Magnetic recording device

Abstract

Embodiments of the present invention relate to a magnetic recording apparatus. According to one embodiment, the magnetic recording apparatus includes: a disc-shaped recording medium having a recording surface coated with a lubricant; a magnetic head including a recording element, a light source, and a light-emitting element that illuminates the recording surface of the recording medium; and a controller including a light source control circuit that controls the driving current value of the light source, a cleaning execution circuit that performs a cleaning action to remove deposits adhering to the magnetic head, and a setting circuit that sets a cleaning interval for performing the cleaning action.

Description

[0001] This application enjoys priority based on Japanese Patent Application No. 2024-220992 (filed on December 17, 2024). This application incorporates the entire contents of that basic application by reference. Technical Field

[0002] Embodiments of the present invention relate to magnetic recording apparatus. Background Technology

[0003] As a magnetic recording device, a magnetic recording device using a heat-assisted magnetic recording (HAMR) head has been proposed. HAMR is a technique that increases recording capacity by heating the recording medium with a laser during recording.

[0004] In high-performance magnetic resonance (HAMR) systems, as the temperature of the recording medium rises, a product formed from components present on the recording medium adheres between the light-emitting element of the magnetic head and the recording medium, creating a solidified product (hereinafter referred to as a build-up). This build-up functions as a layer that improves the thermal conductivity of the laser. Therefore, it is possible to increase the temperature of the recording medium without increasing the laser output.

[0005] The amount of buildup sometimes depends on the environment and / or the ratio of silicon (Si)-based materials in the recording medium. However, silicon-based materials, such as siloxanes, are a cause of smear on the magnetic head. For example, if a large amount of buildup adheres to the magnetic head, it can cause malfunctions between the head and the recording medium. Summary of the Invention

[0006] According to an embodiment, the magnetic recording apparatus includes: a disc-shaped recording medium having a recording surface coated with a lubricant; a magnetic head including a recording element, a light source, and a light-emitting element that illuminates the recording surface of the recording medium; and a controller including a light source control circuit that controls the driving current value of the light source, a cleaning execution circuit that performs a cleaning action to remove (remove) deposits adhering to the magnetic head, and a setting circuit that sets the cleaning interval for performing the cleaning action.

[0007] According to embodiments of the present invention, a magnetic recording apparatus is provided that can prevent malfunctions caused by deposits and improve recording density. Attached Figure Description

[0008] Figure 1 This is a block diagram that schematically represents the hard disk drive (HDD) according to the first embodiment.

[0009] Figure 2 It is a side view that roughly represents the read / write heads, suspension, and disk in the HDD.

[0010] Figure 3 It is a cross-sectional view showing the head of the magnetic head magnified.

[0011] Figure 4 This is a schematic diagram of the head of the magnetic head in a state where the write head portion is protruding due to a thermal actuator.

[0012] Figure 5 This is a graph showing the correlation between the drive current setpoint IOP and the track density TPI.

[0013] Figure 6 This is a graph showing the relationship between the cleaning interval and the track density TPI.

[0014] Figure 7 This is a graph showing the relationship between the cleaning interval and the laser drive current setting value IOP.

[0015] Figure 8 This is a graph showing the relationship between head action time and bit error rate (BER).

[0016] Figure 9 This is a graph showing the relationship between head movement time and head positioning accuracy.

[0017] Figure 10 This is a flowchart illustrating an example of HDD operation.

[0018] Figure 11 It is a diagram that schematically illustrates the movement of the read / write head corresponding to the operating state of an HDD.

[0019] Explanation of reference numerals in the attached figures

[0020] 10 Disk drive; 11 Housing; 12 Disk; 15 Slider; 16 Head; 17 Head; 18 Head actuator; 25 LDU (laser diode unit); 30 Head amplifier IC; 40 Main controller; 46e Setting circuit; 46f Decision circuit; 46g Cleaning execution circuit; 46i Calculation circuit; 54 Read head; 58 Write head; 65 Near-field light generating element (light-emitting element); 66 Waveguide; 76a First heater; 76b Second heater; HR thermal resistance sensor; HM deposited product. Detailed Implementation

[0021] Hereinafter, the magnetic recording apparatus according to the embodiments will be described with reference to the accompanying drawings.

[0022] Furthermore, the disclosure is merely an example, and appropriate modifications that maintain the spirit of the invention and are readily conceived by those skilled in the art are naturally included within the scope of this invention. Additionally, to make the description clearer, the drawings sometimes schematically represent the width, thickness, shape, etc., of various parts compared to the actual form; however, this is merely an example and does not constitute a limitation on the interpretation of the invention. Furthermore, in this specification and the drawings, for the same elements as those previously described with respect to existing figures, the same reference numerals are sometimes used, and detailed descriptions are appropriately omitted or simplified.

[0023] (First Embodiment)

[0024] As an example of a magnetic recording device, a hard disk drive (HDD) according to the first embodiment will be described in detail. Figure 1 This is a block diagram that schematically represents the HDD according to the first embodiment. Figure 2 This is a side view showing the read / write head and disk in the floating state.

