JP2000195211A - Magnetic disk device and read channel applied to the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a function for monitoring the variation of floating which is sufficient for actual usage as a result by measuring the variation amount of the floating amount by taking each characteristic value of the amplitude value, half-value width and jitter amount of the waveform of reproduced signal of a head as a kind of parameter, and also measuring the variation amount of the accurate floating amount in a manner so as not to depend on the tracking accuracy of the head at measurement. SOLUTION: In this magnetic disk device furnished with the monitor means for the floating amount for monitoring the variation of the floating amount of a head 2 based on the variation of each characteristic value of the amplitude value, half-value width and jitter amount of the waveform of reproduced signal read out by the head 2, the monitor means for the floating amount is provided with a flying high(FH) measuring circuit 20 for measuring each characteristic value of the amplitude values, half-value width and jitter amount of the waveform of reproduced signal, and an FH monitor 21 for calculating the variation amount of the floating amount, based on the comparison result of the measurement result and the default value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive particularly applied to a hard disk drive and having a function of monitoring a fluctuation of a flying height of a head for reading / writing data from / on a disk storage medium.

[0002]

2. Description of the Related Art Conventionally, a hard disk drive (HD)
In D), data read / write is executed while the head is floating on a disk storage medium (hereinafter simply referred to as a disk). Specifically, the head has a structure in which a head element is mounted on a slider, and is configured to be mounted on an actuator and to rotate and move in a state of floating in the radial direction of the disk. In the head element, an MR element forming a read head element and an inductive thin film head element forming a write head element are separately mounted on the same slider.

[0003] The head is moved by a small distance (for example, 10 minutes) by air pressure (air bearing) due to the rotational movement of the disk.
(0 nm or less). The distance between the head and the disk is determined by the flying height or flying height.
gh, hereinafter sometimes referred to as FH). HDD
In order to promote a higher recording density, a low-flying technique for reducing the flying height is an important factor.

[0004] The low flying height technology requires improvement in processing accuracy and assembling accuracy of parts such as HDD heads and actuators. On the other hand, after the HDD is shipped as a product, there is a high possibility that the flying height of the head fluctuates from an initial set value at the time of manufacture due to environmental changes and time-measuring changes. If the flying height of the head becomes too low in accordance with the fluctuation of the flying height, there is a high possibility that a crash (damage to the head or the disk surface) due to contact or collision between the head and the disk surface occurs. On the other hand, if it rises too much, the recording / reproducing performance of the head decreases. Therefore, particularly for HDDs having a high recording density, a technique for monitoring the fluctuation of the flying height is important together with the promotion of low flying height.

[0005] Monitoring of flying height fluctuation requires a function of measuring the fluctuation amount of the flying height of the head. Conventionally, it has been confirmed that the fluctuation of the flying height of the head is related to the fluctuation of the characteristics of the reproduced signal. More specifically, as shown in FIG. 7A, the flying height of the head increases (that is, the flying height of the head increases in the reproduction signal waveform 70 whose output amplitude value and half width (PW50) are default values (initial settings at the time of manufacture)). , A rise in flying height) results in a reproduced signal waveform 71 that changes so that the output amplitude value decreases by about 10% and the PW50 increases by about 10%. FIG. 7B shows a reproduced signal waveform 70 having a default value when the signal passes through an AGC amplifier and a low-pass filter (LPF), and a reproduced signal waveform 72 corresponding to a change in flying height.
Is shown.

[0006]

As described above, it is possible to monitor the fluctuation of the flying height of the HDD by measuring the change of each characteristic value of the amplitude value or half-value width of the reproduced signal waveform read from the head. It is possible. For this reason, a method has been proposed in which a circuit for measuring the amplitude value of a reproduced signal waveform and a circuit for measuring a half-value width are provided in a read channel (read / write circuit). However, the conventional method requires recording a special measurement signal for flying height measurement at a predetermined position on the disk, and moving the head to the recording position of the measurement signal during measurement. Therefore, the measurement accuracy depends on the accuracy of head tracking (positioning control). Further, since only a circuit for measuring one of the amplitude value and the half width is provided, it is not always possible to obtain practically sufficient flying fluctuation monitoring performance.

