JP2000090615A - Disc storage apparatus and method applied to the apparatus for measuring head flying height - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a function of particularly monitoring a change in flying height by measuring the flying height of a head independently of a normal data record reproduction operation after a drive is assembled. SOLUTION: The apparatus is an HDD using a disc 1 having a measurement area with projecting parts of different heights of six levels as well as a data area for recording data. A CPU 10 measures the flying height of a head 2 on the basis of a collision state of the head 2 sought to the measurement area with each projecting part at a time other than a normal data record reproduction operation, and monitors generation of an abnormal change in the flying height.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to, for example, a hard disk drive using a disk as a recording medium, and more particularly to a disk storage device for recording and reproducing data with a head floating on the disk.

[0002]

2. Description of the Related Art Conventionally, hard disk drives (H
2. Description of the Related Art In a disk storage device such as a DD), a method of executing a data recording operation or a reproducing operation (read / write operation) with a head floating above a disk is employed. The head has a structure in which a head element (separated into a read head and a write head, as will be described later) is mounted on a slider which is a main body. The flying height of the head means a physical distance between the slider and the disk surface. Hereinafter, the head means a slider unless otherwise specified.

In recent HDDs, as the recording density increases, a read / write head composed of an MR (GMR) element and a write head composed of an inductive head are separately provided on the same slider. Separate heads have become mainstream. With the use of such a high-performance head,
In order to promote higher recording densities, lower flying heights have been achieved to further reduce the flying height of the head. For low levitation,
In order to prevent the occurrence of a head crash in which the head collides with the surface of the disk and to obtain the desired recording / reproducing characteristics, the allowable variation of the flying height is extremely limited.

For this reason, it is required to measure the flying height of the head to confirm whether the flying height is set within an allowable range. In the HDD manufacturing process, there is a step of measuring the flying height of each head by an optical flying height measuring device using a glass disk, for example. Further, a measuring disk is formed in which projections having different heights on dots are formed over the entire surface from the inner circumference to the outer circumference of the disk, and the height is gradually reduced from the innermost side to the outermost side. A method of using is also being developed.

[0005]

As described above, in order to reduce the flying height of the head with the increase in recording density,
Measurement of flying height is an important factor. Conventionally, H
In the process of assembling the DD, there is a process of measuring the head flying height, and a mechanism related to the head is assembled so that an appropriate flying height can be secured. However, in recent years, with a decrease in flying height due to an increase in recording density, it has been required to monitor a change in a flying height occurring after assembling a drive in order to secure sufficient reliability. That is, there is a demand for a function capable of executing a measurement process for monitoring the flying height of the head together with the recording / reproducing operation of data on the disk. Both the method using the conventional optical flying height measurement device as described above and the method using the measurement disc with projections with different heights are the methods used during the assembly process. It cannot be applied to the measurement function of the HDD that has been set.

Therefore, an object of the present invention is to make it possible to measure the flying height of the head independently of a normal data recording / reproducing operation after assembling the drive, and to realize a function capable of monitoring fluctuations in the flying height. It is in.

[0007]

SUMMARY OF THE INVENTION The present invention is applied to a disk storage device for recording and reproducing data by a head floating on a disk, and has at least two different heights together with a data area for recording data. And a disk having a measurement area provided with a plurality of the respective projections. Further, the apparatus according to the present invention includes a detecting means for detecting that the head sought to the measurement area collides with each protrusion during the flying height measurement operation, and a determination for judging the position of the head at the time of collision. Means, and measuring means for measuring the flying height of the head based on the height of the colliding projection.

Specifically, the measurement area on the disk is
It has a protrusion (corresponding to a glide height by polishing on the disk surface) of at least two levels, which is arranged on the innermost side where no trouble occurs in the normal data recording / reproducing operation. The relatively high protrusion is used as a reference for determining the upper limit of the flying height within an allowable range. The relatively low protrusion is used as a reference for determining the lower limit of the flying height within an allowable range. As the detection means, a collision sensor (AE sensor) arranged on a support member (suspension) for supporting the head is used. The determining means determines the position of the head in the measurement area based on, for example, servo data recorded in the data area.

With this configuration, when the head seeks to the measurement area and the head collides with a relatively low projection, the flying height is reduced to the lower limit within the allowable range. Can be measured.
When the head does not collide with the relatively high protrusion, it can be measured that the flying height has increased to a height exceeding the upper limit within the allowable range. Based on this measurement result, it is possible to monitor whether the head has moved out of the allowable range.

