JP2007200508A - Magnetic disk device and control method of magnetic disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic disk device wherein a risk that a head element comes into contact with a medium upon an impact can be reduced. <P>SOLUTION: A magnetic head 5 is positioned on the track of a magnetic disk 3 via an ABS (Air Bearing Surface). When an impact is sensed by an impact sensor 14, it is decided whether an impact level is a head retreating standard value or more. When the impact level is the head retreating standard value or more, power supply to a heater element is stopped and the magnetic head 5 is made to retreat to the outside from the magnetic disk 3. When the impact level is the head retreating standard value or less, it is decided whether the impact level is a heater-OFF standard value or more and the heater element is turned OFF when the impact level is the heater-OFF standard value or more. Collision with the magnetic disk 3 can be prevented by turning a flying height controlling element 8 off and recessing a writing head 6 and a reading head 7 from the surface of the ABS when the impact of the standard value or more is detected. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic disk device, and more particularly to a technique for controlling the flying height of a magnetic head.

  In recent years, in a magnetic disk device, the flying height of a head for reading and writing tends to decrease as the recording density of media increases. In response to a decrease in the flying height of the head, a technique (DFH: Dynamic Flying Height Control) that controls the flying height with a current that is supplied to the head has begun to be applied. In an actual use state of a magnetic disk device to which DFH is applied, there is a risk that a read / write element protruding from an ABS (Air Bearing Surface) due to DFH may come into contact with the medium to cause a head failure or damage to the medium.

Various control techniques have been devised for avoiding contact between the head and the medium and improving reliability. Patent Document 1 describes a technique for correcting the head flying height using a mechanical / electrical conversion element provided in a suspension. When an impact from the outside is detected, the voltage applied to the suspension is released, and the slider is moved away from the medium to prevent contact between the head and the medium.
Japanese Patent No. 3082929

  However, in the case of the above method, the applied voltage to the suspension is released and the head is moved away from the medium by the suspension, so the response at the time of impact is delayed.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a magnetic disk device capable of reducing the risk of contact between a head element and a medium at the time of impact.

  In order to achieve the above object, a magnetic disk apparatus according to the present invention includes a magnetic disk, a recording / reproducing element for recording / reproducing data on the magnetic disk, and a head slider mounted with the recording / reproducing element and flying close to the magnetic disk. Positioning means for positioning the head slider, a displacement control element provided in the vicinity of the recording / reproducing element, for projecting the recording / reproducing element with respect to the air bearing surface direction of the head slider by supplying electric power, A power supply means for supplying power to the displacement control element; and an impact detection means for detecting an impact from the outside of the magnetic disk device, and when the impact is detected by the impact detection means, the displacement control element And the recording / reproducing element protruding in the direction of the air bearing surface of the head slider is retracted. .

  According to the present invention, it is possible to provide a magnetic disk device capable of reducing the risk of contact between the head element and the medium at the time of impact.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing the overall configuration of a magnetic disk apparatus according to the present invention. The magnetic disk device 1 is driven in accordance with a read / write command issued by the host 2. The magnetic disk 3 is a recording medium that holds magnetic information, and is rotationally driven by a spindle motor (SPM) 4. The magnetic head 5 mainly includes a write head 6 that writes data to the magnetic disk 3, a read head 7 that reads data, and a flying control element 8. A heater element or the like is used as the levitation control element 8. The read head 6 and the write head 7 are mounted on a head slider (not shown) that floats on the rotating magnetic disk 3, and an arbitrary radial position on the magnetic disk 3 by a voice coil motor (VCM: Voice Coil Motor) 9. Can be moved to. The magnetic head 5 can cause the write head 6 and the read head 7 to arbitrarily protrude from the lower surface of the head slider ABS (Air Bearing Surface) by the flying control element 8.

  The magnetic head 5 is connected to a head amplifier 10. The head amplifier 10 controls input / output of read / write signals with the magnetic head 5. It has a recording amplification function for supplying a recording current to the write head 6 in synchronization with a recording signal from a write channel, which will be described later, and a reproduction signal amplification function for amplifying a signal from the read head 7. It also has a function of supplying power to the levitation control element 8 and supplies power in synchronization with the write, read gate, and the like.

  The channel 10 encodes the write signal from the host 2. A write channel function for transmitting to the head amplifier 11 and a read channel function for decoding a read signal from the head amplifier 11 are mounted. The environmental sensor 12 acquires environmental information such as temperature / humidity and atmospheric pressure in accordance with an instruction from the CPU 13. The impact sensor 14 is composed of, for example, an acceleration sensor. The impact sensor 14 detects an impact on the magnetic disk device 1 and the slider, and reports to the CPU 13 when the impact is detected.