[0025] like Figure 1 As shown, the HDD 10 includes: a rectangular housing 11; a disk 12 serving as a recording medium disposed within the housing 11; a spindle motor 14 supporting and rotating the disk 12; and multiple magnetic heads 16 for recording (writing) and reproducing (reading) data on the disk 12. The HDD 10 includes a head actuator 18 that moves and positions the magnetic heads 16 on any track of the disk 12. The head actuator 18 includes a carriage assembly 20 that supports the magnetic heads 16 for movement and a voice coil motor (VCM) 22 that rotates the carriage assembly 20.

[0026] The HDD10 includes a controller comprising a head amplifier IC30 for driving the magnetic head 16, a main controller 40, and a driver IC48. The head amplifier IC30 is, for example, located in the carriage assembly 20 and electrically connected to the magnetic head 16. The head amplifier IC30 includes: a recording current supply circuit (recording current supply section) 30a that supplies recording current to the recording coil of the magnetic head 16; a heater power supply circuit 30b that supplies drive power to the thermal actuator (heater) of the magnetic head 16 (described later); a sensor output amplifier circuit 30c that amplifies the detection signal from the thermal resistance sensor HR; a read signal amplifier circuit 30d that amplifies the signal read by the magnetic head 16; and a light source drive current supply circuit 30e that supplies drive current to a laser oscillator, such as a laser diode unit (LDU) (described later), etc.

[0027] The main controller 40 and driver IC 48 are configured, for example, on a control circuit board (not shown) located on the rear side of the housing 11. The main controller 40 includes a read / write channel (R / W channel) 42, a hard disk controller (HDC) 44, a microprocessor (MPU) 46, and a memory 47. The main controller 40 is electrically connected to the read / write head 16 via a 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 the host computer 45.

[0028] In the main controller 40, 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; a light source control unit 46d that controls the drive current of the light source; a setting circuit 46e that sets the light source drive current value (laser drive current setting value) IOP and the number of tracks per inch (TPI) of the recording medium; a determination circuit 46f that sets the cleaning interval; a cleaning execution circuit 46g that performs cleaning; a drive circuit 46h included in the cleaning execution circuit 46g; and an arithmetic circuit 46i that calculates the cumulative time of the write operation of each magnetic head and the cumulative time of device operation. As described below, the memory 47 stores various data such as the set laser drive current setting value IOP, TPI, cleaning interval, cumulative operation time, and heater power setting value.

[0029] HDD10 comprises multiple disks 12, for example, 10 disks 12 (only one is shown in the figure). The multiple disks 12 are coaxially mounted on the hub of the spindle motor 14. The disks 12 are rotated at a predetermined speed in the direction of the arrow by the spindle motor 14.

[0030] like Figure 1 and Figure 2 As shown, the disk 12 is configured as a perpendicular magnetic recording medium. The disk 12 has a substrate 101 formed of a non-magnetic material in a circular plate shape. On the upper and lower surfaces of the substrate 101, the following are sequentially stacked: a heat sink layer 102; a crystal alignment layer 103; a magnetic recording layer 104 having magnetic anisotropy in a direction perpendicular to the surface of the disk 12; and a protective layer 105 coated with a lubricant. The crystal alignment layer 103 is provided to improve the orientation of the magnetic recording layer 104. The heat sink layer 102 is disposed below the crystal alignment layer 103 to suppress the expansion of the heated area. Furthermore, the disk 12 includes a silicon-based material, such as SiOx.

[0031] like Figure 1As shown, a large number of concentric recording tracks T1 to Tn are formed on each surface (magnetic recording layer) of the disk 12. Each recording track T1 to Tn includes multiple sectors arranged circumferentially. As described below, the track density (TPI) of the disk 12 is set to maximize the surface recording density of the disk.

[0032] The carriage assembly 20 has a rotatable bearing portion 24 supported on the housing 11, and a plurality of arms and suspensions 26 extending from the bearing portion 24. For example... Figure 2 As shown, the magnetic head 16 is supported on the extension ends of each suspension 26. The magnetic head 16 is electrically connected to the head amplifier IC 30 via a wiring component (flexure) 28 provided on the carriage assembly 20.

[0033] like Figure 2 As shown, the magnetic head 16 is configured as a floating head, having a slider 15 formed in a generally rectangular parallelepiped shape and a head 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 of alumina and titanium carbide (AlTiC), and the head 17 is formed from a multilayer thin film. The slider 15 is mounted on the gimbal portion 28a of the wiring component 28.

[0034] The slider 15 has a generally rectangular disk-facing surface (air bearing surface (ABS)) 13 facing (opposing) the surface of the disk 12, and a back surface mounted on the universal joint portion 28a. A laser oscillator, such as a laser diode unit (LDU), which functions as a light source, is fixed to the back surface of the slider 15. The slider 15 is maintained at a predetermined position above the surface of the disk 12 by utilizing the airflow generated between the disk surface and the ABS 13 due to the rotation of the disk 12. As the disk 12 rotates, the read / write head 16 moves relative to the disk 12 in the direction of arrow A (head movement direction), that is, in the opposite direction to the rotation direction of the disk.

[0035] Figure 3 It is a cross-sectional view showing the head 17 of the read / write head 16 and the disk 12 in an enlarged manner.

