KR20010042723A - Method for controlling bias current for magnetoresistive head, fixed magnetic recording device, and magnetic disc therefor - Google Patents

Abstract

It is an object of the present invention to enable the bias current for the MR head to be optimized as appropriate to suppress asymmetrical distortion caused by saturation of the signal reproduced from the MR head during operation of the stationary magnetic recording apparatus. Therefore, the error rate is reduced while reading data.

The stationary magnetic recording apparatus according to the present invention has an optimized measuring means 10 for performing a measurement to optimize the bias current value for the MR head of the head structure 1 each time the MR head accesses the magnetic disk. The computer 8 controls the optimization measuring means 10 and instructs the MR head to update the measured bias current value for storage of the bias current value for the MR head, and to update the MR head with the updated and stored optimum bias current. It acts as a processing means for outputting a command to supply.

Description

METHOD FOR CONTROLLING BIAS CURRENT FOR MAGNETORESISTIVE HEAD, FIXED MAGNETIC RECORDING DEVICE, AND MAGNETIC DISC THEREFOR}

Recently, a fixed magnetic recording device (HDD) uses an MR (magnetic resistance) head in response to a demand for increasing recording density. The MR head is based on a regeneration method using a so-called magnetoresistance effect in which the electric resistance is changed by an external magnetic field. Some hard disk devices utilize MR / inductive coupling heads that include an MR head and a thin film head that are integrally coupled to each other. The MR / inductive coupling head uses the thin film head to record data, while the read data uses an MR head adjacent to the thin film head. Thus, the MR head provides a higher reproduction power than the thin film head despite being used only for reading, and the reproduction output is smaller than the track width of the recording thin film head, regardless of the peripheral speed of the magnetic disk. Thus, the influence of adjacent tracks can be minimized during reading. Therefore, MR heads are usually used as HDD heads. In addition, a GMR (Giant MagnetoResistive) head with improved sensitivity has been put into practical use.

Disadvantageously, however, the MR head requires a bias current due to its operating principle, and the signal waveform reproduced by the MR head may be distorted if the bias current is not optimally controlled. The distortion is caused by the offset of the bias point of the bias current, thereby saturating the positive side or the negative side of the reproduced signal waveform. In this case, the positive side and the negative side of the reproduced signal waveform are asymmetric.

Therefore, the following three problems must be solved in order to optimally control the bias current of the MR head.

The first problem is the deviation of the head resistance value due to the dimensional variability of the MR head. The dimensions of the MR head decrease continuously, but the dimensional error does not improve as quickly as the above dimensions. In recent general design of the device, the error of MR stripe height is ± 33%, or the ratio of the highest part to the lowest part is 2: 1. The tolerance of the MR stripe width (length in the current flow direction) is ± 20%. The tolerance of MR stripe thickness is ± 10%. If these are regarded as independent deviations, the total resistance variation of the elements is about 40%, or has a height ratio of 2.33: 1.

Measurement of the head resistance value of the multiple (eg, 80) MR heads showed changed values between the MR heads, as shown in FIG. 17. In this figure, the horizontal axis represents the head resistance value, while the vertical value represents the number of MR heads. Although the deviation distribution of the head resistance values coincides with the standard distribution near the design value, each MR head has different resistance values in the sensor section.

The problem with large dimensional variability is that large differences in power loss occur between different heads in a single device.

In addition, since the cross section of the current (height X thickness of the MR stripe) varies greatly, the current density changes significantly. The lifetime of the product is inversely proportional to the cube of current density. Since the conventional general biasing method uses a constant DC current for all the heads, the lower the stripe height and the thinner the layer thickness, the greater the resistance and current density. The result of power loss results in a significant rise in temperature, and therefore generates more heat than high and thick stripes. Therefore, the combination of temperature and current density results in a much shorter life expectancy for low stripe and thin MR devices compared to high and thick devices.

Another consideration is that all the factors that raise the resistance value also raise the signal level. Thus, the best signal-to-noise ratio occurs at the head with the highest resistance. Thus, low stripes, thin layers, and wide stripes result in signals with good signal-to-noise ratios, while high, thick, narrow stripes produce signals with poor signal-to-noise ratios. The constant bias current must be properly traded off between good quality signal and short lifetime.

When the bias current values for a plurality of MR heads (e.g. four) were changed, the change in output was shown by the waveform shown in FIG. Since the bias current that produces the maximum output value is optimal for reading, FIG. 18 shows that the optimum read bias current characteristic has changed with each head.

The second problem is that the good signal-to-noise ratio varies with the design of the preamplifier. The design of the preamplifier is quite limited because of the goal of reducing its available voltage and lowering power consumption. This design typically has one + 5V voltage source (± 5%). The change in the resistance value of the head is also limited in the amount of bias current that can be used for operation due to the voltage drop across the head and lead. When excessive current flows through the head of a high resistance, the preamplifier stage saturates and distorts the signal, which degrades performance.

A third problem is Gradual Resistance Increase Phenomenon (GRIP) associated with leads in MR heads. The effect of this phenomenon on the performance is greater than expected when adding a few ohms to the MR head's resistance over the lifetime of the stationary magnetic recorder. Thus, the small design margin provided during manufacturing leads to saturation of the amplifier, which leads to an increase in resistance late in the life of the product, resulting in significant performance loss.