According to another aspect of the present invention, the measurement area is provided with projections of three or more different heights, and the measuring means measures the collision of the head with each projection.
Measure the flying height. With such a configuration, it is possible to increase the measurement accuracy of the flying height and accurately monitor fluctuations in the flying height of the head.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an HD related to the embodiment.
FIG. 2 is a block diagram showing a main part of D. FIGS. 2 to 6 are conceptual views for explaining the structure and measurement operation of the disk of the embodiment, and FIG. 8 is a diagram showing the formation of a measurement area related to the embodiment. FIG. 9 is a conceptual diagram for explaining the method, and FIG. 9 is a flowchart for explaining the measuring operation of the embodiment. (Structure of HDD) In this embodiment, an HDD adopting a floating head and a ramp load method (head load / unload method) is assumed. The ramp loading method is a method in which a ramp member is provided outside the disc 1, the head 2 is held by the ramp member during unloading, and is moved from the ramp member onto the disc 1 during loading.

The disk 1 has a spindle motor (SP
M) Fixed at 5 and rotated. As will be described later, the disk 1 of the embodiment has a head flying height measurement area on the innermost circumference side in addition to a data area for recording normal data. In the data area, a large number of concentric tracks are formed in the radial direction from the outer periphery to the inner periphery. In this embodiment, for convenience, the disk 1 is 1
It is assumed that the number of sheets is one. Although the data area and the measurement area are provided on both sides of the disc 1,
In this embodiment, a case will be described in which attention is focused on only one side of the disk 1 for convenience. In the data area, servo data used for head positioning control is recorded at predetermined intervals in each track. That is, in each track, data sectors for recording user data are arranged between a plurality of servo areas where servo data is recorded.

The head 2 is held by a rotary type head actuator 3 and is configured to move in the radial direction of the disk 1. Specifically, the head 2 is held by a suspension 30 as a support member (see FIG. 6). The head actuator 3 is driven by a voice coil motor (VCM) 4 to seek the head 2 to a target track on the disk 1. here,
As described above, the head 2 means a slider having the head element (read head and write head) 2A mounted at the tip. Here, in the embodiment, as described later,
A collision sensor (AE sensor) 20 for detecting a collision of the head 2 is provided on the suspension 30.

The SPM 5 is driven by a drive current supplied from the SPM driver 14. VCM6 is VCM
Driven by a drive current supplied from the driver 13. The SPM driver 14 and the VCM driver 13 are integrated as a one-chip motor driver 12. Each of the drivers 13 and 14 is controlled by a control value (digital value) calculated by the CPU 10.

The head 2 is connected to a head amplifier circuit 6 via an FPC. The head amplifier circuit 6 inputs and outputs a read / write signal between the head 2 and the read / write circuit 7. The read / write circuit 7 has an AGC (automatic gain control) function for maintaining a read signal input from the head amplifier circuit 6 at a constant voltage level, and reads, for example, N signals from the read signal amplified by the AGC function.
It has a decoding function for performing signal processing necessary for reproducing RZ code data, and an encoding function for performing signal processing necessary for recording data on the disk 1.

The servo circuit 8 extracts servo data from the read signal reproduced by the read / write circuit 7 and outputs the servo data to the CPU 10. The CPU 10 is a microprocessor, and a ROM (read only) (not shown).
memory) according to the control program stored in the
It is a main control device that controls each part of the HDD. CP
U10 executes head positioning control for seeking and positioning the head 2 to a target position on the disk 1 based on the servo data obtained from the servo circuit 8. Further, in the same embodiment, the CPU 10
Move the head 2 to the measurement area on the disk 1,
It has a function of executing a measurement operation for measuring the flying height. The memory 11 stores data necessary for various control operations including the measurement operation of the CPU 10 in the embodiment.
A disk controller (HDC) 9 forms an interface with the host system and controls transfer of read / write data. (Structure of Disk) The disk 1 of the embodiment is the same as that shown in FIG.
As shown in (A) is a plan view and (B) is a side view, together with a data area (consisting of a large number of tracks) 100 for recording normal data, It has a measurement area 200 for measuring the flying height. As shown in FIG. 3, the measurement area 200 includes a plurality of projections (glide heights) A1 of different heights in different directions in the radial direction, which is the direction of the center of the disk 1 (the shaft of the SPM 5).
To A6. Here, six levels of height H
Assuming 1 to H6, the height is set stepwise so that the height H1 of the projection in the innermost area A1 is the maximum and the height H6 of the projection in the area A6 on the outermost circumference is the minimum. ing.
Note that a boundary area 201 between the measurement area 200 and the data area 100 is provided.
Is set to a predetermined value as described later. (Measurement of flying height) In addition to FIGS. 1 to 3, FIG.
To FIG. 6 and FIG. 9, the measurement operation of the embodiment will be described.

