JP2885173B2 - Servo track writer and servo track writing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo track writer and a method for writing a servo track, and more particularly to a servo track writer and a servo track writer for correcting the position of a servo track write head with respect to fluctuations in the center of rotation of a magnetic disk. Regarding the writing method.

[0002]

2. Description of the Related Art A conventional servo track writer is disclosed in, for example, Japanese Patent Application Laid-Open No. 64-48276.
It is used for writing servo tracks at equal intervals in a magnetic disk drive.

FIGS. 4 and 5 are a front view and a block diagram of a circuit portion of a conventional servo track writer, respectively. On the base plate 53, a magnetic disk device 54 on which servo tracks are written is accurately set. The spindle motor 55 of the magnetic disk device 54 can rotate the magnetic disk plate 57 via the spindle 56. The reference head 59 is a magnetic disk drive 5
The reference servo track is written to the servo disk 58 of No. 4 and the servo signal is read from the written reference servo track. The servo head 60 writes a servo track on the servo disk 58. The positioner 61 can position the servo head 60 at a required position on the servo disk 58. Further, the laser length measuring device 62 can accurately measure the moving distance of the positioner 61 by the laser reflecting mirror 62a attached to the positioner 61. Thus, the servo head 60 can be accurately positioned at a predetermined position on the servo disk 58.

Next, a write operation will be described mainly with reference to FIG. The logic control circuit 73 is a circuit which is programmed to control the operation of each circuit and execute the writing of the servo drag. First, a servo pattern of the reference servo track is instructed to the servo pattern generation unit 65 under the control of the logic control circuit 73 to write the reference servo track before writing the servo track. Servo pattern signal 7 output by servo pattern generator 65
4 is written by the reference head 59 through the write / read circuit 64. At this time, two servo tracks such as the servo tracks 84a and 84b shown in FIG. 6 are written as the servo tracks to be written. The vertical lines in FIG. 6 indicate boundaries of magnetization reversal. This servo pattern is called a modified dipulse.

FIGS. 7 (a), 7 (b) and 7 (c) show the case where the heads are located at positions a, b and c shown in FIG. 6 in the track width direction. This represents one unit of the servo signal to be read. In general, the position error signal is a pair of servo signals read in this way, and is a signal proportional to the amplitude difference between the position pulses having different phases from each other, that is, the position pulses 85 and 86 in FIG. When the writing is completed, the reference head 59 is positioned almost at the center of the two reference servo tracks just written and operates as a read head. The positioning of the reference head is performed by driving the reference head positioner 63 by the reference head positioning unit 77.

The signal read by the reference head 59 is amplified by a write / read circuit 64 and is amplified by a servo signal 75.
Is input to the demodulation circuit 66. The demodulation circuit 66 demodulates the input servo signal into a reference position error signal 76.
The reference position error signal 76 is converted by the A / D converter 67 into a digital quantity. This is because it is convenient to handle in a logic circuit. The reference position error signal 79 converted into a digital quantity is input to the averaging circuit 68. In this circuit, of the reference position error signal 76 for each rotation angle of the magnetic disk 58, only a signal component synchronized with the rotation of the magnetic disk 58 is extracted. No matter how many rotations are made, the reference position error signal is input and averaged.

The reference position error signal 80 averaged over the entire rotation angle of the magnetic disk 58 is stored in the logic control circuit 73. This completes the pre-processing of the servo track writing operation.

It is to be noted that the change in the position of the magnetic disk 58 which causes the component of the reference position error signal 76 to be synchronized with the rotation of the magnetic disk 58 may be caused by a spindle manufacturing error. The position fluctuation of the magnetic disk 58 includes a component that is not synchronized with the rotation due to thermal expansion of each part of the servo track writer or an external vibration, in addition to a component synchronized with the rotation.

In the servo track writing operation, first, the logic control circuit 73 instructs the servo pattern generation section 71 of a servo pattern to be written as a servo track. The servo pattern generated by the servo pattern generator 71 is written by the servo head 60 through the writing circuit 70. The positioning of the servo head 60 to the writing position is performed by driving the positioner 61 by the positioning unit 72.

Now, consider writing a certain servo track. At the same time as the writing of the servo track is started, the reference servo track is read by the reference head 59, a position error signal is generated from the amplitude of the read signal, and this is converted into a digital quantity by an A / D converter. The difference between the converted position error signal and the previously stored averaged position error signal is calculated. This difference is a component of the fluctuation of the rotation of the magnetic disk plate at the point where the servo track is about to be written, which is asynchronous to the rotation.

