Head gimbal assembly with in-situs adjustable pitch and roll

[0002] The present invention claims priority to Provisional Application Serial No. 60/237,961 filed Oct. 4, 2000 and entitled “PSA/RSA Adjustment Using SMA”.

[0003] The present invention relates to a head suspension assembly of a disc drive. In particular, the present invention relates to a head suspension assembly with adjustable pitch and roll attitudes.

[0004] Data storage devices store digital information on a rotating disc. Heads are supported relative to the disc surface to read data from or write data to the disc. The heads include an air bearing slider which includes a leading edge, a trailing edge and opposed sides. The head or slider is flexibly coupled to a suspension assembly which includes a suspension portion which supplies a load force to the slider at a load point. The load point is positioned between opposed sides of the slider and between the leading and trailing edges of the slider. The load point defines a pitch axis between the leading and trailing edges about which the slider pitches and a roll axis between opposed sides of the slider about which the slider rolls.

[0005] For operation, rotation of the disc creates an air flow along an air bearing surface of the slider to create a hydrodynamic lifting force. The hydrodynamic lifting force is countered by the load force supplied by the suspension portion which defines in part a fly height of the slider above the disc surface. During operation, the slider pitches and rolls about the pitch axis and roll axis. Typically the slider is supported at a pitch angle relative to the disc surface so that the trailing edge of the slider is closer to the disc surface than the leading edge. Pitch and roll parameters of the slider affect the fly height of the slider which affects read/write resolution and clarity.

[0006] Dynamic pitch and roll of the slider relative to the load point is related to the pitch static attitude (PSA) and roll static attitude (RSA) of the slider. PSA and RSA can vary based upon manufacturing processes and manufacturing tolerances, for example variations in flexure or relative stiffness of the suspension components can introduce variations in PSA and/or RSA parameters of the slider. As previously explained, variations in PSA and RSA parameters can affect pitch of the slider relative to the disc surface and fly height parameters for read or write operations of a disc drive. The present invention addresses these and other problems and offers solutions not previously recognized nor appreciated.

[0007] The present invention relates to an in-situs pitch and/or roll attitude adjustment system. The in-situs adjustment system includes a flexure element having an energizable dimension differential. The flexure element is coupled to a suspension assembly and slider and is energizable to supply a flexure force to the slider to adjust pitch or roll attitudes of the slider. These and various other features, as well as advantages which characterize the present invention, will be apparent upon reading the following detailed description and review of the associated drawings.

[0008] FIG. 1 is a perspective illustration of a disc drive.

[0009] FIG. 2 is a schematic illustration of a suspension assembly having a head coupled thereto.

[0010] FIG. 3 schematically illustrates a slider adapted to pitch about a pitch axis so that a trailing edge of the slider flies closer to the disc surface than the leading edge.

[0011] FIG. 4 schematically illustrates a slider adapted to roll relative to a roll axis.

[0012] FIG. 5 schematically illustrates a flexure assembly coupled to a slider to adjust a pitch attitude of the slider relative to a pitch axis.

[0013] FIG. 6 schematically illustrates a flexure assembly coupled to a slider to adjust a roll attitude of the slider relative to a roll axis.

[0014] FIG. 7-1 schematically illustrates one embodiment for coupling a flexure element to a slider to adjust a pitch attitude of the slider.

[0015] FIG. 7-2 schematically illustrates another embodiment for coupling a plurality of flexure elements to a slider to adjust a pitch attitude of the slider.

[0016] FIG. 8 schematically illustrates one embodiment for coupling flexure elements to a slider to adjust a roll attitude of the slider.

[0017] FIG. 9 schematically illustrates an embodiment for coupling a flexure element to a slider and suspension assembly to adjust pitch or roll attitudes of the slider.

[0018] FIG. 10 graphically illustrates an energizable dimension differential as a function of temperature for a shape memory alloy.

[0019] FIG. 11 illustrates one embodiment of a head suspension assembly including flexure elements to adjust pitch or roll attitudes of the slider.

[0020] FIG. 12 is a plan view of another embodiment of a head suspension assembly including flexure elements to adjust pitch or roll attitudes of the slider.

