Magnetic disk device and voltage application method for magnetic disk device

Abstract

An embodiment of the present invention provides a magnetic disk device and a voltage application method for the magnetic disk device, which can suppress the floating amount of the magnetic head even if a voltage is applied to a heater element during a seek operation of the magnetic head, and can make the conditions at the start of writing good. A magnetic disk device involved in one embodiment comprises: a magnetic disk; a magnetic head that reads / writes data on the magnetic disk; a heater that adjusts the distance between the magnetic disk and the magnetic head based on the applied voltage during writing; and a control unit that causes the magnetic head to perform a seek operation from a first position to a second position of the magnetic disk. In addition, when the control unit causes the magnetic head to perform a seek operation from a first position to a second position, the control unit starts to apply a first voltage to the heater during the seek operation, and after applying the first voltage, before the magnetic head is located at the second position and starts writing data through the magnetic head, the voltage applied to the heater is a second voltage greater than the first voltage.

Description

[0001] This application claims the priority of Japanese Patent Application No. 2020-172586 (filing date: October 13, 2020), and the present application incorporates the entire contents of the basic application by reference. Technical Field

[0002] The embodiment relates to a magnetic disk device and a voltage application method for the magnetic disk device. Background Art

[0003] There is known a technique in which, in a magnetic disk device, a voltage is applied to a heater before starting writing.

[0004] When the action of applying voltage to the heater and heating the element unit is insufficient even as described above, the write condition will deteriorate, and therefore, the bit error rate of the first sector among the sectors to which the write is performed will deteriorate, becoming the main cause of weak write errors. Here, when the time for sufficiently heating the element unit in order to stabilize the write action when writing data is defined as the preheating time, by increasing the preheating time, the disk device can perform stable writing and prevent the deterioration of the bit error rate. On the other hand, due to the increase in the preheating time, the write performance of the disk device will deteriorate. In this way, the two can be said to be in a trade-off relationship. In particular, in the case of a seek action accompanied by a magnetic head, the seek time will be added to the preheating time, and therefore, the deterioration of the write performance of the disk device becomes significant.

[0005] Therefore, it is considered to start preheating during the seek action (during the seek action). However, in recent years, the preheating time has become longer, and there is a need to heat the component part from a state where the seek speed is faster than before (the need to apply voltage to the heater element). When the voltage is applied to the heater element from a state where the seek speed is fast, the gap (floating amount) of the magnetic head relative to the recording surface of the disk will change. For example, in a magnetic disk device, the following control is performed during the writing of data: the magnetic head is temporarily brought into contact with the recording surface of the disk, and then floated by a predetermined amount, thereby adjusting the floating amount (gap) between the magnetic head and the recording surface. When a voltage is applied to the heater at a fast seek speed during such control, there is a risk that the floating amount of the magnetic head will be lower than the required amount and the magnetic head will come into contact with the recording surface of the disk. Summary of the invention

[0006] The embodiments of the present invention provide a magnetic disk device and a voltage application method for the magnetic disk device, which can suppress the flying amount of the magnetic head even when a voltage is applied to a heater element during a seek operation of the magnetic head and can improve the conditions when writing is started.

[0007] A magnetic disk device according to one embodiment includes: a magnetic disk; a magnetic head that reads / writes data from / to the magnetic disk; a heater that adjusts the distance between the magnetic disk and the magnetic head based on an applied voltage during the writing; and a control unit that causes the magnetic head to perform a seek operation from a first position to a second position of the magnetic disk. In addition, when the control unit causes the magnetic head to perform the seek operation from the first position to the second position, the control unit starts to apply a first voltage to the heater during the seek operation, and after applying the first voltage, before the magnetic head is located at the second position and data writing starts by the magnetic head, the control unit makes the voltage applied to the heater a second voltage that is greater than the first voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a block diagram showing an example of the configuration of a system including the magnetic disk device according to the first embodiment.

[0009] Figure 2 This is a diagram showing an example of a plurality of functional blocks implemented by the CPU involved in this embodiment.

[0010] Figure 3 This is a diagram for explaining the PH time adjustment process performed in the seek operation during the write process according to the embodiment.

[0011] Figure 4 This is a diagram showing an example of the protruding responsiveness of the DHF according to this embodiment.

[0012] Figure 5 This is a diagram showing an example of the relationship between the warm-up time and the bit error rate (BER) of the first sector according to the present embodiment.

[0013] Figure 6 (a) and (b) are diagrams showing an example of the relationship between the seek speed and the flying distance of the slider during the seek operation according to the embodiment.

[0014] Figure 7 (a) and (b) are diagrams for explaining a method for setting heater power according to this embodiment.

[0015] Figure 8 This is a diagram showing an example of comparison of the floating displacement amounts of the positions of the element parts according to the embodiment.

[0016] Fig. 9 It is a diagram showing an example of the first application control according to this embodiment.

[0017] Fig.10 It is a diagram showing an example of the second application control according to this embodiment.

[0018] Fig.11 It is a diagram showing an example of the third application control according to the embodiment.

[0019] Fig.12 FIG. 1 is a diagram showing an example of the fourth application control according to the present embodiment.

[0020] Fig.13 1 is a diagram showing an example of the fifth application control according to this embodiment.

[0021] Fig.14 FIG. 1 is a diagram showing an example of the sixth application control according to the present embodiment.

[0022] Fig.15 It is a schematic cross-sectional view showing an example of the structure of a thermal assist portion according to the second embodiment.

