Disk device and method for controlling disk device

Abstract

The embodiment relates to a disk device and a control method of the disk device. According to one embodiment, there is provided a disk device having a disk medium, a head, and a controller. The disc medium has a recording surface. The head includes a first reading element and a heater. The first reading element faces the recording surface. The controller detects a first noise at the time of heating the head on the basis of a signal read from the disk medium by the first read element at the time of starting the supply of power to the heater.

Description

[0001] This application enjoys priority over Japanese Patent Application No. 2024-074361 (filed on May 1, 2024). This application is incorporated herein by reference to the entire contents of that earlier application. Technical Field

[0002] This embodiment relates to a disc device and a method for controlling the disc device. Background Technology

[0003] In a disk apparatus comprising a disk medium and a head, the head reads information recorded on the disk medium while simultaneously rising from it. The head is equipped with a heater; by supplying power to the heater, the amount of head protrusion due to thermal expansion can be adjusted, thus controlling the amount of head rising from the disk medium. Therefore, it is desirable to appropriately control the amount of head rising from the disk medium. Summary of the Invention

[0004] According to one embodiment, a disc device is provided, comprising a disc medium, a head, and a controller. The disc medium has a recording surface. The head has a first reading element and a heater. The first reading element faces (opposite to, opposite to) the recording surface. The controller detects a first noise during head heating based on a signal read from the disc medium by the first reading element when power is initially supplied to the heater.

[0005] According to one embodiment, a disk device and a method for controlling the disk device are provided that are suitable for appropriately controlling the amount of head rising from the disk medium. Attached Figure Description

[0006] Figure 1 This is a diagram illustrating the configuration of the disk device involved in the implementation method.

[0007] Figure 2 This is a plan view showing the configuration of the head in the implementation method.

[0008] Figure 3 This is a cross-sectional view showing the structure of the head in the implementation method.

[0009] Figure 4 This is a graph showing the change in the amount of head protrusion caused by thermal expansion in the implementation method.

[0010] Figure 5 This is a diagram illustrating the shape of noise in the implementation method.

[0011] Figure 6 This is a waveform diagram showing the change in reading voltage when the head is heated in the embodiment.

[0012] Figure 7 This is a waveform diagram showing the change in reading voltage when the head is heated in the embodiment.

[0013] Figure 8 This is a waveform diagram showing the change in reading voltage when the head is heated in the embodiment.

[0014] Figure 9 This is a waveform diagram showing the change in reading voltage when the head is heated in the embodiment.

[0015] Figure 10 This is a flowchart illustrating the operation of the disk device involved in the implementation method.

[0016] Figure 11 This is a flowchart illustrating the noise detection process in the implementation method.

[0017] Figure 12 This is a flowchart illustrating the noise countermeasures in the implementation method.

[0018] Figure 13 It is a waveform diagram representing the noise timing in the implementation method.

[0019] Figure 14 This is a waveform diagram representing the noise timing in the implementation method.

[0020] Figure 15 This is a plan view showing the configuration of the head in the first variation of the implementation.

[0021] Figure 16 This is a cross-sectional view showing the configuration of the head in the first modified embodiment.

[0022] Figure 17 This is a flowchart illustrating the noise countermeasure processing in the first variation of the implementation method.

[0023] Figure 18 This is a diagram showing the offset setting of the head in the first variation of the implementation.

[0024] Figure 19 It is a waveform diagram showing the change in reading voltage when the head is heated.

[0025] Figure 20 It is a waveform diagram showing the change in reading voltage when the head is heated.

[0026] Figure 21 This is a flowchart illustrating the noise detection process in the second variation of the implementation method.

[0027] Figure 22 This is a waveform diagram showing the operation of the disk device according to the third variation of the embodiment.

[0028] Figure 23This is a graph showing the change in positioning accuracy as the heater power changes in the second variation of the embodiment.

[0029] Figure 24 This is a flowchart illustrating the noise detection process in the third variation of the implementation method.

[0030] Figure 25 This is a graph showing the change in the detection accuracy of the servo interval as the heater power changes in the third variation of the implementation.

[0031] Explanation of reference numerals in the attached figures

[0032] 1 reel device; 11 reels of media; 22 heads; 32 controllers. Detailed Implementation

[0033] The disk device according to the embodiments will be described in detail below with reference to the accompanying drawings. However, the present invention is not limited to these embodiments.

[0034] (Implementation Method)

[0035] The disk device involved in the embodiment has a heater on the head. By supplying power to the heater, the amount of head protrusion caused by thermal expansion can be adjusted, the amount of head rising from the disk medium can be controlled, and efforts can be made to appropriately control the amount of rising.

[0036] Disk device 1 can be as Figure 1 That's how it's structured. Figure 1 This is a diagram showing the configuration of disk device 1.

