Magnetic disk device

Abstract

To provide a magnetic disk device that can improve the reliability.SOLUTION: According to one embodiment, a magnetic disk device includes a magnetic disk, a gimbal, and a controller. The magnetic disk rotates around a first rotary axis. The gimbal has a magnetic head and a piezoelectric element. The piezoelectric element is deformed in accordance with an applied drive voltage to move the magnetic head. The controller applies a polarization voltage to the piezoelectric element to give spontaneous polarization to the piezoelectric element. The polarization voltage satisfies a relation of ΔV=(2πf)A ΔT<ΔVmax where ΔV is a voltage change amount of the polarization voltage per unit time, f is a frequency of the polarization voltage, A is an amplitude of the polarization voltage, ΔT is a time resolution of the polarization voltage, ΔVmax is a voltage change amount per unit time that excites the main resonance of the gimbal by being applied to the piezoelectric element.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a magnetic disk drive. [Background technology]

[0002] A magnetic disk drive such as a hard disk drive is provided with a gimbal, which includes a part of a suspension and a magnetic head and a piezoelectric element mounted on the suspension. When a voltage is applied to the piezoelectric element, the piezoelectric element deforms due to the inverse piezoelectric effect, thereby adjusting the position of the magnetic head.

[0003] For example, when an overvoltage is applied to a piezoelectric element due to electrostatic discharge, the spontaneous polarization of the piezoelectric element may disappear. A piezoelectric element whose spontaneous polarization has disappeared can be given spontaneous polarization again by, for example, applying a high voltage. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 8,929,022 Summary of the Invention [Problem to be solved by the invention]

[0005] When a high voltage is applied to a piezoelectric element, the gimbal may resonate, causing the magnetic head to vibrate. For example, if the piezoelectric element causes the gimbal to resonate above the data zone of a magnetic disk, the magnetic head floating above the magnetic disk may fluctuate, potentially causing the magnetic head to come into contact with the data zone. If contact between the magnetic head and the data zone can be prevented, the reliability of the magnetic disk drive can be improved.

[0006] One example of a problem to be solved by the present invention is to provide a magnetic disk drive that can improve reliability. [Means for solving the problem]

[0007] A magnetic disk drive according to one embodiment includes a magnetic disk, a gimbal, and a controller. The magnetic disk is configured to rotate around a first rotation axis. The gimbal has a magnetic head and a piezoelectric element. The magnetic head is configured to record and reproduce data on the magnetic disk. The piezoelectric element is configured to move the magnetic head by deforming in response to an applied drive voltage. The controller is configured to apply a polarization voltage to the piezoelectric element to impart spontaneous polarization to the piezoelectric element. Given that the voltage change per unit time of the polarization voltage is ΔV, the frequency of the polarization voltage is f, the amplitude of the polarization voltage is A, the time resolution of the polarization voltage is ΔT, and the voltage change per unit time applied to the piezoelectric element to excite resonance of the gimbal is ΔVmax, the polarization voltage satisfies the relationship ΔV=(2πf)A·ΔT<ΔVmax. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is an exemplary diagram showing the configuration of a magnetic disk device according to the first embodiment. [Figure 2] FIG. 2 is an exemplary plan view showing the configuration of the magnetic disk device of the first embodiment. [Figure 3] FIG. 3 is an exemplary plan view showing the gimbal of the first embodiment. [Figure 4] FIG. 4 is an exemplary flowchart showing an example of the operation of the magnetic disk device of the first embodiment. [Figure 5] FIG. 5 is an exemplary flowchart showing an example of the operation of the magnetic disk device according to the second embodiment. [Figure 6] FIG. 6 is an exemplary flowchart showing an example of the operation of the magnetic disk device according to the third embodiment. [Figure 7] FIG. 7 is an exemplary flowchart showing an example of the operation of the magnetic disk device according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] (First embodiment) The first embodiment will be described below with reference to FIGS. 1 to 4. In this specification, components according to the embodiment and descriptions of the components may be described using multiple expressions. The components and their descriptions are merely examples and are not limited by the expressions in this specification. The components may also be identified by names different from those in this specification. Furthermore, the components may also be described using expressions different from those in this specification.

[0010] In the following description, "suppress" is defined as, for example, preventing an event, action, or influence from occurring, or reducing the severity of an event, action, or influence. Also, in the following description, "restrict" is defined as, for example, preventing movement or rotation, or allowing movement or rotation within a predetermined range and preventing movement or rotation beyond the predetermined range.

[0011] 1 is an exemplary diagram showing the configuration of a magnetic disk device 10 according to the first embodiment. The magnetic disk device 10 is, for example, a hard disk drive (HDD). Note that the magnetic disk device 10 may also be another type of magnetic disk device, such as a hybrid HDD.

[0012] The magnetic disk device 10 can be connected to a host 2. The magnetic disk device 10 and the host 2 can communicate with each other in accordance with, for example, the SAS (Serial Attached SCSI) standard. Note that the standard of the communication path between the magnetic disk device 10 and the host 2 is not limited to this example.

