearing Surface (ABS) formed on the slider body is used to provide sufficient lift under the influence of an air flow to "fly" the slider body and transducer above the disk data tracks. The high speed rotation of the disk generates a stream of air flow or wind along its surface in a direction substantially parallel to the tangential velocity of the disk. This air flow cooperates with the ABS of the slider to enable the slider to fly above the spinning disk. In fact, the suspended slider is separated from the disk surface by the self-actuating air bearing. The ABS of the slider is typically formed on the surface of the slider facing the turntable and significantly affects the ability of the slider to fly above the disk under a variety of conditions.

Some of the primary goals in ABS designs are to fly the slider and its accompanying transducer as close as possible to the surface of the rotating disk while uniformly maintaining a constant approach distance regardless of varying flying conditions. The separation gap or height between the air bearing slider and the turntable is generally defined as the flying height. Typically, the mounted transducer or read/write device floats only a few micro-inches above the surface of the turntable. Many advantages are obtained when reducing or having a reduced flying height, for example. A smaller flying height allows for higher resolution between different data bit locations and the magnetic field emanating from closely defined areas on the disk surface. It is also known that low flying sliders improve the high density recording or storage capability of magnetic disks, which is generally limited by the distance between such transducers and the magnetic medium. The narrow pitch results in allowing shorter wavelength signals to be recorded or read. At the same time, with the proliferation of lightweight and compact notebook computers that utilize smaller but more powerful disk drives, there is an increasing need for a floating body that has a lower flying height and is more compact.

It is also noted that a constant flying height can provide the desired advantages that can be more quickly obtained with a particular ABS design. Fluctuations in flying height are known to be detrimental to the resolution and data transfer capabilities of the accompanying transducer or read/write device. The recorded or read signal amplitude does not vary much when the flying height is relatively constant. In addition, variations in flying height may cause unintended contact between the slider assembly and the turntable. The slider is generally considered to be either a direct contact, a pseudo-contact, or a floating slider of the type described as making intentional contact with the turntable. Regardless of the type of slider, it is often desirable to avoid unnecessary contact with the turntable surface to reduce wear on both the slider and the turntable. Deterioration or wear of the recording medium can result in loss of recorded data, and wear of the slider can eventually damage the transducer and magnetic device.

The reason for the variation in flying height is often that the slider moves through the turntable at a continuous high speed for read/write operations. For example, depending on the radial position of the slider, the relative linear velocity of the turntable will vary. Higher velocities are observed at the outer edge of the disk and lower velocities are observed at its inner edge. As a result, such air-cushion sliders float at different relative speeds at different radial positions with respect to the turntable. Because the slider generally floats higher at higher speeds, there is a tendency for the slider to increase its flying height when positioned on the outer region of the turntable. At the same time, the lower speed of the inner region of the turntable causes the slider to float lower. Therefore, the design of the slider must take into account the significant effect of the change in radial position and relative velocity on the flying height.

The flying height of the slider is also adversely affected by changes in skew angle. The skew angle is defined as the angle formed between the longitudinal axis of the slider and the direction of the airflow tangent to the disk rotation, and is measured by this side. When the mounted slider is located near the inner or outer edge of the turntable, its longitudinal axis is often skewed with respect to the direction of the airflow. The longitudinal axis of the slider body may be defined as a central reference line extending along the length of the slider body. This angular orientation or skew angle typically varies as the rotary actuator arm and gimbal suspension assembly is rotated about its pivot point, thereby causing the slider to move in a precise path through the turntable. In view of the increasing demand for drives having smaller disks with smaller actuator arms, larger skew angles are increasingly emerging due to the shortened length of the actuator arm. It has been observed that at skew angle values greater than zero, the slider is under a lower pressure value, which causes an undesirable reduction in flying height. Even at relatively moderate skew angles, the floating capacity of the slider is adversely affected. As a result, ABS designs continue to attempt to minimize slider sensitivity to changes in skew angle.

