Disk device

Abstract

To provide a disk device capable of suppressing fluctuations in a gap between a recording medium and a head and improving reliability.SOLUTION: According to an embodiment, a disk device includes: a disk-shaped recording medium; a magnetic head having a heater that adjusts a gap between a write head, a read head, and the recording medium; a suspension assembly that supports the magnetic head; a microactuator including a piezoelectric element provided in the suspension assembly; and a controller that sets a driving voltage of the piezoelectric element according to the difference between the piezoelectric element and a touchdown output at driving, and the piezoelectric element and a touchdown output at non-driving.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a disk device. [Background technology]

[0002] As a disk device, for example, a magnetic disk device is equipped with a rotatable disk-shaped recording medium having a magnetic recording layer, and a magnetic head for recording and reproducing data on the magnetic recording layer of the recording medium. The magnetic head is supported by a head actuator so as to be movable in the radial direction of the recording medium. In recent years, magnetic disk devices equipped with a microactuator for finely adjusting the position of the magnetic head have been proposed.

[0003] In a magnetic disk device, in order to improve the recording density, especially the linear recording density, it is necessary to set the gap between the magnetic head and the recording medium small. However, when the microactuator is driven, the magnetic head moves not only in the track direction (radial direction) of the recording medium, but also slightly in a direction intersecting the surface of the recording medium. Therefore, the gap between the magnetic head and the recording medium fluctuates, and it may not be possible to maintain the desired set gap. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-190907 [Patent Document 2] U.S. Patent No. 6,950,287 [Patent Document 3] U.S. Patent No. 10,014,027 [Patent Document 4] U.S. Patent No. 9,142,225 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of an embodiment of the present invention is to provide a disk drive capable of suppressing fluctuations in the gap between a recording medium and a head and improving reliability. [Means for solving the problem]

[0006] According to an embodiment, a disk device includes a disk-shaped recording medium, a magnetic head having a write head, a read head, and a heater that adjusts the gap between the recording medium, a suspension assembly that supports the magnetic head, a microactuator including a piezoelectric element provided in the suspension assembly, and a controller that sets the drive voltage of the piezoelectric element in accordance with the difference between the touchdown output of the piezoelectric element when driven and the touchdown output of the piezoelectric element when not driven. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is an exploded perspective view showing a top cover of a hard disk drive (HDD) according to a first embodiment. [Diagram 2] FIG. 2 is a side view that diagrammatically shows a magnetic head, a suspension, and a magnetic disk in the HDD. [Diagram 3] FIG. 3 is a perspective view showing one head suspension assembly of an actuator assembly in the HDD. [Figure 4] FIG. 4 is a plan view of a tip portion of the head suspension assembly. [Diagram 5] FIG. 5 is an enlarged cross-sectional view showing a head portion of a magnetic head in the HDD. [Figure 6] FIG. 6 is a block diagram showing a schematic configuration of the entire HDD including a controller. [Figure 7] FIG. 7 is a side view of a head portion of a magnetic head and a magnetic disk, showing a typical floating state of the magnetic head. [Figure 8] FIG. 8 is a flowchart showing an operation of adjusting a drive voltage of a microactuator provided in the head suspension assembly. [Figure 9] FIG. 9 is a diagram showing a schematic diagram of the relationship between the drive voltage and frequency (differential voltage clip) of the microactuator. [Figure 10] FIG. 10 is a flowchart showing the operation of adjusting the drive voltage of the microactuator in the HDD according to the second embodiment. [Figure 11] FIG. 11 is a flowchart showing the operation of adjusting the drive voltage of the microactuator in the HDD according to the third embodiment. [Figure 12] FIG. 12 is a diagram illustrating a relationship between the drive voltage and frequency (differential voltage clip) of the microactuator in the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] A disk device according to an embodiment will be described with reference to the drawings. The disclosure is merely an example, and appropriate modifications that are within the spirit of the invention and that can be easily conceived by a person skilled in the art are naturally included in the scope of the present invention. In addition, in order to make the explanation clearer, the width, thickness, shape, etc. of each part may be shown diagrammatically compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present invention. In this specification and each figure, elements similar to those described above with respect to the previous figures may be given the same reference numerals, and detailed explanations may be omitted or simplified as appropriate.

[0009] (First embodiment) As an example of a disk device, a hard disk drive (HDD) according to a first embodiment will be described in detail. Fig. 1 is an exploded perspective view showing a top cover of the HDD according to the first embodiment. Fig. 2 is a block diagram showing a schematic configuration of the entire HDD including a controller. As shown in FIG. 1, the HDD 11 includes a rectangular housing 10. The housing 10 has a rectangular box-shaped base 12 with an open top, and a cover (top cover) 14. The base 12 has a rectangular bottom wall 12a and a side wall 12b standing along the periphery of the bottom wall 12a, and is integrally molded from, for example, aluminum. The cover 14 is formed into a rectangular plate shape from, for example, stainless steel. The cover 14 is fixed onto the side wall 12b of the base 12 with a plurality of screws 13, and air-tightly closes the upper opening of the base 12.

