JP3080354B2 - Magnetic latch release method for magnetic disk drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive having a mechanism for latching a magnetic head portion by a magnet which is generally effective for a magnetic disk drive, particularly a small and highly portable magnetic disk drive. The present invention relates to a method for releasing a magnetic latch of a magnetic disk device suitable for preventing destruction of data on a magnetic disk due to an impact of a magnetic head runaway when releasing a magnetic head.

[0002]

2. Description of the Related Art In the prior art, after the power of a magnetic disk drive is turned on, the magnetic head is first moved at a very low speed toward the inner circumferential side of the magnetic medium in order to surely release the magnetic latch of the magnetic head. ing. At this time, in order to drive the actuator for a fixed time, a predetermined VCM drive current is applied to a VCM (voice coil motor) for a fixed time. This is performed in order to release the magnetic head from the magnetic disk in consideration of the state where the magnetic head is fixed to the magnetic disk due to adhesion or the like. Next, after returning the VCM drive current to the original value (zero), a servo signal necessary for causing the magnetic head to follow the data track on the magnetic medium is detected from the read signal of the magnetic head. Therefore, the VCM is applied to the VCM so as to move the magnetic head toward the outer peripheral side where the data area of the magnetic medium exists (hereinafter, this operation is referred to as “kick-out”).
The CM drive current is supplied for a fixed time. At this time, due to the variation of the magnet for each magnetic disk device, etc.
When the driving force of M is insufficient, the magnetic head may not reach the data area of the magnetic medium, or the servo signal may not be detected even though it has reached the data area. In such a case, the VCM drive current is stepped up, the drive is performed again, and the operation is repeated until the kick-out and the servo signal can be reliably detected. Thus, when the servo signal can be detected, it is understood that the magnet latch has been normally released.

There is an invention disclosed in US Pat. No. 5,224,000 related to the present invention.

[0004]

In the above prior art, when the VCM drive current is stepped up, drive is performed again, and the operation is repeated until the kick-out and the servo signal can be reliably detected, the drive speed of the magnetic head portion is increased. Rises and after kicking out, the servo signal cannot be detected, and the magnetic head part becomes unstable, causing runaway, and the stopper part provided on the inner and outer peripheral sides to limit the operation range of the actuator. There has been a problem that an accident such as a crash at a high speed, an injury to a magnetic medium due to an impact, and the like, may cause data destruction. This is a problem that is particularly noticeable in a small magnetic disk drive having a small flying height of the magnetic head. Note that this is a problem particularly when runaway occurs toward the outer peripheral side, and is relieved on the inner peripheral side because there is a shipping zone (CSS zone) where there is no data in the magnetic medium.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art.
After the kick-out operation, the servo signal cannot be detected and the runaway that occurs when the magnetic head becomes unstable is suppressed.
It is an object of the present invention to provide a method of releasing a magnetic latch of a magnetic disk device which is suitable for preventing a data failure due to an impact.

[0006]

According to the present invention, there is provided a method for starting a magnetic disk drive, comprising: in a latch release operation of a magnetic head, kicking out the magnetic head in an outer circumferential direction; A VCM drive current for driving the VCM is supplied to the outer side, a brake is applied to the magnetic head portion which is to move at an increased speed toward the outer peripheral side, and runaway of the magnetic head portion toward the outer peripheral side is suppressed.

[0007]

According to the present invention, while maintaining the VCM drive current control operation for securely releasing the latch of the magnetic head,
After the latch is released, the servo signal cannot be detected, and the brake is applied before the magnetic head unit becomes unstable and runs away, so that a data failure due to the shock of runaway can be prevented beforehand.

[0008]

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

FIG. 2 is a block diagram showing a configuration of a small-sized magnetic disk device showing an embodiment of the present invention, and FIG. 3 is an explanatory top view showing a schematic configuration of the magnetic disk device shown in FIG.

The magnetic disk drive shown in FIG. 2 is roughly divided into a control board section 18 and an HDA (head disk assembly) mechanism section 17. The control board section 18 is used by being connected to a host interface connector section (shown as a connector in the figure) 1 via an interface (not shown) with a host device such as a personal computer.
The control board section 18 includes a host interface connector section 1 and an R / W channel section 2, an interface control section 3, a microprocessor (MPU) section 4, a servo controller section 5, a shock sensor section 6, and a VCM (voice coil motor). ) / A motor driver unit 7 for a spindle motor is included, and exchanges commands with a host device and controls the HDA mechanism unit 17.

