Magnetic recording device

Abstract

The objective is to provide a magnetic recording device that can prevent problems caused by buildup products and improve recording density. [Solution] According to the embodiment, the magnetic recording device comprises a disk-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 irradiates light onto the recording surface of the recording medium, a light source control circuit that controls the drive current value of the light source, a cleaning execution circuit that performs a cleaning operation to remove buildup products adhering to the magnetic head, and a controller including a setting circuit that sets the cleaning interval for performing the cleaning operation.

Description

[Technical Field]

[0001] This embodiment of the invention relates to a magnetic recording device. [Background technology]

[0002] As a magnetic recording device, a magnetic recording device using a heat-assisted magnetic recording (HAMR) magnetic head has been proposed. HAMR is a technology that increases recording capacity by heating the recording medium with a laser during recording. In HAMR, as the temperature of the recording medium rises, a product consisting of components present on the recording medium adheres between the light-emitting element of the magnetic head and the recording medium, forming a hardened material (hereinafter referred to as build-up product). This build-up product functions as a layer that increases the thermal conductivity efficiency of the laser. Therefore, it becomes possible to raise the temperature of the recording medium without increasing the laser output.

[0003] The amount of buildup generated can be determined by the environment and the proportion of Si-based materials contained in the recording medium. However, Si-based materials, including siloxanes, can cause smearing (contamination) on the magnetic head. For example, if a very large amount of buildup product adheres to the magnetic head, it can cause problems between the magnetic head and the recording medium. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] U.S. Patent Application Publication No. 2017 / 0221511 [Patent Document 2] U.S. Patent No. 10,410,660 [Patent Document 3] U.S. Patent No. 9,916,847 [Patent Document 4] U.S. Patent No. 9,601,140 [Patent Document 5] U.S. Patent No. 9,858,953 [Overview of the project] [Problems that the invention aims to solve]

[0005] The object of the embodiments of the present invention is to provide a magnetic recording device that can prevent problems caused by buildup products and improve recording density. [Means for solving the problem]

[0006] According to one embodiment, the magnetic recording apparatus comprises a disk-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 irradiates light onto the recording surface of the recording medium; a light source control circuit that controls the drive current value of the light source; a cleaning execution circuit that performs a cleaning operation to remove buildup products adhering to the magnetic head; and a controller that includes a setting circuit that sets the cleaning interval for performing the cleaning operation. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic block diagram showing a hard disk drive (HDD) according to the first embodiment. [Figure 2] Figure 2 is a schematic side view showing the magnetic head, suspension, and magnetic disk in the HDD. [Figure 3] Figure 3 is a cross-sectional view showing an enlarged view of the head portion of the magnetic head. [Figure 4] Figure 4 schematically shows the head portion of a magnetic head in a state where the light head portion is protruding by a thermal actuator. [Figure 5] Figure 5 shows the correlation between the drive current setting value IOP and the track density TPI. [Figure 6] Figure 6 shows the relationship between cleaning interval and track density TPI. [Figure 7]FIG. 7 is a diagram showing the relationship between the cleaning interval and the set value IOP of the laser drive current. [Figure 8] FIG. 8 is a diagram showing the relationship between the head operation time and the bit error rate (BER). [Figure 9] FIG. 9 is a diagram showing the relationship between the head operation time and the positioning accuracy of the magnetic head. [Figure 10] FIG. 10 is a flowchart showing an example of the operation of the HDD. [Figure 11] FIG. 11 is a diagram schematically showing the operation of the magnetic head corresponding to the operation state of the HDD.

Mode for Carrying Out the Invention

[0008] The magnetic recording apparatus according to the embodiment will be described below with reference to the drawings. Note that the disclosure is merely an example, and for those skilled in the art, appropriate changes that can be easily conceived while maintaining the gist of the invention are naturally included in the scope of the present invention. Also, for the purpose of making the description clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual aspect, but this is merely an example and does not limit the interpretation of the present invention. Further, in this specification and each drawing, elements that are the same as those described above with respect to the previously shown drawings may be denoted by the same reference numerals, and detailed descriptions may be omitted or simplified as appropriate.

[0009] (First Embodiment) As an example of a magnetic recording apparatus, the hard disk drive (HDD) according to the first embodiment will be described in detail. FIG. 1 is a block diagram schematically showing the HDD according to the first embodiment, and FIG. 2 is a side view showing the magnetic head and the magnetic disk in the floating state. As shown in Figure 1, the HDD 10 comprises a rectangular housing 11, a magnetic disk 12 as a recording medium disposed within the housing 11, a spindle motor 14 that supports and rotates the magnetic disk 12, and a plurality of magnetic heads 16 that record (write) and read (play) data from the magnetic disk 12. The HDD 10 also includes a head actuator 18 that moves and positions the magnetic heads 16 on any track on the magnetic disk 12. The head actuator 18 includes a carriage assembly 20 that movably supports the magnetic heads 16, and a voice coil motor (VCM) 22 that rotates the carriage assembly 20.

