Magnetic disk device

Abstract

To provide a magnetic disk device which is improved in reliability by preventing a magnetic head from being damaged due to a defect on a recording medium.SOLUTION: According to an 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 reproducing 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 on an arbitrary recording track of the recording medium; a detection circuit configured to detect a defect on a surface of the recording medium based on a sensor output of the thermal resistance sensor; and a controller configured to set a feed pitch of the magnetic head in a width direction of the recording tracks to be within one-half of the third width and equal to or more than three recording tracks when a surface state of the recording medium is inspected by the thermal resistance sensor.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a magnetic disk drive. [Background technology]

[0002] As an example of a disk device, 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 and a read head and a write head attached to the slider. In such a magnetic disk device, in order to improve 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 minute gap of about 1 nm, so the recording surface of the recording medium is required to be smooth. However, the recording surface of a recording medium contains defects that arise during the manufacturing process of the recording medium, such as minute protrusions about 3 to 8 nm in height. When a magnetic head runs over the recording surface with a small gap, the magnetic head collides with the minute protrusions. Repeated collisions with the minute protrusions can damage the magnetic head, making it difficult to perform recording and reproduction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 6,216,242 [Patent Document 2] Japanese Patent Application Publication No. 9-304009 [Patent Document 3] U.S. Patent No. 6,262,572 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the embodiments of the present invention is to provide a magnetic disk drive that prevents damage to the magnetic head due to defects on the recording medium and has improved reliability. [Means for solving the problem]

[0005] According to an embodiment, a magnetic disk device includes a magnetic head having a rotatable disk-shaped recording medium having a plurality of concentric recording tracks, a recording element having a first width in a direction intersecting the recording tracks, a reproducing element having a second width in a direction intersecting the recording tracks, and a thermal resistance sensor having a third width in a direction intersecting the recording tracks that is wider than the first and second widths and that detects the surface condition of the recording medium, a head actuator that positions the magnetic head at any recording track of the recording medium, a detection circuit that detects defects on the surface of the recording medium based on the sensor output of the thermal resistance sensor, and a controller that sets the feed pitch of the magnetic head in the width direction of the recording tracks to within 1 / 2 of the third width of the thermal resistance sensor and to at least three recording tracks when inspecting the surface condition of the recording medium with the thermal resistance sensor. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a block diagram schematically showing a hard disk drive (HDD) according to a first embodiment. [Figure 2] FIG. 2 is a side view schematically showing the magnetic head, suspension, and magnetic disk in the HDD. [Figure 3] FIG. 3 is an enlarged cross-sectional view of a head portion of the magnetic head. [Figure 4] FIG. 4 is a plan view of the head portion of the magnetic head as seen from the ABS side. [Figure 5] FIG. 5 is a side view schematically showing the magnetic head and the head portion in a state where the recording head portion is protruded by a thermal actuator. [Figure 6] FIG. 6 is a circuit diagram of the inspection circuit of the HDD. [Figure 7]FIG. 7 is a diagram showing a schematic diagram of the output of a thermal resistance sensor when it comes into contact with a protrusion on a recording medium. [Figure 8] FIG. 8 is a diagram showing a schematic diagram of the output of a thermal resistance sensor when passing a depression on a recording medium. [Figure 9] FIG. 9 is a diagram schematically showing the relationship between the thermal resistance sensor, the recording track, and the protrusions. [Figure 10] FIG. 10 is a diagram showing a schematic diagram of the positional relationship between a recording track during recording, a reproduction element, a recording element, and a thermal resistance sensor. [Figure 11] FIG. 11 is a diagram showing a schematic diagram of the positional relationship between a recording track during playback, a playback element, a recording element, and a thermal resistance sensor. [Figure 12] FIG. 12 is a diagram showing the relationship between the radial position of the magnetic head and the yaw angle. [Figure 13] FIG. 13 is a diagram showing a typical setting operation of a write-inhibited track. [Figure 14A] FIG. 14A is a diagram showing the positional relationship between the width (when wide) of a thermal resistance sensor and an element portion. [Figure 14B] FIG. 14B is a diagram showing the positional relationship between the width (narrow case) of the thermal resistance sensor and the element part. [Figure 15] FIG. 15 is a diagram showing the transition of the peak value of the thermal resistance sensor when a protrusion is detected. [Figure 16] FIG. 16 is a plan view schematically showing a detection operation 1 for detecting surface defects (protrusions or recesses) and a setting operation for write-prohibited tracks or write-prohibited sectors. [Figure 17] FIG. 17 is a plan view schematically showing a detection operation 2 for detecting surface defects (protrusions or recesses) and a setting operation for write-inhibited tracks or write-inhibited sectors. [Figure 18] FIG. 18 is a plan view schematically showing a detection operation 3 for detecting surface defects (protrusions or recesses) and a setting operation for write-inhibited tracks or write-inhibited sectors. [Figure 19] FIG. 19 is a plan view schematically showing a detection operation 1 for detecting surface defects (protrusions or recesses) and an operation for setting write-prohibited tracks or write-prohibited sectors in an HDD according to a second embodiment. [Figure 20]FIG. 20 is a plan view schematically showing a detection operation 2 for detecting surface defects (protrusions or recesses) and a setting operation of write-prohibited tracks or write-prohibited sectors in an HDD according to a second embodiment. [Figure 21] FIG. 21 is a plan view schematically showing a detection operation 3 for detecting surface defects (protrusions or recesses) and an operation for setting write-prohibited tracks or write-prohibited sectors in an HDD according to a second embodiment. [Figure 22A] FIG. 22A is a diagram showing the positional relationship between the width of a thermal resistance sensor and an element portion of a magnetic head according to a first modified example. [Figure 22B] FIG. 22B 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. [Figure 23A] FIG. 23A is a diagram showing the positional relationship between the width of a thermal resistance sensor and an element portion of a magnetic head according to a third modified example. [Figure 23B] FIG. 23B 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 modification. DETAILED DESCRIPTION OF THE INVENTION