Accordingly, an object of the present invention is to measure the variation of the flying height using the characteristic values of the amplitude, half width, and jitter amount of the reproduced signal waveform of the head as a kind of parameter, and to improve the tracking accuracy of the head during the measurement. Therefore, it is an object of the present invention to measure a fluctuation amount of the flying height with high accuracy without realizing the function, and to realize a practically sufficient monitoring function of the flying height.

[0008]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for monitoring a fluctuation of a flying height of a head based on a fluctuation of each characteristic value of an amplitude value, a half width and a jitter amount of a reproduced signal waveform read by a head. This is a magnetic disk drive provided with a flying height monitoring means. Specifically, the flying height monitoring means, when measuring the characteristic values, reproduces a reproduction signal waveform read by the head from an AGC area or a gap area for AGC operation in a servo area provided on the disk. Use Further, the present invention is a means for judging a flying height variation of a head based on a comparison result between each characteristic value of an amplitude value, a half width, and a jitter amount of a reproduction signal waveform and a corresponding reference value prepared in advance. Having.

According to the configuration of the present invention, a special measuring signal recorded on a disk is not used,
Since the reproduction signal waveform from a part of the servo data recorded in the servo area (specifically, the AGC area and the gap area) is used, the flying height fluctuation is measured without being affected by the head tracking accuracy at the time of measurement. It is possible to do. In addition, as a measurement parameter of flying height fluctuation,
Since each characteristic value of the amplitude value, half width and jitter amount of the reproduction signal waveform is used, the measurement accuracy is improved, and as a result, a practically sufficient monitoring function can be realized.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. (Configuration of HDD and Read Channel) In this embodiment, an HDD is assumed as a magnetic disk device, and a flying height (flying height) measuring circuit (hereinafter, referred to as an FH measuring circuit) 20 and a flying height monitor circuit (hereinafter, an FH monitor circuit) 2)
1 is provided. The configuration of the head / disk assembly, data reproduction system, and peripheral circuits will be mainly described below with reference to FIG.

The head / disk assembly has a disk 1 as a recording medium, a head 2, a spindle motor (SPM) 3 for rotating the disk 1, and an actuator 6 on which the head 2 is mounted. The head 2 has a structure in which a read head element (such as an MR element) and a write head element are separated and mounted on the same slider. However, in the embodiment, the head 2 means a read head because it is related to the data reproducing operation. The actuator 6 includes a voice coil motor (VCM) as a drive source, and moves (adjusts the position of) the head 2 in the radial direction of the disk 1 in accordance with the current supplied from the VCM driver 7. The VCM driver 7 supplies a current according to control data from a servo controller 22 described later. SPM
3 is SP based on the control from the motor controller 5
A driving current is supplied from the M driver 4.

Next, the data reproduction system is roughly divided into a preamplifier (head amplifier) 8 and a read channel 10.
And a disk controller (HDC) 23.
The preamplifier 8 amplifies the reproduction signal read from the head 2 and sends out the signal to the read channel 10. The read channel 10 includes a fixed gain amplifier 11, an amplifier (VGA) 12 having a variable gain function, and a gain controller 1
3, LPF 15 for user data, and L for servo data
It has a PF 16, a user data signal processing circuit 18, and a servo data signal processing circuit 19.

The fixed gain amplifier 11, VGA 12, and gain controller 13 constitute an AGC amplifier circuit for keeping the amplitude of the reproduced signal constant. The output of the fixed gain amplifier 11 of the embodiment is connected to the input of the VGA 12 and the input of an FH measurement circuit 20 described later. The output of the VGA 12 is supplied to the LPF 15 for user data and the LPF for servo data through the switch circuit 14.
16 are connected. That is, the switch circuit 14 sends out the output of the VGA 12 to the user data LPF 15 when reproducing the user data. When reproducing servo data, the output of the VGA 12 is connected to the LPF 1 for servo data.
Send to 6. Further, each output of the LPFs 15 and 16 is
It is connected to the gain controller 13 via the switch circuit 17. That is, the switch circuit 17 sends the output of the LPF 15 to the gain controller 13 when reproducing the user data. When reproducing servo data,
The output of the LPF 16 is sent to the gain controller 13. The gain controller 13 outputs a gain control amount for controlling the gain of the VGA 12 according to the amplitude value of the reproduction signal.