First, in the HDD, as shown in FIG. 4A, the head 2 seeks the range of the data area 100, and a normal data recording / reproducing operation is performed. here,
The distance from the position of the edge 2B on the inner peripheral side of the head 2 to the center of the disk 1 is denoted by “R”. Therefore, head 2
The distance R changes in accordance with the seek operation of.

Next, the CPU 10 starts the flying height measurement operation of the head 2 in response to a specific command from the host system via the HDC 9, for example. First, the CPU 10
Starts a seek operation from the data area 100 to the inner circumference side, as shown in FIG. 4B, and moves the measurement area 200 as a target position (step S1). Where CP
U10 determines whether or not the head 2 has entered the range of the measurement area 200 based on the servo data recorded in the data area 100 (steps S2 and S2).
3). That is, as shown in FIG. 6, the distance L between the inner peripheral edge 2B of the head 2 and the head element (particularly, the read head) 2A in the radial direction of the disk 1 is set in advance in the design stage. Therefore, the CPU 10 can estimate the position of the inner peripheral edge 2B of the head 2 based on the track address included in the servo data reproduced by the read head. That is, the servo track TR (the track on which the reproduced servo data is recorded) where the read head is located can be determined from the track address. Here, in order to detect the position of the head 2 within the measurement area 200 (actually, the position of the inner peripheral edge 2B), the CPU 10 is set as a so-called measurement dedicated area 101 in the data area 100. Will be used.

When the head 2 enters the range of the measurement area 200, the CPU 10 inputs a detection signal from the collision sensor 20, and the inner peripheral edge 2B of the head 2 collides with the projection of any of the areas A1 to A6. It is detected whether or not to perform (YES in step S3, S4). That is, the CPU 10 determines the areas A1 to A where the inner peripheral edge 2B has collided (does not collide).
6. In other words, the flying height of the head 2 is measured (estimated) based on the heights H1 to H6 of the protrusions (steps S5 to S5).
7). Hereinafter, a specific description will be given particularly with reference to FIG.

Here, in the design stage, the flying height H within the allowable range of the head is determined in each area A1 of the measurement area 200.
Converted to the heights H1 to H6 of the projections of A5 to A6, "H5
It is assumed that <H ≦ H4 ”. When the head 2 moves to the innermost peripheral side of the measurement area 200 without colliding with any of the areas A1 to A6, the CPU 10 determines that the head 2 has far exceeded the upper limit within the allowable range and ends the measurement operation. (NO in step S5, S8, S9).

As shown in FIG. 5A, when the head 2 collides within the area A4 of the measurement area 200 (R4 <R ≦ R5), the CPU 10 sets the flying height H of the head 2 to "H".
It is determined that 5 <H ≦ H4 ”. That is, in this case, the flying height of the head 2 is a normal value within an allowable range, and it can be confirmed that no abnormal fluctuation occurs.

On the other hand, as shown in FIG.
Collides in the area A6 of the measurement area 200,
The CPU 10 measures that the flying height H of the head 2 is “H ≦ H6”. That is, in this case, it can be confirmed that the flying height of the head 2 is lower than the lower limit value H4 within the allowable range and fluctuates below the height H6. Here, in a region (boundary area 201) continuous with the area A6, the range BW having the same glide height as the protrusion of the area A6 needs to be sufficiently larger than the radial width SW of the head 2. It is.

Further, as shown in FIG. 5C, when the head 2 collides in the area A1 of the measurement area 200, the CPU 10 determines that the flying height H of the head 2 is "H2 <H≤H".
H1 ". That is, in this case, it can be confirmed that the flying height of the head 2 is larger than the upper limit value within the allowable range and abnormally fluctuates.

As described above, according to the present embodiment, the flying of the head 2 is performed independently of the normal data recording / reproducing operation by using the measuring area 200 arranged on the innermost peripheral side of the disk 1. The amount can be measured and monitored for abnormal fluctuations relative to normal values. In other words, HDD
The flying height of the head 2 can be measured and monitored not only during the manufacturing process but also after the product is manufactured.

Incidentally, the measurement area 200 of the embodiment is
Is an area that cannot be used as a normal data recording area, and therefore is desirably a minimum in order to suppress a decrease in the storage capacity of the disk 1. In this embodiment, six areas A1 to A6 are assumed.
In order to reduce the number, it is only necessary that each area has at least two levels of protrusions. In this case, only the fluctuation exceeding the upper limit and the lower limit within the allowable range of the flying height can be measured. On the other hand, if the number of steps (the number of areas) of the height of the protrusion is increased, the measurement accuracy can be increased accordingly.

