Magnetic disk device

Abstract

The embodiment of the invention relates to a magnetic disk device. According to one embodiment, a magnetic disk device includes: a rotatable disk-shaped recording medium having a plurality of concentric recording tracks; a magnetic head including a recording element having a first width, a reproduction element having a second width, and a thermal resistance sensor having a third width wider than the first width and the second width; a head actuator that positions the magnetic head in an arbitrary recording track of the recording medium; a detection circuit that detects a defect on the surface of the recording medium on the basis of the sensor output of the thermal resistance sensor; and a controller that sets a feed pitch in the width direction of the recording tracks of the magnetic head to be within 1 / 2 of the third width and to be equal to or greater than the number of three recording tracks when the surface state of the recording medium is inspected by the thermal resistance sensor.

Description

[0001] This application claims the benefit of priority based on Japanese Patent Application No. 2024-043554 (filing date: March 19, 2024), the entire contents of which are incorporated herein by reference. Technical Field

[0002] An embodiment of the present invention relates to a magnetic disk device. Background Art

[0003] For example, a magnetic disk device includes a rotatable disk-shaped recording medium having a magnetic recording layer and a magnetic head for recording and reproducing data on the magnetic recording layer of the recording medium. The magnetic head includes a slider, a read head, and a write head mounted on the slider. In such a magnetic disk device, to increase recording density, particularly linear recording density, it is necessary to reduce the gap between the magnetic head and the recording medium. The magnetic head records and reproduces information by moving relative to the recording surface of the recording medium with a small gap of approximately 1 nm. Therefore, the recording surface of the recording medium must be smooth.

[0004] However, the recording surface of the recording medium may contain defects caused during the manufacturing process of the recording medium, such as tiny protrusions with a height of approximately 3 to 8 nm. When the magnetic head moves with a small gap on the recording surface, it may collide with the tiny protrusions. Repeated collisions with tiny protrusions can damage the magnetic head, sometimes making recording and playback difficult. Summary of the Invention

[0005] According to an embodiment, a magnetic disk device comprises: a rotatable disk-shaped recording medium having a plurality of concentric recording tracks; a magnetic head comprising a recording element, a reproducing element and a thermistor sensor, wherein the recording element has a first width in a direction intersecting the recording tracks, the reproducing element has a second width in a direction intersecting the recording tracks, the thermistor sensor has a third width in a direction intersecting the recording tracks that is wider than the first width and the second width, and the thermistor sensor detects the surface condition of the recording medium; a head actuator for positioning the magnetic head at an arbitrary recording track of the recording medium; a detection circuit for detecting defects on the surface of the recording medium based on the sensor output of the thermistor sensor; and a controller for setting the feed pitch of the magnetic head in the width direction of the recording track to within 1 / 2 of the third width of the thermistor sensor and more than the amount of 3 recording tracks when the surface condition of the recording medium is inspected by the thermistor sensor.

[0006] According to the embodiment of the present invention, it is possible to provide a magnetic disk device with improved reliability, which prevents damage to a magnetic head caused by defects on a recording medium. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is a block diagram schematically showing a hard disk drive (HDD) according to the first embodiment.

[0008] Figure 2 This is a side view schematically showing the magnetic head, suspension, and magnetic disk in the HDD.

[0009] Figure 3 It is a cross-sectional view showing an enlarged portion of the magnetic head.

[0010] Figure 4 It is a plan view of the head portion of the magnetic head as viewed from the ABS side.

[0011] Figure 5 It is a side view schematically showing a magnetic head and the head portion in a state where the recording head portion is protruded by a thermal actuator.

[0012] Figure 6 is a circuit diagram of the inspection circuit of the HDD.

[0013] Figure 7 Schematically shows the output of the thermal resistance sensor when the thermal resistance sensor contacts a protrusion on a recording medium.

[0014] Figure 8 Schematically shows the output of the thermal resistance sensor when the recording medium passes through a depression.

[0015] Figure 9 FIG. 1 is a diagram schematically showing the relationship among the thermal resistance sensor, the recording track, and the protrusion.

[0016] Figure 10 This is a diagram schematically showing the positional relationship between a recording track during recording, a reproducing / recording element, and a thermal resistance sensor.

[0017] Figure 11 This is a diagram schematically showing the positional relationship between a recording track during reproduction, a reproducing / recording element, and a thermal resistance sensor.

[0018] Figure 12 Graph showing the relationship between the radial position of the magnetic head and the yaw angle.

[0019] Figure 13 It is a diagram schematically showing the operation of setting a recording-prohibited track.

[0020] Figure 14A It is a diagram showing the positional relationship between the width (in the case of wide) of the thermal resistance sensor and the element portion.

[0021] Figure 14BThis is a diagram showing the positional relationship between the width (narrow case) of the thermal resistance sensor and the element portion.

[0022] Figure 15 Graph showing the transition of the peak value of the thermal resistance sensor when detecting a protrusion.

[0023] Figure 16 It is a plan view schematically showing a detection operation 1 for detecting a surface defect (protrusion or recess) and an operation for setting a recording-prohibited track or a recording-prohibited sector.

[0024] Figure 17 It is a plan view schematically showing a detection operation 2 for detecting a surface defect (protrusion or recess) and an operation for setting a recording-prohibited track or a recording-prohibited sector.

[0025] Figure 18 It is a plan view schematically showing a detection operation 3 for detecting a surface defect (protrusion or recess) and an operation for setting a recording-prohibited track or a recording-prohibited sector.

[0026] Figure 19 It is a plan view schematically showing a detection operation 1 for detecting a surface defect (protrusion or recess) and a setting operation for a recording-prohibited track or a recording-prohibited sector in the HDD according to the second embodiment.

