JP3532112B2 - Fixed magnetic recording device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixed magnetic recording device.
About the.

[0002]

2. Description of the Related Art In recent years, most fixed magnetic recording devices (HDD: hard disk drives) have adopted MR (magnetoresistive) heads in response to the demand for recording density which is increasing year by year.
The MR head is a reproducing system utilizing a so-called magnetoresistive effect, the electric resistance of which changes with an external magnetic field.
Some HDDs use an MR / inductive composite type head in which an MR head and a thin film head are integrally combined. This MR / inductive composite type head uses a thin film head to write data,
Data is read by using an MR head arranged adjacent to the thin film head. Therefore, although the MR head is read-only, the read output obtained is larger than that of the thin film head, and the read output does not depend on the peripheral speed of the magnetic disk. Therefore, the read track width is made smaller than that of the write thin film head. By setting this, there is a feature that the influence from the adjacent track at the time of reading can be reduced. Therefore, it is widely used as a head for the current HDD. Furthermore, in the future, GM with improved sensitivity of MR element
R (giant magnetoresistive) heads are also being put to practical use.

However, the MR head requires a bias current due to its operating principle, and there is a problem that the reproduced signal waveform is distorted unless the bias current is optimally controlled. This occurs because either the positive or negative of the reproduced signal waveform is saturated due to the shift of the bias point due to the bias current, and the reproduced signal waveform in this case becomes positive and negative and becomes asymmetric.

As described above, in order to optimally control the bias current of the MR head, it is necessary to solve the following three problems. The first problem is variations in head resistance value due to variations in MR head dimensions. MR
Although head dimensions are becoming smaller and smaller, tolerances for dimensional variations are not improving as rapidly as the dimensions themselves. According to a recent device design example, the variation over MR stripe height allows a +/- 33% change, with a 2: 1 ratio for the highest to lowest ratio. Furthermore, the variation of the width (length in the direction of current) of the MR stripe is +
/ -20%. MR stripe thickness tolerance is +
/ -10%. If these are considered independent variations, the overall variation in the resistance of the device is about +/-.
40%, or a high / low ratio of 2.33: 1.

When the head resistance values of a plurality of MR heads (for example, 80 heads) are actually measured, as shown in FIG.
It can be seen that the head resistance value varies. The horizontal axis represents the head resistance value, and the vertical axis represents the number. The distribution of variations in the head resistance value is a normal distribution centered on the design value, but the resistance values of the sensor parts are different for each MR head.

Problems due to large dimensional variations can affect the large differences in power consumption when there are different heads in a single device. Furthermore, when the cross section (MR stripe height x thickness) with respect to the current changes greatly, the current density also changes in conjunction. Product life is inversely related to the cube of current density.
Since the conventional biasing method uses a constant DC current for all heads, low stripe height and thin layer thickness result in high resistance and high current density. The resulting power consumption is much higher and the temperature rise is much higher than with high stripes.
That is, heat is generated. Therefore, the temperature and current density are
This can cause the average lifetime to be much shorter for MR elements with low stripe height and thinner than those for high and thick stripe elements.

Another possibility is that all elements that increase resistance also increase the signal level. Therefore, the best signal-to-noise ratio is to choose the head with the highest resistance. Thus, low stripe heights, thin layers, and wide stripes can produce good signal-to-noise ratios, while high, thick, narrow stripes produce poor signal-to-noise ratios. Occurs. Therefore, a constant bias current must be a compromise between good signal and short lifetime.

A change in the output when the bias current value is changed for a plurality of MR heads (for example, four) has a waveform as shown in FIG. 18, and the bias when the output value becomes the maximum is obtained. Since the current is the optimum bias current when reading, it can be seen that the optimum bias current characteristics when reading differ from head to head. Two
The second problem is that a good electronic signal to noise ratio depends on the design of the preamplifier circuit. The design of the preamplifier is due to the reduced power supply voltage to the available preamplifier circuit and the reduced target power consumption.
It has big restrictions. Current designs typically have a single +5 volt power supply (+/- 5%). Variations in head resistance also limit the value of operable bias current due to the voltage drop across the head and leads. If an excessively large current flows through the high resistance head, the preamplifier stage may saturate and distort its signal, resulting in poor performance.

The third problem is a gradual increase in resistance (GRIP) of the leads in the MR head. If the MR head resistance increases by several ohms over the lifetime of the fixed magnetic recording device, the effect on the performance becomes larger than expected. Therefore, one with too little design margin in manufacturing can induce pre-amplifier saturation and subsequent large performance loss as resistance increases thereafter in the life of the product.

