Patent ID: 12198735

DETAILED DESCRIPTION

In general, according to one embodiment, a magnetic disk device includes a magnetic head including a write element for data writing with respect to a rotatable magnetic disk and a plurality of read elements for data read from the disk, the magnetic head freely movable in a radial direction of the magnetic disk; and a controller configured to control rotation and movement of the magnetic disk. The controller includes a first control section configured to write a first reference pattern, which is a reference for a predetermined process with respect to the magnetic disk, to the magnetic disk by the write element while moving the magnetic head in the radial direction of the magnetic disk at a regulated speed; a second control section configured to move the magnetic head in the radial direction of the magnetic disk at the regulated speed in order to track the first reference pattern written by the first control section with each of the read elements; a detection section configured to detect a shift between a locus of the magnetic head moved by the second control section and the first reference pattern written by the first control section based on read signals of each of the read elements; a correction section configured to correct the regulated speed in a direction by which the shift detected by the detection section is canceled, and a third control section configured to write a second reference pattern which is a reference for the predetermined process to the magnetic disk by the write element while moving the magnetic head in a radial direction of the magnetic disk at the regulated speed corrected by the correction section where a predetermined gap is maintained between the first reference pattern and the second reference pattern.

Embodiments will be described hereinafter with reference to the accompanying drawings. Common structures through embodiments will be referred to by the same reference numbers, and explanation considered redundant will be omitted. In addition, each figure is a schematic diagram for better understanding to the embodiments, and the widths, thicknesses, shapes, etc., may differ from the actual devices, and may be arbitrarily changed based on the following description and a publically-known techniques.

(1) First Embodiment

A magnetic disk device of a first embodiment is illustrated inFIG.1.

A disk shaped magnetic disk1has a center part attached to a rotation shaft of a spindle motor (SPM)2, and rotates in the direction of an arrow in the figure in response to the motion of the spindle motor (SPM)2. In the proximity of the magnetic disk1, an arm-like actuator3is disposed.

The actuator3has a base end portion which is rotatably supported at a position apart from the magnetic disk1, and a tip end portion extending to the proximity of the center portion of the magnetic disk1. A voice coil motor (VCM)4is disposed at a position corresponding to the base end portion of the actuator3, and powered by the voice coil motor4, the tip end portion of the actuator3moves in a radial direction between the inner periphery and the outer periphery of the magnetic disk1.

A magnetic head10corresponding to a two-dimensional magnetic recording (TDMR) is disposed on the tip end portion of the actuator3. The magnetic head10includes a write element11configured to write magnetic data to the magnetic disk1and two read elements12aand12bconfigured to read magnetic data from the magnetic disk1, and moves (seeks) in the radial direction of the magnetic disk1in accordance to the movement of the actuator3.

The read element (first read element)12aand the read element (second read element)12bare arranged to be aligned along the rotational movement direction of the actuator3(radial direction of magnetic disk1). A gap between the read elements12aand12bin the rotational movement direction of the actuator3(radial direction of magnetic disk1) is less than each width of spiral patterns D1to D2to be written by the write element11, which will be described in the latter section. Thus, both the read elements12aand12bcan be opposed to one spiral pattern.

To a controller20which is a central controller of the magnetic disk device, a motor driver21configured to drive the spindle motor2, motor driver22configured to drive the voice coil motor4, signal processor circuit23configured to convert write data supplied from the controller20to the magnetic disk1into analog signals and to amplify the analog signals to the write element11, signal processor circuit24configured to amplify each read signal from the read elements12aand12b, to convert the read signals into digital signals, and to supply the digital signals to the controller20, and a movement speed table30configured to determine a movement speed (seeking speed) of the magnetic head10are connected.

The movement speed table30stores, as inFIG.2, regulation speeds of the magnetic head10in the radial direction of the magnetic disk1, used in order to regulate the movement speed of the magnetic head10corresponding to movement positions (seeking positions) thereof. The regulation speed is accelerated from zero to a certain value which is maintained for a while, and then is decreased to zero when the magnetic head10moves from the innermost periphery to the outermost periphery (forward movement) to and moves from the outermost periphery to the innermost periphery (return movement).

The controller20includes, as a main function to control the rotation of the magnetic disk1and the movement of the magnetic head10, which is related to reference pattern writing to the magnetic disk1, a first control section20a, second control section20b, detection section20c, correction section20d, third control section20e, and fourth control section20f.