Another fluctuation in flying height is manifested in the slider roll point. The roll angle is measured and defined by the difference in flying height of the two longitudinal boundaries of the slider body. There may be an uneven pressure distribution between the ABS and the disk whenever the slider flies obliquely with respect to the direction of air flow. This imbalance causes the slider to roll, bringing one side of the slider closer to the disk surface than the other. The slider is preferably positioned at a constant slider roll angle regardless of any changes in the float conditions, including: the tangential speed difference between the inner and outer tracks of the turntable; continuous lateral movement over the surface of the turntable or varying skew angles.

As shown in FIG. 1, a known ABS design for use in a dual body slider 5 may be formed from a pair of parallel rails 2 and 4 extending along the outer edges of the slider surface facing the disk. Other ABS configurations have also been developed, including three or more other tracks and various surface areas and geometries. The two rails 2 and 4 generally extend along at least a portion of the length of the slider from a front edge 6 to a rear edge 8. The front edge 6 is defined as the edge of the slide 5 through which the turntable passes before passing the full length of the slide towards the rear edge 8. As shown, the leading edge 6 may be tapered, although machining in this regard often introduces undesirably large tolerances. As can be seen from fig. 1, the translator or magnetic member 7 is typically mounted at a position along the rear edge 8 of the slide. The rails 2 and 4 form an air bearing surface on which the slider body floats, while providing the necessary lift for contact with the air stream formed by the turntable. As the disk rotates, the resulting wind or air flow facilitates flow under and between the dual body slider rails 2 and 4. As this air flow passes under the tracks 2 and 4, the air pressure between the tracks and the turntable increases, providing a positive pressure and a positive lift. The two-piece slider typically generates a sufficient amount of lift or positive loading force to allow the slider to float at the proper height above the turntable. Without the rails 2 and 4, the large surface area of the slider 5 would create an excessive air bearing surface area. Generally, as the air bearing surface area increases, the lift created increases. Without the rails, the slider would fly too far from the turntable and all of the aforementioned advantages due to the low flying height would be lost. As shown in fig. 1, the use of a flexible universal joint (not shown) generally provides the slider with multiple degrees of freedom, such as in describing the vertical spacing of the slider's flying height, or pitch and roll angles.

Although dual body sliders initially provide adequate flying height, such sliders are particularly sensitive to variations in skew angle and other adverse flying conditions. As the skew angle increases, for example, as a floating slider passes over a turntable, the air pressure distribution under the track may change. When access is made to the inside and outside of the turntable at higher speeds, the air introduced in non-uniform amounts under the respective rails will normally cause the sliders to roll, as shown in fig. 1. As a result, the slider rolls in one direction under the influence of the uneven pressure distribution, resulting in uneven flying height between the ABS rails. The installed converter may therefore not be able to work efficiently or perform its data transfer job accurately. Regardless of the degree to which ABS rails are sensitive to various skew angle ranges and other adverse float conditions, such rail designs are widely believed to have a general configuration that provides effective boost or lift for slider float.

To provide a low constant flying height, in order to counteract the positive boost of the flying slider, it is known to form an ABS that also provides a negative or low pressure to pull the slider toward the disk. Negative pressure air cushions (NPAN) or self-contained sliders are known, for example, to provide a counteracting negative pressure load. In such dual pressure systems, the ABS may generally consist of a front edge, a rear edge, side rails, and a cross rail that extends between the pair of side rails in a substantially H-shaped orientation. The cross rail is often located closer to the front edge of the slider body than to the rear edge thereof, creating a low pressure zone behind the cross rail and between the two side rails. This low pressure region creates a negative pressure or load that counteracts the positive pressure created along the side rail portion of the ABS. The cancellation of this negative and positive pressure is known to improve slider stability and air bearing stiffness to facilitate quick slider removal while reducing sensitivity to changes in conditions that can cause fluctuations in flying height, such as disk speed and radial motion changes. Compensating for variations in positive and negative pressure based on the unequal velocity between the inner and outer tracks of the disk helps maintain the overall goal of a substantially constant flying height. However, such counteracting forces developed in low pressure systems often have the deleterious effect of causing fluctuations in flying height that in fact will result. NPAB sliders also often produce significant roll and lower flying height at skew conditions due to air pressurization or maldistribution under the track.