In order to solve the above three problems, as a conventional HDD, the one described in JP-A-7-201105 is generally known. This HD
As shown in FIG. 19, D is a plurality (for example, four) of MR heads 31a to 31d, a preamplifier 32, and a GEM.
(Generalized Error Measurement) 33, a head / disk assembly controller 34, and a microprocessor 35. This HDD stores the optimum bias current value of each head on the disk surface at the time of manufacture, and when the power is turned on, these values are transferred to a random access memory and the random access is executed when each head switching command is executed. The bias current is applied to an active MR head as a memory, the MR head is measured, the bias current is reoptimized and updated by the GEM 33, and the updated bias current is applied to the MR head.

The measurement of the MR head is realized by the circuit shown in FIG. For example, when measuring the MR head 31a, only the switches 36a and 37a are connected in the conductive state, the bias current is supplied from the feedback control circuit 40, and the measured value Vcap of the voltage of the capacitor 39 is measured.
Then, the head resistance value Rmr of the MR head is calculated from the known bias current value Ib. This MR head resistance value Rmr
Is calculated based on the following (Equation 1).

Rmr = (Vcap-Vbe) / Ib (Equation 1) An optimum current value is determined based on the calculated head resistance value Rmr of the MR head. Thus, in the conventional HDD,
MR recorded on the disc surface at factory shipment each time the power is turned on
The bias current value is optimized based on the head resistance value of the head.

[0013]

However, in the conventional fixed magnetic recording apparatus, when the power is turned on, the bias current value is optimized based on the head resistance value of the MR head recorded on the disk surface at factory shipment. It is not possible to deal with head characteristics that change from moment to moment over time. Therefore, when the MR head resistance value changes, the bias current value determined to be optimum at the time of factory shipment is used for a lifetime, or the bias current value determined to be optimum in the previous measurement is set to the next time. It will be adopted until the time of periodic reoptimization update. This bias current value is not necessarily guaranteed to be the optimum value for the current head, and the head output characteristics may deteriorate and the error rate may deteriorate. Generally, the life of the head is inversely proportional to the cube of the current density, so that there is a problem that the average life will be shortened if an excessive bias current is applied.

Further, the judgment of the life due to the resistance change is only made by comparison with the guaranteed number of times of activation, and the presence or absence of the actual resistance change cannot be detected, so that there is a problem that the life cannot be accurately judged. By the way, a fixed magnetic recording device using an amplitude detection type reproduction system such as a partial response in which the amplitude value of the read signal is directly used for processing a signal read from the magnetic disk is becoming mainstream.
When an MR head is used in such a fixed magnetic recording apparatus, the reproduced signal from the MR head is distorted, and the absolute values of the waveforms that should have the same level of positive and negative with respect to the baseline are different. However, a problem arises that the asymmetry of the amplitude width of the detected reproduction signal becomes large. The error of the amplitude width deteriorates the error rate of the reproduction signal read by the MR head, resulting in a problem that the reliability of the entire system is impaired. Further, in the fixed magnetic recording device using the conventional peak detection type reproducing system, when the same distortion occurs in the reproduction signal when the MR head is used, the differential value at the peak of the reproduction signal waveform is Since it becomes smaller on the saturated side, the influence of noise also becomes large, and the error rate of the reproduction signal is similarly deteriorated.

In the fixed magnetic recording apparatus using the MR head for reading data and adopting the amplitude detection type reproducing method such as partial response as described above, unless the bias current of the MR head is optimally adjusted, the reproduced signal Despite the problem that the error rate deteriorates, there is a drawback that a method for optimally adjusting the bias current of the MR head has not been established. Even in the fixed magnetic recording apparatus using the MR head and employing the peak detection type reproducing method, unless the bias current of the MR head is adjusted optimally, the influence of noise becomes large and the error rate of the reproduced signal deteriorates. Therefore, there are similar drawbacks.

According to the present invention, the bias current of the MR head can be optimized as needed during the operation of the fixed magnetic recording device.
An object of the present invention is to provide a bias current control method for a magnetoresistive head, a fixed magnetic recording device, and a magnetic disk thereof, which suppresses asymmetrical distortion due to saturation of a reproduction signal waveform from the MR head and reduces an error rate during data reading. .