[0010] The HDD10 includes a controller that includes a head amplifier IC30 for driving the magnetic head 16, a main controller 40, and a driver IC48. The head amplifier IC30 is provided, for example, on the carriage assembly 20 and is electrically connected to the magnetic head 16. The head amplifier IC30 includes a recording current supply circuit (recording current supply unit) 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 amplification circuit 30c that amplifies the detection signal of the thermal resistance sensor HR, a read signal amplification circuit 30d that amplifies the signal read by the magnetic head 16, a light source drive current supply circuit 30e that supplies drive current to a laser oscillator, for example, a laser diode unit (LDU) (described later), etc.

[0011] The main controller 40 and the driver IC 48 are configured, for example, on a control circuit board (not shown) provided on the back side of the housing 11. The main controller 40 includes a read / write channel (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 the host computer 45.

[0012] 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 set value) IOP and the track per inch (TPI) of the recording medium, a determination circuit 46f that sets the cleaning interval, a cleaning execution circuit 46g that executes cleaning, a drive circuit 46h included in the cleaning execution circuit 46g, an arithmetic circuit 46i that calculates the integrated time of the write operation for each magnetic head and the integrated time of the device operation time, etc. As will be described later, the memory 47 stores various data such as the set laser drive current set value IOP, TPI, cleaning interval, integrated operation time, heater power set value, etc.

[0013] The HDD 10 includes a plurality of, for example, 10 magnetic disks 12 (only one is shown). The plurality of magnetic disks 12 are coaxially fitted to the hub of the spindle motor 14. The magnetic disk 12 is rotated in the direction of the arrow at a predetermined speed by the spindle motor 14. As shown in Figures 1 and 2, the magnetic disk 12 is configured as a perpendicular magnetic recording medium. The magnetic disk 12 has a substrate 101 made of a non-magnetic material formed in the shape of a disk. A heat sink layer 102, a crystal orientation layer 103, a magnetic recording layer 104 having magnetic anisotropy perpendicular to the surface of the magnetic disk 12, and a protective layer 105 with a lubricant applied to its surface are sequentially laminated on the upper and lower surfaces of the substrate 101. The crystal orientation layer 103 is provided to improve the orientation of the magnetic recording layer 104. The heat sink layer 102 is placed below the crystal orientation layer 103 to suppress the spread of the heated area. The magnetic disk 12 contains a Si-based material, such as SiOx.

[0014] As shown in Figure 1, numerous 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 contains multiple sectors arranged in the circumferential direction. As will be described later, the track density (TPI: Track per Inch) of the magnetic disk 12 is set to maximize the areal recording density of the magnetic disk.

[0015] The carriage assembly 20 includes a bearing portion 24 rotatably supported by the housing 11, and a plurality of arms and suspensions 26 extending from the bearing portion 24. As shown in Figure 2, the magnetic head 16 is supported at the extended end of each suspension 26. The magnetic head 16 is electrically connected to the head amplifier IC 30 via a wiring member (flexi-sha) 28 provided on the carriage assembly 20.

[0016] As shown in Figure 2, the magnetic head 16 is configured as a levitation head and has 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 from, for example, a sintered body of alumina and titanium carbide (Altic), and the head portion 17 is formed from multiple thin films. The slider 15 is attached to the gimbal portion 28a of the 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 and a back surface attached to the gimbal portion 28a. A laser oscillator, such as a laser diode unit (LDU) 25, which functions as a light source, is fixed to the back surface of the slider 15. The slider 15 is maintained in a state where it floats a predetermined amount above the surface of the magnetic disk 12 by the airflow generated between the disk surface and the ABS 13 as the magnetic disk 12 rotates. As the magnetic disk 12 rotates, the magnetic head 16 travels in the direction of arrow A (head travel direction) relative to the magnetic disk 12, that is, in the direction opposite to the direction of disk rotation.

[0018] Figure 3 is a cross-sectional view showing an enlarged view of the head portion 17 of the magnetic head 16 and the magnetic disk 12. As shown in Figure 3, the head unit 17 has a read head (sometimes referred to as a playback 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 non-magnetic protective insulating film 53, except for the portion exposed to the ABS 13 of the slider 15. The protective insulating film 53 constitutes the outer shape of the head unit 17. Furthermore, the head unit 17 includes a light-emitting element that irradiates light onto the magnetic disk surface, in this case a near-field light-generating element, a waveguide 66 that propagates laser light oscillated by the LDU 25 to the near-field light-generating element 65, a thermal resistance sensor HR that detects contact with 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.