[0023] Fig.16 It is a diagram showing an example of the seventh application control involved in this embodiment.

[0024] Fig.17 It is a diagram showing an example of the eighth application control involved in this embodiment.

[0025] Fig.18 FIG. 1 is a diagram showing an example of the ninth application control according to the present embodiment.

[0026] Fig.19 1 is a diagram showing an example of the tenth application control according to the present embodiment.

[0027] Description of symbols

[0028] 1 disk, 2 sliders, 3 arms, 4 voice coil motors, 10 disk devices, 22 head amplifier ICs, 62 CPUs, 200 thermal assist units, 210 light sources, HE heater elements, RH read heads, WH write heads DETAILED DESCRIPTION

[0029] Hereinafter, the embodiments will be described with reference to the accompanying drawings. In addition, the disclosure is only an example, and the invention is not limited by the contents described in the following embodiments. Deformations that can be easily thought of by a person skilled in the art are of course included in the scope of the disclosure. In order to make the description clearer, in the accompanying drawings, the size, shape, etc. of each part are sometimes schematically represented relative to the actual implementation form. In multiple drawings, the same reference numerals are sometimes marked on corresponding elements, and detailed descriptions are omitted.

[0030] (First embodiment)

[0031] Figure 1It is a block diagram showing an example of the structure of a system 150 having a disk device 10. The disk device 10 is a hard disk drive (hereinafter also referred to as HDD10). The system 150 has a host 100 and a HDD10. The host I / F120 connects the host 100 with the HDD10, and is used for sending and receiving commands, user data, command responses or status reports between the host 100 and the HDD10. The host I / F120, for example, follows the SATA (Serial Advanced Technology Attachment) standard and the SAS (Serial Attached SCSI) standard. The HDD10 is connected to the host 100 via the host I / F120, and functions as a data storage unit of the host 100. For example, the system 150 is a personal computer, a mobile device or a server device. For example, the host 100 is a chipset IC possessed in a personal computer or a mobile device or a server controller possessed in a server device.

[0032] HDD10 has a head-disk assembly (HDA) including a magnetic disk 1, a slider (magnetic head) 2, an arm 3, a voice coil motor (VCM) 4, and a spindle motor (SPM) 5. The HDA is housed inside a housing (not shown) of the HDD10. The slider 2 has a read head RH, a write head WH, and a heater element HE. In addition, the HDD10 has a circuit block including a motor driver IC (hereinafter also referred to as a driver IC) 21, a head amplifier IC 22, a buffer memory 23, a nonvolatile memory 24, and a controller 60. The controller 60 has a read-write channel (hereinafter also referred to as RWC) 61, a CPU (control unit) 62, and a hard disk controller (hereinafter also referred to as HDC) 63. The head amplifier IC 22 has at least a heater driver HD.

[0033] The HDD 10 at least performs a process of recording data on the magnetic disk 1 (write process), a process of reading data recorded on the magnetic disk 1 (read process), and a process of controlling the flying height of a part of the slider 2 relative to the magnetic disk 1 (floating control process). The floating control process is sometimes referred to as DFH (Dynamic Fly Height) control, and in the following description, the floating control process is also referred to as DFH control. Here, the flying height corresponds to, for example, the floating amount of the head of the slider 2 from the surface of the magnetic disk 1. In the DFH control, by applying a voltage (or current) to the heater element HE provided on the slider 2, a part of the slider 2 (the heater element HE and the peripheral part of the head) is heated, deformed due to thermal expansion, and protrudes toward the magnetic disk 1. In addition, in the following description, the current or voltage supplied to the heater element HE is referred to as the voltage applied to the heater element HE.

[0034] The amount of protrusion of a portion of the slider 2 can be controlled based on information corresponding to the voltage applied to the heater element HE. The change in the amount of protrusion of a portion of the slider 2 relative to the change in the voltage applied to the heater element HE does not respond instantly, but responds with a delay corresponding to a certain time constant. Therefore, in the present embodiment, a preheating process is performed to heat the heater element HE at a timing before the timing of the head passing the target position of the DFH control. By performing the preheating process in the DFH control, it is possible to obtain an appropriate floating amount of the described portion of the slider 2 at the timing of the head passing the target position of the read process or the write process. In addition, in the subsequent description, unless otherwise specified, the floating control process (DFH control) is described as a process including the preheating process.

[0035] The writing process, the reading process, the floating control process, and the warm-up process described later are executed according to a command sent from the host 100 or a spontaneous request from within the HDD 10. These processes are controlled according to a program (firmware) executed by the CPU 62. The data of the program is stored in the nonvolatile memory 24 and / or the magnetic disk 1 in a nonvolatile manner.

[0036] The disk 1 is rotated by the SPM 5. The SPM 5 is rotationally controlled by a driving voltage or a driving current from the driver IC 21. The arm 3 and the VCM 4 constitute an actuator. The slider 2 is mounted on one end of the arm 3. The actuator moves the slider 2 to a target position on the disk 1. That is, the actuator moves the slider 2 mounted on the arm 3 in a radial direction on the disk 1 by the drive of the VCM 4. The VCM 4 is controlled by a driving voltage or a driving current from the driver IC 21.