[0036] like Figure 3As shown, the head 17 has a read head (sometimes called a playback element) 54 and a write head (sometimes called a recording element) 58 formed on the trailing end 15b of the slider 15 using a thin-film process. The read head 54 and write head 58, except for the portions exposed on the ABS 13 of the slider 15, are covered by a non-magnetic protective insulating film 53. The protective insulating film 53 forms the shape of the head 17. Furthermore, the head 17 includes: a light-emitting element that illuminates the disk surface, here a near-field light generating element; a waveguide 66 that propagates the laser oscillated by the LDU 25 to the near-field light generating element 65; a thermal resistance sensor HR that detects contact with the disk surface; a first thermal actuator that controls the amount of protrusion of the write head 58; and a second thermal actuator that controls the amount of protrusion of the read head 54.

[0037] The long dimension direction (circumferential direction) of the recording track formed in the magnetic recording layer 104 of the disk 12 is defined as the track direction DT, and the width direction of the recording track orthogonal to the long dimension direction is defined as the cross track direction.

[0038] The read head 54 has: a magnetic film 55 exhibiting a magnetoresistive effect; and shielding films 56 and 57 disposed on the trailing and leading sides of the magnetic film 55, sandwiching it. The magnetic film 55 and the shielding films 56 and 57 extend substantially perpendicularly to the ABS 13. The lower ends of the magnetic film 55 and the shielding films 56 and 57 are exposed in the ABS 13 of the slider 15.

[0039] Relative to the read head 54, the write head 58 is disposed on the trailing end 15b side of the slider 15. The write head 58 has: a main magnetic pole 60 that generates a recording magnetic field in a direction perpendicular to the surface of the disk 12; a trailing yoke 62 made of soft magnetic material that engages with the trailing side of the main magnetic pole 60 and allows magnetic flux to flow through the main magnetic pole 60; a return shield magnetic pole 64 made of soft magnetic material that is disposed opposite to the main magnetic pole 60 on the leading side of the main magnetic pole 60, separated by a write gap; a joint 67 that physically engages the upper part of the trailing yoke 62 with the return shield magnetic pole 64; and a recording coil 70 that is configured to be wound around a magnetic circuit including the trailing yoke 62 and the return shield magnetic pole 64 in order to allow magnetic flux to flow through the main magnetic pole 60.

[0040] The front end face of the main magnetic pole 60, the front end face of the trailing yoke 62, the front end face of the near-field light generating element 65, and the front end face of the return shielding magnetic pole 64 are exposed on the ABS13 of the slider 15.

[0041] The main magnetic pole 60 is formed of a soft magnetic material with high permeability and high saturation magnetic flux density, and extends approximately perpendicularly to ABS13. The main magnetic pole 60 has a front end face exposed on ABS43 and a magnetic end face extending upward from ABS13, i.e., in a direction away from ABS13, and facing the near-field light generating element 65.

[0042] A near-field light generating element (plasma generator, near-field transducer) 65 is disposed between the main magnetic pole 60 and the return shielding magnetic pole 64, and is parallel to and opposite to the magnetic end face of the main magnetic pole 60 with a gap (gap length) between them. The end of the near-field light generating element 65 located on the ABS13 side is formed to be parallel to and coplanar with the ABS13.

[0043] The near-field light generating element 65 is preferably formed of an alloy of Au, Pd, Pt, Rh, or Ir, or a combination thereof. An insulating layer exists between the main magnetic pole 60 and the near-field light generating element 65. This insulating layer is preferably an oxide containing SiO2, Al2O3, etc.

[0044] Waveguide 66 extends from ABS13 to the back face of slider 15, i.e., the suspension side end face, and is optically connected to LDU25. The end of waveguide 66 on the ABS13 side (the extended end) faces the near-field light generating element 65 in a generally parallel manner. An insulating layer exists between waveguide 66 and near-field light generating element 65.

[0045] The first thermal actuator, for example, has a heater 76a as a heating element. The heater 76a is embedded within the protective insulating film 53 and located near the write head 58. The second thermal actuator, for example, has a heater 76b as a heating element. The heater 76b is embedded within the protective insulating film 53 and located near the read head 54.

[0046] The thermal resistance sensor HR is embedded within the protective insulating film 53, located between the write head 58 and the read head 54. The sensing end (front end) of the thermal resistance sensor HR is exposed in or slightly protrudes from the ABS13. Furthermore, the thermal resistance sensor HR is used as an example of an HDI (head / disk interface) sensor.

[0047] The recording coil 70 is connected to the head amplifier IC 30 via wiring (not shown) and a flexible element 28. When a signal is written to the disk 12, a recording current is supplied to the recording coil 70 through the recording current supply circuit 30a of the head amplifier IC 30, thereby energizing the main magnetic pole 60 and allowing magnetic flux to flow through it. The recording current supplied to the recording coil 70 is controlled by the write control unit 46a of the main controller 40.

[0048] The read head 54 is connected to the head amplifier IC 30 via wiring and a flexible element 28 (not shown). The signal read by the read head 54 is amplified by the read signal amplification circuit 30d of the head amplifier IC 30 and sent to the main controller 40.

[0049] The first heater 76a and the second heater 76b are connected to the head amplifier IC 30 via wiring and flexible element 28, respectively. By applying drive power to the first heater 76a and the second heater 76b from the heater power supply circuit 30b of the head amplifier IC 30, the heaters and their surroundings are heated, causing the write head 58 or the read head 54 to bulge towards the disk 12. That is, by adjusting the bulge amount, the upward movement of the magnetic head 16 can be adjusted. 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.