The user data signal processing circuit 18 executes a reproduction process for generating digital reproduction data from the reproduction signal output from the user data LPF 15, and sends the reproduction data 109 to the HDC 23. The user data signal processing circuit 18 performs a reproduction process (decoding process) of the reproduction data at the timing of the read gate 108 output from the HDC 23. The servo data signal processing circuit 19 executes the reproduction process of the servo data at the timing of the servo gate 105 output from the servo controller 22, and performs seek data (cylinder address code) and position error data (servo burst A).
The servo data 104 including the position information (.about.D) is sent to the servo controller 22. The servo controller 22 calculates the control data based on the servo data 104, and executes the positioning control of the head 2. The servo controller 22 outputs data (such as the end of the seek operation) 106 related to the head positioning control to the HDC 23. The HDC 23 configures an interface between the HDD and the host system, and executes data transfer control and notification processing of a monitoring result of flying fluctuation related to the embodiment.

The read channel 10 of the embodiment has F
An H measurement circuit 20 is provided. FH measurement circuit 20
Represents a reproduction signal 100 output from the fixed gain amplifier 11.
(Amplitude value) and a servo signal (AGC pattern or gap pattern) 101 output from the servo data LPF 16. The FH measurement circuit 20
The H monitor 21 executes the FH measurement processing in accordance with the timing of the detection control signal 102, and sends out the measurement result (FH detection data) 103 to the FH monitor 21. (Monitoring operation of flying height variation) The monitoring operation of flying height variation of the embodiment will be described below with reference to FIG. 1 and FIGS. Here, FIG. 2 shows the above-described FH measurement circuit 20 and FH measurement circuit.
FIG. 2 is a block diagram showing a specific configuration of an H monitor 21.

First, in this embodiment, the FH measurement circuit 20
In the measurement operation, a part of the servo data recorded in the servo area on the disk 1 is used. As shown in FIG. 3, the servo data includes an AGC pattern, an erase, an address code (cylinder address), servo burst patterns A to D, and a gap pattern, and is recorded continuously with an adjacent track. In the embodiment, an AGC pattern or a gap pattern is used for measurement. The AGC pattern is used for AGC operation, that is, for adjusting the amplitude of a reproduced signal. The gap pattern is used for identifying a boundary between the servo area and the data area. Each pattern has a single frequency, and even when a track offset of the head 2 occurs, a reproduced signal waveform of the same level can always be obtained. It is desirable that one of the patterns used for measurement is slightly longer than the conventional one.

The servo controller 22 outputs the servo gate 105 at the timing shown in FIG. 3, and outputs the servo data signal processing circuit 19, the switch circuits 14, 17, and the FH
The monitor 21 is controlled. The FH monitor 21 outputs the FH detection control signal 102 of the FH detection (1) when the gap pattern is used, and outputs the FH detection control signal 102 of the FH detection (1) when the AGC pattern is used. I do. Here, it is assumed that an AGC pattern is used.

Now, when the head 2 is positioned in the servo area and reads the AGC pattern, the AGC operation (AGC mode) by the AGC amplifier circuit starts, and the gain controller 13 sets the gain (sets the gain control amount). (See FIG. 3). At this time, the fixed gain amplifier 11 outputs a reproduced signal waveform 1 as shown in FIG.
00 is output. The FH measurement circuit 20 executes a process of inputting the reproduction signal waveform 100 and calculating an amplitude value. On the other hand, the servo data LPF 16 receives a reproduction signal waveform from the VGA 12 via the switch 14 and outputs a signal waveform 101 as shown in FIG. The FH measurement circuit 20 receives the reproduction signal waveform 101 and executes a process of calculating a predetermined area of the waveform area.