[0027] Figure 20 It is a plan view schematically showing a detection operation 2 for detecting a surface defect (protrusion or recess) and a setting operation for a recording-prohibited track or a recording-prohibited sector in the HDD according to the second embodiment.

[0028] Figure 21 It is a plan view schematically showing a detection operation 3 for detecting a surface defect (protrusion or recess) and a setting operation for a recording-prohibited track or a recording-prohibited sector in the HDD according to the second embodiment.

[0029] Figure 22A It is a diagram showing the positional relationship between the width of the thermal resistance sensor and the element portion of the magnetic head according to the first modified example.

[0030] Figure 22B It is a diagram showing the positional relationship between the width of the thermal resistance sensor and the element portion of the magnetic head according to the second modification.

[0031] Figure 23A It is a diagram showing the positional relationship between the width of the thermal resistance sensor and the element portion of the magnetic head according to the third modified example.

[0032] Figure 23B It is a diagram showing the positional relationship between the width of the thermal resistance sensor and the element portion of the magnetic head according to the fourth modified example.

[0033] Description of labels

[0034] 10 magnetic disk device; 11 housing; 12 magnetic disk; 13 ABS;

[0035] 15 slider; 16 magnetic head; 17 head; 18 head actuator;

[0036] 30 head amplifier IC; 40 main controller; 46d inspection circuit;

[0037] 54 read head; 58 write head; 76a first heater;

[0038] 76b: Second heater; HR thermal resistor sensor. DETAILED DESCRIPTION

[0039] Hereinafter, a disk device according to an embodiment will be described with reference to the drawings.

[0040] Furthermore, the present disclosure is merely an example, and any suitable modifications that can be readily conceived by those skilled in the art while maintaining the spirit of the invention are naturally also within the scope of the present invention. Furthermore, in order to clarify the description, the drawings sometimes schematically illustrate the width, thickness, shape, etc. of each part compared to the actual form. These are merely examples and do not limit the interpretation of the present invention. Furthermore, in this specification and the drawings, elements identical to those previously described in relation to the drawings are denoted by the same reference numerals, and detailed descriptions may be appropriately omitted or simplified.

[0041] (First embodiment)

[0042] As an example of a magnetic disk device, a hard disk drive (HDD) according to the first embodiment will be described in detail. Figure 1 is a block diagram schematically showing an HDD according to the first embodiment. Figure 2 It is a side view showing the magnetic head and magnetic disk in a floating state.

[0043] like Figure 1 As shown, the HDD 10 includes a rectangular housing 11, a magnetic disk 12 serving as a recording medium disposed within the housing 11, a spindle motor 14 that supports and rotates the magnetic disk 12, and a plurality of magnetic heads 16 that record (write) and reproduce (read) data from the magnetic disk 12. The HDD 10 includes a head actuator 18 that moves the magnetic head 16 to a desired track on the magnetic disk 12 and positions it. The head actuator 18 includes a carriage assembly 20 that movably supports the magnetic head 16 and a voice coil motor (VCM) 22 that rotates the carriage assembly 20.

[0044] The HDD 10 includes a controller including a head amplifier IC 30 for driving the magnetic head 16, a main controller 40, and a driver IC 48. The head amplifier IC 30 is disposed, for example, in the carriage assembly 20 and is electrically connected to the magnetic head 16. The head amplifier IC 30 includes a recording current supply circuit (recording current supply unit) for supplying recording current to the recording coil of the magnetic head 16, a heater power supply circuit for supplying driving power to a thermal actuator (heater) of the magnetic head 16 (described later), and an amplifier for amplifying signals read by the magnetic head 16.

[0045] The main controller 40 and the driver IC 48 are configured, for example, on a control circuit board (not shown) provided on the back side of the housing 11. The main controller 40 includes an R / W channel 42, a hard disk controller (HDC) 44, a microprocessor (MPU) 46, a memory 47, and the like. The main controller 40 is electrically connected to the magnetic head 16 via the head amplifier IC 30. The main controller 40 is electrically connected to the VCM 22 and the spindle motor 14 via the driver IC 48. The HDC 44 can be connected to a host computer 45.

[0046] In the main controller 40, for example, the MPU 46 includes a write control unit 46a for controlling the write head, a read control unit 46b for controlling the read head, a heater control unit 46c for controlling the power supplied to the thermal actuator, and a check circuit 46d. As will be described later, the check circuit 46d checks for defects on the surface of the magnetic disk 12. A memory 47 stores various data, such as the inspection results, recording-prohibited tracks, recording-prohibited sectors, and heater power setting values.

[0047] like Figure 1 and Figure 2 As shown, the magnetic disk 12 is configured as a perpendicular magnetic recording medium. The magnetic disk 12 has a substrate 101 formed of a non-magnetic material and formed into a circular plate shape with a diameter of, for example, 96 mm (approximately 3.5 inches). On each surface of the substrate 101, a soft magnetic layer 102 formed of a material exhibiting soft magnetic properties as a base layer, a perpendicular magnetic recording layer 103 having magnetic anisotropy in a direction perpendicular to the surface of the magnetic disk 12 on its upper layer, and a protective film 104 are sequentially stacked. The magnetic disk 12 is coaxially fitted into the hub of the spindle motor 14. The magnetic disk 12 is rotated in the direction of arrow B at a predetermined speed by the spindle motor 14.

[0048] like Figure 1 As shown, a plurality of concentric recording tracks T1 to Tn are formed on each surface (magnetic recording layer) of the magnetic disk 12. Each recording track includes a plurality of sectors arranged in the circumferential direction.