Another type of ABS track modification that has been developed is known as the transverse isobars (TPC). TPCs can be formed at different locations on the ABS along the edges of its air bearing surface area. This has been observed to provide some reduction in fly height variation at skew angles in some applications. When there is a lateral flow split of the air across the surface of the track, the isobars provided by the lateral edges of the TPC are affected by the positive pressure, while the isobars along the other lateral edge of the track create a negative pressure that balances the negative pressure. As a result, the overall pressure distribution across the ABS may remain relatively stable over some range of skew angle variations, where the lateral component of the airflow may result in uneven pressurization.

All of the above-described ABS configurations and modifications thereof for air bearing sliders are intended to achieve a low and constant flying height. These ABS designs provide varying degrees of effectiveness, but none of them provide good control of flying height or pitch and roll angles. For example, many existing ABS designs have been observed to significantly increase the slider roll angle over the outer track area of the disk. These designs also generally fail to control the increase in slider pitch angle when moving from the inner tracks to the outer tracks. Accordingly, there is a need for an ABS configuration for an air bearing slider that is effective in maintaining a constant flying height and controlling roll angle regardless of changing flying conditions, such as differences in the relative speeds of the outer and inner disk regions, the relative positioning of the slider on the turntable, and varying skew angle ranges.

Summary of The Invention

The present invention provides a low pressure air bearing slider having an Air Bearing Surface (ABS) that provides a low and constant flying height in the presence of a variable direction air flow. In addition, the slider design of the present invention provides a "rigid" air "cushion" that allows the slider to resist changes due to gram-order loading, allowing for a narrow distribution of variation in flying height and roll and pitch angles.

The rigid air cushion of the present invention is achieved by providing an auxiliary structure in the vicinity of at least one of the rails and in the low pressure region of the slider body. The auxiliary structure has a height lower than that of the rail, and serves to reduce the amount of load caused by the skew angle with the slider in the low pressure region.

Brief Description of Drawings

FIG. 1 is a perspective view of a floating slider with a read/write device assembly having a conventional dual body air bearing slider structure with a bevel.

Figure 2 is a plan view (not to scale) of an installed air slide of the present invention.

Figure 3 is a bottom plan view of a low pressure slide constructed in accordance with one embodiment of the invention.

Fig. 4 is a perspective view of the slider body of fig. 3.

Detailed Description

FIG. 3 is a bottom plan view of an ABS 10 for use with a low pressure slider of the present invention. It should be understood that for purposes of the following description of details of ABS, it is not shown that a substrate material such as Al may be used₂O₃TiC forming the whole slide. The ABS 10 shown in FIG. 3 includes a pair of rails 12 and 14, each having an effective air pad area 24 and 26. The inner rail 12 and outer rail 14 generally extend from a front edge 16 of the ABS to a rear edge 18. As shown in FIG. 3, the ABS rails 12 and 14 are formed into the desired configuration by conventional techniques in accordance with an aspect of the present invention. The rails 12 and 14 are joined together by a front portion 15 at a slider front edge 16. In this embodiment of the invention this front portion 15 forms a step with the bearing area 17 of the slide. In FIG. 3, the step structure is formed by etching the slider in the bearing region 17 to, for example, 10 to 50 microinchesIs formed by the depth of (a). This step structure extends between the front edge 16 and the front portion 15. And to the outside of rails 12 and 14. Alternatively, a ramp structure extending from the front edge 16 of the slider body 10 to the front portion 10 may be used, as is well known in the art.