[0013] The host 2 is, for example, a processor, a personal computer, or a server. The magnetic disk device 10 can receive access commands (read commands and write commands) from the host 2.

[0014] 2 is an exemplary plan view showing the configuration of a magnetic disk device 10 according to the first embodiment. As shown in FIGS. 1 and 2, the magnetic disk device 10 includes a spindle motor (SPM) 11, a plurality of magnetic disks 12, a plurality of magnetic heads 13, an actuator 14, a voice coil motor (VCM) 15, a plurality of microactuators (MA) 16, a ramp load mechanism 17, an outer stopper 21, an inner stopper 22, a system-on-chip (SoC) 23, a head amplifier 24, and a servo controller (SVC) 25.

[0015] The magnetic head 13 may also be referred to as a slider. The MA 16 is an example of a piezoelectric element. The ramp load mechanism 17 is an example of a ramp. The inner stopper 22 is an example of a stopper. The SVC 25 is an example of a controller. The SVC 25 may also be referred to as a servo combo.

[0016] As shown in Fig. 1, a plurality of magnetic disks 12 are held by, for example, a clamp on the hub of the SPM 11. The SPM 11 can rotate the plurality of magnetic disks 12 integrally around a central axis Axd. In other words, the magnetic disks 12 rotate around the central axis Axd. The central axis Axd is an example of a first rotation axis, and is, for example, the central axis of the magnetic disks 12.

[0017] 2, each of the magnetic disks 12 has a recording surface 12s. For example, a recording surface 12s is provided on each of both sides of the magnetic disk 12. Each recording surface 12s has a data zone 12sd, an inner zone 12si, and an outer zone 12so.

[0018] The data zone 12sd is located between the inner peripheral zone 12si and the outer peripheral zone 12so, and data is recorded in the data zone 12sd. The inner peripheral zone 12si is closer to the central axis Axd than the data zone 12sd and the outer peripheral zone 12so. The outer peripheral zone 12so is farther from the central axis Axd than the data zone 12sd and the inner peripheral zone 12si.

[0019] The number of the magnetic heads 13 is set so that the magnetic heads 13 can access the recording surfaces 12s of the magnetic disks 12. Each of the magnetic heads 13 is provided so that it can be positioned on the recording surface 12s of the corresponding magnetic disk 12. Each of the magnetic heads 13 can record data to and reproduce data from the data zone 12sd of the magnetic disk 12 corresponding to that magnetic head 13.

[0020] The actuator 14 has a carriage 31 and a plurality of suspensions 32. The actuator 14 may have a plurality of carriages 31. The carriage 31 has a block 41, a plurality of arms 42, and a holder 43.

[0021] The block 41 is rotatable around the central axis Axc. The central axis Axc extends substantially parallel to the central axis Axd and is spaced apart from the central axis Axd. The number of arms 42 is set corresponding to the number of magnetic heads 13. The multiple arms 42 protrude substantially parallel to each other from the block 41 in a direction substantially perpendicular to the central axis Axc. The holder 43 protrudes from the block 41 and is disposed on the opposite side of the multiple arms 42.

[0022] The number of suspensions 32 is set to correspond to the number of magnetic heads 13. Each of the plurality of suspensions 32 has a base plate 45, a load beam 46, and a flexure 47. The base plate 45 and the load beam 46 are made of, for example, stainless steel.

[0023] The base plate 45 is attached to the tip of the arm 42. The load beam 46 is formed in the shape of a thin, elastically deformable plate. The load beam 46 is attached to the base plate 45 so as to extend from the base plate 45. The load beam 46 has a lift tab 46a provided at the tip of the actuator 14.

[0024] The flexure 47 is a type of flexible printed circuit board (FPC) and includes multiple insulating layers, a conductive layer, and a backing plate. The conductive layer is, for example, provided between two insulating layers and includes multiple wirings and multiple pads. The backing plate is made of, for example, stainless steel and reinforces the flexure 47.

[0025] The backing plate of the flexure 47 is attached to the load beam 46 by, for example, welding. Each of the plurality of magnetic heads 13 is mounted on the flexure 47 near the tip of a corresponding one of the plurality of suspensions 32.

[0026] The VCM 15 has a voice coil, a pair of yokes, and a magnet attached to the yoke. The voice coil is held by a holder 43. The VCM 15 rotates the actuator 14 around a central axis Axc within a predetermined range. By rotating around the central axis Axc, the actuator 14 moves the magnetic head 13 mounted on the suspension 32 relative to the magnetic disk 12.

[0027] The VCM 15 can rotate the actuator 14 in a first direction Dr1 and a second direction Dr2 around the central axis Axc. The second direction Dr2 is the opposite direction to the first direction Dr1. By rotating in the first direction Dr1, the actuator 14 moves the magnetic head 13 away from the central axis Axd. By rotating in the second direction Dr2, the actuator 14 moves the magnetic head 13 closer to the central axis Axd.

