JPH02232807A - Method for measuring off-set quantity in circumferential direction of magnetic disk device - Google Patents

Abstract

PURPOSE:To measure off-set quantity in the track circumferential direction of a magnetic head by measuring a distance to a data recording area with an index as a reference by utilizing an index signal and a read clock signal. CONSTITUTION:From an index signal 13, which is outputted from a magnetic disk device by the index, to a data recording area 12, a number n1 of read clock signals 14 is counted. Next, prescribed environmental stress is applied to the magnetic disk device. Then, from the signal 13 to the area 12, a number n2 of the signals 14 is counted again. After that, the off-set quantity, which is generated in the circumferential direction of the magnetic head by the environmental stress, is calculated from difference n1-n2 in the count number of the signal 14 and difference between a circumferential length L0 of a measuring track and a total number n0 of the read clocks per one rotation of the track. A servo pulse signal 14a to be obtained from a servo track for controlling the positioning mechanism of the magnetic head can also be used in place of the signal 14.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for measuring the amount of offset in the circumferential direction of a magnetic head of a magnetic disk device used as a file device of a computer system, the amount of offset in the circumferential direction of a track of the magnetic head is measured. By establishing a measurement method, it is possible to more specifically understand the offset between the magnetic head and the track, and the objective is to dramatically improve the reliability of magnetic disk drives. After counting the number of read clock signals between the index signal and the data recording area and applying a predetermined environmental stress to the magnetic disk device,
Count the number of read clock signals between the index signal and the data recording area again, and calculate the difference in the number of read clock signals, the circumference length of the measurement track, and the total number of read clocks per revolution of the track. From this, the configuration is configured to find the amount by which the magnetic head is offset in the circumferential direction due to the environmental stress. [Industrial Application Field] The present invention relates to a method for measuring the amount of circumferential offset of a magnetic head in a magnetic disk device used as a file device in a computer system. [Overview of Mechanism of Magnetic Disk Device] FIG. 3 is a perspective view illustrating an overview of the mechanism of the magnetic disk device.

In the magnetic disk device, a plurality of magnetic disk media 1 are mounted on a spindle 2 and rotated at high speed by a motor 3. Each magnetic disk medium 1 is provided with a magnetic head 4 facing the surface thereof, and is floated by the wind force generated by the high speed rotation of the magnetic disk medium 1. Also, information read (read)/write}
(Write) is performed by moving the magnetic head 4 to a predetermined track position using the positioning mechanism 6. The track position is determined by using one of the magnetic disk media 1 as a servo disk, recording servo signals on the tracks of the servo disk, and reading the servo signals. That is, the magnetic heads 4 disposed on each surface of the magnetic disk medium 1 are driven simultaneously by the positioning mechanism 6.
The tracks on each disk are aligned using the servo disk tracks as a reference. Therefore, when the magnetic disk device is in use, changes in the relative positions between the disks of the magnetic disk medium 1 and between the heads of the magnetic head 4 cannot occur.
This becomes a factor that fundamentally destroys the reliability of the magnetic disk device. In other words, the magnetic head 4 may not be positioned on a predetermined track, resulting in off-track, resulting in an error in the read data, or in extreme cases, it may become impossible to read the recorded data, or the data may be lost due to data writing. This is because data in adjacent tracks will be destroyed. Additionally, with the miniaturization and increased storage capacity of magnetic disk devices, the recording density on magnetic disk media has increased.
The existence of off-track is an important factor that determines the reliability of a magnetic disk device.

The present invention relates to a method of measuring the amount of offset in the circumferential direction of a magnetic head, which has a close relationship with this off-track. [Prior Art] (1) Off-track FIG. 4 is a plan view illustrating off-track.

In FIG. 4, the magnetic head 4 is on track with respect to the track 7 under normal conditions. However, due to some reason, the position of the magnetic disk medium or the magnetic head 4
If the position of the magnetic head 4 moves, the position of the magnetic head 4 and the position of the track no longer match. This is off-track. In the figure, the distance ΔC between the track 8 and the magnetic head 4 when off-track occurs is the off-track amount. That is, it is defined by the distance of the vertical component with respect to the track.

Therefore, the distance of the horizontal component with respect to the track is not an issue here.

FIG. 5 is a diagram explaining the relationship between the inclination of the rotation axis of the magnetic disk medium and the off-track of the magnetic head, in which (a) is a side view of the magnetic disk medium, magnetic head, and positioning mechanism, (b) and (c). ) is a diagram explaining the relationship between each magnetic head and the amount of off-track. Same figure (b). (c) shows the off-track amount when the rotating shaft 9 is tilted to the left in the figure.

