JPH07134824A - Method and equipment for evaluation test of hard disk - Google Patents

Abstract

PURPOSE:To perform an evaluation test in a short time by calculating an added value for determination of the durability of a disk by measuring a collision strength for one turn of a disk base from the position of the original point for each rotational speed and by adding up the collision strength at each rotational speed. CONSTITUTION:A motor 2 which drives a disk base 1 to rotate and of which the rotational speed is variable and a rotary encoder (not shown in the figure) which detects the position of the original point of the disk base 1 when it is driven by the motor 2 are provided. An AE sensor 5 which measures a collision strength at the time when a head 3 collides with the disk base 1 for one turn of the disk base 1 from the position of the original point detected by the encoder, and a computer 10 being a rotation command means which outputs a command to change the rotational speed every time when the collision strength for one round of the base 1 is measured by the sensor 5, are also provided. Besides, an addition means (not shown in the figure) which calculates an added value for determination of good or bad of the durability by adding up the measured collision strength for one round of the disk base 1 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard disk evaluation test method and apparatus.

[0002]

2. Description of the Related Art A hard disk (hereinafter referred to as "HD") is a disk (substrate) made of, for example, an aluminum disk, on which a magnetic film, a protective film, a lubricant, etc. are attached for large-capacity recording and high-speed signal reading / writing. It is a possible magnetic recording medium, and the disk is rotated at high speed (currently around 3600 RPM) to obtain high-speed reading and writing of signals. Further, both the disk and the head are formed of a hard solid, and when they come into contact with each other, both are damaged. Therefore, in the hard disk, while the disk is rotating, the head is levitated by the air flow generated by the disk rotation. The flying height is currently about 0.2 μm, but it is advantageous to reduce the flying height in order to increase the recording density.

As a recent tendency, space saving of computers such as notebook type personal computers has progressed, the size of HD has been reduced, and space has become unacceptable. Therefore, when the disk is stopped, it is no longer possible to secure a space for retracting the head on the side of the disk in order to avoid contact / collision between the head and the disk, further reducing the startup time from the viewpoint of high speed. Therefore, there is a problem with the mechanism that retracts the head, so when the disk rotates, the head is levitated,
A CSS (contact start and stop) method that employs a mechanism in which the head is landed on the innermost circumference of the disk where signals are not read or written when the disk is stopped is being considered.

However, when the motor is started and stopped, the head and the disk eventually come into contact with each other and take off and land.
The above-mentioned problem that the disc and the head are worn out similarly occurs. The place where the head takes off and land is a place that is not related to reading and writing on the disc, but the abrasion powder generated by abrasion remains between the head and the disc,
When the head moves to the place where the signal is read and written, the disk is fatally damaged by the abrasion powder. This problem is even more important because the flying height is becoming very small.

Therefore, it is necessary to improve the durability of the HD as much as possible so that the abrasion powder is not generated as much as possible even when the head takes off and land on the disk. At that time, the evaluation test for accurately evaluating the durability of the HD is required. Method becomes a problem.

[0006]

There are currently two methods for examining the durability of such HD, one of which is called the CSS method and the other is called the DRAG method. . FIG. 6 is a diagram showing an evaluation method by the CSS method, and this method is a method in which the motor is repeatedly tested on and off at regular time intervals. That is, the rotation speed of the disk is 0 → 3600 in 12 to 20 seconds.
→ It is set to 0 rpm and this is repeated as one cycle, and the durability of the disk is evaluated by using the number of cycles when the friction coefficient becomes a predetermined value or more as the limit value of the durability. Although it has an advantage that it is similar to the operation of, the disadvantage is that it usually takes about 3 to 4 days to give a test result, and a lot of time is required for the durability test.

On the other hand, FIG. 7 is a diagram showing an evaluation method by the DRAG method, which is a constant low rotation speed (100 rpm to 200 rp) with the head and the disk always in contact with each other.
This is a method of testing durability in m). In this method, the operation of HD at the time of testing is different from the actual operation, but CSS
Compared with the method, there is an advantage that the result can be obtained in a short time.

Currently, the CSS system is the mainstream, but in the future,
To check the durability of many discs in a short time, D
The RAG method is considered to be advantageous. However, in any case, this is an evaluation test in which the frictional condition between the disk and the head is measured to judge the frictional condition, and it is difficult to obtain a correlation between both equations by focusing only on the frictional coefficient.