[0010] In the housing 10, there are provided a plurality of magnetic disks 18 (for example, ten) as disk-shaped recording media, and a spindle motor 19 for supporting and rotating the magnetic disks 18. The spindle motor 19 is disposed on the bottom wall 12a. Each magnetic disk 18 has a substrate formed in a disk shape with a diameter of, for example, 95 mm (3.5 inches) and a magnetic recording layer formed on the upper and lower surfaces of the substrate. Each magnetic disk 18 is coaxially fitted to the hub of the spindle motor 19, and is further clamped by a clamp spring 20. As a result, the magnetic disks 18 are supported in a state in which they are positioned parallel to the bottom wall 12a of the base 12. The plurality of magnetic disks 18 are rotated by the spindle motor 19 in the direction of the arrow B at a predetermined number of revolutions. The number of magnetic disks 18 mounted is not limited to ten, and may be nine or less, or ten or more, or twelve or less.

[0011] Inside the housing 10, there are provided a plurality of magnetic heads 16 which record and reproduce information on the magnetic disks 18, and an actuator assembly 22 which supports these magnetic heads 16 so that they can move freely relative to the magnetic disks 18. Also provided inside the housing 10 are a voice coil motor (VCM) 24 which rotates and positions the actuator assembly 22, a ramp load mechanism 25 which holds the magnetic heads 16 at an unload position separated from the magnetic disks 18 when the magnetic heads 16 move to the outermost periphery of the magnetic disks 18, and a board unit (FPC unit) 21 on which electronic components such as a conversion connector are mounted.

[0012] The actuator assembly 22 has an actuator block 29 supported rotatably around a support shaft 28, a plurality of arms 32 extending from the actuator block 29, and a suspension assembly 30 extending from each arm 32. The support shaft 28 is erected on the bottom wall 12a. A magnetic head 16 is supported on the tip of each suspension assembly 30. The actuator assembly 22 has a support frame (not shown) that extends from the actuator block 29 in the opposite direction to the arm 32, and this support frame supports a voice coil 33. The voice coil 33 is located between a pair of yokes 37 fixed onto the base 12, and constitutes the VCM 24 together with these yokes 37 and a magnet fixed to one of the yokes.

[0013] The FPC unit 21 has a substantially rectangular base portion 21a fixed to the bottom wall 12a, a thin strip-like relay portion 21b extending from one side edge of the base portion 21a, and a joint portion 21c provided continuously to the tip of the relay portion 21b. The base portion 21a, the relay portion 21b, and the joint portion 21c are formed of a flexible printed circuit board (FPC). The joint portion 21c is attached to an actuator block 29. A head amplifier IC 80, which will be described later, is mounted on the joint portion 21c. A printed circuit board 27 is screwed to the outer surface of the bottom wall 12a of the base 12. The base portion 21a of the FPC unit 21 is connected to the printed circuit board 27 via a connector (not shown). The printed circuit board 27 constitutes a controller for the HDD 11. The controller controls the operation of the spindle motor 19, and also controls the operation of the VCM 24 and the magnetic head 16 via the board unit 21.

[0014] FIG. 2 is a side view that shows a schematic diagram of the magnetic head and the magnetic disk in a floating state. As shown in the figure, the magnetic disk 18 has a disk-shaped substrate 101 made of a non-magnetic material, for example, glass. An underlayer 102, a magnetic recording layer 103, and a protective film 104 are laminated in this order on each surface of the substrate 101. The magnetic disk 18 is rotated in the direction of arrow B at a predetermined speed by a spindle motor 19. The suspension assembly 30 has a suspension 34, a wiring member (flexure) 42 attached onto the suspension 34, and a tab 40 protruding from the tip of the suspension 34. The magnetic head 16 is supported by a gimbal portion 44 of the flexure 42. The magnetic head 16 is electrically connected to the head amplifier IC 80 and the FPC unit 21 described above via the flexure 42.

[0015] The magnetic head 16 is configured as a floating type head. The magnetic head 16 has a substantially rectangular parallelepiped slider 15 having an inflow end 15a, an outflow end (trailing end) 15b, and a disk-facing surface (ABS) 13, and a head section 17 formed at the end of the slider 15 on the outflow end 15b side. The head section 17 includes a write head element and a read head element. The magnetic head 16 is maintained in a state of floating a predetermined amount above the surface of the magnetic disk 18 by an air flow C generated between the disk surface and the slider 15 by the rotation of the magnetic disk 18. The direction of the air flow C coincides with the rotation direction B of the magnetic disk 18. As the magnetic disk 18 rotates, the magnetic head 16 runs in a direction (circumferential direction) A opposite to the rotation direction B relative to the magnetic disk 18.