[0028] The VCM 15 moves the suspension 32 and the arm 42 substantially parallel to the recording surface 12s of the magnetic disk 12. The VCM 15 of this embodiment moves the magnetic head 13 relative to the magnetic disk 12 in a radial direction substantially perpendicular to Axd.

[0029] 3 is an exemplary plan view showing the gimbal G of the first embodiment. As shown in FIG. 3, the magnetic disk drive 10 is provided with the gimbal G for adjusting the position of the magnetic head 13. The gimbal G has the magnetic head 13, a plurality of MAs 16, and a part of the suspension 32.

[0030] The MA 16 is mounted on the suspension 32. For example, two MAs 16 are mounted on one suspension 32. The MA 16 in this embodiment is located near the magnetic head 13 and is mounted on the flexure 47. However, the MA 16 is not limited to this example. For example, the MA 16 may be located near the position where the base plate 45 and the load beam 46 are connected.

[0031] Each MA 16 has a piezoelectric body 16a and two electrodes 16b and 16c. The electrodes 16b and 16c are provided on the surface of the piezoelectric body 16a and are spaced apart from each other. The electrode 16b is electrically connected to the SVC 25 through the flexure 47. The electrode 16c is electrically connected to, for example, the load beam 46 through the conductive layer and backing plate of the flexure 47, and is set to ground potential. When a voltage is applied to the electrode 16b, the MA 16 deforms due to the inverse piezoelectric effect of the piezoelectric body 16a. For example, the piezoelectric body 16a expands and contracts in the longitudinal direction of the suspension 32.

[0032] As the two MAs 16 expand and contract independently, the suspension 32 on which the MAs 16 are mounted bends substantially parallel to the recording surface 12s. The magnetic head 13 is mounted on the flexure 47 of the suspension 32, and is therefore moved relative to the magnetic disk 12 by the deformation of the MAs 16.

[0033] 2, the lift tab 46a of the actuator 14 can move along a locus T relative to the recording surface 12s. The ramp load mechanism 17 is provided on the locus T near the outer edge of the magnetic disk 12. The central axis Axd of the magnetic disk 12 is located near the locus T. The actuator 14 can move the lift tab 46a between the ramp load mechanism 17 and the central axis Axc.

[0034] The ramp load mechanism 17 is spaced apart from the central axis Axd in the first direction Dr1. The ramp load mechanism 17 parks the multiple magnetic heads 13, for example, during unloading. For example, the ramp load mechanism 17 supports the lift tab 46a of the load beam 46 to hold the actuator 14 and hold the magnetic heads 13 in the retracted position.

[0035] The outer stopper 21 and the inner stopper 22 are spaced apart from each other around the central axis Axc. The actuator 14 is located between the outer stopper 21 and the inner stopper 22.

[0036] When the actuator 14 rotates in the first direction Dr1 to a predetermined position, the actuator 14 abuts against the outer stopper 21. By abutting against the actuator 14, the outer stopper 21 restricts the rotation of the actuator 14 in the first direction Dr1. When the actuator 14 contacts the outer stopper 21, the ramp load mechanism 17 holds the actuator 14, and the magnetic head 13 is positioned at the retracted position.

[0037] When the actuator 14 rotates in the second direction Dr2 to a predetermined position, it abuts against the inner stopper 22. By abutting against the actuator 14, the inner stopper 22 restricts the rotation of the actuator 14 in the second direction Dr2. When the actuator 14 contacts the inner stopper 22, the magnetic head 13 is positioned above the inner peripheral zone 12si. In other words, the magnetic head 13 is positioned outside the data zone 12sd.

[0038] 1, the SoC 23 includes a micro-processing unit (MPU) 51 and a hard disk controller (HDC) 52. The MPU 51 may also be referred to as a processor.

[0039] The MPU 51 operates according to a firmware program. The firmware program is stored in a predetermined non-volatile storage area. This storage area may be the magnetic disk 12 or a ROM (Read Only Memory) of the SoC 23. The MPU 51 controls the overall operation of the magnetic disk device 10. For example, the MPU 51 controls the HDC 52 and the SVC 25.

[0040] The HDC 52 controls the transmission and reception of data to and from the host 2. The HDC 52 interprets access commands from the host 2 and, based on the interpretation results, executes various controls such as access to the magnetic disk 12. Specifically, the HDC 52 controls access to the magnetic disk 12 using the magnetic head 13 via the read / write channel (RWC) of the SoC 23 and the head amplifier 24.

[0041] The head amplifier 24 amplifies and outputs the signal read by the magnetic head 13 from the magnetic disk 12 and supplies it to the RWC of the SoC 23. The RWC demodulates the signal supplied from the head amplifier 24 into digital data and supplies it to the HDC 52.