The FH measuring circuit 20, as shown in FIG.
An amplitude value is calculated from the reproduced signal waveform 100 by the peak detection circuit 31 and stored in the data register 33 (see FIG. 4). On the other hand, the reproduction signal waveform 101 is input by the area integration circuit 30, a predetermined area of the waveform area is calculated, and stored in the data register 32 (see FIG. 5). The FH measurement circuit 20 sends out each data of the amplitude value or the waveform area value stored in the data registers 32 and 33 to the register controller 40 of the FH monitor 21 through the register control port 34. Here, each of the peak detection circuit 31 and the area integration circuit 30 has a full-wave rectification circuit (not shown) on the input side, and passes the reproduction signal waveforms 100 and 101 to input the full-wave rectification waveform ( 4 and 5). Further, the peak detection circuit 31 and the area integration circuit 3
0 is the timing generator 45 of the FH monitor 21
It operates at the timing of the FH detection control signal 102 output from the controller.

Next, in the FH monitor 21, as shown in FIG.
The amplitude value (peak detection data) and the waveform area value (area integration data), which are the two types of data sent from the, are converted into the corresponding average value calculation units 41 and 43 and the standard deviation (STD).
The data is transferred to the calculation unit 42. Each of them operates at the timing of the clock output from the counter 44.

The average value calculating section 41 averages the continuously measured area integrated data, calculates half value width (PW50) data, and outputs it to the comparator 49. That is, the average value calculation unit 41 calculates a change in the width of the waveform as a change in the waveform area. The average value calculation unit 43 calculates the average value of the continuously measured amplitude value data, and outputs the average value to the comparator 51. By these averaging, it is possible to average the variation of the measurement and to catch even a minute change.
Further, the STD calculation unit 42 calculates the fluctuation amount of the jitter noise from the area integrated data. It has been confirmed that the increase in jitter noise is proportional to the increase in the standard deviation of the area integrated data.

Each of the comparators 49 to 51 compares each default value (PW50, jitter amount, amplitude value) set at the time of manufacture with each measurement result (each calculation result), and compares each change amount with the corresponding data. These are stored in registers 52 to 54. The register control port 55 is connected to each data register 5
The fluctuation amounts of the PW 50, jitter noise, and amplitude value stored in 2 to 54 are sent to the HDC 23.

As described above, according to the embodiment, the AGC pattern or the gap pattern of the servo data is used as the measurement signal, and the PW50, the jitter noise, and the amplitude value of the reproduction signal waveform are used as the flying height measurement parameters. Are measured, and the amount of variation with respect to a default value (reference value) is calculated from the measurement result. Therefore, HD
By transferring each variation amount to the host system by the C23, it is possible to monitor the variation in the flying height (flying height) of the head 2 on the host system side.

The monitoring method of the embodiment uses an AGC pattern or a gap pattern of servo data as a measurement signal. Since these are recorded continuously with the adjacent track, a reproduced signal waveform of the same level can always be obtained even when a track offset of the head 2 occurs. Therefore, the tracking accuracy of the head 2 does not affect the measurement accuracy. Also, as a parameter for monitoring the fluctuation of the flying height, PW5 of the reproduced signal waveform
In order to measure each characteristic value of 0, jitter noise and amplitude value,
A practically sufficient monitoring function can be realized. (Modification) FIG. 6 is a block diagram showing a modification of the embodiment. This modification employs a digital PRML signal processing method as the REIT channel 60, and utilizes a change in the amount of gain feedback of the digital AGC circuit (output of the gain controller 63) for detecting an amplitude value. The FH measurement circuit 64 has a digital area integration circuit, and performs an area integration operation of the digital signal waveform of the AGC pattern or the gap pattern output from the A / D converter 62. Note that 101D and 104
D means digital data corresponding to the reproduction signal waveform 101 and the servo data 104 of the embodiment, respectively.