(b) shows the case where the disk D1 of the magnetic disk medium 1 is a servo disk, and the lower surface of the disk D1 is the servo surface in the figure. Therefore, among the magnetic heads 4, the off-track of the head Hla that traces the servo track is O (zero), and the higher the magnetic head is located in the diagram, the larger the off-track amount.

(c) shows the case where the disk D3 of the magnetic disk medium 1 is a servo disk, and the lower surface of the disk D3 is the servo surface in the figure. Therefore, among the magnetic heads 4, the off-track of the head H3a that traces the servo track is 0 (zero), and the off-track amount of the other magnetic heads increases as the distance from the head H3a increases. FIG. 6 is a diagram illustrating off-track due to eccentricity of the magnetic disk medium.

This figure explains a case where eccentricity occurs in the disk D3. (a) shows the case where the disk Di is a servo disk, and off-track occurs only in heads H3a and H3b of the magnetic head 4. (b) shows the case where the disk D3 is a servo disk, and all magnetic heads other than heads H3a and H3b of the magnetic head 4 are off-track.

(2) Off-track measurement method This off-track measurement is performed by an operator visually reading the observed waveform on an oscilloscope. FIG. 7 is a diagram illustrating a method for measuring the whirling off-track amount using an analog method, in which (a) is the signal pattern of the measurement track, (b) is the output voltage waveform of the magnetic head when there is no off-track, (c) illustrates the output voltage waveform of the magnetic head when there is off-track, and (d) illustrates the amount of off-track calculated from the difference in output voltage in (c). In Figures (a), (b), (c), and (d), the horizontal axis in (a) represents the track distance;
b). The horizontal axes in (c) and (d) represent time. However, since the magnetic disk medium rotates at a constant cycle, each position of the measurement track seen from the magnetic head and the time axis of the output voltage of the magnetic head have a correlation that repeats at a constant cycle. Therefore, in Figure 7, these are treated as the same. The measurement procedure is explained below. Procedure ■... Record the measurement signal on the measurement track.

Signal patterns A and B having the same frequency and the same level are written on the measurement track by moving the magnetic head off-track to positions in opposite directions with a certain amount of offset from the on-track position. (a) The figure shows this. Procedure ■...Apply environmental stress such as temperature stress to the magnetic disk drive. Magnetic disk drives expand and contract due to changes in temperature and other factors, resulting in irreversible misalignment.

Procedure ■: Observe the output voltage waveform of the magnetic head with an oscilloscope. The measurement recording signals on the magnetic disk medium are recorded at positions opposite to each other and offset by a certain amount with respect to the on-track position.

Therefore, if there is no off-track in the magnetic head, the output voltages of the magnetic head will match between the recording signal A part and the recording signal B part in the diagram (a).

However, if off-track exists in the magnetic head,
The output voltage of the recording signal in the direction of the position where off-track occurs increases, and the output voltage of the recording signal in the opposite position decreases.

(b) shows the output voltage of the magnetic head when there is no off-track, and the output voltage Va of the recording signal A portion and the output voltage vb of the recording signal B portion are Va = Vb.

In addition, FIG. 3(c) shows a case where off-track occurs on the recording signal A side, and the output voltage Vaa of the recording signal A portion and the output voltage vbb of the recording signal B portion satisfy Vaa>Vbb. Step ■... Convert the amount of off-track from the output voltage of the magnetic head.

Figure (d) shows the change in off-track ΔC of the magnetic head calculated from the difference in output voltage shown in Figure (c).

The off-track amount of the magnetic head was measured as described above. [Problems to be Solved by the Invention] FIG. 8 is a perspective view illustrating vertical offset and horizontal offset.

With the conventional off-track measurement method, it is possible to measure an offset amount of 10 in the vertical direction (off-track amount) with respect to the track, but it is not possible to measure an offset amount of 1 l in the horizontal direction with respect to the track. do not have. In other words, only the offset amount of the vertical component of the magnetic head 4 can be measured, and it is not possible to know in what direction the magnetic head 4 is offset. Off-track has traditionally been considered important because it can cause data reading errors.

However, with the miniaturization of magnetic disk drives and the increase in recording density due to the increase in recording capacity, the horizontal offset of the magnetic head on the track has become an important problem. In other words, it is required to know in which direction the offset is actually occurring. Therefore, it is strongly desired to establish a method to measure the amount of horizontal offset. The technical problem of the present invention is to solve the above-mentioned problems in the conventional off-track amount measuring method and to establish a method for measuring the offset amount in the track circumferential direction of a magnetic head.
This makes it possible to understand the offset between the magnetic head and the track more specifically, thereby improving reliability of the magnetic disk device.
The goal is to achieve dramatic improvements. [Means for Solving the Problems] Fig. 1 is a diagram explaining the basic principle of the present invention, in which (a) shows the positional relationship between the index on the track and the data recording area, (b) shows the index signal, and (c) ) beam clock signal; (d) is a measurement flowchart;

The measuring method of the present invention uses an index, which is the physical origin of a track, as a reference position, and uses an index signal 13 outputted by the magnetic disk device at this index, and a read clock signal 14 outputted as a synchronization signal when reading data. However, the feature is that the distance to the data recording area l2 is measured using the index as a reference position.