The HDA mechanism 17 includes a magnetic head 11,
It includes a magnetic medium unit 12, an actuator unit 13 for driving a magnetic head, an R / W preamplifier unit 10, a magnet latch mechanism unit 9, a spindle motor unit 14, and a VCM (voice coil motor) unit 8.

In FIG. 3, the same parts as those shown in FIG. 2 are denoted by the same reference numerals. As shown in FIG. 3, the magnet latch mechanism 9 includes stoppers 21 and 22, a magnet latch base-side magnet 23, and a magnet latch magnetic head actuator-side magnet 24.

When the magnetic disk drive is not operating,
The magnetic head unit 11 always operates in a shipping zone (CSS zone) by the action of the magnet latch mechanism unit 9 due to the magnet force of the magnet latch base side magnet unit 23 and the magnet latch magnetic head actuator side magnet unit 24 shown in FIG. ) It is fixed so as to be located on 19. Here, in the shipping zone 19 where there is no data, the shock is applied, so that even if the magnetic head 11 comes into contact with the surface of the magnetic medium 12, no problem occurs.

On the other hand, when the magnetic disk drive operates, a force that overcomes the magnet force is applied to the magnetic head unit 11 so that the data area 20
You need to kick it out. For this reason, the microprocessor unit 4 outputs the DAC command value 15 to the motor driver unit 7 for the VCM (voice coil motor) / spindle motor. The motor driver unit 7 receives the DAC command value 15 and outputs a VCM drive current 16 to the VCM unit 8. As a result, the magnetic head unit 11 overcomes the magnet force and is kicked out to the data area unit 20 of the magnetic medium unit 12.

Next, the details of the above operation will be described. First, the microprocessor unit 4 of the magnetic disk device
Starts the spindle motor unit 14 after power on,
It is detected that the rotation of the spindle motor unit 14 is normal. Thereafter, the microprocessor unit 4 starts the operation of releasing the magnet latch.

First, the microprocessor unit 4 includes a DAC
The command value 15 is output to the motor driver 7 for a VCM (voice coil motor) / spindle motor. As a result, the motor driver unit 7 for the VCM (voice coil motor) / spindle motor reliably releases the magnetic latch of the magnetic head unit 11 (the magnetic head driving actuator unit 13). A VCM driving current 16 is supplied to a VCM (voice coil motor) unit 8 for a fixed time so that the head driving actuator unit 13) moves at a very low speed in the inner circumferential direction of the magnetic medium. This is performed in order to release the state where the magnetic head 11 is fixed on the shipping zone 19 due to adhesion or the like. Next, the microprocessor unit 4
Outputs the DAC command value 15 and controls the VCM drive current 16 to return to the original value (zero). Thereafter, the motor driver 7 releases the magnet latch based on the DAC command value 15 and detects a servo signal necessary for causing the magnetic head unit 11 to follow the data track 20 on the magnetic medium unit 12. Therefore, a VCM drive current 16 is supplied to a VCM (voice coil motor) unit 8 for a certain period of time.
As a result, the magnetic head unit 11 is kicked out to the outer peripheral side where the data area of the magnetic medium unit 12 is located.

In the above-described kicking-out operation, VCM is generated due to variations in the magnet force of each magnetic disk device.
In the case where the driving force of the unit 8 is insufficient and the magnetic head unit 11 does not reach the data area 20 of the magnetic medium unit 12 or the servo signal is detected from the read signal of the magnetic head even though the magnetic head unit 11 has reached the data area 20. If not, the microprocessor unit 4 steps up the DAC command value 15 and executes the kicking operation again. That is, the VCM drive current 16 output from the motor driver 7 is stepped up. As a result, the magnetic head unit 11 is re-driven, the magnetic head unit 11 is reliably ejected to the data track 20, and the same operation is repeated until a servo signal can be detected.