As a solution to the above three problems, a well known conventional hard disk device is described in JPA7-2010005.

As shown in Fig. 19, this hard disk drive includes a plurality of MR heads (e.g., four) 31a-31d, a preamplifier 32, a gem (common error meter) 33, and a head / disk. An assembly controller 34, and a central processing unit 35. The optimum current value for each head is stored on the disk surface of the hard disk device at the time of manufacture. When the hard disk device is started, the values are moved to RAM. Each head performs a switching command and is used to supply an active MR head with a bias current accompanying the ram. The gem 33 then re-optimizes and updates the bias current by applying the updated bias current to the MR head.

The measurement of the MR head is performed by the circuit shown in FIG. For example, switches 36a and 36b may be electrically connected to the MR head to measure the MR head 31a to supply a bias current of the feedback control circuit 40 to the MR head. Then, the measured Vcap value is obtained by measuring the voltage of the capacitor 39, and the Vacp value and the known bias current value Ib are used to calculate the head resistance value Rmr of the MR head. do. The resistance value Rmr of the MR head is calculated by equation (1) shown below.

Rmr = (Vcap-Vbe) / Ib ......... (Equation 1)

The optimum current is determined based on the calculated head resistance value Rmr of the MR head. In this way, the bias current values for a conventional hard disk device are optimized in each driven state based on the head resistance value for the magnetoresistive head recorded on the disk surface before delivery from the factory.

However, since the bias current values are optimized in each driven state based on the head resistance values for the MR heads recorded on the disk surface before they are delivered from the factory, the conventional fixed magnetic recording apparatus changes instantaneously in the MR heads. Cannot be processed. Therefore, if the head resistance changes, the bias current value is determined to be optimized before delivery from the factory and may be used beyond the life of the product, and the bias current to optimize while the previous measurement is reoptimized for the next cycle of update. The value is determined. The bias current value is not always optimal for the current head because the head output characteristic decreases with increasing error rate. Since the lifetime value of the head is inversely proportional to the cube of the current density, unnecessarily high current flow may reduce the average lifetime value. In addition, the determination of the effect of the change in resistance on lifetime is based on a comparison with the number of guaranteed requests. As a result, the actual change in resistance is not detected, thus preventing it from having a correctly determined lifetime.

On the other hand, fixed magnetic recording apparatuses using amplitude-detection reproducing methods such as partial response of reading and processing signals from a magnetic disk using direct amplification of the read signals are becoming increasingly popular. If such a stationary magnetic recording device includes an MR head, and if the signal reproduced by the MR head is distorted, the positive and negative waveforms have different absolute values with respect to the baseline (the values must be the same), The amplification of the detected reproduction signal may be quite asymmetric.

Disadvantageously, this error in the amplifier may increase the error rate of the signal reproduced by the MR head, which reduces the reliability of the overall system. In addition, if the MR head is used in a fixed magnetoresistive recording apparatus using a conventional peak-detection reproduction method and distortion similar to the above occurs, the derivative value at the peak value (maximum value) of the waveform of the reproduced signal is reduced. Smaller than the derivative on the saturated side. As a result, the device is significantly affected by noise, thus increasing the error rate of the reproduced signal.

As described above, the disadvantage of the fixed magnetic recording apparatus using an MR head for reading data and using an amplitude-detection reproduction method such as partial response is that the error rate of the reproduced signal can be reduced without optimizing the bias current for the MR head. Nonetheless, no method of controlling the bias current for the MR head was made. Fixed magnetic recording apparatuses using the MR head and the peak-detection reproduction method have similar disadvantages without optimizing the bias current for the MR head. The device is significantly affected by noise which increases the error rate.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fixed magnetic recording apparatus and a magnetic disk as well as a method for controlling the bias current of an MR head, for which asymmetric distortion caused by saturation of a signal reproduced from the MR head during operation of the fixed magnetic recording apparatus. To suppress this, the bias current for the MR head can be optimized. Therefore, the error rate is reduced while reading data.

The present invention relates to a method of controlling a bias current of a magnetoresistive head, a stationary magnetic recording apparatus and a magnetic disk thereof.

1 is a block diagram showing the configuration of a fixed magnetic recording apparatus according to a first embodiment of the present invention;

2 is an explanatory diagram showing the format of the recording surface of the magnetic disk according to the first embodiment;

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

4 is an explanatory diagram showing a measurement pattern of pattern area measurement of a magnetic disk according to the first embodiment;

5 is a waveform diagram showing a reproduced waveform obtained when the pattern region measurement according to the first embodiment is reproduced;

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

7 is a block diagram showing a configuration of a fixed magnetic recording apparatus according to the second embodiment;

8 is a table showing a correspondence between a head resistance value and an optimum bias current according to the second embodiment;

Fig. 9 is a block diagram showing the construction of a fixed magnetic recording apparatus according to the third embodiment of the present invention;

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

11 is a table showing the correspondence between head resistance value and temperature;

12 is a block diagram showing a configuration of a fixed magnetic recording apparatus according to a fourth embodiment of the present invention;

Fig. 13 is a block diagram showing the construction of a fixed magnetic recording apparatus according to a fifth embodiment of the present invention;

