JP2000235769A - Magnetic recording / reproducing device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent data recording / reproduction from becoming impossible due to aging of a device. SOLUTION: When a read / write IC 301 performs decoding by using a maximum likelihood decoding reproduction parameter by a waveform equalizer for equalizing a data reproduction waveform, and an error rate of reproduced data does not fall within a predetermined range. In a magnetic recording / reproducing apparatus for setting a parameter value to a parameter value in which an error rate falls within a predetermined range, a change over time of the parameter value is monitored, and when a variation amount of the parameter value exceeds a preset value or when a predetermined value is exceeded. An alarm that predicts the occurrence of an error when the number of times exceeds the number of times, thereby preventing a failure that makes recording and reproduction of the apparatus impossible, and maintaining reliability for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus such as a magnetic disk drive, and more particularly to a signal processing system employing a partial response maximum likelihood decoding system and using a magnetoresistive head (MR head). The present invention relates to a magnetic recording / reproducing device such as a magnetic disk device.

[0002]

2. Description of the Related Art Recent demands for high-density and large-capacity storage in magnetic disk drives have led to a PRML class 4 (Partial Response Maximum Likelih
Using a signal processing method called ood class 4), by reducing the distance of the change in magnetization when data is recorded at high density, it is possible to prevent the interference of the magnetic field corresponding to the change in magnetization from increasing, By reducing the waveform interference of the reproduced waveform using a linear filter and decoding based on the time-series change of the signal amplitude by the maximum likelihood decoding method, the recorded data can be reproduced stably.

Further, a data recording system and a reproducing system in a magnetic recording / reproducing system such as a magnetic disk device of a recent magnetic disk device cope with variations in characteristics of a magnetic head and other factors, and in advance, under optimum conditions for each head. Various parameters are set for each head so that data can be recorded and reproduced. To describe this setting specifically, in the conventional technology, for each magnetic head or for each area called a zone obtained by dividing the disk radial direction of the magnetic recording medium into several zones, under certain environmental conditions such as normal temperature and normal pressure environment, Various parameters are set so that the error rate per bit for data reproduction becomes the best. Techniques for optimizing these various parameters are described in, for example, JP-A-7-78302 or JP-A-8-96312.

In a magnetic disk drive in which the above-described various parameters are set for each magnetic head, data is recorded and reproduced using parameters optimized at the time of shipment when the drive is operating. Environmental changes /
Even if there is a change over time of the apparatus, specifically, if there is a deterioration in the magnetic characteristics due to the deterioration of the recording / reproducing element of the head or a change in the surface of the magnetic disk medium, it is necessary to ensure a good data error rate, A method of automatically adjusting the values of various parameters to optimal values at the time in response to changes in the environment (temperature / pressure / humidity, etc.) of these devices and changes over time such as a decrease in lubricant / deterioration of a slider. See, for example,
293165 proposes this. This method
For example, the magnetic disk is divided into zones, a recording / reproducing (R / W) check is performed for each zone, and various parameters are reset to a specified value by comparing with a default value. Is automatically adjusted to the optimum value.

On the other hand, in recent magnetic disk devices, the flying gap between the head and the disk medium has been reduced to about submicron in order to improve magnetic recording characteristics with a rapid increase in recording density. In magnetic recording and reproduction, it is advantageous from the viewpoint of increasing the reproduction output and the resolution that the floating gap (magnetic distance) is as small as possible, so that the floating gap becomes narrow to some extent due to an environmental change of the apparatus or a change with time. In such a case, the error rate does not worsen, but tends to be better.

However, the deterioration of the head characteristics is caused by a change in the surface condition of the medium due to the contact between the head and the surface of the disk medium, that is, a defect of the magnetic layer due to a contact scratch on the head and the surface of the disk medium. There is a possibility that a possible situation may occur, and if this deterioration is corrected automatically, the deterioration of the magnetic head cannot be predicted, and a situation may occur in which data recording / reproduction cannot be performed during operation. There was sex. In the prior art, in order to solve this problem, Japanese Patent Laid-Open Publication No. Hei 9-1 is to detect the fluctuation of the flying height of the head by paying attention to the change of the read / reproduced signal, and detect the deterioration of the magnetic head using the fluctuation of the flying height as a factor.
No. 39040 proposes this. However, this technique has a low sensitivity of the S / N ratio (Signal / Noise ratio) of the data signal to fluctuations in the flying height of the head, so that sufficient detection accuracy cannot be obtained, and is not very practical.