[0042] Furthermore, a signal corresponding to the digital data is supplied from the RWC to the head amplifier 24. The head amplifier 24 amplifies the signal supplied from the RWC and supplies it to the magnetic head 13. The magnetic head 13 records the signal supplied from the head amplifier 24 in the data zone 12sd of the magnetic disk 12.

[0043] The SVC 25 controls the driving of the SPM 11, the VCM 15, and the MA 16. Specifically, the SVC 25 drives the VCM 15 and the MA 16 based on instructions from the MPU 51, thereby positioning the magnetic head 13 at a position instructed by the MPU 51.

[0044] The MPU 51 calculates the command values ​​for the drive voltage of the VCM 15 and the MA 16 in order to make the position of the magnetic head 13 follow the target position. The MPU 51 calculates each command value using, as a feedback input, a position signal that the magnetic head 13 reads from the servo information formed on the recording surface 12s of the magnetic disk 12, and transmits the obtained command values ​​to the SVC 25.

[0045] The SVC 25 applies a voltage according to the command value of the drive voltage of the VCM 15 to the VCM 15, and applies a voltage according to the command value of the drive voltage of the MA 16 to the MA 16. This positions the magnetic head 13 at the target position.

[0046] The SVC 25 applies a drive voltage corresponding to the command value to the electrode 16b of the MA 16. The piezoelectric element 16a of the MA 16 is deformed by the potential difference between the electrode 16b to which the drive voltage is applied and the electrode 16c set to ground potential. That is, the MA 16 is deformed in response to the drive voltage applied to the electrode 16b. This adjusts the position of the magnetic head 13.

[0047] The SVC 25 controls the loading and unloading of the actuator 14 by driving the VCM 15 based on instructions from the MPU 51. During unloading, the SVC 25 drives the VCM 15 to rotate the actuator 14 in a first direction Dr1. As a result, the lift tab 46a of the load beam 46 is supported by the ramp load mechanism 17, and the magnetic head 13 is separated from the magnetic disk 12. During loading, the SVC 25 drives the VCM 15 to rotate the actuator 14 in a second direction Dr2. As a result, the lift tab 46a of the load beam 46 is separated from the ramp load mechanism 17, and the magnetic head 13 is positioned above the recording surface 12s of the magnetic disk 12.

[0048] The SVC 25 drives the SPM 11 based on instructions from the MPU 51. The SVC 25 drives the SPM 11 so that the rotation speed of the SPM 11 is approximately constant at a predetermined target speed.

[0049] During unloading, the ramp load mechanism 17 comes into contact with the lift tab 46a of the load beam 46. The surface of the ramp load mechanism 17 that comes into contact with the lift tab 46a is made of, for example, synthetic resin. Therefore, friction between the surface of the ramp load mechanism 17 and the lift tab 46a can cause the ramp load mechanism 17 to become statically charged.

[0050] When the ramp load mechanism 17 generates electrostatic discharge (ESD), static electricity flows from the lift tab 46a to the load beam 46. The load beam 46 is connected to the backing plate of the flexure 47 by welding. Furthermore, the backing plate of the flexure 47 is electrically connected to the electrode 16c of the MA 16 through a via and a conductive layer of the flexure 47. Therefore, static electricity is applied to the electrode 16c.

[0051] When an overvoltage is applied to the MA 16 due to ESD, the spontaneous polarization of the MA 16 may disappear or be altered. For example, the orientation of the spontaneous polarization of the multiple crystals in the piezoelectric body 16a may become random or may be oriented in a direction different from the desired direction. The SVC 25 applies a voltage to the MA 16, thereby restoring the spontaneous polarization to the MA 16 in the desired direction.

[0052] 3, the magnetic disk device 10 further includes a resistor 55. The resistor 55 is provided, for example, in a circuit that drives the MA 16, and is arranged on a wiring that connects the SVC 25 and the electrode 16b of the MA 16. For example, the SoC 23 detects the current between the resistor 55 and the SVC 25 and the current between the resistor 55 and the electrode 16b, and detects the occurrence of ESD based on the detected currents. Note that the magnetic disk device 10 may also detect the occurrence of ESD using other methods.

[0053] 4 is an exemplary flowchart showing an example of the operation of the magnetic disk device 10 according to the first embodiment. Hereinafter, an example of the repolarization operation of the MA 16 according to this embodiment will be described with reference to FIG.

[0054] First, the MPU 51 drives the VCM 15 via the SVC 25 to perform unload control (S101). The VCM 15 rotates the actuator 14 in the first direction Dr1, causing the lift tab 46a of the load beam 46 to be supported by the ramp load mechanism 17. This unload control is performed during normal operation of the magnetic disk device 10, regardless of the occurrence of ESD. However, the unload control is not limited to this example.

[0055] Next, the MPU 51 drives the VCM 15 via the SVC 25 to perform load control (S102). The VCM 15 rotates the actuator 14 in the second direction Dr2, which causes the actuator 14 held by the ramp load mechanism 17 to move in the second direction Dr2 from the ramp load mechanism 17, and the magnetic head 13 moves onto the recording surface 12s of the magnetic disk 12.