[0049] The carriage assembly 20 includes a bearing portion 24 rotatably supported by the housing 11, and a plurality of arms and a suspension 26 extending from the bearing portion 24. Figure 2As shown, the magnetic head 16 is supported by the extended ends of the suspensions 26. The magnetic head 16 is electrically connected to the head amplifier IC 30 via a wiring member (flexure) 28 provided in the carriage assembly 20.

[0050] like Figure 2 As shown, the magnetic head 16 is constructed as a floating head and includes a slider 15 formed in a substantially rectangular parallelepiped shape and a head 17 formed at the end of the slider 15 on the outflow (trailing) side. The slider 15 is formed, for example, from a sintered body of aluminum oxide and titanium carbide (AlTiC), and the head 17 is formed from a multilayer thin film. The slider 15 is attached to the gimbal portion 28a of the wiring member 28.

[0051] The slider 15 has a disk-facing surface (air bearing surface (ABS)) 13 that is substantially rectangular and faces the surface of the magnetic disk 12. The slider 15 is maintained in a state of floating a predetermined amount from the surface of the magnetic disk 12 by utilizing air flow C generated between the disk surface and the ABS 13 as the magnetic disk 12 rotates. The direction of the air flow C coincides with the rotational direction B of the magnetic disk 12. The slider 15 has a leading end 15a located on the inflow side of the air flow C and a trailing end 15b located on the outflow side of the air flow C. As the magnetic disk 12 rotates, the magnetic head 16 moves relative to the magnetic disk 12 in the direction of arrow A (head movement direction), i.e., in the direction opposite to the rotational direction B of the magnetic disk.

[0052] Figure 3 It is a cross-sectional view showing the head portion 17 of the magnetic head 16 and the magnetic disk 12 in an enlarged manner.

[0053] like Figure 3 As shown, the head 17 includes a read head (sometimes called a reproduction element) 54 and a write head (sometimes called a recording element) 58 formed using a thin film process at the trailing end 15b of the slider 15, forming a separate type magnetic head. The read head 54 and the write head 58 are covered by a non-magnetic protective insulating film 53, except for the portion exposed at the ABS 13 of the slider 15. The protective insulating film 53 forms the outer shape of the head 17. Furthermore, the head 17 includes a thermistor sensor HR for detecting the surface condition (defect state) of the magnetic disk surface, a first thermal actuator for controlling the protrusion of the write head 58, and a second thermal actuator for controlling the protrusion of the read head 54. As will be described later, the surface condition of the magnetic disk is defined as the presence or absence of defects (protrusions or depressions) on the magnetic disk surface, that is, the presence or absence of defects (protrusions or depressions) on the disk surface.

[0054] The longitudinal direction (circumferential direction) of the recording track of the perpendicular magnetic recording layer 103 formed on the magnetic disk 12 is defined as a track circumferential direction DT, and the width direction of the recording track perpendicular to the longitudinal direction is defined as a cross track direction WT.

[0055] The read head 54 includes a magnetoresistive element 55, a first magnetic shielding film 56, and a second magnetic shielding film 57. The first magnetic shielding film 56 and the second magnetic shielding film 57 are arranged on the leading (inflow) and trailing (outflow) sides of the magnetoresistive element 55 in the track direction DT, sandwiching the magnetoresistive element 55. The magnetoresistive element 55, the first magnetic shielding film 56, and the second magnetic shielding film 57 extend substantially perpendicularly to the ABS 13. The lower ends (front ends) of the magnetoresistive element 55, the first magnetic shielding film 56, and the second magnetic shielding film 57 slightly protrude from the ABS 13.

[0056] The write head 58 is disposed on the trailing end 15b side of the slider 15 relative to the read head 54. The write head 58 includes a main magnetic pole 60 that generates a recording magnetic field perpendicular to the surface of the magnetic disk 12; a trailing shield 62 disposed on the trailing side of the main magnetic pole 60 and facing the main magnetic pole 60 with a write gap therebetween; a leading shield 64 facing the leading side of the main magnetic pole 60; and a pair of side shields (not shown) integrally formed with the trailing shield 62. The main magnetic pole 60 and the trailing shield 62 form a first magnetic core that forms a magnetic circuit, while the main magnetic pole 60 and the leading shield 64 form a second magnetic core that forms a magnetic circuit. The write head 58 includes a first recording coil 70 wound around the first magnetic core and a second recording coil 72 wound around the second magnetic core.

[0057] The main magnetic pole 60 is formed from a soft magnetic material with high magnetic permeability and high saturation magnetic flux density, and extends approximately perpendicular to the ABS 13. A tip portion 60a of the main magnetic pole 60 on the ABS 13 side tapers toward the ABS 13, forming a columnar shape that is narrower than the rest of the main magnetic pole 60. The tip portion 60a of the main magnetic pole 60 slightly protrudes from the ABS 13 of the slider 15.

[0058] The trailing shield 62 is formed of a soft magnetic material and is provided to efficiently close the magnetic circuit via the soft magnetic layer 102 of the magnetic disk 12 directly below the main magnetic pole 60. The trailing shield 62 is formed into a generally L-shape, with its front end 62a formed into an elongated rectangular shape. The front end 62a of the trailing shield 62 slightly protrudes from the ABS 13 of the slider 15.

[0059] The trailing shield 62 includes a first connecting portion 50 connected to the main magnetic pole 60. The first connecting portion 50 is magnetically connected to the upper portion of the main magnetic pole 60, i.e., the portion of the main magnetic pole 60 separated from the ABS 13, via a non-conductive member 52. A first recording coil 70 is wound around the first connecting portion 50 in the first magnetic core, for example. When writing a signal to the magnetic disk 12, a recording current flows through the first recording coil 70, energizing the main magnetic pole 60 and causing magnetic flux to flow through the main magnetic pole 60.