[0037] The magnetic disk 1 has a recording surface, and a track (data track) is formed by recording data on the recording surface. That is, the magnetic disk 1 is configured as a recording medium having a recording surface for recording data. The recording surface of the magnetic disk 1 has at least a servo area in which servo data for controlling the position of the slider 2 on the recording surface is recorded, a user data area for recording user data sent from the host 100, and a system area for recording system data for managing the user data recorded in the user data area. The recording surface of the magnetic disk 1 may also have a cache area for temporarily recording user data to be recorded in the user data area.

[0038] Servo data is data recorded in the manufacturing process of HDD 10 and not recorded after HDD 10 is shipped. System data includes data to be managed in the write process and the read process performed by HDD 10. In addition, system data may be recorded in the nonvolatile memory 24 instead of the system area of ​​​​the disk 1. User data includes not only data sent from the host 100 and then recorded, but also data already recorded in the user data area or the cache area and data read from the user data area or the cache area.

[0039] The slider 2 has at least a head and a heater element HE, and the head includes a read head RH and a write head WH. The read head RH reads the data recorded on the track on the disk 1. The read data includes servo data, user data, and system data. The write head WH writes the user data and system data on the disk 1. The heater element HE generates heat in response to the applied voltage, and heats a portion of the slider 2. The heated portion of the slider 2 thermally expands and protrudes toward the disk 1. In this embodiment, a heater element HE is provided between the read head RH and the write head WH, or a heater element HE is provided near the read head RH and near the write head WH. The heater element HE is formed by a resistor or a coil as a circuit element. Figure 1 Although a single magnetic disk 1 and a slider 2 are shown in the figure, the HDD 10 may be provided with a plurality of magnetic disks 1 and a plurality of sliders 2 corresponding to the recording surfaces of the plurality of magnetic disks 1 .

[0040] The head amplifier IC22 includes a read amplifier, a write driver (all not shown), and a heater driver HD. The read amplifier amplifies the read signal read by the read head RH and outputs it to the RWC61. The write driver outputs a write current corresponding to the write data supplied from the RWC61 to the write head WH. The heater driver HD applies a heater voltage (or heater current) corresponding to the heater data supplied from the CPU62 or the HDC63 to the heater element HE. The heater data is data indicating a value corresponding to the heater voltage (or heater current).

[0041] The controller 60 is configured as a single-chip integrated circuit that at least integrally includes RWC 61, CPU 62, and HDC 63. The controller 60 is configured as a semiconductor circuit such as SoC, FPGA, ASIC, LSI, etc. The buffer memory 23 is a volatile memory that can transfer data at a higher speed than the disk 1, and DRAM (SDRAM) or SRAM can be applied. The non-volatile memory 24 is a non-volatile recording unit, and semiconductor memories such as NOR type and NAND type flash memories can be applied. The buffer memory 23 and the non-volatile memory 24 can also be disconnected from the outside of the controller 60 and be provided inside the controller 60. The non-volatile memory 24 can also be applied to a part of the recording area of ​​the disk 1.

[0042] RWC61 includes a read channel and a write channel (both are omitted in the figure). The read channel processes the amplified read signal supplied from the head amplifier IC22 and decodes the data including servo data and user data. RWC61 performs processing related to the detection and correction of errors in user data in the read channel, and generates information for evaluating the read user data. This information can be sent to CPU62 according to the request from CPU62. The read channel includes a Viterbi decoding circuit and an LDPC decoding circuit. The write channel outputs the write data after encoding the data to be written supplied from HDC63 to the head amplifier IC22.

[0043] The HDC 63 is connected to the buffer memory 23 and the non-volatile memory 24, and controls the transmission and reception of data transmitted between them. The data transmitted between the HDC 63 and the buffer memory 23 include read data and write data transmitted between the host 100 and data related to the floating control process. The read data is user data read from the disk 1, and the write data is user data written to the disk 1. The data related to the floating control process includes heater data and heater sensitivity data for setting the voltage applied to the heater element HE. The heater data is represented by a value corresponding to the current, voltage, power or heat generated for the heater element HE. The heater sensitivity data is data corresponding to the amount of change in the protrusion or floating amount of the slider 2 corresponding to the amount of change in the voltage applied to the heater element HE, the heat generated by the heater element HE, or the thermal expansion of the peripheral portion of the heater element HE. The data transmitted between the HDC 63 and the non-volatile memory 24 include the program executed by the CPU 62, system data, and data related to the floating control process. The HDC 63 is connected to the RWC 61 and performs processing on data input from or output to the RWC 61. For example, the HDC 63 provides the CPU 62 with data input from the RWC 61 and used in the PH time adjustment processing according to the control of the CPU 62.

[0044] Furthermore, HDC63 is connected to the host 100, and performs processing for commands and user data sent from the host 100 or command responses, status reports, and user data output to the host 100. The processing of user data includes processing related to write gate in write processing, processing related to read gate in read processing, and processing related to servo gate required in servo control. HDC63 notifies CPU62 of the execution request of the floating control processing corresponding to the command input from the host 100. HDC63 is composed of an interface circuit for controlling the transmission and reception of data between the buffer memory 23, the non-volatile memory 24, the RWC61, and the host 100. HDC63 can output heater data to the heater driver HD. In this case, HDC63 can generate heater data based on instructions from CPU62 and output the generated heater data, or it can be provided with heater data from CPU62 and output the provided heater data.