[0016] Next, an example of the suspension assembly 30 will be described in detail. FIG. 3 is a perspective view showing one suspension assembly, and FIG. 4 is a plan view of the tip portion of the suspension assembly. 3, each suspension assembly 30 has a suspension 34 extending from an arm 32, and the magnetic head 16 is attached to the tip of this suspension 34. The magnetic head 16 and the suspension assembly 30 that supports it may be collectively referred to as a head suspension assembly.

[0017] The suspension 34, which functions as a support plate, has a rectangular base plate 36 made of a metal plate several hundred microns thick, and a long, thin, leaf-spring-like load beam 38 made of a metal plate several tens of microns thick. The base end of the base plate 36 is fixed to the tip of the arm 32. The base end of the load beam 38 is placed over the tip of the base plate 36 and is fixed to the base plate 36 by welding at multiple points. A rod-shaped tab 40 protrudes from the tip of the load beam 38.

[0018] The suspension assembly 30 has a long, thin, strip-shaped flexure (wiring member) 42 for transmitting recording signals, reproducing signals, and driving signals for the piezoelectric elements, and a pair of piezoelectric elements (e.g., PZT elements) 50 mounted on the flexure 42. The flexure 42 has a tip portion 42a disposed on the load beam 38 and the base plate 36, a base portion 42b extending outward from the side edge of the base plate 36 and extending along the side edge of the arm 32 to the actuator block 29, and a connection end portion (not shown) extending from the base portion 42b. The connection end portion has a number of connection pads arranged side by side. These connection pads are electrically connected to connection terminals of the joint portion 21c mounted on the actuator block 29.

[0019] The tip of the flexure 42 is located on the tip of the load beam 38 and constitutes a gimbal portion 44 that functions as an elastic support portion. The magnetic head 16 is placed on and fixed to the gimbal portion 44, and is supported by the load beam 38 via the gimbal portion 44. A pair of piezoelectric elements 50 serving as drive elements are mounted on the gimbal portion 44 and disposed in the vicinity of the magnetic head 16. The pair of piezoelectric elements 50 constitute a microactuator.

[0020] The flexure 42 has a thin metal plate (metal plate) 46 such as stainless steel as a base, and a strip-shaped laminate member (flexible printed circuit board: FPC) 48 attached or fixed on the thin metal plate 46, forming a long and narrow laminate plate. The laminate member (FPC) 48 has a base insulating layer (first insulating layer) most of which is fixed to the thin metal plate 46, a conductive layer (wiring pattern) formed on the base insulating layer and constituting a plurality of signal wirings, drive wirings, and a plurality of connection pads, and a cover insulating layer (second insulating layer) laminated on the base insulating layer to cover the conductive layer. At the tip side portion 42a of the flexure 42, the thin metal plate 46 is attached to the surfaces of the load beam 38 and the base plate 36, or spot-welded at a plurality of welding points.

[0021] As shown in Figures 3 and 4, in the gimbal portion 44, the thin metal plate 46 integrally has a substantially rectangular tongue portion (support portion) 44a located on the tip side, a substantially rectangular base end portion 44b located on the base end side across a space from the tongue portion 44a, and a pair of elastically deformable outriggers (link portions) 44c each connecting the base end portion 44b and the tongue portion 44a.

[0022] The tongue portion 44a is formed in a size and shape capable of mounting the magnetic head 16, for example, in a substantially rectangular shape. The tongue portion 44a is disposed so that the central axis line in the width direction thereof coincides with the central axis line C of the suspension 34 (see FIG. 4). The tongue portion 44a is in contact with a dimple 47 protruding from the tip of the load beam 38 at approximately its center. The tongue portion 44a can be displaced in various directions with the dimple 47 as a fulcrum due to elastic deformation of the pair of outriggers 44c. This allows the tongue portion 44a and the magnetic head 16 mounted on the tongue portion 44a to flexibly follow surface fluctuations of the magnetic disk 18 and displace in the roll or pitch direction, thereby maintaining a minute gap between the surface of the magnetic disk 18 and the magnetic head 16.

[0023] In the gimbal portion 44, the laminated member 48 of the flexure 42 is disposed on the metal plate 46 and extends from the base end 44b to above the tongue portion 44a along the central axis C1. That is, the laminated member 48 has a base end 48a attached onto the base end 44b, a tip end 48b attached to the tongue portion 44a, and a pair of band-shaped bridge portions 48c extending in a bifurcated manner from the base end 48a to the tip end 48b.

[0024] A plurality of connection pads (electrode pads) 45 are provided in the tip portion 48b in a line in the width direction. A plurality of connection pads (electrode pads) 51 for connecting the piezoelectric elements 50 are provided in the base end portion 48a. The laminated member 48 has a plurality of signal wirings W1 that extend from the connection pads 45 around both side edges of the tip portion 48b to the base end portion 48a side, and a plurality of drive wirings W2 that extend from the connection pads 51 to the base end portion 48a side. These signal wirings W1 and drive wirings W2 extend over almost the entire length of the laminated member 48 and are connected to the connection pads 43 of the connection end portion 42c.

