AN AIR BEARING SLIDER

Abstract: The underside of an air bearing slider comprises a recessed section (18) disposed between a pair of corresponding side rails (12,14) which extend from the leading end (20) to the trailing end (22) of the slider. The leading end of each side rail is chamfered and the leading portion of each side rail is wider than an intermediate portion of the rail. The trailing portion of each rail may (FIG. 10) flare outwards to accommodate a relatively wide transducer head (24). The structure produces a combined pressure profile which causes the slider to fly with the leading end at a desired pitch angle relative to a moving record medium, with the minimum spacing between the slider and the record medium at the trailing end, where the transducer is mounted.

Description: This invention relates to an air bearing slider for supporting a transducer relative to a moving record medium. Magnetic head assemblies that fly relative to magnetic media have been used extensively. These assemblies provide a noncontact transducing relationship between a magnetic transducer and a magnetic recording medium, such as a rotating magnetic disk, so that a stable constant spacing can be maintained between the transducer and the disk. In magnetic recording technology it is continually desired to improve the areal density at which information can be recorded and reliably read. This desire has led to a trend toward greater bit density along a magnetic recording track and a shrinking track width. The greater bit density requires increasingly narrow transducing gaps, so it becomes more difficult to achieve the low flying height required and to maintain this flying height constant to the degree required to reliably record and read data at the higher data rates. The so-called taper-flat air bearing slider has been widely used, and this slider comprises two side rails, a recessed area between the side rails and a taper formed across the leading end of the side rails. A three rail embodiment is disclosed in U.S. - A- 3,823,416. A variant of this in which the side rails are not of constant width is disclosed in JP-A-60101781. EP-A-76361 discloses a transducer slider with a cross rail at the front joining a pair of side rails so that there is a recessed section trailing the cross rail and defined by the three rails. Each of the side rails has an initial portion of constant width extending back from the cross rail to a break point and a wider portion extending back from the break point to the trailing edge of the slider. A similar device, but with the trailing portion of each of the rails narrower than the leading portion, is disclosed in EP-A-0110212. Some taper-flat air bearing sliders have the pivot point for suspension attachment located behind the centre line of the slider. A disadvantage of this slider occurs since the resulting imbalance produces increased yaw motion during accessing which results in a longer settling time once the desired track is reached and therefore a longer access time. A central pivot suspension attachment eliminates this impact to access time. However, this solution results in a decrease of the flying pitch angle and an increase in the flying height. While it is possible to reduce the side rail width to maintain the original flying height, the flying pitch angle may not be optimum for stability and dynamic performance thereby making it difficult to meet the reliability requirements for recording and reading data at the higher data rates. Independent of suspension attachment, one way to produce a lower flying height for a taper-flat air bearing slider to meet the greater bit density requirements is to reduce the slider rail width. While this proposal is operable to achieve a lower flying height, a resultant disadvantage is that the slider flies at a pitch angle that is not optimum. This invention seeks to provide an air bearing slider which produces a pressure profile which causes the slider to fly at a reduced flying height and at a desired pitch angle with respect to a moving record medium without increasing the access time. The invention provides an air bearing slider for supporting a transducer relative to a moving record medium, the underside of the slider being formed to provide a pair of corresponding spaced apart side rails; there is a recessed section open at both ends extending from the leading end of the slider to its trailing end, each of the side rails being chamfered at its leading end and having a leading portion, an intermediate portion and a trailing portion, the leading portion being wider than the intermediate portion and the trailing portion over substantially the whole of their respective lengths said leading and trailing portions being of substantially constant width and said intermediate portion becoming progressively