Disk device, and control method for disk device

Abstract

To provide a disk device suitable for appropriately controlling a floating amount of a head from a disk medium, and a control method for the disk device.SOLUTION: According to one embodiment, a disk device having a disk medium, a head, and a controller is provided. The disk medium has a recording surface. The head has a first read element and a heater. The first read element faces the recording surface. The controller detects a first noise at heating the head corresponding to a signal read from the disk medium by the first read element when power is started to be supplied to the heater.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present embodiment relates to a disk device and a method for controlling the disk device. [Background technology]

[0002] In a disk drive having a disk medium and a head, the head reads information recorded on the disk medium while floating above the disk medium. In disk drives, a heater is provided on the head, and by supplying power to the heater, the amount of head protrusion due to thermal expansion can be adjusted, thereby controlling the amount of head floating above the disk medium. In this case, it is desirable to appropriately control the amount of head floating above the disk medium. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 09401161 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one embodiment is to provide a disk device and a method for controlling a disk device that are suitable for appropriately controlling the flying height of a head from a disk medium. [Means for solving the problem]

[0005] According to one embodiment, there is provided a disk drive having a disk medium, a head, and a controller. The disk medium has a recording surface. The head has a first read element and a heater. The first read element faces the recording surface. When power supply to the heater is started, the controller detects a first noise generated when the head heats up in response to a signal read from the disk medium by the first read element. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram showing the configuration of a disk device according to an embodiment. [Figure 2] FIG. 2 is a plan view showing the configuration of a head in the embodiment. [Figure 3] FIG. 2 is a cross-sectional view showing the configuration of a head according to the embodiment. [Figure 4] 5A and 5B are diagrams showing changes in the protrusion amount of the head due to thermal expansion in the embodiment. [Figure 5] 5A and 5B are diagrams showing noise forms in the embodiment. [Figure 6] FIG. 6 is a waveform diagram showing a change in read voltage when the head is heated in the embodiment. [Figure 7] FIG. 6 is a waveform diagram showing a change in read voltage when the head is heated in the embodiment. [Figure 8] FIG. 6 is a waveform diagram showing a change in read voltage when the head is heated in the embodiment. [Figure 9] FIG. 6 is a waveform diagram showing a change in read voltage when the head is heated in the embodiment. [Figure 10] 4 is a flowchart showing the operation of the disk device according to the embodiment. [Figure 11] 10 is a flowchart showing a noise detection process according to an embodiment. [Figure 12] 4 is a flowchart showing a noise reduction process according to the embodiment. [Figure 13] FIG. 4 is a waveform diagram showing noise timing in the embodiment. [Figure 14] FIG. 4 is a waveform diagram showing noise timing in the embodiment. [Figure 15] FIG. 10 is a plan view showing the configuration of a head according to a first modified example of the embodiment. [Figure 16] FIG. 10 is a cross-sectional view showing the configuration of a head according to a first modified example of the embodiment. [Figure 17] 10 is a flowchart showing a noise countermeasure process in a first modified example of the embodiment. [Figure 18] FIG. 10 is a diagram showing offset settings of a head in a first modified example of an embodiment. [Figure 19] FIG. 10 is a waveform diagram showing a change in read voltage when the head is heated. [Figure 20] FIG. 10 is a waveform diagram showing a change in read voltage when the head is heated. [Figure 21] 10 is a flowchart showing a noise detection process according to a second modified example of the embodiment. [Figure 22] FIG. 10 is a waveform diagram showing the operation of a disk device according to a third modified example of the embodiment. [Figure 23] FIG. 10 is a diagram showing a change in positioning accuracy with a change in heater power in a second modified example of the embodiment. [Figure 24] 10 is a flowchart showing a noise detection process according to a third modified example of the embodiment. [Figure 25] FIG. 11 is a diagram showing a change in detection accuracy of the servo interval with a change in heater power in a third modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] A disk drive according to an embodiment will be described in detail below with reference to the accompanying drawings, but the present invention is not limited to this embodiment.

[0008] (Embodiment) The disk device according to the embodiment is provided with a heater in the head, and by supplying power to the heater, the amount of head protrusion due to thermal expansion can be adjusted, and the amount of head floating above the disk medium can be controlled, but the device is designed to appropriately control this amount of floating.

[0009] The disk device 1 can be configured as shown in Fig. 1. Fig. 1 is a diagram showing the configuration of the disk device 1.

[0010] The disk device 1 is, for example, a hard disk drive, and functions as an external storage device for the host 40 .