14 is a sketch showing the shape of a bump according to the fifth embodiment;

Fig. 15 is a waveform diagram showing a change in output caused by a magnetoresistance phenomenon in the normal case according to the fifth embodiment;

Fig. 16 is a waveform diagram showing variation in output caused by magnetoresistance in an abnormal case according to the fifth embodiment;

17 is a distribution chart showing deviations in head resistance values for a conventional MR head;

18 is a waveform diagram showing the dependence of a conventional head on a bias current;

19 is a block diagram showing the configuration of a conventional fixed magnetic recording apparatus; And

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

1. The method for controlling the bias current of an MR head according to the present invention is executed by controlling the bias current supplied to the MR head to read data recorded on the magnetic disk, and when the MR head accesses the magnetic disk. Making a measurement to optimize the bias current value for the MR head each time; Updating a bias current value for the MR head with the measured optimal bias current value for storage; Supplying the stored optimal bias current to the MR head to read the data.

According to this aspect of the invention, it is possible to optimize the bias current of the MR head appropriately in accordance with the operation of the MR head during the operation of the fixed magnetic recording apparatus so as to maintain the optimum bias current despite thermal changes in the operating characteristics of the MR head. Can be. In addition, the asymmetry distortion induced by the saturation of the waveform of the reproduction signal from the MR head can be limited to lower the error rate during data reading. In addition, by supplying an optimum bias current to the MR head, it is possible to prevent unnecessary high bias current from flowing, as well as to prevent the average life expectancy of the MR head from being shortened by excess current.

In particular, it is possible to optimize the bias current of the MR head according to the operation of the MR head during the operation of the fixed magnetic recording apparatus, thereby preventing the change of the components of the MR head, the change of the preamplifier circuit, and the degradation of performance due to the gradual resistance increase. Can be. In practice, the optimum value of the bias current can be updated whenever the environment changes, so that the characteristics of the device can be prevented from deteriorating over time. It is also possible to improve the yield by designing a reduced margin at normal temperatures.

2. A method of controlling bias current for an MR head according to the present invention is performed to control a bias current supplied to an MR head for reading data written on a magnetic disk, when the MR head enters a standby state. Making a measurement to optimize a bias current value for the MR head; Updating a bias current value for the MR head with the measured optimal bias current value for storage; Supplying the stored optimal bias current to the MR head to read the data.

This feature of the invention works similarly to the features of the method for controlling the bias current of the MR head described in claim 1.

3. The present invention is a fixed magnetic recording apparatus for recording data on a magnetic disk and reading data using an MR head, wherein the bias current value for the MR head is optimized every time the MR head accesses the magnetic disk. Optimization measuring means for performing a measurement for; And a command to control the optimization measuring means, to update the bias current value for the MR head to the measured optimal bias current value for storage, and to supply the updated and stored optimal bias current to the MR head. A magnetic recording device including a processing means for outputting is provided.

This feature of the present invention may implement a method for controlling the bias current of the MR head described in claim 1.

4. The present invention provides a fixed magnetic recording apparatus for recording data on a magnetic disk and reading data using an MR head, wherein the MR current for optimizing a bias current value for the MR head when the MR head enters a standby state. Optimization measuring means for performing a measurement; Control the optimization measuring means, and output a command to update the bias current value for the MR head to the measured optimal bias current value for storage, and to supply the updated and stored optimal bias current to the MR head. A magnetic recording device including a processing means is provided.

This feature of the invention may implement a method for controlling the bias current of the MR head described in claim 2.

5. The present invention relates to a magnetic disk in which a control routine for operating a central processing unit for controlling a stationary magnetic recording apparatus is recorded, wherein the control routine is configured for the MR head whenever the MR head accesses the magnetic disk. A first step of optimizing the bias current value; Updating a bias current value for the MR head with the measured optimal bias current value for storage; And supplying the updated and stored optimum bias current to the MR head in a third step.

According to this aspect of the invention, it is possible to optimize the bias current value of the MR head by executing the control routine recorded on the magnetic disk.

6. According to the magnetic disk according to the present invention, the first step includes a step of optimizing a bias current value for the MR head when the MR head enters a standby state.

This feature of the invention functions similarly to the magnetic disk described in claim 5.

7. The present invention provides a fixed magnetic recording apparatus for recording data on a magnetic disk and reading data using an MR head, comprising: storage means for storing a temperature characteristic of a head resistance value for the MR head; Measuring means for measuring a head resistance value for the MR head when the MR head enters a standby state; And calculating means for calculating a temperature based on the measured head resistance value.

According to this feature of the present invention, the MR head can be used as a temperature monitoring temperature sensor without a separate temperature sensor.

8. The present invention provides a magnetic disk in which a control routine for operating a central processing unit for controlling a stationary magnetic recording apparatus is recorded, wherein the control routine is configured to store a temperature characteristic of a head resistance value for the MR head. step; A second step of measuring a head resistance value for the MR head when the magnetoresistive head enters a standby state; And a third step of calculating a temperature based on the measured head resistance value.

According to this aspect of the invention, the MR head can be used as a temperature sensor by executing the control routine recorded on the magnetic disk.