[0019] The longitudinal direction (circumferential direction) of the recording track formed on the magnetic recording layer 104 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. The read head 54 has a magnetic film 55 that exhibits a magnetoresistive effect, and shield films 56 and 57 that are positioned to sandwich the magnetic film 55 on the trailing and leading sides of the magnetic film 55. The magnetic film 55 and the shield films 56 and 57 extend almost perpendicularly to the ABS 13. The lower ends of the magnetic film 55 and the shield films 56 and 57 are exposed to the ABS 13 of the slider 15.

[0020] The write head 58 is located on the trailing end 15b side of the slider 15 relative to the read head 54. The write head 58 includes a main magnetic pole 60 that generates a recording magnetic field perpendicular to the surface of the magnetic disk 12, a trailing yoke 62 made of a soft magnetic material that is joined to 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 a soft magnetic material that is positioned opposite the main magnetic pole 60 with a light gap, a joint portion 67 that physically joins the upper part of the trailing yoke 62 to the return shield magnetic pole 64, and a recording coil 70 that is arranged to wrap around the magnetic path 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. The leading surfaces of the main magnetic pole 60, the trailing yoke 62, the leading edge of the near-field light generating element 65, and the leading surface of the return shield magnetic pole 64 are exposed to the ABS 13 of the slider 15.

[0021] The main magnetic pole 60 is made of a soft magnetic material having high permeability and high saturation magnetic flux density, and extends almost perpendicular to the ABS 13. The main magnetic pole 60 has a tip surface exposed to the ABS 43 and a magnetic pole end surface that extends upward from the ABS 13, i.e., away from the ABS 13, and faces the near-field light generating element 65.

[0022] The near-field light generator (plasmon generator, near-field transducer) 65 is provided between the main magnetic pole 60 and the return shield magnetic pole 64, and is parallel to and facing the magnetic pole end face of the main magnetic pole 60 with a gap (gap length) between them. The end of the near-field light generator 65 on the ABS 13 side is formed parallel to and flush with the ABS 13. The near-field light generating element 65 is preferably formed of an alloy consisting of Au, Pd, Pt, Rh, or Ir, or a combination of several of these. An insulating layer is interposed between the main magnetic pole 60 and the near-field light generating element 65. This insulating layer is preferably an oxide consisting of SiO2, Al2O3, etc.

[0023] Waveguide 66 extends from ABS13 to the back of slider 15, i.e., the end face on the suspension side, and is optically connected to LDU25. The end of waveguide 66 on the ABS13 side (extended end) faces the near-field light generating element 65 almost parallel to it. An insulating layer is interposed between waveguide 66 and the near-field light generating element 65.

[0024] The first thermal actuator has, for example, a heater 76a as a heating element. The heater 76a is embedded in a protective insulating film 53 and is located near the light head 58. The second thermal actuator has, for example, a heater 76b as a heating element. The heater 76b is embedded in a protective insulating film 53 and is located near the read head 54.

[0025] The thermal resistance sensor HR is embedded within the protective insulating film 53 and is located between the light 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.

[0026] The recording coil 70 is connected to the head amplifier IC 30 via wiring and a flexi 28 (not shown). When writing a signal to the magnetic disk 12, the recording current supply circuit 30a of the head amplifier IC 30 supplies recording current to the recording coil 70, thereby exciting the main magnetic pole 60 and causing magnetic flux to flow through the main magnetic pole 60. The recording current supplied to the recording coil 70 is controlled by the write control unit 46a of the main controller 40. The read head 54 is connected to the head amplifier IC 30 via wiring and a flexi 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.

[0027] The first heater 76a and the second heater 76b are connected to the head amplifier IC 30 via wiring and a flexure 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 the area around them are heated, causing the write head 58 or read head 54 to bulge toward the magnetic disk 12. In other words, the amount of levitation of the magnetic head 16 can be adjusted by adjusting the amount of bulging. 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.

[0028] The thermal resistance sensor HR is connected to the head amplifier IC 30 via wiring and a flexi 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.

[0029] The LDU25 is connected to the head amplifier IC30 via wiring and a flexi 28 (not shown). By applying drive power to the LDU25 from the light source drive current supply circuit 30e of the head amplifier IC30, the LDU25 oscillates laser light. The laser light is supplied to the near-field light generating element 65 through the waveguide 66. The current value of the drive current supplied to the LDU25 is controlled by the light source control unit 46d of the main controller 40.

[0030] The laser power is typically controlled by the current value setting of the light source drive current supply circuit (preamplifier) ​​30e. The energy supplied to the LDU25 is the I of the drive current supplied from the light source drive current supply circuit 30e. total = I th(or IB) + I eff (or IOP). The base current value I th Until, even if a current is applied to LDU25, laser oscillation does not occur. When the current value I th exceeding this is applied, laser oscillation is generated from LDU25. When the generated laser light is propagated to the near-field light generating element 65, near-field light is generated from the near-field light generating element 65 and irradiates the magnetic disk 12. As a result, the magnetic disk 12 is locally heated. eff The base current value I th varies depending on the environmental temperature and individual differences. Therefore, in HDD10, the base current value I th is held in the memory 47 as the device parameter IB. Also, the light source control unit 46d controls the laser power by changing the laser drive current setting value (I eff corresponding to I total -IB = IOP).