The procedure of the measuring method of the present invention will be explained below.

Procedure ■ Record the reference data on the measurement track of the magnetic disk medium. Procedure■ From index signal (13) to data recording area (12)
The number of read clock signals (14) (n1) until
Count. Procedure■ Apply specified environmental stress such as temperature and vibration to the magnetic disk drive. Procedure ■ Count the number (n2) of read clock signals (14) again between the index signal (l3) and the data recording area (l2). Procedure ■ Calculate the environmental stress from the difference in the number of counts of the read clock signal (14) (nl - n2), the circumference length of the measurement track (L0), and the total number of read clocks per one rotation of the track (n0). This is more than just finding the amount by which the magnetic head is offset in the circumferential direction, which is the cause.

Note that the servo pulse signal (14a) obtained from the servo track for controlling the positioning mechanism of the magnetic head is
It can also be used in place of the read clock signal (14).

[Effect]

The measuring method according to the present invention focuses on the fact that the total number of read clocks per round of a track is constant, and is characterized in that the distance on the circumference is measured by the number of read clocks.

In other words, when an offset occurs in the circumferential direction of the track, that is, in the horizontal direction, between the magnetic head on the servo surface and the magnetic head on the data surface, the circumferential distance Lid from the index to the data recording area 12 changes. The offset l-1 is determined from the change in the circumferential distance Lid. Now, if the circumferential length of one track round is L0, and the total number of read clocks per one rotation of the track is n0, the circumferential length ΔL per one read clock can be expressed by the following equation.

ΔL=L6/n6 Therefore, the horizontal offset ΔH caused by applying environmental stress to the magnetic disk drive can be determined by the following equation.

ΔH=ΔL−nl−ΔL−n2 =ΔL・(nl −n2)=(Lo/no)・(nl −n2) Also,
It is exactly the same when a servo pulse signal is used instead of a read clock signal. [Example] Figure 2 is a diagram explaining the example, (a) is a connection diagram between a magnetic disk device and a test device, (b) is a diagram explaining the synchronization byte of the data recording area, and (c) is a diagram explaining the example. A flowchart explaining the procedure for counting the number of read clocks from the index to the data recording area, and (d) a diagram explaining the offset in the circumferential direction of the magnetic head. (1) Connection of magnetic disk device and test equipment In this example,
As shown in FIG. 2(a), the magnetic disk device 15 and the test device 16 are connected to an SMD (small device), which is the mainstream interface for small magnetic disk devices.
The offset of the magnetic head relative to the track in the circumferential direction is measured.

The SMD interface provides information from the magnetic disk device side to the upper control device to which the magnetic disk device is connected.
As a data write/read control signal, (1)
Outputs index signal, (2) interface write clock signal, and (3) read clock signal.

The meaning of each signal is explained below. (1) Index signal The index signal is generated from a servo signal that controls the positioning of the magnetic head and the rotation of the magnetic disk medium, and is generated at the index position once per rotation of the magnetic disk medium. (2) Interface write clock signal Used to synchronize when a host controller writes data to a magnetic disk device.

(3) Read clock signal Indicates the start of the bit cell in the recording area, and read data is transferred to the upper control device in synchronization with this signal. That's it. (2) Measurement On the other hand, the test device 16 side has a position counter that is triggered by the index signal and counts up based on the read clock signal, and counts the read clock signal.

On the other hand, as shown in FIG. 2(b), a synchronization byte 18 indicating the beginning of the data recording area is provided at the beginning of the data recording area 12 of the measurement track.

In addition, for the reference data written from the test device 16 to the measurement track of the magnetic disk device 15, incorrect synchronization byte data is written in the synchronization byte 18, and the next time the test device 16 reads the reference data, it is not synchronized. Cause a byte data comparison error to occur.

Therefore, it can be determined that the time point at which the comparison error occurs is at the beginning of the data recording area.

The measurement method of this embodiment is to count the number of read clocks from the index to the data recording area l2 by using the index signal as the count start trigger signal of the read clock and using the error signal as the count stop signal. be.

By configuring the test device 16 with a microcomputer system, the above-mentioned read clock counting and start/stop control can be realized on software. Since the basic procedure for measurement is the same as that shown in FIG. 1(d), the procedure for counting the number of read clocks will be explained here with reference to the flowchart in FIG. 2(C).

