Magnetic disk drive

Abstract

To provide a magnetic disk device capable of suppressing performance deterioration caused by minute projections on a recording medium.SOLUTION: According to an embodiment, a magnetic disk device includes a magnetic head including a rotatable disk-shaped recording medium having a plurality of recording tracks, a write element which writes information to the recording tracks, a heating element, and a sensor which detects a surface state of the recording medium, and a controller including an inspection circuit which detects presence or absence of a bump on a surface of the recording medium and a height and a width of the bump based on a sensor output of the sensor, and a memory which records the detected height and width of the bump.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 a magnetic disk device, in order to improve 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 such as minute scratches and sputter flakes that occur during the manufacturing process of the recording medium, such as minute protrusions (bumps) with a height of about 1 to 8 nm. When a magnetic head runs over the recording surface with a minute 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.

[0003] Therefore, a defect scan of the recording surface is performed using an HDI (head-disk interface) sensor to check in advance for tracks with bumps, and write-prohibited tracks (track slips) are set around the bumps. In this case, the more bumps there are on the recording surface of the recording medium, the greater the number of track slips, and the less recording capacity the recording medium will have.

[0004] Furthermore, if a bump is present in the magnetic head's seek area, the magnetic head's flying height is first increased, then the seek operation begins. Once the magnetic head has completely passed the bump, the flying height of the magnetic head is lowered. Therefore, if there are many bumps on the recording medium, the cooling wait time for the magnetic head's flying height adjustment increases. This slows down magnetic information processing and causes a decrease in read / write performance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-243310 [Patent Document 2] U.S. Patent No. 9,368,152 [Patent Document 3] US Patent Application Publication No. 2023 / 0282231 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of an embodiment of the present invention is to provide a magnetic disk drive that can suppress performance degradation caused by minute protrusions on a recording medium. [Means for solving the problem]

[0007] 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 write element for writing information to the recording tracks, a heating element, and a sensor for detecting the surface condition of the recording medium, a detection circuit for detecting the presence or absence of bumps on the surface of the recording medium, and the width and height of the bumps based on the sensor output of the sensor, and a controller including a memory for recording the width and height of the detected bumps. [Brief explanation of the drawings]

[0008] [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 diagram showing the output of a thermal resistance sensor when it comes into contact with a protrusion on a recording medium. [Figure 7] FIG. 7 is a diagram showing the relationship between the height of minute protrusions (bumps) on a recording medium and the number of track slips. [Figure 8] FIG. 8 is a diagram schematically showing a magnetic disk and a magnetic head in an HDD according to a second embodiment. [Figure 9] FIG. 9 is a diagram schematically showing a magnetic disk and a magnetic head in an HDD according to a third embodiment. [Figure 10] FIG. 10 is a schematic plan view of a magnetic disk and a magnetic head in an HDD according to a fourth embodiment. [Figure 11] FIG. 11 is a flowchart showing a seek operation in an HDD according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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.

[0010] (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.

[0011] 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.

[0012] 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.

[0013] 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, an inspection circuit 46d, a determination circuit 46e, etc. As will be described later, the inspection circuit 46d inspects the presence and size of minute protrusions (bumps) on the surface of the magnetic disk 12 based on the sensor output of the magnetic head 16. A memory 47 stores various data such as the height and width of the bumps, write-prohibited tracks, write-prohibited sectors, and heater power setting values, which are the inspection results.

[0014] As shown in FIGS. 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). A soft magnetic layer 102 made of a material exhibiting soft magnetic properties, a 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 on the upper and lower surfaces of the substrate 101. A plurality of magnetic disks 12, for example, ten magnetic disks 12, are provided. The plurality of magnetic disks 12 are coaxially fitted to the hub of a spindle motor 14. The magnetic disks 12 are 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 of the recording tracks T1 to Tn includes a plurality of sectors aligned in the circumferential direction.

[0015] 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.

[0016] 2, the magnetic head 16 is configured as a floating-type head and includes a slider 15 formed in a substantially rectangular parallelepiped shape and a head portion 17 formed at the end of the slider 15 on the trailing end 15b side. The slider 15 is formed, for example, from a sintered body (AlTiC) of alumina and titanium carbide, and the head portion 17 is formed from multiple thin films. The slider 15 is attached to a gimbal portion 28a of a wiring member 28.

[0017] 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 an air flow C that is 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 rotation 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 rotation direction B of the disk.