  The memory 15 holds a program for controlling the magnetic disk device 1, parameters for control, and the like. The CPU 13 issues a command to each component based on information from each sensor and information held in the memory 15. The memory 15 stores a table for determining the power to be supplied to the levitation control element 8 according to each operation of seek, read, and write and the environment such as temperature, humidity, and atmospheric pressure. The table stored in the memory 15 may be rewritten through input means. The CPU 13 instructs the head amplifier 10 to supply desired power to the levitation control element 8 based on the information acquired from the table and the environment sensor 12.

  A hard disk controller (HDC: Hard Disc Controller) 16 constitutes an interface between the magnetic disk device 1 and the host 2 and exchanges various interfaces and data with the CPU 13. The CPU 13 controls the motor driver 17 according to an instruction from the hard disk controller 16. The spindle motor 4 and the voice coil motor 9 are driven by a motor driver 17.

  FIG. 2 is an external perspective view of the magnetic disk apparatus according to the present invention. The magnetic disk 3 is fixed to the spindle motor 4 and rotates at a predetermined speed. A slider (not shown) is attached to the suspension 20 and given a pressing load to the magnetic disk 3. The slider is positioned at a radius determined by control on the magnetic disk 3 via the arm 21 together with the suspension 20. In response to the air flow generated by the rotation of the magnetic disk 3, the slider floats to a certain height. Signals are recorded and reproduced by a magnetic head (not shown) formed at the tip of the slider. The flying height of the slider is determined by the balance between the load applied to the slider and the wind pressure generated by the rotation of the magnetic disk 3.

FIG. 3 is a schematic diagram showing a cross-section of the head tip of the magnetic disk apparatus according to the present invention. The main body of the slider 22 is made, for example, by processing AlTiC. Properties required for the main body of the slider 22 include non-magnetic properties, electrical conductivity, high rigidity and resistance to deformation, and no cracking or chipping. A magnetic head 5 is attached to the tip of the slider 20 main body. The magnetic head 5 is covered with, for example, Al ₂ O ₃ . The magnetic head 5 includes a write head 6, a read head 7, and a flying control element 8. The recording / reproducing characteristics of the magnetic disk 3 greatly depend on the distance between the magnetic head 5 and the magnetic disk 3. In order to control the distance between the write head 6 and the read head 7 and the magnetic disk 3, a flying control element 8 composed of a heater element or the like is formed. By energizing the flying control element 8, the write head 6 and the read head 7 can be moved closer to or away from the magnetic disk 3. As the write head 6 and the read head 7 approach or move away from the magnetic disk 3, the flying height of the magnetic head 5 with respect to the magnetic disk 3 can be controlled.

  Generally, there is a step between the tip 6a of the read head 6 and the tip 7a of the write head 7 and the bottom surface 22a of the slider 22, and a gap is generated. This interval is called a recess amount D of the recording / reproducing element. The recess amount is provided to retract the read head 6 and the write head 7 protruding from the ABS from the ABS at the time of impact or the like.

  A heater element is widely used as the flying height control element 8. When heated by a heater element provided in the vicinity of the write head 6 and the read head 7, the write head 6 and the read head 7 expand and project. By expanding and the tips of the write head 6 and the read head 7 approaching the magnetic disk 3, the flying height of the magnetic head 5 is consequently reduced. The heater element controls the displacement of the write head 6 and the read head 7 by raising the temperature in the vicinity of the read head 6 and the write head 7. When a large current is passed through the heater element, the temperature increases and the displacement also increases. In DFH, since the write head 6 and the read head 7 are locally projected from the ABS, there is a risk that the write head 6 and the read head 7 may be damaged by direct contact with the magnetic disk 3.

  FIG. 4 is a flowchart showing the head retracting operation during the on-track operation of the magnetic disk apparatus according to the present invention. Here, the shock level used as a reference for executing the head retraction is set as the first reference value, and the lift level of the read head 6 and the write head 7 is increased by the flying control element 8 to be used as a reference for recessing from the ABS surface. The second reference value is used. Hereinafter, a case where a heater element is used as the levitation control element 8 will be described as an example. The magnetic head 5 is located on a track of the magnetic disk 3 through the ABS. Electric power for reading is supplied from the head amplifier 10 to the heater element. When the impact sensor 14 detects an impact (step 4-2), the impact is reported to the CPU 13. The CPU 13 determines whether or not the impact level is greater than or equal to the head retraction reference value (step 4-3). The impact level that is a reference for executing the head retraction can be arbitrarily set. If the impact level is equal to or higher than the head retraction reference value (Yes in step 4-3), the power supply to the heater element is stopped (step 4-4), and the magnetic head 5 is retreated outside the magnetic disk 3 (step 4). 4-5). If the impact level is less than or equal to the head retraction reference value (No in Step 4-3), it is determined whether or not the impact level is equal to or higher than the heater off reference value (Step 4-7). If (Yes in Step 4-7), the heater element is turned off (Step 4-8). When the impact level is less than the heater-off reference value (No in Step 4-7), the magnetic head 5 may continue loading on the magnetic disk 3. When an impact greater than the heater-off reference value is detected, the heater element is turned off, and the write head 6 and the read head 7 are recessed from the ABS, thereby avoiding a collision between the head element and the magnetic disk 3.