[0056] Next, the MPU 51 drives the VCM 15 via the SVC 25 to perform a seek (movement) until the actuator 14 abuts against the inner stopper 22 (S103). Between S101 and S103, the SVC 25 does not drive the MA 16. Note that the SVC 25 is not limited to this example.

[0057] For example, during the unload control and load control described above, ESD may occur due to friction between the surface of the ramp load mechanism 17 and the lift tab 46a. The SoC 23 determines whether ESD has been detected (S104). The SoC 23 detects the occurrence of ESD periodically or during S101 to S103.

[0058] If the occurrence of ESD is detected by S104 (S104: Yes), the SoC 23 transmits a repolarization command to the SVC 25. Note that the SoC 23 may transmit the repolarization command to the SVC 25 before S101 or during S101 to S103.

[0059] When the SVC 25 receives the repolarization command from the SoC 23, it applies a polarization voltage to the electrode 16b of the MA 16 while the actuator 14 is in contact with the inner stopper 22 (S105). That is, when static electricity is applied to the MA 16, the SVC 25 brings the actuator 14 into contact with the inner stopper 22 and applies the polarization voltage to the electrode 16b.

[0060] The polarization voltage is a DC bias voltage or a voltage obtained by superimposing an AC voltage on a DC bias voltage. The polarization voltage is higher than the drive voltage. Furthermore, the absolute value of the polarization voltage is equal to or greater than the voltage that eliminates the spontaneous polarization of MA16.

[0061] The SVC 25 applies a polarization voltage to the electrode 16b, thereby causing spontaneous polarization in the MA 16. That is, when a polarization voltage is applied to the electrode 16b, the spontaneous polarization of the multiple crystals in the piezoelectric body 16a becomes approximately the same direction. As a result, the MA 16 regains spontaneous polarization, and when a drive voltage is applied to the electrode 16b, it undergoes the desired deformation due to the inverse piezoelectric effect.

[0062] The polarization voltage has a predetermined voltage, amplitude, and frequency. The SVC 25 applies the polarization voltage to the electrode 16b for a predetermined time. The voltage, amplitude, frequency, and time are set to values ​​that can impart spontaneous polarization to the MA 16.

[0063] The voltage, amplitude, frequency, and time of the polarization voltage are set to satisfy, for example, the following equations (1) and (2): Note that the polarization voltage is not limited to this example. ΔV=(2πf)A·ΔT<ΔVmax …(1) T=N / f <Tmax …(2)

[0064] In the above equations (1) and (2), ΔV is the amount of change in the polarization voltage per unit time, f is the frequency of the polarization voltage, A is the amplitude of the polarization voltage, ΔT is the time resolution of the polarization voltage, T is the time during which the polarization voltage is applied to the electrode 16b, N is the number of cycles during which the polarization voltage is applied to the electrode 16b, and Tmax is the start time of the MA 16's positioning control of the magnetic head 13. The time resolution of the polarization voltage corresponds to the control sample period of the MA 16.

[0065] In the above formula (1), ΔVmax is the amount of change in voltage per unit time that is applied to the electrode 16b of the MA 16 to excite the main resonance of the gimbal G. ΔVmax is set, for example, by experiment.

[0066] When the primary resonance of the gimbal G occurs, the magnetic head 13 may vibrate (pitch vibration) repeatedly approaching and moving away from the magnetic disk 12. For example, when a voltage whose voltage change per unit time is ΔVmax is applied to the electrode 16b, the gimbal G causes pitch vibration in the magnetic head 13, which may cause the magnetic head 13 to come into contact with the magnetic disk 12. The SVC 25 of this embodiment applies a polarization voltage that satisfies formula (1) to the electrode 16b, thereby suppressing the primary resonance of the gimbal G and preventing the magnetic head 13 from coming into contact with the magnetic disk 12.

[0067] The magnetic head 13 may vibrate vertically. Because the actuator 14 is in contact with the inner stopper 22, the magnetic head 13 is positioned above the inner peripheral zone 12si of the magnetic disk 12. Even if the magnetic head 13 comes into contact with the inner peripheral zone 12si, it does not come into contact with the data zone 12sd. This prevents the magnetic head 13 from damaging the data recorded in the data zone 12sd.

[0068] When the polarization voltage is applied to the MA 16, or if ESD is not detected in S104 (S104: No), the MPU 51 controls the SVC 25 to start positioning control of the magnetic head 13 by the MA 16 (S106).

[0069] The SVC 25 applies the polarization voltage to the electrode 16b for a time that satisfies the formula (2). Therefore, the MPU 51 can start positioning control of the magnetic head 13 as soon as the MA 16 is able to start the positioning control. Furthermore, the shorter the time that the polarization voltage is applied to the electrode 16b, the better the performance of the magnetic disk device 10 can be.