[0018] 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 has 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 exposed to the ABS 13 of the slider 15. 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 refers to the presence or absence of defects (microprotrusions or recesses) on the magnetic disk surface, as well as the height and width of the microprotrusions (bumps), as will be described later.

[0019] The longitudinal direction (circumferential direction) of the recording track formed on the magnetic recording layer 103 of the magnetic disk 12 is defined as the track 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 track direction DT, sandwiching the magnetoresistive element 55 therebetween. The magnetoresistive element 55 and the first and second magnetic shielding films 56, 57 extend approximately 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] The first thermal actuator has a heating element, for example, heater 76a. Heater 76a is embedded in the protective insulating film 53 and is located near the write head 58. The second thermal actuator has a heating element, for example, heater 76b. 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. The thermal resistance sensor HR is used as an example of an HDI (head-disk interface) sensor.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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 of the magnetic head 16 in the longitudinal direction (track direction DT). 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. In one example, the third width W3 is greater than the first width W1 and greater than the second width W2.

[0029] The track width Wt (see FIG. 7) 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 wider than the first width W1, and is set to, for example, several times the width W1.

[0030] 5 is a schematic side view of the magnetic head 16 and head portion 17 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 G (head flying height) between the write head 58 and the surface of the magnetic disk 12.

[0031] Next, we will explain the operation of detecting small protrusions (bumps) on the surface of the magnetic disk 12 and setting write-prohibited tracks or write-prohibited sectors in the HDD 10 configured as described above. The HDD 10 performs bump detection and write-prohibited track setting, for example, after manufacturing, before shipping, or periodically.

[0032] FIG. 6 is a diagram showing a schematic diagram of the output of the thermal resistance sensor when it comes into contact with a protrusion on the recording medium. As shown in Figure 6, if a protrusion (bump) higher than the flying height d1 of the thermal resistance sensor HR occurs on the surface of the magnetic disk 12, the thermal resistance sensor HR will collide with the protrusion as it passes over the protrusion, causing a change in the resistance value of the thermal resistance sensor HR, i.e., a decrease in the resistance value. As a result, the output waveform of the thermal resistance sensor HR will have a lowered portion corresponding to the contact area R1. From the output waveform, the width of the contact area R1 with the protrusion, i.e., the width of the protrusion, can be determined. The height of the protrusion can also be calculated based on the flying height (G or d1) of the magnetic head 16 when the thermal resistance sensor HR collides with the protrusion. As shown in FIG. 6, in this embodiment, the height of the protrusion (bump) is height h in the direction perpendicular to the surface of the magnetic disk 12, and the width of the protrusion (bump) is width W in the track direction.

[0033] In the bump detection operation, the controller 40 scans all tracks T1 to Tn of the magnetic disk 12 with the magnetic head 16 while sequentially changing the flying height of the magnetic head 16. In one example, if the flying height of the magnetic head 16 during normal recording is set to a specified value (e.g., 1 nm), bumps are detected by scanning all tracks T1 to Tn with a flying height smaller than the specified value, e.g., 0.7 nm. Next, bumps are detected by scanning all tracks T1 to Tn with the flying height of the magnetic head 16 set to 1 nm. Subsequently, bumps are detected by scanning all tracks T1 to Tn while increasing the flying height of the magnetic head 16 by 0.3 nm each time. Finally, when a flying height at which no fluctuations in the output of the thermal resistance sensor HR occur is reached, i.e., when a flying height at which bumps are not detected is reached, the detection operation of the magnetic head surface is terminated.

[0034] 1, the sensor output of the thermal resistance sensor HR is amplified by the head amplifier 30 and then sent to the inspection circuit 46d of the main controller 40. Based on the sensor output of the thermal resistance sensor HR, the inspection circuit 46d calculates the position (track), width, and height of bumps present on the surface of the magnetic disk 12. The main controller 40 stores and registers the calculated bump data in the memory 47. In one example, the memory 47 stores a data table indicating the position, height, and width of bumps on each track.

[0035] FIG. 7 is a plan view showing a schematic relationship between the height (large or small) of bumps B located on the tracks of the magnetic disk 12 and the number of write-inhibit tracks (track slips). The determination circuit 46e of the MPU 46 determines the height of the bumps B on each of the tracks T1 to Tn based on the bump data registered in the memory 47, sets write-inhibit tracks Tp in number corresponding to the height of the bumps B, and registers them in the memory 47.

