disk device

Abstract

Embodiments provide a magnetic disk drive capable of reducing dust particle entrapment problems during startup without extending startup time. The magnetic disk drive of the embodiment includes: a magnetic disk; a spindle motor that rotates the magnetic disk; a magnetic head that reads / writes data from / to the magnetic disk; a ramp loading mechanism that loads the magnetic head to a predetermined position on the magnetic disk; a filter that allows airflow generated by the rotation of the magnetic disk to pass through when the magnetic disk is rotated by the spindle motor; and a control unit that, during startup, loads the magnetic head from the ramp loading mechanism to a predetermined position on the magnetic disk after rotating the spindle motor at a second rotational speed higher than a first rotational speed for a predetermined period of time. The first rotational speed is the rotational speed at which the magnetic head reads / writes data from / to the magnetic disk.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2021-073439 (filing date: April 23, 2021), and the entire contents of the basic application are incorporated herein by reference. Technical Field

[0002] The embodiment relates to a magnetic disk device. Background Art

[0003] A magnetic disk drive is known that has a function of setting the rotation speed of a spindle motor to a higher speed than a normal speed at startup and returning the rotation speed to the normal speed after a certain period of time.

[0004] Dust particles generated by components within magnetic disk devices remain a major cause of failure. Generally speaking, improvements to the recording layer, intended to increase the recording density of magnetic disks, are counterproductive to the recording layer's resistance to disk damage caused by dust particles trapped between the magnetic head and the magnetic disk. From a component cost perspective, there are limits to suppressing dust from components. As a result, achieving a balance between recording density and component cleanliness becomes increasingly difficult with each product upgrade. Optimizing the ABS (Air Bearing Surface) design is effective in reducing the incidence of dust particle trapping, but this only works when the magnetic head is suspended above the magnetic disk.

[0005] Furthermore, as a measure to reduce dust particles, disk drives are sometimes equipped with a circulation filter. However, for the circulation filter to function, air must be blown through it. Therefore, to maintain a clean atmosphere within the disk drive, the spindle motor must be operated to generate airflow, and further, a certain period of time must be allowed for the atmosphere within the disk drive to become clean. Therefore, while the disk drive is operating, the interior of the disk drive remains normal. However, during startup, the cleanliness of the atmosphere within the disk drive deteriorates, increasing the risk of dust particles being trapped.

[0006] As its countermeasure, consider to obtain enough time from the time of starting up the magnetic disk device, wait for the atmosphere in the magnetic disk device to become clean and then load the magnetic head to the predetermined position on the magnetic disk. However, it is difficult to realize due to the restriction of the starting time required for the magnetic disk device.

[0007] Furthermore, the magnetic disk drive technology described above does not include any research on the timing of loading the magnetic head. Therefore, depending on the timing of loading the magnetic head, there is a possibility that the magnetic head will be loaded before the cleanliness of the atmosphere within the magnetic disk drive has improved. In such a case, the cleanliness of the atmosphere within the magnetic disk drive will also be poor, increasing the risk of dust particles being trapped. Summary of the Invention

[0008] An object of the embodiment is to provide a magnetic disk device that can reduce dust particle trapping failures during startup without prolonging startup time.

[0009] A magnetic disk device according to one embodiment comprises: a magnetic disk; a spindle motor that rotates the magnetic disk; a magnetic head that reads / writes data on the magnetic disk; a ramp loading mechanism that loads the magnetic head to a predetermined position on the magnetic disk; a filter that allows airflow generated by the rotation of the magnetic disk to pass through when the magnetic disk is rotated by the spindle motor; and a control unit that, when started, loads the magnetic head from the ramp loading mechanism to a predetermined position on the magnetic disk after rotating the spindle motor at a second speed that is higher than a first speed for a certain period of time, wherein the first speed is the speed at which the spindle motor is rotated when the magnetic head reads / writes data on the magnetic disk. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is an exploded perspective view showing an example of a magnetic disk device according to an embodiment, shown with a top cover removed.

[0011] Figure 2 This is a block diagram showing an example of a control structure of the magnetic disk device according to this embodiment.

[0012] Figure 3 This is a flowchart showing an example of the startup process according to this embodiment.

[0013] Figure 4 This is a timing chart for explaining an example of the operation according to this embodiment.

