JP2009134835A - Disk drive device and its clearance adjusting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To more correctly adjusting a clearance between a head and a disk, depending on air pressure, without using an air pressure sensor. <P>SOLUTION: An HDD of an embodiment of the present invention determines a change in clearance corresponding to a change in air pressure based on a change in an operation parameter thereof. When heater power is changed by a TFC depending on a change in air pressure, the HDD performs a write verify process at a clearance Cb higher than a clearance Ca which complies with default settings before a write process is performed with respect to user data. As a result, when clearance adjustment is performed depending on a change in air pressure, poor write performance is reliably prevented or a margin for a change in air pressure after air pressure measurement is insured. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a disk drive device and a clearance adjustment method thereof, and more particularly to a clearance adjustment technique suitable for a disk drive device that does not have a barometric pressure sensor.

  As a disk drive device, a device using a disk of various modes such as an optical disk, a magneto-optical disk, or a flexible magnetic disk is known. Among them, a hard disk drive (HDD) is a computer storage device. As one of the storage devices indispensable in the present computer system, it is widely used. In addition to the computer, the use of the HDD such as a moving image recording / reproducing apparatus, a car navigation system, or a mobile phone is increasing more and more due to its excellent characteristics.

  A magnetic disk used in an HDD has a plurality of data tracks and servo tracks formed concentrically. Each servo track is composed of a plurality of servo data having address information. Each data track is recorded with a plurality of data sectors including user data. Data sectors are recorded between servo data spaced apart in the circumferential direction. The head element part of the head slider supported by the oscillating actuator accesses the desired data sector according to the servo data address information, thereby writing data to the data sector and reading data from the data sector. It can be performed.

  In order to improve the recording density of the magnetic disk, it is important to reduce the clearance (flying height) between the head element portion that floats on the magnetic disk and the magnetic disk and changes thereof. For this reason, several mechanisms for adjusting the clearance have been proposed. One of them includes a heater in the head slider, and the clearance is adjusted by heating the head element portion with the heater (see, for example, Patent Document 1). In this specification, this is called TFC (Thermal Flyheight Control). The TFC supplies a current to the heater to generate heat, and causes the head element portion to protrude by thermal expansion. As a result, the clearance between the magnetic disk and the head element portion is reduced. In addition, a mechanism for adjusting the clearance between the head element portion and the magnetic disk using a piezo element is known.

The clearance changes in accordance with a change in temperature, and also changes in accordance with a change in atmospheric pressure (altitude) (see, for example, Patent Document 2). When the clearance setting value in read / write is 5 nm or more, the clearance change due to the altitude change can be dealt with by the clearance margin. However, when there is only a clearance of 2 or 3 nm or less in read / write, it is required to adjust the clearance according to a change in atmospheric pressure in addition to a change in temperature.
JP 2006-190454 A JP 2006-92709 A

  In a typical TFC, the heater power is increased in response to a decrease in temperature to cause the head element portion to protrude by thermal expansion, and compensates for an increase in clearance due to a decrease in temperature. On the other hand, when the altitude increases and the atmospheric pressure decreases, the flying height of the slider decreases. For this reason, the clearance between the head element portion and the magnetic disk also decreases due to the decrease in the atmospheric pressure. Therefore, if the temperature is constant, the TFC reduces the protrusion amount as the atmospheric pressure decreases.

  The HDD sets many parameters according to the temperature, and accurate temperature detection is indispensable for the normal operation of the HDD. Therefore, a general HDD has a temperature sensor as means for detecting temperature. Similarly, an atmospheric pressure sensor (altitude sensor) is known as one of means for detecting atmospheric pressure. However, the use of the pressure sensor increases the number of HDD members, and the cost of the HDD greatly increases. In addition, since there are almost no parameters to be set according to changes in atmospheric pressure other than parameters for adjusting the clearance, it is preferable to specify the atmospheric pressure without using an atmospheric pressure sensor.

  As described above, the clearance changes according to the change in atmospheric pressure. For this reason, a change in atmospheric pressure can be measured by referring to the clearance. Several techniques for identifying clearance are known. A typical method specifies a clearance (clearance change) from the amplitude of the read signal of the head element portion. As the clearance decreases, the signal strength increases and the gain of the variable gain amplifier decreases.

  Therefore, the signal strength and clearance can be specified by referring to the gain of the variable gain amplifier. A more accurate clearance specifying method specifies the clearance from the resolution in signal strength. Alternatively, although the accuracy is inferior, the atmospheric pressure can be estimated from the current value of the spindle motor (SPM).

  In order to adjust the clearance according to the atmospheric pressure without using the atmospheric pressure sensor, refer to the HDD operating parameters (variable gain / amplifier gain, SPM current value, etc.) as in the above method, and change the clearance. It is necessary to specify. However, unlike a barometric sensor, the accuracy and reliability of barometric pressure measurement using HDD operating parameters is not high. Uncertain barometric measurements can cause incorrect clearance adjustments.