[0011] The disk device 1 has a disk medium 11, a spindle motor 12, a head slider 21, a head 22, an actuator arm 15, a voice coil motor (VCM) 16, a ramp 23, a head amplifier 24, a motor driver 19, a volatile memory 27, a nonvolatile memory 28, a buffer memory 29, and a controller 32. The disk medium 11, the spindle motor 12, the head 22, the actuator arm 15, the voice coil motor (VCM) 16, and the ramp 23 are housed in a housing (not shown). The head amplifier 24, the motor driver 19, the volatile memory 27, the nonvolatile memory 28, the buffer memory 29, and the controller 32 are partially housed in the housing, and partially disposed on a board (outside the housing).

[0012] The controller 32 includes a read / write channel (RWC) 25, a hard disk controller (HDC) 31, and a processor 26. The processor 26 may be a CPU.

[0013] The package of the head amplifier 24 may be disposed on a substrate fixed to the actuator arm 15. The controller 32 may be configured as a one-chip integrated circuit (system-on-chip). The package of the controller 32 may be disposed on a printed circuit board outside the housing.

[0014] The disk medium 11 is a disc-shaped recording medium that magnetically records various types of information, and is rotated by a spindle motor 12. The disk medium 11 has a plurality of concentric tracks TR centered near the center of rotation of the spindle motor 12 on its recording surface 11a (see FIG. 4). Each track TR has a plurality of data areas DT and servo areas SV alternately arranged in the circumferential direction (see FIG. 18). In each track TR, a plurality of servo areas SV can be arranged at equal intervals in the circumferential direction.

[0015] Actuator arm 15 is rotatably attached to pivot 17. Head 22 is attached to one end of this actuator arm 15 via head slider 21. Head 22 can be disposed near the tip of head slider 21 (see FIGS. 2 and 3). VCM 16 is connected to the other end of actuator arm 15. VCM 16 rotates actuator arm 15 around pivot 17, positioning head 22 while it is floating above any radial position on disk medium 11. At this time, processor 26 performs servo control (positioning control) to position head 22 using servo information read from servo area SV by read element RE in head 22.

[0016] In response to a command from the processor 26, the motor driver 19 drives the spindle motor 12 to rotate the disk medium 11 around the rotation axis at a predetermined rotation speed. In addition, in response to a command from the processor 26, the motor driver 19 drives the VCM 16 to move the head 22 at one end of the actuator arm 15 in the radial direction of the disk medium 11.

[0017] The head 22 writes user data to the disk medium 11 and reads information (user data and servo information) recorded on the disk medium 11. The head 22 has a configuration, for example, as shown in FIGS. 2 and 3. FIG. 2 is a plan view showing the configuration of the head 22. FIG. 2(a) is a plan view showing the arrangement of the head 22 on the head slider 21. FIG. 2(b) is an enlarged plan view showing the internal configuration of the head 22. FIG. 3 is a cross-sectional view showing the arrangement of the head 22 on the head slider 21, taken along line AA in FIG. 2(a). FIG. 3(b) is an enlarged cross-sectional view showing the internal configuration of the head 22, taken along line BB in FIG. 2(b).

[0018] 2 and 3, the head 22 is configured to include a write element WE, a read element RE, and a heater HT. The write element WE, read element RE, and heater HT may be aligned along the longitudinal direction of the head 22. The write element WE may be positioned closer to the tip of the head 22 than the read element RE.

[0019] The write element WE faces the recording surface 11a (see FIG. 4) of the disk medium 11. The write element WE writes data to the data area DT of the track TR on the recording surface 11a using a magnetic field generated by its magnetic pole. The read element RE faces the recording surface 11a of the disk medium 11. The surface of the read element RE facing the recording surface 11a is referred to as the facing surface REa. The read element RE reads user data from the data area DT of the track TR on the recording surface 11a and reads servo information from the servo area SV of the track TR on the recording surface 11a by reading changes in the magnetic field on the disk medium 11 as information. When the disk medium 11 is stopped from rotating, the head 22 is retracted onto a ramp 23 (see FIG. 1).

[0020] During a write operation, the head amplifier 24 converts the write signal supplied from the RWC 25 into a write current and outputs it to the write element WE.

[0021] During a read operation, the head amplifier 24 amplifies a signal (read signal) read from the disk medium 11 by the read element RE and outputs the amplified signal to the RWC 25. At this time, the processor 26 controls the head amplifier 24 to pass a bias current through the read element RE. The RWC 25 further amplifies the signal from the head amplifier 24. The RWC 25 performs AGC (Auto Gain Control) control and amplifies the read signal with a gain determined by the processor 26 so that the signal level reaches a target level.

[0022] The heater HT can be provided in the vicinity of the read element RE. When power is applied to the heater HT, the heater HT can thermally expand the vicinity of the read element RE.