The first control section20amoves (seeks), while the magnetic disk1is being rotated at a predetermined certain speed, the magnetic head10in the radial direction of the magnetic disk1from its innermost periphery to its outermost periphery at a regulation speed corresponding to regulation speed data in the movement speed table30, and writes a curved first reference pattern, which is a reference for a predetermined process with respect to the magnetic disk1, to the magnetic disk1by the write element11.

The predetermined process is, for example, a process of writing a servo pattern used for detection of a relative position between each data recording track formed concentrically on the magnetic disk1to the magnetic disk1, that is, a servo pattern writing process.

The control section20bcaptures a starting end of the first reference pattern written by the first control section20aby read signals of the read elements12aand12b, and in order to track the captured first reference pattern by the read elements12aand12b, moves (seeks) the magnetic head10from the innermost periphery to the outermost periphery of the magnetic disk1at the regulation speed which is the same as the first control section20awhile the magnetic disk1is being rotated at the certain speed.

The detection section20cdetects (learns) a shift between the locus of the magnetic head10moved by the second control section20bfor tracking the first reference pattern and the first reference pattern written by the first control section20a(shift includes shifting direction and shifting amount) by comparing the read signals of the read elements12aand12bwhich are decoded at the same timing.

The shifting direction is a sequential indication of shifts of the first reference pattern with respect to the locus of the movement of the magnetic head10when the written first reference pattern and the locus of the movement (seeking) of the magnetic head10do not match, where the shifts are as to which of the inner and outer peripheries in the radial direction of the magnetic head10the written first reference pattern is shifted for the whole area of the locus of the movement of the magnetic head10. For example, if the written first reference pattern is shifted more to the inner periphery in the radial direction of the magnetic head10than is the locus of the movement of the magnetic head10, the shifting direction is the inner periphery. If the written first reference pattern is shifted more to the outer periphery in the radial direction of the magnetic head10than is the locus of the movement of the magnetic head10, the shifting direction is the outer periphery.

The shifting amount is a sequential indication of gaps between the written first reference pattern and the locus of the movement of the magnetic head10in the radial direction of the magnetic disk1when the written first reference pattern and the locus of the magnetic head10do not match for the whole area of the locus of the movement of the magnetic head10.

The correction section20dcorrects (updates) the regulation speed in the direction where the shifts (shifting amount) detected by the detection section20cis canceled, and stores corrected regulation speed data corresponding to the corrected regulation speed in the movement speed table30.

The third control section20emoves, while the magnetic head1is being rotated at the certain speed, the head10in the radial direction of the magnetic disk1from its innermost periphery to its outermost periphery at the regulation speed corrected by the correction section20d(regulation speed corresponding to corrected regulation speed data), and writes a curved second reference pattern which is a reference for the predetermined process to the magnetic disk1by the write element11while a predetermined gap is maintained between the first and second reference patterns.

The fourth control section20frepeats the control of the first control section20a, control of the second control section20b, detection of the detection section20c, correction of the correction section20d, and control of the third control section20ein order to curved first to Nth reference patterns which are references for the predetermined process to the magnetic disk1while predetermined gaps are maintained between the first to Nth reference patterns.

Now, the control executed by the controller20will be explained with reference to a flowchart ofFIG.3.

The controller20sets pattern number data K to 1 as an initial process in the writing of each reference pattern with respect to the magnetic disk1(S1). Then, as inFIG.4, the controller20moves the magnetic head10in the radial direction of the magnetic disk1form the innermost periphery to the outermost periphery at a regulation speed corresponding to the regulation speed data in the movement speed table30while the magnetic disk1is being rotated at a certain speed, and writes a first reference pattern which is based on the pattern number data K (=1), that is, spiral pattern D1to the magnetic disk1by the write element11(S2).

The spiral pattern D1is a magnetic pattern strength of magnetization of which is changed along the writing direction at certain intervals, and is written in a curved shape in accordance with the rotation of the magnetic disk1and the movement of the magnetic head10on the magnetic disk1. InFIG.4, the spiral pattern D1is shown as having a short entire length; however, the spiral pattern D1may have a long entire length which repeatedly rounds in the circumferential direction of the magnetic disk1in a spiral shape from the inner periphery to the outer periphery of the magnetic disk1.