[0021] FIG. 13 is a side elevational view illustrating opposed flexure elements for selectively increasing or decreasing pitch attitude of the slider.

[0022] FIG. 14 illustrates another embodiment of a head suspension assembly including flexure elements to adjust pitch or roll attitudes of the slider.

[0023] FIG. 15 is a cross-sectional view taken along line 15—15 of FIG. 14.

[0024] FIG. 16 is a flow chart illustrating steps for adjusting pitch and/or roll attitudes of the slider.

[0025] FIG. 1 illustrates an embodiment of a disc drive 100 in which digital information is stored on a plurality of discs 102. Heads 104 are positioned relative to the disc surface to read data from or write data to the disc 102. Heads 104 are coupled to an actuator assembly 106 via a suspension assembly 108 which is staked to or secured to actuator arms 110 of the actuator assembly 106. The actuator assembly 106 is powered by a voice coil motor 112 to position heads relative to selected data tracks on the disc surface. As shown, discs 102 are supported on a spindle motor (not shown) which rotates the discs as illustrated by arrow 114 for operation. Rotation of the discs by the spindle motor creates a hydrodynamic lifting force for read/write operations. Components of the disc drive are supported relative to a base chassis 116 of the disc drive. Although a particular disc drive embodiment is shown, application is not limited to the particular embodiment shown.

[0026] FIG. 2 is a detailed illustration of the head 104 coupled to a suspension arm 118 through a gimbal spring 120. Head 104 includes a slider 122 having a leading edge 124, a trailing edge 126 and opposed sides 128, 130. In the illustrated embodiment, the slider 122 includes transducer elements located proximate to the trailing edge 126 of the slider 122. The suspension arm 118 includes a load portion which supplies a pre-load force to the slider at a load point 190. The gimbal spring 120 flexibly supports the slider 122 to pitch about axis 192 defined through load point 190 between the leading and trailing edges 124, 126 of the slider and roll about axis 194 defined through load point 190 between opposed sides of the slider 122 for read/write operations.

[0027] In particular, in the embodiment shown, gimbal spring 120 includes opposed spaced gimbal arms 196, 198 which flexibly support the slider 122 relative to load point 190 of suspension arm 118 to pitch and roll relative to axis 192, 194. The slider 122 is secured to or coupled to the gimbal spring 120 via a slider tab 200 coupled to opposed ends of the gimbal arms 196, 198. For operation, as illustrated in FIG. 3, rotation of discs 102 create an air flow as illustrated by arrow 202 along a raised bearing surface of the slider 122 to provide the hydrodynamic lifting force which is countered by the preload force to define in part a fly height H_flyof the slider for read/write operations.

[0028] As illustrated in FIG. 3, during operation, the slider 122 pitches about axis 192 so that the trailing edge 126 of the slider is positioned closer to the disc surface 204 than the leading edge 124 of the slider. The pitch angle Θ_pof the slider 122 is related to the pitch static attitude PSA of the slider which is typically optically measured when the slider is lifted against the load force. The PSA can vary depending upon manufacturing process or tolerance variations, such as variations in the flexibility or alignment of the suspension components. Variations in the pitch angle of the slider as comparatively illustrated between Θ_pand Θ_p′ provides different fly heights parameters H_flyand H_fly′ which affects desired read/write clarity and resolution of the disc drive.

[0029] As illustrated in FIG. 4, during operation, the slider 122 rolls about axis 194. Slider roll attitude during operation is related to the roll static attitude RSA of the slider. The RSA of the slider 120 can be optically measured and can also vary depending upon manufacturing process and tolerance variations such as variations in the relative stiffness of opposed sides of the suspension components. Variations in the RSA can also similarly affect fly height and operating parameters of the slider.