  In particular, when the clearance is high in the write process, a problem of poor write (insufficient writing intensity) may occur. Since the HDD does not perform the write / verify processing in the normal operation, it does not confirm the pre-write. Also, read errors due to poor write often cannot be recovered by error recovery processing. Therefore, in an HDD that adjusts the clearance according to the atmospheric pressure without using the atmospheric pressure sensor, it is important to reliably prevent the poor write in the user data write process and improve the reliability.

  A disk drive device according to an aspect of the present invention includes a head that accesses a disk, a moving mechanism that holds the head and moves the head on the disk, and adjusts a clearance between the head and the disk. And an adjustment mechanism, a temperature sensor, and a controller that controls the head, the moving mechanism, and the adjustment mechanism. The controller corrects the temperature change in the change in the operation parameter of the disk drive device using the temperature detected by the temperature sensor, and then determines the clearance change amount from the operation parameter. Further, a write test is performed with the clearance higher than the default setting corresponding to the detected temperature and the amount of change in clearance. Thereby, the clearance adjustment between the head and the disk according to the atmospheric pressure can be performed more accurately without using the atmospheric pressure sensor.

  The controller preferably performs the write test when the clearance change amount exceeds a reference range. As a result, the number of write tests can be reduced while ensuring the effectiveness of the test. Furthermore, it is preferable that the controller performs the write test when performing a clearance adjustment corresponding to the determined clearance change amount. As a result, the number of write tests can be reduced while ensuring the effectiveness of the test more appropriately.

  Preferably, the write test is a write verify test. Thereby, an efficient and effective test can be performed. When the controller fails the write test, the controller preferably repeats the write test while gradually reducing the clearance. Thereby, an appropriate clearance adjustment amount can be specified. Furthermore, it is preferable that the controller changes a default setting based on a clearance that passes the light test. The controller preferably corrects the default setting based on a difference between a clearance that passes the write test and a clearance when the write test is started. Thereby, an appropriate clear run can be realized in normal processing.

  The retreat position of the head slider is preferably outside the disk, and the data track for performing the write test is preferably located on the inner periphery side of the area for recording user data. This can reduce the possibility of erroneous test results.

  Another aspect of the present invention is a clearance adjustment method in a disk drive device having a clearance adjustment function. In this method, the temperature is detected by a temperature sensor. Obtain operational parameters of the disk drive device. The detected temperature is used to correct the temperature change due to the change in the operating parameter. After the correction, a clearance change amount is determined from the operation parameter. A write test is performed with the clearance higher than the default setting corresponding to the detected temperature and the amount of change in clearance. The clearance is adjusted based on the result of the light test. Thereby, the clearance adjustment between the head and the disk according to the atmospheric pressure can be performed more accurately without using the atmospheric pressure sensor.

  According to the present invention, the clearance adjustment between the head and the disk according to the atmospheric pressure can be more accurately performed without using the atmospheric pressure sensor.

  Hereinafter, embodiments to which the present invention can be applied will be described. 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, embodiments of the present invention will be described by taking a hard disk drive (HDD) as an example of a disk drive device as an example.

  The HDD of this embodiment adjusts the clearance between a head element unit, which is an example of a head, and a magnetic disk, which is an example of a disk, by TFC (Thermal Fly height Control), which is an example of a clearance adjustment mechanism. The TFC adjusts the clearance by the thermal expansion of the head element portion due to the heat from the heater on the slider. The TFC of this embodiment adjusts the clearance according to changes in atmospheric pressure. The HDD has a temperature sensor but does not have an atmospheric pressure sensor.

  For this reason, the HDD determines a clearance change from the change in the operation parameter, and further corrects the operation parameter based on the temperature detected by the temperature sensor. Thus, the HDD determines the clearance change corresponding to the change in atmospheric pressure, excluding the temperature change in the clearance change (operation parameter change). Environmental conditions that change the clearance include humidity in addition to temperature and atmospheric pressure, but substantial changes are due to temperature and atmospheric pressure. In the following, it is assumed that the clearance change with temperature correction is due to atmospheric pressure changes. explain.

  When the heater power is changed by TFC in accordance with the change in atmospheric pressure, the HDD of this embodiment performs a high clearance write test before performing user data write processing. In particular, a write verify process is performed as a preferred write test. In the example described below, a high-clear write-verify process is performed in the initial setting process at startup (power-on reset process (POR process)). In the high-clearance write-verify process, the write-verify process is performed with a clearance higher than the default setting of TFC under the same conditions.

  Unlike a barometric sensor, the accuracy and reliability of barometric pressure measurement (clearance measurement) using operating parameters is not high. For this reason, by confirming that data can be normally written at a clearance higher than the default setting in the user data read / write processing, it is possible to more reliably prevent the TFC from being overwritten in response to a change in atmospheric pressure. A margin for atmospheric pressure change can be guaranteed. As described above, according to this embodiment, the reliability of the HDD that does not use the atmospheric pressure sensor can be improved.