[0017]

According to a first aspect of the present invention, there is provided a magnetic disk for reading data recorded on a magnetic disk.
In a fixed magnetic recording device having a plurality of air resistance heads,
Temperature gradient of the head resistance value of each of the magnetoresistive heads
And memorize the head resistance value at the specified constant temperature
The storage means and the magnetoresistive head are in a standby state
And a meter for measuring the head resistance value of the magnetoresistive head
Measuring means and the head resistance value measured by the measuring means
And the head resistance value at the constant temperature and the head resistance value
The temperature gradient causes the temperature of each magnetoresistive head to be
Calculate the temperature that is projected against the calculated temperature.
The temperature of the magnetoresistive head shown is more than the constant temperature
When the value is more than the value, the magnetoresistive head has deteriorated characteristics.
Fixed magnetic recording provided with a prediction means for predicting that
This is a device for monitoring the secular change of the magnetoresistive head.
Can predict the life of the fixed magnetic recording device.
You can The invention according to claim 2 of the present invention, prior to
The predictive means predicts the deterioration of the characteristics of the magnetoresistive head.
2. The fixed magnet according to claim 1, further comprising warning means for warning
It is used as a recording device and issues a warning to the user.
You can

[0018]

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The fixed magnetic recording apparatus of the present invention will be described below.
Will be described with reference to specific embodiments the.

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

(First Embodiment) As shown in FIG. 1, the fixed magnetic recording apparatus according to the first embodiment of the present invention, each time the MR (magnetoresistive) head of the head forming section 1 accesses the magnetic disk 2. The optimization measuring means 10 for executing the measurement for optimizing the bias current value of the MR head and the optimization measuring means 10 are controlled, and the bias current value of the MR head is updated to the measured optimum bias current value. And a microcomputer 8 as processing means for outputting an instruction to supply the optimum bias current updated and stored to the MR head.

The optimization measuring means 10 comprises a magnetic disk 2, a preamplifier 3, a data channel 4, a GEM 5, a hard disk controller 6 and a buffer 7. As shown in FIG. 2, the magnetic disk 2 usually has a plurality of circumferential tracks from the inner circumference to the outer circumference, and each track has a plurality of servo areas A and data areas B.
When the MR head accesses the data region B to read or write data, the position information written in the servo region A is always read and confirmed, and then the desired position is accessed. In order to
The magnetic disk 2 of the first embodiment is provided with a measurement pattern area C (area between the servo area A and the first data which is the first data of the data area B) immediately after all the servo areas A. A measurement pattern for measuring the signal-to-noise ratio for optimizing the bias current value is formed in the measurement pattern area C. Whichever data area B is accessed, this measurement pattern area C is always accessed and passes the measurement pattern before reading or writing the data in the data area B. As shown in FIG. 3, a plurality of identical measurement patterns are formed on every track. In the measurement pattern region C, as shown in FIG. 4, a signal having a certain periodicity is written and recorded at the time of factory shipment. The signal having the constant periodicity is a signal indicated as precode data in a pattern having a period of 1 to 127T (T is a time determined by the performance of the MR head, for example, 5 ns). is there.

The head structure 1 has an MR head and is connected to each line leading to the preamplifier 3. The output of the preamplifier 3 is supplied to the data channel 4. The addressed MR head is connected to a bias current source (not shown) by setting the respective switches shown in FIG. The GEM 5 has a general-purpose error measurement function and performs signal-to-noise ratio measurement, and is realized by connecting a measurement test system data storage device and a recovery system such as a conventional digital oscilloscope and logic analyzer. The test system is designed so that it can be executed onboard by the fixed magnetic recording device itself.

The buffer 7 contains optimum bias current values of the respective MR heads at the time of factory shipment, and 1 to 127 shown in FIG.
An ideal signal waveform obtained by sampling and standardizing precoded data having T as one cycle is stored in advance.
Here, the operation of updating the bias current value of the MR head to the optimum bias current value in this fixed magnetic recording device will be described.

The hard disk controller 6 sends an instruction to access the magnetic disk 2 to the microcomputer 8
Then, the head structure 1 having the MR head is controlled so as to access a desired position of the magnetic disk 2 rotating at high speed. When the MR head accesses the measurement pattern area C after accessing the desired servo area A of the magnetic disk 2, a current source (not shown) for supplying a bias current to the MR head is set to, for example, 7 mA and supplied to the MR head. , GEM5 compares the level difference between the actual reproduced waveform as shown in FIG. 5 in which the measurement pattern is read and the standardized ideal signal waveform stored in the buffer 7 for one cycle (1 to 127T). Analyze to calculate signal to noise ratio. Next, the current source is set to 8 mA, and the signal-to-noise ratio is calculated as described above. In this way, the current source
The signal-to-noise ratio is calculated in the same manner as described above until it becomes 1 mA. The change in the signal-to-noise ratio with respect to the change in the bias current has a waveform having a peak, as shown in FIG.

