JP2011113573A - Disk drive and method of measuring clearance between head slider and disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce damage to a head slider caused when the head slider touches down to a disk in measuring clearance between the head slider and the disk. <P>SOLUTION: The HDD temporarily reduces the clearance of the head slider for touch down in measuring clearance, thereafter the clearance is enlarged, and the clearance is maintained in the range of a value larger than that of the reduced clearance. A vibration of the head slider is monitored by the HDD. When the monitored vibration satisfies a predetermined standard, the HDD determines that the head slider and the magnetic disk are in contact with each other. Thus, contact time (the number of contacts) between the head slider and the magnetic disk is reduced, and reliability of a head disk interface can be improved. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a disk drive and a method for measuring a clearance between a head slider and a disk, and more particularly to a clearance measurement in a disk drive having an actuator for adjusting the clearance.

  In a disk drive such as a magnetic disk drive, an optical disk drive, or a magneto-optical disk drive, the information recording density can be improved as the distance between the recording layer of the disk and the recording / reproducing element of the head slider decreases. Therefore, as the information recording density of the disk drive is increased, the flying height of the slider is increasing.

  For example, in order to improve the information recording density of an HDD which is one of magnetic disk drives, a recording element / reproducing element mounted on a head slider and a magnetic film formed by sputtering or the like on the surface of the magnetic disk It is necessary to narrow the spacing, so-called magnetic spacing. In current magnetic disk drives, a DLC (Diamond Like Carbon) protective film is formed on the magnetic film, and a lubricant is applied on the DLC protective film. A DLC protective film is also formed on the rail surface of the head slider air bearing surface. The clearance between the magnetic disk and the head / slider, that is, the distance from the DLC protective film of the magnetic disk to the lowest flying point of the head / slider at the time of flying, has been reduced to several nanometers as a design value.

  As described above, in the HDD in which the head slider floats extremely low, the flying height (clearance) of the head slider fluctuates in accordance with changes in temperature or pressure in the HDD or around the HDD. Further, the flying height of the head slider varies from one slider to another due to a shape processing error of the head / slider floating surface, an assembly error when the head slider is attached to the suspension, and the like. Due to these various factors, the flying height of the head / slider varies, but from the viewpoint of magnetic recording / reproducing, the magnetic spacing variation of each head / slider during recording / reproducing operation is within a certain range. This is very important.

  Further, the flying height variation for each head slider causes contact between the magnetic disk and the head slider in the apparatus depending on the operating environment of the magnetic disk drive. The contact between the magnetic disk and the head slider induces adhesion of lubricant applied on the magnetic disk and contamination generated by friction between the magnetic disk and the head slider to the flying surface of the head slider. This destabilizes the flying of the slider, which in turn can induce contact between the magnetic disk and the head slider, leading to physical destruction.

  As described above, the flying height variation of the head slider can be a factor that significantly reduces the reliability of the HDD. Therefore, in the HDD, it is necessary to secure a predetermined clearance between the magnetic disk and the head slider in consideration of variations in the flying height of the head slider due to the operating environment.

  In response to these problems, Patent Document 1 discloses that the head slider is brought into contact with a magnetic disk by using a clearance adjusting actuator to reduce the clearance of the head slider, and the contact of the head slider is detected by detecting the contact. A technique for checking the current clearance amount is disclosed. In this technique, the head slider is brought into contact with the magnetic disk while vibrating the head slider in the flying direction. The vibration frequency is the air film frequency of the head slider or the resonance frequency of the suspension.

JP 2009-151890 A

  In order to accurately measure the clearance between the head slider and the magnetic disk, it is useful to bring the head slider into contact with the magnetic disk (touch down). As in the above-described prior art, by causing the head slider to contact the magnetic disk while vibrating the head slider at the resonance frequency in the flying direction, slider vibration easily occurs at the contact between the magnetic disk and the head slider. -Disc contact can be detected with high sensitivity and reliability.

  However, in measuring the clearance between the head slider and the magnetic disk, it is important to consider damage to the head slider due to contact with the magnetic disk. Therefore, a technique capable of minimizing damage to the head / slider in touchdown of the head / slider in clearance measurement is desired.