[0037] Disk device 1, for example, is a hard disk drive, which functions as an external storage device relative to host 40.

[0038] The disk assembly 1 includes a disk medium 11, a spindle motor 12, a 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 non-volatile memory 28, a buffer memory 29, and a controller 32. The disk medium 11, spindle motor 12, head 22, actuator arm 15, voice coil motor (VCM) 16, and ramp 23 are housed within a housing (not shown). A portion of the head amplifier 24, motor driver 19, volatile memory 27, non-volatile memory 28, buffer memory 29, and controller 32 are housed within the housing, while another portion is disposed on a base plate (outside the housing).

[0039] The controller 32 has a read / write channel (RWC) 25, a hard disk controller (HDC) 31, and a processor 26. The processor 26 may also be a CPU.

[0040] Furthermore, the package of the head amplifier 24 can be mounted on a substrate fixed to the actuator arm 15. The controller 32 can be configured as a single-chip integrated circuit (system on chip). The package of the controller 32 can be mounted on a printed circuit board on the outside of the housing.

[0041] The disk medium 11 is a disk-shaped recording medium for magnetic recording of various information, driven by the spindle motor 12. The disk medium 11 has its recording surface 11a (see reference). Figure 4 The spindle motor 12 has multiple concentric tracks TR centered near its rotation center. On each track TR, multiple data areas DT and servo areas SV are alternately arranged circumferentially (see reference). Figure 18 On each track TR, multiple servo regions SV can be configured circumferentially at equal intervals.

[0042] The actuator arm 15 is rotatably mounted on the pivot 17. A head 22 is mounted on one end of the actuator arm 15 via a head slider 21. The head 22 can be positioned near the front end of the head slider 21 (see reference). Figure 2 , Figure 3 A VCM16 is connected to the other end of the actuator arm 15. The VCM16 rotates the actuator arm 15 about the pivot 17, positioning the head 22 in an above-floating state at an arbitrary radius position on the disk medium 11. At this time, the processor 26 uses the servo information read from the servo area SV by the read element RE in the head 22 to perform servo control (positioning control) for the positioning of the head 22.

[0043] According to instructions from the processor 26, the motor driver 19 drives the spindle motor 12, causing the disk medium 11 to rotate around the rotation axis at a predetermined speed. In addition, according to instructions from the processor 26, the motor driver 19 drives the VCM 16, causing the head 22 at one end of the actuator arm 15 to move in the radial direction of the disk medium 11.

[0044] Head 22 writes user data to disk medium 11 and reads information (user data and servo information) recorded on disk medium 11. Head 22, for example, has... Figure 2 and Figure 3 The structure shown. Figure 2 This is a plan view showing the structure of head 22. Figure 2 (a) is a plan view showing the configuration of head 22 in head slider 21. Figure 2 (b) is an enlarged plan view showing the structure inside head 22. Figure 3 This is a cross-sectional view showing the structure of head 22. Figure 3 (a) is a cross-sectional view showing the configuration of head 22 in head slider 21, indicating that... Figure 2(a) The cross section obtained by cutting along line AA. Figure 3 (b) is an enlarged cross-sectional view showing the structure inside head 22, indicating that... Figure 2 (b) The cross section obtained by cutting along line BB.

[0045] like Figure 2 and Figure 3 As shown, the head 22 is configured to include a write element WE, a read element RE, and a heater HT. The write element WE, the read element RE, and the heater HT can also be arranged along the length of the head 22. The write element WE can also be positioned further forward of the head 22 than the read element RE.

[0046] The writing element WE and the recording surface 11a of the disk medium 11 (see reference) Figure 4 The write element WE uses the magnetic field generated from its magnetic poles to write data to the data area DT of the track TR on the recording surface 11a. 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 called the opposing surface REa. The read element RE reads user data from the data area DT of the track TR on the recording surface 11a or 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. In addition, when the rotation of the disk medium 11 stops, etc., the head 22 retracts to the ramp 23 (see reference). Figure 1 )superior.

[0047] During the write operation, the head amplifier 24 converts the write signal supplied by RWC25 into a write current and outputs it to the write element WE.

[0048] During the read operation, head amplifier 24 amplifies the signal (read signal) read from disk medium 11 by read element RE and outputs it to RWC 25. At this time, processor 26 controls the flow of bias current from head amplifier 24 to read element RE. RWC 25 further amplifies the signal from head amplifier 24. RWC 25 performs automatic gain control (AGC) to amplify the read signal with the gain determined in processor 26 so that the signal level reaches the target level.

[0049] The heater HT can be placed near the read element RE. When the heater HT is energized, it causes thermal expansion in the vicinity of the read element RE.

