JPH0520811A - Fixed magnetic-disk apparatus - Google Patents

Abstract

PURPOSE:To reduce a failure rate by specifying an acceleration at the start of a magnetic-head seek operation and an acceleration at the start of a magnetic-head turning operation. CONSTITUTION:In conventional magnetic disk devices, an acceleration at the start of a magnetic-head seek operation and an acceleration at the start of a magnetic-disk turning operation are too large. As a result, the levitation posture of a head slider at their start becomes unstable, and finally a high failure rate is caused. Therefore, an acceleration at the start of a magnetic-head seek operation is set at 500m/sec<2> or lower and an acceleration at the start of a disk turning operation is set at 500m/sec<2> or lower. When the set accelerations are exceeded, they are restrained by applying an actuator-driving power supply to power amplifiers 4a, 4b for actuators 3a, 3b on the other side via cross-feed forward compensation elements 5a, 5b. As a result, a failure rate is 6X10<-5> and can be reduced to about 1/10 that of conventional cases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixed type magnetic disk device.

[0002]

2. Description of the Related Art A fixed type magnetic disk device, which is commonly called a hard magnetic disk device, is superior in high-speed accessibility to other file storage devices and has a large capacity comparable to that of an optical disk device. Widely used as an external storage device for online computers and personal computers. In order to make the most of its high-speed accessibility, the fixed magnetic disk device currently on the market has an acceleration of 700 m / sec ² at the time of starting the disk rotation.
Above, the acceleration at the start of the magnetic head seek is 600m /
It is set to sec ² or more.

[0003]

The disadvantage of the fixed type magnetic disk device is that the probability that the magnetic head mechanically contacts the magnetic disk rotating at high speed during recording / reproducing / erasing cannot be eliminated. Moreover, some recording / reproducing cannot be performed due to damage to the disk recording area or the magnetic head, or in the worst case, a total recording / reproducing state called head crash may occur. Incidentally, the market failure rate of fixed magnetic disk devices is said to be in the range of 10 ⁻³ to 10 ⁻⁴ . Further, the decrease in the flying height of the magnetic head accompanying the recent increase in recording density tends to increase the failure rate.

An object of the present invention is to provide a magnetic disk device having a low failure rate.

[0005]

The fixed magnetic disk drive of the present invention has an acceleration of 50 when the magnetic head seek is started.
0 m / sec ² or less, characterized in that the acceleration during rotation of the magnetic disk starts and 500 meters / sec ² or less.

[0006]

[Function] Regarding the cause of the above-mentioned head crash,
Some factors have been cited, such as dust intrusion between the head and the disk, an increase in contact probability due to instability of the head flying posture, and changes in temperature and humidity inside the disk device during continuous operation. At present, it has not been clarified. At present, the idea that a head crash occurs when the above-mentioned several factors are superimposed is dominant. The inventors have clarified the factors that cause pulling, based on the idea that these factors may be divided into factors that cause pulling of head crush and factors that accelerate head crushing. In other words, 1) magnetic disk through the measurement of the slider flying posture by a vibration measuring instrument using the Doppler effect of laser light, the in-situ measurement of dust generation state using a dust counter, and the detection of contact between the disk and slider by ultrasonic waves. When the magnetic head is sought after the rotation start, the attitude of the slider becomes unstable, the contact state deteriorates, and the contact probability increases. 2) The destabilization of the slider posture that occurs when the magnetic disk rotation is started and when the magnetic head seek is started is the main reason for promoting the generation of a large amount of dust. 3) The degree of destabilization of the slider posture changes depending on the acceleration at startup. That is, the dynamic characteristics of the slider supported by an elastic body such as a gimbal spring are strongly influenced by inertia, and the higher the acceleration, the more unstable the posture becomes, and the more violent contact occurs between the disk and the slider.
Therefore, the moving speed and its acceleration while the disk and slider are relatively moving have almost no influence on the flying posture of the slider. 4) As the acceleration at disk rotation start increases,
The state in which the front part of the slider is lowered and the rear part is lifted is strengthened, resulting in more violent contact in front of the slider, and the degree of damage and dust generated on the disk surface is also increased. 5) When the seek operation is performed under the conditions of the disk rotation speed of 20 m / sec and the average slider flying height of 0.22 μm, the slider flying height variation Δh is almost proportional to the acceleration G at the start of the seek operation, and G = 1200 m / sec ² Then Δh = 0.
08 μm, G = 500 m / sec ² , Δh = 0.035
μm. That is, the contact probability increases as the seek motion acceleration increases. Etc. From this, the increase in acceleration at the time of disk rotation start or seek start accelerates the continuous phenomenon of destabilization of the slider flying posture → contact between the disk and head → damage to the disk surface → generation of dust, and finally It was found that the disk drive failure rate increases. Further, the acceleration at the time of starting the magnetic head seek is set to 500 m / sec ² or less, and the acceleration at the time of starting the disk rotation is set to 500 m / sec ² or less, thereby making the slider flying posture unstable, which is a cause of the continuous phenomenon. Is less likely to occur, and as a result, phenomena such as subsequent contact, surface damage, and dust generation that occur subsequently are significantly suppressed.
In the magnetic disk device of the present invention based on the above-described actions and principles, the probability of failure caused by superposition of these phenomena is significantly reduced.