[0070] Next, the SVC 25 drives the SPM 11 to rotate the actuator 14 in the first direction Dr1. This separates the actuator 14 from the inner stopper 22, and the magnetic head 13 moves (on-track) from the inner zone 12si to the data zone 12sd (S107). As a result, the magnetic disk device 10 can adjust the position of the magnetic head 13 by using the MA 16, which has been given the desired spontaneous polarization again.

[0071] In the magnetic disk drive 10 according to the first embodiment described above, the magnetic disk 12 is configured to rotate around a central axis Axd. The gimbal G includes a magnetic head 13 and an MA 16. The magnetic head 13 is configured to record and reproduce data on the magnetic disk 12. The MA 16 is configured to move the magnetic head 13 by deforming in response to an applied drive voltage. The SVC 25 is configured to apply a polarization voltage to the MA 16 to impart spontaneous polarization to the MA 16. Given that the voltage change per unit time of the polarization voltage is ΔV, the frequency of the polarization voltage is f, the amplitude of the polarization voltage is A, the time resolution of the polarization voltage is ΔT, and the voltage change per unit time applied to the MA 16 to excite resonance of the gimbal G is ΔVmax, the polarization voltage satisfies the relationship ΔV=(2πf)A·ΔT<ΔVmax.

[0072] For example, when an overvoltage is applied to MA16 due to ESD, the spontaneous polarization of MA16 may disappear. SVC25 can apply a polarization voltage to electrode 16b of MA16 to give MA16 spontaneous polarization again. Therefore, even if the spontaneous polarization of MA16 temporarily disappears, the magnetic disk drive 10 can recover the spontaneous polarization of MA16, and thus can more accurately adjust the position of the magnetic head 13 by MA16. Also, the voltage change amount ΔV per unit time of the polarization voltage is lower than the voltage change amount ΔVmax per unit time that excites the resonance of the gimbal G. For this reason, the magnetic disk drive 10 can suppress the occurrence of vibrations of the magnetic head 13 that would cause it to contact the magnetic disk 12 while the polarization voltage is applied to electrode 16b of MA16. From the above, the magnetic disk drive 10 can improve its reliability.

[0073] Assuming that the time for which the polarization voltage is applied to MA16 is T, the number of cycles for which the polarization voltage is applied to MA16 is N, and the startup time is Tmax, the polarization voltage satisfies the relationship T = N / f < Tmax.

[0074] SVC25 applies a polarization voltage to electrode 16b of MA16 in a time shorter than the startup time. Thereby, the magnetic disk drive 10 can give MA16 spontaneous polarization before the magnetic head 13 starts recording and reproducing data with respect to the magnetic disk 12. Therefore, the magnetic disk drive 10 can suppress the extension of the time until the magnetic head 13 starts recording and reproducing data with respect to the magnetic disk 12, and can more reliably adjust the position of the magnetic head 13 by MA16.

[0075] The actuator 14 is configured to rotate about a central axis Axc to move the magnetic head 13 relative to the magnetic disk 12. The ramp load mechanism 17 is spaced from the central axis Axd in a first direction Dr1 about the central axis Axc and is capable of holding the actuator 14. The inner stopper 22 is configured to abut against the actuator 14 to restrict rotation of the actuator 14 in a second direction Dr2 opposite to the first direction Dr1. The SVC 25 is configured to apply a polarization voltage to the electrode 16b when the actuator 14 is in contact with the inner stopper 22.

[0076] When the actuator 14 is in contact with the inner stopper 22, the magnetic head 13 is located outside the data zone 12sd of the magnetic disk 12. Therefore, even if the MA 16, to which a polarization voltage is applied to the electrode 16b, excites resonance of the gimbal G, the magnetic disk device 10 can prevent the magnetic head 13 from coming into contact with the data zone 12sd of the magnetic disk 12, thereby improving reliability.

[0077] The SVC 25 is configured to bring the actuator 14 into contact with the inner stopper 22 and apply a polarization voltage to the MA 16 when static electricity is applied to the MA 16 .

[0078] For example, when the actuator 14 held by the ramp load mechanism 17 moves, friction between the ramp load mechanism 17 and the actuator 14 may cause the ramp load mechanism 17 to become statically charged. When ESD occurs, static electricity from the ramp load mechanism 17 is applied to the electrode 16c of the MA 16 through, for example, the load beam 46 of the actuator 14 and the backing plate and wiring of the flexure 47. This static electricity may cause the spontaneous polarization of the MA 16 to disappear. However, the SVC 25 of this embodiment applies a polarization voltage to the electrode 16b of the MA 16 when static electricity is applied to the MA 16. This allows the magnetic disk drive 10 to efficiently recover the spontaneous polarization of the MA 16.