Specifically, the signal-to-noise ratio for each actually measured bias current value is 25 dB when the current source is 7 mA, 26 dB when the current source is 8 mA, and 9 mA when the current source is 9 mA. Signal-to-noise ratio of 26.8
dB, signal-to-noise ratio of 27 dB when the current source is 10 mA,
If the signal-to-noise ratio when the current source is 11 mA is 26.9 dB and the waveform is a, the bias current value when the signal-to-noise ratio is the largest is the optimum bias current value. 8 determines that 10 mA is the optimum bias current value.

In this MR head, the bias current is measured in the range of 7 mA to 11 mA.
Stores the optimum bias current at the time of factory shipment of this MR head, or at least the optimum bias current at the time of the previous measurement when the measurement was performed before, and here, the optimum bias current for the buffer 7 is stored. Since the bias current value is stored as 9 mA, centering around 9 mA, for example, ± 2
The actual reproduced waveform is measured within the mA range.

The microcomputer 8 stores the optimum bias current value (9 mA) stored in the buffer 7.
Is updated and recorded to a new optimum bias current value (10 mA). The microcomputer 8 uses the newly recorded new optimum bias current value (10 mA) for MR.
Instruct to feed to the head.

With this configuration, the bias current of the MR head can be optimized during the operation of the fixed magnetic recording apparatus according to the operation of the MR head, and the characteristics of the MR head during operation can be changed with time. It is possible to maintain the optimum bias current even when it changes.
Asymmetrical distortion due to saturation of the reproduced signal waveform from the MR head can be suppressed, the error rate at the time of data reading can be reduced, and an optimum bias current is supplied to the MR head, so that a bias current more than necessary is flowed. It is possible to prevent this, and to prevent the average life from being shortened due to overcurrent.

In the first embodiment, the microcomputer 8 is provided with a control routine for operating the fixed magnetic recording apparatus. However, each time the MR head accesses the magnetic disk 2, the control routine of the MR head is changed. A first step of optimizing a bias current value; a second step of updating the bias current value of the MR head to the measured optimum bias current value;
When the control routine constituted by the third step for supplying the updated and stored optimum bias current to the head is recorded in the disk wear (DISKWARE) for storing the program of the magnetic disk 2 or in the buffer 7. Even if it does, it has the same effect.

(Second Embodiment) As shown in FIG. 7, the fixed magnetic recording apparatus according to the second embodiment of the present invention is replaced with an MR (magnetic resistance) instead of the optimizing measuring means 10 of the first embodiment. ) When the head is in the operation waiting state, the optimization measuring means 11 for performing the measurement for optimizing the bias current value of the MR head is provided, and the magnetic disk 12 is formed with the measurement pattern area C of the first embodiment. It also has no measurement pattern.

The optimization measuring means 11 is composed of a plurality (for example, two) of preamplifiers 3a and 3b, a data channel 4, a GEM 13, a hard disk controller 14 and a buffer 15. The head structure portions 1a and 1b having the MR head include the preamplifiers 3a and 3b.
It is also configured to be connectable to. Preamplifier 3
The outputs of a and 3b are supplied to the data channel 4.
The addressed MR head is connected to a current source (not shown) that supplies a bias current by setting the respective switches shown in FIG.

The GEM 13 has a general-purpose error measurement function and M
The R head resistance value Rmr is measured, and the test system, which has been realized by connecting the measurement test system data storage device and the recovery system such as the conventional digital oscilloscope and logic analyzer, to the on-board. The fixed magnetic recording apparatus is designed so that it can be executed by itself.

The buffer 15 stores in advance the optimum bias current value of each MR head at the time of factory shipment. MR
The optimum head bias current is set, for example, as a function of MR head resistance. Here, the operation of updating the bias current value of the MR head to the optimum bias current value in this fixed magnetic recording device will be described.

When normal data is being sent from the head structure unit 1a through the preamplifier 3a and the head structure unit 1b is in an operation waiting state, the hard disk controller 14
Receives an instruction from the microcomputer 8 and controls the preamplifier 3b to be connected to the head structure 1b.
The measurement of the MR head is performed by measuring the BHV (Buffered H) of the preamplifiers 3a and 3b arranged near the head structures 1a and 1b.
ead Voltage Monitor) terminal, voltage value V between heads
detect mr.

The hard disk controller 14 calculates the MR head resistance value Rmr based on the following (formula 2). However, the current value Ib from the current source supplied to the MR head is known as a fixed current value. Rmr = Vmr / Ib (Equation 2) In the hard disk controller 14, the optimum bias current value Ib corresponding to the head resistance value Rmr of the MR head is statistically obtained according to the corresponding characteristic shown in FIG. The bias current value Ib is determined. The signal from the BHV terminal is an analog output, and the hard disk controller 14
Convert an analog signal into a digital signal with.