  Before describing the details of the write verify processing in the TFC and high clearance of this embodiment, the overall configuration of the HDD will be described. FIG. 1 is a block diagram schematically showing the overall configuration of the HDD 1. The HDD 1 has a magnetic disk 11 that is a disk for storing data in the enclosure 10. The spindle motor (SPM) rotates the magnetic disk 11 at a predetermined angular velocity. Corresponding to each recording surface of the magnetic disk 11, a head slider 12 for accessing (reading or writing) the magnetic disk 11 is provided. Access is a superordinate concept of read and write. Each head slider 12 includes a slider that floats on the magnetic disk, and a head element unit that is fixed to the slider and converts between a magnetic signal and an electric signal.

  The head slider 12 of this embodiment includes a heater for TFC that expands and projects the head element portion by heat and adjusts the clearance (flying height) from the magnetic disk 11. The structure of the head slider 12 will be described in detail later with reference to FIG. Each head slider 12 is fixed to the tip of the actuator 16. The actuator 16 is connected to a voice coil motor (VCM) 15, and moves in the radial direction on the magnetic disk 11 that rotates the head slider 12 by rotating about a rotation axis. The actuator 16 and the VCM 15 are moving mechanisms for the head slider 12.

  Circuit elements are mounted on the circuit board 20 fixed to the outside of the enclosure 10. The motor driver unit 22 drives the SPM 14 and the VCM 15 according to control data from the HDC / MPU 23. The RAM 24 functions as a buffer that temporarily stores read data and write data. An arm electronic circuit (AE: Arm Electronics) 13 in the enclosure 10 selects the head slider 12 that accesses the magnetic disk 11 from among the plurality of head sliders 12, amplifies the reproduction signal, Send to the write channel (RW channel) 21. Further, the recording signal from the RW channel 21 is sent to the selected head slider 12. The AE 13 further functions as an adjustment circuit that supplies power to the heater of the selected head slider 12 and adjusts the amount of power.

  In the read process, the RW channel 21 uses a variable gain amplifier (VGA) to amplify the read signal supplied from the AE 13 to have a constant amplitude, extract data from the acquired read signal, and perform a decoding process. I do. The data to be read includes user data and servo data. The decoded read user data and servo data are supplied to the HDC / MPU 23. In the write process, the RW channel 21 code-modulates the write data supplied from the HDC / MPU 23, further converts the code-modulated write data into a write signal, and supplies the write signal to the AE 13.

  The HDC / MPU 23, which is an example of a controller, performs read / write processing control, command execution order management, positioning control (servo control) of the head slider 12 using servo signals, interface control with the host 51, and defect management. Necessary processing related to data processing such as error handling processing when an error occurs and overall control of the HDD 1 are executed. In particular, the HDC / MPU 23 of the present embodiment performs TFC according to the temperature detected by the temperature sensor 17 and further performs TFC according to the atmospheric pressure. Further, the HDC / MPU 23 performs a write verify process in a high clearance when the heater power is changed by a change in atmospheric pressure specified by the operation parameter. These points will be described later.

  FIG. 2 is a cross-sectional view showing a configuration in the vicinity of the air outflow end surface (trailing side end surface) 121 of the head slider 12. The slider 123 supports the head element unit 122. The head element unit 122 includes a read element 32 and a write element 31. The write element 31 generates a magnetic field between the magnetic poles 312 with a current flowing through the write coil 311 and writes magnetic data to the magnetic disk 11. The read element 32 includes a magnetoresistive element 32 a having magnetic anisotropy, and reads out magnetic data by a resistance value that changes due to a magnetic field from the magnetic disk 11.

  The head element portion 122 is formed on an AlTiC (AlTiC) substrate constituting the slider 123 by a thin film formation process. The magnetoresistive element 32 a is sandwiched between magnetic shields 33 a and 33 b, and the write coil 311 is surrounded by an insulating film 313. A protective film 34 such as alumina is formed around the write element 31 and the read element 32. A heater 124 exists in the vicinity of the write element 31 and the read element 32. The heater 124 can be formed by meandering a thin film resistor using permalloy or the like and filling the gap with alumina.

  When the AE 13 supplies a current to the heater 124, the head element portion 122 protrudes due to the heat of the heater 124 due to the difference in thermal expansion coefficient between the slider 123 and the head element portion 122. For example, when not heated, the ABS surface 35 of the head slider 12 has a shape indicated by S1, and a clearance, which is a distance between the head element portion 122 and the magnetic disk, is indicated by C1. The protruding shape S2 when the heater 124 is heated is indicated by a broken line. The head element portion 122 approaches the magnetic disk 11, and the clearance C2 at this time is smaller than the clearance C1. FIG. 2 is a conceptual diagram, and the dimensional relationship is not accurate. The protrusion amount and clearance of the head element portion 122 change according to the heater power value supplied to the heater 124.