[0050] In disk drive 1, heater HT is sometimes used for DFH (Dynamic Flying Height) control during reading operations. In DFH control, processor 26 controls the supply of power from power supply unit 24e to heater HT via bias circuit 24a. That is, as... Figure 4 As shown, the processor 26 supplies heater power to the heater HT mounted on the head 22 via the head amplifier 24, causing the head 22 to thermally expand. Figure 4 This is a diagram showing the change in the amount of protrusion of the head 22 due to thermal expansion. Based on the protrusion of the head 22 caused by thermal expansion, the distance (pitch ΔSP) from the opposing surface REa of the read element RE to the recording surface 11a of the disk medium 11 can be adjusted.

[0051] When the power supply to the heater HT is turned off, such as Figure 4 As shown in (a), the height position of the opposing surface REa in head 22 is the same as the height position of the opposing surface 21a in head slider 21.

[0052] At this point, the amount by which head 22 rises from medium 11 is represented by the gap ΔSP. The power supplied to heater HT is called heater power P. HT The power supply to heater HT is turned off, and heater power P... HT ≒0 Correspondingly, the amount of protrusion H of head 22 due to thermal expansion 22 ≒0. Therefore, as... Figure 4 As shown in (a), the spacing ΔSP becomes larger ΔSP0, and the amplitude of the read voltage of the read element RE becomes smaller V0.

[0053] Under the control of controller 32, head amplifier 24 supplies power to heater HT. Heater HT receives power and heats the area near the reading element RE in head 22. This heating causes thermal deformation of head 22, thus changing the spacing ΔSP.

[0054] When supplying heater power P to heater HT HT =P A In the case of (>0), such as Figure 4 As shown in (b), the height position of the opposing surface REa is closer to the recording surface 11a than the height position of the opposing surface 21a.

[0055] At this time, with the heater power P HT ≒P A Correspondingly, the amount of protrusion H of head 22 due to thermal expansion 22 Become H 22A (>0). Therefore, as Figure 4 As shown in (b), the spacing ΔSP becomes smaller than ΔSP. A (≒ΔSP0-H 22A The amplitude of the read voltage of the read element RE becomes a relatively large V. A (>V0).

[0056] When supplying heater power P to heater HT HT=P B (>P A In the case of, such as Figure 4 As shown in (c), the height position of the opposing surface REa is closer to the recording surface 11a than the height position of the opposing surface 21a.

[0057] At this time, with the heater power P HT ≒P B Correspondingly, the amount of protrusion H of head 22 due to thermal expansion 22 Become H 22B (>H 22A Therefore, as Figure 4 As shown in (c), the spacing ΔSP becomes a smaller ΔSP. B (≒ΔSP0-H 22B The amplitude of the read voltage of the read element RE becomes a larger V. B (>V A ).

[0058] The following method can be used to detect noise in the read voltage during thermal protrusion. Data is prepared in advance during the manufacturing process and written to the disk medium 11 at a uniform frequency. The data is then read immediately after the heater power is applied using the read element RE. The read voltage waveform is verified for the data read by the read element RE as the thermal protrusion gradually increases.

[0059] As a method for confirming the read voltage waveform, disk unit 1 can also utilize the defect scan function installed on RWC25. Regarding the defect scan function, such as... Figure 5 As shown, this is a function that detects protrusions and deficiencies in the disk medium 11 and identifies abnormal reading voltage waveforms as errors. Figure 5 This is a graph representing the noise pattern. With the heater HT off, for data written at a single frequency, if it's normal, it looks like... Figure 5 As in (a), the read voltage of the read element RE of disk device 1 becomes a constant amplitude. Figure 5 In (a), the upper and lower target values ​​are represented by dashed lines. Figure 5 In case (a), at timing t100, the read voltage reaches the upper limit target value.

[0060] In the defect scanning function, it is possible to detect defects such as... Figure 5 The sudden drop in the output voltage waveform shown in (b) is detected as an error. Figure 5 In case (b), at time t101, which corresponds to time t100, the read voltage does not reach the upper limit target value. The disk device 1 can also detect the insufficient read voltage value relative to the upper limit target value by the amount ΔV. 101If the threshold TH1 is exceeded, a sudden drop in the output of the read voltage waveform is detected.

[0061] In the defect scanning function, it is possible to detect defects such as... Figure 5 The sudden rise in the output voltage waveform shown in (c) is detected as an error. Figure 5 In case (c), at time t102, which corresponds to time t100, the read voltage exceeds the upper limit target value. The disk device 1 can also detect the excess amount ΔV of the read voltage value relative to the upper limit target value. 102 If the threshold TH2 is exceeded, a sudden increase in the output voltage waveform is detected.