Specifically, the voltage value Vm detected by the BHV terminal when the current value I from the current source is set to 9 mA.
Assuming that r is 0.3 V, the head resistance value Rmr of the MR head is calculated to be about 33.3Ω based on the above-mentioned (Equation 2), and the head resistance value Rmr of the MR head (about 3
3.3Ω) is in the range of 30 to 35Ω, the optimum bias current value Ib is set to 9.
Determine to 5 mA. This optimum bias current value (9.5
mA is, for example, 4-bit serial data (001
0) is stored in the buffer 15.

4-bit serial data (0010) is sent to and set in the head structure portion 1b, and the optimum bias current value (9.5 mA) is MR in a normal operating state.
Supplied to the head. When the head structure portion 1b is in a normal operation state and the head structure portion 1a is in an operation standby state,
Upon receiving an instruction from the microcomputer 8, the hard disk controller 14 controls the preamplifier 3b to be connected to the head structure 1b, and optimizes the bias current of the MR head of the head structure 1a as described above. .

Incidentally, in the current fixed magnetic recording apparatus, the system side logically manages the sector and reads / writes for each sector. However, which MR head is physically accessed to which sector is determined by the design of the drive side, so the user side does not need to pay attention to this.
At present, the time required for head switching is often shorter than the time required for track seek. Therefore, when writing to a certain sector and then moving to the next sector, head switching is often given priority. That is, the MR heads are frequently switched.

With this configuration, the bias current of the MR head can be optimized in the operation waiting state of the MR head, and even if the MR head characteristic during operation changes momentarily with time, it is optimal. Bias current can be maintained, asymmetrical distortion due to saturation of the reproduction signal waveform from the MR head can be suppressed, the error rate at the time of data reading can be reduced, and the optimum bias current for the MR head can be obtained. Since it is supplied, it is possible to prevent the bias current from flowing more than necessary, and it is possible to prevent the average life from being shortened by the overcurrent.

Further, the magnetic disk 12 can be made unnecessary with the measurement pattern area C for forming the measurement pattern as in the first embodiment. In the second embodiment, the microcomputer 8 is provided with a control routine for operating the fixed magnetic recording device. However, when the MR head enters the operation waiting state, the M
A first step of optimizing the bias current value of the R head; a second step of updating the bias current value of the MR head to the measured optimum bias current value; When the control routine configured by the third step of supplying the updated and stored optimum bias current is recorded in the diskware (DISKWARE) for storing the program of the magnetic disk 12 or in the buffer 15. However, it has the same effect.

In the second embodiment, a plurality of preamplifiers are provided. However, even when the preamplifier is a single preamplifier, no MR head accesses the magnetic disk 12 while the MR is in an operation waiting state. An optimum bias current value can be set by measuring the head resistance value of the head. (Third Embodiment) As shown in FIG. 9, the fixed magnetic recording apparatus of the third embodiment of the present invention stores the temperature characteristic of the head resistance value of the MR head in the buffer 15 of the second embodiment. The buffer 16 is used, and the microcomputer 8 of the second embodiment described above is replaced with a microcomputer 17 to which a calculation function for calculating the temperature based on the measured head resistance value is added.

The buffer 16 stores the temperature characteristics of the head resistance value of each MR head. Although the head resistance value of the MR head differs depending on the design of the MR element, the change of the head resistance value due to the temperature change of a plurality (for example, 6) of MR heads shows that the temperature dependence characteristic of the head resistance value is As shown in FIG. 10, it can be seen that the temperature changes almost linearly with respect to temperature, and linear approximation is possible. The temperature gradient of the head resistance value is known at the time of design.

For example, the temperature gradient of a certain model is 0.15Ω
/ ° C. It is assumed that the head resistance value is 25Ω during the shipping inspection process at a constant temperature of 20 ° C. The head resistance value at a known temperature at the time of shipment is stored in the buffer 16. The relationship between the head resistance value and the temperature is as shown in FIG. Here, the operation of measuring the head resistance value of the MR head and controlling the temperature in this fixed magnetic recording device will be described.

Similarly to the second embodiment, when the MR head of the head structure portion 1b is in the operation waiting state, the hard disk controller 14 causes the microcomputer 17 to operate.
In response to an instruction from the preamplifier 3b, the head structure unit 1b
The voltage value Vmr between the heads is measured at the BHV terminal of the preamplifier 3b, and the current value Ib from the current source (not shown) supplied to the MR head is known as a fixed current value. Therefore, based on (Equation 2) above, M
The R head resistance value Rmr is calculated.