  Whether the head is retracted or the heater is turned off when an impact is detected is determined by the impact level. If it is above the head retraction reference, the power supply to the heater is stopped and the head is retreated out of the disk. In the case of an impact to the extent that the head and the disk surface come into contact, a method of dealing with the heater off can be considered.

  FIG. 5 is a flowchart showing the head retracting operation during the read operation of the magnetic disk apparatus according to the present invention.

  When a read command is received from the host 2 (step 5-2), power for reading is supplied to the heater element in synchronization with the read gate (step 5-3), and the read operation is started (step 5-4). When the impact sensor 14 detects an impact during the read operation (step 5-5), it is determined whether the impact level is equal to or higher than the head retraction reference value (step 5-6). If the impact level is equal to or higher than the head retraction reference value (Yes in step 5-6), power supply to the heater element is stopped (step 5-7), and the magnetic head 5 is retreated after the read operation is interrupted (step 5). -9).

  If the impact level is less than or equal to the head retraction reference value (No in step 5-6), it is determined whether the impact level is less than or equal to a reference value for turning off the heater element (step 5-10). If it is equal to or greater than the reference value for turning off the heater element (Yes in step 5-11), power supply to the heater element is stopped (step 5-12). When the impact level is equal to or lower than the reference value for stopping the heater element (No in Step 5-11), a read operation is performed (Step 5-13), and it is confirmed whether the read operation can be performed normally (Step 5-14). ). If the read operation can be performed normally (Yes in step 5-14), the read operation is terminated (step 5-15). When the read operation cannot be performed normally (No in Step 5-14), if the number of read operations is less than the reference (No in Step 5-17), the read operation is repeated. If the number of read operations is equal to or greater than the reference (Yes in Step 5-17), it is determined as a read error (Step 5-18), and is reported to the host 2 after completing the read operation.

  When an impact is detected during the read operation, it is possible to prevent the head and the disk from colliding by stopping the power supply to the heater element.

  FIG. 6 is a flowchart showing the head retracting operation during the write operation of the magnetic disk apparatus according to the present invention. When a write command is received from the host 2 (step 6-2), power is supplied to the heater element (step 6-3), and a write operation is started (step 6-4). When the impact sensor 14 detects an impact during the write operation (step 6-5), it is determined whether the impact level is equal to or higher than the head retraction reference value (step 6-6). If the impact level is equal to or higher than the head retraction reference value (Yes in step 6-6), power supply to the heater element is stopped (step 6-7), and the magnetic head 5 is retreated after the write operation is interrupted (step 6). -9). If the impact level is less than or equal to the head retraction reference value (No in step 6-6), it is determined whether the impact level is less than or equal to a reference value for stopping the heater element (step 6-11). If it is equal to or higher than the reference value for stopping the heater element (Yes in step 6-11), the power supply to the heater element is stopped (step 6-12). After stopping the power supply to the heater element, the write operation is stopped and finished (step 6-13). As will be described later, a process of confirming data by a write operation after stopping the heater element may be inserted. When the impact level is equal to or lower than the reference value for stopping the levitation control element 8 (No in Step 6-11), a write operation is performed (Step 6-14) to check whether the write operation can be performed normally.

  FIG. 7 is a flowchart showing a data confirmation operation during a write operation of the magnetic disk apparatus according to the present invention. When power supply to the heater element is stopped, the read head 6 and the write head 7 are recessed from the ABS surface of the magnetic disk 3. If data recording is performed with the write head 7 being away from the magnetic disk 3, data may not be written normally. Therefore, it is necessary not to perform data recording when power supply to the heater element is stopped. is there. One method is to stop the write operation after turning off the heater, as shown in the flowchart of FIG. As another method, there is a method of performing a write retry after performing data recording in a state where power supply to the heater element is stopped.