[0036] 7, for a bump B that is low in height (low), for example, 0 to 1 nm, the decision circuit 46e sets five tracks including the bump B as write-inhibit tracks (track slip) Tp. A total of five write-inhibit tracks Tp are set, two on the inner periphery and two on the outer periphery, with the track where the bump B is located at the center. For bump B with a medium height (e.g., 1 to 5 nm), the determination circuit 46e sets 11 tracks including the bump B as write-inhibit tracks (track slip) Tp. A total of 11 write-inhibit tracks Tp are set, five on the inner periphery and five on the outer periphery, with the track where the bump B is located at the center. For bumps B that are high (high), for example, 5 nm or higher, the determination circuit 46e sets 17 tracks including the bumps B as write-inhibit tracks (track slips) Tp. A total of 11 write-inhibit tracks Tp are set, five on the inner periphery and five on the outer periphery, centered around the track where the bump B exists. The number of write-prohibited tracks is not limited to the above example, and can be increased or decreased as needed. The number of write-prohibited tracks can be determined according to the height of the bumps, and the number of write-prohibited tracks can be set so that the higher the bump height, the greater the number of write-prohibited tracks. Furthermore, the threshold values ​​for the bump height, low, medium, and high are not limited to the above example, and can be changed as needed.

[0037] When the HDD 10 is in operation, the main controller 40 performs a data recording operation on the recording tracks T other than the write-inhibit tracks Tp registered in the memory 47. After setting the write-inhibit tracks Tp, the main controller 40 prohibits recording operations on the write-inhibit tracks Tp, i.e., prohibits the magnetic head 16 from accessing the write-inhibit tracks Tp. After setting the write-inhibit tracks Tp, the magnetic head 16 will not come into contact with or collide with bumps B on the disk surface. This prevents damage to the magnetic head and magnetic disk and improves reliability.

[0038] According to the first embodiment configured as described above, the position, width, and height of minute protrusions (bumps) on the surface of the recording medium are detected, and bump data including the detected bump height is stored and registered in memory 47. This makes it possible to apply the bump height data to various controls, thereby improving the recording density and reliability of the HDD. According to the first embodiment, the number of write-prohibited tracks (track slips) is set according to the height of the bump. Specifically, the higher the bump height, the more write-prohibited tracks are set, and the lower the bump height, the fewer write-prohibited tracks are set. As a result, according to this embodiment, the number of write-prohibited tracks can be reduced by approximately 60 to 75% compared to when a common maximum number of write-prohibited tracks is set for all bumps, and as a result, it is possible to prevent a decrease in the recording capacity of the disk drive. As described above, according to this embodiment, it is possible to provide a magnetic disk drive that can suppress performance degradation (reduction in recording capacity) caused by minute protrusions on the recording medium.

[0039] 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 parts that are different from the first embodiment.

[0040] (Second embodiment) FIG. 8 is a diagram schematically showing a magnetic disk and a magnetic head in an HDD according to the second embodiment. As in the first embodiment, the main controller 40 of the HDD 10 detects minute protrusions (bumps) on the surfaces of the magnetic disks 12, and stores and registers bump data including the height, width, and position of the bumps in the memory 47. The main controller 40 determines the height of the bumps, and sets, for each magnetic disk 12, a number of write-inhibit tracks Tp corresponding to the height of the bumps B.

[0041] 8, for example, if the height of bumps B on the surface of the intermediate magnetic disk 12 is higher than an arbitrary specified value, for example, 5 nm, the main controller 40 sets write-inhibit tracks Tp on the intermediate magnetic disk 12 in a number corresponding to the height of the bumps B. At the same time, the main controller 40 sets multiple tracks located at the same radial position as the write-inhibit track Tp as write-inhibit tracks Tp on the surfaces of all other magnetic disks 12, and registers these in the memory 47. This results in a configuration in which access to and recording operations on write-inhibit tracks Tp located at the same radial position are prohibited for all magnetic disks 12 and all magnetic heads 16.

[0042] According to the second embodiment described above, even when writing / reading to a magnetic disk other than a magnetic disk having bumps higher than a specified value, the magnetic head does not remain on the write-protect track Tp. This makes it possible to more reliably prevent contact or collision between the bumps B higher than the specified value and the magnetic head 16. When writing / reading to a magnetic disk other than a magnetic disk having high bumps, collision between the bumps and the magnetic head is suppressed, and vibrations caused by the collision are prevented from degrading the write / read quality. In the second embodiment, the other configurations of the HDD are the same as those of the HDD according to the first embodiment.