The present invention has been made in view of such conventional problems, and the operating state of the head of the hard disk is similar to that in actual use, and it is possible to determine the quality of the disk in a short time. Hard disk evaluation test method and device.

[0010]

Therefore, according to the present invention, when a head for signal recording / reading is levitated from the disk substrate by the air flow generated by the rotation of the disk substrate, and the head is taken off and landed on the disk substrate. When evaluating the durability due to wear of the disk substrate, a rotational speed command is output to the rotational driving means to rotationally drive the disk substrate, and the origin position of the disk substrate is detected.
During the rotation, the collision strength when the head collides with the disk substrate is measured, and every time the collision strength for one round of the disk substrate is measured, a rotation speed command is output to the rotation driving means to rotate the disk substrate. The speed was changed and the measured collision strengths were added to calculate the added value for determining the durability.

Further, as shown in FIG. 1, a signal recording / reading head is floated above the disk substrate by the flow of air generated by the rotation of the disk substrate.
In a hard disk evaluation test apparatus for evaluating durability due to wear when a head takes off and land on a disk substrate, a rotation driving unit that rotationally drives the disk substrate and changes a rotation speed, and a rotation driving unit when driven by the rotation driving unit. Origin position detecting means for detecting the origin position of the disk substrate, and collision strength for measuring the collision strength when the head collides with the disk substrate while the disk substrate makes one round from the origin position detected by the origin position detecting means. The measuring means, the rotation command means for outputting a rotation speed command for changing the rotation speed every time the collision strength for one revolution of the disk substrate is measured by the collision strength measuring means, and the measured collision for one revolution of the disk substrate. And an addition unit that adds strengths to calculate an added value for determining durability.

[0012]

According to the above construction, the origin position of the disk substrate when the disk substrate is rotationally driven by the rotary driving means is detected by the origin position detecting means. The collision strength is measured by the collision strength detection means while the disk substrate makes one round from the origin position. The rotation speed of the disk substrate is
It is measured every time the collision strength for one round of the disk substrate is measured. The measured collision strength for one round of the disk substrate is added by the adding means, and the added value for determining the quality of durability is calculated.

Therefore, since the collision strength for one round of the disk can be investigated by changing the rotation speed, it is possible to measure in a short time, and the collision strength is measured in a state where the hard disk is actually used, Correlation can be obtained even when the conventional CSS method is used.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The same elements as those in FIGS. 6 and 7 are designated by the same reference numerals and the description thereof will be omitted. FIG. 2 shows a hard disk evaluation test apparatus of this embodiment for evaluating the durability of the HD (hard disk) substrate 1. This device is configured to detect the collision strength as the strength of the AE signal for each rotational speed and determine the durability of the HD1. The detailed evaluation test method will be described later.

In FIG. 2, the HD1 to be evaluated is a large disk capable of recording / reading at high speed by bringing a magnetic film, a protective film, a lubricant and the like into close contact with a disk type disk substrate made of aluminum or the like. It is a magnetic recording medium of capacity. A spindle motor (hereinafter, simply referred to as a motor) 2 as a rotation driving means drives the HD 1 for rotation and has a variable rotation speed. Also, this motor 2 has information on the angle during rotation,
A rotary encoder (not shown) for obtaining the origin signal is attached.

The head slider 3 is made of, for example, Al ₂ O ₃ .Ti.
Ceramics such as C is used, and the surface contacting the HD 1 serves as a head, which is carried by the head arm 4 so as to be fixed at a predetermined radial position on the disk. An AE (acoustic emssion) sensor 5 as a collision strength detecting means is a sensor that detects an elastic wave generated when a small crack is generated in the solid as a precursor when the solid is destroyed, and a collision between the head and the HD1. Is used as an AE signal via the head arm 4, and the AE signal is amplified by the preamplifier 6.

The AE signal from the AE sensor 5 is input to the AD converter 8 via the sample hold circuit 7, and the angle information and the origin signal are input from the rotary encoder. And these information are AD converter 8
Digitized by. In the measurement, if the sampling frequency of the AD converter 8 is fast, the number of data becomes so large that it cannot be processed. Therefore, the AD converter 8 of the present embodiment has a slow sampling frequency. Further, the peak hold circuit 7 includes an AD converter 8
If the sampling frequency is slow, all AE signals cannot be taken in, and data will be missed. Therefore, this is a circuit interposed in front of the AD converter 8 so as to hold the peak value of the AE signal only within a predetermined time. .