[0025] The magnetic head 16 is fixed to the tongue portion 44a by adhesive. The magnetic head 16 is disposed so that its longitudinal central axis coincides with the central axis C of the suspension 34, and the approximate center of the magnetic head 16 is located above the dimple 47. Connection pads PT of the magnetic head 16, which will be described later, are electrically connected to a plurality of connection pads 45 on the tip portion 48b by a conductive adhesive such as solder or silver paste. As a result, the magnetic head 16 is connected to the signal wiring W1 of the laminate member 48 via the connection pads 45.

[0026] 4, the pair of piezoelectric elements 50 are, for example, rectangular plate-shaped thin film piezoelectric elements (PZT elements). The piezoelectric elements 50 are arranged so that their longitudinal direction (expansion / contraction direction) is parallel to the central axis C of the suspension 34. The two piezoelectric elements 50 are arranged on both sides of the width direction Y of the magnetic head 16, and are arranged parallel to each other. Both longitudinal ends of each piezoelectric element 50 are mounted on and electrically connected to connection pads 51 of the base end portion 48a. As a result, the piezoelectric elements 50 are connected to the drive wiring W2 of the laminated member 48 via the connection pads 51. The piezoelectric element 50 is not limited to a PZT element, and other piezoelectric elements may be used. Furthermore, the driving element is not limited to a piezoelectric element, and other driving elements that can expand and contract when a current is applied may be used. Furthermore, the microactuator is not limited to a pair of driving elements, and may be configured with a single driving element. Furthermore, the piezoelectric element is not limited to being located near the magnetic head 16, and may be located near the boundary between the base plate and the load beam, or may be located both near the magnetic head 16 and near the boundary between the base plate and the load beam.

[0027] By applying a voltage (driving signal) to the piezoelectric element 50, the piezoelectric element 50 expands and contracts along its longitudinal direction (a direction parallel to the central axis C of the suspension). By driving the two piezoelectric elements 50 in opposite directions to each other, the pair of bridge portions 48c also stroke in opposite directions. As shown in FIG. 4, the bridge portion 48c13 swings the tongue portion 44a of the gimbal portion 44 and the magnetic head 16 in the direction of arrow D around the dimple 47. In this way, the expansion and contraction of the piezoelectric element 50 can slightly displace the magnetic head 16. The swing direction D of the magnetic head 16 corresponds to the seek direction (cross-track direction) of the magnetic head 16 on the magnetic disk 18.

[0028] Next, an example of the configuration of the magnetic head 16 will be described in detail. FIG. 5 is an enlarged cross-sectional view showing the head portion 17 of the magnetic head 16 and the magnetic disk 18. As shown in FIG. As shown in FIG. 5, the head section 17 of the magnetic head 16 has a reproducing head (read head) 54 and a recording head (write head) 58 formed by a thin film process on the trailing end 15b of the slider 15, and is formed as a separated type magnetic head. The read head 54 and the write head 58 are covered with a non-magnetic protective insulating film 53 except for the part exposed to the ABS 13 of the slider 15. The protective insulating film 53 forms the outer shape of the head section 17. Furthermore, the head section 17 has a first thermal actuator that controls the protrusion amount of the write head 58 and a second thermal actuator that controls the protrusion amount of the read head 54. The first thermal actuator has, for example, a heater 76a, which is embedded in the protective insulating film 53 and located near the write head 58. The second thermal actuator has, for example, a heater 76b, which is embedded in the protective insulating film 53 and located near the read head 54.

[0029] The longitudinal direction of a recording track formed on the perpendicular magnetic recording layer 103 of the magnetic disk 18 is defined as the down-track direction DT, and the width direction of the recording track perpendicular to the longitudinal direction is defined as the cross-track direction. The read head 54 has a magnetoresistive element 55, and a first magnetic shield film 56 and a second magnetic shield film 57 arranged on the leading side (inflow side) and trailing side (outflow side) of the magnetoresistive element 55 in the downtrack direction DT, so as to sandwich the magnetoresistive element 55. The magnetoresistive element 55 and the first and second magnetic shield films 56, 57 extend almost perpendicular to the ABS 13. The lower ends (tips) of the magnetoresistive element 55 and the first and second magnetic shield films 56, 57 slightly protrude from the ABS 13.

[0030] The write head 58 is provided on the side of the trailing end 15b of the slider 15 with respect to the read head 54. The write head 58 has a main pole 60 that generates a recording magnetic field perpendicular to the surface of the magnetic disk 18, a trailing shield 62 that is provided on the trailing side of the main pole 60 and faces the main pole 60 with a write gap therebetween, a leading shield 64 that faces the leading side of the main pole 60, and a pair of side shields (not shown) that are formed integrally with the trailing shield 62. The main pole 60 and the trailing shield 62 form a first magnetic core that forms a magnetic path, and the main pole 60 and the leading shield 64 form a second magnetic core that forms a magnetic path. The write head 58 has a first recording coil 70 wound around the first magnetic core and a second recording coil 72 wound around the second magnetic core.

