JPH09245428A - Magnetic disk device and method for control of its spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend operation life of a disk by remarkably shortening the time required for stopping a spindle motor(SPM) and a friction time between the disk and head in the CSS(contact start stop zone). SOLUTION: This SPM brake circuit is structured so that retraction is performed using an inverse electromotive force generated in all 3-phase coils 21, 22, 23 when SPM is rotating depending on its inertia after the power is turned off, when a combining voltage VC of such inverse electromotive force is lower than the reference voltage Vref, the retraction judged to be already completed and 3-phase coils 21, 22, 23 are all terminated to the ground to provide an intensive braking force. Therefore, the time required for stopping the SPM and friction time between disk and head in the CSS zone can remarkably shortened. As a result, wear of CSS zone can effectively be suppressed to extend the operation life of the disk.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device such as a hard disk drive and a spindle motor braking method for the same.

[0002]

2. Description of the Related Art Hard disk drive (hereinafter referred to as HDD
Call. ), The spindle motor for driving the disk (hereinafter referred to as SPM) rotates the head within the range of the number of rotations required for floating the head on the disk surface when the power is turned off. (Contact Start St
op) Performs an operation called retract to move to the zone. The CSS zone is a place on the disc where contact and rubbing with the head are allowed, and is usually provided at the outermost peripheral portion of the disc.

In such an operation when the HDD is powered off, if it takes too long to stop the SPM, the contact time between the disk and the head in the CSS zone becomes long on average, which accelerates the wear of the CSS zone. Become. Therefore, it is required to provide a brake circuit for stopping the SPM in a shorter time.

FIG. 5 shows the configuration of an SPM brake circuit in a conventional HDD. In the figure, reference numerals 1, 2 and 3 denote coils of each phase in a three-phase SPM such as a brushless DC motor. Reference numerals 4 and 5 are FETs for applying a power generation brake to the SPM by short-circuiting and connecting the two-phase coils 2 and 3 in the SPM to the ground when the power is off. 6
Is a Schottky diode that rectifies the counter electromotive force generated in the coil 1 by the action of electromagnetic induction with the motor magnet during inertial rotation of the SPM after the power is turned off. FETs 7 and 8 supply the output of the Schottky diode 6 to the voice coil motor (hereinafter, referred to as VCM) 10 for the head positioning mechanism through the retract current adjusting resistor 9 when the power is off. Then, 11 indicates the RESET signal output from the controller when the power is off to each FET 4, 5,
It is an inverter that is applied as a gate voltage for turning on 7 and 8.

The operation of this SPM brake circuit will be described below. When the RESET signal is output from the controller, the RESET signal is output to each F through the inverter 11.
It is applied to the gates of ET4, 5, 7, 8 and each FET4,
5, 7, and 8 are turned on. When the FETs 4 and 5 are turned on, the two-phase coils 2 and 3 are short-circuited to the ground, respectively, and the SPM is effectively braked. As a result, as shown in FIG. 6, the SPM stops earlier than the time when the brake circuit is not used by T1 time (for example, about 2 seconds).

On the other hand, when the FETs 7 and 8 are turned on, the coil 1 is actuated by electromagnetic induction between the coil 1 of the SPM and the motor magnet which continue to rotate due to inertia.
A back electromotive force is induced in. As shown in FIG. 7, the counter electromotive force is half-wave rectified by the Schottky diode 6, and then supplied to the VCM 10 via the retract current adjusting resistor 9 to perform the retract operation.

[0007]

According to the above-described conventional SPM braking method, as shown in FIG. 6, the SPM stop time T2 is T1 time (about 2 seconds) as compared with the case where the brake circuit is not used. Therefore, it is possible to shorten the contact time between the disk and the head in the CSS zone.

However, the lower limit value of the head floating rotational speed is about half the normal rotational speed (for example, the normal rotational speed is 42
In the case of 00 rpm, the lower limit of the head flying speed is about 200.
Therefore, the conventional SPM brake system still requires at least about half the time T2 required to stop SPM as the friction time T3 between the disk and the head in the CSS zone. ing.