[0023] In the disk device 1, during a read operation, DFH (Dynamic Flying Height) control may be performed using the heater HT. In DFH control, the processor 26 controls the power supply unit 24e to supply power to the heater HT via the bias circuit 24a. That is, as shown in FIG. 4, the processor 26 applies heater power to the heater HT mounted on the head 22 via the head amplifier 24, causing the head 22 to thermally expand. FIG. 4 is a diagram showing changes in the protrusion amount of the head 22 due to thermal expansion. The protrusion of the head 22 due to thermal expansion can adjust the distance (spacing ΔSP) from the facing surface REa of the read element RE to the recording surface 11a of the disk medium 11.

[0024] When the heater HT is de-energized, the height position of the facing surface REa of the head 22 is approximately the same as the height position of the facing surface 21a of the head slider 21, as shown in FIG. 4(a).

[0025] At this time, the flying height of the head 22 from the disk medium 11 is represented by a spacing ΔSP. The power supplied to the heater HT is represented by a heater power P HT The heater HT is turned off and the heater power P HT ≒0, the protrusion amount H of the head 22 due to thermal expansion 22 ≈0. As a result, the spacing ΔSP becomes a relatively large ΔSP0 as shown in FIG. 4(a), and the amplitude of the read voltage by the read element RE becomes a relatively small V0.

[0026] The head amplifier 24 supplies power to the heater HT under the control of the controller 32. The heater HT receives the power supply and heats the area of ​​the head 22 near the read element RE. This heating causes thermal deformation of the head 22, which changes the spacing ΔSP.

[0027] Heater HT to heater power P HT =P AWhen (>0) is supplied, as shown in FIG. 4(b), the height position of the facing surface REa is closer to the recording surface 11a than the height position of the facing surface 21a.

[0028] At this time, the heater power P HT ≒P A In response to this, the protrusion amount H of the head 22 due to thermal expansion 22 H 22A (>0). This results in a relatively small spacing ΔSP, as shown in FIG. 4(b). A (≒ΔSP0-H 22A ) and the amplitude of the read voltage by the read element RE is relatively large V A (>V0).

[0029] Heater HT to heater power P HT =P B (>P A ) is supplied, the height position of the facing surface REa becomes closer to the recording surface 11a than the height position of the facing surface 21a, as shown in FIG. 4(c).

[0030] At this time, the heater power P HT ≒P B In response to this, the protrusion amount H of the head 22 due to thermal expansion 22 H 22B (>H 22A ) As a result, the spacing ΔSP becomes even smaller as shown in FIG. 4(c). B (≒ΔSP0-H 22B ) and the amplitude of the read voltage by the read element RE is even larger V B (>V A )

[0031] The presence or absence of noise in the read voltage during thermal protrusion can be detected by the following method: Data is written to the disk medium 11 in advance at a uniform frequency during the manufacturing process, and the data is read by the read element RE immediately after applying heater power. The read voltage waveform is confirmed for the data read by the read element RE while gradually increasing the thermal protrusion.

[0032] The disk drive 1 may use a defect scan function implemented in the RWC 25 as a method for checking the read voltage waveform. As shown in FIG. 5, the defect scan function detects abnormalities in the read voltage waveform as errors in order to detect protrusions and defects on the disk medium 11. FIG. 5 illustrates noise patterns. With the heater HT off, if data written at a single frequency is normal, the read voltage of the read element RE in the disk drive 1 will have a constant amplitude, as shown in FIG. 5(a). In FIG. 5(a), the upper and lower target values ​​are indicated by dotted lines. In the case of FIG. 5(a), the read voltage reaches the upper target value at timing t100.

[0033] The defect scan function can detect a sudden drop in the output of the read voltage waveform as an error, as shown in FIG. 5(b). In the case of FIG. 5(b), the read voltage does not reach the upper limit target value at timing t101, which corresponds to timing t100. The disk device 1 calculates the shortage ΔV of the read voltage value relative to the upper limit target value. 101 may detect a sudden drop in the output of the read voltage waveform when the read voltage exceeds the threshold TH1.

[0034] The defect scan function can detect a sudden output rise in the read voltage waveform as an error, as shown in FIG. 5(c). In the case of FIG. 5(c), the read voltage exceeds the upper limit target value at timing t102, which corresponds to timing t100. The disk device 1 calculates the excess amount ΔV of the read voltage value relative to the upper limit target value. 102 may detect a sudden increase in output of the read voltage waveform when the read voltage exceeds the threshold TH2.

[0035] The defect scan function can detect a baseline change as an error, as shown in FIG. 5(d). The disk device 1 may obtain the baseline BL as a locus of average values ​​in one cycle of the read voltage waveform, as shown by the dashed line in FIG. 5(d). In the case of FIG. 5(d), the baseline BL deviates significantly from the target value at a predetermined timing t103. The disk device 1 calculates the amount of variation ΔV of the baseline BL relative to the target value. 103 may detect a baseline BL change by exceeding a threshold TH3.