The logic control circuit 73 controls the positioning section 72 so as to correct this difference, and corrects the write position of the servo head 60.

The servo track written in this way undergoes fluctuation due to rotational vibration as shown by a servo track 81 in FIG.
All the servo tracks are subjected to the same fluctuation, and the uniformity of the servo track interval is improved.

[0013]

The above-mentioned conventional servo track writer measures the radial displacement of the magnetic disk based on the read signal of the reference head and writes the servo signal so as to correct the displacement. Writing is performed while moving the head to improve the uniformity of the servo track interval. However, because the amplitude of the read signal is used as a method of measuring the amount of misalignment,
The amplitude of the read signal fluctuates irrespective of the displacement of the disk due to non-uniformity of the magnetic susceptibility of the magnetic surface of the disk, fluctuation of the flying height of the reference head, fluctuation of the write current, noise of the read signal, and the like. For this reason, even if the servo signal writing head is moved so as to correct the measured positional shift amount, the servo signal writing head does not come to a correct position, and the track interval is hardly uniform.

[0014]

According to the present invention, there is provided a servo track writer comprising: a servo head for writing a servo signal on a rotating magnetic disk; and a servo head which is symmetrically disposed with respect to the center of the magnetic disk. A main reference head and a sub reference head for reading reference signals written at a constant pitch on a concentric circle, and the servo head is orthogonal to a straight line passing through the center of the magnetic disk and connecting the main reference head and the sub reference head. And a main pulsing unit that outputs a main pulse signal corresponding to the reading of the reference signal of the main reference head, and a reading unit that reads the reference signal of the sub reference head. A sub-pulsing section for outputting a sub-pulse signal; and a time difference calculating section for calculating a time difference between the main pulse signal and the sub-pulse signal. And an averaging unit that outputs an average time difference consisting of an average of the time differences in a plurality of rotations of the magnetic disk obtained for each rotation angle around the center of the magnetic disk. At each point in time, the time difference output section is asynchronous with the rotation of the moving amount of the magnetic disk obtained from the difference between the time difference obtained by the time difference output section and the value of the previously stored average time difference at the rotation angle of the magnetic disk at that time. A control unit that corrects the position corresponding to the track where the servo signal is to be written only by the component and positions the servo head in the positioning unit, so that the servo head is equidistant from the center of the magnetic disk with the main reference head and the sub reference head. And the servo head writes a reference signal on the magnetic disk by the servo head. It can be made to be alternately inverted.

According to the servo track writer writing method of the present invention, a reference signal is written on a magnetic disk at a constant pitch on a concentric circle, and a main reference head and a sub-reference head arranged symmetrically with respect to the center of the magnetic disk. The magnetic disk obtained by reading the reference signal, obtaining a time difference between a reading time of the reference signal by the sub-reference head and a reading time of the reference signal by the main reference head, for each rotation angle around the center of the magnetic disk Storing in advance an average time difference consisting of the average of the time differences in a plurality of rotations, and moving the servo head in a direction perpendicular to a straight line connecting the main reference head and the sub reference head through the center of the magnetic disk. And a servo signal is written on the magnetic disk by the servo head. The time difference between the time difference at each point in time when the servo signal is being written to the magnetic disk by the servo head and the difference between the previously stored average time difference and the value of the rotation angle of the magnetic disk at the time point. It is characterized in that the position corresponding to the track on which the servo signal is written is corrected only for the component asynchronous to the rotation of the moving amount of the magnetic disk.

[0016]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of a circuit section of a servo track writer according to an embodiment of the present invention.

The servo track writer shown in FIG. 1 comprises a servo head 1 for writing a servo signal and a reference signal (reference numeral 20 in FIG. 2) to a magnetic disk, a write circuit 4 for applying a write current to the servo head 1, and a servo signal. A servo pattern generation unit 8 for generating a reference signal; a positioning unit 7 for positioning the servo head 1; a main reference head 2 and a sub-reference head 3 for reproducing a reference signal; A reading unit 6 for amplifying the output of the sub-reference head 3; a pulsating unit 9 for pulsing the signal of the reading unit 5; a pulsing unit 10 for pulsing the signal of the reading unit 6; A time difference detecting section 11 for outputting a time difference 16 between the pulse outputs of the section 9 and the pulsing section 10, and a time difference 16 for each rotation angle of the magnetic disk.
Is averaged over a plurality of rotations of the magnetic disk and outputs an average time difference 17, and a logical control circuit 13 programmed to control the operation of each circuit and execute servo writing.