[0060] A leading shield 64 formed of a soft magnetic material is provided on the leading side of the main magnetic pole 60, facing the main magnetic pole 60. The leading shield 64 is formed into a substantially L-shape, with a front end 64a on the ABS 13 side formed into an elongated rectangular shape. The front end 64a slightly protrudes from the ABS 13 of the slider 15.

[0061] The leading shield 64 also includes a second connecting portion 68 that is joined to the main magnetic pole 60 at a position separated from the ABS 13. This second connecting portion 68 is formed, for example, from a soft magnetic material and is magnetically connected to the upper portion of the main magnetic pole 60, i.e., the portion of the main magnetic pole 60 separated from the ABS 13, via a non-conductive member 69. Thus, the second connecting portion 68, the main magnetic pole 60, and the leading shield 64 form a magnetic circuit. The second recording coil 72 of the write head 58 is wound around the second connecting portion 68, for example, to apply a magnetic field to this magnetic circuit.

[0062] The first thermal actuator includes, for example, a heater 76 a . The heater 76 a is embedded in the protective insulating film 53 and is located near the write head 58 . The second thermal actuator includes, for example, a heater 76 b . The heater 76 b is embedded in the protective insulating film 53 and is located near the read head 54 .

[0063] The thermal resistance sensor HR is embedded in the protective insulating film 53 and positioned between the write head 58 and the read head 54. The detection end (front end) of the thermal resistance sensor HR is exposed at the ABS 13 or slightly protrudes from the ABS 13.

[0064] like Figure 3 As shown, a plurality of connection terminals 43 are provided at the trailing end 15b of the slider 15. The first recording coil 70 and the second recording coil 72 are each connected to the connection terminals 43 via wiring, and are further connected to the head amplifier IC 30 via the flexure 28. When writing a signal to the magnetic disk 12, a recording current is supplied from the recording current supply circuit of the head amplifier IC 30 to the first recording coil 70 and the second recording coil 72, thereby exciting the main magnetic pole 60 and causing magnetic flux to flow through the main magnetic pole 60. The recording current supplied to the first recording coil 70 and the second recording coil 72 is controlled by the main controller 40.

[0065] The magnetoresistive element 55 of the read head 54 is connected to the connection terminal 43 via wiring (not shown), and further connected to the head amplifier IC 30 via the flexure 28. The signal read by the read head 54 is amplified by the head amplifier IC 30 and sent to the main controller 40.

[0066] The first heater 76a and the second heater 76b are each connected to the connection terminal 43 via wiring, and further connected to the head amplifier IC 30 via the flexure 28. By applying driving power to the first heater 76a and the second heater 76b from the heater power supply circuit of the head amplifier IC 30, the heaters and their surroundings are heated, causing the write head 58 or the read head 54 to expand toward the magnetic disk 12. The heater power supplied to the first heater 76a and the second heater 76b is controlled by the heater control unit 46c of the main controller 40.

[0067] Thermistor sensor HR is connected to the connection terminal 43 via wiring, and further connected to the head amplifier IC 30 via the flexure 28. The detection signal (sensor output) of thermistor sensor HR is sent to the inspection circuit 46d of the main controller 40 via the head amplifier IC 30.

[0068] Figure 4 This is a plan view of the head portion 17 of the magnetic head 16 as viewed from the ABS side. As shown in the figure, the write head 58, thermistor sensor HR, and the read head 54 are arranged in sequence along the central axis C1 of the long dimension (track circumference DT) of the magnetic head 16. The front end portion (main magnetic pole front end portion) of the write head 58 exposed at the ABS 13 has a first width W1 in a direction perpendicular to the central axis C1. The front end portion (detection end) of the read head 54 exposed at the ABS 13 has a second width W2 in a direction perpendicular to the central axis C1. The front end portion (detection end) of thermistor sensor HR exposed at the ABS 13 has a third width W3 in a direction perpendicular to the central axis C1. The third width W3 is larger than the first width W1 and larger than the second width W2.

[0069] The track width Wt of the recording track formed on the magnetic disk 12 (see Figure 9 ) is approximately the same as the width W1 of the write head 58. Strictly speaking, the track width Wt is the same as the width of the recording magnetic field generated by the write head 58. The width W3 of the thermal resistance sensor HR is set to be sufficiently wider than the first width W1, for example, several tens of times wider than the width W1. In one example, when the track width Wt is 0.05 μm, the width W3 of the thermal resistance sensor HR is set to approximately 20 times the width Wt, 1 μm.

[0070] The tip of the write head 58, the tip of the read head 54, and the tip of the thermal resistor sensor HR each extend in a direction perpendicular to the central axis C1. In this embodiment, in the ABS 13, the centers of the width directions of the tip of the write head 58, the tip of the read head 54, and the tip of the thermal resistor sensor HR are each located on the central axis C1, and the ABS 13 is arranged bilaterally symmetrically with respect to the central axis C1.

[0071] In the ABS 13, the tip of the thermal resistor sensor HR is located between the tip of the write head 58 and the tip of the read head 54. In this embodiment, the distance D1 between the write head 58 and the thermal resistor sensor HR, and the distance D2 between the read head 54 and the thermal resistor sensor HR, along a direction parallel to the central axis C1, are set such that D1 > D2. The distances D1 and D2 are not limited to the embodiment and can be modified in various ways.

[0072] Figure 5 This is a side view schematically showing a magnetic head and the head portion thereof, with the recording head portion protruding by a thermal actuator. As shown in the figure, for example, by applying driving power to the first heater 76a, the first heater 76a and its surroundings are heated, causing the write head 58 portion to bulge toward the magnetic disk 12. This allows adjustment of the gap (head flying height) between the write head 58 and the surface of the magnetic disk 12.