Here, as shown in FIG. 6, it is desirable that the width of the measurement area 200 is smaller than the width SW of the head 2 in the radial direction. As described above, in the range of the measurement area 200, the position of the inner peripheral edge 2B of the head 2 may be determined. In this position determination, as described above, the determination is made based on the position of the servo track TR on the disk 1. Here, the servo track TR used as the dedicated measurement area 101 is naturally determined by the distance L between the inner peripheral edge 2B of the head 2 and the head element (particularly, the read head) 2A. Therefore, the CPU 10 preliminarily sets the measurement-dedicated area 101 on the disk 1,
A servo area for performing position determination only within the range of 00 may be set. (Modification) FIG. 7 is a conceptual diagram showing a modification of the embodiment.

This modification is a modification of the collision sensor 20 of the embodiment.
Is a method that utilizes the detection of thermal asperity of the MR head. That is, it is assumed that the HDD of the embodiment uses an MR (or GMR) head as the read head mounted on the head 2. The MR head has a phenomenon called thermal asperity which shows a characteristic reproduction signal waveform due to a heat generation effect when the MR head collides with a projection or the like. Circuits for detecting thermal asperity are already known. Therefore,
In this modification, as shown in FIG. 7, it is detected based on the detection of thermal asperity that the read head 2A of the head 2 enters the range of the measurement area 200 and collides with any one of the areas A1 to A6. . However, in such a method, in order to determine the position where the head 2 has collided, it is necessary to arrange the measurement dedicated area 101 having the servo track TR in the range of the measurement area 200. The other configuration is the same as that of the embodiment.

This modification has the advantage that the AE sensor 20 can be dispensed with. However, on the other hand, measurement area 2
00, the width AW of each area A1 to A6
Must be greater than the distance L of Therefore, in this modification, the area occupied by the measurement area 200 where normal data recording is not possible relatively increases. (Method of Forming Measurement Area) On the disc 1 of the embodiment, as described above, a measurement area 200 is formed in addition to the normal data area 100. The measurement area 200 is formed by using the processing on the disk surface by the conventional head burnish method for defining the glide height. Hereinafter, description will be made with reference to FIG.

In the head burnishing method, the burnishing head 80 is caused to travel in the radial direction on the disk 1 with a flying height corresponding to a desired glide height (ie, corresponding to the height of the projection), and This is a method of shaving off the projection. The protrusions may use the irregularities on the disk as they are, or may use a texture formed by a mechanical or chemical method.

As a specific method of forming the measurement area 200 of the embodiment, first, in the area corresponding to the measurement area 200 on the disk 1, a projection having a height H1 or more of the area A1 is formed by the above-described method. To form Next, FIG.
As shown in (A), in order to form the area A1, the flying height of the burnishing head 80 is adjusted to “H1”.
Burnish (cut off) the range of the radii R1 to R6.
Here, the adjustment of the flying height “H1” is performed by measuring the disk rotation speed dependency of the flying height in the range of the radii R1 to R6 in advance. That is, the flying height of the burnishing head 80 is adjusted by controlling the drive of the SPM 5 and adjusting the rotation speed of the disk 1.

Next, as shown in FIG.
In order to form No. 2, the flying height of the burnishing head 80 is adjusted to “H2”, and the range of the radii R2 to R6 is burnished. Thereafter, similarly, the range of the areas A3 to A5 is burnished by the burnishing head 80 according to the set heights H3 to H5.

Finally, as shown in FIG.
In order to form the area A6, the burnishing head 80
Is adjusted to "H6" and burnished. At this time, the position of the burnishing head 80 is not moved. Here, the area A6 is formed as a range corresponding to the width SW of the burnishing head 80. In this case, area A6
May be larger than the width SW of the burnishing head 80. In the embodiment, since the area A6 is an area for detecting that the head 2 has floated below the lower limit value within the allowable range, if the flying height is a normal value, a collision occurs even during a normal seek operation. do not do. Therefore, this area A6
To the normal data recording area or the above-mentioned measurement dedicated area 1
01 (area where servo data for measurement is recorded) may be used.

[0033]

As described in detail above, according to the present invention, in a disk storage device using a flying head, the flying height of the head is measured independently of a normal data recording / reproducing operation, and a normal value is obtained. It can be monitored whether or not there is an abnormal change. That is, the flying height of the head can be measured and monitored not only during the manufacturing process of the device but also after the device is commercialized. Therefore, when the flying height of the head is reduced due to the increase in the recording density, the fluctuation of the flying height can be monitored, so that a highly reliable disk storage device can be provided.