[0031] As shown in FIG. 1, according to HDD10, by driving the VCM 22, the head actuator 18 rotates, and the magnetic head 16 is moved and positioned on a desired track of the magnetic disk 12. As shown in FIG. 2, during the operation of HDD10, the magnetic head 16 faces the magnetic disk surface while maintaining a gap. The magnetic head 16 floats in an inclined posture in which the light head 58 portion of the head portion 17 is closest to the surface of the magnetic disk 12. In this state, while reading the recorded information by the read head 54 with respect to the magnetic disk 12, information (recording signal) is written (write operation) by the light head 58.

[0032] FIG. 4 is a cross-sectional view schematically showing a part of the head portion 17 of the magnetic head 16 and the magnetic disk 12 during the write operation. As shown in Figure 4, when the magnetic head 16 is writing, driving power is applied to the first heater 76a, which heats the first heater 76a and its surroundings, causing the write head 58 to bulge out toward the magnetic disk 12. As a result, the gap (head levitation amount) d1 between the write head 58 and the surface of the magnetic disk 12 is set to approximately 5 to 0.1 nm.

[0033] In the write operation, a recording current is supplied from the recording current supply circuit 30a to the recording coil 70, and the recording coil 70 excites the main magnetic pole 60. By applying a recording magnetic field perpendicular to the magnetic recording layer 104 of the magnetic disk 12 directly below from the main magnetic pole 60, information is written to the magnetic recording layer 104 with the desired track width. In addition, in heat-assisted magnetic recording, during the write operation, a drive current of a predetermined laser drive current setting value IOP is supplied from the light source drive current supply circuit 30e to the LDU 25, and laser light is emitted from the LDU 25. The laser light is supplied to the near-field light generating element 65 through the waveguide 66, and the near-field light generating element 65 generates near-field light and irradiates the magnetic disk 12. By locally heating the magnetic recording layer 104 of the magnetic disk 12 with the near-field light, the coercivity of the recording area is reduced. The recording magnetic field from the main magnetic pole 60 is applied to this coercivity reduction area to write the recording signal. In this way, high-density recording becomes possible by locally heating the magnetic recording layer 104 and writing the recording signal to the region where the coercivity has sufficiently decreased.

[0034] On the other hand, when the magnetic head 16 with a levitation amount d1 travels over the protective layer 105, lubricant is filled between the lubricant layer 106 applied to the protective layer 105 and the tip 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, and a build-up product HM is generated from the hardened components present on the magnetic disk 12. The build-up product HM adheres to the tip of the near-field light generating element 65. By irradiating with near-field light for a predetermined time, a build-up product HM with a height of d1 or less adheres to the tip of the near-field light generating element 65. This build-up product HM functions as a layer that increases the thermal conductivity efficiency of the laser light (near-field light). Therefore, it is possible to raise the temperature of the recording medium without increasing the laser output.

[0035] The components of the build-up product HM are lubricants and materials that make up the magnetic disk, but the main components are oxides that are particularly rich in Si, Ti, Ta, Al, C, Fe, Co, etc. The amount of build-up generated depends on the siloxanes contained in the environment and elements such as Si contained in the magnetic disk 12. If the amount of Si is high, the amount of build-up product HM generated will be large. According to the HDD 10 of this embodiment, the main controller 40 monitors the time until the build-up product HM is generated and measures the correlation between the generation time and the generation height of the product HM. The measurement results are registered in the memory 47 as generation time data.

[0036] As mentioned above, Si-based materials, including siloxanes, can cause smears (dirt) to adhere to the ABS 13 of the magnetic head 16. If the build-up product HM becomes excessively large, it may cause a malfunction between the magnetic head 16 and the magnetic disk 12. Therefore, the HDD 10 according to this embodiment is configured to perform periodic cleaning and regeneration of the build-up product. The operation of the HDD 10, including the cleaning operation and setting of the cleaning interval, will be described below.

[0037] According to HDD10, when cleaning the build-up 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 track density TPI of the LDU25, and stores it in memory 47.

[0038] The aforementioned laser drive current setting value IOP and track density TPI are determined during the manufacturing and adjustment process of the HDD 10. Typically, the areal recording density of the magnetic disk 12 is determined by the track density TPI and BPI (bits per inch), and the TPI and BPI that maximize the areal recording density are set. In the HDD 10 according to 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 in the memory 47 as a device parameter.