[0036] By performing a read operation immediately after applying heater power and using the defect scan function, it becomes possible to detect noise at the time of thermal protrusion. In addition, the defect scan function can also identify the location of an error, so if the timing of the start of the read operation and the timing of the start of application of heater power are known, the disk device 1 can detect the timing of noise occurrence at the start of application of heater power. The disk device 1 may perform this operation for each of the read elements RE installed.

[0037] For example, if the amplitude of the read voltage gradually increases from the time when heater power starts to be applied until a predetermined time is reached, as shown in Figures 6 and 7, the disk drive 1 will detect that there is no noise when the head 22 is heated. Figures 6 and 7 are waveform diagrams showing changes in the read voltage when the head 22 is heated. In Figures 6 and 7, the vertical axis represents the read voltage and the horizontal axis represents time. Figure 7 is a waveform diagram in which part C of Figure 6 is enlarged in the time direction.

[0038] 6 and 7, at timing t1, heater power is applied and the thermal protrusion begins to increase gradually, and accordingly, the amplitude of the read voltage begins to increase gradually.

[0039] At timing t2, when the predetermined time is reached, the thermal protrusion is maintained at the predetermined value, and accordingly, the increase in the amplitude of the read voltage is completed and the amplitude of the read voltage is maintained approximately constant.

[0040] In addition, periodic upper and lower convexes can be seen in the read voltage waveform, which indicate that the amplitude of the read voltage temporarily increases at the timing when servo information is read (servo timing).

[0041] On the other hand, if the amplitude of the read voltage suddenly increases or decreases from the timing when heater power starts to be applied until a predetermined time, as shown in Figures 8 and 9, the disk drive 1 may detect the presence of noise during heating of the head 22. Figures 8 and 9 are waveform diagrams showing changes in the read voltage during heating of the head 22. In each of Figures 8 and 9, the vertical axis represents the read voltage and the horizontal axis represents time. Figure 9 is a waveform diagram in which part D of Figure 8 is enlarged in the time direction.

[0042] 8 and 9, at timing t11, heater power is applied and the thermal protrusion gradually increases, and accordingly, the amplitude of the read voltage gradually begins to increase.

[0043] At timing t12, the read voltage exceeds the upper limit target value. The disk device 1 calculates the excess amount ΔV of the read voltage value relative to the upper limit target value. 12 exceeds the threshold value TH2, a sudden increase in the output of the read voltage waveform can be detected.

[0044] At timing t13, the read voltage falls below the lower limit target value. The disk device 1 calculates the amount by which the read voltage falls below the lower limit target value, ΔV 13 exceeds the threshold value TH2, a sudden increase in the output of the read voltage waveform can be detected.

[0045] At timing t14, when the predetermined time is reached, the thermal protrusion is maintained at the predetermined value, and accordingly, the increase in the amplitude of the read voltage is completed, and the amplitude of the read voltage is maintained approximately constant.

[0046] Next, the general operation of the disk device 1 will be described with reference to Fig. 10. Fig. 10 is a flowchart showing the operation of the disk device.

[0047] In the disk device 1, the controller 32 performs a noise detection process (S1) when it is started up. In the noise detection process, the controller 32 detects noise generated when the head 22 is heated in response to a signal read from the disk medium 11 by the read element RE immediately after power is supplied to the heater HT in the head 22.

[0048] The controller 32 performs noise countermeasure processing (S2) depending on the result of the noise detection processing (S1). The noise countermeasure processing is processing that counters noise. The noise countermeasure processing may include processing that adjusts the read start timing when the head 22 is heated. The noise countermeasure processing may also include processing that selects whether the head 22 is usable.

[0049] The disk device 1 may perform the operation shown in FIG. 10 for each of all the read elements RE mounted thereon.

[0050] Next, the noise detection process (S1) will be described with reference to Fig. 11. Fig. 11 is a flowchart showing the noise detection process.

[0051] In the disk device 1, the controller 32 turns on the defect scan function to start the noise detection process, and also turns on the heater power to start supplying power to the heater HT (S11).

[0052] The protrusion amount of the head 22 increases due to thermal expansion, the facing surface REa of the read element RE approaches the recording surface 11a of the disk medium 11, and the spacing ΔS decreases.

[0053] The controller 32 uses the defect scan function to monitor the amplitude of the read voltage from the read element RE (S13), and determines whether or not an error is detected based on the monitoring result (S14).

[0054] The controller 32 acquires the read voltage from the read element RE via the head amplifier 24. If the read voltage reaches the upper limit target value at the timing when it should reach the upper limit, the controller 32 determines that no error is detected (No in S14) and detects the absence of noise (S15).