The present invention is intended to solve such a problem, and it is a CS operation during the VCM stop operation period after the power is turned off.
A magnetic disk device and a spindle motor braking method for the same that can further shorten the contact time between the disk and the head in the S zone, thereby significantly suppressing the wear rate of the CSS zone and extending the disk life. The purpose is to provide.

[0010]

In order to achieve the above object, a magnetic disk apparatus of the present invention has a spindle motor for driving a disk and a spindle motor after the power is turned off. The retract means for performing the retract operation using the counter electromotive force generated in the coil, the comparing means for comparing the number of revolutions of the spindle motor after the power is turned off with the preset number of revolutions, the result of the comparison by the comparing means, the spindle When the number of rotations of the motor is lower than a preset number of rotations, a motor braking means for shorting the coil of the spindle motor to brake the spindle motor is provided.

According to a fifth aspect of the present invention, there is provided a spindle motor braking method for a magnetic disk device, wherein the back electromotive force generated in the coil of the spindle motor after the power is turned off is used to perform the retract operation and the power source is supplied. Compare the number of revolutions of the spindle motor after turning off with a preset number of revolutions, and if the number of revolutions of the spindle motor is lower than the preset number of revolutions, short-circuit the coil of the spindle motor to brake the spindle motor. It is characterized by making a call.

That is, in the invention according to claim 1 and claim 2, immediately after the power is turned off, the counter electromotive force generated in the coil is consumed by the retract means. For this reason, a weak braking force is applied to the spindle motor, and the rotation speed of the spindle motor gradually decreases. After that, when the rotation speed of the spindle motor becomes lower than the set rotation speed, the coil of the spindle motor is short-circuited, so that the spindle motor is strongly braked, and the rotation speed of the spindle motor is rapidly lowered to stop.

At this time, for example, as described in claims 2 and 6, all coils of the spindle motor are short-circuited to strongly brake the spindle motor, and also in claims 3 and 7. As described, by performing the retract operation at high speed by using the back electromotive force generated in all coils of the spindle motor after the power is turned off, it is necessary to stop the spindle motor compared to the conventional two-phase braking method. The time can be greatly shortened, and the contact time between the disk and the head in the CSS zone can be greatly shortened.

Further, in the invention described in claims 3 and 7, since the counter electromotive force generated in all the coils of the spindle motor after the power supply is turned off is supplied to the retract means, the retract power having a small fluctuation is drawn. Means are provided, which guarantees a very smooth retract operation.

Here, the rotation speed for comparison with the rotation speed of the spindle motor is set within the range of the rotation speed of the spindle motor at which the head can be levitated, as described in claims 4 and 8. It is desirable to do. If the number of rotations is set to a value outside this range, the spindle motor stop time and the disk-head rubbing time in the CSS zone will be unnecessarily extended.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the magnetic disk device of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing the configuration of the SPM brake circuit of the HDD according to this embodiment.

In the figure, reference numerals 21, 22, and 23 denote coils of each phase in a three-phase SPM such as a brushless DC motor. Reference numerals 24, 25 and 26 are FETs for short-circuiting and connecting the respective three-phase coils 21, 22, 23 of the SPM to the ground when the power is turned off to apply the power braking to the SPM
It is.

27, 28 and 29 are SPMs after the power is turned off
It is a Schottky diode that rectifies the counter electromotive voltage generated in the coils 21, 22, and 23 of each phase by the action of electromagnetic induction with the motor magnet during inertial rotation. Reference numeral 30 compares the combined voltage Vc of the counter electromotive voltages after rectification output from the Schottky diodes 27, 28 and 29 with a preset reference voltage Vref, and the combined voltage Vc is the reference voltage Vre.
It is a comparator that applies a gate voltage to each FET 24, 25, 26 so as to apply a power generation brake to the SPM when it is lower than f.