[0030] The present invention relates to an in-situs adjustment system for pitch and roll attitudes of the slider to provide desired read/write control. The in-situs adjustment can be based upon measured deviations of the PSA and RSA from desired or optimum attitudes as will be explained and provides drive level adjustment for deviations in the PSA and RSA. FIG. 5 schematically illustrates in-situs pitch attitude adjustment of the slider 122 including at least one raised air bearing surface illustrated schematically at 206. As shown, the adjustment includes an energizable flexure assembly 220 coupled to the slider 122 which is energizable by power source 222 to pivot slider 122 about axis 192 as illustrated by arrow 224 to adjust the pitch attitude of the slider. FIG. 6 illustrates in-situs roll attitude adjustment which includes a flexure assembly 226 which is energizable by power source 222 to pivot slider 122 about axis 194 as illustrated by arrow 228 to adjust the roll attitude of the slider 122. Although the air bearing surface is illustrated schematically, it should be understood that the in-situs adjustment can be applied to sliders with various air bearing designs including various raised or stepped bearing surfaces.

[0031] FIG. 7-1 is a schematic illustration of one embodiment of a flexure assembly 220-1 to adjust pitch attitude of the slider. As shown the assembly includes a flexure element 240 coupled to the slider 122 at a distance 242 spaced from the pitch axis 192. The flexure element 240 is energized to supply a flexure force F₂₄₀to the slider to rotate the slider relative to the pitch axis 192 for in-situs pitch attitude adjustment based upon:

[0032] T=F₂₄₀*x₂₄₂  Equation 1.

[0033] where:

[0034] T is the torque applied to the slider by the energized flexure element 240;

[0035] F₂₄₀is the flexure force to the slider;

[0036] x₂₄₂is the distance of the force F₂₄₀from the pitch axis 192; and

[0037] P_A=T/K_P  Equation 2.

[0038] where P_Ais the pitch attitude adjustment; and

[0039] K_Pis a stiffness constant for pitch stiffness of the suspension.

[0040] In the particular embodiment shown, application of F₂₄₀in the direction shown decreases the pitch attitude for in-situs control. Although in the illustrated embodiment, the flexure force is illustrated at the trailing edge of the slider, the flexure force can be supplied at any distance from the pitch axis 192 and application is not limited to the specific embodiments shown.

[0041] FIG. 7-2 illustrates another embodiment of a flexure assembly 220-2 for in-situs pitch attitude control. As shown, the illustrated embodiment includes opposed flexure elements 244, 246 coupled to the slider at a distance 248 spaced from the pitch axis 192. As shown, the first flexure element 244 is coupled to the slider to supply a first flexure force F₂₄₄in a first direction and the second flexure element 246 is coupled to the slider to supply a second flexure force F₂₄₆in a second direction opposed to the first direction to selectively increase or decrease the pitch attitude of the slider based upon:

[0042] P_A=F₂₄₄*x₂₄₈−F₂₄₆*x₂₄₈/K_P  Equation 3.

[0043] where P_Ais the pitch attitude adjustment, F₂₄₄, F₂₄₆are the flexure forces supplied by flexure elements 244, 246, x₂₄₈is the distance of F₂₄₄, F₂₄₆from the pitch axis 192 and K_Pis the stiffness constant for pitch stiffness of the suspension. Although FIG. 7-2 illustrates an embodiment of a flexure assembly for selectively increasing or decreasing the pitch attitude of the slider, application is not limited to the particular embodiment or arrangement shown and other arrangements can be used to rotate the slider 122 in opposed directions to increase or decrease the pitch attitude of the slider.

[0044] FIG. 8 schematically illustrates one embodiment of a flexure assembly 226-1 for in-situs adjustment of the roll attitude of the slider 122. As shown, the flexure assembly 226-1 embodiment includes flexure elements 250, 252 coupled to the slider 122 on opposed sides of the roll axis 194. As shown flexure element 250 is spaced a distance 254 in a first direction from the roll axis 194 and flexure element 252 is spaced a distance 256 in a second direction from the roll axis 194. The flexure elements 250, 252 are selectively energized via power source 222 coupled to the flexure elements 250, 252 to supply forces F₂₅₀or F₂₅₂to adjust the roll attitude of the slider 122 based upon:

[0045] R_A=F₂₅₀*x₂₅₄+F₂₅₂*x₂₅₆/K_R  Equation 4.