[0055] If the read voltage is insufficient relative to the upper limit target value at the timing when the read voltage should reach the upper limit, the controller 32 determines that an error has been detected (Yes in S14) and detects the presence of noise (S16).

[0056] If the amount of deficiency of the read voltage value relative to the lower limit target value exceeds the threshold value TH1 at the timing when the read voltage should reach the lower limit, the controller 32 determines that an error has been detected (Yes in S14) and detects the presence of noise (S16).

[0057] If the excess of the read voltage value relative to the upper limit target value exceeds the threshold value TH2 at the timing when the read voltage should reach the upper limit, the controller 32 determines that an error has been detected (Yes in S14) and detects the presence of noise (S16).

[0058] If the excess of the read voltage value relative to the lower limit target value exceeds the threshold value TH2 at the timing when the read voltage should reach the lower limit, the controller 32 determines that an error has been detected (Yes in S14) and detects the presence of noise (S16).

[0059] If the amount of variation of the baseline BL relative to the target value exceeds the threshold value TH3 at a predetermined timing, the controller 32 determines that an error has been detected (Yes in S14) and detects the presence of noise (S16).

[0060] The controller 32 ends the noise detection process and maintains the heater power to continue supplying power to the heater HT (S18).

[0061] Next, the noise countermeasure processing (S2) will be described with reference to Fig. 12. Fig. 12 is a flowchart showing the noise countermeasure processing.

[0062] The controller 32 acquires the results of the noise detection process (S1) (S21) and determines whether the timing (noise timing) NT at which the noise occurs is within the read wait time (S22). The read wait time is the time from when the heater HT starts to be energized until the read gate opens and the read operation starts.

[0063] If the noise timing NT is within the read wait time (Yes in S22), the controller 32 determines the timing to open the read gate (read start timing) (S23), and sets the target head 22 to be usable (S24).

[0064] If the noise timing NT is not within the read wait time (No in S22), the controller 32 delays the read start timing by a predetermined amount (S25). The predetermined amount can be experimentally determined in advance as an appropriate delay amount for adjusting the read start timing.

[0065] For example, if the normal read latency is the time from timing t21 to t22 shown in Fig. 13, the noise timing NT is assumed to be timing t23, which is after timing t22. Fig. 13 is a waveform diagram showing the noise timing NT. In this case, the controller 32 determines that the noise timing NT is not within the read latency, and delays the timing of opening the read gate by a predetermined amount from t22.

[0066] Alternatively, if the normal read latency is the time from timing t21 to t22 shown in Figure 14, the noise timing NT is assumed to be timing t25, which is after timing t22. Figure 14 is a waveform diagram showing the noise timing NT. In this case, the controller 32 determines that the noise timing NT is not within the read latency, and delays the timing at which the read gate is opened by a predetermined amount from t22.

[0067] Returning to FIG. 12, the controller 32 repeats the loop of S22 to S26 until the read start timing exceeds the limit timing (limit timing) that can be delayed (No in S26).

[0068] In this repetition, if the noise timing falls within the read wait time (Yes in S22), the controller 32 determines the timing to open the read gate (read start timing) (S23) and sets the target head 22 to be used (S24).

[0069] 13, for example, by delaying the timing of opening the read gate until timing t24 when the read latency reaches limit Tth, the noise timing t23 falls within the read latency. In response to this, the controller 32 determines the read start timing to be t24 and sets the target head 22 to be usable.

[0070] When the read start timing exceeds the limit of delayable timing (Yes in S26), the controller 32 sets the head 22 to be processed as unusable (S27) and ends the process.

[0071] 14, for example, even if the timing to open the read gate is delayed until timing t24 when the read latency reaches limit Tth, the noise timing t25 does not fall within the read latency. In response to this, the controller 32 fixes the read gate closed and sets the target head 22 to be unusable.

[0072] For reference, in FIGS. 13 and 14, the timing at which the servo information is read (servo timing) is shown as the timing at which the servo gate is opened.

[0073] As described above, in the disk device 1 of this embodiment, the controller 32 detects noise generated when the head 22 is heated, based on a signal read from the disk medium 11 by the read element RE immediately after supplying power to the heater HT. The controller 32 then performs processing to address the noise based on the noise detection results. For example, the controller 32 adjusts the read start timing when the head 22 is heated based on the noise detection results. This allows the noise timing NT to be within the read latency time, thereby avoiding the effects of noise when the head 22 is heated. Alternatively, the controller 32 determines whether or not to use the head 22 based on the noise detection results. This disables the head 22 that generates noise, thereby avoiding its use. This allows the floating amount of the head 22 above the disk medium 11 to be appropriately controlled during a read operation.