In the prior art, at this time, the magnetic head 11
VCM drive current 16 whose drive speed has been stepped up
After the magnetic head unit 11 is kicked out, a servo signal cannot be detected in the data track 20 and the magnetic head unit 11 becomes unstable, causing a runaway and restricting the operating range of the actuator 13. There is a problem that the stoppers 22 and 21 provided on the inner and outer sides may collide at a high speed, damaging the magnetic medium unit 12 by an impact and causing data destruction.
This is a problem particularly noticeable in a small-sized magnetic disk device in which the flying height of the magnetic head unit 11 with respect to the magnetic medium unit 12 is small. Note that this is a problem particularly when runaway occurs on the outer circumference side, and is saved on the inner circumference side because the magnetic medium has a shipping (CSS) zone section 19 having no data.

In this embodiment, in the operation of releasing the magnetic latch of the magnetic head unit 11, if a certain time has elapsed after the magnetic head unit 11 has been kicked out, the magnetic head unit 11 moves at an increased speed toward the outer peripheral side. , And an operation of suppressing runaway of the magnetic head unit 11 toward the outer peripheral side is performed. That is, the DAC command value 15 is output by the microprogram control of the microprocessor unit 4 so that the magnetic head unit 11 moves in the inner circumferential direction. This D
Based on the AC command value 15, the motor driver 7 for the VCM (voice coil motor) / spindle motor supplies a VCM drive current 16 for the actuator, thereby suppressing runaway of the magnetic head 11 to the outer peripheral side. The operation is performed.

FIG. 1 is a flowchart showing a microprogram control for the runaway suppressing operation. First, in step 100, the power of the magnetic disk drive is turned on. Next, in step 101, the control DAC command value 15 is initialized (zero) to enter the latch release operation. Next, in step 102, a DAC command value 15 having a low gain is set, and in step 103, a VCM drive current 16 is passed to move the magnetic head unit 11 at an extremely low speed to the inner peripheral side. )
Return to

Subsequently, the operation of kicking out the magnetic head portion to the outer peripheral side is started. At this time, in order to prevent runaway of the magnetic head portion 11, a counter (timer) for limiting the time of the kicking out operation is initialized. A value (timeout value) is set in step 104. This timer can be easily realized by using a timer or counter function inside the MPU. The initial value set at this time can be stepped up until the DAC command value 15 indicates the maximum speed of the magnetic head unit 11 in order to surely release the magnet latch, and the magnetic head unit 11 may run away. A time of no degree is chosen. If there is enough memory capacity, the time until a runaway occurs can be stored, and the learning function can be used to change the set value at the time of retry or for each magnetic disk unit. It is. Next, in step 105, the timer is started immediately before the first kick to the outer peripheral side.

Thereafter, in step 106, a DAC command value 15 having a large gain for kicking out is set,
In step 107, the VCM drive current 16 is supplied for a certain period of time, and the magnetic head 11 is kicked out. In step 108, the kicked-out magnetic head unit 11 searches for a servo signal written in the data area on the surface of the magnetic medium, and if found, terminates this flowchart normally, pulls in the servo, and performs control to follow this. Switch to However, if no servo signal is found, it is determined that the magnetic head unit 11 has not reached the data area 20 of the magnetic medium unit 12, and steps 109 and 115 are determined.
To step up until the DAC command value 15 indicates the highest speed, and repeat the process many times until a servo signal is found.

However, no servo signal was found for a long time,
If the magnetic head unit 11 is repeatedly kicked out in an unstable state, the magnetic head unit 11 collides with the stopper 21 on the outer peripheral side at the highest speed or a high speed near the maximum speed, and the risk of destroying data on the magnetic medium surface increases. Conventionally, it has been regarded as important that the magnetic latch of the magnetic head unit 11 is reliably released, and it is extremely rare that a servo signal of the magnetic medium unit 12 cannot be found. Runaway behavior was not considered.
However, when the flying height of the magnetic head 11 is extremely small as in the case of a small magnetic disk drive, data destruction due to this runaway is serious and needs to be considered. Therefore, in step 109, the DAC command value 15
Indicates the maximum speed, and in step 1109, if the timer set in steps 104 and 105 times out, in step 111, the DAC command value 1 is set so that the magnetic head unit 11 is driven inward for a predetermined time.
5 is set, and the brake is applied to the inner peripheral side in step 112. As a result, the magnetic head unit 11 kicked out at the highest speed or a high speed near the highest speed is braked, and runaway can be prevented.