[0073] Figure 6 46d is a circuit diagram showing an example of an inspection circuit. The inspection circuit 46d is provided with a dedicated frequency filter according to the size of the defect to be detected, and determines whether the defect exists based on whether the value exceeds a preset threshold. Figure 6 As shown, in one example, the inspection circuit 46d includes a sensor bias device (Sensorbias) 50a that applies a bias voltage to the thermistor sensor HR, an amplifier (Amp) 50b that amplifies the detection signal of the thermistor sensor HR, a low-pass filter (LPF) 50c, and a high-pass filter 50d. The sensor bias device 50a and the amplifier 50b may also be configured within the head amplifier IC 30.

[0074] Inspection circuit 46d includes an amplifier (Amp) 50e that amplifies the output signal of low-pass filter 50c, an analog-to-digital converter (ADC) 50f, a comparator 50g that compares the output signal of amplifier 50e with a threshold value Th1 for wide defects, and a counter 50h that counts the output signal of comparator 50g. Furthermore, inspection circuit 46d includes a low-pass filter (LPF) 50i following high-pass filter 50d, an amplifier (Amp) 50j, an analog-to-digital converter (ADC) 50k, a comparator 50m that compares the output signal of amplifier 50j with a threshold value Th2 for narrow defects, and a counter 50n that counts the output signal of comparator 50m.

[0075] Next, the operation of detecting defects (protrusions or depressions) on the surface of the magnetic disk 12 and setting recording-prohibited tracks or recording-prohibited sectors in the HDD 10 configured as described above will be described. When the HDD 10 is shipped from the factory, defect detection and recording-prohibited track setting are performed at regular intervals or for each recording operation.

[0076] Figure 7 is a diagram schematically showing the output of the thermal resistance sensor when it contacts a protrusion on a recording medium. Figure 8 Schematically shows the output of the thermal resistance sensor when the recording medium passes through a depression.

[0077] like Figure 7 As shown in FIG. 1 , if a protrusion higher than the floating height d1 of the thermal resistor sensor HR is formed on the surface of the magnetic disk 12, when the thermal resistor sensor HR passes over the protrusion, the thermal resistor sensor HR collides with the protrusion, causing the resistance value of the thermal resistor sensor HR to change, that is, to decrease. Therefore, the output waveform of the thermal resistor sensor HR decreases in the portion corresponding to the contact area R1.

[0078] like Figure 8 As shown, when a depression is formed on the surface of the magnetic disk 12, the resistance value of the thermal resistance sensor HR increases when the thermal resistance sensor HR passes over the depression. Therefore, the output waveform of the thermal resistance sensor HR becomes a waveform that increases in the portion corresponding to the passing region R2 on the depression.

[0079] Therefore, by moving the magnetic head 16 along each track of the magnetic disk 12 while observing and analyzing the output waveform of the thermal resistance sensor HR, it is possible to detect the presence or absence of protrusions / depressions on the surface of the magnetic disk 12 and determine whether they are protrusions or depressions. In other words, the inspection circuit 46d of the main controller 40 processes the output signal (output waveform) sent from the thermal resistance sensor HR to detect the presence or absence of protrusions / depressions on the surface of the magnetic disk 12, determine whether they are protrusions or depressions, and detect the positions of the protrusions / depressions.

[0080] Figure 9 1 is a diagram schematically showing the relationship between the thermal resistance sensor HR, the recording track, and the protrusion. Figure 9 As shown in FIG. 1 , the track with the protrusion is set as a record-forbidden track. After the main controller 40 sets the record-forbidden track, the main controller 40 prohibits the recording operation on the record-forbidden track, that is, prohibits the magnetic head 16 from accessing the record-forbidden track. Thus, after the record-forbidden track is set, the magnetic head 16 will not collide with the protrusion on the disk surface.

[0081] On the other hand, in order to improve the recording density of the magnetic disk device, it is necessary to increase the number of recording tracks formed on the recording medium, which means that the track width Wt of one recording track is narrowed. In this case, when protrusions of the same size are present on the recording medium, the number of recording tracks is prohibited from increasing. In addition, when the number of recording tracks increases, it takes a long time to check all the recording tracks. Therefore, the HDD involved in this embodiment is configured to shorten the time required for defect inspection of the magnetic disk 12.

[0082] like Figure 9 As shown, the width W3 of the thermal resistance sensor HR mounted on the magnetic head 16 is set to a width that spans multiple recording tracks, for example, 1 μm. On the other hand, the track width Wt of the recording track on the magnetic disk 12 is, for example, 0.05 μm, and is set so that multiple recording tracks exist below the thermal resistance sensor HR.

[0083] like Figure 1 and Figure 4 As shown, the thermal resistance sensor HR of the magnetic head 16 , the recording head 58 , and the reading head 54 are arranged side by side on a central axis C1 passing through the center of the bearing portion 24 of the carriage assembly 20 and the center of the magnetic head 16 .

[0084] Figure 10 This is a diagram schematically showing the positional relationship among a recording track during recording, a reproducing element, a recording element, and a thermal resistance sensor. Figure 11 This is a diagram schematically showing the positional relationship among a recording track during reproduction, a reproduction element, a recording element, and a thermal resistance sensor.

[0085] Figure 10 The figure shows the positional relationship between the read head 54, thermistor sensor HR, and the write head 58 when the carriage assembly 20 is rotated in the HDD 10 by the VCM 22, for example, when the magnetic head 16 is moved near the outer periphery of the magnetic disk 12. In the figure, the angle θ formed between the recording track and the center axis C1 of the head 17 represents the yaw angle. The read head 54 is positioned on the recording track n, and the write head 58 is positioned on the recording track n-3. When setting the recording-prohibited track, it is necessary to consider the positional relationship between the write and read heads.