[0074] As a first modification of the embodiment, the head 22i may be a TDMR (Two Dimension Magnetic Recording) head as shown in FIGS. 15 and 16. FIG. 15 is a plan view showing the configuration of the head 22i. FIG. 15(a) is a plan view showing the arrangement of the head 22i in the head slider 21. FIG. 15(b) is an enlarged plan view showing the internal configuration of the head 22i. FIG. 16 is a cross-sectional view showing the arrangement of the head 22i in the head slider 21, taken along line FF in FIG. 15(a). FIG. 16(b) is an enlarged cross-sectional view showing the internal configuration of the head 22i, taken along line GG in FIG. 15(b).

[0075] 15 and 16, the head 22i is configured to include a write element WE, multiple read elements RE1 and RE2, and a heater HT. The write element WE, multiple read elements RE1 and RE2, and heater HT may be aligned along the longitudinal direction of the head 22i. The write element WE may be positioned closer to the tip of the head 22i than the multiple read elements RE1 and RE2.

[0076] The read element RE1 faces the recording surface 11a of the disk medium 11. The surface of the read element RE1 facing the recording surface 11a is called the facing surface RE1a. The read element RE1 reads changes in the magnetic field on the disk medium 11 as information, thereby reading user data from a data area DT of the track TR on the recording surface 11a and reading servo information from a servo area SV of the track TR on the recording surface 11a.

[0077] Similarly, the read element RE2 faces the recording surface 11a of the disk medium 11. The surface of the read element RE2 facing the recording surface 11a is called the facing surface RE2a. The read element RE2 reads the changes in the magnetic field on the disk medium 11 as information, thereby reading user data from the data area DT of the track TR on the recording surface 11a and reading servo information from the servo area SV of the track TR on the recording surface 11a.

[0078] The heater HT may be provided near the read element RE1 or near the read element RE2. When power is applied to the heater HT, it can thermally expand the areas near the read elements RE1 and RE2.

[0079] Furthermore, in the noise reduction process (S2), a process that differs from that of the embodiment in the following respects may be performed as shown in Fig. 17. Fig. 17 is a flowchart showing the noise reduction process in a first modified example of the embodiment.

[0080] The controller 32 selects a read element RE to be processed from the plurality of read elements RE1 and RE2, and performs S21 and S22 for the selected read element RE in the same manner as in the embodiment. If the noise timing NT is within the read waiting time (Yes in S22), the controller 32 determines the timing to open the read gate (read start timing) (S23), and sets the read element RE to be processed as usable (S31).

[0081] If the noise timing NT is not within the read wait time (No in S22), the controller 32 delays the read start timing by a predetermined amount (S25). The predetermined amount can be determined experimentally in advance as an appropriate delay amount for adjusting the read start timing. The controller 32 repeats the loop of S22 to S26 until the read start timing exceeds the maximum delayable timing (limit timing) (No in S26).

[0082] In this repetition, if the noise timing falls within the read wait time (Yes in S22), the controller 32 determines the timing to open the read gate (read start timing) (S23) and sets the read element RE to be processed as usable (S31).

[0083] When the read start timing exceeds the delayable limit (Yes in S26), the controller 32 sets the read element RE to be processed as unusable (S32), and checks whether there is an undetected read element RE (S33).

[0084] If there is an undetected read element RE (Yes in S33), the controller 32 returns the process to S21.

[0085] If there is no undetected read element RE (No in S33), the controller 32 sets the read element RE that is set as usable among the plurality of read elements RE1, RE2 as the read element RE to be used (S34).

[0086] For example, when the read element RE1 is set as the read element RE to be used, the controller 32 sets the radial offset of the head 22 during reading so that the center of the read element RE1 is positioned at the track center RC of the target track TR, as shown in Fig. 18(a). Fig. 18 is a diagram showing the offset setting of the head in a first modified example of the embodiment.

[0087] Alternatively, when setting read element RE2 as the read element RE to be used, the controller 32 sets the radial offset of the head 22 during reading so that the center of the read element RE2 is positioned at the track center RC of the target track TR during reading, as shown in Figure 18(b).

[0088] In this way, if the head 22i is a TDMR head, the controller 32 can take measures against noise in accordance with the noise detection result, taking into account that it is a TDMR head.

[0089] For example, noise timing NT may overlap with servo timing, as shown in Figures 19 and 20. Figures 19 and 20 are waveform diagrams showing changes in read voltage when head 22 is heated. In Figures 19 and 20, the vertical axis represents read voltage and the horizontal axis represents time. Figure 20 is a waveform diagram in which part E in Figure 19 is enlarged in the time direction.