[0007] A disk device according to an embodiment will be described below with reference to the drawings. The disclosure is merely an example, and appropriate modifications that are easily conceivable by those skilled in the art while maintaining the gist of the invention are naturally included within the scope of the present invention. Furthermore, in order to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present invention. Furthermore, in this specification and each drawing, elements similar to those described above with reference to the previous drawings may be designated by the same reference numerals, and detailed descriptions may be omitted or simplified as appropriate.

[0008] (First embodiment) As an example of a magnetic disk device, a hard disk drive (HDD) according to a first embodiment will be described in detail. Fig. 1 is a block diagram showing a schematic diagram of the HDD according to the first embodiment, and Fig. 2 is a side view showing a magnetic head and a magnetic disk in a floating state. 1, HDD 10 includes a rectangular housing 11, a magnetic disk 12 as a recording medium disposed within housing 11, a spindle motor 14 that supports and rotates magnetic disk 12, and a plurality of magnetic heads 16 that record (write) and reproduce (read) data on magnetic disk 12. HDD 10 includes a head actuator 18 that moves and positions magnetic head 16 over any track on magnetic disk 12. Head actuator 18 includes a carriage assembly 20 that movably supports magnetic head 16, and a voice coil motor (VCM) 22 that rotates carriage assembly 20.

[0009] The HDD 10 is equipped with a controller including a head amplifier IC 30 that drives the magnetic head 16, a main controller 40, and a driver IC 48. The head amplifier IC 30 is provided, 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) that supplies a recording current to the recording coil of the magnetic head 16, a heater power supply circuit that supplies driving power to a thermal actuator (heater) of the magnetic head 16, which will be described later, an amplifier that amplifies a signal read by the magnetic head 16, and the like.

[0010] The main controller 40 and driver IC 48 are configured, for example, on a control circuit board (not shown) provided on the rear 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, etc. 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.

[0011] In the main controller 40, for example, the MPU 46 includes a write control unit 46a that controls the write head, a read control unit 46b that controls the read head, a heater control unit 46c that controls the power supplied to the thermal actuator, and an inspection circuit 46d. As will be described later, the inspection circuit 46d inspects defects on the surface of the magnetic disk 12. A memory 47 stores various data such as inspection results, write-prohibited tracks, write-prohibited sectors, and heater power setting values.

[0012] As shown in Figures 1 and 2, the magnetic disk 12 is configured as a perpendicular magnetic recording medium. The magnetic disk 12 has a substrate 101 made of a non-magnetic material and formed into a disk 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 made of a material exhibiting soft magnetic properties is formed as an underlayer, and on top of that, a perpendicular magnetic recording layer 103 having magnetic anisotropy in a direction perpendicular to the surface of the magnetic disk 12 and a protective film 104 are sequentially laminated. The magnetic disk 12 is coaxially fitted to the hub of a spindle motor 14. The magnetic disk 12 is rotated by the spindle motor 14 at a predetermined speed in the direction of arrow B. 1, a large number 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 aligned in the circumferential direction.

[0013] The carriage assembly 20 has a bearing 24 rotatably supported on the housing 11, and a plurality of arms and suspensions 26 extending from the bearing 24. As shown in Fig. 2, the magnetic head 16 is supported on the extending ends of the suspensions 26. The magnetic head 16 is electrically connected to a head amplifier IC 30 via a wiring member (flexure) 28 provided on the carriage assembly 20.

[0014] 2, magnetic head 16 is configured as a floating-type head and includes slider 15 formed in a substantially rectangular parallelepiped shape and head portion 17 formed at the trailing end of slider 15. Slider 15 is formed, for example, from a sintered body (AlTiC) of alumina and titanium carbide, and head portion 17 is formed from multiple thin film layers. Slider 15 is attached to gimbal portion 28a of wiring member 28.