[0007]

The method for automatically adjusting the values of various parameters to the optimum values at that time with respect to the environmental change and the aging change of the device according to the prior art does not allow data recording / reproduction. However, there is a problem in that it is not possible to detect a precursor to the occurrence of the situation, which lowers the reliability of the apparatus. Further, the method of detecting the flying fluctuation of the head by focusing on the change history of the data reproduction signal has a disadvantage that the detection accuracy cannot be ensured and is not practical.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned disadvantages of the prior art, and focus on changes in the values of various parameters of a recording / reproducing system with the lapse of time so that recording / reproducing of the apparatus becomes impossible. An object of the present invention is to provide a magnetic recording / reproducing device such as a magnetic disk device capable of preventing a failure and maintaining reliability for a long period of time.

[0009]

In order to achieve the above object, the present invention provides a spindle motor for rotating a magnetic disk, a magnetic head for recording / reproducing data recorded on the magnetic disk, and a carriage for moving the magnetic head to a carriage. And a voice coil motor that performs rotational positioning on an arbitrary track on the magnetic disk, and decodes data read by the magnetic head based on a time-series change in signal amplitude by a maximum likelihood decoding method. A read / write circuit for setting a data reproduction parameter value at the time of decoding; and a memory for recording the parameter value, wherein a default value of the parameter is initialized in the read / write circuit to read data from the magnetic disk. If the error rate of the decoded data does not fall within a predetermined range, the parameter value is set to an error rate. In a magnetic recording / reproducing apparatus that sets a parameter value within a predetermined range and records the parameter value in the memory, a change over time of the parameter value is monitored, and a variation amount of the parameter value exceeds a preset value. Alternatively, the first is to detect that the number of times has exceeded a predetermined number.
The feature of.

According to the present invention, in the magnetic recording / reproducing apparatus having the above characteristics, the read / write circuit includes a waveform equalizer for equalizing a data reproduction waveform from the magnetic disk, and the parameter value of the data reproduction is equal to the waveform or the like. The apparatus according to the first aspect, wherein the read / write circuit includes a waveform equalizer for equalizing a data reproduction waveform from the magnetic disk, wherein the equalizer coefficient value is an equalizer coefficient value of the equalizer. A second feature is that the parameter value is an equalizer coefficient value of the waveform equalizer, and that a change in the parameter value exceeds a preset value two or more times out of ten times.

Further, according to the present invention, in the magnetic recording / reproducing apparatus having the above-mentioned features, when the variation of the parameter value exceeds a preset value or exceeds a predetermined number of times, the head zone replacement processing or the head replacement processing is performed. The third feature is that when the variation of the parameter value exceeds a preset value or exceeds a predetermined number of times, the device of each of the above features performs a warning of predicting occurrence of an error.
The feature of.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a magnetic recording / reproducing apparatus according to an embodiment of the present invention, specifically, a magnetic disk drive will be described in detail with reference to the drawings. FIG. 1 is a diagram for explaining the configuration of the magnetic disk device according to the present embodiment, FIGS. 2 and 3 are diagrams for explaining the operation of the magnetic disk device,
4 and 5 are diagrams showing measured data of the head floating gap.

As shown in FIG. 1, the magnetic disk drive according to the present embodiment includes a magnetic disk 1 as a storage medium, a magnetic head 2 for recording and reproducing data on and from the magnetic disk 1, and A disk drive mechanism 10 for rotational drive, and a magnetic head 2
Drive mechanism 20 for moving radially above
And a control mechanism 30 for controlling these. In general, a plurality of disks 1 are usually provided in one magnetic disk device in an actual device, but in this specification, one disk will be described for convenience.

The magnetic head 2 is a thin-film inductive head (inductive head) 21 used as a recording head.
And a magnetoresistive head (MR head) 22 used for reproduction.

The disk drive mechanism 10 comprises a spindle motor 101 for driving a spindle at the center of rotation of the magnetic disk 1 and a motor driver 102 for driving the motor 101.
Is driven to rotate by supplying a drive current to the spindle motor 101 under the control of the CPU 306 of the control mechanism 30.

The head drive mechanism 20 includes a carriage 201 that rotates while supporting the thin film induction type head 21 and the MR head 22 at one end, a voice coil motor (VCM) 202 that rotates the carriage 201, Voice coil motor driver (VC
M driver) 203.