Hereinafter, the write verify processing in the TFC and high clearance of the present embodiment will be described in more detail. As described above, the HDC / MPU 23 of the present embodiment performs TFC according to temperature and atmospheric pressure. The heater power P applied to the heater 124 is represented by the sum (P (t) + P (p)) of the heater power P (t) depending on the temperature and the heater power P (p) depending on the atmospheric pressure. The It should be noted that the constant term is incorporated in any of the mathematical expressions, and the coefficient of each mathematical expression can be changed according to environmental conditions such as temperature and atmospheric pressure, the head slider 12 or the radial position thereof. Specifically, the heater power P is expressed by the following mathematical formula.
P = (TDP × eff [DEFAULT] −Target
−dt × t_comp−dp × p_comp) / eff

  eff is the heater power efficiency, and changes according to the atmospheric pressure and the radial position. eff [DEFAULT] is the heater power efficiency in the default state. TDP is the heater power at which the head slider 12 and the magnetic disk 11 are in contact in the default state, Target is the target clearance, dt is the temperature change from the default condition, t_comp is the clearance change rate with respect to temperature, and dp is from the default condition P_comp is a clearance change rate with respect to the atmospheric pressure. The signs of t_comp and p_comp are opposite. TDP, t_comp, and p_comp typically vary with radial position. The default conditions are typically environmental conditions of 30 ° C. (room temperature) and 1 atmosphere (altitude 0 m).

  The HDC / MPU 23 controls the heater power P according to the temperature detected by the temperature sensor 17. Specifically, data indicating the relationship between the detected temperature and the heater power is set in the HDD 1, and the HDC / MPU 23 determines the heater power depending on the temperature according to the data and the detected temperature. The relationship between temperature and heater power depends on the head slider 12, the radial position (or zone) of the magnetic disk 11, and the atmospheric pressure.

  Since the HDD 1 of this embodiment does not have an atmospheric pressure sensor, it cannot directly measure the atmospheric pressure. Therefore, the HDC / MPU 23 performs TFC according to the atmospheric pressure by measuring the clearance. The clearance changes according to the atmospheric pressure. Therefore, the HDC / MPU 23 measures the clearance and identifies the change in atmospheric pressure from the change in clearance. Since the clearance also changes depending on the temperature, the HDC / MPU 23 can specify the clearance change due to the change in atmospheric pressure by correcting the clearance change due to the temperature change from the measured clearance. Note that by defining a default condition having a specified default temperature and pressure and a default clearance in the default condition, a change in each value is associated with a current value. The default condition is, for example, an environmental condition of 30 ° C. and 1 atmosphere, and the default clearance is a clearance under the condition.

  The temperature-corrected clearance change represents a change in atmospheric pressure. The HDC / MPU 23 controls the heater power P in accordance with the specified atmospheric pressure (atmospheric pressure change) due to the clearance change. Specifically, the HDD 1 is set with data representing the relationship between the atmospheric pressure change represented by the clearance change and the heater power, and the HDC / MPU 23 sets the heater power according to the data and the measured atmospheric pressure. P (p) is determined.

  The HDD 1 of this embodiment specifies a clearance or a clearance change from the default clearance from the read signal of the head slider 12. More specifically, the clearance is specified from the resolution of the read signal (resolution of the frequency component). For example, the resolution can be expressed by a ratio of a specific low frequency signal to a high frequency signal in the read signal. There are several operating parameters to identify pressure changes or clearance changes due to pressure changes, among which the identification of clearance changes using resolution is one of the most accurate methods. . When the clearance is reduced, the amplitude of the high frequency component of the read signal is increased, and the signal resolution, that is, the resolution is increased.

  The resolution and the clearance are in a linear relationship, and the clearance can be expressed as a linear function of the resolution by applying an appropriate linear transformation to the resolution. Typically, the linear function that links the resolution and the clearance is different for each head slider 12. The relationship between the resolution of each head slider 12 and the clearance is specified in a test process in manufacturing the HDD 1, and control parameters corresponding to the relationship are registered in the HDD 1.

  The HDC / MPU 23 can specify the resolution by analyzing the read signal and calculating the ratio of the high frequency signal gain (amplitude) to the low frequency signal gain (amplitude). However, in order for the HDC / MPU 23 to perform the process, an additional function is required in addition to the function necessary for the normal operation. In addition, the MPU requires a lot of processing time to perform the processing. Therefore, it is preferable to measure the resolution using a function mounted on the HDD 1. The RW channel 21 has a function of adjusting the reproduction waveform of the read signal in order to accurately extract data from the read signal. The RW channel 21 performs this waveform shaping using a digital filter.

  A digital filter (adaptive cosine filter) that corrects a frequency component of a reproduction signal is known as a digital filter mounted on the RW channel 21. The RW channel 21 corrects the tap value of this filter from the measurement result of the read signal. This correction value has a linear relationship with the clearance (resolution) and is a value representing the resolution. This digital filter is an existing technology as disclosed in Japanese Patent Laid-Open No. 5-81807 and US Pat. No. 5,168,413, and will not be described in detail. The HDC / MPU 23 can specify the clearance change by referring to the correction value. Hereinafter, this correction value is referred to as Kgrad. In a test process in manufacturing, the relationship between Kgrad and clearance is specified for each head slider 12.

  In the following description, the HDC / MPU 23 specifies the clearance (clearance change) with reference to Kgrad, which is one of the channel parameters, but the HDC / MPU 23 uses other channel parameters representing the resolution. May be. For example, when the RW channel 21 has a digital filter for restoring the reproduction signal of the specific pattern to the reference pattern, the HDC / MPU 23 corrects the resolution component correction value in the correction coefficient of the tap of the digital filter. Can be used to identify clearance.