  A disk drive according to an aspect of the present invention includes a disk that stores data, a head slider that floats on the disk, a moving mechanism that supports the head slider and moves the head slider, A clearance actuator that changes the clearance between the slider and the disk, and the clearance actuator is used to reduce the clearance in stages, and the contact between the head slider and the disk is determined at each stage. Having a controller. The controller uses the clearance actuator to reduce the clearance. The clearance actuator is used to increase the reduced clearance, and to maintain the clearance in a range larger than the clearance value when the clearance is reduced. The vibration of the head is monitored while the clearance is reduced and maintained within the range, and the contact between the head and the previous disk is determined from the monitored vibration. As a result, damage to the head slider due to the touch-down of the head slider to the disk in the clearance measurement between the head slider and the disk can be reduced.

In a preferred configuration, the controller reduces the clearance from the clearance value in the immediately preceding stage. Thereby, a clearance measurement can be performed efficiently.
In a preferred configuration, the controller vibrates the head slider during the reduction and maintenance of the clearance. Thereby, it is possible to detect the contact between the head slider and the disk with high sensitivity.

In a preferred configuration, the controller vibrates the head slider in the in-disk direction. Thereby, more accurate clearance measurement can be performed.
In a preferred configuration, the controller vibrates the head slider in the head flying direction, and the vibration amplitude of the vibration is larger than a difference between the clearance value when the reduction is performed and a lower limit of the range. small. Thereby, accurate clearance measurement can be performed.

In a preferred configuration, the vibration causes resonance of an assembly of the head slider and a suspension that supports the head slider. Thereby, it is possible to detect the contact between the head slider and the disk with high sensitivity.
In a preferred configuration, the vibration causes resonance in the air film of the head slider. Thereby, it is possible to detect the contact between the head slider and the disk with high sensitivity.

  According to another aspect of the present invention, the clearance between the head slider and the disk is reduced stepwise using a clearance actuator, and the contact between the head slider and the disk is determined in each step. This is a clearance measurement method. This method performs the following steps at each stage. The clearance actuator is controlled to reduce the clearance. The reduced clearance is increased, and the clearance is maintained within a range larger than a clearance value when the clearance is reduced. The head vibration is monitored during maintenance within the range after the clearance is reduced. From the monitored vibration, contact between the head and the disk is determined. As a result, damage to the head slider due to the touch-down of the head slider to the disk in the clearance measurement between the head slider and the disk can be reduced.

  According to the present invention, damage to the head slider due to the touch-down of the head slider to the disk in the clearance measurement between the head slider and the disk can be reduced.

It is a figure which shows typically the structure of the head slider in this embodiment. 1 is a block diagram schematically showing the overall configuration of a hard disk drive in the present embodiment. In this embodiment, it is a figure which shows typically the preferable example of the change of the heater power in clearance measurement. In this embodiment, it is a figure which shows typically the preferable example of the change of the clearance in response to the change of the heater power in clearance measurement. In this embodiment, it is a figure which shows typically the other example of the change of the heater power in clearance measurement. 6 is a flowchart illustrating a flow of a preferable example of processing for detecting vibration generated when the head slider is in contact with the magnetic disk in a state where the head slider is slightly vibrated in the present embodiment.

  Embodiments to which the present invention is applied will be described below. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. Moreover, in each drawing, the same code | symbol is attached | subjected to the same element and the duplication description is abbreviate | omitted as needed for clarification of description. In the following, an embodiment of the present invention will be described in a hard disk drive (HDD) which is an example of a disk drive.

  This embodiment is characterized by measuring the clearance between the head slider and the magnetic disk. The clearance measurement is performed in a test process in manufacturing a head gimbal assembly (HGA), which is an assembly of a head slider and a suspension, a test process in manufacturing an HDD, or an HDD as a product. Each apparatus has a magnetic disk, a head slider that floats on the magnetic disk, and a suspension that supports the head slider. In this specification, all of these devices are referred to as disk drives. Hereinafter, an example of clearance measurement performed by the HDD as a product will be described.

  In the HDD of this embodiment, the head slider and the magnetic disk are brought into contact with each other in clearance measurement (head slider touchdown). The HDD uses a clearance actuator that adjusts the clearance to reduce the clearance of the head slider and bring the head slider into contact with the magnetic disk. The amount of clearance change by the clearance actuator for touchdown indicates the clearance measurement value. By measuring the clearance by detecting the touch-down of the head slider, the accurate clearance of the head slider can be measured.

  As a clearance actuator, a heater element, a piezo element, or one using a Coulomb force is known. In the following, an example of an HDD having a clearance actuator that uses a heater element will be described. The present invention can be applied to an HDD having any type of clearance actuator.