[0062] In the defect scanning function, you can see things like... Figure 5 The baseline change detection shown in (d) is incorrect. Disk device 1 can also be like... Figure 5 As shown by the dashed line in (d), the baseline BL is obtained as the trajectory of the average value over one period of the reading voltage waveform. Figure 5 In case (d), at a predetermined time t103, the baseline BL changes significantly from the target value. The disk device 1 can also detect the change in baseline BL relative to the target value, ΔV. 103 The baseline BL change was detected when the threshold TH3 was exceeded.

[0063] If the reading operation is performed immediately after the heater power is applied, and the defect scanning function is used, noise detection during thermal outbursts can be achieved. Furthermore, the defect scanning function can also determine the location of the error. Therefore, by knowing the timing of the start of the reading operation and the timing of the start of the heater power application, the disk unit 1 can detect the timing of noise generation at the start of the heater power application. The disk unit 1 can also perform this operation individually for each of its mounted reading elements RE.

[0064] For example, from the time when the heater power is first applied until the predetermined time is reached, such as... Figure 6 , Figure 7 As shown, if the amplitude of the reading voltage gradually increases, the disk device 1 detects that there is no noise during the heating of the head 22. Figure 6 and Figure 7 These are waveforms representing the changes in the reading voltage when head 22 is heated. Figure 6 and Figure 7 The vertical axis represents the voltage reading, and the horizontal axis represents the time. Figure 7 It is Figure 6 The waveform of part C magnified in the time direction.

[0065] exist Figure 6 and Figure 7During the process, at time t1, the heater power is applied, and the thermal spike begins to gradually increase. Correspondingly, the amplitude of the reading voltage begins to gradually increase.

[0066] At time t2, if the predetermined time is reached, the thermal spike remains at the predetermined value. Correspondingly, the increase in the amplitude of the read voltage is completed, and the amplitude of the read voltage remains approximately constant.

[0067] Furthermore, periodic convexities are visible in the read voltage waveform, indicating that the amplitude of the read voltage increases instantaneously during the timing of reading servo information (servo timing).

[0068] On the other hand, from the time the heater power is first applied until the predetermined time, such as Figure 8 , Figure 9 As shown, if the amplitude of the reading voltage suddenly increases or decreases, the disk device 1 can detect noise during the heating of the head 22. Figure 8 and Figure 9 These are waveforms representing the changes in the reading voltage when head 22 is heated. Figure 8 and Figure 9 The vertical axis represents the voltage reading, and the horizontal axis represents the time. Figure 9 It is Figure 8 The waveform of part D magnified in the time direction.

[0069] exist Figure 8 and Figure 9 During the process, at time t11, the heater power is applied, and the heat output gradually increases. Correspondingly, the amplitude of the reading voltage begins to gradually increase.

[0070] At time t12, the read voltage exceeds the upper limit target value. Disk device 1 measures the excess voltage value relative to the upper limit target value by ΔV. 12 If the threshold TH2 is exceeded, a sudden increase in the output voltage waveform can be detected.

[0071] At time t13, the read voltage is lower than the lower limit target value. Disk device 1 measures the difference in voltage value relative to the lower limit target value by a quantity ΔV. 13 If the threshold TH2 is exceeded, a sudden increase in the output voltage waveform can be detected.

[0072] At time t14, if the predetermined time is reached, the thermal spike remains at the predetermined value. Correspondingly, the increase in the amplitude of the read voltage is completed, and the amplitude of the read voltage remains approximately constant.

[0073] Next, use Figure 10 The general operation of the disk device 1 will be explained. Figure 10 This is a flowchart illustrating the operation of the disk device.

[0074] In the disk assembly 1, when the controller 32 is activated, noise detection processing (S1) is performed. In the noise detection processing, the controller 32 detects the noise during the heating of the head 22 based on the 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.

[0075] Based on the result of the noise detection processing (S1), the controller 32 performs noise countermeasure processing (S2). Noise countermeasure processing is the process of taking measures against noise. Noise countermeasure processing may also include adjusting the timing of the start of reading when the head 22 is heated. Noise countermeasure processing may also include selecting whether the head 22 can be used.

[0076] Furthermore, disk unit 1 can also perform separate operations on all the read elements RE mounted thereon. Figure 10 The actions shown.

[0077] Next, use Figure 11 The noise detection and processing (S1) is explained. Figure 11 This is a flowchart representing the noise detection and processing.

[0078] In the disk device 1, the controller 32 activates the defect scanning function to begin noise detection and processing, and powers on the heater to begin supplying power to the heater HT (S11).

[0079] Due to the increase in the amount of protrusion of the head 22 caused by thermal expansion, the opposing surface REa of the read element RE approaches the recording surface 11a of the disk medium 11, and the spacing ΔS decreases.

[0080] The controller 32 uses the defect scanning function to monitor the amplitude of the read voltage of the read element RE (S13), and determines whether an error has been detected based on the monitoring results (S14).