[0039] For the same magnetic head, magnetic disk, and magnetic head-to-disk distance, increasing the laser drive current setting value (IOP) increases the laser spot diameter. That is, a larger spot diameter results in a larger magnetic recording pattern (recording track width), and thus a decrease in recording density. Furthermore, the laser spot diameter is proportional to the diameter of the build-up product. Therefore, a larger laser spot diameter leads to a larger build-up product diameter, increasing the risk of smearing. Consequently, a larger IOP requires a shorter cleaning interval for the build-up product.

[0040] Figure 5 shows the correlation between the drive current setting value IOP and the track density TPI. As shown in the figure, IOP and TPI are inversely proportional, so the smaller the track density TPI, the shorter the cleaning interval needs to be. Figure 6 shows the relationship between the cleaning interval and the track density TPI, and Figure 7 shows the relationship between the cleaning interval L and the laser drive current setting value IOP. As shown in Figure 6, the higher the TPI, the longer the cleaning interval is set. For 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). As shown in Figure 7, the larger the IOP, the shorter the cleaning interval L is set to. For 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).

[0041] Further explanation on how to set the cleaning interval L will follow. Build-up product HMs increase in size over time after their formation, and friction with the magnetic disk can potentially affect magnetic head operations such as positioning. Figure 8 shows the relationship between the write operation time from the initial state of the magnetic head and the bit error rate (BER), and Figure 9 shows the relationship between the write operation time from the initial state of the magnetic head and the positioning accuracy of the magnetic head. In each figure, the solid line shows the relationship when the build-up generation rate T is fast, and the dashed line shows the relationship when the build-up generation rate T is slow.

[0042] As shown in Figure 8, a faster build-up generation rate T leads to a faster improvement in the bit error rate. In other words, the faster the build-up generation rate T, the more the build-up product HM contributes to improving write performance. On the other hand, as shown in Figure 9, a faster build-up generation rate T also leads to faster deterioration of positioning. This is because, as the build-up product grows, it exceeds a certain area, causing friction between the magnetic head and the magnetic disk, which hinders the smooth operation of the magnetic head and deteriorates positioning.

[0043] In Figure 9, the critical time at which deterioration occurs when the BER generation rate T is fast is denoted as T1lim, and the critical time at which deterioration occurs when the BER generation rate T is slow is denoted as T2lim. For IOP and TPI, Tlim can be expressed using a relationship such as Tlim = p × IOP + q or Tlim = s × TPI + t. Here, the cleaning interval L for a given magnetic head is determined by a value that takes into account the variability from the time Tlim at which positioning deteriorates. For example, the cleaning interval L is determined by a value such as L = Tlim × 0.8.

[0044] From the above relationship, the cleaning interval L is determined using the BER generation rate T. It can be expressed as a linear equation such as L = aT × b. Here, the coefficients a and b can be determined by the least squares method from multiple cleaning intervals Lx and buildup generation rate Tx.

[0045] Furthermore, the cleaning interval L may be set based on, for example, the operating time while the HDD is powered on. For example, the setting circuit 46e sets an arbitrary reference cumulative operating time as the cleaning interval L and registers it in the memory 47. The calculation circuit 46i of the main controller 40 monitors the operating time of the HDD 10, calculates and accumulates the cumulative operating time, and registers 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 when the reference cumulative operating time is reached, it instructs the cleaning execution circuit 46g to perform cleaning.

[0046] Furthermore, the cleaning interval L can also be set based on the total accumulated time of the magnetic head's writing operation. For example, the setting circuit 46e sets an arbitrary reference accumulated operating time as the cleaning interval L and registers it in the memory 47. The calculation circuit 46i of the main controller 40 calculates and accumulates the writing operation time of each magnetic head 16 to obtain the total accumulated operating time and registers it in the memory 47. The determination circuit 46f of the main controller 40 determines whether the total accumulated operating time of the magnetic head's writing operation has reached the set reference accumulated operating time, and when the reference accumulated operating time is reached, it instructs the cleaning execution circuit 46g to perform cleaning of the corresponding magnetic head.

[0047] In this case, since the cumulative writing time differs for each magnetic head, the main controller 40 checks the cumulative writing time of each magnetic head registered in the memory 47 at regular intervals and performs cleaning on the magnetic heads in order of their cumulative time exceeding the reference cumulative time. When a magnetic head reaches the cleaning interval L, cleaning may be performed on the corresponding magnetic head alone, or multiple magnetic heads or all magnetic heads may be cleaned.