  In the HDD according to this embodiment, the head slider is touched down (contact with the magnetic disk) in the clearance measurement, and then the clearance of the head slider is once reduced by the clearance actuator and then the reduced clearance is increased. After the clearance is increased, the HDD maintains the clearance within a range of values larger than the reduced clearance value.

  The HDD monitors the vibration of the head slider while maintaining the clearance in the above range after reducing the clearance. If the monitored vibration satisfies a predetermined standard, the HDD determines that the head slider and the magnetic disk are in contact (touchdown). By performing such clearance control, the contact time (number of times of contact) between the head slider and the magnetic disk can be reduced, and the reliability of the head disk interface can be improved.

  Since the contact time between the head slider and the magnetic disk is short, it becomes difficult to detect touchdown by the HDD (decrease in sensitivity of touchdown detection). Therefore, in a preferred configuration, the HDD performs the clearance control while vibrating the head slider. Thereby, the vibration change of the head slider due to the head-disk contact appears clearly, and the head-disk contact can be reliably detected with high sensitivity. The frequency of vibration is a frequency that causes resonance in the air film between the head slider and the magnetic disk or resonance in the off-track direction of the suspension (HGA).

  Before describing the clearance measurement of this embodiment more specifically, the configuration of the head slider and HDD of this embodiment will be described. FIG. 1 is a diagram schematically showing a head slider 1 of this embodiment. The upper diagram in FIG. 1 shows the head slider 1 in a normal state, and the lower diagram in FIG. 1 shows a state when recording and reproduction are performed.

  The head slider 1 has a slider 12 that floats on the magnetic disk 2 and a thin film head portion 10 formed on the slider 12. In the configuration example of FIG. 1, the head slider 1 slides from the right side to the left side, and the thin film head portion 10 is formed at the trailing end of the slider 12. The thin film head unit 10 includes a reproducing element 11 and a recording element 13. Hereinafter, the reproducing element 11 and the recording element 13 are collectively referred to as a recording / reproducing element.

  The thin film head unit 10 has a heater element 15. The heater element 15 is a clearance actuator and changes the clearance of the thin film head unit 10. In the present specification, the clearance control by the heater element 15 is referred to as TFC (Thermal Fly-height Control). The reproducing element 11, the recording element 13, and the periphery thereof are expanded by the heat of the heater element 15, and the clearance between these elements and the magnetic disk 2 is adjusted. In clearance control using thermal deformation by the heater element 15, the vicinity of the recording / reproducing element is deformed by expansion due to heat generated by the heater element 15, and the apex of the thermal expansion deformation is the lowest flying point of the head slider 1.

  In the example of the normal state shown in the upper diagram of FIG. 1, the heater element 15 does not generate heat, and the reproducing element 11 and the recording element 13 do not protrude. As shown in the lower part of FIG. 1, the head slider 1 generates heat in the heater element 15 in recording / reproducing user data, thereby reducing the clearance of the recording / reproducing element. The HDD of this embodiment controls the clearance in the touch-down of the head slider 1 by controlling the power applied to the heater element 15.

  As described above, the heater element 15 head slider 1 is controlled by the control circuit mounted on the HDD. FIG. 2 is a block diagram schematically showing the overall configuration of the HDD 100. The HDD 100 has a magnetic disk 2 that is a disk for storing data in the enclosure. A spindle motor (SPM) 104 rotates the magnetic disk 2 at a predetermined angular velocity. Corresponding to each recording surface of the magnetic disk 2, a head slider 1 for accessing the magnetic disk 2 is provided.

  Each head slider 1 is fixed to the tip of the actuator 106. The actuator 106 is connected to a voice coil motor (VCM) 105 and rotates about the rotation axis, thereby rotating the head slider 1 on the magnetic disk 2 rotating (contact or non-contact) in the radial direction. Moving. The actuator 106 has a suspension that supports the head slider 1 and an arm that supports the suspension.

  The actuator 106 of this embodiment has a secondary actuator 107. The secondary actuator 107 finely moves to finely position the head slider 1 in the disk radial direction. Typically, the secondary actuator 107 has one or a plurality of piezo elements and a deforming portion that is deformed by expansion and contraction of the piezo elements. The actuator 106 and the VCM 105 are moving mechanisms for the head slider 1. The present invention can also be applied to an HDD that does not have the secondary actuator 107.