Similarly, 31, 32 and 33 are Schottky diodes for retract which rectify the counter electromotive force generated in the coils 21, 22, 23 of each phase by the action of electromagnetic induction. Reference numerals 34 and 35 are FETs that supply a combination of the rectified back electromotive forces output from the Schottky diodes 31, 32, and 33 when the power is off to the VCM 37 for the head positioning mechanism through the retract current adjusting resistor 36.
It is. And 38 is each FET for retract operation of the RESET signal output from the controller when the power is off.
It is an inverter applied to 34 and 35.

This SPM brake circuit includes all three-phase coils 21, 22 during inertial rotation of the SPM after the power is turned off.
When the combined voltage VC of the back electromotive force is lower than the reference voltage Vref, it is determined that the retract operation has already been completed, and the retract operation is completed. , 22, and 23 are short-circuited to the ground to apply a dynamic braking. The details of the operation of this SPM brake circuit will be described below.

When the RESET signal is output from the controller, the RESET signal is applied to the gates of the FETs 34 and 35 for retract operation via the inverter 38, and the FETs 34 and 35 are both turned on. By turning on the FETs 34 and 35 for these retract operations, the electromagnetic induction works between all the three-phase coils 21, 22 and 23 and the motor magnet that continue to rotate due to inertia even after the power is turned off. A back electromotive force is induced in the coils 21, 22, and 23 of each phase. These back electromotive forces are rectified by the retract Schottky diodes 31, 32, and 33, respectively, and then combined, and supplied to the VCM 36 via the retract current adjusting resistor 36. Thereby, the retract operation is performed.

FIG. 2 shows a three-phase composite voltage waveform after rectification. In this way, the back electromotive force of the conventional one-phase coil is rectified by supplying the VCM 36 through the retract current adjusting resistor 36 by rectifying and combining the back electromotive force of all three-phase coils. Compared to the method that supplies the VCM to the VCM
, And fast and smooth retract operation is guaranteed.

On the other hand, all three-phase coils 21, 22, 2
The back electromotive force induced in 3 is the Schottky diode 2
After being rectified by 7, 28 and 29 respectively, a combined voltage Vc is applied to the negative terminal of the comparator 30.
The comparator 30 compares the combined voltage Vc with a preset reference voltage Vref, and if the combined voltage Vc is lower than the reference voltage Vref, the gate voltage is applied to the FETs 24, 25 and 26 so as to apply the power generation braking to the SPM. Is applied.

That is, after the power is turned off, the rotational speed of the SPM is gradually reduced by the back electromotive force of each coil 21, 22, 23 being consumed by the retract circuit, and after some time, the reference voltage Vref is set. Reach the corresponding set speed. When the SPM rotation speed becomes lower than the set rotation speed, the coils 21, 22, and 23 of all three phases are short-circuited, and as a result, the strong braking for three phases is applied to the SPM, and the rotation speed of the SPM decreases rapidly. And then stop.

FIG. 3 shows how the SPM rotation speed is reduced by the SPM brake circuit according to the present embodiment in comparison with the conventional two-phase brake system. As described above, according to the SPM brake circuit of the present embodiment, the time T5 required for stopping the SPM is T4 hours (3 to 5) longer than that of the conventional two-phase brake system.
Therefore, the friction time T6 between the disk and the head in the CSS zone can be significantly shortened compared to the conventional case. As a result, it becomes possible to effectively suppress the wear of the CSS zone and prolong the disk life.

As another embodiment of the present invention, as shown in FIG. 4, for example, only the back electromotive force generated in the coils 21 of some of the three phases is rectified by the Schottky diode 31 and retracted. The circuit may be configured to supply the circuit. With this configuration as well, after the retract operation is completed, the effect of shortening the SPM stop time and the rubbing time between the disk and the head in the CSS zone due to strong three-phase power generation braking applied to the SPM can be obtained.