Then, the controller20determines whether or not the pattern number data K is below N (S3). The pattern number data K (=1) is currently below N (YES in S3), the controller20captures an inner peripheral starting end of the written spiral pattern D1by read signals of the read elements12aand12b, and in order to track the captured spiral pattern D1from its starting end to its finishing end by the read elements12aand12b, moves the magnetic head10in the radial direction of the magnetic disk1from the innermost periphery to the outermost periphery at the same regulation speed as in the writing time of the spiral pattern D1while the magnetic disk1is being rotated at the same certain speed as in the writing time of the spiral pattern D1(S4).

The width of the spiral pattern D1in a direction orthogonal to the writing direction thereof is greater than a gap between the read elements12aand12b. Changes in the corresponding positions between the spiral pattern D1and the read elements12aand12b, and voltage waveforms of output signals R1and R2of the read elements12aand12bcorresponding to the corresponding positions are illustrated inFIG.6.

When an opposing area of the read element12awith respect to the spiral pattern D1becomes greater, a voltage amplitude of the output signal R1of the read element12abecomes greater. Even if the spiral pattern D1and the read element12aare not opposed to each other, when the spiral pattern D1and the read element12aare closer, the voltage amplitude of the output signal R1of the read element12abecomes greater. When an opposing area of the read element12bwith respect to the spiral pattern D1becomes greater, a voltage amplitude of the output signal of the read element12bbecomes greater. Even if the spiral pattern D1and the read element12bare not opposed to each other, when the spiral pattern D1and the read element12bare closer, the voltage amplitude of the output signal R2of the read element12bbecomes greater.

Specifically, at a corresponding position P1where the read elements12aand12bare shifted from the spiral pattern D1toward the right area in the figure, a voltage amplitude of the output signal R1of the read element12acloser to the spiral pattern D1is slightly detected, and a voltage amplitude of the output signal R2of the read element12bbecomes zero. At corresponding positions P2and P3where only the read element12ais opposed to the spiral pattern D1, the voltage amplitude of the output signal R1of the read element12abecomes great, and the voltage amplitude of the output signal R2of the read element12bbecomes small.

At a corresponding position P4where the read elements12aand12bare both opposed to the spiral pattern D1with equal areas, the voltage amplitudes of the output signals R1and R2of the read elements12aand12bgrow approximately the same. At corresponding positions P5and P6where only the read element12bis opposed to the spiral pattern D1, the voltage amplitude of the output signal R2of the read element12bbecomes great, and the voltage amplitude of the output signal R1of the read element12abecomes small. At a corresponding position P7where the read elements12aand12bare shifted from the spiral pattern D1toward the left area in the figure, the voltage amplitude of the output signal R2of the read element12bcloser to the spiral pattern D1is slightly detected, and the voltage amplitude of the output signal R1of the read element12abecomes zero.

The controller20detects a shift between the locus of the magnetic head10moved for tracking the spiral pattern D1and the spiral pattern D1actually written (shift includes shifting direction and shifting amount) by comparing the read signals of the read elements12aand12b, for the entirety of the locus of the movement of the magnetic head10(S5).

The locus of the magnetic head10moved for tracking the spiral pattern D1corresponds to a target writing position of the spiral pattern D1determined based on the regulation speed (initial value).FIG.7indicates an example where a shift occurs between the target writing position of the spiral pattern D1and an actual writing position thereof because of various external forces inside the magnetic disk device.

InFIG.7, a dotted line indicates a target writing position of the spiral pattern D1(locus of magnetic head10) and a solid line indicates an actual writing position of the spiral pattern D1. In this example, the actual writing position of the spiral pattern D1is shifted to be gradually curving to the inner periphery of the radial direction of the magnetic disk1with respect to the target writing position of the spiral pattern D1. A gap between the actual writing position of the spiral pattern D1and the target writing position of the spiral pattern D1in the radial direction of the magnetic disk1is the aforementioned shifting amount. In this case, the shifting amount becomes gradually increase and gradually decrease according to the curving.

If the above detected shifting amount exceeds a threshold value (NO in S6), the controller20determines that the locus of the magnetic head10moved for tracking the spiral pattern D1is not proper, and repeats the processes of S4and S5.

If the above detected shifting amount is within the threshold value (YES in S6), the controller20determines that the movement of the magnetic head10is proper, and corrects the regulation speed in a direction where the detected shifting amount is canceled, and stores corrected regulation speed data corresponding to the corrected regulation speed in the movement speed table30(S7). The corrected regulation speed data stored here is indicated in a dotted line inFIG.2.