FIG. 2 shows the positional relationship between the magnetic disk and the heads 1, 2, and 3. The main reference head 2 and the sub reference head 3 are arranged at positions symmetrical with respect to the rotation center 25 of the magnetic disk 19. The servo head 1 moves on a straight line orthogonal to the straight line connecting the main reference head 2 and the sub reference head 3 with the rotation center 25.

The mechanism of the servo track writer shown in FIG. 1 is substantially the same as that shown in FIG. 4 except for the main reference head 2 and the sub reference head 3. That is, the magnetic disk 19 mounted on the magnetic disk device mounted on the base plate
Is incorporated. The servo head 1 is accurately positioned by the laser length measuring device and the positioner. However, the reference head 59 shown in FIG.
The main reference head 2 and the sub reference head 3 are provided symmetrically with respect to the rotation center of the magnetic disk 19 on a line orthogonal to the moving direction of the magnetic disk 19. Main reference head 2 and sub reference head 3
No positioner for moving the magnetic disk in the radial direction of the magnetic disk 19 is required.

Next, the operation of the embodiment constructed as described above will be described. First, the logical control circuit 13 issues a command to the head positioning unit 7 to move the servo head 1 to the same radial position as the main reference head 2 and the sub reference head 3. In response to a command from the logic control circuit 13, the servo pattern generator 8 outputs a reference signal having a constant frequency. The reference signal passes through the write circuit 4 and is written on the magnetic disk 19. Reference numeral 20 in FIG. 2 is a written reference signal. The straight line in the radial direction of the reference signal 20 indicates the boundary of the reversal of the magnetization, and is arranged at a constant pitch on the circumference. When the writing is completed, the main reference head 2 and the sub reference head 3 start reading the reference signal 20. The signal read by the main reference head 2 is input to the pulsing unit 9 through the reading unit 5. The signal read by the sub-reference head 3 is input to the pulsing unit 10 through the reading unit 6. Pulsing unit 9
The pulsing unit 10 pulsates the input signal and outputs a main pulse 14 and a sub-pulse 15 that are output when the main reference head 2 and the sub-reference head 3 read the boundary of the inversion of the magnetization of the reference signal 20.

FIG. 3 shows the relative relationship between the main pulse 14 and the sub-pulse 15 when the magnetic disk 19 is rotating clockwise.
Shown in Note that FIG. 3 shows that the center of rotation of the magnetic disk 19 when the reference signal 20 is written by the servo head 1 is fixed at the center of the main reference head 2 and the sub reference head 3 without swinging. . When the position of the magnetic disk 19 does not fluctuate even when the reference signal 20 is read and the rotation center 25 of the magnetic disk 19 does not move and is located at the center between the main reference head 2 and the sub reference head 3, FIG. As shown in (1), the timings of the main pulse 14 and the sub-pulse 15 coincide. When the position of the magnetic disk 19 fluctuates and the rotation center 25 moves to the left in FIG. 2 from the center of the main reference head 2 and the sub reference head 3, as shown in FIG. It comes out before 15. Conversely, when the rotation center 25 moves to the right in FIG. 2 from the center of the main reference head 2 and the sub reference head 3, the main pulse 14 is delayed from the sub pulse 15 as shown in FIG. become. The time difference between the main pulse 14 and the sub-pulse 15 is proportional to the amount of movement of the rotation center 25. Thus, the amount of movement of the rotation center 2 of the magnetic disk 19, that is, the amount of movement in the lateral direction can be detected from the time difference between the main pulse 14 and the sub-pulse 15.

The time difference detector 11 outputs a signal indicating a time difference 16 between the main pulse 14 and the sub-pulse 15. The averaging unit 12 rotates the magnetic disk 19 a plurality of times, and outputs an average time difference 17 obtained by averaging the time difference 16 for each rotation angle around the center of the magnetic disk 19. The rotation angle of the magnetic disk 19 can be obtained by counting the pulses of the reference signal 20. The average time difference 17 is an amount representing a rotation synchronous component of a lateral movement amount of the magnetic disk 19 for each rotation angle (accurately, an amount proportional to the rotation synchronization component). The average time difference 17 over the entire circumference of the magnetic disk 19 is stored in the logic control circuit 13.

This means that the pre-processing of the servo track writing operation has been completed.