[0007]

EXAMPLES Next, examples of the present invention will be described.

Table 1 shows the main specifications of the magnetic disk device (embodiment 1) which is an embodiment of the present invention.

[0009]

[Table 1]

The acceleration at the start of rotation is 500 m / sec
^The voltage was varied by controlling the voltage applied to the plasticless DC motor so that it was ² or less, and the acceleration was obtained by differentiating the rotational speed measured by a speedometer using an optical sensor. FIG. 1 shows a block configuration of a seek operation control loop of the head. For head positioning, two-phase position signal control using position information obtained from the two heads 1a and 1b and a standard deceleration signal was adopted. The observer circuit systems 2a and 2b have a function of synthesizing the first-order lag signal of the sum signal of the drive current of the actuator and the position differential signal, and enable highly accurate control of the seek speed. In the acceleration control of the actuator that performs the drive seek operation, the driving force, that is, the acceleration changes depending on the seek distance, so the change in acceleration with the seek distance is measured by a laser Doppler vibrometer, and if the set seek acceleration is exceeded, The actuator drive power supply during the seek operation is suppressed by the feedforward control method in which the power supply 4a (4b) of the other actuator 3a (3b) is added via the cross feedforward compensation element 5a (5b).

Further, in the present invention, since the acceleration at the start of the seek operation is low, the acceleration after the start must be made larger than that of the conventional one in order to obtain the same average acceleration as the conventional one. For this reason, it is necessary to increase the rigidity of the entire actuator system. The integrating elements 6a and 6b are intended to have high rigidity when the actuator is driven, particularly to reduce low frequency component noise due to disturbance such as vibration, and guarantee a high rigidity actuator system by an electrical compensation circuit. Although the seek acceleration was controlled by the above configuration, the start-up acceleration was kept low and the average seek time could be kept 1.04 times that of the conventional disk device.

Table 2 shows the main specifications of the magnetic disk device (Comparative Example 1) before the improvement according to the present invention.

[0013]

[Table 2]

The storage capacity and the like are all the same except that the seek acceleration is twice and the acceleration at disk rotation start is 2.3 times.

When the failure rates of the above two types of magnetic disk devices are obtained by statistical Weibull distributed distribution processing, the failure rate of the conventional magnetic disk device, which is a comparative example, is 5%.
The failure rate of the magnetic disk device of the present invention was 6 × 10 ^−5, which was reduced to about 1/10, while the value was × 10 ⁻⁴ .

[0016]

As described above, the present invention is to provide a magnetic disk device having a significantly lower failure rate than the conventional magnetic disk device.

[Brief description of drawings]

FIG. 1 is a block diagram of an example of a magnetic head seek operation control loop of a fixed magnetic disk device according to the present invention.

[Explanation of symbols]

 1a, 1b Magnetic heads 2a, 2b Observer circuit system 3a, 3b Actuator 4a, 4b Power amplifier 5a, 5b Cross feed forward compensation element 6a, 6b Integral element

Claims (1)

What is claimed is: 1. A magnetic head seek seek acceleration is 50.
A magnetic disk device characterized in that the acceleration when the magnetic disk starts rotating is set to 0 m / sec ² or less and to 500 m / sec ² or less.