Then, the controller20adds 1 to the pattern number data K (=1) (K←K+1), and determines whether or not the pattern number data K (=2) is equal to or greater than N (S9). At that time, the pattern number data K is 2 which is below N (NO in S9), and thus, the controller20returns to aforementioned S2, and moves the magnetic head10in the radial direction of the magnetic disk1from the innermost periphery to the innermost periphery at a corrected regulation speed corresponding to the corrected regulation speed data in the movement speed table30while the magnetic disk1is being rotated at the same certain speed as in the writing of the spiral pattern D1, and writes a second reference pattern which is a second pattern based on the pattern number data K (=2), that is, spiral pattern D2to the magnetic disk1by the write element11while a certain gap is maintained between the spiral patterns D1and D2(S2).

The spiral pattern D2is, as with the spiral pattern D1, a magnetic pattern strength of magnetization of which is changed along the writing direction at certain intervals, and is written in a curved shape in accordance with the rotation of the magnetic disk1and the movement of the magnetic head10.

In the example ofFIG.7, a locus (dotted line) of the target writing position of the spiral pattern D2corresponding to the corrected regulation speed, and an actual position (solid line) of the spiral pattern D2actually written based on the corrected regulation speed are similar to the locus (dotted line) of the spiral pattern D1written under the influence of various external forces in the magnetic disk device. Thus, the spiral pattern D2does not cross the adjacent spiral pattern D1, and is written while a certain gap is constantly maintained therebetween. The shifting amount in that case, that is, a gap between the actual writing position of the spiral pattern D2and the target writing position of the spiral pattern D2is small.

Then, the controller20determines whether or not the pattern number data K is below N (S3). At that time, the pattern number data K is 2 which is below N (YES in S3), and thus, the controller20captures an inner peripheral starting end of the written spiral pattern D2by the read signals of the read elements12aand12b, and in order to track the captured spiral pattern D2from its starting end to its finishing end by the read elements12aand12b, moves the magnetic head10in the radial direction of the magnetic disk1from the innermost periphery to the outermost periphery at the same corrected regulation speed as with the writing time of the spiral pattern D2while the magnetic disk1is being rotated at the same certain speed as in the writing time of the spiral pattern D2(S4).

Then, the controller20detects a shift between the locus of the magnetic head10moved for tracking the spiral pattern D2and the actually written spiral pattern D2(shift includes shifting direction and shifting amount) by comparison between voltage amplitudes of read signals of the read elements12aand12b(S5).

If the shifting amount between the locus of the magnetic head10moved for tracking the spiral pattern D2and the actually written spiral pattern D2is equal to or less than a threshold value (YES in S6), the controller20determines that the movement of the magnetic head10is proper, and again corrects the corrected regulation speed in a direction where the detected shifting amount is canceled, and updates and stores corrected regulation speed data corresponding to the again-corrected regulation speed in the movement speed table30(S7).

Then, the controller20adds 1 to the pattern number data K (=2) (K←K+1), and determines whether or not the pattern number data K (=2) is equal to or greater than N (S9). At that time, the pattern number data K is 3 which is below N (NO in S9), and thus, the controller20returns to aforementioned S2, and moves the magnetic head10in the radial direction of the magnetic disk1from the innermost periphery to the innermost periphery at a corrected regulation speed corresponding to the updated corrected regulation speed data in the movement speed table30while the magnetic disk1is being rotated at the same certain speed as in the writing of the spiral pattern D2, and writes a third reference pattern which is a third pattern based on the pattern number data K (=3), that is, spiral pattern D3to the magnetic disk1by the write element11while a certain gap is maintained between the spiral patterns D2and D3(S2).

The spiral pattern D3is, as with the spiral patterns D1and D2, a magnetic pattern strength of magnetization of which is changed along the writing direction at certain intervals, and is written in a curved shape in accordance with the rotation of the magnetic disk1and the movement of the magnetic head10.

In the example ofFIG.7, a locus (dotted line) of the target writing position of the spiral pattern D3corresponding to the corrected regulation speed, and an actual position (solid line) of the spiral pattern D3actually written based on the corrected regulation speed are similar to the locus (dotted line) of the spiral pattern D2written under the influence of various external forces in the magnetic disk device. Thus, the spiral pattern D3does not cross the adjacent spiral pattern D2, and is written while a certain gap is constantly maintained therebetween. The shifting amount in that case, that is, a gap between the actual writing position of the spiral pattern D3and the target writing position of the spiral pattern D3is small.