[0014] Label Description

[0015] 1 Magnetic disk device, 17 Magnetic head, 18 Magnetic disk, 19 Spindle motor, 22 Actuator assembly, 24 Voice coil motor, 25 Ramp loading mechanism, 140 MPU, 160 Memory, 161 First rotation speed storage unit, 162 Second rotation speed storage unit, Time t1 to t4 DETAILED DESCRIPTION

[0016] The following describes the embodiments with reference to the accompanying drawings. In addition, the disclosure is merely an example, and the invention is not limited by the contents described in the following embodiments. Deformations that can be easily thought of by those skilled in the art are of course included in the scope of the disclosure. In order to make the description clearer, the dimensions, shapes, etc. of each part are sometimes changed relative to the actual implementation scheme in the accompanying drawings and are shown in a schematic manner. In multiple drawings, the same reference numerals are sometimes marked on corresponding elements, and detailed descriptions are omitted.

[0017] Figure 1 This is an exploded perspective view of an example of a magnetic disk device, shown with the top cover removed. The magnetic disk device 1 includes a housing 10 having a flat, generally rectangular shape. The housing 10 includes a rectangular box-shaped base 12 with an open top surface and a top cover 14. The base 12 includes a rectangular bottom wall 12a that faces the top cover 14 with a gap therebetween, and side walls 12b that extend along the periphery of the bottom wall 12a, and are formed integrally from, for example, aluminum. The top cover 14 is formed into a rectangular plate shape from, for example, stainless steel. The top cover 14 is screwed onto the side walls 12b of the base 12 by a plurality of screws 13, thereby sealing the upper opening of the base 12.

[0018] A plurality of magnetic disks 18 as disk-shaped recording media and a spindle motor 19 that supports and rotates the magnetic disks 18 are provided in the housing 10. The spindle motor 19 is disposed on the bottom wall 12a. Each magnetic disk 18 is formed to have a diameter of, for example, 88.9 mm (3.5 inches) and has a magnetic recording layer on its upper surface or lower surface. Each magnetic disk 18 is coaxially fitted with a hub (not shown) of the spindle motor 19 and is clamped and fixed to the hub by a clamping spring 20. Thus, each magnetic disk 18 is supported in a state of being located parallel to the bottom wall 12a of the base 12. Each magnetic disk 18 is rotated at a predetermined speed by the spindle motor 19. In addition, as Figure 1 As shown, in this embodiment, for example, seven magnetic disks 18 are arranged in the housing 10 , but the number of magnetic disks 18 is not limited thereto.

[0019] Disposed within the housing 10 are a plurality of magnetic heads 17 for recording and reproducing information on a magnetic disk 18, and an actuator assembly 22 for supporting these magnetic heads 17 so that they can move freely relative to the magnetic disk 18. Also disposed within the housing 10 are a voice coil motor (VCM) 24 for rotating and positioning the actuator assembly 22, a ramp loading mechanism 25 for maintaining the magnetic heads 17 in an unloaded position away from the magnetic disk 18 when the magnetic heads 17 have moved to the outermost periphery of the magnetic disk 18, and a substrate unit (FPC unit) 21 on which electronic components such as a conversion connector are mounted.

[0020] A printed circuit board 27 is screwed onto the outer surface of the bottom wall 12 a of the base 12 . The printed circuit board 27 controls the operation of the spindle motor 19 and controls the operations of the VCM 24 and the magnetic head 17 via the board unit 21 .

[0021] The actuator assembly 22 includes an actuator block 29, a plurality of arms 30 (e.g., eight) extending in the same direction from the actuator block 29, and a plurality of head gimbal assemblies (HGAs) 32 mounted on the extended ends of each arm 30. The actuator block 29 is rotatably supported on a support shaft (pivot) 26 erected on the bottom wall 12a via a unit bearing. Each HGA 32 includes a suspension (load beam) extending from the arm 30, a flexure (wiring member) (not shown) disposed on the load beam and arm 30, and a magnetic head 17 mounted on the gimbal portion of the flexure.

[0022] The actuator assembly 22 also includes a support frame (not shown) extending from the actuator block 29 in a direction opposite to the arm 30, and a voice coil mounted on the support frame. The voice coil is positioned between a pair of yokes 38 provided on the bottom wall 12a, and together with these yokes 38 and a magnet fixed to one of the yokes 38, constitutes the VCM 24. During standby mode, the actuator assembly 22 is positioned in the unloaded position of the ramp loading mechanism 25. Furthermore, during normal operation (other than standby mode, when reading or writing data), the actuator assembly 22 is positioned at a predetermined position on the magnetic disk 18, as shown in the figure. Thus, the actuator assembly 22 is positioned in the unloaded position outside the magnetic disk 18 during standby mode and moves to a predetermined position on the magnetic disk 18 during data reading or writing.