In fig. 3, there is provided a low pressure zone 19 extending between the rails 12 and 14 and the front portion 15. The low pressure region 19 can be formed, for example, by etching the region to a depth of 70-200 microinches (e.g., 100 microinches). Another embodiment of the present invention is illustrated in figure 3 by a bottom view of a preferred low pressure air bearing slider body. The general directions of the air flow in the outer, middle and inner regions of the disk with respect to the variation position of the slider ABS 10 are indicated by arrows AF in FIG. 3_CD、AF_MD、AF_IDAnd (4) showing. It is again noted that the slider is typically attached to an actuator arm and gimbal assembly that pivots about a pivot point, thereby changing the direction of the air flow relative to the slider's ABS as the slider moves across the rotating disk between the inner diameter region and the outer diameter region. The present invention can be used with sliders of various sizes, but the dimensional ratios provided in FIG. 3 indicate that the overall dimensions of the slider ABS 10 are approximately 0.05 inches long, 0.039 inches wide and 0.012 inches high (not shown), with sliders having the relative dimensions described above generally referred to as subminiature sliders. As is known in the art, the low pressure region creates a pressure region of less than 1 atmosphere (atm) when the slider is flying above the surface of the moving disk. This low pressure acts against the compression effect created by the slider ABS 24 and ABS 26, pulling the slider closer to the moving disk.

Referring to fig. 3, the tracks 12 and 14 are "balloon-shaped" to provide a unique effective air bearing surface for each track, respectively. Details regarding this shape and its effect on flying height are described in U.S. patent application No.081705774 filed on 1996, 8/30, the entire contents of which are incorporated herein by reference. For example, the inner rail 12 is formed of an effective air bearing surface area and a compressed length. As the skew angle changes and the slider moves toward the outer diameter zone, the reduction in effective surface area and compression length caused by side leakage (reduced lift at the side of the track where air leaks) is minimized as a result of the profiled air bearing surfaces of the tracks 12 and 14 shown in fig. 3. When the slide is moved towards the inner diameter area, the effective surface area and the compression length are also reduced for the same reason. Furthermore, the superior configuration of the air bearing surface minimizes the loss effects of effective surface area and compression length in the inner diameter region. The particular configuration of the air bearing surface of outer rail 14 provides similar results in various regions of the disk.

According to an embodiment of the present invention, the slider 10 is provided with auxiliary structures 21 and 23 with respect to the rails 12 and 14, respectively. The auxiliary structures 21 and 23 are located in the low-voltage region 19 and have a height lower than the height of the rails 12 and 14. In this embodiment, the auxiliary structures 21 and 23 are etched to a depth equal to the support region 17. As previously described, rails 12 and 14 have a "balloon" shape characterized by a neck 25, 27 and a rear 29, 31, the rear having a width greater than the neck. Each rear portion 29, 31 comprises an inner rail edge 33, 35 facing the low-pressure area 19 of the slide 10. In particular, the respective inner rail edges are angled relative to the longitudinal axis 40 of the slider body 10.

In operation, the air flow AF occurs when the slider 10 is in the outer diameter region of a moving disk_oDThe auxiliary structure 23 is impacted, creating a pressure greater than the pressure of the low-pressure zone 19 but less than 1 atm. The secondary structure 23 in this embodiment is about 6.0mils (0.006 inches) wide. The auxiliary structure 21 will also have a pressure greater than the pressure of the low-pressure zone 19, but less than the pressure of the auxiliary structure 23 (e.g., about 0.7 atm). When the sliding body 10 moves from the outer diameter region to the inner diameter region, the pressure of the auxiliary structure 23 is decreased and the pressure of the auxiliary structure 21 is increased to an amount less than 1 atm. The width of the auxiliary structure 21 in this embodiment is about 5.0 mils (or 0.005 inches). The width of the auxiliary structures 21, 23 (measured from the inner edge 33 to the low-pressure region 19) can be chosen such that the above-mentioned region of pressurization is enlarged. For example, in the embodiment of fig. 3, the width of the auxiliary structure 21 is greater than that of the auxiliary structure 23. Thus, when the slider is in the outer diameter region, the pressure in this low pressure region 19 is at its lowest value (i.e. provides the greatest suction to the moving disk), while the auxiliary structure 21 serves to counteract this effect (i.e. to increase the total pressure in the low pressure region). The width of the auxiliary structure 23 is selected to achieve thisAnd (4) pressurization is required. Having a narrower auxiliary structure (i.e. structure 23) may be advantageous to counteract this effect when the pressure in the low pressure region is higher when the slide is in the region of the inner diameter. It will be appreciated by those skilled in the art that the slider design of figure 3 may be modified to provide only one auxiliary structure.