  Circuit elements are mounted on a circuit board outside the enclosure. The motor driver unit 202 drives the SPM 104 and the VCM 105 in accordance with control data from the HDC / MPU 203. The RAM 204 functions as a buffer that temporarily stores read data and write data.

  The arm electronic circuit (AE) 103 in the enclosure selects the head slider 1 that accesses the magnetic disk 2 from among the plurality of head sliders 1, amplifies the reproduction signal, and reads / write channels ( RW channel) 201. Further, the recording signal from the RW channel 201 is sent to the selected head slider 1. The AE 103 further functions as an adjustment circuit that supplies power to the heater element 15 of the selected head slider 1 and adjusts the amount of power.

  In the reproduction process, the RW channel 201 extracts data from the reproduction signal supplied from the AE 103 and performs a decoding process. The data to be read includes user data and servo data. The decoded data is transferred to the HDC / MPU 203. In the write process, the RW channel 201 code-modulates the write data supplied from the HDC / MPU 203, converts the code-modulated write data into a recording signal, and supplies the recording signal to the AE 103.

  The HDC / MPU 203 which is the controller of the HDD 1 performs recording / playback processing control, command execution order management, head slider 1 positioning control using servo signals (servo control), interface control with the host 501, defect management, Necessary processing related to data processing such as error handling processing when an error occurs and overall control of the HDD 100 are executed. In particular, the HDC / MPU 203 of the present embodiment measures the clearance between the head slider 1 and the magnetic disk.

  The present embodiment is characterized by clearance control in touch-down detection of the head slider 1 in clearance measurement and movement control of the head slider 1. The HDC / MPU 23 controls the heater element 15 (thermal actuator) via the AE 103 and controls the clearance between the head slider 1 and the magnetic disk 2. The clearance can be controlled by the power to the heater element 15.

  In the clearance measurement by touchdown, the HDC / MPU 23 decreases the clearance step by step, and determines the contact between the head slider 1 and the magnetic disk 2 at each step. The HDC / MPU 23 changes the clearance by controlling the heater power to the heater element 15 which is a clearance actuator. FIG. 3 is a diagram schematically showing a preferable example of a change in heater power in the clearance measurement. FIG. 4 is a diagram schematically showing a change in clearance in response to a change in heater power shown in FIG. 3 in the clearance measurement.

  As the heater power increases, the thin film head portion 10 protrudes and the clearance decreases. There is a slight time lag in the clearance change with respect to the heater power change. In the schematic diagram of FIG. 4, if the heater power is constant, the clearance is constant. However, in an actual HDD, there is a slight clearance change even if the heater power is constant.

  In the example of FIGS. 3 and 4, three stages are shown in the heater power change and clearance change. The HDC / MPU 23 detects contact between the head slider 1 and the magnetic disk 2 in the third stage. In the preferred example of FIG. 3, the HDC / MPU 23 once increases the heater power at each stage to the maximum value at that stage.

  Thereafter, the HDC / MPU 23 decreases the heater power and maintains it at a value smaller than the maximum value. In order to avoid control simplicity and unexpected behavior of the head slider, the reduced heater power is preferably not changed at that stage. However, depending on the design, the heater power may be changed after the heater power is reduced. The value of the heater power at that time is a value smaller than the maximum value at that stage.

  As shown in FIG. 4, the clearance shows a change according to the change of the heater power. The clearance once decreases to the minimum value at that stage. Thereafter, as the heater power decreases, the clearance increases and maintains a value larger than the minimum value. In the schematic diagram of FIG. 3, the clearance value after the increase is constant at each stage. In an actual system, there is a slight clearance variation even if the heater power is constant.

  The HDC / MPU 23 monitors the vibration of the head slider 1 at each stage while the clearance is reduced to the minimum value and the clearance is maintained within a larger value range thereafter. The period during which the vibration is monitored includes a predetermined period after the heater power is reduced from the maximum value. Preferably, the monitoring period at each stage includes a timing at which the heater power is maximum, and starts immediately before the heater power is maximized at that stage. The HDC / MPU 23 may monitor vibration from the start to the end of each stage. The HDC / MPU 203 can detect the vibration of the head slider 1 generated by the contact between the head slider 1 and the magnetic disk 2 by several known methods.