  As described above, the test process in manufacturing HDD1 specifies the relationship between heater power and clearance, the relationship between temperature and clearance, the relationship between temperature-corrected Kgrad and clearance, and sets data representing them in HDD1. sign up. Kgrad changes due to a temperature change in the characteristics of the RW channel 21 in addition to a clearance change due to a temperature change. The Kgrad temperature correction is performed by combining these changes. By using these setting data, the HDC / MPU 23 can determine an appropriate heater power value from the detected temperature of the temperature sensor 17 and the measured value of Kgrad.

  The HDC / MPU 23 can acquire Kgrad from the RW channel 21 at an arbitrary timing. However, unlike temperature, the air pressure does not change significantly during operation, and typically the air pressure after startup is constant. Therefore, although the HDC / MPU 23 of this embodiment controls the heater power according to the temperature change after startup, the atmospheric pressure (Kgrad) is measured only in the POR process, and the atmospheric pressure during operation after POR is the same as that at startup. TFC is performed assuming that it is the same as the atmospheric pressure. The HDC / MPU 23 may measure the atmospheric pressure during the operation after POR and control the heater power according to the change.

  The feature of this embodiment is the verification of the atmospheric pressure measurement by the write / verify processing in the high clearance. The HDC / MPU 23 of this embodiment performs a write / verify process in high clearance when the change in atmospheric pressure exceeds the reference range. As a preferred mode, the HDC / MPU 23 of this embodiment performs a write verify process in high clearance when the heater power is changed from the default setting value of the TFC in accordance with a change in atmospheric pressure.

  For example, the HDC / MPU 23 performs the write verify process in the high clearance when the heater power value different from the heater power value at the default atmospheric pressure of 1 atmospheric pressure is given to the heater 124. For example, the HDC / MPU 23 does not adjust the heater power when the atmospheric pressure change is small, and adjusts the heater power when the atmospheric pressure change exceeds the reference. This reference atmospheric pressure change is larger than the atmospheric pressure change corresponding to the minimum unit of heater power adjustment.

  As described above, the HDC / MPU 23 determines the atmospheric pressure change (representing the clearance change) from the Kgrad and the temperature detected by the temperature sensor 17 in the POR process. When supplying a heater power different from the heater power at the default atmospheric pressure (for example, 1 atmospheric pressure) according to the atmospheric pressure change determined in the POR, the HDC / MPU 23 verifies the atmospheric pressure measurement by the write verification in the high clearance.

  Measurement of changes in atmospheric pressure with Kgrad is not as accurate and stable as sensors. For this reason, when the heater power is adjusted by measuring the atmospheric pressure change by Kgrad, it is possible to improve the reliability of the subsequent user data write processing by verifying the atmospheric pressure measurement by the write verification in the high clearance. Further, by verifying the head-disk contact when the change in atmospheric pressure exceeds the reference, it is possible to avoid an excessive increase in processing time for verification.

  The HDC / MPU 23 performs a write verify process at a heater power smaller than the heater power set by default TFC. In other words, in the write verify process of this embodiment, data is written in a clearance higher than the clearance in the default setting TFC according to the temperature detected by the temperature sensor 17 and the Kgrad measurement value. As a result, a margin corresponding to atmospheric pressure fluctuation after the atmospheric pressure measurement can be secured, and the reliability with respect to the poor write in the user data write processing can be further increased. In particular, when the atmospheric pressure is measured only in the POR, the margin for the subsequent atmospheric pressure change is important.

  FIG. 3A shows the head slider 12 provided with heater power in a deo default setting according to the temperature and pressure conditions at the time of POR, and FIG. 3B shows the write verify processing in high clearance. A head slider 12 is shown. The clearance Cb in FIG. 3B is larger than the clearance Ca in FIG. That is, the heater power Pb in FIG. 3B is smaller than the heater power Pa in FIG.

  FIG. 4 is a diagram schematically showing the relationship between the measurement result of altitude change (atmospheric pressure change) and the write / verify processing in high clearance. As the altitude increases, the air pressure decreases. FIG. 3 shows a reference range K_criteria for determining whether or not to perform a write verify process at altitude, Kgrad measurement value, default Kgrad, and high clearance. Kgrad is a temperature-corrected value. When the reference range is exceeded, the HDC / MPU 23 adjusts the heater power corresponding to the atmospheric pressure fluctuation. As described above, the default Kgrad is a value specified in the test process (TEST). As illustrated in FIG. 3, Kgrad does not completely follow altitude (atmospheric pressure).

  In the first three PORs, altitude A and measured Kgrad are within the reference range K_criteria. Therefore, the HDC / MPU 23 does not perform the write verify process in the high clearance. In the fourth POR, the altitude and measured Kgrad exceed the reference range K_criteria. The HDC / MPU 23 performs a write verify process in the high clearance in this POR. Thereafter, in the fifth POR, the altitude A and the measured Kgrad are within the reference range K_criteria. Therefore, the HDC / MPU 23 does not perform the write verify process in the high clearance.