Then, the controller20determines whether or not the pattern number data K is below N (S3). At that time, the pattern number data K is 3 which is below N (YES in S3), and thus, the controller20captures an inner peripheral starting end of the written spiral pattern D3by the read signals of the read elements12aand12b, and in order to track the captured spiral pattern D3from its starting end to its finishing end by the read elements12aand12b, moves the magnetic head10in the radial direction of the magnetic disk1from the innermost periphery to the outermost periphery at the same corrected regulation speed as with the writing time of the spiral pattern D3while the magnetic disk1is being rotated at the same certain speed as in the writing time of the spiral pattern D3(S4).

Then, the controller20detects a shift between the locus of the magnetic head10moved for tracking the spiral pattern D3and the actually written spiral pattern D3(shift includes shifting direction and shifting amount) by comparison between the read signals (voltage amplitudes) of the read elements12aand12b(S5).

If the shifting amount between the locus of the magnetic head10moved for tracking the spiral pattern D3and the actually written spiral pattern D3is equal to or less than a threshold value (YES in S6), the controller20determines that the movement of the magnetic head10is proper, and again corrects the corrected regulation speed in a direction where the detected shifting amount is canceled, and updates and stores corrected regulation speed data corresponding to the again-corrected regulation speed in the movement speed table30(S7).

The controller20repeats the processes of aforementioned S1to S9, and thus, sequentially detects (learns) shifts of writing positions of first to N−1th spiral patterns D1to Dn−1, sequentially corrects (updates) regulation speeds in a direction where each shift is canceled, and at the same time, sequentially writes spiral patterns D2to Dn based on each of the corrected regulation speeds. Thus, first to Nth spiral patterns D1to Dn can be written in the magnetic disk1at proper intervals without crossing each other. Since the spiral patterns D1to Dn do not cross each other, the servo pattern writing process can be properly executed thereafter.

A corresponding relationship of writing positions of spiral patterns in a conventional case is indicated inFIG.9as a reference. Since regulation speed data is fixed, gaps between written spiral patterns are unstable. In a worst case, multiple spiral patterns may possibly cross each other. In such a case, the servo pattern writing process cannot be executed. The present embodiment can resolve such a problematic case.

(2) Second Embodiment

Throughout the first control section20a, second control section20b, detection section20c, correction section20d, third control section20e, fourth control section20fof the controller20, only the fourth control section20fis different from the aforementioned first embodiment.

The fourth control section20fexecutes the control of the first control section20a, control of the second control section20b, detection of the detection section20c, and correction of the correction section20d, and then, repeats the control of the third control section20e, and thereby, writes curved first to Nth reference patterns which are references for the servo pattern writing process to the magnetic disk1while certain gaps are maintained therebetween.

The controls executed by the controller20include, as in the flowchart ofFIG.10, S3aand S4ainstead of S3and S4of the first embodiment.

That is, the controller20determines whether or not the pattern number data K is one after writing a first spiral pattern D1based on the pattern number data K (=1) (S3a). If the pattern number data K is one (YES in S3a), in order to track the spiral pattern D1from its starting end to its finishing end by the read elements12aand12b, the controller20moves the magnetic head10in the radial direction of the magnetic disk1from the innermost periphery to the outermost periphery at the same corrected regulation speed as in the writing time of the spiral pattern D2while the magnetic disk1is being rotated at the same certain speed as in the writing time of the spiral pattern D2(S4a). If the pattern number data K is more than one (NO in S3a), the controller20goes to S8to add 1 to the pattern number data K (K←K+1), and if the pattern number data K is below N (NO in S9), repeats the processes from aforementioned S2.

Other processes are the same as in the first embodiment.

That is, the controller20detects (learns) a shift of writing positions of the first spiral pattern D1, corrects (updates) the regulation speed in a direction where the shift is canceled, and writes second to Nth spiral patterns D2to Dn based on the corrected regulation speed. Thus, first to Nth spiral patterns D1to Dn can be written in the magnetic disk1at proper intervals without crossing each other. Since the spiral patterns D1to Dn do not cross each other, the servo pattern writing process can be properly executed thereafter.

(3) Variation

In each of the aforementioned embodiments, in the detection of shifts of writing positions of spiral patterns, statistical average values of detection results and weighted average values may be calculated, and based on such calculation results, regulation speeds may be corrected.

In each of the aforementioned embodiments, in the reading of regulation speed data and corrected regulation speed data in the movement speed table30, the data read may be passed through a noise filter or the like for the use such that values of the data read are used as smooth values.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.