The microcomputer 17 calculates the temperature based on the measured head resistance value. For example, if the measured head resistance value is 26.5Ω, the microcomputer 17 calculates that the temperature is 30 ° C. based on the temperature dependence characteristic of the head resistance value shown in FIG. 11.

Further, when the MR head of the head structure portion 1a instead of the head structure portion 1b is in the operation waiting state, the hard disk controller 14 controls the preamplifier 3a to be connected to the head structure portion 1a, and the same as above. Then, the head resistance value is measured to calculate the temperature. Since the MR heads are switched frequently, the head resistance value of the MR head is frequently measured and the temperature is calculated.

With this configuration, the temperature can be controlled by monitoring the head resistance value. Although the guaranteed operating temperature of the hard disk differs depending on the design, for example, when the guaranteed operating temperature is from 0 ° C. to 50 ° C., the head resistance value is 22Ω to 29.5Ω due to the temperature dependence of the head resistance value shown in FIG. It can be inferred that the range up to is within the compensation range. If the head resistance value is out of the range of 22Ω to 29.5Ω, it can be inferred that the ambient temperature is out of the guaranteed range. In addition, if you continue to use this device at ambient temperature that is out of this guarantee range,
In the worst case, there is a risk that the device and data will be destroyed. Therefore, if a warning means for issuing a warning to the user is connected to the interface 8 and the measured head resistance value is outside the range of 22Ω to 29.5Ω, a warning signal is issued to the user through the interface 8 to notify the user. A warning can be issued, and the destruction of this device and data can be prevented.

In the third embodiment, the microcomputer 17 is provided with a control routine for operating the fixed magnetic recording device, but the first routine stores the temperature characteristic of the head resistance value of the MR head. Steps, a second step of measuring a head resistance value of the MR head when the MR head is in an operation waiting state, and a third step of calculating a temperature based on the measured head resistance value. The control routine is executed by the diskware (DISKWAR) for storing the program of the magnetic disk 12.
Even when recorded in E), etc., it has the same effect.

(Fourth Embodiment) As shown in FIG. 12, a fixed magnetic recording apparatus according to the fourth embodiment of the present invention measures the heads of a plurality of MR heads obtained by measuring the microcomputer 17 of the third embodiment. The microcomputer 18 additionally has a function of calculating the temperature based on the resistance value and the temperature characteristic and predicting the degree of characteristic deterioration of the MR head based on the calculated temperature.

As in the third embodiment described above, when the MR head is in the operation waiting state, the head resistance value of the MR head is calculated and stored in the buffer 16, and the head resistance values of all MR heads are measured. Store the value. Further, the measured values obtained by measuring the head resistance values of a plurality of MR heads that require measurement may be stored. In general, these MR heads are constantly operating or waiting for operation.

The microcomputer 18 uses the buffer 1
The respective temperatures are calculated based on the measured head resistance values of the MR heads stored in No. 6. If there is an MR head that exhibits a temperature that is prominent with respect to the whole, it is predicted that this MR head has aged. With this configuration, the head resistance value or its change is stored in the buffer 16
It is possible to predict the secular change by storing it in the memory and constantly monitoring the fluctuation with respect to the latest value. Generally, the head resistance value largely changes even when the ambient temperature is constant, which means that the MR element is aged. However, it is difficult to determine whether the resistance change is due to the ambient temperature or the secular change by monitoring only a single head except when the resistance value is momentarily increased due to the thermal asperity (TA) phenomenon. Therefore, by using a plurality of MR heads, it is possible to estimate whether the change in the head resistance value is due to the ambient temperature or is permanent. For example, in a fixed magnetic recording device having four MR heads, when the head resistance values of all the four MR heads are changing, it is considered that the temperature is changing. When only the head resistance value of one MR head among the four MR heads changes, it is considered that this MR head characteristically changes from the factory shipment. As a result of design considerations, statistically acquire data on how much the head resistance value significantly affects performance.

For example, when the head resistance value fluctuates by 10% or more due to factors other than the temperature, it is considered that some kind of damage is given to the MR element. While constantly monitoring the secular change of the value, whether or not a change of 10% or more has occurred is constantly compared with the value before shipment. If the change exceeds 10%, the user data recorded on the medium may be lost or the device may be destroyed.

Therefore, warning means 19 for warning the user of the degree of characteristic deterioration is connected to the interface 8, and when the change exceeds 10%, a warning signal is issued to the warning means 19 through the interface 8 to warn the user. Can be issued, the user can be warned of the degree of characteristic deterioration, and the destruction of this device and data can be prevented.