Also in this modified example, a practically sufficient monitoring function can be realized by obtaining the fluctuation amounts of the respective characteristic values of the PW50, the jitter noise, and the amplitude value of the reproduced signal waveform as in the embodiment. it can.

[0026]

As described above in detail, according to the present invention, it is possible to measure the fluctuation of each characteristic value such as the amplitude value, half width and jitter amount of the reproduced signal waveform of the head as the fluctuation amount of the flying height of the head. it can. In addition, the influence of the tracking accuracy of the head during measurement can be eliminated. Therefore, it is possible to measure the variation of the flying height with high accuracy, and as a result, it is possible to realize a practically sufficient monitoring function of the flying height.
It is particularly effective to apply the present invention to a magnetic disk drive having a low flying height and a high recording density.

[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 block diagram showing a configuration of a flying height measurement circuit and a flying height monitor circuit related to the embodiment.

FIG. 3 is a conceptual diagram showing servo data related to the embodiment.

FIG. 4 is a signal waveform diagram for explaining the operation of the flying height measurement circuit according to the embodiment.

FIG. 5 is a signal waveform diagram for explaining the operation of the flying height measurement circuit according to the embodiment.

FIG. 6 is an exemplary block diagram showing a main part of an HDD according to a modification of the embodiment;

FIG. 7 is a diagram showing the relationship between a conventional flying height variation and a change in a reproduced signal waveform.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Disk 2 ... Head 3 ... Spindle motor (SPM) 4 ... SPM driver 5 ... Motor controller 6 ... Actuator 7 ... VCM driver 8 ... Preamplifier (head amplifier) 23 10 ... Read channel 11 ... Fixed gain amplifier 12 ... VGA 13 ... Gain controller 14 ... Switch circuit 15 ... LPF for user data 16 ... LPF for servo data 17 ... Switch circuit 18 ... Signal processing circuit for user data 19 ... Signal processing circuit for servo data 20 ... FH measurement circuit 21 ... FH monitor 22 ... Servo Controller 23 ... Disk controller (HDC)

Claims (5)

[Claims] 1. A disk storage medium having a servo area on which servo data is recorded and a data area for recording user data, and performing a data write operation and a read operation while floating on the disk storage medium. A head; a reproduction processing unit for performing predetermined signal processing on a reproduction signal read from the servo area by the head; an amplitude value, a half width, and a jitter amount of the reproduction signal waveform obtained by the reproduction processing unit Based on the variation of each characteristic value of
A magnetic disk drive comprising a flying height monitoring means for monitoring a flying height variation of the head. 2. The flying height monitoring means according to claim 1, wherein said flying height monitoring means controls the head based on a change in the characteristic value of a reproduction signal waveform read by the head from an AGC area or a gap area for an AGC operation in the servo area. 2. The magnetic disk drive according to claim 1, wherein a flying height variation is determined. 3. The flying height monitoring means includes an area integrating means for calculating a waveform area in a predetermined range of the reproduction signal waveform, and a means for calculating an amplitude value of the reproduction signal waveform. 3. The magnetic disk drive according to claim 1, further comprising means for calculating each of the half width and the jitter amount from an output value of an integrating means. 4. The flying height monitoring means includes: a measuring means for measuring characteristic values of an amplitude value, a half value width, and a jitter amount of the reproduced signal waveform; and a characteristic value measured by the measuring means and 2. The magnetic disk drive according to claim 1, further comprising: means for determining a flying height variation of the head based on a comparison result with a corresponding reference value prepared. 5. A read channel applied to a magnetic disk device including a disk storage medium having a servo area on which servo data is recorded, and a head for performing a data reading operation while flying above the disk storage medium. A means for measuring an amplitude value of a reproduction signal read from the servo area by the head; and an area integration means for calculating a waveform area in a predetermined range of a reproduction signal waveform read from the head. Have
Means for measuring the characteristic values of the half-width and the jitter amount of the reproduced signal; and outputting the amplitude value or the output value of the area integrating means as data for determining the flying height fluctuation of the head. A read channel comprising output means.