  In one preferred method, the HDC / MPU 203 can detect a contact by monitoring a position error signal (PES). For example, the HDC / MPU 203 determines that contact between the head slider 1 and the magnetic disk 2 occurs when the size of the PES or the change in the PES exceeds a threshold value. Alternatively, the touch-down of the head slider can be detected by referring to the amplitude of the read back signal, the value of the servo VGA or data VGA, or the control signal of the VCM 105. These methods are widely known and will not be described in detail here.

  When an AE (Acoustic Emission) sensor can be used in an HGA or HDD test process in HDD manufacture, vibration of the head slider (HGA) due to touchdown can be detected using the AE (Acoustic Emission) sensor. For example, the HDC / MPU 203 can monitor the vibration of the head slider 1 with an AE sensor attached to the actuator 106 and determine contact between the head slider 1 and the magnetic disk 2 based on the output.

  As shown in FIG. 3, the contact between the head slider 1 and the magnetic disk 2 occurs only while the heater power is at the maximum value at that stage. After the clearance increases, the head slider 1 is separated from the magnetic disk 2. In each stage, the HDC / MPU 203 increases the heater power to the maximum value only once. Therefore, the contact time between the head and the disk is short, and the possibility of data damage on the thin film head 10 or the magnetic disk 2 can be reduced.

  As shown in FIG. 3, it is preferable that the clearance change and the heater power change have an overshoot shape. That is, the HDC / MPU 23 reduces the clearance from the clearance value at the previous stage and reduces it to the minimum value at this stage. Thereafter, the clearance is maintained within a range of values greater than the minimum value. As for the heater power, the HDC / MPU 23 increases the heater power from the heater power value at the previous stage and increases it to the maximum value at this stage. Thereafter, the heater power is maintained at a value smaller than the maximum value.

  Thus, the clearance change and the heater power change have an overshoot shape, so that the time at each stage for detecting the touch-down of the head slider 1 can be shortened. Depending on the design, as shown in FIG. 5, the HDC / MPU 23 increases the heater power from the heater power at the previous stage to the heater power value that is the reference for this stage, and then further increases the heater power. After increasing to the maximum value of the stage, it may be returned to the above standard.

  The heater power change amount ΔP0 (change amount of the reference heater power value at each stage) between the stages may be the same value or a different value. The overshoot amount ΔP1 may be a common value or a different value at each stage. The HDC / MPU 23 determines the maximum heater power value at that stage as the touchdown power value when determining the heater power value (touchdown power value) when the magnetic disk and the head slider come into contact with each other. Alternatively, a value calculated from the reference heater power value and the maximum heater power value, for example, an intermediate value thereof may be determined as the touchdown power value.

  Preferably, the HDC / MPU 23 maintains the heater power at each stage for a specified time at the maximum value at that stage. Compared to the case where the heater power is changed in a spike shape, contact detection can be performed more reliably while avoiding damage to the head slider 1 and the magnetic disk 2. The time for maintaining the heater power at the maximum value (the time for maintaining the clearance at the minimum value (range)) is shorter than the time for maintaining the smaller reference heater power value (larger clearance value (range)).

  As described above, when the clearance is once reduced and the touchdown is performed, and then the clearance is increased and the head slider 1 is separated from the surface of the magnetic disk 2, the vibration due to the touchdown of the head slider 1 is small. Touchdown may not be detected properly. Therefore, in a preferred configuration, the HDC / MPU 203 uses a minute drive function when detecting contact between the head slider 1 and the magnetic disk 2. The HDC / MPU 203 vibrates the head slider 1 while performing measurement for contact determination. Specifically, excitation is started before the heater power is once increased at each stage, and the excitation is continued while the heater power once increased is reduced and maintained.

  Specifically, the HDC / MPU 203 vibrates the head slider 1 by the above minute driving function. Then, contact detection between the head slider 1 and the magnetic disk 2 is performed in a state where the head slider 1 is vibrating. By detecting the touchdown while minutely vibrating the head-slider 1, it is possible to reliably detect the slider-disk contact with high sensitivity. Further, since small contact can be detected with high sensitivity, the influence on the reliability of the head disk interface in the contact detection can be reduced.