[0081] The controller 32 obtains 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 the read voltage should reach the upper limit, the controller 32 detects no noise as no error is detected (S14: No) (S15).

[0082] If, at the timing when the read voltage should reach the upper limit, the insufficient amount of the read voltage value relative to the upper limit target value exceeds the threshold TH1, then the controller 32 detects an error (S14: Yes) and detects noise (S16).

[0083] If, at the timing when the read voltage should reach the lower limit, the insufficient amount of the read voltage value relative to the lower limit target value exceeds the threshold TH1, then the controller 32 detects an error (S14: Yes) and detects noise (S16).

[0084] If, at the timing when the read voltage should reach the upper limit, the read voltage value exceeds the threshold TH2 by an amount that exceeds the upper limit target value, the controller 32 detects an error (S14: Yes) and identifies it as noisy (S16).

[0085] If, at the timing when the read voltage should reach the lower limit, the read voltage value exceeds the threshold TH2 by an amount that exceeds the lower limit target value, the controller 32 detects an error (S14: Yes) and identifies it as noisy (S16).

[0086] If, at a predetermined time, the change in baseline BL relative to the target value exceeds the threshold TH3, the controller 32 detects an error (S14: Yes) and identifies it as noisy (S16).

[0087] The controller 32 terminates the noise detection and processing, and maintains the heater power to continue supplying power to the heater HT (S18).

[0088] Next, use Figure 12 The noise countermeasures (S2) are explained. Figure 12 This is a flowchart illustrating noise countermeasures.

[0089] The controller 32 obtains the result of the noise detection processing (S1) (S21) and determines whether the noise timing (noise timing) NT is within the read waiting time (S22). The read waiting time is the time from the start of powering on the heater HT to the opening of the read gate and the start of the read operation.

[0090] If the noise timing NT is within the read waiting time (S22: Yes), the controller 32 determines the timing for opening the read strobe (read start timing) (S23) and sets the head 22 of the processing object to be usable (can be used) (S24).

[0091] If the noise timing NT is not within the read wait time (S22: No), the controller 32 delays the read start timing by a predetermined amount (S25). The predetermined amount can be determined in advance through experimentation as a delay amount suitable for adjusting the read start timing.

[0092] For example, in the typical read wait time is Figure 13 Given the timings t21 to t22, the noise timing NT is set to timing t23, which is later than timing t22. Figure 13 This is a waveform diagram representing the noise timing NT. In this case, the controller 32, as the noise timing NT, is not within the read wait time, causing the timing for opening the read strobe to be delayed by a predetermined amount from t22.

[0093] Or, during the typical read wait time is Figure 14Given the timings t21 to t22, the noise timing NT is set to t25, which is later than timing t22. Figure 14 This is a waveform diagram representing the noise timing NT. In this case, the controller 32, as the noise timing NT, is not within the read wait time, causing the timing for opening the read strobe to be delayed by a predetermined amount from t22.

[0094] Back Figure 12 The controller 32 repeats the cycle from S22 to S26 until the timing of the start of reading exceeds the delay limit (limit timing) (S26: No).

[0095] During this repetitive process, if the noise timing becomes within the read waiting time (S22: Yes), the controller 32 determines the timing for opening the read strobe (read start timing) (S23) and sets the head 22 of the processing object to be usable (S24).

[0096] For example, Figure 13 In this case, an example is shown where the timer for opening the read strobe is delayed until the read wait time reaches the limit Tth, at timer t24, and the noisy timer t23 becomes within the read wait time. Accordingly, the controller 32 determines the read start timer at t24 and sets the head 22 of the object to be processed to be available.

[0097] If the read start time exceeds the delay limit (S26: Yes), the controller 32 sets the head 22 of the processing object to be unusable (S27) and ends the processing.

[0098] For example, Figure 14 In this case, even if the timing for opening the read strobe is delayed until the read wait time reaches the limit Tth at time t24, the noise timing t25 is not within the read wait time. Accordingly, the controller 32 keeps the read strobe permanently closed, setting the head 22 of the object to be processed as unusable (unavailable).

[0099] In addition, Figure 13 , Figure 14 For reference, the timing for reading servo information (servo timing) is represented as the timing for enabling servo strobe.

[0100] As described above, in this embodiment, in the disk device 1, the controller 32 detects noise during the heating of the head 22 based on a signal read from the disk medium 11 by the read element RE immediately after power is supplied to the heater HT. The controller 32 then performs noise countermeasures based on the noise detection results. For example, the controller 32 adjusts the read start timing during the heating of the head 22 based on the noise detection results. Therefore, if the noise timing NT falls within the read waiting time, the influence of noise during the heating of the head 22 can be avoided. Alternatively, the controller 32 selects whether the head 22 can be used based on the noise detection results. This makes the head 22, which generates noise, unusable, thus avoiding its use. Therefore, the amount of head 22 rising from the disk medium 11 during the read operation can be appropriately controlled.