[0048] Furthermore, within the recording area of ​​the magnetic disk 12, the laser drive current setting value IOP during write operations may differ between zones; that is, the laser drive current setting value IOP may differ for each radial position of the magnetic head 16 relative to the magnetic disk 12. Therefore, in calculating the write operation integration time, the laser drive current setting value IOP may be weighted for each zone or radial position in the write operation integration time. For example, the write operation integration time can be calculated using the following formula.

number

[0049] Next, we will describe an example of the cleaning operation for build-up product HM. Cleaning of the build-up product HM is performed by reducing the levitation amount of the magnetic head 16 from the levitation amount of the magnetic head 16 during normal write operation, thereby bringing the build-up product HM into contact with the magnetic disk surface and causing wear. For example, if the levitation amount setting during normal operation is 1 nm, during cleaning, the levitation amount can be reduced to 0.5 nm and held for about 1 second.

[0050] The reduction in the amount of levitation is not limited to 0.5 nm; various values ​​can be taken, such as lowering the magnetic head until it contacts the surface of the magnetic disk (touchdown), or lowering the magnetic head even further by several Å from the touchdown position (overpush).

[0051] Generally, maintaining a high levitation level results in a weak cleaning effect, but touching down the magnetic head provides sufficient cleaning. For more complete cleaning, the head can be pushed further towards the magnetic disk (over-push) by a few angstroms beyond the touchdown point. Alternatively, cleaning can be performed by touching down the magnetic head once or multiple times. Furthermore, the cleaning time is not limited to 1 second; it can be increased or decreased as needed depending on the cleaning status.

[0052] Since the cleaning of the generated material does not generate heat and does not erase recorded data, cleaning can be performed in the data recording area. Alternatively, to avoid the risk of the magnetic head becoming contaminated by wear material generated during cleaning, dedicated cleaning areas R1 and R2 (see Figure 1) may be provided in the non-data recording area of ​​the magnetic disk 12, for example, in the innermost or outermost area. Furthermore, in the case of a tile recording method (SMR), a dedicated cleaning area may be provided in the interband area of ​​the recording track.

[0053] In this embodiment, the HDD 10 performs regeneration of the build-up product HM after the cleaning operation is completed. Specifically, after the cleaning is completed, 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 heater drive power value during normal writing operation and sets the levitation amount of the magnetic head 16 to d1. At the same time, under the control of the light source control unit 46d, the drive circuit 46h supplies a laser drive current to the LDU 25 and generates near-field light from the near-field light generating element 65. As a result, the lubricant on the magnetic disk 12 is wound up and filled between the magnetic head and the surface of the magnetic disk, regenerating the build-up product HM. Generation takes place from the moment the near-field light is applied, over a period of time ranging from a few milliseconds to several hours, depending on the conditions of the laser light and lubricant. As a result, the build-up product HM grows to a height approximately the same as the levitation amount d1 of the magnetic head 16.

[0054] The generation of build-up product HM requires the application of laser light to heat the magnetic disk 12 to a high temperature, and it is not necessarily required to supply recording current to the magnetic head 16. In other words, the regeneration of build-up product HM is performed by applying laser light (near-field light) and then performing a seek or write operation on the magnetic head 16.

[0055] The regeneration of the build-up product HM may be performed by providing a dedicated area for playback on the magnetic disk 12, or, in the case of the street mirror recording (SMR) method, a dedicated area for regeneration may be provided in the interband area of ​​the recording track. When laser light is applied, if the temperature of the magnetic disk 12 exceeds the Curie temperature, the recorded pattern may be erased. Therefore, when generating build-up product HM in the data recording area of ​​the magnetic disk 12, it is desirable to use an area that is scheduled to be rewritten or to write the same pattern as that already recorded.

[0056] An example of the overall operation of an HDD configured as described above will be explained. Figure 10 is a flowchart showing an example of HDD operation, and Figure 11 is a schematic diagram showing the operation of the magnetic head corresponding to the operating state of the HDD. As shown in Figure 10, in the manufacturing or adjustment process, the main controller 40 of the HDD 10 first sets at least one or both of the aforementioned laser drive current setting value IOP and track density TPI (ST1). Typically, the areal recording density of the magnetic disk 12 is determined by the track density TPI and BPI, and the TPI and BPI that maximize the areal recording density are set. In the HDD 10 according to this embodiment, the setting circuit 46e adjusts the optimal value of the laser drive current setting value IOP simultaneously with TPI and BPI, and stores the optimized values ​​in the memory 47.

[0057] Next, the setting circuit 46e of the main controller 40 sets the execution interval for the cleaning operation of the generated HM, that is, the interval (cleaning interval L) between the completion of cleaning and the start of the next cleaning operation (ST2). For example, the setting circuit 46e targets the writing operation time of the magnetic head and sets an arbitrary reference integrated operation time (for example, several minutes to several tens of hours) as the cleaning interval L, and registers it in the memory 47.

[0058] As mentioned above, the cleaning interval L setting time is not limited to the cumulative write operation time of the magnetic head, but may also be a reference cumulative operating time, for example, based on the operating time when the HDD is powered on. Furthermore, the cleaning interval (time) L can also be set based on at least one of the set laser drive current setting value IOP and track density TPI.