narrower to a breakpoint. The air bearing slider structure produces a combined pressure profile which causes the slider to fly with the leading end at a desired pitch angle with respect to a moving record medium, such as a magnetic disk, with the minimum spacing between the slider and the record medium at the trailing end, where the transducer is mounted. This air bearing slider structure also permits the flying pitch angle to be chosen independent of the flying height so that the desired dynamic performance and stability can be achieved in order to minimise contact with the record medium. In addition, this slider structure does not adversely affect the access time for the storage system in which the slider is used. In a second preferred embodiment, the side rails are flared out at the trailing end of the slider. This embodiment has the advantage of providing a greater area at the trailing end of the side rails so that this added area is available for deposition of the transducer, if required. How the invention can be carried out will now be described by way of example, with reference to the accompanying drawings, in which:- FIG. 1 is a bottom plan of an air bearing slider embodying the invention. FIG. 2a shows a three dimensional front bottom view of a preferred embodiment of an air bearing slider; FIG. 2b is a bottom plan view of the slider shown in FIGS. 2a and 2b; FIG. 3 is a side elevation of the sliders of FIG. 1 and FIGS. 2a and 2b; FIG. 4 is a representation of a pressure profile indicating the distribution of pressure, as measured along the air bearing surface of the slider of FIG. 2; FIG. 5 is a graph plotting the change in flying height vs. relief depth for the embodiment of the slider shown in FIGS. 2a and 2b; FIG. 6 is a graph plotting the change in pitch angle vs. rail ratio for a slider similar to that shown in FIGS. 2a and 2b; FIG. 7 is a graph plotting spacing change vs. rail ratio for the slider of FIGS. 2a and 2b; FIG. 8 is a graph plotting the change in pitch angle vs. length ratio for a slider similar to that shown in FIGS. 2a and 2b; FIG. 9 is a graph plotting spacing change vs. length ratio for the slider of FIGS. 2a and 2b; FIG. 10 is a bottom plan of another air bearing slider embodying the present invention. With reference to the drawings, a magnetic head slider 10 is formed with two side rails 12 and 14. The inner sides of the two rails border on a recessed section 18 that is formed by etching, ion milling, or some other machining technique. The recessed section 18, which is open at both ends extends from the leading end 20 of the slider to the trailing end 22 of the slider. Magnetic transducers 24, preferably of the thin film type, are bonded at the trailing ends of the rails 12 and 14 with their transducing gaps flush with the rail surface. The side rails 12 and 14 have a chamfered or tapered height section 16 at the leading end 20 and a width that decreases from the leading end to a point remote from the leading end. In the embodiment of the invention shown in FIG. 1, the side rails 12 and 14 are widest at the leading end 20 and decrease to their narrowest point at the trailing end 22 of the slider. In the preferred embodiment of the invention shown in FIGS. 2a and 2b, each of the side rails 12 and 14 has the leading end formed as a taper section 16. Each of the side rails 12 and 14 includes a wide section 26 and 28 at the leading end 20 of the slider having substantially parallel sides and a width W1 followed by a flared section 30 and 32. Flared sections 30 and 32 extend to a break point from which they are followed by narrow sections 34 and 36 having substantially parallel sides and a width W2 that is less than the width W1. Narrow sections 34 and 36 extend to the trailing end 22 of the rails 12 and 14. The configuration of the slider 10 which is shown in FIGS. 1, 2a and 2b has different pressure zones as can be seen by reference to FIG. 3. The pressure zones are formed when the slider is positioned adjacent to a record surface 38 (FIG. 3) moving in the direction of arrow 39 to provide load forces on the slider assembly that are balanced in such a manner that the desired flying characteristics for the slider can be achieved. The slider has a positive pressure zone along the side rails 12 and 14, a near ambient zone in recessed section 18, and a small negative pressure zone adjacent the flared sections 30 and 32. The pressure components are combined so that the slider 10 flies at a desired pitch angle ϑ (Fig. 3) relative to a moving record disk surface 38 with an attitude by which the trailing end 22 of slider 10, where the transducer 24 is mounted, is closest to the disk surface 38. Two of the factors which establish the pitch angle ϑ are the ratio of the width W1 of the wide rail section 26 and 28 to the width W2 of the narrow