[0050] The thermal resistance sensor HR is connected to the head amplifier IC 30 via wiring and flexible element 28. The detection signal (sensor output) of the thermal resistance sensor HR is amplified by the sensor output amplification circuit 30c of the head amplifier IC 30 and sent to the MPU 46 of the main controller 40.

[0051] LDU25 is connected to head amplifier IC30 via wiring and flexible element 28 (not shown). LDU25 oscillates to produce laser light by applying drive power to the head amplifier IC30's light source drive current supply circuit 30e. The laser light is supplied to near-field light generating element 65 via waveguide 66. The value of the drive current supplied to LDU25 is controlled by the light source control unit 46d of the main controller 40.

[0052] Laser power is typically controlled by setting the current value of the light source drive current supply circuit (preamplifier) ​​30e. The energy supplied to LDU25 is the drive current I supplied from the light source drive current supply circuit 30e. total =I th (or IB)+I eff (or IOP) definition. Base current value I th Up to this point, even when a current is applied to the LDU25, no laser oscillation is produced; when an application exceeding I... th The current value I eff At that time, laser light is oscillated from LDU25. When the oscillating laser light propagates to the near-field light generating element 65, near-field light is generated from the near-field light generating element 65 and irradiates the disk 12. As a result, the disk 12 is locally heated.

[0053] Base current value I th It varies depending on ambient temperature and individual differences. Therefore, in HDD10, the base current value I... th The parameter IB of the device is stored in the memory 47. In addition, the light source control unit 46d controls the corresponding I by... eff Laser drive current setting value (I total The laser power is controlled by changing the -IB=IOP.

[0054] like Figure 1 As shown, according to HDD10, by driving VCM22, head actuator 18 rotates, and read / write head 16 moves and positions itself on the desired track of disk 12. Figure 2 As shown, when HDD10 is in operation, the read / write head 16 is positioned with a gap relative to the disk surface. The read / write head 16 is tilted upwards with the write head 58 portion of the head 17 closest to the surface of the disk 12. In this state, for the disk 12, the read head 54 reads the recorded information, and the write head 58 writes the information (recording signal) (write operation).

[0055] Figure 4 It is a schematic cross-sectional view showing the head 17 of the read / write head 16 and a portion of the disk 12 during a write operation.

[0056] like Figure 4 As shown, during the write operation of the magnetic head 16, by applying driving power to the first heater 76a, the first heater 76a and its surroundings are heated, and the write head 58 partially bulges towards the disk 12. As a result, the gap (head buoyancy) d1 between the write head 58 and the surface of the disk 12 is set to about 5 to 0.1 nm (nanometers).

[0057] During the writing operation, a recording current is supplied from the recording current supply circuit 30a to the recording coil 70, which energizes the main magnetic pole 60. A vertically oriented recording magnetic field is applied from the main magnetic pole 60 to the magnetic recording layer 104 of the disk 12 directly below, writing information into the magnetic recording layer 104 with the desired track width. In heat-assisted magnetic recording, during the writing operation, a predetermined laser drive current setting value IOP is supplied from the light source drive current supply circuit 30e to the LDU 25, causing laser light to oscillate from the LDU 25. The laser light is supplied to the near-field light generating element 65 via the waveguide 66, which generates near-field light and illuminates the disk 12. By locally heating the magnetic recording layer 104 of the disk 12 using the near-field light, the coercivity of the recording area is reduced. A recording magnetic field from the main magnetic pole 60 is applied to this area with reduced coercivity, and a recording signal is written. High-density recording is possible by writing recording signals into regions where coercivity is sufficiently reduced by locally heating the magnetic recording layer 104 in this way.

[0058] On the other hand, when the magnetic head 16 with an upward displacement of d1 moves on the protective layer 105, lubricant is filled between the lubricant layer 106 coated on the protective layer 105 and the front end of the near-field light generating element 65. In this state, when near-field light is irradiated onto the magnetic recording layer 104 and the lubricant layer 106, the magnetic recording layer 104 and the lubricant are heated, generating a deposit product HM formed by the solidification of components present on the disk 12. The deposit product HM adheres to the front end of the near-field light generating element 65. By irradiating the near-field light for a predetermined time, a deposit product HM with a height of less than d1 is attached to the front end of the near-field light generating element 65. This deposit product HM functions as a layer that improves the thermal conductivity of the laser (near-field light). Therefore, the temperature of the recording medium can be increased without increasing the laser output.

[0059] The components of the deposited product HM are lubricants and materials that make up the disk, but in particular, oxides rich in Si, Ti, Ta, Al, C, Fe, Co and other elements are the main components.

[0060] The amount of buildup depends on elements such as siloxanes present in the environment and Si present in the disk 12. The more Si present, the larger the buildup HM. According to the HDD 10 of this embodiment, the main controller 40 monitors the time until the buildup HM is generated and measures the correlation between the generation time and the buildup HM. The measurement results are registered in the memory 47 as generation time data.