[Brief description of the drawings]

FIG. 1 is an exemplary block diagram showing a main part of an HDD according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram for explaining the structure and measurement operation of the disk of the embodiment.

FIG. 3 is a conceptual diagram for explaining the structure and measurement operation of the disk of the embodiment.

FIG. 4 is an exemplary conceptual diagram for explaining the structure and measurement operation of the disk of the embodiment.

FIG. 5 is an exemplary conceptual diagram for explaining the structure and measurement operation of the disk of the embodiment.

FIG. 6 is an exemplary conceptual diagram for explaining the structure and measurement operation of the disk of the embodiment.

FIG. 7 is a conceptual diagram for explaining a modification of the embodiment.

FIG. 8 is a conceptual diagram for explaining a method of forming a measurement area related to the embodiment.

FIG. 9 is a flowchart for explaining the measurement operation of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Disk 2 ... Head (slider) 2A ... Head element (read head) 3 ... Head actuator 4 ... Voice coil motor 5 ... Spindle motor 6 ... Head amplifier circuit 7 ... Read / write circuit 8 ... Servo circuit 9 ... Disk controller 10 ... CPU 11 ... memory 12 ... motor driver 13 ... VCM driver 14 ... SPM driver 20 ... collision sensor (AE sensor) 30 ... suspension 100 ... data area 200 ... measurement area

Claims (10)

[Claims] 1. A disk storage device for recording / reproducing data to / from a disk by means of a head floating above the disk, comprising a data area for recording data and projections having at least two different heights. A disk having a measurement area provided with a plurality of the respective projections, a head moving means for seeking the head to the measurement area during a flying height measurement operation, and a range of the measurement area A detecting unit for detecting that the head collides with each of the protrusions, and a determining unit for determining a position of the head in the measurement area when the collision is detected by the detecting unit. A projection having a height at which the head has collided is specified based on the position of the head determined by the determination means, and based on the height of the projection. Disk storage, characterized in that it comprises a measuring means for measuring the flying height of the head Te. 2. The disk storage device according to claim 1, wherein the measurement area is arranged on an innermost peripheral side of the disk. 3. The disk storage device according to claim 1, wherein said detecting means is a collision sensor which constitutes said head moving means and is arranged on a support member supporting said head. 4. The data area includes a servo area in which servo data is recorded, and the determination unit is configured to perform, based on the servo data reproduced by the head moved by the head moving unit, 2. The disk storage device according to claim 1, further comprising: means for estimating a position of the head in a range of the measurement area. 5. The measurement area includes a first protrusion having a height serving as a reference for determining an upper limit within an allowable range as a flying height of a head, and a reference for determining a lower limit within the allowable range. A height of a second protrusion, wherein the measuring means measures that the flying height of the head exceeds the upper limit of an allowable range when the head does not collide with the first protrusion, 2. The disk storage device according to claim 1, further comprising means for measuring that the flying height of the head is lower than a lower limit of an allowable range when the head collides with the second protrusion. 6. The measurement area has a plurality of projections having different heights in multiple stages in accordance with the measurement accuracy of the flying height of the head, and the measuring unit is configured to determine a height of the projection on which the head has collided. 2. The disk storage device according to claim 1, further comprising means for estimating a variation in the flying height of the head. 7. An area corresponding to a boundary area between the measurement area and the data area has a glide height less than a minimum height of the projection within a range not less than a width of a slider which is a main body of the head. 7. The disk storage device according to claim 1, wherein the disk storage device is provided. 8. A head flying height measuring method applied to a disk storage device for recording and reproducing data on and from a disk by using a head floating on the disk, wherein the disk has data for recording data. Along with the area, there are at least two levels of different heights of projections, each having a plurality of measurement areas provided with the respective projections, and during the flying height measurement operation, the head is sought to the measurement area. Causing the head to collide with each of the protrusions within the range of the measurement area; and, when a collision is detected in the detection step, the position of the head in the measurement area. Determining the position of the head based on the position of the head determined by the determining step, Identify and,
Measuring the flying height of the head based on the height of the protrusion. 9. A magnetic disk used for a disk storage device for recording and reproducing data by a flying head, wherein the magnetic disk is provided in a data area for recording the data, and in an area on the inner peripheral side of the data area. Being
A measuring area for measuring a flying height of the head based on the height of each of the projections colliding with the head, the projection area having at least two different heights; Magnetic disk. 10. The measurement area is characterized in that the projections having the different heights are formed by using a processing by a head burnish method for forming a glide height on the data area. The magnetic disk according to claim 9.