[0023] The FPC unit 21 has a main body 21a formed of a flexible printed circuit board, and the main body 21a is fixed to the bottom wall 12a of the base 12. Electronic components such as a conversion connector are mounted on the main body 21a. The conversion connector passes through the bottom wall 12a and is connected to the printed circuit board 27. The FPC unit 21 has a relay flexible printed circuit board (hereinafter referred to as a relay FPC) 21b extending from the main body 21a. The extended end of the relay FPC 21b is mounted on the side surface (installation surface) of the actuator block 29. The extended end of the relay FPC 21b is electrically connected to the magnetic head 17 via the aforementioned flexible member.

[0024] A circulation filter (filter) 31 is provided in the housing 10 near the side wall 12b, outside the magnetic disk 18. The circulation filter 31 is configured to receive airflow generated by the rotation of the magnetic disk 18 caused by the operation of the movable parts such as the spindle motor 19. This allows dust particles (dust) present on the magnetic disk 18 to be captured.

[0025] Here, the collection performance of the circulation filter 31 will be described.

[0026] The theory related to the collection performance of the circulation filter has been established. The time required to reduce the number of dust particles in the atmosphere to one tenth (1 / 10 reduction period) T 10 It is represented by the following formula (1).

[0027]

[0028] Wherein, V0 represents the internal volume of the magnetic disk device 1, Q represents the flow rate of the fluid flowing into the circulation filter 31 per unit time, and η represents the filter collection efficiency. 10 , increase the flow rate Q or improve the filter collection efficiency η. The flow rate Q is proportional to the pressure difference Δp between the upstream and downstream sides of the circulation filter 31. The pressure difference Δp is expressed by the following formula (2).

[0029]

[0030] Here, λ is the coefficient for converting dynamic pressure into static pressure, ρ is the density of the fluid, and U is the peripheral speed of the outer end of the magnetic disk 18. Therefore, in the case of a magnetic disk device with a design value of 7200 revolutions per minute (hereinafter referred to as 7200 rpm (Round Per Minute)), when the rotation speed of the spindle motor 19 is increased to 10000 rpm, 12000 rpm, and 15000 rpm, the 1 / 10 reduction period T 10 The shortening rates were 48%, 64%, and 77%.

[0031] Therefore, in this embodiment, when the magnetic disk device 1 is started, the spindle motor 19 is rotated at a speed higher than the design value. For example, in the case of a magnetic disk device 1 with a design value of 7200 rpm, after the magnetic disk 18 is rotated at approximately 10,000 rpm for a predetermined time, the magnetic disk 18 is restored to 7200 rpm and the magnetic head 17 is loaded onto the magnetic disk 18. Here, when the time for high-speed and stable rotation is defined as the high-speed stable rotation time, it is preferable to set the high-speed stable rotation time to 1 / 10 minus the period T 10 The time, specifically, can also be set to about 2 seconds to 60 seconds. The 2 seconds as the shortest time for high-speed stable rotation is the case where the dust particles are not allowed to be reduced to one-tenth but to be reduced to one-half. That is, when the dust concentration is reduced from the initial state to 50%, the magnetic head 17 is loaded. At this time, the 1 / 2 reduction period is about 3 to 4 seconds in the case of the conventional magnetic disk device. Therefore, the margin for the 1 / 2 reduction period due to the design change of the circulation filter is taken and set to 2 seconds. In addition, for 60 seconds as the longest time for high-speed stable rotation, the 1 / 10 reduction period T of the conventional magnetic disk device is 10 It is about 35 to 45 seconds, so this is also taken for 1 / 10 minus period T 10 The time is set to 60 seconds to allow for changes due to, for example, changes in the circulation filter design.

[0032] Next, the control structure of the magnetic disk device 1 will be described. Figure 2This is a block diagram showing an example of a control configuration of a magnetic disk device.

[0033] like Figure 2 As shown, the magnetic disk device 1 includes the magnetic disk 18 , the spindle motor (SPM) 19 , the actuator assembly 22 , the voice coil motor (VCM) 24 , and the magnetic head 17 , as already described.