Procedure ■ Clear the read clock counter. In other words, set it to 0 (zero).

Procedure (2) Wait until the index signal is received, and when the index signal is received, start counting the read clock.

Procedure (1) Continue counting the read clock until a synchronization byte error occurs, and stop counting at the time the error occurs.

That's it. That is, the count number counted in step (2) is the number of read clocks from the index to the data recording area.

Therefore, the amount of offset of the magnetic head in the track circumferential direction can be determined from the difference in the counts before and after applying environmental stress such as temperature stress or vibration stress to the magnetic disk drive. FIG. 2(d) shows the measurement track 7b, the synchronization byte 18,
This is a diagram schematically explaining the relationship of the magnetic head 4, and ΔH shown in the diagram is the amount of offset in the circumferential direction. [Effects of the Invention] As described above, according to the measuring method according to the present invention, it is possible to measure the offset amount of a magnetic head in the track circumferential direction in a magnetic disk device.

Therefore, it becomes possible to understand the movement of the magnetic head in the track circumferential direction, which was unknown until now, and it becomes possible to understand the offset between the magnetic head and the track more specifically. As a result, it becomes possible to add more precision to the design and testing of magnetic disk drives, and the reliability of magnetic disk drives can be dramatically improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the basic principle of the present invention, in which (a) is the positional relationship between the index on the track and the data recording area, (b) is the index signal, (c) is the read clock signal, and (d) is the positional relationship between the index and the data recording area. 2 is a flowchart of measurement; FIG. 2 is a diagram explaining an example; (a) is a connection diagram between a magnetic disk device and a test device; (b) is a diagram explaining a synchronization byte of a data recording area; (c) 3 is a flowchart explaining the procedure for counting the number of dots from the index to the data recording area, (d) is a diagram explaining the offset in the circumferential direction of the magnetic head, and FIG. 3 is the mechanism of the magnetic disk device. FIG. 4 is a perspective view explaining the outline of the off-track, FIG.
Figures illustrating the relationship between the inclination of the rotation axis of the magnetic disk medium and the off-track of the magnetic head, in which (a) is a side view of the magnetic disk medium, magnetic head, and positioning mechanism, and (b) and (c) are views of each magnetic head. FIG. 6 is a diagram illustrating off-track due to eccentricity of the magnetic disk medium. FIG. 7 is a diagram illustrating a method for measuring the whirling off-track amount using an analog method. , (a) is the signal pattern of the measurement track, (b) is the output voltage waveform of the magnetic head when there is no off-track, (c) is the output voltage waveform of the magnetic head when there is off-track, and (d) is the output voltage waveform of the magnetic head when there is off-track. (c) is a diagram illustrating the off-track amount converted from the difference in output voltage; FIG. 8 is a perspective view illustrating vertical offset and horizontal offset; FIG. In the figure, 1 is a magnetic disk medium, 2 is a spindle,
3 is a motor, 4 is a magnetic head, 5 is a drive arm, 6 is a positioning mechanism, 7 is a normal track, 7a is a track,
7b is a measurement track, 8 is a track when off-track occurs, 9 is a rotation axis, 10 is a vertical offset, 11 is a horizontal offset, 12 is a data recording area, 13 is an index signal, 14 is a read clock signal, 14a
15 indicates a servo pulse signal, 15 indicates a magnetic disk device, 16 indicates a test device, 17 indicates an SMD interface, and 18 indicates a synchronization byte.

Claims (1)

[Claims] 1. In a magnetic disk device, an index signal 13 that is output by the magnetic disk device at the index and a synchronization signal when reading data is output with an index that is the physical origin of a track as a reference position. The reference data is recorded on the measurement track of the magnetic disk medium using the read clock signal 14, and the data recording area (12) is read from the index signal (13).
The number of read clock signals (14) (n1) until
After counting and applying a predetermined environmental stress to the magnetic disk device, the data recording area (
12), the number of read clock signals (14) (
n2), and calculates the difference (n2) between the counts of the read clock signal (14).
1-n2), the circumferential length of the measurement track (L_0), and the total number of read clocks per track rotation (n_0), it is determined that the magnetic head is offset in the circumferential direction due to the environmental stress. 1. A method for measuring an amount of offset in a circumferential direction in a magnetic disk device, the method comprising: determining the amount of offset in a circumferential direction in a magnetic disk device. 2. In the measuring method according to claim 1, the servo pulse signal (14a) obtained from the servo track for controlling the positioning mechanism of the magnetic head is used in place of the read clock signal (14). A method for measuring the amount of offset in the circumferential direction in a magnetic disk device.