[0090] 19 and 20, at timing t31, heater power is applied and the thermal protrusion gradually increases, and accordingly, the amplitude of the read voltage gradually begins to increase.

[0091] At timing t32, the read voltage exceeds the upper limit target value, but this overlaps with the servo timing. For this reason, it is difficult to distinguish whether the read voltage exceeding the upper limit target value is due to an abnormality or simply due to the reading of servo information, and it is also difficult to determine whether there is an error in the read voltage waveform.

[0092] That is, from timing t31 when heater power starts to be applied to timing t33 ​​when the predetermined time is reached, it is difficult for the defect scan function to detect noise that overlaps with the servo timing.

[0093] In contrast, as a second variant of the embodiment, the disk device 1 may utilize the fact that when there is noise that depends on the application of heater power and the servo information being read contains noise, an abnormality occurs in the servo demodulation and a large change in positioning accuracy synchronized with the pulse frequency is observed.

[0094] The noise detection process (S1) may be performed by observing changes in the positioning accuracy of the head 22 when the heater power is changed periodically, as shown in Fig. 21. Fig. 21 is a flowchart showing the noise detection process in a second modified example of the embodiment.

[0095] In the disk device 1, the controller 32 reads servo information while periodically changing the heater power (S41). The controller 32 reads the servo information with the read element RE at the servo timing while repeating the operation of changing the heater power in a pulsed manner at intervals equal to a multiple of the servo interval.

[0096] For example, the controller 32 may change the heater power in a pulse shape as shown in FIG. 22. FIG. 22 is a waveform diagram showing the operation of the disk device 1 according to a third modified example of the embodiment. The pulse shape of the heater power can be defined by a lower limit heater power Pa, an upper limit heater power Pb, a pulse interval Ta, and a shift time Tb from the start of the servo to the heater power change timing. The pulse interval Ta is n times the servo interval Ts, where n is any integer equal to or greater than 2.

[0097] The controller 32 calculates the positioning accuracy synchronized with the pulse frequency according to the read servo information (S42). The controller 32 demodulates the current position of the head 22 using the read servo information, and determines the deviation between the demodulated current position and the target position of the head 22. The controller 32 performs a Fourier transform on the deviation to extract the component synchronized with the pulse frequency. The controller 32 uses the extracted component to calculate the positioning accuracy synchronized with the pulse frequency.

[0098] The controller 32 may obtain the positioning accuracy for each heater power and determine the relationship between the heater power and the change in positioning accuracy. The controller 32 may obtain the positioning accuracy by multiplying the reciprocal of the deviation (off-track amount) between the demodulated current position and the target position of the head 22 by the track width.

[0099] For example, because the heater power at which noise is generated by the read element RE and the timing at which it occurs after application of the heater differ, the controller 32 checks the lower limit heater power Pa, upper limit heater power Pb, and pulse interval Ta shown in Figure 22 under multiple conditions. If the upper limit heater power Pb is set too high, the spacing ΔS between the facing surface REa of the read element RE and the recording surface 11a of the disk medium 11 will be nearly zero, causing contact and disturbances due to the contact, resulting in changes in positioning accuracy. In the disk device 1, the heater power at which contact is made is measured during the normal testing process to adjust the spacing ΔS. The upper limit heater power Pb can be preset in the controller 32 as a power that is a certain amount lower than the heater power at which contact occurs.

[0100] By determining the positioning accuracy for each heater power, the controller 32 can obtain the relationship between heater power and changes in positioning accuracy as shown in Fig. 23. Fig. 23 is a diagram showing changes in positioning accuracy with changes in heater power in a second modified example of the embodiment. Fig. 23 illustrates the relationship between heater power and changes in positioning accuracy for Sample 1 to Sample 12, which correspond to 12 heads 22.

[0101] If the positioning accuracy is equal to or greater than the threshold Ath1 (Yes in S43), the controller 32 detects that there is no noise (S15).

[0102] In the case of FIG. 23, for Sample 1 to Sample 11, the positioning accuracy is equal to or greater than the threshold Ath1 in the entire range of heater power detection targets, and it is detected that there is no noise.

[0103] If the positioning accuracy is less than the threshold Ath1 (No in S43), the controller 32 detects the presence of noise (S16).

[0104] In the case of FIG. 23, for Sample 12, the positioning accuracy is less than the threshold Ath1 in both the high-power range and the low-power range of the heater power detection target, and it is detected that there is noise.

[0105] In this way, in the disk drive 1, the controller 32 can detect noise when the head 22 is heated by using the change in positioning accuracy when the heater power is periodically changed instead of the defect scan function.

[0106] Alternatively, as a third variant of the embodiment, the disk device 1 may utilize the fact that when the servo information being read contains noise, an abnormality occurs in the servo demodulation and a large change is observed in the detection accuracy of the spacing between the servo marks OK synchronized with the pulse frequency.