[0101] Furthermore, as a first variation of the implementation, the head 22i can also be as follows: Figure 15 and Figure 16 The TDMR (Two Dimension Magnetic Recording) head shown. Figure 15 This is a plan view showing the structure of head 22i. Figure 15 (a) is a plan view showing the configuration of head 22i in head slider 21. Figure 15 (b) is an enlarged plan view showing the structure within head 22i. Figure 16 This is a cross-sectional view showing the structure of head 22i. Figure 16 (a) is a cross-sectional view showing the configuration of head 22i in head slider 21, indicating that... Figure 15 (a) The cross section obtained by cutting along line FF. Figure 16 (b) is an enlarged cross-sectional view showing the structure within the head 22i, indicating that... Figure 15 (b) The cross section obtained by cutting along line GG.

[0102] like Figure 15 and Figure 16 As shown, the head 22i is configured to include a write element WE, multiple read elements RE1, RE2, and a heater HT. The write element WE, multiple read elements RE1, RE2, and heater HT can also be arranged along the length of the head 22i. The write element WE can also be positioned further towards the front end of the head 22i than the multiple read elements RE1, RE2.

[0103] The read element RE1 faces the recording surface 11a of the disk medium 11. The surface of the read element RE1 that faces the recording surface 11a is called the opposing surface RE1a. The read element RE1 reads information by taking the change of the magnetic field on the disk medium 11 as information, reading user data from the data area DT of the track TR on the recording surface 11a, or reading servo information from the servo area SV of the track TR on the recording surface 11a.

[0104] Similarly, the read element RE2 faces the recording surface 11a of the disk medium 11. The surface of the read element RE2 that faces the recording surface 11a is called the opposing surface RE2a. The read element RE2 reads information by taking the changes in the magnetic field on the disk medium 11 as information, reading user data from the data area DT of the track TR on the recording surface 11a, or reading servo information from the servo area SV of the track TR on the recording surface 11a.

[0105] The heater HT can be placed near either the reading element RE1 or the reading element RE2. When energized, the heater HT causes thermal expansion in the vicinity of the reading elements RE1 and RE2.

[0106] In addition, in noise countermeasure processing (S2), such as Figure 17 As shown, the following processes may also be performed differently from the implementation method. Figure 17 This is a flowchart illustrating the noise countermeasure processing in the first variation of the implementation method.

[0107] Selecting a read element RE from multiple read elements RE1 and RE2 as the target read element, the controller 32 performs S21 and S22 in the same manner as in the implementation method for the selected read element RE. If the noise timing NT is within the read waiting time (S22: Yes), the controller 32 determines the timing for opening the read strobe (read start timing) (S23) and sets the target read element RE to be usable (S31).

[0108] If the noise timing NT is not within the read wait time (S22: No), the controller 32 delays the read start timing by a predetermined amount (S25). The predetermined amount can be determined in advance through experimentation to be a suitable amount of delay for adjusting the read start timing. The controller 32 repeats the cycle from S22 to S26 until the read start timing exceeds the delay limit (limit timing) (S26: No).

[0109] In this repetition, if the noise timing becomes within the read waiting time (S22: Yes), the controller 32 determines the timing for opening the read strobe (read start timing) (S23) and sets the read element RE of the processing object to be usable (S31).

[0110] If the read start timing exceeds the delay limit (S26: Yes), the controller 32 sets the read element RE of the object to be processed as unusable (S32) and determines whether there is an undetected read element RE (S33).

[0111] If an undetected read element RE exists (S33: Yes), the controller 32 returns the process to S21.

[0112] If there is no undetected read element RE (S33: No), the controller 32 sets one of the multiple read elements RE1 and RE2 that has been set as usable as the read element RE to be used (S34).

[0113] For example, if read element RE1 is set as the read element RE to be used, such as Figure 18 As shown in (a), the controller 32 sets the radial offset of the head 22 during reading so that the center of the reading element RE1 is located at the track center RC of the target track TR during reading. Figure 18 This is a diagram showing the head bias setting in the first variation of the implementation.

[0114] Alternatively, if read element RE2 is set as the read element RE to be used, such as Figure 18 As shown in (b), the controller 32 sets the radial offset of the head 22 during reading so that the center of the reading element RE2 is located at the track center RC of the target track TR during reading.

[0115] Thus, if head 22i is a TDMR head, the controller 32 can take into account the case of a TDMR head based on the noise detection results and perform noise countermeasures.