[0059] As shown in Figures 10 and 11, during the operating period when the HDD 10 is powered on, the main controller 40 performs write and read operations in response to instructions from the host 45 (ST3). In addition, the arithmetic circuit 46i of the main controller 40 calculates and accumulates the write operation time of each magnetic 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 the HDD 10 and registers it in the memory 47.

[0060] While the HDD10 is operating, the determination circuit 46f of the MPU46 monitors the cumulative operation time of each magnetic head 16 and determines whether the cumulative operation time since the last cleaning has reached the reference cumulative operation time (cleaning interval L) (ST5). The determination circuit 46f continues to monitor and accumulate the write operation time until the cumulative operation time reaches the cleaning interval L. When the accumulated operating time reaches the reference accumulated operating time (cleaning interval L), the determination circuit 46f commands the cleaning execution circuit 46g to perform a cleaning operation and resets the registered accumulated operating time.

[0061] The cleaning execution circuit 46g starts the cleaning operation in response to a command (ST6). 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 and reduces the amount of levitation of the magnetic head 16. In one example, the heater drive current value is increased until the magnetic head 16 touches down on the surface of the magnetic disk 12, and this state is maintained for several seconds, for example, about 1 to 2 seconds. As a result, the buildup product HM adhering to the magnetic head 16 is worn away and removed by friction with the magnetic disk surface.

[0062] As mentioned above, the amount of levitation of the magnetic head during cleaning can be adjusted arbitrarily. While the normal setting for levitation during light operation is 1 nm, it may be reduced to 0.5 nm during cleaning, or it may be pushed in several Å beyond the touchdown position (overpush). Furthermore, the cleaning operation is not limited to a single operation, but may be performed multiple times consecutively.

[0063] After cleaning is complete, the main controller 40 performs build-up product regeneration (ST7). Specifically, the MPU 46, under the control of the heater control unit 46c, returns the heater drive power value to the heater drive power value during normal writing operation and sets the levitation amount of the magnetic head 16 to d1. Almost simultaneously, the MPU 46, under the control of the writing control unit 46a, supplies laser drive current to the LDU 25 of the magnetic head 16 and generates near-field light from the near-field light generating element 65. This causes the lubricant on the magnetic disk 12 to be drawn up and filled between the magnetic head and the surface of the magnetic disk, regenerating the build-up product HM. Regeneration takes place over a period of time, for example, several milliseconds to several hours, from the moment the near-field light is applied. This generates build-up product HM that has grown to approximately the same height as the levitation amount d1 of the magnetic head 16.

[0064] Thereafter, the main controller 40 performs write and read operations in response to instructions from the host 45, and further repeats the processing operations ST3 to ST7 described above.

[0065] The following shows the setting of the cleaning interval L and an example of the cleaning operation. (Example 1) Twenty HDDs were prepared; 10 were configured with cleaning as an example, and 10 were configured without the cleaning process (interval L set to infinity) as a comparative example. The initial bit error rate (BER) and positioning information were measured, and then the drives were run for 500 hours. Magnetic head cleaning was performed on all magnetic heads at the same time, once every 20 hours of HDD operation. The cleaning operation was performed by reducing the levitation height of the magnetic head during write operation to 0.5 nm and holding it in the recording area for 1 second.

[0066] After 500 hours of running time, we checked the magnetic head positioning accuracy and BER for both HDDs that had been cleaned and those that had not. Both HDDs showed similar or improved BER, but the positioning was significantly worse in the HDD without cleaning. This result confirms that cleaning can suppress the deterioration of positioning.

[0067] (Example 2) Twenty HDDs were prepared; 10 were configured with cleaning as an example, and 10 were configured without the cleaning process (interval L set to infinity) as a comparative example. The initial bit error rate (BER) and positioning accuracy information were measured, and then 1000 hours of running were performed. The magnetic head cleaning interval was set to a time value based on the IOP setting. For example, the cleaning interval is: When IOP > 10mA, 1.2·IOP(mA) - 1 hour. The setting was changed to 2 hours when IOP ≤ 10mA. Cleaning was performed when the light operation time of each magnetic head reached the set time.

[0068] Cleaning was performed by lowering the magnetic head's levitation level to 0 nm (touchdown state) during write operation and holding it for 2 seconds. For cleaning, the closest location within the interband region during SMR recording was used relative to the head's position at that time.

[0069] After 1000 hours of running time, we checked the magnetic head positioning accuracy and BER for both HDDs that had been cleaned and those that had not. Both HDDs showed similar or improved BER, but the positioning was significantly worse in the HDD without cleaning. This result confirms that cleaning can suppress the deterioration of positioning.