[0107] The noise detection process (S1) may be performed by observing a change in detection accuracy of the servo interval when the heater power is changed periodically, as shown in Fig. 24. Fig. 24 is a flowchart showing the noise detection process in a third modified example of the embodiment.

[0108] In the disk device 1, the controller 32 reads servo information while periodically changing the heater power (S41). The controller 32 reads the servo information with the read element RE at the servo timing while repeating the operation of changing the heater power in a pulsed manner at intervals equal to a multiple of the servo interval.

[0109] The controller 32 calculates the detection accuracy of the servo interval synchronized with the pulse frequency according to the read servo information (S51). The controller 32 demodulates the interval of the servo mark OK using the read servo information and determines the deviation between the demodulated interval and the default servo interval. The controller 32 performs a Fourier transform on the deviation to extract the component synchronized with the pulse frequency. The controller 32 uses the extracted component to calculate the detection accuracy of the servo interval synchronized with the pulse frequency.

[0110] The controller 32 may obtain the servo interval detection accuracy for each heater power and determine the relationship between the heater power and the change in servo interval detection accuracy by multiplying the reciprocal of the deviation between the demodulated interval and the default servo interval by the default servo interval.

[0111] By determining the servo interval detection accuracy for each heater power, the controller 32 can obtain the relationship between heater power and changes in servo interval detection accuracy as shown in Fig. 25. Fig. 25 is a diagram showing changes in servo interval detection accuracy with changes in heater power in a third modified example of the embodiment. Fig. 25 illustrates the relationship between heater power and changes in servo interval detection accuracy for Sample 1 to Sample 12, which correspond to 12 heads 22.

[0112] If the detection accuracy of the servo interval is equal to or greater than the threshold Ath2 (Yes in S52), the controller 32 detects that there is no noise (S15).

[0113] In the case of FIG. 25, for Sample 1 to Sample 11, the positioning accuracy is equal to or greater than the threshold Ath2 in the entire range of heater power detection targets, and it is detected that there is no noise.

[0114] If the positioning accuracy is less than the threshold Ath2 (No in S52), the controller 32 detects the presence of noise (S16).

[0115] In the case of FIG. 25, for Sample 12, the positioning accuracy is less than the threshold Ath2 in both the high-power range and the low-power range of the heater power detection target, and it is detected that there is noise.

[0116] In this way, in the disk drive 1, the controller 32 can detect noise when the head 22 is heated by using the change in detection accuracy of the servo interval when the heater power changes periodically, instead of the defect scan function.

[0117] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0118] 1 disk device, 11 disk media, 22 heads, 32 controllers.

Claims

1. a disk medium having a recording surface; a head having a first read element facing the recording surface and a heater; a controller that detects a first noise generated when the head is heated in response to a signal read from the disk medium by the first read element when power supply to the heater is started; A disk device comprising:

2. The controller adjusts the read start timing when the head is heated according to the detection result of the first noise.

2. The disk device according to claim 1.

3. The controller determines whether the head is usable or not depending on the detection result of the first noise.

2. The disk device according to claim 1.

4. the head further has a second read element facing the recording surface, the controller further detects a second noise generated when the head is heated in response to a signal read from the disk medium by the second read element when power supply to the heater is started; The controller selects a read element to be used from the first read element and the second read element according to a detection result of the first noise and a detection result of the second noise.

2. The disk device according to claim 1.

5. The disk medium has a plurality of concentric tracks, Each of the plurality of tracks has a plurality of servo areas spaced equally apart in a circumferential direction, The controller determines a change in positioning accuracy corresponding to the first frequency when the head is heated in accordance with servo information read from a servo area of ​​the disk medium by the first read element while changing the power supplied to the heater at a first frequency corresponding to a servo interval, and detects the first noise in accordance with the change in positioning accuracy corresponding to the first frequency.

2. The disk device according to claim 1.

6. The disk medium has a plurality of concentric tracks, Each of the plurality of tracks has a plurality of servo areas spaced equally apart in a circumferential direction, The controller determines a change in detection accuracy of the servo interval when the head is heated in accordance with servo information read from a servo area of ​​the disk medium by the first read element while changing the power supplied to the heater at a first frequency, and detects the first noise in accordance with the change in detection accuracy of the servo interval.

2. The disk device according to claim 1.

7. a disk device including a disk medium having a recording surface, and a head having a first read element and a heater facing the recording surface, detecting a first noise generated when the head is heated in response to a signal read by the first read element from the disk medium when power supply to the heater is started; performing a process to deal with the first noise according to a result of the detection; A method for controlling a disk device including:

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