9. The present invention provides a fixed magnetic recording apparatus having a plurality of MR heads for reading data recorded on a magnetic disk, comprising: storage means for storing temperature characteristics of head resistance values for the plurality of MR heads; Measuring means for measuring a head resistance value for each MR head when the MR head enters a standby state; And predicting means for calculating the temperatures of the plurality of MR heads based on the measured head resistance value and the temperature characteristic, and predicting a reduction level of the characteristic of each MR head based on the calculated temperature. A recording device is provided.

According to this aspect of the invention, it is possible to estimate the life of the fixed magnetic recording apparatus by monitoring the transient changes of the MR head.

10. According to the stationary magnetic recording apparatus of the present invention, the apparatus further includes alarm means for informing the user of the reduction level of the characteristic of each MR head predicted by the prediction means.

11. The present invention provides a fixed magnetic recording apparatus for recording data on a magnetic disk and reading the data using an MR head, comprising: a projector provided at a specific position on the magnetic disk; And monitor means for monitoring a change in the displacement of the MR head based on a change in output from the MR head observed when the MR head passes over the projector.

According to this aspect of the invention, it is possible to monitor the change of the floating state in the MR head to prevent the risk of breakage.

12. According to the stationary magnetic recording apparatus of the present invention, the apparatus further comprises an alarm means for informing the user when the output change exceeds a threshold.

This feature of the invention can warn the user of the risk of breakage.

13. The present invention relates to a magnetic disk on which a control routine for operating a central processing unit for controlling a fixed magnetic recording apparatus is recorded, wherein the control routine is obtained from the MR head observed when the control routine passes over the projector. A first step of measuring and storing a change in the output of the; A second step of determining whether the stored output change exceeds a threshold; And a third step of alerting the user when the threshold is exceeded.

According to the present invention, the MR head can monitor the change in the floating state by executing the control routine recorded on the magnetic disk.

14. According to the present invention, said first step described in step 13 measures and stores possible changes in the output from the observed MR head as the control routine passes over the projector after the MR head enters the standby state. It includes a step.

The present invention functions similarly to the magnetic disk described in 13.

The method of controlling the bias current for the stationary magnetic recording apparatus, the magnetic disk and the MR head will be described below on the basis of specific embodiments.

First embodiment

As shown in Fig. 1, the fixed magnetic recording apparatus according to the first embodiment of the present invention measures to optimize the bias current value for the MR head of the head structure 1 each time the MR head accesses the magnetic disk. Microcomputer 8 controls the optimization measurement means 10 and updates the measured bias current value for storage of the bias current value for the MR head. And a processing means for outputting a command to supply the updated and stored optimum bias current to the MR head.

The optimization measuring means 10 comprises a magnetic disk 2, a preceding amplifier 3, a data channel 4, a hard disk controller 6, and a buffer 7.

The magnetic disk 2 has a plurality of circular tracks that generally extend from the inner circumference to the outer circumference, as shown in FIG. Each track has a number of servo areas A and data areas B, and if the MR head accesses any of the data areas B or the magnetic disk to read / write data, the MR head will Before accessing the desired position at all times, the positional information recorded in the servo A is first read. Therefore, the magnetic disk 2 of the first embodiment has a measurement pattern area C provided immediately after each servo area A (area between the servo area A and the first data of the data area B). In addition, the measurement pattern area C has a measurement pattern for measuring a signal-to-noise ratio in order to optimize the bias current. Even if the data area B is accessed, the MR head accesses the measurement pattern area C before reading / writing data to the data area B to pass the measurement pattern. As shown in Fig. 3, each track has the same measurement patterns. The measurement pattern area C has a fixed periodic signal which is recorded before being delivered from the factory. The fixed periodic signal represents the precoded data in one pattern and uses 1-12 Ts (T is the total of time determined by the performance of the MR head, for example 5 ns) in one cycle.

The head structure 1 has an MR head and is connected via wire to the preamplifier 3. The output of the preceding amplifier 3 is fed to the data channel 4. Once accessed, the MR head is connected to a bias current source (not shown) when the switches shown in FIG. 20 are set.

Gem 5 has a universal error measurement function for measuring the signal-to-noise ratio, and connects a test system realized by connecting a fixed magnetic recording device with devices such as measurement test system data storage devices such as conventional digital oscilloscopes and logical analyzers. It was designed to allow mounting.

The buffer 7 stores therein the optimum bias current value for the MR head and the ideal signal waveform normalized by the data sampling shown in FIG. 4 and is stored before being delivered from the factory using one cycle of 1 to 127 Ts. Precode the current value and the ideal signal waveform.

Next, the operation of the fixed magnetic recording apparatus for updating the bias current value for the MR head to the optimum value will be described.

When a command is received from the microcomputer 8 to access the magnetic disk 2, the hard disk controller 6 has a head structure having an MR head for accessing a desired position of the magnetic disk 2 rotating at a very high speed. Control (1).

When the MR head accesses the desired servo area A of the magnetic disk 2 and then the measurement pattern C, a current source (not shown) for supplying a bias current to the MR head is set, for example. , Approximately 7mA of current is supplied to the MR head. The gem 5 performs analysis by comparing the actual reproduced waveform obtained by reading the measurement pattern (shown in FIG. 5) and the ideally normalized waveform stored in the buffer 7 in terms of level difference for one period.