Further, the control mechanism 30 includes the thin film induction type head 2
1 and a read / write IC 301 for recording and reproducing data with the MR head 22, and a read / write channel 302 for switching between the magnetic head 21 and the MR head 22 and the like.
A read / write circuit 303 for recording and reproducing data with the magnetic head 2, and a servo data detecting circuit 304 for detecting a head position based on servo data (position information) on a magnetic disk reproduced by the MR head 22.
A servo control circuit 305 for controlling the positioning servo of the magnetic head 2 based on the servo data; and a memory 307 for storing various parameters and the like for the magnetic head.
And

The magnetic disk drive configured as above is
Under the control of the CPU 306, the VCM 202 drives the carriage 201 to rotate via the servo control circuit 305 and the like, thereby positioning the magnetic head 2 and the MR head 22 on the target track on the magnetic disk 1.
Read / write IC for read signal from R head 22
The read / write channel 302 transmits the data to the read / write channel 302 for equalization, and sends the data reproduction signal of the equalized read signal to the read / write circuit 303 to demodulate the read data.

Next, the present apparatus comprises a servo data detecting circuit 30.
4 to detect track information and off-track information from the servo data and output them to the CPU 306.
Reference numeral 06 sends a position control signal to the VCM driver 203 based on the track information and the like, and controls the positioning of the magnetic 2 and the MR head 22 using the VCM 202. The read / write circuit 303, the servo data examination circuit 3
04, various parameters of the servo control circuit 305 are CP
All the settings are possible by U306, for example,
In the read / write circuit 303, various reproduction parameters relating to the data recording system and the reproduction system are set in advance for each head from the equalized read signal. The values of these various reproduction parameters are stored in the memory 307 by the CPU 306.
The setting method is described later.

The read / write IC 301 of the magnetic disk device according to the present embodiment performs stable reproduction of data to be decoded based on a time-series change in signal amplitude by a maximum likelihood decoding method. General data reproduction parameters used when equalizing a read reproduction signal include an equalizer coefficient of a waveform equalizer, and particularly, a tap coefficient of a transversal equalizer. For example, tap 0, tap ± 1, tap ± 2
... and so on. Other examples of this setting include an offset amount of the AD converter and a write pre-compensation (WPC) amount.

Next, a method of setting an initial value of an equalizer coefficient for setting the various parameters will be described with reference to a flowchart shown in FIG. This setting method is first C
The PU 306 controls the servo control circuit 306 to seek and position the head 2 on a predetermined track (step 4).
01, 402), and then read /
A default value (initial setting value) of an equalizer coefficient is set to the write circuit 303 to demodulate a signal (step 403).

Next, the CPU 306 uses the read / write circuit 303 to read the data by setting the default value or to read the data (track) by the write / read.
(Step 404), it is determined from the result whether or not the equalizer coefficient is in an optimal state (step 405). If it is determined that the equalizer coefficient is not in an optimal state (No in step 405), Then, the equalizer coefficients are shifted and set (step 406), and the same operation is repeated to obtain an optimum state. The optimum value is defined as an error rate of R / W data within a predetermined margin value required for the apparatus, for example, performing a read / write operation 10 times, so that a read waveform is a predetermined attenuation / amplification / The determination is made based on whether the phase shift is within the range of the margin or whether the written data has been correctly reproduced.

The CPU 306 stores the parameter values (coefficients) in this optimum state as initial values in the memory 307 (Yes in Step 405, 407), and performs these series of operations for all coefficients and for all heads. And the zone are optimized (step 409). With the above operation, the CPU 306 obtains and stores the optimized initial value of the equalizer coefficient.

Next, a process corresponding to a temporal change when a predetermined operation time has elapsed after the operation of the apparatus will be described with reference to the flowchart of FIG. First, the CPU 306 controls the servo control circuit 306 to seek the head 2 to a predetermined track to perform positioning (steps 501 and 50).
2), an initial value of an equalizer coefficient for demodulating a signal from the memory 307 to the read / write circuit 303 (initial value optimized in the flow of FIG. 2) is set (step 50).
3). The read / write circuit 303 measures the error rate at that location by reading or writing / reading the data based on the initial value (step 504), and from this result, the CPU 306 determines that the equalizer coefficient is optimal in the current operating condition of the apparatus. It is determined whether the state is the state, specifically, whether the error rate of the R / W data is within the predetermined margin value required for the above-described device (step 505), and when it is determined that the state is not the optimum state. In (No in Step 505), the equalizer coefficient is set shifted (Step 506), and the same operation is repeated to find a coefficient in an optimum state, and each coefficient at this time is stored in the memory 307 as a new coefficient ( Y in step 505
es, step 507). The change of the equalizer coefficient is performed by, for example, assigning the tap coefficient to tap 0, tap ± 1, tap ± 2, or the like.