[0045] CPU62 is an IC also called a microprocessor or a microcontroller. CPU62 controls VCM4 via driver IC21 and performs positioning control (servo control) of the head (read head RH and write head WH). Servo control includes at least control of positioning slider 2 at a certain position in the radial direction of disk 1 and control of moving slider 2 from the current position to the target position on disk 1. In addition, CPU62 controls the writing process and reading process of disk 1 at least via RWC61. CPU62 controls the floating control process in parallel with the writing process and the reading process. In addition, the servo process can be executed as a part of the writing process and the reading process. CPU62 outputs heater data to the heater driver HD in the floating control process. In the control of these multiple processes, CPU62 uses the HDA and circuit blocks described above according to the program. CPU62 is configured as a control unit or control circuit that controls multiple processes.

[0046] With the configuration described above, the HDD 10 according to the present embodiment can execute a plurality of processes described in detail below.

[0047] Next, use Figure 2 The operation of the CPU 62 will be described. Figure 2 This is a diagram showing an example of a plurality of functional blocks implemented by the CPU 62 .

[0048] The CPU 62 realizes a plurality of functional units by operating according to a program. The CPU 62 includes a floating control unit 301, a preheating adjustment unit (hereinafter also referred to as a PH adjustment unit) 302, a write control unit 303, and a read control unit 304. These functional units control at least the RWC 61 and the HDC 63. In addition, the functional units of the CPU 62 cooperate with the HDA and the circuit blocks of the HDD 10 to perform various processes. The functional units of the CPU 62 are configured to share information with each other and synchronize the processing timing. In addition, the functional units of the CPU 62 are configured to perform processing in parallel.

[0049] The floating control unit 301 controls the floating control process in response to the execution request input from the HDC63. Here, the floating control process includes a preheating process. The floating control unit 301 controls the floating control process in parallel with the write process performed by the write control unit 303 or the read process performed by the read control unit 304. The floating control unit 301 receives the data required in the control of the floating control process from the HDC63, and outputs the data to be stored in the control of the floating control process to the HDC63. In addition, the floating control unit 301 shares the data required in the control of the floating control process with the write control unit 303 or the read control unit 304. For example, the floating control unit 301 receives the data for setting the floating amount at the track and the data related to the start timing of the floating control process from the HDC63 in response to the write process or the execution request of the write process for a certain track. The data for setting the floating amount and the data related to the start timing of the floating control process sometimes need to be corrected (updated) during the execution of the floating control process. Accordingly, the floating control unit 301 outputs the corrected (updated) data to the HDC 63. The data for setting the floating amount includes at least heater data and heater sensitivity data. The data related to the start timing of the floating control process is data corresponding to time. In addition, for example, the floating control unit 301 shares data for determining the write process or the target track of the write process with the write control unit 303 or the read control unit 304.

[0050] The PH adjustment unit 302 adjusts the preheating time used in the floating control process controlled by the floating control unit 301. The PH adjustment unit 302 adjusts the preheating time in accordance with the execution request input from the HDC 63. The preheating time is data related to the time and magnitude of the voltage applied to the heater element HE (heater activation) before the timing when the head passes the target position (e.g., the position determined by the head, track, and sector) of the floating control process. The PH adjustment unit 302 adjusts the preheating time for the write process (hereinafter also referred to as the WPH time) and the preheating time for the read process (hereinafter also referred to as the RPH time). The PH adjustment unit 302 may adjust at least the WPH time and the magnitude of the voltage applied to the heater element HE. The PH adjustment unit 302 adjusts the preheating time in parallel with the floating control process, the write process, or the read process. In the following description, the process of adjusting the preheating time controlled by the PH adjustment unit 302 is also referred to as the preheating time adjustment process (PH time adjustment process). In addition, the control related to the magnitude of the voltage applied to the heater element HE is referred to as application control. The PH adjustment unit 302, like the floating control unit 301, sends and receives data related to the PH time adjustment process with the HDC63. For example, before the start of the PH time adjustment process, the PH adjustment unit 302 receives data required for the floating control process in the target track to be processed from the HDC63. In addition, during the PH time adjustment process, the PH adjustment unit 302 receives data related to the quality of the data read from the disk 1 from the HDC63. In addition, for example, the PH adjustment unit 302 shares data for determining the target track for the PH time adjustment process with the write control unit 303 or the read control unit 304.

[0051] The write control unit 303 controls the writing process of data on the magnetic disk 1. The write control unit 303 controls the writing process in accordance with the execution request input from the HDC 63. The write control unit 303 controls the writing process in parallel with the floating control process based on the floating control unit 301 and the PH time adjustment process based on the PH adjustment unit 302. The write control unit 303 controls the writing process based on the shingle recording method or the normal writing process that is not the shingle recording method. The writing process based on the shingle recording method refers to a method in which new data is recorded overlapping with a part of the recorded data (overwriting a part of the recorded data). The normal writing process refers to a method in which new data is recorded without overlapping with the recorded data (without overwriting a part of the recorded data). In addition, as a part of the writing process, a servo process can be performed.

[0052] The read control unit 304 controls the reading process of the data on the magnetic disk 1. The read control unit 304 controls the reading process in accordance with the execution request input from the HDC 63. The read control unit 304 controls the reading process in parallel with the floating control process by the floating control unit 301 and the PH time adjustment process by the PH adjustment unit 302. Along with the reading process, the read control unit 304 receives evaluation data from the HDC 63, which is information for evaluating the read data. The read control unit 304 outputs the received evaluation data to the PH adjustment unit 302 in accordance with the request from the PH adjustment unit 302. In addition, a servo process can be executed as a part of the reading process.