In particular, when each current source is set to 7, 8, 9, 10, and 11, the actual measured signal of the signal-to-noise ratio for each bias current value is 25, 26, 26.8, 27, and 26.9 dB and the waveform If a, the microcomputer 8 determines the optimum bias current value as 10 mA since the optimum bias current value is obtained when the signal-to-noise ratio has the largest value.

The MR head has been measured with a bias current between 7-11 mA; The buffer 7 stores the optimum bias current value for the MR head obtained before delivery from the factory in the buffer, or in this case the optimum bias current of 9 mA if at least one measurement has been performed during the last measurement, Thus, the actual reproduced waveform is obtained with a bias current in the range of about ± 2 mA of the optimum bias current value.

The microcomputer 8 instructs to store the optimum bias current value (9 mA) stored in the buffer 7 as a new value (10 mA).

The microcomputer 8 then instructs the MR head to supply the updated and stored new optimum bias current value (10 mA).

In the above structure, the bias current for the MR head can be optimized to operate the MR head while the fixed magnetic recording device is operating. In addition, even though the operating characteristic of the MR head changes, the optimum bias current can be maintained. In addition, asymmetrical distortion due to saturation of the signal waveform reproduced from the MR head is prevented in order to reduce the error rate occurring during reading of the data. In addition, the supply of the optimum bias current to the MR head can prevent unnecessarily high bias current flow, and can prevent the MR head life value from being reduced by excessive current.

Although, in the first embodiment, the microcomputer 8 is provided with a control routine for controlling a fixed magnetic disk, a similar effect is provided in the diskware or buffer 7 for storing a program on the magnetic disk 2. Can be obtained through recording, and the control routine stores the first step of optimizing the bias current value for the MR head each time the MR head accesses the magnetic disk 2, storing the bias current value for the MR head. And a second step of updating the measured optimal bias current value and a third step of supplying the updated and stored optimum bias current to the MR head.

Second embodiment

As shown in Fig. 7, the stationary magnetic recording apparatus according to the second embodiment of the present invention replaces the MR head when the MR head enters the standby state instead of the optimization measuring means 10 in the first embodiment. Optimization measuring means 11 for performing measurements for optimizing the bias current value. The magnetic disk 12 is independent of the measurement pattern area C and the measurement pattern described in the first embodiment.

The optimization measuring means 11 comprises a plurality of preceding amplifiers 3a and 3b, a data channel 4, a gem 13, a hard disk controller 14, and a buffer 15.

The head structures 1a, 1b with MR heads are configured to be connected with any of the preceding amplifiers 3a, 3b. The outputs of the preceding amplifiers 3a, 3b are fed to the data channel 4. When the switches shown in FIG. 20 are set, either of the accessed MR heads is connected to a current source (not shown) to supply a bias current.

Gem 13 has a universal error measurement function for measuring MR head resistance value (Rmr), and is connected to the fixed magnetic recording device with devices such as measurement test system data storage devices such as conventional digital oscilloscopes and logical analyzers. It is designed to allow the mounting of test systems realized by doing so.

The buffer 15 has in advance an optimum bias current value for the MR head stored in the buffer before leaving the factory. The optimum bias current for each MR head is set as the resistance of the MR head.

Next, the operation of the fixed magnetic recording apparatus for updating and optimizing the bias current value for each MR head will be described.

When data from the head structure 1a is moved through the preceding amplifier 3a, and the head structure 1a enters the standby state, the hard disk controller 14 is transferred from the microcomputer 8 to the head structure 1b. It is commanded to control the preamplifier 3a to connect.

To measure the accompanying MR heads, an internal head voltage value Vmr is detected using the BHV (Buffered Head Voltage Monitor) terminals of the preceding amplifiers 3a, 3b, which are located close to the head structures 1a, 1b, respectively. .

The hard disk controller 14 calculates the MR head resistance value Rmr based on equation (2) shown below. However, the IB value, which is the current supplied to the MR head by the current source, is a fixed value and is known.

Rmr = Vmr / IB ....... (Equation 2)

The hard disk controller 14 determines an optimum bias current value Ib that matches the characteristics shown in FIG. 8, and statistically determines the optimum bias current value Ib determined in dependence on the head resistance value Rmr of the MR head. Instruct. The signal coming out of the BHV terminal is an analog output, and the hard disk controller 14 converts the analog signal into a digital signal.

In particular, after the current value of the current I from the current source is set to 9 mA and the voltage Vmr value is detected as 0.3 V at the BHV terminal, the hard disk controller determines that the MR head at about 33? The head resistance value is calculated and the optimum bias current value Ib is determined to be 9.5 mA in accordance with the characteristics shown in FIG. This is because the head resistance value (Rmr approximately 33.3Ω) of the MR head is between 30-35Ω. The optimum bias current value (9.5 mA) is stored in the buffer 15 as 4-bit serial data (e.g. 0010).

Four-bit serial data is moved to the head structure 1b to set the data, so that an optimum bias current value (9.5 mA) can be supplied to the MR head during normal operation.