The AE signal from the AE sensor 5, the angle information from the rotary encoder, and the origin signal are also input to the digital oscilloscope 9. And, for example, the origin (0
(°: origin output of the rotary encoder) The detailed waveform of the AE signal is displayed on the digital oscilloscope 9. Incidentally, since it is said that the AE signal generated at the time of destruction has a frequency component of about 1 MHz,
A digital oscilloscope 9 having a high sampling frequency is used so that the waveform of the AE signal can be captured as it is.

The computer 10 controls the rotation speed of the motor 2, head movement control, etc., and digitizes the angle information from the AD converter 8, the origin signal, the AE signal data for one rotation, and the digital oscilloscope 9.
This is a device for evaluating whether the durability of the HD1 is good or bad by alternately inputting the data in the vicinity of the origin from the. The computer 10 and the digital oscilloscope 9 are, for example, GP
It is connected via the IB interface. Computer
The 10 is connected to an external storage device for recording input data, is provided with a screen for displaying the input data, and software for storing the input data and evaluating the durability of the disk based on the input data. It has a built-in memory and so on.

Next, the processing of the durability evaluation test of this disk will be described in detail with reference to the flowchart of FIG. Step (indicated as "S" in the figure, and so on)
In 1, the measurement conditions and parameters such as the maximum rotation speed, the minimum rotation speed, and the rotation speed difference per step when lowering the rotation speed (for example, 200 rpm) are input.

In step 2, the head is moved to the origin position of the stage (not shown). In step 3, the motor 2 is rotated at a rotational speed of 36 when a hard disk is used, for example.
Command the high speed so that it will be 00 rpm. The head slider 3 floats above the HD1 as the rotational speed of the HD1 increases. In step 4, the head slider 3 is moved so that the head is located at a designated position, for example, the innermost circumference where no signal is read or written.

In step 5, the origin (0 °) position of the rotary encoder attached to the motor 2 is detected,
Until the HD1 makes one rotation from this origin position (0 to 360
°), AE signal is detected and this data is captured. This step and the rotary encoder correspond to the origin position detecting means. In step 6, the AE signal detected by the AE sensor 5 is input, and from this AE signal, for example, 20 kHz
The frequency components of are sampled. This step and AE
The sensor 3 corresponds to a collision strength measuring means.

In step 7, the input AE signal is stored in the built-in memory. In step 8, the online statistic process is performed by calculating the average value of the AE signals for one round sampled at the sampling frequency of 20 kHz. That is, HD
Since the intensity of the AE signal sequentially changes while 1 makes one round,
This average value is for comparing the data.

In step 9, this AE signal data (average value) subjected to the online statistical processing is stored in the external storage device. In step 10, raw data / processed data is displayed on a screen or the like. When it is desired to obtain data on another track, the head is moved and the process proceeds from step 11 to step 4 and the same process is performed.

If only the data of one point can be correlated with the data at all the radial positions, step 11 can be omitted. In that case, if the data is measured at the innermost circumference where no signal is read, the linear velocity on the disk is the slowest at the innermost circumference and the flying height of the head slider 3 is also the smallest, so the tightest test is performed. You can Next, at step 12, the rotational speed of the motor 2 is reduced by the rotational speed difference of 200 rpm given at step 1 to the next rotational speed.

In step 13, the motor 2 is instructed to drive at the next rotation speed. This step and step 3 correspond to rotation command means. And wait in step 14 until the motor 2 becomes constant speed rotation, and when it becomes constant speed rotation,
The process proceeds to step 14 → 4 and the same process is performed. When the measurement of the AE signal data at all the rotational speeds to be measured is completed in this way, the process proceeds to steps 12 → 15.

FIG. 4 shows the AE signal data at each rotation speed, and the data A and B are measured when the object to be measured is changed. The decrease in the rotation speed and the increase in the intensity of the AE signal indicate that the flying height of the head from the HD1 decreases and the head collides with the HD1. In step 15, the motor 2 is rotated again at high speed to float the head.