[0079] (Second embodiment) The second embodiment will be described below with reference to Fig. 5. In the following description of the embodiments, components having the same functions as components already described are given the same reference numerals as the components already described, and further description may be omitted. Furthermore, components given the same reference numerals do not necessarily have all the same functions and properties, and may have different functions and properties according to each embodiment.

[0080] 5 is an exemplary flowchart showing an example of the operation of the magnetic disk device 10 according to the second embodiment. An example of the repolarization operation of the MA 16 according to the second embodiment will be described below with reference to FIG. 5. The magnetic disk device 10 according to the second embodiment re-polarizes the MA 16 when ESD is detected.

[0081] First, the SoC 23 determines whether or not ESD has been detected (S201). If ESD has not been detected (S201: No), the SoC 23 repeats S201 until ESD is detected.

[0082] If the SoC 23 detects ESD (S201: Yes), the HDC 52 sends a repolarization command to the SVC 25. In accordance with the repolarization command, the SVC 25 drives the VCM 15 and performs a seek until the actuator 14 abuts against the inner stopper 22 (S103).

[0083] Next, the SVC 25 applies a polarization voltage to the electrode 16b of the MA 16 while the actuator 14 is in contact with the inner stopper 22 (S105). That is, when static electricity is applied to the MA 16, the SVC 25 brings the actuator 14 into contact with the inner stopper 22 and applies the polarization voltage to the electrode 16b. Thereafter, S106 and S107 are executed, as in the first embodiment.

[0084] In the magnetic disk device 10 of the second embodiment described above, when static electricity is applied to the MA 16, the SVC 25 is configured to bring the actuator 14 into contact with the inner stopper 22 to apply a polarization voltage to the MA 16. This allows the magnetic disk device 10 to efficiently recover the spontaneous polarization of the MA 16.

[0085] (Third embodiment) The third embodiment will be described below with reference to FIG. 6. FIG. 6 is an exemplary flowchart showing an example of the operation of the magnetic disk device 10 according to the third embodiment. An example of the repolarization operation of the MA 16 in the third embodiment will be described below with reference to FIG. 6. The magnetic disk device 10 of the third embodiment re-introduces spontaneous polarization to the MA 16 during loading / unloading.

[0086] As in the first embodiment, the MPU 51 performs unload control in S101, load control in S102, and seek control in S103 up to the inner stopper 22. When the actuator 14 abuts against the inner stopper 22, the HDC 52 transmits a repolarization command to the SVC 25.

[0087] Upon receiving the repolarization command from the HDC 52, the SVC 25 applies a polarization voltage to the electrode 16b of the MA 16 when the actuator 14 is in contact with the inner stopper 22 (S105). That is, when the actuator 14 held by the ramp load mechanism 17 moves in the second direction Dr2 from the ramp load mechanism 17, the SVC 25 brings the actuator 14 into contact with the inner stopper 22 and applies the polarization voltage to the electrode 16b. Thereafter, steps S106 and S107 are executed, as in the first embodiment.

[0088] In the magnetic disk device 10 of the third embodiment described above, the SVC 25 is configured to bring the actuator 14 into contact with the inner stopper 22 and apply a polarization voltage to the MA 16 when the actuator 14 held by the ramp load mechanism 17 moves from the ramp load mechanism 17 in the second direction Dr2.

[0089] For example, if a polarization voltage is applied to the electrode 16b of the MA 16 while the actuator 14 is held by the ramp load mechanism 17, there is a risk that the spontaneous polarization of the MA 16 will be lost due to ESD before the actuator 14 is separated from the ramp load mechanism 17. However, the SVC 25 applies the polarization voltage to the electrode after the actuator 14 separates from the ramp load mechanism 17 and abuts against the inner stopper 22. This allows the magnetic disk device 10 to prevent the spontaneous polarization of the MA 16 from being lost again.

[0090] (Fourth embodiment) The fourth embodiment will be described below with reference to FIG. 7. FIG. 7 is an exemplary flowchart showing an example of the operation of the magnetic disk device 10 according to the fourth embodiment. An example of the repolarization operation of the MA 16 in the fourth embodiment will be described below with reference to FIG. 7. The magnetic disk device 10 of the fourth embodiment re-polarizes the MA 16 at regular time intervals.

[0091] First, the HDC 52 determines whether a predetermined time has elapsed (S401). If the predetermined time has not elapsed (S401: No), the HDC 52 repeats S401 until the predetermined time has elapsed.

[0092] If the predetermined time has elapsed (S401: Yes), the HDC 52 sends a repolarization command to the SVC 25. In accordance with the repolarization command, the SVC 25 drives the VCM 15 and performs a seek (movement) until the actuator 14 abuts against the inner stopper 22 (S103). Note that if the magnetic head 13 is accessing the magnetic disk 12, the MPU 51 may perform seek control after the access is completed.

[0093] Next, the SVC 25 applies a polarization voltage to the electrode 16b of the MA 16 while the actuator 14 is in contact with the inner stopper 22 (S105). That is, the SVC 25 brings the actuator 14 into contact with the inner stopper 22 at regular time intervals to apply the polarization voltage to the electrode 16b. Thereafter, steps S106 and S107 are executed, as in the first embodiment.