When the head structure 1b enters the normal operating state or when the head structure 1b enters the standby state, the hard disk controller 14 connects the preceding amplifier (I) to the head structure 1a from the microcomputer 8. A command to control 3b) is received, thereby optimizing the bias current for the MR head of the head structure 1a as described above.

In the current of the fixed magnetic recording apparatus, the system side theoretically controls the sectors to perform reading and writing for each sector. However, the sector is accessed by a specific head depending on the settings of the device, so the user does not have to consider this point of view. In general, most fixed magnetic recording devices require a shorter head switching time than the track searching time, so if the MR head writes data in one sector and then moves to another sector, priority is given to head switching. Is given first. In other words, the MR head is frequently switched.

In the above configuration, the bias current for each MR head can be optimized when the MR head is in the standby state, and thus it is possible for the optimum bias current to be maintained even if the operating characteristics of the MR head change momentarily. In addition, asymmetrical distortion due to saturation of the signal waveform reproduced from the MR head is prevented in order to reduce the error rate occurring during reading of the data. In addition, the supply of the optimum bias current to the MR head can prevent unnecessarily high bias current flow, and can prevent the MR head life value from being reduced by excessive current.

In addition, the magnetic disk 12 does not need the measurement pattern area C for forming the measurement pattern as in the first embodiment.

Although, in the second embodiment, the microcomputer 8 is provided with a control routine for controlling the stationary magnetic recording apparatus, a similar effect is provided with a diskware or a buffer 15 for storing a program on the magnetic disk 12. Can be obtained through recording, and the control routine is a first step of optimizing the bias current value for the MR head when the MR head enters the standby state, the bias current value for the MR head for storage. And a second step of updating the measured optimum bias current value, and a third step of supplying the updated and stored optimum bias current value to the MR head.

In the second embodiment, a plurality of preamplifiers are provided, but only one while the MR resistance of the MR head is measured to set the optimum bias current value and all MR heads are in standby without access to the MR head. A preamplifier is provided.

Third embodiment

As shown in Fig. 9, the fixed magnetic recording apparatus according to the third embodiment of the present invention has a buffer 16 for storing the temperature characteristic of the head resistance value for the MR head instead of the buffer 15 of the second embodiment. In addition to the microcomputer 8 of the second embodiment, it also has a microcomputer 17 to which a calculation function for calculating the temperature based on the measured head resistance value is added.

The buffer 16 has a temperature characteristic of the head resistance value for each MR head, and the temperature characteristic is stored in the buffer.

The head resistance value for the MR head depends on the design involving the MR head component, but for a number of MR heads (eg, six) associated with changes in temperature of the MR head as shown in FIG. 10. As shown in the change of the head resistance value, it is predictable because the head resistance value changes almost linearly with respect to temperature. The slope of the temperature with respect to the head resistance is known before design.

For example, assume that an MR head has a temperature gradient of 0.15Ω / ° C. It is assumed that the head resistance value was determined to be 25 Ω during the delivery inspection process performed at a constant temperature of 20 ° C. The head resistance value at the known temperature is stored in buffer 16 before delivery. The relationship between the temperature and the head resistance value is shown in FIG.

Next, the operation of the fixed magnetic recording apparatus for measuring the head resistance value for the MR head to control the temperature will be described.

Similar to the second embodiment, when the MR head of the head structure 1b enters the standby state, the hard disk controller 14 receives the preceding amplifier 3b from the microcomputer 17 to connect to the head structure 1b. Receive a command to control. The voltage value Vmr of the inner head is measured using the BVH terminal of the preceding amplifier 3b. The hard disk controller 14 calculates the MR head resistance value Rmr based on the above equation (2), where the value Ib of the current supplied to the MR head by the current source (not shown) is a known fixed value. Because.

The microcomputer 17 calculates the temperature based on the measured head resistance value.

If the measured head resistance value is about 26.5Ω, the microcomputer 17 calculates at 30 ° C. based on the head resistance value dependence on the temperature shown in FIG.

In addition, when the head structure 1a in place of the head structure 1b enters the standby state, the hard disk controller 14 controls the preceding amplifier 3a to connect to the head structure 1a, and as described above. Measure the head resistance together to calculate the temperature. Because of frequent switching of the MR heads, the head resistance value of the MR head for calculating the temperature is frequently measured.

In the above structure, the temperature can be controlled by monitoring the head resistance value. Although guaranteed temperature operation of the hard disk depends on the design, if the temperature is 0 to 50 ° C, the guaranteed range is between 22 and 29.5 Ω head resistance values based on the dependence of the head resistance values on the temperature shown in FIG. Suppose it matches a range. In addition, if the device operates continuously at this ambient temperature (outside the guaranteed range), the device or data may be destroyed in the worst case. Therefore, an alarm means for alarming the user can be connected to the interface 8, and if the measured head resistance value is out of the range of the head resistance value between 22-29.5? 8) can be generated from the alarm means.

Although, in the third embodiment, the microcomputer 17 is provided with a control routine for controlling the operation of the stationary magnetic recording apparatus, similar effects are those for storing the program in the diskware or the magnetic disk 12. Can be obtained through the recording, and the control routine is a first step of storing the temperature characteristic of the head resistance value for each MR head, and the head resistance value for the MR head when the MR head enters the standby state. A second step of measuring, and a third step of calculating a temperature based on the measured head resistance value.