[0046] where:

[0047] R_Ais the roll attitude adjustment based upon application of forces F₂₅₀and F₂₅₂on opposed sides of the roll axis 194 spaced distances x₂₅₄, x₂₅₆from the roll axis 194, respectively and roll stiffness K_Rof the suspension.

[0048] As shown in FIG. 9, flexure elements 240, 244, 246, 250, 252 are coupled between the slider (or gimbal spring) as illustrated by block 258 and the suspension 118 and include an energizable length or dimension differential. The energized length or dimension differential supplies a flexure force to the slider to bend or flex the slider relative to the suspension as previously described for in-situs pitch or roll attitude adjustment. The magnitude of the flexure force is dependent upon the energized length or dimension differential.

[0049] FIG. 10 graphically illustrates an energizable length differential as illustrated by axis 260 for a shape memory alloy, such as Nitinol (a nickel titanium alloy). As shown, a length dimension of the shape memory alloy undergoes a length dimension change as illustrated by line 262 when heated or energized as illustrated by temperature axis 264. As shown by line 262, the length dimension constricts as the material structure changes from a martensite to austenite. After heat or the power source is removed, the shape memory alloy or material recovers its original length dimension as illustrated by line 266 to provide shape memory. Thus, the flexure element or shape memory alloy or material is energized by supplying a voltage potential across a length dimension of the flexure element or shape memory alloy to induce a dimensional change to supply a flexure force as described for in-situs pitch and roll attitude adjustment.

[0050] FIG. 11 is a plan view of one embodiment of a head suspension assembly 270-1 with in-situs pitch and roll attitude adjustment where like numbers are used to like parts in the previous FIGS. In the illustrated embodiment shown, the head suspension assembly 270-1 includes two shape memory alloy wires 272-1, 272-2 having an energizable length differential. The shape memory alloy wires 272-1, 272-2 include a first end coupled to the suspension 118-1 and a second end coupled to the slider 122 or gimbal spring 120-1 at a distance spaced from the pitch axis 192 of the slider (in the particular embodiment the second end of the wires 272-1, 272-1 are coupled proximate to a trailing edge 126 of the slider). Wires 272-1, 272-1 are collectively energized to supply a flexure force to adjust the pitch attitude of the slider. Wires 272-1, 272-2 are collectively energized by supplying a voltage potential to terminals at opposed first and second ends of the wires. In the particular embodiment shown, the second ends of the wires 272-1, 272-1 are grounded although application is not limited to grounding any particular end.

[0051] In the illustrated embodiment, the second ends of wires 272-1, 272-2 are coupled to opposed sides of the roll axis 194. Wires 272-1, 272-2 are selectively energized to adjust the roll attitude of the slider. Thus, to adjust roll attitude in a first direction, a voltage potential is supplied to wire 272-1 and to adjust roll attitude in a second direction, a voltage potential is supplied to wire 272-2 which selectively causes a length of the wires to constrict for in-situs roll attitude adjustment. As shown, wires 272-1, 272-2 cross and connect to opposed sides of the suspension and slider for desired stability.

[0052] FIGS. 12-13 illustrate another embodiment of a head suspension assembly 270-2 with in-situs pitch and roll attitude adjustment. As shown, the suspension assembly 270-2 includes shape memory alloy wires 272-1, 272-2, 272-3 having an energizable length differential. Wires 272-1, 272-2 have a first end coupled to first surface 274 of the suspension 118-1 and a second end coupled to the slider (or first surface 276 of a gimbal spring) at a distance spaced from the pitch axis 192. Wires 272-1, 272-2 are energizable to supply a flexure force in a first direction to adjust pitch attitude of the slider in a first direction.

[0053] Wire 272-3, as illustrated by dotted line in FIG. 12, has a first end coupled to an opposed second suspension surface 278 and a second end coupled a second surface 279 of the gimbal spring 120-1 and is energizable to supply a flexure force in a second direction to adjust the pitch attitude of the slider in a second opposed direction to provide dual direction in-situs pitch attitude adjustment. As shown, wire 272-3 or flexure element extends between gimbal spring 120-1 and slider 122 to couple to the slider forward of the pitch axis 192. In one example, wire 273-3 or flexure element extends through an elongated slot formed in the gimbal spring or slider so that the slider and gimbal spring are in abutting relation with the flexure element or wire 272-3 extending therebetween.