[0053] As described above, the plurality of processes according to the present embodiment are controlled by the plurality of functional units implemented by the CPU 62 .

[0054] Next, the details of the PH time adjustment process performed by the PH adjustment unit will be described.

[0055] Figure 3 This is a diagram for explaining the PH time adjustment process performed in the seek operation during the write process.

[0056] like Figure 3 As shown, three modes of PH time adjustment processing are shown. Mode P1 represents the following PH time adjustment processing: preheating starts after the seek action is completed, and writing processing starts after the preheating is completed. Mode P2 represents the following PH time adjustment processing: preheating starts at a timing when the seek action speed slows down, and writing processing starts after the preheating is completed. Mode P3 represents the following PH time adjustment processing: preheating starts at a timing when the seek action speed is still fast, and writing processing starts after the preheating is completed.

[0057] Thus, there are three modes of PH time adjustment processing, but according to mode P1, the time until the writing condition is good at the beginning of writing becomes longer. According to mode P2, the preheating is started from near the time when the seek speed becomes slow, and the time until the writing condition is good is shorter than that in mode 1. Furthermore, according to mode P3, in response to the increase in preheating time in recent years, the preheating process is started from the period when the seek speed is fast, but in this case, as already described, there is a possibility that the heater element HE will contact the surface of the disk 1. Therefore, it is necessary to avoid the contact of the heater element HE with the surface of the disk 1 while adopting mode P3. In this embodiment, in order to avoid this contact, the CPU 62 executes the control of applying the voltage to the heater element HE (refer to Figures 9 to 14 to be described later).

[0058] Here, refer to Figures 4 to 8, the reason for performing the control of the voltage application to the heater element HE will be described in detail.

[0059] Figure 4 is a diagram showing an example of the outstanding responsiveness of DHF control. Figure 4 In the figure, the horizontal axis represents the voltage application time (ms), and the vertical axis represents the responsiveness of the DFH control (%). The responsiveness of the DHF control has the following characteristics: when the voltage is applied to the heater element HE, it rapidly protrudes to about 80% in a short time, and then becomes a protrusion amount of about 100% in about 1.0 ms. It can be seen that the protrusion achieved by the heater element HE has a time constant. Therefore, when the writing process is started before the protrusion is sufficient and before the thermal stability, the writing process is performed in a state where the floating amount of the slider 2 relative to the magnetic disk 1 (the gap of the element part) is large, and the bit error rate (BER) deteriorates.

[0060] Figure 5 1 is a graph showing an example of the relationship between the warm-up time and the bit error rate (BER) of the first sector. Here, the first sector refers to the sector where data is first written after writing starts. Figure 5 In the figure, the horizontal axis represents the preheating time, and the vertical axis represents the BER of the first sector. Time T1 and time T2 represent the necessary preheating time. As shown by the thick line in the figure, it can be seen that when the BER whose degradation is allowed is set to the allowable dBER, there is a risk of a write error if the preheating time is not extended to at least time T1. In recent years, in the magnetic disk device 10, the sensitivity to the BER due to the influence of the floating change and the like has become higher, as shown by the thin line in the figure. Therefore, the necessary preheating time is extended from time T1 to time T2. That is, when the preheating time is extended in the processing of the mode P1 already described, the seek time + preheating time becomes before the start of writing, and therefore, the time until the start of writing becomes cumulatively longer, and the write performance deteriorates. In order to avoid this situation, as described already Figure 3 When the preheating process is performed in the middle of the seek, as in the pattern P2 of FIG. 1 , the time until the start of writing can be shortened by the amount of overlap of the seek action and the preheating time. However, as in the pattern P3, when the amount of overlap of the seek action and the preheating time increases in consideration of the fact that the preheating time has become longer in recent years, the time until the start of writing becomes shorter, and on the other hand, the preheating is started during the period when the seek speed is fast. In this way, the upward movement of the slider 2 occurs due to the influence of the air volume generated by the seek action.

[0061] Figure 6 FIG. 2 is a diagram showing an example of the relationship between the seek speed and the floating amount of the slider 2 during the seek operation. Figure 6 , the horizontal axis is time (ms). Figure 6 The vertical axis of (a) represents the seek speed, Figure 6The vertical axis of (b) represents the change in the floating amount of the slider 2 (nm). In addition, the time reference is the time when the positioning is completed after the seek. Figure 6 As shown in (a), the closer to the completion of positioning, the greater the seek speed before the seek action is completed. The floating amount change is roughly proportional to the seek speed, so the floating change of the slider 2 becomes as follows: Figure 6 Due to the superposition of this floating fluctuation and the outstanding responsiveness of the heater element HE described above, there is a risk that the element portion will fall below the predetermined gap.

[0062] Figure 7 This is a diagram for explaining the method of setting the heater power. Figure 7 In the graph, the horizontal axis represents time (ms) and the vertical axis represents heater power (%).

[0063] Figure 7 (a) corresponds to the already described mode P1, Figure 7 (b) corresponds to the mode P3 described above. The overlap time with the seek operation is 0 ms and -2.0 ms respectively. In either case, the voltage applied to the heater element HE is 100% or 0%, and 100% voltage is applied to the heater element HE at each time 0 ms and -2.0 ms. When the voltage applied to the heater element HE is controlled, the time until the write process may be longer ( Figure 7 (a)), or the disk 1 may be in contact with the element portion of the slider 2 ( Figure 7 (b)). To avoid this situation, in this embodiment, while adopting mode P3, the following is performed. Figures 9 to 14 The control applied to the heater element HE is described.