[0043] (Third embodiment) FIG. 9 is a diagram schematically showing a magnetic disk and a magnetic head in an HDD according to the third embodiment. As in the first embodiment, the main controller 40 of the HDD 10 detects minute protrusions (bumps) on the surfaces of the magnetic disks 12, and stores and registers bump data including the height, width, and position of the bumps in the memory 47. The main controller 40 determines the height of the bumps, and sets, for each magnetic disk 12, a number of write-inhibit tracks Tp corresponding to the height of the bumps B.

[0044] As shown in Figure 9, for example, if the height of bump B on the surface of the intermediate magnetic disk 12 is higher than an arbitrary specified value, for example, 5 nm, the main controller 40 head-skips the magnetic head 16(X) corresponding to the magnetic disk surface on which bump B exists, i.e., prohibits the use of the magnetic head 16(X). In the third embodiment, the other configurations of the HDD are the same as those of the HDD according to the first embodiment described above.

[0045] According to the third embodiment described above, the quality of the magnetic disk drive can be guaranteed by not using a magnetic head that carries the risk of degrading recording quality due to a collision.

[0046] (Fourth embodiment) Fig. 10 is a plan view schematically showing a magnetic disk and a magnetic head in an HDD according to the fourth embodiment, and Fig. 11 is a flowchart showing the operation during head seek in the HDD according to the fourth embodiment. As in the first embodiment, the main controller 40 of the HDD 10 detects minute protrusions (bumps) on the surfaces of the magnetic disks 12, and stores and registers bump data including the height, width, and position of the bumps in the memory 47. The main controller 40 determines the height of the bumps, and sets, for each magnetic disk 12, a number of write-inhibit tracks Tp corresponding to the height of the bumps B.

[0047] According to the fourth embodiment, the HDD 10 is configured to control the seek operation of the magnetic head 16 in accordance with the height of the bump B. As shown in FIGS. 10 and 11, when the magnetic head 16 seeks from the seek start sector SS to the target sector TS, the MPU 46 of the main controller 40 receives a seek command SS to TS (ST1), reads the bumps B1 and B2 present in the seek section SD (S1-S2) from the memory 47, and inputs the bump information (heights of B1 and B2) to the determination circuit 46e (ST2). The determination circuit 46e pre-measures the flying height FH of the magnetic head 16 at the seek start sector SS (ST3). The determination circuit 46e compares the measured flying height FH with the input heights of the bumps B1 and B2 (ST4) to determine whether there are any bumps that affect the control of the flying height FH.

[0048] If the heights of all bumps B1 and B2 in the seek section SD are lower than the flying height FH of the magnetic head 16, the determination circuit 46e determines that there are no bumps that affect the control of the flying height FH. In this case, the MPU 46 starts the seek operation of the magnetic head 16 without changing the drive voltage of the heaters 76a and 76b, i.e., without changing the flying height FH of the magnetic head 16 (ST5). The MPU 46 ends the seek operation when the magnetic head 16 reaches the target sector TS via the R / W preparation sector RS (ST6). The R / W preparation sector RS is located adjacent to the target sector TS on the same track as the target sector TS and upstream of it.

[0049] On the other hand, if there are bumps higher than the flying height FH of the magnetic head 16 in step ST4, the determination circuit 46e determines that there are bumps that affect the control of the flying height FH. In this case, the MPU 46 adjusts the heater drive voltage according to the difference between the flying height FH and the heights of the bumps B1 and B2 (ST7). That is, the MPU 46 reduces the heater drive voltage so that the flying height FH of the magnetic head 16 is higher than the bump height. Note that the adjustment amount of the heater drive voltage is not uniform, but varies depending on the bump height. The determination circuit 46e compares the changed flying height FH with the height of bumps B1 and B2 (ST8), and determines that seeking can begin when flying height FH is higher. The MPU 46 starts the seek operation of the magnetic head 16 based on the determination result of the determination circuit 46e (ST9). The MPU 46 ends the seek operation when the magnetic head 16 passes through the R / W preparation sector RS and reaches the target sector TS (ST10). Furthermore, when the magnetic head 16 has completely passed over bumps B1 and B2, the MPU 46 increases the heater drive voltage to the target value and begins to lower the flying height FH of the magnetic head 16 to the target value (ST11).