[0054] For roll attitude adjustment, the second ends of wires 272-1, 272-2 are coupled to opposed sides of the slider 122 spaced in opposed directions from the roll axis 194 as shown in FIG. 12. Wires 272-1, 272-2 are selectively energized to adjust the roll attitude of the slider. Although a particular number of wires is shown in the illustrated embodiments, application is not limited to the particular number of wires shown and alternate designs can be used which supply a flexure force spaced from the pitch axis for pitch attitude adjustment and which supply a flexure force spaced from the roll axis for roll attitude adjustment.

[0055] FIGS. 14-15 illustrate another embodiment of a head suspension assembly 270-3 with in-situs pitch and roll attitude adjustment. As shown, the embodiment includes shape memory flexure elements 272-4, 272-5 formed on a flexible suspension circuit 280 including a plurality of transducer leads 282 fabricated on a flexible base material 284 (such as a polyimide material shown in FIG. 15) to electrically couple transducers on the slider 122 to drive circuitry 286. The shape memory flexure elements 272-4, 272-5 are printed on the flexible base material by known fabrication techniques.

[0056] As shown, the flexure elements 272-4, 272-5 are printed on an extended portion of the flexible suspension circuit 280 which extends to and is coupled to an exposed or extended portion 288 of the gimbal spring 120-1 so that flexure elements 272-4, 272-5 extend from the suspension to a distance spaced from the pitch axis 192 of the slider 122 to adjust pitch attitude of the slider 122. Flexure elements 272-4, 272-5 are fabricated on opposed sides of the flexible base material spaced from the roll axis 194 so that the flexure elements 272-4, 272-5 are energizable to adjust roll attitude of the slider. Flexure leads 290 are also printed on the base material 284 to provide a voltage potential across opposed terminals of the flexure elements 272-4, 272-5 as shown in FIG. 14. Although a particular integrated arrangement is shown, other designs can be used and integrated to provide dual direction pitch and roll attitude adjustment.

[0057] FIG. 16 is a flow chart illustrating steps for in-situs adjustment of pitch or roll attitudes of the slider. As shown by block 200, should pitch attitude need adjusting a flexure element is energized to adjust the pitch attitude of the slider as illustrated by block 202. As shown by block 204, should the roll attitude need to be adjusted, a flexure element is energized to adjust the roll attitude of the slider as illustrated by block 206. Thus, as described pitch and/or roll attitudes can be adjusted based upon measured variances of the PSA or RSA from desired or optimum parameters.

[0058] The present invention relates to an in-situs pitch and/or roll attitude adjustment system. The in-situs adjustment system includes at least one flexure element (such as 240, 244, 246, 250, 252, 272) having an energizable dimension differential. The flexure element (such as 240, 244, 246, 250, 252, 272) is coupled to a suspension assembly 118 and slider 122 and is energizable to supply a flexure force to the slider 122 to adjust pitch or roll attitudes of the slider 122. In one embodiment, at least one flexure element is coupled to the slider 122 at a distance spaced from a pitch axis 192 of the slider and is energized to adjust the pitch attitude of the slider. For roll attitude adjustment, flexure elements are coupled to the slider on opposed sides of a roll axis 194 and selectively energized to adjust a roll attitude of the slider.

[0059] It is to be understood that even though numerous characteristics and advantages of various embodiments of the invention have been set forth in the foregoing description, together with details of the structure and function of various embodiments of the invention, this disclosure is illustrative only, and changes may be made in detail, especially in matters of structure and arrangement of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. For example, the particular elements may vary depending on the particular application while maintaining substantially the same functionality without departing from the scope and spirit of the present invention. In addition, although the preferred embodiment described herein is directed to a particular disc drive system, it will be appreciated by those skilled in the art that the teachings of the present invention can be applied to other systems, like an optical disc drive system, without departing from the scope and spirit of the present invention.