[0086] Figure 11 The magnetic head 16 is shown positioned with Figure 10 States at different radial positions: As shown in the figure, although the write head 58 is positioned on the same recording track n, the read head 54 is located on the recording track n+3.

[0087] By pre-assigning the positional relationship between the write head 58, the read head 54, and the thermal resistance sensor HR corresponding to the radial position of the magnetic head 16 and storing it in the memory 47, the approximate positional relationship between the write head 58, the read head 54, and the protrusion detection position can be determined. Recording inhibit tracks can be set reflecting this positional relationship.

[0088] In addition, it is necessary to know in advance the yaw angle θ corresponding to the radial position of the magnetic head 16. Figure 1 As shown, the yaw angle θ can be uniquely determined by the distance L1 between the center of the bearing 24 and the center of the spindle motor, the distance L2 between the center of the bearing 24 and the magnetic head 16 , and the radial position of the magnetic head 16 on the magnetic disk 12 . Figure 12An example of calculating the yaw angle θ corresponding to the radial position of the magnetic head is shown.

[0089] Figure 13 1 is a plan view showing an example of setting an ideal recording-prohibited track. In the figure, the track marked with oblique lines corresponds to the recording-prohibited track.

[0090] As shown in the figure, when surface protrusions span three recording tracks, n-1, n, and n+1, recording tracks n-5 to n+5, which include four tracks on the outer circumference and four tracks on the inner circumference, are designated as prohibited recording tracks. This prevents contact between the write head 58 and the read head 54 and the surface protrusions, even when the write head 58 is positioned on recording track n-6. Furthermore, when the read head 54 is positioned on recording track n+6, the write head 58 also does not come into contact with the surface protrusions.

[0091] However, since there is a limit to accurately measuring the size of the surface protrusions in units of tracks, it is preferable to set a recording-inhibited track with a width having a margin of 1 to 2 tracks.

[0092] Figure 14A : is a diagram showing the positional relationship between the width (wide case) of the thermal resistance sensor and the element portion. Figure 14B This is a diagram showing the positional relationship between the width (narrow case) of the thermal resistance sensor and the element portion.

[0093] As shown in the figure, when the yaw angle θ increases (maximum yaw angle), the write head 58 and the read head 54 may sometimes be out of the range of the width W3 of the thermal resistance sensor HR. Figure 14A As shown, when the width W3 of the thermal resistance sensor HR is wide, the write head 58 and the read head 54 enter the range of the width W3 of the thermal resistance sensor HR in the track circumferential direction. Figure 14B As shown, if the width W3 of the thermal resistance sensor HR is narrow, the write head 58 will be out of the range of the width W3 of the thermal resistance sensor HR in the track circumferential direction. Therefore, it is preferable to also know in advance where the write head 58 and the read head 54 are located relative to the recording track detected by the thermal resistance sensor HR.

[0094] Figure 15 It is a diagram schematically showing the positional relationship between the surface protrusions and the magnetic head, and the relationship between the surface protrusions and the sensor output of the thermal resistance sensor.

[0095] As shown in the figure, when defect detection is performed on all recording tracks using thermistor sensor HR, for example, when surface protrusions are located on recording tracks n-1, n, and n+1, the sensor output of thermistor sensor HR when detecting each recording track is as shown in the figure on the right. Specifically, when thermistor sensor HR passes over or near the surface protrusion, the resistance of thermistor sensor HR increases, and the sensor output decreases. The number of recording tracks detected by the recording track where the center of the surface protrusion is located and thermistor sensor HR is the sum of the width W3 of thermistor sensor HR and the width of the surface protrusion. In the example shown, the center of the defect detection position deviates by an amount corresponding to the yaw angle θ taken into account for the distance between the read head 54 and thermistor sensor HR. This geometric error can be accurately estimated. Because the number of contacts between the write head 58 and the read head 54 and the surface protrusion also increases, it is preferable to set the prohibited recording tracks with a margin of one to two tracks, as described above.

[0096] In the HDD according to the present embodiment, detection of surface defects and setting of recording-prohibited tracks or recording-prohibited sectors are performed in consideration of the above-mentioned points.

[0097] Figure 16 、 Figure 17 、 Figure 18 These are plan views showing the operation of detecting defects (protrusions or recesses) on the surface of the magnetic disk 12 and the operation of setting recording-prohibited tracks or recording-prohibited sectors in the HDD according to the present embodiment.

[0098] According to this embodiment, in order to shorten the defect inspection time, the thermal resistance sensor HR does not perform defect inspection on each recording track, but Figure 16 As shown, multiple recording tracks covered by the width W3 of the thermal resistance sensor HR are inspected simultaneously as a bundle. In the example shown, the width W3 of the thermal resistance sensor HR is set to a width corresponding to approximately seven tracks. The thermal resistance sensor HR simultaneously inspects a width of + / - three tracks centered on the recording track it is positioned on.

[0099] In one example, the thermal resistor sensor HR starts checking from the outermost recording tracks 0 to 6, and each time the disk 12 rotates at least one revolution, it moves in the radial direction (the width direction of the recording tracks) by a predetermined feed pitch (feed width), for example, the amount of multiple tracks, and checks the recording tracks of the next beam. The inspection circuit 46d of the controller 40 detects the presence or absence of surface defects and the position of the surface defects (here, surface protrusions) based on the sensor output of the thermal resistor sensor HR, and then determines whether it is a protrusion or a recess. When the controller 40 detects a protrusion, it determines that it is Figure 16 There is a protrusion in the shaded area (for example, tracks 2 to 9, sectors 10 and 11), and the above area is registered in the memory 47.