Next, the CPU 306 compares the re-detected new coefficient with the initial value coefficient to determine a coefficient variation (step 508), and determines the allowable variation set in advance for each coefficient. It is determined whether or not it exceeds (step 509). If the variation does not exceed the allowable amount (No in step 509), the same operation is repeated to find the optimum state of the coefficient in the current operation state, and the allowable operation is repeated. If it exceeds the allowable range (Yes in step 509), the variation of the coefficient is stored in the memory 307 (step 510). The determination as to whether or not the variation of the coefficient exceeds an allowable variation previously set for each coefficient is made by, for example, ± 2 compared to the initial set value set in the flow of FIG. Depending on the upper position (a head number to be described later), it is conceivable to use a case where the value fluctuates by ± 3 or more as a reference.

Further, the CPU 306 determines whether or not the history of the past fluctuation amount exceeds the predetermined criterion for the same coefficient (step 511), and when it does not exceed the criterion (No in step 511). , The same operation is repeated, and when the judgment criterion is exceeded (Yes in step 511), an error occurrence prediction warning is issued for the head and the zone (step 51).
2). This error occurrence prediction warning is not limited to the case where the judgment criterion is exceeded once in step 511, but the history of the past variation amount for the same coefficient is previously determined a predetermined number of times or more, for example, twice or more in 10 error rate measurements. If the set criterion is exceeded, an expected error occurrence warning may be issued. Incidentally, it is determined whether or not the history of the past fluctuation amount exceeds a predetermined criterion by, for example, determining whether or not the tap coefficient has changed by ± 2 or more compared to the previous set value, and comparing with the initial set value. It is conceivable to use the case where the value fluctuates by ± 3 or more as a reference.

Next, the CPU 306 performs some process such as a zone replacement process for moving the data of the zone to another position or a head replacement process for moving the data of the zone to another head, for the head and the zone. A process is performed to prevent it from occurring (step 513).

As described above, in the magnetic disk drive according to the present embodiment, the equalizer coefficient for setting various parameters is set to the initial value and set to an optimum state according to the flow shown in FIG. 2, and then the apparatus is operated. Reset various parameters in accordance with the flow shown in FIG. 3 in order to cope with a change over time when a predetermined time has passed since then, and when the fluctuation value of the equalizer coefficient exceeds a predetermined margin, issue an error occurrence prediction warning Accordingly, it is possible to prevent a failure due to a change with time.

Next, with reference to the graphs of FIGS. 4 and 5, an example of an experimental result of a change amount of the tap coefficient of the equalizer performed by actually reducing the head floating gap will be described.

FIGS. 4 and 5 show the measurement results under the outer circumference condition and the inner circumference condition of the apparatus, respectively. The horizontal axis shows the head numbers measured in the actual apparatus, and the vertical axis shows the transformer. It is a result of taking tap ± 1 of the tap coefficient of the versal equalizer as an example.

The set values indicated by (a) in FIGS. 4 and 5 show the tap coefficients when the equalizer coefficient is set under the normal pressure environment, and FIG.
This is the tap coefficient when the equalizer coefficient is set under a considerable environment, that is, in a state where the head floating gap is narrowed.

As is apparent from the experimental results, the equalizer coefficient in the state where the head floating gap is narrowed is smaller than that in the normal state under both the outer circumference and the inner circumference of the magnetic disk. Figure 3 of
It can be seen that a decrease in the head flying height can be detected by using the decrease in the equalizer coefficient value based on the result of the adjustment of the equalizer coefficient at the time of the change described with reference to FIG.

Therefore, by monitoring the amount of change in the tap coefficient of the equalizer over time using the above-described embodiment,
It is possible to accurately measure a change in the head floating gap, and prevent a failure from occurring.