[0061] As described above, silicon-based materials, such as siloxanes, are the cause of smears adhering to the ABS13 of the read / write head 16. If the buildup (HM) becomes bloated, it may cause malfunctions between the read / write head 16 and the disk 12. Therefore, the HDD 10 according to this embodiment is configured to perform periodic cleaning and regeneration of the buildup. The operation of the HDD 10, including the cleaning action and the setting of the cleaning interval, will be described below.

[0062] According to HDD10, when cleaning the accumulated product HM, the setting circuit 46e of the main controller 40 pre-sets the cleaning interval, i.e. the cleaning interval, based on the laser drive current setting value IOP or the track density TPI of LDU25, and stores it in the memory 47.

[0063] The aforementioned laser drive current setting value IOP and track density TPI are determined during the manufacturing and adjustment processes of HDD10. Typically, the surface recording density of disk 12 depends on the track density TPI and BPI (bits per inch), and is set to maximize both TPI and BPI. In the HDD10 of this embodiment, the optimal value of the laser drive current setting value IOP is adjusted simultaneously with TPI and BPI, and the optimized value is stored as a device parameter in memory 47.

[0064] With the same read / write head, disk, and head-to-disk distance, increasing the laser drive current setting (IOP) increases the laser spot diameter. That is, a larger spot diameter results in a larger magnetic recording pattern (track width) and a lower recording density. Furthermore, the laser spot diameter is directly proportional to the diameter of the deposited material. Therefore, a larger laser spot diameter also leads to a larger deposited material diameter, increasing the risk of contamination. Consequently, a higher IOP necessitates a shorter cleaning interval for the deposited material.

[0065] Figure 5 This graph shows the correlation between the drive current setpoint IOP and the track density TPI. As shown, IOP and TPI are inversely proportional; therefore, the lower the track density TPI, the shorter the cleaning interval needs to be.

[0066] Figure 6 This is a graph showing the relationship between the cleaning interval and the track density TPI. Figure 7 This is a graph showing the relationship between the cleaning interval L and the laser drive current setting value IOP.

[0067] like Figure 6 As shown, the higher the TPI, the longer the cleaning interval should be. In one example, when the TPI is low (T1), the cleaning interval is set to L1, and when the TPI is high (T2), the cleaning interval is set to L2 (>L1).

[0068] like Figure 7 As shown, the larger the IOP, the shorter the cleaning interval L should be. In one example, when the IOP is large (T1), the cleaning interval is set to L1, and when the IOP is small (T2), the cleaning interval is set to L2 (>L1).

[0069] The method for setting the cleaning interval L will be further explained.

[0070] The size of the accumulated buildup (HM) increases over time after its formation, and may affect the movement of the read / write head, such as positioning, due to friction with the disk.

[0071] Figure 8This is a graph showing the relationship between write operation time and bit error rate (BER) from the initial state of the read / write head. Figure 9 This is a graph showing the relationship between the write operation time from the initial state of the read / write head and the positioning accuracy of the read / write head. In each graph, the solid line represents the relationship when the stacking speed T is high, and the dashed line represents the relationship when the stacking speed T is low.

[0072] like Figure 8 As shown, with a faster stack generation speed T, the improvement in bit error rate is also accelerated. That is, it can be seen that the faster the stack generation speed T, the more the stacked product HM contributes to improved write performance. On the other hand, as... Figure 9 As shown, when the buildup rate T is high, positioning degradation also occurs quickly. This is because, as the buildup grows, it exceeds a certain area and becomes a source of friction between the read / write head and the disk, thus hindering the smooth movement of the head and leading to positioning degradation.

[0073] exist Figure 9 In this context, the threshold time for deterioration when the accumulation rate T is fast is denoted as T1lim, and the threshold time for deterioration when the accumulation rate T is slow is denoted as T2lim.

[0074] For IOP and TPI, Tlim can be expressed by the relationship Tlim = p × IOP + q or Tlim = s × TPI + t.

[0075] Here, the cleaning interval L for a particular head is determined by taking into account the time Tlim during which positioning deterioration occurs. For example, it can be determined by a value such as cleaning interval L = Tlim × 0.8.

[0076] Based on the above relationship, the cleaning interval L can be expressed using the buildup rate T as a linear equation such as L = aT × b. Here, the coefficients a and b can be obtained from multiple cleaning intervals Lx and buildup rates Tx using the least squares method.

[0077] Alternatively, the cleaning interval L can also be set based on the operating time of the HDD's power-on. For example, the setting circuit 46e sets an arbitrary reference cumulative operating time as the cleaning interval L and records it in the memory 47. The arithmetic circuit 46i of the main controller 40 monitors the operating time of the HDD 10, calculates the cumulative operating time by performing calculations and accumulation, and records it in the memory 47. The determination circuit 46f of the main controller 40 determines whether the cumulative operating time of the HDD 10 has reached the reference cumulative operating time, and instructs the cleaning execution circuit 46g to perform cleaning at the time point when the reference cumulative operating time has been reached.