[0064] Figure 8 2 is a diagram showing an example of comparison of the floating displacement of the element portion of the slider 2. In other words, Figure 8 The figure shows the change in the difference (space) of the element part relative to the predetermined gap. The figure shows the change in the space (floating amount) when the overlap time between the seek operation and the warm-up time is set to 0ms (pattern P1), 1ms, 1.5ms, and 2ms. Figure 8 When the overlap time is 1.5ms and 2.0ms, the floating amount of the element part is lower than the predetermined value. This shows that in this case, there is a risk that the element part will contact the disk 1. According to such a situation, there is a limit to overlapping the seek time and the warm-up time. When the overlap time is prolonged, the element part will contact the disk 1, and the write performance of the disk device 10 will deteriorate. In addition, by executing the reference to the following Figures 9 to 14The control of the heater element HE described above shows that, as shown by the bold line (this embodiment), even if the overlap time of the seek operation and the warm-up time is prolonged, the floating amount of the element portion does not fall below a predetermined value, thereby preventing the element portion from contacting the magnetic disk 1.

[0065] Below, refer to Figures 9 to 14 The control of applying the voltage to the heater element HE according to the present embodiment will be described. Figures 9 to 14 The first to sixth application controls respectively correspond to: starting application of the first voltage to the heater element HE during a seek operation in which the slider 2 moves from the current position (first position) to the target position (second position), and applying a second voltage greater than the first voltage to the heater element HE after the first voltage is applied and before the slider 2 is located at the target position and data is written by the slider 2. Figures 9 to 14 In the figure, the horizontal axis represents time (ms), and time 0 (0ms) is when the positioning after the seek is completed, which is the end time of the seek operation and the start time of writing. The vertical axis represents the magnitude of the voltage applied to the heater element HE (hereinafter also referred to as the heater power), and the state of the maximum heater power is set to 100%. In this embodiment, the first to sixth application controls are set to be executed by the CPU 62 reading the firmware and instructing the head amplifier IC 22, but it can also be that the head amplifier IC 22 is executed based on the preheating time instructed by the PH adjustment unit 302 based on a preset voltage value.

[0066] Fig. 9 1 is a diagram showing an example of the first application control. The first application control is an application control for starting application of power to the heater element HE from the seek operation and gradually increasing the heater power to a maximum voltage value (maximum).

[0067] More specifically, in this embodiment, if Fig. 9 As shown in FIG. 1 , 2.0 ms before time 0 (hereinafter, the period before time 0 is also referred to as “-”), a voltage is applied to the heater element HE so that the heater power becomes 90%. And, from this state, the heater power gradually increases linearly so that the heater power becomes the maximum (100%) at 0 ms. In this way, the voltage applied to the heater element HE is controlled by the CPU 62.

[0068] Fig.10 2 is a diagram showing an example of the second application control. The second application control is an application control for gradually increasing the heater power to the heater element HE to a maximum voltage value (maximum) from the start of the seek operation, and further setting the heater power to zero as an initial value.

[0069] More specifically, in this embodiment, if Fig.10 As shown, the heater power gradually increases linearly so that the initial value at -2.0 ms is 0% of the heater power and the heater power becomes 100% at 0 ms. In this way, the voltage applied to the heater element HE is controlled by the CPU 62 .

[0070] Fig.11 : is a diagram showing an example of the third application control. The third application control is an application control in which application to the heater element HE is started from the seek operation, and the heater power is increased in a curve to a maximum voltage value (maximum) in consideration of the outstanding responsiveness achieved by the heater.

[0071] More specifically, in this embodiment, if Fig.11 As shown, consider the reference Figure 4 The heater power is gradually increased in a curve manner with the outstanding responsiveness described above, so that the heater power is about 90% at -2.0 ms and the heater power becomes 100% at 0 ms from this state. In this way, the voltage applied to the heater element HE is controlled by the CPU 62.

[0072] Fig.12 : is a diagram showing an example of the fourth application control. The fourth application control is an application control for starting application of voltage to the heater element HE during a seek operation and increasing the voltage to a maximum voltage value (maximum) before the seek operation is completed.

[0073] More specifically, in this embodiment, if Fig.12 As shown in FIG. 1 , the heater power gradually increases linearly so that the heater power is about 90% at -2.0 ms and 100% at -0.5 ms. In this way, the voltage applied to the heater element HE is controlled by the CPU 62. Here, the seek speed is quite slow before the seek is completed and this speed can be ignored. Therefore, the heater power is controlled synchronously with the seek speed so that it becomes 100% before the seek is completed.

[0074] Fig.13 : is a diagram showing an example of the fifth application control. The fifth application control is an application control in which the voltage is increased stepwise to a maximum voltage value (maximum) by applying the heater power to the heater element HE from the start of the seek operation so as to make the heater power less than the heater power of the maximum protrusion amount.

[0075] More specifically, in this embodiment, if Fig.13As shown in FIG. 1 , at -2.0 ms, the heater power is about 90%, and at -0.5 ms, the heater power is 100%. In this way, the voltage applied to the heater element HE is controlled by the CPU 62. In this way, the heater power is controlled stepwise at a heater power below the heater power that becomes the maximum protrusion amount. Therefore, compared with the control of gradually increasing the heater power, the circuit structure of the head amplifier IC 22 can be simplified.