[0015] The slider 15 has a substantially rectangular disk-facing surface (air bearing surface (ABS)) 13 that faces the surface of the magnetic disk 12. The slider 15 is maintained in a state where it is lifted a predetermined distance above the surface of the magnetic disk 12 by airflow C that is generated between the disk surface and the ABS 13 as the magnetic disk 12 rotates. The direction of the airflow C coincides with the rotation direction B of the magnetic disk 12. The slider 15 has a leading end 15a located on the inflow side of the airflow C and a trailing end 15b located on the outflow side of the airflow 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 rotation direction B of the disk.

[0016] FIG. 3 is an enlarged cross-sectional view showing the head portion 17 of the magnetic head 16 and the magnetic disk 12. As shown in FIG. As shown in FIG. 3, the head section 17 is formed as a separate magnetic head, having a read head (sometimes referred to as a reproducing element) 54 and a write head (sometimes referred to as a recording element) 58 formed by a thin-film process on the trailing end 15b of the slider 15. The read head 54 and the write head 58 are covered with a nonmagnetic protective insulating film 53, except for the portions of the slider 15 exposed to the ABS 13. The protective insulating film 53 forms the outer shape of the head section 17. The head section 17 also has a thermal resistance sensor HR that detects the surface condition (defect condition) of the magnetic disk surface, a first thermal actuator that controls the protrusion amount of the write head 58, and a second thermal actuator that controls the protrusion amount of the read head 54. Note that the surface condition of the magnetic disk is defined as the presence or absence of defects (protrusions or recesses) on the magnetic disk surface, as will be described later.

[0017] The longitudinal direction (circumferential direction) of the recording track formed on the perpendicular magnetic recording layer 103 of the magnetic disk 12 is defined as the track circumferential direction DT, and the width direction of the recording track perpendicular to the longitudinal direction is defined as the cross-track direction WT. The read head 54 has 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 side (inflow side) and trailing side (outflow side) of the magnetoresistive element 55 in the circumferential direction DT of the track, sandwiching the magnetoresistive element 55 therebetween. The magnetoresistive element 55 and the first and second magnetic shielding films 56, 57 extend substantially perpendicular to the ABS 13. The lower ends (tips) of the magnetoresistive element 55 and the first and second magnetic shielding films 56, 57 slightly protrude from the ABS 13.

[0018] The write head 58 is located closer to the trailing end 15b of the slider 15 than the read head 54. The write head 58 has a main pole 60 that generates a recording magnetic field perpendicular to the surface of the magnetic disk 12, a trailing shield 62 that is located on the trailing side of the main pole 60 and faces the main pole 60 across a write gap, a leading shield 64 that faces the leading side of the main pole 60, and a pair of side shields (not shown) that are formed integrally with the trailing shield 62. The main pole 60 and the trailing shield 62 form a first magnetic core that forms a magnetic path, and the main pole 60 and the leading shield 64 form a second magnetic core that also forms a magnetic path. The write head 58 has a first recording coil 70 wound around the first magnetic core and a second recording coil 72 wound around the second magnetic core.

[0019] The main pole 60 is made of a soft magnetic material with high magnetic permeability and high saturation magnetic flux density, and extends approximately perpendicular to the ABS 13. The tip 60a of the main pole 60 on the ABS 13 side tapers toward the ABS 13 and is formed into a columnar shape that is narrower than the other parts. The tip 60a of the main pole 60 protrudes slightly from the ABS 13 of the slider 15.

[0020] The trailing shield 62 is made of a soft magnetic material and is provided to efficiently close the magnetic path through the soft magnetic layer 102 of the magnetic disk 12 directly below the main pole 60. The trailing shield 62 is formed in a substantially L-shape, and its tip 62a is formed in an elongated rectangular shape. The tip 62a of the trailing shield 62 protrudes slightly from the ABS 13 of the slider 15. The trailing shield 62 has a first connection part 50 connected to the main pole 60. The first connection part 50 is magnetically connected to the top of the main pole 60, i.e., a part of the main pole 60 away from the ABS 13, via a non-conductor 52. The first write coil 70 is wound around the first connection part 50 in the first magnetic core, for example. When writing a signal to the magnetic disk 12, a write current is passed through the first write coil 70, which excites the main pole 60 and causes magnetic flux to flow through the main pole 60.

[0021] The leading shield 64, made of a soft magnetic material, is provided on the leading side of the main pole 60, facing the main pole 60. The leading shield 64 is formed in a substantially L-shape, with a tip 64a on the ABS 13 side formed in an elongated rectangular shape. The tip 64a protrudes slightly from the ABS 13 of the slider 15. The leading shield 64 also has a second connection part 68 joined to the main pole 60 at a position away from the ABS 13. This second connection part 68 is formed of, for example, a soft magnetic material and is magnetically connected to the upper part of the main pole 60, i.e., the part of the main pole 60 away from the ABS 13, via a non-conductor 69. This allows the second connection part 68 to form a magnetic circuit together with the main pole 60 and the leading shield 64. The second write coil 72 of the write head 58 is arranged, for example, wound around the second connection part 68, and applies a magnetic field to this magnetic circuit.