  The vibration at an appropriate frequency of the head slider 1 in the touchdown detection causes resonance in the off-track direction of the suspension or resonance of the air film between the head slider 1 and the magnetic disk 2. When the head slider 1 and the magnetic disk 2 are brought into contact with each other by the heater element 15 while applying vibration at an appropriate frequency to the HGA, resonance of the HGA occurs. The resonance in the off-track direction is a vibration corresponding to the natural frequency (sway mode and yaw mode) of the HGA, and the resonance in the flying height direction is the air generated between the head slider 1 and the magnetic disk 2 surface. It is a vibration according to the natural frequency of the film.

  Regarding the vibration of the head slider 1 in the off-track direction, the frictional force generated when the contact between the head slider 1 and the magnetic disk 2 is the excitation source of the slider vibration. Immediately after the start of contact, the frictional force is small and the slider vibration in the off-track direction is so small that it cannot be detected. However, if the head slider 1 (HGA) is microvibrated at an appropriate frequency, contact between the head slider 1 and the magnetic disk 2 occurs at the frequency of the microvibration, and slider vibration at the resonance frequency of the HGA begins to occur. . Since the frictional force between the head slider 1 and the magnetic disk 2 is generated at the resonance frequency of the HGA, a large off-track vibration is generated.

  As described above, due to the small contact between the head slider 1 and the magnetic disk 2, a larger vibration of the head slider 1 (HGA) is generated in the off-track direction. In particular, when a vibration that fluctuates at the resonance frequency of the HGA in the sway mode or the yaw mode or a frequency in the vicinity thereof is applied to the head slider 1, a particularly large vibration occurs in the off-track direction. In the configuration in which the touch-down detection is performed by the head-slider vibration in the off-track direction, it is preferable to perform the touch-down while vibrating the head-slider 1 at these frequencies. The micro-vibration direction of the head slider 1 for causing resonance may be either the off-track direction or the flying direction.

  Regarding the vibration in the flying direction, the contact between the head slider 1 and the magnetic disk 2 is the excitation source of the slider vibration. When the head slider 1 (HGA) is microvibrated at an appropriate frequency, slider vibration occurs at the resonance frequency of the air film. Thereby, a large levitating high vibration occurs. In order to cause resonance in the flying direction, it is preferable to vibrate the head slider 1 in the flying direction.

  In order to obtain a larger movement of the head slider 1 by touchdown, it is preferable to match the resonance frequency (the flying direction or the off-track direction), but a frequency that is a multiple of these constants can be used. . Further, a value near the resonance frequency or a frequency that is a constant multiple thereof can be used. Typically, the sensitivity of contact detection can be sufficiently increased by a minute vibration having a frequency twice the resonance frequency.

  The vibration frequency of the head slider is preferably in the range of 3/4 times to 5/4 times the target resonance frequency or a constant multiple of the resonance frequency. In the contact detection, the HDC / MPU 203 may change the frequency of the minute vibrations. However, typically, the head slider 1 is moved at a predetermined constant frequency from the viewpoint of easy control and improved contact detection sensitivity. Microvibrates.

  Since the resonance frequency varies depending on the design of the HGA, an appropriate excitation frequency is selected according to the target HGA. Further, the resonance frequency of the HGA varies depending on the individual HGA. In the test process in HDD manufacture, it is preferable to specify the resonance frequency of each HGA. When the variation in the resonance frequency is small, the same minute vibration frequency may be applied to the magnetic disk drive having the same design.

  As described above, the direction of excitation of the head slider 1 in contact detection is the normal direction (the flying height direction) of the magnetic disk 2 or the in-plane direction (off-track direction) of the magnetic disk 2 perpendicular to the normal direction. It is. In a preferred configuration, the HDC / MPU 203 vibrates the head slider 12 in the disk in-plane direction in contact detection. Thereby, the clearance change by vibration itself can be reduced. In the configuration in which the head slider 1 is vibrated in the flying direction, it is important that the clearance amplitude is smaller than the overshoot amount.

  In a configuration in which touchdown detection is performed while applying vibration in the off-track direction, the HDC / MPU 203 monitors the vibration amplitude (change) of the head slider 1 in the off-track direction and makes a determination regarding touchdown. Is preferred. Accordingly, in a preferred configuration, the HDC / MPU 203 reduces the clearance of the head slider 1 while applying minute vibrations that cause resonance in the yaw mode or sway mode of the suspension to the head slider 1, and monitors the off-track vibration. To do.