  The reference range K_criteria preferably has boundaries above and below the default Kgrad as shown in FIG. This is because a typical default altitude is 0 m, but in an actual use environment, the altitude may be under a pressurized environment or may be 0 m or less. However, the write verify processing in the high clearance may be performed only when the altitude exceeds the reference value by design.

  With reference to the flowchart of FIG. 5 and the block diagram of FIG. 6, the flow of the write verification process in the atmospheric pressure measurement and high clearance of this embodiment will be described. The HDC / MPU 23 performs atmospheric pressure measurement in the POR process. First, the HDC / MPU 23 measures Kgrad at the heater power 0 (S11). Specifically, the HDC / MPU 23 selects one head slider 12 and controls the VCM 15 via the motor driver unit 22 to move the head slider 12 to a predetermined data track. The head slider 12 reads access destination data under the control of the HDC / MPU 23. The RW channel 21 calculates Kgrad from the read signal of the head slider 12 and stores it in a register in the RW channel 21. The HDC / MPU 23 accesses the register of the RW channel 21 and acquires Kgrad.

  The data track used for the measurement of Kgrad is preferably a data track with excellent characteristics. For this reason, it is preferable to be in an area that is not used for recording user data and is not accessed from the host 51. Further, in the HDD 1 having a ramp that gives the retraction position of the head slider 12 outside the magnetic disk 11, it is preferable that the HDD 1 is located on the inner peripheral side with respect to the innermost peripheral end of the user area. This is because the head slider 12 does not pass through this region in normal operation. When the actuator 16 is on the ramp, the head slider 12 is outside the magnetic disk 11.

  Next, the HDC / MPU 23 specifies a clearance from Kgrad (S12). Specifically, the amount of clearance change from the default clearance is specified from the difference between the default Kgrad and the measured Kgrad under default conditions (for example, 30 ° C. and 1 atm). The clearance change amount can be expressed by, for example, a heater power value. The default Kgrad is a temperature-corrected value, and the HDC / MPU 23 similarly corrects the temperature of the Kgrad measurement value according to the detected temperature. By comparing the temperature-corrected default Kgrad and the measured value, the HDC / MPU 23 can specify a change in atmospheric pressure from the default atmospheric pressure (for example, 1 atmospheric pressure) from the Kgrad.

  FIG. 7 schematically shows the relationship between Kgrad, clearance, heater power, and atmospheric pressure (altitude). Kgrad is a value after temperature correction. As shown in FIG. 7, the above values are in a linear relationship with each other. Therefore, the HDC / MPU 23 can directly specify another value from any of the above values, and one value can represent another value.

  In the above process, Kgrad at heater power 0 is measured and the value is corrected by the detected temperature. However, the HDC / MPU 23 may measure Kgrad in a state where the heater power value corresponding to the detected temperature and the radial position is given to the heater 124 according to the default setting of the TFC. A value obtained by correcting the temperature change of the channel characteristic with respect to the measured Kgrad shows a change in Kgrad corresponding to the change in atmospheric pressure. Thus, the temperature correction of Kgrad can be performed by calculation alone or by adjusting the clearance by TFC.

  Next, the HDC / MPU 23 determines whether or not the clearance change specified from Kgrad is within the reference range (S13). In this embodiment, the value for adjusting the heater power corresponding to the change in atmospheric pressure is the boundary of the reference range. The HDC / MPU 23 adjusts the heater power according to the change in atmospheric pressure in the default setting of TFC. At this time, when the change in atmospheric pressure exceeds the reference range, the heater power is changed. The reference range may be the same as the minimum variable amount of the heater power, or may be a different value.

  The clearance change is expressed by, for example, Kgrad, heater power, or nanometer. The HDC / MPU 23 compares the measured clearance change with the boundary value of the reference range, and when the clearance change is within the reference range (Y in S13), the write verify process is performed with the clearance according to the default setting (S15). ). If no error occurs in this process (N in S16), the HDC / NPU 23 enters the normal read / write processing mode (S17). If an error occurs (Y in S16), the error recovery process is performed. Perform (S18).

  When the measured clearance change exceeds the reference range (N in S13), that is, when adjusting the heater power separately from the heater power adjustment due to the temperature change in the default setting of TFC, the HDC / MPU 23 is in the high clearance. Write verify processing is performed (S14). The write verification process (S14) in the high clearance of this embodiment will be described with reference to the flowchart of FIG. 8 and the schematic diagram of the head slider 12 of FIG. The HDC / MPU 23 performs TFC resetting for user data read / write processing as well as write-verify processing. In the following, a case where the altitude increases and the atmospheric pressure decreases will be described.

  The HDC / MPU 23 determines the heater power value in the read / write operation in the default setting of TFC from the detected temperature of the temperature sensor 17 and the measured Kgrad (S141). The HDC / MPU 23 determines a heater power value corresponding to the detected temperature and Kgrad from control data such as functions and tables that are set and registered in advance. FIG. 9A shows the head slider 12 at the heater power value Pa. The clearance at this time is Ca. The HDC / MPU 23 does not actually perform such heater adjustment.