[0022] The first thermal actuator includes, for example, a heater 76a. The heater 76a 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 76b. The heater 76b is embedded in the protective insulating film 53 and is located near the read head 54. The thermal resistance sensor HR is embedded in the protective insulating film 53 and is located between the write head 58 and the read head 54. The detection end (tip) of the thermal resistance sensor HR is exposed to the ABS 13 or protrudes slightly from the ABS 13.

[0023] As shown in FIG. 3, a plurality of connection terminals 43 are provided on the trailing end 15b of the slider 15. The first and second write coils 70 and 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 write current is supplied from a write current supply circuit in the head amplifier IC 30 to the first and second write coils 70 and 72, thereby exciting the main pole 60 and causing magnetic flux to flow through the main pole 60. The write current supplied to the first and second write coils 70 and 72 is controlled by the main controller 40. The magnetoresistive element 55 of the read head 54 is connected to the connection terminal 43 via wiring (not shown), and is 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.

[0024] 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 drive 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 the area around the heaters are heated, causing the write head 58 or the read head 54 to bulge 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. The thermal resistance sensor HR is connected to the connection terminal 43 via a wire, and is further connected to the head amplifier IC 30 via the flexure 28. A detection signal (sensor output) of the thermal resistance sensor HR is sent to the inspection circuit 46d of the main controller 40 via the head amplifier IC 30.

[0025] FIG. 4 is a plan view of the head portion 17 of the magnetic head 16 as viewed from the ABS side. As shown, the write head 58, thermal resistance sensor HR, and read head 54 are aligned in this order along the central axis C1 in the longitudinal direction (track circumferential direction DT) of the magnetic head 16. The tip of the write head 58 (main pole tip) exposed at the ABS 13 has a first width W1 in a direction perpendicular to the central axis C1. The tip 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 tip of the thermal resistance sensor HR (detection end) 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.

[0026] The track width Wt (see FIG. 9) of the recording track formed on the magnetic disk 12 is approximately equal to the width W1 of the write head 58. Strictly speaking, the track width Wt is equal to 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 the width W1. In one example, when the track width Wt is 0.05 μm, the width W3 of the thermal resistance sensor is set to 1 μm, which is approximately 20 times the width W1.

[0027] The tip of the write head 58, the tip of the read head 54, and the tip of the thermal resistance sensor HR each extend in a direction perpendicular to the central axis C1. In this embodiment, in the ABS 13, the tip of the write head 58, the tip of the read head 54, and the tip of the thermal resistance sensor HR each have their widthwise centers positioned on the central axis C1 and are arranged symmetrically with respect to the central axis C1. In the ABS 13, the tip of the thermal resistance 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 resistance sensor HR along the direction parallel to the central axis C1, and the distance D2 between the read head 54 and the thermal resistance sensor HR, are set so that D1 > D2. Note that the distances D1 and D2 are not limited to those in this embodiment and can be changed in various ways.

[0028] 5 is a schematic side view of the magnetic head and the head portion with the recording head portion protruding due to a thermal actuator. As shown in the figure, for example, by applying drive power to the first heater 76a, the first heater 76a and its surroundings are heated, causing the write head 58 portion to protrude toward the magnetic disk 12. This makes it possible to adjust the gap (head flying height) between the write head 58 and the surface of the magnetic disk 12.

[0029] FIG. 6 is a circuit diagram showing an example of an inspection circuit. The inspection circuit 46d includes a dedicated frequency filter according to the size of the defect to be detected, and determines whether or not a defect exists based on whether a preset threshold is exceeded. As shown in FIG. 6, in one example, the inspection circuit 46d includes a sensor bias 50a that applies a bias voltage to the thermal resistance sensor HR, an amplifier (Amp) 50b that amplifies the detection signal of the thermal resistance sensor HR, a low-pass filter (LPF) 50c, and a high-pass filter 50d. The sensor bias 50a and amplifier 50b may be configured within the head amplifier IC 30. The inspection circuit 46d includes an amplifier (Amp) 50e that amplifies the output signal of the low-pass filter 50c, an AD converter (ADC) 50f, a comparator 50g that compares the output signal of the amplifier 50e with a wide defect threshold Th1, and a counter 50h that counts the output signal of the comparator 50g. The inspection circuit 46d further includes a low-pass filter (LPF) 50i subsequent to the high-pass filter 50d, an amplifier (Amp) 50j, an AD converter (ADC) 50k, a comparator 50m that compares the output signal of the amplifier 50j with a narrow defect threshold Th2, and a counter 50n that counts the output signal of the comparator 50m.