In particular, in the conventional method of monitoring the change over time of the read / reproduced signal waveform itself, the detection accuracy is low and there is a problem in the credibility of the fault determination. Thus, since the failure sign is detected based on the more sensitive coefficient of the transversal equalizer, the detection accuracy is high and the reliability of the failure determination can be improved.

In the prior art, since the coefficient is only automatically adjusted with respect to the environmental change and the aging change of the apparatus, when the flying height of the head is gradually reduced, the resolution of the reproduced signal is rather improved, and the head and the head are improved. Although it was difficult to detect a sign of contact between disks, according to the present embodiment, recording and reproduction of data including contact between the head and the disk becomes impossible by using history information of coefficient values. Occurrence of a situation can be prevented.

[0036]

As described above, the magnetic recording / reproducing apparatus according to the present invention uses a partial response maximum likelihood decoding system as a signal processing system, and when a failure corresponding to a temporal change of the apparatus is prevented, the apparatus is operated during operation. Monitoring the change over time of the equalizer coefficient, and when the data reproduction parameter value at the time of decoding, specifically, when the fluctuation amount of the equalizer coefficient value of the waveform equalizer exceeds a preset value or exceeds a predetermined number of times By giving a warning to predict the occurrence of an error, a change in the head floating gap can be measured with high accuracy, and a failure can be prevented before it occurs.

[Brief description of the drawings]

FIG. 1 is an exemplary view for explaining the configuration of a magnetic disk drive according to an embodiment of the present invention;

FIG. 2 is an exemplary view for explaining an initial setting operation of a reproduction parameter of a waveform equalization circuit in the magnetic disk device according to the embodiment.

FIG. 3 is an exemplary view for explaining a setting operation when a reproduction parameter of the waveform equalization circuit in the magnetic disk device according to the embodiment changes over time.

FIG. 4 is a diagram showing actually measured data of a floating gap on the outer periphery of a disk of a head.

FIG. 5 is a view showing actually measured data of a floating gap on the inner periphery of a head disk.

[Explanation of symbols]

1: magnetic disk, 2: magnetic head, 10: disk drive mechanism, 101: spindle motor, 102: motor driver, 20: head moving mechanism, 30: control mechanism, 3
01: read / write IC, 302: read / write channel, 303: read / write circuit, 304: servo data detection circuit, 305: servo control circuit, 306: C
PU, 307: memory.

Claims (5)

[Claims] 1. A spindle motor for driving a magnetic disk to rotate, a magnetic head for recording and reproducing data recorded on the magnetic disk, and a magnetic head supported via a carriage and rotating on an arbitrary track on the magnetic disk. A voice coil motor that performs dynamic positioning, and a read / write that decodes data read by the magnetic head based on a time-series change in signal amplitude by a maximum likelihood decoding method, and sets a data reproduction parameter value when performing the decoding. A write circuit; and a memory for recording the parameter value, a default value of the parameter is initially set in a read / write circuit to decode data from the magnetic disk, and an error rate of the decoded data falls within a predetermined range. If the parameter value does not fall within the range, the parameter value may be set to a parameter value such that the error rate falls within a predetermined range. In the magnetic recording / reproducing apparatus that records data in the memory, it is possible to monitor a change over time of the parameter value and detect that a variation amount of the parameter value exceeds a preset value or exceeds a predetermined number of times. Characteristic magnetic recording / reproducing device. 2. The method according to claim 1, wherein the read / write circuit includes a waveform equalizer for equalizing a data reproduction waveform from the magnetic disk, and a parameter value of the data reproduction is an equalizer coefficient value of the waveform equalizer. The magnetic recording / reproducing apparatus according to claim 1, wherein 3. The read / write circuit includes a waveform equalizer for equalizing a data reproduction waveform from a magnetic disk, wherein a parameter value for the data reproduction is an equalizer coefficient value of the waveform equalizer. 2. The magnetic recording / reproducing apparatus according to claim 1, wherein it is detected that the amount of change of the value exceeds a preset value two or more times out of ten times. 4. A head replacement process or a head replacement process when a variation amount of the parameter value exceeds a preset value or exceeds a predetermined number of times. 3. The magnetic recording and reproducing apparatus according to 3. 5. An alarm for predicting occurrence of an error when an amount of change in the parameter value exceeds a preset value or exceeds a predetermined number of times.
Or the magnetic recording / reproducing apparatus according to 3 or 4.