[0116] For example, such as Figure 19 , Figure 20 As shown, the noise timing NT sometimes overlaps with the servo timing. Figure 19 and Figure 20 These are waveforms representing the changes in the reading voltage when head 22 is heated. Figure 19 and Figure 20 The vertical axis represents the voltage reading, and the horizontal axis represents the time. Figure 20 It is Figure 19 The waveform of part E magnified in the time direction.

[0117] exist Figure 19 , Figure 20 During the process, at time t31, the heater power is applied, and the heat output gradually increases. Correspondingly, the amplitude of the reading voltage begins to gradually increase.

[0118] At timer t32, the read voltage exceeds the upper limit target value, but this overlaps with the servo timing. Therefore, it is difficult to distinguish whether the reading voltage value exceeding the upper limit target value is caused by an anomaly or simply by reading servo information, and it is difficult to determine whether there is an error in the read voltage waveform.

[0119] That is, from the time t31 when the heater power is first applied to the time t33 when the predetermined time is reached, it is difficult to detect noise that overlaps with the servo timing through the defect scanning function.

[0120] In this regard, as a second variation of the implementation, the disk device 1 can also utilize the following situation: when there is noise that depends on the applied power of the heater and the read servo information contains noise, the servo demodulation is abnormal and the positioning accuracy that is synchronized with the frequency of the pulse can be seen to change significantly.

[0121] like Figure 21 As shown, noise detection processing (S1) can also be performed by observing the change in the positioning accuracy of head 22 when the heater power changes periodically. Figure 21 This is a flowchart illustrating the noise detection process in the second variation of the implementation method.

[0122] In the disk device 1, the controller 32 reads servo information while periodically changing the heater power (S41). The controller 32 repeatedly performs the action of changing the heater power in a pulse pattern at intervals that are multiples of the servo interval, and reads the servo information by the read element RE at the servo timing.

[0123] For example, controller 32 can also adjust the heater power according to... Figure 22 The pulse shape change is shown. Figure 22 This is a waveform diagram illustrating the operation of the disk device 1 according to the third variation of the embodiment. The pulse shape of the heater power can be defined by the lower limit heater power Pa, the upper limit heater power Pb, the pulse interval Ta, and the offset 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. n is any integer greater than or equal to 2.

[0124] The controller 32 calculates the positioning accuracy synchronized with the pulse frequency based on the read servo information (S42). Using the read servo information, the controller 32 demodulates the current position of the head 22 and calculates 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. Using the extracted component, the controller 32 calculates the positioning accuracy synchronized with the pulse frequency.

[0125] The controller 32 can also calculate the positioning accuracy for each heater power and the relationship between the heater power and the change in positioning accuracy. The controller 32 can also calculate 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.

[0126] For example, the heater power that generates noise and the timing of noise generation after applying the heater power differ depending on the read element RE. Therefore, the controller 32 adjusts the power according to multiple conditions. Figure 22The lower limit heater power Pa, upper limit heater power Pb, and pulse interval Ta are confirmed. If the upper limit heater power Pb is set too high, the distance ΔS between the opposing surface REa of the reading element RE and the recording surface 11a of the disk medium 11 will be almost zero, resulting in contact. Due to the interference caused by the contact, the positioning accuracy will change. In the disk device 1, the heater power that causes contact during the normal test procedure to adjust the distance ΔS is measured. 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 that causes contact.

[0127] The controller 32 can obtain the positioning accuracy by calculating the power of each heater, such as... Figure 23 The relationship between heater power and positioning accuracy is shown. Figure 23 This is a graph showing how the positioning accuracy changes with the heater power in the second variation of the embodiment. Figure 23 The example illustrates the relationship between heater power and positioning accuracy for Sample 1 to Sample 12 (samples 1 to 12), which correspond to 12 heads 22.

[0128] When the positioning accuracy is above the threshold Ath1 (S43: Yes), the controller 32 detects no noise (S15).

[0129] exist Figure 23 In the case of Sample1 to Sample11, the positioning accuracy is above the threshold Ath1 throughout the entire range of the heater power detection object, and the detection is noiseless.

[0130] When the positioning accuracy is lower than the threshold Ath1 (S43: No), the controller 32 detects noise (S16).

[0131] exist Figure 23 In the case of Sample12, if the positioning accuracy is lower than the threshold Ath1 in each range of the high-power side and low-power side range of the heater power detection object, the detection is considered noisy.

[0132] Thus, in the disc device 1, the controller 32 can also detect the noise of the head 22 during heating by using the change in positioning accuracy when the heater power changes periodically instead of the defect scanning function.

[0133] Alternatively, as a third variation of the implementation, the disk device 1 can also be used in the case where, when the read servo information contains noise, servo demodulation is abnormal, and the detection accuracy of the interval of the servo mark OK, which is synchronized with the frequency of the pulse, changes significantly.