(Fifth Embodiment) As shown in FIG. 13, a fixed magnetic recording apparatus according to a fifth embodiment of the present invention is provided with a bump 23 as a protrusion at a specific position of a magnetic disk 20, and an MR (magnetic A resistance means is provided with a monitoring means 21 for monitoring the fluctuation of the flying height of the MR head based on the fluctuation of the output when the head passes over the bump 23.

On the surface of the magnetic disk 20, as shown in FIG. 14, bumps 23 are formed of the same material as the magnetic disk 20. The diameter of the bottom surface of the bump 23 is, for example, 2.0 to 3.0 μm, and the height of the bump 23 is, for example, 0.1 to 0.15 μm. This bump 23 is
A plurality of magnetic disks 20 may be formed. A desired bump 23 is formed on the surface of the magnetic disk 20 by using the laser zone texture technique. The basic principle of the MR head is to detect and output a change in resistance value, but the thermal stability of the sensor part becomes important. In normal operation, when the MR portion touches an abnormal protrusion on the surface of the magnetic disk 20, the head resistance value instantly rises and output fluctuation occurs. Generally, this phenomenon is called thermal asperity (TA), and in designing a magnetic disk, this phenomenon is corrected by a circuit, and the smoothness of the magnetic disk is improved to improve the phenomenon.

In the thermal asperity phenomenon, if the bumps have the same degree of output fluctuation, the collision becomes more severe as the flying height becomes lower, and therefore the fluctuation becomes large. Here, the operation of measuring the output value of the MR head and preventing the crash in this fixed magnetic recording device will be described. When the preamplifier 3 receives an instruction from the microcomputer 22, each time the MR head of the head structure 1 passes over the bump 23 formed at a predetermined position of the disk 20, the head resistance value of the MR head is changed. It is observed that the output value of the MR head rises as it rises.

The monitoring means 21 stores in advance the amount of output fluctuation when the MR head passes over the bump 23 during manufacturing as an initial value. Upon receiving an instruction from the microcomputer 22, the output fluctuation amount is periodically measured, the measured value is compared with the initial value, and the change in the flying height is estimated,
Monitor the risk of crashes. Specifically, when the flying height is good, as shown in FIG.
The output fluctuation amount when passing over the above is, for example, about 100 mV, and the monitoring unit 21 stores in advance an output fluctuation amount of the MR head of 100 mV as an initial value. For example, the monitoring unit 21 sets a threshold value of 120 mV, which indicates that there is a risk of crash when there is a large variation of 20% or more and there is a risk of crash. When the output fluctuation amount is regularly measured and the flying height is decreased, the output fluctuation amount when passing over the bump 23 increases to about 170 mV as shown in FIG.
If the threshold value of 120 mV is exceeded, a warning signal is output to the warning means via the interface 8 to inform the user that there is a risk of crash.

With this configuration, it is possible to infer a change in the flying height of the MR head by monitoring the output fluctuation amount, and if the fluctuation amount exceeds a predetermined value, there is a risk that the user will crash in advance. Can warn you that
It is possible to prevent the destruction of this device and data. In the fifth embodiment, the microcomputer 22 is provided with a control routine for operating to control the fixed magnetic recording device. However, the output fluctuation amount when passing over the bump 23 of the MR head is measured. A control routine including a first step of storing, a second step of determining whether the stored output fluctuation amount exceeds a threshold value, and a third step of issuing a warning when the stored output fluctuation amount exceeds the threshold value. Is recorded in diskware (DISKWARE) for storing the program of the magnetic disk 20, the same effect can be obtained.

In the fifth embodiment, M during normal operation is
Although the output fluctuation amount of the R head is measured and stored, the same effect can be obtained even when the output fluctuation amount of the MR head in the operation waiting state is measured and stored. Further, in each of the above-described embodiments, the read-only head is the MR (magnetoresistive) head, but the same effect can be obtained even when the read-only head is a GMR (giant magnetoresistive) head.

[0070]

According to the fixed magnetic recording apparatus of the first aspect of the present invention, the data recorded on the magnetic disk is read.
In a fixed magnetic recording device having a plurality of magnetoresistive heads
The head resistance value of each of the multiple magnetoresistive heads.
Describes the head resistance value at the specified gradient and the specified constant temperature.
Memorizing storage means and the magnetoresistive head in an operation waiting state
Then, the head resistance value of the magnetoresistive head is measured.
Measuring means and a head measured by the measuring means
The resistance value and the head resistance value at the constant temperature and the head resistance value
With the temperature gradient of the resistance value,
The temperature was calculated, and it was projected with respect to the entire calculated temperature.
The temperature of the magnetoresistive head indicating the temperature is higher than the constant temperature.
If the magnetic resistance head exceeds a predetermined value,
The prediction means for predicting that the property has deteriorated has been provided.
Therefore, it is possible to monitor the aging of the magnetoresistive head.
The life of this fixed magnetic recording device can be predicted.
It

Further, the fixed magnet according to claim 2 of the present invention.
According to the recording device , the fixed magnetic recording according to claim 1 described above.
If the recording device is used, the predicting means causes
Due to the provision of warning means to warn that
Therefore, a warning can be issued to the user.