[0078] Furthermore, the cleaning interval L can also be set based on the total cumulative time of the write operations of the magnetic head. For example, the setting circuit 46e sets an arbitrary reference cumulative operation time as the cleaning interval L and registers it in the memory 47. The arithmetic circuit 46i of the main controller 40 calculates and accumulates the write operation time of each magnetic head 16 to obtain the total cumulative operation time and registers it in the memory 47. The determination circuit 46f of the main controller 40 determines whether the total cumulative operation time of the write operations of the magnetic head 16 has reached the set reference cumulative operation time, and instructs the cleaning execution circuit 46g to perform cleaning of the magnetic head when the reference cumulative operation time is reached.

[0079] In this case, the cumulative write operation time varies for each head. Therefore, the main controller 40 checks the cumulative write operation time of each head registered in the memory 47 at regular intervals, and performs cleaning sequentially starting from the head whose cumulative operation time exceeds the reference cumulative operation time. When a head reaches the cleaning interval L, cleaning can be performed on the corresponding head. Alternatively, cleaning can be performed on multiple heads or all heads.

[0080] Furthermore, in the recording area of ​​disk 12, the laser drive current setting value IOP during write operations sometimes differs between zones; that is, the laser drive current setting value IOP sometimes varies according to the radius position of the read / write head 16 relative to disk 12. Therefore, in the calculation of the cumulative write operation time, the laser drive current setting value IOP can be weighted according to zone or radius position. In one example, the cumulative write operation time can be calculated using the following formula.

[0081]

[0082] Here, f(IOP) is a function that depends on IOP (e.g., a linear expression of IOP).

[0083] Alternatively, the formula can be set up to use TPI instead of IOP. The optimal value of IOP varies by head / disk, therefore, when using IOP for calculation, the function needs to be common to all heads. When using TPI, the function can be made common.

[0084] Next, an example of a cleaning operation for the accumulated product HM will be described.

[0085] Cleaning of the accumulated debris (HM) is performed by lowering the head 16 from its normal write position, causing the accumulated debris (HM) to contact and wear against the disk surface. For example, if the normal write position is set to 1 nm, cleaning can be performed by reducing the write position to 0.5 nm and holding it there for about one second.

[0086] The reduction in the head lift is not limited to 0.5nm; it can take various values, such as lowering the head until it contacts the disk surface (touchdown), or lowering the head further from the touchdown position by a few more nanometers. (Emi) (over push) etc.

[0087] Generally, maintaining a high buoyancy level results in weak cleaning, while grounding the read / write head provides sufficient cleaning. For a more thorough cleaning, if several... Alternatively, you can push the head further towards the disk from the ground position (over-push). Or, you can clean it by performing one or more ground contact operations to bring the read / write head into contact with the disk.

[0088] In addition, the cleaning action time is not limited to 1 second and can be increased or decreased arbitrarily according to the cleaning situation.

[0089] The cleaning process itself does not generate heat or erase recorded data; therefore, cleaning can be performed in the data recording area. Alternatively, to avoid the risk of the read / write head becoming dirty due to abrasive material generated during cleaning, dedicated cleaning areas R1 and R2 can be set in the non-data recording areas of disk 12, such as the innermost and / or outermost peripheral areas (see [reference]). Figure 1 Furthermore, in the case of Single Magnetic Recording (SMR), a dedicated cleaning area can also be set up in the inter-band region of the recording track.

[0090] In this embodiment, the HDD 10 regenerates the buildup HM after the cleaning operation. Specifically, after cleaning, the drive circuit 46h of the main controller 40, under the control of the heater control unit 46c, returns the heater drive power to the normal value for write operations, setting the head 16's rise to d1. Simultaneously, under the control of the light source control unit 46d, the drive circuit 46h supplies laser drive current to the LDU 25, generating near-field light from the near-field light generating element 65. This causes the lubricant on the disk 12 to be rolled up and filled between the head and the disk surface, regenerating the buildup HM. "Generation" occurs from the moment the near-field light is applied, taking, for example, several milliseconds to several hours, depending on the conditions of the laser and lubricant. This generates buildup HM that grows to approximately the same height as the head 16's rise d1.

[0091] In the generation of the accumulation product HM, applying a laser to make the disk 12 reach a high temperature is a necessary condition, but it is not necessarily necessary to supply recording current to the magnetic head 16. That is, the regeneration of the accumulation product HM is performed by causing the magnetic head 16 to perform seek or write operations while a laser (near field light) is applied.

[0092] Regarding the regeneration of the accumulated product HM, it can also be performed by setting a dedicated regeneration area on disk 12. In the case of SMR recording mode, a dedicated regeneration area can also be set in the inter-band area of ​​the recording track.

[0093] If the temperature of disk 12 exceeds the Curie temperature when the laser is applied, the recorded pattern may disappear. Therefore, when generating the stacking product HM in the data recording area of ​​disk 12, it is preferable to use the area to be rewritten and / or write the same pattern as the already recorded pattern.

[0094] An example of the overall operation of an HDD configured as described above will be explained.

[0095] Figure 10 This is a flowchart illustrating an example of HDD operation. Figure 11 It is a diagram that schematically illustrates the movement of the read / write head corresponding to the operating state of an HDD.

[0096] like Figure 10 As shown, in the manufacturing or adjustment process, firstly, the main controller 40 of HDD10 sets at least one or both of the aforementioned laser drive current setting value IOP and track density TPI (ST1). Typically, the surface recording density of disk 12 depends on track density TPI and BPI, and the settings maximize TPI and BPI. In the HDD10 of this embodiment, the setting circuit 46e adjusts the optimal value of the laser drive current setting value IOP while setting TPI and BPI, and stores the optimized values ​​in memory 47.