[0134] like Figure 24As shown, noise detection processing (S1) can also be performed by observing the change in the detection accuracy of the servo interval when the heater power changes periodically. Figure 24 This is a flowchart illustrating the noise detection process in the third variation of the implementation method.

[0135] In the disk device 1, the controller 32 reads servo information while periodically changing the heater power (S41). The controller 32 repeatedly performs the action of changing the heater power in a pulse pattern at intervals that are multiples of the servo interval, and reads the servo information by the read element RE at the servo timing.

[0136] The controller 32 calculates the detection accuracy of the servo interval synchronized with the pulse frequency based on the read servo information (S51). Using the read servo information, the controller 32 demodulates the interval marked OK by the servo flag and calculates the deviation between the demodulated interval and the predetermined servo interval. The controller 32 performs a Fourier transform on the deviation to extract the component synchronized with the pulse frequency. Using the extracted component, the controller 32 calculates the detection accuracy of the servo interval synchronized with the pulse frequency.

[0137] The controller 32 can also calculate the detection accuracy of the servo interval for each heater power and determine the relationship between the change in the detection accuracy of the heater power and the servo interval. The controller 32 can also calculate this by multiplying the reciprocal of the deviation between the demodulated interval and the predetermined servo interval by the predetermined servo interval.

[0138] The controller 32 can obtain, by calculating the detection accuracy of the servo interval for each heater power, such as... Figure 25 The relationship between heater power and the change in the detection accuracy of the servo interval is shown. Figure 25 This is a graph showing the change in the detection accuracy of the servo interval as the heater power changes in the third variation of the implementation method. Figure 25 The example illustrates the relationship between the heater power and the detection accuracy of the servo interval for Sample 1 to Sample 12, which correspond to 12 heads 22.

[0139] When the detection accuracy of the servo interval is above the threshold Ath2 (S52: Yes), the controller 32 detects noise-free (S15).

[0140] exist Figure 25 In the case of Sample1 to Sample11, the positioning accuracy is above the threshold Ath2 throughout the entire range of the object being tested for heater power, and the detection is noiseless.

[0141] When the positioning accuracy is lower than the threshold Ath2 (S52: No), the controller 32 detects noise (S16).

[0142] exist Figure 25 In the case of Sample12, if the positioning accuracy is lower than the threshold Ath2 in each range of the high-power side and low-power side range of the heater power detection object, the detection is considered noisy.

[0143] Thus, in the disk device 1, the controller 32 can also detect the noise of the head 22 during heating by replacing the defect scanning function with the change in the detection accuracy of the servo interval when the heater power changes periodically.

[0144] Several embodiments of the present invention have been described, but these embodiments are provided by way of example and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, and are included within the scope of the invention as described in the claims and its equivalents.

Claims

1. A disk device comprising: Disk media, having a recording surface; The head has a first read element and a heater facing the recording surface; and The controller detects a first noise during the heating of the head based on a signal read from the disk medium by the first reading element when power is supplied to the heater.

2. The disk device according to claim 1, The controller adjusts the reading start timing when the head is heated based on the detection result of the first noise.

3. The disk device according to claim 1, The controller determines whether the head can be used based on the detection result of the first noise.

4. The disc device according to claim 1, The head also has a second read element facing the recording surface. The controller also detects a second noise during the heating of the head based on a signal read from the disk medium by the second reading element when power is supplied to the heater. The controller selects the reading element to be used from the first reading element and the second reading element based on the detection results of the first noise and the second noise.

5. The disk device according to claim 1, The disk medium has multiple concentric circular tracks. Each of the multiple tracks has multiple servo regions at equal intervals in the circumferential direction. The controller calculates the change in positioning accuracy corresponding to the first frequency during head heating based on servo information read by the first reading element from the servo area of ​​the disk medium while the power supply to the heater changes at a first frequency corresponding to the servo interval, and detects the first noise based on the change in positioning accuracy corresponding to the first frequency.

6. The disk device according to claim 1, The disk medium has multiple concentric circular tracks. Each of the multiple tracks has multiple servo regions at equal intervals in the circumferential direction. The controller calculates the change in the detection accuracy of the servo interval during the heating of the head based on servo information read by the first reading element from the servo area of ​​the disk medium while the power supplied to the heater is varied at a first frequency, and detects the first noise based on the change in the detection accuracy of the servo interval.

7. A control method for a disc device, the disc device comprising a disc medium and a head, the disc medium having a recording surface, the head having a first reading element and a heater facing the recording surface, the control method comprising: The first noise during the heating of the head is detected based on the signal read from the disk medium by the first reading element when power is supplied to the heater in the disk device. and Based on the detection results, processing is performed to counteract the first noise.

Images