Although the three-phase SPM brake circuit has been described above, it goes without saying that the present invention is also applicable to SPMs having two-phase coils and four-phase coils or more.

[0029]

As described above, according to the magnetic disk device and the spindle motor braking method of the present invention, the time required to stop the spindle motor can be greatly shortened, and the disk and head in the CSS zone can be shortened. The rubbing time with can also be shortened significantly. As a result, C
The wear rate of the SS zone is significantly suppressed, and the life of the disk can be extended.

Further, according to the present invention, since the counter electromotive force generated in all the coils of the spindle motor after the power is turned off is supplied to the retract means, the retract electric power with little fluctuation is supplied to the retract means. This ensures a fast and smooth retract operation.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of an SPM brake circuit of an HDD according to an embodiment of the present invention.

2 is a waveform diagram showing a three-phase composite voltage after rectification in the SPM brake circuit of the HDD of FIG.

3 is an SP by the SPM brake circuit of the HDD of FIG.
The figure which shows the state of the decrease of M rotation speed compared with the conventional two-phase brake system.

FIG. 4 is a circuit diagram showing another embodiment of the present invention.

FIG. 5 is a circuit diagram showing a configuration of a conventional HDD SPM brake circuit.

FIG. 6 SP by the SPM brake circuit of the conventional HDD
Diagram showing how the number of M revolutions decreases

FIG. 7 is a waveform diagram showing a retract voltage in a conventional HDD SPM brake circuit.

[Explanation of reference numerals] 21, 22, 23 ... coils of each phase in SPM 24, 25, 26 ... FETs 27, 28, 29 for generating brake operation ... Schottky diode 30 ... comparators 31, 32, 33 ...... Schottky diodes for retract 34, 35 ...... FET for retract operation 36 ...... Retract current adjustment resistor 37 ...... VCM 38 ...... Inverter

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Koji Sugiyama 2-9 Suehiro-cho, Ome-shi, Tokyo Toshiba Personal System Engineering Co., Ltd. In-house

Claims (8)

[Claims] 1. A spindle motor for driving a disk, a retracting means for performing a retracting operation by using a back electromotive force generated in a coil of the spindle motor after the power is turned off, a rotation speed of the spindle motor after the power is turned off, and a rotation speed of the spindle motor in advance. When the rotation speed of the spindle motor is lower than a preset rotation speed as a result of comparison by the comparison means for comparing the set rotation speed with the rotation speed of the spindle motor, the coil of the spindle motor is short-circuited to the spindle motor. A magnetic disk device comprising: a motor braking unit that brakes the magnetic disk. 2. The magnetic disk device according to claim 1, wherein the motor braking means short-circuits all the coils of the spindle motor to brake the spindle motor. 3. The magnetic disk device according to claim 1, wherein the retract means performs a retract operation by using a back electromotive force generated in all coils of the spindle motor after the power is turned off. Disk device. 4. The magnetic disk device according to claim 1, wherein the set rotation speed is set within a rotation speed range of the spindle motor capable of flying the head. And a magnetic disk device. 5. A retract operation is performed by using a back electromotive force generated in a coil of the spindle motor after the power is turned off, and the number of revolutions of the spindle motor after the power is turned off is compared with a preset number of revolutions. A spindle motor braking method for a magnetic disk device, wherein when the rotation speed of the motor is lower than a preset rotation speed, the coil of the spindle motor is short-circuited to brake the spindle motor. 6. The magnetic disk drive according to claim 5, wherein all the coils of the spindle motor are short-circuited to brake the spindle motor. 7. The spindle motor for a magnetic disk device according to claim 5, wherein the retract operation is performed by using a back electromotive force generated in all coils of the spindle motor after power-off. Braking method. 8. The magnetic disk drive according to claim 5, wherein the set rotation speed is set within a rotation speed range of the spindle motor capable of flying the head. Spindle motor braking method for magnetic disk drive.