  Next, the HDC / MPU 23 controls the AE 13 to provide the heater 124 with a heater power Pb smaller than the heater power in the default setting (S142). FIG. 9B shows the head slider 12 in this state. The difference (Pa−Pb) between the default set value Pa and the heater power Pb that is actually applied to the heater 124 is set in advance, for example, a heater power value corresponding to 1 nm.

  The head slider 12 writes data in a predetermined data sector at a heater power Pb less than the default setting Pa, that is, at a clearance Cb higher than the default setting Ca (S143). Typically, the head slider 12 writes data to all data sectors of the data track. In order to perform an accurate write verify test, there must be no error in the data sector to which data is written. Therefore, in the HDD 1 manufacturing process, a data track that does not have an error sector is selected. This data track is preferably used in an area where it is not used for recording user data and is not accessed by the host 51. Further, in an HDD having a ramp outside the magnetic disk 11, it is preferable that the HDD be on the inner peripheral side than the innermost peripheral end of the user area. This is because the head slider 12 does not pass through this region in normal operation.

  Subsequently, the HDC / MPU 23 performs a read process on the data written in the high clearance, and determines whether the data can be read accurately (S144). Specifically, the HDC / MPU 23 reads the data written in step S143 by the head slider 12 and determines whether the correct data has been written. If the read data cannot be repaired by the error correction function, or if the read data is different from the written data, the HDC / MPU 23 determines that an error has occurred in the high clearance write process (BAD in S144). . The heater power value in this read process is typically a heater power value under the same conditions as data writing in high clearance. Even under the same environmental conditions, the heater power value differs between the read process and the write process.

  When the determination in step S144 is “BAD”, the HDC / MPU 23 sets the current heater power setting Pb and the heater power setting before adjusting the heater power corresponding to the atmospheric pressure change (Pe in FIG. 9E). Are compared (S145). That is, the latter heater power setting Pe is a heater power setting corresponding to the detected temperature and the radial position, and is the heater power value at the current detected temperature, the radial position, and the default atmospheric pressure. Specifically, the heater power Pa is the sum Pa (t) + Pa (p) of Pa (t) that depends on temperature and Pa (p) that depends on atmospheric pressure, and Pe is Pe (t) + Pe (p ). In the case described, Pe (p)> Pa (p) because the process is performed when the atmospheric pressure decreases (clearance decreases).

  Accordingly, the heater power Pe is larger than the default heater power Pa corresponding to the atmospheric pressure change, and the clearance Ce at this time is smaller than the clearance Ca. When the current heater power setting value Pb is smaller than the heater power setting value Pe ignoring the change in atmospheric pressure (Y in S145), the HDC / MPU 23 slightly reduces the heater power for the next write verification. To increase the clearance (S146).

  The HDC / MPU 23 performs a write verify process at the increased heater power setting (Pc in FIG. 9C) (S143, S144). That is, the heater power value in the write process and the read process is larger than the value Pb in the previous write verify process. The HDC / MPU 23 performs a read process on the data written in the heater power Pc, and determines whether the data can be read accurately (S144). When accurate data is not written (BAD in S144), the HDC / MPU 23 sets the current heater power setting Pc and the heater power setting before adjusting the heater power corresponding to the atmospheric pressure change (FIG. 9E). (Pe) in the above are compared (S145).

Since the heater power Pc is smaller than the heater power Pe (Y in S145), the HDC / MPU 23 slightly increases the heater power and decreases the clearance for the next write verification (S146). .
Even if the heater power is increased little by little and the write verify process is repeated, the data cannot be written accurately. As shown in FIG. 9 (e), the heater power setting ignores the change in atmospheric pressure. When the value Pe is reached (N in S145), the HDC / MPU 23 starts error recovery processing (S147). Even when there is no heater power corresponding to atmospheric pressure fluctuation, if accurate data writing is not possible, there is a high possibility that an error different from the error in atmospheric pressure measurement has occurred. Therefore, the HDC / MPU 23 starts an error recovery process when the heater power reaches the heater power Pe depending on the temperature.

  When the HDC / MPU 23 determines that the data has been correctly written (GOOD in S144), the heater power value P (p) corresponding to the atmospheric pressure in the TFC is changed from the default setting (S148), and the normal user data is stored. Read / write processing is performed (S149). Specifically, the HDC / MPU 23 calculates the difference between the heater power value when data can be written correctly and the first heater power value in the write verify process in the high clearance. Then, the difference is added to the heater power P (p) corresponding to the atmospheric pressure in the default TFC setting. Note that a predetermined calculation may be performed on the difference to add a smaller value. In the example, the heater power P (p), which depends on the atmospheric pressure, is determined in the POR and is constant until the next POR.

  Assuming that the heater power value when data can be written correctly is P2, and the initial heater power value in the high-clearance write verify process is P1, the difference ΔP is (P2−P1). . The HDC / MPU 23 calculates a value obtained by adding (P2−P1) to the default setting P (p) (P (p) + (P2−P1)), and in the subsequent read / write processing, Use as power value. Typically, P (p) is a different value between the read process and the write process, but the corrected value (P2−P1) may be the same.