[0031] The main pole 60 is made of a soft magnetic material with high magnetic permeability and high saturation magnetic flux density, and extends almost perpendicular to the ABS 13. A tip 60a of the main pole 60 on the ABS 13 side tapers toward the ABS 13 and is formed in a columnar shape that is narrower than the other parts. The tip 60a of the main pole 60 protrudes slightly from the ABS 13 of the slider 15.

[0032] The trailing shield 62 is made of a soft magnetic material and is provided to efficiently close the magnetic path through the soft magnetic layer 102 of the magnetic disk 18 directly below the main pole 60. The trailing shield 62 is formed in a substantially L-shape, and its tip portion 62a is formed in a long and narrow rectangular shape. The tip portion 62a of the trailing shield 62 protrudes slightly from the ABS 13 of the slider 15. The trailing shield 62 has a first connection portion 63 connected to the main pole 60. The first connection portion 63 is magnetically connected to an upper portion of the main pole 60, i.e., a portion of the main pole 60 away from the ABS 13, via a non-conductor 65. The first write coil 70 is wound around the first connection portion 63 in the first magnetic core, for example. When writing a signal to the magnetic disk 18, a write current is passed through the first write coil 70, whereby the first write coil 70 excites the main pole 60 and passes a magnetic flux through the main pole 60.

[0033] The leading shield 64 made of a soft magnetic material is provided on the leading side of the main pole 60 so as to face the main pole 60. The leading shield 64 is formed in a substantially L-shape, and a tip portion 64a on the ABS 13 side is formed in a long and narrow rectangular shape. The tip portion 64a protrudes slightly from the ABS 13 of the slider 15. The leading shield 64 also has a second connection portion 68 joined to the main pole 60 at a position spaced apart from the ABS 13. The second connection portion 68 is formed of, for example, a soft magnetic material, and is magnetically connected to the upper portion of the main pole 60, i.e., the portion of the main pole 60 spaced apart from the ABS 13, via a non-conductive material 69. This allows the second connection portion 68 to form a magnetic circuit together with the main pole 60 and the leading shield 64. The second write coil 72 of the write head 58 is disposed, for example, wound around the second connection portion 68, and applies a magnetic field to this magnetic circuit.

[0034] A plurality of connection pads PT are provided on the trailing end 15b of the slider 15. The first write coil 70 and the second write coil 72 are each connected to the connection pads PT via wiring, and are further connected to a head amplifier IC 80 via a flexure 42. When writing a signal to the magnetic disk 18, a write current is supplied to the first write coil 70 and the second write coil 72, thereby exciting the main pole 60 and causing a magnetic flux to flow through the main pole 60. Similarly, the magnetoresistance effect element 55 of the read head 54 is connected to a connection pad PT via a wire (not shown), and is further connected to a head amplifier IC 80 via a flexure 42. The signal read by the read head 54 is amplified by the head amplifier IC 80 and sent to the main controller.

[0035] The first heater 76a and the second heater 76b are each connected to a connection pad PT via a wire, and further connected to a head amplifier IC 80 via a flexure 42. By applying driving power from the head amplifier IC 80 to the first heater 76a and the second heater 76b, the heaters and the surroundings of the heaters are heated, and the write head 58 or the read head 54 can be caused to bulge toward the magnetic disk 18.

[0036] 6 is a block diagram showing a schematic configuration of the entire HDD 11 including the main controller. As shown in the figure, the HDD 11 includes a controller including a head amplifier IC 80 for driving the magnetic head 16, a main controller 90, and a driver IC 52. The head amplifier IC 80 is provided, for example, in the actuator assembly 22, and is electrically connected to the magnetic head 16 via the flexure 42. The head amplifier IC 80 includes a recording current supply circuit (recording current supply unit) 82 for supplying a recording current to the recording coils 70 and 72 of the magnetic head 16, a heater power supply circuit 84 for supplying driving power to the thermal actuators (heaters 76a and 76b) of the magnetic head 16, an amplifier 86 for amplifying a signal read by the magnetic head 16, a PZT power supply circuit 88 for supplying a driving voltage to the piezoelectric element (microactuator) 50, and the like.

[0037] The main controller 90 and the driver IC 52 are configured on the aforementioned printed circuit board 27 provided on the rear side of the housing 10. The main controller 90 includes an R / W channel 92, a hard disk controller (HDC) 94, a microprocessor (MPU) 96, a memory 97, etc. The main controller 90 is electrically connected to the magnetic head 16 via the head amplifier IC 80. The main controller 90 is electrically connected to the VCM 24 and the spindle motor 19 via the driver IC 52. The HDC 94 is connectable to a host computer 95.