In the servo track writing operation, first, the logic control circuit 13 instructs the servo pattern generation unit 8 on a servo pattern to be written as a servo track. The servo pattern generated by the servo pattern generator 8 is written by the servo head 1 through the writing circuit 4. The positioning of the servo head 1 at the writing position is performed by the positioning unit 7.

Now, consider writing a servo track on a certain track of the magnetic disk 19. At the same time as the writing of the servo track is started, the reference signal 20 is read by the main reference head 2 and the quasi-reference head 3, and the time difference 16 is generated by the time difference detection unit 11. At this time, the difference between the average time difference 17 stored in the logic control circuit 13 for the rotation angle of the magnetic disk 19 and the time difference 16 output from the time difference detection unit 11 is calculated. The movement amount obtained from this difference in a proportional relationship is a component of the movement amount of the magnetic disk 19 at the point where the servo track is about to be written, which is asynchronous with the rotation.

In order to correct this difference, that is, the position corresponding to the track on which the servo signal is written is set to the average time difference 17.
The logic control circuit 13 controls the positioning unit 7 so that the servo head 1 is located at a position corrected by the movement amount of the magnetic disk 19 obtained from the difference between the servo head 1 and the time difference 16, and corrects the write position of the servo head 1.

The servo track written in this way undergoes fluctuation due to rotational vibration synchronized with the rotation as shown in the servo track 81 in FIG. 8, so that the servo track deviates from the concentric circle 82, but the influence of the fluctuation asynchronous with the rotation is not affected. When servo tracks are written on multiple tracks to be removed, all servo tracks are subject to similar fluctuations at any rotation angle of the magnetic disk, making it possible to improve the uniformity of servo track intervals Further, the variation itself can be reduced.

The reference signal 20 from the servo head 1
Also, when writing, when the rotation center of the magnetic disk is deviated from the centers of the main reference head 2 and the sub reference head 3, the temporal relationship between the main pulse 14 and the sub pulse 15 is as shown in FIG. Even in such a case, even in such a case, the time difference detection unit 11 obtains the time difference 16 between the main pulse 14 and the sub-pulse 15, and the averaging unit 12 obtains the average time difference 17 of the average of the time differences 16. The value of the rotation angle of the magnetic disk 19 with the average time difference 17 and the time difference 1
By correcting the position of the servo head 1 by the amount of movement determined from the difference from 6, the uniformity of the servo track interval can be improved except for the influence of the non-periodic fluctuation on the rotation of the position of the magnetic disk 19.

In the present invention, the writing of the reference signal to the magnetic disk may be performed by the main reference head or the sub reference head instead of the servo head, or may be performed by providing a completely different magnetic head.

The reference signal is not limited to a signal in which the magnetization direction is alternately inverted at a constant pitch, and any signal can be used as long as it can identify a portion at a constant pitch.

[0032]

As described above, according to the present invention, the reference signal written on the magnetic disk is read out by the main reference head and the sub-reference head arranged symmetrically with respect to the center of the magnetic disk, and the reference signal read by these two heads is read. Of the magnetic disk based on this time difference, that is, the amount of movement is obtained.A component of the amount of movement that is inactive during the rotation of the magnetic disk is obtained. By correcting the position of the servo head according to the asynchronous component, there is an effect that the uniformity of the intervals between the servo tracks can be improved.

Since the amplitude of the read signal is not used unlike the conventional servo track writer, the magnetic susceptibility of the magnetic disk is not uniform, the flying height of the reference head fluctuates, the write current fluctuates, The movement of the magnetic disk in the radial direction can be detected without being affected by signal noise or the like.

[Brief description of the drawings]

FIG. 1 is a block diagram of a circuit section of a servo track writer according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a magnetic disk 19 and a servo head 1, a main reference head 2, and a sub reference head 3 in the servo track writer shown in FIG.

FIG. 3 is a diagram showing a relationship between a main pulse 14 and a non-pulse 15 in FIG. FIG. 4A is a diagram when the rotation center 25 of the magnetic disk 19 is located at the center of the main reference head 2 and the sub reference head 3. FIG. 3B is a diagram when the rotation center 25 of the magnetic disk 19 moves to the left in FIG. 2 from the centers of the main reference head 2 and the sub reference head 3. FIG. 3C is a diagram when the rotation center 25 of the magnetic disk 19 has moved to the right in FIG. 2 from the centers of the main reference head 2 and the sub reference head 3.

FIG. 4 is a front view of a mechanism of a conventional servo track writer.

5 is a block diagram of a circuit section of the servo track writer shown in FIG.