[0030] Next, we will explain how the HDD 10 configured as described above detects defects (protrusions or recesses) on the surface of the magnetic disk 12 and sets write-prohibited tracks or write-prohibited sectors. The HDD 10 performs defect detection and write-prohibited track setting before shipping, periodically, or after each recording operation.

[0031] FIG. 7 is a diagram showing the output of the thermal resistance sensor when it comes into contact with a protrusion on the recording medium, and FIG. 8 is a diagram showing the output of the thermal resistance sensor when it passes over a depression on the recording medium. 7, if a protrusion higher than the flying height d1 of the thermal resistance sensor HR is present on the surface of the magnetic disk 12, the thermal resistance sensor HR will collide with the protrusion as it passes over it, causing the resistance value of the thermal resistance sensor HR to change, i.e., to decrease. As a result, the output waveform of the thermal resistance sensor HR will have a lowered portion corresponding to the contact area R1.

[0032] 8, if a depression occurs 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. As a result, the output waveform of the thermal resistance sensor HR has a rising portion corresponding to the passing region R2 above the depression. Therefore, by observing and analyzing the output waveform of the thermal resistance sensor HR while moving the magnetic head 16 along each track of the magnetic disk 12, it is possible to detect the presence or absence of protrusions or dents on the surface of the magnetic disk 12 and determine whether they are protrusions or dents. That is, 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 or dents on the surface of the magnetic disk 12, determine whether they are protrusions or dents, and detect the positions of the protrusions and dents.

[0033] Figure 9 is a diagram showing a schematic diagram of the relationship between the thermal resistance sensor HR, the recording track, and the protrusion. If a protrusion is determined to exist, the main controller 40 sets the track on which the protrusion exists as a write-inhibit track, as shown in Figure 9. After the setting, the main controller 40 prohibits recording operations on the write-inhibit track, i.e., prohibits the magnetic head 16 from accessing the write-inhibit track. This prevents the magnetic head 16 from colliding with the protrusion on the disk surface after the write-inhibit track has been set.

[0034] On the other hand, to increase the recording density of a magnetic disk drive, it is necessary to increase the number of recording tracks formed on the recording medium, which means that the track width Wt of each recording track becomes narrower. In this case, if protrusions of the same size exist on the recording medium, the number of write-prohibited tracks will increase. Furthermore, as the number of recording tracks increases, it will take more time to inspect all of the recording tracks. Therefore, the HDD according to this embodiment is configured to shorten the time required to inspect the magnetic disk 12 for defects.

[0035] 9, the width W3 of the thermal resistance sensor HR mounted on the magnetic head 16 is set to a width spanning 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 set to, for example, 0.05 μm, so that multiple recording tracks are present below the thermal resistance sensor HR. As shown in Figures 1 and 4, the thermal resistance sensor HR, recording head 58, and read head 54 of the magnetic head 16 are arranged side by side on a central axis C1 that passes through the center of the bearing portion 24 of the carriage assembly 20 and the center of the magnetic head 16.

[0036] Fig. 10 is a diagram showing the positional relationship between a recording track during recording, a reproduction element, a recording element, and a thermal resistance sensor. Fig. 11 is a diagram showing the positional relationship between a recording track during reproduction, a reproduction element, a recording element, and a thermal resistance sensor. 10 shows the relative positions of the read head 54, thermal resistance sensor HR, and write head 58 when the carriage assembly 20 in the HDD 10 is rotated by the VCM 22 and, for example, the magnetic head 16 moves near the outer periphery of the magnetic disk 12. In the figure, the angle θ formed between the recording track and the central axis C1 of the head unit 17 indicates the yaw angle. The read head 54 is positioned on recording track n, and the write head 58 is located on recording track n-3. When setting write-inhibit tracks, the relative positions of the write head and read head must be taken into consideration.

[0037] Figure 11 shows the magnetic head 16 positioned at a different radial position than in Figure 10. As shown, the write head 58 is positioned over the same recording track n, but the read head 54 is positioned over recording track n+3. By determining in advance the relative positions of the write head 58, read head 54, and thermal resistance sensor HR corresponding to the radial position of the magnetic head 16 and storing them in memory 47, it is possible to know the approximate relative positions of the write head 58 and read head 54 and the protrusion detection position. This makes it possible to set write-inhibit tracks that reflect the above-mentioned relative positions.

[0038] It is also necessary to know the yaw angle θ corresponding to the radial position of the magnetic head 16. As shown in Fig. 1, the yaw angle θ can be uniquely determined from 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. Fig. 12 shows an example of calculating the yaw angle θ corresponding to the radial position of the magnetic head.