[0100] Then, if Figure 17 As shown, the controller 40 moves the magnetic head 16 radially (in the track width direction) inward by a predetermined feed spacing (for example, the amount of 3 tracks equivalent to half the track conversion width of the thermistor sensor HR), and performs defect detection on the recording tracks 6 to 11 through the thermistor sensor HR.

[0101] In addition, the controller 40 sets the feed pitch of the magnetic head 16 during defect inspection in advance and stores the set value in the memory 47. The feed pitch (feed width) of the magnetic head is preferably set to within 1 / 2 of the third width W3 of the thermal resistance sensor HR and at least the amount of three recording tracks. In this embodiment, as an example, the feed pitch is set to the track width of three tracks.

[0102] Then, if Figure 18 As shown, the controller 40 repeatedly moves the magnetic head 16 radially by three tracks each time the magnetic disk 12 rotates once, thereby identifying recording tracks where surface protrusions are likely to be present. After completing the inspection of all recording tracks, the controller 40 sets the recording tracks detected as those where surface protrusions are likely to be present as prohibited recording tracks and registers the set prohibited recording tracks in the memory 47. Furthermore, the prohibited recording tracks can be set in consideration of the relative positions of the write head 58, the read head 54, and the thermal resistance sensor HR.

[0103] During normal recording operation, the controller 40 prohibits recording of information on the registered recording-prohibited tracks, that is, prohibits the magnetic head 16 from accessing the recording-prohibited tracks. This prevents the magnetic head 16 from colliding with the surface protrusions of the magnetic disk 12.

[0104] According to the HDD of this embodiment, for example, if the total number of tracks is 600,000 and the recording medium rotates at 7200 rpm, and a 1 μm-wide thermal resistance sensor is used to simultaneously inspect a number of recording tracks equivalent to 70% of the width, all recording tracks can be inspected in approximately 12 minutes. In contrast, using conventional methods to inspect defects one track at a time, it would take approximately 160 minutes to inspect all recording tracks on a single side of the recording medium, assuming one cycle of inspection and one cycle of track movement.

[0105] As described above, the HDD according to this embodiment can significantly shorten the defect detection time of the disk surface, can perform defect detection and prohibit the setting of recording tracks in a short time. Thus, according to this embodiment, it is possible to provide a disk device that prevents the damage of the magnetic head caused by the defect on the recording medium and that has improved reliability.

[0106] In the other embodiments described below, the same parts as those in the first embodiment are denoted by the same reference numerals, and their detailed description is omitted or simplified, with the description focusing on the parts different from the first embodiment.

[0107] (Second embodiment)

[0108] Figure 19 、 Figure 20 、 Figure 21 These are plan views showing the operation of detecting defects (protrusions or recesses) on the surface of the magnetic disk 12 and the operation of setting recording-prohibited tracks or recording-prohibited sectors, respectively, in the HDD according to the second embodiment.

[0109] In the first embodiment described above, during defect inspection on the disk surface, the magnetic head is moved by a predetermined feed pitch (amount of three tracks) in the track width direction each time the disk rotates one revolution. That is, in the first embodiment, one revolution is spent on defect inspection and one revolution is spent on track movement of the magnetic head.

[0110] On the other hand, according to the HDD involved in the second embodiment, as shown in FIG. Figure 19 、 Figure 20 、 Figure 21 As shown in the figure, when inspecting defects on the disk surface, the controller 40 continuously moves the magnetic head 16 in the radial direction (track width direction) by a predetermined feed pitch, for example, three tracks, during one rotation of the disk 12, thereby inspecting defects in the recording tracks. In other words, as shown by the dotted line in the figure, the controller 40 performs defect inspection while moving the magnetic head 16 spirally relative to the surface of the disk 12. That is, according to the second embodiment, defect inspection and radial head movement are performed simultaneously.

[0111] According to the second embodiment configured as described above, the time it takes for the magnetic head to move between tracks can be reduced by moving the magnetic head in a spiral shape. According to the second embodiment, the inspection time in the first embodiment can be further shortened, and defect inspection can be performed in about 6 minutes.

[0112] For example, in an HDD equipped with 10 magnetic disks (recording media), the number of recording medium surfaces to be inspected for defects is 20. While conventional HDDs require 3,200 minutes to inspect for defects, the HDD according to the second embodiment can reduce this time to 120 minutes.

[0113] According to the HDD involved in the second embodiment, the defect detection time of the magnetic disk surface can be further shortened, and the defect detection and the setting of the prohibited recording tracks can be performed in a shorter time. Thus, according to this embodiment, a disk device with improved reliability can be provided, which prevents damage to the magnetic head caused by defects on the recording medium.

[0114] The arrangement relationship among the read head 54 , the write head 58 , and the thermal resistance sensor HR in the magnetic head 16 is not limited to that in the first embodiment described above, and various changes can be made.

[0115] (First Modification)

[0116] Figure 22A This figure shows the positional relationship between the thermal resistance sensor and the element portion of the magnetic head according to the first modification. As shown in the figure, according to the first modification, the thermal resistance sensor HR of the magnetic head 16 is arranged at a position close to the write head 58. That is, the distance D1 between the write head 58 and the thermal resistance sensor HR and the distance D2 between the read head 54 and the thermal resistance sensor HR in the direction parallel to the central axis C1 are set to D1. <D2。

[0117] When the recording track width is set to 0.05 μm, the width W3 of the thermal resistance sensor HR is set to a sufficiently wide width of approximately 1 μm. In other words, the width W3 of the thermal resistance sensor HR is set to be sufficiently wider than the width W1 of the tip of the write head 58, and is several times, for example, approximately 20 times, the width W1.