[0097] Next, the setting circuit 46e of the main controller 40 sets the execution interval of the cleaning action of the generated HM, that is, the interval from the end of cleaning to the start of the next cleaning action (cleaning interval L) (ST2). For example, the setting circuit 46e takes the write operation time of the magnetic head as the object, sets any reference cumulative operation time (e.g., a few minutes to tens of hours) as the cleaning interval L, and registers it in the memory 47.

[0098] Furthermore, as mentioned above, the cleaning interval L is not limited to the cumulative write operation time of the magnetic head; for example, it can also be set as the cumulative operating time based on the power-on time of the HDD. Moreover, the cleaning interval (time) L can also be set based on at least one of the set laser drive current setting value IOP and the track density TPI.

[0099] like Figure 10 and Figure 11As shown, during the operation of HDD10 when it is powered on, the main controller 40 performs write and read operations according to instructions from the host 45 (ST3). Additionally, the arithmetic circuit 46i of the main controller 40 calculates and accumulates the write operation time of each read / write head 16, and sequentially registers the accumulated results in the memory 47 (ST4). Furthermore, the arithmetic circuit 46i calculates and accumulates the operating time of HDD10 and registers it in the memory 47.

[0100] During HDD10 operation, the decision circuit 46f of MPU46 monitors the cumulative operation time of each head 16 and determines whether the cumulative operation time since the end of the last cleaning has reached the reference cumulative operation time (cleaning interval L) (ST5). The decision circuit 46f continues to monitor and accumulate the write operation time until the cumulative operation time reaches the cleaning interval L. When the cumulative operation time reaches the reference cumulative operation time (cleaning interval L), the decision circuit 46f instructs the cleaning execution circuit 46g to perform the cleaning operation and resets the registered cumulative operation time.

[0101] The cleaning execution circuit 46g initiates the cleaning operation (ST6) according to the instruction. Under the control of the heater control unit 46c and the heater power supply circuit 30b, the cleaning execution circuit 46g increases the drive current value of the first heater 76a, thereby reducing the upward movement of the read / write head 16. In one example, the heater drive current value is increased until the read / write head 16 contacts the surface of the disk 12 (grounding), and this state is maintained for a few seconds, for example, about 1 to 2 seconds. As a result, the deposits HM adhering to the read / write head 16 are worn away and removed through friction with the disk surface.

[0102] As mentioned above, the head levitation during cleaning can be adjusted arbitrarily. With a normal write operation levitation setting of 1 nm, during cleaning, it can be reduced to 0.5 nm, or it can be further pushed in (over-push) from the ground position. In addition, the cleaning action is not limited to one time, but can be performed multiple times in succession.

[0103] After cleaning, the main controller 40 performs the regeneration of the accumulated buildup (ST7). That is, under the control of the heater control unit 46c, the MPU 46 returns the heater drive power value to the normal write operation value and sets the head 16's rise to d1. Approximately simultaneously, under the control of the write control unit 46a, the MPU 46 supplies laser drive current to the LDU 25 of the head 16, generating near-field light from the near-field light generating element 65. As a result, the lubricant on the disk 12 is rolled up and filled between the head and the disk surface, regenerating the accumulated buildup HM. This "regeneration" takes, for example, a few milliseconds to a few hours, from the moment the near-field light is applied. Thus, accumulated buildup HM grows to approximately the same height as the head 16's rise d1.

[0104] Then, the main controller 40 performs write and read operations according to the instructions from the host 45, and then repeatedly performs the above-mentioned processing operations ST3 to ST7.

[0105] The following are examples of setting the cleaning interval L and the cleaning operation.

[0106] (Example 1)

[0107] Twenty HDDs were prepared, ten of which were configured with a cleaning process as an example, and the other ten were configured without a cleaning process as a comparative example (with the interval L set to infinity). After measuring the bit error rate (BER) and location information in the initial state, they were run for 500 hours.

[0108] The HDD heads were cleaned at the same timing, once every 20 hours of actual operating time. The cleaning was performed by reducing the head's float to 0.5 nm during write operations and holding it in the recording area for 1 second.

[0109] After 500 hours of operation, the head positioning accuracy and BER were assessed for both cleaned and uncleaned HDDs. The results showed that the BER of both HDDs improved similarly, while the positioning accuracy of the uncleaned HDD deteriorated significantly. Based on these results, it can be confirmed that "positioning degradation was suppressed by implementing cleaning."

[0110] (Example 2)

[0111] Twenty HDDs were prepared, with 10 configured for the implementation example and subjected to a cleaning process, and the other 10 configured for the comparative example and subjected to a non-cleaning process (with the interval L set to infinity). After measuring the initial bit error rate (BER) and positioning accuracy, the HDDs were run for 1000 hours. The head cleaning interval was set to a value based on the IOP setting.

[0112] In one example, when IOP > 10mA, the cleaning interval is set to 1.2·IOP(mA) - 10 hours, and when IOP ≤ 10mA, the cleaning interval is set to 2 hours.