[0039] 13 is a plan view showing an example of ideal write-prohibited tracks, in which the hatched tracks correspond to write-prohibited tracks. As shown in the figure, if a surface protrusion exists across three recording tracks n-1, n, and n+1, recording tracks n-5 to n+5, including the four outermost tracks and the four innermost tracks, are set as write-inhibited tracks. This prevents the write head 58 and read head 54 from coming into contact with the surface protrusion, even when the write head 58 is positioned on recording track n-6. Furthermore, even when the read head 54 is positioned on recording track n+6, the write head 58 will not come into contact with the surface protrusion. However, since there is a limit to how accurately the size of the surface protrusions can be measured in track units, it is desirable to set a write-protect track with a margin of one to two tracks.

[0040] FIG. 14A is a diagram showing the positional relationship between the width (when wide) of the thermal resistance sensor and the element part, and FIG. 14B is a diagram showing the positional relationship between the width (when narrow) of the thermal resistance sensor and the element part. As shown in the figure, when the yaw angle θ becomes large (maximum yaw angle), depending on the width W3 of the thermal resistance sensor HR, the write head 58 and read head 54 may move out of the range of the width W3 of the thermal resistance sensor HR. As shown in FIG. 14A, when the width W3 of the thermal resistance sensor HR is wide, the write head 58 and read head 54 are within the range of the width W3 of the thermal resistance sensor HR in the circumferential direction of the track. As shown in FIG. 14B, when the width W3 of the thermal resistance sensor HR is narrow, the write head 58 moves out of the range of the width W3 of the thermal resistance sensor HR in the circumferential direction of the track. Therefore, it is desirable to know the positions of the write head 58 and read head 54 relative to the recording track detected by the thermal resistance sensor HR.

[0041] FIG. 15 is a diagram showing a schematic diagram of 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. As shown in the figure, if the thermal resistance sensor HR is used to detect defects on all recording tracks, for example, if a surface protrusion is located on recording tracks n-1, n, and n+1, the sensor output of the thermal resistance sensor HR when detecting each recording track will be as shown in the figure on the right. That is, when the thermal resistance sensor HR passes over or near the surface protrusion, the resistance of the thermal resistance sensor HR increases, causing the sensor output to decrease. The number of recording tracks on which the center of the surface protrusion is located and the number of recording tracks detected by the thermal resistance sensor HR is calculated by adding the width W3 of the thermal resistance sensor HR to the width of the surface protrusion. In the example shown, the center of the defect detection position is shifted by the distance between the read head 54 and the thermal resistance sensor HR, taking into account the yaw angle θ. It is possible to accurately estimate such geometric errors. Because the number of contacts between the write head 58 and the read head 54 and the surface protrusion increases, it is desirable to set the write-protected tracks with a margin of one to two tracks, as mentioned above.

[0042] In the HDD according to this embodiment, the above points are taken into consideration when detecting surface defects and setting write-prohibited tracks or write-prohibited sectors. 16, 17 and 18 are plan views respectively showing the operation of detecting defects (protrusions or recesses) on the surface of the magnetic disk 12 and the operation of setting write-prohibited tracks or write-prohibited sectors in the HDD according to this embodiment.

[0043] According to this embodiment, in order to shorten the time required for defect inspection, the thermal resistance sensor HR does not inspect each recording track for defects, but instead simultaneously inspects a bundle of multiple recording tracks covered by the width W3 of the thermal resistance sensor HR, as shown in Fig. 16. In the illustrated example, the width W3 of the thermal resistance sensor HR is set to a width equivalent to approximately seven tracks. The thermal resistance sensor HR simultaneously inspects ±3 tracks around the positioned recording track.

[0044] In one example, the thermal resistance sensor HR starts inspection from the outermost recording tracks 0 to 6, and moves radially (in the width direction of the recording tracks) by a predetermined feed pitch (feed width), for example, a number of tracks, each time the magnetic disk 12 makes at least one revolution, to inspect the next batch of recording tracks. The inspection circuit 46d of the controller 40 detects the presence or absence of a surface defect and the location of the surface defect (here, a surface protrusion) based on the sensor output of the thermal resistance sensor HR, and further determines whether the defect is a protrusion or a recess. When a protrusion is detected, the controller 40 determines that a protrusion exists in the shaded area in FIG. 16 (e.g., tracks 2 to 9, sectors 10 and 11), and registers the area in the memory 47.

[0045] Next, as shown in FIG. 17, the controller 40 moves the magnetic head 16 radially (in the track width direction) inward by a predetermined feed pitch (for example, three tracks, which corresponds to half the track equivalent width of the thermal resistance sensor HR), and performs defect detection on the recording tracks 6 to 11 using the thermal resistance sensor HR. 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 half the third width W3 of the thermal resistance sensor HR and equal to or greater than three recording tracks. In this embodiment, as an example, the feed pitch is set to a track width of three tracks.