[0034] Furthermore, the magnetic disk drive 1 includes a head amplifier IC 110, an R / W channel 120, a hard disk controller (HDC) 130, a microprocessor (MPU) 140, a driver IC 150, and a memory 160. Furthermore, the magnetic disk drive 1 can be connected to a host computer (host) 170. Alternatively, the R / W channel 120, HDC 130, and MPU 140 may be incorporated into a single-chip integrated circuit.

[0035] The magnetic head 17 includes a write head (recording head: writer) 17W, a read head (reproducing head: reader) 17R, and a spin-torque oscillator (STO) 100 as a high-frequency oscillation element.

[0036] The spindle motor 19 is driven by a driving current (or a driving voltage) supplied from the driver IC 150. The magnetic head 17 records and reproduces data patterns on the magnetic disk 18.

[0037] The voice coil is actuated by the voice coil motor 24, causing the actuator assembly 22 to rotate from the unloaded position of the ramp load mechanism 25. As a result, the magnetic head 17 moves to a desired track on the magnetic disk 18 and is positioned at a predetermined position on the magnetic disk 18. The voice coil motor 24 is driven by a drive current (or drive voltage) supplied from the driver IC 150.

[0038] The head amplifier IC110 includes circuits related to driving the STO 100 and detecting oscillation characteristics. The head amplifier IC110 drives the STO 100, detects drive signals, and performs other functions. Furthermore, the head amplifier IC110 supplies a write signal (write current) corresponding to write data supplied from the R / W channel 120 to the write head 17W. Furthermore, the head amplifier IC110 amplifies the read signal output from the read head 17R and transmits it to the R / W channel 120.

[0039] The R / W channel 120 is a signal processing circuit that processes signals related to reading and writing. It includes a read channel that processes read data and a write channel that processes write data. The read channel converts the read signal into digital data and demodulates the read data from the digital data. The write channel encodes the write data transmitted from the HDC 130 and transmits the encoded write data to the head amplifier IC 110.

[0040] The HDC 130 controls the writing of data to and reading of data from the magnetic disk 18 via the magnetic head 17, the head amplifier IC 110, the R / W channel 120, and the MPU 140. The HDC 130 forms the interface between the magnetic disk drive 1 and the host computer 170, controlling the transfer of read and write data. Specifically, the HDC 130 functions as a host interface controller, receiving signals transferred from the host computer 170 and transferring them to the host computer 170. When transferring signals to the host computer 170, the HDC 130 corrects the data of the reproduced signal obtained by reading and demodulating the signal via the magnetic head 17 by the MPU 140. Furthermore, the HDC 130 receives commands (such as write commands and read commands) transferred from the host computer 170 and transmits the received commands to the MPU 140.

[0041] The MPU 140 is the main controller (control unit) of the magnetic disk device 1 and performs the control of the read / write operation and the servo control required for the positioning of the magnetic head 17. Furthermore, the MPU 140 controls the startup process of the magnetic disk device 1. For details of the startup process, please refer to Figure 3 , which will be described later.

[0042] The driver IC 150 controls the driving of the spindle motor 19 and the voice coil motor 24 according to the control of the MPU 140 . The voice coil motor 24 is driven to position the magnetic head 17 at a target track on the magnetic disk 18 .

[0043] The memory 160 includes a volatile memory and a non-volatile memory. For example, the memory 160 includes a buffer memory formed of a DRAM and a flash memory. The memory 160 stores programs and parameters required for processing by the MPU 140. In this embodiment, the memory 160 includes a first rotational speed storage unit 161 and a second rotational speed storage unit 162. The first rotational speed storage unit 161 stores a first rotational speed (7200 rpm in this embodiment) as a design value. The design value is the rotational speed at which the spindle motor 19, in other words, the magnetic disk 18, rotates when the magnetic head 17 reads or writes data to or from the magnetic disk 18. The second rotational speed storage unit 162 stores a second rotational speed (10,000 rpm in this embodiment) that is higher than the first rotational speed. The first rotational speed storage unit 161 and the second rotational speed storage unit 162 are stored in the non-volatile memory that constitutes the memory 16. In addition, in this embodiment, the first rotational speed is described as 7200 rpm and the second rotational speed is 10,000 rpm, but the present invention is not limited to these rotational speeds. For example, when the first rotation speed is any one of 5400 rpm, 7200 rpm, 10000 rpm, 12000 rpm, and 15000 rpm, the second rotation speed may be a rotation speed higher than at least the rotation speed that becomes the first rotation speed.