  The heater element is stopped (step 6-12), and a write operation is performed (step 7-1). It is confirmed whether data is correctly recorded after the write operation (step 7-2). If the data has been recorded correctly (Yes in step 7-3), the write operation is completed, but if it has not been recorded correctly (No in step 7-3), a write retry is performed, and the recording data is recorded for each retry. Confirm. If the number of retries is less than the standard (No in step 7-5), the retry operation is repeated. When the number of retries exceeds the reference number (Yes in Step 7-5), the write operation is stopped (Step 7-6) and reported as NG to the host 2.

  In order to prevent a collision with the magnetic disk 3, even when the read head 6 and the write head 7 are recessed, the reliability of data recording can be improved by performing a retry during the write operation.

  When this embodiment is implemented, the risk of contact between the head element and the medium at the time of impact can be reduced.

  The present invention is not limited to the above embodiment as long as it does not depart from the gist of the present invention, and various modifications are possible.

1 is an external perspective view of a magnetic disk device according to the present invention. 1 is a block diagram showing an overall configuration of a magnetic disk device according to the present invention. FIG. 3 is a schematic diagram showing a cross-section of the head tip of the magnetic disk apparatus according to the present invention. 6 is a flowchart showing a head retracting operation during on-track of the magnetic disk apparatus according to the present invention. 6 is a flowchart showing a head retracting operation during a read operation of the magnetic disk apparatus according to the present invention. 6 is a flowchart showing a head retracting operation during a write operation of the magnetic disk apparatus according to the present invention. 6 is a flowchart showing a data confirmation operation during a write operation of the magnetic disk device according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Magnetic disk apparatus, 2 ... Host, 3 ... Magnetic disk, 4 ... Spindle motor, 5 ... Magnetic head, 6 ... Read head, 7 ... Write head, 8 ... Flying control element (heater element), 9 ... Voice coil motor 10 channels ..., 11 ... head amplifier, 12 ... environmental sensor, 13 ... CPU, 14 ... impact sensor, 15 ... memory, 16 ... hard disk controller, 17 ... motor driver, 20 ... suspension, 21 ... arm, 22 ... slider,

Claims (6)

A magnetic disk;
A recording / reproducing element for recording / reproducing data on the magnetic disk;
A head slider mounted with the recording / reproducing element and flying close to the magnetic disk;
Positioning means for positioning the head slider;
A displacement control element provided in the vicinity of the recording / reproducing element and configured to project the recording / reproducing element with respect to the air bearing surface direction of the head slider by supplying power;
Power supply means for supplying power to the displacement control element;
An impact detection means for detecting an impact from outside the magnetic disk device,
When an impact is detected by the impact detection means, the power supply to the displacement control element is stopped, and the recording / reproducing element protruding in the direction of the air bearing surface of the head slider is retracted. apparatus.   When the detected impact is greater than or equal to a first reference value, the positioning means retracts the head slider from the magnetic disk surface, and when the detected impact is greater than or equal to a second reference value, 2. The magnetic disk apparatus according to claim 1, wherein power supply to the displacement control element is stopped and the recording / reproducing element protruding in the direction of the air bearing surface of the head slider is retracted.   When the recording / reproducing operation of the data is performed by the recording / reproducing element, if the impact detected by the impact detecting means is smaller than the first reference value, the recording / reproducing operation is continued, and after the recording / reproducing operation is completed. 2. The magnetic disk apparatus according to claim 1, wherein the written data is confirmed. In a control method of a magnetic disk device, comprising: a magnetic disk; a recording / reproducing element for recording / reproducing data on the magnetic disk; and a head slider mounted with the recording / reproducing element and flying close to the magnetic disk.
Positioning the head slider;
The recording / reproducing element protrudes with respect to the air bearing surface direction of the head slider by supplying power,
Detecting an impact from outside the magnetic disk device,
When the impact is detected, the power supply is stopped, and the recording / reproducing element protruding in the direction of the air bearing surface of the head slider is retracted.   When the detected impact is greater than or equal to a first reference value, the positioning means retracts the head slider from the magnetic disk surface, and when the detected impact is greater than or equal to a second reference value, 5. The magnetic disk apparatus according to claim 4, wherein power supply to the recording / reproducing element is stopped, and the recording / reproducing element protruding from the air bearing surface of the head slider is retracted from the air bearing surface of the head slider. Control method. When performing the recording / reproducing operation of data by the recording / reproducing element, if the detected impact is smaller than the first reference value, the recording / reproducing operation is continued, and the data written after the recording / reproducing operation is completed. 5. The method of controlling a magnetic disk device according to claim 4, wherein the confirmation is performed.

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