[0094] In the magnetic disk device 10 of the fourth embodiment described above, the SVC 25 brings the actuator 14 into contact with the inner stopper 22 at regular time intervals to apply a polarization voltage to the MA 16. This allows the magnetic disk device 10 to periodically recover the spontaneous polarization of the MA 16, thereby improving reliability.

[0095] In the above embodiments, the polarization voltage restores spontaneous polarization to the MA 16 whose spontaneous polarization has been lost due to ESD. However, the polarization voltage is not limited to this example. For example, the polarization voltage may restore spontaneous polarization to the MA 16 whose spontaneous polarization has been lost due to other causes.

[0096] In the above embodiments, the SVC 25 applies the polarization voltage to the electrode 16b by bringing the actuator 14 into contact with the inner stopper 22. However, the SVC 25 may apply the polarization voltage to the electrode 16b when the actuator 14 is separated from the inner stopper 22 and the magnetic head 13 is positioned above the data zone 12sd or the outer circumferential zone 12so, or when the magnetic head 13 is separated from the magnetic disk 12.

[0097] Although several 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 novel embodiments can be embodied 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 within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0098] 10...magnetic disk device, 12...magnetic disk, 13...magnetic head, 14...actuator, 16...MA, 16b...electrode, 17...ramp load mechanism, 22...inner stopper, 25...servo controller (SVC), Axd, Axc...center axis, Dr1...first direction, Dr2...second direction, G...gimbal.

Claims

1. a magnetic disk configured to rotate about a first axis of rotation; a gimbal having a magnetic head configured to record and reproduce data on the magnetic disk and a piezoelectric element configured to move the magnetic head by deforming in response to an applied drive voltage; a controller configured to apply a polarization voltage to the piezoelectric element to impart spontaneous polarization to the piezoelectric element; Equipped with If the voltage change amount per unit time of the polarization voltage is ΔV, the frequency of the polarization voltage is f, the amplitude of the polarization voltage is A, the time resolution of the polarization voltage is ΔT, and the voltage change amount per unit time that is applied to the piezoelectric element to excite resonance of the gimbal is ΔVmax, the polarization voltage satisfies the relationship ΔV=(2πf)A·ΔT<ΔVmax. Magnetic disk device.

2. When the time during which the polarization voltage is applied to the piezoelectric element is T, the number of cycles during which the polarization voltage is applied to the piezoelectric element is N, and the start-up time is Tmax, the polarization voltage satisfies the relationship T=N / f<Tmax.

2. The magnetic disk drive according to claim 1.

3. an actuator configured to rotate about a second axis of rotation to move the magnetic head relative to the magnetic disk; a ramp spaced apart from the first rotation axis in a first direction around the second rotation axis and capable of holding the actuator; a stopper configured to contact the actuator to limit rotation of the actuator in a second direction opposite the first direction; Further comprising: the controller is configured to apply the polarization voltage to the piezoelectric element when the actuator is in contact with the stopper.

2. The magnetic disk drive according to claim 1.

4. the controller is configured to bring the actuator into contact with the stopper and apply the polarization voltage to the piezoelectric element when static electricity is applied to the piezoelectric element.

4. The magnetic disk drive according to claim 3.

5. the controller is configured to bring the actuator into contact with the stopper at regular time intervals to apply the polarization voltage to the piezoelectric element; 4. The magnetic disk drive according to claim 3.

6. the controller is configured to bring the actuator into contact with the stopper and apply the polarization voltage to the piezoelectric element when the actuator held by the lamp moves in the second direction from the lamp.

4. The magnetic disk drive according to claim 3.

7. The polarization voltage has a DC bias voltage or a voltage in which an AC voltage is superimposed on a DC bias voltage.

7. A magnetic disk drive according to claim 1.

8. The polarization voltage is higher than the driving voltage.

7. A magnetic disk drive according to claim 1.

9. The polarization voltage has an absolute value equal to or greater than a voltage that eliminates the spontaneous polarization of the piezoelectric element.

7. A magnetic disk drive according to claim 1.

10. a magnetic disk configured to rotate about a first axis of rotation; a gimbal having a magnetic head configured to record and reproduce data on the magnetic disk and a piezoelectric element configured to move the magnetic head by deforming in response to an applied drive voltage; an actuator configured to rotate about a second axis of rotation to move the magnetic head relative to the magnetic disk; a ramp spaced apart from the first rotation axis in a first direction around the second rotation axis and capable of holding the actuator; a stopper configured to contact the actuator to limit rotation of the actuator in a second direction opposite the first direction; a controller configured to apply a polarization voltage to the piezoelectric element when the actuator is in contact with the stopper, thereby imparting spontaneous polarization to the piezoelectric element; A magnetic disk device comprising:

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