It should be noted that in order to avoid the large skew angles known to significantly impede the boost and lift of the sliding body, a zero skew angle is typically set near the mid-diameter region. In this manner, the value of skew angle can be kept low regardless of how the slider is skewed toward the outer or inner region of the disk. Of course, the zero skew angle may also be defined near the inner region of the disk where the effective surface area and compression length of the ABS may be maximized to compensate for the lower air flow velocity in this region. The skew angle value generally becomes significantly higher than in the above-described arrangement and often has an adverse effect on slider pressurization as the slider moves outward over other areas of the disk. In either of the above examples, the pressure and lift drop that typically occurs with a generally rectangular track when floating diagonally is minimized by the contoured air bearing surface and auxiliary structure formed in accordance with the present invention. The overall result of the ABS configuration provided by the present invention is a slider that floats at a relatively constant height under skew conditions while controlling the pitch and roll angles to a greater degree.

Fig. 4 is a perspective view of the slider 10 of fig. 3.

Referring to FIG. 2, there is shown another embodiment of the invention in which a slider (not drawn to scale) is mounted suspended from a rotating magnetic disk 70 by an actuator or knuckle arm and gimbal assembly 72. The slider is mounted on a gimbal 74 that allows the degree of free movement of the slider relative to the disk surface 76 to be varied. This track arm may be moved in a manner known as linear access (not shown) to where the read/write device travels a relatively straight path through the turntable. Alternatively, the arm and gimbal assembly 72 may rotate about an axis or fulcrum in what is commonly referred to as a rotary actuator. The gimbal 74 and slider may be connected by a rotary actuator via a knuckle arm and gimbal suspension assembly to position the slider along precise paths 78 over selected data tracks on the disk surface 76. In either system, the gimbal 74 provides a flexible and resilient connection that allows the floating slider and attached transducer to follow the contour of the turntable at different locations on the disk. In this example, when the slider ABS 40 (shown as device 10 in FIGS. 3 and 4) is located in the mid-diameter region (MD) of the turntable, the skew angle is zero because the longitudinal axis of the slider is parallel to the airflow. The intermediate effect of this pressurization is seen in the mid-diameter region of the disk due to the presence of the auxiliary structure. However, as the slider ABS 40 moves outward toward the outer diameter region (OD), air flows substantially perpendicular to the auxiliary structure 23, increasing the pressure in the outer diameter region. As the slider ABS 40 moves toward the inner diameter region (ID), the airflow is substantially perpendicular to the auxiliary structure 21, providing the necessary pressure for pressurization of the inner diameter region.

While the invention has been described in connection with the above applications, the description of the preferred embodiments is not intended to be limiting. It is to be understood that the aspects of the present invention are not limited to the specific depictions, configurations or dimensions set forth herein which depend upon a variety of aerodynamic principles and variables and which may be determined by computer modeling methodologies utilizing, for example, computer modeling programs developed by the computer mechanics laboratory at the university of California, Burkhelli, California. Various modifications in form and detail of the disclosed apparatus, as well as other variations of the disclosed apparatus, will be apparent to persons skilled in the art upon reference to the disclosure herein. It is therefore contemplated that the appended claims will cover any such modifications and variations of the described embodiments as falling within the true spirit and scope of the present invention.

Claims

1. A low pressure air bearing slider comprising:

a slider body defined by a front edge and two side edges extending longitudinally of the slider body, having an air bearing surface comprising a front portion and first and second longitudinally extending rails connected together by the front portion, each of the first and second rails comprising a neck portion and a rear portion, wherein the rear portion has a greater width than the neck portion, the front portion and the first and second rails forming a low pressure region when the slider floats above a moving recording medium, and each of the rear portions comprising an inner rail edge facing the low pressure region such that each of the inner rail edges forms an angle of greater than 0 ° with a longitudinal axis of the slider; and

a first auxiliary structure, the height of which is lower than the height of the first and the second tracks and is arranged near one of the edges of the inner track.