  An example using specific numbers will be described. The default P (t) in the light processing corresponding to the temperature and pressure in the POR is 14 mW, and P (p) is 6 mW. The heater power P given to the heater 124 is 20 mW. The heater power P1 in the first write verify process is set to 12 mW. The heater power value P2 when data can be written accurately is 14 mW. The difference ΔP = (P2−P1) between P2 and P1 is 2 mW. Therefore, the HDC / MPU 23 uses 8 mW obtained by adding 2 mW to P (p) = 6 mW in the default setting as P (p) in the subsequent user data write processing. P (p) is the same or different value in the read and write processes, but the difference ΔP = (P2−P1) uses the same value for each.

  As mentioned above, although this invention was demonstrated taking the 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. The present invention can be applied to a disk drive apparatus having a clearance adjustment mechanism other than TFC such as a piezo element. As described above, it is preferable to measure the change in atmospheric pressure using a read signal, particularly resolution, but other operational parameters such as SPM current may be used to measure the atmospheric pressure change.

  The HDC / MPU 23 may perform the write / verify processing in the high clearance at every POR regardless of the atmospheric pressure change amount. Further, the write / verify processing in the high clearance may be performed at a timing other than POR. Although write verify is preferable in terms of processing time and reliability, the HDC / MPU 23 may perform other write tests. The present invention may be applied to an HDD on which a head slider having only a read element is mounted, or to a disk drive device other than the HDD.

In this embodiment, it is a block diagram which shows typically the whole structure of HDD. In this embodiment, it is sectional drawing which shows typically the structure of the head slider provided with the heater for TFC. In this embodiment, it is a figure which shows typically the head slider to which the heater power according to default setting was given, and the head slider in the write verification process in a high clearance. In this embodiment, it is a figure which shows typically the relationship of the reference | standard range which determines the measurement result of an altitude change (atmospheric pressure change), verification of head-disk contact, and the implementation of verification. In this embodiment, it is a flowchart which shows the flow of the initial setting process at the time of starting. 2 is a block diagram showing logical components for performing a write verify process in high clearance in the present embodiment. In this embodiment, it is a figure which shows typically the relationship between Kgrad, clearance, heater power, and atmospheric pressure (altitude). 5 is a flowchart showing a flow of write / verify processing in high clearance in the present embodiment. In this embodiment, it is a figure which shows typically the change of the state of a head slider in the write verification process in a high clearance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hard disk drive, 10 Enclosure, 11 Magnetic disk 12 Head slider, 14 Spindle motor, 15 Voice coil motor 16 Actuator, 20 Circuit board, 21 Read / write channel 22 Motor driver unit, 23 Hard disk drive Controller / MPU
24 RAM, 31 Write element, 32 Read element, 32a Magnetoresistive element 33a, b Shield, 34 Protective film, 51 Host, 121 Trailing side end face 122 Head element part, 123 Slider, 124 Heater, 311 Write coil 312 Magnetic pole, 313 Insulating film

Claims (15)

A head to access the disk;
A moving mechanism for holding the head and moving the head on the disk;
An adjustment mechanism for adjusting the clearance between the head and the disk;
A temperature sensor;
A controller for controlling the head, the moving mechanism, and the adjusting mechanism;
Have
The controller is
After correcting the temperature change in the change in the operation parameter of the disk drive device using the temperature detected by the temperature sensor, the clearance change amount is determined from the operation parameter,
A light test is performed with the clearance higher than the default setting corresponding to the detected temperature and clearance change amount,
Disk drive device. The controller performs the write test when the clearance change amount exceeds a reference range.
The disk drive device according to claim 1. The controller performs the write test when performing a clearance adjustment corresponding to the determined clearance change amount.
The disk drive device according to claim 2. The write test is a write verify test.
The disk drive device according to claim 1. When the controller fails the light test, the clearance is gradually lowered and the light test is repeated.
The disk drive device according to claim 1. The controller changes a default setting based on a clearance that passes the light test.
6. The disk drive device according to claim 5. The controller corrects the default setting by using a difference between a clearance that passes the light test and a clearance when the light test is started.
The disk drive device according to claim 6. The retracted position of the head slider is outside the disk,
The data track for performing the write test is located on the inner circumference side of the area for recording user data.
The disk drive device according to claim 1. A clearance adjustment method in a disk drive device having a clearance adjustment function,
The temperature is detected by the temperature sensor,
Obtaining operating parameters of the disk drive device;
Using the detected temperature to correct the temperature change in the change of the operating parameter,
After the correction, the clearance change amount is determined from the operation parameter,
Perform a light test with the clearance higher than the default setting corresponding to the detected temperature and clearance change amount,
Adjusting the clearance based on the result of the light test;
Method. When the clearance change amount exceeds a reference range, the light test is performed.
The method of claim 9. When the clearance adjustment corresponding to the determined clearance change amount is performed, the light test is performed.
The method of claim 10. The write test is a write verify test.
The method of claim 9. When the light test is failed, the clearance is gradually lowered and the light test is repeated.
The method of claim 9. Change the default setting based on the clearance that passed the light test,
The method of claim 13. The default setting is corrected by the difference between the clearance that passed the light test and the clearance according to the default setting.
The method according to claim 14.

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