[0038] Various measurement values, heater power setting values, etc., which will be described later, are stored in the memory 97 of the main controller 90. In the main controller 90, for example, the MPU 96 includes a write control unit 96a that controls the write head, a read control unit 96b that controls the read head, a heater control unit 96c that controls the power supplied to the thermal actuator, and a PZT control unit 96d that controls the power (voltage) supplied to the piezoelectric element 50.

[0039] Next, an operation of measuring and adjusting the distance (gap) between the magnetic head 16 and the surface of the magnetic disk 18 (sometimes called the flying height or back-off (BO)) in the HDD 11 configured as above will be described. The HDD 11 performs the gap measurement and adjustment operation at the time of shipment, at regular intervals, or after each recording operation. 7 is a diagram showing an example of a flying state of the magnetic head 16. In the diagram, BO indicates the back-off amount of the magnetic head 16, and SP indicates the desired gap of the recording head 58. θ indicates the inclination angle of the ABS 13 with respect to the surface of the magnetic disk 18 , and r indicates the distance between the trailing end of the slider and the main pole 60 .

[0040] During normal recording operation, the main controller 90 supplies heater power of a predetermined power value from the heater power supply circuit 84 to the first heater 76a and the second heater 76b, and heats the first heater 76a and the second heater 76b. As a result, the write head 58 and its surrounding area are heated, and the write head 58 bulges toward the surface of the magnetic disk 18, and the gap (back-off amount) BO between the write head 58 and the disk surface is set to a predetermined value. By increasing the power value supplied to the heater, the protrusion amount increases and the gap decreases. By reducing the power value supplied to the heater, the protrusion amount decreases and the gap increases. The heater control unit 96c and the heater power supply circuit 84 control the heating degree (supply power value) of the first and second heaters 76a, 76b so that the gap BO is a desired value. The magnetic head 16 performs a recording operation with the gap BO set to the predetermined gap BO.

[0041] FIG. 8 is a flowchart showing an example of the measurement and adjustment operations. As shown in the figure, for example, in the measurement and adjustment operation of the gap BO at the time of shipping the HDD, the main controller 90 first selects an arbitrary suspension assembly 30 and its magnetic head N (magnetic head 16). The PZT control unit 96d of the main controller 90 supplies the maximum driving voltage Vmax (V) of the microactuator to the pair of piezoelectric elements 50 of the selected suspension assembly 30 from the PZT power supply circuit 88 to drive the pair of piezoelectric elements 50 to expand and contract. With the piezoelectric elements 50 driven, the main controller 90 supplies heater power from the heater power supply circuit 84 to the first heater 76a and the second heater 76b to make the magnetic head 16 bulge toward the surface of the magnetic disk 18. The main controller 90 increases the heater power value until the lower end corner of the magnetic head 16 contacts (touches down) the surface of the magnetic disk 18, measures the heater power value at the time of touchdown, and stores it in the memory 97 as the touchdown output (TDP) MA1 (mW) (ST1).

[0042] Next, the main controller 90 reduces the heater power value to a normal value to return the magnetic head 16 to the normal flying height BO, and further stops the power supply to the piezoelectric element 50, i.e., returns the piezoelectric element 50 to a non-energized state. With the piezoelectric element 50 in a non-driven state, the main controller 90 supplies heater power from the heater power supply circuit 84 to the first heater 76a and the second heater 76b to cause the magnetic head 16 to bulge toward the surface of the magnetic disk 18. The main controller 90 increases the heater power value until the lower end corner of the magnetic head 16 contacts (touches down) the surface of the magnetic disk 18, measures the heater power value at the time of touchdown, and stores it in the memory 97 as touchdown output (TDP) MA2 (mW) (ST2).

[0043] The main controller 90 calculates the difference ΔMA=(MA2-MA1) (mW) between the touchdown output MA1 (mW) when the microactuator is driven and the touchdown output MA2 when the microactuator is not driven, and stores this in the memory 97 (ST3). ΔMA corresponds to the variation in the flying height when the piezoelectric element 50 is driven at the maximum driving voltage.

[0044] Usually, the flying height (back-off OB) of the magnetic head 16 is determined by an accumulation of fluctuation factors. Fluctuations in flying height caused by driving the piezoelectric element are one of those fluctuation factors. Here, the target value for the fluctuations in flying height caused by driving the piezoelectric element is defined as BOMA. If the output difference ΔMA is larger than the target value BOMA, there is an increased risk of contact between the magnetic disk 18 and the slider of the magnetic head 16. The target value BOMA is stored in advance in memory 97. Therefore, according to this embodiment, the main controller 90 compares the calculated output difference ΔMA with the target value BOMA (ST4), and if ΔMA is greater than the target value BOMA, multiplies the maximum drive voltage Vmax by the ratio of BOMA to ΔMA (BOMA / ΔMA) to calculate a correction value Vma (ST5). The main controller 90 sets the obtained correction value Vma as the maximum drive voltage Vmax of the piezoelectric element 50 and stores it in the memory 97. On the other hand, if ΔMA is smaller than the target value BOMA, the main controller 90 stores the maximum drive voltage Vmax in the memory 97 without changing it (ST7).