[0046] 18, the controller 40 repeatedly moves the magnetic head 16 in the radial direction by three tracks each time the magnetic disk 12 makes one rotation, thereby identifying recording tracks where surface protrusions may exist. After inspecting all recording tracks, the controller 40 sets the detected recording tracks where surface protrusions may exist as write-inhibit tracks and registers the set write-inhibit tracks in memory 47. The write-inhibit tracks can be set in consideration of the relative positions of the write head 58, read head 54, and thermal resistance sensor HR. In normal recording operations, the controller 40 prohibits information from being recorded on the registered write-prohibited tracks, i.e., prohibits the magnetic head 16 from accessing the write-prohibited tracks. This prevents the magnetic head 16 from colliding with protrusions on the surface of the magnetic disk 12.

[0047] According to the HDD of the present embodiment described above, for example, if the total number of tracks is 600,000 and the rotation speed of the recording medium is 7,200 rpm, and a thermal resistance sensor with a width of 1 μm is used to simultaneously inspect a number of recording tracks equivalent to 70% of the width for defects, all of the recording tracks can be inspected in approximately 12 minutes. In contrast, when inspecting each track one by one using the conventional method, assuming that it takes one rotation for inspection and one rotation for track movement, it takes approximately 160 minutes to inspect all of the recording tracks on one side of the recording medium for defects.

[0048] As described above, the HDD according to this embodiment can significantly reduce the time required to inspect the surface of a magnetic disk for defects, enabling defect inspection and write-prohibited track setting to be completed in a short time. As a result, this embodiment can provide a magnetic disk drive that prevents damage to the magnetic head due to defects on the recording medium and has improved reliability.

[0049] Next, an HDD according to another embodiment will be described. In the following description of the other embodiment, the same parts as those in the first embodiment will be assigned the same reference numerals, and detailed descriptions thereof will be omitted or simplified. The following description will focus on the parts that are different from the first embodiment.

[0050] (Second embodiment) 19, 20 and 21 are plan views respectively showing the operation of detecting defects (protrusions or recesses) on the surface of the magnetic disk 12 and the operation of setting write-prohibited tracks or write-prohibited sectors in the HDD according to the second embodiment. In the first embodiment described above, in the defect inspection of the magnetic disk surface, the magnetic head is moved in the track width direction by a predetermined feed pitch (three tracks) every time the magnetic disk makes one revolution. That is, in the first embodiment, one revolution is required for the defect inspection and one revolution is required for the track movement of the magnetic head.

[0051] In contrast, in the HDD according to the second embodiment, as shown in Figures 19, 20, and 21, when inspecting the magnetic disk surface for defects, the controller 40 inspects the recording tracks for defects while continuously moving the magnetic head 16 in the radial direction (track width direction) by a predetermined feed pitch, for example, by three tracks, while the magnetic disk 12 makes one revolution. In other words, the controller 40 inspects the recording tracks for defects while moving the magnetic head 16 in a spiral relative to the surface of the magnetic disk 12, as shown by the dashed line in the figures. That is, according to the second embodiment, the defect inspection and the radial movement of the magnetic head are configured to proceed simultaneously.

[0052] According to the second embodiment configured as described above, by moving the magnetic head in a spiral shape, the time for the magnetic head to move between tracks can be reduced. According to the second embodiment, the inspection time in the above-described first embodiment can be further shortened, and it becomes possible to perform defect inspection in about 6 minutes. For example, in the case of an HDD with 10 magnetic disks (recording media) mounted, the surface of the recording media to be defect-inspected is 20 surfaces. In the conventional HDD, it takes 3200 minutes for defect inspection, whereas in the HDD according to the second embodiment, the inspection time can be shortened to 120 minutes. According to the HDD according to the second embodiment, the defect inspection time on the surface of the magnetic disk can be further shortened, and it becomes possible to perform defect inspection and setting of a recording prohibited track in a shorter time. Thereby, according to the present embodiment, it is possible to prevent damage to the magnetic head due to defects on the recording media and provide a disk device with improved reliability.

[0053] The positional 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 the first embodiment described above, and can be variously changed. (First Modified Example) FIG. 22A is a diagram showing the positional relationship between the thermal resistance sensor and the element part of the magnetic head according to the first modified example. As shown in the figure, according to the first modified example, the thermal resistance sensor HR of the magnetic head 16 is disposed at a position close to the side of 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 along the direction parallel to the central axis C1 are set such that D1 < D2. When the recording track width is 0.05 μm, the width W3 of the thermal resistance sensor HR is set to a sufficiently wide width of about 1 μm. That is, the width W3 of the thermal resistance sensor HR is sufficiently wider than the width W1 of the tip of the write head 58, and is set to several times the width W1, for example, about 20 times.

[0054] (Second Modified Example) FIG. 22B is a diagram showing 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 side of the light head 58. That is, the distance D1 between the light head 58 and the thermal resistance sensor HR, and the distance D2 between the lead head 54 and the thermal resistance sensor HR along the direction parallel to the central axis C1 are set such that D1 < D2. When the recording track width is 0.05 μm, the width W3 of the thermal resistance sensor HR is set to a narrow width of about 0.5 μm. That is, the width W3 of the thermal resistance sensor HR is wider than the width W1 of the tip of the light head 58, and is set to several times the width W1, for example, about 10 times.