In particular, in the present embodiment, hardware is not used, and the control is performed by microprogram control of the microprocessor 4, so that a low-cost operation method can be provided.

Further, in step 113, a global timeout is detected, and if no global timeout is detected, the above steps 106 to 113 are repeated. If a global timeout is detected in step 113,
After the retraction operation, an error (retry) process is started.

In the flowchart shown in FIG. 1, in step 109, the process proceeds to step 115 only when the DAC command value 15 has not reached the maximum speed. However, the present invention is not limited to this. Instead, for example, the process may proceed to step 115 if it is determined in step 110 that the timeout has not been reached, without performing the determination in step 109.

FIG. 4 is a schematic diagram of a waveform of the DAC command value 15 from the microprocessor 4 controlling the VCM drive current 16 for controlling the actuator. In FIG. 4, reference numeral 201 denotes a transition of the DAC command value 15 according to the conventional method. In the related art, the runaway of the magnetic head unit 11 is likely to occur at the portion 203 after many step-ups (after timeout). In the present embodiment, the runaway of the magnetic head unit 11 is prevented by shifting to the DAC command value 15 indicated by 202 after the timeout.

According to the above embodiment, the operation for preventing runaway of the magnetic head unit 11 is realized by microprogram control without requiring special hardware. Therefore, it is possible to provide a safe, reliable, and low-cost operation method of preventing a data failure due to a shock of a runaway of the magnetic head portion due to the undetected servo signal.

[0029]

According to the present invention, in a magnetic disk drive having a magnet latch mechanism, it is possible to prevent a data failure due to an impact caused by a runaway of a magnetic head portion during a release operation of a magnetic latch. .

[Brief description of the drawings]

FIG. 1 shows a flowchart of a method for releasing a latch of a magnetic disk drive according to the present invention.

FIG. 2 is a block diagram showing a magnetic disk drive with a magnet latch to which the present invention is applied.

FIG. 3 is an explanatory top view showing a schematic configuration of the magnetic disk device shown in FIG. 2;

FIG. 4 is a waveform chart schematically showing a DAC command value output from the microprocessor shown in FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Host interface connector part, 2 ... R / W channel part, 3 ... Interface control part, 4 ... Microprocessor (MPU) part, 5 ... Servo controller part, 6 ... Shock sensor part, 7 ... VCM (voice coil motor)
/ Motor driver for spindle motor, 8 ... VCM
(Voice coil motor) section, 9 ... magnet latch mechanism section, 10 ... R / W preamplifier section, 11 ... magnetic head section, 12 ... magnetic medium section, 13 ... magnetic head drive actuator section, 14 ... spindle motor section , 15 ... DA
C command value, 16: VCM drive current, 17: HDA (head disk assembly) mechanism, 18: control board, 19: magnetic medium shipping zone (C
SS) portion, 20: data area portion of magnetic medium, 21: outer peripheral side stopper for actuator, 22: inner peripheral side stopper for actuator, 23 ... base side magnet portion for magnet latch, 24 ... magnetism for magnet latch Head actuator side magnet section.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-128754 (JP, A) JP-A-4-301278 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 21 / 02,21 / 12,21 / 22

Claims (1)

(57) [Claims] 1. A magnetic disk drive having a mechanism for magnetically latching a magnetic head, a first step of setting a predetermined time in a timer and starting time counting, and A second step of driving the magnetic disk unit with a predetermined driving force, and detecting a servo signal based on a read signal of a data area of a magnetic medium unit output from the magnetic head unit, and detecting the servo signal successfully. A third step of determining whether or not the detection of the servo signal has failed in the third step; determining whether or not the time set in the first step has elapsed; If it is determined that the magnetic head has run out, the magnetic head is driven inward to prevent runaway of the magnetic head toward the outer circumference. A fourth step of driving the magnetic head section to the outer peripheral side of the magnetic medium section with a driving force stepped up from the driving force of driving the drive section, and executing the third step; and And a fifth step of terminating the process when it is determined that the detection of the servo signal has been successful.