[0045] During a recording operation, the main controller 90 drives the piezoelectric element 50 within the range of the maximum drive voltage VMax set as described above. This ensures that the fluctuation in the flying height (BO) of the magnetic head 16 when the microactuator (piezoelectric element) is driven is equal to or less than the target value BOMA. Therefore, even when the microactuator is driven, the fluctuation in the flying height BO of the magnetic head 16 can be suppressed, and the risk of contact between the magnetic disk and the head slider can be reduced.

[0046] According to the HDD of the first embodiment configured as described above, the driving voltage of the microactuator is adjusted according to the difference between the touchdown output when the microactuator is driven and the touchdown output when the microactuator is not driven, thereby suppressing the fluctuation of the flying height of the magnetic head when the microactuator is driven to a predetermined target value or less. This reduces the risk of contact between the magnetic disk and the head slider, and improves the reliability of the HDD. Furthermore, it becomes possible to set the flying height BO of the magnetic head 16, i.e., the gap between the surface of the magnetic disk and the magnetic head 16, to a minimum value, thereby improving the recording density of the HDD. As described above, according to the first embodiment, it is possible to provide a disk drive that is capable of suppressing fluctuations in the gap between the recording medium and the head and improving reliability. In the first embodiment, for an HDD having a plurality of suspension assemblies and a plurality of magnetic heads, the measurement and adjustment of the maximum driving voltage of the microactuator may be performed for each suspension assembly.

[0047] Next, an HDD according to another embodiment will be described. In the following description of the other embodiment, the same parts as those in the first embodiment described above are given the same reference numerals, and detailed descriptions thereof will be omitted or simplified, and the detailed description will focus on parts that are different from the first embodiment.

[0048] Second embodiment FIG. 9 is a schematic diagram of a differential voltage clip used to set the drive voltage for the microactuator in the HDD according to the second embodiment. In the second embodiment, a differential voltage clip is applied to control the drive voltage of the microactuator (piezoelectric element 50). In this embodiment, the differential voltage clip is defined as a control that suppresses the voltage difference for each servo frame as the frequency of the voltage input to the piezoelectric element 50 becomes higher. 9, in the second embodiment, the drive voltage at the sampling frequency is set to a set voltage of Vs. In this case, the drive voltage is limited to Vs at the sampling frequency.

[0049] FIG. 10 is a flowchart showing an example of the operation of measuring and adjusting the drive voltage in the second embodiment. As shown in the figure, in the second embodiment, as in the first embodiment described above, the main controller 90 measures the touchdown output MA1 when the microactuator is driven (ST1), measures the touchdown output MA2 when the microactuator is not driven (ST2), and calculates the difference ΔMA (ST3). Next, the main controller 90 compares the calculated output difference ΔMA with the target value BOMA (ST4), and if ΔMA is greater than the target value BOMA, the main controller 90 sets the voltage Vf1 corresponding to the frequency f1 based on the differential voltage clip shown in FIG. 9, assuming that the driving voltage frequency of the piezoelectric element 50 at the time of touchdown is f1. The main controller 90 multiplies the voltage Vf1 by the ratio (BOMA / ΔMA) between BOMA and ΔMA to calculate the correction value Vsf1 (ST5). The main controller 90 sets the obtained correction value Vsf1 to the driving voltage Vf1 at the frequency f1 and stores it in the memory 97 (ST6). Furthermore, if the frequency range at the time of touchdown is set to f1 to f2, the main controller 90 may carry out the same process as above at a frequency fm between f1 and f2. On the other hand, if ΔMA is smaller than the target value BOMA in ST4, the main controller 90 stores the drive voltage Vf1 as a predetermined drive voltage Vf1 in the memory 97 without changing the drive voltage Vf1 (ST7).

[0050] During a recording operation, the main controller 90 drives the piezoelectric element 50 within the range of the drive voltage Vf1 set as described above. This ensures that the fluctuation in the flying height (BO) of the magnetic head 16 when the microactuator (piezoelectric element) is driven is equal to or less than the target value BOMA. Therefore, even when the microactuator is driven, the fluctuation in the flying height BO of the magnetic head 16 can be suppressed, and the risk of contact between the magnetic disk and the head slider can be reduced. As described above, according to the second embodiment, it is possible to provide a disk drive that is capable of suppressing fluctuations in the gap between the recording medium and the head and improving reliability.

[0051] Third embodiment Fig. 11 is a flowchart showing an example of the operation of measuring and adjusting the drive voltage in the third embodiment. Fig. 12 is a schematic diagram of a differential voltage clip used to set the drive voltage of the microactuator in the third embodiment.