6 is a diagram showing servo tracks written on a magnetic disk 58 by a reference head 59 in FIG.

FIG. 7 is a waveform diagram showing a servo signal read from the servo track shown in FIG. 6 by a reference head 59; 7A is a waveform diagram when the reference head 59 is located at a position a shown in FIG. 7B is a waveform diagram when the reference head 59 is located at the position b shown in FIG. 7C is a waveform diagram when the reference head 59 is located at the position c shown in FIG.

8 is a diagram showing servo tracks written on a magnetic disk 58 by the servo head 60 shown in FIG.

[Explanation of symbols]

 Reference Signs List 1 servo head 2 main reference head 3 sub reference head 4 writing circuit 5 reading unit 6 reading unit 7 positioning unit 8 servo pattern generation unit 9 pulsing unit 10 pulsing unit 11 time difference detection unit 12 averaging unit 13 logic control circuit 14 main Pulse 15 Sub-pulse 16 Time difference 17 Average time difference 19 Magnetic disk 20 Reference signal 24 Servo signal 25 Center of rotation 53 Base plate 54 Magnetic disk device 55 Spindle motor 56 Spindle 57 Magnetic disk plate 58 Servo disk 59 Reference head 60 Servo head 61 Positioner 62 Laser measurement Long device 62a Laser reflecting mirror 63 Reference head positioner 64 Write / read circuit 65 Servo pattern generator 66 Demodulation circuit 67 A / D converter 68 Averaging circuit 70 Write circuit 71 Writer B pattern generation unit 72 Positioning unit 73 Logical control circuit 74 Servo pattern signal 75 Servo signal 76 Reference position error signal 77 Reference head positioning unit 79 Reference position error signal converted to digital quantity 80 Averaged reference position error signal 81 Servo track 82 ideal concentric track 83 base plate 84a servo track 84b servo track 85 position pulse 86 position pulse

Claims (4)

(57) [Claims] A servo head for writing a servo signal to a rotating magnetic disk; and a servo head arranged symmetrically with respect to the center of the magnetic disk and written at a constant pitch on a circumference of the magnetic disk concentric with the magnetic disk. A main reference head and a sub-reference head that read a reference signal, and a positioning unit that positions the servo head by moving the servo head through a center of the magnetic disk in a direction orthogonal to a straight line connecting the main reference head and the sub-reference head, A main pulsing unit that outputs a main pulse signal corresponding to reading of the reference signal of the main reference head, and a sub pulsing unit that outputs a sub pulse signal corresponding to reading of the reference signal of the sub reference head, A time difference output section for calculating a time difference between the main pulse signal and the sub-pulse signal, and a rotation angle around the center of the magnetic disk. An averaging unit that outputs an average time difference obtained by averaging the obtained time differences in a plurality of rotations of the magnetic disk; and a time difference obtained by the time difference output unit at each time during the writing of the servo signal by the servo head and pre-stored. The position corresponding to the track on which the servo signal is written by a component that is asynchronous to the rotation of the amount of movement of the magnetic disk determined from the difference between the average time difference and the value of the rotation angle of the magnetic disk at that time is corrected. And a control unit for positioning the servo head on the positioning unit. 2. The magnetic disk according to claim 1, wherein the servo head is positioned equidistant from the center of the magnetic disk with the main reference head and the sub reference head, and the servo head writes a reference signal on the magnetic disk. Servo track writer. 3. The servo track writer according to claim 1, wherein the description signal alternates the magnetization direction at a constant pitch. 4. A reference signal is written on a magnetic disk at a constant pitch on a concentric circle, and said reference signal is read by a main reference head and a sub-reference head arranged symmetrically with respect to the center of said magnetic disk. The time difference between the time when the sub-reference head reads the reference signal and the time when the reference signal is read by the head is determined, and the average of the time differences in a plurality of rotations of the magnetic disk determined for each rotation angle around the center of the magnetic disk Is stored in advance, and the servo head is positioned by moving the servo head through a center of the magnetic disk in a direction orthogonal to a straight line connecting the main reference head and the sub reference head. A servo signal is written on the magnetic disk, and the servo head writes the servo signal to the magnetic disk. A rotation amount of the magnetic disk determined from a difference between the time difference at each time point during the writing of the servo signal and the value of the previously stored average time difference at the rotation angle of the magnetic disk at the time point. A method for writing a servo track, wherein a position corresponding to a track to which a servo signal is written is corrected only for an asynchronous component.