2. The low pressure air bearing slider body of claim 1, further comprising a second auxiliary structure having a height less than the height of said first and second tracks and disposed adjacent to the other of said inner rail edges.

3. The low pressure air bearing slider body of claim 1, wherein the pressure at said first auxiliary structure is less than 1 atmosphere when said slider body is positioned over a moving medium.

4. The low pressure air bearing slider body of claim 3, wherein the pressure at said first auxiliary structure is less than 1 atmosphere across all diametrical regions of said moving media.

5. The low pressure air bearing slider body of claim 2, wherein the pressure at said first and secondary structures is less than 1 atmosphere when said slider body is positioned over a moving medium.

6. The low pressure air bearing slider body as described in claim 5, wherein the pressure at said first and auxiliary structures is less than 1 atmosphere across all diameter regions of said moving media.

7. A head suspension assembly comprising;

a flexible member, which is provided with a plurality of flexible parts,

a slider body connected to the flexure, the slider body including a slider body defined by a front edge and two side edges extending longitudinally along the body, and having an air bearing surface comprising a front portion and first and second longitudinally extending rails connected together by the front portion, each of the first and second rails including a neck portion and a rear portion, wherein the rear portion has a greater width than the neck portion, the front portion and the first and second rails forming a low pressure region when the slider floats above a moving recording medium, and each of the rear portions including an inner rail edge facing the low pressure region such that each of the inner rail edges forms an angle greater than 0 ° with a longitudinal axis of the slider body; and

8. The head suspension assembly of claim 7 wherein the slider further includes a second auxiliary structure having a height less than the height of the first and second rails and disposed proximate another of the inner rail edges.

9. The head suspension assembly of claim 7 wherein the pressure at the first auxiliary structure is less than 1 atmosphere when the slider is positioned over a moving medium.

10. The head suspension assembly as recited in claim 9 wherein the pressure at said first auxiliary structure is less than 1 atmosphere across all diameter regions of said moving media.

11. The head suspension assembly of claim 8 wherein the pressure at the first and auxiliary structures is less than 1 atmosphere when the slider is positioned over a moving medium.

12. The head suspension assembly as recited in claim 11 wherein the pressure at said first and auxiliary structures is less than 1 atmosphere across all diameter regions of said moving media.

13. A disk drive, comprising:

a rotated magnetic disk;

a flexible member; and

a slider body connected to the flexure, the slider body including a slider body defined by a front edge and two side edges extending longitudinally of the slider body, and having an air bearing surface comprising a front portion and first and second longitudinally extending rails connected together by the front portion, each of the first and second rails including a neck portion and a back portion, wherein the back portion has a greater width than the neck portion, the front portion and the first and second rails form a low pressure region when the slider body floats above a moving recording medium, and each of the back portions includes an inner rail edge facing the low pressure region such that each of the inner rail edges forms an angle of greater than 0 ° with a longitudinal axis of the slider body; and

14. The disk drive of claim 13 wherein said slider further includes a second auxiliary structure having a height less than the height of said first and second tracks and disposed adjacent the other of said inner rail edges.

15. The disk drive of claim 13 wherein the pressure at said first auxiliary structure is less than 1 atmosphere when said slider is positioned over said disk in rotation.

16. The disk drive set forth in claim 15 wherein the pressure at said first auxiliary structure is less than 1 atmosphere across all diameter regions of said moving media.

17. The disk drive of claim 13 wherein the pressure at the first and auxiliary structures is less than 1 atmosphere when the slider is positioned over the rotating disk.

18. The disk drive set forth in claim 17 wherein the pressure at said first and auxiliary structures is less than 1 atmosphere across all diameter regions of said moving media.