[0052] As shown in FIG. 11, in the third embodiment, as in the first embodiment described above, the main controller 90 measures the touchdown output MA1 when the microactuator is driven (ST1), measures the touchdown output MA2 when the microactuator is not driven (ST2), and calculates the difference ΔMA (ST3). Next, the main controller 90 compares the calculated output difference ΔMA with the target value BOMA (ST4), and if ΔMA is greater than the target value BOMA, the main controller 90 sets the voltage Vs corresponding to the drive voltage frequency of the piezoelectric element 50 at the time of touchdown based on the differential voltage clip shown in FIG. 12, assuming that the drive voltage frequency of the piezoelectric element 50 at the time of touchdown is f1. The main controller 90 multiplies the voltage Vs by the ratio (BOMA / ΔMA) between BOMA and ΔMA to calculate the correction value Vsma (ST5). The main controller 90 sets the obtained correction value Vsma as the set value Vs of the differential voltage clip at the sampling frequency, and stores it in the memory 97 (ST6). On the other hand, if ΔMA is smaller than the target value BOMA in ST4, the main controller 90 stores the drive voltage set value Vs in the memory 97 without changing the drive voltage Vs (ST7).

[0053] During a recording operation, the main controller 90 drives the piezoelectric element 50 within the range of the drive voltage Vs set as described above. In this case, as shown by the dashed line in Fig. 12, the frequency characteristics of the differential voltage clip are suppressed according to the correction value Vsma, so that the fluctuation in the flying height (BO) of the magnetic head 16 when the microactuator (piezoelectric element) is driven is equal to or less than the target value BOMA. Therefore, even when the microactuator is driven, the fluctuation in the flying height BO of the magnetic head 16 can be suppressed, and the risk of contact between the magnetic disk and the head slider can be reduced. As described above, according to the third embodiment, it is possible to provide a disk drive that is capable of suppressing fluctuations in the gap between the recording medium and the head and improving reliability. In both the first and second embodiments, for HDDs having multiple suspension assemblies and multiple magnetic heads, the drive voltage of the microactuator may be measured and adjusted for each suspension assembly (each magnetic head). By setting a drive voltage for each magnetic head, the variation in spacing between the individual heads can be kept below a certain level, enabling more accurate back-off control.

[0054] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. For example, the material, shape, size, etc. of the elements constituting the head portion of the magnetic head can be changed as needed. In the magnetic disk device, the number of magnetic disks and magnetic heads can be increased or decreased as needed, and various sizes of magnetic disks can be selected. [Explanation of symbols]

[0055] 10: housing; 11: magnetic disk device; 12: base; 15: slider; 16: magnetic head; 17: head portion; 30: suspension assembly; 34... suspension, 42... wiring member (flexure), 44... gimbal portion, 54: read head, 58: write head, 76a: first heater, 76b...second heater, 80...head amplifier IC, 90...main controller

Claims

1. A disk-shaped recording medium; a magnetic head having a heater for adjusting a gap between a write head, a read head, and the recording medium; a suspension assembly for supporting the magnetic head; a microactuator including a piezoelectric element provided on the suspension assembly; a controller that sets a drive voltage for the piezoelectric element in accordance with a difference between a touchdown output when the piezoelectric element is driven and a touchdown output when the piezoelectric element is not driven; A disk device comprising:

2. If the touchdown output of the piezoelectric element when driven is MA1, the touchdown output of the piezoelectric element when not driven is MA2, the difference is ΔMA, the target value of the variation in the gap is BOMA, and the maximum drive voltage of the piezoelectric element is VMax, then:

2. The disk device of claim 1, wherein when the difference ΔMA is greater than the target value BOMA, the controller calculates a correction value Vma by multiplying the ratio of the BOMA to the ΔMA by the maximum drive voltage VMax, and sets the calculated correction value Vma as the maximum drive voltage VMax of the piezoelectric element.

3. a plurality of suspension assemblies each having the magnetic head and the piezoelectric element; 2. The disk drive according to claim 1, wherein the controller sets a drive voltage for the piezoelectric element for each suspension assembly in accordance with a difference between a touchdown output when the piezoelectric element is driven and a touchdown output when the piezoelectric element is not driven.

4. A disk-shaped recording medium; a magnetic head having a heater for adjusting a gap between a write head, a read head, and the recording medium; a suspension assembly for supporting the magnetic head; a microactuator including a piezoelectric element provided on the suspension assembly; a controller that sets a differential voltage clip of the piezoelectric element such that a variation in the gap caused by driving the piezoelectric element is equal to or smaller than a target value according to a difference between a touchdown output when the piezoelectric element is driven and a touchdown output when the piezoelectric element is not driven; A disk device comprising:

5. a plurality of suspension assemblies each having the magnetic head and the piezoelectric element; The disk device described in claim 4, wherein the controller sets, for each suspension assembly, a differential voltage clip of the piezoelectric element such that the variation in the gap due to driving of the piezoelectric element is below a target value, depending on the difference between the touchdown output of the piezoelectric element when driven and the touchdown output of the piezoelectric element when not driven.

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