  As described above, in a preferred configuration, the suspension includes the secondary actuator 107 that is finely driven in the disk radial direction for positioning. The secondary actuator 107 is controlled via the motor driver unit 202 or the AE 103 by a control signal supplied from the HDC / MPU 203. The HDC / MPU 203 preferably vibrates the head slider 1 by the secondary actuator 107 in order to accurately perform minute vibration of the head slider 1 at a high frequency.

  The configuration of the secondary actuator 107 is not particularly limited. For example, the present invention can be applied to a magnetic disk drive having a secondary actuator 107 that is fixed on a suspension and finely moves the head slider 1 directly. Further, an actuator that arranges a piezo element (or a heater element) between the slider 12 and the thin film magnetic head unit 10 and finely moves the thin film magnetic head unit 14 left and right may be mounted as the secondary actuator 107.

  The HDC / MPU 203 may control the VCM 105 to vibrate the head slider 1 together with the actuator 106 in the in-disk direction. However, in the HDD having the secondary actuator 107 like the HDD 1 of this embodiment, the HDC / MPU 203 preferably vibrates the head slider 12 using the secondary actuator 107.

  When the secondary actuator 107 is not mounted and the minute vibration control by the rotary actuator 106 is difficult in design, the minute vibration in the flying direction is preferable. As a method of vibrating the head slider 1 in the flying height direction, the HDC / MPU 203 may use thermal expansion in the vicinity of the recording element 13 due to heat generated during the write operation or thermal expansion by the flying height adjustment actuator 15. The head slider 1 can be vibrated at a predetermined frequency in the flying height direction. The center of gravity of the head slider 1 vibrates in the vertical direction due to thermal expansion and contraction that slightly vibrate, and the head slider 1 (suspension) can be microvibrated.

  As another method of minutely vibrating the head slider 1 in the flying height direction, a potential fluctuation is applied between the magnetic disk 2 and the head slider 1. Application of a varying potential to the slider 12 can be realized by applying a potential to the entire head slider 1 via the suspension 3 or applying a potential to the recording element 13 or the reproducing element 11, for example. For example, the HDC / MPU 203 gives a minute vibration signal to the entire head slider 1 via the suspension. Alternatively, a minute vibration signal via the RW channel 201 is amplified by the AE 103 and applied to both ends of the reproducing element 11 / recording element 13.

  The HDC / MPU 203 may simultaneously perform micro vibrations in the vertical direction of the head slider 1 and micro vibrations in the off-track direction in contact detection. When the head slider 1 is vibrated in both the vertical direction and the horizontal direction, the movement of the head slider 1 in the off-track direction at the time of contact may increase. Therefore, a suitable method is selected from the viewpoint of micro vibration control of the head slider 1 and contact detection. When the head slider 1 is vibrated minutely in both the vertical direction and the off-track direction, the frequencies are preferably the same from the viewpoint of easy control and improved contact sensitivity.

  In the following, a preferred flow of processing for detecting vibration generated when the head slider 1 and the magnetic disk 2 are in contact with each other with the head slider 1 vibrated slightly will be described. In this example, the head slider 1 approaches the magnetic disk 2 while vibrating in the off-track direction, and the HDC / MPU 203 determines contact by monitoring the head-slider vibration in the off-track direction.

  As shown in the flowchart of FIG. 6, the HDC / MPU 203 first moves the head slider 1 to the track on which the clearance measurement is performed, and enters the following mode (S11). The HDC / MPU 203 controls the VCM 105 to turn the arm of the actuator 106 in the radial direction, and the secondary slider 107 finely drives the head slider 1 in the radial direction of the disk to move the head slider 1 to a desired data track. Move and position there. The secondary actuator 107 typically rotates the head slider 12 within the disk surface. As a result, the thin film head unit 10 moves in the disk radial direction.

  The HDC / MPU 203 sets the frequency F as a frequency when the head slider 1 is minutely vibrated in the off-track direction, and starts minute vibration (S12). Specifically, the HDC / MPU 203 controls the driving of the secondary actuator 107 to cause the head slider 1 to vibrate slightly in the off-track direction at the frequency F.

  The HDC / MPU 203 reduces the clearance stepwise in a state where the head slider 1 is slightly vibrated, and performs touchdown detection of the head slider 1 to the magnetic disk 2 at each step (see FIG. 3). Specifically, the HDC / MPU 203 increases the power supplied to the heater element 15 by (ΔP0 + ΔP1) (S13). After a predetermined time has elapsed, the HDC / MPU 203 reduces the power supplied to the heater element 15 by ΔP1 and maintains the power supplied (S13). That is, the heater power value before the increase is set to a value increased by ΔP0 and the value is maintained.