[0050] In the fourth embodiment, the other configurations of the HDD are the same as those of the HDD according to the first embodiment. According to the fourth embodiment having the above configuration, the seek operation is controlled according to the height of the bumps present in the seek section of the magnetic head, thereby shortening the time required for the seek operation and improving read / write performance. According to this embodiment, the height of the bumps present in the seek section is compared with the current flying height of the magnetic head, and if it is determined that all the bumps are lower than the flying height, the seek operation can be performed without changing the heater power supply voltage, i.e., without adjusting the flying height of the magnetic head. This eliminates the need for a cooling wait time when adjusting the flying height, and allows for faster seek processing.

[0051] Furthermore, if it is determined that there is a bump that is higher than the flying height of the magnetic head, the heater power supply voltage and cooling time can be adjusted according to the difference between the flying height and the bump height, thereby making it possible to set the minimum necessary voltage adjustment amount and cooling time. Therefore, even in this case, the seek processing time can be shortened. As described above, according to this embodiment, it is possible to provide a magnetic disk drive that can suppress performance degradation caused by minute protrusions on the recording medium.

[0052] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments are included within the scope and spirit of the invention, as well as within the scope of the inventions described in the claims and their equivalents. For example, the number of write-prohibited tracks set according to the height of the bumps is not limited to the above-described embodiment, and can be increased or decreased as necessary. The above-described embodiment can also be applied to HDDs that use a shingled recording method. 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 device, the number of magnetic disks and the number of magnetic heads can be increased or decreased as needed. Various sizes of magnetic disks can be selected. [Explanation of symbols]

[0053] 10...magnetic disk device, 11...casing, 12...magnetic disk, 15...slider, 16...magnetic head, 17...head unit, 18...head actuator, 30...head amplifier IC, 40...main controller, 46d...inspection circuit, 46e...determination circuit, 54...read head, 58...write head, 76a...first heater, 76b...second heater, HR...thermal resistance sensor, T1 to Tn...recording track, Tp: Record-protected track, B, B1, B2: Bump

Claims

1. a rotatable disk-shaped recording medium having a plurality of concentric recording tracks; a magnetic head including a write element for writing information onto the recording track, a heating element, and a sensor for detecting the surface condition of the recording medium; a controller including an inspection circuit that detects the presence or absence of bumps on the surface of the recording medium, and the height and width of the bumps based on the sensor output of the sensor, and a memory that records the height and width of the detected bumps; A magnetic disk device comprising:

2. the controller sets the track on which the bump exists and several tracks located on both sides of the track in the radial direction as recording-prohibited tracks and registers them in the memory; 2. The magnetic disk drive according to claim 1, wherein the number of write-protected tracks varies depending on the height of the bump.

3. the controller has a determination circuit for determining the height of the bump registered in the memory, 3. The magnetic disk drive according to claim 2, wherein the controller increases the number of write-inhibit tracks set around the bump as the height of the bump determined by the determination circuit increases.

4. the controller has a determination circuit for determining the height of the bump registered in the memory, 2. The magnetic disk drive according to claim 1, wherein, when the determination circuit determines that a bump is higher than a specified value, the controller sets a plurality of write-inhibit tracks around the bump, and sets a plurality of tracks at the same radial positions as the plurality of write-inhibit tracks as write-inhibit tracks on all other recording media.

5. the controller has a determination circuit for determining the height of the bump registered in the memory, 2. The magnetic disk drive according to claim 1, wherein when the determination circuit determines that a bump is higher than a specified value, the controller prohibits use of a magnetic head corresponding to the recording medium on which the bump exists.

6. the controller includes a determination circuit that determines the height of the bumps registered in the memory, and a heating element control unit that controls a power supply voltage supplied to the heating element; the determination circuit determines whether or not there is a bump in a seek section of the magnetic head that may affect flying height control of the magnetic head; 2. The magnetic disk drive according to claim 1, wherein when the determination circuit determines that there is no bump that affects flying height control, the controller executes a seek of the magnetic head without changing the drive voltage of the heating element.

7. 7. The magnetic disk drive according to claim 6, wherein the determination circuit determines whether the bump has an effect on the control of the flying height of the magnetic head by comparing the flying height of the magnetic head at the seek start position with the height of the bump recorded in the memory.

8. 7. The magnetic disk drive of claim 6, wherein when the determination circuit determines that there is a bump that affects flying height control, the controller changes the power supply voltage of the heating element according to the height of the bump that affects the flying height control, thereby increasing the flying height of the magnetic head.

9. 9. The magnetic disk drive according to claim 8, wherein the controller changes the power supply voltage and the cooling wait time of the heating element according to the difference between the flying height of the magnetic head at the seek start position and the height of the bump recorded in the memory.

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