Fourth embodiment

As shown in Fig. 12, the fixed magnetic recording apparatus according to the fourth embodiment of the present invention is characterized in that a plurality of MR heads are based on the measured head resistance values and temperature characteristics instead of the microcomputer 17 of the third embodiment. A microcomputer 18 has additional functions for calculating the temperature and additional functions for predicting the reduction level of each MR head based on the calculated temperature.

Similar to the third embodiment, when one of the MR heads enters the standby state, the head resistance value for this MR head is calculated and stored in the buffer 16, and the measured head resistance value for all MR heads is also It is stored in the buffer 16. Optionally, measured head resistance values for the plurality of MR heads may be measured and stored in the buffer 16. Generally, such multiple MR heads are constantly operating selectively or waiting.

The microcomputer 18 calculates the temperatures of the plurality of MR heads based on the measured head resistance values stored in the buffer 16. If one of the MR heads exhibits a temperature that is extremely higher than the temperature of the other MR head, it is expected that this MR head is subject to instantaneous changes.

In the above structure, the instantaneous change can be predicted by monitoring the last value for the change of the head resistance value or the head resistance value stored in the buffer and the change amount associated with the stored value. In general, if the head resistance changes significantly despite the constant ambient temperature, it is assumed that the accompanying magnetoresistive elements are subject to instantaneous changes. However, it is very difficult to determine whether the change in resistance value is due to the instantaneous change in ambient temperature, except for the instantaneous increase in resistance due to the TA (thermal asperity) effect. Therefore, a plurality of MR heads can be used assuming that the head resistance value is changed or constant by the ambient temperature. In a stationary magnetic recording apparatus having four heads, if all four MR heads have changed head resistance values, it should be assumed that this is due to a change in temperature. In addition, if only one of the MR heads has a changed head resistance value, it should be assumed that the characteristics of the changed head have changed compared to those before delivery from the factory. During the design, statistical data indicative of the level of change in the head resistance value must be obtained, which can significantly compromise performance.

If the head resistance value is changed by more than 10% for reasons other than the temperature factor, it is assumed that the accompanying magnetoresistive element is slightly damaged. For a disk device that is considered to be near the end of its life, the device should be constantly monitored during instantaneous changes to check whether the resistance value changes by more than 10% in the factory compared to the disk device before the delivery. If so, the user's data recorded on the device may be lost or the device may be destroyed.

Thus, an alarm means 19 is connected to the interface 8 that alerts the user to the level of reduction of the characteristic, and if the change occurred with more than 10% an alarm signal is alarmed through the interface 8. Occurs in the Sudan. By alerting the user, it is possible for the user to be alerted about the reduced level of the property and thus prevent the device or data from being destroyed.

Fifth Embodiment

As shown in Fig. 14, in the fixed magnetic recording apparatus according to the fifth embodiment of the present invention, the bump 23 is provided as a projector on a specific portion of the magnetic disk 20, and the MR head is placed on the bump 23. Each MR head has a monitoring means 21 (see FIG. 13) for changes in the displacement based on the amount of change in output from the MR head observed when passing.

On the surface of the magnetic disk 20, as shown in FIG. 14, the bump 23 is formed of the same material as the magnetic disk 20. The bump 23 has a diameter of about 2.0 to 3.0 mu m and a height of 0.1 to 0.15 mu m. A plurality of bumps 23 are formed in the magnetic disk 20. Laser zone texture technology is used to form dump 23 on magnetic disk 20. The MR head essentially detects and outputs a change in the resistance value and is sensitively dependent on the thermal stability of the sensor portion of the MR head. During normal operation, if the MR head portion comes in contact with an abnormal projector on the surface of the magnetic disk 20, the head resistance value increases momentarily to change the output. This phenomenon is commonly referred to as "thermal emissivity" (TA), and magnetic disk designs must cope with this phenomenon by increasing the flexibility of the magnetic disk or by using improved circuitry.

Considering the thermal efferentiation phenomenon in the same bump, the displacement increases with reduced collision due to the increased level of output variation.

Next, the operation of the stationary magnetic recording apparatus will be described which prevents possible crashes due to measuring the output value for each MR head.

When a command is received from the microcomputer 22, the preamplifier 3 monitors whether the head resistance value of each MR head of the head structure 1 increases, and the MR head has a predetermined value of the magnetic disk 20. Each time it passes over the bump 23 formed in the position, the head resistance value increases its output value.

The monitor means 21 stores in itself the output change from the observed MR head as the MR head passes over the bump 21, which change is initially stored at the initial value at the time of manufacture. In response to the command from the microcomputer 22, since the monitor means 21 periodically measures the output change to compare with the measured value having an initial value to determine the change in the displacement, the MR Monitoring the head causes a crash.

In particular, if the displacement is appropriate, the observed change in output as the MR head passes over bump 23 is about 100 mV, as shown in FIG. 15. Thus, the monitor means 21 has an output change stored at 100 mV as an initial value at the time of manufacture. Assuming that a crash occurs when the change increases to 20% or more, the monitoring means 21 has a threshold at which a crash can occur at 120 mV. If the measurement of the periodic power change indicates a decrease in the displacement, the observed power change as the MR head passes over the bumps 23 increases to about 170 mV as shown in FIG. Since this value is larger than the threshold value 120 mV, an alarm signal is output to the alarm signal means via the interface 8 to notify the user of a possible crash.