[0118] (Second Modification)

[0119] Figure 22B This figure shows the positional relationship between the thermal resistance sensor and the element portion of the magnetic head according to the second modification. As shown in the figure, according to the second modification, the thermal resistance sensor HR of the magnetic head 16 is arranged at a position close to the write head 58. That is, the distance D1 between the write head 58 and the thermal resistance sensor HR and the distance D2 between the read head 54 and the thermal resistance sensor HR in the direction parallel to the central axis C1 are set to D1. <D2。

[0120] When the recording track width is set to 0.05 μm, the width W3 of the thermal resistance sensor HR is set to a narrow width of approximately 0.5 μm. In other words, the width W3 of the thermal resistance sensor HR is set to be wider than the width W1 of the tip of the write head 58, and is several times, for example, approximately 10 times, the width W1.

[0121] (Third Modification)

[0122] Figure 23AThis figure illustrates the positional relationship between the thermal resistance sensor and the element portion of a magnetic head according to a third modification. As shown, according to the third modification, the distance D1 between the write head 58 and the thermal resistance sensor HR, and the distance D2 between the read head 54 and the thermal resistance sensor HR, along a direction parallel to the central axis C1, are set such that D1 > D2. The center of the thermal resistance sensor HR in the width direction is positioned at a position offset (deviated) from the central axis C1 in a width direction perpendicular to the central axis.

[0123] When the recording track width is set to 0.05 μm, the width W3 of the thermal resistance sensor HR is set to be as wide as approximately 1 μm. In other words, the width W3 of the thermal resistance sensor HR is set to be wider than the width W1 of the tip of the write head 58, and is several times, for example, approximately 20 times, greater than the width W1.

[0124] The write head 58 and the read head 54 are located at positions overlapping with the thermal resistance sensor HR in the track circumferential direction.

[0125] (Fourth Modification)

[0126] Figure 23B This diagram illustrates the positional relationship between the thermal resistance sensor and the element portion of a magnetic head according to a fourth modification. As shown, according to the fourth modification, the distance D1 between the write head 58 and the thermal resistance sensor HR, and the distance D2 between the read head 54 and the thermal resistance sensor HR, along a direction parallel to the central axis C1, are set such that D1 > D2. The center of the thermal resistance sensor HR in the width direction is positioned offset from the central axis C1.

[0127] When the recording track width is set to 0.05 μm, the width W3 of the thermal resistance sensor HR is set to a narrow width of approximately 0.5 μm. In other words, the width W3 of the thermal resistance sensor HR is set to be wider than the width W1 of the tip of the write head 58, and is several times, for example, approximately 10 times, the width W1.

[0128] The write head 58 and the read head 54 are located at positions overlapping with the thermal resistance sensor HR in the track circumferential direction.

[0129] When any of the magnetic heads of the first to fourth modified examples configured as described above is used, the same operational effects as those of the first embodiment can be obtained.

[0130] While several embodiments and variations of the present invention have been described, these embodiments and variations are provided as examples and are not intended to limit the scope of the invention. These embodiments and variations can be implemented in various other ways and can be omitted, replaced, or modified without departing from the gist of the invention. These embodiments and variations are included within the scope and gist of the invention and, likewise, within the scope of the invention set forth in the claims and their equivalents.

[0131] For example, the head feed pitch during defect inspection is not limited to three tracks, but can be changed within a range of 1 / 2 of the third width W3 and more than three recording tracks. By increasing the feed pitch, defect inspection time can be further shortened.

[0132] The material, shape, size, etc. of the elements constituting the head portion of the magnetic head can be changed as needed. In a magnetic disk device, the number of magnetic disks and magnetic heads can be increased or decreased as needed, and the size of the magnetic disk can also be selected from various options.

Claims

1. A magnetic disk device comprising: A rotatable disk-shaped recording medium having a plurality of concentric recording tracks; A magnetic head comprising a recording element, a reproducing element, and a thermal resistance sensor, wherein the recording element has a first width in a direction intersecting the recording tracks, the reproducing element has a second width in a direction intersecting the recording tracks, and the thermal resistance sensor has a third width in a direction intersecting the recording tracks that is wider than the first and second widths, and detects a surface condition of the recording medium. a head actuator for positioning the magnetic head at an arbitrary recording track of the recording medium; a detection circuit for detecting defects on the surface of the recording medium based on a sensor output of the thermal resistance sensor; as well as The controller sets the feed pitch of the magnetic head in the width direction of the recording track to within 1 / 2 of the third width of the thermal resistance sensor and more than 3 recording tracks when the surface condition of the recording medium is inspected by the thermal resistance sensor.

2. The magnetic disk device according to claim 1, When checking the surface condition of the recording medium, the controller drives the head actuator so that the magnetic head moves within 1 / 2 of the third width of the thermistor sensor and more than 3 tracks in the feed pitch direction each time the recording medium rotates one circle.

3. The magnetic disk device according to claim 1, When inspecting the surface condition of the recording medium, the controller drives the head actuator so that the magnetic head continuously moves within 1 / 2 of the third width of the thermistor sensor and more than 3 tracks in the feed pitch direction during one rotation of the recording medium.

4. The magnetic disk device according to claim 1, The recording element and the reproducing element are arranged at intervals in a first direction intersecting the recording track, and the thermal resistance sensor is arranged in the first direction with the recording element and the reproducing element, and the thermal resistance sensor is located between the recording element and the reproducing element.

5. The magnetic disk device according to claim 4, The centers of the recording element, the reproducing element, and the thermal resistance sensor in the width direction are located on a central axis extending in the first direction.

6. The magnetic disk device according to claim 4, The centers of the recording element and the reproducing element in the width direction are located on a central axis extending in the first direction. The center of the thermal resistance sensor in the width direction is located at a position spaced apart from the central axis in a direction orthogonal to the central axis.

7. The magnetic disk device according to claim 1, The magnetic head includes a thermal actuator.

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