[0072]

[0073]

[0074]

[0075]

[0076]

[0077]

[0078]

[0079]

[0080]

[0081]

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a fixed magnetic recording device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a format of a recording surface of the magnetic disk of the first embodiment.

FIG. 3 is an explanatory diagram showing a measurement pattern area of the magnetic disk according to the first embodiment.

FIG. 4 is an explanatory diagram showing a measurement pattern in a measurement pattern area according to the first embodiment.

FIG. 5 is a reproduction waveform diagram when reproducing the measurement pattern area according to the first embodiment.

FIG. 6 is an explanatory diagram showing a change in signal-to-noise ratio with respect to a change in bias current according to the first embodiment.

FIG. 7 is a block diagram showing a configuration of a fixed magnetic recording device according to a second embodiment of the present invention.

FIG. 8 is a correspondence diagram showing an optimum bias current value according to a head resistance value according to the second embodiment.

FIG. 9 is a block diagram showing a configuration of a fixed magnetic recording device according to a third embodiment of the present invention.

FIG. 10 is a characteristic diagram showing the temperature dependence of the head resistance value according to the third embodiment.

FIG. 11 is a temperature correspondence diagram of the head resistance value of the third embodiment.

FIG. 12 is a block diagram showing a configuration of a fixed magnetic recording device according to a fourth embodiment of the present invention.

FIG. 13 is a block diagram showing a configuration of a fixed magnetic recording device according to a fifth embodiment of the present invention.

FIG. 14 is a schematic external view showing the shape of bumps according to the fifth embodiment.

FIG. 15 is a waveform chart showing the amount of output fluctuation due to the TA phenomenon in the favorable case of the fifth embodiment.

FIG. 16 is a waveform chart showing an output fluctuation amount due to the TA phenomenon in the abnormal case of the fifth embodiment.

FIG. 17 is a resistance value distribution chart showing variations in the head resistance value of a conventional MR head.

FIG. 18 is a waveform chart showing the bias current dependency of the conventional head output.

FIG. 19 is a block diagram showing the configuration of a conventional fixed magnetic recording device.

FIG. 20 is a block diagram showing a configuration of a main part for measuring a head resistance value of a conventional MR head.

[Explanation of symbols]

1 Head structure 1a, 1b Head structure section 2,12 magnetic disk 3 Preamplifier 3a, 3b preamplifier 4 data channels 5, 13 GEM 6, 14 Hard disk controller 7,15 buffer 8, 16 microcomputer 9 Interface 10, 11 Optimization measuring means 17, 18 Microcomputer 19 Warning means 20 magnetic disk 21 Monitoring means 22 Microcomputer 23 bump

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-6-295404 (JP, A) JP-A-9-180142 (JP, A) JP-A-11-195211 (JP, A) JP-A-10- 308001 (JP, A) JP 8-293165 (JP, A) JP 7-220257 (JP, A) JP 10-260089 (JP, A) JP 11-39839 (JP, A) JP-A-10-105909 (JP, A) JP-A-7-201005 (JP, A) JP-A-8-167121 (JP, A) JP-A-10-241333 (JP, A) International Publication 96/39697 ( WO, A1) International Publication 98/16918 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B 5/00-5/02 G11B 5/39

Claims (2)

(57) [Claims] 1. Reading data recorded on a magnetic disk
In a fixed magnetic recording device having a plurality of magnetoresistive heads
Te, the temperature gradient of the head resistance values of the magnetoresistive head
And memorize the head resistance value at the specified constant temperature
When the storage means and the magnetoresistive head are in an operation standby state, the magnetic
Measuring means for measuring the head resistance value of the air resistance head, and the head resistance value measured by the measuring means and the constant value.
Head resistance at temperature and temperature gradient of the head resistance
Calculate the temperature of each of the magnetoresistive heads by
Of the above-mentioned magnets, which shows a temperature that is prominent with respect to the entire calculated temperature of
If the temperature of the air resistance head is more than a specified value above the certain temperature,
If the magnetic resistance head is deteriorated,
A fixed magnetic recording device provided with a prediction means for predicting . 2. The characteristic of the magnetoresistive head by the predicting means.
A warning means for warning that deterioration is predicted is provided.
The fixed magnetic recording device described.