rail section 34 and 36, and the ratio of the length L1 of the wide rail section to the overall length L of the slider. In the accompanying drawings, the ratio W1/W2 is referred to as the rail ratio, and the ratio L1/L is referred to as the length ratio and the length of the flared sections 30 and 32 is a constant K. A rail ratio and a length ratio can be chosen to produce the pitch angle ϑ desired to compensate for a forward movement of the suspension attachment, the lowering of the flying height or any other reason. Another factor which establishes the flying characteristics of the slider is the relief depth of the recessed section 18. As shown in FIG. 5, the flying height of the embodiment shown in the drawings varies significantly when the depth is small. However, for depths greater than about 15 microns, the flying height changes very little with depth, thus allowing reasonable manufacturing tolerances. FIG. 6 shows that, in embodiments similar to that shown in FIGS. 2a and 2b, the change in pitch angle ϑ increases approximately linearly with increasing rail ratio for a specific length ratio. Increasing the length ratio causes the pitch to be more sensitive to rail ratio. FIG. 7 shows a plot for sliders having the same length ratio as FIG. 6, and FIG. 7 shows that the change in spacing goes down for rail ratios over about 1.2 for the length ratio plotted. As the length ratio is increased, the curve tends to flatten and eventually goes positive. FIG. 8 shows that the change in pitch angle ϑ increases to a length ratio of about 0.4 and then begins to decrease for the value of rail ratio plotted. Increasing the rail ratio causes increased sensitivity of the length ratio to changes in flying height. FIG. 9 shows that the change in spacing increases with length ratio for the same rail ratio as that plotted in FIG. 8. The change is gradual to a length ratio of about 0.25 and then increases at a greater rate for length ratios above 0.25. Increasing the rail ratio causes an increased sensitivity of length ratio to spacing change. Another embodiment of the invention is shown in FIG. 10. To meet the requirements for track width and recording density, the magnetic transducer may need to have a greater area than that provided by the rails in the FIGS. 1, 2a and 2b embodiment. To provide additional area for the magnetic transducer 40 the trailing end of the rails 42 and 44 is provided with a flared-out section 46 and 48. Since the flared section 46 and 48 produces only a slight change in the positive pressure at the trailing end of the rails, no significant effect on flying attitude of the slider is produced. Suitable contours, other than those shown in the drawings, can also be used for both the inner and outer sides of the side rails to obtain the desired flying characteristics for the slider, and these contours are characterised by a width that is wide at the leading end and decreases to a point near to the trailing end of the slider.

Claims: An air bearing slider for supporting a transducer (24, 40) relative to a moving record medium, the underside of the slider being formed to provide a pair of corresponding spaced apart side rails (12, 14, 42, 44) so that there is a recessed section (18) open at both ends extending from the leading end (20) of the slider to its trailing end (22), each of the side rails being chamfered (16) at its leading end and having a leading portion, an intermediate portion and a trailing portion, the leading portion being wider than the intermediate portion and the trailing portion over substantially the whole of their respective lengths, said leading and trailing portions being of substantially constant width and said intermediate portion becoming progressively narrower to a breakpoint, and the side rails and the recessed section producing a combined pressure profile when the slider is positioned adjacent a moving record medium, such that the slider assumes an orientation having a predetermined pitch angle with respect to the moving record medium in which the minimum spacing between the slider and the record medium occurs at the trailing end (22) of the slider. An assembly comprising a slider as claimed in claim 1 and an individual magnetic transducer head (24, 40) supported on the trailing edge (22) of each of the side rails. An air bearing slider as claimed in claim 2 in which the trailing portion of each of the rails (42, 44) flares outwardly at the trailing edge to provide a greater support area for said individual transducer (40), the flared portion (46, 48) being small enough not to significantly affect said predetermined pitch angle and minimum spacing (fig. 10).

Inventors: NISHIHIRA, HENRY SHUSEI
Applicants: INTERNATIONAL BUSINESS MACHINES CORPORATION
Application year: 1987
Main classification: G11B5
IPC codes: G11B21, G11B5