[0044] Next, the processing when the magnetic disk device 1 is activated will be described. Figure 3 1 is a flowchart showing an example of the startup process executed by MPU 140. This process is realized by, for example, MPU 140 reading and executing a program stored in memory 160.

[0045] like Figure 3 As shown, when power is supplied (not shown), the MPU 140 starts rotation speed control (ST101) and increases (ST102) the rotation speed of the magnetic disk 18. In this embodiment, the MPU 140 increases the rotation speed of the magnetic disk 18 with the goal of making the rotation speed of the spindle motor 19 reach the second rotation speed stored in the second rotation speed storage unit 162 (10,000 rpm in this embodiment).

[0046] Next, MPU 140 determines whether the rotational speed of magnetic disk 18 has been 10,000 rpm - 1% or higher for three consecutive times (ST103). If MPU 140 determines that the rotational speed has not been 10,000 rpm - 1% or higher for three consecutive times (ST103: No), the process repeats step ST103. If MPU 140 determines that the rotational speed has been 10,000 rpm - 1% or higher for three consecutive times (ST103: Yes), the process proceeds to step ST104. In this embodiment, the determination in step ST103 is based on whether the rotational speed has been 10,000 rpm - 1% or higher for three consecutive times, but this is not limiting.

[0047] Next, MPU 140 begins feedback control (ST104), and when the high-speed stable rotation time has elapsed (ST105), terminates feedback control (ST106). Consequently, during the high-speed stable rotation time, magnetic disk 18 rotates stably at 10,000 rpm (the second rotation speed). Therefore, during this high-speed stable rotation time, magnetic disk 18 rotates at a higher speed than the first rotation speed, which is the design value.

[0048] Next, the MPU 140 reduces the rotation speed of the magnetic disk 18 ( ST107 ). In this embodiment, the MPU 140 reduces the rotation speed of the magnetic disk 18 so that the rotation speed of the spindle motor 19 reaches the first rotation speed (7200 rpm) stored in the first rotation speed storage unit 161 .

[0049] Next, MPU 140 determines whether the rotational speed of magnetic disk 18 has been below 7200 rpm + 1% for three consecutive times (ST108). If MPU 140 determines that the rotational speed has not been below 7200 rpm + 1% for three consecutive times (ST108: No), the process repeats step ST108. If MPU 140 determines that the rotational speed has been below 7200 rpm + 1% for three consecutive times (ST108: Yes), the process proceeds to step ST109. In this embodiment, the determination in step ST108 is based on whether the rotational speed has been below 7200 rpm + 1% for three consecutive times, but the present invention is not limited to this.

[0050] Next, MPU 140 begins feedback control (ST108). Next, MPU 140 determines whether the rotational speed of magnetic disk 18 has remained within 7200 rpm ± 0.1% for eight consecutive times (ST110). If MPU 140 determines that it has not remained within 7200 rpm ± 1% for eight consecutive times (ST110: No), the process repeats step ST110. If it determines that it has remained within 7200 rpm ± 1% for eight consecutive times (ST110: Yes), the process proceeds to step ST111. Thus, the rotational speed of magnetic disk 18 stabilizes at 7200 rpm. While the determination in step ST111 is based on whether it has remained within 7200 rpm ± 1% for eight consecutive times in this embodiment, the present invention is not limited thereto.

[0051] Next, MPU 140 loads magnetic head 17 (ST111). More specifically, MPU 14 activates actuator assembly 22, which is located at the unloading position of ramp loading mechanism 25. As a result, magnetic head 17 is positioned at a predetermined position on magnetic disk 18. In this embodiment, the predetermined position is system area 18a of magnetic disk 18. Next, MPU 140 reads data from system area 18a (ST112). Thus, the startup process of magnetic disk device 1 is completed.

[0052] Next, the operations of the spindle motor 19 and the voice coil motor 24 at the time of startup according to this embodiment will be described. Figure 4 This is a timing chart for explaining an example of the operation of this embodiment. Figure 4 The upper side is a diagram showing an example of the relationship between time and the current applied to the spindle motor 19. Figure 4 The lower side is a graph showing an example of the relationship between time and the voltage applied to the voice coil motor 24 .

[0053] like Figure 4As shown above, first, during time t1 to time t2, current is applied to the spindle motor 19 to increase the rotation speed of the magnetic disk 18 (processing of ST101 to ST103 already described).