  The HDC / MPU 203 monitors the vibration of the head slider 1 in the off-track direction at each stage (S14). Specifically, at each stage, vibration measurement is continued from the time when each overshoot power is applied until the contact determination is made at that stage after the heater power is reduced by ΔP1. In this method, when the contact between the head slider 1 and the magnetic disk 2 starts, the vibration in the off-track direction changes greatly. Accordingly, the HDC / MPU 203 detects the contact between the head slider 1 and the magnetic disk 2 based on parameter fluctuations such as a positioning error signal (PES) and a VCM control signal.

  When the HDC / MPU 203 detects contact (Y in S15), the HDC / MPU 203 stops the minute vibration of the head slider 1 (S16) and calculates the clearance (S17). When the contact is not detected (N in S15), the HDC / MPU 203 returns to Step S13 and increases the power supplied to the heater element 15 by (ΔP0 + ΔP1). Thereafter, the subsequent steps are repeated.

  As mentioned above, although this invention was demonstrated taking preferable embodiment as an example, this invention is not limited to said embodiment. A person skilled in the art can easily change, add, and convert each element of the above-described embodiment within the scope of the present invention. For example, the present invention can be applied to a disk drive different from the HDD.

DESCRIPTION OF SYMBOLS 1 Head slider, 2 Magnetic disk, 10 Thin film head part, 11 Playback element 12 Slider, 13 Recording element, 15 TFC heater element 103 Arm electronics, 106 Actuator 107 Secondary actuator, 201 Read / write channel 202 Motor・ Driver unit, 203 Hard disk controller / MPU
501 host

Claims (16)

A disk for storing data;
A head slider floating above the disk;
A moving mechanism for supporting the head slider and moving the head slider;
A clearance actuator for changing a clearance between the head slider and the disk;
A controller that reduces the clearance step by step using the clearance actuator, and determines the contact between the head slider and the disk at each step; and
The controller is
Using the clearance actuator to reduce the clearance;
Using the clearance actuator, increasing the reduced clearance, maintaining the clearance in a range of values larger than the clearance value when the clearance is reduced,
Monitoring the vibration of the head during the clearance reduction and maintenance within the range;
From the monitored vibration, the contact between the head and the previous disk is determined.
Disk drive. The controller reduces the clearance from the clearance value in the immediately preceding stage,
The disk drive of claim 1. The controller vibrates the head slider during the reduction and maintenance of the clearance.
The disk drive according to claim 2. The controller vibrates the head slider during the reduction and maintenance of the clearance.
The disk drive of claim 1. The controller vibrates the head slider in a disk in-plane direction.
The disk drive according to claim 4. The controller vibrates the head slider in the head flying direction,
The vibration amplitude of the vibration is smaller than the difference between the clearance value when reduced and the lower limit of the range,
The disk drive according to claim 4. The vibration causes resonance of an assembly of the head slider and a suspension that supports the head slider.
The disk drive according to claim 4. The vibration causes resonance in the air film of the head slider.
The disk drive according to claim 4. A clearance measuring method, wherein a clearance between a head slider and a disk is reduced stepwise using a clearance actuator, and contact between the head slider and the disk is determined in each step. In the stage
Control the clearance actuator to reduce the clearance,
Increase the reduced clearance, maintain the clearance within a range larger than the clearance value when the clearance is reduced,
During the maintenance within the range after the clearance is reduced, the head vibration is monitored,
Determining contact between the head and the disk from the monitored vibration;
Method. The reduction of the clearance reduces the clearance from the clearance value in the immediately preceding stage.
The clearance measuring method according to claim 9. Vibrating the head slider during the reduction and maintenance of the clearance;
The clearance measuring method according to claim 10. Vibrating the head slider during the reduction and maintenance of the clearance;
The clearance measuring method according to claim 9. The head slider is vibrated in the in-disk direction,
The clearance measuring method according to claim 12. The head slider is vibrated in the head flying direction,
The vibration amplitude of the vibration is smaller than the difference between the clearance value when reduced and the lower limit of the range,
The clearance measuring method according to claim 12. The vibration causes resonance of an assembly of the head slider and a suspension that supports the head slider.
The clearance measuring method according to claim 12. The vibration causes resonance in the air film of the head slider.
The clearance measuring method according to claim 12.

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