[0070] (Example 3) Twenty HDDs were prepared; 10 were configured with cleaning as an example, and 10 were configured without the cleaning process (interval L set to infinity) as a comparative example. The initial bit error rate (BER) and positioning accuracy information were measured, and then 5000 hours of running were performed. The magnetic head cleaning interval was set to a time value based on the TPI setting. For example, if the cleaning interval is set to X, where X is the TPI setting value (kTPI), When X > 510, the setting was X × 0.1 - 50 hours; when X ≤ 510, it was set to 1 hour. Cleaning was performed when the light operation time of each magnetic head reached the set time.

[0071] The cleaning was performed by reducing the magnetic head's levitation level during write operation to +0.5 nm of the touchdown state (over-push condition) and holding it for 0.5 seconds. In addition, a dedicated cleaning area R2 located at the outermost edge outside the recording area was used for cleaning.

[0072] After 1000 hours of running time, we checked the magnetic head positioning accuracy and BER for both HDDs that had been cleaned and those that had not. Both HDDs showed similar or improved BER, but the positioning was significantly worse in the HDD without cleaning. This result confirms that cleaning can suppress the deterioration of positioning.

[0073] According to the HDD of the first embodiment configured as described above, the build-up product HM is cleaned, i.e., removed, at each preset cleaning interval L. This prevents problems such as a decrease in head positioning accuracy and a decrease in recording density caused by the expansion of the build-up product HM. Therefore, according to this embodiment, it is possible to obtain a magnetic recording device that can prevent problems caused by build-up products and improve recording density.

[0074] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments are included in the scope and spirit of the invention, as well as in the claims and their equivalents. For example, the cleaning interval L is not limited to the reference cumulative operating time of the magnetic head as shown in the embodiment, but may also be a reference cumulative operating time based on the operating time of the HDD, or a time set based on the laser drive current setting value IOP and track density TPI. The amount of magnetic head levitation during cleaning can be set to any value, not limited to 0.5 nm, 0 nm, or 0-several Å. The cleaning time and number of cycles can be changed as needed. [Explanation of Symbols]

[0075] 10...Magnetic disk drive, 11...Enclosure, 12...Magnetic disk, 15...Slider 16...Magnetic head, 17...Head section, 18...Head actuator, 25...LDU, 30...Head amplifier IC, 40...Main controller, 46e...Setting circuit, 46f...Decision circuit, 46g...Cleaning execution circuit, 46i...arithmetic 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...Build-up product

Claims

1. 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 irradiates light onto the recording surface of the recording medium, A controller including a light source control circuit that controls the drive current value of the light source, a cleaning execution circuit that performs a cleaning operation to remove buildup products attached to the magnetic head, and a setting circuit that sets the cleaning interval for performing the cleaning operation, A magnetic recording device equipped with the following features.

2. The magnetic recording apparatus according to claim 1, wherein the setting circuit sets the cleaning interval according to at least one of the drive current setting value (IOP) of the light source and the track density (TPI) of the recording medium.

3. The magnetic recording apparatus according to claim 2, wherein the setting circuit sets the cleaning interval to be shorter as the drive current setting value (IOP) of the light source increases.

4. The magnetic recording apparatus according to claim 2, wherein the setting circuit sets the cleaning interval to be shorter as the track density (TPI) decreases.

5. The setting circuit sets the reference integrated operation time of the light operation of the magnetic head to the cleaning interval. The magnetic recording apparatus according to claim 1, wherein the controller comprises: a calculation circuit for accumulating the operation time of the writing operation of the magnetic head; and a determination circuit for comparing the accumulated operation time with a set reference accumulated operation time, and for starting the cleaning operation when the accumulated operation time reaches the reference accumulated operation time.

6. The setting circuit sets the standard cumulative operating time of the magnetic recording device to the cleaning interval. The magnetic recording apparatus according to claim 1, wherein the controller comprises a calculation circuit for accumulating the operating time of the magnetic recording apparatus, and a determination circuit that compares the accumulated operating time with the set reference accumulated operating time and starts the cleaning operation when the accumulated operating time reaches the reference accumulated operating time.

7. The magnetic recording apparatus according to claim 1, wherein the cleaning execution circuit performs cleaning by reducing the amount of levitation of the magnetic head from the amount of levitation during writing operation.

8. The magnetic recording apparatus according to claim 1, wherein 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 apparatus according to claim 1, wherein the cleaning execution circuit performs the cleaning operation in the innermost or outermost non-data recording area of ​​the recording medium.

10. The magnetic recording apparatus according to claim 1, wherein the cleaning execution circuit is performed in the region between the bands of the tile-written recording data in the data recording area of ​​the recording medium.

11. The magnetic recording apparatus according to claim 1, wherein the cleaning execution circuit includes a drive circuit that performs the regeneration of buildup products after the completion of the cleaning operation.

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