[0076] Fig.14 : is a diagram showing an example of the sixth application control. The sixth application control is an application control in which the application to the heater element HE is started from the seek operation so that the heater power becomes less than the heater power of the maximum protrusion amount, and the voltage is increased in stages to the maximum voltage value (maximum). Here, the term "staged" means having a plurality of stages.

[0077] More specifically, in this embodiment, if Fig.14 As shown in FIG. 1 , the heater power is controlled to be about 90% at -2.0 ms, about 93% at -1.5 ms, about 96% at -1.0 ms, and 100% at -0.5 ms. In this way, the voltage applied to the heater element HE is controlled by the CPU 62. The heater power is controlled in stages at a heater power below the heater power that becomes the maximum protrusion amount. Therefore, compared with the control of gradually increasing the heater power, the circuit structure of the head amplifier IC 22 can be made simple, and further, compared with the case of increasing the heater power in stages in the fifth application control already described, the voltage application control can be performed with higher accuracy.

[0078] In this way, by executing the first application control to the sixth application control already described, the magnetic disk device 10 can suppress the heater power before time 0, that is, the timing when the seek action ends and the write action is completed. Therefore, even if the preheating process is started during the seek action when the seek speed is fast, the change in the floating amount of the slider 2 can be suppressed, and the writing conditions can be made good when writing starts.

[0079] (Second embodiment)

[0080] The second embodiment is different from the first embodiment described above in that a thermal assist portion for assisting data writing is provided on the slider 2. Therefore, the structure and control resulting from the provision of the thermal assist portion will be described in detail. In addition, the same reference numerals are given to the same structures as those in the first embodiment, and detailed description thereof will be omitted.

[0081] Fig.15 It is a schematic cross-sectional view showing an example of the structure of a thermal assist portion included in the slider 2 .

[0082] like Fig.15 As shown, the slider 2 includes two heater elements HE, a read head RH, a write head WH, and a thermal assist unit 200. The thermal assist unit 200 includes a light source 210 that emits laser light, a light guide 220 for the laser light, and an optical element (near-field optical element) 230. In the magnetic disk device 10 having such a structure, when writing data to the magnetic disk 1 by the write head WH, the laser light from the light source 210 passes through the light guide 220 and is irradiated to the magnetic disk 1 via the optical element 230, and the writing of data is assisted by the laser light. Therefore, when controlling the floating amount of the element part of the slider 2, in addition to the heater power of the heater element HE, it is necessary to consider the heating by the laser light. In this case, by considering the heating by the laser light (hereinafter also referred to as the laser power) in addition to the heater power, even if the preheating process is started during a period of high seek speed, the fluctuation of the floating amount of the slider 2 can be suppressed, and the writing conditions can be made good at the start of writing.

[0083] Here, in the case where the time constants of the thermal deformation caused by the heater power and the thermal deformation caused by the laser power are taken into consideration, the responsiveness of the thermal deformation caused by the laser power is faster. Therefore, it is not necessary to make the timing of applying the voltage to the heater element HE coincide with the timing of applying the voltage to the light source 210. In other words, if the responsiveness is taken into consideration, it can also be set as follows: after the voltage is applied to the heater element HE, the voltage is applied to the light source 210 after a predetermined time. The details will be described later, and the following seventh application control and eighth application control are controls that take this responsiveness into consideration.

[0084] Below, refer to Figure 16 to Figure 19 The voltage application control according to the present embodiment will be described. Figure 16 to Figure 19 The seventh to tenth application controls respectively correspond to: starting to apply the first voltage to the heater element HE during a seek operation in which the slider 2 moves from the current position (first position) to the target position (second position), applying a second voltage greater than the first voltage to the heater element HE after the first voltage is applied and before the slider 2 is located at the target position and data is written by the slider 2, and increasing the voltage to the second voltage, and controlling the voltage based on the total value of the voltage applied to the heater element HE and the intensity of the laser. In addition, Figure 16 to Figure 19 In the figure, the horizontal axis represents time (ms), and time 0 is the end time of the seek action and the start time of writing. In addition, the vertical axis represents the heater power. Further, the thin line in the figure is the heater power (DFH) of the heater element HE, and the thick line in the figure represents the heater power of the total value of DFH and laser power. The total value (100%) is the heater power required to make the writing condition good.

[0085] Fig.16 : is a diagram showing an example of the seventh application control. The seventh application control is an application control in which the voltage application to the heater element HE is started during the seek operation, and then the voltage is applied to the laser light source 210 before time 0 so that the voltage increases to the maximum voltage value (maximum).

[0086] More specifically, in this embodiment, if Fig.16 As shown in FIG. 1 , a voltage is applied to the heater element HE so that the voltage becomes about 80% at -2.0 ms, and the voltage applied to the heater element HE continues in this state. Furthermore, a voltage is applied to the laser light source 210 at -0.5 ms, and the total value of the heater power of the heater element HE plus the laser power becomes 100%. In this way, the voltage application control of the heater element HE and the light source 210 is performed by the CPU 62. This application control is the simplest control among the seventh application control to the tenth application control.

[0087] Fig.17 8 is a diagram showing an example of the eighth application control. The eighth application control is to first start applying voltage to the heater element HE during the seek operation, and then apply voltage to the laser light source 210 before time 0, which is similar to the above-described Fig.16 The difference is that the voltage applied to the heater element HE is gradually increased to the maximum voltage value (maximum).