Then, in step 16, the head is returned to its original position, and in step 17, the motor is stopped. As a result, the head loses its levitation force and lands at the original position on the HD1. In step 18, all the AE signal data measured for each rotation speed are added and offline statistical processing is performed. For example, in FIG. 4, all the AE signal data measured for each rotational speed of the data A and B respectively are added to obtain the data A and B respectively.
Areas S _A and S _B surrounded by are calculated. When the data A is compared with the data B, the intensity of the AE signal of the data A is very large at the rotation speed of 1000 rpm or less, and the area S _A
> S _B

FIG. 5 is a diagram showing the relationship between the data measured by the conventional CSS method and the data measured by this embodiment, where the horizontal axis indicates the CSS method, that is, It shows the number of cycles when the friction coefficient becomes a predetermined value or more by repeating one cycle in which the rotation speed of HD1 is changed from 0 to 3600 to 0 rpm. The durability of HD1 by the CSS method is shown. This is the data showing the limit value.
The vertical axis is data showing the area value (added value of the AE signal data) calculated according to the present invention. From this figure, it can be seen that the larger the area value, the lower the durability measured by the CSS method. That is, the added value and HD1
Of the data A and B as described above, the area S _A > S _B is satisfied. Therefore, the measured object of the data A is more than the measured object of the data B. You can see that the durability is not good.

It should be noted that this measurement time is about 3 to 4 days in order to check the durability of the HD1 in the conventional CSS system, whereas the measurement time is 2 according to the measurement method of the present invention. It is about a minute, and the quality of durability of the HD 1 can be determined in a short time. This step corresponds to the adding means. According to such a configuration, the added value of the intensity of the AE signal for one rotation of the disk for each rotational speed measured when the rotational speed of the HD1 is changed from the high speed to the low speed is calculated, and the disk is calculated based on the added value. The durability of the disk substrate can be determined in a short time by determining the durability of the disk, and the operating state of the head in the HD is almost the same as when actually used, so that the reliability is high. An evaluation test can be conducted. Further, although only the radial direction information can be obtained by general shape measurement and evaluation, this evaluation test can obtain the shape determination in the circumferential direction, particularly the shape information felt by the actual head.

[0031]

As described above, according to the present invention, the collision strength is measured for each rotation speed while the disk substrate makes one revolution from the origin position, and the collision strength for each rotation speed is added. By calculating the additional value for determining the durability of the disc, the collision strength for one round of the disc can be examined by changing the rotation speed, so that the evaluation test can be performed in a short time and the disc substrate Since it is possible to measure the operating state of the head in the same manner as in actual use, it is possible to perform a highly reliable evaluation test.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a configuration diagram showing a hard disk evaluation test apparatus according to an embodiment of the present invention.

FIG. 3 is a flowchart showing the operation of FIG.

FIG. 4 is a diagram showing the characteristics of the intensity of the AE signal for each rotation speed of the disk substrate.

FIG. 5 is a diagram showing a relationship between an added value and conventional CSS system data.

FIG. 6 is an explanatory diagram of a conventional CSS measurement method.

FIG. 7 is an explanatory diagram of a conventional measuring method by the DRAG method.

[Explanation of symbols]

 1 hard disk (HD) 2 (spindle) motor 3 head slider 5 AE (acoustic emssion) sensor 10 computer

Claims (2)

[Claims] 1. When evaluating the durability due to wear when the head for signal recording / reading is levitated from the disk substrate by the flow of air generated by the rotation of the disk substrate, and the head is taken off and landed on the disk substrate, A rotation speed command is output to the rotation driving means to rotate the disk substrate, the origin position of the disk substrate is detected, and the collision strength when the head collides with the disk substrate while the disk substrate makes one revolution is measured. Then, every time the collision strength for one round of the disk substrate is measured, a rotation speed command is output to the rotation driving means to change the rotation speed of the disk substrate, and the measured collision strength is added to determine durability. A hard disk evaluation test method characterized by calculating an added value for quality judgment. 2. A hard disk evaluation for evaluating the durability due to abrasion when the head for signal recording / reading is levitated from the disk substrate by the flow of air generated by the rotation of the disk substrate and the head is taken off and landed on the disk substrate. In the test apparatus, the disk substrate is rotationally driven to rotate the rotational speed of the disk substrate, the rotational position of the disk substrate when it is driven by the rotational driving means, the origin position detecting means for detecting the origin position of the disk substrate, and the origin position detection. Collision strength measuring means for measuring the collision strength when the head collides with the disk substrate while the disk substrate makes one revolution from the origin position detected by the means; and the collision strength for one revolution of the disk substrate by the collision strength measuring means. Rotation command means that outputs a rotation speed command that changes the rotation speed each time the Hard disk evaluation test apparatus characterized by comprising adding means for calculating a sum value for quality determination of the durability by adding the crash severity of one round substrate.