[0055] (Third modification) FIG. 23A is a diagram showing the positional relationship between the thermal resistance sensor and the element portion of the magnetic head according to the third modification. As shown in the figure, according to the third modification, the distance D1 between the light head 58 and the thermal resistance sensor HR, and the distance D2 between the lead head 54 and the thermal resistance sensor HR along the direction parallel to the central axis C1 are set such that D1 > D2. The thermal resistance sensor HR is arranged at a position where the center in the width direction is separated (shifted) from the central axis C1 in the width direction orthogonal to the central axis. When the recording track width is 0.05 μm, the width W3 of the thermal resistance sensor HR is set to a wide width of about 1 μm. That is, the width W3 of the thermal resistance sensor HR is wider than the width W1 of the tip of the light head 58, and is set to several times the width W1, for example, about 20 times. The light head 58 and the lead head 54 are positioned overlapping the thermal resistance sensor HR in the track circumferential direction.

[0056] (Fourth modification) 23B is a diagram showing the positional relationship between the thermal resistance sensor and the element portion of a magnetic head according to a fourth modified example. As shown in the figure, according to the fourth modified example, the distance D1 between the write head 58 and the thermal resistance sensor HR along the direction parallel to the central axis C1, and the distance D2 between the read head 54 and the thermal resistance sensor HR are set so that D1 > D2. The thermal resistance sensor HR is positioned so that its center in the width direction is shifted from the central axis C1 in the width direction. When the recording track width is 0.05 μm, the width W3 of the thermal resistance sensor HR is set to a narrow width of about 0.5 μm. That is, the width W3 of the thermal resistance sensor HR is wider than the width W1 of the tip of the write head 58, and is set to be several times, for example, about 10 times, the width W1. The write head 58 and the read head 54 are positioned so as to overlap the thermal resistance sensor HR in the circumferential direction of the track. When any of the magnetic heads of the first to fourth modified examples configured as above is used, the same effects as those of the first embodiment described above can be obtained.

[0057] Although several embodiments and modifications of the present invention have been described, these embodiments and modifications are presented as examples and are not intended to limit the scope of the invention. These embodiments and modifications 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 modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims. For example, the feed pitch of the magnetic head 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 at least three recording tracks. By widening the feed pitch, the defect inspection time can be further reduced. The materials, shapes, sizes, etc. of the elements that make up the head portion of the magnetic head can be changed as needed. In a magnetic disk drive, the number of magnetic disks and magnetic heads can be increased or decreased as needed, and various sizes of magnetic disks can also be selected. [Explanation of symbols]

[0058] 10...magnetic disk device, 11...casing, 12...magnetic disk, 13...ABS, 15: slider; 16: magnetic head; 17: head portion; 18: head actuator; 30...head amplifier IC, 40...main controller, 46d...inspection circuit, 54...read head, 58...write head, 76a...first heater, 76b...second heater, HR...thermal resistance sensor

Claims

1. a rotatable disk-shaped recording medium having a plurality of concentric recording tracks; a magnetic head including a recording element having a first width in a direction intersecting the recording track, a reproducing element having a second width in a direction intersecting the recording track, and a thermal resistance sensor having a third width in a direction intersecting the recording track that is wider than the first width and the second width, and that detects a surface condition of the recording medium; a head actuator for positioning the magnetic head on 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; a controller that sets a feed pitch of the magnetic head in the width direction of the recording track to within half of a third width of the thermal resistance sensor and to at least three recording tracks when inspecting the surface condition of the recording medium with the thermal resistance sensor; A magnetic disk device comprising:

2. 2. The magnetic disk drive of claim 1, wherein when inspecting the surface condition of the recording medium, the controller drives the head actuator to move the magnetic head in the feed pitch direction within 1 / 2 of the third width of the thermal resistance sensor and by at least three tracks each time the recording medium rotates once.

3. 2. The magnetic disk drive of claim 1, wherein when inspecting the surface condition of the recording medium, the controller drives the head actuator to continuously move the magnetic head in the feed pitch direction within 1 / 2 of the third width of the thermal resistance sensor and for three or more tracks while the recording medium makes one rotation.

4. 2. The magnetic disk drive of claim 1, wherein the recording element and the reproducing element are arranged side by side and spaced apart in a first direction intersecting the recording track, and the thermal resistance sensor is arranged side by side with the recording element and the reproducing element in the first direction and is located between the recording element and the reproducing element.

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

6. the centers in the width direction of the recording element and the reproducing element are each located on a central axis extending in the first direction, 5. The magnetic disk drive according to claim 4, wherein the center of the thermal resistance sensor in the width direction is positioned away from the central axis in a direction perpendicular to the central axis.

7. 2. The magnetic disk drive according to claim 1, wherein the magnetic head includes a thermal actuator.

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