[0088] More specifically, in this embodiment, if Fig.17 As shown, a voltage is applied to the heater element HE so that the heater power of the heater element HE is slightly over 60% at -2.0 ms, and the heater power is gradually increased so that it reaches 70% at -0.5 ms. In addition, it is assumed that a voltage is applied to the light source 210 at -1.0 ms, and the total value becomes 100% at -0.5 ms when the laser power is added. In this way, the voltage applied to the heater element HE and the light source 210 is controlled by the CPU 62.

[0089] Fig.18 : is a diagram showing an example of the 9th application control. The 9th application control is an application control in which a voltage is applied to the heater element HE and a voltage is applied to the light source 210 at the same time, and the voltage applied to the heater element HE is increased in stages to a maximum voltage value (maximum), and the total value is 100% before time 0.

[0090] More specifically, in this embodiment, if Fig.18As shown in FIG. 1 , the voltage is applied to the heater element HE and the light source 210 simultaneously so that the voltage becomes 90% at -2.0 ms, and the voltage applied to the heater element HE is increased stepwise at -1.5 ms, -1.0 ms, and -0.5 ms, and the total value is increased accordingly, and the total value is 100% at -0.5 ms. In this way, the voltage applied to the heater element HE and the light source 210 is controlled by the CPU 62.

[0091] Fig.19 10 is a diagram showing an example of the 10th application control. The 10th application control is an application control in which a voltage is applied to the heater element HE and a voltage is applied to the light source 210 at the same time, and the voltage applied to the heater element HE is gradually increased so that the total value increases to a maximum voltage value (maximum), i.e., 100%, before time 0.

[0092] More specifically, in this embodiment, if Fig.19 As shown in FIG. 1 , the voltage is applied to the heater element HE and the light source 210 in such a manner that the voltage becomes 90% at −2.0 ms, and the voltage applied to the heater element HE is gradually increased to the maximum voltage value (maximum) so that the total value becomes 100% at −0.5 ms. In this way, the voltage applied to the heater element HE and the light source 210 is controlled by the CPU 62.

[0093] As described above, in the magnetic disk device 10 having the thermal assist portion 200, by executing the already described 7th application control to 10th application control, it is possible to suppress the heater power of the magnetic disk device before reaching time 0, as in the first embodiment. Therefore, even if the preheating process is started during a period when the seek speed is fast in the seek action, the change in the floating amount of the slider 2 can be suppressed, and the writing conditions can be made good when writing starts.

[0094] In addition, several embodiments of the present invention are described above, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the scope of the purpose of the invention. These embodiments and their variations are included in the scope and purpose of the invention, and are included in the invention described in the claims and their equivalents.

Claims

1. A magnetic disk device comprising: disk; A magnetic head for reading / writing data from / to the magnetic disk; a heater that adjusts the distance between the magnetic disk and the magnetic head based on an applied voltage during the writing; and a control unit that causes the magnetic head to perform a seek operation from a first position to a second position of the magnetic disk, The control unit starts applying a first voltage to the heater during the seek operation when the magnetic head is caused to perform the seek operation from the first position to the second position, and after applying the first voltage, before the magnetic head is located at the second position and data is written by the magnetic head, makes the voltage applied to the heater a second voltage greater than the first voltage, The voltage applied to the heater gradually increases from the first voltage to the second voltage.

2. The magnetic disk device according to claim 1, The control unit sets the second applied voltage to a maximum voltage value among voltage values ​​applied to the heater.

3. The magnetic disk device according to claim 1, The first voltage is zero.

4. The magnetic disk device according to claim 2, The control unit increases the voltage applied to the heater in a curved manner from when application of the first voltage starts until the voltage reaches the maximum voltage value.

5. The magnetic disk device according to claim 2, The control unit increases the voltage applied to the heater in stages from when application of the first voltage starts until the voltage reaches the maximum voltage value.

6. The magnetic disk device according to claim 1, The control unit changes the magnitude of the voltage applied to the heater according to the seek speed of the magnetic head after applying the first voltage.

7. The magnetic disk device according to claim 2, A thermal assist unit is provided, wherein when the magnetic head writes data to the magnetic disk, the thermal assist unit assists the writing of the data by using a laser, The thermal assist unit irradiates the laser light based on a voltage applied to the light source. The control unit controls the magnitude of the voltage from the start of application of the first voltage until the voltage reaches the maximum voltage value based on the total value of the magnitude of the voltage applied to the heater and the intensity of the laser light.

8. The magnetic disk device according to claim 7, The control unit starts applying a voltage to the light source after starting applying the first voltage to the heater.

9. A method for applying voltage to a magnetic disk device, The magnetic disk device comprises: disk; A magnetic head for reading / writing data from / to the magnetic disk; a heater that adjusts the distance between the magnetic disk and the magnetic head based on an applied voltage during the writing; and a control unit that causes the magnetic head to perform a seek operation from a first position to a second position of the magnetic disk, The voltage application method include: The control unit, When the magnetic head is caused to perform a seek operation from the first position to the second position, application of a first voltage to the heater starts during the seek operation. After the first voltage is applied, the voltage applied to the heater is set to a second voltage greater than the first voltage before the magnetic head is located at the second position and data writing starts by the magnetic head. The voltage applied to the heater is gradually increased from the first voltage to the second voltage.

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