[0113] Cleaning was performed at a set time when the write operation time of each head reached the set time. Cleaning was performed by reducing the head's float to 0nm (grounding state) during the write operation and holding it there for 2 seconds. In addition, during cleaning, the area between the bands during SMR recording that was closest to the head position at that time point was used.

[0114] After 1000 hours of operation, the head positioning accuracy and BER were verified for both cleaned and uncleaned HDDs. The results showed that the BER of both HDDs improved equally, while the positioning of the uncleaned HDD deteriorated significantly. Based on these results, it can be confirmed that "positioning degradation was suppressed by implementing cleaning."

[0115] (Example 3)

[0116] Twenty HDDs were prepared, with 10 configured for the implementation example and equipped with a cleaning process, and the other 10 configured for the comparative example and equipped without a cleaning process (with the interval L set to infinity). After measuring the initial bit error rate (BER) and positioning accuracy, the HDDs were run for 5000 hours. The head cleaning interval was set to a value based on the TPI setting.

[0117] In one example, if the TPI setting (kTPI) is set to X, then when X > 510, the cleaning interval is set to X × 0.1 - 50 hours, and when X ≤ 510, the cleaning interval is set to 1 hour. Cleaning is performed at the set time when the write operation time of each head reaches the set time.

[0118] Cleaning was performed by reducing the head's upward movement during a write operation to +0.5 nm (over-push state) upon grounding and holding this position for 0.5 seconds. Additionally, a dedicated cleaning zone R2, located at the outermost periphery outside the recording area, was used during cleaning.

[0119] After 1000 hours of operation, the head positioning accuracy and BER were verified for both cleaned and uncleaned HDDs. The results showed that the BER of both HDDs improved equally, while the positioning of the uncleaned HDD deteriorated significantly. Based on these results, it can be confirmed that "positioning degradation was suppressed by implementing cleaning."

[0120] According to the HDD constructed as described in the first embodiment, by cleaning, i.e. removing the deposited material HM at a predetermined cleaning interval L, it is possible to prevent the reduction in head positioning accuracy and recording density caused by the enlargement of the deposited material HM. As can be seen from the above, according to this embodiment, a magnetic recording device capable of preventing malfunctions caused by deposited material and achieving increased recording density can be obtained.

[0121] Several embodiments of the present invention have been described. These embodiments are provided by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, 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 invention as described in the claims and its equivalents.

[0122] For example, the cleaning interval L is not limited to the reference cumulative operating time of the magnetic head shown in the embodiment, but may also be a reference cumulative operating time based on the HDD's operating time, or a time set based on the laser drive current setting value IOP and the track density TPI.

[0123] The amount of head levitation during cleaning is not limited to 0.5nm, 0nm, or 0-several. It can be set to any value. The cleaning time and frequency can be changed as needed.

Claims

1. A magnetic recording device, comprising: A disc-shaped recording medium with a recording surface coated with lubricant; A magnetic head includes a recording element, a light source, and a light-emitting element that illuminates the recording surface of the recording medium; and The controller includes a light source control circuit that controls the drive current value of the light source, a cleaning execution circuit that performs a cleaning action to remove the deposits attached to the magnetic head, and a setting circuit that sets the cleaning interval for performing the cleaning action.

2. The magnetic recording device according to claim 1, The setting circuit sets the cleaning interval based on at least one of the driving current setting value of the light source, i.e., IOP, and the track density of the recording medium, i.e., TPI.

3. The magnetic recording device according to claim 2, The larger the driving current setting value (IOP) of the light source, the shorter the cleaning interval will be set by the setting circuit.

4. The magnetic recording device according to claim 2, The smaller the track density (TPI), the shorter the cleaning interval will be set by the setting circuit.

5. The magnetic recording device according to claim 1, The setting circuit sets the reference cumulative operation time of the write operation of the magnetic head as the cleaning interval. The controller includes an arithmetic circuit and a determination circuit. The arithmetic circuit accumulates the writing time of the magnetic head, and the determination circuit compares the accumulated time with a set reference accumulated time. The cleaning operation is started when the accumulated time reaches the reference accumulated time.

6. The magnetic recording apparatus according to claim 1, The setting circuit sets the reference cumulative operating time of the magnetic recording device to the cleaning interval. The controller includes an arithmetic circuit and a determination circuit. The arithmetic circuit accumulates the working time of the magnetic recording device, and the determination circuit compares the accumulated working time with a set reference accumulated working time. The cleaning action is started when the accumulated working time reaches the reference accumulated working time.

7. The magnetic recording device according to claim 1, The cleaning execution circuit performs cleaning by reducing the amount of the read / write head rising from the amount of the read / write operation.

8. The magnetic recording device according to claim 1, The cleaning execution circuit performs cleaning by bringing the magnetic head into contact with the recording surface of the recording medium.

9. The magnetic recording device according to claim 1, The cleaning execution circuit performs the cleaning action in the non-data recording area at the innermost or outermost periphery of the recording medium.

10. The magnetic recording apparatus according to claim 1, Within the data recording area of ​​the recording medium, the cleaning execution circuit performs the cleaning action in the area between the tapes of the written data.

11. The magnetic recording apparatus according to claim 1, The cleaning execution circuit includes a drive circuit that performs the regeneration of the accumulated products after the cleaning action is completed.

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