[0054] Next, during time t2 to time t3, current is applied to the spindle motor 19 to maintain the high-speed rotation of the magnetic disk 18 (ST104 to ST106 already described). This causes the magnetic disk 18 to rotate at the second high speed, causing airflow to flow into the circulation filter 31, where dust particles are captured. In this embodiment, the time from time t3 to time t4 is set to 30 seconds.

[0055] Next, between time t3 and time t4, current is applied to the spindle motor 19 to reduce the rotational speed of the magnetic disk 18 (steps ST107 and ST108 already described). This reduces the rotational speed of the magnetic disk 18 from the second rotational speed to the first rotational speed. After time t4, feedback control is executed to maintain the rotational speed of the magnetic disk 18 at the first rotational speed (steps ST109 and ST110 already described).

[0056] On the other hand, no voltage is applied to the voice coil motor 24 that activates the actuator assembly 22 until time t4. Specifically, after the magnetic disk 18 rotates at the second high speed, voltage is applied to the voice coil motor 24 starting at time t4, when the magnetic disk 18 begins to rotate stably at the first speed (step ST111 already described). Consequently, the airflow generated by the high-speed rotation of the magnetic disk 18 flows into the circulation filter 31 from time t2 to time t3 (30 seconds in this embodiment), trapping any dust particles that may be on the magnetic disk 18. The actuator assembly 22 then moves from the unloading position of the ramp loading mechanism 25 to the system area 18a of the magnetic disk 18.

[0057] Therefore, according to the magnetic disk device 1 of this embodiment, the dust particle entrapment failure at the time of startup can be reduced without extending the startup time. More specifically, the magnetic disk device 1 can reduce the dust particles in the magnetic disk device 1 by 1 / 10 of the time T by rotating the magnetic disk 18 at a second rotation speed higher than the first rotation speed as the design value for a certain period of time. 10 This is shortened to about half, and as a result, the dust particles can be sufficiently collected by the circulation filter 31 without prolonging the startup time. Then, by loading the magnetic head 17 onto the magnetic disk 18, the magnetic disk device 1 can improve reliability.

[0058] The technology of this embodiment is effective as a control when a magnetic disk device is started, for example. The control is: when the magnetic head 17 is loaded onto the magnetic disk 18 at startup, the head surface of the magnetic head 17 is temporarily brought into contact with the disk surface of the magnetic disk 18, and the distance between the disk surface and the head surface is controlled by detecting the contact.

[0059] In addition, several embodiments of the present invention have been described above, but these embodiments are provided as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways and can be omitted, replaced, or modified without departing from the scope of the invention. These embodiments and / or their variations are included within the scope and spirit of the invention and are included within the invention described in the claims and their equivalents.

Claims

1. A magnetic disk device comprising: disk; a spindle motor that rotates the magnetic disk; a magnetic head for reading and writing data from and to the magnetic disk; a ramp loading mechanism for loading the magnetic head to a predetermined position on the magnetic disk; a filter that allows an airflow generated by the rotation of the magnetic disk to pass therethrough when the magnetic disk is rotated by the spindle motor; and a control unit that, when started, loads the magnetic head from the ramp loading mechanism to a predetermined position on the magnetic disk after rotating the spindle motor at a second rotational speed higher than a first rotational speed for a predetermined period of time, wherein the first rotational speed is a rotational speed at which the spindle motor is rotated when the magnetic head reads or writes data on the magnetic disk; After rotating the spindle motor at the second rotational speed for a certain period of time, the control unit performs feedback control to rotate the magnetic disk at the first rotational speed. After the rotational speed of the magnetic disk stabilizes at the first rotational speed through the feedback control, the control unit loads the magnetic head from the ramp loading mechanism to the predetermined position on the magnetic disk. The predetermined time is a time required for the filter to reduce the dust in the gas present in the housing of the magnetic disk to 1 / 10 of the original amount.

2. The magnetic disk device according to claim 1, The control unit maintains the rotation speed of the magnetic disk at the second rotation speed through feedback control during the predetermined period of time.

3. The magnetic disk device according to claim 1, The first rotation speed is any one of 5400 rpm, 7200 rpm, 10000 rpm, 12000 rpm, and 15000 rpm.

4. The magnetic disk device according to claim 1, A memory for storing the first rotation speed and the second rotation speed is provided.

5. The magnetic disk device according to claim 1, The disk has a system area that manages data written to the disk. The predetermined position is a position where the magnetic head reads data from the system area.

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