Although, in the fifth embodiment, the microcomputer 22 is provided with a control routine for operating the fixed magnetic recording apparatus, it is possible to decode the program or the like for storing the program for the magnetic disk 20. Similar effects can be obtained, wherein the control routine is a first step of storing the output change from the MR head when the MR head passes over the bump 23, and a second step of determining if the stored output change exceeds a threshold. And a third step of alarming the user when the threshold is exceeded.

Although the fifth embodiment measures and stores the output change of the MR head in normal operation, a similar effect can be obtained if the output change of the MR head is measured and stored during the standby state.

In addition, although the above embodiments each use an MR head (MR) as an exclusive-reproduction head, a similar effect can be obtained using a large MR head (GMR).

Claims (14)

CLAIMS What is claimed is: 1. A method of controlling a bias current for an MR head, the method being performed to control a bias current supplied to an MR head for reading data written on a magnetic disk, Making a measurement to optimize a bias current value for the MR head each time the MR head accesses a magnetic disk; Updating a bias current value for the MR head with the measured optimal bias current value for storage; And supplying said stored optimal bias current to said MR head to read said data. CLAIMS What is claimed is: 1. A method of controlling a bias current for an MR head, the method being performed to control a bias current supplied to an MR head for reading data written on a magnetic disk, Making a measurement to optimize a bias current value for the MR head when the MR head enters a standby state; Updating a bias current value for the MR head with the measured optimal bias current value for storage; And supplying said stored optimal bias current to said MR head to read said data. A fixed magnetic recording apparatus for recording data on a magnetic disk and reading data using an MR head, Optimization measuring means for performing a measurement to optimize a bias current value for the MR head each time the MR head accesses a magnetic disk; And Control the optimization measuring means, and output a command to update the bias current value for the MR head to the measured optimal bias current value for storage, and to supply the updated and stored optimal bias current to the MR head. A stationary magnetic recording apparatus comprising a processing means. A fixed magnetic recording apparatus for recording data on a magnetic disk and reading data using an MR head, Optimization measuring means for performing a measurement to optimize a bias current value for the MR head when the MR head enters a standby state; Control the optimization measuring means, and output a command to update the bias current value for the MR head to the measured optimal bias current value for storage, and to supply the updated and stored optimal bias current to the MR head. A stationary magnetic recording apparatus comprising a processing means. In a magnetic disk on which a control routine for operating a central processing unit for controlling a stationary magnetic recording apparatus is recorded, the control routine includes: A first step of optimizing a bias current value for the MR head each time the MR head accesses a magnetic disk; Updating a bias current value for the MR head with the measured optimal bias current value for storage; And And a third step of supplying the updated and stored optimum bias current to the MR head. 6. The magnetic disk of claim 5, wherein the first step includes optimizing a bias current value for the MR head when the MR head enters a standby state. A fixed magnetic recording apparatus for recording data on a magnetic disk and reading data using an MR head, Storage means for storing a temperature characteristic of a head resistance value for the MR head; Measuring means for measuring a head resistance value for the MR head when the MR head enters a standby state; And And calculating means for calculating a temperature based on the measured head resistance value. In a magnetic disk on which a control routine for operating a central processing unit for controlling a stationary magnetic recording apparatus is recorded, the control routine includes: A first step of storing temperature characteristics of a head resistance value for the MR head; A second step of measuring a head resistance value for the MR head when the magnetoresistive head enters a standby state; And And a third step of calculating a temperature based on the measured head resistance value. A fixed magnetic recording apparatus having a plurality of MR heads for reading data recorded on a magnetic disk, Storage means for storing temperature characteristics of head resistance values for the plurality of MR heads; Measuring means for measuring a head resistance value for each MR head when the MR head enters a standby state; And And predicting means for calculating a temperature of the plurality of MR heads based on the measured head resistance value and the temperature characteristic, and predicting a reduction level of the characteristic of each MR head based on the calculated temperature. Fixed magnetic recording device. 10. The stationary magnetic recording apparatus according to claim 9, further comprising alarm means for informing a user of a reduction level of a characteristic of each MR head predicted by said predicting means. A fixed magnetic recording apparatus for recording data on a magnetic disk and reading out the data using an MR head, A projector provided at a specific position on the magnetic disk; And And monitor means for monitoring a change in the displacement of the MR head based on an output change from the MR head observed when the MR head passes over the projector. 12. The stationary magnetic recording apparatus of claim 11, further comprising alarm means for notifying a user when the output change exceeds a threshold. In a magnetic disk on which a control routine for operating a central processing unit for controlling a stationary magnetic recording apparatus is recorded, the control routine includes: A first step of measuring and storing a change in output from the MR head observed as the control routine passes over a projector; A second step of determining whether the stored output change exceeds a threshold; And And a third step of alerting the user when the threshold is exceeded. 14. The method of claim 13, wherein the first step includes measuring and storing possible changes in the output from the observed MR head as the control routine passes over the projector after the MR head enters the standby state. Magnetic disk, characterized in that.